Adelphi, MD, United States
Adelphi, MD, United States

The University of Maryland University College is an American public university located in the unincorporated community of Adelphi in Prince George's County, Maryland in the United States. It is known primarily for its distance learning classes and programs, but UMUC also offers classes on campus at its Academic Center in Largo, and at satellite campuses across the Baltimore-Washington Metropolitan Area, throughout Maryland, as well as in Europe, the Middle East, and Asia. UMUC serves over 90,000 students worldwide and is one of the largest distance learning institutions in the world. UMUC is open to all applicants with a 100 percent acceptance rate for undergraduate programs. The university offers 120 academic programs in instructor-led and online classes, including bachelor, masters, and doctoral degrees as well as undergraduate and graduate certificates. UMUC is a member of the University System of Maryland, which includes eleven separate public universities in Maryland. Wikipedia.

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University of Maryland University College, United States Of America, George Mason University and George Washington University | Date: 2016-10-19

A nanostructure sensing device comprises a semiconductor nanostructure having an outer surface, and at least one of metal or metal-oxide nanoparticle clusters functionalizing the outer surface of the nanostructure and forming a photoconductive nanostructure/nanocluster hybrid sensor enabling light-assisted sensing of a target analyte.

The United States Of America and University of Maryland University College | Date: 2015-04-17

An approach is presented to recontruct image data for an object using a partial set of magnetic resonance (MR) measurements. A subset of data points in a data space representing an object are selected (e.g. through random sampling) for MR data acquisition. Partial MR data corresponding to the subset of data points is received and used for image reconstruction. The overall speed of image reconstruction can be reduced dramatically by relying on acquisition of data for the subset of data points rather than for all data points in the data space representing the object. Compressive sensing type arguments are used to fill in missing measurements, using a priori knowledge of the structure of the data. A compressed data matrix can be recovered from measurements that form a tight frame. It can be established that these measurements satisfy the restricted isometry property (RIP). The zeroth-order regularization minimization problem can then be solved, for example, using a 2D ILT approach.

Shackman A.J.,University of Maryland University College | Fox A.S.,University of California at Davis
Journal of Neuroscience | Year: 2016

It is widely thought that phasic and sustained responses to threat reflect dissociable circuits centered on the central nucleus of the amygdala (Ce) and the bed nucleus of the stria terminalis (BST), the two major subdivisions of the central extended amygdala. Early versions of this hypothesis remain highly influential and have been incorporated into the National Institute of Mental Health Research Research Domain Criteria framework. However, new observations encourage a different perspective. Anatomical studies show that the Ce and BST form a tightly interconnected unit, where different kinds of threat-relevant information can be integrated and used to assemble states of fear and anxiety. Imaging studies in humans and monkeys show that the Ce and BST exhibit similar functional profiles. Both regions are sensitive to a range of aversive challenges, including uncertain or temporally remote threat; both covary with concurrent signs and symptoms of fear and anxiety; both show phasic responses to short-lived threat; and both show heightened activity during sustained exposure to diffusely threatening contexts. Mechanistic studies demonstrate that both regions can control the expression of fear and anxiety during sustained exposure to diffuse threat. These observations compel a reconsideration of the central extended amygdala’s contributions to fear and anxiety and its role in neuropsychiatric disease. © 2016 the authors.

Mandal D.,University of Maryland University College | Quan H.T.,University of Maryland University College | Quan H.T.,Peking University | Jarzynski C.,University of Maryland University College
Physical Review Letters | Year: 2013

We describe a simple and solvable model of a device that - like the "neat-fingered being" in Maxwell's famous thought experiment - transfers energy from a cold system to a hot system by rectifying thermal fluctuations. In order to accomplish this task, our device requires a memory register to which it can write information: the increase in the Shannon entropy of the memory compensates the decrease in the thermodynamic entropy arising from the flow of heat against a thermal gradient. We construct the nonequilibrium phase diagram for this device, and find that it can alternatively act as an eraser of information. We discuss our model in the context of the second law of thermodynamics. © 2013 American Physical Society.

Langmead B.,University of Maryland University College | Salzberg S.L.,University of Maryland University College | Salzberg S.L.,Johns Hopkins University
Nature Methods | Year: 2012

As the rate of sequencing increases, greater throughput is demanded from read aligners. The full-text minute index is often used to make alignment very fast and memory-efficient, but the approach is ill-suited to finding longer, gapped alignments. Bowtie 2 combines the strengths of the full-text minute index with the flexibility and speed of hardware-accelerated dynamic programming algorithms to achieve a combination of high speed, sensitivity and accuracy. © 2012 Nature America, Inc. All rights reserved.

Kirkpatrick T.R.,University of Maryland University College | Belitz D.,University of Oregon
Physical Review Letters | Year: 2012

We develop a theory for a generic instability of a Fermi liquid in dimension d>1 against the formation of a Luttinger-liquid-like state. The density of states at the Fermi level is the order parameter for the ensuing quantum phase transition, which is driven by the effective interaction strength. A scaling theory in conjunction with an effective field theory for clean electrons is used to obtain the critical behavior of observables. In the Fermi-liquid phase the order-parameter susceptibility, which is measurable by tunneling, is predicted to diverge for 1

He Y.,Zhejiang Normal University | Zhou W.,Center for Neutron Research | Zhou W.,University of Maryland University College | Qian G.,Zhejiang University | Chen B.,University of Texas at San Antonio
Chemical Society Reviews | Year: 2014

Natural gas (NG), whose main component is methane, is an attractive fuel for vehicular applications. Realization of safe, cheap and convenient means and materials for high-capacity methane storage can significantly facilitate the implementation of natural gas fuelled vehicles. The physisorption based process involving porous materials offers an efficient storage methodology and the emerging porous metal-organic frameworks have been explored as potential candidates because of their extraordinarily high porosities, tunable pore/cage sizes and easily immobilized functional sites. In this view, we provide an overview of the current status of metal-organic frameworks for methane storage. This journal is © the Partner Organisations 2014.

Kirkpatrick T.R.,University of Maryland University College | Belitz D.,University of Oregon
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

An earlier theory of the quantum phase transition in metallic ferromagnets is revisited and generalized in three ways. It is shown that the mechanism that leads to a fluctuation-induced first-order transition in metallic ferromagnets with a low Curie temperature is valid, (1) irrespective of whether the magnetic moments are supplied by the conduction electrons or by electrons in another band, (2) for ferromagnets in the XY and Ising universality classes as well as for Heisenberg ferromagnets, and (3) for any systems with a nonzero homogeneous magnetization, such as ferrimagnets or canted ferromagnets. This vastly expands the class of materials for which a first-order transition at low temperatures is expected, and it explains why strongly anisotropic ferromagnets, such as UGe 2, display a first-order transition as well as Heisenberg magnets. © 2012 American Physical Society.

Timme R.E.,University of Maryland University College | Bachvaroff T.R.,Smithsonian Environmental Research Center | Delwiche C.F.,University of Maryland University College
PLoS ONE | Year: 2012

The tremendous diversity of land plants all descended from a single charophyte green alga that colonized the land somewhere between 430 and 470 million years ago. Six orders of charophyte green algae, in addition to embryophytes, comprise the Streptophyta s.l. Previous studies have focused on reconstructing the phylogeny of organisms tied to this key colonization event, but wildly conflicting results have sparked a contentious debate over which lineage gave rise to land plants. The dominant view has been that 'stoneworts,' or Charales, are the sister lineage, but an alternative hypothesis supports the Zygnematales (often referred to as "pond scum") as the sister lineage. In this paper, we provide a well-supported, 160-nuclear-gene phylogenomic analysis supporting the Zygnematales as the closest living relative to land plants. Our study makes two key contributions to the field: 1) the use of an unbiased method to collect a large set of orthologs from deeply diverging species and 2) the use of these data in determining the sister lineage to land plants. We anticipate this updated phylogeny not only will hugely impact lesson plans in introductory biology courses, but also will provide a solid phylogenetic tree for future green-lineage research, whether it be related to plants or green algae. © 2012 Timme et al.

Kirkpatrick T.R.,University of Maryland University College | Belitz D.,University of Oregon
Physical Review Letters | Year: 2010

It is shown that columnar fluctuations, in conjunction with weak quenched disorder, lead to a T3/2 temperature dependence of the electrical resistivity. This is proposed as an explanation of the observed non-Fermi-liquid behavior in the helimagnet MnSi, with one possible realization of the columnar fluctuations provided by Skyrmion lines that have independently been proposed to be present in this material. © 2010 The American Physical Society.

Green D.,Institute for Advanced Study | Komargodski Z.,Institute for Advanced Study | Katz A.,University of Maryland University College
Physical Review Letters | Year: 2011

We describe renormalizable supersymmetric four-dimensional theories which lead to gaugino mediation and various generalizations thereof. Even though these models are strongly coupled, we can demonstrate the parametric suppression of soft scalar masses via Seiberg duality. We show that our models have a parameter which continuously interpolates between suppressed soft scalar masses and their conventional gauge mediated contribution. The main physical effect which we utilize is the general relation between massive deformations in one frame and the Higgs mechanism in the dual frame. Some compelling and relatively unexplored phenomenological scenarios arise naturally in this framework. We offer preliminary comments on various aspects of the phenomenology and outline several of the outstanding open problems. © 2011 American Physical Society.

Green K.M.,University of Maryland University College
Journal of Consulting and Clinical Psychology | Year: 2014

Objective: This study provides guidance on how propensity score methods can be combined with moderation analyses (i.e., effect modification) to examine subgroup differences in potential causal effects in nonexperimental studies. As a motivating example, we focus on how depression may affect subsequent substance use differently for men and women. Method: Using data from a longitudinal community cohort study (N = 952) of urban African Americans with assessments in childhood, adolescence, young adulthood, and midlife, we estimate the influence of depression by young adulthood on substance use outcomes in midlife, and whether that influence varies by gender. We illustrate and compare 5 different techniques for estimating subgroup effects using propensity score methods, including separate propensity score models and matching for men and women, a joint propensity score model for men and women with matching separately and together by gender, and a joint male/female propensity score model that includes theoretically important gender interactions with matching separately and together by gender. Results: Analyses showed that estimating separate models for men and women yielded the best balance and, therefore, is a preferred technique when subgroup analyses are of interest, at least in this data. Results also showed substance use consequences of depression but no significant gender differences. Conclusions: It is critical to prespecify subgroup effects before the estimation of propensity scores and to check balance within subgroups regardless of the type of propensity score model used. Results also suggest that depression may affect multiple substance use outcomes in midlife for both men and women relatively equally. © 2014 American Psychological Association.

De Los Reyes A.,University of Maryland University College | Thomas S.A.,University of Maryland University College | Kundey S.M.A.,Hood College
Annual Review of Clinical Psychology | Year: 2013

Researchers use multiple informants' reports to assess and examine behavior. However, informants' reports commonly disagree. informants' reports often disagree in their perceived levels of a behavior ("low" versus "elevated" mood), and examining multiple reports in a single study often results in inconsistent findings. Although researchers often espouse taking a multi-informant assessment approach, they frequently address informant discrepancies using techniques that treat discrepancies as measurement error. Yet, recent work indicates that researchers in a variety of fields often may be unable to justify treating informant discrepancies as measurement error. In this review, the authors advance a framework (Operations Triad Model) outlining general principles for using and interpreting informants' reports. Using the framework, researchers can test whether or not they can extract meaningful information about behavior from discrepancies among multiple informants' reports. The authors provide supportive evidence for this framework and discuss its implications for hypothesis testing, study design, and quantitative review. Copyright © 2013 by Annual Reviews.

Nakayama Y.,Tokyo Gakugei University | Yoshimura K.,University of Maryland University College | Iida H.,Tokyo Gakugei University
Nature Communications | Year: 2012

A key molecule of sensing machineries essential for survival upon hypo-osmotic shock is the mechanosensitive channel. The bacterial mechanosensitive channel MscS functions directly for this purpose by releasing cytoplasmic solutes out of the cell, whereas plant MscS homologues are found to function in chloroplast organization. Here we show that the fission yeast MscS homologues, designated Msy1 and Msy2, participate in the hypo-osmotic shock response by a mechanism different from that operated by the bacterial MscS. Upon hypo-osmotic shock, msy2 ĝ€" and msy1 ĝ€" msy2 ĝ€" cells display greater cell swelling than wild-type cells and undergo cell death. Cell swelling precedes an intracellular Ca 2+ increase, which was greater in msy1 ĝ€" and msy1 ĝ€" msy2 ĝ€" cells than in wild-type cells. Fluorescent microscopy showed that Msy1 and Msy2 localize mainly to the endoplasmic reticulum. These observations suggest that organellar Msy1 and Msy2 regulate intracellular Ca 2+ and cell volume for survival upon hypo-osmotic shock. © 2012 Macmillan Publishers Limited. All rights reserved.

Adler P.B.,Utah State University | Fajardo A.,Austral University of Chile | Kleinhesselink A.R.,Utah State University | Kraft N.J.B.,University of Maryland University College
Ecology Letters | Year: 2013

Recent functional trait studies have shown that trait differences may favour certain species (environmental filtering) while simultaneously preventing competitive exclusion (niche partitioning). However, phenomenological trait-dispersion analyses do not identify the mechanisms that generate niche partitioning, preventing trait-based prediction of future changes in biodiversity. We argue that such predictions require linking functional traits with recognised coexistence mechanisms involving spatial or temporal environmental heterogeneity, resource partitioning and natural enemies. We first demonstrate the limitations of phenomenological approaches using simulations, and then (1) propose trait-based tests of coexistence, (2) generate hypotheses about which plant functional traits are likely to interact with particular mechanisms and (3) review the literature for evidence for these hypotheses. Theory and data suggest that all four classes of coexistence mechanisms could act on functional trait variation, but some mechanisms will be stronger and more widespread than others. The highest priority for future research is studies of interactions between environmental heterogeneity and trait variation that measure environmental variables at within-community scales and quantify species' responses to the environment in the absence of competition. Evidence that similar trait-based coexistence mechanisms operate in many ecosystems would simplify biodiversity forecasting and represent a rare victory for generality over contingency in community ecology. © 2013 John Wiley & Sons Ltd/CNRS.

Kirkpatrick T.R.,University of Maryland University College | Belitz D.,University of Oregon
Physical Review Letters | Year: 2015

The third law of thermodynamics constrains the phase diagram of systems with a first-order quantum phase transition. For a zero conjugate field, the coexistence curve has an infinite slope at T=0. If a tricritical point exists at T>0, then the associated tricritical wings are perpendicular to the T=0 plane, but not to the zero-field plane. These results are based on the third law and basic thermodynamics only, and are completely general. As an explicit example we consider the ferromagnetic quantum phase transition in clean metals, where a first-order quantum phase transition is commonly observed. © 2015 American Physical Society. © 2015 American Physical Society.

Thirumalai D.,University of Maryland University College | Liu Z.,Beijing Normal University | O'Brien E.P.,University of Cambridge | Reddy G.,University of Maryland University College
Current Opinion in Structural Biology | Year: 2013

A quantitative theory of protein folding should make testable predictions using theoretical models and simulations performed under conditions that closely mimic those used in experiments. Typically, in laboratory experiments folding or unfolding is initiated using denaturants or external mechanical force, whereas theories and simulations use temperature as the control parameter, thus making it difficult to make direct comparisons with experiments. The molecular transfer model (MTM), which incorporates environmental changes using measured quantities in molecular simulations, overcomes these difficulties. Predictions of the folding thermodynamics and kinetics of a number of proteins using MTM simulations are in remarkable agreement with experiments. The MTM and all atom simulations demonstrating the presence of dry globules represent major advances in the proteins folding field. © 2012 Elsevier Ltd.

Mithas S.,University of Maryland University College | Tafti A.,University of Illinois at Urbana - Champaign | Bardhan I.,University of Texas at Dallas | Goh J.M.,IE Business School
MIS Quarterly: Management Information Systems | Year: 2012

Do information technology investments improve firm profitability? If so, is this effect because such investments help improve sales, or is it because they help reduce overall operating expenses? How does the effect of IT on profitability compare with that of advertising and of research and development? These are important questions because investments in IT constitute a large part of firms' discretionary expenditures, and managers need to understand the likely impacts and mechanisms to justify and realize value from their IT and related resource allocation processes. The empirical evidence in this paper, derived using archival data from 1998 to 2003 for more than 400 global firms, suggests that IT has a positive impact on profitability. Importantly, the effect of IT investments on sales and profitability is higher than that of other discretionary investments, such as advertising and R & D. A significant portion of the impact of IT on firm profitability is accounted for by ITenabled revenue growth, but there is no evidence for the effect of IT on profitability through operating cost reduction. Taken together, these findings suggest that firms have had greater success in achieving higher profitability through IT-enabled revenue growth than through IT-enabled cost reduction. They also provide important implications for managers to make allocations among discretionary expenditures such as IT, advertising, and R & D. With regard to IT expenditures, the results imply that firms should accord higher priority to IT projects that have revenue growth potential over those that focus mainly on cost savings.

University of Maryland University College and Schlumberger | Date: 2014-03-31

A downhole tool conveyable within a wellbore extending into a subterranean formation, wherein the downhole tool comprises a first component, a second component, and a solder electrically and mechanically coupling the first and second components, wherein the solder comprises or consists of: from 0.001 to 1.0 weight % of copper; from 2.5 to 4.0 weight % of silver; from 0.01 to 0.25 weight % of manganese; and tin.

University of Maryland, Baltimore, St. Jude Medical and University of Maryland University College | Date: 2013-08-08

A motion sensor applicable to medical procedures includes a source of light with a wavelength bandwidth and an optical detector. A first optical coupler terminates in a first probe tip and couples the light into the first probe tip. A second optical coupler terminates in a second probe tip and directs onto the detector scattered light returning through the second probe tip. A presentation device outputs a signal that indicates motion in a target volume of a sample in a vicinity of the probe tips based on a Doppler shift of the scattered light. The volume depends on coherence distance determined by the bandwidth. In variations, the first and second tips are the same tip, a multimode fiber is included, the bandwidth is between 0.1% and 5% of a center wavelength, or the presentation device is a speaker, or some combination.

News Article | November 1, 2016
Site:, a leading career and education website focused on the field of psychology, has released its ranking of the 2016 Top Schools with Undergraduate Online Psychology Degree Programs. To be considered for inclusion, schools were screened for having an online undergraduate psychology program, not-for-profit status, and regional accreditation from one of the six regional accreditation agencies in the U.S. recognized by the U.S. Department of Education. The rankings were based on a broad set of data points measuring academic quality and the overall student experience. The ranking uses a unique methodology that takes into account multiple factors, including the average tuition cost per online credit hour, the percentage of students enrolled only in distance education courses, the overall graduation rate of enrolled students, and school rankings according to U.S. News & World Report in the regional, national, and online categories. Graduate program accreditation by the American Psychological Association (APA) and the percentage of tenured faculty at each school were also factors included in the ranking methodology. In addition, the online degrees from the regionally accredited schools on this list are the same degrees granted to traditional, on-campus students. “As technology advances and more students and schools embrace distance education, the number of online degree programs in psychology available in the U.S. has increased at a rapid pace,” said Rob Voce, founder of “We designed and released our rankings to help prospective students learn about online degree options and quickly find and compare programs based on markers of quality as well as value.” In total, 29 schools with online psychology programs met the screening criteria and ranked on this year’s list. As well as providing schools’ results on ranking factors, the 2016 Top Schools with Online Psychology Degree Programs ranking includes in-depth information on schools’ admissions statistics and requirements; tuition comparisons for in-state, out-of-state, and online students; and the services and support available to online students. Users can also view: -In-depth profiles of select online undergraduate psychology degree programs -Online faculty experience, including the percentage of faculty with terminal degrees -Foundational psychology courses for profiled programs -Financial aid statistics for undergraduates The top schools on this year’s list are: 1. University of Florida College of Liberal Arts and Sciences (Gainesville, FL) 2. Oregon State University School of Psychological Science (Corvallis, OR) 3. Fort Hays State University College of Arts and Sciences (Hays, KS) 4. Northeastern University College of Professional Studies (Boston, MA) 5. Pennsylvania State University World Campus and Penn State College of the Liberal Arts (State College, PA) 6. Colorado State University Division of Continuing Education (Fort Collins, CO) 7. University of Central Florida College of Sciences (Orlando, FL) 8. Eastern Oregon University Psychology Department (La Grande, OR) 9. Arizona State University New College of Interdisciplinary Arts and Sciences (Tempe, AZ) 10. Washington State University College of Arts and Sciences (Pullman, WA) 11. University of Massachusetts - Lowell Division of Online and Continuing Education (Lowell, MA) 12. Oregon Institute of Technology, Oregon Tech Online (Klamath Falls, OR) 13. University of North Dakota College of Arts and Sciences (Grand Forks, ND) 14. Old Dominion University College of Sciences (Norfolk, VA) 15. Southern New Hampshire University School of Arts and Sciences (Hooksett, NH) 16. Eastern Kentucky University College of Letters, Arts, and Social Sciences (Richmond, KY) 17. Fayetteville State University College of Arts and Sciences (Fayetteville, NC) 18. University of Maine - Presque Isle College of Arts and Sciences (Presque Isle, ME) 19. McKendree University College of Arts and Sciences (Lebanon, IL) 20. University of Minnesota - Duluth College of Education and Human Service Professions (Duluth, MN) 21. University of Memphis College of Arts and Sciences (Memphis, TN) 22. University of Houston College of Liberal Arts and Social Sciences (Houston, TX) 23. Brescia University Division of Social and Behavioral Sciences (Owensboro, KY) 24. DePaul University College of Science and Health (Chicago, IL) 25. Wilmington University College of Social and Behavioral Sciences (New Castle, DE) 26. Central Washington University College of the Sciences (Ellensburg, WA) 27. University of Maryland University College Undergraduate School (College Park, MD) 28. Notre Dame College Division of Science and Mathematics (South Euclid, OH) 29. Indiana University East School of Humanities and Social Sciences (Richmond, IN) *See the full rankings and program details here: About is an informative resource on beginning or advancing a career in the field of psychology. PsychologyDegree411 provides information about education options in psychology from the associate’s to the doctoral level, including tools to help research online, campus, and hybrid school options, as well as career resources associated with each degree level.

News Article | February 17, 2017

— The ranking took into account accreditation, costs, acceptance rate, student satisfaction, and other factors that accounting students look for in potential programs, such as salary outcomes of each program. University of Massachusetts Amherst took the top spot. The second and third spots went to, Northeastern University and Auburn University, respectively. Six of the sixteen schools in the ranking have achieved AACSB accreditation, which is highly prestigious and has only been given to 170 schools in the nation. Along with rankings, the report includes pertinent information about each ranked school and degree program. The complete list of schools can be seen below (listed alphabetically): Auburn University Bellevue University Indiana Wesleyan University Liberty University Northeastern University Penn State World Campus Regis University Saint Leo University Southern New Hampshire University Southern Oregon University University of Alabama Birmingham University of Maryland University College University of Massachusetts Amherst University of the Incarnate Word Washington State University Western Governors University The ranking placement and information about each school can be found at According to managing editor of, Ivor Lee, “These schools stand out from among their peers not because of their size, or their reputation but because of their dedication to making education available to all students online. Online education is a field that is constantly changing and these schools have made the effort to stay relevant and agile--and in doing so have been able to help many students earn their accounting degrees.” Lee says, “Congratulations to these schools for maintaining high standards in their traditional and online programs and ensuring an equitable and educational experience for their students. This award is a testament to the hard work and dedication of the staff and faculty at these schools.” Top Accounting is an independent and objective resource for current and prospective accounting students. We offer data-based rankings of on-campus and online accounting degree programs, as well as career and education advice. The site is regularly updated by a committed team of writers and researchers, who produce accounting school and program rankings and accounting resources. For more information, please visit

News Article | October 29, 2016

The Mid-Atlantic Higher Education Recruitment Consortium (HERC), a regional collaboration of colleges and universities, teaching hospitals, research labs and government agencies is advancing its commitment to hiring transitioning military, veterans, and military spouses/partners by hosting its second annual event on the campus of University of Maryland University College’s Academic Center at Largo. The Career Expo & Job Fair, which will take place on Tuesday, October 18, 2016 from 11:00 a.m. – 2:00 p.m. at The Academic Center at Largo (MD), will be the second annual opportunity to offer an in-depth look at diverse career opportunities through the "Discover Jobs at Smart Places" regional initiative. “With such diverse and prominent employers in the region, we have a tremendous opportunity and responsibility to help veterans and military spouses/partners explore an array of jobs in industries they might not necessarily consider,” said Paula Alfone, Director of the Mid-Atlantic HERC. Many of the consortium member institutions and government agencies will be actively recruiting for positions in a variety of career fields such as accounting, IT, public relations, office management, STEM, campus police, and facilities/maintenance, as well as faculty and research positions. The Career Fair will include representatives from Johns Hopkins University, Howard University, Howard University Hospital, NIH, NSF, Chase Brexton Health Care, American University, Virginia Tech and CCBC to name a few. A webinar will be offered after the event to provide information on career paths within higher education, resume and interview preparation, and articulating transferable military skills in the civilian workplace. The event is free, however, registration is encouraged by Monday, October 17, 2016. More details about the Career Expo & Job Fair can be found at . All registrants are encouraged to bring a resume with them and be prepared for on-the-spot interviews. Media wishing to attend should call Paula Alfone, Director, Mid-Atlantic HERC at 410.617.1650 prior to the event. About the Mid-Atlantic HERC The Mid-Atlantic HERC is a non-profit consortium of over 60 colleges, universities, teaching hospitals, research laboratories, and government agencies throughout Maryland, Virginia and Washington, D.C. dedicated to advancing the ability of our members to recruit and retain the most talented and diverse staff, administrators, health care providers, researchers and faculty, and to assist dual-career couples in their pursuit to find positions within a commutable distance of one another. The Mid-Atlantic HERC is a proud partner of the Military Spouse Employment Partnership (MSEP). For more information about the Mid-Atlantic HERC, please go to

News Article | March 1, 2017

SR Education Group, a leading education research publisher founded in 2004, just published the results of their research and analysis of military-friendly online colleges. The organization evaluated accredited colleges offering online degrees on the basis of key factors of military-friendly education in an online environment in order to develop a list of the 2017 Top Military-Friendly Online Schools. Additionally, SR Education Group highlights colleges with outstanding financial support for military students in the 2017 Top Yellow Ribbon Online Schools, and features military-friendly schools with the lowest annual tuition rates in the 2017 Most Affordable Military-Friendly Online Colleges. In order to be considered for the Military-Friendly Online Colleges lists, schools were required to offer at least 10 fully online degrees. After meeting the requirements for inclusion, colleges were evaluated on key factors of military support in online education. The rankings employ data collected from KMI Media Group, an organization that conducts an annual Military Advanced Education & Transition (MAE&T) survey of schools. SR Education Group considered four of the MAE&T categories in their research: military culture, online support, financial aid, and flexibility. Colleges were given a weighted average based on these factors. Over 400 schools were surveyed by KMI Media Group, and 70 made the 2017 Top Military-Friendly Online Schools. Each school on the list earned a military-friendly score of at least 65 points out of 100. University of Maryland University College and Excelsior College tied for the highest military-friendly score, earning 98.31 points each. In addition to the comprehensive list of Military-Friendly Online Schools, SR Education Group also highlights the top 15 online colleges that offer unlimited financial contributions to an unlimited number of students through the Yellow Ribbon Program. The Yellow Ribbon Program is a part of the Post-9/11 GI Bill which allows schools to elect to support a certain number of veterans with additional funds, which the U.S. Department of Veterans Affairs agrees to match. Online colleges offering uncapped support through the Yellow Ribbon Program were ranked according to their weighted military-friendly score and named the 2017 Top Yellow Ribbon Online Schools. University of Maryland University College, which offers 111 online degrees, earned the #1 spot with 98.31 points. SR Education Group also researched annual tuition rates at each of the military-friendly institutions. After calculating and verifying annual tuition rates, the organization ranked the schools based on affordability. The 25 colleges with the lowest annual rates were named the 2017 Most Affordable Military-Friendly Online Colleges. Western Governor’s University ranked #1 for affordability, with an annual tuition rate of $5,780. Each school on the list offers annual tuitions of $11,100 or lower. SR Education Group has been publishing rankings of Military-Friendly Online Colleges since 2013. The organization plans to continue researching military support factors in online education and update the rankings annually. About SR Education Group Headquartered in Kirkland, WA, SR Education Group was founded in 2004 by CEO Sung Rhee. The company’s mission is to create authoritative online resources for students seeking an online education program that best suits their budget and career aspirations. SR Education Group is passionate about making quality education attainable for everyone and believes that objective information about education, careers, and educational financing should be free and easily accessible. For more information, please visit

Jobs in the cybersecurity sector have increased by 73 percent over the past five years, making it one of the hottest career fields for America’s students and young adults. However, recent headlines about cyber warfare, cyber crime, and cyber espionage demonstrate the need for qualified professionals with the skills to succeed in cybersecurity—a field that is growing 12 times faster than the average American industry. That’s why career exploration organization Roadtrip Nation and University of Maryland University College (UMUC) are teaming up to send three people interested in cybersecurity on a three-week road trip across the nation. The journey—termed the “Cybersecurity Roadtrip”—will be filmed and produced into a one-hour documentary, set to air on public television in 2017. “Cybersecurity is an often misunderstood field—that’s why we are excited to collaborate with UMUC and showcase conversations with real world leaders who challenge stereotypical images and reveal the many opportunities available to individuals in this career space,” said Mike Marriner, cofounder of Roadtrip Nation. UMUC has enrolled and graduated thousands of cybersecurity students in the past five years, answering a call from military and business leaders for a new generation of specialists to protect vital digital resources. The university serves more than 84,000 students worldwide each year (more than half of whom are active duty military personnel, dependents and veterans) and is one of the largest distance-learning institutions in the world. “Education is a lifelong journey, and UMUC is pleased to partner with Roadtrip Nation on a project that promises to enlighten people nationwide about one of the 21st century’s most exciting and challenging career fields – cybersecurity,” said UMUC President Javier Miyares. The Cybersecurity Roadtrip launches on November 27, 2016, in New York City, with a celebratory kickoff event at UMUC and the National Cryptologic Museum in Maryland on December 2. Winding their way across the country with highlighted stops in New Orleans, Austin, and Los Angeles, the road-trippers will book and conduct a slate of in-depth interviews with leaders from different specializations within the cybersecurity field. Candidates selected for the opportunity have unique backgrounds and challenges; all possess a passion for cybersecurity. Mansi Thakar is pursuing a master’s degree in cybersecurity, Emily Cox recently discovered a love for the field after attending an immersive coding boot camp, and Antwan King is enrolled in a master’s program in digital forensics and cyber investigation. They are looking forward to finding new mentors and exploring the diversity of career paths available within the field. To stay up to date on the journey, follow @Roadtrip Nation, @UMUC and #CybersecurityRoadtrip on Twitter. About Roadtrip Nation Roadtrip Nation, renowned for its New York Times best-selling career guide, award-winning documentary television series, and acclaimed classroom curriculum, is a career exploration organization that creates content, products, and experiences to help individuals pursue fulfilling careers. Combining self-reflection with real-world exposure, Roadtrip Nation’s tools enable youth to connect their interests to relevant life pathways and stay engaged with their futures. For more information, visit and About University of Maryland University College UMUC is a world leader in innovative educational models, with award-winning online programs in disciplines including biotechnology, cybersecurity, data analytics, and information technology that are in high demand in today's increasingly technical, global workplace. UMUC offers open access with a global footprint and a specific mission—to meet the learning needs of adult students whose responsibilities may include jobs, family and military service. For more information about UMUC, visit

News Article | February 15, 2017

Kevin Lovell has joined Stanley Consultants as a Senior Project Manager. Assigned to the Federal and International Group, his focus is on project and program management for Department of Defense projects worldwide. Stanley Consultants is a consulting engineering firm that provides program management, planning, engineering, environmental, and construction services worldwide. Lovell is based in the firm’s Chicago office. After a distinguished 21-year career, Lovell recently retired from the US Army Corps of Engineers (USACE) as the Chicago District Deputy Commander. He was second in command of the 200-person organization and oversaw an annual $150 million design and construction program. Prior to that he was the first Engineering Analyst to serve in the Army’s Office of Business Transformation at the Pentagon and helped establish the Army’s Energy Initiative Office. The new position with Stanley Consultants fits Lovell like a glove. “The company’s areas of focus – military, water/wastewater, energy – were my areas of focus at the USACE,” said Lovell. “I was attracted by Stanley Consultants’ excellent reputation that spans across multiple USACE districts. The company is large enough to punch above its weight class but small enough to be nimble and responsive to client needs.” During his military career Lovell was awarded three Army Bronze Stars, and multiple Meritorious Service and Campaign Medals. This including a Bronze Star for leading the first engineering unit to deploy to central Asia after 9/11, which was the first Army construction unit to deploy equipment by air. He is active in the Society of American Military Engineers (SAME), currently serving on the organization’s National Board of Direction and national committees. He remains active in the local SAME Chicago Post, and is active in the local International Facility Management Association (IFMA) post. Lovell is also a member of the Project Management Institute (PMI.) Lovell is a graduate of the U.S. Army Command and General Staff College. He has a bachelor’s degree in mechanical engineering from Marquette University, and a master’s degree in management, with a project management concentration, from the University of Maryland University College. He is a certified Project Management Professional. About Stanley Consultants: Founded in 1913, Stanley Consultants is a global consulting engineering firm that provides program management, planning, engineering, environmental and construction services worldwide. Recognized for its commitment to client service and a passion to make a difference, Stanley Consultants brings global knowledge, experience and capabilities to serve clients in the energy, water, transportation and Federal markets. Since 1913, Stanley Consultants has successfully completed more than 25,000 engagements in all 50 states, U.S. territories, and in 110 countries. For more information on Stanley Consultants, please visit

News Article | November 2, 2016

SILVER SPRING, MD, November 02, 2016-- Dr. Stephen Holowenzak has been included in Marquis Who's Who. As in all Marquis Who's Who biographical volumes, individuals profiled are selected on the basis of current reference value. Factors such as position, noteworthy accomplishments, visibility, and prominence in a field are all taken into account during the selection process.Dr. Holowenzak is a retired professor, patriot and humanitarian who is noted for teaching at 125 military bases around the world. Prior to starting his career as an educator, he received a Bachelor of Arts in philosophy and English at Mount St. Paul College. He then attended the Catholic University of America; where he earned a Master of Arts (MA) degree in counseling, guidance and personnel management, and later went on to earn the advanced Doctor of Philosophy (Ph.D.) degree with academic concentrations in educational psychology, technology, statistics and measurements.Having spent much of his career with the University of Maryland University College (UMUC), Dr. Holowenzak is now an honored professor emeritus of the university system, with its mission educating adult learners by providing educational courses and services in multiple locations and on military installations wherever they were and included many hazardous and dangerous assignments. His positions with UMUC included senior lecturer, distance educator, academic director of education and student teaching services, collegiate professor, adjunct professor of psychology, senior program manager of faculty services and communication, and instructor and trainer in computer studies and math. Dr. Holowenzak's work with the university brought him to Germany and Japan, and his work at military bases brought him all over Europe, the Middle East and Asia. He wanted to "go the distance to teach" and be where our USA military forces were at their time in history.Aside from his work with UMUC, Dr. Holowenzak also held roles with Ford Aerospace Corporation and the Fulbright Japan-U.S. Education Commission. He also authored a piece for the Maryland Public Television series, "A Maryland State of Mind," in 1996. Dr. Holowenzak has been featured in UMUC's magazine, The Achiever, multiple times. More recently, at the Overseas Maryland Association Reunion Gathering (in Heidelberg, Germany on October 7-9, 2016) of former UMUC presidents, administrators and faculty members, Dr. Holowenzak was presented with a legacy disc of his 30 years of work within UMUC history - 1947-2017. His work and others became professional lifelong stories in the UMUC / OMA Oral History Project: IMPACT UMUC - Supporting Today's Students and Tomorrows Leaders.His accomplishments were taken into account when he was chosen to appear in the 66th through 70th editions of Who's Who in America, and the 39th through 43rd editions of Who's Who in the West.Along with his "occupational-passion" of teaching and administrating programs for adult learners worldwide, Dr. Holowenzak gave decades of voluntary support and services to many U.S. military commands overseas and ministered to U.S. based chapel communities in four branches of military service. Some examples are: Yokota AB, Community Chapel Food for Homeless Program and the Kanto Plains Special Olympics and Catholic Ministries in other countries. In Germany, he became a member of the Knights of Columbus (K of C) in service to our Lord and His people, while overseas and stateside, he held K of C service, leadership and officer roles.At St. Michael the Archangel Council No. 15084, as Grand Knight - Fraternal Year 2014-15, Council 15084 in statewide competition was evaluated, highly rated and recognized by the K of C Maryland State Council for its programs, services and activities. At the K of C Maryland State 117th Annual Convention, May 2015, Council 15084 won multiple first place service awards for its Church, Council, Community, Family, Culture of Life, Youth Activities; the Award for General Programs Excellence and two National K of C Awards for Church and Community Services. For Fraternal Year 2014-15, Council 15084 became a K of C State of Maryland Star Council.Dr. Holowenzak was elected Faithful Navigator of Fourth Degree Assembly 386 for Fraternal Year 2016-17. In this capacity, as Chief Executive Officer, the Assembly was charged with building and advancing "U.S Patriotism" in the Maryland and Washington, DC region. The patriotic programs and activities of the Assembly for Fraternal Year 2016-17 include: The Washing of the Vietnam Memorial Wall, The Placing of a Wreath at the Tomb of the Unknowns, participating in "The Wreaths Across America" Program at Arlington National Cemetery and other patriotic ceremonies, events and functions planned throughout the year. Knights' Council work can be found in the publications... and the Knights activities and work for the Assembly to our nation can be found the publication namedAbout Marquis Who's Who :Since 1899, when A. N. Marquis printed the First Edition of Who's Who in America , Marquis Who's Who has chronicled the lives of the most accomplished individuals and innovators from every significant field of endeavor, including politics, business, medicine, law, education, art, religion and entertainment. Today, Who's Who in America remains an essential biographical source for thousands of researchers, journalists, librarians and executive search firms around the world. Marquis now publishes many Who's Who titles, including Who's Who in America , Who's Who in the World , Who's Who in American Law , Who's Who in Medicine and Healthcare , Who's Who in Science and Engineering , and Who's Who in Asia . Marquis publications may be visited at the official Marquis Who's Who website at

Ji X.,Shanghai JiaoTong University | Ji X.,University of Maryland University College
Physical Review Letters | Year: 2013

I show that the parton physics related to correlations of quarks and gluons on the light cone can be studied through the matrix elements of frame-dependent, equal-time correlators in the large momentum limit. This observation allows practical calculations of parton properties on a Euclidean lattice. As an example, I demonstrate how to recover the leading-twist quark distribution by boosting an equal-time correlator to a large momentum. © 2013 American Physical Society.

Shcherbakov R.V.,University of Maryland University College | Penna R.F.,Harvard - Smithsonian Center for Astrophysics | McKinney J.C.,Kavli Institute for Particle Astrophysics and Cosmology
Astrophysical Journal | Year: 2012

We obtain estimates of Sgr A* accretion flow and black hole parameters by fitting polarized submillimeter observations with spectra computed using three-dimensional general relativistic (GR) magnetohydrodynamical (MHD) (GRMHD) simulations. Observations are compiled from averages over many epochs from reports in 29 papers for estimating the mean fluxes F ν, linear polarization (LP) fractions, circular polarization (CP) fractions, and electric vector position angles. GRMHD simulations are computed with dimensionless spins a * = 0, 0.5, 0.7, 0.9, 0.98 over a 20, 000M time interval. We perform fully self-consistent GR polarized radiative transfer using our new code to explore the effects of spin a *, inclination angle θ, position angle (P.A.), accretion rate , and electron temperature Te (Te is reported for radius 6M). By fitting the mean submillimeter fluxes and LP/CP fractions, we obtain estimates for these model parameters and determine the physical effects that could produce polarization signatures. Our best-bet model has a * = 0.5, θ = 75°, P.A. = 115°, , and Te = 3.1 × 10 10 K at 6M. The submillimeter CP is mainly produced by Faraday conversion as modified by Faraday rotation, and the emission region size at 230GHz is consistent with the very long baseline interferometry size of 37 μas. Across all spins, model parameters are in the ranges θ = 42°-75°, , and Te = (3-4) × 1010 K. Polarization is found both to help differentiate models and to introduce new observational constraints on the effects of the magnetic field that might not be fit by accretion models so far considered. © 2012. The American Astronomical Society. All rights reserved.

Gupta V.,University of Notre Dame | Martins N.C.,University of Maryland University College
IEEE Transactions on Automatic Control | Year: 2010

Consider a discrete-time networked control system, in which the controller has direct access to noisy measurements of the output of the plant. However, information flows from the controller to the actuator via a channel that features Bernoulli erasure events. If an erasure occurs, the channel outputs an erasure symbol; otherwise, it transmits a real finite-dimensional vector. We determine necessary and sufficient conditions for the stabilizability of an unstable linear time-invariant finite-dimensional plant. Given a minimal state-space representation for the plant, the necessary and sufficient conditions for stabilizability are expressed in terms of the probability of erasure at the channel and of the spectral radius of the one-step state transition matrix. There are two main results in the technical note. The first result shows that if the actuator has processing capabilities, then the necessary and sufficient conditions for stabilizability remain unchanged with or without acknowledgements from the actuator to the controller. The second result shows that the stabilizability conditions are identical for two types of actuators: (Type I) Processing at the actuator has access to the plant's model; © 2009 IEEE.

Pillai J.K.,University of Maryland University College | Puertas M.,Autonomous University of Madrid | Chellappa R.,University of Maryland University College
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2014

Due to the increasing popularity of iris biometrics, new sensors are being developed for acquiring iris images and existing ones are being continuously upgraded. Re-enrolling users every time a new sensor is deployed is expensive and time-consuming, especially in applications with a large number of enrolled users. However, recent studies show that cross-sensor matching, where the test samples are verified using data enrolled with a different sensor, often lead to reduced performance. In this paper, we propose a machine learning technique to mitigate the cross-sensor performance degradation by adapting the iris samples from one sensor to another. We first present a novel optimization framework for learning transformations on iris biometrics. We then utilize this framework for sensor adaptation, by reducing the distance between samples of the same class, and increasing it between samples of different classes, irrespective of the sensors acquiring them. Extensive evaluations on iris data from multiple sensors demonstrate that the proposed method leads to improvement in cross-sensor recognition accuracy. Furthermore, since the proposed technique requires minimal changes to the iris recognition pipeline, it can easily be incorporated into existing iris recognition systems. © 1979-2012 IEEE.

Davoudiasl H.,Brookhaven National Laboratory | Mohapatra R.N.,University of Maryland University College
New Journal of Physics | Year: 2012

The similar cosmological energy budgets in visible baryons and dark matter motivate one to consider a common origin for the generation of both. We outline the key features of scenarios that can accommodate a unified framework for the genesis of cosmic matter. In doing so, we provide a brief overview of some of the past and recent developments and discuss the main predictions of a number of models. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Moraal H.,North West University South Africa | McCracken K.G.,University of Maryland University College
Space Science Reviews | Year: 2012

In a recent paper McCracken et al. (J. Geophys. Res. 113:A12101, 2008) proposed that the Ground Level Enhancement (GLE) of 20 January 2005 may have been produced by more than one acceleration mechanism, with the first acceleration due to the solar flare and the second one due to the CME associated with that event. They also noted several other GLEs with similar multiple pulse structures. This paper systematically investigates all the GLEs of solar cycle 23, from GLE 55 on 6 November 1997 to GLE 70 on 13 December 2006, to study their morphology and pulse structure, and to determine whether the multiple structures that may be found in these events are qualitatively similar to that of the GLE of 20 January 2005. We use all the data of all NMs that saw each event, to have as much directional and spectral information as possible. It is shown that three of these 16 events do contain such double-pulse structures, and the properties of these three are discussed in some detail. © 2011 Springer Science+Business Media B.V.

Basar G.,University of Maryland University College | Dunne G.V.,University of Connecticut
Journal of High Energy Physics | Year: 2015

Abstract: The Nekrasov-Shatashvili limit for the low-energy behavior of N=2 and N=2* supersymmetric SU(2) gauge theories is encoded in the spectrum of the Mathieu and Lamé equations, respectively. This correspondence is usually expressed via an all-orders Bohr-Sommerfeld relation, but this neglects non-perturbative effects, the nature of which is very different in the electric, magnetic and dyonic regions. In the gauge theory dyonic region the spectral expansions are divergent, and indeed are not Borel-summable, so they are more properly described by resurgent trans-series in which perturbative and non-perturbative effects are deeply entwined. In the gauge theory electric region the spectral expansions are convergent, but nevertheless there are non-perturbative effects due to poles in the expansion coefficients, and which we associate with worldline instantons. This provides a concrete analog of a phenomenon found recently by Drukker, Mariño and Putrov in the large N expansion of the ABJM matrix model, in which non-perturbative effects are related to complex space-time instantons. In this paper we study how these very different regimes arise from an exact WKB analysis, and join smoothly through the magnetic region. This approach also leads to a simple proof of a resurgence relation found recently by Dunne and Ünsal, showing that for these spectral systems all non-perturbative effects are subtly encoded in perturbation theory, and identifies this with the Picard-Fuchs equation for the quantized elliptic curve. © 2015, The Author(s).

Zolkos S.G.,Woods Hole Oceanographic Institution | Goetz S.J.,Woods Hole Oceanographic Institution | Dubayah R.,University of Maryland University College
Remote Sensing of Environment | Year: 2013

Estimating biomass of terrestrial vegetation is not only a rapidly expanding research area, but also a subject of tremendous interest for reducing carbon emissions associated with deforestation and forest degradation (REDD). The accuracy of biomass estimates, and rate of biomass change, is not only important in the context of carbon markets emerging under REDD, but also for characterizing uncertainty in estimates of carbon cycling and the global carbon budget. There is particular interest in mapping biomass so that carbon stocks and stock changes can be monitored consistently across a range of scales - from relatively small projects (tens of hectares) to national or continental scales - but also so that other benefits of forest conservation can be factored into decision making (e.g. biodiversity and habitat corridors). We conducted an analysis of reported biomass accuracy estimates from more than 70 refereed articles using different remote sensing platforms (airborne and spaceborne) and sensor types (optical, radar, and lidar), with a particular focus on lidar since those papers reported the lowest errors when used in a synergistic manner with other coincident multi-sensor measurements. We show systematic differences in accuracy between different types of lidar systems flown on different platforms but, perhaps more importantly, differences between forest types (biomes) and plot sizes used for field calibration and assessment. We discuss these findings in relation to monitoring, reporting and verification under REDD, and also in the context of more systematic assessment of factors that influence accuracy and error estimation. © 2012 Elsevier Inc.

Kirkpatrick T.R.,University of Maryland University College | Ortiz De Zarate J.M.,Complutense University of Madrid | Sengers J.V.,University of Maryland University College
Physical Review Letters | Year: 2015

In this Letter, we consider a liquid mixture confined between two thermally conducting walls subjected to a stationary temperature gradient. While in a one-component liquid nonequilibrium fluctuation forces appear inside the liquid layer, nonequilibrium fluctuations in a mixture induce a Casimir-like force on the walls. The physical reason is that the temperature gradient induces large concentration fluctuations through the Soret effect. Unlike temperature fluctuations, nonequilibrium concentration fluctuations are also present near a perfectly thermally conducting wall. The magnitude of the fluctuation-induced Casimir force is proportional to the square of the Soret coefficient and is related to the concentration dependence of the heat and volume of mixing. © 2015 American Physical Society. © 2015 American Physical Society.

Day R.W.,University of Connecticut | Cramton P.,University of Maryland University College
Operations Research | Year: 2012

We report on the use of a quadratic programming technique in recent and upcoming spectrum auctions in Europe. Specifically, we compute a unique point in the core that minimizes the sum of squared deviations from a reference point, for example, from the Vickrey-Clarke-Groves payments. Analyzing the Karush-Kuhn-Tucker conditions, we demonstrate that the resulting payments can be decomposed into a series of economically meaningful and equitable penalties. Furthermore, we discuss the benefits of this combinatorial auction, explore the use of alternative reserve pricing approaches in this context, and indicate the results of several hundred computational runs using CATS data. © 2012 INFORMS.

Horowitz J.M.,Complutense University of Madrid | Vaikuntanathan S.,University of Maryland University College
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

We extend the framework of forward and reverse processes commonly utilized in the derivation and analysis of the nonequilibrium work relations to thermodynamic processes with repeated discrete feedback. Within this framework, we derive a generalization of the detailed fluctuation theorem, which is modified by the addition of a term that quantifies the change in uncertainty about the microscopic state of the system upon making measurements of physical observables during feedback. As an application, we extend two nonequilibrium work relations: the nonequilibrium work fluctuation theorem and the relative-entropy work relation. © 2010 The American Physical Society.

News Article | December 13, 2016

The International Society for Technology in Education (ISTE®) today announced the results of its 2016 election for board of directors. Newly elected to the ISTE board is Randy Hansen, Ed.D., professor, University of Maryland University College, Columbia; and re-elected for a second term is Janet Zanetis, managing director, Center for Interactive Learning and Collaboration, Louisville, Kentucky, who will continue to serve as board secretary. These board members were elected by vote of ISTE membership. In addition, newly appointed board member Gary Brantley, chief information officer, DeKalb County School District, Stone Mountain, Georgia, will join the board for a three-year term, and the board appointed S. Dallas Dance, Ph.D., superintendent, Baltimore County Public Schools, Towson, Maryland, to a third one-year term. All new terms begin in January 2017. In the new year, Mila Thomas Fuller, Ed.D., assistant director of online learning, College of Education, University of Illinois at Urbana-Champaign, becomes ISTE president, and Kecia Ray, Ed.D., executive director, Center for Digital Education, Smyrna, Tennessee, becomes past president. “We welcome Randy and Gary to the ISTE board and are excited to have Janet and Dallas continue to serve. ISTE membership will benefit from the diverse experiences and insights they have to offer,” said Fuller. “On behalf of the entire board, I would like to thank Kari Stubbs and John Keller, both of whom are completing second terms as at-large representatives, for their service on the board. Each brought a unique perspective and made outstanding contributions to the organization.” Continuing board members are Bill Bass, innovation coordinator, Parkway School District, St. Louis; Laurie Conzemius, technology trainer, Park Rapids Area Schools, Park Rapids, Minnesota; Hall Davidson, senior director, Global Learning Initiatives, Discovery Education, Los Angeles; Paige Johnson, K12 Cloud Strategist, Amazon Web Services, Portland, Oregon; Sheryl Nussbaum-Beach, CEO, Powerful Learning Practice, Virginia Beach, Virginia; and Karen Swift, head of department, business and technologies, James Nash State High School, Gympie, Queensland, Australia. For more information about the ISTE Board of Directors, visit About ISTE The International Society for Technology in Education (ISTE®) is the premier nonprofit membership organization serving educators and education leaders committed to empowering connected learners in a connected world. ISTE serves more than 100,000 education stakeholders throughout the world. Innovative offerings include the widely adopted ISTE Standards for learning, teaching and leading in the digital age – as well as the ISTE Conference & Expo– the world’s most comprehensive ed tech event. The organization’s robust suite of professional learning resources feature online courses, consulting services for schools and districts, books, and peer-reviewed journals and publications. For more information, visit Connect with ISTE via Twitter, Facebook and LinkedIn.

Blichert-Toft J.,University Claude Bernard Lyon 1 | Puchtel I.S.,University of Maryland University College
Earth and Planetary Science Letters | Year: 2010

In this study, we present Lu-Hf isotope systematics and Lu and Hf abundances for komatiites from the lowermost part of the 2.8Ga Kostomuksha greenstone belt in the Baltic Shield and compare these, as well as available Sm-Nd isotope data, with those for the best characterized Archean komatiite systems. The Lu-Hf isotope compositions of four spatially associated differentiated lava flows from the Kostomuksha greenstone belt yield an isochron (MSWD=1.6) with an age of 2931±300Ma, which represents the first Lu-Hf isochron obtained for a suite of co-magmatic komatiite lavas. The calculated mean initial 176Hf/177Hf for the Kostomuksha komatiite samples is 0.281107±3 (2σmean), which corresponds to an initial ε176Hf of +4.9±0.1 (2σmean). Assuming that mantle differentiation occurred 10Ma after Earth's accretion at 4.558Ga, this precise initial ratio requires a time-integrated 176Lu/177Hf=0.03759±8, which is identical to the average time-integrated 176Lu/177Hf=0.0375±6 calculated for the best characterized late Archean komatiite systems. Together with the calculated average time-integrated 147Sm/144Nd=0.2091±4 for the same late Archean komatiite systems, these parameters represent our best estimate of the Lu/Hf and Sm/Nd properties in the late Archean mantle and indicate derivation of komatiite magmas from around the globe from long-term melt-depleted sources that were remarkably homogenous in terms of lithophile trace element systematics. These time-integrated ratios are identical to the respective values of 0.0375 and 0.209 calculated by Boyet and Carlson (2006) for the so-called Early Depleted Reservoir (EDR), and may indicate that the late Archean mantle was similar in composition to the putative EDR, whereas early Archean systems had higher, and Proterozoic systems lower time-integrated Lu/Hf and Sm/Nd ratios. The observed decrease in time-integrated Lu/Hf and Sm/Nd in komatiite sources over time is interpreted as strong evidence for the existence of a hidden enriched reservoir complementary to the EDR that has been gradually mixed back into the mantle over time. The overall depletion of the early mantle likely occurred very early in Earth's history as a result of either global magma ocean differentiation or extraction and subsequent long-term isolation of primordial terrestrial crust. © 2010 Elsevier B.V.

Miller M.C.,University of Maryland University College | Davies M.B.,Lund Observatory
Astrophysical Journal | Year: 2012

Massive black holes have been discovered in all closely examined galaxies with high velocity dispersion. The case is not as clear for lower-dispersion systems such as low-mass galaxies and globular clusters. Here we suggest that above a critical velocity dispersion 40kms-1, massive central black holes will form in relaxed stellar systems at any cosmic epoch. This is because above this dispersion primordial binaries cannot support the system against deep core collapse. If, as previous simulations show, the black holes formed in the cluster settle to produce a dense subcluster, then given the extremely high densities reached during core collapse the holes will merge with each other. For low velocity dispersions and hence low cluster escape speeds, mergers will typically kick out all or all but one of the holes due to three-body kicks or the asymmetric emission of gravitational radiation. If one hole remains, it will tidally disrupt stars at a high rate. If none remain, one is formed after runaway collisions between stars, and then it tidally disrupts stars at a high rate. The accretion rate after disruption is many orders of magnitude above Eddington. If, as several studies suggest, the hole can accept matter at that rate because the generated radiation is trapped and advected, then it will grow quickly and form a massive central black hole. © 2012 The American Astronomical Society. All rights reserved.

Han B.,Pohang University of Science and Technology | Davis L.S.,University of Maryland University College
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2012

Background modeling and subtraction is a natural technique for object detection in videos captured by a static camera, and also a critical preprocessing step in various high-level computer vision applications. However, there have not been many studies concerning useful features and binary segmentation algorithms for this problem. We propose a pixelwise background modeling and subtraction technique using multiple features, where generative and discriminative techniques are combined for classification. In our algorithm, color, gradient, and Haar-like features are integrated to handle spatio-temporal variations for each pixel. A pixelwise generative background model is obtained for each feature efficiently and effectively by Kernel Density Approximation (KDA). Background subtraction is performed in a discriminative manner using a Support Vector Machine (SVM) over background likelihood vectors for a set of features. The proposed algorithm is robust to shadow, illumination changes, spatial variations of background. We compare the performance of the algorithm with other density-based methods using several different feature combinations and modeling techniques, both quantitatively and qualitatively. © 2012 IEEE.

Rupke D.S.N.,Rhodes College | Veilleux S.,University of Maryland University College
Astrophysical Journal Letters | Year: 2011

The quasi-stellar object (QSO)/merger Mrk 231 is arguably the nearest and best laboratory for studying QSO feedback. It hosts several outflows, including broad-line winds, radio jets, and a poorly understood kpc-scale outflow. In this Letter, we present integral field spectroscopy from the Gemini telescope that represents the first unambiguous detection of a wide-angle, kiloparsec-scale outflow from a powerful QSO. Using neutral gas absorption, we show that the nuclear region hosts an outflow with blueshifted velocities reaching 1100kms-1, extending 2-3kpc from the nucleus in all directions in the plane of the sky. A radio jet impacts the outflow north of the nucleus, accelerating it to even higher velocities (up to 1400kms-1). Finally, 3.5 kpc south of the nucleus, star formation is simultaneously powering an outflow that reaches more modest velocities of only 570kms-1. Blueshifted ionized gas is also detected around the nucleus at lower velocities and smaller scales. The mass and energy flux from the outflow are ≳2.5 times the star formation rate and ≳0.7% of the active galactic nucleus luminosity, consistent with negative feedback models of QSOs. © 2011. The American Astronomical Society. All rights reserved.

Babu K.S.,Oklahoma State University | Mohapatra R.N.,University of Maryland University College
Physical Review Letters | Year: 2012

We show that grand unified theories based on SO(10) generate quite naturally baryon number violating dimension seven operators that violate B-L, and lead to novel nucleon decay modes such as n→e -K +, e -π + and p→νπ +. We find that in two-step breaking schemes of nonsupersymmetric SO(10), the partial lifetimes for these modes can be within reach of experiments. The interactions responsible for these decay modes also provide a new way to understand the origin of matter in the Universe via the decays of grand unified theory (GUT) scale scalar bosons of SO(10). Their (B-L)-violating nature guarantees that the GUT scale induced baryon asymmetry is not washed out by the electroweak sphaleron interactions. In minimal SO(10) models this asymmetry is closely tied to the masses of quarks, leptons and the neutrinos. © 2012 American Physical Society.

Chen B.,University of Maryland University College | Zuo X.,U.S. National Cancer Institute | Wang Y.-X.,U.S. National Cancer Institute | Dayie T.K.,University of Maryland University College
Nucleic Acids Research | Year: 2012

Riboswitches are a newly discovered large family of structured functional RNA elements that specifically bind small molecule targets out of a myriad of cellular metabolites to modulate gene expression. Structural studies of ligand-bound riboswitches by X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy have provided insights into detailed RNA-ligand recognition and interactions. However, the structures of ligand-free riboswitches remain poorly characterized. In this study, we have used a variety of biochemical, biophysical and computational techniques including small-angle X-ray scattering and NMR spectroscopy to characterize the ligand-free and ligand-bound forms of SAM-II riboswitch. Our data demonstrate that the RNA adopts multiple conformations along its folding pathway and suggest that the RNA undergoes marked conformational changes upon Mg 2+ compaction and S-adenosylmethionine (SAM) metabolite binding. Further studies indicated that Mg 2+ ion is not essential for the ligand binding but can stabilize the complex by facilitating loop/stem interactions. In the presence of millimolar concentration of Mg 2+ ion, the RNA samples a more compact conformation. This conformation is near to, but distinct from, the native fold and competent to bind the metabolite. We conclude that the formation of various secondary and tertiary structural elements, including a pseudoknot, occur to sequester the putative Shine-Dalgarno sequence of the RNA only after metabolite binding. © 2011 The Author(s).

Babu K.S.,Oklahoma State University | Mohapatra R.N.,University of Maryland University College
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

We show that unification of the three gauge couplings can be realized consistently in a class of non-supersymmetric SO(10) models with a one-step breaking to the Standard Model if a color sextet scalar field survives down to the TeV scale. Such scalars, which should be accessible to the LHC for direct detection, arise naturally in SO(10) as remnants of the seesaw mechanism for neutrino masses. The diquark couplings of these scalars lead to δ. B= 2 baryon number violating processes such as neutron-antineutron oscillation. We estimate the free neutron-antineutron transition time to be τn-n-≈(10 9-10 12) s, which is in the interesting range for next generation n- n- oscillation experiments. These models also realize naturally the recently proposed (B- L) violating GUT scale baryogenesis which survives to low temperatures unaffected by the electroweak sphaleron interactions. © 2012 Elsevier B.V.

Webber W.R.,New Mexico State University | McDonald F.B.,University of Maryland University College
Geophysical Research Letters | Year: 2013

At the Voyager 1 (V1) spacecraft in the outer heliosphere, the intensities of both anomalous cosmic rays and galactic cosmic rays (GCRs) changed suddenly and decisively on 25 August (121.7 AU from the Sun). Within a matter of a few days, the intensity of 1.9-2.7 MeV protons and helium nuclei had decreased to less than 0.1 of their previous value, and eventually the intensities decreased by factors of at least 300-500. Also, on 25 August, the GCR protons, helium, and electrons increased suddenly in just 2 or 3 days by a factor of up to 2. The intensities of the GCR nuclei of all energies from 2 to 400 MeV then remained essentially constant with intensity levels and spectra that may represent the local GCR. The suddenness of these intensity changes indicates that V1 has crossed a well-defined boundary for energetic particles at this time possibly related to the heliopause. Key PointsBoundary of heliosphere is very suddenLocal galactic cosmic ray spectra have peak at 60 MeVParticle layers observed near heliospheric boundary ©2013. American Geophysical Union. All Rights Reserved.

Rupke D.S.N.,Rhodes College | Rupke D.S.N.,University of Hawaii at Manoa | Veilleux S.,University of Maryland University College
Astrophysical Journal | Year: 2013

Massive, galaxy-scale outflows are known to be ubiquitous in major mergers of disk galaxies in the local universe. In this paper, we explore the multiphase structure and power sources of galactic winds in six ultraluminous infrared galaxies (ULIRGs) at z < 0.06 using deep integral field spectroscopy with the Gemini Multi-Object Spectrograph (GMOS) on Gemini North. We probe the neutral, ionized, and dusty gas phases using Na I D, strong emission lines ([O I], Hα, and [N II]), and continuum colors, respectively. We separate outflow motions from those due to rotation and tidal perturbations, and find that all of the galaxies in our sample host high-velocity flows on kiloparsec scales. The properties of these outflows are consistent with multiphase (ionized, neutral, and dusty) collimated bipolar winds emerging along the minor axis of the nuclear disk to scales of 1-2 kpc. In two cases, these collimated winds take the form of bipolar superbubbles, identified by clear kinematic signatures. Less collimated (but still high-velocity) flows are also present on scales up to 5 kpc in most systems. The three galaxies in our sample with obscured QSOs host higher velocity outflows than those in the three galaxies with no evidence for an active galactic nucleus. The peak outflow velocity in each of the QSOs is in the range 1450-3350 km s-1, and the highest velocities (2000-3000 km s-1) are seen only in ionized gas. The outflow energy and momentum in the QSOs are difficult to produce from a starburst alone, but are consistent with the QSO contributing significantly to the driving of the flow. Finally, when all gas phases are accounted for, the outflows are massive enough to provide negative feedback to star formation. © 2013. The American Astronomical Society. All rights reserved.

Rupke D.S.N.,Rhodes College | Veilleux S.,University of Maryland University College
Astrophysical Journal Letters | Year: 2013

We present Keck laser guide star adaptive optics observations of the nearby buried quasi-stellar object (QSO) F08572+3915:NW. We use near-infrared integral field data taken with the OH-Suppressing Infra-Red Imaging Spectrograph to reveal a compact disk and molecular outflow using Paα and H2 rotational-vibrational transitions at a spatial resolution of 100 pc. The outflow emerges perpendicular to the disk into a bicone of one-sided opening angle 100° up to distances of 400 pc from the nucleus. The integrated outflow velocities, which reach at least -1300 km s-1, correspond exactly to those observed in (unresolved) OH absorption, but are smaller (larger) than those observed on larger scales in the ionized (neutral atomic) outflow. These data represent a factor of >10 improvement in the spatial resolution of molecular outflows from mergers/QSOs, and plausibly represent the early stages of the excavation of the dust screen from a buried QSO. © 2013. The American Astronomical Society. All rights reserved..

Colombini M.,University of Maryland University College | Mannella C.A.,New York State Department of Health
Biochimica et Biophysica Acta - Biomembranes | Year: 2012

VDAC is now universally accepted as the channel in the mitochondrial outer membrane responsible for metabolite flux in and out of mitochondria. Its discovery occurred over two independent lines of investigation in the 1970s and 80s. This retrospective article describes the history of VDAC's discovery and how these lines merged in a collaboration by the authors. The article was written to give the reader a sense of the role played by laboratory environment, personalities, and serendipity in the discovery of the molecular basis for the unusual permeability properties of the mitochondrial outer membrane. This article is part of a Special Issue entitled: VDAC structure, function, and regulation of mitochondrial metabolism. © 2011 Elsevier B.V. All rights reserved.

Blanchard J.J.,University of Maryland University College | Kring A.M.,University of California at Berkeley | Horan W.P.,University of California at Los Angeles | Gur R.,University of Pennsylvania
Schizophrenia Bulletin | Year: 2011

Negative symptoms in schizophrenia are related to poor functional outcome, persistent over time, a source of burden for caregivers, and only minimally responsive to currently available medications. A major challenge to developing efficacious interventions concerns the valid and reliable assessment of negative symptoms. In a recent consensus statement on negative symptoms, a central recommendation was the need to develop new assessment approaches that address the limitations of existing instruments. In the current report, we summarize the background and rationale for the Collaboration to Advance Negative Symptom Assessment in Schizophrenia (CANSAS). The CANSAS project is an National Institute of Mental Health-funded multisite study that is constructing a next-generation negative symptom scale, the Clinical Assessment Interview for Negative Symptoms (CAINS). The CAINS is being developed within a data-driven iterative process that seeks to ensure the measure's reliability, validity, and utility for both basic psychopathology and treatment development research. © The Author 2011. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved.

Babu K.S.,Oklahoma State University | Mohapatra R.N.,University of Maryland University College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We present a simple model for a 7 keV scalar dark matter particle which also explains the recently reported anomalous peak in the extragalactic x-ray spectrum at 3.55 keV in terms of its two photon decay. The model is arguably the simplest extension of the Standard Model, with the addition of a real scalar gauge singlet field subject to a reflection symmetry. This symmetry breaks spontaneously at a temperature of order few GeV which triggers the decay of the dark matter particle into two photons. In this framework, the Higgs boson of the Standard Model is also the source of dark matter in the Universe. The model fits the relic dark matter abundance and the partial lifetime for two photon decay, while being consistent with constraints from domain wall formation and dark matter self-interactions. We show that all these features of the model are preserved in its natural embedding into a simple dark U(1) gauge theory with a Higgs mechanism. The properties of the dark photon get determined in such a scenario. High precision cosmological measurements can potentially test these models, as there are residual effects from domain wall formation and non-negligible self-interactions of dark matter. © 2014 American Physical Society.

Babu K.S.,Oklahoma State University | Mohapatra R.N.,University of Maryland University College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We show that grand unified theories based on SO(10) generate naturally the next-to-leading baryon number violating operators of dimension seven. These operators, which violate (B-L), lead to unconventional decays of the nucleon such as n→e -K +, e -π + and p→νπ +. In two-step breaking schemes of nonsupersymmetric SO(10), nucleon lifetime for decays into these modes is found to be within reach of experiments. We also identify supersymmetric scenarios where these decays may be accessible, consistent with gauge coupling unification. Further, we show that the (B-L) asymmetry generated in the decays of GUT scale scalar bosons and/or gauge bosons can explain consistently the observed baryon asymmetry of the universe. The induced (B-L) asymmetry is sphaleron-proof, and survives down to the weak scale without being erased by the electroweak interactions. This mechanism works efficiently in a large class of nonsupersymmetric and supersymmetric SO(10) models, with either a 126 H or a 16 H Higgs field employed for rank reduction. In minimal models the induced baryon asymmetry is tightly connected to the masses of quarks, leptons and neutrinos and is found to be compatible with observations. © 2012 American Physical Society.

Boggs C.L.,Rocky Mountain Biological Laboratory | Boggs C.L.,Stanford University | Inouye D.W.,Rocky Mountain Biological Laboratory | Inouye D.W.,University of Maryland University College
Ecology Letters | Year: 2012

Weather drives population dynamics directly, through effects on vital rates, or indirectly, through effects on the population's competitors, predators or prey and thence on vital rates. Indirect effects may include non-additive interactions with density dependence. Detection of climate drivers is critical to predicting climate change effects, but identification of potential drivers may depend on knowing the underlying mechanisms. For the butterfly Speyeria mormonia, one climate driver, snow melt date, has multiple effects on population growth. Snow melt date in year t has density-dependent indirect effects. Through frost effects, early snow melt decreases floral resources, thence per-capita nectar availability, which determines fecundity in the lab. Snow melt date in year t+1 has density-independent direct effects. These effects explain 84% of the variation in population growth rate. One climate parameter thus has multiple effects on the dynamics of a species with non-overlapping generations, with one effect not detectable without understanding the underlying mechanism. © 2012 Blackwell Publishing Ltd/CNRS.

Fushman D.,University of Maryland University College | Walker O.,University Claude Bernard Lyon 1
Journal of Molecular Biology | Year: 2010

Posttranslational modification of proteins by covalent attachment of a small protein ubiquitin (Ub) or a polymeric chain of Ub molecules (called polyubiquitin) is involved in controlling a vast variety of processes in eukaryotic cells. The question of how different polyubiquitin signals are recognized is central to understanding the specificity of various types of polyubiquitination. In polyubiquitin, monomers are linked to each other via an isopeptide bond between the C-terminal glycine of one Ub and a lysine of the other. The functional outcome of polyubiquitination depends on the particular lysine involved in chain formation and appears to rely on linkage-dependent conformation of polyubiquitin. Thus, K48-linked chains, a universal signal for proteasomal degradation, under physiological conditions adopt a closed conformation where functionally important residues L8, I44, and V70 are sequestered at the interface between two adjacent Ub monomers. By contrast, K63-linked chains, which act as a nonproteolytic regulatory signal, adopt an extended conformation that lacks hydrophobic interubiquitin contact. Little is known about the functional roles of the so-called "noncanonical" chains (linked via K6, K11, K27, K29, or K33, or linked head-to-tail), and no structural information on these chains is available, except for information on the crystal structure of the head-to-tail-linked diubiquitin (Ub2). In this study, we use molecular modeling to examine whether any of the noncanonical chains can adopt a closed conformation similar to that in K48-linked polyubiquitin. Our results show that the eight possible Ub2 chains can be divided into two groups: chains linked via K6, K11, K27, or K48 are predicted to form a closed conformation, whereas chains linked via K29, K33, or K63, or linked head-to-tail are unable to form such a contact due to steric occlusion. These predictions are validated by the known structures of K48-, K63-, and head-to-tail-linked chains. Our study also predicts structural models for Ub2 chains linked via K6, K11, or K27. The implications of these findings for linkage-selective recognition of noncanonical polyubiquitin signals by various receptors are discussed. © 2009 Elsevier Ltd. All rights reserved.

University of Maryland University College and Earth Networks | Date: 2012-12-28

Described herein are methods and systems, including computer program products, for optimizing and controlling the energy consumption of a building. A first computing device generates a set of thermal response coefficients for the building based on energy characteristics of the building and weather data associated with the location of the building. The first computing device predicts an energy response of the building based on the set of thermal response coefficients and forecasted weather associated with the location of the building. The first computing device selects minimal energy requirements of the building based on an energy consumption cost associated with the building. The first computing device determines one or more temperature set points for the building based on the energy response and the minimal energy requirements. The first computing device transmits the one or more temperature set points to a thermostat of the building.

Earth Networks and University of Maryland University College | Date: 2015-01-02

Described herein are methods and systems, including computer program products, for optimizing and controlling a buildings energy consumption and comfort. A computing device receives measurements from a plurality of sensors, at least some of which are located inside the building, where the measurements include temperature readings and comfort characteristics. The computing device generates a set of thermal response coefficients based on energy characteristics of the building, the measurements from the sensors, and weather data associated with the buildings location. The computing device predicts an energy response of the building based on the set of thermal response coefficients and forecasted weather. The computing device selects minimal energy requirements of the building based on an energy consumption cost associated with the building and determines energy control points based on the energy response and the minimal energy requirements. The computing device transmits the energy control points to comfort devices in the building.

News Article | October 28, 2016

Some 82% of IT professionals report a shortage of cybersecurity skills in their business, according to a July survey from Intel—and 71% cited this shortage as responsible for direct and measurable damage to organizations whose lack of talent makes them easier hacking targets. Job postings in the cybersecurity field have gone up 74% over the past five years. And US News and World Report ranked a career in information security analysis fifth on its list of best technology jobs. Average salaries nationally are $88,890, and significantly higher in cities such as San Francisco and New York. Interested in a career in cybersecurity? Here are 10 bachelors, masters, and certifications that can help you get started at any education level. Drexel University's BS in Computing and Security Technology consistently tops lists of cybersecurity preparation programs, and is recognized as a National Center of Academic Excellence in Information Assurance Education by the NSA. It offers hands-on experience managing and operating computer servers, networks, web and mobile systems, and databases, with a focus on security. Students can enroll in either the full-time, on-campus degree program, or in the online, part-time degree completion program, targeted to people who have already earned an associate's degree. BS in Computer Networks and Cybersecurity, BS in Cybersecurity Management and Policy, BS in Software Development and Security University of Maryland University College offers three bachelor's, four master's, and four certificate programs focused on different aspects of cybersecurity. The school is designated as a National Center of Academic Excellence in Cyber Defense Education by the NSA, and is headquartered between the DoD's Cyber Command in Maryland and the Cyber Corridor in Virginia. Plus, the UMUC Cyber Padawans cybersecurity competition team took home the first place prize in last year's Cyber DiploHack event. BS in Security and Risk Analysis-Information and Cyber Security Penn State's BS in Security and Risk Analysis degree, named one of the top online bachelor's programs by US News & World Report, focuses on the technologies, education, and policies needed to protect people and information. Students learn to design secure systems, evaluate and measure risk, and ensure privacy maintenance for individual users, businesses, and governments. Penn State is also recognized as an NSA Center of Academic Excellence in Cyber Defense. The program is available online. The University of Denver's MS in Cybersecurity program immerses students into the field, allowing them to work with local industry partners on real-world problems. The one-year, fast-track master's degree comes with a discounted scholarship of nearly 50%, and does not require students to have an undergraduate degree in computer science. University of Denver's program is also designated as an NSA Center of Academic Excellence in Cyber Defense. Champlain College offers online bachelor's, master's, and certificate programs in cybersecurity designed for working adults. It is the two-time winner of SC Magazine's Best Cybersecurity Higher Education award, and is designated as an NSA National Centers of Academic Excellence in Cyber Defense. The curriculum is career-focused, and provides strategic thinking skills and solution sets applicable to the workforce. Illinois Institute of Technology offers several security-oriented programs at the undergraduate, graduate, and certificate levels. The Masters of Cyber Forensics and Security program is unique, in that while students take cybersecurity courses, they also take legal courses alongside law students of the Illinois Institute of Technology Chicago-Kent College of Law. The program is designed to help students and experienced IT professionals become cybersecurity managers. The school is also designated as an NSA National Center of Academic Excellence in Cyber Defense. SEE: Help wanted: Universities double down on security to help fill 1 million open jobs The International Council of E-Commerce Consultants (EC-Council) is the world's largest cybersecurity technical certification organization. Its Certified Ethical Hacker certification involves a training course that teaches students to look for weaknesses and vulnerabilities in a system using the same tools as a malicious hacker, but in a lawful way to assess the security systems. It is a vendor-neutral certification. Those who want to take the certification exam without training must demonstrate two years of information security experience. With more than 250,000 credential holders, CompTIA Security+ is a popular, vendor-neutral security certification with an available online learning tool for preparation. Exam content stems from a combination of industry-wide survey feedback, and contributions from a team of security experts. The certification is approved by the US Department of Defense to fulfill cybersecurity position requirements, and is compliant with government regulations under the Federal Information Security Management Act. Companies that recognize the certification include Apple, Dell, HP, IBM, and Intel. The GIAC Security Essentials Certification (GSEC) is intended for security professionals who want to demonstrate that they are qualified for IT systems hands-on roles in terms of security tasks. Credential holders will demonstrate knowledge and technical skills in areas including network mapping, access controls, password management, and cryptography fundamentals. No specific training is required, but CIAC recommends a "boot camp" style preparation course from SANS. The Certified Information Systems Security Professional (CISSP) is an advanced-level, vendor-neutral certification for IT professionals looking to expand their career into information security. The certification is meant to prove credibility in designing, implementing, and managing overall information security programs to protect organizations from sophisticated attacks. In-person and online training programs are available though (ISC)2 and third-party companies. Interested individuals must have a minimum of five years of full-time work experience in two or more of the eight domains listed here.

News Article | November 29, 2016

Liquidware Labs, a leading provider of desktop transformation solutions for virtual, physical, and cloud-based desktops, today announced that the company’s Workspace Environment Management suite, known as Liquidware Labs Essentials, now fully supports Amazon WorkSpaces. Liquidware Labs has partnered with Amazon WorkSpaces (AWS) to offer Liquidware Labs Essentials, including its Stratusphere solutions, ProfileUnity and FlexApp, to organizations that can benefit from the company’s Workspace Environment Management offerings. The Liquidware Labs products for Amazon Workspaces are available on the AWS Marketplace or by downloading at AWS provides a powerful global infrastructure fabric upon which desktops can be rapidly provisioned and sized, based not only on initial design, but more importantly, as the environment grows and changes over time. This ease and flexibility – combined with the enhanced security the AWS cloud offers – makes cloud desktops an increasingly attractive option for many large organizations. Cloud-based desktops can be rapidly provisioned for peak usages times, to establish consistent user experience after mergers or acquisitions or to support remote workers more effectively. Liquidware Labs solutions will be highlighted in a presentation to be given at re:Invent that will be co-presented by Nick Frank, Practice Lead at AHEAD, a Liquidware Labs channel partner. “Liquidware Labs has been an AHEAD partner for six years in the on-premises VDI space. As our End-User Computing team has expanded its focus into the public cloud space with Amazon WorkSpaces, we needed solutions that can scale and support a hybrid cloud architecture,” says Nick Frank, Practice Lead for Mobility and End User Computing at AHEAD. “We wanted to present a perspective to help our customers understand why you need best-of-breed solutions when moving desktops to the cloud and how to accomplish that successfully.” For more information and to register for this re:Invent session, follow this link. ENT201 - Deploying Amazon WorkSpaces at Enterprise Scale to Deliver a New Desktop Experience AWS Solutions are increasingly an option for many types of organizations looking for a more streamlined approach to scaling their virtual desktops. “In September, we integrated the AWS WorkSpaces offering into our learning process. To better understand how our students used the newly introduced platform, we looked to Liquidware Labs to help us. Being able to use both Stratusphere and ProfileUnity allowed us to provide better support to our students and allowed us to maintain our ‘student first’ focus,” said Greg M. Smith, Associate VP, Enterprise Operations, University of Maryland University College. Liquidware Labs Essentials adds the following capabilities to Amazon WorkSpaces: “Liquidware Labs is a pioneer in the Workspace Environment Management space in the virtual desktop market and has helped many Citrix and VMware customers achieve success when rolling out both on premises virtual desktops and cloud-based desktops, said Mark Bowker, Senior Analyst, Enterprise Strategies Group. “It is exciting to see them fully embrace and extend their innovative products’ support for Amazon Workspaces. When Liquidware Labs user experience, user environment management and layering solutions are leveraged in Amazon Workspaces environment, customers gain a very mature and comprehensive desktop DaaS offering.” In addition to Amazon WorkSpaces, Liquidware Labs solutions support any Windows desktop including virtual, physical or cloud-based environments. The solutions also support Citrix XenApp and XenDesktop, VMware Horizon running on premises or in any cloud such as Amazon AWS, Microsoft Azure, or Google Cloud. Therefore, organizations do not need to choose among platforms – virtual or physical – they can use Liquidware Labs solutions for all of their desktops in their environment. “We see a future where on-premises desktops will be consistently paired with cloud-based desktops,” said Tyler Rohrer, who spearheads alliances for Liquidware Labs and manages the Amazon relationship. “When extending our solutions to Amazon WorkSpaces, as well as all desktops in their environment, organizations can enter a new era of simplicity, scalability and control over provisioning and managing their Windows desktops.” For more information on the complementary nature of the Liquidware Labs Workspace Solutions Stack for Amazon WorkSpaces, please visit the Liquidware Labs website at: About Liquidware Labs Liquidware Labs™ provides industry leading platform-agnostic desktop solutions for hybrid Windows desktop environments including Citrix® XenApp/XenDesktop, VMware Horizon View®, and physical Microsoft® Windows PCs. Stratusphere™ FIT and Stratusphere™ UX products deliver visibility into desktop environments and support assessment, design, monitoring and diagnostics (Health Checks). ProfileUnity provides just in time delivery of User Profiles, application and user rights management and context-aware policies. ProfileUnity’s FlexApp feature delivers advanced Application Layering. Flex-IO supports IOPS acceleration in virtual desktop environments. The solutions are available in an extremely cost-effectively priced bundle called Liquidware Labs Essentials. Liquidware Labs products are Citrix Ready, VMware-certified, and are available through a global network of partners. Visit for further information.

Belov G.A.,University of Maryland University College | Sztul E.,University of Alabama at Birmingham
Journal of virology | Year: 2014

Viruses are obligatory intracellular parasites and utilize host elements to support key viral processes, including penetration of the plasma membrane, initiation of infection, replication, and suppression of the host's antiviral defenses. In this review, we focus on picornaviruses, a family of positive-strand RNA viruses, and discuss the mechanisms by which these viruses hijack the cellular machinery to form and operate membranous replication complexes. Studies aimed at revealing factors required for the establishment of viral replication structures identified several cellular-membrane-remodeling proteins and led to the development of models in which the virus used a preexisting cellular-membrane-shaping pathway "as is" for generating its replication organelles. However, as more data accumulate, this view is being increasingly questioned, and it is becoming clearer that viruses may utilize cellular factors in ways that are distinct from the normal functions of these proteins in uninfected cells. In addition, the proteincentric view is being supplemented by important new studies showing a previously unappreciated deep remodeling of lipid homeostasis, including extreme changes to phospholipid biosynthesis and cholesterol trafficking. The data on viral modifications of lipid biosynthetic pathways are still rudimentary, but it appears once again that the viruses may rewire existing pathways to generate novel functions. Despite remarkable progress, our understanding of how a handful of viral proteins can completely overrun the multilayered, complex mechanisms that control the membrane organization of a eukaryotic cell remains very limited. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

Gopal A.,University of Maryland University College | Koka B.R.,Rice University
MIS Quarterly: Management Information Systems | Year: 2012

In this paper, the interacting effect of formal contracts and relational governance on vendor profitability and quality in the software outsourcing industry are examined. We focus on a critical manifestation of relational governance-The presence of relational flexibility in the exchange relationship-and argue that the enacted observation of relational flexibility is driven by perceptions of exchange hazards. In a departure from extant literature, however, we propose that the benefits accruing from it are asymmetric and depend on how the exchange risks are apportioned by the formal contract. Formally, we hypothesize that relational flexibility provides greater benefits to an exchange partner that faces the greater proportion of risk in a project, induced through the contract. In addition, we hypothesize that these benefits manifest on the performance dimensions that are of importance to the risk-exposed partner. We test our hypotheses on 105 software projects completed by a software outsourcing vendor for multiple clients. The results show that relational flexibility positively affects profitability in only fixed price contracts, where the vendor faces greater risk, while positively affecting quality only in time and materials contracts, where the client is at greater risk. We thus provide evidence for the asymmetric benefits from relational governance, thereby arguing for a more contingent and limited view of the value of relational governance, based on risk-exposure, rather than the more expansive view prevalent in the literature contending that relational governance provides benefits for all parties to an exchange. We conclude with a discussion of the research and managerial implications of our findings.

Edelson R.,University of Maryland University College | Malkan M.,University of California at Los Angeles
Astrophysical Journal | Year: 2012

We have developed the ''S IX'' statistic to identify bright, highly likely active galactic nucleus (AGN) candidates solely on the basis of Wide-field Infrared Survey Explorer (WISE), Two Micron All-Sky Survey (2MASS), and ROSAT all-sky survey (RASS) data. This statistic was optimized with data from the preliminary WISE survey and the Sloan Digital Sky Survey, and tested with Lick 3 m Kast spectroscopy. We find that sources with S IX< 0 have a ≳95% likelihood of being an AGN (defined in this paper as a Seyfert 1, quasar, or blazar). This statistic was then applied to the full WISE/2MASS/RASS dataset, including the final WISE data release, to yield the ''W2R'' sample of 4316 sources with S IX< 0. Only 2209 of these sources are currently in the Veron-Cetty and Veron (VCV) catalog of spectroscopically confirmed AGNs, indicating that the W2R sample contains nearly 2000 new, relatively bright (J ≲ 16) AGNs. We utilize the W2R sample to quantify biases and incompleteness in the VCV catalog. We find that it is highly complete for bright (J< 14), northern AGNs, but the completeness drops below 50% for fainter, southern samples and for sources near the Galactic plane. This approach also led to the spectroscopic identification of 10 new AGNs in the Kepler field, more than doubling the number of AGNs being monitored by Kepler. The W2R sample contains better than 1 bright AGN every 10 deg2, permitting construction of AGN samples in any sufficiently large region of sky. © 2012. The American Astronomical Society. All rights reserved.

Rocheleau T.,Cornell University | Ndukum T.,Cornell University | MacKlin C.,Cornell University | Hertzberg J.B.,University of Maryland University College | And 2 more authors.
Nature | Year: 2010

Cold, macroscopic mechanical systems are expected to behave contrary to our usual classical understanding of reality; the most striking and counterintuitive predictions involve the existence of states in which the mechanical system is located in two places simultaneously. Various schemes have been proposed to generate and detect such states, and all require starting from mechanical states that are close to the lowest energy eigenstate, the mechanical ground state. Here we report the cooling of the motion of a radio-frequency nanomechanical resonator by parametric coupling to a driven, microwave-frequency superconducting resonator. Starting from a thermal occupation of 480 quanta, we have observed occupation factors as low as 3.8 1.3 and expect the mechanical resonator to be found with probability 0.21 in the quantum ground state of motion. Further cooling is limited by random excitation of the microwave resonator and heating of the dissipative mechanical bath. This level of cooling is expected to make possible a series of fundamental quantum mechanical observations including direct measurement of the Heisenberg uncertainty principle and quantum entanglement with qubits. © 2010 Macmillan Publishers Limited. All rights reserved.

Shetty R.,University of Heidelberg | Ostriker E.C.,University of Maryland University College
Astrophysical Journal | Year: 2012

We explore the self-regulation of star formation using a large suite of high-resolution hydrodynamic simulations, focusing on molecule-dominated regions (galactic centers and [U]LIRGS) where feedback from star formation drives highly supersonic turbulence. In equilibrium, the total midplane pressure, dominated by turbulence, must balance the vertical weight of the interstellar medium. Under self-regulation, the momentum flux injected by feedback evolves until it matches the vertical weight. We test this flux balance in simulations spanning a wide range of parameters, including surface density Σ, momentum injected per stellar mass formed (p */m *), and angular velocity. The simulations are two-dimensional radial-vertical slices, and include both self-gravity and an external potential that helps to confine gas to the disk midplane. After the simulations reach a steady state in all relevant quantities, including the star formation rate Σ SFR, there is remarkably good agreement between the vertical weight, the turbulent pressure, and the momentum injection rate from supernovae. Gas velocity dispersions and disk thicknesses increase with p */m *. The efficiency of star formation per free-fall time at the midplane density, εff(n 0), is insensitive to the local conditions and to the star formation prescription in very dense gas. We measure εff(n 0) 0.004-0.01, consistent with low and approximately constant efficiencies inferred from observations. For Σ ∈ (100-1000) M pc-2, we find ΣSFR ∈ (0.1-4) M kpc-2 yr-1, generally following a ΣSFR Σ2 relationship. The measured relationships agree very well with vertical equilibrium and with turbulent energy replenishment by feedback within a vertical crossing time. These results, along with the observed Σ-ΣSFR relation in high-density environments, provide strong evidence for the self-regulation of star formation. © 2012. The American Astronomical Society. All rights reserved.

Margono B.A.,University of Maryland University College | Potapov P.V.,University of Maryland University College | Turubanova S.,University of Maryland University College | Stolle F.,World Resource Institute | Hansen M.C.,University of Maryland University College
Nature Climate Change | Year: 2014

Extensive clearing of Indonesian primary forests results in increased greenhouse gas emissions and biodiversity loss. However, there is no consensus on the areal extent and temporal trends of primary forest clearing in Indonesia. Here we report a spatially and temporally explicit quantification of Indonesian primary forest loss, which totalled over 6.02 Mha from 2000 to 2012 and increased on average by 47,600 ha per year. By 2012, annual primary forest loss in Indonesia was estimated to be higher than in Brazil (0.84 Mha and 0.46 Mha, respectively). Proportional loss of primary forests in wetland landforms increased and almost all clearing of primary forests occurred within degraded types, meaning logging preceded conversion processes. Loss within official forest land uses that restrict or prohibit clearing totalled 40% of all loss within national forest land. The increasing loss of Indonesian primary forests has significant implications for climate change mitigation and biodiversity conservation efforts. © 2014 Macmillan Publishers Limited. All rights reserved.

Wang B.,Qualcomm | Liu K.J.R.,University of Maryland University College
IEEE Journal on Selected Topics in Signal Processing | Year: 2011

With the rapid deployment of new wireless devices and applications, the last decade has witnessed a growing demand for wireless radio spectrum. However, the fixed spectrum assignment policy becomes a bottleneck for more efficient spectrum utilization, under which a great portion of the licensed spectrum is severely under-utilized. The inefficient usage of the limited spectrum resources urges the spectrum regulatory bodies to review their policy and start to seek for innovative communication technology that can exploit the wireless spectrum in a more intelligent and flexible way. The concept of cognitive radio is proposed to address the issue of spectrum efficiency and has been receiving an increasing attention in recent years, since it equips wireless users the capability to optimally adapt their operating parameters according to the interactions with the surrounding radio environment. There have been many significant developments in the past few years on cognitive radios. This paper surveys recent advances in research related to cognitive radios. The fundamentals of cognitive radio technology, architecture of a cognitive radio network and its applications are first introduced. The existing works in spectrum sensing are reviewed, and important issues in dynamic spectrum allocation and sharing are investigated in detail. © 2011 IEEE.

Goswami P.,Florida State University | Roy B.,University of Maryland University College
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

We consider the competition between the conventional s-wave and the triplet Balian-Werthamer or the B-phase pairings in doped three-dimensional narrow-gap semiconductors, such as CuxBi2Se3 and Sn1-xInxTe. When the coupling constants of the two contending channels are comparable, we find a simultaneously time-reversal and parity violating p+is state at low temperatures, which provides an example of a dynamic axionic state of matter. In contradistinction to the time-reversal invariant, topological B phase, the p+is state possesses gapped Majorana fermions as surface Andreev bound states, which give rise to an anomalous surface thermal Hall effect. The anomalous gravitational and electrodynamic responses of the p+is state can be described by the θ vacuum structure, where θ≠0 or π. © 2014 American Physical Society.

Roy B.,Florida State University | Roy B.,University of Maryland University College
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

A variational ground state for insulating bilayer graphene (BLG), subject to quantizing magnetic fields, is proposed. Due to the Zeeman coupling, the layer antiferromagnet (LAF) order parameter in fully gapped BLG gets projected onto the spin easy plane, and simultaneously a ferromagnet order, which can further be enhanced by exchange interaction, develops in the direction of the magnetic field. The activation gap for the ν=0 Hall state then displays a crossover from quadratic to linear scaling with the magnetic field, as it gets stronger, and I obtain excellent agreement with a number of recent experiments with realistic strengths for the ferromagnetic interaction. A component of the LAF order, parallel to the external magnetic field, gives birth to additional incompressible Hall states at filling ν=±2, whereas the remote hopping in BLG yields ν=±1 Hall states. Evolution of the LAF order in tilted magnetic fields, scaling of the gap at ν=2, the effect of external electric fields on various Hall plateaus, and different possible hierarchies of fractional quantum Hall states are highlighted. © 2014 American Physical Society.

Deng Z.,U.S. National Institute of Standards and Technology | Deng Z.,University of Maryland University College | Smolyanitsky A.,U.S. National Institute of Standards and Technology | Li Q.,Tsinghua University | And 2 more authors.
Nature Materials | Year: 2012

From the early tribological studies of Leonardo da Vinci to Amontons' law, friction has been shown to increase with increasing normal load. This trend continues to hold at the nanoscale, where friction can vary nonlinearly with normal load. Here we present nanoscale friction force microscopy (FFM) experiments for a nanoscale probe tip sliding on a chemically modified graphite surface in an atomic force microscope (AFM). Our results demonstrate that, when adhesion between the AFM tip and surface is enhanced relative to the exfoliation energy of graphite, friction can increase as the load decreases under tip retraction. This leads to the emergence of an effectively negative coefficient of friction in the low-load regime. We show that the magnitude of this coefficient depends on the ratio of tip-sample adhesion to the exfoliation energy of graphite. Through both atomistic- and continuum-based simulations, we attribute this unusual phenomenon to a reversible partial delamination of the topmost atomic layers, which then mimic few- to single-layer graphene. Lifting of these layers with the AFM tip leads to greater deformability of the surface with decreasing applied load. This discovery suggests that the lamellar nature of graphite yields nanoscale tribological properties outside the predictive capacity of existing continuum mechanical models. © 2012 Macmillan Publishers Limited. All rights reserved.

Bedaque P.,University of Maryland University College | Steiner A.W.,University of Washington | Steiner A.W.,University of Tennessee at Knoxville | Steiner A.W.,Oak Ridge National Laboratory
Physical Review Letters | Year: 2015

It has been conjectured that the velocity of sound in any medium is smaller than the velocity of light in vacuum divided by 3. Simple arguments support this bound in nonrelativistic and/or weakly coupled theories. The bound has been demonstrated in several classes of strongly coupled theories with gravity duals and is saturated only in conformal theories. We point out that the existence of neutron stars with masses around two solar masses combined with the knowledge of the equation of state of hadronic matter at "low" densities is in strong tension with this bound. © 2015 American Physical Society.

Ostriker E.C.,University of Maryland University College | Shetty R.,University of Heidelberg
Astrophysical Journal | Year: 2011

Star formation rates in the centers of disk galaxies often vastly exceed those at larger radii, whether measured by the surface density of star formation ΣSFR, by the star formation rate per unit gas mass, ΣSFR/Σ, or even by total output. In this paper, we investigate the idea that central starbursts are self-regulated systems in which the momentum flux injected to the interstellar medium (ISM) by star formation balances the gravitational force confining the ISM gas in the disk. For most starbursts, supernovae are the largest contributor to the momentum flux, and turbulence provides the main pressure support for the predominantly molecular ISM. If the momentum feedback per stellar mass formed is p */m * ∼3000 km s-1, the predicted star formation rate is ΣSFR ∼2πGΣ2 m */p * 0.1 M ⊙ kpc-2 yr-1(Σ/100 M ⊙ pc-2)2 in regions where gas dominates the vertical gravity. We compare this prediction with numerical simulations of vertically resolved disks that model star formation including feedback, finding good agreement for gas surface densities in the range Σ ∼ 102-103 M ⊙ pc-2. We also compare to a compilation of star formation rates and gas contents from local and high-redshift galaxies (both mergers and normal galaxies), finding good agreement provided that the conversion factor X CO from integrated CO emission to H2 surface density decreases modestly as Σ and ΣSFR increase. Star formation rates in dense, turbulent gas are also expected to depend on the gravitational free-fall time at the corresponding mean ISM density ρ0; if the star formation efficiency per free-fall time is εff(ρ 0) 0.01, the turbulent velocity dispersion driven by feedback is expected to be vz = 0.4 εff(ρ0)p */m * ∼ 10 km s-1, relatively independent of Σ or ΣSFR. Turbulence-regulated starbursts (controlled by kinetic momentum feedback) are part of the larger scheme of self-regulation; primarily atomic low-Σ outer disks may have star formation regulated by ultraviolet heating feedback, whereas regions at extremely high Σ may be regulated by feedback of stellar radiation that is reprocessed into trapped infrared. © 2011. The American Astronomical Society. All rights reserved.

Dzero M.,University of Maryland University College | Sun K.,University of Maryland University College | Galitski V.,University of Maryland University College | Coleman P.,Rutgers University
Physical Review Letters | Year: 2010

Kondo insulators are a particularly simple type of heavy electron material, where a filled band of heavy quasiparticles gives rise to a narrow band insulator. Starting with the Anderson lattice Hamiltonian, we develop a topological classification of emergent band structures for Kondo insulators and show that these materials may host three-dimensional topological insulating phases. We propose a general and practical prescription of calculating the Z2 topological indices for various lattice structures. Experimental implications of the topological Kondo insulating behavior are discussed. © 2010 The American Physical Society.

Ho H.T.,University of Maryland University College | Gopalan R.,ATandT Labs Research
International Journal of Computer Vision | Year: 2014

Many classification algorithms see a reduction in performance when tested on data with properties different from that used for training. This problem arises very naturally in face recognition where images corresponding to the source domain (gallery, training data) and the target domain (probe, testing data) are acquired under varying degree of factors such as illumination, expression, blur and alignment. In this paper, we account for the domain shift by deriving a latent subspace or domain, which jointly characterizes the multifactor variations using appropriate image formation models for each factor. We formulate the latent domain as a product of Grassmann manifolds based on the underlying geometry of the tensor space, and perform recognition across domain shift using statistics consistent with the tensor geometry. More specifically, given a face image from the source or target domain, we first synthesize multiple images of that subject under different illuminations, blur conditions and 2D perturbations to form a tensor representation of the face. The orthogonal matrices obtained from the decomposition of this tensor, where each matrix corresponds to a factor variation, are used to characterize the subject as a point on a product of Grassmann manifolds. For cases with only one image per subject in the source domain, the identity of target domain faces is estimated using the geodesic distance on product manifolds. When multiple images per subject are available, an extension of kernel discriminant analysis is developed using a novel kernel based on the projection metric on product spaces. Furthermore, a probabilistic approach to the problem of classifying image sets on product manifolds is introduced. We demonstrate the effectiveness of our approach through comprehensive evaluations on constrained and unconstrained face datasets, including still images and videos. © 2014 Springer Science+Business Media New York.

Kelley D.R.,University of Maryland University College | Schatz M.C.,Simons Center for Quantitative Biology | Salzberg S.L.,University of Maryland University College
Genome Biology | Year: 2010

We introduce Quake, a program to detect and correct errors in DNA sequencing reads. Using a maximum likelihood approach incorporating quality values and nucleotide specific miscall rates, Quake achieves the highest accuracy on realistically simulated reads. We further demonstrate substantial improvements in de novo assembly and SNP detection after using Quake. Quake can be used for any size project, including more than one billion human reads, and is freely available as open source software from © 2010 Kelley et al.; licensee BioMed Central Ltd.

Wallace J.M.,University of Maryland University College | Vukoslavcevic P.V.,University of Montenegro
Annual Review of Fluid Mechanics | Year: 2010

This article reviews the principal experimental methods currently available to simultaneously measure all the terms of the velocity gradient tensor of turbulent flows. These methods have been available only for a little more than 20 years. They have provided access to the most fundamental and defining properties of turbulence. The methods include small, multisensor, hot-wire probes that provide single-location, time-resolved measurements of the tensor and various optical arrangements, most of which provide the tensor information over a larger spatial extent but, in most cases, without resolution in time. Data-reduction algorithms, spatial-resolution issues, and the use of Taylor's hypothesis are addressed in evaluating the accuracy of the various methods. Copyright © 2010 by Annual Reviews. All rights reserved.

Le Tiec A.,University of Maryland University College | Blanchet L.,University Pierre and Marie Curie | Whiting B.F.,University of Florida
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

First laws of black hole mechanics, or thermodynamics, come in a variety of different forms. In this paper, from a purely post-Newtonian (PN) analysis, we obtain a first law for binary systems of point masses moving along an exactly circular orbit. Our calculation is valid through 3PN order and includes, in addition, the contributions of logarithmic terms at 4PN and 5PN orders. This first law of binary point-particle mechanics is then derived from first principles in general relativity, and analogies are drawn with the single and binary black hole cases. Some consequences of the first law are explored for PN spacetimes. As one such consequence, a simple relation between the PN binding energy of the binary system and Detweiler's redshift observable is established. Through it, we are able to determine with high precision the numerical values of some previously unknown high-order PN coefficients in the circular-orbit binding energy. Finally, we propose new gauge-invariant notions for the energy and angular momentum of a particle in a binary system. © 2012 American Physical Society.

Veeraraghavan A.,MItsubishi Electric | Reddy D.,University of Maryland University College | Raskar R.,Massachusetts Institute of Technology
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2011

We show that, via temporal modulation, one can observe and capture a high-speed periodic video well beyond the abilities of a low-frame-rate camera. By strobing the exposure with unique sequences within the integration time of each frame, we take coded projections of dynamic events. From a sequence of such frames, we reconstruct a high-speed video of the high-frequency periodic process. Strobing is used in entertainment, medical imaging, and industrial inspection to generate lower beat frequencies. But this is limited to scenes with a detectable single dominant frequency and requires high-intensity lighting. In this paper, we address the problem of sub-Nyquist sampling of periodic signals and show designs to capture and reconstruct such signals. The key result is that for such signals, the Nyquist rate constraint can be imposed on the strobe rate rather than the sensor rate. The technique is based on intentional aliasing of the frequency components of the periodic signal while the reconstruction algorithm exploits recent advances in sparse representations and compressive sensing. We exploit the sparsity of periodic signals in the Fourier domain to develop reconstruction algorithms that are inspired by compressive sensing. © 2006 IEEE.

Silk M.L.,University of Bath | Andrews D.L.,University of Maryland University College
Sociology of Sport Journal | Year: 2011

Within this paper we offer what is hopefully both a suggestive (as opposed to definitive) and generative (as opposed to suppressive) signposting of the ontological, epistemological, and methodological boundaries framing the putative intellectual project that is Physical Cultural Studies (PCS). Ground in a commitment toward engaging varied dimensions or expressions of active physicality, we deliberate on an understanding of, and approach to, the corporeal practices, discourses, and subjectivities through which active bodies become organized, represented, and experienced in relation to the operations of social power. Further, drawing on Toby Miller, we suggest that this approach requires a motivation toward progressive social change. We consider the political and axiological contingencies of PCS, how it is differentiated from the "sociology of sport," and how we may produce the type of knowledge that is able to intervene into the broader social world and make a difference. We are sure many will disagree-perhaps with good reason-with our assumptions. Indeed, such differences are welcomed for we feel that there is greater progressive potential in a field in tension, in healthy contestation, and, in which debates surrounding ontology, epistemology, political intent, method, interpretation, expression, and impact flow freely. © 2011 Human Kinetics, Inc.

Van Nguyen H.,University of Maryland University College | Porikli F.,MItsubishi Electric
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2013

We introduce a novel implicit representation for 2D and 3D shapes based on Support Vector Machine (SVM) theory. Each shape is represented by an analytic decision function obtained by training SVM, with a Radial Basis Function (RBF) kernel so that the interior shape points are given higher values. This empowers support vector shape (SVS) with multifold advantages. First, the representation uses a sparse subset of feature points determined by the support vectors, which significantly improves the discriminative power against noise, fragmentation, and other artifacts that often come with the data. Second, the use of the RBF kernel provides scale, rotation, and translation invariant features, and allows any shape to be represented accurately regardless of its complexity. Finally, the decision function can be used to select reliable feature points. These features are described using gradients computed from highly consistent decision functions instead from conventional edges. Our experiments demonstrate promising results. © 1979-2012 IEEE.

Herzberg C.,Rutgers University | Rudnick R.,University of Maryland University College
Lithos | Year: 2012

The formation of cratonic mantle peridotite of Archean age is examined within the time frame of Earth's thermal history, and how it was expressed by temporal variations in magma and residue petrology. Peridotite residues that occupy the lithospheric mantle are rare owing to the effects of melt-rock reaction, metasomatism, and refertilization. Where they are identified, they are very similar to the predicted harzburgite residues of primary magmas of the dominant basalts in greenstone belts, which formed in a non-arc setting (referred to here as "non-arc basalts"). The compositions of these basalts indicate high temperatures of formation that are well-described by the thermal history model of Korenaga. In this model, peridotite residues of extensive ambient mantle melting had the highest Mg-numbers, lowest FeO contents, and lowest densities at ~. 2.5-3.5. Ga. These results are in good agreement with Re-Os ages of kimberlite-hosted cratonic mantle xenoliths and enclosed sulfides, and provide support for the hypothesis of Jordan that low densities of cratonic mantle are a measure of their high preservation potential. Cratonization of the Earth reached its zenith at ~. 2.5-3.5. Ga when ambient mantle was hot and extensive melting produced oceanic crust 30-45. km thick. However, there is a mass imbalance exhibited by the craton-wide distribution of harzburgite residues and the paucity of their complementary magmas that had compositions like the non-arc basalts. We suggest that the problem of the missing basaltic oceanic crust can be resolved by its hydration, cooling and partial transformation to eclogite, which caused foundering of the entire lithosphere. Some of the oceanic crust partially melted during foundering to produce continental crust composed of tonalite-trondhjemite-granodiorite (TTG). The remaining lithosphere gravitationally separated into 1) residual eclogite that continued its descent, and 2) buoyant harzburgite diapirs that rose to underplate cratonic nuclei composed of non-arc basalts and TTG. Finally, assembly of cratonic nuclei into cratons at convergent boundaries substantially modified harzburgite residues by melt-rock reaction. © 2012 Elsevier B.V.

Anastopoulos C.,University of Patras | Hu B.L.,University of Maryland University College
New Journal of Physics | Year: 2014

We examine the origin of the Newton-Schrödinger equations (NSEs) that play an important role in alternative quantum theories (AQT), macroscopic quantum mechanics and gravity-induced decoherence. We show that NSEs for individual particles do not follow from general relativity (GR) plus quantum field theory (QFT). Contrary to what is commonly assumed, the NSEs are not the weak-field (WF), non-relativistic (NR) limit of the semi-classical Einstein equation (SCE) (this nomenclature is preferred over the 'Moller-Rosenfeld equation') based on GR+QFT. The wave-function in the NSEs makes sense only as that for a mean field describing a system of N particles as , not that of a single or finite many particles. From GR+QFT the gravitational self-interaction leads to mass renormalization, not to a non-linear term in the evolution equations of some AQTs. The WF-NR limit of the gravitational interaction in GR+QFT involves no dynamics. To see the contrast, we give a derivation of the equation (i) governing the many-body wave function from GR+QFT and (ii) for the non-relativistic limit of quantum electrodynamics. They have the same structure, being linear, and very different from NSEs. Adding to this our earlier consideration that for gravitational decoherence the master equations based on GR+QFT lead to decoherence in the energy basis and not in the position basis, despite some AQTs desiring it for the 'collapse of the wave function', we conclude that the origins and consequences of NSEs are very different, and should be clearly demarcated from those of the SCE equation, the only legitimate representative of semiclassical gravity, based on GR+QFT. © 2014 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Childrens National Medical Center and University of Maryland University College | Date: 2015-04-13

Compositions comprising biomedical polymers, and in particular unique blends of poly(lactic-co-glycolic acid) (PLGA) and poly(ethylene glycol) (PEG) are provided. Methods of forming polymer fibers using such compositions and solution blow spinning techniques are also provided, as well as methods of delivering the blow spun polymer fibers onto a surface (e.g., such as tissue for use as a surgical scaffold, sealant or tissue adhesive).

Childrens National Medical Center and University of Maryland University College | Date: 2014-03-14

A method for transdermal drug delivery provides for the topical administration of liposome encapsulated nanoparticles. The encapsulated nanoparticles define a nearly monodisperse population of liposomes having an average diameter within a selected size range. Liposomal nanoparticle formulations and methods of treatment therewith are also provided.

University of Maryland University College, Childrens National Medical Center and The United States Of America | Date: 2014-09-02

The present disclosure relates to a bio-sensor capable of measuring the total concentration of one or a plurality of ammonia or ammonium ions with the use of indophenol reagents in the presence of an ionomer. In some embodiments, the biosensor comprises a perflurinated membrane that comprises an ionomer in contact with an alkaline buffer in a vessel configured to receive a sample, such as whole blood. The disclosure also relates to a method of detecting or quantifying the ammonia or ammonium ion concentration in whole blood in a point of care biosensor without reliance on gas chromatography or any measurement that takes more than about twenty minutes.

University of Maryland University College and MItsubishi Electric | Date: 2011-01-05

In image decoding a region of interest coordinate information and a bit shift value are obtained from a header in a bit stream, said bit shift value being assigned to each region of interest. The coded digital image data is coded starting from a bit field of a higher bit significance level and continuing down to the bit field of a lower bit significance level to obtain transform coefficients. The transform coefficients corresponding to each region of interest are scaled down, wherein the scaling down is performed by shifting bits of said transform coefficients by said bit shift value specified by a priority assigned to said region of interest to place the transform coefficients in lower bit significance level planes, wherein the lowest bit plane of the region of interest is placed at the same bit plane as the lowest bit plane of the other transform coefficients. An inverse wavelet transform is then performed on said transform coefficients.

Childrens National Medical Center and University of Maryland University College | Date: 2014-06-06

A composition including PPF or a PPF copolymer that can be used to fabricate biodegradable structures. The composition can be used in 3-D patterning (e.g., 3-D printing and sterolighography) methods. For example, 3-D patternable compositions include PPF or a PPF copolymer, a photoinitiator or photoinitiators, and a resolution control inhibitor or inhibitors. The compositions can be used to make biodegradable structures (such as cardivascular scaffolds). The biodegradable structures can be surface functionalized. The biodegradable structures can be used in methods of blood delivery in an individual.

University of Maryland University College and MItsubishi Electric | Date: 2011-01-05

In compressing digital image data a wavelet transform of all the pixel values in the digital image data is performed to obtain transform coefficients composed of bit planes. The transform coefficients corresponding to each region of interest are scaled up to place the transform coefficients in higher bit significance level planes than bit significance level planes of the other transform coefficients, wherein the scaling up is performed based on a maximum bit shift value if a priority assigned to the region of interest indicates the maximum bit shift value. The transform coefficients are then entropy encoded to form a bit stream, wherein the transform coefficients in the higher bit significance level planes are encoded at earlier stages of the encoding process than transform coefficients in lower bit significance level planes. A corresponding process of decoding is also disclosed.

Montesi L.G.J.,University of Maryland University College
Journal of Structural Geology | Year: 2013

Lithospheric deformation on Earth is localized under both brittle and ductile deformation conditions. As high-temperature ductile rheologies are fundamentally strain-rate hardening, the formation of localized ductile shear zones must involve a structural or rheological change or a change in deformation conditions such as an increase in temperature. In this contribution, I develop a localization potential that quantifies the weakening associated with these changes. The localization potential corresponds to the increase in strain rate resulting from that change under constant stress conditions. I provide analytical expressions for the localization potential associated with a temperature increase, grain size reduction, an increase in water fugacity, melt content, or the abundance of a weak mineral phase. I show that these processes cannot localize deformation from a mantle convection scale (103 km) to a ductile shear zone scale (1 km). To achieve this, is it necessary to invoke a structural transition whereby the weak phase in a rock forms interconnected layers. This process is efficient only if one phase is much weaker than the others or if the weakest phase has a highly non-linear rheology. Micas, melt, and fine-grained aggregates - unless dry rheologies are used - have the necessary characteristics. As none of these phases is expected to be present in the dry lithosphere of Venus, this concept can explain why Venus, unlike the Earth, does not display a global network of plate boundaries. The diffuse plate boundary in the Central Indian Ocean may be as yet non-localized because serpentinization has not reached the ductile levels of the lithosphere. © 2013 Elsevier Ltd.

Fang W.,Zhejiang University | St. Leger R.J.,University of Maryland University College
PLoS ONE | Year: 2012

The low survival of microbial pest control agents exposed to UV is the major environmental factor limiting their effectiveness. Using gene disruption we demonstrated that the insect pathogenic fungus Metarhizium robertsii uses photolyases to remove UV-induced cyclobutane pyrimidine dimers (CPD) and pyrimidine (6-4) photoproducts [(6-4)PPs] from its DNA. However, this photorepair is insufficient to fix CPD lesions and prevent the loss of viability caused by seven hours of solar radiation. Expression of a highly efficient archaeal (Halobacterium salinarum) CPD photolyase increased photorepair &30-fold in both M. robertsii and Beauveria bassiana. Consequently, transgenic strains were much more resistant to sunlight and retained virulence against the malaria vector Anopheles gambiae. In the field this will translate into much more efficient pest control over a longer time period. Conversely, our data shows that deleting native photolyase genes will strictly contain M. robertsii to areas protected from sunlight, alleviating safety concerns that transgenic hypervirulent Metarhizium spp will spread from mosquito traps or houses. The precision and malleability of the native and transgenic photolyases allows design of multiple pathogens with different strategies based on the environments in which they will be used. © 2012 Fang, St. Leger.

Brown M.,University of Maryland University College
Bulletin of the Geological Society of America | Year: 2013

At low temperatures (<750 °C at moderate to high crustal pressures), the production of sufficient melt to reach the melt connectivity transition (~7 vol%), enabling melt drainage, requires an influx of aqueous fluid along structurally controlled pathways or recycling of fluid via migration of melt and exsolution during crystallization. At higher temperatures, melting occurs by fluid-absent reactions, particularly hydrate-breakdown reactions involving micas and/or amphibole in the presence of quartz and feldspar. These reactions produce 20-70 vol%, melt according to protolith composition, at temperatures up to 1000 °C. Calculated phase diagrams for pelite are used to illustrate the mineralogical controls on melt production and the consequences of different clockwise pressure-temperature (P-T) paths on melt composition. Preservation of peritectic minerals in residual granulites requires that most of the melt produced was extracted, implying a flux of melt through the suprasolidus crust, although some may be trapped during transport, as recorded by composite migmatitegranite complexes. Peritectic minerals may be entrained during melt drainage, consistent with observations from leucosomes in migmatites, and dissolution of these minerals during ascent may be important in the evolution of some crustal magmas. Since siliceous melt wets grains, suprasolidus crust may become porous at only a few volume % melt, as evidenced by microstructures in residual migmatites in which quartz or feldspar pseudomorphs form after melt films and pockets. With increasing melt volume and decreasing effective pressure, assuming the residue is able to deform and compact, the source becomes permeable at the melt connectivity transition. At this threshold, a change from distributed shear-enhanced compaction to localized dilatant shear failure enables melt segregation. The result is a highly permeable vein network that allows transfer of melt to ascent conduits at the initiation of a melt-extraction event. Melt is drained from the anatectic zone via several extraction events, consistent with evidence for incremental construction of plutons from multiple batches of magma. Buoyancy-driven magma ascent occurs via dikes in fractures or via high-permeability zones controlled by tectonic fabrics; the way in which these features relate to compaction and the generation of porosity waves is discussed. Emplacement of laccoliths (horizontal tabular intrusions) and wedge-shaped plutons occurs around the ductile-to-brittle transition zone, whereas steep tabular sheeted and blobby plutons represent back freezing of melt in the ascent conduit or lateral expansion localized by instabilities in the magma-wallrock system, respectively. © 2013 Geological Society of America.

Kelley D.R.,University of Maryland University College | Salzberg S.L.,University of Maryland University College
Genome Biology | Year: 2010

Diploid genomes with divergent chromosomes present special problems for assembly software as two copies of especially polymorphic regions may be mistakenly constructed, creating the appearance of a recent segmental duplication. We developed a method for identifying such false duplications and applied it to four vertebrate genomes. For each genome, we corrected mis-assemblies, improved estimates of the amount of duplicated sequence, and recovered polymorphisms between the sequenced chromosomes. © 2010 Kelley and Salzberg; licensee BioMed Central Ltd.

Flores-Lopez C.A.,University of Maryland University College
PLoS neglected tropical diseases | Year: 2011

The genetic diversity of Trypanosoma cruzi, the etiological agent of Chagas disease, has been traditionally divided in two major groups, T. cruzi I and II, corresponding to discrete typing units TcI and TcII-VI under a recently proposed nomenclature. The two major groups of T. cruzi seem to differ in important biological characteristics, and are thus thought to represent a natural division relevant for epidemiological studies and development of prophylaxis. To understand the potential connection between the different manifestations of Chagas disease and variability of T. cruzi strains, it is essential to have a correct reconstruction of the evolutionary history of T. cruzi. Nucleotide sequences from 32 unlinked loci (>26 Kilobases of aligned sequence) were used to reconstruct the evolutionary history of strains representing the known genetic variability of T. cruzi. Thorough phylogenetic analyses show that the original classification of T. cruzi in two major lineages does not reflect its evolutionary history and that there is only strong evidence for one major and recent hybridization event in the history of this species. Furthermore, estimates of divergence times using Bayesian methods show that current extant lineages of T. cruzi diverged very recently, within the last 3 million years, and that the major hybridization event leading to hybrid lineages TcV and TcVI occurred less than 1 million years ago, well before the contact of T. cruzi with humans in South America. The described phylogenetic relationships among the six major genetic subdivisions of T. cruzi should serve as guidelines for targeted epidemiological and prophylaxis studies. We suggest that it is important to reconsider conclusions from previous studies that have attempted to uncover important biological differences between the two originally defined major lineages of T. cruzi especially if those conclusions were obtained from single or few strains.

Link L.E.,University of Maryland University College
Ocean Engineering | Year: 2010

Hurricane Katrina created the one of the worst natural disaster in the history of the United States, resulting in over 1600 fatalities and $30B in direct economic losses in southern Louisiana. The Louisiana and Mississippi coastlines experienced the highest surge level recorded in North America and Katrina-generated waves in the Gulf of Mexico that equaled the highest previously measured by NOAA buoys. What happened in New Orleans epitomizes the risk of living below sea level in a coastal city, depending on structures that were the result of considerable compromise and piecemeal funding and construction. The Interagency Performance Evaluation Task Force was established to examine the performance of the New Orleans and southeast Louisiana hurricane protection system and provide real-time input to the repairs and rebuilding of the system. In addition to this atypical just-in-time forensic analysis, the task force examined the risk of living in New Orleans prior to and following the repairs to the hurricane protection system. Much of the forensic analysis depended on modeling and simulation of hurricane surge and waves. With virtually all measurement instruments swept away by Katrina, only models and high-water marks were available to recreate the conditions that the structures experienced during the storm. Because of the complexities of the region and the processes involved, simulation of hurricane surge and waves required many fresh ideas and new approaches and these topics, along with new concepts for future planning and design, are the focus of this special issue. Yet, the need to influence the repair and rebuilding of the damaged structures prior to the next hurricane season (roughly 9 months) dictated using existing computational tools that were ready to go. The same modeling and simulation approach was put to work to define the surge and wave hazard New Orleans faces for the future. To put this important body of work in context, this paper provides a broad overview of the entire scope of work of the task force and summarizes its principal findings. © 2009 Elsevier Ltd.

Cheng M.,Microsoft | Cheng M.,University of Maryland University College | Gu Z.-C.,California Institute of Technology
Physical Review Letters | Year: 2014

It has been shown that the symmetry-protected topological (SPT) phases with finite Abelian symmetries can be described by Chern-Simons field theory. We propose a topological response theory to uniquely identify the SPT orders, which allows us to obtain a systematic scheme to classify bosonic SPT phases with any finite Abelian symmetry group. We point out that even for finite Abelian symmetry, there exist bosonic SPT phases beyond the current Chern-Simons theory framework. We also apply the theory to fermionic SPT phases with Zm symmetry and find the classification of SPT phases depends on the parity of m: for even m there are 2m classes, m out of which is intrinsically fermionic SPT phases and cannot be realized in any bosonic system. Finally we propose a classification scheme of fermionic SPT phases for any finite, Abelian symmetry. © 2014 American Physical Society.

Senthil T.,Massachusetts Institute of Technology | Levin M.,University of Maryland University College
Physical Review Letters | Year: 2013

A simple physical realization of an integer quantum Hall state of interacting two dimensional bosons is provided. This is an example of a symmetry-protected topological (SPT) phase which is a generalization of the concept of topological insulators to systems of interacting bosons or fermions. Universal physical properties of the boson integer quantum Hall state are described and shown to correspond with those expected from general classifications of SPT phases. © 2013 American Physical Society.

Cooper E.D.,University of Maryland University College
Trends in Plant Science | Year: 2014

Phylogenetic analysis is an increasingly common and valuable component of plant science. Knowledge of the phylogenetic relationships between plant groups is a prerequisite for understanding the origin and evolution of important plant features, and phylogenetic analysis of individual genes and gene families provides fundamental insights into how those genes and their functions evolved. However, despite an active research community exploring and improving phylogenetic methods, the analytical methods commonly used, and the phylogenetic results they produce, are accorded far more confidence than they warrant. In this opinion article, I emphasise that important parts of the green plant phylogeny are inconsistently resolved and I argue that the lack of consistency arises due to inadequate modelling of changes in the substitution process. © 2014 Elsevier Ltd.

Baraldi A.,University of Maryland University College
IEEE Transactions on Geoscience and Remote Sensing | Year: 2011

Proposed in recent literature, a novel two-stage stratified hierarchical hybrid remote-sensing image understanding system (RS-IUS) architecture comprises the following: 1) a first-stage pixel-based application-independent top-down (physical-model-driven and prior-knowledge-based) preliminary classifier and 2) a second-stage battery of stratified hierarchical context-sensitive application-dependent modules for class-specific feature extraction and classification. The first-stage preliminary classifier is implemented as an operational automatic near-real-time per-pixel multisource multiresolution application-independent spectral-rule-based decision-tree classifier (SRC). To the best of the author's knowledge, SRC provides the first operational example of an automatic multisensor multiresolution Earth-observation (EO) system of systems envisaged under ongoing international research programs such as the Global Earth Observation System of Systems (GEOSS) and the Global Monitoring for the Environment and Security (GMES). For the sake of simplicity, the original SRC formulation adopts crisp (hard) membership functions unsuitable for dealing with component cover classes of mixed pixels (class mixture). In this paper, the crisp (hierarchical) SRC first stage of a two-stage hybrid RS-IUS is replaced by a fuzzy (horizontal) SRC. In operational terms, a relative comparison of the fuzzy SRC against its crisp counterpart reveals that the former features the following: 1) the same degree of automation which cannot be surpassed, i.e., they are both "fully automatic"; 2) a superior map information/knowledge representation where component cover classes of mixed pixels are modeled; 3) the same robustness to changes in the input multispectral imagery acquired across time, space, and sensors; 4) a superior maintainability/scalability/reusability guaranteed by an internal horizontal (flat) modular structure independent of hierarchy; and 5) a computation time increased by 30% in a single-process single-thread implementation. This computation overload would reduce to zero in a single-process multithread implementation. In line with theory, the conclusion of this work is that the operational qualities of the fuzzy and crisp SRCs differ, but both SRCs are suitable for the development of operational automatic near-real-time multisensor satellite-based measurement systems such as those conceived as a visionary goal by the ongoing GEOSS and GMES research initiatives. © 2011 IEEE.

Fisher D.R.,University of Maryland University College
Environment and Planning C: Government and Policy | Year: 2013

In this paper, I look at how subnational policies in the United States are interacting with policy making at the federal level to address the issue of global climate change. I focus on a coordinated attempt to get the national government to fund local efforts to address climate change. Although local climate initiatives in the US were successfully translated into a national policy to support these local efforts, their implementation through hybrid arrangements that are being formed between business and local governmental actors will potentially create additional challenges to federal policy making. I introduce the notion of boomerang federalism, which builds on the extant research on federalism and vertical policy integration, to explain the process through which local efforts mobilize initiatives at the national level that, in turn, provide support for the local initiatives themselves. Reviewing the implementation process of this effort, I discuss the ways that businesses are working alongside local governments to address climate change.

McGaugh S.S.,University of Maryland University College
Physical Review Letters | Year: 2011

The current cosmological paradigm, the cold dark matter model with a cosmological constant, requires that the mass-energy of the Universe be dominated by invisible components: dark matter and dark energy. An alternative to these dark components is that the law of gravity be modified on the relevant scales. A test of these ideas is provided by the baryonic Tully-Fisher relation (BTFR), an empirical relation between the observed mass of a galaxy and its rotation velocity. Here, I report a test using gas rich galaxies for which both axes of the BTFR can be measured independently of the theories being tested and without the systematic uncertainty in stellar mass that affects the same test with star dominated spirals. The data fall precisely where predicted a priori by the modified Newtonian dynamics. The scatter in the BTFR is attributable entirely to observational uncertainty, consistent with a single effective force law. © 2011 American Physical Society.

Wilson J.H.,University of Maryland University College | Galitski V.,University of Maryland University College
Physical Review Letters | Year: 2011

We show how the time-continuous coherent state path integral breaks down for both the single-site Bose-Hubbard model and the spin-path integral. Specifically, when the Hamiltonian is quadratic in a generator of the algebra used to construct coherent states, the path integral fails to produce correct results following from an operator approach. As suggested by previous authors, we note that the problems do not arise in the time-discretized version of the path integral. © 2011 American Physical Society.

Chacko Z.,University of Maryland University College | Mishra R.K.,University of Maryland University College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We consider scenarios where strong conformal dynamics constitutes the ultraviolet completion of the physics that drives electroweak symmetry breaking. We show that in theories where the operator responsible for the breaking of conformal symmetry is close to marginal at the breaking scale, the dilaton mass can naturally lie below the scale of the strong dynamics. However, in general, this condition is not satisfied in the scenarios of interest for electroweak symmetry breaking, and so the presence of a light dilaton in these theories is associated with mild tuning. We construct the effective theory of the light dilaton in this framework and determine the form of its couplings to Standard Model states. We show that corrections to the form of the dilaton interactions arising from conformal symmetry violating effects are suppressed by the square of the ratio of the dilaton mass to the strong coupling scale and are under good theoretical control. These corrections are generally subleading, except in the case of dilaton couplings to marginal operators, when symmetry violating effects can sometimes dominate. We investigate the phenomenological implications of these results for models of technicolor, and for models of the Higgs as a pseudo-Nambu-Goldstone boson, that involve strong conformal dynamics in the ultraviolet. © 2013 American Physical Society.

Dheeraj P.R.,University of Maryland University College | Strohmayer T.E.,NASA
Astrophysical Journal | Year: 2012

We present results of new XMM-Newton observations of the ultraluminous X-ray source (ULX) NGC5408 X-1, one of the few ULXs to show quasi-periodic oscillations (QPOs). We detect QPOs in each of four new (100ks) pointings, expanding the range of frequencies observed from 10 to 40mHz. We compare our results with the timing and spectral correlations seen in stellar-mass black hole systems, and find that the qualitative nature of the timing and spectral behavior of NGC5408 X-1 is similar to systems in the steep power-law state exhibiting Type-C QPOs. However, in order for this analogy to quantitatively hold we must only be seeing the so-called saturated portion of the QPO frequency - photon index (or disk flux) relation. Assuming this to be the case, we place a lower limit on the mass of NGC5408 X-1 of ≳ 800 M . Alternatively, the QPO frequency is largely independent of the spectral parameters, in which case a close analogy with the Type-C QPOs in stellar systems is problematic. Measurement of the source's timing properties over a wider range of energy spectral index is needed to definitively resolve this ambiguity. We searched all the available data for both a broad Fe emission line as well as high-frequency QPO analogs (0.1-1Hz), but detected neither. We place upper limits on the equivalent width of any Fe emission feature in the 6-7keV band and of the amplitude (rms) of a high-frequency QPO analog of 10eV and 4%, respectively. © 2012. The American Astronomical Society. All rights reserved..

Gralla S.E.,University of Maryland University College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

Previous work established a universal form for the equation of motion of small bodies in theories of a metric and other tensor fields that have second-order field equations following from a covariant Lagrangian in four spacetime dimensions. Differences in the motion of the "same" body in two different theories are entirely accounted for by differences in the body's effective mass and charges in those different theories. Previously the process of computing the mass and charges for a particular body was left implicit, to be determined in each particular theory as the need arises. I now obtain explicit expressions for the mass and charges of a body as surface integrals of the fields it generates, where the integrand is constructed from the symplectic current for the theory. This allows the entire prescription for computing the motion of a small body to be written down in a few lines, in a manner universal across bodies and theories. For simplicity I restrict to scalar and vector fields (in addition to the metric), but there is no obstacle to treating higher-rank tensor fields. I explicitly apply the prescription to work out specific equations for various body types in Einstein gravity, generalized Brans-Dicke theory (in both Jordan and Einstein frames), Einstein-Maxwell theory and the Will-Nordvedt vector-tensor theory. In the scalar-tensor case, this clarifies the origin and meaning of the "sensitivities" defined by Eardley and others, and provides explicit formulas for their evaluation. © 2013 American Physical Society.

Cooley S.,University of Maryland University College | Killen M.,University of Maryland University College
Developmental Psychology | Year: 2015

This study investigated children's evaluations of peer group members who deviated from group norms about equal and unequal allocation of resources. Children, ages 3.5 to 4 years and 5 to 6 years (N = 73), were asked to evaluate a peer group member who deviated from 1 of 2 group allocation norms: (a) equal allocation of resources, or (b) unequal allocation of resources. Most children negatively evaluated deviant group members who espoused an unequal allocation, even when it benefitted the group, and explained their evaluation with reference to fairness. However, participants who liked unequal deviants (who advocated for an unequal allocation of resources) reasoned about group functioning and the benefits that an unequal allocation would have for the group. With age, children displayed social acumen by differentiating their own evaluation of the deviant act from their expectations of the group's favorability toward that deviant member. Findings revealed age-related increases for social acumen about group norms, as well as the use of fairness reasoning regarding resource allocation. © 2015 American Psychological Association.

Rossi E.,College of William and Mary | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2011

The inhomogenous real-space electronic structure of gapless and gapped disordered bilayer graphene is calculated in the presence of quenched charge impurities. For gapped bilayer graphene, we find that for current experimental conditions the amplitude of the fluctuations of the screened disorder potential is of the order of (or often larger than) the intrinsic gap Δ induced by the application of a perpendicular electric field. We calculate the crossover chemical potential Δcr, separating the insulating regime from a percolative regime in which less than half of the area of the bilayer graphene sample is insulating. We find that most of the current experiments are in the percolative regime with ΔcrΔ. The huge suppression of Δcr compared with Δ provides a possible explanation for the large difference between the theoretical band gap Δ and the experimentally extracted transport gap. © 2011 American Physical Society.

Smolyaninov I.I.,University of Maryland University College
Physical Review Letters | Year: 2011

As demonstrated by Chernodub, vacuum in a strong magnetic field behaves as Abrikosov vortex lattice in a type-II superconductor. We investigate electromagnetic behavior of vacuum in this state and demonstrate that vacuum behaves as a hyperbolic metamaterial. If the magnetic field is constant, low frequency extraordinary photons experience this medium as a (3+1) Minkowski spacetime in which the role of time is played by the spatial z coordinate. Variations of the magnetic field curve this spacetime, and may lead to formation of "electromagnetic black holes." Since hyperbolic metamaterials behave as diffractionless "perfect lenses," and large enough magnetic fields probably existed in the early Universe, the demonstrated hyperbolic behavior of early vacuum may have imprints in the large scale structure of the present-day Universe. © 2011 American Physical Society.

Park K.,University of Maryland University College | Ricotti M.,University of Maryland University College
Astrophysical Journal | Year: 2012

This paper, the second in a series on radiation-regulated accretion onto black holes (BHs) from galactic scales, focuses on the effects of radiation pressure and angular momentum of the accreting gas. We simulate accretion onto intermediate-mass black holes, but we derive general scaling relationships that are solutions of the Bondi problem with radiation feedback valid for any mass of the BH M bh. Thermal pressure of the ionized sphere around the BH regulates the accretion rate, producing periodic and short-lived luminosity bursts. We find that for ambient gas densities exceeding n cr H, ∞M -1 bh, the period of the oscillations decreases rapidly and the duty cycle increases from 6%, in agreement with observations of the fraction of active galactic nuclei at z ∼ 3, to 50%. The mean accretion rate becomes Eddington limited for n H, ∞ > n Edd H, ∞ ≃ n cr H, ∞ T ∞, 4 -1 where T ∞, 4 is the gas temperature in units of 104K. In the sub-Eddington regime, the mean accretion rate onto BHs is about 1%T 2.5 ∞, 4 of the Bondi rate, and thus is proportional to the thermal pressure of the ambient medium. The period of the oscillations coincides with the depletion timescale of the gas inside the ionized bubble surrounding the BH. Gas depletion is dominated by a pressure gradient pushing the gas outward if n H, ∞ < n cr H, ∞ and by accretion onto the BH otherwise. Generally, for n H, ∞ < n cr H, ∞ angular momentum does not significantly affect the accretion rate and period of the oscillations. © 2012 The American Astronomical Society. All rights reserved.

Paoletti M.S.,Institute for Research in Electronics and Applied Physics | Lathrop D.P.,Institute for Research in Electronics and Applied Physics | Lathrop D.P.,University of Maryland University College
Physical Review Letters | Year: 2011

We present measurements of the angular momentum flux (torque) in Taylor-Couette flow of water between independently rotating cylinders for all regions of the (Ω1, Ω2) parameter space at high Reynolds numbers, where Ω1 (Ω2) is the inner (outer) cylinder angular velocity. We find that the Rossby number Ro=(Ω1-Ω2)/Ω2 fully determines the state and torque G as compared to G(Ro=∞)≡G ∞. The ratio G/G∞ is a linear function of Ro⊃-1 in four sections of the parameter space. For flows with radially increasing angular momentum, our measured torques greatly exceed those of previous experiments, but agree with the analysis of Richard and Zahn. © 2011 The American Physical Society.

Plunk G.G.,University of Maryland University College | Tatsuno T.,University of Maryland University College
Physical Review Letters | Year: 2011

The question of how nonlinear interactions redistribute the energy of fluctuations across available degrees of freedom is of fundamental importance in the study of turbulence and transport in magnetized weakly collisional plasmas, ranging from space settings to fusion devices. In this Letter, we present a theory for the dual cascade found in such plasmas, which predicts a range of new behavior that distinguishes this cascade from that of neutral fluid turbulence. These phenomena are explained in terms of the constrained nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory are the first observations of these phenomena, obtained via direct numerical simulations using the gyrokinetic code AstroGK. The basic mechanisms that are found provide a framework for understanding the turbulent energy transfer that couples scales both locally and nonlocally. © 2011 American Physical Society.

Cui Y.,University of Maryland University College | Sundrum R.,University of Maryland University College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We propose a robust, unified framework, in which the similar baryon and dark matter cosmic abundances both arise from the physics of weakly interacting massive particles (WIMPs), with the rough quantitative success of the so-called "WIMP miracle." In particular the baryon asymmetry arises from the decay of a metastable WIMP after its thermal freeze-out at or below the weak scale. A minimal model and its embedding in R-parity violating supersymmetry are studied as examples. The new mechanism saves R-parity violating supersymmetry from the potential crisis of washing out primordial baryon asymmetry. Phenomenological implications for the LHC and precision tests are discussed. © 2013 American Physical Society.

Hyeon C.,Korea Institute for Advanced Study | Hinczewski M.,University of Maryland University College | Thirumalai D.,University of Maryland University College
Physical Review Letters | Year: 2014

Heterogeneity in biological molecules, resulting in molecule-to-molecule variations in their dynamics and function, is an emerging theme. To elucidate the consequences of heterogeneous behavior at the single molecule level, we propose an exactly solvable model in which the unfolding rate due to mechanical force depends parametrically on an auxiliary variable representing an entropy barrier arising from fluctuations in internal dynamics. When the rate of fluctuations - a measure of dynamical disorder - is comparable to or smaller than the rate of force-induced unbinding, we show that there are two experimentally observable consequences: nonexponential survival probability at constant force, and a heavy-tailed rupture force distribution at constant loading rate. By fitting our analytical expressions to data from single molecule pulling experiments on proteins and DNA, we quantify the extent of disorder. We show that only by analyzing data over a wide range of forces and loading rates can the role of disorder due to internal dynamics be quantitatively assessed. © 2014 American Physical Society.

Mosleh A.,University of Maryland University College
Nuclear Engineering and Technology | Year: 2014

Probabilistic risk assessment (PRA) has been used in various technological fields to assist regulatory agencies, managerial decision makers, and systems designers in assessing and mitigating the risks inherent in these complex arrangements. Has PRA delivered on its promise? How do we gage PRA performance? Are our expectations about value of PRA realistic? Are there disparities between what we get and what we think we are getting form PRA and its various derivatives? Do current PRAs reflect the knowledge gained from actual events? How do we address potential gaps? These are some of the questions that have been raised over the years since the inception of the field more than forty years ago. This paper offers a brief assessment of PRA as a technical discipline in theory and practice, its key strengths and weaknesses, and suggestions on ways to address real and perceived shortcomings.

Kim K.,University of Maryland University College | Murphy T.E.,University of Maryland University College
Optics Express | Year: 2013

Optical waveguides comprised of nanoporous materials are uniquely suited for on-chip sensing applications, because they allow for a target chemical or analyte to directly infiltrate the optical material that comprises the core of the waveguide. We describe here the fabrication and characterization of nanoporous waveguides, and demonstrate their usefulness in measuring small changes in refractive index when exposed to a test analyte. We use a process of electrochemical etching and laser oxidation to produce channel waveguides and integrated on-chip Mach-Zehnder structures, and we compare the responsivity and interferometric stability of the integrated sensor to that of a fiber-based interferometer. We quantify the detection capability by selectively applying isopropanol to a 200μm length waveguide segment in one arm of the interferometer, which produces a phase shift of 9.7π. The integrated interferometer is shown to provide a more stable response in comparison to a comparable fiber-based implementation. © 2013 Optical Society of America.

Gupta S.,University of Maryland University College | Waks E.,University of Maryland University College
Optics Express | Year: 2013

We demonstrate spontaneous emission rate enhancement and saturable absorption of cadmium selenide colloidal quantum dots coupled to a nanobeam photonic crystal cavity. We perform time-resolved lifetime measurements and observe an average enhancement of 4.6 for the spontaneous emission rate of quantum dots located at the cavity as compared to those located on an unpatterned surface. We also demonstrate that the cavity linewidth narrows with increasing pump intensity due to quantum dot saturable absorption. © 2013 Optical Society of America.

Yan J.,University of Maryland University College | Fuhrer M.S.,University of Maryland University College
Physical Review Letters | Year: 2011

We study electron transport properties of graphene in the presence of correlated charged impurities via adsorption and thermal annealing of potassium atoms. For the same density of charged scattering centers, the sample mobility sensitively depends on temperature which sets the correlation length between the scatterers. The data are well-understood by a recent theory that allows us to quantitatively extract the temperature dependence of the correlation length. Impurity correlations also offer a self-consistent explanation to the puzzling sublinear carrier-density dependence of conductivity commonly observed in monolayer graphene samples on substrates. © 2011 American Physical Society.

Appelbaum I.,University of Maryland University College
Applied Physics Letters | Year: 2013

I address the measurement of density of states within and beyond the superconducting gap in tunnel-coupled finite-size nanostructures using a capacitive method. Third-harmonic generation is used to yield the full differential conductance spectrum without destruction of the low dimensionality otherwise induced by intimate ohmic coupling to an electrode. The method is particularly relevant to attempts to discern the presence of the fragile Majorana fermion quasiparticle at the end of spin-orbit-coupled nanowires in appropriate magnetic field conditions by their signature mid-gap density of states. © 2013 AIP Publishing LLC.

Zhou Q.,University of Maryland University College | Ho T.-L.,Ohio State University
Physical Review Letters | Year: 2011

Quantum simulation is a highly ambitious program in cold atom research currently being pursued in laboratories worldwide. The goal is to use cold atoms in optical lattices to simulate models for unsolved strongly correlated systems, so as to deduce their properties directly from experimental data. An important step in this effort is to determine the temperature of the system, which is essential for deducing all thermodynamic functions. This step, however, remains difficult for lattice systems at the moment. Here, we propose a method based on a generalized fluctuation-dissipation theorem. It does not rely on numerical simulations and gives a universal thermometry scheme for quantum gas systems including mixtures and spinor gases, provided that the local density approximation is valid. © 2011 American Physical Society.

Lin G.-D.,University of Michigan | Monroe C.,University of Maryland University College | Duan L.-M.,University of Michigan
Physical Review Letters | Year: 2011

Sharp quantum phase transitions typically require a large system with many particles. Here we show that, for a frustrated fully connected Ising spin network represented by trapped atomic ions, the competition between different spin orders leads to rich phase transitions whose sharpness scales exponentially with the number of spins. This unusual finite-size scaling behavior opens up the possibility of observing sharp quantum phase transitions in a system of just a few trapped ion spins. © 2011 American Physical Society.

Reames D.V.,University of Maryland University College
Astrophysical Journal | Year: 2012

We have searched for evidence of significant shock acceleration of He ions of ∼1-10MeVamu-1 in situ at 258interplanetary traveling shock waves observed by the Wind spacecraft. We find that the probability of observing significant acceleration, and the particle intensity observed, depends strongly upon the shock speed and less strongly upon the shock compression ratio. For most of the 39 fast shocks with significant acceleration, the observed spectral index agrees with either that calculated from the shock compression ratio or with the spectral index of the upstream background, when the latter spectrum is harder, as expected from diffusive shock theory. In many events the spectra are observed to roll downward at higher energies, as expected from Ellison-Ramaty and from Lee shock-acceleration theories. The dearth of acceleration at ∼85% of the shocks is explained by (1) a low shock speed, (2) a low shock compression ratio, and (3) a low value of the shock-normal angle with the magnetic field, which may cause the energy spectra that roll downward at energies below our observational threshold. Quasi-parallel shock waves are rarely able to produce measurable acceleration at 1AU. The dependence of intensity on shock speed, seen here at local shocks, mirrors the dependence found previously for the peak intensities in large solar energetic-particle events upon speeds of the associated coronal mass ejections which drive the shocks. © 2012 The American Astronomical Society. All rights reserved.

Barnes E.,University of Maryland University College | Economou S.E.,U.S. Navy
Physical Review Letters | Year: 2011

We introduce a method for solving the problem of an externally controlled electron spin in a quantum dot interacting with host nuclei via the hyperfine interaction. Our method accounts for generalized (nonunitary) evolution effected by external controls and the environment, such as coherent lasers combined with spontaneous emission. As a concrete example, we develop the microscopic theory of the dynamics of nuclear-induced frequency focusing as first measured in Science 317, 1896 (2007)SCIEAS0036-807510.1126/science.1146850; we find that the nuclear relaxation rates are several orders of magnitude faster than those quoted in that work. © 2011 American Physical Society.

Adelfio M.D.,University of Maryland University College | Samet H.,University of Maryland University College
Proceedings of the VLDB Endowment | Year: 2013

Tabular data is an abundant source of information on the Web, but remains mostly isolated from the latter's interconnections since tables lack links and computer-accessible descriptions of their structure. In other words, the schemas of these tables-attribute names, values, data types, etc.- are not explicitly stored as table metadata. Consequently, the structure that these tables contain is not accessible to the crawlers that power search engines and thus not accessible to user search queries. We address this lack of structure with a new method for leveraging the principles of table construction in order to extract table schemas. Discovering the schema by which a table is constructed is achieved by harnessing the similarities and differences of nearby table rows through the use of a novel set of features and a feature processing scheme. The schemas of these data tables are determined using a classification technique based on conditional random fields in combination with a novel feature encoding method called logarithmic binning, which is specifically designed for the data table extraction task. Our method provides considerable improvement over the wellknown WebTables schema extraction method. In contrast with previous work that focuses on extracting individual relations, our method excels at correctly interpreting full tables, thereby being capable of handling general tables such as those found in spreadsheets, instead of being restricted to HTML tables as is the case with theWebTables method. We also extract additional schema characteristics, such as row groupings, which are important for supporting information retrieval tasks on tabular data. © 2013 VLDB Endowment.

Akamatsu Y.,Nagoya University | Yamamoto N.,Kyoto University | Yamamoto N.,University of Maryland University College
Physical Review Letters | Year: 2013

We study the collective modes in relativistic electromagnetic or quark-gluon plasmas with an asymmetry between left- and right-handed chiral fermions, based on the recently formulated kinetic theory with Berry curvature corrections. We find that there exists an unstable mode, signaling the presence of a plasma instability. We argue the fate of this "chiral plasma instability" including the effect of collisions, and briefly discuss its relevance in heavy ion collisions and compact stars. © 2013 American Physical Society.

Hu L.,University of Maryland University College | Wu H.,Stanford University | Cui Y.,Stanford University
MRS Bulletin | Year: 2011

Metals possess the highest conductivity among all room-temperature materials; however, ultrathin metal films demonstrate decent optical transparency but poor sheet conductance due to electron scattering from the surface and grain boundaries. This article discusses engineered metal nanostructures in the form of nanogrids, nanowires, or continuous nanofibers as efficient transparent and conductive electrodes. Metal nanogrids are discussed, as they represent an excellent platform for understanding the fundamental science. Progress toward low-cost, nano-ink-based printed silver nanowire electrodes, including silver nanowire synthesis, film fabrication, wire-wire junction resistance, optoelectronic properties, and stability, are also discussed. Another important factor for low-cost application is to use earth-abundant materials. Copper-based nanowires and nanofibers are discussed in this context. Examples of device integrations of these materials are also given. Such metal nanostructure-based transparent electrodes are particularly attractive for solar cell applications. © 2011 Materials Research Society.

Oard D.W.,University of Maryland University College | Webber W.,University of Maryland University College
Foundations and Trends in Information Retrieval | Year: 2013

E-discovery refers generally to the process by which one party (for example, the plaintiff) is entitled to "discover" evidence in the form of "electronically stored information" that is held by another party (for example, the defendant), and that is relevant to some matter that is the subject of civil litigation (that is, what is commonly called a "lawsuit"). This survey describes the emergence of the field, identifies the information retrieval issues that arise, reviews the work to date on this topic, and summarizes major open issues. © 2013 D. W. Oard and W. Webber.

Son D.T.,University of Chicago | Yamamoto N.,Kyoto University | Yamamoto N.,University of Maryland University College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

A kinetic theory can be modified to incorporate triangle anomalies and the chiral magnetic effect by taking into account the Berry curvature flux through the Fermi surface. We show how such a kinetic theory can be derived from underlying quantum field theories. Using the new kinetic theory, we also compute the parity-odd correlation function that is found to be identical to the result in the perturbation theory in the next-to-leading order hard dense loop approximation. © 2013 American Physical Society.

Das S.,University of Maryland University College
Colloids and Surfaces A: Physicochemical and Engineering Aspects | Year: 2014

A charged soft interface is characterized by a charged polyelectrolyte layer (PEL) sandwiched between an uncharged rigid surface and an electrolyte solution. The PEL harbors or consists of a particular kind of ion (henceforth denoted as PEL ion), different from the electrolyte ions. The PEL ions remain excluded from locations outside the PEL. This gives rise to a Donnan potential (ψD) deep within the PEL, with the PEL-electrolyte interface (having an electrostatic potential, also called the surface potential, ψ0) behaving as a possible ion-selective permeable membrane. In this paper, we provide closed-form explicit analytical expressions for the interrelationship between ψD and ψ0 for both positively and negatively charged PEL with pH-dependent charge densities. We demonstrate that for a given magnitude of ψD, magnitude of ψ0 is identical for both positively and negatively charged PEL, dictated only by a parameter α, which depends on the difference between pH and pKa values for negatively charged PEL or the difference between pKb and pOH values for positively charged PEL. Most importantly, derivation of explicit form of interrelationship between ψD and ψ0, hitherto missing in the existing literature, allows us to provide substantially new insights into the relative variation of ψD and ψ0 and at the same time helps us to rectify several earlier misconceptions. Further, using this explicit relationship, it becomes possible to quantify the capacitance of a soft interface as explicit functions of α and the Donnan potential, with relevance for development of possible soft-interface-based energy storage system. © 2014 Elsevier B.V.

Chakraborty P.,University of Maryland University College | Zachariah M.R.,University of Maryland University College
Combustion and Flame | Year: 2014

It is axiomatic that the burning time dependence on particle size follows an integer power law dependence. However, a considerable body of experimental data show a power dependence less than unity. In this paper, we focus on what might be responsible for the fractional power dependence observed for the burning time for nanoparticles (e.g. Al and B). Specifically we employ reactive molecular dynamics simulations of oxide-coated aluminum nanoparticles (Al-NPs). Since most nanomaterials experimentally investigated are aggregates, we study the behavior of the simplest aggregate - a doublet of two spheres. The thermo-mechanical response of an oxide coated Al-NP is found to be very different than its solid alumina counterpart, and in particular we find that the penetration of the core aluminum cations into the shell significantly softens it, resulting in sintering well below the melting point of pure alumina. For such coated nanoparticles, we find a strong induced electric field exists at the core-shell interface. With heating, as the core melts, this electric field drives the core Al cations into the shell. The shell, now a sub-oxide of aluminum, melts at a temperature that is lower than the melting point of aluminum oxide. Following melting, the forces of surface tension drive two adjacent particles to fuse. The characteristic sintering time (heating time+. fusion time) is seen to be comparable to the characteristic reaction time, and thus it is quite possible for nanoparticle aggregates to sinter into structures with larger length scales, before the bulk of the combustion can take place. This calls into question what the appropriate 'effective size' of nanoparticle aggregates is. © 2013 The Combustion Institute.

Ball M.O.,University of Maryland University College
Surveys in Operations Research and Management Science | Year: 2011

This paper provides a survey of heuristics that make use of mathematical programming models and methods. The first class of methods covered break down a problem into a sequence of subproblems where each subproblem is modeled as a mathematical program and solved optimally. The second class of methods are improvement algorithms that solve a mathematical program to generate an improved solution from a known feasible solution. This class of techniques is also referred to as large-scale neighborhood search. The third class of methods considered employ a mathematical programming algorithm, most notably branch-and-bound, to generate an approximate solution to the problem of interest. Finally, we consider methods that solve a relaxation to the original problem of interest as a first step in generating a good feasible solution. © 2010 Elsevier Ltd.

Walker R.J.,University of Maryland University College
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2014

Discovery of small enrichments in 182W/184Win some Archaean rocks, relative to modern mantle, suggests both exogeneous and endogenous modifications to highly siderophile element (HSE) and moderately siderophile element abundances in the terrestrial mantle. Collectively, these isotopic enrichments suggest the formation of chemically fractionated reservoirs in the terrestrial mantle that survived the putative Moon-forming giant impact, and also provide support for the late accretion hypothesis. The lunar mantle sources of volcanic glasses and basalts were depleted in HSEs relative to the terrestrialmantle by at least a factor of 20. The most likely explanations for the disparity between the Earth and Moon are either that the Moon received a disproportionately lower share of late accreted materials than the Earth, such as may have resulted from stochastic late accretion, or the major phase of late accretion occurred prior to the Moon-forming event, and the putative giant impact led to little drawdown of HSEs to the Earth's core. High precision determination of the 182W isotopic composition of the Moon can help to resolve this issue. © 2014 The Author(s) Published by the Royal Society.

Bertrand C.E.,University of Maryland University College | Anisimov M.A.,University of Maryland University College
Journal of Physical Chemistry B | Year: 2011

On the basis of the principle of critical-point universality, we examine the peculiar thermodynamics of the liquid-liquid critical point in supercooled water. We show that the liquid-liquid criticality in water represents a special kind of critical behavior in fluids, intermediate between two limiting cases: the lattice gas, commonly used to model liquid-vapor transitions, and the lattice liquid, a weakly compressible liquid with an entropy-driven phase separation. While the ordering field in the lattice gas is associated with the chemical potential and the order parameter with the density, in the lattice liquid the ordering field is the temperature and the order parameter is the entropy. The behavior of supercooled water is much closer to lattice-liquid behavior than to lattice-gas behavior. Using new experimental data recently obtained by Mishima [ J. Chem. Phys. 2010, 133, 144503 ], we have revised the parametric scaled equation of state, previously suggested by Fuentevilla and Anisimov [ Phys. Rev. Lett. 2006, 97, 195702 ], and obtain a consistent description of the thermodynamic anomalies of supercooled water by adjusting linear backgrounds, one critical amplitude, and the critical pressure. We also show how the lattice-liquid description affects the finite-size scaling description of supercooled water in confined media. © 2011 American Chemical Society.

Sharia O.,University of Maryland University College | Kuklja M.M.,University of Maryland University College
Journal of Physical Chemistry B | Year: 2011

Exploration of initiation of chemistry in materials is especially challenging when several coexisting chemical mechanisms are possible and many reactions' products are produced. It is even more difficult for complex materials, such as molecular, supramolecular, and hierarchical materials and systems. A strategy to draw a complete picture of the earliest stages of rapid decomposition reactions in molecular materials is presented in this study. The strategy is based on theoretical and computational modeling of chemical decomposition reactions in the gaseous and crystalline molecular material that has been performed by means of combined density functional theory and transition state theory. This study reveals how a crystalline field affects materials chemical degradation. We also demonstrate how incomplete results, which are often used due to difficulties in obtaining comprehensive data, can lead to erroneous conclusions and predictions. We discuss our approach in the context of the obtained reaction energies, activation barriers, structures of transition states, and reaction rates with the example of a representative molecular material, β-HMX, which tends to decompose violently with large energy release upon an external perturbation. The performed analysis helps to provide a consistent interpretation of available experimental data. The article illustrates that the complete picture of decomposition reactions of complex molecular materials, while theoretically challenging and computationally demanding, is possible and even practical at this point in time. © 2011 American Chemical Society.

Reames D.V.,University of Maryland University College
Solar Physics | Year: 2014

This is a study of abundances of the elements He, C, N, O, Ne, Mg, Si, S, Ar, Ca, and Fe in solar energetic particles (SEPs) in the 2 - 15 MeV amu-1 region measured on the Wind spacecraft during 54 large SEP events occurring between November 1994 and June 2012. The origin of most of the temporal and spatial variations in abundances of the heavier elements lies in rigidity-dependent scattering during transport of the particles away from the site of acceleration at shock waves driven out from the Sun by coronal mass ejections (CMEs). Variation in the abundance of Fe is correlated with the Fe spectral index, as expected from scattering theory but not previously noted. Clustering of Fe abundances during the "reservoir" period, late in SEP events, is also newly reported. Transport-induced enhancements in one region are balanced by depletions in another, thus, averaging over these variations produces SEP abundances that are energy independent, confirms previous SEP abundances in this energy region, and provides a credible measure of element abundances in the solar corona. These SEP-determined coronal abundances differ from those in the solar photosphere by a well-known function that depends upon the first ionization potential (FIP) or ionization time of the element. © 2013 Springer Science+Business Media Dordrecht.

Erlebacher J.,Johns Hopkins University | Margetis D.,University of Maryland University College
Physical Review Letters | Year: 2014

Shape fluctuations in nanoparticles strongly influence their stability. Here, we introduce a quantitative model of such shape fluctuations and apply this model to the important case of Pt-shell/transition metal-core nanoparticles. By using a Gibbs distribution for the initial shapes, we find that there is typically enough thermal energy at room temperature to excite random shape fluctuations in core-shell nanoparticles, whose amplitudes are sufficiently high that the cores of such particles are transiently exposed to the surrounding environment. If this environment is acidic and dissolves away the core, then a hollow shell containing a pinhole is formed; however, this pinhole quickly closes, leaving a hollow nanoparticle. These results favorably compare to experiment, much more so than competing models based on the room-temperature Kirkendall effect. © 2014 American Physical Society.

Vishkin U.,University of Maryland University College
Communications of the ACM | Year: 2014

The current generation of general-purpose multicore hardware must be fixed to support more application domains and to allow cost-effective parallel programming. Open-ended problems and programming is characterized by the way problems may be posed and computer programs developed rather than by a particular application. Many problems whose initial understanding does not imply clear output, or sometimes even input, definitions lend themselves to irregular programming. Today's general-purpose multicore hardware does not provide sufficient support for any of these domains. Today's general-purpose multicore hardware does not provide sufficient support for any of these domains. It must be fixed to support more of them, and to allow cost-effective parallel programming. A fix will require changes both to current hardware, and to the overall ecological system comprising them, including programming practice and compilers.

Denesyuk N.A.,University of Maryland University College | Thirumalai D.,University of Maryland University College
Journal of the American Chemical Society | Year: 2011

Formation of a pseudoknot (PK) in the conserved RNA core domain in the ribonucleoprotein human telomerase is required for function. In vitro experiments show that the PK is in equilibrium with an extended hairpin (HP) structure. We use molecular simulations of a coarse-grained model, which reproduces most of the salient features of the experimental melting profiles of PK and HP, to show that crowding enhances the stability of PK relative to HP in the wild type and in a mutant associated with dyskeratosis congenita. In monodisperse suspensions, small crowding particles increase the stability of compact structures to a greater extent than larger crowders. If the sizes of crowders in a binary mixture are smaller than that of the unfolded RNA, the increase in melting temperature due to the two components is additive. In a ternary mixture of crowders that are larger than the unfolded RNA, which mimics the composition of ribosome, large enzyme complexes and proteins in Escherichia coli, the marginal increase in stability is entirely determined by the smallest component. We predict that crowding can partially restore telomerase activity in mutants with decreased PK stability. © 2011 American Chemical Society.

Hofmann J.,University of Maryland University College | Barnes E.,University of Maryland University College | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2014

We address the puzzling weak-coupling perturbative behavior of graphene interaction effects as manifested experimentally, in spite of the effective fine structure constant being large, by calculating the effect of Coulomb interactions on the quasiparticle properties to next-to-leading order in the random phase approximation (RPA). The focus of our work is graphene suspended in vacuum, where electron-electron interactions are strong and the system is manifestly in a nonperturbative regime. We report results for the quasiparticle residue and the Fermi velocity renormalization at low carrier density. The smallness of the next-to-leading order corrections that we obtain demonstrates that the RPA theory converges rapidly and thus, in contrast to the usual perturbative expansion in the bare coupling constant, constitutes a quantitatively predictive theory of graphene many-body physics for any coupling strength. © 2014 American Physical Society.

Hofmann J.,University of Maryland University College | Natu S.S.,University of Maryland University College | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2014

We study the dynamics of domain formation and coarsening in a binary Bose-Einstein condensate that is quenched across a miscible-immiscible phase transition. The late-time evolution of the system is universal and governed by scaling laws for the correlation functions. We numerically determine the scaling forms and extract the critical exponents that describe the growth rate of domain size and autocorrelations. Our data are consistent with inviscid hydrodynamic domain growth, which is governed by a universal dynamical critical exponent of 1/z=0.68(2). In addition, we analyze the effect of domain wall configurations which introduce a nonanalytic term in the short-distance structure of the pair correlation function, leading to a high-momentum "Porod" tail in the static structure factor, which can be measured experimentally. © 2014 American Physical Society.

Hafezi M.,University of Maryland University College
Physical Review Letters | Year: 2014

Motivated by the recent theoretical and experimental progress in implementing topological orders with photons, we analyze photonic systems with different topologies and present a scheme to probe their topological features. Specifically, we propose a scheme to modify the boundary phases to manipulate edge state dynamics. Such a scheme allows one to measure the winding number of the edge states. Furthermore, we discuss the effect of loss and disorder on the validity of our approach. © 2014 American Physical Society.

Ganeshan S.,University of Maryland University College | Sun K.,University of Maryland University College | Sun K.,University of Michigan | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2013

The Aubry-André or Harper (AAH) model has been the subject of extensive theoretical research in the context of quantum localization. Recently, it was shown that one-dimensional quasicrystals described by the incommensurate AAH model has a nontrivial topology. In this Letter, we show that the commensurate off-diagonal AAH model is topologically nontrivial in the gapless regime and supports zero-energy edge modes. Unlike the incommensurate case, the nontrivial topology in the off-diagonal AAH model is attributed to the topological properties of the one-dimensional Majorana chain. We discuss the feasibility of experimental observability of our predicted topological phase in the commensurate AAH model. © 2013 American Physical Society.

Zhu H.,University of Maryland University College | Fang Z.,University of Maryland University College | Preston C.,University of Maryland University College | Li Y.,University of Maryland University College | Hu L.,University of Maryland University College
Energy and Environmental Science | Year: 2014

Although paper electronics is a compelling concept, the large surface roughness and opaqueness of most paper substrates has hindered its development from a dormant idea to a thriving technology. A recent demonstration of transparent paper with nanoscale surface roughness has revived an interest in using renewable cellulose substrates for electronics and optoelectronics. In this short review, we will first summarize the recent progress of transparent paper electronics through structure engineering. We will also discuss the properties and functionalization of transparent paper, such as surface roughness, printability, thermal stability, etc. Finally, we will summarize the recent achievements on proof-of-concepts of transparent paper, which pave the way for next-generation green electronics fabricated with roll-to-roll printing methods. Advantages of transparent paper over traditional flexible plastic substrates and its challenges will also be discussed. © 2014 The Royal Society of Chemistry.

Jankowski N.R.,U.S. Army | Jankowski N.R.,University of Maryland University College | McCluskey F.P.,University of Maryland University College
Applied Energy | Year: 2014

The use of latent heat thermal energy storage for thermally buffering vehicle systems is reviewed. Vehicle systems with transient thermal profiles are classified according to operating temperatures in the range of 0-800. °C. Thermal conditions of those applications are examined relative to their impact on thermal buffer requirements, and prior phase change thermal enhancement studies for these applications are discussed. In addition a comprehensive overview of phase change materials covering the relevant operating range is given, including selection criteria and a detailed list of over 700 candidate materials from a number of material classes. Promising material candidates are identified for each vehicle system based on system temperature, specific and volumetric latent heat, and thermal conductivity. Based on the results of previous thermal load leveling efforts, there is the potential for making significant improvements in both emissions reduction and overall energy efficiency by further exploration of PCM thermal buffering on vehicles. Recommendations are made for further material characterization, with focus on the need for improved data for metallic and solid-state phase change materials for high energy density applications. © 2013.

Luo Y.,University of Maryland University College | Wang Q.,University of Maryland University College
Journal of Applied Polymer Science | Year: 2014

Zein is the major storage protein from corn with strong hydrophobicity and unique solubility and has been considered as a versatile food biopolymer. Due to the special tertiary structures, zein can self-assemble to form micro- and nano-particles through liquid-liquid dispersion or solvent evaporation approaches. Zein-based delivery systems have been particularly investigated for hydrophobic drugs and nutrients. Recently, increasing attention has been drawn to fabricate zein-based advanced drug delivery systems for various applications. In this review, the molecular models of zein tertiary structure and possible mechanisms involved in zein self-assembly micro- and nano-particles are briefly introduced. Then, a state-of-the-art introduction and discussion are given in terms of preparation, characterization, and application of zein-based particles as delivery systems in the fields of food science, pharmaceutics, and biomedicine. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40696. Copyright © 2014 Wiley Periodicals, Inc.

Wahlstrand J.K.,University of Maryland University College | Cheng Y.-H.,University of Maryland University College | Chen Y.-H.,University of Maryland University College | Milchberg H.M.,University of Maryland University College
Physical Review Letters | Year: 2011

We directly measure the nonlinear optical response in argon and nitrogen in a thin gas target to laser intensities near the ionization threshold. No instantaneous negative nonlinear refractive index is observed, nor is saturation, in contrast with a previous measurement and calculations. In addition, we are able to cleanly separate the instantaneous and rotational components of the nonlinear response in nitrogen. In both Ar and N2, the peak instantaneous index response scales linearly with the laser intensity until the point of ionization, whereupon the response turns abruptly negative and ∼constant, consistent with plasma generation. © 2011 American Physical Society.

Lee C.-H.,University of Maryland University College | Dev P.S.B.,University of Manchester | Mohapatra R.N.,University of Maryland University College
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We present a TeV-scale left-right ultraviolet completion of the type-I seesaw for neutrino masses based on the SU(2)L×SU(2) R×U(1)B-L gauge group without parity, which leads to "large" light-heavy neutrino mixing while keeping the neutrino masses small in a natural manner guaranteed by discrete symmetries. We point out specific observable implications of this class of models if the SU(2) R-breaking scale is of order 5 TeV, in searches for lepton flavor violating processes such as μ→eγ, μ→3e and μ→e conversion in nuclei, and lepton number violating processes such as neutrinoless double beta decay as well as at the LHC. In particular, if the upper limit on BR(μ→eγ) improves by 1 order of magnitude, a large range of the parameters of the model would be ruled out. © 2013 American Physical Society.

Nguyen D.,University of Maryland University College
Environment and Planning B: Planning and Design | Year: 2010

Sprawl opponents have blamed sprawl for weakening linkages among the residents and social capital but there is a lack of empirical evidence to support their argument. This study examines the relationship between the county sprawl index and social-capital factors from the 2000 Social Capital Community Benchmark Survey data. Using 3-level hierarchical models, this study shows that for the US, urban sprawl may support some types of social capital while negatively impacting the others. Furthermore, changing urban form via population density and street accessibility at the county level may not be ideal to improve social capital. © 2010 Pion Ltd and its Licensors.

Subramanian D.,University of Maryland University College | Anisimov M.A.,University of Maryland University College
Journal of Physical Chemistry B | Year: 2011

We have resolved a long-standing issue in the discussion on the origin of the mesoscale inhomogeneities observed in aqueous solutions of tertiary butyl alcohol (TBA). We have shown that the formation of stable mesoscale particles (of about 100 nm in size) can be triggered by the addition of trace amounts of propylene oxide (an impurity expected to be present in all commercial samples of TBA) to a solution, which was previously filtered at a low temperature to remove these inhomogeneities. We hypothesize that these particles are aggregates of mixed clathrate-hydrates that are formed through the stabilization of fluctuations of the intrinsic structure in TBA aqueous solutions by the clathrate-forming ability of propylene oxide. © 2011 American Chemical Society.

Nacev A.,University of Maryland University College
International journal of nanomedicine | Year: 2011

A nanoparticle delivery system termed dynamic magnetic shift (DMS) has the potential to more effectively treat metastatic cancer by equilibrating therapeutic magnetic nanoparticles throughout tumors. To evaluate the feasibility of DMS, histological liver sections from autopsy cases of women who died from breast neoplasms were studied to measure vessel number, size, and spatial distribution in both metastatic tumors and normal tissue. Consistent with prior studies, normal tissue had a higher vascular density with a vessel-to-nuclei ratio of 0.48 ± 0.14 (n = 1000), whereas tumor tissue had a ratio of 0.13 ± 0.07 (n = 1000). For tumors, distances from cells to their nearest blood vessel were larger (average 43.8 μm, maximum 287 μm, n ≈ 5500) than normal cells (average 5.3 μm, maximum 67.8 μm, n ≈ 5500), implying that systemically delivered nanoparticles diffusing from vessels into surrounding tissue would preferentially dose healthy instead of cancerous cells. Numerical simulations of magnetically driven particle transport based on the autopsy data indicate that DMS would correct the problem by increasing nanoparticle levels in hypovascular regions of metastases to that of normal tissue, elevating the time-averaged concentration delivered to the tumor for magnetic actuation versus diffusion alone by 1.86-fold, and increasing the maximum concentration over time by 1.89-fold. Thus, DMS may prove useful in facilitating therapeutic nanoparticles to reach poorly vascularized regions of metastatic tumors that are not accessed by diffusion alone.

Hu B.L.,University of Maryland University College
International Journal of Modern Physics D | Year: 2011

Happy Birthday Mario, the philosopher, the king and the philosopher king! - This was explained in the first few slides of my talk at Mariofest. In an earlier, different occasion I had compared Mario, in his capacity of an inspiring mentor and a chief architect, in building up an eminent school of theoretical physics and astrophysics in Argentina, to my own Ph.D. advisor, the late Professor John Archibald Wheeler, in the USA. The nature of this meeting could perhaps allow me to also relate some of my past experience with Wheeler, and to pay homage to his influence on me in the same capacity as is done here by many young researchers, leaders in their own rights in different fields of physics and astrophysics, with Mario. So please forgive me if you find me delving at times into the past, referring to what I was thinking when I was a graduate student, some 40 years ago, on certain topics, some still of current interest. One of these ideas bears on the present theme of gravity in relation to thermodynamics, another on the philosophy I use for understanding it. © 2011 World Scientific Publishing Company.

Hu M.,University of Maryland University College | Mi B.,University of Maryland University College
Journal of Membrane Science | Year: 2014

We fabricated a novel type of water purification membrane by layer-by-layer assembling negatively charged graphene oxide (GO) nanosheets on a porous poly(acrylonitrile) support and interconnecting them with positively charged poly(allylamine hydrochloride) (PAH) via electrostatic interaction. A series of characterization techniques were used to confirm the successful assembly of multiple GO-PAH bilayers, quantify their composition and thickness, and understand the structure of the GO membrane. Quartz crystal microbalance-dissipation (QCM-D) results showed that each GO-PAH bilayer in the membrane is around 16.5. nm thick and dominated by GO (mass of GO is 2-5 times higher than that of PAH), indicating multiple layers of GO nanosheets exist in each bilayer. This is most likely because the mass-to-charge ratio of GO is much higher than that of PAH. Transport of water and selected solutes in the GO membrane was investigated in a pressurized system and also in a forward osmosis (FO) and pressure retarded osmosis (PRO) system. Water permeability of the GO membrane was found to be about one order of magnitude higher than that of a commercial FO membrane. The solute flux of the GO membrane for sucrose (as a representative uncharged species) was much lower than that for an ionic species, although the hydrated radius of the ions is comparable to that of sucrose. This is most likely because the GO-PAH bilayers tend to swell in ionic solutions. In solutions of low ionic strength, the GO membrane retained a tight structure and exhibited high rejection to sucrose (~99%), indicating an MWCO of around 342 or an equivalent pore size of around 1. nm. Therefore, at the present stage, the GO membrane can be well suited for applications such as FO-based emergency water purification using sugary draw solutions and water treatment not requiring high ionic strength. © 2014 Elsevier B.V.

Khraiwesh B.,King Abdullah University of Science and Technology | Zhu J.-K.,King Abdullah University of Science and Technology | Zhu J.-K.,Purdue University | Zhu J.,University of Maryland University College
Biochimica et Biophysica Acta - Gene Regulatory Mechanisms | Year: 2012

Small, non-coding RNAs are a distinct class of regulatory RNAs in plants and animals that control a variety of biological processes. In plants, several classes of small RNAs with specific sizes and dedicated functions have evolved through a series of pathways. The major classes of small RNAs include microRNAs (miRNAs) and small interfering RNAs (siRNAs), which differ in their biogenesis. miRNAs control the expression of cognate target genes by binding to reverse complementary sequences, resulting in cleavage or translational inhibition of the target RNAs. siRNAs have a similar structure, function, and biogenesis as miRNAs but are derived from long double-stranded RNAs and can often direct DNA methylation at target sequences. Besides their roles in growth and development and maintenance of genome integrity, small RNAs are also important components in plant stress responses. One way in which plants respond to environmental stress is by modifying their gene expression through the activity of small RNAs. Thus, understanding how small RNAs regulate gene expression will enable researchers to explore the role of small RNAs in biotic and abiotic stress responses. This review focuses on the regulatory roles of plant small RNAs in the adaptive response to stresses. This article is part of a Special Issue entitled: Plant gene regulation in response to abiotic stress. © 2011 Elsevier B.V.

Arevalo Jr. R.,University of Maryland University College | McDonough W.F.,University of Maryland University College
Chemical Geology | Year: 2010

An assemblage of MORB analyses (n = 792 samples), including a suite of new, high-precision LA-ICP-MS measurements (n = 79), has been critically compiled in order to provide a window into the chemical composition of these mantle-derived materials and their respective source region(s), commonly referred to as the depleted MORB mantle (DMM). This comprehensive MORB data set, which includes both "normal-type" (N-MORB, defined by (La/Sm)N < 1.00) and "enriched-type" samples (E-MORB, (La/Sm)N ≥ 1.00), defines a global MORB composition that is more enriched in incompatible elements than previous models. A statistical evaluation of the true constancy of "canonical" trace element ratios using this data set reveals that during MORB genesis Ti/Eu, Y/Ho and Ce/Pb remain constant at the 95% confidence-level; thus, the ratios recorded in MORB (Ti/Eu = 7060 ± 1270, 2σ; Y/Ho = 28.4 ± 3.6, 2σ; Ce/Pb = 22.2 ± 9.7, 2σ) may reflect the composition of the DMM, presuming the degree of source heterogeneity, component mixing and conditions of melting/crystallization of the DMM are adequately recorded by global MORB. Conversely, Ba/Th, Nb/U, Zr/Hf, Nb/Ta, Sr/Nd, and Th/U are shown to fractionate as a function of MORB genesis, and thus these ratios do not faithfully record the composition of the DMM. Compared to samples from the Pacific and Indian Oceans, MORB derived from Atlantic ridge segments are characterized by statistically significant (≥ 95% confidence-level) enrichments in both highly incompatible elements (e.g., light REE, TITAN group elements, Sr, Ba, Pb, Th, and U) as well as less incompatible elements (e.g., heavy REE), indicating: i) a prominent recycled source component; ii) variable proportions of pyroxenite in the Atlantic source region; and/or, most likely iii) smaller degrees of melting and/or greater extents of fractional crystallization due to slower ridge spreading rates. Conversely, Pacific MORB has the most depleted regional signatures with regard to highly incompatible elements (e.g., Ba, Pb, Th, and U), likely due to faster ridge spreading rates. Indian Ocean MORB exhibit limited variation in incompatible element enrichments/depletions but are generally the most depleted in more compatible elements (e.g., Ti, Cr, Sc, and heavy REE), potentially due to distinct source characteristics or deep source melting in the garnet field. Atlantic, Pacific and Indian MORB can also be distinguished by trace element ratios, particularly Ce/Pb and Th/U, which is distinct at the > 99% confidence-level. Global MORB, and by inference the DMM, are characterized by enrichments in Y/Ho and depletions in Th/U relative to the chondritic ratios, and are complementary to the continental crust. However, the median of global MORB and the bulk continental crust both have sub-chondritic Ti/Eu and Nb/Ta ratios, suggesting an under-represented Ti- and Nb-rich reservoir in the Earth, potentially refractory, rutile-bearing eclogite at depth in the mantle. © 2009 Elsevier B.V. All rights reserved.

Adomaitis R.A.,University of Maryland University College
Journal of Crystal Growth | Year: 2010

A multiscale model of atomic layer deposition (ALD) inside a nanoporous material is developed in this paper. The overall model couples a lattice Monte Carlo simulator describing molecular-scale growth of the ALD film to a continuum description of the precursor transport within the nanopore. The multiscale simulation approach is used to study how intra-pore precursor depletion leads to nonuniform ALD films and to examine whether film properties, such as composition and surface roughness, are functions of position within the pore. © 2010 Elsevier B.V. All rights reserved.

Kahn J.D.,University of Maryland University College
Biophysical Journal | Year: 2014

Investigators have constructed dsDNA molecules with several different base modifications and have characterized their bending and twisting flexibilities using atomic force microscopy, DNA ring closure, and single-molecule force spectroscopy with optical tweezers. The three methods provide persistence length measurements that agree semiquantitatively, and they show that the persistence length is surprisingly similar for all of the modified DNAs. The circular dichroism spectra of modified DNAs differ substantially. Simple explanations based on base stacking strength, polymer charge, or groove occupancy by functional groups cannot explain the results, which will guide further high-resolution theory and experiments. © 2014 Biophysical Society.

Hebert L.B.,University of Maryland University College | Montesi L.G.J.,University of Maryland University College
Geochemistry, Geophysics, Geosystems | Year: 2010

Melt focusing at mid-ocean ridges is necessary to explain the narrowness of the zone of crustal accretion and the formation of large but localized on-axis seamounts at slow and ultraslow spreading centers. It has been proposed that melt focusing is facilitated by the presence of a barrier to upward melt migration at the base of the thermal boundary layer (TBL). We assess the development of a melt impermeable boundary by modeling the geochemical evolution and crystallization history of melts as they rise into the TBL of mid-ocean ridges with different spreading rates. A permeability barrier, associated with a crystallization front controlled by the conductive thermal regime, exists for melt trajectories at slow to fast spreading ridges (≥10 mm/yr half rate). The effective lateral scope of the barrier, where the slope of the barrier exceeds a critical value that allows buoyant melt transport to the axis, generally increases with spreading rate. At all distances from the axis at ultraslow ridges and off-axis at slow spreading ridges, the weak crystallization front may prohibit formation of an efficient barrier and lead to the possibility that some fraction of melt may be incorporated into the lithospheric mantle, allowing refertilization. The protracted crystallization history and potential absence of an effective permeability barrier may explain the dearth of volcanism at ultraslow ridges and calls for a revision of lateral melt focusing scenarios at ultraslow spreading rates. Copyright 2010 by the American Geophysical Union.

Jiang Z.,University of Maryland University College | Lin Z.,Adobe Systems | Davis L.,University of Maryland University College
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2012

A shape-motion prototype-based approach is introduced for action recognition. The approach represents an action as a sequence of prototypes for efficient and flexible action matching in long video sequences. During training, an action prototype tree is learned in a joint shape and motion space via hierarchical K-means clustering and each training sequence is represented as a labeled prototype sequence; then a look-up table of prototype-to-prototype distances is generated. During testing, based on a joint probability model of the actor location and action prototype, the actor is tracked while a frame-to-prototype correspondence is established by maximizing the joint probability, which is efficiently performed by searching the learned prototype tree; then actions are recognized using dynamic prototype sequence matching. Distance measures used for sequence matching are rapidly obtained by look-up table indexing, which is an order of magnitude faster than brute-force computation of frame-to-frame distances. Our approach enables robust action matching in challenging situations (such as moving cameras, dynamic backgrounds) and allows automatic alignment of action sequences. Experimental results demonstrate that our approach achieves recognition rates of 92.86 percent on a large gesture data set (with dynamic backgrounds), 100 percent on the Weizmann action data set, 95.77 percent on the KTH action data set, 88 percent on the UCF sports data set, and 87.27 percent on the CMU action data set. © 2012 IEEE.

The formation and differentiation of the continental crust occurs at convergent plate margins in accretionary and collisional orogenic belts where sufficient heat is generated to achieve high-grade metamorphism and anatexis. Volumetrically significant H2O-present melting requires an influx of aqueous fluid along zones of high-strain deformation or via fracture networks, or recycling of the fluid dissolved in melt via melt migration and fluid exsolution during crystallization. In contrast, in "dry" crust, melting occurs via hydrate-breakdown melting reactions at higher temperatures than H2O-present melting; volumetrically significant melt production requires temperatures above ~800 8C. Melting wets residual grains, and anatectic crust becomes porous at a few vol.% melt. Feedback between deformation and melting creates a dynamic rheological environment; as melt volume increases to the melt connectivity transition, which varies but is around 7 vol.% (see discussion later in the text), melt may escape from the source in the first of several melt-loss events with increasing temperature. Major and accessory phase controls on melt production and melt composition for different pressure-temperature-time paths are evaluated using calculated phase equilibria for average pelite. The pristine to slightly retrogressed condition of peritectic minerals in residual crust requires significant loss of melt from the system. The consequences of melt loss are evaluated here. In residual crust, evidence of melt at the grain scale may be preserved in microstructures, whereas evidence of melt extraction pathways at outcrop scale is recorded by leucosome networks. Strain and anisotropy of permeability control the form of mesoscale melt channels with strong anisotropy promoting high-melt focusing. The sequence of structures observed in nature records a transition from storage to drainage; focused melt flow occurs by dilatant shear failure of low-melt-fraction rocks, leading to the formation of networks of channels that allow accumulation and storage of melt and that form the link for melt flow from grain boundaries to ascent conduits. Melt ascent is via ductile-to-brittle fracture; ductile fractures may propagate along foliation as sills or from dilation or shear bands as dikes. Emplacement of horizontal tabular and wedge-shaped plutons occurs around the brittle-ductile transition zone, whereas vertical lozenge-shaped plutons represent crystallization of magma in the ascent conduit. Blobby plutons form by lateral expansion in the ascent conduit localized by thermal or mechanical instabilities.

Brown M.,University of Maryland University College
Gondwana Research | Year: 2010

The modern plate tectonics regime is characterized by a duality of thermal environments, one representing the subduction zone and the other representing the arc-backarc or orogenic hinterland. This duality is the hallmark of one-sided (asymmetric) subduction, and the characteristic imprint of one-sided subduction in the geological record is predicted to be the broadly contemporaneous occurrence of two contrasting types of metamorphic belt, one of high dT/dP type and the other low dT/dP type. The broadly contemporaneous occurrence of granulite and ultrahigh-temperature metamorphism with eclogite-high-pressure granulite metamorphism in the geological record since the Neoarchean Era is evidence of dual thermal environments and indicates that subduction has operated on Earth since that time. Classic 'paired' metamorphic belts in which an inboard high dT/dP metamorphic belt is juxtaposed against an outboard low dT/dP metamorphic belt along a tectonic contact-such as the Ryoke and Sanbagawa belts in Japan-are found in Phanerozoic accretionary orogens of the circum-Pacific. Generally, they appear to result from juxtaposition of terranes with different metamorphic facies series that may or may not be exactly contemporaneous and that may or may not be far-traveled. This is a consequence of the difference between globally-continuous subduction, generating a low-to-intermediate dT/dP environment in the subduction zone and a high dT/dP environment in the arc-backarc system, and metamorphic imprints in the geological record that represent discrete 'events' due to changes in plate kinematics or subduction boundary dynamics, or as a result of collision of ridges, arcs or continents with the upper plate at the trench. The concept of 'paired' metamorphic belts may be generalized and extended more widely than in the original proposition to subduction-to-collision orogenic systems in addition to accretionary orogenic systems. In this wider application, the term "paired metamorphic belts" may be used for "penecontemporaneous belts of contrasting type of metamorphism that record different apparent thermal gradients, one warmer and the other colder, juxtaposed by plate tectonics processes" (Brown, 2009). This extends the original concept of Miyashiro (1961) beyond the simple pairing of high dT/dP and low dT/dP metamorphic belts in circum-Pacific accretionary orogens, and makes it more useful in the context of our better understanding of the relationship between thermal regimes and tectonic settings. This is particularly useful in subduction-to-collision orogenic systems, where the suture and lower plate materials will register the imprint of low-to-intermediate dT/dP and the upper plate will register penecontemporaneous high dT/dP metamorphism commonly manifested at shallow crustal levels by the occurrence of granites in the rock record. © 2009 Elsevier B.V. All rights reserved.

Na S.-M.,University of Maryland University College | Flatau A.B.,University of Maryland University College
Scripta Materialia | Year: 2012

Nearly single-grain-oriented Fe-Ga thin sheets with a sharp Goss (0 1 1)[1 0 0] orientation have been developed through rolling and annealing processes. Annealing of rolled samples at 1200°C under a sulfur atmosphere produced abnormal Goss (0 1 1) grain growth, covering ∼98% of the sample surface. Compared with previous results from anneals under argon, the sulfur anneal resulted in the acceleration of abnormal (0 1 1) grain growth and a ∼79% increase in the observed magnetostriction, from 163 to 292 ppm, for the same anneal protocol. © 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Briken V.,University of Maryland University College
Cell Host and Microbe | Year: 2012

The uptake of apoptotic cells by phagocytes is defined as efferocytosis. In this issue of Cell Host & Microbe, Martin et al. (2012) and Yang et al. (2012) report that macrophage- and neutrophil-mediated efferocytosis of apoptotic cells containing mycobacteria is an innate antibacterial effector mechanism. © 2012 Elsevier Inc.

Zambrana R.E.,University of Maryland University College | Carter-Pokras O.,University of Maryland University College
American Journal of Public Health | Year: 2010

An impressive body of public health knowledge on health care disparities among Latinos has been produced. However, inconclusive and conflicting results on predictors of health care disparities remain. We examined the theoretical assumptions and methodological limitations of acculturation research in understanding Latino health caredisparities, the evidence for socioeconomic position as a predictor of health care disparities and the effectiveness of cultural competency practice. Persistent use of culture-driven acculturation models decenters social determinants of health as key factors in health disparities and diminishes the effectiveness of cultural competency practice. Social and economic determinants are more important predictors than isculture in understanding health care disparities. Improvements in the material conditions of low-income Latinos can effectively reduce health care disparities.

Fernandes M.C.,University of Maryland University College | Andrews N.W.,University of Maryland University College
FEMS Microbiology Reviews | Year: 2012

The intracellular protozoan parasite Trypanosoma cruzi is the causative agent of Chagas' disease, a serious disorder that affects millions of people in Latin America. Despite the development of lifelong immunity following infections, the immune system fails to completely clear the parasites, which persist for decades within host tissues. Cardiomyopathy is one of the most serious clinical manifestations of the disease, and a major cause of sudden death in endemic areas. Despite decades of study, there is still debate about the apparent preferential tropism of the parasites for cardiac muscle, and its role in the pathology of the disease. In this review, we discuss these issues in light of recent observations, which indicate that T. cruzi invades host cells by subverting a highly conserved cellular pathway for the repair of plasma membrane lesions. Plasma membrane injury and repair is particularly prevalent in muscle cells, suggesting that the mechanism used by the parasites for cell invasion may be a primary determinant of tissue tropism, intracellular persistence, and Chagas' disease pathology. © 2012 Federation of European Microbiological Societies.

Vedernikov A.N.,University of Maryland University College
Topics in Organometallic Chemistry | Year: 2010

Reactions of high valent platinum and palladium complexes leading to the formation of C(sp2)-O and C(sp3)-O bonds are involved in various catalytic applications such as oxidative functionalization of hydrocarbons, which are especially rich in the case of palladium chemistry. This Chapter emphasizes on the mechanisms of C-O reductive elimination from octahedral d6 Pt(IV) and, in part, from Pd(IV) complexes. The nature of the leaving groups, the metal center, the presence of soft/hard spectator ligands, the number of hydrocarbyl ligands at the metal, and some other factors affecting the reactivity of such complexes are considered. As shown here, there are still uncharted territories in the area of high valent organoplatinum and organopalladium chemistry: C(sp2)-O reductive elimination from PtIV, reactivity and reaction mechanisms of PtIII and PdIII organometallic derivatives, synthesis and reactivity of monoalkyl and monoaryl palladium(IV) complexes stabilized by O-donor ligands, and others. The rapid progress observed in this field of chemistry suggests that some of these areas will soon be explored. © 2010 Springer-Verlag Berlin Heidelberg.

Pearlin L.I.,University of Maryland University College
Journals of Gerontology - Series B Psychological Sciences and Social Sciences | Year: 2010

This paper compares the meanings and applications of concepts relevant to both the life course and the stress process frameworks. Some of these concepts bear the same labels but serve quite different scholarly agendas. Other concepts have different labels but have closely related applications. The purpose of this kind of comparative analysis is to help both fields clarify the conceptual tools needed to advance their scholarly goals.

Vitak J.,University of Maryland University College
Journal of Broadcasting and Electronic Media | Year: 2012

A large body of research argues that self-presentation strategies vary based on audience. But what happens when the technical features of Web sites enable-or even require-users to make personal disclosures to multiple audiences at once, as is often the case on social network sites (SNSs)? Do users apply a lowest common denominator approach, only making disclosures that are appropriate for all audience members? Do they employ technological tools to disaggregate audiences? When considering the resources that can be harnessed from SNS interactions, researchers suggest users need to engage with their network in order to reap benefits. The present study presents a model including network composition, disclosures, privacy-based strategies, and social capital. Results indicate that (1) audience size and diversity impacts disclosures and use of advanced privacy settings, (2) privacy concerns and privacy settings impact disclosures in varying ways; and (3) audience and disclosure characteristics predict bridging social capital. © 2012 Copyright Taylor and Francis Group, LLC.

Dively G.P.,University of Maryland University College | Kamel A.,U.S. Environmental Protection Agency
Journal of Agricultural and Food Chemistry | Year: 2012

Neonicotinoids are systemic insecticides widely used on many pollinated agricultural crops, and increasing evidence indicates that they move to some extent into pollen and nectar. This study measured levels of neonicotinoid residues in pollen and nectar from a pumpkin crop treated with formulated products containing imidacloprid, dinotefuran, and thiamethoxam using different timings and application methods. Environmental conditions have a significant effect on overall residue levels; nectar residues were 73.5-88.8% less than pollen residues, and metabolites accounted for 15.5-27.2% of the total residue amounts. Foliar-applied treatments and chemigated insecticides applied through drip irrigation during flowering resulted in the highest residues of parent insecticide and metabolites, which may reach average levels up to 122 ng/g in pollen and 17.6 ng/g in nectar. The lowest levels of residues were detected in treatment regimens involving applications of insecticides at planting, as either seed dressing, bedding tray drench, or transplant water treatment. © 2012 American Chemical Society.

Barrie D.B.,University of Maryland University College | Kirk-Davidoff D.B.,University of Maryland University College
Atmospheric Chemistry and Physics | Year: 2010

Electrical generation by wind turbines is increasing rapidly, and has been projected to satisfy 15% of world electric demand by 2030. The extensive installation of wind farms would alter surface roughness and significantly impact the atmospheric circulation due to the additional surface roughness forcing. This forcing could be changed deliberately by adjusting the attitude of the turbine blades with respect to the wind, which would enable the "management" of a large array of wind turbines. Using a General Circulation Model (GCM), we represent a continent-scale wind farm as a distributed array of surface roughness elements. Here we show that initial disturbances caused by a step change in roughness grow within four and a half days such that the flow is altered at synoptic scales. The growth rate of the induced perturbations is largest in regions of high atmospheric instability. For a roughness change imposed over North America, the induced perturbations involve substantial changes in the track and development of cyclones over the North Atlantic, and the magnitude of the perturbations rises above the level of forecast uncertainty.

Vaikuntanathan S.,University of Maryland University College | Jarzynski C.,University of Maryland University College
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

Following recent work by Marathe and Parrondo [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.245704 104, 245704 (2010)], we construct a classical Hamiltonian system whose energy is reduced during the adiabatic cycling of external parameters when initial conditions are sampled microcanonically. Combining our system with a device that measures its energy, we propose a cyclic procedure during which energy is extracted from a heat bath and converted to work, in apparent violation of the second law of thermodynamics. This paradox is resolved by deriving an explicit relationship between the average work delivered during one cycle of operation and the average information gained when measuring the system's energy. © 2011 American Physical Society.

Motsch S.,University of Maryland University College | Tadmor E.,University of Maryland University College
Journal of Statistical Physics | Year: 2011

We introduce a model for self-organized dynamics which, we argue, addresses several drawbacks of the celebrated Cucker-Smale (C-S) model. The proposed model does not only take into account the distance between agents, but instead, the influence between agents is scaled in term of their relative distance. Consequently, our model does not involve any explicit dependence on the number of agents; only their geometry in phase space is taken into account. The use of relative distances destroys the symmetry property of the original C-S model, which was the key for the various recent studies of C-S flocking behavior. To this end, we introduce here a new framework to analyze the phenomenon of flocking for a rather general class of dynamical systems, which covers systems with non-symmetric influence matrices. In particular, we analyze the flocking behavior of the proposed model as well as other strongly asymmetric models with "leaders". The methodology presented in this paper, based on the notion of active sets, carries over from the particle to kinetic and hydrodynamic descriptions. In particular, we discuss the hydrodynamic formulation of our proposed model, and prove its unconditional flocking for slowly decaying influence functions. © 2011 Springer Science+Business Media, LLC.

Yoon J.-H.,University of Maryland University College | Zeng N.,The Interdisciplinary Center
Climate Dynamics | Year: 2010

Rainfall variability over the Amazon basin has often been linked to variations in Pacific sea surface temperature (SST), and in particular, to the El Niño/Southern Oscillation (ENSO). However, only a fraction of Amazon rainfall variability can be explained by ENSO. Building upon the recent work of Zeng (Environ Res Lett 3:014002, 2008), here we provide further evidence for an influence on Amazon rainfall from the tropical Atlantic Ocean. The strength of the North Atlantic influence is found to be comparable to the better-known Pacific ENSO connection. The tropical South Atlantic Ocean also shows some influence during the wet-to-dry season transition period. The Atlantic influence is through changes in the north-south divergent circulation and the movement of the ITCZ following warm SST. Therefore, it is strongest in the southern part of the Amazon basin during the Amazon's dry season (July-October). In contrast, the ENSO related teleconnection is through anomalous east-west Walker circulation with largely concentrated in the eastern (lower) Amazon. This ENSO connection is seasonally locked to boreal winter. A complication due to the influence of ENSO on Atlantic SST causes an apparent North Atlantic SST lag of Amazon rainfall. Removing ENSO from North Atlantic SST via linear regression resolves this causality problem in that the residual Atlantic variability correlates well and is in phase with the Amazon rainfall. A strong Atlantic influence during boreal summer and autumn is particularly significant in terms of the impact on the hydro-ecosystem which is most vulnerable during the dry season, as highlighted by the severe 2005 Amazon drought. Such findings have implications for both seasonal-interannual climate prediction and understanding the longer-term changes of the Amazon rainforest. © Springer-Verlag 2009.

Tartaglino-Mazzucchelli G.,University of Maryland University College
Journal of High Energy Physics | Year: 2010

We propose a new superspace formulation for N = (4, 4) conformal supergravity in two dimensions. This is based on a geometry where the structure group of the curved superspace is chosen to be SO(1,1)×SU(2) L×SU(2) R. The off-shell supergravity multiplet possesses super-Weyl transformations generated by an unconstrained real scalar superfield. The new supergravity formulation turns out to be an extension of the minimal multiplet introduced in 1988 by Gates et. al. and it allows the existence of various off-shell matter supermultiplets. Covariant twisted-II and twisted-I multiplets respectively describe the field strength of an Abelian vector multiplet and its prepotential. Moreover, we introduce covariant bi-projective superfields. These define a large class of matter multiplets coupled to 2D N = (4, 4) conformal supergravity. They are the analogue of the covariant projective superfields recently introduced for 4D and 5D matter-coupled supergravity but they differ by the fact that bi-projective superfields are defined with the use of two CP1 instead of one. We conclude by giving a manifestly locally supersymmetric and super-Weyl invariant action principle in bi-projective superspace. © SISSA 2010.

Nigam S.,University of Maryland University College | Bollasina M.,University of Maryland University College
Journal of Geophysical Research: Atmospheres | Year: 2010

The viability of the elevated heat pump hypothesis, a mechanism proposed by Lau and Kim (2006) for absorbing aerosols' impact on South Asian summer monsoon hydroclimate, is assessed from a careful review of these authors' own analysis and others since then. The lack of appreciation of the spatial distribution of the aerosol-related precipitation signal over the Indian subcontinent, its east-west asymmetric structure, in particular, apparently led to the development of this hypothesis. Its key elements have little observational support, and the hypothesis is thus deemed untenable. Quite telling is the observation that local precipitation signal over the core aerosol region is negative, i.e., increased loadings are linked with suppressed precipitation and not more as claimed by the hypothesis. Finally, motivated by the need to address causality, the analysis of contemporaneous aerosol-monsoon links by Bollasina et al. (2008) is extended by examining the structure of hydroclimate lagged regressions on aerosols. It is shown that findings obtained from contemporaneous analysis can be safely interpreted as representing the impact of aerosols on precipitation, not vice versa. The possibility that both are shaped by a slowly evolving, large-scale circulation pattern cannot however be ruled out. Copyright 2010 by the American Geophysical Union.

Cohen T.D.,University of Maryland University College
Journal of High Energy Physics | Year: 2010

It is shown that large Nc QCD must have a Hagedorn spectrum (i.e., a spectrum of hadron which grows exponentially with the hadrons' mass) provided that certain technical assumptions concerning the applicability of perturbation theory to a certain class of correlation functions apply. The basic argument exploits the interplay of confinement and asymptotic freedom. © SISSA 2010.

Carson Smith J.,University of Maryland University College
Medicine and Science in Sports and Exercise | Year: 2013

Purpose: Despite the well-known anxiolytic effect of acute exercise, it is unknown if anxiety reductions after acute exercise conditions survive in the face of a subsequently experienced arousing emotional exposure. The purpose of this study was to compare the effects of moderate-intensity cycle ergometer exercise to a seated rest control condition on state anxiety symptoms after exposure to a variety of highly arousing pleasant and unpleasant stimuli. Methods: Thirty-seven healthy and normally physically active young adults completed two conditions on separate days: 1) 30 min of seated rest and 2) 30 min of moderate-intensity cycle ergometer exercise (RPE = 13; "somewhat hard"). After each condition, participants viewed 90 arousing pleasant, unpleasant, and neutral pictures from the International Affective Picture System for 30 min. State anxiety was measured before and 15 min after each condition, and again after exposure to the affective pictures. Results: State anxiety significantly decreased from baseline to after the exercise and seated rest conditions (P = 0.003). After the emotional picture-viewing period, state anxiety significantly increased to baseline values after the seated rest condition (P = 0.001) but remained reduced after the exercise condition. Conclusion: These findings suggest that the anxiolytic effects of acute exercise may be resistant to the potentially detrimental effects on mood after exposure to arousing emotional stimuli. © 2012 by the American College of Sports Medicine.

Straub J.E.,Boston University | Thirumalai D.,University of Maryland University College
Current Opinion in Structural Biology | Year: 2010

Identifying the principles that describe the formation of protein oligomers and fibrils with distinct morphologies is a daunting problem. Here we summarize general principles of oligomer formation gleaned from molecular dynamics simulations of A. β-peptides. The spectra of high free energy structures sampled by the monomer provide insights into the plausible fibril structures, providing a rationale for the 'strain phenomenon.' Heterogeneous growth dynamics of small oligomers of A. β16-22, whose lowest free energy structures are like nematic droplets, can be broadly described using a two-stage dock-lock mechanism. In the growth process, water is found to play various roles depending on the oligomer size, and peptide length, and sequence. Water may be an explicit element of fibril structure linked to various fibril morphologies. © 2010 Elsevier Ltd.

Zhang B.,University of Maryland University College | Isaacs L.,University of Maryland University College
Journal of Medicinal Chemistry | Year: 2014

We studied the influence of the aromatic sidewalls on the ability of acyclic CB[n]-type molecular containers (1a-1e) to act as solubilizing agents for 19 insoluble drugs including the developmental anticancer agent PBS-1086. All five containers exhibit good water solubility and weak self-association (Ks ≤ 624 M-1). We constructed phase solubility diagrams to extract Krel and Ka values for the container·drug complexes. The acyclic CB[n]-type containers generally display significantly higher Ka values than HP-β-CD toward drugs. Containers 1a-1e bind the steroidal ring system and aromatic moieties of insoluble drugs. Compound 1b displays highest affinity toward most of the drugs studied. Containers 1a and 1b are broadly applicable and can be used to formulate a wider variety of insoluble drugs than was previously possible with cyclodextrin technology. For drugs that are solubilized by both HP-β-CD and 1a-1e, lower concentrations of 1a-1e are required to achieve identical [drug]. © 2014 American Chemical Society.

Nurmis J.,University of Maryland University College
Wiley Interdisciplinary Reviews: Climate Change | Year: 2016

During the last decade (2005–2015), artists from all over the world have taken on climate change as the subject matter of their work. Encouraged by activists (most notably Bill McKibben), artists have appropriated climate change as a social problem and decided that they too, alongside journalists, scientists, and activists, were called upon to engage with this issue. Dozens of noteworthy exhibitions, most notably in Boulder (2007), London and Copenhagen (2009), Paris (2012), New York (2013), Boston (2014), and Melbourne (2015), have placed climate change art on the map as a new and timely genre, displaying relevant artworks both alongside climate negotiations and in dedicated gallery spaces such as the Barbican in London. I argue that much progress has been made in appropriating climate change art as an essentially artistic, rather than propagandistic or activist practice. Although caught in the net of many criticisms, climate change art plays a crucial role in allowing the public to rethink the role of human beings’ everyday activities in irrevocably altering the climate system. In effect, climate change art makes the Anthropocene a cultural reality. However, the review points out a strong artistic trend toward the imagery of apocalyptic sublime, which results in art that may be poignant, but falls out of step with the self-professed motivations of artists and curators alike. WIREs Clim Change 2016, 7:501–516. doi: 10.1002/wcc.400. For further resources related to this article, please visit the WIREs website. © 2016 Wiley Periodicals, Inc.

Highton R.,University of Maryland University College
Molecular Phylogenetics and Evolution | Year: 2014

A study of DNA sequence variation in the plethodontid salamander Batrachoseps attenuatus by Martínez-Solano et al. (2007) revealed more species than acknowledged by the authors. They sequenced 677 base pairs of the cytochrome-b mitochondrial gene in 178 individuals from 123 populations of the currently recognized species B. attenuatus from throughout most of its known range in southwestern Oregon and northern and central California. Their data show that the common ancestor of the species diverged into five clades during the late Miocene Epoch, an estimated 9.2-5.5. mya, with subsequent divergences producing at least 39 living lineages that replace each other geographically. These groups have been diverging independently from each other throughout the Pleistocene Epoch and many of them have probably reached the species level of divergence. © 2013 Elsevier Inc.

Bazinet A.L.,University of Maryland University College | Zwickl D.J.,University of Arizona | Cummings M.P.,University of Maryland University College
Systematic Biology | Year: 2014

We introduce, a publicly available gateway for high-throughput, maximum-likelihood phylogenetic analysis powered by grid computing. The gateway features a GARLI 2.0web service that enables a user to quickly and easily submit thousands of maximum likelihood tree searches or bootstrap searches that are executed in parallel on distributed computing resources. The GARLI web service allows one to easily specify partitioned substitution models using a graphical interface, and it performs sophisticated post-processing of phylogenetic results. Although the GARLI web service has been used by the research community for over three years, here we formally announce the availability of the service, describe its capabilities, highlight new features and recent improvements, and provide details about how the grid system efficiently delivers high-quality phylogenetic results. © The Author(s) 2014.

Goh J.M.,IE Business School | Gao G.,University of Maryland University College | Agarwal R.,University of Maryland University College
Information Systems Research | Year: 2011

Despite the significant potential for performance gains from health IT (HIT), there has been limited study of the mechanisms underlying successful HIT implementations. We conducted an extensive longitudinal field study to gain an understanding of the interplay between technology and patterns of clinical work embodied in routines. We use the analytical device of narrative networks to identify where and how HIT influences patterns of work. We further draw upon adaptive structuration theory to conceptualize HIT as an intervention that alters the flow of events in a narrative network. Our findings suggest that the key to successful implementation is to manage the co-evolution process between routines and HIT and to actively orchestrate a virtuous cycle through agentic action. We propose a dynamic process model of adaptive routinization of HIT that delineates the major channels through which HIT and routines interact, identifies the different stages in the dynamic co-evolution process, and isolates the pivotal role of two forms of agency in enabling the virtuous cycle of co-evolution. This is one of the first studies to offer a processual, microlevel analysis of HIT implementation in a clinical setting. © 2011 INFORMS.

Rotkowitz M.C.,University of Maryland University College | Martins N.C.,University of Maryland University College
IEEE Transactions on Automatic Control | Year: 2012

Quadratic invariance is a condition which has been shown to allow for optimal decentralized control problems to be cast as convex optimization problems. The condition relates the constraints that the decentralization imposes on the controller to the structure of the plant. In this technical note, we consider the problem of finding the closest subset and superset of the decentralization constraint which are quadratically invariant when the original problem is not. We show that this can itself be cast as a convex problem for the case where the controller is subject to delay constraints between subsystems, but that this fails when we only consider sparsity constraints on the controller. For that case, we develop an algorithm that finds the closest superset in a fixed number of steps, and discuss methods of finding a close subset. © 2012 IEEE.

Koenig M.A.,University of Minnesota | Woodward A.L.,University of Maryland University College
Developmental Psychology | Year: 2010

Three studies examined 24-month-olds' sensitivity to the prior accuracy of the source of information and the way in which young children modify their word learning from inaccurate sources. In Experiments 1A, 2, and 3, toddlers interacted with an accurate or inaccurate speaker who trained and tested children's comprehension of a new word-object link. In Experiment 1, children performed less systematically in response to an inaccurate than to an accurate source. In Experiments 2 and 3, after toddlers' comprehension of the new word-object links was tested by the original source, a second speaker requested the target objects. In Experiment 2, children responded randomly in response to the second speaker's requests when novel words were previously presented by an inaccurate source. In Experiment 3, toddlers responded randomly in response to both speakers in the inaccurate condition when their memory for words was taxed by a brief delay period. Taken together, these findings suggest that toddlers attend to accuracy information, that they treat inaccuracy as a feature of a particular individual, and that the word-object representations formed as a result may be fragile and short lived. Findings are discussed in terms of possible mechanisms by which children adjust their word learning from problematic speakers. © 2010 American Psychological Association.

Mohapatra R.N.,University of Maryland University College
AIP Conference Proceedings | Year: 2012

I review a recent work on gauged flavor with left-right symmetry, where all masses and all Yukawa couplings owe their origin to spontaneous flavor symmetry breaking. This is suggested as a precursor to a full understanding of flavor of quarks and leptons. An essential ingredient of this approach is the existence of heavy vector-like fermions, which is the home of flavor, which subsequently gets transmitted to the familiar quarks and leptons via the seesaw mechanism. I then discuss implications of extending this idea to include supersymmetry and finally speculate on a possible grand unified model based on the gauge group SU(5)L×SU(5)R which provides a group theoretic origin for the vector-like fermions. © 2012 American Institute of Physics.

Yang J.,University of Wisconsin - Madison | Ozel O.,University of Maryland University College | Ulukus S.,University of Maryland University College
IEEE Transactions on Wireless Communications | Year: 2012

In this paper, we investigate the transmission completion time minimization problem in an additive white Gaussian noise (AWGN) broadcast channel, where the transmitter is able to harvest energy from the nature, using a rechargeable battery. The harvested energy is modeled to arrive at the transmitter during the course of transmissions. The transmitter has a fixed number of packets to be delivered to each receiver. The objective is to minimize the time by which all of the packets are delivered to their respective destinations. To this end, we optimize the transmit powers and transmission rates in a deterministic setting. We first analyze the structural properties of the optimal transmission policy in a two-user broadcast channel via the dual problem of maximizing the departure region by a fixed time T. We prove that the optimal total transmit power sequence has the same structure as the optimal single-user transmit power sequence in. In addition, the total power is split optimally based on a cut-off power level; if the total transmit power is lower than this cut-off level, all transmit power is allocated to the stronger user; otherwise, all transmit power above this level is allocated to the weaker user. We then extend our analysis to an M-user broadcast channel. We show that the optimal total power sequence has the same structure as the two-user case and optimally splitting the total power among M users involves M-1 cut-off power levels. Using this structure, we propose an algorithm that finds the globally optimal policy. Our algorithm is based on reducing the broadcast channel problem to a single-user problem as much as possible. Finally, we illustrate the optimal policy and compare its performance with several suboptimal policies under different settings. © 2012 IEEE.

Liu Y.-C.,University of Maryland University College | Chopra N.,University of Maryland University College
IEEE Transactions on Robotics | Year: 2012

Passivity-based control has emerged as an important paradigm for synchronization of networked robotic systems. Despite the practical utility of task-space algorithms, the previous results focused on joint-space synchronization and were primarily derived for kinematically identical manipulators. Hence, in this paper, the problem of task-space synchronization of (possibly redundant) heterogeneous robotic systems is studied. By exploiting passivity-based synchronization results that are developed previously, an adaptive control algorithm is proposed to guarantee task-space synchronization of networked robotic manipulators in the presence of dynamic uncertainties and time-varying communication delays. To demonstrate the efficacy of the proposed framework, numerical simulations and experiments are conducted with redundant and nonredundant manipulators, respectively. © 2006 IEEE.

Dev P.S.B.,University of Manchester | Dev P.S.B.,TU Munich | Mohapatra R.N.,University of Maryland University College
Physical Review Letters | Year: 2015

We show that the excess events observed in a number of recent LHC resonance searches can be simultaneously explained within a nonsupersymmetric left-right inverse seesaw model for neutrino masses with WR mass around 1.9 TeV. The minimal particle content that leads to gauge coupling unification in this model predicts gR≃0.51 at the TeV scale, which is consistent with data. The extra color singlet, SU(2)-triplet fermions required for unification can be interpreted as the dark matter of the Universe. Future measurements of the ratio of same-sign to opposite-sign dilepton events can provide a way to distinguish this scenario from the canonical cases of type-I and inverse seesaw, i.e., provide a measure of the relative magnitudes of the Dirac and Majorana masses of the right-handed neutrinos in the SU(2)R doublet of the left-right symmetric model. © 2015 American Physical Society. © 2015 American Physical Society.

Stearns F.W.,University of Maryland University College
Genetics | Year: 2010

Pleiotropy is defined as the phenomenon in which a single locus affects two or more distinct phenotypic traits. The term was formally introduced into the literature by the German geneticist Ludwig Plate in 1910, 100 years ago. Pleiotropy has had an important influence on the fields of physiological and medical genetics as well as on evolutionary biology. Different approaches to the study of pleiotropy have led to incongruence in the way that it is perceived and discussed among researchers in these fields. Furthermore, our understanding of the term has changed quite a bit since 1910, particularly in light of modern molecular data. This review traces the history of the term " pleiotropy" and reevaluates its current place in the field of genetics. Copyright © 2010 by the Genetics Society of America.

Colombini M.,University of Maryland University College
Biochimica et Biophysica Acta - Bioenergetics | Year: 2010

A key, decision-making step in apoptosis is the release of proteins from the mitochondrial intermembrane space. Ceramide can self-assemble in the mitochondrial outer membrane to form large stable channels capable of releasing said proteins. Ceramide levels measured in mitochondria early in apoptosis are sufficient to form ceramide channels in the outer membrane. The channels are in dynamic equilibrium with non-conducting forms of ceramide in the membrane. This equilibrium can be strongly influenced by other sphingolipids and Bcl-2 family proteins. The properties of ceramide channels formed in a defined system, planar phospholipid membranes, demonstrate that proteins are not required for channel formation. In addition, experiments in the defined system reveal structural information. The results indicated that the channels are barrel-like structures whose staves are ceramide columns that span the membrane. Ceramide channels are good candidates for the protein release pathway that initiates the execution phase of apoptosis. © 2010 Elsevier B.V.

Anderson M.L.,Franklin And Marshall College | Anderson M.L.,University of Maryland University College
Behavioral and Brain Sciences | Year: 2010

Abstract An emerging class of theories concerning the functional structure of the brain takes the reuse of neural circuitry for various cognitive purposes to be a central organizational principle. According to these theories, it is quite common for neural circuits established for one purpose to be exapted (exploited, recycled, redeployed) during evolution or normal development, and be put to different uses, often without losing their original functions. Neural reuse theories thus differ from the usual understanding of the role of neural plasticity (which is, after all, a kind of reuse) in brain organization along the following lines: According to neural reuse, circuits can continue to acquire new uses after an initial or original function is established; the acquisition of new uses need not involve unusual circumstances such as injury or loss of established function; and the acquisition of a new use need not involve (much) local change to circuit structure (e.g., it might involve only the establishment of functional connections to new neural partners). Thus, neural reuse theories offer a distinct perspective on several topics of general interest, such as: the evolution and development of the brain, including (for instance) the evolutionary-developmental pathway supporting primate tool use and human language; the degree of modularity in brain organization; the degree of localization of cognitive function; and the cortical parcellation problem and the prospects (and proper methods to employ) for function to structure mapping. The idea also has some practical implications in the areas of rehabilitative medicine and machine interface design. © 2010 Cambridge University Press.

Ganesan V.,University of Maryland University College | Colombini M.,University of Maryland University College
FEBS Letters | Year: 2010

Mitochondrial outer membrane permeabilization to proteins, an irreversible step in apoptosis by which critical proteins are released, is tightly regulated by Bcl-2 family proteins. The exact nature of the release pathway is still undefined. Ceramide is an important sphingolipid, involved in various cellular processes including apoptosis. Here we describe the structural properties of ceramide channels and their regulation by the anti-apoptotic and pro-apoptotic proteins of the Bcl-2 family. The evolutionarily conserved regulation of ceramide channels by Bcl-2 family proteins, consistent with their role in apoptosis, lends credibility to the notion that ceramide channels constitute the protein release pathway. © 2010 Federation of European Biochemical Societies.

Cresce A.V.,U.S. Army | Russell S.M.,U.S. Army | Baker D.R.,U.S. Army | Gaskell K.J.,University of Maryland University College | Xu K.,U.S. Army
Nano Letters | Year: 2014

Despite its importance in dictating electrochemical reversibility and cell chemistry kinetics, the solid electrolyte interphase (SEI) on graphitic anodes remains the least understood component in Li ion batteries due to its trace presence, delicate chemical nature, heterogeneity in morphology, elusive formation mechanism, and lack of reliable in situ quantitative tools to characterize it. This work summarizes our systematic approach to understand SEI live formation, via in situ electrochemical atomic force microscopy, which provides topographic images and quantitative information about the structure, hierarchy, and thickness of interphases as function of electrolyte composition. Complemented by an ex situ chemical analysis, a comprehensive and dynamic picture of interphase formation during the first lithiation cycle of the graphitic anode is described. This combined approach provides an in situ and quantitative tool to conduct quality control of formed interphases. © 2014 American Chemical Society.

Records A.R.,University of Maryland University College
Molecular Plant-Microbe Interactions | Year: 2011

Whether they live in the soil, drift in the ocean, survive in the lungs of human hosts or reside on the surfaces of leaves, all bacteria must cope with an array of environmental stressors. Bacteria have evolved an impressive suite of protein secretion systems that enable their survival in hostile environments and facilitate colonization of eukaryotic hosts. Collectively, gram-negative bacteria produce six distinct secretion systems that deliver proteins to the extracellular milieu or directly into the cytosol of host cells. The type VI secretion system (T6SS) was discovered recently and is encoded in at least one fourth of all sequenced gramnegative bacterial genomes. T6SS proteins are evolutionarily and structurally related to phage proteins, and it is likely that the T6SS apparatus is reminiscent of phage injection machinery. Most studies of T6SS function have been conducted in the context of host-pathogen interactions. However, the totality of data suggests that the T6SS is a versatile tool with roles in virulence, symbiosis, interbacterial interactions, and antipathogenesis. This review gives a brief history of T6SS discovery and an overview of the pathway's predicted structure and function. Special attention is paid to research addressing the T6SS of plant-associated bacteria, including pathogens, symbionts and plant growth-promoting rhizobacteria. © 2011 The American Phytopathological Society.

Li Z.,University of Maryland University College
Journal of Transportation Engineering | Year: 2011

This study presents an arterial signal optimization model that can consider queue blockage among intersection lane groups under oversaturated conditions. The proposed model captures traffic dynamics with the cell transmission concept, which takes into account complex flow interactions among different lane groups. With the embedded formulations for forward wave, backward wave, and the horizontal queue, the proposed arterial signal optimization model can yield effective signal plans for both saturated and under-saturated intersections. To evaluate the performance of the proposed model, this study has conducted extensive simulation experiments with a segment of Georgia Avenue intersecting the Capital Beltway in Silver Spring, Maryland. Through comparisons with signal-timing plans from TRANSYT-7F (Release 10), the proposed model shows its promise for signal-timing optimization, particularly under congested conditions. © 2011 American Society of Civil Engineers.

Huang J.,University of Maryland University College | Yin Z.,CAS Fujian Institute of Research on the Structure of Matter | Zheng Q.,CAS Fujian Institute of Research on the Structure of Matter
Energy and Environmental Science | Year: 2011

As an n-type inorganic semiconductor, ZnO has been widely used in organic solar cells (OSCs) and hybrid solar cells (HSCs) due to its salient characteristics such as low cost, easy synthesis, non-toxicity, high stability, and good optoelectronic properties. This article reviews the applications of ZnO in solar cells, including ZnO/organic HSCs, and OSCs with ZnO acting as electrode buffer layers or transparent electrodes. For ZnO/organic HSCs, ZnO serves as the electron acceptor material, while organic semiconductors act as electron donor materials. For the buffer layers or electrode applications, ZnO is used as an electron collection and hole blocking material where its structure plays an important role in the determination of the device performance (e.g., power conversion efficiency, lifetime, stability, etc.). Special emphasis goes to the device performance of OSCs and HSCs, which depends not only on the active materials and the device configurations, but also on the structural characteristics of the ZnO buffer layer. Finally, we briefly give an analysis on the opportunities and challenges for this promising semiconductor in OSCs and HSCs. © 2011 The Royal Society of Chemistry.

Smith R.S.,University of Maryland University College | Araneda R.C.,University of Maryland University College
Journal of Neurophysiology | Year: 2010

The accessory olfactory bulb (AOB), the first relay of chemosensory information in the Vomeronasal system, receives extensive cholinergic innervation from the basal forebrain. Cholinergic modulation of neuronal activity in the olfactory bulb has been hypothesized to play an important role in olfactory processing; however, little is known about the cellular actions of acetylcholine (ACh) within the AOB. Here using in vitro slice preparation, we show that muscarinic acetylcholine receptor (mAChR) activation increases neuronal excitability of granule and mitral/tufted cells (GCs and MCs) in the AOB. Activation of mAChRs increased excitability of GCs by three distinct mechanisms: induction of a long-lasting depolarization, activation of a slow afterdepolarization (sADP), and an increase in excitatory glutamatergic input due to MC depolarization. The depolarization and sADP were elicited by the selective agonist 4-[[[(3-chlorophenyl)amino] carbonyl]oxy]-N,N,N-trimethyl-2- butyn-1-aminium chloride (100 μM) and blocked by low concentrations of pirenzepine (300 nM), indicating that they result from activation of M1-like mAChRs. In contrast, cholinergic stimulation increased the excitability of MCs via recruitment of nicotinic AChRs (nAChRs) and M1-like mAChRs. Submaximal activation of these receptors, however, decreased the excitability of MCs. Surprisingly, we found that unlike GCs in the main olfactory bulb, GCs in the AOB are excited by mAChR activation in young postnatal neurons, suggesting marked differences in cholinergic regulation of development between these two regions of the olfactory bulb. Copyright © 2010 The American Physiological Society.

Jarzynski C.,University of Maryland University College
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Transitionless quantum driving achieves adiabatic evolution in a hurry, using a counterdiabatic Hamiltonian to stifle nonadiabatic transitions. Here this shortcut to adiabaticity is cast in terms of a generator of adiabatic transport. This yields a classical analog of transitionless driving, and provides a strategy for constructing quantal counterdiabatic Hamiltonians. As an application of this framework, exact classical and quantal counterdiabatic terms are obtained for a particle in a box and for even-power-law potentials in one degree of freedom. © 2013 American Physical Society.

Li T.,University of Maryland University College
Modelling and Simulation in Materials Science and Engineering | Year: 2011

Graphene is intrinsically non-flat and corrugates randomly. Since the corrugating physics of atomically thin graphene is strongly tied to its electronics properties, randomly corrugating morphology of graphene poses a significant challenge to its application in nanoelectronic devices for which precise (digital) control is the key. Recent studies revealed that the morphology of substrate-supported graphene is regulated by the graphene-substrate interaction, thus is distinct from the random intrinsic morphology of freestanding graphene. The regulated extrinsic morphology of graphene sheds light on new pathways to fine tune the properties of graphene. To guide further research to explore these fertile opportunities, this paper reviews recent progress on modeling and experimental studies of the extrinsic morphology of graphene under a wide range of external regulation, including two-dimensional and one-dimensional substrate surface features and one-dimensional and zero-dimensional nanoscale scaffolds (e.g. nanowires and nanoparticles). © 2011 IOP Publishing Ltd.

Bederson B.B.,University of Maryland University College
Behaviour and Information Technology | Year: 2011

Zoomable user interfaces (ZUIs) have received a significant amount of attention in the 18 years since they were introduced. They have enjoyed some success, and elements of ZUIs are widely used in computers today, although the grand vision of a zoomable desktop has not materialised. This paper describes the premise and promise of ZUIs along with their challenges. It describes design guidelines, and offers a cautionary tale about research and innovation. © 2011 Taylor & Francis.

Cavanagh J.F.,University of New Mexico | Shackman A.J.,University of Maryland University College
Journal of Physiology Paris | Year: 2015

Evidence from imaging and anatomical studies suggests that the midcingulate cortex (MCC) is a dynamic hub lying at the interface of affect and cognition. In particular, this neural system appears to integrate information about conflict and punishment in order to optimize behavior in the face of action-outcome uncertainty. In a series of meta-analyses, we show how recent human electrophysiological research provides compelling evidence that frontal-midline theta signals reflecting MCC activity are moderated by anxiety and predict adaptive behavioral adjustments. These findings underscore the importance of frontal theta activity to a broad spectrum of control operations. We argue that frontal-midline theta provides a neurophysiologically plausible mechanism for optimally adjusting behavior to uncertainty, a hallmark of situations that elicit anxiety and demand cognitive control. These observations compel a new perspective on the mechanisms guiding motivated learning and behavior and provide a framework for understanding the role of the MCC in temperament and psychopathology. © 2014 Elsevier Ltd.

Kesar A.S.,University of Maryland University College
IEEE Transactions on Antennas and Propagation | Year: 2011

A method for the detection of underground anomalies by electromagnetic (EM) shock waves is presented. Following Grischkowsky [Phys. Rev. Lett., vol. 59, pp. 16631666, 1987], an EM shock wave will develop in a dielectric medium by exciting a pulse which leaks into the dielectric bulk from a transmission line. A shock wave occurs when the group velocity in the line exceeds the phase velocity in the dielectric. This mechanism is similar to Cherenkov radiation. In this paper the transmission and reception of the EM shock wave between two identical leaky transmission lines is introduced. For underground detection, the two lines are placed in boreholes and are made in a manner in which the speed of propagation in the line is faster than the speed of propagation in the ground. The effect on the shock wave by an underground anomaly such as a dielectric or metallic pipeline located between the two boreholes is studied. The anomaly scatters the shock wave, resulting in a detectable disturbance in the received signal. The time delay of this disturbance, with respect to the time when the pulse was transmitted, is correlated with the location of the object. Numerical examples are presented by using a two-dimensional finite-difference time-domain algorithm. © 2006 IEEE.

Demb J.B.,Yale University | Singer J.H.,University of Maryland University College
Visual Neuroscience | Year: 2012

Amacrine cells represent the most diverse class of retinal neuron, comprising dozens of distinct cell types. Each type exhibits a unique morphology and generates specific visual computations through its synapses with a subset of excitatory interneurons (bipolar cells), other amacrine cells, and output neurons (ganglion cells). Here, we review the intrinsic and network properties that underlie the function of the most common amacrine cell in the mammalian retina, the AII amacrine cell. The AII connects rod and cone photoreceptor pathways, forming an essential link in the circuit for rod-mediated (scotopic) vision. As such, the AII has become known as the rod amacrine cell. We, however, now understand that AII function extends to cone-mediated (photopic) vision, and AII function in scotopic and photopic conditions utilizes the same underlying circuit: AIIs are electrically coupled to each other and to the terminals of some types of ON cone bipolar cells. The direction of signal flow, however, varies with illumination. Under photopic conditions, the AII network constitutes a crossover inhibition pathway that allows ON signals to inhibit OFF ganglion cells and contributes to motion sensitivity in certain ganglion cell types. We discuss how the AII's combination of intrinsic and network properties accounts for its unique role in visual processing. © Copyright Cambridge University Press 2012.

Yarmola T.,University of Maryland University College
Communications in Mathematical Physics | Year: 2011

We consider steady states for a class of mechanical systems with particle-disk interactions coupled to two, possibly unequal, heat baths. We show that any steady state that satisfies some natural assumptions is ergodic and absolutely continuous with respect to a Lebesgue-type reference measure and conclude that there exists at most one absolutely continuous steady state. © 2011 Springer-Verlag.

Barnes E.,University of Maryland University College
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

A simple algorithm is presented based on a type of partial reverse engineering that generates an unlimited number of exact analytical solutions to the Schrödinger equation for a general time-dependent two-level Hamiltonian. I demonstrate this method by deriving exact solutions corresponding to fast control pulses that contain arbitrarily many tunable parameters. It is shown that the formalism is naturally suited to generating analytical control protocols that perform precise nonadiabatic rapid passage and Landau-Zener interferometry near the quantum speed limit. A general, exact formula for Landau-Zener interference patterns is derived. © 2013 American Physical Society.

Butail S.,University of Maryland University College | Paley D.A.,University of Maryland University College
Journal of the Royal Society Interface | Year: 2012

Information transmission via non-verbal cues such as a fright response can be quantified in a fish school by reconstructing individual fish motion in three dimensions. In this paper, we describe an automated tracking framework to reconstruct the full-body trajectories of densely schooling fish using two-dimensional silhouettes in multiple cameras. We model the shape of each fish as a series of elliptical cross sections along a flexible midline. We estimate the size of each ellipse using an iterated extended Kalman filter. The shape model is used in a modelbased tracking framework in which simulated annealing is applied at each step to estimate the midline. Results are presented for eight fish with occlusions. The tracking system is currently being used to investigate fast-start behaviour of schooling fish in response to looming stimuli. © 2011 The Royal Society.

Cho S.,University of Maryland University College | Fuhrer M.,University of Maryland University College
Nano Research | Year: 2011

Electron transport through short, phase-coherent metal-graphene-metal devices occurs via resonant transmission through particle-in-a-box-like states defined by the atomically-sharp metal leads. We study the spectrum of particle-in-a-box states for single- and bi-layer graphene, corresponding to massless and massive two-dimensional (2-D) fermions. The density of states D as a function of particle number n shows the expected relationships D(n) ~ n 1/2 for massless 2-D fermions (electrons in single-layer graphene) and D(n) ~ constant for massive 2-D fermions (electrons in bi-layer graphene). The single parameters of the massless and massive dispersion relations are found, namely Fermi velocity υ F = 1.1 × 10 6 m/s and effective mass m* = 0.032 m e, where m e is the electron mass, in excellent agreement with theoretical expectations.[Figure not available: see fulltext.] © 2011 Tsinghua University Press and Springer-Verlag Berlin Heidelberg.

Liang B.,Changsha University of Science and Technology | Liu Y.,Changsha University of Science and Technology | Xu Y.,University of Maryland University College
Journal of Power Sources | Year: 2014

Silicon (Si)-based materials have the highest capacity among the investigated anode materials and have been recognized as one of the most promising materials for lithium-ion batteries. However, it is still a significant challenge to obtain good performance for practical applications due to the huge volume change during the electrochemical process. To date, the most successful strategy is to introduce other components into Si to form composite or alloy materials. In this review, the recent progress in Si-based materials utilized in lithium-ion batteries is reviewed in terms of composite systems, nano-structure designs, material synthesis methods, and electrochemical performances. The merits and disadvantages of different Si-based materials, the understanding of the mechanisms behind the performance enhancement as well as the challenges faced in Si anodes are also discussed. We are trying to present a full scope of the Si-based materials, and help understand and design future structures of Si anodes in lithium-ion batteries. © 2014 Elsevier B.V. All rights reserved.

O'Brochta D.A.,University of Maryland University College
G3 (Bethesda, Md.) | Year: 2012

Transposon-based forward and reverse genetic technologies will contribute greatly to ongoing efforts to study mosquito functional genomics. A piggyBac transposon-based enhancer-trap system was developed that functions efficiently in the human malaria vector, Anopheles stephensi. The system consists of six transgenic lines of Anopheles stephensi, each with a single piggyBac-Gal4 element in a unique genomic location; six lines with a single piggyBac-UAStdTomato element; and two lines, each with a single Minos element containing the piggyBac-transposase gene under the regulatory control of the hsp70 promoter from Drosophila melanogaster. Enhancer detection depended upon the efficient remobilization of piggyBac-Gal4 transposons, which contain the yeast transcription factor gene Gal4 under the regulatory control of a basal promoter. Gal4 expression was detected through the expression of the fluorescent protein gene tdTomato under the regulatory control of a promoter with Gal4-binding UAS elements. From five genetic screens for larval- and adult-specific enhancers, 314 progeny were recovered from 24,250 total progeny (1.3%) with unique patterns of tdTomato expression arising from the influence of an enhancer. The frequency of piggyBac remobilization and enhancer detection was 2.5- to 3-fold higher in female germ lines compared with male germ lines. A small collection of enhancer-trap lines are described in which Gal4 expression occurred in adult female salivary glands, midgut, and fat body, either singly or in combination. These three tissues play critical roles during the infection of Anopheles stephensi by malaria-causing Plasmodium parasites. This system and the lines generated using it will be valuable resources to ongoing mosquito functional genomics efforts.

Geng C.,University of Maryland University College | Paukstelis P.J.,University of Maryland University College
Journal of the American Chemical Society | Year: 2014

Here we demonstrate that protein enzymes captured in the solvent channels of three-dimensional DNA crystals are catalytically active. Using RNase A as a model enzyme system, we show that crystals infused with enzyme can cleave a dinucleotide substrate with similar kinetic restrictions as other immobilized enzyme systems. This new vehicle for immobilized enzymes, created entirely from biomolecules, opens possibilities for developing modular solid-state catalysts that could be both biocompatible and biodegradable. © 2014 American Chemical Society.

Echeverria I.,University of Maryland University College | Makarov D.E.,University of Texas at Austin | Papoian G.A.,University of Maryland University College
Journal of the American Chemical Society | Year: 2014

Protein chains undergo conformational diffusion during folding and dynamics, experiencing both thermal kicks and viscous drag. Recent experiments have shown that the corresponding friction can be separated into wet friction, which is determined by the solvent viscosity, and dry friction, where frictional effects arise due to the interactions within the protein chain. Despite important advances, the molecular origins underlying dry friction in proteins have remained unclear. To address this problem, we studied the dynamics of the unfolded cold-shock protein at different solvent viscosities and denaturant concentrations. Using extensive all-atom molecular dynamics simulations we estimated the internal friction time scales and found them to agree well with the corresponding experimental measurements (Soranno et al. Proc. Natl. Acad. Sci. U.S.A. 2012, 109, 17800-17806). Analysis of the reconfiguration dynamics of the unfolded chain further revealed that hops in the dihedral space provide the dominant mechanism of internal friction. Furthermore, the increased number of concerted dihedral moves at physiological conditions suggest that, in such conditions, the concerted motions result in higher frictional forces. These findings have important implications for understanding the folding kinetics of proteins as well as the dynamics of intrinsically disordered proteins. © 2014 American Chemical Society.

Peer W.A.,University of Maryland University College | Cheng Y.,Purdue University | Murphy A.S.,University of Maryland University College
Journal of Experimental Botany | Year: 2013

Indole-3-acetic acid (IAA) is the principle auxin in Arabidopsis and is synthesized primarily in meristems and nodes. Auxin is transported to distal parts of the plant in response to developmental programming or environmental stimuli to activate cell-specific responses. As with any signalling event, the signal must be attenuated to allow the system to reset. Local auxin accumulations are thus reduced by conjugation or catabolism when downstream responses have reached their optima. In most cell types, localized auxin accumulation increases both reactive oxygen species (ROS) and an irreversible catabolic product 2-oxindole-3-acid acid (oxIAA). oxIAA is inactive and does not induce expression of the auxin-responsive reporters DR5 or 2XD0. Here it is shown that oxIAA is not transported from cell to cell, although it appears to be a substrate for the ATP-binding cassette subfamily G (ABCG) transporters that are positioned primarily on the outer lateral surface of the root epidermis. However, oxIAA and oxIAA-Glc levels are higher in ABCB mutants that accumulate auxin due to defective cellular export. Auxin-induced ROS production appears to be at least partially mediated by the NAD(P)H oxidase RbohD. oxIAA levels are higher in mutants that lack ROS-scavenging flavonoids (tt4) and are lower in mutants that accumulate excess flavonols (tt3). These data suggest a model where IAA signalling is attenuated by IAA catabolism to oxIAA. Flavonoids appear to buffer ROS accumulations that occur with localized increases in IAA. This buffering of IAA oxidation would explain some growth responses observed in flavonoid-deficient mutants that cannot be explained by their established role in partially inhibiting auxin transport. © 2013 © The Author [2013]. Published by Oxford University Press [on behalf of the Society for Experimental Biology]. All rights reserved.

Schatz M.C.,University of Maryland University College | Delcher A.L.,University of Maryland University College | Salzberg S.L.,University of Maryland University College
Genome Research | Year: 2010

Second-generation sequencing technology can now be used to sequence an entire human genome in a matter of days and at low cost. Sequence read lengths, initially very short, have rapidly increased since the technology first appeared, and we now are seeing a growing number of efforts to sequence large genomes de novo from these short reads. In this Perspective, we describe the issues associated with short-read assembly, the different types of data produced by second-gen sequencers, and the latest assembly algorithms designed for these data. We also review the genomes that have been assembled recently from short reads and make recommendations for sequencing strategies that will yield a high-quality assembly. © 2010 by Cold Spring Harbor Laboratory Press.

Torrens P.M.,University of Maryland University College
Annals of GIS | Year: 2015

Virtual geographic environments (VGEs) have long enjoyed significant synergy with geosimulation as a visual medium for model results, but more could be done to fashion two-way harmony between them, with the potential benefit that geosimulation could usefully serve as a process engine for VGEs and as a unifying scaffold for connecting VGEs to other systems. In this article, I argue for three promising bridges between geosimulation and VGEs. First, geosimulation could be relied upon in introducing synthetic human characters in VGEs to augment the significant physical detail that VGEs currently provide with ambient behavioural processes. Second, building blocks of geosimulation, based around polyspatial automata, could help to resolve long-standing requirements for common data and process models for VGEs. Finally, slipstreaming of geographic information across geosimulation and VGE scaffolds could be useful in reconciling diverse and many-model processes, with disparate form and scales, in a cohesive pipeline. Together, these three variations can facilitate the exchange of diverse model objects, processes, and information between geosimulation and VGEs, greatly expanding their interoperability and explorative reach. I demonstrate the usefulness of these developments with example scenarios that focus on urban mobilities, urban complexity, and urban failures in both ordinary and extraordinary scenarios. Applications to urban phenomena, in particular, may have particular value as we approach new vantages on cities supported by big data, big awareness, and immersive media that greatly expand the volume, breadth, and depth of questioning that our VGEs may be called on to support. © 2015 Paul Torrens.

Coasne B.,Charles Gerhardt Institute | Fourkas J.T.,University of Maryland University College
Journal of Physical Chemistry C | Year: 2011

The structure and dynamics of benzene confined at 293 K in silica nanopores of different diameters (D = 2.0 nm and D = 3.6 nm) are investigated by means of grand canonical Monte Carlo and molecular dynamics simulations. In order to account in a realistic way for the interactions between benzene and the silica surface, we consider a recent model that accounts for the π-electrons of the aromatic cycle in the benzene molecule. Confined benzene exhibits significant layering and orientational ordering in the vicinity of the silica surface (up to two adsorbed layers) and tends to recover its bulk properties in the pore center. Using suitable order parameters, we show that benzene molecules close to the pore surface tend to have their ring lying flat on the silica surface (and hence perpendicular to the pore axis). Such a preferential parallel orientation with respect to the silica surface suggests that a proper description of the π-electrons of the benzene aromatic ring and its specific Coulombic interaction with the partial charges carried by the silica atoms is crucial. The dynamics of benzene confined in the silica nanopores is always slower than in the bulk. Both the translational and rotational dynamics of confined benzene can be described as a bulklike contribution in the pore center that depends on the pore size and a surface contribution that is nearly insensitive to the pore size. These simulation results are discussed in the light of available experimental data on the structure and dynamics of benzene confined in nanoporous silicas. © 2011 American Chemical Society.

Lu H.,University of Massachusetts Amherst | Akgun B.,U.S. National Institute of Standards and Technology | Akgun B.,University of Maryland University College | Russell T.P.,University of Massachusetts Amherst
Advanced Energy Materials | Year: 2011

Understanding the morphology of polymer-based bulk heterojunction (BHJ) solar cells is necessary to improve device efficiencies. Blends of a lowbandgap silole-containing conjugated polymer, poly[(4,4 ′ -bis(2-ethylhexyl) dithieno[3,2-b;2 ′,3 ′ -d]silole)-2,6-diyl-alt-(4,7-bis(2-thienyl)- 2,1,3-benzothiadiazole)-5,5 ′ -diyl] (PSBTBT) with [6,6]phenyl-C61-butyric acid methyl ester (PCBM) were investigated under different processing conditions. The surface morphologies and vertical segregation of the "As-Spun", "Pre-Annealed", and "Post-Annealed" fi lms were studied by scanning force microscopy, contact angle measurements, X-ray photoelectron spectroscopy, near-edge X-ray absorption fi ne structure spectroscopy, dynamic secondary ion mass spectrometry, and neutron reflectivity. The results showed that PSBTBT was enriched at the cathode interface in the "As-Spun" films and thermal annealing increased the segregation of PSBTBT to the free surface, while thermal annealing after deposition of the cathode increased the PCBM concentration at the cathode interface. Grazing-incidence X-ray diffraction and small-angle neutron scattering showed that the crystallization of PSBTBT and segregation of PCBM occurred during spin coating, and thermal annealing increased the ordering of PSBTBT and enhanced the segregation of the PCBM, forming domains ∼10 nm in size, leading to an improvement in photo voltaic performance. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Antolovich S.D.,Georgia Institute of Technology | Antolovich S.D.,Washington State University | Armstrong R.W.,University of Maryland University College
Progress in Materials Science | Year: 2014

This article focuses on the mechanisms and consequences of plastic strain localizations exhibited in tensile stress-strain behaviors, fracture and fatigue. A broad overview is first presented, including important practical considerations and historical background; then dislocation mechanics based details are developed in subsequent sections. Material characterizations are portrayed beginning from the macroscopic and extending down to the critical nanoscale. Controlling influences of temperature, strain rate, grain size and deformation mode on strain localization are evaluated. Relations are established between otherwise apparently disparate variations in phenomena, materials, applied conditions, and size scales. Strengths and weaknesses of various model descriptions of material behaviors are discussed in light of experimental evidence and suggestions are put forward for further research into promising model approaches and for areas where new approaches appear to be needed. A paradigm is suggested for the development of improvements in understanding based on the needed evolution of ever-increasingly precise experimental results, accurate theoretical model descriptions and incorporation of this information into the rapidly progressing development of numerical/computer modelling of real material behaviors. © 2013 Elsevier Ltd. All rights reserved.

Hyeon C.,Korea Institute for Advanced Study | Thirumalai D.,University of Maryland University College
Nature Communications | Year: 2011

The distances over which biological molecules and their complexes can function range from a few nanometres, in the case of folded structures, to millimetres, for example, during chromosome organization. Describing phenomena that cover such diverse length, and also time, scales requires models that capture the underlying physics for the particular length scale of interest. Theoretical ideas, in particular, concepts from polymer physics, have guided the development of coarse-grained models to study folding of DNA, RNA and proteins. More recently, such models and their variants have been applied to the functions of biological nanomachines. Simulations using coarse-grained models are now poised to address a wide range of problems in biology. © 2011 Macmillan Publishers Limited. All rights reserved.

Ceccagnoli M.,Georgia Institute of Technology | Forman C.,Georgia Institute of Technology | Huang P.,University of Maryland University College | Wu D.J.,Georgia Institute of Technology
MIS Quarterly: Management Information Systems | Year: 2012

It has been argued that platform technology owners cocreate business value with other firms in their platform ecosystems by encouraging complementary invention and exploiting indirect network effects. In this study, we examine whether participation in an ecosystem partnership improves the business performance of small independent software vendors (ISVs) in the enterprise software industry and how appropriability mechanisms influence the benefits of partnership. By analyzing the partnering activities and performance indicators of a sample of 1,210 small ISVs over the period 1996-2004, we find that joining a major platform owner's platform ecosystem is associated with an increase in sales and a greater likelihood of issuing an initial public offering (IPO). In addition, we show that these impacts are greater when ISVs have greater intellectual property rights or stronger downstream capabilities. This research highlights the value of interoperability between software products, and stresses that value cocreation and appropriation are not mutually exclusive strategies in interfirm collaboration.

Liu R.,University of Maryland University College | Duay J.,University of Maryland University College | Lee S.B.,University of Maryland University College | Lee S.B.,Korea Institute of Science and Technology
Chemical Communications | Year: 2011

In order to fulfil the future requirements of electrochemical energy storage, such as high energy density at high power demands, heterogeneous nanostructured materials are currently studied as promising electrode materials due to their synergic properties, which arise from integrating multi-nanocomponents, each tailored to address a different demand (e.g., high energy density, high conductivity, and excellent mechanical stability). In this article, we discuss these heterogeneous nanomaterials based on their structural complexity: zero-dimensional (0-D) (e.g. core-shell nanoparticles), one-dimensional (1-D) (e.g. coaxial nanowires), two-dimensional (2-D) (e.g. graphene based composites), three-dimensional (3-D) (e.g. mesoporous carbon based composites) and the even more complex hierarchical 3-D nanostructured networks. This review tends to focus more on ordered arrays of 1-D heterogeneous nanomaterials due to their unique merits. Examples of different types of structures are listed and their advantages and disadvantages are compared. Finally a future 3-D heterogeneous nanostructure is proposed, which may set a goal toward developing ideal nano-architectured electrodes for future electrochemical energy storage devices. © 2011 The Royal Society of Chemistry.

Kapit E.,University of Oxford | Hafezi M.,University of Maryland University College | Simon S.H.,University of Oxford
Physical Review X | Year: 2014

Recent progress in nanoscale quantum optics and superconducting qubits has made the creation of strongly correlated, and even topologically ordered, states of photons a real possibility. Many of these states are gapped and exhibit anyon excitations, which could be used for a robust form of quantum information processing. However, while numerous qubit array proposals exist to engineer the Hamiltonian for these systems, the question of how to stabilize the many-body ground state of these photonic quantum simulators against photon losses remains largely unanswered. We here propose a simple mechanism that achieves this goal for Abelian and non-Abelian fractional quantum Hall states of light. Our construction uses a uniform two-photon drive field to couple the qubits of the primary lattice with an auxiliary "shadow" lattice, composed of qubits with a much faster loss rate than the qubits of the primary quantum simulator itself. This coupling causes hole states created by photon losses to be rapidly refilled, and the system's manybody gap prevents further photons from being added once the strongly correlated ground state is reached. The fractional quantum Hall state (with a small, transient population of quasihole excitations) is thus the most stable state of the system, and all other configurations will relax toward it over time. The physics described here could be implemented in a circuit QED architecture, and the device parameters needed for our scheme to succeed are in reach of current technology.We also propose a simple six-qubit device, which could easily be built in the near future, that can act as a proof of principle for our scheme.

Heffer A.,University of Maryland University College | Pick L.,University of Maryland University College
Annual Review of Entomology | Year: 2013

Evolutionary developmental biology, or evo-devo, broadly investigates how body plan diversity and morphological novelties have arisen and persisted in nature. The discovery of Hox genes in Drosophila, and their subsequent identification in most other metazoans, led biologists to try to understand how embryonic genes crucial for proper development have changed to promote the vast morphological variation seen in nature. Insects are ideal model systems for studying this diversity and the mechanisms underlying it because phylogenetic relationships are well established, powerful genetic tools have been developed, and there are many examples of evolutionary specializations that have arisen in nature in different insect lineages, such as the jumping leg of orthopterans and the helmet structures of treehoppers. Here, we briefly introduce the field of evo-devo and Hox genes, discuss functional tools available to study early developmental genes in insects, and provide examples in which changes in Hox genes have contributed to changes in body plan or morphology. © 2013 by Annual Reviews. All rights reserved.

Anderson C.M.,NASA | Samuelson R.E.,University of Maryland University College
Icarus | Year: 2011

Vertical distributions and spectral characteristics of Titan's photochemical aerosol and stratospheric ices are determined between 20 and 560cm-1 (500-18μm) from the Cassini Composite Infrared Spectrometer (CIRS). Results are obtained for latitudes of 15°N, 15°S, and 58°S, where accurate temperature profiles can be independently determined. In addition, estimates of aerosol and ice abundances at 62°N relative to those at 15°S are derived. Aerosol abundances are comparable at the two latitudes, but stratospheric ices are ∼3 times more abundant at 62°N than at 15°S. Generally, nitrile ice clouds (probably HCN and HC3N), as inferred from a composite emission feature at ∼160cm-1, appear to be located over a narrow altitude range in the stratosphere centered at ∼90km. Although most abundant at high northern latitudes, these nitrile ice clouds extend down through low latitudes and into mid southern latitudes, at least as far as 58°S. There is some evidence of a second ice cloud layer at ∼60km altitude at 58°S associated with an emission feature at ∼80cm-1. We speculate that the identify of this cloud may be due to C2H6 ice, which in the vapor phase is the most abundant hydrocarbon (next to CH4) in the stratosphere of Titan. Unlike the highly restricted range of altitudes (50-100km) associated with organic condensate clouds, Titan's photochemical aerosol appears to be well-mixed from the surface to the top of the stratosphere near an altitude of 300km, and the spectral shape does not appear to change between 15°N and 58°S latitude. The ratio of aerosol-to-gas scale heights range from 1.3-2.4 at about 160km to 1.1-1.4 at 300km, although there is considerable variability with latitude. The aerosol exhibits a very broad emission feature peaking at ∼140cm-1. Due to its extreme breadth and low wavenumber, we speculate that this feature may be caused by low-energy vibrations of two-dimensional lattice structures of large molecules. Examples of such molecules include polycyclic aromatic hydrocarbons (PAHs) and nitrogenated aromatics. Finally, volume extinction coefficients NχE derived from 15°S CIRS data at a wavelength of λ=62.5μm are compared with those derived from the 10°S Huygens Descent Imager/Spectral Radiometer (DISR) data at 1.583μm. This comparison yields volume extinction coefficient ratios NχE(1.583μm)/NχE(62.5μm) of roughly 70 and 20, respectively, for Titan's aerosol and stratospheric ices. The inferred particle cross-section ratios χE(1.583μm)/χE(62.5μm) appear to be consistent with sub-micron size aerosol particles, and effective radii of only a few microns for stratospheric ice cloud particles. © 2011.

Das Sarma S.,University of Maryland University College | Sau J.D.,Harvard University | Stanescu T.D.,West Virginia University
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Recent observations of a zero-bias conductance peak in tunneling transport measurements in superconductor-semiconductor nanowire devices provide evidence for the predicted zero-energy Majorana modes, but not the conclusive proof of their existence. We establish that direct observation of a splitting of the zero-bias conductance peak can serve as the smoking gun evidence for the existence of the Majorana mode. We show that the splitting has an oscillatory dependence on the Zeeman field (chemical potential) at fixed chemical potential (Zeeman field). By contrast, when the density is constant rather than the chemical potential - the likely situation in the current experimental setups - the splitting oscillations are generically suppressed. Our theory predicts the conditions under which the splitting oscillations can serve as the smoking gun for the experimental confirmation of the elusive Majorana mode. © 2012 American Physical Society.

Cheng M.,University of Maryland University College
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We study the superconducting proximity effect on the helical edge states of time-reversal-symmetric fractional topological insulators (FTI). The Cooper pairing of physical electrons results in many-particle condensation of the fractionalized excitations on the edge. We find localized zero-energy modes emerge at interfaces between superconducting regions and magnetically insulating regions, which are responsible for the topological degeneracy of the ground states. By mapping the low-energy effective Hamiltonian to the quantum chiral Potts model, we determine the operator algebra of the zero modes and show that they exhibit nontrivial braiding properties. We then demonstrate that the Josephson current in the junction between superconductors mediated by the edge states of the FTI exhibit fractional Josephson effect with period as multiples of 4π. © 2012 American Physical Society.

Smolyaninov I.I.,University of Maryland University College | Narimanov E.E.,Purdue University
Physical Review Letters | Year: 2010

We demonstrate that the extraordinary waves in indefinite metamaterials experience an ( - ++) effective metric signature. During a metric signature change transition in such a metamaterial, a Minkowski space-time is created together with a large number of particles populating the space-time. Such metamaterial models provide a tabletop realization of metric signature change events suggested to occur in Bose-Einstein condensates and quantum gravity theories. © 2010 The American Physical Society.

Bertrand C.E.,University of Maryland University College | Anisimov M.A.,University of Maryland University College
Physical Review Letters | Year: 2010

Complete scaling, which maps asymmetric fluid criticality onto the symmetric Ising model, is extended to spatially inhomogeneous fluids. This extension enables us to obtain a fluctuation-modified asymmetric interfacial density profile, which incorporates leading effects from the asymmetry of fluid phase coexistence and the asymmetry of the correlation length. The derived asymmetric interfacial profile is used to calculate Tolman's length, the diverging coefficient of the curvature correction to the surface tension. The amplitude of the divergent Tolman length is found to depend on the asymmetry of the correlation length. © 2010 The American Physical Society.

Sau J.D.,University of Maryland University College | Lutchyn R.M.,University of Maryland University College | Tewari S.,University of Maryland University College | Tewari S.,Clemson University | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2010

We show that a film of a semiconductor in which s-wave superconductivity and Zeeman splitting are induced by the proximity effect, supports zero-energy Majorana fermion modes in the ordinary vortex excitations. Since time-reversal symmetry is explicitly broken, the edge of the film constitutes a chiral Majorana wire. The heterostructure we propose-a semiconducting thin film sandwiched between an s-wave superconductor and a magnetic insulator-is a generic system which can be used as the platform for topological quantum computation by virtue of the existence of non-Abelian Majorana fermions. © 2010 The American Physical Society.

Jacobson T.,University of Maryland University College | Sotiriou T.P.,University of Cambridge
Physical Review Letters | Year: 2010

It has recently been pointed out that particles falling freely from rest at infinity outside a Kerr black hole can in principle collide with an arbitrarily high center of mass energy in the limiting case of maximal black hole spin. Here we aim to elucidate the mechanism for this fascinating result, and to point out its practical limitations, which imply that ultraenergetic collisions cannot occur near black holes in nature. © 2010 The American Physical Society.

Banerjee A.,University of Maryland University College | Yakovenko V.M.,University of Maryland University College
New Journal of Physics | Year: 2010

Probability distributions of money, income and energy consumption per capita are studied for ensembles of economic agents. The principle of entropy maximization for partitioning of a limited resource gives exponential distributions for the investigated variables. A non-equilibrium difference of money temperatures between different systems generates net fluxes of money and population. To describe income distribution, a stochastic process with additive and multiplicative components is introduced. The resultant distribution interpolates between exponential at the low end and power law at the high end, in agreement with the empirical data for the USA. We show that the increase in income inequality in the USA originates primarily from the increase in the income fraction going to the upper tail, which now exceeds 20% of the total income. Analyzing the data from the World Resources Institute, we find that the distribution of energy consumption per capita around the world can be approximately described by the exponential function. Comparing the data for 1990, 2000 and 2005, we discuss the effect of globalization on the inequality of energy consumption. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Biddle J.,University of Maryland University College | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2010

Localization properties of noninteracting quantum particles in one-dimensional incommensurate lattices are investigated with an exponential short-range hopping that is beyond the minimal nearest-neighbor tight-binding model. Energy dependent mobility edges are analytically predicted in this model and verified with numerical calculations. The results are then mapped to the continuum Schrödinger equation, and an approximate analytical expression for the localization phase diagram and the energy dependent mobility edges in the ground band is obtained. © 2010 The American Physical Society.

Storni M.,Paul Scherrer Institute | Morf R.H.,Paul Scherrer Institute | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2010

Using exact diagonalization we show that the spin-polarized Coulomb ground state at ν=52 is adiabatically connected with the Moore-Read wave function for systems with up to 18 electrons on the surface of a sphere. The ground state is protected by a large gap for all system sizes studied. Furthermore, varying the Haldane pseudopotentials v1 and v3, keeping all others at their value for the Coulomb interaction, energy gap and overlap between ground- and Moore-Read state form hills whose positions and extent in the (v1,v3) plane coincide. We conclude that the physics of the Coulomb ground state at ν=52 is captured by the Moore-Read state. Such an adiabatic connection is not found at ν=12, unless the width of the interface wave function or Landau level mixing effects are large enough. Yet, a Moore-Read-phase at ν=12 appears unlikely in the thermodynamic limit. © 2010 The American Physical Society.

Zhou Q.,University of Maryland University College | Ho T.-L.,Ohio State University
Physical Review Letters | Year: 2010

In recent years, there has been considerable experimental effort using cold atoms to study strongly correlated many-body systems. One class of phenomena of particular interest is quantum critical (QC) phenomena. While prevalent in many materials, these phenomena pose notoriously difficult theoretical problems due to the vanishing of energy scales in the QC region. So far, there are no systematic ways to deduce the QC behavior of bulk systems from the data of trapped atomic gases. Here, we present a simple algorithm to use the experimental density profile to determine the T=0 phase boundary of bulk systems, as well as the scaling functions in the QC regime. We also present another scheme for removing finite-size effects of the trap. We demonstrate the validity of our schemes using exactly soluble models. © 2010 The American Physical Society.

Lutchyn R.M.,University of Maryland University College | Sau J.D.,University of Maryland University College | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2010

We propose and analyze theoretically an experimental setup for detecting the elusive Majorana particle in semiconductor-superconductor heterostructures. The experimental system consists of one-dimensional semiconductor wire with strong spin-orbit Rashba interaction embedded into a superconducting quantum interference device. We show that the energy spectra of the Andreev bound states at the junction are qualitatively different in topologically trivial (i.e., not containing any Majorana) and nontrivial phases having an even and odd number of crossings at zero energy, respectively. The measurement of the supercurrent through the junction allows one to discern topologically distinct phases and observe a topological phase transition by simply changing the in-plane magnetic field or the gate voltage. The observation of this phase transition will be a direct demonstration of the existence of Majorana particles. © 2010 The American Physical Society.

Ahmed I.I.,University of Maryland University College | Gupta A.K.,University of Maryland University College
Applied Energy | Year: 2010

Characteristics of syngas from the pyrolysis and gasification of food waste has been investigated. Characteristic differences in syngas properties and overall yields from pyrolysis and gasification were determined at two distinct high temperatures of 800 and 900 °C. Pyrolysis and gasification behavior were evaluated in terms of syngas flow rate, hydrogen flow rate, output power, total syngas yield, total hydrogen yield, total energy yield, and apparent thermal efficiency. Gasification was more beneficial than pyrolysis based on investigated criteria, but longer time was needed to finish the gasification process. Longer time of gasification is attributed to slow reactions between the residual char and gasifying agent. Consequently, the char gasification kinetics was investigated. Inorganic constituents of food char were found to have a catalytic effect. Char reactivity increased with increased degree of conversion. In the conversion range from 0.1 to 0.9 the increase in reactivity was accompanied by an increase in pre-exponential factor, which suggested an increase in gasifying agent adsorption rate to char surface. However, in the conversion range from 0.93 to 0.98 the increase in reactivity was accompanied by a decrease in activation energy. A compensation effect was observed in this range of conversion of 0.93-0.98. © 2009 Elsevier Ltd. All rights reserved.

A'Hearn M.F.,University of Maryland University College
Annual Review of Astronomy and Astrophysics | Year: 2011

Recent results, many but not all from flybys of comets by spacecraft, particularly the results from Deep Impact, have dramatically improved our understanding of the physical properties of cometary nuclei. Characteristic features are modest size (R<20 km), high porosity, low strength, and heterogeneity. There is also evidence that can be interpreted as showing the original cometesimals in a cometary nucleus and suggesting radial migration of macroscopic cometesimals during the aggregation of nuclei, which in turn aggregated into the cores of the giant planets. © 2011 by Annual Reviews. All rights reserved.

Levin M.,University of Maryland University College | Stern A.,Weizmann Institute of Science
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We present a general framework for analyzing fractionalized, time-reversal invariant electronic insulators in two dimensions. The framework applies to all insulators whose quasiparticles have Abelian braiding statistics. First, we construct the most general Chern-Simons theories that can describe these states. We then derive a criterion for when these systems have protected gapless edge modes, that is, edge modes that cannot be gapped out without breaking time-reversal or charge-conservation symmetry. The systems with protected edge modes can be regarded as fractionalized analogues of topological insulators. We show that previous examples of 2D fractional topological insulators are special cases of this general construction. As part of our derivation, we define the concept of "local Kramers degeneracy" and prove a local version of Kramers theorem. © 2012 American Physical Society.

Pershoguba S.S.,University of Maryland University College | Yakovenko V.M.,University of Maryland University College
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Surface states in topological insulators can be understood based on the well-known Shockley model, a one-dimensional tight-binding model with two atoms per elementary cell, connected via alternating tunneling amplitudes. We generalize the one-dimensional model to the three-dimensional case representing a sequence of layers connected via tunneling amplitudes t, which depend on the in-plane momentum p=(p x,p y). The Hamiltonian of the model is a 2×2 matrix with the off-diagonal element t(k,p) depending also on the out-of-plane momentum k. We show that the existence of the surface states depends on the complex function t(k,p). The surface states exist for those in-plane momenta p where the winding number of the function t(k,p) is nonzero when k is changed from 0 to 2π. The sign of the winding number determines the sublattice on which the surface states are localized. The equation t(k,p)=0 defines a vortex line in the three-dimensional momentum space. Projection of the vortex line onto the space of the two-dimensional momentum p encircles the domain where the surface states exist. We illustrate how this approach works for a well-known model of a topological insulator on the diamond lattice. We find that different configurations of the vortex lines are responsible for the "weak" and "strong" topological insulator phases. A topological transition occurs when the vortex lines reconnect from spiral to circular form. We apply the Shockley model to Bi 2Se 3 and discuss applicability of a continuous approximation for the description of the surface states. We conclude that the tight-binding model gives a better description of the surface states. © 2012 American Physical Society.

Shekhar S.,University of Maryland University College | Patel V.M.,University of Maryland University College | Nasrabadi N.M.,U.S. Army | Chellappa R.,University of Maryland University College
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2014

Traditional biometric recognition systems rely on a single biometric signature for authentication. While the advantage of using multiple sources of information for establishing the identity has been widely recognized, computational models for multimodal biometrics recognition have only recently received attention. We propose a multimodal sparse representation method, which represents the test data by a sparse linear combination of training data, while constraining the observations from different modalities of the test subject to share their sparse representations. Thus, we simultaneously take into account correlations as well as coupling information among biometric modalities. A multimodal quality measure is also proposed to weigh each modality as it gets fused. Furthermore, we also kernelize the algorithm to handle nonlinearity in data. The optimization problem is solved using an efficient alternative direction method. Various experiments show that the proposed method compares favorably with competing fusion-based methods. © 1979-2012 IEEE.

Guadagnoli D.,TU Munich | Mohapatra R.N.,University of Maryland University College
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

In minimal left-right symmetric models, the mass of the neutral Higgs field mediating tree-level flavor changing effects (FCNH) is directly related to the parity breaking scale. Specifically, the lower bound on the Higgs mass coming from Higgs-induced tree-level effects, and exceeding about 15 TeV, would tend to imply a WR mass bound much higher than that required by gauge exchange loop effects - the latter allowing WR masses as low as 2.5 TeV. Since a WR mass below 4 TeV is accessible at the LHC, it is important to investigate ways to decouple the FCNH effects from the WR mass. In this Letter, we present a model where this happens, providing new motivation for LHC searches for WR in the 1-4 TeV mass range. © 2010 Elsevier B.V.

Pessoa L.,University of Maryland University College
Behavioral and Brain Sciences | Year: 2012

Lindquist et al. provide a convincing case against what they call the locationist account of emotion. Their quantitative approach elegantly illustrates the shortcomings of this still-entrenched viewpoint. Here, I discuss how a network perspective will advance our understanding of structure-function mappings in general, and the relationship between emotion and cognition in the brain. © 2012 Cambridge University Press.

Webber W.,University of Maryland University College
ACM Transactions on Information Systems | Year: 2013

Recall, the proportion of relevant documents retrieved, is an important measure of effectiveness in information retrieval, particularly in the legal, patent, and medical domains. Where document sets are too large for exhaustive relevance assessment, recall can be estimated by assessing a random sample of documents, but an indication of the reliability of this estimate is also required. In this article, we examine several methods for estimating two-tailed recall confidence intervals. We find that the normal approximation in current use provides poor coverage in many circumstances, even when adjusted to correct its inappropriate symmetry. Analytic and Bayesian methods based on the ratio of binomials are generally more accurate but are inaccurate on small populations. The method we recommend derives beta-binomial posteriors on retrieved and unretrieved yield, with fixed hyperparameters, and a Monte Carlo estimate of the posterior distribution of recall. We demonstrate that this method gives mean coverage at or near the nominal level, across several scenarios, while being balanced and stable. We offer advice on sampling design, including the allocation of assessments to the retrieved and unretrieved segments, and compare the proposed beta-binomial with the officially reported normal intervals for recent TREC Legal Track iterations. © 2013 ACM 1046-8188/2013/01-ART2 s15.00.

Chun S.H.,Samsung | La R.J.,University of Maryland University College
IEEE/ACM Transactions on Networking | Year: 2013

Recently, dynamic spectrum sharing has been gaining interest as a potential solution to scarcity of available spectrum. We investigate the problem of designing a secondary spectrum-trading market when there are multiple sellers and multiple buyers and propose a general framework for the trading market based on an auction mechanism. To this end, we first introduce a new optimal auction mechanism, called the generalized Branco's mechanism (GBM). The GBM, which is both incentive-compatible and individually rational, is used to determine the assigned frequency bands and prices for them. Second, we assume that buyers of the spectrum are selfish and model their interaction as a noncooperative game. Using this model, we prove that when the sellers employ the GBM to vend their frequency bands, they can guarantee themselves the largest expected profits by selling their frequency bands jointly. Third, based on the previous finding, we model the interaction among the sellers as a cooperative game and demonstrate that, for any fixed strategies of the buyers, the core of the cooperative game is nonempty. This suggests that there exists a way for the sellers to share the profits from the joint sale of the spectrum so that no subset of sellers will find it beneficial to vend their frequency bands separately without the remaining sellers. Finally, we propose a profit-sharing scheme that can achieve any expected profit vector in the nonempty core of the cooperative game while satisfying two desirable properties. © 1993-2012 IEEE.

Xu X.,University of Maryland University College | Zavalij P.Y.,University of Maryland University College | Doyle M.P.,University of Maryland University College
Angewandte Chemie - International Edition | Year: 2012

A versatile cascade of reactions, triggered by RhII-catalyzed diazo decomposition followed by a vinylogous N-H insertion/Lewis acid catalyzed Mannich addition, that produces highly substituted 1,2,3,6-tetrahydropyridazines in up to 97% ee with high yield and diastereocontrol has been developed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pershoguba S.S.,University of Maryland University College | Kechedzhi K.,University of Maryland University College | Yakovenko V.M.,University of Maryland University College
Physical Review Letters | Year: 2013

We propose a novel chiral order parameter to explain the unusual polar Kerr effect in underdoped cuprates. It is based on the loop-current model by Varma, which is characterized by the in-plane anapole moment N and exhibits the magnetoelectric effect. We propose a helical structure where the vector N( n) in the layer n is twisted by the angle π/2 relative to N(n -1), thus breaking inversion symmetry. We show that coupling between magnetoelectric terms in the neighboring layers for this structure produces optical gyrotropy, which results in circular dichroism and the polar Kerr effect. © 2013 American Physical Society.

Bazinet A.L.,University of Maryland University College | Cummings M.P.,University of Maryland University College
BMC Bioinformatics | Year: 2012

Background: A fundamental problem in modern genomics is to taxonomically or functionally classify DNA sequence fragments derived from environmental sampling (i.e., metagenomics). Several different methods have been proposed for doing this effectively and efficiently, and many have been implemented in software. In addition to varying their basic algorithmic approach to classification, some methods screen sequence reads for 'barcoding genes' like 16S rRNA, or various types of protein-coding genes. Due to the sheer number and complexity of methods, it can be difficult for a researcher to choose one that is well-suited for a particular analysis.Results: We divided the very large number of programs that have been released in recent years for solving the sequence classification problem into three main categories based on the general algorithm they use to compare a query sequence against a database of sequences. We also evaluated the performance of the leading programs in each category on data sets whose taxonomic and functional composition is known.Conclusions: We found significant variability in classification accuracy, precision, and resource consumption of sequence classification programs when used to analyze various metagenomics data sets. However, we observe some general trends and patterns that will be useful to researchers who use sequence classification programs. © 2012 Bazinet and Cummings; licensee BioMed Central Ltd.

Ottinger M.A.,University of Maryland University College
Annals of the New York Academy of Sciences | Year: 2010

The interplay of neuroendocrine processes and gonadal function is exquisitely expressed during aging. In females, loss of ovarian function results in decreased circulating estradiol. As a result, estrogen-dependent endocrine and behavioral responses decline, including impaired cognitive function reflecting the impact of declining estrogen on the hippocampus circuits, and decreased metabolic endocrine function. Concurrently, age-related changes in neuroendocrine response also contribute to the declining reproductive function. Our session considered key mechanisms in reproductive aging including the roles of ovarian function (Finch and Holmes) and the hypothalamic median eminence (Yin and Gore) with an associated age-related cognitive decline that accompanies estrogen loss (Morrison and colleagues). Effects of smoking, obesity, and insulin resistance (Sowers and colleagues) impact the timing of the perimenopause transition in women. Animal models provide excellent insights into conserved mechanisms and key overarching events that bring about endocrine and behavioral aging. Environmental factors are key triggers in timing endocrine aging with implications for eventual disease. Session presentations will be considered in the context of the broader topic of indices and predictors of aging-related change. © 2010 New York Academy of Sciences.

Deffayet C.,CNRS Astroparticle and Cosmology Lab | Jacobson T.,University of Maryland University College
Classical and Quantum Gravity | Year: 2012

We discuss the structure of horizons in spacetimes with two metrics, with applications to the Vainshtein mechanism and other examples. We show, without using the field equations, that if the two metrics are static, spherically symmetric, nonsingular and diagonal in a common coordinate system, then a Killing horizon for one must also be a Killing horizon for the other. We then generalize this result to the axisymmetric case. We also show that the surface gravities must agree if the bifurcation surface in one spacetime lies smoothly in the interior of the spacetime of the other metric. These results imply for example that the Vainshtein mechanism of nonlinear massive gravity theories cannot work to recover black holes if the dynamical metric and the non-dynamical flat metric are both diagonal. They also explain the global structure of some known solutions of bigravity theories with one diagonal and one non-diagonal metric, in which the bifurcation surface of the Killing field lies in the interior of one spacetime and on the conformal boundary of the other. © 2012 IOP Publishing Ltd.

Skinner M.A.,University of Maryland University College | Ostriker E.C.,University of Maryland University College
Astrophysical Journal, Supplement Series | Year: 2010

A method for implementing cylindrical coordinates in the Athena magnetohydrodynamics (MHD) code is described. The extension follows the approach of Athena's original developers and has been designed to alter the existing Cartesian-coordinates code as minimally and transparently as possible. The numerical equations in cylindrical coordinates are formulated to maintain consistency with constrained transport (CT), a central feature of the Athena algorithm, while making use of previously implemented code modules such as the Riemann solvers. Angular momentum transport, which is critical in astrophysical disk systems dominated by rotation, is treated carefully. We describe modifications for cylindrical coordinates of the higher-order spatial reconstruction and characteristic evolution steps as well as the finite-volume and CT updates. Finally, we present a test suite of standard and novel problems in one, two, and three dimensions designed to validate our algorithms and implementation and to be of use to other code developers. The code is suitable for use in a wide variety of astrophysical applications and is freely available for download on the Web. © 2010. The American Astronomical Society. All rights reserved.

Wolff C.L.,NASA | Patrone P.N.,University of Maryland University College
Solar Physics | Year: 2010

We derive a perturbation inside a rotating star that occurs when the star is accelerated by orbiting bodies. If a fluid element has rotational and orbital components of angular momentum with respect to the inertially fixed point of a planetary system that are of opposite sign, then the element may have potential energy that could be released by a suitable flow. We demonstrate the energy with a very simple model in which two fluid elements of equal mass exchange positions, calling to mind a turbulent field or natural convection. The exchange releases potential energy that, with a minor exception, is available only in the hemisphere facing the barycenter of the planetary system. We calculate its strength and spatial distribution for the strongest case ("vertical") and for weaker horizontal cases whose motions are all perpendicular to gravity. The vertical cases can raise the kinetic energy of a few well positioned convecting elements in the Sun's envelope by a factor ≤7. This is the first physical mechanism by which planets can have a nontrivial effect on internal solar motions. Occasional small mass exchanges near the solar center and in a recently proposed mixed shell centered at 0.16Rs would carry fresh fuel to deeper levels. This would cause stars like the Sun with appropriate planetary systems to burn somewhat more brightly and have shorter lifetimes than identical stars without planets. The helioseismic sound speed and the long record of sunspot activity offer several bits of evidence that the effect may have been active in the Sun's core, its envelope, and in some vertically stable layers. Additional proof will require direct evidence from helioseismology or from transient waves on the solar surface. © 2010 US Government.

Levin M.,University of Maryland University College
Physical Review X | Year: 2013

We discuss the question of when a gapped two-dimensional electron system without any symmetry has a protected gapless edge mode. While it is well known that systems with a nonzero thermal Hall conductance, KH ≠ 0, support such modes, here we show that robust modes can also occur when KH = 0-if the system has quasiparticles with fractional statistics. We show that some types of fractional statistics are compatible with a gapped edge, while others are fundamentally incompatible. More generally, we give a criterion for when an electron system with Abelian statistics and KH = 0 can support a gapped edge: We show that a gapped edge is possible if and only if there exists a subset of quasiparticle typesMsuch that (1) all the quasiparticles inMhave trivial mutual statistics, and (2) every quasiparticle that is not in M has nontrivial mutual statistics with at least one quasiparticle in M. We derive this criterion using three different approaches: a microscopic analysis of the edge, a general argument based on braiding statistics, and finally a conformal field theory approach that uses constraints from modular invariance. We also discuss the analogous result for two-dimensional boson systems. © Published by the American Physical Society.

Cao L.,University of Maryland University College | Isaacs L.,University of Maryland University College
Organic Letters | Year: 2012

The building block synthesis of a derivative of CB[6] that bears a reactive propargyloxy group and its functionalization by click chemistry to yield 1 which contains a covalently attached isobutylammonium group is presented. Compound 1 undergoes self-assembly to yield a cyclic [c2] daisy chain assembly (1 2) in water. The behavior of 1 2 in response to various stimuli (e.g., guests and CB[n] receptors) is described. © 2012 American Chemical Society.

Kishek R.A.,University of Maryland University College
Physical Review Letters | Year: 2012

The multipactor is a vacuum discharge based on a secondary electron emission. A novel resonant form is proposed that combines one- and two-surface impacts within a single period, provided the total transit time is an odd number of rf half-periods and the product of secondary yields exceeds unity. For low fD products, the simplest such mode is shown to significantly increase the upper electric field boundary of the multipacting region and lead to overlap of higher-order bands. The results agree nicely with 3D particle-in-cell code simulations. Practical implications of the findings are discussed. © 2012 American Physical Society.

Nelson R.H.,University of Maryland University College
Forest Policy and Economics | Year: 2013

Traditionally, forestry professionals in the United States have believed that forest management is a scientific discipline that should be undertaken by value-neutral experts. This understanding originated in the progressive era, typically dated from 1890 to 1920, as part of a wider progressive belief in the "scientific management" of American society. The U.S. Forest Service was created in 1905 to advance this mission, including on the national forests directly managed by the Forest Service itself. In the last few decades of the twentieth century, however, such core tenets of professional forestry came under increasing challenge from the environmental movement. Instead of seeing a forest as a "natural resource" to be used to advance the economic progress of American society, environmentalists now saw forests as having an "intrinsic value" independent of human welfare. By the early twenty-first century, reflecting such new thinking in American society, the old idea of "multiple-use management" of the national forests (and other natural systems) had lost out to "ecosystem management." This article finds that this shift in forest management philosophy reflected new (secular) religious directions in American society, as the progressive "gospel of efficiency" increasingly lost out to a new environmental "gospel of naturalness.". © 2013 Published by Elsevier B.V.

Malkov M.A.,University of California at San Diego | Diamond P.H.,University of California at San Diego | Sagdeev R.Z.,University of Maryland University College
Physical Review Letters | Year: 2012

The much-anticipated proof of cosmic ray (CR) acceleration in supernova remnants must hinge on the full consistency of acceleration theory with the observations; direct proof is impossible because of CR-orbit scrambling. Recent observations indicate deviations between helium and proton CR rigidity spectra inconsistent with the theory. By considering an initial (injection) phase of the diffusive shock acceleration, where elemental similarity does not apply, we demonstrate that the spectral difference is, in fact, a unique signature of the acceleration mechanism. Collisionless shocks inject more He2 + when they are stronger and so produce harder He2 + spectra. The injection bias is due to Alfvén waves driven by the more abundant protons, so the He2 + ions are harder to trap by these waves. By fitting the p/He ratio to the PAMELA data, we bolster the diffusive shock acceleration case for resolving the century-old mystery of CR origin. © 2012 American Physical Society.

Le Tiec A.,University of Maryland University College | Barausse E.,University of Maryland University College | Buonanno A.,University of Maryland University College | Buonanno A.,Harvard University
Physical Review Letters | Year: 2012

Using the first law of binary black-hole mechanics, we compute the binding energy E and total angular momentum J of two nonspinning compact objects moving on circular orbits with frequency Ω, at leading order beyond the test-particle approximation. By minimizing E(Ω) we recover the exact frequency shift of the Schwarzschild innermost stable circular orbit induced by the conservative piece of the gravitational self-force. Comparing our results for the coordinate-invariant relation E(J) to those recently obtained from numerical simulations of comparable-mass nonspinning black-hole binaries, we find a remarkably good agreement, even in the strong-field regime. Our findings confirm that the domain of validity of perturbative calculations may extend well beyond the extreme mass-ratio limit. © 2012 American Physical Society.

Twedt K.A.,University of Maryland University College | Rolston S.L.,University of Maryland University College
Physical Review Letters | Year: 2012

Using a new technique to directly detect current induced on a nearby electrode, we measure plasma oscillations in ultracold plasmas, which are influenced by the inhomogeneous and time-varying density and changing neutrality. Electronic detection avoids heating and evaporation dynamics associated with previous measurements and allows us to test the importance of the plasma neutrality. We apply dc and pulsed electric fields to control the electron loss rate and find that the charge imbalance of the plasma has a significant effect on the resonant frequency, in excellent agreement with recent predictions suggesting coupling to an edge mode. © 2012 American Physical Society.

Cohen T.D.,University of Maryland University College
Physical Review Letters | Year: 2012

It is shown that at sufficiently large N c for incident momenta which are much larger than the QCD scale, the total nucleon-nucleon cross section is independent of incident momentum and given by σtotal= 2π log2(N c)/(mπ2). This result is valid in the extreme large N c regime of log (N c)1 and has corrections of relative order log (log (N c))/log (N c). A possible connection of this result to the Froissart-Martin bound is discussed. © 2012 American Physical Society.

Fermo R.L.,Boston University | Drake J.F.,University of Maryland University College | Swisdak M.,University of Maryland University College
Physical Review Letters | Year: 2012

Magnetic islands or flux ropes produced by magnetic reconnection have been observed on the magnetopause, in the magnetotail, and in coronal current sheets. Particle-in-cell simulations of magnetic reconnection with a guide field produce elongated electron current layers that spontaneously produce secondary islands. Here, we explore the seed mechanism that gives birth to these islands. The most commonly suggested theory for island formation is the tearing instability. We demonstrate that in our simulations these structures typically start out, not as magnetic islands, but as electron flow vortices within the electron current sheet. When some of these vortices first form, they do not coincide with closed magnetic field lines, as would be the case if they were islands. Only after they have grown larger than the electron skin depth do they couple to the magnetic field and seed the growth of finite-sized islands. The streaming of electrons along the magnetic separatrix produces the flow shear necessary to drive an electron Kelvin-Helmholtz instability and produce the initial vortices. The conditions under which this instability is the dominant mechanism for seeding magnetic islands are explored. © 2012 American Physical Society.

Bambi C.,University of Tokyo | Barausse E.,University of Maryland University College
Astrophysical Journal | Year: 2011

Black holes in general relativity are known as Kerr black holes and are characterized solely by two parameters, the mass M and the spin J. All the higher multipole moments of the gravitational field are functions of these two parameters. For instance, the quadrupole moment is Q = -J 2/M, which implies that a measurement of M, J, and Q for black hole candidates would allow one to test whether these objects are really black holes as described by general relativity. While future gravitational-wave experiments will be able to test the Kerr nature of these objects with very high accuracy, in this paper we show that it is possible to put constraints on the quadrupole moment of stellar-mass black hole candidates by using presently available X-ray data of the thermal spectrum of their accretion disk. © 2011. The American Astronomical Society. All rights reserved.

Gong H.,University of Maryland University College | Ostriker E.C.,University of Maryland University College
Astrophysical Journal | Year: 2011

We use numerical hydrodynamic simulations to investigate prestellar core formation in the dynamic environment of giant molecular clouds, focusing on planar post-shock layers produced by colliding turbulent flows. A key goal is to test how core evolution and properties depend on the velocity dispersion in the parent cloud; our simulation suite consists of 180 models with inflow Mach numbers M ≡ v/cs = 1.19. At all Mach numbers, our models show that turbulence and self-gravity collect gas within post-shock regions into filaments at the same time as overdense areas within these filaments condense into cores. This morphology, together with the subsonic velocities we find inside cores, is similar to observations. We extend previous results showing that core collapse develops in an "outside-in" manner, with density and velocity approaching the Larson-Penston asymptotic solution. The time for the first core to collapse depends on Mach number as tcoll α M-1/2 ρ0-1/2, for ρ0 the mean pre-shock density, consistent with analytic estimates. Core building takes 10 times as long as core collapse, which lasts a few ×105 yr, consistent with observed prestellar core lifetimes. Core shapes change from oblate to prolate as they evolve. To define cores, we use isosurfaces of the gravitational potential. We compare to cores defined using the potential computed from projected surface density, finding good agreement for core masses and sizes; this offers a new way to identify cores in observed maps. Cores with masses varying by three orders of magnitude (∼0.05-50 M⊙) are identified in our high- simulations, with a much smaller mass range for models having low . We halt each simulation when the first core collapses; at that point, only the more massive cores in each model are gravitationally bound, with E th + Eg < 0. Stability analysis of post-shock layers predicts that the first core to collapse will have mass M α v -1/2ρ-1/2 0 T 7/4, and that the minimum mass for cores formed at late times will have M α v -1ρ-1/2 0 T 2, with T being the temperature. From our simulations, the median mass lies between these two relations. At the time we halt the simulations, the M versus v relation is shallower for bound cores than unbound cores; with further evolution the small cores may evolve to become bound, steeping the M versus v relation. © 2011. The American Astronomical Society. All rights reserved.

Cameron M.K.,University of Maryland University College
Journal of Computational Physics | Year: 2013

We propose an approach for finding dominant reactive channels and calculating percentages of reactive flux through each channel in chemical systems driven by a deterministic potential force and a small thermal noise. We assume that the temperature is low enough so that the reactive flux focuses around a finite number of paths connecting the reactant and the product states. These paths can be found in a systematic way by solving a Hamilton-Jacobi equation for the so called MaxFlux functional. We argue that the name "MaxFlux" is misleading: it should be called the resistivity functional instead. Once the network of transition paths is found, one can define an equivalent electric circuit and find the currents through each of its wires. These currents give estimates of the reactive flux along the corresponding transition paths. We test our approach on the problem of finding transition paths in the Alanine-Dipeptide with two dihedral angles where the reactive current can be computed exactly. The percentages of the reactive flux through each reactive channel given by our approach turn out to be in remarkable agreement with the exact ones. We apply this approach to the problem of finding escape paths of a CO molecule from a Myoglobin protein. We find a collection of exit locations and establish percentages of the reactive flux through each of them. © 2013 Elsevier Inc.

Godfrey B.B.,University of Maryland University College | Vay J.-L.,Lawrence Berkeley National Laboratory
Journal of Computational Physics | Year: 2013

Rapidly growing numerical instabilities routinely occur in multidimensional particle-in-cell computer simulations of plasma-based particle accelerators, astrophysical phenomena, and relativistic charged particle beams. Reducing instability growth to acceptable levels has necessitated higher resolution grids, high-order field solvers, current filtering, etc. except for certain ratios of the time step to the axial cell size, for which numerical growth rates and saturation levels are reduced substantially. This paper derives and solves the cold beam dispersion relation for numerical instabilities in multidimensional, relativistic, electromagnetic particle-in-cell programs employing either the standard or the Cole-Karkkainnen finite difference field solver on a staggered mesh and the common Esirkepov current-gathering algorithm. Good overall agreement is achieved with previously reported results of the WARP code. In particular, the existence of select time steps for which instabilities are minimized is explained. Additionally, an alternative field interpolation algorithm is proposed for which instabilities are almost completely eliminated for a particular time step in ultra-relativistic simulations. © 2013 Elsevier Inc..

Bovill M.S.,University of Maryland University College | Ricotti M.,University of Maryland University College
Astrophysical Journal | Year: 2011

We use a new set of cold dark matter simulations of the local universe to investigate the distribution of fossils of primordial dwarf galaxies within and around the Milky Way. Throughout, we build upon previous results showing agreement between the observed stellar properties of a subset of the ultra-faint dwarfs and our simulated fossils. Here, we show that fossils of the first galaxies have galactocentric distributions and cumulative luminosity functions consistent with observations. In our model, we predict 300 luminous satellites orbiting the Milky Way, 50%-70% of which are well-preserved fossils. Within the Milky Way virial radius, the majority of these fossils have luminosities L V < 106L ⊙. Despite our multidimensional agreement with observations at low masses and luminosities, the primordial model produces an overabundance of bright dwarf satellites (L V > 104 L ⊙) with respect to observations where observations are nearly complete. The "bright satellite problem" is most evident in the outer parts of the Milky Way. We estimate that, although relatively bright, the primordial stellar populations are very diffuse, producing a population with surface brightnesses below surveys' detection limits, and are easily stripped by tidal forces. Although we cannot yet present unmistakable evidence for the existence of the fossils of first galaxies in the Local Group, the results of our studies suggest observational strategies that may demonstrate their existence: (1) the detection of "ghost halos" of primordial stars around isolated dwarfs would prove that stars formed in minihalos (M < 108 M ⊙) before reionization and strongly suggest that at least a fraction of the ultra-faint dwarfs are fossils of the first galaxies; and (2) the existence of a yet unknown population of 150 Milky Way ultra-faints with half-light radii r hl 100-1000 pc and luminosities LV < 104L ⊙, detectable by future deep surveys. These undetected dwarfs would have the mass-to-light ratios, stellar velocity dispersions, and metallicities predicted in this work. © 2011 The American Astronomical Society. All rights reserved.

Bovill M.S.,University of Maryland University College | Ricotti M.,University of Maryland University College
Astrophysical Journal | Year: 2011

We present a new method for generating initial conditions for ΛCDM N-body simulations which provides the dynamical range necessary to follow the evolution and distribution of the fossils of the first galaxies on Local Volume, 5-10Mpc, scales. The initial distribution of particles represents the position, velocity, and mass distribution of the dark and luminous halos extracted from pre-reionization simulations. We confirm previous results that ultra-faint dwarfs have properties compatible with being well-preserved fossils of the first galaxies. However, because the brightest pre-reionization dwarfs form preferentially in biased regions, they most likely merge into non-fossil halos with circular velocities >20-30kms-1. Hence, we find that the maximum luminosity of true fossils in the Milky Way is LV < 106 L ⊙, casting doubts on the interpretation that some classical dSphs are true fossils. In addition, we argue that most ultra-faints at small galactocentric distance, R < 50kpc, had their stellar properties modified by tides, while a large population of fossils is still undetected due to their extremely low surface brightness log (ΣV) < -1.4. We estimate that the region outside R 50 (400kpc) up to 1Mpc from the Milky Way contains about a hundred true fossils of the first galaxies with V-band luminosity 103-10 5 L ⊙ and half-light radii, r hl 100-1000pc. © 2011 The American Astronomical Society. All rights reserved.

Zhu Y.,University of Maryland University College | Wang C.,University of Maryland University College
Journal of Physical Chemistry C | Year: 2011

Phase transformation cyclic voltammetry (CV) was developed by integrating mixed-control phase transformation theory and charge transfer effect with traditional CV model. This mixed-control phase transformation CV model was validated by good agreement between experimental CV data and simulated values from phase transformation CV for LiFePO4. The lithium ion diffusion coefficient (10-16 m2 s-1) of LiFePO 4 obtained from the phase transformation CV model was 2 orders of magnitude higher than apparent values (10-18 m2 s -1) determined from traditional CV. The low diffusion coefficient from traditional CV is attributed to the disregard of phase transformation. In addition to the lithium ion diffusion coefficient, the interface mobility (on the magnitude of 10-14 m mol J-1 s-1) of the LiFePO4 electrode, which cannot be measured from traditional CV, was obtained using phase transformation CV. Using the phase transformation CV model, the CV curves of LiFePO4 and LiMnPO4 phase transformation electrodes were characterized, and the effects of lithium ion diffusion coefficient, interface mobility, exchange current density, and particle size on the CV profiles of phase transformation electrodes were systemically investigated. © 2010 American Chemical Society.

Ball G.F.,University of Maryland University College
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2016

The song-control system, a neural circuit that controls the learning and production of birdsong, provided the first example in vertebrates of prominent macro-morphological sex differences in the brain. Forebrain nuclei HVC, robust nucleus of the arcopallium (RA) and area X all exhibit prominent male-biased sex differences in volume in zebra finches and canaries. Subsequent studies compared species that exhibited different degrees of a sex difference in song behaviour and revealed an overall positive correlation between male biases in song behaviour and male biases in the volume of the song nuclei. However, several exceptions have been described in which male biases in HVC and RA are observed even though song behaviour is equal or even female-biased. Other phenotypic measures exhibit lability in both sexes. In the duetting plain-tailed wren (Pheugopedius euophrys), males and females have auditory cells in the song system that are tuned to the joint song the two sexes produce rather than just male or female components. These findings suggest that there may be constraints on the adaptive response of the song system to ecological conditions as assessed by nucleus volume but that other critical variables regulating song can respond so that each sex can modify its song behaviour as needed. © 2016 The Author(s) Published by the Royal Society. All rights reserved.

Liu Z.,University of Maryland University College | Jackson G.S.,University of Maryland University College | Eichhorn B.W.,University of Maryland University College
Angewandte Chemie - International Edition | Year: 2010

(Figure Presented) More order, more tolerance: PtSn intermetallic and alloy nanoparticles (NPs) were prepared by the co-reduction of [Pt(acac)2] (acac=acetylacetonate) and SnCl4. The intermetallic NPs can convert to PtSn@Pt core-shell NPs after potential cycling in CO-saturated H 2SO4 solution. Electrochemical studies demonstrated the core-shell and intermetallic electrocatalysts had substantially higher CO tolerance than PtSn alloy, PtRu alloy, and monometallic Pt. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Almeida M.,University of Maryland University College
ISME Journal | Year: 2016

The Human Microbiome Project (HMP) identified the 16S rRNA gene sequences of 'most wanted' taxa—prevalent in the healthy human microbiota but distant from previously known sequences. Since 2012, few of the corresponding genomes have been isolated and sequenced, and only through advanced isolation techniques. We demonstrate that the genomes of the most wanted taxa can be identified computationally through their correlation in abundance across multiple public metagenomic data sets. We link over 200 most wanted sequences with nearly complete genome sequences, including half of the taxa identified as high-priority targets by the HMP. The genomes we identify have strong similarity to genomes reconstructed through expensive isolation techniques, and provide a more complete functional characterization of these organisms than can be extrapolated from their 16S rRNA gene. We also provide insights into the function of organisms for which 16S rRNA gene signatures were recently reported to be associated with health and host genetic factors.The ISME Journal advance online publication, 4 March 2016; doi:10.1038/ismej.2016.35. © 2016 International Society for Microbial Ecology

Wang H.,University of Maryland University College | Rokita S.E.,University of Maryland University College
Angewandte Chemie - International Edition | Year: 2010

Figure Presented Strands may come and go, but crosslinking is forever: Dynamic combinatorial chemistry can respond to changing environments, a characteristic that is now demonstrated with DNA cross-linking based on reversible alkylation of a quinone methide intermediate (see picture). © 2010 wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Arina C.,University of Amsterdam | Mohapatra R.N.,University of Maryland University College | Sahu N.,Indian Institute of Technology Hyderabad
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

We discuss aspects of a scenario for co-genesis of matter and dark matter which extends the standard model by adding a fourth generation vector-like lepton doublet and show that if the fourth neutrino is a massive pseudo-Dirac fermion with mass in the few hundred GeV range and mass splitting of about 100 keV, its lighter component can be a viable inelastic dark matter candidate. Its relic abundance is produced by the CP violating out-of-equilibrium decay of the type-II seesaw scalar triplet, which also gives rise to the required baryon asymmetry of the Universe via type-II leptogenesis, thus providing a simultaneous explanation of dark matter and baryon abundance observed today. Moreover, the induced vacuum expectation value of the same scalar triplet is responsible for the sub-eV Majorana masses to the three active neutrinos. A stable fourth generation of neutrinos is elusive at collider, however might be detected by current dark matter direct search experiments. © 2013 Elsevier B.V.

Ranganathan M.,Indian Institute of Technology Kanpur | Weeks J.D.,University of Maryland University College
Physical Review Letters | Year: 2013

We extend the terrace-step-kink model of crystal growth to impure solutions where the impurities act as barriers to step motion. The effects of supersaturation, step curvature, step repulsions, and impurities on step motion are treated in a unified free energy framework. The model reproduces several features seen in experiments on growth of potassium dihydrogen phosphate crystals, wherein a dead zone at low supersaturations and a recovery of crystal growth by motion of large coherent step bunches at larger supersaturations are observed. We identify a key feature of solution growth that leads to these effects. © 2013 American Physical Society.

Veeraragavan A.,Massachusetts Institute of Technology | Cadou C.P.,University of Maryland University College
Combustion and Flame | Year: 2011

An analytical model for flame stabilization in meso-scale channels is developed by solving the two-dimensional partial differential equations associated with heat transport in the gas and structure and species transport in the gas. It improves on previous models by eliminating the need to assume values for the Nusselt numbers in the pre and post-flame regions. The effects of heat loss to the environment, wall thermal conductivity, and wall geometry on the burning velocity and extinction are explored. Extinction limits and fast and slow burning modes are identified but their dependence on structure thermal conductivity and heat losses differ from previous quasi one-dimensional analyses. Heat recirculation from the post-flame to the pre-flame is shown to be the primary mechanism for flame stabilization and burning rate enhancement in micro-channels. Combustor design parameters like the wall thickness ratio, thermal conductivity ratio, and heat loss to the environment each influence the flame speed through their influence on the total heat recirculation. These findings are used to propose a simple methodology for preliminary micro-combustor design. © 2011 The Combustion Institute.

Carruthers P.,University of Maryland University College
Consciousness and Cognition | Year: 2015

This paper argues that our awareness of the mental states of other agents is often perceptual in character. It draws partly on recent experimental findings concerning perception of animacy and intentionality. But it also emphasizes the unencapsulated nature of perception generally, and argues that concepts (including mental-state concepts) can be bound into the contents of conscious perception. One of the main arguments used in support of this conclusion draws on recent work concerning the nature and contents of working memory. © 2015 Elsevier Inc.

Park K.,University of Maryland University College | Ricotti M.,University of Maryland University College
Astrophysical Journal | Year: 2011

We study the effect of radiative feedback on accretion onto intermediate-mass black holes (IMBHs) using the hydrodynamical code ZEUS-MP with a radiative transfer algorithm. In this paper, the first of a series, we assume accretion from a uniformly dense gas with zero angular momentum and extremely low metallicity. Our one-dimensional (1D) and 2D simulations explore how X-ray and UV radiation emitted near the black hole regulates the gas supply from large scales. Both 1D and 2D simulations show similar accretion rates and periods between peaks in accretion, meaning that the hydro-instabilities that develop in 2D simulations do not affect the mean flow properties. We present a suite of simulations exploring accretion across a large parameter space, including different radiative efficiencies and radiation spectra, black hole masses, density, and temperature, T ∞, of the neighboring gas. In agreement with previous studies, we find regular oscillatory behavior of the accretion rate, with duty cycle ∼6%, mean accretion rate 3% (T ∞/104 K)2.5 of the Bondi rate and peak accretion ∼10 times the mean for T ∞ ranging between 3000K and 15, 000K. We derive parametric formulae for the period between bursts, the mean accretion rate, and the peak luminosity of the bursts and thus provide a formulation of how feedback-regulated accretion operates. The temperature profile of the hot ionized gas is crucial in determining the accretion rate, while the period of the bursts is proportional to the mean size of the Strömgren sphere, and we find qualitatively different modes of accretion in the high versus low density regimes. We also find that a softer radiation spectrum produces a higher mean accretion rate. However, it is still unclear what the effect of a significant time delay is between the accretion rate at our inner boundary and the output luminosity. Such a delay is expected in realistic cases with non-zero angular momentum and may affect the time-dependent phenomenology presented here. This study is a first step to model the growth of seed black holes in the early universe and to make a prediction of the number and the luminosity of ultraluminous X-ray sources in galaxies produced by IMBHs accreting from the interstellar medium. © 2011. The American Astronomical Society. All rights reserved..

You Y.S.,University of Maryland University College | Oh T.I.,University of Maryland University College | Kim K.Y.,University of Maryland University College
Physical Review Letters | Year: 2012

We observe off-axis phase-matched terahertz generation in long air-plasma filaments produced by femtosecond two-color laser focusing. Here, phase matching naturally occurs due to off-axis constructive interference between locally generated terahertz waves, and this determines the far-field terahertz radiation profiles and yields. For a filament longer than the characteristic two-color dephasing length, it emits conical terahertz radiation in the off-axis direction, peaked at 4-7° depending on the radiation frequencies. The total terahertz yield continuously increases with the filament length, well beyond the dephasing length. The phase-matching condition observed here provides a simple method for scalable terahertz generation in elongated plasmas. © 2012 American Physical Society.

Barnes E.,University of Maryland University College | Cywinski L.,Polish Academy of Sciences | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2012

We solve the long-standing central spin problem for a general set of inhomogeneous bath couplings and a large class of initial bath states. We compute the time evolution of the coherence of a central spin coupled to a spin bath by resumming all orders of the time-convolutionless master equation, thus avoiding the need to assume weak coupling to the bath. The fully quantum, non-Markovian solution is obtained in the large-bath limit and is valid up to a time scale set by the largest coupling constant. Our result captures the full decoherence of an electron spin qubit coupled to a nuclear spin bath in a GaAs quantum dot for experimentally relevant parameters. In addition, our solution is quite compact and can readily be used to make quantitative predictions for the decoherence process and to guide the design of nuclear state preparation protocols. © 2012 American Physical Society.

Liu X.-J.,University of Maryland University College
Physical Review Letters | Year: 2012

We study the charge character of the Andreev bound states (ABSs) in one-dimensional topological superconductors with spatial inversion symmetry (SIS) breaking. Despite the absence of the SIS, we show a hidden symmetry for the Bogoliubov-de Gennes equations around Fermi points in addition to the particle-hole symmetry. This hidden symmetry protects that the charge of the ABSs is solely dependent on the corresponding Fermi velocities. On the other hand, if the SIS is present, the ABSs are charge neutral, similar to Majorana fermions. We also propose that the charge of the ABSs can be experimentally measured in the tunneling transport spectroscopy from the resonant differential tunneling conductance. © 2012 American Physical Society.

Wahlstrand J.K.,University of Maryland University College | Cheng Y.-H.,University of Maryland University College | Milchberg H.M.,University of Maryland University College
Physical Review Letters | Year: 2012

The nonlinear optical response to high fields is absolutely measured for the noble gas atoms He, Ne, Ar, Kr, and Xe. We find that the response is quadratic in the laser field magnitude up to the ionization threshold of each gas. Its size and quadratic dependence are well predicted by a Kramers-Kronig analysis employing known ionization probabilities, and the results are consistent with calculations using the time-dependent Schrödinger equation. © 2012 American Physical Society.

Baloch K.H.,University of Maryland University College | Voskanian N.,University of Maryland University College | Bronsgeest M.,University of Maryland University College | Cumings J.,University of Maryland University College
Nature Nanotechnology | Year: 2012

Minimizing Joule heating remains an important goal in the design of electronic devices 1,2. The prevailing model of Joule heating relies on a simple semiclassical picture in which electrons collide with the atoms of a conductor, generating heat locally and only in regions of non-zero current density, and this model has been supported by most experiments. Recently, however, it has been predicted that electric currents in graphene and carbon nanotubes can couple to the vibrational modes of a neighbouring material 3,4, heating it remotely 5. Here, we use in situ electron thermal microscopy to detect the remote Joule heating of a silicon nitride substrate by a single multiwalled carbon nanotube. At least 84% of the electrical power supplied to the nanotube is dissipated directly into the substrate, rather than in the nanotube itself. Although it has different physical origins, this phenomenon is reminiscent of induction heating or microwave dielectric heating. Such an ability to dissipate waste energy remotely could lead to improved thermal management in electronic devices 6. © 2012 Macmillan Publishers Limited. All rights reserved.

Lobos A.M.,University of Maryland University College | Lutchyn R.M.,Microsoft | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2012

We study the interplay between disorder and interaction in one-dimensional topological superconductors which carry localized Majorana zero-energy states. Using Abelian bosonization and the perturbative renormalization group approach, we obtain the renormalization group flow and the associated scaling dimensions of the parameters and identify the critical points of the low-energy theory. We predict a quantum phase transition from a topological superconducting phase to a nontopological localized phase, and obtain the phase boundary between these two phases as a function of the electron-electron interaction and the disorder strength in the nanowire. Based on an instanton analysis which incorporates the effect of disorder, we also identify a large regime of stability of the Majorana-carrying topological phase in the parameter space of the model. © 2012 American Physical Society.

Nicholson A.N.,University of Maryland University College
Physical Review Letters | Year: 2012

The ground state energies of universal N-body clusters tied to Efimov trimers, for N even, are shown to be encapsulated in the statistical distribution of two particles interacting with a background auxiliary field at large Euclidean time when the interaction is tuned to the unitary point. Numerical evidence that this distribution is log normal is presented, allowing one to predict the ground state energies of the N-body system. © 2012 American Physical Society.

Powell S.,University of Maryland University College
Physical Review Letters | Year: 2012

Certain frustrated systems, including spin ice and dimer models, exhibit a Coulomb phase at low temperatures, with power-law correlations and fractionalized monopole excitations. Transitions out of this phase, at which the effective gauge theory becomes confining, provide examples of unconventional criticality. This Letter studies the behavior at nonzero monopole density near such transitions, using scaling theory to arrive at universal expressions for the crossover phenomena. For a particular transition in spin ice, quantitative predictions are made by mapping to the XY model and confirmed using Monte Carlo simulations. © 2012 American Physical Society.

Barnes E.,University of Maryland University College | Das Sarma S.,University of Maryland University College
Physical Review Letters | Year: 2012

Analytical solutions to the time-dependent Schrödinger equation describing a driven two-level system are invaluable to many areas of physics, but they are also extremely rare. Here, we present a simple algorithm that generates an unlimited number of exact analytical solutions. We show that a general single-axis driving term and its corresponding evolution operator are determined by a single real function which is constrained only by a certain inequality and initial conditions. Any function satisfying these constraints yields an exact analytical solution. We demonstrate this method by presenting several new exact solutions to the time-dependent Schrödinger equation. Our general method and many of the new solutions we present are particularly relevant to qubit control in quantum computing applications. © 2012 American Physical Society.

Margetis D.,University of Maryland University College
Multiscale Modeling and Simulation | Year: 2012

We study stationary quantum fluctuations around a mean field limit in trapped, dilute atomic gases of repulsively interacting bosons at zero temperature. Our goal is to describe quantum-mechanically the lowest macroscopic many-body bound state consistent with a microscopic Hamiltonian that accounts for inhomogeneous particle scattering processes. In the mean field limit, the wave function of the condensate (macroscopic quantum state) satisfies a defocusing cubic nonlinear Schrödinger-type equation, the Gross-Pitaevskii equation. We include consequences of pair excitation, i.e., the scattering of particles in pairs from the condensate to other states, proposed in [T. T. Wu, J. Math. Phys., 2 (1961), pp. 105-123]. Our derivations rely on an uncontrolled yet physically motivated assumption for the many-body wave function. By relaxing mathematical rigor, from a particle Hamiltonian with a spatially varying interaction strength we derive via heuristics an integro-partial differential equation for the pair collision kernel, K, under a stationary condensate wave function, φ. For a scattering length with periodic microstructure of subscale ε, we formally describe via classical homogenization the lowest many-body bound state in terms of φ and K up to second order in ε. If the external potential is slowly varying, we solve the homogenized equations via boundary layer theory. As an application, we describe the partial depletion of the condensate. © 2012 Society for Industrial and Applied Mathematics.

Baker R.H.,American Museum of Natural History | Wilkinson G.S.,University of Maryland University College
PLoS Genetics | Year: 2010

Chromosomal location has a significant effect on the evolutionary dynamics of genes involved in sexual dimorphism, impacting both the pattern of sex-specific gene expression and the rate of duplication and protein evolution for these genes. For nearly all non-model organisms, however, knowledge of chromosomal gene content is minimal and difficult to obtain on a genomic scale. In this study, we utilized Comparative Genomic Hybridization (CGH), using probes designed from EST sequence, to identify genes located on the X chromosome of four species in the stalk-eyed fly genus Teleopsis. Analysis of log2 ratio values of female-to-male hybridization intensities from the CGH microarrays for over 3,400 genes reveals a strongly bimodal distribution that clearly differentiates autosomal from X-linked genes for all four species. Genotyping of 33 and linkage mapping of 28 of these genes in Teleopsis dalmanni indicate the CGH results correctly identified chromosomal location in all cases. Syntenic comparison with Drosophila indicates that 90% of the X-linked genes in Teleopsis are homologous to genes located on chromosome 2L in Drosophila melanogaster, suggesting the formation of a nearly complete neo-X chromosome from Muller element B in the dipteran lineage leading to Teleopsis. Analysis of gene movement both relative to Drosophila and within Teleopsis indicates that gene movement is significantly associated with 1) rates of protein evolution, 2) the pattern of gene duplication, and 3) the evolution of eyespan sexual dimorphism. Overall, this study reveals that diopsids are a critical group for understanding the evolution of sex chromosomes within Diptera. In addition, we demonstrate that CGH is a useful technique for identifying chromosomal sex-linkage and should be applicable to other organisms with EST or partial genomic information. © 2010 Baker, Wilkinson.

Xu X.,University of Maryland University College | Doyle M.P.,University of Maryland University College
Accounts of Chemical Research | Year: 2014

ConspectusThe combination of two or more unsaturated structural units to form cyclic organic compounds is commonly referred to as cycloaddition, and the combination of two unsaturated structural units that forms a six-membered ring is formally either a [5 + 1]-, [4 + 2]-, [2 + 2 + 2]-, or [3 + 3]-cycloaddition. Occurring as concerted or stepwise processes, cycloaddition reactions are among the most useful synthetic constructions in organic chemistry. Of these transformations, the concerted [4 + 2]-cycloaddition, the Diels-Alder reaction, is by far the best known and most widely applied. However, although symmetry disallowed as a concerted process and lacking certifiable examples until recently, stepwise [3 + 3]-cycloadditions offer advantages for the synthesis of a substantial variety of heterocyclic compounds, and they are receiving considerable attention.In this Account, we present the development of stepwise [3 + 3]-cycloaddition reactions from virtual invisibility in the 1990s to a rapidly growing synthetic methodology today, involving organocatalysis or transition metal catalysis. With origins in organometallic or vinyliminium ion chemistry, this area has blossomed into a viable synthetic transformation for the construction of six-membered heterocyclic compounds containing one or more heteroatoms. The development of [3 + 3]-cycloaddition transformations has been achieved through identification of suitable and compatible reactive dipolar adducts and stable dipoles. The reactive dipolar species is an energetic dipolar intermediate that is optimally formed catalytically in the reaction. The stepwise process occurs with the reactive dipolar adduct reacting as an electrophile or as a nucleophile to form the first covalent bond, and this association provides entropic assistance for the construction of the second covalent bond and the overall formal [3 + 3]-cycloaddition. Organocatalysis is well developed for both inter- and intramolecular synthetic transformations, but the potential of transition metal catalysis for [3 + 3]-cycloaddition has only recently emerged. The key to the rapid development of the transition metal-based methodology has been recognition that certain catalytically generated vinylcarbenes are effective dipolar adducts for reactions with stable dipolar compounds, including aryl and vinyl ylides. In particular, metallo-enolcarbenes that are generated catalytically from conveniently prepared stable enoldiazoacetates or from donor-acceptor cyclopropenes are highly effective dipolar adducts for [3 + 3]-cycloaddition. The electron-donating oxygen of the silyl ether enhances electrophilic ring closure to the metal-bound carbon of the initial adduct from vinylogous addition, and this enhancement inhibits the alternative [3 + 2]-cycloaddition across the carbon-carbon double bond of the vinylcarbene.Catalytically generated metallo-enolcarbenes react under mild conditions with a broad spectrum of compatible stable dipoles, including nitrones, azomethine imines, ylides, and certain covalent precursors of stable dipoles, to form [3 + 3]-cycloaddition products having the β-ketoester functionality (in dihydrooxazines, tetrahydropyridazines, pyrazolidinone and pyraxole derivatives, dihydroquinolines, and quinolizidines, for example) in high yield. Two ways to access these metallo-enolcarbenes, either by dinitrogen extrusion from enoldiazoacetate esters or by rearrangement of donor-acceptor cyclopropenes, enhance the versatility of the process. The [3 + 3]-cycloaddition methodology is a complementary strategy to [4 + 2]-cycloaddition for the synthesis of heterocyclic compounds having six-membered rings. High levels of enantioselectivity are obtained with the use of chiral ligands on transition metal catalysts that include those on dirhodium(II) and silver(I). © 2014 American Chemical Society.

Isaacs L.,University of Maryland University College
Accounts of Chemical Research | Year: 2014

ConspectusThis Account focuses on stimuli responsive systems that function in aqueous solution using examples drawn from the work of the Isaacs group using cucurbit[n]uril (CB[n]) molecular containers as key recognition elements. Our entry into the area of stimuli responsive systems began with the preparation of glycoluril derived molecular clips that efficiently distinguish between self and nonself by H-bonds and π-π interactions even within complex mixtures and therefore undergo self-sorting. We concluded that the selectivity of a wide variety of H-bonded supramolecular assemblies was higher than previously appreciated and that self-sorting is not exceptional behavior. This lead us to examine self-sorting within the context of CB[n] host-guest chemistry in water.We discovered that CB[n] homologues (CB[7] and CB[8]) display remarkably high binding affinity (Ka up to 1017 M-1) and selectivity toward their guests, which renders CB[n]s prime components for the construction of stimuli responsive host-guest systems. The CB[7] ·adamantaneammonium ion complex, which is particularly privileged (K a = 4.2 × 1012 M-1), was introduced by us as a stimulus to trigger constitutional changes in multicomponent self-sorting systems. For example, we describe how the free energy associated with the formation of host-guest complexes of CB[n]-type receptors can drive conformational changes of included guests like triazene-arylene foldamers and cationic calix[4]arenes, as well as induced conformational changes (e.g., ammonium guest size dependent homotropic allostery, metal ion triggered folding, and heterochiral dimerization) of the hosts themselves.Many guests display large pKa shifts within their CB[n]-guest complexes, which we used to promote pH controlled guest swapping and thermal trans-to-cis isomerization of azobenzene derivatives. We also used the high affinity and selectivity of CB[7] toward its guests to outcompete an enzyme (bovine carbonic anhydrase) for a two-faced inhibitor, which allowed stimuli responsive regulation of enzymatic activity. These results prompted us to examine the use of CB[n]-type receptors in both in vitro and in vivo biological systems. We demonstrated that adamantaneammonium ion can be used to intracellularly sequester CB[7] from gold nanoparticles passivated with hexanediammonium ion·CB[7] complexes and thereby trigger cytotoxicity. CB[7] derivatives bearing a biotin targeting group enhance the cytotoxicity of encapsulated oxaliplatin toward L1210FR cells. Finally, acyclic CB[n]-type receptors function as solubilizing excipients for insoluble drugs for drug delivery purposes and as a broad spectrum reversal agent for the neuromuscular blocking agents rocuronium, vecuronium, and cis-atracurium in rats. The work highlights the great potential for integration of CB[n]-type receptors with biological systems. © 2014 American Chemical Society.

Wigginton K.R.,University of Maryland University College | Kohn T.,Ecole Polytechnique Federale de Lausanne
Current Opinion in Virology | Year: 2012

Drinking waters are treated for enteric virus via a number of disinfection techniques including chemical oxidants, irradiation, and heat, however the inactivation mechanisms during disinfection remain elusive. Owing to the fact that a number of significant waterborne virus strains are not readily culturable in vitro at this time (e.g. norovirus, hepatitis A), the susceptibility of these viruses to disinfection is largely unknown. An in-depth understanding of the mechanisms involved in virus inactivation would aid in predicting the susceptibility of non-culturable virus strains to disinfection and would foster the development of improved disinfection methods. Recent technological advances in virology research have provided a wealth of information on enteric virus compositions, structures, and biological functions. This knowledge will allow for physical/chemical descriptions of virus inactivation and thus further our understanding of virus disinfection to the most basic mechanistic level. © 2011 Elsevier B.V. All rights reserved.

Garcia-Romero D.,University of Maryland University College | Espy-Wilson C.Y.,University of Maryland University College
Proceedings of the Annual Conference of the International Speech Communication Association, INTERSPEECH | Year: 2011

We present a method to boost the performance of probabilistic generative models that work with i-vector representations. The proposed approach deals with the non-Gaussian behavior of i-vectors by performing a simple length normalization. This non-linear transformation allows the use of probabilistic models with Gaussian assumptions that yield equivalent performance to that of more complicated systems based on Heavy-Tailed assumptions. Significant performance improvements are demonstrated on the telephone portion of NIST SRE 2010. Copyright © 2011 ISCA.

Polisensky E.,U.S. Navy | Ricotti M.,University of Maryland University College | Ricotti M.,University of Paris Pantheon Sorbonne
Monthly Notices of the Royal Astronomical Society | Year: 2014

We investigate the claim that the largest subhaloes in high-resolution dissipationless cold dark matter (CDM) simulations of the Milky Way are dynamically inconsistent with observations of its most luminous satellites.We find that the inconsistency is largely attributable to the large values of s8 and ns adopted in the discrepant simulations, producing satellites that form too early and therefore are too dense. We find the tension between observations and simulations adopting parameters consistent with WMAP9 is greatly diminished, making the satellites a sensitive test of CDM. We find the Via Lactea II halo to be atypical for haloes in a WMAP3 cosmology, a discrepancy that we attribute to its earlier formation epoch than the mean for its mass. We also explore warm dark matter (WDM) cosmologies for 1-4 keV thermal relics. In 1 keV cosmologies, subhaloes have circular velocities at kpc scales ~60 per cent lower than their CDM counterparts, but are reduced by only 10 per cent in 4 keV cosmologies. Since relic masses < 2-3 keV are ruled out by constraints from the number of Milky Way satellites and Lyman a forest,WDM has a minor effect in reducing the densities of massive satellites. Given the uncertainties on the mass and formation epoch of the Milky Way, the need for reducing the satellite densities with baryonic effects or WDM is alleviated. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.

Yan J.,University of Maryland University College | Fuhrer M.S.,University of Maryland University College
Nano Letters | Year: 2010

The resistance of dual-gated bilayer graphene is measured as a function of temperature and gating electric fields in the Corbino geometry which precludes edge transport. The temperature-dependent resistance is quantitatively described by a two-channel conductance model including parallel thermal activation and variable range hopping channels, which gives the electric-field-dependent band gap whose magnitude is found to be in good agreement with infrared absorption experiments. Low-temperature transport is similar to that seen in previous studies of dual-gated bilayer graphene with edges, suggesting that edge transport does not play an important role. © 2010 American Chemical Society.

Sharia O.,University of Maryland University College | Kuklja M.M.,University of Maryland University College
Journal of Physical Chemistry C | Year: 2012

First principles total energy calculations were combined with variational transition state theory to reveal a surface-induced effect on the decomposition of a molecular material. Explored decomposition reactions were illustrated with energetic molecular solid β-cyclotetramethylene-tetranitramine. Simulated N-NO 2 homolysis reactions demonstrated that initiation of molecular material's degradation is characterized by a reduced activation barrier and significantly accelerated reaction rates for molecules that are placed on a free surface, an internal void, or a vacancy as compared to the perfect bulk crystal. © 2012 American Chemical Society.

Lips K.R.,University of Maryland University College
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2016

Chytridiomycosis is an emerging infectious disease of amphibians that affects over 700 species on all continents where amphibians occur. The amphibian– chytridiomycosis system is complex, and the response of any amphibian species to chytrid depends on many aspects of the ecology and evolutionary history of the amphibian, the genotype and phenotype of the fungus, and how the biological and physical environment can mediate that interaction. Impacts of chytridiomycosis on amphibians are varied; some species have been driven extinct, populations of others have declined severely, whereas still others have not obviously declined. Understanding patterns and mechanisms of amphibian responses to chytrids is critical for conservation and management. Robust estimates of population numbers are needed to identify species at risk, prioritize taxa for conservation actions, design management strategies for managing populations and species, and to develop effective measures to reduce impacts of chytrids on amphibians. © 2016 The Author(s) Published by the Royal Society. All rights reserved.

Park S.-Y.,University of Maryland University College | Dimitrakopoulos P.,University of Maryland University College
Soft Matter | Year: 2013

In this paper we investigate computationally the transient dynamics of an elastic capsule flowing in a square microchannel with a rectangular constriction, and compare it with that of a droplet. The confinement and expansion dynamics of the fluid flow results in a rich deformation behavior for the capsule, from an elongated shape at the constriction entrance, to a flattened parachute shape at its exit. Larger capsules are shown to take more time to pass the constriction and cause higher additional pressure difference, owing to higher flow blocking. Our work highlights the effects of two different mechanisms for non-tank-treading transient capsule dynamics. The capsule deformation results from the combined effects of the surrounding and inner fluids' normal stresses on the soft particle's interface, and thus when the capsule viscosity increases, its transient deformation decreases, as for droplets. However, the capsule deformation is not able to create a strong enough inner circulation (owing to restrictions imposed by the material membrane), and thus the viscosity ratio does not affect much the capsule velocity and the additional pressure difference. In addition, the weak inner circulation results in a positive additional pressure difference ΔP+ even for low-viscosity capsules, in direct contrast to low-viscosity droplets which create a negative ΔP+. Our findings suggest that the high cytoplasmatic viscosity, owing to the protein hemoglobin required for oxygen transport, does not affect adversely the motion of non-tank-trading erythrocytes in vascular capillaries. © 2013 The Royal Society of Chemistry.

Carter G.G.,University of Maryland University College
Proceedings. Biological sciences / The Royal Society | Year: 2013

Common vampire bats often regurgitate food to roost-mates that fail to feed. The original explanation for this costly helping behaviour invoked both direct and indirect fitness benefits. Several authors have since suggested that food sharing is maintained solely by indirect fitness because non-kin food sharing could have resulted from kin recognition errors, indiscriminate altruism within groups, or harassment. To test these alternatives, we examined predictors of food-sharing decisions under controlled conditions of mixed relatedness and equal familiarity. Over a 2 year period, we individually fasted 20 vampire bats (Desmodus rotundus) and induced food sharing on 48 days. Surprisingly, donors initiated food sharing more often than recipients, which is inconsistent with harassment. Food received was the best predictor of food given across dyads, and 8.5 times more important than relatedness. Sixty-four per cent of sharing dyads were unrelated, approaching the 67 per cent expected if nepotism was absent. Consistent with social bonding, the food-sharing network was consistent and correlated with mutual allogrooming. Together with past work, these findings support the hypothesis that food sharing in vampire bats provides mutual direct fitness benefits, and is not explained solely by kin selection or harassment.

Kuriakose S.,University of Maryland University College | Dimitrakopoulos P.,University of Maryland University College
Soft Matter | Year: 2013

In the present study we investigate computationally the deformation of an elastic capsule in a rectangular microfluidic channel and compare it with that of a droplet. In contrast to the bullet or parachute shape in a square or cylindrical channel where the capsule extends along the flow direction, in a rectangular channel the capsule extends mainly along the less-confined lateral direction of the channel cross-section (i.e. the channel width), obtaining a pebble-like shape. The different shape evolution in these two types of solid channels results from the different tension development on the capsule membrane required for interfacial stability. Furthermore, in asymmetric channel flows, capsules show a different deformation compared to droplets with constant surface tension (which extend mainly along the flow direction) and to vesicles which extend along the more-confined channel height. Therefore, our study highlights the different stability dynamics associated with these three types of interfaces. Our findings suggest that the erythrocyte deformation in asymmetric vessels (which is similar to that of capsules) results from the erythrocyte's inner spectrin skeleton rather than from its outer lipid bilayer. © 2013 The Royal Society of Chemistry.

Harris D.G.,University of Maryland University College
Proceedings of the Annual ACM-SIAM Symposium on Discrete Algorithms | Year: 2015

The Lopsided Lovász Local Lemma (LLLL) is a powerful probabilistic principle which has been used in a variety of combinatorial constructions. While this principle began as a general statement about probability spaces, it has recently been transformed into a variety of polynomial-time algorithms. The resampling algorithm of Moser & Tardos is the most well-known example of this. A variety of criteria have been shown for the LLLL; the strongest possible criterion was shown by Shearer, and other criteria which are easier to use computationally have been shown by Bissacot et al, Pegden, and Kolipaka & Szegedy. We show a new criterion for the Moser-Tardos algorithm to converge. This criterion is stronger than the LLLL criterion, and in fact can yield better results even than the full Shearer criterion. This is possible because it does not apply in the same generality as the original LLLL; yet, it is strong enough to cover many applications of the LLLL in combinatorics. We show a variety of new bounds and algorithms. A noteworthy application is for k-SAT, with bounded occurences of variables. As shown in Gebauer, Szábo, and Tardos, a k-SAT instance in which every variable appears L ≤ 2k+1/e(k+1) times, is satisfiable. Although this bound is asymptotically tight (in k), we improve it to L ≤ 2k+1 (1-1/k)k/k-1 -2/k which can be significantly stronger when k is small. We introduce a new parallel algorithm for the LLLL. While Moser & Tardos described a simple parallel algorithm for the Lovász Local Lemma, and described a simple sequential algorithm for a form of the Lopsided Lemma, they were not able to combine the two. Our new algorithm applies in nearly all settings in which the sequential algorithm works-this includes settings covered by our new stronger LLLL criterion. Copyright © 2015 by the Society for Industrial and Applied Mathmatics.

Guan W.,University of Maryland University College | Liu K.J.R.,University of Maryland University College
IEEE Transactions on Wireless Communications | Year: 2011

This work focuses on a two-way denoise-and-forward relaying system using non-coherent Differential Binary Phase-Shift Keying (DBPSK) modulation, which has the well-defined relay denoising function when channel state information is unknown. We first design the relay denoising function and source decoders using Maximum Likelihood (ML) principles for the general case with K parallel relays. As the ML denoising function is hard to manipulate, we approximate it as a multi-user detector followed by a physical layer network coding encoder and obtain the closed-form relay decoding error. For the single-relay case, we show that the ML source decoder is actually equivalent to the typical DBPSK decoder for the relay-source channel and thus derive the exact end-to-end Bit Error Rate (BER). To minimize the average BER, we also investigate the power allocation problem by use of asymptotic analysis at high Signal-to-Noise Ratio (SNR). We show that the optimal source power is inversely proportional to the square root of the channel gain of the source-relay channel, and the optimal relay power decreases with SNR. For the multi-relay case, though the exact analysis is intractable, we develop upper bound and lower bound on BER and show that the diversity order is exactly \lceil {K/2}. © 2011 IEEE.

Lipsa G.M.,University of Maryland University College | Martins N.C.,University of Maryland University College
IEEE Transactions on Automatic Control | Year: 2011

Consider a first order linear time-invariant discrete time system driven by process noise, a pre-processor that accepts causal measurements of the state of the system, and a state estimator. The pre-processor and the state estimator are not co-located, and, at every time-step, the pre-processor transmits either a real number or a free symbol to the estimator. We seek the pre-processor and the estimator that jointly minimize a cost that combines two terms; the expected squared state estimation error and a communication cost. In our formulation, the transmission of a real number from the pre-processor to the estimator incurs a positive cost while free symbols induce zero cost. This paper proves analytically that a symmetric threshold policy at the pre-processor and a Kalman-like filter at the estimator, which updates its estimate linearly in the presence of free symbols, are jointly optimal for our problem. © 2010 IEEE.

Hwang E.,University of Maryland University College | Smolyaninov I.I.,University of Maryland University College | Davis C.C.,University of Maryland University College
Nano Letters | Year: 2010

We experimentally demonstrate the enhancement of fluorescence from quantum dots excited by interaction with surface plasmon polaritons on nanostructured metal surfaces. The relationship between observed enhancement and geometrical factors of the surface structure has been used to explore the behavior of quantum dots on different substrates. Imaging using standard fluorescence optical microscopy clearly demonstrates a strong dependence of fluorescence enhancement on fundamental parameters for periodic surface structures. © 2010 American Chemical Society.

Fan J.,University of Maryland University College
Nature Photonics | Year: 2016

A hallmark feature of topological physics is the presence of one-way propagating chiral modes at the system boundary. The chirality of edge modes is a consequence of the topological character of the bulk. For example, in a non-interacting quantum Hall model, edge modes manifest as mid-gap states between two topologically distinct bulk bands. The bulk–boundary correspondence dictates that the number of chiral edge modes, a topological invariant called the winding number, is completely determined by the bulk topological invariant, the Chern number. Here, for the first time, we measure the winding number in a 2D photonic system. By inserting a unit flux quantum at the edge, we show that the edge spectrum resonances shift by the winding number. This experiment provides a new approach for unambiguous measurement of topological invariants, independent of the microscopic details, and could possibly be extended to probe strongly correlated topological orders. © 2016 Nature Publishing Group

Sarbach O.,Universidad Michoacana de San Nicolás de Hidalgo | Tiglio M.,University of Maryland University College
Living Reviews in Relativity | Year: 2012

Many evolution problems in physics are described by partial differential equations on an infinite domain; therefore, one is interested in the solutions to such problems for a given initial dataset. A prominent example is the binary black-hole problem within Einstein's theory of gravitation, in which one computes the gravitational radiation emitted from the inspiral of the two black holes, merger and ringdown. Powerful mathematical tools can be used to establish qualitative statements about the solutions, such as their existence, uniqueness, continuous dependence on the initial data, or their asymptotic behavior over large time scales. However, one is often interested in computing the solution itself, and unless the partial differential equation is very simple, or the initial data possesses a high degree of symmetry, this computation requires approximation by numerical discretization. When solving such discrete problems on a machine, one is faced with a finite limit to computational resources, which leads to the replacement of the infinite continuum domain with a finite computer grid. This, in turn, leads to a discrete initial-boundary value problem. The hope is to recover, with high accuracy, the exact solution in the limit where the grid spacing converges to zero with the boundary being pushed to infinity. The goal of this article is to review some of the theory necessary to understand the continuum and discrete initial boundary-value problems arising from hyperbolic partial differential equations and to discuss its applications to numerical relativity; in particular, we present wellposed initial and initial-boundary value formulations of Einstein's equations, and we discuss multi-domain high-order finite difference and spectral methods to solve them.

Seo E.S.,University of Maryland University College
Astroparticle Physics | Year: 2012

Direct measurements of cosmic rays with balloon-borne detectors are used for understanding cosmic ray origin, acceleration and propagation, as well as exploring the supernova acceleration limit and searching for exotic sources such as dark matter. The energy reach of direct measurements is currently limited to ∼1015 eV by the detector size and exposure time, but incident particles are identified element-by-element with excellent charge resolution. A challenge of balloon-borne experiments is that the detectors must be large enough to collect adequate statistics, yet stay within the weight limit available for balloon flight. Innovative approaches now promise high quality measurements over an energy range that was not previously possible. Recent results and their implications are reviewed. The outlook of existing and future experiments is also discussed. © 2012 Elsevier B.V. All rights reserved.

Leventon I.T.,University of Maryland University College | Stoliarov S.I.,University of Maryland University College
Proceedings of the Combustion Institute | Year: 2013

The heat feedback profile across 5 cm wide and 15 cm tall samples of poly(methyl methacrylate) was studied from ignition until total sample involvement as a flame spread vertically upward. Incident heat flux to a water-cooled gauge was measured at 1 cm intervals. At 6-15 cm above the bottom edge of the flame, the maximum heat flux value was found to be on the order of 35 kW m-2. Lower in the sample, 2-5 cm above the flame bottom, where the flame is thinner and thus closer to the sample's surface, the maximum heat flux is slightly higher, about 40 kW m-2. Using these results and finely resolved measurements of sample burning rate recorded throughout the length of experiments, an analytical model that accurately predicts the measured heat flux profile along the vertical dimension of samples solely as a function of the burning rate was developed. Coupling this model with an accurate pyrolysis solver, which predicts material burning rate based on incident heat flux, is expected to enable highly accurate simulations of the flame spread dynamics. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Mi B.,University of Maryland University College | Elimelech M.,Yale University
Desalination | Year: 2013

This study investigated the silica scaling and cleaning behavior in forward osmosis (FO) and how it compared with that in reverse osmosis (RO). The comparison between FO and RO modes shows that, under the hydrodynamic conditions tested, the flux decline rates under silica scaling are very similar in the two modes, but the flux recovery is close to 100% in the FO mode while it is only around 80% in the RO mode. Cellulose acetate (CA) and polyamide (PA) membranes were used to study the effects of membrane materials on silica scaling and cleaning. It is found that the flux decline rates for both membranes are similar, but the flux recovery of the CA membrane is 30-40% higher than that of the PA membrane. AFM force measurements indicate that membrane surface roughness increases the adhesion force between the PA membrane and a silica gel layer, significantly decreasing the cleaning efficiency of the PA membrane. Results from dynamic light scattering and energy-dispersive X-ray spectroscopy indicate that silica scaling is initiated as monosilicic acid deposits on the membrane surface, followed by polymerization/condensation that forms an amorphous silica gel layer at the interface between the membrane and silica particles. © 2012 Elsevier B.V..

Mishra A.N.,Georgia State University | Agarwal R.,University of Maryland University College
Information Systems Research | Year: 2010

The process by which organizations incorporate technological innovations into existing routines and use them on a regular basis persists as a central concern in the literature. Although we now have a fairly robust understanding of the drivers of innovation adoption, the use of innovations is less understood. In this paper, we draw on two streams of literature, managerial and organizational sensemaking, and organizational capabilities that have hitherto been used independently, to investigate organizational use of information technology (IT)-based innovations. Building on and extending prior work, we posit that organizational capabilities serve as complements to managers' technological frames related to an innovation. We focus on the use of an important technological innovation-business-to-business (B2B) electronic markets for procurement. We examine interactions between three technological frames-benefits frame, threat frame, and adjustment frame, and two organizational capabilities-technological opportunism and technological sophistication, and their relationship with the use of B2B electronic markets in firms. We test our research model using survey data collected from 292 firms. Results largely support the proposed conceptualization and shed new light on the key factors associated with firms' use of B2B electronic markets. Theoretical and practical implications of the findings are discussed. © 2010 INFORMS.

Gopal A.,University of Maryland University College | Gosain S.,CA Capital
Information Systems Research | Year: 2010

Past research has studied how the selection and use of control portfolios in software projects is based on environmental and task characteristics. However, little research has examined the consequences of control mode choices on project performance. This paper reports on a study that addresses this issue in the context of outsourced software projects. In addition, we propose that boundary-spanning activities between the vendor and the client enable knowledge sharing across organizational and knowledge domain boundaries. This is expected to lead to facilitation of control through specific incentives and performance norms that are suited to client needs as well as the vendor context. Therefore, we argue that boundary spanning between the vendor and client moderates the relationship between formal controls instituted by the vendor on the development team and project performance. We also hypothesize the effect of collaboration as a clan control on project performance. We examine project performance in terms of software quality and project efficiency. The research model is empirically tested in the Indian software industry setting on a sample of 96 projects. The results suggest that formal and informal control modes have a significant impact on software project outcomes, but need to be finely tuned and directed toward appropriate objectives. In addition, boundary-spanning activities significantly improve the effectiveness of formal controls. Finally, we find that collaborative culture has provided mixed benefits by enhancing quality but reducing efficiency. © 2010 INFORMS.

Anderson C.L.,University of Maryland University College | Agarwal R.,University of Maryland University College
MIS Quarterly: Management Information Systems | Year: 2010

Although firms are expending substantial resources to develop technology and processes that can help safeguard the security of their computing assets, increased attention is being focused on the role people play in maintaining a safe computing environment. Unlike employees in a work setting, home users are not subject to training, nor are they protected by a technical staff dedicated to keeping security software and hardware current. Thus, with over one billion people with access to the Internet, individual home computer users represent a significant point of weakness in achieving the security of the cyber infrastructure. We study the phenomenon of conscientious cybercitizens, defined as individuals who are motivated to take the necessary precautions under their direct control to secure their own computer and the Internet in a home setting. Using a multidisciplinary, phased approach, we develop a conceptual model of the conscientious cybercitizen. We present results from two studies-a survey and an experiment-conducted to understand the drivers of intentions to perform security-related behavior, and the interventions that can positively influence these drivers. In the first study, we use protection motivation theory as the underlying conceptual foundation and extend the theory by drawing upon the public goods literature and the concept of psychological ownership. Results from a survey of 594 home computer users from a wide range of demographic and socioeconomic backgrounds suggest that a home computer user's intention to perform security-related behavior is influenced by a combination of cognitive, social, and psychological components. In the second study, we draw upon the concepts of goal framing and self-view to examine how the proximal drivers of intentions to perform security-related behavior identified in the first study can be influenced by appropriate messaging. An experiment with 101 subjects is used to test the research hypotheses. Overall, the two studies shed important new light on creating more conscientious cybercitizens. Theoretical and practical implications of the findings are discussed.

Ganeshan S.,University of Maryland University College | Das Sarma S.,University of Maryland University College
Physical Review B - Condensed Matter and Materials Physics | Year: 2015

Topological semimetals in three-dimensions (e.g., a Weyl semimetal) can be built by stacking two-dimensional topological phases. The interesting aspect of such a construction is that even though the topological building blocks in the low dimension may be gapped, the higher dimensional semimetallic phase emerges as a gapless critical point of a topological phase transition between two distinct insulating phases. In this work, we extend this idea by constructing three-dimensional topological semimetallic phases akin to Weyl systems by stacking one-dimensional Aubry-Andre-Harper (AAH) lattice tight-binding models with nontrivial topology. The generalized AAH model is a family of one-dimensional tight-binding models with cosine modulations in both hopping and on-site energy terms. In this paper, we pr