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Newark, DE, United States

The University of Delaware is the largest university in Delaware. The main campus is in Newark, with satellite campuses in Dover, Wilmington, Lewes, and Georgetown. It is medium-sized – approximately 16,000 undergraduate and 3,500 graduate students. UD is a private university and receives public funding for being a land-grant, sea-grant, space-grant and urban-grant state-supported research institution. As of 2013, the school's endowment is valued at about US$1.171 billion. Delaware has been labeled one of the "Public Ivies," a publicly funded university considered as providing a quality of education comparable to those of the Ivy League.UD is classified as a research university with very high research activity by the Carnegie Classification of Institutions of Higher Education. The university's programs in engineering, science, business, hospitality management, education, urban affairs and public policy, public administration, agriculture, history, chemical and biomolecular engineering, chemistry and biochemistry have been highly ranked with some drawing from the historically strong presence of the nation's chemical and pharmaceutical industries in the state of Delaware, such as DuPont and W. L. Gore and Associates. It is one of only four schools in North America with a major in art conservation. UD was the first American university to begin a study abroad program.The school from which the university grew was founded in 1743, making it one of the oldest in the nation. However, UD was not chartered as an institution of higher learning until 1833. Its original class of ten students included George Read, Thomas McKean, and James Smith, all three of whom would go on to sign the Declaration of Independence. Wikipedia.


Campbell B.J.,University of Delaware | Campbell B.J.,Clemson University | Kirchman D.L.,Clemson University
ISME Journal | Year: 2013

Very little is known about growth rates of individual bacterial taxa and how they respond to environmental flux. Here, we characterized bacterial community diversity, structure and the relative abundance of 16S rRNA and 16S rRNA genes (rDNA) using pyrosequencing along the salinity gradient in the Delaware Bay. Indices of diversity, evenness, structure and growth rates of the surface bacterial community significantly varied along the transect, reflecting active mixing between the freshwater and marine ends of the estuary. There was no positive correlation between relative abundances of 16S rRNA and rDNA for the entire bacterial community, suggesting that abundance of bacteria does not necessarily reflect potential growth rate or activity. However, for almost half of the individual taxa, 16S rRNA positively correlated with rDNA, suggesting that activity did follow abundance in these cases. The positive relationship between 16S rRNA and rDNA was less in the whole water community than for free-living taxa, indicating that the two communities differed in activity. The 16S rRNA:rDNA ratios of some typically marine taxa reflected differences in light, nutrient concentrations and other environmental factors along the estuarine gradient. The ratios of individual freshwater taxa declined as salinity increased, whereas the 16S rRNA:rDNA ratios of only some typical marine bacteria increased as salinity increased. These data suggest that physical and other bottom-up factors differentially affect growth rates, but not necessarily abundance of individual taxa in this highly variable environment. © 2013 International Society for Microbial Ecology All rights reserved. Source


Grzelczak M.,University of Vigo | Grzelczak M.,University of Trieste | Vermant J.,Catholic University of Leuven | Furst E.M.,University of Delaware | Liz-Marzan L.M.,University of Vigo
ACS Nano | Year: 2010

Within the field of nanotechnology, nanoparticles are one of the most prominent and promising candidates for technological applications. Self-assembly of nanoparticles has been identified as an important process where the building blocks spontaneously organize into ordered structures by thermodynamic and other constraints. However, in order to successfully exploit nanoparticle self-assembly in technological applications and to ensure efficient scale-up, a high level of direction and control is required. The present review critically investigates to what extent self-assembly can be directed, enhanced, or controlled by either changing the energy or entropy landscapes, using templates or applying external fields. © 2010 American Chemical Society. Source


Szalewicz K.,University of Delaware
Accounts of Chemical Research | Year: 2014

Until recently, it had been impossible to predict structures of molecular crystals just from the knowledge of the chemical formula for the constituent molecule(s). A solution of this problem has been achieved using intermolecular force fields computed from first principles. These fields were developed by calculating interaction energies of molecular dimers and trimers using an ab initio method called symmetry-adapted perturbation theory (SAPT) based on density-functional theory (DFT) description of monomers [SAPT(DFT)]. For clusters containing up to a dozen or so atoms, interaction energies computed using SAPT(DFT) are comparable in accuracy to the results of the best wave function-based methods, whereas the former approach can be applied to systems an order of magnitude larger than the latter. In fact, for monomers with a couple dozen atoms, SAPT(DFT) is about equally time-consuming as the supermolecular DFT approach. To develop a force field, SAPT(DFT) calculations are performed for a large number of dimer and possibly also trimer configurations (grid points in intermolecular coordinates), and the interaction energies are then fitted by analytic functions. The resulting force fields can be used to determine crystal structures and properties by applying them in molecular packing, lattice energy minimization, and molecular dynamics calculations. In this way, some of the first successful determinations of crystal structures were achieved from first principles, with crystal densities and lattice parameters agreeing with experimental values to within about 1%. Crystal properties obtained using similar procedures but empirical force fields fitted to crystal data have typical errors of several percent due to low sensitivity of empirical fits to interactions beyond those of the nearest neighbors. The first-principles approach has additional advantages over the empirical approach for notional crystals and cocrystals since empirical force fields can only be extrapolated to such cases.As an alternative to applying SAPT(DFT) in crystal structure calculations, one can use supermolecular DFT interaction energies combined with scaled dispersion energies computed from simple atom-atom functions, that is, use the so-called DFT+D approach. Whereas the standard DFT methods fail for intermolecular interactions, DFT+D performs reasonably well since the dispersion correction is used not only to provide the missing dispersion contribution but also to fix other deficiencies of DFT. The latter cancellation of errors is unphysical and can be avoided by applying the so-called dispersionless density functional, dlDF. In this case, the dispersion energies are added without any scaling. The dlDF+D method is also one of the best performing DFT+D methods.The SAPT(DFT)-based approach has been applied so far only to crystals with rigid monomers. It can be extended to partly flexible monomers, that is, to monomers with only a few internal coordinates allowed to vary. However, the costs will increase relative to rigid monomer cases since the number of grid points increases exponentially with the number of dimensions. One way around this problem is to construct force fields with approximate couplings between inter- and intramonomer degrees of freedom. Another way is to calculate interaction energies (and possibly forces) "on the fly", i.e., in each step of lattice energy minimization procedure. Such an approach would be prohibitively expensive if it replaced analytic force fields at all stages of the crystal predictions procedure, but it can be used to optimize a few dozen candidate structures determined by other methods. © 2014 American Chemical Society. Source


Holder J.,University of Delaware
Astroparticle Physics | Year: 2012

The field of TeV gamma-ray astronomy has produced many exciting results over the last decade. Both the source catalogue, and the range of astrophysical questions which can be addressed, continue to expand. This article presents a topical review of the field, with a focus on the observational results of the imaging atmospheric Cherenkov telescope arrays. The results encompass pulsars and their nebulae, supernova remnants, gamma-ray binary systems, star forming regions and starburst and active galaxies. © 2012 Elsevier B.V. All rights reserved. Source


When blood vessels undergo remodeling because of the buildup of atherosclerotic plaque, it is thought that they first undergo compensatory or outward remodeling, followed by inward remodeling: the lumen area stays roughly constant or increases slightly and then decreases rapidly. The second phase of remodeling is supposed to start after the plaque burden exceeds about 40%. These changes in the vessel were first observed by S. Glagov who examined cross-sections of coronary arteries at different stages of the disease. In this paper, we use a mathematical model based on growth and elasticity theory to verify the main aspects of Glagov's result. However, both our model and curve-fitting to the data suggest that the critical stenosis is around 20% rather than 40%. Our model and data from the PROSPECT trial also show that Glagov remodeling is qualitatively different depending on whether measurements are taken ex-vivo or in-vivo. Our results suggest that the first outward phase of "Glagov remodeling" is largely absent for in-vivo measurements: that is, the lumen area always decreases as plaque builds up. We advocate that care must be taken when infering how in-vivo vessels remodel from ex-vivo data. © 2016 Pak-Wing Fok. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source


Jungck J.R.,University of Delaware
Advances in Applied Microbiology | Year: 2012

Microbiology is a rich area for visualizing the importance of mathematics in terms of designing experiments, data mining, testing hypotheses, and visualizing relationships. Historically, Nobel Prizes have acknowledged the close interplay between mathematics and microbiology in such examples as the fluctuation test and mutation rates using Poisson statistics by Luria and Delbrück and the use of graph theory of polyhedra by Caspar and Klug. More and more contemporary microbiology journals feature mathematical models, computational algorithms and heuristics, and multidimensional visualizations. While revolutions in research have driven these initiatives, a commensurate effort needs to be made to incorporate much more mathematics into the professional preparation of microbiologists. In order not to be daunting to many educators, a Bloom-like "Taxonomy of Quantitative Reasoning" is shared with explicit examples of microbiological activities for engaging students in (a) counting, measuring, calculating using image analysis of bacterial colonies and viral infections on variegated leaves, measurement of fractal dimensions of beautiful colony morphologies, and counting vertices, edges, and faces on viral capsids and using graph theory to understand self assembly; (b) graphing, mapping, ordering by applying linear, exponential, and logistic growth models of public health and sanitation problems, revisiting Snow's epidemiological map of cholera with computational geometry, and using interval graphs to do complementation mapping, deletion mapping, food webs, and microarray heatmaps; (c) problem solving by doing gene mapping and experimental design, and applying Boolean algebra to gene regulation of operons; (d) analysis of the "Bacterial Bonanza" of microbial sequence and genomic data using bioinformatics and phylogenetics; (e) hypothesis testing-again with phylogenetic trees and use of Poisson statistics and the Luria-Delbrück fluctuation test; and (f) modeling of biodiversity by using game theory, of epidemics with algebraic models, bacterial motion by using motion picture analysis and fluid mechanics of motility in multiple dimensions through the physics of "Life at Low Reynolds Numbers," and pattern formation of quorum sensing bacterial populations. Through a developmental model for preprofessional education that emphasizes the beauty, utility, and diversity of microbiological systems, we hope to foster creativity as well as mathematically rigorous reasoning. © 2012 Elsevier Inc. Source


Porosoff M.D.,University of Delaware | Chen J.G.,Columbia University
Journal of Catalysis | Year: 2013

The reduction of CO2 by hydrogen has been conducted on supported catalysts in a batch reactor. Catalysts synthesized on a reducible support (CeO2) showed higher activity than on an irreducible support (γ-Al2O3). The active metal also played an important role in controlling the selective reduction of CO2 to CO instead of CH4. Extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) confirmed the formation of uniform, bimetallic particles. Among the monometallic and bimetallic catalysts evaluated in the current study, PdNi/CeO2 was the most active bimetallic catalyst, but also formed the greatest amount of CH4, while PtCo/γ-Al2O3 showed the highest selectivity to CO with little CH4 production. The selectivity was correlated with electronic properties of the supported catalysts by using values of surface d-band center. The general trends observed should provide insights in identifying desirable catalysts for the reduction of CO2. © 2013 Elsevier Inc. All rights reserved. Source


Lopez-Barron C.R.,ExxonMobil | Porcar L.,Laue Langevin Institute | Eberle A.P.R.,U.S. National Institute of Standards and Technology | Wagner N.J.,University of Delaware
Physical Review Letters | Year: 2012

Shear-induced structural transitions of a micellar cubic phase during large amplitude oscillatory shear flow is studied with time-resolved oscillatory rheological small angle neutron scattering. This technique allows us to resolve the structural changes within a cycle of oscillation. By applying a strain rate near the critical melting shear rate, melting and recrystallization occurs in a cyclic mode. The maximum degree of order is observed when the shear stress reaches a plateau value during the large amplitude oscillatory shear cycle, whereas melting is maximized at the strain rate wave peaks. This structural evolution confirms the cyclic mechanism of sticking and sliding of 2D hexagonal close-packed layers. © 2012 American Physical Society. Source


Grabowski W.W.,U.S. National Center for Atmospheric Research | Wang L.-P.,University of Delaware
Annual Review of Fluid Mechanics | Year: 2013

Motivated by the need to resolve the condensation-coalescence bottleneck in warm rain formation, a significant number of studies have emerged in the past 15 years concerning the growth of cloud droplets by water-vapor diffusion and by collision-coalescence in a turbulent environment. With regard to condensation, recent studies suggest that small-scale turbulence alone does not produce a significant broadening of the cloud-droplet spectrum because of the smearing of droplet-scale fluctuations by rapid turbulent and gravitational mixing. However, different diffusional-growth histories associated with large-eddy hopping could lead to a significant spectral broadening. In contrast, small-scale turbulence in cumulus clouds makes a significant contribution to the collision-coalescence of droplets, enhancing the collection kernel up to a factor of 5, especially for droplet pairs with a low gravitational collision rate. This moderate level of enhancement has a significant impact on warm rain initiation. The multiscale nature of turbulent cloud microphysical processes and open research issues are delineated throughout. Copyright © 2013 by Annual Reviews. All rights reserved. Source


Ness N.F.,University of Delaware
Space Science Reviews | Year: 2010

This chapter gives a brief overview of the major observational advances in our quantitative knowledge of the intrinsic magnetic fields of the 8 planets, except Earth, from Mercury to Neptune, since "The Space Age" began on 4 October 1957 with the USSR launching of the world's first artificial satellite SPUTNIK I. © 2009 Springer Science+Business Media B.V. Source


Boyd E.F.,University of Delaware
Advances in Virus Research | Year: 2012

The role of bacteriophages as natural vectors for some of the most potent bacterial toxins is well recognized and includes classical type I membrane-acting superantigens, type II pore-forming lysins, and type III exotoxins, such as diphtheria and botulinum toxins. Among Gram-negative pathogens, a novel class of bacterial virulence factors called effector proteins (EPs) are phage encoded among pathovars of Escherichia coli, Shigella spp., and Salmonella enterica. This chapter gives an overview of the different types of virulence factors encoded within phage genomes based on their role in bacterial pathogenesis. It also discusses phage-pathogenicity island interactions uncovered from studies of phage-encoded EPs. A detailed examination of the filamentous phage CTXφ that encodes cholera toxin is given as the sole example to date of a single-stranded DNA phage that encodes a bacterial toxin. © 2012 Elsevier Inc. Source


Cary S.C.,University of Waikato | Cary S.C.,University of Delaware | McDonald I.R.,University of Waikato | Barrett J.E.,Virginia Polytechnic Institute and State University | Cowan D.A.,University of the Western Cape
Nature Reviews Microbiology | Year: 2010

The arid soils of the Antarctic Dry Valleys constitute some of the oldest, coldest, driest and most oligotrophic soils on Earth. Early studies suggested that the Dry Valley soils contained, at best, very low levels of viable microbiota. However, recent applications of molecular methods have revealed a dramatically contrasting picture a very wide diversity of microbial taxa, many of which are uncultured and taxonomically unique, and a community that seems to be structured solely by abiotic processes. Here we review our understanding of these extreme Antarctic terrestrial microbial communities, with particular emphasis on the factors that are involved in their development, distribution and maintenance in these cold desert environments. © 2010 Macmillan Publishers Limited. All rights reserved. Source


Miller G.A.,University of Delaware | Miller G.A.,University of Konstanz | Miller G.A.,University of Illinois at Urbana - Champaign | Rockstroh B.,University of Konstanz
Annual Review of Clinical Psychology | Year: 2013

Endophenotypes for psychopathology have been conceived as latent, unobserved, but measureable manifestations of phenomena that causally connect genetic liability to clinical disorder. Several decades of research have led to refinement of the construct and identification of some candidate endophenotypes, but rather limited progress on finding the genes involved or the mechanisms by which endophenotypes are driven by genetic and environmental factors and in turn drive psychopathology. Currently promising avenues for research involve development of transdiagnostic concepts not limited to traditional diagnostic categories, measures of endophenotypic and manifest psychopathology that have higher validity than those categories, and methods for modeling complex relationships among diverse contributors to etiology. With more grounding in animal neuroscience and other aspects of basic biological and psychological science, exemplified in the Research Domain Criteria initiative, there is every reason to anticipate that the endophenotype concept will grow more central in the psychopathology literature. Copyright © 2013 by Annual Reviews. Source


Hoover D.G.,University of Delaware | Rodriguez-Palacios A.,Case Western Reserve University
Infectious Disease Clinics of North America | Year: 2013

Clostridium difficile is a human intestinal pathogen most frequently involved in diarrheal illnesses following the administration of antibiotics. There is growing concern that some C difficile infections (CDI) may be acquired from ingestion of C difficile spores in contaminated foods. The number of CDI cases is increasing with a heightening in the severity of disease symptoms and an increasing number of community-associated infections not connected to health care-associated risk. This article provides an overview of information related to assessing the risk of foodborne transmission of CDI, highlighting studies on C difficile relevant to food safety in health care settings. © 2013 Elsevier Inc. Source


Jaisi D.P.,University of Delaware
Journal of Contaminant Hydrology | Year: 2013

Characterizing reactivity and fate of contaminants in subsurface environments that are isolated from direct visualization is a major challenge. Stable isotopes coupled with concentration could be used as a potential tool to quantitatively analyze the chemical variability of the contaminant during reactive transport processes in the subsurface environment. This study was aimed at determining whether abiotic reactions of phosphate during its transport involve fractionation of oxygen isotopes in phosphate (δ 18Op). It included the effects of solution chemistry and hydrodynamics on δ18Op values during phosphate transport through a packed-bed column prepared by using natural sediment collected from the Cape Cod aquifer in Massachusetts. Results show that the isotopic fractionation between effluent and influent phosphate at early stage of transport could be ∼ 1.3‰ at higher flow rates with isotopically-light phosphate (P16O4) preferentially retained in the sediment column. This fractionation, however, decreased and became insignificant as more phosphate passed through the column. Mobilization of phosphate initially sorbed onto sediments caused a large kinetic isotopic fractionation with isotopically-light phosphate preferentially remobilized from the sediment column, but over longer time periods, this fractionation decreased and became insignificant as well. These results collectively suggest that abiotic reactive transport processes exert minimal influence on the δ18Op composition of subsurface systems. Alternatively, fluctuation in flow rate and subsequent remobilization of phosphate could be detectable through transient changes in δ 18Op values. These findings extend the burgeoning application of δ18Op to identify the different sources and geochemical processes of phosphate in the subsurface environments. © 2013 Elsevier B.V. Source


Sandler S.I.,University of Delaware
Journal of Supercritical Fluids | Year: 2010

The important insight of J. D. van der Waals in developing the equation of state that bears his name was the analysis of the separate contributions of the attractive and hard-core repulsive interactions to the equation of state. This insight led him to important advances in understanding fluids and their phase transitions. This same separation of attractive and hard core interactions have been used in statistical mechanics in the form of perturbation theory, and also as here in a form referred to as the Generalized van der Waals partition function. This partition function has been used in the literature to understand the assumptions that underlie equations of state, and to develop equations with a better theoretical basis. Here, we demonstrate how the generalized van der Waals partition function can be used to elucidate the assumptions inherent in all of the commonly used correlative activity coefficient models. © 2010 Elsevier B.V. All rights reserved. Source


Marmon A.R.,University of Delaware
Arthritis care & research | Year: 2013

Lower extremity functional performance and perception of functional abilities influence clinical management in people diagnosed with unilateral or bilateral knee osteoarthritis (OA). The purpose of this study was to determine if there were differences in perception of function and performance during functional tasks between individuals with unilateral and bilateral knee OA. The functional abilities of patients with symptomatic and radiographic diagnosed unilateral (n = 84) or bilateral (n = 68) knee OA were evaluated with self-report measures and performance-based tests. Self-report measures included the Knee Outcome Survey, the Global Rating Scale, and the physical component of the Short Form 36 health survey; functional tests included the Timed Up-and-Go Test, the Stair Climbing Test, and the 6-Minute Walk Test. Multivariate analyses of variance were performed separately for men and women to determine if perception (self-report measures) and performance (functional tests) were dependent on the number of involved knees. No significant main effects were observed in functional performance between groups for either sex. Similarly, the perception measures did not differ between groups. In general, individuals diagnosed with unilateral and bilateral knee OA both performed functional tasks and perceived their functional ability similarly. Regardless of the number of involved knees, individuals with knee OA perform and perceive their functional ability similarly, which suggests that clinicians need to consider other factors, such as how long the disease has been progressing or how functional abilities have changed, when treating patients with knee OA. Copyright © 2013 by the American College of Rheumatology. Source


Desiati P.,University of Wisconsin - Madison | Gaisser T.K.,University of Delaware
Physical Review Letters | Year: 2010

The intensity of TeV atmospheric muons and neutrinos depends on the temperature in the stratosphere. We show that the energy dependence in the 100 TeV range of the correlation with temperature is sensitive to the fraction of muons and neutrinos from decay of charmed hadrons. We discuss the prospects for using the temperature effect as observed in gigaton neutrino detectors to measure the charm contribution. © 2010 The American Physical Society. Source


Michalec B.,University of Delaware
Advances in Health Sciences Education | Year: 2011

Utilizing interviews with students and a key administrator, analyses of academic schedules, and observations of courses, labs, and small groups, this study examines if and how elements of the explicit preclinical curriculum may have deleterious effects on medical students' humanitarian attributes, namely empathy. Findings from this case-study of a medical school in the United States suggest that the lack of frequent formal testing in the psycho-social aspects of patient care during the preclinical years, as well as a general reduction in curriculum hours devoted to teaching the social aspects of medicine, may serve as mechanisms behind the diminution of medical students' levels of empathy and other positive attributes as found by previous research. Following the basic tenets of the Testing Effect and the assumption that assessment drives learning, it is argued that a feasible way to maintain and potentially cultivate these traits among medical students, without saturating an overwhelmed medical curriculum, would be to install periodic, formally graded exams into preclinical curriculums that evaluate empathy and the psycho-social aspects of care. © 2010 Springer Science+Business Media B.V. Source


This review provides a comprehensive overview of the vascularization of the avian growth plate and its subsequent role in the pathogenesis of bacterial chondronecrosis with osteomyelitis (BCO, femoral head necrosis). BCO sporadically causes high incidences of lameness in rapidly growing broiler (meat-type) chickens. BCO is believed to be initiated by micro-trauma to poorly mineralized columns of cartilage cells in the proximal growth plates of the leg bones, followed by colonization by hematogenously distributed opportunistic bacteria. Inadequate blood flow to the growth plate, vascular occlusion, and structural limitations of the microvasculature all have been implicated in the pathogenesis of BCO. Treatment strategies have been difficult to investigate because under normal conditions the incidence of BCO typically is low and sporadic. Rearing broilers on wire flooring triggers the spontaneous development of high incidences of lameness attributable to pathogno-monic BCO lesions. Wire flooring imposes persistent footing instability and is thought to accelerate the development of BCO by amplifying the torque and shear stress imposed on susceptible leg joints.Wire flooring per se also constitutes a significant chronic stressor that promotes bacterial proliferation attributed to stress-mediated immunosuppression. Indeed, dexamethasone-mediated immunosuppression causes broilers to develop lameness primarily associated with avascular necrosis and BCO. Prophylactic probiotic administration consistently reduces the incidence of lameness in broilers reared on wire flooring, presumably by reducing bacterial translocation from the gastrointestinal tract that likely contributes to hematogenous infection of the leg bones.The pathogenesis of BCO in broilers is directly relevant to osteomyelitis in growing children, as well as to avascular femoral head necrosis in adults. Our new model for reliably triggering spontaneous osteomyelitis in large numbers of animals represents an important opportunity to conduct translational research focused on developing effective prophylactic and therapeutic treatments. © 2013 Wideman and Prisby. Source


Roth T.L.,University of Delaware
Developmental Psychobiology | Year: 2012

Gene-environment interactions have long been recognized for their important role in mediating the development and functions of the central nervous system (CNS). The study of DNA methylation and histone modifications, biochemical processes collectively referred to as epigenetic mechanisms, is helping to elucidate how gene-environmental interactions alter neurobiology and behavior over the course of the lifespan. In this review, landmark and recent studies that highlight the role of epigenetic mechanisms in the sustained effects of early-life experiences on gene activity and behavioral outcome will be discussed. Likewise, studies that implicate epigenetics in CNS and behavioral plasticity in the adult animal will be discussed. As our current understanding of epigenetics in these capacities is still evolving, epigenetic research will continue to be of considerable interest for understanding the molecular mechanisms mediating neurobiology and behavior both within and outside of sensitive periods of development. © 2012 Wiley Periodicals, Inc. Source


Singh A.,University of Delaware | Bokes P.,Comenius University
Biophysical Journal | Year: 2012

Homogeneous cell populations can exhibit considerable cell-to-cell variability in protein levels arising from the stochastic nature of the gene-expression process. In particular, transcriptional bursting of mRNAs from the promoter has been implicated as a major source of stochasticity in the expression of many genes. In eukaryotes, transcribed pre-mRNAs have to be exported outside the nucleus and in many cases, export rates can be slow and comparable to mRNA turnover rates. We investigate whether such export processes can be effective mechanisms in buffering protein levels from transcriptional bursting of pre-mRNAs in the nucleus. For a stochastic gene-expression model with both transcriptional bursting and export, we derive an exact solution of the steady-state probability-generating function for both the nuclear and the cytoplasmic mRNA levels. These formulas reveal that decreasing export rates can dramatically reduce variability in cytoplasmic mRNA levels. However, our results also show that decreasing export rates enhance mRNA autocorrelation times, which function to increase heterogeneity in protein levels. Our overall analysis concludes that under physiologically relevant parameter regimes, a pre-mRNA export step can decrease steady-state variability at the mRNA level but not at the protein level. Finally, we reinforce previous observations that saturation in the pre-mRNA transport machinery can be an important mechanism in suppressing protein variability from underlying transcriptional bursts. © 2012 Biophysical Society. Source


Schultz J.M.,University of Delaware
Macromolecules | Year: 2013

An 83/17 random copolymer of 3-hydroxybutyrate and 3-hydroxyhexanoate (PHBHHx-17) was studied for its unusual twisting morphology. When PHBHHx-17 is crystallized isothermally from the melt at 45°C, it forms spherulites which exhibit normal radial banding under crossed polarizers. At this temperature, crystallization is sufficiently slow that the growth front can be followed at relatively high resolution in an AFM. The bifurcated tips grow over each other, forming giant screw dislocations. While large rotations are observed commonly, such a consistently large rotation appears to be outside normal experience. The unusual reorientation could be observed unambiguously only from edge-on to face-on orientations. Source


Jaric S.,University of Delaware | Markovic G.,University of Zagreb
European Journal of Applied Physiology | Year: 2013

It is well known that in vitro muscles maximize their power output when acting against a moderate resistance regarding their maximum strength. Similar behavior has been observed from in vivo muscular systems in both single-joint and most of the multi-joint maximum performance tasks. We refer to that phenomenon as a strength-dependent behavior, since the optimum external load that maximizes the mechanical power output of particular muscle(s) or neuro-musculoskeletal system corresponds to a certain percent of maximum strength. In this review paper, we present evidence that the optimum load in maximum vertical jumps is one's own body mass, regardless of the strength of the lower limb muscles (i.e., the strength-independent behavior). Although the discussed phenomenon is still underexplored, we believe that several neuro-mechanical mechanisms are involved. Among these are a long-term adaptation of the muscular force-velocity relationship to the body weight and inertia, alteration of the jumping technique, load-specific muscle activation and jumping skills. Further exploration of the discussed strength-independent behavior of the lower limb muscles is of importance for refining various training and rehabilitation procedures, as well as for understanding the design and function of lower limb muscles. © 2013 Springer-Verlag Berlin Heidelberg. Source


Szczesny S.E.,University of Pennsylvania | Elliott D.M.,University of Delaware
Acta Biomaterialia | Year: 2014

Despite the critical role tendons play in transmitting loads throughout the musculoskeletal system, little is known about the microstructural mechanisms underlying their mechanical function. Of particular interest is whether collagen fibrils in tendon fascicles bear load independently or if load is transferred between fibrils through interfibrillar shear forces. We conducted multiscale experimental testing and developed a microstructural shear lag model to explicitly test whether interfibrillar shear load transfer is indeed the fibrillar loading mechanism in tendon. Experimental correlations between fascicle macroscale mechanics and microscale interfibrillar sliding suggest that fibrils are discontinuous and share load. Moreover, for the first time, we demonstrate that a shear lag model can replicate the fascicle macroscale mechanics as well as predict the microscale fibrillar deformations. Since interfibrillar shear stress is the fundamental loading mechanism assumed in the model, this result provides strong evidence that load is transferred between fibrils in tendon and possibly other aligned collagenous tissues. Conclusively establishing this fibrillar loading mechanism and identifying the involved structural components should help develop repair strategies for tissue degeneration and guide the design of tissue engineered replacements. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source


Antoniewicz M.R.,University of Delaware
Current Opinion in Biotechnology | Year: 2015

Metabolic pathway models provide the foundation for quantitative studies of cellular physiology through the measurement of intracellular metabolic fluxes. For model organisms metabolic models are well established, with many manually curated genome-scale model reconstructions, gene knockout studies and stable-isotope tracing studies. However, for non-model organisms a similar level of knowledge is often lacking. Compartmentation of cellular metabolism in eukaryotic systems also presents significant challenges for quantitative 13C-metabolic flux analysis (13C-MFA). Recently, innovative 13C-MFA approaches have been developed based on parallel labeling experiments, the use of multiple isotopic tracers and integrated data analysis, that allow more rigorous validation of pathway models and improved quantification of metabolic fluxes. Applications of these approaches open new research directions in metabolic engineering, biotechnology and medicine. © 2015 Elsevier Ltd. Source


Vinik A.I.,Eastern Virginia Medical School | Maser R.E.,University of Delaware | Ziegler D.,Heinrich Heine University Dusseldorf
Diabetic Medicine | Year: 2011

It has long been recognized that cardiac autonomic neuropathy increases morbidity and mortality in diabetes and may have greater predictive power than traditional risk factors for cardiovascular events. Significant morbidity and mortality can now be attributable to autonomic imbalance between the sympathetic and parasympathetic nervous system regulation of cardiovascular function. New and emerging syndromes include orthostatic tachycardia, orthostatic bradycardia and an inability to use heart rate as a guide to exercise intensity because of the resting tachycardia. Recent studies have shown that autonomic imbalance may be a predictor of risk of sudden death with intensification of glycaemic control. This review examines an association of autonomic dysregulation and the role of inflammatory cytokines and adipocytokines that promote cardiovascular risk. In addition, conditions of autonomic imbalance associated with cardiovascular risk are discussed. Potential treatment for restoration of autonomic balance is outlined. © 2011 The Authors. Diabetic Medicine © 2011 Diabetes UK. Source


Picollelli M.E.,University of Delaware
Combinatorics Probability and Computing | Year: 2011

We consider the following random graph process: starting with n isolated vertices, add edges uniformly at random provided no such edge creates a copy of C4. We show that, with probability tending to 1 as n →∞, the final graph produced by this process has maximum degree O((nlogn) 1/3) and consequently size O(n 4/3(logn) 1/3), which are sharp up to constants. This confirms conjectures of Bohman and Keevash and of Osthus and Taraz, and improves upon previous bounds due to Bollobás and Riordan and Osthus and Taraz. © 2011 Cambridge University Press. Source


Noda I.,University of Delaware
Journal of Molecular Structure | Year: 2014

Two-dimensional codistribution spectroscopy (2DCDS), a technique designed specifically for the analysis of population dynamics, such as temporal distributions of species during a chemical reaction, is described. 2D codistribution analysis focus on the signal features reflecting the distributed presence of species, instead of the variation patterns of perturbation-induced deviations from the reference state, which has been traditionally analyzed by two-dimensional correlation spectroscopy (2DCOS). This technique is derived from the moment analysis of spectral intensity distributions along the perturbation variable axis within a well-defined observation interval. Derivation and properties of 2D codistribution spectra are provided, and comparison is made to 2D correlation spectroscopy with the help of simulated IR spectra generated from model chemical reactions. © 2014 Elsevier B.V. All rights reserved. Source


Noteworthy experimental practices, which are advancing forward the frontiers of the field of two-dimensional (2D) correlation spectroscopy, are reviewed with the focus on various perturbation methods currently practiced to induce spectral changes, pertinent examples of applications in various fields, and types of analytical probes employed. Types of perturbation methods found in the published literature are very diverse, encompassing both dynamic and static effects. Although a sizable portion of publications report the use of dynamic perturbatuions, much greater number of studies employ static effect, especially that of temperature. Fields of applications covered by the literature are also very broad, ranging from fundamental research to practical applications in a number of physical, chemical and biological systems, such as synthetic polymers, composites and biomolecules. Aside from IR spectroscopy, which is the most commonly used tool, many other analytical probes are used in 2D correlation analysis. The ever expanding trend in depth, breadth and versatility of 2D correlation spectroscopy techniques and their broad applications all point to the robust and healthy state of the field. © 2014 Elsevier B.V. All rights reserved. Source


Ma X.,Beijing Institute of Technology | Arce G.R.,University of Delaware
Optics Express | Year: 2011

Optical proximity correction (OPC) methods are resolution enhancement techniques (RET) used extensively in the semiconductor industry to improve the resolution and pattern fidelity of optical lithography. In pixel-based OPC (PBOPC), the mask is divided into small pixels, each of which is modified during the optimization process. Two critical issues in PBOPC are the required computational complexity of the optimization process, and the manufacturability of the optimized mask. Most current OPC optimization methods apply the steepest descent (SD) algorithm to improve image fidelity augmented by regularization penalties to reduce the complexity of the mask. Although simple to implement, the SD algorithm converges slowly. The existing regularization penalties, however, fall short in meeting the mask rule check (MRC) requirements often used in semiconductor manufacturing. This paper focuses on developing OPC optimization algorithms based on the conjugate gradient (CG) method which exhibits much faster convergence than the SD algorithm. The imaging formation process is represented by the Fourier series expansion model which approximates the partially coherent system as a sum of coherent systems. In order to obtain more desirable manufacturability properties of the mask pattern, a MRC penalty is proposed to enlarge the linear size of the sub-resolution assistant features (SRAFs), as well as the distances between the SRAFs and the main body of the mask. Finally, a projection method is developed to further reduce the complexity of the optimized mask pattern. © 2011 Optical Society of America. Source


Allmon W.D.,Cornell University | Martin R.E.,University of Delaware
Paleobiology | Year: 2014

We review and synthesize multiple biotic and abiotic proxies for marine nutrient and food availability, primary productivity, and food quality (stoichiometry) and propose what their relationships may have been to macroevolutionary processes, especially speciation. This review confirms earlier suggestions that there has been an overall increase in marine primary productivity over the Phanerozoic, but indicates that the increase has been irregular and that present levels may not be the peak. We integrate these indicators into a new estimate of relative primary productivity in the global ocean through the Phanerozoic. We then combine multiple, frequently conflicting ecological-evolutionary hypotheses into a general model for how primary production may affect speciation over geological time scales. This model, an elaboration and extension of the "speciation cycle" previously proposed by Grant and Grant, attempts to explain why an increase in food supply sometimes is associated with decreased diversity, and at other times with increased diversification. We propose some simple tests for the application of this model to the fossil record. © 2014 The Paleontological Society. Source


Hussain S.,University of Delaware
Advances in Space Research | Year: 2014

Located at the South Pole, IceCube is a particle-astrophysics observatory composed of a square-kilometer surface air shower array (IceTop) and a 1.4 km deep cubic-kilometer optical Cherenkov detector array. We review results of measurements of the cosmic ray spectrum and average mass in the energy range 1 PeV to 1 EeV. © 2013 COSPAR. Published by Elsevier Ltd. All rights reserved. Source


Kirchman D.L.,University of Delaware
Annual Review of Marine Science | Year: 2016

A microbe's growth rate helps to set its ecological success and its contribution to food web dynamics and biogeochemical processes. Growth rates at the community level are constrained by biomass and trophic interactions among bacteria, phytoplankton, and their grazers. Phytoplankton growth rates are approximately 1 d-1, whereas most heterotrophic bacteria grow slowly, close to 0.1 d-1; only a few taxa can grow ten times as fast. Data from 16S rRNA and other approaches are used to speculate about the growth rate and the life history strategy of SAR11, the most abundant clade of heterotrophic bacteria in the oceans. These strategies are also explored using genomic data. Although the methods and data are imperfect, the available data can be used to set limits on growth rates and thus on the timescale for changes in the composition and structure of microbial communities. © 2016 by Annual Reviews. All rights reserved. Source


Munchow A.,University of Delaware
Journal of Physical Oceanography | Year: 2016

Time series observations of velocity, salinity, pressure, and ice draft provide estimates of advective fluxes in Nares Strait from 2003 to 2009 at daily to interannual time scales. Velocity and salinity are integrated across the 36-km-wide and 350-m-deep channel for two distinct multiyear periods of sea ice cover. These observations indicate multiyear mean fluxes that range from 0.71 ± 0.09 to 1.03 ± 0.11 Sverdrups (Sv; 1 Sv = 106 m3 s-1 = 31 536 km3 yr-1) for volume and from 32 ± 5.7 to 54 ± 9.3 mSv (1 mSv = 103 m3 s-1) for oceanic freshwater relative to a salinity of 34.8 for the first (2003-06) and second (2007-09) periods, respectively. Advection of ice adds another 8 ± 2 mSv or 260 ± 70 km3 yr-1 to the freshwater export. Flux values are larger when the sea ice is mobile all year. About 75% of the oceanic volume and freshwater flux variability is correlated at daily to interannual time scales. Flux variability peaks at a 20-day time scale and correlates strongly with along-channel pressure gradients (r2 = 0.68). The along-channel pressure gradient peaks in early spring when the sea ice is often motionless with higher sea level in the Arctic that drives the generally southward ocean circulation. Local winds contribute only when the sea ice is mobile, when they explain 60% of its variance (r2 = 0.60). Observed annual to interannual change in the duration of motionless sea ice conditions impacts ocean stratification and freshwater flux, while seasonal variations are small. © 2016 American Meteorological Society. Source


Safronova M.S.,University of Delaware | Safronova U.I.,University of Nevada, Reno | Safronova U.I.,Russian Academy of Sciences
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

A systematic study of Ca+ atomic properties is carried out using a high-precision relativistic all-order method where all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for the levels up to n=7. Recommended values and estimates of their uncertainties are provided for a large number of electric-dipole transitions. Electric-dipole scalar polarizabilities for the 5s, 6s, 7s, 8s, 4pj, 5pj, 3dj, and 4dj states and tensor polarizabilities for the 4p3/2, 5p3/2, 3dj, and 4dj states in Ca+ are calculated. Methods are developed to accurately treat the contributions from highly excited states, resulting in significant (factor of 3) improvement in the accuracy of the 3d5/2 static polarizability value, 31.8(3)a03, in comparison with the previous calculation [Arora, Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.76.064501 76, 064501 (2007).]. The blackbody radiation shift of the 4s-3d5/2 clock transition in Ca+ is calculated to be 0.381(4) Hz at room temperature, T=300 K. Electric-quadrupole 4s-nd and electric-octupole 4s-nf matrix elements are calculated to obtain the ground-state multipole E2 and E3 static polarizabilities. Excitation energies of the ns, np, nd, nf, and ng states with n≤ 7 in are evaluated and compared with experiment. Recommended values are provided for the 7p1/2, 7p3/2, 8p1/2, and 8p3/2 removal energies for which experimental measurements are not available. The hyperfine constants A are determined for the low-lying levels up to n=7. The quadratic Stark effect on hyperfine structure levels of Ca43+ ground state is investigated. These calculations provide recommended values critically evaluated for their accuracy for a number of Ca+ atomic properties for use in planning and analysis of various experiments as well as theoretical modeling. © 2011 The American Physical Society. Source


Xi W.,University of Colorado at Boulder | Scott T.F.,University of Michigan | Kloxin C.J.,50 Academy Street | Kloxin C.J.,University of Delaware | Bowman C.N.,University of Colorado at Boulder
Advanced Functional Materials | Year: 2014

Despite originating only a little more than a decade ago, click chemistry has become one of the most powerful paradigms in materials science, synthesis, and modification. By developing and implementing simple, robust chemistries that do not require difficult separations or harsh conditions, the ability to form, modify, and control the structure of materials on various length scales has become more broadly available to those in the materials science community. As such, click chemistry has seen broad implementation in polymer functionalization, surface modification, block copolymer and dendrimer synthesis, biomaterials fabrication, biofunctionalization, and in many other areas of materials science. Here, the basic reactions, approaches, and applications of click chemistry in materials science are highlighted, and a brief look is taken into the future enabling developments in this field. Click chemistry has become one of the most powerful paradigms in materials science, synthesis and modification. This feature article delivers highlights of the basic reactions, approaches, and applications of click chemistry in materials science as well as briefly looking to the future, enabling developments in this field. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


McCloskey S.,Honeywell | Ding Y.,Epson Research and Development Inc. | Yu J.,University of Delaware
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2012

We address the problem of motion deblurring using coded exposure. This approach allows for accurate estimation of a sharp latent image via well-posed deconvolution and avoids lost image content that cannot be recovered from images acquired with a traditional shutter. Previous work in this area has used either manual user input or alpha matting approaches to estimate the coded exposure Point Spread Function (PSF) from the captured image. In order to automate deblurring and to avoid the limitations of matting approaches, we propose a Fourier-domain statistical approach to coded exposure PSF estimation that allows us to estimate the latent image in cases of constant velocity, constant acceleration, and harmonic motion. We further demonstrate that previously used criteria to choose a coded exposure PSF do not produce one with optimal reconstruction error, and that an additional 30 percent reduction in Root Mean Squared Error (RMSE) of the latent image estimate can be achieved by incorporating natural image statistics. © 1979-2012 IEEE. Source


Tanner H.G.,University of Delaware | Piovesan J.L.,University of New Mexico
IEEE Transactions on Automatic Control | Year: 2010

The note combines (weak) control Lyapunov function-based nonlinear receding horizon control, with randomized optimization. This approach is applied to the problem of robot navigation in the presence of state and input constraints. It is shown that under certain conditions, relaxing the definiteness requirements on the terminal cost function allows one to select control inputs through a Monte-Carlo optimization scheme in a way that preserves the stability and convergence properties of the closed loop system. While the particular randomized optimization scheme used here can be substituted for the nonlinear optimal control method of choice, the introduction of randomization in receding horizon optimization is anticipated to offer additional trade-offs between performance and computation speed compared to the fixed-overhead nonlinear optimal control strategies typically employed. © 2006 IEEE. Source


Ding R.,Nankai University | Wang L.,University of Delaware | Zhu B.,Nankai University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

Neutralino can be the dark matter candidate in the gauge-mediated supersymmetry breaking models if the conformal sequestered mechanism is assumed in the hidden sector. In this paper, we study this mechanism by using the current experimental results after the run I of LHC and LUX. By adding new Yukawa couplings between the messenger fields and Higgs fields, we find that this mechanism can predict a neutralino dark matter with correct relic density and a Higgs boson with mass around 125 GeV. All our survived points have some common features. First, the Higgs sector falls into the decoupling limit. So the properties of the light Higgs boson are similar to the predictions of the Standard Model one. Second, the correct EWSB hints a relatively small μ-term, which makes the lightest neutralino lighter than the lightest stau. So a bino-higgsino dark matter with correct relic density can be achieved. And the relatively small μ-term results in a small fine-tuning. Finally, this bino-higgsino dark matter can pass all current bounds, including both spin-independent and spin-dependent direct searches. The spin-independent cross section of our points can be examined by further experiments. © 2014 The Authors. Source


Mangone G.J.,University of Delaware
Ocean and Coastal Management | Year: 2010

The beaches of the United States are subject to profound physical changes and some bitter legal and political disputes. A misinterpreted public trust doctrine went far in allowing government control over the foreshore, further strengthened by doctrines of prescription, dedication, and custom to increase public access to the beach and even the dry sands regarded as private property. But the struggle over vertical access to the beach through private property by the public or unlimited use of the foreshore and private dry sand has not ceased. Judicial interpretations and policies vary in different State with the promise of more costly litigation. The challenge is for State legislatures to provide comprehensive legislation that will clearly define the public's right to beach access. © 2010 Elsevier Ltd. Source


In Liquid Composite Molding (LCM) processes, the process design requires an infusion and venting scheme which will saturate all the empty spaces between the fibers during mold filling resulting in a composite part without voids. However, the inherent material and process variability can change the filling patterns significantly which complicate this task. The objective of this work is to develop methodologies and tools to automate infusion process design and integrate it within the CAD design environment. The methodologies and algorithms developed examine the designed part geometry and material layups for ease of manufacturing with feasible infusion schemes by accounting for the inherent variability of the material and preform layup during the infusion processes. To accomplish this, the integrated tool has to automatically identify possible regions that are likely to introduce variability in resin flow, such as racetracking channels near corners, edges and inserts, which will cause dramatically different resin flow patterns and could result in voids. These possible scenarios are then simulated and evaluated to formulate an injection and venting scheme that is sufficiently robust to manufacture a part without any voids despite these variations. An example is presented to demonstrate the methodology of infusion design which identifies and accounts for material variability introduced due to geometric features. Copyright © 2012 Tech Science Press. Source


Leshchinsky D.,University of Delaware
Geosynthetics | Year: 2010

The article examines an apparent magic related to measured geosynthetic reinforcement force. Soil is strong in compression but has virtually no strength in tension. Geosynthetics are relatively strong in tension. Combining the two materials produces a composite structure that is strong under both compression and tension. Sandcastles are formed with steep slopes, even negative batters and overhanging cliffs that are realistically sculptured. This magical phenomenon is observed in wet sand, a cohesion-less material and without inclusion of reinforcement. The observation related to the Indian River Bridge is commonly noticed in construction. It is presented not to warn designers to ignore cohesion, as this should be an obvious practice in design of geogrid reinforced walls. Design should produce structures that are safe and economical for a set life span. Often, field measurements indicate that the load in geosynthetic reinforcement used in constructed walls and slopes is significantly smaller than predicted in design. Source


Letessier-Selvon A.,University Pierre and Marie Curie | Stanev T.,University of Delaware
Reviews of Modern Physics | Year: 2011

This is a review of the most resent results from the investigation of the ultrahigh energy cosmic rays, particles of energy exceeding 1018eV. After a general introduction to the topic and a brief review of the lower energy cosmic rays and the detection methods, the two most recent experiments, the High Resolution Fly's Eye and the Southern Auger Observatory, are described. Results from these two experiments on the cosmic ray energy spectrum, the chemical composition of these cosmic rays, and searches for their sources are presented. An analysis of the controversies in these results and the projects in development and construction that can help solve the remaining problems with these particles is also presented. © 2011 American Physical Society. Source


Singh A.,University of Delaware
Biophysical Journal | Year: 2014

Protein levels differ considerably between otherwise identical cells, and these differences significantly affect biological function and phenotype. Previous work implicated various noise mechanisms that drive variability in protein copy numbers across an isogenic cell population. For example, transcriptional bursting of mRNAs has been shown to be a major source of noise in the expression of many genes. Additional expression variability, referred to as extrinsic noise, arises from intercellular variations in mRNA transcription and protein translation rates attributed to cell-to-cell differences in cell size, abundance of ribosomes, etc. We propose a method to determine the magnitude of different noise sources in a given gene of interest. The method relies on blocking transcription and measuring changes in protein copy number variability over time. Our results show that this signal has sufficient information to quantify both the extent of extrinsic noise and transcription bursting in gene expression. Moreover, if the mean mRNA count is known, then the relative contributions of transcription versus translation rate fluctuations to extrinsic noise can also be determined. In summary, our study provides an easy-to-implement method for characterizing noisy protein expression that complements existing techniques for studying stochastic dynamics of genetic circuits. © 2014 Biophysical Society. Source


Alia S.M.,National Renewable Energy Laboratory | Yan Y.S.,University of Delaware | Pivovar B.S.,National Renewable Energy Laboratory
Catalysis Science and Technology | Year: 2014

Spontaneous galvanic displacement has been utilized in the development of novel electrocatalysts. The process occurs when a less noble metal template contacts a more noble metal cation and combines aspects of corrosion and electrodeposition. The cost of platinum (Pt) limits the commercial deployment of proton exchange membrane fuel cells. Although carbon-supported Pt typically has a moderate mass activity for oxygen reduction, it is limited by a relatively modest specific activity (activity per unit surface area). Conversely, extended Pt surfaces typically have high specific activity for oxygen reduction but commonly have low surface areas. Catalysts formed by spontaneous galvanic displacement are ideally situated, being able to take advantage of the specific activities generally associated with the catalyst type while significantly improving upon the surface area. In addition to acidic oxygen reduction, spontaneous galvanic displacement has been used in the development of catalysts for a variety of electrochemical reactions: hydrogen oxidation, alcohol oxidation, and basic oxygen reduction. Materials for these reactions have been incorporated into this perspective. Spontaneous galvanic displacement is a promising route in catalyst synthesis and cases exist where these electrocatalysts have demonstrated state-of-the-art performance. This journal is © the Partner Organisations 2014. Source


Hess T.J.,University of Massachusetts Amherst | McNab A.L.,Niagara University | Basoglu K.A.,University of Delaware
MIS Quarterly: Management Information Systems | Year: 2014

A reliability generalization study (a meta-analysis of reliability coefficients) was conducted on three widely studied information systems constructs from the technology acceptance model (TAM): perceived ease of use, perceived usefulness, and behavioral intentions. This form of meta-analysis summarizes the reliability coefficients of the scores on a specified scale across studies and identifies the study characteristics that influence the reliability of these scores. Reliability is a critical issue in conducting empirical research as the reliability of the scores on well-established scales can vary with study characteristics, attenuating effect sizes. In conducting this study, an extensive literature search was conducted, with 380 articles reviewed and coded to perform reliability generalization. Study characteristics, including technology, sample, and measurement characteristics, for these articles were recorded along with effect size data for the relationships among these variables. After controlling for number of items, sample size, and sampling error, differences in reliability coefficients were found with several study characteristics for the three technology acceptance constructs. The reliability coefficients of PEOU and PU were lower in hedonic contexts than in utilitarian contexts, and were higher when the originally validated scales were used as compared to when other items were substituted. Only 27 percent of the studies that provided the measurement items used the original PEOU items, while 39 percent used the original PU items. Scales that were administered in English had higher reliability coefficients for PU and BI, with a marginal effect for PEOU. Reliability differences were also found for other study characteristics, including reliability type, subject experience, and gender composition. While average reliability coefficients were high, the results show that, on average, relationships among these constructs are attenuated by 12 percent with maximum attenuation in the range of 35 to 43 percent. Implications for technology acceptance research are discussed and suggestions for addressing variation in reliability coefficients across studies are provided. Source


Arguello H.,Industrial University of Santander | Arce G.R.,University of Delaware
IEEE Transactions on Image Processing | Year: 2014

Compressive spectral imaging (CSI) senses the spatio-spectral information of a scene by measuring 2D coded projections on a focal plane array. A ℓ1-norm-based optimization algorithm is then used to recover the underlying discretized spectral image. The coded aperture snapshot spectral imager (CASSI) is an architecture realizing CSI where the reconstruction image quality relies on the design of a 2D set of binary coded apertures which block-unblock the light from the scene. This paper extends the compressive capabilities of CASSI by replacing the traditional blocking-unblocking coded apertures by a set of colored coded apertures. The colored coded apertures are optimized such that the number of projections is minimized while the quality of reconstruction is maximized. The optimal design of the colored coded apertures aims to better satisfy the restricted isometry property in CASSI. The optimal designs are compared with random colored coded aperture patterns and with the traditional blocking-unblocking coded apertures. Extensive simulations show the improvement in reconstruction PSNR attained by the optimal colored coded apertures designs. © 2014 IEEE. Source


In the aquatic geochemical literature, a redox half-reaction is normally written for a multi-electron process (n > 2); e. g., sulfide oxidation to sulfate. When coupling two multi-electron half-reactions, thermodynamic calculations indicate possible reactivity, and the coupled half-reactions are considered favorable even when there is a known barrier to reactivity. Thermodynamic calculations should be done for one or two-electron transfer steps and then compared with known reactivity to determine the rate controlling step in a reaction pathway. Here, thermodynamic calculations are presented for selected reactions for compounds of C, O, N, S, Fe, Mn and Cu. Calculations predict reactivity barriers and agree with one previous analysis showing the first step in reducing O2 to O2- with Fe2+ and Mn2+ is rate limiting. Similar problems occur for the first electron transfer step in these metals reducing NO3-, but if reactive oxygen species form or if two-electron transfer steps with O atom transfer occur, reactivity becomes favorable. H2S and NH4+ oxidation in a one-electron transfer step by O2 is also not favorable unless activation of oxygen can occur. H2S oxidation by Cu2+, Fe(III) and Mn(III, IV) phases in two-electron transfer steps is favorable but not in one-electron steps indicating that (nano)particles with bands of orbitals are needed to accept two electrons from H2S. NH4+ oxidation by Fe(III) and Mn(III, IV) phases is generally not favorable for both one- and two-electron transfer steps, but their reaction with hydroxylamine and hydrazine to form N2O and N2, respectively, is favorable. The anammox reaction using hydroxylamine via nitrite reduction is the most favorable for NH4+ oxidation. Other chemical processes including photosynthesis and chemosynthesis are considered for these element-element transformations. © Springer Science+Business Media B.V. 2009. Source


Safronova M.S.,University of Delaware | Safronova U.I.,University of Nevada, Reno
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

Systematic study of Rb atomic properties is carried out using a high-precision relativistic all-order method. Excitation energies of the ns, np, nd, and nf (n≤10) states in neutral rubidium are evaluated. Reduced matrix elements, oscillator strengths, transition rates, and lifetimes are determined for the levels up to n=8. Recommended values and estimates of their uncertainties are provided for a large number of electric-dipole transitions. Electric-dipole (5s-np, n=5-26), electric-quadrupole (5s-ndj, n=4-26), and electric-octupole (5s-nfj, n=4-26) matrix elements are calculated to obtain the ground state E1, E2, and E3 static polarizabilities. Scalar polarizabilities of the ns, np, and nd states, and tensor polarizabilities of the np3/2 and nd excited states of Rb are evaluated. The hyperfine A and B values in Rb87 are determined for the first low-lying levels up to n=9. These calculations provide recommended values critically evaluated for their accuracy for a number of Rb atomic properties useful for a variety of applications. © 2011 American Physical Society. Source


Han Y.,Tsinghua University | Davidson R.A.,University of Delaware
Earthquake Engineering and Structural Dynamics | Year: 2012

Two key issues distinguish probabilistic seismic risk analysis of a lifeline or portfolio of structures from that of a single structure. Regional analysis must consider the correlation among lifeline components or structures in the portfolio, and the larger scope makes it much more computationally demanding. In this paper, we systematically identify and compare alternative methods for regional hazard analysis that can be used as the first part of a computationally efficient regional probabilistic seismic risk analysis that properly considers spatial correlation. Specifically, each method results in a set of probabilistic ground motion maps with associated hazard-consistent annual occurrence probabilities that together represent the regional hazard. The methods are compared according to how replicable and computationally tractable they are and the extent to which the resulting maps are physically realistic, consistent with the regional hazard and regional spatial correlation, and few in number. On the basis of a conceptual comparison and an empirical comparison for Los Angeles, we recommend a combination of simulation and optimization approaches: (i) Monte Carlo simulation with importance sampling of the earthquake magnitudes to generate a set of probabilistic earthquake scenarios (defined by source and magnitude); (ii) the optimization-based probabilistic scenario method, a mixed-integer linear program, to reduce the size of that set; (iii) Monte Carlo simulation to generate a set of probabilistic ground motion maps, varying the number of maps sampled from each earthquake scenario so as to minimize the sampling variance; and (iv) the optimization-based probabilistic scenario again to reduce the set of probabilistic ground motion maps. © 2012 John Wiley & Sons, Ltd. Source


Huq P.,University of Delaware | Franzese P.,Ecology and Environment Inc.
Boundary-Layer Meteorology | Year: 2013

Water-tunnel measurements of velocity, turbulence and scalar concentration for three model urban canopies with aspect ratios Ar of building height-to-width of 0. 25, 1 and 3 are presented. The measurements for the canopies with Ar = 1 and 3 are new, while the measurements for Ar = 0. 25 were previously published. A passive scalar was continuously released from a near-ground point source, and the concentration was measured at several distances from the source and at different heights above the ground. Plume spreads, concentration and distance from the source were non-dimensionalized using length, time and velocity scales reflecting the geometry of the buildings. The scaling collapses the data for all aspect ratios and is valid when the vertical extent of the plume is smaller than the canopy height. The observed plume spreads are compared with analytical relations, which predict linear growth in both transverse and vertical directions. The observed mean concentration is compared with a Gaussian dispersion model that predicts a -2 power-law decay with distance from the source. © 2012 Springer Science+Business Media Dordrecht. Source


Legates D.R.,University of Delaware | Mccabe G.J.,U.S. Geological Survey
International Journal of Climatology | Year: 2013

Willmott et al. [Willmott CJ, Robeson SM, Matsuura K. 2012. A refined index of model performance. International Journal of Climatology, forthcoming. DOI:10.1002/joc.2419.] recently suggest a refined index of model performance (dr) that they purport to be superior to other methods. Their refined index ranges from - 1.0 to 1.0 to resemble a correlation coefficient, but it is merely a linear rescaling of our modified coefficient of efficiency (E1) over the positive portion of the domain of dr. We disagree with Willmott et al. (2012) that dr provides a better interpretation; rather, E1 is more easily interpreted such that a value of E1 = 1.0 indicates a perfect model (no errors) while E1 = 0.0 indicates a model that is no better than the baseline comparison (usually the observed mean). Negative values of E1 (and, for that matter, dr < 0.5) indicate a substantially flawed model as they simply describe a 'level of inefficacy' for a model that is worse than the comparison baseline. Moreover, while dr is piecewise continuous, it is not continuous through the second and higher derivatives. We explain why the coefficient of efficiency (E or E2) and its modified form (E1) are superior and preferable to many other statistics, including dr, because of intuitive interpretability and because these indices have a fundamental meaning at zero. We also expand on the discussion begun by Garrick et al. [Garrick M, Cunnane C, Nash JE. 1978. A criterion of efficiency for rainfall-runoff models. Journal of Hydrology 36: 375-381.] and continued by Legates and McCabe [Legates DR, McCabe GJ. 1999. Evaluating the use of "goodness-of-fit" measures in hydrologic and hydroclimatic model validation. Water Resources Research 35(1): 233-241.] and Schaefli and Gupta [Schaefli B, Gupta HV. 2007. Do Nash values have value? Hydrological Processes 21: 2075-2080. DOI: 10.1002/hyp.6825.]. This important discussion focuses on the appropriate baseline comparison to use, and why the observed mean often may be an inadequate choice for model evaluation and development. © 2012 Royal Meteorological Society. Source


Jaisi D.P.,University of Delaware | Blake R.E.,Yale University
Advances in Agronomy | Year: 2014

Phosphorus (P) is universally recognized as an essential nutrient for all known forms of life and a key element in mediating between living and nonliving parts of the biosphere. Here, we provide a comprehensive review of the development of oxygen isotope methods of phosphate and application to understand the biogeochemical cycling of P. With the advent of robust analytical techniques able to accurately determine stable oxygen isotope ratios in phosphate (δ18OP) and the increased understanding of isotope effects from controlled process- or reaction-based studies, δ18OP values have been increasingly applied to identify sources and cycling of P in many natural environments. Because different sources have distinct isotopic compositions and various processes impart specific isotopic fractionation or produce distinct pathways of isotopic evolution, application of δ18OP values as a tracer for P in biogeochemical processes is expected to continue to expand as an exciting field of research in the future. © 2014 Elsevier Inc. Source


Klemas V.,University of Delaware
International Journal of Remote Sensing | Year: 2013

To plan for wetland protection and responsible coastal development, scientists and managers need to monitor changes in the coastal zone, as the sea level continues to rise and the coastal population keeps expanding. Advances in sensor design and data analysis techniques are now making remote-sensing systems practical and cost-effective for monitoring natural and human-induced coastal changes. Multispectral and hyperspectral imagers, light detection and ranging (lidar), and radar systems are available for mapping coastal marshes, submerged aquatic vegetation, coral reefs, beach profiles, algal blooms, and concentrations of suspended particles and dissolved substances in coastal waters. Since coastal ecosystems have high spatial complexity and temporal variability, they should be observed with high spatial, spectral, and temporal resolutions. New satellites, carrying sensors with fine spatial (0.4-4 m) or spectral (200 narrow bands) resolution, are now more accurately detecting changes in coastal wetland extent, ecosystem health, biological productivity, and habitat quality. Using airborne lidars, one can produce topographic and bathymetric maps, even in moderately turbid coastal waters. Imaging radars are sensitive to soil moisture and inundation and can detect hydrologic features beneath the vegetation canopy. Combining these techniques and using time-series of images enables scientists to study the health of coastal ecosystems and accurately determine long-term trends and short-term changes. © 2013 Copyright Taylor and Francis Group, LLC. Source


Xie K.,Northwestern Polytechnical University | Wei B.,Northwestern Polytechnical University | Wei B.,University of Delaware
Advanced Materials | Year: 2014

Stretchable energy storage and conversion devices (ESCDs) are attracting intensive attention due to their promising and potential applications in realistic consumer products, ranging from portable electronics, bio-integrated devices, space satellites, and electric vehicles to buildings with arbitrarily shaped surfaces. Material synthesis and structural design are core in the development of highly stretchable supercapacitors, batteries, and solar cells for practical applications. This review provides a brief summary of research development on the stretchable ESCDs in the past decade, from structural design strategies to novel materials synthesis. The focuses are on the fundamental insights of mechanical characteristics of materials and structures on the performance of the stretchable ESCDs, as well as challenges for their practical applications. Finally, some of the important directions in the areas of material synthesis and structural design facing the stretchable ESCDs are discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Zhang T.,University of Electronic Science and Technology of China | Xia N.-G.,University of Delaware
IEEE Transactions on Geoscience and Remote Sensing | Year: 2015

The existing linear-frequency-modulated (or step frequency) and random noise synthetic aperture radar (SAR) systems may correspond to the frequency-hopping and direct-sequence spread spectrum systems in the past second- and third-generation wireless communications. Similar to the current and future wireless communications generations, in this paper, we propose the orthogonal frequency-division multiplexing (OFDM) SAR imaging, where a sufficient cyclic prefix (CP) is added to each OFDM pulse. The sufficient CP insertion converts an intersymbol interference (ISI) channel from multipaths into multiple ISI-free subchannels as the key in a wireless communications system, and analogously, it provides an inter-range-cell interference (IRCI)-free (high range resolution) SAR image in a SAR system. The sufficient CP insertion along with our newly proposed SAR imaging algorithm, particularly for the OFDM signals, also differentiates this paper from all the existing studies in the literature on OFDM radar signal processing. Simulation results are presented to illustrate the high-range-resolution performance of our proposed CP-based OFDM SAR imaging algorithm. © 2014 IEEE. Source


Mim C.,Northwestern University | Cui H.,University of Chicago | Gawronski-Salerno J.A.,Northwestern University | Frost A.,University of Utah | And 3 more authors.
Cell | Year: 2012

Functioning as key players in cellular regulation of membrane curvature, BAR domain proteins bend bilayers and recruit interaction partners through poorly understood mechanisms. Using electron cryomicroscopy, we present reconstructions of full-length endophilin and its N-terminal N-BAR domain in their membrane-bound state. Endophilin lattices expose large areas of membrane surface and are held together by promiscuous interactions between endophilin's amphipathic N-terminal helices. Coarse-grained molecular dynamics simulations reveal that endophilin lattices are highly dynamic and that the N-terminal helices are required for formation of a stable and regular scaffold. Furthermore, endophilin accommodates different curvatures through a quantized addition or removal of endophilin dimers, which in some cases causes dimerization of endophilin's SH3 domains, suggesting that the spatial presentation of SH3 domains, rather than affinity, governs the recruitment of downstream interaction partners. © 2012 Elsevier Inc. Source


Dentel S.K.,University of Delaware
Drying Technology | Year: 2010

Particularly for suspensions and slurries of biological origin, efficient solid-liquid separation is highly dependent on proper chemical conditioning. This review first describes the material properties that may be sought through chemical conditioning and then it reviews the nature of colloidal stability, considering whether classical theory can be successfully related to practical application or whether newer models of suspension slurry behavior are required. Finally, the chemical agents used as conditioners are described, with important attributes explained. © 2010 Taylor & Francis Group, LLC. Source


Kim S.H.,University of California at Los Angeles | Kiick K.L.,University of Delaware
Macromolecular Rapid Communications | Year: 2010

We have previously reported a novel polymeric delivery vehicle that is assembled via interaction between heparin and the vascular endothelial growth factor (VEGF). Here, the cell-responsiveness of this hydrogel -including the delivery of VEGF in response to VEGFR-2 overexpressing PAE/KDR cells (porcine aortic endothelial cells (PAE) equipped with the transcript for the kinase insert domain receptor (KDR)), consequent erosion of the hydrogel matrix, and cellular response -are highlighted. The release of VEGF and hydrogel erosion reached 100% only in the presence of PAE/KDR. The [PEG-LMWH/VEGF] hydrogel (PEG = polyethylene glycol), LMWH = low molecular weight heparin) correspondingly prompted increases in VEGFR-2 phosphorylation and proliferation of PAE/KDR cells. This study proves that growth factor-crosslinked hydrogels can liberate VEGF in response to specific receptors, causing gel erosion and desired cell responses. The promise of these approaches in therapeutic applications, including targeted delivery, is suggested. (Figure Presented) © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Matthaeus W.H.,University of Delaware | Velli M.,Jet Propulsion Laboratory
Space Science Reviews | Year: 2011

The significant influences of turbulence in neutral fluid hydrodynamics are well accepted but the potential for analogous effects in space and astrophysical plasmas is less widely recognized. This situation sometimes gives rise to the question posed in the title; "Who need turbulence?" After a brief overview of turbulence effects in hydrodynamics, some likely effects of turbulence in solar and heliospheric plasma physics are reviewed here, with the goal of providing at least a partial answer to the posed question. © 2011 Springer Science+Business Media B.V. Source


Barr S.M.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

It is shown that by a simple extension of the fermion sector of flipped SU(5) models and other flipped models, proton decay coming from dimension-six operators can be suppressed by fermion mixing angles by an arbitrary amount in a natural way. © 2013 American Physical Society. Source


Xi W.,University of Colorado at Boulder | Krieger M.,University of Colorado at Boulder | Kloxin C.J.,University of Delaware | Bowman C.N.,University of Colorado at Boulder
Chemical Communications | Year: 2013

The utilization of 2-(2-nitrophenyl)propyloxycarbonyl (NPPOC) as a photolabile primary amine cage enables the thiol-Michael 'click' reaction to be photo-triggered. The photolabile amine exhibits efficient catalytic activity upon UV irradiation and is shown to initiate the photopolymerization of tetrathiol and diacrylate comonomers via Michael addition. © 2013 The Royal Society of Chemistry. Source


Hu J.,University of Delaware
Optics Express | Year: 2010

In this paper, I systematically investigated Micro-Cavity PhotoThermal Spectroscopy (MC-PTS), a novel technique for ultrasensitive detection of chemical molecular species. I first derive the photothermal enhancement factor and noise characteristics of the technique using a generic theoretical model, followed by numerical analysis of a design example using chalcogenide glass micro-disk cavities. Guidelines for sensor material selection and device design are formulated based on the theoretical insight. The numerical analysis shows that this technique features a record photothermal enhancement factor of 10 4 with respect to conventional cavity-enhanced (multi-pass) infrared absorption spectroscopy, and is capable of detecting non-preconcentrated chemical vapor molecules down to the ppt level with a moderate cavity quality factor of 105 and a pump laser power of 0.1 W. Such performance qualifies this technique as one of the most sensitive methods for chemical vapor spectroscopic analysis. © 2010 Optical Society of America. Source


Soon W.,Harvard - Smithsonian Center for Astrophysics | Legates D.R.,University of Delaware
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2013

Using thermometer-based air temperature records for the period 1850-2010, we present empirical evidence for a direct relationship between total solar irradiance (TSI) and the Equator-to-Pole (Arctic) surface temperature gradient (EPTG). Modulation of the EPTG by TSI is also shown to exist, in variable ways, for each of the four seasons. Interpretation of the positive relationship between the TSI and EPTG indices suggests that solar-forced changes in the EPTG may represent a hemispheric-scale relaxation response of the system to a reduced Equator-to-Pole temperature gradient, which occurs in response to an increasing gradient of incoming solar insolation. Physical bases for the TSI-EPTG relationship are discussed with respect to their connections with large-scale climate dynamics, especially a critical relationship with the total meridional poleward energy transport. Overall, evidence suggests that a net increase in the TSI, or in the projected solar insolation gradient which reflects any net increase in solar radiation, has caused an increase in both oceanic and atmospheric heat transport to the Arctic in the warm period since the 1970s, resulting in a reduced temperature gradient between the Equator and the Arctic. We suggest that this new interpretative framework, which involves the extrinsic modulation of the total meridional energy flux beyond the implicit assumptions of the Bjerknes Compensation rule, may lead to a better understanding of how global and regional climate has varied through the Holocene and even the Quaternary (the most recent 2.6 million years of Earth's history). Similarly, a reassessment is now required of the underlying mechanisms that may have governed the equable climate dynamics of the Eocene (35-55 million years ago) and late Cretaceous (65-100 million years ago), both of which were warm geological epochs. This newly discovered relationship between TSI and the EPTG represents the "missing link" that was implicit in the empirical relationship that Soon (2009) recently demonstrated to exist between multi-decadal TSI and Arctic and North Atlantic climatic change. © 2012 Elsevier Ltd. Source


Puleo J.A.,University of Delaware
Journal of Waterway, Port, Coastal and Ocean Engineering | Year: 2010

An approach to estimating sediment transport along the Delaware-Maryland coast is described. Wave information study (second generation model, WISWAVE 2.0) hindcast frequency-direction spectra from 1980 to 1999 are used to generate a radiation stress-conserving angle for bringing offshore waves to breaking to estimate alongshore sediment transport. Using standard values for the coefficients in the United States Army Corps of Engineers' Coastal Engineering Research Center (CERC) equation yields 20-year mean alongshore sediment transport rates between 470,942 and -517,088 m3/year depending on alongshore location after shoaling waves to shore. Interannual variability is large with SDs between 95,078 and 241,313 m3/year again depending on alongshore location. Alongshore sediment transport rate estimates are commensurate with past studies using WIS data but overpredict the typically cited value of ∼100,000 m3/year near Indian River Inlet, Delaware based on sediment budget data by a factor of 3-4. This overestimation could be compensated for by altering the constant K in the CERC transport equation or slight variations in the shoreline normal. The yearly estimates of the nodal point location where the sediment transport rate reverses direction were just south of the Delaware-Maryland border. The nodal point experienced interannual variability on the order of several thousand meters and is mainly attributed to the interannual variability in wave forcing. It is found that estimating alongshore sediment transport rates from offshore wave data are dependent on proper preservation of the radiation stress (using a radiation stress-conserving wave angle) and accurate determination of the shoreline normal. © 2010 ASCE. Source


Houdebine E.R.,College Hill | Mullan D.J.,University of Delaware
Astrophysical Journal | Year: 2015

We have measured v sin i with high precision for a sample of dM3 stars (86 targets). We detected rotation in 82 stars (73 dM3 stars and nine dM3e stars). We compare our measurements of v sin i for all of the stars in our dM0, dM2, dM3, and dM4 samples to those from other authors. We find a good agreement down to v sin i values of less than 1 km s-1. The mean of the differences between measurements is only 0.42 km s-1. We find that the distribution of P/sini for our dM3 stars is different from the distribution of P/sini among our samples of dM2 and dM4 stars. The mean rotation rate for the dM3 stars (excluding dM3e and sdM3 stars) is significantly slower (25.8 days) than for dM2 (14.4 days) and dM4 stars (11.4 days). Analogous behavior also emerges among the faster rotators (dMe stars): we find that a longer rotation period also occurs at spectral subtype dM3e. Our data suggest that, as regards the rotational properties of lower main-sequence stars, spectral subtype dM3 stands out as exhibiting unusually slow rotation compared to that of adjoining subtypes. Our data lead us to suggest that the unusual rotational properties of M3 dwarfs may represent a signature of the transition to complete convection. © 2015. The American Astronomical Society. All rights reserved. Source


Klemas V.,University of Delaware
Journal of Coastal Research | Year: 2011

To plan for wetland protection and sensible coastal development, scientists and managers need to monitor the changes in coastal wetlands as the sea level continues to rise and the coastal population keeps expanding. Advances in sensor design and data analysis techniques are making remote sensing systems practical and attractive for monitoring natural and man-induced wetland changes. The objective of this paper is to review and compare wetland remote sensing techniques that are cost-effective and practical and to illustrate their use through two case studies. The results of the case studies show that analysis of satellite and aircraft imagery, combined with on-the-ground observations, allows researchers to effectively determine long-term trends and short-term changes of wetland vegetation and hydrology. © 2011, the Coastal Education & Research Foundation (CERF). Source


Barr S.M.,University of Delaware | Kim J.E.,Kyung Hee University
Physical Review Letters | Year: 2014

The serious cosmological problems created by the axion-string-axion-domain-wall system in standard axion models are alleviated by positing the existence of a new confining force. The instantons of this force can generate an axion potential that erases the axion strings long before QCD effects become important, thus preventing QCD-generated axion walls from ever appearing. Axion walls generated by the new confining force would decay so early as not to contribute significantly to the energy in axion dark matter. © 2014 American Physical Society. Source


Bell A.V.,University of Delaware
Sociology of Health and Illness | Year: 2014

Research in the area of the sociology of diagnosis has recently expanded. Despite this development, the foundations of the social aspects of diagnoses, including race, class and gender, are relatively unexplored. Understanding such diversity is important, however, as researchers have shown that diagnoses have significant repercussions on the illness experience. This article is an effort to overcome this gap in the literature by examining class diversity in interpretations and understandings of diagnoses. Using the medicalised condition of infertility as a case example of class differences around diagnoses, I conducted 58 in-depth interviews with infertile women of various class backgrounds in the USA. By comparing the lived experiences of infertility between higher and lower class women, I explore differences in the understanding, interpretation and outcomes of diagnoses, specifically. Furthermore, among lower class women, I examine how they understand infertility outside the medical diagnostic framework. The findings reveal how interpretations and experiences of diagnoses vary depending on an individual's social location. In other words, the study demonstrates that class matters in terms of diagnoses and their understanding. © 2013 The Author. Sociology of Health & Illness © 2013 Foundation for the Sociology of Health & Illness/John Wiley & Sons Ltd. Source


Edwards D.A.,University of Delaware
Journal of Physical Chemistry C | Year: 2013

One technique to study electrochemical oxidation phenomena in thin polymer films is the generation of electrogenerated chemiluminescence (ECL) waves. Such waves are sharp and easy to image, and recent experiments have shown both constant-speed and Fickian-style wave behavior. One way to model such waves mathematically is to track the concentration of the ion clusters in the polymer film. One such model has a standard Fickian form but with a highly nonlinear diffusion coefficient. This model is analyzed numerically, and the results are compared with previous asymptotic analysis. The results demonstrate that ECL waves corresponding to this model are indeed sharp and move in a Fickian way. Hence more complicated effects must be included in the model if constant-speed behavior is to be observed. © 2013 American Chemical Society. Source


Pizzuto J.,University of Delaware
Water Resources Research | Year: 2012

Mercury was introduced into the South River, Virginia, as a result of industrial use from 1929 to 1950. To guide remediation, an analytical model is developed to predict the mercury inventory resulting from deposition of mercury-contaminated sediment on subhorizontal surfaces adjacent to the river channel from 1930 to 2007. Sediment cores and geomorphic data were obtained from 27 sites. Mercury inventories range from 0.00019 to 0.573 kg m-2. High mercury inventories are associated with frequent inundation by floodwaters, forested riparian vegetation, and (at only four sites) unusually high sediment accumulation. Over the 10 km study reach, mercury inventories do not vary with downstream distance. The frequency of inundation at each coring site is determined from hydrologic data and a streamtube stage-discharge model. Water levels are exponentially distributed. A simple parameterization represents the enhanced ability of forested vegetation to trap mercury-contaminated sediments compared to nonforest vegetation. The calibrated model explains 62% of the observed variation in mercury inventories; 15 of the 27 predicted values are within a factor of 1.8 of the observed values. Calibration indicates a mercury deposition rate during inundation of 0.040 kg m-2 yr-1 (95% C.I. 0.032-0.048), that forested areas accumulate mercury-contaminated sediment 3.05 (95% C.I. 2.43-3.67) times faster than nonforested areas, and that floodwaters deeper than 0.98 (95% C.I. 0.45-1.53) m do not accumulate suspended sediment or mercury. At four sites, floodplain accumulation of 0.8-1.2 m occurred over a period of 39 (95% C.I. 22-56) years, while sedimentation is negligible (mean: 0.1 m, median: 0.03 m) at other sites. © 2012. American Geophysical Union. All Rights Reserved. Source


Mullally S.L.,University College London | Intraub H.,University of Delaware | Maguire E.A.,University College London
Current Biology | Year: 2012

Background: When we view a scene, we construct an internal representation of the scene that extends beyond its given borders. This cognitive phenomenon is revealed by a subsequent memory error when we confidently misremember the extended scene instead of the original. This effect is known as "boundary extension" and is apparent in adults, children, and babies. Results: Here we show that seven patients with selective bilateral hippocampal damage and amnesia, who cannot imagine spatially coherent scenes, displayed attenuated levels of boundary extension on three separate measures. Paradoxically, this reduced boundary extension resulted in better memory for the stimuli compared with matched control participants, because the patients' recall was less encumbered by the boundary extension error. A further test revealed that although patients could generate appropriate semantic, conceptual, and contextual information about what might be beyond the view in a scene, their representation of the specifically spatial aspect of extended scenes was markedly impoverished. Conclusions: The patients' superior memory performance betrayed a fundamental deficit in scene processing. Our findings indicate that the hippocampus supports the internal representation of scenes and extended scenes when they are not physically in view, and this may involve providing a spatial framework in scenes. We suggest that interference with the ability to internally represent space may prevent the construction of spatially coherent scenes, with possible consequences for navigation, recollection of the past, and imagination of the future, which depend on this function. © 2012 Elsevier Ltd. All rights reserved. Source


Szalewicz K.,University of Delaware
Wiley Interdisciplinary Reviews: Computational Molecular Science | Year: 2012

Basic concepts and most recent developments of symmetry-adapted perturbation theory (SAPT) are described. In particular, the methods that combine SAPT with density-functional theory are discussed. It is explained how SAPT allows one to predict and understand the structure and properties of clusters and condensed phase. The broadest range of such predictions can be achieved by constructing potential energy surfaces from a set of SAPT interaction energies and using these surfaces in nuclear dynamics calculations. © 2011 John Wiley & Sons, Ltd. Source


For biomass-derived oxygenate molecules to be fully utilized for chemicals and fuels, control of the bond scission sequence is necessary. Particularly, the C-O, C-H, and C-C bonds must be selectively broken to produce hydrocarbons, aldehydes, and syngas, respectively. Molybdenum carbide (Mo2C) and metal-modified Mo2C may be used to tune the selectivity towards different bond scission pathways. We have investigated how the admetal modification of Mo2C can shift the selectivity towards breaking certain bonds, using ethanol as a probe molecule. Density functional theory (DFT) was used to predict the binding energies of ethanol and reaction intermediates on the Mo2C surfaces. Ultrahigh vacuum (UHV) techniques such as temperature programmed desorption (TPD) and high-resolution electron energy loss spectroscopy (HREELS) were used to verify the activity and reaction pathways on Mo2C and metal-modified Mo2C surfaces. It was seen that the bare Mo2C surface was active for C-O cleavage to produce ethylene. Surface modification with Ni resulted in the preferential C-C bond scission to form syngas, while modification by Cu led to the C-H scission to produce acetaldehyde. © 2014 The Royal Society of Chemistry. Source


Gaisser T.,University of Delaware | Halzen F.,University of Wisconsin - Madison
Annual Review of Nuclear and Particle Science | Year: 2014

IceCube is the first kilometer-scale neutrino detector. Built primarily for neutrino astronomy, it has recently discovered events with energies above 100 TeV that are likely to be from distant sources beyond the solar system. Among the events are three with deposited energies of more than 1 PeV, the highest-energy neutrinos ever detected. We review the astrophysical arguments that motivate such a large detector, and we describe how it works and how the high-energy events are reconstructed and identified above the background of atmospheric neutrinos. We also describe the broad range of neutrino physics and particle astrophysics topics addressed by IceCube, as well as its potential for the future. Copyright © 2014 by Annual Reviews. All rights reserved. Source


Antoniewicz M.R.,University of Delaware
Methods in Molecular Biology | Year: 2013

13C-Metabolic flux analysis (13C-MFA) is a powerful technique for quantifying intracellular metabolic fluxes in living cells. These in vivo fluxes provide important information on the physiology of cells in culture, which can be used for metabolic engineering purposes and serve as inputs for systems biology modeling. The 13C-MFA technique consists of several steps: (1) selecting appropriate tracers for a given system of interest, (2) performing isotopic labeling experiments, (3) measuring isotopic labeling distributions in metabolic products, (4) estimating metabolic fluxes using least-squares regression, and (5) evaluating the goodness of fit and computing confidence intervals for estimated fluxes. In this chapter, we provide guidelines for performing 13C-MFA studies using multiple isotopic tracers, a technique that is especially useful for elucidating fluxes in complex biological systems where multiple carbon sources are present. Here, as an example, we describe key steps and decision points for designing 13C-MFA studies for microbes grown on mixtures of glucose and xylose. The general concepts described in this chapter are applicable to many other biological systems. For example, the same procedures can be applied to design 13C-MFA studies in mammalian cells, which are generally grown in complex media containing multiple substrates such as glucose and amino acids. © Springer Science+Business Media, LLC 2013. Source


Brown M.,University of Washington | Rasmussen C.,University of Delaware
Environment and Planning D: Society and Space | Year: 2010

We provide an account of a bizarre sex panic from rural Washington State, USA. There, a man died after having sex with a horse and a panic ensued because there was no law against human - animal sex. Quickly a law was placed on the books outlawing bestiality, but only after a series of interlocking-yet-disparate arguments enjoined the local public sphere over just why a law prohibiting sex with animals was necessary. We deconstruct those shifting arguments with respect to their imaginative geographies, and their political theories. Tracing the borders between, and hybridities of, nature - culture, we show that there are broader issues at stake than just sex acts in otherwise moral, rural space. Resisting liberationist accounts of sexuality that buy into assumptions of sexuality as one's authentic self, we suggest that these borders and hybrids around nature might be one tack towards a queerer queer geography. © 2009 Pion Ltd and its Licensors. Source


Wehmiller J.F.,University of Delaware
Quaternary Geochronology | Year: 2013

It has been nearly three decades since the last systematic interlaboratory comparison of amino acid racemization (AAR) measurements among active laboratories. The advent of new methods and improved instrumentation for existing techniques requires that these comparisons be conducted more frequently than has occurred. The present study represents a first step in this process. Five homogeneous liquid samples were distributed to six participating laboratories that use one or more of the following analytical methods: Ion-exchange liquid chromatography (IEx), Reverse-phase liquid chromatography (RP), or Gas chromatography (GC). The five samples have been used in previous formal or informal interlaboratory comparisons: three are Pleistocene mollusk samples, two are Pleistocene eggshell samples. Use of homogeneous liquids eliminated variables involved in the majority of the sample preparative steps (sample cleaning, hydrolysis, desalting), so any observed variability between laboratories can be attributed to instrumental factors or possible small effects associated with the hydration procedures employed prior to instrumental analysis. Although most results indicate good agreement (within 10%) for all amino acid d/l values, there are some notable exceptions for certain amino acids or certain samples. For the five amino acids that are most commonly used in geochronological applications (Asx, Glx, Leu, Val, and A/I), inter-method comparisons reported here provide quantitative regressions that can be used when results from one method are compared with those from another. © 2012 Elsevier B.V. Source


The field of amino acid racemization (AAR) geochronology had its beginnings in the 1960's with the analysis of Quaternary mollusks of known relative age from United States Atlantic coast sites. Subsequent AAR studies of sites from Florida, California and then the entire western and eastern coasts of the U.S. have documented two important concepts: 1) in both uplifted marine terrace and subsurface sections, it can be demonstrated that D/L values increase with increasing geologic age; 2) D/L values in samples of equal age increase with decreasing latitude (increasing temperature). These two north-south coastlines with broad latitude ranges (Pacific sites span more than 20°, Atlantic sites more than 15°) provide an ideal, rare framework to test these principles, and the contrast in thermal histories of these two coasts (one maritime, the other more continental) adds additional insights into issues of aminozone correlation over latitude ranges as small as 2°. The trend of D/L values vs. latitude (isochrons) is established using calibrations based primarily on U-Th coral dating, the best of these calibrated trends seen for multiple sites on the Pacific coast. Pacific coast isochrons follow smooth trends and have been used to create and evaluate kinetic models using the modern latitudinal temperature gradient for comparison. Atlantic coast isochrons are more difficult to reconcile with the modern temperature gradient and available U-Th coral ages, suggesting either complex effective temperatures or unknown diagenetic effects on the AAR results. In addition to these studies that used local or regional field studies to test and evaluate AAR methods, relative or numerical ages based on AAR studies on both coasts have contributed to research on coastal uplift or subsidence rates, coastal stratigraphy and sea-level history, age mixing, and diagenesis of carbonate fossils. © 2012 Elsevier B.V. Source


Adams F.,University of Delaware
Cognitive Systems Research | Year: 2010

What makes a process a cognitive process? I'm not just asking for a list of cognitive processes, but for what makes an item on that list a cognitive process. Why should it be on the list? This is a question that has been ignored far too long in the domain of research calling itself cognitive science. It is time to give an answer and that is what I propose in this paper. I contrast my answer with others that have been given and defend the need against some claims in the literature that a mark of the cognitive is not needed. © 2010 Elsevier B.V. Source


Altman A.R.,University of Delaware | Davis I.S.,Harvard University
Current Sports Medicine Reports | Year: 2012

Despite the technological developments in modern running footwear, up to 79% of runners today get injured in a given year. As we evolved barefoot, examining this mode of running is insightful. Barefoot running encourages a forefoot strike pattern that is associated with a reduction in impact loading and stride length. Studies have shown a reduction in injuries to shod forefoot strikers as compared with rearfoot strikers. In addition to a forefoot strike pattern, barefoot running also affords the runner increased sensory feedback from the foot-ground contact, as well as increased energy storage in the arch. Minimal footwear is being used to mimic barefoot running, but it is not clear whether it truly does. The purpose of this article is to review current and past research on shod and barefoot/minimal footwear running and their implications for running injuries. Clearly more research is needed, and areas for future study are suggested. Copyright © 2012 by the American College of Sports Medicine. Source


Caplan S.E.,University of Delaware
Computers in Human Behavior | Year: 2010

This study tested an updated cognitive-behavioral model of generalized problematic Internet use and reports results of a confirmatory analysis of the Generalized Problematic Internet Use Scale 2 (GPIUS2). Overall, the results indicated that a preference for online social interaction and use of the Internet for mood regulation, predict deficient self-regulation of Internet use (i.e., compulsive Internet use and a cognitive preoccupation with the Internet). In turn, deficient self-regulation was a significant predictor of the extent to which one's Internet use led to negative outcomes. Results indicated the model fit the data well and variables in the model accounted for 27% of the variance in mood regulation scores, 65% of variance in participants' deficient self-regulation scores, and 61% of variance in the negative outcome scores. © 2010 Elsevier Ltd. All rights reserved. Source


Pallis C.,University of Valencia | Shafi Q.,University of Delaware
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014

Motivated by the reported discovery of inflationary gravity waves by the Bicep2 experiment, we propose an inflationary scenario in supergravity, based on the standard superpotential used in hybrid inflation. The new model yields a tensor-to-scalar ratio r ≃ 0.14 and scalar spectral index ns ≃ 0.964, corresponding to quadratic (chaotic) inflation. The important new ingredients are the high-scale, (1.6-10) {dot operator} 1013GeV, soft supersymmetry breaking mass for the gauge singlet inflaton field and a shift symmetry imposed on the Kähler potential. The end of inflation is accompanied, as in the earlier hybrid inflation models, by the breaking of a gauge symmetry at (1.2-7.1) {dot operator} 1016GeV, comparable to the grand-unification scale. © 2014 Elsevier B.V. Source


Kaisare N.S.,Indian Institute of Technology Madras | Vlachos D.G.,University of Delaware
Progress in Energy and Combustion Science | Year: 2012

Microcombustion research has flourished over the past decade. Yet, most of the commercial potential of microcombustion is still to come. Aside from portable electronics, emerging drivers stem from the energy problem of declining fossil fuel reserves and their large environmental footprint upon combustion. The need to capitalize on underutilized energy sources and renewables further stimulate energy research in microsystems. In this review paper, technological drivers, applications, devices, and fabrication protocols of microburners are presented. Then, a review of homogeneous, catalytic, homogeneous-heterogeneous and heat recirculating microburners is given. Results are presented that interpret literature findings. An outlook of microcombustion research is finally outlined. © 2011 Elsevier Ltd. All rights reserved. Source


Tessonnier J.-P.,Fritz Haber Institute of the Max Planck Society | Tessonnier J.-P.,University of Delaware | Su D.S.,Fritz Haber Institute of the Max Planck Society | Su D.S.,CAS Shenyang Institute of Metal Research
ChemSusChem | Year: 2011

Tremendous progress has been achieved during the past 20 years on not only improving the yields of carbon nanotubes and move progressively towards their mass production, but also on gaining a profound fundamental understanding of the nucleation and the growth processes. Parameters that influence the yield but also the quality (e.g., microstructure, homogeneity within a batch) are better understood. The influence of the carbon precursor, the reaction conditions, the presence of a catalyst, the chemical and physical status of the latter, and other factors have been extensively studied. The purpose of the present Review is not to list all the experiments reported in the literature, but rather to identify trends and provide a comprehensive summary on the role of selected parameters. The role of the catalyst occupies a central place in this Review as a careful control of the metal particle size, particle dispersion on the support, the metastable phase formed under reaction conditions, its possible reconstruction, and faceting strongly influence the diameter of the carbon nanotubes, their structure (number of walls, graphene sheet orientation, chirality), their alignment, and the yield. The identified trends will be compared with recent observations on the growth of graphene. Recent results on metal-free catalysts will be analyzed from a different perspective. CNT Growth: the latest progress in carbon nanotube synthesis is reported and analyzed in this Review. We focus in particular on the dynamic nature of the metal active phase and its evolution when interacting with both the catalyst support or matrix, and the gas phase. A different light is shed on parameters crucial for large-scale production and for controlling their chirality. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Ceria nanoparticles were added to the electrodes of proton exchange membrane fuel cells as free-radical scavengers to minimize the degradation of membrane electrode assembly (MEA) components. Acceler-ated durability tests were performed at low humidity under open circuit voltage (OCV) conditions, and the results were compared with traditional MEAs without CeO2. Gas crossover was monitored during the durability test, and the MEAs were examined by SEM before and after the durability test. The results showed that adding CeO2as free-radical scavengers to the electrode greatly improves the chemical sta-bility of the membrane. The degradation rate of the MEA with CeO2 in the anode was similar to that of the MEA with CeO 2in the cathode. The fuel cell with CeO2in the cathode showed better MEA performance that the fuel cell with CeO2 in the anode. © 2013 Elsevier Ltd. All rights reserved. Source


Rappazzo A.F.,University of Delaware | Parker E.N.,University of Chicago
Astrophysical Journal Letters | Year: 2013

We investigate the dynamical evolution of magnetic fields in closed regions of solar and stellar coronae. To understand under which conditions current sheets form, we examine dissipative and ideal reduced magnetohydrodynamic models in Cartesian geometry, where two magnetic field components are present: the strong guide field B 0, extended along the axial direction, and the dynamical orthogonal field b. Magnetic field lines thread the system along the axial direction that spans the length L and are line-tied at the top and bottom plates. The magnetic field b initially has only large scales, with its gradient (current) length scale of the order of ℓb . We identify the magnetic intensity threshold b/B 0 ∼ ℓb /L. For values of b below this threshold, field-line tension inhibits the formation of current sheets, while above the threshold they form quickly on fast ideal timescales. In the ideal case, above the magnetic threshold, we show that current sheets thickness decreases in time until it becomes smaller than the grid resolution, with the analyticity strip width δ decreasing at least exponentially, after which the simulations become underresolved. © 2013. The American Astronomical Society. All rights reserved. Source


Pallis C.,University of Cyprus | Shafi Q.,University of Delaware
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013

The minimal supersymmetric (or F-term) hybrid inflation is defined by a unique renormalizable superpotential, fixed by a U(1) R-symmetry, and it employs a canonical Kähler potential. The inflationary potential takes into account both radiative and supergravity corrections, as well as an important soft supersymmetry breaking term, with a mass coefficient in the range (0.1-10) TeV. The latter term assists in obtaining a scalar spectral index ns close to 0.96, as strongly suggested by the PLANCK and WMAP 9 yr measurements. The minimal model predicts that the tensor-to-scalar r is extremely tiny, of order 10-12, while the spectral index running, |dns/dlnk|~10-4. If inflation is associated with the breaking of a local U(1)B-L symmetry, the corresponding symmetry breaking scale M is (0.7-1.6){dot operator}1015 GeV with ns≃0.96. This scenario is compatible with the bounds on M from cosmic strings, formed at the end of inflation from B-L symmetry breaking. We briefly discuss non-thermal leptogenesis which is readily implemented in this class of models. © 2013 Elsevier B.V. Source


Freitag M.,Rutgers University | Gundlach L.,Rutgers University | Gundlach L.,University of Delaware | Piotrowiak P.,Rutgers University | Galoppini E.,Rutgers University
Journal of the American Chemical Society | Year: 2012

A viologen derivative, 1,1′-di-p-tolyl-(4,4′-bipyridine)-1, 1′-diium dichloride (DTV 2+), was studied in solution and encapsulated in cucurbit[7]uril (CB7), a macrocyclic host. Upon encapsulation, DTV 2+ exhibited dramatically enhanced fluorescence. Aqueous solutions of DTV 2+ were weakly fluorescent (Φ = 0.01, τ < 20 ps), whereas the emission of the DTV 2+@2CB7 complex was enhanced by 1 order of magnitude (Φ = 0.12, τ = 0.7 ns) and blue-shifted by 35 nm. Similar properties were observed in the presence of NaCl. DTV 2+ in a poly(methyl methacrylate) matrix was fluorescent with a spectrum similar to that observed for the complex in solution. 1H NMR and UV-vis titrations indicated that the DTV 2+@2CB7 complex is formed in aqueous solutions with complexation constants K 1 = (1.2 ± 0.3) × 10 4 M -1 and K 2= (1.0 ± 0.4) × 10 4 M -1 in water. Density functional theory and configuration interaction singles calculations suggested that the hindrance of the rotational relaxation of the S 1 state of DTV 2+ caused by encapsulation within the host or a polymer matrix plays a key role in the observed emission enhancement. The absorption and emission spectra of DTV 2+@2CB7 in water exhibited a large Stokes shift (ΔSt ∼ 9000 cm -1) and no fine structure. DTV 2+ is a good electron acceptor [E°(DTV 2+/DTV •+) = -0.30 V vs Ag/AgCl] and a strong photooxidant [E°(DTV 2+/DTV •+) = 0.09 V vs NHE]). © 2012 American Chemical Society. Source


Aysal T.C.,Cornell University | Barner K.E.,University of Delaware
IEEE Transactions on Information Theory | Year: 2010

We consider consensus algorithms in their most general setting and provide conditions under which such algorithms are guaranteed to converge, almost surely, to a consensus. Let {A(t), B(t)} ∈ RN × N be (possibly) stochastic, nonstationary matrices and {x(t), m(t)} ∈ R N × 1 be state and perturbation vectors, respectively. For any consensus algorithm of the form x(t+1) = A(t)x(t) + B(t)m(t), we provide conditions under which consensus is achieved almost surely, i.e., Pr{lim t→∞x(t) = c1} = 1 for some c ∈ R. Moreover, we show that this general result subsumes recently reported results for specific consensus algorithms classes, including sum-preserving, nonsum-preserving, quantized, and noisy gossip algorithms. Also provided are the ε-converging time for any such converging iterative algorithm, i.e., the earliest time at which the vector x(t) is ε close to consensus, and sufficient conditions for convergence in expectation to the average of the initial node measurements. Finally, mean square error bounds of any consensus algorithm of the form discussed above are presented. © 2006 IEEE. Source


Hehman E.,Dartmouth College | Volpert H.I.,University of Missouri | Simons R.F.,University of Delaware
Social Cognitive and Affective Neuroscience | Year: 2014

The current research examined the viability of the N400, an event-related potential (ERP) related to the detection of semantic incongruity, as an index of both stereotype accessibility and interracial prejudice. Participants' EEG was recorded while they completed a sequential priming task, in which negative or positive, stereotypically black (African American) or white (Caucasian American) traits followed the presentation of either a black or white face acting as a prime. ERP examination focused on the N400, but additionally examined N100 and P200 reactivity. Replicating and extending previous N400 stereotype research, results indicated that the N400 can indeed function as an index of stereotype accessibility in an interracial domain, as greater N400 reactivity was elicited by trials in which the face prime was incongruent with the target trait than when primes and traits matched. Furthermore, N400 activity was moderated by participants' self-reported explicit bias. More explicitly biased participants demonstrated greater N400 reactivity to stereotypically white traits following black faces than black traits following black faces. P200 activity was additionally associated with participants' implicit biases, as more implicitly biased participants similarly demonstrated greater P200 reactivity to stereotypically white traits following black faces than black traits following black faces. © The Author (2013). Published by Oxford University Press. Source


Hu X.,Texas A&M University-Corpus Christi | Cai W.-J.,University of Delaware
Geophysical Research Letters | Year: 2013

This study uses a simulation method to explore how estuarine pH is affected by mixing between river water, anthropogenic CO2 enriched seawater, and by respiration. Three rivers with different levels of weathering products (Amazon, Mississippi, and St. Johns) are selected for this simulation. The results indicate that estuaries that receive low to moderate levels of weathering products (Amazon and St. Johns) exhibit a maximum pH decrease in the midsalinity region as a result of anthropogenic CO2 intrusion. This maximum pH decrease coincides with a previously unrecognized mid-salinity minimum buffer zone (MBZ). In addition, water column oxygen consumption can further depress pH for all simulated estuaries. We suggest that recognition of the estuarine MBZs may be important for studying estuarine calcifying organisms and pH-sensitive biogeochemical processes. Key Points Ocean acidification and O2 consumption can both lead to estuarine acidification An previously undefined estuarine minimum buffer zone (MBZ) is demonstrated Both estuarine carbonate chemistry and temperature affect the MBZ ©2013. American Geophysical Union. All Rights Reserved. Source


Poultry products are important vehicles for Salmonella transmission to humans and have been incriminated in several Salmonella outbreaks. Thymol (THY) from thyme oil has wide inhibitory effects against foodborne pathogens including Salmonella, and has shown great potential as a natural alternative to chlorine. In order to improve the cost-effectiveness of thymol-based washing solutions, formulas of THY with combination of organic acid or surfactant were developed and their efficacies to reduce Salmonella on chicken breast were investigated in the current study. Surface-inoculated chicken breasts were washed with the two thymol-based washing solutions: 0.2 mg/mL THY+5% (w/v) sodium dodecyl sulfate (SDS)+2 mg/mL acetic acid (AA) or 0.2 mg/mL THY+2 mg/mL AA for 2 min. Both solutions achieved around 2.2 log reductions of Salmonella on chicken breast and their efficacy was comparable to log reduction obtained by 200 ppm chlorine washing. Addition of SDS did not result in more log reduction of Salmonella on chicken meat samples. More than 3.3 log reduction in the used THY washing solutions was determined and it was similar to log reduction from the spent chlorine solution. None of these antimicrobial agents changed the pH and texture values of chicken breasts. Therefore, 0.2 mg/mL THY+2 mg/mL AA has great potential to be a natural alternative to chlorine-based washing solution for reducing Salmonella contamination on chicken breast meat. Copyright © 2011 Elsevier B.V. All rights reserved. Source


Chen X.,University of Delaware | Agrawal S.K.,Columbia University
IEEE Transactions on Neural Systems and Rehabilitation Engineering | Year: 2013

Previous work has shown that training with the 'assist-as-needed' method using a force-feedback joystick can improve the driving performance of children and adults. This paper is the first study to evaluate training with a repelling force versus an assisting force for learning of a line following task in a wheelchair through a force-feedback joystick. We designed a robotic training wheelchair, that can accurately localize itself in the training environment, and implemented assisting and repelling force fields on the force-feedback joystick. The training protocol included three groups. The control (CT) group received no force feedback. The assisting force (AF) group was trained using the 'assist-as-needed' paradigm. The repelling force (RF) group was trained with the repelling force field. We observed that both the AF and RF groups improved their driving skills. The error reductions of both groups were not statistically different under the current setting. We believe that this pilot study could provide a promising foundation regarding the effects of a robotic wheelchair training algorithm on motor learning. © 2013 IEEE. Source


Schultz J.M.,University of Delaware
Frontiers of Chemistry in China | Year: 2010

The morphology and kinetics of crystallization from melt-miscible blends is reviewed for binary systems in which either one or both polymer components are crystallizable. In systems in which one component (component A) crystallizes first, the other component (B) may reside finally between spherulites, between growth arms (composed of a stack of A crystalline lamellae), or between crystal lamellae of A. The kinetics of component redistribution dictates which site must become primary. It is shown that the diffusivity D of the components in the melt and the velocity V of spherulite growth combine through the diffusion length δ = D/V to define the final location for component B and to also define whether spherulite propagation will be linear or parabolic in time. When crystallization of both components proceeds concurrently, by forming spherulites of A and of B, the spherulites are prone to interpenetrate or to form concentric spherulites. Cooperative crystallization, in which the kinetics of a rapidly crystallizing component and a slowly crystallizing component are both affected such that the two crystallize nearly simultaneously, is discussed. Finally, the competition between liquid-liquid phase separation and crystallization in systems with either an upper or lower critical solution temperature is reviewed. © 2010 Higher Education Press and Springer-Verlag Berlin Heidelberg. Source


The concept, science, and technology of biofuels has captured the public's imagination as well as the attention of the academic and industrial R&D communities over the last 10 years. The 2006 US DOE report has been the basis for funding three US Bioenergy Centers, and has precipitated increased research funding worldwide. Despite the large funding resources, there is little evidence to support that processes for advanced biofuels (i.e., fuel molecules more dense than ethanol) are anywhere near achieving economic feasibility. In assessing the current status of the field for biology-based processes, there has been tremendous progress in metabolic and pathway engineering and the development of synthetic-biology tools that can be applied to engineer strains. However, the economic feasibility of what is currently possible remains in doubt, especially in light of the recent low prices of oil and natural gas. Issues liming the economic feasibility are assessed and strategies to take advantage of the successful achievements are suggested. Analysis suggests that for biofuel molecules larger than four carbons, purely biological processes cannot be currently justified, but hybrid biological/catalytic technologies may offer the necessary economies to produce such biofuels. © 2015 American Chemical Society. Source


Baer H.,University of Oklahoma | Raza S.,University of Oklahoma | Shafi Q.,University of Delaware
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2012

Supersymmetric models with t-b-τ Yukawa coupling unification and unified gaugino masses at the GUT scale-with μ>0-show a mild preference for light gluino masses mg~≲500GeV. This range of mg~ is now essentially ruled out by LHC searches. We show that a heavier gluino with mg~~0.5-3TeV can also be compatible with excellent t-b-τ Yukawa coupling unification in supersymmetric models with non-universal Higgs masses (NUHM2). The gluino in such models is the lightest colored sparticle, while the squark sector displays an inverted mass hierarchy with mq~~5-20TeV. We present some LHC testable benchmark points for which the lightest Higgs boson mass m h≃125GeV. We also discuss LHC signatures of Yukawa-unified models with heavier gluinos. We expect gluino pair production followed by decay to final states containing four b-jets plus four W-bosons plus missing E T to occur at possibly observable rates at LHC. © 2012 Elsevier B.V. Source


Lee J.-Y.,University of Delaware
Plant Science | Year: 2014

Effective cell-to-cell communication is critical for the survival of both unicellular and multicellular organisms. In multicellular plants, direct cell coupling across the cell wall boundaries is mediated by long membrane-lined cytoplasmic bridges, the plasmodesmata. Exciting recent discoveries suggest that the occurrence of such membrane-lined intercellular channels is not unique to plant lineages but more prevalent across biological kingdoms than previously assumed. Striking functional analogies exist among those channels, in that not only do they all facilitate the exchange of various forms of macromolecules, but also they are exploited by some opportunistic pathogens to spread infection from one host cell to another. However, host cells may have also evolved strategies to offset such exploitation of the critical cellular infrastructure by the pathogen. Indeed, recent studies support an emerging paradigm that cellular connectivity via plasmodesmata plays an important role in innate immune responses. Preliminary hypotheses are proposed as to how various regulatory mechanisms integrating plasmodesmata into immune signaling pathways may have evolved. © 2014 Elsevier Ireland Ltd. Source


Zaykowski H.,University of Delaware
Crime and Delinquency | Year: 2015

Research consistently demonstrates that severity, often measured by victim injury, is the most influential factor to predict reporting crimes to the police. However, less is known with regard to how the victim’s perception of the incident or their involvement in offending behavior inhibits this decision. The current study examines how traditional indicators (i.e., victim, offender and incident characteristics), the victim’s offending behavior, and perceptual measures influence police awareness of criminal victimization. Results suggest that victim injury and offending status does not significantly predict police awareness when subjective measures are controlled. However, multiple offenders, community crime, and parental knowledge significantly increased the odds that the police were aware that the victimization occurred. © 2011 SAGE Publications. Source


Dirks-Naylor A.J.,Wingate University | Lennon-Edwards S.,University of Delaware
Journal of Steroid Biochemistry and Molecular Biology | Year: 2011

It is thought that every cell in the body expresses the vitamin D receptor, and therefore vitamin D may play a role in health and homeostasis of every organ system, including skeletal muscle. Human, animal, and cell culture studies have collectively shown that vitamin D affects muscle strength and function. Vitamin D functions in a plethora of cellular processes in skeletal muscle including calcium homeostasis, cell proliferation, cell differentiation, fiber size, prevention of fatty degeneration, protection against insulin resistance and arachidonic acid mobilization. These processes appear to be mediated by several signaling pathways affected by vitamin D. This review aims to explore the effects of vitamin D on skeletal muscle in each model system and to delineate potential cell signaling pathways affected by vitamin D. © 2011 Elsevier Ltd. All rights reserved. Source


Fendorf S.,Stanford University | Michael H.A.,University of Delaware | Van Geen A.,Lamont Doherty Earth Observatory
Science | Year: 2010

Over the past few decades, groundwater wells installed in rural areas throughout the major river basins draining the Himalayas have become the main source of drinking water for tens of millions of people. Groundwater in this region is much less likely to contain microbial pathogens than surface water but often contains hazardous amounts of arsenic - a known carcinogen. Arsenic enters groundwater naturally from rocks and sediment by coupled biogeochemical and hydrologic processes, some of which are presently affected by human activity. Mitigation of the resulting health crisis in South and Southeast Asia requires an understanding of the transport of arsenic and key reactants such as organic carbon that could trigger release in zones with presently low groundwater arsenic levels. Source


Mullan D.J.,University of Delaware
Astrophysical Journal | Year: 2010

Magnetic reconnection events in the atmospheres of low-mass dwarf stars can be classified as either slow or fast, depending on whether ohmic diffusion or Hall currents dominate in the reconnection process. We suggest that the separation of reconnection into slow and fast categories can help to explain some systematics of low-mass dwarfs as regards their emissions in X-rays, Hα, and radio. On the one hand, in the warmer dwarfs (M7) are inefficient emitters in Hα and X-rays but strong emitters in radio, may be understood in the context that only slow reconnection is permitted to occur in those stars, as a result of high electrical resistivity. However, even though only slow reconnection is permitted in the latter stars, the speed of the outflow jets from reconnection sites can serve as efficient sources of radio emission as a result of the electron cyclotron maser instability. © 2010. The American Astronomical Society. All rights reserved. Source


Trabulsi J.C.,University of Delaware | Mennella J.A.,Monell Chemical Senses Center
International Review of Psychiatry | Year: 2012

Diet in early infancy has an impact on early growth and the formation of flavour preferences, as well as on later life health outcomes. Although breast milk is the preferred source of nutrition during infancy, more than half of American infants receive infant formula by the age of 4 months. As a group, formula-fed infants weigh more by the age of one year and have a greater risk for later obesity than breastfed infants. However, a recent randomized study found that, when compared to breastfed infants, infants fed an extensively hydrolysed protein formula (ePHF) had more normative weight gain velocity than infants fed cow's milk formula (CMF). Therefore, grouping all formula-fed infants together with respect to certain health outcomes such as obesity may not be appropriate. Scientific evidence also suggests that there are sensitive periods for flavour learning. Infants become familiar with and learn to accept the flavours they experience through their mother's amniotic fluid and breast milk as well as formula. These early experiences influence flavour preferences of children that may affect food choices and therefore later life health. Further research on the influence of early diet on growth, flavour preferences, and food choices is imperative. © 2012 Institute of Psychiatry. Source


Quinn P.C.,University of Delaware | Liben L.S.,Pennsylvania State University
Infancy | Year: 2014

Quinn and Liben (2008) reported a sex difference on a mental rotation task in which 3- to 4-month-olds were familiarized with a shape in different rotations and then tested with a novel rotation of the familiar shape and its mirror image. As a group, males but not females showed a significant preference for the mirror image, a pattern paralleled at the individual level (with most males but less than half the females showing the preference). Experiment 1 examined a possible explanation for this performance difference, namely, that females were more sensitive to the angular differences in the familiarized shape. Three- to 4-month-olds were given a discrimination task involving familiarization with a shape at a given rotation and preference testing with the shape in the familiarized versus a novel rotation. Females and males preferred the novel rotation, with no sex difference observed. This finding did not provide support for the suggestion that the sex difference in mental rotation is explained by differential sensitivity to angular rotation. Experiment 2 revealed that the sex difference in mental rotation is observed in 6- to 7-month-olds and 9- to 10-month-olds, suggesting that a sex difference in mental rotation is present at multiple ages during infancy. © International Society on Infant Studies (ISIS). Source


Powers T.M.,University of Delaware
IEEE Robotics and Automation Magazine | Year: 2011

Approaches to programming ethical behavior for computer systems face challenges that are both technical and philosophical in nature. In response, an incrementalist account of machine ethics is developed: a successive adaptation of programmed constraints to new, morally relevant abilities in computers. This approach allows progress under conditions of limited knowledge in both ethics and computer systems engineering and suggests reasons that we can circumvent broader philosophical questions about computer intelligence and autonomy. © 2006 IEEE. Source


Kuholski K.,University of Delaware
Journal of public health management and practice : JPHMP | Year: 2010

Housing conditions such as leaky roofs, peeling paint, structural problems, chronic dampness, improperly vented combustion appliances, and poor ventilation can cause injury, illness, and increased energy consumption. Homes with moderate and severe housing hazards are more likely to be occupied by families with limited incomes because of the lack of affordable housing choices. As a result, children and older adults in these communities face disproportionate impacts from these housing hazards, including higher asthma and injury rates, greater prevalence of lead poisoning, and higher household energy burdens. Programs and policies addressing home health and energy issues have historically operated in categorical silos, which in turn cause fragmented service delivery and inefficient use of scarce resources by the agencies providing these services. A "one-touch" approach for home interventions that strategically integrates public health and energy efficiency has many potential direct and indirect benefits. Also, this approach plays an important role in housing policy due to the increasing support for green housing and residential energy efficiency. Source


Hayward R.C.,University of Massachusetts Amherst | Pochan D.J.,University of Delaware
Macromolecules | Year: 2010

Block copolymers have the capacity to self-organize into a myriad of aggregate structures when placed in selective solvents, offering great promise for the construction of delivery vehicles and complex nanoscale assemblies. A key feature of these materials is their propensity to become kinetically trapped in nonequilibrium states, meaning that the structures they adopt depend sensitively on the processing route taken. While this makes it challenging to fully explore the landscape of possible morphologies, it also means that careful attention to the pathway of self-assembly can allow for remarkable control over the resulting nonequilibrium structures. In this Perspective, we highlight several recent advances in processing approaches that provide new levels of tailorability to the structures and encapsulated contents of block copolymer assemblies in solution. © 2010 American Chemical Society. Source


Cutting K.J.,University of Waikato | Hough-Goldstein J.,University of Delaware
Restoration Ecology | Year: 2013

Disturbed natural areas frequently experience invasion by introduced plant species that can reduce native biodiversity. Biological control can suppress these introduced species, but without restoration another introduced species can invade. Integration of biological control with concurrent revegetation can both aid in weed reduction via interspecific plant competition and establish a restored native plant community. This 3-year study investigated an integrated approach to controlling the introduced annual Mile-a-minute weed (Persicaria perfoliata [L.] H. Gross [Polygonaceae]) using the biocontrol weevil Rhinoncomimus latipes Korotyaev (Coleoptera: Curculionidae) and restoration planting using a native seed mix. A fully factorial design tested weevils and seeding, separately and together, using insecticide to eliminate weevils. The weevils together with the native seed mix reduced P. perfoliata percent cover in 2009 and 2010, and peak seed cluster production in 2010, compared to the insecticide-no seed control treatment. Persicaria perfoliata final dry biomass was reduced by 75% in 2010 and by 57% in 2011 in the weevils plus seed treatment compared to the control, with weevils having the greatest effect in 2010 and the seed treatment having the greatest impact in 2011. Results suggest an additive effect of biocontrol and seeding in suppressing P. perfoliata. Seeded treatments also developed the highest native plant species richness and diversity, comprised of spontaneous recolonization in addition to species from the seed mix. Results support the use of integrated management of this invasive weed, with suppression through biological control and native revegetation together helping prevent reinvasion while restoring native plant biodiversity. © 2012 Society for Ecological Restoration. Source


Kniel K.E.,University of Delaware
Current Opinion in Virology | Year: 2014

Norovirus is undoubtedly a leading cause of acute gastroenteritis. A large limitation to the study of human norovirus is the lack of consensus research using norovirus surrogates. Over two decades of research have included vast comparisons of norovirus surrogates within the Calicivirus family. A discussion on the continued use of norovirus surrogates includes use of surrogates to adequately assess environmental persistence and food preservation technologies. Choice of proper surrogate may be influenced by a myriad of issues, including ease of propagation, genetic similarities, and binding properties. While it remains impossible to routinely culture human norovirus in vitro the continued use of a variety of norovirus surrogates remains crucial to facilitate an understanding of norovirus in order to reduce the public health impact of the disease. © 2014 Elsevier B.V. All rights reserved. Source


David J.M.,University of Delaware | David J.M.,DuPont Company | Rajasekaran A.K.,DuPont Company
Cancer Research | Year: 2012

Strong cell-cell interactions represent a major barrier against cancer cell mobility, and loss of intercellular adhesion by E-cadherin is a fundamental change that occurs during the progression of cancer to invasive disease. However, some aggressive carcinomas retain characteristics of differentiated epithelial cells, including E-cadherin expression. Emerging evidence indicates that proteolysis of E-cadherin generates fragments that promote tumor growth, survival, and motility, suggesting that E-cadherin cleavage converts this tumor suppressor into an oncogenic factor. In this review we discuss the emerging roles of cleaved E-cadherin fragments as modulators of cancer progression, and explore the translational and clinical implications of this research. ©2012 AACR. Source


Zondlo N.J.,University of Delaware
Accounts of Chemical Research | Year: 2013

Proline residues have unique roles in protein folding, structure, and function. Proline and the aromatic amino acids comprise the encoded cyclic protein residues. Aromatic protein side chains are defined by their negatively charged π faces, while the faces of the proline ring are partially positively charged. This polarity results from their two-point connection of the side chain to the electron-withdrawing protein backbone, and the lower electronegativity of hydrogen compared to carbon, nitrogen, and oxygen. The hydrogens adjacent to the carbonyl and amide nitrogen, Hα and Hδ, respectively, are the most partially positive. Proline's side chain is also conformationally restricted, allowing for interaction with aromatic residues with minimal entropic or steric penalty. Proline and aromatic residues can interact favorably with each other, due to both the hydrophobic effect and the interaction between the π aromatic face and the polarized C-H bonds, called a CH/π interaction. Aromatic-proline interactions can occur locally, for example, to stabilize cis-amide bonds, and over larger distances, in the tertiary structures of proteins, and intermolecularly in protein-protein interactions. In peptides and proteins, aromatic-proline sequences more readily adopt cis-prolyl amide bonds, where the aromatic ring interacts with the proline ring in the cis conformation. In aromatic-proline sequences, Trp and Tyr are more likely to induce cis-amide bonds than Phe, suggesting an aromatic electronic effect. This result would be expected for a CH/π interaction, in which a more electron-rich aromatic would have a stronger (more cis-stabilizing) interaction with partial positive charges on prolyl hydrogens.In this Account, we describe our investigations into the nature of local aromatic-proline interactions, using peptide models. We synthesized a series of 26 peptides, TXPN, varying X from electron-rich to electron poor aromatic amino acids, and found that the population of cis-amide bond (Ktrans/cis) is tunable by aromatic electronics. With 4-substituted phenylalanines, we observed a Hammett correlation between aromatic electronics and Ktrans/cis, with cis-trans isomerism electronically controllable by 1.0 kcal/mol. All aromatic residues exhibit a higher cis population than Ala or cyclohexylalanine, with Trp showing the strongest aromatic-proline interaction. In addition, proline stereoelectronic effects can modulate cis-trans isomerism by an additional 1.0 kcal/mol. The aromatic-proline interaction is enthalpic, consistent with its description as a CH/π interaction. Proline-aromatic sequences can also promote cis-prolyl bonds, either through interactions of the aromatic ring with the preceding cis-proline or with the Hα prior to cis-proline. Within proline-rich peptides, sequences commonly found in natively disordered proteins, aromatic residues promote multiple cis-amide bonds due to multiple favorable aromatic-proline interactions. Collectively, we found aromatic-proline interactions to be significantly CH/π in nature, tunable by aromatic electronics. We discuss these data in the context of aromatic-proline and aromatic-glycine interactions in local structure, in tertiary structure, in protein-protein interactions, and in protein assemblies. © 2012 American Chemical Society. Source


Riordan C.G.,University of Delaware
Coordination Chemistry Reviews | Year: 2010

This review traces the development and application of the tris(thioether)borate ligands, tripodal ligands with highly polarizable thioether donors. Areas of emphasis include the basic coordination chemistry of the mid-to-late first row transition metals (Fe, Ni, Co, Cu), and the role of the thioether substituent in directing complex formation, the modeling of zinc thiolate protein active sites, high-spin organo-iron and organo-cobalt chemistry, the preparation of monovalent complexes of Fe, Co and Ni, and dioxygen and sulfur activation by monovalent nickel complexes. © 2010 Elsevier B.V. All rights reserved. Source


Okada N.,University of Alabama | Shafi Q.,University of Delaware
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

We present an inflationary model in which the Standard Model Higgs doublet field with non-minimal coupling to gravity drives inflation, and the effective Higgs potential is stabilized by new physics which includes a dark matter particle and right-handed neutrinos for the seesaw mechanism. All of the new particles are fermions, so that the Higgs doublet is the unique inflaton candidate. With central values for the masses of the top quark and the Higgs boson, the renormalization group improved Higgs potential is employed to yield the scalar spectral index ns≃0.968, the tensor-to-scalar ratio r≃0.003, and the running of the spectral index α=dns/dlnk≃-5.2×10-4 for the number of e-folds N0=60 (ns≃0.962, r≃0.004, and α≃-7.5×10-4 for N0=50). The fairly low value of r≃0.003 predicted in this class of models means that the ongoing space and land based experiments are not expected to observe gravity waves generated during inflation. © 2015 The Authors. Source


Boer K.W.,University of Delaware
Energy Conversion and Management | Year: 2011

A thin layer of CdS of about 200 Å enhances the solar conversion efficiency of CdS/CdTe solar cells from 8% to 15%. A similar enhancement of the efficiency is observed on other solar cells, based on CuInSe2 or similar compounds. The reason for this efficiency enhancement that is typical for CdS, but not observed with similar semiconductors, is briefly described. The technical and economical importance of these solar cells on the energy conversion market is summarized. © 2010 Elsevier Ltd. All rights reserved. Source


Chatani S.,University of Colorado at Boulder | Kloxin C.J.,University of Delaware | Bowman C.N.,University of Colorado at Boulder
Polymer Chemistry | Year: 2014

As the demand for polymeric materials transitions towards the need for customizable, high value, specialty polymeric materials, the ability to use light to initiate various physicochemical changes in polymers represents one of the most powerful and rapidly evolving approaches. Whether for polymer formation, polymer modification, shape change, or inducing smart material responses, light has the unique capacity for enabling 4D manipulation of each of those processes. Given the simple, 3D ability to focus light on a targeted voxel and the even simpler ability to turn a light on and off to facilitate temporal control, light has been used widely in various polymer modifications. Further, in addition to the ability to enhance the control of various reactive processes, due to the much greater energy available in a photon as compared to the thermal energy available, light enables chemical processes to occur at ambient conditions that are otherwise inaccessible without heating. In particular, within the polymer chemistry field, light has been used to cause bond formation, bond degradation, and isomerization, with subsequent reactions including polymerization, polymer degradation, polymer functionalization, and responsive changes in properties of smart materials. Here, this article attempts to provide a fundamental basis for the various photochemical processes implemented in polymer systems, followed by selected examples of that implementation in various polymerization, functionalization, degradation, and other reactions. © 2014 The Royal Society of Chemistry. Source


Hoffman L.H.,University of Delaware
Journal of Information Technology and Politics | Year: 2012

This study clarifies the differences between political participation and political communication online. Although many studies have examined the nature and effects of online activity, none has effectively distinguished between the two types of behavior. This lack of clarity has arguably led to conflicting findings and confusion about what demarks a truly participatory act online. Using Pew 2008 data, online political behaviors are defined and examined. Results suggest that online communication and participation do appear to be different constructs, and while online participation predicts voting, online communication does not. Implications for conceptualizing these behaviors and directions for future research are discussed. © 2012 Copyright Taylor and Francis Group, LLC. Source


Sharma V.K.,Florida Institute of Technology | Luther G.W.,University of Delaware
Chemosphere | Year: 2011

The oxidation of organosulfur compounds requires the transfer of oxygen atoms and is important in decontamination of chemical warfare agents, desulfurization of fossil fuel for high quality, deodorization of wastewater and sludge, and remediation of industrial effluents. The kinetics of the oxidation of organosulfur compounds (sulfur-containing amino acids, aliphatic and aromatic thiols, and mercaptans) by the environmentally-friendly oxidant, ferrate(VI) FeO42-, was quantitatively examined in this study using a kinetic model considering possible reactions among the species of ferrate(VI) and organosulfur compounds. The ratios of ferrate(VI) to the various organosulfur compounds for the one oxygen-atom transfer were 0.50 and 0.67 for Fe(II) and Fe(III) as final products, respectively. The second-order rate constants for the oxidation of organosulfur compounds by protonated ferrate(VI) HFeO4- ion were correlated with thermodynamic 1-e - and 2-e - reduction potentials in order to understand the mechanisms of the reactions. The oxidation of the compounds involved a 1-e - transfer step from Fe(VI) to Fe(V), followed by 2-e - transfer to Fe(III) as the reduced product (Fe(VI)→Fe(V)→Fe(III)). The 2-e - transfer steps resulted in the formation of Fe(II) (Fe(VI)→Fe(IV)→Fe(II)). Conclusions drawn from the correlations are consistent with the experimentally determined stoichiometries and products of the reactions. The calculated half-lives for the oxidation were in the range of ms to s at a dose of 10mg K 2FeO 4L -1 and hence ferrate(VI) has a great potential in treating organosulfur compounds present in water and wastewater. © 2010 Elsevier Ltd. Source


It is generally accepted that muscles may have different mechanical capacities, such as those for producing high force (F), velocity (V), and power (P) outputs. Nevertheless, standard procedures for evaluation of muscle function both in research and in routine testing are typically conducted under a single mechanical condition, such as a single external load. Therefore, the observed outcomes do not allow for distinguishing between the different muscle capacities. As a result, the outcomes of most routine testing procedures are of limited informational value, whereas a number of issues debated in research have originated from arbitrarily interpreted experimental findings regarding specific muscle capacities. A solution for this problem could be based on the approximately linear and exceptionally strong F–V relationship typically observed from various functional tasks performed under different external loads. These findings allow for the ‘two-load method’ proposed here: the functional movement tasks (e.g., maximum jumping, cycling, running, pushing, lifting, or throwing) should be tested against just two distinctive external loads. That is, the F–V relationship determined by two pairs of the F and V data could provide the parameters depicting the maximum F (i.e., the F-intercept), V (V-intercept), and P (calculated from the product of F and V) output of the tested muscles. Therefore, the proposed two-load method applied in both research and routine testing could provide a deeper insight into the mechanical properties and function of the tested muscles and resolve a number of issues debated in the literature. © 2016 Springer International Publishing Switzerland Source


Nagarajan V.K.,University of Delaware | Smith A.P.,Louisiana State University
Plant and Cell Physiology | Year: 2012

Phosphate (Pi) is a common limiter of plant growth due to its low availability in most soils. Plants have evolved elaborate mechanisms for sensing Pi deficiency and for initiating adaptive responses to low Pi conditions. Pi signaling pathways are modulated by both local and long-distance, or systemic, sensing mechanisms. Local sensing of low Pi initiates major root developmental changes aimed at enhancing Pi acquisition, whereas systemic sensing governs pathways that modulate expression of numerous genes encoding factors involved in Pi transport and distribution. The gaseous phytohormone ethylene has been shown to play an integral role in regulating local, root developmental responses to Pi deficiency. Comparatively, a role for ethylene in systemic Pi signaling has been more circumstantial. However, recent studies have revealed that ethylene acts to modulate a number of systemically controlled Pi starvation responses. Herein we highlight the findings from these studies and offer a model for how ethylene biosynthesis and responsiveness are integrated into both local and systemic Pi signaling pathways. © 2011 The Author. Source


Mennella J.A.,Monell Chemical Senses Center | Trabulsi J.C.,University of Delaware
Annals of Nutrition and Metabolism | Year: 2012

Increased fruit and vegetable consumption early in life may lead to life-long intake of fruits and vegetables, which in turn may be beneficial for weight control and other health outcomes in later life. Although health officials worldwide recommend delaying solid foods until 6 months of age, younger infants often receive solid food, which may affect later obesity rates. The timing of introduction to solid foods is important both nutritionally and developmentally and may affect acceptance of foods both in infancy and later in life. Infants can clearly discriminate the flavors of different fruits and vegetables. Repeated flavor experiences promote the willingness to eat a variety of foods: infants will consume more of foods that have a familiar flavor and are more accepting of novel flavors if they have experience with flavor variety. Many flavors that the mother either ingests or inhales are transmitted to her milk and/or amniotic fluid. Mothers can help the transition from a diet exclusively of milk or formula to a mixed diet by providing the infant familiar flavors in both milk or formula and solid foods. Exposure to a variety of flavors during and between meals appears to facilitate acceptance of novel foods. Providing novelty in the context of a familiar food might prove to be an optimal combination to progressively accustom infants to a diversity of novel foods. When repeatedly exposing infants to flavors of some vegetables that have bitter tastes, mothers should focus not on infants' facial expressions but on their willingness to eat the food and should continue to provide repeated opportunities to taste the food. Introducing children repeatedly to individual as well as a variety of fruits and vegetables, both within and between meals, might help them be more accepting of fruits and vegetables, which is difficult to enhance beyond toddlerhood. Copyright © 2012 S. Karger AG, Basel. Source


Knight E.K.,University of Delaware
Journal of Public Health Management and Practice | Year: 2014

Context: While the evidence base regarding the social determinants of health and their relationship to health inequities grows, the field of public health is challenged to translate this knowledge into practice changes that advance health equity. Objective: Drawing on the knowledge, beliefs, and experiences of public health experts and community leaders working to advance health equity, our objective was to develop and disseminate recommendations for changing public health practice to better address this problem. Design: We conducted semistructured, qualitative telephone interviews (n = 25) with key informants. Interviews were recorded and transcribed, and data were coded and analyzed using both inductive and deductive methods. Member checks were used to enhance quality. Setting and Participants: A purposeful sample of key informants was selected from content experts and community leaders involved with the development of the Unnatural Causes public impact campaign. Participants represented state and local health departments, community-based organizations, national research/advocacy organizations, and academic institutions across the country. Results: Participants distinguished between social determinants of health and their structural precursors in social and political institutions. They believed that the field of public health has an obligation to address health inequities and shifts in practice are needed that focus more attention on societal factors that underlie such inequities. According to participants, specific practice changes are difficult to identify because actions should be community specific and community driven. Recommended approaches that may be adapted to community-based needs and assets include building nontraditional partnerships, engaging in political advocacy, promoting community leadership, collecting better data on social conditions and institutional factors, and enhancing communication for health equity. Conclusions: Recommended shifts in practice may be facilitated by revisiting our understanding of the 3 core functions of public health - assessment, assurance, and policy development. Copyright © 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins. Source


Sarzynski A.,University of Delaware
Urban Studies | Year: 2012

This paper investigates the pressure placed by cities on their environment with respect to urban air pollution. The analysis employs a spatially explicit global dataset of emissions to estimate urban emissions of four pollutants from a sample of 8038 cities world-wide in 2005. A cross-sectional regression analysis is then conducted to examine the association of urban air pollution with socioeconomic and geographical factors. The results confirm that urban pollution is associated primarily, but not exclusively, with demographics. The results suggest that urban pollution is likely to increase with population growth and that economic modernisation is unlikely to provide much relief from the pressures placed by coming population growth. The findings suggest that policy-makers must focus on reducing the emissions intensity of production activities within cities, especially from the energy sector, if they are to avoid rapid growth in urban air pollution in coming decades. © 2012 Urban Studies Journal Limited. Source


Glyde H.R.,University of Delaware
Journal of Low Temperature Physics | Year: 2013

We review the formulation and measurement of Bose-Einstein condensation (BEC) in liquid and solid helium. BEC is defined for a Bose gas and subsequently for interacting systems via the one-body density matrix (OBDM) valid for both uniform and non-uniform systems. The connection between the phase coherence created by BEC and superflow is made. Recent measurements show that the condensate fraction in liquid 4He drops from 7.25±0.75 % at saturated vapor pressure (p≈0) to 2.8±0.2 % at pressure p=24 bars near the solidification pressure (p=25.3 bar). Extrapolation to solid densities suggests a condensate fraction in the solid of 1 % or less, assuming a frozen liquid structure such as an amorphous solid. Measurements in the crystalline solid have not been able to detect a condensate with an upper limit set at n 0≤0.3 %. Opportunities to observe BEC directly in liquid 4He confined in porous media, where BEC is localized to patches by disorder, and in amorphous solid helium is discussed. © 2013 Springer Science+Business Media New York. Source


Hall IV W.A.,U.S. Department of Agriculture | Johnston M.V.,University of Delaware
Journal of the American Society for Mass Spectrometry | Year: 2012

Secondary organic aerosol (SOA) is formed when organic molecules react with oxidants in the gas phase to form particulate matter. Recent measurements have shown that more than half of the mass of laboratory-generated SOA consists of high molecular weight oligomeric compounds. In this work, the formation mechanisms of oligomers produced in the laboratory by ozonolysis of a-pinene, an important SOA precursor in ambient air, are studied by MS and MS/MS measurements with high accuracy and resolving power to characterize monomer building blocks and the reactions that couple them together. The distribution of oligomers in an SOA sample is complex, typically yielding over 1000 elemental formulas that can be assigned from an electrospray ionization mass spectrum. Despite this complexity, MS/MS spectra can be found that give strong evidence for specific oligomer formation pathways that have been postulated but not confirmed. These include aldol and gem-diol reactions of carbonyls as well as peroxyhemiacetal formation from hydroperoxides. The strongest evidence for carbonyl reactions is in the formation of hydrated products. Less compelling evidence is found for dehydrated products and secondary ozonide formation. The number of times that a monomer building block is observed as a fragmentation product in the MS/MS spectra is shown to be independent of the monomer vapor pressure, suggesting that oligomer formation is not driven by equilibrium partitioning of a monomer between the gas and particle phases, but rather by reactive uptake where a monomer collides with the particle surface and rapidly forms an oligomer. © American Society for Mass Spectrometry, 2012. Source


Pallis C.,University of Cyprus | Shafi Q.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We consider a phenomenological extension of the minimal supersymmetric standard model (MSSM) which incorporates nonminimal chaotic inflation, driven by a quadratic potential in conjunction with a linear term in the frame function. Inflation is followed by a Peccei-Quinn phase transition, based on renormalizable superpotential terms, which resolves the strong CP and μ problems of MSSM and provide masses lower than about 1012GeV for the right-handed (RH) (s)neutrinos. Baryogenesis occurs via nonthermal leptogenesis, realized by the out-of-equilibrium decay of the RH sneutrinos, which are produced by the inflaton's decay. Confronting our scenario with the current observational data on the inflationary observables, the light-neutrino masses, the baryon asymmetry of the universe and the gravitino limit on the reheat temperature, we constrain the strength of the gravitational coupling to rather large values (∼45-2950) and the Dirac neutrino masses to values between about 1 and 10 GeV. © 2012 American Physical Society. Source


Rehman M.U.,University of Basel | Shafi Q.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We consider a simplified version of supersymmetric smooth hybrid inflation which contains a single ultraviolet cutoff m P=2.4×1018GeV, instead of the two cutoffs m P and M *∼few× 1017GeV that are normally employed. With global supersymmetry the scalar spectral index n s0.97, which is in very good agreement with the WMAP observations. With a nonminimal Kähler potential, the supergravity version of the model is compatible with the current central values of n s and also yields potentially observable gravity waves (tensor to scalar ratio r0.02). © 2012 American Physical Society. Source


Manierre M.J.,University of Delaware
Social Science and Medicine | Year: 2015

Self-directed health information seeking has become increasingly common in recent years, yet there is a substantial body of evidence suggesting that females are more likely to engage in information seeking than males. Previous research has largely ignored the significance of this difference as both an empirical and a theoretical finding. The current study has two goals, seeking to track this sex gap over time and to test explanations for its existence. The three explanations tested are based in past findings of gendered division of childcare labor, gendered reactivity to illness, and gendered perceived risk of illness. These were tested using multiple dependent variables from both repeated cross sectional data and 2012 data from the Health Information Trends Survey (HINTS). Results show that females are significantly more likely to look for cancer information, information in general, and information over the Internet over time than males, though the gap may be closing in the case of cancer information. The three explanations also received little clear support though perceived risk of getting cancer acted as a mediator through which men may be less likely to look for cancer information. Based on this analysis it is clear that a sex gap in information seeking is present and theories of masculinity and health may hold promise in some contexts but additional explanations are needed. © 2015 Elsevier Ltd. Source


Vermeulen P.B.,University of Antwerp | Van Golen K.L.,University of Delaware | Dirix L.Y.,University of Antwerp
Cancer | Year: 2010

This objective of the current review was to provide the reader with a comprehensive summary of the literature related to 3 important and inter-related features of the biology of inflammatory breast cancer (IBC): angiogenesis, lymphangiogenesis, and the formation of tumor emboli. Information derived from animal models of IBC as well as from translational studies using tissue samples of patients with IBC are discussed. © 2010 American Cancer Society. Source


Park M.,University of Delaware
Sensors (Basel, Switzerland) | Year: 2013

Whole-cell biosensors are a good alternative to enzyme-based biosensors since they offer the benefits of low cost and improved stability. In recent years, live cells have been employed as biosensors for a wide range of targets. In this review, we will focus on the use of microorganisms that are genetically modified with the desirable outputs in order to improve the biosensor performance. Different methodologies based on genetic/protein engineering and synthetic biology to construct microorganisms with the required signal outputs, sensitivity, and selectivity will be discussed. Source


Roth T.L.,University of Alabama at Birmingham | Sweatt J.D.,University of Delaware
Hormones and Behavior | Year: 2011

Studies over the past half-century have made it clear that environmental influences in development, particularly stress and traumatic experiences, can remain pervasive across the lifespan. Though it has been hypothesized for some time that the long-term consequences of early-life adversity represent epigenetic influences, it has not been until recently that studies have begun to provide empirical support of experience-driven epigenetic modifications to the genome. Here we focus on this theme, and review current knowledge pertaining to the epigenetics of behavioral development. At the center of our discussion is the brain-derived neurotrophic factor (BDNF) gene, as abnormal BDNF gene activity is a leading etiological hypothesis by which early-life adverse experiences persistently modify brain and behavioral plasticity. © 2010 Elsevier Inc. Source


Dunn K.W.,Indiana University | Kamocka M.M.,Indiana University | McDonald J.H.,University of Delaware
American Journal of Physiology - Cell Physiology | Year: 2011

Fluorescence microscopy is one of the most powerful tools for elucidating the cellular functions of proteins and other molecules. In many cases, the function of a molecule can be inferred from its association with specific intracellular compartments or molecular complexes, which is typically determined by comparing the distribution of a fluorescently labeled version of the molecule with that of a second, complementarily labeled probe. Although arguably the most common application of fluorescence microscopy in biomedical research, studies evaluating the "colocalization" of two probes are seldom quantified, despite a diversity of image analysis tools that have been specifically developed for that purpose. Here we provide a guide to analyzing colocalization in cell biology studies, emphasizing practical application of quantitative tools that are now widely available in commercial and free image analysis software. © 2011 the American Physiological Society. Source


Paredes J.L.,University of Los Andes, Venezuela | Arce G.R.,University of Delaware
IEEE Transactions on Signal Processing | Year: 2011

In this paper, we propose a simple and robust algorithm for compressive sensing (CS) signal reconstruction based on the weighted median (WM) operator. The proposed approach addresses the reconstruction problem by solving a l 0-regularized least absolute deviation (l0-LAD) regression problem with a tunable regularization parameter, being suitable for applications where the underlying contamination follows a statistical model with heavier-than-Gaussian tails. The solution to this regularized LAD regression problem is efficiently computed, under a coordinate descent framework, by an iterative algorithm that comprises two stages. In the first stage, an estimation of the sparse signal is found by recasting the reconstruction problem as a parameter location estimation for each entry in the sparse vector leading to the minimization of a sum of weighted absolute deviations. The solution to this one-dimensional minimization problem turns out to be the WM operator acting on a shifted-and-scaled version of the measurement samples with weights taken from the entries in the measurement matrix. The resultant estimated value is then passed to a second stage that identifies whether the corresponding entry is relevant or not. This stage is achieved by a hard threshold operator with adaptable thresholding parameter that is suitably tuned as the algorithm progresses. This two-stage operation, WM operator followed by a hard threshold operator, adds the desired robustness to the estimation of the sparse signal and, at the same time, ensures the sparsity of the solution. Extensive simulations demonstrate the reconstruction capability of the proposed approach under different noise models. We compare the performance of the proposed approach to those yielded by state-of-the-art CS reconstruction algorithms showing that our approach achieves a better performance for different noise distributions. In particular, as the distribution tails become heavier the performance gain achieved by the proposed approach increases significantly. © 2011 IEEE. Source


Stamatakis M.,University College London | Vlachos D.G.,University of Delaware
ACS Catalysis | Year: 2012

Over the past two decades, the necessity for predictive models of chemical kinetics on catalytic surfaces has motivated the development of ab initio kinetic Monte Carlo (KMC) simulation frameworks. These frameworks have been successfully used to investigate chemistries of academic interest and industrial importance, such as CO oxidation, NO oxidation and reduction, ethylene hydrogenation, CO hydrogenation to ethanol, and water-gas shift. These studies have shed light on the effect of catalyst composition, surface structure, lateral interactions, and operating conditions on the apparent turnover frequency of the chemistries of interest. Yet, extending the existing KMC approaches to study large chemistries on complex catalytic structures poses several challenges. In this review, we discuss the recent milestones in the area of KMC simulation of chemical kinetics on catalytic surfaces and review a number of studies that have furthered our fundamental understanding of specific chemistries. In addition, we provide directions for future research aiming toward incorporating detailed physics and chemistry, as well as assessing and improving the accuracy of KMC methods, toward developing quantitative models of surface kinetics. © 2012 American Chemical Society. Source


Lopez-Barron C.R.,ExxonMobil | Wagner N.J.,University of Delaware
Langmuir | Year: 2012

Micellar solutions of hexadecyltrimethylammonium bromide (CTAB) in a protic ionic liquid, ethylammonium nitrate (EAN), are studied by shear rheology, polarizing optical microscopy (POM), conductivity measurements, and small angle neutron scattering (SANS). Three concentration regimes are examined: A dilute regime (with concentrations [CTAB] < 5 wt %) consisting of noninteracting spherical micelles, a semidilute regime (5 wt % < [CTAB] < 45 wt %) where micelles interact via electrostatic repulsions, and a concentrated regime (45 wt % < [CTAB] < 62 wt %) where a reversible, temperature-dependent isotropic (L 1) to hexatic (Hex) phase transition is observed. The L 1 Hex transition, which has been predicted but not previously observed, is characterized by (1) a sharp increase in the shear viscosity, (2) the formation of focal conical birefringence textures (observed by POM), and (3) enhancement of the crystalline order, evidenced by the appearance of Bragg reflections in the SANS profiles. Ionic conductivity is not sensitive to the L 1 Hex transition, which corroborates the absence of topological transitions. © 2012 American Chemical Society. Source


Roth T.L.,University of Delaware
Development and Psychopathology | Year: 2013

In the past decade, there have been exciting advances in the field of behavioral epigenetics that have provided new insights into a biological basis of neural and behavioral effects of gene-environment interactions. It is now understood that changes in the activity of genes established through epigenetic alterations occur as a consequence of exposure to environmental adversity, social stress, and traumatic experiences. DNA methylation in particular has thus emerged as a leading candidate biological pathway linking gene-environment interactions to long-term and even multigenerational trajectories in behavioral development, including the vulnerability and resilience to psychopathology. This paper discusses what we have learned from research using animal models and from studies in which the translation of these findings has been made to humans. Studies concerning the significance of DNA methylation alterations in outcomes associated with stress exposure later in life and dysfunction in the form of neuropsychiatric disorders are highlighted, and several avenues of future research are suggested that promise to advance our understanding of epigenetics both as a mechanism by which the environment can contribute to the development of psychiatric disorders and as an avenue for more effective intervention and treatment strategies. © 2013 Cambridge University Press. Source


Hoja J.,University of Graz | Sax A.F.,University of Graz | Szalewicz K.,University of Delaware
Chemistry - A European Journal | Year: 2014

The stability and geometry of a hydrogen-bonded dimer is traditionally attributed mainly to the central moiety A-H×××B, and is often discussed only in terms of electrostatic interactions. The influence of substituents and of interactions other than electrostatic ones on the stability and geometry of hydrogen-bonded complexes has seldom been addressed. An analysis of the interaction energy in the water dimer and several alcohol dimers - performed in the present work by using symmetry-adapted perturbation theory - shows that the size and shape of substituents strongly influence the stabilization of hydrogen-bonded complexes. The larger and bulkier the substituents are, the more important the attractive dispersion interaction is, which eventually becomes of the same magnitude as the total stabilization energy. Electrostatics alone are a poor predictor of the hydrogen-bond stability trends in the sequence of dimers investigated, and in fact, dispersion interactions predict these trends better. Predicting hydrogen-bond strength: The interaction energy of the dimer of water and those of various alcohols is investigated by using symmetry-adapted perturbation theory. Other than electrostatic interactions, exchange, induction, and dispersion interactions are also important. The picture shows the dependence of the interaction contributions on intermolecular separation for the tert-butanol dimer. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Barr S.M.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In grand unified theories with gauge groups larger than SU(5), the multiplets that contain the known quarks and leptons also contain fermions that are singlets under the standard model gauge group. Some of these could be the dark matter of the Universe. Grand unified theories can also have accidental U(1) global symmetries (analogous to B-L in minimal SU(5)) that can stabilize dark matter. These ideas are illustrated in an SU(6) model. © 2012 American Physical Society. Source


Barr S.M.,University of Delaware | Calmet X.,University of Sussex
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

In the Standard Model, no dim-5 ΔB≠0 operators exist, so that Planck-scale-induced proton decay amplitudes are suppressed by at least 1/MPℓ2. If the Standard Model is augmented by a light, color-nonsinglet boson, then O(1/MPℓ) proton-decay amplitudes are possible. These always conserve B+L, so that the dominant decay modes are p→Π +ν and p→Π+Π+ℓ-, where Π+=π+ or K+. © 2012 American Physical Society. Source


Mudd S.M.,University of Edinburgh | Yoo K.,University of Delaware
Journal of Geophysical Research: Earth Surface | Year: 2010

Linking mineral weathering rates measured in the laboratory to those measured at the landscape scale is problematic. In laboratory studies, collections of minerals are exposed to the same weathering environment over a fixed amount of time. In natural soils, minerals enter, are mixed within, and leave the soil via erosion and dissolution/leaching over the course of soil formation. The key to correctly comparing mineral weathering studies from laboratory experiments and field soils is to consistently define time. To do so, we have used reservoir theory. Residence time of a mineral, as defined by reservoir theory, describes the time length between the moment that a mineral enters (via soil production) and leaves (via erosion and dissolution/leaching) the soil. Age of a mineral in a soil describes how long the mineral has been present in the soil. Turnover time describes the time needed to deplete a species of minerals in the soil by sediment efflux from the soil. These measures of time are found to be sensitive to not only sediment flux, which controls the mineral fluxes in and out of a soil, but also internal soil mixing that controls the probability that a mineral survives erosion. When these measures of time are combined with published data suggesting that a mineral's dissolution reaction rate decreases during the course of weathering, we find that internal soil mixing, by partially controlling the age distribution of minerals within a soil, might significantly alter the soil's mass loss rate via chemical weathering. Copyright 2010 by the American Geophysical Union. Source


Fok P.-W.,University of Delaware
Mathematical Medicine and Biology | Year: 2012

Plaques are fatty deposits that grow mainly in arteries and develop as a result of a chronic inflammatory response. Plaques are characterized as 'vulnerable' when they have large internal regions of necrosis and are heavily infiltrated by macrophages. The particular composition of a vulnerable plaque renders it susceptible to rupture, which releases thrombogenic agents into the bloodstream and can result in myocardial infarction. In this paper, we propose a mathematical model to predict the development of a plaque's necrotic core. By solving coupled reaction-diffusion equations for macrophages and dead cells, we focus on the joint effects of hypoxic cell death and chemoattraction to oxidized low-density lipoprotein (Ox-LDL), a molecule that is strongly linked to atherosclerosis. We do not model the mechanical properties of the plaque, its growth or rupture. Our model predicts cores that have approximately the right size and shape when compared to ultrasound images. Because our model is linear and autonomous, normal mode analysis and subsequent calculation of the smallest eigenvalue allow us to compute the times taken for the necrotic core to form. We find that the spatial distribution of Ox-LDL within the plaque determines not only the placement and size of cores, but their time of formation. Although plaques are biochemically complex, our study shows that certain aspects of their composition can be predicted and are, in fact, governed by simple physical models. © The Author 2011. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved. Source


Szeri A.Z.,University of Delaware
International Journal of Engineering Science | Year: 2010

From time-to-time, experts endeavor to estimate the amount of energy lost due to friction and wear. According to one such estimate, over 4.22 × 10 18 J of energy were lost in the United States in 1978 alone - enough to supply New York city for the entire year. A major factor in limiting our energy efficiency is energy loss through friction in tribo-elements is [1]. In recognition of this, there have been significant efforts made during the past decades towards increasing the efficiency of bearing operations. The major influencing aspects of hydrodynamic lubrication are the structure of the lubricant film, the properties of the bearing surfaces, and the properties of the lubricant. Major past approaches for seeking efficiency improvement focused on the latter two of these aspects and concerned surface modification techniques and modification of lubricant properties. Here we advocate the third approach, modification of the structure of the lubricant film; this approach leads to what we call composite-film bearings (CFB). Composite-film bearings rely on a double layer, composite lubricant film to separate the load-bearing surfaces. We show in this paper that, while maintaining safe film dimensions, composite-film bearings perform with considerably lower frictional losses then do traditional bearings. In designing the CFB scheme, we rely on nature to seek out and maintain a configuration that minimizes viscous dissipation [4]. This will be achieved in our case by the localization of deformation, and thus of viscous dissipation, to the low-viscosity component of the film. The CFB construction appears to be particularly suitable to power generating equipment. The journal bearings of these large rotating apparatus dissipate considerable energy [5]; the CFB has the potential to cut these losses. © 2010 Elsevier Ltd. All rights reserved. Source


Lazarides G.,Aristotle University of Thessaloniki | Shafi Q.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2016

Inspired by the 750 GeV diphoton state recently reported by ATLAS and CMS, we propose a U(1)B-L extension of the MSSM which predicts the existence of four spin zero resonance states that are degenerate in mass in the supersymmetric limit. Vectorlike fields, a gauge singlet field, as well as the MSSM Higgsinos are prevented from acquiring arbitrary large masses by a U(1) R symmetry. Indeed, these masses can be considerably lighter than the Z′ gauge boson mass. Depending on kinematics, the resonance states could decay into right-handed neutrinos and sneutrinos, and/or MSSM Higgs fields and Higgsinos with total decay widths in the multi-GeV range. © 2016 American Physical Society. Source


Klemas V.,University of Delaware
Fisheries Research | Year: 2013

During the past 40 years the fisheries productivity of the world has been declining due to pressures from overfishing, habitat change, pollution, and climate change. Sustainable use of marine resources requires effective monitoring and management of the world's fish stocks. Remote sensing techniques are being used to help manage fisheries at sustainable levels, while also guiding fishing fleets to locate fish schools more efficiently. Fish tend to aggregate in ocean areas that exhibit conditions favored by specific fish species. Some of the relevant oceanographic conditions, such as sea surface temperature, ocean color (productivity) and oceanic fronts, which strongly influence natural fluctuations of fish stocks, can be observed and measured by remote sensors on satellites and aircraft. The remotely sensed data are provided in near-real time to help fishermen save fuel and ship time during their search for fish; to modelers who produce fisheries forecasts; and to scientists who help develop strategies for sustainable fisheries management. This article describes how acoustic, optical and radar sensors on ships, satellites and aircraft are used with forecast models to improve the management and harvesting of fisheries resources. © 2012 Elsevier B.V. Source


When the electron density decreases stronger than linearly with the electric field in photoconductive CdS due to field quenching, high-field domains must occur that remain attached to either the cathode or anode in slit electrode geometry with blocking cathodes. These Böer domains1 are easily seen by their shift in optical absorption due to the Franz-Keldysh effect and offer unique opportunities to analyze field dependent parameters within the range of constant electron density and electric field, such as the carrier density or mobility as a function of the field, and give information of the light dependent work function. They also provide insight why a 200 Å thick cover layer of CdS on top of a CdTe solar cell increases its efficiency from 8 to 16%. The behavior of these Böer domains escapes conventional current voltage analyses except for their visual observation, while other high-field domains with their current fluctuations or oscillations are easily observed and are the subjects of thousands of publications and many books. In this review we will exclude detailed discussion of dynamic domains, but include some new specifics that help to understand the mechanisms of the Böer domains and their applications. Only properties at low optical excitation intensities are discussed that exclude Joules heating. Within the p-type regime of the anode-adjacent domain extremely steep electronic quenching signal becomes visible that could signalize an intrinsic donor level slightly above the middle of the band gap that may be responsible for not allowing CdS to ever become p-type by doping. When the electron density decreases stronger than linearly with the electric field in photoconductive CdS due to field quenching, high-field domains must occur that remain attached to either the cathode or anode in slit electrode geometry with blocking cathodes. These Böer domains are easily seen by their shift in optical absorption due to the Franz-Keldysh effect and offer unique opportunities to analyze field dependent parameters within the range of constant electron density and electric field. In this article some new specifics are included that help to understand the mechanisms of the Böer domains and their applications. Only properties at low optical excitation intensities are discussed that exclude Joules heating. © 2015 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Sun G.,Beijing Normal University | Dong B.,Beijing Normal University | Cao M.,Beijing Institute of Technology | Wei B.,University of Delaware | Hu C.,Beijing Institute of Technology
Chemistry of Materials | Year: 2011

Iron-based microstructured or nanostructured materials, including Fe, γ-Fe2O3, and Fe3O4, are highly desirable for magnetic applications because of their high magnetization and a wide range of magnetic anisotropy. An important application of these materials is use as an electromagnetic wave absorber to absorb radar waves in the centimeter wave (2-18 GHz). Dendrite-like microstructures were achieved with the phase transformation from dendritic α-Fe2O3 to Fe3O4, Fe by partial and full reduction, and γ-Fe2O3 by a reduction-oxidation process, while still preserving the dendritic morphology. The investigation of the magnetic properties and microwave absorbability reveals that the three hierarchical microstructures are typical ferromagnets and exhibit excellent microwave absorbability. In addition, this also confirms that the microwave absorption properties are ascribed to the dielectric loss for Fe and the combination of dielectric loss and magnetic loss for Fe3O4 and γ-Fe2O3. © 2011 American Chemical Society. Source


Gunter W.D.,Western Michigan University | Daly K.,University of Delaware
Computers in Human Behavior | Year: 2012

Throughout the past decade, numerous states have passed legislation to prohibit the sale of violent video games to children, usually in conjunction with an argument that exposure to violent media increases violent behavior. However, the link between video games and violence is not yet fully understood. This study uses propensity score matching as a method to more adequately address the underlying issue of causality. Using a sample of 6567 8th grade students, these analyses test whether there is a causal link between playing violent video games and violence, non-violent deviance and substance use. Results indicate a substantial decrease in the relationship between video games and these outcomes when a matched sample is used. This suggests that the strength of evidence supporting a relationship has likely been overestimated using other methodologies. © 2012 Elsevier Ltd. All rights reserved. Source


Cassak P.A.,West Virginia University | Shay M.A.,University of Delaware
Space Science Reviews | Year: 2012

Magnetic reconnection may play an important role in heating the corona through a release of magnetic energy. An understanding of how reconnection proceeds can contribute to explaining the observed behavior. Here, recent theoretical work on magnetic reconnection for coronal conditions is reviewed. Topics include the rate that collisionless (Hall) reconnection proceeds, the conditions under which Hall reconnection begins, and the effect of secondary islands (plasmoids) both on the scaling and properties of collisional (Sweet-Parker) reconnection and on the onset of Hall reconnection. Applications to magnetic energy storage and release in the corona are discussed. © 2011 Springer Science+Business Media B.V. Source


Guyenne P.,University of Delaware | Parau E.I.,University of East Anglia
Journal of Fluid Mechanics | Year: 2012

This paper is concerned with the two-dimensional problem of nonlinear gravity waves travelling at the interface between a thin ice sheet and an ideal fluid of infinite depth. The ice-sheet model is based on the special Cosserat theory of hyperelastic shells satisfying Kirchhoff's hypothesis, which yields a conservative and nonlinear expression for the bending force. A Hamiltonian formulation for this hydroelastic problem is proposed in terms of quantities evaluated at the fluid-ice interface. For small-amplitude waves, a nonlinear Schrödinger equation is derived and its analysis shows that no solitary wavepackets exist in this case. For larger amplitudes, both forced and free steady waves are computed by direct numerical simulations using a boundary-integral method. In the unforced case, solitary waves of depression as well as of elevation are found, including overhanging waves with a bubble-shaped profile for wave speeds c much lower than the minimum phase speed c min. It is also shown that the energy of depression solitary waves has a minimum at a wave speed cm slightly less than cmin, which suggests that such waves are stable for c< cm and unstable for c> cm. This observation is verified by time-dependent computations using a high-order spectral method. These computations also indicate that solitary waves of elevation are likely to be unstable. © 2012 Cambridge University Press. Source


Huang C.P.,University of Delaware | Wang J.,Missouri University of Science and Technology
Bioresource Technology | Year: 2014

The adsorption of metals onto biological surfaces was studied exemplified by municipal sludge particulates of the primary, the secondary, and the tertiary sludge types from four regional wastewater treatment plants. Major factors affecting the extent of metal adsorption including pH, DOM, total biomass, and total metal loading were studied. The acidity-basicity characteristics of the DOM, the metal ions (Lewis acids), and the surface of the sludge particulates make pH the most important parameter in metal adsorption. Change in pH can modify the speciation of the metal ions, the DOM, and the surface acidity of the sludge particulates and subsequently determines the degree of metal distribution between the aqueous phase and the sludge solids. Information on the acidity-basicity characteristics of the DOM and the sludge particulates are used to calculate the stability constant of metal ion-sludge complexes. © 2014 Elsevier Ltd. Source


Nilakantan G.,University of Southern California | Nilakantan G.,University of Delaware
Composite Structures | Year: 2013

For the past decade, numerical ballistic fabric impact research has centered on homogenized yarn based models. However there has been an increasing emphasis in recent years to study the behavior of woven aramid fabrics at the filament scale to investigate the various deformation and energy dissipating mechanisms at the micron length scale. Such an investigation cannot be accomplished through experimental testing. A large gap still exists between the filament-to-yarn length scales. In this study single yarn transverse impact tests of a Kevlar KM2 yarn are simulated using a finite element analysis. All of the 400 filaments in the yarn are explicitly modeled using 3D solid elements and assigned experimentally characterized material properties. The effects of projectile-yarn and inter-filament friction, and filament material properties on the impact response are studied by considering two scenarios where the filaments are either constrained from spreading laterally during the impact event or are left unconstrained. The packing pattern, filament redistribution, and filament energies are monitored during the impact event. The high degree of model resolution provides invaluable insight into the impact behavior of the ballistic yarn and demonstrates the sensitivity of the impact response to filament friction, material properties, and spreading and redistribution. © 2013 Elsevier Ltd. Source


Jaric S.,University of Delaware
International Journal of Sports Medicine | Year: 2015

Manipulation of external loads typically provides a range of force, velocity, and power data that allows for modeling muscle mechanical characteristics. While a typical force-velocity relationship obtained from either in vitro muscles or isolated muscle groups can be described by a hyperbolic equation, the present review paper reveals the evidence that the same relationship obtained from maximum-performance multi-joint movements could be approximately linear. As a consequence, this pattern also results in a relatively simple shape of the power-velocity relationship. The parameters of the linear force-velocity relationship reveal the maximum force, velocity and power. Recent studies conducted on various functional movement tasks reveal that these parameters could be reliable, on average moderately valid, and typically sensitive enough to detect differences among populations of different physical abilities. Therefore, the linear force-velocity relationship together with the associated parabolic power-velocity relationship could provide both a new and simplified approach to studies of the design and function of human muscular system and its modeling. Regarding the practical applications, the reviewed findings also suggest that the loaded multi-joint movements could be developed into relatively simple routine tests of the force-, velocity- and power-generating capacity of the neuromuscular system. Source


Antoniewicz M.R.,University of Delaware
Journal of Industrial Microbiology and Biotechnology | Year: 2015

Metabolic flux analysis (MFA) is one of the pillars of metabolic engineering. Over the past three decades, it has been widely used to quantify intracellular metabolic fluxes in both native (wild type) and engineered biological systems. Through MFA, changes in metabolic pathway fluxes are quantified that result from genetic and/or environmental interventions. This information, in turn, provides insights into the regulation of metabolic pathways and may suggest new targets for further metabolic engineering of the strains. In this mini-review, we discuss and classify the various methods of MFA that have been developed, which include stoichiometric MFA, 13C metabolic flux analysis, isotopic non-stationary 13C metabolic flux analysis, dynamic metabolic flux analysis, and 13C dynamic metabolic flux analysis. For each method, we discuss key advantages and limitations and conclude by highlighting important recent advances in flux analysis approaches. © 2015, Society for Industrial Microbiology and Biotechnology. Source


Klemas V.,University of Delaware
Journal of Coastal Research | Year: 2011

Light detection and ranging (LIDAR) techniques, combined with Global Positioning Systems (GPSs), make it possible to obtain accurate topographical and bathymetric maps, including maps of shoreline positions. LIDAR surveys can produce 10- to 15-cm vertical accuracy at a spatial resolution greater than one elevation measurement per square meter. This meets the requirements of many coastal research and management applications of LIDAR, including flood zone delineation, monitoring beach-nourishment projects, and mapping changes along sandy coasts and shallow benthic environments from storms or long-term sedimentary processes. Typically, a LIDAR sensor may collect data down to depths of about three times the Secchi depth. If the depth or the water turbidity is too great, acoustic echo-sounding is used. Airborne LIDARs have also been applied with hyperspectral imagers to map wetlands, beaches, coral reefs, and submerged aquatic vegetation (SAV). The objective of this article is to review the use of LIDAR techniques for collecting topographic and bathymetric data and to present three case studies, including lessons learned from each. © 2011 Coastal Education & Research Foundation. Source


Klemas V.,University of Delaware
Journal of Coastal Research | Year: 2011

Sea surface salinity (SSS) is critical for studying biological and physical processes in the ocean, such as the global water balance, ocean currents, and evaporation rates. The water and heat fluxes associated with precipitation and evaporation over global oceans are fundamental in regulating climate and weather. Yet measurements of global SSSs are sparse and do not show the required temporal and spatial variability of SSS distributions. Airborne microwave radiometers, such as the Scanning Low-Frequency Microwave Radiometer (SLFMR) and the Salinity, Temperature, and Roughness Remote Scanner (STARRS), have been used successfully to map SSS and its variability, but only in estuaries and coastal waters. Since 2009, SSS has been measured from satellite orbit by the European Soil Moisture and Ocean Salinity satellite, which is designed to provide synthesized SSS maps with a high accuracy. Other salinity-related satellites are being developed, such as Aquarius, which will provide the global view of salinity variability needed for climate studies. The objectives of this paper are to review remote sensing techniques for mapping SSS and to demonstrate the application of microwave radiometry by presenting two case studies. © 2011, the Coastal Education & Research Foundation (CERF). Source


Bell A.V.,University of Delaware
Qualitative Health Research | Year: 2014

Health information influences an individual's health outcomes. Indeed, researchers have found that communication inequalities contribute to health inequalities. We do not have a clear understanding of why and how the communication disparities exist, however, particularly the social forces behind such differences. The qualitative nature of this article reveals the nuances of health information seeking using the case of infertility. Through 58 in-depth interviews, I demonstrate how differences in social and cultural capital between women of low and high socioeconomic status (SES) result in different ways of learning about health. Women of high SES have access to support groups, physicians, and the Internet, whereas women of low SES do not discuss their health problems with their peers, and lack access to and distrust physicians. I explore how these differences in health information shape the illness experience. I conclude with policy implications. © The Author(s) 2014. Source


Gaisser T.K.,University of Delaware
EPJ Web of Conferences | Year: 2013

The flux of high-energy (GeV) neutrinos consists primarily of those produced by cosmic-ray interactions in the atmosphere. The contribution from extraterrestrial sources is still unknown. Current limits suggest that the observed spectrum is dominated by atmospheric neutrinos up to at least 100 TeV. The contribution of charmed hadrons to the flux of atmospheric neutrinos is important in the context of the search for astrophysical neutrinos because the spectrum of such "prompt" neutrinos is harder than that of "conventional" neutrinos from decay of pions and kaons. The prompt component therefore becomes increasingly important as energy increases. This paper reviews the status of the search for prompt muons and neutrinos with emphasis on the complementary aspects of muons, electron neutrinos and muon neutrinos. © Owned by the authors, published by EDP Sciences, 2013. Source


Bishop J.B.,University of Delaware
Journal of College Student Psychotherapy | Year: 2016

University and college counseling centers continue to meet emerging challenges in higher education. This article addresses three issues: the need for a more unified organizational structure to represent the profession, the potential value for counseling centers in seeking accreditation, and the importance of specialized training for those entering this professional field. © 2016 Taylor & Francis. Source


Swanik C.B.,University of Delaware
Journal of Athletic Training | Year: 2015

Small mental errors in judgment or coordination at illtimed phases of movement planning could lead to the rapid, premature onset of large joint forces during sports. If these loads are not fully anticipated, then preprogrammed muscle contractions may be insufficient for stiffness levels to provide dynamic restraint, regardless of sex. This sequence of events would limit the capacity of muscles to act in a load-compensating manner, thereby exposing capsuloligamentous structures to failure. The importance of various neuropsychological characteristics in injury proneness should be explored to enhance prevention and rehabilitation strategies. Source


Feng N.,Tianjin University | Wang H.J.,University of Delaware | Li M.,Tianjin University
Information Sciences | Year: 2014

With the increasing organizational dependence on information systems, information systems security has become a very critical issue in enterprise risk management. In information systems, security risks are caused by various interrelated internal and external factors. A security vulnerability could also propagate and escalate through the causal chains of risk factors via multiple paths, leading to different system security risks. In order to identify the causal relationships among risk factors and analyze the complexity and uncertainty of vulnerability propagation, a security risk analysis model (SRAM) is proposed in this paper. In SRAM, a Bayesian network (BN) is developed to simultaneously define the risk factors and their causal relationships based on the knowledge from observed cases and domain experts. Then, the security vulnerability propagation analysis is performed to determine the propagation paths with the highest probability and the largest estimated risk value. SRAM enables organizations to establish proactive security risk management plans for information systems, which is validated via a case study. © 2013 Elsevier Inc. All rights reserved. Source


Boer K.W.,University of Delaware
Journal of Applied Physics | Year: 2010

A cover layer of CdS enhances the efficiency of CdTe and CuInSe2 based solar cells. The experimental results are summarized, giving the reasons why a CdS layer causes Voc and the fill factor to increase. Field quenching by Frenkel-Poole excitation in copper doped CdS leads to a negative differential conductivity and a high-field domain with a field of 50 kV/cm, limiting the maximum field in the CdS/CdTe junction. This prevents tunneling through the junction and reducing electron leakage. Other evidence indicates an adjustment of the electron affinity, hence in a shift of the band connection at different bias conditions. A band model of the CdS/CdTe cell is proposed. © 2010 American Institute of Physics. Source


Braun R.J.,University of Delaware
Annual Review of Fluid Mechanics | Year: 2011

This review discusses the current understanding of tear-film physiology and mathematical models for some of its dynamics. First, a brief introduction to the tear film and the ocular surface is given. Next, mathematical models for the tear film are discussed, with an emphasis on models that describe the formation and relaxation of the tear film from blinking. Finally, future issues in tear film modeling are presented. Source


Lyons E.J.,University of Texas Medical Branch | Hatkevich C.,University of Delaware
Journal of Medical Internet Research | Year: 2013

Background: Fitness video games are popular, but little is known about their content. Because many contain interactive tools that mimic behavioral strategies from weight loss intervention programs, it is possible that differences in content could affect player physical activity and/or weight outcomes. There is a need for a better understanding of what behavioral strategies are currently available in fitness games and how they are implemented. Objective: The purpose of this study was to investigate the prevalence of evidence-based behavioral strategies across fitness video games available for home use. Games available for consoles that used camera-based controllers were also contrasted with games available for a console that used handheld motion controllers. Methods: Fitness games (N=18) available for three home consoles were systematically identified and play-tested by 2 trained coders for at least 3 hours each. In cases of multiple games from one series, only the most recently released game was included. The Sony PlayStation 3 and Microsoft Xbox360 were the two camera-based consoles, and the Nintendo Wii was the handheld motion controller console. A coding list based on a taxonomy of behavioral strategies was used to begin coding. Codes were refined in an iterative process based on data found during play-testing. Results: The most prevalent behavioral strategies were modeling (17/18), specific performance feedback (17/18), reinforcement (16/18), caloric expenditure feedback (15/18), and guided practice (15/18). All games included some kind of feedback on performance accuracy, exercise frequency, and/or fitness progress. Action planning (scheduling future workouts) was the least prevalent of the included strategies (4/18). Twelve games included some kind of social integration, with nine of them providing options for real-time multiplayer sessions. Only two games did not feature any kind of reward. Games for the camera-based consoles (mean 12.89, SD 2.71) included a greater number of strategies than those for the handheld motion controller console (mean 10.00, SD 2.74, P=.04). Conclusions: Behavioral strategies for increasing self-efficacy and self-regulation are common in home console fitness video games. Social support and reinforcement occurred in approximately half of the studied games. Strategy prevalence varies by console type, partially due to greater feedback afforded by camera-based controllers. Experimental studies are required to test the effects of these strategies when delivered as interactive tools, as this medium may represent an innovative platform for disseminating evidence-based behavioral weight loss intervention components. Source


Akhtar F.,University of Stockholm | Liu Q.,University of Stockholm | Liu Q.,University of Delaware | Hedin N.,University of Stockholm | Bergstrom L.,University of Stockholm
Energy and Environmental Science | Year: 2012

Mechanically strong monoliths of zeolite NaKA with a hierarchy of pores displayed very high CO2-over-N2 selectivity. The zeolite monoliths were produced by pulsed current processing (PCP) without the use of added binders and with a preserved microporous crystal structure. Adsorption isotherms of CO2 and N2 were determined and used to predict the co-adsorption of CO2 and N2 using ideal adsorbed solution theory (IAST). The IAST predictions showed that monolithic adsorbents of NaKA could reach an extraordinarily high CO2-over- N2 selectivity in a binary mixture with a composition similar to flue gas (15 mol% CO2 and 85 mol% N2 at 25°C and 101 kPa). Structured NaKA monoliths with a K+ content of 9.9 at% combined a CO2-over-N2 selectivity of >1100 with a high CO 2 adsorption capacity (4 mmol g-1) and a fast adsorption kinetics (on the order of one minute). Estimates of a figure of merit (F) based on IAST CO2-over-N2 selectivity, and time-dependent CO2 uptake capacity, suggest that PCP-produced structured NaKA with a K+ content of 9.9 at% offers a performance far superior to 13X adsorbents, in particular at short cycle times. This journal is © 2012 The Royal Society of Chemistry. Source


Roberts C.J.,University of Delaware
Current Opinion in Biotechnology | Year: 2014

Protein pharmaceutical products are typically active as folded monomers that are composed of one or more protein chains, such as the heavy and light chains in monoclonal antibodies that are a mainstay of current drug pipelines. There are numerous possible aggregated states for a given protein, some of which are potentially useful, while most of which are considered deleterious from the perspective of pharmaceutical product quality and performance. This review provides an overview of how and why different aggregated states of proteins occur, how this potentially impacts product quality and performance, fundamental approaches to control aggregate formation, and the practical approaches that are currently used in the pharmaceutical industry. © 2014 Elsevier Ltd. Source


Conjugated polymers are being considered for use at the interface between hard inorganic metallic and semiconducting electrodes and soft biological tissues. These organic materials have properties that are intermediate to these two extremes, and their chemistry, structure, and performance can be precisely manipulated over a large range. Examples of current interest included copolymers of poly(3,4-ethylene dioxythiophene) and poly(3,4-propylene dioxythiophene). This paper will review past efforts, recent activities, and future possibilities in this rapidly expanding area of materials research and technology. Copyright © Materials Research Society 2015. Source


Simons R.F.,University of Delaware
Psychophysiology | Year: 2010

Negative feedback, either internal or external, is a fundamental guide to human learning and performance. The neural system that underlies the monitoring of performance and the adjustment of behavior has been subject to multiple neuroimaging investigations that uniformly implicate the anterior cingulate cortex and other prefrontal structures as crucial to these executive functions. The present article describes a series of experiments that employed event-related potentials to study a variety of processes associated with internal or external feedback. Three medial-frontal negativities (error-related negativity, correct-response negativity, feedback-related negativity) are highlighted, each of which plays an important role in the monitoring and dynamic adjustment of behavior. Extensions of basic research on these ERPs to questions relevant to clinical-science are also provided. © 2009 Society for Psychophysiological Research. Source


Coyne K.J.,University of Delaware
Journal of Phycology | Year: 2010

Heterosigma akashiwo (Hada) Hada ex Y. Hara et Chihara is a bloom-forming alga that has been associated with fish kills in coastal regions worldwide. Dense blooms of this species occur annually in Delaware's inland bays, USA. Under static laboratory conditions, however, H. akashiwo is a poor competitor compared to other algal species. Instead, Heterosigma may proliferate under dynamic conditions due to its ability to respond quickly to nutrient input. The objectives of this investigation were to examine changes in transcriptional expression of nitrate reductase (NR) as a proxy for nitrate assimilation in Heterosigma. Here, the gene sequence for H. akashiwo nitrate reductase (NR1) was amplified by PCR, and the full-length gene sequence was obtained and characterized. Using quantitative reverse transcriptase real-time PCR (QRT-PCR), changes in NR1 expression were evaluated in relation to temperature and nitrogen status. Expression of NR1 was not significantly different for cultures acclimated to temperatures ranging from 18°C to 28°C. Results also demonstrated that NR1 was expressed constitutively, even in the absence of nitrate and in the presence of ammonium. An apparent biphasic expression of NR1 was observed upon addition of nitrate to N-starved cultures, with significant increases at 15 and 60 min after addition. In contrast, addition of nitrate to nitrate-replete cultures resulted in a significant decrease in NR1 transcript abundance, likely due to repression by downstream products of nitrate assimilation. These results suggest that Heterosigma responds rapidly to changes in the environment by up-or down-regulating the NR transcript pool in relation to the nitrogen status of the cell. © 2009 Phycological Society of America. Source


Safronova M.S.,University of Delaware | Kozlov M.G.,RAS Petersburg Nuclear Physics Institute | Clark C.W.,U.S. National Institute of Standards and Technology
Physical Review Letters | Year: 2011

We show that three group IIIB divalent ions, B +, Al +, and In +, have anomalously small blackbody radiation (BBR) shifts of the ns2 S01-nsnp P0o3 clock transitions. The fractional BBR shifts for these ions are at least 10 times smaller than those of any other present or proposed optical frequency standards at the same temperature, and are less than 0.3% of the Sr clock shift. We have developed a hybrid configuration-interaction + coupled-cluster method that provides accurate treatment of correlation corrections in such ions and yields a rigorous upper bound on the uncertainty of the final results. We reduce the BBR contribution to the fractional frequency uncertainty of the Al + clock to 4×10 -19 at T=300K. We also reduce the uncertainties due to this effect at room temperature to 10 -18 level for B + and In + to facilitate further development of these systems for metrology and quantum sensing. © 2011 American Physical Society. Source


Vargas R.,CICESE | Vargas R.,University of Delaware
Environmental Research Letters | Year: 2012

A current challenge is to understand what are the legacies left by disturbances on ecosystems for predicting response patterns and trajectories. This work focuses on the ecological implications of a major hurricane and analyzes its influence on forest gross primary productivity (GPP; derived from the moderate-resolution imaging spectroradiometer, MODIS) and soil CO 2 efflux. Following the hurricane, there was a reduction of nearly 0.5kgCm2yr1, equivalent to 15% of the long-term mean GPP (3.0±0.2kgCm2yr1; years 2003-8). Annual soil CO2 emissions for the year following the hurricane were >3.9±0.5kgCm2yr1, whereas for the second year emissions were 1.7±0.4kgCm2yr1. Higher annual emissions were associated with higher probabilities of days with extreme soil CO2 efflux rates (>9.7μmolCO2m2s 1). The variance of GPP was highly variable across years and was substantially increased following the hurricane. Extreme soil CO2 efflux after the hurricane was associated with deposition of nitrogen-rich fresh organic matter, higher basal soil CO2 efflux rates and changes in variance of the soil temperature. These results show that CO2 dynamics are highly variable following hurricanes, but also demonstrate the strong resilience of tropical forests following these events. © 2012 IOP Publishing Ltd. Source


Bach R.D.,University of Delaware
Journal of Organic Chemistry | Year: 2012

Quantum mechanical calculations at the B3LYP/6-311+G(d,p) level have examined the overall mechanism of the Baeyer-Villiger (BV) reaction with peroxyacetic acid. A series of reactions that include both the addition step and the subsequent alkyl group migration step included ketones, acetone, t-butyl methyl ketone, acetophenone, cyclohexyl methyl ketone, and cyclohexyl phenyl ketone. The combined data suggested that the first step for addition of the peroxyacetic acid oxidation catalyst to the ketone carbonyl to produce the Criegee or tetrahedral intermediate is rate-limiting and has activation barriers that range from 38 to 41 kcal/mol without the aid of a catalyst. The rate of addition is markedly reduced by the catalytic action of a COOH functionality acting as a donor-acceptor group affecting both its proton transfer to the ketone C=O oxygen in concert with transfer of the OOH proton to the carboxylic acid carbonyl. The second or alkyl group migration step has a much reduced activation barrier, and its rate is not markedly influenced by acid catalysis. The rate of both steps in the BV reaction is greatly influenced by the catalytic action of very strong acids. © 2012 American Chemical Society. Source


Farquhar S.,Anderson Orthopaedic Clinic | Snyder-Mackler L.,University of Delaware
Clinical Orthopaedics and Related Research | Year: 2010

The long-term functional abilities of patients after a unilateral total knee arthroplasty (TKA) are influenced by the status of the nonoperated knee at the time of the TKA. We hypothesized that in the 3 years after TKA, the nonoperated limb would become more painful, and the quadriceps muscles would weaken; pain and strength would influence performance on functional testing by 3 years after TKA. Healthy control subjects were tested over the same time interval; we hypothesized the controls would also decline in strength and function over time. Individuals with unilateral knee pain (less than 4/10 on a verbal analog scale) were recruited preoperatively. We tested patients 1, 2, and 3 years after TKA to determine changes in strength, self-report outcome measures, and performance on a stair climbing test and the 6-minute walk test. Control subjects without osteoarthritis were tested twice, 2 years apart. The nonoperated limb of patients with TKA weakened from 1 to 2 years, and further weakened from 2 to 3 years after TKA; by 3 years after TKA, the nonoperated limb was more painful compared to the operated limb. Three years after TKA, nonoperated knee pain contributed 44% of the variability in the 6-minute walk and 33% of the variability in the stair climbing test. Patients with TKA were weaker, slower, and had lower self-report outcome measures compared with control subjects at both time intervals. Control subjects also weakened over time, yet were stable on self-report outcome measures and the 6 minute walk test. Weakening of the quadriceps muscles in all participants represents changes due to ageing; however on average the nonoperated limb weakened over time, possibly representing not only changes resulting from aging, but progression of osteoarthrosis in some patients with unilateral TKA. Level of Evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence. © 2009 The Association of Bone and Joint Surgeons®. Source


Holder J.,University of Delaware
Brazilian Journal of Physics | Year: 2014

This paper is the write-up of a rapporteur talk given by the author at the 33rd International Cosmic Ray Conference in Rio de Janeiro, Brazil, in 2013. It attempts to summarize results and developments in ground-based gamma-ray observations and instrumentation from among the ∼300 submissions to the gamma-ray sessions of the meeting. Satellite observations and theoretical developments were covered by a companion rapporteur (Stawarz, L., 33rd ICRC, Rio de Janeiro, Brazil, Rapporteur talk: Space-based Gamma-Ray Astronomy, 2013). Any review of this nature is unavoidably subjective and incomplete. Nevertheless, the article should provide a useful status report for those seeking an overview of this exciting and fast-moving field. © 2014, Sociedade Brasileira de Física. Source


Timilsina G.R.,The World Bank | Kurdgelashvili L.,University of Delaware | Narbel P.A.,Norwegian School of Economics and Business Administration
Renewable and Sustainable Energy Reviews | Year: 2012

Solar energy has experienced phenomenal growth in recent years due to both technological improvements resulting in cost reductions and government policies supportive of renewable energy development and utilization. This study analyzes the technical, economic and policy aspects of solar energy development and deployment. While the cost of solar energy has declined rapidly in the recent past, it still remains much higher than the cost of conventional energy technologies. Like other renewable energy technologies, solar energy benefits from fiscal and regulatory incentives, including tax credits and exemptions, feed-in-tariff, preferential interest rates, renewable portfolio standards and voluntary green power programs in many countries. The emerging carbon credit markets are expected to provide additional incentives to solar energy deployment; however, the scale of incentives provided by the existing carbon market instruments, such as, the Clean Development Mechanism of the Kyoto Protocol is limited. Despite the huge technical potential, the development and large scale deployment of solar energy technologies world-wide still has to overcome a number of technical, financial, regulatory and institutional barriers. The continuation of policy supports might be necessary for several decades to maintain and enhance the growth of solar energy in both developed and developing countries. © 2011 Elsevier Ltd. All rights reserved. Source


Young D.G.,University of Delaware
Journal of Broadcasting and Electronic Media | Year: 2013

This project integrates a uses and gratifications perspective into the study of political satire, to explore the reasons why young people prefer (or avoid) political satire programming, and to understand how viewing and avoidance motivations relate to political and psychological constructs. Results indicate that respondents who prefer political satire report watching for the humor, to learn about current events, because they see it as unbiased, to make news fun, and to contextualize the news. Analyses also reveal significant differences in the demographic and psychological profiles of respondents who watch (and avoid) political satire for different reasons. © 2013 Copyright Taylor and Francis Group, LLC. Source


Martin-Deleon P.A.,University of Delaware
International Journal of Andrology | Year: 2011

Hyaluronidases (hyases) are a family of enzymes that catalyse the breakdown of hyaluronic acid (HA), which is abundant in the extracellular matrix. Two unlinked gene clusters encode these six proteins: three each in the somatic (or ubiquitous) acid-active subgroup and the neutral-active germ-cell subgroup. This review analyses the data on the expression and role of hyases in gamete biology and fertilization, using electronic databases until October 2010. Evidence indicates that hyases are membrane proteins with multifunctional essential, enzymatic and non-enzymatic, roles (cumulus penetration, zona binding and HA receptor) in fertilization. While sperm adhesion molecule-1 (SPAM1), which has neutral and acidic (bimodal) activity, is the widely conserved mammalian sperm hyase, it co-exists with an acidic hyase in murine and human spermatozoa. Thus, sperm function depends on the concerted activity of both germ cell and 'somatic' hyases. Some hyases are in low abundance in the ovary, somatic testicular cells, the male accessory organs and the male and female genital tracts where they are secreted and acquired by spermatozoa. The latter opens up the possibility of treating hyase-deficient spermatozoa via assisted reproductive technology. The findings challenge the existing classification of hyases, and support the notion that hyase activities are polygenic traits controlled by as many as five hyase genes in mice. Multiple sperm hyases may function cooperatively in a quantitative system and/or serve redundant roles. Unsolved problems include functional redundancy, which can be addressed by double gene-knockouts, and identifying the murine hyase(s) involved in zona binding or whether this role shows species specificity. © 2011 The Author. International Journal of Andrology © 2011 European Academy of Andrology. Source


Zurakowski R.,University of Delaware
BioMedical Engineering Online | Year: 2011

Mathematical models of the immune response to the Human Immunodeficiency Virus demonstrate the potential for dynamic schedules of Highly Active Anti-Retroviral Therapy to enhance Cytotoxic Lymphocyte-mediated control of HIV infection.Methods: In previous work we have developed a model predictive control (MPC) based method for determining optimal treatment interruption schedules for this purpose. In this paper, we introduce a nonlinear observer for the HIV-immune response system and an integrated output-feedback MPC approach for implementing the treatment interruption scheduling algorithm using the easily available viral load measurements. We use Monte-Carlo approaches to test robustness of the algorithm.Results: The nonlinear observer shows robust state tracking while preserving state positivity both for continuous and discrete measurements. The integrated output-feedback MPC algorithm stabilizes the desired steady-state. Monte-Carlo testing shows significant robustness to modeling error, with 90% success rates in stabilizing the desired steady-state with 15% variance from nominal on all model parameters.Conclusions: The possibility of enhancing immune responsiveness to HIV through dynamic scheduling of treatment is exciting. Output-feedback Model Predictive Control is uniquely well-suited to solutions of these types of problems. The unique constraints of state positivity and very slow sampling are addressable by using a special-purpose nonlinear state estimator, as described in this paper. This shows the possibility of using output-feedback MPC-based algorithms for this purpose. © 2011 Zurakowski; licensee BioMed Central Ltd. Source


Naik U.P.,University of Delaware
Blood | Year: 2014

In this issue of Blood, Arman et al show that bacteria use immunoglobulin G (IgG) from plasma to engage platelet surface receptors FcγRIIA and integrin αIIbβ3 to induce platelet activation, which is further facilitated by platelet factor 4 (PF4). © 2014 by The American Society of Hematology. Source


Antoniewicz M.R.,University of Delaware
Current Opinion in Biotechnology | Year: 2013

Measuring metabolic rates by 13C-metabolic flux analysis (13C-MFA) is of central importance for metabolic engineers and biomedical investigators. Enhanced knowledge of in vivo fluxes can be applied to reengineer the metabolic, regulatory, and phenotypic characteristics of organisms and help uncover the mechanisms of human ailments such as cancer and diabetes. To determine accurate and precise fluxes by 13C-MFA advanced methods for measuring stable-isotope labeling are needed. The application of tandem mass spectrometry is emerging as a new promising technique that has significant advantages over traditional MS and NMR based methods. With further refinement, tandem MS has the potential to become the new gold standard for measuring isotopic labeling for 13C-flux studies. © 2012 Elsevier Ltd. Source


Barr S.M.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2010

A class of nonsupersymmetric extensions of the standard model is proposed in which there is a multiplicity of light scalar doublets in a multiplet of a nonabelian family group with the standard model Higgs doublet. Anthropic tuning makes the latter light, and consequently the other scalar doublets remain light because of the family symmetry. The family symmetry greatly constrains the pattern of flavor-changing neutral-current interactions (FCNC) and p decay operators coming from scalar-exchange. Such models show that useful constraints on model-building can come from an extended naturalness principle when the electroweak scale is anthropically tuned. © 2010 The American Physical Society. Source


Martin-Deleon P.A.,University of Delaware
Asian Journal of Andrology | Year: 2015

A variety of glycosylphosphatidylinositol (GPI)-linked proteins are acquired on spermatozoa from epididymal luminal fluids (ELF) during sperm maturation. These proteins serve roles in immunoprotection and in key steps of fertilization such as capacitation, acrosomal exocytosis and sperm-egg interactions. Their acquisition on sperm cells is mediated both by membrane vesicles (epididymosomes, EP) which were first reported to dock on the sperm surface, and by lipid carriers which facilitate the transfer of proteins associated with the membrane-free fraction of ELF. While the nonvesicular fraction is more efficient, both pathways are dependent on hydrophobic interactions between the GPI-anchor and the external lipid layer of the sperm surface. More recently proteomic and hypothesis-driven studies have shown that EP from several mammals carry transmembrane (TM) proteins, including plasma membrane Ca 2 +-ATPase 4 (PMCA4). Synthesized in the testis, PMCA4 is an essential protein and the major Ca 2 + efflux pump in murine spermatozoa. Delivery of PMCA4 to spermatozoa from bovine and mouse EP during epididymal maturation and in vitro suggests that the docking of EP on the sperm surface precedes fusion, and experimental evidence supports a fusogenic mechanism for TM proteins. Fusion is facilitated by CD9, which generates fusion-competent sites on membranes. On the basis of knowledge of PMCA4's interacting partners a number of TM and membrane-associated proteins have been identified or are predicted to be present, in the epididymosomal cargo deliverable to spermatozoa. These Ca 2 +-dependent proteins, undetected in proteomic studies, play essential roles in sperm motility and fertility, and their detection highlights the usefulness of the hypothesis-driven approach. Source


Papafragou A.,University of Delaware
Cognitive Science | Year: 2010

Recent research has demonstrated an asymmetry between the origins and endpoints of motion events, with preferential attention given to endpoints rather than beginnings of motion in both language and memory. Two experiments explore this asymmetry further and test its implications for language production and comprehension. Experiment 1 shows that both adults and 4-year-old children detect fewer within-category changes in source than goal objects when tested for memory of motion events; furthermore, these groups produce fewer references to source than goal objects when describing the same motion events. Experiment 2 asks whether the specificity of encoding source/goal relations differs in both spatial memory and the comprehension of novel spatial vocabulary. Results show that endpoint configuration changes are detected more accurately than source configuration changes by both adults and young children. Furthermore, when interpreting novel motion verbs, both age groups expect more fine-grained lexical distinctions in the domain of endpoint configurations compared to that of source configurations. These studies demonstrate that a cognitive-attentional bias in spatial representation and memory affects both the detail of linguistic encoding during the use of spatial language and the specificity of hypotheses about spatial referents that learners build during the acquisition of the spatial lexicon. © 2010 Cognitive Science Society, Inc. Source


Woodcock L.V.,University of Delaware
AIChE Journal | Year: 2012

The number densities (ν/V) above or below which "pockets" of additional-sphere excluded volume (ρ pe) and available volume (ρ pa) begin to percolate the whole volume of the system, sometimes referred to as percolation thresholds, have been determined for the equilibrium hard-sphere fluid of diameter σ using a Monte Carlo (MC) approach. Values obtained are ρ peσ 3 = 0.0785 ± 0.01 and ρ paσ 3 = 0.537 ± 0.005. The present value of ρ peσ 3 agrees with an interpolation of previous data for the percolation diameter (σ p) for various densities from Heyes et al. The available volume (V a) can be resolved as a "radial acceptance function" (u(r)), which is easily obtained from MC acceptance ratio statistics providing a direct route to the chemical potential up to liquid-like densities. The closed-virial equation-of-state of the hard-sphere fluid is found to deviate slightly, but significantly from thermodynamic pressures at densities exceeding ρ pa. Knowledge of the hard-sphere fluid percolation transitions could lead to a more formal description of the critical point and origins of the liquid state, in the spirit of van der Waals. © 2011 American Institute of Chemical Engineers (AIChE). Source


Winther J.R.,Copenhagen University | Thorpe C.,University of Delaware
Biochimica et Biophysica Acta - General Subjects | Year: 2014

Background: Disulfide bond formation is a key posttranslational modification, with implications for structure, function and stability of numerous proteins. While disulfide bond formation is a necessary and essential process for many proteins, it is deleterious and disruptive for others. Cells go to great lengths to regulate thiol-disulfide bond homeostasis, typically with several, apparently redundant, systems working in parallel. Dissecting the extent of oxidation and reduction of disulfides is an ongoing challenge due, in part, to the facility of thiol/disulfide exchange reactions. Scope of review: In the present account, we briefly survey the toolbox available to the experimentalist for the chemical determination of thiols and disulfides. We have chosen to focus on the key chemical aspects of current methodology, together with identifying potential difficulties inherent in their experimental implementation. Major conclusions: While many reagents have been described for the measurement and manipulation of the redox status of thiols and disulfides, a number of these methods remain underutilized. The ability to effectively quantify changes in redox conditions in living cells presents a continuing challenge. General significance: Many unresolved questions in the metabolic interconversion of thiols and disulfides remain. For example, while pool sizes of redox pairs and their intracellular distribution are being uncovered, very little is known about the flux in thiol-disulfide exchange pathways. New tools are needed to address this important aspect of cellular metabolism. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn. © 2013 Elsevier B.V. All rights reserved. Source


Woodcock L.V.,University of Delaware
Industrial and Engineering Chemistry Research | Year: 2011

A nonadditive hard-sphere (NAHS) reference model for ionic liquids with truncated ion-ion pair interaction potentials represented by collision diameters defined as σ ij = σ (1+δ ijε) (using the Kronecker δ) is investigated. In a reference 1:1 ionic salt (e.g., AB ) NaCl), the nonadditivity parameter (σ) is positive; hence, like ions interact with a larger diameter than unlike ions; that is, σ AA= σ BB = (1+ε)σ ABThe NAHS model is found to show remarkable similarity of structure to the full-Hamiltonian for electrostatic charged ion models of ionic liquids, their crystalline phases, and freezing properties. Molecular dynamics computations are used to show that the structures of ionic liquids and crystals are determined mainly by short-range geometric and symmetry effects rather than the long-range electrostatic potentials. A preliminary phase diagram for nonadditive hard spheres has been determined for the range of positive nonadditivity for stable cubic lattices CsCl (body-centered), rock salt, NaCl (simple cubic), and sphelerite ZnS (tetrahedral). Model NAHS ionic liquids obey a scaling law for the freezing temperature T f ) T 0(1 + ε) 3, where T 0 is the HS freezing temperature. NAHS is an effective reference model, analogous to the HS model for molecular and atomic liquids, as a starting point for describing the structures and phase diagrams of ionic liquids and crystals. © 2011 American Chemical Society. Source


Lack D.A.,National Oceanic and Atmospheric Administration | Lack D.A.,University of Colorado at Boulder | Corbett J.J.,University of Delaware
Atmospheric Chemistry and Physics | Year: 2012

The International Maritime Organization (IMO) has moved to address the health and climate impact of the emissions from the combustion of low-quality residual fuels within the commercial shipping industry. Fuel sulfur content (F S) limits and an efficiency design index for future ships are examples of such IMO actions. The impacts of black carbon (BC) emissions from shipping are now under review by the IMO, with a particular focus on the potential impacts of future Arctic shipping. Recognizing that associating impacts with BC emissions requires both ambient and onboard observations, we provide recommendations for the measurement of BC. We also evaluate current insights regarding the effect of ship speed (engine load), fuel quality and exhaust gas scrubbing on BC emissions from ships. Observations demonstrate that BC emission factors (EF BC) increases 3 to 6 times at very low engine loads (<25% compared to EFBC at 85-100% load); absolute BC emissions (per nautical mile of travel) also increase up to 100% depending on engine load, even with reduced load fuel savings. If fleets were required to operate at lower maximum engine loads, presumably associated with reduced speeds, then engines could be re-tuned, which would reduce BC emissions. Ships operating in the Arctic are likely running at highly variable engine loads (25-100%) depending on ice conditions and ice breaking requirements. The ships operating at low load may be emitting up to 50% more BC than they would at their rated load. Such variable load conditions make it difficult to assess the likely emissions rate of BC. Current fuel sulfur regulations have the effect of reducing EF BC by an average of 30% and potentially up to 80% regardless of engine load; a removal rate similar to that of scrubbers. Uncertainties among current observations demonstrate there is a need for more information on a) the impact of fuel quality on EF BC using robust measurement methods and b) the efficacy of scrubbers for the removal of particulate matter by size and composition. © 2012 Author(s). Source


Mercer I.,University of Delaware
IEEE Transactions on Information Theory | Year: 2013

Chu sequences are a family of polyphase sequences that have perfect periodic autocorrelations and good aperiodic autocorrelations. It has previously been proved that the maximum offpeak (aperiodic) autocorrelation (in absolute value) of the Chu sequence of length n is asymptotically equal to 0.480261 n. It has also been empirically observed that the merit factor of Chu sequences appears to grow like a constant times n. In this note, we provide an analytic proof that the merit factor of the Chu sequence of length n is bounded below by a constant multiple of n for all n. To the author's knowledge, this is the first time a family of polyphase sequences of all lengths has been proved to have merit factor growing at least like order n. © 1963-2012 IEEE. Source


Colby D.W.,University of California at San Francisco | Colby D.W.,University of Delaware | Prusiner S.B.,University of California at San Francisco
Cold Spring Harbor Perspectives in Biology | Year: 2011

The discovery of infectious proteins, denoted prions, was unexpected. After much debate over the chemical basis of heredity, resolution of this issue began with the discovery that DNA, not protein, from pneumococcus was capable of genetically transforming bacteria (Avery et al. 1944). Four decades later, the discovery that a protein could mimic viral and bacterial pathogens with respect to the transmission of some nervous system diseases (Prusiner 1982) met with great resistance. Overwhelming evidence nowshows that Creutzfeldt-Jakob disease (CJD) and related disorders are caused by prions. The prion diseases are characterized by neurodegeneration and lethality. In mammals, prions reproduce by recruiting the normal, cellular isoform of the prion protein (PrPC) and stimulating its conversion into the disease-causing isoform (PrPSc). PrPC and PrPSc have distinct conformations: PrPC is rich in a-helical content and has little b-sheet structure, whereas PrPSc has less a-helical content and is rich in b-sheet structure (Pan et al. 1993). The conformational conversion of PrPC to PrPSc is the fundamental event underlying prion diseases. In this article, we provide an introduction to prions and the diseases they cause. © 2011 Cold Spring Harbor Laboratory Press. Source


Ruffolo D.,Mahidol University | Matthaeus W.H.,University of Delaware
Physics of Plasmas | Year: 2013

When a magnetic field consists of a mean part and fluctuations, the stochastic wandering of its field lines is often treated as a diffusive process. Under suitable conditions, a stable value is found for the mean square transverse displacement per unit parallel displacement relative to the mean field. Here, we compute the associated field line diffusion coefficient for a highly anisotropic "noisy" reduced magnetohydrodynamic model of the magnetic field, which is useful in describing low frequency turbulence in the presence of a strong applied DC mean magnetic field, as may be found, for example, in the solar corona, or in certain laboratory devices. Our approach is nonperturbative, based on Corrsin's independence hypothesis, and makes use of recent advances in understanding factors that control decorrelation over a range of parameters described by the Kubo number. Both Bohm and quasilinear regimes are identified. © 2013 American Institute of Physics. Source


Klemas V.,University of Delaware
Journal of Coastal Research | Year: 2012

High concentrations of nutrients from agricultural and urban runoff, or those produced by coastal upwelling, are causing algal blooms in many estuaries and coastal waters. Algal blooms induce eutrophic conditions, depleting oxygen levels needed by organic life, limiting aquatic plant growth by reducing water transparency, and producing toxins that can harm fish, benthic animals, and humans. The magnitude and frequency of phytoplankton blooms have increased globally in recent decades, as shown in data from ocean-color sensors on-board satellites. Satellite and airborne measurements of spectral reflectance (ocean color) represent an effective way for monitoring phytoplankton by its proxy, chlorophyll-a, the green pigment that is present in all algae. This article reviews the use of remote sensing techniques for detecting phytoplankton and mapping algal blooms. Two case studies are presented, illustrating the advantages and limitations of satellite and airborne remote sensing. © 2012, the Coastal Education & Research Foundation (CERF). © 2012 Coastal Education & Research Foundation. Source


Klemas V.,University of Delaware
Journal of Coastal Research | Year: 2012

Ocean currents influence the global heat transport; weather and climate; larval transport; drift of water pollutants; sediment transport; and marine transportation. As a result, oceanographers, coastal managers, and ships need up-to-date information on ocean and coastal currents. Arrays of current meter moorings can measure currents at local scales. Shore-based high-frequency radars are able to map coastal currents over a range of up to 200 km. Ocean drifters can be tracked to obtain circulation patterns over larger areas, but may take months to accomplish it. Only satellite remote sensors can determine currents synoptically over extensive ocean and coastal regions. Satellite altimetry is one of the essential remote-sensing techniques for monitoring dynamic ocean conditions, including surface currents, local wind speed, and significant wave height. Satellite altimetry measures sea surface heights, providing data on geostrophic circulation, including major ocean currents. Ocean currents can also be determined by satellite synthetic aperture radar (SAR) or tracking the movement of thermal and color features in the ocean. The flow patterns of currents like the Gulf Stream are being mapped with satellite infrared scanners. The objective of this paper is to review practical remote-sensing techniques for measuring and mapping coastal and ocean currents. © 2012, the Coastal Education & Research Foundation (CERF). Source


Xu T.,InterDigital Communications | Xia X.-G.,University of Delaware
IEEE Transactions on Information Theory | Year: 2014

Gomadam recently proposed two distributed interference alignment algorithms, namely the zero-forcing and the maximal signal to interference plus noise ratio (max-SINR) algorithms. Both of them only require local channel state information and no symbol extension is needed. Then, Ning showed that when only one stream of information symbols is sent by each user, interference alignment may achieve receive diversity using the max-SINR algorithm. This result was, however, derived only based on an assumption. In this paper, using a different approach, we prove that interference alignment using the max-SINR algorithm indeed achieves receive diversity without the assumption used by Ning The result in this paper not only completes the proof of the result by Ning , but also generalizes it by allowing more than one stream of information symbols to be sent by each user. © 1963-2012 IEEE. Source


Klemas V.,University of Delaware
Journal of Coastal Research | Year: 2012

Coastal plumes, which carry run-off from land, influence the circulation patterns and ecology of nearby coastal areas, causing eutrophication, turbidity, and spread of harmful pollutants. They can be observed along many coasts. Estuarine and ocean fronts result when denser water under-rides lighter water giving rise to an inclined interface and a strong convergence at the surface, which can concentrate phytoplankton and pollutants. To detect and map fronts and plumes, remote sensors exploit their differences in turbidity, color, temperature, or salinity from ambient background water. The most effective remote sensing techniques for observing coastal plumes and estuarine/ocean fronts are reviewed. Studies are presented, which use data from multispectral and hyperspectral imagers, thermal infrared (TIR) radiometers, microwave radiometers, and Synthetic Aperture Radar (SAR). Mounted on satellites and aircraft, these sensors provide the spatial/temporal resolution and coverage needed for tracking plumes and fronts, including their high temporal and spatial variability. This article reviews the most effective remote sensing techniques for observing coastal plumes and ocean fronts and illustrates the application of these techniques in a case study. © 2012, the Coastal Education & Research Foundation (CERF). © 2012 Coastal Education & Research Foundation. Source


Klemas V.,University of Delaware
Journal of Coastal Research | Year: 2012

Oceanic internal waves can form at the interface (pycnocline) between layers of different water density and propagate long distances along the pycnocline. Internal waves on continental shelves are important because they can attain large amplitudes and affect acoustic wave propagation, submarine navigation, nutrient mixing in the euphotic zone, sediment resuspension, cross-shore pollutant transport, coastal engineering, and oil exploration. Internal waves induce local currents that modulate surface wavelets and slicks, causing patterns of alternating brighter and darker bands to appear on the surface. The surface patterns can be mapped by satellites using synthetic aperture radar (SAR) or visible imagers. The objectives of this article are to discuss methods for remotely studying and mapping ocean internal waves and to present examples illustrating the application of satellite remote sensing. © 2012, the Coastal Education & Research Foundation (CERF). Source


McDonald J.H.,University of Delaware
Genome Biology and Evolution | Year: 2010

Whether particular amino acids are favored by selection at high temperatures over others has long been an open question in protein evolution. One way to approach this question is to compare homologous sites in proteins from one thermophile and a closely related mesophile; asymmetrical substitution patterns have been taken as evidence for selection favoring certain amino acids over others. However, most pairs of prokaryotic species that differ in optimum temperature also differ in genome-wide GC content, and amino acid content is known to be associated with GC content. Here, I compare homologous sites in nine thermophilic prokaryotes and their mesophilic relatives, all with complete published genome sequences. After adjusting for the effects of differing GC content with logistic regression, 139 of the 190 pairs of amino acids show significant substitutional asymmetry, evidence of widespread adaptive amino acid substitution. The patterns are fairly consistent across the nine pairs of species (after taking the effects of differing GC content into account), suggesting that much of the asymmetry results from adaptation to temperature. Some amino acids in some species pairs deviate from the overall pattern in ways indicating that adaptation to other environmental or physiological differences between the species may also play a role. The property that is best correlated with the patterns of substitutional asymmetry is transfer free energy, a measure of hydrophobicity, with more hydrophobic amino acids favored at higher temperatures. The correlation of asymmetry and hydrophobicity is fairly weak, suggesting that other properties may also be important. © The Author(s) 2010. Source


Okada N.,University of Alabama | Shafi Q.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

We present a successful inflation model based on λφ4 potential in which a standard model (SM) singlet inflaton φ, with mass of around a TeV or less, also plays the role of a weakly interacting scalar dark matter particle (WIMP). The WIMP relic abundance generated after inflation is in accord with the current observations. The spectral index n s lies within the Wilkinson Microwave Anisotropy Probe (WMAP) satellite 1-σ bounds, while the Planck satellite may observe the tensor-to-scalar ratio, a canonical measure of gravity waves, which we estimate lies between 0.003 and 0.007. An unbroken Z 2 parity ensures that the scalar WIMP is absolutely stable. © 2011 American Physical Society. Source


The purposes of this study were to evaluate the effects of different formats of online group support (moderated vs peer-led) on depressive symptoms and extent of participation in women with breast cancer. A randomized longitudinal design was used to address the study aims. The setting was a secure password-protected Web page. Fifty women with breast cancer, at least 21 years old, who had Internet access participated. Subjects were randomly assigned to moderated or peer-led groups, given a password, and instructed to complete the study questionnaires at baseline and again at 6, 12, and 16 weeks. The independent variables were types of online support (moderated or peer-led), and the dependent variables were depressive symptoms and extent of participation. There were no significant differences in depressive symptoms by group or by extent of group participation. Moderated groups read and posted significantly more messages than did peer-led groups. This study adds to the research base on different group formats for online support and the extent of participation and nonparticipation (lurking) in online groups. It provides a springboard for additional studies that include ethnic minorities, people with different types of cancer, and men. © 2012 Lippincott Williams & Wilkins. Source


Sofla A.Y.N.,University of Toronto | Martin C.,University of Delaware
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2010

A straightforward and inexpensive method to increase the adhesion strength of polydimethylsiloxane (PDMS) and glass is described. In this method the targeted PDMS-glass sample is exposed to a fluoroalkyl trichlorosilane vapor in an enclosed container for a certain time. It is experimentally shown that the adhesion strength of the resulted interface depends on the exposure duration. Permanently bonded PDMS-glass interfaces were reliably achieved upon sufficient exposure to the vapor. This vapor-assisted method for adhering PDMS and glass does not require any special skill or equipment and therefore can be implemented at any laboratory. This method can be used for the simultaneous bonding of components and is suitable for the mass production of microfluidic devices. © 2010 The Royal Society of Chemistry. Source


Barr S.M.,University of Delaware
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

In the absence of low-energy supersymmetry, a multiplicity of weak-scale Higgs doublets would require additional fine-tunings unless they formed an irreducible multiplet of a non-Abelian symmetry. Remnants of such symmetry typically render some Higgs fields stable, giving several dark matter particles of various masses. The non-Abelian symmetry also typically gives simple, testable mass relations. © 2011 American Physical Society. Source


Heinz J.,University of Delaware | Idsardi W.,University of Maryland University College
Science | Year: 2011

Do humans learn the sentence and sound patterns of natural languages through distinct learning mechanisms? Source


Glass B.P.,University of Delaware | Simonson B.M.,Oberlin College
Elements | Year: 2012

During the formation of large impact structures, layers of melted and crushed rock (ejecta) are deposited over large areas of the Earth's surface. Ejecta thrown farther than 2.5 crater diameters are called distal ejecta. At distances greater than ∼10 crater diameters, the distal ejecta layers consist primarily of millimeter-scale glassy bodies (impact spherules) that form from melt and vapor-condensate droplets. At least 28 distal ejecta layers have been identified. Distal ejecta layers can be used to place constraints on cratering models, help fill gaps in the cratering record, and provide direct correlation between impacts and other terrestrial events. Source


Schultz J.M.,University of Delaware
Macromolecules | Year: 2012

The creation of thermal, compositional, and stress fields during the crystallization of polymers from the melt is described. The treatment of crystallization under self-generated fields is reviewed, including classical moving boundary problems, the treatment of dendrite growth, and coupled growth. The extension of these treatments to polymer crystallization requires that the velocity of interface motion be defined by the temperature and composition of the melt at the solid-liquid interface, a feature not found in extant analyses suitable for small-molecule systems and metals. Inclusion of this feature renders analytical solutions difficult and usually requires the use of numerical methods. The role of the diffusion length in defining morphological features is described. Methods of simulating the growth of polymer spherulites are reviewed. These include finite element, analytical, and phase field approaches. The role of thermal fields in fiber processing is discussed. Finally, speculations regarding the role of stress fields are presented. © 2012 American Chemical Society. Source


Oh S..-Y.,University of Ulsan | Son J..-G.,University of Ulsan | Chiu P.C.,University of Delaware
Environmental Toxicology and Chemistry | Year: 2013

Biochar, a subset of black carbon produced via pyrolysis of biomass, has received much attention in recent years due to its potential to address many important issues, from energy and climate to agriculture and environmental quality. Biochar is known to influence the fate and transport of organic contaminants, although its role has been generally assumed to be as an adsorbent. In this study, the authors investigated the ability of biochar to catalyze the reductive reactions of nitro herbicides and explosives. Two biochars, derived from poultry litter and wastewater biosolids, were found to promote the reductive removal of the dinitro herbicides pendimethalin and trifluralin and the explosives 2,4-dinitrotoluene and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by dithiothreitol. Parallel experiments using another black carbon material, graphite powder or granular activated carbon, in place of a biochar resulted in comparable rate enhancement to show reduction products, such as 2,4-diaminotoluene and formaldehyde. A cyclization product of trifluralin and reduction products of dinitrotoluene and RDX were detected only when biochar and dithiothreitol were both present, supporting the ability of biochar to promote redox reactions. Three possible catalysts, including graphene moieties, surface functional groups, and redox-active metals, in biochar may be responsible for the biochar-mediated reactions. The environmental significance, implications, and applications of this previously unrecognized role of biochar are discussed. Environ. Toxicol. Chem. 2013;32:501-508. © 2013 SETAC. Source


Hwang W.R.,Gyeongsang National University | Advani S.G.,University of Delaware
Physics of Fluids | Year: 2010

A new finite-element scheme to solve the Stokes-Brinkman equation for flow analyses in dual scale porous media is presented and has been applied to predict the effective permeability of dual scale fibrous media. Both continuous and discontinuous stress conditions at the interface between a porous media and a surrounding fluid are explored by introducing an equivalent momentum equation for the Brinkman equation. The proposed scheme uses a uniform structured regular rectangular mesh to discretize the domain and employs the level-set method to describe the porous media allowing for inclusion of complex geometrical features easily. Biperiodic boundary conditions have been applied to conduct the flow analysis in a representative volume of mesoscale porous structures. Numerical solutions in a parallel channel flow over a porous media are presented and compared with analytic solutions to assess the accuracy of the proposed scheme. The scheme is then applied to flow past two regular periodic geometries of elliptic porous media in two dimension, representing unidirectional fiber tow (bundle of aligned fibers) in a textile fabric, to predict the effective permeability and its dependence on the fiber volume fraction, the aspect ratio, the fiber tow permeability, and the degree of compaction of the fiber tows. In addition, we propose a simple relationship between the effective permeability and the permeability of fiber tow, based on numerical and analytic results. © 2010 American Institute of Physics. Source


Carterette B.A.,University of Delaware
ACM Transactions on Information Systems | Year: 2012

High-quality reusable test collections and formal statistical hypothesis testing together support a rigorous experimental environment for information retrieval research. But as Armstrong et al. [2009b] recently argued, global analysis of experiments suggests that there has actually been little real improvement in ad hoc retrieval effectiveness over time. We investigate this phenomenon in the context of simultaneous testing of many hypotheses using a fixed set of data. We argue that the most common approaches to significance testing ignore a great deal of information about the world. Taking into account even a fairly small amount of this information can lead to very different conclusions about systems than those that have appeared in published literature.We demonstrate how to model a set of IR experiments for analysis both mathematically and practically, and show that doing so can cause p-values from statistical hypothesis tests to increase by orders of magnitude. This has major consequences on the interpretation of experimental results using reusable test collections: it is very difficult to conclude that anything is significant once we have modeled many of the sources of randomness in experimental design and analysis. © 2012 ACM. Source


Porosoff M.D.,University of Delaware | Yang X.,Brookhaven National Laboratory | Boscoboinik J.A.,Brookhaven National Laboratory | Chen J.G.,Columbia University
Angewandte Chemie - International Edition | Year: 2014

Rising atmospheric CO2 is expected to have negative effects on the global environment from its role in climate change and ocean acidification. Utilizing CO2 as a feedstock to make valuable chemicals is potentially more desirable than sequestration. A substantial reduction of CO2 levels requires a large-scale CO2 catalytic conversion process, which in turn requires the discovery of low-cost catalysts. Results from the current study demonstrate the feasibility of using the non-precious metal material molybdenum carbide (Mo2C) as an active and selective catalyst for CO2 conversion by H2. Active, selective, and cheap: Mo2C and cobalt-modified Mo2C were both shown to be effective catalysts for CO2 conversion by hydrogen in flow reactor experiments over powder catalysts. In-situ XANES measurements verified that Mo2C can undergo an oxidation-carburization cycle. Modifying Mo 2C with small amounts of cobalt further improved catalytic performance. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Lenhoff A.M.,University of Delaware
Journal of Chromatography A | Year: 2011

A wide variety of stationary phases is available for use in preparative chromatography of proteins, covering different base matrices, pore structures and modes of chromatography. There has recently been significant growth in the number of such materials in which the base matrix is derivatized to add a covalently attached or grafted polymer layer or, in some cases, a hydrogel that fills the pore space. This review summarizes the main structural and functional features of ion exchangers of this kind, which represent the largest class of such materials. Although the adsorption and transport properties may generally be used operationally and modeled phenomenologically using the same methods as are used for proteins in conventional media, there are noteworthy mechanistic differences in protein behavior in these adsorbents. A fundamental difference in protein retention is that it may be portrayed as partitioning into a three-dimensional polymer phase rather than adsorption at an extended two-dimensional surface, as applies in more conventional media. Beyond this partitioning behavior, however, the polymer-functionalized media often display rapid intraparticle transport that, while qualitatively comparable to that in conventional media, is sufficiently rapid quantitatively under certain conditions that it can lead to clear benefits in key measures of performance such as the dynamic binding capacity. Although possible mechanistic bases for the retention and transport properties are discussed, appreciable areas of uncertainty make detailed mechanistic modeling very challenging, and more detailed experimental characterization is likely to be more productive. © 2011 Elsevier B.V. Source


Bhatt R.S.,University of Kentucky | Quinn P.C.,University of Delaware
Infancy | Year: 2011

Pattern perception and organization are critical functions of the visual cognition system. Many organizational processes are available early in life, such that infants as young 3 months of age are able to readily utilize a variety of cues to organize visual patterns. However, other processes are not readily evident in young infants, and their development involves perceptual learning. We describe a theoretical framework that addresses perceptual learning in infancy and the manner in which it affects visual organization and development. It identifies five kinds of experiences that induce learning, and suggests that they work via attentional and unitization mechanisms to modify visual organization. In addition, the framework proposes that this kind of learning is abstract, domain general, functional at different ages in a qualitatively similar manner, and has a long-term impact on development through a memory reactivation process. Although most models of development assume that experience is fundamental to development, very little is actually known about the process by which experience affects development. The proposed framework is an attempt to account for this process in the domain of perception. Copyright © International Society on Infant Studies (ISIS). Source


Dodson-Robinson S.E.,University of Delaware
Icarus | Year: 2016

Voyager 2 observations revealed that Neptune's internal luminosity is an order of magnitude higher than that of Uranus. If the two planets have similar interior structures and cooling histories, Neptune's luminosity can only be explained by invoking some energy source beyond gravitational contraction. This paper investigates whether centaur impacts could provide the energy necessary to produce Neptune's luminosity. The major findings are (1) that impacts on both Uranus and Neptune are too infrequent to provide luminosities of order Neptune's observed value, even for optimistic impact-rate estimates and (2) that Uranus and Neptune rarely have significantly different impact-generated luminosities at any given time. Uranus and Neptune most likely have structural differences that force them to cool and contract at different rates. © 2015 Elsevier Inc. Source


Holder J.,University of Delaware
Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011 | Year: 2011

The VERITAS telescope array has been operating smoothly since 2007, and has detected gammaray emission above 100 GeV from 40 astrophysical sources. These include blazars, pulsar wind nebulae, supernova remnants, gamma-ray binary systems, a starburst galaxy, a radio galaxy, the Crab pulsar, and gamma-ray sources whose origin remains unidentified. In 2009, the array was reconfigured, greatly improving the sensitivity. We summarize the current status of the observatory, describe some of the scientific highlights since 2009, and outline plans for the future. Source


Mustafa S.K.,Agency for Science, Technology and Research Singapore | Agrawal S.K.,University of Delaware
IEEE Transactions on Robotics | Year: 2012

It has been mathematically proven that a completely restrained n- degree-of-freedom (n-DOF) single rigid-bodied cable-driven platform requires a minimum of n + 1 cables with positive tension to fully constrain it. However, the force-closure analysis of open chains that are driven by cables is still an open question. For the case of an n -DOF cable-driven open chain, the following two important questions arise. 1) How can the force-closure analysis be carried out for a given cable routing configuration, while retaining the geometric insights of the problem? 2) Are n + 1 cables sufficient to fully constrain the entire chain? This paper addresses these issues by proposing a systematic and novel approach based on the reciprocal screw theory. The key idea is to express wrenches acting on the open chain as linear combinations of the reciprocal screws and determine the total required torques at each joint. This is followed by equating the joint torques that are provided by the cable forces with the joint torques, which are required by the external wrenches, and checking for force closure. The proposed methodology can analyze open chains with arbitrary cable routing configuration. The analysis shows that the entire n-DOF open chain requires a minimum of n + 1 cables to fully constrain it. © 2006 IEEE. Source


Jolit A.,University of Hawaii at Manoa | Walleser P.M.,University of Hawaii at Manoa | Yap G.P.A.,University of Delaware | Tius M.A.,University of Hawaii at Manoa
Angewandte Chemie - International Edition | Year: 2014

The diastereoselective asymmetric synthesis of vicinal all-carbon-atom quaternary stereocenters is a challenging problem in organic synthesis for which only few solutions have been described. A catalytic asymmetric Nazarov cyclization of fully substituted dienones that provides cyclopentenone derivatives with vicinal quaternary stereocenters in high optical purity and as single diastereoisomers is now reported. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Lee J.-Y.,University of Delaware | Lu H.,University of Maryland Baltimore County
Trends in Plant Science | Year: 2011

Plasmodesmata are intercellular channels that establish a symplastic communication pathway between neighboring cells in plants. Owing to this role, opportunistic microbial pathogens have evolved to exploit plasmodesmata as gateways to spread infection from cell to cell within the plant. However, although these pathogens have acquired the capacity to breach the plasmodesmal trafficking pathway, plants are unlikely to relinquish control over a structure essential for their survival so easily. In this review, we examine evidence that suggests plasmodesmata play an active role in plant immunity against viral, fungal and bacterial pathogens. We discuss how these pathogens differ in their lifestyles and infection modes, and present the defense strategies that plants have adopted to prevent the intercellular spread of an infection. © 2011 Elsevier Ltd. Source


Taber D.F.,University of Delaware | Tirunahari P.K.,Accel Synthesis Inc.
Tetrahedron | Year: 2011

The indole alkaloids, ranging from lysergic acid to vincristine, have long inspired organic synthesis chemists. Interest in developing new methods for indole synthesis has burgeoned over the past few years. These new methods have been fragmented across the literature of organic chemistry. In this review, we present a framework for the classification of all indole syntheses. © 2011 Elsevier Ltd. Source


Antoniewicz M.R.,University of Delaware
Current Opinion in Biotechnology | Year: 2013

Computational approaches for analyzing dynamic states of metabolic networks provide a practical framework for design, control, and optimization of biotechnological processes. In recent years, two promising modeling approaches have emerged for characterizing transients in cellular metabolism, dynamic metabolic flux analysis (DMFA), and dynamic flux balance analysis (DFBA). Both approaches combine metabolic network analysis based on pseudo steady-state (PSS) assumption for intracellular metabolism with dynamic models for extracellular environment. One strategy to capture dynamics is by combining network analysis with a kinetic model. Predictive models are thus established that can be used to optimize bioprocessing conditions and identify useful genetic manipulations. Alternatively, by combining network analysis with methods for analyzing extracellular time-series data, transients in intracellular metabolic fluxes can be determined and applied for process monitoring and control. © 2013 Elsevier Ltd. Source


Faraz A.,HEC School of Management | Saniga E.,University of Delaware
Quality and Reliability Engineering International | Year: 2013

Control charts are the primary tools of statistical process control. These charts may be designed by using a simple rule suggested by Shewhart, a statistical criterion, an economic criterion, or a joint economic statistical criterion. Each method has its strengths and weaknesses. One weakness of the methods of design listed is their lack of flexibility and adaptability, a primary objective of practical mathematical models. In this article, we explore multiobjective models as an alternative for the methods listed. These provide a set of optimal solutions rather than a single optimal solution and thus allow the user to tailor their solution to the temporal imperative of a specific industrial situation. We present a solution to a well-known industrial problem and compare optimal multiobjective designs with economic designs, statistical designs, economic statistical designs, and heuristic designs. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd. Source


Herres J.,Drexel University | Kobak R.,University of Delaware
Journal of Abnormal Child Psychology | Year: 2014

Negative interpersonal events have been consistently identified as both antecedents and sequalae of adolescent depressive symptoms. However, little is known about the relative contributions of specific domains of interpersonal events (parents, peers or teachers) to the maintenance of depressive symptoms during early adolescence or whether a lack of positive interpersonal interactions plays a direct role in maintaining depressive symptoms. Further, few studies have examined whether positive interpersonal events moderate associations between negative events and adolescents’ depressive symptoms. This study combined stress generation and exposure models to evaluate the contribution of daily events to the maintenance of depressive symptoms in a sample of 132 adolescents (53 % female) followed from ages 13 to 15. Daily phone diaries collected at age 14 assessed adolescents’ negative and positive interactions with parents, teachers, and peers in a sample of adolescents from economically disadvantaged families. Negative peer events uniquely accounted for the maintenance of depressive symptoms over the 2 years period. Results did not differ by gender; however, positive parent events buffered the effects of negative parent events for females but not for males. Findings highlight the significance of peer relationships during a period of vulnerability for depressive symptoms. © 2014, Springer Science+Business Media New York. Source


Tamburro A.,University of Delaware
Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment | Year: 2014

Analysis of cosmic ray surface data collected with the IceTop array of Cherenkov detectors at the South Pole provides an accurate measurement of the cosmic ray spectrum and its features in the "knee" region up to energies of about 1 EeV. IceTop is part of the IceCube Observatory that includes a deep-ice cubic kilometer detector that registers signals of penetrating muons and other particles. Surface and in-ice signals detected in coincidence provide clear insights into the nuclear composition of cosmic rays. IceCube already measured an increase of the average primary mass as a function of energy. We present preliminary results on both IceTop-only and coincident events analysis. Furthermore, we review the recent measurement of the cosmic ray anisotropy with IceCube. © 2013 Elsevier B.V. Source


Messer K.D.,University of Delaware
Ecological Economics | Year: 2010

Protecting endangered species that offer poachers from low-income countries high economic benefits remains a policy challenge. A broadly applicable economic model of poaching shows why CITES international bans have not always been successful, especially in situations where black markets exist and nonpoaching wages are low. In these situations, poachers may have nothing left to lose, since low nonpoaching wages impose a practical cap on the potential economic costs of fines and imprisonment. Thus, the model suggests "shoot-on-sight" policies as the only viable option. Trends in animal populations appear to support the efficacy of the shoot-on-sight policies, which also suggests an inherent value of life traditionally not captured in Value of a Statistical Life estimates. © 2010 Elsevier B.V. Source


Singh A.,University of Delaware
IEEE Transactions on Nanobioscience | Year: 2011

Genetically identical cell populations exposed to the same environment can exhibit considerable cell-to-cell variation in the levels of specific proteins. This variation or expression noise arises from the inherent stochastic nature of biochemical reactions that constitute gene expression. Negative feedback loops are common motifs in gene networks that reduce expression noise and intercellular variability in protein levels. Using stochastic models of gene expression we here compare different feedback architectures in their ability to reduce stochasticity in protein levels. A mathematically controlled comparison shows that in physiologically relevant parameter regimes, feedback regulation through the mRNA provides the best suppression of expression noise. Consistent with our theoretical results we find negative feedback loops though the mRNA in essential eukaryotic genes, where feedback is mediated via intron-derived microRNAs. Finally, we find that contrary to previous results, protein-mediated translational regulation may not always provide significantly better noise suppression than protein-mediated transcriptional regulation. © 2006 IEEE. Source


Sharp J.H.,University of Delaware
Limnology and Oceanography | Year: 2010

Hypoxia and anoxia occurred in the upper Delaware Estuary throughout much of the 20th century and diminished over the past several decades. I reviewed 30 yr of data from my laboratory's research efforts, 40 yr of consistent monitoring data from a multistate agency, results from inconsistent data collection from the past century and anecdotal information to construct a long-time picture of the decline and increase of dissolved oxygen concentrations (DO) in the urban region of the estuary. The primary cause of the DO decline appeared to be inputs or allochthonous materials from urban sources (reduced nitrogen and carbon). In spite of extremely high nutrient concentrations, excess algal production did not influence DO anywhere along the tidal freshwater stretch or the saline portion of the well-mixed Delaware Estuary; and it does not have an influence today. The nutrient loading to the Delaware Estuary is very high, yet the typical signs of eutrophication are not obvious. Based on a model of apparent oxygen utilization, the Delaware Bay apparently had higher primary production 50 yr ago, a time when nutrient concentrations were as high or higher than today, shellfish and finfish production were apparently also higher and DO was close to saturation. This analysis is offered as guidance in assessing and managing estuarine eutrophication, which is too of ten considered narrowly to be the result of inadvertent overfertilization by nutrients or a single nutrient element. © 2010, by the American Society of Limnology and Oceanography, Inc. Source


Warren J.M.,University of Delaware
Lithos | Year: 2016

Abyssal peridotites are ultramafic rocks collected from mid-ocean ridges that are the residues of adiabatic decompression melting. Their compositions provide information on the degree of melting and melt-rock interaction involved in the formation of oceanic lithosphere, as well as providing constraints on pre-existing mantle heterogeneities. This review presents a compilation of abyssal peridotite geochemical data (modes, mineral major elements, and clinopyroxene trace elements) for > 1200 samples from 53 localities on 6 major ridge systems. On the basis of composition and petrography, peridotites are classified into one of five lithological groups: (1) residual peridotite, (2) dunite, (3) gabbro-veined and/or plagioclase-bearing peridotite, (4) pyroxenite-veined peridotite, and (5) other types of melt-added peridotite. Almost a third of abyssal peridotites are veined, indicating that the oceanic lithospheric mantle is more fertile, on average, than estimates based on residual peridotites alone imply. All veins appear to have formed recently during melt transport beneath the ridge, though some pyroxenites may be derived from melting of recycled oceanic crust.A limited number of samples are available at intermediate and fast spreading rates, with samples from the East Pacific Rise indicating high degrees of melting. At slow and ultra-slow spreading rates, residual abyssal peridotites define a large (0-15% modal clinopyroxene and spinel Cr# = 0.1-0.6) compositional range. These variations do not match the prediction for how degree of melting should vary as a function of spreading rate. Instead, the compositional ranges of residual peridotites are derived from a combination of melting, melt-rock interaction and pre-existing compositional variability, where melt-rock interaction is used here as a general term to refer to the wide range of processes that can occur during melt transport in the mantle. Globally, ~10% of abyssal peridotites are refractory (0% clinopyroxene, spinel Cr# > 0.5, bulk Al2O3 < 1 wt.%) and some ridge sections are dominated by harzburgites while lacking a significant basaltic crust. Abyssal ultramafic samples thus indicate that the mantle is multi-component, probably consisting of at least three components (lherzolite, harzburgite, and pyroxenite). Overall, the large compositional range among residual and melt-added peridotites implies that the oceanic lithospheric mantle is heterogeneous, which will lead to the generation of further heterogeneities upon subduction back into the mantle. © 2016 The Author. Source


Driscoll T.A.,University of Delaware
Journal of Computational Physics | Year: 2010

Automatic Chebyshev spectral collocation methods for Fredholm and Volterra integral and integro-differential equations have been implemented as part of the chebfun software system. This system enables a symbolic syntax to be applied to numerical objects in order to pose and solve problems without explicit references to discretization. The same objects can be used in matrix-free iterative methods in linear algebra, in order to avoid very large dense matrices or allow application to problems with nonsmooth coefficients. As a further application of the ability to implement operator equations, a method of Greengard . [1] for the recasting of differential equations as integral equations is generalized to . mth order boundary value and generalized eigenvalue problems. In the integral form, large condition numbers associated with differentiation matrices in high-order problems are avoided. The ability to implement the recasting process generally follows from implementation of the operator expressions in chebfun. The integral method also can be extended to first-order systems, although chebfun syntax does not currently allow easy implementation in this case. © 2010 Elsevier Inc. Source


Kumar D.,University of Delaware
Journal of orthopaedic research : official publication of the Orthopaedic Research Society | Year: 2012

It is important to know the magnitude and patterns of joint loading in people with knee osteoarthritis (OA), since altered loads are implicated in onset and progression of the disease. We used an EMG-driven forward dynamics model to estimate joint loads during walking in a subject with knee OA and a healthy control subject. Kinematic, kinetic, and surface EMG data were used to predict muscle forces using a Hill-type muscle model. The muscle forces were used to balance the frontal plane moment to obtain medial and lateral condylar loads. Loads were normalized to body weight (BWs) and the mean of three trials taken. The OA subject had greater medial and lower lateral loads compared to the control subject. Seventy-five to 80% of the total load was borne on the medial compartment in the control subject, compared to 90-95% in the OA subject. In fact, complete lateral unloading occurred during midstance for the OA subject. Loading for the healthy subject was consistent with the data from instrumented knee studies. In the future, the model can be used to analyze the impact of various interventions to reduce the loads on the medial compartment in people with knee OA. Copyright © 2011 Orthopaedic Research Society. Source


Pallis C.,University of Valencia | Shafi Q.,University of Delaware