Time filter

Source Type

Raleigh, NC, United States

North Carolina State University, officially North Carolina State University at Raleigh, is a public, coeducational, research university located in Raleigh, North Carolina, United States. Commonly known as NC State or simply State, the university is part of the University of North Carolina system and is a land, sea, and space grant institution. The university forms one of the corners of the Research Triangle together with Duke University in Durham and The University of North Carolina at Chapel Hill.The North Carolina General Assembly founded the North Carolina College of Agriculture and Mechanic Arts, now NC State, on March 7, 1887, as a land-grant college. Today, NC State has an enrollment of more than 34,000 students, making it the largest university in the Carolinas. NC State has historical strengths in engineering, agriculture, life science, textiles and design and now offers 106 bachelor's degrees. The graduate school offers 104 master's degrees, 61 doctoral degrees, and a Doctor of Veterinary Medicine. Wikipedia.

Tracy J.B.,North Carolina State University | Crawford T.M.,University of South Carolina
MRS Bulletin | Year: 2013

This article reviews the principles of magnetic field-directed self-assembly (MFDSA) of magnetic nanoparticles (MNPs), along with recent studies that advance the fundamental understanding and potential capabilities of MNP MFDSA. This technology could eventually find application in manufacturing novel materials and components for biomedicine, energy, optics, functional composites, and microfluidics. In MFDSA, an externally applied field drives the assembly of MNPs. Uniform fields can create complex chains of MNPs, while inhomogeneous fields (such as those created by permanent magnets) apply attractive forces to MNPs that pull them toward the region of strongest field strength. Thus, MNPs can be self-organized as well as directed into user-designed patterns by controlling the external field arrangement. Because of its biocompatibility, nanoscale resolution, and low cost, MFDSA is a highly versatile technique that could enable high volume nanomanufacturing of MNPs into complex, finished materials. © 2013 Materials Research Society.

Vale M.M.,Federal University of Rio de Janeiro | Jenkins C.N.,North Carolina State University
Journal of Biogeography | Year: 2012

If biological collections tend to be taken near accessible areas, and the number of such areas is limited, then we should expect a similar spatial distribution of collecting effort across taxa. Alternatively, if researchers working on a given taxon pick collection localities based on idiosyncratic criteria, then there should be no spatial similarity in collecting effort. This study compares the spatial distribution of collecting effort for plants and birds in Amazonia. Collection localities were transformed into a Thiessen network where polygon size works as a surrogate for collecting effort. A correlation between botanical and ornithological datasets, with an adjustment for spatial autocorrelation, showed little congruence in the spatial distribution of collecting effort between the two taxa. This incongruence of the distribution of collection effort among taxa suggests that the identification of priority areas for research, and correction for Wallacean and Linnean shortfalls based on taxon-specific studies, should not be generalized. © 2012 Blackwell Publishing Ltd.

Bonner J.C.,North Carolina State University
Proceedings of the American Thoracic Society | Year: 2010

Nanotechnology holds the promise of revolutionizing our society, bringing numerous beneficial innovations to improve structural materials, electronics, energy, medical imaging, and drug delivery, among other applications. However, nanomaterials present potential safety concerns, and there is accumulating evidence to suggest that nanoparticles may exert adverse effects on the lung and other organ systems. This article will overview the potential risks of engineered nanoparticles and nanotechnology on the respiratory system and highlight recent findings related to pulmonary and systemic effects of inhaled nanoparticles. Special emphasis will be given to carbon nanotubes and the possibility that these nanoparticles could represent an emerging risk for environmental and occupational lung disease, especially in individuals with pre-existing respiratory diseases such as asthma.

Dunn R.R.,North Carolina State University
Biotropica | Year: 2010

Increasingly, we view nature through a utilitarian lens that leads us to attempt to measure and manage the services that species, habitats and ecosystems provide. Surprisingly, we have tended to consider only the positive values of ecosystems, their ecosystem services. In addition to providing our food and water, Nature also kills us, primarily through disease. If we are to effectively manage the terrestrial Earth, we need to also manage species, habitats and ecosystems so as to minimize such 'ecosystem disservices'. I consider what we know about the spatial pattern of one disservice, pathogen prevalence and how changes in habitat influence it. I consider the effects of habitat changes on pathogen prevalence and, consequently, ecosystem disservices. In the end, we need to weigh both the costs and the benefits of particular ecosystems, habitats and species - to consider the bad with the good. Doing so requires that we learn much more about the biota than we currently know. © 2010 The Author(s). Journal compilation © 2010 by The Association for Tropical Biology and Conservation.

Wohlgenant M.K.,North Carolina State University
American Journal of Agricultural Economics | Year: 2010

An imperfectly competitive model of processor (packer) behavior is formulated to estimate welfare effects from restricting alternative marketing arrangements of livestock procured by packers. Pork was aggregated into a composite good and hog supply was partitioned into negotiated (spot), contract, and packer-owned. The model was estimated with the dynamic SUR method using weekly Mandatory Price Reporting (MPR) hog and pork data from 2001 to 2005. The model incorporates production uncertainty by modeling expected pork output as expected output in the input demand functions. The welfare effects from banning packer-owned hogs indicate that independent producers, consumers, and packers all would lose. © The Author (2010).

Magwire M.M.,North Carolina State University
PLoS genetics | Year: 2010

Understanding the genetic and environmental factors that affect variation in life span and senescence is of major interest for human health and evolutionary biology. Multiple mechanisms affect longevity, many of which are conserved across species, but the genetic networks underlying each mechanism and cross-talk between networks are unknown. We report the results of a screen for mutations affecting Drosophila life span. One third of the 1,332 homozygous P-element insertion lines assessed had quantitative effects on life span; mutations reducing life span were twice as common as mutations increasing life span. We confirmed 58 mutations with increased longevity, only one of which is in a gene previously associated with life span. The effects of the mutations increasing life span were highly sex-specific, with a trend towards opposite effects in males and females. Mutations in the same gene were associated with both increased and decreased life span, depending on the location and orientation of the P-element insertion, and genetic background. We observed substantial--and sex-specific--epistasis among a sample of ten mutations with increased life span. All mutations increasing life span had at least one deleterious pleiotropic effect on stress resistance or general health, with different patterns of pleiotropy for males and females. Whole-genome transcript profiles of seven of the mutant lines and the wild type revealed 4,488 differentially expressed transcripts, 553 of which were common to four or more of the mutant lines, which include genes previously associated with life span and novel genes implicated by this study. Therefore longevity has a large mutational target size; genes affecting life span have variable allelic effects; alleles affecting life span exhibit antagonistic pleiotropy and form epistatic networks; and sex-specific mutational effects are ubiquitous. Comparison of transcript profiles of long-lived mutations and the control line reveals a transcriptional signature of increased life span.

Staicu A.-M.,North Carolina State University
Biometrika | Year: 2010

We present new approaches to analyzing case-control studies using prospective likelihood methods. In the classical framework, we extend the equality of the profile likelihoods to the Barndorff-Nielsen modified profile likelihoods for prospective and retrospective models. This enables simple and accurate approximate conditional inference for stratified case-control studies of moderate stratum size. In the Bayesian framework, we provide sufficient conditions on priors for the prospective model parameters to yield a prospective marginal posterior density equal to its retrospective counterpart. Our results extend the prospective-retrospective equivalence in the Bayesian paradigm with a more general class of priors than has previously been investigated. © 2010 Biometrika Trust.

Moore S.R.,North Carolina State University
Renewable Agriculture and Food Systems | Year: 2010

Modern agriculture relies heavily on fossil energy for food production. Reducing fossil energy and replacing that energy with renewable energy is critical in attaining a sustainable food system. Hand-scale intensive food production offers a reduction in fossil energy and an increased use of renewable human-based energy. Using biointensive production techniques, onions (Allium cepa) were grown in Pennsylvania, USA. A life-cycle analysis was performed to monitor energy utilization. Individual human labor tasks were evaluated using the factor method. This method accounts for the type and duration of physical activity. The average yield of eight onion varieties utilizing biointensive production in standard-sized beds (9.3 m2;100 ft2) was 160.2 kg. The US average for mechanical onion production is 46.1 kg/9.3 m 2 (100 ft2). The energy efficiency ratio, specific energy and energy productivity were 51.5, 0.03 MJ kg1 and 32.2 kg MJ 1 (MJ=megajoule), respectively. When defined within common boundaries, these three relationships: energy input, energy output and yield productivity allow researchers, farmers and policy-makers to select production systems and/or practices that better manage fossil and renewable energy for food production. Current mechanized agriculture has an energy efficiency ratio of 0.9. With most energy being supplied by fossil fuels. The energy efficiency for biointensive production of onions in our study was over 50 times higher than this value (51.5) and 83% of the total energy required is renewable energy. Biointensive production offers a viable energy use alternative to current production practices and may contribute to a more sustainable food system. Copyright © Cambridge University Press 2010.

Nadakuditi R.R.,University of Michigan | Silverstein J.W.,North Carolina State University
IEEE Journal on Selected Topics in Signal Processing | Year: 2010

The detection problem in statistical signal processing can be succinctly formulated: given $m$ (possibly) signal bearing, $n$ -dimensional signal-plus-noise snapshot vectors (samples) and $N$ statistically independent $n$-dimensional noise-only snapshot vectors, can one reliably infer the presence of a signal? This problem arises in the context of applications as diverse as radar, sonar, wireless communications, bioinformatics, and machine learning and is the critical first step in the subsequent signal parameter estimation phase. The signal detection problem can be naturally posed in terms of the sample generalized eigenvalues. The sample generalized eigenvalues correspond to the eigenvalues of the matrix formed by whitening the signal-plus-noise sample covariance matrix with the noise-only sample covariance matrix. In this paper, we prove a fundamental asymptotic limit of sample generalized eigenvalue-based detection of signals in arbitrarily colored noise when there are relatively few signal bearing and noise-only samples. Specifically, we show why when the (eigen) signal-to-noise ratio (SNR) is below a critical value, that is a simple function of $n$ , $m$, and $N$, then reliable signal detection, in an asymptotic sense, is not possible. If, however, the eigen-SNR is above this critical value then a simple, new random matrix theory-based algorithm, which we present here, will reliably detect the signal even at SNRs close to the critical value. Numerical simulations highlight the accuracy of our analytical prediction, permit us to extend our heuristic definition of the effective number of identifiable signals in colored noise and display the dramatic improvement in performance relative to the classical estimator by Zhao We discuss implications of our result for the detection of weak and/or closely spaced signals in sensor array processing, abrupt change detection in sensor networks, and clustering methodologies in machine learning. © 2010 IEEE.

Krim J.,North Carolina State University
Advances in Physics | Year: 2012

This review provides an overview of recent advances that have been achieved in understanding the basic physics of friction and energy dissipation in molecularly thin adsorbed films and the associated impact on friction at microscopic and macroscopic length scales. Topics covered include a historical overview of the fundamental understanding of macroscopic friction, theoretical treatments of phononic and electronic energy dissipation mechanisms in thin films, and current experimental methods capable of probing such phenomena. Measurements performed on adsorbates sliding in unconfined geometries with the quartz crystal microbalance technique receive particular attention. The final sections review the experimental literature of how measurements of sliding friction in thin films reveal energy dissipation mechanisms and how the results can be linked to film-spreading behavior, lubrication, film phase transitions, superconductivity-dependent friction, and microelectromechanical systems applications. Materials systems reported on include adsorbed films comprised of helium, neon, argon, krypton, xenon, water, oxygen, nitrogen, carbon monoxide, ethane, ethanol, trifluoroethanol, methanol, cyclohexane, ethylene, pentanol, toluene, tricresylphosphate, t-butylphenyl phosphate, benzene, and iodobenzene. Substrates reported on include silver, gold, aluminum, copper, nickel, lead, silicon, graphite, graphene, fullerenes, C60, diamond, carbon, diamond-like carbon, and YBa2Cu3O7, and self-assembled monolayers consisting of tethered polymeric molecules. © 2012 Taylor & Francis Group.

Aiyyer A.,North Carolina State University | Thorncroft C.,Albany State University
Journal of Climate | Year: 2011

Spatiotemporal patterns of tropics-wide vertical shear variability are extracted after separating a 58-yr data record into high-frequency (HF, periods of 1.5-8 yr) and low-frequency (LF, periods greater than 8 yr) components. The HF vertical shear variability is dominated by circulation anomalies associated with the El Niño-Southern Oscillation (ENSO). The LF variability is primarily contained in two multidecadal patterns and a near-decadal pattern. The multidecadal modes are strongest within the tropical Atlantic and are correlated with Sahel precipitation and interhemispheric sea surface temperature (SST) anomalies. The results suggest that the multidecadal variability of vertical shear over the Atlantic is linked to atmospheric circulation anomalies forced by the variability in Sahel precipitation. The decadal mode is strongest within the central Pacific and is correlated with Pacific decadal oscillation (PDO)-like SST anomalies. The circulation associated with this anomalous shear pattern appears to be consistent with the atmospheric response to the PDO-related diabatic heating anomaly over the central Pacific. The relationship between vertical shear and seasonal tropical cyclone activity, as defined by the accumulated cyclone energy (ACE), is examined for the Atlantic, eastern Pacific, and western Pacific Oceans. The results show that global modes of vertical shear and seasonal average ACE are not consistently related in all three regions. It is only in the Atlantic Ocean that seasonal ACE is most consistently limited by vertical shear. This calls into question the utility of vertical shear as an independent predictor of seasonal tropical cyclone activity, particularly over the western Pacific Ocean. © 2011 American Meteorological Society.

Patisaul H.B.,North Carolina State University | Jefferson W.,National Health Research Institute
Frontiers in Neuroendocrinology | Year: 2010

Phytoestrogens are plant derived compounds found in a wide variety of foods, most notably soy. A litany of health benefits including a lowered risk of osteoporosis, heart disease, breast cancer, and menopausal symptoms, are frequently attributed to phytoestrogens but many are also considered endocrine disruptors, indicating that they have the potential to cause adverse health effects as well. Consequently, the question of whether or not phytoestrogens are beneficial or harmful to human health remains unresolved. The answer is likely complex and may depend on age, health status, and even the presence or absence of specific gut microflora. Clarity on this issue is needed because global consumption is rapidly increasing. Phytoestrogens are present in numerous dietary supplements and widely marketed as a natural alternative to estrogen replacement therapy. Soy infant formula now constitutes up to a third of the US market, and soy protein is now added to many processed foods. As weak estrogen agonists/antagonists with molecular and cellular properties similar to synthetic endocrine disruptors such as Bisphenol A (BPA), the phytoestrogens provide a useful model to comprehensively investigate the biological impact of endocrine disruptors in general. This review weighs the evidence for and against the purported health benefits and adverse effects of phytoestrogens. © 2010.

Jewett S.A.,Purdue University | Ivanisevic A.,North Carolina State University
Accounts of Chemical Research | Year: 2012

In a variety of applications where the electronic and optical characteristics of traditional, siliconbased materials are inadequate, recently researchers have employed semiconductors made from combinations of group III and V elements such as InAs. InAs has a narrow band gap and very high electron mobility in the near-surface region, which makes it an attractive material for high performance transistors, optical applications, and chemical sensing. However, silicon-based materials remain the top semiconductors of choice for biological applications, in part because of their relatively low toxicity. In contrast to silicon, InAs forms an unstable oxide layer under ambient conditions, which can corrode over time and leach toxic indium and arsenic components. To make InAs more attractive for biological applications, researchers have investigated passivation, chemical and electronic stabilization, of the surface by adlayer adsorption. Because of the simplicity, low cost, and flexibility in the type of passivating molecule used, many researchers are currently exploring wet-chemical methods of passivation.This Account summarizes much of the recent work on the chemical passivation of InAs with a particular focus on the chemical stability of the surface and prevention of oxide regrowth. We review the various methods of surface preparation and discuss how crystal orientation affects the chemical properties of the surface. The correct etching of InAs is critical as researchers prepare the surface for subsequent adlayer adsorption. HCl etchants combined with a postetch annealing step allow the tuning of the chemical properties in the near-surface region to either arsenic- or indium-rich environments. Bromine etchants create indium-rich surfaces and do not require annealing after etching; however, bromine etchants are harsh and potentially destructive to the surface. The simultaneous use of NH4OH etchants with passivating molecules prevents contact with ambient air that can occur during sample transfer between solutions. The passivation of InAs is dominated by sulfur-based molecules, which form stable In-S bonds on the InAs surface. Both sulfides and alkanethiols form well-defined monolayers on InAs and are dominated by In-S interactions. Sulfur-passivated InAs surfaces prevent regrowth of the surface oxide layer and are more stable in air than unpassivated surfaces.Although functionalization of InAs with sulfur-based molecules effectively passivates the surface, future sensing applications may require the adsorption of functional biomolecules onto the InAs surface. Current research in this area focuses on the passivation abilities of biomolecules such as collagen binding peptides and amino acids. These biomolecules can physically adsorb onto InAs, and they demonstrate some passivation ability but not to the extent of sulfur-based molecules. Because these adsorbents do not form covalent bonds with the InAs surface, they do not effectively block oxide regrowth. A mixed adlayer containing a biomolecule and a thiol on the InAs surface provides one possible solution: these hybrid surfaces enhance passivation but also maintain the presence of a biomolecule on the surface. Such surface functionalization strategies on InAs could provide long-term stability and make these surfaces suitable for biological applications. © 2012 American Chemical Society.

Fiske I.J.,North Carolina State University | Chandler R.B.,U.S. Geological Survey
Journal of Statistical Software | Year: 2011

Ecological research uses data collection techniques that are prone to substantial and unique types of measurement error to address scientic questions about species abundance and distribution. These data collection schemes include a number of survey methods in which unmarked individuals are counted, or determined to be present, at spatially- referenced sites. Examples include site occupancy sampling, repeated counts, distance sampling, removal sampling, and double observer sampling. To appropriately analyze these data, hierarchical models have been developed to separately model explanatory variables of both a latent abundance or occurrence process and a conditional detection process. Because these models have a straightforward interpretation paralleling mecha- nisms under which the data arose, they have recently gained immense popularity. The common hierarchical structure of these models is well-suited for a unied modeling in- terface. The R package unmarked provides such a unied modeling framework, including tools for data exploration, model tting, model criticism, post-hoc analysis, and model comparison.

Birge B.,North Carolina State University
2003 IEEE Swarm Intelligence Symposium, SIS 2003 - Proceedings | Year: 2013

A particle swarm optimization toolbox (PSOt) for use with the Matlab scientific programming environment has been developed. PSO is introduced briefly and then the use of the toolbox is explained with some examples. A link to downloadable code is provided. © 2003 IEEE.

Taluja P.S.,MaxLinear Inc. | Hughes B.L.,North Carolina State University
IEEE Journal on Selected Areas in Communications | Year: 2013

In order to support multiple antennas on compact wireless devices, transceivers are often designed with matching networks that compensate for mutual coupling. Some works have suggested that when optimal matching is applied to such a system, performance at the center frequency can be improved at the expense of an apparent reduction in the system bandwidth. This paper addresses the question of how coupling impacts bandwidth in the context of circular arrays. It will be shown that mutual coupling creates eigen-modes (virtual antennas) with diverse frequency responses, using the standard matching techniques. We shall also demonstrate how common communications techniques such as Diversity-OFDM would need to be optimized in order to compensate for these effects. © 1983-2012 IEEE.

Breitschwerdt E.B.,North Carolina State University
Parasites and Vectors | Year: 2015

Bartonella henselae, a flea-transmitted bacterium, causes chronic, zoonotic, blood stream infections in immunocompetent and immunocompromised patients throughout the world. As an intra-erythrocytic and endotheliotropic bacterium, B. henselae causes a spectrum of symptomatology ranging from asymptomatic bacteremia to fever, endocarditis and death. Veterinary workers are at occupational risk for acquiring bartonellosis. As an emerging, and incompletely understood, stealth bacterial pathogen, B. henselae may or may not have been responsible for the deaths of two veterinarians; however, recent evidence indicates that this genus is of much greater medical importance than is currently appreciated by the majority of the biomedical community. © 2015 Breitschwerdt; licensee BioMed Central.

Peters K.,North Carolina State University
Smart Materials and Structures | Year: 2011

Polymer optical fibers (POFs) have significant advantages for many sensing applications, including high elastic strain limits, high fracture toughness, high flexibility in bending, high sensitivity to strain and potential negative thermo-optic coefficients. The recent emergence of single-mode POFs has enabled high precision, large deformation optical fiber sensors. This article describes recent advances in both multi-mode and single-mode POF based strain and temperature sensors. The mechanical and optical properties of POFs relevant to strain and temperature applications are first summarized. POFs considered include multi-mode POFs, solid core single-mode POFs and microstructured single-mode POFs. Practical methods for applying POF sensors, including connecting and embedding sensors in structural materials, are also described. Recent demonstrations of multi-mode POF sensors in structural applications based on new interrogation methods, including backscattering and time-of-flight measurements, are outlined. The phase - displacement relation of a single-mode POF undergoing large deformation is presented to build a fundamental understanding of the response of single-mode POF sensors. Finally, this article highlights recent single-mode POF based sensors based on polymer fiber Bragg gratings and microstructured POFs.

Su W.,University of Michigan | Huang A.Q.,North Carolina State University
Applied Energy | Year: 2014

This paper proposes an innovative game theoretic framework for a next-generation retail electricity market (". Energy Internet") with high penetration of distributed residential electricity suppliers (". Energy Cells"). The envisioned Energy Internet is developed for plug-and-play of a large number of distributed renewable energy generation and energy storage. The residential customers, referred as Energy Cells, are not only the electricity consumers but can also be the electricity suppliers by locally operating and managing their own distributed generators, distributed energy storage devices, and dispatchable loads. This paper formulates a set of mathematical models of the retail electricity market participants with a number of local and global constraints. A numerical case study is performed to validate the proposed next-generation retail electricity market framework using game-theoretic methodologies. The numerical simulation results demonstrate the effectiveness of the proposed market clearing scheme with high penetration of distributed residential electricity suppliers. © 2014 Elsevier Ltd.

Cheng J.J.,North Carolina State University | Timilsina G.R.,The World Bank
Renewable Energy | Year: 2011

Development of biofuels from renewable resources is critical to the sustainability of the world's economy and to slow down the global climate change. Currently, a significant amount of bioethanol and biodiesel are produced as biofuels to partially replace gasoline and diesel, respectively, in the transportation sector worldwide. However, these biofuels represent a tiny portion (<4%) of the total fuels consumed. Furthermore, bioethanol is produced predominantly from sugarcane and corn, and biodiesel from crop and plant oils. Production of these raw materials is competing for the limited arable land against food and feed production. It is not feasible to tremendously increase biofuel production using the current technologies. Therefore, it is critical to investigate advanced or 2nd generation biofuel production technologies. This article is trying to summarize the current status of the 2nd generation biofuel technologies including bioethanol from lignocellulosic materials and biodiesel from microalgae. The summary includes the descriptions of the technologies, their advantages and challenges, feedstocks for the 2nd generation biofuels, the key barriers to their commercial applications, and future perspectives of the advanced technologies. © 2011 Elsevier Ltd.

Wallace A.D.,North Carolina State University
Progress in Molecular Biology and Translational Science | Year: 2012

Human exposure to chemicals in the environment can occur in an acute or chronic manner causing toxicity to different organs or resulting in other adverse health effects. To assess if chemicals encountered by humans in different environments have the potential to be toxic, both in vitro and in vivo testing models can be utilized and will be discussed in this chapter. The structures and function of different organs of the body often predispose these organs to being especially sensitive to chemical exposures. Specificity, a general description of endpoints of toxic action will be discussed in relation to carcinogenesis, hepatotoxicity, renal toxicity, neurotoxicity, reproductive toxicity, endocrine toxicity, and immunotoxicity. Examples of environmental chemicals causing toxicity will be provided, and endpoints will be discussed ranging from histopathological characteristics to gene expression profiling. © 2012 Elsevier Inc. All rights reserved.

When non-covalently bonded crystalline inclusion compounds (ICs) are formed by threading the host cyclic starches, cyclodextrins (CDs), onto guest polymer chains, and excess polymer is employed, non-stoichiometric (n-s)-polymer-CD-ICs, with partially uncovered and "dangling" chains result. The crystalline host CD lattice is stable to ~300 °C, and the uncovered, yet constrained, portions of the guest chains emanating from the CD-IC crystal surfaces behave very distinctly from their neat bulk samples. In CD-IC crystals formed with α- and γ-CD hosts, each containing, respectively, six and eight 1,4-α-linked glucose units, the channels constraining the threaded portions of the guest polymer chains are ~0.5 and 1.0 nm in diameter and are separated by ~1.4 and 1.7 nm. This results in dense brushes with ~0.6 and 0.4 chains/nm2 (or 0.8 if two guest chains are included in each γ-CD channel) of the un-included portions of guest polymers emanating from the host CD-IC crystal surfaces. In addition, at least some of the guest chains leaving from a crystalline CD-IC surface re-enter another CD-IC crystal creating a network structure that leads to shape-memory behavior for (n-s)-polymer-CD-ICs. To some extent, (n-s)-polymer-CD-ICs can be considered as dense polymer brushes with chains that are tethered on both ends. Not surprisingly, the behavior of the un-included portions of the guest polymer chains in (n-s)-polymer-CD-ICs are quite different from those of their neat bulk samples, with higher glass-transition and melt crystallization temperatures and crystallinities. Here we additionally compare their behaviors to samples coalesced from their stoichiometric ICs, and more importantly to dense polymer brushes formed by polymer chains chemically bonded to surfaces at only one end. Judging on the basis of their glass-transition, crystallization and melting temperatures, and crystallinities, we generally find the un-included portions of chains in (n-s)-polymer-CD-ICs to be more constrained than those in neat bulk as-received and coalesced samples and in high density brushes. The last observation is likely because many of the un-included chain portions in (n-s)-polymer-CD-ICs are tethered/constrained at both ends, while the chains in their dense brushes are tethered at only one end. © 2014 by the authors.

Schreck C.J.,North Carolina State University
Monthly Weather Review | Year: 2015

Convectively coupled atmospheric Kelvin waves are among the most prominent sources of synoptic-scale rainfall variability in the tropics, but large uncertainties surround their role in tropical cyclogenesis. This study identifies the modulation of tropical cyclones relative to the passage of a Kelvin wave's peak rainfall (i.e., its crest) in each basin. Tropical cyclogenesis is generally inhibited for 3 days before the crest and enhanced for 3 days afterward. Composites of storms forming in the most favorable lags illustrate the dynamical impacts of the waves. In most basins, the tropical cyclone actually forms during the convectively suppressed phase of the wave. The 850-hPa equatorial westerly anomalies provide the cyclonic vorticity for the nascent storm, and 200-hPa easterly anomalies enhance the outflow. The wind anomalies persist at both levels longer than the Kelvin wave's period and are often related to the Madden-Julian oscillation (MJO). The onset of these wind anomalies occurs with the Kelvin wave passage, while the MJO apparently establishes their duration. Many of the composites also show evidence of an easterly wave from which the tropical cyclone develops. The composite easterly wave amplifies or even initiates within the Kelvin wave crest. These results show the importance of Kelvin waves interacting with the MJO and easterly waves during tropical cyclogenesis. Given that Kelvin waves often circumnavigate the globe, these results show promise for long-range forecasting of tropical cyclogenesis in all basins. © 2015 American Meteorological Society.

Enck W.,North Carolina State University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Smartphone security research has become very popular in response to the rapid, worldwide adoption of new platforms such as Android and iOS. Smartphones are characterized by their ability to run third-party applications, and Android and iOS take this concept to the extreme, offering hundreds of thousands of "apps" through application markets. In response, smartphone security research has focused on protecting users from apps. In this paper, we discuss the current state of smartphone research, including efforts in designing new OS protection mechanisms, as well as performing security analysis of real apps. We offer insight into what works, what has clear limitations, and promising directions for future research. © 2011 Springer-Verlag.

Castellano F.N.,North Carolina State University
Accounts of Chemical Research | Year: 2015

Photofunctional molecules and assemblies lie at the heart of many important fundamental processes in nature, and researchers have generated multitudes of artificial chromophores intended to mimic these naturally occurring systems. As dynamic spectroscopic techniques are becoming more widely available, ultrafast techniques in particular, substantial insight continues to be gleaned from the initial photon stimulation event through internal conversion, structural rearrangements, intersystem crossing, energy migration, electron transfer events, and ultimately regeneration of the ground state chromophores in both naturally occurring and inspired chromophores.This Account details research endeavors motivated by the concept that merging organic and inorganic chromophores can lead to new molecules exhibiting novel excited state properties. Moreover, these excited state properties can be fundamentally understood using combinations of static and dynamic spectroscopic tools, yielding systematic improvements to molecules poised for application in diverse research areas including light-harvesting, lifetime engineering, photocatalysis, and photochemical upconversion. Initial explorations focused on utilizing Förster energy transfer processes in RuII-based metal-organic chromophores for solar light-harvesting while maintaining long excited state lifetimes. This eventually led to molecules exhibiting triplet-triplet energy transfer between energetically proximate triplet states featuring thermally activated photoluminescence from the upper charge transfer excited state with markedly extended lifetimes. Interest in systematically producing long-lived excited states with concomitant large Stokes shifts inspired the development of numerous PtII bipyridyl and terpyridyl acetylide charge transfer chromophores featuring ultrafast intramolecular energy migration, high quantum yield ligand-localized phosphorescence at room temperature, and synthetically tunable excited state absorption properties. This structural motif also made it possible to access the triplet excited states of perylenediimide chromophores, permitting quantitative examination of internal conversion and intersystem crossing processes in these complex molecules. The generation of new metal-organic structures featuring unique photophysics appears limitless and simply requires the continued ingenuity of researchers. (Figure Presented). © 2015 American Chemical Society.

Ksepka D.T.,North Carolina State University | Thomas D.B.,University of Cape Town
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

Africa hosts a single breeding species of penguin today, yet the fossil record indicates that a diverse array of now-extinct taxa once inhabited southern African coastlines. Here, we show that the African penguin fauna had a complex history involving multiple dispersals and extinctions. Phylogenetic analyses and biogeographic reconstructions incorporating new fossil material indicate that, contrary to previous hypotheses, the four Early Pliocene African penguin species do not represent an endemic radiation or direct ancestors of the living Spheniscus demersus (blackfooted penguin). A minimum of three dispersals to Africa, probably assisted by the eastward-flowing Antarctic Circumpolar and South Atlantic currents, occurred during the Late Cenozoic. As regional sea-level fall eliminated islands and reduced offshore breeding areas during the Pliocene, all but one penguin lineage ended in extinction, resulting in today's depleted fauna. © 2011 The Royal Society.

Andrady A.L.,North Carolina State University
Marine Pollution Bulletin | Year: 2011

This review discusses the mechanisms of generation and potential impacts of microplastics in the ocean environment. Weathering degradation of plastics on the beaches results in their surface embrittlement and microcracking, yielding microparticles that are carried into water by wind or wave action. Unlike inorganic fines present in sea water, microplastics concentrate persistent organic pollutants (POPs) by partition. The relevant distribution coefficients for common POPs are several orders of magnitude in favour of the plastic medium. Consequently, the microparticles laden with high levels of POPs can be ingested by marine biota. Bioavailability and the efficiency of transfer of the ingested POPs across trophic levels are not known and the potential damage posed by these to the marine ecosystem has yet to be quantified and modelled. Given the increasing levels of plastic pollution of the oceans it is important to better understand the impact of microplastics in the ocean food web. © 2011 Elsevier Ltd.

Barrangou R.,North Carolina State University
Current Opinion in Immunology | Year: 2015

Clustered regularly interspaced short palindromic repeats (CRISPR) and accompanying Cas proteins constitute the adaptive CRISPR-Cas immune system in bacteria and archaea. This DNA-encoded, RNA-mediated defense system provides sequence-specific recognition, targeting and degradation of exogenous nucleic acid. Though the primary established role of CRISPR-Cas systems is in bona fide adaptive antiviral defense in bacteria, a growing body of evidence indicates that it also plays critical functional roles beyond immunity, such as endogenous transcriptional control. Furthermore, benefits inherent to maintaining genome homeostasis also come at the cost of reduced uptake of beneficial DNA, and preventing strategic adaptation to the environment. This opens new avenues for the investigation of CRISPR-Cas systems and their functional characterization beyond adaptive immunity. © 2014 Elsevier Ltd.

Mihaly S.R.,North Carolina State University
Cell Death and Differentiation | Year: 2014

Programmed cell death, a physiologic process for removing cells, is critically important in normal development and for elimination of damaged cells. Conversely, unattended cell death contributes to a variety of human disease pathogenesis. Thus, precise understanding of molecular mechanisms underlying control of cell death is important and relevant to public health. Recent studies emphasize that transforming growth factor-β-activated kinase 1 (TAK1) is a central regulator of cell death and is activated through a diverse set of intra- and extracellular stimuli. The physiologic importance of TAK1 and TAK1-binding proteins in cell survival and death has been demonstrated using a number of genetically engineered mice. These studies uncover an indispensable role of TAK1 and its binding proteins for maintenance of cell viability and tissue homeostasis in a variety of organs. TAK1 is known to control cell viability and inflammation through activating downstream effectors such as NF-κB and mitogen-activated protein kinases (MAPKs). It is also emerging that TAK1 regulates cell survival not solely through NF-κB but also through NF-κB-independent pathways such as oxidative stress and receptor-interacting protein kinase 1 (RIPK1) kinase activity-dependent pathway. Moreover, recent studies have identified TAK1's seemingly paradoxical role to induce programmed necrosis, also referred to as necroptosis. This review summarizes the consequences of TAK1 deficiency in different cell and tissue types from the perspective of cell death and also focuses on the mechanism by which TAK1 complex inhibits or promotes programmed cell death. This review serves to synthesize our current understanding of TAK1 in cell survival and death to identify promising directions for future research and TAK1's potential relevance to human disease pathogenesis.Cell Death and Differentiation advance online publication, 22 August 2014; doi:10.1038/cdd.2014.123.

Breitschwerdt E.B.,North Carolina State University
ILAR Journal | Year: 2014

In recent years, an increasing number of Bartonella species have been identified as zoonotic pathogens, transmitted by animal bites, scratches, arthropods and even by needle sticks. Considering the diversity of newly discovered Bartonella species and subspecies and the large number and ecologically diverse animal reservoir hosts and the evolving spectrum of arthropod vectors that can transmit these bacteria among animals and humans, the clinical and diagnostic challenges posed by Bartonella transmission in nature are presumably much more complex than is currently appreciated by diagnosticians, vector biologists, ecologists, physicians, or veterinarians. Historically the term "bartonellosis" was attributed to infections with Bartonella bacilliformis, transmitted by sandflies in the Peruvian Andes. Currently, however, bartonellosis now includes infections caused by any Bartonella sp. anywhere in the world. Potentially, because Bartonella spp. can infect erythrocytes, endothelial cells, pericytes, CD34+ progenitor cells, and various macrophage-type cells, including microglial cells, dendritic cells, and circulating monocytes in vitro, the clinical and pathological manifestations of bartonellosis appear to be very diverse in both sick animals and human patients. Because 75% of emerging infectious diseases are zoonoses, many of which are vector-transmitted by an arthropod, a One Health approach to bartonellosis and other zoonotic infections is needed to properly address animal health, public health, and environmental factors that influence the distribution and transmission of these bacteria. The One Health concept encourages a spirit of cooperation among animal, environmental, and human health professionals and promotes developing integrated solutions for complex problems that impact the health of animals, humans, and the planet. Importantly, substantial research is needed to define the medical importance of this genus as a cause of animal and human illnesses. © The Author 2014. Published by Oxford University Press on behalf of the Institute for Laboratory Animal Research. All rights reserved.

Freeman H.S.,North Carolina State University
Frontiers in Bioscience | Year: 2013

This chapter provides an overview of the chemical structures and properties of aromatic amines and their role in the development and utility of azo dyes. Approaches to the design of environmentally benign alternatives to genotoxic primary aromatic amines, as azo dye precursors, are included.

De Queiroz A.R.,North Carolina State University
Renewable and Sustainable Energy Reviews | Year: 2016

This paper presents an overview about the hydro-thermal scheduling problem. In an electrical power system power generators have to be scheduled over a time horizon in order to supply system demand. The scheduling problem consists in dispatching the available generators to meet the system electric load while minimizing the operational costs related to fuel and possible load curtailments. In a system with a large share of hydro generation, different from a thermal dominant power system, the uncertainty of water inflows play an important role in the decision-making process. In this setting the scheduling of generators has to be determined considering different future possibilities for water availability. Also, in the existence of a cascade system, the availability of water to produce electricity in hydro plants is influenced by decisions taken in upstream reservoirs. These issues complicate the hydro-thermal scheduling problem that often in the literature is modeled as a multi-stage stochastic program. In this paper we aim to give an overview about the main ideas behind this problem. We present model formulations, a solution technique, and point out to new developments related to this research. © 2016 Elsevier Ltd.

Cisneros G.A.,Wayne State University | Karttunen M.,University of Waterloo | Ren P.,University of Texas at Austin | Sagui C.,North Carolina State University
Chemical Reviews | Year: 2014

Electrostatic interactions are crucial for biomolecular simulations, as their calculation is the most time-consuming when computing the total classical forces, and their representation has profound consequences for the accuracy of classical force fields. Long-range electrostatic interactions are crucial for the stability of proteins, nucleic acids, glycomolecules, lipids, and other macromolecules, and their interactions with solvent, ions, and other molecules. Traditionally, electrostatic interactions have been modeled using a set of fixed atom-centered point charges or partial charges. The most popular methods for extracting charges from molecular wave functions are based on a fitting of the atomic charges to the molecular electrostatic potential (MEP) computed with ab initio or semiempirical methods outside the van der Waals surface. Computationally, the electrostatic potential for a system with explicit solvent is calculated by either solving Poisson's equation or explicitly adding the individual charge potentials.

Schmidt T.W.,University of New South Wales | Castellano F.N.,North Carolina State University
Journal of Physical Chemistry Letters | Year: 2014

Incoherent photochemical upconversion is a process by which low-energy light can be converted into a higher-energy form with promising applications in solar energy conversion and storage, photocatalysis, biological imaging, and photochemical drug activation. Despite intensive research in recent years, there remains an underappreciation of the chemical kinetics that controls the efficiency of the upconversion process. Here, we provide a brief overview of research into photochemical upconversion and provide a tutorial to guide the design of efficient upconversion compositions. We further provide our perspective on where this area of research is heading and how very efficient systems will be developed. (Graph Presented). © 2014 American Chemical Society.

Harlim J.,North Carolina State University
Journal of Computational Physics | Year: 2011

In this paper, we present a fast numerical strategy for filtering stochastic differential equations with multiscale features. This method is designed such that it does not violate the practical linear observability condition and, more importantly, it does not require the computationally expensive cross correlation statistics between multiscale variables that are typically needed in standard filtering approach. The proposed filtering algorithm comprises of a " macro-filter" that borrows ideas from the Heterogeneous Multiscale Methods and a " micro-filter" that reinitializes the fast microscopic variables to statistically reflect the unbiased slow macroscopic estimate obtained from the macro-filter and macroscopic observations at asynchronous times. We will show that the proposed micro-filter is equivalent to solving an inverse problem for parameterizing differential equations. Numerically, we will show that this microscopic reinitialization is an important novel feature for accurate filtered solutions, especially when the microscopic dynamics is not mixing at all. © 2010 Elsevier Inc.

Isik F.,North Carolina State University
New Forests | Year: 2014

Using large numbers of DNA markers to predict genetic merit [genomic selection (GS)] is a new frontier in plant and animal breeding programs. GS is now routinely used to select superior bulls in dairy cattle breeding. In forest trees, a few empirical proof of-concept studies suggest that GS could be successful. However, application of GS in forest tree breeding is still in its infancy. The major hurdle is lack of high throughput genotyping platforms for trees, and the high genotyping costs, though, the cost of genotyping will likely decrease in the future. There has been a growing interest in GS among tree breeders, forest geneticists, and tree improvement managers. A broad overview of pedigree reconstruction and GS is presented. Underlying reasons for failures of marker-assisted selection were summarized and compared with GS. Challenges of GS in forest tree breeding and the outlook for the future are discussed, and a GS plan for a cloned loblolly pine breeding population is presented. This review is intended for tree breeders, forest managers, scientist and students who are not necessarily familiar with genomic or quantitative genetics jargon. © 2014 Springer Science+Business Media Dordrecht.

Kuznetsov A.V.,North Carolina State University | Nield D.A.,University of Auckland
International Journal of Thermal Sciences | Year: 2010

The natural convective boundary-layer flow of a nanofluid past a vertical plate is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. A similarity solution is presented. This solution depends on a Lewis number Le, a buoyancy-ratio number Nr, a Brownian motion number Nb, and a thermophoresis number Nt. For various values of Pr and Le, the variation of the reduced Nusselt number with Nr, Nb and Nt is expressed by correlation formulas. It was found that the reduced Nusselt number is a decreasing function of each of Nr, Nb and Nt. © 2009 Elsevier Masson SAS. All rights reserved.

Botero C.A.,North Carolina State University | Botero C.A.,Washington University in St. Louis | Weissing F.J.,University of Groningen | Wright J.,Norwegian University of Science and Technology | Rubenstein D.R.,Columbia University
Proceedings of the National Academy of Sciences of the United States of America | Year: 2015

In an era of rapid climate change, there is a pressing need to understand how organisms will cope with faster and less predictable variation in environmental conditions. Here we develop a unifying model that predicts evolutionary responses to environmentally driven fluctuating selection and use this theoretical framework to explore the potential consequences of altered environmental cycles. We first show that the parameter space determined by different combinations of predictability and timescale of environmental variation is partitioned into distinct regions where a single mode of response (reversible phenotypic plasticity, irreversible phenotypic plasticity, bet-hedging, or adaptive tracking) has a clear selective advantage over all others. We then demonstrate that, although significant environmental changes within these regions can be accommodated by evolution, most changes that involve transitions between regions result in rapid population collapse and often extinction. Thus, the boundaries between response mode regions in our model correspond to evolutionary tipping points, where even minor changes in environmental parameters can have dramatic and disproportionate consequences on population viability. Finally, we discuss how different life histories and genetic architectures may influence the location of tipping points in parameter space and the likelihood of extinction during such transitions. These insights can help identify and address some of the cryptic threats to natural populations that are likely to result from any natural or human-induced change in environmental conditions. They also demonstrate the potential value of evolutionary thinking in the study of global climate change. © 2015, National Academy of Sciences. All rights reserved.

Fink A.,North Carolina State University
Journal of Combinatorial Theory. Series A | Year: 2012

We show that the lattice games of Guo and Miller support universal computation, disproving their conjecture that all lattice games have rational strategies. We also state an explicit counterexample to that conjecture: a three dimensional lattice game whose set of winning positions does not have a rational generating function. © 2011 Elsevier Inc.

Kuznetsov A.V.,North Carolina State University
Journal of Porous Media | Year: 2012

The theory of nanofluid bioconvection in porous media is presented. The major motivation of using bioconvection is to enhance mixing and mass transfer in microvolumes, but before this goal can be implemented in practical microdevices, nanofluid bioconvection must be understood at the fundamental level. The developed theory is applied to investigating the onset of nanofluid bioconvection in a horizontal porous layer heated from below. The cases of non-oscillatory and oscillatory convection are investigated. The obtained results indicate that the effect of microorganisms on the stability of the suspension may depend on the value of bioconvection Peclét number. © 2012 by Begell House, Inc.

Choi H.-M.,Kyungpook National University | Ji C.-R.,North Carolina State University
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2011

We study the light-front zero-mode contribution to the tensor form factors Ti (i=1,2,3) for the exclusive rare P→Vl+l- decays using a covariant fermion field theory model in (3+1) dimensions. While the zero-mode contribution in principle depends on the form of the vector meson vertex Γμ=γμ-(2k-PV)μ/D, the three tensor form factors Ti (i=1,2,3) are found to be free from the zero mode if the denominator D contains the term proportional to the light-front energy or the longitudinal momentum fraction factor (1/x)n of the struck quark with the power n>0. Since the denominator D used in the light-front quark model (LFQM) has the power n=1/2, the three tensor form factors Ti (i=1,2,3) can be computed in LFQM safely without involving any complicate zero-mode contribution. The lack of zero-mode contribution benefits the phenomenology with LFQM. © 2011 Elsevier B.V.

Ksepka D.T.,North Carolina State University | Clarke J.A.,University of Texas at Austin
Bulletin of the American Museum of Natural History | Year: 2010

We present the first detailed description of Perudyptes devriesi, a basal penguin from the middle Eocene (∼42 Ma) Paracas Formation of Peru, and a new analysis of all published extinct penguin species as well as controversial fragmentary specimens. The Perudyptes devriesi holotype includes key regions of the skull and significant postcranial material, thus helping to fill a major phylogenetic and stratigraphic (∼20 million year) gap between the earliest fossil penguins (Waimanu manneringi and Waimanu tuatahi, ∼5861.6 Ma) and the next oldest partial skeletons. Perudyptes devriesi is diagnosable by five autapomorphies: (1) an anteroventrally directed postorbital process, (2) marked anterior expansion of the parasphenoid rostrum, (3) posterior trochlear ridge of the humerus projecting distal to the middle trochlear ridge and conformed as a large, broadly curved surface, (4) convex articular surface for the antitrochanter of the femur, and (5) extremely weak anterior projection of the lateral condyle of the tibiotarsus. The skull of Perudyptes is characterized by deep temporal fossae and an elongate, narrow beak that differs from other reported stem penguins in its short mandibular symphysis. The wing skeleton of Perudyptes preserves a combination of plesiomorphic features also observed in the basal penguin Waimanu and derived features shared with more crownward penguins. Features of the wing optimized as primitive for Sphenisciformes include retention of a discrete dorsal supracondylar tubercle on the humerus and presence of a modestly projected pisiform process on the carpometacarpus. Derived features present in Perudyptes and all more crownward penguins, but absent in Waimanu, include a more flattened humerus, development of a trochlea for the tendon of m. scapulotriceps at the distal end of the humerus, and bowing of the anterior face of the carpometacarpus. A combined molecular and morphological dataset for Spheniciformes was expanded by adding 25 osteological and soft tissue characters as well as 11 taxa. In agreement with previous results, Perudyptes devriesi is identified as one of the most basal members of Sphenisciformes. This analysis also confirms the placement of the middle/late Miocene (∼1113 Ma) fossil Spheniscus muizoni as a member of the Spheniscus clade and places the late Miocene (∼10 Ma) Madrynornis mirandus as sister taxon to extant Eudyptes. These two species, known from relatively complete partial skeletons, are the oldest crown clade penguin fossils and represent well-corroborated temporal calibration points for the Spheniscus-Eudyptula divergence and Megadyptes-Eudyptes divergence, respectively. Our results reaffirm that the Miocene penguin taxon Palaeospheniscus, recently proposed to represent a member of the crown radiation, belongs outside of the crown clade Spheniscidae. The phylogenetic positions of small Eocene Antarctic penguin taxa (Delphinornis, Marambiornis, and Mesetaornis) recently proposed as possible direct ancestors to crown Spheniscidae were further evaluated using alternate coding strategies for incorporating scorings from isolated elements that preserve critical morphologies and are thought to represent these taxa, although they cannot yet be reliably assigned to individual species. Under all scoring regimes, Delphinornis, Marambiornis, and Mesetaornis were recovered as distantly related to Spheniscidae. Using synapomorphies identified in the primary analysis, we evaluated the phylogenetic position of fragmentary specimens, including the holotypes of valid but poorly known species, specimens currently unassignable to the species level, and morphologically distinct specimens that have not yet been named. All pre-Miocene specimens can be excluded from Spheniscidae based on presence of plesiomorphies lost in all crown penguins, consistent with a recent radiation for the penguin crown clade. This study provides additional support for a scenario of penguin evolution characterized by an origin of flightlessness near the K-T boundary, dispersal throughout the Southern Hemisphere during the early Paleogene, and a late Cenozoic origin for the crown clade Spheniscidae. Stratigraphic distribution and phylogenetic relationships of fossil penguins are consistent with distinct radiations during the Eocene, Oligocene, and Miocene. While the Eocene and Oligocene penguin faunas are similar in many respects, the Miocene fauna is characterized by smaller average size and novel cranial morphologies, suggesting that an ecological shift in diet occurred close to the origin of crown Spheniscidae. © American Museum of Natural History 2010.

Jagannadham K.,North Carolina State University
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science | Year: 2012

Samples of graphene composites with matrix of copper were prepared by electrochemical codeposition from CuSO 4 solution with graphene oxide suspension. The thermal conductivity of the composite samples with different thickness and that of electrodeposited copper was determined by the three-omega method. Copper-graphene composite films with thickness greater than 200 μm showed an improvement in thermal conductivity over that of electrolytic copper from 380 W/m.K to 460 W/m.K at 300 K (27 °C). The thermal conductivity of copper-graphene films decreased from 510 W/m.K at 250 K (-23 °C) to 440 W/m.K at 350 K (77 °C). Effective medium approximation (EMA) was used to model the thermal conductivity of the composite samples and determine the interfacial thermal conductance between copper and graphene. The values of interface thermal conductance greater than 1.2 GW/m 2.K obtained from the acoustic and the diffuse mismatch models and from the EMA modeling of the experimental results indicate that the interface thermal resistance is not a limiting factor to improve the thermal conductivity of the copper-graphene composites. © The Minerals, Metals & Materials Society and ASM International 2011.

Franzen S.,North Carolina State University
Current Opinion in Molecular Therapeutics | Year: 2010

The catalytic role of ribozymes in RNA processing is well established. However, the proposal that ribozymes can be discovered by in vitro selection has resulted in the identification of a relatively small number of novel ribozyme catalysts. The limited repertoire of the native functional groups of RNA and its inherent instability have led to the hypothesis that ribozymes that contain non-natural functional groups (ie, modified nucleic acids) would provide greater catalytic activity toward non-RNA substrates. Moreover, because of their greater stability, reduced cost and ease of synthesis, native and modified deoxyribozymes have recently dominated the in vitro selection of enzymes that catalyze reactions involving non-RNA substrates. Deoxyribozymes bind easily to metal cofactors and provide a scaffold for templating chemical reactions, representing two significant advantages of deoxyribozymes compared with ribozymes for the catalytic transformation of non-RNA substrates. In addition, RNA processing illustrates the natural functions and limitations of ribozymes that have led to the shift in the emphasis of research from ribozymes to deoxyribozymes. © Thomson Reuters (Scientific) Ltd.

Berens A.J.,Iowa State University | Hunt J.H.,North Carolina State University | Toth A.L.,Iowa State University
Molecular biology and evolution | Year: 2015

An area of great interest in evolutionary genomics is whether convergently evolved traits are the result of convergent molecular mechanisms. The presence of queen and worker castes in insect societies is a spectacular example of convergent evolution and phenotypic plasticity. Multiple insect lineages have evolved environmentally induced alternative castes. Given multiple origins of eusociality in Hymenoptera (bees, ants, and wasps), it has been proposed that insect castes evolved from common genetic "toolkits" consisting of deeply conserved genes. Here, we combine data from previously published studies on fire ants and honey bees with new data for Polistes metricus paper wasps to assess the toolkit idea by presenting the first comparative transcriptome-wide analysis of caste determination among three major hymenopteran social lineages. Overall, we found few shared caste differentially expressed transcripts across the three social lineages. However, there is substantially more overlap at the levels of pathways and biological functions. Thus, there are shared elements but not on the level of specific genes. Instead, the toolkit appears to be relatively "loose," that is, different lineages show convergent molecular evolution involving similar metabolic pathways and molecular functions but not the exact same genes. Additionally, our paper wasp data do not support a complementary hypothesis that "novel" taxonomically restricted genes are related to caste differences. © The Author 2014. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Nichol K.,Leiden University | Daniels K.E.,North Carolina State University
Physical Review Letters | Year: 2012

Experiments quantifying the rotational and translational motion of particles in a dense, driven, 2D granular gas floating on an air table reveal that kinetic energy is divided equally between the two translational and one rotational degrees of freedom. This equipartition persists when the particle properties, confining pressure, packing density, or spatial ordering are changed. While the translational velocity distributions are the same for both large and small particles, the angular velocity distributions scale with the particle radius. The probability distributions of all particle velocities have approximately exponential tails. Additionally, we find that the system can be described with a granular Boyle's law with a van der Waals-like equation of state. These results demonstrate ways in which conventional statistical mechanics can unexpectedly apply to nonequilibrium systems. © 2012 American Physical Society.

Ellison D.C.,North Carolina State University | Bykov A.M.,RAS Ioffe Physical - Technical Institute
Astrophysical Journal | Year: 2011

We present a model of gamma-ray emission from core-collapse supernovae (SNe) originating from the explosions of massive young stars. The fast forward shock of the supernova remnant (SNR) can accelerate particles by diffusive shock acceleration (DSA) in a cavern blown by a strong, pre-SN stellar wind. As a fundamental part of nonlinear DSA, some fraction of the accelerated particles escape the shock and interact with a surrounding massive dense shell producing hard photon emission. To calculate this emission, we have developed a new Monte Carlo technique for propagating the cosmic rays (CRs) produced by the forward shock of the SNR, into the dense, external material. This technique is incorporated in a hydrodynamic model of an evolving SNR which includes the nonlinear feedback of CRs on the SNR evolution, the production of escaping CRs along with those that remain trapped within the remnant, and the broadband emission of radiation from trapped and escaping CRs. While our combined CR-hydro-escape model is quite general and applies to both core collapse and thermonuclear SNe, the parameters we choose for our discussion here are more typical of SNRs from very massive stars whose emission spectra differ somewhat from those produced by lower mass progenitors directly interacting with a molecular cloud. © 2011. The American Astronomical Society. All rights reserved.

Krings A.,North Carolina State University
Systematic Botany | Year: 2011

The last treatment of Gonolobinae (Apocynaceae, Asclepiadoideae) in the West Indies is over a hundred years old and a number of new species have been described since. Although Fischeria and Gonolobus s. s. were revised recently, a complementary, comprehensive, recent regional treatment of Matelea s. l. is lacking. Considering the rarity of taxa of Matelea s. l. in the West Indies, thirty-three of thirty-six taxa are endemic to a single island each, and that nearly half of the known species have been described since Schlechter's treatment of 1899, the objective of the present study is to provide a synopsis of the genus in the area to facilitate field recognition and future collections. The treatment is based on critical study of ca. 250 specimens of the fifty-some known species in Caribbean Gonolobinae, fieldwork in the region, and molecular analyses. In addition to a comprehensive key and descriptions, illustrations of the complex gynostegial coronas are provided here for the first time for numerous taxa. A new combination is made in Matelea for Gonolobus haitiensis: Matelea haitiensis. © 2011 by the American Society of Plant Taxonomists.

Dickey M.D.,North Carolina State University
ACS Applied Materials and Interfaces | Year: 2014

Gallium and several of its alloys are liquid metals at or near room temperature. Gallium has low toxicity, essentially no vapor pressure, and a low viscosity. Despite these desirable properties, applications calling for liquid metal often use toxic mercury because gallium forms a thin oxide layer on its surface. The oxide interferes with electrochemical measurements, alters the physicochemical properties of the surface, and changes the fluid dynamic behavior of the metal in a way that has, until recently, been considered a nuisance. Here, we show that this solid oxide "skin" enables many new applications for liquid metals including soft electrodes and sensors, functional microcomponents for microfluidic devices, self-healing circuits, shape-reconfigurable conductors, and stretchable antennas, wires, and interconnects. © 2014 American Chemical Society.

Kuznetso A.V.,North Carolina State University
Theoretical and Computational Fluid Dynamics | Year: 2012

The aim of this paper is to develop a theory describing the onset of convection instability (called here nanofluid bioconvecion) that is induced by simultaneous effects produced by oxytactic microorganisms, nanoparticles, and vertical temperature variation. The theory is developed for the situation when the nanofluid occupies a shallow horizontal layer of finite depth. The layer is defined as shallow as long as oxygen concentration at the bottom of the layer is above the minimum concentration required for the bacteria to be active (to actively swim up the oxygen gradient). The lower boundary of the layer is assumed rigid, while at the upper boundary both situations when the boundary is rigid or stress free are considered. Physical mechanisms responsible for the slip velocity between the nanoparticles and the base fluid, such as Brownian motion and thermophoresis, are accounted for in the model. A linear instability analysis is performed, and the resulting eigenvalue problem is solved analytically using the Galerkin method. © Springer-Verlag 2011.

Petters M.D.,North Carolina State University | Kreidenweis S.M.,Colorado State University
Atmospheric Chemistry and Physics | Year: 2013

Atmospheric particles can serve as cloud condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Köhler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud condensation nucleus activity. The presented formulation incorporates analytical approximations of surfactant partitioning to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code. © 2013 Author(s).

Barrangou R.,North Carolina State University
Genome Biology | Year: 2015

Bacterial adaptive immunity hinges on CRISPR-Cas systems that provide DNA-encoded, RNA-mediated targeting of exogenous nucleic acids. A plethora of CRISPR molecular machines occur broadly in prokaryotic genomes, with a diversity of Cas nucleases that can be repurposed for various applications. © 2015 Barrangou.

Hammond R.G.,North Carolina State University
International Journal of Industrial Organization | Year: 2010

I analyze the market for compact discs using an original data set of items listed for sale online. Over 5000 listings of both new and used compact discs were collected from eBay (which provides sellers a choice between two mechanisms: auction or posted price) and its subsidiary, Half.com (which features only posted prices). Despite the often cited revenue-dominance property of auctions, many sellers choose to post a fixed price. To explain this anomaly, I examine empirically the determinants of the revenue earned by sellers in this market. I find that posted-price goods sell for higher prices, while auctioned goods sell with a higher probability. Further results suggest that the size of a seller's inventory is the key factor in the choice between selling in an auction and posting a fixed price. In particular, sellers with large inventories are more likely to use the posted-price mechanism. © 2009 Elsevier B.V. All rights reserved.

Lindsey J.S.,North Carolina State University | Bocian D.F.,University of California at Riverside
Accounts of Chemical Research | Year: 2011

The inexorable drive to miniaturize information storage and processing devices has fueled the dreams of scientists pursuing molecular electronics: researchers in the field envisage exquisitely tailored molecular materials fulfilling the functions now carried out by semiconductors. A bottom-up assembly of such all-molecular devices would complement, if not supplant, the present top-down lithographic procedures of modern semiconductor fabrication. Short of these grand aspirations, a more near-term objective is to construct hybrid architectures wherein molecules are incorporated in semiconductor-based devices. Such a combined approach exploits the advantages of molecules for selected device functions while retaining the well-developed lithographic approaches for fabrication of the overall chip.In this Account, we survey more than a decade of results from our research programs to employ porphyrin molecules as charge-storage elements in hybrid semiconductor-molecular dynamic random access memory. Porphyrins are attractive for a variety of reasons: they meet the stability criteria for use in real-world applications, they are readily prepared and tailored synthetically, they undergo read-write processes at low potential, and they store charge for extended periods (up to minutes) in the absence of applied potential. Porphyrins typically exhibit two cationic redox states. Molecular architectures with greater than two cationic redox states are achieved by combinations of porphyrins in a variety of structures (for example, dyads, wherein the porphyrins have distinct potentials, triple deckers, and dyads of triple deckers). The incorporation of porphyrins in hybrid architectures has also required diverse tethers (alkyl, alkenyl, alkynyl, aryl, and combinations thereof) and attachment groups (alcohol, thiol, selenol, phosphonate, and hydrocarbon) for linkage to a variety of surfaces (Au, Si, SiO2, TiN, Ge, and so forth).The porphyrins as monolayers exhibit high charge density and are robust to high-temperature excursions (400 °C for 30 min) under inert atmosphere conditions. Even higher charge densities, which are invaluable for device applications, were achieved by in situ formation of porphyrin polymers or by stepwise growth of porphyrin-imide oligomers. The various molecular architectures have been investigated by diverse surface characterization methods, including ellipsometry, atomic force microscopy, FTIR spectroscopy, and X-ray photoelectron spectroscopy, as well as a variety of electrochemical methods. These studies have further revealed that the porphyrin layers are robust under conditions of deposition of a top metal contact.The results to date indicate the superior features of selected molecular architectures for molecular electronics applications. The near-term utilization of such materials depends on further work for appropriate integration in semiconductor-based devices, whereas ultimate adoption may depend on advances that remain far afield, such as the development of fully bottom-up assembly processes. © 2011 American Chemical Society.

Kuznetsov A.V.,North Carolina State University | Nield D.A.,University of Auckland
International Journal of Thermal Sciences | Year: 2014

The problem of natural convective boundary-layer flow of a nanofluid past a vertical plate is revisited. The model, which includes the effects of Brownian motion and thermophoresis, is revised so that the nanofluid particle fraction on the boundary is passively rather than actively controlled. In this respect the model is more realistic physically than that employed by previous authors. © 2013 Elsevier B.V. All rights reserved.

Prat O.P.,North Carolina State University | Nelson B.R.,National Oceanic and Atmospheric Administration
Journal of Climate | Year: 2013

The objective of this paper is to characterize the precipitation amounts originating from tropical cyclones (TCs) in the southeastern United States during the tropical storm season from June to November. Using 12 years of precipitation data from the Tropical RainfallMeasurementMission (TRMM), the authors estimate the TC contribution on the seasonal, interannual, and monthly precipitation budget using TC information derived from the International Best Track Archive for Climate Stewardship (IBTrACS). Results derived from the TRMM Multisatellite Precipitation Analysis (TMPA) 3B42 showed that TCs accounted for about 7% of the seasonal precipitation total from 1998 to 2009. Rainfall attributable to TCs was found to contribute as much as 8%-12% for inland areas located between 150 and 300 km from the coast and up to 15%-20% for coastal areas from Louisiana to the Florida Panhandle, southern Florida, and coastal Carolinas. The interannual contribution varied from 1.3% to 13.8% for the period 1998-2009 and depended on the TC seasonal activity, TC intensity, and TC paths as they traveled inland. For TCs making landfall, the rainfall contribution could be locally above 40% and, on a monthly basis, TCs contributed as much as 20% of September rainfall. The probability density functions of rainfall attributable to tropical cyclones showed that the percentage of rainfall associated with TC over land increased with increasing rain intensity and represent about 20% of heavy rainfall (>20 mm h-1), while TCs account for less than 5% of all seasonal precipitation events. © 2013 American Meteorological Society.

Hamner C.,Washington State University | Chang J.J.,Washington State University | Engels P.,Washington State University | Hoefer M.A.,North Carolina State University
Physical Review Letters | Year: 2011

The dynamics of two penetrating superfluids exhibit an intriguing variety of nonlinear effects. Using two distinguishable components of a Bose-Einstein condensate, we investigate the counterflow of two superfluids in a narrow channel. We present the first experimental observation of trains of dark-bright solitons generated by the counterflow. Our observations are theoretically interpreted by three-dimensional numerical simulations for the coupled Gross-Pitaevskii equations and the analysis of a jump in the two relatively flowing components' densities. Counterflow-induced modulational instability for this miscible system is identified as the central process in the dynamics. © 2011 American Physical Society.

Dusling K.,North Carolina State University | Venugopalan R.,Brookhaven National Laboratory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

In a recent article, we showed that high multiplicity dihadron proton-proton (p+p) data from the CMS experiment are in excellent agreement with computations in the color glass condensate effective field theory. This agreement of the theory with several hundred data points provides a nontrivial description of both nearside ("ridge") and awayside azimuthal collimations of long range rapidity correlations in p+p collisions. Our prediction in Dusling and Venugopalan for proton-lead (p+Pb) collisions is consistent with results from the recent CMS p+Pb run at √s NN=5.02 TeV for the largest track multiplicity Ntrack∼ 40 we considered. The CMS p+Pb data shows the following striking features: (i) a strong dependence of the ridge yield on Ntrack, with a significantly larger signal than in p+p for the same Ntrack, (ii) a stronger pT dependence than in p+p for large Ntrack, and (iii) a nearside collimation for large Ntrack comparable to the awayside for the lower pT=pTtrig=pTassoc dihadron windows. We show here that these systematic features of the CMS p+Pb di-hadron data are all described by the color glass condensate (with parameters fixed by the p+p data) when we extend our prediction in Dusling and Venugopalan to rarer high multiplicity events. We also predict the azimuthally collimated yield for yet unpublished windows in the pTtrig and pTassoc matrix. © 2013 American Physical Society.

Dusling K.,North Carolina State University | Venugopalan R.,Brookhaven National Laboratory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We demonstrate that rapidity separated dihadron spectra in high multiplicity proton-proton collisions at the LHC can be quantitatively described by a combination of Balitsky-Fadin-Kuraev-Lipatov and saturation dynamics. Based on these results, we predict the systematics of dihadron spectra in proton-nucleus collisions at the LHC. © 2013 American Physical Society.

Collier T.S.,North Carolina State University
Rapid communications in mass spectrometry : RCM | Year: 2011

Protein quantification is one of the principal goals of mass spectrometry (MS)-based proteomics, and many strategies exist to achieve it. Several approaches involve the incorporation of a stable-isotope label using either chemical derivatization, enzymatically catalyzed incorporation of (18)O, or metabolic labeling in a cell or tissue culture. These techniques can be cost or time prohibitive or not amenable to the biological system of interest. Label-free techniques including those utilizing integrated ion abundance and spectral counting offer an alternative to stable-isotope-based methodologies. Herein, we present the comparison of stable-isotope labeling of amino acids in cell culture (SILAC) with spectral counting for the quantification of human embryonic stem cells as they differentiate toward the trophectoderm at three time points. Our spectral counting experimental strategy resulted in the identification of 2641 protein groups across three time points with an average sequence coverage of 30.3%, of which 1837 could be quantified with more than five spectral counts. SILAC quantification was able to identify 1369 protein groups with an average coverage of 24.7%, of which 1027 could be quantified across all time points. Within this context we further explore the capacity of each strategy for proteome coverage, variation in quantification, and the relative sensitivity of each technique to the detection of change in relative protein expression. Copyright © 2011 John Wiley & Sons, Ltd.

McCormick M.A.,North Carolina State University
Mycologia | Year: 2013

The wood-decay fungi Fomes fasciatus and F. fomentarius share many morphological characters that historically have made species delimitation challenging. We examined morphological, molecular and physiological characters of basidiomata and pure cultures of F. fasciatus and F. fomentarius sampled from multiple plant hosts and geographic regions in the United States to determine whether they support separation of the two species. We find that mean basidiospore size is significantly larger in F. fomentarius and represents the most informative morphological character for delineating the species. Basidiomata and pore-surface shape provided additional resolution of the species, but these characters often overlap and are more variable than basidiospore size. Phylogenetic analyses of ITS and RPB2 sequences suggest that F. fasciatus and F. fomentarius represent distinct evolutionary lineages. The two species share less than 88% maximum identity for the ITS region. Limited intraspecific sequence variation at each locus also was observed. In vitro experiments of hyphal-growth response to a wide range of temperatures support differences in physiology between the two species.

Horvath P.,DuPont Company | Barrangou R.,DuPont Company | Barrangou R.,North Carolina State University
Cell Research | Year: 2013

Two recent papers in Science illustrate how the prokaryotic CRISPR-Cas immune system machinery, which typically targets invasive genetic elements such as viruses and plasmids, can be converted into a sophisticated molecular tool for next-generation human genome editing. The versatile Cas9 RNA-guided endonuclease can be readily reprogrammed using customizable small RNAs for sequence-specific single- or double-stranded DNA cleavage. © 2013 IBCB, SIBS, CAS All rights reserved.

O'Flaherty S.,North Carolina State University
Annual review of food science and technology | Year: 2011

The advent of the molecular biology era in the 1950s and the subsequent emergence of new technologies positively impacted on all areas of biology. New discoveries in molecular biology and experimental tools were developed over the next 60 years that have revolutionized the study of food microbiology. Previously, food microbiology relied on classic microbiology techniques, which had remained relatively unchanged since the discoveries of Louis Pasteur in the 1800s. More recently, new advances resulting in "omic" technologies have exploded the areas of genomics, transcriptomics, and proteomics and revealed many fundamental processes driven by both pathogens and commensals. This review outlines advances in omic technologies and how these have impacted food microbiology through providing examples of recently published landmark work.

Schiffman J.D.,University of Utah | Breen M.,North Carolina State University
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2015

Over 1.66 million humans (approx. 500/100 000 population rate) and over 4.2 million dogs (approx. 5300/100 000 population rate) are diagnosed with cancer annually in the USA. The interdisciplinary field of comparative oncology offers a unique and strong opportunity to learn more about universal cancer risk and development through epidemiology, genetic and genomic investigations. Working across species, researchers from human and veterinary medicine can combine scientific findings to understand more quickly the origins of cancer and translate these findings to novel therapies to benefit both human and animals. This review begins with the genetic origins of canines and their advantage in cancer research. We next focus on recent findings in comparative oncology related to inherited, or genetic, risk for tumour development. We then detail the somatic, or genomic, changes within tumours and the similarities between species. The shared cancers between humans and dogs thatwe discuss include sarcoma(osteosarcoma, soft tissue sarcoma, histiocytic sarcoma, hemangiosarcoma), haematological malignancies (lymphoma, leukaemia), bladder cancer, intracranial neoplasms (meningioma, glioma) and melanoma. Tumour risk in other animal species is also briefly discussed. As the field of genomics advances, we predict that comparative oncology will continue to benefit both humans and the animals that live among us. 2015 The Author(s) Published by the Royal Society. All rights reserved.

Couillet R.,Supelec | Debbah M.,Supelec | Silverstein J.W.,North Carolina State University
IEEE Transactions on Information Theory | Year: 2011

In this article, novel deterministic equivalents for the Stieltjes transform and the Shannon transform of a class of large dimensional random matrices are provided. These results are used to characterize the ergodic rate region of multiple antenna multiple access channels, when each point-to-point propagation channel is modelled according to the Kronecker model. Specifically, an approximation of all rates achieved within the ergodic rate region is derived and an approximation of the linear precoders that achieve the boundary of the rate region as well as an iterative water-filling algorithm to obtain these precoders are provided. An original feature of this work is that the proposed deterministic equivalents are proved valid even for strong correlation patterns at both communication sides. The above results are validated by Monte Carlo simulations. © 2011 IEEE.

Several hydrolysate-based diets have been commercialized for helping diagnose or treat dogs with cutaneous adverse food reactions (CAFR). This systematic review was performed to examine the evidence in favour of reduced immunological and clinical allergenicity of hydrolysates in dogs with CAFR. Citation databases, meeting abstracts and article bibliographies were scanned for relevant citations, and companies were contacted to provide unpublished reports. Eleven studies relevant to this study were identified. Some evidence of reduced serum IgE binding to a soy hydrolysate (1 study) and decreased intradermal test reactivity to hydrolysed proteins (three studies) was found. In four reports, the feeding of dogs suspected of having CAFR with hydrolysate-based diets reduced or eliminated clinical signs in a variable proportion of subjects. The percentage of dogs with CAFR that still reacted to these hydrolysate-based diets could not be assessed, however. Importantly, up to 50% of dogs with CAFR enrolled in three controlled studies exhibited increases in clinical signs after ingesting partial hydrolysates derived from foods to which they were hypersensitive. In conclusion, the limited number of studies undertaken point to reduced - but not eliminated - immunological and clinical allergenicity of hydrolysate-based commercial diets. A variable proportion of dogs with CAFR will exhibit a worsening of clinical signs when fed partial hydrolysates. Clinicians must weigh the clinical benefit of these diets versus their high cost and low risk of reduced appetence or gastrointestinal sign development. At this time, hydrolysate-containing diets are probably best used in dogs suspected not to be hypersensitive to their individual components.

Bakker B.L.G.,VU University Amsterdam | Ji C.-R.,North Carolina State University
Progress in Particle and Nuclear Physics | Year: 2014

With the acceptance of QCD as the fundamental theory of strong interactions, one of the basic problems in the analysis of nuclear phenomena became how to consistently account for the effects of the underlying quark/gluon structure of nucleons and nuclei. Besides providing more detailed understanding of conventional nuclear physics, QCD may also point to novel phenomena accessible by new or upgraded nuclear experimental facilities. We review several interesting applications of QCD to nuclear physics. © 2013 Elsevier B.V. All rights reserved.

Schafer T.,North Carolina State University
Annual Review of Nuclear and Particle Science | Year: 2014

We review the modern view of fluid dynamics as an effective low-energy, long-wavelength theory of many-body systems at finite temperature. We introduce the concept of a nearly perfect fluid, defined by a ratio η/s of shear viscosity to entropy density of order ℏ/kB or less. Nearly perfect fluids exhibit hydrodynamic behavior at all distances down to the microscopic length scale of the fluid. We summarize arguments that suggest that there is fundamental limit to fluidity, and we review the current experimental situation of measurements of η/s in strongly coupled quantum fluids. © 2014 by Annual Reviews. All rights reserved.

Beratan K.K.,North Carolina State University
Ecology and Society | Year: 2014

Translating the attractive concept of collaborative adaptive management (CAM) into practice has proven very difficult. The papers included in this Special Feature explore why this is true and suggest how the challenges might be addressed. This summary highlights common themes, major challenges, and implications for research and practice. Many of the included papers emphasize the central importance of collaboration and stakeholder engagement as a response to complexity and uncertainty. Collectively, the papers make the case that a lack of knowledge about how to manage the human dynamics of comanagement poses a major challenge to implementing CAM. Human activities are the primary drivers of system change in most natural resource management systems, so attention to human dynamics is essential for developing useful change hypotheses and leading indicators that can provide useful and timely feedback for adaptive management. Institutions need to evolve to support adaptive and collaborative management processes. This will require thoughtful design of CAM processes, along with commitment of sufficient time and resources. Implementation challenges should be considered as a major focus for research rather than as simply barriers to progress. More effective ways of capturing practitioners' experiential knowledge are required to improve the practice of CAM. This Special Feature suggests that the concept of a CAM practitioners' journal has promise, but realization of that promise will require careful attention to the needs of and constraints on practitioners. © 2014 by the author(s).

Godwin J.,North Carolina State University | Thompson R.,Bowdoin College
Hormones and Behavior | Year: 2012

The nonapeptide hormones arginine vasotocin and isotocin play important roles in mediating social behaviors in fishes. Studies in a diverse range of species demonstrate variation in vasotocin neuronal phenotypes across within and between sexes and species as well as effects of hormone administration on aggressive and sexual behaviors. However, patterns vary considerably across species and a general explanatory model for the role of vasotocin in teleost sociosexual behaviors has proven elusive. We review these findings, examine potential explanations for the lack of agreement across studies, and propose a model based on the parvocellular AVT neurons primarily mediating social approach and subordinance functions while the magnocellular and gigantocellular AVT neurons mediate courtship and aggressive behaviors. Isotocin neuronal phenotypes and effects on behavior are relatively unstudied, but research to date suggests this will be a fruitful line of inquiry.This article is part of a Special Issue entitled Oxytocin, Vasopressin, and Social Behavior. © 2012 Elsevier Inc.

Yu H.,North Carolina State University
Nature Photonics | Year: 2016

Infrared-to-visible upconversion devices made by integrating an infrared quantum dot photodetector with an organic light-emitting diode potentially offer a route to low-cost, pixel-free infrared imaging. However, making such devices sufficiently efficient for practical use is a challenge. Here, we report a high-gain vertical phototransistor with a perforated metallic source electrode having an EQE up to 1 × 105% and a detectivity of 1.2 × 1013 Jones. By incorporating a phosphorescent organic light-emitting diode in this phototransistor, an infrared-to-visible upconversion LEPT with a photon-to-photon conversion efficiency of over 1,000% is demonstrated. © 2016 Nature Publishing Group

Williams L.,North Carolina State University
Communications of the ACM | Year: 2012

The 12 original agile principles created by 17 software engineers in 2001 defined the agile trend that continues to transform the entire software industry. Rather than view one another solely as competition, these same engineers also wrote the Agile Manifesto, cooperatively focusing on their common interest in agile development and greatly magnifying any of their potential individual contributions. Two surveys in 2010 were conducted at North Carolina State University to weigh the community's view of the principles and use of associated practices. Respondents' commentary emphasized delivery of a solution with high business value to a customer early and often, along with willingness to respond to feedback. Principle 7 attracted the most comments, with respondents saying that it, in particular, along with the full set of principles, in general, did not adequately emphasize the need to produce high-quality software and test and elicit non-functional requirements. Concerning principle 11, several commenters suggested the need for a release vision.

Stone E.A.,North Carolina State University
Genome Research | Year: 2012

High-throughput sequencing is enabling remarkably deep surveys of genomic variation. It is now possible to completely sequence multiple individuals from a single species, yet the identification of variation among them remains an evolving computational challenge. This challenge is compounded for experimental organisms when strains are studied instead of individuals. In response, we present the Joint Genotyper for Inbred Lines (JGIL) as a method for obtaining genotypes and identifying variation among a large panel of inbred strains or lines. JGIL inputs the sequence reads from each line after their alignment to a common reference. Its probabilistic model includes site-specific parameters common to all lines that describe the frequency of nucleotides segregating in the population from which the inbred panel was derived. The distribution of line genotypes is conditional on these parameters and reflects the experimental design. Site-specific error probabilities, also common to all lines, parameterize the distribution of reads conditional on line genotype and realized coverage. Both sets of parameters are estimated per site from the aggregate read data, and posterior probabilities are calculated to decode the genotype of each line. We present an application of JGIL to 162 inbred Drosophila melanogaster lines from the Drosophila Genetic Reference Panel. We explore by simulation the effect of varying coverage, sequencing error, mapping error, and the number of lines. In doing so, we illustrate how JGIL is robust to moderate levels of error. Supported by these analyses, we advocate the importance of modeling the data and the experimental design when possible. © 2012, Published by Cold Spring Harbor Laboratory Press.

Conrad H.,North Carolina State University
Journal of the American Ceramic Society | Year: 2011

An analytical procedure is developed which provides the magnitudes of the space charge potential and the corresponding grain boundary energy in ionic oxides from the effect of an applied dc electric field on grain growth. Reasonable agreement occurred between the calculated values and expectations or other measurements. The agreement indicates that the physical mechanism governing the retardation of grain growth by an electric field in 3Y-TZP is through reduction in the grain boundary energy by the interaction of the field with the space charge. © 2011 The American Ceramic Society.

Casper J.M.,North Carolina State University
Journal of physical activity & health | Year: 2011

Organized sport is viewed as a viable medium for promoting more physical activity among youth. However, participation in youth sport declines significantly among both boys and girls during their middle school years. This study examined middle school students' perceived constraints to sport participation. Middle school students from 4 schools (6th-8th grade, N = 2465) completed a web based survey (97.3% response rate). Descriptive analysis, t tests, and ANOVA were used to assess extent of perceived constraints and differences among demographic and sport participation level subgroups. The most salient constraint perceived by respondents was time, while knowledge was perceived as the lowest among the overall sample. Significant (P < .01) differences in perceived constraints were found among all comparisons groups. Girls, Latinos, lower SES students, and students who did not play sports reported more constraints than respective comparisons groups. The sociodemographic characteristics of middle school students appear to be a significant factor in their perception of constraints to sport participation. Identifying constraints associated with sport participation can enable policy-makers and administrators to be more deliberate in channeling resources.

Kuznetsov A.V.,North Carolina State University
European Journal of Mechanics, B/Fluids | Year: 2011

The onset of bio-thermal convection in a suspension containing both nanoparticles and gyrotactic microorganisms, such as algae, is considered. Physical mechanisms responsible for the slip velocity between the nanoparticles and the base fluid, such as Brownian motion and thermophoresis, are included in the model. The suspension occupies a horizontal layer of finite depth. The lower boundary of the layer is assumed rigid while at the upper boundary both cases of either rigid or stress-free top boundaries are considered. A linear instability analysis is performed and the resulting eigenvalue problem is solved analytically using the Galerkin method. The cases of oscillatory and non-oscillatory convection are studied. Investigation of the dependence of the thermal Rayleigh number on the nanoparticle Rayleigh number and the bioconvection Rayleigh number is performed. The boundaries of oscillatory and non-oscillatory instability are established. The effect of nanoparticles can be either stabilizing or destabilizing, depending on whether the basic nanoparticle distribution is bottom-heavy or top-heavy. The effect of upswimming microorganisms is generally destabilizing. © 2010 Elsevier Masson SAS. All rights reserved.

Nevzorov A.A.,North Carolina State University
Journal of Physical Chemistry B | Year: 2011

A unified theory for the NMR line shapes of aligned membrane proteins arising from uniaxial disorder (mosaic spread) and global rotational diffusion about the director axis is presented. A superoperator formalism allows one to take into account the effects of continuous radiofrequency irradiation and frequency offsets in the presence of dynamics. A general method based on the Stochastic Liouville Equation makes it possible to bridge the static and dynamic limits in a single model. Simulations of solid-state NMR spectra are performed for a uniform α helix by considering orientational disorder and diffusion of the helix as a whole relative to the alignment axis. The motional narrowing of the resonance lines is highly inhomogeneous and can be used as an additional angular restraint in structure calculations. Experimental solid-state NMR spectra of Pf1 coat protein support the conclusions of the theory for two limiting cases. The static disorder dominates the 15N NMR spectra of Pf1 aligned on a phage, while fast uniaxial diffusion provides a line narrowing mechanism for the Pf1 protein reconstituted in magnetically aligned bicelles. © 2011 American Chemical Society.

Carmona D.,National Autonomous University of Mexico | Lajeunesse M.J.,National Evolutionary Synthesis Center | Johnson M.T.,North Carolina State University
Functional Ecology | Year: 2011

1. Although secondary metabolites are recognized as fundamental to the defence of plants against insect and mammalian herbivores, their relative importance compared to other potential defensive plant traits (e.g. physical resistance, gross morphology, life-history, primary chemistry and physiology) are not well understood. 2.We conducted a meta-analysis to answer the question: What types of genetically variable plant traits most strongly predict resistance against herbivores? We performed a comprehensive literature search and obtained 499 separate measurements of the strength of covariation (measured as genetic correlations) between plant traits and herbivore susceptibility - these were extracted from 72 studies involving 19 plant families. 3.Surprisingly, we found no overall association between the concentrations of secondary metabolites and herbivore susceptibility - plant traits other than secondary metabolites most strongly predicted herbivore susceptibility. Specifically, genetic variation in life-history traits (e.g. flowering time, growth rate) consistently exhibited the strongest genetic correlations with susceptibility. Genetic variation in gross morphological traits (e.g. no. branches, plant size) and physical resistance traits (e.g. latex, trichomes) were also frequently correlated with variation in herbivore susceptibility, but these relationships depended on attributes of the herbivores (e.g. feeding guild) and plants (e.g. longevity). 4.These results call into question the conventional wisdom that secondary metabolites are the most important anti-herbivore defence of plants. We propose the hypothesis that herbivores select most strongly on genetic variation in life-history, morphological and physical resistance traits, but the greater pleiotropic effects of genes controlling these traits impose strong constraints on their evolution. Meanwhile, secondary metabolites could have evolved to be important defensive mechanisms not because they have the largest effect on herbivores, but because the constraints on their evolution are the weakest. © 2010 The Authors. Journal compilation © 2010 British Ecological Society.

Brassinosteroid (BR) signal transduction research has progressed rapidly from the initial discovery of the BR receptor to a complete definition of the basic molecular components required to relay the BR signal from perception by receptor kinases at the cell surface to activation of a small family of transcription factors that regulate the expression of more than a thousand genes in a BR-dependent manner. These mechanistic advances have helped answer the intriguing question of how a single molecule, such as a hormone, can have dramatic pleiotropic effects on a broad range of diverse developmental pathways and have shed light on how BRs interact with other plant hormones and environmental cues to shape the growth of the whole plant. This review summarizes the current state of BR signal transduction research and then examines recent articles uncovering gene regulatory networks through which BR influences both vegetative and reproductive development. © 2011 American Society of Plant Biologists.

Olivry T.,North Carolina State University
Chemical Immunology and Allergy | Year: 2012

Besides humans, dogs are the only animals that naturally develop skin lesions of atopic dermatitis (AD). In the last two decades, numerous studies have helped establish the close similarity between human and canine AD at the pathogenesis, clinical, epidemiological and therapeutic levels. The study of dogs with AD could potentially be very useful to human AD research because of the species' historical inbred selection that would permit breed-specific genetic, epidemiological or mechanistic studies. Clinical trials enrolling privately owned dogs are helpful for testing the validity of novel preventive or therapeutic interventions before these are used in human patients. Finally, skin lesions of AD can be provoked via environmental, systemic or epicutaneous allergen challenges in dogs that are spontaneously or experimentally sensitized to common dietary or environmental allergens. These experimental canine AD models have proven their utility to test the efficacy of novel treatment modalities in a preclinical setting. In conclusion, natural or experimental canine AD can provide researchers with a unique model to investigate genetic, epidemiological, mechanistic or treatment facets of the human disease. Due to the unique similarity of the disease in both species, the obtained information would very likely be translatable to human patients. © 2012 S. Karger AG, Basel.

Liem M.,Harvard University | Richardson N.J.,North Carolina State University
Criminal Justice and Behavior | Year: 2014

Research on desistance emphasizes the importance of the transformation narrative, in which the individual has replaced his old, criminal self with a new, law-abiding self. Key elements of the transformation narrative are generative motivations, the core self, and a sense of agency. Thus far, it is not known what role these elements play in desistance among released lifers. To fill this caveat, we conducted in-depth life interviews with 67 individuals who had served a life sentence. Almost all interviewees presented a transformation narrative that included a good core self and generative motivations, including those who persisted in criminal behavior. We found that individual agency was a key factor distinguishing the paroled lifers from the re-incarcerated lifers. Findings suggest that rather than learning to present a transformation narrative focused on reflecting a good core self and generative motivations, (post-)prison programs should focus on restoring agency to ensure successful re-entry. © 2014 International Association for Correctional and Forensic Psychology.

Allen Klaiber H.,Pennsylvania State University | Phaneuf D.J.,North Carolina State University
Journal of Environmental Economics and Management | Year: 2010

We present an analysis of how open space amenities affect residential location choices using a horizontal sorting model to estimate household preferences for open space. To parameterize the model, a new and rich dataset spanning 17 years of home sales in the seven-county Twin Cities area of Minnesota was assembled. Heterogeneity across types of open space and across households is shown to be a critical determinant of the welfare impacts of open space conservation. Our general equilibrium simulations allow housing prices to re-equilibrate in response to policy-induced demand shifts, demonstrating that as the scale of intervention becomes larger, general equilibrium and partial equilibrium welfare measures increasingly diverge. Finally, we find that the spatial structure of policy is an important component of policy design, suggesting open space policy should be place-specific in its design and implementation. © 2010 Elsevier Inc.

The public perceives that the nutritional quality of eggs produced as free range is superior to that of eggs produced in cages. Therefore, this study compared the nutrient content of free-range vs. cageproduced shell eggs by examining the effects of the laboratory, production environment, and hen age. A flock of 500 Hy-Line Brown layers were hatched simultaneously and received the same care (i.e., vaccination, lighting, and feeding regimen), with the only difference being access to the range. The nutrient content of the eggs was analyzed for cholesterol, n-3 fatty acids, saturated fat, monounsaturated fat, polyunsaturated fat, β-carotene, vitamin A, and vitamin E. The same egg pool was divided and sent to 4 different laboratories for analysis. The laboratory was found to have a significant effect on the content of all nutrients in the analysis except for cholesterol. Total fat content in the samples varied (P < 0.001) from a high of 8.88% to a low of 6.76% in laboratories D and C, respectively. Eggs from the range production environment had more total fat (P < 0.05), monounsaturated fat (P < 0.05), and polyunsaturated fat (P < 0.001) than eggs produced by caged hens. Levels of n-3 fatty acids were also higher (P < 0.05), at 0.17% in range eggs vs. 0.14% in cage eggs. The range environment had no effect on cholesterol (163.42 and 165.38 mg/50 g in eggs from caged and range hens, respectively). Vitamin A and E levels were not affected by the husbandry to which the hens were exposed but were lowest at 62 wk of age. The age of the hens did not influence the fat levels in the egg, but cholesterol levels were highest (P < 0.001) at 62 wk of age (172.54 mg/50 g). Although range production did not influence the cholesterol level in the egg, there was an increase in fat levels in eggs produced on the range. © 2011 Poultry Science Association Inc.

Dusling K.,North Carolina State University | Venugopalan R.,Brookhaven National Laboratory
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We perform a detailed comparison of long-range rapidity correlations in the color glass condensate framework to high multiplicity dihadron data in proton-proton and proton-lead collisions from the CMS, ALICE and ATLAS experiments at the LHC. The overall good agreement thus far of the nontrivial systematics of theory with data is strongly suggestive of gluon saturation and the presence of subtle quantum interference effects between rapidity separated gluons. In particular, the yield of pairs collimated in their relative azimuthal angle Δφ∼0, is sensitive to the shape of unintegrated gluon distributions in the hadrons that are renormalization group evolved in rapidity from the beam rapidities to those of the measured hadrons. We present estimates for the collimated dihadron yield expected in central deuteron-gold collisions at the Relativistic Heavy Ion Collider. © 2013 American Physical Society.

DeCarolis J.F.,North Carolina State University
Energy Economics | Year: 2011

Energy-economy optimization models - encoded with a set of structured, self-consistent assumptions and decision rules - have emerged as a key tool for the analysis of energy and climate policy at the national and international scale. Given the expansive system boundaries and multi-decadal timescales involved, addressing future uncertainty in these models is a critical challenge. The approach taken by many modelers is to build larger models with greater complexity to deal with structural uncertainty, and run a few highly detailed scenarios under different input assumptions to address parametric uncertainty. The result is often large and inflexible models used to conduct analysis that offers little insight. This paper introduces a technique borrowed from the operations research literature called modeling to generate alternatives (MGA) as a way to flex energy models and systematically explore the feasible, near-optimal solution space in order to develop alternatives that are maximally different in decision space but perform well with regard to the modeled objectives. The resultant MGA alternatives serve a useful role by challenging preconceptions and highlighting plausible alternative futures. A simple, conceptual model of the U.S. electric sector is presented to demonstrate the utility of MGA as an energy modeling technique. © 2010 Elsevier B.V.

Lackmann G.M.,North Carolina State University
Bulletin of the American Meteorological Society | Year: 2015

The results of a set of high-resolution numerical simulations, utilizing change fields computed from a subset of five IPCC AR4 GCM projections, demonstrate that large-scale thermodynamic change can influence the track and intensity of Hurricane Sandy even within the limits imposed by a highly similar initial synoptic weather pattern. land-use changes and coastal development and population growth undoubtedly increased vulnerability and the severity of societal impacts during the observed Hurricane Sandy relative to what would have happened in the past. It must be understood that past changes are estimates, and that future projections are uncertain and depend on many factors. The GCM projections designed to elucidate the impacts of an increase in anthropogenic greenhouse gas forcing and are not intended to account for all types of climate forcing. GCM simulations can accurately reproduce the global surface temperature trends during the simulation period, there is considerable uncertainty in regional changes. Future work will utilize alternate datasets, including the more recent CMIP5 GCM data, and explore different initialization times.

Jagannadham K.,North Carolina State University
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2013

Copper-graphene composite films were deposited on copper foil using electrochemical deposition. Four electrolyte solutions that each consist of 250 mL of graphene oxide suspension in distilled water and increasing volume of 0.2 M solution of CuSO4 in steps of 250 mL were used to deposit the composite films with and without a magnetic stirrer. Graphene oxide in the films was reduced to graphene by hydrogen treatment for 6 hours at 673 K (400 C). The samples were characterized by X-ray diffraction for identification of phases, scanning electron microscopy for distribution of graphene, energy dispersive spectrometry for evaluation of elemental composition, electrical resistivity and temperature coefficient of electrical resistance and thermal conductivity. Effective mean field analysis (EMA) was used to determine the volume fraction and electrical conductivity of graphene and interfacial thermal conductance between graphene and copper. The electrical resistivity was reduced from 2.031 to 1.966 μΩ cm and the thermal conductivity was improved from 3.8 to 5.0 W/cm K upon addition of graphene platelets to electrolytic copper. The use of stirrer during deposition of the films increased the average size and the thickness of the graphene platelets and as a result the improvement in electrical conductivity was lower compared to the values obtained without the stirrer. Using the EMA, the volume fraction of graphene platelets that was responsible for the improvement in the electrical conductivity was found to be lower than that for the improvement in the thermal conductivity. The results of the analysis are used to determine the volume fraction of the thinner and the thicker graphene platelets in the composite films. © 2012 The Minerals, Metals & Materials Society and ASM International.

Frank S.D.,North Carolina State University
Biological Control | Year: 2010

The goal of banker plant systems is to sustain a reproducing population of natural enemies within a crop that will provide long-term pest suppression. The most common banker plant system consists of cereal plants infested with Rhopalosiphum padi L. as a host for the parasitoid Aphidius colemani L. Aphidius colemani continually reproduce and emerge from the banker plants to suppress aphid pests such as Aphis gossypii Glover and Myzus persicae Sulzer. Banker plant systems have been investigated to support 19 natural enemy species targeting 11 pest species. Research has been conducted in the greenhouse and field on ornamental and food crops. Despite this there is little consensus of an optimal banker plant system for even the most frequently targeted pests. Optimizing banker plant systems requires future research on how banker plants, crop species, and alternative hosts interact to affect natural enemy preference, dispersal, and abundance. In addition, research on the logistics of creating, maintaining, and implementing banker plant systems is essential. An advantage of banker plant systems over augmentative biological control is preventative control without repeated, expensive releases of natural enemies. Further, banker plants conserve a particular natural enemy or potentially the 'right diversity' of natural enemies with specific alternative resources. This may be an advantage compared to conserving natural enemy diversity per se with other conservation biological control tactics. Demonstrated grower interest in banker plant systems provides an opportunity for researchers to improve biological control efficacy, economics, and implementation to reduce pesticide use and its associated risks. © 2009 Elsevier Inc. All rights reserved.

Holland J.B.,North Carolina State University
Genome Biology | Year: 2015

A multiparent advanced-generation intercross population of maize has been developed to help plant geneticists identify sequence variants affecting important agricultural traits. © 2015.

Hunt W.F.,North Carolina State University | Davis A.P.,University of Maryland University College | Traver R.G.,Villanova University
Journal of Environmental Engineering (United States) | Year: 2012

Bioretention is one of the most commonly used stormwater control measures (SCMs) in North America and Australasia. However, current design is not targeted to regulatory need, often reflecting an outdated understanding of how and why bioretention works. The purpose of this manuscript is to synthesize research to recommend a suite of design standards focused on the purpose of bioretention SCM. Both hydrologic (peak flow mitigation, infiltration, annual hydrology, and stream stability) and water quality [total suspended solids (TSS) and particulates, pathogen-indicator species, metals, hydrocarbons, phosphorus, nitrogen, and temperature] regulatory and stream ecology needs are addressed. Bioretention cells designed to meet a prioritized subset of those measures would be substantially different than cells that are designed for a different subset of needs. Designers have the ability to adjust bowl volume, media composition, media depth, underdrainage configuration, and vegetation type. This study examines how each of those design parameters can be adjusted such that a "one size fits all" approach is no longer the norm. © 2012 American Society of Civil Engineers.

Schreck III C.J.,North Carolina State University | Molinari J.,Albany State University
Monthly Weather Review | Year: 2011

The Madden-Julian oscillation (MJO) influences tropical cyclone formation around the globe. Convectively coupled Kelvin waves are often embedded within the MJO, but their role in tropical cyclogenesis remains uncertain. This case study identifies the influences of the MJO and a series of Kelvin waves on the formation of two tropical cyclones. Typhoons Rammasun and Chataan developed in the western North Pacific on 28 June 2002. Two weeks earlier, conditions had been unfavorable for tropical cyclogenesis because of uniform trade easterlies and a lack of organized convection. The easterlies gave way to equatorial westerlies as the convective envelope of the Madden-Julian oscillation moved into the region. A series of three Kelvin waves modulated the development of the westerlies. Cyclonic potential vorticity (PV) developed in a strip between the growing equatorial westerlies and the persistent trade easterlies farther poleward. Rammasun and Chataan emerged from the apparent breakdown of this strip. The cyclonic PV developed in association with diabatic heating from both the MJO and the Kelvin waves. The tropical cyclones also developed during the largest superposition of equatorial westerlies from the MJO and the Kelvin waves. This chain of events suggests that the MJO and the Kelvin waves each played a role in the development of Rammasun and Chataan. © 2011 American Meteorological Society.

Williams G.J.,North Carolina State University
Current Opinion in Structural Biology | Year: 2013

Naturally occurring polyketides and nonribosomal peptides with broad and potent biological activities continue to inspire the discovery of new and improved analogs. The biosynthetic apparatus responsible for the construction of these natural products has been the target of intensive protein engineering efforts. Traditionally, engineering has focused on substituting individual enzymatic domains or entire modules with those of different building block specificity, or by deleting various enzymatic functions, in an attempt to generate analogs. This review highlights strategies based on site-directed mutagenesis of substrate binding pockets, semi-rational mutagenesis, and whole-gene random mutagenesis to engineer the substrate specificity, activity, and protein interactions of polyketide and nonribosomal peptide biosynthetic machinery. © 2013 Elsevier Ltd.

Schafer T.,North Carolina State University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

We compute second-order transport coefficients of the dilute Fermi gas at unitarity. The calculation is based on kinetic theory and the Boltzmann equation at second order in the Knudsen expansion. The second-order transport coefficients describe the shear stress relaxation time, nonlinear terms in the strain-stress relation, and nonlinear couplings between vorticity and strain. An exact calculation in the dilute limit gives τR=η/P, where τR is the shear stress relaxation time, η is the shear viscosity, and P is pressure. This relation is identical to the result obtained using the Bhatnagar-Gross-Krook approximation to the collision term, but other transport coefficients are sensitive to the exact collision integral. © 2014 American Physical Society.

Lange K.,University of California at Los Angeles | Zhou H.,North Carolina State University
Mathematical Programming | Year: 2014

This paper derives new algorithms for signomial programming, a generalization of geometric programming. The algorithms are based on a generic principle for optimization called the MM algorithm. In this setting, one can apply the geometric-arithmetic mean inequality and a supporting hyperplane inequality to create a surrogate function with parameters separated. Thus, unconstrained signomial programming reduces to a sequence of one-dimensional minimization problems. Simple examples demonstrate that the MM algorithm derived can converge to a boundary point or to one point of a continuum of minimum points. Conditions under which the minimum point is unique or occurs in the interior of parameter space are proved for geometric programming. Convergence to an interior point occurs at a linear rate. Finally, the MM framework easily accommodates equality and inequality constraints of signomial type. For the most important special case, constrained quadratic programming, the MM algorithm involves very simple updates. © 2012 Springer-Verlag Berlin Heidelberg and Mathematical Optimization Society.

Xu J.,North Carolina State University | Shen G.,Shanghai Academy of Environmental Science
Bioresource Technology | Year: 2011

Spirodela oligorrhiza, a promising duckweed identified in previous studies, was examined under different cropping conditions for nutrient recovery from swine wastewater and biomass production. To prevent algae bloom during the start-up of a duckweed system, inoculating 60% of the water surface with duckweed fronds was required. In the growing season, the duckweed system was capable of removing 83.7% and 89.4% of total nitrogen (TN) and total phosphorus (TP) respectively from 6% swine lagoon water in eight weeks at a harvest frequency of twice a week. The total biomass harvested was 5.30 times that of the starting amount. In winter, nutrients could still be substantially removed in spite of the limited duckweed growth, which was probably attributed to the improved protein accumulation of duckweed plants and the nutrient uptake by the attached biofilm (algae and bacteria) on duckweed and walls of the system. © 2010 Elsevier Ltd.

Kuznetsov A.V.,North Carolina State University
Nanoscale Research Letters | Year: 2011

The aim of this article is to propose a novel type of a nanofluid that contains both nanoparticles and motile (oxytactic) microorganisms. The benefits of adding motile microorganisms to the suspension include enhanced mass transfer, microscale mixing, and anticipated improved stability of the nanofluid. In order to understand the behavior of such a suspension at the fundamental level, this article investigates its stability when it occupies a shallow horizontal layer. The oscillatory mode of nanofluid bioconvection may be induced by the interaction of three competing agencies: oxytactic microorganisms, heating or cooling from the bottom, and top or bottom- heavy nanoparticle distribution. The model includes equations expressing conservation of total mass, momentum, thermal energy, nanoparticles, microorganisms, and oxygen. Physical mechanisms responsible for the slip velocity between the nanoparticles and the base fluid, such as Brownian motion and thermophoresis, are accounted for in the model. An approximate analytical solution of the eigenvalue problem is obtained using the Galerkin method. The obtained solution provides important physical insights into the behavior of this system; it also explains when the oscillatory mode of instability is possible in such system. © 2011 Kuznetsov.

Handfield R.,North Carolina State University
Journal of Supply Chain Management | Year: 2011

This essay explores the reasons why studies with non-significant results often do not get published, by looking back on a subset of submissions from the past 15 years. Suggestions are then provided to authors who face the dilemma of non-significance. © 2011 Institute for Supply Management, Inc.™.

Lazzati D.,North Carolina State University | Begelman M.C.,University of Colorado at Boulder
Astrophysical Journal | Year: 2010

We study the spectrum of high-frequency radiation emerging from mildly dissipative photospheres of long-duration gamma-ray burst outflows. Building on the results of recent numerical investigations, we assume that electrons are heated impulsively to mildly relativistic energies by either shocks or magnetic dissipation at Thomson optical depths of several and subsequently cool by inverse Compton, scattering off the thermal photons of the photosphere. We show that even in the absence of magnetic field and non-thermal leptons, inverse Compton scattering produces power-law tails that extend from the peak of the thermal radiation, at several hundred keV, to several tens of MeV, and possibly up to GeV energies. The slope of the high-frequency power law is predicted to vary substantially during a single burst, and the model can easily account for the diversity of high-frequency spectra observed by BATSE. Our model works in baryonic as well as in magnetically dominated outflows, as long as the magnetic field component is not overwhelmingly dominant. © 2010. The American Astronomical Society.

Narayan R.J.,North Carolina State University
Journal of Biomedical Nanotechnology | Year: 2014

Treatment of insulin-dependent diabetes mellitus, also known as Type 1 diabetes mellitus, requires delivery of exogenous insulin via injection or pump. An alternative to syringe-based subcutaneous delivery of insulin involves use of microneedles. These < 300 μm diameter, 50-900 μm long needle shaped devices may be used for intradermal delivery of insulin. Benefits associated with microneedle-based delivery of insulin include minimal training for use, painless insertion, as well as the potential to combine microneedles with sensors and drug delivery devices to create an autonomous artificial pancreas. In this review, the efforts of academic and industrial researchers over the past decade to examine the functionality of microneedles for delivery of insulin, including insulin-containing nanomaterials, via in vitro, ex vivo, and in vivo studies are considered. Copyright © 2014 American Scientific Publishers. All rights reserved.

Trussell H.J.,North Carolina State University
Proceedings of the IEEE | Year: 2015

I have mentioned several tools that are available for creating effective analytical problems for online access for ECE students. This capability will be of particular interest for massive open online courses (MOOCs).While I am very familiar with only one of these tools, it is enough to convince me that we have the capability to use these tools to begin bringing W. L. Everitt's predictions to fruition. What we need is for others to recognize these resources and develop themto serve the community. I hope we will not have to wait another 50 years to see more progress © 2014 IEEE.

Graham J.P.,George Washington University | Polizzotto M.L.,North Carolina State University
Environmental Health Perspectives | Year: 2013

Background: Pit latrines are one of the most common human excreta disposal systems in low-income countries, and their use is on the rise as countries aim to meet the sanitation-related target of the Millennium Development Goals. There is concern, however, that discharges of chemical and microbial contaminants from pit latrines to groundwater may negatively affect human health. Objectives: Our goals were to a) calculate global pit latrine coverage, b) systematically review empirical studies of the impacts of pit latrines on groundwater quality, c) evaluate latrine siting standards, and d) identify knowledge gaps regarding the potential for and consequences of groundwater contamination by latrines. Methods: We used existing survey and population data to calculate global pit latrine coverage. We reviewed the scientific literature on the occurrence of contaminants originating from pit latrines and considered the factors affecting transport of these contaminants. Data were extracted from peer-reviewed articles, books, and reports identified using Web of ScienceSM, PubMed, Google, and document reference lists. Discussion: We estimated that approximately 1.77 billion people use pit latrines as their primary means of sanitation. Studies of pit latrines and groundwater are limited and have generally focused on only a few indicator contaminants. Although groundwater contamination is frequently observed downstream of latrines, contaminant transport distances, recommendations based on empirical studies, and siting guidelines are variable and not well aligned with one another. Conclusions: In order to improve environmental and human health, future research should examine a larger set of contextual variables, improve measurement approaches, and develop better criteria for siting pit latrines.

Lindsey J.S.,North Carolina State University
Accounts of Chemical Research | Year: 2010

(Figure Presented) Synthetic meso-substituted porphyrins offer significant attractions compared with naturally occurring β-substituted porphyrins. The attractions include the rectilinear arrangement of the four meso substituents and potential synthetic amenability from pyrrole and simple acyl reactants, thereby avoiding the cumbersome syntheses of β-substituted pyrroles. In practice, however, the classical methods for the synthesis of meso-substituted porphyrins were characterized by hightemperature reactions, limited scope of substituents, and statistical mixtures accompanied by laborious chromatography if porphyrins bearing two different types of substituents were sought. Such methods left unrealized the tremendous utility of meso-substituted porphyrins across the enormously broad field of porphyrin science, which touches pure chemistry; energy, life and materials sciences; and medicine. This Account surveys a set of strategies, developed over a generation, that provide rational access to porphyrins bearing up to four distinct meso substituents. A "2 + 2" route employs a dipyrromethane-1,9-dicarbinol and a dipyrromethane (bearing ABC- and D-substituents, respectively) in a two-step, one-flask process of acid-catalyzed condensation followed by oxidation at room temperature to form the free base "ABCD-porphyrin." A "bilane" route relies on the acid-catalyzed reaction of a 1-acyldipyrromethane (CD substituents) and a 9-bromodipyrromethane-1-carbinol (AB substituents) to form the corresponding 19-acyl-1-bromobilane. Reaction of the latter compound in the presence of MgBr2,1,8-diazabicyclo[5.4.0]undec7-ene (DBU), and toluene at reflux exposed to air affords the corresponding magnesium(II) porphyrin. The two routes are complementary, both in scope and in implementation. A suite of methods also affords trans-A2B2-porphyrins by reaction of a dipyrromethane and an aldehyde, self-condensation of a dipyrromethane-1 -carbinol, or self-condensation of a 1-acyldipyrromethane. These new routes are also useful for preparing sparsely substituted porphyrins, which bear fewer than four meso substituents (e.g., trans-AB-porphyrins, A-porphyrins). Because of their compact size and the ability to incorporate hydrophilic or amphipathic groups, such molecules are ideal for biological applications. The success of these new synthetic strategies has relied on a number of advances including (1) the development of simple yet efficient routes to dipyrromethanes, acyldipyrromethanes, and dipyrromethane-carbinols, (2) the identification of acid catalysts and reaction conditions for condensations of pyrromethane species without accompanying acidolysis (which underlies scrambling and formation of a mixture of porphyrin products), (3) the development of analytical methods to rapidly screen for scrambling and to characterize the distribution of oligopyrromethanes and macrocycles, (4) selection and refinement of synthetic methods to increase yields and to limit or avoid use of chromatography, thereby achieving scalability to multigram levels, and (5) exploitation of discoveries concerning the fundamental chemistry of pyrrolic species. With these developments, the prior era of porphyrin synthesis has been supplanted with rational routes that proceed under very mild conditions and afford a single porphyrin bearing up to four distinct meso substituents. The meso substituents encompass a very wide range of molecular complexity. The resulting porphyrins can serve as building blocks in the construction of model systems, as components of molecular materials, and as surrogates for naturally occurring tetrapyrrole macrocycles. © 2010 American Chemical Society.

Saaem I.,Duke University | Labean T.H.,North Carolina State University
Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology | Year: 2013

Judging by the number of atoms and the precision with which they are organized in three-dimensional space, DNA origami assemblies represent the current acme of human molecular engineering accomplishments. A subset of structural DNA nanotechnology, DNA origami makes use of the programmable molecular recognition of complementary DNA cohesions to assemble designed structures. This review will discuss the development of concepts and methods involved in DNA origami with an eye toward future increases in origami size and sequence complexity, as well as exploring different methods for the production of the DNA molecular components (long biologically synthesized scaffold strands and the complex set of chemically synthesized staple strands). In future applications, the incorporation and organization of other materials (metals and other inorganics, protein enzymes, and other nanomaterials) upon or within DNA origami should result in tools for "bottom-up" nanofabrication of biomedical, electronic, and photonic devices and materials. WIREs Nanomed Nanobiotechnol 2013, 5:150-162. doi: 10.1002/wnan.1204 For further resources related to this article, please visit the WIREs website. © 2013 Wiley Periodicals, Inc.

Bruno-Barcena J.M.,North Carolina State University | Azcarate-Peril M.A.,University of North Carolina at Chapel Hill
Journal of Functional Foods | Year: 2015

Prebiotics are ingredients selectively fermented by the intestinal microbiota that promote changes in its structure and/or metabolism, conferring health benefits to the host. Studies show that β (1-4) galacto-oligosaccharides [β (1-4) GOS], lactulose and fructo-oligosaccharides increase intestinal concentration of lactate and short chain fatty acids, and stool frequency and weight, and they decrease fecal concentration of secondary bile acids, fecal pH, and nitroreductase and β-glucuronidase activities suggesting a clear role in colorectal cancer (CRC) prevention. This review summarizes research on prebiotics bioassimilation, specifically β (1-4) GOS, and their potential role in CRC. We also evaluate research that shows that the impact of prebiotics on host physiology can be direct or through modulation of the gut intestinal microbiome, specifically the probiome (autochtonous beneficial bacteria). We present studies on a potential role in CRC progression to finally describe the current state of β (1-4) GOS generation for industrial production. © 2014 Elsevier Ltd.

Barrangou R.,North Carolina State University
Wiley Interdisciplinary Reviews: RNA | Year: 2013

Clustered regularly interspaced short palindromic repeats (CRISPR) together with associated sequences (cas) form the CRISPR-Cas system, which provides adaptive immunity against viruses and plasmids in bacteria and archaea. Immunity is built through acquisition of short stretches of invasive nucleic acids into CRISPR loci as 'spacers'. These immune markers are transcribed and processed into small noncoding interfering CRISPR RNAs (crRNAs) that guide Cas proteins toward target nucleic acids for specific cleavage of homologous sequences. Mechanistically, CRISPR-Cas systems function in three distinct stages, namely: (1) adaptation, where new spacers are acquired from invasive elements for immunization; (2) crRNA biogenesis, where CRISPR loci are transcribed and processed into small interfering crRNAs; and (3) interference, where crRNAs guide the Cas machinery to specifically cleave homologous invasive nucleic acids. A number of studies have shown that CRISPR-mediated immunity can readily increase the breadth and depth of virus resistance in bacteria and archaea. CRISPR interference can also target plasmid sequences and provide a barrier against the uptake of undesirable mobile genetic elements. These inheritable hypervariable loci provide phylogenetic information that can be insightful for typing purposes, epidemiological studies, and ecological surveys of natural habitats and environmental samples. More recently, the ability to reprogram CRISPR-directed endonuclease activity using customizable small noncoding interfering RNAs has set the stage for novel genome editing and engineering avenues. This review highlights recent studies that revealed the molecular basis of CRISPR-mediated immunity, and discusses applications of crRNA-guided interference. © 2013 John Wiley & Sons, Ltd.

Sozzani R.,North Carolina State University | Busch W.,Gregor Mendel Institute of Molecular Plant Biology | Spalding E.P.,University of Wisconsin - Madison | Benfey P.N.,Howard Hughes Medical Institute
Trends in Plant Science | Year: 2014

A variety of imaging methodologies are being used to collect data for quantitative studies of plant growth and development from living plants. Multi-level data, from macroscopic to molecular, and from weeks to seconds, can be acquired. Furthermore, advances in parallelized and automated image acquisition enable the throughput to capture images from large populations of plants under specific growth conditions. Image-processing capabilities allow for 3D or 4D reconstruction of image data and automated quantification of biological features. These advances facilitate the integration of imaging data with genome-wide molecular data to enable systems-level modeling. © 2013 Elsevier Ltd.

Water utilities can prepare for water distribution hazards, such as the presence of contaminants in the pipe network and failure of physical components. In contamination events, the complex interactions among managers' operational decisions, consumers' water consumption choices, and the hydraulics and contaminant transport in the water distribution system may influence the contaminant plume so that a typical engineering model may not properly predict public health consequences. A complex adaptive system (CAS) approach couples engineering models of a water distribution system with agent-based models of consumers and public officials. Development of threat management strategies, which prescribe a set of actions to mitigate public health consequences, is enabled through a simulation-optimization framework that couples evolutionary algorithms with the CAS model. Evolution strategies and genetic algorithm-based approaches are developed and compared for an illustrative case study to identify a flushing strategy for opening hydrants to minimize the number of exposed consumers and maintain acceptable levels of service in the network. © IWA Publishing 2013.

Gautier A.,Medical Research Council | Deiters A.,North Carolina State University | Chin J.W.,Medical Research Council
Journal of the American Chemical Society | Year: 2011

We report a general strategy for creating protein kinases in mammalian cells that are poised for very rapid activation by light. By photoactivating a caged version of MEK1, we demonstrate the specific, rapid, and receptor independent activation of an artificial subnetwork within the Raf/MEK/ERK pathway. Time-lapse microscopy allowed us to precisely characterize the kinetics of elementary steps in the signaling cascade and provided insight into adaptive feedback and rate-determining processes in the pathway. © 2011 American Chemical Society.

Kolorenc J.,ASCR Institute of Physics Prague | Kolorenc J.,University of Hamburg | Mitas L.,North Carolina State University
Reports on Progress in Physics | Year: 2011

Quantum Monte Carlo methods represent a powerful and broadly applicable computational tool for finding very accurate solutions of the stationary Schrödinger equation for atoms, molecules, solids and a variety of model systems. The algorithms are intrinsically parallel and are able to take full advantage of present-day high-performance computing systems. This review paper concentrates on the fixed-node/fixed-phase diffusion Monte Carlo method with emphasis on its applications to the electronic structure of solids and other extended many-particle systems. © 2011 IOP Publishing Ltd.

Nield D.A.,University of Auckland | Kuznetsov A.V.,North Carolina State University
International Journal of Heat and Mass Transfer | Year: 2014

We develop an extension of our previous thermal instability analysis of a nanofluid-saturated porous layer. The extension is based on a new boundary condition for the nanoparticle fraction, which is physically more realistic. In the previous model we imposed both temperature and nanoparticle volume fractions at the boundaries of the layer. It is now assumed that the value of the temperature can be imposed on the boundaries, but the nanoparticle fraction adjusts so that the nanoparticle flux is zero on the boundaries. The new boundary condition on the nanoparticle volume fraction is made possible by accounting for the contributions of the effect of thermophoresis to the nanoparticle flux. It is shown that, with the new boundary conditions, oscillatory convection cannot occur. The effect of the nanoparticles on non-oscillatory convection is destabilizing. © 2013 Elsevier Ltd. All rights reserved.

Baeza C.,University of Concepcion | Knappe D.R.U.,North Carolina State University
Water Research | Year: 2011

Factors controlling photolysis and UV/H 2O 2 photooxidation rates of the biochemically active compounds (BACs) sulfamethoxazole, sulfamethazine, sulfadiazine, trimethoprim, bisphenol A, and diclofenac were determined. Experiments were conducted with a quasi-collimated beam apparatus equipped with low-pressure UV lamps. The effects of pH, H 2O 2 concentration, and background water matrix (ultrapure water, lake water, wastewater treatment plant effluent) on BAC transformation rates were evaluated. For the sulfa drugs, solution pH affected direct photolysis rates but had little effect on the hydroxyl radical oxidation rate. For sulfamethoxazole, the neutral form photolyzed more easily than the anionic form while the reverse was the case for sulfamethazine and sulfadiazine. For trimethoprim, the hydroxyl radical oxidation rate was higher for the cationic form (pH 3.6) than for the neutral form (pH 7.85). Quantum yields and second order rate constants describing the reaction between the hydroxyl radical and BACs were determined and used together with background water quality data to predict fluence-based BAC transformation rate constants (k′). For both the lake water and wastewater treatment plant effluent matrices, predicted k′ values were generally in good agreement with experimentally determined k′ values. At typical UV/H 2O 2 treatment conditions (fluence = 540 mJ cm -2, H 2O 2 dose = 6 mg L -1), BAC transformation percentages in North Carolina lake water ranged from 43% for trimethoprim to 98% for diclofenac. In wastewater treatment plant effluent, BAC transformation percentages were lower (31-97%) at the same treatment conditions because the hydroxyl radical scavenging rate was higher. © 2011 Elsevier Ltd.

Gu Y.,Iowa State University | Wang G.,North Carolina State University | Fang N.,Iowa State University
ACS Nano | Year: 2013

Superlocalization of single molecules and nanoparticles has become an essential procedure to bring new insights into nanoscale structures and dynamics of biological systems. In the present study, superlocalization is combined with the newly introduced differential interference contrast (DIC) microscopy-based single-particle orientation and rotational tracking. The new technique overcomes the difficulty in localization of the antisymmetric DIC point spread function by using a dual-modality microscope configuration for simultaneous rotational tracking and localization of single gold nanorods with nanometer-scale precision. The new imaging setup has been applied to study the steric hindrance induced by relatively large cargos in the microtubule gliding assay and to track nanocargos in the crowded cellular environment. This technique has great potential in the study of biological processes where both localization and rotational information are required. © 2013 American Chemical Society.

Zhu Y.T.,North Carolina State University | Liao X.Z.,University of Sydney | Wu X.L.,CAS Institute of Mechanics
Progress in Materials Science | Year: 2012

Nanocrystalline (nc) materials can be defined as solids with grain sizes in the range of 1-100 nm. Contrary to coarse-grained metals, which become more difficult to twin with decreasing grain size, nanocrystalline face-centered-cubic (fcc) metals become easier to twin with decreasing grain size, reaching a maximum twinning probability, and then become more difficult to twin when the grain size decreases further, i.e. exhibiting an inverse grain-size effect on twinning. Molecular dynamics simulations and experimental observations have revealed that the mechanisms of deformation twinning in nanocrystalline metals are different from those in their coarse-grained counterparts. Consequently, there are several types of deformation twins that are observed in nanocrystalline materials, but not in coarse-grained metals. It has also been reported that deformation twinning can be utilized to enhance the strength and ductility of nanocrystalline materials. This paper reviews all aspects of deformation twinning in nanocrystalline metals, including deformation twins observed by molecular dynamics simulations and experiments, twinning mechanisms, factors affecting the twinning, analytical models on the nucleation and growth of deformation twins, interactions between twins and dislocations, and the effects of twins on mechanical and other properties. It is the authors' intention for this review paper to serve not only as a valuable reference for researchers in the field of nanocrystalline metals and alloys, but also as a textbook for the education of graduate students. © 2011 Elsevier Ltd. All rights reserved.

Markham S.K.,North Carolina State University
Journal of Product Innovation Management | Year: 2013

This paper describes and tests a model of the impact of front-end innovation activities on product performance. Data were collected from 272 companies to test the hypothesis that front-end performance impacts new product performance in the marketplace while controlling for new product development (NPD) processes and strategy. The data support the hypothesis that front-end performance favorably and independently impacts overall product success, time to market, market penetration, and financial performance. Front-end performance is predicted by a set of activities, including: the actual amount of front-end work done in various areas, specifically marketing, R&D, and concept development; the existence of a front-end process; the existence of a champion; and agreement on the order of developmental steps in the front end. Front-end activities are related to front-end performance, and front-end performance is related to NPD performance. This relationship highlights the distinction between front-end activities and standard product development practices and the importance of building competency in the front end. This is the first study that quantifies both the nature and amount of work done in the front end and relates that work to commercial performance. This research empirically demonstrates the distinction between the front-end and formal stages and gates types of systems. This suggests that the concept of the front end needs it own set of theoretical constructs to adequately describe and predict this categorically different set of activities. While this study demonstrates the difference between front-end and stage-gate systems, it does not establish the limits of those activities. From a managerial point of view recognizing that formal development and front-end activities are different mandates that these activities must be managed differently. In particular, the skills, structures, processes, governance, leadership, performance metrics, and resources must be assessed separately and differently. These findings suggest that firms should actively manage the flow of ideas from the front end into the more formal development programs. © 2013 Product Development & Management Association.

Butler-Ajibade P.,North Carolina State University
The ABNF journal : official journal of the Association of Black Nursing Faculty in Higher Education, Inc | Year: 2012

Health disparities related to cardiovascular disease (e.g., heart disease, high blood pressure, diabetes, and stroke) have remained higher in the African-American community than in other populations. African Americans living in the stroke belt are at an even higher risk for these conditions. Recently, increasing numbers of health agencies and researchers have successfully partnered with the black church to respond to the troubling statistics regarding these health disparities. Because the black church has a long history of being in the forefront of addressing critical social, economic, political, and health issues of African Americans, it is clear they are the principal gatekeepers in reversing these negative health trends. Working with churches to reduce cardiovascular disease is not a new concept. Hypertension screening programs were established at churches approximately 30 years ago. This article shares findings of elements to improve relations between community agencies and pastors, explores the strengths and challenges of working with churches, examines the role of the pastors in establishing successful programs, and identifies model programs. This article will identify key factors that are essential to cardiovascular health programs that purport to reach high-risk populations for cardiovascular disease with life saving environmental policies and behavior change strategies. Suggestions are provided for working with pastors, churches, and church resources to maximize the desired outcomes of future health promotion interventions. Examples of strategies include serving healthier choices during church meals; the inclusion of relevant scriptural citations in promotional materials; the implementation of instruction, training, and exercise programs; and, the provision of tangible compensation to the churches and congregants facilitating the health initiatives.

Morrill M.S.,North Carolina State University
Journal of Health Economics | Year: 2011

The effects of maternal employment on children's health are theoretically ambiguous and challenging to identify. There are trade-offs between income and time, and a mother's decision to work reflects, in part, her children's health and her underlying preferences. I utilize exogenous variation in each child's youngest sibling's eligibility for kindergarten as an instrument. Using the restricted-access National Health Interview Survey (1985-2004), I identify the effects on overnight hospitalizations, asthma episodes, and injuries/poisonings for children ages 7-17. Maternal employment increases the probability of each adverse health event by nearly 200 percent. These effects are robust and do not reflect a non-representative local effect. © 2011 Elsevier B.V.

Berman D.,Argonne National Laboratory | Krim J.,North Carolina State University
Progress in Surface Science | Year: 2013

Micro- and Nano-Electro-Mechanical Systems (MEMS and NEMS) represent existing (MEMS) and emerging (NEMS) technologies based on microfabrication of micron to nanometer scale miniature mechanical components (gears, latches, mirrors, etc.) that are integrated with electrical elements to allow for electro-mechanical actuation and/or capacitive displacement detection. One common aspect of MEMS and NEMS devices is that they have mechanical functionality that may include moveable parts whose motion is controlled by external electrical connections. Current fabrication methods, along with high surface to volume ratios, make MEMS and NEMS devices highly susceptible to surface forces and adsorbed surface species, to the point where the devices are now being increasingly utilized as sensitive probes in fundamental surface science studies. This sensitivity can potentially be used to great advantage if the devices can be made to operate reproducibly in well controlled environments. This review highlights a number of such recent studies, beginning with an overview of the fabrication processes employed for silicon, metal, diamond, graphene and carbon nanotube - based device technologies. A discussion of how traditional surface science studies on passive two-dimensional substrates compare to and contrast with studies performed on, or by, MEMS and/or NEMS devices, is also included. The overall goal is to highlight areas of current opportunity for surface scientists in the flourishing arena of micro- and nano-device fabrication and technology. © 2013 Elsevier Ltd. All rights reserved.

Riedl M.O.,Georgia Institute of Technology | Young R.M.,North Carolina State University
Journal of Artificial Intelligence Research | Year: 2010

Narrative, and in particular storytelling, is an important part of the human experience. Consequently, computational systems that can reason about narrative can be more effective communicators, entertainers, educators, and trainers. One of the central challenges in computational narrative reasoning is narrative generation, the automated creation of mean- ingful event sequences. There are many factors { logical and aesthetic { that contribute to the success of a narrative artifact. Central to this success is its understandability. We argue that the following two attributes of narratives are universal: (a) the logical causal progression of plot, and (b) character believability. Character believability is the percep- tion by the audience that the actions performed by characters do not negatively impact the audience's suspension of disbelief. Specifically, characters must be perceived by the audience to be intentional agents. In this article, we explore the use of refinement search as a technique for solving the narrative generation problem { to find a sound and believable sequence of character actions that transforms an initial world state into a world state in which goal propositions hold. We describe a novel refinement search planning algorithm { the Intent-based Partial Order Causal Link (IPOCL) planner { that, in addition to creating causally sound plot progression, reasons about character intentionality by identifying possi- ble character goals that explain their actions and creating plan structures that explain why those characters commit to their goals. We present the results of an empirical evaluation that demonstrates that narrative plans generated by the IPOCL algorithm support audi- ence comprehension of character intentions better than plans generated by conventional partial-order planners. © 2010 AI Access Foundation. All rights reserved.

Zhou G.-P.,Gordon Life Science Institute | Zhou G.-P.,North Carolina State University
Journal of Theoretical Biology | Year: 2011

Wenxiang diagram is a new two-dimensional representation that characterizes the disposition of hydrophobic and hydrophilic residues in α-helices. In this research, the hydrophobic and hydrophilic residues of two leucine zipper coiled-coil (LZCC) structural proteins, cGKIα 1-59 and MBS CT35 are dispositioned on the wenxiang diagrams according to heptad repeat pattern (abcdefg) n, respectively. Their wenxiang diagrams clearly demonstrate that the residues with same repeat letters are laid on same side of the spiral diagrams, where most hydrophobic residues are positioned at a and d, and most hydrophilic residues are localized on b, c, e, f and g polar position regions. The wenxiang diagrams of a dimetric LZCC can be represented by the combination of two monomeric wenxiang diagrams, and the wenxiang diagrams of the two LZCC (tetramer) complex structures can also be assembled by using two pairs of their wenxiang diagrams. Furthermore, by comparing the wenxiang diagrams of cGKIα 1-59 and MBS CT35, the interaction between cGKIα 1-59 and MBS CT35 is suggested to be weaker. By analyzing the wenxiang diagram of the cGKIα 1-59.MBS CT42 complex structure, most affected residues of cGKIα 1-59 by the interaction with MBS CT42 are proposed at positions d, a, e and g of the LZCC structure. These findings are consistent with our previous NMR results. Incorporating NMR spectroscopy, the wenxiang diagrams of LZCC structures may provide novel insights into the interaction mechanisms between dimeric, trimeric, tetrameric coiled-coil structures. © 2011 Elsevier Ltd.

Bonner J.C.,North Carolina State University
Expert Review of Respiratory Medicine | Year: 2011

Nanoparticle drug-delivery systems offer the potential for improved efficacy of treatment, and yet there are also potential risks associated with these novel therapeutic strategies. An attractive property of carbon nanotubes (CNTs) is that the tube- or fiber-like structure allows for extensive functionalization and loading of cargo. However, a large body of evidence indicates that CNTs may have adverse effects if used in drug delivery as they have been shown to cause pulmonary fibrosis and exacerbate lung disease in rodents with pre-existing lung diseases. Major factors that cause these toxic effects are the high aspect ratio, durability and residual metal content that generate reactive oxygen species. Therefore, careful consideration should be given to the possibility that lung inflammation or fibrosis could be significant side effects caused by a CNT-based drug-delivery system, thereby outweighing any potential beneficial effects of therapeutic treatment. However, functionalization of CNTs to modulate aspect ratio, biodegradability and to remove residual metals could allow for safe design of CNTs for use in drug delivery in certain circumstances. © 2011 Expert Reviews Ltd.

Line D.E.,North Carolina State University
Environmental Monitoring and Assessment | Year: 2013

In this study, baseflow and storm discharges were monitored in seven watersheds of varying development density to document the effects of development on stream water quality. In addition, two of the watersheds contained package wastewater treatment facilities, which were evaluated as an alternative to residential on-site septic systems. Monthly grab samples of baseflow and flow-proportional samples of storm event discharge were collected and analyzed for nitrogen, phosphorus, sediment, and bacteria. For the five watersheds without wastewater treatment facilities, a significant linear relationship was documented between fecal coliform and enterococci levels in baseflow samples and the percentage of residential or impervious area. For the two watersheds with wastewater discharge, bacteria levels were significantly greater than those from the two relatively undeveloped watersheds. These results indicate that bacteria levels increased with increasing residential development even if many of the septic systems were replaced by a community wastewater treatment system. Computed annual export rates for ammonia nitrogen (NH3-N) were correlated to the percentage of impervious surfaces in the watersheds, while the rates for other nitrogen forms, total phosphorus, and total suspended sediment were not. Annual export rates from the two mostly undeveloped watersheds were greater than a compilation of rates for undeveloped areas across the USA. Export from the four watersheds with more than 68 % residential land use was less than those reported from local and national studies of residential areas. © 2013 Springer Science+Business Media Dordrecht.

Narayan J.,North Carolina State University
Acta Materialia | Year: 2013

This paper discusses recent progress in thin film epitaxy across the misfit scale through the paradigm of domain matching epitaxy (DME). This epitaxy across the misfit scale is critical for integrating multifunctionality on a chip and creating smart structures for next-generation solid-state devices. There are three sources of strains that are cumulative at the growth temperature, and the relaxation process starts during the growth process. Upon cooling, unrelaxed lattice, thermal and defect strains give rise to net residual strains. In large misfit (* ≥ 10%) systems, where lattice misfit strain is predominant, it can be relaxed completely, and then only thermal and defect strains remain upon cooling. In low misfit systems, all three sources contribute to the residual strain upon cooling, as result of incomplete lattice relaxation. The predominant strain relaxation mechanism in thin films is by nucleation of dislocations at the free surface, as the nucleation energy in the bulk is considerably higher. At the free surface, the activation barrier for dislocation nucleation is considerably lower at the steps. Since the step formation energy is lower under a compressive stress compared with tensile stress, it reduces nucleation energy under compressive stress and lowers the critical thickness compared with tensile stresses in thin films. Once the dislocation nucleates, it propagates or glides to the interface to relieve the strain. However, if lattice frictional stress in the film is high, most dislocations may not reach the interface, depending upon the growth temperature and rate. Thus, these two key steps, dislocation nucleation and propagation, play a critical role in the thin film relaxation process. Once the dislocations reach the interface, the atomic structure of the dislocation at the heterointerfaces determines its electronic properties, specifically trapping and recombination characteristics. It is found that the atomic structure of the dislocation is determined by the interplay between strain and chemical free energies. Thus, the dislocations (representing missing or extra planes) play a critical role in the relaxation of thin film heterostructures. This paper focuses on epitaxy across the misfit scale, based upon matching of integral multiples of lattice planes. If the misfit falls between the integral multiples, it is accommodated by the principle of domain variation, where domains alternate to accommodate the misfit. Details of epitaxy from low misfit (∼4%) in Ge/Si) to large misfit (∼22%) in TiN/Si are shown. In III-nitride/sapphire and II-oxide/sapphire systems, this paper deals with polar orientations, where misfit is uniform in the basal plane, and non-polar orientations, where misfit varies over an order of magnitude in the film plane. It is shown that the DME paradigm is key to the integration of thin film heterostructures across the misfit scale and other complex systems such as vanadium oxide and PZT systems on Si(1 0 0) substrates for the integration of functionalities on a computer chip. Finally, it is shown that the formation of epitaxial and self-assembled nanodots on Si(1 0 0) provides a critical advance, with tremendous implications for information and data storage and related nanomagnetics applications. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Zheng L.,University of Victoria | Lu N.,North Carolina State University | Cai L.,University of Victoria
IEEE Transactions on Smart Grid | Year: 2013

This paper presents methodologies for deriving reliability performance of wireless communication networks to support demand response (DR) control. First, the impact of communication impairments on a direct DR control program is investigated. Second, the outage probability of a wireless link is modelled and quantified, considering the multipath fading, shadowing, and random path loss given the location distribution of smart meters. Third, the distributions of packet delivery ratio are derived for two wireless network architectures: the single-hop infrastructure-based network and the multi-hop mesh network. Simulation results verify the above reliability models and provide important insights on the coverage of wireless communication networks considering the reliability requirements of DR programs. © 2012 IEEE.

Simone-Finstrom M.D.,North Carolina State University | Spivak M.,University of Minnesota
PLoS ONE | Year: 2012

The constant pressure posed by parasites has caused species throughout the animal kingdom to evolve suites of mechanisms to resist infection. Individual barriers and physiological defenses are considered the main barriers against parasites in invertebrate species. However, behavioral traits and other non-immunological defenses can also effectively reduce parasite transmission and infection intensity. In social insects, behaviors that reduce colony-level parasite loads are termed "social immunity." One example of a behavioral defense is resin collection. Honey bees forage for plant-produced resins and incorporate them into their nest architecture. This use of resins can reduce chronic elevation of an individual bee's immune response. Since high activation of individual immunity can impose colony-level fitness costs, collection of resins may benefit both the individual and colony fitness. However the use of resins as a more direct defense against pathogens is unclear. Here we present evidence that honey bee colonies may self-medicate with plant resins in response to a fungal infection. Self-medication is generally defined as an individual responding to infection by ingesting or harvesting non-nutritive compounds or plant materials. Our results show that colonies increase resin foraging rates after a challenge with a fungal parasite (Ascophaera apis: chalkbrood or CB). Additionally, colonies experimentally enriched with resin had decreased infection intensities of this fungal parasite. If considered self-medication, this is a particularly unique example because it operates at the colony level. Most instances of self-medication involve pharmacophagy, whereby individuals change their diet in response to direct infection with a parasite. In this case with honey bees, resins are not ingested but used within the hive by adult bees exposed to fungal spores. Thus the colony, as the unit of selection, may be responding to infection through self-medication by increasing the number of individuals that forage for resin. © 2012 Simone-Finstrom, Spivak.

Hatua K.,North Carolina State University
IEEE Transactions on Power Electronics | Year: 2011

Till date load-commutated inverter (LCI)-fed synchronous motor drive configuration is popular in high power applications (>10MW). The leading power factor operation of synchronous motor by excitation control offers this simple and rugged drive structure. On the contrary, LCI-fed induction motor drive is absent as it always draws lagging power factor current. Therefore, complicated commutation circuit is required to switch off thyristors for a current source inverter (CSI)-driven induction motor. It poses the major hindrance to scale up the power rating of CSI-fed induction motor drive. A new power topology for LCI-fed induction motor drive for medium-voltage drive application is proposed. A new induction machine (active-reactive induction machine) with two sets of three-phase winding is introduced as a drive motor. The proposed power configuration ensures sinusoidal voltage and current at the motor terminals. The total drive power is shared among a thyristor-based LCI, an insulated gate bipolar transistor (IGBT)-based two-level voltage source inverter (VSI), and a three-level VSI. The benefits of SCRs and IGBTs are explored in the proposed drive. Experimental results from a prototype drive verify the basic concepts of the drive. © 2006 IEEE.

Hodgson E.,North Carolina State University
Progress in Molecular Biology and Translational Science | Year: 2012

Toxins are produced by numerous microorganisms and invertebrates as well as by higher plants and animals. Venoms are produced by many groups of animals, from coelenterates to vertebrates. While toxins and venoms are the primary toxicological concern in natural ecosystems, they are frequently of importance in agroecosystems and in military deployments. They belong to a very large number of chemical classes and consequently are usually classified according to the groups of organisms producing them, for example, mycotoxins, algal toxins, and insect venoms. Plant toxins are representative of a larger group of phytochemicals known as secondary plant chemicals or plant allelochemicals. They may be acutely toxic, have chronic toxicity, or may be toxic at one dose but therapeutic at a lower dose. Some drugs of abuse are plant toxins abuse. A representative selection of the more important members of each category is provided. © 2012 Elsevier Inc. All rights reserved.

Narayan J.,North Carolina State University
MRS Communications | Year: 2013

Electrical fields can be used to heat selectively dislocations and grain boundaries to a much higher temperature compared with the bulk. This selective joule heating, if uncontrolled by limiting the current flow, can lead to melting of grain boundaries and sintering of poly- and nanocrystalline materials close to the theoretical density in a much shorter time due to fast diffusivities of the order of 10-4 to 10-5 cm2/s in the liquid. I refer to this sintering mode as selective-melt sintering, which can occur at lower overall temperatures with much lower energy consumption compared with conventional sintering involving solid-state diffusion. © Materials Research Society 2013.

Physiologic relaxation of vascular smooth muscle is induced by the cyclic guanosine monophosphate (cGMP)- dependent protein kinase Iα enzyme (cGKIα), which activates myosin phosphatase (MLCP). This activation process is thought to occur through the interaction involving both N- and C-terminal leucine zipper coiled-coil (LZCC) domains of the kinase enzyme (cGKIα) with the myosin binding subunit (MBS) of MLCP. In this review, I summarize how to define the LZCC domains in both N-terminal cGKIα 1-59and C-terminal MBS proteins using predictive and experimental methods, how to make a rapid and accurate structure determination of a cGKIα 1-59 molecule using NMR's residual dipolar coupling (RDC) measurements, and how to indentify the existence of a weak protein interaction between N-terminal LZCC domain (cGKIα 1-59) and a LZCC domain (MBSCT42) within the C-terminal MBS. In addition, the location and orientation of the residues in LZCC proteins can be readily visualized using a novel diagram, the so-called "wenxiang diagram", which is more advantageous than traditional helical wheel diagrams in analyzing LZCC protein structures and their action mechanisms. Using the composed wenxiang diagrams, we have characterized the interaction between cGKIα 1-59 and another LZCC molecule (MBS CT42), and deduced that the most affected residues of these two LZCC molecules might be at the positions d, a, e and g. These studies and findings are also covered in this review. It is intriguing to see that the successful incorporation of wenxiang diagrams and NMR spectroscopy in the LZCC structural and functional studies may provide some insights into protein-protein interaction mechanisms. © 2011 Bentham Science Publishers.

Hoefer M.A.,North Carolina State University
Journal of Nonlinear Science | Year: 2014

The long-time behavior of an initial step resulting in a dispersive shock wave (DSW) for the one-dimensional isentropic Euler equations regularized by generic, third-order dispersion is considered by use of Whitham averaging. Under modest assumptions, the jump conditions (DSW locus and speeds) for admissible, weak DSWs are characterized and found to depend only upon the sign of dispersion (convexity or concavity) and a general pressure law. Two mechanisms leading to the breakdown of this simple wave DSW theory for sufficiently large jumps are identified: a change in the sign of dispersion, leading to gradient catastrophe in the modulation equations, and the loss of genuine nonlinearity in the modulation equations. Large amplitude DSWs are constructed for several particular dispersive fluids with differing pressure laws modeled by the generalized nonlinear Schrödinger equation. These include superfluids (Bose-Einstein condensates and ultracold fermions) and "optical fluids." Estimates of breaking times for smooth initial data and the long-time behavior of the shock tube problem are presented. Detailed numerical simulations compare favorably with the asymptotic results in the weak to moderate amplitude regimes. Deviations in the large amplitude regime are identified with breakdown of the simple wave DSW theory. © 2014 Springer Science+Business Media New York.

Felder R.M.,North Carolina State University | Brent R.,Education Designs Inc.
Journal of Engineering Education | Year: 2010

The National Effective Teaching Institute (NETI) is a three-day teaching workshop that has been given annually since 1991 in conjunction with the Annual ASEE Conference. Its goals are to improve the participants' teaching effectiveness, promote their engagement in scholarly teaching and educational scholarship, and motivate them to engage in instructional development on their campuses. To evaluate the impact of the NETI on its participants, a Web-based survey was administered to alumni of NETI offerings from 1993 to 2006. The study was designed to test the hypothesis that the NETI met its stated goals, and to the extent that it did, to identify factors in the workshop's structure and delivery that might have contributed to its success. An online survey collected information regarding the participants' awareness and use of selected teaching strategies, their students' and their own ratings of their teaching, and their engagement in scholarly teaching, educational research, and giving their own teaching workshops and seminars. The validity of the survey structure is supported by several published studies that compared self-assessments of teaching with external evaluations by trained observers. The NETI has motivated many of its participants to adopt or increase their use of proven teaching strategies known to correlate with improved student learning; made them more student-centered, scholarly, and reflective in their teaching practice; and induced many of them to engage in instructional development and educational scholarship. The NETI has satisfactorily met its goals. When interpreted in the light of a theory of adult motivation, the results support the effectiveness of disciplinespecific faculty development for engineering educators. © 2010.

Blondin J.M.,North Carolina State University
Astrophysical Journal | Year: 2013

We investigate the flip-flop instability observed in two-dimensional planar hydrodynamic simulations of Hoyle-Lyttleton accretion in the case of an accreting object with a radius much smaller than the nominal accretion radius, as one would expect in astrophysically relevant situations. Contrary to previous results with larger accretors, accretion from a homogenous medium onto a small accretor is characterized by a robust, quasi-Keplerian accretion disk. For gas with a ratio of specific heats of 5/3, such a disk remains locked in one direction for a uniform ambient medium. The accretion flow is more variable for gas with a ratio of specific heats of 4/3, with more dynamical interaction of the disk flow with the bow shock leading to occasional flips in the direction of rotation of the accretion disk. In both cases the accretion of angular momentum is determined by the flow pattern behind the accretion shock rather than by the parameters of the upstream flow. © 2013. The American Astronomical Society. All rights reserved.

de los Reyes F.L.,North Carolina State University
Water Research | Year: 2010

The use of molecular biological techniques for determining the levels and types of different microbial populations in bioreactors has led to the emergence of the microbial community 'structure-function' paradigm that is often used in research. Typically, lab- or full-scale systems are monitored for the relevant parameters, and these parameters are related to the changes in microbial populations. Research in activated sludge phenomena, such as filamentous bulking, filamentous foaming, nitrogen removal, and phosphorus removal, are replete with many examples of this 'structure-function' paradigm, most commonly those that involve 16S rRNA gene-based analysis of the microbial populations. In many cases, such studies assume a causal microbial population (e.g., a species that causes bulking or foaming), or conclude in identifying a causal population. However, assigning cause to specific organisms and populations is problematic in a complex environment such as wastewater bioreactors. The Koch-Henle postulates, the gold standard in evaluating causation of disease, have limitations when applied to systems with mixed microbial communities with complex interactions, particularly if pure cultures are not available. Molecular techniques that allow specific identification and quantification of organisms have been used by researchers to overcome the limitations of culture-based techniques, and at the same time, raised new questions on the applicability of causation postulates in environmental systems. In this paper, various causation criteria improving on the Koch-Henle postulates are presented. Complicating issues in assigning cause in wastewater bioreactors are identified. Approaches for determining cause-effect relationships are illustrated using 16S rDNA-based investigations of filaments that cause bulking and foaming in activated sludge. The hope is that a causation framework that accounts for the assumptions in molecular studies, as applied to wastewater treatment research, will lead to improved experimental design and analysis of data. © 2010 Elsevier Ltd.

Baliga B.J.,North Carolina State University
Semiconductor Science and Technology | Year: 2013

Recent success with the fabrication of high-performance GaN-on-Si high-voltage HFETs has made this technology a contender for power electronic applications. This paper discusses the properties of GaN that make it an attractive alternative to established silicon and emerging SiC power devices. Progress in development of vertical power devices from bulk GaN is reviewed followed by analysis of the prospects for GaN-on-Si HFET structures. Challenges and innovative solutions to creating enhancement-mode power switches are reviewed. © 2013 IOP Publishing Ltd.

Findlay S.D.,Monash University | LeBeau J.M.,North Carolina State University
Ultramicroscopy | Year: 2013

A non-uniform response across scanning transmission electron microscope annular detectors has been found experimentally, but is seldom incorporated into simulations. Through case study simulations, we establish the nature and scale of the discrepancies which may arise from failing to account for detector non-uniformity. If standard detectors are used at long camera lengths such that the detector is within or near to the bright field region, we find errors in contrast of the order of 10%, sufficiently small for qualitative work but non-trivial as experiments become more quantitative. In cases where the detector has been characterized in advance, we discuss the detector response normalization and how it may be incorporated in simulations. © 2012 Elsevier B.V.

Kuznetsov A.V.,North Carolina State University
Computer Methods in Biomechanics and Biomedical Engineering | Year: 2013

A model describing the propagation of positive injury signals from the lesion site in an axon towards the neuron soma is described. It is assumed that these signals are driven by dynein molecular motors. An analytical solution that accounts for the probability density function (pdf) of a dynein velocity distribution is obtained. Two examples of pdf of dynein velocity distributions that follow from the results published in Ross et al. (2006, Processive bidirectional motion of dynein-dynactin complexes in vitro. Nat Cell Biol. 8:562-570) and Deinhardt et al. (2006, Rab5 and Rab7 control endocytic sorting along the axonal retrograde transport pathway. Neuron 52:293-305) are considered. The effect of dynein velocity distribution on the rate of spreading of the signal wave is discussed. It is demonstrated that the obtained solution can be applied to the problem of how neurons measure the distance between the lesion site and the neuron soma. © 2013 © 2013 Taylor & Francis.

Weninger K.R.,North Carolina State University
Nature Structural and Molecular Biology | Year: 2011

Mechanistic details about complexin's contradictory double life as both a facilitator and an inhibitor of SNARE-mediated synaptic vesicle fusion have been challenging to uncover. A series of studies in this issue addresses the problem by revealing a switchable complexin conformation in which fusion arrest occurs when complexin clamps neighboring SNAREs. © 2011 Nature America, Inc. All rights reserved.

Genzer J.,North Carolina State University
Annual Review of Materials Research | Year: 2012

We provide a succinct account of surface-bound gradient structures created from soft materials or those facilitating the study of soft materials behavior. We commence by classifying the chief attributes of gradient structures and offer a few examples of fabrication methods employed to generate such structures. We then illustrate the versatility of gradient assemblies in functioning as recording media for monitoring a physico-chemical process, facilitating fast screening of physico-chemical phenomena, and playing an important part in the design and fabrication of surface-anchored molecular and macromolecular engines for the directed transport of soft materials. © Copyright ©2012 by Annual Reviews. All rights reserved.

Schafer T.,North Carolina State University
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

The shear viscosity of a two-dimensional Fermi gas interacting via a short-range potential with scattering length a 2d in kinetic theory is computed. It is found that classical kinetic theory predicts that the shear viscosity to entropy density ratio of a strongly interacting two-dimensional gas is comparable to that of the three-dimensional unitary gas. Results are applied to the damping of collective modes of a trapped Fermi gas, and compared to experimental data recently obtained by Vogt. © 2012 American Physical Society.

Deiters A.,North Carolina State University
AAPS Journal | Year: 2010

Recently, the RNA interference (RNAi) pathway has become the target of small molecule inhibitors and activators. RNAi has been well established as a research tool in the sequence-specific silencing of genes in eukaryotic cells and organisms by using exogenous, small, double-stranded RNA molecules of approximately 20 nucleotides. Moreover, a recently discovered post-transcriptional gene regulatory mechanism employs microRNAs (miRNAs), a class of endogenously expressed small RNA molecules, which are processed via the RNAi pathway. The chemical modulation of RNAi has important therapeutic relevance, because a wide range of miRNAs has been linked to a variety of human diseases, especially cancer. Thus, the activation of tumor-suppressive miRNAs and the inhibition of oncogenic miRNAs by small molecules have the potential to provide a fundamentally new approach for the development of cancer therapeutics. © 2009 American Association of Pharmaceutical Scientists.

Nalepa C.A.,North Carolina State University
Evolution and Development | Year: 2010

Basal termites possess two developmental features that eusocial Hymenoptera lack: the majority of colony members are juveniles whose somatic and reproductive development is temporarily or permanently suspended, and individual development is characterized by extreme phenotypic plasticity. An examination of the literature indicates that the basis for these unique ontogenetic characters is not the prolongation of a pronymphal stage into postembryonic development, as recently suggested. Like other hemimetabolous insects, termites have three embryonic cuticles, and the pronymphal (EC3) cuticle is shed during or shortly after hatch. Nonetheless, a different developmental landmark, dorsal closure, occurs later during embryogenesis in termites than it does in their cockroach relatives, clearly indicating ontogenetic repatterning from an ancestral state. An alternate hypothesis for the origin of isopteran phenotypic plasticity becomes apparent if we remain focused on the phylogenetic and social context of termite evolution. Altricial development occurs in both vertebrate and invertebrate taxa, evolves in response to the parental environment, and is displayed by two distantly related, biparental, wood-feeding cockroaches, including Cryptocercus, the sister-group to termites. It is therefore likely the condition was present in subsocial termite ancestors, and played a complex, multidimensional role in the transition to eusociality. Most relevant to current arguments is that a shift in responsibility for the care of altricial dependents, from parents to the first nutritionally independent nymphs in the family (alloparents), resulted in the developmental stasis of alloparents at a relatively young age. Because early instar cockroaches are not metamorphically competent, these young alloparents would have provided a novel developmental template on which selection could act. © 2010 Wiley Periodicals, Inc.

Lu Z.,Kennesaw State University | Breidt F.,North Carolina State University
Frontiers in Microbiology | Year: 2015

A novel phage, F241, specific for Escherichia coli O157:H7 was isolated from an industrial cucumber fermentation where both acidity (pH ≤ 3.7) and salinity (≥5% NaCl) were high. The phage belongs to the Myoviridae family. Its latent period was 15 min and average burst size was 53 phage particles per infected cell. The phage was able to lyse 48 E. coli O157:H7 strains, but none of the 18 non-O157 strains (including E. coli O104:H7) or the 2 O antigen-negative mutants of O157:H7 strain, 43895Δper (also lacking H7 antigen) and F12 (still expressing H7 antigen). However, the phage was able to lyse a per-complemented strain (43895ΔperComp) which expresses O157 antigen. These results indicated that phage Φ241 is specific for O157 antigen, and E. coli strains lacking O157 antigen were resistant to the phage infection, regardless of the presence or absence of H7 antigen. SDS-PAGE profile revealed at least 13 structural proteins of the phage. The phage DNA was resistant to many commonly used restriction endonucleases, suggesting the presence of modified nucleotides in the phage genome. At the multiplicity of infection of 10, 3, or 0.3, the phage caused a rapid cell lysis within 1 or 2 h, resulting in 3.5- or 4.5-log-unit reduction in cell concentration. The high lytic activity, specificity and tolerance to low pH and high salinity make phage Φ241 a potentially ideal biocontrol agent of E. coli O157:H7 in various foods. To our knowledge, this is the first report on E. coli O157:H7 phage isolated from high acidity and salinity environment. © 2015 Lu and Breidt.

Armored scale insects are among the most difficult to manage and economically important arthropod pests in the production and maintenance of urban landscape plants. This is because of morphological traits that protect them from contact insecticides. I compared initial and season-long control of euonymus scale, Unaspis euonymi Comstock (Hemiptera: Diaspidae), by reduced-risk insecticides (insect growth regulators [IGRs], neonicotinoids, spirotetramat) to determine if they controlled scale as well as more toxic insecticides such as the organophosphate, acephate, and pyrethroid, bifenthrin. I also evaluated how these insecticides affected natural enemy abundance on experimental plants and survival when exposed to insecticide residue. All insecticides tested reduced first generation euonymus scale abundance. In 2009, reinfestation by second generation euonymus scale was highest on plants treated with acetamiprid and granular dinotefuran. In 2010, systemic neonicotinoids and spirotetramat prevented cottony cushion scale infestation 133 d after treatment whereas scale readily infested plants treated with bifenthrin and horticultural oil. Encarsia spp. and Cybocephalus spp. abundance was related to scale abundance. These natural enemies were generally less abundant than predicted by scale abundance on granular dinotefuran treated plants and more abundant on granular thiamethoxam treated plants. Bifenthrin residue killed 90100% of O. insidiosus and E. citrina within 24 h. My results indicate that reduced risk insecticides can provide season-long scale control with less impact on natural enemies than conventional insecticides. This could have economic and environmental benefits by reducing the number of applications necessary to protect nursery and landscape plants from scale. © 2012 Entomological Society of America.

Powell R.A.,North Carolina State University | Mitchell M.S.,University of Montana
Journal of Mammalogy | Year: 2012

Home range is a standard concept in animal ecology and behavior but few people try to understand what home ranges mean to the animals that have them and often assume that a home-range estimate, quantified using some method, is the home range. This leads to 2 problems. First, researchers put much energy into discerning and using the best methods for estimating home ranges while no one understands, really, what a home range is. Second, maps delineating home-range estimates may have little connection with what home ranges are and what they mean to the animals that have them. To gain insight into these problems, Roger Powell (hereafter, Roger) documented his own use of space for 65 days, obtaining complete data on where he went, what he did, and how much energy and money he expended and gained in each place. Roger's use of space is consistent with how other mammals use space and, therefore, examination of his data provides insight into what a home range is and how ecologists should approach quantifying other animals' home ranges. We present estimates of Roger's home range in 5 different metrics, or currencies, that provide important and different insights. Home-range estimators that combine different types of information to estimate the spatial distribution and qualities of resources that structure animal behavior (i.e., fitness surfaces) will probably provide the most insight into animals' home ranges. To make reasonable estimates of home ranges, researchers must collect data on habitat, resources, and other attributes of the landscape, so that they can understand basic behaviors of animals and understand how animals may view their environment. We propose that the best concept of a home range is that part of an animal's cognitive map of its environment that it chooses to keep updated. © 2012 American Society of Mammalogists.

Powell R.A.,North Carolina State University
Journal of Mammalogy | Year: 2012

Home ranges relate to all aspects of a mammal's biology. The 5 papers in this Special Feature provide statistical, economic, game theoretic, mechanistic, information dependent, and conceptual approaches to understanding home ranges and why animals have them. All the papers emphasize the importance of testing a priori hypotheses, especially hypotheses that elucidate why animals behave as they do. All the papers relate resources and habitat quality to home ranges. Finally, the authors oppose viewing home ranges as the product of measurements and suggest viewing home ranges as the cognitive maps that animals maintain and update. © 2012 American Society of Mammalogists.

Majda A.J.,Courant Institute of Mathematical Sciences | Harlim J.,North Carolina State University
Nonlinearity | Year: 2013

A central issue in contemporary science is the development of data driven statistical nonlinear dynamical models for time series of partial observations of nature or a complex physical model. It has been established recently that ad hoc quadratic multi-level regression (MLR) models can have finite-time blow up of statistical solutions and/or pathological behaviour of their invariant measure. Here a new class of physics constrained multi-level quadratic regression models are introduced, analysed and applied to build reduced stochastic models from data of nonlinear systems. These models have the advantages of incorporating memory effects in time as well as the nonlinear noise from energy conserving nonlinear interactions. The mathematical guidelines for the performance and behaviour of these physics constrained MLR models as well as filtering algorithms for their implementation are developed here. Data driven applications of these new multi-level nonlinear regression models are developed for test models involving a nonlinear oscillator with memory effects and the difficult test case of the truncated Burgers-Hopf model. These new physics constrained quadratic MLR models are proposed here as process models for Bayesian estimation through Markov chain Monte Carlo algorithms of low frequency behaviour in complex physical data. © 2013 IOP Publishing Ltd & London Mathematical Society.

Jambeck J.R.,University of Georgia | Geyer R.,University of California at Santa Barbara | Wilcox C.,Commonwealth Scientific and Industrial Research Organization | Siegler T.R.,DSM Environmental Services | And 4 more authors.
Science | Year: 2015

Plastic debris in the marine environment is widely documented, but the quantity of plastic entering the ocean from waste generated on land is unknown. By linking worldwide data on solid waste, population density, and economic status, we estimated the mass of land-based plastic waste entering the ocean. We calculate that 275 million metric tons (MT) of plastic waste was generated in 192 coastal countries in 2010, with 4.8 to 12.7 million MT entering the ocean. Population size and the quality of waste management systems largely determine which countries contribute the greatest mass of uncaptured waste available to become plastic marine debris. Without waste management infrastructure improvements, the cumulative quantity of plastic waste available to enter the ocean from land is predicted to increase by an order of magnitude by 2025. © 2015 American Association for the Advancement of Science. All rights reserved.

Bowen S.,North Carolina State University
Sociologia Ruralis | Year: 2011

Sociologists have used the concept of embeddedness to examine the relationships between social networks, social capital, cultural and cognitive elements and the construction of markets. Yet important questions remain regarding how local and extra-local actors actively construct embedded markets and how networks exhibit both embedding and disembedding tendencies. I use qualitative data on a case study of Comté cheese, an origin-labelled cheese produced in eastern France, to develop a more critical and precise analysis of what embeddedness means in the context of (localised) food systems. I demonstrate the importance of horizontal and vertical forms of embeddedness. The expansion of the market and the entry of extra-local actors into the chain put a strain on the proximity and close ties that have historically constituted the basis of the social embeddedness of the Comté supply chain. The institutions that the Inter-professional Committee for Gruyère from Comté has developed, the support offered by the French state and the actors' shared belief in terroir are forms of vertical embeddedness that all act to re-embed the Comté supply chain in its particular territory, even in the context of these destabilising forces. © 2011 The Author. Sociologia Ruralis © 2011 European Society for Rural Sociology.

Havner K.S.,North Carolina State University
International Journal of Plasticity | Year: 2011

The set of geometrically based slip-systems hardening inequalities introduced in Havner [Havner, K.S., 2005. Philos. Mag. 85, 2861-2894] is applied to the analysis and prediction of experimental response of fcc crystals in the singular 'Goss' orientation of the channel die test - loading direction (1 1 0), lateral constraint direction (1̄10). In addition, perspectives from my previous analyses of (1 1 0) channel die compression (2007-10) are presented and relationships between hardening moduli and compressive stress-strain curves evaluated for aluminum and copper in each lattice-orientation range. In the Goss orientation and for all orientation ranges in (1 1 0) compression, theoretical results for active slip planes, principal slip-rates, lattice rotation or stability, and finite crystal shearing are fully consistent with the gross-scale, finite-deformation experimental response of aluminum and copper crystals. © 2011 Elsevier Ltd. All rights reserved.

Johnson M.T.J.,North Carolina State University
Population Ecology | Year: 2011

In this review, I consider the contribution that common evening primrose (Oenothera biennis) has made towards integrating the ecology, evolution and genetics of species interactions. Oenothera biennis was among the earliest plant models in genetics and cytogenetics and it played an important role in the modern synthesis of evolutionary biology. More recently, population and ecological genetics approaches have provided insight into the patterns of genetic variation within and between populations, and how a combination of abiotic and biotic factors maintain and select on heritable variation within O. biennis populations. From an ecological perspective, field experiments show that genetic variation and evolution within populations can have cascading effects throughout communities. Plant genotype affects the preference and performance of individual arthropod populations, as well as the composition, biomass, total abundance and diversity of arthropod species on plants. A combination of experiments and simulation models show that natural selection on specific plant traits can drive rapid ecological changes in these same community variables. At the patch level, increasing genotypic diversity leads to a greater abundance and diversity of omnivorous and predaceous arthropods, which is also associated with increased biomass and fecundity of plants in genetically diverse patches. Finally, in questioning whether a community genetics perspective is needed in biology, I review several multifactorial experiments which show that plant genotype often explains as much variation in community variables as other ecological factors typically identified as most important in ecology. As a whole, research in the O. biennis system has contributed to a more complete understanding of the dynamic interplay between ecology, evolution and genetics. © 2010 The Society of Population Ecology and Springer.

Lackmann G.M.,North Carolina State University
Journal of Climate | Year: 2013

Previous studies have documented a feedback mechanism involving the cyclonic low-level jet (LLJ), poleward moisture flux and flux convergence, and condensational heating. Increased water vapor content and potentially heavier precipitation accompanying climate warming suggest the hypothesis that this feedback could strengthen with warming, contributing to amplification of precipitation extremes beyond what the thermodynamically controlled vapor increase would provide. Here, this hypothesis is tested with numerical simulations of a severe flooding event that took place in early May 2010 in the south-central United States. Control simulations with a mesoscale model capture the main features of the May 2010 flooding event. A pseudo-global warming approach is used to modify the current initial, surface, and boundary conditions by applying thermodynamic changes projected by an ensemble of GCMs for the A2 emission scenario. The observed synoptic pattern of the flooding event is replicated but with modified future thermodynamics, allowing isolation of thermodynamic changes on the moisture feedback. This comparison does not indicate a strengthening of the LLJ in the future simulation. Analysis of the lower-tropospheric potential vorticity evolution reveals that the southern portion of the LLJ over the Gulf of Mexico in this event was strengthened through processes involving the terrain of the Mexican Plateau; this aspect is largely insensitive to climate change. Despite the lack of LLJ strengthening, precipitation in the future simulation increased at a super Clausius-Clapeyron rate because of strengthened convective updrafts. © 2013 American Meteorological Society.

Hauenstein J.D.,North Carolina State University | Wampler C.W.,General Motors
Foundations of Computational Mathematics | Year: 2013

This article introduces the concept of isosingular sets, which are irreducible algebraic subsets of the set of solutions to a system of polynomial equations constructed by taking the closure of points with a common singularity structure. The definition of these sets depends on deflation, a procedure that uses differentiation to regularize solutions. A weak form of deflation has proven useful in regularizing algebraic sets, making them amenable to treatment by the algorithms of numerical algebraic geometry. We introduce a strong form of deflation and define deflation sequences, which, in a different context, are the sequences arising in Thom-Boardman singularity theory. We then define isosingular sets in terms of deflation sequences. We also define the isosingular local dimension and examine the properties of isosingular sets. While isosingular sets are of theoretical interest as constructs for describing singularity structures of algebraic sets, they also expand the kinds of algebraic set that can be investigated with methods from numerical algebraic geometry. © 2013 SFoCM.

Lee H.J.,North Carolina State University
Journal of Materials Science | Year: 2012

An anti-icing material can be created by mimicking one of nature's best known performances superhydrophobicity that is observed at many plant leaves. The anti-icing properties of a superhydrophobic surface depend on the surface morphology as well as the surface tension of the substrate. This implies that both the chemistry and the topography of the anti-icing coating material are important.Therefore, the relationship between the anti-icing properties and the morphology of a superhydrophobic surface should be understood and the study has to be extended beyond the bio-inspired superhydrophobic properties of the materials to similar properties toward ice. In this research, fluorosilane-treated superhydrophobic textile nonwovenfabric is prepared via wet-processing, and the anti-icing properties of the surface are observed and compared to those of three controls: an untreated fabric, a fluorosilanetreated smooth surface, and an untreated film. In order toevaluate anti-icing properties of superhydrophobic surfaces, super-cooled water was dropped on the surface of theprepared superhydrophobic fabric and all three controls. In addition, water drops were deposited on a superhydrophobic surface and the controls, and then the samples along with water drops were placed in a freezer to make the water drops completely freeze. After the samples were removed from the freezer, they were placed on a plate inclined at 45° to compare the ice removal process of the superhydrophobic surface with those of the controls. It was found that a superhydrophobic surface, which was created by combining low surface energy and micro/nano rough structures, could provide anti-icing properties to the surface. © 2012 Springer Science+Business Media, LLC.

Hernandez-Soriano M.C.,North Carolina State University | Jimenez-Lopez J.C.,Purdue University
Science of the Total Environment | Year: 2012

The mobility and bioavailability of cadmium, copper, lead and zinc were evaluated in three soils amended with different organic materials for two moisture regimes. Agricultural and reclamation activities impose fresh inputs of organic matter on soil while intensive irrigation and rainstorm increase soil waterlogging incidence. Moreover, scarcity of irrigation water has prompted the use of greywater, which contain variable concentrations of organic compounds such as anionic surfactants. Soils added with hay, maize straw or peat at 1% w/w were irrigated, at field capacity (FC) or saturated (S), with an aqueous solution of the anionic surfactant Aerosol 22 (A22), corresponding to an addition of 200. mg. C/kg. soil/day. Soil solution was extracted after one month and analysed for total soluble metals, dissolved soil organic matter and UV absorbance at 254. nm. Speciation analyses were performed with WHAM VI for Cd, Cu, Pb, and Zn. For selected scenarios, metal uptake by barley was determined. Metal mobility increased for all treatments and soils (Pb > Cu > Cd ≥ Zn) compared to control assays. The increase was significantly correlated (p < 0.05) with soil organic matter solubilisation for Cd (R = 0.68), Cu (R = 0.73) and Zn (R = 0.86). Otherwise, Pb release was related to aluminium solubilisation (R = 0.75), which suggests that Pb was originally co-precipitated with Al-DOC complexes in the solid phase. The effect of A22 in metal bioavailability, determined as free ion activities (FIA), was mainly controlled by soil moisture regime. For soil 3, metal bioavailability was up to 20 times lower for soil amended with hay, peat or maize compared to soil treated only with A22. When soil was treated with A22 at FC barley yield significantly decreased (p < 0.05) for the increase of Pb (R = 0.71) and Zn (R = 0.79) concentrations in shoot, while for saturated conditions such uptake was up to 3 times lower. Overall, metal bioavailability was controlled by solubilisation of soil organic matter and formation of metal-organo complexes. © 2012 Elsevier B.V.

Fitzpatrick S.M.,North Carolina State University
Radiocarbon | Year: 2011

The Caribbean Archaic Age (about 3000-500 BC) is thought to represent the earliest migration of humans from South America into the Lesser Antilles. However, there is a conspicuous absence of these early sites on islands south of the Guadeloupe Passage. To date, only a single radiocarbon date derived from a Queen conch (Strombus [Eustrombus] gigas) shell at the Heywoods site on Barbados was indicative of an Archaic occupation in the southern Antilles apart from a scattering of poorly reported (and mostly undated) sites. Given a number of issues associated with reliance on a single date to establish a cultural horizon, along with other problems derived from possible carbonate cement contamination and dating marine shells of a longer-lived species such as Queen conch, 2 additional samples were taken from the same unit and context at Heywoods to confirm whether the site is truly representative of an occupation during the Archaic Age. Results from a Queen conch shell adze in Context 7 dated to 2530-2200 BC (2 σ) and overlaps with the only other Archaic date from the site dating to 2320-1750 cal BC, while a juvenile specimen of the same species from Context 8 at 3280-2940 BC (2 σ) indicates that Barbados may have been settled even earlier. This suggests that Heywoods may be the oldest site between Trinidad and Puerto Rico. While further confirmation is required, these new dates have implications for understanding the nature of migratory ventures in the Caribbean, such as whether the "Southward Route" hypothesis-which postulates that earlier migration events from South America during the Ceramic Age (beginning ~500 BC) initially bypassed the southern Lesser Antilles-also applies to the Archaic, and if other phenomena such as active volcanism may have played a role in structuring settlement patterns. Questions also remain as to why Heywoods does not exhibit the typical lithic Archaic tool kit. © 2011 by the Arizona Board of Regents on behalf of the University of Arizona.

Scott M.J.,North Carolina State University
BMC Genetics | Year: 2014

The Australian sheep blowfly Lucilia cuprina (Wiedemann) is a major pest of sheep in Australia and New Zealand. From the 1960s to the 1980s there was a major effort to develop "field female killing" or FFK strains of L. cuprina that could be used for a cost-effective genetic control program. The FFK strains carried eye color mutations that were lethal to females in the field but not under conditions in the mass rearing facility. Males did not die in the field as normal copies of the eye color genes had been translocated to the Y chromosome and an autosome. Although the FFK strains showed some promise in field tests, a genetic control program in mainland Australia was never implemented for several reasons including instability of the FFK strains during mass rearing. A stable transgenic strain of L. cuprina that carried one or more dominant repressible female lethal genes offered the potential for efficient genetic control of blowfly populations. Here I review our research on tetracycline-repressible female lethal genetic systems, Lucilia germ-line transformation and sex determination genes that ultimately led to the successful development of transgenic "male-only" strains of L. cuprina. The technology developed for L. cuprina should be directly transferable to other blowfly livestock pests including L. sericata and the New World and Old World screwworm. 29. © 2014 Scott.

Okamoto K.W.,University of California at Los Angeles | Okamoto K.W.,North Carolina State University | Grether G.F.,University of California at Los Angeles
Ecology Letters | Year: 2013

Sympatric divergence in traits affecting species recognition can result from selection against cross-species mating (reproductive character displacement, RCD) or interspecific aggression (agonistic character displacement, ACD). When the same traits are used for species recognition in both contexts, empirically disentangling the relative contributions of RCD and ACD to observed character shifts may be impossible. Here, we develop a theoretical framework for partitioning the effects of these processes. We show that when both mate and competitor recognition depend on the same trait, RCD sets the pace of character shifts. Moreover, RCD can cause divergence in competitor recognition, but ACD cannot cause divergence in mate recognition. This asymmetry arises because males with divergent recognition traits may avoid needless interspecific conflicts, but suffer reduced attractiveness to conspecific females. Therefore, the key empirical issue is whether the same or different traits are used for mate recognition and competitor recognition. © 2013 Blackwell Publishing Ltd/CNRS.

Ade H.,North Carolina State University
European Physical Journal: Special Topics | Year: 2012

The use of soft X-rays near the carbon absorption edge (~270-300 eV) for small angle X-ray scattering and X-ray reflectivity experiments has significantly expanded the scientific capabilities to investigate thin films of soft matter that are primarily composed of carbon and low Z heteroatoms. In this perspective, we will delineate the basic operating principles and underlying physics of these methods and exemplify their impact by discussing a few recent applications. An extension of these methods to the fluorine edge is also included, demonstrating that the general concepts are also applicable to absorption edges of hetero atoms in soft matter. A short perspective of some future developments is provided. © 2012 EDP Sciences, Springer-Verlag.

Young J.D.,North Carolina State University
Requirements Engineering | Year: 2011

Online privacy policies describe organizations' privacy practices for collecting, storing, using, and protecting consumers' personal information. Users need to understand these policies in order to know how their personal information is being collected, stored, used, and protected. Organizations need to ensure that the commitments they express in their privacy policies reflect their actual business practices, especially in the United States where the Federal Trade Commission regulates fair business practices. Requirements engineers need to understand the privacy policies to know the privacy practices with which the software must comply and to ensure that the commitments expressed in these privacy policies are incorporated into the software requirements. In this paper, we present a methodology for obtaining requirements from privacy policies based on our theory of commitments, privileges, and rights, which was developed through a grounded theory approach. This methodology was developed from a case study in which we derived software requirements from seventeen healthcare privacy policies. We found that legal-based approaches do not provide sufficient coverage of privacy requirements because privacy policies focus primarily on procedural practices rather than legal practices. © 2010 Springer-Verlag London Limited.

The fabrication of multifunctional materials with tunable structure and properties requires programmed binding of their building blocks. For example, particles organized in long-ranged structures by external fields can be bound permanently into stiff chains through electrostatic or van der Waals attraction, or into flexible chains through soft molecular linkers such as surface-grafted DNA or polymers. Here, we show that capillarity-mediated binding between magnetic nanoparticles coated with a liquid lipid shell can be used for the assembly of ultraflexible microfilaments and network structures. These filaments can be magnetically regenerated on mechanical damage, owing to the fluidity of the capillary bridges between nanoparticles and their reversible binding on contact. Nanocapillary forces offer opportunities for assembling dynamically reconfigurable multifunctional materials that could find applications as micromanipulators, microbots with ultrasoft joints, or magnetically self-repairing gels. © 2015 Nature Publishing Group

Utilizing the so-called Thorpe scale as a measure of the turbulence outer scale, we propose a physically-based approach for the estimation of C2 n profiles in the lower atmosphere. This approach only requires coarse-resolution temperature profiles (a.k.a., soundings) as input, yet it has the intrinsic ability to capture layers of high optical turbulence. The prowess of this computationally inexpensive approach is demonstrated by validations against observational data from a field campaign over Mauna Kea, Hawaii. © 2015 Optical Society of America.

Mitchell G.E.,North Carolina State University | Mitchell G.E.,Triangle Universities Nuclear Laboratory | Richter A.,TU Darmstadt | Weidenmuller H.A.,Max Planck Institute for Nuclear Physics
Reviews of Modern Physics | Year: 2010

The application of random-matrix theory (RMT) to compound-nucleus (CN) reactions is reviewed. An introduction into the basic concepts of nuclear scattering theory is followed by a survey of phenomenological approaches to CN scattering. The implementation of a random-matrix approach into scattering theory leads to a statistical theory of CN reactions. Since RMT applies generically to chaotic quantum systems, that theory is, at the same time, a generic theory of quantum chaotic scattering. It uses a minimum of input parameters (average S matrix and mean level spacing of the CN). Predictions of the theory are derived with the help of field-theoretical methods adapted from condensed-matter physics and compared with those of phenomenological approaches. Thorough tests of the theory are reviewed, as are applications in nuclear physics, with special attention given to violation of symmetries (isospin and parity) and time-reversal invariance. © 2010 The American Physical Society.

Sinnott S.B.,University of Florida | Brenner D.W.,North Carolina State University
MRS Bulletin | Year: 2012

A brief history of atomic simulation as it was used in chemistry, physics, and materials science is presented starting with seminal work by Eyring in the 1930s through to current work and future challenges. This article provides the background and perspective needed to understand the ways in which reactive many-body potentials developed over the last three decades and have impacted materials research. It also explains the way in which this substantial impact on the field has been facilitated by increases in computational resources and traces the development of reactive potentials, which have steadily increased in complexity and sophistication over time. Together with the other contributions in this issue of MRS Bulletin, this article will help guide and inspire the next generation of computational materials scientists and engineers as they build on current capabilities to expand atomic simulation into new and exciting areas of materials research. © 2012 Materials Research Society.

Ladenburg J.,Danish Institute for Local Government Analysis and Research | Lutzeyer S.,North Carolina State University
Renewable and Sustainable Energy Reviews | Year: 2012

The offshore wind power generation market is currently experiencing large growth rates on a global scale and investments exceeding several billion euro are being made. From a welfare economic point of view there is a non-trivial economic trade-off between offshore wind generation costs and the visual impacts from offshore wind farms. Offshore wind farms close to the shore generate cheaper electricity, but also cause higher levels of visual impacts compared to locations at larger distances. In the present paper we carry out a review of the stated preference studies that have elicited the demand for visual disamenity reduction from offshore wind farms. The review has three objectives: (a) to present the results of the different surveys; (b) to explore the more technical parts of the different surveys; and (c) to present the frontiers in the assessment of the demand for visual disamenity reductions associated with offshore wind farm locations. The paper is based on the results from five different studies. The review indicates that locations of offshore wind farms which are close to the shore generate significant welfare losses and that these can be reduced by locating the wind farms at more distant locations. The results also show that the welfare economic costs vary in terms of a range of socio demographic characteristics, experience with wind turbines and recreational activities. Finally, the review suggests that the welfare impacts related to the spatial distribution of the wind farms, intergenerational effects and experience with wind turbines are potential areas that would be beneficial to explore in future studies. © 2012 Elsevier Ltd.

Croissant A.E.,North Carolina State University
Annual review of food science and technology | Year: 2011

Comprehensive food flavor analysis requires a multidisciplinary approach. This article presents a comprehensive review of the relationship between sensory and instrumental analysis in the research of food flavor. Common practices for aroma flavor compound isolation, separation, and identification are discussed with strengths and weaknesses of the respective methodologies. A review of whey protein flavor research is presented to demonstrate the range of techniques available for the investigation of food flavors. These techniques are applicable to all food categories. The complexity introduced by food texture regarding flavor analysis is discussed using the attribute creaminess as an example.

Clemens N.T.,University of Texas at Austin | Narayanaswamy V.,North Carolina State University
Annual Review of Fluid Mechanics | Year: 2014

Shock wave/boundary layer interactions occur in a wide range of supersonic internal and external flows, and often these interactions are associated with turbulent boundary layer separation. The resulting separated flow is associated with large-scale, low-frequency unsteadiness whose cause has been the subject of much attention and debate. In particular, some researchers have concluded that the source of low-frequency motions is in the upstream boundary layer, whereas others have argued for a downstream instability as the driving mechanism. Owing to substantial recent activity, we are close to developing a comprehensive understanding, albeit only in simplified flow configurations. A plausible model is that the interaction responds as a dynamical system that is forced by external disturbances. The low-frequency dynamics seem to be adequately described by a recently proposed shear layer entrainment-recharge mechanism. Upstream boundary layer fluctuations seem to be an important source of disturbances, but the evidence suggests that their impact is reduced with increasing size of the separated flow. Copyright © 2014 by Annual Reviews. All rights reserved.

Ksepka D.T.,North Carolina State University
Proceedings. Biological sciences / The Royal Society | Year: 2013

A feathered specimen of a new species of Eocypselus from the Early Eocene Green River Formation of Wyoming provides insight into the wing morphology and ecology in an early part of the lineage leading to extant swifts and hummingbirds. Combined phylogenetic analysis of morphological and molecular data supports placement of Eocypselus outside the crown radiation of Apodiformes. The new specimen is the first described fossil of Pan-Apodiformes from the pre-Pleistocene of North America and the only reported stem taxon with informative feather preservation. Wing morphology of Eocypselus rowei sp. nov. is intermediate between the short wings of hummingbirds and the hyper-elongated wings of extant swifts, and shows neither modifications for the continuous gliding used by swifts nor modifications for the hovering flight style used by hummingbirds. Elongate hindlimb elements, particularly the pedal phalanges, also support stronger perching capabilities than are present in Apodiformes. The new species is the smallest bird yet described from the Green River Formation, and supports the hypothesis that a decrease in body size preceded flight specializations in Pan-Apodiformes. The specimen also provides the first instance of melanosome morphology preserved in association with skeletal remains from the Green River Formation.

Rate-independent crystal plasticity theory and a classic viscoplastic power-law are investigated, contrasted and compared for finite deformation analysis of fcc crystals in channel die compression, including full consideration of lattice straining. Both experiment-based anisotropic and isotropic (Taylor) hardenings are evaluated in rate-independent theory; and an unlimited range of power-law exponent n is considered in viscoplasticity. The focus is on predictions of lateral constraint stress, lattice rotation and crystal shear, and their comparison with experiment. General elastic-plastic equations (for both theories) are given for the range of unstable lattice orientations in (1 1 0) compression ('range I') and evaluated before and after a finite rotation of the lattice about the load axis. Equations also are given and evaluated for the 'Brass' orientation. It is shown that the theories can be in close agreement at the onset of finite deformation in range I, but that viscoplasticity gives results (for any n) after finite rotation that are in sharp contrast to rate-independent theory. The latter's predictions for crystal shear and lattice rotation are in good to very good agreement with finite deformation experiments on aluminium and copper. The inclusion of lattice elasticity is found to have a negligible effect in range I. In contrast, for finite deformation in the stable Brass orientation, elastic-viscoplastic theory can be made to agree very closely with rate-independent theory and with experiment. © 2014 © 2014 Taylor & Francis.

Pilo-Pais M.,Duke University | Watson A.,Duke University | Demers S.,Duke University | Labean T.H.,North Carolina State University | Finkelstein G.,Duke University
Nano Letters | Year: 2014

DNA origami is a novel self-assembly technique allowing one to form various two-dimensional shapes and position matter with nanometer accuracy. We use DNA origami templates to engineer surface-enhanced Raman scattering substrates. Specifically, gold nanoparticles were selectively placed on the corners of rectangular origami and subsequently enlarged via solution-based metal deposition. The resulting assemblies exhibit "hot spots" of enhanced electromagnetic field between the nanoparticles. We observed a significant Raman signal enhancement from molecules covalently attached to the assemblies, as compared to control nanoparticle samples that lack interparticle hot spots. Furthermore, Raman molecules are used to map out the hot spots' distribution, as they are burned when experiencing a threshold electric field. Our method opens up the prospects of using DNA origami to rationally engineer and assemble plasmonic structures for molecular spectroscopy. © 2014 American Chemical Society.

Mackay T.F.C.,North Carolina State University
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2010

A central issue in evolutionary quantitative genetics is to understand how genetic variation for quantitative traits is maintained in natural populations. Estimates of genetic variation and of genetic correlations and pleiotropy among multiple traits, inbreeding depression, mutation rates for fitness and quantitative traits and of the strength and nature of selection are all required to evaluate theoretical models of the maintenance of genetic variation. Studies in Drosophila melanogaster have shown that a substantial fraction of segregating variation for fitness-related traits in Drosophila is due to rare deleterious alleles maintained by mutation-selection balance, with a smaller but significant fraction attributable to intermediate frequency alleles maintained by alleles with antagonistic pleiotropic effects, and late-age-specific effects. However, the nature of segregating variation for traits under stabilizing selection is less clear and requires more detailed knowledge of the loci, mutation rates, allelic effects and frequencies of molecular polymorphisms affecting variation in suites of pleiotropically connected traits. Recent studies in D. melanogaster have revealed unexpectedly complex genetic architectures of many quantitative traits, with large numbers of pleiotropic genes and alleles with sex-, environment- and genetic background-specific effects. Future genome wide association analyses of many quantitative traits on a common panel of fully sequenced Drosophila strains will provide much needed empirical data on the molecular genetic basis of quantitative traits. © 2010 The Royal Society.

Ronquist F.,Swedish Museum of Natural History | Deans A.R.,North Carolina State University
Annual Review of Entomology | Year: 2010

Bayesian inference and Markov chain Monte Carlo techniques have enjoyed enormous popularity since they were introduced into phylogenetics about a decade ago. We provide an overview of the field, with emphasis on recent developments of importance to empirical systematists. In particular, we describe a number of recent advances in the stochastic modeling of evolution that address major deficiencies in current models in a computationally efficient way. These include models of process heterogeneity across sites and lineages, as well as alignment-free models and model averaging approaches. Many of these methods should find their way into standard analyses in the near future. We also summarize the influence of Bayesian methods on insect systematics, with particular focus on current practices and how they could be improved using existing and emerging techniques. © 2010 by Annual Reviews All rights reserved.

Cobb M.D.,North Carolina State University
Journal of Nanoparticle Research | Year: 2011

Many people believe that ordinary citizens should influence scientific and technological developments, but the American public is routinely uninformed about these issues. As a solution, some scholars advocate creating informed public opinions by encouraging citizens to deliberate about the issues. Although this idea is currently widely applauded in the science and technology literature, deliberative outcomes are infrequently measured and the practice of deliberation is routinely criticized in other disciplines. This research contributes to our understanding of the effectiveness of citizen deliberation as a method for increasing public engagement with science. I report data measuring results of deliberation in a national citizens' technology forum (NCTF) about nanotechnologies for human enhancement. The NCTF was a month-long process involving six groups of 9-15 ordinary citizens who deliberated in different locations across the United States with the goal of reaching consensus about policy recommendations within their groups. I find that structured deliberation generated informed opinions, sometimes meaningful shifts in preferences, and increased trust and internal efficacy among the participants. Nevertheless, the NCTF has important shortcomings, and it is not obvious that consensus conferences should be preferred over other mechanisms for creating informed opinions. Future research is needed to corroborate the findings of this study and to systematically compare outcomes of structured citizen deliberation to other less resource intensive forms of engagement. © 2011 Springer Science+Business Media B.V.

Kuznetsov A.V.,North Carolina State University
International Communications in Heat and Mass Transfer | Year: 2010

The purpose of this paper is to study the onset of bioconvection in a horizontal layer filled with a nanofluid that also contains gyrotactic microorganisms. The idea is to use microorganisms to induce or enhance convection in a nanofluid. A linear instability analysis is used to solve this problem. A Galerkin method is utilized to obtain an analytical solution for the critical Rayleigh number for the non-oscillatory situation. As in the case of a regular nanofluid (without the microorganisms), the presence of nanoparticles can either reduce or increase the value of the critical Rayleigh number, depending on whether the basic nanoparticle distribution is top-heavy or bottom-heavy. In contrast, the effect of gyrotactic microorganisms is always destabilizing. © 2010 Elsevier Ltd.

Gubbins K.E.,North Carolina State University
Molecular Physics | Year: 2013

Starting with the work of van der Waals in 1873, a historical review is given of theories of non-electrolyte mixtures that are based on a well-defined Hamiltonian, and thus can be tested against molecular simulation, as well as experiment. Most of the first 100 years covered here were devoted to attempts to find a successful theory of simple mixtures, culminating in the van der Waals 1-fluid theory of conformal solutions, and perturbation theories based on a hard-sphere reference fluid. The last 40 years has seen the more rapid development of theories for fluids of more complex molecules, including strongly polar liquids, chain molecules and liquids in which molecular association is important. 1 Based on a Molecular Physics Lecture, The Theory of Non-Electrolyte Solutions: A Recent History, delivered at Imperial College London, 25 September 2009. © 2013 Taylor and Francis Group, LLC.

Jagannadham K.,North Carolina State University
Journal of Electronic Materials | Year: 2011

Samples of graphene composites with a matrix of indium or indium-gallium alloy were prepared in the form of foils using exfoliated graphene dispersions. The thermal conductivity of the composite samples with different thicknesses was determined using the three-omega method. Indium-graphene composite samples with a thickness of 430 μm exhibited a twofold increase in thermal conductivity, whereas indium-gallium-graphene composite samples with a thickness of 330 μm exhibited a threefold improvement in thermal conductivity over that of the matrix at 300 K. The effective medium approximation (EMA) was used to model the thermal conductivity of the composite samples. The graphene platelet size distribution was used to determine the average thermal conductivity of graphene in the composite samples. The interfacial thermal conductance between graphene and indium or indium-gallium alloy determined from EMA was not the limiting factor in the improvement of the thermal conductivity of the composite samples, although the increase in thermal conductivity was found to be slightly lower than predicted theoretically using acoustic and diffuse mismatch models. The smaller size of the graphene platelets obtained by exfoliation prior to dispersion in the matrix appears to be the limiting factor. © 2010 TMS.

Gan J.,Kansas State University | Yuan W.,North Carolina State University
Applied Energy | Year: 2013

The effect of reaction temperature, retention time, biomass content, and catalyst loading on bio-oil yield, carbon content, and carbon recovery of corncob hydrothermal conversion was investigated and optimized via response surface methodology (RSM). The four variables ranged from 280 to 340. °C for temperature, 12-48. min for retention time, 9-21% for biomass solid content, and 0.76-2.25% for catalyst loading. It was found from RSM modeling that higher bio-oil yield and higher carbon recovery could be achieved at relatively low temperatures and short retention times with high biomass solid contents and moderate alkaline catalyst loadings in the test ranges. A maximum bio-oil yield of 41.3% and maximum carbon recovery of 47.1% were obtained at 280. °C, 12. min, and 21% biomass solid content with 1.03-1.56% catalyst loading. Bio-oil carbon content was found affected only by the reaction temperature and biomass solid content in the RSM model. Higher temperature and lower biomass solid content were favored. The highest bio-oil carbon content of 74.8% was achieved at 340. °C with 9% biomass solid content. The predicted bio-oil yield, carbon content and carbon recovery were in close agreement with validation experiment results, indicating that the RSM models were accurate in designing and optimizing the hydrothermal conversion of corncobs. © 2012 Elsevier Ltd.

Tai W.,Carnegie Mellon University | Carley L.R.,Carnegie Mellon University | Ricketts D.S.,North Carolina State University
Digest of Technical Papers - IEEE International Solid-State Circuits Conference | Year: 2013

In this paper, we report a fully integrated power amplifier (PA) architecture that combines the power of 16 on-chip PAs using a 16-way zero-degree combiner to achieve an output power of 0.7W with a power-added efficiency (PAE) of 10% at 42GHz and a -3dB bandwidth of 9GHz. This is 2.6 times more output power than a recently reported millimeter-Wave (mm-Wave) silicon-based PA [1]. The circuit is a fully integrated mm-Wave PA achieving a leading output power approaching 1 Watt in a silicon process. © 2013 IEEE.

Chang H.H.,Emory University | Reich B.J.,North Carolina State University | Miranda M.L.,Duke University
American Journal of Epidemiology | Year: 2012

Exposure to air pollution during pregnancy has been suggested to be a risk factor for preterm birth; however, epidemiologic evidence remains mixed and limited. The authors examined the association between ambient levels of particulate matter <2.5 μm in aerodynamic diameter (PM 2.5) and the risk of preterm birth in North Carolina during the period 2001-2005. They estimated the risks of cumulative and lagged average exposures to PM 2.5 during pregnancy via a 2-stage discrete-time survival model. The authors also considered exposure metrics derived from 1) ambient concentrations measured by the Air Quality System (AQS) monitoring network and 2) concentrations predicted by statistically fusing AQS data with process-based numerical model output (the Statistically Fused Air and Deposition Surfaces (FSD) database). Using the AQS measurements, an interquartile-range (1.73 μg/m 3) increase in cumulative PM2.5 exposure was associated with a 6.8% (95% posterior interval: 0.5, 13.6) increase in the risk of preterm birth. Using the FSD-predicted levels and accounting for prediction error, the authors also found significant adverse associations between trimester 1, trimester 2, and cumulative PM 2.5 exposure and preterm birth. These findings suggest that exposure to ambient PM 2.5 during pregnancy is associated with increased risk of preterm birth, even in a region characterized by relatively good air quality. © The Author 2011. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved.

Sinclair T.R.,North Carolina State University
Trends in Plant Science | Year: 2011

Crop genetic improvement for environmental stress at the molecular and physiological level is very complex and challenging. Unlike the example of the current major commercial transgenic crops for which biotic stress tolerance is based on chemicals alien to plants, the complex, redundant and homeostatic molecular and physiological systems existing in plants must be altered for drought tolerance improvement. Sophisticated tools must be developed to monitor phenotype expression at the crop level to characterize variation among genotypes across a range of environments. Once stress-tolerant cultivars are developed, regional probability distributions describing yield response across years will be necessary. This information can then aid in identifying environmental conditions for positive and negative responses to genetic modification to guide farmer selection of stress-tolerant cultivars. © 2011 Elsevier Ltd.

Rojas-Pierce M.,North Carolina State University
Plant Science | Year: 2013

Vacuoles are essential for plant growth and development, and are dynamic compartments that require constant deposition of integral membrane proteins. These membrane proteins carry out many critical functions of the vacuole such as transporting ions and metabolites for vacuolar storage. Understanding the mechanisms for targeting proteins to the vacuolar membrane, or tonoplast, is important for developing novel applications for biotechnology. The mechanisms to target tonoplast proteins to the vacuole are quite complex. Multiple routes, including both Golgi-dependent and Golgi-independent mechanisms, have been implicated in tonoplast protein trafficking. A few endomembrane proteins that regulate this traffic at the level of the endoplasmic reticulum, the pre-vacuolar compartment and the tonoplast are now known. Recent reports indicate that the Golgi-dependent and independent pathways may merge at the level of the pre-vacuolar compartment. Finally, the small GTP-binding protein Rab7 and the SNARE protein SYP21 have been implicated in the traffic of tonoplast proteins from the pre-vacuolar compartment to the tonoplast. With multiple cargo proteins being analyzed under a variety of experimental systems, a clearer picture for targeting mechanisms for tonoplast proteins is starting to emerge. © 2013 Elsevier Ireland Ltd.

Melito H.S.,North Carolina State University
Annual review of food science and technology | Year: 2011

Rheological methods are continually evolving to encompass novel technologies and measurement methods. This review highlights novel techniques used to analyze the rheological properties of foods over the previous decade. Techniques reviewed include large amplitude oscillatory shear (LAOS) testing and rheological techniques coupled with other measurement methods, such as microscopy and nuclear magnetic resonance (NMR). Novel techniques are briefly overviewed and discussed in terms of advantages and disadvantages, previous use, and suggested future utilization.

Narayan R.,North Carolina State University
Materials Today | Year: 2010

The recent earthquake in Haiti has focused worldwide attention on the need for improved water purification materials and systems. Numerous individuals, religious charities, non-governmental organizations, and private companies have sent water purifications systems to Haiti in recent months in order to stem the spread of waterborne diseases. This recent tragedy has placed a spotlight on the ongoing problem of inadequate access to safe water in developing countries. The United Nations estimates that 1.1 billion people, or eighteen per cent of the world population, cannot obtain safe water at this time 1. In developing countries, waterborne diseases such as cholera, dysentery, enteric fever, and hepatitis A are quite common 2. Endemic diarrheal diseases place individuals, particularly children, at risk of arrested growth, malnutrition, and neurological conditions. The World Health Organization states that 1.6 million individuals, mostly young children, die from diarrheal diseases each year 1. © 2010 Elsevier Ltd.

Hyman M.,North Carolina State University
Current Opinion in Biotechnology | Year: 2013

Ether oxygenates such as methyl tertiary butyl ether (MTBE) are added to gasoline to improve fuel combustion and decrease exhaust emissions. Ether oxygenates and their tertiary alcohol metabolites are now an important group of groundwater pollutants. This review highlights recent advances in our understanding of the microorganisms, enzymes and pathways involved in both the aerobic and anaerobic biodegradation of these compounds. This review also aims to illustrate how these microbiological and biochemical studies have guided, and have helped refine, molecular and stable isotope-based analytical approaches that are increasingly being used to detect and quantify biodegradation of these compounds in contaminated environments. © 2013 Elsevier Ltd.

Narayan J.,North Carolina State University
Scripta Materialia | Year: 2013

This paper proposes a model to explain interesting features of grain growth retardation and saturation during electric field-assisted processing and flash sintering of materials. It is argued that electric field-induced defect generation and segregation of these defects at dislocations and grain boundaries can retard the grain growth rate and reduce it to zero as a result of grain boundary melting under flash sintering. Grain growth rates are derived taking into account kinetic and various thermodynamic factors under an applied field and compared with other models. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Wheeler E.A.,North Carolina State University
IAWA Journal | Year: 2011

Inside Wood is an Internet-accessible wood anatomy reference, research, and teaching tool. The Inside Wood database has coded wood anatomical descriptions based on the IAWA List of Microscopic Features for Hardwood Identification and is accompanied by a collection of photomicrographs. As of November 2010 there were over 5,800 descriptions and 36,000 images of modern woods, and over 1,600 descriptions and 2,000 images of fossil woods. CITES-listed timber species and other endangered woody plants are included in this digital collection hosted by North Carolina State University's library. This web site has value in helping with wood identification because it has a multiple entry key that allows searching by presence or absence of IAWA features and it serves as a virtual reference collection whereby descriptions and images can be retrieved by searching by scientific or common name or other keywords.

Kuznetsov A.V.,North Carolina State University
International Communications in Heat and Mass Transfer | Year: 2011

An analytical solution representing a wave of viral concentration as it propagates from the axon synapse toward the neuron soma is obtained. The obtained solution is based on a model of molecular motor-assisted retrograde transport of a neurotropic virus in an axon of a peripheral nervous system. It is established that the velocity of the viral concentration wave is almost independent of the rate of viral destruction in the axon, but depends on viral diffusivity, especially right after viral uptake at the synapse, when viral concentration gradient is large. As time progresses, the velocity of the viral concentration wave approaches that of a dynein motor, which indicates that for a large time viral transport in an axon is almost exclusively motor-driven. © 2011 Elsevier Ltd.

Nield D.A.,University of Auckland | Kuznetsov A.V.,North Carolina State University
International Journal of Heat and Mass Transfer | Year: 2011

The paper presents an analytical treatment of double-diffusive nanofluid convection in a porous medium. The problem treated is natural convection past a vertical plate when the base fluid of the nanofluid is itself a binary fluid such as salty water. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis, while the Darcy model is used for the porous medium. In addition the thermal energy equations include regular diffusion and cross-diffusion terms. A similarity solution is presented. © 2010 Elsevier Ltd. All rights reserved.

Nield D.A.,University of Auckland | Kuznetsov A.V.,North Carolina State University
International Journal of Heat and Fluid Flow | Year: 2011

The onset of double-diffusive convection in a horizontal layer of a nanofluid is studied analytically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. In addition the thermal energy equations include regular diffusion and cross-diffusion terms. The stability boundaries for both non-oscillatory and oscillatory cases have been approximated by simple analytical expressions. Physical significance of the obtained results is discussed. © 2011 Elsevier Inc.

Dunne G.V.,University of Connecticut | Unsal M.,North Carolina State University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We illustrate the physical significance and mathematical origin of resurgent trans-series expansions for energy eigenvalues in quantum mechanical problems with degenerate harmonic minima, by using the uniform WKB approach. We provide evidence that the perturbative expansion, combined with a global eigenvalue condition, contains all information needed to generate all orders of the nonperturbative multi-instanton expansion. This provides a dramatic realization of the concept of resurgence, whose structure is naturally encoded in the resurgence triangle. We explain the relation between the uniform WKB approach, multi-instantons, and resurgence theory. The essential idea applies to any perturbative expansion, and so is also relevant for quantum field theories with degenerate minima which can be continuously connected to quantum mechanical systems. © 2014 American Physical Society.

Hooshyar H.,Lulea University of Technology | Baran M.E.,North Carolina State University
IEEE Transactions on Power Systems | Year: 2013

Fault current profile on a PV-dominated distribution feeder is rather different than a conventional feeder. To estimate the fault current profile on such a feeder, the paper proposes a new method which extends the capability of conventional short-circuit analysis method. The paper also shows that this time-varying fault current profile makes it also more difficult to estimate the time it will take for an overcurrent relay/device to interrupt such a fault current. The paper proposes a method for estimation of this operating time also. Performance of the proposed methods has been assessed by simulations on a sample distribution feeder. © 1969-2012 IEEE.

Schafer T.,North Carolina State University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We study the viscosity spectral function of a holographic 2+1 dimensional fluid with Schrödinger symmetry. The model is based on a twisted compactification of AdS5×S5. We numerically compute the spectral function of the stress tensor correlator for all frequencies, and analytically study the limits of high and low frequency. We compute the shear viscosity, the viscous relaxation time, and the quasinormal mode spectrum in the shear channel. We find a number of unexpected results: The high frequency behavior is governed by a fractional 1/3 power law, the viscous relaxation time is negative, and the quasinormal mode spectrum in the shear channel is not doubled. © 2014 American Physical Society.

Kuznetsov A.V.,North Carolina State University | Nield D.A.,University of Auckland
International Journal of Heat and Mass Transfer | Year: 2013

The classical Cheng-Minkowycz problem considers natural convection past a vertical plate in a fluid-saturated porous medium. In our previous work we extended the Cheng-Minkowycz problem to the case when a porous medium is saturated by a nanofluid. We utilized Buongiorno's nanofluid model that includes the effects of Brownian motion and thermophoresis. The major limitation of our previous model was active control of nanoparticle volume fraction at the boundary. Here we revisited our previous model and extended it to the case when the nanofluid particle fraction on the boundary is passively rather than actively controlled. This makes the model physically more realistic than our previous model as well as models employed by other authors simulating nanofluid flow in porous media. © 2013 Elsevier B.V. All rights reserved.

Bear J.E.,University of North Carolina at Chapel Hill | Bear J.E.,Howard Hughes Medical Institute | Haugh J.M.,North Carolina State University
Current Opinion in Cell Biology | Year: 2014

Cell migration directed by spatial cues, or taxis, is a primary mechanism for orchestrating concerted and collective cell movements during development, wound repair, and immune responses. Compared with the classic example of amoeboid chemotaxis, in which fast-moving cells such as neutrophils are directed by gradients of soluble factors, directed migration of slow-moving mesenchymal cells such as fibroblasts is poorly understood. Mesenchymal cells possess a distinctive organization of the actin cytoskeleton and associated adhesion complexes as its primary mechanical system, generating the asymmetric forces required for locomotion without strong polarization. The emerging hypothesis is that the molecular underpinnings of mesenchymal taxis involve distinct signaling pathways and diverse requirements for regulation. © 2014 Elsevier Ltd.

Kuznetsov A.V.,North Carolina State University
International Communications in Heat and Mass Transfer | Year: 2011

This paper develops a theory of bio-thermal convection in a suspension that contains two species of microorganisms exhibiting different taxes, gyrotactic and oxytactic microorganisms. The developed theory is applied to investigating the onset of bio-thermal convection in such a suspension occupying a horizontal layer of finite depth. A linear stability analysis is utilized to derive the equations for the amplitudes of disturbances. The obtained eigenvalue problem is solved by the Galerkin method. The case of non-oscillatory instability in a layer with a rigid lower boundary and a stress-free upper boundary is investigated. The resulting eigenvalue equation relates three Rayleigh numbers, the traditional Rayleigh number (Ra) and two bioconvection Rayleigh numbers, one for gyrotactic (Rbg) and one for oxytactic (Rbo) microorganisms. The neutral stability boundary is presented in the form of a diagram showing that boundary in the (Ra, Rag) plane for different values of Rao. © 2011 Elsevier Ltd.

Kuznetsov A.V.,North Carolina State University
International Communications in Heat and Mass Transfer | Year: 2011

This paper is motivated by recent experimental research that demonstrated pharmacological efficiency of axonal transport drug delivery. The purpose is to develop a model of this process and to study how the rate of destruction of pharmaceutical agent complexes (PACs) affects their transport in the axon. The model includes two populations of PACs: PACs in the state when they are driven retrogradely (from the axon terminal toward the neuron soma) by dynein motors and PACs residing in the accumulated state (but can still be re-released to the dynein-driven state). The coupling between the kinetic states is accounted for by first-order reactions. Utilizing Laplace transform, analytical solutions for concentrations of these two populations of PACs are obtained. The effect of PAC destruction is investigated for different values of other parameters. It is shown that the shapes of the waves describing the PAC concentrations can be significantly affected by transport parameters. © 2011 Elsevier Ltd.

Mackay T.F.C.,North Carolina State University
Nature Reviews Genetics | Year: 2014

The role of epistasis in the genetic architecture of quantitative traits is controversial, despite the biological plausibility that nonlinear molecular interactions underpin the genotype-phenotype map. This controversy arises because most genetic variation for quantitative traits is additive. However, additive variance is consistent with pervasive epistasis. In this Review, I discuss experimental designs to detect the contribution of epistasis to quantitative trait phenotypes in model organisms. These studies indicate that epistasis is common, and that additivity can be an emergent property of underlying genetic interaction networks. Epistasis causes hidden quantitative genetic variation in natural populations and could be responsible for the small additive effects, missing heritability and the lack of replication that are typically observed for human complex traits. © 2014 Macmillan Publishers Limited.

Choi H.-M.,Kyungpook National University | Ji C.-R.,North Carolina State University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

Although the meson decay amplitude described by a two-point function may be regarded as one of the simplest possible physical observables, it is interesting that this apparently simple amplitude bears abundant fundamental information on QCD vacuum dynamics and chiral symmetry. The light-front zero-mode issue of the vector meson decay constant fV is in this respect highly nontrivial and deserves careful analysis. We discuss the zero-mode issue in the light-front quark model (LFQM) prediction of fV from the perspective of the vacuum fluctuation consistent with the chiral symmetry of QCD. We extend the exactly solvable, manifestly covariant Bethe-Salpeter model calculation to the more phenomenologically accessible, realistic light-front quark model and present a self-consistent covariant description of fV, analyzing the twist-2 and twist-3 quark-antiquark distribution amplitudes with even chirality. © 2014 American Physical Society.

Theil E.C.,Childrens Hospital Oakland Research Institute | Theil E.C.,North Carolina State University
Inorganic Chemistry | Year: 2013

At the center of iron and oxidant metabolism is the ferritin superfamily: protein cages with Fe2+ ion channels and two catalytic Fe/O redox centers that initiate the formation of caged Fe2O3· H2O. Ferritin nanominerals, initiated within the protein cage, grow inside the cage cavity (5 or 8 nm in diameter). Ferritins contribute to normal iron flow, maintenance of iron concentrates for iron cofactor syntheses, sequestration of iron from invading pathogens, oxidant protection, oxidative stress recovery, and, in diseases where iron accumulates excessively, iron chelation strategies. In eukaryotic ferritins, biomineral order/crystallinity is influenced by nucleation channels between active sites and the mineral growth cavity. Animal ferritin cages contain, uniquely, mixtures of catalytically active (H) and inactive (L) polypeptide subunits with varied rates of Fe 2+/O2 catalysis and mineral crystallinity. The relatively low mineral order in liver ferritin, for example, coincides with a high percentage of L subunits and, thus, a low percentage of catalytic sites and nucleation channels. Low mineral order facilitates rapid iron turnover and the physiological role of liver ferritin as a general iron source for other tissues. Here, current concepts of ferritin structure/function/genetic regulation are discussed and related to possible therapeutic targets such as mini-ferritin/Dps protein active sites (selective pathogen inhibition in infection), nanocage pores (iron chelation in therapeutic hypertransfusion), mRNA noncoding, IRE riboregulator (normalizing the ferritin iron content after therapeutic hypertransfusion), and protein nanovessels to deliver medicinal or sensor cargo. © 2013 American Chemical Society.

Brown J.D.,North Carolina State University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2011

An action principle for the generalized harmonic formulation of general relativity is presented. The action is a functional of the spacetime metric and the gauge source vector. An action principle for the Z4 formulation of general relativity has been proposed recently by Bona, Bona-Casas, and Palenzuela. The relationship between the generalized harmonic action and the Bona, Bona-Casas, and Palenzuela action is discussed in detail. © 2011 American Physical Society.

Aiyyer A.,North Carolina State University
Geophysical Research Letters | Year: 2015

Data from an ensemble prediction system are used to examine the impact of recurving tropical cyclones on downstream midlatitude forecasts. The ensemble spread, normalized by its climatology, increases after recurvature and peaks approximately 4-5 days later. It returns to climatological levels within a week after recurvature. Initially, the spread increases around the position of the tropical storm. Subsequently, it increases after extratropical transition, and it is associated with a developing wave packet in the midlatitude storm track. The enhanced spread propagates downstream approximately at the group speed of the wave packet. These results suggest that relative to the model's baseline, recurvature-related increase in loss of forecast skill is spatially and temporally localized. Further, energy dispersion of the developing wave packet may constrain the rate at which the forecast errors propagate downstream. © 2015 American Geophysical Union. All Rights Reserved.

Pao C.V.,North Carolina State University
Nonlinear Analysis: Real World Applications | Year: 2015

This paper deals with a class of Lotka-Volterra cooperation system where the densities of the cooperating species are governed by a finite number of degenerate reaction-diffusion equations. Three basic types of Dirichlet, Neumann, and Robin boundary conditions and two types of reaction functions, with and without saturation, are considered. The aim of the paper is to show the existence of positive minimal and maximal steady-state solutions, including the uniqueness of the positive solution, the existence and uniqueness of a global time-dependent solution, and the asymptotic behavior of the time-dependent solution in relation to the steady-state solutions. Some very simple conditions on the physical parameters for the above objectives are obtained. Also discussed is the finite-time blow up property of the time-dependent solution and the non-existence of positive steady-state solution for the system with Neumann boundary condition. © 2014 Elsevier Ltd. All rights reserved.

Raymer E.,North Carolina State University
Monthly Notices of the Royal Astronomical Society | Year: 2012

Recent observations have shown that the direct-impact Algol systems UCrB and RSVul possess gas located outside of the orbital plane, including a tilted accretion disc in UCrB. Observations of circumstellar gas surrounding the mass donor in RSVul suggest magnetic effects could be responsible for deflecting the accretion stream out of the orbital plane, resulting in a tilted disc. To determine whether a tilted disc is possible due to a deflected stream, we use three-dimensional hydrodynamic simulations of the mass transfer process in RSVul. By deflecting the stream 45° out of the orbital plane and boosting the magnitude of the stream's velocity to Mach30, we mimic the effects of magnetic activity near the first Lagrange point. We find that the modified stream parameters change the direct-impact nature of the system. The stream misses the surface of the star, and a slightly warped accretion disc forms with no more than 3° of disc tilt. The stream-disc interaction for the deflected stream forces a large degree of material above the orbital plane, increasing the out-of-plane flow drastically. Plotting the Hα emissivity in velocity space allows us to compare our results with tomographic observations. Deflecting and boosting the stream increases the emissivity in each v z slice of the out-of-plane flow by at least three and up to eight orders of magnitude compared to the undeflected case. We conclude that a deflected stream is a viable mechanism for producing the strong out-of-plane flows seen in the tomographic images of UCrB and RSVul. © 2012 The Author Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Barrangou R.,North Carolina State University | Marraffini L.A.,Rockefeller University
Molecular Cell | Year: 2014

Clustered regularly interspaced short palindromic repeats (CRISPR), and associated proteins (Cas) comprise the CRISPR-Cas system, which confers adaptive immunity against exogenic elements in many bacteria and most archaea. CRISPR-mediated immunization occurs through the uptake of DNA from invasive genetic elements such as plasmids and viruses, followed by its integration into CRISPR loci. These loci are subsequently transcribed and processed into small interfering RNAs that guide nucleases for specific cleavage of complementary sequences. Conceptually, CRISPR-Cas shares functional features with the mammalian adaptive immune system, while also exhibiting characteristics of Lamarckian evolution. Because immune markers spliced from exogenous agents are integrated iteratively in CRISPR loci, they constitute a genetic record of vaccination events and reflect environmental conditions and changes over time. Cas endonucleases, which can be reprogrammed by small guide RNAs have shown unprecedented potential and flexibility for genome editing and can be repurposed for numerous DNA targeting applications including transcriptional control. © 2014 Elsevier Inc.

Parker M.D.,North Carolina State University
Journal of the Atmospheric Sciences | Year: 2012

Adiabatic lapse rates appear to be a common feature in the lower troposphere on tornado days. This article reviews physical reasons why lapse rates may influence surface vortex intensification and reports on numerical simulations designed to study the key processes. In the idealized numerical model, an initial mesocyclone-like vortex and nonvarying convection-like heat source are used in different environmental stability profiles. The scales of interest in these simulations typify those of a parent supercell, and the developing circulations constitute direct responses to the imposed heating. Downward parcel displacements are needed for surface vortex development in environments with no preexisting surface vorticity. In the simulations, under neutral stratification there is strong heating-induced subsidence anchored near the storm edge, whereas under stable stratification there are instead gravity waves that propagate away to the far field. In addition, under weak or neutral low-level stratification there is very little resistance to downward parcel displacements. In the simulations, these two effects combine to bring high angular momentum air from aloft downward to the surface under neutral lapse rates; this in turn leads to surface vortex genesis, even without precipitation processes. When the lower troposphere is stable, surface vortex intensification is only simulated when there is already preexisting vertical vorticity at the ground. When the initial vortex is elevated (vertical vorticity falls off to zero above the ground), surface vortex intensification is only simulated under neutral low-level stability. The results are interpreted within the controlled experimental framework, after which the possible ramifications to processes in real storms are discussed. © 2012 American Meteorological Society.

Bae H.,North Carolina State University
Urban Forestry and Urban Greening | Year: 2011

Urban streams in Korea, which until recently were channeled and served only flood control functions, have increasingly attracted attention for their potential as urban parks or residential open spaces. Consequently, urban stream restoration has been booming and a number of restoration projects have been carried out since 1990s. However, increased flash flood risks created by climate change are reigniting controversies regarding the vulnerability of restored streams to flooding. Furthermore, implementation issues including landscape/greening and facility design considerations have been under-investigated. This study explores these ongoing issues associated with urban stream restoration in Korea, as well as attempts to estimate consumers' willingness to pay for the restoration process. In particular, this study estimates the partial values of natural and recreational attributes of urban streams, which can be improved through various types of urban stream restoration measures, using conjoint analysis. The findings indicate that improving natural attributes by transforming existing concrete-encased streams into natural state streams increases the value of an urban stream by about 50 USD per household. Improving recreational attributes, either by creating a walkway where there is no bank or by expanding facilities to the existing walkway, increases the value of an urban stream by about 25 USD per household. These estimated partial values of urban stream attributes imply the relative importance of each attribute and suggest policy implications for priority setting and trade-offs in urban restoration projects. © 2011 Elsevier GmbH.

Ledon-Rettig C.C.,North Carolina State University
Integrative and Comparative Biology | Year: 2013

Phenotypic variation arises from interactions between environmental and genetic variation, and the emergence of such variation is, in part, mediated by epigenetic mechanisms: factors that modify gene expression but do not change the gene sequence, per se. The role of epigenetic variation and inheritance in natural populations, however, remains poorly understood. The budding field of Ecological Epigenetics seeks to extend our knowledge of epigenetic mechanisms and processes to natural populations, and recent conceptual and technical advances have made progress toward this goal more feasible. In light of these breakthroughs, now is a particularly opportune time to develop a framework that will guide and facilitate exceptional studies in Ecological Epigenetics. Toward this goal, the Ecological Epigenetics symposium brought together researchers with diverse strengths in theory, developmental genetics, ecology, and evolution, and the proceedings from their talks are presented in this issue. By characterizing environmentally dependent epigenetic variation in natural populations, we will enhance our understanding of developmental, ecological, and evolutionary phenomena. In particular, ecological epigenetics has the potential to explain how populations endure (or fail to endure) profound and rapid environmental change. Here, my goal is to introduce some of the common goals and challenges shared by those pursuing this critical field. © The Author 2013.

Bereman M.S.,North Carolina State University
Proteomics | Year: 2015

With advances in liquid chromatography coupled to tandem mass spectrometry technologies combined with the continued goals of biomarker discovery, clinical applications of established biomarkers, and integrating large multiomic datasets (i.e. "big data"), there remains an urgent need for robust tools to assess instrument performance (i.e. system suitability) in proteomic workflows. To this end, several freely available tools have been introduced that monitor a number of peptide identification (ID) and/or peptide ID free metrics. Peptide ID metrics include numbers of proteins, peptides, or peptide spectral matches identified from a complex mixture. Peptide ID free metrics include retention time reproducibility, full width half maximum, ion injection times, and integrated peptide intensities. The main driving force in the development of these tools is to monitor both intra- and interexperiment performance variability and to identify sources of variation. The purpose of this review is to summarize and evaluate these tools based on versatility, automation, vendor neutrality, metrics monitored, and visualization capabilities. In addition, the implementation of a robust system suitability workflow is discussed in terms of metrics, type of standard, and frequency of evaluation along with the obstacles to overcome prior to incorporating a more proactive approach to overall quality control in liquid chromatography coupled to tandem mass spectrometry based proteomic workflows. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ollis D.,North Carolina State University
Applied Catalysis B: Environmental | Year: 2010

We develop simple reaction kinetic models for photocatalyzed removal of carbonaceous and sulfur films, and demonstrate their applicability to a common range of deposited film-catalyst configurations studied in the photocatalyst literature:. 1. Non-porous photocatalyst, non-porous transparent organic overlayer (stearic, palmitic acids). 2. Porous photocatalyst: transparent organic (stearic acid) in catalyst void volume. 3. Non-porous photocatalyst, non-transparent porous overlayer (sulfur). 4. Non-porous photocatalyst, adjacent organic layer (soot). In each case, we consider a simple film-catalyst configuration, propose a corresponding one-dimensional physical model for reaction, and compare model results with literature data to evaluate the correspondence between model and experiment. These examples cover both direct and lateral oxidation by photocatalysis. The respective physical and chemical phenomena which determine these rates of film removal include intrinsic catalyst kinetics (1), simultaneous reaction and light attenuation (2), reaction with light absorption by non-transparent organic film (3), and oxidant lateral transport (surface diffusion) (4). In each case, a simple model suffices to represent the key kinetic phenomena. In all cases, the true kinetic order is zero, but the apparent order may be influenced by light absorption (case 2). The apparent rate constant may be influenced by catalyst light absorption (case 2) or overlayer (case 3), or by catalyst-reactant separation (case 4). © 2010 Elsevier B.V.

Liu Y.,North Carolina State University | Whitt W.,Columbia University
Operations Research | Year: 2012

An algorithm is developed to determine time-dependent staffing levels to stabilize the time-dependent abandonment probabilities and expected delays at positive target values in the Mt/GI/st + GI many-server queueing model, which has a nonhomogeneous Poisson arrival process (the M t), has general service times (the first GI), and allows customer abandonment according to a general patience distribution (the +GI). New offered-load and modified-offered-load approximations involving infinite-server models are developed for that purpose. Simulations show that the approximations are effective. A many-server heavy-traffic limit in the efficiency-driven regime shows that (i) the proposed approximations achieve the goal asymptotically as the scale increases, and (ii) it is not possible to simultaneously stabilize the mean queue length in the same asymptotic regime. © 2012 INFORMS.

Chen Y.,North Carolina State University
Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2010

Using model interaction Hamiltonians for both electrons and phonons and Green's function formalism for ballistic transport, we have studied the thermal conductance and the thermoelectric properties of graphene nanoribbons (GNR), GNR junctions and periodic superlattices. Among our findings we have established the role that interfaces play in determining the thermoelectric response of GNR systems both across single junctions and in periodic superlattices. In general, increasing the number of interfaces in a single GNR system increases the peak ZT values that are thus maximized in a periodic superlattice. Moreover, we proved that the thermoelectric behavior is largely controlled by the width of the narrower component of the junction. Finally, we have demonstrated that chevron-type GNRs recently synthesized should display superior thermoelectric properties.

Wilson J.W.,North Carolina State University
Biology letters | Year: 2013

Predator-prey interactions are fundamental in the evolution and structure of ecological communities. Our understanding, however, of the strategies used in pursuit and evasion remains limited. Here, we report on the hunting dynamics of the world's fastest land animal, the cheetah, Acinonyx jubatus. Using miniaturized data loggers, we recorded fine-scale movement, speed and acceleration of free-ranging cheetahs to measure how hunting dynamics relate to chasing different sized prey. Cheetahs attained hunting speeds of up to 18.94 m s(-1) and accelerated up to 7.5 m s(-2) with greatest angular velocities achieved during the terminal phase of the hunt. The interplay between forward and lateral acceleration during chases showed that the total forces involved in speed changes and turning were approximately constant over time but varied with prey type. Thus, rather than a simple maximum speed chase, cheetahs first accelerate to decrease the distance to their prey, before reducing speed 5-8 s from the end of the hunt, so as to facilitate rapid turns to match prey escape tactics, varying the precise strategy according to prey species. Predator and prey thus pit a fine balance of speed against manoeuvring capability in a race for survival.

Piedrahita J.A.,North Carolina State University
Birth Defects Research Part A - Clinical and Molecular Teratology | Year: 2011

Epigenetics, and in particular imprinted genes, have a critical role in the development and function of the placenta, which in turn has a central role in the regulation of fetal growth and development. A unique characteristic of imprinted genes is their expression from only one allele, maternal or paternal and dependent on parent of origin. This unique expression pattern may have arisen as a mechanism to control the flow of nutrients from the mother to the fetus, with maternally expressed imprinted genes reducing the flow of resources and paternally expressed genes increasing resources to the fetus. As a result, any epigenetic deregulation affecting this balance can result in fetal growth abnormalities. Imprinting-associated disorders in humans, such as Beckwith-Wiedemann and Angelman syndrome, support the role of imprinted genes in fetal growth. Similarly, assisted reproductive technologies in animals have been shown to affect the epigenome of the early embryo and the expression of imprinted genes. Their role in disorders such as intrauterine growth restriction appears to be more complex, in that imprinted gene expression can be seen as both causative and protective of fetal growth restriction. This protective or compensatory effect needs to be explored more fully. © 2011 Wiley-Liss, Inc.

Kuznetsov A.V.,North Carolina State University
Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2012

This paper presents an exact solution for a two kinetic state model of slow axonal transport that is based on the stop-and-go hypothesis. The model accounts for two populations of cytoskeletal elements (CEs): pausing and running. The model also accounts for a finite half-life of CEs involved in slow axonal transport. It is assumed that initially CEs are injected into the axon such that their concentration forms a rectangular pulse; initially all CEs are assumed to be in the pausing state. Kinetic processes quickly redistribute CEs between the pausing and running states. After less than a minute, equilibrium is established, forming two pulses, representing concentrations of pausing and running CEs, respectively. As these pulses propagate, their shape changes and they turn to bell-shaped waves. The amplitude of the waves decreases, and the waves spread out as they propagate down the axon. The rate of the amplitude decrease is larger for CEs with a shorter half-life, but even if CE half-life is infinitely long, some decrease of the waves amplitudes is observed. The velocity of the waves propagation is found to be independent of the CE half-life and is in good agreement with published experimental data for slow axonal transport of neurofilaments. © 2012 The Royal Society.

Tonelli A.E.,North Carolina State University
Beilstein Journal of Organic Chemistry | Year: 2012

During the past several years my students and I have been utilizing certain small-molecule hosts to create nanostructured polymers. This is accomplished by first forming noncovalently bonded inclusion complexes (ICs) between these small-molecule hosts and guest polymers, followed by the careful removal of the host crystalline lattice to obtain a coalesced bulk polymer. We have repeatedly observed that such coalesced polymer samples behave distinctly from those produced from their solutions or melts. Coalesced amorphous homopolymers exhibit higher glass-transition temperatures, while crystallizable homopolymers coalesced from their ICs display higher melting and crystallization temperatures, and sometimes different crystalline polymorphs. When ICs are formed with block copolymers or with two or more different homopolymers, the resulting coalesced samples can exhibit intimate mixing between the copolymer blocks, or between entire homopolymer chains. Each of the distinct behaviors observed for polymers coalesced from their ICs is a consequence of the structural organization of the polymer-host-ICs. Polymer chains in host-IC crystals are confined to occupy narrow channels (diameter ∼0.5-1.0 nm) formed by the small-molecule hosts around the included guest polymers during IC crystallization. This results in the separation and high extension of the included guest polymer chains, which leads, following the careful removal of the host molecule lattice, to unique behaviors for the bulk coalesced polymer samples. Apparently, substantial degrees of the extended and unentangled natures of the IC-included chains are retained upon coalescence. In this review we summarize the behaviors and uses of coalesced polymers, and attempt to draw conclusions on the relationship between their behavior and the organization/structures/conformations of the constituent polymer chains achieved upon coalescence from their ICs. © 2012 Tonelli; licensee Beilstein-Institut.

Sinclair T.R.,North Carolina State University
Functional Plant Biology | Year: 2012

Increased transpiration efficiency - commonly the ratio of mass accumulation to transpiration is often suggested as a critical opportunity for genetic improvement for increased crop yields in water-limited environments. However, close inspection of transpiration efficiency (TE) shows that it is a complex term that is explicitly dependent upon both physiological and environmental variables. Physiological variables include leaf photosynthetic capacity, biochemical composition of the plant productions and possible hydraulic limitation on water flow in the plant. Environmental variables include atmospheric CO2 concentration and atmospheric vapour pressure deficit. To complicate the resolution of transpiration efficiency, a weighted integration over the daily cycle and over the dates of interest needs to be resolved. Consequently, it is concluded that transpiration efficiency is not a variable easily resolved for use in many breeding programs. Instead, component traits contributing to TE need to be studied to increase the effective use of available water through the growing season to ultimately maximise growth and yield of the crop. © 2012 CSIRO.

Meade A.W.,North Carolina State University
Journal of Applied Psychology | Year: 2010

Much progress has been made in the past 2 decades with respect to methods of identifying measurement invariance or a lack thereof. Until now, the focus of these efforts has been to establish criteria for statistical significance in items and scales that function differently across samples. The power associated with tests of differential functioning, as with all significance tests, is affected by sample size and other considerations. Additionally, statistical significance need not imply practical importance. There is a strong need as such for meaningful effect size indicators to describe the extent to which items and scales function differently. Recently developed effect size measures show promise for providing a metric to describe the amount of differential functioning present between groups. Expanding upon recent developments, this article presents a taxonomy of potential differential functioning effect sizes; several new indices of item and scale differential functioning effect size are proposed and illustrated with 2 data samples. Software created for computing these indices and graphing item- and scale-level differential functioning is described. © 2010 American Psychological Association.

Nield D.A.,University of Auckland | Kuznetsov A.V.,North Carolina State University
European Journal of Mechanics, B/Fluids | Year: 2010

This paper presents a linear stability analysis for the onset of natural convection in a horizontal nanofluid layer. The employed model incorporates the effects of Brownian motion and thermophoresis. Both monotonic and oscillatory convection for free-free, rigid-rigid, and rigid-free boundaries are investigated. The oscillatory instability is possible when nanoparticles concentrate near the bottom of the layer, so that the density gradient caused by such a bottom-heavy nanoparticle distribution competes with the density variation caused by heating from the bottom. It is established that the instability is almost purely a phenomenon due to buoyancy coupled with the conservation of nanoparticles. It is independent of the contributions of Brownian motion and thermophoresis to the thermal energy equation. Rather, the Brownian motion and thermophoresis enter to produce their effects directly into the equation expressing the conservation of nanoparticles so that the temperature and the particle density are coupled in a particular way, and that results in the thermal and concentration buoyancy effects being coupled in the same way. © 2010 Elsevier Masson SAS. All rights reserved.

Tang L.,University of Illinois at Urbana - Champaign | Fan T.M.,University of Illinois at Urbana - Champaign | Borst L.B.,North Carolina State University | Cheng J.,University of Illinois at Urbana - Champaign
ACS Nano | Year: 2012

Drug-containing nanoparticles (NPs) with monodisperse, controlled particle sizes are highly desirable for drug delivery. Accumulating evidence suggests that NPs with sizes less than 50 nm demonstrate superior performance in vitro and in vivo. However, it is difficult to fabricate monodisperse, drug-containing NPs with discrete sizes required for studying and characterizing existing relationships among particle size, biologic processing, and therapeutic functionality. Here, we report a scalable process of fabricating drug-silica conjugated nanoparticles, termed drug-silica nanoconjugates (drug-NCs), which possess monodisperse size distributions and desirable particle sizes as small as 20 nm. We find that 20 nm NCs are superior to their 50 and 200 nm NC analogues by 2-5- and 10-20-fold, respectively, with regard to tumor accumulation and penetration and cellular internalization. These fundamental findings underscore the importance and necessity of further miniaturizing nanomedicine size for optimized drug delivery applications. © 2012 American Chemical Society.

Chakrabortty A.,North Carolina State University
IEEE Transactions on Smart Grid | Year: 2012

In this paper we present a FACTS (Flexible AC Transmission Systems)-based control design for electromechanical oscillation damping in large power systems, facilitated by aggregate models that can be constructed using Synchronized phasor measurements. Our approach consists of three steps, namely1. Model Reduction, where Synchrophasors are used to identify second-order models of the oscillation clusters of the power system retaining the inter-ties on which FACTS devices such as Thyristor Controlled Series Compensators (TCSC) are installed, 2. Aggregate Control, where feedback controllers are designed to achieve a desired closed-loop transient response between every pair of clusters, and finally 3. Control Inversion, where the aggregate control design is distributed and tuned to actual TCSC controllers in the full-order model until its inter-area responses match the respective inter-machine responses of the reduced-order system. It is shown that the inversion problem can be posed equivalently as decomposing the swing dynamics into fast and slow states, and designing the controllers such that the slow dynamics can optimally track a desired closed-loop signal designed for the aggregate model. Application of the approach to two-area power systems is demonstrated through topological examples inspired by the US west coast grid. © 2010-2012 IEEE.

Erie D.A.,University of North Carolina at Chapel Hill | Weninger K.R.,North Carolina State University
DNA Repair | Year: 2014

DNA mismatch repair, which involves is a widely conserved set of proteins, is essential to limit genetic drift in all organisms. The same system of proteins plays key roles in many cancer related cellular transactions in humans. Although the basic process has been reconstituted in vitro using purified components, many fundamental aspects of DNA mismatch repair remain hidden due in part to the complexity and transient nature of the interactions between the mismatch repair proteins and DNA substrates. Single molecule methods offer the capability to uncover these transient but complex interactions and allow novel insights into mechanisms that underlie DNA mismatch repair. In this review, we discuss applications of single molecule methodology including electron microscopy, atomic force microscopy, particle tracking, FRET, and optical trapping to studies of DNA mismatch repair. These studies have led to formulation of mechanistic models of how proteins identify single base mismatches in the vast background of matched DNA and signal for their repair. © 2014 Elsevier B.V.

Kuznetsov A.V.,North Carolina State University
Journal of Porous Media | Year: 2012

This paper investigates a new type of a nanofluid that contains, in addition to nanoparticles, oxytactic motile mi- croorganisms. One of the paradigmic problems, the Horton-Rogers-Lapwood problem (i.e., the stability of a horizontal fluid-saturated porous layer of finite depth), is solved for this new nanofluid. The stability of this nanofluid is controlled by three agencies: the nanoparticle distribution, the density stratification induced by the vertical temperature gradient, and the density stratification induced by upswimming of oxytactic microorganisms. Both non-oscillatory and oscillatory instability situations are investigated. Oscillatory instability is shown to be possible when the nanoparticle distribution is stabilizing (bottom heavy) and the vertical temperature variation is destabilizing (heating from the bottom). It is also shown that the presence of oxytactic microorganisms makes the suspension less stable but tends to destroy the oscillatory instability in favor of non-oscillatory instability. © 2012 by Begell House, Inc.

Cardoza Y.J.,North Carolina State University
Pest Management Science | Year: 2011

BACKGROUND: Vermicompost is an organic soil amendment produced by earthworm digestion of organic waste. Studies show that plants grown in soil amended with vermicompost grow faster, are more productive and are less susceptible to a number of arthropod pests. In light of these studies, the present study was designed to determine the type of insect resistance (antixenosis or antibiosis) present in plants grown in vermicompost-amended potting soil. Additionally, the potential role of microarthropods, entomopathogenic organisms and non-pathogenic microbial flora found in vermicompost on insect resistance induction was investigated.RESULTS: Findings show that vermicompost from two different sources (Raleigh, North Carolina, and Portland, Oregon) were both effective in causing Arabidopsis plants to be resistant to the generalist herbivore Helicoverpa zea (Boddie). However, while the Raleigh (Ral) vermicompost plant resistance was expressed as both non-preference (antixenosis) and milder (lower weight and slower development) toxic effect (antibiosis) resistance, Oregon (OSC) vermicompost plant resistance was expressed as acute antibiosis, resulting in lower weights and higher mortality rates.CONCLUSION: Vermicompost causes plants to have non-preference (antixenosis) and toxic (antibiosis) effects on insects. This resistance affects insect development and survival on plants grown in vermicompost-amended soil. Microarthropods and entomopathogens do not appear to have a role in the resistance, but it is likely that resistance is due to interactions between the microbial communities in vermicompost with plant roots, as is evident from vermicompost sterilization assays conducted in this study. © 2010 Society of Chemical Industry Copyright © 2010 Society of Chemical Industry.

Leung Y.-F.,North Carolina State University
Journal for Nature Conservation | Year: 2012

Recreation ecology, the scientific study of visitor impacts and their effective management, has been developed largely in North America, Europe, and more recently in Australia, in response to growing impacts of visitor use to protected area resources. A body of literature has been accumulated that contributes to sustainable visitor management in protected areas. This paper traces the development of recreation ecology research in East Asia and examines the field's relevance to East Asia's protected natural areas which endure both a long history of human utilisation and contemporary recreation and tourism pressure, much of which originates from surrounding densely populated urban areas. The formative, expanding and strengthening stages of recreation ecology research in this region were identified through an extensive review of literature published in English and East Asian languages. Each of these three developmental stages was illustrated with examples and compared with the general state of research during the same period. Key challenges and opportunities for future recreation ecology research in the region are discussed in light of this review. © 2012 Elsevier GmbH.

One of the strategies to decrease inappropriate antimicrobial use in veterinary medicine is to apply pharmacokinetic-pharmacodynamic (PK-PD) principles to dosing regimens. If antimicrobials are used appropriately by applying these principles to attain targets for area-under-the-curve to MIC ratio (AUC/MIC), peak concentration to MIC ratio (CMAX/MIC), and time above MIC (T>MIC), more effective antibiotic therapy is possible, thus avoiding ineffective administration. Another mechanism whereby inappropriate antibiotic administration can be avoided is to use accurate Interpretive Criteria established by the Clinical Laboratory Standards Institute (CLSI) for breakpoint selection. Inaccurate breakpoints will encourage antibiotic administration that is likely to be ineffective. For newly approved antimicrobials, three criteria are used for determining breakpoints: PK-PD criteria, MIC distributions, and clinical response. For older (often generic drugs) evaluated by the CLSI, recent clinical data may not be available and breakpoints are derived from PK-PD principles, wild-type distributions, and Monte Carlo simulations. It is the goal of the CLSI subcommittee that these revised breakpoints will encourage more effective antimicrobial use and avoid unnecessary antimicrobial administration. © 2014 Elsevier B.V.

Schweitzer M.H.,North Carolina State University
Proceedings. Biological sciences / The Royal Society | Year: 2014

The persistence of original soft tissues in Mesozoic fossil bone is not explained by current chemical degradation models. We identified iron particles (goethite-αFeO(OH)) associated with soft tissues recovered from two Mesozoic dinosaurs, using transmission electron microscopy, electron energy loss spectroscopy, micro-X-ray diffraction and Fe micro-X-ray absorption near-edge structure. Iron chelators increased fossil tissue immunoreactivity to multiple antibodies dramatically, suggesting a role for iron in both preserving and masking proteins in fossil tissues. Haemoglobin (HB) increased tissue stability more than 200-fold, from approximately 3 days to more than two years at room temperature (25°C) in an ostrich blood vessel model developed to test post-mortem 'tissue fixation' by cross-linking or peroxidation. HB-induced solution hypoxia coupled with iron chelation enhances preservation as follows: HB + O2 > HB - O2 > -O2 >> +O2. The well-known O2/haeme interactions in the chemistry of life, such as respiration and bioenergetics, are complemented by O2/haeme interactions in the preservation of fossil soft tissues.

Anekella K.,North Carolina State University | Orsat V.,McGill University
LWT - Food Science and Technology | Year: 2013

Aims: Probiotics were microencapsulated in raspberry juice through spray drying. Methods & Results: A combination of probiotics (Lactobacillus acidophilus NRRL B-4495 and Lactobacillus rhamnosus NRRL B-442) was chosen to offer high viability. Maltodextrin's role as a carbon source was also assessed for its prebiotic potential. Spray drying inlet temperature (°C), total solids: maltodextrin ratio, and inlet feed rate (mL/min) were fixed as independent variables while % recovery, % survival and color were the dependent outputs. Conclusions & Significance: High temperatures during spray drying are detrimental to probiotics and can be circumvented by sub-lethal thermal shock (50 °C for L. acidophilus and 52.5 °C for L. rhamnosus). Increasing the microencapsulating material concentration increased the survival rate of the probiotics. Non-dairy probiotic foods are becoming popular as they do not pose problems of lactose intolerance while they offer an alternative. © 2012 Elsevier Ltd.

Davis J.K.,North Carolina State University
Frontiers in Plant Science | Year: 2012

Extracellular polysaccharides are synthesized by a wide variety of species, from unicellular bacteria and Archaea to the largest multicellular plants and animals in the biosphere. In every case, the biosynthesis of these polymers requires transport across a membrane, from the cytosol to either the lumen of secretory pathway organelles or directly into the extracellular space. Although some polysaccharide biosynthetic substrates are moved across the membrane to sites of polysaccharide synthesis by separate transporter proteins before being incorporated into polymers by glycosyltransferase proteins, many polysaccharide biosynthetic enzymes appear to have both transporter and transferase activities. In these cases, the biosynthetic enzymes utilize substrate on one side of the membrane and deposit the polymer product on the other side. This review discusses structural characteristics of plant cell wall glycan synthases that couple synthesis with transport, drawing on what is known about such dual-function enzymes in other species. © 2012 Davis.

Foolad M.R.,Pennsylvania State University | Panthee D.R.,North Carolina State University
Critical Reviews in Plant Sciences | Year: 2012

The cultivated tomato, Solanum lycopersicum L., is the second most consumed vegetable crop after potato and unquestionably the most popular garden crop in the world. There are more varieties of tomato sold worldwide than any other vegetable crop. Most of the commercial cultivars of tomato have been developed through phenotypic selection and traditional breeding. However, with the advent of molecular markers and marker-assisted selection (MAS) technology, tomato genetics and breeding research has entered into a new and exciting era. Molecular markers have been used extensively for genetic mapping as well as identification and characterization of genes and QTLs for many agriculturally important traits in tomato, including disease and insect resistance, abiotic stress tolerance, and flower- and fruit-related characteristics. The technology also has been utilized for marker-assisted breeding for several economically important traits, in particular disease resistance. However, the extent to which MAS has been employed in public and private tomato breeding programs has not been clearly determined. The objectives of this study were to review the publically-available molecular markers for major disease resistance traits in tomato and assess their current and potential use in public and private tomato breeding programs. A review of the literature indicated that although markers have been identified for most disease resistance traits in tomato, not all of them have been verified or are readily applicable in breeding programs. For example, many markers are not validated across tomato genotypes or are not polymorphic within tomato breeding populations, thus greatly reducing their utility in crop improvement programs. However, there seems to be a considerable use of markers, particularly in the private sector, for various purposes, including testing hybrid purity, screening breeding populations for disease resistance, and marker assisted backcross breeding. Here we provide a summary of molecular markers available for major disease resistance traits in tomato and discuss their actual use in tomato breeding programs. It appears that many of the available markers may need to be further refined or examined for trait association and presence of polymorphism in breeding populations. However, with the recent advances in tomato genome and transcriptome sequencing, it is becoming increasingly possible to develop new and more informative PCR-based markers, including single nucleotide polymorphisms (SNPs), to further facilitate the use of markers in tomato breeding. It is also expected that more markers will become available via the emerging technology of genotyping by sequencing (GBS). © 2012 Copyright Taylor and Francis Group, LLC.

Deiters A.,North Carolina State University
ChemBioChem | Year: 2010

(Figure Presented) In the cage: Photochemical control over biological processes is commonly achieved with caged molecules. While the first reported examples of caged compounds were small molecules, recent advances in caging technologies have enabled the photochemical regulation of oligonucleotide and protein function. This article discusses different approaches to the caging of small molecules, DNA, and proteins, and the requirements for efficient light regulation of cellular processes by using caged molecules. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

Morioka S.,North Carolina State University
Oncogene | Year: 2016

Sterol-regulatory element-binding proteins (SREBPs) are key transcription factors regulating cholesterol and fatty acid biosynthesis. SREBP activity is tightly regulated to maintain lipid homeostasis, and is modulated upon extracellular stimuli such as growth factors. While the homeostatic SREBP regulation is well studied, stimuli-dependent regulatory mechanisms are still elusive. Here we demonstrate that SREBPs are regulated by a previously uncharacterized mechanism through transforming growth factor-β activated kinase 1 (TAK1), a signaling molecule of inflammation. We found that TAK1 binds to and inhibits mature forms of SREBPs. In an in vivo setting, hepatocyte-specific Tak1 deletion upregulates liver lipid deposition and lipogenic enzymes in the mouse model. Furthermore, hepatic Tak1 deficiency causes steatosis pathologies including elevated blood triglyceride and cholesterol levels, which are established risk factors for the development of hepatocellular carcinoma (HCC) and are indeed correlated with Tak1-deficiency-induced HCC development. Pharmacological inhibition of SREBPs alleviated the steatosis and reduced the expression level of the HCC marker gene in the Tak1-deficient liver. Thus, TAK1 regulation of SREBP critically contributes to the maintenance of liver homeostasis to prevent steatosis, which is a potentially important mechanism to prevent HCC development.Oncogene advance online publication, 14 March 2016; doi:10.1038/onc.2015.453. © 2016 Macmillan Publishers Limited

Narayan J.,North Carolina State University
Scripta Materialia | Year: 2013

A unified mechanism for field-assisted phenomena such as enhanced rapid flash sintering, reduction in flow stress and grain growth retardation is proposed. It is argued that defect segregation causes enhanced ionic and electronic transport along dislocations and grain boundaries, which leads to enhanced mobility of dislocations and their selective Joule heating. This selective heating, if uncontrolled, can lead to an avalanche and selective melting of grain boundaries, which is proposed to be the primary mechanism for flash sintering of oxides. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Tabashnik B.E.,University of Arizona | Gould F.,North Carolina State University
Journal of Economic Entomology | Year: 2012

Transgenic crops producing Bacillus thuringiensis (Bt) toxins for insect control have been successful, but their efficacy is reduced when pests evolve resistance. To delay pest resistance to Bt crops, the U.S. Environmental Protection Agency (EPA) has required refuges of host plants that do not produce Bt toxins to promote survival of susceptible pests. Such refuges are expected to be most effective if the Bt plants deliver a dose of toxin high enough to kill nearly all hybrid progeny produced by matings between resistant and susceptible pests. In 2003, the EPA first registered corn, Zea mays L., producing a Bt toxin (Cry3Bb1) that kills western corn rootworm, Diabrotica virgifera virgifera LeConte, one of the most economically important crop pests in the United States. The EPA requires minimum refuges of 20% for Cry3Bb1 corn and 5% for corn producing two Bt toxins active against corn rootworms. We conclude that the current refuge requirements are not adequate, because Bt corn hybrids active against corn rootworms do not meet the high-dose standard, and western corn rootworm has rapidly evolved resistance to Cry3Bb1 corn in the laboratory, greenhouse, and field. Accordingly, we recommend increasing the minimum refuge for Bt corn targeting corn rootworms to 50% for plants producing one toxin active against these pests and to 20% for plants producing two toxins active against these pests. Increasing the minimum refuge percentage can help to delay pest resistance, encourage integrated pest management, and promote more sustainable crop protection. © 2012 Entomological Society of America.

McNeill C.R.,Monash University | Ade H.,North Carolina State University
Journal of Materials Chemistry C | Year: 2013

Organic semiconductor devices such as organic solar cells and organic field-effect transistors are based on blended and/or multilayered structures. Many organic semiconductors used in high-performance devices are also semicrystalline or liquid crystalline with a complex relationship between film microstructure and device performance. Unravelling structure-function relationships in organic semiconductor devices therefore requires structural probes that have high chemical specificity, sensitivity to molecular orientation and order and high spatial resolution. Soft X-rays have proven to be versatile in spectroscopy, microspectroscopy and scattering experiments providing contrast derived from differences in the near-edge X-ray absorption spectra of different organic semiconductors. Furthermore, the sensitivity of polarised soft X-ray beams to the orientation of bonds in organic materials makes them a unique probe of molecular orientation. This feature article provides an overview of the range of microscopy, reflectivity and scattering techniques based on soft X-rays that have been developed in recent years and their utility for providing new insight into the complex structure of organic semiconductor thin films. © 2013 The Royal Society of Chemistry.

Increased concentration at the retail, food processing and farm input manufacturing levels has brought increased attention to patterns in retail-to-farm price spreads. Most studies documenting asymmetric price transmission focus on nonlinear error correction processes, as opposed to the current study which analyses potential nonlinearities in the long-run relationship between the farm and retail prices. The null hypothesis of nonlinearity in the long-run relationship between farm and retail prices in the US hog/pork supply chain is rejected in favour of a Smooth Transition Cointegration (STC) framework. The STC framework predicts downward price stickiness in retail prices. The predicted residuals of the nonlinear model are used to investigate whether it is possible to disentangle nonlinearity in the long-run price relationship from nonlinearity in the adjustment towards the long-run equilibrium. The results underline the importance of testing for linearity in the long-run price relationship before modelling nonlinearity in short-run dynamics. © 2011 Taylor & Francis.

Richards D.,Purdue University | Ivanisevic A.,North Carolina State University
Chemical Society Reviews | Year: 2012

Inorganic materials have become an increasingly researched topic due to their applications in many areas especially health care. One major problem with them is the effect that their surface coatings have on cells. The same coatings that are meant to increase biocompatibility can actually invoke cytotoxicity. This tutorial review focuses on the various types of coatings and how their properties, such as electrostatic charge and hydrophobicity, affect the observed toxicity. The theorized mechanisms by which the coatings induce toxicity are also presented. Finally, the prospects for the future of this field are discussed. © The Royal Society of Chemistry 2012.

Wiegers T.C.,North Carolina State University
Database : the journal of biological databases and curation | Year: 2012

The Critical Assessment of Information Extraction systems in Biology (BioCreAtIvE) challenge evaluation is a community-wide effort for evaluating text mining and information extraction systems for the biological domain. The 'BioCreative Workshop 2012' subcommittee identified three areas, or tracks, that comprised independent, but complementary aspects of data curation in which they sought community input: literature triage (Track I); curation workflow (Track II) and text mining/natural language processing (NLP) systems (Track III). Track I participants were invited to develop tools or systems that would effectively triage and prioritize articles for curation and present results in a prototype web interface. Training and test datasets were derived from the Comparative Toxicogenomics Database (CTD; http://ctdbase.org) and consisted of manuscripts from which chemical-gene-disease data were manually curated. A total of seven groups participated in Track I. For the triage component, the effectiveness of participant systems was measured by aggregate gene, disease and chemical 'named-entity recognition' (NER) across articles; the effectiveness of 'information retrieval' (IR) was also measured based on 'mean average precision' (MAP). Top recall scores for gene, disease and chemical NER were 49, 65 and 82%, respectively; the top MAP score was 80%. Each participating group also developed a prototype web interface; these interfaces were evaluated based on functionality and ease-of-use by CTD's biocuration project manager. In this article, we present a detailed description of the challenge and a summary of the results.

Hunt J.H.,North Carolina State University
Journal of Evolutionary Biology | Year: 2012

In a model based on the wasp family Vespidae, the origin of worker behaviour, which constitutes the eusociality threshold, is not based on relatedness, therefore the origin of eusociality does not depend on inclusive fitness, and workers at the eusociality threshold are not altruistic. Instead, incipient workers and queens behave selfishly and are subject to direct natural selection. Beyond the eusociality threshold, relatedness enables 'soft inheritance' as the framework for initial adaptations of eusociality. At the threshold of irreversibility, queen and worker castes become fixed in advanced eusociality. Transitions from solitary to facultative, facultative to primitive, and primitive to advanced eusociality occur via exaptation, phenotypic accommodation and genetic assimilation. Multilevel selection characterizes the solitary to highly eusocial transition, but components of multilevel selection vary across levels of eusociality. Roles of behavioural flexibility and developmental plasticity in the evolutionary process equal or exceed those of genotype. © 2011 The Author. Journal of Evolutionary Biology © 2011 European Society For Evolutionary Biology.

Roberts M.J.,North Carolina State University | Schlenker W.,Columbia University
American Economic Review | Year: 2013

We present a new framework to identify supply elasticities of storable commodities where past shocks are used as exogenous price shifters. In the agricultural context, past yield shocks change inventory levels and futures prices of agricultural commodities. We use our estimated elasticities to evaluate the impact of the 2009 Renewable Fuel Standard on commodity prices, quantities, and food consumers' surplus for the four basic staples: corn, rice, soybeans, and wheat. Prices increase 20 percent if one-third of commodities used to produce ethanol are recycled as feedstock, with a positively skewed 95 percent confidence interval that ranges from 14 to 35 percent.

Agency: NSF | Branch: Standard Grant | Program: | Phase: Computing Ed for 21st Century | Award Amount: 438.83K | Year: 2013

The University of California, Berkeley and the University of North Carolina, Charlotte propose a collaborative effort?called FRABJOUS?to develop and deploy a proposed, new Advanced Placement (AP) computing course that can successfully achieve outreach ? attracting women and underrepresented minorities ? while having a technically rigorous programming component. The work extends the PIs? previous work on the Berkeley ?Beauty and Joy of Computing? course and the College Board?s CS Principles course to the high school level, addressing the development and study of new instructional materials as well as the impact of teacher professional development on student learning outcomes. The course uses a visually rich programming environment, called Snap, that is based on Scratch. Scratch has had well-documented success in teaching computer programming to 8-14 year olds because of the power of its visual metaphor. Snap extends the metaphor to teach more advanced methods, including recursion, higher order procedures, and object-oriented programming, to 14-19 year olds. Specifically the FRABJOUS project will
? Develop a core group of mentor teachers in the Berkeley and Charlotte areas,
? Conduct and evaluate intensive summer professional development workshops for in-service high school teachers,
? Develop regional partnerships between universities and high schools, creating CSTA chapters and connecting them through the STARS Alliance,
? Study university and high school student learning outcomes,
disaggregating data by race, gender, age, course, and curricular models to
understand the curriculums effectiveness, ease of use, and impact, particularly
the introduction of advanced concepts (higher order functions, recursion,
distributed computing, concurrency, simulation) at this early level,
? Compare outcomes for students and teaches trained directly by the PIs with those trained by the mentor teachers, and
? Expand the capability of Snap.
The project thus includes tool and materials development, assessments of student learning outcomes, and study of the impact of teacher professional development via workshops and school year support activities, including peer-to-peer and online support.

Bilisik K.,North Carolina State University
Journal of Reinforced Plastics and Composites | Year: 2010

In this study, multiaxis 3D woven preform was developed with five yarn sets: + bias, -bias, warp, filling, and z-yarns. The orientation of the yarns on the five axis have improved the mechanical properties of the preform. The yarns of the preforms, which were made of polyacrylonitrile (PAN)-based carbon fibers, were consolidated with an epoxy resin. These preforms were tested and compared with the 3D orthogonal woven carbon composites. It was found that in-plane shear strength and modulus of multiaxis 3D woven composite were higher than that of the 3D orthogonal woven composite. However the bending strength, bending modulus, and the interlaminar shear strength of the multiaxis 3D woven composite were slightly lower than that of the 3D orthogonal woven composite because of the orientations of +/-bias yarns on both surfaces of the multiaxis 3D woven structure. The failures of both woven samples were also analyzed for the assessment of their mechanical behaviors. The unit cell of the multiaxis 3D woven preform was described. Depending on the unit cell geometry, some relationships were developed to predict the volume fraction of each yarn set in the preform and these predicted results were also compared with the measured values. © 2010 SAGE Publications.

Agency: NSF | Branch: Standard Grant | Program: | Phase: S-STEM:SCHLR SCI TECH ENG&MATH | Award Amount: 652.94K | Year: 2014

Improving mathematics instruction and learning is a priority for increasing the success and persistence of undergraduate students interested in careers in science, technology, engineering, and mathematics. The central goal of this collaborative project (including Virginia Polytechnic Institute and State University, Florida State University and North Carolina State University) is to develop an understanding of what is needed to support instructional change in undergraduate mathematics. In particular, the project will design, investigate, and evaluate a system of supports for mathematics instructors interested in implementing student-centered curricular innovations. Such curricular innovations have been shown to support conceptual learning gains, diminish the achievement gap, and improve STEM retention rates. However, research has also found that simply developing and disseminating curricular innovations fails to support meaningful instructional change. By developing and researching a system of supports for instructional change, the project will address this particularly important (and often missing) component needed for taking curricular innovations to scale. By supporting instructional change, and therefore supporting the propagation of research-based curricular innovations, the project will have broad impacts on undergraduate STEM education. These impacts include: improving instruction for STEM students, thus broadening the pipeline for undergraduate students pursuing STEM careers; advancing teaching practices and instruction that have been shown to be particularly beneficial for women and minority students in STEM; and, developing an infrastructure and model that can be used to support instructional change and professional development in other undergraduate STEM areas.

The project will research the following question: How can the program better support instructional improvement in undergraduate mathematics? More specifically, what are the relationships among instructional supports, instructors, and instruction that are important for informing effective instructional change? To do this, the project will design, investigate, and evaluate a system of supports for mathematicians interested in instructional change. The instructional support model will consist of three interrelated components: curricular support materials, summer workshops, and online instructor work groups. These supports will be developed using design-based research including iterative cycles of designing, field-testing, analyzing, and refining. The project will then investigate instructor change in the context of our model. This investigation will focus on the relationships and interactions between the supports, the instructors, and their instructional practices. Finally, in order to evaluate the programs instructional support model, the project will assess student learning and develop a measure for inquiry-oriented instruction. In addition to assessing the efficacy of the support model, the project will use the evaluation tools to identify aspects of the supports and instruction that have a positive impact on students learning.