Virginia Polytechnic Institute and State University, popularly known as Virginia Tech, is a public land-grant university with a main campus in Blacksburg, Virginia, educational facilities in six regions statewide, and a study-abroad site in Switzerland. The commonwealth's third-largest university and a leading research institution, Virginia Tech offers 225 undergraduate and graduate degree programs to some 31,000 students and manages a research portfolio of $454 million. The university fulfills its land-grant mission of transforming knowledge to practice through technological leadership and by fueling economic growth and job creation locally, regionally, and across Virginia.The Virginia Tech Board of Visitors serves as the university's governing body. The board comprises 13 members who are appointed by the governor of Virginia. Serving as ex-officio, non-voting representatives are the president of the state Board of Agriculture and Consumer Services; the presidents of the university's faculty senate and staff senate; and an undergraduate student and a graduate student selected through a competitive review process. Wikipedia.
The University Of Texas System, Virginia Polytechnic Institute and State University | Date: 2016-09-19
Disclosed are polybenzimidazoles containing sulfonyl groups. The polymers can be synthesized in Eatons reagent from 3,3,4,4-tetraaminodiphenylsulfone, which itself can be synthesized from 4,4-dichlorodiphenylsulfone. Methods of synthesizing the polymers are disclosed. The disclosed polymers can be used for high temperature H_(2)/CO_(2 )separation membranes and other uses.
Virginia Polytechnic Institute and State University | Date: 2015-05-01
The present disclosure relates to keratin nanomaterials, methods for obtaining keratin nanomaterials, and biomaterials made from keratin nanomaterials. In particular, keratin nanomaterials comprising Type I and Type II monomer pairs are disclosed as well as a method for obtaining keratin nanomaterials comprising obtaining a solution of keratin and processing the solution by ultrafiltration with buffer solution containing phosphate.
Virginia Polytechnic Institute and State University | Date: 2015-04-23
A system and method for monitoring the health of dialysis patients with Raman spectroscopy measurements of one or more target analytes is described. The methods include irradiating one or more fluids of interest with light to produce one or more spectrum and detecting the spectrum with a detector. The fluids of interest are preferably those related to dialysis, including hemodialysis and peritoneal dialysis. In a preferred embodiment, the fluids are irradiated with monochromatic light, and one or more Raman spectra are detected as a result of the irradiation. The fluids may be irradiated within the dialysis tubing itself, or removed from the dialysis tubing and irradiated in a separate chamber. The Raman spectra of one or more target analytes of a dialysis patient may be followed over time or compared to one or more reference spectra, thereby providing information on the health of dialysis patients.
Virginia Polytechnic Institute and State University | Date: 2016-08-17
Aspects of capacitor voltage ripple reduction in modular multilevel converters are described herein. In one embodiment, a power converter system includes a modular multilevel converter (MMC) electrically coupled and configured to convert power between two different power systems. The MMC includes one or more phase legs having a cascade arrangement of switching submodules, where the switching submodules include an arrangement of switching power transistors and capacitors. The MMC further includes a control loop including a differential mode control loop and a common mode control loop. The differential control loop is configured to generate a differential control signal based on a target modulation index to reduce fundamental components of voltage ripple on the capacitors, and the common mode control loop is configured to inject 2^(nd )order harmonic current into a common mode control signal to reduce 2^(nd )order harmonic components of the voltage ripple on the capacitors.
Intel Corporation, Virginia Polytechnic Institute and State University | Date: 2016-11-02
Embodiments of the present disclosure describe methods, apparatuses, and systems related to a wireless communication device using time-variant antenna. Other embodiments may be described and/or claimed.
Intel Corporation, Virginia Polytechnic Institute and State University | Date: 2016-08-12
A plug-and-play antenna may be used with many different types of wireless communication devices. An antenna may be coupled to an impedance tuning component and a waveform generator. A calibration control module receives radio status information, controls the waveform generator to vary a response of the antenna, and tunes the impedance tuning component to match impedances between a radio and the antenna.
Intel Corporation, Virginia Polytechnic Institute and State University | Date: 2017-04-05
Embodiments of the present disclosure describe methods, apparatuses, and systems related to a wireless communication device using time-variant antenna. Other embodiments may be described and/or claimed.
Bian K.,Peking University |
Park J.-M.J.,Virginia Polytechnic Institute and State University
IEEE Transactions on Mobile Computing | Year: 2013
In decentralized cognitive radio (CR) networks, establishing a link between a pair of communicating nodes requires that the radios 'rendezvous in a common channel such a channel is called a rendezvous channel-to exchange control information. When unlicensed (secondary) users opportunistically share spectrum with licensed (primary or incumbent) users, a given rendezvous channel may become unavailable due to the appearance of licensed user signals. Ideally, every node pair should be able to rendezvous in every available channel (i.e., maximize the rendezvous diversity) so that the possibility of rendezvous failures is minimized. Channel hopping (CH) protocols have been proposed previously for establishing pairwise rendezvous. Some of them enable pairwise rendezvous over all channels but require global clock synchronization, which may be very difficult to achieve in decentralized networks. Maximizing the pairwise rendezvous diversity in decentralized CR networks is a very challenging problem. In this paper, we present a systematic approach for designing CH protocols that maximize the rendezvous diversity of any node pair in decentralized CR networks. The resulting protocols are resistant to rendezvous failures caused by the appearance of primary user (PU) signals and do not require clock synchronization. The proposed approach, called asynchronous channel hopping (ACH), has two noteworthy features: 1) any pair of CH nodes are able to rendezvous on every channel so that the rendezvous process is robust to disruptions caused by the appearance of PU signals; and 2) an upper bounded time-to-rendezvous (TTR) is guaranteed between the two nodes even if their clocks are asynchronous. We propose two optimal ACH designs that maximize the rendezvous diversity between any pair of nodes and show their rendezvous performance via analytical and simulation results. © 2002-2012 IEEE.
Van Dyke M.,Virginia Polytechnic Institute and State University
Acta Biomaterialia | Year: 2013
Natural extracellular matrix (ECM) proteins possess critical biological characteristics that provide a platform for cellular adhesion and activation of highly regulated signaling pathways. However, ECM-based biomaterials can have several limitations, including poor mechanical properties and risk of immunogenicity. Synthetic biomaterials alleviate the risks associated with natural biomaterials but often lack the robust biological activity necessary to direct cell function beyond initial adhesion. A thorough understanding of receptor-mediated cellular adhesion to the ECM and subsequent signaling activation has facilitated development of techniques that functionalize inert biomaterials to provide a biologically active surface. Here we review a range of approaches used to modify biomaterial surfaces for optimal receptor-mediated cell interactions, as well as provide insights into specific mechanisms of downstream signaling activation. In addition to a brief overview of integrin receptor-mediated cell function, so-called "biomimetic" techniques reviewed here include (i) surface modification of biomaterials with bioadhesive ECM macromolecules or specific binding motifs, (ii) nanoscale patterning of the materials and (iii) the use of "natural-like" biomaterials. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Tauber U.C.,Virginia Polytechnic Institute and State University |
Diehl S.,University of Innsbruck |
Diehl S.,Austrian Academy of Sciences
Physical Review X | Year: 2014
The universal critical behavior of the driven-dissipative nonequilibrium Bose-Einstein condensation transition is investigated employing the field-theoretical renormalization group method. Such criticality may be realized in broad ranges of driven open systems on the interface of quantum optics and many-body physics, from exciton-polariton condensates to cold atomic gases. The starting point is a noisy and dissipative Gross-Pitaevski equation corresponding to a complex-valued Landau-Ginzburg functional, which captures the near critical nonequilibrium dynamics, and generalizes model A for classical relaxational dynamics with nonconserved order parameter. We confirm and further develop the physical picture previously established by means of a functional renormalization group study of this system. Complementing this earlier numerical analysis, we analytically compute the static and dynamical critical exponents at the condensation transition to lowest nontrivial order in the dimensional ε expansion about the upper critical dimension dc = 4 and establish the emergence of a novel universal scaling exponent associated with the nonequilibrium drive.We also discuss the corresponding situation for a conserved order parameter field, i.e., (sub)diffusive model B with complex coefficients.
Agency: National Science Foundation | Branch: | Program: STTR | Phase: Phase I | Award Amount: 225.00K | Year: 2014
This Small Business Innovation Research (SBIR) Phase I project focuses on the development of a minimally invasive endoscopic surgical device for the treatment of pancreatic cancer. Alarmingly, more than 38,000 Americans will die this year from pancreatic cancer and the average survival time following diagnosis will typically be 6-9 months; a statistic that has not changed significantly over the last 3 decades. Most cases of pancreatic cancer are diagnosed by symptomatic detection once infiltration and metastasis has already occurred, with no effective therapies for late-stage, regionally infiltrative, or metastatic pancreatic tumors. The proposed platform uses very brief, yet intense pulsed electric fields to disrupt the membrane of cells within a solid tumor. The research objectives of this project are to precisely define the electric field necessary to achieve a therapeutic effect without damaging surrounding healthy tissue. The technical objectives of this project are to develop a clinically viable pulse generation system and endoscopic probe for the treatment of oncological disease. The endoscopic-based platform will provide a feasible avenue to treat, monitor, and confirm the success of the therapy at the time of outpatient biopsy without additional surgical procedures. The broader impact/commercial potential of this project is that technology facilitates the treatment of tumors currently inoperable with surgical resection or other focal ablation technologies due to their proximity to critical structures such as nerve bundles and major blood vessels. The scientific results achieved in this proposal will enhance our understanding of how high frequency electric fields affect cells and tissues and produce the tools necessary for their use in other therapeutic capacities. proposed platform is a non-thermal treatment mechanism and is immune to heat-sink effects caused by local blood vessels. Our proof-of-concept experiments will accelerate the commercialization of the endoscopic-based proposed technology and demonstrate the potential to treat other diseases tissues including lung and colorectal cancers, venous eczema, lipodermatosclerosis, and arrhythmic cardiac tissue. The global ablation market is anticipated to grow to $12.4 billion by 2016 and the proposed platform is uniquely positioned to gain a significant market share.
Acetylon Pharmaceuticals, Inc., Virginia Polytechnic Institute and State University | Date: 2014-09-19
An HDAC6 inhibitor (a compound of Formula I) is shown to reduce the pathogenesis associated with the B cell mediated autoimmune disease, systemic lupus erythematosus (SLE) Administration of a compound of Formula I attenuated many of the symptoms characteristic of SLE including splenomegaly, abnormal B cell differentiation, an increase in the number double-negative thymic T cells, an increase in the level of auto-antibodies such as anti-dsDNA, immune complex-mediated glomerulonephritis and an increase in inflammatory cytokine production. Treatment with a compound of Formula I also increased the number of the subjects splenic Treg cells while removing circulating auto-antibodies Inhibition of HDAC6 altered bone marrow B cell differentiation by increasing the percentage of cells in the early-stage developmental fractions of both pro- and pre-B cells. These results demonstrate HDAC6 inhibition with a compound of Formula I can treat SLE disease by altering aberrant T and B cell differentiation.
Agency: Cordis | Branch: FP7 | Program: CP-FP | Phase: KBBE-2008-1-4-05 | Award Amount: 3.08M | Year: 2009
The overall objective of the project is to collect and analyze new data on non-tariff measures (NTMs), particularly on governmental standards and regulations that prescribe the conditions for importing agri-food products into the EU market and into the markets of the main competing players. Furthermore, impacts from EU NTBs on least developing country (LDC) exports are examined. The project will deliver the following results: 1. An analytical framework for defining measures, methods, products and countries. 2. A data base on NTMs in EU, USA, Canada, Japan, China, India, Brazil, Argentina, Australia, Russia and New Zealand. 3. Comparative analyses on the impact of NTMs on agri-food trade of the EU. 4. Policy recommendations from case studies for quantifying NTMs on fruits and vegetables, meat and dairy trade clusters with the EU. 5. Policy recommendations from case studies on the impacts of EU private and public standards in LDCs. 6. Dissemination of project results to key stakeholders. This will be achieved: A. By optimizing complementarities of the project with ongoing NTM research on the TRAINS data base at UNCTAD. B. By organizing the research work in research, database, management and dissemination work packages. C. By developing research methodologies that are innovative and robust, optimizing the direct usefulness of the end results for the end users. D. By proposing a partner consortium that together reunites the relevant needs, for: Scientific excellence and international project experience Appropriate geographic coverage to collect the required data in all countries Linkages and complementarities with ongoing international NTM analyses (UNCTAD, OECD, World Bank, IFPRI) Policy contacts, dialogue and influence Efficient and effective project management E. With a budget of 314.5 person months, 2.372 M EC request, for 19 partners, over 30 months.
Agency: Department of Health and Human Services | Branch: | Program: STTR | Phase: Phase II | Award Amount: 1.37M | Year: 2011
DESCRIPTION (provided by applicant): Research and development of new drugs is a protracted and expensive endeavor. The typical drug discovery process evolves from lead identification for a disease target to lead optimization, in vitro/in vivo evaluation, preclinical and clinical testing, and FDA approval. Several studies estimate the average cost of development of a single, approved new drug in excess of 800 million. A large portion of this expense is attributed to abandoned lead candidates that are obtained initially from screening vast, unfocussed libraries of compounds for activity against the target but which fail for various reasons along the pipeline. Thus, having a well stocked pipeline of drug candidates is integral to guaranteeing success in any drug discovery endeavor. Recent vast strides in unraveling the human proteome and interactome have allowed mapping of the complex network of protein-protein interactions (PPIs). PPIs are involved in all cellular processes, including growth, maintenance, anddeath, and it is documented that the dysregulation of certain PPIs underlies the pathology of various diseases. The identification of modulators of these PPIs, and consequently protein function, and the process of transforming these into high-content leadseries are key activities in modern drug discovery. We have proposed a rapid, knowledge-based methodology to develop several high-affinity peptide drug candidates able to modulate key protein interactions, and having high potential for success as drug leads. Peptides are high value targets in drug discovery and peptide-based leads derived from PPI sites currently comprise gt50% of pharmaceutical pipelines. In Phase I studies, Lynntech and the Garner group at VBI have demonstrated unequivocally that it is feasible to obtain biologically active peptide ligands to target proteins, from their primary sequence alone, using our unique approach that combines systems biology and bioinformatics tools with an advanced, high-density peptide microarray for high-throughput screening of candidate ligands. Several high- affinity peptide ligands (of nM range affinity) were obtained from array based affinity maturation, and a subset of these ligands displayed a clear proclivity to modulate ESRRG interactions. Our Phase I efforts also have resulted in the successful development of a web-accessible discovery engine and database which enables user-assisted pseudo-automation of the various steps involved in the approach, thereby vastly expediting the process. Further enhancementsare required to make this a potent drug discovery engine for lead generation, lead optimization, and lead explosion. The Phase II proposal will not only develop graphic-user interface tools for data analysis and informed down-selection of ligands in a pipeline but also elucidate selection rules that will inform the quickest way to obtain a high value lead drug candidate from protein sequence. PUBLIC HEALTH RELEVANCE: The high cost of modern drugs in the US is related directly to the various wasted efforts spent chasing compounds selected from random, unfocussed libraries with only a promise of 'drug-like' properties. Our methodology starts from an 'informed' and defined starting point and takes rapid, meaningful strides across the mountainous 'fitness' landscape of peptide ligand space to efficiently reach the summit of ligand fitness. The surfeit of high-value hit-to-lead candidates from our approach will doubtlessly enhance the probability of success for finding new drugs, and will drastically changethe approach currently taken for drug discovery.
Cuevas K.,University of Connecticut |
Bell M.A.,Virginia Polytechnic Institute and State University
Child Development | Year: 2014
Individual differences in infant attention are theorized to reflect the speed of information processing and are related to later cognitive abilities (i.e., memory, language, and intelligence). This study provides the first systematic longitudinal analysis of infant attention and early childhood executive function (EF; e.g., working memory, inhibitory control, cognitive flexibility). A group of 5-month-olds (n = 201) were classified as short or long lookers. At 24, 36, and 48 months of age, children completed age-appropriate EF tasks. Infant short lookers (i.e., more efficient information processors) exhibited higher EF throughout early childhood as compared to infant long lookers, even after controlling for verbal ability (a potential indicator of intelligence). These findings are discussed in relation to the emergence of executive attention. Child Development © 2014 The Society for Research in Child Development, Inc.
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 150.00K | Year: 2014
ABSTRACT: SA Photonics is pleased to propose the development of the Micro Interferometer Pressures Sensor (MIPS). MIPS uses an innovative sensing head structure being developed by our research partner, Virgina Tech. The pressure sensing head is then coupled to SA Photonics"high performance AccuSense photonic distance measurement system. AccuSense has demonstrated the capability of precision Fabry-Perot cavity length interrogation at rates greater than 100 kHz. The result of combining the unique sensing head with AccuSense is a very compact and robust pressure sensor with a sensitivity of better than 0.002 psi per rt-Hz and a high bandwidth of greater than 1 MHz. Furthermore, the unique Virginia Tech sensing head design enable robust operation in extreme environments of greater than 1300°C and exposure to corrosive materials. BENEFIT: The Air Force and DoD are investigating the next generation of hypersonic aerial vehicles. It is critical to have instrumentation to support theoretical modeling and wind tunnel testing of such vehicles. The MIPS sernsor will bring substantial pressure sensor performance improvement in a package that will be compact, robust, manufacturable ,and compatible wind tunnel and field testing. SA Photonics will utilize its AccuSense technology that was originally developed in an MDA Phase II and then refined under Phase III programs form primes. This allows the Air Force and the DoD to leverage past investment into this critical need area.
Agency: Department of Defense | Branch: Air Force | Program: STTR | Phase: Phase I | Award Amount: 149.99K | Year: 2015
ABSTRACT: We exploit recent advances in magnetoelectric/piezoelectric (ME/PE) composite materials to enable the development of efficient sub-wavelength radio frequency (RF) transmitting antennas. With these materials will be possible to achieve high dielectric permittivity and magnetic permeability, slow electromagnetic propagation and low RF loss tangents. Together, these special properties make it possible to design electrically "short" antennas for applications where conventional antennas would be too large. Innovative use of DC fields generated by applying voltages to the ME/PE materials makes it possible to have antennas tune in frequency or to dynamically select radiation patterns. The resulting antennas will improve gain for small unmanned aerial vehicles (UAVs) and other wireless systems. Wide-ranging applications to consumer wireless devices such as portable computers, data-enabled tablets and the like are also possible. BENEFIT: The development of sub-wavelength RF antennas with high gain, and their deployment on small UAVs and small wireless devices, will improve usable range and reduce RF transmitter load on system batteries.
Virginia Polytechnic Institute, State University and Purdue Research Foundation | Date: 2013-01-09
Provided are cellulose esters useful for inhibiting solution crystallization of drugs. Specific polymers include cellulose esters of formula I: is 3, 4, 6, or 8 to provide a -carboxyalkanoyl group chosen from succinoyl, glutaroyl, adipoyl, sebacyl, and suberyl groups; and wherein R is chosen from: a hydrogen atom; and an alkanoyl group chosen from acetyl, propionyl, butyryl, valeroyl, hexanoyl, nonanoyl, decanoyl, lauroyl, palmitoyl, and stearoyl groups; wherein there is a total degree of substitution of the alkanoyl group and the -carboxyalkanoyl group of at least 2.0; and wherein the polymer comprises m repeating units where n=1 to 1,000,000, or 10 to 100,000, or 100 to 1,000, such as 1 to 6,000. Embodiments further include compositions comprising cellulose esters and poorly water-soluble drugs, which compositions exhibit greater solubility and stability in solution as compared to the drugs alone.
Virginia Polytechnic Institute, State University and Huntington Ingalls Inc. | Date: 2013-07-30
A method for impedance measurement using chirp signal injection is provided. The method includes injecting at least one chirp signal into the three-phase AC system, and collecting at least one response to the at least one chirp signal. The method further includes transferring the at least one response from abc coordinates to dq coordinates. At least one impedance is calculated based on the at least one response to the at least one chirp signal.
Virginia Polytechnic Institute, State University and Huntington Ingalls Inc. | Date: 2013-07-30
A method for impedance measurement in a three-phase AC system is provided. The method includes injecting a shunt perturbation signal into the three-phase AC system and collecting a response to the shunt perturbation signal, and injecting a series perturbation signal into the three-phase AC system and collecting a response to the series perturbation signal. The response to the shunt perturbation signal and the response to the series perturbation signal are then transferred from abc coordinate to dq coordinates. At least one impedance of the three-phase AC system is calculated based on the response to the shunt perturbation signal and the response to the series perturbation signal.
Santos W.L.,Virginia Polytechnic Institute and State University |
Lynch K.R.,University of Virginia
ACS Chemical Biology | Year: 2015
The transfer of the gamma phosphate from ATP to sphingosine (Sph) to generate a small signaling molecule, sphingosine 1-phosphate (S1P), is catalyzed by sphingosine kinases (SphK), which exist as two isoforms, SphK1 and SphK2. SphK is a key regulator of S1P and the S1P:Sph/ceramide ratio. Increases in S1P levels have been linked to diseases including sickle cell disease, cancer, and fibrosis. Therefore, SphKs are potential targets for drug discovery. However, the current chemical biology toolkit needed to validate these enzymes as drug targets is inadequate. With this review, we survey in vivo active SphK inhibitors and highlight the need for developing more potent and selective inhibitors. © 2014 American Chemical Society.
Klauer S.G.,Virginia Polytechnic Institute and State University |
Guo F.,Virginia Polytechnic Institute and State University |
Simons-Morton B.G.,Eunice Kennedy Shriver National Institute of Child Health and Human Development |
Ouimet M.C.,Université de Sherbrooke |
And 2 more authors.
New England Journal of Medicine | Year: 2014
BACKGROUND: Distracted driving attributable to the performance of secondary tasks is a major cause of motor vehicle crashes both among teenagers who are novice drivers and among adults who are experienced drivers. METHODS: We conducted two studies on the relationship between the performance of secondary tasks, including cell-phone use, and the risk of crashes and near-crashes. To facilitate objective assessment, accelerometers, cameras, global positioning systems, and other sensors were installed in the vehicles of 42 newly licensed drivers (16.3 to 17.0 years of age) and 109 adults with more driving experience. RESULTS: During the study periods, 167 crashes and near-crashes among novice drivers and 518 crashes and near-crashes among experienced drivers were identified. The risk of a crash or near-crash among novice drivers increased significantly if they were dialing a cell phone (odds ratio, 8.32; 95% confidence interval [CI], 2.83 to 24.42), reaching for a cell phone (odds ratio, 7.05; 95% CI, 2.64 to 18.83), sending or receiving text messages (odds ratio, 3.87; 95% CI, 1.62 to 9.25), reaching for an object other than a cell phone (odds ratio, 8.00; 95% CI, 3.67 to 17.50), looking at a roadside object (odds ratio, 3.90; 95% CI, 1.72 to 8.81), or eating (odds ratio, 2.99; 95% CI, 1.30 to 6.91). Among experienced drivers, dialing a cell phone was associated with a significantly increased risk of a crash or near-crash (odds ratio, 2.49; 95% CI, 1.38 to 4.54); the risk associated with texting or accessing the Internet was not assessed in this population. The prevalence of high-risk attention to secondary tasks increased over time among novice drivers but not among experienced drivers. CONCLUSIONS: The risk of a crash or near-crash among novice drivers increased with the performance of many secondary tasks, including texting and dialing cell phones. Copyright © 2014 Massachusetts Medical Society. All rights reserved.
Murray-Tuite P.,Virginia Polytechnic Institute and State University |
Wolshon B.,Louisiana State University
Transportation Research Part C: Emerging Technologies | Year: 2013
This paper presents a review of highway-based evacuation modeling and simulation and its evolution over the past decade. The review includes the major components of roadway transportation planning and operations, including the current state of modeling in the forecasting of evacuation travel demand, distribution and assignment of evacuation demand to regional road networks to reach destinations, assignment of evacuees to various modes of transportation, and evaluation and testing of alternative management strategies to increase capacity of evacuation networks or manage demand. Although this discussion does not cover recent work in other modes used in evacuation such as air, rail, and pedestrian, this paper does highlight recent interdisciplinary modeling work in evacuation to help bridge the gap between the behavioral sciences and engineering and the application of emerging techniques for the verification, validation, and calibration of models. The manuscript also calls attention to special considerations and logistical difficulties, which have received limited attention to date. In addition to these concerns, the following future directions are discussed: further interdisciplinary efforts, including incorporating the medical community; using new technologies for communication of warnings and traffic condition information, data collection, and increased modeling resolution and confidence; using real-time information; and further model refinements and validation. © 2012 Elsevier Ltd.
Chou T.,University of California at Los Angeles |
Mallick K.,CEA Saclay Nuclear Research Center |
Zia R.K.P.,Virginia Polytechnic Institute and State University
Reports on Progress in Physics | Year: 2011
Unlike equilibrium statistical mechanics, with its well-established foundations, a similar widely accepted framework for non-equilibrium statistical mechanics (NESM) remains elusive. Here, we review some of the many recent activities on NESM, focusing on some of the fundamental issues and general aspects. Using the language of stochastic Markov processes, we emphasize general properties of the evolution of configurational probabilities, as described by master equations. Of particular interest are systems in which the dynamics violates detailed balance, since such systems serve to model a wide variety of phenomena in nature. We next review two distinct approaches for investigating such problems. One approach focuses on models sufficiently simple to allow us to find exact, analytic, non-trivial results. We provide detailed mathematical analyses of a one-dimensional continuous-time lattice gas, the totally asymmetric exclusion process. It is regarded as a paradigmatic model for NESM, much like the role the Ising model played for equilibrium statistical mechanics. It is also the starting point for the second approach, which attempts to include more realistic ingredients in order to be more applicable to systems in nature. Restricting ourselves to the area of biophysics and cellular biology, we review a number of models that are relevant for transport phenomena. Successes and limitations of these simple models are also highlighted. © 2011 IOP Publishing Ltd.