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Sample records for eranos based equilibrium

  1. Sensitivity analysis of Monju using ERANOS with JENDL-4.0

    SciTech Connect

    Tamagno, P.; Van Rooijen, W. F. G.; Takeda, T.; Konomura, M.

    2012-07-01

    This paper deals with sensitivity analysis using JENDL-4.0 nuclear data applied to the Monju reactor. In 2010 the Japan Atomic Energy Agency - JAEA - released a new set of nuclear data: JENDL-4.0. This new evaluation is expected to contain improved data on actinides and covariance matrices. Covariance matrices are a key point in quantification of uncertainties due to basic nuclear data. For sensitivity analysis, the well-established ERANOS [1] code was chosen because of its integrated modules that allow users to perform a sensitivity analysis of complex reactor geometries. A JENDL-4.0 cross-section library is not available for ERANOS. Therefore a cross-section library had to be made from the original nuclear data set, available as ENDF formatted files. This is achieved by using the following codes: NJOY, CALENDF, MERGE and GECCO in order to create a library for the ECCO cell code (part of ERANOS). In order to make sure of the accuracy of the new ECCO library, two benchmark experiments have been analyzed: the MZA and MZB cores of the MOZART program measured at the ZEBRA facility in the UK. These were chosen due to their similarity to the Monju core. Using the JENDL-4.0 ECCO library we have analyzed the criticality of Monju during the restart in 2010. We have obtained good agreement with the measured criticality. Perturbation calculations have been performed between JENDL-3.3 and JENDL-4.0 based models. The isotopes {sup 239}Pu, {sup 238}U, {sup 241}Am and {sup 241}Pu account for a major part of observed differences. (authors)

  2. YALINA analytical benchmark analyses using the deterministic ERANOS code system.

    SciTech Connect

    Gohar, Y.; Aliberti, G.; Nuclear Engineering Division

    2009-08-31

    The growing stockpile of nuclear waste constitutes a severe challenge for the mankind for more than hundred thousand years. To reduce the radiotoxicity of the nuclear waste, the Accelerator Driven System (ADS) has been proposed. One of the most important issues of ADSs technology is the choice of the appropriate neutron spectrum for the transmutation of Minor Actinides (MA) and Long Lived Fission Products (LLFP). This report presents the analytical analyses obtained with the deterministic ERANOS code system for the YALINA facility within: (a) the collaboration between Argonne National Laboratory (ANL) of USA and the Joint Institute for Power and Nuclear Research (JIPNR) Sosny of Belarus; and (b) the IAEA coordinated research projects for accelerator driven systems (ADS). This activity is conducted as a part of the Russian Research Reactor Fuel Return (RRRFR) Program and the Global Threat Reduction Initiative (GTRI) of DOE/NNSA.

  3. Evaluation of AGNI SFR core neutronics parameters with VESTA and ERANOS

    NASA Astrophysics Data System (ADS)

    Ecrabet, Fabrice; Haeck, Wim; Chaitanya Tadepalli, Sai

    2014-06-01

    This paper presents the calculation of core neutronics parameters for so called AGNI Sodium Fast Reactor (SFR) model performed with ERANOS code and Monte Carlo depletion interface software VESTA. The AGNI core has been developed at IRSN for its own R&D needs, i.e. to test performance of calculation codes for safety assessment of a generation IV SFR project. The ERANOS code is used as reference code for SFR core calculations at IRSN. In this work, VESTA calculations have been performed and compared with corresponding ERANOS results. These calculations have a double purpose: mastering the use of tools for the evaluation of SFR core static neutronics parameters and validate the use of VESTA for SFR cores.

  4. Trunk biomechanical models based on equilibrium at a single-level violate equilibrium at other levels.

    PubMed

    Arjmand, N; Shirazi-Adl, A; Parnianpour, M

    2007-05-01

    Accurate estimation of muscle forces in various occupational tasks is critical for a reliable evaluation of spinal loads and subsequent assessment of risk of injury and management of back disorders. The majority of biomechanical models of multi-segmental spine estimate muscle forces and spinal loads based on the balance of net moments at a single level with no consideration for the equilibrium at remaining levels. This work aimed to quantify the extent of equilibrium violation and alterations in estimations when such models are performed at different levels. Results are compared with those of kinematics-driven model that satisfies equilibrium at all levels and EMG data. Regardless of the method used (optimization or EMG-assisted), single-level free body diagram models yielded estimations that substantially altered depending on the level considered (i.e., level dependency). Equilibrium of net moment was also grossly violated at remaining levels with the error increasing in more demanding tasks. These models may, however, be used to estimate spinal compression forces. PMID:17136359

  5. Learning of Chemical Equilibrium through Modelling-Based Teaching

    ERIC Educational Resources Information Center

    Maia, Poliana Flavia; Justi, Rosaria

    2009-01-01

    This paper presents and discusses students' learning process of chemical equilibrium from a modelling-based approach developed from the use of the "Model of Modelling" diagram. The investigation was conducted in a regular classroom (students 14-15 years old) and aimed at discussing how modelling-based teaching can contribute to students learning…

  6. Equilibrium reconstruction based on core magnetic measurement and its applications on equilibrium transition in Joint-TEXT tokamak

    SciTech Connect

    Chen, J.; Zhuang, G. Jian, X.; Li, Q.; Liu, Y.; Gao, L.; Wang, Z. J.

    2014-10-15

    Evaluation and reconstruction of plasma equilibrium, especially to resolve the safety factor profile, is imperative for advanced tokamak operation and physics study. Based on core magnetic measurement by the high resolution laser polarimeter-interferometer system (POLARIS), the equilibrium of Joint-TEXT (J-TEXT) plasma is reconstructed and profiles of safety factor, current density, and electron density are, therefore, obtained with high accuracy and temporal resolution. The equilibrium reconstruction procedure determines the equilibrium flux surfaces essentially from the data of POLARIS. Refraction of laser probe beam, a major error source of the reconstruction, has been considered and corrected, which leads to improvement of accuracy more than 10%. The error of reconstruction has been systematically assessed with consideration of realistic diagnostic performance and scrape-off layer region of plasma, and its accuracy has been verified. Fast equilibrium transitions both within a single sawtooth cycle and during the penetration of resonant magnetic perturbation have been investigated.

  7. Punctuated equilibrium based on a locally ambiguous niche.

    PubMed

    Gunji, Yukio-Pegio; Sakiyama, Tomoko; Murakami, Hisashi

    2014-09-01

    Punctuated equilibrium, recently regarded as the power law distribution of lifespan, is estimated with respect to self-organized criticality. Previous explanations were based on a global property, such as the selection of species depending on their fitness, however a particular entity defined through such global property cannot be relevant to the notion of "self". Here, we introduce local ambiguity of a niche with respect to function and define a function network by using two types of maps. Due to the local complex structure of the function network, motif and lateral connections, some species are easily replaced by others, and other species have long lives. Punctuated equilibrium can, therefore, be explained by local ambiguous interaction, which suggests the notion of self and supports the idea of self-organized criticality. PMID:24905426

  8. Multi-period equilibrium/near-equilibrium in electricity markets based on locational marginal prices

    NASA Astrophysics Data System (ADS)

    Garcia Bertrand, Raquel

    In this dissertation we propose an equilibrium procedure that coordinates the point of view of every market agent resulting in an equilibrium that simultaneously maximizes the independent objective of every market agent and satisfies network constraints. Therefore, the activities of the generating companies, consumers and an independent system operator are modeled: (1) The generating companies seek to maximize profits by specifying hourly step functions of productions and minimum selling prices, and bounds on productions. (2) The goals of the consumers are to maximize their economic utilities by specifying hourly step functions of demands and maximum buying prices, and bounds on demands. (3) The independent system operator then clears the market taking into account consistency conditions as well as capacity and line losses so as to achieve maximum social welfare. Then, we approach this equilibrium problem using complementarity theory in order to have the capability of imposing constraints on dual variables, i.e., on prices, such as minimum profit conditions for the generating units or maximum cost conditions for the consumers. In this way, given the form of the individual optimization problems, the Karush-Kuhn-Tucker conditions for the generating companies, the consumers and the independent system operator are both necessary and sufficient. The simultaneous solution to all these conditions constitutes a mixed linear complementarity problem. We include minimum profit constraints imposed by the units in the market equilibrium model. These constraints are added as additional constraints to the equivalent quadratic programming problem of the mixed linear complementarity problem previously described. For the sake of clarity, the proposed equilibrium or near-equilibrium is first developed for the particular case considering only one time period. Afterwards, we consider an equilibrium or near-equilibrium applied to a multi-period framework. This model embodies binary

  9. Linear irreversible heat engines based on local equilibrium assumptions

    NASA Astrophysics Data System (ADS)

    Izumida, Yuki; Okuda, Koji

    2015-08-01

    We formulate an endoreversible finite-time Carnot cycle model based on the assumptions of local equilibrium and constant energy flux, where the efficiency and the power are expressed in terms of the thermodynamic variables of the working substance. By analyzing the entropy production rate caused by the heat transfer in each isothermal process during the cycle, and using the endoreversible condition applied to the linear response regime, we identify the thermodynamic flux and force of the present system and obtain a linear relation that connects them. We calculate the efficiency at maximum power in the linear response regime by using the linear relation, which agrees with the Curzon-Ahlborn (CA) efficiency known as the upper bound in this regime. This reason is also elucidated by rewriting our model into the form of the Onsager relations, where our model turns out to satisfy the tight-coupling condition leading to the CA efficiency.

  10. Calculation of the Phenix end-of-life test 'Control Rod Withdrawal' with the ERANOS code

    SciTech Connect

    Tiberi, V.

    2012-07-01

    The Inst. of Radiological Protection and Nuclear Safety (IRSN) acts as technical support to French public authorities. As such, IRSN is in charge of safety assessment of operating and under construction reactors, as well as future projects. In this framework, one current objective of IRSN is to evaluate the ability and accuracy of numerical tools to foresee consequences of accidents. Neutronic studies step in the safety assessment from different points of view among which the core design and its protection system. They are necessary to evaluate the core behavior in case of accident in order to assess the integrity of the first barrier and the absence of a prompt criticality risk. To reach this objective one main physical quantity has to be evaluated accurately: the neutronic power distribution in core during whole reactor lifetime. Phenix end of life tests, carried out in 2009, aim at increasing the experience feedback on sodium cooled fast reactors. These experiments have been done in the framework of the development of the 4. generation of nuclear reactors. Ten tests have been carried out: 6 on neutronic and fuel aspects, 2 on thermal hydraulics and 2 for the emergency shutdown. Two of them have been chosen for an international exercise on thermal hydraulics and neutronics in the frame of an IAEA Coordinated Research Project. Concerning neutronics, the Control Rod Withdrawal test is relevant for safety because it allows evaluating the capability of calculation tools to compute the radial power distribution on fast reactors core configurations in which the flux field is very deformed. IRSN participated to this benchmark with the ERANOS code developed by CEA for fast reactors studies. This paper presents the results obtained in the framework of the benchmark activity. A relatively good agreement was found with available measures considering the approximations done in the modeling. The work underlines the importance of burn-up calculations in order to have a fine

  11. An Equilibrium-Based Model of Gas Reaction and Detonation

    SciTech Connect

    Trowbridge, L.D.

    2000-04-01

    During gaseous diffusion plant operations, conditions leading to the formation of flammable gas mixtures may occasionally arise. Currently, these could consist of the evaporative coolant CFC-114 and fluorinating agents such as F2 and ClF3. Replacement of CFC-114 with a non-ozone-depleting substitute is planned. Consequently, in the future, the substitute coolant must also be considered as a potential fuel in flammable gas mixtures. Two questions of practical interest arise: (1) can a particular mixture sustain and propagate a flame if ignited, and (2) what is the maximum pressure that can be generated by the burning (and possibly exploding) gas mixture, should it ignite? Experimental data on these systems, particularly for the newer coolant candidates, are limited. To assist in answering these questions, a mathematical model was developed to serve as a tool for predicting the potential detonation pressures and for estimating the composition limits of flammability for these systems based on empirical correlations between gas mixture thermodynamics and flammability for known systems. The present model uses the thermodynamic equilibrium to determine the reaction endpoint of a reactive gas mixture and uses detonation theory to estimate an upper bound to the pressure that could be generated upon ignition. The model described and documented in this report is an extended version of related models developed in 1992 and 1999.

  12. Benchmark of Advanced Burner Test Reactor Model Using MCNPX 2.6.0 and ERANOS 2.1

    SciTech Connect

    Kenneth Allen; Travis Knight; Samuel Bays

    2011-08-01

    Significant research is currently being performed whereby fast reactor cores have been designed to burn transuranic materials reducing the volume and long-term radiotoxicity of spent nuclear fuel. These core and depletion models depend on various computer codes. This research used MCNPX 2.6.0 and ERANOS 2.1 to model a standard 250MWt Advanced Burner Test Reactor (ABTR) core. The intent was to benchmark criticality and burnup results from a stochastic Monte Carlo code and a deterministic depletion code using a standard ABTR model created by Argonne National Laboratory. Because each of these codes solve the transport and burnup problem differently, there is a need to benchmark the core models in order to verify results and identify root causes for significant differences in results between codes. Flux calculations in ERANOS were performed using diffusion theory, Legendre polynomial approximations (using the VARIANT module) and discrete ordinates methods. The k-effective for the higher-order transport models remained within 1000 pcm of the MCNPX model. The difference between the total heavy nuclide mass balance in ERANOS using the various flux calculations and the MCNPX depletion model was less than 0.4% out to a burnup of 1095 days (67.45 GWd/MTHM). For individual heavy nuclides, the depletion models closely matched (< 5.0 % difference) throughout the depletion for isotopes of Uranium, Neptunium and Plutonium and most of the higher transuranics. Notable exceptions were 242Am, 242Cm, 243Cm and 246Cm where differences ranged from 0.1 – 0.2% after 26 days and increased to 11 - 136% at 1095 days.

  13. Evidence-Based Approaches to Improving Chemical Equilibrium Instruction

    ERIC Educational Resources Information Center

    Davenport, Jodi L.; Leinhardt, Gaea; Greeno, James; Koedinger, Kenneth; Klahr, David; Karabinos, Michael; Yaron, David J.

    2014-01-01

    Two suggestions for instruction in chemical equilibrium are presented, along with the evidence that supports these suggestions. The first is to use diagrams to connect chemical reactions to the effects of reactions on concentrations. The second is the use of the majority and minority species (M&M) strategy to analyze chemical equilibrium…

  14. Effectiveness of Instruction Based on the Constructivist Approach on Understanding Chemical Equilibrium Concepts

    ERIC Educational Resources Information Center

    Akkus, Huseyin; Kadayifci, Hakki; Atasoy, Basri; Geban, Omer

    2003-01-01

    The purpose of this study was to identify misconceptions concerning chemical equilibrium concepts and to investigate the effectiveness of instruction based on the constructivist approach over traditional instruction on 10th grade students' understanding of chemical equilibrium concepts. The subjects of this study consisted of 71 10th grade…

  15. Equilibrium II: Acids and Bases. Independent Learning Project for Advanced Chemistry (ILPAC). Unit P3.

    ERIC Educational Resources Information Center

    Inner London Education Authority (England).

    This unit on equilibrium is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit, which consists of two levels, focuses on the application of equilibrium principles to equilibria involving weak acids and bases, including buffer solutions and indicators. Level one uses Le Chatelier's…

  16. Quasi-Three-Dimensional Mathematical Modeling of Morphological Processes Based on Equilibrium Sediment Transport

    NASA Astrophysics Data System (ADS)

    Charafi, My. M.; Sadok, A.; Kamal, A.; Menai, A.

    A quasi-three-dimensional mathematical model has been developed to study the morphological processes based on equilibrium sediment transport method. The flow velocities are computed by a two-dimensional horizontal depth-averaged flow model (H2D) in combination with logarithmic velocity profiles. The transport of sediment particles by a flow water has been considered in the form of bed load and suspended load. The bed load transport rate is defined as the transport of particles by rolling and saltating along the bed surface and is given by the Van Rijn relationship (1987). The equilibrium suspended load transport is described in terms of an equilibrium sediment concentration profile (ce) and a logarithmic velocity (u). Based on the equilibrium transport, the bed change rate is given by integration of the sediment mass-balance equation. The model results have been compared with a Van Rijn results (equilibrium approach) and good agreement has been found.

  17. Using the Logarithmic Concentration Diagram, Log "C", to Teach Acid-Base Equilibrium

    ERIC Educational Resources Information Center

    Kovac, Jeffrey

    2012-01-01

    Acid-base equilibrium is one of the most important and most challenging topics in a typical general chemistry course. This article introduces an alternative to the algebraic approach generally used in textbooks, the graphical log "C" method. Log "C" diagrams provide conceptual insight into the behavior of aqueous acid-base systems and allow…

  18. Opicinus de Canistris: some notes from Jung's unpublished Eranos Seminar on the medieval Codex Palatinus Latinus 1993.

    PubMed

    Quaglino, Gian Piero; Romano, Augusto; Bernardini, Riccardo

    2010-06-01

    Jung held an informal seminar for a limited number of students after the end of the Eranos Conference in August, 1943. All traces of this seminar were lost until the notes taken on it by one of the students, Alwine von Keller, were found in 2006. Jung's talk consisted of a psychological commentary on a series of images in the medieval Codex Palatinus Latinus 1993, attributed to Opicinus de Canistris (1296-c.1352), a fourteenth-century Italian clergyman, mystic, miniaturist, and cartographer. Jung interpreted Opicinus' images as a series of mandalas in which the Shadow, the dark principle, does not manage to be integrated into a balanced system. Opicinus tried to settle this division into opposites, which constitutes the main problem in modern times, while remaining inside the system of Christian doctrine. However, he did not succeed in his attempt to integrate the principle of the Shadow on the doctrinal level because he was not aware of the very same division in his own unconscious. Our article points out the features in the seminar where Jung seemed to show much more originality in his interpretation than other psychoanalytic studies on Opicinus or other analytical-psychological readings of medieval Christian art. PMID:20629782

  19. Development of facile property calculation model for adsorption chillers based on equilibrium adsorption cycle

    NASA Astrophysics Data System (ADS)

    Yano, Masato; Hirose, Kenji; Yoshikawa, Minoru; Thermal management technology Team

    Facile property calculation model for adsorption chillers was developed based on equilibrium adsorption cycles. Adsorption chillers are one of promising systems that can use heat energy efficiently because adsorption chillers can generate cooling energy using relatively low temperature heat energy. Properties of adsorption chillers are determined by heat source temperatures, adsorption/desorption properties of adsorbent, and kinetics such as heat transfer rate and adsorption/desorption rate etc. In our model, dependence of adsorption chiller properties on heat source temperatures was represented using approximated equilibrium adsorption cycles instead of solving conventional time-dependent differential equations for temperature changes. In addition to equilibrium cycle calculations, we calculated time constants for temperature changes as functions of heat source temperatures, which represent differences between equilibrium cycles and real cycles that stemmed from kinetic adsorption processes. We found that the present approximated equilibrium model could calculate properties of adsorption chillers (driving energies, cooling energies, and COP etc.) under various driving conditions quickly and accurately within average errors of 6% compared to experimental data.

  20. A Simple System for Observing Dynamic Phase Equilibrium via an Inquiry-Based Laboratory or Demonstration

    ERIC Educational Resources Information Center

    Cloonan, Carrie A.; Andrew, Julie A.; Nichol, Carolyn A.; Hutchinson, John S.

    2011-01-01

    This article describes an activity that can be used as an inquiry-based laboratory or demonstration for either high school or undergraduate chemistry students to provide a basis for understanding both vapor pressure and the concept of dynamic phase equilibrium. The activity includes a simple setup to create a closed system of only water liquid and…

  1. An equilibrium-based model for measuring environmental radon using charcoal canisters.

    PubMed

    Lehnert, A L; Kearfott, K J

    2010-08-01

    Radon in indoor air is often measured using canisters of activated charcoal that function by adsorbing radon gas. The use of a diffusion barrier charcoal canister (DBCC) minimizes the effects of environmental humidity and extends the useful exposure time by several days. Many DBCC protocols model charcoal canisters as simple integrating detectors, which introduces errors due to the fact that radon uptake changes over the exposure period. Errors are compensated for by calculating a calibration factor that is nonlinear with respect to exposure time. This study involves the development and testing of an equilibrium-based model and corresponding measurement protocol that treats the charcoal canisters as a system coming into equilibrium with the surrounding radon environment. This model applies to both constant and temporally varying radon concentration situations, which was essential, as efforts are currently underway using a temporally varying radon chamber. It was found that the DBCCs equilibrate following the relationship E = (1 - e) where E is a measure of how close the DBCC is to equilibrium, t is exposure time, and q is the equilibration constant. This equilibration constant was empirically determined to be 0.019 h. The proposed model was tested in a blind test as well as compared with the currently accepted U.S. Environmental Protection Agency (U.S. EPA) model. Comparisons between the two methods showed a slight decrease in measurement error when using the equilibrium-based method as compared to the U.S. EPA method. PMID:20622564

  2. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers

    NASA Astrophysics Data System (ADS)

    Nap, R. J.; Tagliazucchi, M.; Szleifer, I.

    2014-01-01

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads

  3. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers.

    PubMed

    Nap, R J; Tagliazucchi, M; Szleifer, I

    2014-01-14

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads

  4. Born energy, acid-base equilibrium, structure and interactions of end-grafted weak polyelectrolyte layers

    SciTech Connect

    Nap, R. J.; Tagliazucchi, M.; Szleifer, I.

    2014-01-14

    This work addresses the effect of the Born self-energy contribution in the modeling of the structural and thermodynamical properties of weak polyelectrolytes confined to planar and curved surfaces. The theoretical framework is based on a theory that explicitly includes the conformations, size, shape, and charge distribution of all molecular species and considers the acid-base equilibrium of the weak polyelectrolyte. Namely, the degree of charge in the polymers is not imposed but it is a local varying property that results from the minimization of the total free energy. Inclusion of the dielectric properties of the polyelectrolyte is important as the environment of a polymer layer is very different from that in the adjacent aqueous solution. The main effect of the Born energy contribution on the molecular organization of an end-grafted weak polyacid layer is uncharging the weak acid (or basic) groups and consequently decreasing the concentration of mobile ions within the layer. The magnitude of the effect increases with polymer density and, in the case of the average degree of charge, it is qualitatively equivalent to a small shift in the equilibrium constant for the acid-base equilibrium of the weak polyelectrolyte monomers. The degree of charge is established by the competition between electrostatic interactions, the polymer conformational entropy, the excluded volume interactions, the translational entropy of the counterions and the acid-base chemical equilibrium. Consideration of the Born energy introduces an additional energetic penalty to the presence of charged groups in the polyelectrolyte layer, whose effect is mitigated by down-regulating the amount of charge, i.e., by shifting the local-acid base equilibrium towards its uncharged state. Shifting of the local acid-base equilibrium and its effect on the properties of the polyelectrolyte layer, without considering the Born energy, have been theoretically predicted previously. Account of the Born energy leads

  5. New lifting relations for estimating LBM distribution functions from corresponding macroscopic quantities, based on equilibrium and non-equilibrium moments

    NASA Astrophysics Data System (ADS)

    Salimi, M. R.; Taeibi-Rahni, M.

    2015-12-01

    Due to superior accuracy and stability of multiple relaxation time (MRT) collision operator over its single relaxation time (SRT) counterpart, new lifting relations are proposed here to construct single particle distribution functions for MRT-LBM from macroscopic variables. Using these lifting relations, a new hybrid FVM-LB method is presented (called Finite type-LB hybrid method), which is consistent with MRT-LBM. In this new hybrid method, single-particle distribution functions in MRT-LBM sub-domain boundaries are computed, using equilibrium and non-equilibrium moments. These moments are computed in Navier-Stokes/FVM sub-domain boundaries, using macroscopic variables and their derivatives. The new method is validated by solving three benchmark problems, i.e., two- and three-dimensional lid driven cavity flows and two-dimensional unsteady flow around a squared section cylinder. These problems are analyzed with pure FVM, pure LBM, and Finite type-LB hybrid method (FTLBHM) and the related results are compared with each other and with benchmark data. These comparisons clearly demonstrate the accuracy of the present novel methodology for simulating steady/unsteady flow fields in two and three dimensions.

  6. A process-based model for non-equilibrium clumped isotope effects in carbonates

    NASA Astrophysics Data System (ADS)

    Watkins, J. M.; Hunt, J. D.

    2015-12-01

    The equilibrium clumped isotope composition of carbonate minerals is independent of the composition of the aqueous solution. However, many carbonate minerals grow at rates that place them in a non-equilibrium regime with respect to carbon and oxygen isotopes with unknown consequences for clumped isotopes. We develop a process-based model that allows one to calculate the oxygen, carbon, and clumped isotope composition of calcite as a function of temperature, crystal growth rate, and solution pH. In the model, carbon and oxygen isotope fractionation occurs through the mass-dependent attachment/detachment kinetics of the isotopologues of HCO-3 and CO2-3 to and from the calcite surface, which in turn, influence the clumped isotope composition of calcite. At experimental and biogenic growth rates, the mineral is expected to inherit a clumped isotopic composition that is similar to that of the DIC pool, which helps to explain (1) why different organisms share the same clumped isotope versus temperature calibration curves, (2) why many inorganic calibration curves are slightly different from one another, and (3) why foraminifera, coccoliths, and deep sea corals can have near-equilibrium clumped isotope compositions but far-from-equilibrium carbon and oxygen isotope compositions. Some aspects of the model can be generalized to other mineral systems and should serve as a useful reference in future efforts to quantify kinetic clumped isotope effects.

  7. Equilibrium theory-based design of simulated moving bed processes under reduced purity requirements linear isotherms.

    PubMed

    Rajendran, Arvind

    2008-03-28

    The design of simulated moving bed processes under reduced purity requirements for systems whose isotherm is linear is considered. Based on the equilibrium theory of chromatography, explicit equations to uniquely identify the separation region that will ensure specified extract and raffinate purities are derived. The identification of the region requires only the knowledge of Henry constants of the solutes, the concentration of the solutes in the feed and the purity specifications. These results are validated using numerical simulations. PMID:18281052

  8. Equilibrium partition ratios, densities, and transport phenomena in nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Sung, Pil Kyung

    To simulate transport phenomena, macrosegregation and segregation defects known as "freckles" during directional solidification of Ni-base superalloys, numerical modeling can be used; hence it is essential to have reasonably accurate values of the thermodynamic and transport properties for the alloys. In this research, therefore, the equilibrium partition ratios of the solutes in the Ni-Al-Ta-Cr quaternary system, as a model alloy, were measured, and the solid- and liquid-densities in Ni-base superalloys. were estimated. Also, the importance of these properties on the sensitivity of the results of numerical simulations was studied. The partition ratios apply to equilibria between melts and gamma-phase in the range of 1615 K to 1694 K, and it was found that the equilibrium partition ratio of Ta varies from approximately 0.6 at dilute Ta to 0.85 at 17 wt.% Ta. For the same range of Ta-contents, the partition ratios of Al and Cr vary much less and range from about 0.92 to 0.96. In addition to the partition ratios, the liquidus temperatures of the liquid in equilibrium with gamma in the Ni-Al-Ta-Cr system were estimated with a multidimensional regression analysis. To calculate the densities of solid Ni-base superalloys as functions of temperature and composition, lattice parameters at 20°C and coefficients of thermal expansion (CTEs) were estimated by combining available data. The CTEs calculated from the regressions result in densities that are within 0.5% error or less for seventeen alloys. To estimate the densities of liquid Ni-base superalloys, the densities and temperature coefficients of density of the liquid transition-metals, which are used as alloy elements in Ni-base superalloys, were applied to a simple correlation. By using this approach, the estimates of the liquid densities of five Ni-base superalloys agree with the measured values to +/-2.5%. Finally, the importance of using reasonably accurate estimates of the transport properties was illustrated by

  9. Reactive solute transport in streams. 1. Development of an equilibrium- based model

    USGS Publications Warehouse

    Runkel, R.L.; Bencala, K.E.; Broshears, R.E.; Chapra, S.C.

    1996-01-01

    An equilibrium-based solute transport model is developed for the simulation of trace metal fate and transport in streams. The model is formed by coupling a solute transport model with a chemical equilibrium submodel based on MINTEQ. The solute transport model considers the physical processes of advection, dispersion, lateral inflow, and transient storage, while the equilibrium submodel considers the speciation and complexation of aqueous species, precipitation/dissolution and sorption. Within the model, reactions in the water column may result in the formation of solid phases (precipitates and sorbed species) that are subject to downstream transport and settling processes. Solid phases on the streambed may also interact with the water column through dissolution and sorption/desorption reactions. Consideration of both mobile (water-borne) and immobile (streambed) solid phases requires a unique set of governing differential equations and solution techniques that are developed herein. The partial differential equations describing physical transport and the algebraic equations describing chemical equilibria are coupled using the sequential iteration approach.

  10. Accelerated equilibrium core composition search using a new MCNP-based simulator

    NASA Astrophysics Data System (ADS)

    Seifried, Jeffrey E.; Gorman, Phillip M.; Vujic, Jasmina L.; Greenspan, Ehud

    2014-06-01

    MocDown is a new Monte Carlo depletion and recycling simulator which couples neutron transport with MCNP and transmutation with ORIGEN. This modular approach to depletion allows for flexible operation by incorporating the accelerated progression of a complex fuel processing scheme towards equilibrium and by allowing for the online coupling of thermo-fluids feedback. MocDown also accounts for the variation of decay heat with fuel isotopics evolution. In typical cases, MocDown requires just over a day to find the equilibrium core composition for a multi-recycling fuel cycle, with a self-consistent thermo-fluids solution-a task that required between one and two weeks using previous Monte Carlo-based approaches.

  11. Equilibrium strategy-based optimization method for the coal-water conflict: A perspective from China.

    PubMed

    Xu, Jiuping; Lv, Chengwei; Zhang, Mengxiang; Yao, Liming; Zeng, Ziqiang

    2015-09-01

    Environmental water problems have become increasingly severe, with the coal-water conflict becoming one of the most difficult issues in large scale coal mining regions. In this paper, a bi-level optimization model based on the Stackelberg-Nash equilibrium strategy with fuzzy coefficients is developed to deal with environmental water problems in large scale coal fields, in which both the groundwater quality and quantity are considered. Using the proposed model, and fully considering the relationship between the authority and the collieries and also the equilibrium between economic development and environmental protection, an environmental protection based mining quotas competition mechanism is established. To deal with the inherent uncertainties, the model is defuzzified using a possibility measure, and a solution approach based on the Karush-Kuhn-Tucker condition is designed to search for the solutions. A case study is presented to demonstrate the practicality and efficiency of the model, and different constraint violation risk levels and related results are also obtained. The results showed that under the environmental protection based mining quotas competition mechanism, collieries attempt to conduct environmentally friendly exploitation to seek greater mining quotas. This demonstrates the practicality and efficiency in the proposed model of reducing the coal-water conflict. Finally, a comprehensive discussion is provided and some propositions is given as a foundation for the proposed management recommendations. PMID:26144559

  12. Unusual dileptions at RHIC a field theoretic approach based on a non-equilibrium chiral phase transition

    SciTech Connect

    Cooper, F.

    1997-09-22

    This paper contains viewgraphs on unusual dileptons at Brookhaven RHIC. A field theory approach is used based on a non-equilibrium chiral phase transformation utilizing the schroedinger and Heisenberg picture.

  13. Conjugate Acid-Base Pairs, Free Energy, and the Equilibrium Constant

    ERIC Educational Resources Information Center

    Beach, Darrell H.

    1969-01-01

    Describes a method of calculating the equilibrium constant from free energy data. Values of the equilibrium constants of six Bronsted-Lowry reactions calculated by the author's method and by a conventional textbook method are compared. (LC)

  14. Magnetic measurement based methods in determination of plasma equilibrium parameters in Damavand tokamak

    NASA Astrophysics Data System (ADS)

    Noori, E.; Sadeghi, Y.; Mehdian, H.

    2016-06-01

    Determination of plasma equilibrium parameters such as poloidal beta (βp) with half of plasma internal inductance (li) known as Shafranov parameter (asymmetry factor) (βp+𝔡li2) and edge safety factor plays very important role in primary equilibrium and stability analysis and control of tokamak plasma. In this study, the well known Shafranov semi-empirical model, based on external magnetic measurements is used to extract Shafranov parameter and effective edge safety factor in low-β operating regime of Damavand tokamak. The well known integral representation of βp+𝔡li2 was modified for non-circular tokamaks with ellipse-like cross section. After calibration of magnetic pick-up coils, Shafranov parameter was estimated with respect to the first and second Fourier harmonic of radial and poloidal components of magnetic field. The results were compared with approximate, semi-analytical determination of Shafranov parameter which is based on analytical solution of Grad-Shafranov equation (GSE). Founding evolution of Shafranov parameter, effective edge safety factor was obtained in terms of Shafranov parameter and compared with semi-empirical description. It was found that between the ramp-up and ramp-down domain of the plasma current, the result from Shafranov model is approximately in good agreement with the semi-analytical and semi-empirical benchmarks and the integral model provides more reliable trace of the Shafranov parameter in out of ramp domains of the discharge.

  15. Multi-equilibrium system based on sertraline and β-cyclodextrin supramolecular complex in aqueous solution.

    PubMed

    Passos, Joel J; De Sousa, Frederico B; Lula, Ivana S; Barreto, Elison A; Lopes, Juliana Fedoce; De Almeida, Wagner B; Sinisterra, Rubén D

    2011-12-12

    Sertraline (SRT) is a widely used antidepressant whose poor solubility in water limits its oral applicability. Thus, the aim of this work was the evaluation of a multi-equilibrium system based on β-cyclodextrin (βCD) and SRT. The inclusion compounds (ICs) were investigated by infrared spectroscopy, isothermal titration calorimetry (ITC) and (1)H and 2D ROESY nuclear magnetic resonance experiments. SRT solubility was predicted in vitro in water and biomimetic fluids. The SRT in presence of βCD at 1:1 and 1:2 molar ratios was more soluble than free SRT in all biomimetics media investigated. The FTIR-HATR showed that βCD νC-O-C stretching band was reduced in presence of SRT, suggesting the interactions between them. Additionally, titration process and Job's plot provided information on the ICs stoichiometry and evidenced the multi-equilibrium coexistence in aqueous solution. According to the ITC, SRT:βCD interaction process was spontaneous and exothermic with a high affinity binding constant (K=14,726 M(-1)). Additionally, the stoichiometry coefficient (n) was 1.63, which was comparable to that found by FITR-HATR. The (1)H and 2D ROESY verified multiple SRT sites included into the host cavity. Theoretical calculations depicted the relative energy of different proposed ICs structures, in which the 1:2 IC was the most stable. PMID:21963467

  16. Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

    ERIC Educational Resources Information Center

    Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

    2013-01-01

    A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

  17. Non-equilibrium photoexcited carrier effects in a graphene-based Josephson junction

    NASA Astrophysics Data System (ADS)

    Tsumura, Kohei; Furukawa, Naoki; Ito, Hironori; Watanabe, Eiichiro; Tsuya, Daiju; Takayanagi, Hideaki

    2016-01-01

    We studied the superconducting proximity effect under photoexcitation by illuminating a superconductor/monolayer graphene/superconductor (SGS) Josephson junction with monochromatic light at a wavelength of 1.31 μm. Although the critical current Ic can be controlled by the irradiation power P, its variation cannot be explained by modification of the carrier density, which has been reported for semiconductor-based Josephson junctions. The estimated electron temperature of graphene is proportional to P δ , where δ ≃ 1 / 3 . This relation clearly indicates that photogenerated non-equilibrium carrier dynamics are responsible for the variation of Ic with P. We suggest that the SGS junction can directly mediate interactions between the optical field and the superconducting state.

  18. Chemicals loading in acetylated bamboo assisted by supercritical CO2 based on phase equilibrium data

    NASA Astrophysics Data System (ADS)

    Silviana, Petermann, M.

    2015-12-01

    Indonesia has a large tropical forest. However, the deforestation still appears annually and vastly. This reason drives a use of bamboo as wood alternative. Recently, there are many modifications of bamboo in order to prolong the shelf life. Unfortunately, the processes need more chemicals and time. Based on wood modification, esterifying of bamboo was undertaken in present of a dense gas, i.e. supercritical CO2. Calculation of chemicals loading referred to ASTM D1413-99 by using the phase equilibrium data at optimum condition by a statistical design. The results showed that the acetylation of bamboo assisted by supercritical CO2 required 14.73 kg acetic anhydride/m3 of bamboo for a treatment of one hour.

  19. Meat-based functional foods for dietary equilibrium omega-6/omega-3.

    PubMed

    Reglero, Guillermo; Frial, Paloma; Cifuentes, Alejandro; García-Risco, Mónica R; Jaime, Laura; Marin, Francisco R; Palanca, Vicente; Ruiz-Rodríguez, Alejandro; Santoyo, Susana; Señoráns, Francisco J; Soler-Rivas, Cristina; Torres, Carlos; Ibañez, Elena

    2008-10-01

    Nutritionists encourage improving the diet by combining meat products with fish or other sea-related foods, in order to equilibrate the omega-6/omega-3 ratio. Strong scientific evidence supports the beneficial health effects of a balanced omega-6/omega-3 PUFA (poly unsaturated fatty acids) diets. In the present work, the scientific bases of new functional meat products with both a balanced omega-6/omega-3 ratio and a synergic combination of antioxidants are discussed. The aim is to contribute to the dietary equilibrium omega-6/omega-3 and to increase the antioxidant intake. Conventional meat products supplemented with a specific fatty acids and antioxidants combination led to functional foods with healthier nutritional parameters. PMID:18686293

  20. Non-equilibrium quantum theory for nanodevices based on the Feynman-Vernon influence functional

    NASA Astrophysics Data System (ADS)

    Jin, Jinshuang; Wei-Yuan Tu, Matisse; Zhang, Wei-Min; Yan, YiJing

    2010-08-01

    In this paper, we present a non-equilibrium quantum theory for transient electron dynamics in nanodevices based on the Feynman-Vernon influence functional. Applying the exact master equation for nanodevices we recently developed to the more general case in which all the constituents of a device vary in time in response to time-dependent external voltages, we obtained non-perturbatively the transient quantum transport theory in terms of the reduced density matrix. The theory enables us to study transient quantum transport in nanostructures with back-reaction effects from the contacts, with non-Markovian dissipation and decoherence being fully taken into account. For a simple illustration, we apply the theory to a single-electron transistor subjected to ac bias voltages. The non-Markovian memory structure and the nonlinear response functions describing transient electron transport are obtained.

  1. A rigorous multiple independent binding site model for determining cell-based equilibrium dissociation constants.

    PubMed

    Drake, Andrew W; Klakamp, Scott L

    2007-01-10

    A new 4-parameter nonlinear equation based on the standard multiple independent binding site model (MIBS) is presented for fitting cell-based ligand titration data in order to calculate the ligand/cell receptor equilibrium dissociation constant and the number of receptors/cell. The most commonly used linear (Scatchard Plot) or nonlinear 2-parameter model (a single binding site model found in commercial programs like Prism(R)) used for analysis of ligand/receptor binding data assumes only the K(D) influences the shape of the titration curve. We demonstrate using simulated data sets that, depending upon the cell surface receptor expression level, the number of cells titrated, and the magnitude of the K(D) being measured, this assumption of always being under K(D)-controlled conditions can be erroneous and can lead to unreliable estimates for the binding parameters. We also compare and contrast the fitting of simulated data sets to the commonly used cell-based binding equation versus our more rigorous 4-parameter nonlinear MIBS model. It is shown through these simulations that the new 4-parameter MIBS model, when used for cell-based titrations under optimal conditions, yields highly accurate estimates of all binding parameters and hence should be the preferred model to fit cell-based experimental nonlinear titration data. PMID:17141800

  2. Stability analysis of the Gravito-Electrostatic Sheath-based solar plasma equilibrium

    NASA Astrophysics Data System (ADS)

    Karmakar, P. K.; Goutam, H. P.; Lal, M.; Dwivedi, C. B.

    2016-08-01

    We present approximate solutions of non-local linear perturbational analysis for discussing the stability properties of the Gravito-Electrostatic Sheath (GES)-based solar plasma equilibrium, which is indeed non-uniform on both the bounded and unbounded scales. The relevant physical variables undergoing perturbations are the self-solar gravity, electrostatic potential and plasma flow along with plasma population density. We methodologically derive linear dispersion relation for the GES fluctuations, and solve it numerically to identify and characterize the existent possible natural normal modes. Three distinct natural normal modes are identified and named as the GES-oscillator mode, GES-wave mode and usual (classical) p-mode. In the solar wind plasma, only the p-mode survives. These modes are found to be linearly unstable in wide-range of the Jeans-normalized wavenumber, k. The local plane-wave approximation marginally limits the validity or reliability of the obtained results in certain radial- and k-domains only. The phase and group velocities, time periods of these fluctuation modes are investigated. It is interesting to note that, the oscillation time periods of these modes are 3-10 min, which match exactly with those of the observed helio-seismic waves and solar surface oscillations. The proposed GES model provides a novel physical view of the waves and oscillations of the Sun from a new perspective of plasma-wall interaction physics. Due to simplified nature of the considered GES equilibrium, it is a neonatal stage to highlight its applicability in the real Sun. The proposed GES model and subsequent fluctuation analysis need further improvements to make it more realistic.

  3. Hidden Conformation Events in DNA Base Extrusions: A Generalized Ensemble Path Optimization and Equilibrium Simulation Study.

    PubMed

    Cao, Liaoran; Lv, Chao; Yang, Wei

    2013-08-13

    DNA base extrusion is a crucial component of many biomolecular processes. Elucidating how bases are selectively extruded from the interiors of double-strand DNAs is pivotal to accurately understanding and efficiently sampling this general type of conformational transitions. In this work, the on-the-path random walk (OTPRW) method, which is the first generalized ensemble sampling scheme designed for finite-temperature-string path optimizations, was improved and applied to obtain the minimum free energy path (MFEP) and the free energy profile of a classical B-DNA major-groove base extrusion pathway. Along the MFEP, an intermediate state and the corresponding transition state were located and characterized. The MFEP result suggests that a base-plane-elongation event rather than the commonly focused base-flipping event is dominant in the transition state formation portion of the pathway; and the energetic penalty at the transition state is mainly introduced by the stretching of the Watson-Crick base pair. Moreover to facilitate the essential base-plane-elongation dynamics, the surrounding environment of the flipped base needs to be intimately involved. Further taking the advantage of the extended-dynamics nature of the OTPRW Hamiltonian, an equilibrium generalized ensemble simulation was performed along the optimized path; and based on the collected samples, several base-flipping (opening) angle collective variables were evaluated. In consistence with the MFEP result, the collective variable analysis result reveals that none of these commonly employed flipping (opening) angles alone can adequately represent the base extrusion pathway, especially in the pre-transition-state portion. As further revealed by the collective variable analysis, the base-pairing partner of the extrusion target undergoes a series of in-plane rotations to facilitate the base-plane-elongation dynamics. A base-plane rotation angle is identified to be a possible reaction coordinate to represent

  4. Game Theory Based Security in Wireless Body Area Network with Stackelberg Security Equilibrium.

    PubMed

    Somasundaram, M; Sivakumar, R

    2015-01-01

    Wireless Body Area Network (WBAN) is effectively used in healthcare to increase the value of the patient's life and also the value of healthcare services. The biosensor based approach in medical care system makes it difficult to respond to the patients with minimal response time. The medical care unit does not deploy the accessing of ubiquitous broadband connections full time and hence the level of security will not be high always. The security issue also arises in monitoring the user body function records. Most of the systems on the Wireless Body Area Network are not effective in facing the security deployment issues. To access the patient's information with higher security on WBAN, Game Theory with Stackelberg Security Equilibrium (GTSSE) is proposed in this paper. GTSSE mechanism takes all the players into account. The patients are monitored by placing the power position authority initially. The position authority in GTSSE is the organizer and all the other players react to the organizer decision. Based on our proposed approach, experiment has been conducted on factors such as security ratio based on patient's health information, system flexibility level, energy consumption rate, and information loss rate. Stackelberg Security considerably improves the strength of solution with higher security. PMID:26759829

  5. Game Theory Based Security in Wireless Body Area Network with Stackelberg Security Equilibrium

    PubMed Central

    Somasundaram, M.; Sivakumar, R.

    2015-01-01

    Wireless Body Area Network (WBAN) is effectively used in healthcare to increase the value of the patient's life and also the value of healthcare services. The biosensor based approach in medical care system makes it difficult to respond to the patients with minimal response time. The medical care unit does not deploy the accessing of ubiquitous broadband connections full time and hence the level of security will not be high always. The security issue also arises in monitoring the user body function records. Most of the systems on the Wireless Body Area Network are not effective in facing the security deployment issues. To access the patient's information with higher security on WBAN, Game Theory with Stackelberg Security Equilibrium (GTSSE) is proposed in this paper. GTSSE mechanism takes all the players into account. The patients are monitored by placing the power position authority initially. The position authority in GTSSE is the organizer and all the other players react to the organizer decision. Based on our proposed approach, experiment has been conducted on factors such as security ratio based on patient's health information, system flexibility level, energy consumption rate, and information loss rate. Stackelberg Security considerably improves the strength of solution with higher security. PMID:26759829

  6. Statistical enhancement of a dynamic equilibrium-based damage identification strategy: Theory and experimental validation

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Lu, Bo; Su, Zhongqing; Cheng, Li

    2015-09-01

    A previously developed damage identification strategy, named Pseudo-Excitation (PE), was enhanced using a statistical processing approach. In terms of the local dynamic equilibrium of the structural component under inspection, the distribution of its vibration displacements, which are of necessity to construct the damage index in the PE, was re-defined using sole dynamic strains based on the statistical method. On top of those advantages inheriting from the original PE compared with traditional vibration-based damage detection including the independence of baseline signals and pre-developed benchmark structures, the enhanced PE (EPE) possesses improved immunity to the interference of measurement noise. Moreover, the EPE can facilitate practical implementation of online structural health monitoring, benefiting from the use of sole strain information. Proof-of-concept numerical study was conducted to examine the feasibility and accuracy of the EPE, and the effectiveness of the proposed statistical enhancement in re-constructing the vibration displacements was evaluated under noise influence; experimental validation was followed up by characterizing multi-cracks in a beam-like structure, in which the dynamic strains were measured using Lead zirconium titanate (PZT) sensors. For comparison, the original PE, the Gapped Smoothing Method (GSM), and the EPE were respectively used to evaluate the cracks. It was observed from the damage identification results that both the GSM and EPE were able to achieve higher identification accuracy than the original PE, and the robustness of the EPE in damage identification was proven to be superior than that of the GSM.

  7. Pluto's atmosphere - Models based on refraction, inversion, and vapor-pressure equilibrium

    NASA Technical Reports Server (NTRS)

    Eshleman, Von R.

    1989-01-01

    Viking spacecraft radio-occultation measurements indicate that, irrespective of substantial differences, the polar ice cap regions on Mars have inversions similar to those of Pluto, and may also share vapor pressure equilibrium characteristics at the surface. This temperature-inversion phenomenon occurs in a near-surface boundary layer; surface pressure-temperature may correspond to the vapor-pressure equilibrium with CH4 ice, or the temperature may be slightly higher to match the value derived from IRAS data.

  8. A body-force based method to generate supersonic equilibrium turbulent boundary layer profiles

    NASA Astrophysics Data System (ADS)

    Waindim, M.; Gaitonde, D. V.

    2016-01-01

    We further develop a simple counterflow body force-based approach to generate an equilibrium spatially developing turbulent boundary layer suitable for Direct Numerical Simulations (DNS) or Large Eddy Simulations (LES) of viscous-inviscid interactions. The force essentially induces a small separated region in an incoming specified laminar boundary layer. The resulting unstable shear layer then transitions and breaks down to yield the desired unsteady profile. The effects of wall thermal conditions are explored to demonstrate the capability of the method for both fixed wall and adiabatic wall conditions. We then describe an efficient method to select parameters that ensure transition by examining precursor signatures using generalized stability variables. These precursors are shown to be evident in a computational domain spanning only a small region around the trip and can also be detected using 2D simulations. Finally, the method is tested for different Mach numbers ranging from 1.7 to 2.9, with emphasis on flow field surveys, Reynolds stresses, and energy spectra. These results provide guidance on boundary conditions for desired boundary layer thickness at each Mach number. The consequences of using a much lower Reynolds number in computation relative to experiment are evident at the higher Mach number, where a self sustaining turbulent boundary layer is more difficult to obtain.

  9. Efficient Nash Equilibrium Resource Allocation Based on Game Theory Mechanism in Cloud Computing by Using Auction

    PubMed Central

    Nezarat, Amin; Dastghaibifard, GH

    2015-01-01

    One of the most complex issues in the cloud computing environment is the problem of resource allocation so that, on one hand, the cloud provider expects the most profitability and, on the other hand, users also expect to have the best resources at their disposal considering the budget constraints and time. In most previous work conducted, heuristic and evolutionary approaches have been used to solve this problem. Nevertheless, since the nature of this environment is based on economic methods, using such methods can decrease response time and reducing the complexity of the problem. In this paper, an auction-based method is proposed which determines the auction winner by applying game theory mechanism and holding a repetitive game with incomplete information in a non-cooperative environment. In this method, users calculate suitable price bid with their objective function during several round and repetitions and send it to the auctioneer; and the auctioneer chooses the winning player based the suggested utility function. In the proposed method, the end point of the game is the Nash equilibrium point where players are no longer inclined to alter their bid for that resource and the final bid also satisfies the auctioneer’s utility function. To prove the response space convexity, the Lagrange method is used and the proposed model is simulated in the cloudsim and the results are compared with previous work. At the end, it is concluded that this method converges to a response in a shorter time, provides the lowest service level agreement violations and the most utility to the provider. PMID:26431035

  10. Efficient Nash Equilibrium Resource Allocation Based on Game Theory Mechanism in Cloud Computing by Using Auction.

    PubMed

    Nezarat, Amin; Dastghaibifard, G H

    2015-01-01

    One of the most complex issues in the cloud computing environment is the problem of resource allocation so that, on one hand, the cloud provider expects the most profitability and, on the other hand, users also expect to have the best resources at their disposal considering the budget constraints and time. In most previous work conducted, heuristic and evolutionary approaches have been used to solve this problem. Nevertheless, since the nature of this environment is based on economic methods, using such methods can decrease response time and reducing the complexity of the problem. In this paper, an auction-based method is proposed which determines the auction winner by applying game theory mechanism and holding a repetitive game with incomplete information in a non-cooperative environment. In this method, users calculate suitable price bid with their objective function during several round and repetitions and send it to the auctioneer; and the auctioneer chooses the winning player based the suggested utility function. In the proposed method, the end point of the game is the Nash equilibrium point where players are no longer inclined to alter their bid for that resource and the final bid also satisfies the auctioneer's utility function. To prove the response space convexity, the Lagrange method is used and the proposed model is simulated in the cloudsim and the results are compared with previous work. At the end, it is concluded that this method converges to a response in a shorter time, provides the lowest service level agreement violations and the most utility to the provider. PMID:26431035

  11. A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions

    SciTech Connect

    Zhang, Fan; Yeh, Gour-Tsyh; Parker, Jack C; Brooks, Scott C; Pace, Molly; Kim, Young Jin; Jardine, Philip M; Watson, David B

    2007-01-01

    This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing NE equilibrium reactions and a set of reactive transport equations of M-NE kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.

  12. The Effect of Cooperative Learning Approach Based on Conceptual Change Condition on Students' Understanding of Chemical Equilibrium Concepts

    ERIC Educational Resources Information Center

    Bilgin, Ibrahim; Geban, Omer

    2006-01-01

    The purpose of this study is to investigate the effects of the cooperative learning approach based on conceptual change conditions over traditional instruction on 10th grade students' conceptual understanding and achievement of computational problems related to chemical equilibrium concepts. The subjects of this study consisted of 87 tenth grade…

  13. Binary mixtures of rod-like colloids under shear: microscopically-based equilibrium theory and order-parameter dynamics

    NASA Astrophysics Data System (ADS)

    Lugo-Frías, Rodrigo; Klapp, Sabine H. L.

    2016-06-01

    This paper is concerned with the dynamics of a binary mixture of rod-like, repulsive colloidal particles driven out of equilibrium by means of a steady shear flow (Couette geometry). To this end we first derive, starting from a microscopic density functional in Parsons–Lee approximation, a mesoscopic free energy functional whose main variables are the orientational order parameter tensors. Based on this mesoscopic functional we then explore the stability of isotropic and nematic equilibrium phases in terms of composition and rod lengths. Second, by combining the equilibrium theory with the Doi–Hess approach for the order parameter dynamics under shear, we investigate the orientational dynamics of binary mixtures for a range of shear rates and coupling parameters. We find a variety of dynamical states, including synchronized oscillatory states of the two components, but also symmetry breaking behavior where the components display different in-plane oscillatory states.

  14. Binary mixtures of rod-like colloids under shear: microscopically-based equilibrium theory and order-parameter dynamics.

    PubMed

    Lugo-Frías, Rodrigo; Klapp, Sabine H L

    2016-06-22

    This paper is concerned with the dynamics of a binary mixture of rod-like, repulsive colloidal particles driven out of equilibrium by means of a steady shear flow (Couette geometry). To this end we first derive, starting from a microscopic density functional in Parsons-Lee approximation, a mesoscopic free energy functional whose main variables are the orientational order parameter tensors. Based on this mesoscopic functional we then explore the stability of isotropic and nematic equilibrium phases in terms of composition and rod lengths. Second, by combining the equilibrium theory with the Doi-Hess approach for the order parameter dynamics under shear, we investigate the orientational dynamics of binary mixtures for a range of shear rates and coupling parameters. We find a variety of dynamical states, including synchronized oscillatory states of the two components, but also symmetry breaking behavior where the components display different in-plane oscillatory states. PMID:27115342

  15. Community-Based Global Health Program for Maltreated Children and Adolescents in Brazil: The Equilibrium Program.

    PubMed

    Marques, Andrea Horvath; Oliveira, Paula Approbato; Scomparini, Luciana Burim; Silva, Uiara Maria Rêgo E; Silva, Angelica Cristine; Doretto, Victoria; de Medeiros Filho, Mauro Victor; Scivoletto, Sandra

    2015-01-01

    The maltreatment of children and adolescents is a global public health problem that affects high- and low-middle income countries ("LMICs"). In the United States, around 1.2 million children suffer from abuse, while in LMICs, such as Brazil, these rates are much higher (an estimated 28 million children). Exposition to early environmental stress has been associated with suboptimal physical and brain development, persistent cognitive impairment, and behavioral problems. Studies have reported that children exposed to maltreatment are at high risk of behavioral problems, learning disabilities, communication and psychiatric disorders, and general clinical conditions, such as obesity and systemic inflammation later in life. The aim of this paper is to describe The Equilibrium Program ("TEP"), a community-based global health program implemented in São Paulo, Brazil to serve traumatized and neglected children and adolescents. We will describe and discuss TEP's implementation, highlighting its innovation aspects, research projects developed within the program as well as its population profile. Finally, we will discuss TEP's social impact, challenges, and limitations. The program's goal is to promote the social and family reintegration of maltreated children and adolescents through an interdisciplinary intervention program that provides multi-dimensional bio-psycho-social treatment integrated with the diverse services needed to meet the unique demands of this population. The program's cost effectiveness is being evaluated to support the development of more effective treatments and to expand similar programs in other areas of Brazil. Policy makers should encourage early evidence-based interventions for disadvantaged children to promote healthier psychosocial environments and provide them opportunities to become healthy and productive adults. This approach has already shown itself to be a cost-effective strategy to prevent disease and promote health. PMID:26283972

  16. Community-Based Global Health Program for Maltreated Children and Adolescents in Brazil: The Equilibrium Program

    PubMed Central

    Marques, Andrea Horvath; Oliveira, Paula Approbato; Scomparini, Luciana Burim; Silva, Uiara Maria Rêgo e; Silva, Angelica Cristine; Doretto, Victoria; de Medeiros Filho, Mauro Victor; Scivoletto, Sandra

    2015-01-01

    The maltreatment of children and adolescents is a global public health problem that affects high- and low-middle income countries (“LMICs”). In the United States, around 1.2 million children suffer from abuse, while in LMICs, such as Brazil, these rates are much higher (an estimated 28 million children). Exposition to early environmental stress has been associated with suboptimal physical and brain development, persistent cognitive impairment, and behavioral problems. Studies have reported that children exposed to maltreatment are at high risk of behavioral problems, learning disabilities, communication and psychiatric disorders, and general clinical conditions, such as obesity and systemic inflammation later in life. The aim of this paper is to describe The Equilibrium Program (“TEP”), a community-based global health program implemented in São Paulo, Brazil to serve traumatized and neglected children and adolescents. We will describe and discuss TEP’s implementation, highlighting its innovation aspects, research projects developed within the program as well as its population profile. Finally, we will discuss TEP’s social impact, challenges, and limitations. The program’s goal is to promote the social and family reintegration of maltreated children and adolescents through an interdisciplinary intervention program that provides multi-dimensional bio-psycho-social treatment integrated with the diverse services needed to meet the unique demands of this population. The program’s cost effectiveness is being evaluated to support the development of more effective treatments and to expand similar programs in other areas of Brazil. Policy makers should encourage early evidence-based interventions for disadvantaged children to promote healthier psychosocial environments and provide them opportunities to become healthy and productive adults. This approach has already shown itself to be a cost-effective strategy to prevent disease and promote health. PMID

  17. Equilibrium Shaping

    NASA Astrophysics Data System (ADS)

    Izzo, Dario; Petazzi, Lorenzo

    2006-08-01

    We present a satellite path planning technique able to make identical spacecraft aquire a given configuration. The technique exploits a behaviour-based approach to achieve an autonomous and distributed control over the relative geometry making use of limited sensorial information. A desired velocity is defined for each satellite as a sum of different contributions coming from generic high level behaviours: forcing the final desired configuration the behaviours are further defined by an inverse dynamic calculation dubbed Equilibrium Shaping. We show how considering only three different kind of behaviours it is possible to acquire a number of interesting formations and we set down the theoretical framework to find the entire set. We find that allowing a limited amount of communication the technique may be used also to form complex lattice structures. Several control feedbacks able to track the desired velocities are introduced and discussed. Our results suggest that sliding mode control is particularly appropriate in connection with the developed technique.

  18. Entropy-based artificial viscosity stabilization for non-equilibrium Grey Radiation-Hydrodynamics

    SciTech Connect

    Delchini, Marc O. Ragusa, Jean C. Morel, Jim

    2015-09-01

    The entropy viscosity method is extended to the non-equilibrium Grey Radiation-Hydrodynamic equations. The method employs a viscous regularization to stabilize the numerical solution. The artificial viscosity coefficient is modulated by the entropy production and peaks at shock locations. The added dissipative terms are consistent with the entropy minimum principle. A new functional form of the entropy residual, suitable for the Radiation-Hydrodynamic equations, is derived. We demonstrate that the viscous regularization preserves the equilibrium diffusion limit. The equations are discretized with a standard Continuous Galerkin Finite Element Method and a fully implicit temporal integrator within the MOOSE multiphysics framework. The method of manufactured solutions is employed to demonstrate second-order accuracy in both the equilibrium diffusion and streaming limits. Several typical 1-D radiation-hydrodynamic test cases with shocks (from Mach 1.05 to Mach 50) are presented to establish the ability of the technique to capture and resolve shocks.

  19. Effect of Non-Equilibrium Surface Thermochemistry in Simulation of Carbon Based Ablators

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq; Gokcen, Tahir

    2012-01-01

    This study demonstrates that coupling of a material thermal response code and a flow solver using non-equilibrium gas/surface interaction model provides time-accurate solutions for the multidimensional ablation of carbon based charring ablators. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and AblatioN Program (TITAN), which predicts charring material thermal response and shape change on hypersonic space vehicles. Its governing equations include total energy balance, pyrolysis gas mass conservation, and a three-component decomposition model. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation (DPLR) method. Loose coupling between the material response and flow codes is performed by solving the surface mass balance in DPLR and the surface energy balance in TITAN. Thus, the material surface recession is predicted by finite-rate gas/surface interaction boundary conditions implemented in DPLR, and the surface temperature and pyrolysis gas injection rate are computed in TITAN. Two sets of nonequilibrium gas/surface interaction chemistry between air and the carbon surface developed by Park and Zhluktov, respectively, are studied. Coupled fluid-material response analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities are considered. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator (PICA). Computational predictions of in-depth material thermal response and surface recession are compared with the experimental measurements for stagnation cold wall heat flux ranging from 107 to 1100 Watts per square centimeter.

  20. PC-based package for interactive assessment of MHD equilibrium and poloidal field coil design in axisymmetric toroidal geometry

    SciTech Connect

    Kelleher, W.P.

    1987-01-01

    In the assessment of Magnetohydrodynamic (MHD) equilibrium and Poloidal Field Coil (PFC) arrangement for toroidal axisymmetric geometry, the Grad-Shafranov equation must be solved, either analytically or numerically. Existing numerical tools have been developed primarily for mainframe usage and can prove cumbersome for screening assessments and parametric evaluations. The objective of this thesis was to develop a personal computer (PC)-based calculational tool for assessing MHD/PFC problems in a highly interactive mode, well suited for scoping studies. The approach adopted involves a two-step process: first the MHD equilibrium is calculated and then the PFC arrangement, consistent with the equilibrium, is determined in an interactive design environment. The PC-based system developed consists of two programs: (1) PCEQ, which solve the MHD equilibrium problem and (2) PFDE-SIGN, which is employed to arrive at a PFC arrangement. PCEQ provides an output file including, but not limited to, the following: poloidal beta, total beta, safety factors, q, on axis and on edge. PCEQ plots the following contours and/or profiles: flux, pressure and toroidal current density, safety factor, and ratio of plasma toroidal field to vacuum field.

  1. Partition Equilibrium

    NASA Astrophysics Data System (ADS)

    Feldman, Michal; Tennenholtz, Moshe

    We introduce partition equilibrium and study its existence in resource selection games (RSG). In partition equilibrium the agents are partitioned into coalitions, and only deviations by the prescribed coalitions are considered. This is in difference to the classical concept of strong equilibrium according to which any subset of the agents may deviate. In resource selection games, each agent selects a resource from a set of resources, and its payoff is an increasing (or non-decreasing) function of the number of agents selecting its resource. While it has been shown that strong equilibrium exists in resource selection games, these games do not possess super-strong equilibrium, in which a fruitful deviation benefits at least one deviator without hurting any other deviator, even in the case of two identical resources with increasing cost functions. Similarly, strong equilibrium does not exist for that restricted two identical resources setting when the game is played repeatedly. We prove that for any given partition there exists a super-strong equilibrium for resource selection games of identical resources with increasing cost functions; we also show similar existence results for a variety of other classes of resource selection games. For the case of repeated games we identify partitions that guarantee the existence of strong equilibrium. Together, our work introduces a natural concept, which turns out to lead to positive and applicable results in one of the basic domains studied in the literature.

  2. Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation.

    PubMed

    Yin, Yudan; Niu, Lin; Zhu, Xiaocui; Zhao, Meiping; Zhang, Zexin; Mann, Stephen; Liang, Dehai

    2016-01-01

    Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and applying a range of electric field strengths, we produce protocells that exhibit repetitive cycles of vacuolarization, dynamical fluctuations in size and shape, chaotic growth and fusion, spontaneous ejection and sequestration of matter, directional capture of solute molecules, and pulsed enhancement of enzyme cascade reactions. Our results highlight new opportunities for the study of non-equilibrium phenomena in synthetic protocells, provide a strategy for inducing complex behaviour in electrostatically assembled soft matter microsystems and illustrate how dynamical properties can be activated and sustained in microcompartmentalized media. PMID:26876162

  3. Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation

    PubMed Central

    Yin, Yudan; Niu, Lin; Zhu, Xiaocui; Zhao, Meiping; Zhang, Zexin; Mann, Stephen; Liang, Dehai

    2016-01-01

    Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and applying a range of electric field strengths, we produce protocells that exhibit repetitive cycles of vacuolarization, dynamical fluctuations in size and shape, chaotic growth and fusion, spontaneous ejection and sequestration of matter, directional capture of solute molecules, and pulsed enhancement of enzyme cascade reactions. Our results highlight new opportunities for the study of non-equilibrium phenomena in synthetic protocells, provide a strategy for inducing complex behaviour in electrostatically assembled soft matter microsystems and illustrate how dynamical properties can be activated and sustained in microcompartmentalized media. PMID:26876162

  4. Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation

    NASA Astrophysics Data System (ADS)

    Yin, Yudan; Niu, Lin; Zhu, Xiaocui; Zhao, Meiping; Zhang, Zexin; Mann, Stephen; Liang, Dehai

    2016-02-01

    Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and applying a range of electric field strengths, we produce protocells that exhibit repetitive cycles of vacuolarization, dynamical fluctuations in size and shape, chaotic growth and fusion, spontaneous ejection and sequestration of matter, directional capture of solute molecules, and pulsed enhancement of enzyme cascade reactions. Our results highlight new opportunities for the study of non-equilibrium phenomena in synthetic protocells, provide a strategy for inducing complex behaviour in electrostatically assembled soft matter microsystems and illustrate how dynamical properties can be activated and sustained in microcompartmentalized media.

  5. Development of a non-equilibrium quantum transport calculation method based on constrained density functional

    NASA Astrophysics Data System (ADS)

    Kim, Han Seul; Kim, Yong-Hoon

    2015-03-01

    We report on the development of a novel first-principles method for the calculation of non-equilibrium quantum transport process. Within the scheme, non-equilibrium situation and quantum transport within the open-boundary condition are described by the region-dependent Δ self-consistent field method and matrix Green's function theory, respectively. We will discuss our solutions to the technical difficulties in describing bias-dependent electron transport at complicated nanointerfaces and present several application examples. Global Frontier Program (2013M3A6B1078881), Basic Science Research Grant (2012R1A1A2044793), EDISON Program (No. 2012M3C1A6035684), and 2013 Global Ph.D fellowship program of the National Research Foundation. KISTI Supercomputing Center (KSC-2014-C3-021).

  6. Helical equilibrium

    SciTech Connect

    Yoshikawa, S.

    1981-08-01

    A straight, helical plasma equilibrium equation is solved numerically for a plasma with a helical magnetic axis. As is expected, by a suitable choice of the plasma boundary, the vacuum configuration is made line ..integral.. dl/B stable. As the plasma pressure increases, the line ..integral.. dl/B criterion will improve (again as expected). There is apparently no limit on the plasma ..beta.. from the equilibrium consideration. Thus helical-axis stellarator ..beta.. will presumably be limited by MHD stability ..beta.., and not by equilibrium ..beta...

  7. Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Pauly, S.; Tang, M. Q.; Eckert, J.; Zhang, H. F.

    2016-01-01

    The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated.

  8. Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites

    PubMed Central

    Zhang, L.; Pauly, S.; Tang, M. Q.; Eckert, J.; Zhang, H. F.

    2016-01-01

    The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated. PMID:26754315

  9. Reconciling kinetic and equilibrium observations of iron(III) solubility in aqueous solutions with a polymer-based model

    NASA Astrophysics Data System (ADS)

    Rose, Andrew L.; David Waite, T.

    2007-12-01

    Due to hydrolysis reactions, iron(III) forms oxyhydroxide precipitates in natural waters that minimise its availability to living organisms. Thermodynamic studies have established equilibrium concentrations of dissolved iron at various pH values, however these studies offer no insight into the kinetics of iron(III) polymerisation and subsequent precipitation. In recent work, the kinetics of iron(III) precipitation and dissolution of the precipitate have been investigated, but there are apparent discrepancies between the equilibrium solubility of iron(III) calculated from the kinetic parameters and its solubility measured by separation of the solid and dissolved phases at equilibrium. In this work, we reconcile kinetic and thermodynamic measurements using a polymer-based mechanistic model of the processes responsible for iron(III) precipitation in aqueous solutions based on a variety of previously published experimental data. This model is used to explain the existence of a solubility limit, including the effect of precipitate ageing on its solubility. We suggest that the model provides a unified approach for examining aqueous systems containing dissolved, solid-phase and surface species.

  10. Two-phase quasi-equilibrium in β-type Ti-based bulk metallic glass composites.

    PubMed

    Zhang, L; Pauly, S; Tang, M Q; Eckert, J; Zhang, H F

    2016-01-01

    The microstructural evolution of cast Ti/Zr-based bulk metallic glass composites (BMGCs) containing β-Ti still remains ambiguous. This is why to date the strategies and alloys suitable for producing such BMGCs with precisely controllable volume fractions and crystallite sizes are still rather limited. In this work, a Ti-based BMGC containing β-Ti was developed in the Ti-Zr-Cu-Co-Be system. The glassy matrix of this BMGC possesses an exceptional glass-forming ability and as a consequence, the volume fractions as well as the composition of the β-Ti dendrites remain constant over a wide range of cooling rates. This finding can be explained in terms of a two-phase quasi-equilibrium between the supercooled liquid and β-Ti, which the system attains on cooling. The two-phase quasi-equilibrium allows predicting the crystalline and glassy volume fractions by means of the lever rule and we succeeded in reproducing these values by slight variations in the alloy composition at a fixed cooling rate. The two-phase quasi-equilibrium could be of critical importance for understanding and designing the microstructures of BMGCs containing the β-phase. Its implications on the nucleation and growth of the crystalline phase are elaborated. PMID:26754315

  11. Renal regulation of acid-base equilibrium during chronic administration of mineral acid.

    PubMed

    De Sousa, R C; Harrington, J T; Ricanati, E S; Shelkrot, J W; Schwartz, W B

    1974-02-01

    load is the inability of the distal exchange mechanism to conserve the Na+ increment fully by means of H+ exchange. Escape of Na+ and K+ into the urine and the resulting stimulus to Na(+)-H+ exchange remove this constraint and are responsible for establishment of a new steady-state of acid-base equilibrium at plasma [HCO3-] levels significantly higher than those seen with HCl. The feeding of HCl in the presence of a normal salt intake led to a degree of metabolic acidosis not significantly different from that seen in dogs ingesting a low-salt diet. We suggest that the presence of dietary sodium at distal exchange sites did not enhance acid excretion because it is only after a loss of body sodium stores that sodium avidity is increased sufficiently to allow full removal of the acid load. The present findings indicate that the fundamental factors controlling acid excretion and bicarbonate reabsorption in metabolic acidosis are closely similar to those operative in metabolic alkalosis. PMID:11344560

  12. Effect of Acid-Base Equilibrium on Absorption Spectra of Humic acid in the Presence of Copper Ions

    NASA Astrophysics Data System (ADS)

    Lavrik, N. L.; Mulloev, N. U.

    2014-03-01

    The reaction between humic acid (HA, sample IHSS) and a metal ion (Cu2+) that was manifested as absorption bands in the range 210-350 nm was recorded using absorption spectroscopy. The reaction was found to be more effective as the pH increased. These data were interpreted in the framework of generally accepted concepts about the influence of acid-base equilibrium on the dissociation of salts, according to which increasing the solution pH increases the concentration of HA anions. It was suggested that [HA-Cu2+] complexes formed.

  13. Novel tannin-based adsorbent in removing cationic dye (Methylene Blue) from aqueous solution. Kinetics and equilibrium studies.

    PubMed

    Sánchez-Martín, J; González-Velasco, M; Beltrán-Heredia, J; Gragera-Carvajal, J; Salguero-Fernández, J

    2010-02-15

    Natural tannin-based adsorbent has been prepared on the basis of the gelification of Quebracho bark extract. The resulting product, Quebracho Tannin Gel (QTG) was tested as cationic dye adsorbent with Methylene Blue (MB). Kinetics of adsorption process were studied out and a period of 15 days was determined for reaching equilibrium. The influences of pH and temperature were evaluated. As pH or temperature raise q capacity of QTG increases. Theoretical modelization of dye-QTG adsorption was carried out by multiparametric adjustment according to Langmuir's hypothesis. Values of the k(l1), k(l2) and activation energies were calculated. PMID:19782466

  14. Speciation and equilibrium relations of soluble aluminum in a headwater stream at base flow and during rain events

    USGS Publications Warehouse

    Burns, Douglas A.

    1989-01-01

    In the Shenandoah National Park, Virginia, the short-term dynamics of soluble aluminum in stream water sampled during rain events differed significantly from stream water sampled during base flow conditions. Three fractions of dissolved aluminum were measured. The inorganic monomeric fraction made up approximately two thirds of the total reactive aluminum at base flow, followed by the acid-soluble and organic monomeric fractions, respectively. Equilibrium modeling showed that hydroxide complexes were the most abundant form of inorganic monomeric aluminum followed by fluoride, free aluminum ion, and sulfate. The activity of inorganic monomeric aluminum at base flow appears to be in equilibrium with an Al(OH)3 phase with solubility intermediate between microcrystalline gibbsite and natural gibbsite. During two rain events, the concentration of all three aluminum fractions increased significantly. The primary cause of the transient increase in the Al(OH)3 saturation index appears to have been the neutralization of excess H+ added by soil water through reaction with stream water HCO3- at a more rapid rate than excess inorganic monomeric aluminum could be removed from solution by hydroxide mineral precipitation. -from Author

  15. Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS

    NASA Astrophysics Data System (ADS)

    Gualda, G. A.; Ghiorso, M. S.; Begue, F.; Pamukcu, A. S.; Gravley, D. M.

    2013-12-01

    Constraining the pressure of crystallization of magmas is an important but elusive task. We propose here a method to derive crystallization pressures for rocks that preserve glass compositions (either glass inclusions or matrix glass) representative of equilibration between melt, quartz, and 1 or 2 feldspars. The method relies on the shift of the quartz-feldspar saturation surface towards higher silica with decreasing pressure. The critical realization is that melt, quartz and feldspars need to be in equilibrium at the liquidus for the melt composition of interest. Thus, this method consists of calculating the saturation surfaces for quartz and feldspars using rhyolite-MELTS over a range of pressures, and searching for the pressure at which the expected assemblage (quartz+1 feldspar or quartz+2 feldspars) is found at the liquidus. We evaluate errors resulting from uncertainties in glass composition using Monte Carlo simulations, which reveal errors of ~20-45 MPa for the quartz+2 feldspars constraint and of ~25-100 MPa for the quartz+1 feldspar constraint; actual errors are likely closer to the lower bounds of these ranges. We demonstrate that the effect of fluid-saturation is more important at higher pressures (~300 MPa) than at lower pressures (~100 MPa), but reasonable pressure estimates can be derived irrespective of fluid saturation for geologically relevant H2O concentrations (>3 wt. %). And, we show that pressures calculated using the rhyolite-MELTS geobarometer compare well with those resulting from H2O-CO2 glass inclusion barometry and Al-in-hornblende barometry for an array of natural systems for which data has been compiled from the literature. We apply the rhyolite-MELTS barometer to three systems we are currently studying in detail: (1) For the Bishop Tuff (CA, USA), we find that quartz-hosted glass inclusion compositions yield indistinguishable crystallization pressures for early-erupted and late-erupted pumice, consistent with the Bishop Tuff having

  16. Equilibrium-Based Movement Endpoints Elicited from Primary Motor Cortex Using Repetitive Microstimulation

    PubMed Central

    Van Acker, Gustaf M.; Amundsen, Sommer L.; Messamore, William G.; Zhang, Hongyu Y.; Luchies, Carl W.

    2014-01-01

    High-frequency, long-duration intracortical microstimulation (HFLD-ICMS) is increasingly being used to deduce how the brain encodes coordinated muscle activity and movement. However, the full movement repertoire that can be elicited from the forelimb representation of primary motor cortex (M1) using this method has not been systematically determined. Our goal was to acquire a comprehensive M1 forelimb representational map of movement endpoints elicited with HFLD-ICMS, using stimulus parameters optimal for evoking stable forelimb spatial endpoints. The data reveal a 3D forelimb movement endpoint workspace that is represented in a patchwork fashion on the 2D M1 cortical surface. Although cortical maps of movement endpoints appear quite disorderly with respect to movement space, we show that the endpoint locations in the workspace evoked with HFLD-ICMS of two adjacent cortical points are closer together than would be expected if the organization were random. Although there were few obvious consistencies in the endpoint maps across the two monkeys tested, one notable exception was endpoints bringing the hand to the mouth, which was located at the boundary between the hand and face representation. Endpoints at the extremes of the monkey's workspace and locations above the head were largely absent. Our movement endpoints are best explained as resulting from coactivation of agonist and antagonist muscles driving the joints toward equilibrium positions determined by the length–tension relationships of the muscles. PMID:25411500

  17. Modeling of methane and ethane hydrate formation kinetics based on non-equilibrium thermodynamics

    NASA Astrophysics Data System (ADS)

    Mottahedin, Mona; Varaminian, Farshad; Mafakheri, Kaveh

    2011-05-01

    In this study, experimental data of the kinetics of methane and ethane hydrate formation at constant volume were collected. The experiments were carried out in a batch reactor at different temperatures and pressures. The property of chemical affinity was used in the modeling of hydrate formation rate in a constant volume process. In this model a macroscopic driving force was defined which only needed the initial (experimental condition, temperature, and pressure) and final conditions (equilibrium conditions); thus, this model did not have the limitations of microscopic models, such as heat and mass transfer coefficients or population of particles, which may differ for each experiment. The experiments were carried out at temperatures 273, 274, 275.5, and 276 K for methane and 272, 273, 274, and 275 K for ethane with different initial pressures. The parameters of the model, Ar and tK , were obtained for each experiment, and the results show that the parameter of for each gas has a constant value. Subsequently, parameters of the model were used to predict experimental data and the variation of pressures with time. The results indicated that this model can well predict constant volume experimental data for crystals I hydrate former.

  18. Dynamic Acid/Base Equilibrium in Single Component Switchable Ionic Liquids and Consequences on Viscosity.

    PubMed

    Cantu, David C; Lee, Juntaek; Lee, Mal-Soon; Heldebrant, David J; Koech, Phillip K; Freeman, Charles J; Rousseau, Roger; Glezakou, Vassiliki-Alexandra

    2016-05-01

    The deployment of transformational nonaqueous CO2-capture solvent systems is encumbered by high viscosities even at intermediate uptakes. Using single-molecule CO2 binding organic liquids as a prototypical example, we present key molecular features that control bulk viscosity. Fast CO2-uptake kinetics arise from close proximity of the alcohol and amine sites involved in CO2 binding in a concerted fashion, resulting in a Zwitterion containing both an alkyl-carbonate and a protonated amine. The population of internal hydrogen bonds between the two functional groups determines the solution viscosity. Unlike the ion pair interactions in ionic liquids, these observations are novel and specific to a hydrogen-bonding network that can be controlled by chemically tuning single molecule CO2 capture solvents. We present a molecular design strategy to reduce viscosity by shifting the proton transfer equilibrium toward a neutral acid/amine species, as opposed to the ubiquitously accepted zwitterionic state. The molecular design concepts proposed here are readily extensible to other CO2 capture technologies. PMID:27019342

  19. Development of an identification method of pressure anisotropy based on equilibrium analysis and magnetics

    SciTech Connect

    Asahi, Y.; Suzuki, Y.; Watanabe, K. Y.; Cooper, W. A.

    2013-02-15

    We evaluate the fluxes measured by the magnetic flux loops installed in LHD by using a three dimensional MHD equilibrium analysis code, ANIMEC, which enable us to directly determine the calibration function between the anisotropic pressure and the measured fluxes for the non-axisymmetric plasmas for the first time. The result indicates that the diamagnetic flux represents a nearly single-valued function of the beta perpendicular with respect to the field, and the saddle loop flux represents a nearly single-valued function of an equally weighted average of the beta values parallel and perpendicular to the field, regardless of the pressure anisotropy or the amount of energetic trapped particles. The values of the beta perpendicular to the field and the equal weighting averaged beta estimated by the single-valued functions (calibration functions) are investigated in order to clarify the magnitude of deviation from those original values, and the range of anisotropy where the beta value evaluated by the magnetic flux measurement is calculated within a 10% error.

  20. Comparative analysis of quantum cascade laser modeling based on density matrices and non-equilibrium Green's functions

    SciTech Connect

    Lindskog, M. Wacker, A.; Wolf, J. M.; Liverini, V.; Faist, J.; Trinite, V.; Maisons, G.; Carras, M.; Aidam, R.; Ostendorf, R.

    2014-09-08

    We study the operation of an 8.5 μm quantum cascade laser based on GaInAs/AlInAs lattice matched to InP using three different simulation models based on density matrix (DM) and non-equilibrium Green's function (NEGF) formulations. The latter advanced scheme serves as a validation for the simpler DM schemes and, at the same time, provides additional insight, such as the temperatures of the sub-band carrier distributions. We find that for the particular quantum cascade laser studied here, the behavior is well described by simple quantum mechanical estimates based on Fermi's golden rule. As a consequence, the DM model, which includes second order currents, agrees well with the NEGF results. Both these simulations are in accordance with previously reported data and a second regrown device.

  1. Tropical forests are non-equilibrium ecosystems governed by interspecific competition based on universal 1/6 niche width.

    PubMed

    Fort, Hugo; Inchausti, Pablo

    2013-01-01

    Tropical forests are mega-diverse ecosystems that display complex and non-equilibrium dynamics. However, theoretical approaches have largely focused on explaining steady-state behaviour and fitting snapshots of data. Here we show that local and niche interspecific competition can realistically and parsimoniously explain the observed non-equilibrium regime of permanent plots of nine tropical forests, in eight different countries. Our spatially-explicit model, besides predicting with accuracy the main biodiversity metrics for these plots, can also reproduce their dynamics. A central finding is that tropical tree species have a universal niche width of approximately 1/6 of the niche axis that echoes the observed widespread convergence in their functional traits enabling them to exploit similar resources and to coexist despite of having large niche overlap. This niche width yields an average ratio of 0.25 between interspecific and intraspecific competition that corresponds to an intermediate value between the extreme claims of the neutral model and the classical niche-based model of community assembly (where interspecific competition is dominant). In addition, our model can explain and yield observed spatial patterns that classical niche-based and neutral theories cannot. PMID:24386115

  2. Numerical analysis of unsteady cavitating flow by using a modification based on an assumption of apparent phase equilibrium

    NASA Astrophysics Data System (ADS)

    Iga, Y.

    2014-03-01

    The prediction accuracy of cavitation by CFD is still not so high even in a simplest flow field around a single hydrofoil especially in transient condition at higher angle of attack, which is common problem in both commercial software and in-house solvers. In the transient condition, unsteady cavitation occurs, in which sheet cavity breaks off and cloud cavity sheds downstream periodically. At that time, the sheet cavity length tends to be underestimated in usual CFD. In the present study, modification for the phase change model is suggested, which is based on an idea of apparent phase equilibrium on gas-liquid interface with unsteady and disturbed flow. At first, a preliminary experiment has been done for evaporation on two gas- liquid interfaces with and without flow, the result contributes the evidence of the idea of apparent phase equilibrium with flow. In the result, the pressure around gas-liquid interface with flow was higher than that without flow on the occasion of evaporation, it means flow accelerates evaporation. I treat the gap of the pressure as a gap of phase equilibrium pressure macroscopically. Then, numerical simulation of cavitating flow around a hydrofoil is performed with a modification of phase change model in the transient condition at higher angle of attack which is most difficult to predict by the present solvers. In the modification, the gap of the pressure with and without flow is taken into account according to a value of a local variation of velocity in the cavitating flow filed. The formulation is similar to the PDF model for phase change model in cavitation by Singhal. The numerical results by the present modification are compared among few pressure variation components which are assumed to accelerate the evaporation in transient cavitation.

  3. Generator Control Based on Equilibrium Point Analysis of Standard One-Machine Infinite-Bus System Model—Comparison with PSS—

    NASA Astrophysics Data System (ADS)

    Kawamoto, Shunji; Zhang, Jian; Yamamoto, Hiroyoshi; Fujimoto, Koji

    We have recently proposed a new controller based on the equilibrium point analysis for model power systems. In this paper, first the Japanese standard one-machine infinite-bus system model is formulated, and the equilibrium points are analyzed. Next, complementary control inputs for AVR and GOV with limiters of the model system are determined on the basis of the analysis. Finally, it is shown that the unstable equilibrium point is eliminated by adding the proposed inputs, and then the critical clearing time can be improved in comparison with PSS of the standard model.

  4. A personal-computer-based package for interactive assessment of magnetohydrodynamic equilibrium and poloidal field coil design in axisymmetric toroidal geometry

    SciTech Connect

    Kelleher, W.P. ); Steiner, D. . Dept. of Nuclear Science)

    1989-07-01

    A personal-computer (PC)-based calculational approach assesses magnetohydrodynamic (MHD) equilibrium and poloidal field (PF) coil arrangement in a highly interactive mode, well suited for tokamak scoping studies. The system developed involves a two-step process: the MHD equilibrium is calculated and then a PF coil arrangement, consistent with the equilibrium is determined in an interactive design environment. In this paper the approach is used to examine four distinctly different toroidal configurations: the STARFIRE rector, a spherical torus (ST), the Big Dee, and an elongated tokamak. In these applications the PC-based results are benchmarked against those of a mainframe code for STARFIRE, ST, and Big Dee. The equilibrium and PF coil arrangement calculations obtained with the PC approach agree within a few percent with those obtained with the mainframe code.

  5. Comparative Analysis of the Flax Immune Receptors L6 and L7 Suggests an Equilibrium-Based Switch Activation Model.

    PubMed

    Bernoux, Maud; Burdett, Hayden; Williams, Simon J; Zhang, Xiaoxiao; Chen, Chunhong; Newell, Kim; Lawrence, Gregory J; Kobe, Bostjan; Ellis, Jeffrey G; Anderson, Peter A; Dodds, Peter N

    2016-01-01

    NOD-like receptors (NLRs) are central components of the plant immune system. L6 is a Toll/interleukin-1 receptor (TIR) domain-containing NLR from flax (Linum usitatissimum) conferring immunity to the flax rust fungus. Comparison of L6 to the weaker allele L7 identified two polymorphic regions in the TIR and the nucleotide binding (NB) domains that regulate both effector ligand-dependent and -independent cell death signaling as well as nucleotide binding to the receptor. This suggests that a negative functional interaction between the TIR and NB domains holds L7 in an inactive/ADP-bound state more tightly than L6, hence decreasing its capacity to adopt the active/ATP-bound state and explaining its weaker activity in planta. L6 and L7 variants with a more stable ADP-bound state failed to bind to AvrL567 in yeast two-hybrid assays, while binding was detected to the signaling active variants. This contrasts with current models predicting that effectors bind to inactive receptors to trigger activation. Based on the correlation between nucleotide binding, effector interaction, and immune signaling properties of L6/L7 variants, we propose that NLRs exist in an equilibrium between ON and OFF states and that effector binding to the ON state stabilizes this conformation, thereby shifting the equilibrium toward the active form of the receptor to trigger defense signaling. PMID:26744216

  6. Acid-base equilibrium during capnoretroperitoneoscopic nephrectomy in patients with end-stage renal failure: a preliminary report.

    PubMed

    Demian, A D; Esmail, O M; Atallah, M M

    2000-04-01

    We have studied the acid-base equilibrium in 12 patients with end-stage renal failure (ESRF) during capnoretroperitoneoscopic nephrectomy. Bupivacaine (12 mL, 0.375%) and morphine (2mg) were given in the lumbar epidural space, and fentanyl (0.5 microg kg(-1)) and midazolam (50 microg kg(-1)) were given intravenously. Anaesthesia was induced by thiopental, maintained with halothane carried by oxygen enriched air (inspired oxygen fraction = 0.35), and ventilation was achieved with a tidal volume of 10 mL kg(-1) at a rate of 12 min(-1). This procedure resulted in a mild degree of respiratory acidosis that was cleared within 60 min. We conclude that capnoretroperitoneoscopic nephrectomy can be performed in patients with end-stage renal failure with minimal transient respiratory acidosis that can be avoided by increased ventilation. PMID:10866009

  7. Design and Quasi-Equilibrium Analysis of a Distributed Frequency-Restoration Controller for Inverter-Based Microgrids

    SciTech Connect

    Ainsworth, Nathan G; Grijalva, Prof. Santiago

    2013-01-01

    This paper discusses a proposed frequency restoration controller which operates as an outer loop to frequency droop for voltage-source inverters. By quasi-equilibrium analysis, we show that the proposed controller is able to provide arbitrarily small steady-state frequency error while maintaing power sharing between inverters without need for communication or centralized control. We derive rate of convergence, discuss design considerations (including a fundamental trade-off that must be made in design), present a design procedure to meet a maximum frequency error requirement, and show simulation results verifying our analysis and design method. The proposed controller will allow flexible plug-and-play inverter-based networks to meet a specified maximum frequency error requirement.

  8. Mechanistic Sediment Quality Guidelines Based on Contaminant Bioavailability: Equilibrium Partitioning Sediment Benchmarks

    EPA Science Inventory

    Globally, billions of metric tons of contaminated sediments are present in aquatic systems representing a potentially significant ecological risk. Estimated costs to manage (i.e., remediate and monitor) these sediments are in the billions of U.S. dollars. Biologically-based app...

  9. Calculation of acid-base equilibrium constants at the oxide-electrolyte interface from the dependence of oxide surface charge on pH of the electrolyte

    SciTech Connect

    Gorichev, I.G.; Dorofeev, M.V.; Batrakov, V.V.

    1994-09-01

    The dependences of the catalytic activity of oxides and acid-base properties on ph of solution are similar. A procedure is developed for calculating acid-base equilibrium constants from the dependence of the oxide surface charge q on pH. The values q can be determined by potentiometric titration of aqueous suspensions of oxides. The acid-base equilibrium constants for Fe{sub 3}O{sub 4} and CuO were calculated in accordance with the proposed procedure.

  10. Sub-Tg relaxation patterns in Cu-based metallic glasses far from equilibrium

    NASA Astrophysics Data System (ADS)

    Wang, Caiwei; Hu, Lina; Wei, Chen; Tong, Xu; Zhou, Chao; Sun, Qijing; Hui, Xidong; Yue, Yuanzheng

    2014-10-01

    We investigate the sub-Tg relaxation patterns (RPs) in binary and quaternary Cu-based glass ribbons (GRs) by using the hyperquenching-sub-Tg annealing-calorimetric approach. This study contributes to revealing the structural or dynamic evolution in liquids related to the observed three-stage sub-Tg relaxation processes in GRs. In this work, we have achieved the following three findings. First, the abnormal three-stage relaxation behavior is not a general phenomenon for Cu-based metallic glasses and could not be simply predicted by the large difference in the enthalpy of mixing between different elements in alloys. Second, the abnormal three-stage RP is associated with the non-monotonic change of cluster size with medium range order in supercooled liquids. Third, the existence of the liquid-liquid phase transition depicted by anomalous viscosity drop during cooling in superheated liquids could be a signature of the unusual structural change causing the abnormal three-step sub-Tg RP in the GRs. This work helps to better understand the complex structural evolution from superheated to supercooled liquids approaching Tg.

  11. Adair-based hemoglobin equilibrium with oxygen, carbon dioxide and hydrogen ion activity.

    PubMed

    Mateják, Marek; Kulhánek, Tomáš; Matoušek, Stanislav

    2015-04-01

    As has been known for over a century, oxygen binding onto hemoglobin is influenced by the activity of hydrogen ions (H⁺), as well as the concentration of carbon dioxide (CO₂). As is also known, the binding of both CO₂and H⁺ on terminal valine-1 residues is competitive. One-parametric situations of these hemoglobin equilibria at specific levels of H⁺, O₂or CO₂are also well described. However, we think interpolating or extrapolating this knowledge into an 'empirical' function of three independent variables has not yet been completely satisfactory. We present a model that integrates three orthogonal views of hemoglobin oxygenation, titration, and carbamination at different temperatures. The model is based only on chemical principles, Adair's oxygenation steps and Van't Hoff equation of temperature dependences. Our model fits the measurements of the Haldane coefficient and CO₂hemoglobin saturation. It also fits the oxygen dissociation curve influenced by simultaneous changes in H⁺, CO₂and O₂, which makes it a strong candidate for integration into more complex models of blood acid-base with gas transport, where any combination of mentioned substances can appear. PMID:25594800

  12. Estimates of sustainable agricultural water use in northern China based on the equilibrium of groundwater

    NASA Astrophysics Data System (ADS)

    Yali, Y.; Yu, C.

    2015-12-01

    The northern plain is the important food production region in China. However, due to the lack of surface water resources, it needs overmuch exploitation of groundwater to maintain water use in agriculture, which leads to serious environmental problems. Based on the assumption that the reserves of groundwater matches the statistics and keeps on stable, the author explores the reasonable agricultural water and its spatial distribution based on the principle of sustainable utilization of water resources. According to the priorities of water resources allocation (domestic water and ecological water>industrial water>agricultural water), it is proposed to reduce agricultural water use to balance the groundwater reserves on condition that the total water supply is constant. Method: Firstly, we calculate annual average of northern groundwater reserves changes from 2004 to 2010, which is regarded as the reduction of agricultural water; Then, we estimate the food production changes using variables of typical crop water requirements and unit yields assuming that the efficiency of water use keeps the same during the entire study period; Finally, we evaluate the usage of sustainable agricultural water. The results reveal that there is a significant reduction of groundwater reserves in Haihe river basin and Xinjiang oasis regions; And the annual loss of the corn and wheat production is about 1.86 billion kg and 700 million kg respectively due to the reduction of agricultural water; What's more, in order to ensure China's food security and sustainable agricultural water use, in addition to great efforts to develop water-saving agriculture, an important adjustment in the distribution of food production is in need. This study provided a basis to the availability of agricultural water and a new perspective was put forth for an estimation of agricultural water.

  13. Chemical Equilibrium, Unit 4: Equilibria in Acid-Base Systems. A Computer-Enriched Module for Introductory Chemistry. Student's Guide and Teacher's Guide.

    ERIC Educational Resources Information Center

    Settle, Frank A., Jr.

    Presented are the teacher's guide and student materials for one of a series of self-instructional, computer-based learning modules for an introductory, undergraduate chemistry course. The student manual for this acid-base equilibria unit includes objectives, prerequisites, pretest, a discussion of equilibrium constants, and 20 problem sets.…

  14. Force-based optimization of pseudopotentials for non-equilibrium configurations

    NASA Astrophysics Data System (ADS)

    Brock, Casey N.; Paikoff, Brandon C.; Md Sallih, Muhammad I.; Tackett, Alan R.; Walker, D. Greg

    2016-04-01

    We have used a multi-objective genetic algorithm to optimize pseudopotentials for force accuracy and computational efficiency. Force accuracy is determined by comparing interatomic forces generated using the pseudopotentials and forces generated using the full-potential linearized augmented-plane wave method. This force-based optimization approach is motivated by applications where interatomic forces are important, including material interfaces, crystal defects, and molecular dynamics. Our method generates Pareto sets of optimized pseudopotentials containing various compromises between accuracy and efficiency. We have tested our method for LiF, Si0.5Ge0.5, and Mo and compared the performance of our pseudopotentials with pseudopotentials available from the ABINIT library. We show that the optimization can generate pseudopotentials with comparable accuracy (in terms of force matching and equation of state) to pseudopotentials in the literature while sometimes significantly improving computational efficiency. For example, we generated pseudopotentials for one system tested that reduced computational work by 71% without loss of accuracy. These results suggest our method can be used to generate pseudopotentials on demand that are tuned for a user's specific application, affording gains in computational efficiency.

  15. [Materno-fetal acid-base equilibrium evaluation in parturients submitted to ketamine anesthesia (author's transl)].

    PubMed

    Mauad Filho, F; Meirelles, R S

    1975-01-01

    In the present work ketamine was used as anesthetic during the labor in order to evaluate the effect of this anesthetic on the binominal fetus-mother. Two groups of parturients and their fetuses, were studied: 1) The experimental group, with 22 parturients and their fetuses submitted to ketamine anesthesia during the labord, and 2) The control group, with 20 parturients and their fetuses without any analgesic treatment during the labor. In 20 cases of the experimental group the anesthetic was injected during the delivery labor and the other two just before it. It were evaluated in the mother's blood the biochemical parameters of the acid-base balance and others collateral effects of the anesthesia; on the fetus's side the same parameters also and the cardiac frequency. The newborn were evaluated by Apgar Score during the first and fifth minutes of life. The incidence of the spontaneous delivery in the experimental group, was 78%; in 22% of these patients the forceps of relief was used. In 22 cases in which Ketamine was applied it were observed, the following events: elevation of the blood pressure (50%), perineum rigidness (18%), dreams and or hallucinations (18%), increase of the cardiac frequency (9%), apneia (4%) and nausea (4%). It was also observed an increase of uterine tonus an abolishment of abdominal press during the delivery labor, studied through the uterine electromyography register. It was noted after the Ketamine application a fall in the pH of the maternal peripherical venous blood, fetal skull blood and the pH of the blood of the umbilical vein. 22% of the newborns, from the experimental group, presented a depression in the first minute of life (Apgar less than or equals to 6). The pCO2 values in the blood of the umbilical artery were higher in the experimental group than in the control one. PMID:1241148

  16. Prediction of the Chapman-Jouguet chemical equilibrium state in a detonation wave from first principles based reactive molecular dynamics.

    PubMed

    Guo, Dezhou; Zybin, Sergey V; An, Qi; Goddard, William A; Huang, Fenglei

    2016-01-21

    The combustion or detonation of reacting materials at high temperature and pressure can be characterized by the Chapman-Jouguet (CJ) state that describes the chemical equilibrium of the products at the end of the reaction zone of the detonation wave for sustained detonation. This provides the critical properties and product kinetics for input to macroscale continuum simulations of energetic materials. We propose the ReaxFF Reactive Dynamics to CJ point protocol (Rx2CJ) for predicting the CJ state parameters, providing the means to predict the performance of new materials prior to synthesis and characterization, allowing the simulation based design to be done in silico. Our Rx2CJ method is based on atomistic reactive molecular dynamics (RMD) using the QM-derived ReaxFF force field. We validate this method here by predicting the CJ point and detonation products for three typical energetic materials. We find good agreement between the predicted and experimental detonation velocities, indicating that this method can reliably predict the CJ state using modest levels of computation. PMID:26688211

  17. Uncertainty analysis for an equilibrium partitioning-based estimator of polynuclear aromatic hydrocarbon bioaccumulation potential in sediments

    SciTech Connect

    Clarke, J.U.; McFarland, V.A.

    2000-02-01

    In regulatory evaluations of contaminated sediments, an equilibrium partitioning-based screening test called theoretical bioaccumulation potential (TBP) is often performed to estimate the probable concentrations of neutral organic contaminants that would eventually accumulate in aquatic organisms from continuous exposure to a sediment. The TBP is calculated from contaminant concentration and organic carbon content of the sediment, lipid content of target organisms, and a partition coefficient, usually the biota-sediment accumulation factor (BSAF). However, routine applications of TBP have not included analysis of uncertainty. This paper demonstrates two methods for uncertainty analysis of TBP: a computational method that incorporates random and systematic error and a simulation method using bootstrap resampling of replicated model input parameters to calculate statistical uncertainty measures. For prediction of polynuclear aromatic hydrocarbon (PAH) bioaccumulation in bivalves exposed to contaminated sediments, uncertainty as a factor of TBP ranged from 1.2 to 4.8 using the computational method and 0.5 to 1.9 based on bootstrap 95% confidence intervals. Sensitivity analysis indicated that BSAF parameters, especially tissue contaminant concentration and lipid content, contributed most to TBP uncertainty. In bootstrap tests of significance, TBP significantly over- or underestimated actual PAH bioaccumulation in bivalves in 41% and 10% of comparisons, respectively.

  18. Non-equilibrium Green's function calculation of AlGaAs-well-based and GaSb-based terahertz quantum cascade laser structures

    SciTech Connect

    Yasuda, H. Hosako, I.

    2015-03-16

    We investigate the performance of terahertz quantum cascade lasers (THz-QCLs) based on Al{sub x}Ga{sub 1−x}As/Al{sub y}Ga{sub 1−y}As and GaSb/AlGaSb material systems to realize higher-temperature operation. Calculations with the non-equilibrium Green's function method reveal that the AlGaAs-well-based THz-QCLs do not show improved performance, mainly because of alloy scattering in the ternary compound semiconductor. The GaSb-based THz-QCLs offer clear advantages over GaAs-based THz-QCLs. Weaker longitudinal optical phonon–electron interaction in GaSb produces higher peaks in the spectral functions of the lasing levels, which enables more electrons to be accumulated in the upper lasing level.

  19. A PC-based package for interactive assessment of MHD equilibrium and poloidal field coil design in axisymmetric toroidal geometry

    SciTech Connect

    Kelleher, W.; Steiner, D.

    1989-03-01

    A personal computer system was developed for use in the assessment of magnetohydrodynamic (MHD) equilibrium and Poloidal Field Coil (PFC) arrangement in toroidal axisymmetric geometry. This system involves two steps: first MHD equilibrium is calculated with the program PCEQ, then the PFC arrangement, consistent with the equilibrium, is determined in an interactive design environment using the program PFDESIGN. The PCEQ/PFDESIGN system was used to examine equilibrium for the STARFIRE reactor concept, including the design of two different PFC arrangements. The MHD/PFC calculations agree to within a few percent of mainframe code results, demonstrating the utility and accuracy of PCEQ/PFDESIGN, proving it to be an ideal tool for scoping studies.

  20. A fitting formula for radiative cooling based on non-local thermodynamic equilibrium population from weakly-ionized air plasma

    NASA Astrophysics Data System (ADS)

    Ogino, Yousuke; Nagano, Atsushi; Ishihara, Tomoaki; Ohnishi, Naofumi

    2013-08-01

    A fitting formula for radiative cooling with collisional-radiative population for air plasma flowfield has been developed. Population number densities are calculated from rate equations in order to evaluate the effects of nonequilibrium atomic and molecular processes. Many elementary processes are integrated to be applied to optically-thin plasmas in the number density range of 1012/cm3 <= N <= 1019/cm3 and the temperature range of 300 K <= T <= 40,000 K. Our results of the total radiative emissivity calculated from the collisional-radiative population are fitted in terms of temperature and total number density. To validate the analytic fitting formula, numerical simulation of a laser-induced blast wave propagation with the nonequilibrium radiative cooling is conducted and successfully reproduces the shock and plasma wave front time history observed by experiments. In addition, from the comparison between numerical simulations with the radiation cooling effect based on the fitting formula and those with a gray gas radiation model that assumes local thermodynamic equilibrium, we find that the displacement of the plasma front is slightly different due to the deviation of population probabilities. By using the fitting formula, we can easily and more accurately evaluate the radiative cooling effect without solving detailed collisional-radiative rate equations.

  1. A study of the scour-fill threshold based on Lane's equilibrium relation: The lower Yellow River

    NASA Astrophysics Data System (ADS)

    Xu, Jiongxin

    2015-12-01

    The scour-fill threshold in river channels is an expression of scour-fill equilibrium, which may be understood as the balance between the river's sediment carrying capability and the sediment load imposed by the drainage basin. In the present study, the above capability-load relation is quantified using Lane's relation, γQJ-QsD50, wherein Q is water discharge, J is channel slope, Qs is sediment transport rate, D50 is median size of bed material, and γ is the specific weight of water. On this basis, we have established scour-fill thresholds for the lower Yellow River based on data from 141 flood events. The results show that the QsD50-γQJ relation may well distinguish between the scour and fill flood events. The following equation has been established: SDRFE = 0.00099(γQJ)0.90(QsD50)- 0.60, wherein SDRFE is channel sediment delivery ratio. From the equation, the scour-fill threshold is established as: QsD50 = 0.00001(γQJ)1.5. Starting from this formula, four possible options are proposed for sediment management of the lower Yellow River.

  2. Kinetics, equilibrium, and thermodynamics investigation on the adsorption of lead(II) by coal-based activated carbon.

    PubMed

    Yi, Zhengji; Yao, Jun; Zhu, Mijia; Chen, Huilun; Wang, Fei; Liu, Xing

    2016-01-01

    The goal of this research is to investigate the feasibility of using activated coal-based activated carbon (CBAC) to adsorb Pb(II) from aqueous solutions through batch tests. Effects of contact time, pH, temperature and initial Pb(II) concentration on the Pb(II) adsorption were examined. The Pb(II) adsorption is strongly dependent on pH, but insensitive to temperature. The best pH for Pb(II) removal is in the range of 5.0-5.5 with more than 90 % of Pb(II) removed. The equilibrium time was found to be 60 min and the adsorption data followed the pseudo-second-order kinetics. Isotherm data followed Langmuir isotherm model with a maximum adsorption capacity of 162.33 mg/g. The adsorption was exothermic and spontaneous in nature. The Fourier transform infrared spectroscopy and scanning electron microscopy analysis suggested that CBAC possessed a porous structure and was rich in carboxyl and hydroxyl groups on its surface, which might play a major role in Pb(II) adsorption. These findings indicated that CBAC has great potential as an alternative adsorbent for Pb(II) removal. PMID:27504258

  3. The Gellyfish: An In-Situ Equilibrium-Based Sampler for Determining Multiple Free Metal Ion Concentrations in Marine Ecosystems

    PubMed Central

    Dong, Zhao; Lewis, Christopher G.; Burgess, Robert M.; Shine, James P.

    2016-01-01

    Free metal ions are usually the most bioavailable and toxic metal species to aquatic organisms, but they are difficult to measure due to their extremely low concentrations in the marine environment. Many of the current methods for determining free metal ions are complicated, time-consuming, and can only measure one metal at a time. We developed a new version of the ‘Gellyfish’, an in-situ equilibrium-based sampler, with significantly reduced equilibration time and the capability of measuring multiple free metal ions simultaneously. By calibrating the Gellyfish to account for its uptake of cationic metal complexes and validating them in multi-metal competition experiments, we were able to determine free metal ion concentrations previously collected over ten months at five locations in Boston Harbor for Cu, Zn, Pb, Ni, and Cd. This work generated one of the largest free metal ion datasets and demonstrated the applicability of the Gellyfish as an easy-to-use and inexpensive tool for monitoring free ion concentrations of metal mixtures in marine ecosystems. PMID:25598362

  4. Equilibrium surface tension, dynamic surface tension, and micellization properties of lactobionamide-type sugar-based gemini surfactants.

    PubMed

    Yoshimura, Tomokazu; Umezawa, Shin; Fujino, Akihiko; Torigoe, Kanjiro; Sakai, Kenichi; Sakai, Hideki; Abe, Masahiko; Esumi, Kunio

    2013-01-01

    A sugar-based gemini surfactant N,N'-dialkyl-N,N'-dilactobionamideethylenediamine (2C(n)Lac, where n represents alkyl chain lengths of 8, 10, 12, and 14) was synthesized by reacting N,N'-dialkylethylenediamine with lactobionic acid. The adsorption properties of 2C(n)Lac were characterized by equilibrium and dynamic surface tension measurements. Their micellization properties were investigated by steady-state fluorescence using pyrene as a probe and dynamic light scattering (DLS) techniques. The dependence of these properties on the alkyl chain length and the number of sugars was determined through a comparison with the corresponding monomeric surfactants C(n)MLA and previously reported sugar-based gemini surfactants containing monosaccharide gluconamide or disaccharide lactobionamide groups with a hexanediamide spacer. The critical micelle concentration (cmc) and surface tension of 2C(n)Lac are both lower than those of C(n)MLA surfactants. These lower values indicate that the synthesized sugar-based gemini surfactants have excellent micelle-forming ability in solution and high adsorption ability at the air-water interface, which result from strong interactions of the hydrogen bonds between the hydroxyls in lactobionamide groups. When the alkyl chain length of 2C(n)Lac increases to 14, premicellar formation occurs in the solution along with adsorption at the air-water interface at concentrations below the cmc. Furthermore, 2C(n)Lac forms micelles measuring 4 to 12 nm in solution, with no dependence on the alkyl chain length, and their size slightly increases with increasing concentration. PMID:23728326

  5. Optical sensor for amine vapors based on dimer-monomer equilibrium of indium(III) octaethylporphyrin in a polymeric film.

    PubMed

    Qin, Wei; Parzuchowski, Pawel; Zhang, Wei; Meyerhoff, Mark E

    2003-01-15

    A novel transduction chemistry for the development of a polymer film-based optical sensor that responds reversibly to gas-phase amine species at sub-ppm levels is described. The sensor is based on the equilibrium of a indium(III) octaethylporphyrin hydroxide ion-bridged dimer species with corresponding monomeric porphyrins within a thin poly(vinyl chloride) film as a function of the level of volatile amine in the surrounding gas phase. The presence of amines causes the dimeric species to be converted to monomer via the ligation of the amine with the In(III) center of the porphyrin structure. This yields a significant change in the visible absorption spectrum of the film, with a decrease in the intensity of the Soret band corresponding to the dimer (lambdamax = 390 nm) and a concomitant increase in the Soret band for the monomer lambdamax = 406-408 nm). Response to different amines is based on their relative partition coefficient into the polymer film and their strength of axial ligation reactions, with a selectivity pattern of 1-butylamine > 1-propylamine > pyridine > triethylamine > ethylamine > methylamine > diethylamine > tert-butylamine > ammonia. It is further shown that a significant concentration of dimeric species within the polymer film can only be achieved if appropriate amounts of lipophilic anionic sites are also incorporated into the polymer in the form of a tetraphenylborate derivative and the resulting film is equilibrated briefly with water prior to gas-phase measurements. With optimized film compositions, 1-butylamine can be detected in the gas phase to levels approaching 0.1 ppm, while less lipophilic ammonia can be monitored down to 10 ppm, with fully reversible responses to each species. A simple mathematical model for the response of the amine sensor is presented and shown to predict the optical behavior observed. PMID:12553770

  6. Detachment-Based Equilibrium of Anoikic Cell Death and Autophagic Cell Survival Through Adaptor Protein p66(Shc).

    PubMed

    Cai, Zeyuan; Zhao, Dan; Sun, Yanan; Gao, Dan; Li, Xia; Yang, Jie; Ma, Zhenyi

    2016-03-01

    Anoikis (detachment-induced cell death) confers a tumor-suppressive function in metastatic cancer cells. Autophagy, a conserved self-degradative process, enhances the anoikis resistance of detached cancer cells by maintaining cellular homeostasis. However, the mechanism of regulating cell fate-decision by balancing anoikis and autophagy has been poorly understood. Our previous studies have shown that the adaptor protein p66(Shc) mediates anoikis through RhoA activation and inhibits tumor metastasis in vivo. We also found that p66(Shc) depletion mitigates nutrient-deprivation-induced autophagy. These findings suggest p66(Shc) may coordinately regulate these two processes. To verify this hypothesis, we investigated the effect of p66(Shc) on the cell death of detached lung cancer cells, and measured autophagy markers and autophagic flux. Results showed that p66(Shc) depletion significantly inhibited anoikis, and reduced the formation of LC3B-II and the degradation of Sequestosome 1 (SQSTM1, p62) in detachment-induced cells. Using monodansylcadaverine (MDC)-LysoTracker double staining and monomeric Cherry (mCherry)-GFP-LC3 assay, we found that the autophagic flux was also mitigated by p66(Shc) depletion. In addition, p66(Shc) knockdown increased the formation of full-length X-linked inhibitor of apoptosis (XIAP)-associated factor 1 (XAF1), which enhances anoikis sensitivity. In conclusion, p66(Shc) plays an essential role in detachment-based equilibrium of anoikic cell death and autophagic cell survival. Anat Rec, 299:325-333, 2016. © 2015 Wiley Periodicals, Inc. PMID:26643258

  7. The equilibrium dayside magnetosphere

    NASA Technical Reports Server (NTRS)

    Zavriyev, Anton; Hasegawa, Akira

    1989-01-01

    A method is presented of computing the dayside global earth magnetic field which is in equilibrium with the plasma pressure, based on satellite observations at a local region of the magnetosphere. The method, which utilizes a perturbation around a dipole magnetic field, involves computation of the global plasma pressure profile based on the equatorial (anisotropic) pressure data, derivation of the current profile which satisfies the equilibrium condition, and computation of the magnetic field using the current profile and the boundary current produced by the solar wind. The method is applied for the Active Magnetospheric Particle Tracer Explorers data, and the result of the computation is found to compare reasonably well with the observed magnetic field profile near the geomagnetic equator.

  8. A Laser Induced Breakdown Spectroscopy application based on Local Thermodynamic Equilibrium assumption for the elemental analysis of alexandrite gemstone and copper-based alloys

    NASA Astrophysics Data System (ADS)

    De Giacomo, A.; Dell'Aglio, M.; Gaudiuso, R.; Santagata, A.; Senesi, G. S.; Rossi, M.; Ghiara, M. R.; Capitelli, F.; De Pascale, O.

    2012-04-01

    Laser Induced Breakdown Spectroscopy (LIBS) is an appealing technique to study laser-induced plasmas (LIPs), both from the basic diagnostics point of view and for analytical applications. LIPs are complex dynamic systems, expanding at supersonic velocities and undergoing a transition between different plasma regimes. If the Local Thermodynamic Equilibrium (LTE) condition is valid for such plasmas, several analytical methods can be employed and fast quantitative analyses can be performed on a variety of samples. In the present paper, a discussion about LTE is carried out and an innovative application to the analysis of the alexandrite gemstone is presented. In addition, a study about the influence of plasma parameters on the performance of LTE-based methods is reported for bronze and brass targets.

  9. Equilibrium Constants You Can Smell.

    ERIC Educational Resources Information Center

    Anderson, Michael; Buckley, Amy

    1996-01-01

    Presents a simple experiment involving the sense of smell that students can accomplish during a lecture. Illustrates the important concepts of equilibrium along with the acid/base properties of various ions. (JRH)

  10. Nonlinear Generator Control Based on Equilibrium Point Analysis for Standard One-Machine Infinite-Bus System Model

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Fujimoto, Koji; Kawamoto, Shunji

    The aim of this letter is to show that the unstable equilibrium point of the Japanese standard one-machine infinite-bus system model is eliminated by adding a simple nonlinear complementary control input to the AVR, and then the critical clearing time of the system can be more enhanced in comparison with the PSS by introducing the proposed nonlinear generator control.

  11. Is Soret equilibrium a non-equilibrium effect?

    NASA Astrophysics Data System (ADS)

    Würger, Alois

    2013-04-01

    Recent thermophoretic experiments on colloidal suspensions revived an old debate, namely whether the Soret effect is properly described by thermostatics, or necessarily requires non-equilibrium thermodynamics. Based on colloidal transport theory and the entropy production of the related viscous flow, our analysis leads to the conclusion that the equilibrium approach may work for small ions, yet fails for colloidal particles and polymers. Regarding binary molecular mixtures, our results shed some doubt on the validity of thermostatic approaches that derive the Soret coefficient from equilibrium potentials.

  12. Helical axis stellarator equilibrium model

    SciTech Connect

    Koniges, A.E.; Johnson, J.L.

    1985-02-01

    An asymptotic model is developed to study MHD equilibria in toroidal systems with a helical magnetic axis. Using a characteristic coordinate system based on the vacuum field lines, the equilibrium problem is reduced to a two-dimensional generalized partial differential equation of the Grad-Shafranov type. A stellarator-expansion free-boundary equilibrium code is modified to solve the helical-axis equations. The expansion model is used to predict the equilibrium properties of Asperators NP-3 and NP-4. Numerically determined flux surfaces, magnetic well, transform, and shear are presented. The equilibria show a toroidal Shafranov shift.

  13. Understanding of surface pit formation mechanism of GaN grown in MOCVD based on local thermodynamic equilibrium assumption

    NASA Astrophysics Data System (ADS)

    Zhi-Yuan, Gao; Xiao-Wei, Xue; Jiang-Jiang, Li; Xun, Wang; Yan-Hui, Xing; Bi-Feng, Cui; De-Shu, Zou

    2016-06-01

    Frank’s theory describes that a screw dislocation will produce a pit on the surface, and has been evidenced in many material systems including GaN. However, the size of the pit calculated from the theory deviates significantly from experimental result. Through a careful observation of the variations of surface pits and local surface morphology with growing temperature and V/III ratio for c-plane GaN, we believe that Frank’s model is valid only in a small local surface area where thermodynamic equilibrium state can be assumed to stay the same. If the kinetic process is too vigorous or too slow to reach a balance, the local equilibrium range will be too small for the center and edge of the screw dislocation spiral to be kept in the same equilibrium state. When the curvature at the center of the dislocation core reaches the critical value 1/r 0, at the edge of the spiral, the accelerating rate of the curvature may not fall to zero, so the pit cannot reach a stationary shape and will keep enlarging under the control of minimization of surface energy to result in a large-sized surface pit. Project supported by the National Natural Science Foundation of China (Grant Nos. 11204009 and 61204011) and the Beijing Municipal Natural Science Foundation, China (Grant No. 4142005).

  14. Ionization and thermal equilibrium models for O star winds based on time-independent radiation-driven wind theory

    NASA Technical Reports Server (NTRS)

    Drew, J. E.

    1989-01-01

    Ab initio ionization and thermal equilibrium models are calculated for the winds of O stars using the results of steady state radiation-driven wind theory to determine the input parameters. Self-consistent methods are used for the roles of H, He, and the most abundant heavy elements in both the statistical and the thermal equilibrium. The model grid was chosen to encompass all O spectral subtypes and the full range of luminosity classes. Results of earlier modeling of O star winds by Klein and Castor (1978) are reproduced and used to motivate improvements in the treatment of the hydrogen equilibrium. The wind temperature profile is revealed to be sensitive to gross changes in the heavy element abundances, but insensitive to other factors considered such as the mass-loss rate and velocity law. The reduced wind temperatures obtained in observing the luminosity dependence of the Si IV lambda 1397 wind absorption profile are shown to eliminate any prospect of explaining the observed O VI lambda 1036 line profiles in terms of time-independent radiation-driven wind theory.

  15. Equilibrium frequency of endosymbionts in multiple infections based on the balance between vertical transmission and cytoplasmic incompatibility.

    PubMed

    Kawasaki, Yuuki; Ito, Hiroshi; Kajimura, Hisashi

    2014-01-01

    Cytoplasmic incompatibility (CI)-inducing endosymbiotic bacteria, such as Wolbachia and Cardinium, have been well studied through field data and validations on the basis of numerical simulations. However, the analytically derived equilibrium frequency of multiple infections has not yet been determined, although the equilibrium for cases of single infection has been reported. In this study, we considered the difference equation for endosymbionts using three parameters: the probability of the failure of vertical transmission ([Formula: see text]), CI strength ([Formula: see text]), and the level of host inbreeding ([Formula: see text]). To analyze this model, we particularly focused on [Formula: see text], i.e., the frequency of host individuals completely infected with all [Formula: see text]-bacterial strains in the population. [Formula: see text], [Formula: see text] at the equilibrium state, was analytically calculated in the cases where [Formula: see text] and [Formula: see text] is any arbitrary value. We found that [Formula: see text] can be described using two parameters: [Formula: see text] and [Formula: see text], which is identical to [Formula: see text]. [Formula: see text] has a larger value in a system with a smaller [Formula: see text]. In addition, [Formula: see text] determines the maximum number of strains that infect a single host. Our results revealed the following: i) three parameters can be reduced to a single parameter, i.e., [Formula: see text] and ii) the threshold of the maximum number of infections is defined by [Formula: see text], which prevents additional invasions by endosymbionts. PMID:24747216

  16. Quantitative Analysis of Caspase-1 Activity in Living Cells Through Dynamic Equilibrium of Chlorophyll-Based Nano-assembly Modulated Photoacoustic Signals.

    PubMed

    Li, Li-Li; Zeng, Qian; Liu, Wei-Jiao; Hu, Xue-Feng; Li, Yongsheng; Pan, Jie; Wan, Dong; Wang, Hao

    2016-07-20

    In situ construction of self-assemblies with unique property in living systems is a promising direction in the biomedical field. The noninvasive methods for significant enzyme activity in living cells or living subjects are imperative and meantime challenge tasks. The dynamic process of self-assembly of chlorophyll-based molecules in complex biological systems can be monitored by photoacoustic signals, which supports a noninvasive way to understand and quantitatively measure the activity of caspase-1. Furthermore, the activity of caspase-1 enables reflection of the bacterial infection in the early stage. Here, we present a biocompatible self-assembly from chlorophyll-peptide derivatives and first correlate the dynamic equilibrium with ratiometric photoacoustic signals. The intracellular equilibrium was managed by a bacterial infection precaution protein, i.e., caspase-1. This system offers a trial of noninvasive method to quantitative detection and real-time monitoring of bacterial infection in the early stage. PMID:27341352

  17. Evaporation kinetics of laser heated silica in reactive and inert gases based on near-equilibrium dynamics.

    PubMed

    Elhadj, Selim; Matthews, Manyalibo J; Yang, Steven T; Cooke, Diane J

    2012-01-16

    Evaporation kinetics of fused silica were measured up to ≈3000K using CO(2) laser heating, while solid-gas phase chemistry of silica was assessed with hydrogen, air, and nitrogen. Enhanced evaporation in hydrogen was attributed to an additional reduction pathway, while oxidizing conditions pushed the reaction backwards. The observed mass transport limitations supported use of a near-equilibrium analysis for interpreting kinetic data. A semi-empirical model of the evaporation kinetics is derived that accounts for heating, gas chemistry and transport properties. The approach described should have application to materials laser processing, and in applications requiring knowledge of thermal decomposition chemistry under extreme temperatures. PMID:22274500

  18. Estimation of EEC, unattached fraction and equilibrium factor for the assessment of radiological dose using pin-hole cup dosimeters and deposition based progeny sensors.

    PubMed

    Bangotra, Pargin; Mehra, Rohit; Kaur, Kirandeep; Kanse, Sandeep; Mishra, Rosaline; Sahoo, B K

    2015-10-01

    High concentration of radon ((222)Rn), thoron ((220)Rn) and their decay products in environment may increase the risk of radiological exposure to the mankind. The (222)Rn, (220)Rn concentration and their separate attached and unattached progeny concentration in units of EEC have been measured in the dwellings of Muktsar and Mansa districts of Punjab (India), using Pin-hole cup dosimeters and deposition based progeny sensors (DTPS/DRPS). The indoor (222)Rn and (220)Rn concentration was found to vary from 21 Bqm(-3) to 94 Bqm(-3) and 17 Bqm(-3) to 125 Bqm(-3). The average EEC (attached + unattached) of (222)Rn and (220)Rn was 25 Bqm(-3) and 1.8 Bqm(-3). The equilibrium factor for (222)Rn and (220)Rn in studied area was 0.47 ± 0.13 and 0.05 ± 0.03. The equilibrium factor and unattached fraction of (222)Rn and (220)Rn has been calculated separately. Dose conversion factors (DCFs) of different models have been calculated from unattached fraction for the estimation of annual effective dose in the studied area. From the experimental data a correlation relationship has been observed between unattached fraction (f(p)(Rn)) and equilibrium factor (F(Rn)). The present work also aims to evaluate an accurate expression among available expression in literature for the estimation of f(p)(Rn). PMID:26117280

  19. A Differential Evolution Algorithm Based on Nikaido-Isoda Function for Solving Nash Equilibrium in Nonlinear Continuous Games.

    PubMed

    He, Feng; Zhang, Wei; Zhang, Guoqiang

    2016-01-01

    A differential evolution algorithm for solving Nash equilibrium in nonlinear continuous games is presented in this paper, called NIDE (Nikaido-Isoda differential evolution). At each generation, parent and child strategy profiles are compared one by one pairwisely, adapting Nikaido-Isoda function as fitness function. In practice, the NE of nonlinear game model with cubic cost function and quadratic demand function is solved, and this method could also be applied to non-concave payoff functions. Moreover, the NIDE is compared with the existing Nash Domination Evolutionary Multiplayer Optimization (NDEMO), the result showed that NIDE was significantly better than NDEMO with less iterations and shorter running time. These numerical examples suggested that the NIDE method is potentially useful. PMID:27589229

  20. Thermodynamic equilibrium composition analysis of methanol autothermal reforming for proton exchanger membrane fuel cell based on FLUENT Software

    NASA Astrophysics Data System (ADS)

    Wang, Sheng; Wang, Shudong

    Methanol autothermal reforming was thermodynamically analyzed using FLUENT software. The calculation methodology using this software is simple and convenient, and its validity was confirmed by comparing the obtained data with previous studies. As a function of the effects of temperature, pressure, molar steam-to-carbon ratio (S/C), and molar oxygen-to-carbon ratio (O/C) on the objective products, favorable operational parameters were evaluated, under which H 2 yield maximizes, the CO molar fraction minimizes and carbon deposition can be eliminated. The equilibrium constants of the possible reactions involved in oxidative methanol steam reforming, coupled with the reaction mechanism for the entire investigated temperature range, were elucidated and discussed. On the basis of the concluded possible mechanisms, three areas are inferred. In each individual area, H 2 or CO yield reached a maximum, or solid C was efficiently suppressed. Therein, a favorable operational range is proposed to assure the most optimized product yield.

  1. Calculation of the acid-base equilibrium constants at the alumina/electrolyte interface from the ph dependence of the adsorption of singly charged ions (Na+, Cl-)

    NASA Astrophysics Data System (ADS)

    Gololobova, E. G.; Gorichev, I. G.; Lainer, Yu. A.; Skvortsova, I. V.

    2011-05-01

    A procedure was proposed for the calculation of the acid-base equilibrium constants at an alumina/electrolyte interface from experimental data on the adsorption of singly charged ions (Na+, Cl-) at various pH values. The calculated constants (p K {1/0}= 4.1, p K {2/0}= 11.9, p K {3/0}= 8.3, and p K {4/0}= 7.7) are shown to agree with the values obtained from an experimental pH dependence of the electrokinetic potential and the results of potentiometric titration of Al2O3 suspensions.

  2. Electrospray mass spectrometry of some proteins and the aqueous solution acid/base equilibrium model in the negative ion detection mode

    NASA Astrophysics Data System (ADS)

    Le Blanc, J. C. Y.; Guevremont, R.; Siu, K. W. M.

    1993-06-01

    Basic solutions of myoglobin, [beta]-lactoglobulin, pepsin and ubiquitin have been examined by means of electrospray mass spectrometry in the negative ion detection mode. The distribution of protein ions in the mass spectra was found to correlate well with the distribution of protein species in solution calculated from published titration data. These results lend further credibility to an earlier proposed aqueous solution acid/base equilibrium model, which relates the "bellshape" ion distribution observed in the electrospray mass spectrometry of proteins to the distribution of protein ions in solution.

  3. Removal of aluminium from aqueous solutions using PAN-based adsorbents: characterisation, kinetics, equilibrium and thermodynamic studies.

    PubMed

    Aly, Zaynab; Graulet, Adrien; Scales, Nicholas; Hanley, Tracey

    2014-03-01

    Economic adsorbents in bead form were fabricated and utilised for the adsorption of Al(3+) from aqueous solutions. Polyacrylonitrile (PAN) beads, PAN powder and the thermally treated PAN beads (250 °C/48 h/Ar and 600 °C/48 h/Ar-H2) were characterised using different techniques including Fourier transform infrared spectroscopy, X-ray diffraction, specific surface analysis (Brunauer-Emmett-Teller), thermogravimetric analysis as well as scanning electron microscopy. Effects of pH, contact time, kinetics and adsorption isotherms at different temperatures were investigated in batch mode experiments. Aluminium kinetic data best fit the Lagergren pseudo-second-order adsorption model indicating a one-step, surface-only, adsorption process with chemisorption being the rate limiting step. Equilibrium adsorption data followed a Langmuir adsorption model with fairly low monolayer adsorption capacities suitable for freshwater clean-up only. Various constants including thermodynamic constants were evaluated from the experimental results obtained at 20, 40 and 60 °C. Positive values of ΔH° indicated that the adsorption of Al(3+) onto all three adsorbents was endothermic with less energy input required for PAN powder compared to PAN beads and low-temperature thermally treated PAN. Negative ΔG° values indicated that the aluminium adsorption process was spontaneous for all adsorbents examined. PMID:24297464

  4. Soft-spring wall based non-periodic boundary conditions for non-equilibrium molecular dynamics of dense fluids

    NASA Astrophysics Data System (ADS)

    Ghatage, Dhairyashil; Tomar, Gaurav; Shukla, Ratnesh K.

    2015-03-01

    Non-equilibrium molecular dynamics (MD) simulations require imposition of non-periodic boundary conditions (NPBCs) that seamlessly account for the effect of the truncated bulk region on the simulated MD region. Standard implementation of specular boundary conditions in such simulations results in spurious density and force fluctuations near the domain boundary and is therefore inappropriate for coupled atomistic-continuum calculations. In this work, we present a novel NPBC model that relies on boundary atoms attached to a simple cubic lattice with soft springs to account for interactions from particles which would have been present in an untruncated full domain treatment. We show that the proposed model suppresses the unphysical fluctuations in the density to less than 1% of the mean while simultaneously eliminating spurious oscillations in both mean and boundary forces. The model allows for an effective coupling of atomistic and continuum solvers as demonstrated through multiscale simulation of boundary driven singular flow in a cavity. The geometric flexibility of the model enables straightforward extension to nonplanar complex domains without any adverse effects on dynamic properties such as the diffusion coefficient.

  5. Antarctic seawater temperature evaluation based on stable isotope measurements on Adamussium colbecki shells: kinetic effects vs. isotopic equilibrium

    NASA Astrophysics Data System (ADS)

    Trevisiol, A.; Bergamasco, A.; Montagna, P.; Sprovieri, M.; Taviani, M.

    2013-10-01

    A year-long controlled growth experiment of 60 specimens of the Antarctic bivalve Adamussium colbecki was conducted in Terra Nova Bay (Ross Sea) to evaluate its reliability as a suitable archive of water mass properties. Nine shells were sub-sampled for stable oxygen and carbon isotope analysis to study the inter and intra specimen variations. Slow-growing A. colbecki precipitate their calcitic shells close to the expected oxygen and carbon isotopic equilibrium, whereas the fast-growing individuals are strongly influenced by biogenetic and kinetic effects. The equation of Kim and O'Neil (1997) is considered a fair approximation for the δ18O-temperature relationship in slow-growing individuals. The reconstructed temperature is closer to the mean experimental summer temperature than the annual one. This fact is interpreted as reflecting a possible winter decrease of shell growth, the salinity variation and the corrections for negative temperature on calibrating the δ18O-temperature relationship. Our results support the hypothesis that A. colbecki might represent a good archive for encoding Antarctic Shelf water summer temperature information. Further improvements in adopting A. colbecki as a paleotemperature archive will require the evaluation of the seasonal variability in shell growth rate through culturing slow-growing A. colbecki individuals at near-freezing temperatures to calibrate a species-specific δ18O-temperature equation.

  6. Soft-spring wall based non-periodic boundary conditions for non-equilibrium molecular dynamics of dense fluids

    SciTech Connect

    Ghatage, Dhairyashil; Tomar, Gaurav Shukla, Ratnesh K.

    2015-03-28

    Non-equilibrium molecular dynamics (MD) simulations require imposition of non-periodic boundary conditions (NPBCs) that seamlessly account for the effect of the truncated bulk region on the simulated MD region. Standard implementation of specular boundary conditions in such simulations results in spurious density and force fluctuations near the domain boundary and is therefore inappropriate for coupled atomistic-continuum calculations. In this work, we present a novel NPBC model that relies on boundary atoms attached to a simple cubic lattice with soft springs to account for interactions from particles which would have been present in an untruncated full domain treatment. We show that the proposed model suppresses the unphysical fluctuations in the density to less than 1% of the mean while simultaneously eliminating spurious oscillations in both mean and boundary forces. The model allows for an effective coupling of atomistic and continuum solvers as demonstrated through multiscale simulation of boundary driven singular flow in a cavity. The geometric flexibility of the model enables straightforward extension to nonplanar complex domains without any adverse effects on dynamic properties such as the diffusion coefficient.

  7. The effect of parameters of equilibrium-based 3-D biomechanical models on extracted muscle synergies during isometric lumbar exertion.

    PubMed

    Eskandari, A H; Sedaghat-Nejad, E; Rashedi, E; Sedighi, A; Arjmand, N; Parnianpour, M

    2016-04-11

    A hallmark of more advanced models is their higher details of trunk muscles represented by a larger number of muscles. The question is if in reality we control these muscles individually as independent agents or we control groups of them called "synergy". To address this, we employed a 3-D biomechanical model of the spine with 18 trunk muscles that satisfied equilibrium conditions at L4/5, with different cost functions. The solutions of several 2-D and 3-D tasks were arranged in a data matrix and the synergies were computed by using non-negative matrix factorization (NMF) algorithms. Variance accounted for (VAF) was used to evaluate the number of synergies that emerged by the analysis, which were used to reconstruct the original muscle activations. It was showed that four and six muscle synergies were adequate to reconstruct the input data of 2-D and 3-D torque space analysis. The synergies were different by choosing alternative cost functions as expected. The constraints affected the extracted muscle synergies, particularly muscles that participated in more than one functional tasks were influenced substantially. The compositions of extracted muscle synergies were in agreement with experimental studies on healthy participants. The following computational methods show that the synergies can reduce the complexity of load distributions and allow reduced dimensional space to be used in clinical settings. PMID:26747515

  8. Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS. Part 2: application to Taupo Volcanic Zone rhyolites

    NASA Astrophysics Data System (ADS)

    Bégué, Florence; Gualda, Guilherme A. R.; Ghiorso, Mark S.; Pamukcu, Ayla S.; Kennedy, Ben M.; Gravley, Darren M.; Deering, Chad D.; Chambefort, Isabelle

    2014-11-01

    Constraining the pressure of crystallisation of large silicic magma bodies gives important insight into the depth and vertical extent of magmatic plumbing systems; however, it is notably difficult to constrain pressure at the level of detail necessary to understand shallow magmatic systems. In this study, we use the recently developed rhyolite-MELTS geobarometer to constrain the crystallisation pressures of rhyolites from the Taupo Volcanic Zone (TVZ). As sanidine is absent from the studied deposits, we calculate the pressures at which quartz and feldspar are found to be in equilibrium with melt now preserved as glass (the quartz +1 feldspar constraint of Gualda and Ghiorso, Contrib Mineral Petrol 168:1033. doi:10.1007/s00410-014-1033-3. 2014). We use glass compositions (matrix glass and melt inclusions) from seven eruptive deposits dated between ~320 and 0.7 ka from four distinct calderas in the central TVZ, and we discuss advantages and limitations of the rhyolite-MELTS geobarometer in comparison with other geobarometers applied to the same eruptive deposits. Overall, there is good agreement with other pressure estimates from the literature (amphibole geobarometry and H2O-CO2 solubility models). One of the main advantages of this new geobarometer is that it can be applied to both matrix glass and melt inclusions—regardless of volatile saturation. The examples presented also emphasise the utility of this method to filter out spurious glass compositions. Pressure estimates obtained with the new rhyolite-MELTS geobarometer range between ~250 to ~50 MPa, with a large majority at ~100 MPa. These results confirm that the TVZ hosts some of the shallowest rhyolitic magma bodies on the planet, resulting from the extensional tectonic regime and thinning of the crust. Distinct populations with different equilibration pressures are also recognised, which is consistent with the idea that multiple batches of eruptible magma can be present in the crust at the same time and

  9. Ab Initio Path-Integral Calculations of Kinetic and Equilibrium Isotope Effects on Base-Catalyzed RNA Transphosphorylation Models

    PubMed Central

    Wong, Kin-Yiu; Yuqing, Xu; York, Darrin M.

    2014-01-01

    Detailed understandings of the reaction mechanisms of RNA catalysis in various environments can have profound importance for many applications, ranging from the design of new biotechnologies to the unraveling of the evolutionary origin of life. An integral step in the nucleolytic RNA catalysis is self-cleavage of RNA strands by 2′-O-transphosphorylation. Key to elucidating a reaction mechanism is determining the molecular structure and bonding characteristics of transition state. A direct and powerful probe of transition state is measuring isotope effects on biochemical reactions, particularly if we can reproduce isotope effect values from quantum calculations. This paper significantly extends the scope of our previous joint experimental and theoretical work in examining isotope effects on enzymatic and non-enzymatic 2′-O-transphosphorylation reaction models that mimic reactions catalyzed by RNA enzymes (ribozymes), and protein enzymes such as ribonuclease A (RNase A). Native reactions are studied, as well as reactions with thio substitutions representing chemical modifications often used in experiments to probe mechanism. Here, we report and compare results from eight levels of electronic-structure calculations for constructing the potential energy surfaces in kinetic and equilibrium isotope effects (KIE and EIE) computations, including a “gold-standard” coupled-cluster level of theory [CCSD(T)]. In addition to the widely-used Bigeleisen equation for estimating KIE and EIE values, internuclear anharmonicity and quantum tunneling effects were also computed using our recently-developed ab initio path-integral method, i.e., automated integration-free path-integral (AIF-PI) method. The results of this work establish an important set of benchmarks that serve to guide calculations of KIE and EIE for RNA catalysis. PMID:24841935

  10. Shape characteristics of equilibrium and non-equilibrium fractal clusters

    NASA Astrophysics Data System (ADS)

    Mansfield, Marc L.; Douglas, Jack F.

    2013-07-01

    It is often difficult in practice to discriminate between equilibrium and non-equilibrium nanoparticle or colloidal-particle clusters that form through aggregation in gas or solution phases. Scattering studies often permit the determination of an apparent fractal dimension, but both equilibrium and non-equilibrium clusters in three dimensions frequently have fractal dimensions near 2, so that it is often not possible to discriminate on the basis of this geometrical property. A survey of the anisotropy of a wide variety of polymeric structures (linear and ring random and self-avoiding random walks, percolation clusters, lattice animals, diffusion-limited aggregates, and Eden clusters) based on the principal components of both the radius of gyration and electric polarizability tensor indicates, perhaps counter-intuitively, that self-similar equilibrium clusters tend to be intrinsically anisotropic at all sizes, while non-equilibrium processes such as diffusion-limited aggregation or Eden growth tend to be isotropic in the large-mass limit, providing a potential means of discriminating these clusters experimentally if anisotropy could be determined along with the fractal dimension. Equilibrium polymer structures, such as flexible polymer chains, are normally self-similar due to the existence of only a single relevant length scale, and are thus anisotropic at all length scales, while non-equilibrium polymer structures that grow irreversibly in time eventually become isotropic if there is no difference in the average growth rates in different directions. There is apparently no proof of these general trends and little theoretical insight into what controls the universal anisotropy in equilibrium polymer structures of various kinds. This is an obvious topic of theoretical investigation, as well as a matter of practical interest. To address this general problem, we consider two experimentally accessible ratios, one between the hydrodynamic and gyration radii, the other

  11. Shape characteristics of equilibrium and non-equilibrium fractal clusters.

    PubMed

    Mansfield, Marc L; Douglas, Jack F

    2013-07-28

    It is often difficult in practice to discriminate between equilibrium and non-equilibrium nanoparticle or colloidal-particle clusters that form through aggregation in gas or solution phases. Scattering studies often permit the determination of an apparent fractal dimension, but both equilibrium and non-equilibrium clusters in three dimensions frequently have fractal dimensions near 2, so that it is often not possible to discriminate on the basis of this geometrical property. A survey of the anisotropy of a wide variety of polymeric structures (linear and ring random and self-avoiding random walks, percolation clusters, lattice animals, diffusion-limited aggregates, and Eden clusters) based on the principal components of both the radius of gyration and electric polarizability tensor indicates, perhaps counter-intuitively, that self-similar equilibrium clusters tend to be intrinsically anisotropic at all sizes, while non-equilibrium processes such as diffusion-limited aggregation or Eden growth tend to be isotropic in the large-mass limit, providing a potential means of discriminating these clusters experimentally if anisotropy could be determined along with the fractal dimension. Equilibrium polymer structures, such as flexible polymer chains, are normally self-similar due to the existence of only a single relevant length scale, and are thus anisotropic at all length scales, while non-equilibrium polymer structures that grow irreversibly in time eventually become isotropic if there is no difference in the average growth rates in different directions. There is apparently no proof of these general trends and little theoretical insight into what controls the universal anisotropy in equilibrium polymer structures of various kinds. This is an obvious topic of theoretical investigation, as well as a matter of practical interest. To address this general problem, we consider two experimentally accessible ratios, one between the hydrodynamic and gyration radii, the other

  12. Mathematical modeling of non-equilibrium sorption

    NASA Astrophysics Data System (ADS)

    Kaliev, Ibragim A.; Mukhambetzhanov, Saltanbek T.; Sabitova, Gulnara S.; Sakhit, Anghyz E.

    2016-08-01

    We consider the system of equations modeling the process of non-equilibrium sorption. Difference approximation of differential problem by the implicit scheme is formulated. The solution of the difference problem is constructed using the sweep method. Based on the numerical results we can conclude the following: when the relaxation time decreases to 0, then the solution of non-equilibrium problem tends with increasing time to solution of the equilibrium problem.

  13. An investigation of equilibrium concepts

    NASA Technical Reports Server (NTRS)

    Prozan, R. J.

    1982-01-01

    A different approach to modeling of the thermochemistry of rocket engine combustion phenomena is presented. The methodology described is based on the hypothesis of a new variational principle applicable to compressible fluid mechanics. This hypothesis is extended to treat the thermochemical behavior of a reacting (equilibrium) gas in an open system.

  14. Getting Freshman in Equilibrium.

    ERIC Educational Resources Information Center

    Journal of Chemical Education, 1983

    1983-01-01

    Various aspects of chemical equilibrium were discussed in six papers presented at the Seventh Biennial Conference on Chemical Education (Stillwater, Oklahoma 1982). These include student problems in understanding hydrolysis, helping students discover/uncover topics, equilibrium demonstrations, instructional strategies, and flaws to kinetic…

  15. Application of Molecular Interaction Volume Model for Phase Equilibrium of Sn-Based Binary System in Vacuum Distillation

    NASA Astrophysics Data System (ADS)

    Kong, Lingxin; Yang, Bin; Xu, Baoqiang; Li, Yifu

    2014-09-01

    Based on the molecular interaction volume model (MIVM), the activities of components of Sn-Sb, Sb-Bi, Sn-Zn, Sn-Cu, and Sn-Ag alloys were predicted. The predicted values are in good agreement with the experimental data, which indicate that the MIVM is of better stability and reliability due to its good physical basis. A significant advantage of the MIVM lies in its ability to predict the thermodynamic properties of liquid alloys using only two parameters. The phase equilibria of Sn-Sb and Sn-Bi alloys were calculated based on the properties of pure components and the activity coefficients, which indicates that Sn-Sb and Sn-Bi alloys can be separated thoroughly by vacuum distillation. This study extends previous investigations and provides an effective and convenient model on which to base refining simulations for Sn-based alloys.

  16. Lysozyme adsorption in pH-responsive hydrogel thin-films: the non-trivial role of acid-base equilibrium.

    PubMed

    Narambuena, Claudio F; Longo, Gabriel S; Szleifer, Igal

    2015-09-01

    We develop and apply a molecular theory to study the adsorption of lysozyme on weak polyacid hydrogel films. The theory explicitly accounts for the conformation of the network, the structure of the proteins, the size and shape of all the molecular species, their interactions as well as the chemical equilibrium of each titratable unit of both the protein and the polymer network. The driving forces for adsorption are the electrostatic attractions between the negatively charged network and the positively charged protein. The adsorption is a non-monotonic function of the solution pH, with a maximum in the region between pH 8 and 9 depending on the salt concentration of the solution. The non-monotonic adsorption is the result of increasing negative charge of the network with pH, while the positive charge of the protein decreases. At low pH the network is roughly electroneutral, while at sufficiently high pH the protein is negatively charged. Upon adsorption, the acid-base equilibrium of the different amino acids of the protein shifts in a nontrivial fashion that depends critically on the particular kind of residue and solution composition. Thus, the proteins regulate their charge and enhance adsorption under a wide range of conditions. In particular, adsorption is predicted above the protein isoelectric point where both the solution lysozyme and the polymer network are negatively charged. This behavior occurs because the pH in the interior of the gel is significantly lower than that in the bulk solution and it is also regulated by the adsorption of the protein in order to optimize protein-gel interactions. Under high pH conditions we predict that the protein changes its charge from negative in the solution to positive within the gel. The change occurs within a few nanometers at the interface of the hydrogel film. Our predictions show the non-trivial interplay between acid-base equilibrium, physical interactions and molecular organization under nanoconfined conditions

  17. General equilibrium of an ecosystem.

    PubMed

    Tschirhart, J

    2000-03-01

    Ecosystems and economies are inextricably linked: ecosystem models and economic models are not linked. Consequently, using either type of model to design policies for preserving ecosystems or improving economic performance omits important information. Improved policies would follow from a model that links the systems and accounts for the mutual feedbacks by recognizing how key ecosystem variables influence key economic variables, and vice versa. Because general equilibrium economic models already are widely used for policy making, the approach used here is to develop a general equilibrium ecosystem model which captures salient biological functions and which can be integrated with extant economic models. In the ecosystem model, each organism is assumed to be a net energy maximizer that must exert energy to capture biomass from other organisms. The exerted energies are the "prices" that are paid to biomass, and each organism takes the prices as signals over which it has no control. The maximization problem yields the organism's demand for and supply of biomass to other organisms as functions of the prices. The demands and supplies for each biomass are aggregated over all organisms in each species which establishes biomass markets wherein biomass prices are determined. A short-run equilibrium is established when all organisms are maximizing and demand equals supply in every biomass market. If a species exhibits positive (negative) net energy in equilibrium, its population increases (decreases) and a new equilibrium follows. The demand and supply forces in the biomass markets drive each species toward zero stored energy and a long-run equilibrium. Population adjustments are not based on typical Lotka-Volterra differential equations in which one entire population adjusts to another entire population thereby masking organism behavior; instead, individual organism behavior is central to population adjustments. Numerical simulations use a marine food web in Alaska to

  18. Novel free-boundary equilibrium and transport solver with theory-based models and its validation against ASDEX Upgrade current ramp scenarios

    NASA Astrophysics Data System (ADS)

    Fable, E.; Angioni, C.; Casson, F. J.; Told, D.; Ivanov, A. A.; Jenko, F.; McDermott, R. M.; Medvedev, S. Yu; Pereverzev, G. V.; Ryter, F.; Treutterer, W.; Viezzer, E.; the ASDEX Upgrade Team

    2013-12-01

    Tokamak scenario development requires an understanding of the properties that determine the kinetic profiles in non-steady plasma phases and of the self-consistent evolution of the magnetic equilibrium. Current ramps are of particular interest since many transport-relevant parameters explore a large range of values and their impact on transport mechanisms has to be assessed. To this purpose, a novel full-discharge modelling tool has been developed, which couples the transport code ASTRA (Pereverzev et al 1991 IPP Report 5/42) and the free boundary equilibrium code SPIDER (Ivanov et al 2005 32nd EPS Conf. on Plasma Physics vol 29C (ECA) P-5.063 and http://epsppd.epfl.ch/Tarragona/pdf/P5_063.pdf), utilizing a specifically designed coupling scheme. The current ramp-up phase can be accurately and reliably simulated using this scheme, where a plasma shape, position and current controller is applied, which mimics the one of ASDEX Upgrade. Transport of energy is provided by theory-based models (e.g. TGLF (Staebler et al 2007 Phys. Plasmas 14 055909)). A recipe based on edge-relevant parameters (Scott 2000 Phys. Plasmas 7 1845) is proposed to resolve the low current phase of the current ramps, where the impact of the safety factor on micro-instabilities could make quasi-linear approaches questionable in the plasma outer region. Current ramp scenarios, selected from ASDEX Upgrade discharges, are then simulated to validate both the coupling with the free-boundary evolution and the prediction of profiles. Analysis of the underlying transport mechanisms is presented, to clarify the possible physics origin of the observed L-mode empirical energy confinement scaling. The role of toroidal micro-instabilities (ITG, TEM) and of non-linear effects is discussed.

  19. Equilibrium sampling by reweighting nonequilibrium simulation trajectories

    NASA Astrophysics Data System (ADS)

    Yang, Cheng; Wan, Biao; Xu, Shun; Wang, Yanting; Zhou, Xin

    2016-03-01

    Based on equilibrium molecular simulations, it is usually difficult to efficiently visit the whole conformational space of complex systems, which are separated into some metastable regions by high free energy barriers. Nonequilibrium simulations could enhance transitions among these metastable regions and then be applied to sample equilibrium distributions in complex systems, since the associated nonequilibrium effects can be removed by employing the Jarzynski equality (JE). Here we present such a systematical method, named reweighted nonequilibrium ensemble dynamics (RNED), to efficiently sample equilibrium conformations. The RNED is a combination of the JE and our previous reweighted ensemble dynamics (RED) method. The original JE reproduces equilibrium from lots of nonequilibrium trajectories but requires that the initial distribution of these trajectories is equilibrium. The RED reweights many equilibrium trajectories from an arbitrary initial distribution to get the equilibrium distribution, whereas the RNED has both advantages of the two methods, reproducing equilibrium from lots of nonequilibrium simulation trajectories with an arbitrary initial conformational distribution. We illustrated the application of the RNED in a toy model and in a Lennard-Jones fluid to detect its liquid-solid phase coexistence. The results indicate that the RNED sufficiently extends the application of both the original JE and the RED in equilibrium sampling of complex systems.

  20. Equilibrium sampling by reweighting nonequilibrium simulation trajectories.

    PubMed

    Yang, Cheng; Wan, Biao; Xu, Shun; Wang, Yanting; Zhou, Xin

    2016-03-01

    Based on equilibrium molecular simulations, it is usually difficult to efficiently visit the whole conformational space of complex systems, which are separated into some metastable regions by high free energy barriers. Nonequilibrium simulations could enhance transitions among these metastable regions and then be applied to sample equilibrium distributions in complex systems, since the associated nonequilibrium effects can be removed by employing the Jarzynski equality (JE). Here we present such a systematical method, named reweighted nonequilibrium ensemble dynamics (RNED), to efficiently sample equilibrium conformations. The RNED is a combination of the JE and our previous reweighted ensemble dynamics (RED) method. The original JE reproduces equilibrium from lots of nonequilibrium trajectories but requires that the initial distribution of these trajectories is equilibrium. The RED reweights many equilibrium trajectories from an arbitrary initial distribution to get the equilibrium distribution, whereas the RNED has both advantages of the two methods, reproducing equilibrium from lots of nonequilibrium simulation trajectories with an arbitrary initial conformational distribution. We illustrated the application of the RNED in a toy model and in a Lennard-Jones fluid to detect its liquid-solid phase coexistence. The results indicate that the RNED sufficiently extends the application of both the original JE and the RED in equilibrium sampling of complex systems. PMID:27078486

  1. Optical Fluoride Sensor Based on Monomer-Dimer Equilibrium of Scandium(III)-Octaethylporphyrin in a Plasticized Polymeric Film

    PubMed Central

    Kang, Youngjea; Kampf, Jeff W.; Meyerhoff, Mark E.

    2007-01-01

    A fluoride-selective optical sensor based on scandium(III) octaethylporphyrin (Sc(III)OEP) as an ionophore within a plasticized PVC film is described. The presence of fluoride ion in the aqueous sample phase increases the formation of a difluoro-bridged Sc(III)OEP dimer species in the polymer film. The ability of the Sc(III) porphyrin to form the dimeric structure in the presence of fluoride is confirmed by UV-Vis spectroscopy and X-ray crystallography. For more practical sensing applications, a pH chromoionophore (ETH 7075) is added to the plasticized PVC film along with Sc(III)OEP and the observed optical response is based on co-extraction of protons with sample phase fluoride to create the dimeric porphyrin and a protonated chromoionophore species. The selectivity pattern observed is F-≫ClO4-, SCN-, NO3->Br-, Cl-. Only organic salicylate is a significant interferent. Fast and reversible fluoride response is observed over the range of 10-4 ~10-2 M fluoride, allowing use of the sensing film in a waveguide configuration for flow-injection measurements. PMID:17719905

  2. Chemical Principles Revisited: Chemical Equilibrium.

    ERIC Educational Resources Information Center

    Mickey, Charles D.

    1980-01-01

    Describes: (1) Law of Mass Action; (2) equilibrium constant and ideal behavior; (3) general form of the equilibrium constant; (4) forward and reverse reactions; (5) factors influencing equilibrium; (6) Le Chatelier's principle; (7) effects of temperature, changing concentration, and pressure on equilibrium; and (8) catalysts and equilibrium. (JN)

  3. A Lakatosian Conceptual Change Teaching Strategy Based on Student Ability to Build Models with Varying Degrees of Conceptual Understanding of Chemical Equilibrium

    NASA Astrophysics Data System (ADS)

    Niaz, M.

    The main objective of this study is to construct a Lakatosian teaching strategy that can facilitate conceptual change in students'' understanding of chemical equilibrium. The strategy is based on the premise that cognitive conflicts must have been engendered by the students themselves in trying to cope with different problem solving strategies. Results obtained (based on Venezuelan freshman students) show that the performance of the experimental group of students was generally better (especially on the immediate post tests) than that of the control group. It is concluded that a conceptual change teaching strategy must take into consideration the following aspects: a) core beliefs of the students in the topic (cf. ''hard core'', Lakatos 1970); b) exploration of the relationship between core beliefs and student alternative conceptions (misconceptions); c) cognitive complexity of the core belief can be broken down into a series of related and probing questions; d) students resist changes in their core beliefs by postulating ''auxiliary hypotheses'' in order to resolve their contradictions; e) students'' responses based on their alternative conceptions must be considered not as wrong, but rather as models, perhaps in the same sense as used by scientists to break the complexity of a problem; and f) students'' misconceptions be considered as alternative conceptions (theories) that compete with the present scientific theories and at times recapitulate theories scientists held in the past.

  4. Computing Equilibrium Chemical Compositions

    NASA Technical Reports Server (NTRS)

    Mcbride, Bonnie J.; Gordon, Sanford

    1995-01-01

    Chemical Equilibrium With Transport Properties, 1993 (CET93) computer program provides data on chemical-equilibrium compositions. Aids calculation of thermodynamic properties of chemical systems. Information essential in design and analysis of such equipment as compressors, turbines, nozzles, engines, shock tubes, heat exchangers, and chemical-processing equipment. CET93/PC is version of CET93 specifically designed to run within 640K memory limit of MS-DOS operating system. CET93/PC written in FORTRAN.

  5. Napoleon Is in Equilibrium

    PubMed Central

    Phillips, Rob

    2016-01-01

    It has been said that the cell is the test tube of the twenty-first century. If so, the theoretical tools needed to quantitatively and predictively describe what goes on in such test tubes lag sorely behind the stunning experimental advances in biology seen in the decades since the molecular biology revolution began. Perhaps surprisingly, one of the theoretical tools that has been used with great success on problems ranging from how cells communicate with their environment and each other to the nature of the organization of proteins and lipids within the cell membrane is statistical mechanics. A knee-jerk reaction to the use of statistical mechanics in the description of cellular processes is that living organisms are so far from equilibrium that one has no business even thinking about it. But such reactions are probably too hasty given that there are many regimes in which, because of a separation of timescales, for example, such an approach can be a useful first step. In this article, we explore the power of statistical mechanical thinking in the biological setting, with special emphasis on cell signaling and regulation. We show how such models are used to make predictions and describe some recent experiments designed to test them. We also consider the limits of such models based on the relative timescales of the processes of interest. PMID:27429713

  6. Napoleon Is in Equilibrium

    NASA Astrophysics Data System (ADS)

    Phillips, Rob

    2015-03-01

    It has been said that the cell is the test tube of the twenty-first century. If so, the theoretical tools needed to quantitatively and predictively describe what goes on in such test tubes lag sorely behind the stunning experimental advances in biology seen in the decades since the molecular biology revolution began. Perhaps surprisingly, one of the theoretical tools that has been used with great success on problems ranging from how cells communicate with their environment and each other to the nature of the organization of proteins and lipids within the cell membrane is statistical mechanics. A knee-jerk reaction to the use of statistical mechanics in the description of cellular processes is that living organisms are so far from equilibrium that one has no business even thinking about it. But such reactions are probably too hasty given that there are many regimes in which, because of a separation of timescales, for example, such an approach can be a useful first step. In this article, we explore the power of statistical mechanical thinking in the biological setting, with special emphasis on cell signaling and regulation. We show how such models are used to make predictions and describe some recent experiments designed to test them. We also consider the limits of such models based on the relative timescales of the processes of interest.

  7. Large-scale screening of metal hydrides for hydrogen storage from first-principles calculations based on equilibrium reaction thermodynamics.

    PubMed

    Kim, Ki Chul; Kulkarni, Anant D; Johnson, J Karl; Sholl, David S

    2011-04-21

    Systematic thermodynamics calculations based on density functional theory-calculated energies for crystalline solids have been a useful complement to experimental studies of hydrogen storage in metal hydrides. We report the most comprehensive set of thermodynamics calculations for mixtures of light metal hydrides to date by performing grand canonical linear programming screening on a database of 359 compounds, including 147 compounds not previously examined by us. This database is used to categorize the reaction thermodynamics of all mixtures containing any four non-H elements among Al, B, C, Ca, K, Li, Mg, N, Na, Sc, Si, Ti, and V. Reactions are categorized according to the amount of H(2) that is released and the reaction's enthalpy. This approach identifies 74 distinct single step reactions having that a storage capacity >6 wt.% and zero temperature heats of reaction 15 ≤ΔU(0)≤ 75 kJ mol(-1) H(2). Many of these reactions, however, are likely to be problematic experimentally because of the role of refractory compounds, B(12)H(12)-containing compounds, or carbon. The single most promising reaction identified in this way involves LiNH(2)/LiH/KBH(4), storing 7.48 wt.% H(2) and having ΔU(0) = 43.6 kJ mol(-1) H(2). We also examined the complete range of reaction mixtures to identify multi-step reactions with useful properties; this yielded 23 multi-step reactions of potential interest. PMID:21409194

  8. Estimation of polycyclic aromatic hydrocarbon concentrations in the water column based on tissue residues in mussels and salmon: An equilibrium partitioning approach

    SciTech Connect

    Neff, J.M.; Burns, W.A.

    1996-12-01

    Equilibrium partitioning was used to estimate concentrations of dissolved polycyclic aromatic hydrocarbons (PAHs) in the water column from PAH residues in tissues of mussels and juvenile pink salmon collected from coastal marine waters affected by the Exxon Valdez oil spill. Estimated concentrations were within factors of 2 to 5 for fish and 5 to 10 for mussels of average total dissolved and particulate PAHs measured in concurrent water samples. Temporal trends of estimated and measured water-column PAH concentrations were comparable. Water-column PAH concentrations estimated from residues in tissues of mussels (Mytilus trossulus) were higher than estimates based on residues in tissues of juvenile pink salmon (Oncorhynchus gorbuscha). Possible reasons for this difference include seasonal variations in mussel lipid content, differences in PAH uptake and depuration rates between fish and mussels, differences in how fish and mussels interact with particulate oil, and possible short exposure times for juvenile pink salmon. All of these factors may play a role. In any event, estimates of dissolved PAHs in the water column, based on PAH residues in either fish or mussel tissue, confirm that PAH concentrations generally did not exceed water quality standards for protection of marine life.

  9. Equilibrium games in networks

    NASA Astrophysics Data System (ADS)

    Li, Angsheng; Zhang, Xiaohui; Pan, Yicheng; Peng, Pan

    2014-12-01

    It seems a universal phenomenon of networks that the attacks on a small number of nodes by an adversary player Alice may generate a global cascading failure of the networks. It has been shown (Li et al., 2013) that classic scale-free networks (Barabási and Albert, 1999, Barabási, 2009) are insecure against attacks of as small as O(logn) many nodes. This poses a natural and fundamental question: Can we introduce a second player Bob to prevent Alice from global cascading failure of the networks? We proposed a game in networks. We say that a network has an equilibrium game if the second player Bob has a strategy to balance the cascading influence of attacks by the adversary player Alice. It was shown that networks of the preferential attachment model (Barabási and Albert, 1999) fail to have equilibrium games, that random graphs of the Erdös-Rényi model (Erdös and Rényi, 1959, Erdös and Rényi, 1960) have, for which randomness is the mechanism, and that homophyly networks (Li et al., 2013) have equilibrium games, for which homophyly and preferential attachment are the underlying mechanisms. We found that some real networks have equilibrium games, but most real networks fail to have. We anticipate that our results lead to an interesting new direction of network theory, that is, equilibrium games in networks.

  10. A Lakatosian Conceptual Change Teaching Strategy Based on Student Ability To Build Models with Varying Degrees of Conceptual Understanding of Chemical Equilibrium.

    ERIC Educational Resources Information Center

    Niaz, Mansoor

    1998-01-01

    Reports on a study that constructs a Lakatosian teaching strategy that can facilitate conceptual change in students' understanding of chemical equilibrium. Results indicate that the experimental group performed better on tests. Contains 81 references. (DDR)

  11. A New Methodology for Open Pit Slope Design in Karst-Prone Ground Conditions Based on Integrated Stochastic-Limit Equilibrium Analysis

    NASA Astrophysics Data System (ADS)

    Zhang, Ke; Cao, Ping; Ma, Guowei; Fan, Wenchen; Meng, Jingjing; Li, Kaihui

    2016-07-01

    Using the Chengmenshan Copper Mine as a case study, a new methodology for open pit slope design in karst-prone ground conditions is presented based on integrated stochastic-limit equilibrium analysis. The numerical modeling and optimization design procedure contain a collection of drill core data, karst cave stochastic model generation, SLIDE simulation and bisection method optimization. Borehole investigations are performed, and the statistical result shows that the length of the karst cave fits a negative exponential distribution model, but the length of carbonatite does not exactly follow any standard distribution. The inverse transform method and acceptance-rejection method are used to reproduce the length of the karst cave and carbonatite, respectively. A code for karst cave stochastic model generation, named KCSMG, is developed. The stability of the rock slope with the karst cave stochastic model is analyzed by combining the KCSMG code and the SLIDE program. This approach is then applied to study the effect of the karst cave on the stability of the open pit slope, and a procedure to optimize the open pit slope angle is presented.

  12. Reversible inhibition of proton release activity and the anesthetic-induced acid-base equilibrium between the 480 and 570 nm forms of bacteriorhodopsin.

    PubMed Central

    Boucher, F; Taneva, S G; Elouatik, S; Déry, M; Messaoudi, S; Harvey-Girard, E; Beaudoin, N

    1996-01-01

    In purple membrane added with general anesthetics, there exists an acid-base equilibrium between two spectral forms of the pigment: bR570 and bR480 (apparent pKa = 7.3). As the purple 570 nm bacteriorhodopsin is reversibly transformed into its red 480 nm form, the proton pumping capability of the pigment reversibly decreases, as indicated by transient proton release measurements and proton translocation action spectra of mixture of both spectral forms. It happens in spite of a complete photochemical activity in bR480 that is mostly characterized by fast deprotonation and slow reprotonation steps and which, under continuous illumination, bleaches with a yield comparable to that of bR570. This modified photochemical activity has a correlated specific photoelectrical counterpart: a faster proton extrusion current and a slower reprotonation current. The relative areas of all photocurrent phases are reduced in bR480, most likely because its photochemistry is accompanied by charge movements for shorter distances than in the native pigment, reflecting a reversible inhibition of the pumping activity. PMID:8789112

  13. Princeton spectral equilibrium code: PSEC

    SciTech Connect

    Ling, K.M.; Jardin, S.C.

    1984-03-01

    A fast computer code has been developed to calculate free-boundary solutions to the plasma equilibrium equation that are consistent with the currents in external coils and conductors. The free-boundary formulation is based on the minimization of a mean-square error epsilon while the fixed-boundary solution is based on a variational principle and spectral representation of the coordinates x(psi,theta) and z(psi,theta). Specific calculations using the Columbia University Torus II, the Poloidal Divertor Experiment (PDX), and the Tokamak Fusion Test Reactor (TFTR) geometries are performed.

  14. [Principle of genetic equilibrium for two gene loci].

    PubMed

    Pan, Shen-Yuan; Qu, Ai; Hui, Peng; Li, Ai-Ling

    2004-03-01

    Because linkage equilibrium is introduced by directly quoting the conclusions or imprecise mathematical reasoning in most of textbooks, many students are puzzled with the problem of linkage equilibrium when they learn population genetics. Based on the radical conditions of genetic equilibrium, the principle of linkage equilibrium condition and process, for two gene loci is introduced by precise mathematical reasoning. The article may provide reference to teachers and students in the teaching and learning of population genetics. PMID:15639991

  15. An Updated Equilibrium Machine

    ERIC Educational Resources Information Center

    Schultz, Emeric

    2008-01-01

    A device that can demonstrate equilibrium, kinetic, and thermodynamic concepts is described. The device consists of a leaf blower attached to a plastic container divided into two chambers by a barrier of variable size and form. Styrofoam balls can be exchanged across the barrier when the leaf blower is turned on and various air pressures are…

  16. Stochastic approach to equilibrium and nonequilibrium thermodynamics.

    PubMed

    Tomé, Tânia; de Oliveira, Mário J

    2015-04-01

    We develop the stochastic approach to thermodynamics based on stochastic dynamics, which can be discrete (master equation) and continuous (Fokker-Planck equation), and on two assumptions concerning entropy. The first is the definition of entropy itself and the second the definition of entropy production rate, which is non-negative and vanishes in thermodynamic equilibrium. Based on these assumptions, we study interacting systems with many degrees of freedom in equilibrium or out of thermodynamic equilibrium and how the macroscopic laws are derived from the stochastic dynamics. These studies include the quasiequilibrium processes; the convexity of the equilibrium surface; the monotonic time behavior of thermodynamic potentials, including entropy; the bilinear form of the entropy production rate; the Onsager coefficients and reciprocal relations; and the nonequilibrium steady states of chemical reactions. PMID:25974471

  17. Stochastic approach to equilibrium and nonequilibrium thermodynamics

    NASA Astrophysics Data System (ADS)

    Tomé, Tânia; de Oliveira, Mário J.

    2015-04-01

    We develop the stochastic approach to thermodynamics based on stochastic dynamics, which can be discrete (master equation) and continuous (Fokker-Planck equation), and on two assumptions concerning entropy. The first is the definition of entropy itself and the second the definition of entropy production rate, which is non-negative and vanishes in thermodynamic equilibrium. Based on these assumptions, we study interacting systems with many degrees of freedom in equilibrium or out of thermodynamic equilibrium and how the macroscopic laws are derived from the stochastic dynamics. These studies include the quasiequilibrium processes; the convexity of the equilibrium surface; the monotonic time behavior of thermodynamic potentials, including entropy; the bilinear form of the entropy production rate; the Onsager coefficients and reciprocal relations; and the nonequilibrium steady states of chemical reactions.

  18. Local Nash Equilibrium in Social Networks

    PubMed Central

    Zhang, Yichao; Aziz-Alaoui, M. A.; Bertelle, Cyrille; Guan, Jihong

    2014-01-01

    Nash equilibrium is widely present in various social disputes. As of now, in structured static populations, such as social networks, regular, and random graphs, the discussions on Nash equilibrium are quite limited. In a relatively stable static gaming network, a rational individual has to comprehensively consider all his/her opponents' strategies before they adopt a unified strategy. In this scenario, a new strategy equilibrium emerges in the system. We define this equilibrium as a local Nash equilibrium. In this paper, we present an explicit definition of the local Nash equilibrium for the two-strategy games in structured populations. Based on the definition, we investigate the condition that a system reaches the evolutionary stable state when the individuals play the Prisoner's dilemma and snow-drift game. The local Nash equilibrium provides a way to judge whether a gaming structured population reaches the evolutionary stable state on one hand. On the other hand, it can be used to predict whether cooperators can survive in a system long before the system reaches its evolutionary stable state for the Prisoner's dilemma game. Our work therefore provides a theoretical framework for understanding the evolutionary stable state in the gaming populations with static structures. PMID:25169150

  19. A DFT-based comparative equilibrium study of thermal dehydration and hydrolysis of CaCl₂ hydrates and MgCl₂ hydrates for seasonal heat storage.

    PubMed

    Pathak, Amar Deep; Nedea, Silvia; Zondag, Herbert; Rindt, Camilo; Smeulders, David

    2016-04-21

    Salt hydrates store solar energy in chemical form via a reversible dehydration-hydration reaction. However, as a side reaction to dehydration, hydrolysis (HCl formation) may occur in chloride based salt hydrates (specially in MgCl2 hydrates), affecting the durability of the storage system. The mixture of CaCl2 and MgCl2 hydrates has been shown experimentally to have exceptional cycle stability and improved kinetics. However, the optimal operating conditions for the mixture are unknown. To understand the appropriate balance between dehydration and hydrolysis kinetics in the mixtures, it is essential to gain in-depth insight into the mixture components. We present a GGA-DFT level study to investigate the various gaseous structures of CaCl2 hydrates and to understand the relative stability of their conformers. The hydration strength and relative stability of conformers are dominated by electrostatic interactions. A wide network of intramolecular homonuclear and heteronuclear hydrogen bonds is observed in CaCl2 hydrates. Equilibrium product concentrations are obtained during dehydration and hydrolysis reactions under various temperature and pressure conditions. The trend of the dehydration curve with temperature in CaCl2 hydrates is similar to the experiments. Comparing these results to those of MgCl2 hydrates, we find that CaCl2 hydrates are more resistant towards hydrolysis in the temperature range of 273-800 K. Specifically, the present study reveals that the onset temperatures of HCl formation, a crucial design parameter for MgCl2 hydrates, are lower than for CaCl2 hydrates except for the mono-hydrate. PMID:27004734

  20. Higher-order compositional modeling of three-phase flow in 3D fractured porous media based on cross-flow equilibrium

    SciTech Connect

    Moortgat, Joachim Firoozabadi, Abbas

    2013-10-01

    Numerical simulation of multiphase compositional flow in fractured porous media, when all the species can transfer between the phases, is a real challenge. Despite the broad applications in hydrocarbon reservoir engineering and hydrology, a compositional numerical simulator for three-phase flow in fractured media has not appeared in the literature, to the best of our knowledge. In this work, we present a three-phase fully compositional simulator for fractured media, based on higher-order finite element methods. To achieve computational efficiency, we invoke the cross-flow equilibrium (CFE) concept between discrete fractures and a small neighborhood in the matrix blocks. We adopt the mixed hybrid finite element (MHFE) method to approximate convective Darcy fluxes and the pressure equation. This approach is the most natural choice for flow in fractured media. The mass balance equations are discretized by the discontinuous Galerkin (DG) method, which is perhaps the most efficient approach to capture physical discontinuities in phase properties at the matrix-fracture interfaces and at phase boundaries. In this work, we account for gravity and Fickian diffusion. The modeling of capillary effects is discussed in a separate paper. We present the mathematical framework, using the implicit-pressure-explicit-composition (IMPEC) scheme, which facilitates rigorous thermodynamic stability analyses and the computation of phase behavior effects to account for transfer of species between the phases. A deceptively simple CFL condition is implemented to improve numerical stability and accuracy. We provide six numerical examples at both small and larger scales and in two and three dimensions, to demonstrate powerful features of the formulation.

  1. An Updated Equilibrium Machine

    NASA Astrophysics Data System (ADS)

    Schultz, Emeric

    2008-08-01

    A device that can demonstrate equilibrium, kinetic, and thermodynamic concepts is described. The device consists of a leaf blower attached to a plastic container divided into two chambers by a barrier of variable size and form. Styrofoam balls can be exchanged across the barrier when the leaf blower is turned on and various air pressures are applied. Equilibrium can be approached from different distributions of balls in the container under different conditions. The Le Châtelier principle can be demonstrated. Kinetic concepts can be demonstrated by changing the nature of the barrier, either changing the height or by having various sized holes in the barrier. Thermodynamic concepts can be demonstrated by taping over some or all of the openings and restricting air flow into container on either side of the barrier.

  2. Absolute Equilibrium Entropy

    NASA Technical Reports Server (NTRS)

    Shebalin, John V.

    1997-01-01

    The entropy associated with absolute equilibrium ensemble theories of ideal, homogeneous, fluid and magneto-fluid turbulence is discussed and the three-dimensional fluid case is examined in detail. A sigma-function is defined, whose minimum value with respect to global parameters is the entropy. A comparison is made between the use of global functions sigma and phase functions H (associated with the development of various H-theorems of ideal turbulence). It is shown that the two approaches are complimentary though conceptually different: H-theorems show that an isolated system tends to equilibrium while sigma-functions allow the demonstration that entropy never decreases when two previously isolated systems are combined. This provides a more complete picture of entropy in the statistical mechanics of ideal fluids.

  3. Solids Far from Equilibrium

    NASA Astrophysics Data System (ADS)

    Godrèche, C.

    2011-03-01

    Preface; 1. Shape and growth of crystals P. Nozières; 2. Instabilities of planar solidification fronts B. Caroli, C. Caroli and B. Roulet; 3. An introduction to the kinetics of first-order phase transition J. S. Langer; 4. Dendritic growth and related topics Y. Pomeau and M. Ben Amar; 5. Growth and aggregation far from equilibrium L. M. Sander; 6. Kinetic roughening of growing surfaces J. Krug and H. Spohn; Acknowledgements; References; Index.

  4. Exoplanet Equilibrium Chemistry Calculations

    NASA Astrophysics Data System (ADS)

    Blumenthal, Sarah; Harrington, J.; Bowman, M.; Blecic, J.

    2013-10-01

    Recently, Agundez et al. (2012, A&A 548, A73) used a chemical kinetics code to study a model HD 209458b (equilibrium temperature of 1450 K, assuming full redistribution and 0 albedo). They found that thermochemistry dominates most of the dayside, but that significant compositional gradients may exist across the dayside. We calculate equilibrium-chemistry molecular abundances for several model exoplanets, using NASA's open-source Chemical Equilibrium Abundances code (McBride and Gordon 1996). We vary the degree of radiation redistribution to the dark side, ranging from total redistribution to instantaneous reradiation. Atomically, both the solar abundance multiple and the carbon fraction vary. Planet substellar temperatures range from just above 1200 K, where photochemistry should no longer be important, to those of hot planets (3000 K). We present synthetic abundance images for the key spectroscopic molecules CO, CH4, and H2O for several hot-Jupiter model planets. This work was supported by the NASA Planetary Atmospheres grant NNX12AI69G.

  5. Equilibrium Electroconvective Instability

    NASA Astrophysics Data System (ADS)

    Rubinstein, I.; Zaltzman, B.

    2015-03-01

    Since its prediction 15 years ago, hydrodynamic instability in concentration polarization at a charge-selective interface has been attributed to nonequilibrium electro-osmosis related to the extended space charge which develops at the limiting current. This attribution had a double basis. On the one hand, it has been recognized that neither equilibrium electro-osmosis nor bulk electroconvection can yield instability for a perfectly charge-selective solid. On the other hand, it has been shown that nonequilibrium electro-osmosis can. The first theoretical studies in which electro-osmotic instability was predicted and analyzed employed the assumption of perfect charge selectivity for the sake of simplicity and so did the subsequent studies of various time-dependent and nonlinear features of electro-osmotic instability. In this Letter, we show that relaxing the assumption of perfect charge selectivity (tantamount to fixing the electrochemical potential of counterions in the solid) allows for the equilibrium electroconvective instability. In addition, we suggest a simple experimental test for determining the true, either equilibrium or nonequilibrium, origin of instability in concentration polarization.

  6. A numerical study of EGS heat extraction process based on a thermal non-equilibrium model for heat transfer in subsurface porous heat reservoir

    NASA Astrophysics Data System (ADS)

    Chen, Jiliang; Jiang, Fangming

    2016-02-01

    With a previously developed numerical model, we perform a detailed study of the heat extraction process in enhanced or engineered geothermal system (EGS). This model takes the EGS subsurface heat reservoir as an equivalent porous medium while it considers local thermal non-equilibrium between the rock matrix and the fluid flowing in the fractured rock mass. The application of local thermal non-equilibrium model highlights the temperature-difference heat exchange process occurring in EGS reservoirs, enabling a better understanding of the involved heat extraction process. The simulation results unravel the mechanism of preferential flow or short-circuit flow forming in homogeneously fractured reservoirs of different permeability values. EGS performance, e.g. production temperature and lifetime, is found to be tightly related to the flow pattern in the reservoir. Thermal compensation from rocks surrounding the reservoir contributes little heat to the heat transmission fluid if the operation time of an EGS is shorter than 15 years. We find as well the local thermal equilibrium model generally overestimates EGS performance and for an EGS with better heat exchange conditions in the heat reservoir, the heat extraction process acts more like the local thermal equilibrium process.

  7. Phase-equilibrium geobarometers for silicic rocks based on rhyolite-MELTS—Part 3: Application to the Peach Spring Tuff (Arizona-California-Nevada, USA)

    NASA Astrophysics Data System (ADS)

    Pamukcu, Ayla S.; Gualda, Guilherme A. R.; Ghiorso, Mark S.; Miller, Calvin F.; McCracken, Reba G.

    2015-03-01

    Establishing the depths of magma accumulation is critical to understanding how magmas evolve and erupt, but developing methods to constrain these pressures is challenging. We apply the new rhyolite-MELTS phase-equilibria geobarometer—based on the equilibrium between melt, quartz, and two feldspars—to matrix glass compositions from Peach Spring Tuff (Arizona-California-Nevada, USA) high-silica rhyolite. We compare the results to those from amphibole geothermobarometry, projection of glass compositions onto the haplogranitic ternary, and glass SiO2 geobarometry. Quartz + 2 feldspar rhyolite-MELTS pressures span a relatively small range (185-230 MPa), consistent with nearly homogeneous crystal compositions, and are similar to estimates based on projection onto the haplogranitic ternary (250 ± 50 MPa) and on glass SiO2 (255-275 MPa). Amphibole geothermobarometry gives much wider pressure ranges (temperature-independent: ~65-300 MPa; temperature-dependent: ~75-295 MPa; amphibole-only: ~80-950 MPa); average Anderson and Smith (Am Mineral 80:549-559, 1995) + Blundy and Holland (Contrib Miner Petrol 104:208-224, 1990) or Holland and Blundy (Contrib Miner Petrol 116:433-447, 1994—Thermometer A, B) pressures are most similar to phase-equilibria results (~220, 210, 190 MPa, respectively). Crystallization temperatures determined previously with rhyolite-MELTS (742 °C), Zr-in-sphene (769 ± 20 °C), and zircon saturation (770-780 °C) geothermometry are similar, but temperatures from amphibole geothermometry (~450-955 °C) are notably different; the average Anderson and Smith + Holland and Blundy (1994—Thermometer B; ~710 °C) temperature is most consistent with previous estimates. The rhyolite-MELTS geobarometer effectively culls glass compositions affected by alteration or analytical issues; Peach Spring glass compositions that yield pressure estimates reveal a tight range of plausible Na2O and K2O contents, suggesting that low Na2O and high K2O contents of many

  8. Structural design using equilibrium programming

    NASA Technical Reports Server (NTRS)

    Scotti, Stephen J.

    1992-01-01

    Multiple nonlinear programming methods are combined in the method of equilibrium programming. Equilibrium programming theory has been appied to problems in operations research, and in the present study it is investigated as a framework to solve structural design problems. Several existing formal methods for structural optimization are shown to actually be equilibrium programming methods. Additionally, the equilibrium programming framework is utilized to develop a new structural design method. Selected computational results are presented to demonstrate the methods.

  9. Theory for non-equilibrium statistical mechanics.

    PubMed

    Attard, Phil

    2006-08-21

    This paper reviews a new theory for non-equilibrium statistical mechanics. This gives the non-equilibrium analogue of the Boltzmann probability distribution, and the generalization of entropy to dynamic states. It is shown that this so-called second entropy is maximized in the steady state, in contrast to the rate of production of the conventional entropy, which is not an extremum. The relationships of the new theory to Onsager's regression hypothesis, Prigogine's minimal entropy production theorem, the Langevin equation, the formula of Green and Kubo, the Kawasaki distribution, and the non-equilibrium fluctuation and work theorems, are discussed. The theory is worked through in full detail for the case of steady heat flow down an imposed temperature gradient. A Monte Carlo algorithm based upon the steady state probability density is summarized, and results for the thermal conductivity of a Lennard-Jones fluid are shown to be in agreement with known values. Also discussed is the generalization to non-equilibrium mechanical work, and to non-equilibrium quantum statistical mechanics. As examples of the new theory two general applications are briefly explored: a non-equilibrium version of the second law of thermodynamics, and the origin and evolution of life. PMID:16883388

  10. Iron isotope fractionation between aqueous Fe(II) and goethite revisited: New insights based on a multi-direction approach to equilibrium and isotopic exchange rate modification

    NASA Astrophysics Data System (ADS)

    Frierdich, Andrew J.; Beard, Brian L.; Reddy, Thiruchelvi R.; Scherer, Michelle M.; Johnson, Clark M.

    2014-08-01

    The Fe isotope compositions of naturally occurring Fe oxide minerals provide insights into biogeochemical processes that occur in modern and ancient environments. Key to understanding isotopic variations in such minerals is knowledge of the equilibrium Fe isotope fractionation factors between common minerals and aqueous Fe species. Because experimental measurements of isotopic fractionation may reflect a combination of kinetic and equilibrium fractionations during rapid dissolution and precipitation, even in experiments that employ the three-isotope method, assessment of the attainment of equilibrium is often difficult. Here, we re-examine Fe isotope exchange, via a 57Fe tracer, and natural mass-dependent fractionation, through changes in initial 56Fe/54Fe ratios, between aqueous Fe(II) (Fe(II)aq) and goethite. This approach uses the three-isotope method, but is distinct in its evaluation of kinetic isotope fractionation and the attainment of equilibrium by: (i) employing a multi-direction approach to equilibrium at 22 °C via reaction of three Fe(II)aq solutions that had different initial 56Fe/54Fe ratios, (ii) conducting isotopic exchange experiments at elevated temperature (50 °C), and (iii) modifying the rate of isotopic exchange through a combination of trace-element substitutions and particle coarsening to evaluate corresponding temporal changes in fractionation trajectories that may reflect changing instantaneous fractionation factors. We find that rapid isotopic exchange produces kinetic isotope effects between Fe(II)aq and goethite, which shifts the 56Fe/54Fe ratios of Fe(II)aq early in reactions toward that of goethite, indicating that the instantaneous Fe(II)aq-goethite fractionation factor under kinetic conditions is small. Importantly, however, this kinetic fractionation is “erased” with continued reaction, and this is evident by the congruence for multiple-exchange trajectories of distinct initial Fe(II)aq solutions toward the same final value

  11. Non-equilibrium DMFT - Polaritonics

    NASA Astrophysics Data System (ADS)

    Lubatsch, Andreas; Frank, Regine

    Non-equilibrium physics recently really becomes important with the progress of ultrafast laser sciences. However in our understanding there is still a gap between equilibrium physics and the non-equilibrium, even though numerical methods have been advanced in recent years. We compare in this talk novel results at hand with equilibrium physics. The comparison will show that especially theoretical efforts are needed to explain many - so far - unresolved problems and to predict novel research on the basis of ab initio computing. We specifically discuss several non-equilibrium extensions of DMFT, numerical methods as well as semi-analytical solvers.

  12. On applicability of the photochemical-equilibrium approach for retrieval of O and H mesospheric distributions from the satellite-based measurements of the airglow emission and ozone concentration

    NASA Astrophysics Data System (ADS)

    Feigin, Alexander; Belikovich, Mikhail; Kulikov, Mikhail

    2016-04-01

    Atomic oxygen and hydrogen are known to be among key components for the photochemistry and energy balance of the Earth's atmosphere between approximately 80 and 100 km altitude (mesopause region). Therefore, obtaining information about the vertical distributions of O and H concentrations is an important task in studies of this region. Solving of this problem is rather difficult due to the absence of regular methods which allow one to direct measurements of distributions of these components in mesosphere. However, indirect methods used to retrieve O and H distributions from the satellite-based measurements of the OH and O2(1D) airglow emission, as well as the data of IR and microwave O3 measurements have a sufficiently long development history. These methods are rooted in the use of the condition of photochemical equilibrium of ozone density in the range of altitudes from 50 to 100 km. A significant factor is that an insufficient volume of such measurement data forces researchers to use approximate ("truncated") photochemical-equilibrium conditions. In particular, it is assumed that in the daytime the ozone production reaction is perfectly balanced by ozone photodissociation, whereas during the night the only ozone sink is the reaction of ozone with atomic hydrogen, which, in its turn, leads to formation of excited OH and airglow emission of the latter. The presentation analyzes applicability of the photochemical-equilibrium conditions both in the total and truncated forms for description of the spatio-temporal evolution of mesospheric ozone during a year. The analysis is based on year-long time series generated by a 3D chemical transport model, which reproduces correctly various types of atmosphere dynamics in the range of altitudes from 50 to 100 km. These data are used to determine statistics of the ratio between the correct (calculated dynamically) distributions of the O3 density and its uncontracted and truncated equilibrium values for the conditions of the

  13. Thermal equilibrium of goats.

    PubMed

    Maia, Alex S C; Nascimento, Sheila T; Nascimento, Carolina C N; Gebremedhin, Kifle G

    2016-05-01

    The effects of air temperature and relative humidity on thermal equilibrium of goats in a tropical region was evaluated. Nine non-pregnant Anglo Nubian nanny goats were used in the study. An indirect calorimeter was designed and developed to measure oxygen consumption, carbon dioxide production, methane production and water vapour pressure of the air exhaled from goats. Physiological parameters: rectal temperature, skin temperature, hair-coat temperature, expired air temperature and respiratory rate and volume as well as environmental parameters: air temperature, relative humidity and mean radiant temperature were measured. The results show that respiratory and volume rates and latent heat loss did not change significantly for air temperature between 22 and 26°C. In this temperature range, metabolic heat was lost mainly by convection and long-wave radiation. For temperature greater than 30°C, the goats maintained thermal equilibrium mainly by evaporative heat loss. At the higher air temperature, the respiratory and ventilation rates as well as body temperatures were significantly elevated. It can be concluded that for Anglo Nubian goats, the upper limit of air temperature for comfort is around 26°C when the goats are protected from direct solar radiation. PMID:27157333

  14. Equilibrium gas flow computations. I - Accurate and efficient calculation of equilibrium gas properties

    NASA Technical Reports Server (NTRS)

    Liu, Yen; Vinokur, Marcel

    1989-01-01

    This paper treats the accurate and efficient calculation of thermodynamic properties of arbitrary gas mixtures for equilibrium flow computations. New improvements in the Stupochenko-Jaffe model for the calculation of thermodynamic properties of diatomic molecules are presented. A unified formulation of equilibrium calculations for gas mixtures in terms of irreversible entropy is given. Using a highly accurate thermo-chemical data base, a new, efficient and vectorizable search algorithm is used to construct piecewise interpolation procedures with generate accurate thermodynamic variable and their derivatives required by modern computational algorithms. Results are presented for equilibrium air, and compared with those given by the Srinivasan program.

  15. Statistical physics ""Beyond equilibrium

    SciTech Connect

    Ecke, Robert E

    2009-01-01

    The scientific challenges of the 21st century will increasingly involve competing interactions, geometric frustration, spatial and temporal intrinsic inhomogeneity, nanoscale structures, and interactions spanning many scales. We will focus on a broad class of emerging problems that will require new tools in non-equilibrium statistical physics and that will find application in new material functionality, in predicting complex spatial dynamics, and in understanding novel states of matter. Our work will encompass materials under extreme conditions involving elastic/plastic deformation, competing interactions, intrinsic inhomogeneity, frustration in condensed matter systems, scaling phenomena in disordered materials from glasses to granular matter, quantum chemistry applied to nano-scale materials, soft-matter materials, and spatio-temporal properties of both ordinary and complex fluids.

  16. Exploring Chemical Equilibrium with Poker Chips: A General Chemistry Laboratory Exercise

    ERIC Educational Resources Information Center

    Bindel, Thomas H.

    2012-01-01

    A hands-on laboratory exercise at the general chemistry level introduces students to chemical equilibrium through a simulation that uses poker chips and rate equations. More specifically, the exercise allows students to explore reaction tables, dynamic chemical equilibrium, equilibrium constant expressions, and the equilibrium constant based on…

  17. Forebody and base region real gas flow in severe planetary entry by a factored implicit numerical method. II - Equilibrium reactive gas

    NASA Technical Reports Server (NTRS)

    Davy, W. C.; Green, M. J.; Lombard, C. K.

    1981-01-01

    The factored-implicit, gas-dynamic algorithm has been adapted to the numerical simulation of equilibrium reactive flows. Changes required in the perfect gas version of the algorithm are developed, and the method of coupling gas-dynamic and chemistry variables is discussed. A flow-field solution that approximates a Jovian entry case was obtained by this method and compared with the same solution obtained by HYVIS, a computer program much used for the study of planetary entry. Comparison of surface pressure distribution and stagnation line shock-layer profiles indicates that the two solutions agree well.

  18. Thermodynamic equilibrium at heterogeneous pressure

    NASA Astrophysics Data System (ADS)

    Vrijmoed, Johannes C.; Podladchikov, Yuri Y.

    2014-05-01

    Recent advances in metamorphic petrology point out the importance of grain-scale pressure variations in high-temperature metamorphic rocks. Pressures derived from chemical zonation using unconventional geobarometry based on equal chemical potentials fit mechanically feasible pressure variations. Here a thermodynamic equilibrium method is presented that predicts chemical zoning as a result of pressure variations by Gibbs energy minimization. Equilibrium thermodynamic prediction of the chemical zoning in the case of pressure heterogeneity is done by constraint Gibbs minimization using linear programming techniques. Compositions of phases considered in the calculation are discretized into 'pseudo-compounds' spanning the entire compositional space. Gibbs energies of these discrete compounds are generated for a given range and resolution of pressures for example derived by barometry or from mechanical model predictions. Gibbs energy minimization is subsequently performed considering all compounds of different composition and pressure. In addition to constraining the system composition a certain proportion of the system is constraint at a specified pressure. Input pressure variations need to be discretized and each discrete pressure defines an additional constraint for the minimization. The proportion of the system at each different pressure is equally distributed over the number of input pressures. For example if two input pressures P1 and P2 are specified, two constraints are added: 50 percent of the system is constraint at P1 while the remaining 50 percent is constraint at P2. The method has been tested for a set of 10 input pressures obtained by Tajčmanová et al. (2014) using their unconventional geobarometry method in a plagioclase rim around kyanite. Each input pressure is added as constraint to the minimization (1/10 percent of the system for each discrete pressure). Constraining the system composition to the average composition of the plagioclase rim

  19. Neoclassical equilibrium in gyrokinetic simulations

    SciTech Connect

    Garbet, X.; Dif-Pradalier, G.; Nguyen, C.; Sarazin, Y.; Grandgirard, V.; Ghendrih, Ph.

    2009-06-15

    This paper presents a set of model collision operators, which reproduce the neoclassical equilibrium and comply with the constraints of a full-f global gyrokinetic code. The assessment of these operators is based on an entropy variational principle, which allows one to perform a fast calculation of the neoclassical diffusivity and poloidal velocity. It is shown that the force balance equation is recovered at lowest order in the expansion parameter, the normalized gyroradius, hence allowing one to calculate correctly the radial electric field. Also, the conventional neoclassical transport and the poloidal velocity are reproduced in the plateau and banana regimes. The advantages and drawbacks of the various model operators are discussed in view of the requirements for neoclassical and turbulent transport.

  20. Equilibrium Potentials of Membrane Electrodes

    PubMed Central

    Wang, Jui H.; Copeland, Eva

    1973-01-01

    A simple thermodynamic theory of the equilibrium potentials of membrane electrodes is formulated and applied to the glass electrode for measurement of pH. The new formulation assumes the selective adsorption or binding of specific ions on the surface of the membrane which may or may not be permeable to the ion, and includes the conventional derivation based on reversible ion transport across membranes as a special case. To test the theory, a platinum wire was coated with a mixture of stearic acid and methyl-tri-n-octyl-ammonium stearate. When this coated electrode was immersed in aqueous phosphate solution, its potential was found to be a linear function of pH from pH 2 to 12 with a slope equal to the theoretical value of 59.0 mV per pH unit at 24°. PMID:4516194

  1. The Nash equilibrium: a perspective.

    PubMed

    Holt, Charles A; Roth, Alvin E

    2004-03-23

    In 1950, John Nash contributed a remarkable one-page PNAS article that defined and characterized a notion of equilibrium for n- person games. This notion, now called the "Nash equilibrium," has been widely applied and adapted in economics and other behavioral sciences. Indeed, game theory, with the Nash equilibrium as its centerpiece, is becoming the most prominent unifying theory of social science. In this perspective, we summarize the historical context and subsequent impact of Nash's contribution. PMID:15024100

  2. Grinding kinetics and equilibrium states

    NASA Technical Reports Server (NTRS)

    Opoczky, L.; Farnady, F.

    1984-01-01

    The temporary and permanent equilibrium occurring during the initial stage of cement grinding does not indicate the end of comminution, but rather an increased energy consumption during grinding. The constant dynamic equilibrium occurs after a long grinding period indicating the end of comminution for a given particle size. Grinding equilibrium curves can be constructed to show the stages of comminution and agglomeration for certain particle sizes.

  3. Chemical Equilibrium Composition of Aqueous Systems

    Energy Science and Technology Software Center (ESTSC)

    1996-12-30

    MINEQL is a subroutine package to calculate equilibrium composition of an aqueous system, accounting for mass transfer. MINEQL-EIR contains an additional base on enthalpy and heat capacity data and has the option to do calculations at temperatures different from 25 degrees C.

  4. Analytic prediction of airplane equilibrium spin characteristics

    NASA Technical Reports Server (NTRS)

    Adams, W. M., Jr.

    1972-01-01

    The nonlinear equations of motion are solved algebraically for conditions for which an airplane is in an equilibrium spin. Constrained minimization techniques are employed in obtaining the solution. Linear characteristics of the airplane about the equilibrium points are also presented and their significance in identifying the stability characteristics of the equilibrium points is discussed. Computer time requirements are small making the method appear potentially applicable in airplane design. Results are obtained for several configurations and are compared with other analytic-numerical methods employed in spin prediction. Correlation with experimental results is discussed for one configuration for which a rather extensive data base was available. A need is indicated for higher Reynolds number data taken under conditions which more accurately simulate a spin.

  5. Modeling equilibrium Fe isotope fractionation

    NASA Astrophysics Data System (ADS)

    Anbar, A.; Jarzecki, A.; Spiro, T.

    2003-04-01

    Research into the stable isotope biogeochemistry of Fe and other transition metals has been driven primarily by analytical innovations which have revealed significant isotope effects in nature and the laboratory. Further development of these new isotope systems requires complementary theoretical research to guide analytical efforts. The results of the first such studies show some discrepancies with experiments. For example, Johnson et al. (2002) report an experimentally-determined 56Fe/54Fe equilibrium fractionation factor between Fe(II) and Fe(III) aquo complexes of ˜1.0025. This effect is ˜50% smaller than predicted theoretically by Schauble et al. (2001). It is important to resolve such discrepancies. Equilibrium isotope fractionation factors can be predicted from vibrational spectroscopic data of isotopically-substituted complexes, or from theoretical predictions of some or all of these frequencies obtained using force field models. The pioneering work of Schauble et al. (2001) utilized a modified Urey-Bradley force field (MUBFF) model. This approach is limiting in at least three ways: First, it is not ab initio, requiring as input some measured vibrational frequencies. Such data are not always available, or may have significant uncertainties. Second, the MUBFF does not include potentially important effects of solvent interaction. Third, because it makes certain assumptions about molecular symmetry, the MUBFF-based approach is not able to model the spectra of mixed-ligand complexes. To address these limitations, we are evaluating the use of density functional theory (DFT) as an ab initio method to predict vibrational frequencies of isotopically-substituted complexes and, hence, equilibrium fractionation factors. In a preliminary examination of the frequency shift upon isotope substitution of the bending and asymmetric stretching modes of the tetrahedral FeCl_42- complex, we find substantial differences between MUBFF and DFT predictions. Results for other Fe

  6. Rapid-Equilibrium Enzyme Kinetics

    ERIC Educational Resources Information Center

    Alberty, Robert A.

    2008-01-01

    Rapid-equilibrium rate equations for enzyme-catalyzed reactions are especially useful because if experimental data can be fit by these simpler rate equations, the Michaelis constants can be interpreted as equilibrium constants. However, for some reactions it is necessary to use the more complicated steady-state rate equations. Thermodynamics is…

  7. Using Analogies to Prevent Misconceptions about Chemical Equilibrium

    ERIC Educational Resources Information Center

    Sahin Pekmez, Esin

    2010-01-01

    The main purpose of this study was to find the effectiveness of using analogies to prevent misconceptions about chemical equilibrium. Nineteen analogies, which were based on dynamic aspects of chemical equilibrium and application of Le Chatelier's principle, were developed. The participations of this study consisted of 11th grade students (n: 151)…

  8. Understanding Chemical Reaction Kinetics and Equilibrium with Interlocking Building Blocks

    ERIC Educational Resources Information Center

    Cloonan, Carrie A.; Nichol, Carolyn A.; Hutchinson, John S.

    2011-01-01

    Chemical reaction kinetics and equilibrium are essential core concepts of chemistry but are challenging topics for many students, both at the high school and undergraduate university level. Visualization at the molecular level is valuable to aid understanding of reaction kinetics and equilibrium. This activity provides a discovery-based method to…

  9. Chemical Equilibrium, Unit 3: Chemical Equilibrium Calculations. A Computer-Enriched Module for Introductory Chemistry. Student's Guide and Teacher's Guide.

    ERIC Educational Resources Information Center

    Jameson, Cynthia J.

    Presented are the teacher's guide and student materials for one of a series of self-instructional, computer-based learning modules for an introductory, undergraduate chemistry course. The student manual for this unit on chemical equilibrium calculations includes objectives, prerequisites, a discussion of the equilibrium constant (K), and ten…

  10. Spin-polarization and spin-dependent logic gates in a double quantum ring based on Rashba spin-orbit effect: Non-equilibrium Green's function approach

    SciTech Connect

    Eslami, Leila Esmaeilzadeh, Mahdi

    2014-02-28

    Spin-dependent electron transport in an open double quantum ring, when each ring is made up of four quantum dots and threaded by a magnetic flux, is studied. Two independent and tunable gate voltages are applied to induce Rashba spin-orbit effect in the quantum rings. Using non-equilibrium Green's function formalism, we study the effects of electron-electron interaction on spin-dependent electron transport and show that although the electron-electron interaction induces an energy gap, it has no considerable effect when the bias voltage is sufficiently high. We also show that the double quantum ring can operate as a spin-filter for both spin up and spin down electrons. The spin-polarization of transmitted electrons can be tuned from −1 (pure spin-down current) to +1 (pure spin-up current) by changing the magnetic flux and/or the gates voltage. Also, the double quantum ring can act as AND and NOR gates when the system parameters such as Rashba coefficient are properly adjusted.

  11. Study on an effective industrial waste-based adsorbent for the adsorptive removal of phosphorus from wastewater: equilibrium and kinetics studies.

    PubMed

    Xie, Ruzhen; Chen, Yao; Cheng, Ting; Lai, Yuguo; Jiang, Wenju; Yang, Zhishan

    2016-01-01

    In this work, an effective adsorbent for removing phosphate from aqueous solution was developed from modifying industrial waste--lithium silica fume (LSF). The characterization of LSF before and after modification was investigated using an N2 adsorption-desorption technique (Brunauer-Emmett-Teller, BET), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Studies were conducted to investigate the effect of adsorbent dose, initial solution pH, contact time, phosphate concentration, and temperature on phosphate removal using this novel adsorbent. The specific surface area for modified LSF (LLSF) is 24.4024 m(2)/g, improved 69.8% compared with unmodified LSF. XRD result suggests that the lanthanum phosphate complex was formed on the surface of LLSF. The maximum phosphate adsorption capacity was 24.096 mg P/g for LLSF, and phosphate removal was favored in the pH range of 3-8. The kinetic data fitted pseudo-second-order kinetic equation, intra-particle diffusion was not the only rate controlling step. The adsorption isotherm results illustrated that the Langmuir model provided the best fit for the equilibrium data. The change in free energy (△G(0)), enthalpy (△H(0)) and entropy (△S(0)) revealed that the adsorption of phosphate on LLSF was spontaneous and endothermic. It was concluded that by modifying with lanthanum, LSF can be turned to be a highly efficient adsorbent in phosphate removal. PMID:27120644

  12. Application of novel, low-cost, laterite-based adsorbent for removal of lead from water: Equilibrium, kinetic and thermodynamic studies.

    PubMed

    Chatterjee, Somak; De, Sirshendu

    2016-01-01

    Contamination of groundwater by carcinogenic heavy metal, e.g., lead is an important issue and possibility of using a natural rock, laterite, is explored in this work to mitigate this problem. Treated laterite (TL- prepared using hydrochloric acid and sodium hydroxide) was successfully utilized for this purpose. The adsorbent was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), and Fourier Transform Infrared Spectroscopy (FTIR) to highlight its physical and chemical properties. Optimized equilibrium conditions were 1 g L(-1) adsorbent concentration, 0.26 mm size and a pH of 7 ± 0.2. Monolayer adsorption capacity of lead on treated laterite was 15 mg/g, 14.5 and 13 mg g(-1) at temperatures of 303 K, 313 K and 323 K, respectively. The adsorption was exothermic and physical in nature. At 303 K, value of effective diffusivity of (De) and mass transfer co-efficient (Kf) of lead onto TL were 6.5 × 10(-10) m(2)/s and 3.3 × 10(-4) m/s, respectively (solved from shrinking core model of adsorption kinetics). Magnesium and sulphate show highest interference effect on the adsorption of lead by TL. Efficacy of the adsorbent has been verified using real-life contaminated groundwater. Thus, this work demonstrates performance of a cost-effective media for lead removal. PMID:26646980

  13. Unified theory of quantized electrons, phonons, and photons out of equilibrium: A simplified ab initio approach based on the generalized Baym-Kadanoff ansatz

    NASA Astrophysics Data System (ADS)

    de Melo, Pedro Miguel M. C.; Marini, Andrea

    2016-04-01

    We present a full ab initio description of the coupled out-of-equilibrium dynamics of photons, phonons, and electrons. In the present approach, the quantized nature of the electromagnetic field as well as of the nuclear oscillations is fully taken into account. The result is a set of integrodifferential equations, written on the Keldysh contour, for the Green's functions of electrons, phonons, and photons where the different kinds of interactions are merged together. We then concentrate on the electronic dynamics in order to reduce the problem to a computationally feasible approach. By using the generalized Baym-Kadanoff ansatz and the completed collision approximation, we introduce a series of efficient but controllable approximations. In this way, we reduce all equations to a set of decoupled equations for the density matrix that describe all kinds of static and dynamical correlations. The final result is a coherent, general, and inclusive scheme to calculate several physical quantities: carrier dynamics, transient photoabsorption, and light emission, all of which include, at the same time, electron-electron, electron-phonon, and electron-photon interactions. We further discuss how all these observables can be easily calculated within the present scheme using a fully atomistic ab initio approach.

  14. Understanding thermal equilibrium through activities

    NASA Astrophysics Data System (ADS)

    Pathare, Shirish; Huli, Saurabhee; Nachane, Madhura; Ladage, Savita; Pradhan, Hemachandra

    2015-03-01

    Thermal equilibrium is a basic concept in thermodynamics. In India, this concept is generally introduced at the first year of undergraduate education in physics and chemistry. In our earlier studies (Pathare and Pradhan 2011 Proc. episteme-4 Int. Conf. to Review Research on Science Technology and Mathematics Education pp 169-72) we found that students in India have a rather unsatisfactory understanding of thermal equilibrium. We have designed and developed a module of five activities, which are presented in succession to the students. These activities address the students’ alternative conceptions that underlie their lack of understanding of thermal equilibrium and aim at enhancing their understanding of the concept.

  15. Philicities, Fugalities, and Equilibrium Constants.

    PubMed

    Mayr, Herbert; Ofial, Armin R

    2016-05-17

    The mechanistic model of Organic Chemistry is based on relationships between rate and equilibrium constants. Thus, strong bases are generally considered to be good nucleophiles and poor nucleofuges. Exceptions to this rule have long been known, and the ability of iodide ions to catalyze nucleophilic substitutions, because they are good nucleophiles as well as good nucleofuges, is just a prominent example for exceptions from the general rule. In a reaction series, the Leffler-Hammond parameter α = δΔG(⧧)/δΔG° describes the fraction of the change in the Gibbs energy of reaction, which is reflected in the change of the Gibbs energy of activation. It has long been considered as a measure for the position of the transition state; thus, an α value close to 0 was associated with an early transition state, while an α value close to 1 was considered to be indicative of a late transition state. Bordwell's observation in 1969 that substituent variation in phenylnitromethanes has a larger effect on the rates of deprotonation than on the corresponding equilibrium constants (nitroalkane anomaly) triggered the breakdown of this interpretation. In the past, most systematic investigations of the relationships between rates and equilibria of organic reactions have dealt with proton transfer reactions, because only for few other reaction series complementary kinetic and thermodynamic data have been available. In this Account we report on a more general investigation of the relationships between Lewis basicities, nucleophilicities, and nucleofugalities as well as between Lewis acidities, electrophilicities, and electrofugalities. Definitions of these terms are summarized, and it is suggested to replace the hybrid terms "kinetic basicity" and "kinetic acidity" by "protophilicity" and "protofugality", respectively; in this way, the terms "acidity" and "basicity" are exclusively assigned to thermodynamic properties, while "philicity" and "fugality" refer to kinetics

  16. Equilibrium Molecular Thermodynamics from Kirkwood Sampling

    PubMed Central

    2015-01-01

    We present two methods for barrierless equilibrium sampling of molecular systems based on the recently proposed Kirkwood method (J. Chem. Phys.2009, 130, 134102). Kirkwood sampling employs low-order correlations among internal coordinates of a molecule for random (or non-Markovian) sampling of the high dimensional conformational space. This is a geometrical sampling method independent of the potential energy surface. The first method is a variant of biased Monte Carlo, where Kirkwood sampling is used for generating trial Monte Carlo moves. Using this method, equilibrium distributions corresponding to different temperatures and potential energy functions can be generated from a given set of low-order correlations. Since Kirkwood samples are generated independently, this method is ideally suited for massively parallel distributed computing. The second approach is a variant of reservoir replica exchange, where Kirkwood sampling is used to construct a reservoir of conformations, which exchanges conformations with the replicas performing equilibrium sampling corresponding to different thermodynamic states. Coupling with the Kirkwood reservoir enhances sampling by facilitating global jumps in the conformational space. The efficiency of both methods depends on the overlap of the Kirkwood distribution with the target equilibrium distribution. We present proof-of-concept results for a model nine-atom linear molecule and alanine dipeptide. PMID:25915525

  17. Generalized convective quasi-equilibrium principle

    NASA Astrophysics Data System (ADS)

    Yano, Jun-Ichi; Plant, Robert S.

    2016-03-01

    A generalization of Arakawa and Schubert's convective quasi-equilibrium principle is presented for a closure formulation of mass-flux convection parameterization. The original principle is based on the budget of the cloud work function. This principle is generalized by considering the budget for a vertical integral of an arbitrary convection-related quantity. The closure formulation includes Arakawa and Schubert's quasi-equilibrium, as well as both CAPE and moisture closures as special cases. The formulation also includes new possibilities for considering vertical integrals that are dependent on convective-scale variables, such as the moisture within convection. The generalized convective quasi-equilibrium is defined by a balance between large-scale forcing and convective response for a given vertically-integrated quantity. The latter takes the form of a convolution of a kernel matrix and a mass-flux spectrum, as in the original convective quasi-equilibrium. The kernel reduces to a scalar when either a bulk formulation is adopted, or only large-scale variables are considered within the vertical integral. Various physical implications of the generalized closure are discussed. These include the possibility that precipitation might be considered as a potentially-significant contribution to the large-scale forcing. Two dicta are proposed as guiding physical principles for the specifying a suitable vertically-integrated quantity.

  18. Equilibrium ignition for ICF capsules

    SciTech Connect

    Lackner, K.S.; Colgate, S.A.; Johnson, N.L.; Kirkpatrick, R.C.; Menikoff, R.; Petschek, A.G.

    1993-12-31

    There are two fundamentally different approaches to igniting DT fuel in an ICF capsule which can be described as equilibrium and hot spot ignition. In both cases, a capsule which can be thought of as a pusher containing the DT fuel is imploded until the fuel reaches ignition conditions. In comparing high-gain ICF targets using cryogenic DT for a pusher with equilibrium ignition targets using high-Z pushers which contain the radiation. The authors point to the intrinsic advantages of the latter. Equilibrium or volume ignition sacrifices high gain for lower losses, lower ignition temperature, lower implosion velocity and lower sensitivity of the more robust capsule to small fluctuations and asymmetries in the drive system. The reduction in gain is about a factor of 2.5, which is small enough to make the more robust equilibrium ignition an attractive alternative.

  19. Equilibrium and Orientation in Cephalopods.

    ERIC Educational Resources Information Center

    Budelmann, Bernd-Ulrich

    1980-01-01

    Describes the structure of the equilibrium receptor system in cephalopods, comparing it to the vertebrate counterpart--the vestibular system. Relates the evolution of this complex system to the competition of cephalopods with fishes. (CS)

  20. Edge equilibrium code for tokamaks

    SciTech Connect

    Li, Xujing; Drozdov, Vladimir V.

    2014-01-15

    The edge equilibrium code (EEC) described in this paper is developed for simulations of the near edge plasma using the finite element method. It solves the Grad-Shafranov equation in toroidal coordinate and uses adaptive grids aligned with magnetic field lines. Hermite finite elements are chosen for the numerical scheme. A fast Newton scheme which is the same as implemented in the equilibrium and stability code (ESC) is applied here to adjust the grids.

  1. A search for equilibrium states

    NASA Technical Reports Server (NTRS)

    Zeleznik, F. J.

    1982-01-01

    An efficient search algorithm is described for the location of equilibrium states in a search set of states which differ from one another only by the choice of pure phases. The algorithm has three important characteristics: (1) it ignores states which have little prospect for being an improved approximation to the true equilibrium state; (2) it avoids states which lead to singular iteration equations; (3) it furnishes a search history which can provide clues to alternative search paths.

  2. Ringed Accretion Disks: Equilibrium Configurations

    NASA Astrophysics Data System (ADS)

    Pugliese, D.; Stuchlík, Z.

    2015-12-01

    We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

  3. Use of a physiologically based pharmacokinetic model to study the time to reach brain equilibrium: an experimental analysis of the role of blood-brain barrier permeability, plasma protein binding, and brain tissue binding.

    PubMed

    Liu, Xingrong; Smith, Bill J; Chen, Cuiping; Callegari, Ernesto; Becker, Stacey L; Chen, Xi; Cianfrogna, Julie; Doran, Angela C; Doran, Shawn D; Gibbs, John P; Hosea, Natilie; Liu, Jianhua; Nelson, Frederick R; Szewc, Mark A; Van Deusen, Jeffery

    2005-06-01

    This study was designed 1) to examine the effects of blood-brain barrier (BBB) permeability [quantified as permeability-surface area product (PS)], unbound fraction in plasma (f(u,plasma)), and brain tissue (f(u,brain)) on the time to reach equilibrium between brain and plasma and 2) to investigate the drug discovery strategies to design and select compounds that can rapidly penetrate the BBB and distribute to the site of action. The pharmacokinetics of seven model compounds: caffeine, CP-141938 [methoxy-3-[(2-phenyl-piperadinyl-3-amino)-methyl]-phenyl-N-methyl-methane-sulfonamide], fluoxetine, NFPS [N[3-(4'-fluorophenyl)-3-(4'-phenylphenoxy)propyl]sarcosine], propranolol, theobromine, and theophylline in rat brain and plasma after subcutaneous administration were studied. The in vivo log PS and log f(u,brain) calculated using a physiologically based pharmacokinetic model correlates with in situ log PS (R(2) = 0.83) and in vitro log f(u,brain) (R(2) = 0.69), where the in situ PS and in vitro f(u,brain) was determined using in situ brain perfusion and equilibrium dialysis using brain homogenate, respectively. The time to achieve brain equilibrium can be quantitated with a proposed parameter, intrinsic brain equilibrium half-life [t(1/2eq,in) = V(b)ln2/(PS . f(u,brain))], where V(b) is the physiological volume of brain. The in vivo log t(1/2eq,in) does not correlate with in situ log PS (R(2) < 0.01) but correlates inversely with log(PS . f(u,brain)) (R(2) = 0.85). The present study demonstrates that rapid brain equilibration requires a combination of high BBB permeability and low brain tissue binding. A high BBB permeability alone cannot guarantee a rapid equilibration. The strategy to select compounds with rapid brain equilibration in drug discovery should identify compounds with high BBB permeability and low nonspecific binding in brain tissue. PMID:15743928

  4. Study Modules for Calculus-Based General Physics. [Includes Modules 11-14: Collisions; Equilibrium of Rigid Bodies; Rotational Dynamics; and Fluid Mechanics].

    ERIC Educational Resources Information Center

    Fuller, Robert G., Ed.; And Others

    This is part of a series of 42 Calculus Based Physics (CBP) modules totaling about 1,000 pages. The modules include study guides, practice tests, and mastery tests for a full-year individualized course in calculus-based physics based on the Personalized System of Instruction (PSI). The units are not intended to be used without outside materials;…

  5. Exploring Chemical and Thermal Non-equilibrium in Nitrogen Arcs

    NASA Astrophysics Data System (ADS)

    Ghorui, S.; Das, A. K.

    2012-12-01

    Plasma torches operating with nitrogen are of special importance as they can operate with usual tungsten based refractory electrodes and offer radical rich non-oxidizing high temperature environment for plasma chemistry. Strong gradients in temperature as well as species densities and huge convective fluxes lead to varying degrees of chemical non-equilibrium in associated regions. An axi-symmetric two-temperature chemical non-equilibrium model of a nitrogen plasma torch has been developed to understand the effects of thermal and chemical non-equilibrium in arcs. A 2-D finite volume CFD code in association with a non-equilibrium property routine enabled extraction of steady state self-consistent distributions of various plasma quantities inside the torch under various thermal and chemical non-equilibrium conditions. Chemical non-equilibrium has been incorporated through computation of diffusive and convective fluxes in each finite volume cell in every iteration and associating corresponding thermodynamic and transport properties through the scheme of 'chemical non-equilibrium parameter' introduced by Ghorui et. al. Recombination coefficient data from Nahar et. al. and radiation data from Krey and Morris have been used in the simulation. Results are presented for distributions of temperature, pressure, velocity, current density, electric potential, species densities and chemical non-equilibrium effects. Obtained results are compared with similar results under LTE.

  6. Uniqueness of Nash equilibrium in vaccination games.

    PubMed

    Bai, Fan

    2016-12-01

    One crucial condition for the uniqueness of Nash equilibrium set in vaccination games is that the attack ratio monotonically decreases as the vaccine coverage level increasing. We consider several deterministic vaccination models in homogeneous mixing population and in heterogeneous mixing population. Based on the final size relations obtained from the deterministic epidemic models, we prove that the attack ratios can be expressed in terms of the vaccine coverage levels, and also prove that the attack ratios are decreasing functions of vaccine coverage levels. Some thresholds are presented, which depend on the vaccine efficacy. It is proved that for vaccination games in homogeneous mixing population, there is a unique Nash equilibrium for each game. PMID:27465224

  7. Tuning universality far from equilibrium

    PubMed Central

    Karl, Markus; Nowak, Boris; Gasenzer, Thomas

    2013-01-01

    Possible universal dynamics of a many-body system far from thermal equilibrium are explored. A focus is set on meta-stable non-thermal states exhibiting critical properties such as self-similarity and independence of the details of how the respective state has been reached. It is proposed that universal dynamics far from equilibrium can be tuned to exhibit a dynamical transition where these critical properties change qualitatively. This is demonstrated for the case of a superfluid two-component Bose gas exhibiting different types of long-lived but non-thermal critical order. Scaling exponents controlled by the ratio of experimentally tuneable coupling parameters offer themselves as natural smoking guns. The results shed light on the wealth of universal phenomena expected to exist in the far-from-equilibrium realm. PMID:23928853

  8. Adiabatic evolution of plasma equilibrium

    PubMed Central

    Grad, H.; Hu, P. N.; Stevens, D. C.

    1975-01-01

    A new theory of plasma equilibrium is introduced in which adiabatic constraints are specified. This leads to a mathematically nonstandard structure, as compared to the usual equilibrium theory, in which prescription of pressure and current profiles leads to an elliptic partial differential equation. Topologically complex configurations require further generalization of the concept of adiabaticity to allow irreversible mixing of plasma and magnetic flux among islands. Matching conditions across a boundary layer at the separatrix are obtained from appropriate conservation laws. Applications are made to configurations with planned islands (as in Doublet) and accidental islands (as in Tokamaks). Two-dimensional, axially symmetric, helically symmetric, and closed line equilibria are included. PMID:16578729

  9. Phase coexistence far from equilibrium

    NASA Astrophysics Data System (ADS)

    Dickman, Ronald

    2016-04-01

    Investigation of simple far-from-equilibrium systems exhibiting phase separation leads to the conclusion that phase coexistence is not well defined in this context. This is because the properties of the coexisting nonequilibrium systems depend on how they are placed in contact, as verified in the driven lattice gas with attractive interactions, and in the two-temperature lattice gas, under (a) weak global exchange between uniform systems, and (b) phase-separated (nonuniform) systems. Thus, far from equilibrium, the notions of universality of phase coexistence (i.e., independence of how systems exchange particles and/or energy), and of phases with intrinsic properties (independent of their environment) are lost.

  10. Fundamental Research in Engineering Education. Development of Concept Questions and Inquiry-Based Activities in Thermodynamics and Heat Transfer: An Example for Equilibrium vs. Steady-State

    ERIC Educational Resources Information Center

    Vigeant, Margot; Prince, Michael; Nottis, Katharyn

    2011-01-01

    This study examines the use of inquiry-based instruction to promote the understanding of critical concepts in thermodynamics and heat transfer. Significant research shows that students frequently enter our courses with tightly held misconceptions about the physical world that are not effectively addressed through traditional instruction. Students'…

  11. Chemical Principles Revisited: Using the Equilibrium Concept.

    ERIC Educational Resources Information Center

    Mickey, Charles D., Ed.

    1981-01-01

    Discusses the concept of equilibrium in chemical systems, particularly in relation to predicting the position of equilibrium, predicting spontaneity of a reaction, quantitative applications of the equilibrium constant, heterogeneous equilibrium, determination of the solubility product constant, common-ion effect, and dissolution of precipitates.…

  12. Modeling of bi-equilibrium states in dielectric elastomer

    NASA Astrophysics Data System (ADS)

    Peng, Longgui

    2014-03-01

    Dielectric elastomer is a soft active material, producing fast deformation under voltage-activation. Under a specific boundary condition, trussed dielectric elastomer elongates mimicking the behavior of biological muscle. During this process, dielectric elastomer experiences a snap from one deformation mode to another, though both at the electromechanical equilibrium states. Based on thermodynamics, models are established to investigate electromechanical coupling at the two equilibrium states. Particular emphasis is devoted to establishing the governing equations of the two deformation modes with physical interpretations. The transition of equilibrium state is discussed, to predict the attainable stable state for application.

  13. TEA: A Code Calculating Thermochemical Equilibrium Abundances

    NASA Astrophysics Data System (ADS)

    Blecic, Jasmina; Harrington, Joseph; Bowman, M. Oliver

    2016-07-01

    We present an open-source Thermochemical Equilibrium Abundances (TEA) code that calculates the abundances of gaseous molecular species. The code is based on the methodology of White et al. and Eriksson. It applies Gibbs free-energy minimization using an iterative, Lagrangian optimization scheme. Given elemental abundances, TEA calculates molecular abundances for a particular temperature and pressure or a list of temperature–pressure pairs. We tested the code against the method of Burrows & Sharp, the free thermochemical equilibrium code Chemical Equilibrium with Applications (CEA), and the example given by Burrows & Sharp. Using their thermodynamic data, TEA reproduces their final abundances, but with higher precision. We also applied the TEA abundance calculations to models of several hot-Jupiter exoplanets, producing expected results. TEA is written in Python in a modular format. There is a start guide, a user manual, and a code document in addition to this theory paper. TEA is available under a reproducible-research, open-source license via https://github.com/dzesmin/TEA.

  14. Understanding Thermal Equilibrium through Activities

    ERIC Educational Resources Information Center

    Pathare, Shirish; Huli, Saurabhee; Nachane, Madhura; Ladage, Savita; Pradhan, Hemachandra

    2015-01-01

    Thermal equilibrium is a basic concept in thermodynamics. In India, this concept is generally introduced at the first year of undergraduate education in physics and chemistry. In our earlier studies (Pathare and Pradhan 2011 "Proc. episteme-4 Int. Conf. to Review Research on Science Technology and Mathematics Education" pp 169-72) we…

  15. DYNAMIC EQUILIBRIUM IN THERAPEUTIC SITUATIONS.

    ERIC Educational Resources Information Center

    CARROLL, EDWARD J.

    THE CONCEPT OF DYNAMIC EQUILIBRIUM IS USED TO EXAMINE THE OCCURRENCE OF CHANGE IN A THERAPEUTIC INTERVIEW AND TO PROPOSE A THEORY OF THERAPY. BY ANALYZING THE WORKINGS OF THE PSYCHOSOCIAL SYSTEM THROUGH THE GENERAL SYSTEMS THEORY, IT IS POSSIBLE TO SEE HOW CHANGE OCCURS IN AN INDIVIDUAL FAMILY OR COMMUNITY. APPLIED TO A FAMILY INTERVIEW, THE MODEL…

  16. Magnetospheric equilibrium with anisotropic pressure

    SciTech Connect

    Cheng, C.Z.

    1991-07-01

    Self-consistent magnetospheric equilibrium with anisotropic pressure is obtained by employing an iterative metric method for solving the inverse equilibrium equation in an optimal flux coordinate system. A method of determining plasma parallel and perpendicular pressures from either analytic particle distribution or particle distribution measured along the satellite's path is presented. The numerical results of axisymmetric magnetospheric equilibrium including the effects of finite beta, pressure anisotropy, and boundary conditions are presented for a bi-Maxwellian particle distribution. For the isotropic pressure cases, the finite beta effect produces an outward expansion of the constant magnetic flux surfaces in relation to the dipole field lines, and along the magnetic field the toroidal ring current is maximum at the magnetic equator. The effect of pressure anisotropy is found to further expand the flux surfaces outward. Along the magnetic field lines the westward ring current can be peak away from the equator due to an eastward current contribution resulting from pressure anisotropy. As pressure anisotropy increases, the peak westward current can become more singular. The outer boundary flux surface has significant effect on the magnetospheric equilibrium. For the outer flux boundary resembling dayside compressed flux surface due to solar wind pressure, the deformation of the magnetic field can be quite different from that for the outer flux boundary resembling the tail-like surface. 23 refs., 17 figs.

  17. ISIDORE, a probe for in situ trace metal speciation based on Donnan membrane technique with related electrochemical detection part 1: Equilibrium measurements.

    PubMed

    Parat, Corinne; Pinheiro, J P

    2015-10-01

    This work presents the development of a new probe (ISIDORE probe) based on the hyphenation of a Donnan Membrane Technique device (DMT) to a screen-printed electrode through a flow-cell to determine the free zinc, cadmium and lead ion concentration in natural samples, such as a freshwater river. The probe displays many advantages namely: (i) the detection can be performed on-site, which avoids all problems inherent to sampling, transport and storage; (ii) the low volume of the acceptor solution implies shorter equilibration times; (ii) the electrochemical detection system allows monitoring the free ion concentration in the acceptor solution without sampling. PMID:26481984

  18. A collision history-based approach to Sensitivity/Perturbation calculations in the continuous energy Monte Carlo code SERPENT

    SciTech Connect

    Giuseppe Palmiotti

    2015-05-01

    In this work, the implementation of a collision history-based approach to sensitivity/perturbation calculations in the Monte Carlo code SERPENT is discussed. The proposed methods allow the calculation of the eects of nuclear data perturbation on several response functions: the eective multiplication factor, reaction rate ratios and bilinear ratios (e.g., eective kinetics parameters). SERPENT results are compared to ERANOS and TSUNAMI Generalized Perturbation Theory calculations for two fast metallic systems and for a PWR pin-cell benchmark. New methods for the calculation of sensitivities to angular scattering distributions are also presented, which adopts fully continuous (in energy and angle) Monte Carlo estimators.

  19. Synthesis, characterization, equilibrium study and biological activity of Cu(II), Ni(II) and Co(II) complexes of polydentate Schiff base ligand.

    PubMed

    El-Sherif, Ahmed A; Shehata, Mohamed R; Shoukry, Mohamed M; Barakat, Mohammad H

    2012-10-01

    Schiff base ligand, 1,4-bis[(2-hydroxybenzaldehyde)propyl]piperazine (BHPP), and its Cu(II), Ni(II) and Co(II) metal complexes were synthesized and characterized by elemental analysis, magnetic susceptibility, molar conductance and spectral (IR and UV-vis) studies. The ground state of BHPP ligand was investigated using the BUILDER module of MOE. Metal complexes are formed in the 1:1 (M:L) ratio as found from the elemental analysis and found to have the general formula [ML]·nH(2)O, where M=Co(II), Ni(II) and Cu(II), L=BHPP. In all the studied complexes, the (BHPP) ligand behaves as a hexadentate divalent anion with coordination involving the two azomethine nitrogen's, the two nitrogen atoms of piperazine ring and the two deprotonated phenolic OH-groups. The magnetic and spectral data indicates octahedral geometry of metal(II) complexes. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. They were found to be more active against Gram-positive than Gram-negative bacteria. Protonation constants of (BHPP) ligand and stability constants of its Cu(2+), Co(2+) and Ni(2+) complexes were determined by potentiometric titration method in 50% DMSO-water solution at ionic strength of 0.1 M sodium nitrate. It has been observed that the protonated Schiff base ligand (BHPP) have four protonation constants. The divalent metal ions Cu(2+), Ni(2+) and Co(2+) form 1:1 complexes. PMID:22935596

  20. Synthesis, characterization, equilibrium study and biological activity of Cu(II), Ni(II) and Co(II) complexes of polydentate Schiff base ligand

    NASA Astrophysics Data System (ADS)

    El-Sherif, Ahmed A.; Shehata, Mohamed R.; Shoukry, Mohamed M.; Barakat, Mohammad H.

    2012-10-01

    Schiff base ligand, 1,4-bis[(2-hydroxybenzaldehyde)propyl]piperazine (BHPP), and its Cu(II), Ni(II) and Co(II) metal complexes were synthesized and characterized by elemental analysis, magnetic susceptibility, molar conductance and spectral (IR and UV-vis) studies. The ground state of BHPP ligand was investigated using the BUILDER module of MOE. Metal complexes are formed in the 1:1 (M:L) ratio as found from the elemental analysis and found to have the general formula [ML]·nH2O, where M = Co(II), Ni(II) and Cu(II), L = BHPP. In all the studied complexes, the (BHPP) ligand behaves as a hexadentate divalent anion with coordination involving the two azomethine nitrogen's, the two nitrogen atoms of piperazine ring and the two deprotonated phenolic OH-groups. The magnetic and spectral data indicates octahedral geometry of metal(II) complexes. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. They were found to be more active against Gram-positive than Gram-negative bacteria. Protonation constants of (BHPP) ligand and stability constants of its Cu2+, Co2+ and Ni2+ complexes were determined by potentiometric titration method in 50% DMSO-water solution at ionic strength of 0.1 M sodium nitrate. It has been observed that the protonated Schiff base ligand (BHPP) have four protonation constants. The divalent metal ions Cu2+, Ni2+ and Co2+ form 1:1 complexes.

  1. Non-Equilibrium Properties from Equilibrium Free Energy Calculations

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; Wilson, Michael A.

    2012-01-01

    Calculating free energy in computer simulations is of central importance in statistical mechanics of condensed media and its applications to chemistry and biology not only because it is the most comprehensive and informative quantity that characterizes the eqUilibrium state, but also because it often provides an efficient route to access dynamic and kinetic properties of a system. Most of applications of equilibrium free energy calculations to non-equilibrium processes rely on a description in which a molecule or an ion diffuses in the potential of mean force. In general case this description is a simplification, but it might be satisfactorily accurate in many instances of practical interest. This hypothesis has been tested in the example of the electrodiffusion equation . Conductance of model ion channels has been calculated directly through counting the number of ion crossing events observed during long molecular dynamics simulations and has been compared with the conductance obtained from solving the generalized Nernst-Plank equation. It has been shown that under relatively modest conditions the agreement between these two approaches is excellent, thus demonstrating the assumptions underlying the diffusion equation are fulfilled. Under these conditions the electrodiffusion equation provides an efficient approach to calculating the full voltage-current dependence routinely measured in electrophysiological experiments.

  2. Methane on Mars: Thermodynamic Equilibrium and Photochemical Calculations

    NASA Technical Reports Server (NTRS)

    Levine, J. S.; Summers, M. E.; Ewell, M.

    2010-01-01

    The detection of methane (CH4) in the atmosphere of Mars by Mars Express and Earth-based spectroscopy is very surprising, very puzzling, and very intriguing. On Earth, about 90% of atmospheric ozone is produced by living systems. A major question concerning methane on Mars is its origin - biological or geological. Thermodynamic equilibrium calculations indicated that methane cannot be produced by atmospheric chemical/photochemical reactions. Thermodynamic equilibrium calculations for three gases, methane, ammonia (NH3) and nitrous oxide (N2O) in the Earth s atmosphere are summarized in Table 1. The calculations indicate that these three gases should not exist in the Earth s atmosphere. Yet they do, with methane, ammonia and nitrous oxide enhanced 139, 50 and 12 orders of magnitude above their calculated thermodynamic equilibrium concentration due to the impact of life! Thermodynamic equilibrium calculations have been performed for the same three gases in the atmosphere of Mars based on the assumed composition of the Mars atmosphere shown in Table 2. The calculated thermodynamic equilibrium concentrations of the same three gases in the atmosphere of Mars is shown in Table 3. Clearly, based on thermodynamic equilibrium calculations, methane should not be present in the atmosphere of Mars, but it is in concentrations approaching 30 ppbv from three distinct regions on Mars.

  3. Adaptive Implicit Non-Equilibrium Radiation Diffusion

    SciTech Connect

    Philip, Bobby; Wang, Zhen; Berrill, Mark A; Rodriguez Rodriguez, Manuel; Pernice, Michael

    2013-01-01

    We describe methods for accurate and efficient long term time integra- tion of non-equilibrium radiation diffusion systems: implicit time integration for effi- cient long term time integration of stiff multiphysics systems, local control theory based step size control to minimize the required global number of time steps while control- ling accuracy, dynamic 3D adaptive mesh refinement (AMR) to minimize memory and computational costs, Jacobian Free Newton-Krylov methods on AMR grids for efficient nonlinear solution, and optimal multilevel preconditioner components that provide level independent solver convergence.

  4. Phonon Mapping in Flowing Equilibrium

    NASA Astrophysics Data System (ADS)

    Ruff, J. P. C.

    2015-03-01

    When a material conducts heat, a modification of the phonon population occurs. The equilibrium Bose-Einstein distribution is perturbed towards flowing-equilibrium, for which the distribution function is not analytically known. Here I argue that the altered phonon population can be efficiently mapped over broad regions of reciprocal space, via diffuse x-ray scattering or time-of-flight neutron scattering, while a thermal gradient is applied across a single crystal sample. When compared to traditional transport measurements, this technique offers a superior, information-rich new perspective on lattice thermal conductivity, wherein the band and momentum dependences of the phonon thermal current are directly resolved. The proposed method is benchmarked using x-ray thermal diffuse scattering measurements of single crystal diamond under transport conditions. CHESS is supported by the NSF & NIH/NIGMS via NSF Award DMR-1332208.

  5. Punctuated equilibrium comes of age

    NASA Astrophysics Data System (ADS)

    Gould, Stephan Jay; Eldredge, Niles

    1993-11-01

    The intense controversies that surrounded the youth of punctuated equilibrium have helped it mature to a useful extension of evolutionary theory. As a complement to phyletic gradualism, its most important implications remain the recognition of stasis as a meaningful and predominant pattern within the history of species, and in the recasting of macroevolution as the differential success of certain species (and their descendants) within clades.

  6. Connective stability of competitive equilibrium

    NASA Technical Reports Server (NTRS)

    Siljak, D. D.

    1975-01-01

    The purpose of this paper is to derive necessary and sufficient conditions for the connective stability of nonlinear matrix systems described by the equation x-dot = A(t, x) x, where the matrix A(t, x) has time-varying nonlinear elements. The results obtained can be used to study the stability of competitive equilibrium in fields as diverse as economics and engineering, model ecosystems, and the arms race.-

  7. Equilibrium and non-equilibrium properties of finite-volume crystallites

    NASA Astrophysics Data System (ADS)

    Degawa, Masashi

    Finite volume effects on equilibrium and non-equilibrium properties of nano-crystallites are studied theoretically and compared to both experiment and simulation. When a system is isolated or its size is small compared to the correlation length, all equilibrium and close-to-equilibrium properties will depend on the system boundary condition. Specifically for solid nano-crystallites, their finite size introduces global curvature to the system, which alters its equilibrium properties compared to the thermodynamic limit. Also such global curvature leads to capillary-induced morphology changes of the surface. Interesting dynamics can arise when the crystallite is supported on a substrate, with crossovers of the dominant driving force from the capillary force and crystallite-substrate interactions. To address these questions, we introduce thermodynamic functions for the boundary conditions, which can be derived from microscopic models. For nano-crystallites, the boundary is the surface (including interfaces), the thermodynamic description is based on the steps that define the shape of the surface, and the underlying microscopic model includes kinks. The global curvature of the surface introduces metastable states with different shapes governed by a constant of integration of the extra boundary condition, which we call the shape parameter c. The discrete height of the steps introduces transition states in between the metastable states, and the lowest energy accessible structure (energy barrier less 10k BT) as a function of the volume has been determined. The dynamics of nano-crystallites as they relax from a non-equilibrium structure is described quantitatively in terms of the motion of steps in both capillary-induced and interface-boundary-induced regimes. The step-edge fluctuations of the top facet are also influenced by global curvature and volume conservation and the effect yields different dynamic scaling exponents from a pure 1D system. Theoretical results are

  8. Multicomponent Equilibrium Models for Testing Geothermometry Approaches

    SciTech Connect

    Cooper, D. Craig; Palmer, Carl D.; Smith, Robert W.; McLing, Travis L.

    2013-02-01

    Geothermometry is an important tool for estimating deep reservoir temperature from the geochemical composition of shallower and cooler waters. The underlying assumption of geothermometry is that the waters collected from shallow wells and seeps maintain a chemical signature that reflects equilibrium in the deeper reservoir. Many of the geothermometers used in practice are based on correlation between water temperatures and composition or using thermodynamic calculations based a subset (typically silica, cations or cation ratios) of the dissolved constituents. An alternative approach is to use complete water compositions and equilibrium geochemical modeling to calculate the degree of disequilibrium (saturation index) for large number of potential reservoir minerals as a function of temperature. We have constructed several “forward” geochemical models using The Geochemist’s Workbench to simulate the change in chemical composition of reservoir fluids as they migrate toward the surface. These models explicitly account for the formation (mass and composition) of a steam phase and equilibrium partitioning of volatile components (e.g., CO2, H2S, and H2) into the steam as a result of pressure decreases associated with upward fluid migration from depth. We use the synthetic data generated from these simulations to determine the advantages and limitations of various geothermometry and optimization approaches for estimating the likely conditions (e.g., temperature, pCO2) to which the water was exposed in the deep subsurface. We demonstrate the magnitude of errors that can result from boiling, loss of volatiles, and analytical error from sampling and instrumental analysis. The estimated reservoir temperatures for these scenarios are also compared to conventional geothermometers. These results can help improve estimation of geothermal resource temperature during exploration and early development.

  9. Modulation and Salt-Induced Reverse Modulation of the Excited-State Proton-Transfer Process of Lysozymized Pyranine: The Contrasting Scenario of the Ground-State Acid-Base Equilibrium of the Photoacid.

    PubMed

    Das, Ishita; Panja, Sudipta; Halder, Mintu

    2016-07-28

    Here we report on the excited-state behavior in terms of the excited-state proton-transfer (ESPT) reaction as well as the ground-state acid-base property of pyranine [8-hydroxypyrene-1,3,6-trisulfonate (HPTS)] in the presence of an enzymatic protein, human lysozyme (LYZ). HPTS forms a 1:1 ground-state complex with LYZ having the binding constant KBH = (1.4 ± 0.05) × 10(4) M(-1), and its acid-base equilibrium gets shifted toward the deprotonated conjugate base (RO(-)), resulting in a downward shift in pKa. This suggests that the conjugate base (RO(-)) is thermodynamically more favored over the protonated (ROH) species inside the lysozyme matrix, resulting in an increased population of the deprotonated form. However, for the release of the proton from the excited photoacid, interestingly, the rate of proton transfer gets slowed down due to the "slow" acceptor biological water molecules present in the immediate vicinity of the fluorophore binding region inside the protein. The observed ESPT time constants, ∼140 and ∼750 ps, of protein-bound pyranine are slower than in bulk aqueous media (∼100 ps, single exponential). The molecular docking study predicts that the most probable binding location of the fluorophore is in a region near to the active site of the protein. Here we also report on the effect of external electrolyte (NaCl) on the reverse modulation of ground-state prototropy as well as the ESPT process of the protein-bound pyranine. It is found that there is a dominant role of electrostatic forces in the HPTS-LYZ interaction process, because an increase in ionic strength by the addition of NaCl dislodges the fluorophore from the protein pocket to the bulk again. The study shows a considerably different perspective of the perturbation offered by the model macromolecular host used, unlike the available literature reports on the concerned photoacid. PMID:27355857

  10. The assumption of equilibrium in models of migration.

    PubMed

    Schachter, J; Althaus, P G

    1993-02-01

    In recent articles Evans (1990) and Harrigan and McGregor (1993) (hereafter HM) scrutinized the equilibrium model of migration presented in a 1989 paper by Schachter and Althaus. This model used standard microeconomics to analyze gross interregional migration flows based on the assumption that gross flows are in approximate equilibrium. HM criticized the model as theoretically untenable, while Evans summoned empirical as well as theoretical objections. HM claimed that equilibrium of gross migration flows could be ruled out on theoretical grounds. They argued that the absence of net migration requires that either all regions have equal populations or that unsustainable regional migration propensities must obtain. In fact some moves are inter- and other are intraregional. It does not follow, however, that the number of interregional migrants will be larger for the more populous region. Alternatively, a country could be divided into a large number of small regions that have equal populations. With uniform propensities to move, each of these analytical regions would experience in equilibrium zero net migration. Hence, the condition that net migration equal zero is entirely consistent with unequal distributions of population across regions. The criticisms of Evans were based both on flawed reasoning and on misinterpretation of the results of a number of econometric studies. His reasoning assumed that the existence of demand shifts as found by Goldfarb and Yezer (1987) and Topel (1986) invalidated the equilibrium model. The equilibrium never really obtains exactly, but economic modeling of migration properly begins with a simple equilibrium model of the system. A careful reading of the papers Evans cited in support of his position showed that in fact they affirmed rather than denied the appropriateness of equilibrium modeling. Zero net migration together with nonzero gross migration are not theoretically incompatible with regional heterogeneity of population, wages, or

  11. Morphodynamic equilibrium of alluvial estuaries

    NASA Astrophysics Data System (ADS)

    Tambroni, Nicoletta; Bolla Pittaluga, Michele; Canestrelli, Alberto; Lanzoni, Stefano; Seminara, Giovanni

    2014-05-01

    The evolution of the longitudinal bed profile of an estuary, with given plan-form configuration, subject to given tidal forcing at the mouth and prescribed values of water and sediment supply from the river is investigated numerically. Our main goal is to ascertain whether, starting from some initial condition, the bed evolution tends to reach a unique equilibrium configuration asymptotically in time. Also, we investigate the morphological response of an alluvial estuary to changes in the tidal range and hydrologic forcing (flow and sediment supply). Finally, the solution helps characterizing the transition between the fluvially dominated region and the tidally dominated region of the estuary. All these issues play an important role also in interpreting how the facies changes along the estuary, thus helping to make correct paleo-environmental and sequence-stratigraphic interpretations of sedimentary successions (Dalrymple and Choi, 2007). Results show that the model is able to describe a wide class of settings ranging from tidally dominated estuaries to fluvially dominated estuaries. In the latter case, the solution is found to compare satisfactory with the analytical asymptotic solution recently derived by Seminara et al. (2012), under the hypothesis of fairly 'small' tidal oscillations. Simulations indicate that the system always moves toward an equilibrium configuration in which the net sediment flux in a tidal cycle is constant throughout the estuary and equal to the constant sediment flux discharged from the river. For constant width, the bed equilibrium profile of the estuarine channel is characterized by two distinct regions: a steeper reach seaward, dominated by the tide, and a less steep upstream reach, dominated by the river and characterized by the undisturbed bed slope. Although the latter reach, at equilibrium, is not directly affected by the tidal wave, however starting from an initial uniform stream with the constant 'fluvial' slope, the final

  12. Torque equilibrium attitude control for Skylab reentry

    NASA Technical Reports Server (NTRS)

    Glaese, J. R.; Kennel, H. F.

    1979-01-01

    All the available torque equilibrium attitudes (most were useless from the standpoint of lack of electrical power) and the equilibrium seeking method are presented, as well as the actual successful application during the 3 weeks prior to Skylab reentry.

  13. Temperature of systems out of thermodynamic equilibrium

    NASA Astrophysics Data System (ADS)

    Garden, J.-L.; Richard, J.; Guillou, H.

    2008-07-01

    Two phenomenological approaches are currently used in the study of the vitreous state. One is based on the concept of fictive temperature introduced by Tool [J. Res. Natl. Bur. Stand. 34, 199 (1945)] and recently revisited by Nieuwenhuizen [Phys. Rev. Lett. 80, 5580 (1998)]. The other is based on the thermodynamics of irreversible processes initiated by De Donder at the beginning of the last century [L'Affinité (Gauthier-Villars, Paris, 1927)] and recently used by Möller et al. for a thorough study of the glass transition [J. Chem. Phys. 125, 094505 (2006)]. This latter approach leads to the possibility of describing the glass transition by means of the freezing-in of one or more order parameters connected to the internal structural degrees of freedom involved in the vitrification process. In this paper, the equivalence of the two preceding approaches is demonstrated, not only for glasses but in a very general way for any system undergoing an irreversible transformation. This equivalence allows the definition of an effective temperature for all systems departed from equilibrium generating a positive amount of entropy. In fact, the initial fictive temperature concept of Tool leads to the generalization of the notion of temperature for systems out of thermodynamic equilibrium, for which glasses are just particular cases.

  14. Open problems in non-equilibrium physics

    SciTech Connect

    Kusnezov, D.

    1997-09-22

    The report contains viewgraphs on the following: approaches to non-equilibrium statistical mechanics; classical and quantum processes in chaotic environments; classical fields in non-equilibrium situations: real time dynamics at finite temperature; and phase transitions in non-equilibrium conditions.

  15. A survey of upwind methods for flows with equilibrium and non-equilibrium chemistry and thermodynamics

    NASA Technical Reports Server (NTRS)

    Grossman, B.; Garrett, J.; Cinnella, P.

    1989-01-01

    Several versions of flux-vector split and flux-difference split algorithms were compared with regard to general applicability and complexity. Test computations were performed using curve-fit equilibrium air chemistry for an M = 5 high-temperature inviscid flow over a wedge, and an M = 24.5 inviscid flow over a blunt cylinder for test computations; for these cases, little difference in accuracy was found among the versions of the same flux-split algorithm. For flows with nonequilibrium chemistry, the effects of the thermodynamic model on the development of flux-vector split and flux-difference split algorithms were investigated using an equilibrium model, a general nonequilibrium model, and a simplified model based on vibrational relaxation. Several numerical examples are presented, including nonequilibrium air chemistry in a high-temperature shock tube and nonequilibrium hydrogen-air chemistry in a supersonic diffuser.

  16. A continuum model for flocking: Obstacle avoidance, equilibrium, and stability

    NASA Astrophysics Data System (ADS)

    Mecholsky, Nicholas Alexander

    The modeling and investigation of the dynamics and configurations of animal groups is a subject of growing attention. In this dissertation, we present a partial-differential-equation based continuum model of flocking and use it to investigate several properties of group dynamics and equilibrium. We analyze the reaction of a flock to an obstacle or an attacking predator. We show that the flock response is in the form of density disturbances that resemble Mach cones whose configuration is determined by the anisotropic propagation of waves through the flock. We investigate the effect of a flock 'pressure' and pairwise repulsion on an equilibrium density distribution. We investigate both linear and nonlinear pressures, look at the convergence to a 'cold' (T → 0) equilibrium solution, and find regions of parameter space where different models produce the same equilibrium. Finally, we analyze the stability of an equilibrium density distribution to long-wavelength perturbations. Analytic results for the stability of a constant density solution as well as stability regimes for constant density solutions to the equilibrium equations are presented.

  17. Conformations of Proteins in Equilibrium

    NASA Astrophysics Data System (ADS)

    Micheletti, Cristian; Banavar, Jayanth R.; Maritan, Amos

    2001-08-01

    We introduce a simple theoretical approach for an equilibrium study of proteins with known native-state structures. We test our approach with results on well-studied globular proteins, chymotrypsin inhibitor (2ci2), barnase, and the alpha spectrin SH3 domain, and present evidence for a hierarchical onset of order on lowering the temperature with significant organization at the local level even at high temperatures. A further application to the folding process of HIV-1 protease shows that the model can be reliably used to identify key folding sites that are responsible for the development of drug resistance.

  18. Thermal equilibrium in Einstein's elevator.

    PubMed

    Sánchez-Rey, Bernardo; Chacón-Acosta, Guillermo; Dagdug, Leonardo; Cubero, David

    2013-05-01

    We report fully relativistic molecular-dynamics simulations that verify the appearance of thermal equilibrium of a classical gas inside a uniformly accelerated container. The numerical experiments confirm that the local momentum distribution in this system is very well approximated by the Jüttner function-originally derived for a flat spacetime-via the Tolman-Ehrenfest effect. Moreover, it is shown that when the acceleration or the container size is large enough, the global momentum distribution can be described by the so-called modified Jüttner function, which was initially proposed as an alternative to the Jüttner function. PMID:23767501

  19. Non-equilibrium phase transitions

    SciTech Connect

    Mottola, E.; Cooper, F.M.; Bishop, A.R.; Habib, S.; Kluger, Y.; Jensen, N.G.

    1998-12-31

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Non-equilibrium phase transitions play a central role in a very broad range of scientific areas, ranging from nuclear, particle, and astrophysics to condensed matter physics and the material and biological sciences. The aim of this project was to explore the path to a deeper and more fundamental understanding of the common physical principles underlying the complex real time dynamics of phase transitions. The main emphasis was on the development of general theoretical tools to deal with non-equilibrium processes, and of numerical methods robust enough to capture the time-evolving structures that occur in actual experimental situations. Specific applications to Laboratory multidivisional efforts in relativistic heavy-ion physics (transition to a new phase of nuclear matter consisting of a quark-gluon plasma) and layered high-temperature superconductors (critical currents and flux flow at the National High Magnetic Field Laboratory) were undertaken.

  20. Equilibrium Studies of Designed Metalloproteins.

    PubMed

    Gibney, B R

    2016-01-01

    Complete thermodynamic descriptions of the interactions of cofactors with proteins via equilibrium studies are challenging, but are essential to the evaluation of designed metalloproteins. While decades of studies on protein-protein interaction thermodynamics provide a strong underpinning to the successful computational design of novel protein folds and de novo proteins with enzymatic activity, the corresponding paucity of data on metal-protein interaction thermodynamics limits the success of computational metalloprotein design efforts. By evaluating the thermodynamics of metal-protein interactions via equilibrium binding studies, protein unfolding free energy determinations, proton competition equilibria, and electrochemistry, a more robust basis for the computational design of metalloproteins may be provided. Our laboratory has shown that such studies provide detailed insight into the assembly and stability of designed metalloproteins, allow for parsing apart the free energy contributions of metal-ligand interactions from those of porphyrin-protein interactions in hemeproteins, and even reveal their mechanisms of proton-coupled electron transfer. Here, we highlight studies that reveal the complex interplay between the various equilibria that underlie metalloprotein assembly and stability and the utility of making these detailed measurements. PMID:27586343

  1. Magnetospheric equilibrium with anisotropic pressure

    SciTech Connect

    Cheng, C.Z. )

    1992-02-01

    Self-consistent magnetospheric equilibria with anisotropic pressure are obtained by employing an iterative metric method for solving the inverse equilibrium equation in an optimal flux coordinate system. A method of determining plasma parallel and perpendicular pressures from either analytic particle distributions or particle distributions measured along a satellite's path is presented. The numerical results of axisymmetric magnetospheric equilibria including the effects of finite beta, pressure anisotropy, and boundary conditions are presented for a bi-Maxwellian particle distribution. For the isotropic pressure cases the finite beta effect produces an outward expansion of the constant magnetic flux surfaces in relation to the dipole field lines, and along the magnetic field the toroidal ring current is maximum at the magnetic equator. The effect of pressure anisotropy is found to further expand the flux surfaces outward. Along the magnetic field lines the westward ring current can be peak away from the equator owing to an eastward current contribution resulting from pressure anisotropy. As pressure anisotropy increases, the peak westward current can become more singular. The outer boundary flux surface has a significant effect on the magnetospheric equilibrium. For the outer flux boundary resembling the dayside compressed flux surface due to solar wind pressure, the deformation of the magnetic field can be quite different from that for the outer flux boundary resembling the taillike flux surface.

  2. Are the Concepts of Dynamic Equilibrium and the Thermodynamic Criteria for Spontaneity, Nonspontaneity, and Equilibrium Compatible?

    ERIC Educational Resources Information Center

    Silverberg, Lee J.; Raff, Lionel M.

    2015-01-01

    Thermodynamic spontaneity-equilibrium criteria require that in a single-reaction system, reactions in either the forward or reverse direction at equilibrium be nonspontaneous. Conversely, the concept of dynamic equilibrium holds that forward and reverse reactions both occur at equal rates at equilibrium to the extent allowed by kinetic…

  3. Typicality of Thermal Equilibrium and Thermalization in Isolated Macroscopic Quantum Systems

    NASA Astrophysics Data System (ADS)

    Tasaki, Hal

    2016-06-01

    Based on the view that thermal equilibrium should be characterized through macroscopic observations, we develop a general theory about typicality of thermal equilibrium and the approach to thermal equilibrium in macroscopic quantum systems. We first formulate the notion that a pure state in an isolated quantum system represents thermal equilibrium. Then by assuming, or proving in certain classes of nontrivial models (including that of two bodies in thermal contact), large-deviation type bounds (which we call thermodynamic bounds) for the microcanonical ensemble, we prove that to represent thermal equilibrium is a typical property for pure states in the microcanonical energy shell. We believe that the typicality, along with the empirical success of statistical mechanics, provides a sound justification of equilibrium statistical mechanics. We also establish the approach to thermal equilibrium under two different assumptions; one is that the initial state has a moderate energy distribution, and the other is the energy eigenstate thermalization hypothesis.

  4. Equilibrium Model of Precipitation in Microalloyed Steels

    NASA Astrophysics Data System (ADS)

    Xu, Kun; Thomas, Brian G.; O'Malley, Ron

    2011-02-01

    The formation of precipitates during thermal processing of microalloyed steels greatly influences their mechanical properties. Precipitation behavior varies with steel composition and temperature history and can lead to beneficial grain refinement or detrimental transverse surface cracks. This work presents an efficient computational model of equilibrium precipitation of oxides, sulfides, nitrides, and carbides in steels, based on satisfying solubility limits including Wagner interaction between elements, mutual solubility between precipitates, and mass conservation of alloying elements. The model predicts the compositions and amounts of stable precipitates for multicomponent microalloyed steels in liquid, ferrite, and austenite phases at any temperature. The model is first validated by comparing with analytical solutions of simple cases, predictions using the commercial package JMat-PRO, and previous experimental observations. Then it is applied to track the evolution of precipitate amounts during continuous casting of two commercial steels (1004 LCAK and 1006Nb HSLA) at two different casting speeds. This model is easy to modify to incorporate other precipitates, or new thermodynamic data, and is a useful tool for equilibrium precipitation analysis.

  5. Structural design using equilibrium programming formulations

    NASA Astrophysics Data System (ADS)

    Scotti, Stephen J.

    1995-06-01

    Solutions to increasingly larger structural optimization problems are desired. However, computational resources are strained to meet this need. New methods will be required to solve increasingly larger problems. The present approaches to solving large-scale problems involve approximations for the constraints of structural optimization problems and/or decomposition of the problem into multiple subproblems that can be solved in parallel. An area of game theory, equilibrium programming (also known as noncooperative game theory), can be used to unify these existing approaches from a theoretical point of view (considering the existence and optimality of solutions), and be used as a framework for the development of new methods for solving large-scale optimization problems. Equilibrium programming theory is described, and existing design techniques such as fully stressed design and constraint approximations are shown to fit within its framework. Two new structural design formulations are also derived. The first new formulation is another approximation technique which is a general updating scheme for the sensitivity derivatives of design constraints. The second new formulation uses a substructure-based decomposition of the structure for analysis and sensitivity calculations. Significant computational benefits of the new formulations compared with a conventional method are demonstrated.

  6. The empirical equilibrium structure of diacetylene

    NASA Astrophysics Data System (ADS)

    Thorwirth, Sven; Harding, Michael E.; Muders, Dirk; Gauss, Jürgen

    2008-09-01

    High-level quantum-chemical calculations are reported at the MP2 and CCSD(T) levels of theory for the equilibrium structure and the harmonic and anharmonic force fields of diacetylene, H sbnd C tbnd C sbnd C tbnd C sbnd H. The calculations were performed employing Dunning's hierarchy of correlation-consistent basis sets cc-pV XZ, cc-pCV XZ, and cc-pwCV XZ, as well as the ANO2 basis set of Almlöf and Taylor. An empirical equilibrium structure based on experimental rotational constants for 13 isotopic species of diacetylene and computed zero-point vibrational corrections is determined (reemp:r=1.0615 Å,r=1.2085 Å,r=1.3727 Å) and in good agreement with the best theoretical structure (CCSD(T)/cc-pCV5Z: r=1.0617 Å, r=1.2083 Å, r=1.3737 Å). In addition, the computed fundamental vibrational frequencies are compared with the available experimental data and found in satisfactory agreement.

  7. Non-equilibrium many body dynamics

    SciTech Connect

    Creutz, M.; Gyulassy, M.

    1997-09-22

    This Riken BNL Research Center Symposium on Non-Equilibrium Many Body Physics was held on September 23-25, 1997 as part of the official opening ceremony of the Center at Brookhaven National Lab. A major objective of theoretical work at the center is to elaborate on the full spectrum of strong interaction physics based on QCD, including the physics of confinement and chiral symmetry breaking, the parton structure of hadrons and nuclei, and the phenomenology of ultra-relativistic nuclear collisions related to the up-coming experiments at RHIC. The opportunities and challenges of nuclear and particle physics in this area naturally involve aspects of the many body problem common to many other fields. The aim of this symposium was to find common theoretical threads in the area of non-equilibrium physics and modern transport theories. The program consisted of invited talks on a variety topics from the fields of atomic, condensed matter, plasma, astrophysics, cosmology, and chemistry, in addition to nuclear and particle physics. Separate abstracts have been indexed into the database for contributions to this workshop.

  8. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

    SciTech Connect

    Jian-Zhou Zhu and Gregory W. Hammett

    2011-01-10

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.

  9. Structural design using equilibrium programming formulations

    NASA Technical Reports Server (NTRS)

    Scotti, Stephen J.

    1995-01-01

    Solutions to increasingly larger structural optimization problems are desired. However, computational resources are strained to meet this need. New methods will be required to solve increasingly larger problems. The present approaches to solving large-scale problems involve approximations for the constraints of structural optimization problems and/or decomposition of the problem into multiple subproblems that can be solved in parallel. An area of game theory, equilibrium programming (also known as noncooperative game theory), can be used to unify these existing approaches from a theoretical point of view (considering the existence and optimality of solutions), and be used as a framework for the development of new methods for solving large-scale optimization problems. Equilibrium programming theory is described, and existing design techniques such as fully stressed design and constraint approximations are shown to fit within its framework. Two new structural design formulations are also derived. The first new formulation is another approximation technique which is a general updating scheme for the sensitivity derivatives of design constraints. The second new formulation uses a substructure-based decomposition of the structure for analysis and sensitivity calculations. Significant computational benefits of the new formulations compared with a conventional method are demonstrated.

  10. String fluid in local equilibrium

    NASA Astrophysics Data System (ADS)

    Schubring, Daniel; Vanchurin, Vitaly

    2014-10-01

    We study the solutions of string fluid equations under the assumption of a local equilibrium which was previously obtained in the context of the kinetic theory. We show that the fluid can be foliated into noninteracting submanifolds whose equations of motion are exactly that of the wiggly strings considered previously by Vilenkin and Carter. In a special case of negligible statistical variance in either the left- or the right-moving directions of microscopic strings, the submanifolds are described by the action of a null-current-carrying chiral string. When both variances vanish the submanifolds are described by the Nambu-Goto action and the string fluid reduces to the string dust introduced by Stachel.