Infinitely dilute partial molar properties of proteins from computer simulation.

PubMed

Ploetz, Elizabeth A; Smith, Paul E

2014-11-13

A detailed understanding of temperature and pressure effects on an infinitely dilute protein's conformational equilibrium requires knowledge of the corresponding infinitely dilute partial molar properties. Established molecular dynamics methodologies generally have not provided a way to calculate these properties without either a loss of thermodynamic rigor, the introduction of nonunique parameters, or a loss of information about which solute conformations specifically contributed to the output values. Here we implement a simple method that is thermodynamically rigorous and possesses none of the above disadvantages, and we report on the method's feasibility and computational demands. We calculate infinitely dilute partial molar properties for two proteins and attempt to distinguish the thermodynamic differences between a native and a denatured conformation of a designed miniprotein. We conclude that simple ensemble average properties can be calculated with very reasonable amounts of computational power. In contrast, properties corresponding to fluctuating quantities are computationally demanding to calculate precisely, although they can be obtained more easily by following the temperature and/or pressure dependence of the corresponding ensemble averages.

Computer program for calculation of ideal gas thermodynamic data

NASA Technical Reports Server (NTRS)

Gordon, S.; Mc Bride, B. J.

1968-01-01

Computer program calculates ideal gas thermodynamic properties for any species for which molecular constant data is available. Partial functions and derivatives from formulas based on statistical mechanics are provided by the program which is written in FORTRAN 4 and MAP.

Critical parameters, thermodynamic functions, and shock Hugoniot of aluminum fluid at high energy density

NASA Astrophysics Data System (ADS)

Zaghloul, Mofreh R.

2018-03-01

We present estimates of the critical properties, thermodynamic functions, and principal shock Hugoniot of hot dense aluminum fluid as predicted from a chemical model for the equation-of-state of hot dense, partially ionized and partially degenerate plasma. The essential features of strongly coupled plasma of metal vapors, such as multiple ionization, Coulomb interactions among charged particles, partial degeneracy, and intensive short range hard core repulsion are taken into consideration. Internal partition functions of neutral, excited, and multiply ionized species are carefully evaluated in a statistical-mechanically consistent way. Results predicted from the present model are presented, analyzed and compared with available experimental measurements and other theoretical predictions in the literature.

A Tightly Coupled Non-Equilibrium Magneto-Hydrodynamic Model for Inductively Coupled RF Plasmas

DTIC Science & Technology

2016-02-29

development a tightly coupled magneto-hydrodynamic model for Inductively Coupled Radio- Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE...for Inductively Coupled Radio-Frequency (RF) Plasmas. Non Local Thermodynamic Equilibrium (NLTE) effects are described based on a hybrid State-to-State... thermodynamic variable. This choice allows one to hide the non-linearity of the gas (total) thermal conductivity κ and can partially alle- 2 viate numerical

Thermodynamic and Kinematic Flow Characteristics of Some Developing and Non-Developing Disturbances in Predict

DTIC Science & Technology

2014-12-01

normal ( 1S ) and parallel ( 2S ) strain rates squared. U and V are the zonal and meridional velocities and the x and y subscripts indicate partial...between developing and non-developing tropical disturbances appears to lie with the kinematic flow boundary structure and thermodynamic properties ...tropical disturbances appears to lie with the kinematic flow boundary structure and thermodynamic properties hypothesized in the marsupial paradigm

Thermodynamic properties of rare earth elements in La-RE-Ga-In alloys (RE = Nd, Y)

NASA Astrophysics Data System (ADS)

Raguzina, Ekaterina V.; Maltsev, Dmitry S.; Volkovich, Vladimir A.; Yamshchikov, Leonid F.; Chukin, Andrey V.

2017-09-01

Thermodynamic properties of La, Nd, and Y were studied in pseudo-quaternary systems La-Nd-(Ga-In)eut and La-Y-(Ga-In)eut. Temperature dependences of lanthanum, neodymium, and yttrium activity in the alloys were determined at 300-800 °C employing the e.m.f. method. Partial thermodynamic functions of lanthanum in the alloys studied were calculated on the basis of the experimental data.

Thermodynamics and Mechanism of the Interaction of Willardiine Partial Agonists with a Glutamate Receptor: Implications for Drug Development

PubMed Central

2015-01-01

Understanding the thermodynamics of binding of a lead compound to a receptor can provide valuable information for drug design. The binding of compounds, particularly partial agonists, to subtypes of the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptor is, in some cases, driven by increases in entropy. Using a series of partial agonists based on the structure of the natural product, willardiine, we show that the charged state of the ligand determines the enthalpic contribution to binding. Willardiines have uracil rings with pKa values ranging from 5.5 to 10. The binding of the charged form is largely driven by enthalpy, while that of the uncharged form is largely driven by entropy. This is due at least in part to changes in the hydrogen bonding network within the binding site involving one water molecule. This work illustrates the importance of charge to the thermodynamics of binding of agonists and antagonists to AMPA receptors and provides clues for further drug discovery. PMID:24850223

Infinitely Dilute Partial Molar Properties of Proteins from Computer Simulation

PubMed Central

2015-01-01

A detailed understanding of temperature and pressure effects on an infinitely dilute protein’s conformational equilibrium requires knowledge of the corresponding infinitely dilute partial molar properties. Established molecular dynamics methodologies generally have not provided a way to calculate these properties without either a loss of thermodynamic rigor, the introduction of nonunique parameters, or a loss of information about which solute conformations specifically contributed to the output values. Here we implement a simple method that is thermodynamically rigorous and possesses none of the above disadvantages, and we report on the method’s feasibility and computational demands. We calculate infinitely dilute partial molar properties for two proteins and attempt to distinguish the thermodynamic differences between a native and a denatured conformation of a designed miniprotein. We conclude that simple ensemble average properties can be calculated with very reasonable amounts of computational power. In contrast, properties corresponding to fluctuating quantities are computationally demanding to calculate precisely, although they can be obtained more easily by following the temperature and/or pressure dependence of the corresponding ensemble averages. PMID:25325571

Propulsion System Simulation Using the Toolbox for the Modeling and Analysis of Thermodynamic System (T-MATS)

NASA Technical Reports Server (NTRS)

Chapman, Jeffryes W.; Lavelle, Thomas M.; May, Ryan D.; Litt, Jonathan S.; Guo, Ten-Huei (OA)

2014-01-01

A simulation toolbox has been developed for the creation of both steady-state and dynamic thermodynamic software models. This presentation describes the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS), which combines generic thermodynamic and controls modeling libraries with a numerical iterative solver to create a framework for the development of thermodynamic system simulations, such as gas turbine engines. The objective of this presentation is to present an overview of T-MATS, the theory used in the creation of the module sets, and a possible propulsion simulation architecture.

Advanced development receiver thermal vacuum tests with cold wall

NASA Technical Reports Server (NTRS)

Sedgwick, Leigh M.

1991-01-01

The first ever testing of a full size solar dynamic heat receiver using high temperature thermal energy storage was completed. The heat receiver was designed to meet the requirements for operation on the Space Station Freedom. The purpose of the test program was to quantify the receiver thermodynamic performance, its operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber with liquid nitrogen cold shrouds and an aperture cold plate to partially simulate a low Earth orbit environment. The cavity of the receiver was heated by an infrared quartz lamp heater with 30 independently controllable zones to produce flux distributions typical of candidate concentrators. A closed Brayton cycle engine simulator conditioned a helium xenon gas mixture to specific interface conditions to simulate various operational modes of the solar dynamic power module. Inlet gas temperature, pressure, and flow rate were independently varied. A total of 58 simulated orbital cycles were completed during the test conduct period. The test hardware, execution of testing, test data, and post test inspections are described.

Thermodynamic properties of gadolinium in Ga-Sn and Ga-Zn eutectic based alloys

NASA Astrophysics Data System (ADS)

Maltsev, Dmitry S.; Volkovich, Vladimir A.; Yamshchikov, Leonid F.; Chukin, Andrey V.

2016-09-01

Thermodynamic properties of gadolinium in Ga-Sn and Ga-Zn eutectic based alloys were studied. Temperature dependences of gadolinium activity in the studied alloys were determined at 573-1073 K employing the EMF method. Solubility of gadolinium in the Ga-Sn and Ga-Zn alloys was measured at 462-1073 K using IMCs sedimentation method. Activity coefficients as well as partial and excess thermodynamic functions of gadolinium in the studied alloys were calculated on the basis of the obtained experimental data.

Chemical equilibrium. [maximizing entropy of gas system to derive relations between thermodynamic variables

NASA Technical Reports Server (NTRS)

1976-01-01

The entropy of a gas system with the number of particles subject to external control is maximized to derive relations between the thermodynamic variables that obtain at equilibrium. These relations are described in terms of the chemical potential, defined as equivalent partial derivatives of entropy, energy, enthalpy, free energy, or free enthalpy. At equilibrium, the change in total chemical potential must vanish. This fact is used to derive the equilibrium constants for chemical reactions in terms of the partition functions of the species involved in the reaction. Thus the equilibrium constants can be determined accurately, just as other thermodynamic properties, from a knowledge of the energy levels and degeneracies for the gas species involved. These equilibrium constants permit one to calculate the equilibrium concentrations or partial pressures of chemically reacting species that occur in gas mixtures at any given condition of pressure and temperature or volume and temperature.

Modeling of outgassing and matrix decomposition in carbon-phenolic composites

NASA Technical Reports Server (NTRS)

Mcmanus, Hugh L.

1994-01-01

Work done in the period Jan. - June 1994 is summarized. Two threads of research have been followed. First, the thermodynamics approach was used to model the chemical and mechanical responses of composites exposed to high temperatures. The thermodynamics approach lends itself easily to the usage of variational principles. This thermodynamic-variational approach has been applied to the transpiration cooling problem. The second thread is the development of a better algorithm to solve the governing equations resulting from the modeling. Explicit finite difference method is explored for solving the governing nonlinear, partial differential equations. The method allows detailed material models to be included and solution on massively parallel supercomputers. To demonstrate the feasibility of the explicit scheme in solving nonlinear partial differential equations, a transpiration cooling problem was solved. Some interesting transient behaviors were captured such as stress waves and small spatial oscillations of transient pressure distribution.

The effect of various quantum mechanically derived partial atomic charges on the bulk properties of chloride-based ionic liquids

NASA Astrophysics Data System (ADS)

Zolghadr, Amin Reza; Ghatee, Mohammad Hadi; Moosavi, Fatemeh

2016-08-01

Partial atomic charges using various quantum mechanical calculations for [Cnmim]Cl (n = 1, 4) ionic liquids (ILs) are obtained and used for development of molecular dynamics simulation (MD) force fields. The isolated ion pairs are optimized using HF, B3LYP, and MP2 methods for electronic structure with 6-311++G(d,p) basis set. Partial atomic charges are assigned to the atomic center with CHELPG and NBO methods. The effect of these sets of partial charges on the static and dynamic properties of ILs is evaluated by performing a series of MD simulations and comparing the essential thermodynamic properties with the available experimental data and available molecular dynamics simulation results. In contrast to the general trends reported for ionic liquids with BF4, PF6, and iodide anions (in which restrained electrostatic potential (RESP) charges are preferred), partial charges derived by B3LYP-NBO method are relatively good in prediction of the structural, dynamical, and thermodynamic energetic properties of the chloride based ILs.

Oxygen stoichiometry, phase stability, and thermodynamic behavior of the lead-doped and lead-free Bi-2212 systems

NASA Astrophysics Data System (ADS)

Tetenbaum, M.; Hash, M.; Tani, B. S.; Maroni, V. A.

1996-02-01

Electromotive-force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made on lead-doped and lead-free Bi 2- zPb zSr 2Ca 1Cu 2O x superconducting ceramics in the temperature range ≈ 700-815°C by means of an oxygen-titration techique that employs an yttria-stabilized zirconia electrolyte. Equations for the variation of oxygen partial pressure with composition and temperature have been derived from our EMF measurements. Thermodynamic assessments of the partial molar quantities Δ overlineH(O 2) and Δ overlineS(O 2) for lead-doped Bi-2212 and lead-free Bi-2212 indicate that the solid-state decomposition of these bismuth cuprates at low oxygen partial pressure can be represented by the diphasic CuOCu 2O system.

Some aspects of the thermodynamic behaviour of the lead-doped Bi-2223 system

NASA Astrophysics Data System (ADS)

Tetenbaum, M.; Maroni, V. A.

1996-02-01

A thermodynamic assessment of lead-doped Bi-2223 with emphasis on compositions and oxygen partial pressures within the homogeneity region prior to solid-state decomposition is presented. Equations for the variation of oxygen partial pressure with composition and temperature have been derived from our EMF measurements. Long-term metastability was indicated during cycling over a temperature range of ∼ 700-815°C of a lead-doped Bi-2223 sample having an oxygen-deficient stoichiometry of 9.64 prior to solid-state decomposition corresponding to the diphasic CuOCu 2O system. A trend of increasing negative values of the partial molar enthalpy Δ overlineH( O 2) and entropy Δ overlineS( O2 with increasing oxygen deficiency of the condensed phase indicated an increase in ordering of the cuprate structure prior to solid-state decomposition.

Entropy and convexity for nonlinear partial differential equations

PubMed Central

Ball, John M.; Chen, Gui-Qiang G.

2013-01-01

Partial differential equations are ubiquitous in almost all applications of mathematics, where they provide a natural mathematical description of many phenomena involving change in physical, chemical, biological and social processes. The concept of entropy originated in thermodynamics and statistical physics during the nineteenth century to describe the heat exchanges that occur in the thermal processes in a thermodynamic system, while the original notion of convexity is for sets and functions in mathematics. Since then, entropy and convexity have become two of the most important concepts in mathematics. In particular, nonlinear methods via entropy and convexity have been playing an increasingly important role in the analysis of nonlinear partial differential equations in recent decades. This opening article of the Theme Issue is intended to provide an introduction to entropy, convexity and related nonlinear methods for the analysis of nonlinear partial differential equations. We also provide a brief discussion about the content and contributions of the papers that make up this Theme Issue. PMID:24249768

Entropy and convexity for nonlinear partial differential equations.

PubMed

Ball, John M; Chen, Gui-Qiang G

2013-12-28

Partial differential equations are ubiquitous in almost all applications of mathematics, where they provide a natural mathematical description of many phenomena involving change in physical, chemical, biological and social processes. The concept of entropy originated in thermodynamics and statistical physics during the nineteenth century to describe the heat exchanges that occur in the thermal processes in a thermodynamic system, while the original notion of convexity is for sets and functions in mathematics. Since then, entropy and convexity have become two of the most important concepts in mathematics. In particular, nonlinear methods via entropy and convexity have been playing an increasingly important role in the analysis of nonlinear partial differential equations in recent decades. This opening article of the Theme Issue is intended to provide an introduction to entropy, convexity and related nonlinear methods for the analysis of nonlinear partial differential equations. We also provide a brief discussion about the content and contributions of the papers that make up this Theme Issue.

The effect of dilatancy on the unloading behavior of Mt. Helen tuff

DOE Office of Scientific and Technical Information (OSTI.GOV)

Attia, A.V.; Rubin, M.B.

1993-11-01

In order to understand the role of rock dilatancy in modeling the response of partially saturated rock formations to underground nuclear explosions, we have developed a thermodynamically consistent model for a porous material, partially saturated with fluid. This model gives good predictions of the unloading behavior of dry, partially saturated, and fully saturated Mt. Helen tuff, as measured by Heard.

Heading in the right direction: thermodynamics-based network analysis and pathway engineering.

PubMed

Ataman, Meric; Hatzimanikatis, Vassily

2015-12-01

Thermodynamics-based network analysis through the introduction of thermodynamic constraints in metabolic models allows a deeper analysis of metabolism and guides pathway engineering. The number and the areas of applications of thermodynamics-based network analysis methods have been increasing in the last ten years. We review recent applications of these methods and we identify the areas that such analysis can contribute significantly, and the needs for future developments. We find that organisms with multiple compartments and extremophiles present challenges for modeling and thermodynamics-based flux analysis. The evolution of current and new methods must also address the issues of the multiple alternatives in flux directionalities and the uncertainties and partial information from analytical methods. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Viscous fingering with partially miscible fluids

NASA Astrophysics Data System (ADS)

Fu, Xiaojing; Cueto-Felgueroso, Luis; Juanes, Ruben

2017-10-01

Viscous fingering—the fluid-mechanical instability that takes place when a low-viscosity fluid displaces a high-viscosity fluid—has traditionally been studied under either fully miscible or fully immiscible fluid systems. Here we study the impact of partial miscibility (a common occurrence in practice) on the fingering dynamics. Through a careful design of the thermodynamic free energy of a binary mixture, we develop a phase-field model of fluid-fluid displacements in a Hele-Shaw cell for the general case in which the two fluids have limited (but nonzero) solubility into one another. We show, by means of high-resolution numerical simulations, that partial miscibility exerts a powerful control on the degree of fingering: fluid dissolution hinders fingering while fluid exsolution enhances fingering. We also show that, as a result of the interplay between compositional exchange and the hydrodynamic pattern-forming process, stronger fingering promotes the system to approach thermodynamic equilibrium more quickly.

Impact Assessment of Problem-Based Learning in an Engineering Science Course

ERIC Educational Resources Information Center

Nasr, Karim J.; Ramadan, Bassem H.

2008-01-01

This paper presents the development and implementation of Problem-Based Learning (PBL) in an engineering thermodynamics course at Kettering University. In this project, the thermodynamics course was restructured as modules presenting practical applications first, whereas principles were introduced just-in-time and as encountered. Theoretical…

Partially ionized hydrogen plasma in strong magnetic fields.

PubMed

Potekhin, A Y; Chabrier, G; Shibanov, Y A

1999-08-01

We study the thermodynamic properties of a partially ionized hydrogen plasma in strong magnetic fields, B approximately 10(12)-10(13) G, typical of neutron stars. The properties of the plasma depend significantly on the quantum-mechanical sizes and binding energies of the atoms, which are strongly modified by thermal motion across the field. We use new fitting formulas for the atomic binding energies and sizes, based on accurate numerical calculations and valid for any state of motion of the atom. In particular, we take into account decentered atomic states, neglected in previous studies of thermodynamics of magnetized plasmas. We also employ analytic fits for the thermodynamic functions of nonideal fully ionized electron-ion Coulomb plasmas. This enables us to construct an analytic model of the free energy. An ionization equilibrium equation is derived, taking into account the strong magnetic field effects and the nonideality effects. This equation is solved by an iteration technique. Ionization degrees, occupancies, and the equation of state are calculated.

Oxygen stoichiometry, phase stability, and thermodynamic behavior of the lead-doped Bi-2223 and Ag/Bi-2223 systems

NASA Astrophysics Data System (ADS)

Tetenbaum, M.; Hash, M.; Tani, B. S.; Luo, J. S.; Maroni, V. A.

1995-02-01

Electromotive-force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made in the lead-doped Bi-2223 superconducting system in the temperature range 700-815°C by means of an oxygen titration technique that employs an yttria-stabilized zirconia electrolyte. The results of our studies indicate that processing or annealing lead-doped Bi-2223 at temperatures ranging from 750 to 815°C and at oxygen partial pressures ranging from ∼ 0.02 to 0.2 atm should preserve Bi-2223 as essentially single-phase material. Thermodynamic assessments of the partial molar quantities ΔS¯( O2) andΔH¯( O2) indicate that the plateau regions in the plot of oxygen partial pressure versus oxygen stoichiometry ( x) can be represented by the diphasic CuOCu 2O system. In accord with the EMF measurements, it was found that lead-doped Bi-2223 in a silver sheath is stable at 815°C for oxygen partial pressures between 0.02 and 0.13 atm.

Thermodynamic and nonstoichiometric behavior of the lead-doped Bi-2223 system

NASA Astrophysics Data System (ADS)

Tetenbaum, M.; Hash, M.; Tani, B. S.; Luo, J. S.; Maroni, V. A.

1994-12-01

Electromotive force (EMF) measurements of oxygen fugacities as a function of stoichiometry have been made in the lead-doped Bi-2223 superconducting system in the temperature range 700-815°C by means of an oxygen titration technique. The results of our studies indicate that processing or annealing lead-doped Bi-2223 at temperatures ranging from 700 to 815°C and at oxygen partial pressures ranging from ∼0.02 to 0.2 atm should tend to preserve Bi-2223 as essentially single-phase material. Thermodynamic assessments of partial molar quantities indicate that the plateau regions can be represented by the diphasic CuOCu 2O system. In accord with the EMF measurements, it was found that lead-doped Bi-2223 in a silver sheath is stable at 815°C for oxygen partial pressures between 0.02 and 0.13 atm. Long-duration post anneals of silver-clad Bi-2223 filaments at 825°C and an oxygen partial pressure of 0.075 atm eliminated Bi-2212 intergrowths with a concomitant increase in the superconducting transition sharpness.

Ground test program for a full-size solar dynamic heat receiver

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Kaufmann, K. J.; Mclallin, K. L.; Kerslake, T. W.

1991-01-01

Test hardware, facilities, and procedures were developed to conduct ground testing of a full-size, solar dynamic heat receiver in a partially simulated, low earth orbit environment. The heat receiver was designed to supply 102 kW of thermal energy to a helium and xenon gas mixture continuously over a 94 minute orbit, including up to 36 minutes of eclipse. The purpose of the test program was to quantify the receiver thermodynamic performance, its operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber using liquid nitrogen cold shrouds and an aperture cold plate. Special test equipment was designed to provide the required ranges in interface boundary conditions that typify those expected or required for operation as part of the solar dynamic power module on the Space Station Freedom. The support hardware includes an infrared quartz lamp heater with 30 independently controllable zones and a closed-Brayton cycle engine simulator to circulate and condition the helium-xenon gas mixture. The test article, test support hardware, facilities, and instrumentation developed to conduct the ground test program are all described.

Ground test program for a full-size solar dynamic heat receiver

NASA Technical Reports Server (NTRS)

Sedgwick, L. M.; Kaufmann, K. J.; Mclallin, K. L.; Kerslake, T. W.

1991-01-01

Test hardware, facilities, and procedures were developed to conduct ground testing of a full size, solar dynamic heat receiver in a partially simulated, low Earth orbit environment. The heat receiver was designed to supply 102 kW of thermal energy to a helium and xenon gas mixture continuously over a 94 minute orbit, including up to 36 minutes of eclipse. The purpose of the test program was to quantify the receiver thermodynamic performance, its operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber using liquid nitrogen cold shrouds and an aperture cold plate. Special test equipment were designed to provide the required ranges in interface boundary conditions that typify those expected or required for operation as part of the solar dynamic power module on the Space Station Freedom. The support hardware includes an infrared quartz lamp heater with 30 independently controllable zones and a closed Brayton cycle engine simulator to circulate and condition the helium xenon gas mixture. The test article, test support hardware, facilities, and instrumentation developed to conduct the ground test program are all described.

Ground test program for a full-size solar dynamic heat receiver

NASA Astrophysics Data System (ADS)

Sedgwick, L. M.; Kaufmann, K. J.; McLallin, K. L.; Kerslake, T. W.

Test hardware, facilities, and procedures were developed to conduct ground testing of a full-size, solar dynamic heat receiver in a partially simulated, low earth orbit environment. The heat receiver was designed to supply 102 kW of thermal energy to a helium and xenon gas mixture continuously over a 94 minute orbit, including up to 36 minutes of eclipse. The purpose of the test program was to quantify the receiver thermodynamic performance, its operating temperatures, and thermal response to changes in environmental and power module interface boundary conditions. The heat receiver was tested in a vacuum chamber using liquid nitrogen cold shrouds and an aperture cold plate. Special test equipment was designed to provide the required ranges in interface boundary conditions that typify those expected or required for operation as part of the solar dynamic power module on the Space Station Freedom. The support hardware includes an infrared quartz lamp heater with 30 independently controllable zones and a closed-Brayton cycle engine simulator to circulate and condition the helium-xenon gas mixture. The test article, test support hardware, facilities, and instrumentation developed to conduct the ground test program are all described.

Measuring Thermodynamic Properties of Metals and Alloys With Knudsen Effusion Mass Spectrometry

NASA Technical Reports Server (NTRS)

Copland, Evan H.; Jacobson, Nathan S.

2010-01-01

This report reviews Knudsen effusion mass spectrometry (KEMS) as it relates to thermodynamic measurements of metals and alloys. First, general aspects are reviewed, with emphasis on the Knudsen-cell vapor source and molecular beam formation, and mass spectrometry issues germane to this type of instrument are discussed briefly. The relationship between the vapor pressure inside the effusion cell and the measured ion intensity is the key to KEMS and is derived in detail. Then common methods used to determine thermodynamic quantities with KEMS are discussed. Enthalpies of vaporization, the fundamental measurement, are determined from the variation of relative partial pressure with temperature using the second-law method or by calculating a free energy of formation and subtracting the entropy contribution using the third-law method. For single-cell KEMS instruments, measurements can be used to determine the partial Gibbs free energy if the sensitivity factor remains constant over multiple experiments. The ion-current ratio method and dimer-monomer method are also viable in some systems. For a multiple-cell KEMS instrument, activities are obtained by direct comparison with a suitable component reference state or a secondary standard. Internal checks for correct instrument operation and general procedural guidelines also are discussed. Finally, general comments are made about future directions in measuring alloy thermodynamics with KEMS.

Thermodynamic Stability of Ice II and Its Hydrogen-Disordered Counterpart: Role of Zero-Point Energy.

PubMed

Nakamura, Tatsuya; Matsumoto, Masakazu; Yagasaki, Takuma; Tanaka, Hideki

2016-03-03

We investigate why no hydrogen-disordered form of ice II has been found in nature despite the fact that most of hydrogen-ordered ices have hydrogen-disordered counterparts. The thermodynamic stability of a set of hydrogen-ordered ice II variants relative to ice II is evaluated theoretically. It is found that ice II is more stable than the disordered variants so generated as to satisfy the simple ice rule due to the lower zero-point energy as well as the pair interaction energy. The residual entropy of the disordered ice II phase gradually compensates the unfavorable free energy with increasing temperature. The crossover, however, occurs at a high temperature well above the melting point of ice III. Consequently, the hydrogen-disordered phase does not exist in nature. The thermodynamic stability of partially hydrogen-disordered ices is also scrutinized by examining the free-energy components of several variants obtained by systematic inversion of OH directions in ice II. The potential energy of one variant is lower than that of the ice II structure, but its Gibbs free energy is slightly higher than that of ice II due to the zero-point energy. The slight difference in the thermodynamic stability leaves the possibility of the partial hydrogen-disorder in real ice II.

Defect formation in LaGa(Mg,Ni)O3-δ : A statistical thermodynamic analysis validated by mixed conductivity and magnetic susceptibility measurements

NASA Astrophysics Data System (ADS)

Naumovich, E. N.; Kharton, V. V.; Yaremchenko, A. A.; Patrakeev, M. V.; Kellerman, D. G.; Logvinovich, D. I.; Kozhevnikov, V. L.

2006-08-01

A statistical thermodynamic approach to analyze defect thermodynamics in strongly nonideal solid solutions was proposed and validated by a case study focused on the oxygen intercalation processes in mixed-conducting LaGa0.65Mg0.15Ni0.20O3-δ perovskite. The oxygen nonstoichiometry of Ni-doped lanthanum gallate, measured by coulometric titration and thermogravimetric analysis at 923-1223K in the oxygen partial pressure range 5×10-5to0.9atm , indicates the coexistence of Ni2+ , Ni3+ , and Ni4+ oxidation states. The formation of tetravalent nickel was also confirmed by the magnetic susceptibility data at 77-600K , and by the analysis of p -type electronic conductivity and Seebeck coefficient as function of the oxygen pressure at 1023-1223K . The oxygen thermodynamics and the partial ionic and hole conductivities are strongly affected by the point-defect interactions, primarily the Coulombic repulsion between oxygen vacancies and/or electron holes and the vacancy association with Mg2+ cations. These factors can be analyzed by introducing the defect interaction energy in the concentration-dependent part of defect chemical potentials expressed by the discrete Fermi-Dirac distribution, and taking into account the probabilities of local configurations calculated via binomial distributions.

Study on the intrinsic defects in ZnO by combing first-principle and thermodynamic calculations

NASA Astrophysics Data System (ADS)

Ma, Changmin; Liu, Tingyu; Chang, Qiuxiang

2015-11-01

In this paper, the intrinsic point defects in ZnO crystal have been studied by the approach that integrates first-principles, thermodynamic calculations and the contributions of vibrational entropy. With temperature increasing and oxygen partial pressure decreasing, the formation energies of oxygen vacancy (VO), zinc interstitial (Zni) and zinc anti-site (ZnO) are decreasing, while it increases for zinc vacancy (VZn), oxygen interstitial (Oi) and oxygen anti-site (OZn). They are more sensitive to temperature than oxygen partial pressure. There are two interesting phenomena. First, VO or VZn have the lowest formation energies for whole Fermi level at special environment condition (such as at T = 300K, about PO2 = 10-10atm or T = 1500K, about PO2 = 104atm) and intrinsic p-type doping of ZnO is possible by VZn at these special conditions. Second, VO as donors have lowest formation energy for all Fermi level at high temperature and low oxygen partial pressure (T = 1500K, PO2 = 10-10atm). According to our analysis, the VO could produce n-type doping in ZnO at these special conditions and change p-type ZnO to n-type ZnO at condition from low temperature and high oxygen partial pressure to high temperature and low oxygen partial pressure.

Thermodynamics and structural analysis of positive allosteric modulation of the ionotropic glutamate receptor GluA2.

PubMed

Krintel, Christian; Frydenvang, Karla; Olsen, Lars; Kristensen, Maria T; de Barrios, Oriol; Naur, Peter; Francotte, Pierre; Pirotte, Bernard; Gajhede, Michael; Kastrup, Jette S

2012-01-01

Positive allosteric modulators of the ionotropic glutamate receptor-2 (GluA2) are promising compounds for the treatment of cognitive disorders, e.g. Alzheimer's disease. These modulators bind within the dimer interface of the LBD (ligand-binding domain) and stabilize the agonist-bound conformation slowing receptor desensitization and/or deactivation. In the present study, we employ isothermal titration calorimetry to determine binding affinities and thermodynamic details of binding of modulators of GluA2. A mutant of the LBD of GluA2 (LBD-L483Y-N754S) that forms a stable dimer in solution was used. The potent GluA2 modulator BPAM-97 was used as a reference compound. Evidence that BPAM-97 binds in the same pocket as the well-known GluA2 modulator cyclothiazide was obtained from X-ray structures. The LBD-L483Y-N754S:BPAM-97 complex has a Kd of 5.6 μM (ΔH=-4.9 kcal/mol, -TΔS=-2.3 kcal/mol; where 1 kcal≈4.187 kJ). BPAM-97 was used in a displacement assay to determine a Kd of 0.46 mM (ΔH=-1.2 kcal/mol, -TΔS=-3.3 kcal/mol) for the LBD-L483Y-N754S:IDRA-21 complex. The major structural factors increasing the potency of BPAM-97 over IDRA-21 are the increased van der Waals contacts to, primarily, Met496 in GluA2 imposed by the ethyl substituent of BPAM-97. These results add important information on binding affinities and thermodynamic details, and provide a new tool in the development of drugs against cognitive disorders.

The Hydrothermal Chemistry of Gold, Arsenic, Antimony, Mercury and Silver

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bessinger, Brad; Apps, John A.

2003-03-23

A comprehensive thermodynamic database based on the Helgeson-Kirkham-Flowers (HKF) equation of state was developed for metal complexes in hydrothermal systems. Because this equation of state has been shown to accurately predict standard partial molal thermodynamic properties of aqueous species at elevated temperatures and pressures, this study provides the necessary foundation for future exploration into transport and depositional processes in polymetallic ore deposits. The HKF equation of state parameters for gold, arsenic, antimony, mercury, and silver sulfide and hydroxide complexes were derived from experimental equilibrium constants using nonlinear regression calculations. In order to ensure that the resulting parameters were internally consistent,more » those experiments utilizing incompatible thermodynamic data were re-speciated prior to regression. Because new experimental studies were used to revise the HKF parameters for H2S0 and HS-1, those metal complexes for which HKF parameters had been previously derived were also updated. It was found that predicted thermodynamic properties of metal complexes are consistent with linear correlations between standard partial molal thermodynamic properties. This result allowed assessment of several complexes for which experimental data necessary to perform regression calculations was limited. Oxygen fugacity-temperature diagrams were calculated to illustrate how thermodynamic data improves our understanding of depositional processes. Predicted thermodynamic properties were used to investigate metal transport in Carlin-type gold deposits. Assuming a linear relationship between temperature and pressure, metals are predicted to predominantly be transported as sulfide complexes at a total aqueous sulfur concentration of 0.05 m. Also, the presence of arsenic and antimony mineral phases in the deposits are shown to restrict mineralization within a limited range of chemical conditions. Finally, at a lesser aqueous sulfur concentration of 0.01 m, host rock sulfidation can explain the origin of arsenic and antimony minerals within the paragenetic sequence.« less

An equation of state for partially ionized plasmas: The Coulomb contribution to the free energy

NASA Astrophysics Data System (ADS)

Kilcrease, D. P.; Colgan, J.; Hakel, P.; Fontes, C. J.; Sherrill, M. E.

2015-09-01

We have previously developed an equation of state (EOS) model called ChemEOS (Hakel and Kilcrease, Atomic Processes in Plasmas, Eds., J. Cohen et al., AIP, 2004) for a plasma of interacting ions, atoms and electrons. It is based on a chemical picture of the plasma and is derived from an expression for the Helmholtz free energy of the interacting species. All other equilibrium thermodynamic quantities are then obtained by minimizing this free energy subject to constraints, thus leading to a thermodynamically consistent EOS. The contribution to this free energy from the Coulomb interactions among the particles is treated using the method of Chabrier and Potekhin (Phys. Rev. E 58, 4941 (1998)) which we have adapted for partially ionized plasmas. This treatment is further examined and is found to give rise to unphysical behavior for various elements at certain values of the density and temperature where the Coulomb coupling begins to become significant and the atoms are partially ionized. We examine the source of this unphysical behavior and suggest corrections that produce acceptable results. The sensitivity of the thermodynamic properties and frequency-dependent opacity of iron is examined with and without these corrections. The corrected EOS is used to determine the fractional ion populations and level populations for a new generation of OPLIB low-Z opacity tables currently being prepared at Los Alamos National Laboratory with the ATOMIC code.

Damage in Monolithic Thin-Film Photovoltaic Modules Due to Partial Shade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, Timothy J.; Mansfield, Lorelle; Repins, Ingrid

2016-09-01

The typical configuration of monolithic thin-film photovoltaic modules makes it possible for partial shade to place one or more cells in such a module in reverse bias. Reverse bias operation leads to high voltage, current density, and power density conditions, which can act as driving forces for failure. We showed that a brief outdoor shadow event can cause a 7% permanent loss in power. We applied an indoor partial shade durability test that moves beyond the standard hot spot endurance test by using more realistic mask and bias conditions and by carefully quantifying the permanent change in performance due tomore » the stress. With the addition of a pass criterion based on change in maximum power, this procedure will soon be proposed as a part of the module-type qualification test. All six commercial copper indium gallium diselenide and cadmium telluride modules we tested experienced permanent damage due to the indoor partial shade test, ranging from 4% to 14% loss in maximum power. We conclude by summarizing ways to mitigate partial shade stress at the cell, module, and system levels.« less

Thermodynamics of Iron Oxidation in Metallurgical Slags

NASA Astrophysics Data System (ADS)

Matousek, Jan

2012-11-01

The state of oxidation of a pyrometallurgical process, given by the partial pressure of oxygen and the temperature, is one of the important properties monitored and controlled in the smelting and refining of iron and the nonferrous metals. This article reviews the thermodynamic background for this quantity and examines some empirical methods for its estimation and use. The emphasis is on copper smelting, but the same principles apply to iron, nickel, lead, and zinc processes.

Calculation of the standard partial molal thermodynamic properties and dissociation constants of aqueous HCl{sup 0} and HBr{sup 0} at temperatures to 1000 C and pressures to 5 kbar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pokrovskii, V.A.

1999-04-01

Dissociation constants of aqueous ion pairs HCl{sup 0} and HBr{sup 0} derived in the literature from vapor pressure and supercritical conductance measurements (Quist and Marshall, 1968b; Frantz and Marshall, 1984) were used to calculate the standard partial molal thermodynamic properties of the species at 25 C and 1 bar. Regression of the data with the aid of revised Helgeson-Kirkham-Flowers equations of state (Helgeson et al., 1981; Tanger and Helgeson, 1988; Shock et al., 1989) resulted in a set of equations-of-state parameters that permits accurate calculation of the thermodynamic properties of the species at high temperatures and pressures. These properties andmore » parameters reproduce generally within 0.1 log unit (with observed maximum deviation of 0.23 log unit) the log K values for HBr{sup 0} and HCl{sup 0} given by Quist and Marshall (1968b) and Frantz and Marshall (1984), respectively, at temperatures to 800 C and pressures to 5 kbar.« less

Continuous information flow fluctuations

NASA Astrophysics Data System (ADS)

Rosinberg, Martin Luc; Horowitz, Jordan M.

2016-10-01

Information plays a pivotal role in the thermodynamics of nonequilibrium processes with feedback. However, much remains to be learned about the nature of information fluctuations in small-scale devices and their relation with fluctuations in other thermodynamics quantities, like heat and work. Here we derive a series of fluctuation theorems for information flow and partial entropy production in a Brownian particle model of feedback cooling and extend them to arbitrary driven diffusion processes. We then analyze the long-time behavior of the feedback-cooling model in detail. Our results provide insights into the structure and origin of large deviations of information and thermodynamic quantities in autonomous Maxwell's demons.

The effect of water on thermal stresses in polymer composites

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

1994-01-01

The fundamentals of the thermodynamic theory of mixtures and continuum thermochemistry are reviewed for a mixture of condensed water and polymer. A specific mixture which is mechanically elastic with temperature and water concentration gradients present is considered. An expression for the partial pressure of water in the mixture is obtained based on certain assumptions regarding the thermodynamic state of the water in the mixture. Along with a simple diffusion equation, this partial pressure expression may be used to simulate the thermostructural behavior of polymer composite materials due to water in the free volumes of the polymer. These equations are applied to a specific polymer composite material during isothermal heating conditions. The thermal stresses obtained by the application of the theory are compared to measured results to verify the accuracy of the approach.

Study Modules for Calculus-Based General Physics. [Includes Modules 18-20: Sound; Temperature, Heat, and Thermodynamics: First Law; and Kinetic Theory of Gases].

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;…

Partial Shade Stress Test for Thin-Film Photovoltaic Modules: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, Timothy J.; Deceglie, Michael G.; Deline, Chris

2015-09-02

Partial shade of monolithic thin-film PV modules can cause reverse-bias conditions leading to permanent damage. In this work, we propose a partial shade stress test for thin-film PV modules that quantifies permanent performance loss. We designed the test with the aid of a computer model that predicts the local voltage, current and temperature stress that result from partial shade. The model predicts the module-scale interactions among the illumination pattern, the electrical properties of the photovoltaic material and the thermal properties of the module package. The test reproduces shading and loading conditions that may occur in the field. It accounts formore » reversible light-induced performance changes and for additional stress that may be introduced by light-enhanced reverse breakdown. We present simulated and experimental results from the application of the proposed test.« less

Propulsion System Simulation Using the Toolbox for the Modeling and Analysis of Thermodynamic System T-MATS

NASA Technical Reports Server (NTRS)

Chapman, Jeffryes W.; Lavelle, Thomas M.; May, Ryan D.; Litt, Jonathan S.; Guo, Ten-Huei

2014-01-01

A simulation toolbox has been developed for the creation of both steady-state and dynamic thermodynamic software models. This paper describes the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS), which combines generic thermodynamic and controls modeling libraries with a numerical iterative solver to create a framework for the development of thermodynamic system simulations, such as gas turbine engines. The objective of this paper is to present an overview of T-MATS, the theory used in the creation of the module sets, and a possible propulsion simulation architecture. A model comparison was conducted by matching steady-state performance results from a T-MATS developed gas turbine simulation to a well-documented steady-state simulation. Transient modeling capabilities are then demonstrated when the steady-state T-MATS model is updated to run dynamically.

Propulsion System Simulation Using the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS)

NASA Technical Reports Server (NTRS)

Chapman, Jeffryes W.; Lavelle, Thomas M.; May, Ryan D.; Litt, Jonathan S.; Guo, Ten-Huei

2014-01-01

A simulation toolbox has been developed for the creation of both steady-state and dynamic thermodynamic software models. This paper describes the Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS), which combines generic thermodynamic and controls modeling libraries with a numerical iterative solver to create a framework for the development of thermodynamic system simulations, such as gas turbine engines. The objective of this paper is to present an overview of T-MATS, the theory used in the creation of the module sets, and a possible propulsion simulation architecture. A model comparison was conducted by matching steady-state performance results from a T-MATS developed gas turbine simulation to a well-documented steady-state simulation. Transient modeling capabilities are then demonstrated when the steady-state T-MATS model is updated to run dynamically.

Reducing treatment of coppersmelting slag: Thermodynamic analysis of impurities behavior

NASA Astrophysics Data System (ADS)

Komkov, Alexey; Kamkin, Rostislav

2011-01-01

A thermodynamic mathematical model, describing behavior of Pb, Zn, and As during reducing slag cleaning in the Vanyukov furnace has been developed. Using a developed model, the influence of different factors, such as temperature, oxygen partial pressure, the ratio of the formed phases on the behavior of impurities, was analyzed. It was found that arsenic can significantly move to the bottom phase, and zinc can be significantly vaporized under conditions in the Vanyukov furnace.

Improvement in low-temperature and instantaneous high-rate output performance of Al-free AB5-type hydrogen storage alloy for negative electrode in Ni/MH battery: Effect of thermodynamic and kinetic regulation via partial Mn substituting

NASA Astrophysics Data System (ADS)

Zhou, Wanhai; Zhu, Ding; Tang, Zhengyao; Wu, Chaoling; Huang, Liwu; Ma, Zhewen; Chen, Yungui

2017-03-01

A series of Al-free Mn-modified AB5-type hydrogen storage alloys have been designed and the effects of thermodynamic stability and electrochemical kinetics on electrochemical performance via Mn substituting have been investigated. Compared with high-Al alloys, the Al-free alloys in this study have better low-temperature performance and instantaneous high-rate output because of the higher surface catalytic ability. After partial substitution of Ni by Mn, both the hydrogen desorption capacity and plateau pressure decrease, and correspondingly results in an improved thermodynamic stability which is adverse to low-temperature delivery. Additionally, with the improvement of charge acceptance ability and anti-corrosion property via Mn substitution, the room-temperature discharge capacity and cycling stability increase slightly. However, Mn adversely affects the electrochemical kinetics and deteriorates both the surface catalytic ability and the bulk hydrogen diffusion ability, leading to the drop of low-temperature dischargeability, high-rate dischargeability and peak power (Ppeak). Based on the thermodynamic and kinetic regulation and overall electrochemical properties, the optimal composition is obtained when x = 0.2, the discharge capacity is 243.6 mAh g-1 at -40 °C with 60 mA g-1, and the Ppeak attains to 969.6 W kg-1 at -40 °C.

Direct computation of thermodynamic properties of chemically reacting air with consideration to CFD

NASA Astrophysics Data System (ADS)

Iannelli, Joe

2003-10-01

This paper details a two-equation procedure to calculate exactly mass and mole fractions, pressure, temperature, specific heats, speed of sound and the thermodynamic and jacobian partial derivatives of pressure and temperature for a five-species chemically reacting equilibrium air. The procedure generates these thermodynamic properties using as independent variables either pressure and temperature or density and internal energy, for CFD applications. An original element in this procedure consists in the exact physically meaningful solution of the mass-fraction and mass-action equations. Air-equivalent molecular masses for oxygen and nitrogen are then developed to account, within a mixture of only oxygen and nitrogen, for the presence of carbon dioxide, argon and the other noble gases within atmospheric air. The mathematical formulation also introduces a versatile system non-dimensionalization that makes the procedure uniformly applicable to flows ranging from shock-tube flows with zero initial velocity to aerothermodynamic flows with supersonic/hypersonic free-stream Mach numbers. Over a temperature range of more than 10000 K and pressure and density ranges corresponding to an increase in altitude in standard atmosphere of 30000 m above sea level, the predicted distributions of mole fractions, constant-volume specific heat, and speed of sound for the model five species agree with independently published results, and all the calculated thermodynamic properties, including their partial derivatives, remain continuous, smooth, and physically meaningful.

Beyond heat baths II: framework for generalized thermodynamic resource theories

NASA Astrophysics Data System (ADS)

Yunger Halpern, Nicole

2018-03-01

Thermodynamics, which describes vast systems, has been reconciled with small scales, relevant to single-molecule experiments, in resource theories. Resource theories have been used to model exchanges of energy and information. Recently, particle exchanges were modeled; and an umbrella family of thermodynamic resource theories was proposed to model diverse baths, interactions, and free energies. This paper motivates and details the family’s structure and prospective applications. How to model electrochemical, gravitational, magnetic, and other thermodynamic systems is explained. Szilárd’s engine and Landauer’s Principle are generalized, as resourcefulness is shown to be convertible not only between information and gravitational energy, but also among diverse degrees of freedom. Extensive variables are associated with quantum operators that might fail to commute, introducing extra nonclassicality into thermodynamic resource theories. An early version of this paper partially motivated the later development of noncommutative thermalization. This generalization expands the theories’ potential for modeling realistic systems with which small-scale statistical mechanics might be tested experimentally.

Modulation of the multistate folding of designed TPR proteins through intrinsic and extrinsic factors

PubMed Central

Phillips, J J; Javadi, Y; Millership, C; Main, E R G

2012-01-01

Tetratricopeptide repeats (TPRs) are a class of all alpha-helical repeat proteins that are comprised of 34-aa helix-turn-helix motifs. These stack together to form nonglobular structures that are stabilized by short-range interactions from residues close in primary sequence. Unlike globular proteins, they have few, if any, long-range nonlocal stabilizing interactions. Several studies on designed TPR proteins have shown that this modular structure is reflected in their folding, that is, modular multistate folding is observed as opposed to two-state folding. Here we show that TPR multistate folding can be suppressed to approximate two-state folding through modulation of intrinsic stability or extrinsic environmental variables. This modulation was investigated by comparing the thermodynamic unfolding under differing buffer regimes of two distinct series of consensus-designed TPR proteins, which possess different intrinsic stabilities. A total of nine proteins of differing sizes and differing consensus TPR motifs were each thermally and chemically denatured and their unfolding monitored using differential scanning calorimetry (DSC) and CD/fluorescence, respectively. Analyses of both the DSC and chemical denaturation data show that reducing the total stability of each protein and repeat units leads to observable two-state unfolding. These data highlight the intimate link between global and intrinsic repeat stability that governs whether folding proceeds by an observably two-state mechanism, or whether partial unfolding yields stable intermediate structures which retain sufficient stability to be populated at equilibrium. PMID:22170589

Determination of thermodynamic properties of poly (cyclohexyl methacrylate) by inverse gas chromatography.

PubMed

Kaya, Ismet; Pala, Cigdem Yigit

2014-07-01

In this work, some thermodynamic properties of poly (cyclohexyl methacrylate) were studied by inverse gas chromatography (IGC). For this purpose, the polymeric substance was coated on Chromosorb W and which was filled into a glass column. The retention times (t(r)) of the probes were determined from the interactions of poly (cyclohexyl methacrylate) with n-pentane, n-hexane, n-heptane, n-octane, n-decane, methanol, ethanol, 2-propanol, butanol, acetone, ethyl methyl ketone, benzene, toluene and o-xylene by IGC technique. Then, the specific volume (Vg(0)) was determined for each probe molecule. By using (1/T; lnVg(0)) graphics, the glass transition temperature of poly (cyclohexyl methacrylate) was found to be 373 K. The adsorption heat under the glass transition temperature (deltaH(a)), and partial molar heat of sorption above the glass transition (deltaH1(S)), partial molar free energy of sorption (deltaG1(S)) and partial molar entropy of sorption (deltaS1(S)) belonging to sorption for every probe were calculated. The partial molar heat of mixing at infinite dilution (deltaH1(infinity)), partial molar free energy of mixing at infinite dilution (deltaG1(infinity)), Flory-Huggins interaction parameter (chi12(infinity)) and weight fraction activity coefficient (a1/w1)(infinity) values of polymer-solute systems were calculated at different column temperatures. The solubility parameters (delta2) of the polymer were obtained by IGC technique.

Thermodynamic behavior of glassy state of structurally related compounds.

PubMed

Kaushal, Aditya Mohan; Bansal, Arvind Kumar

2008-08-01

Thermodynamic properties of amorphous pharmaceutical forms are responsible for enhanced solubility as well as poor physical stability. The present study was designed to investigate the differences in thermodynamic parameters arising out of disparate molecular structures and associations for four structurally related pharmaceutical compounds--celecoxib, valdecoxib, rofecoxib, and etoricoxib. Conventional and modulated temperature differential scanning calorimetry were employed to study glass forming ability and thermodynamic behavior of the glassy state of model compounds. Glass transition temperature of four glassy compounds was in a close range of 327.6-331.8 K, however, other thermodynamic parameters varied considerably. Kauzmann temperature, strength parameter and fragility parameter showed rofecoxib glass to be most fragile of the four compounds. Glass forming ability of the compounds fared similar in the critical cooling rate experiments, suggesting that different factors were determining the glass forming ability and subsequent behavior of the compounds in glassy state. A comprehensive understanding of such thermodynamic facets of amorphous form would help in rationalizing the approaches towards development of stable glassy pharmaceuticals.

Thermodynamic models for bounding pressurant mass requirements of cryogenic tanks

NASA Technical Reports Server (NTRS)

Vandresar, Neil T.; Haberbusch, Mark S.

1994-01-01

Thermodynamic models have been formulated to predict lower and upper bounds for the mass of pressurant gas required to pressurize a cryogenic tank and then expel liquid from the tank. Limiting conditions are based on either thermal equilibrium or zero energy exchange between the pressurant gas and initial tank contents. The models are independent of gravity level and allow specification of autogenous or non-condensible pressurants. Partial liquid fill levels may be specified for initial and final conditions. Model predictions are shown to successfully bound results from limited normal-gravity tests with condensable and non-condensable pressurant gases. Representative maximum collapse factor maps are presented for liquid hydrogen to show the effects of initial and final fill level on the range of pressurant gas requirements. Maximum collapse factors occur for partial expulsions with large final liquid fill fractions.

An equation of state for partially ionized plasmas: The Coulomb contribution to the free energy

DOE PAGES

Kilcrease, D. P.; Colgan, J.; Hakel, P.; ...

2015-06-20

We have previously developed an equation of state (EOS) model called ChemEOS (Hakel and Kilcrease, Atomic Processes in Plasmas, Eds., J. Cohen et al., AIP, 2004) for a plasma of interacting ions, atoms and electrons. It is based on a chemical picture of the plasma and is derived from an expression for the Helmholtz free energy of the interacting species. All other equilibrium thermodynamic quantities are then obtained by minimizing this free energy subject to constraints, thus leading to a thermodynamically consistent EOS. The contribution to this free energy from the Coulomb interactions among the particles is treated using themore » method of Chabrier and Potekhin (Phys. Rev. E 58, 4941 (1998)) which we have adapted for partially ionized plasmas. This treatment is further examined and is found to give rise to unphysical behavior for various elements at certain values of the density and temperature where the Coulomb coupling begins to become significant and the atoms are partially ionized. We examine the source of this unphysical behavior and suggest corrections that produce acceptable results. The sensitivity of the thermodynamic properties and frequency-dependent opacity of iron is examined with and without these corrections. Lastly, the corrected EOS is used to determine the fractional ion populations and level populations for a new generation of OPLIB low-Z opacity tables currently being prepared at Los Alamos National Laboratory with the ATOMIC code.« less

On a partial differential equation method for determining the free energies and coexisting phase compositions of ternary mixtures from light scattering data.

PubMed

Ross, David S; Thurston, George M; Lutzer, Carl V

2008-08-14

In this paper we present a method for determining the free energies of ternary mixtures from light scattering data. We use an approximation that is appropriate for liquid mixtures, which we formulate as a second-order nonlinear partial differential equation. This partial differential equation (PDE) relates the Hessian of the intensive free energy to the efficiency of light scattering in the forward direction. This basic equation applies in regions of the phase diagram in which the mixtures are thermodynamically stable. In regions in which the mixtures are unstable or metastable, the appropriate PDE is the nonlinear equation for the convex hull. We formulate this equation along with continuity conditions for the transition between the two equations at cloud point loci. We show how to discretize this problem to obtain a finite-difference approximation to it, and we present an iterative method for solving the discretized problem. We present the results of calculations that were done with a computer program that implements our method. These calculations show that our method is capable of reconstructing test free energy functions from simulated light scattering data. If the cloud point loci are known, the method also finds the tie lines and tie triangles that describe thermodynamic equilibrium between two or among three liquid phases. A robust method for solving this PDE problem, such as the one presented here, can be a basis for optical, noninvasive means of characterizing the thermodynamics of multicomponent mixtures.

Determination of thermodynamic properties of isotactic poly(1-butene) at infinite dilution using density and inverse gas chromatography.

PubMed

Kozłowska, Marta Karolina; Domańska, Urszula; Lempert, Małgorzata; Rogalski, Marek

2005-03-18

The partial molar volumes, V1(M), and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V1, have been calculated from the measured density of {iPBu-1 + solvent (n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons (n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of inverse gas chromatography at various temperatures. The weight fraction activity coefficients of the solvent at infinite dilution, omega2(infinity) and the Flory-Huggins thermodynamic interaction parameters, chi21(infinity), between polymer and solvents were determined. The partial molar free energy, deltaG2(infinity), the partial molar heat of mixing, deltaH2(infinity), at infinite dilution and the polymer solubility parameter, delta1, were calculated. Additionally, the (solid + liquid) binary mixtures equilibria, SLE, of iPBu-1 with three hydrocarbons (n-octane, n-decane and m-xylene) were studied by a dynamic method. By performing these experiments over a large concentration range, the T-x phase diagrams of the polymer-solvent systems were constructed. The excess Gibbs energy models were used to describe the nonideal behaviour of the liquid phase. The omega2(infinity) were determined from the solubility measurements and were predicted by using the UNIFAC FV model.

A review of reaction rates and thermodynamic and transport properties for the 11-species air model for chemical and thermal nonequilibrium calculations to 30000 K

NASA Technical Reports Server (NTRS)

Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.

1989-01-01

Reaction rate coefficients and thermodynamic and transport properties are provided for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in such environments.

Biological modulation of planetary atmospheres: The early Earth scenario

NASA Technical Reports Server (NTRS)

Schidlowski, M.

1985-01-01

The establishment and subsequent evolution of life on Earth had a profound impact on the chemical regime at the planet's surface and its atmosphere. A thermodynamic gradient was imposed on near-surface environments that served as the driving force for a number on important geochemical transformations. An example is the redox imbalance between the modern atmosphere and the material of the Earth's crust. Current photochemical models predict extremely low partial pressures of oxygen in the Earth's prebiological atmosphere. There is widespread consensus that any large-scale oxygenation of the primitive atmosphere was contingent on the advent of biological (autotrophic) carbon fixation. It is suggested that photoautotrophy existed both as a biochemical process and as a geochemical agent since at least 3.8 Ga ago. Combining the stoichiometry of the photosynthesis reaction with a carbon isotope mass balance and current concepts for the evolution of the stationary sedimentary mass as a funion of time, it is possible to quantify, the accumulation of oxygen and its photosynthetic oxidation equivalents through Earth history.

Thermodynamic properties of a liquid crystal carbosilane dendrimer

NASA Astrophysics Data System (ADS)

Samosudova, Ya. S.; Markin, A. V.; Smirnova, N. N.; Ogurtsov, T. G.; Boiko, N. I.; Shibaev, V. P.

2016-11-01

The temperature dependence of the heat capacity of a first-generation liquid crystal carbosilane dendrimer with methoxyphenyl benzoate end groups is studied for the first time in the region of 6-370 K by means of precision adiabatic vacuum calorimetry. Physical transformations are observed in this interval of temperatures, and their standard thermodynamic characteristics are determined and discussed. Standard thermodynamic functions C p ° ( T), H°( T) - H°(0), S°( T) - S°(0), and G°( T) - H°(0) are calculated from the obtained experimental data for the region of T → 0 to 370 K. The standard entropy of formation of the dendrimer in the partially crystalline state at T = 298.15 K is calculated, and the standard entropy of the hypothetic reaction of its synthesis at this temperature is estimated. The thermodynamic properties of the studied dendrimer are compared to those of second- and fourth-generation liquid crystal carbosilane dendrimers with the same end groups studied earlier.

Determination of partial molar volumes from free energy perturbation theory†

PubMed Central

Vilseck, Jonah Z.; Tirado-Rives, Julian

2016-01-01

Partial molar volume is an important thermodynamic property that gives insights into molecular size and intermolecular interactions in solution. Theoretical frameworks for determining the partial molar volume (V°) of a solvated molecule generally apply Scaled Particle Theory or Kirkwood–Buff theory. With the current abilities to perform long molecular dynamics and Monte Carlo simulations, more direct methods are gaining popularity, such as computing V° directly as the difference in computed volume from two simulations, one with a solute present and another without. Thermodynamically, V° can also be determined as the pressure derivative of the free energy of solvation in the limit of infinite dilution. Both approaches are considered herein with the use of free energy perturbation (FEP) calculations to compute the necessary free energies of solvation at elevated pressures. Absolute and relative partial molar volumes are computed for benzene and benzene derivatives using the OPLS-AA force field. The mean unsigned error for all molecules is 2.8 cm3 mol−1. The present methodology should find use in many contexts such as the development and testing of force fields for use in computer simulations of organic and biomolecular systems, as a complement to related experimental studies, and to develop a deeper understanding of solute–solvent interactions. PMID:25589343

Determination of partial molar volumes from free energy perturbation theory.

PubMed

Vilseck, Jonah Z; Tirado-Rives, Julian; Jorgensen, William L

2015-04-07

Partial molar volume is an important thermodynamic property that gives insights into molecular size and intermolecular interactions in solution. Theoretical frameworks for determining the partial molar volume (V°) of a solvated molecule generally apply Scaled Particle Theory or Kirkwood-Buff theory. With the current abilities to perform long molecular dynamics and Monte Carlo simulations, more direct methods are gaining popularity, such as computing V° directly as the difference in computed volume from two simulations, one with a solute present and another without. Thermodynamically, V° can also be determined as the pressure derivative of the free energy of solvation in the limit of infinite dilution. Both approaches are considered herein with the use of free energy perturbation (FEP) calculations to compute the necessary free energies of solvation at elevated pressures. Absolute and relative partial molar volumes are computed for benzene and benzene derivatives using the OPLS-AA force field. The mean unsigned error for all molecules is 2.8 cm(3) mol(-1). The present methodology should find use in many contexts such as the development and testing of force fields for use in computer simulations of organic and biomolecular systems, as a complement to related experimental studies, and to develop a deeper understanding of solute-solvent interactions.

The conformational flexibility of the carboxy terminal residues 105–114 is a key modulator of the catalytic activity and stability of Macrophage Migration Inhibitory Factor (MIF)†

PubMed Central

El-Turk, Farah; Cascella, Michele; Ouertatani-Sakouhi, Hajer; Narayanan, Raghavendran Lakshmi; Leng, Lin; Bucala, Richard; Hweckstetter, Markus; Rothlisberger, Ursula; Lashuel, Hilal A.

2013-01-01

Macrophage migration inhibitory factor (MIF) is a multifunctional protein and a major mediator of innate immunity. Although X-ray crystallography revealed that MIF exists as a homotrimer, its oligomerization state in vivo as well as the factors governing its oligomerization and stability remain poorly understood. The C-terminal region of MIF is highly conserved and participates in several intramolecular interactions that suggest a role in modulating the stability and biochemical activity of MIF. To determine the importance of these interactions, point mutations (A48P, L46A), insertions (P107) at the monomer-monomer interfaces, and C-terminal deletion (Δ110-114NSTFA and Δ105–114NVGWNNSTFA) variants were designed and their structural properties, thermodynamic stability, oligomerization state, catalytic activity and receptor binding were characterized using a battery of biophysical methods. The C-terminal deletion mutants ΔC5 huMIF1-109 and ΔC10 huMIF1-104 were enzymatically inactive and thermodynamically less stable than wild type MIF. Analytical ultracentrifugation studies demonstrate that both C-terminal mutants sediment as trimers and exhibit similar binding to CD74 as the wild type protein. Disrupting the conformation of the C-terminal region 105–114 and increasing its conformational flexibility through the insertion of a proline residue at position 107 was sufficient to reproduce the structural, biochemical and thermodynamic properties of the deletion mutants. P107 MIF forms an enzymatically inactive trimer and exhibits reduced thermodynamic stability relative to the wild type protein. To provide a rationale for the changes induced by these mutations at the molecular level, we also performed molecular dynamics simulations on these mutants in comparison to the wild type MIF. Together, our studies demonstrate that inter-subunit interactions involving the C-terminal region 105–114, including a salt-bridge interaction between Arg73 of one monomer and the carboxy terminus of a neighbouring monomer, play critical roles in modulating tertiary structure stabilization, enzymatic activity, and thermodynamic stability of MIF, but not its oligomerization state and receptor binding properties. Our results suggest that targeting the C-terminal region could provide new strategies for allosteric modulation of MIF enzymatic activity and the development of novel inhibitors of MIF tautomerase activity. PMID:18795803

Chemical Thermodynamics of Aqueous Atmospheric Aerosols: Modeling and Microfluidic Measurements

NASA Astrophysics Data System (ADS)

Nandy, L.; Dutcher, C. S.

2017-12-01

Accurate predictions of gas-liquid-solid equilibrium phase partitioning of atmospheric aerosols by thermodynamic modeling and measurements is critical for determining particle composition and internal structure at conditions relevant to the atmosphere. Organic acids that originate from biomass burning, and direct biogenic emission make up a significant fraction of the organic mass in atmospheric aerosol particles. In addition, inorganic compounds like ammonium sulfate and sea salt also exist in atmospheric aerosols, that results in a mixture of single, double or triple charged ions, and non-dissociated and partially dissociated organic acids. Statistical mechanics based on a multilayer adsorption isotherm model can be applied to these complex aqueous environments for predictions of thermodynamic properties. In this work, thermodynamic analytic predictive models are developed for multicomponent aqueous solutions (consisting of partially dissociating organic and inorganic acids, fully dissociating symmetric and asymmetric electrolytes, and neutral organic compounds) over the entire relative humidity range, that represent a significant advancement towards a fully predictive model. The model is also developed at varied temperatures for electrolytes and organic compounds the data for which are available at different temperatures. In addition to the modeling approach, water loss of multicomponent aerosol particles is measured by microfluidic experiments to parameterize and validate the model. In the experimental microfluidic measurements, atmospheric aerosol droplet chemical mimics (organic acids and secondary organic aerosol (SOA) samples) are generated in microfluidic channels and stored and imaged in passive traps until dehydration to study the influence of relative humidity and water loss on phase behavior.

Thermodynamic properties of hydrogen dissociation reaction from the small system method and reactive force field ReaxFF

NASA Astrophysics Data System (ADS)

Trinh, Thuat T.; Meling, Nora; Bedeaux, Dick; Kjelstrup, Signe

2017-03-01

We present thermodynamic properties of the H2 dissociation reaction by means of the Small System Method (SSM) using Reactive Force Field (ReaxFF) simulations. Thermodynamic correction factors, partial molar enthalpies and heat capacities of the reactant and product were obtained in the high temperature range; up to 30,000 K. The results obtained from the ReaxFF potential agree well with previous results obtained with a three body potential (TBP). This indicates that the popular reactive force field method can be combined well with the newly developed SSM in realistic simulations of chemical reactions. The approach may be useful in the study of heat and mass transport in combination with chemical reactions.

Thermodynamic properties of liquid Au–Cu–Sn alloys determined from electromotive force measurements

PubMed Central

Guo, Zhongnan; Hindler, Michael; Yuan, Wenxia; Mikula, Adolf

2011-01-01

The thermodynamic properties of the ternary Au–Cu–Sn system were determined with the electromotive force (EMF) method using a liquid electrolyte. Three different cross-sections with constant Au:Cu ratios of 3:1, 1:1, and 1:3 were applied to measure the thermodynamic properties of the ternary system in the temperature range between the liquidus temperature of the alloys and 1023 K. The partial free energies of Sn in liquid Au–Cu–Sn alloys were obtained from EMF data. The integral Gibbs free energy and the integral enthalpy at 900 K were calculated by Gibbs–Duhem integration. The ternary interaction parameters were evaluated using the Redlich–Kister–Muggianu polynomial. PMID:22039311

Aldehydes in hydrothermal solution - Standard partial molal thermodynamic properties and relative stabilities at high temperatures and pressures

NASA Technical Reports Server (NTRS)

Schulte, Mitchell D.; Shock, Everett L.

1993-01-01

Aldehydes are common in a variety of geologic environments and are derived from a number of sources, both natural and anthropogenic. Experimental data for aqueous aldehydes were taken from the literature and used, along with parameters for the revised Helgeson-Kirkham-Flowers (HKF) equations of state, to estimate standard partial molal thermodynamic data for aqueous straight-chain alkyl aldehydes at high temperatures and pressures. Examples of calculations involving aldehydes in geological environments are given, and the stability of aldehydes relative to carboxylic acids is evaluated. These calculations indicate that aldehydes may be intermediates in the formation of carboxylic acids from hydrocarbons in sedimentary basin brines and hydrothermal systems like they are in the atmosphere. The data and parameters summarized here allow evaluation of the role of aldehydes in the formation of prebiotic precursors, such as amino acids and hydroxy acids on the early Earth and in carbonaceous chondrite parent bodies.

Applications of the First Law to Ecological Systems. Physical Processes in Terrestrial and Aquatic Ecosystems, Thermodynamics.

ERIC Educational Resources Information Center

Stevenson, R. D.

These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. This report describes concepts presented in another module called "The First Law of…

Metal-organic complexes in geochemical processes: Estimation of standard partial molal thermodynamic properties of aqueous complexes between metal cations and monovalent organic acid ligands at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Shock, Everetr L.; Koretsky, Carla M.

1995-04-01

Regression of standard state equilibrium constants with the revised Helgeson-Kirkham-Flowers (HKF) equation of state allows evaluation of standard partial molal entropies ( overlineSo) of aqueous metal-organic complexes involving monovalent organic acid ligands. These values of overlineSo provide the basis for correlations that can be used, together with correlation algorithms among standard partial molal properties of aqueous complexes and equation-of-state parameters, to estimate thermodynamic properties including equilibrium constants for complexes between aqueous metals and several monovalent organic acid ligands at the elevated pressures and temperatures of many geochemical processes which involve aqueous solutions. Data, parameters, and estimates are given for 270 formate, propanoate, n-butanoate, n-pentanoate, glycolate, lactate, glycinate, and alanate complexes, and a consistent algorithm is provided for making other estimates. Standard partial molal entropies of association ( Δ -Sro) for metal-monovalent organic acid ligand complexes fall into at least two groups dependent upon the type of functional groups present in the ligand. It is shown that isothermal correlations among equilibrium constants for complex formation are consistent with one another and with similar correlations for inorganic metal-ligand complexes. Additional correlations allow estimates of standard partial molal Gibbs free energies of association at 25°C and 1 bar which can be used in cases where no experimentally derived values are available.

Vaporization and thermodynamics of forsterite-rich olivine and some implications for silicate atmospheres of hot rocky exoplanets

NASA Astrophysics Data System (ADS)

Costa, Gustavo C. C.; Jacobson, Nathan S.; Fegley, Bruce, Jr.

2017-06-01

We describe an experimental and theoretical study of olivine [Mg2SiO4 (Fo)-Fe2SiO4 (Fa)] vaporization. The vaporization behavior and thermodynamic properties of a fosterite-rich olivine (Fo95Fa5) have been explored by high-temperature Knudsen effusion mass spectrometry (KEMS) from 1750 to 2250 K. The gases observed (in order of decreasing partial pressure) are Fe, SiO, Mg, O2 and O. We measured the solidus temperature (∼2050 K), partial pressures of individual gases, the total vapor pressure, and thermodynamic activities and partial molar enthalpies of MgO, 'FeO', and SiO2 for the Fo95Fa5 olivine. The results are compared to other measurements and models of the olivine system. Our experimental data show olivine vaporizes incongruently. We discuss this system both as a psuedo-binary of Fo-Fa and a psuedo-ternary of MgO-'FeO'-SiO2. Iron/magnesium molar ratios in the sample before (∼0.05) and after (∼0.04) vaporization are consistent with the small positive deviations from ideality of fayalite (γ ∼ 1.17) in olivine of the composition studied (e.g., Nafziger and Muan, 1967). Our data for olivine + melt confirm prior theoretical models predicting fractional vaporization of Fe relative to Mg from molten silicates (Fegley and Cameron, 1987; Schaefer and Fegley, 2009; Ito et al., 2015). If loss of silicate atmospheres occurs from hot rocky exoplanets with magma oceans the residual planet may be enriched in magnesium relative to iron.

Thermodynamics of protein folding using a modified Wako-Saitô-Muñoz-Eaton model.

PubMed

Tsai, Min-Yeh; Yuan, Jian-Min; Teranishi, Yoshiaki; Lin, Sheng Hsien

2012-09-01

Herein, we propose a modified version of the Wako-Saitô-Muñoz-Eaton (WSME) model. The proposed model introduces an empirical temperature parameter for the hypothetical structural units (i.e., foldons) in proteins to include site-dependent thermodynamic behavior. The thermodynamics for both our proposed model and the original WSME model were investigated. For a system with beta-hairpin topology, a mathematical treatment (contact-pair treatment) to facilitate the calculation of its partition function was developed. The results show that the proposed model provides better insight into the site-dependent thermodynamic behavior of the system, compared with the original WSME model. From this site-dependent point of view, the relationship between probe-dependent experimental results and model's thermodynamic predictions can be explained. The model allows for suggesting a general principle to identify foldon behavior. We also find that the backbone hydrogen bonds may play a role of structural constraints in modulating the cooperative system. Thus, our study may contribute to the understanding of the fundamental principles for the thermodynamics of protein folding.

University Physics, Study Guide, Revised Edition

NASA Astrophysics Data System (ADS)

Benson, Harris

1996-01-01

Partial table of contents: Vectors. One-Dimensional Kinematics. Particle Dynamics II. Work and Energy. Linear Momentum. Systems of Particles. Angular Momentum and Statics. Gravitation. Solids and Fluids. Oscillations. Mechanical Waves. Sound. First Law of Thermodynamics. Kinetic Theory. Entropy and the Second Law of Thermodynamics. Electrostatics. The Electric Field. Gauss's Law. Electric Potential. Current and Resistance. The Magnetic Field. Sources of the Magnetic Field. Electromagnetic Induction. Light: Reflection and Refraction. Lenses and Optical Instruments. Wave Optics I. Special Relativity. Early Quantum Theory. Nuclear Physics. Appendices. Answers to Odd-Numbered Exercises and Problems. Index.

A petrologic, thermodynamic and experimental study of brachinites: Partial melt residues of an R chondrite-like precursor

NASA Astrophysics Data System (ADS)

Gardner-Vandy, Kathryn G.; Lauretta, Dante S.; McCoy, Timothy J.

2013-12-01

The primitive achondrites provide a window into the initial melting of asteroids in the early solar system. The brachinites are olivine-dominated meteorites with a recrystallized texture that we and others interpret as evidence of partial melting and melt removal on the brachinite parent body. We present a petrologic, thermodynamic and experimental study of the brachinites to evaluate the conditions under which they formed and test our hypothesis that the precursor material to the brachinites was FeO-rich compared to the precursors of other primitive achondrites. Petrologic analysis of six brachinites (Brachina, Allan Hills (ALH) 84025, Hughes 026, Elephant Moraine (EET) 99402, Northwest Africa (NWA) 3151, and NWA 4969) and one brachinite-like achondrite (NWA 5400) shows that they are meteorites with recrystallized texture that are enriched in olivine (⩾80 vol.%) and depleted in other minerals with respect to a chondritic mineralogy. Silicates in the brachinites are FeO-rich (Fa32-36). Brachinite-like achondrite Northwest Africa 5400 is similar in mineralogy and texture to the brachinites but with a slightly lower FeO-content (Fa30). Thermodynamic calculations yield equilibration temperatures above the Fe,Ni-FeS cotectic temperature (∼950 °C) for all meteorites studied here and temperatures above the silicate eutectic (∼1050 °C) for all but two. Brachina formed at an fO2 of ∼IW, and the other brachinites and NWA 5400 formed at ∼IW - 1. All the meteorites show great evidence of formation by partial melting having approximately chondritic to depleted chondritic mineralogies, equilibrated mineral compositions, and recrystallized textures, and having reached temperatures above that required for melt generation. In an attempt to simulate the formation of the brachinite meteorites, we performed one-atmosphere, gas-mixing partial melting experiments of R4 chondrite LaPaz Ice Field 03639. Experiments at 1250 °C and an oxygen fugacity of IW - 1 produce residual phases that are within the mineralogy and mineral compositions of the brachinites. These experiments provide further evidence for the formation of brachinites as a result of partial melting of a chondritic precursor similar in mineralogy and mineral compositions to the R chondrites.

Isentropic expansion and related thermodynamic properties of non-ionic amphiphile-water mixtures.

PubMed

Reis, João Carlos R; Douhéret, Gérard; Davis, Michael I; Fjellanger, Inger Johanne; Høiland, Harald

2008-01-28

A concise thermodynamic formalism is developed for the molar isentropic thermal expansion, ES,m = ( partial differential Vm/ partial differential T)(Sm,x), and the ideal and excess quantities for the molar, apparent molar and partial molar isentropic expansions of binary liquid mixtures. Ultrasound speeds were determined by means of the pulse-echo-overlap method in aqueous mixtures of 2-methylpropan-2-ol at 298.15 K over the entire composition range. These data complement selected extensive literature data on density, isobaric heat capacity and ultrasound speed for 9 amphiphile (methanol, ethanol, propan-1-ol, propan-2-ol, 2-methylpropan-2-ol, ethane-1,2-diol, 2-methoxyethanol, 2-ethoxyethanol or 2-butoxyethanol)-water binary systems, which form the basis of tables listing molar and excess molar isobaric expansions and heat capacities, and molar and excess molar isentropic compressions and expansions at 298.15 K and at 65 fixed mole fractions spanning the entire composition range and fine-grained in the water-rich region. The dependence on composition of these 9 systems is graphically depicted for the excess molar isobaric and isentropic expansions and for the excess partial molar isobaric and isentropic expansions of the amphiphile. The analysis shows that isentropic thermal expansion properties give a much stronger response to amphiphile-water molecular interactions than do their isobaric counterparts. Depending on the pair property-system, the maximum excess molar isentropic value is generally twenty- to a hundred-fold greater than the corresponding maximum isobaric value, and occurs at a lower mole fraction of the amphiphile. Values at infinite dilution of the 9 amphiphiles in water are given for the excess partial molar isobaric heat capacity, isentropic compression, isobaric expansion and isentropic expansion. These values are interpreted in terms of the changes occurring when amphiphile molecules cluster into an oligomeric form. Present results are discussed from theoretical and experimental thermodynamic viewpoints. It is concluded that isentropic thermal expansion properties constitute a new distinct resource for revealing particular features and trends in complex mixing processes, and that analyses using these new properties compare favourably with conventional approaches.

Relationships between CO 2, thermodynamic limits on silicate weathering, and the strength of the silicate weathering feedback

DOE PAGES

Winnick, Matthew J.; Maher, Kate

2018-01-27

Recent studies have suggested that thermodynamic limitations on chemical weathering rates exert a first-order control on riverine solute fluxes and by extension, global chemical weathering rates. As such, these limitations may play a prominent role in the regulation of carbon dioxide levels (pCO 2) over geologic timescales by constraining the maximum global weathering flux. In this study, we develop a theoretical scaling relationship between equilibrium solute concentrations and pCO 2 based on equilibrium constants and reaction stoichiometry relating primary mineral dissolution and secondary mineral precipitation. Here, we test this theoretical scaling relationship against reactive transport simulations of chemical weathering profilesmore » under open-and closed-system conditions, representing partially and fully water-saturated regolith, respectively. Under open-system conditions, equilibrium bicarbonate concentrations vary as a power-law function of pCO 2(y =kx n)where nis dependent on reaction stoichiometry and kis dependent on both reaction stoichiometry and the equilibrium constant. Under closed-system conditions, bicarbonate concentrations vary linearly with pCO 2 at low values and approach open-system scaling at high pCO 2. To describe the potential role of thermodynamic limitations in the global silicate weathering feedback, we develop a new mathematical framework to assess weathering feedback strength in terms of both (1) steady-state atmospheric pCO 2 concentrations, and (2) susceptibility to secular changes in degassing rates and transient carbon cycle perturbations, which we term 1st and 2nd order feedback strength, respectively. Finally, we discuss the implications of these results for the effects of vascular land plant evolution on feedback strength, the potential role of vegetation in controlling modern solute fluxes, and the application of these frameworks to a more complete functional description of the silicate weathering feedback. Most notably, the dependence of equilibrium solute concentrations on pCO 2 may represent a direct weathering feedback largely independent of climate and modulated by belowground organic carbon respiration.« less

Relationships between CO 2, thermodynamic limits on silicate weathering, and the strength of the silicate weathering feedback

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winnick, Matthew J.; Maher, Kate

Recent studies have suggested that thermodynamic limitations on chemical weathering rates exert a first-order control on riverine solute fluxes and by extension, global chemical weathering rates. As such, these limitations may play a prominent role in the regulation of carbon dioxide levels (pCO 2) over geologic timescales by constraining the maximum global weathering flux. In this study, we develop a theoretical scaling relationship between equilibrium solute concentrations and pCO 2 based on equilibrium constants and reaction stoichiometry relating primary mineral dissolution and secondary mineral precipitation. Here, we test this theoretical scaling relationship against reactive transport simulations of chemical weathering profilesmore » under open-and closed-system conditions, representing partially and fully water-saturated regolith, respectively. Under open-system conditions, equilibrium bicarbonate concentrations vary as a power-law function of pCO 2(y =kx n)where nis dependent on reaction stoichiometry and kis dependent on both reaction stoichiometry and the equilibrium constant. Under closed-system conditions, bicarbonate concentrations vary linearly with pCO 2 at low values and approach open-system scaling at high pCO 2. To describe the potential role of thermodynamic limitations in the global silicate weathering feedback, we develop a new mathematical framework to assess weathering feedback strength in terms of both (1) steady-state atmospheric pCO 2 concentrations, and (2) susceptibility to secular changes in degassing rates and transient carbon cycle perturbations, which we term 1st and 2nd order feedback strength, respectively. Finally, we discuss the implications of these results for the effects of vascular land plant evolution on feedback strength, the potential role of vegetation in controlling modern solute fluxes, and the application of these frameworks to a more complete functional description of the silicate weathering feedback. Most notably, the dependence of equilibrium solute concentrations on pCO 2 may represent a direct weathering feedback largely independent of climate and modulated by belowground organic carbon respiration.« less

Relationships between CO2, thermodynamic limits on silicate weathering, and the strength of the silicate weathering feedback

NASA Astrophysics Data System (ADS)

Winnick, Matthew J.; Maher, Kate

2018-03-01

Recent studies have suggested that thermodynamic limitations on chemical weathering rates exert a first-order control on riverine solute fluxes and by extension, global chemical weathering rates. As such, these limitations may play a prominent role in the regulation of carbon dioxide levels (pCO2) over geologic timescales by constraining the maximum global weathering flux. In this study, we develop a theoretical scaling relationship between equilibrium solute concentrations and pCO2 based on equilibrium constants and reaction stoichiometry relating primary mineral dissolution and secondary mineral precipitation. We test this theoretical scaling relationship against reactive transport simulations of chemical weathering profiles under open- and closed-system conditions, representing partially and fully water-saturated regolith, respectively. Under open-system conditions, equilibrium bicarbonate concentrations vary as a power-law function of pCO2 (y = kxn) where n is dependent on reaction stoichiometry and k is dependent on both reaction stoichiometry and the equilibrium constant. Under closed-system conditions, bicarbonate concentrations vary linearly with pCO2 at low values and approach open-system scaling at high pCO2. To describe the potential role of thermodynamic limitations in the global silicate weathering feedback, we develop a new mathematical framework to assess weathering feedback strength in terms of both (1) steady-state atmospheric pCO2 concentrations, and (2) susceptibility to secular changes in degassing rates and transient carbon cycle perturbations, which we term 1st and 2nd order feedback strength, respectively. Finally, we discuss the implications of these results for the effects of vascular land plant evolution on feedback strength, the potential role of vegetation in controlling modern solute fluxes, and the application of these frameworks to a more complete functional description of the silicate weathering feedback. Most notably, the dependence of equilibrium solute concentrations on pCO2 may represent a direct weathering feedback largely independent of climate and modulated by belowground organic carbon respiration.

Toward Fast and Accurate Binding Affinity Prediction with pmemdGTI: An Efficient Implementation of GPU-Accelerated Thermodynamic Integration.

PubMed

Lee, Tai-Sung; Hu, Yuan; Sherborne, Brad; Guo, Zhuyan; York, Darrin M

2017-07-11

We report the implementation of the thermodynamic integration method on the pmemd module of the AMBER 16 package on GPUs (pmemdGTI). The pmemdGTI code typically delivers over 2 orders of magnitude of speed-up relative to a single CPU core for the calculation of ligand-protein binding affinities with no statistically significant numerical differences and thus provides a powerful new tool for drug discovery applications.

Early Earth Felsic Crust Formation: Insights from Numerical Modelling of High-MgO Archaean Basalt Partial Melting

NASA Astrophysics Data System (ADS)

Riel, N., Jr.

2015-12-01

The Tonalite-Trondhjemite-Granodiorite series (TTGs) represent the bulk of the felsic continental crust that formed between 4.4 and 2.5 Ga and is preserved in Archaean craton (3.8-2.5 Ga). It is now recognized that the petrogenesis of TTG series derives from an hydrous mafic system at high pressure. However, the source of the early TTGs (3.5-3.2 Ga) have not been preserved and its characteristics are still debated. In this study we use thermodynamical modelling coupled with two-phase flow to investigate the products of partial melting of high-MgO primary mafic crust. Our model setup is made of a 45-km thick hydrated mafic crust and is heated above the solidus from 50 to 200°C. To explore the effects of melt-rock interactions during melt transfer (via two-phase flow), the melt composition is modelled either in thermodynamic equilibrium with the rock or in thermodynamic disequilibrium. Our modelling results show that partial melting of hydrous high-MgO metabasalt crust can produce significant volumes of felsic melt. The average composition of these melts is SiO2-rich > 62%, Mg# = 40-50, Na2O ~6%, MgO = 0.5-1% which is consistent with the composition of TTGs. The residual rock after melt segregation is composed of olivine + garnet + pyroxene which is in agreement with Archaean eclogites found in mantle xenoliths of Archaean cratons. Moreover, the depleted residual rock is denser than the mantle and is likely to be recycled in the mantle. We show that the early felsic crust with a TTGs signature could have been formed by partial melting of high-MgO hydrated metabasaltic crust, and propose that plume-related activity and/or rapid burial due to high volcanic activity are likely geodynamic conditions to generate an early felsic crust.

Collaborative Research: A Model of Partially Ionized Plasma Flows with Kinetic Treatment of Neutral Atoms and Nonthermal Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pogorelov, Nikolai; Zhang, Ming; Borovikov, Sergey

Interactions of flows of partially ionized, magnetized plasma are frequently accompanied by the presence of both thermal and non-thermal (pickup) ion components. Such interactions cannot be modeled using traditional MHD equations and require more advanced approaches to treat them. If a nonthermal component of ions is formed due to charge exchange and collisions between the thermal (core) ions and neutrals, it experiences the action of magnetic field, its distribution function is isotropized, and it soon acquires the velocity of the ambient plasma without being thermodynamically equilibrated. This situation, e. g., takes place in the outer heliosphere - the part ofmore » interstellar space beyond the solar system whose properties are determined by the solar wind interaction with the local interstellar medium. This is also possible in laboratory, at million degrees and above, when plasma is conducting electricity far too well, which makes Ohmic heating ineffective. To attain the target temperatures one needs additional heating eventually playing a dominant role. Among such sources is a so-called neutral particle beam heating. This is a wide-spread technique (Joint European Torus and International Thermonuclear Experimental Reactor experiments) based on the injection of powerful beams of neutral atoms into ohmically preheated plasma. In this project we have investigated the energy and density separation between the thermal and nonthermal components in the solar wind and interstellar plasmas. A new model has been developed in which we solve the ideal MHD equations for mixture of all ions and the kinetic Boltzmann equation to describe the transport of neutral atoms. As a separate capability, we can treat the flow of neutral atoms in a multi-component fashion, where neutral atoms born in each thermodynamically distinct regions are governed by the Euler gas dynamic equations. We also describe the behavior of pickup ions either kinetically, using the Fokker–Planck equation, or as a separate fluid. Our numerical simulations have demonstrated that pickup ions play a major role in the interaction of the solar wind and (partially ionized) interstellar medium plasmas. Our teams have investigated the stability of the surface (the heliopause) that separates the solar wind from the local interstellar medium, the transport of galactic cosmic rays, the properties of the heliotail flow, and modifications to the bow wave in front of the heliopause due to charge exchange between the neutral H atoms born in the solar wind and interstellar ions. Modeling results have been validated against observational data, such as obtained by the Interstellar Boundary Explorer (IBEX), and made it possible to shed light on the structure of energetic neutral atom maps created by this spacecraft.. We have also demonstrated that charge-exchange modulated heliosphere is a source of anisotropy of the multi-TeV cosmic ray flux observed in a number of Earth-bound air shower experiments. Newly developed codes are implemented within a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), a publicly available code being developed by our team for over 12 years. MS-FLUKSS scales well up to 160,000 computing cores and has been ported on major supercomputers in the country. Efficient parallelization and data choreography in the continuum simulation modules are provided by Chombo, an adaptive mesh refinement framework managed by Phillip Colella’s team at LBNL. We have implemented in-house, hybrid (MPI+OpenMP) parallelization of the kinetic modules that solve the Boltzmann equation with a Monte Carlo method. Currently, the kinetic modules are being rewritten to take advantage of the modern CPU-GPU supercomputer architecture. The scope of the project allowed us to enhance plasma research and education in such broad, multidis- ciplinary field as physics of partially ionized plasma and its application to space physics and fusion science. Besides the impact on the modeling of complex physical systems, our approach to computational resource management for complex codes utilizing multiple algorithm technologies appears to be a major advance on current approaches. The development of sophisticated resource management will be essential for all future modeling efforts that incorporate a diversity of scales and physical processes. Our effort provided leadership in promoting computational science and plasma physics within the UAH and FIT campuses and, through the training of a broad spectrum of scientists and engineers, foster new technologies across the country.« less

Collaborative Research: A Model of Partially Ionized Plasma Flows with Kinetic Treatment of Neutral Atoms and Nonthermal Ions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pogorelov, Nikolai; Zhang, Ming

Interactions of flows of partially ionized, magnetized plasma are frequently accompanied by the presence of both thermal and non-thermal (pickup) ion components. Such interactions cannot be modeled using traditional MHD equations and require more advanced approaches to treat them. If a nonthermal component of ions is formed due to charge exchange and collisions between the thermal (core) ions and neutrals, it experiences the action of magnetic field, its distribution function is isotropized, and it soon acquires the velocity of the ambient plasma without being thermodynamically equilibrated. This situation, e. g., takes place in the outer heliosphere –- the part ofmore » interstellar space beyond the solar system whose properties are determined by the solar wind interaction with the local interstellar medium. This is also possible in laboratory, at million degrees and above, when plasma is conducting electricity far too well, which makes Ohmic heating ineffective. To attain the target temperatures one needs additional heating eventually playing a dominant role. Among such sources is a so-called neutral particle beam heating. This is a wide-spread technique (Joint European Torus and International Thermonuclear Experimental Reactor experiments) based on the injection of powerful beams of neutral atoms into ohmically preheated plasma. In this project we have investigated the energy and density separation between the thermal and nonthermal components in the solar wind and interstellar plasmas. A new model has been developed in which we solve the ideal MHD equations for mixture of all ions and the kinetic Boltzmann equation to describe the transport of neutral atoms. As a separate capability, we can treat the flow of neutral atoms in a multi-component fashion, where neutral atoms born in each thermodynamically distinct region are governed by the Euler gas dynamic equations. We also describe the behavior of pickup ions either kinetically, using the Fokker--Planck equation, or as a separate fluid. Our numerical simulations have demonstrated that pickup ions play a major role in the interaction of the solar wind and (partially ionized) interstellar medium plasmas. Our teams have investigated the stability of the surface (the heliopause) that separates the solar wind from the local interstellar medium, the transport of galactic cosmic rays, the properties of the heliotail flow, and modifications to the bow wave in front of the heliopause due to charge exchange between the neutral H atoms born in the solar wind and interstellar ions. Modeling results have been validated against observational data, such as obtained by the Interstellar Boundary Explorer (IBEX), and made it possible to shed light on the structure of energetic neutral atom maps created by this spacecraft.. We have also demonstrated that charge-exchange modulated heliosphere is a source of anisotropy of the multi-TeV cosmic ray flux observed in a number of Earth-bound air shower experiments. Newly developed codes are implemented within a Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS), a publicly available code being developed by our team for over 12 years. MS-FLUKSS scales well up to 160,000 computing cores and has been ported on major supercomputers in the country. Efficient parallelization and data choreography in the continuum simulation modules are provided by Chombo, an adaptive mesh refinement framework managed by Phillip Colella's team at LBNL. We have implemented in-house, hybrid (MPI+OpenMP) parallelization of the kinetic modules that solve the Boltzmann equation with a Monte Carlo method. Currently, the kinetic modules are being rewritten to take advantage of the modern CPU-GPU supercomputer architecture. The scope of the project allowed us to enhance plasma research and education in such broad, multidisciplinary field as physics of partially ionized plasma and its application to space physics and fusion science. Besides the impact on the modeling of complex physical systems, our approach to computational resource management for complex codes utilizing multiple algorithm technologies appears to be a major advance on current approaches. The development of sophisticated resource management will be essential for all future modeling efforts that incorporate a diversity of scales and physical processes. Our effort provided leadership in promoting computational science and plasma physics within the UAH and FIT campuses and, through the training of a broad spectrum of scientists and engineers, fostering new technologies across the country.« less

Frequency Hopping, Multiple Frequency-Shift Keying, Coding, and Optimal Partial-Band Jamming.

DTIC Science & Technology

1982-08-01

receivers appropriate for these two strategies. Each receiver is noncoherent (a coherent receiver is generally impractical) and implements hard...Advances in Coding and Modulation for Noncoherent Channels Affected by Fading, Partial Band, and Multiple- . Access Interference, in A. J. Viterbi...Modulation for Noncoherent Channels Affected by Fading, Partial Band, and Multiple-Access interference, in A. J. Viterbi, ed., Advances in Coumunication

Interpreting equilibrium-conductivity and conductivity-relaxation measurements to establish thermodynamic and transport properties for multiple charged defect conducting ceramics.

PubMed

Zhu, Huayang; Ricote, Sandrine; Coors, W Grover; Kee, Robert J

2015-01-01

A model-based interpretation of measured equilibrium conductivity and conductivity relaxation is developed to establish thermodynamic, transport, and kinetics parameters for multiple charged defect conducting (MCDC) ceramic materials. The present study focuses on 10% yttrium-doped barium zirconate (BZY10). In principle, using the Nernst-Einstein relationship, equilibrium conductivity measurements are sufficient to establish thermodynamic and transport properties. However, in practice it is difficult to establish unique sets of properties using equilibrium conductivity alone. Combining equilibrium and conductivity-relaxation measurements serves to significantly improve the quantitative fidelity of the derived material properties. The models are developed using a Nernst-Planck-Poisson (NPP) formulation, which enables the quantitative representation of conductivity relaxations caused by very large changes in oxygen partial pressure.

Thermodynamics of reaction of praseodymium with gallium-indium eutectic alloy

NASA Astrophysics Data System (ADS)

Melchakov, S. Yu.; Ivanov, V. A.; Yamshchikov, L. F.; Volkovich, V. A.; Osipenko, A. G.; Kormilitsyn, M. V.

2013-06-01

Thermodynamic properties of Ga-In eutectic alloys saturated with praseodymium were determined for the first time employing the electromotive force method. The equilibrium potentials of the Pr-In alloys saturated with praseodymium (8.7-12.1 mol.% Pr) and Pr-Ga-In alloys (containing 0.0012-6.71 mol.% Pr) were measured between 573-1073 K. Pr-In alloy containing solid PrIn3 with known thermodynamic properties was used as the reference electrode when measuring the potentials of ternary Pr-In-Ga alloys. Activity, partial and excessive thermodynamic functions of praseodymium in alloys with indium and Ga-In eutectic were calculated. Activity (a), activity coefficients (γ) and solubility (X) of praseodymium in the studied temperature range can be expressed by the following equations: lgaα-Pr(In) = 4.425 - 11965/T ± 0.026. lgаα-Pr(Ga-In) = 5.866 - 14766/T ± 0.190. lgγα-Pr(Ga-In) = 2.351 - 9996/T ± 0.39. lgХPr(Ga-In) = 3.515 - 4770/T ± 0.20.

Grid inhomogeneous solvation theory: hydration structure and thermodynamics of the miniature receptor cucurbit[7]uril.

PubMed

Nguyen, Crystal N; Young, Tom Kurtzman; Gilson, Michael K

2012-07-28

The displacement of perturbed water upon binding is believed to play a critical role in the thermodynamics of biomolecular recognition, but it is nontrivial to unambiguously define and answer questions about this process. We address this issue by introducing grid inhomogeneous solvation theory (GIST), which discretizes the equations of inhomogeneous solvation theory (IST) onto a three-dimensional grid situated in the region of interest around a solute molecule or complex. Snapshots from explicit solvent simulations are used to estimate localized solvation entropies, energies, and free energies associated with the grid boxes, or voxels, and properly summing these thermodynamic quantities over voxels yields information about hydration thermodynamics. GIST thus provides a smoothly varying representation of water properties as a function of position, rather than focusing on hydration sites where solvent is present at high density. It therefore accounts for full or partial displacement of water from sites that are highly occupied by water, as well as for partly occupied and water-depleted regions around the solute. GIST can also provide a well-defined estimate of the solvation free energy and therefore enables a rigorous end-states analysis of binding. For example, one may not only use a first GIST calculation to project the thermodynamic consequences of displacing water from the surface of a receptor by a ligand, but also account, in a second GIST calculation, for the thermodynamics of subsequent solvent reorganization around the bound complex. In the present study, a first GIST analysis of the molecular host cucurbit[7]uril is found to yield a rich picture of hydration structure and thermodynamics in and around this miniature receptor. One of the most striking results is the observation of a toroidal region of high water density at the center of the host's nonpolar cavity. Despite its high density, the water in this toroidal region is disfavored energetically and entropically, and hence may contribute to the known ability of this small receptor to bind guest molecules with unusually high affinities. Interestingly, the toroidal region of high water density persists even when all partial charges of the receptor are set to zero. Thus, localized regions of high solvent density can be generated in a binding site without strong, attractive solute-solvent interactions.

Grid inhomogeneous solvation theory: Hydration structure and thermodynamics of the miniature receptor cucurbit[7]uril

PubMed Central

Nguyen, Crystal N.; Kurtzman Young, Tom; Gilson, Michael K.

2012-01-01

The displacement of perturbed water upon binding is believed to play a critical role in the thermodynamics of biomolecular recognition, but it is nontrivial to unambiguously define and answer questions about this process. We address this issue by introducing grid inhomogeneous solvation theory (GIST), which discretizes the equations of inhomogeneous solvation theory (IST) onto a three-dimensional grid situated in the region of interest around a solute molecule or complex. Snapshots from explicit solvent simulations are used to estimate localized solvation entropies, energies, and free energies associated with the grid boxes, or voxels, and properly summing these thermodynamic quantities over voxels yields information about hydration thermodynamics. GIST thus provides a smoothly varying representation of water properties as a function of position, rather than focusing on hydration sites where solvent is present at high density. It therefore accounts for full or partial displacement of water from sites that are highly occupied by water, as well as for partly occupied and water-depleted regions around the solute. GIST can also provide a well-defined estimate of the solvation free energy and therefore enables a rigorous end-states analysis of binding. For example, one may not only use a first GIST calculation to project the thermodynamic consequences of displacing water from the surface of a receptor by a ligand, but also account, in a second GIST calculation, for the thermodynamics of subsequent solvent reorganization around the bound complex. In the present study, a first GIST analysis of the molecular host cucurbit[7]uril is found to yield a rich picture of hydration structure and thermodynamics in and around this miniature receptor. One of the most striking results is the observation of a toroidal region of high water density at the center of the host's nonpolar cavity. Despite its high density, the water in this toroidal region is disfavored energetically and entropically, and hence may contribute to the known ability of this small receptor to bind guest molecules with unusually high affinities. Interestingly, the toroidal region of high water density persists even when all partial charges of the receptor are set to zero. Thus, localized regions of high solvent density can be generated in a binding site without strong, attractive solute-solvent interactions. PMID:22852591

Thermodynamic equilibrium calculations of hydrogen production from the combined processes of dimethyl ether steam reforming and partial oxidation

NASA Astrophysics Data System (ADS)

Semelsberger, Troy A.; Borup, Rodney L.

Thermodynamic analyses of producing a hydrogen-rich fuel-cell feed from the combined processes of dimethyl ether (DME) partial oxidation and steam reforming were investigated as a function of oxygen-to-carbon ratio (0.00-2.80), steam-to-carbon ratio (0.00-4.00), temperature (100 °C-600 °C), pressure (1-5 atm) and product species. Thermodynamically, dimethyl ether processed with air and steam generates hydrogen-rich fuel-cell feeds; however, the hydrogen concentration is less than that for pure DME steam reforming. Results of the thermodynamic processing of dimethyl ether indicate the complete conversion of dimethyl ether to hydrogen, carbon monoxide and carbon dioxide for temperatures greater than 200 °C, oxygen-to-carbon ratios greater than 0.00 and steam-to-carbon ratios greater than 1.25 at atmospheric pressure (P = 1 atm). Increasing the operating pressure has negligible effects on the hydrogen content. Thermodynamically, dimethyl ether can produce concentrations of hydrogen and carbon monoxide of 52% and 2.2%, respectively, at a temperature of 300 °C, and oxygen-to-carbon ratio of 0.40, a pressure of 1 atm and a steam-to-carbon ratio of 1.50. The order of thermodynamically stable products (excluding H 2, CO, CO 2, DME, NH 3 and H 2O) in decreasing mole fraction is methane, ethane, isopropyl alcohol, acetone, n-propanol, ethylene, ethanol and methyl-ethyl ether; trace amounts of formaldehyde, formic acid and methanol are observed. Ammonia and hydrogen cyanide are also thermodynamically favored products. Ammonia is favored at low temperatures in the range of oxygen-to-carbon ratios of 0.40-2.50 regardless of the steam-to-carbon ratio employed. The maximum ammonia content (i.e., 40%) occurs at an oxygen-to-carbon ratio of 0.40, a steam-to-carbon ratio of 1.00 and a temperature of 100 °C. Hydrogen cyanide is favored at high temperatures and low oxygen-to-carbon ratios with a maximum of 3.18% occurring at an oxygen-to-carbon ratio of 0.40 and a steam-to-carbon ratio of 0.00 in the temperature range of 400 °C-500 °C. Increasing the system pressure shifts the equilibrium toward ammonia and hydrogen cyanide.

Determining Membrane Protein-Lipid Binding Thermodynamics Using Native Mass Spectrometry.

PubMed

Cong, Xiao; Liu, Yang; Liu, Wen; Liang, Xiaowen; Russell, David H; Laganowsky, Arthur

2016-04-06

Membrane proteins are embedded in the biological membrane where the chemically diverse lipid environment can modulate their structure and function. However, the thermodynamics governing the molecular recognition and interaction of lipids with membrane proteins is poorly understood. Here, we report a method using native mass spectrometry (MS), to determine thermodynamics of individual ligand binding events to proteins. Unlike conventional methods, native MS can resolve individual ligand binding events and, coupled with an apparatus to control the temperature, determine binding thermodynamic parameters, such as for protein-lipid interactions. We validated our approach using three soluble protein-ligand systems (maltose binding protein, lysozyme, and nitrogen regulatory protein) and obtained similar results to those using isothermal titration calorimetry and surface plasmon resonance. We also determined for the first time the thermodynamics of individual lipid binding to the ammonia channel (AmtB), an integral membrane protein from Escherichia coli. Remarkably, we observed distinct thermodynamic signatures for the binding of different lipids and entropy-enthalpy compensation for binding lipids of variable chain length. Additionally, using a mutant form of AmtB that abolishes a specific phosphatidylglycerol (PG) binding site, we observed distinct changes in the thermodynamic signatures for binding PG, implying these signatures can identify key residues involved in specific lipid binding and potentially differentiate between specific lipid binding sites.

Integrating Computational Science Tools into a Thermodynamics Course

NASA Astrophysics Data System (ADS)

Vieira, Camilo; Magana, Alejandra J.; García, R. Edwin; Jana, Aniruddha; Krafcik, Matthew

2018-01-01

Computational tools and methods have permeated multiple science and engineering disciplines, because they enable scientists and engineers to process large amounts of data, represent abstract phenomena, and to model and simulate complex concepts. In order to prepare future engineers with the ability to use computational tools in the context of their disciplines, some universities have started to integrate these tools within core courses. This paper evaluates the effect of introducing three computational modules within a thermodynamics course on student disciplinary learning and self-beliefs about computation. The results suggest that using worked examples paired to computer simulations to implement these modules have a positive effect on (1) student disciplinary learning, (2) student perceived ability to do scientific computing, and (3) student perceived ability to do computer programming. These effects were identified regardless of the students' prior experiences with computer programming.

Minimal universal quantum heat machine.

PubMed

Gelbwaser-Klimovsky, D; Alicki, R; Kurizki, G

2013-01-01

In traditional thermodynamics the Carnot cycle yields the ideal performance bound of heat engines and refrigerators. We propose and analyze a minimal model of a heat machine that can play a similar role in quantum regimes. The minimal model consists of a single two-level system with periodically modulated energy splitting that is permanently, weakly, coupled to two spectrally separated heat baths at different temperatures. The equation of motion allows us to compute the stationary power and heat currents in the machine consistent with the second law of thermodynamics. This dual-purpose machine can act as either an engine or a refrigerator (heat pump) depending on the modulation rate. In both modes of operation, the maximal Carnot efficiency is reached at zero power. We study the conditions for finite-time optimal performance for several variants of the model. Possible realizations of the model are discussed.

A fast and robust TOUGH2 module to simulate geological CO2 storage in saline aquifers

NASA Astrophysics Data System (ADS)

Shabani, Babak; Vilcáez, Javier

2018-02-01

A new TOUGH2 module to simulate geological CO2 storage (GCS) in saline aquifers is developed based on the widely employed ECO2N module of TOUGH2. The newly developed TOUGH2 module uses a new non-iterative fugacity-activity thermodynamic model to obtain the partitioning of CO2 and H2O between the aqueous and gas phases. Simple but robust thermophysical correlations are used to obtain density, viscosity, and enthalpy of the gas phase. The implementation and accuracy of the employed thermophysical correlations are verified by comparisons against the national institute of standards and technology (NIST) online thermophysical database. To assess the computation accuracy and efficiency, simulation results obtained with the new TOUGH2 module for a one-dimensional non-isothermal radial and a three-dimensional isothermal system are compared against the simulation results obtained with the ECO2N module. Treating salt mass fraction in the aqueous phase as a constant, along with the inclusion of a non-iterative fugacity-activity thermodynamic model, and simple thermophysical correlations, resulted in simulations much faster than simulations with ECO2N module, without losing numerical accuracy. Both modules yield virtually identical results. Additional field-scale simulations of CO2 injection into an actual non-isothermal and heterogeneous geological formation confirmed that the new module is much faster than the ECO2N module in simulating complex field-scale conditions. Owing to its capability to handle CO2-CH4-H2S-N2 gas mixtures and its compatibility with TOUGHREACT, this new TOUGH2 module offers the possibility of developing a fast and robust TOUGHREACT module to predict the fate of CO2 in GCS sites under biotic conditions where CO2, CH4, H2S, and N2 gases can be formed.

The Climate Space Concept: Analysis of the Steady State Heat Energy Budget of Animals. Physical Processes in Terrestrial and Aquatic Ecosystems, Transport Processes.

ERIC Educational Resources Information Center

Stevenson, R. D.

These materials were designed to be used by life science students for instruction in the application of physical theory to ecosystem operation. Most modules contain computer programs which are built around a particular application of a physical process. Several modules in the thermodynamic series considered the application of the First Law to…

Experimental Techniques for Thermodynamic Measurements of Ceramics

NASA Technical Reports Server (NTRS)

Jacobson, Nathan S.; Putnam, Robert L.; Navrotsky, Alexandra

1999-01-01

Experimental techniques for thermodynamic measurements on ceramic materials are reviewed. For total molar quantities, calorimetry is used. Total enthalpies are determined with combustion calorimetry or solution calorimetry. Heat capacities and entropies are determined with drop calorimetry, differential thermal methods, and adiabatic calorimetry . Three major techniques for determining partial molar quantities are discussed. These are gas equilibration techniques, Knudsen cell methods, and electrochemical techniques. Throughout this report, issues unique to ceramics are emphasized. Ceramic materials encompass a wide range of stabilities and this must be considered. In general data at high temperatures is required and the need for inert container materials presents a particular challenge.

Silicon Photoelectrode Thermodynamics and Hydrogen Evolution Kinetics Measured by Intensity-Modulated High-Frequency Resistivity Impedance Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Nicholas C.; Carroll, Gerard M.; Pekarek, Ryan T.

Here, we present an impedance technique based on light intensity-modulated high-frequency resistivity (IMHFR) that provides a new way to elucidate both the thermodynamics and kinetics in complex semiconductor photoelectrodes. We apply IMHFR to probe electrode interfacial energetics on oxide-modified semiconductor surfaces frequently used to improve the stability and efficiency of photoelectrochemical water splitting systems. Combined with current density-voltage measurements, the technique quantifies the overpotential for proton reduction relative to its thermodynamic potential in Si photocathodes coated with three oxides (SiO x, TiO 2, and Al 2O 3) and a Pt catalyst. In pH 7 electrolyte, the flatband potentials of TiOmore » 2- and Al 2O 3-coated Si electrodes are negative relative to samples with native SiO x, indicating that SiO x is a better protective layer against oxidative electrochemical corrosion than ALD-deposited crystalline TiO 2 or Al 2O 3. Adding a Pt catalyst to SiO x/Si minimizes proton reduction overpotential losses but at the expense of a reduction in available energy characterized by a more negative flatband potential relative to catalyst-free SiO x/Si.« less

Silicon Photoelectrode Thermodynamics and Hydrogen Evolution Kinetics Measured by Intensity-Modulated High-Frequency Resistivity Impedance Spectroscopy

DOE PAGES

Anderson, Nicholas C.; Carroll, Gerard M.; Pekarek, Ryan T.; ...

2017-10-05

Here, we present an impedance technique based on light intensity-modulated high-frequency resistivity (IMHFR) that provides a new way to elucidate both the thermodynamics and kinetics in complex semiconductor photoelectrodes. We apply IMHFR to probe electrode interfacial energetics on oxide-modified semiconductor surfaces frequently used to improve the stability and efficiency of photoelectrochemical water splitting systems. Combined with current density-voltage measurements, the technique quantifies the overpotential for proton reduction relative to its thermodynamic potential in Si photocathodes coated with three oxides (SiO x, TiO 2, and Al 2O 3) and a Pt catalyst. In pH 7 electrolyte, the flatband potentials of TiOmore » 2- and Al 2O 3-coated Si electrodes are negative relative to samples with native SiO x, indicating that SiO x is a better protective layer against oxidative electrochemical corrosion than ALD-deposited crystalline TiO 2 or Al 2O 3. Adding a Pt catalyst to SiO x/Si minimizes proton reduction overpotential losses but at the expense of a reduction in available energy characterized by a more negative flatband potential relative to catalyst-free SiO x/Si.« less

Ab initio atomistic thermodynamics study on the oxidation mechanism of binary and ternary alloy surfaces

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Shi-Yu, E-mail: buaasyliu@gmail.com; Department of Mechanical and Biomedical Engineering, City University of Hong Kong, Kowloon, Hong Kong; Liu, Shiyang

Utilizing a combination of ab initio density-functional theory and thermodynamics formalism, we have established the microscopic mechanisms for oxidation of the binary and ternary alloy surfaces and provided a clear explanation for the experimental results of the oxidation. We construct three-dimensional surface phase diagrams (SPDs) for oxygen adsorption on three different Nb-X(110) (X = Ti, Al or Si) binary alloy surfaces. On the basis of the obtained SPDs, we conclude a general microscopic mechanism for the thermodynamic oxidation, that is, under O-rich conditions, a uniform single-phase SPD (type I) and a nonuniform double-phase SPD (type II) correspond to the sustainedmore » complete selective oxidation and the non-sustained partial selective oxidation by adding the X element, respectively. Furthermore, by revealing the framework of thermodynamics for the oxidation mechanism of ternary alloys through the comparison of the surface energies of two separated binary alloys, we provide an understanding for the selective oxidation behavior of the Nb ternary alloy surfaces. Using these general microscopic mechanisms, one could predict the oxidation behavior of any binary and multi-component alloy surfaces based on thermodynamics considerations.« less

Thermodynamic design of natural gas liquefaction cycles for offshore application

NASA Astrophysics Data System (ADS)

Chang, Ho-Myung; Lim, Hye Su; Choe, Kun Hyung

2014-09-01

A thermodynamic study is carried out for natural gas liquefaction cycles applicable to offshore floating plants, as partial efforts of an ongoing governmental project in Korea. For offshore liquefaction, the most suitable cycle may be different from the on-land LNG processes under operation, because compactness and simple operation are important as well as thermodynamic efficiency. As a turbine-based cycle, closed Claude cycle is proposed to use NG (natural gas) itself as refrigerant. The optimal condition for NG Claude cycle is determined with a process simulator (Aspen HYSYS), and the results are compared with fully-developed C3-MR (propane pre-cooled mixed refrigerant) JT cycles and various N2 (nitrogen) Brayton cycles in terms of efficiency and compactness. The newly proposed NG Claude cycle could be a good candidate for offshore LNG processes.

Prediction of the electronic structures, thermodynamic and mechanical properties in manganese doped magnesium-based alloys and their saturated hydrides based on density functional theory

NASA Astrophysics Data System (ADS)

Zhang, Ziying; Zhang, Huizhen; Zhao, Hui; Yu, Zhishui; He, Liang; Li, Jin

2015-04-01

The crystal structures, electronic structures, thermodynamic and mechanical properties of Mg2Ni alloy and its saturated hydride with different Mn-doping contents are investigated using first-principles density functional theory. The lattice parameters for the Mn-doped Mg2Ni alloys and their saturated hydrides decreased with an increasing Mn-doping content because of the smaller atomic size of Mn compared with that of Mg. Analysis of the formation enthalpies and electronic structures reveal that the partial substitution of Mg with Mn reduces the stability of Mg2Ni alloy and its saturated hydride. The calculated elastic constants indicate that, although the partial substitution of Mg with Mn lowers the toughness of the hexagonal Mg2Ni alloy, the charge/discharge cycles are elevated when the Mn-doping content is high enough to form the predicted intermetallic compound Mg3MnNi2.

Oxygen nonstoichiometry and thermodynamic quantities in solid solution SrFe1-xSnxO3-δ

NASA Astrophysics Data System (ADS)

Merkulov, O. V.; Markov, A. A.; Leonidov, I. A.; Patrakeev, M. V.; Kozhevnikov, V. L.

2018-06-01

The oxygen content (3-δ) variations in tin substituted derivatives SrFe1-xSnxO3-δ, where x = 0.05, 0.1, 0.17 and 0.25, of perovskite-like strontium ferrite, have been studied by coulometric titration measurements within oxygen partial pressure (pO2) range 10-19-10-2 atm at 800-950 °С. The obtained dependencies of (3-δ) from pO2 and temperature are used for calculations of partial molar thermodynamic functions of oxygen in the oxide structure. It is found that a satisfactory explanation of the experimental results can be attained within frameworks of the ideal solution model with ion and electron defects appearing in the result of oxidation and disproportionation of iron cations. The increase of the oxidation reaction enthalpy with tin content is consistent with the increase of the unit cell parameter, i.e., the stretch and relaxation of Fe-O chemical bonds.

Thermodynamic analysis of vapor-phase epitaxial growth of GaAsN on Ge

NASA Astrophysics Data System (ADS)

Kawano, Jun; Kangawa, Yoshihiro; Ito, Tomonori; Kakimoto, Koichi; Koukitu, Akinori

2012-03-01

In this paper, we use thermodynamic analysis to determine how the nitrogen (N) ratio in the source gases affects the solid composition of coherently grown GaAs1-xNx(x˜0.03). The source gases for Ga, As, and N are trimethylgallium ((CH3)3Ga), arsine (AsH3), and ammonia (NH3), respectively. The growth occurs on a Ge substrate, and the analysis includes the stress from the substrate-crystal lattice mismatch. Calculation results indicate that to have just a few percent N incorporation into the grown solid, the V/III ratio in the source gases should be several thousands and the input-gas partial-pressure ratio NH3/(NH3+AsH3) should exceed 0.99. We also find that the lattice mismatch stress from the Ge substrate increases the V/III source-gas ratio required for stable growth, whereas an increase in input Ga partial pressure ratio has the opposite effect.

Efficient automatic OCR word validation using word partial format derivation and language model

NASA Astrophysics Data System (ADS)

Chen, Siyuan; Misra, Dharitri; Thoma, George R.

2010-01-01

In this paper we present an OCR validation module, implemented for the System for Preservation of Electronic Resources (SPER) developed at the U.S. National Library of Medicine.1 The module detects and corrects suspicious words in the OCR output of scanned textual documents through a procedure of deriving partial formats for each suspicious word, retrieving candidate words by partial-match search from lexicons, and comparing the joint probabilities of N-gram and OCR edit transformation corresponding to the candidates. The partial format derivation, based on OCR error analysis, efficiently and accurately generates candidate words from lexicons represented by ternary search trees. In our test case comprising a historic medico-legal document collection, this OCR validation module yielded the correct words with 87% accuracy and reduced the overall OCR word errors by around 60%.

Incorporating partial shining effects in proton pencil-beam dose calculation

NASA Astrophysics Data System (ADS)

Li, Yupeng; Zhang, Xiaodong; Fwu Lii, Ming; Sahoo, Narayan; Zhu, Ron X.; Gillin, Michael; Mohan, Radhe

2008-02-01

A range modulator wheel (RMW) is an essential component in passively scattered proton therapy. We have observed that a proton beam spot may shine on multiple steps of the RMW. Proton dose calculation algorithms normally do not consider the partial shining effect, and thus overestimate the dose at the proximal shoulder of spread-out Bragg peak (SOBP) compared with the measurement. If the SOBP is adjusted to better fit the plateau region, the entrance dose is likely to be underestimated. In this work, we developed an algorithm that can be used to model this effect and to allow for dose calculations that better fit the measured SOBP. First, a set of apparent modulator weights was calculated without considering partial shining. Next, protons spilled from the accelerator reaching the modulator wheel were simplified as a circular spot of uniform intensity. A weight-splitting process was then performed to generate a set of effective modulator weights with the partial shining effect incorporated. The SOBPs of eight options, which are used to label different combinations of proton-beam energy and scattering devices, were calculated with the generated effective weights. Our algorithm fitted the measured SOBP at the proximal and entrance regions much better than the ones without considering partial shining effect for all SOBPs of the eight options. In a prostate patient, we found that dose calculation without considering partial shining effect underestimated the femoral head and skin dose.

Comparative ecology of H2 cycling in sedimentary and phototrophic ecosystems

NASA Technical Reports Server (NTRS)

Hoehler, Tori M.; Albert, Daniel B.; Alperin, Marc J.; Bebout, Brad M.; Martens, Christopher S.; Des Marais, David J.

2002-01-01

The simple biochemistry of H2 is critical to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. The sensitivity of each of these processes to H2 can be described collectively, through the quantitative language of thermodynamics. A necessary prerequisite is to understand the factors that, in turn, control H2 partial pressures. These factors are assessed for two distinctly different ecosystems. In anoxic sediments from Cape Lookout Bight (North Carolina, USA), H2 partial pressures are strictly maintained at low, steady-state levels by H2-consuming organisms, in a fashion that can be quantitatively predicted by simple thermodynamic calculations. In phototrophic microbial mats from Baja California (Mexico), H2 partial pressures are controlled by the activity of light-sensitive H2-producing organisms, and consequently fluctuate over orders of magnitude on a daily basis. The differences in H2 cycling can subsequently impact any of the H2-sensitive microbial processes in these systems. In one example, methanogenesis in Cape Lookout Bight sediments is completely suppressed through the efficient consumption of H2 by sulfate-reducing bacteria; in contrast, elevated levels of H2 prevail in the producer-controlled phototrophic system, and methanogenesis occurs readily in the presence of 40 mM sulfate.

Computational and biochemical characterization of two partially overlapping interfaces and multiple weak-affinity K-Ras dimers

NASA Astrophysics Data System (ADS)

Prakash, Priyanka; Sayyed-Ahmad, Abdallah; Cho, Kwang-Jin; Dolino, Drew M.; Chen, Wei; Li, Hongyang; Grant, Barry J.; Hancock, John F.; Gorfe, Alemayehu A.

2017-01-01

Recent studies found that membrane-bound K-Ras dimers are important for biological function. However, the structure and thermodynamic stability of these complexes remained unknown because they are hard to probe by conventional approaches. Combining data from a wide range of computational and experimental approaches, here we describe the structure, dynamics, energetics and mechanism of assembly of multiple K-Ras dimers. Utilizing a range of techniques for the detection of reactive surfaces, protein-protein docking and molecular simulations, we found that two largely polar and partially overlapping surfaces underlie the formation of multiple K-Ras dimers. For validation we used mutagenesis, electron microscopy and biochemical assays under non-denaturing conditions. We show that partial disruption of a predicted interface through charge reversal mutation of apposed residues reduces oligomerization while introduction of cysteines at these positions enhanced dimerization likely through the formation of an intermolecular disulfide bond. Free energy calculations indicated that K-Ras dimerization involves direct but weak protein-protein interactions in solution, consistent with the notion that dimerization is facilitated by membrane binding. Taken together, our atomically detailed analyses provide unique mechanistic insights into K-Ras dimer formation and membrane organization as well as the conformational fluctuations and equilibrium thermodynamics underlying these processes.

Thermal and Electrical Effects of Partial Shade in Monolithic Thin-Film Photovoltaic Modules: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, Timothy J.; Deceglie, Michael G.; Sun, Xingshu

2015-09-02

Photovoltaic cells can be damaged by reverse bias stress, which arises during service when a monolithically integrated thin-film module is partially shaded. We introduce a model for describing a module's internal thermal and electrical state, which cannot normally be measured. Using this model and experimental measurements, we present several results with relevance for reliability testing and module engineering: Modules with a small breakdown voltage experience less stress than those with a large breakdown voltage, with some exceptions for modules having light-enhanced reverse breakdown. Masks leaving a small part of the masked cells illuminated can lead to very high temperature andmore » current density compared to masks covering entire cells.« less

Thermal and Electrical Effects of Partial Shade in Monolithic Thin-Film Photovoltaic Modules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, Timothy J.; Deceglie, Michael G.; Sun, Xingshu

2015-06-14

Photovoltaic cells can be damaged by reverse bias stress, which arises during service when a monolithically integrated thin-film module is partially shaded. We introduce a model for describing a module's internal thermal and electrical state, which cannot normally be measured. Using this model and experimental measurements, we present several results with relevance for reliability testing and module engineering: Modules with a small breakdown voltage experience less stress than those with a large breakdown voltage, with some exceptions for modules having light-enhanced reverse breakdown. Masks leaving a small part of the masked cells illuminated can lead to very high temperature andmore » current density compared to masks covering entire cells.« less

Use of Flowtran Simulation in Education

ERIC Educational Resources Information Center

Clark, J. Peter; Sommerfeld, Jude T.

1976-01-01

Describes the use in chemical engineering education of FLOWTRAN, a large steady-state simulator of chemical processes with extensive facilities for physical and thermodynamic data-handling and a large library of equipment modules, including cost estimation capability. (MLH)

Reactive solute transport in acidic streams

USGS Publications Warehouse

Broshears, R.E.

1996-01-01

Spatial and temporal profiles of Ph and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. Input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pH and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.

Striking Similarity in the Gene Expression Levels of Individual Myc Module Members among ESCs, EpiSCs, and Partial iPSCs

PubMed Central

Hirasaki, Masataka; Hiraki-Kamon, Keiko; Kamon, Masayoshi; Suzuki, Ayumu; Katano, Miyuki; Nishimoto, Masazumi; Okuda, Akihiko

2013-01-01

Predominant transcriptional subnetworks called Core, Myc, and PRC modules have been shown to participate in preservation of the pluripotency and self-renewality of embryonic stem cells (ESCs). Epiblast stem cells (EpiSCs) are another cell type that possesses pluripotency and self-renewality. However, the roles of these modules in EpiSCs have not been systematically examined to date. Here, we compared the average expression levels of Core, Myc, and PRC module genes between ESCs and EpiSCs. EpiSCs showed substantially higher and lower expression levels of PRC and Core module genes, respectively, compared with those in ESCs, while Myc module members showed almost equivalent levels of average gene expression. Subsequent analyses revealed that the similarity in gene expression levels of the Myc module between these two cell types was not just overall, but striking similarities were evident even when comparing the expression of individual genes. We also observed equivalent levels of similarity in the expression of individual Myc module genes between induced pluripotent stem cells (iPSCs) and partial iPSCs that are an unwanted byproduct generated during iPSC induction. Moreover, our data demonstrate that partial iPSCs depend on a high level of c-Myc expression for their self-renewal properties. PMID:24386274

The Size of the Internal Loop in DNA Hairpins Influences Their Targeting with Partially Complementary Strands

PubMed Central

2015-01-01

Targeting of noncanonical DNA structures, such as hairpin loops, may have significant diagnostic and therapeutic potential. Oligonucleotides can be used for binding to mRNA, forming a DNA/RNA hybrid duplex that inhibits translation. This kind of modulation of gene expression is called the antisense approach. In order to determine the best strategy to target a common structural motif in mRNA, we have designed a set of stem-loop DNA molecules with sequence: d(GCGCTnGTAAT5GTTACTnGCGC), where n = 1, 3, or 5, “T5” is an end loop of five thymines. We used a combination of calorimetric and spectroscopy techniques to determine the thermodynamics for the reaction of a set of hairpins containing internal loops with their respective partially complementary strands. Our aim was to determine if internal- and end-loops are promising regions for targeting with their corresponding complementary strands. Indeed, all targeting reactions were accompanied by negative changes in free energy, indicating that reactions proceed spontaneously. Further investigation showed that these negative free energy terms result from a net balance of unfavorable entropy and favorable enthalpy contributions. In particular, unfolding of hairpins and duplexes is accompanied by positive changes in heat capacity, which may be a result of exposure of hydrophobic groups to the solvent. This study provides a new method for the targeting of mRNA in order to control gene expression. PMID:25486129

Thermodynamics of Oxygen Ordering in Yttrium BARIUM(2) COPPER(3) OXYGEN(6+X)

NASA Astrophysics Data System (ADS)

Schieger, Paul Richard

An apparatus has been built to study and manipulate the oxygen in high temperature superconductors. It uses the principle of cryogenically assisted volumetric titration to precisely set changes in the oxygen content of high -T_{c} samples. The apparatus has been used to study the thermodynamics of oxygen in YBa_2Cu_3O _{6 + x} in order to help determine the correct model for oxygen thermodynamics as well as to provide standard curves for materials preparation by other methods. In particular, extensive measurements have been made on the oxygen pressure isotherms as a function of x for temperatures between 450^circ C and 650^circC. The measurement technique also allows one to extract the thermodynamic response function, (partial x/ partialmu)_{T}, ( mu is the chemical potential), which is sensitive to the oxygen configuration and which can be calculated by any candidate theory of the oxygen thermodynamics. Several existing theoretical models for the oxygen ordering thermodynamics are presented and compared to the experimental results. The models considered are classed into two basic approaches: lattice gas models and defect chemical models. It is found that the lattice gas models which assume static effective pair interactions between oxygen atoms, do not fit the experimental data very well, especially in the orthorhombic phase. The defect chemical models, which incorporate additional degrees of freedom (spin and charge) due to the creation of electronic defects, fit significantly better, but make crude assumptions for the configurational entropy of oxygen atoms. Using a commonly accepted picture for the creation of mobile electron holes and unpaired spins on the copper sites, it is possible to relate these quantities in terms of short range cluster probabilities defined in mean field approximations to the 2D lattice gas models. Based upon this connection, a thermodynamical model is developed, which takes into account interactions between oxygen atoms and the additional spin and charge degrees of freedom, assuming a narrow band, high temperature limit for the motion of the charge carriers. The model, containing the nearest-neighbour oxygen interaction (0.241eV) and the single site oxygen binding energy (-0.82eV - D/2; D is the dissociation energy of an oxygen molecule) as the only adjustable parameters, is compared to experimental results for the chemical potential, kT(partial x/partialmu)_{T}, fractional site occupancies, structural phase diagram, the number of monovalent coppers, and the total number of mobile electron holes. Qualitative agreement is found for all compared quantities, and quantitative agreement is found for the chemical potential, fractional site occupancies and kT(partial x/partialmu)_ {T} in the orthorhombic phase. Improvements to the model are outlined which should result in a quantitative fit to all results, in particular the valence and hole count vs. x. In addition to illuminating what is lacking in the commonly used two dimensional lattice gas models, the theory may form the basis for accurately predicting the electron hole count of the CuO_2 plane of YBa_2Cu_3 O_{6 + x} as a function of the sample preparation conditions.

Iron(III) solubility and speciation in aqueous solutions. experimental study and modelling: part 1. hematite solubility from 60 to 300°C in NaOH-NaCl solutions and thermodynamic properties of Fe(OH) 4 -(aq)

NASA Astrophysics Data System (ADS)

Diakonov, Igor I.; Schott, Jacques; Martin, Francois; Harrichourry, Jean-Claude; Escalier, Jocelyne

1999-08-01

The solubility of natural and synthetic hematite (α-Fe 2O 3) was measured in NaOH-NaCl solutions (0.007 ≤ m(NaOH) ≤ 2.0) between 60 and 300°C at saturated water vapour pressure and under excess oxygen. Solubility constants determined in the present study and by Yishan et al. (1986) at 300°C were combined with the thermodynamic properties of hematite (Hemingway, 1990) and water (SUPCRT92, Johnson et al., 1992) to generate within the framework of the revised Helgeson-Kirkham-Flowers (HKF) model the standard partial molal thermodynamic properties at 25°C and 1 bar, and the revised HKF equations of state parameters of Fe(OH) 4 -. The extrapolated value for the Gibbs energy of formation for Fe(OH) 4 - at 25°C is -201.97 kcal/mol. Thermodynamic calculations show that Fe(OH) 4 - exhibits a chemical behaviour different from that of Ga(OH) 4 - and Al(OH) 4 -.

Thermodynamic properties of La-Ga-Al and U-Ga-Al alloys and the separation factor of U/La couple in the molten salt-liquid metal system

NASA Astrophysics Data System (ADS)

Novoselova, A.; Smolenski, V.; Volkovich, V. A.; Ivanov, A. B.; Osipenko, A.; Griffiths, T. R.

2015-11-01

The electrochemical behaviour of lanthanum and uranium was studied in fused 3LiCl-2KCl eutectic and Ga-Al eutectic liquid metal alloy between 723 and 823 K. Electrode potentials were recorded vs. Cl-/Cl2 reference electrode and the temperature dependencies of the apparent standard potentials of La-(Ga-Al) and U-(Ga-Al) alloys were determined. Lanthanum and uranium activity coefficients and U/La couple separation factor were calculated. Partial excess free Gibbs energy, partial enthalpy of mixing and partial excess entropy of La-(Ga-Al) and U-(Ga-Al) alloys were estimated.

Thermodynamic Driving Force of Hydrogen on Rumen Microbial Metabolism: A Theoretical Investigation

PubMed Central

van Lingen, Henk J.; Plugge, Caroline M.; Fadel, James G.; Kebreab, Ermias; Bannink, André; Dijkstra, Jan

2016-01-01

Hydrogen is a key product of rumen fermentation and has been suggested to thermodynamically control the production of the various volatile fatty acids (VFA). Previous studies, however, have not accounted for the fact that only thermodynamic near-equilibrium conditions control the magnitude of reaction rate. Furthermore, the role of NAD, which is affected by hydrogen partial pressure (PH2), has often not been considered. The aim of this study was to quantify the control of PH2 on reaction rates of specific fermentation pathways, methanogenesis and NADH oxidation in rumen microbes. The control of PH2 was quantified using the thermodynamic potential factor (FT), which is a dimensionless factor that corrects a predicted kinetic reaction rate for the thermodynamic control exerted. Unity FT was calculated for all glucose fermentation pathways considered, indicating no inhibition of PH2 on the production of a specific type of VFA (e.g., acetate, propionate and butyrate) in the rumen. For NADH oxidation without ferredoxin oxidation, increasing PH2 within the rumen physiological range decreased FT from unity to zero for different NAD+ to NADH ratios and pH of 6.2 and 7.0, which indicates thermodynamic control of PH2. For NADH oxidation with ferredoxin oxidation, increasing PH2 within the rumen physiological range decreased FT from unity at pH of 7.0 only. For the acetate to propionate conversion, FT increased from 0.65 to unity with increasing PH2, which indicates thermodynamic control. For propionate to acetate and butyrate to acetate conversions, FT decreased to zero below the rumen range of PH2, indicating full thermodynamic suppression. For methanogenesis by archaea without cytochromes, FT differed from unity only below the rumen range of PH2, indicating no thermodynamic control. This theoretical investigation shows that thermodynamic control of PH2 on individual VFA produced and associated yield of hydrogen and methane cannot be explained without considering NADH oxidation. PMID:27783615

Thermodynamic assessment of the U–La–O system

DOE PAGES

McMurray, J. W.; Shin, D.; Besmann, T. M.

2014-10-03

The CALPHAD methodology was used to develop a thermodynamic assessment of the U-La-O system. The solid solution and liquid phases are described with the compound energy formalism and the partially ionic two-sublattice liquid model respectively. A density functional theory (DFT) calculation for the lattice stability of the fictive lanthanum oxide fluorite structure compound is used to determine the Gibbs energies for the La containing end-members in the CEF model for U 1-yLa yO 2+x. Experimental thermodynamic and phase equilibria data were then used in optimizations to develop representations of the phases in the system that can be extended to includemore » other actinide and fission products to develop multi-component models. The models that comprise this assessment very well reproduce experimentally determined oxygen potentials and the observed phase relations for the U-La-O system.« less

A combined experimental and computational thermodynamic investigation of the U-Th-O system

DOE PAGES

McMurray, Jake Wesley; Voit, Stewart L.; Besmann, Theodore M.

2016-03-21

Here, the thermodynamics of the U–Th–O system have been assessed using the Calphad method. The compound energy formalism (CEF) and a partially ionic two-sublattice liquid model (TSLM) were used for the fluorite U 1–yTh yO 2±x, γ-(U,Th) 4O 9, and the U–Th–O melt. The O 2 activity of fluorite U 1–yTh yO 2±x with temperature and composition was determined by thermogravimetric analysis. Thermodynamic studies for the Th–O binary and U–Th–O ternary available in the open literature were critically reviewed. A self-consistent data set was selected and compiled with the equilibrium oxygen pressures determined by thermogravimetry in order to optimize themore » adjustable parameters of models selected to represent the phases in the Th–O and U–Th–O systems.« less

Characterization, kinetic, and thermodynamic studies of marine pectinase from Bacillus subtilis.

PubMed

Joshi, Manasi; Nerurkar, Madhura; Adivarekar, Ravindra

2015-01-01

Characterization, kinetic and thermodynamic parameters of purified pectinase from Bacillus subtilis, isolated from a marine sediment sample collected from Chinchani beach at Tarapore, India, were studied. Marine pectinase produced under submerged growth conditions was purified by ammonium sulfate precipitation followed by gel filtration chromatography using DEAE cellulose. Partial characterization of the marine pectinase was carried out in terms of effect of pH, temperature, substrate concentration, and metal ions. It was found that pectinase from marine B. subtilis showed maximal activity in alkaline buffer at pH 9.0 and at 40°C. It was also found that metal ions, namely, Mn(2+) and Fe(2+), stimulate pectinase activity. Marine pectinase followed Michaelis-Menten kinetics. The kinetics and thermodynamic parameters of the purified marine pectinase from B. subtilis were studied as the characterization of the enzyme is vital for its use in industrial processes.

Thermodynamics of information processing based on enzyme kinetics: An exactly solvable model of an information pump.

PubMed

Cao, Yuansheng; Gong, Zongping; Quan, H T

2015-06-01

Motivated by the recent proposed models of the information engine [Proc. Natl. Acad. Sci. USA 109, 11641 (2012)] and the information refrigerator [Phys. Rev. Lett. 111, 030602 (2013)], we propose a minimal model of the information pump and the information eraser based on enzyme kinetics. This device can either pump molecules against the chemical potential gradient by consuming the information to be encoded in the bit stream or (partially) erase the information initially encoded in the bit stream by consuming the Gibbs free energy. The dynamics of this model is solved exactly, and the "phase diagram" of the operation regimes is determined. The efficiency and the power of the information machine is analyzed. The validity of the second law of thermodynamics within our model is clarified. Our model offers a simple paradigm for the investigating of the thermodynamics of information processing involving the chemical potential in small systems.

Schaeffler-Type Phase Diagram of Ti-Based Alloys

NASA Astrophysics Data System (ADS)

Ishida, K.

2017-10-01

The α(hcp)/β(bcc) phase equilibria of Ti-based multi-component alloys can be described by a Schaeffler-type diagram, where Al and Mo equivalents (Aleq and Moeq) are used. Aleq is thermodynamically defined by the ratio of partial molar free energy changes transfer of one mole of each α forming element and Al from a dilute solution of α to β phases, while Moeq is also deduced by similar thermodynamic quantities of β forming element and Mo. Aleq and Moeq for 40 alloying elements are estimated from the thermodynamic parameters assessed by Kaufman and Murray. It is shown that three types of Ti alloys, i.e., α and near α, α+β, and β alloys, can be exactly classified using Aleq and Moeq. The Ms and β transus temperatures can also be predicted by Aleq and Moeq. The proposed Aleq and Moeq are very useful for alloy design, heat treatment, and microstructural evolution of Ti-based alloys.

A circuit-based photovoltaic module simulator with shadow and fault settings

NASA Astrophysics Data System (ADS)

Chao, Kuei-Hsiang; Chao, Yuan-Wei; Chen, Jyun-Ping

2016-03-01

The main purpose of this study was to develop a photovoltaic (PV) module simulator. The proposed simulator, using electrical parameters from solar cells, could simulate output characteristics not only during normal operational conditions, but also during conditions of partial shadow and fault conditions. Such a simulator should possess the advantages of low cost, small size and being easily realizable. Experiments have shown that results from a proposed PV simulator of this kind are very close to that from simulation software during partial shadow conditions, and with negligible differences during fault occurrence. Meanwhile, the PV module simulator, as developed, could be used on various types of series-parallel connections to form PV arrays, to conduct experiments on partial shadow and fault events occurring in some of the modules. Such experiments are designed to explore the impact of shadow and fault conditions on the output characteristics of the system as a whole.

The SMS4 cryptographic system design based on dynamic partial self-reconfiguration technology

NASA Astrophysics Data System (ADS)

Wang, Jianxin; Gao, Xianwei; Li, Xiuying; Sui, Meili

2013-03-01

This paper describes SMS4 algorithm by using dynamic partial self-reconfiguration. The design is implemented on Xilinx VirtexII-Pro XC2VP30 FPGA devices. The partial self-reconfiguration encryption/decryption module data throughput is up to 50Mb/s, key expansion and encryption/decryption modules use 1606 and 1570 slices respectively, and the resource utilization ratio of the key expansion by using partial self-reconfiguration technology is less 32.03% and slices are less 757 than the non-reconfiguration technology. SMS4 implementation gets a good balance between high performance and low complexity in area. The theoretical and practical research of dynamic partial self-reconfiguration has a broad space for development and application prospect.

Thermodynamic aspect in using modified Boltzmann model as an acoustic probe for URu2Si2

NASA Astrophysics Data System (ADS)

Kwang-Hua, Chu Rainer

2018-05-01

The approximate system of equations describing ultrasonic attenuation propagating in many electrons of the heavy-fermion materials URu2Si2 under high magnetic fields were firstly derived and then calculated based on the modified Boltzmann model considering the microscopic contributions due to electronic fluids. A system of nonlinear partial differential coupled with integral equations were linearized firstly and approximately solved considering the perturbed thermodynamic equilibrium states. Our numerical data were compared with previous measurements using non-dimensional or normalized physical values. The rather good fit of our numerical calculations with experimental measurements confirms our present approach.

Thermodynamic properties of gases dissolved in electrolyte solutions.

NASA Technical Reports Server (NTRS)

Tiepel, E. W.; Gubbins, K. E.

1973-01-01

A method based on perturbation theory for mixtures is applied to the prediction of thermodynamic properties of gases dissolved in electrolyte solutions. The theory is compared with experimental data for the dependence of the solute activity coefficient on concentration, temperature, and pressure; calculations are included for partial molal enthalpy and volume of the dissolved gas. The theory is also compared with previous theories for salt effects and found to be superior. The calculations are best for salting-out systems. The qualitative feature of salting-in is predicted by the theory, but quantitative predictions are not satisfactory for such systems; this is attributed to approximations made in evaluating the perturbation terms.

Numerical Modeling of Nonlinear Thermodynamics in SMA Wires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reynolds, D R; Kloucek, P

We present a mathematical model describing the thermodynamic behavior of shape memory alloy wires, as well as a computational technique to solve the resulting system of partial differential equations. The model consists of conservation equations based on a new Helmholtz free energy potential. The computational technique introduces a viscosity-based continuation method, which allows the model to handle dynamic applications where the temporally local behavior of solutions is desired. Computational experiments document that this combination of modeling and solution techniques appropriately predicts the thermally- and stress-induced martensitic phase transitions, as well as the hysteretic behavior and production of latent heat associatedmore » with such materials.« less

Thermodynamic study on the role of hydrogen during the MOVPE growth of group III nitrides

NASA Astrophysics Data System (ADS)

Koukitu, Akinori; Taki, Tetsuya; Takahashi, Naoyuki; Seki, Hisashi

1999-02-01

The role of hydrogen during the MOVPE growth of group III nitrides is investigated from a thermodynamic point of view. The effect of hydrogen is reported for the driving force for the deposition of binary nitrides as functions of growth temperature and V/III ratio. The effect of hydrogen for the InGaN growth is discussed for the vapor-solid relationship, the formation of compositional inhomogeneity and input partial pressure of the group III elements. The difference between the growth reaction of the indium containing nitrides and that of other III-V compounds is also discussed.

Reversibility between glass and melting transitions of poly(oxyethylene)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qui, Wulin; Pyda, Marek; Nowak-Pyda, Elisabieta

2005-01-01

The heat capacities, C{sub p}, of poly(oxyethylene), POE, with molar masses from 1500 to 900,000 Da, were analyzed by differential scanning calorimetry (DSC), quasi-isothermal, temperature-modulated DSC (TMDSC), and wide-angle X-ray diffraction (WAXD). There is no change in crystal structure before melting, but the lattice parameters increase rapidly in the melting region. Perfected extended-chain and once- or twice-folded crystals of the oligomers with a molar mass above 1100 Da melt practically fully irreversibly and permit direct measurement of the thermodynamic C{sub p}. The folded-chain crystals of high molar mass show some locally reversible melting. The reversing, apparent C{sub p} depends onmore » molar mass and amplitude and frequency of modulation. After separation from the latent heat effects, the reversible, thermodynamic C{sub p} depends on the melting temperature for low molar masses and increases beyond the vibrational C{sub p} due to conformational motion. Molar masses of 8000-20,000 have almost the same C{sub p}. These observations permit a quantitative discussion of the thermodynamic C{sub p} and the locally reversible melting of the globally metastable POE in the melting range. The increase in C{sub p} between 250 K and the melting temperature is interpreted as a glass transition within the crystal.« less

Mechanism of superoxide and hydrogen peroxide generation by human electron-transfer flavoprotein and pathological variants.

PubMed

Rodrigues, João V; Gomes, Cláudio M

2012-07-01

Reactive oxygen species production by mitochondrial enzymes plays a fundamental role both in cellular signaling and in the progression of dysfunctional states. However, sources of reactive oxygen species and the mechanisms by which enzymes produce these reactive species still remain elusive. We characterized the generation of reactive oxygen species by purified human electron-transfer flavoprotein (ETF), a mitochondrial enzyme that has a central role in the metabolism of lipids, amino acids, and choline. The results showed that ETF produces significant amounts of both superoxide and hydrogen peroxide in the presence of its partner enzyme medium-chain acyl-CoA dehydrogenase (MCAD). ETF-mediated production of reactive oxygen species is partially inhibited at high MCAD/ETF ratios, whereas it is enhanced at high ionic strength. Determination of the reduction potentials of ETF showed that thermodynamic properties of the FAD cofactor are changed upon formation of a complex between ETF and MCAD, supporting the notion that protein:protein interactions modulate the reactivity of the protein with dioxygen. Two pathogenic ETF variants were also studied to determine which factors modulate the reactivity toward molecular oxygen and promote reactive oxygen species production. The results obtained show that destabilized conformations and defective protein:protein interactions increase the ability of ETF to generate reactive oxygen species. A possible role for these processes in mitochondrial dysfunction in metabolic disorders of fatty acid β-oxidation is discussed. Copyright © 2012 Elsevier Inc. All rights reserved.

Deconstructing thermodynamic parameters of a coupled system from site-specific observables.

PubMed

Chowdhury, Sandipan; Chanda, Baron

2010-11-02

Cooperative interactions mediate information transfer between structural domains of a protein molecule and are major determinants of protein function and modulation. The prevalent theories to understand the thermodynamic origins of cooperativity have been developed to reproduce the complex behavior of a global thermodynamic observable such as ligand binding or enzyme activity. However, in most cases the measurement of a single global observable cannot uniquely define all the terms that fully describe the energetics of the system. Here we establish a theoretical groundwork for analyzing protein thermodynamics using site-specific information. Our treatment involves extracting a site-specific parameter (defined as χ value) associated with a structural unit. We demonstrate that, under limiting conditions, the χ value is related to the direct interaction terms associated with the structural unit under observation and its intrinsic activation energy. We also introduce a site-specific interaction energy term (χ(diff)) that is a function of the direct interaction energy of that site with every other site in the system. When combined with site-directed mutagenesis and other molecular level perturbations, analyses of χ values of site-specific observables may provide valuable insights into protein thermodynamics and structure.

Students' Understanding of Mathematical Expressions in Physical Chemistry Contexts: An Analysis Using Sherin's Symbolic Forms

ERIC Educational Resources Information Center

Becker, Nicole; Towns, Marcy

2012-01-01

Undergraduate physical chemistry courses require students to be proficient in calculus in order to develop an understanding of thermodynamics concepts. Here we present the findings of a study that examines student understanding of mathematical expressions, including partial derivative expressions, in two undergraduate physical chemistry courses.…

An Introduction to Equilibrium Thermodynamics: A Rational Approach to Its Teaching. Part 1: Notation and Mathematics.

ERIC Educational Resources Information Center

Williams, Donald F.; Glasser, David

1991-01-01

Introduces and develops mathematical notation to assist undergraduate students in overcoming conceptual difficulties involving the underlying mathematics of state functions, which tend to be different from functions encountered by students in previous mathematical courses, because of the need to manipulate special types of partial derivatives and…

Folding cooperativity in a three-stranded beta-sheet model.

PubMed

Roe, Daniel R; Hornak, Viktor; Simmerling, Carlos

2005-09-16

The thermodynamic behavior of a previously designed three-stranded beta-sheet was studied via several microseconds of standard and replica exchange molecular dynamics simulations. The system is shown to populate at least four thermodynamic minima, including two partially folded states in which only a single hairpin is formed. Simulated melting curves show different profiles for the C and N-terminal hairpins, consistent with differences in secondary structure content in published NMR and CD/FTIR measurements, which probed different regions of the chain. Individual beta-hairpins that comprise the three-stranded beta-sheet are observed to form cooperatively. Partial folding cooperativity between the component hairpins is observed, and good agreement between calculated and experimental values quantifying this cooperativity is obtained when similar analysis techniques are used. However, the structural detail in the ensemble of conformations sampled in the simulations permits a more direct analysis of this cooperativity than has been performed on the basis of experimental data. The results indicate the actual folding cooperativity perpendicular to strand direction is significantly larger than the lower bound obtained previously.

Folding cooperativity in a 3-stranded β-sheet model

PubMed Central

Roe, Daniel R.; Hornak, Viktor

2015-01-01

Summary The thermodynamic behavior of a previously designed three-stranded β-sheet was studied via several µs of standard and replica exchange molecular dynamics simulations. The system is shown to populate at least four thermodynamic minima, including 2 partially folded states in which only a single hairpin is formed. Simulated melting curves show different profiles for the C and N-terminal hairpins, consistent with differences in secondary structure content in published NMR and CD/FTIR measurements, which probed different regions of the chain. Individual β-hairpins that comprise the 3-stranded β-sheet are observed to form cooperatively. Partial folding cooperativity between the component hairpins is observed, and good agreement between calculated and experimental values quantifying this cooperativity is obtained when similar analysis techniques are used. However, the structural detail in the ensemble of conformations sampled in the simulations permits a more direct analysis of this cooperatively than has been performed based on experimental data. The results indicate the actual folding cooperativity perpendicular to strand direction is significantly larger than the lower bound obtained previously. PMID:16095612

Digital high speed programmable convolver

NASA Astrophysics Data System (ADS)

Rearick, T. C.

1984-12-01

A circuit module for rapidly calculating a discrete numerical convolution is described. A convolution such as finding the sum of the products of a 16 bit constant and a 16 bit variable is performed by a module which is programmable so that the constant may be changed for a new problem. In addition, the module may be programmed to find the sum of the products of 4 and 8 bit constants and variables. RAM (Random Access Memories) are loaded with partial products of the selected constant and all possible variables. Then, when the actual variable is loaded, it acts as an address to find the correct partial product in the particular RAM. The partial products from all of the RAMs are shifted to the appropriate numerical power position (if necessary) and then added in adder elements.

Modulation transfer function of partial gating detector by liquid crystal auto-controlling light intensity

NASA Astrophysics Data System (ADS)

Yang, Xusan; Tang, Yuanhe; Liu, Kai; Liu, Hanchen; Gao, Haiyang; Li, Qing; Zhang, Ruixia; Ye, Na; Liang, Yuan; Zhao, Gaoxiang

2008-12-01

Based on the electro-optical properties of liquid crystal, we have designed a novel partial gating detector. Liquid crystal can be taken to change its own transmission according to the light intensity outside. Every single pixel of the image is real-time modulated by liquid crystal, thus the strong light is weakened and low light goes through the detector normally .The purpose of partial-gating strong light (>105lx) can be achieved by this detector. The modulation transfer function (MTF) equations of the main optical sub-systems are calculated in this paper, they are liquid crystal panels, linear fiber panel and CCD array detector. According to the relevant size, the MTF value of this system is fitted out. The result is MTF= 0.518 at Nyquist frequency.

Computational method and system for modeling, analyzing, and optimizing DNA amplification and synthesis

DOEpatents

Vandersall, Jennifer A.; Gardner, Shea N.; Clague, David S.

2010-05-04

A computational method and computer-based system of modeling DNA synthesis for the design and interpretation of PCR amplification, parallel DNA synthesis, and microarray chip analysis. The method and system include modules that address the bioinformatics, kinetics, and thermodynamics of DNA amplification and synthesis. Specifically, the steps of DNA selection, as well as the kinetics and thermodynamics of DNA hybridization and extensions, are addressed, which enable the optimization of the processing and the prediction of the products as a function of DNA sequence, mixing protocol, time, temperature and concentration of species.

High-temperature mass spectrometric study of the vaporization processes and thermodynamic properties of melts in the PbO-B2O3-SiO2 system.

PubMed

Stolyarova, V L; Lopatin, S I; Shilov, A L; Shugurov, S M

2013-07-15

The unique properties of the PbO-B2O3-SiO2 system, especially its extensive range of glass-forming compositions, make it valuable for various practical applications. The thermodynamic properties and vaporization of PbO-B2O3-SiO2 melts are not well established so far and the data obtained on these will be useful for optimization of technology and thermodynamic modeling of glasses. High-temperature Knudsen effusion mass spectrometry was used to study vaporization processes and to determine the partial pressures of components of the PbO-B2O3-SiO2 melts. Measurements were performed with a MS-1301 mass spectrometer. Vaporization was carried out using two quartz effusion cells containing the sample under study and pure PbO (reference substance). Ions were produced by electron ionization at an energy of 25 eV. To facilitate interpretation of the mass spectra, the appearance energies of ions were also measured. Pb, PbO and O2 were found to be the main vapor species over the samples studied at 1100 K. The PbO activities as a function of the composition of the system were derived from the measured PbO partial pressures. The B2O3 and SiO2 activities, the Gibbs energy of formation, the excess Gibbs energy of formation and mass losses in the samples studied were calculated. Partial pressures of the vapor species over PbO-B2O3-SiO2 melts were measured at 1100 K in the wide range of compositions using the Knudsen mass spectrometric method. The data enabled the PbO, B2O3, and SiO2 activities in these melts to be derived and provided evidence of their negative deviations from ideal behavior. Copyright © 2013 John Wiley & Sons, Ltd.

Density functional theory study of defects in unalloyed δ-Pu

DOE PAGES

Hernandez, S. C.; Freibert, F. J.; Wills, J. M.

2017-03-19

Using density functional theory, we explore in this paper various classical point and complex defects within the face-centered cubic unalloyed δ-plutonium matrix that are potentially induced from self-irradiation. For plutonium only defects, the most energetically stable defect is a distorted split-interstitial. Gallium, the δ-phase stabilizer, is thermodynamically stable as a substitutional defect, but becomes unstable when participating in a complex defect configuration. Finally, complex uranium defects may thermodynamically exist as uranium substitutional with neighboring plutonium interstitial and stabilization of uranium within the lattice is shown via partial density of states and charge density difference plots to be 5f hybridization betweenmore » uranium and plutonium.« less

Thermodynamics and Dynamics of Bose condensation in a quasi-homogeneous gas

NASA Astrophysics Data System (ADS)

Navon, Nir; Schmidutz, Tobias; Gotlibovych, Igor; Gaunt, Alexander; Robert-de-Saint-Vincent, Martin; Smith, Robert; Hadzibabic, Zoran

2014-05-01

We present an experimental study of the thermodynamics and dynamics of Bose-Einstein condensation (BEC) in an optical-box trap. We first characterize the critical point for BEC, and observe saturation of the thermal component in a partially condensed cloud, in agreement with Einstein's textbook picture of a purely statistical phase transition. We also observed the quantum Joule-Thomson effect, namely isoenthalpic cooling of a non-interacting gas. We then investigate the dynamics of Bose condensation in the box potential following a rapid temperature quench through the phase transition, and focus on the time-evolution of the condensed fraction, the coherence length and the mean-field shift, that we probe via Bragg spectroscopy.

Thermodynamic confinement and alpha-helix persistence length in poly(gamma-benzyl-L-glutamate)-b-poly(dimethyl siloxane)-b-poly(gamma-benzyl-L-glutamate) triblock copolymers.

PubMed

Papadopoulos, P; Floudas, G; Schnell, I; Lieberwirth, I; Nguyen, T Q; Klok, H-A

2006-02-01

The structure and the associated dynamics of a series of poly(gamma-benzyl-L-glutamate)-b-poly(dimethyl siloxane)-b-poly(gamma-benzyl-L-glutamate) (PBLG-b-PDMS-b-PBLG) triblock copolymers were investigated using small- and wide-angle X-ray scattering, NMR, transmission electron microscopy, and dielectric spectroscopy, respectively. The structural analysis revealed phase separation in the case of the longer blocks with defected alpha-helical segments embedded within the block copolymer nanodomains. The alpha-helical persistence length was found to depend on the degree of segregation; thermodynamic confinement and chain stretching results in the partial annihilation of helical defects.

Thermodynamically self-consistent theory for the Blume-Capel model.

PubMed

Grollau, S; Kierlik, E; Rosinberg, M L; Tarjus, G

2001-04-01

We use a self-consistent Ornstein-Zernike approximation to study the Blume-Capel ferromagnet on three-dimensional lattices. The correlation functions and the thermodynamics are obtained from the solution of two coupled partial differential equations. The theory provides a comprehensive and accurate description of the phase diagram in all regions, including the wing boundaries in a nonzero magnetic field. In particular, the coordinates of the tricritical point are in very good agreement with the best estimates from simulation or series expansion. Numerical and analytical analysis strongly suggest that the theory predicts a universal Ising-like critical behavior along the lambda line and the wing critical lines, and a tricritical behavior governed by mean-field exponents.

The optical method for determining the thermodynamic parameters of hot gases

NASA Astrophysics Data System (ADS)

Egorov, O. V.; Voitsekhovskaya, O. K.; Kashirskii, D. E.; Tsvyk, R. Sh.; Sazanovich, V. M.; Sherstobitov, M. V.

2014-11-01

The research conducted on the thermodynamic parameters of a flame was based on its experimental transmission spectra in the 2.7 μm and 4.3 μm ranges. To produce the flame, alcohol was burned under atmospheric conditions. The hot gases resulting from the burning of ethanol (H2O, CO, and CO2) were accelerated and spun by the rotation of an impeller. The optical method developed by the authors was employed for predicting the temperature and partial pressure of the hot gases. The results demonstrate the practical significance of the method suggested. The spectroscopic database HITEMP 2010 was used for all line-by-line calculations presented in the article.

Density functional theory study of defects in unalloyed δ-Pu

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hernandez, S. C.; Freibert, F. J.; Wills, J. M.

Using density functional theory, we explore in this paper various classical point and complex defects within the face-centered cubic unalloyed δ-plutonium matrix that are potentially induced from self-irradiation. For plutonium only defects, the most energetically stable defect is a distorted split-interstitial. Gallium, the δ-phase stabilizer, is thermodynamically stable as a substitutional defect, but becomes unstable when participating in a complex defect configuration. Finally, complex uranium defects may thermodynamically exist as uranium substitutional with neighboring plutonium interstitial and stabilization of uranium within the lattice is shown via partial density of states and charge density difference plots to be 5f hybridization betweenmore » uranium and plutonium.« less

Development of a Thermoelectric Module Suitable for Vehicles and Based on CoSb3 Manufactured Close to Production

NASA Astrophysics Data System (ADS)

Klein Altstedde, Mirko; Sottong, Reinhard; Freitag, Oliver; Kober, Martin; Dreißigacker, Volker; Zabrocki, Knud; Szabo, Patric

2015-06-01

Despite the ongoing electrification of vehicle propulsion systems, vehicles with combustion engines will continue to bear the brunt of passenger services worldwide for the next few decades. As a result, the German Aerospace Center Institute of Vehicle Concepts, the Institute of Materials Research and the Institute of Technical Thermodynamics have focused on utilising the exhaust heat of internal combustion engines by means of thermoelectric generators (TEGs). Their primary goal is the development of cost-efficient TEGs with long-term stability and maximised energy yield. In addition to the overall TEG system design, the development of long-term stable, efficient thermoelectric modules (TEMs) for high-temperature applications is a great challenge. This paper presents the results of internal development work and reveals an expedient module design for use in TEGs suitable for vehicles. The TEM requirements identified, which were obtained by means of experiments on the test vehicle and test bench, are described first. Doped semiconductor materials were produced and characterised by production methods capable of being scaled up in order to represent series application. The results in terms of thermoelectric properties (Seebeck coefficient, electrical conductivity and thermal conductivity) were used for the simulative design of a thermoelectric module using a constant-property model and with the aid of FEM calculations. Thermomechanical calculations of material stability were carried out in addition to the TEM's thermodynamic and thermoelectric design. The film sequence within the module represented a special challenge. Multilayer films facilitated adaptation of the thermal and mechanical properties of plasma-sprayed films. A joint which dispenses with solder additives was also possible using multilayer films. The research resulted in a functionally-optimised module design, which was enhanced for use in motor vehicles using process flexibility and close-to-production manufacturing methods.

Partial Pressures of Te2 and Thermodynamic Properties of Ga-Te System

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Curreri, Peter A. (Technical Monitor)

2001-01-01

The partial pressures of Te2 in equilibrium with Ga(1-x)Te(x) samples were measured by optical absorption technique from 450 to 1100 C for compositions, x, between 0.333 and 0.612. To establish the relationship between the partial pressure of Te, and the measured optical absorbance, the calibration runs of a pure Te sample were also conducted to determine the Beer's Law constants. The partial pressures of Te2 in equilibrium with the GaTe(s) and Ga2Te3(s)compounds, or the so-called three-phase curves, were established. These partial pressure data imply the existence of the Ga3Te4(s) compound. From the partial pressures of Te2 over the Ga-Te melts, partial molar enthalpy and entropy of mixing for Te were derived and they agree reasonable well with the published data. The activities of Te in the Ga-Te melts were also derived from the measured partial pressures of Te2. These data agree well with most of the previous results. The possible reason for the high activity of Te measured for x less than 0.60 is discussed.

Morphological Transformation between Nanocoils and Nanoribbons via Defragmentation Structural Rearrangement or Fragmentation-recombination Mechanism

NASA Astrophysics Data System (ADS)

Zhang, Yibin; Zheng, Yingxuan; Xiong, Wei; Peng, Cheng; Zhang, Yifan; Duan, Ran; Che, Yanke; Zhao, Jincai

2016-06-01

Kinetic control over the assembly pathways towards novel metastable functional materials or far-from-equilibrium systems has been much less studied compared to the thermodynamic equilibrium self-assembly. Herein, we report the distinct morphological transformation between nanocoils and nanoribbons in the self-assembly of unsymmetric perylene diimide (PDI) molecules. We demonstrate that the morphological transformation of the kinetically trapped assemblies into the thermodynamically stable forms proceeds via two distinct mechanisms, i.e., a direct structural rearrangement (molecule 1 or 2) and a fragmentation-recombination mechanism (molecule 4), respectively. The subtle interplay of the steric hindrance of the bulky substituents and the flexibility of the linker structure between the bulky moiety and the perylene core was demonstrated to enable the effective modulation of the energetic landscape of the assemblies and thus modulation of the assembly pathways. Herein, our work presents a new approach to control the self-assembly pathways and thereby can be used to achieve novel far-from-equilibrium systems.

Periodic thermodynamics of open quantum systems.

PubMed

Brandner, Kay; Seifert, Udo

2016-06-01

The thermodynamics of quantum systems coupled to periodically modulated heat baths and work reservoirs is developed. By identifying affinities and fluxes, the first and the second law are formulated consistently. In the linear response regime, entropy production becomes a quadratic form in the affinities. Specializing to Lindblad dynamics, we identify the corresponding kinetic coefficients in terms of correlation functions of the unperturbed dynamics. Reciprocity relations follow from symmetries with respect to time reversal. The kinetic coefficients can be split into a classical and a quantum contribution subject to an additional constraint, which follows from a natural detailed balance condition. This constraint implies universal bounds on efficiency and power of quantum heat engines. In particular, we show that Carnot efficiency cannot be reached whenever quantum coherence effects are present, i.e., when the Hamiltonian used for work extraction does not commute with the bare system Hamiltonian. For illustration, we specialize our universal results to a driven two-level system in contact with a heat bath of sinusoidally modulated temperature.

Periodic thermodynamics of open quantum systems

NASA Astrophysics Data System (ADS)

Brandner, Kay; Seifert, Udo

2016-06-01

The thermodynamics of quantum systems coupled to periodically modulated heat baths and work reservoirs is developed. By identifying affinities and fluxes, the first and the second law are formulated consistently. In the linear response regime, entropy production becomes a quadratic form in the affinities. Specializing to Lindblad dynamics, we identify the corresponding kinetic coefficients in terms of correlation functions of the unperturbed dynamics. Reciprocity relations follow from symmetries with respect to time reversal. The kinetic coefficients can be split into a classical and a quantum contribution subject to an additional constraint, which follows from a natural detailed balance condition. This constraint implies universal bounds on efficiency and power of quantum heat engines. In particular, we show that Carnot efficiency cannot be reached whenever quantum coherence effects are present, i.e., when the Hamiltonian used for work extraction does not commute with the bare system Hamiltonian. For illustration, we specialize our universal results to a driven two-level system in contact with a heat bath of sinusoidally modulated temperature.

Kinetic control over pathway complexity in supramolecular polymerization through modulating the energy landscape by rational molecular design.

PubMed

Ogi, Soichiro; Fukui, Tomoya; Jue, Melinda L; Takeuchi, Masayuki; Sugiyasu, Kazunori

2014-12-22

Far-from-equilibrium thermodynamic systems that are established as a consequence of coupled equilibria are the origin of the complex behavior of biological systems. Therefore, research in supramolecular chemistry has recently been shifting emphasis from a thermodynamic standpoint to a kinetic one; however, control over the complex kinetic processes is still in its infancy. Herein, we report our attempt to control the time evolution of supramolecular assembly in a process in which the supramolecular assembly transforms from a J-aggregate to an H-aggregate over time. The transformation proceeds through a delicate interplay of these two aggregation pathways. We have succeeded in modulating the energy landscape of the respective aggregates by a rational molecular design. On the basis of this understanding of the energy landscape, programming of the time evolution was achieved through adjusting the balance between the coupled equilibria. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An interactive computer lab of the galvanic cell for students in biochemistry.

PubMed

Ahlstrand, Emma; Buetti-Dinh, Antoine; Friedman, Ran

2018-01-01

We describe an interactive module that can be used to teach basic concepts in electrochemistry and thermodynamics to first year natural science students. The module is used together with an experimental laboratory and improves the students' understanding of thermodynamic quantities such as Δ r G, Δ r H, and Δ r S that are calculated but not directly measured in the lab. We also discuss how new technologies can substitute some parts of experimental chemistry courses, and improve accessibility to course material. Cloud computing platforms such as CoCalc facilitate the distribution of computer codes and allow students to access and apply interactive course tools beyond the course's scope. Despite some limitations imposed by cloud computing, the students appreciated the approach and the enhanced opportunities to discuss study questions with their classmates and instructor as facilitated by the interactive tools. © 2017 by The International Union of Biochemistry and Molecular Biology, 46(1):58-65, 2018. © 2017 The International Union of Biochemistry and Molecular Biology.

Thermodynamically optimal whole-genome tiling microarray design and validation.

PubMed

Cho, Hyejin; Chou, Hui-Hsien

2016-06-13

Microarray is an efficient apparatus to interrogate the whole transcriptome of species. Microarray can be designed according to annotated gene sets, but the resulted microarrays cannot be used to identify novel transcripts and this design method is not applicable to unannotated species. Alternatively, a whole-genome tiling microarray can be designed using only genomic sequences without gene annotations, and it can be used to detect novel RNA transcripts as well as known genes. The difficulty with tiling microarray design lies in the tradeoff between probe-specificity and coverage of the genome. Sequence comparison methods based on BLAST or similar software are commonly employed in microarray design, but they cannot precisely determine the subtle thermodynamic competition between probe targets and partially matched probe nontargets during hybridizations. Using the whole-genome thermodynamic analysis software PICKY to design tiling microarrays, we can achieve maximum whole-genome coverage allowable under the thermodynamic constraints of each target genome. The resulted tiling microarrays are thermodynamically optimal in the sense that all selected probes share the same melting temperature separation range between their targets and closest nontargets, and no additional probes can be added without violating the specificity of the microarray to the target genome. This new design method was used to create two whole-genome tiling microarrays for Escherichia coli MG1655 and Agrobacterium tumefaciens C58 and the experiment results validated the design.

Thermodynamics of Micelle Formation and Membrane Fusion Modulate Antimicrobial Lipopeptide Activity

PubMed Central

Lin, Dejun; Grossfield, Alan

2015-01-01

Antimicrobial lipopeptides (AMLPs) are antimicrobial drug candidates that preferentially target microbial membranes. One class of AMLPs, composed of cationic tetrapeptides attached to an acyl chain, have minimal inhibitory concentrations in the micromolar range against a range of bacteria and fungi. Previously, we used coarse-grained molecular dynamics simulations and free energy methods to study the thermodynamics of their interaction with membranes in their monomeric state. Here, we extended the study to the biologically relevant micellar state, using, to our knowledge, a novel reaction coordinate based on hydrophobic contacts. Using umbrella sampling along this reaction coordinate, we identified the critical transition states when micelles insert into membranes. The results indicate that the binding of these AMLP micelles to membranes is thermodynamically favorable, but in contrast to the monomeric case, there are significant free energy barriers. The height of these free energy barriers depends on the membrane composition, suggesting that the AMLPs’ ability to selectively target bacterial membranes may be as much kinetic as thermodynamic. This mechanism highlights the importance of considering oligomeric state in solution as criterion when optimizing peptides or lipopeptides as antibiotic leads. PMID:26287627

Analysis of High Power IGBT Short Circuit Failures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pappas, G.

2005-02-11

The Next Linear Collider (NLC) accelerator proposal at SLAC requires a highly efficient and reliable, low cost, pulsed-power modulator to drive the klystrons. A solid-state induction modulator has been developed at SLAC to power the klystrons; this modulator uses commercial high voltage and high current Insulated Gate Bipolar Transistor (IGBT) modules. Testing of these IGBT modules under pulsed conditions was very successful; however, the IGBTs failed when tests were performed into a low inductance short circuit. The internal electrical connections of a commercial IGBT module have been analyzed to extract self and mutual partial inductances for the main current pathsmore » as well as for the gate structure. The IGBT module, together with the partial inductances, has been modeled using PSpice. Predictions for electrical paths that carry the highest current correlate with the sites of failed die under short circuit tests. A similar analysis has been carried out for a SLAC proposal for an IGBT module layout. This paper discusses the mathematical model of the IGBT module geometry and presents simulation results.« less

Thermodynamic assessment of the LiF-ThF4-PuF3-UF4 system

NASA Astrophysics Data System (ADS)

Capelli, E.; Beneš, O.; Konings, R. J. M.

2015-07-01

The LiF-ThF4-PuF3-UF4 system is the reference salt mixture considered for the Molten Salt Fast Reactor (MSFR) concept started with PuF3. In order to obtain the complete thermodynamic description of this quaternary system, two binary systems (ThF4-PuF3 and UF4-PuF3) and two ternary systems (LiF-ThF4-PuF3 and LiF-UF4-PuF3) have been assessed for the first time. The similarities between CeF3/PuF3 and ThF4/UF4 compounds have been taken into account for the presented optimization as well as in the experimental measurements performed, which have confirmed the temperatures predicted by the model. Moreover, the experimental results and the thermodynamic database developed have been used to identify potential compositions for the MSFR fuel and to evaluate the influence of partial substitution of ThF4 by UF4 in the salt.

Thermodynamics of information processing based on enzyme kinetics: An exactly solvable model of an information pump

NASA Astrophysics Data System (ADS)

Cao, Yuansheng; Gong, Zongping; Quan, H. T.

2015-06-01

Motivated by the recent proposed models of the information engine [Proc. Natl. Acad. Sci. USA 109, 11641 (2012), 10.1073/pnas.1204263109] and the information refrigerator [Phys. Rev. Lett. 111, 030602 (2013), 10.1103/PhysRevLett.111.030602], we propose a minimal model of the information pump and the information eraser based on enzyme kinetics. This device can either pump molecules against the chemical potential gradient by consuming the information to be encoded in the bit stream or (partially) erase the information initially encoded in the bit stream by consuming the Gibbs free energy. The dynamics of this model is solved exactly, and the "phase diagram" of the operation regimes is determined. The efficiency and the power of the information machine is analyzed. The validity of the second law of thermodynamics within our model is clarified. Our model offers a simple paradigm for the investigating of the thermodynamics of information processing involving the chemical potential in small systems.

Two distinct DNA sequences recognized by transcription factors represent enthalpy and entropy optima

PubMed Central

Yin, Yimeng; Das, Pratyush K; Jolma, Arttu; Zhu, Fangjie; Popov, Alexander; Xu, You; Nilsson, Lennart

2018-01-01

Most transcription factors (TFs) can bind to a population of sequences closely related to a single optimal site. However, some TFs can bind to two distinct sequences that represent two local optima in the Gibbs free energy of binding (ΔG). To determine the molecular mechanism behind this effect, we solved the structures of human HOXB13 and CDX2 bound to their two optimal DNA sequences, CAATAAA and TCGTAAA. Thermodynamic analyses by isothermal titration calorimetry revealed that both sites were bound with similar ΔG. However, the interaction with the CAA sequence was driven by change in enthalpy (ΔH), whereas the TCG site was bound with similar affinity due to smaller loss of entropy (ΔS). This thermodynamic mechanism that leads to at least two local optima likely affects many macromolecular interactions, as ΔG depends on two partially independent variables ΔH and ΔS according to the central equation of thermodynamics, ΔG = ΔH - TΔS. PMID:29638214

Glass Formation, Phase Equilibria, and Thermodynamic Assessment of the Al-Ce-Co System Assisted by First-Principles Energy Calculations

NASA Astrophysics Data System (ADS)

Gao, Michael C.; Ünlü, Necip; Mihalkovic, Marek; Widom, Michael; Shiflet, G. J.

2007-10-01

This study investigates glass formation, phase equilibria, and thermodynamic descriptions of the Al-rich Al-Ce-Co ternary system using a novel approach that combines critical experiments, CALPHAD modeling, and first-principles (FP) calculations. The glass formation range (GFR) and a partial 500 °C isotherm are determined using a range of experimental techniques including melt spinning, transmission electron microscopy (TEM), electron probe microanalysis (EPMA), X-ray diffraction, and differential thermal analysis (DTA). Three stable ternary phases are confirmed, namely, Al8CeCo2, Al4CeCo, and AlCeCo, while a metastable phase, Al5CeCo2, was discovered. The equilibrium and metastable phases identified by the present and earlier reported experiments, together with many hypothetical ternary compounds, are further studied by FP calculations. Based on new experimental data and FP calculations, the thermodynamics of the Al-rich Al-Co-Ce system is optimized using the CALPHAD method. Application to glass formation is discussed in light of present studies.

Identification and Analysis of Partial Shading Breakdown Sites in CuIn xGa (1-x)Se 2 Modules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palmiotti, Elizabeth; Johnston, Steven; Gerber, Andreas

In this paper, CuIn xGa (1-x) (CIGS) mini-modules are stressed under reverse bias, resembling partial shading conditions, to predict and characterize where failures occur. Partial shading can cause permanent damage in the form of 'wormlike' defects on thin-film modules due to thermal runaway. This results in module-scale power losses. We have used dark lock-in thermography (DLIT) to spatially observe localized heating when reverse-bias breakdown occurs on various CIGS mini-modules. For better understanding of how and where these defects originated and propagated, we have developed techniques where the current is limited during reverse-bias stressing. This allows for DLIT-based detection and detailedmore » studying of the region where breakdown is initiated before thermal runaway leads to permanent damage. Statistics of breakdown sites using current-limited conditions has allowed for reasonable identification of the as-grown defects where permanent breakdown will likely originate. Scanning electron microscope results and wormlike defect analysis show that breakdown originates in defects such as small pits, craters, or cracks in the CIGS layer, and the wormlike defects propagate near the top CIGS interface.« less

Identification and Analysis of Partial Shading Breakdown Sites in CuIn xGa (1-x)Se 2 Modules

DOE PAGES

Palmiotti, Elizabeth; Johnston, Steven; Gerber, Andreas; ...

2017-12-20

In this paper, CuIn xGa (1-x) (CIGS) mini-modules are stressed under reverse bias, resembling partial shading conditions, to predict and characterize where failures occur. Partial shading can cause permanent damage in the form of 'wormlike' defects on thin-film modules due to thermal runaway. This results in module-scale power losses. We have used dark lock-in thermography (DLIT) to spatially observe localized heating when reverse-bias breakdown occurs on various CIGS mini-modules. For better understanding of how and where these defects originated and propagated, we have developed techniques where the current is limited during reverse-bias stressing. This allows for DLIT-based detection and detailedmore » studying of the region where breakdown is initiated before thermal runaway leads to permanent damage. Statistics of breakdown sites using current-limited conditions has allowed for reasonable identification of the as-grown defects where permanent breakdown will likely originate. Scanning electron microscope results and wormlike defect analysis show that breakdown originates in defects such as small pits, craters, or cracks in the CIGS layer, and the wormlike defects propagate near the top CIGS interface.« less

Long-term leaching of photovoltaic modules

NASA Astrophysics Data System (ADS)

Nover, Jessica; Zapf-Gottwick, Renate; Feifel, Carolin; Koch, Michael; Metzger, Jörg W.; Werner, Jürgen H.

2017-08-01

Some photovoltaic module technologies use toxic materials. We report long-term leaching on photovoltaic module pieces of 5 × 5 cm2 size. The pieces are cut out from modules of the four major commercial photovoltaic technologies: crystalline and amorphous silicon, cadmium telluride as well as from copper indium gallium diselenide. To simulate different environmental conditions, leaching occurs at room temperature in three different water-based solutions with pH 3, 7, and 11. No agitation is performed to simulate more representative field conditions. After 360 days, about 1.4% of lead from crystalline silicon module pieces and 62% of cadmium from cadmium telluride module pieces are leached out in acidic solutions. The leaching depends heavily on the pH and the redox potential of the aqueous solutions and it increases with time. The leaching behavior is predictable by thermodynamic stability considerations. These predictions are in good agreement with the experimental results.

Peptide self-assembly: thermodynamics and kinetics.

PubMed

Wang, Juan; Liu, Kai; Xing, Ruirui; Yan, Xuehai

2016-10-21

Self-assembling systems play a significant role in physiological functions and have therefore attracted tremendous attention due to their great potential for applications in energy, biomedicine and nanotechnology. Peptides, consisting of amino acids, are among the most popular building blocks and programmable molecular motifs. Nanostructures and materials assembled using peptides exhibit important potential for green-life new technology and biomedical applications mostly because of their bio-friendliness and reversibility. The formation of these ordered nanostructures pertains to the synergistic effect of various intermolecular non-covalent interactions, including hydrogen-bonding, π-π stacking, electrostatic, hydrophobic, and van der Waals interactions. Therefore, the self-assembly process is mainly driven by thermodynamics; however, kinetics is also a critical factor in structural modulation and function integration. In this review, we focus on the influence of thermodynamic and kinetic factors on structural assembly and regulation based on different types of peptide building blocks, including aromatic dipeptides, amphiphilic peptides, polypeptides, and amyloid-relevant peptides.

Competing Thermodynamic and Dynamic Factors Select Molecular Assemblies on a Gold Surface

NASA Astrophysics Data System (ADS)

Haxton, Thomas K.; Zhou, Hui; Tamblyn, Isaac; Eom, Daejin; Hu, Zonghai; Neaton, Jeffrey B.; Heinz, Tony F.; Whitelam, Stephen

2013-12-01

Controlling the self-assembly of surface-adsorbed molecules into nanostructures requires understanding physical mechanisms that act across multiple length and time scales. By combining scanning tunneling microscopy with hierarchical ab initio and statistical mechanical modeling of 1,4-substituted benzenediamine (BDA) molecules adsorbed on a gold (111) surface, we demonstrate that apparently simple nanostructures are selected by a subtle competition of thermodynamics and dynamics. Of the collection of possible BDA nanostructures mechanically stabilized by hydrogen bonding, the interplay of intermolecular forces, surface modulation, and assembly dynamics select at low temperature a particular subset: low free energy oriented linear chains of monomers and high free energy branched chains.

Experimental and Thermodynamic Constraints on Serpentinization: Implications for Fluid Chemistry, Abiotic Synthesis of Hydrocarbons, and Subsurface Microbial Processes

NASA Astrophysics Data System (ADS)

McCollom, T. M.

2005-12-01

Serpentinized rocks have received a great deal of attention in recent years, primarily because they are believed to play significant roles in supporting autotrophic, hydrogen-based microbial communities and in the abiotic synthesis of methane and other organic compounds. Both of these processes are a consequence of the high H2 concentrations generated by reaction of water with ultramafic rocks during serpentinization. The amount of H2 produced during serpentinization is dependent on both thermodynamic and kinetic constraints, which can be evaluated through numerical thermodynamic models and laboratory experiments. Because olivine is thermodynamically stable at temperatures above ~375°C, alteration of ultramafic rocks at higher temperatures generates only minor amounts of H2. Even at lower temperatures olivine may equilibrate with the fluid after only partial reaction, so that olivine may persist stably in partially serpentinized rocks. Olivine only becomes completely unstable at ~315°C, so that the maximum potential for H2 production only occurs at or below this temperature. At high temperatures, serpentinization proceeds rapidly, so that thermodynamic constraints provide the primary control on H2 production. However, the rate of serpentinization becomes sufficiently slow below ~150°C that the residence of time of fluids may prevent high concentrations of H2 from accumulating. Since H2 generation during serpentinization is primarily attributable to conversion of ferrous Fe in olivine to ferric Fe in magnetite, another factor that may limit H2 production is the sequestration of ferrous Fe in brucite or serpentine. Some serpentines and brucites are reported to contain significant amounts of Fe, but these data are somewhat uncertain because the analyses may include microcrystalline magnetite. Although the thermodynamic properties of solid solutions of these minerals are highly uncertain, the available data suggest that the Fe content of serpentines and brucite may increase with decreasing temperature. Together, these factors indicate that maximum H2 production may occur during serpentinization at temperatures around 300°C. Production of H2 in many cases may exceed its solubility in water, leading to the exsolution of H2-rich vapor, which may promote abiotic organic synthesis if the reactions are more favorable in a vapor phase. Each kg of ultramafic rock undergoing serpentinization can supply as much as 90 kJ of energy to H2-oxidizing microbes, which is sufficient to produce about 3 grams of biomass.

Impact of heavy soiling on the power output of PV modules

NASA Astrophysics Data System (ADS)

Schill, Christian; Brachmann, Stefan; Heck, Markus; Weiss, Karl-Anders; Koehl, Michael

2011-09-01

Fraunhofer ISE is running a PV-module outdoor testing set-up on the Gran Canaria island, one of the Canary Island located west of Morroco in the Atlantic Ocean. The performance of the modules is assessed by IV-curve monitoring every 10 minutes. The electronic set-up of the monitoring system - consisting of individual electronic loads for each module which go into an MPP-tracking mode between the IV-measurements - will be described in detail. Soiling of the exposed modules happened because of building constructions nearby. We decided not to clean the modules, but the radiation sensors and recorded the decrease of the power output and the efficiency over time. The efficiency dropped to 20 % within 5 months before a heavy rain and subsequently the service personnel on site cleaned the modules. A smaller rain-fall in between washed the dust partly away and accumulated it at the lower part of the module, what could be concluded from the shape of the IV-curves, which were similar to partial shading by hot-spot-tests and by partial snow cover.

Water anomalous thermodynamics, attraction, repulsion, and hydrophobic hydration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cerdeiriña, Claudio A., E-mail: calvarez@uvigo.es; Debenedetti, Pablo G., E-mail: pdebene@princeton.edu

A model composed of van der Waals-like and hydrogen bonding contributions that simulates the low-temperature anomalous thermodynamics of pure water while exhibiting a second, liquid-liquid critical point [P. H. Poole et al., Phys. Rev. Lett. 73, 1632 (1994)] is extended to dilute solutions of nonionic species. Critical lines emanating from such second critical point are calculated. While one infers that the smallness of the water molecule may be a relevant factor for those critical lines to move towards experimentally accessible regions, attention is mainly focused on the picture our model draws for the hydration thermodynamics of purely hydrophobic and amphiphilicmore » non-electrolyte solutes. We first focus on differentiating solvation at constant volume from the corresponding isobaric process. Both processes provide the same viewpoint for the low solubility of hydrophobic solutes: it originates from the combination of weak solute-solvent attractive interactions and the specific excluded-volume effects associated with the small molecular size of water. However, a sharp distinction is found when exploring the temperature dependence of hydration phenomena since, in contrast to the situation for the constant-V process, the properties of pure water play a crucial role at isobaric conditions. Specifically, the solubility minimum as well as enthalpy and entropy convergence phenomena, exclusively ascribed to isobaric solvation, are closely related to water’s density maximum. Furthermore, the behavior of the partial molecular volume and the partial molecular isobaric heat capacity highlights the interplay between water anomalies, attraction, and repulsion. The overall picture presented here is supported by experimental observations, simulations, and previous theoretical results.« less

Thermodynamic properties of uranium in liquid gallium, indium and their alloys

NASA Astrophysics Data System (ADS)

Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Osipenko, A. G.

2015-09-01

Activity, activity coefficients and solubility of uranium was determined in gallium, indium and gallium-indium alloys containing 21.8 (eutectic), 40 and 70 wt.% In. Activity was measured at 573-1073 K employing the electromotive force method, and solubility between room temperature (or the alloy melting point) and 1073 K employing direct physical measurements. Activity coefficients were obtained from the difference of experimentally determined temperature dependencies of uranium activity and solubility. Intermetallic compounds formed in the respective alloys were characterized using X-ray diffraction. Partial and excess thermodynamic functions of uranium in the studied alloys were calculated. Liquidus lines in U-Ga and U-In phase diagrams from the side rich in gallium or indium are proposed.

Sharpening the second law of thermodynamics with the quantum Bayes theorem.

PubMed

Gharibyan, Hrant; Tegmark, Max

2014-09-01

We prove a generalization of the classic Groenewold-Lindblad entropy inequality, combining decoherence and the quantum Bayes theorem into a simple unified picture where decoherence increases entropy while observation decreases it. This provides a rigorous quantum-mechanical version of the second law of thermodynamics, governing how the entropy of a system (the entropy of its density matrix, partial-traced over the environment and conditioned on what is known) evolves under general decoherence and observation. The powerful tool of spectral majorization enables both simple alternative proofs of the classic Lindblad and Holevo inequalities without using strong subadditivity, and also novel inequalities for decoherence and observation that hold not only for von Neumann entropy, but also for arbitrary concave entropies.

TOUGH2: A general-purpose numerical simulator for multiphase nonisothermal flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pruess, K.

1991-06-01

Numerical simulators for multiphase fluid and heat flows in permeable media have been under development at Lawrence Berkeley Laboratory for more than 10 yr. Real geofluids contain noncondensible gases and dissolved solids in addition to water, and the desire to model such `compositional` systems led to the development of a flexible multicomponent, multiphase simulation architecture known as MULKOM. The design of MULKOM was based on the recognition that the mass-and energy-balance equations for multiphase fluid and heat flows in multicomponent systems have the same mathematical form, regardless of the number and nature of fluid components and phases present. Application ofmore » MULKOM to different fluid mixtures, such as water and air, or water, oil, and gas, is possible by means of appropriate `equation-of-state` (EOS) modules, which provide all thermophysical and transport parameters of the fluid mixture and the permeable medium as a function of a suitable set of primary thermodynamic variables. Investigations of thermal and hydrologic effects from emplacement of heat-generating nuclear wastes into partially water-saturated formations prompted the development and release of a specialized version of MULKOM for nonisothermal flow of water and air, named TOUGH. TOUGH is an acronym for `transport of unsaturated groundwater and heat` and is also an allusion to the tuff formations at Yucca Mountain, Nevada. The TOUGH2 code is intended to supersede TOUGH. It offers all the capabilities of TOUGH and includes a considerably more general subset of MULKOM modules with added capabilities. The paper briefly describes the simulation methodology and user features.« less

Simulation-Based e-Learning Tools for Science,Engineering, and Technology Education(SimBeLT)

NASA Astrophysics Data System (ADS)

Davis, Doyle V.; Cherner, Y.

2006-12-01

The focus of Project SimBeLT is the research, development, testing, and dissemination of a new type of simulation-based integrated e-learning set of modules for two-year college technical and engineering curricula in the areas of thermodynamics, fluid physics, and fiber optics that can also be used in secondary schools and four-year colleges. A collection of sophisticated virtual labs is the core component of the SimBeLT modules. These labs will be designed to enhance the understanding of technical concepts and underlying fundamental principles of these topics, as well as to master certain performance based skills online. SimBeLT software will help educators to meet the National Science Education Standard that "learning science and technology is something that students do, not something that is done to them". A major component of Project SimBeLT is the development of multi-layered technology-oriented virtual labs that realistically mimic workplace-like environments. Dynamic data exchange between simulations will be implemented and links with instant instructional messages and data handling tools will be realized. A second important goal of Project SimBeLT labs is to bridge technical skills and scientific knowledge by enhancing the teaching and learning of specific scientific or engineering subjects. SimBeLT builds upon research and outcomes of interactive teaching strategies and tools developed through prior NSF funding (http://webphysics.nhctc.edu/compact/index.html) (Project SimBeLT is partially supported by a grant from the National Science Foundation DUE-0603277)

A project based on multi-configuration Dirac-Fock calculations for plasma spectroscopy

NASA Astrophysics Data System (ADS)

Comet, M.; Pain, J.-C.; Gilleron, F.; Piron, R.

2017-09-01

We present a project dedicated to hot plasma spectroscopy based on a Multi-Configuration Dirac-Fock (MCDF) code, initially developed by J. Bruneau. The code is briefly described and the use of the transition state method for plasma spectroscopy is detailed. Then an opacity code for local-thermodynamic-equilibrium plasmas using MCDF data, named OPAMCDF, is presented. Transition arrays for which the number of lines is too large to be handled in a Detailed Line Accounting (DLA) calculation can be modeled within the Partially Resolved Transition Array method or using the Unresolved Transition Arrays formalism in jj-coupling. An improvement of the original Partially Resolved Transition Array method is presented which gives a better agreement with DLA computations. Comparisons with some absorption and emission experimental spectra are shown. Finally, the capability of the MCDF code to compute atomic data required for collisional-radiative modeling of plasma at non local thermodynamic equilibrium is illustrated. In addition to photoexcitation, this code can be used to calculate photoionization, electron impact excitation and ionization cross-sections as well as autoionization rates in the Distorted-Wave or Close Coupling approximations. Comparisons with cross-sections and rates available in the literature are discussed.

Note: Nonpolar solute partial molar volume response to attractive interactions with water.

PubMed

Williams, Steven M; Ashbaugh, Henry S

2014-01-07

The impact of attractive interactions on the partial molar volumes of methane-like solutes in water is characterized using molecular simulations. Attractions account for a significant 20% volume drop between a repulsive Weeks-Chandler-Andersen and full Lennard-Jones description of methane interactions. The response of the volume to interaction perturbations is characterized by linear fits to our simulations and a rigorous statistical thermodynamic expression for the derivative of the volume to increasing attractions. While a weak non-linear response is observed, an average effective slope accurately captures the volume decrease. This response, however, is anticipated to become more non-linear with increasing solute size.

Note: Nonpolar solute partial molar volume response to attractive interactions with water

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, Steven M.; Ashbaugh, Henry S., E-mail: hanka@tulane.edu

2014-01-07

The impact of attractive interactions on the partial molar volumes of methane-like solutes in water is characterized using molecular simulations. Attractions account for a significant 20% volume drop between a repulsive Weeks-Chandler-Andersen and full Lennard-Jones description of methane interactions. The response of the volume to interaction perturbations is characterized by linear fits to our simulations and a rigorous statistical thermodynamic expression for the derivative of the volume to increasing attractions. While a weak non-linear response is observed, an average effective slope accurately captures the volume decrease. This response, however, is anticipated to become more non-linear with increasing solute size.

Experts' understanding of partial derivatives using the partial derivative machine

NASA Astrophysics Data System (ADS)

Roundy, David; Weber, Eric; Dray, Tevian; Bajracharya, Rabindra R.; Dorko, Allison; Smith, Emily M.; Manogue, Corinne A.

2015-12-01

[This paper is part of the Focused Collection on Upper Division Physics Courses.] Partial derivatives are used in a variety of different ways within physics. Thermodynamics, in particular, uses partial derivatives in ways that students often find especially confusing. We are at the beginning of a study of the teaching of partial derivatives, with a goal of better aligning the teaching of multivariable calculus with the needs of students in STEM disciplines. In this paper, we report on an initial study of expert understanding of partial derivatives across three disciplines: physics, engineering, and mathematics. We report on the central research question of how disciplinary experts understand partial derivatives, and how their concept images of partial derivatives differ, with a focus on experimentally measured quantities. Using the partial derivative machine (PDM), we probed expert understanding of partial derivatives in an experimental context without a known functional form. In particular, we investigated which representations were cued by the experts' interactions with the PDM. Whereas the physicists and engineers were quick to use measurements to find a numeric approximation for a derivative, the mathematicians repeatedly returned to speculation as to the functional form; although they were comfortable drawing qualitative conclusions about the system from measurements, they were reluctant to approximate the derivative through measurement. On a theoretical front, we found ways in which existing frameworks for the concept of derivative could be expanded to include numerical approximation.

Algebraic and geometric structures of analytic partial differential equations

NASA Astrophysics Data System (ADS)

Kaptsov, O. V.

2016-11-01

We study the problem of the compatibility of nonlinear partial differential equations. We introduce the algebra of convergent power series, the module of derivations of this algebra, and the module of Pfaffian forms. Systems of differential equations are given by power series in the space of infinite jets. We develop a technique for studying the compatibility of differential systems analogous to the Gröbner bases. Using certain assumptions, we prove that compatible systems generate infinite manifolds.

Coherent detection of frequency-hopped quadrature modulations in the presence of jamming. II - QPR Class I modulation. [Quadrature Partial Response

NASA Technical Reports Server (NTRS)

Simon, M. K.

1981-01-01

This paper considers the performance of quadrature partial response (QPR) in the presence of jamming. Although a QPR system employs a single sample detector in its receiver, while quadrature amplitude shift keying (or quadrature phase shift keying) requires a matched-filter type of receiver, it is shown that the coherent detection performances of the two in the presence of the intentional jammer have definite similarities.

Thermodynamic Parameterization of Subduction-Zone Devolatilization and Application to Quantify Carbon Fluxes from Slab

NASA Astrophysics Data System (ADS)

Tian, M.; Katz, R. F.; Rees Jones, D. W.; May, D.

2017-12-01

Compared with other plate-tectonic boundaries, subduction zones (SZ) host the most drastic mechanical, thermal, and chemical changes. The transport of carbon through this complex environment is crucial to mantle carbon budget but remains the subject of active debate. Synthesis of field studies suggests that carbon subducted with the incoming slab is almost completely returned to the surface environment [Kelemen and Manning, 2015], whereas thermodynamic modelling indicates that a significant portion of carbon is retained in the slab and descends into the deep mantle [Gorman et al., 2006]. To address this controversy and quantify the carbon fluxes within SZs, it is necessary to treat the chemistry of fluid/volatile-rock interaction and the mechanics of porous fluid/volatile migration in a consistent modelling framework. This requirement is met by coupling a thermodynamic parameterization of de/re-volatilization with a two-phase flow model of subduction zones. The two-phase system is assumed to comprise three chemical components: rock containing only non-volatile oxides, H2O and CO2; the fluid phase includes only the latter two. Perple_X is used to map out the binary subsystems rock+H2O and rock+CO2; the results are parameterised in terms of volatile partition coefficients as a function of pressure and temperature. In synthesising the binary subsystems to describe phase equilibria that incorporate all three components, a Margules coefficient is introduced to account for non-ideal mixing of CO2/H2O in the fluid, such that the partition coefficients depend further on bulk composition. This procedure is applied to representative compositions of sediment, MORB, and gabbro for the slab, and peridotite for the mantle. The derived parameterization of each rock type serves as a lightweight thermodynamic module interfaceable with two-phase flow models of SZs. We demonstrate the application of this thermodynamic module through a simple model of carbon flux with a prescribed flow direction through (and out of) the slab. This model allows us to evaluate the effects of flow path and lithology on carbon storage within the slab.

Thermodynamic modeling of the solar wind plasma in the presence of envelope-modulated low-frequency Alfvén waves

NASA Astrophysics Data System (ADS)

Nariyuki, Y.

2018-06-01

Alfvénic fluctuation is a typical state of the solar wind turbulence. Due to its finite amplitude and envelope modulation, the Alfvénic fluctuation becomes compressible. In the present study, an analytical model of the specific heat ratio in the presence of envelope-modulated Alfvén waves is derived. Ion kinetic effects are modeled by using a semi-ideal (perfect) gas model, in which the specific heat ratio depends on temperature. It is shown that the fourth order polynomial approximation is in good agreement with the kinetic theory. The resultant model is also applied to the fast solar wind plasma.

Development of high temperature liquid metal test facilities for qualification of materials and investigations of thermoelectrical modules

NASA Astrophysics Data System (ADS)

Onea, A.; Hering, W.; Reiser, J.; Weisenburger, A.; Diez de los Rios Ramos, N.; Lux, M.; Ziegler, R.; Baumgärtner, S.; Stieglitz, R.

2017-07-01

Three classes of experimental liquid metal facilities have been completed during the LIMTECH project aiming the qualification of materials, investigation of thermoelectrical modules, investigation of sodium transitional regimes and fundamental thermo-dynamical flows in concentrating solar power (CSP) relevant geometries. ATEFA facility is dedicated to basic science investigation focussed on the alkali metal thermal-to-electric converter (AMTEC) technology. Three SOLTEC facilities are aimed to be used in different laboratories for long term material investigation sodium environment up to a 1000 K temperature and for long term tests of AMTEC modules. The medium scale integral facility KASOLA is planned as the backbone for CSP development and demonstration.

Effect of chemotherapy counseling by pharmacists on quality of life and psychological outcomes of oncology patients in Malaysia: a randomized control trial.

PubMed

Periasamy, Ummavathy; Mohd Sidik, Sherina; Rampal, Lekhraj; Fadhilah, Siti Irma; Akhtari-Zavare, Mehrnoosh; Mahmud, Rozi

2017-05-15

Cancer is now becoming a leading cause of death. Chemotherapy is an important treatment for cancer patients. These patients also need consultation during their treatment to improve quality of life and decrease psychological disorders. The objectives of the study were to develop, implement and evaluate the effectiveness of a chemotherapy counseling module by pharmacists among oncology patients on their quality of life and psychological outcomes in Malaysia. A single-blind randomized controlled trial was carried out among 162 oncology patients undergoing chemotherapy from July 2013 to February 2014 in a government hospital with oncology facilities in Malaysia. Participants were randomized to either the intervention group or the control group. Chemotherapy counseling using the module on 'Managing Patients on Chemotherapy' by Pharmacists was delivered to the intervention group. The outcome measures were assessed at baseline, first follow-up and second follow-up and third follow-up post-intervention. Chi-square, independent samples t-test and two-way repeated measures ANOVA were conducted in the course of the data analyses. In assessing the impact of the chemotherapy counseling module, the study revealed that the module along with repetitive counseling showed significant improvement of quality of life in the intervention group as compared to the control group with a large effect size in physical health (p = 0.001, partial Ƞ 2  = 0.66), psychological (p = 0.001, partial Ƞ 2  = 0.65), social relationships (p = 0.001, partial Ƞ 2  = 0.30), and environment (p = 0.001, partial Ƞ 2  = 0.67) and decrease in the anxiety (p = 0.000; partial Ƞ 2  = 0.23), depression (p = 0.000; partial Ƞ 2  = 0.40). The module on 'Managing Patients on Chemotherapy' along with repetitive counseling by pharmacists has been shown to be effective in improving quality of life and decreasing anxiety and depression among oncology patients undergoing chemotherapy. National Medical Research Register (NMRR) of Malaysia and given a registration number NMRR-12-1057-12,363 on 21 December 2012.

Partial knowledge, entropy, and estimation

PubMed Central

MacQueen, James; Marschak, Jacob

1975-01-01

In a growing body of literature, available partial knowledge is used to estimate the prior probability distribution p≡(p1,...,pn) by maximizing entropy H(p)≡-Σpi log pi, subject to constraints on p which express that partial knowledge. The method has been applied to distributions of income, of traffic, of stock-price changes, and of types of brand-article purchases. We shall respond to two justifications given for the method: (α) It is “conservative,” and therefore good, to maximize “uncertainty,” as (uniquely) represented by the entropy parameter. (β) One should apply the mathematics of statistical thermodynamics, which implies that the most probable distribution has highest entropy. Reason (α) is rejected. Reason (β) is valid when “complete ignorance” is defined in a particular way and both the constraint and the estimator's loss function are of certain kinds. PMID:16578733

A masking level difference due to harmonicity.

PubMed

Treurniet, W C; Boucher, D R

2001-01-01

The role of harmonicity in masking was studied by comparing the effect of harmonic and inharmonic maskers on the masked thresholds of noise probes using a three-alternative, forced-choice method. Harmonic maskers were created by selecting sets of partials from a harmonic series with an 88-Hz fundamental and 45 consecutive partials. Inharmonic maskers differed in that the partial frequencies were perturbed to nearby values that were not integer multiples of the fundamental frequency. Average simultaneous-masked thresholds were as much as 10 dB lower with the harmonic masker than with the inharmonic masker, and this difference was unaffected by masker level. It was reduced or eliminated when the harmonic partials were separated by more than 176 Hz, suggesting that the effect is related to the extent to which the harmonics are resolved by auditory filters. The threshold difference was not observed in a forward-masking experiment. Finally, an across-channel mechanism was implicated when the threshold difference was found between a harmonic masker flanked by harmonic bands and a harmonic masker flanked by inharmonic bands. A model developed to explain the observed difference recognizes that an auditory filter output envelope is modulated when the filter passes two or more sinusoids, and that the modulation rate depends on the differences among the input frequencies. For a harmonic masker, the frequency differences of adjacent partials are identical, and all auditory filters have the same dominant modulation rate. For an inharmonic masker, however, the frequency differences are not constant and the envelope modulation rate varies across filters. The model proposes that a lower variability facilitates detection of a probe-induced change in the variability, thus accounting for the masked threshold difference. The model was supported by significantly improved predictions of observed thresholds when the predictor variables included envelope modulation rate variance measured using simulated auditory filters.

Using Peltier Cells to Study Solid-Liquid-Vapour Transitions and Supercooling

ERIC Educational Resources Information Center

Torzo, Giacomo; Soletta, Isabella; Branca, Mario

2007-01-01

We propose an apparatus for teaching experimental thermodynamics in undergraduate introductory courses, using thermoelectric modules and a real-time data acquisition system. The device may be made at low cost, still providing an easy approach to the investigation of liquid-solid and liquid-vapour phase transitions and of metastable states…

Partial polarizer filter

NASA Technical Reports Server (NTRS)

Title, A. M. (Inventor)

1978-01-01

A birefringent filter module comprises, in seriatum. (1) an entrance polarizer, (2) a first birefringent crystal responsive to optical energy exiting the entrance polarizer, (3) a partial polarizer responsive to optical energy exiting the first polarizer, (4) a second birefringent crystal responsive to optical energy exiting the partial polarizer, and (5) an exit polarizer. The first and second birefringent crystals have fast axes disposed + or -45 deg from the high transmitivity direction of the partial polarizer. Preferably, the second crystal has a length 1/2 that of the first crystal and the high transmitivity direction of the partial polarizer is nine times as great as the low transmitivity direction. To provide tuning, the polarizations of the energy entering the first crystal and leaving the second crystal are varied by either rotating the entrance and exit polarizers, or by sandwiching the entrance and exit polarizers between pairs of half wave plates that are rotated relative to the polarizers. A plurality of the filter modules may be cascaded.

The importance of ion fluxes for cancer proliferation and metastasis: A thermodynamic analysis.

PubMed

Lucia, Umberto; Deisboeck, Thomas S

2018-05-14

Following a thermodynamic approach, we develop a new theoretical analysis of ion transfer across cell membranes. Supported also by experimental data from the literature, we highlight that ion channels determine the typical features of cancer cells, i.e. independence from growth-regulatory signals, avoidance of apoptosis, indefinite proliferative potential, and the capability of inducing angiogenesis. Specifically, we analyse how ion transport, with particular regards to Ca 2+ fluxes, modulates cancer cell proliferation, and regulates cell cycle checkpoints. Finally, our analysis also suggests that in malignant tumours aerobic glycolysis is the more efficient metabolic process when taking the required solvent capacity into account. Copyright © 2018 Elsevier Ltd. All rights reserved.

The HumanIndexMod and New Calculations Demonstrating Heat Stress Effects All Aspects of Human Life Through Industry, Agriculture, and Daily Life.

NASA Astrophysics Data System (ADS)

Buzan, J. R.; Huber, M.

2014-12-01

We show the new climatic tool, HumanIndexMod (HIM), for quantitatively assessing key climatic variables that are critical for decision making. The HIM calculates 9 different heat stress and 4 moist thermodynamic quantities using meteorological inputs of T, P, and Q. These heat stress metrics are commonly used throughout the world. We show new methods for integrating and standardizing practices for applying these metrics with the latest Earth system models. We implemented the HIM into CLM4.5, a component of CESM, maintained by NCAR. These heat stress metrics cover philosophical approaches of comfort, physiology, and empirically based algorithms. The metrics are directly connected to the Urban, Canopy, Bare Ground, and Lake modules, to differentiate distinct regimes within each grid cell. The module calculates the instantaneous moisture-temperature covariance at every model time step and in every land surface type, capturing all aspects of non-linearity. The HIM uses the most accurate and computationally efficient moist thermodynamic algorithms available. Additionally, we show ways that the HIM may be effectively integrated into climate modeling and observations. The module is flexible. The user may decide which metrics to call, and there is an offline version of the HIM that is available to be used with weather and climate datasets. Examples include using high temporal resolution CMIP5 archive data, local weather station data, and weather and forecasting models. To provide comprehensive standards for applying the HIM to climate data, we executed a CLM4.5 simulation using the RCP8.5 boundary conditions. Preliminary results show moist thermodynamic and heat stress quantities have smaller variability in the extremes as compared to extremes in T (both at the 95th percentile). Additionally, the magnitude of the moist thermodynamic changes over land is similar to sea surface temperature changes. The metric changes from the early part of the 21st century as compared to the end of the 21st century show that many portions of the world switch from moderate levels of heat stress for the top 2 weeks of a year to severe heat stress for the top 2 weeks of a year. These changes are reflected in livestock (THI); evaporative cooling (SWMP80) and air-conditioning; and industrial, military, and athletic heat stress (sWBGT, DI, HI, etc.).

Deformation of interface in a partially miscible system during favorable displacement

NASA Astrophysics Data System (ADS)

Suzuki, Ryuta; Nagatsu, Yuichiro; Mishra, Manoranjan; Ban, Takahiko

2017-11-01

The Saffman-Taylor instability triggers a well-known viscous fingering (VF, called unfavorable displacement), occurring when a less viscous fluid displaces a more viscous one in porous media or in a Hele-Shaw cell because the boundary of the two fluids becomes hydrodynamically unstable. In the reverse situation (called favorable displacement) in which a more viscous fluid displaces a less viscous one, no instabilities occur due to hydrodynamically stable system. It has been reported that the favorable displacements become unstable by several physicochemical effects. So far, studies of both displacements have focused on fluids that are either fully miscible or immiscible. However, little attention has been paid to displacements in partially miscible system. Here, we have discovered that a partial miscibility triggers fingering instability in a favorable displacement without any chemical reactions. The occurrence of this new instability is induced by not hydrodynamic effects but a thermodynamic effect that is so-called Korteweg effect in which convection is induced during phase separation process in a partially miscible system.

Density contrast sedimentation velocity for the determination of protein partial-specific volumes.

PubMed

Brown, Patrick H; Balbo, Andrea; Zhao, Huaying; Ebel, Christine; Schuck, Peter

2011-01-01

The partial-specific volume of proteins is an important thermodynamic parameter required for the interpretation of data in several biophysical disciplines. Building on recent advances in the use of density variation sedimentation velocity analytical ultracentrifugation for the determination of macromolecular partial-specific volumes, we have explored a direct global modeling approach describing the sedimentation boundaries in different solvents with a joint differential sedimentation coefficient distribution. This takes full advantage of the influence of different macromolecular buoyancy on both the spread and the velocity of the sedimentation boundary. It should lend itself well to the study of interacting macromolecules and/or heterogeneous samples in microgram quantities. Model applications to three protein samples studied in either H(2)O, or isotopically enriched H(2) (18)O mixtures, indicate that partial-specific volumes can be determined with a statistical precision of better than 0.5%, provided signal/noise ratios of 50-100 can be achieved in the measurement of the macromolecular sedimentation velocity profiles. The approach is implemented in the global modeling software SEDPHAT.

Critical Evaluations and Thermodynamic Optimizations of the MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 Systems

NASA Astrophysics Data System (ADS)

Kang, Youn-Bae; Jung, In-Ho

2017-06-01

A critical evaluation and thermodynamic modeling for thermodynamic properties of all oxide phases and phase diagrams in the Fe-Mn-Si-O system (MnO-Mn2O3-SiO2 and FeO-Fe2O3-MnO-Mn2O3-SiO2 systems) are presented. Optimized Gibbs energy parameters for the thermodynamic models of the oxide phases were obtained which reproduce all available and reliable experimental data within error limits from 298 K (25°C) to above the liquidus temperatures at all compositions covering from known oxide phases, and oxygen partial pressure from metal saturation to 0.21 bar. The optimized thermodynamic properties and phase diagrams are believed to be the best estimates presently available. Slag (molten oxide) was modeled using the modified quasichemical model in the pair approximation. Olivine (Fe2SiO4-Mn2SiO4) was modeled using two-sublattice model in the framework of the compound energy formalism (CEF), while rhodonite (MnSiO3-FeSiO3) and braunite (Mn7SiO_{12} with excess Mn2O3) were modeled as simple Henrian solutions. It is shown that the already developed models and databases of two spinel phases (cubic- and tetragonal-(Fe, Mn)3O4) using CEF [Kang and Jung, J. Phys. Chem. Solids (2016), vol. 98, pp. 237-246] can successfully be integrated into a larger thermodynamic database to be used in practically important higher order system such as silicate. The database of the model parameters can be used along with a software for Gibbs energy minimization in order to calculate any type of phase diagram section and thermodynamic properties.

Metal-organic complexes in geochemical processes: temperature dependence of the standard thermodynamic properties of aqueous complexes between metal cations and dicarboxylate ligands

NASA Astrophysics Data System (ADS)

Prapaipong, Panjai; Shock, Everett L.; Koretsky, Carla M.

1999-10-01

By combining results from regression and correlation methods, standard state thermodynamic properties for aqueous complexes between metal cations and divalent organic acid ligands (oxalate, malonate, succinate, glutarate, and adipate) are evaluated and applied to geochemical processes. Regression of experimental standard-state equilibrium constants with the revised Helgeson-Kirkham-Flowers (HKF) equation of state yields standard partial molal entropies (S¯°) of aqueous metal-organic complexes, which allow determination of thermodynamic properties of the complexes at elevated temperatures. In cases where S¯° is not available from either regression or calorimetric measurement, the values of S¯° can be estimated from a linear correlation between standard partial molal entropies of association (ΔS¯°r) and standard partial molal entropies of aqueous cations (S¯°M). The correlation is independent of cation charge, which makes it possible to predict S¯° for complexes between divalent organic acids and numerous metal cations. Similarly, correlations between standard Gibbs free energies of association of metal-organic complexes (ΔḠ°r) and Gibbs free energies of formation (ΔḠ°f) for divalent metal cations allow estimates of standard-state equilibrium constants where experimental data are not available. These correlations are found to be a function of ligand structure and cation charge. Predicted equilibrium constants for dicarboxylate complexes of numerous cations were included with those for inorganic and other organic complexes to study the effects of dicarboxylate complexes on the speciation of metals and organic acids in oil-field brines. Relatively low concentrations of oxalic and malonic acids affect the speciation of cations more than similar concentrations of succinic, glutaric, and adipic acids. However, the extent to which metal-dicarboxylate complexes contribute to the speciation of dissolved metals depends on the type of dicarboxylic acid ligand; relative concentration of inorganic, mono-, and dicarboxylate ligands; and the type of metal cation. As an example, in the same solution, dicarboxylic acids have a greater influence on the speciation of Fe+2 and Mg+2 than on the speciation of Zn+2 and Mn+2.

Nitrogen expander cycles for large capacity liquefaction of natural gas

NASA Astrophysics Data System (ADS)

Chang, Ho-Myung; Park, Jae Hoon; Gwak, Kyung Hyun; Choe, Kun Hyung

2014-01-01

Thermodynamic study is performed on nitrogen expander cycles for large capacity liquefaction of natural gas. In order to substantially increase the capacity, a Brayton refrigeration cycle with nitrogen expander was recently added to the cold end of the reputable propane pre-cooled mixed-refrigerant (C3-MR) process. Similar modifications with a nitrogen expander cycle are extensively investigated on a variety of cycle configurations. The existing and modified cycles are simulated with commercial process software (Aspen HYSYS) based on selected specifications. The results are compared in terms of thermodynamic efficiency, liquefaction capacity, and estimated size of heat exchangers. The combination of C3-MR with partial regeneration and pre-cooling of nitrogen expander cycle is recommended to have a great potential for high efficiency and large capacity.

Continuum mechanics and thermodynamics in the Hamilton and the Godunov-type formulations

NASA Astrophysics Data System (ADS)

Peshkov, Ilya; Pavelka, Michal; Romenski, Evgeniy; Grmela, Miroslav

2018-01-01

Continuum mechanics with dislocations, with the Cattaneo-type heat conduction, with mass transfer, and with electromagnetic fields is put into the Hamiltonian form and into the form of the Godunov-type system of the first-order, symmetric hyperbolic partial differential equations (SHTC equations). The compatibility with thermodynamics of the time reversible part of the governing equations is mathematically expressed in the former formulation as degeneracy of the Hamiltonian structure and in the latter formulation as the existence of a companion conservation law. In both formulations the time irreversible part represents gradient dynamics. The Godunov-type formulation brings the mathematical rigor (the local well posedness of the Cauchy initial value problem) and the possibility to discretize while keeping the physical content of the governing equations (the Godunov finite volume discretization).

Determination of Gibbs energies of formation in aqueous solution using chemical engineering tools.

PubMed

Toure, Oumar; Dussap, Claude-Gilles

2016-08-01

Standard Gibbs energies of formation are of primary importance in the field of biothermodynamics. In the absence of any directly measured values, thermodynamic calculations are required to determine the missing data. For several biochemical species, this study shows that the knowledge of the standard Gibbs energy of formation of the pure compounds (in the gaseous, solid or liquid states) enables to determine the corresponding standard Gibbs energies of formation in aqueous solutions. To do so, using chemical engineering tools (thermodynamic tables and a model enabling to predict activity coefficients, solvation Gibbs energies and pKa data), it becomes possible to determine the partial chemical potential of neutral and charged components in real metabolic conditions, even in concentrated mixtures. Copyright © 2016 Elsevier Ltd. All rights reserved.

Enhanced densification under shock compression in porous silicon

NASA Astrophysics Data System (ADS)

Lane, J. Matthew D.; Thompson, Aidan P.; Vogler, Tracy J.

2014-10-01

Under shock compression, most porous materials exhibit lower densities for a given pressure than that of a full-dense sample of the same material. However, some porous materials exhibit an anomalous, or enhanced, densification under shock compression. We demonstrate a molecular mechanism that drives this behavior. We also present evidence from atomistic simulation that silicon belongs to this anomalous class of materials. Atomistic simulations indicate that local shear strain in the neighborhood of collapsing pores nucleates a local solid-solid phase transformation even when bulk pressures are below the thermodynamic phase transformation pressure. This metastable, local, and partial, solid-solid phase transformation, which accounts for the enhanced densification in silicon, is driven by the local stress state near the void, not equilibrium thermodynamics. This mechanism may also explain the phenomenon in other covalently bonded materials.

Thermochemistry of Rare Earth Silicates for Environmental Barrier Coatings

NASA Technical Reports Server (NTRS)

Costa, Gustavo; Jacobson, Nathan

2015-01-01

Rare earth silicates are promising candidates as environmental protective coatings (EBCs) for silica-forming ceramics and composites in combustion environments since they are predicted to have lower reactivity with the water vapor combustion products. The reactivity of rare earth silicates is assessed by the thermodynamic activity of the silica component which is best measured by Knudsen effusion mass spectrometry (KEMS). Here, we discuss a novel method based on a reducing agent to increase the partial pressure of SiO(g) which is then used to calculate thermodynamic activity of silica in Y2O3-SiO2 and Yb2O3-SiO2 systems. After the KEMS measurements, samples were probed by X-ray diffraction and their phase content was calculated from Rietveld refinement.

On the Experimental and Theoretical Investigations of Lean Partially Premixed Combustion, Burning Speed, Flame Instability and Plasma Formation of Alternative Fuels at High Temperatures and Pressures

NASA Astrophysics Data System (ADS)

Askari, Omid

This dissertation investigates the combustion and injection fundamental characteristics of different alternative fuels both experimentally and theoretically. The subjects such as lean partially premixed combustion of methane/hydrogen/air/diluent, methane high pressure direct-injection, thermal plasma formation, thermodynamic properties of hydrocarbon/air mixtures at high temperatures, laminar flames and flame morphology of synthetic gas (syngas) and Gas-to-Liquid (GTL) fuels were extensively studied in this work. These subjects will be summarized in three following paragraphs. The fundamentals of spray and partially premixed combustion characteristics of directly injected methane in a constant volume combustion chamber have been experimentally studied. The injected fuel jet generates turbulence in the vessel and forms a turbulent heterogeneous fuel-air mixture in the vessel, similar to that in a Compressed Natural Gas (CNG) Direct-Injection (DI) engines. The effect of different characteristics parameters such as spark delay time, stratification ratio, turbulence intensity, fuel injection pressure, chamber pressure, chamber temperature, Exhaust Gas recirculation (EGR) addition, hydrogen addition and equivalence ratio on flame propagation and emission concentrations were analyzed. As a part of this work and for the purpose of control and calibration of high pressure injector, spray development and characteristics including spray tip penetration, spray cone angle and overall equivalence ratio were evaluated under a wide range of fuel injection pressures of 30 to 90 atm and different chamber pressures of 1 to 5 atm. Thermodynamic properties of hydrocarbon/air plasma mixtures at ultra-high temperatures must be precisely calculated due to important influence on the flame kernel formation and propagation in combusting flows and spark discharge applications. A new algorithm based on the statistical thermodynamics was developed to calculate the ultra-high temperature plasma composition and thermodynamic properties. The method was applied to compute the thermodynamic properties of hydrogen/air and methane/air plasma mixtures for a wide range of temperatures (1,000-100,000 K), pressures (10-6-100 atm) and different equivalence ratios within flammability limit. In calculating the individual thermodynamic properties of the atomic species, the Debye-Huckel cutoff criterion has been used for terminating the series expression of the electronic partition function. A new differential-based multi-shell model was developed in conjunction with Schlieren photography to measure laminar burning speed and to study the flame instabilities for different alternative fuels such as syngas and GTL. Flame instabilities such as cracking and wrinkling were observed during flame propagation and discussed in terms of the hydrodynamic and thermo-diffusive effects. Laminar burning speeds were measured using pressure rise data during flame propagation and power law correlations were developed over a wide range of temperatures, pressures and equivalence ratios. As a part of this work, the effect of EGR addition and substitution of nitrogen with helium in air on flame morphology and laminar burning speed were extensively investigated. The effect of cell formation on flame surface area of syngas fuel in terms of a newly defined parameter called cellularity factor was also evaluated. In addition to that the experimental onset of auto-ignition and theoretical ignition delay times of premixed GTL/air mixture were determined at high pressures and low temperatures over a wide range of equivalence ratios.

Partial view of the deployed Apollo Lunar Surface Experiments Package

NASA Image and Video Library

1972-04-21

AS16-113-18347 (21 April 1972) --- A partial view of the Apollo 16 Apollo Lunar Surface Experiments Package (ALSEP) in deployed configuration on the lunar surface as photographed during the mission's first extravehicular activity (EVA), on April 21, 1972. The Passive Seismic Experiment (PSE) is in the foreground center; Central Station (C/S) is in center background, with the Radioisotope Thermoelectric Generator (RTG) to the left. One of the anchor flags for the Active Seismic Experiment (ASE) is at right. While astronauts John W. Young, commander; and Charles M. Duke Jr., lunar module pilot; descended in the Apollo 16 Lunar Module (LM) "Orion" to explore the Descartes highlands landing site on the moon, astronaut Thomas K. Mattingly II, command module pilot, remained with the Command and Service Modules (CSM) "Casper" in lunar orbit.

New Comment on Gibbs Density Surface of Fluid Argon: Revised Critical Parameters, L. V. Woodcock, Int. J. Thermophys. (2014) 35, 1770-1784

NASA Astrophysics Data System (ADS)

Umirzakov, I. H.

2018-01-01

The author comments on an article by Woodcock (Int J Thermophys 35:1770-1784, 2014), who investigates the idea of a critical line instead of a single critical point using the example of argon. In the introduction, Woodcock states that "The Van der Waals critical point does not comply with the Gibbs phase rule. Its existence is based upon a hypothesis rather than a thermodynamic definition". The present comment is a response to the statement by Woodcock. The comment mathematically demonstrates that a critical point is not only based on a hypothesis that is used to define values of two parameters of the Van der Waals equation of state. Instead, the author argues that a critical point is a direct consequence of the thermodynamic phase equilibrium conditions resulting in a single critical point. It is shown that the thermodynamic conditions result in the first and second partial derivatives of pressure with respect to volume at constant temperature at a critical point equal to zero which are usual conditions of an existence of a critical point.

Thermodynamics of Boron Removal from Silicon Using CaO-MgO-Al2O3-SiO2 Slags

NASA Astrophysics Data System (ADS)

Jakobsson, Lars Klemet; Tangstad, Merete

2018-04-01

Slag refining is one of few metallurgical methods for removal of boron from silicon. It is important to know the thermodynamic properties of boron in slags to understand the refining process. The relation of the distribution coefficient of boron to the activity of silica, partial pressure of oxygen, and capacity of slags for boron oxide was investigated. The link between these parameters explains why the distribution coefficient of boron does not change much with changing slag composition. In addition, the thermodynamic properties of dilute boron oxide in CaO-MgO-Al2O3-SiO2 slags was determined. The ratio of the activity coefficient of boron oxide and silica was found to be the most important parameter for understanding changes in the distribution coefficient of boron for different slags. Finally, the relation between the activity coefficient of boron oxide and slag structure was investigated. It was found that the structure can explain how the distribution coefficient of boron changes depending on slag composition.

Thermodynamic Properties of Liquid Silver-Antimony-Tin Alloys Determined from Electrochemical and Calorimetric Measurements

NASA Astrophysics Data System (ADS)

Łapsa, Joanna; Onderka, Bogusław

2016-08-01

The thermodynamic properties of liquid Ag-Sb-Sn alloys were obtained through use of the drop solution calorimetric method and electromotive force (emf) measurements of galvanic cells with a yttria stabilized zirconia (YSZ) solid electrolyte. The experiments were carried out along Ag0.25Sb0.75, Ag0.5Sb0.5 and Ag0.75Sb0.25 sections of the ternary system in the temperature range from 973 K to 1223 K. From the measured emf, the tin activity in liquid solutions of Ag-Sb-Sn was determined for the first time. The partial and integral enthalpy of mixing were determined from calorimetric measurements at two temperatures. These measurements were performed along two cross-sections: Sb0.5Sn0.5 at 912 K and 1075 K, and Ag0.75Sb0.25 at 1075 K. Both experimental data sets were used to find ternary interaction parameters by applying the Redlich-Kister-Muggianu model of the substitutional solution. Consequently, the set of parameters describing the thermodynamic properties of the liquid phase was derived.

Formation, Physicochemical Characterization, and Thermodynamic Stability of the Amorphous State of Drugs and Excipients.

PubMed

Martino, Piera Di; Magnoni, Federico; Peregrina, Dolores Vargas; Gigliobianco, Maria Rosa; Censi, Roberta; Malaj, Ledjan

2016-01-01

Drugs and excipients used for pharmaceutical applications generally exist in the solid (crystalline or amorphous) state, more rarely as liquid materials. In some cases, according to the physicochemical nature of the molecule, or as a consequence of specific technological processes, a compound may exist exclusively in the amorphous state. In other cases, as a consequence of specific treatments (freezing and spray drying, melting and co-melting, grinding and compression), the crystalline form may convert into a completely or partially amorphous form. An amorphous material shows physical and thermodynamic properties different from the corresponding crystalline form, with profound repercussions on its technological performance and biopharmaceutical properties. Several physicochemical techniques such as X-ray powder diffraction, thermal methods of analysis, spectroscopic techniques, gravimetric techniques, and inverse gas chromatography can be applied to characterize the amorphous form of a compound (drug or excipient), and to evaluate its thermodynamic stability. This review offers a survey of the technologies used to convert a crystalline solid into an amorphous form, and describes the most important techniques for characterizing the amorphous state of compounds of pharmaceutical interest.

Outcome of chemotherapy counseling by pharmacists on psychological effects and self esteem among oncology patients in a Government Hospital in Malaysia.

PubMed

Ummavathy, P; Sherina, M S; Rampal, L; Siti Irma Fadhilah, I

2015-06-01

Chemotherapy is the most common form of treatment among cancer patients. It is also known to cause many physical and psychological side-effects. This study developed, implemented and evaluated the outcome of a chemotherapy counseling module among oncology patients by pharmacists based on their psychological effects (depression, anxiety) and selfesteem. A randomized, single blind, placebo controlled study was conducted among 162 patients undergoing chemotherapy in a government hospital in Malaysia. Counseling sessions were conducted using the 'Managing Patients on Chemotherapy' module for oncology patients undergoing chemotherapy at each treatment cycle. The outcome of repetitive chemotherapy counseling using the module was determined at baseline, first follow-up, second follow-up and third follow-up. The findings revealed that there was significant improvement in the intervention group as compared to the control group with large effect size on depression (p = 0.001, partial η(2) = 0.394), anxiety (p = 0.001, partial η(2) = 0.232) and self-esteem (p = 0.001, partial η(2) = 0.541). Repetitive counseling using the 'Managing Patients on Chemotherapy' module was found to be effective in improving psychological effects and self-esteem among patients undergoing chemotherapy.

Solvation Structure and Thermodynamic Mapping (SSTMap): An Open-Source, Flexible Package for the Analysis of Water in Molecular Dynamics Trajectories.

PubMed

Haider, Kamran; Cruz, Anthony; Ramsey, Steven; Gilson, Michael K; Kurtzman, Tom

2018-01-09

We have developed SSTMap, a software package for mapping structural and thermodynamic water properties in molecular dynamics trajectories. The package introduces automated analysis and mapping of local measures of frustration and enhancement of water structure. The thermodynamic calculations are based on Inhomogeneous Fluid Solvation Theory (IST), which is implemented using both site-based and grid-based approaches. The package also extends the applicability of solvation analysis calculations to multiple molecular dynamics (MD) simulation programs by using existing cross-platform tools for parsing MD parameter and trajectory files. SSTMap is implemented in Python and contains both command-line tools and a Python module to facilitate flexibility in setting up calculations and for automated generation of large data sets involving analysis of multiple solutes. Output is generated in formats compatible with popular Python data science packages. This tool will be used by the molecular modeling community for computational analysis of water in problems of biophysical interest such as ligand binding and protein function.

Prediction of retention times in comprehensive two-dimensional gas chromatography using thermodynamic models.

PubMed

McGinitie, Teague M; Harynuk, James J

2012-09-14

A method was developed to accurately predict both the primary and secondary retention times for a series of alkanes, ketones and alcohols in a flow-modulated GC×GC system. This was accomplished through the use of a three-parameter thermodynamic model where ΔH, ΔS, and ΔC(p) for an analyte's interaction with the stationary phases in both dimensions are known. Coupling this thermodynamic model with a time summation calculation it was possible to accurately predict both (1)t(r) and (2)t(r) for all analytes. The model was able to predict retention times regardless of the temperature ramp used, with an average error of only 0.64% for (1)t(r) and an average error of only 2.22% for (2)t(r). The model shows promise for the accurate prediction of retention times in GC×GC for a wide range of compounds and is able to utilize data collected from 1D experiments. Copyright © 2012 Elsevier B.V. All rights reserved.

Clinical experience with image-guided radiotherapy in an accelerated partial breast intensity-modulated radiotherapy protocol.

PubMed

Leonard, Charles E; Tallhamer, Michael; Johnson, Tim; Hunter, Kari; Howell, Kathryn; Kercher, Jane; Widener, Jodi; Kaske, Terese; Paul, Devchand; Sedlacek, Scot; Carter, Dennis L

2010-02-01

To explore the feasibility of fiducial markers for the use of image-guided radiotherapy (IGRT) in an accelerated partial breast intensity modulated radiotherapy protocol. Nineteen patients consented to an institutional review board approved protocol of accelerated partial breast intensity-modulated radiotherapy with fiducial marker placement and treatment with IGRT. Patients (1 patient with bilateral breast cancer; 20 total breasts) underwent ultrasound guided implantation of three 1.2- x 3-mm gold markers placed around the surgical cavity. For each patient, table shifts (inferior/superior, right/left lateral, and anterior/posterior) and minimum, maximum, mean error with standard deviation were recorded for each of the 10 BID treatments. The dose contribution of daily orthogonal films was also examined. All IGRT patients underwent successful marker placement. In all, 200 IGRT treatment sessions were performed. The average vector displacement was 4 mm (range, 2-7 mm). The average superior/inferior shift was 2 mm (range, 0-5 mm), the average lateral shift was 2 mm (range, 1-4 mm), and the average anterior/posterior shift was 3 mm (range, 1 5 mm). This study shows that the use of IGRT can be successfully used in an accelerated partial breast intensity-modulated radiotherapy protocol. The authors believe that this technique has increased daily treatment accuracy and permitted reduction in the margin added to the clinical target volume to form the planning target volume. Copyright 2010 Elsevier Inc. All rights reserved.

The effect of water on the thermal expansion behavior of FM5055 carbon phenolic

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.

1995-01-01

The effect of water on the thermal expansion behavior of FM5055 carbon phenolic is studied using a theory of mixtures approach. A partial pressure expression for the water constituent was obtained based upon certain assumptions regarding the thermodynamic state of water as it resides in the free volumes of the polymer. A simple constitutive model is used to simulate the polymer strain due to the application of the partial pressure of water. The resulting theory is applied to model the effect of moisture on the thermal expansion of FM5055 carbon phenolic specimens. The application of the theory results in calculated strains which were in close agreement with the measured strains.

Theoretical and experimental study on the effects of particle size and temperature on the reaction kinetics of cubic nano-Cu2O

NASA Astrophysics Data System (ADS)

Tang, Huanfeng; Huang, Zaiyin; Xiao, Ming; Liang, Min; Chen, Liying; Tan, XueCai

2017-09-01

The activities, selectivities, and stabilities of nanoparticles in heterogeneous reactions are size-dependent. In order to investigate the influencing laws of particle size and temperature on kinetic parameters in heterogeneous reactions, cubic nano-Cu2O particles of four different sizes in the range of 40-120 nm have been controllably synthesized. In situ microcalorimetry has been used to attain thermodynamic data on the reaction of Cu2O with aqueous HNO3 and, combined with thermodynamic principles and kinetic transition-state theory, the relevant reaction kinetic parameters have been evaluated. The size dependences of the kinetic parameters are discussed in terms of the established kinetic model and the experimental results. It was found that the reaction rate constants increased with decreasing particle size. Accordingly, the apparent activation energy, pre-exponential factor, activation enthalpy, activation entropy, and activation Gibbs energy decreased with decreasing particle size. The reaction rate constants and activation Gibbs energies increased with increasing temperature. Moreover, the logarithms of the apparent activation energies, pre-exponential factors, and rate constants were found to be linearly related to the reciprocal of particle size, consistent with the kinetic models. The influence of particle size on these reaction kinetic parameters may be explained as follows: the apparent activation energy is affected by the partial molar enthalpy, the pre-exponential factor is affected by the partial molar entropy, and the reaction rate constant is affected by the partial molar Gibbs energy. [Figure not available: see fulltext.

Comparative Ecology of H2 Cycling in Organotrophic and Phototrophic Ecosystems

NASA Technical Reports Server (NTRS)

Hoehler, Tori M.; Alperin, Marc J.; Albert, Daniel B.; Bebout, Brad M.; Martens, Christopher S.; DesMarais, David J.; DeVincenzi, Don (Technical Monitor)

2001-01-01

The simple biochemistry of H2 is critical to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. The sensitivity of these many processes to H2 can be described quantitatively, at a basic thermodynamic level. This shared dependence on H2 may provide a means for interpreting the ecology and system-level biogeochemistry of widely variant microbial ecosystems on a common (and quantitative) level. Understanding the factors that control H2 itself is a critical prerequisite. Here, we examine two ecosystems that vary widely with respect to H2 cycling. In anoxic, 'organotrophic' sediments from Cape Lookout Bight (North Carolina, USA), H2 partial pressures are strictly maintained at low, steady-state levels by H2-consuming organisms, in a fashion that can be quantitatively predicted by simple thermodynamic calculations. In phototrophic microbial mats from Baja, Mexico, H2 partial pressures are instead controlled by the activity of light-sensitive H2-producing organisms. In consequence, H2 partial pressures within the system fluctuate by orders of magnitude on hour-long time scales. The differences in H2 cycling subsequently impact H2-sensitive microbial processes, such as methanogenesis. For example, the presence of sulfate in the organotrophic system always yielded low levels of H2 that were inhibitory to methanogenesis; however, the elevated levels of H2 in the phototrophic system favored methane production at significant levels, even in the presence of high sulfate concentrations. The myriad of other H2-sensitive microbial processes are expected to exhibit similar behavior.

Ab initio investigation of the thermodynamics of cation distribution and of the electronic and magnetic structures in the LiMn2O4 spinel

NASA Astrophysics Data System (ADS)

Santos-Carballal, David; Ngoepe, Phuti E.; de Leeuw, Nora H.

2018-02-01

The spinel-structured lithium manganese oxide (LiMn2O4 ) is a material currently used as cathode for secondary lithium-ion batteries, but whose properties are not yet fully understood. Here, we report a computational investigation of the inversion thermodynamics and electronic behavior of LiMn2O4 derived from spin-polarized density functional theory calculations with a Hubbard Hamiltonian and long-range dispersion corrections (DFT+U-D3). Based on the analysis of the configurational free energy, we have elucidated a partially inverse equilibrium cation distribution for the LiMn2O4 spinel. This equilibrium degree of inversion is rationalized in terms of the crystal field stabilization effects and the difference between the size of the cations. We compare the atomic charges with the oxidation numbers for each degree of inversion. We found segregation of the Mn charge once these ions occupy the tetrahedral and octahedral sites of the spinel. We have obtained the atomic projections of the electronic band structure and density of states, showing that the normal LiMn2O4 has half-metallic properties, while the fully inverse spinel is an insulator. This material is in the ferrimagnetic state for the inverse and partially inverse cation arrangement. The optimized lattice and oxygen parameters, as well as the equilibrium degree of inversion, are in agreement with the available experimental data. The partial equilibrium degree of inversion is important in the interpretation of the lithium ion migration and surface properties of the LiMn2O4 spinel.

Projected Improvements in Accelerated Partial Breast Irradiation Using a Novel Breast Stereotactic Radiotherapy Device: A Dosimetric Analysis.

PubMed

Snider, James W; Mutaf, Yildirim; Nichols, Elizabeth; Hall, Andrea; Vadnais, Patrick; Regine, William F; Feigenberg, Steven J

2017-01-01

Accelerated partial breast irradiation has caused higher than expected rates of poor cosmesis. At our institution, a novel breast stereotactic radiotherapy device has demonstrated dosimetric distributions similar to those in brachytherapy. This study analyzed comparative dose distributions achieved with the device and intensity-modulated radiation therapy accelerated partial breast irradiation. Nine patients underwent computed tomography simulation in the prone position using device-specific immobilization on an institutional review board-approved protocol. Accelerated partial breast irradiation target volumes (planning target volume_10mm) were created per the National Surgical Adjuvant Breast and Bowel Project B-39 protocol. Additional breast stereotactic radiotherapy volumes using smaller margins (planning target volume_3mm) were created based on improved immobilization. Intensity-modulated radiation therapy and breast stereotactic radiotherapy accelerated partial breast irradiation plans were separately generated for appropriate volumes. Plans were evaluated based on established dosimetric surrogates of poor cosmetic outcomes. Wilcoxon rank sum tests were utilized to contrast volumes of critical structures receiving a percentage of total dose ( Vx). The breast stereotactic radiotherapy device consistently reduced dose to all normal structures with equivalent target coverage. The ipsilateral breast V20-100 was significantly reduced ( P < .05) using planning target volume_10mm, with substantial further reductions when targeting planning target volume_3mm. Doses to the chest wall, ipsilateral lung, and breast skin were also significantly lessened. The breast stereotactic radiotherapy device's uniform dosimetric improvements over intensity-modulated accelerated partial breast irradiation in this series indicate a potential to improve outcomes. Clinical trials investigating this benefit have begun accrual.

Thermodynamic studies of aqueous solutions of 2,2,2-cryptand at 298.15 K: enthalpy-entropy compensation, partial entropies, and complexation with K+ ions.

PubMed

Shaikh, Vasim R; Terdale, Santosh S; Ahamad, Abdul; Gupta, Gaurav R; Dagade, Dilip H; Hundiwale, Dilip G; Patil, Kesharsingh J

2013-12-19

The osmotic coefficient measurements for binary aqueous solutions of 2,2,2-cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8] hexacosane) in the concentration range of ~0.009 to ~0.24 mol·kg(-1) and in ternary aqueous solutions containing a fixed concentration of 2,2,2-cryptand of ~0.1 mol·kg(-1) with varying concentration of KBr (~0.06 to ~0.16 mol·kg(-1)) have been reported at 298.15 K. The diamine gets hydrolyzed in aqueous solutions and needs proper approach to obtain meaningful thermodynamic properties. The measured osmotic coefficient values are corrected for hydrolysis and are used to determine the solvent activity and mean ionic activity coefficients of solute as a function of concentration. Strong ion-pair formation is observed, and the ion-pair dissociation constant for the species [CrptH](+)[OH(-)] is reported. The excess and mixing thermodynamic properties (Gibbs free energy, enthalpy, and entropy changes) have been obtained using the activity data from this study and the heat data reported in the literature. Further, the data are utilized to compute the partial molal entropies of solvent and solute at finite as well as infinite dilution of 2,2,2-cryptand in water. The concentration dependent non-linear enthalpy-entropy compensation effect has been observed for the studied system, and the compensation temperature along with entropic parameter are reported. Using solute activity coefficient data in ternary solutions, the transfer Gibbs free energies for transfer of the cryptand from water to aqueous KBr as well as transfer of KBr from water to aqueous cryptand were obtained and utilized to obtain the salting constant (ks) and thermodynamic equilibrium constant (log K) values for the complex (2,2,2-cryptand:K(+)) at 298.15 K. The value of log K = 5.8 ± 0.1 obtained in this work is found to be in good agreement with that reported by Lehn and Sauvage. The standard molar entropy for complexation is also estimated for the 2,2,2-cryptand-KBr complex in aqueous medium.

Thermodynamics and Kinetics of Sulfide Oxidation by Oxygen: A Look at Inorganically Controlled Reactions and Biologically Mediated Processes in the Environment

PubMed Central

Luther, George W.; Findlay, Alyssa J.; MacDonald, Daniel J.; Owings, Shannon M.; Hanson, Thomas E.; Beinart, Roxanne A.; Girguis, Peter R.

2011-01-01

The thermodynamics for the first electron transfer step for sulfide and oxygen indicates that the reaction is unfavorable as unstable superoxide and bisulfide radical ions would need to be produced. However, a two-electron transfer is favorable as stable S(0) and peroxide would be formed, but the partially filled orbitals in oxygen that accept electrons prevent rapid kinetics. Abiotic sulfide oxidation kinetics improve when reduced iron and/or manganese are oxidized by oxygen to form oxidized metals which in turn oxidize sulfide. Biological sulfur oxidation relies on enzymes that have evolved to overcome these kinetic constraints to affect rapid sulfide oxidation. Here we review the available thermodynamic and kinetic data for H2S and HS• as well as O2, reactive oxygen species, nitrate, nitrite, and NOx species. We also present new kinetic data for abiotic sulfide oxidation with oxygen in trace metal clean solutions that constrain abiotic rates of sulfide oxidation in metal free solution and agree with the kinetic and thermodynamic calculations. Moreover, we present experimental data that give insight on rates of chemolithotrophic and photolithotrophic sulfide oxidation in the environment. We demonstrate that both anaerobic photolithotrophic and aerobic chemolithotrophic sulfide oxidation rates are three or more orders of magnitude higher than abiotic rates suggesting that in most environments biotic sulfide oxidation rates will far exceed abiotic rates due to the thermodynamic and kinetic constraints discussed in the first section of the paper. Such data reshape our thinking about the biotic and abiotic contributions to sulfide oxidation in the environment. PMID:21833317

A Thermodynamic Model for Genome Packaging in Hepatitis B Virus.

PubMed

Kim, Jehoon; Wu, Jianzhong

2015-10-20

Understanding the fundamentals of genome packaging in viral capsids is important for finding effective antiviral strategies and for utilizing benign viral particles for gene therapy. While the structure of encapsidated genomic materials has been routinely characterized with experimental techniques such as cryo-electron microscopy and x-ray diffraction, much less is known about the molecular driving forces underlying genome assembly in an intracellular environment and its in vivo interactions with the capsid proteins. Here we study the thermodynamic basis of the pregenomic RNA encapsidation in human Hepatitis B virus in vivo using a coarse-grained molecular model that captures the essential components of nonspecific intermolecular interactions. The thermodynamic model is used to examine how the electrostatic interaction between the packaged RNA and the highly charged C-terminal domains (CTD) of capsid proteins regulate the nucleocapsid formation. The theoretical model predicts optimal RNA content in Hepatitis B virus nucleocapsids with different CTD lengths in good agreement with mutagenesis measurements, confirming the predominant role of electrostatic interactions and molecular excluded-volume effects in genome packaging. We find that the amount of encapsidated RNA is not linearly correlated with the net charge of CTD tails as suggested by earlier theoretical studies. Our thermodynamic analysis of the nucleocapsid structure and stability indicates that ∼10% of the CTD residues are free from complexation with RNA, resulting in partially exposed CTD tails. The thermodynamic model also predicts the free energy of complex formation between macromolecules, which corroborates experimental results for the impact of CTD truncation on the nucleocapsid stability. Copyright © 2015 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Theoretical study of the partial molar volume change associated with the pressure-induced structural transition of ubiquitin

PubMed Central

Imai, Takashi; Ohyama, Shusaku; Kovalenko, Andriy; Hirata, Fumio

2007-01-01

The partial molar volume (PMV) change associated with the pressure-induced structural transition of ubiquitin is analyzed by the three-dimensional reference interaction site model (3D-RISM) theory of molecular solvation. The theory predicts that the PMV decreases upon the structural transition, which is consistent with the experimental observation. The volume decomposition analysis demonstrates that the PMV reduction is primarily caused by the decrease in the volume of structural voids in the protein, which is partially canceled by the volume expansion due to the hydration effects. It is found from further analysis that the PMV reduction is ascribed substantially to the penetration of water molecules into a specific part of the protein. Based on the thermodynamic relation, this result implies that the water penetration causes the pressure-induced structural transition. It supports the water penetration model of pressure denaturation of proteins proposed earlier. PMID:17660257

Theoretical study of the partial molar volume change associated with the pressure-induced structural transition of ubiquitin.

PubMed

Imai, Takashi; Ohyama, Shusaku; Kovalenko, Andriy; Hirata, Fumio

2007-09-01

The partial molar volume (PMV) change associated with the pressure-induced structural transition of ubiquitin is analyzed by the three-dimensional reference interaction site model (3D-RISM) theory of molecular solvation. The theory predicts that the PMV decreases upon the structural transition, which is consistent with the experimental observation. The volume decomposition analysis demonstrates that the PMV reduction is primarily caused by the decrease in the volume of structural voids in the protein, which is partially canceled by the volume expansion due to the hydration effects. It is found from further analysis that the PMV reduction is ascribed substantially to the penetration of water molecules into a specific part of the protein. Based on the thermodynamic relation, this result implies that the water penetration causes the pressure-induced structural transition. It supports the water penetration model of pressure denaturation of proteins proposed earlier.

Fast Computation of Solvation Free Energies with Molecular Density Functional Theory: Thermodynamic-Ensemble Partial Molar Volume Corrections.

PubMed

Sergiievskyi, Volodymyr P; Jeanmairet, Guillaume; Levesque, Maximilien; Borgis, Daniel

2014-06-05

Molecular density functional theory (MDFT) offers an efficient implicit-solvent method to estimate molecule solvation free-energies, whereas conserving a fully molecular representation of the solvent. Even within a second-order approximation for the free-energy functional, the so-called homogeneous reference fluid approximation, we show that the hydration free-energies computed for a data set of 500 organic compounds are of similar quality as those obtained from molecular dynamics free-energy perturbation simulations, with a computer cost reduced by 2-3 orders of magnitude. This requires to introduce the proper partial volume correction to transform the results from the grand canonical to the isobaric-isotherm ensemble that is pertinent to experiments. We show that this correction can be extended to 3D-RISM calculations, giving a sound theoretical justification to empirical partial molar volume corrections that have been proposed recently.

Analyzing the power coupled between partially coherent waveguide fields in different states of coherence.

PubMed

Withington, Stafford; Yassin, Ghassan

2002-07-01

A procedure is described for calculating the power coupled between partially coherent waveguide fields that are in different states of coherence. The method becomes important when it is necessary to calculate the power transferred from a distributed source S to a distributed load L through a length of multimode metallic, or dielectric, waveguide. It is shown that if the correlations between the transverse components of the electric and magnetic fields of S and L are described by coherence matrices M and M', respectively, then the normalized average power coupled between them is (eta) = Tr[MM']/Tr[M]Tr[M'], where Tr denotes the trace. When the modal impedances are equal, this expression for the coupled power reduces to an equation derived in a previous paper [J. Opt. Soc. Am. A 18, 3061 (2001)], by use of thermodynamic arguments, for the power coupled between partially coherent free-space beams.

CO2 content of andesitic melts at graphite-saturated upper mantle conditions with implications for redox state of oceanic basalt source regions and remobilization of reduced carbon from subducted eclogite

NASA Astrophysics Data System (ADS)

Eguchi, James; Dasgupta, Rajdeep

2017-03-01

We have performed experiments to determine the effects of pressure, temperature and oxygen fugacity on the CO2 contents in nominally anhydrous andesitic melts at graphite saturation. The andesite composition was specifically chosen to match a low-degree partial melt composition that is generated from MORB-like eclogite in the convective, oceanic upper mantle. Experiments were performed at 1-3 GPa, 1375-1550 °C, and fO2 of FMQ -3.2 to FMQ -2.3 and the resulting experimental glasses were analyzed for CO2 and H2O contents using FTIR and SIMS. Experimental results were used to develop a thermodynamic model to predict CO2 content of nominally anhydrous andesitic melts at graphite saturation. Fitting of experimental data returned thermodynamic parameters for dissolution of CO2 as molecular CO2: ln( K 0) = -21.79 ± 0.04, Δ V 0 = 32.91 ± 0.65 cm3mol-1, Δ H 0 = 107 ± 21 kJ mol-1, and dissolution of CO2 as CO3 2-: ln (K 0 ) = -21.38 ± 0.08, Δ V 0 = 30.66 ± 1.33 cm3 mol-1, Δ H 0 = 42 ± 37 kJ mol-1, where K 0 is the equilibrium constant at some reference pressure and temperature, Δ V 0 is the volume change of reaction, and Δ H 0 is the enthalpy change of reaction. The thermodynamic model was used along with trace element partition coefficients to calculate the CO2 contents and CO2/Nb ratios resulting from the mixing of a depleted MORB and the partial melt of a graphite-saturated eclogite. Comparison with natural MORB and OIB data suggests that the CO2 contents and CO2/Nb ratios of CO2-enriched oceanic basalts cannot be produced by mixing with partial melts of graphite-saturated eclogite. Instead, they must be produced by melting of a source containing carbonate. This result places a lower bound on the oxygen fugacity for the source region of these CO2-enriched basalts, and suggests that fO2 measurements made on cratonic xenoliths may not be applicable to the convecting upper mantle. CO2-depleted basalts, on the other hand, are consistent with mixing between depleted MORB and partial melts of a graphite-saturated eclogite. Furthermore, calculations suggest that eclogite can remain saturated in graphite in the convecting upper mantle, acting as a reservoir for C.

Statistical physics inspired energy-efficient coded-modulation for optical communications.

PubMed

Djordjevic, Ivan B; Xu, Lei; Wang, Ting

2012-04-15

Because Shannon's entropy can be obtained by Stirling's approximation of thermodynamics entropy, the statistical physics energy minimization methods are directly applicable to the signal constellation design. We demonstrate that statistical physics inspired energy-efficient (EE) signal constellation designs, in combination with large-girth low-density parity-check (LDPC) codes, significantly outperform conventional LDPC-coded polarization-division multiplexed quadrature amplitude modulation schemes. We also describe an EE signal constellation design algorithm. Finally, we propose the discrete-time implementation of D-dimensional transceiver and corresponding EE polarization-division multiplexed system. © 2012 Optical Society of America

Retrograde adsorption isotherms: an impossible fact?

PubMed

Helfferich, Friedrich G

2005-06-24

"Retrograde" adsorption isotherms have been reported, but seem to violate thermodynamics and would cause concentration steps to migrate against the direction of fluid-phase flow. In general, what appears to be retrograde behavior is caused by one or more additional, uncontrolled variables. This is illustrated with adsorption of sulfonate on a weak-acid ion exchanger, where adsorption is accompanied by partial conversion of the ion exchanger to the sodium form.

Evolution of a Western Arctic Ice Ocean Boundary Layer and Mixed Layer Across a Developing Thermodynamically Forced Marginal Ice Zone

DTIC Science & Technology

2016-09-01

Submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY IN PHYSICAL OCEANOGRAPHY from the NAVAL POSTGRADUATE...SCHOOL September 2016 Approved by: Timothy P. Stanton William J. Shaw Research Professor of Research Associate Professor Oceanography of... Oceanography Dissertation Committee Chair Timour Radko Andrew Roberts Associate Professor of Research Assistant Professor Oceanography of Oceanography

Bioregenerative Life Support Experiment for 90-days in a Closed Integrative Experimental Facility LUNAR PALACE 1

NASA Astrophysics Data System (ADS)

Liu, Hong

A 90-day bioregenerative life support experiment with three-member crew was carried out in the closed integrative experimental facility, LUNAR PALACE 1 regenerating basic living necessities and disposing wastes to provide life support for crew. It was composed of higher plant module, animal module, and waste treatment module. The higher plant module included wheat, chufa, pea, carrot and green leafy vegetables, with aim to satisfy requirement of 60% plant food and 100% O2 and water for crew. The yellow mealworm was selected as animal module to provide partial animal protein for crew, and reared on plant inedible biomass. The higher plant and yellow mealworm were both cultivated and harvested in the conveyor-type manner. The partial plant inedible biomass and human feces were mixed and co- fermented in the waste treatment module for preparation of soil-like substrate by bioconversion, maintaining gas balance and increasing closure degree. Meanwhile, in the waste treatment module, the water and partial nitrogen from human urine were recovered by physical-chemical means. Circulation of O2 and water as well as food supply from crops cultivated in the LUNAR PALACE 1 were investigated and calculated, and simultaneously gas exchange, mass flow among different components and system closure degree were also analyzed, respectively. Furthermore, the system robustness with respect to internal variation was tested and evaluated by sensitivity analysis of the aggregative index consisting of key performance indicators like crop yield, gaseous equilibrium concentration, microbial community composition, biogenic elements dynamics, etc., and comprehensively evaluating the operating state, to number change of crew from 2 to 4 during the 90-day closed experiment period.

Thin-Film Module Reverse-Bias Breakdown Sites Identified by Thermal Imaging: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, Steven; Sulas, Dana; Guthrey, Harvey L

Thin-film module sections are stressed under reverse bias to simulate partial shading conditions. Such stresses can cause permanent damage in the form of 'wormlike' defects due to thermal runaway. When large reverse biases with limited current are applied to the cells, dark lock-in thermography (DLIT) can detect where spatially-localized breakdown initiates before thermal runaway leads to permanent damage. Predicted breakdown defect sites have been identified in both CIGS and CdTe modules using DLIT. These defects include small pinholes, craters, or voids in the absorber layer of the film that lead to built-in areas of weakness where high current densities maymore » cause thermal damage in a partial-shading event.« less

Thin-Film Module Reverse-Bias Breakdown Sites Identified by Thermal Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnston, Steven; Sulas, Dana; Guthrey, Harvey L

Thin-film module sections are stressed under reverse bias to simulate partial shading conditions. Such stresses can cause permanent damage in the form of 'wormlike' defects due to thermal runaway. When large reverse biases with limited current are applied to the cells, dark lock-in thermography (DLIT) can detect where spatially-localized breakdown initiates before thermal runaway leads to permanent damage. Predicted breakdown defect sites have been identified in both CIGS and CdTe modules using DLIT. These defects include small pinholes, craters, or voids in the absorber layer of the film that lead to built-in areas of weakness where high current densities maymore » cause thermal damage in a partial-shading event.« less

Thermodynamics and mechanics of stretch-induced crystallization in rubbers

NASA Astrophysics Data System (ADS)

Guo, Qiang; Zaïri, Fahmi; Guo, Xinglin

2018-05-01

The aim of the present paper is to provide a quantitative prediction of the stretch-induced crystallization in natural rubber, the exclusive reason for its history-dependent thermomechanical features. A constitutive model based on a micromechanism inspired molecular chain approach is formulated within the context of the thermodynamic framework. The molecular configuration of the partially crystallized single chain is analyzed and calculated by means of some statistical mechanical methods. The random thermal oscillation of the crystal orientation, considered as a continuous random variable, is treated by means of a representative angle. The physical expression of the chain free energy is derived according to a two-step strategy by separating crystallization and stretching. This strategy ensures that the stretch-induced part of the thermodynamic crystallization force is null at the initial instant and allows, without any additional constraint, the formulation of a simple linear relationship for the crystallinity evolution law. The model contains very few physically interpretable material constants to simulate the complex mechanism: two chain-scale constants, one crystallinity kinetics constant, three thermodynamic constants related to the newly formed crystallites, and a function controlling the crystal orientation with respect to the chain. The model is used to discuss some important aspects of the micromechanism and the macroresponse under the equilibrium state and the nonequilibrium state involved during stretching and recovery, and continuous relaxation.

N2 and P3 modulation during partial inhibition in a modified go/nogo task.

PubMed

Nguyen, An T; Moyle, Jonson J; Fox, Allison M

2016-09-01

The neural response following the partial inhibition of responses can provide insight into the processes underlying response inhibition. We examined the N2 and P3 on trials where participants correctly responded to go stimuli, successfully inhibited their response to nogo stimuli, and nogo trials where they initiated but did not complete their response (partial inhibitions) in an adult sample (N=24, M(age)=21.17, SD(age)=3.52). An enhanced and delayed N2 was observed on partially inhibited compared to successfully inhibited nogo trials. Further analysis showed that this modulation was error-related. An enhanced central P3 was observed following successful inhibitions compared to correct go trials, but not following partial inhibitions. The results suggest that the central P3 enhancement is specific to the complete and successful inhibition of responses. Therefore, the absence of a central P3 on partial inhibitions could reflect insufficient inhibition or a monitored failure in inhibiting the response. Although, our findings provide support for the role of P3 in response inhibition, it raises questions about the processes involved in the subsequent inhibition or correction of the erroneous response. Further research examining the neural response following both partial and unsuccessful inhibitions could provide insight regarding these processes. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of temperature modulations on TEMPO-mediated regioselective oxidation of unprotected carbohydrates and nucleosides.

PubMed

Yadav, Mahipal; Liotta, Charles L; Krishnamurthy, Ramanarayanan

2018-02-02

Regioselective oxidation of unprotected and partially protected oligosaccharides is a much sought-after goal. Herein, we report a notable improvement in the efficiency of TEMPO-catalyzed oxidation by modulating the temperature of the reaction. Mono-, di-, and tri-saccharides are oxidized regioselectively in yields of 75 to 92%. The present method is simple to implement and is also applicable for selective oxidations of other mono- and poly-hydroxy compounds including unprotected and partially protected nucleosides. Copyright © 2018 Elsevier Ltd. All rights reserved.

Extreme Entropy-Enthalpy Compensation in a Drug Resistant Variant of HIV-1 Protease

PubMed Central

King, Nancy M.; Prabu-Jeyabalan, Moses; Bandaranayake, Rajintha M.; Nalam, Madhavi N. L.; Nalivaika, Ellen A.; Özen, Ayşegül; Haliloglu, Türkan; Yılmaz, Neşe Kurt; Schiffer, Celia A.

2012-01-01

The development of HIV-1 protease inhibitors has been the historic paradigm of rational structure-based drug design, where structural and thermodynamic analyses have assisted in the discovery of novel inhibitors. While the total enthalpy and entropy change upon binding determine the affinity, often the thermodynamics are considered in terms of inhibitor properties only. In the current study, profound changes are observed in the binding thermodynamics of a drug resistant variant compared to wild-type HIV-1 protease, irrespective of the inhibitor bound. This variant (Flap+) has a combination of flap and active site mutations and exhibits extremely large entropy-enthalpy compensation compared to wild-type protease, 5–15 kcal/mol, while losing only 1–3 kcal/mol in total binding free energy for any of six FDA approved inhibitors. Although entropy-enthalpy compensation has been previously observed for a variety of systems, never have changes of this magnitude been reported. The co-crystal structures of Flap+ protease with four of the inhibitors were determined and compared with complexes of both the wildtype protease and another drug resistant variant that does not exhibit this energetic compensation. Structural changes conserved across the Flap+ complexes, which are more pronounced for the flaps covering the active site, likely contribute to the thermodynamic compensation. The finding that drug resistant mutations can profoundly modulate the relative thermodynamic properties of a therapeutic target independent of the inhibitor presents a new challenge for rational drug design. PMID:22712830

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kagan, D. N., E-mail: d.n.kagan@mtu-net.ru; Krechetova, G. A.; Shpil'rain, E. E.

A detailed procedural analysis is given and results of implementation of the new version of the effusion method for determining the Gibbs energy (thermodynamic activity) of binary and ternary systems of alkali metals Cs-Na, K-Na, Cs-K, and Cs-K-Na are presented. The activity is determined using partial pressures of the components measured according the effusion method by the intensity of their atomic beams. The pressure range used in the experiment is intermediate between the Knudsen and hydrodynamic effusion modes. A generalized version of the effusion method involves the pressure range beyond the limits of the applicability of the Hertz-Knudsen equation. Employmentmore » of this method provides the differential equation of chemical thermodynamics; solution of this equation makes it possible to construct the Gibbs energy in the range of temperatures 400 {<=} T {<=} 1200 K and concentrations 0 {<=} x{sub i} {<=} 1.« less

Ab-intio study of phonon and thermodynamic properties of Znic-blende ZnSe

NASA Astrophysics Data System (ADS)

Khatta, Swati; Kaur, Veerpal; Tripathi, S. K.; Prakash, Satya

2018-04-01

The Phonon and thermodynamic properties of ZnSe are investigated using density functional perturbation theory (DFPT) and quasi-harmonic approximation (QHA) implemented in Quantum espresso code. The phonon dispersion curve and phonon density of states of ZnSe are obtained. It is shown that high symmetries D→X and D→L directions, there are four branches of dispersion curves which split into six branches along the X→W, W→X and X→D directions. The LO-TO splitting frequencies (in cm-1) at the zone center (D point) are LO=255 and TO=215. The total and partial phonon density of states is used to compute the entropy and specific heat capacity of ZnSe. The computed values are in reasonable agreement with experimental data and other with available theoretical calculations.

Ordering relations for quantum states

NASA Astrophysics Data System (ADS)

Durham, Ian

2015-03-01

It is often desirable to model physical states in an order-theoretic manner, e.g. as a partially ordered set. Classical states are known to possess a unique ordering relation corresponding to a neo-realist interpretation of these states. No such unique relation exists for quantum states. This lack of a unique ordering relation for quantum states turns out to be a manifestation of quantum contextuality vis-à-vis the Kochen-Specker theorem. It also turns out that this provides a link to certain large-scale thermodynamic processes. The suggestion that the ordering of quantum states leads to macroscopic thermodynamic processes is at least five decades old. The suggestion that the mechanism that drives the ordering is contextuality, is unique to this work. The argument is framed in the language of the theories of domains, categories, and topoi. Financial support provided by FQXi.

A thermodynamic study of the gaseous thorium carbides, ThC, ThC2, ThC3, ThC4, ThC5, and ThC6

NASA Astrophysics Data System (ADS)

Gupta, Satish K.; Gingerich, Karl A.

1980-02-01

Six gaseous carbides of thorium, ThCn(n=1-6), have been identified in a Knudsen effusion mass spectrometric investigation of the vapor phase above a thorium-uranium-rhodium-graphite system at high temperatures. The partial pressures of the thorium containing species were measured as a function of temperature in the 2300-2700 °K range. Third law enthalpies for the reactions Th(g)+nC(graphite) =ThCn, n=1 to 6, and of various other homogeneous and heterogeneous reactions were evaluated. By combining the experimental enthalpies with appropriate thermodynamic data taken from literature, the following values for the atomization energies ΔH °at,298, and standard heats of formation ΔH °f,298 of thorium carbides have been derived:

A teaching module about stellar structure and evolution

NASA Astrophysics Data System (ADS)

Colantonio, Arturo; Galano, Silvia; Leccia, Silvio; Puddu, Emanuella; Testa, Italo

2017-01-01

In this paper, we present a teaching module about stellar structure, functioning and evolution. Drawing from literature in astronomy education, we designed the activities around three key ideas: spectral analysis, mechanical and thermal equilibrium, energy and nuclear reactions. The module is divided into four phases, in which the key ideas for describing stars' functioning and physical mechanisms are gradually introduced. The activities (20 hours) build on previously learned laws in mechanics, thermodynamics, and electromagnetism and help students combine them meaningfully in order to get a complete picture of processes that happens in stars. The module was piloted with two intact classes of secondary school students (N = 59 students, 17-18 years old), using a ten-question multiple-choice questionnaire as research instrument. Results support the effectiveness of the proposed activities. Implications for the teaching of advanced physics topics using stars as fruitful context are briefly discussed.

Astronaut Russell Schweickart photographed during EVA

NASA Technical Reports Server (NTRS)

1969-01-01

Astronaut Russell L. Schweickart, lunar module pilot, operates a 70mm Hasselblad camera during his extravehicular activity on the fourth day of the Apollo 9 earth-orbital mission. The Command/Service Module and the Lunar Module 3 'Spider' are docked. This view was taken form the Command Module 'Gumdrop'. Schweickart, wearing an Extravehicular Mobility Unit (EMU), is standing in 'golden slippers' on the Lunar Module porch. On his back, partially visible, are a Portable Life Support System (PLSS) and an Oxygen Purge System (OPS).

Solute-solvent interactions in 2,4-dihydroxyacetophenone isonicotinoylhydrazone solutions in N, N-dimethylformamide and dimethyl sulfoxide at 298-313 K on ultrasonic and viscometric data

NASA Astrophysics Data System (ADS)

Dikkar, A. B.; Pethe, G. B.; Aswar, A. S.

2016-02-01

The speed of sound ( u), density (ρ), and viscosity (η) of 2,4-dihydroxyacetophenone isonicotinoylhydrazone (DHAIH) have been measured in N, N-dimethyl formamide and dimethyl sulfoxide at equidistance temperatures 298.15, 303.15, 308.15, and 313.15 K. These data were used to calculate some important ultrasonic and thermodynamic parameters such as apparent molar volume ( V ϕ s st ), apparent molar compressibility ( K ϕ), partial molar volume ( V ϕ 0 ) and partial molar compressibility ( K ϕ 0 ), were estimated by using the values of ( V ϕ 0 ) and ( K ϕ), at infinite dilution. Partial molar expansion at infinite dilution, (ϕ E 0 ) has also been calculated from temperature dependence of partial molar volume V ϕ 0 . The viscosity data have been analyzed using the Jones-Dole equation, and the viscosity, B coefficients are calculated. The activation free energy has been calculated from B coefficients and partial molar volume data. The results have been discussed in the term of solute-solvent interaction occurring in solutions and it was found that DHAIH acts as a structure maker in present systems.

Modulation of Tropical Cyclone Genesis by Boreal Summer Intraseasonal Oscillation: An Anomalous Dynamic Genesis Potential Index

NASA Astrophysics Data System (ADS)

Moon, J.; Wang, B.

2016-12-01

The large scale circulation anomalies associated with boreal summer intraseasonal oscillation (BSISO) strongly controls the genesis of tropical cyclone in a global perspective. The present study attempts to reveal factors by which BSISO modulation of tropical cyclone genesis (TCG) using two genesis potential indices (GPI): Dynamic GPI (DGPI) and Emanuel and Nolan's GPI (ENGPI). The ENGPI contains two dynamic (the vertical wind shear and absolute vorticity at 850 hPa) and two thermodynamic factors (relative humidity at 600 hPa and maximum potential intensity), while DPGI replaced the two thermodynamic factors by two additional dynamic factors (500 hPa vertical velocity and meridional shear of zonal winds). The major basins of tropical cyclone genesis during May to October from 1979 to 2014 are divided into North Indian Ocean (NIO), Western North Pacific (WNP), Eastern North Pacific (ENP), and North Atlantic (NAT). The genesis numbers of tropical cyclone at each basin increased distinctively at its maximum active phase of BSISO, showing the significant modulation of ISO on tropical cyclone genesis in the Northern Hemisphere. Analysis of the individual contribution of each factors in GPI reveals that the vertical velocity at 500hPa of DGPI and the relative humidity at 600hPa of ENGPI play the most important role in modulating TCG by BSISO. The SST and maximum potential intensity of ENGPI did not represent important physical processes by which the BSISO circulation anomalies affect TCG. The evolution of eight-phase BSISO with intraseasonal prediction of TCG revealed great improvement by DGPI. The evolution of TCG associated with BSISO by basins, such as NIO, WNP, ENP, and NAT showed good performance in featuring the TCG variability, indicating the possibility of improving subseasonal prediction of TCG by our new DGPI.

Density Contrast Sedimentation Velocity for the Determination of Protein Partial-Specific Volumes

PubMed Central

Brown, Patrick H.; Balbo, Andrea; Zhao, Huaying; Ebel, Christine; Schuck, Peter

2011-01-01

The partial-specific volume of proteins is an important thermodynamic parameter required for the interpretation of data in several biophysical disciplines. Building on recent advances in the use of density variation sedimentation velocity analytical ultracentrifugation for the determination of macromolecular partial-specific volumes, we have explored a direct global modeling approach describing the sedimentation boundaries in different solvents with a joint differential sedimentation coefficient distribution. This takes full advantage of the influence of different macromolecular buoyancy on both the spread and the velocity of the sedimentation boundary. It should lend itself well to the study of interacting macromolecules and/or heterogeneous samples in microgram quantities. Model applications to three protein samples studied in either H2O, or isotopically enriched H2 18O mixtures, indicate that partial-specific volumes can be determined with a statistical precision of better than 0.5%, provided signal/noise ratios of 50–100 can be achieved in the measurement of the macromolecular sedimentation velocity profiles. The approach is implemented in the global modeling software SEDPHAT. PMID:22028836

Entropy of adsorption of mixed surfactants from solutions onto the air/water interface

USGS Publications Warehouse

Chen, L.-W.; Chen, J.-H.; Zhou, N.-F.

1995-01-01

The partial molar entropy change for mixed surfactant molecules adsorbed from solution at the air/water interface has been investigated by surface thermodynamics based upon the experimental surface tension isotherms at various temperatures. Results for different surfactant mixtures of sodium dodecyl sulfate and sodium tetradecyl sulfate, decylpyridinium chloride and sodium alkylsulfonates have shown that the partial molar entropy changes for adsorption of the mixed surfactants were generally negative and decreased with increasing adsorption to a minimum near the maximum adsorption and then increased abruptly. The entropy decrease can be explained by the adsorption-orientation of surfactant molecules in the adsorbed monolayer and the abrupt entropy increase at the maximum adsorption is possible due to the strong repulsion between the adsorbed molecules.

Simulation of the modulation transfer function dependent on the partial Fourier fraction in dynamic contrast enhancement magnetic resonance imaging.

PubMed

Takatsu, Yasuo; Ueyama, Tsuyoshi; Miyati, Tosiaki; Yamamura, Kenichirou

2016-12-01

The image characteristics in dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) depend on the partial Fourier fraction and contrast medium concentration. These characteristics were assessed and the modulation transfer function (MTF) was calculated by computer simulation. A digital phantom was created from signal intensity data acquired at different contrast medium concentrations on a breast model. The frequency images [created by fast Fourier transform (FFT)] were divided into 512 parts and rearranged to form a new image. The inverse FFT of this image yielded the MTF. From the reference data, three linear models (low, medium, and high) and three exponential models (slow, medium, and rapid) of the signal intensity were created. Smaller partial Fourier fractions, and higher gradients in the linear models, corresponded to faster MTF decline. The MTF more gradually decreased in the exponential models than in the linear models. The MTF, which reflects the image characteristics in DCE-MRI, was more degraded as the partial Fourier fraction decreased.

Modulated heat pulse propagation and partial transport barriers in chaotic magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Castillo-Negrete, Diego del; Blazevski, Daniel

2016-04-15

Direct numerical simulations of the time dependent parallel heat transport equation modeling heat pulses driven by power modulation in three-dimensional chaotic magnetic fields are presented. The numerical method is based on the Fourier formulation of a Lagrangian-Green's function method that provides an accurate and efficient technique for the solution of the parallel heat transport equation in the presence of harmonic power modulation. The numerical results presented provide conclusive evidence that even in the absence of magnetic flux surfaces, chaotic magnetic field configurations with intermediate levels of stochasticity exhibit transport barriers to modulated heat pulse propagation. In particular, high-order islands andmore » remnants of destroyed flux surfaces (Cantori) act as partial barriers that slow down or even stop the propagation of heat waves at places where the magnetic field connection length exhibits a strong gradient. Results on modulated heat pulse propagation in fully stochastic fields and across magnetic islands are also presented. In qualitative agreement with recent experiments in large helical device and DIII-D, it is shown that the elliptic (O) and hyperbolic (X) points of magnetic islands have a direct impact on the spatio-temporal dependence of the amplitude of modulated heat pulses.« less

Healthy Lifestyles of University Students in China and Influential Factors

PubMed Central

Xing, Xiao-Hui; Wu, Xian-Bo

2013-01-01

This study was conducted to analyze to what extent university students exhibit healthy lifestyles and which sociodemographic variables influence healthy lifestyles. 4809 university students randomly selected were measured by use of the Healthy Lifestyle Scale for University Students questionnaire. When controlling for the other variables, the total healthy lifestyles score was predicted by gender, grade, father's level of education, and type of institution; exercise behaviour was partially predicted by gender, grade, type of institution, and family monthly income; regular behaviour was modulated by gender, grade, type of institution, family monthly income, and father's educational level; nutrition behaviour was partially affected by type of institution, family monthly income, and father's educational level; health risk behaviour was modulated by gender, mother's level of education, and family monthly income; health responsibility was modulated by gender, grade, type of institution, and father's educational level; social support was modulated by gender, grade, and father's educational level; stress management was modulated by gender, grade, type of institution, and mother's education level; life appreciation was modulated by grade, type of institution, and mother's educational level. These influences should be taken into account in designing interventions for specific socio-demographic profiles that might be at higher risk for certain behaviours. PMID:23935418

Biochemical thermodynamics: applications of Mathematica.

PubMed

Alberty, Robert A

2006-01-01

The most efficient way to store thermodynamic data on enzyme-catalyzed reactions is to use matrices of species properties. Since equilibrium in enzyme-catalyzed reactions is reached at specified pH values, the thermodynamics of the reactions is discussed in terms of transformed thermodynamic properties. These transformed thermodynamic properties are complicated functions of temperature, pH, and ionic strength that can be calculated from the matrices of species values. The most important of these transformed thermodynamic properties is the standard transformed Gibbs energy of formation of a reactant (sum of species). It is the most important because when this function of temperature, pH, and ionic strength is known, all the other standard transformed properties can be calculated by taking partial derivatives. The species database in this package contains data matrices for 199 reactants. For 94 of these reactants, standard enthalpies of formation of species are known, and so standard transformed Gibbs energies, standard transformed enthalpies, standard transformed entropies, and average numbers of hydrogen atoms can be calculated as functions of temperature, pH, and ionic strength. For reactions between these 94 reactants, the changes in these properties can be calculated over a range of temperatures, pHs, and ionic strengths, and so can apparent equilibrium constants. For the other 105 reactants, only standard transformed Gibbs energies of formation and average numbers of hydrogen atoms at 298.15 K can be calculated. The loading of this package provides functions of pH and ionic strength at 298.15 K for standard transformed Gibbs energies of formation and average numbers of hydrogen atoms for 199 reactants. It also provides functions of temperature, pH, and ionic strength for the standard transformed Gibbs energies of formation, standard transformed enthalpies of formation, standard transformed entropies of formation, and average numbers of hydrogen atoms for 94 reactants. Thus loading this package makes available 774 mathematical functions for these properties. These functions can be added and subtracted to obtain changes in these properties in biochemical reactions and apparent equilibrium constants.

Effects of N/C Ratio on Solidification Behaviors of Novel Nb-Bearing Austenitic Heat-Resistant Cast Steels for Exhaust Components of Gasoline Engines

NASA Astrophysics Data System (ADS)

Zhang, Yinhui; Li, Mei; Godlewski, Larry A.; Zindel, Jacob W.; Feng, Qiang

2017-03-01

In order to comply with more stringent environmental and fuel consumption regulations, novel Nb-bearing austenitic heat-resistant cast steels that withstand exhaust temperatures as high as 1,323 K (1,050 °C) is urgently demanded from automotive industries. In the current research, the solidification behavior of these alloys with variations of N/C ratio is investigated. Directional solidification methods were carried out to examine the microstructural development in mushy zones. Computational thermodynamic calculations under partial equilibrium conditions were performed to predict the solidification sequence of different phases. Microstructural characterization of the mushy zones indicates that N/C ratio significantly influenced the stability of γ-austenite and the precipitation temperature of NbC/Nb(C,N), thereby altering the solidification path, as well as the morphology and distribution of NbC/Nb(C,N) and γ-ferrite. The solidification sequence of different phases predicted by thermodynamic software agreed well with the experimental results, except the specific precipitation temperatures. The generated data and fundamental understanding will be helpful for the application of computational thermodynamic methods to predict the as-cast microstructure of Nb-bearing austenitic heat-resistant steels.

Kinetic and thermodynamic parameters, and partial characterization of the crude extract of tannase produced by Saccharomyces cerevisiae CCMB 520.

PubMed

Lopes, Lúzia Morgana de Melo; Costa Batista, Larissa Hayannyelly; Gouveia, Marcos Juliano; Leite, Tonny Cley Campos; de Mello, Marcelo Rodrigues Figueira; de Assis, Sandra Aparecida; de Sena, Amanda Reges

2018-05-01

Tannase can be used in different industrial sectors such as in food (juices and wine) and pharmaceutical production (trimethoprim) because it catalyses the hydrolysis of hydrolysable tannins. The aim of the current study is to assess the tannase found in the crude extract of Saccharomyces cerevisiae CCMB 520, and to set its catalytic and thermodynamic properties. The enzyme was optimally active at pH 6.0 and temperature 30 °C. Tannase was activated by Na + , Ca 2+ , K + at 5 × 10 -3  mol/L. The half-life at 30 °C was 3465.7 min. The activation energy was 40.32 kJ/mol. The Gibbs free energy, enthalpy and entropy at 30 °C were 85.40, 48.10 and -0.12 kJ/mol K, respectively. Our results suggest that the tannase found in the crude extract of S. cerevisiae is an attractive enzyme for industrial applications, such as for beverage manufacturing and gallic acid production, due its catalytic and thermodynamic properties (heat-stable and resistant to metal ions).

Modelling of the reactive transport for rock salt-brine in geological repository systems based on improved thermodynamic database (Invited)

NASA Astrophysics Data System (ADS)

Müller, W.; Alkan, H.; Xie, M.; Moog, H.; Sonnenthal, E. L.

2009-12-01

The release and migration of toxic contaminants from the disposed wastes is one of the main issues in long-term safety assessment of geological repositories. In the engineered and geological barriers around the nuclear waste emplacements chemical interactions between the components of the system may affect the isolation properties considerably. As the chemical issues change the transport properties in the near and far field of a nuclear repository, modelling of the transport should also take the chemistry into account. The reactive transport modelling consists of two main components: a code that combines the possible chemical reactions with thermo-hydrogeological processes interactively and a thermodynamic databank supporting the required parameters for the calculation of the chemical reactions. In the last decade many thermo-hydrogeological codes were upgraded to include the modelling of the chemical processes. TOUGHREACT is one of these codes. This is an extension of the well known simulator TOUGH2 for modelling geoprocesses. The code is developed by LBNL (Lawrence Berkeley National Laboratory, Univ. of California) for the simulation of the multi-phase transport of gas and liquid in porous media including heat transfer. After the release of its first version in 1998, this code has been applied and improved many times in conjunction with considerations for nuclear waste emplacement. A recent version has been extended to calculate ion activities in concentrated salt solutions applying the Pitzer model. In TOUGHREACT, the incorporated equation of state module ECO2N is applied as the EOS module for non-isothermal multiphase flow in a fluid system of H2O-NaCl-CO2. The partitioning of H2O and CO2 between liquid and gas phases is modelled as a function of temperature, pressure, and salinity. This module is applicable for waste repositories being expected to generate or having originally CO2 in the fluid system. The enhanced TOUGHREACT uses an EQ3/6-formatted database for both Pitzer ion-interaction parameters and thermodynamic equilibrium constants. The reliability of the parameters is as important as the accuracy of the modelling tool. For this purpose the project THEREDA (www.thereda.de)was set up. The project aims at a comprehensive and internally consistent thermodynamic reference database for geochemical modelling of near and far-field processes occurring in repositories for radioactive wastes in various host rock formations. In the framework of the project all data necessary to perform thermodynamic equilibrium calculations for elevated temperature in the system of oceanic salts are under revision, and it is expected that related data will be available for download by 2010-03. In this paper the geochemical issues that can play an essential role for the transport of radioactive contaminants within and around waste repositories are discussed. Some generic calculations are given to illustrate the geochemical interactions and their probable effects on the transport properties around HLW emplacements and on CO2 generating and/or containing repository systems.

Dynamic and thermodynamic crossover scenarios in the Kob-Andersen mixture: Insights from multi-CPU and multi-GPU simulations.

PubMed

Coslovich, Daniele; Ozawa, Misaki; Kob, Walter

2018-05-17

The physical behavior of glass-forming liquids presents complex features of both dynamic and thermodynamic nature. Some studies indicate the presence of thermodynamic anomalies and of crossovers in the dynamic properties, but their origin and degree of universality is difficult to assess. Moreover, conventional simulations are barely able to cover the range of temperatures at which these crossovers usually occur. To address these issues, we simulate the Kob-Andersen Lennard-Jones mixture using efficient protocols based on multi-CPU and multi-GPU parallel tempering. Our setup enables us to probe the thermodynamics and dynamics of the liquid at equilibrium well below the critical temperature of the mode-coupling theory, [Formula: see text]. We find that below [Formula: see text] the analysis is hampered by partial crystallization of the metastable liquid, which nucleates extended regions populated by large particles arranged in an fcc structure. By filtering out crystalline samples, we reveal that the specific heat grows in a regular manner down to [Formula: see text] . Possible thermodynamic anomalies suggested by previous studies can thus occur only in a region of the phase diagram where the system is highly metastable. Using the equilibrium configurations obtained from the parallel tempering simulations, we perform molecular dynamics and Monte Carlo simulations to probe the equilibrium dynamics down to [Formula: see text]. A temperature-derivative analysis of the relaxation time and diffusion data allows us to assess different dynamic scenarios around [Formula: see text]. Hints of a dynamic crossover come from analysis of the four-point dynamic susceptibility. Finally, we discuss possible future numerical strategies to clarify the nature of crossover phenomena in glass-forming liquids.

Adsorption and dissociation of H2O on the (001) surface of uranium mononitride: energetics and mechanism from first-principles investigation.

PubMed

Bo, Tao; Lan, Jian-Hui; Zhang, Yu-Juan; Zhao, Yao-Lin; He, Chao-Hui; Chai, Zhi-Fang; Shi, Wei-Qun

2016-05-21

The interfacial interaction of uranium mononitride (UN) with water from the environment unavoidably leads to corrosion of nuclear fuels, which affects a lot of processes in the nuclear fuel cycle. In this work, the microscopic adsorption behaviors of water on the UN(001) surface as well as water dissociation and accompanying H2 formation mechanisms have been investigated on the basis of DFT+U calculations and ab initio atomistic thermodynamics. For adsorption of one H2O monomer, the predicted adsorption energies are -0.88, -2.07, and -2.07 eV for the most stable molecular, partially dissociative, and completely dissociative adsorption, respectively. According to our calculations, a water molecule dissociates into OH and H species via three pathways with small energy barriers of 0.78, 0.72, and 0.85 eV, respectively. With the aid of the neighboring H atom, H2 formation through the reaction of H* + OH* can easily occur via two pathways with energy barriers of 0.61 and 0.36 eV, respectively. The molecular adsorption of water shows a slight coverage dependence on the surface while this dependence becomes obvious for partially dissociative adsorption as the water coverage increases from 1/4 to 1 ML. In addition, based on the "ab initio atomistic thermodynamic" simulations, increasing H2O partial pressure will enhance the stability of the adsorbed system and water coverage, while increasing temperature will decrease the H2O coverage. We found that the UN(001) surface reacts easily with H2O at room temperature, leading to dissolution and corrosion of the UN fuel materials.

Project COLD.

ERIC Educational Resources Information Center

Kazanjian, Wendy C.

1982-01-01

Describes Project COLD (Climate, Ocean, Land, Discovery) a scientific study of the Polar Regions, a collection of 35 modules used within the framework of existing subjects: oceanography, biology, geology, meterology, geography, social science. Includes a partial list of topics and one activity (geodesic dome) from a module. (Author/SK)

Water Mediated Ligand Functional Group Cooperativity: The Contribution of a Methyl Group to Binding Affinity is Enhanced by a COO− Group Through Changes in the Structure and Thermo dynamics of the Hydration Waters of Ligand-Thermolysin Complexes

PubMed Central

Nasief, Nader N; Tan, Hongwei; Kong, Jing; Hangauer, David

2012-01-01

Ligand functional groups can modulate the contributions of one another to the ligand-protein binding thermodynamics, producing either positive or negative cooperativity. Data presented for four thermolysin phosphonamidate inhibitors demonstrate that the differential binding free energy and enthalpy caused by replacement of a H with a Me group, which binds in the well-hydrated S2′ pocket, are more favorable in presence of a ligand carboxylate. The differential entropy is however less favorable. Dissection of these differential thermodynamic parameters, X-ray crystallography, and density-functional theory calculations suggest that these cooperativities are caused by variations in the thermodynamics of the complex hydration shell changes accompanying the H→Me replacement. Specifically, the COO− reduces both the enthalpic penalty and the entropic advantage of displacing water molecules from the S2′ pocket, and causes a subsequent acquisition of a more enthalpically, less entropically, favorable water network. This study contributes to understanding the important role water plays in ligand-protein binding. PMID:22894131

Fluorescence Spectroscopy in Thermodynamic and Kinetic Analysis of pH-Dependent Membrane Protein Insertion

PubMed Central

Ladokhin, Alexey S.

2016-01-01

Experimental determination of the free energy stabilizing the structure of membrane proteins in their native lipid environment is undermined by a lack of appropriate methods and suitable model systems. Here, we demonstrate how fluorescence correlation spectroscopy can be used to characterize thermodynamics of pH-triggered bilayer insertion of nonconstitutive membrane proteins (e.g., bacterial toxins, colicins). The experimental design is guided by the appropriate thermodynamic scheme which considers two independent processes: pH-dependent formation of a membrane-competent form and its insertion into the lipid bilayer. Measurements of a model protein annexin B12 under conditions of lipid saturation demonstrate that protonation leading to the formation of the membrane-competent state occurs near membrane interface. Lipid titration experiments demonstrate that the free energy of transfer to the intermediate interfacial state is especially favorable, while the free energy of final insertion is modulated by interplay of hydrophobic and electrostatic interactions on the bilayer interface. The general principles of kinetic measurements along the insertion pathway containing interfacial intermediate are discussed and practical examples emphasizing appropriate fitting and normalization procedures are presented. PMID:21609856

Metallo-supramolecular modules as a paradigm for materials science

PubMed Central

Kurth, Dirk G.

2008-01-01

Metal ion coordination in discrete or extended metallo-supramolecular assemblies offers ample opportunity to fabricate and study devices and materials that are equally important for fundamental research and new technologies. Metal ions embedded in a specific ligand field offer diverse thermodynamic, kinetic, chemical, physical and structural properties that make these systems promising candidates for active components in functional materials. A key challenge is to improve and develop methodologies for placing these active modules in suitable device architectures, such as thin films or mesophases. This review highlights recent developments in extended, polymeric metallo-supramolecular systems and discrete polyoxometalates with an emphasis on materials science. PMID:27877929

Supplementing monosodium glutamate to partial enteral nutrition slows gastric emptying in preterm pigs

USDA-ARS?s Scientific Manuscript database

Emerging evidence suggests that free glutamate may play a functional role in modulating gastroduodenal motor function. We hypothesized that supplementing monosodium glutamate (MSG) to partial enteral nutrition stimulates gastric emptying in preterm pigs. Ten-day-old preterm, parenterally fed pigs re...

Thermodynamic properties and atomic structure of Ca-based liquid alloys

NASA Astrophysics Data System (ADS)

Poizeau, Sophie

To identify the most promising positive electrodes for Ca-based liquid metal batteries, the thermodynamic properties of diverse Ca-based liquid alloys were investigated. The thermodynamic properties of Ca-Sb alloys were determined by emf measurements. It was found that Sb as positive electrode would provide the highest voltage for Ca-based liquid metal batteries (1 V). The price of such a battery would be competitive for the grid-scale energy storage market. The impact of Pb, a natural impurity of Sb, was predicted successfully and confirmed via electrochemical measurements. It was shown that the impact on the open circuit voltage would be minor. Indeed, the interaction between Ca and Sb was demonstrated to be much stronger than between Ca and Pb using thermodynamic modeling, which explains why the partial thermodynamic properties of Ca would not vary much with the addition of Pb to Sb. However, the usage of the positive electrode would be reduced, which would limit the interest of a Pb-Sb positive electrode. Throughout this work, the molecular interaction volume model (MIVM) was used for the first time for alloys with thermodynamic properties showing strong negative deviation from ideality. This model showed that systems such as Ca-Sb have strong short-range order: Ca is most stable when its first nearest neighbors are Sb. This is consistent with what the more traditional thermodynamic model, the regular association model, would predict. The advantages of the MIVM are the absence of assumption regarding the composition of an associate, and the reduced number of fitting parameters (2 instead of 5). Based on the parameters derived from the thermodynamic modeling using the MIVM, a new potential of mixing for liquid alloys was defined to compare the strength of interaction in different Ca-based alloys. Comparing this trend with the strength of interaction in the solid state of these systems (assessed by the energy of formation of the intermetallics), the systems with the most stable intermetallics were found to have the strongest interaction in the liquid state. Eventually, a new criteria was formulated to select electrode materials for liquid metal batteries. Systems with the most stable intermetallics, which can be evaluated by the enthalpy of formation of these systems, will yield the highest voltage when assembled as positive and negative electrodes in a liquid metal battery. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs@mit.edu)

Context-Dependent Modulation of GABAAR-Mediated Tonic Currents.

PubMed

Patel, Bijal; Bright, Damian P; Mortensen, Martin; Frølund, Bente; Smart, Trevor G

2016-01-13

Tonic GABA currents mediated by high-affinity extrasynaptic GABAA receptors, are increasingly recognized as important regulators of cell and neuronal network excitability. Dysfunctional GABAA receptor signaling that results in modified tonic GABA currents is associated with a number of neurological disorders. Consequently, developing compounds to selectively modulate the activity of extrasynaptic GABAA receptors underlying tonic inhibition is likely to prove therapeutically useful. Here, we examine the GABAA receptor subtype selectivity of the weak partial agonist, 5-(4-piperidyl)isoxazol-3-ol (4-PIOL), as a potential mechanism for modulating extrasynaptic GABAA receptor-mediated tonic currents. By using recombinant GABAA receptors expressed in HEK293 cells, and native GABAA receptors of cerebellar granule cells, hippocampal neurons, and thalamic relay neurons, 4-PIOL evidently displayed differential agonist and antagonist-type profiles, depending on the extrasynaptic GABAA receptor isoforms targeted. For neurons, this resulted in differential modulation of GABA tonic currents, depending on the cell type studied, their respective GABAA receptor subunit compositions, and critically, on the ambient GABA levels. Unexpectedly, 4-PIOL revealed a significant population of relatively low-affinity γ2 subunit-containing GABAA receptors in the thalamus, which can contribute to tonic inhibition under specific conditions when GABA levels are raised. Together, these data indicate that partial agonists, such as 4-PIOL, may be useful for modulating GABAA receptor-mediated tonic currents, but the direction and extent of this modulation is strongly dependent on relative expression levels of different extrasynaptic GABAA receptor subtypes, and on the ambient GABA levels. A background level of inhibition (tonic) is important in the brain for controlling neuronal excitability. Increased levels of tonic inhibition are associated with some neurological disorders but there are no specific ligands capable of selectively reducing tonic inhibition. Here we explore the use of a GABA partial agonist as a selective chemical tool in three different brain regions. We discover that the activity of a partial agonist is heavily dependent upon the GABAA receptor subunit composition underpinning tonic inhibition, and on the ambient levels of GABA in the brain. Copyright © 2016 Patel et al.

Context-Dependent Modulation of GABAAR-Mediated Tonic Currents

PubMed Central

Patel, Bijal; Bright, Damian P.; Mortensen, Martin; Frølund, Bente

2016-01-01

Tonic GABA currents mediated by high-affinity extrasynaptic GABAA receptors, are increasingly recognized as important regulators of cell and neuronal network excitability. Dysfunctional GABAA receptor signaling that results in modified tonic GABA currents is associated with a number of neurological disorders. Consequently, developing compounds to selectively modulate the activity of extrasynaptic GABAA receptors underlying tonic inhibition is likely to prove therapeutically useful. Here, we examine the GABAA receptor subtype selectivity of the weak partial agonist, 5-(4-piperidyl)isoxazol-3-ol (4-PIOL), as a potential mechanism for modulating extrasynaptic GABAA receptor-mediated tonic currents. By using recombinant GABAA receptors expressed in HEK293 cells, and native GABAA receptors of cerebellar granule cells, hippocampal neurons, and thalamic relay neurons, 4-PIOL evidently displayed differential agonist and antagonist-type profiles, depending on the extrasynaptic GABAA receptor isoforms targeted. For neurons, this resulted in differential modulation of GABA tonic currents, depending on the cell type studied, their respective GABAA receptor subunit compositions, and critically, on the ambient GABA levels. Unexpectedly, 4-PIOL revealed a significant population of relatively low-affinity γ2 subunit-containing GABAA receptors in the thalamus, which can contribute to tonic inhibition under specific conditions when GABA levels are raised. Together, these data indicate that partial agonists, such as 4-PIOL, may be useful for modulating GABAA receptor-mediated tonic currents, but the direction and extent of this modulation is strongly dependent on relative expression levels of different extrasynaptic GABAA receptor subtypes, and on the ambient GABA levels. SIGNIFICANCE STATEMENT A background level of inhibition (tonic) is important in the brain for controlling neuronal excitability. Increased levels of tonic inhibition are associated with some neurological disorders but there are no specific ligands capable of selectively reducing tonic inhibition. Here we explore the use of a GABA partial agonist as a selective chemical tool in three different brain regions. We discover that the activity of a partial agonist is heavily dependent upon the GABAA receptor subunit composition underpinning tonic inhibition, and on the ambient levels of GABA in the brain. PMID:26758848

A subsequent closed-form description of propagated signaling phenomena in the membrane of an axon

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melendy, Robert F., E-mail: rfmelendy@liberty.edu

2016-05-15

I recently introduced a closed-form description of propagated signaling phenomena in the membrane of an axon [R.F. Melendy, Journal of Applied Physics 118, 244701 (2015)]. Those results demonstrate how intracellular conductance, the thermodynamics of magnetization, and current modulation, function together in generating an action potential in a unified, closed-form description. At present, I report on a subsequent closed-form model that unifies intracellular conductance and the thermodynamics of magnetization, with the membrane electric field, E{sub m}. It’s anticipated this work will compel researchers in biophysics, physical biology, and the computational neurosciences, to probe deeper into the classical and quantum features ofmore » membrane magnetization and signaling, informed by the computational features of this subsequent model.« less

PHAST: Protein-like heteropolymer analysis by statistical thermodynamics

NASA Astrophysics Data System (ADS)

Frigori, Rafael B.

2017-06-01

PHAST is a software package written in standard Fortran, with MPI and CUDA extensions, able to efficiently perform parallel multicanonical Monte Carlo simulations of single or multiple heteropolymeric chains, as coarse-grained models for proteins. The outcome data can be straightforwardly analyzed within its microcanonical Statistical Thermodynamics module, which allows for computing the entropy, caloric curve, specific heat and free energies. As a case study, we investigate the aggregation of heteropolymers bioinspired on Aβ25-33 fragments and their cross-seeding with IAPP20-29 isoforms. Excellent parallel scaling is observed, even under numerically difficult first-order like phase transitions, which are properly described by the built-in fully reconfigurable force fields. Still, the package is free and open source, this shall motivate users to readily adapt it to specific purposes.

Quantum thermodynamics for driven dissipative bosonic systems

NASA Astrophysics Data System (ADS)

Ochoa, Maicol A.; Zimbovskaya, Natalya; Nitzan, Abraham

2018-02-01

We investigate two prototypical dissipative bosonic systems under slow driving and arbitrary system-bath coupling strength, recovering their dynamic evolution as well as the heat and work rates, and we verify that thermodynamic laws are respected. Specifically, we look at the damped harmonic oscillator and the damped two-level system. For the former, we study independently the slow time-dependent perturbation in the oscillator frequency and in the coupling strength. For the latter, we concentrate on the slow modulation of the energy gap between the two levels. Importantly, we are able to find the entropy production rates for each case without explicitly defining nonequilibrium extensions for the entropy functional. This analysis also permits the definition of phenomenological friction coefficients in terms of structural properties of the system-bath composite.

A hybrid density functional study of silicon and phosphorus doped hexagonal boron nitride monolayer

NASA Astrophysics Data System (ADS)

Mapasha, R. E.; Igumbor, E.; Chetty, N.

2016-10-01

We present a hybrid density functional study of silicon (Si) and phosphorus (P) doped hexagonal boron nitride (h-BN). The local geometry, electronic structure and thermodynamic stability of Si B , Si N , P B and P N are examined using hybrid Heyd-Scuseria- Ernzerhof (HSE) functional. The defect induced buckling and the local bond distances around the defect are sensitive to charge state modulation q = -2, -1, 0, +1 and +2. The +1 charge state is found to be the most energetically stable state and significantly reduces the buckling. Based on the charge state thermodynamic transition levels, we noted that the Si N , Si N and P B defects are too deep to be ionized, and can alter the optical properties of h-BN material.

Solar Polarimetry and Magnetic Field Measurements

NASA Astrophysics Data System (ADS)

del Toro Iniesta, J. C.

2001-05-01

The magnetic nature of most solar (spatially resolved or unresolved) structures is amply recognized. Magnetic fields of the Sun play a paramount rôle in the overall thermodynamic and dynamic state of our star. The main observable manifestation of solar magnetic fields is the polarization of light either through the Zeeman effect on spectral lines or through the Hanle effect (depolarization by very weak magnetic fields of light previously polarized by scattering). Hence, one can easily understand the increasing importance that polarimetry is experimenting continuously in solar physics. Under the title of this contribution a six-hour course was given during the summer school. Clearly, the limited extension allocated for the notes in these proceedings avoids an extensive account of the several topics discussed: 1) a description of light as an electromagnetic wave and the polarization properties of monochromatic, time-harmonic, plane waves; 2) the polarization properties of polychromatic light and, in particular, of quasi-monochromatic light; 3) the transformations of (partially) polarized light by linear optical systems and a description of the ways we measure the Stokes parameters by spatially and/or temporally modulating the polarimetric signal; 4) a discussion on specific problems relevant to solar polarimetry like seeing-induced and instrumental polarization, or modulation and demodulation, along with a brief description of current solar polarimeters; 5) the vector radiative transfer equation for polarized light and its links to the scalar one for unpolarized light, together with a summary of the Zeeman effect and its consequences on line formation in a magnetized stellar atmosphere; 7) an introduction of the paramount astrophysical problem, i.e., that of finding diagnostics that enable the solar physicist to interpret the observables in terms of the solar atmospheric quantities, including a discussion on contribution and response functions; and 8) a brief outline of inversion techniques as a recommended way to infer values of the vector magnetic field and other thermodynamic and dynamic quantities. Since most of the material presented in the lectures can be found in the literature, I decided to focus these pages to those topics that, in my opinion, need a particular stress and/or do not have received much attention in previous reviews or textbooks. These notes have been written with mostly didactical purposes so that, skipping the customary usage, just a few references will be cited within the text. Instead, a classified (and necessarily incomplete) bibliography is recommended at the end.

Discussion of enthalpy, entropy and free energy of formation of GaN

NASA Astrophysics Data System (ADS)

Jacob, K. T.; Rajitha, G.

2009-07-01

Presented in this letter is a critical discussion of a recent paper on experimental investigation of the enthalpy, entropy and free energy of formation of gallium nitride (GaN) published in this journal [T.J. Peshek, J.C. Angus, K. Kash, J. Cryst. Growth 311 (2008) 185-189]. It is shown that the experimental technique employed detects neither the equilibrium partial pressure of N 2 corresponding to the equilibrium between Ga and GaN at fixed temperatures nor the equilibrium temperature at constant pressure of N 2. The results of Peshek et al. are discussed in the light of other information on the Gibbs energy of formation available in the literature. Entropy of GaN is derived from heat-capacity measurements. Based on a critical analysis of all thermodynamic information now available, a set of optimized parameters is identified and a table of thermodynamic data for GaN developed from 298.15 to 1400 K.

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique

PubMed Central

Nigl, Thomas P.; Smith, Nathan D.; Lichtenstein, Timothy; Gesualdi, Jarrod; Kumar, Kuldeep; Kim, Hojong

2017-01-01

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition. PMID:29155770

Thermodynamic evaluation of oxygen behavior in Ti powder deoxidized by Ca reductant

NASA Astrophysics Data System (ADS)

Kim, Sun-Joong; Oh, Jung-Min; Lim, Jae-Won

2016-07-01

To produce low oxygen Ti powder of less than 1000 mass ppm, commercial Ti powder was deoxidized by two types of Ca reductants: a solid Ca and a Ca vapor. Compared with the iso-oxygen partial pressure in the Ti-O binary phase diagram, the PO2 in the raw Ti powder increased with temperature compared to the reduction reaction of Ca. Therefore, the O2 content in the Ti powder decreased as the deoxidation temperature increased from 873 K, showing a local minima at 1273 K. The oxygen concentration at 1373 K was greater than that at 1273 K because the oxygen solubility of the Ti powder was increased by the equilibrium relation between Ca and CaO. On the basis of the thermodynamic assessment, the deoxidation of Ti powder can be improved by increasing the temperature and lowering the oxygen solubility with the saturation of CaO.

Group additivity calculations of the thermodynamic properties of unfolded proteins in aqueous solution: a critical comparison of peptide-based and HKF models.

PubMed

Hakin, A W; Hedwig, G R

2001-02-15

A recent paper in this journal [Amend and Helgeson, Biophys. Chem. 84 (2000) 105] presented a new group additivity model to calculate various thermodynamic properties of unfolded proteins in aqueous solution. The parameters given for the revised Helgeson-Kirkham-Flowers (HKF) equations of state for all the constituent groups of unfolded proteins can be used, in principle, to calculate the partial molar heat capacity, C(o)p.2, and volume, V2(0), at infinite dilution of any polypeptide. Calculations of the values of C(o)p.2 and V2(0) for several polypeptides have been carried out to test the predictive utility of the HKF group additivity model. The results obtained are in very poor agreement with experimental data, and also with results calculated using a peptide-based group additivity model. A critical assessment of these two additivity models is presented.

Phase relations in the Fe-Ni-Cr-S system and the sulfidation of an austenitic stainless steel

NASA Technical Reports Server (NTRS)

Jacob, K. T.; Rao, D. B.; Nelson, H. G.

1977-01-01

The stability fields of various sulfide phases that form on Fe-Cr, Fe-Ni, Ni-Cr and Fe-Cr-Ni alloys were developed as a function of temperature and the partial pressure of sulfur. The calculated stability fields in the ternary system were displayed on plots of log P sub S sub 2 versus the conjugate extensive variable which provides a better framework for following the sulfidation of Fe-Cr-Ni alloys at high temperatures. Experimental and estimated thermodynamic data were used in developing the sulfur potential diagrams. Current models and correlations were employed to estimate the unknown thermodynamic behavior of solid solutions of sulfides and to supplement the incomplete phase diagram data of geophysical literature. These constructed stability field diagrams were in excellent agreement with the sulfide phases and compositions determined during a sulfidation experiment.

Study on the intrinsic defects in tin oxide with first-principles method

NASA Astrophysics Data System (ADS)

Sun, Yu; Liu, Tingyu; Chang, Qiuxiang; Ma, Changmin

2018-04-01

First-principles and thermodynamic methods are used to study the contribution of vibrational entropy to defect formation energy and the stability of the intrinsic point defects in SnO2 crystal. According to thermodynamic calculation results, the contribution of vibrational entropy to defect formation energy is significant and should not be neglected, especially at high temperatures. The calculated results indicate that the oxygen vacancy is the major point defect in undoped SnO2 crystal, which has a higher concentration than that of the other point defect. The property of negative-U is put forward in SnO2 crystal. In order to determine the most stable defects much clearer under different conditions, the most stable intrinsic defect as a function of Fermi level, oxygen partial pressure and temperature are described in the three-dimensional defect formation enthalpy diagrams. The diagram visually provides the most stable point defects under different conditions.

Thermodynamic study of the gaseous thorium carbides, ThC, ThC/sub 2/, ThC/sub 3/, ThC/sub 4/, ThC/sub 5/, and ThC/sub 6/

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, S.K.; Gingerich, K.A.

Six gaseous carbides of thorium, ThC/sub n/(n=1--6), have been identified in a Knudsen effusion mass spectrometric investigation of the vapor phase above a thorium--uranium--rhodium--graphite system at high temperatures. The partial pressures of the thorium containing species were measured as a function of temperature in the 2300--2700 /sup 0/K range. Third law enthalpies for the reactions Th(g)+nC(graphite) =ThC/sub n/, n=1 to 6, and of various other homogeneous and heterogeneous reactions were evaluated. By combining the experimental enthalpies with appropriate thermodynamic data taken from literature, the following values for the atomization energies ..delta..H /sup 0//sub at,298/, and standard heats of formation ..delta..H/supmore » tsdegree//sub f/,298 of thorium carbides have been derived:« less

Analysis performance of proton exchange membrane fuel cell (PEMFC)

NASA Astrophysics Data System (ADS)

Mubin, A. N. A.; Bahrom, M. H.; Azri, M.; Ibrahim, Z.; Rahim, N. A.; Raihan, S. R. S.

2017-06-01

Recently, the proton exchange membrane fuel cell (PEMFC) has gained much attention to the technology of renewable energy due to its mechanically ideal and zero emission power source. PEMFC performance reflects from the surroundings such as temperature and pressure. This paper presents an analysis of the performance of the PEMFC by developing the mathematical thermodynamic modelling using Matlab/Simulink. Apart from that, the differential equation of the thermodynamic model of the PEMFC is used to explain the contribution of heat to the performance of the output voltage of the PEMFC. On the other hand, the partial pressure equation of the hydrogen is included in the PEMFC mathematical modeling to study the PEMFC voltage behaviour related to the input variable input hydrogen pressure. The efficiency of the model is 33.8% which calculated by applying the energy conversion device equations on the thermal efficiency. PEMFC’s voltage output performance is increased by increasing the hydrogen input pressure and temperature.

A review of reaction rates and thermodynamic and transport properties for an 11-species air model for chemical and thermal nonequilibrium calculations to 30000 K

NASA Technical Reports Server (NTRS)

Gupta, Roop N.; Yos, Jerrold M.; Thompson, Richard A.; Lee, Kam-Pui

1990-01-01

Reaction rate coefficients and thermodynamic and transport properties are reviewed and supplemented for the 11-species air model which can be used for analyzing flows in chemical and thermal nonequilibrium up to temperatures of 3000 K. Such flows will likely occur around currently planned and future hypersonic vehicles. Guidelines for determining the state of the surrounding environment are provided. Curve fits are given for the various species properties for their efficient computation in flowfield codes. Approximate and more exact formulas are provided for computing the properties of partially ionized air mixtures in a high energy environment. Limitations of the approximate mixing laws are discussed for a mixture of ionized species. An electron number-density correction for the transport properties of the charged species is obtained. This correction has been generally ignored in the literature.

One-man electrochemical air revitalization system evaluation

NASA Technical Reports Server (NTRS)

Schbert, F. H.; Marshall, R. D.; Hallick, T. M.; Woods, R. R.

1976-01-01

A program to evaluate the performance of a one man capacity, self contained electrochemical air revitalization system was successfully completed. The technology readiness of this concept was demonstrated by characterizing the performance of this one man system over wide ranges in cabin atmospheric conditions. The electrochemical air revitalization system consists of a water vapor electrolysis module to generate oxygen from water vapor in the cabin air, and an electrochemical depolarized carbon dioxide concentrator module to remove carbon dioxide from the cabin air. A control/monitor instrumentation package that uses the electrochemical depolarized concentrator module power generated to partially offset the water vapor electrolysis module power requirements and various structural fluid routing components are also part of the system. The system was designed to meet the one man metabolic oxygen generation and carbon dioxide removal requirements, thereby controlling cabin partial pressure of oxygen at 22 kN/sq m and cabin pressure of carbon dioxide at 400 N/sq m over a wide range in cabin air relative humidity conditions.

A thermodynamic definition of protein domains.

PubMed

Porter, Lauren L; Rose, George D

2012-06-12

Protein domains are conspicuous structural units in globular proteins, and their identification has been a topic of intense biochemical interest dating back to the earliest crystal structures. Numerous disparate domain identification algorithms have been proposed, all involving some combination of visual intuition and/or structure-based decomposition. Instead, we present a rigorous, thermodynamically-based approach that redefines domains as cooperative chain segments. In greater detail, most small proteins fold with high cooperativity, meaning that the equilibrium population is dominated by completely folded and completely unfolded molecules, with a negligible subpopulation of partially folded intermediates. Here, we redefine structural domains in thermodynamic terms as cooperative folding units, based on m-values, which measure the cooperativity of a protein or its substructures. In our analysis, a domain is equated to a contiguous segment of the folded protein whose m-value is largely unaffected when that segment is excised from its parent structure. Defined in this way, a domain is a self-contained cooperative unit; i.e., its cooperativity depends primarily upon intrasegment interactions, not intersegment interactions. Implementing this concept computationally, the domains in a large representative set of proteins were identified; all exhibit consistency with experimental findings. Specifically, our domain divisions correspond to the experimentally determined equilibrium folding intermediates in a set of nine proteins. The approach was also proofed against a representative set of 71 additional proteins, again with confirmatory results. Our reframed interpretation of a protein domain transforms an indeterminate structural phenomenon into a quantifiable molecular property grounded in solution thermodynamics.

Group Combustion Module (GCM) Installation

NASA Image and Video Library

2016-09-27

ISS049e011638 (09/27/2016) --- Expedition 49 crewmember Takuya Onishi of JAXA works on the setup of the Group Combustion Module (GCM) inside the Japanese Experiment Module. The GCM will be used to house the Group Combustion experiment from the Japan Aerospace Exploration Agency (JAXA) to test a theory that fuel sprays change from partial to group combustion as flames spread across a cloud of droplets.

Modeling of ultrasonic processes utilizing a generic software framework

NASA Astrophysics Data System (ADS)

Bruns, P.; Twiefel, J.; Wallaschek, J.

2017-06-01

Modeling of ultrasonic processes is typically characterized by a high degree of complexity. Different domains and size scales must be regarded, so that it is rather difficult to build up a single detailed overall model. Developing partial models is a common approach to overcome this difficulty. In this paper a generic but simple software framework is presented which allows to coupe arbitrary partial models by slave modules with well-defined interfaces and a master module for coordination. Two examples are given to present the developed framework. The first one is the parameterization of a load model for ultrasonically-induced cavitation. The piezoelectric oscillator, its mounting, and the process load are described individually by partial models. These partial models then are coupled using the framework. The load model is composed of spring-damper-elements which are parameterized by experimental results. In the second example, the ideal mounting position for an oscillator utilized in ultrasonic assisted machining of stone is determined. Partial models for the ultrasonic oscillator, its mounting, the simplified contact process, and the workpiece’s material characteristics are presented. For both applications input and output variables are defined to meet the requirements of the framework’s interface.

Raman Line Imaging of Poly(ε-caprolactone)/Carbon Dioxide Solutions at High Pressures: A Combined Experimental and Computational Study for Interpreting Intermolecular Interactions and Free-Volume Effects.

PubMed

Pastore Carbone, Maria Giovanna; Musto, Pellegrino; Pannico, Marianna; Braeuer, Andreas; Scherillo, Giuseppe; Mensitieri, Giuseppe; Di Maio, Ernesto

2016-09-01

In the present study, a Raman line-imaging setup was employed to monitor in situ the CO2 sorption at elevated pressures (from 0.62 to 7.10 MPa) in molten PCL. The method allowed the quantitative measurement of gas concentration in both the time-resolved and the space-resolved modes. The combined experimental and theoretical approach allowed a molecular level characterization of the system. The dissolved CO2 was found to occupy a volume essentially coincident with its van der Waals volume and the estimated partial molar volume of the probe did not change with pressure. Lewis acid-Lewis base interactions with the PCL carbonyls was confirmed to be the main interaction mechanism. The geometry of the supramolecular complex and the preferential interaction site were controlled more by steric than electronic effects. On the basis of the indications emerging from Raman spectroscopy, an equation of state thermodynamic model for the PCL-CO2 system, based upon a compressible lattice fluid theory endowed with specific interactions, has been tailored to account for the interaction types detected spectroscopically. The predictions of the thermodynamic model in terms of molar volume of solution have been compared with available volumetric measurements while predictions for CO2 partial molar volume have been compared with the values estimated on the basis of Raman spectroscopy.

The partial coherence modulation transfer function in testing lithography lens

NASA Astrophysics Data System (ADS)

Huang, Jiun-Woei

2018-03-01

Due to the lithography demanding high performance in projection of semiconductor mask to wafer, the lens has to be almost free in spherical and coma aberration, thus, in situ optical testing for diagnosis of lens performance has to be established to verify the performance and to provide the suggesting for further improvement of the lens, before the lens has been build and integrated with light source. The measurement of modulation transfer function of critical dimension (CD) is main performance parameter to evaluate the line width of semiconductor platform fabricating ability for the smallest line width of producing tiny integrated circuits. Although the modulation transfer function (MTF) has been popularly used to evaluation the optical system, but in lithography, the contrast of each line-pair is in one dimension or two dimensions, analytically, while the lens stand along in the test bench integrated with the light source coherent or near coherent for the small dimension near the optical diffraction limit, the MTF is not only contributed by the lens, also by illumination of platform. In the study, the partial coherence modulation transfer function (PCMTF) for testing a lithography lens is suggested by measuring MTF in the high spatial frequency of in situ lithography lens, blended with the illumination of partial and in coherent light source. PCMTF can be one of measurement to evaluate the imperfect lens of lithography lens for further improvement in lens performance.

Thermodynamic Cconstraints on Coupled Carbonate-Pyrite Weathering Dynamics and Carbon Fluxes

NASA Astrophysics Data System (ADS)

Winnick, M.; Maher, K.

2017-12-01

Chemical weathering within the critical zone regulates global biogeochemical cycles, atmospheric composition, and the supply of key nutrients to terrestrial and aquatic ecosystems. Recent studies suggest that thermodynamic limits on solute production act as a first-order control on global chemical weathering rates; however, few studies have addressed the factors that set these thermodynamic limits in natural systems. In this presentation, we investigate the effects of soil CO2 concentrations and pyrite oxidation rates on carbonate dissolution and associated carbon fluxes in the East River watershed in Colorado, using concentration-discharge relationships and thermodynamic constraints. Within the shallow subsurface, soil respiration rates and moisture content determine the extent of carbonic acid-promoted carbonate dissolution through their modulation of soil pCO2 and the balance of open- v. closed-system weathering processes. At greater depths, pyrite oxidation generates sulfuric acid, which alters the approach to equilibrium of infiltrating waters. Through comparisons of concentration-discharge data and reactive transport model simulations, we explore the conditions that determine whether sulfuric acid reacts to dissolve additional carbonate mineral or instead reacts with alkalinity already in solution - the balance of which determines watershed carbon flux budgets. Our study highlights the importance of interactions between the chemical structure of the critical zone and the hydrologic regulation of flowpaths in determining concentration-discharge relationships and overall carbon fluxes.

Evidence for the principle of minimal frustration in the evolution of protein folding landscapes.

PubMed

Tzul, Franco O; Vasilchuk, Daniel; Makhatadze, George I

2017-02-28

Theoretical and experimental studies have firmly established that protein folding can be described by a funneled energy landscape. This funneled energy landscape is the result of foldable protein sequences evolving following the principle of minimal frustration, which allows proteins to rapidly fold to their native biologically functional conformations. For a protein family with a given functional fold, the principle of minimal frustration suggests that, independent of sequence, all proteins within this family should fold with similar rates. However, depending on the optimal living temperature of the organism, proteins also need to modulate their thermodynamic stability. Consequently, the difference in thermodynamic stability should be primarily caused by differences in the unfolding rates. To test this hypothesis experimentally, we performed comprehensive thermodynamic and kinetic analyses of 15 different proteins from the thioredoxin family. Eight of these thioredoxins were extant proteins from psychrophilic, mesophilic, or thermophilic organisms. The other seven protein sequences were obtained using ancestral sequence reconstruction and can be dated back over 4 billion years. We found that all studied proteins fold with very similar rates but unfold with rates that differ up to three orders of magnitude. The unfolding rates correlate well with the thermodynamic stability of the proteins. Moreover, proteins that unfold slower are more resistant to proteolysis. These results provide direct experimental support to the principle of minimal frustration hypothesis.

Calculation of Derivative Thermodynamic Hydration and Aqueous Partial Molar Properties of Ions Based on Atomistic Simulations.

PubMed

Dahlgren, Björn; Reif, Maria M; Hünenberger, Philippe H; Hansen, Niels

2012-10-09

The raw ionic solvation free energies calculated on the basis of atomistic (explicit-solvent) simulations are extremely sensitive to the boundary conditions and treatment of electrostatic interactions used during these simulations. However, as shown recently [Kastenholz, M. A.; Hünenberger, P. H. J. Chem. Phys.2006, 124, 224501 and Reif, M. M.; Hünenberger, P. H. J. Chem. Phys.2011, 134, 144104], the application of an appropriate correction scheme allows for a conversion of the methodology-dependent raw data into methodology-independent results. In this work, methodology-independent derivative thermodynamic hydration and aqueous partial molar properties are calculated for the Na(+) and Cl(-) ions at P° = 1 bar and T(-) = 298.15 K, based on the SPC water model and on ion-solvent Lennard-Jones interaction coefficients previously reoptimized against experimental hydration free energies. The hydration parameters considered are the hydration free energy and enthalpy. The aqueous partial molar parameters considered are the partial molar entropy, volume, heat capacity, volume-compressibility, and volume-expansivity. Two alternative calculation methods are employed to access these properties. Method I relies on the difference in average volume and energy between two aqueous systems involving the same number of water molecules, either in the absence or in the presence of the ion, along with variations of these differences corresponding to finite pressure or/and temperature changes. Method II relies on the calculation of the hydration free energy of the ion, along with variations of this free energy corresponding to finite pressure or/and temperature changes. Both methods are used considering two distinct variants in the application of the correction scheme. In variant A, the raw values from the simulations are corrected after the application of finite difference in pressure or/and temperature, based on correction terms specifically designed for derivative parameters at P° and T(-). In variant B, these raw values are corrected prior to differentiation, based on corresponding correction terms appropriate for the different simulation pressures P and temperatures T. The results corresponding to the different calculation schemes show that, except for the hydration free energy itself, accurate methodological independence and quantitative agreement with even the most reliable experimental parameters (ion-pair properties) are not yet reached. Nevertheless, approximate internal consistency and qualitative agreement with experimental results can be achieved, but only when an appropriate correction scheme is applied, along with a careful consideration of standard-state issues. In this sense, the main merit of the present study is to set a clear framework for these types of calculations and to point toward directions for future improvements, with the ultimate goal of reaching a consistent and quantitative description of single-ion hydration thermodynamics in molecular dynamics simulations.

Optimization of classical nonpolarizable force fields for OH(-) and H3O(+).

PubMed

Bonthuis, Douwe Jan; Mamatkulov, Shavkat I; Netz, Roland R

2016-03-14

We optimize force fields for H3O(+) and OH(-) that reproduce the experimental solvation free energies and the activities of H3O(+) Cl(-) and Na(+) OH(-) solutions up to concentrations of 1.5 mol/l. The force fields are optimized with respect to the partial charge on the hydrogen atoms and the Lennard-Jones parameters of the oxygen atoms. Remarkably, the partial charge on the hydrogen atom of the optimized H3O(+) force field is 0.8 ± 0.1|e|--significantly higher than the value typically used for nonpolarizable water models and H3O(+) force fields. In contrast, the optimal partial charge on the hydrogen atom of OH(-) turns out to be zero. Standard combination rules can be used for H3O(+) Cl(-) solutions, while for Na(+) OH(-) solutions, we need to significantly increase the effective anion-cation Lennard-Jones radius. While highlighting the importance of intramolecular electrostatics, our results show that it is possible to generate thermodynamically consistent force fields without using atomic polarizability.

Pressure effects on the structure, kinetic, and thermodynamic properties of heat-induced aggregation of protein studied by FT-IR spectroscopy

NASA Astrophysics Data System (ADS)

Taniguchi, Y.; Okuno, A.; Kato, M.

2010-03-01

Pressure can retrain the heat-induced aggregation and dissociate the heat-induced aggregates. We observed the aggregation-preventing pressure effect and the aggregates-dissociating pressure effect to characterize the heat-induced aggregation of equine serum albumin (ESA) by FT-IR spectroscopy. The results suggest the α-helical structure collapses at the beginning of heat-induced aggregation through the swollen structure, and then the rearrangement of structure to the intermolecular β-sheet takes place through partially unfolded structure. We determined the activation volume for the heat-induced aggregation (ΔV# = +93 ml/mol) and the partial molar volume difference between native state and heat-induced aggregates (ΔV=+32 ml/mol). This positive partial molar volume difference suggests that the heat-induced aggregates have larger internal voids than the native structure. Moreover, the positive volume change implies that the formation of the intermolecular β-sheet is unfavorable under high pressure.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karabourniotis, D.; Couris, S.; Damelincourt, J.J.

The partial pressure of thallium in high-pressure Hg-TlI discharges with different mercury, thallium, and electron pressures has been measured by using the optically thin line Tl 655 nm and the self-reversed line Tl 535 nm. The partial pressure of the arc axis has been measured from the line Tl 655nm. The effective partial pressure has been measured from the self-reversed line Tl 535 nm on the basis of the multiparameter method, and it has been calculated from the known axis pressure of thallium and the calculation of its radial variation by taking into account the chemical reactions. The experimental resultsmore » confirm the dispersion character of the blue wing of the line Tl 535 nm. The systematic difference obtained between the measured and calculated effective pressure, particularly at the moment of minimum electron density, may be interpreted by deviations from the local thermodynamic equilibrium (LTE) caused by overpopulation of the upper level of the line Tl 535 nm.« less

Role of density modulation in the spatially resolved dynamics of strongly confined liquids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saw, Shibu, E-mail: shibu.saw@sydney.edu.au; Dasgupta, Chandan, E-mail: cdgupta@physics.iisc.ernet.in

Confinement by walls usually produces a strong modulation in the density of dense liquids near the walls. Using molecular dynamics simulations, we examine the effects of the density modulation on the spatially resolved dynamics of a liquid confined between two parallel walls, using a resolution of a fraction of the interparticle distance in the liquid. The local dynamics is quantified by the relaxation time associated with the temporal autocorrelation function of the local density. We find that this local relaxation time varies in phase with the density modulation. The amplitude of the spatial modulation of the relaxation time can bemore » quite large, depending on the characteristics of the wall and thermodynamic parameters of the liquid. To disentangle the effects of confinement and density modulation on the spatially resolved dynamics, we compare the dynamics of a confined liquid with that of an unconfined one in which a similar density modulation is induced by an external potential. We find several differences indicating that density modulation alone cannot account for all the features seen in the spatially resolved dynamics of confined liquids. We also examine how the dynamics near a wall depends on the separation between the two walls and show that the features seen in our simulations persist in the limit of large wall separation.« less

Thermodynamic Effect of Platinum Addition to beta-NiAl: An Initial Investigation

NASA Technical Reports Server (NTRS)

2005-01-01

An initial investigation was conducted to determine the effect of platinum addition on the activities of aluminum and nickel in beta-NiAl(Pt) over the temperature range 1354 to 1692 K. These measurements were made with a multiple effusion-cell configured mass spectrometer (multi-cell KEMS). The results of this study show that Pt additions act to decreased alpha(Al) and increased the alpha(Ni) in beta-NiAl(Pt) for constant X(sub Ni)/X(sub Al) approx. = 1.13, while at constant X(sub Al) the affect of Pt on Al is greatly reduced. The measured partial enthalpies of mixing indicate Al-atoms have a strong self interaction while Ni- and Pt-atoms in have similar interactions with Al-atoms. Conversely the binding of Ni-atoms in beta-NiAl decreases with Pt addition independent of Al concentration. These initial results prove the technique can be applied to the Ni-Al-Pt system but more activity measurements are required to fully understand the thermodynamics of this system and how Pt additions improved the scaling behavior of nickel-based superalloys. In addition, with the choice of a suitable oxide material for the effusion-cell, the "closed" isothermal nature of the effusion-cell allows the direct investigation of an alloy-oxide equilibrium which resembles the "local-equilibrium" description of the metal-scale interface observed during high temperature oxidation. It is proposed that with an Al(l) + Al2O3(s) experimental reference state together with the route measurement of the relative partial-pressures of Al(g) and Al2O(g) allows the activities of O and Al2O3 to be determined along with the activities of Ni and Al. These measurements provide a direct method of investigating the thermodynamics of the metal-scale interface of a TGO-scale.

Metallic iron for water treatment: leaving the valley of confusion

NASA Astrophysics Data System (ADS)

Makota, Susanne; Nde-Tchoupe, Arnaud I.; Mwakabona, Hezron T.; Tepong-Tsindé, Raoul; Noubactep, Chicgoua; Nassi, Achille; Njau, Karoli N.

2017-12-01

Researchers on metallic iron (Fe0) for environmental remediation and water treatment are walking in a valley of confusion for 25 years. This valley is characterized by the propagation of different beliefs that have resulted from a partial analysis of the Fe0/H2O system as (1) a reductive chemical reaction was considered an electrochemical one and (2) the mass balance of iron has not been really addressed. The partial analysis in turn has been undermining the scientific method while discouraging any real critical argumentation. This communication re-establishes the complex nature of the Fe0/H2O system while recalling that, finally, proper system analysis and chemical thermodynamics are the most confident ways to solve any conflicting situation in Fe0 environmental remediation.

High-Efficiency Photovoltaic System Using Partially-Connected DC-DC Converter

NASA Astrophysics Data System (ADS)

Uno, Masatoshi; Kukita, Akio; Tanaka, Koji

Power conversion electronics for photovoltaic (PV) systems are desired to operate as efficiently as possible to exploit the power generated by PV modules. This paper proposes a novel PV system in which a dc-dc converter is partially connected to series-connected PV modules. The proposed system achieves high power-conversion efficiency by reducing the passing power and input/output voltages of the converter. The theoretical operating principle was experimentally validated. Resultant efficiency performances of the proposed and conventional systems demonstrated that the proposed system was more efficient in terms of power conversion though the identical converter was used for the both systems.

Contemporary Cambodian: The Social Institutions.

ERIC Educational Resources Information Center

Kheang, Lim Hack; And Others

"Contemporary Cambodian" consists of seven parts: the "Grammatical Sketch," the "Introduction," four intermediate modules, and a Cambodian-English glossary containing all the words in the series. After completing the "Introduction," a student can study the intermediate modules in any order, since each serves as a partial review of the others. This…

Energy conservation by oxidation of formate to carbon dioxide and hydrogen via a sodium ion current in a hyperthermophilic archaeon

PubMed Central

Lim, Jae Kyu; Mayer, Florian; Kang, Sung Gyun; Müller, Volker

2014-01-01

Thermococcus onnurineus NA1 is known to grow by the anaerobic oxidation of formate to CO2 and H2, a reaction that operates near thermodynamic equilibrium. Here we demonstrate that this reaction is coupled to ATP synthesis by a transmembrane ion current. Formate oxidation leads to H+ translocation across the cytoplasmic membrane that then drives Na+ translocation. The ion-translocating electron transfer system is rather simple, consisting of only a formate dehydrogenase module, a membrane-bound hydrogenase module, and a multisubunit Na+/H+ antiporter module. The electrochemical Na+ gradient established then drives ATP synthesis. These data give a mechanistic explanation for chemiosmotic energy conservation coupled to formate oxidation to CO2 and H2. Because it is discussed that the membrane-bound hydrogenase with the Na+/H+ antiporter module are ancestors of complex I of mitochondrial and bacterial electron transport these data also shed light on the evolution of ion transport in complex I-like electron transport chains. PMID:25049407

Energy conservation by oxidation of formate to carbon dioxide and hydrogen via a sodium ion current in a hyperthermophilic archaeon.

PubMed

Lim, Jae Kyu; Mayer, Florian; Kang, Sung Gyun; Müller, Volker

2014-08-05

Thermococcus onnurineus NA1 is known to grow by the anaerobic oxidation of formate to CO2 and H2, a reaction that operates near thermodynamic equilibrium. Here we demonstrate that this reaction is coupled to ATP synthesis by a transmembrane ion current. Formate oxidation leads to H(+) translocation across the cytoplasmic membrane that then drives Na(+) translocation. The ion-translocating electron transfer system is rather simple, consisting of only a formate dehydrogenase module, a membrane-bound hydrogenase module, and a multisubunit Na(+)/H(+) antiporter module. The electrochemical Na(+) gradient established then drives ATP synthesis. These data give a mechanistic explanation for chemiosmotic energy conservation coupled to formate oxidation to CO2 and H2. Because it is discussed that the membrane-bound hydrogenase with the Na(+)/H(+) antiporter module are ancestors of complex I of mitochondrial and bacterial electron transport these data also shed light on the evolution of ion transport in complex I-like electron transport chains.

Coordination Environment of a Site-Bound Metal Ion in the Hammerhead Ribozyme Determined by 15N and 2H ESEEM Spectroscopy

PubMed Central

Vogt, Matthew; Lahiri, Simanti; Hoogstraten, Charles G.; Britt, R. David; DeRose, Victoria J.

2010-01-01

Although site-bound Mg2+ ions have been proposed to influence RNA structure and function, establishing the molecular properties of such sites has been challenging due largely to the unique electrostatic properties of the RNA biopolymer. We have previously determined that, in solution, the hammerhead ribozyme (a self-cleaving RNA) has a high-affinity metal ion binding site characterized by a Kd,app < 10 µM for Mn2+ in 1 M NaCl and speculated that this site has functional importance in the ribozyme cleavage reaction. Here we determine both the precise location and the hydration level of Mn2+ in this site using ESEEM (electron spin–echo envelope modulation) spectroscopy. Definitive assignment of the high-affinity site to the activity-sensitive A9/G10.1 region is achieved by site-specific labeling of G10.1 with 15N guanine. The coordinated metal ion retains four water ligands as measured by 2H ESEEM spectroscopy. The results presented here show that a functionally important, specific metal binding site is uniquely populated in the hammerhead ribozyme even in a background of high ionic strength. Although it has a relatively high thermodynamic affinity, this ion remains partially hydrated and is chelated to the RNA by just two ligands. PMID:17177426

Bubble memory module

NASA Technical Reports Server (NTRS)

Bohning, O. D.; Becker, F. J.

1980-01-01

Design, fabrication and test of partially populated prototype recorder using 100 kilobit serial chips is described. Electrical interface, operating modes, and mechanical design of several module configurations are discussed. Fabrication and test of the module demonstrated the practicality of multiplexing resulting in lower power, weight, and volume. This effort resulted in the completion of a module consisting of a fully engineered printed circuit storage board populated with 5 of 8 possible cells and a wire wrapped electronics board. Interface of the module is 16 bits parallel at a maximum of 1.33 megabits per second data rate on either of two interface buses.

Long Distance Modulation of Disorder-to-Order Transitions in Protein Allostery.

PubMed

Wang, Jingheng; Custer, Gregory; Beckett, Dorothy; Matysiak, Silvina

2017-08-29

Elucidation of the molecular details of allosteric communication between distant sites in a protein is key to understanding and manipulating many biological regulatory processes. Although protein disorder is acknowledged to play an important thermodynamic role in allostery, the molecular mechanisms by which this disorder is harnessed for long distance communication are known for a limited number of systems. Transcription repression by the Escherichia coli biotin repressor, BirA, is allosterically activated by binding of the small molecule effector biotinoyl-5'-AMP. The effector acts by promoting BirA dimerization, which is a prerequisite for sequence-specific binding to the biotin biosynthetic operon operator sequence. A 30 Å distance separates the effector binding and dimerization surfaces in BirA, and previous studies indicate that allostery is mediated, in part, by disorder-to-order transitions on the two coupled sites. In this work, combined experimental and computational methods have been applied to investigate the molecular basis of allosteric communication in BirA. Double-mutant cycle analysis coupled with thermodynamic measurements indicates functional coupling between residues in disordered loops on the two distant surfaces. All atom molecular dynamics simulations reveal that this coupling occurs through long distance reciprocal modulation of the structure and dynamics of disorder-to-order transitions on the two surfaces.

Docking, thermodynamics and molecular dynamics (MD) studies of a non-canonical protease inhibitor, MP-4, from Mucuna pruriens.

PubMed

Kumar, Ashish; Kaur, Harmeet; Jain, Abha; Nair, Deepak T; Salunke, Dinakar M

2018-01-12

Sequence and structural homology suggests that MP-4 protein from Mucuna pruriens belongs to Kunitz-type protease inhibitor family. However, biochemical assays showed that this protein is a poor inhibitor of trypsin. To understand the basis of observed poor inhibition, thermodynamics and molecular dynamics (MD) simulation studies on binding of MP-4 to trypsin were carried out. Molecular dynamics simulations revealed that temperature influences the spectrum of conformations adopted by the loop regions in the MP-4 structure. At an optimal temperature, MP-4 achieves maximal binding while above and below the optimum temperature, its functional activity is hampered due to unfavourable flexibility and relative rigidity, respectively. The low activity at normal temperature is due to the widening of the conformational spectrum of the Reactive Site Loop (RSL) that reduces the probability of formation of stabilizing contacts with trypsin. The unique sequence of the RSL enhances flexibility at ambient temperature and thus reduces its ability to inhibit trypsin. This study shows that temperature influences the function of a protein through modulation in the structure of functional domain of the protein. Modulation of function through appearance of new sequences that are more sensitive to temperature may be a general strategy for evolution of new proteins.

Low temperature binary gas mixtures

NASA Astrophysics Data System (ADS)

McIntosh, Glen E.; Leonard, Kenneth R.

2017-12-01

Application of partial pressure technology to combinations of one gas above its critical temperature (helium) mixed with a two-phase liquid (nitrogen) can result in liquid temperatures down to and below the nitrogen triple point. The thermodynamics of this process is developed and an experimental apparatus is described which was used to produce a helium/nitrogen bath temperature of 59.17 K, 4 K lower than the 63.2 K nitrogen triple point and lower than any liquid nitrogen temperature reported in the literature.

Nucleate Pool Boiling Performance of Smooth and Finned Tube Bundles in R-113 and R-114/Oil Mixtures

DTIC Science & Technology

1989-06-01

tfilm Film thermodynamic temperature (K) Tfilm Film Celcius temperature (C) Tldl Liquid temperature (C) Tld2 Liquid temperature (C) Tn Tube wall local...surface immersed in a pool of saturated liquid is the most thoroughly studied boiling heat-transfer mechanism, when compared to partial film boiling and... film boiling. Figure 2.1 shows the characteristic boiling curve of a heated surface immersed in a froon. As the surface is heated up, heat is

Driving force of stacking-fault formation in SiC p-i-n diodes.

PubMed

Ha, S; Skowronski, M; Sumakeris, J J; Paisley, M J; Das, M K

2004-04-30

The driving force of stacking-fault expansion in SiC p-i-n diodes was investigated using optical emission microscopy and transmission electron microscopy. The stacking-fault expansion and properties of the partial dislocations were inconsistent with any stress as the driving force. A thermodynamic free energy difference between the perfect and a faulted structure is suggested as a plausible driving force in the tested diodes, indicating that hexagonal polytypes of silicon carbide are metastable at room temperature.

Restrictions of Non Associated Plastic Flow Laws Imposed by Thermodynamics and Uniqueness

DTIC Science & Technology

1986-05-20

which have been discussed by Kestin and Rice (1970). Valanis (1971c) and Nemat-Nasser (1975b). lie in the concepts of entropy and temperature. As a...to the concept of entropy. As an example. consider the case of a rigid heat conductor in thermal equilibrium. If heat is added to the conductor, the...entropy for such systems mathematically. Using the concept of partial integrability of Pfaffian forms, Valanis finds the temperature 0 = 0(j.eL) > 0 as

Phase equilibria of H2SO4, HNO3, and HCl hydrates and the composition of polar stratospheric clouds

NASA Technical Reports Server (NTRS)

Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

1995-01-01

Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

Phase Equilibria of H2SO4, HNO3, and HCl Hydrates and the Composition of Polar Stratospheric Clouds

NASA Technical Reports Server (NTRS)

Wooldridge, Paul J.; Zhang, Renyi; Molina, Mario J.

1995-01-01

Thermodynamic properties and phase equilibria behavior for the hydrates and coexisting pairs of hydrates of common acids which exist in the stratosphere are assembled from new laboratory measurements and standard literature data. The analysis focuses upon solid-vapor and solid-solid-vapor equilibria at temperatures around 200 K and includes new calorimetric and vapor pressure data. Calculated partial pressures versus 1/T slopes for the hydrates and coexisting hydrates agree well with experimental data where available.

Physical principles of intracellular organization via active and passive phase transitions

NASA Astrophysics Data System (ADS)

Berry, Joel; Brangwynne, Clifford P.; Haataja, Mikko

2018-04-01

Exciting recent developments suggest that phase transitions represent an important and ubiquitous mechanism underlying intracellular organization. We describe key experimental findings in this area of study, as well as the application of classical theoretical approaches for quantitatively understanding these data. We also discuss the way in which equilibrium thermodynamic driving forces may interface with the fundamentally out-of-equilibrium nature of living cells. In particular, time and/or space-dependent concentration profiles may modulate the phase behavior of biomolecules in living cells. We suggest future directions for both theoretical and experimental work that will shed light on the way in which biological activity modulates the assembly, properties, and function of viscoelastic states of living matter.

Physical principles of intracellular organization via active and passive phase transitions.

PubMed

Berry, Joel; Brangwynne, Clifford P; Haataja, Mikko

2018-04-01

Exciting recent developments suggest that phase transitions represent an important and ubiquitous mechanism underlying intracellular organization. We describe key experimental findings in this area of study, as well as the application of classical theoretical approaches for quantitatively understanding these data. We also discuss the way in which equilibrium thermodynamic driving forces may interface with the fundamentally out-of-equilibrium nature of living cells. In particular, time and/or space-dependent concentration profiles may modulate the phase behavior of biomolecules in living cells. We suggest future directions for both theoretical and experimental work that will shed light on the way in which biological activity modulates the assembly, properties, and function of viscoelastic states of living matter.

CANNABINOID AND OPIOID MODULATION OF SOCIAL PLAY BEHAVIOR IN ADOLESCENT RATS: DIFFERENTIAL BEHAVIORAL MECHANISMS

PubMed Central

Trezza, Viviana; Vanderschuren, Louk J.M.J.

2008-01-01

We have recently shown that the pharmacological mechanisms through which cannabinoid and opioid drugs influence social play behavior in adolescent rats can be partially dissociated. Here, we characterize the effects of the direct cannabinoid agonist WIN55,212-2, the indirect cannabinoid agonist URB597 and the opioid agonist morphine on social play at the behavioral level. By treating either one or both partners of the test dyad, we show that these drugs differentially affect play solicitation and play responsiveness. By testing these drugs in animals which were either familiar or unfamiliar to the test cage, we show that environmental factors differentially modulate the effects of cannabinoid and opioid drugs on social play. These results support and extend our previous findings suggesting that, although cannabinoid and opioid systems interact in the modulation of social play behavior in adolescent rats, they do so through partially dissociable behavioral and pharmacological mechanisms. PMID:18434104

Solubility enhancement of simvastatin by arginine: thermodynamics, solute-solvent interactions, and spectral analysis.

PubMed

Meor Mohd Affandi, M M R; Tripathy, Minaketan; Shah, Syed Adnan Ali; Majeed, A B A

2016-01-01

We examined the solubility of simvastatin in water in 0.01 mol·dm(-3), 0.02 mol·dm(-3), 0.04 mol·dm(-3), 0.09 mol·dm(-3), 0.18 mol·dm(-3), 0.36 mol·dm(-3), and 0.73 mol·dm(-3) arginine (ARG) solutions. The investigated drug is termed the solute, whereas ARG the cosolute. Phase solubility studies illustrated a higher extent of solubility enhancement for simvastatin. The aforementioned system was subjected to conductometric and volumetric measurements at temperatures (T) of 298.15 K, 303.15 K, 308.15 K, and 313.15 K to illustrate the thermodynamics involved and related solute-solvent interactions. The conductance values were used to evaluate the limiting molar conductance and association constants. Thermodynamic parameters (ΔG (0), ΔH (0), ΔS (0), and E s) for the association process of the solute in the aqueous solutions of ARG were calculated. Limiting partial molar volumes and expansibilities were evaluated from the density values. These values are discussed in terms of the solute-solvent and solute-cosolute interactions. Further, these systems were analyzed using ultraviolet-visible analysis, Fourier-transform infrared spectroscopy, and (13)C, (1)H, and two-dimensional nuclear overhauser effect spectroscopy nuclear magnetic resonance to complement thermophysical explanation.

Thermodynamic Properties of AgIn2Te3I and AgIn2Te3Br, Determined by EMF Method

NASA Astrophysics Data System (ADS)

Moroz, M. V.; Prokhorenko, M. V.; Prokhorenko, S. V.; Yatskov, M. V.; Reshetnyak, O. V.

2018-01-01

Differential thermal analysis (DTA), X-ray diffraction (XRD), and electromotive force (EMF) are used to triangulate Ag-In-Te-I(Br) systems in the vicinity of compounds AgIn2Te3I and AgIn2Te3Br. The three-dimensional position of the AgIn2Te3I-InTe-Ag2Te-AgI and AgIn2Te3Br-InTe-Ag3TeBr phase areas with respect to the figurative points of silver is used to create equations of potential-determining chemical reactions. The potential-determining reactions are conducted in (-)C|Ag|Ag3GeS3I(Br) glass|D|C(+) electrochemical cells (ECCs), where C stands for inert (graphite) electrodes, Ag and D are ECC electrodes (D denotes alloys of one-, three-, and four-phase areas), and Ag3GeS3I and Ag3GeS3Br glasses are membranes with purely ionic Ag+ conductivity. Linear parts of the temperature dependences of the cell EMFs are used to calculate the standard integral thermodynamic functions of saturated solid solutions based on AgIn2Te3I and AgIn2Te3Br, and the relative partial thermodynamic functions of silver in the stoichiometric quaternary compounds.

Thermodynamics and structural transition of binary atomic Bose-Fermi mixtures in box or harmonic potentials: A path-integral study

NASA Astrophysics Data System (ADS)

Kim, Tom; Chien, Chih-Chun

2018-03-01

Experimental realizations of a variety of atomic binary Bose-Fermi mixtures have brought opportunities for studying composite quantum systems with different spin statistics. The binary atomic mixtures can exhibit a structural transition from a mixture into phase separation as the boson-fermion interaction increases. By using a path-integral formalism to evaluate the grand partition function and the thermodynamic grand potential, we obtain the effective potential of binary Bose-Fermi mixtures. Thermodynamic quantities in a broad range of temperatures and interactions are also derived. The structural transition can be identified as a loop of the effective potential curve, and the volume fraction of phase separation can be determined by the lever rule. For 6Li-7Li and 6Li-41K mixtures, we present the phase diagrams of the mixtures in a box potential at zero and finite temperatures. Due to the flexible densities of atomic gases, the construction of phase separation is more complicated when compared to conventional liquid or solid mixtures where the individual densities are fixed. For harmonically trapped mixtures, we use the local density approximation to map out the finite-temperature density profiles and present typical trap structures, including the mixture, partially separated phases, and fully separated phases.

Electronic and thermodynamic properties of layered Hf2Sfrom first-principles calculations

NASA Astrophysics Data System (ADS)

Nandadasa, Chandani; Yoon, Mina; Kim, Seong-Gon; Erwin, Steve; Kim, Sungho; Kim, Sung Wng; Lee, Kimoon

Theoretically we explored two stable phases of inorganic fullerene-like structure of the layered dihafnium sulfide (Hf2 S) . We investigated structural and electronic properties of the two phases of Hf2 S by using first-principles calculations. Our calculation identifies experimentally observed anti-NbS2 structure of Hf2 S . Our electronic calculation results indicate that the density of states of anti- NbS2 structure of Hf2 S at fermi level is less than that of the other phase of Hf2 S . To study the relative stability of different phases at finite temperature Helmholtz free energies of two phases are obtained using density functional theory and density functional perturbation theory. The free energy of the anti-NbS2 structure of Hf2 S always lies below the free energy of the other phase by confirming the most stable structure of Hf2 S . The phonon dispersion, phonon density of states including partial density of states and total density of states are obtained within density functional perturbation theory. Our calculated zero-pressure phonon dispersion curves confirm that the thermodynamic stability of Hf2 S structures. For further investigation of thermodynamic properties, the temperature dependency of thermal expansion, heat capacities at constant pressure and volume are evaluated within the quasiharmonic approximations (QHA).

Solubility enhancement of simvastatin by arginine: thermodynamics, solute–solvent interactions, and spectral analysis

PubMed Central

Meor Mohd Affandi, MMR; Tripathy, Minaketan; Shah, Syed Adnan Ali; Majeed, ABA

2016-01-01

We examined the solubility of simvastatin in water in 0.01 mol·dm−3, 0.02 mol·dm−3, 0.04 mol·dm−3, 0.09 mol·dm−3, 0.18 mol·dm−3, 0.36 mol·dm−3, and 0.73 mol·dm−3 arginine (ARG) solutions. The investigated drug is termed the solute, whereas ARG the cosolute. Phase solubility studies illustrated a higher extent of solubility enhancement for simvastatin. The aforementioned system was subjected to conductometric and volumetric measurements at temperatures (T) of 298.15 K, 303.15 K, 308.15 K, and 313.15 K to illustrate the thermodynamics involved and related solute–solvent interactions. The conductance values were used to evaluate the limiting molar conductance and association constants. Thermodynamic parameters (ΔG0, ΔH0, ΔS0, and Es) for the association process of the solute in the aqueous solutions of ARG were calculated. Limiting partial molar volumes and expansibilities were evaluated from the density values. These values are discussed in terms of the solute–solvent and solute–cosolute interactions. Further, these systems were analyzed using ultraviolet–visible analysis, Fourier-transform infrared spectroscopy, and 13C, 1H, and two-dimensional nuclear overhauser effect spectroscopy nuclear magnetic resonance to complement thermophysical explanation. PMID:27041998

Effect of total and pair configurational entropy in determining dynamics of supercooled liquids over a range of densities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Banerjee, Atreyee; Nandi, Manoj Kumar; Bhattacharyya, Sarika Maitra, E-mail: mb.sarika@ncl.res.in

2016-07-21

In this paper, we present a study of supercooled liquids interacting with the Lennard Jones potential and the corresponding purely repulsive (Weeks-Chandler-Andersen) potential, over a range of densities and temperatures, in order to understand the origin of their different dynamics in spite of their structures being similar. Using the configurational entropy as the thermodynamic marker via the Adam Gibbs relation, we show that the difference in the dynamics of these two systems at low temperatures can be explained from thermodynamics. At higher densities both the thermodynamical and dynamical difference between these model systems decrease, which is quantitatively demonstrated in thismore » paper by calculating different parameters. The study also reveals the origin of the difference in pair entropy despite the similarity in the structure. Although the maximum difference in structure is obtained in the partial radial distribution function of the B type of particles, the rdf of AA pairs and AB pairs gives rise to the differences in the entropy and dynamics. This work supports the observation made in an earlier study [A. Banerjee et al., Phys. Rev. Lett. 113, 225701 (2014)] and shows that they are generic in nature, independent of density.« less

Microscopic insight into thermodynamics of conformational changes of SAP-SLAM complex in signal transduction cascade

NASA Astrophysics Data System (ADS)

Samanta, Sudipta; Mukherjee, Sanchita

2017-04-01

The signalling lymphocytic activation molecule (SLAM) family of receptors, expressed by an array of immune cells, associate with SLAM-associated protein (SAP)-related molecules, composed of single SH2 domain architecture. SAP activates Src-family kinase Fyn after SLAM ligation, resulting in a SLAM-SAP-Fyn complex, where, SAP binds the Fyn SH3 domain that does not involve canonical SH3 or SH2 interactions. This demands insight into this SAP mediated signalling cascade. Thermodynamics of the conformational changes are extracted from the histograms of dihedral angles obtained from the all-atom molecular dynamics simulations of this structurally well characterized SAP-SLAM complex. The results incorporate the binding induced thermodynamic changes of individual amino acid as well as the secondary structural elements of the protein and the solvent. Stabilization of the peptide partially comes through a strong hydrogen bonding network with the protein, while hydrophobic interactions also play a significant role where the peptide inserts itself into a hydrophobic cavity of the protein. SLAM binding widens SAP's second binding site for Fyn, which is the next step in the signal transduction cascade. The higher stabilization and less fluctuation of specific residues of SAP in the Fyn binding site, induced by SAP-SLAM complexation, emerge as the key structural elements to trigger the recognition of SAP by the SH3 domain of Fyn. The thermodynamic quantification of the protein due to complexation not only throws deeper understanding in the established mode of SAP-SLAM interaction but also assists in the recognition of the relevant residues of the protein responsible for alterations in its activity.

Microscopic insight into thermodynamics of conformational changes of SAP-SLAM complex in signal transduction cascade.

PubMed

Samanta, Sudipta; Mukherjee, Sanchita

2017-04-28

The signalling lymphocytic activation molecule (SLAM) family of receptors, expressed by an array of immune cells, associate with SLAM-associated protein (SAP)-related molecules, composed of single SH2 domain architecture. SAP activates Src-family kinase Fyn after SLAM ligation, resulting in a SLAM-SAP-Fyn complex, where, SAP binds the Fyn SH3 domain that does not involve canonical SH3 or SH2 interactions. This demands insight into this SAP mediated signalling cascade. Thermodynamics of the conformational changes are extracted from the histograms of dihedral angles obtained from the all-atom molecular dynamics simulations of this structurally well characterized SAP-SLAM complex. The results incorporate the binding induced thermodynamic changes of individual amino acid as well as the secondary structural elements of the protein and the solvent. Stabilization of the peptide partially comes through a strong hydrogen bonding network with the protein, while hydrophobic interactions also play a significant role where the peptide inserts itself into a hydrophobic cavity of the protein. SLAM binding widens SAP's second binding site for Fyn, which is the next step in the signal transduction cascade. The higher stabilization and less fluctuation of specific residues of SAP in the Fyn binding site, induced by SAP-SLAM complexation, emerge as the key structural elements to trigger the recognition of SAP by the SH3 domain of Fyn. The thermodynamic quantification of the protein due to complexation not only throws deeper understanding in the established mode of SAP-SLAM interaction but also assists in the recognition of the relevant residues of the protein responsible for alterations in its activity.

Embedded-atom-method study of structural, thermodynamic, and atomic-transport properties of liquid Ni-Al alloys

NASA Astrophysics Data System (ADS)

Asta, Mark; Morgan, Dane; Hoyt, J. J.; Sadigh, Babak; Althoff, J. D.; de Fontaine, D.; Foiles, S. M.

1999-06-01

Structural, thermodynamic, and atomic-transport properties of liquid Ni-Al alloys have been studied by Monte Carlo and molecular-dynamics simulations based upon three different embedded-atom method (EAM) interatomic potentials, namely those due to Foiles and Daw (FD) [J. Mater. Res. 2, 5 (1987)], Voter and Chen (VC) [in Characterization of Defects in Materials, edited by R. W. Siegel et al. MRS Symposia Proceedings. No. 82 (Materials Research Society, Pittsburgh, 1987), p.175] and Ludwig and Gumbsch (LG) [Model. Simul. Mater. Sci. Eng. 3, 533 (1995)]. We present detailed comparisons between calculated results and experimental data for structure factors, atomic volumes, enthalpies of mixing, activities, and viscosities. Calculated partial structure factors are found to be in semiquantitative agreement with published neutron scattering measurements for Ni20Al80 alloys, indicating that short-range order in the liquid phase is qualitatively well described. Calculated thermodynamic properties of mixing are found to agree very well with experimental data for Ni compositions greater than 75 atomic %, while for alloys richer in Al the magnitudes of the enthalpies and entropies of mixing are significantly underestimated. The VC and LG potentials give atomic densities and viscosities in good agreement with experiment for Ni-rich compositions, while FD potentials consistently underestimate both properties at all concentrations. The results of this study demonstrate that VC and LG potentials provide a realistic description of the thermodynamic and atomic transport properties for NixAl1-x liquid alloys with x>=0.75, and point to the limitations of EAM potentials for alloys richer in Al.

Bio-inspired intelligent evaporation modulation in a thermo-sensitive nanogel colloid solution for self-thermoregulation.

PubMed

Huang, Zhi; Liu, Kang; Feng, Yanhui; Zhou, Jun; Zhang, Xinxin

2017-06-28

Intelligent evaporation and temperature modulation plays an important role in self-regulation of living organisms and many industrial applications. Here we demonstrate that a poly(N-isopropylacrylamide) (PNIPAM) nanogel colloid solution can spontaneously and intelligently modulate its evaporation rate with temperature variation, which has a larger evaporation rate than distilled water at a temperature higher than its lower critical solution temperature (LCST) and a smaller evaporation rate at a temperature lower than its LCST. It performs just like human skin. Theoretical analysis based on the thermodynamic derivation reveals that the evaporation rate transition around the LCST may originate from the saturated vapor pressure transition caused by the status transformation of the PNIPAM additives. An intelligent thermoregulation system based on the PNIPAM colloid solution is also demonstrated, illustrating its potential for intelligent temperature control and acting as an artificial skin.

A System Approach to Navy Medical Education and Training. Appendix 44. Competency Curriculum for Dental Assistant.

DTIC Science & Technology

1974-08-31

Prosthodontic Appliances - Partial Dentures .... ....... ....... .... 59 2. Removable Prosthodontic Appliances - Full Dentures ..... ........... . 60 3...PROCEDURES I This unit includes the following Modules: Number Title Page 1 Removable Prosthodontic Appliances - Partial Dentures 59. ......... ...... 2...Removable Prostbodontic Appliances - Full Dentures ..... ...... a .. .. .. . 60 3 Fixed Prosthodontic Appliances - Fixed Bridge. . 61 4 Mouthquard

Apollo 9 Mission image - Astronaut Russell L. Schweickart, lunar module pilot, during EVA

NASA Image and Video Library

1969-03-03

Astronaut Russell L. Schweickart, lunar module pilot, operates a 70mm Hasselblad camera during his extravehicular activity on the fourth day of the Apollo 9 earth-orbital mission. The Command/Service Module and the Lunar Module 3 "Spider" are docked. This view was taken form the Command Module "Gumdrop". Schweickart, wearing an Extravehicular Mobility Unit (EMU), is standing in "golden slippers" on the Lunar Module porch. On his back, partially visible, are a Portable Life Support System (PLSS) and an Oxygen Purge System (OPS). Film magazine was A,film type was SO-368 Ektachrome with 0.460 - 0.710 micrometers film / filter transmittance response and haze filter,80mm lens.

Multiple-Color-Generating Cu(In,Ga)(S,Se)2 Thin-Film Solar Cells via Dichroic Film Incorporation for Power-Generating Window Applications.

PubMed

Yoo, Gang Yeol; Jeong, Jae-Seung; Lee, Soyoung; Lee, Youngki; Yoon, Hee Chang; Chu, Van Ben; Park, Gi Soon; Hwang, Yun Jeong; Kim, Woong; Min, Byoung Koun; Do, Young Rag

2017-05-03

There are four prerequisites when applying all types of thin-film solar cells to power-generating window photovoltaics (PVs): high power-generation efficiency, longevity and high durability, semitransparency or partial-light transmittance, and colorful and aesthetic value. Solid-type thin-film Cu(In,Ga)S 2 (CIGS) or Cu(In,Ga)(S,Se) 2 (CIGSSe) PVs nearly meet the first two criteria, making them promising candidates for power-generating window applications if they can transmit light to some degree and generate color with good aesthetic value. In this study, the mechanical scribing process removes 10% of the window CIGSSe thin-film solar cell with vacant line patterns to provide a partial-light-transmitting CIGSSe PV module to meet the third requirement. The last concept of creating distinct colors could be met by the addition of reflectance colors of one-dimensional (1D) photonic crystal (PC) dichroic film on the black part of a partial-light-transmitting CIGSSe PV module. Beautiful violets and blues were created on the cover glass of a black CIGSSe PV module via the addition of 1D PC blue-mirror-yellow-pass dichroic film to improve the aesthetic value of the outside appearance. As a general result from the low external quantum efficiency (EQE) and absorption of CIGSSe PVs below a wavelength of 400 nm, the harvesting efficiency and short-circuit photocurrent of CIGSSe PVs were reduced by only ∼10% without reducing the open-circuit voltage (V OC ) because of the reduced overlap between the absorption spectrum of CIGSSe PV and the reflectance spectrum of the 1D PC blue-mirror-yellow-pass dichroic film. The combined technology of partial-vacancy-scribed CIGSSe PV modules and blue 1D PC dichroic film can provide a simple strategy to be applied to violet/blue power-generating window applications, as such a strategy can improve the transparency and aesthetic value without significantly sacrificing the harvesting efficiency of the CIGSSe PV modules.

An acceleration system for Laplacian image fusion based on SoC

NASA Astrophysics Data System (ADS)

Gao, Liwen; Zhao, Hongtu; Qu, Xiujie; Wei, Tianbo; Du, Peng

2018-04-01

Based on the analysis of Laplacian image fusion algorithm, this paper proposes a partial pipelining and modular processing architecture, and a SoC based acceleration system is implemented accordingly. Full pipelining method is used for the design of each module, and modules in series form the partial pipelining with unified data formation, which is easy for management and reuse. Integrated with ARM processor, DMA and embedded bare-mental program, this system achieves 4 layers of Laplacian pyramid on the Zynq-7000 board. Experiments show that, with small resources consumption, a couple of 256×256 images can be fused within 1ms, maintaining a fine fusion effect at the same time.

EVA view of the Zenith (-ZA/FGB Plane III) side of the Functional Cargo Block (FGB).

NASA Image and Video Library

1998-12-12

STS088-353-008 (4-15 Dec. 1998) --- Astronaut James H. Newman, mission specialist, translates along a hand rail on the Russian-built Zarya Module in this Extravehicular Activity (EVA) photograph taken by astronaut Jerry L. Ross, mission specialist. Ross and Newman shared three space walks altogether to perform cable connection tasks and to put finishing touches on the exteriors of the recently-joined Zarya and the United States-built Unity (Node 1) modules. Unity is partially visible beneath Zarya, as is most of the cargo bay of the Space Shuttle Endeavour. The Canadian-built Remote Manipulator System (RMS) arm is partially visible, also.

Modulated heat pulse propagation and partial transport barriers in chaotic magnetic fields

DOE PAGES

del-Castillo-Negrete, Diego; Blazevski, Daniel

2016-04-01

Direct numerical simulations of the time dependent parallel heat transport equation modeling heat pulses driven by power modulation in 3-dimensional chaotic magnetic fields are presented. The numerical method is based on the Fourier formulation of a Lagrangian-Green's function method that provides an accurate and efficient technique for the solution of the parallel heat transport equation in the presence of harmonic power modulation. The numerical results presented provide conclusive evidence that even in the absence of magnetic flux surfaces, chaotic magnetic field configurations with intermediate levels of stochasticity exhibit transport barriers to modulated heat pulse propagation. In particular, high-order islands and remnants of destroyed flux surfaces (Cantori) act as partial barriers that slow down or even stop the propagation of heat waves at places where the magnetic field connection length exhibits a strong gradient. The key parameter ismore » $$\\gamma=\\sqrt{\\omega/2 \\chi_\\parallel}$$ that determines the length scale, $$1/\\gamma$$, of the heat wave penetration along the magnetic field line. For large perturbation frequencies, $$\\omega \\gg 1$$, or small parallel thermal conductivities, $$\\chi_\\parallel \\ll 1$$, parallel heat transport is strongly damped and the magnetic field partial barriers act as robust barriers where the heat wave amplitude vanishes and its phase speed slows down to a halt. On the other hand, in the limit of small $$\\gamma$$, parallel heat transport is largely unimpeded, global transport is observed and the radial amplitude and phase speed of the heat wave remain finite. Results on modulated heat pulse propagation in fully stochastic fields and across magnetic islands are also presented. In qualitative agreement with recent experiments in LHD and DIII-D, it is shown that the elliptic (O) and hyperbolic (X) points of magnetic islands have a direct impact on the spatio-temporal dependence of the amplitude and the time delay of modulated heat pulses.« less

Partial discharges and breakdown in C3F8

NASA Astrophysics Data System (ADS)

Koch, M.; Franck, C. M.

2014-10-01

Traditional search processes of gases or gas mixtures for replacing SF6 involve time consuming measurements of partial discharges and breakdown behaviour for several voltage waveforms and different field configurations. Recently a model for prediction of this behaviour for SF6 was described in literature. The model only requires basic properties of the gas such as the critical field strength and the effective ionization coefficient, which can be obtained by swarm parameter measurements, and thermodynamic properties, which can be calculated. In this paper, we show for the well-known and electronegative gas octafluoropropane (C3F8) that it is possible to transfer the model developed for SF6 to this gas to describe the breakdown behaviour of C3F8. Thus the model can be beneficial in the screening process of new insulation gases.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Checco, A.; Hofmann, T.; DiMasi, E.

The details of air nanobubble trapping at the interface between water and a nanostructured hydrophobic silicon surface are investigated using X-ray scattering and contact angle measurements. Large-area silicon surfaces containing hexagonally packed, 20 nm wide hydrophobic cavities provide ideal model surfaces for studying the morphology of air nanobubbles trapped inside cavities and its dependence on the cavity depth. Transmission small-angle X-ray scattering measurements show stable trapping of air inside the cavities with a partial water penetration of 5-10 nm into the pores, independent of their large depth variation. This behavior is explained by consideration of capillary effects and the cavitymore » geometry. For parabolic cavities, the liquid can reach a thermodynamically stable configuration - a nearly planar nanobubble meniscus - by partially penetrating into the pores. This microscopic information correlates very well with the macroscopic surface wetting behavior.« less

Investigation of uranium plasma emission from 1050 to 6000 A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mack, J.M. Jr.

1977-12-01

Absolute emission coefficient measurements on arc-generated uranium plasmas in local thermodynamic equilibrium are described for a wavelength bandwidth of 1050 to 6000A. Low- and high-pressure arcs were investigated for their emission properties, characteristic temperatures and uranium partial pressures. Temperatures from 5500 to 8000 K and uranium partial pressures from 0.001 to 0.01 atm were found at the arc centerline. The new emission data are compared with other similar experimental results and to existing theoretical calculations. The effects of cold-layer UF/sub 6/ photoabsorption on uranium plasma emission characteristics are established for UF/sub 6/ molecular densities ranging from 1.0 x 10/sup 16/more » to 1.0 x 10/sup 17/ cm/sup -3/ and layer thickness from 1.0 to 5.0 cm.« less

Vulnerability of Space Station Freedom Modules: A Study of the Effects of Module Perforation on Crew and Equipment. Volume 2; Analytical Modeling of Internal Debris Cloud Effects

NASA Technical Reports Server (NTRS)

Schonberg, William P.; Davenport, Quint

1995-01-01

In this part of the report, a first-principles based model is developed to predict the overpressure and temperature effects of a perforating orbital debris particle impact within a pressurized habitable module. While the effects of a perforating debris particles on crew and equipment can be severe, only a limited number of empirical studies focusing on space vehicles have been performed to date. Traditionally, crew loss or incapacitation due to a perforating impact has primarily been of interest to military organizations and as such have focused on military vehicles and systems. The module wall considered in this study is initially assumed to be a standard Whippletype dual-wall system in which the outer wall protects the module and its inhabitants by disrupting impacting particles. The model is developed in a way such that it sequentially characterizes the phenomena comprising the impact event, including the initial impact, the creation and motion of a debris cloud within the dual-wall system, the impact of the debris cloud on the inner wall, the creation and motion of the debris cloud that enters the module interior, and the effects of the debris cloud within the module on module pressure and temperature levels. This is accomplished through the application of elementary shock physics and thermodynamic theory.

Hybrid Parallelization of Adaptive MHD-Kinetic Module in Multi-Scale Fluid-Kinetic Simulation Suite

DOE PAGES

Borovikov, Sergey; Heerikhuisen, Jacob; Pogorelov, Nikolai

2013-04-01

The Multi-Scale Fluid-Kinetic Simulation Suite has a computational tool set for solving partially ionized flows. In this paper we focus on recent developments of the kinetic module which solves the Boltzmann equation using the Monte-Carlo method. The module has been recently redesigned to utilize intra-node hybrid parallelization. We describe in detail the redesign process, implementation issues, and modifications made to the code. Finally, we conduct a performance analysis.

Interactions of urea with native and unfolded proteins: a volumetric study.

PubMed

Son, Ikbae; Shek, Yuen Lai; Tikhomirova, Anna; Baltasar, Eduardo Hidalgo; Chalikian, Tigran V

2014-11-26

We describe a statistical thermodynamic approach to analyzing urea-dependent volumetric properties of proteins. We use this approach to analyze our urea-dependent data on the partial molar volume and adiabatic compressibility of lysozyme, apocytochrome c, ribonuclease A, and α-chymotrypsinogen A. The analysis produces the thermodynamic properties of elementary urea-protein association reactions while also yielding estimates of the effective solvent-accessible surface areas of the native and unfolded protein states. Lysozyme and apocytochrome c do not undergo urea-induced transitions. The former remains folded, while the latter is unfolded between 0 and 8 M urea. In contrast, ribonuclease A and α-chymotrypsinogen A exhibit urea-induced unfolding transitions. Thus, our data permit us to characterize urea-protein interactions in both the native and unfolded states. We interpreted the urea-dependent volumetric properties of the proteins in terms of the equilibrium constant, k, and changes in volume, ΔV0, and compressibility, ΔKT0, for a reaction in which urea binds to a protein with a concomitant release of two waters of hydration to the bulk. Comparison of the values of k, ΔV0, and ΔKT0 with the similar data obtained on small molecules mimicking protein groups reveals lack of cooperative effects involved in urea-protein interactions. In general, the volumetric approach, while providing a unique characterization of cosolvent-protein interactions, offers a practical way for evaluating the effective solvent accessible surface area of biologically significant fully or partially unfolded polypeptides.

Some general remarks on hyperplasticity modelling and its extension to partially saturated soils

NASA Astrophysics Data System (ADS)

Lei, Xiaoqin; Wong, Henry; Fabbri, Antonin; Bui, Tuan Anh; Limam, Ali

2016-06-01

The essential ideas and equations of classic plasticity and hyperplasticity are successively recalled and compared, in order to highlight their differences and complementarities. The former is based on the mathematical framework proposed by Hill (The mathematical theory of plasticity. Oxford University Press, Oxford, 1950), whereas the latter is founded on the orthogonality hypothesis of Ziegler (An introduction to thermomechanics. Elsevier, North-Holland, 1983). The main drawback of classic plasticity is the possibility of violating the second principle of thermodynamics, while the relative ease to conjecture the yield function in order to approach experimental results is its main advantage. By opposition, the a priori satisfaction of thermodynamic principles constitutes the chief advantage of hyperplasticity theory. Noteworthy is also the fact that this latter approach allows a finer energy partition; in particular, the existence of frozen energy emerges as a natural consequence from its theoretical formulation. On the other hand, the relative difficulty to conjecture an efficient dissipation function to produce accurate predictions is its main drawback. The two theories are thus better viewed as two complementary approaches. Following this comparative study, a methodology to extend the hyperplasticity approach initially developed for dry or saturated materials to the case of partially saturated materials, accounting for interface energies and suction effects, is developed. A particular example based on the yield function of modified Cam-Clay model is then presented. It is shown that the approach developed leads to a model consistent with other existing works.

Thermodynamic properties of calcium-bismuth alloys determined by emf measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, H; Boysen, DA; Bradwell, DJ

2012-01-15

The thermodynamic properties of Ca-Bi alloys were determined by electromotive force (emf) measurements to assess the suitability of Ca-Bi electrodes for electrochemical energy storage applications. Emf was measured at ambient pressure as a function of temperature between 723 K and 1173 K using a Ca(s)vertical bar CaF2(s)vertical bar Ca(in Bi) cell for twenty different Ca-Bi alloys spanning the entire range of composition from chi(Ca) = 0 to 1. Reported are the temperature-independent partial molar entropy and enthalpy of calcium for each Ca-Bi alloy. Also given are the measured activities of calcium, the excess partial molar Gibbs energy of bismuth estimatedmore » from the Gibbs-Duhem equation, and the integral change in Gibbs energy for each Ca-Bi alloy at 873 K, 973 K, and 1073 K. Calcium activities at 973 K were found to be nearly constant at a value a(Ca) = 1 x 10(-8) over the composition range chi(Ca) = 0.32-0.56, yielding an emf of similar to 0.77 V. Above chi(Ca) = 0.62 and coincident with Ca5Bi3 formation, the calcium activity approached unity. The Ca-Bi system was also characterized by differential scanning calorimetry over the entire range of composition. Based upon these data along with the emf measurements, a revised Ca-Bi binary phase diagram is proposed. (C) 2011 Elsevier Ltd. All rights reserved.« less

Modeling solubility of CO2/hydrocarbon gas in ionic liquid ([emim][FAP]) using Aspen Plus simulations.

PubMed

Bagchi, Bishwadeep; Sati, Sushmita; Shilapuram, Vidyasagar

2017-08-01

The Peng-Robinson equation of state with quadratic van der Waals (vdW) mixing rule model was chosen to perform the thermodynamic calculations in Flash3 column of Aspen Plus to predict the solubility of CO 2 or any one of the hydrocarbons (HCs) among methane, ethane, propane, and butane in an ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate ([emim][FAP]). Bubble point pressure, solubility, bubble point temperature, fugacity, and partial molar volume at infinite dilution were obtained from the simulations, and enthalpy of absorption, Gibbs free energy of solvation, and entropy change of absorption were estimated by thermodynamic relations. Results show that carbon chain length has a significant effect on the bubble point pressure. Methane has the highest bubble point pressure among all the considered HCs and CO 2 . The bubble point pressure and fugacity variation with temperature is different for CO 2 as compared to HCs for mole fractions above 0.2. Two different profiles are noticed for enthalpy of absorption when plotted as a function of mole fraction of gas soluble in IL. Partial molar volume of CO 2 decreases with increase in temperature in [emim][FAP], while it is increased for HCs. Bubble point temperature decreases with increase in the mole fraction of the solute. Entropy of solvation increases with temperature till a particular value followed by a decrease with further increase in temperature. Gibbs free energy change of solvation showed that the process of solubility was spontaneous.

Towards driving mantle convection by mineral physics

NASA Astrophysics Data System (ADS)

Piazzoni, A. S.; Bunge, H.; Steinle-Neumann, G.

2005-12-01

Models of mantle convection have become increasingly sophisticated over the past decade, accounting, for example, for 3 D spherical geometry, and changes in mantle rheology due to variations in temperature and stress. In light of such advances it is surprising that growing constraints on mantle structure derived from mineral physics have not yet been fully brought to bear on mantle convection models. In fact, despite much progress in our understanding of mantle mineralogy a partial description of the equation of state is often used to relate density changes to pressure and temperature alone, without taking into account compositional and mineralogical models of the mantle. Similarly, for phase transitions an incomplete description of thermodynamic constraints is often used, resulting in significant uncertainties in model behavior. While a number of thermodynamic models (some with limited scope) have been constructed recently, some lack the rigor in thermodynamics - for example with respect to the treatment of solid solution - that is needed to make predictions about mantle structure. Here we have constructed a new thermodynamic database for the mantle and have coupled the resulting density dynamically with mantle convection models. The database is build on a self-consistent Gibb's free energy minimization of the system MgO-FeO-SiO2-CaO-Al2O3 that is appropriate for standard (dry) chemical models of the Earth's mantle for relevant high pressure and temperature phases. We have interfaced the database with a high-resolution 2-D convection code (2DTERRA), dynamically coupling the thermodynamic model (density) with the conservation equations of mantle flow. The coupled model is run for different parameterizations of viscosity, initial temperature conditions, and varying the internal vs. external heating. We compare the resulting flow and temperature fields to cases with the Boussinesq approximation and other classical descriptions of the equation of state in mantle dynamics to assess the influence of realistic mineralogical density on mantle convection.

Partial Genetic Deletion of Neuregulin 1 Modulates the Effects of Stress on Sensorimotor Gating, Dendritic Morphology, and HPA Axis Activity in Adolescent Mice

PubMed Central

Chohan, Tariq W.; Boucher, Aurelie A.; Spencer, Jarrah R.; Kassem, Mustafa S.; Hamdi, Areeg A.; Karl, Tim; Fok, Sandra Y.; Bennett, Maxwell R.; Arnold, Jonathon C.

2014-01-01

Stress has been linked to the pathogenesis of schizophrenia. Genetic variation in neuregulin 1 (NRG1) increases the risk of developing schizophrenia and may help predict which high-risk individuals will transition to psychosis. NRG1 also modulates sensorimotor gating, a schizophrenia endophenotype. We used an animal model to demonstrate that partial genetic deletion of Nrg1 interacts with stress to promote neurobehavioral deficits of relevance to schizophrenia. Nrg1 heterozygous (HET) mice displayed greater acute stress-induced anxiety-related behavior than wild-type (WT) mice. Repeated stress in adolescence disrupted the normal development of higher prepulse inhibition of startle selectively in Nrg1 HET mice but not in WT mice. Further, repeated stress increased dendritic spine density in pyramidal neurons of the medial prefrontal cortex (mPFC) selectively in Nrg1 HET mice. Partial genetic deletion of Nrg1 also modulated the adaptive response of the hypothalamic-pituitary-adrenal axis to repeated stress, with Nrg1 HET displaying a reduced repeated stress-induced level of plasma corticosterone than WT mice. Our results demonstrate that Nrg1 confers vulnerability to repeated stress-induced sensorimotor gating deficits, dendritic spine growth in the mPFC, and an abberant endocrine response in adolescence. PMID:24442851

BurnMan: Towards a multidisciplinary toolkit for reproducible deep Earth science

NASA Astrophysics Data System (ADS)

Myhill, R.; Cottaar, S.; Heister, T.; Rose, I.; Unterborn, C. T.; Dannberg, J.; Martin-Short, R.

2016-12-01

BurnMan (www.burnman.org) is an open-source toolbox to compute thermodynamic and thermoelastic properties as a function of pressure and temperature using published mineral physical parameters and equations-of-state. The framework is user-friendly, written in Python, and modular, allowing the user to implement their own equations of state, endmember and solution model libraries, geotherms, and averaging schemes. Here we introduce various new modules, which can be used to: Fit thermodynamic variables to data from high pressure static and shock wave experiments, Calculate equilibrium assemblages given a bulk composition, pressure and temperature, Calculate chemical potentials and oxygen fugacities for given assemblages Compute 3D synthetic seismic models using output from geodynamic models and compare these results with global seismic tomographic models, Create input files for synthetic seismogram codes. Users can contribute scripts that reproduce the results from peer-reviewed articles and practical demonstrations (e.g. Cottaar et al., 2014).

Nonlinear machine learning and design of reconfigurable digital colloids.

PubMed

Long, Andrew W; Phillips, Carolyn L; Jankowksi, Eric; Ferguson, Andrew L

2016-09-14

Digital colloids, a cluster of freely rotating "halo" particles tethered to the surface of a central particle, were recently proposed as ultra-high density memory elements for information storage. Rational design of these digital colloids for memory storage applications requires a quantitative understanding of the thermodynamic and kinetic stability of the configurational states within which information is stored. We apply nonlinear machine learning to Brownian dynamics simulations of these digital colloids to extract the low-dimensional intrinsic manifold governing digital colloid morphology, thermodynamics, and kinetics. By modulating the relative size ratio between halo particles and central particles, we investigate the size-dependent configurational stability and transition kinetics for the 2-state tetrahedral (N = 4) and 30-state octahedral (N = 6) digital colloids. We demonstrate the use of this framework to guide the rational design of a memory storage element to hold a block of text that trades off the competing design criteria of memory addressability and volatility.

Automation of data processing and calculation of retention parameters and thermodynamic data for gas chromatography

NASA Astrophysics Data System (ADS)

Makarycheva, A. I.; Faerman, V. A.

2017-02-01

The analyses of automation patterns is performed and the programming solution for the automation of data processing of the chromatographic data and their further information storage with a help of a software package, Mathcad and MS Excel spreadsheets, is developed. The offered approach concedes the ability of data processing algorithm modification and does not require any programming experts participation. The approach provides making a measurement of the given time and retention volumes, specific retention volumes, a measurement of differential molar free adsorption energy, and a measurement of partial molar solution enthalpies and isosteric heats of adsorption. The developed solution is focused on the appliance in a small research group and is tested on the series of some new gas chromatography sorbents. More than 20 analytes were submitted to calculation of retention parameters and thermodynamic sorption quantities. The received data are provided in the form accessible to comparative analysis, and they are able to find sorbing agents with the most profitable properties to solve some concrete analytic issues.

Integrated Experimental and Modelling Research for Non-Ferrous Smelting and Recycling Systems

NASA Astrophysics Data System (ADS)

Jak, Evgueni; Hidayat, Taufiq; Shishin, Denis; Mehrjardi, Ata Fallah; Chen, Jiang; Decterov, Sergei; Hayes, Peter

The chemistries of industrial pyrometallurgical non-ferrous smelting and recycling processes are becoming increasingly complex. Optimisation of process conditions, charge composition, temperature, oxygen partial pressure, and partitioning of minor elements between phases and different process streams require accurate description of phase equilibria and thermodynamics which are the focus of the present research. The experiments involve high temperature equilibration in controlled gas atmospheres, rapid quenching and direct measurement of equilibrium phase compositions with quantitative microanalytical techniques including electron probe X-ray microanalysis and Laser Ablation ICP-MS. The thermodynamic modelling is undertaken using computer package FactSage with the quasi-chemical model for the liquid slag phase and other advanced models. Experimental and modelling studies are combined into an integrated research program focused on the major elements Cu-Pb-Fe-O-Si-S system, slagging Al, Ca, Mg and other minor elements. The ongoing development of the research methodologies has resulted in significant advances in research capabilities. Examples of applications are given.

Fulde-Ferrell-Larkin-Ovchinnikov correlation and free fluids in the one-dimensional attractive Hubbard model

NASA Astrophysics Data System (ADS)

Cheng, Song; Yu, Yi-Cong; Batchelor, M. T.; Guan, Xi-Wen

2018-03-01

In this Rapid Communication, we show that low-energy macroscopic properties of the one-dimensional (1D) attractive Hubbard model exhibit two fluids of bound pairs and of unpaired fermions. Using the thermodynamic Bethe ansatz equations of the model, we first determine the low-temperature phase diagram and analytically calculate the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing correlation function for the partially polarized phase. We then show that for such an FFLO-like state in the low-density regime the effective chemical potentials of bound pairs and unpaired fermions behave like two free fluids. Consequently, the susceptibility, compressibility, and specific heat obey simple additivity rules, indicating the "free" particle nature of interacting fermions on a 1D lattice. In contrast to the continuum Fermi gases, the correlation critical exponents and thermodynamics of the attractive Hubbard model essentially depend on two lattice interacting parameters. Finally, we study scaling functions, the Wilson ratio and susceptibility, which provide universal macroscopic properties and dimensionless constants of interacting fermions at low energy.

Roles of water in protein structure and function studied by molecular liquid theory.

PubMed

Imai, Takashi

2009-01-01

The roles of water in the structure and function of proteins have not been completely elucidated. Although molecular simulation has been widely used for the investigation of protein structure and function, it is not always useful for elucidating the roles of water because the effect of water ranges from atomic to thermodynamic level. The three-dimensional reference interaction site model (3D-RISM) theory, which is a statistical-mechanical theory of molecular liquids, can yield the solvation structure at the atomic level and calculate the thermodynamic quantities from the intermolecular potentials. In the last few years, the author and coworkers have succeeded in applying the 3D-RISM theory to protein aqueous solution systems and demonstrated that the theory is useful for investigating the roles of water. This article reviews some of the recent applications and findings, which are concerned with molecular recognition by protein, protein folding, and the partial molar volume of protein which is related to the pressure effect on protein.

Energy and exergy analysis of an ethanol reforming process for solid oxide fuel cell applications.

PubMed

Tippawan, Phanicha; Arpornwichanop, Amornchai

2014-04-01

The fuel processor in which hydrogen is produced from fuels is an important unit in a fuel cell system. The aim of this study is to apply a thermodynamic concept to identify a suitable reforming process for an ethanol-fueled solid oxide fuel cell (SOFC). Three different reforming technologies, i.e., steam reforming, partial oxidation and autothermal reforming, are considered. The first and second laws of thermodynamics are employed to determine an energy demand and to describe how efficiently the energy is supplied to the reforming process. Effect of key operating parameters on the distribution of reforming products, such as H2, CO, CO2 and CH4, and the possibility of carbon formation in different ethanol reformings are examined as a function of steam-to-ethanol ratio, oxygen-to-ethanol ratio and temperatures at atmospheric pressure. Energy and exergy analysis are performed to identify the best ethanol reforming process for SOFC applications. Copyright © 2014 Elsevier Ltd. All rights reserved.

An approach to get thermodynamic properties from speed of sound

NASA Astrophysics Data System (ADS)

Núñez, M. A.; Medina, L. A.

2017-01-01

An approach for estimating thermodynamic properties of gases from the speed of sound u, is proposed. The square u2, the compression factor Z and the molar heat capacity at constant volume C V are connected by two coupled nonlinear partial differential equations. Previous approaches to solving this system differ in the conditions used on the range of temperature values [Tmin,Tmax]. In this work we propose the use of Dirichlet boundary conditions at Tmin, Tmax. The virial series of the compression factor Z = 1+Bρ+Cρ2+… and other properties leads the problem to the solution of a recursive set of linear ordinary differential equations for the B, C. Analytic solutions of the B equation for Argon are used to study the stability of our approach and previous ones under perturbation errors of the input data. The results show that the approach yields B with a relative error bounded basically by that of the boundary values and the error of other approaches can be some orders of magnitude lager.

Thermodynamic Analysis for the Refining Ability of Salt Flux for Aluminum Recycling

PubMed Central

Hiraki, Takehito; Miki, Takahiro; Nakajima, Kenichi; Matsubae, Kazuyo; Nakamura, Shinichiro; Nagasaka, Tetsuya

2014-01-01

The removability of impurities during the aluminum remelting process by oxidation was previously investigated by our research group. In the present work, alternative impurity removal with chlorination has been evaluated by thermodynamic analysis. For 43 different elements, equilibrium distribution ratios among metal, chloride flux and oxide slag phases in the aluminum remelting process were calculated by assuming the binary systems of aluminum and an impurity element. It was found that the removability of impurities isn’t significantly affected by process parameters such as chloride partial pressure, temperature and flux composition. It was shown that Ho, Dy, Li, La, Mg, Gd, Ce, Yb, Ca and Sr can be potentially eliminated into flux by chlorination from the remelted aluminum. Chlorination and oxidation are not effective to remove other impurities from the melting aluminum, due to the limited parameters which can be controlled during the remelting process. It follows that a proper management of aluminum scrap such as sorting based on the composition of the products is important for sustainable aluminum recycling. PMID:28788144

Overcoming the Cutaneous Barrier with Microemulsions

PubMed Central

Lopes, Luciana B.

2014-01-01

Microemulsions are fluid and isotropic formulations that have been widely studied as delivery systems for a variety of routes, including the skin. In spite of what the name suggests, microemulsions are nanocarriers, and their use as topical delivery systems derives from their multiple advantages compared to other dermatological formulations, such as ease of preparation, thermodynamic stability and penetration-enhancing properties. Composition, charge and internal structure have been reported as determinant factors for the modulation of drug release and cutaneous and transdermal transport. This manuscript aims at reviewing how these and other characteristics affect delivery and make microemulsions appealing for topical and transdermal administration, as well as how they can be modulated during the formulation design to improve the potential and efficacy of the final system. PMID:24590260

A Digital Map From External Forcing to the Final Surface Warming Pattern and its Seasonal Cycle

NASA Astrophysics Data System (ADS)

Cai, M.

2015-12-01

Historically, only the thermodynamic processes (e.g., water vapor, cloud, surface albedo, and atmospheric lapse rate) that directly influence the top of the atmosphere (TOA) radiative energy flux balance are considered in climate feedback analysis. One of my recent research areas is to develop a new framework for climate feedback analysis that explicitly takes into consideration not only the thermodynamic processes that the directly influence the TOA radiative energy flux balance but also the local dynamical (e.g., evaporation, surface sensible heat flux, vertical convections etc) and non-local dynamical (large-scale horizontal energy transport) processes in aiming to explain the warming asymmetry between high and low latitudes, between ocean and land, and between the surface and atmosphere. In the last 5-6 years, we have developed a coupled atmosphere-surface climate feedback-response analysis method (CFRAM) as a new framework for estimating climate feedback and sensitivity in coupled general circulation models with a full physical parameterization package. In the CFRAM, the isolation of partial temperature changes due to an external forcing alone or an individual feedback is achieved by solving the linearized infrared radiation transfer model subject to individual energy flux perturbations (external or due to feedbacks). The partial temperature changes are addable and their sum is equal to the (total) temperature change (in the linear sense). The CFRAM is used to isolate the partial temperature changes due to the external forcing, due to water vapor feedback, clouds, surface albedo, local vertical convection, and non-local atmospheric dynamical feedbacks, as well as oceanic heat storage. It has been shown that seasonal variations in the cloud feedback, surface albedo feedback, and ocean heat storage/dynamics feedback, directly caused by the strong annual cycle of insolation, contribute primarily to the large seasonal variation of polar warming. Furthermore, the CO2 forcing, and water vapor and atmospheric dynamics feedbacks add to the maximum polar warming in fall/winter.

Sulfuric Acid Monohydrate: Formation and Heterogeneous Chemistry in the Stratosphere

NASA Technical Reports Server (NTRS)

Zhang, Renyi; Leu, Ming-Taun; Keyser, Leon F.

1995-01-01

We have investigated some thermodynamic properties (i.e., freezing/melting points) and heterogeneous chemistry of sulfuric acid monohydrate (SAM, H2SO4.H2O), using a fast flow reactor coupled to a quadrupole mass spectrometer. The freezing point observations of thin liquid sulfuric acid films show that for acid contents between 75 and 85 wt % the monohydrate crystallizes readily at temperatures between 220 and 240 K on a glass substrate. Once formed, SAM can be thermodynamically stable in the H2O partial pressure range of (1-4) x 10(exp -4) torr and in the temperature range of 220-240 K. For a constant H2O partial pressure, lowering the temperature causes SAM to melt when the temperature and water partial pressure conditions are out of its stability regime. The reaction probability measurements indicate that the hydrolysis of N2O5 is significantly suppressed owing to the formation of crystalline SAM: The reaction probability on water-rich SAM (with higher relative humidity, or RH) is of the order of 10(exp -3) at 210 K and decreases by more than an order of magnitude for the acid-rich form (with lower RH). The hydrolysis rate of ClONO2 on water-rich SAM is even smaller, of the order of 10(exp -4) at 195 K. These reported values on crystalline SAM are much smaller than those on liquid solutions. No enhancement of these reactions is observed in the presence of HCl vapor at the stratospheric concentrations. In addition, Brunauer, Emmett, and Teller analysis of gas adsorption isotherms and photomicrography have been performed to characterize the surface roughness and porosities of the SAM substrate. The results suggest the possible formation of SAM in some regions of the middle- or low-latitude stratosphere and, consequently, much slower heterogeneous reactions on the frozen aerosols.

Steam tables for pure water as an ActiveX component in Visual Basic 6.0

NASA Astrophysics Data System (ADS)

Verma, Mahendra P.

2003-11-01

The IAPWS-95 formulation for the thermodynamic properties of pure water was implemented as an ActiveX component ( SteamTables) in Visual Basic 6.0. For input parameters as temperature ( T=190-2000 K) and pressure ( P=3.23×10 -8-10,000 MPa) the program SteamTables calculates the following properties: volume ( V), density ( D), compressibility factor ( Z0), internal energy ( U), enthalpy ( H), Gibbs free energy ( G), Helmholtz free energy ( A), entropy ( S), heat capacity at constant pressure ( Cp), heat capacity at constant volume ( Cv), coefficient of thermal expansion ( CTE), isothermal compressibility ( Ziso), velocity of sound ( VelS), partial derivative of P with T at constant V (d Pd T), partial derivative of T with V at constant P (d Td V), partial derivative of V with P at constant T (d Vd P), Joule-Thomson coefficient ( JTC), isothermal throttling coefficient ( IJTC), viscosity ( Vis), thermal conductivity ( ThrmCond), surface tension ( SurfTen), Prandtl number ( PrdNum) and dielectric constant ( DielCons) for the liquid and vapor phases of pure water. It also calculates T as a function of P (or P as a function of T) along the sublimation, saturation and critical isochor curves, depending on the values of P (or T). The SteamTables can be incorporated in a program in any computer language, which supports object link embedding (OLE) in the Windows environment. An application of SteamTables is illustrated in a program in Visual Basic 6.0 to tabulate the values of the thermodynamic properties of water and vapor. Similarly, four functions, Temperature(Press), Pressure(Temp), State(Temp, Press) and WtrStmTbls(Temp, Press, Nphs, Nprop), where Temp, Press, Nphs and Nprop are temperature, pressure, phase number and property number, respectively, are written in Visual Basic for Applications (VBA) to use the SteamTables in a workbook in MS-Excel.

Thermodynamics Behavior of Germanium During Equilibrium Reactions between FeOx-CaO-SiO2-MgO Slag and Molten Copper

NASA Astrophysics Data System (ADS)

Shuva, M. A. H.; Rhamdhani, M. A.; Brooks, G. A.; Masood, S.; Reuter, M. A.

2016-10-01

The distribution ratio of germanium (Ge), L_{{Ge}}^{s/m} during equilibrium reactions between magnesia-saturated FeOx-CaO-SiO2 (FCS) slag and molten copper has been measured under oxygen partial pressures from 10-10 to 10-7 atm and at temperatures 1473 to 1623 K (1200 to 1350 °C). It was observed that the Ge distribution ratio increases with increasing oxygen partial pressure, and with decreasing temperature. It was also observed that the distribution ratio is strongly dependent on slag basicity. The distribution ratio was observed to increase with increasing optical basicity. At fixed CaO concentration in the slag, the distribution ratio was found to increase with increasing Fe/SiO2 ratio, tending to a plateau at L_{{Ge}}^{s/m} = 0.8. This behavior is consistent with the assessment of ionic bond fraction carried out in this study, and suggested the acidic nature of germanium oxide (GeO2) in the slag system studied. The characterisation results of the quenched slag suggested that Ge is present in the FeOx-CaO-SiO2-MgO slag predominantly as GeO2. At 1573 K (1300 °C) and p_{{{{O}}2 }} = 10-8 atm, the activity coefficient of GeO2 in the slag was calculated to be in the range of 0.24 to 1.50. The results from the current study suggested that less-basic slag, high operating temperature, and low oxygen partial pressure promote a low Ge distribution ratio. These conditions are desired for maximizing Ge recovery, for example, during pyrometallurgical processing of Ge-containing e-waste through secondary copper smelting. Overall, the thermodynamics data generated from this study can be used for process modeling purposes for improving recovery of Ge in primary and secondary copper smelting processes.

Simulation, measurement, and emulation of photovoltaic modules using high frequency and high power density power electronic circuits

NASA Astrophysics Data System (ADS)

Erkaya, Yunus

The number of solar photovoltaic (PV) installations is growing exponentially, and to improve the energy yield and the efficiency of PV systems, it is necessary to have correct methods for simulation, measurement, and emulation. PV systems can be simulated using PV models for different configurations and technologies of PV modules. Additionally, different environmental conditions of solar irradiance, temperature, and partial shading can be incorporated in the model to accurately simulate PV systems for any given condition. The electrical measurement of PV systems both prior to and after making electrical connections is important for attaining high efficiency and reliability. Measuring PV modules using a current-voltage (I-V) curve tracer allows the installer to know whether the PV modules are 100% operational. The installed modules can be properly matched to maximize performance. Once installed, the whole system needs to be characterized similarly to detect mismatches, partial shading, or installation damage before energizing the system. This will prevent any reliability issues from the onset and ensure the system efficiency will remain high. A capacitive load is implemented in making I-V curve measurements with the goal of minimizing the curve tracer volume and cost. Additionally, the increase of measurement resolution and accuracy is possible via the use of accurate voltage and current measurement methods and accurate PV models to translate the curves to standard testing conditions. A move from mechanical relays to solid-state MOSFETs improved system reliability while significantly reducing device volume and costs. Finally, emulating PV modules is necessary for testing electrical components of a PV system. PV emulation simplifies and standardizes the tests allowing for different irradiance, temperature and partial shading levels to be easily tested. Proper emulation of PV modules requires an accurate and mathematically simple PV model that incorporates all known system variables so that any PV module can be emulated as the design requires. A non-synchronous buck converter is proposed for the emulation of a single, high-power PV module using traditional silicon devices. With the proof-of-concept working and improvements in efficiency, power density and steady-state errors made, dynamic tests were performed using an inverter connected to the PV emulator. In order to improve the dynamic characteristics, a synchronous buck converter topology is proposed along with the use of advanced GaNFET devices which resulted in very high power efficiency and improved dynamic response characteristics when emulating PV modules.

Vacancies and holes in bulk and at 180° domain walls in lead titanate

NASA Astrophysics Data System (ADS)

Paillard, Charles; Geneste, Grégory; Bellaiche, Laurent; Dkhil, Brahim

2017-12-01

Domain walls (DWs) in ferroic materials exhibit a plethora of unexpected properties that are different from the adjacent ferroic domains. Still, the intrinsic/extrinsic origin of these properties remains an open question. Here, density functional theory calculations are used to investigate the interaction between vacancies and 180° DWs in the prototypical ferroelectric PbTiO3, with a special emphasis on cationic vacancies and released holes. All vacancies are more easily formed within the DW than in the domains. This is interpreted, using a phenomenological model, as the partial compensation of an extra-tensile stress when the defect is created inside the DW. Oxygen vacancies are found to be always fully ionized, independently of the thermodynamic conditions, while cationic vacancies can be either neutral or partially ionized (oxygen-rich conditions), or fully ionized (oxygen-poor conditions). Therefore, in oxidizing conditions, holes are induced by neutral and partially ionized Pb vacancies. In the bulk PbTiO3, these holes are more stable as delocalized rather than small polarons, but at DWs, the two forms are found to be possible.

CNGA3 achromatopsia-associated mutation potentiates the phosphoinositide sensitivity of cone photoreceptor CNG channels by altering intersubunit interactions

PubMed Central

Dai, Gucan

2013-01-01

Cyclic nucleotide-gated (CNG) channels are critical for sensory transduction in retinal photoreceptors and olfactory receptor cells; their activity is modulated by phosphoinositides (PIPn) such as phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-trisphosphate (PIP3). An achromatopsia-associated mutation in cone photoreceptor CNGA3, L633P, is located in a carboxyl (COOH)-terminal leucine zipper domain shown previously to be important for channel assembly and PIPn regulation. We determined the functional consequences of this mutation using electrophysiological recordings of patches excised from cells expressing wild-type and mutant CNG channel subunits. CNGA3-L633P subunits formed functional channels with or without CNGB3, producing an increase in apparent cGMP affinity. Surprisingly, L633P dramatically potentiated PIPn inhibition of apparent cGMP affinity for these channels. The impact of L633P on PIPn sensitivity depended on an intact amino (NH2) terminal PIPn regulation module. These observations led us to hypothesize that L633P enhances PIPn inhibition by altering the coupling between NH2- and COOH-terminal regions of CNGA3. A recombinant COOH-terminal fragment partially restored normal PIPn sensitivity to channels with COOH-terminal truncation, but L633P prevented this effect. Furthermore, coimmunoprecipitation of channel fragments, and thermodynamic linkage analysis, also provided evidence for NH2-COOH interactions. Finally, tandem dimers of CNGA3 subunits that specify the arrangement of subunits containing L633P and other mutations indicated that the putative interdomain interaction occurs between channel subunits (intersubunit) rather than exclusively within the same subunit (intrasubunit). Collectively, these studies support a model in which intersubunit interactions control the sensitivity of cone CNG channels to regulation by phosphoinositides. Aberrant channel regulation may contribute to disease progression in patients with the L633P mutation. PMID:23552282

CNGA3 achromatopsia-associated mutation potentiates the phosphoinositide sensitivity of cone photoreceptor CNG channels by altering intersubunit interactions.

PubMed

Dai, Gucan; Varnum, Michael D

2013-07-15

Cyclic nucleotide-gated (CNG) channels are critical for sensory transduction in retinal photoreceptors and olfactory receptor cells; their activity is modulated by phosphoinositides (PIPn) such as phosphatidylinositol 4,5-bisphosphate (PIP2) and phosphatidylinositol 3,4,5-trisphosphate (PIP3). An achromatopsia-associated mutation in cone photoreceptor CNGA3, L633P, is located in a carboxyl (COOH)-terminal leucine zipper domain shown previously to be important for channel assembly and PIPn regulation. We determined the functional consequences of this mutation using electrophysiological recordings of patches excised from cells expressing wild-type and mutant CNG channel subunits. CNGA3-L633P subunits formed functional channels with or without CNGB3, producing an increase in apparent cGMP affinity. Surprisingly, L633P dramatically potentiated PIPn inhibition of apparent cGMP affinity for these channels. The impact of L633P on PIPn sensitivity depended on an intact amino (NH2) terminal PIPn regulation module. These observations led us to hypothesize that L633P enhances PIPn inhibition by altering the coupling between NH2- and COOH-terminal regions of CNGA3. A recombinant COOH-terminal fragment partially restored normal PIPn sensitivity to channels with COOH-terminal truncation, but L633P prevented this effect. Furthermore, coimmunoprecipitation of channel fragments, and thermodynamic linkage analysis, also provided evidence for NH2-COOH interactions. Finally, tandem dimers of CNGA3 subunits that specify the arrangement of subunits containing L633P and other mutations indicated that the putative interdomain interaction occurs between channel subunits (intersubunit) rather than exclusively within the same subunit (intrasubunit). Collectively, these studies support a model in which intersubunit interactions control the sensitivity of cone CNG channels to regulation by phosphoinositides. Aberrant channel regulation may contribute to disease progression in patients with the L633P mutation.

A Study of a Standard BIT Circuit.

DTIC Science & Technology

1977-02-01

IENDED BIT APPROACHES FOR QED MODULES AND APPLICATION OF THE ANALYTIC MEASURES 36 4.1 Built-In-Test for Memory Class Modules 37 4.1.1 Random Access...Implementation 68 4.1.5.5 Criti cal Parameters 68 4.1.5.6 QED Module Test Equipment Requirements 68 4.1.6 Application of Analytic Measures to the...Microprocessor BIT Techniques.. 121 4.2.9 Application of Analytic Measures to the Recommended BIT App roaches 125 4.2.10 Process Class BIT by Partial

Discharging a DC bus capacitor of an electrical converter system

DOEpatents

Kajouke, Lateef A; Perisic, Milun; Ransom, Ray M

2014-10-14

A system and method of discharging a bus capacitor of a bidirectional matrix converter of a vehicle are presented here. The method begins by electrically shorting the AC interface of the converter after an AC energy source is disconnected from the AC interface. The method continues by arranging a plurality of switching elements of a second energy conversion module into a discharge configuration to establish an electrical current path from a first terminal of an isolation module, through an inductive element, and to a second terminal of the isolation module. The method also modulates a plurality of switching elements of a first energy conversion module, while maintaining the discharge configuration of the second energy conversion module, to at least partially discharge a DC bus capacitor.

Solar dynamic power for the Space Station

NASA Technical Reports Server (NTRS)

Archer, J. S.; Diamant, E. S.

1986-01-01

This paper describes a computer code which provides a significant advance in the systems analysis capabilities of solar dynamic power modules. While the code can be used to advantage in the preliminary analysis of terrestrial solar dynamic modules its real value lies in the adaptions which make it particularly useful for the conceptualization of optimized power modules for space applications. In particular, as illustrated in the paper, the code can be used to establish optimum values of concentrator diameter, concentrator surface roughness, concentrator rim angle and receiver aperture corresponding to the main heat cycle options - Organic Rankine and Brayton - and for certain receiver design options. The code can also be used to establish system sizing margins to account for the loss of reflectivity in orbit or the seasonal variation of insolation. By the simulation of the interactions among the major components of a solar dynamic module and through simplified formulations of the major thermal-optic-thermodynamic interactions the code adds a powerful, efficient and economic analytical tool to the repertory of techniques available for the design of advanced space power systems.

Structure of phospholipid-cholesterol membranes: an x-ray diffraction study.

PubMed

Karmakar, Sanat; Raghunathan, V A

2005-06-01

We have studied the phase behavior of mixtures of cholesterol with dipalmitoyl phosphatidylcholine (DPPC), dimyristoyl phosphatidylcholine (DMPC), and dilauroyl phosphatidylethanolamine (DLPE), using x-ray diffraction techniques. Phosphatidylcholine (PC)-cholesterol mixtures are found to exhibit a modulated phase for cholesterol concentrations around 15 mol % at temperatures below the chain melting transition. Lowering the relative humidity from 98% to 75% increases the temperature range over which it exists. An electron density map of this phase in DPPC-cholesterol mixtures, calculated from the x-ray diffraction data, shows bilayers with a periodic height modulation, as in the ripple phase observed in many PCs in between the main- and pretransitions. However, these two phases differ in many aspects, such as the dependence of the modulation wavelength on the cholesterol content and thermodynamic stability at reduced humidities. This modulated phase is found to be absent in DLPE-cholesterol mixtures. At higher cholesterol contents the gel phase does not occur in any of these three systems, and the fluid lamellar phase is observed down to the lowest temperature studied (5 degrees C).

Finite coupling corrections to holographic predictions for hot QCD

DOE PAGES

Waeber, Sebastian; Schafer, Andreas; Vuorinen, Aleksi; ...

2015-11-13

Finite ’t Hooft coupling corrections to multiple physical observables in strongly coupled N=4 supersymmetric Yang-Mills plasma are examined, in an attempt to assess the stability of the expansion in inverse powers of the ’t Hooft coupling λ. Observables considered include thermodynamic quantities, transport coefficients, and quasinormal mode frequencies. Furthermore large λ expansions for quasinormal mode frequencies are notably less well behaved than the expansions of other quantities, we find that a partial resummation of higher order corrections can significantly reduce the sensitivity of the results to the value of λ.

Direct Logistic Fuel JP-8 Conversion in a Liquid Tin Anode Solid Oxide Fuel Cell (LTA-SOFC)

DTIC Science & Technology

2008-04-09

GeSnOOSn sgl [1] As governed by the Nernst equation Open Circuit Voltage (OCV) is inversely proportional to temperature. The OCV of...inherently stable at 1,000°C. The LTA-SOFC electrochemical reaction is based on the following thermodynamic equation . C1000T kJ 311 42 o)(2... equation 1 is 0.8V at 1000°C, using an oxygen partial pressure of one. This equation gives the OCV for a LTA–SOFC functioning as a battery. The tin oxide

Gesellschaft fuer angewandte Mathematik und Mechanik, Annual Scientific Meeting, Technische Universitaet Berlin, Berlin, West Germany, April 8-11, 1980, Reports. Parts 1 & 2

NASA Astrophysics Data System (ADS)

1981-04-01

The main topics discussed were related to nonparametric statistics, plane and antiplane states in finite elasticity, free-boundary-variational inequalities, the numerical solution of free boundary-value problems, discrete and combinatorial optimization, mathematical modelling in fluid mechanics, a survey and comparison regarding thermodynamic theories, invariant and almost invariant subspaces in linear systems with applications to disturbance isolation, nonlinear acoustics, and methods of function theory in the case of partial differential equations, giving particular attention to elliptic problems in the plane.

Transport-induced shifts in condensate dew-point and composition in multicomponent systems with chemical reaction

NASA Technical Reports Server (NTRS)

Rosner, D. E.; Nagarajan, R.

1985-01-01

Partial heterogeneous condensation phenomena in multicomponent reacting systems are analyzed taking into consideration the chemical element transport phenomena. It is demonstrated that the dew-point surface temperature in chemically reactive systems is not a purely thermodynamic quantity, but is influenced by the multicomponent diffusion and Soret-mass diffusion phenomena. Several distinct dew-points are shown to exist in such systems and, as a result of transport constraints, the 'sharp' locus between two chemically distinct condensates is systematically moved to a difference mainstream composition.

A notable difference between ideal gas and infinite molar volume limit of van der Waals gas

NASA Astrophysics Data System (ADS)

Liu, Q. H.; Shen, Y.; Bai, R. L.; Wang, X.

2010-05-01

The van der Waals equation of state does not sufficiently represent a gas unless a thermodynamic potential with two proper and independent variables is simultaneously determined. The limiting procedures under which the behaviour of the van der Waals gas approaches that of an ideal gas are letting two van der Waals coefficients be zero rather than letting the molar volume become infinitely large; otherwise, the partial derivative of internal energy with respect to pressure at a fixed temperature does not vanish.

Folding-unfolding transitions of Rv3221c on the pressure-temperature plane

NASA Astrophysics Data System (ADS)

Somkuti, Judit; Jain, Sriyans; Ramachandran, Srinivasan; ászló Smeller, L.

2013-06-01

Rv3221c is a biotin-binding protein found in Mycobacterium tuberculosis. It has been reported that an elevated temperature is needed for it to adopt a folded conformation. We determined the complete pressure-temperature phase diagram, and determined the thermodynamical parameters of the denaturation. The phase diagram follows well the Hawley theory. The secondary structure of the protein was found to contain predominantly beta sheet. The pressure unfolding was partially reversible, resulting in pressure-sensitive aggregates, besides the correctly refolded and biotin-bound fraction of proteins.

Role of the Disulfide Bond in Prion Protein Amyloid Formation: A Thermodynamic and Kinetic Analysis.

PubMed

Honda, Ryo

2018-02-27

Prion diseases are associated with the structural conversion of prion protein (PrP) to a β-sheet-rich aggregate, PrP Sc . Previous studies have indicated that a reduction of the disulfide bond linking C179 and C214 of PrP yields an amyloidlike β-rich aggregate in vitro. To gain mechanistic insights into the reduction-induced aggregation, here I characterized how disulfide bond reduction modulates the protein folding/misfolding landscape of PrP, by examining 1) the equilibrium stabilities of the native (N) and aggregated states relative to the unfolded (U) state, 2) the transition barrier separating the U and aggregated states, and 3) the final structure of amyloidlike misfolded aggregates. Kinetic and thermodynamic experiments revealed that disulfide bond reduction decreases the equilibrium stabilities of both the N and aggregated states by ∼3 kcal/mol, without changing either the amyloidlike aggregate structure, at least at the secondary structural level, or the transition barrier of aggregation. Therefore, disulfide bond reduction modulates the protein folding/misfolding landscape by entropically stabilizing disordered states, including the U and transition state of aggregation. This also indicates that the equilibrium stability of the N state, but not the transition barrier of aggregation, is the dominant factor determining the reduction-induced aggregation of PrP. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

NMDA Receptor Modulators in the Treatment of Drug Addiction.

PubMed

Tomek, Seven E; Lacrosse, Amber L; Nemirovsky, Natali E; Olive, M Foster

2013-02-06

Glutamate plays a pivotal role in drug addiction, and the N-methyl-D-aspartate (NMDA) glutamate receptor subtype serves as a molecular target for several drugs of abuse. In this review, we will provide an overview of NMDA receptor structure and function, followed by a review of the mechanism of action, clinical efficacy, and side effect profile of NMDA receptor ligands that are currently in use or being explored for the treatment of drug addiction. These ligands include the NMDA receptor modulators memantine and acamprosate, as well as the partial NMDA agonist D-cycloserine. Data collected to date suggest that direct NMDA receptor modulators have relatively limited efficacy in the treatment of drug addiction, and that partial agonism of NMDA receptors may have some efficacy with regards to extinction learning during cue exposure therapy. However, the lack of consistency in results to date clearly indicates that additional studies are needed, as are studies examining novel ligands with indirect mechanisms for altering NMDA receptor function.

Astronaut Russell Schweickart photographed during EVA

NASA Image and Video Library

1969-03-06

AS09-19-2983 (6 March 1969) --- Astronaut Russell L. Schweickart, lunar module pilot, operates a 70mm Hasselblad camera during his extravehicular activity (EVA) on the fourth day of the Apollo 9 Earth-orbital mission. The Command and Service Modules (CSM) and Lunar Module (LM) "Spider" are docked. This view was taken from the Command Module (CM) "Gumdrop". Schweickart, wearing an Extravehicular Mobility Unit (EMU), is standing in "golden slippers" on the LM porch. On his back, partially visible, are a Portable Life Support System (PLSS) and an Oxygen Purge System (OPS). Astronaut James A. McDivitt, Apollo 9 commander, was inside the "Spider". Astronaut David R. Scott, command module pilot, remained at the controls in the CM.

Modulation format dependence of digital nonlinearity compensation performance in optical fibre communication systems.

PubMed

Xu, Tianhua; Shevchenko, Nikita A; Lavery, Domaniç; Semrau, Daniel; Liga, Gabriele; Alvarado, Alex; Killey, Robert I; Bayvel, Polina

2017-02-20

The relationship between modulation format and the performance of multi-channel digital back-propagation (MC-DBP) in ideal Nyquist-spaced optical communication systems is investigated. It is found that the nonlinear distortions behave independent of modulation format in the case of full-field DBP, in contrast to the cases of electronic dispersion compensation and partial-bandwidth DBP. It is shown that the minimum number of steps per span required for MC-DBP depends on the chosen modulation format. For any given target information rate, there exists a possible trade-off between modulation format and back-propagated bandwidth, which could be used to reduce the computational complexity requirement of MC-DBP.

Imparting albumin-binding affinity to a human protein by mimicking the contact surface of a bacterial binding protein.

PubMed

Oshiro, Satoshi; Honda, Shinya

2014-04-18

Attachment of a bacterial albumin-binding protein module is an attractive strategy for extending the plasma residence time of protein therapeutics. However, a protein fused with such a bacterial module could induce unfavorable immune reactions. To address this, we designed an alternative binding protein by imparting albumin-binding affinity to a human protein using molecular surface grafting. The result was a series of human-derived 6 helix-bundle proteins, one of which specifically binds to human serum albumin (HSA) with adequate affinity (KD = 100 nM). The proteins were designed by transferring key binding residues of a bacterial albumin-binding module, Finegoldia magna protein G-related albumin-binding domain (GA) module, onto the human protein scaffold. Despite 13-15 mutations, the designed proteins maintain the original secondary structure by virtue of careful grafting based on structural informatics. Competitive binding assays and thermodynamic analyses of the best binders show that the binding mode resembles that of the GA module, suggesting that the contacting surface of the GA module is mimicked well on the designed protein. These results indicate that the designed protein may act as an alternative low-risk binding module to HSA. Furthermore, molecular surface grafting in combination with structural informatics is an effective approach for avoiding deleterious mutations on a target protein and for imparting the binding function of one protein onto another.

Thermodynamic characterization of two homologous protein complexes: Associations of the semaphorin receptor plexin-B1 RhoGTPase binding domain with Rnd1 and active Rac1

PubMed Central

Hota, Prasanta K; Buck, Matthias

2009-01-01

Plexin receptors function in response to semaphorin guidance cues in a variety of developmental processes involving cell motility. Interactions with Rho, as well as Ras family small GTPases are critical events in the cell signaling mechanism. We have recently determined the structure of a cytoplasmic domain (RBD) of plexin-B1 and mapped its binding interface with several Rho-GTPases, Rac1, Rnd1, and RhoD. All three GTPases associate with a similar region of this plexin domain, but show different functional behavior in cells. To understand whether thermodynamic properties of the GTPase–RBD interaction contribute to such different behavior, we have examined the interaction at different temperatures, buffer, and pH conditions. Although the binding affinity of both Rnd1 and Rac1 with the plexin-B1 RBD is similar, the detailed thermodynamic properties of the interactions are considerably different. These data suggest that on Rac1 binding to the plexin-B1 RBD, the proteins become more rigid in the complex. By contrast, Rnd1 binding is consistent with unchanged or slightly increased flexibility in one or both proteins. Both GTPases show an appreciable reduction in affinity for the dimeric plexin-B1 RBD indicating that GTPase binding is not cooperative with dimer formation, but that a partial steric hindrance destabilizes the dimer. However, a reduced affinity binding mode to a disulphide stabilized model for the dimeric RBD is also possible. Consistent with cellular studies, the interaction thermodynamics imply that further levels of regulation involving additional binding partners and/or regions outside of the RhoGTPase binding domain are required for receptor activation. PMID:19388051

Maier-Saupe model of polymer nematics: Comparing free energies calculated with Self Consistent Field theory and Monte Carlo simulations.

PubMed

Greco, Cristina; Jiang, Ying; Chen, Jeff Z Y; Kremer, Kurt; Daoulas, Kostas Ch

2016-11-14

Self Consistent Field (SCF) theory serves as an efficient tool for studying mesoscale structure and thermodynamics of polymeric liquid crystals (LC). We investigate how some of the intrinsic approximations of SCF affect the description of the thermodynamics of polymeric LC, using a coarse-grained model. Polymer nematics are represented as discrete worm-like chains (WLC) where non-bonded interactions are defined combining an isotropic repulsive and an anisotropic attractive Maier-Saupe (MS) potential. The range of the potentials, σ, controls the strength of correlations due to non-bonded interactions. Increasing σ (which can be seen as an increase of coarse-graining) while preserving the integrated strength of the potentials reduces correlations. The model is studied with particle-based Monte Carlo (MC) simulations and SCF theory which uses partial enumeration to describe discrete WLC. In MC simulations the Helmholtz free energy is calculated as a function of strength of MS interactions to obtain reference thermodynamic data. To calculate the free energy of the nematic branch with respect to the disordered melt, we employ a special thermodynamic integration (TI) scheme invoking an external field to bypass the first-order isotropic-nematic transition. Methodological aspects which have not been discussed in earlier implementations of the TI to LC are considered. Special attention is given to the rotational Goldstone mode. The free-energy landscape in MC and SCF is directly compared. For moderate σ the differences highlight the importance of local non-bonded orientation correlations between segments, which SCF neglects. Simple renormalization of parameters in SCF cannot compensate the missing correlations. Increasing σ reduces correlations and SCF reproduces well the free energy in MC simulations.

Partially coherent polarized atmospheric transmission characteristics and application technology research

NASA Astrophysics Data System (ADS)

Fu, Qiang; Gao, Duorui; Liu, Zhi; Chen, Chunyi; Lou, Yan; Jiang, Huilin

2014-11-01

Based on partially coherent polarized light transmission characteristics of the atmosphere, an intensity expression of completely coherent flashing light is derived from Andrews scale modulation method. According to the generalized Huygens-Fresnel principle and Rytov theory, the phase fluctuation structure function is obtained on condition that the refractive index profile in the atmosphere meet Von Karman spectrum, then get the arrival Angle fluctuation variance. Through the RMS beam width of gaussian beams in turbulent atmosphere, deviation angle formula of fully coherent gaussian beams in turbulence atmosphere is attained, then get the RMS beam width of partially coherent and derivation angle expression of GSM beam in turbulent atmosphere. Combined with transmission properties of radial polarized laser beam, cross spectral density matrix of partially coherent radially polarized light can be gained by using generalized huygens-fresnel principle. And light intensity and polarization after transmission can be known according to the unity of coherence and polarization theory. On the basis of the analysis model and numerical simulation, the simulation results show that: the light spot caused by atmospheric turbulence of partially coherent polarization will be superior to completely polarized light.Taking advantage of this feature, designed a new wireless suppression technology of atmospheric turbulence, that is the optimization criterion of initial degree of coherent light beam. The optimal initial degree of coherent light beam will change along with the change of atmospheric turbulence conditions,make control the beam's initial degree of coherence to realize the initial degree of coherence of light beam in real time and dynamic control. A spatial phase screen before emission aperture of fully coherent light is to generate the partially coherent light, liquid crystal spatial light modulator is is a preferable way to realize the dynamic random phase. Finally look future of the application research of partially coherent light.

STS 61-A crewmembers in Spacelab D-1 science module

NASA Image and Video Library

1985-10-30

61A-01-030 (30 Oct.-6 Nov. 1985) --- Mission specialist Guion S. Bluford prepares to perform a physics experiment onboard the D-1 science module in the cargo bay of the earth-orbiting Space Shuttle Challenger. In the backgroud, three European payload specialists busy themselves with experiment chores: (L-R) Wubbo J. Ockels (partially obscured), Reinhard Furrer and Ernst Messerschmid.

The Partially Flipped Classroom: The Effects of Flipping a Module on "Junk Science" in a Large Methods Course

ERIC Educational Resources Information Center

Burgoyne, Stephanie; Eaton, Judy

2018-01-01

Flipped classrooms are gaining popularity, especially in psychology statistics courses. However, not all courses lend themselves to a fully flipped design, and some instructors might not want to commit to flipping every class. We tested the effectiveness of flipping just one component (a module on junk science) of a large methods course. We…

Isotherm-Based Thermodynamic Model for Solute Activities of Asymmetric Electrolyte Aqueous Solutions.

PubMed

Nandy, Lucy; Dutcher, Cari S

2017-09-21

Adsorption isotherm-based statistical thermodynamic models can be used to determine solute concentration and solute and solvent activities in aqueous solutions. Recently, the number of adjustable parameters in the isotherm model of Dutcher et al. J. Phys. Chem. A/C 2011, 2012, 2013 were reduced for neutral solutes as well as symmetric 1:1 electrolytes by using a Coulombic model to describe the solute-solvent energy interactions (Ohm et al. J. Phys. Chem. A 2015, Nandy et al. J. Phys. Chem. A 2016). Here, the Coulombic treatment for symmetric electrolytes is extended to establish improved isotherm model equations for asymmetric 1-2 and 1-3 electrolyte systems. The Coulombic model developed here results in prediction of activities and other thermodynamic properties in multicomponent systems containing ions of arbitrary charge. The model is found to accurately calculate the osmotic coefficient over the entire solute concentration range with two model parameters, related to intermolecular solute-solute and solute-solvent spacing. The inorganic salts and acids treated here are generally considered to be fully dissociated. However, there are certain weak acids that do not dissociate completely, such as the bisulfate ion. In this work, partial dissociation of the bisulfate ion from sulfuric acid is treated as a mixture, with an additional model parameter that accounts for the dissociation ratio of the dissociated ions to nondissociated ions.

Theoretical investigation of flash vaporisation in a screw expander

NASA Astrophysics Data System (ADS)

Vasuthevan, Hanushan; Brümmer, Andreas

2017-08-01

In the present study flash vaporisation of liquid injection in a twin screw expander for a Trilateral Flash Cycle (TFC) is examined theoretically. The TFC process comprises a pressure increase in the working fluid, followed by heating the liquid close to boiling point. The hot liquid is injected into the working chamber of a screw expander. During this process the pressure of the liquid drops below the saturation pressure, while the temperature of the liquid remains virtually constant. Hence the liquid is superheated and in a metastable state. The liquid jet seeks to achieve a stable state in thermodynamic equilibrium and is therefore partially vaporised. This effect is referred to as flash vaporisation. Accordingly, a two-phase mixture, consisting of vapour and liquid, exists in the working chamber. Thermodynamic simulations were carried out using water as the working fluid for representative screw expander geometry. The simulations presented are performed from two different aspects during the filling process of a screw expander. The first case is the vaporisation of the injected liquid in a state of thermodynamic equilibrium, whereby the two-phase mixture is treated entirely as a compressible and homogeneous gas. The second case considers flashing efficiency. It describes the quantity of flashed vapour and consists of a liquid and vapour domain. Both models are compared and analysed with respect to the operational behaviour of a screw expander.

Accurate Estimation of Solvation Free Energy Using Polynomial Fitting Techniques

PubMed Central

Shyu, Conrad; Ytreberg, F. Marty

2010-01-01

This report details an approach to improve the accuracy of free energy difference estimates using thermodynamic integration data (slope of the free energy with respect to the switching variable λ) and its application to calculating solvation free energy. The central idea is to utilize polynomial fitting schemes to approximate the thermodynamic integration data to improve the accuracy of the free energy difference estimates. Previously, we introduced the use of polynomial regression technique to fit thermodynamic integration data (Shyu and Ytreberg, J Comput Chem 30: 2297–2304, 2009). In this report we introduce polynomial and spline interpolation techniques. Two systems with analytically solvable relative free energies are used to test the accuracy of the interpolation approach. We also use both interpolation and regression methods to determine a small molecule solvation free energy. Our simulations show that, using such polynomial techniques and non-equidistant λ values, the solvation free energy can be estimated with high accuracy without using soft-core scaling and separate simulations for Lennard-Jones and partial charges. The results from our study suggest these polynomial techniques, especially with use of non-equidistant λ values, improve the accuracy for ΔF estimates without demanding additional simulations. We also provide general guidelines for use of polynomial fitting to estimate free energy. To allow researchers to immediately utilize these methods, free software and documentation is provided via http://www.phys.uidaho.edu/ytreberg/software. PMID:20623657

Thermodynamic limits on the size and size distribution of nucleic acids synthesized in vitro: the role of pyrophosphate hydrolysis.

PubMed

Peller, L

1977-02-08

The free-energy change of phosphodiester bond formation from nucleoside triphosphates is more favorable than with nucleoside diphosphates as substrates. Base-stacking interactions can make significant contributions to both delta G degrees ' values. Pyrophosphate hydrolysis when it accompanies the former reaction dominates all thermodynamic considerations. Three experimental situations are discussed in which high-molecular-weight polynucleotides are synthesized without a strong driving force for covalent bond formation. For one of these, a kinetic scheme is presented which encompasses an early narrow Poisson distribution of chain lengths with ultimate passage to a disperse equilibrium population of chain sizes. Hydrolytic removal of pyrophosphate expands the time scale for this undesirable process by a factor of 10(9), while it enormously elevates the thermodynamic ceiling for the average degrees of polymerization in the other two examples. The electron micrographically revealed broad size population from an early study of partial replication of a T7 DNA template is found to adhere (fortuitously) to a disperse most probable representation. Some possible origins are examined for the branched structures in this product, as well as in a later investigation of replication of this nucleic acid. The achievement of both very high molecular weights and sharply peaked size distributions in polynucleotides synthesized in vitro will require coupling to inorganic pyrophosphatase action as in vivo.

Structure, thermodynamic and transport properties of imidazolium-based bis(trifluoromethylsulfonyl)imide ionic liquids from molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Androulaki, Eleni; Vergadou, Niki; Ramos, Javier; Economou, Ioannis G.

2012-06-01

Molecular dynamics (MD) simulations have been performed in order to investigate the properties of [C n mim+][Tf2N-] (n = 4, 8, 12) ionic liquids (ILs) in a wide temperature range (298.15-498.15 K) and at atmospheric pressure (1 bar). A previously developed methodology for the calculation of the charge distribution that incorporates ab initio quantum mechanical calculations based on density functional theory (DFT) was used to calculate the partial charges for the classical molecular simulations. The wide range of time scales that characterize the segmental dynamics of these ILs, especially at low temperatures, required very long MD simulations, on the order of several tens of nanoseconds, to calculate the thermodynamic (density, thermal expansion, isothermal compressibility), structural (radial distribution functions between the centers of mass of ions and between individual sites, radial-angular distribution functions) and dynamic (relaxation times of the reorientation of the bonds and the torsion angles, self-diffusion coefficients, shear viscosity) properties. The influence of the temperature and the cation's alkyl chain length on the above-mentioned properties was thoroughly investigated. The calculated thermodynamic (primary and derivative) and structural properties are in good agreement with the experimental data, while the extremely sluggish dynamics of the ILs under study renders the calculation of their transport properties a very complicated and challenging task, especially at low temperatures.

Roles of the amino group of purine bases in the thermodynamic stability of DNA base pairing.

PubMed

Nakano, Shu-ichi; Sugimoto, Naoki

2014-08-05

The energetic aspects of hydrogen-bonded base-pair interactions are important for the design of functional nucleotide analogs and for practical applications of oligonucleotides. The present study investigated the contribution of the 2-amino group of DNA purine bases to the thermodynamic stability of oligonucleotide duplexes under different salt and solvent conditions, using 2'-deoxyriboinosine (I) and 2'-deoxyribo-2,6-diaminopurine (D) as non-canonical nucleotides. The stability of DNA duplexes was changed by substitution of a single base pair in the following order: G • C > D • T ≈ I • C > A • T > G • T > I • T. The apparent stabilization energy due to the presence of the 2-amino group of G and D varied depending on the salt concentration, and decreased in the water-ethanol mixed solvent. The effects of salt concentration on the thermodynamics of DNA duplexes were found to be partially sequence-dependent, and the 2-amino group of the purine bases might have an influence on the binding of ions to DNA through the formation of a stable base-paired structure. Our results also showed that physiological salt conditions were energetically favorable for complementary base recognition, and conversely, low salt concentration media and ethanol-containing solvents were effective for low stringency oligonucleotide hybridization, in the context of conditions employed in this study.

Bulk viscosity of the Lennard-Jones fluid for a wide range of states computed by equilibrium molecular dynamics

NASA Astrophysics Data System (ADS)

Hoheisel, C.; Vogelsang, R.; Schoen, M.

1987-12-01

Accurate data for the bulk viscosity ηv have been obtained by molecular dynamics calculations. Many thermodynamic states of the Lennard-Jones fluid were considered. The Green-Kubo integrand of ηv is analyzed in terms of partial correlation functions constituting the total one. These partial functions behave rather differently from those found for the shear viscosity or the thermal conductivity. Generally the total autocorrelation function of ηv shows a steeper initial decay and a more pronounced long time form than those of the shear viscosity or the thermal conductivity. For states near transition to solid phases, like the pseudotriple point of argon, the Green-Kubo integrand of ηv has a significantly longer ranged time behavior than that of the shear viscosity. Hence, for the latter states, a systematic error is expected for ηv using equilibrium molecular dynamics for its computation.

Salt potentiates methylamine counteraction system to offset the deleterious effects of urea on protein stability and function.

PubMed

Rahman, Safikur; Rehman, Md Tabish; Singh, Laishram R; Warepam, Marina; Ahmad, Faizan; Dar, Tanveer Ali

2015-01-01

Cellular methylamines are osmolytes (low molecular weight organic compounds) believed to offset the urea's harmful effects on the stability and function of proteins in mammalian kidney and marine invertebrates. Although urea and methylamines are found at 2:1 molar ratio in tissues, their opposing effects on protein structure and function have been questioned on several grounds including failure to counteraction or partial counteraction. Here we investigated the possible involvement of cellular salt, NaCl, in urea-methylamine counteraction on protein stability and function. We found that NaCl mediates methylamine counteracting system from no or partial counteraction to complete counteraction of urea's effect on protein stability and function. These conclusions were drawn from the systematic thermodynamic stability and functional activity measurements of lysozyme and RNase-A. Our results revealed that salts might be involved in protein interaction with charged osmolytes and hence in the urea-methylamine counteraction.

Entropy Constraints in the Ground State Formation of Magnetically Frustrated Systems

NASA Astrophysics Data System (ADS)

Sereni, Julian G.

2018-01-01

A systematic modification of the entropy trajectory (S_m(T)) is observed at very low temperature in magnetically frustrated systems as a consequence of the constraint (S_mg 0) imposed by the Nernst postulate. The lack of magnetic order allows to explore and compare new thermodynamic properties by tracing the specific heat (C_m) behavior down to the sub-Kelvin range. Some of the most relevant findings are: (i) a common C_m/T|_{T→ 0} ≈ 7 J/mol K^2 `plateau' in at least five Yb-based very-heavy-fermions (VHF) compounds; (ii) quantitative and qualitative differences between VHF and standard non-Fermi-liquids; (iii) entropy bottlenecks governing the change of S_m(T) trajectories in a continuous transition into alternative ground states. A comparative analysis of S_m(T→ 0) dependencies is performed in compounds suitable for adiabatic demagnetization processes according to their partial ^2 S_m/partial T^2 derivatives.

Partial molar enthalpies and reaction enthalpies from equilibrium molecular dynamics simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schnell, Sondre K.; Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720; Department of Chemistry, Faculty of Natural Science and Technology, Norwegian University of Science and Technology, 4791 Trondheim

2014-10-14

We present a new molecular simulation technique for determining partial molar enthalpies in mixtures of gases and liquids from single simulations, without relying on particle insertions, deletions, or identity changes. The method can also be applied to systems with chemical reactions. We demonstrate our method for binary mixtures of Weeks-Chandler-Anderson particles by comparing with conventional simulation techniques, as well as for a simple model that mimics a chemical reaction. The method considers small subsystems inside a large reservoir (i.e., the simulation box), and uses the construction of Hill to compute properties in the thermodynamic limit from small-scale fluctuations. Results obtainedmore » with the new method are in excellent agreement with those from previous methods. Especially for modeling chemical reactions, our method can be a valuable tool for determining reaction enthalpies directly from a single MD simulation.« less

CTserver: A Computational Thermodynamics Server for the Geoscience Community

NASA Astrophysics Data System (ADS)

Kress, V. C.; Ghiorso, M. S.

2006-12-01

The CTserver platform is an Internet-based computational resource that provides on-demand services in Computational Thermodynamics (CT) to a diverse geoscience user base. This NSF-supported resource can be accessed at ctserver.ofm-research.org. The CTserver infrastructure leverages a high-quality and rigorously tested software library of routines for computing equilibrium phase assemblages and for evaluating internally consistent thermodynamic properties of materials, e.g. mineral solid solutions and a variety of geological fluids, including magmas. Thermodynamic models are currently available for 167 phases. Recent additions include Duan, Møller and Weare's model for supercritical C-O-H-S, extended to include SO2 and S2 species, and an entirely new associated solution model for O-S-Fe-Ni sulfide liquids. This software library is accessed via the CORBA Internet protocol for client-server communication. CORBA provides a standardized, object-oriented, language and platform independent, fast, low-bandwidth interface to phase property modules running on the server cluster. Network transport, language translation and resource allocation are handled by the CORBA interface. Users access server functionality in two principal ways. Clients written as browser- based Java applets may be downloaded which provide specific functionality such as retrieval of thermodynamic properties of phases, computation of phase equilibria for systems of specified composition, or modeling the evolution of these systems along some particular reaction path. This level of user interaction requires minimal programming effort and is ideal for classroom use. A more universal and flexible mode of CTserver access involves making remote procedure calls from user programs directly to the server public interface. The CTserver infrastructure relieves the user of the burden of implementing and testing the often complex thermodynamic models of real liquids and solids. A pilot application of this distributed architecture involves CFD computation of magma convection at Volcan Villarrica with magma properties and phase proportions calculated at each spatial node and at each time step via distributed function calls to MELTS-objects executing on the CTserver. Documentation and programming examples are provided at http://ctserver.ofm- research.org.

Negative specific heat with trapped ultracold quantum gases

NASA Astrophysics Data System (ADS)

Strzys, M. P.; Anglin, J. R.

2014-01-01

The second law of thermodynamics normally prescribes that heat tends to disperse, but in certain cases it instead implies that heat will spontaneously concentrate. The spontaneous formation of stars out of cold cosmic nebulae, without which the universe would be dark and dead, is an example of this phenomenon. Here we show that the counter-intuitive thermodynamics of spontaneous heat concentration can be studied experimentally with trapped quantum gases, by using optical lattice potentials to realize weakly coupled arrays of simple dynamical subsystems, so that under the standard assumptions of statistical mechanics, the behavior of the whole system can be predicted from ensemble properties of the isolated components. A naive application of the standard statistical mechanical formalism then identifies the subsystem excitations as heat in this case, but predicts them to share the peculiar property of self-gravitating protostars, of having negative micro-canonical specific heat. Numerical solution of real-time evolution equations confirms the spontaneous concentration of heat in such arrays, with initially dispersed energy condensing quickly into dense ‘droplets’. Analysis of the nonlinear dynamics in adiabatic terms allows it to be related to familiar modulational instabilities. The model thus provides an example of a dictionary mesoscopic system, in which the same non-trivial phenomenon can be understood in both thermodynamical and mechanical terms.

Comprehensive Approaches to Multiphase Flows in Geophysics - Application to nonisothermal, nonhomogenous, unsteady, large-scale, turbulent dusty clouds I. Hydrodynamic and Thermodynamic RANS and LES Models

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. Dartevelle

2005-09-05

The objective of this manuscript is to fully derive a geophysical multiphase model able to ''accommodate'' different multiphase turbulence approaches; viz., the Reynolds Averaged Navier-Stokes (RANS), the Large Eddy Simulation (LES), or hybrid RANSLES. This manuscript is the first part of a larger geophysical multiphase project--lead by LANL--that aims to develop comprehensive modeling tools for large-scale, atmospheric, transient-buoyancy dusty jets and plume (e.g., plinian clouds, nuclear ''mushrooms'', ''supercell'' forest fire plumes) and for boundary-dominated geophysical multiphase gravity currents (e.g., dusty surges, diluted pyroclastic flows, dusty gravity currents in street canyons). LES is a partially deterministic approach constructed on either amore » spatial- or a temporal-separation between the large and small scales of the flow, whereas RANS is an entirely probabilistic approach constructed on a statistical separation between an ensemble-averaged mean and higher-order statistical moments (the so-called ''fluctuating parts''). Within this specific multiphase context, both turbulence approaches are built up upon the same phasic binary-valued ''function of presence''. This function of presence formally describes the occurrence--or not--of any phase at a given position and time and, therefore, allows to derive the same basic multiphase Navier-Stokes model for either the RANS or the LES frameworks. The only differences between these turbulence frameworks are the closures for the various ''turbulence'' terms involving the unknown variables from the fluctuating (RANS) or from the subgrid (LES) parts. Even though the hydrodynamic and thermodynamic models for RANS and LES have the same set of Partial Differential Equations, the physical interpretations of these PDEs cannot be the same, i.e., RANS models an averaged field, while LES simulates a filtered field. In this manuscript, we also demonstrate that this multiphase model fully fulfills the second law of thermodynamics and fulfills the necessary requirements for a well-posed initial-value problem. In the next manuscripts, we will further develop specific closures for multiphase RANS, LES, and hybrid-LES.« less

Plant-Level Modeling and Simulation of Used Nuclear Fuel Dissolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

de Almeida, Valmor F.

2012-09-07

Plant-level modeling and simulation of a used nuclear fuel prototype dissolver is presented. Emphasis is given in developing a modeling and simulation approach to be explored by other processes involved in the recycle of used fuel. The commonality concepts presented in a previous communication were used to create a model and realize its software module. An initial model was established based on a theory of chemical thermomechanical network transport outlined previously. A software module prototype was developed with the required external behavior and internal mathematical structure. Results obtained demonstrate the generality of the design approach and establish an extensible mathematicalmore » model with its corresponding software module for a wide range of dissolvers. Scale up numerical tests were made varying the type of used fuel (breeder and light-water reactors) and the capacity of dissolution (0.5 t/d to 1.7 t/d). These tests were motivated by user requirements in the area of nuclear materials safeguards. A computer module written in high-level programing languages (MATLAB and Octave) was developed, tested, and provided as open-source code (MATLAB) for integration into the Separations and Safeguards Performance Model application in development at Sandia National Laboratories. The modeling approach presented here is intended to serve as a template for a rational modeling of all plant-level modules. This will facilitate the practical application of the commonality features underlying the unifying network transport theory proposed recently. In addition, by example, this model describes, explicitly, the needed data from sub-scale models, and logical extensions for future model development. For example, from thermodynamics, an off-line simulation of molecular dynamics could quantify partial molar volumes for the species in the liquid phase; this simulation is currently at reach for high-performance computing. From fluid mechanics, a hold-up capacity function is needed for the dissolver device; this simulation is currently at reach for computational fluid mechanics given the existing CAD geometry. From chemical transport phenomena, a simulation of the particle-scale dissolution front is needed to derive an improved solid dissolution kinetics law by predicting the local surface area change; an example was provided in this report. In addition, the associated reaction mechanisms for dissolution are presently largely untested and simplified, hence even a parallel experimental program in reaction kinetics is needed to support modeling and simulation efforts. Last but not least, a simple account of finite rates of solid feed and transfer can be readily introduced via a coupled delayed model. These are some of the theoretical benefits of a rational plant-level modeling approach which guides the development of smaller length and time scale modeling. Practical, and other theoretical benefits have been presented on a previous report.« less

Quantifying Solar Cell Cracks in Photovoltaic Modules by Electroluminescence Imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spataru, Sergiu; Hacke, Peter; Sera, Dezso

2015-06-14

This article proposes a method for quantifying the percentage of partially and totally disconnected solar cell cracks by analyzing electroluminescence images of the photovoltaic module taken under high- and low-current forward bias. The method is based on the analysis of the module's electroluminescence intensity distribution, applied at module and cell level. These concepts are demonstrated on a crystalline silicon photovoltaic module that was subjected to several rounds of mechanical loading and humidity-freeze cycling, causing increasing levels of solar cell cracks. The proposed method can be used as a diagnostic tool to rate cell damage or quality of modules after transportation.more » Moreover, the method can be automated and used in quality control for module manufacturers, installers, or as a diagnostic tool by plant operators and diagnostic service providers.« less

Multiple-object tracking as a tool for parametrically modulating memory reactivation

PubMed Central

Poppenk, J.; Norman, K.A.

2017-01-01

Converging evidence supports the “non-monotonic plasticity” hypothesis that although complete retrieval may strengthen memories, partial retrieval weakens them. Yet, the classic experimental paradigms used to study effects of partial retrieval are not ideally suited to doing so, because they lack the parametric control needed to ensure that the memory is activated to the appropriate degree (i.e., that there is some retrieval, but not enough to cause memory strengthening). Here we present a novel procedure designed to accommodate this need. After participants learned a list of word-scene associates, they completed a cued mental visualization task that was combined with a multiple-object tracking (MOT) procedure, which we selected for its ability to interfere with mental visualization in a parametrically adjustable way (by varying the number of MOT targets). We also used fMRI data to successfully train an “associative recall” classifier for use in this task: this classifier revealed greater memory reactivation during trials in which associative memories were cued while participants tracked one, rather than five MOT targets. However, the classifier was insensitive to task difficulty when recall was not taking place, suggesting it had indeed tracked memory reactivation rather than task difficulty per se. Consistent with the classifier findings, participants’ introspective ratings of visualization vividness were modulated by MOT task difficulty. In addition, we observed reduced classifier output and slowing of responses in a post-reactivation memory test, consistent with the hypothesis that partial reactivation, induced by MOT, weakened memory. These results serve as a “proof of concept” that MOT can be used to parametrically modulate memory retrieval – a property that may prove useful in future investigation of partial retrieval effects, e.g., in closed-loop experiments. PMID:28387587

Isotherm-Based Thermodynamic Models for Solute Activities of Organic Acids with Consideration of Partial Dissociation.

PubMed

Nandy, Lucy; Ohm, Peter B; Dutcher, Cari S

2016-06-23

Organic acids make up a significant fraction of the organic mass in atmospheric aerosol particles. The calculation of gas-liquid-solid equilibrium partitioning of the organic acid is therefore critical for accurate determination of atmospheric aerosol physicochemical properties and processes such as new particle formation and activation to cloud condensation nuclei. Previously, an adsorption isotherm-based statistical thermodynamic model was developed for capturing solute concentration-activity relationships for multicomponent aqueous solutions over the entire concentration range (Dutcher et al. J. Phys. Chem. C/A 2011, 2012, 2013), with model parameters for energies of adsorption successfully related to dipole-dipole electrostatic forces in solute-solvent and solvent-solvent interactions for both electrolytes and organics (Ohm et al. J. Phys. Chem. A 2015). However, careful attention is needed for weakly dissociating semivolatile organic acids. Dicarboxylic acids, such as malonic acid and glutaric acid are treated here as a mixture of nondissociated organic solute (HA) and dissociated solute (H(+) + A(-)). It was found that the apparent dissociation was greater than that predicted by known dissociation constants alone, emphasizing the effect of dissociation on osmotic and activity coefficient predictions. To avoid additional parametrization from the mixture approach, an expression was used to relate the Debye-Hückel hard-core collision diameter to the adjustable solute-solvent intermolecular distance. An improved reference state treatment for electrolyte-organic aqueous mixtures, such as that observed here with partial dissociation, has also been proposed. This work results in predictive correlations for estimation of organic acid and water activities for which there is little or no activity data.

Differential Effects of Hydrophobic Core Packing Residues for Thermodynamic and Mechanical Stability of a Hyperthermophilic Protein.

PubMed

Tych, Katarzyna M; Batchelor, Matthew; Hoffmann, Toni; Wilson, Michael C; Hughes, Megan L; Paci, Emanuele; Brockwell, David J; Dougan, Lorna

2016-07-26

Proteins from organisms that have adapted to environmental extremes provide attractive systems to explore and determine the origins of protein stability. Improved hydrophobic core packing and decreased loop-length flexibility can increase the thermodynamic stability of proteins from hyperthermophilic organisms. However, their impact on protein mechanical stability is not known. Here, we use protein engineering, biophysical characterization, single-molecule force spectroscopy (SMFS), and molecular dynamics (MD) simulations to measure the effect of altering hydrophobic core packing on the stability of the cold shock protein TmCSP from the hyperthermophilic bacterium Thermotoga maritima. We make two variants of TmCSP in which a mutation is made to reduce the size of aliphatic groups from buried hydrophobic side chains. In the first, a mutation is introduced in a long loop (TmCSP L40A); in the other, the mutation is introduced on the C-terminal β-strand (TmCSP V62A). We use MD simulations to confirm that the mutant TmCSP L40A shows the most significant increase in loop flexibility, and mutant TmCSP V62A shows greater disruption to the core packing. We measure the thermodynamic stability (ΔGD-N) of the mutated proteins and show that there is a more significant reduction for TmCSP L40A (ΔΔG = 63%) than TmCSP V62A (ΔΔG = 47%), as might be expected on the basis of the relative reduction in the size of the side chain. By contrast, SMFS measures the mechanical stability (ΔG*) and shows a greater reduction for TmCSP V62A (ΔΔG* = 8.4%) than TmCSP L40A (ΔΔG* = 2.5%). While the impact on the mechanical stability is subtle, the results demonstrate the power of tuning noncovalent interactions to modulate both the thermodynamic and mechanical stability of a protein. Such understanding and control provide the opportunity to design proteins with optimized thermodynamic and mechanical properties.

A search for life on Earth from the Galileo spacecraft

NASA Technical Reports Server (NTRS)

Sagan, C.; Thompson, W. R.; Carlson, R.; Gurnett, D.; Hord, C.

1993-01-01

In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum, and atmospheric methane in extreme thermodynamic disequilibrium; together, these are strongly suggestive of life on Earth. Moreover, the presence of narrow-band, pulsed, amplitude-modulated radio transmission seems uniquely attributable to intelligence. These observations constitute a control experiment for the serach for extraterrestrial life by modern interplanetary spacecraft.

Thermal management of closed computer modules utilizing high density circuitry. [in Airborne Information Management System

NASA Technical Reports Server (NTRS)

Hoadley, A. W.; Porter, A. J.

1990-01-01

This paper presents data on a preliminary analysis of the thermal dynamic characteristics of the Airborne Information Management System (AIMS), which is a continuing design project at NASA Dryden. The analysis established the methods which will be applied to the actual AIMS boards as they become available. The paper also describes the AIMS liquid cooling system design and presents a thermodynamic computer model of the AIMS cooling system, together with an experimental validation of this model.

A search for life on Earth from the Galileo spacecraft.

PubMed

Sagan, C; Thompson, W R; Carlson, R; Gurnett, D; Hord, C

1993-10-21

In its December 1990 fly-by of Earth, the Galileo spacecraft found evidence of abundant gaseous oxygen, a widely distributed surface pigment with a sharp absorption edge in the red part of the visible spectrum, and atmospheric methane in extreme thermodynamic disequilibrium; together, these are strongly suggestive of life on Earth. Moreover, the presence of narrow-band, pulsed, amplitude-modulated radio transmission seems uniquely attributable to intelligence. These observations constitute a control experiment for the serach for extraterrestrial life by modern interplanetary spacecraft.

U.S. forest products module : a technical document supporting the Forest Service 2010 RPA Assessment

Treesearch

Peter J. Ince; Andrew D. Kramp; Kenneth E. Skog; Henry N. Spelter; David N. Wear

2011-01-01

The U.S. Forest Products Module (USFPM) is a partial market equilibrium model of the U.S. forest sector that operates within the Global Forest Products Model (GFPM) to provide long-range timber market projections in relation to global economic scenarios. USFPM was designed specifically for the 2010 RPA forest assessment, but it is being used also in other applications...

Technology-Enhanced Learning in Science (TELS)

NASA Astrophysics Data System (ADS)

Linn, Marcia

2006-12-01

The overall research question addressed by the NSF-funded echnologyEnhanced Learning in Science (TELS) Center is whether interactive scientific visualizations embedded in high quality instructional units can be used to increase pre-college student learning in science. The research draws on the knowledge integration framework to guide the design of instructional modules, professional development activities, and assessment activities. This talk reports on results from the first year where 50 teachers taught one of the 12 TELS modules in over 200 classes in 16 diverse schools. Assessments scored with the knowledge integration rubric showed that students made progress in learning complex physics topics such as electricity, mechanics, and thermodynamics. Teachers encountered primarily technological obstacles that the research team was able to address prior to implementation. Powerful scientific visualizations required extensive instructional supports to communicate to students. Currently, TELS is refining the modules, professional development, and assessments based on evidence from the first year. Preliminary design principles intended to help research teams build on the findings will be presented for audience feedback and discussion.

Hybrid Electro-Optic Processor

DTIC Science & Technology

1991-07-01

This report describes the design of a hybrid electro - optic processor to perform adaptive interference cancellation in radar systems. The processor is...modulator is reported. Included is this report is a discussion of the design, partial fabrication in the laboratory, and partial testing of the hybrid electro ... optic processor. A follow on effort is planned to complete the construction and testing of the processor. The work described in this report is the

Experimental study of phase equilibria and thermodynamic optimization of the Fe-Zn-O system

NASA Astrophysics Data System (ADS)

Degterov, Sergei A.; Pelton, Arthur D.; Jak, Evgueni; Hayes, Peter C.

2001-08-01

The Fe-Zn-O phase diagram in air was studied over the temperature range from 900 °C to 1500 °C. The compositions of the phases in quenched samples were obtained by electron probe X-ray microanalysis (EPMA). This experimental technique is not affected by zinc losses resulting from vaporization of zinc at high temperatures. The model for the spinel solid solution was developed within the framework of the compound-energy formalism (CEF). The choice of parameters of the CEF and the sequence of their optimization can have a major influence on the predictions in multicomponent phases. These choices can only be made rationally by reference to the specific model being represented in the CEF. This is discussed for the case of the two-sublattice spinel model. In the limiting case, the proposed model reduces to the model by O’Neill and Navrotsky for spinels. When the CEF is used in combination with the equation of Hillert and Jarl to describe the magnetic contribution to thermodynamic functions of a solution, it is necessary to assign certain values of magnetic properties to all pseudocomponents and to magnetic interaction parameters to obtain the most reasonable approximation of the magnetic properties of a solution. It was shown how this can be done based on very limited experimental data. The same equations can be used when the Murnaghan or the Birch-Murnaghan equation is combined with the CEF to describe the pressure dependence of thermodynamic functions. The polynomial model was used to describe the properties of wustite and zincite, and the modified quasichemical model was used for the liquid slag. All thermodynamic and phase-equilibria data on the Fe-O and Fe-Zn-O systems were critically evaluated, and parameters of the models were optimized to give a self-consistent set of thermodynamic functions of the phases in these systems. All experimental data are reproduced within experimental error limits. These include the thermodynamic properties of phases (such as specific heat, heat content, entropy, enthalpy, and Gibbs energy); the cation distribution between octahedral and tetrahedral sites in spinel; the oxygen partial pressure over single-phase, two-phase, and three-phase regions; the phase boundaries (liquidus, solidus, and subsolidus); and the tie-lines.

First-principles study of atomic and electronic structures of 60° perfect and 30°/90° partial glide dislocations in CdTe

DOE PAGES

Kweon, Kyoung E.; Aberg, Daniel; Lordi, Vincenzo

2016-05-16

The atomic and electronic structures of 60° glide perfect and 30°/90° glide partial dislocations in CdTe are studied using combined semi-empirical and density functional theory calculations. The calculations predict that the dislocation cores tend to undergo significant reconstructions along the dislocation lines from the singly-periodic (SP) structures, yielding either doubly-periodic (DP) ordering by forming a dimer or quadruply-periodic (QP) ordering by alternating a dimer and a missing dimer. Charge modulation along the dislocation line, accompanied by the QP reconstruction for the Cd-/Te-core 60° perfect and 30° partials or the DP reconstruction for the Cd-core 90° partial, results in semiconducting character,more » as opposed to the metallic character of the SP dislocation cores. Dislocation-induced defect states for the 60° Cd-/Te-core are located relatively close to the band edges, whereas the defect states lie in the middle of the band gap for the 30° Cd-/Te-core partial dislocations. In addition to the intracore charge modulation within each QP core, the possibility of intercore charge transfer between two different dislocation cores when they are paired together in the same system is discussed. As a result, the analysis of the electronic structures reveals the potential role of the dislocations on charge transport in CdTe, particularly in terms of charge trapping and recombination.« less

Electrochemical air revitalization system optimization investigation

NASA Technical Reports Server (NTRS)

Woods, R. R.; Schubert, F. H.; Hallick, T. M.

1975-01-01

A program to characterize a Breadboard of an Electrochemical Air Revitalization System (BEARS) was successfully completed. The BEARS is composed of three components: (1) a water vapor electrolysis module (WVEM) for O2 production and partial humidity control, (2) an electrochemical depolarized carbon dioxide concentrator module (EDCM) for CO2 control, and (3) a power-sharing controller, designed to utilize the power produced by the EDCM to partially offset the WVEM power requirements. It is concluded from the results of this work that the concept of electrochemical air revitalization with power-sharing is a viable solution to the problem of providing a localized topping force for O2 generation, CO2 removal and partial humidity control aboard manned spacecraft. Continued development of the EARS concept is recommended, applying the operational experience and limits identified during the BEARS program to testing of a one-man capacity system and toward the development of advanced system controls to optimize EARS operation for given interfaces and requirements. Successful completion of this development will produce timely technology necessary to plan future advanced environmental control and life support system programs and experiments.

Power module assemblies with staggered coolant channels

DOEpatents

Herron, Nicholas Hayden; Mann, Brooks S; Korich, Mark D

2013-07-16

A manifold is provided for supporting a power module assembly with a plurality of power modules. The manifold includes a first manifold section. The first face of the first manifold section is configured to receive the first power module, and the second face of the first manifold section defines a first cavity with a first baseplate thermally coupled to the first power module. The first face of the second manifold section is configured to receive the second power module, and the second face of the second manifold section defines a second cavity with a second baseplate thermally coupled to the second power module. The second face of the first manifold section and the second face of the second manifold section are coupled together such that the first cavity and the second cavity form a coolant channel. The first cavity is at least partially staggered with respect to second cavity.

Coupled incompressible Smoothed Particle Hydrodynamics model for continuum-based modelling sediment transport

NASA Astrophysics Data System (ADS)

Pahar, Gourabananda; Dhar, Anirban

2017-04-01

A coupled solenoidal Incompressible Smoothed Particle Hydrodynamics (ISPH) model is presented for simulation of sediment displacement in erodible bed. The coupled framework consists of two separate incompressible modules: (a) granular module, (b) fluid module. The granular module considers a friction based rheology model to calculate deviatoric stress components from pressure. The module is validated for Bagnold flow profile and two standardized test cases of sediment avalanching. The fluid module resolves fluid flow inside and outside porous domain. An interaction force pair containing fluid pressure, viscous term and drag force acts as a bridge between two different flow modules. The coupled model is validated against three dambreak flow cases with different initial conditions of movable bed. The simulated results are in good agreement with experimental data. A demonstrative case considering effect of granular column failure under full/partial submergence highlights the capability of the coupled model for application in generalized scenario.

Sulfur control in ion-conducting membrane systems

DOEpatents

Stein, VanEric Edward; Richards, Robin Edward; Brengel, David Douglas; Carolan, Michael Francis

2003-08-05

A method for controlling the sulfur dioxide partial pressure in a pressurized, heated, oxygen-containing gas mixture which is contacted with an ion-conducting metallic oxide membrane which permeates oxygen ions. The sulfur dioxide partial pressure in the oxygen-depleted non-permeate gas from the membrane module is maintained below a critical sulfur dioxide partial pressure, p.sub.SO2 *, to protect the membrane material from reacting with sulfur dioxide and reducing the oxygen flux of the membrane. Each ion-conducting metallic oxide material has a characteristic critical sulfur dioxide partial pressure which is useful in determining the required level of sulfur removal from the feed gas and/or from the fuel gas used in a direct-fired feed gas heater.

Opacplot2: Enabling tabulated EoS and opacity compatibility for HEDLP simulations with the FLASH code

NASA Astrophysics Data System (ADS)

Laune, Jordan; Tzeferacos, Petros; Feister, Scott; Fatenejad, Milad; Yurchak, Roman; Flocke, Norbert; Weide, Klaus; Lamb, Donald

2017-10-01

Thermodynamic and opacity properties of materials are necessary to accurately simulate laser-driven laboratory experiments. Such data are compiled in tabular format since the thermodynamic range that needs to be covered cannot be described with one single theoretical model. Moreover, tabulated data can be made available prior to runtime, reducing both compute cost and code complexity. This approach is employed by the FLASH code. Equation of state (EoS) and opacity data comes in various formats, matrix-layouts, and file-structures. We discuss recent developments on opacplot2, an open-source Python module that manipulates tabulated EoS and opacity data. We present software that builds upon opacplot2 and enables easy-to-use conversion of different table formats into the IONMIX format, the native tabular input used by FLASH. Our work enables FLASH users to take advantage of a wider range of accurate EoS and opacity tables in simulating HELP experiments at the National Laser User Facilities.

Dynamical and thermodynamical modulations of future changes in landfalling atmospheric rivers over North America

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Yang; Lu, Jian; Leung, Lai-Yung R.

This study examines the changes of landfalling atmospheric rivers (ARs) over the west coast of North America in response to future warming using model outputs from the Coupled Model Intercomparison Project phase 5 (CMIP5). The result reveals a strikingly large magnitude of increase of AR days by the end of the 21st century in the RCP8.5 climate change scenario, with fractional increases ranging between ~50% and 600%, depending on the seasons and the landfall locations. These increases are predominantly controlled by the super-Clausius-Clapeyron rate of increase of atmospheric water vapor with warming, while changes of winds that transport moisture inmore » the ARs, or dynamical effect, mostly counter the thermodynamical effect of increasing water vapor, limiting the increase of AR events in the future. The consistent negative effect of wind changes on AR days during spring and fall can be further linked to the robust poleward shift of the subtropical jet in the North Pacific basin.« less

Governing Influence of Thermodynamic and Chemical Equilibria on the Interfacial Properties in Complex Fluids.

PubMed

Harikrishnan, A R; Dhar, Purbarun; Gedupudi, Sateesh; Das, Sarit K

2018-04-12

We propose a comprehensive analysis and a quasi-analytical mathematical formalism to predict the surface tension and contact angles of complex surfactant-infused nanocolloids. The model rests on the foundations of the interaction potentials for the interfacial adsorption-desorption dynamics in complex multicomponent colloids. Surfactant-infused nanoparticle-laden interface problems are difficult to deal with because of the many-body interactions and interfaces involved at the meso-nanoscales. The model is based on the governing role of thermodynamic and chemical equilibrium parameters in modulating the interfacial energies. The influence of parameters such as the presence of surfactants, nanoparticles, and surfactant-capped nanoparticles on interfacial dynamics is revealed by the analysis. Solely based on the knowledge of interfacial properties of independent surfactant solutions and nanocolloids, the same can be deduced for complex surfactant-based nanocolloids through the proposed approach. The model accurately predicts the equilibrium surface tension and contact angle of complex nanocolloids available in the existing literature and present experimental findings.

First-principles studies of Te line-ordered alloys in a MoS2 monolayer

NASA Astrophysics Data System (ADS)

Andriambelaza, N. F.; Mapasha, R. E.; Chetty, N.

2018-04-01

The thermodynamic stability, structural and electronic properties of Te line-ordered alloys are investigated using density functional theory (DFT) methods. Thirty four possible Te line-ordered alloy configurations are found in a 5×5 supercell of a MoS2 monolayer. The calculated formation energies show that the Te line-ordered alloy configurations are thermodynamically stable at 0 K and agree very well with the random alloys. The lowest energy configurations at each concentration correspond to the configuration where the Te atom rows are far apart from each other (avoiding clustering) within the supercell. The variation of the lattice constant at different concentrations obey Vegard's law. The Te line-ordered alloys fine tune the band gap of a MoS2 monolayer although deviating from linearity behavior. Our results suggest that the Te line-ordered alloys can be an effective way to modulate the band gap of a MoS2 monolayer for nanoelectronic, optoelectronic and nanophotonic applications.

Chemical model for the solvent extraction of GdCl3 from a chloride solution with saponified PC88A

NASA Astrophysics Data System (ADS)

Lee, Man-Seung; Lee, Jin-Young; Kim, Joon-Soo

2005-12-01

Solvent extraction experiments of Gd with 40% saponified PC88A have been conducted from a chloride solution under different extraction conditions. The effect of saponification of an acidic extractant on the extraction of Gd was investigated. To analyze the ionic equilibria of a GdCl3 solution, we estimated the necessary thermodynamic properties from reported values. Moreover, when applying the chemical model developed in this study, we used experimental data to estimate the equilibrium constant for the extraction of Gd with partially saponified PC88A.

Tempering Behavior of TiC-Reinforced SKD11 Steel Matrix Composite

NASA Astrophysics Data System (ADS)

Hwang, Ji-In; Kim, Seong Hoon; Heo, Yoon-Uk; Kim, Dae Ha; Hwang, Keum-Cheol; Suh, Dong-Woo

2018-05-01

TiC-reinforced SKD11 steel matrix composite, fabricated by a pressure infiltration casting, undergoes monotonic decrease in hardness as tempering temperature increases. Element mappings by TEM-EDS and thermodynamic calculation indicate that remarkable redistribution of V between the reinforcement and the steel matrix occurs by partial dissolution and re-precipitation of MC carbides upon casting process. The absence of secondary hardening is led by the enrichment of V in the reinforcement that reduces the V content in the steel matrix; this reduction in V content makes the precipitation of fine VC sluggish during the tempering.

Thermodynamics of cell adhesion. II. Freely mobile repellers.

PubMed Central

Torney, D C; Dembo, M; Bell, G I

1986-01-01

The equilibrium adhesion of a cell or vesicle to a substrate is analyzed in a theoretical model in which two types of mobile molecules in the cell membrane are of interest: receptors that can form bonds with fixed ligands in the substrate and repellers that repel the substrate. If the repulsion between the repeller molecule and substrate is greater than kT, there is substantial redistribution of the repellers from the contact area. Coexisting equilibrium states are observed having comparable free energies (a) with unstretched bonds and repeller redistribution and (b) with stretched bonds and partial redistribution. PMID:3955182

Model Systems for the Epitaxial Growth and Capping of GaAs

DTIC Science & Technology

1980-01-01

calculated from the data in Stull and Sinks 20 . This is the origin of the comon procedure of set- ting the As 4 partial pressure nearly equal to one fourth of...Techniques". 3. Cryst. Growth. 31 (1975), pp. 122-129. 20. Stull , D.R. and G.C. Sinke. "Thermodynamic Properties of the Elements". Am. Chem. Soc. Advances...System". Jep. J. AppI. Physics. (1972), pp. 855-a9. 48. Ashen, D.J., P.J. Dean , D.T.J. Hurl*, 3.1. Mullen, A. Boyle, and A.M. White. ’The

Tempering Behavior of TiC-Reinforced SKD11 Steel Matrix Composite

NASA Astrophysics Data System (ADS)

Hwang, Ji-In; Kim, Seong Hoon; Heo, Yoon-Uk; Kim, Dae Ha; Hwang, Keum-Cheol; Suh, Dong-Woo

2018-03-01

TiC-reinforced SKD11 steel matrix composite, fabricated by a pressure infiltration casting, undergoes monotonic decrease in hardness as tempering temperature increases. Element mappings by TEM-EDS and thermodynamic calculation indicate that remarkable redistribution of V between the reinforcement and the steel matrix occurs by partial dissolution and re-precipitation of MC carbides upon casting process. The absence of secondary hardening is led by the enrichment of V in the reinforcement that reduces the V content in the steel matrix; this reduction in V content makes the precipitation of fine VC sluggish during the tempering.

Teaching thermal physics in the paradigms project

NASA Astrophysics Data System (ADS)

Roundy, David

2011-10-01

Thermal physics is probably the most disliked course in the physics major curriculum, with students feeling that they are being led through a mathematical maze, leading to an unsatisfactory conclusion. Classical thermodynamics involves scary derivatives, while statistical mechanics leads to lengthy summations and is difficult to apply to interacting systems. It is unsurprising that students find themselves failing to see the physics for the math. In this talk, I will discuss my experiences teaching the Energy and Entropy paradigm, and will introduce materials we have developed to aide student understanding of partial derivatives and their relationship to experimental observables.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bonthuis, Douwe Jan, E-mail: douwe.bonthuis@physics.ox.ac.uk; Mamatkulov, Shavkat I.; Netz, Roland R.

We optimize force fields for H{sub 3}O{sup +} and OH{sup −} that reproduce the experimental solvation free energies and the activities of H{sub 3}O{sup +} Cl{sup −} and Na{sup +} OH{sup −} solutions up to concentrations of 1.5 mol/l. The force fields are optimized with respect to the partial charge on the hydrogen atoms and the Lennard-Jones parameters of the oxygen atoms. Remarkably, the partial charge on the hydrogen atom of the optimized H{sub 3}O{sup +} force field is 0.8 ± 0.1|e|—significantly higher than the value typically used for nonpolarizable water models and H{sub 3}O{sup +} force fields. In contrast,more » the optimal partial charge on the hydrogen atom of OH{sup −} turns out to be zero. Standard combination rules can be used for H{sub 3}O{sup +} Cl{sup −} solutions, while for Na{sup +} OH{sup −} solutions, we need to significantly increase the effective anion-cation Lennard-Jones radius. While highlighting the importance of intramolecular electrostatics, our results show that it is possible to generate thermodynamically consistent force fields without using atomic polarizability.« less

Thermodynamic properties of hyperbranched polymer, Boltorn U3000, using inverse gas chromatography.

PubMed

Domańska, Urszula; Zołek-Tryznowska, Zuzanna

2009-11-19

Mass-fraction activity coefficients at infinite dilution (Omega13(infinity)) of alkanes (C5-C10), cycloalkanes (C5-C8), alkenes (C5-C8), alkynes (C5-C8), aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-, m-, p-xylene, thiophene), alcohols (C1-C5), water, ethers (tetrahydrofuran (THF), methyl-tert-butylether (MTBE), diethyl-, di-n-propyl-, di-n-butyl ether), and ketones (propanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, cyclopentanone) in the hyperbranched polymer, Boltorn U3000 (B-U3000), have been determined by inverse gas chromatography (IGC) using the polymer as the stationary phase. The measurements were carried out at different temperatures between 308.15 and 348.15 K. The density and thermophysical properties of polymer were described. The specific retention volume (V(g)), the Flory-Huggins interaction parameter (chi13(infinity)), the molar enthalpy of sorption (the partial molar enthalpies of solute dissolution) (Delta(s)H), the partial molar excess enthalpy at infinite dilution of the solute and polymer (DeltaH1(E,infinity)), the partial molar Gibbs excess energy at infinite dilution (DeltaG1(E,infinity)), and the solubility parameter (delta3) were calculated.

Vapor condensation onto a non-volatile liquid drop

DOE Office of Scientific and Technical Information (OSTI.GOV)

Inci, Levent; Bowles, Richard K., E-mail: richard.bowles@usask.ca

2013-12-07

Molecular dynamics simulations of miscible and partially miscible binary Lennard–Jones mixtures are used to study the dynamics and thermodynamics of vapor condensation onto a non-volatile liquid drop in the canonical ensemble. When the system volume is large, the driving force for condensation is low and only a submonolayer of the solvent is adsorbed onto the liquid drop. A small degree of mixing of the solvent phase into the core of the particles occurs for the miscible system. At smaller volumes, complete film formation is observed and the dynamics of film growth are dominated by cluster-cluster coalescence. Mixing into the coremore » of the droplet is also observed for partially miscible systems below an onset volume suggesting the presence of a solubility transition. We also develop a non-volatile liquid drop model, based on the capillarity approximations, that exhibits a solubility transition between small and large drops for partially miscible mixtures and has a hysteresis loop similar to the one observed in the deliquescence of small soluble salt particles. The properties of the model are compared to our simulation results and the model is used to study the formulation of classical nucleation theory for systems with low free energy barriers.« less

Surface thermodynamic stability, electronic and magnetic properties in various (001) surfaces of Zr2CoSn Heusler alloy

NASA Astrophysics Data System (ADS)

Yang, Yan; Feng, Zhong-Ying; Zhang, Jian-Min

2018-05-01

The spin-polarized first-principles are used to study the surface thermodynamic stability, electronic and magnetic properties in various (001) surfaces of Zr2CoSn Heusler alloy, and the bulk Zr2CoSn Heusler alloy are also discussed to make comparison. The conduction band minimum (CBM) of half-metallic (HM) bulk Zr2CoSn alloy is contributed by ZrA, ZrB and Co atoms, while the valence band maximum (VBM) is contributed by ZrB and Co atoms. The SnSn termination is the most stable surface with the highest spin polarizations P = 77.1% among the CoCo, ZrCo, ZrZr, ZrSn and SnSn terminations of the Zr2CoSn (001) surface. In the SnSn termination of the Zr2CoSn (001) surface, the atomic partial density of states (APDOS) of atoms in the surface, subsurface and third layers are much influenced by the surface effect and the total magnetic moment (TMM) is mainly contributed by the atomic magnetic moments of atoms in fourth to ninth layers.

Prediction and Experimental Evidence for Thermodynamically Stable Charged Orbital Domain Walls

DOE PAGES

Li, Qing’an; Gray, K. E.; Wilkins, S. B.; ...

2014-08-18

On theoretical grounds, we show that orbital domain walls (ODWs), which are known to exist in the charge and orbital ordered layered manganite LaSr 2Mn 2O 7, should be partially charged as a result of competition between orbital-induced strain and Coulomb repulsion. Furthermore, this unexpected result provides the necessary condition for the known thermodynamic stability of these ODWs, which are unlike the more typical domain walls that arise only from an external field. We offer experimental data consistent with this theoretical framework through a combined transport and x-ray-diffraction study. In particular, our transport data on this charge and orbital orderedmore » manganite exhibit abrupt transformations to higher conductance at a threshold electric field. As transport phenomena closely resemble effects found for sliding charge-density waves (SCDWs) in pseudo-one-dimensional (1D) materials, a SCDW along such pseudo-1D ODWs provides a natural explanation of our data. Importantly, x-ray-diffraction data eliminate heating and melting of charge order as tenable alternative explanations of our data.« less

Scaled equation of state parameters for gases in the critical region

NASA Technical Reports Server (NTRS)

Sengers, J. M. H. L.; Greer, W. L.; Sengers, J. V.

1976-01-01

In the light of recent theoretical developments, the paper presents an accurate characterization of anomalous thermodynamic behavior of xenon, helium 4, helium 3, carbon dioxide, steam and oxygen in the critical region. This behavior is associated with long range fluctuations in the system and the physical properties depend primarily on a single variable, namely, the correlation length. A description of the thermodynamic behavior of fluids in terms of scaling laws is formulated, and the two successfully used scaled equations of state (NBS equation and Linear Model parametric equation) are compared. Methods for fitting both equations to experimental equation of state data are developed and formulated, and the optimum fit for each of the two scaled equations of the above gases are presented and the results are compared. By extending the experimental data for the above one-component fluids to partially miscible binary liquids, superfluid liquid helium, ferromagnets and solids exhibiting order-disorder transitions, the principle of universality is concluded. Finally by using this principle, the critical regions for nine additional fluids are described.

Deformability of adsorbents during adsorption and principles of the thermodynamics of solid-phase systems

NASA Astrophysics Data System (ADS)

Tovbin, Yu. K.

2017-09-01

A microscopic theory of adsorption, based on a discrete continuum lattice gas model for noninert (including deformable) adsorbents that change their lattice parameters during adsorption, is presented. Cases of the complete and partial equilibrium states of the adsorbent are considered. In the former, the adsorbent consists of coexisting solid and vapor phases of adsorbent components, and the adsorbate is a mobile component of the vapor phase with an arbitrary density (up to that of the liquid adsorbate phase). The adsorptive transitioning to the bound state changes the state of the near-surface region of the adsorbent. In the latter, there are no equilibrium components of the adsorbent between the solid and vapor phases. The adsorbent state is shown to be determined by its prehistory, rather than set by chemical potentials of vapor of its components. Relations between the microscopic theory and thermodynamic interpretations are discussed: (1) adsorption on an open surface, (2) two-dimensional stratification of the adsorbate mobile phase on an open homogeneous surface, (3) small microcrystals in vacuum and the gas phase, and (4) adsorption in porous systems.

Thermodynamic and kinetic aspects of UO 2 fuel oxidation in air at 400-2000 K

NASA Astrophysics Data System (ADS)

Taylor, Peter

2005-09-01

Most nuclear fuel oxidation research has addressed either low-temperature (<700 K) air oxidation related to fuel storage or high-temperature (>1500 K) steam oxidation linked to reactor safety. This paper attempts to unify modelling for air oxidation of UO 2 fuel over a wide range of temperature, and thus to assist future improvement of the ASTEC code, co-developed by IRSN and GRS. Phenomenological correlations for different temperature ranges distinguish between oxidation on the scale of individual grains to U 3O 7 and U 3O 8 below ˜700 K and individual fragments to U 3O 8 via UO 2+ x and/or U 4O 9 above ˜1200 K. Between about 700 and 1200 K, empirical oxidation rates slowly decline as the U 3O 8 product becomes coarser-grained and more coherent, and fragment-scale processes become important. A more mechanistic approach to high-temperature oxidation addresses questions of oxygen supply, surface reaction kinetics, thermodynamic properties, and solid-state oxygen diffusion. Experimental data are scarce, however, especially at low oxygen partial pressures and high temperatures.

A Unified Approach to the Thermodynamics and Quantum Scaling Functions of One-Dimensional Strongly Attractive SU(w) Fermi Gases

NASA Astrophysics Data System (ADS)

Yu, Yi-Cong; Guan, Xi-Wen

2017-06-01

We present a unified derivation of the pressure equation of states, thermodynamics and scaling functions for the one-dimensional (1D) strongly attractive Fermi gases with SU(w) symmetry. These physical quantities provide a rigorous understanding on a universality class of quantum criticality characterized by the critical exponents z = 2 and correlation length exponent ν = 1/2. Such a universality class of quantum criticality can occur when the Fermi sea of one branch of charge bound states starts to fill or becomes gapped at zero temperature. The quantum critical cone can be determined by the double peaks in specific heat, which serve to mark two crossover temperatures fanning out from the critical point. Our method opens to further study on quantum phases and phase transitions in strongly interacting fermions with large SU(w) and non-SU(w) symmetries in one dimension. Supported by the National Natural Science Foundation of China under Grant No 11374331 and the key NSFC under Grant No 11534014. XWG has been partially supported by the Australian Research Council.

Evaluation of thermodynamically favourable operating conditions for production of hydrogen in three different reforming technologies

NASA Astrophysics Data System (ADS)

Seo, Y.-S.; Shirley, A.; Kolaczkowski, S. T.

With the aid of thermodynamic analysis using AspenPlus™, the characteristics of three different types of reforming process are investigated. These include: steam-methane reforming (SMR), partial oxidation (POX) and autothermal reforming (ATR). Thereby, favourable operating conditions are identified for each process. The optimum steam-to-carbon (S:C) ratio of the SMR reactor is found to be 1.9. The optimum air ratio of the POX reactor is 0.3 at a preheat temperature of 312 °C. The optimum air ratio and S:C ratio of the ATR reactor are 0.29 and 0.35, respectively at a preheat temperature of 400 °C. Simulated material and energy balances show that the CH 4 flow rates required to generate 1 mol s -1 of hydrogen are 0.364 mol s -1 for POX, 0.367 mol s -1 for ATR and 0.385 mol s -1 for the SMR. These results demonstrate that the POX reforming system has the lowest energy cost to produce the same amount of hydrogen from CH 4.

Thermodynamics and kinetics of protein folding on the ribosome: Alteration in energy landscapes, denatured state, and transition state ensembles

NASA Astrophysics Data System (ADS)

O'Brien, Edward; Vendruscolo, Michele; Dobson, Christopher

2010-03-01

In vitro experiments examining cotranslational folding utilize ribosome-nascent chain complexes (RNCs) in which the nascent chain is stalled at different points of its biosynthesis on the ribosome. We investigate the thermodynamics, kinetics, and structural properties of RNCs containing five different globular and repeat proteins stalled at ten different nascent chain lengths using coarse grained replica exchange simulations. We find that when the proteins are stalled near the ribosome exit tunnel opening they exhibit altered folding coopserativity, quantified by the van't Hoff enthalpy criterion; a significantly altered denatured state ensemble, in terms of Rg and shape parameters (Rg tensor); and the appearance of partially folded intermediates during cotranslation, evidenced by the appearance of a third basin in the free energy profile. These trends are due in part to excluded volume (crowding) interactions between the ribosome and nascent chain. We perform in silico temperature-jump experiments on the RNCs and examine nascent chain folding kinetics and structural changes in the transition state ensemble at various stall lengths.

Kinetic and thermodynamic studies on the adsorption of anionic surfactant on quaternary ammonium cationic cellulose.

PubMed

Zhang, Yuanzhang; Shi, Wenjian; Zhou, Hualan; Fu, Xing; Chen, Xuan

2010-06-01

Removal of anionic surfactants from aqueous solutions by adsorption onto quaternary ammonium cationic cellulose (QACC) was investigated. The effects of solution acidity, initial concentration, adsorption time, and temperature on the adsorption of sodium dodecyl-benzene sulfonate (SDBS), sodium lauryl sulfate (SLS), and sodium dodecyl sulfonate (SDS) were studied. The kinetic experimental data fit well with the pseudo-second-order model; the rate constant of the adsorption increased with temperature. The values of apparent activation energy for the adsorption were calculated as ranging from 10.2 to 17.4 kJ/ mol. The adsorption isotherm can be described by the Langmuir isotherm. The values of thermodynamic parameters (deltaH0, deltaS0, and deltaG0) for the adsorption indicated that this process was spontaneous and endothermic. At 318 K, the saturated adsorption capacities of QACC for SDBS, SLS, and SDS were 1.75, 1.53, and 1.39 mmol/g, respectively. The adsorption process was mainly chemisorption and partially physisorption. The results show that QACC is effective for the removal of anionic surfactants.

Constraining the hadronic spectrum through QCD thermodynamics on the lattice

NASA Astrophysics Data System (ADS)

Alba, Paolo; Bellwied, Rene; Borsányi, Szabolcs; Fodor, Zoltan; Günther, Jana; Katz, Sandor D.; Mantovani Sarti, Valentina; Noronha-Hostler, Jacquelyn; Parotto, Paolo; Pasztor, Attila; Vazquez, Israel Portillo; Ratti, Claudia

2017-08-01

Fluctuations of conserved charges allow us to study the chemical composition of hadronic matter. A comparison between lattice simulations and the hadron resonance gas (HRG) model suggested the existence of missing strange resonances. To clarify this issue we calculate the partial pressures of mesons and baryons with different strangeness quantum numbers using lattice simulations in the confined phase of QCD. In order to make this calculation feasible, we perform simulations at imaginary strangeness chemical potentials. We systematically study the effect of different hadronic spectra on thermodynamic observables in the HRG model and compare to lattice QCD results. We show that, for each hadronic sector, the well-established states are not enough in order to have agreement with the lattice results. Additional states, either listed in the Particle Data Group booklet (PDG) but not well established, or predicted by the quark model (QM), are necessary in order to reproduce the lattice data. For mesons, it appears that the PDG and the quark model do not list enough strange mesons, or that, in this sector, interactions beyond those included in the HRG model are needed to reproduce the lattice QCD results.

The Component Slope Linear Model for Calculating Intensive Partial Molar Properties: Application to Waste Glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reynolds, Jacob G.

2013-01-11

Partial molar properties are the changes occurring when the fraction of one component is varied while the fractions of all other component mole fractions change proportionally. They have many practical and theoretical applications in chemical thermodynamics. Partial molar properties of chemical mixtures are difficult to measure because the component mole fractions must sum to one, so a change in fraction of one component must be offset with a change in one or more other components. Given that more than one component fraction is changing at a time, it is difficult to assign a change in measured response to a changemore » in a single component. In this study, the Component Slope Linear Model (CSLM), a model previously published in the statistics literature, is shown to have coefficients that correspond to the intensive partial molar properties. If a measured property is plotted against the mole fraction of a component while keeping the proportions of all other components constant, the slope at any given point on a graph of this curve is the partial molar property for that constituent. Actually plotting this graph has been used to determine partial molar properties for many years. The CSLM directly includes this slope in a model that predicts properties as a function of the component mole fractions. This model is demonstrated by applying it to the constant pressure heat capacity data from the NaOH-NaAl(OH{sub 4}H{sub 2}O system, a system that simplifies Hanford nuclear waste. The partial molar properties of H{sub 2}O, NaOH, and NaAl(OH){sub 4} are determined. The equivalence of the CSLM and the graphical method is verified by comparing results detennined by the two methods. The CSLM model has been previously used to predict the liquidus temperature of spinel crystals precipitated from Hanford waste glass. Those model coefficients are re-interpreted here as the partial molar spinel liquidus temperature of the glass components.« less

Modeling Stochastic Kinetics of Molecular Machines at Multiple Levels: From Molecules to Modules

PubMed Central

Chowdhury, Debashish

2013-01-01

A molecular machine is either a single macromolecule or a macromolecular complex. In spite of the striking superficial similarities between these natural nanomachines and their man-made macroscopic counterparts, there are crucial differences. Molecular machines in a living cell operate stochastically in an isothermal environment far from thermodynamic equilibrium. In this mini-review we present a catalog of the molecular machines and an inventory of the essential toolbox for theoretically modeling these machines. The tool kits include 1), nonequilibrium statistical-physics techniques for modeling machines and machine-driven processes; and 2), statistical-inference methods for reverse engineering a functional machine from the empirical data. The cell is often likened to a microfactory in which the machineries are organized in modular fashion; each module consists of strongly coupled multiple machines, but different modules interact weakly with each other. This microfactory has its own automated supply chain and delivery system. Buoyed by the success achieved in modeling individual molecular machines, we advocate integration of these models in the near future to develop models of functional modules. A system-level description of the cell from the perspective of molecular machinery (the mechanome) is likely to emerge from further integrations that we envisage here. PMID:23746505

Control of nanoscale atomic arrangement in multicomponent thin films by temporally modulated vapour fluxes

NASA Astrophysics Data System (ADS)

Sarakinos, Kostas

2016-09-01

Synthesis of multicomponent thin films using vapor fluxes with a modulated deposition pattern is a potential route for accessing a wide gamut of atomic arrangements and morphologies for property tuning. In the current study, we present a research concept that allows for understanding the combined effect of flux modulation, kinetics and thermodynamics on the growth of multinary thin films. This concept entails the combined use of thin film synthesis by means of multiatomic vapor fluxes modulated with sub-monolayer resolution, deterministic growth simulations and nanoscale microstructure probes. Using this research concept we study structure formation within the archetype immiscible Ag-Cu binary system showing that atomic arrangement and morphology at different length scales is governed by diffusion of near-surface Ag atoms to encapsulate 3D Cu islands growing on 2D Ag layers. Moreover, we explore the relevance of the mechanism outlined above for morphology evolution and structure formation within the miscible Ag-Au binary system. The knowledge generated and the methodology presented herein provides the scientific foundation for tailoring atomic arrangement and physical properties in a wide range of miscible and immiscible multinary systems.

Homogeneous hydride formation path in α-Zr: Molecular dynamics simulations with the charge-optimized many-body potential

DOE PAGES

Zhang, Yongfeng; Bai, Xian-Ming; Yu, Jianguo; ...

2016-06-01

A formation path for homogeneous γ hydride formation in hcp α-Zr, from solid solution to the ζ and then the γ hydride, was demonstrated using molecular static calculations and molecular dynamic simulations with the charge-optimized many-body (COMB) potential. Hydrogen has limited solubility in α-Zr. Once the solubility limit is exceeded, the stability of solid solution gives way to that of coherent hydride phases such as the ζ hydride by planar precipitation of hydrogen. At finite temperatures, the ζ hydride goes through a partial hcp-fcc transformation via 1/3 <1¯100> slip on the basal plane, and transforms into a mixture of γmore » hydride and α-Zr. In the ζ hydride, slip on the basal plane is favored thermodynamically with negligible barrier, and is therefore feasible at finite temperatures without mechanical loading. The transformation process involves slips of three equivalent shear partials, in contrast to that proposed in the literature where only a single shear partial was involved. The adoption of multiple slip partials minimizes the macroscopic shape change of embedded hydride clusters and the shear strain accumulation in the matrix, and thus reduces the overall barrier needed for homogeneous γ hydride formation. In conclusion, this formation path requires finite temperatures for hydrogen diffusion without mechanical loading. Therefore, it should be effective at the cladding operating conditions.« less

Subatmospheric vapor pressures for fluoromethane (R41), 1,1-difluoroethane (R152a), and 1,1,1-trifluoroethane (R143a) evaluated from internal-energy measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duarte-Garza, H.A.; Magee, J.W.

1999-09-01

Vapor pressures were evaluated from measured internal-energy changes {Delta}U{sup (2)} in the vapor + liquid two-phase region. The method employed a thermodynamic relationship between the derivative quantity ({partial_derivative}U{sup (2)}/{partial_derivative}V){sub T}, the vapor pressure p{sub {sigma}}, and its temperature derivative ({partial_derivative}p/{partial_derivative}T){sub {sigma}}. This method was applied at temperatures between the triple point and the normal boiling point of three substances: fluoromethane (R41), 1,1-difluoroethane (R152a), and 1,1,1-trifluoroethane (R143a). In the case of R41, vapor pressures up to 1 MPa were calculated to validate the technique at higher pressures. For R152a, the calculated vapor pressure at the triple-point temperature differed from a directmore » experimental measurement by less than the claimed uncertainty (5 Pa) of the measurement. The calculated vapor pressures for R41 helped to resolve discrepancies in several published vapor pressure sources. Agreement with experimentally measured vapor pressures for R152a and for R143a near the normal boiling point (101.325 kPa) was within the experimental uncertainty of approximately 0.04 kPa (0.04%) for the published measurements.« less

Thermodynamic characterization of a tetrahaem cytochrome isolated from a facultative aerobic bacterium, Shewanella frigidimarina: a putative redox model for flavocytochrome c3.

PubMed Central

Pessanha, Miguel; Louro, Ricardo O; Correia, Ilídio J; Rothery, Emma L; Pankhurst, Kate L; Reid, Graeme A; Chapman, Stephen K; Turner, David L; Salgueiro, Carlos A

2003-01-01

The facultative aerobic bacterium Shewanella frigidimarina produces a small c-type tetrahaem cytochrome (86 residues) under anaerobic growth conditions. This protein is involved in the respiration of iron and shares 42% sequence identity with the N-terminal domain of a soluble flavocytochrome, isolated from the periplasm of the same bacterium, which also contains four c -type haem groups. The thermodynamic properties of the redox centres and of an ionizable centre in the tetrahaem cytochrome were determined using NMR and visible spectroscopy techniques. This is the first detailed thermodynamic study performed on a tetrahaem cytochrome isolated from a facultative aerobic bacterium and reveals that this protein presents unique features. The redox centres have negative and different redox potentials, which are modulated by redox interactions between the four haems (covering a range of 8-56 mV) and by redox-Bohr interactions between the haems and an ionizable centre (-4 to -36 mV) located in close proximity to haem III. All of the interactions between the five centres are clearly dominated by electrostatic effects and the microscopic reduction potential of haem III is the one most affected by the oxidation of the other haems and by the protonation state of the molecule. Altogether, this study indicates that the tetrahaem cytochrome isolated from S. frigidimarina (Sfc) has the thermodynamic properties to work as an electron wire between its redox partners. Considering the high degree of sequence identity between Sfc and the cytochrome domain of flavocytochrome c(3), the structural similarities of the haem core, and that the macroscopic potentials are also identical, the results obtained in this work are rationalized in order to put forward a putative redox model for flavocytochrome c(3). PMID:12413396

Thermodynamic changes in mechanochemically synthesized magnesium hydride nanoparticles.

PubMed

Paskevicius, Mark; Sheppard, Drew A; Buckley, Craig E

2010-04-14

The thermodynamic properties of magnesium hydride nanoparticles have been investigated by hydrogen decomposition pressure measurements using the Sieverts technique. A mechanochemical method was used to synthesize MgH(2) nanoparticles (down to approximately 7 nm in size) embedded in a LiCl salt matrix. In comparison to bulk MgH(2), the mechanochemically produced MgH(2) with the smallest particle size showed a small but measurable decrease in the decomposition reaction enthalpy (DeltaH decrease of 2.84 kJ/mol H(2) from DeltaH(bulk) = 74.06 +/- 0.42 kJ/mol H(2) to DeltaH(nano) = 71.22 +/- 0.49 kJ/mol H(2)). The reduction in DeltaH matches theoretical predictions and was also coupled with a similar reduction in reaction entropy (DeltaS decrease of 3.8 J/mol H(2)/K from DeltaS(bulk) = 133.4 +/- 0.7 J/mol H(2)/K to DeltaS(nano) = 129.6 +/- 0.8 J/mol H(2)/K). The thermodynamic changes in the MgH(2) nanoparticle system correspond to a drop in the 1 bar hydrogen equilibrium temperature (T(1 bar)) by approximately 6 degrees C to 276.2 +/- 2.4 degrees C in contrast to the bulk MgH(2) system at 281.8 +/- 2.2 degrees C. The reduction in the desorption temperature is less than that expected from theoretical studies due to the decrease in DeltaS that acts to partially counteract the effect from the change in DeltaH.

Molecular dynamics simulations of β2-microglobulin interaction with hydrophobic surfaces.

PubMed

Dongmo Foumthuim, Cedrix J; Corazza, Alessandra; Esposito, Gennaro; Fogolari, Federico

2017-11-21

Hydrophobic surfaces are known to adsorb and unfold proteins, a process that has been studied only for a few proteins. Here we address the interaction of β2-microglobulin, a paradigmatic protein for the study of amyloidogenesis, with hydrophobic surfaces. A system with 27 copies of the protein surrounded by a model cubic hydrophobic box is studied by implicit solvent molecular dynamics simulations. Most proteins adsorb on the walls of the box without major distortions in local geometry, whereas free molecules maintain proper structures and fluctuations as observed in explicit solvent molecular dynamics simulations. The major conclusions from the simulations are as follows: (i) the adopted implicit solvent model is adequate to describe protein dynamics and thermodynamics; (ii) adsorption occurs readily and is irreversible on the simulated timescale; (iii) the regions most involved in molecular encounters and stable interactions with the walls are the same as those that are important in protein-protein and protein-nanoparticle interactions; (iv) unfolding following adsorption occurs at regions found to be flexible by both experiments and simulations; (v) thermodynamic analysis suggests a very large contribution from van der Waals interactions, whereas unfavorable electrostatic interactions are not found to contribute much to adsorption energy. Surfaces with different degrees of hydrophobicity may occur in vivo. Our simulations show that adsorption is a fast and irreversible process which is accompanied by partial unfolding. The results and the thermodynamic analysis presented here are consistent with and rationalize previous experimental work.

Mechanism of formation and spatial distribution of lead atoms in quartz tube atomizers

NASA Astrophysics Data System (ADS)

Johansson, M.; Baxter, D. C.; Ohlsson, K. E. A.; Frech, W.

1997-05-01

The cross-sectional and longitudinal spatial distributions of lead atoms in a quartz tube (QT) atomizers coupled to a gas chromatograph have been investigated. A uniform analyte atom distribution over the cross-section was found in a QT having an inner diameter (i.d.) of 7 mm, whereas a 10 mm i.d. QT showed an inhomogeneous distribution. These results accentuate the importance of using QTs with i.d.s below 10 mm to fulfil the prerequirement of the Beer—Lambert law to avoid bent calibration curves. The influence of the make up gas on the formation of lead atoms from alkyllead compounds has been studied, and carbon monoxide was found equally efficient in promoting free atom formation as hydrogen. This suggests that hydrogen radicals are not essential for mediating the atomization of alkyllead in QT atomizers at ˜ 1200 K. Furthermore, thermodynamic equilibrium calculations describing the investigated system were performed supporting the experimental results. Based on the presented data, a mechanism for free lead atom formation in continuously heated QT atomizers is proposed; thermal atomization occurs under thermodynamic equilibrium conditions in a reducing gas. The longitudinal atom distribution has been further investigated applying other make up gases, N 2 and He. These results show the effect of the influx of atmospheric oxygen on the free lead atom formation. Calculations of the partial pressure of oxygen in the atomizer gas phase assuming thermodynamic equilibrium have been undertaken using a convective-diffusional model.

NMDA receptor modulation by dextromethorphan and acute stress selectively alters electroencephalographic indicators of partial report processing.

PubMed

Weckesser, Lisa J; Enge, Sören; Riedel, Philipp; Kirschbaum, Clemens; Miller, Robert

2017-10-01

Proceeding from a biophysical network model, the present study hypothesized that glutamatergic neurotransmission across the NMDA receptor (NMDAR) plays a key role in visual perception and its modulation by acute stress. To investigate these hypotheses, behavioral and electroencephalographic (EEG) indicators of partial report task processing were assessed in twenty-four healthy young men who randomly received a non-competitive NMDAR antagonist (0.8 mg/kg dextromethorphan, DXM) or a placebo, and concurrently accomplished a stress-induction (MAST) or control protocol in three consecutive sessions. Saliva samples served to quantify cortisol responses to the MAST, whereas a passive auditory oddball paradigm was implemented to verify the impact of DXM on the EEG-derived mismatch negativity component (MMN). DXM administration significantly increased MMN amplitudes but not salivary cortisol concentrations. By contrast, concurrent MAST exposure significantly reduced MMN latencies but also increased cortisol concentrations. With regard to EEG indicators, DXM administration reduced visually "evoked" (30Hz to 50Hz) and "induced" occipital gamma-band activity (70Hz to 100Hz), which was partly compensated by additional MAST exposure. However, neither the interventions nor EEG activity were significantly associated with behavioral partial report sensitivities. In summary, the present data suggest that glutamatergic neurotransmission across the NMDAR is only one among many determinants of intact visual perception. Accordingly, therapeutic doses of DXM and their inhibitory modulation by stress probably yield more pronounced electroencephalographic as compared with behavioural effects. Copyright © 2017 Elsevier B.V. and ECNP. All rights reserved.

Partial genetic deletion of neuregulin 1 modulates the effects of stress on sensorimotor gating, dendritic morphology, and HPA axis activity in adolescent mice.

PubMed

Chohan, Tariq W; Boucher, Aurelie A; Spencer, Jarrah R; Kassem, Mustafa S; Hamdi, Areeg A; Karl, Tim; Fok, Sandra Y; Bennett, Maxwell R; Arnold, Jonathon C

2014-11-01

Stress has been linked to the pathogenesis of schizophrenia. Genetic variation in neuregulin 1 (NRG1) increases the risk of developing schizophrenia and may help predict which high-risk individuals will transition to psychosis. NRG1 also modulates sensorimotor gating, a schizophrenia endophenotype. We used an animal model to demonstrate that partial genetic deletion of Nrg1 interacts with stress to promote neurobehavioral deficits of relevance to schizophrenia. Nrg1 heterozygous (HET) mice displayed greater acute stress-induced anxiety-related behavior than wild-type (WT) mice. Repeated stress in adolescence disrupted the normal development of higher prepulse inhibition of startle selectively in Nrg1 HET mice but not in WT mice. Further, repeated stress increased dendritic spine density in pyramidal neurons of the medial prefrontal cortex (mPFC) selectively in Nrg1 HET mice. Partial genetic deletion of Nrg1 also modulated the adaptive response of the hypothalamic-pituitary-adrenal axis to repeated stress, with Nrg1 HET displaying a reduced repeated stress-induced level of plasma corticosterone than WT mice. Our results demonstrate that Nrg1 confers vulnerability to repeated stress-induced sensorimotor gating deficits, dendritic spine growth in the mPFC, and an abberant endocrine response in adolescence. © The Author 2014. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: journals.permissions@oup.com.

Negative modulation of α5 GABAA receptors in rats may partially prevent memory impairment induced by MK-801, but not amphetamine- or MK-801-elicited hyperlocomotion

PubMed Central

Stamenić, Tamara Timić; Joksimović, Srdjan; Biawat, Poonam; Stanković, Tamara; Marković, Bojan; Cook, James M; Savić, Miroslav M

2016-01-01

Reportedly, negative modulation of α5 GABAA receptors may improve cognition in normal and pharmacologically-impaired animals, and such modulation has been proposed as an avenue for treatment of cognitive symptoms in schizophrenia. This study assessed the actions of PWZ-029, administered at doses (2, 5 and 10 mg/kg) at which it reached micromolar concentrations in brain tissue with estimated free concentrations adequate for selective modulation of α5 GABAA receptors, in three cognitive tasks in male Wistar rats acutely treated with the noncompetitive N-methyl-D-aspartate – receptor antagonist, MK-801 (0.1 mg/kg), as well in tests of locomotor activity potentiated by MK-801 (0.2 mg/kg) or amphetamine (0.5 mg/kg). In a hormetic-like manner, only 5 mg/kg PWZ-029 reversed MK-801-induced deficits in novel object recognition test (visual recognition memory), whereas in the Morris water maze, the 2 mg/kg dose of PWZ-029 exerted partial beneficial effects on spatial learning impairment. PWZ-029 did not affect recognition memory deficits in social novelty discrimination procedure. Motor hyperactivity induced with MK-801 or amphetamine was not preventable by PWZ-029. Our results show that certain MK-801-induced memory deficits can be ameliorated by negative modulation of α5 GABAA receptors, and point to the need for further elucidation of their translational relevance to cognitive deterioration in schizophrenia. PMID:26105958

Negative modulation of α₅ GABAA receptors in rats may partially prevent memory impairment induced by MK-801, but not amphetamine- or MK-801-elicited hyperlocomotion.

PubMed

Timić Stamenić, Tamara; Joksimović, Srdjan; Biawat, Poonam; Stanković, Tamara; Marković, Bojan; Cook, James M; Savić, Miroslav M

2015-09-01

Reportedly, negative modulation of α5 GABAA receptors may improve cognition in normal and pharmacologically-impaired animals, and such modulation has been proposed as an avenue for treatment of cognitive symptoms in schizophrenia. This study assessed the actions of PWZ-029, administered at doses (2, 5, and 10 mg/kg) at which it reached micromolar concentrations in brain tissue with estimated free concentrations adequate for selective modulation of α5 GABAA receptors, in three cognitive tasks in male Wistar rats acutely treated with the noncompetitive N-methyl-d-aspartate receptor antagonist, MK-801 (0.1 mg/kg), as well in tests of locomotor activity potentiated by MK-801 (0.2 mg/kg) or amphetamine (0.5 mg/kg). In a hormetic-like manner, only 5 mg/kg PWZ-029 reversed MK-801-induced deficits in novel object recognition test (visual recognition memory), whereas in the Morris water maze, the 2 mg/kg dose of PWZ-029 exerted partial beneficial effects on spatial learning impairment. PWZ-029 did not affect recognition memory deficits in social novelty discrimination procedure. Motor hyperactivity induced with MK-801 or amphetamine was not preventable by PWZ-029. Our results show that certain MK-801-induced memory deficits can be ameliorated by negative modulation of α5 GABAA receptors, and point to the need for further elucidation of their translational relevance to cognitive deterioration in schizophrenia. © The Author(s) 2015.

Whitham modulation theory for the two-dimensional Benjamin-Ono equation.

PubMed

Ablowitz, Mark; Biondini, Gino; Wang, Qiao

2017-09-01

Whitham modulation theory for the two-dimensional Benjamin-Ono (2DBO) equation is presented. A system of five quasilinear first-order partial differential equations is derived. The system describes modulations of the traveling wave solutions of the 2DBO equation. These equations are transformed to a singularity-free hydrodynamic-like system referred to here as the 2DBO-Whitham system. Exact reductions of this system are discussed, the formulation of initial value problems is considered, and the system is used to study the transverse stability of traveling wave solutions of the 2DBO equation.

Spectral model for long-term computation of thermodynamics and potential evaporation in shallow wetlands

NASA Astrophysics Data System (ADS)

de la Fuente, Alberto; Meruane, Carolina

2017-09-01

Altiplanic wetlands are unique ecosystems located in the elevated plateaus of Chile, Argentina, Peru, and Bolivia. These ecosystems are under threat due to changes in land use, groundwater extractions, and climate change that will modify the water balance through changes in precipitation and evaporation rates. Long-term prediction of the fate of aquatic ecosystems imposes computational constraints that make finding a solution impossible in some cases. In this article, we present a spectral model for long-term simulations of the thermodynamics of shallow wetlands in the limit case when the water depth tends to zero. This spectral model solves for water and sediment temperature, as well as heat, momentum, and mass exchanged with the atmosphere. The parameters of the model (water depth, thermal properties of the sediments, and surface albedo) and the atmospheric downscaling were calibrated using the MODIS product of the land surface temperature. Moreover, the performance of the daily evaporation rates predicted by the model was evaluated against daily pan evaporation data measured between 1964 and 2012. The spectral model was able to correctly represent both seasonal fluctuation and climatic trends observed in daily evaporation rates. It is concluded that the spectral model presented in this article is a suitable tool for assessing the global climate change effects on shallow wetlands whose thermodynamics is forced by heat exchanges with the atmosphere and modulated by the heat-reservoir role of the sediments.

Thermodynamic modelling of the formation of zinc-manganese ferrite spinel in electric arc furnace dust.

PubMed

Pickles, C A

2010-07-15

Electric arc furnace dust is generated when automobile scrap, containing galvanized steel, is remelted in an electric arc furnace. This dust is considered as a hazardous waste in most countries. Zinc is a major component of the dust and can be of significant commercial value. Typically, the majority of the zinc exists as zinc oxide (ZnO) and as a zinc-manganese ferrite spinel ((Zn(x)Mn(y)Fe(1-x-y))Fe(2)O(4)). The recovery of the zinc from the dust in metal recycling and recovery processes, particularly in the hydrometallurgical extraction processes, is often hindered by the presence of the mixed ferrite spinel. However, there is a paucity of information available in the literature on the formation of this spinel. Therefore, in the present research, the equilibrium module of HSC Chemistry 6.1 was utilized to investigate the thermodynamics of the formation of the spinel and the effect of variables on the amount and the composition of the mixed ferrite spinel. It is proposed that the mixed ferrite spinel forms due to the reaction of iron-manganese particulates with both gaseous oxygen and zinc, at the high temperatures in the freeboard of the furnace above the steel melt. Based on the thermodynamic predictions, methods are proposed for minimizing the formation of the mixed ferrite spinel. 2010 Elsevier B.V. All rights reserved.

Reactivity, characterization, equilibrium thermodynamics and hetero-bimetallic studies of tridentate and tetradentate complexes relevant to syngas catalysis

NASA Astrophysics Data System (ADS)

Imler, Gregory H.

The unifying objective of this work is the study of model systems that will assist in the development of new metal catalysts capable of converting carbon monoxide and hydrogen (syngas) into organic oxygenates at mild temperature and pressure. The selective catalytic transformation of carbon monoxide and hydrogen to liquid fuels and chemical feedstocks represents a major "Grand Challenge" of catalysis science. A core objective is the study of a macrocycle that is related to a porphyrin ligand in order to circumvent some of the disadvantages of utilizing porphyrins in catalysis. The rhodium complex of the macrocycle dibenzotetramethylaza[14]annulene ([(tmtaa)Rh]2]) was reacted with a series of small molecules relevant to CO reduction and hydrogenation. Several complexes were formed that demonstrated the ability to partially reduce and hydrogenate carbon monoxide, including the dirhodium ketone (Rh-C(O)-Rh) and an example of a thermodynamically favorable metal formyl complex ((tmtaa)Rh-C(O)H). An important feature of this work is the measurement of thermodynamic data to provide experimental benchmarks for obtaining key species in CO reduction and hydrogenation. A thorough study of the (tmtaa)Rh system will help in identifying structural features that assist or hinder CO hydrogenation. All reactions are monitored by 1H NMR which permits determination of solution thermodynamics from equilibrium constants obtained by NMR peak integrations. DFT calculations have supplemented experimental results by providing estimates to compare with the experimentally determined thermodynamic data. These computations also provide insight into the structures and thermodynamics of species that cannot be observed directly such as short lived intermediates and thermodynamically unfavorable products. Heterobimetallic complexes of (tmtaa)Rh• with a second metal radical have been utilized to attempt to convert CO to organic products. Reactivity with CO and H2 has been accomplished, with most of these metal systems providing (tmtaa)Rh-C(O)H and M-H as final products. These systems are now ideally set up for catalysis in which M-H can deliver hydrogen to reduce and hydrogenate the rhodium formyl unit. Performing these reactions at high pressures of CO/H2 or with a more sterically hindered analog of tmtaa may provide the conditions necessary for catalysis. Reactivity, thermodynamic and computational studies have been used to analyze and compare bond energies in this current work with previous studies accomplished in the Wayland group. These comparisons permit further understanding into the factors that control bond strength, guiding future studies and allowing tuning of bond strengths based on choice of conditions for a catalytic process. This research has resulted in a more complete understanding of the factors that control the favorability of various intermediates in CO reduction and hydrogenation and the application of these results can be used to guide the next generation of metal ligand systems that will yield organic oxygenates at mild conditions.

Variable-delay Polarization Modulators (VPMs) for Far-infrared through Millimeter Astronomy

NASA Technical Reports Server (NTRS)

Chuss, David T.

2008-01-01

This viewgraph presentation reviews the use of Variable-delay Polarization Modulators (VPMs) for Far-infrared through Millimeter Astronomy. The two science goals are to use polarized emission from the partially-aligned dust that provides a probe of the role of magnetic fields in star formation and to use the polarization of the cosmic microwave background radiation CMB to test theories of the very early universe and provide a probe of fundamental physics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kweon, Kyoung E.; Aberg, Daniel; Lordi, Vincenzo

The atomic and electronic structures of 60° glide perfect and 30°/90° glide partial dislocations in CdTe are studied using combined semi-empirical and density functional theory calculations. The calculations predict that the dislocation cores tend to undergo significant reconstructions along the dislocation lines from the singly-periodic (SP) structures, yielding either doubly-periodic (DP) ordering by forming a dimer or quadruply-periodic (QP) ordering by alternating a dimer and a missing dimer. Charge modulation along the dislocation line, accompanied by the QP reconstruction for the Cd-/Te-core 60° perfect and 30° partials or the DP reconstruction for the Cd-core 90° partial, results in semiconducting character,more » as opposed to the metallic character of the SP dislocation cores. Dislocation-induced defect states for the 60° Cd-/Te-core are located relatively close to the band edges, whereas the defect states lie in the middle of the band gap for the 30° Cd-/Te-core partial dislocations. In addition to the intracore charge modulation within each QP core, the possibility of intercore charge transfer between two different dislocation cores when they are paired together in the same system is discussed. As a result, the analysis of the electronic structures reveals the potential role of the dislocations on charge transport in CdTe, particularly in terms of charge trapping and recombination.« less

Photovoltaic module and laminate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bunea, Gabriela E.; Kim, Sung Dug; Kavulak, David F.J.

A photovoltaic module is disclosed. The photovoltaic module has a first side directed toward the sun during normal operation and a second, lower side. The photovoltaic module comprises a perimeter frame and a photovoltaic laminate at least partially enclosed by and supported by the perimeter frame. The photovoltaic laminate comprises a transparent cover layer positioned toward the first side of the photovoltaic module, an upper encapsulant layer beneath and adhering to the cover layer, a plurality of photovoltaic solar cells beneath the upper encapsulant layer, the photovoltaic solar cells electrically interconnected, a lower encapsulant layer beneath the plurality of photovoltaicmore » solar cells, the upper and lower encapsulant layers enclosing the plurality of photovoltaic solar cells, and a homogenous rear environmental protection layer, the rear environmental protection layer adhering to the lower encapsulant layer, the rear environmental protection layer exposed to the ambient environment on the second side of the photovoltaic module.« less

Microcanonical thermostatistics of coarse-grained proteins with amyloidogenic propensity

NASA Astrophysics Data System (ADS)

Frigori, Rafael B.; Rizzi, Leandro G.; Alves, Nelson A.

2013-01-01

The formation of fibrillar aggregates seems to be a common characteristic of polypeptide chains, although the observation of these aggregates may depend on appropriate experimental conditions. Partially folded intermediates seem to have an important role in the generation of protein aggregates, and a mechanism for this fibril formation considers that these intermediates also correspond to metastable states with respect to the fibrillar ones. Here, using a coarse-grained (CG) off-lattice model, we carry out a comparative analysis of the thermodynamic aspects characterizing the folding transition with respect to the propensity for aggregation of four different systems: two isoforms of the amyloid β-protein, the Src SH3 domain, and the human prion proteins (hPrP). Microcanonical analysis of the data obtained from replica exchange method is conducted to evaluate the free-energy barrier and latent heat in these models. The simulations of the amyloid β isoforms and Src SH3 domain indicated that the folding process described by this CG model is related to a negative specific heat, a phenomenon that can only be verified in the microcanonical ensemble in first-order phase transitions. The CG simulation of the hPrP heteropolymer yielded a continuous folding transition. The absence of a free-energy barrier and latent heat favors the presence of partially unfolded conformations, and in this context, this thermodynamic aspect could explain the reason why the hPrP heteropolymer is more aggregation-prone than the other heteropolymers considered in this study. We introduced the hydrophobic radius of gyration as an order parameter and found that it can be used to obtain reliable information about the hydrophobic packing and the transition temperatures in the folding process.

Hypervelocity atmospheric flight: Real gas flow fields

NASA Technical Reports Server (NTRS)

Howe, John T.

1990-01-01

Flight in the atmosphere is examined from the viewpoint of including real gas phenomena in the flow field about a vehicle flying at hypervelocity. That is to say, the flow field is subject not only to compressible phenomena, but is dominated by energetic phenomena. There are several significant features of such a flow field. Spatially, its composition can vary by both chemical and elemental species. The equations which describe the flow field include equations of state and mass, species, elemental, and electric charge continuity; momentum; and energy equations. These are nonlinear, coupled, partial differential equations that were reduced to a relatively compact set of equations of a self-consistent manner (which allows mass addition at the surface at a rate comparable to the free-stream mass flux). The equations and their inputs allow for transport of these quantities relative to the mass-averaged behavior of the flow field. Thus transport of mass by chemical, thermal, pressure, and forced diffusion; transport of momentum by viscosity; and transport of energy by conduction, chemical considerations, viscosity, and radiative transfer are included. The last of these complicate the set of equations by making the energy equation a partial integrodifferential equation. Each phenomenon is considered and represented mathematically by one or more developments. The coefficients which pertain are both thermodynamically and chemically dependent. Solutions of the equations are presented and discussed in considerable detail, with emphasis on severe energetic flow fields. For hypervelocity flight in low-density environments where gaseous reactions proceed at finite rates, chemical nonequilibrium is considered and some illustrations are presented. Finally, flight where the flow field may be out of equilibrium, both chemically and thermodynamically, is presented briefly.

Hypervelocity atmospheric flight: Real gas flow fields

NASA Technical Reports Server (NTRS)

Howe, John T.

1989-01-01

Flight in the atmosphere is examined from the viewpoint of including real gas phenomena in the flow field about a vehicle flying at hypervelocity. That is to say, the flow field is subject not only to compressible phenomena, but is dominated by energetic phenomena. There are several significant features of such a flow field. Spatially, its composition can vary by both chemical and elemental species. The equations which describe the flow field include equations of state and mass, species, elemental, and electric charge continuity; momentum; and energy equations. These are nonlinear, coupled, partial differential equations that have been reduced to a relatively compact set of equations in a self-consistent manner (which allows mass addition at the surface at a rate comparable to the free-stream mass flux). The equations and their inputs allow for transport of these quantities relative to the mass-average behavior of the flow field. Thus transport of mass by chemical, thermal, pressure, and forced diffusion; transport of momentum by viscosity; and transport of energy by conduction, chemical considerations, viscosity, and radiative transfer are included. The last of these complicate the set of equations by making the energy equations a partial integrodifferential equation. Each phenomenon is considered and represented mathematically by one or more developments. The coefficients which pertain are both thermodynamically and chemically dependent. Solutions of the equations are presented and discussed in considerable detail, with emphasis on severe energetic flow fields. Hypervelocity flight in low-density environments where gaseous reactions proceed at finite rates chemical nonequilibrium is considered, and some illustrations are presented. Finally, flight where the flow field may be out of equilibrium, both chemically and thermodynamically, is presented briefly.

Solar concentrator advanced development project

NASA Technical Reports Server (NTRS)

Corrigan, Robert D.; Ehresman, Derik T.

1987-01-01

A solar dynamic concentrator design developed for use with a solar-thermodynamic power generation module intended for the Space Station is considered. The truss hexagonal panel reflector uses a modular design approach and is flexible in attainable flux profiles and assembly techniques. Preliminary structural, thermal, and optical analysis results are discussed. Accuracy of the surface reflectors should be within 5 mrad rms slope error, resulting in the need for close fabrication tolerances. Significant fabrication issues to be addressed include the facet reflective and protective coating processes and the surface specularity requirements.

Lewis Research Center battery overview

NASA Technical Reports Server (NTRS)

Odonnell, Patricia

1993-01-01

The topics covered are presented in viewgraph form and include the following: the Advanced Communications Technology Satellite; the Space Station Freedom (SSF) photovoltaic power module division; Ni/H2 battery and cell design; individual pressure vessel (IPV) nickel-hydrogen cell testing SSF support; the LeRC Electrochemical Technology Branch; improved design IPV nickel-hydrogen cells; advanced technology for IPV nickel-hydrogen flight cells; a lightweight nickel-hydrogen cell; bipolar nickel-hydrogen battery development and technology; aerospace nickel-metal hydride cells; the NASA Sodium-Sulfur Cell Technology Flight Experiment; and the lithium-carbon dioxide battery thermodynamic model.

Primary Radiometry for the mise-en-pratique: The Laser-Based Radiance Method Applied to a Pyrometer

NASA Astrophysics Data System (ADS)

Briaudeau, S.; Sadli, M.; Bourson, F.; Rougi, B.; Rihan, A.; Zondy, J.-J.

2011-12-01

A new setup has been implemented at LCM-LNE-CNAM for the determination "of the spectral responsivity of radiation thermometers for the determination" of the thermodynamic temperature of high-temperature blackbodies at the temperature of a metal-carbon eutectic phase transition. In this new setup, an innovative acoustic-optic modulator feedback loop is used to stabilize the radiance of a wavelength tunable laser. The effect of residual optical interferences on the calibration of a test pyrometer is analyzed. The full uncertainty budget is presented.

Er{sub 1.33}Pt{sub 3}Ga{sub 8}: A modulated variant of the Er{sub 4}Pt{sub 9}Al{sub 24}-structure type

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oswald, Iain W.H.; Gourdon, Olivier; Bekins, Amy

Single crystals of Er{sub 1.33}Pt{sub 3}Ga{sub 8} were synthesized in a molten Ga flux. Er{sub 1.33}Pt{sub 3}Ga{sub 8} can be considered to be a modulated variant of the Er{sub 4}Pt{sub 9}Al{sub 24}-structure type, where the partial occupancies are ordered. Indeed, the presence of weak satellite reflections indicates a complex organization and distribution of the Er and Ga atoms within the [ErGa] slabs. The structure has been solved based on single crystal X-ray diffraction data in the monoclinic superspace group X2/m(0β0)00 with a commensurate modulated vector q=1/3b*. Precession images also indicate diffusion in the perpendicular direction indicating a partial disorder ofmore » this arrangement from layer to layer. In addition, Er{sub 1.33}Pt{sub 3}Ga{sub 8} shows antiferromagnetic ordering at T{sub N}~5 K. - Graphical abstract: A precession image of the hk0 zone showing weak, periodic, unindexed reflections indicating modulation and representation of the commensurate [ErGa] layer showing the waving modulated occupation. - Highlights: • Single crystals of Er{sub 1.33}Pt{sub 3}Ga{sub 8} were grown from gallium flux. • The structure of Er{sub 1.33}Pt{sub 3}Ga{sub 8} is compared to Er{sub 4}Pt{sub 9}Al{sub 24}. • Structure has been solved in the monoclinic superspace group X2/m(0β0)00 with a commensurate modulated vector q=1/3b*.« less

Thermo-mechanical Processing of TRIP-Aided Steels

NASA Astrophysics Data System (ADS)

Ranjan, Ravi; Beladi, Hossein; Singh, Shiv Brat; Hodgson, Peter D.

2015-07-01

The effects of the partial replacement of Si with Al and the addition of P on the microstructure and mechanical properties of experimental TRIP-aided steels subjected to different thermo-mechanical cycles were studied. Based on the available literature and thermodynamics-based calculations, three steels with different compositions were designed to obtain optimum results from a relatively low number of experiments. Different combinations of microstructure were developed through three different kinds of thermo-mechanical-controlled processing (TMCP) routes, and the corresponding tensile properties were evaluated. The results indicated that partial replacement of Si with Al improved the strength-ductility balance along with providing an improved variation in the incremental change in the strain-hardening exponent. However, the impact of the P addition was found to depend more on the final microstructure obtained by the different TMCP cycles. It has also been shown that an increase in the volume fraction of the retained austenite () or its carbon content () resulted in an improved strength-ductility balance, which can be attributed to better exploitation of the TRIP effect.

Salt Potentiates Methylamine Counteraction System to Offset the Deleterious Effects of Urea on Protein Stability and Function

PubMed Central

Singh, Laishram R.; Warepam, Marina; Ahmad, Faizan; Dar, Tanveer Ali

2015-01-01

Cellular methylamines are osmolytes (low molecular weight organic compounds) believed to offset the urea’s harmful effects on the stability and function of proteins in mammalian kidney and marine invertebrates. Although urea and methylamines are found at 2:1 molar ratio in tissues, their opposing effects on protein structure and function have been questioned on several grounds including failure to counteraction or partial counteraction. Here we investigated the possible involvement of cellular salt, NaCl, in urea-methylamine counteraction on protein stability and function. We found that NaCl mediates methylamine counteracting system from no or partial counteraction to complete counteraction of urea’s effect on protein stability and function. These conclusions were drawn from the systematic thermodynamic stability and functional activity measurements of lysozyme and RNase-A. Our results revealed that salts might be involved in protein interaction with charged osmolytes and hence in the urea-methylamine counteraction. PMID:25793733

Towards an Automated Full-Turbofan Engine Numerical Simulation

NASA Technical Reports Server (NTRS)

Reed, John A.; Turner, Mark G.; Norris, Andrew; Veres, Joseph P.

2003-01-01

The objective of this study was to demonstrate the high-fidelity numerical simulation of a modern high-bypass turbofan engine. The simulation utilizes the Numerical Propulsion System Simulation (NPSS) thermodynamic cycle modeling system coupled to a high-fidelity full-engine model represented by a set of coupled three-dimensional computational fluid dynamic (CFD) component models. Boundary conditions from the balanced, steady-state cycle model are used to define component boundary conditions in the full-engine model. Operating characteristics of the three-dimensional component models are integrated into the cycle model via partial performance maps generated automatically from the CFD flow solutions using one-dimensional meanline turbomachinery programs. This paper reports on the progress made towards the full-engine simulation of the GE90-94B engine, highlighting the generation of the high-pressure compressor partial performance map. The ongoing work will provide a system to evaluate the steady and unsteady aerodynamic and mechanical interactions between engine components at design and off-design operating conditions.

Finite-size versus interface-proximity effects in thin-film epitaxial SrTiO3

NASA Astrophysics Data System (ADS)

De Souza, R. A.; Gunkel, F.; Hoffmann-Eifert, S.; Dittmann, R.

2014-06-01

The equilibrium electrical conductivity of epitaxial SrTiO3 (STO) thin films was investigated as a function of temperature, 950≤ T/K ≤1100, and oxygen partial pressure, 10-23≤ pO2/bar ≤1. Compared with single-crystal STO, nanoscale thin-film STO exhibited with decreasing film thickness an increasingly enhanced electronic conductivity under highly reducing conditions, with a corresponding decrease in the activation enthalpy of conduction. This implies substantial modification of STO's point-defect thermodynamics for nanoscale film thicknesses. We argue, however, against such a finite-size effect and for an interface-proximity effect. Indeed, assuming trapping of oxygen vacancies at the STO surface and concomitant depletion of oxygen vacancies—and accumulation of electrons—in an equilibrium surface space-charge layer, we are able to predict quantitatively the conductivity as a function of temperature, oxygen partial pressure, and film thickness. Particularly complex behavior is predicted for ultrathin films that are consumed entirely by space charge.

Thermodynamic Equilibrium Solubility of Diethanolamine – N-Butyl-1-Methylpyrrolidinium Dicyanamide [DEABMPYRR DCA] Mixtures for Carbon Dioxide Capture

NASA Astrophysics Data System (ADS)

Salleh, R. M.; Jamaludin, S. N.

2018-05-01

Solubility data of carbon dioxide (CO2) in aqueous Diethanolamine (DEA) blended with pyrrolidinium-based ionic liquid: N-Butyl-1-Methylpyrrolidinium Dıcyanamıde [Bmpyrr][DCA] are presented at various temperatures (313.15K-333.15K) and pressure up to about 700 psi. The concentration of [Bmpyrr][DCA] ranges from 0-10wt% and 30-40wt% for DEA. The solubility of CO2 was evaluated by measuring the pressure drop in high pressure stirred absorption cell reactor. The CO2 loading in all studied mixtures increases with an increase in CO2 partial pressure and decreases with temperature. It was also found that the CO2 loading capacity decrease as the concentration of [Bmpyrr][DCA] increases. The experimental data were correlated as a function of temperature and CO2 partial pressure to predict the solubility of CO2 in the mixtures. It was found that the model predicted results in a good agreement with experimental value.

Web service module for access to g-Lite

NASA Astrophysics Data System (ADS)

Goranova, R.; Goranov, G.

2012-10-01

G-Lite is a lightweight grid middleware for grid computing installed on all clusters of the European Grid Infrastructure (EGI). The middleware is partially service-oriented and does not provide well-defined Web services for job management. The existing Web services in the environment cannot be directly used by grid users for building service compositions in the EGI. In this article we present a module of well-defined Web services for job management in the EGI. We describe the architecture of the module and the design of the developed Web services. The presented Web services are composable and can participate in service compositions (workflows). An example of usage of the module with tools for service compositions in g-Lite is shown.

Localization of massless Dirac particles via spatial modulations of the Fermi velocity

NASA Astrophysics Data System (ADS)

Downing, C. A.; Portnoi, M. E.

2017-08-01

The electrons found in Dirac materials are notorious for being difficult to manipulate due to the Klein phenomenon and absence of backscattering. Here we investigate how spatial modulations of the Fermi velocity in two-dimensional Dirac materials can give rise to localization effects, with either full (zero-dimensional) confinement or partial (one-dimensional) confinement possible depending on the geometry of the velocity modulation. We present several exactly solvable models illustrating the nature of the bound states which arise, revealing how the gradient of the Fermi velocity is crucial for determining fundamental properties of the bound states such as the zero-point energy. We discuss the implications for guiding electronic waves in few-mode waveguides formed by Fermi velocity modulation.

SU-F-T-414: Mathematical Formulation of Gantry Starting Angle for Right Medial Tangential Arc in Left Intact Partial Breast Irradiation Using Volumetric Modulated Arc Therapy (VMAT)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Giri, U; Sarkar, B; Kaur, H

Purpose: To choose appropriate gantry starting angle for partial left breast irradiation using volumetric modulated arc therapy (VMAT). Methods: A random patient of left breast carcinoma was selected for this study. The slice which was selected for this mathematical formulation was having maximum breast thickness and maximum medial and lateral tangential distance. After this appropriate isocenter was chosen on that CT slice. The distances between various points were measured by the measuring tool in Monaco 5.00.04. Using the various trigonometric equations, a final equation was derived which shows the relationship between Gantry start angle, isocenter Location and tissue thickness. Results:more » The final equation for gantry start for right medial tangential arc is given asStarting angle = 270°+tan^(−1)(sin(θ)/(x-1/x-2 +cosθ))The above equation was tested for 10 cases and it was found to be appropriate for all the cases. Conclusion: Gantry starting angle for partial arc irradiation depends upon Breast thickness, Distance between Medial and lateral tangent and isocenter location.« less

The Alzheimer Disease Protective Mutation A2T Modulates Kinetic and Thermodynamic Properties of Amyloid-β (Aβ) Aggregation*

PubMed Central

Benilova, Iryna; Gallardo, Rodrigo; Ungureanu, Andreea-Alexandra; Castillo Cano, Virginia; Snellinx, An; Ramakers, Meine; Bartic, Carmen; Rousseau, Frederic; Schymkowitz, Joost; De Strooper, Bart

2014-01-01

Missense mutations in alanine 673 of the amyloid precursor protein (APP), which corresponds to the second alanine of the amyloid β (Aβ) sequence, have dramatic impact on the risk for Alzheimer disease; A2V is causative, and A2T is protective. Assuming a crucial role of amyloid-Aβ in neurodegeneration, we hypothesized that both A2V and A2T mutations cause distinct changes in Aβ properties that may at least partially explain these completely different phenotypes. Using human APP-overexpressing primary neurons, we observed significantly decreased Aβ production in the A2T mutant along with an enhanced Aβ generation in the A2V mutant confirming earlier data from non-neuronal cell lines. More importantly, thioflavin T fluorescence assays revealed that the mutations, while having little effect on Aβ42 peptide aggregation, dramatically change the properties of the Aβ40 pool with A2V accelerating and A2T delaying aggregation of the Aβ peptides. In line with the kinetic data, Aβ A2T demonstrated an increase in the solubility at equilibrium, an effect that was also observed in all mixtures of the A2T mutant with the wild type Aβ40. We propose that in addition to the reduced β-secretase cleavage of APP, the impaired propensity to aggregate may be part of the protective effect conferred by A2T substitution. The interpretation of the protective effect of this mutation is thus much more complicated than proposed previously. PMID:25253695

Modulation of partition and localization of perfume molecules in sodium dodecyl sulfate micelles.

PubMed

Fan, Yaxun; Tang, Haiqiu; Strand, Ross; Wang, Yilin

2016-01-07

The influence of perfume molecules on the self-assembly of the anionic surfactant sodium dodecyl sulfate (SDS) and their localization in SDS micelles have been investigated by ζ potential, small angle X-ray scattering (SAXS), one- and two-dimensional NMR and isothermal titration microcalorimetry (ITC). A broad range of perfume molecules varying in octanol/water partition coefficients P are employed. The results indicate that the surface charge, size and aggregation number of the SDS micelles strongly depend on the hydrophobicity/hydrophilicity degree of perfume molecules. Three distinct regions along the log P values are identified. Hydrophilic perfumes (log P < 2.0) partially incorporate into the SDS micelles and do not lead to micelle swelling, whereas hydrophobic perfumes (log P > 3.5) are solubilized close to the end of the hydrophobic chains in the SDS micelles and enlarge the micelles with higher ζ potential and a larger aggregation number. The incorporated fraction and micelle properties show increasing tendency for the perfumes in the intermediate log P region (2.0 < log P < 3.5). Besides, the molecular conformation of perfume molecules also affects these properties. The perfumes with a linear chain structure or an aromatic group can penetrate into the palisade layer and closely pack with the SDS molecules. Furthermore, the thermodynamic parameters obtained from ITC show that the binding of the perfumes in the intermediate log P region is more spontaneous than those in the other two log P regions, and the micellization of SDS with the perfumes is driven by entropy.

Modeling back-relaxation in ionic polymer metal composites: The role of steric effects and composite layers

NASA Astrophysics Data System (ADS)

Porfiri, Maurizio; Sharghi, Hesam; Zhang, Peng

2018-01-01

Ionic polymer metal composites (IPMCs) are a new class of active materials that are gaining traction as soft actuators in medical and industrial applications. IPMCs can undergo large deformations under modest voltage inputs, in dry and wet environments. Past studies have demonstrated that physical and geometric properties of all the IPMC constituents (ionomer, electrodes, and counterions) may all influence the time scales of the transient response and severity of the back-relaxation. In this study, we present a detailed mathematical model to investigate how the finite size of the counterions and the presence of metal particles in the vicinity of the electrodes modulate IPMC actuation. We build on previous work by our group on thermodynamically consistent modeling of IPMC mechanics and electrochemistry, which attributes IPMC actuation to the interplay between Maxwell stress and osmotic forces. To gain insight into the role of physical and geometric parameters, the resulting nonlinear partial differential equations are solved semianalytically using the method of matched asymptotic expansions, for the initial transient and the steady-state. A numerical solution in COMSOL Multiphysics® is developed to verify semianalytical findings and further explore IPMC actuation. Our model can successfully predict the entire response of IPMCs, from the initial bending toward the anode to the steady-state toward the cathode. We find that the steric effect can abolish the back-relaxation of IPMCs by restraining the counterions' concentration near the electrodes. We also find that increasing the thickness of the ionomer-metal composite layers may enhance IPMC actuation through increased osmotic forces and Maxwell stress.

Supramolecular Assembly of Comb-like Macromolecules Induced by Chemical Reactions that Modulate the Macromolecular Interactions In Situ.

PubMed

Xia, Hongwei; Fu, Hailin; Zhang, Yanfeng; Shih, Kuo-Chih; Ren, Yuan; Anuganti, Murali; Nieh, Mu-Ping; Cheng, Jianjun; Lin, Yao

2017-08-16

Supramolecular polymerization or assembly of proteins or large macromolecular units by a homogeneous nucleation mechanism can be quite slow and require specific solution conditions. In nature, protein assembly is often regulated by molecules that modulate the electrostatic interactions of the protein subunits for various association strengths. The key to this regulation is the coupling of the assembly process with a reversible or irreversible chemical reaction that occurs within the constituent subunits. However, realizing this complex process by the rational design of synthetic molecules or macromolecules remains a challenge. Herein, we use a synthetic polypeptide-grafted comb macromolecule to demonstrate how the in situ modulation of interactions between the charged macromolecules affects their resulting supramolecular structures. The kinetics of structural formation was studied and can be described by a generalized model of nucleated polymerization containing secondary pathways. Basic thermodynamic analysis indicated the delicate role of the electrostatic interactions between the charged subunits in the reaction-induced assembly process. This approach may be applicable for assembling a variety of ionic soft matters that are amenable to chemical reactions in situ.

Proteomic profiling of ATM kinase proficient and deficient cell lines upon blockage of proteasome activity☆

PubMed Central

Marzano, Valeria; Santini, Simonetta; Rossi, Claudia; Zucchelli, Mirco; D'Alessandro, Annamaria; Marchetti, Carlo; Mingardi, Michele; Stagni, Venturina; Barilà, Daniela; Urbani, Andrea

2012-01-01

Ataxia Telangiectasia Mutated (ATM) protein kinase is a key effector in the modulation of the functionality of some important stress responses, including DNA damage and oxidative stress response, and its deficiency is the hallmark of Ataxia Telangiectasia (A-T), a rare genetic disorder. ATM modulates the activity of hundreds of target proteins, essential for the correct balance between proliferation and cell death. The aim of this study is to evaluate the phenotypic adaptation at the protein level both in basal condition and in presence of proteasome blockage in order to identify the molecules whose level and stability are modulated through ATM expression. We pursued a comparative analysis of ATM deficient and proficient lymphoblastoid cells by label-free shotgun proteomic experiments comparing the panel of proteins differentially expressed. Through a non-supervised comparative bioinformatic analysis these data provided an insight on the functional role of ATM deficiency in cellular carbohydrate metabolism's regulation. This hypothesis has been demonstrated by targeted metabolic fingerprint analysis SRM (Selected Reaction Monitoring) on specific thermodynamic checkpoints of glycolysis. This article is part of a Special Issue entitled: Translational Proteomics. PMID:22641158

GVIPS Models and Software

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Gendy, Atef; Saleeb, Atef F.; Mark, John; Wilt, Thomas E.

2007-01-01

Two reports discuss, respectively, (1) the generalized viscoplasticity with potential structure (GVIPS) class of mathematical models and (2) the Constitutive Material Parameter Estimator (COMPARE) computer program. GVIPS models are constructed within a thermodynamics- and potential-based theoretical framework, wherein one uses internal state variables and derives constitutive equations for both the reversible (elastic) and the irreversible (viscoplastic) behaviors of materials. Because of the underlying potential structure, GVIPS models not only capture a variety of material behaviors but also are very computationally efficient. COMPARE comprises (1) an analysis core and (2) a C++-language subprogram that implements a Windows-based graphical user interface (GUI) for controlling the core. The GUI relieves the user of the sometimes tedious task of preparing data for the analysis core, freeing the user to concentrate on the task of fitting experimental data and ultimately obtaining a set of material parameters. The analysis core consists of three modules: one for GVIPS material models, an analysis module containing a specialized finite-element solution algorithm, and an optimization module. COMPARE solves the problem of finding GVIPS material parameters in the manner of a design-optimization problem in which the parameters are the design variables.

A thermodynamic recipe for baking the Earth's lower mantle and core as a whole

NASA Astrophysics Data System (ADS)

Tirone, Max; Faak, Kathi

2016-04-01

A rigorous understanding of the thermal and dynamic evolution of the core and the interaction with the silicate mantle cannot preclude a non-empirical petrological description of the problem which takes the form of a thermodynamic model. Because the Earth's core is predominantly made of iron such model may seem relatively straightforward, simply delivering a representation of the phase transformations in the P,T space. However due to well known geophysical considerations, a certain amount of light elements should be added. With the Occam's razor principle in mind, potential candidates could be the most abundant and easily accessible elements in the mantle, O, Si and Mg. Given these premises, the challenging problems on developing this type of model are: - a thermodynamic formulation should not simply describe phase equilibrium relations at least in the Fe-Si-O system (a formidable task itself) but should be also consistently applicable to evaluate thermophysical properties of liquid components and solids phases at extreme conditions (P=500-2000 kbar, T=1000-5000 K). Presently these properties are unknown for certain mineral and liquid components or partially available from scattered sources. - experimental data on the phase relations for iron rich liquid are extremely difficult to obtain and could not cover the entire P,T,X spectrum. - interaction of the outer core with the silicate mantle requires a melt model that is capable of describing a vast range of compositions ranging from metal-rich liquids to silicate liquids. The compound energy formalism for liquids with variable tendency to ionization developed by Hillert and coworkers is a sublattice model with varying stoichiometry that includes vacancies and neutral species in one site. It represents the ideal candidate for the task in hand. The thermodynamic model unfortunately is rather complex and a detailed description of the formulation for practical applications like chemical equilibrium calculations is nowhere to be found, while the model is only accessible on few commercial thermodynamic programs. The latest developments regarding all these related issues will be discussed in this contribution. In particular some self-consistent but preliminary results will be presented addressing the following topics: - some details regarding the implementation of the liquid model for Gibbs free energy minimizations, - the physically consistent behavior of thermodynamic properties of certain solid phases like (Fe,O,Si) BCC, FCC, HCP and liquid components, - selected phase diagrams at core conditions in the system Fe-Si-O, - derived geotherms linking the inner-outer core with the core-mantle boundary. - brief outline of the future geodynamic applications.

Numerical implementation and oceanographic application of the thermodynamic potentials of water, vapour, ice, seawater and air - Part 2: The library routines

NASA Astrophysics Data System (ADS)

Wright, D. G.; Feistel, R.; Reissmann, J. H.; Miyagawa, K.; Jackett, D. R.; Wagner, W.; Overhoff, U.; Guder, C.; Feistel, A.; Marion, G. M.

2010-03-01

The SCOR/IAPSO1 Working Group 127 on Thermodynamics and Equation of State of Seawater has prepared recommendations for new methods and algorithms for numerical estimation of the thermophysical properties of seawater. As an outcome of this work, a new International Thermodynamic Equation of Seawater (TEOS-10) was endorsed by IOC/UNESCO2 in June 2009 as the official replacement and extension of the 1980 International Equation of State, EOS-80. As part of this new standard a source code package has been prepared that is now made freely available to users via the World Wide Web. This package includes two libraries referred to as the SIA (Sea-Ice-Air) library and the GSW (Gibbs SeaWater) library. Information on the GSW library may be found on the TEOS-10 web site (http://www.TEOS-10.org). This publication provides an introduction to the SIA library which contains routines to calculate various thermodynamic properties as discussed in the companion paper. The SIA library is very comprehensive, including routines to deal with fluid water, ice, seawater and humid air as well as equilibrium states involving various combinations of these, with equivalent code developed in different languages. The code is hierachically structured in modules that support (i) almost unlimited extension with respect to additional properties or relations, (ii) an extraction of self-contained sub-libraries, (iii) separate updating of the empirical thermodynamic potentials, and (iv) code verification on different platforms and between different languages. Error trapping is implemented to identify when one or more of the primary routines are accessed significantly beyond their established range of validity. The initial version of the SIA library is available in Visual Basic and FORTRAN as a supplement to this publication and updates will be maintained on the TEOS-10 web site. 1 SCOR/IAPSO: Scientific Committee on Oceanic Research/International Association for the Physical Sciences of the Oceans 2 IOC/UNESCO: Intergovernmental Oceanographic Commission/United Nations Educational, Scientific and Cultural Organization

Numerical implementation and oceanographic application of the thermodynamic potentials of liquid water, water vapour, ice, seawater and humid air - Part 2: The library routines

NASA Astrophysics Data System (ADS)

Wright, D. G.; Feistel, R.; Reissmann, J. H.; Miyagawa, K.; Jackett, D. R.; Wagner, W.; Overhoff, U.; Guder, C.; Feistel, A.; Marion, G. M.

2010-07-01

The SCOR/IAPSO1 Working Group 127 on Thermodynamics and Equation of State of Seawater has prepared recommendations for new methods and algorithms for numerical estimation of the the thermophysical properties of seawater. As an outcome of this work, a new International Thermodynamic Equation of Seawater (TEOS-10) was endorsed by IOC/UNESCO2 in June 2009 as the official replacement and extension of the 1980 International Equation of State, EOS-80. As part of this new standard a source code package has been prepared that is now made freely available to users via the World Wide Web. This package includes two libraries referred to as the SIA (Sea-Ice-Air) library and the GSW (Gibbs SeaWater) library. Information on the GSW library may be found on the TEOS-10 web site (http://www.TEOS-10.org). This publication provides an introduction to the SIA library which contains routines to calculate various thermodynamic properties as discussed in the companion paper. The SIA library is very comprehensive, including routines to deal with fluid water, ice, seawater and humid air as well as equilibrium states involving various combinations of these, with equivalent code developed in different languages. The code is hierachically structured in modules that support (i) almost unlimited extension with respect to additional properties or relations, (ii) an extraction of self-contained sub-libraries, (iii) separate updating of the empirical thermodynamic potentials, and (iv) code verification on different platforms and between different languages. Error trapping is implemented to identify when one or more of the primary routines are accessed significantly beyond their established range of validity. The initial version of the SIA library is available in Visual Basic and FORTRAN as a supplement to this publication and updates will be maintained on the TEOS-10 web site. 1SCOR/IAPSO: Scientific Committee on Oceanic Research/International Association for the Physical Sciences of the Oceans 2IOC/UNESCO: Intergovernmental Oceanographic Commission/United Nations Educational, Scientific and Cultural Organization

Membrane Lipid Microenvironment Modulates Thermodynamic Properties of the Na+-K+-ATPase in Branchial and Intestinal Epithelia in Euryhaline Fish In vivo

PubMed Central

Díaz, Mario; Dópido, Rosa; Gómez, Tomás; Rodríguez, Covadonga

2016-01-01

We have analyzed the effects of different native membrane lipid composition on the thermodynamic properties of the Na+-K+-ATPase in different epithelia from the gilthead seabream Sparus aurata. Thermodynamic parameters of activation for the Na+-K+-ATPase, as well as contents of lipid classes and fatty acids from polar lipids were determined for gill epithelia and enterocytes isolated from pyloric caeca, anterior intestine and posterior intestine. Arrhenius analyses of control animals revealed differences in thermal discontinuity values (Td) and activation energies determined at both sides of Td between intestinal and gill epithelia. Eyring plots disclosed important differences in enthalpy of activation (ΔH‡) and entropy of activation (ΔS‡) between enterocytes and branchial cells. Induction of n-3 LCPUFA deficiency dramatically altered membrane lipid composition in enterocytes, being the most dramatic changes the increase in 18:1n-9 (oleic acid) and the reduction of n-3 LCPUFA (mainly DHA, docosahexaenoic acid). Strikingly, branchial cells were much more resistant to diet-induced lipid alterations than enterocytes, indicating the existence of potent lipostatic mechanisms preserving membrane lipid matrix in gill epithelia. Paralleling lipid alterations, values of Ea1, ΔH‡ and ΔS‡ for the Na+-K+-ATPase were all increased, while Td values vanished, in LCPUFA deficient enterocytes. In turn, Differences in thermodynamic parameters were highly correlated with specific changes in fatty acids, but not with individual lipid classes including cholesterol in vivo. Thus, Td was positively related to 18:1n-9 and negatively to DHA. Td, Ea1 and ΔH‡ were exponentially related to DHA/18:1n-9 ratio. The exponential nature of these relationships highlights the strong impact of subtle changes in the contents of oleic acid and DHA in setting the thermodynamic properties of epithelial Na+-K+-ATPase in vivo. The effects are consistent with physical effects on the lipid membrane surrounding the enzyme as well as with direct interactions with the Na+-K+-ATPase. PMID:28018232

Thermodynamic and dynamic ice thickness contributions in the Canadian Arctic Archipelago in NEMO-LIM2 numerical simulations

NASA Astrophysics Data System (ADS)

Hu, Xianmin; Sun, Jingfan; Chan, Ting On; Myers, Paul G.

2018-04-01

Sea ice thickness evolution within the Canadian Arctic Archipelago (CAA) is of great interest to science, as well as local communities and their economy. In this study, based on the NEMO numerical framework including the LIM2 sea ice module, simulations at both 1/4 and 1/12° horizontal resolution were conducted from 2002 to 2016. The model captures well the general spatial distribution of ice thickness in the CAA region, with very thick sea ice (˜ 4 m and thicker) in the northern CAA, thick sea ice (2.5 to 3 m) in the west-central Parry Channel and M'Clintock Channel, and thin ( < 2 m) ice (in winter months) on the east side of CAA (e.g., eastern Parry Channel, Baffin Island coast) and in the channels in southern areas. Even though the configurations still have resolution limitations in resolving the exact observation sites, simulated ice thickness compares reasonably (seasonal cycle and amplitudes) with weekly Environment and Climate Change Canada (ECCC) New Ice Thickness Program data at first-year landfast ice sites except at the northern sites with high concentration of old ice. At 1/4 to 1/12° scale, model resolution does not play a significant role in the sea ice simulation except to improve local dynamics because of better coastline representation. Sea ice growth is decomposed into thermodynamic and dynamic (including all non-thermodynamic processes in the model) contributions to study the ice thickness evolution. Relatively smaller thermodynamic contribution to ice growth between December and the following April is found in the thick and very thick ice regions, with larger contributions in the thin ice-covered region. No significant trend in winter maximum ice volume is found in the northern CAA and Baffin Bay while a decline (r2 ≈ 0.6, p < 0.01) is simulated in Parry Channel region. The two main contributors (thermodynamic growth and lateral transport) have high interannual variabilities which largely balance each other, so that maximum ice volume can vary interannually by ±12 % in the northern CAA, ±15 % in Parry Channel, and ±9 % in Baffin Bay. Further quantitative evaluation is required.

[Prediction of the molecular response to pertubations from single cell measurements].

PubMed

Remacle, Françoise; Levine, Raphael D

2014-12-01

The response of protein signalization networks to perturbations is analysed from single cell measurements. This experimental approach allows characterizing the fluctuations in protein expression levels from cell to cell. The analysis is based on an information theoretic approach grounded in thermodynamics leading to a quantitative version of Le Chatelier principle which allows to predict the molecular response. Two systems are investigated: human macrophages subjected to lipopolysaccharide challenge, analogous to the immune response against Gram-negative bacteria and the response of the proteins involved in the mTOR signalizing network of GBM cancer cells to changes in partial oxygen pressure. © 2014 médecine/sciences – Inserm.

Thermodynamic assessment of the U–Y–O system

DOE PAGES

Brese, R. G.; McMurray, J. W.; Shin, D.; ...

2015-02-03

We developed a CALPHAD assessment of the U-Y-O system. To represent the YO2 compound in the compound energy formalism (CEF) for U 1-yY yO 2± x, the lattice stability was calculated using density functional theory (DFT) while a partially ionic liquid sub-lattice model is used to describe the liquid phase. Moreover, a Gibbs function for the stoichiometric rhombohedral UY 6O 12 phase is proposed. Models representing the phases in the U-O and Y-O systems taken from the literature along with the phases that appear in the U-Y-O ternary are combined to form a unified assessment.

Thermodynamic and critical properties of an antiferromagnetically stacked triangular Ising antiferromagnet in a field

NASA Astrophysics Data System (ADS)

Žukovič, M.; Borovský, M.; Bobák, A.

2018-05-01

We study a stacked triangular lattice Ising model with both intra- and inter-plane antiferromagnetic interactions in a field, by Monte Carlo simulation. We find only one phase transition from a paramagnetic to a partially disordered phase, which is of second order and 3D XY universality class. At low temperatures we identify two highly degenerate phases: at smaller (larger) fields the system shows long-range ordering in the stacking direction (within planes) but not in the planes (stacking direction). Nevertheless, crossovers to these phases do not have a character of conventional phase transitions but rather linear-chain-like excitations.

Environmental Resistance in the Mars Atmosphere

NASA Astrophysics Data System (ADS)

Pint, Bruce A.; Tortorelli, Peter F.

2005-02-01

The atmosphere of Mars is ~6mbar of total pressure (compared to ~1 bar on Earth) and 95%CO2. Thermodynamic calculations have been made of the partial pressure of oxygen as a function of temperature assuming various impurities in the remaining 5%. These oxygen pressures are sufficient to oxidize most common metals in the 900-1300K range. Therefore, oxidation resistance will be a concern for materials of construction in a high temperature fission reactor on Mars. An additional environmental resistance consideration is internal carburization during exposures in CO2. The effect of low pressure CO2 exposures on the mechanical properties of austenitic alloys is being investigated.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deline, Chris; Meydbray, Jenya; Donovan, Matt

The 2012 NREL report 'Photovoltaic Shading Testbed for Module-Level Power Electronics' provides a standard methodology for estimating the performance benefit of distributed power electronics under partial shading conditions. Since the release of the report, experiments have been conducted for a number of products and for different system configurations. Drawing from these experiences, updates to the test and analysis methods are recommended. Proposed changes in data processing have the benefit of reducing the sensitivity to measurement errors and weather variability, as well as bringing the updated performance score in line with measured and simulated values of the shade recovery benefit ofmore » distributed PV power electronics. Also, due to the emergence of new technologies including sub-module embedded power electronics, the shading method has been extended to include power electronics that operate at a finer granularity than the module level. An update to the method is proposed to account for these emerging technologies that respond to shading differently than module-level devices. The partial shading test remains a repeatable test procedure that attempts to simulate shading situations as would be experienced by typical residential or commercial rooftop photovoltaic (PV) systems. Performance data for multiple products tested using this method are discussed, based on equipment from Enphase, Solar Edge, Maxim Integrated and SMA. In general, the annual recovery of shading losses from the module-level electronics evaluated is 25-35%, with the major difference between different trials being related to the number of parallel strings in the test installation rather than differences between the equipment tested. Appendix D data has been added in this update.« less

Can Intensity-Modulated Radiotherapy Preserve Oral Health-Related Quality of Life of Nasopharyngeal Carcinoma Patients?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pow, Edmond H.N., E-mail: ehnpow@hku.hk; Kwong, Dora L.W.; Sham, Jonathan S.T.

Purpose: To investigate the changes in salivary function and oral health-related quality of life for patients with nasopharyngeal carcinoma treated by intensity-modulated radiotherapy (IMRT). Methods and Materials: A total of 57 patients with early-stage nasopharyngeal carcinoma received IMRT. The parotid and whole saliva flow was measured, and the Medical Outcomes Study 36-item short form, European Organization for Research and Treatment of Cancer Quality of Life questionnaire-C30, European Organization for Research and Treatment of Cancer Quality of Life questionnaire 35-item head-and-neck module, and Oral Health Impact Profile questionnaires were completed at baseline and 2, 6, 12, 18, and 24 months aftermore » IMRT. Results: Parotid saliva flow recovered fully after 1 year and maintained. Whole saliva flow recovered partially to 40% of baseline. A general trend of deterioration in most quality of life scales was observed after IMRT, followed by gradual recovery. Persistent oral-related symptoms were found 2 years after treatment. Conclusion: IMRT for early-stage nasopharyngeal carcinoma could only partially preserve the whole salivary function and oral health-related quality of life.« less

Heat Shock Partially Dissociates the Overlapping Modules of the Yeast Protein-Protein Interaction Network: A Systems Level Model of Adaptation

PubMed Central

Mihalik, Ágoston; Csermely, Peter

2011-01-01

Network analysis became a powerful tool giving new insights to the understanding of cellular behavior. Heat shock, the archetype of stress responses, is a well-characterized and simple model of cellular dynamics. S. cerevisiae is an appropriate model organism, since both its protein-protein interaction network (interactome) and stress response at the gene expression level have been well characterized. However, the analysis of the reorganization of the yeast interactome during stress has not been investigated yet. We calculated the changes of the interaction-weights of the yeast interactome from the changes of mRNA expression levels upon heat shock. The major finding of our study is that heat shock induced a significant decrease in both the overlaps and connections of yeast interactome modules. In agreement with this the weighted diameter of the yeast interactome had a 4.9-fold increase in heat shock. Several key proteins of the heat shock response became centers of heat shock-induced local communities, as well as bridges providing a residual connection of modules after heat shock. The observed changes resemble to a ‘stratus-cumulus’ type transition of the interactome structure, since the unstressed yeast interactome had a globally connected organization, similar to that of stratus clouds, whereas the heat shocked interactome had a multifocal organization, similar to that of cumulus clouds. Our results showed that heat shock induces a partial disintegration of the global organization of the yeast interactome. This change may be rather general occurring in many types of stresses. Moreover, other complex systems, such as single proteins, social networks and ecosystems may also decrease their inter-modular links, thus develop more compact modules, and display a partial disintegration of their global structure in the initial phase of crisis. Thus, our work may provide a model of a general, system-level adaptation mechanism to environmental changes. PMID:22022244

Study for reducing lung dose of upper thoracic esophageal cancer radiotherapy by auto-planning: volumetric-modulated arc therapy vs intensity-modulated radiation therapy.

PubMed

Chen, Hua; Wang, Hao; Gu, Hengle; Shao, Yan; Cai, Xuwei; Fu, Xiaolong; Xu, Zhiyong

2017-10-27

This study aimed to investigate the dosimetric differences and lung sparing between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) in the treatment of upper thoracic esophageal cancer with T3N0M0 for preoperative radiotherapy by auto-planning (AP). Sixteen patient cases diagnosed with upper thoracic esophageal cancer T3N0M0 for preoperative radiotherapy were retrospectively studied, and 3 plans were generated for each patient: full arc VMAT AP plan with double arcs, partial arc VMAT AP plan with 6 partial arcs, and conventional IMRT AP plan. A simultaneous integrated boost with 2 levels was planned in all patients. Target coverage, organ at risk sparing, treatment parameters including monitor units and treatment time (TT) were evaluated. Wilcoxon signed-rank test was used to check for significant differences (p < 0.05) between datasets. VMAT plans (pVMAT and fVMAT) significantly reduced total lung volume treated above 20 Gy (V 20 ), 25 Gy (V 25 ), 30 Gy (V 30 ), 35 Gy (V 35 ), 40 Gy (V 40 ), and without increasing the value of V 10 , V 13 , and V 15 . For V 5 of total lung value, pVMAT was similar to aIMRT, and it was better than fVMAT. Both pVMAT and fVMAT improved the target dose coverage and significantly decreased maximum dose for the spinal cord, monitor unit, and TT. No significant difference was observed with respect to V 10 and V 15 of body. VMAT AP plan was a good option for treating upper thoracic esophageal cancer with T3N0M0, especially partial arc VMAT AP plan. It had the potential to effectively reduce lung dose in a shorter TT and with superior target coverage and dose homogeneity. Copyright © 2017 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zweifel,M.; Leahy, D.; Barrick, D.

Deltex is a cytosolic effector of Notch signaling thought to bind through its N-terminal domain to the Notch receptor. Here we report the structure of the Drosophila Deltex N-terminal domain, which contains two tandem WWE sequence repeats. The WWE repeats, which adopt a novel fold, are related by an approximate two-fold axis of rotation. Although the WWE repeats are structurally distinct, they interact extensively and form a deep cleft at their junction that appears well suited for ligand binding. The two repeats are thermodynamically coupled; this coupling is mediated in part by a conserved segment that is immediately C-terminal tomore » the second WWE domain. We demonstrate that although the Deltex WWE tandem is monomeric in solution, it forms a heterodimer with the ankyrin domain of the Notch receptor. These results provide structural and functional insight into how Deltex modulates Notch signaling, and how WWE modules recognize targets for ubiquitination.« less

Solar dynamic power module design

NASA Technical Reports Server (NTRS)

Secunde, Richard R.; Labus, Thomas L.; Lovely, Ronald G.

1989-01-01

Studies have shown that use of solar dynamic (SD) power for the growth eras of the Space Station Freedom program will result in life cycle cost savings when compared to power supplied by photovoltaic sources. In the SD power module, a concentrator collects and focuses solar energy into a heat receiver which has integral thermal energy storage. A power conversion unit (PCU) based on the closed Brayton thermodynamic cycle removes thermal energy from the receiver and converts that energy to electrical energy. Since the closed Brayton cycle is a single phase gas cycle, the conversion hardware (heat exchangers, turbine, compressor, etc.) can be designed for operation in low earth orbit, and tested with confidence in test facilities on earth before launch into space. The concentrator subassemblies will be aligned and the receiver/PCU/radiator combination completely assembled and charged with gas and cooling liquid on earth before launch to, and assembly on orbit.

An Iterative, Bimodular Nonribosomal Peptide Synthetase that Converts Anthranilate and Tryptophan into Tetracyclic Asperlicins

PubMed Central

Gao, Xue; Jiang, Wei; Jiménez-Osés, Gonzalo; Choi, Moon Seok; Houk, Kendall N.; Tang, Yi; Walsh, Christopher T.

2013-01-01

The bimodular 276 kDa nonribosomal peptide synthetase AspA from Aspergillus alliaceus, heterologously expressed in Saccharomyces cerevisiae, converts tryptophan and two molecules of the aromatic β-amino acid anthranilate (Ant) into a pair of tetracyclic peptidyl alkaloids asperlicin C and D in a ratio of 10:1. The first module of AspA activates and processes two molecules of Ant iteratively to generate a tethered Ant-Ant-Trp-S-enzyme intermediate on module two. Release is postulated to involve tandem cyclizations, in which the first step is the macrocyclization of the linear tripeptidyl-S-enzyme, by the terminal condensation (CT) domain to generate the regioisomeric tetracyclic asperlicin scaffolds. Computational analysis of the transannular cyclization of the 11-membered macrocyclic intermediate shows that asperlicin C is the kinetically favored product due to the high stability of a conformation resembling the transition state for cyclization, while asperlicin D is thermodynamically more stable. PMID:23890005

Low-complexity approximations to maximum likelihood MPSK modulation classification

NASA Technical Reports Server (NTRS)

Hamkins, Jon

2004-01-01

We present a new approximation to the maximum likelihood classifier to discriminate between M-ary and M'-ary phase-shift-keying transmitted on an additive white Gaussian noise (AWGN) channel and received noncoherentl, partially coherently, or coherently.

The antiproliferative activity of di-2-pyridylketone dithiocarbamate is partly attributed to catalase inhibition: detailing the interaction by spectroscopic methods.

PubMed

Li, Cuiping; Liu, Youxun; Fu, Yun; Huang, Tengfei; Kang, Lixia; Li, Changzheng

2017-08-22

The bioactivity of drugs is attributed to their interaction with biological molecules, embodied in either their direct or indirect influence on enzyme activity and conformation. Di-2-pyridylketone hydrazine dithiocarbamate (DpdtC) exhibits significant antitumor activity in our preliminary study. We speculated that its activity may partly stem from enzyme inhibition due to strong metal chelating ability. To this end, we assessed its effect on catalase from erythrocytes and found evidence of inhibition, which was further confirmed by ROS determination in vivo. Thus, detailing the interaction between the agent and catalase via spectroscopic methods and molecular docking was required to obtain information on both the dynamics and thermodynamic parameters. The Lineweaver-Burk plot implied an uncompetitive pattern between DpdtC and catalase from beef liver, and IC 50 = ∼7 μM. The thermodynamic parameters from fluorescence quenching measurements indicated that DpdtC could bind to catalase with moderate affinity (K a = approximately 10 4 M -1 ). CD spectra revealed that DpdtC could significantly disrupt the secondary structure of catalase. Docking studies indicated that DpdtC bound to a flexible region of catalase, involving hydrogen bonds and salt bond; this was consistent with thermodynamic results from spectral investigations. Our data clearly showed that catalase inhibition of DpdtC was not due to direct chelation of iron from heme (killing), but through an allosteric effect. Thus, it can be concluded that the antiproliferative activity of DpdtC is partially attributed to its catalase inhibition.

Assessment of the thermodynamic properties of poly(2,2,2-trifluoroethyl methacrylate) by inverse gas chromatography.

PubMed

Papadopoulou, Stella K; Panayiotou, Costas

2014-01-10

The thermodynamic properties of poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) were determined by the aid of the inverse gas chromatography technique (IGC), at infinite dilution. The interactions between the polymer and 15 solvents were examined in the temperature range of 120-150 °C via the estimation of the thermodynamic sorption parameters, the parameters of mixing at infinite dilution, the weight fraction activity coefficients and the Flory-Huggins interaction parameters. Additionally, the total and the partial solubility parameters of PTFEMA were estimated. The findings of this work indicate that the type and strength of the intermolecular interactions between the polymer and the solvents are strongly depended on the functional groups of the polymer and the solvents. The proton acceptor character of the polymer is responsible for the preferential solubility of PTFEMA in chloroform which acts as a proton donor solvent. The results also reveal that the polymer is insoluble in alkanes and alcohols whereas it presents good miscibility with polar solvents, especially with 2-butanone, 2-pentanone and 1,4-dioxane. Furthermore, the total and dispersive solubility parameters appear diminishing upon temperature rise, whereas the opposite behavior is noticed for the polar and hydrogen bonding solubility parameters. The latter increase with temperature, probably, due to conformational changes of the polymer on the solid support. Finally, comparison of the solubilization profiles of fluorinated methacrylic polymers studied by IGC, leads to the conclusion that PTFEMA is more soluble compared to polymers with higher fluorine content. Copyright © 2013 Elsevier B.V. All rights reserved.

Modeling stochastic kinetics of molecular machines at multiple levels: from molecules to modules.

PubMed

Chowdhury, Debashish

2013-06-04

A molecular machine is either a single macromolecule or a macromolecular complex. In spite of the striking superficial similarities between these natural nanomachines and their man-made macroscopic counterparts, there are crucial differences. Molecular machines in a living cell operate stochastically in an isothermal environment far from thermodynamic equilibrium. In this mini-review we present a catalog of the molecular machines and an inventory of the essential toolbox for theoretically modeling these machines. The tool kits include 1), nonequilibrium statistical-physics techniques for modeling machines and machine-driven processes; and 2), statistical-inference methods for reverse engineering a functional machine from the empirical data. The cell is often likened to a microfactory in which the machineries are organized in modular fashion; each module consists of strongly coupled multiple machines, but different modules interact weakly with each other. This microfactory has its own automated supply chain and delivery system. Buoyed by the success achieved in modeling individual molecular machines, we advocate integration of these models in the near future to develop models of functional modules. A system-level description of the cell from the perspective of molecular machinery (the mechanome) is likely to emerge from further integrations that we envisage here. Copyright © 2013 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Ion distributions, exclusion coefficients, and separation factors of electrolytes in a charged cylindrical nanopore: a partially perturbative density functional theory study.

PubMed

Peng, Bo; Yu, Yang-Xin

2009-10-07

The structural and thermodynamic properties for charge symmetric and asymmetric electrolytes as well as mixed electrolyte system inside a charged cylindrical nanopore are investigated using a partially perturbative density functional theory. The electrolytes are treated in the restricted primitive model and the internal surface of the cylindrical nanopore is considered to have a uniform charge density. The proposed theory is directly applicable to the arbitrary mixed electrolyte solution containing ions with the equal diameter and different valences. Large amount of simulation data for ion density distributions, separation factors, and exclusion coefficients are used to determine the range of validity of the partially perturbative density functional theory for monovalent and multivalent counterion systems. The proposed theory is found to be in good agreement with the simulations for both mono- and multivalent counterion systems. In contrast, the classical Poisson-Boltzmann equation only provides reasonable descriptions of monovalent counterion system at low bulk density, and is qualitatively and quantitatively wrong in the prediction for the multivalent counterion systems due to its neglect of the strong interionic correlations in these systems. The proposed density functional theory has also been applied to an electrolyte absorbed into a pore that is a model of the filter of a physiological calcium channel.

Modelling and investigation of partial wetting surfaces for drop dynamics using lattice Boltzmann method

NASA Astrophysics Data System (ADS)

Pravinraj, T.; Patrikar, Rajendra

2017-07-01

Partial wetting surfaces and its influence on the droplet movement of micro and nano scale being contemplated for many useful applications. The dynamics of the droplet usually analyzed with a multiphase lattice Boltzmann method (LBM). In this paper, the influence of partial wetting surface on the dynamics of droplet is systematically analyzed for various cases. Splitting of droplets due to chemical gradient of the surface is studied and analyses of splitting time for various widths of the strips for different Weber numbers are computed. With the proposed model one can tune the splitting volume and time by carefully choosing a strip width and droplet position. The droplet spreading on chemically heterogeneous surfaces shows that the spreading can be controlled not only by parameters of Weber number but also by tuning strip width ratio. The transportation of the droplet from hydrophobic surface to hydrophilic surface due to chemical gradient is simulated and analyzed using our hybrid thermodynamic-image processing technique. The results prove that with the progress of time the surface free energy decreases with increase in spreading area. Finally, the transportation of a droplet on microstructure gradient is demonstrated. The model explains the temporal behaviour of droplet during the spreading, recoiling and translation along with tracking of contact angle hysteresis phenomenon.

Medium Chain Fatty Acids Are Selective Peroxisome Proliferator Activated Receptor (PPAR) γ Activators and Pan-PPAR Partial Agonists

PubMed Central

Ayers, Steven D.; Lin, Jean Z.; Cvoro, Aleksandra; Silveira, Rodrigo L.; Martínez, Leandro; Souza, Paulo C. T.; Saidemberg, Daniel; Deng, Tuo; Amato, Angela Angelica; Togashi, Marie; Hsueh, Willa A.; Phillips, Kevin; Palma, Mário Sérgio; Neves, Francisco A. R.; Skaf, Munir S.; Webb, Paul; Polikarpov, Igor

2012-01-01

Thiazolidinediones (TZDs) act through peroxisome proliferator activated receptor (PPAR) γ to increase insulin sensitivity in type 2 diabetes (T2DM), but deleterious effects of these ligands mean that selective modulators with improved clinical profiles are needed. We obtained a crystal structure of PPARγ ligand binding domain (LBD) and found that the ligand binding pocket (LBP) is occupied by bacterial medium chain fatty acids (MCFAs). We verified that MCFAs (C8–C10) bind the PPARγ LBD in vitro and showed that they are low-potency partial agonists that display assay-specific actions relative to TZDs; they act as very weak partial agonists in transfections with PPARγ LBD, stronger partial agonists with full length PPARγ and exhibit full blockade of PPARγ phosphorylation by cyclin-dependent kinase 5 (cdk5), linked to reversal of adipose tissue insulin resistance. MCFAs that bind PPARγ also antagonize TZD-dependent adipogenesis in vitro. X-ray structure B-factor analysis and molecular dynamics (MD) simulations suggest that MCFAs weakly stabilize C-terminal activation helix (H) 12 relative to TZDs and this effect is highly dependent on chain length. By contrast, MCFAs preferentially stabilize the H2-H3/β-sheet region and the helix (H) 11-H12 loop relative to TZDs and we propose that MCFA assay-specific actions are linked to their unique binding mode and suggest that it may be possible to identify selective PPARγ modulators with useful clinical profiles among natural products. PMID:22649490

Medium chain fatty acids are selective peroxisome proliferator activated receptor (PPAR) γ activators and pan-PPAR partial agonists.

PubMed

Liberato, Marcelo Vizoná; Nascimento, Alessandro S; Ayers, Steven D; Lin, Jean Z; Cvoro, Aleksandra; Silveira, Rodrigo L; Martínez, Leandro; Souza, Paulo C T; Saidemberg, Daniel; Deng, Tuo; Amato, Angela Angelica; Togashi, Marie; Hsueh, Willa A; Phillips, Kevin; Palma, Mário Sérgio; Neves, Francisco A R; Skaf, Munir S; Webb, Paul; Polikarpov, Igor

2012-01-01

Thiazolidinediones (TZDs) act through peroxisome proliferator activated receptor (PPAR) γ to increase insulin sensitivity in type 2 diabetes (T2DM), but deleterious effects of these ligands mean that selective modulators with improved clinical profiles are needed. We obtained a crystal structure of PPARγ ligand binding domain (LBD) and found that the ligand binding pocket (LBP) is occupied by bacterial medium chain fatty acids (MCFAs). We verified that MCFAs (C8-C10) bind the PPARγ LBD in vitro and showed that they are low-potency partial agonists that display assay-specific actions relative to TZDs; they act as very weak partial agonists in transfections with PPARγ LBD, stronger partial agonists with full length PPARγ and exhibit full blockade of PPARγ phosphorylation by cyclin-dependent kinase 5 (cdk5), linked to reversal of adipose tissue insulin resistance. MCFAs that bind PPARγ also antagonize TZD-dependent adipogenesis in vitro. X-ray structure B-factor analysis and molecular dynamics (MD) simulations suggest that MCFAs weakly stabilize C-terminal activation helix (H) 12 relative to TZDs and this effect is highly dependent on chain length. By contrast, MCFAs preferentially stabilize the H2-H3/β-sheet region and the helix (H) 11-H12 loop relative to TZDs and we propose that MCFA assay-specific actions are linked to their unique binding mode and suggest that it may be possible to identify selective PPARγ modulators with useful clinical profiles among natural products.