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Chemical Potential (chemical + potential)
Selected AbstractsHigher derivative effects on ,/s at finite chemical potentialFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7-9 2010Article first published online: 17 MAY 2010, K. Hanaki Abstract We review the recent developments on the study of KSS bound violation in the presence of higher derivative corrections. Special emphasis is given to the cases with finite R-charge chemical potential. [source] Single-Crystalline Gallium Nitride Microspindles: Synthesis, Characterization, and Thermal Stability ,ADVANCED FUNCTIONAL MATERIALS, Issue 5 2004F. Xu Abstract This paper describes a facile procedure for synthesizing high-quality gallium nitride microspindles on a large scale using a solid-state reaction of GaI3, NaNH2, and NH4Cl in a sealed system at 500,°C for 6,h. The structures, compositions, and morphologies of the as-synthesized products are derived from X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FE-SEM). The selected-area electron diffraction (SAED) patterns and high-resolution transmission electron microscopy (HRTEM) images show that the as-synthesized GaN spindles are composed of many single-crystalline platelets. The GaN microspindles show different optical properties depending on their shape (e.g., nanowires or nanoparticles) in photoluminescence (PL) emission spectroscopy and Raman spectroscopy. The possible growth mechanism of GaN microspindles is controlled by linear kinetics with a driving force proportional to the difference between a local supersaturation and an equilibrium chemical potential. Furthermore, the thermal stability of the GaN microspindles is investigated under various annealing conditions and discussed on the basis of additional TEM and XRD analyses. [source] Solvent effect on the reactivity of CIS -platinum (II) complexes: A density functional approachINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 8 2008Pubalee Sarmah Abstract The structure and chemical reactivity of some selected cis -platinum(II) complexes, including clinically used drug molecules, cisplatin, carboplatin, and oxaliplatin are investigated using density functional theory (DFT) calculations. Calculated geometries of the complexes are in agreement with their available X-ray data. The global and local reactivity descriptors, such as hardness, chemical potential, electrophilicity index, Fukui function, and local philicity are calculated to investigate the usefulness of these descriptors for understanding the reactive nature and reactive sites of the complexes. Inclusion of solvent effect shows that both global and local descriptors change the trend of reactivity with respect to their trend in the gas phase. The stability of the complexes increases with the inclusion of water molecules. Simple regression analysis is applied to build up a quantitative structure-activity relationship (QSAR) model based on DFT derived electrophilicity index for the Pt(II) complexes against A2780 human ovarian adenocarcinoma cell line to establish the importance of the descriptor in predicting cytotoxicity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Isolation and characterization of a Lactobacillus amylovorus mutant depleted in conjugated bile salt hydrolase activity: relation between activity and bile salt resistanceJOURNAL OF APPLIED MICROBIOLOGY, Issue 4 2000J.P. Grill Growth experiments were conducted on Lactobacillus amylovorus DN-112 053 in batch culture, with or without pH regulation. Conjugated bile salt hydrolase (CBSH) activity was examined as a function of culture growth. The CBSH activity increased during growth but its course depended on bile salts type and culture conditions. A Lact. amylovorus mutant was isolated from the wild-type strain of Lact. amylovorus DN-112 053 after mutagenesis with N-methyl-N,-nitro-N-nitrosoguanidine. An agar plate assay was used to detect mutants without CBSH activity. In resting cell experiments, the strain showed reduced activity. Differences between growth parameters determined for wild-type and mutant strains were not detected. Comparative native gel electrophoresis followed by CBSH activity staining demonstrated the loss of proteins harbouring this activity in the mutant. Four protein bands corresponding to CBSH were observed in the wild-type strain but only one was detected in the mutant. The specific growth rate of the mutant strain was affected more by bile salts than the wild-type strain. Nevertheless, bile was more toxic for the wild-type strain. In viability studies in the presence of nutrients, it was demonstrated that glycodeoxycholic acid exerted a higher toxicity than taurodeoxycholic acid in a pH-dependent manner. No difference was apparent between the two strains. In the absence of nutrients, the wild-type strain died after 2 h whereas no effect was observed for the mutant. The de-energization experiments performed using the ionophores nigericin and valinomycin suggested that the chemical potential of protons (Z,pH) was involved in Lactobacillus bile salt resistance. [source] Ionic conductivity of solid polymer electrolytes for dye-sensitized solar cellsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Joo Wan Kim Abstract We developed an ionic conductivity model of solid polymer electrolytes for dye-sensitized solar cells (DSSCs) based on the Nernst,Einstein equation in which the diffusion coefficient is derived from the molecular thermodynamic model. We introduced concentration-dependence of the diffusion coefficient into the model, and the diffusion coefficient was expressed by differentiating the chemical potential by concentration. The ionic conductivities of polymer electrolytes (PEO/LiI/I2 system) were investigated at various temperatures and compositions. We prepared a set of PEO in which an EO : LiI mole ratio of 10 : 1 was kept constant for PEO·LiI·(I2)n compositions with n = 0.02, 0.05, 0.1, 0.15, 0.2, and 0.3 (mole ratio of LiI : I2). The ionic conductivities of the electrolytes were measured using a stainless steel/polymer-electrolyte/stainless steel sandwich-type electrode structure using alternating current impedance analysis. The values calculated using the proposed model agree well with experimental data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Molecular dynamics simulation in the grand canonical ensembleJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2007Hossein Eslami Abstract An extended system Hamiltonian is proposed to perform molecular dynamics (MD) simulation in the grand canonical ensemble. The Hamiltonian is similar to the one proposed by Lynch and Pettitt (Lynch and Pettitt, J Chem Phys 1997, 107, 8594), which consists of the kinetic and potential energies for real and fractional particles as well as the kinetic and potential energy terms for material and heat reservoirs interacting with the system. We perform a nonlinear scaling of the potential energy parameters of the fractional particle, as well as its mass to vary the number of particles dynamically. On the basis of the equations of motion derived from this Hamiltonian, an algorithm has been proposed for MD simulation at constant chemical potential. The algorithm has been tested for the ideal gas, for the Lennard,Jones fluid over a wide range of temperatures and densities, and for water. The results for the low-density Lennard,Jones fluid are compared with the predictions from a truncated virial equation of state. In the case of the dense Lennard,Jones fluid and water our predicted results are compared with the results reported using other available methods for the calculation of the chemical potential. The method is also applied to the case of vapor-liquid coexistence point predictions. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Retrograde melt,residue interaction and the formation of near-anhydrous leucosomes in migmatitesJOURNAL OF METAMORPHIC GEOLOGY, Issue 6 2010R. W. WHITE Abstract Considering physical segregation of melt from its residue, the chemical potentials of the components (oxides) are the same in both when segregation occurs. Then, as P,T conditions change, gradients in chemical potential are established between the melt-rich domains and residue permitting diffusional interaction to occur. In particular, on cooling, the chemical potential of H2O becomes higher in the melt segregation than in the residue, particularly when biotite becomes stable in the residue assemblage. Diffusion of water from the melt to the residue promotes crystallization of anhydrous products from the melt and hydrous products in the residue. This diffusive process, when coupled with melt loss from the rocks subsequent to some degree of crystallization, can result in a significant degree of anhydrous leucosome being preserved in a migmatite with only minor retrogression of the residue. If H2O can diffuse between the melt segregation and all of the residue, then no apparent selvedge between the two will be observed. Alternatively, if H2O can diffuse between the melt segregation and only part of the residue, then a distinct selvedge may be produced. Diffusion of H2O into the residue may be in part responsible for the commonly anhydrous nature of leucosomes, especially in granulite facies migmatites. Diffusion of other relatively mobile species such as Na2O and K2O has a lesser effect on overall melt crystallization but can change the proportion of quartz, plagioclase and K-feldspar in the resultant leucosome. The diffusion of H2O out of the melt results in the enhanced crystallization of the melt in the segregation and increases the amount of resulting anhydrous leucosome relative to the amount produced if melt crystallized in chemical isolation from the residue. For high residue:melt ratios, the proportion of resulting near-anhydrous leucosome can approach that of the proportion of melt present at the onset of cooling with only minor loss of melt from a given segregation required. Crystallization of melt segregations via the diffusion of H2O out of them into the host may also play a major role in driving melt-rich segregations across key rheological transitions that would allow the expulsion of remaining melt from the system. [source] Kinetics of decompressional reactions in eclogitic rocks , formation of plagioclase coronas around kyaniteJOURNAL OF METAMORPHIC GEOLOGY, Issue 3 2002D. Nakamura Abstract This paper describes a kinetic study on reaction textures in eclogitic rocks from the Sulu region, eastern China. Some of the eclogitic rocks display a decompressional reaction texture, whereby kyanite grains are surrounded by plagioclase coronas and are never in contact with quartz. The change in mineral parageneses with progress of the reaction was predicted by constructing chemical potential diagrams in a model system. The chemical potential diagrams indicated that the chemical potential of 2Na2O + CaO (2µNa2O + µCaO) in intergranular regions between kyanite and quartz should decrease with decreasing pressure, whereas 2µNa2O + µCaO in intergranular regions between garnet and omphacite should increase with decreasing pressure. Thus, upon decompression, an inequality in chemical potential arises in the rock. To reduce this inequality, garnet and omphacite react to produce amphibole and plagioclase and release Na2O and CaO. Then, the released Na2O and CaO components diffuse into the regions between kyanite and quartz grains and react to produce plagioclase between them. This model also indicates that the chemical potential of SiO2 should decrease around kyanite grains during the progress of the decompressional reaction, and Si-undersaturated conditions should have formed around kyanite grains in spite of the presence of quartz in these eclogitic rocks. Thus, spinel or corundum that are not stable in the system with excess quartz can form as a metastable phase, as observed in eclogitic rocks from the study areas. Phase diagrams in the system with excess quartz should be carefully applied for analysis of such reaction textures. [source] Modeling the solid,liquid equilibrium in pharmaceutical-solvent mixtures: Systems with complex hydrogen bonding behaviorAICHE JOURNAL, Issue 3 2009Ioannis Tsivintzelis Abstract A methodology is suggested for modeling the phase equilibria of complex chemical mixtures with an equation of state (EoS) for the case where only limited experimental data exist. The complex hydrogen bonding behavior is explicitly accounted for and the corresponding parameters are adopted from simpler molecules of similar chemical structure and/or are fitted to Hansen's partial solubility parameters. The methodology is applied to modeling the solubility of three pharmaceuticals, namely acetanilide, phenacetin, and paracetamol, using the nonrandom hydrogen bonding (NRHB) EoS. In all cases, accurate correlations were obtained. The prediction ability of the approach was evaluated against predictions from the COSMO-RS model. A thorough discussion is made for the appropriate modeling of solid solubility considering the effect of the difference of the heat capacities of the solute in liquid and solid state, ,Cp = Cpl , Cps, in the determination of solid chemical potential and, also, of the polymorphism of drugs. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Universal scaling in a trapped Fermi super-fluid in the BCS-unitarity crossoverLASER PHYSICS LETTERS, Issue 12 2009S.K. AdhikariArticle first published online: 14 AUG 200 Abstract Using numerical simulation based on a densityfunctional equation for a trapped Fermi super-fluid valid along the BCS-unitarity crossover, we establish robust scaling over many orders of magnitude in the observables of the system as a function of fermion number. This scaling allows to predict the static properties of the system, such as energy, chemical potential, etc., for a large number of fermions, over the crossover, from the knowledge of those for a small number (,4 , 10) of fermions. (© 2009 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Interfacial Thermodynamics of Polymeric MesophasesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 8 2004Alejandro D. Rey Abstract Summary: A complete mechanical-thermodynamical formulation for multicomponent nematic polymer-isotropic fluid interfaces is derived, validated, and used to derive the structure and shape equations for these soft anisotropic polymer interfaces. The fundamental role of liquid crystalline order and long range effects in coupling bulk and interfacial effects, and in coupling thermodynamical/liquid crystalline order/geometrical variables is demonstrated, discussed, and validated. The Gibbs-Duhem nemato-thermodynamics equation emerges from an interfacial tension ,,=,,(,, ,, Q, ,sQ, k) that depends on temperature (,), chemical potential (,), nematic tensor order parameter Q, surface gradients of Q, and geometry k, and leads to new couplings in these enhanced phase spaces. The role of entropy and adsorption, and long range effects on interfacial shape and structure selection is revealed. For flat interfaces the preferred structure emerges from a competition between energy, entropy, and adsorption. [source] Single dopant diffusion in semiconductor technologyMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 2 2004A. Glitzky Abstract The paper deals with the analysis of pair diffusion models in semiconductor technology. The underlying model contains reaction-drift-diffusion equations for the mobile point defects and dopant-defect pairs as well as reaction equations for immobile dopants which are coupled with a non-linear Poisson equation for the chemical potential of the electrons. For homogeneous structures we present an existence and uniqueness result for strong solutions. Starting with energy estimates we derive further a priori estimates such that fixed point arguments due to Leray,Schauder guarantee the solvability of the model equations. Copyright © 2004 John Wiley & Sons, Ltd. [source] First-principles study on the concentrations of native point defects in high-dielectric-constant binary oxide materialsPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 5 2008J. X. Zheng Abstract The intrinsic concentrations of point defects in high- k binary oxide materials of HfO2, ZrO2, Y2O3 and La2O3 are evaluated on the basis of first-principles calculations. Oxygen defects are found to dominate over a wide range of the oxygen chemical potential. Neutral oxygen vacancies are likely to be responsible for electron trapping in the investigated materials. In HfO2 and ZrO2, oxygen Frenkel pairs are likely to form. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Feshbach shape resonance for high Tc superconductivity in superlattices of nanotubesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 11 2006Antonio Bianconi Abstract The case of a Feshbach shape resonance in the pairing mechanism for high Tc superconductivity in a crystalline lattice of doped metallic nanotubes is described. The superlattice of doped metallic nanotubes provides a superconductor with a strongly asymmetric gap. The disparity and different spatial locations of the wave functions of electrons in different subbands at the Fermi level should suppress the single electron impurity interband scattering giving multiband superconductivity in the clean limit. The Feshbach resonances will arise from the component single-particle wave functions out of which the electron pair wave function is constructed: pairs of wave functions which are time inverse of each other. The Feshbach shape resonance increases the critical temperature by tuning the chemical potential at the Lifshitz electronic topological transition (ETT) where the Fermi surface of one of the bands changes from the one dimensional (1D) to the two dimensional (2D) topology (1D/2D ETT). (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Model of a superconducting singular Fermi liquid with a first-order phase transitionPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 2 2004Ryszard Gonczarek Abstract Model of s -wave and d -wave superconductivity in a singular Fermi liquid with a divergent scattering amplitude for particles with the same quasi-momenta and opposite spins is formulated and presented with regard to a narrow, nearly half-filled conduction band. The ground state and other eigenstates for the superconducting phase are found. Thermodynamic functions are obtained by the use of the Bogolubov method. The gap equation along with the equation for the chemical potential is derived in a general form and solved in a self-consistent manner for s -wave pairing. Above a certain temperature there are two solutions of the gap equation, however only for the greater one the superconducting phase remains stable. It is shown that the system undergoes a first-order phase transition between the superconducting and the normal phase. The critical temperature and the heat of the transition are found. The temperature dependence of the entropy and the specific heat of the system is also presented. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Ionization equilibrium and Mott transition in an excited semiconductor, phase diagramPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2009F. Richter Abstract The thermodynamic properties of an electron,hole plasma in a highly excited semiconductor are investigated. Special attention is directed to the influence of many-particle effects like screening, lowering of the ionization energy, and Mott effect on the ionization equilibrium. In particular, the Mott effect limits the region of existence of excitons and, therefore, of a possible Bose,Einstein condensate at low temperatures. Results for the chemical potential and the degree of ionization are presented for cuprous oxide. A possible window for the occurrence of a BEC of excitons taking into account the Mott effect is shown. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of pH on the Photochemical and Electrochemical Reduction of the Dinuclear Ruthenium Complex, [(phen)2Ru(tatpp)Ru(phen)2]Cl4, in Water: Proton-Coupled Sequential and Concerted Multi-Electron ReductionCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2005Norma R. de Tacconi Prof. Abstract The dinuclear ruthenium complex [(phen)2Ru(tatpp)Ru(phen)2]4+ (P; in which phen is 1,10-phenanthroline and tatpp is 9,11,20,22-tetraaza tetrapyrido[3,2-a:2,3,-c:3,,,2,,-l:2,,,,3,,,]-pentacene) undergoes a photodriven two-electron reduction in aqueous solution, thus storing light energy as chemical potential within its structure. The mechanism of this reduction is strongly influenced by the pH, in that basic conditions favor a sequential process involving two one-electron reductions and neutral or slightly acidic conditions favor a proton-coupled, bielectronic process. In this complex, the central tatpp ligand is the site of electron storage and protonation of the central aza nitrogen atoms in the reduced products is observed as a function of the solution pH. The reduction mechanism and characterization of the rich array of products were determined by using a combination of cyclic and AC voltammetry along with UV-visible reflectance spectroelectrochemistry experiments. Both the reduction and protonation state of P could be followed as a function of pH and potential. From these data, estimates of the various reduced species' pKa values were obtained and the mechanism to form the doubly reduced, doubly protonated complex, [(phen)2Ru(H2tatpp)Ru(phen)2]4+ (H2P) at low pH (,7) could be shown to be a two-proton, two-electron process. Importantly, H2P is also formed in the photochemical reaction with sacrificial reducing agents, albeit at reduced yields relative to those at higher pH. [source] Interactions between Brushlike Polyacrylic Acid Side Chains on a Polyacrylate Backbone in Dioxane,WaterCHEMPHYSCHEM, Issue 2 2005Fengjun Hua Dr. Abstract Densely grafted polyacrylic acids (d-PAAs) with overcrowded PAA side chains on the polyacrylate main chains were synthesized and characterized. Acryloyl poly(tert -butyl acrylate) macromonomer [M-P(tert- BA)] was prepared with a definite chain length (n=29) by atom-transfer radical polymerization (ATRP), then homopolymerization was carried out to produce densely grafted P(tert- BA)s with polyacrylate main chains of two different lengths (m=27 and 161). The two d-PAAs were obtained by hydrolyzing d-P(tert- BA)s in the presence of trifluoroacetic acid (TFA). The d-PAAs exhibit intermolecular and intramolecular hydrogen bonding between the carboxylic groups of PAA side chains in dioxane and pyridine; both were investigated using proton nuclear magnetic resonance (1H NMR) spectroscopy. The intermolecular hydrogen bonding was found to be dependent on polymer concentration, temperature, and water content. The intramolecular association between the PAA side chains was found to produce a contraction of the hydrodynamic volume of the d-PAA. Intermolecular hydrogen bonding produces aggregates, as demonstrated by dynamic light scattering (DLS). The clusters were found to shrink as the overall water concentration decreased, and this effect is tentatively explained by considering the gradient in chemical potential of water inside the clusters in comparison with the solvent phase. [source] Retrograde melt,residue interaction and the formation of near-anhydrous leucosomes in migmatitesJOURNAL OF METAMORPHIC GEOLOGY, Issue 6 2010R. W. WHITE Abstract Considering physical segregation of melt from its residue, the chemical potentials of the components (oxides) are the same in both when segregation occurs. Then, as P,T conditions change, gradients in chemical potential are established between the melt-rich domains and residue permitting diffusional interaction to occur. In particular, on cooling, the chemical potential of H2O becomes higher in the melt segregation than in the residue, particularly when biotite becomes stable in the residue assemblage. Diffusion of water from the melt to the residue promotes crystallization of anhydrous products from the melt and hydrous products in the residue. This diffusive process, when coupled with melt loss from the rocks subsequent to some degree of crystallization, can result in a significant degree of anhydrous leucosome being preserved in a migmatite with only minor retrogression of the residue. If H2O can diffuse between the melt segregation and all of the residue, then no apparent selvedge between the two will be observed. Alternatively, if H2O can diffuse between the melt segregation and only part of the residue, then a distinct selvedge may be produced. Diffusion of H2O into the residue may be in part responsible for the commonly anhydrous nature of leucosomes, especially in granulite facies migmatites. Diffusion of other relatively mobile species such as Na2O and K2O has a lesser effect on overall melt crystallization but can change the proportion of quartz, plagioclase and K-feldspar in the resultant leucosome. The diffusion of H2O out of the melt results in the enhanced crystallization of the melt in the segregation and increases the amount of resulting anhydrous leucosome relative to the amount produced if melt crystallized in chemical isolation from the residue. For high residue:melt ratios, the proportion of resulting near-anhydrous leucosome can approach that of the proportion of melt present at the onset of cooling with only minor loss of melt from a given segregation required. Crystallization of melt segregations via the diffusion of H2O out of them into the host may also play a major role in driving melt-rich segregations across key rheological transitions that would allow the expulsion of remaining melt from the system. [source] Theoretical Defect Energetics in Calcium Phosphate BioceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2010Katsuyuki Matsunaga Vacancies, impurities, and foreign ions dissolving in calcium phosphate bioceramics play an important role in the biological properties of the materials. However, little is known about the thermodynamic stability of the defects. In this regard, point defects in hydroxyapatite (HAp) and octacalcium phosphate (OCP) were calculated in a first-principles manner, and the chemical-potential dependence of the defect formation energies was revealed. In particular, because calcium phosphates are usually subjected to an aqueous solution, a methodology to evaluate ionic chemical potentials under chemical equilibrium of the solid,aqueous solution was introduced. In the present article, recent results based on such a methodology (the solution pH dependence of Ca/P molar ratio of HAp and the ion-exchange ability with foreign cations in HAp and OCP) were reviewed. [source] Modeling Studies of the Phase Behavior of Monomer/Polymer/Disk CompositesMACROMOLECULAR THEORY AND SIMULATIONS, Issue 6 2008Francisco Torrens Abstract The model developed by Balazs et al. to explain the phase behavior of polymer/clay composites is extended to monomer/polymer/clay composites, obtaining an expression for the free energy of a monomer/polymer/thin-disk mixture. By minimizing the free energy and calculating the chemical potentials of the three system components, phase diagrams for the monomer/disk and monomer/polymer/disk mixtures are contructed. Through the evolution and comparison of these diagrams, the effects of nanodisk size, polymer molecular mass and interaction parameters (temperature) on mixture stability and attained morphology are then studied. [source] The dynamics of transition layers in solids with discontinuous chemical potentialsMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 5 2006T. Blesgen Abstract We derive a two-phase segregation model in solids under isothermal conditions where due to plastic effects the number of vacancies changes when crossing a transition layer, i.e. a reconstitutive phase transition. We show the thermodynamic correctness of the model and review the existence of weak solutions in suitable spaces. By a formal asymptotic analysis we study the dynamics of the interface and its dependence on the unsymmetric vacancy distribution. Copyright © 2006 John Wiley & Sons, Ltd. [source] Full counting statistics for electron number in quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2008Yasuhiro Utsumi Abstract Measurements of the average current and its fluctuations (noise) have been powerful tools to study the quantumtransport in mesoscopic systems. Recently it became possible to measure the probability distribution of current, ,full counting statistics' (FCS), by using quantum point-contact charge-detectors. Motivated by recent experiments, we developed the FCS theory for the joint probability distribution of the current and the electron number inside quantum dots (QDs). We show that a non-Gaussian exponential distribution appears when there is no dot state close to the lead chemical potentials. We show that the measurement of the joint probability distribution of current and electron number would reveal nontrivial correlations, which reflect the asymmetry of tunnel barriers. We also show that for increasing strength of tunneling, the quantum fluctuations of charge qualitatively change the probability distribution of the electron number. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Extension to mixtures of two robust hard-sphere equations of state satisfying the ordered close-packed limitTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2001Cyrus Ghotbi Abstract Two new hard-sphere EOS are proposed and tested using the same attractive potential terms used by the SAFT EOS. Generalized expressions for the pair RDF at contact value, the compressibility factor, and the excess chemical potentials have been derived. Extension to mixtures is tested using three mixing rules for multicomponent hard-sphere fluids. The proposed EOS combined with the Santos et al. and the Barrio-Solana mixing rules reproduced the compressibility factors and the excess chemical potentials more accurately than the Boublik-Mansoori-Camahan-Starling-Leland (BMCSL) EOS. However the pair RDF at contact value had larger deviations than those obtained with the BMCSL EOS. The combination of the proposed equations and the Barrio-Solana mixing rule gave an accurate reproduction of the compressibility factor for binary hard-sphere fluids with high diameter ratio even in the low concentration regions of the larger spheres. Deux nouvelles équations d'état de sphères dures sont proposées et vérifiées à l'aide des m,mes termes potentiels attractifs utilisés pour l'équation d'état de SAFT. Des expressions généralisées pour le RDF pair à la valeur de contact, le facteur de compressibilité et les potentiels chimiques d'excès ont été calculées. L'extension à des mélanges est vérifiée à l'aide de trois régies de mélange pour fiuides à sphères dures multi-composants. Les équations d'état proposées, combinées aux règles de mélange de Santos et al. et de Barrio-Solana, reproduisent les facteurs de compressibilité et les potentiels chimiques d'excès de façon plus précise que l'équation d'état de Boublik-Mansoori-Camahan-Starling-Leiand (BMCSL). Cependant, le RDF pair à la valeur de contact a des écarts plus grands que ceux obtenus avec l'équation d'état de BMCSL. La combinaison des équations proposées et la régle de mélange de Barrio-Solana donne une reproduction exacte du facteur de compressibilité pour des fluides de sphères dures binaires ayant un rapport de diamètre important m,me dans les régions de faible concentration de sphères les plus grandes. [source] Simulation and Experiment of Temperature and Cosolvent Effects in Reversed Phase Chromatography of PeptidesBIOTECHNOLOGY PROGRESS, Issue 3 2005Kosta Makrodimitris Experiments and simulations have been carried out for several polar protected peptides in reversed phase chromatography in order to demonstrate how simulation can describe the effects of varying temperature and cosolvent fraction. Comparisons of adsorption chemical potentials from mesoscopic simulations and experimental chromatographic retention data show very good agreement with only one temperature-independent solvent parameter from a single peptide. Such simulations should help guide the design of chromatography experiments with biomolecules and predict retention, including conditions for which empirical correlations such as hydrophobicity scales and molecular descriptors have not been developed. [source] | |||||||||||||||||||