Thermodynamic derivation and model calculations of the metal underpotential dependence on electron work function differences

The relationship between the work function of the substrate+adsorbate system and the underpotential shift is derived from a thermodynamic argument. An alternative explanation of the correlation formulated in the literature between the underpotential shift and the work function difference of the metals involved is proposed. A simple model is used to illustrate the meaning of the equations derived. Abrupt adsorption-desorption behaviour is predicted for those electrochemical systems where the work function shows a pronounced minimum as a function of the coverage, provided that this is a first-order contribution to the chemical potential of the system.     

硒对呼吸系统感染的防治作用

介绍了硒的免疫作用机制及在呼吸系统感染性疾病防治中的作用。硒是一种重要的人体必需微量元素。适量的硒可增强细胞免疫、体液免疫及非特异免疫功能 ,缺硒会损害免疫系统的功能 ,硒在呼吸系统感染性疾病防治方面亦有诸多报道     

Husimi representation for stationary states

This paper considers a Husimi representation of quantum mechanics in which the (stationary) state of a system or ensemble is described by a Husimi function and an observable is described by a phase space function or distribution such that the expectation value of the observable is given by an integral over phase space of the product of that function or distribution and the Husimi function. The density matrix, Wigner function, and Husimi function are considered to be alternative ways of describing the state of a system or ensemble, and methods of recovering the Wigner function or density matrix from the Husimi function are discussed. The classical limits of the Wigner and Husimi functions and of the relationship between them are considered. © 1993 John Wiley & Sons, Inc.     

Kohlrausch regulating function and other conservation laws in electrophoresis

The Kohlrausch regulating function (KRF) is a conservation law (conservation function), which is held in electrophoresis and which enables calculation of the so-called adjusted concentrations of constituents. The KRF is not the only conservation function and, depending on the complexity of the electrophoretic system, other conservation laws may be obeyed having a broader range of applicability. The conservation laws are tightly related to system eigenmobilities and system zones (system peaks). In principle, no system eigenmobility is exactly zero, but in most practical cases at least one system's eigenmobility is close to zero. The existence of the close-to-zero eigenmobility inherently points to the existence of a conservation function and a system zone which is stationary. The stationary system zone is called injection zone, stagnant zone, water peak, or solvent dip. Electrophoretic (electromigration) systems can be divided into two types: (i) conservation systems, in which the absolute value of at least one system eigenmobility is close to zero and where at least one conservation law is obeyed and (ii) nonconservation systems, where no system eigenmobility is close to zero and no conservation law is obeyed. The paper reviews work dealing with conservation functions in electromigration, derives some "historical" conservation functions in a new way, derives several conservation functions for systems of multivalent electrolytes, and discusses electrophoretic systems that have nonconservation behavior. In some typical instances, the conservation functions are simulated by means of a dynamic simulation tool and depicted graphically.     

子的配分函数——物理意义与作用

讨论怎样理解子的配分函数的物理意义,以及它和系统的配分函数在计算热力学函数中的作用,指出它既不是系统的广延性质,也不是系统的强度性质,只是联系系统热力学函数与微观信息的纽带。     

On the time evolution of light scattering intensity from binary liquids quenched near and above the critical point

A method is presented for calculating the time evolution and the angular distribution or the intensity intensity scattered by a system which is quenched rapidly above and near its critical point. If the system is quenched exactly to the critical temperature, the two-point, equal-time correlation function has a universal scaling form, as a function of time and wave- number     

Product of group-function expansions for correlated wave functions

A theorem is proved which demonstrates the relationship between a product of group functions describing the correlated motion of a particular group of electrons in an N-electron system and a wave function obtained from the exact wave function which describes the correlation of the same group of electrons. By considering such products of group functions as elements in a variational wave function, an expansion for correlated wave functions is suggested, which emphasizes the correlated motion of groups of electrons in the whole system.     

Computation and interpretation of molecular Omega intracules

The Omega intracule is a three-dimensional function that describes the relative positions, momenta, and directions of motion of pairs of electrons in a system. In this paper, we describe the computation of the Omega intracule for a molecular system whose electronic wave function is expanded in a Gaussian basis set. This is followed by implementation details and numerical tests. Finally, we use the Omega intracules of a number of small systems to illustrate the power of this function to extract simple physical insights from complicated wave functions.     

Dimensional analysis of chronoamperometry: proof and verification of Cottrellian behavior of systems with composition-dependent diffusion coefficients

Chronoamperometry with a Dirichlet boundary condition and semi-infinite linear diffusion exhibits Cottrellian behavior, that is, the product it1/2 is constant as a function of time as long as the system is initially homogeneous, a conclusion that can be reached using only dimensional analysis; no detailed mathematical analysis is required. The generality of this result is known to include purely diffusional systems and systems in which transport also involves migration. In the present work, it is shown that Cottrellian behavior obtains, even when the system diffusion coefficients are a function of system composition, regardless of the exact form of that function. These conclusions are confirmed by simulations of examples for purely diffusional systems as well as for systems with migration. Some experimental examples from the literature are cited.     

剩余函数量子Monte Carlo方法

为量子Ｍｏｎｔｅ Ｃａｒｌｏ方法提出一条新途径－剩余函数法,引入了Ｓｃｈｒｏｅｄｉｎｇｅｒ方程剩余函数的概念,利用剩余函数将一种新的有明显物理意义的试探函数应用到量子Ｍｏｎｔｅ Ｃａｒｌｏ过程中,这种试探函数是通过一种迭进式的方式确定的,它不需要在Ｍｏｎｔｅ Ｃａｒｌｏ过程中优化参数。文中我们将给出这种试探函数的具体形式,证明由这种试探函数求出的能量期望值收敛于体系真实的能量值;文中还给出这种试探     

On the importance of the "density per particle" (shape function) in the density functional theory

The central role of the shape function sigma(r) from the density functional theory (DFT), the ratio of the electron density rho(r) and the number of electrons N of the system (density per particle), is investigated. Moreover, its relationship with DFT based reactivity indices is established. In the first part, it is shown that an estimate for the chemical hardness can be obtained from the long range behavior of the shape function and its derivative with respect to the number of electrons at a fixed external potential. Next, the energy of the system is minimized with the constraint that the shape function should integrate to unity; the associated Lagrange multiplier is shown to be related to the electronic chemical potential micro of the system. Finally, the importance of the shape function for both molecular structure, reactivity, and similarity is outlined.     

Stability criterion for organic ferromagnetism

Stability criterion for organic ferromagnetism is derived from crystal orbital method. For a given flat-band system, there exists a unique set of Wannier functions localized near each unit cell, which should be symmetric with respect to the lattice vector. The set of Wannier functions minimizes the exchange integral of the system within the freedom of degeneracy. When each Wannier function spans common atoms between the adjacent cells, the system becomes ferromagnetic. On the other hand, when each Wannier function spreads only at one unit cell, the system becomes antiferromagnetic. The proof of this rule is given by variational principle.     

Lower work function of thermoelectric material by ordered arrays

In this paper, PbTe nanocubes are assembled on Bi_0.5Sb_1.5Te₃ substrates with both ordered and disordered structures through a straightforward method to form a P-N section. The work function of such semiconductor system is then measured by the ultraviolet photoelectron spectroscopy. This results show that the work function of orderly arrayed PbTe deposition is much lower than the disordered assemblies. Such change of the work function provides the possibility to tune it in a P-N section system. The change of the work function is attributed to the less surface roughness and easier electron escaping in the ordered structures.     

Nonadiabatic quantum-classical reaction rates with quantum equilibrium structure

Time correlation function expressions for quantum reaction-rate coefficients are computed in a quantum-classical limit. This form for the correlation function retains the full quantum equilibrium structure of the system in the spectral density function but approximates the time evolution of the operator by quantum-classical Liouville dynamics. Approximate analytical expressions for the spectral density function, which incorporate quantum effects in the many-body environment and reaction coordinate, are derived. The results of numerical simulations of the reaction rate are presented for a reaction model in which a two-level system is coupled to a bistable oscillator which is, in turn, coupled to a bath of harmonic oscillators. The nonadiabatic quantum-classical dynamics is simulated in terms of an ensemble of surface-hopping trajectories and the effects of the quantum equilibrium structure on the reaction rate are discussed.     

Electron microscope observation of thermal pre-treatment and vaporization processes of Ag–Sb and Pd–Sb systems in graphite furnace atomic absorption spectrometry

As the reproducibility of Sb in river water analysis based on graphite furnace atomic absorption spectrometry is not good, and the reliability is poor when Pd is used as a matrix modifier, Ag was used instead of Pd. The reason Ag has the function of a matrix modifier and Pd does not, was studied by observation of the atomic columns or lattice structures at the atomic level in binary alloys, by using a high-resolution transmission electron microscope. Since the Ag–Sb system has the characteristic of forming an intermetallic compound and a lower value of the activity coefficient of Sb in its intermetallic compound, Ag is able to function as a matrix modifier as a result. In the case of the Pd–Sb system, the phenomenon of radical vaporization that is observed in the Ag–Sb system does not occur through changes of the phases of Pd–Sb intermetallic compounds. This fact means Pd does not have the function of a matrix modifier.     

Three-particle correlation functions of quasi-two-dimensional one-component and binary colloid suspensions

We report the results of experimental determinations of the triplet correlation functions of quasi-two-dimensional one-component and binary colloid suspensions in which the colloid-colloid interaction is short ranged. The suspensions studied range in density from modestly dilute to solid. The triplet correlation function of the one-component colloid system reveals extensive ordering deep in the liquid phase. At the same density the ordering of the larger diameter component in a binary colloid system is greatly diminished by a very small amount of the smaller diameter component. The possible utilization of information contained in the triplet correlation function in the theory of melting of a quasi-two-dimensional system is briefly discussed.     

Analytical calculation of the collimated detector response for the characterization of nuclear waste drums by segmented gamma scanning

Improved methods for the reconstruction of the isotope specific activity content in nuclear waste drums with data obtained by a gamma scanning system developed at Shanghai Jiao Tong University require an analytical function of the detector response. In this work we derive an analytical detector response function for a collimated HPGe detector with a square collimation window. The model is based on a purely geometric model respecting the configuration of the collimated detector system, the positions of radioactive point sources and the absorption of γ-rays in the matrix as well as in the HPGe crystal. We show that the derived analytical detector response function is in good agreement with data simulated by MCNP5.     

Molecular dynamics simulation of the nematic liquid crystal phase in the presence of an intense magnetic field

The influence of an intense external field on the dynamics of the nematic liquid crystal phase is investigated using a molecular dynamics simulation for the Gay-Berne nematogen under isobaric-isothermal conditions. The molecular dynamics as a function of the second-rank orientational order parameter P<2> for a system consisting of a nematic liquid crystal in the presence of an intense magnetic field is compared with that of a similar system without the field. The translational motion of molecules is determined as a function of the translational diffusion coefficient tensor and the anisotropy and compared with the values predicted theoretically. The rotational dynamics of molecules is analyzed using the first- and the second-rank orientational time correlation functions. The translational diffusion coefficient parallel with respect to the director is constrained by the intense field, although the perpendicular one is decreased as the P<2> is increased, just as it is in the system without the field. However, no essential effect of the strong magnetic field is observed in the rotational molecular dynamics. Further, the rotational diffusion coefficient parallel with respect to the director obtained from the first-rank orientational time correlation function in the simulation is qualitatively in agreement with that in the real nematic liquid crystalline molecules. The P<2> dependence of the rotational diffusion coefficient for the system with the intense magnetic field shows a tendency similar to that for the system without the field.