Charged hard dumbbell in the binding mean-spherical approximation

A simple model for charged hard dumbbell is proposed in the binding mean-spherical approximation (BIMSA). The thermodynamic properties are analytical solutions of the unique screening parameter Γ^B with full association. Critical point and vapour-liquid coexistence curve are identical to those of Kalyuzhnyi, Yu. V., 1998, Molec. Phys., 94, 735, where a site-site integral equation has to be solved. Substituting Γ without association for Γ^B, the BIMSA reduces to the simple interpolation scheme (SIS). A simple interpolation between the SIS and the BIMSA is proposed: this gives the critical point (T_c? = 0.0525, p?_c = 0.0640) which, for the time being, is the closest to the computer simulation results. Similarity between the charged hard dumbbell and the restricted primitive model of electrolyte is also addressed.     

ACS Student Affiliates at University of Michigan Use Their Passion for Chemistry to Inspire the Community and Other Students

Going from almost zero to more than sixty active members in less than a year, the University of Michigan American Chemical Society Student Affiliate chapter is a success story about revitalizing a struggling chapter. Innovative officer positions, increased delegation of authority, and courage to try new ideas generated this special chemistry. In order to encourage each member to be creative and reach his or her full chapter potential, the officers stressed, Dream of an outstanding activity, and everyone will make it happen. Strategically, this philosophy was reinforced by electing members who had spearheaded projects to the new officer positions. In the following article, we will present the events and philosophies that created the strong intra-Student Affiliate and inter-Student Affiliate/community chemical bonds.     

Thermodynamic properties and phase equilibria of charged hard sphere chain model for polyelectrolyte solutions

A recent thermodynamic perturbation theory for flexible polyelectrolyte solutions is extended to study thermodynamic properties and phase equilibria for polyelectrolyte solutions with different polyion, chain lengths. Osmotic pressure, activity coefficient of an individual ion (polyion or counterion) and average activity coefficient are calculated. Except for the activity coefficient of the polyion, the chain length dependence of the properties is small. Also presented are vapour-liquid equilibrium coexisting curves, vapour pressures and critical points. As the polyion chain length approaches infinity the critical properties (temperature, pressure and density) become constants.     

Acoustic Wave Propagation in an Underwater Sound Channel 2. Quantitative Theory

By using ray-theoretic-techniques we have developed in our previouspaper, "Acoustic Wave Propagation in an Underwater Sound Channel.1. Qualitative Theory" a certain qualitative understanding ofseveral features of SOFAR propagation in an underwater soundchannel. In the present paper a more penetrating quantitativestudy is done by means of analytical techniques on the governingequations. We study the transient problem for the Epstein profileby employing a double transform to formally derive an integralrepresentation, and we obtain several alternative representationsneeded for asymptotic results which we also present. It is believedthat several new and interesting asymptotic results have beenderived.     

Acoustic Wave Propagation in an Underwater Sound Channel 1. Qualitative Theory

We give a qualitative study of wave propagation in an inhomogeneousmedium principally by geometrical optics and ray theory. Theinhomogeneity is represented by a sound-speed profile whichis dependent upon one coordinate, namely the depth; and we discussthe general characteristics of wave propagation which resultfrom a source placed on the sound channel axis. We show thatour mathematical model of the sound-speed in the ocean actuallypredicts some of the behaviour of the observed physical phenomenain the underwater sound channel. Using ray theoretic techniqueswe investigate the implications of our profile on the followingcharacteristics of SOFAR propagation: (i) the sound energy travellingfurther away from the axis takes less time to travel from sourceto receiver than sound energy travelling closer to the axis,(ii) the focusing of sound energy in the sound channel at certainranges, (iii) the overall ray picture in the sound channel.     

The reduction of hydrogen in the presence of bisulphate on platinum(111) electrodes

A new model for the electroreduction of hydrogen in acidic media is proposed. One of the still open problems is the structure of the intermediate compound of the hydrogen evolution reaction (HER) or alternatively the UPD hydrogen. We propose here a new form of this compound, namely (H₅O₂ ⁺)₃, a honeycomb, hydrogen-bonded lattice which is formed through a first-order phase transition by water and the hydronium H₃O⁺ ion under favourable conditions. The essential point of our theory is the use of a correct water model, which has to be tetrahedral and flexible. Then, as the polarity of the electrode is changed: (1) for positive electrodes the dipole of the water points down, a zig-zag chain of hydrogen-bonded water, is formed which is responsible for the 3^½ x 7^½ structure of the sulphate observed by STM. (2) For negative polarization the water dipole points up. The (bi)sulphate and the water form a periodic structure by incorporating 1/3 of hydronium, which then is adsorbed with a hydrogen down in the hollow sites of the Pt(111) electrode. This compound is neutral and forms a two-dimensional honeycomb arrangement of water with (or without) bisulphate ions. The model is consistent with all known experiments: it reproduces well the experimental voltammogram and the recent radiotracer measurements of bisulphate adsorption. Furthermore it gives a robust explanation of the 2/3 hydrogen yield for this surface.     

Report On ‘The MATCH Program: Integrating Student Learning in Science and Math’

The inability to integrate mathematics and chemistry continues to plague science and math undergraduates. General chemistry students often lack the ability to apply the mathematics they already know to problems given in their chemistry classes, and mathematics students often stumble through word problems. In response to this prevalent compartmentalization, Dr. Donald Wink created a program at the University of Illinois at Chicago to break down illusory mental borders between mathematics and chemistry. Strategically, he accomplished this by creating a single course where students work in teams to answer word problems; by stressing the effective use of graphing calculators in this course; and by giving significant, physical meaning to the symbols used in equations. During Dr. Winks Integrating Student Learning in Math and Science workshop, attendees experienced these three techniques first-hand when they worked through mathematics-based chemistry problems (and vice versa) together.     

A Numerical Method for the Solution of the Double Eigenvalue Problem

A generalization of the Rayleigh quotient iterative method,called the Minimum Residual Quotient Iteration (MRQI), is derivedfor the numerical solution of the 2-parameter eigenvalue problem;i.e. to find scalars µ and a corresponding vector x satisfyingthe following equations, Ax = B₁x + µB₂x, ||x|| = 1, f(x) = 0, where A and B are nxn real matrices, ||.|| denotes the l₂ normand f is a real functional. The method is applied to doubleeigenvalue problems for ordinary differential equations andcomputational results are presented.     

Strong Surface Diffusion Mediated Glancing-Angle Deposition： Growth, Recrystallization and Reorientation of Tin Nanorods

Different from usual glancing-angle deposition where low surface diffusion is necessary to form nanorods, strong surface diffusion mediated glancing-angle deposition is exemplified by growing tin nanorod films on both silicon and glass substrates simultaneously via thermal evaporation. During growth, the nanorods were simultaneously baked by the high-temperature evaporator, and therefore re-crystallized into single crystals in consequence of strong surface diffusion. The monocrystalline tin nanorods have a preferred orientation perpendicular to the substrate surface, which is quite different from the usual uniformly oblique nanorods without recrystallization.