THEORY OF LC BIOMEMBRANE——A PROBE INTO SOFT CONDENSED MATTER PHYSICS

Soft condensed-state physics is a disciplinary frontier of 20th-century physics. An interdiscipline in nature, it involves biology, chemistry and even pure mathematics. Taking the liquid crystal (LC) biomembrane as an example, this article expounds the current development trend of this new and promising branch of contemporary physics.

Solid State Physics View of Liquid State Chemistry Ⅲ. Electrical Conductance of Pure and Impure Water

The ＇abnormally＇ high electrical conductivity ofpure water was recently studied by us using our protonic bond, trap and energy band model, with five host particles： the positive and negative protons, and the amphoteric protonic trap in three charge states, positive, neutral and negative. Our second report described the electrical charge storage capacitance of pure and impure water. This third report presents the theory of particle density and electrical conductance of pure and impure water, including the impuritons, which consist of an impurity ion bonded to a proton, proton-hole or proton trap and which significantly affect impure waters＇ properties.

A classical density functional approach to depletion interaction of Lennard-Jones binary mixtures

In this article,we apply classical density functional theory to investigate the characteristics of depletion interaction in Lennard-Jones(LJ)binary fiuid mixtures.First,to confirm the validity of our adopted density functional formalism,we calculate the radial distribution functions using a theoretical approach and compare them with results obtained by molecular dynamics simulation.Then,this approach is applied to two colloids immersed in LJ solvent systems.We investigate the variation of depletion interaction with respect to the distance of two colloids in LJ binary systems.We find that depletion interaction may be attractive or repulsive,mostly depending on the bulk density of the solvent and the temperature of the binary system.For high bulk densities,the repulsive barrier of depletion force is remarkable when the total excluded volume of colloids touches each other and reaches a maximum.The height of the repulsive barrier is related to the parameters of the LJ potential and bulk density.Moreover,the depletion force may exhibit attractive wells if the bulk density of the solvent is low.The attractive well tends to appear when the surface-surface distance of colloids is half of the size of the polymer and deepens with temperature lowering in a fixed bulk density.In contrast with the hard-sphere system,no oscillation of depletion potential around zero is observed.

DISCRETE MODELLING OF TWO-DIMENSIONAL LIQUID FOAMS

Liquid foam is a dense random packing of gas or liquid bubbles in a small amount of immiscible liquid containing surfactants. The liquid within the Plateau borders, although small in volume, causes considerable difficulties to the investigation of the spatial structure and physical properties of foams, and the situation becomes even more com-plicated as the fluid flows. To solve these problems, a discrete model of two-dimensional liquid foams on the bubble scale is proposed in this work. The bubble surface is represented with finite number of nodes, and the liquid within Plateau borders is discretized into lattice particles. The gas in bubbles is treated as ideal gas at constant temperatures. This model is tested by choosing an arbitrary shape bubble as the initial condition. This then automatically evolves into a cir-cular shape, which indicates that the surface energy minimum routine is obeyed without calling external controlling con-ditions. Without inserting liquid particle among the bubble channels, periodic ordered and disordered dry foams are both simulated, and the fine foam structures are developed. Wet foams are also simulated by inserting fluid among bubble channels. The calculated coordination number, as a function of liquid fractions, agrees well with the standard values.