Re-entrance phenomena in mesomorphic poly-γ-benzyl-l-glutamate (PBLG) solutions

We predict here, using a two-parameter polymer model and a mean field theory, isotropic-nematic-isotropic re-entrance phenomena in PBLG dissolved in denatured solvents, and propose experimental conditions under which the phenomena may be observed.     

Coherent Scattering by Multiple Particles in Phase Doppler Interferometry

A theoretical model has been developed for studying the response of the phase Doppler interferometer when multiple particles are simultaneously present within the measurement probe volume. The developed model incorporates the geometrical optics theory for describing the coherent interaction between the scattered light signals of multiple particles, eachhaving different size, velocity, trajectory, and arrival time. The resulting Doppler signal is processed by a theoretical signal processor which can simulate the performance characteristic of different signal processing schemes that are widely used in phase Doppler interferometry, namely, zero-crossing counter, covariance, autocorrelation and DFT parocessors. The application of the developed model for studying the coherent scattering by two particles has been specifically addressed in this paper. It has been shown that a DFT processor can be used to simultaneously measure the size and velocity of the two particles in most instances. However, for more than two particles, the signal processing scheme becomes more complex because of a quadratic increase in the beat frequency components.     

The Effect of Estimation Risk in Establishing Safety Stock Levels in an Inventory Model

This article illustrates the impact of estimation risk on decisions involving a one-period inventory problem such as the Christmas-tree stocking problem. It is shown that when estimation risk is ignored, stock levels may be incorrectly compiled and service levels may be inadequate. This article describes a regression-based method which adjusts the size of the stock by incorporating an additional safety stock requirement which reflects the uncertainty associated with lack of precise knowledge of the true parameters.     

Metal-insulator and order-disorder phase transitions: Magnetite

A thermodynamic model is presented for a system which exhibits both metal-insulator and order-disorder phase transitions. It is found that transition temperatures could be much lower than those predicted by pure order-disorder -only considerations. A variety of behaviors, including first-order and second-order transitions and critical points is found as the parameters change. The model explains qualitatively the experimental results for magnetite and suggests other possible behaviors for closely related systems.     

6He β-decay from a three-body model of the A=6 system

The rate of ⁶He β-decay is computed from ⁶He and ⁶Li separable-potential three-body wave functions. The value of ft predicted with the wave functions derived from the most complete set of αN and NN interactions is 807±12 s compared to the experimental value of 807±2 s.     

Determination of imaginary components of anomalous scattering of some elements from experimental data

Using the Bijvoet difference data reported in the literature for four compounds,viz./it, zinc sulphide, L-α-glyceryl phosphoryl ethanolamine monohydrate, 1-β-arabinofurinosyl cytosine hydrochloride and lithium aluminium oxide, the anomalous dispersion components Δf″ of the stronger anomalous scatterer in each case is calculated accepting the theoretical values for the lighter anomalous scatterers. For MoKα radiation the values turn out to be Δf″ z _n=1.470 (85), and for CuKα Δf″ _P=0.430 (25) Δf″ _C1=0.715 (18) and Δf″ _A1=0.264 (21). Contribution No. 421 from the Department of Crystallography and Biophysics, University of Madras, Guindy Campus, Madras 600025.