Real-time determination of the slippage length in autophobic polymer dewetting

We investigated the kinetics of autophobic dewetting, caused by differences in entropy, of a polymer melt slipping on a monolayer of end-grafted identical molecules (polymer brush). From simultaneous measures of the dewetted distance and the width of the resulting rim, we obtained in real time and quantitatively the slippage length and the contact angle, a measure of the "incompatibility" between identical molecules. Furthermore, we could directly relate a decrease in the slippage length in the course of the experiments at elevated temperatures to temporal or permanent attachment of polymers from the melt to the brush.     

Generating Relations of the Hypergeometric Functions by the Lie Group-Theoretic Method

In this paper, the generating relations for a set of hypergeometric functions _,,,m (x) are obtained by using the representation of the Lie group SL(2,C) giving a suitable interpretation to the index m in order to derive the elements of Lie algebra. The principle interest in our results lies in the fact that a number of special cases would inevitably yield too many new and known results of the theory of special functions, namely the Laguerre, even and odd generalized Hermite, Meixner, Gottlieb, and Krawtchouk polynomials.     

Very low temperature properties of bosons with repulsive core and attractive tails

The properties of a system of bosons interacting through a two body potential composed of a hard repulsive core followed by an attractive square well and having density of the order of that of liquid⁴He at the-point have been studied. The system is found to have a peculiar behaviour around 1 K and we assert that it may have undergone another phase transition around 1 K. Calculations on the effective mass show that them ^*/m values lie between 2 and 9 so that the interacting bosons may have a transition temperature below 1 K. We have also plottedE _k vs.k graph for temperatures below 1 K.The authors are thankful to Prof. F. C.Auluck, Dr. N. R.Ranganathan, Dr. H. G.Venkatesh and Dr. A. N.Phukan for helpful discussion. Authors thanks are due to Prof. B. R.Seth, D.Sc., F.N.A., Director, B.I.T., Mesra for constant encouragement. The authors thankfully acknowledge the financial assistance provided by the Indian National Science Academy, New Delhi.     

Diffuse x-ray scattering from self-interstitials in zinc

Diffusex-ray scattering in the region between the Bragg peaks has been calculated for self-interstitials in zinc. The required lattice distortions are calculated by the Kanzaki method and the scattering contributions from all equivalent orientations of a defect configuration are averaged. It is shown that a measurement in the (110) plane can clearly establish the stable interstitial configuration.     

Computer simulation of an amorphous antiferromagnet

Computer simulation has been used to study the ground state properties of a system of antiferromagnetically interacting Ising spins located at the centres of close-random-packed spheres. Significant quasi-degeneracy and low energy barriers are found, analogous to the case of a non-ordering periodically frustrated magnet. The local effective field distribution has a zero-field hole, analogous to a spin glass.     

Excitation spectrum for nuclear matter

Properties of an infinite nuclear matter of interacting alpha-particle have been studied. The expression obtained for the excitation spectrum exhibits the existence of the energy gap in the nuclear matter. The energy gap changes withm _* /m , the ratio between effective and true mass of an alpha-particle, and it seems to disappear for higher values ofm _* /m .On leave of absence fromK.G.K. College, Moradabad (U.P.) India.We are highly thankful to Prof. S. Duttamajumdar for valuable comments, and to the Indian National Science Academy, New Delhi, for financial assistance.     

Thermochromism in polydiacetylene solutions

A novel planar ? nonplanar visual thermochromic conformational transition of polydiacetylene molecules in poor solvents is reported. The conformational transition is associated with both a color change (blue or red ? yellow) and a change in the state; the yellow solution (liquid) transforms to a blue or red gel (solid). The color transition occurs within a narrow range of temperature and has a large associated hysteresis. The enthalpy of the conformational transition is 29 kJ/mole of repeat unit. Fourier-transform infrared studies show that molecules acquire a planar conformation in red or blue gels by formation of intramolecular H bonds between the adjacent substituent groups. Virtually all H bonds break (a nonplanar conformation) when the gels turn into yellow solutions.