Study of two-phonon excitations in superfluid 4He

We explain the second branch of excitations in superfluid ⁴He observed by Cowley and Woods, by accounting for two-phonon contributions to the dynamic structure function, S(k, ω). Our theory gives a good fit with the experimental data in the high energy region for several values of momentum transfer. It is observed that the contribution to S(k, ω) due to two-phonon excitations is of the order of k² as against its k⁴ dependence reported in earlier theories.     

Epitaxial morphologies of polyoxymethylene. II. Deposition energetics on alkali halide (001) surfaces

Molecular mechanics energy calculations have been used to assess the relative affinities that an iodobenzene solvent molecule and a segment of a polyoxymethylene chain have for five different alkali halide (001) surfaces. Dispersive-repulsive and coulombic contributions to the interaction energy have been included. The calculated interaction deposition energy correlates well with the nucleation density of rodlike epitaxial crystals formed on these substrates in epitaxial crystallization experiments from solution. Substrates which have a higher preference for solvent (LiF and NaF) than for polymer exhibit relatively low polymer nucleation densities. As the degree of solvent preference decreases, and polymer preference increases, higher nucleation densities are observed (KCI and KI). These results suggest that preferential solvent adsorption may account for the low nucleation densities observed on some substrates in polymer epitaxial crystallization experiments from solution.     

Determination of effective interaction between two plasmons

Using the Bohm-Pines hamiltonian the problem of the bound state of two plasmons is investigated following two different decoupling procedures where the energy transfer $\text{Ω = 0}$ or 2ω_pl. The effective interaction g₄ between the two plasmons is found to be repulsive for $\text{Ω = 2ω}{}_{\mathrm{pl}}$ and attractive when $\text{Ω = 0}$. The case of $\text{Ω= 2ω}{}_{\mathrm{pl}}$ is shown to be analogous to the situation under which the critical coupling g_4c is determined.     

SOME DOUBLE SEQUENCE SPACES OF FUZZY NUMBERS DEFINED BY ORLICZ FUNCTIONS

In this article, we introduce some double sequence spaces of fuzzy real numbers defined by Orlicz function, study some of their properties like solidness, symmetricity, completeness etc, and prove some inclusion results.     

Degradation in polytetrafluoro ethylene by 62 mev protons

The aim of our study is to describe the dose dependent proton induced modifications in Polytetrafluoro ethylene (PTFE) by using Fourier Transform Infra-red spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and X-ray diffraction analysis (XRD). The shifting of the main peak along with a decrease in its intensity, the decrease in thermal stability and melting point and the formation of stable free radicals were observed in the polymer by proton irradiation.