Molecular dynamics simulation of polymer dispersed liquid crystal droplets under competing boundary conditions

This paper is devoted to the molecular dynamics simulation of structural organization inside a polydispersed liquid crystal (LC) droplet under competing boundary conditions. The droplet is assumed to be placed at the liquid crystal interface between two different regions of the solid polymer matrix, which accordingly separates the droplet into two hemispheres: the first of these is under radial boundary conditions; the second hemisphere is under bipolar boundary conditions. The droplet is considered as a jagged sphere filled with LC molecules, modelled as classical spins (unit vectors), whose centres of mass are associated with sites of a cubic lattice inside the cavity. The orienting action of the polymer matrix, and hence the resulting boundary conditions, are modelled by the interaction between the internal LC molecules (possessing only orientational degrees of freedom), and those of a delimiting surface layer (a jagged spherical shell), whose orientations are fixed, radial or bipolar, respectively. All interactions are modelled by the short range McMillan pair potential. The molecular orientation inside the LC droplet has been determined for various anchoring strengths of the interaction between internal spins and boundary layers. We have investigated the structure of the spherical defect resulting in the central region of the droplet, as well as of the boojum - like defects existing near the poles of the droplet. It has been found that a change of relative radial and bipolar anchoring strengths can affect both central and boojum - like defects. The effect of an external field on the molecular orientation inside the droplet has also been investigated. It has been found that a sufficiently strong external field increases the radius of the spherical defect placed in the central region of the droplet.     

Solvent crystallized syndiotactic polystyrene. Thermal and dynamic-mechanical behavior

The syndiotactic polystyrene can crystallize in different forms, depending on thermal and solvent treatments. The influence of the polymorphism on the dynamic-mechanical behavior has been analyzed. Thermogravimetric and calorimetric analysis were also carried out. The effects of phase transitions and solvent release on the relaxation phenomena were observed, and the correlations between structure and dynamic behavior allow to better understand some aspects of the polymorphism phenomena.     

First direct measurement of the total cross-section of 12C(α,γ)16O

The total cross-section of ¹²C(α,γ)¹⁶O was measured for the first time by a direct and ungated detection of the ¹⁶O recoils. This measurement in inverse kinematics using the recoil mass separator ERNA in combination with a windowless He gas target allowed to collect data with high precision in the energy range E = 1.9 to 4.9 MeV. The data represent new information for the determination of the astrophysical S(E) factor.     

An atom efficient and solvent-free synthesis of structurally diverse amides using microwaves

An array of structurally diverse amides was synthesized efficiently by combining (primary and secondary) amines and carboxylic acids in one-pot under solvent-free microwave (MW) conditions. In most cases, no racemization was observed with optically active inputs and chiral amides were obtained in high ee or de.     

Polarization-selective grating mirrors used in the generation of radial polarization

Two novel methods to control the polarization of laser radiation are presented. The discrimination between different polarization distributions isperformed with a corrugation grating in the top high-index layer of a multilayer mirror, which couples the undesired polarization into a lossy waveguidemode of the multilayer. The generation of radially polarized radiation in a laser resonator is presented as a practical verification of the principle.This revised version was published online in May 2005. The Article Category was removed.This revised version was published online in August 2005 with a corrected cover date.     

H,C, Pt NMR study on platinum(II) interaction with sulphur containing Amadori compounds

The NMR study on the interaction of Pt(II) with Amadori compounds is performed. The Amadori compounds are derived from the reaction of β-d-glucose with l-cystine leading to N,N′-di-(1-deoxy-β-fructos-1-yl)-l-cystine [FruCyscys], and with l-methionine leading to N-(1-deoxy-β-fructos-1-yl)-l-methionine [FruMet].     

Limits on neutrino oscillations from a study of νe charged current interactions

We have fully analysed all events with a single electron obtained in an exposure of BEBC to the 350 GeV wide-band neutrino beam at CERN. The data agrees well with expectations based on the calculated ν_e flux and assuming μ?e universality. Using both the rate and the kinematic distributions, improved limits are set on ν_e → ν_X, ν_μ → ν_e, ν_μ → ν_τ mixing.