Is 1-(4-fluorostyryl)-4-nitrostilbene a novel nonlinear optical crystal?

Many details including the reaction scheme of crystal synthesis in a recent paper reporting optical and mechanical properties of 1-(4-fluorostyryl)-4-nitrostilbene (FNS) single crystal, by Dinakaran and Kalainathan (Optik, 2013 [1]), are very similar to those reported earlier by the same authors for another crystal namely 4-fluoro-4′-nitrostilbene (FONS). FNS is not a new NLO crystal but a new code for FONS with a different and obviously wrong chemical name. FNS crystal is a non-existent compound because substitution of a (4-fluorostyryl) moiety at the 1-position of 4-nitrostilbene will result in pentavalency for carbon.     

Resonant amplification of the magnetoelectric effect in ferrite-piezoelectric composites

The magnetoelectric effect in ferrite-piezoelectric composites is considered. A theory of the magnetoelectric effect in the electromechanical-resonance region for disk-shaped samples is presented. The magnetooptical coefficient is calculated for longitudinal and transverse orientations of electric and magnetic fields. It is shown that the effect increases by a few orders of magnitude at the electromechanical-resonance frequency. The frequency dependence of the effect is experimentally studied for a ferrite-nickel spinel-PZT composite. A resonant increase in the effect is observed (in agreement with the theory); the highest value of the magnetoelectric coefficient was 15 V/(cm Oe).     

Bisectors of linearly separable sets

A bisector of two sets is the set of points equidistant form them. Bisectors arise naturally in several areas of computational geometry. We show that bisectors of weakly linearly separable sets inE ^d have many properties of interest. Among these, the bisector of a restricted class of linearly separated sets is a homeomorphic image of the linear separator. We also give necessary and sufficient conditions for the existence of a particular continuous map from (a portion of) any linear separator to the bisector.     

Segmented multigrid domain decomposition procedure for incompressible viscous flows

The application of grid stretching or grid adaptation is generally required in order to optimize the distribution of nodal points for fluid-dynamic simulation. This is necessitated by the presence of disjoint high gradient zones, that represent boundary or free shear layers, reversed flow or vortical flow regions, triple deck structures, etc. A domain decomposition method can be used in conjunction with an adaptive multigrid algorithm to provide an effective methodology for the development of optimal grids. In the present study, the Navier-Stokes (NS) equations are approximated with a reduced Navier-Stokes (RNS) system, that represents the lowest-order terms in an asymptotic Re expansion. This system allows for simplified boundary conditions, more generality in the location of the outflow boundary, and ensures mass conservation in all subdomain grid interfaces, as well as at the outflow boundary. The higher-order (NS) diffusion terms are included through a deferred corrector, in selected subdomains, when necessary. Adaptivity in the direction of refinement is achieved by grid splitting or domain decomposition in each level of the multigrid procedure. Normalized truncation error estimates of key derivatives are used to determine the boundaries of these subdomains. The refinement is optimized in two co-ordinate directions independently. Multidirectional adaptivity eliminates the need for grid stretching so that uniform grids are specified in each subdomain. The overall grid consists of multiple domains with different meshes and is, therefore, heavily graded. Results and computational efficiency are discussed for the laminar flow over a finite length plate and for the laminar internal flow in a backward-facing step channel.     

Superconducting transition temperature for semimetals like bismuth

The superconducting transition temperatureT _c for semimetals like bismuth has been calculated as a function of the densityn _c of the electron and hole charge carriers. A simplified two-band model for describing the longitudinal dielectric function for such a system has been used in our model calculation. We find that the attractive interaction responsible for the instability of the normal ground state comes not only from the exchange of lattice phonons, but also from the electronhole sound mode, provided the ratio of the averaged hole to electron mass,m _h /m _e ≠ 1. We have compared our theoretical values ofT _c (n _c ) with experimental results for bismuth under hydrostatic pressure, and find reasonable agreement ifm _h /m _e is assumed to have a value which is only slightly larger than that at atmospheric pressures. A linear variation of the negative band gap as a function of pressure has been assumed for the sake of this comparison.     

Quantitative 15N NMR spectroscopy

Line intensities in ¹⁵N NMR spectra are strongly influenced by spin-lattice and spin–spin relaxation times, relaxation mechanisms and experimental conditions. Special care has to be taken in using ¹⁵N spectra for quantitative purposes. Quantitative aspects are discussed for the ¹⁵N NMR of molecules with different nitrogen functional groups and also mixtures of nitrogen-containing compounds. It is shown that, in general, quantitative data are obtainable from integration of ¹⁵N lines in proton decoupled ¹⁵N NMR spectra using NOE suppression. Addition of paramagnetic relaxation reagents (PARR) under controlled conditions is frequently needed to accomplish the experiment within reasonable time limits.     

Experimental studies of the magnetic excitations in the 1D Ising-antiferromagnet CsCoCl3

The electronic Raman and infrared absorption spectrum within the ⁴T_1g ground term of the one dimensional antiferromagnet CsCoCl₃ is investigated. At 2K three magnon lines are observed whereas above the magnetic phase transition at 8K the number of lines is increased to twelve. No drastic change of the magnon spectrum is observed in passing the Neél temperature at 21.5K. The magnon spectrum could still be observed at 150K. Theoretically the one-exciton spectrum is described within the molecular field approximation, using an exchange coupling between nearest neighbours along the spin chains only. Satisfactory agreement is obtained between measured and calculated energies.