Studies on diglycine sulphate

Both diglycine sulphate (DGS) and diglycine sulphate monohydrate (DGS.H2O) are reported to crystallize from solution with pH < 1(1,2). DGS.H2O (point group 2/m; Z = 4) shows a dielectric anomaly at 72°C suggestive of antiferroelectric transition(1). The crystals obtained by us from solution with pH < 0.5 at 20-25°C were always DGS (point group mmm; Z = 8) as confirmed by X-ray studies. The measurement of its dielectric constant along [100], [010] and [001] did not indicate any phase transition in the range 5-400°K. Thus DGS is a normal dielectric unlike TGS. The polarized Raman spectra and the infrared spectra were recorded to examine the configuration of glycine in DGS(3). The vibration spectra reveals that both the glycines in DGS exist as NH3+CH2COOH, thus precluding the hydrogen bond of the type N+-H…O- which exists between two glycine units in TGS. This seems to be a good reason for the difference in the dielectric behaviour of these two glycine sulphates.

Crossover frequencies in multicomponent plasma

A method for finding the roots of the equation D = O in a multicomponent plasma with positive and negative ion species is given. The use of dispersion diagrams (omega-k diagrams) for right- and left-circularly polarized waves is made to locate these roots in pass or stop bands. ©1973 American Institute of Physics.

Use of transverse beam polarization to probe anomalous V V H interactions at a Linear Collider

We investigate use of transverse beam polarization in probing anomalous coupling of a Higgs boson to a pair of vector bosons, at the International Linear Collider (ILC). We consider the most general form of V V H (V = W/Z) vertex consistent with Lorentz invariance and investigate its effects on the process e(+)e(-) -> f (f) over barH, f being a light fermion. Constructing observables with definite C P and naive time reversal ((T) over tilde) transformation properties, we find that transverse beam polarization helps us to improve on the sensitivity of one part of the anomalous Z Z H Coupling that is odd under C P. Even more importantly it provides the possibility of discriminating from each other, two terms in the general Z Z H vertex, both of which are even under C P and (T) over bar. Use of transversebeam polarization when combined with information from unpolarized and linearly polarized beams therefore, allows one to have completely independent probes of all the different parts of a general ZZH vertex.

Observation of the intense de-pairing effect in YBa2Cu3O7-delta due to the spin injection from La0.5Sr0.5CoO3

We report experimental evidence for a huge pair breaking effect induced by spin polarized quasiparticles in a YBa2Cu3O7-delta/La0.5Sr0.5CoO3 bi-layer fabricated by pulsed laser deposition. The temperature dependent magnetization measurements show evidence for the presence of both ferromagnetic and diamagnetic phases in the bi-layer. The current dependent electrical transport studies in the bi-layer exhibit a significant reduction in the superconducting transition temperature with the increase in applied current as compared to a single YBa2Cu3O7-delta layer and it follows a I-2/3 dependence in accordance with the pair breaking effect. Here, we find that the current driven from a ferromagnetic electrode with low spin polarization, such as La0.5Sr0.5CoO3 (-11%), into the superconductor can act as a strong pair breaker. This indicates that the spin polarization of the injecting electrode is not the only criterion in determining the pair breaking effect, rather the transparency of the interface for the spin polarization may also be significant. More interestingly, the spin diffusion length for YBa2Cu3O7-delta has a much longer length scale than that reported earlier in the study of ferromagnetic/superconducting heterostructures.

Optical tweezer for probing erythrocyte membrane deformability

We report that the average rotation speed of optically trapped crenated erythrocytes is direct signature of their membrane deformability. When placed in hypertonic buffer, discocytic erythrocytes are subjected to crenation. The deformation of cells brings in chirality and asymmetry in shape that makes them rotate under the scattering force of a linearly polarized optical trap. A change in the deformability of the erythrocytes, due to any internal or environmental factor, affects the rotation speed of the trapped crenated cells. Here we show how the increment in erythrocyte membrane rigidity with adsorption of Ca++ ions can be exhibited through this approach.

Force-free equilibria of magnetized jets

Force-free equilibrium configurations of magnetic-pressure-dominated magnetized supersonic jets confined by slowly varying external pressure are investigated analytically. For the case where internal dissipation mechanisms are active, the lowest-energy field configuration is found to be the superposition of an axisymmetric mode and a helical mode with a wavelength equal to 5 times the jet radius, and the pressure below which the nonaxisymmetric mode becomes energetically favorable is given as 2700 times the product of the 4th power of the magnetic helicity per unit length and the -6th power of the magnetic flux. A model of the total and polarized emission of such a configuration is developed and applied to the extended well-collimated astronomically resolved jet NGC 6251. The model is shown to reproduce significant features such as transverse oscillations of the ridge line, width oscillations and emission knots, the projected magnetic-field configuration, oscillations of the degree of polarization, and the distribution of the Faraday rotation measure.

A complete characterization of pre-Mueller and Mueller matrices in polarization optics

The Mueller-Stokes formalism that governs conventional polarization optics is formulated for plane waves, and thus the only qualification one could require of a 4 x 4 real matrix M in order that it qualify to be the Mueller matrix of some physical system would be that M map Omega((pol)), the positive solid light cone of Stokes vectors, into itself. In view of growing current interest in the characterization of partially coherent partially polarized electromagnetic beams, there is a need to extend this formalism to such beams wherein the polarization and spatial dependence are generically inseparably intertwined. This inseparability brings in additional constraints that a pre-Mueller matrix M mapping Omega((pol)) into itself needs to meet in order to be an acceptable physical Mueller matrix. These additional constraints are motivated and fully characterized. (C) 2010 Optical Society of America

Effect of thione—thiol tautomerism on the inhibition of lactoperoxidase by anti-thyroid drugs and their analogues

The keto-enol type tautomerism in anti-thyroid drugs and their selenium analogues are described. The commonly used anti-thyroid drug methimazole exists predominantly in its thione form, whereas its selenium analogue exists in a zwitterionic form. To understand the effect of thione/thiol and selone/selenol tautomerism on the inhibition of peroxidase-catalysed reactions, we have synthesized some thiones and selones in which the formation of thiol/selenol forms are blocked by different substituents. These compounds were synthesized by a carbene route utilizing an imidazolium salt. The crystal structures of these compounds reveal that the C=Se bonds in the selones are more polarized than the C=S bonds in the corresponding thiones. The structures of selones were studied in solution by NMR spectroscopy and the 77Se NMR chemical shifts for the selones show large upfield shifts in the signals, confirming their zwitterionic structures in solution. The inhibition of lactoperoxidase by the synthetic thiones indicates that the presence of a free N-H moiety is essential for an efficient inhibition. In contrast, such moiety is not required for an inhibition by the selenium compounds.

Hanle-Zeeman redistribution matrix. I. Classical theory expressions in the laboratory frame

Polarized scattering in spectral lines is governed by a 4; 4 matrix that describes how the Stokes vector is scattered and redistributed in frequency and direction. Here we develop the theory for this redistribution matrix in the presence of magnetic fields of arbitrary strength and direction. This general magnetic field case is called the Hanle- Zeeman regime, since it covers both of the partially overlapping weak- and strong- field regimes in which the Hanle and Zeeman effects dominate the scattering polarization. In this general regime, the angle-frequency correlations that describe the so-called partial frequency redistribution (PRD) are intimately coupled to the polarization properties. We develop the theory for the PRD redistribution matrix in this general case and explore its detailed mathematical properties and symmetries for the case of a J = 0 -> 1 -> 0 scattering transition, which can be treated in terms of time-dependent classical oscillator theory. It is shown how the redistribution matrix can be expressed as a linear superposition of coherent and noncoherent parts, each of which contain the magnetic redistribution functions that resemble the well- known Hummer- type functions. We also show how the classical theory can be extended to treat atomic and molecular scattering transitions for any combinations of quantum numbers.

ESR and optical absorption studies in copper diethyldithiocarbamate

ESR investigations at X band and optical-absorption measurements have been reported in single crystals of copper (n) diethyldithiocarbamate Cu[S 2CN(C2H5)2]2 diluted to 0.2% with the corresponding zinc complex. The measurements have been made both at room and liquid-oxygen temperatures. ESR measurements gave the following values for the parameters in spin Hamiltonian g11=2.1085, g=2.023(6), A63= 142.4×10-4 cm-1, A65 = 152.0×10-4 cm-1, B = 22.4×10-4 cm-1, Q~3×10-4 cm-1. Polarized optical absorption study has made possible a proper assignment of the absorption bands to their corresponding transitions. This has led to information regarding the ordering of the MO levels of the complex. The coefficients used in the MO description of the complex have been calculated from the observed parameters. The results show that the metal ligand BIσ bond is purely covalent and that the out-of-plane w bonding is appreciably covalent whereas the in-plane Π bonding is ionic. Further, it is noted that the metal ligand binding is more covalent with sulfur as ligand than with oxygen or nitrogen.

Simplified optical system for holographic subtraction

Subtraction of one complex spatial function from another can be accomplished holographically by shifting the phase of the reference beam by pi between the two exposures. A simple and reliable system for this purpose, which makes use of the fact that the beam from a gas laser is usually plane-polarized, is described, and its application to obtain the equivalent of a dark field with the frozen-fringe technique in holographic interferometry is demonstrated.

Single-File Diffusion of Water Inside Narrow Carbon Nanorings

We use atomistic molecular dynamics (MD) simulations to study the diffusion of water molecules confined inside narrow (6,6) carbon nanorings. The water molecules form two oppositely polarized chains. It is shown that the effective interaction between these two chains is repulsive in nature. The computed mean-squared displacement (MSD) clearly shows a scaling with time similar to t(1/2), which is consistent with single-file diffusion (SFD). The time up to which the water molecules undergo SFD is shown to be the lifetime of the water molecules inside these chains. Simulations of "uncharged" water molecules inside the nanoring show the formation of several water chains and yield SFD. These observations conclusively prove that the diffusion is Fickian when there is a single chain of water and SFD is observed only when two or more chains are present.

Observation of reduced activation energy and the possible existence of decoupled pancake vortices in superconductor/ferromagnet bilayers

Investigations of different superconducting (S)/ferromagnetic (F) heterostructures grown by pulsed laser deposition reveal that the activation energy (U) for the vortex motion in a high T-c superconductor is reduced remarkably by the presence of F layers. The U exhibits a logarithmic dependence on the applied magnetic field in the S/F bilayers suggesting the existence of decoupled two-dimensional (2D) pancake vortices. This result is discussed in terms of the reduction in the effective S layer thickness and the weakening of the S coherence length due to the presence of F layers. In addition, the U and the superconducting T-c in YBa2Cu3O7-delta/La0.5Sr0.5CoO3 bilayers are observed to be much lower than in the YBa2Cu3O7-delta/La0.7Sr0.3MnO3 ones. This in turn suggests that the degree of spin polarization of the F layer might not play a crucial role for the suppression of superconductivity due to a spin polarized induced pair-breaking effect in S/F bilayers.

Ambiguity-free polarization measurements from mixture initial preparations

Starting from beam and target spin systems which are polarized in the usual way by applying external magnetic fields, measurements of appropriate final state tensor parameters, viz., {t0,1k, k=1,...,2j} of particle d with spin j in a reaction a+b→d+c1+c2+. . .are suggested to determine the reaction amplitudes in spin space free from any associated discrete ambiguity.

Carbon nanotube reinforced supramolecular gels with electrically conducting, viscoelastic and near-infrared sensitive properties

Pristine and long-chain functionalized single-walled carbon nanotubes (SWNTs) were incorporated successfully in supramolecular organogels formed by an all-trans tri(p-phenylenevinylene) bis-aldoxime to give rise to new nanocomposites with interesting mechanical, thermal and electrical properties. Variable-temperature UV-vis and fluorescence spectra reveal both pristine and functionalized SWNTs promote aggregation of the gelator molecules and result in quenching of the UV-vis and fluorescence intensity. Electron microscopy and confocal microscopy show the existence of a densely packed and directionally aligned fibrous network in the resulting nanocomposites. Differential scanning calorimetry (DSC) of the composites shows that incorporation of SWNTs increases the gel formation temperature. The DSC of the xerogels of 1-SWNT composites indicates formation of different thermotropic mesophases which is also evident from polarized optical microscopy. The reinforced aggregation of the gelators on SWNT doping was reflected in the mechanical properties of the composites. Rheology of the composites demonstrates the formation of a rigid and viscoelastic solid-like assembly on SWNT incorporation. The composites from gel-SWNTs were found to be semiconducting in nature and showed enhanced electrical conductivity compared to that of the native organogel. Upon irradiation with a near IR laser at 1064 nm for 5 min it was possible to selectively induce a gel-to-sol phase transition of the nanocomposites, while irradiation for even 30 min of the native organogel under identical conditions did not cause any gel-to-sol conversion.