Raman spectrum of rubidium iodide

Raman spectrum of rubidium iodide has been recorded for the first time using the resonance radiation of mercury (λ 2537 ) as the exciter. The frequencies of the 24p limiting modes (p = 2, the number of non-equivalent atoms in the unit cell), postulated by Raman in 1943, which correspond to the frequencies from the critical points Γ, L and X, have been worked out using the shell model of Cochran, taking into account the nearest and the next-nearest neighbour short-range interactions and the polarization of both the ions. The observed Raman lines have been assigned to the overtones and the combinations of the phonon branches from Γ, L and X.

Infrared absorption studies on some derivatives of xanthic, dithiocarbamic and trithiocarbonic acids

The infrared absorption spectra of some of the derivatives of xanthic Image dithiocarbamic Image and trithiocarbonic Image acids are studied in the sodium chloride optics region and the bands assigned to group frequencies. The position of C---O---C and C=S bands in the derivatives of xanthic acid has been discussed from theoretical and experimental evidences and it is suggested that the two strong bands around 1200 and 1030 cm−1 are due to the Image group. The bands around 980 and 1050 cm−1 in the derivatives of dithiocarbamic and trithiocarbonic acids respectively have been assigned to C=S group frequencies. These bands shift to lower frequency in the corresponding ionic compounds while the bands around 1030 and 1200 cm−1 in the ionic compounds of xanthic acid shift to higher and lower frequencies respectively.

The influence of Zr/Ti content on the morphotropic phase boundary in the PZT-PZN system

A quantitative structural investigation was carried out on (1-y)PbZrxTi1-xO3-yPbZn(1/3)Nb(2/3)O(3) where y=0.1 and 0.2 ((1-y)PZT-yPZN). High resolution XRD data have been used for quantitative phase analysis. The nominal compositions were prepared by a two-step low temperature calcining solid-state method. The sintered samples show an average grain size of 1-2 mu m. It is demonstrated that the increase in the concentration of PZN leads to the shift of the morphotropic phase boundary (MPB) of PZT towards the PbZrO3 end member. In the present work, an effort has been made to quantitatively determine the MPB phase contents and to regain the coexistence of tetragonal and monoclinic phases by varying the value of x(i.e. Zr/Ti ratio). The width of the MPB becomes considerably larger for y=0.10 and 0.20 as compared to pure PZT. This is attributed to the considerably lower grain size of our samples resulting from the adopted preparation method. (C) 2010 Elsevier B.V. All rights reserved.

The emission spectrum of bismuth bromide (BiBr)-"A" system

The emission spectrum of bismuth monobromide has been investigated and a vibrational analysis of the A→X system has been made. About 286 bands were recorded in the region λλ 4595–6063 and the isotope effect due to Br79 and Br81 was observed in about 87 bands. A value of 2·74 ev. for the dissociation energy of the excited state has been obtained and arguments have been given to show that the dissociation products in the excited state are Bi(4S3/2) and Br(2P3/2) and that those of the ground state are most probably Bi (4S3/2) and Br (2P1/2) atoms.

Studies in sesquiterpenes-XVI. Zerumbone, a monocyclic sesquiterpene ketone

The structure, previously assigned to zerumbone, has been found to be untenable. The ketone has been shown to be monocyclic containing three ethylenic linkages, and has been further correlated with humulene. Results from ozonolysis, and base-catalysed cleavage allowed the compound to be formulated as 2,6,9,9-tetramethyl-2,6,10-cyclo-undecatrien-1-one.

Inverted V-Notch: Practical Proportional Weir

This paper presents a practical linear proportional weir of simple geometric shape in the form of an inverted V-notch or inward trapezium. The flow through this weir, of half-width w and altitude d, for depths above 0.22d is proportional to the depth of flow measured above a reference plane situated at 0.08d for all heads in the range 0.22d<=h<=0.94d, with a maximum percentage deviation of ±1.5 from the theoretical discharge. The linear relationship between head and discharge is based on numerical optimization procedures. Nearly 75% of the depth of inverted V-notch can be used effectively as the measuring range. Experiments with four weirs, with different vertex angles, show excellent agreement with the theory by giving an average coefficient of discharge for each weir varying from 0.61–0.62.

Influence of propellant choice on MPD arcjet cathode surface current density distribution

The radial current density on an MPD arcjet cathode surface is theoretically investigated for five propellants. It is found that excessive current concentration at the upstream end of the cathode occurs in the case of hydrogen. This undesirable effect is traced to the higher electrical conductivity of hydrogen plasma.

Multi power port converter for hybrid electric vehicles using multi phase bidirectional fly-back topology

For hybrid electric vehicles the batteries and the drive dc-link may be at different voltages. The batteries are at low voltage to obtain higher volumetric efficiencies and the dc-link is at higher voltage to have higher efficiency on the motor side. Therefore a power interface between the batteries and the drive's dc-link is essential. This power interface should handle power flow from battery to motor, motor to battery, external genset to battery and grid to battery. This paper proposes a multi power port topology which is capable of handling multiple power sources and still maintains simplicity and features like obtaining any gain, wide load variations, lower output current ripple and capability of parallel battery energy due to the modular structure. The development and testing of a bi-directional fly-back DC-DC converter for hybrid electric vehicle is described in this paper. Simple hysteresis voltage control is used for DC link voltage regulation. The experimental results are presented to show the working of the proposed converter.

M.tuberculosis Pantothenate Kinase: Dual Substrate Specificity and Unusual Changes in Ligand Locations

Kinetic measurements of enzyme activity indicate that type I pantothenate kinase from Mycobacterium tuberculosis has dual substrate specificity for ATP and GTP, unlike the enzyme from Escherichia coli, which shows a higher specificity for ATP. A molecular explanation for the difference in the specificities of the two homologous enzymes is provided by the crystal structures of the complexes of the M. tuberculosis enzyme with (1) GMPPCP and pantothenate, (2) GDP and phosphopantothenate, (3) GDP, (4) GDP and pantothenate, (5) AMPPCP, and (6) GMPPCP, reported here, and the structures of the complexes of the two enzymes involving coenzyme A and different adenyl nucleotides reported earlier. The explanation is substantially based on two critical substitutions in the amino acid sequence and the local conformational change resulting from them. The structures also provide a rationale for the movement of ligands during the action of the mycobacterial enzyme. Dual specificity of the type exhibited by this enzyme is rare. The change in locations of ligands during action,observed in the case of the M. tuberculosis enzyme, is unusual, so is the striking difference between two homologous enzymes in the geometryof the binding site, locations of ligands, and specificity. Furthermore, the dual specificity of the mycobacterial enzyme appears to have been caused by a biological necessity. (C) 2010 Elsevier Ltd.All rights reserved.

Conformations of peptides containing Z-alpha,beta-dehydroleucine (delta ZLeu). A comparison of Boc-Pro-delta ZLeu-Gly-NHEt and Boc-Pro-delta ZPhe-Gly-NHEt.

Two tripeptides of the type Boc-Pro-ΔZX-Gly-NHEt (where X = Leu, Phe) have been synthesized and their solution conformations investigated by 270 MHz 1H n.m.r. and i.r. spectroscopy. These conformational studies indicated that ΔZLeu, similar to ΔZPhe, has a strong tendency to stabilize folded Type II β-turn conformations when present at i + 2 position.

As-deposited near-single crystalline high Tc and Jc superconducting thin films by a pulsed lased deposition process

As-deposited high Tc superconducting Y1Ba2Cu3O7−x films with zero resistance temperatures of similar, equals89 K and critical current densities about 0.7×106 A/cm2 at 77 K have been reproducibly fabricated at a substrate holder temperature at 650°C, using pulsed laser deposition, without post-annealing. One key to these results is the injection of gaseous oxygen into laser produced plume just in front of the target. In this way, the correct amount of oxygen is incorporated into the as-grown film so that post-deposition treatment becomes unnecessary. Axial ion channeling in these as-deposit high Tc superconducting films on (100) SrTiO3 and X-ray photoelectron spectroscopy (XPS) on the film surfaces were performed. Angular yield profile near the film surface for Ba, and the surface peak intensity were measured using 3 MeV He ions. For channeling normal to the substrate a minimum yield of 7%, compared to similar, equals3% for single crystals, was obtained. The results of ion channeling and XPS studies indicate that the as-deposited films have good crystallinity as well as toichiometry to within similar, equals1 nm of the film surface. The in-situ growth of such high Tc and Jc films is an important step in the use of the laser deposition technique to fabricate multilayer structures and the surface perfection is of importance in tunneling devices such as Josephson junctions.

On the generalized continuum model of dipolar solvation dynamics

The continuum model of dipolar solvation dynamics is reviewed. The effects of non-spherical molecular shapes, of non-Debye dielectric relaxation of the polar solvent and of dielectric inhomogeneity of the solvent around the solute dipole are investigated. Several new theoretical results are presented. It is found that our generalized continuum model, which takes into account the dielectric inhomogeneity of the surrounding solvent, provides a description of solvation dynamics consistent with recent experimental results.

Scaling behavior of plasmon coupling in Au and ReO3 nanoparticles incorporated in polymer matrices

Polymer nanocomposites containing different concentrations of Au nanoparticles have been investigated by small angle X-ray scattering and electronic absorption spectroscopy. The variation in the surface plasmon resonance (SPR) band of Au nanoparticles with concentration is described by a scaling law. The variation in the plasmon band of ReO3 nanoparticles embedded in polymers also follows a similar scaling law. Sistance dependence of plasmon coupling in polymer composites f metal nanoparticles. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.