A molecular theory of collective orientational relaxation in pure and binary dipolar liquids

A molecular theory of collective orientational relaxation of dipolar molecules in a dense liquid is presented. Our work is based on a generalized, nonlinear, Smoluchowski equation (GSE) that includes the effects of intermolecular interactions through a mean‐field force term. The effects of translational motion of the liquid molecules on the orientational relaxation is also included self‐consistently in the GSE. Analytic expressions for the wave‐vector‐dependent orientational correlation functions are obtained for one component, pure liquid and also for binary mixtures. We find that for a dipolar liquid of spherical molecules, the correlation function ϕ(k,t) for l=1, where l is the rank of the spherical harmonics, is biexponential. At zero wave‐vector, one time constant becomes identical with the dielectric relaxation time of the polar liquid. The second time constant is the longitudinal relaxation time, but the contribution of this second component is small. We find that polar forces do not affect the higher order correlation functions (l>1) of spherical dipolar molecules in a linearized theory. The expression of ϕ(k,t) for a binary liquid is a sum of four exponential terms. We also find that the wave‐vector‐dependent relaxation times depend strongly on the microscopic structure of the dense liquid. At intermediate wave vectors, the translational diffusion greatly accelerates the rate of orientational relaxation. The present study indicates that one must pay proper attention to the microscopic structure of the liquid while treating the translational effects. An analysis of the nonlinear terms of the GSE is also presented. An interesting coupling between the number density fluctuation and the orientational fluctuation is uncovered.

Nonclassical rotational inertia in a two-dimensional bosonic solid containing grain boundaries

We study the occurrence of nonclassical rotational inertia (NCRI) arising from superfluidity along grain boundaries in a two-dimensionalbosonic system. We make use of a standard mapping between the zero-temperature properties of this system and the statistical mechanics of interacting vortex lines in the mixed phase of a type-II superconductor. In the mapping, the liquid phase of the vortex system corresponds to the superfluid bosonic phase. We consider numerically obtained polycrystalline configurations of the vortex lines in which the microcrystals are separated by liquidlike grain-boundary regions which widen as the vortex system temperature increases. The NCRI of the corresponding zero-temperature bosonic systems can then be numerically evaluated by solving the equations of superfluid hydrodynamics in the channels near the grain boundaries. We find that the NCRI increases very abruptly as the liquid regions in the vortex system (equivalently, superfluid regions in the bosonic system) form a connected, system-spanning structure with one or more closed loops. The implications of these results for experimentally observed supersolid phenomena are discussed.

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.

sRNAscanner: A Computational Tool for Intergenic Small RNA Detection in Bacterial Genomes

Background:Bacterial non-coding small RNAs (sRNAs) have attracted considerable attention due to their ubiquitous nature and contribution to numerous cellular processes including survival, adaptation and pathogenesis. Existing computational approaches for identifying bacterial sRNAs demonstrate varying levels of success and there remains considerable room for improvement. Methodology/Principal Findings: Here we have proposed a transcriptional signal-based computational method to identify intergenic sRNA transcriptional units (TUs) in completely sequenced bacterial genomes. Our sRNAscanner tool uses position weight matrices derived from experimentally defined E. coli K-12 MG1655 sRNA promoter and rho-independent terminator signals to identify intergenic sRNA TUs through sliding window based genome scans. Analysis of genomes representative of twelve species suggested that sRNAscanner demonstrated equivalent sensitivity to sRNAPredict2, the best performing bioinformatics tool available presently. However, each algorithm yielded substantial numbers of known and uncharacterized hits that were unique to one or the other tool only. sRNAscanner identified 118 novel putative intergenic sRNA genes in Salmonella enterica Typhimurium LT2, none of which were flagged by sRNAPredict2. Candidate sRNA locations were compared with available deep sequencing libraries derived from Hfq-co-immunoprecipitated RNA purified from a second Typhimurium strain (Sittka et al. (2008) PLoS Genetics 4: e1000163). Sixteen potential novel sRNAs computationally predicted and detected in deep sequencing libraries were selected for experimental validation by Northern analysis using total RNA isolated from bacteria grown under eleven different growth conditions. RNA bands of expected sizes were detected in Northern blots for six of the examined candidates. Furthermore, the 5'-ends of these six Northern-supported sRNA candidates were successfully mapped using 5'-RACE analysis. Conclusions/Significance: We have developed, computationally examined and experimentally validated the sRNAscanner algorithm. Data derived from this study has successfully identified six novel S. Typhimurium sRNA genes. In addition, the computational specificity analysis we have undertaken suggests that similar to 40% of sRNAscanner hits with high cumulative sum of scores represent genuine, undiscovered sRNA genes. Collectively, these data strongly support the utility of sRNAscanner and offer a glimpse of its potential to reveal large numbers of sRNA genes that have to date defied identification. sRNAscanner is available from: http://bicmku.in:8081/sRNAscanner or http://cluster.physics.iisc.ernet.in/sRNAscanner/.

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.

Crystal structure of 2-thiophene-2-yl-3(thiophene-2-carboxylideneamino)-1,2-dihydroquinazolin-4(3H)-one and the synthesis, spectral and thermal studies of its transition metal(II) complexes

The synthesis of manganese(II), cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes of a new ligand 2-thiophene-2-yl-3(thiophene-2-carboxylidene-amino)-1,2-dihydroquinazolin-4(3H)-one (TTCADQ) is described. The ligand and metal complexes were characterized by elemental analysis, conductivity measurements, spectral (u.v.-vis., i.r., 1D n.m.r., 2D hetcor and e.p.r.) and thermal studies. The formation of 1,2-dihydroquinazolin-4(3H)-one rather than hydrazone, in the reaction of aromatic aldehyde and o-aminobenzoylhydrazide is proved by single crystal X-ray diffraction and 2D hetcor n.m.r. studies. On the basis of elemental analysis, u.v.-vis.spectroscopy and magnetic moment studies, six coordinate geometry for all the complexes was proposed. The i.r. spectral studies reveal the bidentate behaviour of the ligand.

Crystal structure and conformation study of N-methyl-t-3-methyl-r-2, c-6-diphenylpiperidin-4-one thiosemicarbazone

Thiosemicarbazones are having the ability to bind with metal and inhibit the enzyme ribonucleoside diphosphate reductase(RDR),an enzyme which is involved in the synthesis of DNA precursors in the mammalian cells.The title compound N-methyl-t-3-methyl-r-2, c-6-diphenylpiperidin-4-one thiosemicarbazone (NMMDPT), CCDC 218052, was prepared using Mannich reaction and characterized by X-ray diffraction methods.The crystal data are:C20H24N4S; M.W= 352.49, triclinic,space group P (1) over bar, a = 8.467(2)angstrom, b = 10.228(2)angstrom, c = 12.249(2)angstrom; lpha=92.595(3)degrees, beta=104.173(3)degrees, gamma=13.628(3)degrees; V=930.0(3)angstrom(3), Z=2, D-cal=1.259Mgm(-3),mu=0.184mm(-1),lambda (MoKalpha)=0.71073 angstrom, final R1 and wR2 are 0.0470 and 0.1052, respectively. The piperidine rings adopt chair conformation. The planar phenyl rings are oriented equatorially at 2,6-positions of the piperidine ring. The molecular packing can be viewed as dimers held together by two N-H...S types of intermolecular hydrogen bonds. Weak C-H...pi interactions also support the stability of the molecules in the crystal in addition to van der Waals forces. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatial survival probability for one-dimensional fluctuating interfaces in the steady state

We report numerical and analytic results for the spatial survival probability for fluctuating one-dimensional interfaces with Edwards-Wilkinson or Kardar-Parisi-Zhang dynamics in the steady state. Our numerical results are obtained from analysis of steady-state profiles generated by integrating a spatially discretized form of the Edwards-Wilkinson equation to long times. We show that the survival probability exhibits scaling behavior in its dependence on the system size and the "sampling interval" used in the measurement for both "steady-state" and "finite" initial conditions. Analytic results for the scaling functions are obtained from a path-integral treatment of a formulation of the problem in terms of one-dimensional Brownian motion. A "deterministic approximation" is used to obtain closed-form expressions for survival probabilities from the formally exact analytic treatment. The resulting approximate analytic results provide a fairly good description of the numerical data.

A note on the Berry phase for systems having one degree of freedom

A one-dimensional arbitrary system with quantum Hamiltonian H(q, p) is shown to acquire the 'geometric' phase gamma (C)=(1/2) contour integral c(Podqo-qodpo) under adiabatic transport q to q+q+qo(t) and p to p+po(t) along a closed circuit C in the parameter space (qo(t), po(t)). The non-vanishing nature of this phase, despite only one degree of freedom (q), is due ultimately to the underlying non-Abelian Weyl group. A physical realisation in which this Berry phase results in a line spread is briefly discussed.

Investigations on Bi2CuO4: a quasi-one-dimensional oxide system

The potential of Bi2CuO4 as the first oxide system to show a linear-chain magnetic behaviour is examined. Electron diffraction studies do not resolve the previously reported ambiguity regarding its space group. The magnetic susceptibility data at high temperatures are best fitted to a uniform antiferromagnetic spin-1/2 Heisenberg chain. At low temperatures, however, neither the uniform nor the alternating Heisenberg antiferromagnetic model fits the data. Magnetic susceptibility data over the entire temperature range can be fitted if one assumes dimeric units with a nearly degenerate second singlet state close to the ground state, these states being separated from an excited triplet state by an energy gap. A simple heuristic model of a dimer that gives such an energy level spectrum is examined.

Phase-shift randomness in one-dimensional disordered conductors in the quasi-metallic domain

An invariant imbedding method yields exact analytical results for the distribution of the phase theta (L) of the reflection amplitude and for low-order resistance moments (pn) for a disordered conductor of length L in the quasi-metallic regime L<

Synthesis, structure and DNA cleavage studies of coumarin analogues of tetrahydroisoquinoline and protoberberine alkaloids

Novel molecular matrices have been derived from coumarin-4-acetic acids and beta-phenylethylamines using the Bischler-Napieralski protocol which has led to the synthesis of analogues of tetrahydropapaverine in which the dimethoxybenzene moiety has been replaced by substituted coumarins. One carbon homologation has led to cyclization at the C3 position of coumarin generating the protoberberine skeleton. Structures have been confirmed by diffraction studies. The results showed that compounds 6e, 6f, 7e and 7f were found to be very effective against DNA samples of Gram positive bacterium Staphylococcus aureus and fungus Aspergillus niger. (C) 2010 Elsevier Masson SAS. All rights reserved.