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Shiv Nadar University

(SoNS) School of Natural Sciences

Orthogonal-unitary and symplectic-unitary crossover ensembles of random matrices are relevant in many contexts, especially in the study of time reversal symmetry breaking in quantum chaotic systems. Using skew-orthogonal polynomials we show that the same generic form of n -level correlation functions are obtained for the Jacobi family of crossover ensembles, including the Laguerre and Gaussian cases. For large matrices we find universal forms of unfolded correlation functions when expressed in terms of a rescaled transition parameter with arbitrary initial level density. © 2009 The American Physical Society.

Physics

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Fulltext

Physical Review E - Statistical, Nonlinear, and Soft Matter Physics

Universal spectral correlations in orthogonal-unitary and symplectic-unitary crossover ensembles of random matrices

We have studied the phase behavior of concentrated aqueous solutions of cetylpyridinium bromide (CPB) and sodium 3-hydroxy-2-naphthoate (SHN) using X-ray diffraction and polarizing optical microscopy. The phase behavior of this system is found to be very similar to that of the cetyltrimethylammonium bromide (CTAB) - SHN - water system, reported by us recently (Ghosh, S. K., et al. Langmuir, 2007, 23, 3606), but with the important difference that the mesh-like aggregates in the present system have square symmetry, instead of the hexagonal symmetry seen in the earlier case. A random mesh phase without long-range correlations of the in-plane structure, as well as an ordered mesh phase, where the mesh-like aggregates lock into a three-dimensional lattice, are observed, as in the CTAB - SHN - water system. The mesh-like aggregates do not form when the hydroxynaphthoate counterion is replaced by either salicylate or tosylate, which are also known to bind strongly to the surfactant micelle. Instead, the phase behavior of these ternary mixtures is akin to that of the CPB - water binary system; the only liquid crystalline phase observed being the hexagonal phase made up of cylindrical micelles. These results show the extreme sensitivity of the structure and stability of mesh phases to subtle changes in the interheadgroup interactions. © Copyright 2009 American Chemical Society.

Langmuir

Structure of mesh phases in cationic surfactant systems with strongly bound counterions: Influence of the surfactant headgroup and the counterion

In this paper, we report on modifications in structural and optical properties of CdS thin films due to 190 keV Mn-ion implantation at 573 K. Mn-ion implantation induces disorder in the lattice, but does not lead to the formation of any secondary phase, either in the form of metallic clusters or impurity complexes. The optical band gap was found to decrease with increasing ion fluence. This is explained on the basis of band tailing due to the creation of localized energy states generated by structural disorder. Enhancement in the Raman scattering intensity has been attributed to the enhancement in the surface roughness due to increasing ion fluence. Mn-doped samples exhibit a new band in their photoluminescence spectra at 2.22 eV, which originates from the d-d ( 4 T 1 → 6 A 1 ) transition of tetrahedrally coordinated Mn 2+ ions. © 2009 Elsevier B.V.

Applied Surface Science

Modifications in structural and optical properties of Mn-ion implanted CdS thin films

Titanium(II) solutions, prepared by dissolving titanium metal in triflic acid+HF, react readily with chelated complexes of Ag(III), nickel(IV) and copper(III). Reactions with excess Ti(II) yield Ti(III) and are strongly catalyzed by added Ti(IV), but stoichiometry is unaffected. Rapid reactions of Ti(II) with nonchelated oxidants, VO2+, UO22 + and MnO4- do not exhibit catalysis by Ti(IV). Reductions by Ti(III) are unaffected by Ti(IV). The Ag(III)-Ti(II) reaction, as catalyzed by Ti(IV), is subject to kinetic saturation with an association quotient 4 × 102 M-1 for the Ti(IV)-activated species. It is proposed that the catalyzed reductions of the Ag(III) and Ni(IV) oxidants are initiated by 1e- steps, but that the initially formed cation pairs undergo geminate follow-up reactions to give the observed stable products. © 2008 Elsevier B.V. All rights reserved.

Chemistry

Inorganica Chimica Acta

Electron transfer. Part 166 [1]. Reactions of Ti(II)(aq) with oxidants having strongly positive potentials

Wide band gap InGaZn6O9 films of thickness ~ 350 nm were deposited on sapphire (0001) at room temperature by using the pulsed laser deposition technique. The transparent films showed the optical transmission of &gt; 80% with the room temperature Hall mobility of ~ 10 cm2/V s and conductivity of 4 × 102 S/cm at a carrier density &gt; 1020 cm- 3. The electrical properties as a function of deposition temperatures revealed that the conductivity and mobility almost retained up to the deposition temperature of 200 °C. The films annealed in different atmospheres suggested oxygen vacancy plays an important role in determining the electrical conductivity of the compound. Room temperature grown heterostructure of n-InGaZn6O9/p-SiC showed a good rectifying behavior with a leakage current density of less than 10- 9 A/cm2, current rectifying ratio of 105 with a forward turn on voltage ~ 3 V, and a breakdown voltage greater than 32 V. © 2008 Elsevier B.V. All rights reserved.

Thin Solid Films

Enhanced conductivity of pulsed laser deposited n-InGaZn6O9 films and its rectifying characteristics with p-SiC

This paper reports quasi-periodic pulsing hiss emissions recorded during daytime in the frequency range of 50 Hz-15 kHz at low latitude station Jammu (geomag. lat. = 22°26'N; L = 1.17). It is noted that pulsing VLF emissions are a rare phenomena at low latitudes. The various spectrograms of pulsing VLF hiss emissions presented in this paper clearly show band limited spectrums regularly pulsing with almost equal period of the order of few seconds in the frequency range of ̃3-8kHz. Generation and propagation mechanism of these emissions are briefly discussed. © Printed in India.

Life Sciences

Journal of Earth System Science

Quasi-periodic VLF emissions observed during daytime at a low latitude Indian ground station Jammu

Three series of novel and new fused heterocyclic systems, viz. triazolo[4,3-a]-quinazolin-7-ones (4), [1,2,4,5]-tetrazino[4,3-a]-quinazolin-8-ones (6) and indolo[2,3-c][1,2,4]-triazino[4,3-a]-quinazolin-8-ones (8) have been synthesized from the key intermediate 3-(substituted-phenyl)-2-hydrazino-quinazolin-4-ones (3). Thus, condensation of (3) with appropriate aromatic acids in the presence of DCC in dichloromethane afforded the fused system (4), while reaction of (3) with isatin in methanol gave the corresponding Schiff base (7) which on cyclodehydration furnished another fused heterocyclic system (8). The intermediate (3) on refluxing with substituted-phenylisothiocyanate gave the substituted-thiosemicarbazide (5), which on oxidative cyclization with bromine in CCl4 furnished the novel fused system (6). The structures of intermediate and final compounds have been determined by means of IR, 1H NMR, 13C NMR, UV and elemental analysis. All the synthesized compounds have been screened for their antibacterial activity against Gram-negative bacteria, Escherichia coli, Pseudomonas aeruginosa and Gram-positive bacteria, Streptococcus pneumoniae, Bacillus subtilis, as well as demonstrated significant antifungal activity against fungi viz. Candida albicans, Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger. © 2008 Elsevier Masson SAS. All rights reserved.

European Journal of Medicinal Chemistry

Antimicrobial studies of some novel quinazolinones fused with [1,2,4]-triazole, [1,2,4]-triazine and [1,2,4,5]-tetrazine rings

The discrete VLF chorus emissions recorded at low latitude ground station Jammu (geomag. lat. = 22°26′N, L = 1.17) are reported and their characteristics based on spectral analysis have been carried out. These discrete chorus emissions are falling tone emissions which are rarely observed at low latitude ground stations. These discrete chorus emissions are generated during a strong geomagnetic storm period of 2-7 May, 1998. We have computed the frequency sweep rate, repetition period and source region of the individual chorus elements. It is observed that the sweep rate increases with time. Copyright © The Society of Geomagnetism and Earth.

Earth, Planets and Space

Characteristics of discrete VLF falling-tone chorus emissions observed at low latitude ground station Jammu

Origin recognition complex subunit 1 (ORC1) is essential for DNA replication in eukaryotes. The deadly human malaria parasite Plasmodium falciparum contains an ORC1/CDC6 homolog with several interesting domains at the catalytic carboxyl-terminal region that include a putative nucleoside triphosphate-binding and hydrolysis domain, a putative PCNA-interacting-protein (PIP) motif, and an extreme C-terminal region that shows poor homology with other ORC1 homologs. Due to the unavailability of a dependable inducible gene expression system, it is difficult to study the structure and function of essential genes in Plasmodium. Using a genetic yeast complementation system and biochemical experiments, here we show that the putative PIP domain in ORC1 that facilitates in vitro physical interaction with PCNA is functional in both yeast (Saccharomyces cerevisiae) and Plasmodium in vivo, confirming its essential biological role in eukaryotes. Furthermore, despite having less sequence homology, the extreme C-terminal region can be swapped between S. cerevisiae and P. falciparum and it binds to DNA directly, suggesting a conserved role of this region in DNA replication. These results not only provide us a useful system to study the function of the essential genes in Plasmodium, they help us to identify the previously undiscovered unique features of replication proteins in general. Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Eukaryotic Cell

Functional dissection of the catalytic carboxyl-terminal domain of origin recognition complex subunit 1 (PfORC1) of the human malaria parasite plasmodium falciparum

(Chemical Equation Presented) A powerful intramolecular Schmidt reaction starting from primary azidoalcohols is reported. This approach involves a nonacidic activation of the alcohol via triflation. The synthetic potential offered by the mild reaction conditions is demonstrated by a highly selective synthesis of (-)-indolizidine 167B. {\textcopyright} 2009 American Chemical Society.