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Shiv Nadar University

(SoNS) School of Natural Sciences

Molybdenum disulphide, a diamagnetic layered dichalcogenide solid, is found to show magnetic ordering at room temperature when exposed to a 2 MeV proton beam. The temperature dependence of magnetization displays ferrimagnetic behavior with a Curie temperature of 895 K. A disorder mode corresponding to a zone-edge phonon and a Mo valence higher than +4 has been detected in the irradiated samples using Raman and x-ray photoelectron spectroscopy, respectively. The possible origins of long-range magnetic ordering in irradiated MoS 2 samples are discussed. © 2012 American Institute of Physics.

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Physics

Fulltext

Applied Physics Letters

Magnetism in MoS 2 induced by proton irradiation

Forty eight mango hybrids were analyzed using 17 simple sequence repeat (SSR) markers. Which detected 59 scorable loci, of which 45 were polymorphic. The size of the alleles detected ranged from 100 to 480 bp. SSR markers was highly polymorphic with an average of 3.47 alleles per primer. SSRs gave moderate values of Polymorphis Information Content (PIC) and heterozygosity. The genetic relationship among mango hybrids, based on Jaccard's Similarity Coefficient values ranged from 0.38 (between H-1-13 and H-6-8) to 0.97 (between H-13-4 and H-13-7). The dendrogram, based on UPGMA cluster analysis, grouped the mango hybrids into three major groups. Cluster 'A' comprised of the five most diverse hybrids, namely, H-12-2, H-9-6, Pusa Arunima, H-9-5 and H-1-13. Two unique fingerprints were identified in hybrid H-9-6. The size of unique fingerprints ranged from 90 (MiSHRS-18) to 350 bp (MiSHRS-39). The Principal Coordinate Analysis also exhibited more or less similar distribution of mango hybrids. The tendency of clustering among mango hybrids revealed that they had stronger affinity towards female parent Amrapali.

Life Sciences

Indian Journal of Horticulture

SSR markers reveal genetic diversity in closely related mango hybrids

Excellent studies have been carried by Indian scientists to understand paleoceanographic changes in the Indian Ocean including die Arabian Sea and Bay of Bengal using Ocean Drilling Program cores. These studies revealed both short-term and long-term changes in the Indian Ocean circulation and Indian monsoon system. In general, summer monsoon was intense during warm intervals and weaker during cold intervals. Changes in deep-sea were also observed. The above studies were based on planktic and benthic foraminiferal faunal and geochemical data. Changes in deep sea oxygenation, oxygen minimum zone and surface productivity in the Indian Ocean including the Arabian Sea and Bay of Bengal during the Neogene and Quatemay were driven by the Indian summer monsoon. These changes in nutrient and oxygen levels drove major changes in the fauna and flora of the Indian Ocean. Indian monsoon variability has been suggested as contemporaneous with the southeast Monsoon variability during the last glacial and the Holocene. © Printed in India.

Proceedings of the Indian National Science Academy

Indian contributions in the field of palaeoceanography (2006-2012)

HisC2 from Mycobacterium tuberculosis was overexpressed in M. smegmatis and purified to homogeneity using nickel-nitrilotriacetic acid metal-affinity and gel-filtration chromatography. Diffraction-quality crystals were grown using the hanging-drop vapour-diffusion technique from a condition consisting of 7 mg ml-1 HisC2 (in 20 mM Tris pH 8.8, 50 mM NaCl and 5% glycerol), 1 M succinic acid pH 7.0, 0.1 M HEPES pH 7.0 and 1%(w/v) polyethylene glycol monomethyl ether 2000. The crystals belonged to the orthorhombic space group P21212, with unit-cell parameters a = 255.98, b = 77.09, c = 117.97 {\AA}. X-ray diffraction data were recorded to 2.45 {\AA} resolution from a single crystal using the in-house X-ray facility. {\textcopyright} 2012 International Union of Crystallography. All rights reserved.

Acta Crystallographica Section F: Structural Biology and Crystallization Communications

Molecular cloning, overexpression, purification, crystallization and preliminary X-ray diffraction studies of histidinol phosphate aminotransferase (HisC2) from Mycobacterium tuberculosis

Aspartate-semialdehyde dehydrogenase (Asd; ASADH; EC 1.2.1.11) is the enzyme that lies at the first branch point in the biosynthetic pathway of important amino acids including lysine and methionine and the cell-wall component diamino-pimelate (DAP). The enzymatic reaction of ASADH is the reductive dephosphorylation of aspartyl-$\beta$-phosphate (ABP) to aspartate $\beta$-semialdehyde (ASA). Since the aspartate pathway is absolutely essential for the survival of many microbes and is absent in humans, the enzymes involved in this pathway can be considered to be potential antibacterial drug targets. In this work, the structure of ASADH from Myco-bacterium tuberculosis H37Rv (Mtb-ASADH) has been determined in complex with glycerol and sulfate at 2.18 {\AA} resolution and in complex with S-methyl-l-cysteine sulfoxide (SMCS) and sulfate at 1.95 {\AA} resolution. The overall structure of Mtb-ASADH is similar to those of its orthologues. However, in the Mtb-ASADH-glycerol complex structure the glycerol molecule is noncovalently bound to the active-site residue Cys130, while in the Mtb-ASADH-SMCS complex structure the SMCS (Cys) is covalently linked to Cys130. The Mtb-ASADH-SMCS complex structurally mimics one of the intermediate steps in the proposed mechanism of ASADH enzyme catalysis. Comparison of the two complex structures revealed that the amino acids Glu224 and Arg249 undergo conformational changes upon binding of glycerol. Moreover, the structures reported here may help in the development of species-specific antibacterial drug molecules against human pathogens. {\textcopyright} 2012 International Union of Crystallography Printed in Singapore - all rights reserved.

Acta Crystallographica Section D: Biological Crystallography

Structures of ternary complexes of aspartate-semialdehyde dehydrogenase (Rv3708c) from Mycobacterium tuberculosis H37Rv

Selectively creating regions of spatially varying thickness may enable the utilization of the electronic properties of N-layer (N=1 or more) graphene and other similar layered materials (e.g., topological insulators or layered superconductors) for novel devices and functionalities on a single chip. The ablation threshold energy density increases dramatically for decreasing layer numbers of graphene originating from the dimensional crossover of the specific heat. For the 2D regime of graphite (up to N≈7) the dominant flexural mode specific heat (due to its N-1 dependence) gives rise to a strong layer number-dependence on the pulsed laser ablation threshold energy density, while for 3D regime (N&gt;7) the ablation threshold saturates due to dominant acoustic mode specific heat. As a result, several energy density windows exist between the minimum energy densities that are required for ablating single, bi, or more layers of graphene, allowing layer number selectivity. Copyright © 2011 Author(s).

AIP Advances

A new route to graphene layers by selective laser ablation

We report optical, electrical and magnetotransport properties of oxygen deficient SrTiO3 (SrTiO3-x) thin films fabricated by pulsed laser deposition technique. The oxygen vacancies (Ovac) in the thin film are expected to be uniform. By comparing its electrical properties to those of bulk SrTiO3-x, it was found that Ovac in bulk SrTiO3-x is far from uniform over the whole material. The metal-insulator transition (MIT) observed in the SrTiO3-x film was found to be induced by the carrier freeze-out effect. The low temperature frozen state can be reexcited by Joule heating, electric and intriguingly magnetic field. © 2011 American Physical Society.

Physical Review Letters

Metal-insulator transition in SrTiO3-x thin films induced by frozen-out carriers

We study the importance of inter-site coherences and quantum interference effects in the X-ray absorption spectroscopy (XAS) of mixed-valent systems. We demonstrate its importance, first for a simple diatomic mixed-valent molecule to elucidate the physics involved and finally for mixed-valent Ti oxides, using a model calculation including full spin and orbital multiplicities. Our calculations demonstrate the inefficacy of conventional approaches of describing the XAS from mixed-valent systems as incoherent combinations of XAS from the pure-valent end members and that multiplets forbidden in the single-site approximation can be effectively reached within a multi-site description. These conclusions play an important role in the interpretation of XAS and resonant X-ray scattering (RXS) in terms of the electronic structure of strongly correlated systems. Copyright {\textcopyright} EPLA, 2011.

The importance of inter-site coherences in the X-ray absorption spectra of mixed-valent systems

In a recent paper (S. Kumar, A. Pandey, Phys. Rev. E, 79, 2009, p. 026211) we considered Jacobi family (including Laguerre and Gaussian cases) of random matrix ensembles and reported exact solutions of crossover problems involving time-reversal symmetry breaking. In the present paper we give details of the work. We start with Dyson's Brownian motion description of random matrix ensembles and obtain universal hierarchic relations among the unfolded correlation functions. For arbitrary dimensions we derive the joint probability density (jpd) of eigenvalues for all transitions leading to unitary ensembles as equilibrium ensembles. We focus on the orthogonal-unitary and symplectic-unitary crossovers and give generic expressions for jpd of eigenvalues, two-point kernels and n-level correlation functions. This involves generalization of the theory of skew-orthogonal polynomials to crossover ensembles. We also consider crossovers in the circular ensembles to show the generality of our method. In the large dimensionality limit, correlations in spectra with arbitrary initial density are shown to be universal when expressed in terms of a rescaled symmetry breaking parameter. Applications of our crossover results to communication theory and quantum conductance problems are also briefly discussed. © 2011 Elsevier Inc.

Annals of Physics

Crossover ensembles of random matrices and skew-orthogonal polynomials

The formation of covalent C60 monolayers through [4+2] Diels-Alder cycloaddition between C60 and anthracene monolayers grafted onto a silicon oxide surface was investigated by ellipsometry, fluorescence and by atomic force microscopy. © 2011 The Royal Society of Chemistry.