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Shiv Nadar University

(SoNS) School of Natural Sciences

Potential algebras are extended from Hermitian to non-Hermitian Hamiltonians and shown to provide an elegant method for studying the transition from real to complex eigenvalues for a class of non-Hermitian Hamiltonians associated with the complex Lie algebra A1.

Physics

World University root node

Institute of Physics Conference Series

Non-Hermitian Hamiltonians with real and complex eigenvalues: An sl(2,C) approach

By exploiting the hidden algebraic structure of the Schrödinger Hamiltonian, namely the sl(2), we propose a unified approach of generating both exactly solvable and quasi-exactly solvable potentials. We obtain, in this way, two new classes of quasi-exactly solvable systems one of which is of periodic type while the other hyperbolic.

Fulltext

Journal of Physics A: Mathematical and General

A unified treatment of exactly solvable and quasi-exactly solvable quantum potentials

The transferability of atomic and functional group properties is an implicit concept in chemistry. The work presented here describes the use of Transferable Atom Equivalents (TAE) to represent molecular electrostatic potential fields through the use of integrated atomic multipole moments that are associated with each TAE atom type used in the reconstruction. TAE molecular surface distributions of electrostatic potentials are compared with analytical ab initio and empirical (Gasteiger) partial charge reference models for several conformations of test peptides. Surface electrostatic potential distributions computed using TAE multiple representations were found to converge at the octopole level, with incremental improvement observed when hexadecapoles were included. Molecular electrostatic potential fields that were produced using the TAE method were observed to be responsive to conformational changes and to compare well with ab initio reference distributions, Generation of TAE atom types and their associated multipoles does not involve fitting to sample electrostatic potential fields, but rather utilizes integrated AIM atomic electron density distribution within representative chemical environments. The RECON program was used for TAE reconstruction. RECON is capable of processing 5000 drug-sized molecules or 25 proteins per minute per 1.7 GHz P4 Linux processor.

Chemistry

Journal of Computational Chemistry

Transferable atom equivalent multicentered multipole expansion method

Thin Fe and Ta layers of 30-45 nm thickness, deposited via magnetron sputtering on Si (1 0 0) substrates, were bombarded at room temperature with 100 keV Ar1+ or Ar8+ or with 250 keV Xe1+ or Xe19+ ions in order to test the influence of the ion charge state on the surface sputtering and interface mixing. The samples were characterized by means of Rutherford backscattering at 0.9-3.0 MeV α-particle energy, time-of-flight elastic recoil detection analysis with a 53 MeV 127I10+ beam and atomic force microscopy. No influence of the charge state on the sputtering and athermal mixing rate was observed in the case of the Ta/Si system. However, in the case of the Fe/Si system, the ion charge was observed to have an influence on the mixing rate. © 2003 Elsevier Science B.V. All rights reserved.

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

Ion beam mixing in Fe/Si and Ta/Si bilayers: Possible effects of ion charges

A study on a vertically correlated submonolayer (VCSML) InAs/GaAs quantum-dot (QD) heterostructure was presented. The Tagaki-Taupin equations were used to simulate the high resolution x-ray diffraction (HRXRD) (004) rocking curve. The simulation was achieved assuming that indium-rich VCSML QDs are embedded in a quantum well (QW) with lower indium content and an observed QD coverage of 10%.

Applied Physics Letters

Structure and optical anisotropy of vertically correlated submonolayer InAs/GaAs quantum dots

The paper describes the synthesis of low molecular mass poly(allyl chloride) (PAC) (Mn = 856-3834 g mol-1) using Lewis acid (AlCl3, FeCl3, TiCl4) and Al powder. Branching in PAC was indicated on the basis of elemental analysis and 1H-NMR spectroscopy. Azidation of PAC could be carried out at 100°C by using NaN3 and DMSO as solvent. Curing of poly(allyl azide) (PAA) by cyclic dipolar addition reaction with EGDMA (ethylene glycol dimethacrylate, 5-45 phr) was investigated by differential scanning calorimetry and structure of cured polymer was confirmed by FTIR. A two-step mass loss was exhibited by uncured and cured PAA in nitrogen atmosphere. A mass loss of 20-28% (155-274°C) and 50-61% (330-550°C) was observed.

Journal of Thermal Analysis and Calorimetry

Thermal behaviour of poly(allyl azide)

In order to investigate the swift heavy-ion-induced mixing of nitride coatings we have irradiated Ni3N films on SiO2-, Si 3N4-, SiC- and Si-substrates with Ar, Kr, Xe and Au ions of energies ranging from 90 to 350 MeV, for which electronic energy loss dominates. The Ni-concentration profiles at the interfaces before and after irradiation were determined by means of Rutherford backscattering spectrometry with 900 keV He2+ ions. In all the cases, strong mixing occurred as soon as a material-dependent threshold Sec in the electronic stopping power Se was exceeded. The mixing rate exhibits a squared scaling k = Δσ2/Φ = η2 (Se - Sec)2 and estimation of the effective diffusion constant indicates interdiffusion in molten ion tracks. The threshold value Sec depends on the substrate material and seems to be determined by its melting point and specific heat. © 2003 Published by Elsevier Ltd.

Radiation Measurements

Interface mixing in Ni3N/SiX bilayers induced by swift heavy ions

We report here the expression and purification of a truncated form of the hepatitis E virus ORF2 protein (ORF2Δ111/ΔTM), from the fat bodies of Spodoptera litura larvae infected with a recombinant baculovirus. The purified protein migrated as a doublet of ∼56 kDa on SDS-PAGE and was found to be glycosylated by staining with concanavalin A-linked horseradish peroxidase. The protein was used in a sensitive and specific enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies to HEV. The results showed complete concordance with those obtained using a commercial kit for the detection of anti-HEV antibodies. Antigen expression in the insect larvae system presents a rapid and low-cost method that obviates the need for expensive tissue culture scale-ups or special equipment. © 2002 Elsevier Science (USA). All rights reserved.

Life Sciences

Protein Expression and Purification

Purification and diagnostic utility of a recombinant hepatitis E virus capsid protein expressed in insect larvae

Recent investigations have shown that the inclusion of hybrid shape/property descriptors together with 2D topological descriptors increases the predictive capability of QSAR and QSPR models. Property-Encoded Surface Translator (PEST) descriptors may be computed using ab initio or semi-empirical electron density surfaces and/or electronic properties, as well as atomic fragment-based TAE/RECON property-encoded surface reconstructions. The RECON and PEST algorithms also include rapid fragment-based wavelet coefficient descriptor (WCD) computation. These descriptors enable a compact encoding of chemical information. We also briefly discuss the use of the RECON/PEST methodology in a virtual high-throughput mode, as well as the use of TAE properties for molecular surface autocorrelation analysis.

Journal of Computer-Aided Molecular Design

New developments in PEST shape/property hybrid descriptors

This study examines the effect of different salt types on protein retention and selectivity in anion exchange systems. Particularly, linear retention data for various proteins were obtained on two structurally different anion exchange stationary-phase materials in the presence of three salts with different counterions. The data indicated that the effects are, for the most part, nonspecific, although various specific effects could also be observed. Quantitative structure retention relationship (QSRR) models based on support vector machine feature selection and regression models were developed using the experimental chromatographic data in conjunction with various molecular descriptors computed from protein crystal structure geometries. Star plots for each descriptor used in the final model were generated to aid in interpretation. The resulting QSRR models were predictive, with cross-validated r2 values of 0.9445, 0.9676, and 0.8897 for Source 15Q and 0.9561, 0.9876, and 0.9760 for Q Sepharose resins in the presence of three different salts. The predictive power of these models was validated using a set of test proteins that were not used in the generation of these models. Interpretation of the models revealed that particular trends for proteins and salts could be captured using QSRR techniques.