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Shiv Nadar University

(SoNS) School of Natural Sciences

We analyze a set of three PT-symmetric complex potentials, namely harmonic oscillator, generalized Pöschl-Teller and Scarf II, all of which reveal a double series of energy levels along with the corresponding superpotential. Inspired by the fact that two superpotentials reside naturally in order-two parasupersymmetry (PSUSY) and second-derivative supersymmetry (SSUSY) schemes, we complexify their frameworks to successfully account for the three potentials.

Physics

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International Journal of Modern Physics A

Complexified PSUSY and SSUSY interpretations of some PT-symmetric Hamiltonians possessing two series of real energy eigenvalues

Effect of 100 MeV58Ni+8 ion irradiation on the electrical transport behaviour of Al-Cu-Fe quasicrystalline thin films have been investigated by in situ and ex situ resistivity measurements. The quasicrystalline thin films grown by indirect heating, electron-beam and flash evaporation methods have been used for this purpose. The fluence of 100 MeV58Ni+8 beam is varied from 1 × 109 to 1 × 1013 particles/cm2. A small oscillatory variation of resistivity up to a critical fluence of 5×1012 particles/cm2 is observed in all the samples. A rapid decrease in resistivity is observed at a fluence of 1 × 1013 particles/cm2 for all the quasicrystalline thin films. These thin films also show negative temperature coefficient of resistivity similar to that of unirradiated quasicrystalline thin films. The results of simulation for resistivity versus temperature (unirradiated and irradiated at fluence 1 × 1013 particles/cm2) support the observed behaviour of resistivity with temperature. © 2002 Elsevier Science Ltd. All rights reserved.

Vacuum

Effect of irradiation by 100 MeV58Ni+8 ion on quasicrystalline thin films

Solid phase epitaxial regrowth of α-quartz amorphized by ion implantation of dopants appears to be an attractive method for processing this optoelectronically important material. In an attempt to optimize solid phase epitaxy of α-quartz, we have studied the case of 50 keV 23Na ion implantation and annealing in an 18O atmosphere at 500-850 °C. The damage profiles were monitored by means of Rutherford backscattering-channeling, while the out-diffusion of the implanted 23Na and the 16O ⇔ 18O exchange in the near-surface layers were investigated using the time-of-flight Elastic Recoil Detection analysis technique. As in the case of Cs-irradiated quartz, full epitaxial recrystallization was observed to occur for Na-irradiated quartz, however, at the lower temperature of approximately 650 °C (vs. 875 °C for Cs). Based on these observations, Na appears to offer a good compromise between a low recrystallization temperature (required to avoid oxidation of the dopants) and full recrystallization of the matrix. © 2002 Elsevier Science B.V. All rights reserved.

Surface and Coatings Technology

Epitaxial recrystallization of amorphized α-quartz after sodium ion implantation and oxygen annealing

Quantitative Structure-Retention Relationship (QSRR) models are developed for the prediction of protein retention times in anion-exchange chromatography systems. Topological, subdivided surface area, and TAE (Transferable Atom Equivalent) electron-density-based descriptors are computed directly for a set of proteins using molecular connectivity patterns and crystal structure geometries. A novel algorithm based on Support Vector Machine (SVM) regression has been employed to obtain predictive QSRR models using a two-step computational strategy. In the first step, a sparse linear SVM was utilized as a feature selection procedure to remove irrelevant or redundant information. Subsequently, the selected features were used to produce an ensemble of nonlinear SVM regression models that were combined using bootstrap aggregation (bagging) techniques, where various combinations of training and validation data sets were selected from the pool of available data. A visualization scheme (star plots) was used to display the relative importance of each selected descriptor in the final set of "bagged" models. Once these predictive models have been validated, they can be used as an automated prediction tool for virtual high-throughput screening (VHTS).

Chemistry

Journal of Chemical Information and Computer Sciences

Prediction of protein retention times in anion-exchange chromatography systems using support vector regression

Solid phase epitaxial regrowth of the amorphized layer in α-quartz induced by Rb ion implantations has been studied by thermal annealing in air at 800-1200 K. The Rb+ ions were implanted at 175 keV to fluences of 1.0 × 1016-3.4 × 1016 ions/cm2. The damage profiles and Rb depth distributions were measured by Rutherford backscattering and channeling spectroscopy. Complete epitaxial recrystallization was achieved for the samples implanted with 2.5 × 1016 Rb/cm2 after a 1 h annealing in air at 1173 K. The regrowth process occurs in two steps and has activation energies of EaL = 0.6 ± 0.1 and EaH = 3.6 ± 0.4 eV. The recrystallization rate was found to increase for increasing implanted Rb fluence. The results are discussed by considering the topological structures and network connectivity of SiO2. © 2002 Elsevier Science B.V. All rights reserved.

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

Epitaxial recrystallization of Rb-irradiated α-quartz during thermal annealing in air

Bombyx mori nucleopolyhedrosis virus (BmNPV), a natural pathogen of great economic significance in sericulture, has been exploited to generate recombinant baculoviruses harbouring genes of choice and achieve high level expression of cloned foreign genes. The BmNPV-based expression system offers the advantage of using the larval host rather than the insect-derived cell lines for economic large-scale synthesis of biomolecules. Since commercial rearing of silkworms is routinely practised, a part of the silkworm stocks can be diverted to produce biomolecules other than silk and the more sophisticated tissue culture methodologies can be dispensed with on an industrial scale. Nonetheless, the BmNPV-based expression considerably lags behind the AcMNPV system in vogue today, in terms of the choice of expression-optimized cloning vectors and easy recombinant generation kits that are commercially available. This review provides a brief outline of the current state of knowledge on the basic biology and genomics of BmNPV and how the virus has been made use of to produce biomolecules through its larval host, the mulberry silkworm. Since hyper-transcription from the viral very late gene promoters forms the basis of high level expression through recombinant baculoviruses, some aspects of the viral gene transcription and the role of late gene expression factors have also been included in the review.

Life Sciences

Current Science

Bombyx mori nucleopolyhedrovirus: Molecular biology and biotechnological applications for large-scale synthesis of recombinant proteins

Thin ribbons of stable icosahedral quasicrystal Al65Cu20Fe15 were irradiated with swift heavy ion (SHI) beam of 170 million electron volt (MeV) 58Ni+12 in high and clean vacuum environment at a temperature of 80 K to study the modification of its properties. Dynamic variation of resistance was studied on-line during and after irradiation for the first time, to understand the effect of SHI. The resistance decreased sharply at the time of incidence of ion beam due to creation of a large number of charge carriers by intense ionization by SHI and did oscillate around a mean value during irradiation due to defect creation and annihilation. The resistance increased rapidly just after the beam was stopped from its mean value during irradiation. The quasicrystalline peaks of the XRD data on these samples irradiated by SHI, were prominent till the ion beam fluence of 5 × 1012 particles/cm2, but the peak height consistently decreased with increasing fluence after a fluence of 1012 particles/cm2. © 2001 Elsevier Science Ltd. All rights reserved.

Materials Research Bulletin

Modification of icosahedral quasicrystal Al65Cu20Fe15 by 170-MeV 58Ni+12 beam

We construct two commuting sets of creation and annihilation operators for the PT-symmetric oscillator. We then build coherent states of the latter as eigenstates of such annihilation operators by employing a modified version of the normalization integral that is relevant to PT-symmetric systems. We show that the coherent states are normalizable only in the range (0, 1) of the underlying coupling parameter α.

Modern Physics Letters A

Creation and annihilation operators and coherent states for the PT-symmetric oscillator

We consider a PT-symmetric partner to Khare-Mandal's recently proposed non-Hermitian potential with complex eigen-values. Our potential, which is quasi-exactly solvable, is shown to possess only real eigenvalues. © 2001 Elsevier Science B.V. All rights reserved.

Physics Letters, Section A: General, Atomic and Solid State Physics

A PT-symmetric QES partner to the Khare-Mandal potential with real eigenvalues

The continuity equation relating the change in time of the position probability density to the gradient of the probability current density is generalized to PT-symmetric quantum mechanics. The normalization condition of eigenfunctions is modified in accordance with this new conservation law and illustrated with some detailed examples.