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Shiv Nadar University

(SoNS) School of Natural Sciences

Inside a box of size L we contemplate the simplest PT -symmetric piece-wise constant potential of size ℓ < L and purely imaginary strength ig and describe all its bound states in closed form.

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Physics

Czechoslovak Journal of Physics

Weakly non-Hermitian square well

The luminescent properties of quartz and silica doped with photoactive ions depend on the structural and chemical properties of the matrix and doping elements. The dynamic solid phase epitaxy of α -quartz during Ba+ -ion implantation at 300-1170 K and its relationship to cathodoluminescence emission are investigated in this work. Rutherford backscattering channeling analysis revealed that the amorphous layer created by 1× 1015 175 keV Ba ions cm2 at 300 K almost disappeared when the implantation temperature was raised to 1120 K. Between 770 and 1100 K the cathodoluminescence spectra taken at room temperature exhibit dramatic changes with the implantation temperature and allow to distinguish between color centers related to quartz, ion-irradiated silica, and implanted Ba ions. After achieving almost complete epitaxial recovery, only a violet band at 3.4 eV remained, which we attribute to Ba -related luminescence centers. Samples first implanted with Ba ions and then postannealed in air or O 2 18 atmosphere up to 1320 K did not show full epitaxy of the amorphized layer. © 2005 American Institute of Physics.

Fulltext

Journal of Applied Physics

Cathodoluminescence and solid phase epitaxy in Ba -irradiated α -quartz

Epitaxial thin films of optimally doped, underdoped, and Zn-doped YBa2Cu3O7-δ (YBCO) were grown on single crystal (001) Nb:SrTiO3 substrates by pulsed laser deposition (PLD) and the electrical properties of the corresponding interface junctions were examined. The growth conditions were optimized in each case to get the appropriate crystalline quality of the films as well as the desired normal state and superconducting properties. The films or heterointerfaces were characterized by x-ray diffraction, Rutherford backscattering (RBS) ion channeling spectrometry in normal and oxygen resonance modes, magnetic susceptibility, four probe in-plane resistivity, and the temperature dependent current-voltage (I-V) characteristics. Nonlinear I-V curves (forward and reverse) were obtained in all the cases, revealing some characteristic differences and interesting temperature evolution. These data, when analyzed within the framework of a standard description of transport across the metal-semiconductor (Schottky) interface, suggest lateral intrinsic nanoscale electrical inhomogeneity in the system. Also as compared to the case of optimally doped YBCO a small but definitive lowering of the effective Schottky barrier height ΦB is observed for junctions based on oxygen underdoped and Zn-doped YBCO. © 2005 The American Physical Society.

Physical Review B - Condensed Matter and Materials Physics

Electrical properties of epitaxial junctions between Nb:SrTiO3 and optimally doped, underdoped, and Zn-doped YBa2Cu3O7-δ

The paper deals with the effect of pesticide on the pest affecting a paddy field and also on the fishes living in the soil water. An objective function is formed in terms of projected loss of individual fish, the projected profit of killing a pest and the cost of spraying insecticide for a finite time period. Next the corresponding pest management model is formed by considering the growth equations of paddy, pest, and fish of the soil water. The model is analyzed by control theoretic means to determine the threshold limits of pesticide to be used. Lastly, the optimal value of pesticide is obtained. It is shown that the optimal value lies within the threshold limits. Finally corresponding to this optimal threshold value of pesticide, the optimal values of the biomass of paddy and that of the fish of the soil water are also obtained. The results are finally verified numerically by special choice of parameters compatible with the model. © World Scientific Publishing Company.

Mathematics

Journal of Biological Systems

A new approach to pest management problem

The fabrication of Ge-doped light-emitting devices in single-crystal α-quartz without destroying its crystal structure via the dynamic solid phase epitaxial regrowth technique is being pursued. This paper presents results on the cathodoluminescence (CL) after 120 keV Ge implantation in α-quartz at 1173 K with fluences between 1 × 1014 and 1 × 1016 ions/cm2. Rutherford backscattering-channeling analysis showed that the Ge implantation up to 4 × 1014 ions/cm2 produced isolated damage zones. The transition to an amorphous layer is accompanied by a strong increase in the CL output. The CL spectra taken at 10-300 K show six bands located at 260 nm (4.9 eV, UV), 288 nm (4.3 eV, UV), 383 nm (3.1 eV, violet), 453 nm (2.7 eV, blue), 511 nm (2.4 eV, green) and 620 nm (2.0 eV, red). Only the violet band is associated with the Ge-related defects or the formation of Ge-clusters; it reaches its maximum intensity at 7 × 1014 Ge-ions/cm 2. All the other bands are connected to various defect centers in the SiO2 network. © 2003 Elsevier B.V. All rights reserved.

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

Cathodoluminescence of α-quartz after hot Ge ion irradiation

The crystal structure of the title compound (systematic name: 2H-1-benzothiopyran-2-thione), C9H6S2, also known as dithiocoumarin, has been determined. The molecule is essentially planar and the structure is stabilized via S⋯S and C-H⋯π interactions. © 2004 International Union of Crystallography Printed in Great Britain - all rights reserved.

Chemistry

Acta Crystallographica Section E: Structure Reports Online

2H-Thiochromene-2-thione

Land races adapted to a variety of agro-ecological niches constitute a rich source of rice biodiversity. Large-scale cultivation of high-yielding varieties has resulted in the replacement of the land races, except a few that are still being cultivated by the resource-poor farmers practising subsistence farming. From the viewpoints of their conservation and utilization, it is important to understand the genetic structure of the present-day land races. The present study was designed to explore if the present-day land races of rice still retain a composite genetic structure that forms the basis of their stability. Two land races, which are being grown by the rural farmers in the coastal regions of Orissa over several generations, were characterized and compared with four commercial high-yielding varieties using sequence-tagged microsatellite site (STMS) markers. A high-resolution (3% Metaphor) agarose gel when compared with 6% denaturing PAGE was found useful for the differentiation of the STMS alleles. The DNA profiles based on forty-eight mapped STMS markers revealed a high degree of genetic diversity between the land races and the commercial varieties. Analysis of 18 individual plants of each land race and variety, using ten most informative markers detected a high degree of genetic uniformity in the commercial varieties. Residual heterozygosity for only one of the marker loci was evident in the case of the popular commercial cultivar, Lalat. In both the land races, heterozygosity and heterogeneity were clearly evident with the presence of additional marker locus genotypes carrying new STMS alleles at much lower frequency than the major allele. Of the two land races characterized, one (Galleiganthi) was more heterogeneous than the other (Bankosa).

Life Sciences

Current Science

Composite genetic structure of rice land races revealed by STMS markers

Physical Review B

Ab initio Wannier-function-based many-body approach to Born charges of crystalline insulators

X-ray absorption spectroscopy of transition-metal doped diluted magnetic semiconductors Zn1-xMxO

In this study the kinetics of two electron transactions between the reducing substrates glyoxylic and pyruvic acids and the oxidising complex cation, tris(biguanide)manganese(IV) in aqueous acidic media have been examined. Under the experimental conditions (pH = 1.50-3.78) only the fully protonated form of the oxidant reacts with the anions of the substrates whereas the parent acids, viz. glyoxylic and pyruvic acids, were found to be unreactive. The second-order rate constants for the oxidations of glyoxylate and pyruvate by the title MnIV species are (2.24 ± 0.10) × 10-1 and (5.40 ± 0.30) × 10-2 M-1S-1, respectively, at 25.0 °C and at I = 1.0 M (NaNO3 or NaClO 4). A rate-liming one-electron change between the redox partners seems justified. © Wiley-VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2004.