Synchronized whistlers recorded at Varanasi

Some interesting events of synchronized whistlers recorded at low latitude station Varanasi during magnetic storm period of the year 1977 are presented. The dynamic spectrum analysis shows that the component whistlers are Eckersley whistlers having dispersion 10 s^1/2 and 30 s^1/2. An attempt has been made to explain the dynamic spectra using lightning discharge generated from magnetospheric sources     

New isothermal equation of state of solids applied to high pressures

In the present paper, a new two-parameter inverted equation of state (EOS) is developed which is found to be working very well in the high-pressure region. To check its success and validity, this EOS has been applied in a number of solids. The computed volume compression is found to be in very good agreement with the experimental data in the whole range of pressure in all the solids. The minimum and the maximum pressure range used in the present study is 0–320 kbar and 0–3000 kbar, respectively.     

Vanishing of local homology

 We study the vanishing properties of local homology of complexes of modules without assuming that its homology is artinian. Using vanishing results for local homology and cohomology we prove new vanishing results for Ext- and Tor-modules. Received: 1 August 2002; in final form: 23 September 2002 / Published online: 16 May 2003 Mathematics Subject Classification (1991): 13C12, 13D07, 13D45.     

Gauged harmonic maps,Born‐Infeld electromagnetism,and magnetic vortices

We study maps from a 2‐surface into the standard 2‐sphere coupled with Born‐Infeld geometric electromagnetism through an Abelian gauge field. Such a formalism extends the classical harmonic map model, known as the σ‐model, governing the spin vector orientation in a ferromagnet allows us to obtain the coexistence of vortices and antivortices characterized by opposite, self‐excited, magnetic flux lines. We show that the Born‐Infeld free parameter may be used to achieve arbitrarily high local concentration of magnetic flux lines that the total minimum energy is an additive function of these quantized flux lines realized as the numbers of vortices antivortices. In the case where the underlying surface, or the domain, is compact, we obtain a necessary sufficient condition for the existence of a unique solution representing a prescribed distribution of vortices antivortices. In the case where the domain is the full plane, we prove the existence of a unique solution representing an arbitrary distribution of vortices and antivortices. Furthermore, we also consider the Einstein gravitation induced by these vortices, known as cosmic strings, establish the existence of a solution representing a prescribed distribution of cosmic strings cosmic antistrings under a necessary sufficient condition that makes the underlying surface a complete surface with respect to the induced gravitational metric. © 2003 Wiley Periodicals, Inc.     

A column generation approach for the timetabling problem of Greek high schools

A column generation (CG) approach for the solution of timetabling problems is presented. This methodology could be used for various instances of the timetabling problem, although in this paper the solution of the high-school situation in Greece is presented. The results obtained show clearly that the CG approach that has been extremely successful in recent years in the solution of airline crew scheduling problems could also be very efficient and robust for the solution of timetabling problems. Several large timetabling problems corresponding to real problems have been successfully solved, with the solutions obtained feasible and of very high quality in accordance with the problem definition. In addition, none of the solutions contained any idle hour for any of the teachers, which was one of the main goals of this optimization effort.     

Die Entwicklung kausaler Hypothesen in der qualitativen Sozialforschung

The disregard of causal inference in the methodological literature about qualitative research is highly problematic, since the category of causality is closely linked to the concept of social action. However, it is also clear that causal analysis is burdened with certain difficulties and methodological challenges in the realm of social research. Some of these problems are discussed in this article using Mackie—s concept of 3 “INUS”-conditions. Thereby it will be shown that strategies of causal analysis based on comparative methods proposed for qualitative research, namely “Analytic Induction” and “Qualitative Comparative Analysis” have great difficulties in dealing adequately with these problems. They can only be solved, if case-comparative methods are combined with explorative research strategies which support the researcher in gaining access to the local knowledge of the research field.     

Below-band-gap waveguiding behaviors of a weakly index-guided GaAs/AlGaAs quantum well laser

We report the reduced waveguiding efficiency for the signals around 1560 nm as the injection current of an GaAs/AlGaAs multiple quantum well laser diode (lasing wavelength at 840 nm) with a ridge-loading waveguide configuration increased. This reduction trend stopped when the injection current reached the threshold condition of the laser diode. The decreased waveguide transmission and the more expanded mode profile indicated the variation of the effective refractive index gradient in the lateral dimension with injection current. This variation was due to the refractive index decrease with increasing carrier density even below band gap. A slab waveguide model was used to simulate the lateral mode profile variation with injection current. The refractive index differences between the guiding layer and claddings in the slab waveguide model provided estimates of refractive index contrasts of the laser diode at a concerned wavelength under various injection conditions.     

Dihedral crossed products of exponent 2 are abelian

We prove that assuming enough roots of unity in the base field, a central simple algebra of exponent 2 which is split by a dihedral group, is also split by certain abelian groups.     

生物小分子与铜锌超氧化物歧化酶相互作用的波谱学研究及其应用

本工作以ESR和NMR为主要手段,并结合其它生化方法,考察了氨基酸、核酸碱基、糖等生命基本物质,和抗坏血酸等生命必需物质与钢锌超氧化物歧化酶的相互作用,实验观测到氨基酸、核酸碱基和抗坏血酸在水溶液中可以与酶中的Cu²⁺作用而使其脱离活性部位,以小分子络合物形式游离在溶液中,同时使酶失活,脱离活性部位的Cu²⁺的比例和酶的失活程度取决于小分子配体的加入量及其与Cu²⁺的络合能力。此外,首次尝试使用ESR方法,并借助氨基酸与酶的作用,考察了铜锌超氧化物歧化酶在盐酸胍变性和热变性过程中的构象变化行为,结果表明这一方法是直观而有效的。