β-Diketonates of Cyclopalladated Arylazonaphthalenes: Synthesis, Characterization and Redox Activity

The synthesis of monomeric mixed species of the type [PdLK] (L = cyclopalladated arylazonaphthalenes) have been achieved by splitting the halogeno-bridge in [Pd₂L₂Cl₂] by β-diketones (HK). The compounds have been characterized on the basis of spectral (IR, UV–VIS, FAB mass, ¹H and ¹³C{¹H}NMR) and elemental analysis data. Some of the [PdLK] cyclometallates occur as isomeric mixtures whose composition have been established by ¹H-NMR data. Electron transfer properties of the cyclopalladates in DMF have been thoroughly examined using cyclic voltammetry.     

Stochastic perturbation of solitons for Alfven waves in plasmas

The stochastic perturbation of solitons due to Alfven waves in plasmas, is studied in this paper, in addition to the deterministic perturbation terms. The Langevin equations are derived and it is proved that the soliton travels through the plasma with a fixed mean velocity.     

A harmonic-type maximal principle in commutant lifting

In this note, we prove a harmonic-type maximal principle for the Schur parametrization of all intertwining liftings of an intertwining contraction in the commutant lifting theorem.     

X-ray diffraction and optical birefringence studies on four nematogenic difluorobenzene derivatives

The results of optical microscopy, DSC, X-ray diffraction and optical birefringence studies on four nematogenic difluorobenzene derivatives are presented. The thermal stability of the compounds increases substantially as greater flexibility is introduced into the core structure. Average intermolecular distances, obtained from X-ray data, are found to increase when a comparatively rigid planar phenyl ring is substituted by a flexible non-planar cyclohexyl ring in the core structure. From the values of apparent molecular lengths in the nematic phase, a short range antiferroelectric type of association is found to exist between neighbouring molecules. Density values suggest that the molecular packing is less efficient with increasing flexibility either in chain- or in core-structure. All the refractive indices exhibit normal dispersive behaviour, and a positive optical anisotropy is observed in all the compounds which decreases quickly with temperature. Temperature dependences of orientational order parameters, determined from both X-ray and optical birefringence studies, are presented. Variations of different physical properties with order parameters are discussed.     

Sol–gel based anti-reflection coatings on wedged laser rods using a spin coater

Anti-reflection (AR) sol–gel coatings are deposited on wedge glass optics for high-power lasers using spin coating technique. Characterization of these coatings on BK-7 glass substrates is carried out in terms of thickness profile across the surface, thickness variation w.r.t. wedge angle, and its effect on AR coating reflectivity, at different wedge angles from 1° to 7°. Results of the study are used to deposit AR coatings on inclined end faces of Nd:phosphate glass laser rods.     

Internal down quark's flavour changing contribution to the effective tcZ vertex

The effective vertex may be influenced by tree vertex formed by a mixing with heavy exotic isosinglet down type quarks. To study that the electroweak penguin diagrams involving one insertion of the vertex have been considered and we have calculated the contribution arising out of those diagrams using the Fourth Generation CKM matrix elements; also the applicability of the generalized GIM mechanism is considered. The additional effects of the heavy isosinglets are compared with the effects of exotic heavy isodoublets appearing in multi-generational models. We see that in the effective vertex amplitude, the down flavour changing contribution interferes constructively with the one loop penguin diagrams and experimental data may put constraint on the fourth generation down quark mass. Received: 21 March 1997 / Revised version: 19 August 1997 / Published online: 20 February 1998     

Evidence of Multifractal Structure of Compound Multiplicity Distribution in 24Mg-AgBr Interactions at 4.5AGeV

This paper reports an analysis on fractality using the experimental data of compound multiplicity (pions + target protons) distribution in ²⁴Mg-AgBr interactions at 4.5 AGeV following the method proposed by F. Takagi. Takagi moments have been calculated for 2nd, 3rd, 4th, and 5th order in the emission angle and azimuthal angle space. The results of our study reveal the multi-fractal structure of compound multiplicity distribution.     

Development and use of reference materials in India – status and plans

Reference materials development activities in India started during the period 1955–1960 for quality control in the production and use of drugs and pharmaceuticals. While the practice of import and distribution gradually accelerated in some areas, including medical, environment etc., the earliest known development of Certified Reference Materials (CRMs) within the country began with the preparation of metallurgical CRMs somewhere around 1965. A few more area-specific programs involving preparation of CRMs for quality control in the electronic industries, food and food products etc., began in the past decade. A common national program covering these activities was initiated in 1996, through organization of a national workshop on the subject and formation of a National Task Force for the development and use of reference materials in the country. The existing status and the priority needs of reference materials have been compiled by the Task Force, and a program has also been prepared for development of some of the urgently required CRMs within the country.