Hyperfine fields at implanted119Sn in Fe

Metastable FeSn systems produced by high dose implantation of¹¹⁹Sn into Fe foils are studied by conversion electron Mössbauer spectroscopy. The hyperfine field experienced by Sn implanted in Fe depends on the implantation dose. Clustering and precipitation of Sn take place at doses of 5x10¹⁶/cm² and beyond. Isochronal annealing of the implanted sample at 500 C causes the Sn atoms to move towards the surface, probably due to vacancy assisted migration, resulting in the precipitation of almost the entire implanted Sn on the Fe surface. This precipitate acts as a source for the in-diffusion of Sn into Fe at 600 C.     

Path-length dependent flux from random walk theory

Calculation of the flux Ψ(R, s) due to a point isotropic source in an infinite medium, as a function of the distance R and actual pathlength s is treated as a random walk problem. In the case of isotropic scattering, this method is shown to lead to a standard transport-theoretical result, for the integrated flux. However, for Ψ(R, s) far from the source, the random walk theory predicts a modified maxwellian form.     

Platinum-graphite electrode system for the biamperometric determination of iodine

Ohne Zusammenfassung

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Platinum-graphite electrode system for the biamperometric determination of iodine

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Our thanks are due to Prof. G. B. Singh, Head of the Department of Chemistry for providing necessary facilities. We also express our thanks to Dr. T. S. B. Narasaraju and Dr. V. S. Sankara Rao for their valuable suggestions.     

Redox processes in o-xylene oxidation over V?Ti oxide catalysts

It has been established that fast relaxations are due to catalytic conversion and slow ones are due to the formation of structures with decreasing activity and selectivity.

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Spectrophotometric determination of muzolimine

Five simple, rapid and sensitive spectrophotometric procedures for the determination of muzolimine in bulk samples and pharmaceutical dosage forms are described. The methods are based on the formation of coloured species when muzolimine is reacted with 3-methyl-2-benzothiazolinone hydrazone hydrochloride, p-N,N-dimethylphenylenediamine dihydrochloride or p-N-methylaminophenol sulphate and a suitable oxidant or with 2,6-dichloroquinone chlorimide. The results obtained are reproducible with a coefficient of variation of less than 1.5%.     

CNDO bonding parameters in transition metal atoms

The method of calculating CNDO bonding parameters developed recently is extended to transition metal atoms. It is shown that one of the approximations introduced earlier can also be deduced by a more complete treatment of the imbalance problem in CNDO-MO theory. The conventionally calibrated bonding parameters indirectly incorporate important contributions from two-particle interactions. The parameters developed are used to compute the coefficients of metal-to-ligand transfer of spin in many hexafluro metallate ions of transition metals. The results are compared with those obtained by conventional CNDO-MO calculation. Comparison of the computed bonding parameters with other available values is also made.     

Phase behaviour of thermotropic banana-shaped compounds under pressure

The phase behaviour of two achiral bent core banana-shaped compounds, the hexyloxy (compound I) and decyloxy (compound II) members of the 1,3-phenylene bis[N-(2-hydroxy-4-n-alkoxybenzylidene)-4'-aminobenzoate] series was investigated under hydrostatic pressures up to 300 MPa using high pressure differential thermal analysis and light transmission methods. The reversible transition sequence crystal (Cr₁)-B₁ phase-isotropic liquid (I), observed at room pressure for compound I, remains in the pressure region up to c 70 MPa. At higher pressures a pressure-induced crystalline phase (Cr_i) appears between the Cr₁ and B₁ phases, its temperature region becoming wider with increasing pressure. The temperature vs. pressure phase diagram shows a triple point of 72.9 MPa and 160.3°C for the Cr₁, Cr_i and B₁ phases, indicating the lower limit of pressure for the Cr_i phase. In compound II the reversible transition sequence crystal (Cr₁)-B₂ phase-I is seen over the whole pressure region, and the temperature range of the B₂ phase remains unaltered. It is concluded that both the B₁ and B₂ banana phases are stable over the whole pressure region studied.     

A general and facile synthesis of 1,3‐diaryl‐4‐pyrazoleacetic acid esters

A general synthesis of 1,3‐diaryl‐4‐pyrazoleacetic acid esters has been realized via the condensation of a γ‐carboxy ester hydrazone with the Vilsmeier reagent.