Nuclear magnetic resonance of paramagnetic metalloporphyrins

The present article reviews and discusses proton magnetic resonance studies on metalloporphyrins which provide good models for heme proteins in their physical and chemical properties. Emphasis is given on the discussion of the₁Hnmr work done in our laboratory.     

The Effects of Non-thermal Plasma on the Morphology of Ce-doped ZnO: Synthesis,Characterization and Photocatalytic Activity of Hierarchical Nanostructures

ZnO nanoparticles with and without 8 mol % Ce dopant were synthesized by precipitation method and the prepared samples were treated with various types of non-thermal plasma in order to study their effects on the morphology and photocatalytic activity of the samples. As-prepared Ce-doped ZnO has a hexagonal wurtzite structure and the crystal system was not changed by the plasma treatment. The morphology of Ce-doped ZnO was changed from spherical particle to flower and rod-like shapes by the plasma treatment. The particle size of the treated Ce-doped ZnO is smaller in comparison with that of untreated sample. The photodegradation of methylene blue by the plasma-treated Ce-doped ZnO in aqueous solution is higher than that of the untreated Ce-doped ZnO. The enhancement of the photocatalytic activity by the plasma-treated samples may come from the particle size reduction, enhancement in charge separation efficiency and increase of the surface area.     

Synthesis of 25-oxygenated D:A-friedooleananes from D:A-friedoolean-7β -ol

D:A-Friedoolean-25-ol ( ) and 25-al ( ) have been synthesised from D:A-friedoolean-7β -ol ( ). Substituted tetrahydrofuran rings are opened up on treatment with lithium in ethylene-diamine to yield the corresponding saturated alcohols.     

One-photon absorption in direct gap semiconductors

One-photon absorption coefficients of InSb and GaAs are calculated using the first order perturbation theory assuming a two band model in which the interband energy difference is given by $E(k)=E_g{(1+\frac{h^2{k}^2}{m^{*E}g})}^{1/2}$ The results obtained are in much better agreement with the experimental data than the results of first order perturbation calculations using parabolic bands.     

Covariant and consistent anomalies in even-dimensional chiral gauge theories

This paper is devoted to various aspects of anomalies in even-dimensional chiral gauge theories. The difference between the covariant and consistent anomalies is carefully explained in terms of their different origins. The consistent current is defined in terms of a gauge-variant effectve action constructed from the covariant current. An alternative scheme is set up where the covariant anomaly is unaltered but the consistent anomaly vanishes because the effective actions is gauge-invariant. A discussion of theories with vector and axial currents separately gauged is included: here, apart from the covariant anomalies, two different ways of constructing gauge-variant effective actions are possible, giving rise to different structures of the consistent anomalies.     

Energy levels of a particle confined in a super-circular box

We find the energy levels of a free particle confined in a two dimensional infinite potential well having super-circular boundary (|x|ⁿ+|y|ⁿ=aⁿ where n is a rational number and a is a positive real number) by perturbing about the equivalent circle (n=2). The ground state energies are very accurate over a wide range of n and can be improved further by introducing a phenomenological constant determined from the knowledge of exact results available for diamond (n=1). For excited states, we find that the shape effect can cause parametric resonance which can lead to singlet-triplet crossing.     

Effect of signal-modulated optical radiation on the characteristics of a Modfet

The effect of signal-modulated optical radiation on the characteristics of a GaAlAs/GaAs MODFET has been studied analytically. It is found that the offset voltage increases with modulation frequency and the effect of frequency is negligible above 5 MHz. The drain-source current decreases with increase in signal frequency at a constant radiation flux density, doping concentration and drain-source voltage. Studies on sheet concentration and transconductance also show that the signal frequency has a significant effect upto a certain modulation frequency (5 MHz) above which the effect of frequency is insignificant.     

Diffusion of propylene adsorbed in Na-Y and Na-ZSM5 zeolites: Neutron scattering and FTIR studies

Here we report the quasielastic neutron scattering and FTIR studies on the dynamics of propylene adsorbed in Na-Y and Na-ZSM5 zeolites. QENS data show that although the mechanism of translational motion of propylene is jump diffusion in both the cases of Na-Y and Na-ZSM5 zeolites, the diffusivity is affected by the host size and is hindered in the case of Na-ZSM5. FTIR studies showed that guest-host interaction in Na-ZSM5 is stronger than that in Na-Y zeolite corroborating the QENS results.