Microscopic calculation of proton capture reactions in mass 60-80 region and its astrophysical implications

Microscopic optical potentials obtained by folding the DDM3Y interaction with the densities from Relativistic Mean Field approach have been utilized to evaluate S-factors of low-energy $(p,\gamma)$ reactions in mass 60-80 region and to compare with experiments. The Lagrangian density FSU Gold has been employed. Astrophysical rates for important proton capture reactions have been calculated to study the behaviour of rapid proton nucleosynthesis for waiting point nuclei with mass less than A=80

Environment-induced dynamical chaos

We examine the interplay of nonlinearity of a dynamical system and thermal fluctuation of its environment in the ``physical limit'' of small damping and slow diffusion in a semiclassical context and show that the trajectories of c-number variables exhibit dynamical chaos due to the thermal fluctuations of the bath.Comment: Revtex, 4 pages and 4 figure

A study of the efficiency of the class of WW-states as a quantum channel

Recently, a new class of $W$-states has been defined by Agarwal and Pati \cite{agarwal} and it has been shown that they can be used as a quantum channel for teleportation and superdense coding. In this work, we identify those three-qubit states from the set of the new class of $W$-states which are most efficient or suitable for quantum teleportation. We show that with some probability $|W_1>=(1/2)(|100>+|010>+\sqrt{2}|001>)$ is best suited for teleportation channel in the sense that it does not depend on the input state.Comment: 7 pages, Late

Detailed electronic structure studies on superconducting MgB2_2 and related compounds

In order to understand the unexpected superconducting behavior of MgB$_2$ compound we have made electronic structure calculations for MgB$_2$ and closely related systems. Our calculated Debye temperature from the elastic properties indicate that the average phonon frequency is very large in MgB$_2$ compared with other superconducting intermetallics and the exceptionally high $T_c$ in this material can be explained through BCS mechanism only if phonon softening occurs or the phonon modes are highly anisotropic. We identified a doubly-degenerate quasi-two dimensional key-energy band in the vicinity of $E_{F}$ along $\Gamma$-A direction of BZ which play an important role in deciding the superconducting behavior of this material. Based on this result, we have searched for similar kinds of electronic feature in a series of isoelectronic compounds such as BeB$_2$, CaB$_2$, SrB$_2$, LiBC and MgB$_2$C$_2$ and found that MgB$_2$C$_2$ is one potential material from the superconductivity point of view. There are contradictory experimental results regarding the anisotropy in the elastic properties of MgB$_2$ ranging from isotropic, moderately anisotropic to highly anisotropic. In order to settle this issue we have calculated the single crystal elastic constants for MgB$_2$ by the accurate full-potential method and derived the directional dependent linear compressibility, Young's modulus, shear modulus and relevant elastic properties. We have observed large anisotropy in the elastic properties. Our calculated polarized optical dielectric tensor shows highly anisotropic behavior even though it possesses isotropic transport property. MgB$_2$ possesses a mixed bonding character and this has been verified from density of states, charge density and crystal orbital Hamiltonian population analyses

Generalized quantum Fokker-Planck, diffusion and Smoluchowski equations with true probability distribution functions

Traditionally, the quantum Brownian motion is described by Fokker-Planck or diffusion equations in terms of quasi-probability distribution functions, e.g., Wigner functions. These often become singular or negative in the full quantum regime. In this paper a simple approach to non-Markovian theory of quantum Brownian motion using {\it true probability distribution functions} is presented. Based on an initial coherent state representation of the bath oscillators and an equilibrium canonical distribution of the quantum mechanical mean values of their co-ordinates and momenta we derive a generalized quantum Langevin equation in $c$-numbers and show that the latter is amenable to a theoretical analysis in terms of the classical theory of non-Markovian dynamics. The corresponding Fokker-Planck, diffusion and the Smoluchowski equations are the {\it exact} quantum analogues of their classical counterparts. The present work is {\it independent} of path integral techniques. The theory as developed here is a natural extension of its classical version and is valid for arbitrary temperature and friction (Smoluchowski equation being considered in the overdamped limit).Comment: RevTex, 16 pages, 7 figures, To appear in Physical Review E (minor revision

Use of an Alternative Probe for Improving Flue Gas Collection for Estimation of Hg

Combustion of coal in thermal power stations is one of the major sources of anthropogenic emission of mercury. In view of increased consumption of various fossil fuels such as coal, oil and gas, there is a growing concern in India on environmental degradation brought about by fuel combustion. Proper collection and estimation of mercury in flue gas is essential for assessing and monitoring the level of mercury emissions into the environment. Conventional method of drawing samples from flue gas for mercury estimation generally uses ss-probe (stainless steel probe). This can lead to the problem of sticking of mercury vapour on alloy steel surface, thereby introducing error in estimation. A new technique of using suitably designed glass probe is proposed which can minimize the problems associated with steel probe. A suitable glass probe has been designed and constructed which is provided with easily assembled and demountable parts. The newly constructed glass probe has been tested and verified by drawing Hg vapour samples from simulated Hg-laden gas stream as obtained from simple laboratory arrangements in a nebulised flame system of AAS equipment. A comparative assessment for collection of flue gas has been carried out by inserting the probe inside the sample port of the stack, at the position of the mean velocity point. The flue gas samples are drawn maintaining an iso-kinetic condition. The collection of the gas samples had been done side by side by using a glass probe and a stainless steel probe in a 500MW-boiler unit of a coal based power plant situated at Singrauli region of India. The comparative study shows a slightly improved mercury sample, collected through glass probe as compared to the ss- probe (stainless steel probe)

Application of Instrumental Techniques for Determining the Physico-chemical Properties of Airborne Particulate Matter

Coal mining and other coal utilization technologies need crushing of coal which are usually carried out in dry condition therefore a considerable amount of dust is generated. The characterization of the dust particles for size distribution analysis, important trace metal composition, nature of organic aerosol have been carried out by laser based particle size analyzer, atomic absorption spectroscopy (AAS) and Fourier transform infrared (FT-IR) spectroscopy, the data reveal that more than 50% of suspended particulate matter are in the size range of 6.38 to 9.63µm in the morning area. Further the suspended particulate matters obtained from main roadside contains 10-18% benzene soluble fraction and lead is present in higher concentration in comparison with other areas. The data further revealed that suspended particulate matter of Jharia coalfield contain coal particles, quartz and clay minerals encapsulated with different hydrocarbons compounds probably originated from vehicular exhausts and trace metals, like pb, etc