Rare Metals Extraction from Non-ferrous Resources in India: Present Status and Prospects of R&D

Rare metals comprise of those naturally occurring elements with relatively lesser abundance in the earth 's crust which are difficult to extract by normal metallurgical processes. The present paper summarizes the ore / mineral resource base including the secondary resources, current usage and extraction technology of rare metals in India. The R&D in India has resulted in the exploitation of such processes or poised for gainful utilization. As the tech-nologies for extraction of rare metals follow a different methodology than those applicable to the normal base metals and were not readily available at the early stage of development during 1950-1990s, indigenous developments matured and were put to use; a few such technologies are described. Mention may be made of the applications of special processing options such as: halide metallurgy, strong acid / alkali treatment for breaking down the refractory minerals FIF/ alkali fusion ; solvent extra-ction/ ion exchange for metal separation, and vacuum melting/ electron beam melting/ refining etc for melting/ refining, to meet the stringent specifications of the rare metals . In most cases, extraction is carried out using primary resources , but for metals not present in a substantial quantity in natural ores or in diffused state, secondary resources are exploited. Secondary resources are particularly criticalfor Ga, V, Mo, W, Se, Te etc. Possi- bilities for further research are indicated to ensure secured supply ofthese metals in future

Optical Observations and Multiband Modelling of the Afterglow of GRB 041006: Evidence of A Hard Electron Energy Spectrum

We present the CCD Cousins R band photometric observations of the afterglow of GRB 041006. The multiband afterglow evolution is modelled using an underlying `hard' electron energy spectrum with a $p_1 \sim 1.3$. The burst appears to be of very low energy ($E \sim 10^{48}$ ergs) confined to a narrow cone of opening angle $\theta \sim 2.3^{\circ}$. The associated supernova is compared with SN1998bw and is found to be brighter.Comment: Accepted for publication in Bull. Astr. Soc. India (BASI

Search For A Permanent Electric Dipole Moment Using Atomic Indium

We propose indium (In) as a possible candidate for observing the permanent electric dipole moment (EDM) arising from the violations of parity (P) and time-reversal (T) symmetries. This atom has been laser cooled and therefore the measurement of its EDM has the potential of improving on the current best EDM limit for a paramagnetic atom which comes from thallium. We report the results of our calculations of the EDM enhancement factor due to the electron EDM and the ratio of the atomic EDM to the electron-nucleus scalar-pseudoscalar (S-PS) interaction coupling constant in In in the framework of the relativistic coupled cluster theory. It might be possible to get new limits for the electron EDM and the S-PS CP violating coupling constant by combining the results of our calculations with the measured value of the EDM of In when it is available. These limits could have important implications for the standard model (SM) of particle physics.Comment: 5 pages, 1 fig, Rapid Communicatio

Ion thermal effects in oscillating multi-ion plasma sheath theory

The effects of ion temperature are discussed in a two-ion electron plasma and for a model applicable to the oscillating sheath theory that has recently been much in the focus of researchers. The differences between the fluid and kinetic models have been pointed out, as well as the differences between the approximative kinetic description (which involves the expansion of the plasma dispersion function), and the exact kinetic description. It is shown that the approximative kinetic description, first, can not describe the additional acoustic mode which naturally exists in the plasma with an additional ion population with a finite temperature, and, second, it yields an inaccurate Landau damping of the bulk ion acoustic mode. The reasons for these two failures are described. In addition to this, a fluid model is presented that is capable of capturing both of these features that are missing in the approximative kinetic description, i.e., two (fast and slow) ion acoustic modes, and the corresponding Landau damping of both modes

Bioleaching of a Copper Sulphide Concentrate by two different Strains of Acidophilic Bacteria

Two strains of acidophilic Thiobacillus generae, one isolated from the water of a copper mine and another, a pure culture have been used for the processing of a sulphidic copper concentrate with 14.13% Cu, 10.04% Ni, 0.33% Co, 0.71% Mo, 2.28% Fe, 36.4% S and 1.72% 5102 generated at UCIL Jaduguda, India. The concentrate has chalcopyrite and pentlandite as the major phases along with pyrite, pyrrhotite, violarite, millerite and moly-bdenite as the minor phases. The unadapted isolated culture of Acidithiobacillus ferrooxidans dissolved 41% Ni and 35% Co at 308K and pH 2.0 in 60 days from the mixed size (<200 gm) particles. Pyrite (10 wt%) was found to be an effective additive resulting in bioleaching of 81% Ni and 45% Co under above condition; biorecovery being high (90% Ni and 61% Co) from the finest size particles (<50 /an). A. ferrooxidans strains of another source (OU, Hyderabad) adapted over copper concentrate serially for four times at 2.3 pH and used for leaching, improved the kinetics showing biorecovery of 83% Ni and 88% Co in 30 days only with the mixed size particles

On quantum plasma: a plea for a common sense

The quantum plasma theory has flourished in the past few years without much regard to the physical validity of the formulation or its connection to any real physical system. It is argued here that there is a very limited physical ground for the application of such a theory.Comment: EPL, to be published 201

Optical observations of the bright long duration peculiar GRB 021004 afterglow

The CCD magnitudes in Johnson $B,V$ and Cousins $R$ and $I$ photometric passbands are determined for the bright long duration GRB 021004 afterglow from 2002 October 4 to 16 starting $\sim$ 3 hours after the $\gamma-$ray burst. Light curves of the afterglow emission in $B$,$V$,$R$ and $I$ passbands are obtained by combining these measurements with other published data. The earliest optical emission appears to originate in a revese shock. Flux decay of the afterglow shows a very uncommon variation relative to other well-observed GRBs. Rapid light variations, especially during early times ($\Delta t < 2$ days) is superposed on an underlying broken power law decay typical of a jetted afterglow. The flux decay constants at early and late times derived from least square fits to the light curve are $0.99\pm0.05$ and $2.0\pm0.2$ respectively, with a jet break at around 7 day. Comparison with a standard fireball model indicates a total extinction of $E(B-V)=0.20$ mag in the direction of the burst. Our low-resolution spectra corrected for this extinction provide a spectral slope $\beta = 0.6\pm0.02$. This value and the flux decay constants agree well with the electron energy index $p\sim 2.27$ used in the model. The derived jet opening angle of about $7^{\circ}$ implies a total emitted gamma-ray energy $E_{\gamma} = 3.5\times10^{50}$ erg at a cosmological distance of about 20 Gpc. Multiwavelength observations indicate association of this GRB with a star forming region, supporting the case for collapsar origin of long duration GRBs.Comment: 19 pages, 3 figures, BASI, 31, 1