13,642 research outputs found
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 . The burst
appears to be of very low energy ( ergs) confined to a narrow
cone of opening angle . 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 and Cousins and photometric
passbands are determined for the bright long duration GRB 021004 afterglow from
2002 October 4 to 16 starting 3 hours after the ray burst.
Light curves of the afterglow emission in ,, and 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 (
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 and respectively,
with a jet break at around 7 day. Comparison with a standard fireball model
indicates a total extinction of mag in the direction of the
burst. Our low-resolution spectra corrected for this extinction provide a
spectral slope . This value and the flux decay constants
agree well with the electron energy index used in the model. The
derived jet opening angle of about implies a total emitted
gamma-ray energy 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
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