2,316 research outputs found
Quasi-Spherical Gravitational Collapse in Any Dimension
We study the occurrence and nature of naked singularities for a dust model
with non-zero cosmological constant in ()-dimensional Szekeres space-times
(which possess no Killing vectors) for . We find that central
shell-focusing singularities may be locally naked in higher dimensions but
depend sensitively on the choice of initial data. In fact, the nature of the
initial density determines the possibility of naked singularity in space-times
with more than five dimensions. The results are similar to the collapse in
spherically symmetric Tolman-Bondi-Lema\^{\i}tre space-times.Comment: 11 Latex pages, No figure, Revtex styl
Dietary Phytase: an ideal approach for a cost effective and low-polluting aquafeed
Global fishmeal production from wild-catch sources cannot continue to increase indefinitely; suitable alternatives have to be found for sustainable aquaculture. Plant-based aquafeed seems to be the ideal alternative to this, but has its own limitations. Plant ingredients are rich in phytic acid, which reduces the bioavailability of nutrients like minerals and protein to the fish, thereby causing aquaculture pollution. Dietary phytase treatment reduces the aquaculture pollution by improving the bioavailability of nutrients, and reduces the feed cost as evident from poultry and piggery. Phytase activity is highly dependent upon the pH of the gut. Unlike mammals, fish are either gastric or agastric, and hence, the action of dietary phytase varies from species to species. In this article, the authors attempt to summarise various effects of phytase on nutrient utilization, growth of fish and aquatic pollution
A study of higher dimensional inhomogeneous cosmological model
In this paper we present a class of exact inhomogeneous solutions to
Einstein's equations for higher dimensional Szekeres metric with perfect fluid
and a cosmological constant. We also show particular solutions depending on the
choices of various parameters involved and for dust case. Finally, we examine
the asymptotic behaviour of some of these solutions.Comment: 9 Latex pages, No figure, Revtex styl
Shell Crossing Singularities in Quasi-Spherical Szekeres Models
We investigate the occurrence of shell crossing singularities in
quasi-spherical Szekeres dust models with or without a cosmological constant.
We study the conditions for shell crossing singularity both from physical and
geometrical point of view and they are in agreement.Comment: 10 latex pages, RevTex style, no figure
Ultra-narrow and widely tunable Mn^(2+) Emission from Single Nanocrystals of ZnS-CdS alloy
Extensively studied Mn-doped semiconductor nanocrystals have invariably
exhibited photoluminescence (PL) over a narrow energy window of width <= 149
meV in the orange-red region and a surprisingly large spectral width (>= 180
meV), contrary to its presumed atomic-like origin. Carrying out emission
measurements on individual single nanocrystals and supported by ab initio
calculations, we show that Mn PL emission, in fact, can (i) vary over a much
wider range (~ 370 meV) covering the deep green-deep red region and (ii)
exhibit widths substantially lower (~ 60-75 meV) than reported so far, opening
newer application possibilities and requiring a fundamental shift in our
perception of the emission from Mn-doped semiconductor nanocrystals.Comment: 5 pages, 5 figure
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