8,849 research outputs found
Evolution of Primordial Black Holes in Loop Quantum Gravity
In this work, we study the evolution of Primordial Black Holes within the
context of Loop Quantum Gravity. First we calculate the scale factor and energy
density of the universe for different cosmic era and then taking these as
inputs we study evolution of primordial black holes. From our estimation it is
found that accretion of radiation does not affect evolution of primordial black
holes in loop quantum gravity even though a larger number of primordial black
holes may form in early universe in comparison with Einstein's or scalar-tensor
theories.Comment: 8 pages, 1 figur
Evolution of Primordial Black Hole Mass Spectrum in Brans-Dicke Theory
We investigate the evolution of primordial black hole mass spectrum by
including both accretion of radiation and Hawking evaporation within
Brans-Dicke cosmology in radiation, matter and vacuum-dominated eras. We also
consider the effect of evaporation of primordial black holes on the expansion
dynamics of the universe. The analytic solutions describing the energy density
of the black holes in equilibrium with radiation are presented. We demonstrate
that these solutions act as attractors for the system ensuring stability for
both linear and nonlinear situations. We show, however, that inclusion of
accretion of radiation delays the onset of this equilibrium in all radiation,
matter and vacuum-dominated eras.Comment: 18 pages, one figur
Present Acceleration of Universe, Holographic Dark Energy and Brans-Dicke Theory
The present day accelerated expansion of the universe is naturally addressed
within the Brans-Dicke theory just by using holographic dark energy model with
inverse of Hubble scale as IR cutoff. It is also concluded that if the universe
continues to expand, then one day it might be completely filled with dark
energy.Comment: 10 page
Accretion, Primordial Black Holes and Standard Cosmology
Primordial Black Holes evaporate due to Hawking radiation. We find that the
evaporation time of primordial black holes increase when accretion of radiation
is included.Thus depending on accretion efficiency more and more number of
primordial black holes are existing today, which strengthens the idea that the
primordial black holes are the proper candidate for dark matter.Comment: 11 pages, 3 figure
Effect of accretion on primordial black holes in Brans-Dicke theory
We consider the effect of accretion of radiation in the early universe on
primordial black holes in Brans-Dicke theory. The rate of growth of a
primordial black hole due to accretion of radiation in Brans-Dicke theory is
considerably smaller than the rate of growth of the cosmological horizon, thus
making available sufficient radiation density for the black hole to accrete
causally. We show that accretion of radiation by Brans-Dicke black holes
overrides the effect of Hawking evaporation during the radiation dominated era.
The subsequent evaporation of the black holes in later eras is further modified
due to the variable gravitational ``constant'', and they could survive up to
longer times compared to the case of standard cosmology. We estimate the impact
of accretion on modification of the constraint on their initial mass fraction
obtained from the -ray background limit from presently evaporating
primordial black holes.Comment: 7 pages, 2 figs; matches with published versio
Brans-Dicke Theory and primordial black holes in Early Matter-Dominated Era
We show that primordial black holes can be formed in the matter-dominated era
with gravity described by the Brans-Dicke theory. Considering an early
matter-dominated era between inflation and reheating, we found that the
primordial black holes formed during that era evaporate at a quicker than those
of early radiation-dominated era. Thus, in comparison with latter case, less
number of primordial black holes could exist today. Again the constraints on
primordial black hole formation tend towards the larger value than their
radiation-dominated era counterparts indicating a significant enhancement in
the formation of primordial black holes during the matter-dominaed era.Comment: 9 page
Non-existence of Extended Holographic Dark Energy with Hubble Horizon
The extended holographic dark energy model with the Hubble horizon as the
infrared cutoff avoids the problem of the circular reasoning of the holographic
dark energy model. We show that the infrared cutoff of the extended holographic
dark energy model cannot be the Hubble horizon provided that the Brans-Dicke
parameter satisfies the experimental constraint , and
this is proved as a no-go theorem. The no-go theorem also applies to the case
in which the dark matter interacts with the dark energy.Comment: 12 pages with revtex, 4 figures, v2: minor corrections to match the
version appeared in JCA
Hidden Order in the Cuprates
We propose that the enigmatic pseudogap phase of cuprate superconductors is
characterized by a hidden broken symmetry of d(x^2-y^2)-type. The transition to
this state is rounded by disorder, but in the limit that the disorder is made
sufficiently small, the pseudogap crossover should reveal itself to be such a
transition. The ordered state breaks time-reversal, translational, and
rotational symmetries, but it is invariant under the combination of any two. We
discuss these ideas in the context of ten specific experimental properties of
the cuprates, and make several predictions, including the existence of an
as-yet undetected metal-metal transition under the superconducting dome.Comment: 12 pages of RevTeX, 9 eps figure
Human surfactant protein D alters oxidative stress and HMGA1 expression to induce p53 apoptotic pathway in eosinophil leukemic cell line
This article is made available through the Brunel Open Access Publishing Fund. Copyright: © 2013 Mahajan et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Surfactant protein D (SP-D), an innate immune molecule, has an indispensable role in host defense and regulation of
inflammation. Immune related functions regulated by SP-D include agglutination of pathogens, phagocytosis,
oxidative burst, antigen presentation, T lymphocyte proliferation, cytokine secretion, induction of apoptosis and
clearance of apoptotic cells. The present study unravels a novel ability of SP-D to reduce the viability of leukemic
cells (eosinophilic leukemic cell line, AML14.3D10; acute myeloid leukemia cell line, THP-1; acute lymphoid leukemia
cell lines, Jurkat, Raji; and human breast epithelial cell line, MCF-7), and explains the underlying mechanisms. SP-D
and a recombinant fragment of human SP-D (rhSP-D) induced G2/M phase cell cycle arrest, and dose and timedependent
apoptosis in the AML14.3D10 eosinophilic leukemia cell line. Levels of various apoptotic markers viz.
activated p53, cleaved caspase-9 and PARP, along with G2/M checkpoints (p21 and Tyr15 phosphorylation of cdc2)
showed significant increase in these cells. We further attempted to elucidate the underlying mechanisms of rhSP-D
induced apoptosis using proteomic analysis. This approach identified large scale molecular changes initiated by SPD
in a human cell for the first time. Among others, the proteomics analysis highlighted a decreased expression of
survival related proteins such as HMGA1, overexpression of proteins to protect the cells from oxidative burst, while a
drastic decrease in mitochondrial antioxidant defense system. rhSP-D mediated enhanced oxidative burst in
AML14.3D10 cells was confirmed, while antioxidant, N-acetyl-L-cysteine, abrogated the rhSP-D induced apoptosis.
The rhSP-D mediated reduced viability was specific to the cancer cell lines and viability of human PBMCs from
healthy controls was not affected. The study suggests involvement of SP-D in host’s immunosurveillance and
therapeutic potential of rhSP-D in the eosinophilic leukemia and cancers of other origins.Department of Biotechnology, Indi
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