836 research outputs found
Phase field analysis of eutectic breakdown.
In this paper an isotropic multi-phase-field model is extended to include the effects of anisotropy and the spontaneous nucleation of an absent phase. This model is derived and compared against a published single phase model. Results from this model are compared against results from other multi-phase models, additionally this model is used to examine the break down of a regular two dimensional eutectic into a single phase dendritic front
Non-Supersymmetric Attractor Flow in Symmetric Spaces
We derive extremal black hole solutions for a variety of four dimensional
models which, after Kaluza-Klein reduction, admit a description in terms of 3D
gravity coupled to a sigma model with symmetric target space. The solutions are
in correspondence with certain nilpotent generators of the isometry group. In
particular, we provide the exact solution for a non-BPS black hole with generic
charges and asymptotic moduli in N=2 supergravity coupled to one vector
multiplet. Multi-centered solutions can also be generated with this technique.
It is shown that the non-supersymmetric solutions lack the intricate moduli
space of bound configurations that are typical of the supersymmetric case.Comment: 50 pages, 4 figures; v2: Reference added. To appear in JHE
Entropy Function for Non-Extremal Black Holes in String Theory
We generalize the entropy function formalism to five-dimensional and
four-dimensional non-extremal black holes in string theory. In the near horizon
limit, these black holes have BTZ metric as part of the spacetime geometry. It
is shown that the entropy function formalism also works very well for these
non-extremal black holes and it can reproduce the Bekenstein-Hawking entropy of
these black holes in ten dimensions and lower dimensions.Comment: 19 pages, no figure, JHEP3 style, to appear in JHE
Phase transitions in neutron star and magnetars and their connection with high energetic bursts in astrophysics
The phase transition from normal hadronic matter to quark matter in neutron
stars (NS) could give rise to several interesting phenomena. Compact stars can
have such exotic states up to their surface (called strange stars (SS)) or they
can have quark core surrounded by hadronic matter, known as hybrid stars (HS).
As the state of matter of the resultant SS/HS is different from the initial
hadronic matter, their masses also differ. Therefore, such conversion leads to
huge energy release, sometimes of the order of ergs. In the present
work we study the qualitative energy released by such conversion. Recent
observations reveal huge surface magnetic field in certain stars, termed
magnetars. Such huge magnetic fields can modify the equations of state (EOS) of
the matter describing the star. Therefore, the mass of magnetars are different
from normal NS. The energy released during the conversion process from neutron
magnetar (NM) to strange magnetar/hybrid magnetar (SS/HS) is different from
normal NS to SS/HS conversion. In this work we calculate the energy release
during the phase transition in magnetars. The energy released during NS to
SS/HS conversion exceeds the energy released during NM to SM/HM conversion. The
energy released during the conversion of NS to SS is always of the order of
ergs. The amount of energy released during such conversion can only
be compared to the energy observed during the gamma ray bursts (GRB). The
energy liberated during NM to HM conversion is few times lesser, and is not
likely to power GRB at cosmological distances. However, the magnetars are more
likely to lose their energy from the magnetic poles and can produce giant
flares, which are usually associated with magnetars.Comment: 14 pages, 4 figures, 4 table
Faraday rotation in graphene
We study magneto--optical properties of monolayer graphene by means of
quantum field theory methods in the framework of the Dirac model. We reveal a
good agreement between the Dirac model and a recent experiment on giant Faraday
rotation in cyclotron resonance. We also predict other regimes when the effects
are well pronounced. The general dependence of the Faraday rotation and
absorption on various parameters of samples is revealed both for suspended and
epitaxial graphene.Comment: 10 pp; v2: typos corrected and references added, v3, v4: small
changes and more reference
Relaxing the Cosmological Constraints on Unparticle Dark Component
Unparticle physics has been an active field since the seminal work of Georgi.
Recently, many constraints on unparticles from various observations have been
considered in the literature. In particular, the cosmological constraints on
the unparticle dark component put it in a serious situation. In this work, we
try to find a way out of this serious situation, by including the possible
interaction between dark energy and the unparticle dark component.Comment: 11 pages, 5 figures, revtex4; v2: discussions added, accepted by Eur.
Phys. J. C; v3: published versio
Identification of a novel distal regulatory element of the human Neuroglobin gene by the chromosome conformation capture approach
Neuroglobin (NGB) is predominantly expressed in the brain and retina. Studies suggest that NGB exerts protective effects to neuronal cells and is implicated in reducing the severity of stroke and Alzheimer's disease. However, little is known about the mechanisms which regulate the cell type-specific expression of the gene. In this study, we hypothesized that distal regulatory elements (DREs) are involved in optimal expression of the NGB gene. By chromosome conformation capture we identified two novel DREs located -70 kb upstream and +100 kb downstream from the NGB gene. ENCODE database showed the presence of DNaseI hypersensitive and transcription factors binding sites in these regions. Further analyses using luciferase reporters and chromatin immunoprecipitation suggested that the -70 kb region upstream of the NGB gene contained a neuronalspecific enhancer and GATA transcription factor binding sites. Knockdown of GATA-2 caused NGB expression to drop dramatically, indicating GATA-2 as an essential transcription factor for the activation of NGB expression. The crucial role of the DRE in NGB expression activation was further confirmed by the drop in NGB level after CRISPR-mediated deletion of the DRE. Taken together, we show that the NGB gene is regulated by a cell type-specific loop formed between its promoter and the novel DRE
A Note on Exact Solutions and Attractor Mechanism for Non-BPS Black Holes
We obtain two extremal, spherically symmetric, non-BPS black hole solutions
to 4D supergravity, one of which carries D2-D6 charges and the other carries
D0-D2-D4 charges. For the D2-D6 case, rather than solving the equations of
motion directly, we assume the form of the solution and then find that the
assumption satisfies the equations of motion and the constraint. Our D2-D6
solution is manifestly dual to the solution presented in 0710.4967. The
D0-D2-D4 solution is obtained by performing certain
duality transformations on the D0-D4 solution in 0710.4967.Comment: 20 pages, LaTe
On Entropy Function for Supersymmetric Black Rings
The entropy function for five-dimensional supersymmetric black rings, which
are solutions of minimal supergravity, is calculated via both
on-shell and off-shell formalism. We find that at the tree level, the entropy
function obtained from both perspectives can reproduce the Bekenstein-Hawking
entropy. We also compute the higher order corrections to the entropy arising
form five-dimensional Gauss-Bonnet term as well as supersymmetric
completion respectively and compare the results with previous microscopic
calculations.Comment: 17 pages, no figure, JHEP3 style, to appear in JHEP
Aqueous Extract of Ficus bengalensis Linn. Bark for Inflammatory Bowel Disease
The present study was designed to evaluate the effects of aqueous extract of Ficus bengalensis Linn. bark (AEFB) on inflammatory bowel disease (IBD). Effects of AEFB were studied on 2, 4, 6-trinitrobenzenesulfonic acid (TNBS, 0.25 ml 120 mg/ml in 50% ethanol intrarectally, on first day only)-induced IBD in rats. Effects of co-administration of prednisolone (2 mg/kg) and AEFB (250, 500 mg/kg) for 21 days were also evaluated. Various physical parameters including body weight, food, and water intake measured on 1st and 21st days. At end of the experiment, various histopathological indexes are assessed. The colon homogenate malondialdehyde (MDA), myeloperoxidase (MPO), superoxide dismutase (SOD), and nitric oxide (NO) levels and % mast cell protection in mesentery were also measured. In our study, we found that AEFB has a significant protective effect in the inflammatory bowel disease as compared to prednisolone in rats
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