2,364 research outputs found
Gravitational deflection of light in the Schwarzschild -de Sitter space time
Recent studies suggest that the cosmological constant affects the
gravitational bending of photons although the orbital equation for light in
Schwarzschild-de Sitter space time is free from cosmological constant. Here we
argued that the very notion of cosmological constant independency of photon
orbit in the Schwarzschild-de Sitter space time is not proper. Consequently the
cosmological constant has some clear contribution to the deflection angle of
light rays. We stressed the importance of the study of photon trajectories from
the reference objects in bending calculation, particularly for asymptotically
non-flat space-time. When such an aspect is taken in to consideration the
contribution of cosmological constant to the effective bending is found to
depend on the distances of the source and the reference objects.Comment: 5 pages, no figur
A Hybrid Procreative –Discriminative Based Hashing Method
Hashing method is the one of the main method for searching same and different images based on hash code.For capturing similarities between textual, visual and cross media information; a hashing approaches have been proven. To address these challenges, in this paper we propose semantic level cross media hashing (SCMH) and deep belief network (DBN) is for a co-relation between different modalities
On static spherically symmetric solutions of the vacuum Brans-Dicke theory
It is shown that among the four classes of the static spherically symmetric
solution of the vacuum Brans-Dicke theory of gravity only two are really
independent. Further by matching exterior and interior (due to physically
reasonable spherically symmetric matter source) scalar fields it is found that
only Brans class I solution with certain restriction on solution parameters may
represent exterior metric for a nonsingular massive object. The physical
viability of the black hole nature of the solution is investigated. It is
concluded that no physical black hole solution different from the Schwarzschild
black hole is available in the Brans-Dicke theory.Comment: 15 pages, To be published in Gen. Rel. and Grav, typos in references
correcte
Comparative study of maternal and perinatal outcome in pregnancies with and without umbilical cord around foetal neck
Background: Umbilical cord around neck of the foetus is called the nuchal cord. The aims and objectives are to find out the incidence of nuchal cord around foetal neck at delivery, and to compare and evaluate intrapartum and postpartum maternal and foetal outcome in those with or without nuchal cord at delivery.Methods: It is a prospective cross-sectional study conducted at tertiary care hospital for period of 12 months. Of 1380 patients, 934 patients were enrolled in present study after meeting the inclusion and exclusion criteria of which 150 patients were included in study group who delivered with nuchal cord and 784 patients in control group who delivered without nuchal cord.Results: Present study showed 18.84% incidence of nuchal cord at delivery. Duration of labour was 6.51hrs in study group and 6.15hrs in control group and the difference was statistically significant. Rest of the intrapartum and postpartum events were statistically not significant. Mean length of cord was more in patients delivered with loop of cord around foetal neck as compared to another group and it is statistically significant.Conclusions: Nuchal cord is a common finding at the time of delivery. However, it is per-se not an indication of LSCS and it only increases the operative morbidity
Weak field limit of Reissner-Nordstrom black hole lensing
We study gravitational lensing by a Reissner-Nordstrom (RN) black hole in the
weak field limit. We obtain the basic equations for the deflection angle and
time delay and find analytical expressions for the positions and amplifications
of the primary and secondary images. Due to a net positive charge, the
separation between images increases, but no change in the total magnification
occurs.Comment: 8 pages, to appear in Phys. Rev.
Compatibility of Einstein minimally coupled self interacting scalar field theory with the solar system tests of gravity
We examine the compatibility of the Einstein minimally coupled
self-interacting scalar field theory with the local tests of gravity. We find
that apart from the trivial case of the Schwarzschild-de Sitter solution with
constant scalar field the theory does not admit any other static solution,
which is consistent with the solar system tests of gravity.Comment: 6 pages, a part of the earlier version removed, final version
accepeted by CQ
Ytterbium doped nano-crystalline optical fiber for reduced photodarkening
We report suppression of photodarkening in Yb-doped nano-crystalline fibers in silica host. The photodarkening induced loss reduced by 20 times compared to Yb-doped aluminosilicate fibers. The laser efficiency of the nano-crystalline fiber was 79%
Strong field gravitational lensing in scalar tensor theories
Strong field gravitational lensing in the Brans-Dicke theory has been
studied. The deflection angle for photons passing very close to the photon
sphere is estimated for the static spherically symmetric space-time of the
theory and the position and magnification of the relativistic images are
obtained. Modeling the super massive central object of the galaxy by the
Brans-Dicke space-time, numerical values of different strong lensing observable
are estimated. It is found that against the expectation there is no significant
scalar field effect in the strong field observable lensing parameters. This
observation raises question on the potentiality of the strong field lensing to
discriminate different gravitational theories.Comment: 20 pages, accepted in Class. Quantum Grav., final versio
Effect of Benzothiazole based conjugates in causing apoptosis by Regulating p53, PTEN and MAP Kinase proteins affecting miR-195a and miR-101-1
<p>Abstract</p> <p>Background</p> <p>Hepatocellular carcinoma (HCC) accounts for majority of liver cancers and is the leading cause of cancer related death in Asia. Like any other cancer, HCC develops when there is a mutation to the cellular machinery that causes the cell to replicate at a higher rate and results in the loss of apoptosis. Therefore, a delicate balance between the expression of various genes involved in proliferation and apoptosis decide the ultimate fate of the cell to undergo rapid proliferation (cancer) or cell death.</p> <p>Results</p> <p>The benzothiazole based compounds exhibited effective cytotoxicity at 4 ÎĽM concentration and have shown G1 cell cycle arrest with decrease in levels of G1 cell cycle proteins such as cyclin D1 and Skp2. Involvement of tumour suppressor proteins such as PTEN and p53 was studied. Interestingly these compounds displayed decrease in the phosphorylated forms of AKT, p38 MAPK and ERK1/2 which play a vital role in cell proliferation. Compounds have exhibited strong and significant effect on the expression of micro RNAs such as miR-195a & miR-101-1 which regulate hepatic cell proliferation.</p> <p>Conclusions</p> <p>The cell cycle arrest and apoptotic inducing nature of these compounds was revealed by FACS, BrdU cell proliferation and tunel assays. Compounds affected both tumour suppressor proteins as well as proteins that are involved in active cell proliferation. Micro RNAs whose target is Cyclin D1 such as miR-195a and miR-101-1 that is required for growth of hepatoma cells was drastically affected. These compounds caused apoptosis by activating caspase-3 and PARP.</p
Drosophila Argonaute-1 is critical for transcriptional cosuppression and heterochromatin formation
Argonaute-1 (Ago-1) plays a crucial role in gene regulation and genome stability via biogenesis of small non-coding RNAs. Two “Argonaute” family genes, piwi and Ago-2 in Drosophila are involved in multiple silencing mechanisms in the nucleus, transgene cosuppression, long-distant chromosome interaction, nuclear organization and heterochromatin formation. To investigate whether Ago-1 also plays a similar role, we have generated a series of Ago-1 mutations by excising P element, inserted in the Ago-1 promoter (Ago-1k08121). AGO-1 protein is distributed uniformly in the nucleus and cytosol in early embryos but accumulated predominantly in the cytoplasm during the gastrulation stage. Repeat induced silencing produced by the mini-white (mw) array and transcriptional cosuppression of non-homologous transgenes Adh-w/w-Adh was disrupted by Ago-1 mutation. These effects of Ago-1 are distict from its role in microRNA processing because Dicer-1, a critical enzyme for miRNA biogenesis, has no role on the above silencing. Reduction of AGO-1 protein dislodged the POLYCOMB, EZ (enhancer of zeste) and H3me3K27 binding at the cosuppressed Adh-w transgene insertion sites suggesting its role in Polycomb dependent cosuppression. An overall reduction of methylated histone H3me2K9 and H3me3K27 from the polytene nuclei precisely from the mw promoters was also found that leads to concomitant changes in the chromatin structure. These results suggest a prominent role of Ago-1 in chromatin organization and transgene silencing and demonstrate a critical link between transcriptional transgene cosuppression, heterochromatin formation and chromatin organization. We propose Drosophila Ago-1 as a multifunctional RNAi component that interconnects at least two unrelated events, chromatin organization in the nucleus and microRNA processing in the cytoplasm, which may be extended to the other systems
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