96 research outputs found
Analytic study of properties of holographic p-wave superconductors
In this paper, we analytically investigate the properties of p-wave
holographic superconductors in -Schwarzschild background by two
approaches, one based on the Sturm-Liouville eigenvalue problem and the other
based on the matching of the solutions to the field equations near the horizon
and near the asymptotic region. The relation between the critical
temperature and the charge density has been obtained and the dependence of the
expectation value of the condensation operator on the temperature has been
found. Our results are in very good agreement with the existing numerical
results. The critical exponent of the condensation also comes out to be 1/2
which is the universal value in the mean field theory.Comment: Latex, To appear in JHE
Analytic study of Gauss-Bonnet holographic superconductors in Born-Infeld electrodynamics
Using Sturm-Liouville (SL) eigenvalue problem, we investigate several
properties of holographic s-wave superconductors in Gauss-Bonnet gravity with
Born-Infeld electrodynamics in the probe limit. Our analytic scheme has been
found to be in good agreement with the numerical results. From our analysis it
is quite evident that the scalar hair formation at low temperatures is indeed
affected by both the Gauss-Bonnet as well as the Born-Infeld coupling
parameters. We also compute the critical exponent associated with the
condensation near the critical temperature. The value of the critical exponent
thus obtained indeed suggests a universal mean field behavior.Comment: 9 pages, Latex, minor modifications, To appear in JHE
Back reaction, covariant anomaly and effective action
In the presence of back reaction, we first produce the one-loop corrections
for the event horizon and Hawking temperature of the Reissner-Nordstr\"om black
hole. Then, based on the covariant anomaly cancelation method and the effective
action technique, the modified expressions for the fluxes of gauge current and
energy momentum tensor, due to the effect of back reaction, are obtained. The
results are consistent with the Hawking fluxes of a (1+1)-dimensional blackbody
at the temperature with quantum corrections, thus confirming the robustness of
the covariant anomaly cancelation method and the effective action technique for
black holes with back reaction.Comment: 17 page
Analytical study on holographic superconductors with backreactions
We employ the variational method for the Sturm-Liouville eigenvalue problem
to analytically investigate the properties of the holographic superconductors.
We find that the analytic method is still powerful when the backreaction is
turned on. Reducing step size in the iterative procedure, we observe that the
consistency of results between the analytic and numerical computations can be
further improved. The obtained analytic result can be used to back up the
numerical computations in the holographic superconductor in the fully
backreacted spacetime.Comment: 10 pages, accepted by JHE
Analytic study of properties of holographic superconductors in Born-Infeld electrodynamics
In this paper, based on the Sturm-Liouville eigenvalue problem, we
analytically investigate several properties of holographic s-wave
superconductors in the background of a Schwarzschild-AdS spacetime in the
framework of Born-Infeld electrodynamics. Based on a perturbative approach, we
explicitly find the relation between the critical temperature and the charge
density and also the fact that the Born-Infeld coupling parameter indeed
affects the formation of scalar hair at low temperatures. Higher value of the
Born-Infeld parameter results in a harder condensation to form. We further
compute the critical exponent associated with the condensation near the
critical temperature. The analytical results obtained are found to be in good
agreement with the existing numerical results.Comment: 12 pages, LateX, To appear in JHE
Inter-Cellular Variation in DNA Content of Entamoeba histolytica Originates from Temporal and Spatial Uncoupling of Cytokinesis from the Nuclear Cycle
Accumulation of multiple copies of the genome in a single nucleus and several nuclei in a single cell has previously been noted in Entamoeba histolytica, contributing to the genetic heterogeneity of this unicellular eukaryote. In this study, we demonstrate that this genetic heterogeneity is an inherent feature of the cell cycle of this organism. Chromosome segregation occurs on a variety of novel microtubular assemblies including multi-polar spindles. Cytokinesis in E. histolytica is completed by the mechanical severing of a thin cytoplasmic bridge, either independently or with the help of neighboring cells. Importantly, cytokinesis is uncoupled from the nuclear division cycle, both temporally and spatially, leading to the formation of unequal daughter cells. Sorting of euploid and polyploid cells showed that each of these sub-populations acquired heterogeneous DNA content upon further growth. Our study conclusively demonstrates that genetic heterogeneity originates from the unique mode of cell division events in this protist
Entamoeba Shows Reversible Variation in Ploidy under Different Growth Conditions and between Life Cycle Phases
Under axenic growth conditions, trophozoites of Entamoeba histolytica contain heterogenous amounts of DNA due to the presence of both multiple nuclei and different amounts of DNA in individual nuclei. In order to establish if the DNA content and the observed heterogeneity is maintained during different growth conditions, we have compared E. histolytica cells growing in xenic and axenic cultures. Our results show that the nuclear DNA content of E. histolytica trophozoites growing in axenic cultures is at least 10 fold higher than in xenic cultures. Re-association of axenic cultures with their bacterial flora led to a reduction of DNA content to the original xenic values. Thus switching between xenic and axenic growth conditions was accompanied by significant changes in the nuclear DNA content of this parasite. Changes in DNA content during encystation-excystation were studied in the related reptilian parasite E. invadens. During excystation of E. invadens cysts, it was observed that the nuclear DNA content increased approximately 40 fold following emergence of trophozoites in axenic cultures. Based on the observed large changes in nuclear size and DNA content, and the minor differences in relative abundance of representative protein coding sequences, rDNA and tRNA sequences, it appears that gain or loss of whole genome copies may be occurring during changes in the growth conditions. Our studies demonstrate the inherent plasticity and dynamic nature of the Entamoeba genome in at least two species
Vascular Smooth Muscle Cell Stiffness and Adhesion to Collagen I Modified by Vasoactive Agonists
In vascular smooth muscle cells (VSMCs) integrin-mediated adhesion to extracellular
matrix (ECM) proteins play important roles in sustaining vascular tone and resistance.
The main goal of this study was to determine whether VSMCs adhesion to type I collagen
(COL-I) was altered in parallel with the changes in the VSMCs contractile state induced by
vasoconstrictors and vasodilators. VSMCs were isolated from rat cremaster skeletal muscle
arterioles and maintained in primary culture without passage. Cell adhesion and cell E-modulus
were assessed using atomic force microscopy (AFM) by repetitive nano-indentation of
the AFM probe on the cell surface at 0.1 Hz sampling frequency and 3200 nm Z-piezo travelling
distance (approach and retraction). AFM probes were tipped with a 5 μm diameter
microbead functionalized with COL-I (1mg\ml). Results showed that the vasoconstrictor angiotensin
II (ANG-II; 10−6
) significantly increased (p<0.05) VSMC E-modulus and adhesion
probability to COL-I by approximately 35% and 33%, respectively. In contrast, the vasodilator
adenosine (ADO; 10−4
) significantly decreased (p<0.05) VSMC E-modulus and adhesion
probability by approximately −33% and −17%, respectively. Similarly, the NO donor
(PANOate, 10−6 M), a potent vasodilator, also significantly decreased (p<0.05) the VSMC
E-modulus and COL-I adhesion probability by −38% and −35%, respectively. These observations
support the hypothesis that integrin-mediated VSMC adhesion to the ECM protein
COL-I is dynamically regulated in parallel with VSMC contractile activation. These data suggest
that the signal transduction pathways modulating VSMC contractile activation and relaxation,
in addition to ECM adhesion, interact during regulation of contractile state
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