17,824 research outputs found
Role of nuclear lamins in the regulation of SIRT6
Student Oral Presentation Session 1Sirtuins are a family of proteins which have been involved in a multitude of biological functions, especially longevity expansion. SIRT6 is a mammalian sirtuin with emerging functions in a spectrum of cellular events, such as cellular senescence, premature aging, DNA damage response, metabolism, extending lifespan and also tumor suppression. Although SIRT6 has been established to regulate a range of cellular functioning, its upstream regulation has remained elusive till date. Given its crucial roles in so many vital processes, identification of its ...postprin
SIRTain regulators of premature senescence and accelerated aging.
The sirtuin proteins constitute class III histone deacetylases (HDACs). These evolutionarily conserved NAD(+)-dependent enzymes form an important component in a variety of cellular and biological processes with highly divergent as well as convergent roles in maintaining metabolic homeostasis, safeguarding genomic integrity, regulating cancer metabolism and also inflammatory responses. Amongst the seven known mammalian sirtuin proteins, SIRT1 has gained much attention due to its widely acknowledged roles in promoting longevity and ameliorating age-associated pathologies. The contributions of other sirtuins in the field of aging are also gradually emerging. Here, we summarize some of the recent discoveries in sirtuins biology which clearly implicate the functions of sirtuin proteins in the regulation of premature cellular senescence and accelerated aging. The roles of sirtuins in various cellular processes have been extrapolated to draw inter-linkage with anti-aging mechanisms. Also, the latest findings on sirtuins which might have potential effects in the process of aging have been reviewed.published_or_final_versio
Anisotropic elasticity in confocal studies of colloidal crystals
We consider the theory of fluctuations of a colloidal solid observed in a
confocal slice. For a cubic crystal we study the evolution of the projected
elastic properties as a function of the anisotropy of the crystal using
numerical methods based on the fast Fourier transform. In certain situations of
high symmetry we find exact analytic results for the projected fluctuations.Comment: 6 pages, 7 figure
Realistic Anomaly Mediation with Bulk Gauge Fields
We present a simple general framework for realistic models of supersymmetry
breaking driven by anomaly mediation. We consider a 5-dimensional "brane
universe" where the visible and hidden sectors are localized on different
branes, and the standard model gauge bosons propagate in the bulk. In this
framework there can be charged scalar messengers that have contact interactions
with the hidden sector, either localized in the hidden sector or in the bulk.
These scalars obtain soft masses that feed into visible sector scalar masses at
two loop order via bulk gauge interactions. This contribution is automatically
flavor-blind, and can be naturally positive. If the messengers are in the bulk
this contribution is automatically the same order of magnitude as the anomaly
mediated contribution, independent of the brane spacing. If the messengers are
localized to a brane the two effects are of the same order for relatively small
brane spacings. The gaugino masses and A terms are determined completely by
anomaly mediation. In order for anomaly mediation to dominate over radion
mediation the radion must be is stabilized in a manner that preserves
supersymmetry, with supergravity effects included. We show that this occurs in
simple models. We also show that the mu problem can be solved by the vacuum
expectation value of a singlet in this framework.Comment: 16 pages, LaTeX2e, no figure
The Evolution of Black Holes in the Mini-Superspace Approximation of Loop Quantum Gravity
Using the improved quantization technique to the mini-superspace
approximation of loop quantum gravity, we study the evolution of black holes
supported by a cosmological constant. The addition of a cosmological constant
allows for classical solutions with planar, cylindrical, toroidal and higher
genus black holes. Here we study the quantum analog of these space-times. In
all scenarios studied, the singularity present in the classical counter-part is
avoided in the quantized version and is replaced by a bounce, and in the late
evolution, a series of less severe bounces. Interestingly, although there are
differences during the evolution between the various symmetries and topologies,
the evolution on the other side of the bounce asymptotes to space-times of
Nariai-type, with the exception of the planar black hole analyzed here, whose
-=constant subspaces seem to continue expanding in the long term
evolution. For the other cases, Nariai-type universes are attractors in the
quantum evolution, albeit with different parameters. We study here the quantum
evolution of each symmetry in detail.Comment: 26 pages, 7 figures.V2 has typos corrected, references added, and a
more careful analysis of the planar case. Accepted for publication in
Physical Review
Investigation of Prediction Accuracy, Sensitivity, and Parameter Stability of Large-Scale Propagation Path Loss Models for 5G Wireless Communications
This paper compares three candidate large-scale propagation path loss models
for use over the entire microwave and millimeter-wave (mmWave) radio spectrum:
the alpha-beta-gamma (ABG) model, the close-in (CI) free space reference
distance model, and the CI model with a frequency-weighted path loss exponent
(CIF). Each of these models have been recently studied for use in standards
bodies such as 3GPP, and for use in the design of fifth generation (5G)
wireless systems in urban macrocell, urban microcell, and indoor office and
shopping mall scenarios. Here we compare the accuracy and sensitivity of these
models using measured data from 30 propagation measurement datasets from 2 GHz
to 73 GHz over distances ranging from 4 m to 1238 m. A series of sensitivity
analyses of the three models show that the physically-based two-parameter CI
model and three-parameter CIF model offer computational simplicity, have very
similar goodness of fit (i.e., the shadow fading standard deviation), exhibit
more stable model parameter behavior across frequencies and distances, and
yield smaller prediction error in sensitivity testing across distances and
frequencies, when compared to the four-parameter ABG model. Results show the CI
model with a 1 m close-in reference distance is suitable for outdoor
environments, while the CIF model is more appropriate for indoor modeling. The
CI and CIF models are easily implemented in existing 3GPP models by making a
very subtle modification -- by replacing a floating non-physically based
constant with a frequency-dependent constant that represents free space path
loss in the first meter of propagation.Comment: Open access available at:
http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=743465
Heisenberg antiferromagnet on Cayley trees: low-energy spectrum and even/odd site imbalance
To understand the role of local sublattice imbalance in low-energy spectra of
s=1/2 quantum antiferromagnets, we study the s=1/2 quantum nearest neighbor
Heisenberg antiferromagnet on the coordination 3 Cayley tree. We perform
many-body calculations using an implementation of the density matrix
renormalization group (DMRG) technique for generic tree graphs. We discover
that the bond-centered Cayley tree has a quasidegenerate set of a low-lying
tower of states and an "anomalous" singlet-triplet finite-size gap scaling. For
understanding the construction of the first excited state from the many-body
ground state, we consider a wave function ansatz given by the single-mode
approximation, which yields a high overlap with the DMRG wave function.
Observing the ground-state entanglement spectrum leads us to a picture of the
low-energy degrees of freedom being "giant spins" arising out of sublattice
imbalance, which helps us analytically understand the scaling of the
finite-size spin gap. The Schwinger-boson mean-field theory has been
generalized to nonuniform lattices, and ground states have been found which are
spatially inhomogeneous in the mean-field parameters.Comment: 19 pages, 12 figures, 6 tables. Changes made to manuscript after
referee suggestions: parts reorganized, clarified discussion on Fibonacci
tree, typos correcte
Study of parameter degeneracy and hierarchy sensitivity of NO ν A in presence of sterile neutrino
The first hint of the neutrino mass hierarchy is believed to come from the long-baseline experiment NOνA. Recent results from NOνA shows a mild preference towards the CP phase δ13 ¼ −90° and normal hierarchy. Fortunately this is the favorable area of the parameter space which does not suffer from the hierarchy-δ13 degeneracy and thus NOνA can have good hierarchy sensitivity for this true combination of hierarchy and δ13. Apart from the hierarchy-δ13 degeneracy there is also the octant-δ13 degeneracy. But this does not affect the favorable parameter space of NOνA as this degeneracy can be resolved with a balanced neutrino and antineutrino run. However, if we consider the existence of a light sterile neutrino then there may be additional degeneracies which can spoil the hierarchy sensitivity of NOνA even in the favorable parameter space. In the present work we find that apart from the degeneracies mentioned above, there are additional hierarchy and octant degeneracies that appear with the new phase δ14 in the presence of a light sterile neutrino in the eV scale. In contrast to the hierarchy and octant degeneracies appearing with δ13, the parameter space for hierarchy-δ14 degeneracy is different in neutrinos and antineutrinos though the octant- δ14 degeneracy behaves similarly in neutrinos and antineutrinos. We study the effect of these degeneracies on the hierarchy sensitivity of NOνA for the true normal hierarchy.Monojit Ghosh, Shivani Gupta, Zachary M. Matthews, Pankaj Sharma, and Anthony G. William
Solving relativistic hydrodynamic equation in presence of magnetic field for phase transition in a neutron star
Hadronic to quark matter phase transition may occur inside neutron stars (NS)
having central densities of the order of 3-10 times normal nuclear matter
saturation density (). The transition is expected to be a two-step
process; transition from hadronic to 2-flavour matter and two-flavour to
equilibrated charge neutral three-flavour matter. In this paper we
concentrate on the first step process and solve the relativistic hydrodynamic
equations for the conversion front in presence of high magnetic field. Lorentz
force due to magnetic field is included in the energy momentum tensor by
averaging over the polar angles. We find that for an initial dipole
configuration of the magnetic field with a sufficiently high value at the
surface, velocity of the front increases considerably.Comment: 16 pages, 4 figures, same as published version of JPG, J. Phys. G:
Nucl. Part. Phys. 39 (2012) 09520
Sub-Dominant Pairing Channels in Unconventional Superconductors: Ginzburg-Landau Theory
A Ginzburg-Landau theory is developed for unconventional superconductors with
the three relevant singlet pairing channels. Various consequences of the
sub-dominant channels (i.e., s- and d_{xy}-channels) are examined in detail.
(1) In the case of a d_{x^2-y^2}+is-wave superconductor, The structure of a
single vortex above and below T_{DS} is four-fold and two-fold symmetric,
respectively. (2) In the case of a d_{x^2-y^2}+id_{xy}-wave superconductor,
there is also a second order zero-field phase transition from the pure
d_{x^2-y^2}-phase to the Time-reversal-symmetry-breaking
d_{x^2-y^2}+id_{xy}-wave phase at the temperature T_{DD'}. But the subdominant
phase can (not) be induced by vortices above T_{DD'}. Below the time-reversal-
symmetry-breaking transition, the sub-dominant phase in the mixed state is
nontrivial: it survives at low fields, but may disappear above a field
(increasing with decreasing temperature) presumably via a first-order
transition. (3)By including the strong coupling effects, a
time-reversal-symmetry -breaking coupling term between the d_{x^2-y^2}- and
d_{xy}-waves is found to have significant effects on the low temperature
behavior of d_{x^2-y^2}+id_{xy} superconductors. In a magnetic field, a
d_{x^2-y^2}+id_{xy} state is always established, but the field-dependence of
d_{xy}-amplitude above T_{DD'} is different from that below T_{DD'}. Above but
not very close to T_{DD'}, the induced minimum gap Delta_0 proportional to
B/(T-T_{DD'}).Comment: updated, 7 two-column pages with one embedded figure, one formula
corrected, to appear in Phys. Rev. B 6
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