42,663 research outputs found
Proposed New Test of Spin Effects in General Relativity
The recent discovery of a double-pulsar PSR J0737-3039A/B provides an
opportunity of unequivocally observing, for the first time, spin effects in
general relativity. Existing efforts involve detection of the precession of the
spinning body itself. However, for a close binary system, spin effects on the
orbit may also be discernable. Not only do they add to the advance of the
periastron (by an amount which is small compared to the conventional
contribution) but they also give rise to a precession of the orbit about the
spin direction. The measurement of such an effect would also give information
on the moment of inertia of pulsars
Non-perturbative approach for the time-dependent symmetry breaking
We present a variational method which uses a quartic exponential function as
a trial wave-function to describe time-dependent quantum mechanical systems. We
introduce a new physical variable which is appropriate to describe the
shape of wave-packet, and calculate the effective action as a function of both
the dispersion and . The effective potential
successfully describes the transition of the system from the false vacuum to
the true vacuum. The present method well describes the long time evolution of
the wave-function of the system after the symmetry breaking, which is shown in
comparison with the direct numerical computations of wave-function.Comment: 8 pages, 3 figure
Quantum field and uniformly accelerated oscillator
We present an exact treatment of the influences on a quantum scalar field in
its Minkowski vacuum state induced by coupling of the field to a uniformly
accelerated harmonic oscillator. We show that there are no radiation from the
oscillator in the point of view of a uniformly accelerating observer. On the
other hand, there are radiations in the point of view of an inertial observer.
It is shown that Einstein-Podolsky-Rosen (EPR) like correlations of Rindler
particles in Minkowski vacuum states are modified by a phase factor in front of
the momentum-symmetric Rindler operators. The exact quantization of a
time-dependent oscillator coupled to a massless scalar field was given.Comment: 28 pages, LaTe
Ending Neglect of older people in the response to Humanitarian Emergencies
Older people make up a significant and growing number of those affected by humanitarian crises, yet they are often not sought out or prioritised within the humanitarian response. Humanitarian agencies, donors, and international bodies neglect older people's health and nutrition. The gaps in knowledge and research about the needs of older people in emergencies are considerable. Older people are not monitored in emergencies and they are not prioritised despite evidence of disproportionate mortality and morbidity in this group. We call for policy changes by humanitarian agencies and donors to ensure that the needs of this vulnerable group are met
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Overexpression of MMPs in Corneas Requiring Penetrating and Deep Anterior Lamellar Keratoplasty.
PurposeMatrix metalloproteinases (MMPs) comprise a family of zinc-dependent endopeptidases involved in wound healing processes, including neovascularization and fibrosis. We assessed MMP protein expression levels in diseased corneas of patients requiring penetrating and deep anterior lamellar keratoplasty. The purpose of this study was to test the hypothesis that upregulation of MMPs in diseased corneas is positively associated with clinical levels of corneal neovascularization and fibrosis.MethodsProtein expression levels of nine individual MMPs were quantified simultaneously in human corneal lysates by using the Bio-Plex Pro Human MMP 9-Plex Panel and the MAGPIX technology. Measurements of MMP1, MMP2, MMP3, MMP7, MMP8, MMP9, MMP10, MMP12, and MMP13 were performed on diseased specimens from 21 patients undergoing corneal transplantation (17 for penetrating keratoplasty and 4 for deep anterior lamellar keratoplasty) and 6 normal control corneas.ResultsLuminex-based expression analysis revealed a significant overexpression of four of the nine MMPs tested (MMP2, MMP8, MMP12, and MMP13) in patient samples compared to control. Significant overexpression of MMP1, MMP2, MMP8, MMP12, and MMP13 was observed in diseased corneas with neovascularization compared with diseased corneas without neovascularization. Overexpression of MMP1, MMP2, MMP8, MMP12, and MMP13 also corresponded with the levels of corneal fibrosis. Finally, reduced expression of MMP3 was detected in keratoconus patients.ConclusionsMultiple MMPs are expressed in the corneas of patients with chronic disease requiring keratoplasty even when the pathologic process appears to be clinically inactive. In particular, the expression of several MMPs (MMP2, MMP8, MMP12, and MMP13) is positively associated with increased levels corneal fibrosis and neovascularization
Electrokinetic behavior of two touching inhomogeneous biological cells and colloidal particles: Effects of multipolar interactions
We present a theory to investigate electro-kinetic behavior, namely,
electrorotation and dielectrophoresis under alternating current (AC) applied
fields for a pair of touching inhomogeneous colloidal particles and biological
cells. These inhomogeneous particles are treated as graded ones with physically
motivated model dielectric and conductivity profiles. The mutual polarization
interaction between the particles yields a change in their respective dipole
moments, and hence in the AC electrokinetic spectra. The multipolar
interactions between polarized particles are accurately captured by the
multiple images method. In the point-dipole limit, our theory reproduces the
known results. We find that the multipolar interactions as well as the spatial
fluctuations inside the particles can affect the AC electrokinetic spectra
significantly.Comment: Revised version with minor changes: References added and discussion
extende
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Double layer charging driven carbon dioxide adsorption limits the rate of electrochemical carbon dioxide reduction on Gold.
Electrochemical CO[Formula: see text] reduction is a potential route to the sustainable production of valuable fuels and chemicals. Here, we perform CO[Formula: see text] reduction experiments on Gold at neutral to acidic pH values to elucidate the long-standing controversy surrounding the rate-limiting step. We find the CO production rate to be invariant with pH on a Standard Hydrogen Electrode scale and conclude that it is limited by the CO[Formula: see text] adsorption step. We present a new multi-scale modeling scheme that integrates ab initio reaction kinetics with mass transport simulations, explicitly considering the charged electric double layer. The model reproduces the experimental CO polarization curve and reveals the rate-limiting step to be *COOH to *CO at low overpotentials, CO[Formula: see text] adsorption at intermediate ones, and CO[Formula: see text] mass transport at high overpotentials. Finally, we show the Tafel slope to arise from the electrostatic interaction between the dipole of *CO[Formula: see text] and the interfacial field. This work highlights the importance of surface charging for electrochemical kinetics and mass transport
Gas adsorption/desorption in silica aerogels: a theoretical study of scattering properties
We present a numerical study of the structural correlations associated to gas
adsorption/desorption in silica aerogels in order to provide a theoretical
interpretation of scattering experiments. Following our earlier work, we use a
coarse-grained lattice-gas description and determine the nonequilibrium
behavior of the adsorbed gas within a local mean-field analysis.
We focus on the differences between the adsorption and desorption mechanisms
and their signature in the fluid-fluid and gel-fluid structure factors as a
function of temperature. At low temperature, but still in the regime where the
isotherms are continuous, we find that the adsorbed fluid density, during both
filling and draining, is correlated over distances that may be much larger than
the gel correlation length. In particular, extended fractal correlations may
occur during desorption, indicating the existence of a ramified cluster of
vapor filled cavities. This also induces an important increase of the
scattering intensity at small wave vectors. The similarity and differences with
the scattering of fluids in other porous solids such as Vycor are discussed.Comment: 16 pages, 15 figure
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