83 research outputs found
Effect of vibratory stimulation of foot support areas in rats on the functional state of leg muscles and the content of N2A titin isoforms in gravity relief
In this work, we studied the effect of vibratory stimulation of the foot support zones on the functional state of the leg muscles and the content of N2A titin isoforms in rats under simulated microgravity (suspension model). The results of this study showed that vibratory stimulation of the support zones of the rat foot in a gravity discharge may reduce the drop in the amplitude of leg muscle motor response and undesirable reduction of the titin content. © 2014 Pleiades Publishing, Inc
Towards an Explanation of the Mesoscopic Double-Slit Experiment: a new model for charging of a Quantum Dot
For a quantum dot (QD) in the intermediate regime between integrable and
fully chaotic, the widths of single-particle levels naturally differ by orders
of magnitude. In particular, the width of one strongly coupled level may be
larger than the spacing between other, very narrow, levels. In this case many
consecutive Coulomb blockade peaks are due to occupation of the same broad
level. Between the peaks the electron jumps from this level to one of the
narrow levels and the transmission through the dot at the next resonance
essentially repeats that at the previous one. This offers a natural explanation
to the recently observed behavior of the transmission phase in an
interferometer with a QD.Comment: 4 pages, 2 figures, Journal versio
Scattering phases in quantum dots: an analysis based on lattice models
The properties of scattering phases in quantum dots are analyzed with the
help of lattice models. We first derive the expressions relating the different
scattering phases and the dot Green functions. We analyze in detail the Friedel
sum rule and discuss the deviation of the phase of the transmission amplitude
from the Friedel phase at the zeroes of the transmission. The occurrence of
such zeroes is related to the parity of the isolated dot levels. A statistical
analysis of the isolated dot wave-functions reveals the absence of significant
correlations in the parity for large disorder and the appearance, for weak
disorder, of certain dot states which are strongly coupled to the leads. It is
shown that large differences in the coupling to the leads give rise to an
anomalous charging of the dot levels. A mechanism for the phase lapse observed
experimentally based on this property is discussed and illustrated with model
calculations.Comment: 18 pages, 9 figures. to appear in Physical Review
The Flat Transmission Spectrum of the Super-Earth GJ1214b from Wide Field Camera 3 on the Hubble Space Telescope
Capitalizing on the observational advantage offered by its tiny M dwarf host,
we present HST/WFC3 grism measurements of the transmission spectrum of the
super-Earth exoplanet GJ1214b. These are the first published WFC3 observations
of a transiting exoplanet atmosphere. After correcting for a ramp-like
instrumental systematic, we achieve nearly photon-limited precision in these
observations, finding the transmission spectrum of GJ1214b to be flat between
1.1 and 1.7 microns. Inconsistent with a cloud-free solar composition
atmosphere at 8.2 sigma, the measured achromatic transit depth most likely
implies a large mean molecular weight for GJ1214b's outer envelope. A dense
atmosphere rules out bulk compositions for GJ1214b that explain its large
radius by the presence of a very low density gas layer surrounding the planet.
High-altitude clouds can alternatively explain the flat transmission spectrum,
but they would need to be optically thick up to 10 mbar or consist of particles
with a range of sizes approaching 1 micron in diameter.Comment: 17 pages, 12 figures, accepted for publication in Ap
Quantum characterization of superconducting photon counters
We address the quantum characterization of photon counters based on
transition-edge sensors (TESs) and present the first experimental tomography of
the positive operator-valued measure (POVM) of a TES. We provide the reliable
tomographic reconstruction of the POVM elements up to 11 detected photons and
M=100 incoming photons, demonstrating that it is a linear detector.Comment: 3 figures, NJP (to appear
Effect of vibrostimulation of foot and supporting afferentation on functional state of shin muscles in rats during hindlimb unloading
© 2014, Pleiades Publishing, Inc. The goal of this work was to study the influence of daily 3-hr vibrostimulation of the supporting zones of the foot and 3-hr of usual locomotion on the functional state of the soleus, gastrocnemius, and tibial anterior muscles in rats after 7 and 14 days of hindlimb unloading. After 7 days of unloading the soleus weight decreased, while the weight of gastrocnemius and tibial anterior remained unchanged. After 14 days of hindlimb unloading a weight reduction was observed in all studied muscles. Vibrostimulation of the foot and supporting afferentation prevented the loss of weight in gastrocnemius and tibial anterior during the first week of unloading and reduced the negative effect of hindlimb unloading in 14 days. Our results demonstrate that the amplitude of the M-response after 7 days of hindlimb unloading was decreased predominantly in soleus as compared to gastrocnemius and tibial anterior. By the 14 day we observed restoration of the amplitude of the M-response in gastrocnemius and tibial anterior, and the increased amplitude of the M-response in soleus. Different techniques for foot stimulation in rats during hindlimb unloading demonstrated the positive effect in regard to M-response restoration — the amplitude of the M-response was increased in all studied muscles. Thus, our results demonstrate that foot vibrostimulation or supporting afferentation can completely prevent atrophy caused by hindlimb unloading in gastrocnemius and tibial anterior and decrease atrophy in soleus in rats
Changes in the functional state of spinal-cord cell structures under gravitational unloading
© 2016, Pleiades Publishing, Inc.The functional properties of the spinal-cord structures of experimental rats under a 7-day gravitational unloading were assessed using the method of transcranial magnetic stimulation. Hypogravity was modeled by hanging the animals by their tails in an antiorthostatic position. The gastrocnemius muscle potentials evoked by magnetic stimulation of the efferent structures of the spinal cord were registered. We found that gravitational unloading causes significant changes in motor-potential parameters and the central motor transmission time. We propose that the cause of the revealed transformations is afferent inflow limitation, first of all the motor type, as well as adaptation of the central nervous system to new conditions of motor activity
Effects Metilprednizalonium, Motor of Training and a Combination in Change Parameters of M-Response in the Gastrocnemius Muscle of Rats During Acute and Chronic Period After Experimental Spinal Cord Injury
© 2016, Springer Science+Business Media New York.An increasing number of treatments for spinal cord injury (SCI) out of the laboratories and in clinical trials pass. Many of them are used as soon as possible after the injury with the hope of weakening the secondary damage and maximize the preservation of nerve tissue. The aim of the study was to evaluate the effects metilprednizalonium and motor training at an experimental spinal cord injury in rats. To investigate the status of the peripheral neuromuscular system registered motor response (M-response) muscles. In the early period after spinal cord injury was observed, a decrease of the maximum amplitude of M-response. With that, in the group of animals with the introduction of metilprednizalonium, amplitude of M-response was higher than that without drug therapy. Combined therapy metilprednizalonium and motor training has a positive effect on the recovery of motor function in chronic period after contusion spinal cord injury in rats
Transmission phase lapses in quantum dots: the role of dot-lead coupling asymmetry
Lapses of transmission phase in transport through quantum dots are ubiquitous
already in the absence of interaction, in which case their precise location is
determined by the signs and magnitudes of the tunnelling matrix elements.
However, actual measurements for a quantum dot embedded in an Aharonov-Bohm
interferometer show systematic sequences of phase lapses separated by Coulomb
peaks -- an issue that attracted much attention and generated controversy.
Using a two-level quantum dot as an example we show that this phenomenon can be
accounted for by the combined effect of asymmetric dot-lead couplings (left
lead/right lead asymmetry as well as different level broadening for different
levels) and interaction-induced "population switching" of the levels, rendering
this behaviour generic. We construct and analyse a mean field scheme for an
interacting quantum dot, and investigate the properties of the mean field
solution, paying special attention to the character of its dependence
(continuous vs. discontinuous) on the chemical potential or gate voltage.Comment: 34 LaTeX pages in IOP format, 9 figures; misprints correcte
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