4,059 research outputs found
Confined bulk states as a long-range sensor for impurities and a transfer channel for quantum information
We show that confinement of bulk electrons can be observed at low-dimensional
surface structures and can serve as a long-range sensor for the magnetism and
electronic properties of single impurities or as a quantum information transfer
channel with large coherence lengths. Our ab initio calculations reveal
oscillations of electron density in magnetic chains on metallic surfaces and
help to unambiguously identify the electrons involved as bulk electrons. We
furthermore discuss the possibility of utilizing bulk state confinement to
transfer quantum information, encoded in an atom's species or spin, across
distances of several nanometers with high efficiency.Comment: 5 pages, 2 figure
Beyond the random phase approximation: Stimulated Brillouin backscatter for finite laser coherence times
We develop a statistical theory of stimulated Brillouin backscatter (BSBS) of
a spatially and temporally partially incoherent laser beam for laser fusion
relevant plasma. We find a new collective regime of BSBS (CBSBS) with intensity
threshold controlled by diffraction, an insensitive function of the laser
coherence time, , once light travel time during exceeds a laser
speckle length. The BSBS spatial gain rate is approximately the sum of that due
to CBSBS, and a part which is independent of diffraction and varies linearly
with . We find that the bandwidth of KrF-laser-based fusion systems would
be large enough to allow additional suppression of BSBS.Comment: 8 pages, 5 figures. arXiv admin note: substantial text overlap with
arXiv:1105.209
Transient electrophoretic current in a nonpolar solvent
The transient electric current of surfactants dissolved in a nonpolar solvent
is investigated both experimentally and theoretically in the parallel-plate
geometry. Due to a low concentration of free charges the cell can be completely
polarized by an external voltage of several volts. In this state, all the
charged micelles are compacted against the electrodes. After the voltage is set
to zero the reverse current features a sharp discharge spike and a broad peak.
This shape and its variation with the compacting voltage are reproduced in a
one-dimensional drift-diffusion model. The model reveals the broad peak is
formed by a competition between an increasing number of charges drifting back
to the middle of the cell and a decreasing electric field that drives the
motion. After complete polarization is achieved, the shape of the peak stops
evolving with further increase of the compacting voltage. The spike-peak
separation time grows logarithmically with the charge content in the bulk. The
time peak is a useful measure of the micelle mobility. Time integration of the
peak yields the total charge in the system. By measuring its variation with
temperature, the activation energy of bulk charge generation has been found to
be 0.126 eV.Comment: 7 pages, 5 figure
On the convergence of the gradient expansion in hydrodynamics
Hydrodynamic excitations corresponding to sound and shear modes in fluids are
characterised by gapless dispersion relations. In the hydrodynamic gradient
expansion, their frequencies are represented by power series in spatial
momenta. We investigate the analytic structure and convergence properties of
the hydrodynamic series by studying the associated spectral curve in the space
of complexified frequency and complexified spatial momentum. For the strongly
coupled supersymmetric Yang-Mills plasma, we use the holographic
duality methods to demonstrate that the derivative expansions have finite
non-zero radii of convergence. Obstruction to the convergence of hydrodynamic
series arises from level-crossings in the quasinormal spectrum at complex
momenta.Comment: V3: 5 pages, 2 figures. Final version. Published in Physical Review
Letters with the title "Convergence of the Gradient Expansion in
Hydrodynamics
The complex life of hydrodynamic modes
We study analytic properties of the dispersion relations in classical
hydrodynamics by treating them as Puiseux series in complex momentum. The radii
of convergence of the series are determined by the critical points of the
associated complex spectral curves. For theories that admit a dual
gravitational description through holography, the critical points correspond to
level-crossings in the quasinormal spectrum of the dual black hole. We
illustrate these methods in supersymmetric Yang-Mills theory in
3+1 dimensions, in a holographic model with broken translation symmetry in 2+1
dimensions, and in conformal field theory in 1+1 dimensions. We comment on the
pole-skipping phenomenon in thermal correlation functions, and show that it is
not specific to energy density correlations.Comment: V3: 54 pages, 18 figures. Appendix added. Version to appear in JHE
Types of Angiopathy in Experimental Autoimmune Disease in Rats
The purpose and objectives of this work were to study the nature of the heart, lungs and kidneys angiopathy in rats with a model of systemic autoimmune disease, carrying out comparisons of the results with extravasal morphological manifestations of the pathological process, the state of vascular endothelial function and activity of pro-inflammatory cytokines in the blood. The experiment was conducted on 40 non-linear rats. To simulate the disease animals were injected by complete Freund's adjuvant, a solution of splenic deoxyribonucleic acid cattle, mercaptopurine, methyluracilum and with food rats constantly received sulfate cadmium, lithium hydroxybutyrate and ammonium molybdate. Within two months from the start of the study animals were taken out of the experiment on the background of intraperitoneal nembutal anesthesia. Histological sections of the heart, lung and kidney tissue were stained with hematoxylin -eosin, alcian blue and by van-Gieson, becoming the PAS-reaction. In the animals with the proposed experimental model of systemic autoimmune disease observed morphological characteristics of lesions of the heart blood vessels, lungs and kidneys, the nature of the manifestations of which were interconnected with each other, which confirms the common pathogenetic angiopathy constructions at various diseases in clinical practice. In the genesis of cardiac, pulmonary and renal vessels lesions act the activation of pro-inflammatory cytokines and violation of vascular endothelial function, which has a certain practical significance. In clinical practice, not only purely systemic vasculitis, and other autoimmune diseases should be treated as angiopathy
Implementation of Innovative Technology for Evaluating High-speed Rail Passenger Transportation
The size and content of consumer value (CV) of the service for the transportation of passengers by the railways ofUkrainein long-distance communication by nighttime and daytime trains is determined. A comparison is made of the results of two approaches to researching the attitude of customers to the service – traditional (point-based) and new, taking into account the specific requirements of the total management of the customer value of the service. The directions of the managerial impact of CV on the passenger transportation in long-distance communication by the railways ofUkrainebased on the attitude of customers to the disadvantages and advantages of this service are determined.In three focus groups, discussions were held about travel by Ukrainian railways by daytime and nighttime trains. Based on the results, a list of the disadvantages and advantages that form the consumer value of such a transport service is formed. The list of 19 positive and negative statements reflected all stages of the trip by rail. Behind it, the Likert scale and the corresponding form for conducting an interview were developed. The number of respondents is 823. The sample is random.The results of the polls confidently prove that the prejudiced attitude of passengers towards daytime transportation has been overcome. The ratio of passengers of the railways ofUkrainein daytime transportation in long-distance traffic is better than in nighttime.Only one fifth of those traveling daytime and nighttime are fully satisfied with the level of advantages and disadvantages, which is not enough for most customers to make repeat purchases. However, such a hypothesis needs to be verified in future studies.The feeling of satisfaction among passengers of daytime trains with a positive value of consumer value does not arise in 29 %, which is a threat to the railway operator company. Women are generally worse off on transportation services than men.Personal experience using the train in general does not affect the attitude. However, the experience of using a nighttime train significantly reduces the consumer value of the transport service.The main conclusion is that when several customer segments are served simultaneously in a common space, the total management of the customer value of the service and the corresponding research methods are productive
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