1,242 research outputs found
First-Order Melting of a Moving Vortex Lattice: Effects of Disorder
We study the melting of a moving vortex lattice through numerical simulations
with the current driven 3D XY model with disorder. We find that there is a
first-order phase transition even for large disorder when the corresponding
equilibrium transition is continuous. The low temperature phase is an
anisotropic moving glass.Comment: Important changes from original version. Finite size analysis of
results has been added. Figure 2 has been changed. There is a new additional
Figure. To be published in Physical Review Letter
First-Order Vortex Lattice Melting and Magnetization of YBaCuO$_{7-\delta}
We present the first non-mean-field calculation of the magnetization
of YBaCuO both above and below the flux-lattice melting
temperature . The results are in good agreement with experiment as a
function of transverse applied field . The effects of fluctuations in both
order parameter and magnetic induction are included in the
Ginzburg-Landau free energy functional: fluctuates within the
lowest Landau level in each layer, while fluctuates uniformly according to
the appropriate Boltzmann factor. The second derivative is predicted to be negative throughout the vortex liquid state and
positive in the solid state. The discontinuities in entropy and magnetization
at melting are calculated to be per flux line per layer and
~emu~cm at a field of 50 kOe.Comment: 11 pages, 4 PostScript figures in one uuencoded fil
First order phase transition of the vortex lattice in twinned YBa2Cu3O7 single crystals in tilted magnetic fields
We present an exhaustive analysis of transport measurements performed in
twinned YBa2Cu3O7 single crystals which stablishes that the vortex solid-liquid
transition is first order when the magnetic field H is applied at an angle
theta away from the direction of the twin planes. We show that the resistive
transitions are hysteretic and the V-I curves are non-linear, displaying a
characteristic s-shape at the melting line Hm(T), which scales as
epsilon(theta)Hm(T,theta). These features are gradually lost when the critical
point H*(theta) is approached. Above H*(theta) the V-I characteristics show a
linear response in the experimentally accessible V-I window, and the transition
becomes reversible. Finally we show that the first order phase transition takes
place between a highly correlated vortex liquid in the field direction and a
solid state of unknown symmetry. As a consequence, the available data support
the scenario for a vortex-line melting rather than a vortex sublimation as
recently suggested [T.Sasagawa et al. PRL 80, 4297 (1998)].Comment: 10 pages, 8 figures, submitted to PR
The problem of pasteurellosis as an infection common for animals and humans
pasteurellosis, pasteurella, английский язык, пастереллез, человек, сельскохозяйственные животны
Supercooling of the disordered vortex lattice in Bi_2Sr_2CaCu_2O_8+d
Time-resolved local induction measurements near to the vortex lattice
order-disorder transition in optimally doped
BiSrCaCuO single crystals shows that the
high-field, disordered phase can be quenched to fields as low as half the
transition field. Over an important range of fields, the electrodynamical
behavior of the vortex system is governed by the co-existence of the two phases
in the sample. We interpret the results in terms of supercooling of the
high-field phase and the possible first order nature of the order-disorder
transition at the ``second peak''.Comment: 4 pages, 3 figures. Submitted to Nature, July 10th, 1999; Rejected
August 8th for lack of broad interest Submitted to Physical Review Letters
September 10th, 199
Superconducting zero temperature phase transition in two dimensions and in the magnetic field
We derive the Ginzburg-Landau-Wilson theory for the superconducting phase
transition in two dimensions and in the magnetic field. Without disorder the
theory describes a fluctuation induced first-order quantum phase transition
into the Abrikosov lattice. We propose a phenomenological criterion for
determining the transition field and discuss the qualitative effects of
disorder. Comparison with recent experiments on MoGe films is discussed.Comment: 7 pages, 2 figure
Topological Defects in the Random-Field XY Model and the Pinned Vortex Lattice to Vortex Glass Transition in Type-II Superconductors
As a simplified model of randomly pinned vortex lattices or charge-density
waves, we study the random-field XY model on square () and simple cubic
() lattices. We verify in Monte Carlo simulations, that the average
spacing between topological defects (vortices) diverges more strongly than the
Imry-Ma pinning length as the random field strength, , is reduced. We
suggest that for the simulation data are consistent with a topological
phase transition at a nonzero critical field, , to a pinned phase that is
defect-free at large length-scales. We also discuss the connection between the
possible existence of this phase transition in the random-field XY model and
the magnetic field driven transition from pinned vortex lattice to vortex glass
in weakly disordered type-II superconductors.Comment: LATEX file; 5 Postscript figures are available from [email protected]
The Phase Diagram of Disordered Vortices from London Langevin Simulations
We study the phase diagram of vortex matter in disordered type-II
superconductors. We performed numerical simulations in the London Langevin
approximation, using a new realistic representation of the disorder. At low
magnetic fields we find a disentangled and dislocation free Bragg-glass regime.
Increasing the field introduces disorder-driven entanglement in a discontinuous
manner, leading to a vortex-glass phase, which subsequently melts into the
vortex liquid. The obtained phase boundaries are in quantitative agreement with
the experimental data.Comment: 4 pages, revtex, 8 postscript figures include
Density-functional theory of freezing of vortex-liquid in quasi two-dimensional superconductors
We present a theory of vortex liquid-to-solid transition in homogeneous quasi
2D superconductors. The free energy is written as a functional l of density of
zeroes of the fluctuating order parameter. The transition is weakly first-order
and well below the Hc2(T) line. Transition temperature, discontinuities of the
average Abrikosov ratio and of the average superfluid density, the Debay-Waller
factor and the latent heat are in good agreement with Monte Carlo simulations.
The density is only weakly modulated in the "vortex-solid" phase, consistent
with the density-wave behavior.Comment: 12 pages and 1 figure available upon request, LaTex Version 2.09,
submitted to Phys. Rev. Let
Electrocardiographic changes in patients undergoing targeted temperature management
ObjectivesTargeted temperature management is the recommended therapy for comatose patients after an out‐of‐hospital cardiac arrest resuscitation due to the reduction in neurological damage and improved outcomes. However, there may result in electrocardiographic instability depending on the degree of targeted temperature management, including minor or life‐threatening dysrhythmias or conduction delays. This project aims to describe the frequency of ECG interval changes and clinically relevant dysrhythmias in targeted temperature management patients.MethodsThis is a retrospective observational study from January 2009 to December 2015. Patients who qualified for the study had a non‐traumatic cardiac arrest with a return of spontaneous circulation, received targeted temperature management at 33.5°C for 24 hours followed by 16 hours of rewarming. ECG interval changes and dysrhythmias were recorded immediately after return of spontaneous circulation, and at 24 and 48 hours post return of spontaneous circulation.ResultsA total of 322 patients (age 61.0 ± 16.9 years) had targeted temperature management initiated during the study period, of which 169 had complete data and 13 died prior to completing 24 hours of hypothermia. There were statistically significant changes during targeted temperature management in heart rate (96.7 ± 26.0/min before targeted temperature management; 69.5 ± 19.1/min during, P < 0.001), QRS duration (115.1 ± 32.6 ms before targeted temperature management; 107.8 ± 27.9 ms during targeted temperature management, P < 0.001), and QTc (486.3 ± 52.8 ms before targeted temperature management; 526.9 ± 61.7 ms during targeted temperature management, P < 0.001). There were cardiac dysrhythmias that received treatment during cooling and rewarming.ConclusionDuring the period of targeted temperature management and rewarming, we observed few self‐limiting ECG interval changes and no clinically significant dysrhythmias in this population during the period of targeted temperature management.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156464/2/emp212104_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156464/1/emp212104.pd
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