531 research outputs found
Giant Octupole Resonance Simulation
Using a pseudo-particle technique we simulate large-amplitude isoscalar giant
octupole excitations in a finite nuclear system. Dependent on the initial
conditions we observe either clear octupole modes or over-damped octupole modes
which decay immediately into quadrupole ones. This shows clearly a behavior
beyond linear response. We propose that octupole modes might be observed in
central collisions of heavy ions
The burden of proof: the current state of atrial fibrillation prevention and treatment trials
Atrial fibrillation (AF) is an age-related arrhythmia of enormous socioeconomic significance. In recent years, our understanding of the basic mechanisms that initiate and perpetuate AF has evolved rapidly, catheter ablation of AF has progressed from concept to reality, and recent studies suggest lifestyle modification may help prevent AF recurrence. Emerging developments in genetics, imaging, and informatics also present new opportunities for personalized care. However, considerable challenges remain. These include a paucity of studies examining AF prevention, modest efficacy of existing antiarrhythmic therapies, diverse ablation technologies and practice, and limited evidence to guide management of high-risk patients with multiple comorbidities. Studies examining the long-term effects of AF catheter ablation on morbidity and mortality outcomes are not yet completed. In many ways, further progress in the field is heavily contingent on the feasibility, capacity, and efficiency of clinical trials to incorporate the rapidly evolving knowledge base and to provide substantive evidence for novel AF therapeutic strategies. This review outlines the current state of AF prevention and treatment trials, including the foreseeable challenges, as discussed by a unique forum of clinical trialists, scientists, and regulatory representatives in a session endorsed by the Heart Rhythm Society at the 12th Global CardioVascular Clinical Trialists Forum in Washington, DC, December 3â5, 2015
Survival in equilibrium step fluctuations
We report the results of analytic and numerical investigations of the time
scale of survival or non-zero-crossing probability in equilibrium step
fluctuations described by Langevin equations appropriate for
attachment/detachment and edge-diffusion limited kinetics. An exact relation
between long-time behaviors of the survival probability and the autocorrelation
function is established and numerically verified. is shown to exhibit
simple scaling behavior as a function of system size and sampling time. Our
theoretical results are in agreement with those obtained from an analysis of
experimental dynamical STM data on step fluctuations on Al/Si(111) and Ag(111)
surfaces.Comment: RevTeX, 4 pages, 3 figure
Liquid-Drop Model and Quantum Resistance Against Noncompact Nuclear Geometries
The importance of quantum effects for exotic nuclear shapes is demonstrated.
Based on the example of a sheet of nuclear matter of infinite lateral
dimensions but finite thickness, it is shown that the quantization of states in
momentum space, resulting from the confinement of the nucleonic motion in the
conjugate geometrical space, generates a strong resistance against such a
confinement and generates restoring forces driving the system towards compact
geometries. In the liquid-drop model, these quantum effects are implicitly
included in the surface energy term, via a choice of interaction parameters, an
approximation that has been found valid for compact shapes, but has not yet
been scrutinized for exotic shapes.Comment: 9 pages with 3 figure
Scaling and Crossover in the Large-N Model for Growth Kinetics
The dependence of the scaling properties of the structure factor on space
dimensionality, range of interaction, initial and final conditions, presence or
absence of a conservation law is analysed in the framework of the large-N model
for growth kinetics. The variety of asymptotic behaviours is quite rich,
including standard scaling, multiscaling and a mixture of the two. The
different scaling properties obtained as the parameters are varied are
controlled by a structure of fixed points with their domains of attraction.
Crossovers arising from the competition between distinct fixed points are
explicitely obtained. Temperature fluctuations below the critical temperature
are not found to be irrelevant when the order parameter is conserved. The model
is solved by integration of the equation of motion for the structure factor and
by a renormalization group approach.Comment: 48 pages with 6 figures available upon request, plain LaTe
Formation of superdense hadronic matter in high energy heavy-ion collisions
We present the detail of a newly developed relativistic transport model (ART
1.0) for high energy heavy-ion collisions. Using this model, we first study the
general collision dynamics between heavy ions at the AGS energies. We then show
that in central collisions there exists a large volume of sufficiently
long-lived superdense hadronic matter whose local baryon and energy densities
exceed the critical densities for the hadronic matter to quark-gluon plasma
transition. The size and lifetime of this matter are found to depend strongly
on the equation of state. We also investigate the degree and time scale of
thermalization as well as the radial flow during the expansion of the
superdense hadronic matter. The flow velocity profile and the temperature of
the hadronic matter at freeze-out are extracted. The transverse momentum and
rapidity distributions of protons, pions and kaons calculated with and without
the mean field are compared with each other and also with the preliminary data
from the E866/E802 collaboration to search for experimental observables that
are sensitive to the equation of state. It is found that these inclusive,
single particle observables depend weakly on the equation of state. The
difference between results obtained with and without the nuclear mean field is
only about 20\%. The baryon transverse collective flow in the reaction plane is
also analyzed. It is shown that both the flow parameter and the strength of the
``bounce-off'' effect are very sensitive to the equation of state. In
particular, a soft equation of state with a compressibility of 200 MeV results
in an increase of the flow parameter by a factor of 2.5 compared to the cascade
case without the mean field. This large effect makes it possible to distinguish
the predictions from different theoretical models and to detect the signaturesComment: 55 pages, latex, + 39 figures available upon reques
Dynamical Scaling: the Two-Dimensional XY Model Following a Quench
To sensitively test scaling in the 2D XY model quenched from
high-temperatures into the ordered phase, we study the difference between
measured correlations and the (scaling) results of a Gaussian-closure
approximation. We also directly compare various length-scales. All of our
results are consistent with dynamical scaling and an asymptotic growth law , though with a time-scale that depends on the
length-scale in question. We then reconstruct correlations from the
minimal-energy configuration consistent with the vortex positions, and find
them significantly different from the ``natural'' correlations --- though both
scale with . This indicates that both topological (vortex) and
non-topological (``spin-wave'') contributions to correlations are relevant
arbitrarily late after the quench. We also present a consistent definition of
dynamical scaling applicable more generally, and emphasize how to generalize
our approach to other quenched systems where dynamical scaling is in question.
Our approach directly applies to planar liquid-crystal systems.Comment: 10 pages, 10 figure
An analysis of the FIR/RADIO Continuum Correlation in the Small Magellanic Cloud
The local correlation between far-infrared (FIR) emission and radio-continuum
(RC) emission for the Small Magellanic Cloud (SMC) is investigated over scales
from 3 kpc to 0.01 kpc. Here, we report good FIR/RC correlation down to ~15 pc.
The reciprocal slope of the FIR/RC emission correlation (RC/FIR) in the SMC is
shown to be greatest in the most active star forming regions with a power law
slope of ~1.14 indicating that the RC emission increases faster than the FIR
emission. The slope of the other regions and the SMC are much flatter and in
the range of 0.63-0.85. The slopes tend to follow the thermal fractions of the
regions which range from 0.5 to 0.95. The thermal fraction of the RC emission
alone can provide the expected FIR/RC correlation. The results are consistent
with a common source for ultraviolet (UV) photons heating dust and Cosmic Ray
electrons (CRe-s) diffusing away from the star forming regions. Since the CRe-s
appear to escape the SMC so readily, the results here may not provide support
for coupling between the local gas density and the magnetic field intensity.Comment: 19 pages, 7 Figure
Inferring the intermediate-mass black hole number density from gravitational-wave lensing statistics
The population properties of intermediate-mass black holes remain largely unknown, and understanding their distribution could provide a missing link in the formation of supermassive black holes and galaxies. Gravitational-wave observations can help fill in the gap from stellar mass black holes to supermassive black holes with masses between âŒ100â104 Mâ. In our work, we propose a new method for examining lens populations through lensing statistics of gravitational waves, here focusing on inferring the number density of intermediate-mass black holes through hierarchical Bayesian inference. Simulating âŒ200 lensed gravitational-wave signals, we find that existing gravitational-wave observatories at their design sensitivity could either constrain the number density of 106 Mpcâ3 within a factor of 10, or place an upper bound of âČ104 Mpcâ3 if the true number density is 103 Mpcâ3. More broadly, our method leaves room for incorporation of additional lens populations, providing a general framework for probing the population properties of lenses in the universe
The effect of finite-range interactions in classical transport theory
The effect of scattering with non-zero impact parameters between consituents
in relativistic heavy ion collisions is investigated. In solving the
relativistic Boltzmann equation, the characteristic range of the collision
kernel is varied from approximately one fm to zero while leaving the mean-free
path unchanged. Modifying this range is shown to significantly affect spectra
and flow observables. The finite range is shown to provide effective
viscosities, shear, bulk viscosity and heat conductivity, with the viscous
coefficients being proportional to the square of the interaction range
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