13,729 research outputs found
Meromorphy and topology of localized solutions in the Thomas–MHD model
The one-dimensional MHD system first introduced by J.H. Thomas [Phys. Fluids 11, 1245 (1968)] as a model of the dynamo effect is thoroughly studied in the limit of large magnetic Prandtl number. The focus is on two types of localized solutions involving shocks (antishocks) and hollow (bump) waves. Numerical simulations suggest phenomenological rules concerning their generation, stability and basin of attraction. Their topology, amplitude and thickness are compared favourably with those of the meromorphic travelling waves, which are obtained exactly, and respectively those of asymptotic descriptions involving rational or degenerate elliptic functions. The meromorphy bars the existence of certain configurations, while others are explained by assuming imaginary residues. These explanations are tested using the numerical amplitude and phase of the Fourier transforms as probes of the analyticity properties. Theoretically, the proof of the partial integrability backs up the role ascribed to meromorphy. Practically, predictions are derived for MHD plasmas
Circadian Variations of Ischemic Burden Among Patients with Myocardial Infarction Undergoing Primary Percutaneous Coronary Intervention
Introduction
Le rythmes circadiens influencent différents paramètres de la physiologie et de la
physiopathologie cardiovasculaire. Récemment, une relation entre la taille d'un infarctus et
l'heure du jour à laquelle il se produit a été suggérée dans des modèles expérimentaux
d'infarctus du myocarde. Le but de cette étude a été de déterminer si les rythmes
circadiens pouvaient influencer la gravité d'un infarctus en terme de taille et de mortalité
chez les patients hospitalisés pour un infarctus du myocarde avec sus-décalage du
segment ST (STEMI) ayant bénéficié d'une intervention coronarienne percutanée primaire (ICPP).
Méthode
Chez 353 patients consécutifs admis avec un STEMI et traités par ICPP, l'heure à la survenue des symptômes, le pic de créatine kinase (reflet de la taille d'un infarctus) et le suivi à 30 jours ont été collectés. Les patients ont été répartis en 4 groupes en fonction de l'heure de survenue de leurs symptômes (00 :00 - 05h59, 06:00 - 11 59 12 00-17h59 et 18h00-23h59).
Résultats
Aucune différence statistiquement significative n'a été retrouvée entre les différents groupes en ce qui concerne les caractéristiques des patients ou de leur prise en charge. Après analyse multivariée, nous avons mis en évidence une différence statistiquement significative entre les pics de créatine kinase chez les patients avec survenue des symptômes entre 00 :00 et 05:59, qui étaient plus élevés que les pics de créatine kinase chez les patients avec survenue des symptômes à tout autre moment de la journée (augmentation moyenne de 38,4%, ρ <0.05). A 30 jours, la mortalité des patients avec survenue des symptômes entre 00 :00 et 05:59 était également significativement plus élevé que celle des patients avec survenue à tout autre moment de la journée (p <0.05).
Conclusion
Notre étude démontre une corrélation indépendante entre la taille d'un infarctus STEMI traité par ICPP et le moment de la journée où les symptômes apparaissent. Ces résultats suggèrent que ce moment devrait être un paramètre important à prendre en compte pour évaluer le pronostic des patients
Discrimination of the light CP-odd scalars between in the NMSSM and in the SLHM
The presence of the light CP-odd scalar boson predicted in the
next-to-minimal supersymmetric model (NMSSM) and the simplest little Higgs
model (SLHM) dramatically changes the phenomenology of the Higgs sector. We
suggest a practical strategy to discriminate the underlying model of the CP-odd
scalar boson produced in the decay of the standard model-like Higgs boson. We
define the decay rate of "the non -tagged jet pair" with which we compute
the ratio of decay rates into lepton and jets. They show much different
behaviors between the NMSSM and the SLHM.Comment: 5 pages, 2 figures (5 figure files
On the uniqueness for the spatially homogeneous Boltzmann equation with a strong angular singularity
We prove an inequality on the Wasserstein distance with quadratic cost
between two solutions of the spatially homogeneous Boltzmann equation without
angular cutoff, from which we deduce some uniqueness results. In particular, we
obtain a local (in time) well-posedness result in the case of (possibly very)
soft potentials. A global well-posedeness result is shown for all regularized
hard and soft potentials without angular cutoff. Our uniqueness result seems to
be the first one applying to a strong angular singularity, except in the
special case of Maxwell molecules.
Our proof relies on the ideas of Tanaka: we give a probabilistic
interpretation of the Boltzmann equation in terms of a stochastic process. Then
we show how to couple two such processes started with two different initial
conditions, in such a way that they almost surely remain close to each other
Investigation of powered nacelles on a high aspect ratio NASA supercritical wing, phase 2
A modified wing with the long core separate flow nacelle and several E(3) nacelles was utilized. The effects of nacelle and pylon cant angles and nacelle longitudinal and vertical location were investigated over a Mach number range from 0.70 to 0.83. The results at the cruise condition 0.82 Mach number and 0.55 lift coefficient are presented
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Net solar generation potential from urban rooftops in Los Angeles
Rooftops provide accessible locations for solar energy installations. While rooftop solar arrays can offset in-building electricity needs, they may also stress electric grid operations. Here we present an analysis of net electricity generation potential from distributed rooftop solar in Los Angeles. We integrate spatial and temporal data for property-level electricity demands, rooftop solar generation potential, and grid capacity constraints to estimate the potential for solar to meet on-site demands and supply net exports to the electric grid. In the study area with 1.2 million parcels, rooftop solar could meet 7200 Gigawatt Hours (GWh) of on-site building demands (~29% of demand). Overall potential net generation is negative, meaning buildings use more electricity than they can produce. Yet, cumulative net export potential from solar to grid circuits is 16,400 GWh. Current policies that regulate solar array interconnection to the grid result in unutilized solar power output of 1700 MW. Lower-income and at-risk communities in LA have greater potential for exporting net solar generation to the grid. This potential should be recognized through investments and policy innovations. The method demonstrates the need for considering time-dependent calculations of net solar potential and offers a template for distributed renewable energy planning in cities
Quantitative lower bounds for the full Boltzmann equation, Part I: Periodic boundary conditions
We prove the appearance of an explicit lower bound on the solution to the
full Boltzmann equation in the torus for a broad family of collision kernels
including in particular long-range interaction models, under the assumption of
some uniform bounds on some hydrodynamic quantities. This lower bound is
independent of time and space. When the collision kernel satisfies Grad's
cutoff assumption, the lower bound is a global Maxwellian and its asymptotic
behavior in velocity is optimal, whereas for non-cutoff collision kernels the
lower bound we obtain decreases exponentially but faster than the Maxwellian.
Our results cover solutions constructed in a spatially homogeneous setting, as
well as small-time or close-to-equilibrium solutions to the full Boltzmann
equation in the torus. The constants are explicit and depend on the a priori
bounds on the solution.Comment: 37 page
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