6,438 research outputs found
On conformal measures and harmonic functions for group extensions
We prove a Perron-Frobenius-Ruelle theorem for group extensions of
topological Markov chains based on a construction of -finite conformal
measures and give applications to the construction of harmonic functions.Comment: To appear in Proceedings of "New Trends in Onedimensional Dynamics,
celebrating the 70th birthday of Welington de Melo
Numerical simulation of viscous supersonic flow over a generic fighter configuration
A procedure is presented, as well as some results, to calculate the flow over a generic fighter configuration. A parabolized marching Navier-Stokes code is used to obtain the solution over a wing-canopy body. The flow conditions simulate supersonic cruise with a freestream Mach number of 2.169 and angles of attack of 4 and 10 deg. The body surface is considered to be an adiabatic wall and the flow is assumed to be turbulent for the given Reynolds number
Looking for a light Higgs boson in the overlooked channel
The final state obtained when a Higgs boson decays to a photon and a Z boson
has been mostly overlooked in current searches for a light Higgs boson.
However, when the Z boson decays leptonically, all final state particles in
this channel can be measured, allowing for accurate reconstructions of the
Higgs mass and angular correlations. We determine the sensitivity of the Large
Hadron Collider (LHC) running at center of masses energies of 8 and 14 TeV to
Standard Model (SM) Higgs bosons with masses in the 120 - 130 GeV range. For
the 8 TeV LHC, sensitivity to several times the the SM cross section times
branching ratio may be obtained with 20 inverse femtobarns of integrated
luminosity, while for the 14 TeV LHC, the SM rate is probed with about 100
inverse femtobarns of integrated luminosity.Comment: 4 pages, 4 figures. Improves on version 1 in that 8 and 14 TeV LHC
running is considered, the case of a 125 GeV Higgs is treated specifically,
and the effect of an additional jet in the final state has been taken into
account in studying experimental sensitivit
Identity and Function of a Cardiac Mitochondrial Small Conductance Ca2+-Activated K+ Channel Splice Variant
We provide evidence for location and function of a small conductance, Ca2+-activated K+ (SKCa) channel isoform 3 (SK3) in mitochondria (m) of guinea pig, rat and human ventricular myocytes. SKCa agonists protected isolated hearts and mitochondria against ischemia/reperfusion (IR) injury; SKCa antagonists worsened IR injury. Intravenous infusion of a SKCa channel agonist/antagonist, respectively, in intact rats was effective in reducing/enhancing regional infarct size induced by coronary artery occlusion. Localization of SK3 in mitochondria was evidenced by Western blot of inner mitochondrial membrane, immunocytochemical staining of cardiomyocytes, and immunogold labeling of isolated mitochondria. We identified a SK3 splice variant in guinea pig (SK3.1, aka SK3a) and human ventricular cells (SK3.2) by amplifying mRNA, and show mitochondrial expression in mouse atrial tumor cells (HL-1) by transfection with full length and truncated SK3.1 protein. We found that the N-terminus is not required for mitochondrial trafficking but the C-terminus beyond the Ca2+ calmodulin binding domain is required for Ca2+ sensing to induce mK+ influx and/or promote mitochondrial localization. In isolated guinea pig mitochondria and in SK3 overexpressed HL-1 cells, mK+ influx was driven by adding CaCl2. Moreover, there was a greater fall in membrane potential (ΔΨm), and enhanced cell death with simulated cell injury after silencing SK3.1 with siRNA. Although SKCa channel opening protects the heart and mitochondria against IR injury, the mechanism for favorable bioenergetics effects resulting from SKCa channel opening remains unclear. SKCa channels could play an essential role in restraining cardiac mitochondria from inducing oxidative stress-induced injury resulting from mCa2+ overload
Cerebral small vessel disease burden is associated with poststroke depressive symptoms: A 15-month prospective study
Objective: All types of cerebral small vessel disease (SVD) markers including lacune, white matter hyperintensities (WMH), cerebral microbleeds, and perivascular spaces were found to be associated with poststroke depressive symptoms (PDS). This study explored whether the combination of the four markers constituting an overall SVD burden was associated with PDS.
Methods: A cohort of 563 patients with acute ischemic stroke were followed over a 15-month period after the index stroke. A score of _7 on the 15-item Geriatric Depression Scale was defined as clinically significant PDS. Scores of the four SVD markers ascertained on magnetic resonance imaging were summed up to represent total SVD burden. The association between SVD burden and PDS was assessed with generalized estimating equation models.
Results: The study sample had a mean age of 67.0 _ 10.2 years and mild-moderate stroke [National Institutes of Health Stroke Scale score: 3, interquartile, 1–5]. PDS were found in 18.3%, 11.6%, and 12.3% of the sample at 3, 9, and 15 months after stroke, respectively. After adjusting for demographic characteristics, vascular risk factors, social support, stroke severity, physical and cognitive functions, and size and locations of stroke, the SVD burden was associated with an increased risk of PDS [odds ratio = 1.30; 95% confidence interval = 1.07–1.58; p = 0.010]. Other significant predictors of PDS were time of assessment, female sex, smoking, number of acute infarcts, functional independence, and social support.
Conclusion: SVD burden was associated with PDS examined over a 15-month follow-up in patients with mild to moderate acute ischemic stroke
Interface-Controlled Ferroelectricity at the Nanoscale
Recent experimental results demonstrate that in thin films ferroelectricity
persists down to film thickness of a few unit cells. This finding opens an
avenue for novel electronic devices based on ultathin ferroelectrics, but also
raises questions about factors controlling ferroelectricity and the nature of
the ferroelectric state at the nanoscale. Here we report a first-principles
study of KNbO3 ferroelectric thin films placed between two metal electrodes,
either SrRuO3 or Pt. We show that the bonding at the ferroelectric-metal
interface imposes severe constraints on the displacement of atoms, destroying
the bulk tetragonal soft mode in thin ferroelectric films. This does not,
however, quench local polarization. If the interface bonding is sufficiently
strong the ground state represents a ferroelectric double-domain structure,
driven by the intrinsic oppositely-oriented dipole moments at the two
interfaces. Although the critical thickness for the net polarization of KNbO3
film is finite - about 1 nm for Pt and 1.8 nm for SrRuO3 electrodes - local
polarization persists down to thickness of a unit cell.Comment: 5 pages, 4 figure
Dynamics and Pattern Formation in Large Systems of Spatially-Coupled Oscillators with Finite Response Times
We consider systems of many spatially distributed phase oscillators that
interact with their neighbors. Each oscillator is allowed to have a different
natural frequency, as well as a different response time to the signals it
receives from other oscillators in its neighborhood. Using the ansatz of Ott
and Antonsen (Ref. \cite{OA1}) and adopting a strategy similar to that employed
in the recent work of Laing (Ref. \cite{Laing2}), we reduce the microscopic
dynamics of these systems to a macroscopic partial-differential-equation
description. Using this macroscopic formulation, we numerically find that
finite oscillator response time leads to interesting spatio-temporal dynamical
behaviors including propagating fronts, spots, target patterns, chimerae,
spiral waves, etc., and we study interactions and evolutionary behaviors of
these spatio-temporal patterns
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