1,111 research outputs found
White Light Flare Continuum Observations with ULTRACAM
We present sub-second, continuous-coverage photometry of three flares on the
dM3.5e star, EQ Peg A, using custom continuum filters with WHT/ULTRACAM. These
data provide a new view of flare continuum emission, with each flare exhibiting
a very distinct light curve morphology. The spectral shape of flare emission
for the two large-amplitude flares is compared with synthetic ULTRACAM
measurements taken from the spectra during the large 'megaflare' event on a
similar type flare star. The white light shape during the impulsive phase of
the EQ Peg flares is consistent with the range of colors derived from the
megaflare continuum, which is known to contain a Hydrogen recombination
component and compact, blackbody-like components. Tentative evidence in the
ULTRACAM photometry is found for an anti-correlation between the emission of
these components.Comment: 8 pages, 3 figures. Proceedings of the 16th Workshop on Cool Stars,
Stellar Systems, and the Sun (PASP conference series, in press
Comparative effects of propranolol, timolol and metoprolol on myocardial infarct size after experimental coronary artery occlusion
The effects of equiblocking doses of three beta-adrenergic blocking agents, propranolol, timolol and metoprolol, on myocardial infarct size were evaluated in 28 dogs after acute experimental coronary artery occlusion. Heart rate, arterial pressure and arterial free fatty acid concentration were measured in an attempt to evaluate their effects on the extent of myocardial injury. The zone at risk of infarction in each dog 1 minute after left anterior coronary artery occlusion was assessed by injecting highly radioactive albumin microspheres into the left atrium, and the hypoperfused zone was determined by autoradiography.After 15 minutes, the dogs were randomized into four groups: control dogs (n = 7), propranolol-treated dogs (1.2 mg/kg intravenously, n = 7), timolol-treated dogs (0.2 mg/kg intravenously, n = 7) and metoprolol-treated dogs (1.2 mg/kg intravenously, n = 7). After 6 hours, the dogs were killed. The left ventricle was sliced and stained with triphenyl-tetrazolium chloride for measurement of infarct size. The same slices were then autoradiographed for measurement of the hypoperfused zone. The percent of hypoperfused zone that evolved to infarction (the ratio of infarct size to hypoperfused zone) was 90.4 ± 1.9% in the control group, 72.4 ± 2.4% in the propranolol-treated dogs (p < 0.05 versus control group); 57.9 ± 4.4% in the timolol-treated dogs (p < 0.01 versus control group; p < 0.05 versus propranolol) and 54.4 ± 3.7% in the metoprolol-treated dogs (p < 0.01 versus control group; p < 0.05 versus propranolol).Thus, propranolol, timolol and metoprolol reduced myocardial infarct size in dogs by 20, 36 and 40%, respectively, after experimental coronary artery occlusion. Metoprolol and timolol protected the ischemic myocardium more effectively than did propranolol
Symmetry relation for multifractal spectra at random critical points
Random critical points are generically characterized by multifractal
properties. In the field of Anderson localization, Mirlin, Fyodorov,
Mildenberger and Evers [Phys. Rev. Lett 97, 046803 (2006)] have proposed that
the singularity spectrum of eigenfunctions satisfies the exact
symmetry at any Anderson transition. In the
present paper, we analyse the physical origin of this symmetry in relation with
the Gallavotti-Cohen fluctuation relations of large deviation functions that
are well-known in the field of non-equilibrium dynamics: the multifractal
spectrum of the disordered model corresponds to the large deviation function of
the rescaling exponent along a renormalization trajectory
in the effective time . We conclude that the symmetry discovered on
the specific example of Anderson transitions should actually be satisfied at
many other random critical points after an appropriate translation. For
many-body random phase transitions, where the critical properties are usually
analyzed in terms of the multifractal spectrum and of the moments
exponents X(N) of two-point correlation function [A. Ludwig, Nucl. Phys. B330,
639 (1990)], the symmetry becomes , or equivalently
for the anomalous parts .
We present numerical tests in favor of this symmetry for the 2D random
state Potts model with various .Comment: 15 pages, 3 figures, v2=final versio
Submicron gate InP power MISFET's with improved output power density at 18 and 20 GHz
The microwave characteristics are presented at 18 and 20 GHz of submicron gate indium phosphide (InP) metal-insulator-semiconductor field-effect transistors (MISFET's) for high output power density applications. InP power MISFET's were fabricated and the output power density was investigated as a function of drain-source spacing. The best output power density and gain were obtained for drain-source spacing of 3 microns. The output power density is 2.7 times greater than was previously measured for InP MISFET's at 18 and 20 GHz, and the power-added efficiency also increased
A Nonlinear Adaptive Filter for Gyro Thermal Bias Error Cancellation
Deterministic errors in angular rate gyros, such as thermal biases, can have a significant impact on spacecraft attitude knowledge. In particular, thermal biases are often the dominant error source in MEMS gyros after calibration. Filters, such as J\,fEKFs, are commonly used to mitigate the impact of gyro errors and gyro noise on spacecraft closed loop pointing accuracy, but often have difficulty in rapidly changing thermal environments and can be computationally expensive. In this report an existing nonlinear adaptive filter is used as the basis for a new nonlinear adaptive filter designed to estimate and cancel thermal bias effects. A description of the filter is presented along with an implementation suitable for discrete-time applications. A simulation analysis demonstrates the performance of the filter in the presence of noisy measurements and provides a comparison with existing techniques
Online Pattern Recognition for the ALICE High Level Trigger
The ALICE High Level Trigger has to process data online, in order to select
interesting (sub)events, or to compress data efficiently by modeling
techniques.Focusing on the main data source, the Time Projection Chamber (TPC),
we present two pattern recognition methods under investigation: a sequential
approach "cluster finder" and "track follower") and an iterative approach
("track candidate finder" and "cluster deconvoluter"). We show, that the former
is suited for pp and low multiplicity PbPb collisions, whereas the latter might
be applicable for high multiplicity PbPb collisions, if it turns out, that more
than 8000 charged particles would have to be reconstructed inside the TPC.
Based on the developed tracking schemes we show, that using modeling techniques
a compression factor of around 10 might be achievableComment: Realtime Conference 2003, Montreal, Canada to be published in IEEE
Transactions on Nuclear Science (TNS), 6 pages, 8 figure
Numerical Results For The 2D Random Bond 3-state Potts Model
We present results of a numerical simulation of the 3-state Potts model with
random bond, in two dimension. In particular, we measure the critical exponent
associated to the magnetization and the specific heat. We also compare these
exponents with recent analytical computations.Comment: 9 pages, latex, 3 Postscript figure
Scaling Analysis of the Site-Diluted Ising Model in Two Dimensions
A combination of recent numerical and theoretical advances are applied to
analyze the scaling behaviour of the site-diluted Ising model in two
dimensions, paying special attention to the implications for multiplicative
logarithmic corrections. The analysis focuses primarily on the odd sector of
the model (i.e., that associated with magnetic exponents), and in particular on
its Lee-Yang zeros, which are determined to high accuracy. Scaling relations
are used to connect to the even (thermal) sector, and a first analysis of the
density of zeros yields information on the specific heat and its corrections.
The analysis is fully supportive of the strong scaling hypothesis and of the
scaling relations for logarithmic corrections.Comment: 15 pages, 3 figures. Published versio
Dynamics and Efficiency of Brownian Rotors
Brownian rotors play an important role in biological systems and in future
nano-technological applications. However the mechanisms determining their
dynamics, efficiency and performance remain to be characterized. Here the F0
portion of the F-ATP synthase is considered as a paradigm of a Brownian rotor.
In a generic analytical model we analyze the stochastic rotation of F0-like
motors as a function of the driving free energy difference and of the free
energy profile the rotor is subjected to. The latter is composed of the rotor
interaction with its surroundings, of the free energy of chemical transitions,
and of the workload. The dynamics and mechanical efficiency of the rotor
depends on the magnitude of its stochastic motion driven by the free energy
energy difference and its rectification on the reaction-diffusion path. We
analyze which free energy profiles provide maximum flow and how their
arrangement on the underlying reaction-diffusion path affects rectification and
-- by this -- the efficiency.Comment: 22 pages, 11 figures, pdflatex, JCP in pres
Scaling Relations for Logarithmic Corrections
Multiplicative logarithmic corrections to scaling are frequently encountered
in the critical behavior of certain statistical-mechanical systems. Here, a
Lee-Yang zero approach is used to systematically analyse the exponents of such
logarithms and to propose scaling relations between them. These proposed
relations are then confronted with a variety of results from the literature.Comment: 4 page
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