12,655 research outputs found
Simple Muscle Architecture Analysis (SMA): an ImageJ macro tool to automate measurements in B-mode ultrasound scans
In vivo measurements of muscle architecture (i.e. the spatial arrangement of
muscle fascicles) are routinely included in research and clinical settings to
monitor muscle structure, function and plasticity. However, in most cases such
measurements are performed manually, and more reliable and time-efficient
automated methods are either lacking completely, or are inaccessible to those
without expertise in image analysis. In this work, we propose an ImageJ script
to automate the entire analysis process of muscle architecture in ultrasound
images: Simple Muscle Architecture Analysis (SMA). Images are filtered in the
spatial and frequency domains with built-in commands and external plugins to
highlight aponeuroses and fascicles. Fascicle dominant orientation is then
computed in regions of interest using the OrientationJ plugin. Bland-Altman
plots of analyses performed manually or with SMA indicates that the automated
analysis does not induce any systematic bias and that both methods agree
equally through the range of measurements. Our test results illustrate the
suitability of SMA to analyse images from superficial muscles acquired with a
broad range of ultrasound settings.Comment: 8 pages, 7 figures, 1 appendi
InP and GaAs characterization with variable stoichiometry obtained by molecular spray
Both InP and GaAs surfaces were studied in parallel. A molecular spray technique was used to obtain two semiconductor surfaces with different superficial compositions. The structures of these surfaces were examined by electron diffraction. Electron energy loss was measured spectroscopically in order to determine surface electrical characteristics. The results are used to support conclusions relative to the role of surface composition in establishing a Schottky barrier effect in semiconductor devices
Aeolian sans ripples: experimental study of saturated states
We report an experimental investigation of aeolian sand ripples, performed
both in a wind tunnel and on stoss slopes of dunes. Starting from a flat bed,
we can identify three regimes: appearance of an initial wavelength, coarsening
of the pattern and finally saturation of the ripples. We show that both initial
and final wavelengths, as well as the propagative speed of the ripples, are
linear functions of the wind velocity. Investigating the evolution of an
initially corrugated bed, we exhibit non-linear stable solutions for a finite
range of wavelengths, which demonstrates the existence of a saturation in
amplitude. These results contradict most of the models.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Lett. Title changed,
figures corrected and simplified, more field data included, text clarifie
Practical learning method for multi-scale entangled states
We describe a method for reconstructing multi-scale entangled states from a
small number of efficiently-implementable measurements and fast
post-processing. The method only requires single particle measurements and the
total number of measurements is polynomial in the number of particles. Data
post-processing for state reconstruction uses standard tools, namely matrix
diagonalisation and conjugate gradient method, and scales polynomially with the
number of particles. Our method prevents the build-up of errors from both
numerical and experimental imperfections
Two-Phase Cooling of Targets and Electronics for Particle Physics Experiments
An overview of the LTCM lab’s decade of experience with two-phase cooling research for computer chips and power electronics will be described with its possible beneficial application to high-energy physics experiments. Flow boiling in multi-microchannel cooling elements in silicon (or aluminium) have the potential to provide high cooling rates (up to as high as 350 W/cm2), stable and uniform temperatures of targets and electronics, and lightweight construction while also minimizing the fluid inventory. An overview of two-phase flow and boiling research in single microchannels and multi-microchannel test elements will be presented together with video images of these flows. The objective is to stimulate discussion on the use of two-phase cooling in these demanding applications, including the possible use of CO2
Fine frequency shift of sigle vortex entrance and exit in superconducting loops
The heat capacity of an array of independent aluminum rings has been
measured under an external magnetic field using highly sensitive
ac-calorimetry based on a silicon membrane sensor. Each superconducting vortex
entrance induces a phase transition and a heat capacity jump and hence
oscillates with . This oscillatory and non-stationary behaviour
measured versus the magnetic field has been studied using the Wigner-Ville
distribution (a time-frequency representation). It is found that the
periodicity of the heat capacity oscillations varies significantly with the
magnetic field; the evolution of the period also depends on the sweeping
direction of the field. This can be attributed to a different behavior between
expulsion and penetration of vortices into the rings. A variation of more than
15% of the periodicity of the heat capacity jumps is observed as the magnetic
field is varied. A description of this phenomenon is given using an analytical
solution of the Ginzburg-Landau equations of superconductivity
Lattice gas with ``interaction potential''
We present an extension of a simple automaton model to incorporate non-local
interactions extending over a spatial range in lattice gases. {}From the
viewpoint of Statistical Mechanics, the lattice gas with interaction range may
serve as a prototype for non-ideal gas behavior. {}From the density
fluctuations correlation function, we obtain a quantity which is identified as
a potential of mean force. Equilibrium and transport properties are computed
theoretically and by numerical simulations to establish the validity of the
model at macroscopic scale.Comment: 12 pages LaTeX, figures available on demand ([email protected]
Automated extraction of oscillation parameters for Kepler observations of solar-type stars
The recent launch of the Kepler space telescope brings the opportunity to
study oscillations systematically in large numbers of solar-like stars. In the
framework of the asteroFLAG project, we have developed an automated pipeline to
estimate global oscillation parameters, such as the frequency of maximum power
(nu_max) and the large frequency spacing (Delta_nu), for a large number of time
series. We present an effective method based on the autocorrelation function to
find excess power and use a scaling relation to estimate granulation timescales
as initial conditions for background modelling. We derive reliable
uncertainties for nu_max and Delta_nu through extensive simulations. We have
tested the pipeline on about 2000 simulated Kepler stars with magnitudes of
V~7-12 and were able to correctly determine nu_max and Delta_nu for about half
of the sample. For about 20%, the returned large frequency spacing is accurate
enough to determine stellar radii to a 1% precision. We conclude that the
methods presented here are a promising approach to process the large amount of
data expected from Kepler.Comment: 14 pages, 9 figures, accepted for publication in Communications in
Asteroseismolog
Thermal Operator and Cutting Rules at Finite Temperature and Chemical Potential
In the context of scalar field theories, both real and complex, we derive the
cutting description at finite temperature (with zero/finite chemical potential)
from the cutting rules at zero temperature through the action of a simple
thermal operator. We give an alternative algebraic proof of the largest time
equation which brings out the underlying physics of such a relation. As an
application of the cutting description, we calculate the imaginary part of the
one loop retarded self-energy at zero/finite temperature and finite chemical
potential and show how this description can be used to calculate the dispersion
relation as well as the full physical self-energy of thermal particles.Comment: 17 pages, 13 figures. Added references, version to appear in Physical
Review
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