6,098 research outputs found
An algorithm for quantifying dependence in multivariate data sets
We describe an algorithm to quantify dependence in a multivariate data set.
The algorithm is able to identify any linear and non-linear dependence in the
data set by performing a hypothesis test for two variables being independent.
As a result we obtain a reliable measure of dependence.
In high energy physics understanding dependencies is especially important in
multidimensional maximum likelihood analyses. We therefore describe the problem
of a multidimensional maximum likelihood analysis applied on a multivariate
data set with variables that are dependent on each other. We review common
procedures used in high energy physics and show that general dependence is not
the same as linear correlation and discuss their limitations in practical
application.
Finally we present the tool CAT, which is able to perform all reviewed
methods in a fully automatic mode and creates an analysis report document with
numeric results and visual review.Comment: 4 pages, 3 figure
Relationship Between the Foveal Avascular Zone and Foveal Pit Morphology
Purpose.To assess the relationship between foveal pit morphology and size of the foveal avascular zone (FAZ).
Methods. Forty-two subjects were recruited. Volumetric images of the macula were obtained using spectral domain optical coherence tomography. Images of the FAZ were obtained using either a modified fundus camera or an adaptive optics scanning light ophthalmoscope. Foveal pit metrics (depth, diameter, slope, volume, and area) were automatically extracted from retinal thickness data, whereas the FAZ was manually segmented by two observers to extract estimates of FAZ diameter and area.
Results. Consistent with previous reports, the authors observed significant variation in foveal pit morphology. The average foveal pit volume was 0.081 mm3 (range, 0.022 to 0.190 mm3). The size of the FAZ was also highly variable between persons, with FAZ area ranging from 0.05 to 1.05 mm2 and FAZ diameter ranging from 0.20 to 1.08 mm. FAZ area was significantly correlated with foveal pit area, depth, and volume; deeper and broader foveal pits were associated with larger FAZs.
Conclusions. Although these results are consistent with predictions from existing models of foveal development, more work is needed to confirm the developmental link between the size of the FAZ and the degree of foveal pit excavation. In addition, more work is needed to understand the relationship between these and other anatomic features of the human foveal region, including peak cone density, rod-free zone diameter, and Henle fiber layer
Emergency Medicine Society of South Africa guidelines for the training and credentialing in emergency point-of-care ultrasound
This is the second guideline from the Emergency Medicine Society of South Africa (EMSSA) on the use of emergency point-of-care ultrasound in South Africa. It supersedes and replaces the guidelines produced in 2009. This document contains information on the changes from the 2009 guidelines and details of the training and credentialing processes recommended by EMSSA. It also contains detailed information on the curricula of the Core Emergency Point-of-Care Ultrasound and Advanced Emergency Point-of-Care Ultrasound courses
Implementation of a Non-Metallic Barrier in an Electric Motor
Electric motors that run in pure oxygen must be sealed, or "canned," for safety reasons to prevent the oxygen from entering into the electrical portion of the motor. The current canning process involves designing a metallic barrier around the rotor to provide the separation. This metallic barrier reduces the motor efficiency as speed is increased. In higher-speed electric motors, efficiency is greatly improved if a very thin, nonmetallic barrier can be utilized. The barrier thickness needs to be approximately 0.025-in. (.0.6-mm) thick and can be made of a brittle material such as glass. The motors, however, designed for space applications are typically subject to high-vibration environments. A fragile, non-metallic barrier can be utilized in a motor assembly if held in place by a set of standard rubber O-ring seals. The O-rings provide the necessary sealing to keep oxygen away from the electrical portion of the motor and also isolate the fragile barrier from the harsh motor vibration environment. The compliance of the rubber O-rings gently constrains the fragile barrier and isolates it from the harsh external motor environment. The use of a non-metallic barrier greatly improves motor performance, especially at higher speeds, while isolating the electronics from the working fluid with an inert liner
The Higgs System in and Beyond the Standard Model
After the discovery of the Higgs boson particle on the 4th of July of 2012 at
the Large Hadron Collider, sited at the european CERN laboratory, we are
entering in a fascinating period for Particle Physics where both theorists and
experimentalists are devoted to fully understand the features of this new
particle and the possible consequences for High Energy Physics of the Higgs
system both within and beyond the Standard Model of fundamental particle
interactions. This paper is a summary of the lectures given at the third IDPASC
school (Santiago de Compostela, Feb. 2013, Spain) addressed to PhD students,
and contains a short introduction to the main basic aspects of the Higgs boson
particle in and beyond the Standard Model.Comment: 62 pages, 31 figures, Lectures of the IDPASC School at Santiago de
Compostela, Spain, February 201
Symbolic Algebra and Renormalization of Gauge Theories
Symbolic algebra relevant to the renormalization of gauge theories can be
efficiently performed by machine using modern packages. We devise a scheme for
representing and manipulating the objects involved in perturbative calculations
of gauge theories. This scheme is readily implemented using the general purpose
package, Mathematica. The techniques discussed are used to calculate
renormalization group functions for a non-abelian gauge theory with
massless fermions in a representation R, in the two-loop approximation, and to
simplify some expressions arising in electroweak calculations at the two loop
level.Comment: 16 pages, LaTex, 2 diagrams drawn with FEYNMAN, uses cite.sty Entire
manuscript available as a ps file at
http://www.physics.adelaide.edu.au/theory/home.html Also available via
anonymous ftp at ftp://adelphi.adelaide.edu.au/pub/theory/ADP-95-41.T193.ps
Accepted for publication in Computer Physics Communicatio
An optimality-based model of the dynamic feedbacks between natural vegetation and the water balance
The hypothesis that vegetation adapts optimally to its environment gives rise to a novel framework for modeling the interactions between vegetation dynamics and the catchment water balance that does not rely on prior knowledge about the vegetation at a particular site. We present a new model based on this framework that includes a multilayered physically based catchment water balance model and an ecophysiological gas exchange and photosynthesis model. The model uses optimization algorithms to find those static and dynamic vegetation properties that would maximize the net carbon profit under given environmental conditions. The model was tested at a savanna site near Howard Springs (Northern Territory, Australia) by comparing the modeled fluxes and vegetation properties with long-term observations at the site. The results suggest that optimality may be a useful way of approaching the prediction and estimation of vegetation cover, rooting depth, and fluxes such as transpiration and CO2 assimilation in ungauged basins without model calibration
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