5,516 research outputs found
A WZW model based on a non-semi-simple group
We present a conformal field theory which desribes a homogeneous four
dimensional Lorentz-signature space-time. The model is an ungauged WZW model
based on a central extension of the Poincar\'e algebra. The central charge of
this theory is exactly four, just like four dimensional Minkowski space. The
model can be interpreted as a four dimensional monochromatic plane wave. As
there are three commuting isometries, other interesting geometries are expected
to emerge via duality.Comment: 8 pages, phyzzx, IASSNS-HEP-93/61 Texable versio
R&D results on a CsI-TTGEM based photodetector
The very high momentum particle identification detector proposed for the
ALICE upgrade is a focusing RICH using a C4F10 gaseous radiator. For the
detection of Cherenkov photons, one of the options currently under
investigation is to use a CsI coated Triple-Thick-GEM (CsI-TTGEM) with metallic
or resistive electrodes. We will present results from the laboratory studies as
well as preliminary results of beam tests of a RICH detector prototype
consisting of a CaF2 radiator coupled to a 10x10 cm2 CsI-TTGEM equipped with a
pad readout and GASSIPLEX-based front-end electronics. With such a prototype
the detection of Cherenkov photons simultaneously with minimum ionizing
particles has been achieved for the first time in a stable operation mode
Chern-Simons Field Theories with Non-semisimple Gauge Group of Symmetry
Subject of this work is a class of Chern-Simons field theories with
non-semisimple gauge group, which may well be considered as the most
straightforward generalization of an Abelian Chern-Simons field theory. As a
matter of fact these theories, which are characterized by a non-semisimple
group of gauge symmetry, have cubic interactions like those of non-abelian
Chern-Simons field theories, but are free from radiative corrections. Moreover,
at the tree level in the perturbative expansion,there are only two connected
tree diagrams, corresponding to the propagator and to the three vertex
originating from the cubic interaction terms. For such theories it is derived
here a set of BRST invariant observables, which lead to metric independent
amplitudes. The vacuum expectation values of these observables can be computed
exactly. From their expressions it is possible to isolate the Gauss linking
number and an invariant of the Milnor type, which describes the topological
relations among three or more closed curves.Comment: 16 pages, 1 figure, plain LaTeX + psfig.st
Contribution of the HMPID detector to the high-pT physics at LHC
The LHC will deliver unexplored energy regimes for proton-proton and
heavy-ion collisions. As shown by the RHIC experiments, particle identification
over a large momentum range is essential to disentangle physics processes,
especially in the intermediate p (1 GeV/c) region. The novel
design of the High-Momentum Particle Identification Detector (HMPID), based on
large surface CsI photocathodes, is able to identify , ,
and in the momentum region where bulk medium properties and hard
scatterings interplay. Furthermore, measurement of resonance particles such as
the could provide information on the system evolution. The
HMPID layout and segmentation are optimized to study particle correlations at
high momenta describing the early phase and the dynamical evolution of the
collision. At LHC, the increased hard cross section will significantly be
enhanced compared to RHIC. Jet reconstruction via Deterministic Annealing can
address jet quenching and detailed measurements of jet properties. In this
paper, we present these selected topics from the possible HMPID contributions
to the physics goals of LHC.Comment: 6 pages, 7 figures, Contribution to QCD @ Work 2007: International
Workshop on Quantum Chromodynamics Theory and Experiment, Martina Franca,
Italy, 16-20 June 200
Recognition of Cherenkov patterns in high multiplicity environments
An algorithm for the recognition of Cherenkov patterns based on the Hough Transform Method (HTM), modified for signals with intrinsic width in presence of background, is presented. The method basically consists in a mapping of the pad coordinate space directly to the Cherenkov angle parameter space with a crucial increase of performance in the treatment of different pattern shapes and amount of background. The method has been developed in the framework of the ALICE experiment at CERN for the analysis of data taken in the HMPID (High Momentum Particle IDentification) RICH detector prototype test beam
Observation of a New Fluxon Resonant Mechanism in Annular Josephson Tunnel Structures
A novel dynamical state has been observed in the dynamics of a perdurbed
sine-Gordon system. This resonant state, has been experimentally observed as a
singularity in the dc current voltage characteristic of an annular Josephson
tunnel junction, excited in the presence of a magnetic field. With this
respect, it can be assimilated to self-resonances known as Fiske steps.
Differently from these, however, we demonstrate, on the basis of numerical
simulations, that its detailed dynamics involves rotating fluxon pairs, a
mechanism associated, so far, to self-resonances known as zero-field steps.Comment: 4 pages, 2 figures, submitted to Physical Review Letter
Gait Analysis for Gender Classification in Forensics
Gender Classification (GC) is a natural ability that belongs to the human beings. Recent improvements in computer vision provide the possibility to extract information for different classification/recognition purposes. Gender is a soft biometrics useful in video surveillance, especially in uncontrolled contexts such as low-light environments, with arbitrary poses, facial expressions, occlusions and motion blur. In this work we present a methodology for the construction of a gait analyzer. The methodology is divided into three major steps: (1) data extraction, where body keypoints are extracted from video sequences; (2) feature creation, where body features are constructed using body keypoints; and (3) classifier selection when such data are used to train four different classifiers in order to determine the one that best performs. The results are analyzed on the dataset Gotcha, characterized by user and camera either in motion
Evaluation of aldosterone antagonist utilization in heart failure with reduced and preserved ejection fraction at an academic medical center
Background: Aldosterone antagonists (AA) have historically been underutilized despite evidence that they reduce morbidity, mortality, and readmission rates to the hospital when used appropriately.
Objective: We sought to determine if AAs were being prescribed in accordance with the 2013 ACCF/AHA guidelines and if there was any benefit surrounding 30-day readmissions or 30-day mortality for patients taking AAs with heart failure with reduced ejection fraction (HFrEF) or heart failure with preserved ejection fraction (HFpEF).
Methods: We performed a retrospective chart review of adult patients who were discharged between October 1, 2015 and February 1, 2016 with any ICD-10 code for heart failure to assess compliance with guideline directed medical therapy. At baseline, patients were stratified by HFpEF and HFrEF. Patients were excluded if they died during the admission, discharged with hospice care, received a heart transplant or ventricular assist device, if they were miscoded or left against medical advice. Descriptive statistics, and Chi Square were used to evaluate the data.
Results: We reviewed 601 patient charts for eligibility in our study, and determined 438 met the criteria for inclusion. Ninety-seven patients (22%) received an AA. Within the HFrEF group, only 37% of patients who were eligible per 2013 ACCF/AHA guidelines, received an AA at time of discharge. Fourteen percent of HFpEF patients were discharged on an AA. We found a trend towards decreased rates of our 30-day outcomes in patients who took AAs in both the HFpEF and HFrEF groups.
Conclusions: AAs were underutilized during the timeframe we evaluated, despite the evidence for their use
Gotcha-I: A Multiview Human Videos Dataset
The growing need of security in large open spaces led to the need to use video capture of people in different context and illumination and with multiple biometric traits as head pose, body gait, eyes, nose, mouth, and further more. All these traits are useful for a multibiometric identification or a person re-identification in a video surveillance context. Body Worn Cameras (BWCs) are used by the police of different countries all around the word and their use is growing significantly. This raises the need to develop new recognition methods that consider multibiometric traits on person re-identification. The purpose of this work is to present a new video dataset called Gotcha-I. This dataset has been obtained using more mobile cameras to adhere to the data of BWCs. The dataset includes videos from 62 subjects in indoor and outdoor environments to address both security and surveillance problem. During these videos, subjects may have a different behavior in videos such as freely, path, upstairs, avoid the camera. The dataset is composed by 493 videos including a set of 180° videos for each face of the subjects in the dataset. Furthermore, there are already processed data, such as: the 3D model of the face of each subject with all the poses of the head in pitch, yaw and roll; and the body keypoint coordinates of the gait for each video frame. It’s also shown an application of gender recognition performed on Gotcha-I, confirming the usefulness and innovativeness of the proposed dataset
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