4,003 research outputs found
Flavor-singlet light-cone amplitudes and radiative Upsilon decays in SCET
We study the evolution of flavor-singlet, light-cone amplitudes in the
soft-collinear effective theory (SCET), and reproduce results previously
obtained by a different approach. We apply our calculation to the color-singlet
contribution to the photon endpoint in radiative Upsilon decay. In a previous
paper, we studied the color-singlet contributions to the endpoint, but
neglected operator mixing, arguing that it should be a numerically small
effect. Nevertheless the mixing needs to be included in a consistent
calculation, and we do just that in this work. We find that the effects of
mixing are indeed numerically small. This result combined with previous work on
the color-octet contribution and the photon fragmentation contribution provides
a consistent theoretical treatment of the photon spectrum in radiative Upsilon
decay.Comment: 19 pages with 8 figure
A comparison of charcoal- and slag-based constructed wetlands for acid mine drainage remediation
Subsurface-flow constructed wetlands (CW) with charcoal- or slag-based bed matrices were investigated for their potential use in remediating acid mine drainage (AMD). A CW is effectively a reactor in which some components of the wastewater are broken down by the organisms occurring within the CW, whilst others may be degraded by physico-chemical processes or a combination thereof. Two 200 â„“ small-scale CWs were built at the University. Commercially available charcoal and <19 mm basic oxygen furnace (BOF) slag were used as the bed matrices and the units were planted with a variety of plants. The units were exposed to an artificial AMD. The results showed that the systems removed almost all soluble iron and more than 75% of the sulphate. Both CWs were able to increase the pH of the AMD.Keywords: AMD, charcoal, slag, constructed wetlands, remediatio
Studying the Psychological Impacts of the COVID-19 Pandemic on Frontline Healthcare Workers
Purpose: The purpose of this study was to determine the prevalence of psychological distress in frontline healthcare workers during the COVID 19 pandemic, and to identify if interventions and higher measures of resiliency helped to minimize the prevalence of symptoms.https://scholarlycommons.henryford.com/nursresconf2021/1002/thumbnail.jp
Brain structure in pediatric Tourette syndrome
Previous studies of brain structure in Tourette syndrome (TS) have produced mixed results, and most had modest sample sizes. In the present multicenter study, we used structural magnetic resonance imaging (MRI) to compare 103 children and adolescents with TS to a well-matched group of 103 children without tics. We applied voxel-based morphometry methods to test gray matter (GM) and white matter (WM) volume differences between diagnostic groups, accounting for MRI scanner and sequence, age, sex and total GM+WM volume. The TS group demonstrated lower WM volume bilaterally in orbital and medial prefrontal cortex, and greater GM volume in posterior thalamus, hypothalamus and midbrain. These results demonstrate evidence for abnormal brain structure in children and youth with TS, consistent with and extending previous findings, and they point to new target regions and avenues of study in TS. For example, as orbital cortex is reciprocally connected with hypothalamus, structural abnormalities in these regions may relate to abnormal decision making, reinforcement learning or somatic processing in TS
Using the Forest to See the Trees: Exploiting Context for Visual Object Detection and Localization
Recognizing objects in images is an active area of research in computer vision. In the last two decades, there has been much progress and there are already object recognition systems operating in commercial products. However, most of the algorithms for detecting objects perform an exhaustive search across all locations and scales in the image comparing local image regions with an object model. That approach ignores the semantic structure of scenes and tries to solve the recognition problem by brute force. In the real world, objects tend to covary with other objects, providing a rich collection of contextual associations. These contextual associations can be used to reduce the search space by looking only in places in which the object is expected to be; this also increases performance, by rejecting patterns that look like the target but appear in unlikely places.
Most modeling attempts so far have defined the context of an object in terms of other previously recognized objects. The drawback of this approach is that inferring the context becomes as difficult as detecting each object. An alternative view of context relies on using the entire scene information holistically. This approach is algorithmically attractive since it dispenses with the need for a prior step of individual object recognition. In this paper, we use a probabilistic framework for encoding the relationships between context and object properties and we show how an integrated system provides improved performance. We view this as a significant step toward general purpose machine vision systems.United States. National Geospatial-Intelligence Agency (NEGI-1582-04-0004)United States. Army Research Office. Multidisciplinary University Research Initiative (Grant Number N00014-06-1-0734)National Science Foundation (U.S.). (Contract IIS-0413232)National Defense Science and Engineering Graduate Fellowshi
DMRG analysis of the SDW-CDW crossover region in the 1D half-filled Hubbard-Holstein model
In order to clarify the physics of the crossover from a spin-density-wave
(SDW) Mott insulator to a charge-density-wave (CDW) Peierls insulator in
one-dimensional (1D) systems, we investigate the Hubbard-Holstein Hamiltonian
at half filling within a density matrix renormalisation group (DMRG) approach.
Determining the spin and charge correlation exponents, the momentum
distribution function, and various excitation gaps, we confirm that an
intervening metallic phase expands the SDW-CDW transition in the weak-coupling
regime.Comment: revised versio
Non-equilibrium Differential Conductance through a Quantum Dot in a Magnetic Field
We derive an exact expression for the differential conductance for a quantum
dot in an arbitrary magnetic field for small bias voltage. The derivation is
based on the symmetric Anderson model using renormalized perturbation theory
and is valid for all values of the on-site interaction including the Kondo
regime. We calculate the critical magnetic field for the splitting of the Kondo
resonance to be seen in the differential conductivity as function of bias
voltage. Our calculations for small field show that the peak position of the
component resonances in the differential conductance are reduced substantially
from estimates using the equilibrium Green's function. We conclude that it is
important to take the voltage dependence of the local retarded Green's function
into account in interpreting experimental resultsComment: 8 pages, 4 figures; Replaced by a fully revised version with minor
corrections in the tex
Magnetism, superconductivity and coupling in cuprate heterostructures probed by low-energy muon-spin rotation
We present a low-energy muon-spin-rotation study of the magnetic and
superconducting properties of YBa2Cu3O7/PrBa2Cu3O7 trilayer and bilayer
heterostructures. By determining the magnetic-field profiles throughout these
structures we show that a finite superfluid density can be induced in otherwise
semiconducting PrBa2Cu3O7 layers when juxtaposed to YBa2Cu3O7 "electrodes"
while the intrinsic antiferromagnetic order is unaffected.Comment: 10 pages, 9 figures; figure 9 corrected in version
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