704 research outputs found
Dirac Equation with External Potential and Initial Data on Cauchy Surfaces
With this paper we provide a mathematical review on the initial-value problem
of the one-particle Dirac equation on space-like Cauchy hypersurfaces for
compactly supported external potentials. We, first, discuss the physically
relevant spaces of solutions and initial values in position and mass shell
representation; second, review the action of the Poincar\'e group as well as
gauge transformations on those spaces; third, introduce generalized Fourier
transforms between those spaces and prove convenient Paley-Wiener- and
Sobolev-type estimates. These generalized Fourier transforms immediately allow
the construction of a unitary evolution operator for the free Dirac equation
between the Hilbert spaces of square-integrable wave functions of two
respective Cauchy surfaces. With a Picard-Lindel\"of argument this evolution
map is generalized to the Dirac evolution including the external potential. For
the latter we introduce a convenient interaction picture on Cauchy surfaces.
These tools immediately provide another proof of the well-known existence and
uniqueness of classical solutions and their causal structure
Protecting Against Police Brutality and Official Misconduct: A New Federal Criminal Civil Rights Framework
Congress should make structural changes to our laws to help protect the civil rights of all people. If passed, the legislation recommended in this report would impact how law enforcement, corrections, and other public officials operate nationwide. By more specifically defining what actions violate civil rights, the law would put officials on clearer notice of what is forbidden
Using Discourse to Restore Organisational Legitimacy: ‘CEO-speak’ After an Incident in a German Nuclear Power Plant
ATLAS Monitored Drift Tube Chambers in E = 11 MeV Neutron Background
The influence of fast neutrons on the occupancy and the single tube
resolution of ATLAS muon drift detectors was investigated by exposing a chamber
built out of 3 layers of 3 short standard drift tubes to neutron flux-densities
of up to 16 kHz/cm2 at a neutron energy of E=11 MeV. Pulse shape capable NE213
scintillaton detectors and a calibrated BF3 neutron detector provided
monitoring of the neutron flux-density and energy. The sensitivity of the drift
chamber to the neutrons was measured to be 4*10-4 by comparing data sets with
and without neutron background. For the investigation of tracks of cosmic muons
two silicon-strip detectors above and underneath the chamber allow to compare
measured drift-radii with reference tracks. Alternatively, the single tube
resolution was determined using the triple-sum method. The comparison between
data with and without neutron irradiation shows only a marginal effect on the
resolution and little influence on the muon track reconstruction.Comment: 4 pages, 11 figures, conferenc
Maintaining or Disrupting Inequality: Diversity Statements in the University
The purpose of my study was to identify whether university Diversity Statements aid in maintaining or disrupting inequality in the university. Using critical discourse analysis, I analyzed an initial sample of eleven Diversity Statements to develop a list of common themes found within the diversity statements. Using a maximum variation method, I then reduced my sample to four universities to provide breadth of information for the final study (Miles & Huberman, 1994). In my case analysis, I first conducted an individual analysis of each of the four Diversity Statements using the common themes from my critical case analysis, common functions of the Diversity Statement, and potential limitations from my review of the literature (Doolittle, Horner, Bradley, Sugai, & Vincent, 2007; King & Cleland, 1978; Meacham & Gaff, 2006; Sevier, 2003). Next, for each of the universities I then compared the Mission Statement to the Diversity Statement, analyzed common university statistics, and evaluated website pictures. Last, I conducted a cross-case analysis to identify patterns and considered the implications of those patterns in my findings.
My analysis evidenced similarities across cases and provided insight to be applied in developing a framework for writing a Diversity Statement. Conclusions from my study suggest the Diversity Statement has the potential to be a powerful tool in disrupting inequality in the university. However, limiting factors decrease this ability. The recommendations suggest careful attention in preparing to write a Diversity Statement, appropriate content, and full dissemination of the Diversity Statement can increase the ability of the Diversity Statement to disrupt inequality in the university
Opening new dimensions for e-Tourism
In this paper we describe an e-Tourism environment that takes a community-driven approach to foster a lively society of travelers who exchange travel experiences, recommend tourism destinations or just listen to catch some interesting gossip. Moreover, business transactions such as booking a trip or getting assistance from travel advisors or community members are constituent parts of this environment. All these happen in an integrated, game-like e-Business application where each e-Tourist is impersonated as an avatar. More precisely, we apply 3D Electronic Institutions, a framework developed and employed in the area of multi-agent systems, to the tourism domain. The system interface is realized by means of a 3D game engine that provides sophisticated 3D visualization and enables humans to interact with the environment. We present "itchy feet", a prototype implementing this 3D e-Tourism environment to showcase first visual impressions. This new environment is a perfect research playground for examining heterogeneous societies comprising humans and software agents, and their relationship in e-Tourism. © Springer-Verlag London Limited 2006
Effects of subthalamic nucleus deep brain stimulation on emotional working memory capacity and mood in patients with Parkinson's disease
Background: In Parkinson’s disease (PD), cognitive symptoms and mood changes
may be even more distressing for the patient than motor symptoms. Objective:
Our aim was to determine the effects of bilateral subthalamic nucleus deep
brain stimulation (STN-DBS) on working memory (WM) and mood. Methods: Sixteen
patients with PD were assessed with STN-DBS switched on (DBS-ON) and with
dopaminergic treatment (Med-ON) compared to switched off (DBS-OFF) and without
dopaminergic treatment (Med-OFF). The primary outcome measures were a Visual
Analog Mood Scale (VAMS) and an emotional 2-back WM task at 12 months after
DBS in the optimal DBS-ON/Med-ON setting compared to DBS-OFF/Med-OFF. Results:
Comparison of DBS-OFF/Med-OFF to DBS-ON/Med-ON revealed a significant increase
in alertness (meanoff/off =51.59±24.54; meanon/on =72.75; P=0.016) and
contentedness (meanoff/off =38.73±24.41; meanon/on =79.01±17.66; P=0.001,
n=16), and a trend for reduction in sedation (P=0.060), which was related to
stimulation as shown in a subgroup of seven patients. The N-back task revealed
a significant increase in accuracy with DBS-ON/Med-ON compared to DBS-OFF/Med-
OFF (82.0% vs 76.0%, respectively) (P=0.044), regardless of stimulus valence.
Conclusion: In line with previous studies, we found that patients rated
themselves subjectively as more alert, content, and less sedated during short-
term DBS-ON. Accuracy in the WM task increased with the combination of DBS and
medication, possibly related to higher alertness of the patients. Our results
add to the currently mixed results described for DBS on WM and suggest that
there are no deleterious DBS effects on this specific cognitive domain
Temperature Studies for ATLAS MDT BOS Chambers
Data sets with high statistics taken at the cosmic ray facility, equipped
with 3 ATLAS BOS MDT chambers, in Garching (Munich) have been used to study
temperature and pressure effects on gas gain and drifttime. The deformation of
a thermally expanded chamber was reconstructed using the internal RasNik
alignment monitoring system and the tracks from cosmic data. For these studies
a heating system was designed to increase the temperature of the middle chamber
by up to 20 Kelvins over room temperature. For comparison the temperature
effects on gas properties have been simulated with Garfield. The maximum
drifttime decreased under temperature raise by -2.21 +- 0.08 ns/K, in agreement
with the results of pressure variations and the Garfield simulation. The
increased temperatures led to a linear increase of the gas gain of about 2.1%
1/K. The chamber deformation has been analyzed with the help of reconstructed
tracks. By the comparison of the tracks through the reference chambers with
these through the test chamber the thermal expansion has been reconstructed and
the result shows agreement with the theoretical expansion coefficient. As the
wires are fixed at the end of the chamber, the wire position calculation can
not provide a conclusion for the chamber middle. The complete deformation has
been identified with the analysis of the monitoring system RasNik, whose
measured values have shown a homogeneous expansion of the whole chamber,
overlayed by a shift and a rotation of the chamber middle with respect to the
outer part of the chamber. The established results of both methods are in
agreement. We present as well a model for the position-drifttime correction as
function of temperature.Comment: 4 pages, 12 figures, conferenc
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