233 research outputs found
Thermal and chemical equilibration in a gluon plasma
We show the evolution of a gluon plasma towards equilibrium starting at some
early moment when the momentum distribution in the central region is
momentaneously isotropic. Using HIJING results for Au+Au collision as initial
input, we consider thermalization and chemical equilibration simultaneously at
both LHC and RHIC energies. Thermalization is shown to be driven chiefly by
inelastic process in our scenario contradicting common assumption that this is
the role of elastic process. We argue that only the inelastic dominancy depends
on the initial conditions but not the dominance itself.Comment: 14 pages + 4 postscript figures, latex2e file, final version to
appear in Nucl. Phys.
Wigner functions in covariant and single-time formulations
We will establish the connection between the Lorentz covariant and so-called
single-time formulation for the quark Wigner operator. To this end we will
discuss the initial value problem for the Wigner operator of a field theory and
give a discussion of the gauge-covariant formulation for the Wigner operator
including some new results concerning the chiral limit. We discuss the gradient
or semi-classical expansion and the color and spinor decomposition of the
equations of motion for the Wigner operator. The single-time formulation will
be derived from the covariant formulation by taking energy moments of the
equations for the Wigner operator. For external fields we prove that only the
lowest energy moments of the quark Wigner operator contain dynamical
information.Comment: 92 pages, to appear in Annals of Physics (N.Y.
Impact of Natural Blind Spot Location on Perimetry.
We study the spatial distribution of natural blind spot location (NBSL) and its impact on perimetry. Pattern deviation (PD) values of 11,449 reliable visual fields (VFs) that are defined as clinically unaffected based on summary indices were extracted from 11,449 glaucoma patients. We modeled NBSL distribution using a two-dimensional non-linear regression approach and correlated NBSL with spherical equivalent (SE). Additionally, we compared PD values of groups with longer and shorter distances than median, and larger and smaller angles than median between NBSL and fixation. Mean and standard deviation of horizontal and vertical NBSL were 14.33° ± 1.37° and -2.06° ± 1.27°, respectively. SE decreased with increasing NBSL (correlation: r = -0.14, p \u3c 0.001). For NBSL distances longer than median distance (14.32°), average PD values decreased in the upper central (average difference for significant points (ADSP): -0.18 dB) and increased in the lower nasal VF region (ADSP: 0.14 dB). For angles in the direction of upper hemifield relative to the median angle (-8.13°), PD values decreased in lower nasal (ADSP: -0.11 dB) and increased in upper temporal VF areas (ADSP: 0.19 dB). In conclusion, we demonstrate that NBSL has a systematic effect on the spatial distribution of VF sensitivity
Optimising pharmacotherapy in older cancer patients with polypharmacy
Objective Polypharmacy is frequent among older cancer patients and increases the risk of potential drug-related problems (DRPs). DRPs are associated with adverse drug events, drug-drug interactions and hospitalisations. Since no standardised polypharmacy assessment methods for oncology patients exist, we aimed to develop one that can be integrated into routine care. Methods Based on the Systematic Tool to Reduce Inappropriate Prescribing (STRIP), we developed OncoSTRIP, which includes a polypharmacy anamnesis, a concise geriatric assessment, a polypharmacy analysis taking life expectancy into account and an optimised treatment plan. Patients >= 65 years with >= 5 chronic drugs visiting our outpatient oncology clinic were eligible for the polypharmacy assessment. Results OncoSTRIP was integrated into routine care of our older cancer patients. In 47 of 60 patients (78%), potential DRPs (n = 101) were found. In total, 85 optimisations were recommended, with an acceptance rate of 41%. It was possible to reduce the number of potential DRPs by 41% and the number of patients with at least one potential DRP by 30%. Mean time spent per patient was 71 min. Conclusions Polypharmacy assessment of older cancer patients identifies many pharmacotherapeutic optimisations. With OncoSTRIP, polypharmacy assessments can be integrated into routine care
Experimental tests of hidden variable theories from dBB to Stochastic Electrodynamics
In this paper we present some of our experimental results on testing hidden
variable theories, which range from Bell inequalities measurements to a
conclusive test of stochastic electrodynamics
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An Artificial Intelligence Approach to Detect Visual Field Progression in Glaucoma Based on Spatial Pattern Analysis.
Purpose: To detect visual field (VF) progression by analyzing spatial pattern changes.
Methods: We selected 12,217 eyes from 7360 patients with at least five reliable 24-2 VFs and 5 years of follow-up with an interval of at least 6 months. VFs were decomposed into 16 archetype patterns previously derived by artificial intelligence techniques. Linear regressions were applied to the 16 archetype weights of VF series over time. We defined progression as the decrease rate of the normal archetype or any increase rate of the 15 VF defect archetypes to be outside normal limits. The archetype method was compared with mean deviation (MD) slope, Advanced Glaucoma Intervention Study (AGIS) scoring, Collaborative Initial Glaucoma Treatment Study (CIGTS) scoring, and the permutation of pointwise linear regression (PoPLR), and was validated by a subset of VFs assessed by three glaucoma specialists.
Results: In the method development cohort of 11,817 eyes, the archetype method agreed more with MD slope (kappa: 0.37) and PoPLR (0.33) than AGIS (0.12) and CIGTS (0.22). The most frequently progressed patterns included decreased normal pattern (63.7%), and increased nasal steps (16.4%), altitudinal loss (15.9%), superior-peripheral defect (12.1%), paracentral/central defects (10.5%), and near total loss (10.4%). In the clinical validation cohort of 397 eyes with 27.5% of confirmed progression, the agreement (kappa) and accuracy (mean of hit rate and correct rejection rate) of the archetype method (0.51 and 0.77) significantly (P \u3c 0.001 for all) outperformed AGIS (0.06 and 0.52), CIGTS (0.24 and 0.59), MD slope (0.21 and 0.59), and PoPLR (0.26 and 0.60).
Conclusions: The archetype method can inform clinicians of VF progression patterns
A quantum-like description of the planetary systems
The Titius-Bode law for planetary distances is reviewed. A model describing
the basic features of this rule in the "quantum-like" language of a wave
equation is proposed. Some considerations about the 't Hooft idea on the
quantum behaviour of deterministic systems with dissipation are discussed.Comment: LaTex file, 17 pages, no figures. Version published in Foundations of
Physics, August 200
Testing imaginary vs. real chemical potential in finite-temperature QCD
One suggestion for determining the properties of QCD at finite temperatures
and densities is to carry out lattice simulations with an imaginary chemical
potential whereby no sign problem arises, and to convert the results to real
physical observables only afterwards. We test the practical feasibility of such
an approach for a particular class of physical observables, spatial correlation
lengths in the quark-gluon plasma phase. Simulations with imaginary chemical
potential followed by analytic continuation are compared with simulations with
real chemical potential, which are possible by using a dimensionally reduced
effective action for hot QCD. We find that for imaginary chemical potential the
system undergoes a phase transition at |mu/T| \approx pi/3, and thus
observables are analytic only in a limited range. However, utilising this
range, relevant information can be obtained for the real chemical potential
case.Comment: 14 pages. Some clarifications and references added, figures modified.
To appear in PL
The Quantum as an Emergent System
Double slit interference is explained with the aid of what we call
"21stcentury classical physics". We model a particle as an oscillator
("bouncer") in a thermal context, which is given by some assumed "zero-point"
field of the vacuum. In this way, the quantum is understood as an emergent
system, i.e., a steady-state system maintained by a constant throughput of
(vacuum) energy. To account for the particle's thermal environment, we
introduce a "path excitation field", which derives from the thermodynamics of
the zero-point vacuum and which represents all possible paths a particle can
take via thermal path fluctuations. The intensity distribution on a screen
behind a double slit is calculated, as well as the corresponding trajectories
and the probability density current. Further, particular features of the
relative phase are shown to be responsible for nonlocal effects not only in
ordinary quantum theory, but also in our classical approach.Comment: 24 pages, 2 figures, based on a talk given at "Emergent Quantum
Mechanics (Heinz von Foerster Conference 2011)",
http://www.univie.ac.at/hvf11/congress/EmerQuM.htm
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