11,177 research outputs found
Color conductivity and ladder summation in hot QCD
The color conductivity is computed at leading logarithmic order using a Kubo
formula. We show how to sum an infinite series of planar ladder diagrams,
assuming some approximations based on the dominance of soft scattering
processes between hard particles in the plasma. The result agrees with the one
obtained previously from a kinetical approach.Comment: 15 pages, 4 figures. Explanations enlarged, two figures and some refs
added, typos corrected. Final version to be published in Phys.Rev.
Mechanism of enhanced light output in InGaN-based microlight emitting diodes
Micro-light emitting diode (LED) arrays with diameters of 4 to 20 mum have been fabricated and were found to be much more efficient light emitters compared to their broad-area counterparts, with up to five times enhancement in optical power densities. The possible mechanisms responsible for the improvement in performance were investigated. Strain relaxation in the microstructures as measured by Raman spectroscopy was not observed, arguing against theories of an increase in internal quantum efficiency due to a reduction of the piezoelectric field put forward by other groups. Optical microscope images show intense light emission at the periphery of the devices, as a result of light scattering off the etched sidewalls. This increases the extraction efficiency relative to broad area devices and boosts the forward optical output. In addition, spectra of the forward emitted light reveal the presence of resonant cavity modes [whispering gallery (WG) modes in particular] which appear to play a role in enhancing the optical output
Thiol density dependent classical potential for methyl-thiol on a Au(111) surface
A new classical potential for methyl-thiol on a Au(111) surface has been
developed using density functional theory electronic structure calculations.
Energy surfaces between methyl-thiol and a gold surface were investigated in
terms of symmetry sites and thiol density. Geometrical optimization was
employed over all the configurations while minimum energy and thiol height were
determined. Finally, a new interatomic potential has been generated as a
function of thiol density, and applications to coarse-grained simulations are
presented
Baryon Number and Electric Charge Fluctuations in Pb+Pb Collisions at SPS energies
Event-by-event fluctuations of the net baryon number and electric charge in
nucleus-nucleus collisions are studied in Pb+Pb at SPS energies within the HSD
transport model. We reveal an important role of the fluctuations in the number
of target nucleon participants. They strongly influence all measured
fluctuations even in the samples of events with rather rigid centrality
trigger. This fact can be used to check different scenarios of nucleus-nucleus
collisions by measuring the multiplicity fluctuations as a function of
collision centrality in fixed kinematical regions of the projectile and target
hemispheres. The HSD results for the event-by-event fluctuations of electric
charge in central Pb+Pb collisions at 20, 30, 40, 80 and 158 A GeV are in a
good agreement with the NA49 experimental data and considerably larger than
expected in a quark-gluon plasma. This demonstrate that the distortions of the
initial fluctuations by the hadronization phase and, in particular, by the
final resonance decays dominate the observable fluctuations.Comment: 24 pages, 17 figures, to be published in Phys. Rev. C; new results on
electric charge fluctuations in central Pb+Pb collisions at SPS energies have
been adde
A combined variation of the musculocutaneous nerve associated with a supernumerary head of the biceps brachii muscle
Single anatomical variation in the upper limb is common, but the coexistence of neuromuscular anomalies is still rare. We found a combined neuromuscular variation in the upper limb in a 61-year-old Korean male cadaver, whose cause of death was laryngeal carcinoma, during a routine dissection course for medical students. In his left arm, a supernumerary head of the biceps brachii muscle attached to the anteromedial surface of mid-humerus and united distally with the long and short heads of the biceps brachii muscle (BBM). The musculocutaneous nerve, which did not pierce the coracobrachialis muscle but gave 2 muscular branches, had a communicating branch to the median nerve. Since the presence of the supernumerary head of the BBM might affect the course and branching of the musculocutaneous nerve, knowing different patterns of the musculocutaneous variation associated with the BBM variations is essential for anatomists and clinicians
Shear viscosity of hot scalar field theory in the real-time formalism
Within the closed time path formalism a general nonperturbative expression is
derived which resums through the Bethe-Salpter equation all leading order
contributions to the shear viscosity in hot scalar field theory. Using a
previously derived generalized fluctuation-dissipation theorem for nonlinear
response functions in the real-time formalism, it is shown that the
Bethe-Salpeter equation decouples in the so-called (r,a) basis. The general
result is applied to scalar field theory with pure lambda*phi**4 and mixed
g*phi**3+lambda*phi**4 interactions. In both cases our calculation confirms the
leading order expression for the shear viscosity previously obtained in the
imaginary time formalism.Comment: Expanded introduction and conclusions. Several references and a
footnote added. Fig.5 and its discussion in the text modified to avoid double
counting. Signs in Eqs. (45) and (53) correcte
Production and optical properties of liquid scintillator for the JSNS experiment
The JSNS (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron
Source) experiment will search for neutrino oscillations over a 24 m short
baseline at J-PARC. The JSNS inner detector will be filled with 17 tons
of gadolinium-loaded liquid scintillator (LS) with an additional 31 tons of
unloaded LS in the intermediate -catcher and outer veto volumes.
JSNS has chosen Linear Alkyl Benzene (LAB) as an organic solvent because
of its chemical properties. The unloaded LS was produced at a refurbished
facility, originally used for scintillator production by the RENO experiment.
JSNS plans to use ISO tanks for the storage and transportation of the LS.
In this paper, we describe the LS production, and present measurements of its
optical properties and long term stability. Our measurements show that storing
the LS in ISO tanks does not result in degradation of its optical properties.Comment: 7 pages, 4 figures
Reheating and turbulence
We show that the ''turbulent'' particle spectra found in numerical
simulations of the behavior of matter fields during reheating admit a simple
interpretation in terms of hydrodynamic models of the reheating period. We
predict a particle number spectrum with for Comment: 10 pages, one figure included in tex
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