65,266 research outputs found
Thermal Dileptons from Quark and Hadron Phases of an Expanding Fireball
A fireball model with time evolution based on transport calculations is used
to examine the dilepton emission rate of an ultra-relativistic heavy-ion
collision. We assume a transition from hadronic matter to a quark-gluon plasma
at a critical temperature T_C between 130-170 MeV. We include thermal
corrections to the hadronic spectra below T_C and use perturbation theory above
T_C. The sensitivity of the spectra with respect to the freeze-out temperature,
the initial fireball temperature and the critical temperature is investigated.Comment: 14 pages, 5 figures; paragraph and one figure added; version to
appear in Eur. Phys. J.
Pressure effects on the superconducting properties of YBa_2Cu_4O_8
Measurements of the magnetization under high hydrostatic pressure (up to 10.2
kbar) in YBa_2Cu_4O_8 were carried out. From the scaling analysis of the
magnetization data the pressure induced shifts of the transition temperature
T_c, the volume V and the anisotropy \gamma have been obtained. It was shown
that the pressure induced relative shift of T_c mirrors essentially that of the
anisotropy. This observation uncovers a novel generic property of anisotropic
type II superconductors, that inexistent in the isotropic case.Comment: 4 pages, 3 figure
Implications of the isotope effects on the magnetization, magnetic torque and susceptibility
We analyze the magnetization, magnetic torque and susceptibility data of
La2-xSrxCu(16,18)O4 and YBa2(63,65)CuO7-x near Tc in terms of the universal
3D-XY scaling relations. It is shown that the isotope effect on Tc mirrors that
on the anisotropy. Invoking the generic behavior of the anisotropy the doping
dependence of the isotope effects on the critical properties, including Tc,
correlation lengths and magnetic penetration depths are traced back to a change
of the mobile carrier concentration.Comment: 5 pages, 3 figure
Model for dilepton rates from a fireball
We calculate the dilepton emission rate from a fireball created in an
ultra-relativistic heavy-ion collision. For the partonic phase, we complement
the perturbative results by a phenomenological approach based on lattice QCD
results, whereas in the hadronic phase temperature and finite baryon density
effects on the spectral function are considered. The resulting rates are
compared to data from CERES/NA45.Comment: 4 pages, 3 figures. Talk given at 15th International Conference on
Ultrarelativistic Nucleus-Nucleus Collisions (QM2001), Stony Brook, New York,
15-20 Jan 200
A single-board preprocessor and pulse generator
The Aeronomy Lab. of NOAA has designed and built a single board, programmable radar controller for use with VHF ST (stratosphere troposphere) radars. The controller consists of a coherent integrator preprocessor and a radar pulse generator, both of which are described, as well as interfaces to an antenna beam switch and a receiver bandwidth switch. The controller occupies a single slot in a Data General Nova of Eclipse computer. The integrator and pulse generator take advantage of high density, dual port FIFO chips such as the 512 x 9 Mostek MK 4501. These FIFOs have separate input and output ports and independent read and write cycles with cycle times of less than 200 ns, making them very fast and easy to interface. A simple block diagram of the coherent integrator is shown. The integrator is designed to handle inputs from one receiver (2 channels) with 1 sec sample spacing. The pulse generator is based on controllers designed by R. F. Woodman for the Arecibo and SOUSY radars us a recirculating memory scheme
BILIPROTEINS FROM THE BUTTERFLY Pieris brassicae STUDIED BY TIME-RESOLVED FLUORESCENCE AND COHERENT ANTI-STOKES RAMAN SPECTROSCOPY
The fluorescence decay time of the biliverdin IX7 chromophore present in biliproteins isolated from Pieris brassicae is determined to be 44 ± 3 ps. This value suggests a cyclic helical chromophore structure. The vibrational frequencies determined by CARS-spectroscopy are compared with those of model compounds. The data confirm that the chromophore in the protein-bound state adopts a cyclic-helical, flexible conformation
Scaling of broadband dielectric data of glass-forming liquids and plastic crystals
The Nagel-scaling and the modified scaling procedure proposed recently by
Dendzik et al. have been applied to broadband dielectric data on two glass-
forming liquids (glycerol and propylene carbonate) and three plastic crystals
(ortho-carborane, meta-carborane, and 1-cyano-adamantane). Our data extend the
upper limit of the abscissa range to considerably higher values than in
previously published analyses. At the highest frequencies investigated,
deviations from a single master curve show up which are most pronounced in the
Dendzik-scaling plot. The loss curves of the plastic crystals do not scale in
the Nagel-plot, but they fall onto a separate master curve in the Dendzik-plot.
In addition, we address the question of a possible divergence of the static
susceptibility near the Vogel-Fulcher temperature. For this purpose, the
low-temperature evolution of the high-frequency wing of the dielectric loss
peaks is investigated in detail. No convincing proof for such a divergence can
be deduced from the present broadband data.Comment: 7 pages including 6 figures submitted to Eur. Phys. J.
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