16,302 research outputs found
Chemical freezeout in relativistic A+A collisions: is it close to the QGP?
Preliminary experimental data for particle number ratios in the collisions of Au+Au at the BNL AGS (11A GeV/c) and Pb+Pb at the CERN SPS (160A GeV/c) are analyzed in a thermodynamically consistent hadron gas model with excluded volume. Large values of temperature, T = 140 185 MeV, and baryonic chemical potential, µb = 590 270 MeV, close to the boundary of the quark-gluon plasma phase are found from fitting the data. This seems to indicate that the energy density at the chemical freezeout is tremendous which would be indeed the case for the point-like hadrons. However, a self-consistent treatment of the van der Waals excluded volume reveals much smaller energy densities which are very far below a lowest limit estimate of the quark-gluon plasma energy density. PACS number(s): 25.75.-q, 24.10.P
Time-domain Brillouin Scattering as a Local Temperature Probe in Liquids
We present results of time-domain Brillouin scattering (TDBS) to determine
the local temperature of liquids in contact to an optical transducer. TDBS is
based on an ultrafast pump-probe technique to determine the light scattering
frequency shift caused by the propagation of coherent acoustic waves in a
sample. Since the temperature influences the Brillouin scattering frequency
shift, the TDBS signal probes the local temperature of the liquid. Results for
the extracted Brillouin scattering frequencies recorded at different liquid
temperatures and at different laser powers - i.e. different steady state
background temperatures- are shown to demonstrate the usefulness of TDBS as a
temperature probe. This TDBS experimental scheme is a first step towards the
investigation of ultrathin liquids measured by GHz ultrasonic probing.Comment: arXiv admin note: substantial text overlap with arXiv:1702.0107
Curvature-induced spin-orbit coupling and spin relaxation in a chemically clean single-layer graphene
The study of spin-related phenomena in materials requires knowledge on the
precise form of effective spin-orbit coupling of conducting carriers in the
solid-states systems. We demonstrate theoretically that curvature induced by
corrugations or periodic ripples in single-layer graphenes generates two types
of effective spin-orbit coupling. In addition to the spin-orbit coupling
reported previously that couples with sublattice pseudospin and corresponds to
the Rashba-type spin-orbit coupling in a corrugated single-layer graphene,
there is an additional spin-orbit coupling that does not couple with the
pseudospin, which can not be obtained from the extension of the
curvature-induced spin-orbit coupling of carbon nanotubes. Via numerical
calculation we show that both types of the curvature-induced spin-orbit
coupling make the same order of contribution to spin relaxation in chemically
clean single-layer graphene with nanoscale corrugation. The spin relaxation
dependence on the corrugation roughness is also studied.Comment: 8 pages, 4 figure
A COMPARISON OF ACCURACY AND STROKE CHARACTERISTICS BETWEEN TWO PUTTING GRIP TECHNIQUES
Nowadays PGA golfers are experimenting with various golf putting grips. The purpose of this study was to investigate the traits of using two putting grips; reverse overlapping grip and finger bone grip at three different putting distances. 20 subjects with no previous golf experience participated in this study. The kinematic data of the subject and the putter’s shaft and head was recorded by 8 Qualisys cameras at 100Hz. There was no significant difference between the success rate of getting the ball in the hole at all distances. The finger bone grip produced statistically smaller radial error values than the reverse overlapping grip at the distances for 7 and 11 metres. The finger bone grip provided straighter putter head trajectories and less change in the movement of the COG, which implies more stability of the player and that the ball will travel in the desired path. In conclusion, the finger bone putting technique gave radial errors less than the reverse overlapping grip technique which seems to be due to the added stability and straighter putter head trajectories
First-principles study on the intermediate compounds of LiBH
We report the results of the first-principles calculation on the intermediate
compounds of LiBH. The stability of LiBH and LiBH has been examined with the ultrasoft pseudopotential method based on
the density functional theory. Theoretical prediction has suggested that
monoclinic LiBH is the most stable among the candidate
materials. We propose the following hydriding/dehydriding process of LiBH
via this intermediate compound : LiBHLiBH LiH HLiH B H. The hydrogen content and enthalpy of the first
reaction are estimated to be 10 mass% and 56 kJ/mol H, respectively, and
those of the second reaction are 4 mass% and 125 kJ/mol H. They are in good
agreement with experimental results of the thermal desorption spectra of
LiBH. Our calculation has predicted that the bending modes for the
-phonon frequencies of monoclinic LiBH are lower than
that of LiBH, while stretching modes are higher. These results are very
useful for the experimental search and identification of possible intermediate
compounds.Comment: 7 pages, 5 figures, submitted to PR
Collective patterns arising out of spatio-temporal chaos
We present a simple mathematical model in which a time averaged pattern
emerges out of spatio-temporal chaos as a result of the collective action of
chaotic fluctuations. Our evolution equation possesses spatial translational
symmetry under a periodic boundary condition. Thus the spatial inhomogeneity of
the statistical state arises through a spontaneous symmetry breaking. The
transition from a state of homogeneous spatio-temporal chaos to one exhibiting
spatial order is explained by introducing a collective viscosity which relates
the averaged pattern with a correlation of the fluctuations.Comment: 11 pages (Revtex) + 5 figures (postscript
Asymmetric Fermi superfluid with different atomic species in a harmonic trap
We study the dilute fermion gas with pairing between two species and unequal
concentrations in a harmonic trap using the mean field theory and the local
density approximation. We found that the system can exhibit a superfluid shell
structure sandwiched by the normal fermions. This superfluid shell structure
occurs if the mass ratio is larger then certain critical value which increases
from the weak-coupling BCS region to the strong-coupling BEC side. In the
strong coupling BEC regime, the radii of superfluid phase are less sensitive to
the mass ratios and are similar to the case of pairing with equal masses.
However, the lighter leftover fermions are easier to mix with the superfluid
core than the heavier ones. A partially polarized superfluid can be found if
the majority fermions are lighter, whereas phase separation is still found if
they are heavier.Comment: 12 pages, 7 figure
Effect of Extraction Methods on Antifungal Activity of Sea Cucumber (Stichopus Japonicus)
The objective of this study was to investigate the antifungal activity of the soluble matter (SM) and crude saponins (CS) extracted from Stichopus japonicus using pressurized solvent extraction (PSE) with water or aqueous ethanol as a solvent, in comparison with traditional heat reflux extraction (HRE). The extraction yields were also determined for the SM and CS and compared for each extraction process and solvent. The antifungal activity of the SM and CS, extracted from the body wall of Stichopus japonicus using PSE or HRE with water or 70% aqueous ethanol, were investigated. Both SM and CS exhibited their highest antifungal activity when extracted by HRE with 70% ethanol and by HRE with water, respectively, while their highest yields were obtained when extracted by PSE with water. SM has more antifungal than potassium sorbate but weaker than propyl paraben, while CS has more antifungal than the two antifungal agents
Collimated Jet or Expanding Outflow: Possible Origins of GRBs and X-Ray Flashes
We investigate the dynamics of an injected outflow propagating in a
progenitor in the context of the collapsar model for gamma-ray bursts (GRBs)
through two dimensional axisymmetric relativistic hydrodynamic simulations.
Initially, we locally inject an outflow near the center of a progenitor. We
calculate 25 models, in total, by fixing its total input energy to be 10^{51}
ergs s^{-1} and radius of the injected outflow to be cm while
varying its bulk Lorentz factor, , and its specific
internal energy, . The injected outflow propagates
in the progenitor and drives a large-scale outflow or jet. We find a smooth but
dramatic transition from a collimated jet to an expanding outflow among
calculated models. The maximum Lorentz factor is, on the other hand, sensitive
to both of and ; roughly . Our finding will explain a smooth transition between the
GRBs, X-ray rich GRBs (XRRs) and X-ray Flashes (XRFs) by the same model but
with different values.Comment: Comments 51 pages, 21 figures. accepted for publication in ApJ high
resolution version is available at
http://www.mpa-garching.mpg.de/~mizuta/COLLAPSAR/collapsar.htm
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