1,210 research outputs found
Simplified techniques for predicting the transmission loss of a circular dissipative silencer
A closed-form analytical solution for the transmission loss of a dissipative silencer with a circular cross-section is described. The silencer contains a bulk reacting acoustic absorbent which is separated from a mean gas flow by a perforated screen. Theoretical predictions of the silencer transmission loss for three different dissipative silencers are compared both with experimental data and with another more complex modelling technique. Good agreement is noted between the analytical theory and experimental data in the low-to-medium frequency range. Below a defined upper frequency limit the analytical technique is also shown to provide good agreement with the finite element method. In addition it is observed that, even for relatively high open area porosities, the perforate screen has a significant effect on dissipative silencer performance
Reanalysis of antiproton production in proton-nucleus and nucleus-nucleus reactions at subthreshold energies
We reanalyse the production of pairs in proton-nucleus and
nucleus-nucleus collisions employing novel elementary cross sections for
baryon-baryon and pion-baryon production channels based on a boson-exchange
model. In contrast to previous transport studies performed in the literature
the secondary pion induced channel is found to be most important in both p+A
and A+A collisions at subthreshold energies. A detailed comparison with the
experimental data available indicates that sizeable attractive
potentials in the order of - 100 to - 150 MeV at normal nuclear matter density
are needed to reproduce the size and shape of the experimental spectra.Comment: 25 pages, latex, including 15 ps-figures, UGI-97-21, submitted to
Nucl. Phys.
Plasma S100A8/A9 Correlates With Blood Neutrophil Counts, Traditional Risk Factors, and Cardiovascular Disease in Middle-Aged Healthy Individuals.
The S100 alarmins A8, A9, and A8/A9, secreted by activated neutrophils and monocytes/macrophages, are involved in the pathogenesis of various inflammatory diseases. S100A8/A9 has previously been linked to atherogenesis and cardiovascular (CV) disease. We investigated whether S100A8, A9, and A8/A9 correlate with carotid artery disease and CV risk in apparently healthy individuals
Antiproton production in and collisions close to threshold
The production of antiprotons in collisions is investigated close to
threshold where experimental data about the total cross section are not
available. We analyze the latter reaction within the LUND string model for
inclusive production and within the framework of a one-boson exchange
model for the exclusive reaction . The application
of our new results to the analysis of subthreshold antiproton production in and collisions shows cross sections that are much lower than
expected before. Nevertheless, the comparison of experimental
differential cross sections from and is expected to provide
valuable information about a nonnucleonic component in the deuteron
wavefunction.Comment: 10 pages, LaTeX, plus 4 postscript figures, Phys. Lett. B, in pres
Relativistic Transport Approach for Nucleus-Nucleus Collisions from SIS to SPS Energies
We formulate a covariant transport approach for high energy nucleus-nucleus
collisions where the real part of the nucleon selfenergies is fitted to nuclear
matter properties which are evaluated on the basis of a NJL-type Lagrangian for
the quark degrees of freedom. The parameters of the quark-model Lagrangian are
fixed by the Gell-Mann, Oakes and Renner relation, the pion- nucleon
-term, the nucleon energy as well as the nuclear binding energy at
saturation density . We find the resulting scalar and vector
selfenergies for nucleons to be well in line with either Dirac-Brueckner
computations for or those from the phenomenological
optical potential when accounting for a swelling of the nucleon at finite
nuclear matter density. The meson-baryon interaction density is modelled to
describe a decrease of the meson mass with baryon density. The imaginary part
of the hadron selfenergies is determined by a string fragmentation model which
accounts for the in-medium mass of hadrons in line with the 'chiral' dynamics
employed. The applicability of the transport approach is demonstrated in
comparison with experimental data from SIS to SPS energies. The enhancement of
the K ratio in A + A collisions compared to p + A reactions at AGS
energies is reproduced within the 'chiral' dynamics. Furthermore, detailed
predictions for the stopping in Pb + Pb collisions at 153 GeV/A are presented.Comment: 1 compressed uuencoded postscript file with 23 figures included, 45
page
A Multi-Phase Transport model for nuclear collisions at RHIC
To study heavy ion collisions at energies available from the Relativistic
Heavy Ion Collider, we have developed a multi-phase transport model that
includes both initial partonic and final hadronic interactions. Specifically,
the parton cascade model ZPC, which uses as input the parton distribution from
the HIJING model, is extended to include the quark-gluon to hadronic matter
transition and also final-state hadronic interactions based on the ART model.
Predictions of the model for central Au on Au collisions at RHIC are reported.Comment: 7 pages, 4 figure
Multistrange baryon production in relativistic heavy ion collisions
Using a multiphase transport model, we study the production of multistrange
baryons from the hadronic matter formed in relativistic heavy ion collisions.
The mechanism we introduce is the strangeness-exchange reactions between
antikaons and hyperons. We find that these reactions contribute significantly
to the production of multistrange baryons in heavy ion collisions at SPS
energies, which has been found to be appreciably enhanced. We have also made
predictions for multistrange baryon production in heavy ion collisions at RHIC
and found a similar enhancement.Comment: 6 pages, RevTex, 8 figs include
Dilepton production in proton-nucleus and nucleus-nucleus collisions at SPS energies
Dilepton production in proton- and nucleus-induced reactions is studied in
relativistic transport model using initial conditions determined by the string
dynamics from RQMD. It is found that both the CERES and HELIOS-3 data for
dilepton spectra in proton-nucleus reactions can be well described by the
`conventional' mechanism of Dalitz decay and direct vector meson decay.
However, to provide a quantitative explanation of the observed dilepton spectra
in central S+Au and S+W collisions requires contributions other than these
direct decays. Introducing a decrease of vector meson masses in hot and dense
medium, we find that these heavy-ion data can also be satisfactorily explained.
This agrees with our earlier conclusions based on a fire cylinder model. We
also give predictions for Pb+Au collisions at 160 GeV/nucleon using current
CERES mass resolution and acceptance.Comment: RevTeX, 45 pages, including 21 postscript figures, to be published in
Nuclear Physics
A systematic review of randomised controlled trials on the effectiveness of exercise programs on lumbo pelvic pain among postnatal women
Background: A substantial number of women tend to be affected by Lumbo Pelvic Pain (LPP) following child birth.
Physical exercise is indicated as a beneficial method to relieve LPP, but individual studies appear to suggest mixed
findings about its effectiveness. This systematic review aimed to synthesise evidence from randomised controlled trials on the effectiveness of exercise on LPP among postnatal women to inform policy, practice and future research.
Methods: A systematic review was conducted of all randomised controlled trials published between January 1990 and July 2014, identified through a comprehensive search of following databases: PubMed, PEDro, Embase, Cinahl, Medline, SPORTDiscus, Cochrane Pregnancy and Childbirth Group’s Trials Register, and electronic libraries of authors’institutions.
Randomised controlled trials were eligible for inclusion if the intervention comprised of postnatal exercise for women
with LPP onset during pregnancy or within 3 months after delivery and the outcome measures included changes in
LPP. Selected articles were assessed using the PEDro Scale for methodological quality and findings were synthesised narratively as meta-analysis was found to be inappropriate due to heterogeneity among included studies.
Results: Four randomised controlled trials were included, involving 251 postnatal women. Three trials were rated as
of ‘good’ methodological quality. All trials, except one, were at low risk of bias. The trials included physical exercise
programs with varying components, differing modes of delivery, follow up times and outcome measures. Intervention
in one trial, involving physical therapy with specific stabilising exercises, proved to be effective in reducing LPP
intensity. An improvement in gluteal pain on the right side was reported in another trial and a significant difference in
pain frequency in another.
Conclusion: Our review indicates that only few randomised controlled trials have evaluated the effectiveness of
exercise on LPP among postnatal women. There is also a great amount of variability across existing trials in the
components of exercise programs, modes of delivery, follow up times and outcome measures. While there is some
evidence to indicate the effectiveness of exercise for relieving LPP, further good quality trials are needed to ascertain
the most effective elements of postnatal exercise programs suited for LPP treatment
Excitation functions of hadronic observables from SIS to RHIC energies
We calculate excitation functions for various dynamical quantities as well as
experimental observables from SIS to RHIC energies within the HSD transport
approach which is based on string, quark, diquark () and hadronic degrees of freedom without including any explicit
phase transition to a quark-gluon plasma (QGP). It is argued that the failure
of this more 'conventional' approach in comparison to experimental data should
indicate the presence of a different phase which might be either attributed to
space-time regions of vanishing scalar quark condensate ( = 0) or
to the presence of a QGP phase with strongly interacting partons. We study the
ratio, the low mass dilepton enhancement in the invariant mass regime
from 0.2 -- 1.2 GeV as well as charmonium suppression for central Au + Au
collisions as a function of the bombarding energy and present predictions for
these observables as well as hadron rapiditiy distributions at RHIC energies.
Whereas all observables studied within HSD show smooth increasing/decreasing
excitation functions, the experimental ratio indicates a maximum at
11 AGeV (or above) which is interpreted as a signature for a chirally
restored phase in the course of the reaction.Comment: 34 pages, LaTeX, including 14 postscript figures (high quality color
versions of figs. 3,4 are available from
http://theorie.physik.uni-giessen.de/~brat/own.html), Nucl. Phys.
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