1,615 research outputs found
Analysis of flow effects in relativistic heavy-ion collisions within the CBUU approach
We study flow phenomena in relativistic heavy-ion collisions, both in
transverse and radial direction, in comparison to experimental data. The
collective dynamics of the nucleus-nucleus collision is described within a
transport model of the coupled channel BUU type (CBUU). This recently developed
version includes all nucleonic resonances up to 1.95 GeV in mass and mean-field
potentials both of the Skyrme and momentum dependent MDYI type. We find that
heavy resonances play an important role in the description of transverse flow
above 1 AGeV incident energy. For radial flow we analyse reaction times and
equilibration and extract the parameters and for temperature and
collective flow velocity within different prescriptions. Furthermore, we apply
a coalescence model for fragment production and check the mass dependence of
the flow signals.Comment: 25 pages, 17 figures, submitted to Europ. Phys. J.
Photoabsorption on nuclei
We calculate the total photoabsorption cross section on nuclei in the energy
range from 300 MeV to 1 GeV within the framework of a semi-classical phase
space model. Besides medium modifications like Fermi motion and Pauli blocking
we focus on the collision broadening of the involved resonances. The resonance
contributions to the elementary cross section are fixed by fits to partial wave
amplitudes of pion photoproduction. The cross sections for ,
needed for the calculation of collision broadening, are obtained by detailed
balance from a fit to cross sections. We show that a
reasonable collision broadening is not able to explain the experimentally
observed disappearance of the -resonance in the photoabsorption
cross section on nuclei.Comment: 26 pages Latex including 9 postscript figure
Photoproduction of pions and etas in nuclei
We calculate the cross sections for inclusive one-pion, two-pion and eta
photoproduction in nuclei in the photon energy range from 300 MeV to 900 MeV
within the framework of a semi-classical BUU transport model. Our results are
compared with existing experimental data and discussed with respect to a
calculation of the total photoabsorption cross section.Comment: 30 pages LaTeX including 13 postscript figure
Оценка потоков тяжёлых металлов (Hg, Cd, Se, Pb) и As из атмосферы на снежный покров в окрестностях теплоэлектростанции (на примере г. Томска)
Increased azithromycin susceptibility of multidrug-resistant gram-negative bacteria on RPMI-1640 agar assessed by disk diffusion testing
Increasing antibiotic resistances and a lack of new antibiotics render the treatment of Gram-negative bacterial infections increasingly difficult. Therefore, additional approaches are being investigated. Macrolides are not routinely used against Gram-negative bacteria due to lack of evidence of in vitro effectiveness. However, it has been shown that Pseudomonas spp. are susceptible to macrolides in liquid RPMI-1640 and clinical data suggest improvement in patients' outcomes. So far, these findings have been hardly applicable to the clinical setting due to lack of routine low-complexity antimicrobial susceptibility testing (AST) for macrolides. We therefore optimized and compared broth microdilution and disk diffusion AST. Multidrug-resistant Gram-negative bacteria (Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Pseudomonas aeruginosa) were tested for azithromycin susceptibility by disk diffusion and broth microdilution in Mueller-Hinton and RPMI-1640 media. Azithromycin susceptibility of Enterobacteriaceae and a subgroup of P. aeruginosa increased significantly on RPMI-1640 agar compared to Mueller-Hinton agar. Further, a significant correlation (Kendall, τ, p) of zone diameters and minimal inhibitory concentrations (MICs) was found on RPMI-1640 agar for E. coli (-0.4279, 0.0051), E. cloacae (-0.3783, 0.0237) and P. aeruginosa (-0.6477, <0.0001). Performing routine disk diffusion AST on RPMI-1640 agar may lead to the identification of additional therapeutic possibilities for multidrug-resistant bacterial infections in the routine clinical diagnostic setting
Exposure to a Mixture of Polychlorinated Biphenyls and Polychlorinated Dibenzofurans Resulted in a Prolonged Time to Pregnancy in Women
Probing nuclear expansion dynamics with -spectra
We study the dynamics of charged pions in the nuclear medium via the ratio of
differential - and -spectra in a coupled-channel BUU (CBUU)
approach. The relative energy shift of the charged pions is found to correlate
with the pion freeze-out time in nucleus-nucleus collisions as well as with the
impact parameter of the heavy-ion reaction. Furthermore, the long-range Coulomb
force provides a 'clock' for the expansion of the hot nuclear system. Detailed
comparisons with experimental data for at 1 GeV/A and at
2.0 GeV/A are presented.Comment: 21 pages, latex, figures include
Hadron formation in high energy photonuclear reactions
We present a new method to account for coherence length effects in a
semi-classical transport model. This allows us to describe photo- and
electroproduction at large nuclei (A>12) and high energies using a realistic
coupled channel description of the final state interactions that goes beyond
simple Glauber theory. We show that the purely absorptive treatment of the
final state interactions can lead to wrong estimates of color transparency and
formation time effects in particle production. As an example, we discuss
exclusive rho^0 photoproduction on Pb at a photon energy of 7 GeV as well as
K^+ production in the photon energy range 1-7 GeV.Comment: 14 pages, 6 figures, version published in Phys. Rev.
Pion-Production in Heavy-Ion Collisions at SIS energies
We investigate the production of pions in heavy-ion collisions in the energy
range of - GeV/A. The dynamics of the nucleus-nucleus collisions is
described by a set of coupled transport equations of the
Boltzmann-Uehling-Uhlenbeck type for baryons and mesons. Besides the
and the we also take into account nucleon resonances up to
masses of as well as -, - and -mesons. We study
in detail the influence of the higher baryonic resonances and the
-production channels () on the pion spectra in
comparison to data from collisions at GeV/A and
-data for at 1.0 GeV/A. We, furthermore, present a detailed
comparison of differential pion angular distributions with the BEVALAC data for
Ar + KCl at 1.8 GeV/A. The general agreement obtained indicates that the
overall reactions dynamics is well described by our novel transport approach.Comment: 31 pages, 18 figures (inlcuded), to appear in Z. Phys.
- …