1,125 research outputs found
Effect of the Salmonella Pathogenicity Island 2 Type III Secretion System on Salmonella Survival in Activated Chicken Macrophage-Like HD11 Cells
In order to better identify the role of the Salmonella pathogenicity island 2 (SPI-2) type III secretion system (T3SS) in chickens, we used the well-known gentamicin protection assay with activated HD11 cells. HD11 cells are a macrophage-like chicken cell line that can be stimulated with phorbol 12-myristate 13-acetate (PMA) to exhibit more macrophage-like morphology and greater production of reactive oxygen species (ROS). Activated HD11 cells were infected with a wild-type Salmonella enterica subspecies enterica serovar Typhimurium (S. Typhimurium) strain, a SPI-2 mutant S. Typhimurium strain, a wild-type Salmonella enterica subspecies enterica serovar Enteritidis (S. Enteritidis) strain, a SPI-2 mutant S. Enteritidis strain, or a non-pathogenic Escherichia coli (E. coli) strain. SPI-2 mutant strains were found to survive as well as their parent strain at all time points post-uptake (PU) by the HD11 cells, up to 24 h PU, while the E. coli strain was no longer recoverable by 3 h PU. We can conclude from these observations that the SPI-2 T3SS of S. Typhimurium and S. Enteritidis is not important for survival of Salmonella in the activated macrophage-like HD11 cell line, and that Salmonella must employ other mechanisms for survival in this environment, as E. coli is effectively eliminated
Ray-tracing simulations of a bent crystal X-ray optics for imaging using laser-plasma X-ray sources
Ray-tracing simulations of an optical X-ray system based on a spherically bent crystal operating in Bragg configuration for monochromatic projection imaging of thin samples are presented, obtained using a code developed for that purpose. The code is particularly suited for characterizing experimental arrangements routinely used with laser-produced plasma X-ray sources. In particular, the spatial resolution of the imaging system was investigated and a careful study of the complex pattern of the X-ray backlighting beam was performed
The magnetic properties of Hf and Hf in the strong coupling deformed model
This paper reports NMR measurements of the magnetic dipole moments of two
high-K isomers, the 37/2, 51.4 m, 2740 keV state in Hf and the
8, 5.5 h, 1142 keV state in Hf by the method of on-line nuclear
orientation. Also included are results on the angular distributions of gamma
transitions in the decay of the Hf isotope. These yield high
precision E2/M1 multipole mixing ratios for transitions in bands built on the
23/2, 1.1 s, isomer at 1315 keV and on the 9/2, 0.663 ns, isomer at 321
keV. The new results are discussed in the light of the recently reported
finding of systematic dependence of the behavior of the g parameter
upon the quasi-proton and quasi-neutron make up of high-K isomeric states in
this region.Comment: 9 pages, 9 figures, accepted for publication in Physical Review
Measurement of the magnetic moment of the one-neutron halo nucleus Be
The magnetic moment of Be was measured by detecting nuclear magnetic resonance signals in a beryllium crystal lattice. The experimental technique applied to a Be ion beam from a laser ion source includes in-beam optical polarization, implantation into a metallic single crystal and observation of rf resonances in the asymmetric angular distribution of the -decay (-NMR). The nuclear magnetic moment provides a stringent test for theoretical models describing the structure of the 1/2 neutron halo state
beta-decay study of Cu-77
A beta-decay study of Cu-77 has been performed at the ISOLDE mass separator
with the aim to deduce its beta-decay properties and to obtain spectroscopic
information on Zn-77. Neutron-rich copper isotopes were produced by means of
proton- or neutron-induced fission reactions on U-238. After the production,
Cu-77 was selectively laser ionized, mass separated and sent to different
detection systems where beta-gamma and beta-n coincidence data were collected.
We report on the deduced half-live, decay scheme, and possible spin assignment
of 77Cu
Semiflexible polymer conformation, distribution and migration in microcapillary flows
The flow behavior of a semiflexible polymer in microchannels is studied using
Multiparticle Collision Dynamics (MPC), a particle-based hydrodynamic
simulation technique. Conformations, distributions, and radial cross-streamline
migration are investigated for various bending rigidities, with persistence
lengths Lp in the range 0.5 < Lp/Lr < 30. The flow behavior is governed by the
competition between a hydrodynamic lift force and steric wall-repulsion, which
lead to migration away from the wall, and a locally varying flow-induced
orientation, which drives polymer away from the channel center and towards the
wall. The different dependencies of these effects on the polymer bending
rigidity and the flow velocity results in a complex dynamical behavior.
However, a generic effect is the appearance of a maximum in the monomer and the
center-of-mass distributions, which occurs in the channel center for small flow
velocities, but moves off-center at higher velocities.Comment: in press at J. Phys. Condens. Matte
The Future of Neutrino Mass Measurements: Terrestrial, Astrophysical, and Cosmological Measurements in the Next Decade. Highlights of the NuMass 2013 Workshop. Milano, Italy, February 4 - 7, 2013
The third Workshop of the NuMass series ("The Future of Neutrino Mass
Measurements: Terrestrial, Astrophysical, and Cosmological Measurements in the
Next Decade: NuMass 2013") was held at Dipartimento di Fisica "G. Occhialini,
University of Milano-Bicocca in Milano, Italy, on 4-7 February 2013. The goal
of this international workshop was to review the status and future of direct
and indirect neutrino mass measurements in the laboratory as well as from
astrophysical and cosmological observations. This paper collects most of the
contributions presented during the Workshop
Early onset of ground-state deformation in the neutron-deficient polonium isotopes
In-source resonant ionization laser spectroscopy of the even- polonium
isotopes Po has been performed using the
to ( nm) transition in the polonium atom
(Po-I) at the CERN ISOLDE facility. The comparison of the measured isotope
shifts in Po with a previous data set allows to test for the first
time recent large-scale atomic calculations that are essential to extract the
changes in the mean-square charge radius of the atomic nucleus. When going to
lighter masses, a surprisingly large and early departure from sphericity is
observed, which is only partly reproduced by Beyond Mean Field calculations.Comment: As submitted to PR
Neutron flux and spectrum in the Dresden Felsenkeller underground facility studied by moderated He counters
Ambient neutrons may cause significant background for underground
experiments. Therefore, it is necessary to investigate their flux and energy
spectrum in order to devise a proper shielding. Here, two sets of altogether
ten moderated He neutron counters are used for a detailed study of the
ambient neutron background in tunnel IV of the Felsenkeller facility,
underground below 45 meters of rock in Dresden/Germany. One of the moderators
is lined with lead and thus sensitive to neutrons of energies higher than 10
MeV. For each He counter-moderator assembly, the energy dependent neutron
sensitivity was calculated with the FLUKA code. The count rates of the ten
detectors were then fitted with the MAXED and GRAVEL packages. As a result,
both the neutron energy spectrum from 10 MeV to 300 MeV and the flux
integrated over the same energy range were determined experimentally.
The data show that at a given depth, both the flux and the spectrum vary
significantly depending on local conditions. Energy integrated fluxes of , , and cm
s, respectively, are measured for three sites within Felsenkeller tunnel
IV which have similar muon flux but different shielding wall configurations.
The integrated neutron flux data and the obtained spectra for the three sites
are matched reasonably well by FLUKA Monte Carlo calculations that are based on
the known muon flux and composition of the measurement room walls.Comment: 10 figures, 4 tables; to be published in Phys. Rev.
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