3,264 research outputs found
Role of heparan sulfate for attachment and entry of tick-borne encephalitis virus
AbstractAttachment of the flavivirus tick-borne encephalitis (TBE) virus to different permissive cell lines was investigated by a newly established quantitative assay using fluorescence-labeled virus. Previous work had shown that BHK-21 cell-adapted mutants of TBE virus had acquired potential heparan sulfate (HS) binding sites on the outer surface of protein E. Quantitative analysis of one of these mutants indicated that it attached to HS-expressing cell lines with a 10- to 13-fold higher affinity than wild-type TBE virus strain Neudoerfl. CHO cells deficient in HS synthesis bound less than 5% of the amount of wild-type or mutant virus that could attach to HS-containing CHO cells but were nevertheless found to be highly susceptible to infection with both viruses. Thus, even though HS is a major determinant of TBE virus attachment on HS-expressing cells, our findings suggest the existence of an alternative host cell receptor that is less abundant than HS
Partonic effects on anisotropic flows at RHIC
We report recent results from a multiphase transport (AMPT) model on the
azimuthal anisotropies of particle momentum distributions in heavy ion
collisions at the Relativistic Heavy Ion Collider. These include higher-order
anisotropic flows and their scaling, the rapidity dependence of anisotropic
flows, and the elliptic flow of charm quarks.Comment: 7 pages, 5 figures, talk given at "Hot Quarks 2004", July 18-24,
2004, Taos Valley, NM, US
A study on the anomaly of over ratios in collisions with jet quenching
The ratios of at large transverse momentum in central
collisions at RHIC are studied in the framework of jet quenching based on a
next-to-leading order pQCD parton model. It is shown that theoretical
calculations with a gluon energy loss larger than the quark energy loss will
naturally lead to a smaller ratios at large transverse momentum in
collisions than those in collisions at the same energy. Scenarios
with equal energy losses for gluons and quarks and a strong jet conversion are
both explored and it is demonstrated in both scenarios ratios at high
in central collisions are enhanced and the calculated ratios of
protons over pions approach to the experimental measurements. However, in the latter scenario is found to fit data better than that in the
former scenario.Comment: 20 pages, 13 figures; revised version; accepted for publication in
Journal of Physics
The role of inhibitory feedback for information processing in thalamocortical circuits
The information transfer in the thalamus is blocked dynamically during sleep,
in conjunction with the occurence of spindle waves. As the theoretical
understanding of the mechanism remains incomplete, we analyze two modeling
approaches for a recent experiment by Le Masson {\sl et al}. on the
thalamocortical loop. In a first step, we use a conductance-based neuron model
to reproduce the experiment computationally. In a second step, we model the
same system by using an extended Hindmarsh-Rose model, and compare the results
with the conductance-based model. In the framework of both models, we
investigate the influence of inhibitory feedback on the information transfer in
a typical thalamocortical oscillator. We find that our extended Hindmarsh-Rose
neuron model, which is computationally less costly and thus siutable for
large-scale simulations, reproduces the experiment better than the
conductance-based model. Further, in agreement with the experiment of Le Masson
{\sl et al}., inhibitory feedback leads to stable self-sustained oscillations
which mask the incoming input, and thereby reduce the information transfer
significantly.Comment: 16 pages, 15eps figures included. To appear in Physical Review
Linking Dynamical and Thermal Models of Ultrarelativistic Nuclear Scattering
To analyse ultrarelativistic nuclear interactions, usually either dynamical
models like the string model are employed, or a thermal treatment based on
hadrons or quarks is applied. String models encounter problems due to high
string densities, thermal approaches are too simplistic considering only
average distributions, ignoring fluctuations. We propose a completely new
approach, providing a link between the two treatments, and avoiding their main
shortcomings: based on the string model, connected regions of high energy
density are identified for single events, such regions referred to as quark
matter droplets. Each individual droplet hadronizes instantaneously according
to the available n-body phase space. Due to the huge number of possible hadron
configurations, special Monte Carlo techniques have been developed to calculate
this disintegration.Comment: Complete paper enclosed as postscript file (uuencoded
Pair correlations in nuclei involved in neutrinoless double beta decay: 76Ge and 76Se
Precision measurements were carried out to test the similarities between the
ground states of 76Ge and 76Se. The extent to which these two nuclei can be
characterized as consisting of correlated pairs of neutrons in a BCS-like
ground state was studied. The pair removal (p,t) reaction was measured at the
far forward angle of 3 degrees. The relative cross sections are consistent (at
the 5% level) with the description of these nuclei in terms of a correlated
pairing state outside the N=28 closed shells with no pairing vibrations. Data
were also obtained for 74Ge and 78Se
Kinetic Equation for Gluons in the Background Gauge of QCD
We derive the quantum kinetic equation for a pure gluon plasma, applying the
background field and closed-time-path method. The derivation is more general
and transparent than earlier works. A term in the equation is found which, as
in the classical case, corresponds to the color charge precession for partons
moving in the gauge field.Comment: RevTex 4, 4 pages, no figure, PRL accepted versio
Nuclear Physics Experiments with Ion Storage Rings
In the last two decades a number of nuclear structure and astrophysics
experiments were performed at heavy-ion storage rings employing unique
experimental conditions offered by such machines. Furthermore, building on the
experience gained at the two facilities presently in operation, several new
storage ring projects were launched worldwide. This contribution is intended to
provide a brief review of the fast growing field of nuclear structure and
astrophysics research at storage rings.Comment: XVIth International Conference on Electro-Magnetic Isotope Separators
and Techniques Related to their Applications, December 2--7, 2012 at Matsue,
Japa
Yang-Mills Radiation in Ultra-relativistic Nuclear Collisions
The classical Yang-Mills radiation computed in the McLerran-Venugopalan model
is shown to be equivalent to the gluon bremsstrahlung distribution to lowest
order in pQCD. The classical distribution is also shown to match smoothly onto
the conventional pQCD mini-jet distribution at a scale characteristic of the
initial parton transverse density of the system. The atomic number and energy
dependence of that scale is computed from available structure function
information. The limits of applicability of the classical Yang-Mills
description of nuclear collisions at RHIC and LHC energies are discussed.Comment: 21 pages (Latex) including 2 postscript figures via psfi
Decay modes of 250No
The Fragment Mass Analyzer at the ATLAS facility has been used to
unambiguously identify the mass number associated with different decay modes of
the nobelium isotopes produced via 204Pb(48Ca,xn)(252-x)No reactions.
Isotopically pure (>99.7%) 204Pb targets were used to reduce background from
more favored reactions on heavier lead isotopes. Two spontaneous fission
half-lives (t_1/2 = 3.7+1.1-0.8 us and 43+22-15 us) were deduced from a total
of 158 fission events. Both decays originate from 250No rather than from
neighboring isotopes as previously suggested. The longer activity most likely
corresponds to a K-isomer in this nucleus. No conclusive evidence for an alpha
branch was observed, resulting in upper limits of 2.1% for the shorter lifetime
and 3.4% for the longer activity.Comment: RevTex4, 10 pages, 5 figures, submitted to PR
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