294 research outputs found
Collective effects in microscopic transport models
We give a reminder on the major inputs of microscopic hadronic transport
models and on the physics aims when describing various aspects of relativistic
heavy ion collisions at SPS energies. We then first stress that the situation
of particle ratios being reproduced by a statistical description does not
necessarily mean a clear hint for the existence of a fully isotropic momentum
distribution at hadrochemical freeze-out. Second, a short discussion on the
status of strangeness production is given. Third we demonstrate the importance
of a new collective mechanism for producing (strange) antibaryons within a
hadronic description, which guarantees sufficiently fast chemical
equilibration.Comment: 10 pages, 8 figures; invited talk at the 16th Int. Conf. on
Ultra-Relativistic Nucleus-Nucleus Collisions, QM2002, Nantes, France, 18-24
Jul
Dilepton Enhancement by Thermal Pion Annihilation in the CERES Experiment
We compare the recent CERES data on dielectron production in 200 GeV/u S+Au
collisions with the theoretical predictions due to pion annihilation in a
thermal hadronization and a string fragmentation scenario. Both models yield
similar results for the dilepton mass spectrum. A satisfactory description of
the experimental spectrum requires an in-medium reduction of the rho-mass and a
freeze-out temperature of about 150 MeV in the thermal model. We emphasize and
discuss the influence of experimental acceptance and resolution corrections.Comment: 9 pages, RevTex, 4 eps figures, To appear in Phys. Lett.
Specific antibody-receptor interactions trigger InlAB-independent uptake of listeria monocytogenes into tumor cell lines
<p>Abstract</p> <p>Background</p> <p>Specific cell targeting is an important, yet unsolved problem in bacteria-based therapeutic applications, like tumor or gene therapy. Here, we describe the construction of a novel, internalin A and B (InlAB)-deficient <it>Listeria monocytogenes </it>strain (Lm-spa<sup>+</sup>), which expresses protein A of <it>Staphylococcus aureus </it>(SPA) and anchors SPA in the correct orientation on the bacterial cell surface.</p> <p>Results</p> <p>This listerial strain efficiently binds antibodies allowing specific interaction of the bacterium with the target recognized by the antibody. Binding of Trastuzumab (Herceptin<sup>®</sup>) or Cetuximab (Erbitux<sup>®</sup>) to Lm-spa<sup>+</sup>, two clinically approved monoclonal antibodies directed against HER2/neu and EGFR/HER1, respectively, triggers InlAB-independent internalization into non-phagocytic cancer cell lines overexpressing the respective receptors. Internalization, subsequent escape into the host cell cytosol and intracellular replication of these bacteria are as efficient as of the corresponding InlAB-positive, SPA-negative parental strain. This specific antibody/receptor-mediated internalization of Lm-spa<sup>+ </sup>is shown in the murine 4T1 tumor cell line, the isogenic 4T1-HER2 cell line as well as the human cancer cell lines SK-BR-3 and SK-OV-3. Importantly, this targeting approach is applicable in a xenograft mouse tumor model after crosslinking the antibody to SPA on the listerial cell surface.</p> <p>Conclusions</p> <p>Binding of receptor-specific antibodies to SPA-expressing <it>L. monocytogenes </it>may represent a promising approach to target <it>L. monocytogenes </it>to host cells expressing specific receptors triggering internalization.</p
Shigella Mediated Depletion of Macrophages in a Murine Breast Cancer Model Is Associated with Tumor Regression
A tumor promoting role of macrophages has been described for a transgenic murine breast cancer model. In this model tumor-associated macrophages (TAMs) represent a major component of the leukocytic infiltrate and are associated with tumor progression. Shigella flexneri is a bacterial pathogen known to specificly induce apotosis in macrophages. To evaluate whether Shigella-induced removal of macrophages may be sufficient for achieving tumor regression we have developed an attenuated strain of S. flexneri (M90TΔaroA) and infected tumor bearing mice. Two mouse models were employed, xenotransplantation of a murine breast cancer cell line and spontanous breast cancer development in MMTV-HER2 transgenic mice. Quantitative analysis of bacterial tumor targeting demonstrated that attenuated, invasive Shigella flexneri primarily infected TAMs after systemic administration. A single i.v. injection of invasive M90TΔaroA resulted in caspase-1 dependent apoptosis of TAMs followed by a 74% reduction in tumors of transgenic MMTV-HER-2 mice 7 days post infection. TAM depletion was sustained and associated with complete tumor regression
Thermodynamical Properties of a Spin 1/2 Heisenberg Chain Coupled to Phonons
We performed a finite-temperature quantum Monte Carlo simulation of the
one-dimensional spin-1/2 Heisenberg model with nearest-neighbor interaction
coupled to Einstein phonons. Our method allows to treat easily up to 100
phonons per site and the results presented are practically free from truncation
errors. We studied in detail the magnetic susceptibility, the specific heat,
the phonon occupation, the dimerization, and the spin-correlation function for
various spin-phonon couplings and phonon frequencies. In particular we give
evidence for the transition from a gapless to a massive phase by studying the
finite-size behavior of the susceptibility. We also show that the dimerization
is proportional to for .Comment: 10 pages, 17 Postscript Figure
Probing hadronic formation times with antiprotons in p+A reactions at AGS energies
The production of antiprotons in reactions is calculated in a
microscopic transport approach employing hadronic and string degrees of freedom
(HSD). It is found that the abundancies of antiprotons as observed by the E910
Collaboration in reactions at 12.3 GeV/c as well as 17.5 GeV/c can
approximately be described on the basis of primary proton-nucleon and secondary
meson-baryon production channels for all targets. The transport calculations
demonstrate that the antiproton rapidity distributions for heavy targets are
sensitive to the (or hadron) formation time in the nuclear medium.
Within our analysis the data from the E910 Collaboration are reasonably
described with a formation time of fm/c in the hadron rest frame.Comment: 18 pages, LaTeX, 8 postscript figures; submitted to Nucl. Phys.
Dilepton Production at SPS-energy Heavy Ion Collisions
The production of dileptons is studied within a hadronic transport model. We
investigate the sensitivity of the dilepton spectra to the initial
configuration of the hadronic phase in a ultrarelativistic heavy ion collision.
Possible in medium correction due to the modifications of pions and the pion
form factor in a hadronic gas are discussed.Comment: Dedicated to Gerry Brown in honor of the 32nd celebration of his 39th
birthday. 31 pages Latex including 13 eps-figures, uses psfig.sty and
epsf.st
Two-orbital SU(N) magnetism with ultracold alkaline-earth atoms
Fermionic alkaline-earth atoms have unique properties that make them
attractive candidates for the realization of novel atomic clocks and degenerate
quantum gases. At the same time, they are attracting considerable theoretical
attention in the context of quantum information processing. Here we demonstrate
that when such atoms are loaded in optical lattices, they can be used as
quantum simulators of unique many-body phenomena. In particular, we show that
the decoupling of the nuclear spin from the electronic angular momentum can be
used to implement many-body systems with an unprecedented degree of symmetry,
characterized by the SU(N) group with N as large as 10. Moreover, the interplay
of the nuclear spin with the electronic degree of freedom provided by a stable
optically excited state allows for the study of spin-orbital physics. Such
systems may provide valuable insights into strongly correlated physics of
transition metal oxides, heavy fermion materials, and spin liquid phases.Comment: 15 pages, 10 figures. V2: extended experimental accessibility and
Kondo sections in the main text (including new Fig. 5b) and in the Methods;
reorganized other parts; added reference
SQM 2006: Theory Summary and Perspectives
In this write-up of my SQM 2006 Theory Summary talk I focus on a selection of
key contributions which I consider to have a large impact on the current status
of the field of strangeness physics or which may have the potential to
significantly advance strangeness -- or in general flavor physics -- in the
near future.Comment: 16 pages, 4 figures, SQM 2006 proceedings. Revised version containing
two modifications to the transport theory sectio
Disoriented Chiral Condensate: Theory and Experiment
It is thought that a region of pseudo-vacuum, where the chiral order
parameter is misaligned from its vacuum orientation in isospin space, might
occasionally form in high energy hadronic or nuclear collisions. The possible
detection of such disoriented chiral condensate (DCC) would provide useful
information about the chiral structure of the QCD vacuum and/or the chiral
phase transition of strong interactions at high temperature. We review the
theoretical developments concerning the possible DCC formation in high-energy
collisions as well as the various experimental searches that have been
performed so far. We discuss future prospects for upcoming DCC searches, e.g.
in high-energy heavy-ion collision experiments at RHIC and LHC.Comment: 120 pages, 52 figures. Uses elsart.cls. To appear in Physics Reports.
Minor corrections, references adde
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