7,279 research outputs found
Equation of State and Collective Dynamics
This talk summarizes the present status of a program to quantitatively relate
data from the Relativistic Heavy Ion Collider (RHIC) on collective expansion
flow to the Equation of State (EOS) of hot and dense strongly interacting
matter, including the quark-gluon plasma and the quark-hadron phase transition.
The limits reached with the present state of the art and the next steps
required to make further progress will both be discussed.Comment: 8 pages, 6 two-part figures. Invited talk given at the 5th
International Conference on the Physics and Astrophysics of Quark-Gluon
Plasma (ICPAQGP 2005), Kolkata (India), Feb 8-12, 2005. Proceedings to be
published in Journal of Physics: Conference Series (Jan-E Alam et al., eds.
Fusion of Sendai virus with the target cell membrane is required for T cell cytotoxicity
INFECTION of mice with viruses can generate cytotoxic T lymphocytes (CTL) which show restricted specificity for target cell lysis. Specific lysis requires that the virus used to prime the target cells must be of the same type as that used to sensitise the CTL, and that both target and CTL cells must express the same major histocompatability complex (MHC) gene product(s). The nature of the viral gene product(s) and their interaction with the MHC gene product(s) have been the subject of recent stud1−5. Previously we used Sendai virus to show that lysable target cells can be obtained using membrane vesicles which contain only the viral glycoproteins, indicating that these may be the specific viral gene products involved in target formation5. Sendai virus contains two glycoproteins—the haemagglutinin-neuraminidase (HANA) which promotes attachment of virus to cells and the fusion protein (F) which is involved in subsequent virus cell fusion7−9. Both activities are necessary for insertion of these viral glycoproteins into the plasma membrane of the cell10. In this letter we suggest that the insertion of the viral glycoproteins into the cell membrane is an essential step in target cell formation since we can show that virus containing an inactive fusion protein precursor (F0) cannot elicit T cell cytotoxicity unless the fusion activity is generated by proteolytic cleavage of the precursor. Sugamura et al. 6 have suggested that it is primarily the F glycoprotein of the Sendai virus envelope which is essential for the formation of the target antigen, as virus lacking the functional activities of F following trypsin digestion was inactive in priming target cells for T cell killing. However, we show that proteolytic inactivation of either of the two glycoproteins (F or HANA) of virus used to prime target cells will abolish the cytotoxic response
Techniques in Analytic Lamb Shift Calculations
Quantum electrodynamics has been the first theory to emerge from the ideas of
regularization and renormalization, and the coupling of the fermions to the
virtual excitations of the electromagnetic field. Today, bound-state quantum
electrodynamics provides us with accurate theoretical predictions for the
transition energies relevant to simple atomic systems, and steady theoretical
progress relies on advances in calculational techniques, as well as numerical
algorithms. In this brief review, we discuss one particular aspect connected
with the recent progress: the evaluation of relativistic corrections to the
one-loop bound-state self-energy in a hydrogenlike ion of low nuclear charge
number, for excited non-S states, up to the order of alpha (Zalpha)^6 in units
of the electron mass. A few details of calculations formerly reported in the
literature are discussed, and results for 6F, 7F, 6G and 7G states are given.Comment: 16 pages, LaTe
Annual Report 2005 - Institute of Radiochemistry
The Institute of Radiochemistry (IRC), one of the six institutes of the Forschungszentrum Rossendorf (FZR), performs application-oriented research in the fields of radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Due to their high radiotoxicity and long half-life the actinides are of special interest. Hence our research focuses on the chemical behavior of actinides at the molecular level in order to predict the relevant macroscopic processes in the environment. Within this framework, special emphasis is on the interface between geological and biological systems. In the last year our research topics were as follows: # Aquatic chemistry of actinides # Actinides in bio-systems # Interaction of actinides with solid phases # Reactive transport of actinides About 60 scientists, technicians and PhD students are employed in the Institute of Radiochemistry. We have achieved a wide range of new scientific results in the past year, which are presented in this Annual Report. Among them only a few can be highlighted here in this preface. For the first time it was possible to determine uranium speciation in situ in drinking and mineral waters e.g. by a dedicated fluorescence spectrometer at lowest µg/L concentrations. This methodical progress is an important prerequisite to study the uranium toxicity and its dependence on chemical speciation. We were very successful in the determination of formation pathways and structure of various actinide complexes, e.g., the surface complexes of uranium (VI) onto mica and iron hydroxides over a wide range of pH and carbonate concentration. These results contribute to a better understanding of actinide speciation in geo- and bio-systems, especially with respect to the chemical processes on the interfaces. Studies to the interaction of uranium with biofilms, green algae and bacteria coming from extreme habitats extended our research on the field of bio-systems. Major progress in the structural analysis of multiple uranium species has been achieved by applying Monte Carlo simulations and iterative transformation factor analysis to EXAFS spectroscopy. Furthermore, our new radiochemical experimental station at the Free Electron Laser of the Rossendorf accelerator ELBE is now in full operation. We have started first experiments on the uranium and neptunium complexation on selected mineral surfaces
Optimal quantum control in nanostructures: Theory and application to generic three-level system
Coherent carrier control in quantum nanostructures is studied within the
framework of Optimal Control. We develop a general solution scheme for the
optimization of an external control (e.g., lasers pulses), which allows to
channel the system's wavefunction between two given states in its most
efficient way; physically motivated constraints, such as limited laser
resources or population suppression of certain states, can be accounted for
through a general cost functional. Using a generic three-level scheme for the
quantum system, we demonstrate the applicability of our approach and identify
the pertinent calculation and convergence parameters.Comment: 7 pages; to appear in Phys. Rev.
Quantum Mechanical Carrier of the Imprints of Gravitation
We exhibit a purely quantum mechanical carrier of the imprints of gravitation
by identifying for a relativistic system a property which (i) is independent of
its mass and (ii) expresses the Poincare invariance of spacetime in the absence
of gravitation. This carrier consists of the phase and amplitude correlations
of waves in oppositely accelerating frames. These correlations are expressed as
a Klein-Gordon-equation-determined vector field whose components are the
``Planckian power'' and the ``r.m.s. thermal fluctuation'' spectra. The
imprints themselves are deviations away from this vector field.Comment: 8 pages, RevTex. Html version of this and related papers on
accelerated frames available at http://www.math.ohio-state.edu/~gerlac
Cosmic Rays at the highest energies
After a century of observations, we still do not know the origin of cosmic
rays. I will review the current state of cosmic ray observations at the highest
energies, and their implications for proposed acceleration models and secondary
astroparticle fluxes. Possible sources have narrowed down with the confirmation
of a GZK-like spectral feature. The anisotropy observed by the Pierre Auger
Observatory may signal the dawn of particle astronomy raising hopes for high
energy neutrino observations. However, composition related measurements point
to a different interpretation. A clear resolution of this mystery calls for
much larger statistics than the reach of current observatories.Comment: 8 pages, 4 figures, in the Proceedings of TAUP 201
Modified Signals for Supersymmetry in the NMSSM with a Singlino-like LSP
In the framework of the NMSSM with a singlino-like LSP, we study
quantitatively the impact of the additional bino -> singlino cascade on the
efficiencies in several search channels for supersymmetry of the ATLAS and CMS
collaborations. Compared to the MSSM, the additional cascade reduces the
missing transverse energy, but leads to additional jets or leptons. For the
NMSSM benchmark lines which generalize cMSSM benchmark points, the efficiencies
in the most relevant 2/3 jet + missing energy search channels can drop by
factors ~1/3 to ~1/7, and can reduce the present lower bounds on M_{1/2} by as
much as ~0.9 - 0.75 in the NMSSM for large bino-singlino mass differences. The
larger efficiencies in multijet or multilepton search channels are not strong
enough to affect this conclusion. In the fully constrained cNMSSM, sparticle
decay cascades via the lightest stau can lead to signal cross sections in
multilepton and 2tau search channels which are potentially visible at the LHC
with 7 TeV center of mass energy.Comment: 24 pages, 9 Figures, misprint in Table 1 correcre
MetaboLab - advanced NMR data processing and analysis for metabolomics
Background\ud
Despite wide-spread use of Nuclear Magnetic Resonance (NMR) in metabolomics for the analysis of biological samples there is a lack of graphically driven, publicly available software to process large one and two-dimensional NMR data sets for statistical analysis.\ud
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Results\ud
Here we present MetaboLab, a MATLAB based software package that facilitates NMR data processing by providing automated algorithms for processing series of spectra in a reproducible fashion. A graphical user interface provides easy access to all steps of data processing via a script builder to generate MATLAB scripts, providing an option to alter code manually. The analysis of two-dimensional spectra (1H,13C-HSQC spectra) is facilitated by the use of a spectral library derived from publicly available databases which can be extended readily. The software allows to display specific metabolites in small regions of interest where signals can be picked. To facilitate the analysis of series of two-dimensional spectra, different spectra can be overlaid and assignments can be transferred between spectra. The software includes mechanisms to account for overlapping signals by highlighting neighboring and ambiguous assignments.\ud
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Conclusions\ud
The MetaboLab software is an integrated software package for NMR data processing and analysis, closely linked to the previously developed NMRLab software. It includes tools for batch processing and gives access to a wealth of algorithms available in the MATLAB framework. Algorithms within MetaboLab help to optimize the flow of metabolomics data preparation for statistical analysis. The combination of an intuitive graphical user interface along with advanced data processing algorithms facilitates the use of MetaboLab in a broader metabolomics context.\ud
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