Thermal analysis of hadron multiplicities from relativistic quantum molecular dynamics

Some questions arising in the application of the thermal model to hadron production in heavy ion collisions are studied. We do so by applying the thermal model of hadron production to particle yields calculated by the microscopic transport model RQMD(v2.3). We study the bias of incomplete information about the final hadronic state on the extraction of thermal parameters.It is found that the subset of particles measured typically in the experiments looks more thermal than the complete set of stable particles. The hadrons which show the largest deviations from thermal behaviour in RQMD(v2.3) are the multistrange baryons and antibaryons. We also looked at the influence of rapidity cuts on the extraction of thermal parameters and found that they lead to different thermal parameters and larger disagreement between the RQMD yields and the thermal model.Comment: 12 pages, 2 figures, uses REVTEX, only misprint and stylistic corrections, to appear in Physical Review

Hydrodynamical assessment of 200 AGeV collisions

We are analyzing the hydrodynamics of 200 A GeV S+S collisions using a new approach which tries to quantify the uncertainties arising from the specific implementation of the hydrodynamical model. Based on a previous phenomenological analysis we use the global hydrodynamics model to show that the amount of initial flow, or initial energy density, cannot be determined from the hadronic momentum spectra. We additionally find that almost always a sizeable transverse flow deve- lops, which causes the system to freeze out, thereby limiting the flow velocity in itself. This freeze-out dominance in turn makes a distinction between a plasma and a hadron resonance gas equation of state very difficult, whereas a pure pion gas can easily be ruled out from present data. To complete the picture we also analyze particle multiplicity data, which suggest that chemical equilibrium is not reached with respect to the strange particles. However, the over- population of pions seems to be at most moderate, with a pion chemical potential far away from the Bose divergence.Comment: 19 pages, 11 figs in separate uuencoded file, for LateX, epsf.tex, dvips, TPR-94-5 and BNL-(no number yet

Mapping out the QCD phase transition in multiparticle production

We analyze multiparticle production in a thermal framework for 7 central nucleus nucleus collisions, $e^+$+ $e^-$ annihilation into hadrons on the Z resonance and 4 hadronic reactions (p+p and p+$\bar{p}$ with partial centrality selec tion), with center of mass energies ranging from $\sqrt{s}$= 2.6 GeV (per nucleon pair) to 1.8 TeV. Thermodynamic parameters at chemical freeze-out (temperature and baryon and strangeness fugacities) are obtained from appropriate fits, generally improving in quality for reactions subjected to centrality cuts. All systems with nonvanishing fugacities are extrapolated along trajectories of equal energy density, density and entropy density to zero fugacities. The so obtained temperatures extrapolated to zero fugacities as a function of initial energy density $\epsilon_{in}$ universally show a strong rise followed by a saturating limit of $T_{lim}$ = 155 $\pm$ 6 $\pm$ 20 MeV. We interpret this behaviour as mapping out the boundary between quark gluon plasma and hadronic phases. The ratio of strange antiquarks to light ones as a function of the initial energy density $\epsilon_{in}$ shows the same behaviour as the temperature, saturating at a value of 0.365 $\pm$ 0.033 $\pm$ 0.07. No distinctive feature of 'strangeness enhancement' is seen for heavy ion collisions relative to hadronic and leptonic reactions, when compared at the same initial energy density

The NA49 large acceptance hadron detector

The NA49 detector is a wide acceptance spectrometer for the study of hadron production in p+p, p+A, and A+A collisions at the CERN SPS. The main components are 4 large volume TPCs for tracking and particle identification via $dE/dx$. TOF scintillator arrays complement particle identification. Calorimeters for transverse energy determination and triggering, a detector for centrality selection in p+A collisions, and beam definition detectors complete the set-up. A description of all detector components is given with emphasis on new technical realizations. Performance and operational experience are discussed in particular with respect to the high track density environment of central Pb+Pb collisions

Comparative analyses imply that the enigmatic sigma factor 54 is a central controller of the bacterial exterior

Contains fulltext : 95738.pdf (publisher's version ) (Open Access)BACKGROUND: Sigma-54 is a central regulator in many pathogenic bacteria and has been linked to a multitude of cellular processes like nitrogen assimilation and important functional traits such as motility, virulence, and biofilm formation. Until now it has remained obscure whether these phenomena and the control by Sigma-54 share an underlying theme. RESULTS: We have uncovered the commonality by performing a range of comparative genome analyses. A) The presence of Sigma-54 and its associated activators was determined for all sequenced prokaryotes. We observed a phylum-dependent distribution that is suggestive of an evolutionary relationship between Sigma-54 and lipopolysaccharide and flagellar biosynthesis. B) All Sigma-54 activators were identified and annotated. The relation with phosphotransfer-mediated signaling (TCS and PTS) and the transport and assimilation of carboxylates and nitrogen containing metabolites was substantiated. C) The function annotations, that were represented within the genomic context of all genes encoding Sigma-54, its activators and its promoters, were analyzed for intra-phylum representation and inter-phylum conservation. Promoters were localized using a straightforward scoring strategy that was formulated to identify similar motifs. We found clear highly-represented and conserved genetic associations with genes that concern the transport and biosynthesis of the metabolic intermediates of exopolysaccharides, flagella, lipids, lipopolysaccharides, lipoproteins and peptidoglycan. CONCLUSION: Our analyses directly implicate Sigma-54 as a central player in the control over the processes that involve the physical interaction of an organism with its environment like in the colonization of a host (virulence) or the formation of biofilm

Conflicts about water: Securitizations in a global context

Albert M, Stetter S, Herschinger E, Teichler T. Conflicts about water: Securitizations in a global context. Cooperation and Conflict. 2011;46(4):441-459.In the current literature in International Relations and Conflict Studies, water as a source of conflict is either extremely over- or exceedingly underrated. In order to account for the dynamics of water conflicts, it is argued in this article that the study of water conflicts should be linked to comprehensive theories of social conflict and world society. A theoretical framework is developed based on a combination of securitization theory, modern systems theory and sociological neo-institutionalism. The usefulness of this framework is illustrated through two empirical cases of water conflicts, namely Spain and Egypt/Sudan. This study contributes to an understanding of the evolution of water conflicts as a result of securitization practices, the dynamics of these conflicts as complex social systems and as the outcome of local adaptations to and of 'world cultural' frames