5,196 research outputs found
Chemical Equilibration and the Hadron-QGP Phase Transition
We discuss recent experimental results on hadron multiplicities in
ultra-relativistic nuclear collisions. The data for central collisions are in
quantitative agreement with predictions of a thermal model assuming full
chemical equilibration. It is argued that this provides strong, albeit
indirect, evidence for the formation of a partonic phase in the collision prior
to hadron production.Comment: Contribution to CRIS2000 conference, to be published in Nucl. Phys.
Pseudo resonance induced quasi-periodic behavior in stochastic threshold dynamics
Here we present a simple stochastic threshold model consisting of a
deterministic slowly decaying term and a fast stochastic noise term. The
process shows a pseudo-resonance, in the sense that for small and large
intensities of the noise the signal is irregular and the distribution of
threshold crossings is broad, while for a tuned intermediate value of noise
intensity the signal becomes quasi-periodic and the distribution of threshold
crossings is narrow. The mechanism captured by the model might be relevant for
explaining apparent quasi-periodicity of observed climatic variations where no
internal or external periodicities can be identified.Comment: 8 pages, 4 figures, to appear in Stochastics and Dynamic
Physics of Ultra-Relativistic Nuclear Collisions with Heavy Beams at LHC Energy
We discuss current plans for experiments with ultra-relativistic nuclear
collisions with heavy beams at LHC energy ( TeV/nucleon pair).
Emphasis will be placed on processes which are unique to the LHC program. They
include event-by-event interferometry, complete spectroscopy of the
resonances, and open charm and open beauty measurements.Comment: 11 pages, 6 figures, Quark Matter 99 conference contribution, Nucl.
Phys. A to be publishe
The migration process of mobile agents: implementation, classification, and optimization
Mobile Agenten stellen ein neues faszinierendes Design-Paradigma fĂŒr den Aufbau und die Programmierung von verteilten Systemen dar. Ein mobiler Agent ist eine Software-EntitĂ€t, die von ihrem Besitzer mit einem Auftrag auf einem Knoten eines verteilten Systems gestartet wird und dann zur Laufzeit auf andere Knoten des Netzwerkes migriert. Diese Arbeit konzentriert sich auf den Migrationsprozess fĂŒr mobile Agenten, dem in der Literatur bisher wenig Aufmerksamkeit geschenkt wurde, obwohl er die AusfĂŒhrungsgeschwindigkeit eines Agenten entscheidend beeinflusst. Eine detaillierte Analyse der Netzbelastung von mobilen Agenten im Vergleich zum traditionellen Client-Server Ansatz in mehreren typischen Anwendungsszenarien zeigt das Potential von mobilen Agenten zur Verringerung von Verarbeitungszeiten. Allerdings zeigt die Analyse ebenso die Nachteile der in heutigen Agentensystemen verwendenten sehr einfachen Migrationstechniken. Es wird ein neues Migrationsmodell mit Namen Kalong vorgestellt, das den Nachteil der fehlenden Anpassbarkeit heutiger Agentensysteme beseitigt und dem Programmierer eines mobilen Agenten eine sehr flexible Technik fĂŒr die Migration zur VerfĂŒgung stellt
Confronting fluctuations of conserved charges in central nuclear collisions at the LHC with predictions from Lattice QCD
We construct net baryon number and strangeness susceptibilities as well as
correlations between electric charge and strangeness from experimental data of
the ALICE Collaboration at the CERN LHC. The data were taken in Pb-Pb
collisions at =2.76 TeV. The resulting fluctuations and
correlations are consistent with Lattice QCD results at the chiral crossover
pseudocritical temperature MeV. This agreement lends strong
support to the assumption that the fireball created in these collisions is of
thermal origin and exhibits characteristic properties expected in QCD at the
transition from the quark gluon plasma to the hadronic phase. The volume of the
fireball for one unit of rapidity at is found to exceed 4000 fm. A
detailed discussion on uncertainties in the temperature and volume of the
fireball is presented. The results are linked to pion interferometry
measurements and predictions from percolation theory.Comment: 7 pages, 4 figures Accepted for publication in PL
Semiclassical Prediction of Large Spectral Fluctuations in Interacting Kicked Spin Chains
While plenty of results have been obtained for single-particle quantum
systems with chaotic dynamics through a semiclassical theory, much less is
known about quantum chaos in the many-body setting. We contribute to recent
efforts to make a semiclassical analysis of many-body systems feasible. This is
nontrivial due to both the enormous density of states and the exponential
proliferation of periodic orbits with the number of particles. As a model
system we study kicked interacting spin chains employing semiclassical methods
supplemented by a newly developed duality approach. We show that for this model
the line between integrability and chaos becomes blurred. Due to the
interaction structure the system features (non-isolated) manifolds of periodic
orbits possessing highly correlated, collective dynamics. As with the invariant
tori in integrable systems, their presence lead to significantly enhanced
spectral fluctuations, which by order of magnitude lie in-between integrable
and chaotic cases.Comment: 42 pages, 19 figure
Respiratory electron transfer pathways in plant mitochondria
The respiratory electron transport chain (ETC) couples electron transfer from organic substrates onto molecular oxygen with proton translocation across the inner mitochondrial membrane. The resulting proton gradient is used by the ATP synthase complex for ATP formation. In plants, the ETC is especially intricate. Besides the "classical" oxidoreductase complexes (complex I-IV) and the mobile electron transporters cytochrome c and ubiguinone, it comprises numerous "alternative oxidoreductases." Furthermore, several dehydrogenases localized in the mitochondrial matrix and the mitochondrial intermembrane space directly or indirectly provide electrons for the ETC. Entry of electrons into the system occurs via numerous pathways which are dynamically regulated in response to the metabolic state of a plant cell as well as environmental factors. This mini review aims to summarize recent findings on respiratory electron transfer pathways in plants and on the involved components and supramolecular assemblies.DFG/BR/1829/10-
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