Measurement of photons via conversion pairs in \sqrt{s_{NN}} = 200 GeV Au+Au collisions with the PHENIX experiment at RHIC

Thermal photons can provide information on the temperature of the new state of matter created at RHIC. In the p_T region of 1--3 GeV/c thermal photons are expected to be the dominant direct photon source. Therefore, a possible excess compared to a pure decay photon signal due to a thermal photon contribution should be seen in the double ratio (\gamma/\gamma(\pi^{0}))_{Measured}/(\gamma/\gamma(\pi^{0}))_{Simulated}, if sufficient accuracy can be reached. We present a method to reconstruct direct photons by measuring e^{+}e^{-}--pairs from external photon conversions.Comment: 4 pages, 7 figures. To appear in the proceedings of Hot Quarks 2006: Workshop for Young Scientists on the Physics of Ultrarelativistic Nucleus-Nucleus Collisions, Villasimius, Italy, 15-20 May 200

Cluster and group synchronization in delay-coupled networks

We investigate the stability of synchronized states in delay-coupled networks where synchronization takes place in groups of different local dynamics or in cluster states in networks with identical local dynamics. Using a master stability approach, we find that the master stability function shows a discrete rotational symmetry depending on the number of groups. The coupling matrices that permit solutions on group or cluster synchronization manifolds show a very similar symmetry in their eigenvalue spectrum, which helps to simplify the evaluation of the master stability function. Our theory allows for the characterization of stability of different patterns of synchronized dynamics in networks with multiple delay times, multiple coupling functions, but also with multiple kinds of local dynamics in the networks' nodes. We illustrate our results by calculating stability in the example of delay-coupled semiconductor lasers and in a model for neuronal spiking dynamics.Comment: 11 pages, 7 figure

Experimental Observations of Group Synchrony in a System of Chaotic Optoelectronic Oscillators

We experimentally demonstrate group synchrony in a network of four nonlinear optoelectronic oscillators with time-delayed coupling. We divide the nodes into two groups of two each, by giving each group different parameters and by enabling only inter-group coupling. When coupled in this fashion, the two groups display different dynamics, with no isochronal synchrony between them, but the nodes in a single group are isochronally synchronized, even though there is no intra-group coupling. We compare experimental behavior with theoretical and numerical results

A baseline study of metal contamination along the Namibian coastline for Perna perna and Choromytilus meridionalis.

The use of bivalves such as the brown mussel (Perna perna) and the black mussel (Choromytilus meridionalis) is common in the study of marine pollution and the effect of these pollutants on ecosystems and are important in both economic and ecological roles. Namibian marine ecosystems are threatened by pollution from mining, commercial fishing and population growth. The aims of this study were to determine baseline metal concentrations, spatial variation and variation between species. Metal levels in C. meridionalis from Guano Platform (GP) are the lowest of all the sites. The most polluted sites are Rocky Point (RP), Halifax Island (HIL) and between Walvis Bay and Swakopmund (WS). The bioaccumulation of metals between P. perna and C. meridionalis were not uniform for all metals. Overall the study indicates the condition of the coastline to be mostly normal, with Cd and Pb levels being of concern

Heavy-flavor dynamics in nucleus-nucleus collisions: from RHIC to LHC

The stochastic dynamics of c and b quarks in the fireball created in nucleus-nucleus collisions at RHIC and LHC is studied employing a relativistic Langevin equation, based on a picture of multiple uncorrelated random collisions with the medium. Heavy-quark transport coefficients are evaluated within a pQCD approach, with a proper HTL resummation of medium effects for soft scatterings. The Langevin equation is embedded in a multi-step setup developed to study heavy-flavor observables in pp and AA collisions, starting from a NLO pQCD calculation of initial heavy-quark yields, complemented in the nuclear case by shadowing corrections, k_T-broadening and nuclear geometry effects. Then, only for AA collisions, the Langevin equation is solved numerically in a background medium described by relativistic hydrodynamics. Finally, the propagated heavy quarks are made hadronize and decay into electrons. Results for the nuclear modification factor R_AA of heavy-flavor hadrons and electrons from their semi-leptonic decays are provided, both for RHIC and LHC beam energies.Comment: 4 pages, 2 figures (3 eps files); submitted for publication in the proceedings of "Quark Matter 2011", 23-28 May 2011, Annecy (France

Direct photons ~basis for characterizing heavy ion collisions~

After years of experimental and theoretical efforts, direct photons become a strong and reliable tool to establish the basic characteristics of a hot and dense matter produced in heavy ion collisions. The recent direct photon measurements are reviewed and a future prospect is given.Comment: 8 pages, 8 figures, Invited plenary talk at Quark Matter 200

Temperature change effects on marine fish range shifts: a meta-analysis of ecological and methodological predictors

The current effects of global warming on marine ecosystems are predicted to increase, with species responding by changing their spatial distributions. Marine ectotherms such as fish experience elevated distribution shifts, as temperature plays a key role in physiological functions and delineating population ranges through thermal constraints. Distributional response predictions necessary for population management have been complicated by high heterogeneity in magnitude and direction of movements, which may be explained by both biological as well as methodological study differences. To date, however, there has been no comprehensive synthesis of the interacting ecological factors influencing fish distributions in response to climate change and the confounding methodological factors that can affect their estimation. In this study we analyzed published studies meeting criteria of reporting range shift responses to global warming in 115 taxa spanning all major oceanic regions, totaling 595 three-dimensional population responses (latitudinal, longitudinal, and depth), with temperature identified as a significant driver. We found that latitudinal shifts were the fastest in non-exploited, tropical populations, and inversely correlated with depth shifts which, in turn, dominated at the trailing edges of population ranges. While poleward responses increased with rate of temperature change and latitude, niche was a key factor in predicting both depth (18% of variation) and latitudinal responses (13%), with methodological predictors explaining between 10% and 28% of the observed variance in marine fish responses to temperature change. Finally, we found strong geographical publication bias and limited taxonomical scope, highlighting the need for more representative and standardized research in order to address heterogeneity in distribution responses and improve predictions in face of changing climate

Overview of experimental results in PbPb collisions at sqrt{s_NN} = 2.76 TeV by the CMS Collaboration

The CMS experiment at the LHC is a general-purpose apparatus with a set of large acceptance and high granularity detectors for hadrons, electrons, photons and muons, providing unique capabilities for both proton-proton and ion-ion collisions. The data collected during the November 2010 PbPb run at sqrt{s_NN} = 2.76 TeV was analyzed and multiple measurements of the properties of the hot and dense matter were obtained. Global event properties, detailed study of jet production and jet properties, isolated photons, quarkonia and weak bosons were measured and compared to pp data and Monte Carlo simulations.Comment: 8 pages, 10 figures, proceedings for Quark Matter 2011, Annecy, France, May 23-28, 201

Dynamics of fully coupled rotators with unimodal and bimodal frequency distribution

We analyze the synchronization transition of a globally coupled network of N phase oscillators with inertia (rotators) whose natural frequencies are unimodally or bimodally distributed. In the unimodal case, the system exhibits a discontinuous hysteretic transition from an incoherent to a partially synchronized (PS) state. For sufficiently large inertia, the system reveals the coexistence of a PS state and of a standing wave (SW) solution. In the bimodal case, the hysteretic synchronization transition involves several states. Namely, the system becomes coherent passing through traveling waves (TWs), SWs and finally arriving to a PS regime. The transition to the PS state from the SW occurs always at the same coupling, independently of the system size, while its value increases linearly with the inertia. On the other hand the critical coupling required to observe TWs and SWs increases with N suggesting that in the thermodynamic limit the transition from incoherence to PS will occur without any intermediate states. Finally a linear stability analysis reveals that the system is hysteretic not only at the level of macroscopic indicators, but also microscopically as verified by measuring the maximal Lyapunov exponent.Comment: 22 pages, 11 figures, contribution for the book: Control of Self-Organizing Nonlinear Systems, Springer Series in Energetics, eds E. Schoell, S.H.L. Klapp, P. Hoeve