Analysis of reaction dynamics at RHIC in a combined parton/hadron transport approach

We introduce a transport approach which combines partonic and hadronic degrees of freedom on an equal footing and discuss the resulting reaction dynamics. The initial parton dynamics is modeled in the framework of the parton cascade model, hadronization is performed via a cluster hadronization model and configuration space coalescence, and the hadronic phase is described by a microscopic hadronic transport approach. The resulting reaction dynamics indicates a strong influence of hadronic rescattering on the space-time pattern of hadronic freeze-out and on the shape of transverse mass spectra. Freeze-out times and transverse radii increase by factors of 2 - 3 depending on the hadron species.Comment: 10 pages, 4 eps figures include

Validation de terrain d'un test ELISA de compétition pour la détection de la péripneumonie contagieuse des bovins au Botswana

Le test ELISA de compétition, récemment décrit pour détecter la présence de la péripneumonie, a été utilisé au Laboratoire national vétérinaire du Botswana à Gaborone. L'échantillonnage de sérums a compris un nombre significatif de sérums récoltés durant l'épizootie de 1995 et ensuite en 1998 après que la totalité du cheptel bovin de la zone infectée ait été abattue. Les résultats obtenus ont montré l'excellente spécificité du test avec un seul sérum négatif, sur 895, ayant un titre légèrement supérieur au seuil de positivité. La comparaison avec deux autres tests, la fixation du complément et l'agglutination sur lame, avec des sérums récoltés durant l'épizootie de péripneumonie en 1995 a montré que ces trois tests avaient des sensibilités équivalentes. Les principaux avantages de l'ELISA de compétition sont sa spécificité, sa reproductibilité et la possibilité qu'il offre de pouvoir effectuer un contrôle de qualité fiable en étant utilisé avec des logiciels développés au niveau international comme l'ELISA Data Interchange (EDI). (Résumé d'auteur

Out of Equilibrium Non-perturbative Quantum Field Dynamics in Homogeneous External Fields

The quantum dynamics of the symmetry broken lambda (Phi^2)^2 scalar field theory in the presence of an homogeneous external field is investigated in the large N limit. We choose as initial state the ground state for a constant external field J .The sign of the external field is suddenly flipped from J to - J at a given time and the subsequent quantum dynamics calculated. Spinodal instabilities and parametric resonances produce large quantum fluctuations in the field components transverse to the external field. This allows the order parameter to turn around the maximum of the potential for intermediate times. Subsequently, the order parameter starts to oscillate near the global minimum for external field - J, entering a novel quasi-periodic regime.Comment: LaTex, 30 pages, 12 .ps figures, improved version to appear in Phys Rev

Parton cascade description of relativistic heavy-ion collisions at CERN SPS energies ?

We examine Pb+Pb collisions at CERN SPS energy 158 A GeV, by employing the earlier developed and recently refined parton-cascade/cluster-hadronization model and its Monte Carlo implementation. This space-time model involves the dynamical interplay of perturbative QCD parton production and evolution, with non-perturbative parton-cluster formation and hadron production through cluster decays. Using computer simulations, we are able to follow the entwined time-evolution of parton and hadron degrees of freedom in both position and momentum space, from the instant of nuclear overlap to the final yield of particles. We present and discuss results for the multiplicity distributions, which agree well with the measured data from the CERN SPS, including those for K mesons. The transverse momentum distributions of the produced hadrons are also found to be in good agreement with the preliminary data measured by the NA49 and the WA98 collaboration for the collision of lead nuclei at the CERN SPS. The analysis of the time evolution of transverse energy deposited in the collision zone and the energy density suggests an existence of partonic matter for a time of more than 5 fm.Comment: 16 pages including 7 postscript figure

Heavy resonance production in high energy nuclear collisions

We estimate freezeout conditions for $s$, $c$, and $b$ quarks in high energy nuclear collisions. Freezeout is due either to loss of thermal contact, or to particles ``wandering'' out of the region of hot matter. We then develop a thermal recombination model in which both single-particle (quark and antiquark) and two-particle (quark-antiquark) densities are conserved. Conservation of two-particle densities is necessary because quarks and antiquarks are always produced in coincidence, so that the local two-particle density can be much larger than the product of the single-particle densities. We use the freezeout conditions and recombination model to discuss heavy resonance production at zero baryon density in high energy nuclear collisions.Comment: revtex, 15 pages, no figures, KSUCNR-009-9

MoodBar: Increasing new user retention in Wikipedia through lightweight socialization

Socialization in online communities allows existing members to welcome and recruit newcomers, introduce them to community norms and practices, and sustain their early participation. However, socializing newcomers does not come for free: in large communities, socialization can result in a significant workload for mentors and is hard to scale. In this study we present results from an experiment that measured the effect of a lightweight socialization tool on the activity and retention of newly registered users attempting to edit for the first time Wikipedia. Wikipedia is struggling with the retention of newcomers and our results indicate that a mechanism to elicit lightweight feedback and to provide early mentoring to newcomers improves their chances of becoming long-term contributors.Comment: 9 pages, 5 figures, accepted for presentation at CSCW'1

Multimodal 3D Object Detection from Simulated Pretraining

The need for simulated data in autonomous driving applications has become increasingly important, both for validation of pretrained models and for training new models. In order for these models to generalize to real-world applications, it is critical that the underlying dataset contains a variety of driving scenarios and that simulated sensor readings closely mimics real-world sensors. We present the Carla Automated Dataset Extraction Tool (CADET), a novel tool for generating training data from the CARLA simulator to be used in autonomous driving research. The tool is able to export high-quality, synchronized LIDAR and camera data with object annotations, and offers configuration to accurately reflect a real-life sensor array. Furthermore, we use this tool to generate a dataset consisting of 10 000 samples and use this dataset in order to train the 3D object detection network AVOD-FPN, with finetuning on the KITTI dataset in order to evaluate the potential for effective pretraining. We also present two novel LIDAR feature map configurations in Bird's Eye View for use with AVOD-FPN that can be easily modified. These configurations are tested on the KITTI and CADET datasets in order to evaluate their performance as well as the usability of the simulated dataset for pretraining. Although insufficient to fully replace the use of real world data, and generally not able to exceed the performance of systems fully trained on real data, our results indicate that simulated data can considerably reduce the amount of training on real data required to achieve satisfactory levels of accuracy.Comment: 12 pages, part of proceedings for the NAIS 2019 symposiu

THz conductivity of Sr1−x_{1-x}Cax_xRuO3_3

We investigate the optical conductivity of Sr$_{1-x}$Ca$_x$RuO$_3$ across the ferromagnetic to paramagnetic transition that occurs at $x=0.8$. The thin films were grown by metalorganic aerosol deposition with $0 \leq x \leq 1$ onto NdGaO$_3$ substrates. We performed THz frequency domain spectroscopy in a frequency range from 3~cm$^{-1}$ to 40~cm$^{-1}$ (100~GHz to 1.4~THz) and at temperatures ranging from 5~K to 300~K, measuring transmittivity and phase shift through the films. From this we obtained real and imaginary parts of the optical conductivity. The end-members, ferromagnetic SrRuO$_3$ and paramagnetic CaRuO$_3$, show a strongly frequency-dependent metallic response at temperatures below 20~K. Due to the high quality of these samples we can access pronounced intrinsic electronic contributions to the optical scattering rate, which at 1.4~THz exceeds the residual scattering rate by more than a factor of three. Deviations from a Drude response start at about 0.7~THz for both end-members in a remarkably similar way. For the intermediate members a higher residual scattering originating in the compositional disorder leads to a featureless optical response, instead. The relevance of low-lying interband transitions is addressed by a calculation of the optical conductivity within density functional theory in the local density approximation (LDA)