11,707 research outputs found

    Microdetermination of urea in urine using p-dimethylaminobenzaldehyde /PDAB/

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    Adaptation of the p-dimethylaminobenzaldehyde method for determining urea concentration in urine is an improved micromechanical method. Accuracy and precision are satisfactory. This method avoids extra steps of deproteinizing or removing normal urinary chromogens

    Flash of photons from the early stage of heavy-ion collisions

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    The dynamics of partonic cascades may be an important aspect for particle production in relativistic collisions of nuclei at CERN SPS and BNL RHIC energies. Within the Parton-Cascade Model, we estimate the production of single photons from such cascades due to scattering of quarks and gluons q g -> q gamma, quark-antiquark annihilation q qbar -> g gamma, or gamma gamma, and from electromagnetic brems-strahlung of quarks q -> q gamma. We find that the latter QED branching process plays the dominant role for photon production, similarly as the QCD branchings q -> q g and g -> g g play a crucial role for parton multiplication. We conclude therefore that photons accompanying the parton cascade evolution during the early stage of heavy-ion collisions shed light on the formation of a partonic plasma.Comment: 4 pages including 3 postscript figure

    A case study of effective practice in mathematics teaching and learning informed by Valsiner’s zone theory

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    The characteristics that typify an effective teacher of mathematics and the environments that support effective teaching practices have been a long-term focus of educational research. In this article we report on an aspect of a larger study that investigated ‘best practice’ in mathematics teaching and learning across all Australian states and territories. A case study from one Australian state was developed from data collected via classroom observations and semi-structured interviews with school leaders and teachers and analysed using Valsiner’s zone theory. A finding of the study is that ‘successful’ practice is strongly tied to school context and the cultural practices that have been developed by school leaders and teachers to optimise student learning opportunities. We illustrate such an alignment of school culture and practice through a vignette based on a case of one ‘successful’ school

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

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    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

    Intelligent redundant actuation system requirements and preliminary system design

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    Several redundant actuation system configurations were designed and demonstrated to satisfy the stringent operational requirements of advanced flight control systems. However, this has been accomplished largely through brute force hardware redundancy, resulting in significantly increased computational requirements on the flight control computers which perform the failure analysis and reconfiguration management. Modern technology now provides powerful, low-cost microprocessors which are effective in performing failure isolation and configuration management at the local actuator level. One such concept, called an Intelligent Redundant Actuation System (IRAS), significantly reduces the flight control computer requirements and performs the local tasks more comprehensively than previously feasible. The requirements and preliminary design of an experimental laboratory system capable of demonstrating the concept and sufficiently flexible to explore a variety of configurations are discussed

    Bose-Einstein Final State Symmetrization for Event Generators of Heavy Ion Collisions

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    We discuss algorithms which allow to calculate identical two-particle correlations from numerical simulations of relativistic heavy ion collisions. A toy model is used to illustrate their properties.Comment: Talk given at CRIS'98 (Catania, June 8-12, 1998), to appear in "CRIS'98: Measuring the size of things in the Universe: HBT interferometry and heavy ion physics", (S. Costa et al., eds.), World Scientific, Singapore, 1998. (10 pages Latex, 1 eps-figure, extended version of conference proceedings, Fig1 a,b added and corresponding discussion enlarged

    Taking Aim: New Documentary and War

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    This essay examines some of the contours of new documentary and its relationship to war, first characterizing historical and theoretical frameworks while considering the social and spectatorial impact of moving images that have engaged with war themes and imagery. The focus falls on new documentary and representations of the war in Iraq, asking if these cultural mediations of war might indicate shades of an Iraq syndrome in the making. Finally, a close reading of Michael Moore's Fahrenheit 9/11 considers the film in light of social and representational issues facing new documentary, marking the film's postmodernist and surrealist tendencies. I argue that Moore?s film ends up projecting ambiguous and perhaps self-contradictory conclusions about the US reliance on war as a mechanism for advancing its global social, ideological, and economic agendas. At the same time, the film manages to capture elements of the heterogeneity and instability of Americans' own national and patriotic self-perceptions

    United States Expansionism and the Pacific

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    Bose-Einstein Correlations in a Space-Time Approach to e+ e- Annihilation into Hadrons

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    A new treatment of Bose-Einstein correlations is incorporated in a space-time parton-shower model for e+ e- annihilation into hadrons. Two alternative afterburners are discussed, and we use a simple calculable model to demonstrate that they reproduce successfully the size of the hadron emission region. One of the afterburners is used to calculate two-pion correlations in e+ e- -> Z^0 -> hadrons and e+ e- -> W+ W- -> hadrons. Results are shown with and without resonance decays, for correlations along and transverse to the thrust jet axis in these two classes of events.Comment: 30 pages, Latex, 8 figure

    Deep Convolutional Neural Networks as strong gravitational lens detectors

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    Future large-scale surveys with high resolution imaging will provide us with a few 10510^5 new strong galaxy-scale lenses. These strong lensing systems however will be contained in large data amounts which are beyond the capacity of human experts to visually classify in a unbiased way. We present a new strong gravitational lens finder based on convolutional neural networks (CNNs). The method was applied to the Strong Lensing challenge organised by the Bologna Lens Factory. It achieved first and third place respectively on the space-based data-set and the ground-based data-set. The goal was to find a fully automated lens finder for ground-based and space-based surveys which minimizes human inspect. We compare the results of our CNN architecture and three new variations ("invariant" "views" and "residual") on the simulated data of the challenge. Each method has been trained separately 5 times on 17 000 simulated images, cross-validated using 3 000 images and then applied to a 100 000 image test set. We used two different metrics for evaluation, the area under the receiver operating characteristic curve (AUC) score and the recall with no false positive (Recall0FP\mathrm{Recall}_{\mathrm{0FP}}). For ground based data our best method achieved an AUC score of 0.9770.977 and a Recall0FP\mathrm{Recall}_{\mathrm{0FP}} of 0.500.50. For space-based data our best method achieved an AUC score of 0.9400.940 and a Recall0FP\mathrm{Recall}_{\mathrm{0FP}} of 0.320.32. On space-based data adding dihedral invariance to the CNN architecture diminished the overall score but achieved a higher no contamination recall. We found that using committees of 5 CNNs produce the best recall at zero contamination and consistenly score better AUC than a single CNN. We found that for every variation of our CNN lensfinder, we achieve AUC scores close to 11 within 6%6\%.Comment: 9 pages, accepted to A&
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