31,267 research outputs found

    Kaon Phase Space Density in Heavy Ion Collisions

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    The first measurement of kaon phase space densities are presented as a function of transverse mass, center of mass energy and the number of participants. The kaon phase space density increases with the number of participants from e+e- to Pb+Pb collisions. However the ratio of the kaon and pion phase space densities at low transverse momentum is independent of the number of participants for sqrt{s}=17GeV/nucleon This paper is dedicated to Francis Riccardelli, engineer for the Port Authority, who died on September 11th 2001 while evacuating others.Comment: 4 pages, 2 eps figures, proceedings of Strange Quarks in Matter, Frankfurt 2001, submitted to J. Phys. G In response to referees comments I derived an expresion for the ratio of kaon and pion phase space densites and made several clarifications in the tex

    Thermal and structural modeling of superinsulation

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    Model permits direct physical measurement of the thermal response of critical components of space telescopes, thus providing flexibility for systems studies and design changes

    Theoretical Analysis of STM Experiments at Rutile TiO_2 Surfaces

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    A first-principles atomic orbital-based electronic structure method is used to investigate the low index surfaces of rutile Titanium Dioxide. The method is relatively cheap in computational terms, making it attractive for the study of oxide surfaces, many of which undergo large reconstructions, and may be governed by the presence of Oxygen vacancy defects. Calculated surface charge densities are presented for low-index surfaces of TiO2_2, and the relation of these results to experimental STM images is discussed. Atomic resolution images at these surfaces tend to be produced at positive bias, probing states which largely consist of unoccupied Ti 3dd bands, with a small contribution from O 2pp. These experiments are particularly interesting since the O atoms tend to sit up to 1 angstrom above the Ti atoms, so providing a play-off between electronic and geometric structure in image formation.Comment: 9 pages, Revtex, 3 postscript figures, accepted by Surf. Scienc

    Chemistry in Bioinformatics

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    A preprint of an invited submission to BioMedCentral Bioinformatics. This short manuscript is an overview or the current problems and opportunities in publishing chemical information. Full details of technology are given in the sibling manuscript http://www.dspace.cam.ac.uk/handle/1810/34579 The manuscript is the authors' preprint although it has been automatically transformed into this archived PDF by the submission system. The authors are not responsible for the formattingChemical information is now seen as critical for most areas of life sciences. But unlike Bioinformatics, where data is Openly available and freely re−usable, most chemical information is closed and cannot be re−distributed without permission. This has led to a failure to adopt modern informatics and software techniques and therefore paucity of chemistry in bioinformatics. New technology, however, offers the hope of making chemical data (compounds and properties) Free during the authoring process. We argue that the technology is already available; we require a collective agreement to enhance publication protocols

    A survey of low-velocity collisional features in Saturn's F ring

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    Small (~50km scale), irregular features seen in Cassini images to be emanating from Saturn's F ring have been termed mini-jets by Attree et al. (2012). One particular mini-jet was tracked over half an orbital period, revealing its evolution with time and suggesting a collision with a local moonlet as its origin. In addition to these data we present here a much more detailed analysis of the full catalogue of over 800 F ring mini-jets, examining their distribution, morphology and lifetimes in order to place constraints on the underlying moonlet population. We find mini-jets randomly located in longitude around the ring, with little correlation to the moon Prometheus, and randomly distributed in time, over the full Cassini tour to date. They have a tendency to cluster together, forming complicated `multiple' structures, and have typical lifetimes of ~1d. Repeated observations of some features show significant evolution, including the creation of new mini-jets, implying repeated collisions by the same object. This suggests a population of <~1km radius objects with some internal strength and orbits spread over 100km in semi-major axis relative to the F ring but with the majority within 20km. These objects likely formed in the ring under, and were subsequently scattered onto differing orbits by, the perturbing action of Prometheus. This reinforces the idea of the F ring as a region with a complex balance between collisions, disruption and accretion.Comment: 21 pages, 12 figures. Accepted for publication in Icarus. Supplementary information available at http://www.maths.qmul.ac.uk/~attree/mini-jets

    Anomalous reaction-transport processes: the dynamics beyond the Mass Action Law

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    In this paper we reconsider the Mass Action Law (MAL) for the anomalous reversible reaction A⇄BA\rightleftarrows B with diffusion. We provide a mesoscopic description of this reaction when the transitions between two states AA and BB are governed by anomalous (heavy-tailed) waiting-time distributions. We derive the set of mesoscopic integro-differential equations for the mean densities of reacting and diffusing particles in both states. We show that the effective reaction rate memory kernels in these equations and the uniform asymptotic states depend on transport characteristics such as jumping rates. This is in contradiction with the classical picture of MAL. We find that transport can even induce an extinction of the particles such that the density of particles AA or BB tends asymptotically to zero. We verify analytical results by Monte Carlo simulations and show that the mesoscopic densities exhibit a transient growth before decay.Comment: 4 pages, 3 figure
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