400 research outputs found

    Detailed comparison of the pp -> \pi^+pn and pp -> \pi^+d reactions at 951 MeV

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    The positively charged pions produced in proton-proton collisions at a beam momentum of 1640 MeV/c were measured in the forward direction with a high resolution magnetic spectrograph. The missing mass distribution shows the bound state (deuteron) clearly separated from the pnpn continuum. Despite the very good resolution, there is no evidence for any significant production of the pnpn system in the spin-singlet state. However, the σ(ppπ+pn)/σ(ppπ+d)\sigma(pp\to \pi^+pn)/\sigma(pp\to \pi^+d) cross section ratio is about twice as large as that predicted from SS-wave final-state-interaction theory and it is suggested that this is due to DD-state effects in the pnpn system.Comment: 8 pages, 3 figure

    Toward an internally consistent astronomical distance scale

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    Accurate astronomical distance determination is crucial for all fields in astrophysics, from Galactic to cosmological scales. Despite, or perhaps because of, significant efforts to determine accurate distances, using a wide range of methods, tracers, and techniques, an internally consistent astronomical distance framework has not yet been established. We review current efforts to homogenize the Local Group's distance framework, with particular emphasis on the potential of RR Lyrae stars as distance indicators, and attempt to extend this in an internally consistent manner to cosmological distances. Calibration based on Type Ia supernovae and distance determinations based on gravitational lensing represent particularly promising approaches. We provide a positive outlook to improvements to the status quo expected from future surveys, missions, and facilities. Astronomical distance determination has clearly reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press (chapter 8 of a special collection resulting from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in the Space Age

    Mitogen-induced stimulation and suppression of erythroid burst promoting activity production by human mononuclear cells

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    Exposure of human peripheral blood mononuclear cells or highly enriched monocytes to various plant lectins substantially alters their production of erythroid burst promoting activity (BPA). Neither unstimulated, nor mitogen stimulated, enriched T lymphocytes produced demonstrable BPA. Each of the lectins tested resulted in a different pattern of alteration of BPA production by mononuclear cells. Increasing concentrations of phytohaemagglutinin (PHA) caused a progressive increase in BPA production up to a plateau level at concentrations above 0·25–0·5 Μ1/ml. Concanavalin A (Con A) at concentrations of 0·05–0·1 Μg/ml stimulated BPA production, but Con A concentrations > 1 Μg/ml never augmented BPA production by mononuclear cells. Pokeweed mitogen inhibited BPA production by mononuclear cells in a concentration-dependent manner. Since PHA and Con A can bind to and stimulate both monocytes/macrophages and T lymphocytes, some production of BPA by stimulated T cells in the presence of monocytes cannot be ruled out. Earlier studies demonstrated that T cells augment monocyte production of BPA. Thus, monocyte–T cell interactions, as well as activation of monocytes and perhaps lymphocytes, play an important role in regulation of BPA production in vitro .Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73808/1/j.1365-2141.1983.tb01232.x.pd

    Black Hole, Jet, and Disk: The Universal Engine

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    In this paper I review the results of our ongoing project to investigate the coupling between accretion disk and radio jet in galactic nuclei and stellar mass black holes. We find a good correlation between the UV bump luminosity and the radio luminosities of AGN, which improves upon the usual [OIII]/radio correlations. Taking mass and energy conservation in the jet/disk system into account we can successfully model the correlation for radio-loud and radio-weak quasars. We find that jets are comparable in power to the accretion disk luminosity, and the difference between radio-loud and radio-weak may correspond to two natural stages of the relativistic electron distribution -- assuming that radio weak quasars have jets as well. The distribution of flat- and steep-spectrum sources is explained by bulk Lorentz factors gamma_j ~ 5-10. The absence of radio-loud quasars below a critical optical luminosity coincides with the FR I/FR II break and could be explained by a powerdependent, ``closing'' torus. This points towards a different type of obscuring torus in radio-loud host galaxies which might be a consequence of past mergers (e.g. by the temporary formation of a binary black-hole). Interaction of the jet with the closing torus might in principle also help to make a jet radio-loud. Turning to stellar-mass black holes we find that galactic jet sources can be described with the same coupled jet/disk model as AGN which is suggestive of some kind of universal coupling between jet and accretion disk around compact objects.Comment: to appear in ``Jets from Stars and Galactic Nuclei'', Springer Lecture Notes, plain TeX, 16 pages, also at http://www.astro.umd.edu/~hfalcke/publications.htm

    Therapeutic jurisprudence and procedural justice in Scottish drug courts

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    Scotland, like other Western jurisdictions, has recently witnessed the development of problem-solving courts aimed at responding more effectively to issues that underlie certain types of offending behaviour. The first to be established were two pilot Drug Courts which drew upon experience of Scottish Drug Treatment and Testing Orders. In common with Drug Courts elsewhere, the Scottish pilots combined treatment, drug testing, supervision and judicial oversight. This article focuses upon the role of judicial involvement in the ongoing review of Drug Court participants’ progress, drawing upon court observation and interviews with offenders and Drug Court professionals. Drug Court dialogues were typically encouraging on the part of sheriffs, aimed at recognising and reinforcing the progress made by participants and motivating then to maintain and build upon their achievements to date, while participants were generally responsive to the positive feedback they received from the sheriffs as their orders progressed. Interactions within the Scottish Drug Courts reflect key features of procedural justice (Tyler, 1990), including ethicality, efforts to be fair and representation. By contributing to enhanced perceptions of procedural justice, Drug Court dialogues may, it is argued, increase the perceived legitimacy of the court and by so doing encourage increased compliance with treatment and desistance from crime

    Sediment routing and basin evolution in Proterozoic to Mesozoic east Gondwana: A case study from southern Australia

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    Sedimentary rocks along the southern margin of Australia host an important record of the break-up history of east Gondwana, as well as fragments of a deeper geological history, which collectively help inform the geological evolution of a vast and largely underexplored region. New drilling through Cenozoic cover has allowed examination of the Cretaceous rift-related Madura Shelf sequence (Bight Basin), and identification of two new stratigraphic units beneath the shelf; the possibly Proterozoic Shanes Dam Conglomerate and the interpreted Palaeozoic southern Officer Basin unit, the Decoration Sandstone. Recognition of these new units indicates an earlier basinal history than previously known. Lithostratigraphy of the new drillcore has been integrated with that published from onshore and offshore cores to present isopach maps of sedimentary cover on the Madura Shelf. New palynological data demonstrate progression from more localised freshwater-brackish fluvio-lacustrine clastics in the early Cretaceous (Foraminisporis wonthaggiensis – Valanginian to Barremian) to widespread topography-blanketing, fully marine, glauconitic mudrocks in the mid Cretaceous (Endoceratium ludbrookiae – Albian). Geochronology and Hf-isotope geochemistry show detrital zircon populations from the Madura Shelf are comparable to those from the southern Officer Basin, as well as Cenozoic shoreline and palaeovalley sediments in the region. The detrital zircon population from the Shanes Dam Conglomerate is defined by a unimodal ~1400 Ma peak, which correlates with directly underlying crystalline basement of the Madura Province. Peak ages of ~1150 Ma and ~1650 Ma dominate the age spectra of all other samples, indicating a stable sediment reservoir through much of the Phanerozoic, with sediments largely sourced from the Albany-Fraser Orogen and Musgrave Province (directly and via multiple recycling events). The Madura Shelf detrital zircon population differs from published data for the Upper CretaceousCeduna Delta to the east, indicating significant differences in sediment provenance and routing between the Ceduna Sub-basin and central Bight Basin

    Decoherence effects in Bose-Einstein condensate interferometry. I General Theory

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    The present paper outlines a basic theoretical treatment of decoherence and dephasing effects in interferometry based on single component BEC in double potential wells, where two condensate modes may be involved. Results for both two mode condensates and the simpler single mode condensate case are presented. A hybrid phase space distribution functional method is used where the condensate modes are described via a truncated Wigner representation, and the basically unoccupied non-condensate modes are described via a positive P representation. The Hamiltonian for the system is described in terms of quantum field operators for the condensate and non-condensate modes. The functional Fokker-Planck equation for the double phase space distribution functional is derived. Equivalent Ito stochastic equations for the condensate and non-condensate fields that replace the field operators are obtained, and stochastic averages of products of these fields give the quantum correlation functions used to interpret interferometry experiments. The stochastic field equations are the sum of a deterministic term obtained from the drift vector in the functional Fokker-Planck equation, and a noise field whose stochastic properties are determined from the diffusion matrix in the functional Fokker-Planck equation. The noise field stochastic properties are similar to those for Gaussian-Markov processes in that the stochastic averages of odd numbers of noise fields are zero and those for even numbers of noise field terms are sums of products of stochastic averages associated with pairs of noise fields. However each pair is represented by an element of the diffusion matrix rather than products of the noise fields themselves. The treatment starts from a generalised mean field theory for two condensate mode. The generalized mean field theory solutions are needed for calculations using the Ito stochastic field equations.Comment: To be published in Annals of Physics. Full version of paper, including all Appendices. Journal version only includes Appendix A. Appendices are in online supplementary material. Cross references to material in Appendices improved in Version 2 (5 July 2010). Minor amendments made in Version 3 (23 Nov 2010), including reference to Takagi factorisation of complex symmetric matrice
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