132,567 research outputs found

    Vibrational transfer functions for base excited systems

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    Computer program GD203 develops transfer functions to compute governing vibration environment for complex structures subjected to a base motion

    Nature of fault planes in solid neutron star matter

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    The properties of tectonic earthquake sources are compared with those deduced here for fault planes in solid neutron-star matter. The conclusion that neutron-star matter cannot exhibit brittle fracture at any temperature or magnetic field is significant for current theories of pulsar glitches, and of the anomalous X-ray pulsars and soft-gamma repeaters.Comment: 5 AAS LaTeX pages 1 eps figur

    Public contracts as accountability mechanisms: assuring quality in public healthcare in England and Wales

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    Contracting in the public sector is designed to enhance the accountability of service providers to their funders. The idea is that quality is improved by the use of service specifications, monitoring of performance and imposition of contractual sanctions. Socio-legal and economic theories of contract indicate that it will be difficult to make and enforce contracts to achieve this. The results of a study of National Health Services contracting in England and Wales are reported. We conclude that contracts alone are not sufficient to improve accountability – collibration of various regulatory measures (including more hierarchical mechanisms such as performance targets) is required

    Overview of the Status and Strangeness Capabilities of STAR

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    STAR is a large acceptance spectrometer capable of precision measurements of a wide variety of strange particles. We discuss the STAR detector, its configuration during the first two years of RHIC operation, and its initial performance for Au+Au collisions. The expected performance for strangeness physics and initial data on strange particle reconstruction in Au+Au collisions are presented.Comment: Proceedings of the Fifth International Conference on Strangeness in Quark Matter, Berkeley, California, July 20-25, 200

    Opening angles, Lorentz factors and confinement of X-ray binary jets

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    We present a collation of the available data on the opening angles of jets in X-ray binaries, which in most cases are small (less than 10 degrees). Under the assumption of no confinement, we calculate the Lorentz factors required to produce such small opening angles via the transverse relativistic Doppler effect. The derived Lorentz factors, which are in most cases lower limits, are found to be large, with a mean greater than 10, comparable to those estimated for AGN and much higher than the commonly-assumed values for X-ray binaries of 2 to 5. Jet power constraints do not in most cases rule out such high Lorentz factors. The upper limits on the opening angles show no evidence for smaller Lorentz factors in the steady jets of Cygnus X-1 and GRS 1915+105. In those sources in which deceleration has been observed (notably XTE J1550-564 and Cygnus X-3), some confinement of the jets must be occurring, and we briefly discuss possible confinement mechanisms. It is however possible that all the jets could be confined, in which case the requirement for high bulk Lorentz factors can be relaxed.Comment: 11 pages, 4 figures (2 colour), accepted for publication in MNRA

    The Disturbed 17 keV Cluster Associated with the Radio Galaxy 3C 438

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    We present results from a {\em Chandra} observation of the cluster gas associated with the FR II radio galaxy 3C 438. This radio galaxy is embedded within a massive cluster with gas temperature \sim17 keV and bolometric luminosity of 6×1045\times10^{45} ergs s1^{-1}. It is unclear if this high temperature represents the gravitational mass of the cluster, or if this is an already high (\sim 11 keV) temperature cluster that has been heated transiently. We detect a surface brightness discontinuity in the gas that extends \sim600 kpc through the cluster. The radio galaxy 3C 438 is too small (\sim110 kpc across) and too weak to have created this large disturbance in the gas. The discontinuity must be the result of either an extremely powerful nuclear outburst or the major merger of two massive clusters. If the observed features are the result of a nuclear outburst, it must be from an earlier epoch of unusually energetic nuclear activity. However, the energy required (1063\sim10^{63} ergs) to move the gas on the observed spatial scales strongly supports the merger hypothesis. In either scenario, this is one of the most extreme events in the local Universe.Comment: 13 pages, 4 figures, 1 table - accepted for publication in the Astrophysical Journal Letter

    Cryogenic propellant venting under low pressure conditions Final report

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    Wall temperatures and heat transfer coefficients for solid-vapor mixtures of para hydrogen and nitrogen venting under low pressur

    The Nature of the Low-Metallicity ISM in the Dwarf Galaxy NGC 1569

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    We are modeling the spectra of dwarf galaxies from infrared to submillimeter wavelengths to understand the nature of the various dust components in low-metallicity environments, which may be comparable to the ISM of galaxies in their early evolutionary state. The overall nature of the dust in these environments appears to differ from those of higher metallicity starbursting systems. Here, we present a study of one of our sample of dwarf galaxies, NGC 1569, which is a nearby, well-studied starbursting dwarf. Using ISOCAM, IRAS, ISOPHOT and SCUBA data with the Desert et al. (1990) model, we find consistency with little contribution from PAHs and Very Small Grains and a relative abundance of bigger colder grains, which dominate the FIR and submillimeter wavelengths. We are compelled to use 4 dust components, adding a very cold dust component, to reproduce the submillimetre excess of our observations.Comment: 4 pages, 4 postscript figures. Proceedings of "Infrared and Submillimeter Astronomy. An International Colloquium to Honor the Memory of Guy Serra" (2002
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