24,760 research outputs found

    Entrainment coefficient and effective mass for conduction neutrons in neutron star crust: II Macroscopic treatment

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    Phenomena such as pulsar frequency glitches are believed to be attributable to differential rotation of a current of ``free'' superfluid neutrons at densities above the ``drip'' threshold in the ionic crust of a neutron star. Such relative flow is shown to be locally describable by adaption of a canonical two fluid treatment that emphasizes the role of the momentum covectors constructed by differentiation of action with respect to the currents, with allowance for stratification whereby the ionic number current may be conserved even when the ionic charge number Z is altered by beta processes. It is demonstrated that the gauge freedom to make different choices of the chemical basis determining which neutrons are counted as ``free'' does not affect their ``superfluid'' momentum covector, which must locally have the form of a gradient (though it does affect the ``normal'' momentum covector characterising the protons and those neutrons that are considered to be ``confined'' in the nuclei). It is shown how the effect of ``entrainment'' (whereby the momentum directions deviate from those of the currents) is controlled by the (gauge independent) mobility coefficient K, estimated in recent microscopical quantum mechanical investigations, which suggest that the corresponding (gauge dependent) ``effective mass'' m* of the free neutrons can become very large in some layers. The relation between this treatment of the crust layers and related work (using different definitions of ``effective mass'') intended for the deeper core layers is discussed.Comment: 21 pages Latex. Part II of article whose Part I (Simple microscopic models) is given by nucl-th/0402057. New version extended to include figure

    New concept in brazing metallic honeycomb panels

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    Aluminum oxide coating provides surface which will not be wetted by brazing alloy and which stops metallic diffusion welding of tooling materials to part being produced. This method eliminates loss of tooling materials and parts from braze wetting and allows fall-apart disassembly of tooling after brazing

    Inclusion Polymerization and Doping in Zeolite Channels. Polyaniline

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    Aniline has been polymerized in the three-dimensional channel system of zeolite Y. The monomer was diffused into zeolites with different levels of acidity from hexane solution. Subsequent admission of peroxydisulfate or iodate from aqueous solution yielded the intrazeolite polymers, as demonstrated by FT-IR, electronic absorption data and recovery of the included polymer. With S2O82-, the intrazeolite products are a function of the proton content of the zeolite. Polymer is only formed when a sufficient supply of protons is present in the zeolite host. When neutral iodate solution is used, no polymer is formed in NaY and acid zeolites, but at low pH aniline polymerizes in all zeolites. The open pore system of the zeolite host can be accessed by base such that the intrazeolite protonated polymer is transformed into the corresponding neutral polymer. The polymer chains encapsulated in zeolite hosts represent a new class of low- dimensional electronic materials

    Observation of a possible superflare on Proxima Centauri

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    We report the observation on UT 2017 July 1 of an unusually powerful flare detected in near-infrared continuum photometry of Proxima Centauri. During a campaign monitoring the star for possible exoplanet transits, we identified an increase in Sloan i' flux leading to an observed peak at BJD 2457935.996 that was at least 10 per cent over pre-flare flux in this band. It was followed by a two-component rapid decline in the first 100 s that became a slower exponential decay with time constant of 1350 s. A smaller flare event 1300 s after the first added an incremental peak flux increase of 1 per cent of pre-flare flux. Since the onset of the flare was not fully time resolved at a cadence of 62 s, its actual peak value is unknown but greater than the time average over a single exposure of 20 s. The i' band is representative of broad optical and near-IR continuum flux over which the integrated energy of the flare is 100 times the stellar luminosity. This meets the criteria that established the concept of superflares on similar stars. The resulting implied ultraviolet flux and space weather could have had an extreme effect on the atmospheres of planets within the star's otherwise habitable zone

    Southwest Research Institute assistance to NASA in biomedical areas of the technology utilization program

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    The activities are reported of the NASA Biomedical Applications Team at Southwest Research Institute between 25 August, 1972 and 15 November, 1973. The program background and methodology are discussed along with the technology applications, and biomedical community impacts

    Application of remote sensing to state and regional problems

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    There are no author-identified significant results in this report

    A Puzzling Merger in A3266: the Hydrodynamic Picture from XMM-Newton

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    Using the mosaic of nine XMM-Newton observations, we study the hydrodynamic state of the merging cluster of galaxies Abell 3266. The high quality of the spectroscopic data and large field of view of XMM-Netwon allow us to determine the thermodynamic conditions of the intracluster medium on scales of order of 50 kpc. A high quality entropy map reveals the presence of an extended region of low entropy gas, running from the primary cluster core toward the northeast along the nominal merger axis. The mass of the low entropy gas amounts to approximately 2e13 solar masses, which is comparable to the baryonic mass of the core of a rich cluster. We test the possibility that the origin of the observed low entropy gas is either related to the disruption a preexisting cooling core in Abell 3266 or to the stripping of gas from an infalling subcluster companion. We find that both the radial pressure and entropy profiles as well as the iron abundance of Abell 3266 do not resemble those in other known cooling core clusters (Abell 478). Thus we conclude that the low entropy region is subcluster gas in the process of being stripped off from its dark matter halo. In this scenario the subcluster would be falling onto the core of A3266 from the foreground. This would also help interpret the observed high velocity dispersion of the galaxies in the cluster center, provided that the mass of the subcluster is at most a tenth of the mass of the main cluster.Comment: 6 pages, ApJ sub
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