47,130 research outputs found

    A study of an electric field measuring instrument

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    Cesium ion beam electric field measuring instrument

    Polymeric foams from cross-linkable poly-N-ary lenebenzimidazoles

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    Foamed cross-linked poly-N-arylenebinzimidazoles are prepared by mixing an organic tetraamine and an ortho substituted aromatic dicarboxylic acid anhydride in the presence of a blowing agent, and then heating the prepolymer to a temperature sufficient to complete polymerization and foaming of the reactants. In another embodiment of the process, the reactants are heated to form a prepolymer. The prepolymer is then cured at higher temperatures to complete foaming and polymerization

    Spatial Relationship between Solar Flares and Coronal Mass Ejections

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    We report on the spatial relationship between solar flares and coronal mass ejections (CMEs) observed during 1996-2005 inclusive. We identified 496 flare-CME pairs considering limb flares (distance from central meridian > 45 deg) with soft X-ray flare size > C3 level. The CMEs were detected by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO). We investigated the flare positions with respect to the CME span for the events with X-class, M-class, and C-class flares separately. It is found that the most frequent flare site is at the center of the CME span for all the three classes, but that frequency is different for the different classes. Many X-class flares often lie at the center of the associated CME, while C-class flares widely spread to the outside of the CME span. The former is different from previous studies, which concluded that no preferred flare site exists. We compared our result with the previous studies and conclude that the long-term LASCO observation enabled us to obtain the detailed spatial relation between flares and CMEs. Our finding calls for a closer flare-CME relationship and supports eruption models typified by the CSHKP magnetic reconnection model.Comment: 7 pages; 4 figures; Accepted by the Astrophysical Journa

    Productivity policy

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    In this Briefing Note, we first present internationally comparative evidence on the UK's productivity performance (Section 2) and some of the underlying "drivers" of productivity identified by the government (Section 3). We then provide an overview of productivity policy under both Labour governments since 1997, and discuss the recent direction of policy in this 2005 Election Briefing area (Section 4). Finally, we discuss the proposals of the three main parties in the area of productivity policy (Section 5)

    Reducing driver distraction by utilizing augmented reality head-up display system for rear passengers

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    Institutional and Political Factors Affecting the Development of Smallholder Forestry in Leyte Province

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    The institutional system defines the roles of public and private agencies and the property rights and responsibilities of landholders, and hence has major implications for forestry management. This paper approaches the topic in terms of theoretical perspectives, and applies these to forestry in Leyte Province, drawing on findings of the ACIAR UQ/LSU Smallholder Forestry Project. CBFM and forestry, which have evolved particularly during the last decade, are found to have a number of positive features. At the same time, some limitations and weaknesses in the institutional environment for smallholder forestry are apparent, and potential measures to improve the regulatory environment are examined

    Gamma-Ray Burst Spectral Features: Interpretation as X-ray Emission From A Photoionized Plasma

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    Numerous reports have been made of features, either in emission or absorption, in the 10 - 1000 keV spectra of some gamma-ray bursts. Originally interpreted in the context of Galactic neutron star models as cyclotron line emission and e+−e−e^+ - e^- annihilation features, the recent demonstration that the majority of GRBs lie at cosmological distances make these explanations unlikely. In this letter, we adopt a relativistic fireball model for cosmological GRBs in which dense, metal rich blobs or filaments of plasma are entrained in the relativistic outflow. In the context of this model, we investigate the conditions under which broadband features, similar to those detected, can be observed. We find a limited region of parameter space capable of reproducing the observed GRB spectra. Finally, we discuss possible constraints further high-energy spectral observations could place on fireball model parameters.Comment: Accepted for publication in Astrophysical Journal Letters Four pages, 2 figure

    Gamma-Ray Bursts and the Cosmic Star Formation Rate

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    We have tested several models of GRB luminosity and redshift distribution functions for compatibility with the BATSE 4B number versus peak flux relation. Our results disagree with recent claims that current GRB observations can be used to strongly constrain the cosmic star formation history. Instead, we find that relaxing the assumption that GRBs are standard candles renders a very broad range of models consistent with the BATSE number-flux relation. We explicitly construct two sample distributions, one tracing the star formation history and one with a constant comoving density. We show that both distributions are compatible with the observed fluxes and redshifts of the bursts GRB970508, GRB971214, and GRB980703, and we discuss the measurements required to distinguish the two models.Comment: 12 pages, 2 postscript figures, uses AAS LaTex macros v4.0. To be published in Astrophysical Journal Letters, accepted August 20, 1998. Revised for publicatio

    Transfusion of Blood in War Surgery :

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