904 research outputs found

    Semi-Exclusive Production of Photons at HERA

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    We study the feasibility of measuring semi-exclusive photon production \gamma + p \to \gamma + Y at HERA. The cross section of photons produced at large transverse momenta, recoiling off an inclusive system Y of limited mass, can without photon isolation cuts be simply expressed in terms of hard pQCD subprocesses and standard target parton distributions. With the help of event generators we identify the kinematic region where quark and gluon fragmentation processes can be neglected. The cross section in this semi-exclusive region is large enough to be measured with an upgraded HERA luminosity of L = 100/pb. The subprocesses of lowest order in \alpha_s are suppressed at low recoil masses M_Y, compared to higher order gluon exchange, i.e. BFKL contributions. The distinct M_Y-dependence makes it possible to determine experimentally the kinematic range where the higher order processes dominate.Comment: 11 pages, 7 figures, submitted to Eur. Phys. J. C, minor stylistic changes, references update

    Alaska-Canada Rail Link Economic Benefits

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    Construction of the 1,740 km Alaska-Canada Rail Link (ACRL) between Fort Nelson, BC and Delta Junction, Alaska to join the North American rail system to the Alaska Railroad will result in tremendous economic benefits for Canada and the US. The ACRL will provide valuable additional east-west rail capacity and tidewater access to the Pacific, hugely benefitting not only the Yukon and Eastern Alaska regions, into which it will introduce rail transport for the first time, but throughout both countries. The economic benefits of ACRL construction are consistent with Canadian government’s desire to promote Northern development and comparable in significance to those of Canadian Pacific Railway in the 1880’s and the St. Lawrence Seaway in the 1950’s. Construction of the ACRL alone will bring unprecedented economic stimulus to the region in terms of job creation, wages and income tax revenue over multiple years. Table 7-1 below summarizes the benefits from ACRL construction for the Yukon, BC and Canada as a whole. However, these estimates are conservative as they exclude benefits associated with pre-construction activities, railway operation post-construction, sales taxes and corporate taxes as well as all such benefits that will accrue to Alaska and the US

    Virginia Tech’s Innovative College Librarian Program

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    In 1994, Virginia Polytechnic Institute and State University (Virginia Tech) Libraries founded a College Librarian Program. Begun with four librarians serving four colleges, it has since grown to include eleven librarians providing comprehensive library services to the six of Virginia Tech\u27s eight colleges not served by branch libraries. Other authors have described the early history of the program or outlined some of its specific elements. By reviewing how the program came to be, by analyzing the choice points it presents, especially from an administrative perspective, and by discussing its benefits and costs from a university point of view, the authors hope to illuminate an exciting and potentially beneficial approach that other large institutions might seek to adapt to their own missions

    Administrative Succession in the Academic Library

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    Structure and Subject Interaction: Toward a Sociology of Knowledge in the Social Sciences (Book Review)

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    User Response to and Knowledge about an Online Catalog

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    Geological and Geotechnical Site Investigation for the Design of a CO2 Rich Flue Gas Direct Injection and Storage Facility

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    With international efforts to limit anthropogenic carbon in the atmosphere, various CO{sub 2} sequestration methods have been studied by various facilities worldwide. Basalt rock in general has been referred to as potential host material for mineral carbonation by various authors, without much regard for compositional variations due to depositional environment, subsequent metamorphism, or hydrothermal alteration. Since mineral carbonation relies on the presence of certain magnesium, calcium, or iron silicates, it is necessary to study the texture, mineralogy, petrology, and geochemistry of specific basalts before implying potential for mineral carbonation. The development of a methodology for the characterization of basalts with respect to their susceptibility for mineral carbonation is proposed to be developed as part of this research. The methodology will be developed based on whole rock data, petrography and microprobe analyses for samples from the Caledonia Mine in Michigan, which is the site for a proposed small-scale demonstration project on mineral carbonation in basalt. Samples from the Keweenaw Peninsula will be used to determine general compositional trends using whole rock data and petrography. Basalts in the Keweenaw Peninsula have been subjected to zeolite and prehnite-pumpellyite facies metamorphism with concurrent native copper deposition. Alteration was likely due to the circulation of CO{sub 2}-rich fluids at slightly elevated temperatures and pressures, which is the process that is attempted to be duplicated by mineral carbonation

    A Post-Amadori Inhibitor Pyridoxamine Also Inhibits Chemical Modification of Proteins by Scavenging Carbonyl Intermediates of Carbohydrate and Lipid Degradation

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    Reactive carbonyl compounds are formed during autoxidation of carbohydrates and peroxidation of lipids. These compounds are intermediates in the formation of advanced glycation end products (AGE) and advanced lipoxidation end products (ALE) in tissue proteins during aging and in chronic disease. We studied the reaction of carbonyl compounds glyoxal (GO) and glycolaldehyde (GLA) with pyridoxamine (PM), a potent post-Amadori inhibitor of AGE formation in vitro and of development of renal and retinal pathology in diabetic animals. PM reacted rapidly with GO and GLA in neutral, aqueous buffer, forming a Schiff base intermediate that cyclized to a hemiaminal adduct by intramolecular reaction with the phenolic hydroxyl group of PM. This bicyclic intermediate dimerized to form a five-ring compound with a central piperazine ring, which was characterized by electrospray ionization-liquid chromatography/mass spectrometry, NMR, and x-ray crystallography. PM also inhibited the modification of lysine residues and loss of enzymatic activity of RNase in the presence of GO and GLA and inhibited formation of the AGE/ALE N(epsilon)-(carboxymethyl)lysine during reaction of GO and GLA with bovine serum albumin. Our data suggest that the AGE/ALE inhibitory activity and the therapeutic effects of PM observed in diabetic animal models depend, at least in part, on its ability to trap reactive carbonyl intermediates in AGE/ALE formation, thereby inhibiting the chemical modification of tissue proteins

    Pictures of the past : Benjamin and Barthes on photography.

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    This paper explores the key moments in Benjamin’s and Barthes’s analyses of the cultural significance of the photograph. For Benjamin these are; the optical unconscious, the transmission of aura, the representation of cultural and political decay and proto-surrealist political commentary. For Barthes they are; the techniques of the photographer, the studium, the punctum and the ecstasy of the image. These rather different approaches to photography reveal a common concern with history. Both authors have written about the nature of historical understanding and photography has provided both with a powerful metaphor. What emerges from their analyses of photographs is that each evokes a double moment of historical awareness; of being both in the present and in the past. For Benjamin this is the ‘spark of contingency’ with which the aura of past existence shines in the present. For Barthes it is the ‘ça-a-été’, the emotional stab of awareness that what is present and visible in the photograph is irretrievably lost in the past
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