7,040 research outputs found

    Dispersed air flotation of fine particles

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    Imperial Users onl

    QCD and Rescattering in Nuclear Targets

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    We review the extension of the factorization formalism of perturbative QCD to soft rescattering associated with hard processes in nuclei.Comment: Latex 16 pages, including 18 figures, to appear in the Proceedings of Hard Probe Collaboratio

    Strategies for automatic planning: A collection of ideas

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    The main goal of the Jet Propulsion Laboratory (JPL) is to obtain science return from interplanetary probes. The uplink process is concerned with communicating commands to a spacecraft in order to achieve science objectives. There are two main parts to the development of the command file which is sent to a spacecraft. First, the activity planning process integrates the science requests for utilization of spacecraft time into a feasible sequence. Then the command generation process converts the sequence into a set of commands. The development of a feasible sequence plan is an expensive and labor intensive process requiring many months of effort. In order to save time and manpower in the uplink process, automation of parts of this process is desired. There is an ongoing effort to develop automatic planning systems. This has met with some success, but has also been informative about the nature of this effort. It is now clear that innovative techniques and state-of-the-art technology will be required in order to produce a system which can provide automatic sequence planning. As part of this effort to develop automatic planning systems, a survey of the literature, looking for known techniques which may be applicable to our work was conducted. Descriptions of and references for these methods are given, together with ideas for applying the techniques to automatic planning

    Factorization is not violated

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    We show that existing proofs of factorization imply the cancellation of certain multiladder contributions that Gotsman, Levin, and Maor had suggested would invalidate the basic factorization theorem in QCD. No modifications of the original argument are necessary, although the details of the example offer useful insight into the mechanisms of factorization.Comment: 11 pages including 10 figure

    Momentum Flow Correlations from Event Shapes: Factorized Soft Gluons and Soft-Collinear Effective Theory

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    The distributions of two-jet event shapes contain information on hadronization in QCD. Near the two-jet limit, these distributions can be described by convolutions of nonperturbative event shape functions with the same distributions calculated in resummed perturbation theory. The shape functions, in turn, are determined by correlations of momentum flow operators with each other and with light-like Wilson lines, which describe the coupling of soft, wide-angle radiation to jets. We observe that leading power corrections to the mean values of event shapes are determined by the correlation of a single momentum flow operator with the relevant Wilson lines. This generalizes arguments for the universality of leading power corrections based on the low-scale behavior of the running coupling or resummation. We also show how a study of the angularity event shapes can provide information on correlations involving multiple momentum flow operators, giving a window to the system of QCD dynamics that underlies the variety of event shape functions. In deriving these results, we review, develop and compare factorization techniques in conventional perturbative QCD and soft-collinear effective theory (SCET). We give special emphasis to the elimination of double counting of momentum regions in these two formalisms.Comment: 25 pages revtex

    Complexation of Secondary Amides to Chromium(III): the X-Ray Structure of a Molecule with Two Modes of Monodentate Organic Amide Co-ordination

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    The X-ray crystal structure of the dimer [Cr{H(chba-Et)}(py)_2]_(2)·2py [H_(4)(chba-Et)= 1,2-bis(3,5-dichloro-2-hydroxybenzamido) ethane, py = pyridine] establishes, for the first time, the existence of N-co-ordination of an organic amide to Cr^III, the N-atom and carbonyl O-atom of two separate amide groups being co-ordinated to each Cr^III centre [Cr–N 2.030(6) and Cr–O 1.976(5)Å]; the potentially tetra-anionic chelating ligand leads to a variety of co-ordination modes

    Fragmentation, Factorization and Infrared Poles in Heavy Quarkonium Production

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    We explore the role of soft gluon exchange in heavy quarkonium production at large transverse momentum. We find uncanceled infrared poles at NNLO that are not matched by conventional NRQCD matrix elements. We show, however, that gauge invariance and factorization require that conventional NRQCD production operators be modified to include nonabelian phases or Wilson lines. With appropriately modified operators, factorization is restored at NNLO. We also argue that, in the absence of special cancellations, infrared poles at yet higher orders may require the inclusion of additional nonlocal operators, not present in the NRQCD expansion in relative veloctiy.Comment: 10 pages latex, 6 eps figure

    Trans-Atlantic linkage: a case study of Epthori, Greek Macedonia and its new England connections

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    The aim of this study is to examine the relationship through time between the Greek village of Eptahori, Kastoria and the emigrants from there who settled in the United States. The linkage between Greek-Americans and their area of origin has not been thoroughly investigated by Social Scientists. The causes, mechanics and effects of the relationship relating to both the migrants and village are analyzed. While linkage consists of economic ties in the form of remittance sending and return migration there are also the added dimensions of social and cultural exchange which effect the character of those involved. A brief description of site selection and a succinct breakdown of the village history and physical description are given. Also, a review of the overall Greek-American migration and settlement pattern, using a specific example in the U.S.A. to illustrate the typical Greek-American community, is included. Most important, is the information which was extracted from migrants and villagers during periods of field- work in both the U.S. and Greece. The thesis then attempts to draw conclusions concerning the Eptahori case study and the overall concepts of Greek-American linkage, from a synthesis of data analysis and background information
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