4,664 research outputs found

    Regge Asymptotics of Scattering with Flavour Exchange in QCD

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    The contribution to the perturbative Regge asymptotics of the exchange of two reggeized fermions with opposite helicity is investigated. The methods of conformal symmetry known for the case of gluon exchange are extended to this case where double-logarithmic contributions dominate the asymptotics. The Regge trajectories at large momentum transfer are calculated.Comment: 18 pages LATEX, 3 figures using package FEYNMAN, N3-9

    Orthogonal and symplectic Yangians and Yang-Baxter R-operators

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    Yang-Baxter R operators symmetric with respect to the orthogonal and symplectic algebras are considered in an uniform way. Explicit forms for the spinorial and metaplectic R operators are obtained. L operators, obeying the RLL relation with the orthogonal or symplectic fundamental R matrix, are considered in the interesting cases, where their expansion in inverse powers of the spectral parameter is truncated. Unlike the case of special linear algebra symmetry the truncation results in additional conditions on the Lie algebra generators of which the L operators is built and which can be fulfilled in distinguished representations only. Further, generalised L operators, obeying the modified RLL relation with the fundamental R matrix replaced by the spinorial or metaplectic one, are considered in the particular case of linear dependence on the spectral parameter. It is shown how by fusion with respect to the spinorial or metaplectic representation these first order spinorial L operators reproduce the ordinary L operators with second order truncation.Comment: 24 page

    Making Bread From Broken Eggs: A Basic Recipe for Conflict Resolution Using Earned Sovereignty

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    Questions of state sovereignty are the cause of many conflicts today. The theory of earned sovereignty is an evolving concept. A review of recent practice in southern Sudan, Bougainville, and Aceh shows that the core elements of earned sovereignty offer a three-part roadmap for conflict resolution beginning with shared sovereignty, continuing through institution building, and ending at a determination of final status. Other parts of the theory called, “optional elements,” are tools stakeholders in a conflict situation may use in order to move from one core element to another until a final status solution is obtained. Though the optional elements of phased sovereignty, conditional sovereignty, and constrained sovereignty are parts of earned sovereignty they need not always be used. In-depth analysis of the peace agreements in southern Sudan, Bougainville, and Aceh show that, while the core elements are implemented throughout, the optional elements are used to varying degrees and in some instances not at all

    A rocket ozonesonde for geophysical research and satellite intercomparison

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    The in-situ rocketsonde for ozone profile measurements developed and flown for geophysical research and satellite comparison is reviewed. The measurement principle involves the chemiluminescence caused by ambient ozone striking a detector and passive pumping as a means of sampling the atmosphere as the sonde descends through the atmosphere on a parachute. The sonde is flown on a meteorological sounding rocket, and flight data are telemetered via the standard meteorological GMD ground receiving system. The payload operation, sensor performance, and calibration procedures simulating flight conditions are described. An error analysis indicated an absolute accuracy of about 12 percent and a precision of about 8 percent. These are combined to give a measurement error of 14 percent

    Imaging of Magnetic Microstructures at Surfaces: The Scanning Electron Microscope with Spin Polarization Analysis

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    The scanning electron microscope with spin polarization analysis of secondary electrons has been proven to be a powerful tool for studying magnetic microstructures. Secondary electrons created at the surface of a ferromagnet are spin-polarized and contain information about the sample magnetization and its orientation. The combination of a spin polarization analyzer with a scanning electron microscope yields an unique apparatus for probing magnetic properties on a very small lateral scale. The magnetic resolution of \u3c 40 nm is demonstrated. This type of microscope provides high magnetic contrast, while the surface morphology is strongly or even totally suppressed. The capability of studying magnetic properties of semi- infinite samples as well as in ultrathin films is demonstrated with a Fe(lOO) single crystal, video tape, CoCr perpendicular recording medium and ultrathin cobalt films

    Design research in early literacy within the zone of proximal implementation

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    Despite intentions to the contrary, insights on pedagogically appropriate innovations with representative teachers in everyday school settings are severely limited. In part, this is because (design) research is often conducted at the bleeding edge of what is possible, exploring innovative uses of new technologies and/or emerging theories, while insufficient research and development work focuses on what is practical, today. This leaves a problematic gap between what could be useful research in theory, and what can be useful research in practice. This paper calls for (design) researchers to attend to factors that determine if and how innovations are understood, adopted and used by teachers and schools, and gives one example of how this was tackled in the domain of early literacy. Across ten studies, researchers collected data that helped shape an intervention that can be implemented by representative teachers, for diverse learners, in varied school settings

    Free Thyroxine Level in the High Normal Reference Range Prescribed for Nonpregnant Women May Reduce the Preterm Delivery Rate in Multiparous

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    Preterm birth is the most common reason for perinatal morbidity and mortality in the western world. It has been shown that in euthyreotic pregnant women with thyroid autoimmune antibodies, L-Thyroxine replacement reduces preterm delivery rate in singleton pregnancies. We investigated in a nonrandomized retrospective observational study whether L-Thyroxine replacement, maintaining maternal free thyroxine serum level in the high normal reference range prescribed for nonpregnant women also influences the rate of preterm delivery in women without thyroid autoimmune antibodies. As control group for preterm delivery rate, data from perinatal statistics of the State of Baden-Württemberg from 2006 were used. The preterm delivery rate in the study group was significantly reduced. The subgroup analysis shows no difference in primiparous but a decline in multiparous by approximately 61% with L-Thyroxine replacement. Maintaining free thyroxine serum level in the high normal reference range prescribed for nonpregnant women may reduce the preterm delivery rate

    Collaboration in the Semantic Grid: a Basis for e-Learning

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    The CoAKTinG project aims to advance the state of the art in collaborative mediated spaces for the Semantic Grid. This paper presents an overview of the hypertext and knowledge based tools which have been deployed to augment existing collaborative environments, and the ontology which is used to exchange structure, promote enhanced process tracking, and aid navigation of resources before, after, and while a collaboration occurs. While the primary focus of the project has been supporting e-Science, this paper also explores the similarities and application of CoAKTinG technologies as part of a human-centred design approach to e-Learning
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