7,623 research outputs found

    A Milliped New to Michigan (Pselaphognatha: Polyxenus)

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    The authors wish to report the finding of representatives of the genus Polyxenus for the first time in Michigan (Fig. 1). In Bert M. Johnson\u27s survey (1954) of the millipedes of Michigan, no members of the subclass Pselaphognatha were reported. During the period of September through October 1970, the authors collected over 40 specimens of Polyxenus and observed over 100 in the field. All of the specimens were found in a mature pine stand in Ypsilanti Township

    Frustration in Finite Density QCD

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    We present a detailed analysis of the QCD partition function in the Grand Canonical formalism. Using the fugacity expansion we find evidence for numerical instabilities in the standard evaluation of its coefficients. We discuss the origin of this problem and propose an issue to it. The correct analysis shows no evidence for a discontinuity in the baryonic density in the strong coupling limit. The moderate optimism that was inspired by the Grand Canonical Partition Function calculations in the last years has to be considered ill-founded.Comment: 9 pages, 6 Postscript figures; some comments adde

    Finite density QCD with heavy quarks

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    In the large fermion mass limit of QCD at finite density the structure of the partition function greatly simplifies and can be studied analytically. We show that, contrary to general wisdom, the phase of the Dirac determinant is relevant only at finite temperature and can be neglected for zero temperature fields.Comment: LATTICE98(hightemp), 3 pages, 3 figure

    The geometry of the Barbour-Bertotti theories II. The three body problem

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    We present a geometric approach to the three-body problem in the non-relativistic context of the Barbour-Bertotti theories. The Riemannian metric characterizing the dynamics is analyzed in detail in terms of the relative separations. Consequences of a conformal symmetry are exploited and the sectional curvatures of geometrically preferred surfaces are computed. The geodesic motions are integrated. Line configurations, which lead to curvature singularities for N3N\neq 3, are investigated. None of the independent scalars formed from the metric and curvature tensor diverges there.Comment: 16 pages, 2 eps figures, to appear in Classical and Quantum Gravit

    Universal transloader moves delicate equipment without stress

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    Transloader moves delicate or heavy items over irregular surfaces without transmitting stress to the load. The loader is supported on three pivot points which produce a wrap free base. The base is supported by an artificial four-wheel frame

    Sickness certification system in the United Kingdom: qualitative study of views of general practitioners in Scotland

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    Objectives: To explore how general practitioners operate the sickness certification system, their views on the system, and suggestions for change. Design: Qualitative focus group study consisting of 11 focus groups with 67 participants. Setting: General practitioners in practices in Glasgow, Tayside, and Highland regions, Scotland. Sample: Purposive sample of general practitioners, with further theoretical sampling of key informant general practitioners to examine emerging themes. Results: General practitioners believed that the sickness certification system failed to address complex, chronic, or doubtful cases. They seemed to develop various operational strategies for its implementation. There appeared to be important deliberate misuse of the system by general practitioners, possibly related to conflicts about roles and incongruities in the system. The doctor-patient relationship was perceived to conflict with the current role of general practitioners in sickness certification. When making decisions about certification, the general practitioners considered a wide variety of factors. They experienced contradictory demands from other system stakeholders and felt blamed for failing to make impossible reconciliations. They clearly identified the difficulties of operating the system when there was no continuity of patient care. Many wished either to relinquish their gatekeeper role or to continue only with major changes. Conclusions: Policy makers need to recognise and accommodate the range and complexity of factors that influence the behaviour of general practitioners operating as gatekeepers to the sickness certification system, before making changes. Such changes are otherwise unlikely to result in improvement. Models other than the primary care gatekeeper model should be considered

    Leptons, quarks, and their antiparticles from a phase-space perspective

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    It is argued that antiparticles may be interpreted in macroscopic terms without explicitly using the concept of time and its reversal. The appropriate framework is that of nonrelativistic phase space. It is recalled that a quantum version of this approach leads also, alongside the appearance of antiparticles, to the emergence of `internal' quantum numbers identifiable with weak isospin, weak hypercharge and colour, and to the derivation of the Gell-Mann-Nishijima relation, while simultaneously offering a preonless interpretation of the Harari-Shupe rishon model. Furthermore, it is shown that - under the assumption of the additivity of canonical momenta - the approach entails the emergence of string-like structures resembling mesons and baryons, thus providing a different starting point for the discussion of quark unobservability.Comment: Talk given at Fifth Int. Workshop DICE2010 Space-Time-Matter, Castiglioncello, Italy, September 13-17, 201

    Towards the Unification of Gravity and other Interactions: What has been Missed?

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    Faced with the persisting problem of the unification of gravity with other fundamental interactions we investigate the possibility of a new paradigm, according to which the basic space of physics is a multidimensional space C{\cal C} associated with matter configurations. We consider general relativity in C{\cal C}. In spacetime, which is a 4-dimensional subspace of C{\cal C}, we have not only the 4-dimensional gravity, but also other interactions, just as in Kaluza-Klein theories. We then consider a finite dimensional description of extended objects in terms of the center of mass, area, and volume degrees of freedom, which altogether form a 16-dimensional manifold whose tangent space at any point is Clifford algebra Cl(1,3). The latter algebra is very promising for the unification, and it provides description of fermions.Comment: 11 pages; Talk presented at "First Mediterranean Conference on Classical and Quantum Gravity", Kolymbari, Crete, Greece, 14-18 September 200

    The geometry of the Barbour-Bertotti theories I. The reduction process

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    The dynamics of N3N\geq 3 interacting particles is investigated in the non-relativistic context of the Barbour-Bertotti theories. The reduction process on this constrained system yields a Lagrangian in the form of a Riemannian line element. The involved metric, degenerate in the flat configuration space, is the first fundamental form of the space of orbits of translations and rotations (the Leibniz group). The Riemann tensor and the scalar curvature are computed by a generalized Gauss formula in terms of the vorticity tensors of generators of the rotations. The curvature scalar is further given in terms of the principal moments of inertia of the system. Line configurations are singular for N3N\neq 3. A comparison with similar methods in molecular dynamics is traced.Comment: 15 pages, to appear in Classical and Quantum Gravit
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