251,139 research outputs found

    The customer is always right? Assessing the value of Patron Driven Acquisition at the University of Huddersfield

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    This article discusses a small scale Patron Driven Acquisition (PDA) study at the University of Huddersfield. The authors briefly describe the background to PDA at Huddersfield before discussing data from the 2014 PDA pilot with the e-book supplier EBL. The pilot produced two sets of data, usage reports using COUNTER statistics and a short questionnaire designed by the library. These results led to a major alteration to the collection management and development policy where PDA is now embedded into the library bookfund

    Extension of the HF program to partially filled f-subshells

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    A new version of a Hartree-Fock program is presented that includes extensions for partially filled f-subshells. The program allows the calculation of term dependent Hartree-Fock orbitals and energies in LS coupling for configurations with no more than two open subshells, including f-subshells

    Expected Anomalies in the Fossil Record

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    The problem of intermediates in the fossil record has been frequently discussed ever since Darwin. The extent of `gaps' (missing transitional stages) has been used to argue against gradual evolution from a common ancestor. Traditionally, gaps have often been explained by the improbability of fossilization and the discontinuous selection of found fossils. Here we take an analytical approach and demonstrate why, under certain sampling conditions, we may not expect intermediates to be found. Using a simple null model, we show mathematically that the question of whether a taxon sampled from some time in the past is likely to be morphologically intermediate to other samples (dated earlier and later) depends on the shape and dimensions of the underlying phylogenetic tree that connects the taxa, and the times from which the fossils are sampled

    Aspects of quark mass generation on a torus

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    In this talk we report on recent results for the quark propagator on a compact manifold. The corresponding Dyson-Schwinger equations on a torus are solved on volumes similar to the ones used in lattice calculations. The quark-gluon interaction is fixed such that the lattice results are reproduced. We discuss both the effects in the infinite volume/continuum limit as well as effects when the volume is small.Comment: 3 pages, 3 figures; talk given by CF at QNP06, Madrid, June 200

    Studying unquenching effects in QCD with Dyson-Schwinger equations

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    We summarise recent results on the properties of gluons, quarks and light mesons from the Green's functions approach to QCD. We discuss a self-consistent, infrared power law solution for the Schwinger-Dyson equations of the 1PI-Greens functions of Yang-Mills theory. The corresponding running coupling has a universal fixed point at zero momentum. Based on these analytical results a truncation scheme for the coupled system of Schwinger-Dyson equations for the propagators of QCD and the Bethe-Salpeter equation for light mesons has been formulated. We compare numerical results for charge eigenstate vector and pseudoscalar meson observables with corresponding lattice data. The effects of unquenching the system are found to be small but not negligible.Comment: 8 pages, 8 figures. Invited talk given by C.S.F. at the 'Workshop on computational hadron physics', Sept. 13 - 17, Nikosia, Cypru

    The fundamental groups of subsets of closed surfaces inject into their first shape groups

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    We show that for every subset X of a closed surface M^2 and every basepoint x_0, the natural homomorphism from the fundamental group to the first shape homotopy group, is injective. In particular, if X is a proper compact subset of M^2, then pi_1(X,x_0) is isomorphic to a subgroup of the limit of an inverse sequence of finitely generated free groups; it is therefore locally free, fully residually free and residually finite.Comment: Published by Algebraic and Geometric Topology at http://www.maths.warwick.ac.uk/agt/AGTVol5/agt-5-67.abs.htm

    On the form of the large deviation rate function for the empirical measures of weakly interacting systems

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    A basic result of large deviations theory is Sanov's theorem, which states that the sequence of empirical measures of independent and identically distributed samples satisfies the large deviation principle with rate function given by relative entropy with respect to the common distribution. Large deviation principles for the empirical measures are also known to hold for broad classes of weakly interacting systems. When the interaction through the empirical measure corresponds to an absolutely continuous change of measure, the rate function can be expressed as relative entropy of a distribution with respect to the law of the McKean-Vlasov limit with measure-variable frozen at that distribution. We discuss situations, beyond that of tilted distributions, in which a large deviation principle holds with rate function in relative entropy form.Comment: Published in at http://dx.doi.org/10.3150/13-BEJ540 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

    A new species of Colura (Lejeuneaceae) from the Aberdare Mountains, Kenya

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    The new species Colura zoophaga from the Aberdare Mountains in Kenya is described as new. It differs from C. berghenii and C. hedbergiana in the obtuse apex, which is rounded or only weakly prolonged. C. zoophaga also differs from C. berghenii in the smooth leaf-cells, from C. hedbergiana in the 5-horned perianth keels and from C. calyptrifolia in the papillose perianth. A key to the African taxa of Sectio Macroramphus is provided. The ecology of C. zoophaga is briefly described