285,518 research outputs found
The customer is always right? Assessing the value of Patron Driven Acquisition at the University of Huddersfield
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
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
Studying pion effects in the quark propagator
Within the framework of Schwinger-Dyson and Bethe-Salpeter equations we
investigate the importance of pions for the quark-gluon interaction. To this
end we choose a truncation for the quark-gluon vertex that includes
intermediate pion degrees of freedom and adjust the interaction such that
unquenched lattice results for various current quark masses are reproduced. The
corresponding Bethe-Salpeter kernel is constructed from constraints by chiral
symmetry. After extrapolation to the physical point we find a considerable
contribution of the pion back reaction to the quark mass function as well as to
the chiral condensate. The quark wave function is less affected.Comment: Talk given at 11th International Conference on Meson-Nucleon Physics
and the Structure of the Nucleon (MENU 2007), Julich, Germany, 10-14 Sep 200
Expected Anomalies in the Fossil Record
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
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
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
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
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
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
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