10,628 research outputs found
Core content modules at Leeds Metropolitan University
As part of Leeds Metropolitan University’s review of the postgraduate curriculum in 2012–13, Libraries and Learning Innovation (LLI) was asked to lead a project group to create two core content modules for use at Level 7 (Masters level) in Research Practice and Project Management. The rationale for choosing these two areas was the sheer number of modules in these subjects taught across a wide range of disciplines, each of which is currently designed and populated by individual course teams. The group consisted of representatives from the University’s Centre for Teaching and Learning, academic staff, learning technologists and academic librarians, and was chaired by the Associate Director of LLI, Wendy Luker
Oxidation and protection of fiberglass-epoxy composite masts for photovoltaic arrays in the low Earth orbital environment
Fiberglass-epoxy composites are considered for use as structural members for the mast of the space station solar array panel. The low Earth orbital environment in which space station is to operate is composed mainly of atomic oxygen, which has been shown to cause erosion of many organic materials and some metals. Ground based testing in a plasma asher was performed to determine the extent of degradation of fiberglass-epoxy composites when exposed to a simulated atomic oxygen environment. During exposure, the epoxy at the surface of the composite was oxidized, exposing individual glass fibers which could easily be removed. Several methods of protecting the composite were evaluated in an atomic oxygen environment and with thermal cycling and flexing. The protection techniques evaluated to date include an aluminum braid covering, an indium-tin eutectic and a silicone based paint. The open aluminum braid offered little protection while the CV-1144 coating offered some initial protection against atomic oxygen, but appears to develop cracks which accelerate degradation when flexed. Coatings such as the In-Sn eutectic may provide adequate protection by containing the glass fibers even though mass loss still occurs
Abnormal negative feedback processing in first episode schizophrenia: evidence from an oculomotor rule switching task
Background. Previous studies have shown that patients with schizophrenia are impaired on executive tasks,
where positive and negative feedbacks are used to update task rules or switch attention. However, research to date
using saccadic tasks has not revealed clear deficits in task switching in these patients. The present study used an
oculomotor ‘ rule switching ’ task to investigate the use of negative feedback when switching between task rules in
people with schizophrenia.
Method. A total of 50 patients with first episode schizophrenia and 25 healthy controls performed a task in which the association between a centrally presented visual cue and the direction of a saccade could change from trial to trial. Rule changes were heralded by an unexpected negative feedback, indicating that the cue-response mapping
had reversed.
Results. Schizophrenia patients were found to make increased errors following a rule switch, but these were almost entirely the result of executing saccades away from the location at which the negative feedback had been presented on the preceding trial. This impairment in negative feedback processing was independent of IQ.
Conclusions. The results not only confirm the existence of a basic deficit in stimulus–response rule switching in
schizophrenia, but also suggest that this arises from aberrant processing of response outcomes, resulting in a failure to appropriately update rules. The findings are discussed in the context of neurological and pharmacological
abnormalities in the conditions that may disrupt prediction error signalling in schizophrenia
Executive function in first-episode schizophrenia
BACKGROUND: We tested the hypothesis that schizophrenia is primarily a frontostriatal disorder by examining executive function in first-episode patients. Previous studies have shown either equal decrements in many cognitive domains or specific deficits in memory. Such studies have grouped test results or have used few executive measures, thus, possibly losing information. We, therefore, measured a range of executive ability with tests known to be sensitive to frontal lobe function.
METHODS: Thirty first-episode schizophrenic patients and 30 normal volunteers, matched for age and NART IQ, were tested on computerized test of planning, spatial working memory and attentional set shifting from the Cambridge Automated Neuropsychological Test Battery. Computerized and traditional tests of memory were also administered for comparison. RESULTS: Patients were worse on all tests but the profile was non-uniform. A componential analysis indicated that the patients were characterized by a poor ability to think ahead and organize responses but an intact ability to switch attention and inhibit prepotent responses. Patients also demonstrated poor memory, especially for free recall of a story and associate learning of unrelated word pairs.
CONCLUSIONS: In contradistinction to previous studies, schizophrenic patients do have profound executive impairments at the beginning of the illness. However, these concern planning and strategy use rather than attentional set shifting, which is generally unimpaired. Previous findings in more chronic patients, of severe attentional set shifting impairment, suggest that executive cognitive deficits are progressive during the course of schizophrenia. The finding of severe mnemonic impairment at first episode suggests that cognitive deficits are not restricted to one cognitive domain
Curvaton reheating: an application to braneworld inflation
The curvaton was introduced recently as a distinct inflationary mechanism for
generating adiabatic density perturbations. Implicit in that scenario is that
the curvaton offers a new mechanism for reheating after inflation, as it is a
form of energy density not diluted by the inflationary expansion. We consider
curvaton reheating in the context of a braneworld inflation model, {\em steep
inflation}, which features a novel use of the braneworld to give a new
mechanism for ending inflation. The original steep inflation model featured
reheating by gravitational particle production, but the inefficiency of that
process brings observational difficulties. We demonstrate here that the
phenomenology of steep inflation is much improved by curvaton reheating.Comment: 8 pages RevTeX4 file with two figures incorporated. Improved
referencing, matches PRD accepted versio
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National laboratories` capabilities summaries for the DOE Virtual Center for Multiphase Dynamics (VCMD)
The Virtual Center For Multiphase Dynamics (VCMD) integrates and develops the resources of industry, government, academia, and professional societies to enable reliable analysis in multiphase computational fluid dynamics. The primary means of the VCMD focus will be by the creation, support, and validation of a computerized simulation capability for multiphase flow and multiphase flow applications. This paper briefly describes the capabilities of the National Laboratories in this effort
Primordial Magnetic Fields, Right Electrons, and the Abelian Anomaly
In the standard model there are charges with abelian anomaly only (e.g.
right-handed electron number) which are effectively conserved in the early
universe until some time shortly before the electroweak scale. A state at
finite chemical potential of such a charge, possibly arising due to asymmetries
produced at the GUT scale, is unstable to the generation of hypercharge
magnetic field. Quite large magnetic fields ( gauss at GeV with typical inhomogeneity scale ) can be
generated. These fields may be of cosmological interest, potentially acting as
seeds for amplification to larger scale magnetic fields through non-linear
mechanisms. Previously derived bounds on exotic violating operators may
also be evaded.Comment: Revised version, to appear in Phys. Rev. Lett.. Analysis has been
extended to larger chemical potentials, for which large magnetic fields
survive at the electroweak scale. Previous bounds on violating
operators are also evaded in this cas
Spanning tree generating functions and Mahler measures
We define the notion of a spanning tree generating function (STGF) , which gives the spanning tree constant when evaluated at and gives
the lattice Green function (LGF) when differentiated. By making use of known
results for logarithmic Mahler measures of certain Laurent polynomials, and
proving new results, we express the STGFs as hypergeometric functions for all
regular two and three dimensional lattices (and one higher-dimensional
lattice). This gives closed form expressions for the spanning tree constants
for all such lattices, which were previously largely unknown in all but one
three-dimensional case. We show for all lattices that these can also be
represented as Dirichlet -series. Making the connection between spanning
tree generating functions and lattice Green functions produces integral
identities and hypergeometric connections, some of which appear to be new.Comment: 26 pages. Dedicated to F Y Wu on the occasion of his 80th birthday.
This version has additional references, additional calculations, and minor
correction
Electroweak baryogenesis induced by a scalar field
A cosmological pseudoscalar field coupled to hypercharge topological number
density can exponentially amplify hyperelectric and hypermagnetic fields while
coherently rolling or oscillating, leading to the formation of a time-dependent
condensate of topological number density. The topological condensate can be
converted, under certain conditions, into baryons in sufficient quantity to
explain the observed baryon asymmetry in the universe. The amplified
hypermagnetic field can perhaps sufficiently strengthen the electroweak phase
transition, and by doing so, save any pre-existing baryon number asymmetry from
extinction.Comment: 8 pages, 4 figure
Gene duplication in an African cichlid adaptive radiation
Background Gene duplication is a source of evolutionary innovation and can contribute to the divergence of lineages; however, the relative importance of this process remains to be determined. The explosive divergence of the African cichlid adaptive radiations provides both a model for studying the general role of gene duplication in the divergence of lineages and also an exciting foray into the identification of genomic features that underlie the dramatic phenotypic and ecological diversification in this particular lineage. We present the first genome-wide study of gene duplication in African cichlid fishes, identifying gene duplicates in three species belonging to the Lake Malawi adaptive radiation (Metriaclima estherae, Protomelas similis, Rhamphochromis “chilingali”) and one closely related species from a non-radiated riverine lineage (Astatotilapia tweddlei). Results Using Astatotilapia burtoni as reference, microarray comparative genomic hybridization analysis of 5689 genes reveals 134 duplicated genes among the four cichlid species tested. Between 51 and 55 genes were identified as duplicated in each of the three species from the Lake Malawi radiation, representing a 38%–49% increase in number of duplicated genes relative to the non-radiated lineage (37 genes). Duplicated genes include several that are involved in immune response, ATP metabolism and detoxification. Conclusions These results contribute to our understanding of the abundance and type of gene duplicates present in cichlid fish lineages. The duplicated genes identified in this study provide candidates for the analysis of functional relevance with regard to phenotype and divergence. Comparative sequence analysis of gene duplicates can address the role of positive selection and adaptive evolution by gene duplication, while further study across the phylogenetic range of cichlid radiations (and more generally in other adaptive radiations) will determine whether the patterns of gene duplication seen in this study consistently accompany rapid radiation
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