6,260 research outputs found
Geometry Optimization of Crystals by the Quasi-Independent Curvilinear Coordinate Approximation
The quasi-independent curvilinear coordinate approximation (QUICCA) method
[K. N\'emeth and M. Challacombe, J. Chem. Phys. {\bf 121}, 2877, (2004)] is
extended to the optimization of crystal structures. We demonstrate that QUICCA
is valid under periodic boundary conditions, enabling simultaneous relaxation
of the lattice and atomic coordinates, as illustrated by tight optimization of
polyethylene, hexagonal boron-nitride, a (10,0) carbon-nanotube, hexagonal ice,
quartz and sulfur at the -point RPBE/STO-3G level of theory.Comment: Submitted to Journal of Chemical Physics on 7/7/0
A webometric analysis of Australian Universities using staff and size dependent web impact factors (WIF)
This study describes how search engines (SE) can be employed for automated, efficient data gathering for Webometric studies using predictable URLs. It then compares the usage of staffrelated Web Impact Factors (WIFs) to sizerelated impact factors for a ranking of Australian universities, showing that rankings based on staffrelated WIFs correlate much better with an established ranking from the Melbourne Institute than commonly used sizedependent WIFs. In fact sizedependent WIFs do not correlate with the Melbourne ranking at all. It also compares WIF data for Australian Universities provided by Smith (1999) for a longitudinal comparison of the WIF of Australian Universities over the last decade. It shows that sizedependent WIF values declined for most Australian universities over the last ten years, while staffdependent WIFs rose
Generalized Wilson Chain for solving multichannel quantum impurity problems
The Numerical Renormalization Group is used to solve quantum impurity
problems, which describe magnetic impurities in metals, nanodevices, and
correlated materials within DMFT. Here we present a simple generalization of
the Wilson Chain, which improves the scaling of computational cost with the
number of channels/bands, bringing new problems within reach. The method is
applied to calculate the t-matrix of the three-channel Kondo model at T=0,
which shows universal crossovers near non-Fermi liquid critical points. A
non-integrable three-impurity problem with three bands is also studied,
revealing a rich phase diagram and novel screening/overscreening mechanisms.Comment: 5 pages + 5 pages supplementary materia
Evidence in Classical Statistics
The dominance of classical statistics raises a puzzle for epistemologists. On one hand, science is a paradigmatic source of good evidence, with quantitative experimental science often described in classical statistical terms. On the other, the hybrid of Fisherian and Neyman-Pearsonian techniques is generally rejected by philosophers, statisticians, and scientists who study the foundations of statistics. So why is the use of classical statistics in empirical science so epistemically successful? Do classical “measures” of
evidence actually measure anything epistemically important? This chapter provides some positive answers to these questions
Electric Upgrades - Supercapacitor Electric Bicycle
Supercapacitors provide high current capabilities compared to conventional lithium-ion batteries, allowing for fast charging and discharging of electrical energy. This project seeks to test the benefits of supercapacitors in an electric bicycle unit in order to gain higher regenerative energy. The main components of the bicycle are its regenerative motor, supercapacitor array, and motor controller. Developing the project will provide data on the feasibility of using alternative battery storage and charging
Nestling diet, secondary sexual traits and fitness in the zebra finch
We examined the effect of nestling diet quality on a suite of physiological, morphological and life-history
traits in adult male zebra finches,Taeniopygia guttata. Compared with birds reared on a supplemented diet,
nestlings reared on a seed-only diet showed a reduced rate of growth and reduced cell-mediated immune function as measured by an in vivo response to aT lymphocyte-dependent mitogen. There were no differences between birds reared on the two diets in any of the following adult traits: body size, primary sexual traits (testes mass, numbers of stored sperm, sperm function, velocity and morphology), secondary sexual traits (beak colour and song rate), serological traits or immunological traits. The only differences we detected were a lower body mass and a greater proportion of individuals with plumage abnormalities among those reared on a seed-only diet (this latter effect was transient). The fact that male zebra finches reared on a seed-only diet were, as adults, virtually indistinguishable from those reared on a supple-
mented diet, despite having reduced growth and immune function as nestlings, demonstrates that they
subsequently compensated through the di¡erential allocation of resources. Our results indicate that differ-
ential allocation is costly in terms of fitness since birds reared on a seed-only diet experienced a significantly greater mortality rate than those reared on a supplemented diet. This in turn suggests the existence of a trade-of between the development of traits important for reproduction, such as primary and secondary sexual traits and longevity
A webometric analysis of Australian Universities using staff and size dependent web impact factors (WIF)
This study describes how search engines (SE) can be employed for automated, efficient data gathering for Webometric studies using predictable URLs. It then compares the usage of staffrelated Web Impact Factors (WIFs) to sizerelated impact factors for a ranking of Australian universities, showing that rankings based on staffrelated WIFs correlate much better with an established ranking from the Melbourne Institute than commonly used sizedependent WIFs. In fact sizedependent WIFs do not correlate with the Melbourne ranking at all. It also compares WIF data for Australian Universities provided by Smith (1999) for a longitudinal comparison of the WIF of Australian Universities over the last decade. It shows that sizedependent WIF values declined for most Australian universities over the last ten years, while staffdependent WIFs rose
Improving the recruitment activity of clinicians in randomised controlled trials: a systematic review.
Background Poor recruitment to randomised controlled trials (RCTs) is a widespread problem. Provision of interventions aimed at supporting or incentivising clinicians may improve recruitment to RCTs. Objectives To quantify the effects of strategies aimed at improving the recruitment activity of clinicians in RCTs, complemented with a synthesis of qualitative evidence related to clinicians' attitudes towards recruiting to RCTs. Data sources A systematic review of English and non-English articles identified from: The Cochrane Library, Ovid MEDLINE, Ovid EMBASE, Ovid PsycINFO, Ebsco CINAHL, Index to Theses and Open SIGLE from 2001 to March 2011. Additional reports were identified through citation searches of included articles. Study eligibility criteria Quantitative studies were included if they evaluated interventions aimed at improving the recruitment activity of clinicians or compared recruitment by different groups of clinicians. Information about host trial, study design, participants, interventions, outcomes and host RCT was extracted by one researcher and checked by another. Studies that met the inclusion criteria were assessed for quality using a standardised tool, the Effective Public Health Practice Project tool. Qualitative studies were included if they investigated clinicians' attitudes to recruiting patients to RCTs. All results/findings were extracted, and content analysis was carried out. Overarching themes were abstracted, followed by a metasummary analysis. Studies that met the inclusion criteria were assessed for quality using the Critical Appraisal Skills Programme qualitative checklist. Data extraction Data extraction was carried out by one researcher using predefined data fields, including study quality indicators, and verified by another. Results Eight quantitative studies were included describing four interventions and a comparison of recruiting clinicians. One study was rated as strong, one as moderate and the remaining six as weak when assessed for quality using the Effective Public Health Practice Project tool. Effective interventions included the use of qualitative research to identify and overcome barriers to recruitment, reduction of the clinical workload associated with participation in RCTs and the provision of extra training and protected research time. Eleven qualitative studies were identified, and eight themes were abstracted from the data: understanding of research, communication, perceived patient barriers, patient-clinician relationship, effect on patients, effect on clinical practice, individual benefits for clinicians and methods associated with successful recruitment. Metasummary analysis identified the most frequently reported subthemes to be: difficulty communicating trial methods, poor understanding of research and priority given to patient well-being. Overall, the qualitative studies were found to be of good quality when assessed using the Critical Appraisal Skills Programme checklist. Conclusions There were few high-quality trials that tested interventions to improve clinicians' recruitment activity in RCTs. The most promising intervention was the use of qualitative methods to identify and overcome barriers to clinician recruitment activity. More good quality studies of interventions are needed to add to the evidence base. The metasummary of qualitative findings identified understanding and communicating RCT methods as a key target for future interventions to improve recruitment. Reinforcement of the potential benefits, both for clinicians and for their patients, could also be a successful factor in improving recruitment. A bias was found towards investigating barriers to recruitment, so future work should also encompass a focus on successfully recruiting trials
Dietary Supplementation with Ethyl Ester Concentrates of Fish Oil (n-3) and Borage Oil (n-6) Polyunsaturated Fatty Acids Induces Epidermal Generation of Local Putative Anti-Inflammatory Metabolites
Clinical reports have attributed the amelioration of chronic inflammatory skin disorders to the presence of certain polyunsaturated fatty acids (PUFA) in dietary oils. To test the hypothesis of a local modulatory effect of these PUFA in the epidermis, the basal diet of normal guinea pigs was supplemented with ethyl esters of either fish oil [rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] or borage oi1 [rich in gamma-linolenic acid (GLA)]. Our data demonstrated that dietary oils influence the distribution of PUFA in epidermal phospholipids and the epidermal levels of PUFA-derived hydroxy fatty acids. Specifically, animals supplemented with ethyl esters of fish oil markedly incorporated EPA and DHA into epidermal phospholipids, which paralleled the epidermal accumulation of 1 5-hydroxyeicosapentaenoic acid (15-HEPE) and 17-hydroxydocosahexaenoic acid (17-HDoHE). Similarly, animals supplemented with esters of borage oil preferentially incorporated dihomogammalinolenic acid (DGLA), the epidermal elongase product of GLA, into the epidermal phospholipids, which also was ac- companied by epidermal accumulation of 15-hydroxyeicosatrienoic acid (15-HETrE). By factoring the epidermal levels of the 15-lipoxygenase products and their relative inhibitory potencies, we evolved a measure of the overall potential of dietary oils to exert local anti-inflammatory effect. For example, the leukotriene inhibition potentials (LIP) of both fish oil and borage oil were greatly enhanced when compared to controls. Thus, the altered profiles of epidermal 15-lipoxygenase products generated from particular dietary oils may be responsible, at least in part, for reported ameliorative effects of oils on chronic inflammatory skin disorders
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