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Search Results: 1 - 10 of 463268 matches for " A. Wright "
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Three Evidence Based Methods to Compensate for a Lack of Subject Background when Ordering Chemistry Monographs
Robert A. Wright
Evidence Based Library and Information Practice , 2008,
Abstract: Objective – The aim of this article is to present evidence based methods for the selection of chemistry monographs, particularly for librarians lacking a background in chemistry. These methods will be described in detail, their practical application illustrated, and their efficacy tested by analyzing circulation data. Methods – Two hundred and ninety-five chemistry monographs were selected between 2005 and 2007 using rigorously-applied evidence based methods involving the Library's integrated library system (ILS), Google, and SciFinder Scholar. The average circulation rate of this group of monographs was compared to the average circulation rate of 254 chemistry monographs selected between 2002 and 2004 when the methods were not used or were in an incomplete state of development. Results – Circulations/month were on average 9% greater in the cohort of monographs selected with the rigorously-applied evidence based methods. Further statistical analysis, however, finds that this result can not be attributed to the different application of these methods. Conclusion – The methods discussed in this article appear to provide an evidence base for the selection of chemistry monographs, but their application does not change circulation rates in a statistically significant way. Further research is needed to determine if this lack of statistical significance is real or a product of the organic development and application of these methods over time, making definitive comparisons difficult.
An Empirical Model for the Radio Emission from Pulsars
G. A. E. Wright
Physics , 2002, DOI: 10.1046/j.1365-8711.2003.06815.x
Abstract: A model for slow radio pulsars is proposed which involves the entire magnetosphere in the production of the observed radio emission. It is argued that observations of pulsar profiles suggest that a feedback mechanism exists between the star surface and the null charge surface, requiring particle flow in both directions. In their flow to and from the surface the particles execute an azimuthal drift around the magnetic pole, thereby creating a ring of discrete `emission nodes' close to the surface. Motion of the nodes is observed as the well-known subpulse `drift', but is interpreted here as a small residual component of the real particle drift. The nodes can therefore move in either direction, or even remain stationary. A precise fit is found for the pulsar PSR0943+10. Azimuthal interactions between different regions of the magnetosphere depend on the angle between the magnetic and rotation axes and influence the conal type, as observed. The requirement of intermittent weak pair-production in an outergap suggests a natural evolutionary link between radio and gamma-ray pulsars.
A New Diagnostic of Magnetic Field Strengths in Radiatively-Cooled Shocks
P. Hartigan,A. Wright
Physics , 2015, DOI: 10.1088/0004-637X/811/1/12
Abstract: We show that it is possible to measure Alfv\'enic Mach numbers, defined as the shock velocity in the flow divided by the Alfv\'en velocity, for low-velocity (V$_{shock}$ $\lesssim$ 100 km$\,$s$^{-1}$) radiative shocks. The method combines observations of bright forbidden lines with a measure of the size of the cooling zone, the latter typically obtained from spatial separation between the Balmer emission lines and the forbidden lines. Because magnetic fields become compressed as gas in the postshock region cools, even relatively weak preshock magnetic fields can be detected with this method. We derive analytical formulae that explain how the spatial separations relate to emission-line ratios, and compute a large grid of radiatively-cooled shock models to develop diagnostic diagrams that can be used to derive Alfv\'enic Mach numbers in flows. Applying the method to existing data for a bright knot in the HH 111 jet, we obtain a relatively low Alfv\'enic Mach number of $\sim$ 2, indicative of a magnetized jet that has super-magnetosonic velocity perturbations within it.
Clinical features of spontaneous hypothyroidism in one physician’s practice in Jamaica
Rosemarie A Wright-Pascoe
International Journal of General Medicine , 2010, DOI: http://dx.doi.org/10.2147/IJGM.S10234
Abstract: ical features of spontaneous hypothyroidism in one physician’s practice in Jamaica Original Research (4284) Total Article Views Authors: Rosemarie A Wright-Pascoe Published Date May 2010 Volume 2010:3 Pages 137 - 141 DOI: http://dx.doi.org/10.2147/IJGM.S10234 Rosemarie A Wright-Pascoe Department of Medicine, The University of the West Indies, Kingston, Jamaica Objective: To describe the clinical characteristics of patients with spontaneous hypothyroidism, the frequency of chronic autoimmune thyroiditis, and the thyroid autoantibody most often associated with this condition in a referral population in Jamaica. Methods: A retrospective study of all cases referred to the author’s endocrinology practice from 1995 to 2005 with a diagnosis of spontaneous hypothyroidism was undertaken. The clinical history, examination findings, biochemical test results, thyroid autoimmune antibodies, and imaging data were reviewed. Results: Spontaneous primary hypothyroidism was correctly diagnosed in 53 subjects. Fifty of the patients were females and three were males. Mean age was 43.3 years (range 12–82 years); 24.4% of the patients had a family member with thyroid disease; 27.1% presented because of a goiter; and 54.2% because of symptoms suggestive of hypothyroidism. The thyroid was palpable in 56.3% and thyroid ultrasound was consistent with Hashimoto’s thyroiditis on 64% of occasions. Only 8% of the patients had the atrophic variant of hypothyroidism. Antithyroid peroxidase and antithyroglobulin antibody were positive in 75.8% and 37.5% of patients, respectively. Chronic autoimmune thyroiditis was confirmed in 78.8% of cases. Conclusion: In these cases in Jamaica, spontaneous hypothyroidism was predominantly a female disorder. Chronic autoimmune thyroiditis was the commonest cause, and antithyroid peroxidase antibody was the thyroid antibody most likely to be positive in this population.
Clinical features of spontaneous hypothyroidism in one physician’s practice in Jamaica
Rosemarie A Wright-Pascoe
International Journal of General Medicine , 2010,
Abstract: Rosemarie A Wright-PascoeDepartment of Medicine, The University of the West Indies, Kingston, JamaicaObjective: To describe the clinical characteristics of patients with spontaneous hypothyroidism, the frequency of chronic autoimmune thyroiditis, and the thyroid autoantibody most often associated with this condition in a referral population in Jamaica.Methods: A retrospective study of all cases referred to the author’s endocrinology practice from 1995 to 2005 with a diagnosis of spontaneous hypothyroidism was undertaken. The clinical history, examination findings, biochemical test results, thyroid autoimmune antibodies, and imaging data were reviewed.Results: Spontaneous primary hypothyroidism was correctly diagnosed in 53 subjects. Fifty of the patients were females and three were males. Mean age was 43.3 years (range 12–82 years); 24.4% of the patients had a family member with thyroid disease; 27.1% presented because of a goiter; and 54.2% because of symptoms suggestive of hypothyroidism. The thyroid was palpable in 56.3% and thyroid ultrasound was consistent with Hashimoto’s thyroiditis on 64% of occasions. Only 8% of the patients had the atrophic variant of hypothyroidism. Antithyroid peroxidase and antithyroglobulin antibody were positive in 75.8% and 37.5% of patients, respectively. Chronic autoimmune thyroiditis was confirmed in 78.8% of cases.Conclusion: In these cases in Jamaica, spontaneous hypothyroidism was predominantly a female disorder. Chronic autoimmune thyroiditis was the commonest cause, and antithyroid peroxidase antibody was the thyroid antibody most likely to be positive in this population.Keywords: spontaneous hypothyroidism, Jamaican, thyroid autoantibodies, L-thyroxine, autoimmune thyroiditis, Hashimoto’s thyroiditis
Climate change as a confounding factor in reversibility of acidification: RAIN and CLIMEX projects
R. F. Wright,A. Jenkins
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2001,
Abstract: The RAIN and CLIMEX experiments at Risdalsheia, southernmost Norway, together cover 17 years (1984-2000) of whole-catchment manipulation of acid deposition and climate. A 1200 m2 roof placed over the forest canopy at KIM catchment excluded about 80% of ambient acid deposition; clean rain was sprinkled under the roof. A climate change treatment (3.7°C increase in air temperature and increase in air carbon dioxide concentrations to 560 ppmv) was superimposed on the clean rain treatment for four years (1995-1998). Sea-salt inputs and temperature are climate-related factors that influence water chemistry and can confound long-term trends caused by changes in deposition of sulphur and nitrogen. The RAIN and CLIMEX experiments at Risdalsheia provided direct experimental data that allow quantitative assessment of these factors. Run-off chemistry responded rapidly to the decreased acid deposition. Sulphate concentrations decreased by 50% within three years; nitrate and ammonium concentrations decreased to new steady-state levels within the first year. Acid neutralising capacity increased and hydrogen ion and inorganic aluminium decreased. Similar recovery from acidification was also observed at the reference catchment, ROLF, in response to the general 50% reduction in sulphate deposition over southern Norway in the late 1980s and 1990s. Variations in sea-salt deposition caused large variations in run-off chemistry at the reference catchment ROLF and the year-to-year noise in acid neutralising capacity was as large as the overall trend over the period. These variations were absent at KIM catchment because the sea-salt inputs were held constant over the entire 17 years of the clean rain treatment. The climate change experiment at KIM catchment resulted in increased leaching of inorganic nitrogen, probably due to increased mineralisation and nitrification rates in the soils. Keywords: acid deposition, global change, water, soil, catchment, experiment, Norway.
Relating the Bipolar Spectrum to Dysregulation of Behavioural Activation: A Perspective from Dynamical Modelling
Arno Steinacher, Kim A. Wright
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063345
Abstract: Bipolar Disorders affect a substantial minority of the population and result in significant personal, social and economic costs. Understanding of the causes of, and consequently the most effective interventions for, this condition is an area requiring development. Drawing upon theories of Bipolar Disorder that propose the condition to be underpinned by dysregulation of systems governing behavioural activation or approach motivation, we present a mathematical model of the regulation of behavioural activation. The model is informed by non-linear, dynamical principles and as such proposes that the transition from “non-bipolar” to “bipolar” diagnostic status corresponds to a switch from mono- to multistability of behavioural activation level, rather than an increase in oscillation of mood. Consistent with descriptions of the behavioural activation or approach system in the literature, auto-activation and auto-inhibitory feedback is inherent within our model. Comparison between our model and empirical, observational data reveals that by increasing the non-linearity dimension in our model, important features of Bipolar Spectrum disorders are reproduced. Analysis from stochastic simulation of the system reveals the role of noise in behavioural activation regulation and indicates that an increase of nonlinearity promotes noise to jump scales from small fluctuations of activation levels to longer lasting, but less variable episodes. We conclude that further research is required to relate parameters of our model to key behavioural and biological variables observed in Bipolar Disorder.
Expanders and Property A
A. Khukhro,N. J. Wright
Mathematics , 2011, DOI: 10.2140/agt.2012.12.37
Abstract: We give a cohomological characterisation of expander graphs, and use it to give a direct proof that expander graphs do not have Yu's property A.
Exit manifolds for lattice differential equations
A. Hoffman,J. D. Wright
Mathematics , 2009,
Abstract: We study the weak interaction between a pair of well-separated coherent structures in possibly non-local lattice differential equations. In particular we prove that if a lattice differential equation in one space dimension has asymptotically stable (in the sense of Chow, Mallet-Paret and Shen) traveling wave solutions whose profiles approach limiting equilibria exponentially fast, then the system admits solutions which are nearly the linear superposition of two such traveling waves moving in opposite directions away from one another. Moreover, such solutions are themselves asymptotically stable. This result is meant to complement analytic or numeric studies into interactions of such pulses over finite times which might result in the scenario treated here. Since the traveling waves are moving in opposite directions, these solutions are not shift-periodic and hence the framework of Chow, Mallet-Paret, and Shen does not apply. We overcome this difficulty by embedding the original system in a larger one wherein the linear part can be written as a shift-periodic piece plus another piece which, even though it is non-autonomous and large, has certain properties which allow us to treat it as if it were a small perturbation.
A geometric interpretation of the permutation $p$-value and its application in eQTL studies
Wei Sun,Fred A. Wright
Statistics , 2010, DOI: 10.1214/09-AOAS298
Abstract: Permutation $p$-values have been widely used to assess the significance of linkage or association in genetic studies. However, the application in large-scale studies is hindered by a heavy computational burden. We propose a geometric interpretation of permutation $p$-values, and based on this geometric interpretation, we develop an efficient permutation $p$-value estimation method in the context of regression with binary predictors. An application to a study of gene expression quantitative trait loci (eQTL) shows that our method provides reliable estimates of permutation $p$-values while requiring less than 5% of the computational time compared with direct permutations. In fact, our method takes a constant time to estimate permutation $p$-values, no matter how small the $p$-value. Our method enables a study of the relationship between nominal $p$-values and permutation $p$-values in a wide range, and provides a geometric perspective on the effective number of independent tests.
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