1,144 research outputs found
An Active-shunt Diverter for On-load Tap Changers
This paper presents a new hybrid diverter design for on-load tap changers. The design uses âactive-shuntâ current diversion principles. At its core, the design employs a low-voltage high-current switch-mode amplifier to divert current out of the mechanical contacts and into a pair of anti-parallel thyristors. Commutation between transformer taps may then be performed by the thyristors. The amplifier and thyristors are placed outside the normal load current path and only conduct during a tap change, producing efficiency savings and improving robustness when compared to previous hybrid on-load tap changer implementations. An amplifier control loop that autonomously produces zero-current conditions at switch opening and zero-voltage conditions at switch closure is demonstrated. Experimental results investigating the wear characteristics of contacts operated under the new hybrid diverter are presented, along with comparison results from a passive-type switching scheme. Contact lifetime of more than 25 million operations is demonstrated under the new scheme
Dynamics of Transformation from Segregation to Mixed Wealth Cities
We model the dynamics of the Schelling model for agents described simply by a
continuously distributed variable - wealth. Agents move to neighborhoods where
their wealth is not lesser than that of some proportion of their neighbors, the
threshold level. As in the case of the classic Schelling model where
segregation obtains between two races, we find here that wealth-based
segregation occurs and persists. However, introducing uncertainty into the
decision to move - that is, with some probability, if agents are allowed to
move even though the threshold level condition is contravened - we find that
even for small proportions of such disallowed moves, the dynamics no longer
yield segregation but instead sharply transition into a persistent mixed wealth
distribution. We investigate the nature of this sharp transformation between
segregated and mixed states, and find that it is because of a non-linear
relationship between allowed moves and disallowed moves. For small increases in
disallowed moves, there is a rapid corresponding increase in allowed moves, but
this tapers off as the fraction of disallowed moves increase further and
finally settles at a stable value, remaining invariant to any further increase
in disallowed moves. It is the overall effect of the dynamics in the initial
region (with small numbers of disallowed moves) that shifts the system away
from a state of segregation rapidly to a mixed wealth state.
The contravention of the tolerance condition could be interpreted as public
policy interventions like minimal levels of social housing or housing benefit
transfers to poorer households. Our finding therefore suggests that it might
require only very limited levels of such public intervention - just sufficient
to enable a small fraction of disallowed moves, because the dynamics generated
by such moves could spur the transformation from a segregated to mixed
equilibrium.Comment: 12 pages, 7 figure
Health literacy, health status, and healthcare utilization of Taiwanese adults: results from a national survey
Abstract Background Low health literacy is considered a worldwide health threat. The purpose of this study is to assess the prevalence and socio-demographic covariates of low health literacy in Taiwanese adults and to investigate the relationships between health literacy and health status and health care utilization. Methods A national survey of 1493 adults was conducted in 2008. Health literacy was measured using the Mandarin Health Literacy Scale. Health status was measured based on self-rated physical and mental health. Health care utilization was measured based on self-reported outpatient clinic visits, emergency room visits, and hospitalizations. Results Approximately thirty percent of adults were found to have low (inadequate or marginal) health literacy. They tended to be older, have fewer years of schooling, lower household income, and reside in less populated areas. Inadequate health literacy was associated with poorer mental health (OR, 0.57; 95% CI, 0.35-0.91). No association was found between health literacy and health care utilization even after adjusting for other covariates. Conclusions Low (inadequate and marginal) health literacy is prevalent in Taiwan. High prevalence of low health literacy is not necessarily indicative of the need for interventions. Systematic efforts to evaluate the impact of low health literacy on health outcomes in other countries would help to illuminate features of health care delivery and financing systems that may mitigate the adverse health effects of low health literacy.http://deepblue.lib.umich.edu/bitstream/2027.42/78252/1/1471-2458-10-614.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78252/2/1471-2458-10-614.pdfPeer Reviewe
Spectral quantification of nonlinear behaviour of the nearshore seabed and correlations with potential forcings at Duck, N.C., U.S.A
Local bathymetric quasi-periodic patterns of oscillation are identified from
monthly profile surveys taken at two shore-perpendicular transects at the USACE
field research facility in Duck, North Carolina, USA, spanning 24.5 years and
covering the swash and surf zones. The chosen transects are the two furthest
(north and south) from the pier located at the study site. Research at Duck has
traditionally focused on one or more of these transects as the effects of the
pier are least at these locations. The patterns are identified using singular
spectrum analysis (SSA). Possible correlations with potential forcing
mechanisms are discussed by 1) doing an SSA with same parameter settings to
independently identify the quasi-periodic cycles embedded within three
potentially linked sequences: monthly wave heights (MWH), monthly mean water
levels (MWL) and the large scale atmospheric index known as the North Atlantic
Oscillation (NAO) and 2) comparing the patterns within MWH, MWL and NAO to the
local bathymetric patterns. The results agree well with previous patterns
identified using wavelets and confirm the highly nonstationary behaviour of
beach levels at Duck; the discussion of potential correlations with
hydrodynamic and atmospheric phenomena is a new contribution. The study is then
extended to all measured bathymetric profiles, covering an area of 1100m
(alongshore) by 440m (cross-shore), to 1) analyse linear correlations between
the bathymetry and the potential forcings using multivariate empirical
orthogonal functions (MEOF) and linear correlation analysis and 2) identify
which collective quasi-periodic bathymetric patterns are correlated with those
within MWH, MWL or NAO, based on a (nonlinear) multichannel singular spectrum
analysis (MSSA). (...continued in submitted paper)Comment: 50 pages, 3 tables, 8 figure
Gauge links for transverse momentum dependent correlators at tree-level
In this paper we discuss the incorporation of gauge links in hadronic matrix
elements that describe the soft hadronic physics in high energy scattering
processes. In this description the matrix elements appear in soft correlators
and they contain non-local combinations of quark and gluon fields. In our
description we go beyond the collinear approach in which case also the
dependence on transverse momenta of partons is taken into consideration. The
non-locality in the transverse direction leads to a complex gauge link
structure for the full process, in which color is entangled, even at
tree-level. We show that at tree-level in a 1-parton unintegrated (1PU)
situation, in which only the transverse momentum of one of the initial state
hadrons is relevant, one can get a factorized expression involving transverse
momentum dependent (TMD) distribution functions. We point out problems at the
level of two initial state hadrons, even for relatively simple processes such
as Drell-Yan scattering.Comment: 25 pages, corrected typos and updated reference
Which older people decline participation in a primary care trial of physical activity and why: insights from a mixed methods approach
This article is available through the Brunel Open Access Publishing Fund. Copyright 2014 Rogers et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.Background: Physical activity is of vital importance to older peoplesâ health. Physical activity intervention studies with older people often have low recruitment, yet little is known about non-participants. Methods: Patients aged 60â74 years from three UK general practices were invited to participate in a nurse-supported pedometer-based walking intervention. Demographic characteristics of 298 participants and 690 non-participants were compared. Health status and physical activity of 298 participants and 183 non-participants who completed a survey were compared using age, sex adjusted odds ratios (OR) (95% confidence intervals). 15 non-participants were interviewed to explore perceived barriers to participation. Results: Recruitment was 30% (298/988). Participants were more likely than non-participants to be female (54% v 47%; pâ=â0.04) and to live in affluent postcodes (73% v 62% in top quintile; pâ<â0.001). Participants were more likely than non-participants who completed the survey to have an occupational pension OR 2.06 (1.35-3.13), a limiting longstanding illness OR 1.72 (1.05-2.79) and less likely to report being active OR 0.55 (0.33-0.93) or walking fast OR 0.56 (0.37-0.84). Interviewees supported general practice-based physical activity studies, particularly walking, but barriers to participation included: already sufficiently active, reluctance to walk alone or at night, physical symptoms, depression, time constraints, trial equipment and duration. Conclusion: Gender and deprivation differences suggest some selection bias. However, trial participants reported more health problems and lower activity than non-participants who completed the survey, suggesting appropriate trial selection in a general practice population. Non-participant interviewees indicated that shorter interventions, addressing physical symptoms and promoting confidence in pursuing physical activity, might increase trial recruitment and uptake of practice-based physical activity endeavours.The National Institute for Health Research (NIHR) under its Research for Patient Benefit Programme (Grant Reference Number PB-PG-0909-20055)
Fully-Unintegrated Parton Distribution and Fragmentation Functions at Perturbative k_T
We define and study the properties of generalized beam functions (BFs) and
fragmenting jet functions (FJFs), which are fully-unintegrated parton
distribution functions (PDFs) and fragmentation functions (FFs) for
perturbative k_T. We calculate at one loop the coefficients for matching them
onto standard PDFs and FFs, correcting previous results for the BFs in the
literature. Technical subtleties when measuring transverse momentum in
dimensional regularization are clarified, and this enables us to renormalize in
momentum space. Generalized BFs describe the distribution in the full
four-momentum k_mu of a colliding parton taken out of an initial-state hadron,
and therefore characterize the collinear initial-state radiation. We illustrate
their importance through a factorization theorem for pp -> l^+ l^- + 0 jets,
where the transverse momentum of the lepton pair is measured. Generalized FJFs
are relevant for the analysis of semi-inclusive processes where the full
momentum of a hadron, fragmenting from a jet with constrained invariant mass,
is measured. Their significance is shown for the example of e^+ e^- -> dijet+h,
where the perpendicular momentum of the fragmenting hadron with respect to the
thrust axis is measured.Comment: Journal versio
Identification of plasma lipid biomarkers for prostate cancer by lipidomics and bioinformatics
Background:
Lipids have critical functions in cellular energy storage, structure and signaling. Many individual lipid molecules have been associated with the evolution of prostate cancer; however, none of them has been approved to be used as a biomarker. The aim of this study is to identify lipid molecules from hundreds plasma apparent lipid species as biomarkers for diagnosis of prostate cancer.
Methodology/Principal Findings:
Using lipidomics, lipid profiling of 390 individual apparent lipid species was performed on 141 plasma samples from 105 patients with prostate cancer and 36 male controls. High throughput data generated from lipidomics were analyzed using bioinformatic and statistical methods. From 390 apparent lipid species, 35 species were demonstrated to have potential in differentiation of prostate cancer. Within the 35 species, 12 were identified as individual plasma lipid biomarkers for diagnosis of prostate cancer with a sensitivity above 80%, specificity above 50% and accuracy above 80%. Using top 15 of 35 potential biomarkers together increased predictive power dramatically in diagnosis of prostate cancer with a sensitivity of 93.6%, specificity of 90.1% and accuracy of 97.3%. Principal component analysis (PCA) and hierarchical clustering analysis (HCA) demonstrated that patient and control populations were visually separated by identified lipid biomarkers. RandomForest and 10-fold cross validation analyses demonstrated that the identified lipid biomarkers were able to predict unknown populations accurately, and this was not influenced by patient's age and race. Three out of 13 lipid classes, phosphatidylethanolamine (PE), ether-linked phosphatidylethanolamine (ePE) and ether-linked phosphatidylcholine (ePC) could be considered as biomarkers in diagnosis of prostate cancer.
Conclusions/Significance:
Using lipidomics and bioinformatic and statistical methods, we have identified a few out of hundreds plasma apparent lipid molecular species as biomarkers for diagnosis of prostate cancer with a high sensitivity, specificity and accuracy
Bayesian Hierarchical Models Combining Different Study Types and Adjusting for Covariate Imbalances: A Simulation Study to Assess Model Performance
BACKGROUND: Bayesian hierarchical models have been proposed to combine evidence from different types of study designs. However, when combining evidence from randomised and non-randomised controlled studies, imbalances in patient characteristics between study arms may bias the results. The objective of this study was to assess the performance of a proposed Bayesian approach to adjust for imbalances in patient level covariates when combining evidence from both types of study designs. METHODOLOGY/PRINCIPAL FINDINGS: Simulation techniques, in which the truth is known, were used to generate sets of data for randomised and non-randomised studies. Covariate imbalances between study arms were introduced in the non-randomised studies. The performance of the Bayesian hierarchical model adjusted for imbalances was assessed in terms of bias. The data were also modelled using three other Bayesian approaches for synthesising evidence from randomised and non-randomised studies. The simulations considered six scenarios aimed at assessing the sensitivity of the results to changes in the impact of the imbalances and the relative number and size of studies of each type. For all six scenarios considered, the Bayesian hierarchical model adjusted for differences within studies gave results that were unbiased and closest to the true value compared to the other models. CONCLUSIONS/SIGNIFICANCE: Where informed health care decision making requires the synthesis of evidence from randomised and non-randomised study designs, the proposed hierarchical Bayesian method adjusted for differences in patient characteristics between study arms may facilitate the optimal use of all available evidence leading to unbiased results compared to unadjusted analyses
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