685 research outputs found
Pre-service Teachers\u27 Understandings About ELLs: One Pedagogical Tool for Identifying and Shifting Dispositions
Cowart, Melinda T, Ed.D. Series EditorAnderson, Gina, Ed.D. Managing Edito
Coherent resistance of a disordered 1D wire: Expressions for all moments and evidence for non-Gaussian distribution
We study coherent electron transport in a one-dimensional wire with disorder
modeled as a chain of randomly positioned scatterers. We derive analytical
expressions for all statistical moments of the wire resistance . By means
of these expressions we show analytically that the distribution of the
variable is not exactly Gaussian even in the limit of weak
disorder. In a strict mathematical sense, this conclusion is found to hold not
only for the distribution tails but also for the bulk of the distribution
.Comment: Revised version, 8 pages, 4 figures, RevTeX
Metal-insulator transition in three dimensional Anderson model: universal scaling of higher Lyapunov exponents
Numerical studies of the Anderson transition are based on the finite-size
scaling analysis of the smallest positive Lyapunov exponent. We prove
numerically that the same scaling holds also for higher Lyapunov exponents.
This scaling supports the hypothesis of the one-parameter scaling of the
conductance distribution. From the collected numerical data for quasi one
dimensional systems up to the system size 24 x 24 x infinity we found the
critical disorder 16.50 < Wc < 16.53 and the critical exponent 1.50 < \nu <
1.54. Finite-size effects and the role of irrelevant scaling parameters are
discussed.Comment: 4 pages, 2 figure
Supervised exercise training and increased physical activity to reduce cardiovascular disease risk in women with polycystic ovary syndrome: Study protocol for a randomized controlled feasibility trial
Background: Polycystic ovary syndrome (PCOS) affects up to 20% of women and is characterised by higher amounts of visceral fat, obesity, insulin resistance, dyslipidemia and reproductive and cardiometabolic complications. Increased oxidised low-density lipoprotein (LDL) concentrations have been associated with an increased risk of cardiovascular disease (CVD)-related events. Oxidised LDL is rarely used as a marker for CVD risk in PCOS-related studies despite its widely accepted role in atherogenesis and the increased risk factors associated with PCOS. Additionally, prolonged periods of sedentary behaviour can negatively affect metabolic health. No studies have specifically examined the effects of reducing sedentary behaviour on CVD risk in PCOS with a lifestyle physical activity intervention. The aim of the current study is to measure the feasibility of a randomised controlled trial (RCT) examining the effects of supervised exercise and reducing sedentary behaviour in women with PCOS on CVD risk. Methods/design: A feasibility, exploratory RCT will be conducted. Fifty-one pre-menopausal females will be randomly allocated between an exercise group (EG), a lifestyle physical activity group (LPAG) and a control group. Participants in the EG will undertake a 12-week supervised aerobic exercise programme. The LPAG will aim to increase daily physical activity and reduce sedentary behaviour for 12 weeks. The control group will not take part in any intervention. Primary outcomes are feasibility and acceptability of the intervention and procedures. Secondary outcomes are oxidised LDL, aerobic fitness, blood lipid profile, fasting glucose and insulin, testosterone and inflammatory markers. Discussion: PCOS is associated with various increased risk factors for CVD, including hypertension, dyslipidemia, abdominal obesity, insulin resistance, and inflammation. Whether oxidised LDL has a role in this increased risk is not yet known. The present study aims to measure the feasibility of implementing structured exercise training and/or increased lifestyle physical activity in women with PCOS, so that a subsequent adequately powered RCT can be designed. The results from the study will be used to refine the interventions and determine the acceptability of the study design. A limitation is that some self-monitoring in the lifestyle physical activity group may not be reliable or replicable, for example inputting information about time spent cleaning/gardening
Association of Aerobic Fitness and Metabolic Syndrome in Male Firefighters
Association of Aerobic Fitness and Metabolic Syndrome in Male Firefighters. Durcan, C.M.*, S.E. Martinā”, B.S. Lambertā , N.P. Greeneā , J.M. Markosā , A.F. Carbuhnā , J.S. Greenā”, FACSM and S.F. Crouseā”, FACSM. Department of Health and Kinesiology, Texas A&M University, College Station, TX. Metabolic syndrome has been shown in numerous studies to be related to a higher incidence of coronary artery disease. A study by R. Jurca et.al., in Med. Sci. Sports Exerc 36(38), found a relationship between aerobic fitness and the prevalence of metabolic syndrome in a group of men enrolled in the Aerobics Center Longitudinal Study. Information on this relationship in male firefighters is currently lacking. Purpose: To determine the association of metabolic syndrome and aerobic fitness in male fire fighters. Methods: As part of an annual physical exam, 213 male fire fighters (average age = 37) underwent evaluation of risk factors associated with metabolic syndrome as defined by NCEP III. These include the presence of three or more of the following: Waist circumference \u3e 40 , HDL Cholesterol \u3c 40 mg/dL, Triglycerides \u3e 150 mg/dL, Blood Glucose \u3e 110 mg/dL, and resting blood pressure \u3e 130/85 mm Hg. Aerobic Fitness was determined by estimating VO2max from time on treadmill during a Bruce protocol. Results: The subjects were ranked and divided into quartiles based on VO2max. All data were analyzed using a Chi Square test (p \u3c .05). Prevalence of metabolic syndrome increased significantly across quartiles as aerobic fitness declined. Conclusion: The data suggest that as aerobic fitness improves, the likelihood of male firefighters having metabolic syndrome decreases. These data are similar to the results found by R. Jurca et.al
Effective medium theory of left-handed materials
We analyze the transmission and reflection data obtained through transfer
matrix calculations on metamaterials of finite lengths, to determine their
effective permittivity and permeability. Our study concerns metamaterial
structures composed of periodic arrangements of wires, cut-wires, split ring
resonators (SRRs), closed-SRRs, and both wires and SRRs. We find that the SRRs
have a strong electric response, equivalent to that of cut-wires, which
dominates the behavior of left-handed materials (LHM). Analytical expressions
for the effective parameters of the different structures are given, which can
be used to explain the transmission characteristics of LHMs. Of particular
relevance is the criterion introduced by our studies to identify if an
experimental transmission peak is left- or right-handed.Comment: to be published in Phys. Rev. Let
A Universal Scaling for the Energetics of Relativistic Jets From Black Hole Systems
Black holes generate collimated, relativistic jets which have been observed
in gamma-ray bursts (GRBs), microquasars, and at the center of some galaxies
(active galactic nuclei; AGN). How jet physics scales from stellar black holes
in GRBs to the supermassive ones in AGNs is still unknown. Here we show that
jets produced by AGNs and GRBs exhibit the same correlation between the kinetic
power carried by accelerated particles and the gamma-ray luminosity, with AGNs
and GRBs lying at the low and high-luminosity ends, respectively, of the
correlation. This result implies that the efficiency of energy dissipation in
jets produced in black hole systems is similar over 10 orders of magnitude in
jet power, establishing a physical analogy between AGN and GRBs.Comment: Published in Science, 338, 1445 (2012), DOI: 10.1126/science.1227416.
This is the author's version of the work. It is posted here by permission of
the AAAS for personal use, not for redistribution. Corrected typo in equation
4 of the supplementary materia
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