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Search Results: 1 - 10 of 88111 matches for " Gordon W. Walsh "
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Using Correction Equations Based on Measured Height and Weight Weakens Associations between Obesity Based on Self-Reports and Chronic Diseases
Cynthia L. Murray,Gordon W. Walsh,Sarah Connor Gorber
Epidemiology Research International , 2013, DOI: 10.1155/2013/890762
Abstract:
Using Correction Equations Based on Measured Height and Weight Weakens Associations between Obesity Based on Self-Reports and Chronic Diseases
Cynthia L. Murray,Gordon W. Walsh,Sarah Connor Gorber
Epidemiology Research International , 2013, DOI: 10.1155/2013/890762
Abstract: Objective. Researchers have established a preponderance of height overestimation among men and weight underestimation among women in self-reported anthropometric data, which skews obesity prevalence data and obscures obesity-chronic disease relationships. The objective of this study was to reevaluate associations between obesity and chronic diseases using body mass index (BMI) correction equations derived from measured data. Methods. Measured height and weight (MHW) data were collected on a subsample of the 17,126 Atlantic Canadians who participated in the 2007-2008 Canadian Community Health Survey (CCHS). To obtain corrected BMI estimates for the 17,126 adults, correction equations were developed in the MHW subsample and multiple regression procedures were used to model BMI. To test obesity-chronic disease relationships, logistic regression models were utilized. Results. The correction procedure eliminated statistically significant relations ( ) between obesity and chronic bronchitis and obesity and stroke. Also, correction attenuated many relationships between adiposity and chronic disease. For example, among obese adults, there was a 13%, 12%, and 7% reduction in the adjusted odds ratios for asthma, urinary incontinence, and cardiovascular disease, respectively. Conclusion. Further research is needed to fully understand how the usage of self-reported data alters our understanding of the relationships between overweight or obesity and chronic diseases. 1. Introduction With over one billion people overweight (body mass index (BMI) 25.0–29.9?kg/m2) and 500 million obese (BMI ≥ 30.0?kg/m2), the World Health Organization (WHO) considers obesity to be a global epidemic [1, 2]. Obesity is listed as a risk factor for cardiovascular disease (CVD, that is, hypertension, stroke, congestive heart failure, and coronary artery disease), type 2 diabetes, several types of cancer (i.e., colorectal, kidney, breast, endometrial, ovarian, and pancreatic), asthma, gallbladder disease, osteoarthritis, and chronic back pain [3]. Besides the heavy toll on morbidity and mortality rates exacted especially by severe obesity [4, 5], excess body fat also reportedly has a substantial economic burden on society. In Canada, the direct medical cost of overweight and obesity was $6.0 billion in 2006 [6]. While research has shown that obesity is associated with a number of chronic health conditions [1, 7], the relationships, though still significant, may be weaker than once thought [8–12]. Most studies investigating the link between obesity and adverse health outcomes use
A Comparison between Atlantic Canadian and National Correction Equations to Improve the Accuracy of Self-Reported Obesity Estimates in Atlantic Canada
Cynthia L. Murray,Gordon W. Walsh,Sarah Connor Gorber
Journal of Obesity , 2012, DOI: 10.1155/2012/492410
Abstract: Objectives. To determine whether obesity correction equations for the Canadian general population, which are dependent on the prevalence of obesity, are appropriate for use in Atlantic Canada, which has the highest obesity rates in the country. Also, to compare the accuracy of the national equations to equations developed specifically for the Atlantic Canadian population. Methods. The dataset consisted of Canadian Community Health Survey (CCHS) 2007-2008 data collected on 17,126 Atlantic Canadians and a subsample of adults, who provided measured height and weight (MHW) data. Atlantic correction equations were developed in the MHW subsample. Using separate multiple regression models for men and women, self-reported body mass index (BMI) was corrected by multiplying the self-reported estimate by its corresponding model coefficient and adding the model intercept. Paired t-tests were used to determine whether corrected mean BMI values were significantly more accurate (i.e., closer to measured data) than the equivalent means based on self-reported data. The analyses were repeated using the national equations. Results. Both the Atlantic and the national equations yielded corrected obesity estimates that were significantly more accurate than those based on self-report. Conclusion. The results provide some evidence of the generalizability of the national equations to atypical regions of Canada. 1. Introduction Obesity is a major cause of morbidity in Canada and in many parts of the world and it is increasing worldwide [1]. As indicated by a body mass index (BMI) greater than or equal to 30?kg/m2, obesity is a risk factor for cardiovascular disease, type 2 diabetes, several types of cancer, asthma, gallbladder disease, osteoarthritis, and chronic back pain [1, 2]. Class II+ obesity (BMI ≥ 35?kg/m2) is also associated with an increased risk of all-cause mortality [3]. Obesity and its associated comorbidities exact a heavy toll on health care systems and expenditures. In Canada, the 2006 direct medical cost of overweight and obesity was $6.0 billion [4]. Against a global background comprising of 500 million obese adults [1], obesity has reached a historic high in Canada with one-quarter of adults and 9% of children meeting the definition [5]. Federal government statistical agencies, such as Statistics Canada and the National Center for Health Statistics, use large population-based studies to track nationwide obesity trends. Researchers usually use the BMI as a proxy to gauge obesity in these large national studies. According to Health Canada [6], although the BMI
World-line instantons and the Schwinger effect as a WKB exact path integral
James Gordon,Gordon W. Semenoff
Physics , 2014, DOI: 10.1063/1.4908556
Abstract: A detailed study of the semiclassical expansion of the world line path integral for a charged relativistic particle in a constant external electric field is presented. We show that the Schwinger formula for charged particle pair production is reproduced exactly by the semiclassical expansion around classical instanton solutions when the leading order of fluctuations is taken into account. We prove that all corrections to this leading approximation vanish and that the WKB approximation to the world line path integral is exact.
Edge Modes and Teleportation in a Topologically Insulating Quantum Wire  [PDF]
Majd Ghrear, Brie Mackovic, Gordon W. Semenoff
Journal of Modern Physics (JMP) , 2018, DOI: 10.4236/jmp.2018.911131
Abstract: We find a simple model of an insulating state of a quantum wire which has a single isolated edge mode. We argue that, when brought to proximity, the edge modes on independent wires naturally form Bell entangled states which could be used for elementary quantum processes such as teleportation. We give an example of an algorithm which teleports the spin state of an electron from one quantum wire to another.
EUV Observational consequences of the spatial localisation of nanoflare heating within a multi-stranded atmospheric loop
Aveek Sarkar,Robert W Walsh
Physics , 2009, DOI: 10.1088/0004-637X/699/2/1480
Abstract: Determining the preferred spatial location of the energy input to solar coronal loops would be an important step forward towards a more complete understanding of the coronal heating problem. Following on from Sarkar & Walsh (2008) this paper presents a short 10e9 cm "global loop" as 125 individual strands, where each strand is modelled independently by a one-dimensional hydrodynamic simulation. The strands undergo small-scale episodic heating and are coupled together through the frequency distribution of the total energy input to the loop which follows a power law distribution with index ~ 2.29. The spatial preference of the swarm of heating events from apex to footpoint is investigated. From a theoretical perspective, the resulting emission measure weighted temperature profiles along these two extreme cases does demonstrate a possible observable difference. Subsequently, the simulated output is folded through the TRACE instrument response functions and a re-derivation of the temperature using different filter-ratio techniques is performed. Given the multi-thermal scenario created by this many strand loop model, a broad differential emission measure results; the subsequent double and triple filter ratios are very similar to those obtained from observations. However, any potential observational signature to differentiate between apex and footpoint dominant heating is possibly below instrumental thresholds. The consequences of using a broadband instrument like TRACE and Hinode-XRT in this way are discussed.
Red and Blueshifts in Multi-stranded Coronal Loops: A New Temperature Diagnostic
S. Regnier,R. W. Walsh
Physics , 2014,
Abstract: [...] redshifts are predominantly observed in the core of active regions, while blueshifts are observed at the edge of active regions. [...] Using a nanoflare heating model for multi-stranded coronal loops (Sarkar and Walsh, 2008, 2009), we reproduce the above Dopplershift observations using spectral lines covering a broad range of temperature (from 0.25 MK to 5.6 MK). We first show that red- and blueshifts are ubiquitous in all wavelength ranges; redshifts/downflows dominating cool spectral lines (from O v to Si vii) and blueshifts/upflows dominating the hot lines (from Fe xv to Ca xvii). By computing the average Dopplershift, we derive a new temperature diagnostic for coronal loops: the temperature at which the average Dopplershift vanishes is the mean temperature along the coronal loop. In addition, the temperature estimate at the footpoints of the loop when the average Dopplershift vanishes is a lower bound of the temperature along the loop. To compare closely with observations, we thus model typical Hinode/EIS rasters with a spatial resolution of 1", an exposure time of 50s and a step of 3". Even if the raster reproduce the global features of up and downflows along the loop, we show that this type of raster cannot provide information on the heating mechanism. We also discuss the fact that observing a single spectral line can lead to false interpretation of the physical processes at play. For instance, an observed increased in blueshift velocity in the Fe xii channel can indicate a cooling event (decrease of energy input). We also investigate the existence of coronal loops having Dopplershifts of opposite signs which could characterise a unidirectional flow along the loop: about 50% of loops have opposite Dopplershifts at the footpoints for the spectral line closest to the mean temperature of the loop.
Sleep, Circadian Rhythm, and Drug Abuse
Hal W. Gordon
The Scientific World Journal , 2007, DOI: 10.1100/tsw.2007.227
Abstract:
Electronic zero modes of vortices in Hall states of gapped graphene
Gordon W. Semenoff
Physics , 2010, DOI: 10.1103/PhysRevB.83.115450
Abstract: Recent observation of a metal-insulator phase transition in the $\nu=0$ Hall state of graphene has inspired the idea that charge carriers in the metallic state could be fractionally charged vortices. We examine the question of whether vortices in particular gapped states of graphene and subject to external magnetic and pseudo-magnetic fields could have the mid-gap zero mode electron states which would allow them to be charged.
Chiral Symmetry Breaking in Graphene
Gordon W. Semenoff
Physics , 2011, DOI: 10.1088/0031-8949/2012/T146/014016
Abstract: The question of whether the Coulomb interaction is strong enough to break the sublattice symmetry of un-doped graphene is discussed. We formulate a strong coupling expansion where the ground state of the Coulomb Hamiltonian is found exactly and the kinetic hopping Hamiltonian is treated as a perturbation. We argue that many of the properties of the resulting system would be shared by graphene with a Hubbard model interaction. In particular, the best candidate sublattice symmetry breaking ground state is an antiferromagnetic Mott insulator. We discuss the results of some numerical simulations which indicate that the Coulomb interaction is indeed subcritical. We also point out the curious fact that, if the electron did not have spin degeneracy, the tendency to break chiral symmetry would be much greater and even relatively weak Coulomb interactions would likely gap the spectrum.
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