154 research outputs found
The association between alcohol consumption and self-rated health among adult Norwegian women. A cross-sectional study from the Norwegian Women and Cancer (NOWAC) cohort
Abstract
Background: After 1985, the proportion of women who drink alcohol in Norway has increased, narrowing the gender gap in alcohol consumption. In Norway, more women now drink alcohol than before. There is little evidence of an association between alcohol consumption and self-rated health (SRH) in Norwegian women. Therefore, this study aimed at the association between alcohol consumption and SRH in Norwegian women aged 30 to 70 years.
Methods: This is a cross-sectional study of 172, 472 Norwegian women aged 30 to 70 years, using data from the Norwegian Women and Cancer (NOWAC) cohort. This study only focused on wave 1 from 1991 to 2008. We used multinomial logistic regression to analyze the association between alcohol consumption and SRH. In addition, we adjusted the analysis separately for age and then for multivariable (age, educational status, cigarette smoking, BMI, physical activity). We further stratified the adjusted models based on educational status.
Results: This study found that alcohol nonconsumption was positively associated with poor health, with an odds ratio of 1.64 and a 95% confidence interval of 1.56 to 1.73. High alcohol consumption was positively associated with excellent health with an odds ratio of 1.21 and a 95% confidence interval of 1.16 to 1.26. The positive association between alcohol nondrinking and poor health by educational status was stronger among women with higher levels of education.
Conclusion: Women who drank high amounts of alcohol were positively associated with good SRH, and women who did not drink alcohol were positively associated with poor SRH. Because this study was cross-sectional, it is not possible to determine the direction of the association. Therefore, future prospective longitudinal studies are needed to investigate causality.
Keywords: Self-rated health, Alcohol, Alcohol consumptio
Convertisseurs Ă bobine variable pour applications de transport durables
Abstract: Power electronics converters are key components and enable efficient conversion and management of electrical energy in a wide range of applications. For vehicular use, there is an inevitable need to improve their performance and reducing their size. This is particularly important in case of powertrain DC-DC converters as they are required to have improved performance while respecting the specifications, characteristics and stringent space limitations. These objectives define research targets and a particular progress is essential in the field of passive components, semiconductor devices, converter topologies and control. At the current state of technologies, the passive components particularly the power inductors are dominant components which affect the overall volume, cost and performance of power electronic converters.
Considering the aforementioned critical aspects, this thesis proposes a variable inductor (VI) concept in order to reduce the weight and size power inductors which are traditionally bulky and have fairly limited operating range. By modulating the permeability of the magnetic material, this concept enhances the current handling capability of power inductors, controls the current ripples, reduces the magnetic and switching losses, as well as the stresses applied to switching devices. Furthermore, it enables the use of smaller cores which leads to the reduction of mass and volume allowing improvements in the converter operation and its overall performance. However, to integrate it into powertrain DC-DC converters, it is fundamental, to question the design of the component itself, the selection of suitable magnetic core materials, and the control of current in the auxiliary winding and saturation management of magnetic cores. This thesis systematically addresses these different research challenges.
A particular attention is paid to the experimental study of a VI prototype to demonstrate the concept on a small-scale in order to explore its viability. Subsequently a detailed characterization was developed using finite element analysis to determine the intrinsic functionality of the passive component. Furthermore, this thesis proposed an RMS current based VI design to reduce oversizing of power inductors for electric vehicles application. In this methodology, the selection of a suitable magnetic core material is a crucial step to assure smaller and efficient converters. Hence, this thesis proposes a simplified approach based on weighted property method (WPM) for an appropriate selection of magnetic core in accordance to the needs of the user.
Furthermore, to validate the integration of this concept in DC-DC converter topology used in the powertrain of electrified vehicles, an affine parameterization method is used to design the control parameters and a simple management strategy is proposed to enable dynamic control of the VI. The converter control and the proposed strategy are evaluated through simulations of a complete powertrain of a three-wheel recreational vehicle.
The small-scale experimental and simulations, and full-scale simulations have demonstrated an interesting capacity of the VI for improving the performance of DC-DC converters for electrified vehicles and manage the saturation of the magnetic core while reducing the size and weight of magnetic components.Les convertisseurs d’électroniques de puissance sont des composants clés de la conversion et gestion efficace de l’énergie électrique dans une large gamme d’applications. Pour des utilisations véhiculaires, il est inévitablement nécessaire d’améliorer leurs performances et de réduire leur taille. Ceci est particulièrement important dans le cas des convertisseurs à courant continu (CC) de la chaine de traction où des performances améliorées en réponse à une large gamme de variations de charge sont recherchées tout en respectant les spécificités, caractéristiques et limitation d’espace nécessaires aux véhicules électrifiés. Ces objectifs définissent une cible de recherche et en particulier des progrès sont essentiels dans le domaine des composants passifs, des dispositifs semi-conducteurs, des topologies des convertisseurs et leurs commandes pour généraliser l’utilisation de véhicules électriques. Les composants passifs, en particulier les inductances de puissance, sont des composants dominants qui affectent le volume global, le coût et les performances de ces convertisseurs d’électroniques de puissance.
Compte tenu de ces aspects, cette thèse propose un concept de bobine variable afin de réduire le poids et la taille des inductances de puissance qui sont traditionnellement encombrantes et ont une gamme de fonctionnement assez limitée. En modulant la perméabilité du matériau magnétique, ce concept améliore la capacité de gestion du courant des bobines de puissance, contrôle les ondulations du courant et réduit les pertes magnétiques et par commutation, bien comme les contraintes appliquées aux dispositifs de commutation. En outre, il permet l’utilisation de noyaux plus petits, ce qui entraîne une réduction de masse et de volume, en permettant une amélioration du fonctionnement du convertisseur et de ses performances globales. Cependant, pour l’intégrer aux convertisseurs CC-CC utilisés dans la chaine de traction, il est fondamental de se questionner sur la conception du composant lui-même, la sélection du matériau magnétique, la commande du courant de l’enroulement auxiliaire et la gestion de la saturation du noyau magnétique. Cette thèse aborde de manière systématique ces différents défis de recherche.
Une attention particulière est accordée à l’étude expérimentale d’un prototype de bobine variable pour faire la preuve de concept à petite échelle afin d’explorer sa viabilité. Par la suite, une large caractérisation par éléments finis a été développée pour déterminer le fonctionnement intrinsèque de ce composant passif. De plus, cette thèse propose une méthode systématique de design de bobine variable basée sur le courant RMS pour réduire le surdimensionnement traditionnellement associer aux inductances de puissance pour des applications véhiculaires. Dans cette méthodologie, la sélection appropriée du matériau pour le noyau magnétique est une étape cruciale pour garantir des convertisseurs plus petits et efficaces, donc une démarche de sélection simplifiée basée sur la méthode des propriétés pondérées pour le choix de noyau magnétique approprié au besoin de l’application a été mis au point.
De plus, pour valider l’intégration de ce concept dans une topologie de convertisseur CC-CC traditionnellement utilisée dans la chaine de traction des véhicules électrifiés, une méthode de synthèse affine a été utilisée pour définir les paramètres des contrôleurs de courant et une stratégie de gestion de la saturation du noyau a été proposée pour permettre le contrôle dynamique de la bobine variable. La commande du convertisseur et la stratégie ont été évaluées par simulation d’une chaine de traction complète d’un véhicule récréatif réel.
Les résultats expérimentaux à petite échelle et simulations à pleine échelle ont démontrés des capacités intéressantes de cette bobine variable pour l’amélioration des performances des convertisseurs CC-CC, ayant la capacité de gestion de la saturation du noyau magnétique tout en réduisant la taille et le poids de ces composants passifs, dans le but de son utilisation dans la chaine de traction des véhicules électrifiés
Examining The Relationship between Bicultural Stress, Mental Well-Being, Perceived Social Support, and Education Among People of African Descent
Studies investigating the bicultural experiences of people of African descent are significantly underrepresented in the literature. The primary purpose of this exploratory study was to examine the relationship between experiences of bicultural stress and mental well-being. In investigating this relationship, perceived social support and education were examined as protective factors, and its relationship to bicultural stress for this population. With the ultimate goal of this information contributing to the understanding of bicultural processes within this population and the relationship to mental health outcomes. A non-experimental (non-randomized) research design was utilized to examine the study research questions and hypotheses. The participants include self-identified bicultural adults of African descent. Correlational and regression analyses indicated that in the study’s sample: (a) bicultural stress was related to symptoms of depression, perceived social support and education, (b) symptoms of depression were correlated with bicultural stressors, (c) social support and education served as protective factors against endorsement of depressive symptoms, (d) social support and education were correlated. The findings from this study may help to elucidate mental health outcomes as it relates to bicultural experiences among people of African descent. The findings may also serve to highlight culturally-sensitive approaches and information that better inform psychologists and health practitioners in serving this population. Furthermore, the findings of this study supports continued research that seeks to address the bicultural experiences of this diverse subgroup as it relates to mental health outcomes
Measuring the acute effects of two aerobic exercise training methods on cortical excitability in people with chronic stroke
Background: Aerobic exercise (AE) upregulates neurotrophins and alters brain excitability post-stroke. Using transcranial magnetic stimulation (TMS) we compared the acute effects of moderate intensity continuous exercise (MICE) versus high intensity interval training (HIIT) on cortical excitability in patients with chronic stroke.
Methods: Participants completed 25 min MICE (60 % VOâ‚‚ max) and HIIT (80 % VOâ‚‚ max / 40 % VO2 max), one week apart, matched for workload. Before and after exercise, subjects underwent neuronavigated TMS (figure of eight coil) followed by testing of pinch, grip strength and dexterity.
Results: Short interval intracortical inhibition (SICI) decreased in the less affected hemisphere following MICE (22.03 % (11.14) to 30.5 % (20.63), p = 0.04), while there was no change following HIIT (25.22 % (14.97) to 32.19 % (22.04) (p=0.186). Pinch strength in the affected hand was also significantly lower following MICE.
Conclusion: MICE may be superior to HIIT in acutely influencing neural networks of a non-exercised muscle
Do household coping strategies mitigate perceived household food insecurity among sample households in Dasse administrative area, Gash-Barka zone, Eritrea?
Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.This mini-dissertation sets out to examine the perceptions of farmers in the Dasse Administrative Area of Gash-Barka zone of the impact of agro-ecological, socioeconomic and infrastructural constraints on food insecurity, and the coping strategies employed by 101 sampled farm households in order to understand how these strategies increase vulnerability or mitigate the effect of food shortages. Agricultural productivity was low and average cereal production provided only 39 per cent of annual household requirements. Self-sufficiency in grain obtained from own production sustained households for only four months a year. In line with this, the study examined the impact of agro-ecological, socio-economic, and infrastructural constraints to the problem of food insecurity as perceived by the farmers. Farmers perceived drought, erratic rainfall, and weed infestations as major agro-ecological constraints that hindered self-sufficiency in food production. Shortage of draught animals and labour and lack of cash and off-farm income, were most conceived socio-economic constraints that affected production. Lack of farm credit, health problem (malaria), and inadequate farmers advisory service were most perceived infrastructural constraints that affected production and household food security. This shows that food security interventions need to be built around mitigating these perceived causes. The study also investigated coping strategies and their impact on increasing vulnerability or mitigating the effect of food shortages. The coping strategies applied by the studied households were largely consumption-based and non-erosive, indicating that households were relatively resilient to food security shocks. However, these strategies could be detrimental to the nutritional well being of household members, as they determined dietary intake. These coping strategies were particularly detrimental to household food security, as proper nutrition is critical for active and productive life. Thus, health and nutrition related interventions are highly required to address these problems. Food security interventions need to support livelihoods in ways that protect and buffer the natural resilience of households, providing direct assistance when erosive coping strategies are employed to ensure that households remain resilient to the fragile and variable situations in which they exist
SST prediction methodologies and verification considerations for dynamical mid-summer rainfall forecasts for South Africa
Seasonal-to-interannual hindcasts (re-forecasts) for December-January-February (DJF) produced at a 1-month lead-time by the ECHAM4.5 atmospheric general circulation model (AGCM) are verified after calibrating model output to DJF rainfall at 94 districts across South Africa. The AGCM is forced with SST forecasts produced by (i) statistically predicted SSTs, and (ii) predicted SSTs from a dynamically coupled ocean-atmosphere model. The latter SST forecasts in turn consist of an ensemble mean of SST forecasts, and also by considering the individual ensemble members of the SST forecasts. Probabilistic hindcasts produced for two separate category thresholds are verified over a 24-year test period from 1978/79 to 2001/02 by investigating the various AGCM configurations’ attributes of discrimination (whether the forecasts are discernibly different given different outcomes) and reliability (whether the confidence communicated in the forecasts is appropriate). Deterministic hindcast skill is additionally calculated through a range of correlation estimates between hindcast and observed DJF rainfall. For both probabilistic and deterministic verification the hindcasts produced by forcing the AGCM with dynamically predicted SSTs attain higher skill levels than the AGCM forced with statistical SSTs. Moreover, ensemble mean SST forecasts lead to improved skill over forecasts that considered an ensemble distribution of SST forecasts.Keywords: AGCM, SST predictions, seasonal forecasting, South Afric
Climate change scenario simulations over Eritrea by using a fine resolution limited area climate model : temperature and moisture sensitivity
The climate of the eastern section of the Sahelian latitude, especially over the Eritrean subdomain, is often associated with long drought episodes from which the atmospheric mechanisms are poorly understood. In an effort to improve our knowledge of weather and climate systems over this region, the PRECIS Regional Climate Model (RCM) from the United Kingdom (UK) was obtained and implemented. Such a climate model that is based upon the physical laws of nature has the ability to simulate regional-scale atmospheric patterns, and therefore, may significantly contribute to our understanding of local atmospheric processes. In this dissertation the assessment of past regional climate trends from both observations and model simulations, and the simulation of scenarios for possible future climate change were regarded as important. To investigate this, the PRECIS RCM was first nested over the Eritrean domain into the “atmosphere only” HadAM3H global General Circulation Model (GCM) and forced at its lateral boundaries by a 30-year present-day (1961-1990) integration of the same global model. Secondly, the PRECIS RCM was constrained at its lateral boundary by the “fully coupled” HadCM3 GCM (for Sea Surface Temperatures (SSTs) and sea-ice) and its improved atmospheric component (HadAM3H GCM). The latter simulations provided boundary conditions for the A2 and B2 future emission scenarios (Special Report on Emission Scenarios (SRES)) to simulate a 20-year (2070-2090) projection of future climate. These experiments allowed for verification of both spatial and temporal present-day climate simulations, as well as possible future climate trends as simulated by the PRECIS RCM over the Eritrean domain, with specific emphasis on temperature and moisture related variables. The study indicates that PRECIS RCM climate simulations are mostly in harmony with observed spatial patterns. This skill may be attributed to the full representation of the climatic system (land surface, sea, ice, atmosphere and atmospheric chemistry such as sulphur and greenhouse gasses) in the model configuration. However, when comparing PRECIS RCM results with the much coarser resolution (2.5ox2.5o) National Centre for Environmental Prediction (NCEP) reanalysis data, obvious differences do occur. These differences are not necessarily the result of poor model performance, but may be attributed to more detailed simulations over the finer RCM grid (0.44o x 0.44o). Future climate scenario simulation with the PRECIS RCM over Eritrea produce increased surface temperature in both the A2 and B2 SRES scenario integrations, relative to the present climatology. This temperature increase also appears in the driving GCM (HadCM3) as well as in other GCM results from the Inter Governmental Panel for Climate Change (IPCC) initiative. There are, however, mixed signals in rainfall projections. According to PRECIS RCM results, rainfall is expected to increase in most of the Eritrean region. Copyright 2005, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Beraki, A F 2005, Climate change scenario simulations over Eritrea by using a fine resolution limited area climate model : temperature and moisture sensitivity , MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd Dissertation (MSc)--University of Pretoria, 2007.Geography, Geoinformatics and MeteorologyUnrestricte
Early postnatal infection with neurotropic influenza A virus: effects on gene expression and behavior in mice
UC-25 Woodline Interiors Project Planning Application
Meeting with the client regularly, we’ve established one of the many solutions to their requirements. The client, WoodLine Interiors, needs a well-designed system that can solve product management, client communication, and project management. The main issue that the company is facing is in the area of managing multiple projects and tracking project progress. Their issue is commonly addressed by a large number of companies that create software solutions, but it’s not personalized for their appropriate needs in the field of cabinetry. As a result our solution created the perfect stages and states of the project so there is no more confusion to where the project is situation at.Advisors(s): supervisor : Dr. Reza Parizi project owner : Woodline Interiors (client)Topic(s): Software EngineeringSWE 472
Preliminary Assessment of Low Cost Local Sorbent Materials for Water Defluoridation in Keren, Eritrea
Water in some parts of Eritrea has fluoride level above WHO guideline of 1.5 mg/L. One of the communities in Eritrea exposed to high fluoride in water is Keren community and as a result, they suffer dental and skeletal fluorosis. Fluoride sorbent local materials named crushed burnt clay pot, household ash, Keren and Adigerghish soil were studied in a batch defluoridation. The effect of amount of adsorbent, pH, contact time, particle size and fluoride concentration were examined
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