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Search Results: 1 - 10 of 223854 matches for " R. Laher "
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World Food Day: 16 October 2008
H Laher, R Lekoba
African Safety Promotion: A Journal of Injury and Violence Prevention , 2009,
Abstract:
The Palomar Transient Factory: High Quality Realtime Data Processing in a Cost-Constrained Environment
J. Surace,R. Laher,F. Masci,C. Grillmair,G. Helou
Physics , 2015,
Abstract: The Palomar Transient Factory (PTF) is a synoptic sky survey in operation since 2009. PTF utilizes a 7.1 square degree camera on the Palomar 48-inch Schmidt telescope to survey the sky primarily at a single wavelength (R-band) at a rate of 1000-3000 square degrees a night. The data are used to detect and study transient and moving objects such as gamma ray bursts, supernovae and asteroids, as well as variable phenomena such as quasars and Galactic stars. The data processing system at IPAC handles realtime processing and detection of transients, solar system object processing, high photometric precision processing and light curve generation, and long-term archiving and curation. This was developed under an extremely limited budget profile in an unusually agile development environment. Here we discuss the mechanics of this system and our overall development approach. Although a significant scientific installation in of itself, PTF also serves as the prototype for our next generation project, the Zwicky Transient Facility (ZTF). Beginning operations in 2017, ZTF will feature a 50 square degree camera which will enable scanning of the entire northern visible sky every night. ZTF in turn will serve as a stepping stone to the Large Synoptic Survey Telescope (LSST), a major NSF facility scheduled to begin operations in the early 2020s.
Asteroseismology from space: the Delta Scuti star Theta2 Tauri monitored by the WIRE satellite
Ennio Poretti,D. Buzasi,R. Laher,J. Catanzarite,T. Conrow
Physics , 2001, DOI: 10.1051/0004-6361:20011623
Abstract: The first intensive photometric time-series of a Delta Scuti star was obtained from space. Theta2 Tau was monitored with the star camera on the Wide-Field Infrared Explorer (WIRE) satellite. Twelve independent frequencies were detected down to the 0.5 mmag amplitude level. Their reality was investigated by searching for them using two different algorithms and by some internal checks. All the frequencies are in the range 10.8-14.6 c\d. The histogram of the frequency spacings shows that 81% are below 1.8 c\d; rotation may thus play a role in the mode excitation. The fundamental radial mode is not observed, although it is expected to occur in a region where the noise level is very low (55 micromag). The rms residual is about two times lower than that usually obtained from successful ground--based multisite campaigns. The comparison of the results of previous campaigns with the new ones establishes the amplitude variability of some modes.
16 Days of Activism for No Violence Against Women and Children
H Laher
African Safety Promotion: A Journal of Injury and Violence Prevention , 2009,
Abstract:
Structural equivalence and the Neo-Pi-R: Implications for the applicability of the five-factor model of personality in an African context
Sumaya Laher
South African Journal of Industrial Psychology , 2008, DOI: 10.4102/sajip.v34i1.429
Abstract: The NEO-PI-R is one of the most widely used and researched operationalisations of the Five Factor Model (FFM) of personality (McCrae & Allik, 2002, McCrae & Terraccianno, 2005). Considerable evidence exists in terms of its replicability across cultures leading researchers to conclude that the NEO-PI-R and by extension the FFM are universally applicable. This paper, by virtue of reviewing appropriate literature, argues that evidence for the structural equivalence of the NEO-PI-R, while appropriate in Western cultures, is lacking in non-Western, and specifically African cultures. This is discussed with particular reference to the existence of other factors which are not tapped by this model and which would merit further research.
Using exploratory factor analysis in personality research: Best-practice recommendations
Sumaya Laher
South African Journal of Industrial Psychology , 2010, DOI: 10.4102/sajip.v36i1.873
Abstract: Orientation: Exploratory factor analysis is the method of choice with objective personality instruments, particularly to establish the construct validity and construct equivalence of trait-based instruments. Research purpose: This article presents more objective methods to determine the number of factors, most notably parallel analysis and Velicer’s minimum average partial (MAP). The benefits of rotation are also discussed. The article argues for more consistent use of Procrustes rotation and congruence coefficients in factor analytic studies. Motivation for the study: Exploratory factor analysis is often criticised for not being rigorous and objective enough in terms of the methods used to determine the number of factors, the rotations to be used and ultimately the validity of the factor structure. Research design, approach and method: The article adopts a theoretical stance to discuss the best-practice recommendations for factor analytic research in the field of psychology. Following this, an example located within personality assessment and using the NEO-PI-R specifically is presented. A total of 425 students at the University of the Witwatersrand completed the NEO-PI-R. These responses were subjected to a principal components analysis using varimax rotation. The rotated solution was subjected to a Procrustes rotation with Costa and McCrae’s (1992) matrix as the target matrix. Congruence coefficients were also computed. Main findings: The example indicates the use of the methods recommended in the article and demonstrates an objective way of determining the number of factors. It also provides an example of Procrustes rotation with coefficients of agreement as an indication of how factor analytic results may be presented more rigorously in local research. Practical/managerial implications: It is hoped that the recommendations in this article will have best-practice implications for both researchers and practitioners in the field who employ factor analysis regularly. Contribution/value-add: This article will prove useful to all researchers employing factor analysis and has the potential to set the trend for better use of factor analysis in the South African context. How to cite this article: Laher, S., (2010). Using exploratory factor analysis in personality research: Best-practice recommendations, SA Journal of Industrial Psychology/SA Tydskrif vir Bedryfsielkunde, 36(1), Art. #873, 7 pages. DOI: 10.4102/sajip.v36i1.873
The Detection of Multimodal Oscillations on Alpha UMa
D. Buzasi,J. Catanzarite,R. Laher,T. Conrow,D. Shupe,T. N. Gautier III,T. Kreidl
Physics , 2000, DOI: 10.1086/312573
Abstract: We have used the star camera on the WIRE satellite to observe the K0 III star Alpha UMa, and we report the apparent detection of 10 oscillation modes. The lowest frequency mode is at 1.82 microhertz, and appears to be the fundamental mode. The mean spacing between the mode frequencies is 2.94 microhertz, which implies that all detected modes are radial. The mode frequencies are consistent with the physical parameters of a K0 III star, if we assume that only radial modes are excited. Mode amplitudes are 100 -- 400 micromagnitudes, which is consistent with the scaling relation of Kjeldsen & Beddinge (1995).
Obesity in Arabic-Speaking Countries
Mohammad Badran,Ismail Laher
Journal of Obesity , 2011, DOI: 10.1155/2011/686430
Abstract: Obesity has reached epidemic proportions throughout the globe, and this has also impacted people of the Arabic-speaking countries, especially those in higher-income, oil-producing countries. The prevalence of obesity in children and adolescents ranges from 5% to 14% in males and from 3% to 18% in females. There is a significant increase in the incidence of obesity with a prevalence of 2%–55% in adult females and 1%–30% in adult males. Changes in food consumption, socioeconomic and demographic factors, physical activity, and multiple pregnancies may be important factors that contribute to the increased prevalence of obesity engulfing the Arabic-speaking countries.
Molecular Mechanisms in Exercise-Induced Cardioprotection
Saeid Golbidi,Ismail Laher
Cardiology Research and Practice , 2011, DOI: 10.4061/2011/972807
Abstract: Physical inactivity is increasingly recognized as modifiable behavioral risk factor for cardiovascular diseases. A partial list of proposed mechanisms for exercise-induced cardioprotection include induction of heat shock proteins, increase in cardiac antioxidant capacity, expression of endoplasmic reticulum stress proteins, anatomical and physiological changes in the coronary arteries, changes in nitric oxide production, adaptational changes in cardiac mitochondria, increased autophagy, and improved function of sarcolemmal and/or mitochondrial ATP-sensitive potassium channels. It is currently unclear which of these protective mechanisms are essential for exercise-induced cardioprotection. However, most investigations focus on sarcolemmal KATP channels, NO production, and mitochondrial changes although it is very likely that other mechanisms may also exist. This paper discusses current information about these aforementioned topics and does not consider potentially important adaptations within blood or the autonomic nervous system. A better understanding of the molecular basis of exercise-induced cardioprotection will help to develop better therapeutic strategies. 1. Introduction It is generally accepted that regular exercise is an effective way for reducing cardiovascular morbidity and mortality [1]. Physical inactivity and obesity are also increasingly recognized as modifiable behavioral risk factors for a wide range of chronic diseases, including cardiovascular diseases. Furthermore, epidemiologic investigations indicate that the survival rate of heart attack victims is greater in physically active persons compared to sedentary counterparts [2]. Several large cohort studies have attempted to quantify the protective effect of physical activity on cardiovascular and all cause mortality. Nocon et al. [3] in a meta-analysis of 33 studies with 883,372 participants reported significant risk reductions for physically active participants. All-cause mortality was reduced by 33%, and cardiovascular mortality was associated with a 35% risk reduction. Exercise capacity or cardiorespiratory fitness is inversely related to cardiovascular and all-cause mortality, even after adjustments for other confounding factors [4–6]. The American College of Sports Medicine defines exercise as “Any and all activity involving generation of force by the activated muscle(s) that results in disruption of a homeostatic state”. Exercise is classified by the type, intensity, and duration of activity. Endurance exercise reflects prolonged and continuous periods of contractile activity
Exercise and the Cardiovascular System
Saeid Golbidi,Ismail Laher
Cardiology Research and Practice , 2012, DOI: 10.1155/2012/210852
Abstract: There are alarming increases in the incidence of obesity, insulin resistance, type II diabetes, and cardiovascular disease. The risk of these diseases is significantly reduced by appropriate lifestyle modifications such as increased physical activity. However, the exact mechanisms by which exercise influences the development and progression of cardiovascular disease are unclear. In this paper we review some important exercise-induced changes in cardiac, vascular, and blood tissues and discuss recent clinical trials related to the benefits of exercise. We also discuss the roles of boosting antioxidant levels, consequences of epicardial fat reduction, increases in expression of heat shock proteins and endoplasmic reticulum stress proteins, mitochondrial adaptation, and the role of sarcolemmal and mitochondrial potassium channels in the contributing to the cardioprotection offered by exercise. In terms of vascular benefits, the main effects discussed are changes in exercise-induced vascular remodeling and endothelial function. Exercise-induced fibrinolytic and rheological changes also underlie the hematological benefits of exercise. 1. Introduction The American College of Cardiology/American Heart Association recommends at least 30 minutes of moderate (at 50–70% of maximal predicted heart rate) exercise on most days to reduce the risk of cardiovascular events [1]. Several human studies clearly demonstrate that chronic aerobic exercise regimens improve cardiovascular function. This is true not only in healthy subjects without any underlying risk factors [2], but also in older people [3], and those with cardiovascular risk factors [4]. Indeed, those with cardiovascular risk factor/disease will benefit more. There is a much higher consistency in the results of studies which assess participants with cardiovascular disease/risk factors compared to healthy subjects. Patients with hypertension [5], type 2 diabetes [6], metabolic syndrome [7], stable cardiovascular disease [8], myocardial infarction [9], and congestive heart failure [10], all benefit from exercise training compared to those who do not participate in any training. Importantly, an exercise regimen that improves endothelial function in diabetic patients fails to benefit healthy subjects [6, 11]. In healthy individuals, a longer and more intense exercise protocol is needed to induce measureable changes in cardiovascular parameters, while older and sicker subjects can benefit from less intense exercise regimens. Treatment and control of established known cardiovascular risk factors includes the
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