The spatial scale of density-dependent growth and implications for dispersal from nests in juvenile Atlantic salmon

By dispersing from localized aggregations of recruits, individuals may obtain energetic benefits due to reduced experienced density. However, this will depend on the spatial scale over which individuals compete. Here, we quantify this scale for juvenile Atlantic salmon (Salmo salar) following emergence and dispersal from nests. A single nest was placed in each of ten replicate streams during winter, and information on the individual positions (±1 m) and the body sizes of the resulting young-of-the-year (YOY) juveniles was obtained by sampling during the summer. In six of the ten streams, model comparisons suggested that individual body size was most closely related to the density within a mean distance of 11 m (range 2–26 m). A link between body size and density on such a restricted spatial scale suggests that dispersal from nests confers energetic benefits that can counterbalance any survival costs. For the four remaining streams, which had a high abundance of trout and older salmon cohorts, no single spatial scale could best describe the relation between YOY density and body size. Energetic benefits of dispersal associated with reduced local density therefore appear to depend on the abundance of competing cohorts or species, which have spatial distributions that are less predictable in terms of distance from nests. Thus, given a trade-off between costs and benefits associated with dispersal, and variation in benefits among environments, we predict an evolving and/or phenotypically plastic growth rate threshold which determines when an individual decides to disperse from areas of high local density

Effects of vitamins C and D in type 2 diabetes mellitus

Darshika J Christie-David,1,2 Christian M Girgis,2–4 Jenny E Gunton1–4 1Department of Endocrinology and Diabetes, Westmead Hospital, 2Faculty of Medicine, University of Sydney, 3Westmead Millennium Institute, 4Garvan Institute of Medical Research, Sydney, NSW, Australia Abstract: Scurvy and rickets are largely considered historical diseases in developed countries. However, deficiencies in vitamins C and D are re-emerging due to increased consumption of processed foods and reduced fresh foods in the Western diet, as well as to an indoor sedentary lifestyle away from sun exposure. These dietary and lifestyle factors also predispose one to diabetes and metabolic syndrome. Our understanding of the potential roles of vitamin C (an antioxidant) and vitamin D (a biologically active hormone) in disease is increasing. In this review, we present observational, interventional, and mechanistic studies that examine the potential links between vitamins C and D in reversing defects in glucose homeostasis and the prevention of type 2 diabetes. Studies suggest an association between vitamin C deficiency and diabetes. An association between vitamin D and insulin resistance has been well described; however, the role of vitamin C and D supplementation in diabetes and its prevention requires further controlled trials. Keywords: glucose homeostasis, diabetes, insulin resistance, vitamin C, vitamin

Physical activity - A neat solution to an impending crisis

Childhood obesity is arguably the most significant global public health threat, yet effective strategies to contain or prevent the disease are not available. This review examines the physical activity patterns of children and the role physical activity plays in daily energy expenditure. The prevailing focus on moderate to vigorous activity in childhood means there is limited objective information on either sedentary behaviour or non-exercise activity thermogenesis (NEAT), the energy expended during the activities of daily living. Most strategies targeting the prevention of childhood obesity have focused upon adding moderate to vigorous activity and have not been particularly successful. The low efficacy of more purposeful activity is perhaps not surprising because of the small variance in children's physical activity levels explained by moderate to vigorous activity. Subtle changes in NEAT have in contrast been shown to account for differences in fat-mass gain or resistance in adults. Theoretically, manipulating a child's living environment to enhance NEAT would create a positive gain in TDEE, a gain that could lead to the prevention of excess fat-mass. More careful consideration of the specific aspects of physical activity that are most influential in the maintenance of body weight in childhood is a priority. Appreciating the role NEAT may play in the variation of total daily energy expenditure in children is a future challenge for physical activity research. ©Journal of Sports Science and Medicine (2007).link_to_subscribed_fulltex

The Martensitic Transformation in Indium-Thallium Alloys

This collection is organized around the central theme of “Martensite by Design.” Contributions include design, microstructure, properties, advanced processing and manufacturing, performance, phase transformations, and characterization