The Saskatchewan Pediatric Bone Mineral Accrual Study: Bone mineral acquisition during the growing years

To investigate bone mineral accretion in growing children, the Saskatchewan Pediatric Bone Mineral Accrual Study was initiated in 1991. The study involves the collection of dietary and physical activity information along with anthropometric growth and maturity measurements every 6 months and dual-energy X-ray absorptiometer (DXA) bone scans of the whole body, AP lumbar spine and proximal femur taken annually, The study has now finished its 6th year and 68 males and 72 females from an original sample of 228 elementary schoolchildren are still involved, To investigate how bone mineral at clinically important sites proceeds in relation to maturation we developed distance and velocity growth curves for height and bone mineral content (BMC) for the AP lumbar spine, the femoral neck and the whole body, In both boys and girls, over 35% of total body and AP spine bone mineral and over 27% of the bone mineral at the femoral neck was laid down during the 4-year adolescent period surrounding peak linear growth velocity. The clinical significance of these values can be appreciated by consideration of the fact that as much bone mineral will be laid down during these 4 adolescent growing years as most people will lose during all of adult life.

2m-cycle systems of K2m+1/C-m

For all m greater than or equal to 3 the edges of complete graph on 2m + 1 vertices can he partitioned into m 2m-cycles and an m-cycle.

Improving wheat simulation capabilities in Australia from a cropping systems perspective: water and nitrogen effects on spring wheat in a semi-arid environment

Systems approaches can help to evaluate and improve the agronomic and economic viability of nitrogen application in the frequently water-limited environments. This requires a sound understanding of crop physiological processes and well tested simulation models. Thus, this experiment on spring wheat aimed to better quantify water x nitrogen effects on wheat by deriving some key crop physiological parameters that have proven useful in simulating crop growth. For spring wheat grown in Northern Australia under four levels of nitrogen (0 to 360 kg N ha(-1)) and either entirely on stored soil moisture or under full irrigation, kernel yields ranged from 343 to 719 g m(-2). Yield increases were strongly associated with increases in kernel number (9150-19950 kernels m(-2)), indicating the sensitivity of this parameter to water and N availability. Total water extraction under a rain shelter was 240 mm with a maximum extraction depth of 1.5 m. A substantial amount of mineral nitrogen available deep in the profile (below 0.9 m) was taken up by the crop. This was the source of nitrogen uptake observed after anthesis. Under dry conditions this late uptake accounted for approximately 50% of total nitrogen uptake and resulted in high (>2%) kernel nitrogen percentages even when no nitrogen was applied,Anthesis LAI values under sub-optimal water supply were reduced by 63% and under sub-optimal nitrogen supply by 50%. Radiation use efficiency (RUE) based on total incident short-wave radiation was 1.34 g MJ(-1) and did not differ among treatments. The conservative nature of RUE was the result of the crop reducing leaf area rather than leaf nitrogen content (which would have affected photosynthetic activity) under these moderate levels of nitrogen limitation. The transpiration efficiency coefficient was also conservative and averaged 4.7 Pa in the dry treatments. Kernel nitrogen percentage varied from 2.08 to 2.42%. The study provides a data set and a basis to consider ways to improve simulation capabilities of water and nitrogen effects on spring wheat. (C) 1997 Elsevier Science B.V.