Communications platform payload definition study, executive summary

Large geostationary communications platforms have been investigated in a number of studies since 1974 as a possible means to more effectively utilize the geostationary orbital arc and electromagnetic spectrum and to reduce overall satellite communications system costs. This NASA Lewis sponsored study addresses the commercial feasibility of various communications platform payload concepts circa 1998. It defines promising payload concepts, estimates recurring costs and identifies critical technologies needed to permit eventual commercialization. Ten communications service aggregation scenarios describing potential groupings of services were developed for a range of conditions. Payload concepts were defined for four of these scenarios: (1) Land Mobile Satellite Service (LMSS), meet 100% of CONUS plus Canada demand with a single platform; (2) Fixed Satellite Service (FSS) (Trunking + Customer Premises Service (CPS), meet 20% of CONUS demands; (3) FSS (Trunking + video distribution), 10 to 13% of CONUS demand; and (4) FSS (20% of demand) + Inter Satellite Links (ISL) + TDRSS/TDAS Data Distribution

Double-duty actions for ending malnutrition within a decade

Malnutrition has many forms. Undernutrition can see children dangerously thin for their height (wasting), or their growth permanently impeded (stunting). Inadequate intake of key nutrients may weaken immune systems, impair brain development, and worsen the risk of conditions such as anaemia and blindness. Diets rich in calories well beyond the body's metabolic needs drive the burden of overweight and obesity, while excess dietary fat, sugar, and salt can increase the risks of non-communicable diseases (NCDs)

A small-scale process for manufacturing woodwool/cement slabs in developing countries

Woodwool/cement slabs are made from a mixture of shredded timber (woodwool) and cement, shaped or formed by pressure into required thicknesses and sizes. They are a well-known product already used in many countries around the world. This bulletin outlines the work undertaken by the Natural Resources Institute (NRI) on the development of a low-cost woodwool/cement slab manufacturing process appropriate for conditions in developing countries. Typically, 500 slabs (35m3 ) can be produced per week on a single shift employing 25 people. Demonstration plants have been introduced into Malawi and Zambia. Included in the bulletin are historical background information, details and test data on assessing the suitability of timbers, a description of the process developed and the reasons for the processing techniques employed. Methods of handling and the use of the slabs in the construction industry, particularly in relation to the lower-cost housing market in Zambia, are also outlined. One of the main attractions of the NRI small-scale wood wool/ cement slab process plant is the relatively low initial capita! investment required compared with larger, less labour-intensive processes used in Europe a0d'elsewhere. The principal aim has been to develop a low capital cost, labour-intensive plant which could largely be constructed using local manufacturing and craft skills, and operated and maintained on a routine basis by trained personnel

31P nuclear magnetic resonance and X-ray diffraction study of Na-Sr-phosphate glass-ceramics

A set of Na-Sr-phosphate glass and glass-ceramic samples, with general formula xSrO:(0.55-x)Na2O:0.45P2O5, were prepared and analysed by solid state 31P nuclear magnetic resonance spectroscopy and X-ray powder diffraction. The results show the presence of Q1 and Q2 phosphate species in all samples. At low concentrations of Sr2+ (x £ 0.20) the strontium is preferentially incorporated in Sr2+-Q1 crystalline phases, and only at higher Sr2+ concentrations are crystalline phases present which Sr2+ is associated with Q2 phosphate units

Fitness benefits of prolonged post-reproductive lifespan in women

Most animals reproduce until they die, but in humans, females can survive long after ceasing reproduction. In theory, a prolonged post-reproductive lifespan will evolve when females can gain greater fitness by increasing the success of their offspring than by continuing to breed themselves. Although reproductive success is known to decline in old age, it is unknown whether women gain fitness by prolonging lifespan post-reproduction. Using complete multi-generational demographic records, we show that women with a prolonged post-reproductive lifespan have more grandchildren, and hence greater fitness, in pre-modern populations of both Finns and Canadians. This fitness benefit arises because post-reproductive mothers enhance the lifetime reproductive success of their offspring by allowing them to breed earlier, more frequently and more successfully. Finally, the fitness benefits of prolonged lifespan diminish as the reproductive output of offspring declines. This suggests that in female humans, selection for deferred ageing should wane when one's own offspring become post-reproductive and, correspondingly, we show that rates of female mortality accelerate as their offspring terminate reproduction

Poisson transition rates from time-domain measurements with finite bandwidth

In time-domain measurements of a Poisson two-level system, the observed transition rates are always smaller than those of the actual system, a general consequence of finite measurement bandwidth in an experiment. This underestimation of the rates is significant even when the measurement and detection apparatus is ten times faster than the process under study. We derive here a quantitative form for this correction using a straightforward state-transition model that includes the detection apparatus, and provide a method for determining a system's actual transition rates from bandwidth-limited measurements. We support our results with computer simulations and experimental data from time-domain measurements of quasiparticle tunneling in a single-Cooper-pair transistor.Comment: 4 pages, 5 figure