11,698 research outputs found
Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 1: Executive summary
The likely system concepts which might be representative of NASA and DoD space programs in the 1980-2000 time period were studied along with the programs' likely needs for major space transportation vehicles, orbital support vehicles, and technology developments which could be shared by the military and civilian space establishments in that time period. Such needs could then be used by NASA as an input in determining the nature of its long-range development plan. The approach used was to develop a list of possible space system concepts (initiatives) in parallel with a list of needs based on consideration of the likely environments and goals of the future. The two lists thus obtained represented what could be done, regardless of need; and what should be done, regardless of capability, respectively. A set of development program plans for space application concepts was then assembled, matching needs against capabilities, and the requirements of the space concepts for support vehicles, transportation, and technology were extracted. The process was pursued in parallel for likely military and civilian programs, and the common support needs thus identified
Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 2: Final report
The results are presented of a study which identifies over 100 new and highly capable space systems for the 1980-2000 time period: civilian systems which could bring benefits to large numbers of average citizens in everyday life, much enhance the kinds and levels of public services, increase the economic motivation for industrial investment in space, expand scientific horizons; and, in the military area, systems which could materially alter current concepts of tactical and strategic engagements. The requirements for space transportation, orbital support, and technology for these systems are derived, and those requirements likely to be shared between NASA and the DoD in the time period identified. The high leverage technologies for the time period are identified as very large microwave antennas and optics, high energy power subsystems, high precision and high power lasers, microelectronic circuit complexes and data processors, mosaic solid state sensing devices, and long-life cryogenic refrigerators
Advanced space system concepts and their orbital support needs (1980 - 2000). Volume 3: Detailed data. Part 1: Catalog of initiatives, functional options, and future environments and goals
The following areas were discussed in relation to a study of the commonality of space vehicle applications to future national needs: (1) index of initiatives (civilian observation, communication, support), brief illustrated description of each initiative, time periods (from 1980 to 2000+) for implementation of these initiatives; (2) data bank of functional system options, presented in the form of data sheets, one for each of the major functions, with the system option for near-term, midterm, and far-term space projects applicable to each subcategory of functions to be fulfilled; (3) table relating initiatives and desired goals (public service and humanistic, materialistic, scientific and intellectual); and (4) data on size, weight and cost estimations
Case-Building Behavior, Persistence, and Emergence Success of \u3ci\u3ePycnopsyche Guttifer\u3c/i\u3e (Walker) (Trichoptera: Limnephilidae) in Laboratory and \u3ci\u3ein situ\u3c/i\u3e Environments: Potential Trade-Offs of Material Preference
When removed from their cases in a non-flow laboratory environment, 5th instar Pycnopsyche guttifer (Walker) larvae were always successful in constructing a new case within 24 h when woody debris was present as a material choice. Most were successful within 1 h. Larvae were never successful at case building in the absence of wood in a non-flow environment. These laboratory-constructed ‘emergency cases’ were flimsy, lacking in shape, and larger than field cases. Laboratory case size, shape, and material preference remained constant after repeated daily evacuations over a series of 10 days. Larvae could be induced to construct a case composed of mineral particles only in the absence of wood and when placed in a laboratory stream with simulated flow conditions, or in situ in a natural stream. The emergence success of P. guttifer specimens induced to build these mineral cases, however, was significantly higher than that of larvae remaining in their field cases or of larvae that built wood cases. This result is likely due to a fungal infection that affected only larvae in wood cases. Our results demonstrate a scenario where a clearly non-preferred case construction material appears to increase survival
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Predictors for being physically active to keep fit and/or to lose weight after stroke: South London stroke register
Introduction: Increased physical activity and weight loss (if appropriate) after stroke is recommended for secondary prevention in the National Clinical Guidelines for Stroke (2008). However, there is a lack information about the proportion and the characteristics of stroke patients currently undertaking physical activity to keep fit
and/or lose weight.
Method: Data were collected from the South London Stroke Register (SLSR), a population based stroke register covering a multiethnic source population of 271,817 inhabitants (2001) in South London. Information on stroke patients’ level of physical activity was collected 12 months post stroke. Logistic regression analysis was performed to identify independent predictors for increased
physical activity to keep fit and/or lose weight post stroke, including age, sex, ethnicity, stroke severity (Barthel Index) and risk factors.
Results: Between Jan 2004 and December 2006, 358 first ever stroke patients were followed up 12 months post stroke. Mean age was 69, 45% were female: ethnicity was categorized as white (65%), black (25%) and other (10%).Overall, 45% of surviving stroke patients reported undertaking exercise, 25% and 1% reported exercising to keep fit and lose weight respectively, 19% reported exercising to keep fit and lose weight. In multivariate analysis, being physically active was associated with younger age (p<0.001), less severe disability (p<0.001) and black ethnicity (p<0.005).
Conclusion: This study identified only one half of stroke survivors participate in physical activity at 12 months post stroke. Stroke survivors reported being physically active for different reasons but are less likely to do so to lose weight
Survey for Galaxies Associated with z~3 Damped Lyman alpha Systems I: Spectroscopic Calibration of u'BVRI Photometric Selection
We present a survey for z~3 Lyman break galaxies (LBGs) associated with
damped Lyman alpha systems (DLAs) with the primary purpose of determining the
DLA-LBG cross-correlation. This paper describes the acquisition and analysis of
imaging and spectroscopic data of 9 quasar fields having 11 known z~3 DLAs
covering an area of 465 arcmin^2. Using deep u'BVRI images, 796 LBG candidates
to an apparent R_AB magnitude of 25.5 were photometrically selected from 17,343
sources detected in the field. Spectroscopic observations of 529 LBG candidates
using Keck LRIS yielded 339 redshifts. We have conservatively identified 211
z>2 objects with =3.02+/-0.32. We discuss our method of z~3 LBG
identification and present a model of the u'BVRI photometric selection
function. We use the 339 spectra to evaluate our u'BVRI z~3 Lyman break
photometric selection technique.Comment: 26 pages, 6 tables, 11 figures, accepted for publication in Ap
Cause-specific child and adolescent mortality in the UK and EU15+countries
Objective: To compare cause-specific UK mortality in children and young people (CYP) with EU15+ countries (European Union countries pre-2004, Australia, Canada and Norway).
Design: Mortality estimates were coded from the WHO World Mortality Database. Causes of death were mapped using the Global Burden of Disease mortality hierarchy to 22 cause groups. We compared UK mortality by cause, age group and sex with EU15+ countries in 2015 (or latest available) using Poisson regression models. We then ranked the UK compared with the EU15+ for each cause.
Setting: The UK and EU15+ countries.
Participants CYP aged 1–19.
Main outcome measure: Mortality rate per 100 000 and number of deaths.
Results: UK mortality in 2015 was significantly higher than the EU15+ for common infections (both sexes aged 1–9, boys aged 10–14 and girls aged 15–19); chronic respiratory conditions (both sexes aged 5–14); and digestive, neurological and diabetes/urological/blood/endocrine conditions (girls aged 15–19). UK mortality was significantly lower for transport injuries (boys aged 15–19). The UK had the worst to third worst mortality rank for common infections in both sexes and all age groups, and in five out of eight non-communicable disease (NCD) causes in both sexes in at least one age group. UK mortality rank for injuries in 2015 was in the top half of countries for most causes.
Conclusions UK CYP mortality is higher than a group of comparable countries for common infections and multiple NCD causes. Excess UK CYP mortality may be amenable to health system strengthening
The search for Bose-Einstein condensation of excitons in Cu2O: exciton-Auger recombination versus biexciton formation
Excitons in high-purity crystals of Cu2O undergo a density-dependent lifetime that opposes Bose-Einstein condensation (BEC). This rapid decay rate of excitons at a density n has generally been attributed to Auger recombination having the form dn/dt = -An(2), where A is an exciton-Auger constant. Various measurements of A, however, have reported values that are orders-of-magnitude larger than the existing theory. In response to this conundrum, recent work has suggested that excitons bind into excitonic molecules, or biexcitons, which are short-lived and expected to be optically inactive. Of particular interest is the case of excitons confined to a parabolic strain well-a method that has recently achieved exciton densities approaching BEC. In this paper we report time-and space-resolved luminescence data that supports the existence of short-lived biexcitons in a strain well, implying an exciton loss rate of the form dn/dt = -2 Cn(2) with a biexciton capture coefficient C(T) proportional to 1/T, as predicted by basic thermodynamics. This alternate theory will be considered in relation to recent experiments on the subject
Associations of Adiponectin with Adiposity, Insulin Sensitivity, and Diet in Young, Healthy, Mexican Americans and Non-Latino White Adults.
Low circulating adiponectin levels may contribute to higher diabetes risk among Mexican Americans (MA) compared to non-Latino whites (NLW). Our objective was to determine if among young healthy adult MAs have lower adiponectin than NLWs, independent of differences in adiposity. In addition, we explored associations between adiponectin and diet. This was an observational, cross-sectional study of healthy MA and NLW adults living in Colorado (U.S.A.). We measured plasma total adiponectin, adiposity (BMI, and visceral adipose tissue), insulin sensitivity (IVGTT), and self-reported dietary intake in 43 MA and NLW adults. Mean adiponectin levels were 40% lower among MA than NLW (5.8 ± 3.3 vs. 10.7 ± 4.2 µg/mL, p = 0.0003), and this difference persisted after controlling for age, sex, BMI, and visceral adiposity. Lower adiponectin in MA was associated with lower insulin sensitivity (R² = 0.42, p < 0.01). Lower adiponectin was also associated with higher dietary glycemic index, lower intake of vegetables, higher intake of trans fat, and higher intake of grains. Our findings confirm that ethnic differences in adiponectin reflect differences in insulin sensitivity, but suggest that these are not due to differences in adiposity. Observed associations between adiponectin and diet support the need for future studies exploring the regulation of adiponectin by diet and other environmental factors
Maximizing phonon thermal conductance for ballistic membranes
At low temperatures, phonon scattering can become so weak that phonon
transport becomes ballistic. We calculate the ballistic phonon conductance G
for membranes using elasticity theory, considering the transition from three to
two dimensions. We discuss the temperature and thickness dependence and
especially concentrate on the issue of material parameters. For all membrane
thicknesses, the best conductors have, counter-intuitively, the lowest speed of
sound.Comment: 4 pages, 4 figures, proceedings to phonons 2007 conferenc
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