132,320 research outputs found
Radio astronomy
The activities of the Deep Space Network in support of radio and radar astronomy operations during July and August 1980 are reported. A brief update on the OSS-sponsored planetary radio astronomy experiment is provided. Also included are two updates, one each from Spain and Australia on current host country activities
Development and initial validation of the determinants of physical activity questionnaire
Background: Physical activity interventions are more likely to be effective if they target causal determinants of behaviour change. Targeting requires accurate identification of specific theoretical determinants of physical activity. Two studies were undertaken to develop and validate the Determinants of Physical Activity Questionnaire. Methods In Study 1, 832 male and female university staff and students were recruited from 49 universities across the UK and completed the 66-item measure, which is based on the Theoretical Domains Framework. Confirmatory factor analysis was undertaken on a calibration sample to generate the model, which resulted in a loss of 31 items. A validation sample was used to cross-validate the model. 20 new items were added and Study 2 tested the revised model in a sample of 466 male and female university students together with a physical activity measure. Results: The final model consisted of 11 factors and 34 items, and CFA produced a reasonable fit χ2 (472) = 852.3, p < .001, CFI = .933, SRMR = .105, RMSEA = .042 (CI = .037-.046), as well as generally acceptable levels of discriminant validity, internal consistency, and test-retest reliability. Eight subscales significantly differentiated between high and low exercisers, indicating that those who exercise less report more barriers for physical activity. Conclusions: A theoretically underpinned measure of determinants of physical activity has been developed with reasonable reliability and validity. Further work is required to test the measure amongst a more representative sample. This study provides an innovative approach to identifying potential barriers to physical activity. This approach illustrates a method for moving from diagnosing implementation difficulties to designing and evaluating interventions
Fluoroether modified epoxy composites
Addition of controlled amounts of perfluorinated alkyl ether diacyl fluoride to epoxy resin systems prior to cure results in a formulation which, exhibits improved energy absorbing properties
Exterior powers in Iwasawa theory
The Iwasawa theory of CM fields has traditionally concerned Iwasawa modules
that are abelian pro-p Galois groups with ramification allowed at a maximal set
of primes over p such that the module is torsion. A main conjecture for such an
Iwasawa module describes its codimension one support in terms of a p-adic
L-function attached to the primes of ramification. In this paper, we study more
general and potentially much smaller Iwasawa modules that are quotients of
exterior powers of Iwasawa modules with ramification at a set of primes over p
by sums of exterior powers of inertia subgroups. We show that the higher
codimension support of such quotients can be measured by finite collections of
p-adic L-functions under the relevant CM main conjectures.Comment: 41 pages, to appear in J. Eur. Math. So
A definitive heat of vaporization of silicon through benchmark ab initio calculations on SiF_4
In order to resolve a significant uncertainty in the heat of vaporization of
silicon -- a fundamental parameter in gas-phase thermochemistry -- [Si(g)] has been determined from a thermochemical cycle involving
the precisely known experimental heats of formation of SiF_4(g) and F(g) and a
benchmark calculation of the total atomization energy (TAE_0) of SiF_4 using
coupled-cluster methods. Basis sets up to on Si and
on F have been employed, and extrapolations for residual basis
set incompleteness applied. The contributions of inner-shell correlation (-0.08
kcal/mol), scalar relativistic effects (-1.88 kcal/mol), atomic spin-orbit
splitting (-1.97 kcal/mol), and anharmonicity in the zero-point energy (+0.04
kcal/mol) have all been explicitly accounted for. Our benchmark TAE_0=565.89
\pm 0.22 kcal/mol leads to [Si(g)]=107.15 \pm 0.38
kcal/mol ([Si(g)]=108.19 \pm 0.38 kcal/mol): between
the JANAF/CODATA value of 106.5 \pm 1.9 kcal/mol and the revised value proposed
by Grev and Schaefer [J. Chem. Phys. 97, 8389 (1992}], 108.1 \pm 0.5 kcal/mol.
The revision will be relevant for future computational studies on heats of
formation of silicon compounds.Comment: J. Phys. Chem. A, submitted Feb 1, 199
THE VALUE OF SPORT FISHING IN THE SNAKE RIVER BASIN OF CENTRAL IDAHO
The value of sportfishing in the Snake River Basin in Central Idaho was measured using a two-stage/disequilibrium travel model. The two-stage/disequilibrium model does not require monetization of recreationists? travel time as required of traditional equilibrium labor market travel cost models. The model was estimated using Poisson regression, appropriate for count data when over-dispersion is absent, and adjusted for endogenous stratification (self selection bias) . Contrary to expectations that anglers living close to the sites with low values would be over represented in the sample, the endogenous stratification adjustment caused estimated consumers surplus to decline from 35 after adjustment. The average number of sportfishing trips per year was 6.72, resulting in an average annual willingness-to-pay of $236 per year per angler.Resource /Energy Economics and Policy,
Temperature distributions and thermal stresses in a graded zirconia/metal gas path seal system for aircraft gas turbine engines
A ceramic/metallic aircraft gas turbine outer gas path seal designed for improved engine performance was studied. Transient temperature and stress profiles in a test seal geometry were determined by numerical analysis. During a simulated engine deceleration cycle from sea-level takeoff to idle conditions, the maximum seal temperature occurred below the seal surface, therefore the top layer of the seal was probably subjected to tensile stresses exceeding the modulus of rupture. In the stress analysis both two- and three-dimensional finite element computer programs were used. Predicted trends of the simpler and more easily usable two-dimensional element programs were borne out by the three-dimensional finite element program results
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