2,399 research outputs found

    Results of dynamic stability tests conducted on a .012 scale model modified 089 B shuttle orbiter in the AEDC-VKF tunnel B at a Mach number of 8.0 (LA42)

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    Experimental aerodynamic investigations were conducted on a .012 scale model of a NASA/Langley modified version of the Rockwell 089B Space Shuttle Orbiter. Using the forced oscillation test technique, dynamic stability derivatives were measured in the pitch, yaw and roll planes at a Mach number of 8 over an angle of attack range from -4 deg to 28 deg. Plotted and tabulated results are presented

    Lifetime predictions for the Solar Maximum Mission (SMM) and San Marco spacecraft

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    Lifetime prediction techniques developed by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD) are described. These techniques were developed to predict the Solar Maximum Mission (SMM) spacecraft orbit, which is decaying due to atmospheric drag, with reentry predicted to occur before the end of 1989. Lifetime predictions were also performed for the Long Duration Exposure Facility (LDEF), which was deployed on the 1984 SMM repair mission and is scheduled for retrieval on another Space Transportation System (STS) mission later this year. Concepts used in the lifetime predictions were tested on the San Marco spacecraft, which reentered the Earth's atmosphere on December 6, 1988. Ephemerides predicting the orbit evolution of the San Marco spacecraft until reentry were generated over the final 90 days of the mission when the altitude was less than 380 kilometers. The errors in the predicted ephemerides are due to errors in the prediction of atmospheric density variations over the lifetime of the satellite. To model the time dependence of the atmospheric densities, predictions of the solar flux at the 10.7-centimeter wavelength were used in conjunction with Harris-Priester (HP) atmospheric density tables. Orbital state vectors, together with the spacecraft mass and area, are used as input to the Goddard Trajectory Determination System (GTDS). Propagations proceed in monthly segments, with the nominal atmospheric drag model scaled for each month according to the predicted monthly average value of F10.7. Calibration propagations are performed over a period of known orbital decay to obtain the effective ballistic coefficient. Progagations using plus or minus 2 sigma solar flux predictions are also generated to estimate the despersion in expected reentry dates. Definitive orbits are compared with these predictions as time expases. As updated vectors are received, these are also propagated to reentryto continually update the lifetime predictions

    Contributions of Early Care and Education Programs to Diet Quality in Children Aged 3 to 4 Years in Central North Carolina

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    BACKGROUND: Parents and early care and education (ECE) are the key influencers of young children\u27s diets, but there is limited information about how each contribute to children\u27s overall diet quality. OBJECTIVE: This study aimed to determine what proportion of children\u27s dietary intake occurs within the ECE setting and whether diet quality is higher at ECE centers and, consequently, on weekdays than weekends. DESIGN: This cross-sectional analysis of a larger cluster randomized controlled trial used multiple 24-hour dietary intakes measured through a combination of the Dietary Observation in Child Care protocol and parent-reported food diaries. PARTICIPANTS/SETTING: Participants (N=840) included children aged 3 to 4 years enrolled in ECE centers in central North Carolina for whom 24-hour dietary intake was captured via observation of meals and snacks consumed at ECE and parent-report of all remaining meals and snacks. Data were collected from 2015 to 2016. MAIN OUTCOME MEASURES: Diet quality at ECE and elsewhere was evaluated using the Healthy Eating Index 2015. STATISTICAL ANALYSES PERFORMED: Mixed-effects models were used to determine differences in mean Healthy Eating Index 2015 component and total scores. Models were adjusted for children\u27s age and sex and accounted for clustering within ECE centers and families. RESULTS: Children consumed approximately 40% of daily energy, nutrients, and food groups at ECE centers. The mean total Healthy Eating Index 2015 score was higher for foods and beverages consumed at ECE centers (58.3±0.6) than elsewhere (52.5±0.6) (P \u3c 0.0001). The mean total Healthy Eating Index 2015 score was also higher on weekdays (58.5±0.5) than on weekends (51.3±0.5) (P \u3c 0.0001). CONCLUSIONS: Children consume a majority of dietary intake away from ECE centers. Overall, diet quality is low, but the quality of foods consumed by children at ECE centers is higher than that consumed elsewhere. ECE centers remain an important source of nutrition and further investigation is warranted to identify ways to support both ECE centers and families to provide healthier eating environments

    Minimización del riesgo de extinción mediante el rescate genético

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    According to the genetic rescue hypothesis, immigrants can improve population persistence through their genetic contribution alone. We investigate the potential for such rescue using small, inbred laboratory populations of the bean beetle (Callosobruchus maculatus). We ask how many migrants per generation (MPG) are needed to minimize the genetic component of extinction risk. During Phase 1, population size was made to fluctuate between 6 and 60 (for 10 generations). During this phase, we manipulated the number of MPG, replacing 0, 1, 3, or 5 females every generation with immigrant females. During Phase 2, we simply set an upper limit on population size (.10). Compared with the 0–MPG treatment, the other treatments were equivalently effective at improving reproductive success and reducing extinction risk. A single MPG was sufficient for genetic rescue, apparently because effective migration rate was inflated dramatically during generations when population size was small. An analysis of quasi–extinction suggests that replicate populations in the 1–MPG treatment benefited from initial purging of inbreeding depression. Populations in this treatment performed so well apparently because they received the dual benefit of purging followed by genetic infusion. Our results suggest the need for further evaluation of alternative schemes for genetic rescue.Según la hipótesis del rescate genético, los inmigrantes pueden mejorar la persistencia de una población mediante su contribución genética. Hemos investigado el potencial de un rescate de este tipo, utilizando pequeñas poblaciones endogámicas de laboratorio del gorgojo del haba Callosobruchus maculatus. Nos preguntamos cuántos migrantes por generación (MPG) son necesarios para minimizar el componente genético del riesgo de extinción. Durante la Fase 1, se hizo fluctuar el tamaño de la población entre 6 y 60 (durante 10 generaciones). En dicha fase manipulamos el número de MPGs, reemplazando 0, 1, 3, o 5 hembras nativas por hembras inmigrantes en cada generación. Durante la Fase 2, nos limitamos a poner un límite superior al tamaño de la población (.10). Comparados con el tratamiento de 0–MPG, los otros tratamientos resultaron ser igualmente efectivos en la mejora del éxito reproductivo y la reducción del riesgo de extinción. Un único MPG era suficiente para el rescate genético, aparentemente debido a que la tasa de migración efectiva quedaba espectacularmente sobredimensionada durante generaciones, cuando el tamaño de la población era pequeño. Un análisis de cuasi–extinción sugiere que las poblaciones replicadas durante el tratamiento 1–MPG se beneficiaron de un saneamiento inicial por la disminución de la endogamia. Aparentemente, las poblaciones de este tratamiento se comportaron tan bien debido a que recibieron el doble beneficio del saneamiento seguido de la inyección genética. Nuestros resultados sugieren la necesidad de posteriores evaluaciones del rescate genético mediante esquemas alternativos

    Immunohistochemical Localization of Glutamate Decarboxylase in Rat Cerebellum

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    Design, analysis and test verification of advanced encapsulation systems, phase 2 program results

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    Optical, electrical isolation, thermal structural, structural deflection, and thermal tests are reported. The utility of the optical, series capacitance, and structural deflection models was verified

    Limit on the fermion masses in technicolor models

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    Recently it has been pointed out that no limits can be put on the scale of fermion mass generation (M)(M) in technicolor models, because the relation between the fermion masses (mf)(m_f) and MM depends on the dimensionality of the interaction responsible for generating the fermion mass. Depending on this dimensionality it may happens that mfm_f does not depend on MM at all. We show that exactly in this case mfm_f may reach its largest value, which is almost saturated by the top quark mass. We make few comments on the question of how large can be a dynamically generated fermion mass.Comment: 5 pages, 1 figure, RevTeX

    Screen Time Parenting Practices and Associations with Preschool Children’s TV Viewing and Weight-Related Outcomes

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    The purpose of this study was to examine associations between screen time (ST) parenting practices and 2–5-year-old children’s TV viewing and weight status. Data were collected from 252 parent–child dyads enrolled in a randomized parent-focused childhood obesity prevention trial from 2009–2012. ST parenting practices were assessed at baseline using a validated parent-reported survey. Parent-reported child TV viewing and objectively measured anthropometrics were assessed at baseline, post-intervention (35 weeks), and follow-up (59 weeks). Marginal effect models were developed to test the association between baseline ST parenting practices and children’s TV viewing, BMI z-score, and waist circumference across all time points. Limiting/monitoring ST was associated with decreased weekly TV viewing (β = −1.79, 95% CI: −2.61; −0.95), while exposure to TV was associated with more weekly TV viewing over 59 weeks (β = 1.23, 95% CI: 0.71; 1.75). Greater parent use of ST as a reward was associated with increased child BMI z-score (β = 0.15, 95% CI: 0.03; 0.27), while limiting/monitoring ST was associated with decreased BMI z-score (β = −0.16, 95% CI: −0.30; −0.01) and smaller waist circumference (β = −0.55, 95% CI: −1.04; −0.06) over the study period. These findings suggest that modifying parent ST practices may be an important strategy to reduce ST and promote healthy weight in young children

    Status of the Standard Solar Model Prediction of Solar Neutrino Fluxes

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    The Standard Solar Model (BP04) predicts a total 8B neutrino flux that is 17.2% larger than measured in the salt phase of the SNO detector (and if it were significant it will indicate oscillation to sterile neutrinos). Hence it is important to examine in details uncertainties (and values) of inputs to the SSM. Currently, the largest fractional uncertainty is due to the new evaluation of the surface composition of the sun. We examine the nuclear input on the formation of solar 8B [S17(0)] and demonstrate that it is still quite uncertain due to ill known slope of the measured astrophysical cross section factor and thus ill defined extrapolation to zero energy. This yields an additional reasonably estimated uncertainty due to extrapolation of +0.0 -3.0 eV-b (+0% -14%). Since a large discrepancy exists among measured as well as among predicted slopes, the value of S17(0) is dependent on the choice of data and theory used to extrapolate S17(0). This situation must be alleviated by new measurement(s). The "world average" is driven by the Seattle result due to the very small quoted uncertainty, which we however demonstrate it to be an over-estimated accuracy. We propose more realistic error bars for the Seattle results based on the published Seattle data.Comment: Fifth International Conferenceon Non-Accelerator New Physics, Dubna, June 20-25, 2005. Work Supported by USDOE Grant No. DE-FG02-94ER4087
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