222 research outputs found

    Preparing Our Kids for Education, Work and Life: A Report of the Task Force on Youth Aging Out

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    Summarizes a study of Massachusetts youth transitioning out of foster care, and offers recommendations for policies, practices, and resource conditions, including "Five Core Resources" to prepare them for higher education, work, and adulthood

    Transient Thermal Model and Analysis of the Lunar Surface and Regolith for Cryogenic Fluid Storage

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    A transient thermal model of the lunar surface and regolith was developed along with analytical techniques which will be used to evaluate the storage of cryogenic fluids at equatorial and polar landing sites. The model can provide lunar surface and subsurface temperatures as a function of latitude and time throughout the lunar cycle and season. It also accounts for the presence of or lack of the undisturbed fluff layer on the lunar surface. The model was validated with Apollo 15 and Clementine data and shows good agreement with other analytical models

    Development of ultrasound detection in American shad (Alosa sapidissima)

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    It has recently been shown that a few fish species, including American shad (Alosa sapidissima; Clupeiformes), are able to detect sound up to 180 kHz, an ability not found in most other fishes. Initially, it was proposed that ultrasound detection in shad involves the auditory bullae, swim bladder extensions found in all members of the Clupeiformes. However, while all clupeiformes have bullae, not all can detect ultrasound. Thus, the bullae alone are not sufficient to explain ultrasound detection. In this study, we used a developmental approach to determine when ultrasound detection begins and how the ability to detect ultrasound changes with ontogeny in American shad. We then compared changes in auditory function with morphological development to identify structures that are potentially responsible for ultrasound detection. We found that the auditory bullae and all three auditory end organs are present well before fish show ultrasound detection behaviourally and we suggest that an additional specialization in the utricle (one of the auditory end organs) forms coincident with the onset of ultrasound detection. We further show that this utricular specialization is found in two clupeiform species that can detect ultrasound but not in two clupeiform species not capable of ultrasound detection. Thus, it appears that ultrasound-detecting clupeiformes have undergone structural modification of the utricle that allows detection of ultrasonic stimulation

    From Citywide to Neighborhood-Based: Two Decades of Learning, Prioritization, and Strategic Action to Build the Skillman Foundation’s Youth-Development Systems

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    · This article explores the Skillman Foundation’s shift in its approach to fulfilling its mission to improve the lives of children and youth and to making grants – moving from a traditional grantmaker to a place-based investor and change-maker. · Three aspects of Skillman’s approach have directly shaped the evolution of its youth-development investments: recognizing Detroit’s economic, social, political, and environmental challenges; articulating overarching goals to provide direction and setting priorities for the scope and focus of its programmatic work; and using rapid learning to inform strategic decisions and social-innovation practices designed to tackle deeply entrenched problems. · This article reflects on the foundation’s evolution over two decades of learning, prioritization, and strategic action in its efforts to build and sustain outcome-focused youth-development systems

    Body Composition Characteristics of a Load-Capacity Model: Age-Dependent and Sex-Specific Percentiles in 5- To 17-Year-Old Children

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    Introduction: Body composition assessment is superior to the use of body mass index (BMI) to characterize the nutritional status in pediatric populations. For data interpretation, suitable reference data are needed; hence, we aimed to generate age-dependent and sex-specific body composition reference data in a larger population of children and adolescents in Germany. Methods: This is a cross-sectional study on a representative group of 15,392 5- to 17-year-old children and adolescents. Body composition was assessed by bioelectrical impedance analysis using a population-specific algorithm validated against air displacement plethysmography. Age- and sex-specific percentiles for BMI, fat mass index (FMI), fat-free mass index (FFMI), and a “load-capacity model” (characterized by the ratios of fat mass [FM]/ fatt-free mass [FFM] and FM/FFM2) were modeled using the LMS method. Results: BMI, FMI, FFMI, FM/FFM, and FM/FFM2 curves showed similar shapes between boys and girls with steady increases in BMI, FMI, and FFMI, while FM/FFM2-centiles decreased during early childhood and adolescence. Sex differences were observed in FMI and FM/FFM percentiles with increases in FMI up to age 9 years followed by a steady decrease in FM/FFM during and after puberty with a fast-growing FFMI up to age 17 in boys. The prevalence of low FFM relative to FM reached more than 60% in overweight children and adolescents. Conclusion: These pediatric body composition reference data enable physicians and public health scientists to monitor body composition during growth and development and to interpret individual data. The data point out to an early risk of sarcopenia in overweight children and adolescents

    Methane Lunar Surface Thermal Control Test

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    NASA is considering propulsion system concepts for future missions including human return to the lunar surface. Studies have identified cryogenic methane (LCH4) and oxygen (LO2) as a desirable propellant combination for the lunar surface ascent propulsion system, and they point to a surface stay requirement of 180 days. To meet this requirement, a test article was prepared with state-of-the-art insulation and tested in simulated lunar mission environments at NASA GRC. The primary goals were to validate design and models of the key thermal control technologies to store unvented methane for long durations, with a low-density high-performing Multi-layer Insulation (MLI) system to protect the propellant tanks from the environmental heat of low Earth orbit (LEO), Earth to Moon transit, lunar surface, and with the LCH4 initially densified. The data and accompanying analysis shows this storage design would have fallen well short of the unvented 180 day storage requirement, due to the MLI density being much higher than intended, its substructure collapse, and blanket separation during depressurization. Despite the performance issue, insight into analytical models and MLI construction was gained. Such modeling is important for the effective design of flight vehicle concepts, such as in-space cryogenic depots or in-space cryogenic propulsion stages

    Analysis of Water Surplus at the Lunar Outpost

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    This paper evaluates the benefits to the lunar architecture and outpost of having a surplus of water, or a surplus of energy in the form of hydrogen and oxygen, as it has been predicted by Constellation Program's Lunar Surface System analyses. Assumptions and a scenario are presented leading to the water surplus and the revolutionary surface element options for improving the lunar exploration architecture and mission objectives. For example, some of the elements that can benefit from a water surplus are: the power system energy storage can minimize the use of battery systems by replacing batteries with higher energy density fuel cell systems; battery packs on logistics pallets can also be minimized; mobility asset power system mass can be reduced enabling more consumables and extended roving duration and distance; small robotic vehicles (hoppers) can be used to increase the science exploration range by sending round-trip robotic missions to anywhere on the Moon using in-situ produced propellants

    Investigation into Cryogenic Tank Insulation Systems for the Mars Surface Environment

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    In order to use oxygen that is produced on the surface of Mars from In-Situ production processes in a chemical propulsion system, the oxygen must first be converted from vapor phase to liquid phase and then stored within the propellant tanks of the propulsion system. The oxygen must then be stored in the liquid phase for several years between when the liquefaction operations are initiated and when the ascent stage lifts off the Martian surface. Since the Space Exploration Initiative, NASA has been investing small sums of money into soft vacuum systems for Mars Applications. A study was done into these various insulation systems for soft vacuum insulation, to determine what types of systems might be best to further pursue. Five different architectures or cycles were considered: Aerogel-based multilayer Insulation (MLAI), Space Evacuated Mars Vacuum Jacket (SEMOV) (also known as lightweight vacuum jacket), Load Responsive-Multilayer Insulation, Spray on Foam with MLI, and MLAI in SEMOV. Models of each architecture were developed to give insight into the performance and losses of each of the options. The results were then compared across six categories: Insulation System Mass, Active System Power (both input and heat rejection), Insulation System Cost, Manufacturability, Reliability, and Operational Flexibility. The result was that a trade between reliability and mass was clearly identified. Systems with high mass, also had high perceived reliability; whereas, systems with lower mass and power had a much lower perceived reliability. In the end, the numerical trades of these systems showed nominally identical rankings. As a result it is recommended that NASA focus its Martian insulation development activities on demonstrating and improving the reliability of the lightweight identified systems

    Gestational Weight Gain and Body Mass Index in Children: Results from Three German Cohort Studies

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    Previous studies suggested potential priming effects of gestational weight gain (GWG) on offspring's body composition in later life. However, consistency of these effects in normal weight, overweight and obese mothers is less clear. We combined the individual data of three German cohorts and assessed associations of total and excessive GWG (as defined by criteria of the Institute of Medicine) with offspring's mean body mass index (BMI) standard deviation scores (SDS) and overweight at the age of 5-6 years (total: n = 6,254). Quantile regression was used to examine potentially different effects on different parts of the BMI SDS distribution. All models were adjusted for birth weight, maternal age and maternal smoking during pregnancy and stratified by maternal pre-pregnancy weight status. In adjusted models, positive associations of total and excessive GWG with mean BMI SDS and overweight were observed only in children of non- overweight mothers. For example, excessive GWG was associated with a mean increase of 0.08 (95% CI: 0.01, 0.15) units of BMI SDS (0.13 (0.02, 0.24) kg/m(2) of 'real' BMI) in children of normal-weight mothers. The effects of total and excessive GWG on BMI SDS increased for higher- BMI children of normal-weight mothers. Increased GWG is likely to be associated with overweight in offspring of non-overweight mothers

    Cooperation-based sperm clusters mediate sperm oviduct entry and fertilization

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    Sperm cooperation has been observed in multiple species, yet its existence and benefit for reproductive success in mammals remains underexplored. Here, combining tissue-clearing with deep three-dimensional imaging, we demonstrate that postcopulatory mouse sperm congregate into unidirectional sperm cooperative clusters at the utero-tubal junction (UTJ), a key physical barrier for passage into the oviduct. Reducing sperm number in male mice by unilateral vasoligation or busulfan-treatment impairs sperm cluster formation and oviduct entry. Interestingly, sperm derived from Tex101-/- mouse has normal number, motility and morphology, yet they cannot form sperm cluster and fail to pass through the UTJ, which is at least in part due to the altered tail beating pattern of the Tex101-/- sperm. Moreover, Tex101-/- sperm's defect in oviduct entry cannot be rescued by the presence of wild-type (WT) sperm in the same uteri by sequential mating, suggesting sperm cooperative cluster as an essential behavior contributing to male fertility, which could be related to human infertility or subfertility
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