483 research outputs found
NASA/MSFC Large Stretch Press Study
The purpose of this study was to: A. assess and document the advantages/disadvantages of a government agency investment in a large stretch form press on the order of 5000 tons capacity (per jaw); B. develop a procurement specification for the press; and C. provide trade study data that will permit an optimum site location. Tasks were separated into four major elements: cost study, user survey, site selection, and press design/procurement specification
A Variable Coeficient of Restitution Experiment on a Linear Air Track
A system consisting of two pendula attached to an air cart is mathematically analyzed, and the coefficient of restitution is shown to pass through a deep minimum. The solution to the small angle equation of motion is transcendental and provides an exercise in graphical methods for the beginning mechanics student
STRATIGRAPHIC INVESTIGATIONS AT BARBER CREEK (31PT259) : RECONSTRUCTING THE CULTURE-HISTORY OF A MULTICOMPONENT SITE IN THE NORTH CAROLINA COASTAL PLAIN
Barber Creek is a multicomponent stratified site situated atop a relict sand dune in eastern North Carolina. Previous research has put emphasis on site formation and occupation. The focus of this study was to reconstruct the cultural chronology of the west-central portion of Barber Creek and compare it to previous analyses from other portions of the site. This study resulted in the identification of three former occupation surfaces, or floors, buried in approximately one meter of aeolian sands. These occupation floors date to the Early Archaic, Middle to Late Archaic and Early to Middle Woodland periods. The stratified remains of three discrete occupation floors identified in this investigation are largely consistent with previous investigations at the site. The artifact backplots reconstructed here are the clearest evidence yet for a stratified sequence at Barber Creek. In fact, the results of this study provide the best evidence thus far for the presence of Early Archaic, Middle to Late Archaic, and Woodland components in stratified contexts in the Coastal Plain of North Carolina. Great potential exists at Barber Creek and other such stratified sites along the Tar River to answer questions concerning chronology and typology related to the prehistory of the North Carolina Coastal Plain.  M.A
Ecological Effects of Fear: How Spatiotemporal Heterogeneity in Predation Risk Influences Mule Deer Access to Forage in a Sky‐Island System
Forage availability and predation risk interact to affect habitat use of ungulates across many biomes. Within sky‐island habitats of the Mojave Desert, increased availability of diverse forage and cover may provide ungulates with unique opportunities to extend nutrient uptake and/or to mitigate predation risk. We addressed whether habitat use and foraging patterns of female mule deer (Odocoileus hemionus) responded to normalized difference vegetation index (NDVI), NDVI rate of change (green‐up), or the occurrence of cougars (Puma concolor). Female mule deer used available green‐up primarily in spring, although growing vegetation was available during other seasons. Mule deer and cougar shared similar habitat all year, and our models indicated cougars had a consistent, negative effect on mule deer access to growing vegetation, particularly in summer when cougar occurrence became concentrated at higher elevations. A seemingly late parturition date coincided with diminishing NDVI during the lactation period. Sky‐island populations, rarely studied, provide the opportunity to determine how mule deer respond to growing foliage along steep elevation and vegetation gradients when trapped with their predators and seasonally limited by aridity. Our findings indicate that fear of predation may restrict access to the forage resources found in sky islands
Mechanical Activation of Al-Oxyhydroxide Minerals – Physicochemical Changes, Reactivity and Relevance to Bayer Process
Overview of our research on ‘structure and reactivity’ of gibbsite and boehmite under varied conditions of mechanical activation, e.g. milling energy and presence of a second phase is presented. Bulk and surface changes induced in the solids by milling are characterized in terms of morphology, particle size distribution, specific surface area and nature of porosity, crystallite size and zeta potential. Results on enhanced amorphisation of gibbsite in presence of a second phase (quartz, hematite etc), changes in zeta potential of gibbsite due to loss of texture during milling and anomalous decrease in surface area of boehmite during milling are reported. Reactivity of the activated solids in sodium hydroxide and variation in thermal transformation temperatures is correlated with physicochemical characteristics of the samples and plausible explanation for the observed correlations presented. Significance of the results with specific reference to bauxite and alumina processing in Bayer process is highlighted
What is the importance of climate model bias when projecting the impacts of climate change on land surface processes?
Regional climate change impact (CCI) studies have widely involved
downscaling and bias correcting (BC) global climate model (GCM)-projected
climate for driving land surface models. However, BC may cause uncertainties
in projecting hydrologic and biogeochemical responses to future climate due
to the impaired spatiotemporal covariance of climate variables and a
breakdown of physical conservation principles. Here we quantify the impact
of BC on simulated climate-driven changes in water variables
(evapotranspiration (ET), runoff, snow water equivalent (SWE), and water
demand for irrigation), crop yield, biogenic volatile organic compounds
(BVOC), nitric oxide (NO) emissions, and dissolved inorganic nitrogen (DIN)
export over the Pacific Northwest (PNW) region. We also quantify the impacts
on net primary production (NPP) over a small watershed in the region (HJ-Andrews). Simulation results from the coupled ECHAM5–MPI-OM model with A1B
emission scenario were first dynamically downscaled to 12 km resolution with
the WRF model. Then a quantile-mapping-based statistical downscaling model
was used to downscale them into 1/16° resolution daily climate data
over historical and future periods. Two climate data series were generated,
with bias correction (BC) and without bias correction (NBC). Impact models
were then applied to estimate hydrologic and biogeochemical responses to
both BC and NBC meteorological data sets. These impact models include a
macroscale hydrologic model (VIC), a coupled cropping system model
(VIC-CropSyst), an ecohydrological model (RHESSys), a biogenic emissions model
(MEGAN), and a nutrient export model (Global-NEWS).
Results demonstrate that the BC and NBC climate data provide consistent
estimates of the climate-driven changes in water fluxes (ET, runoff, and
water demand), VOCs (isoprene and monoterpenes) and NO emissions, mean crop
yield, and river DIN export over the PNW domain. However, significant
differences rise from projected SWE, crop yield from dry lands, and HJ-Andrews's ET between BC and NBC data. Even though BC post-processing has no
significant impacts on most of the studied variables when taking PNW as a
whole, their effects have large spatial variations and some local areas are
substantially influenced. In addition, there are months during which BC and
NBC post-processing produces significant differences in projected changes,
such as summer runoff. Factor-controlled simulations indicate that BC
post-processing of precipitation and temperature both substantially
contribute to these differences at regional scales.
We conclude that there are trade-offs between using BC climate data for
offline CCI studies versus directly modeled climate data. These trade-offs
should be considered when designing integrated modeling frameworks for
specific applications; for example, BC may be more important when considering
impacts on reservoir operations in mountainous watersheds than when
investigating impacts on biogenic emissions and air quality, for which VOCs
are a primary indicator
Use of crystal methamphetamine among male adolescents in Cape Town, South Africa: Caregivers' experiences
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Family treatment of child anxiety: outcomes, limitations and future directions
Anxiety of childhood is a common and serious condition. The past decade has seen an increase in treatment-focussed research, with recent trials tending to give greater attention to parents in the treatment process. This review examines the efficacy of family-based cognitive behaviour therapy and attempts to delineate some of the factors that might have an impact on its efficacy. The choice and timing of outcome measure, age and gender of the child, level of parental anxiety, severity and type of child anxiety and treatment format and content are scrutinised. The main conclusions are necessarily tentative, but it seems likely that Family Cognitive Behaviour Therapy (FCBT) is superior to no treatment, and, for some outcome measures, also superior to Child Cognitive Behaviour Therapy (CCBT). Where FCBT is successful, the results are consistently maintained at follow-up. It appears that where a parent is anxious, and this is not addressed, outcomes are less good. However, for children of anxious parents, FCBT is probably more effective than CCBT. What is most clear is that large, well-designed studies, examining these factors alone and in combination, are now needed
Mutations in EDA and EDAR Genes in a Large Mexican Hispanic Cohort with Hypohidrotic Ectodermal Dysplasia
Ectodermal dysplasias (ED) encompass nearly 200 different
genetic conditions identified by the lack, or dysgenesis,
of at least two ectodermal derivatives, such as hair, nails, teeth, and sweat glands. Hypohidrotic/anhidrotic ED (HED) is the most frequent form of ED and it can be inherited as an X-linked (XL)-HED (MIM 305100), autosomal recessive (AR)-HED (MIM 224900), or autosomal dominant (AD)-HED (MIM 229490) condition. HED is caused by mutations in any of the three ectodisplasin pathway genes: ectodisplasin (EDA), which encodes a ligand for the second gene, the EDA receptor (ectodysplasin A-receptor, EDAR), and EDARADD, an intracellular signaling for this pathway. HED is characterized by a triad of clinical features including absent or diminished eccrine sweat glands, missing and/or malformed teeth, and thin, sparse hair. It also includes dryness of the skin, eyes, airways, and mucous membranes, as well as other ectodermal defects and, in some cases, fever, seizures, and rarely, death. XL-HED is caused by mutations in the EDA gene, located on chromosome Xq12-q13.1, which encodes a signaling molecule of the tumor necrosis factor (TNF) superfamily. AR- and AD-HED are caused by mutations in the EDAR gene, located on chromosome 2q11.q13 or the EDARAssociated Death Domain encoding gene, EDARADD, located on chromosome 1q42-q431. Several mutations in the EDA, EDAR, and EDARADD genes have been described as causing HED in different populations. The XL-HED form is the most common and is responsible for 90% of all HED cases2-6. The three forms of HED are clinically indistinguishable. To date, a comprehensive evaluation of HED in the Mexican Hispanic population has not been undertaken. In the present study, we aimed to characterize the mutations in EDA, EDAR, and EDARADD genes present in Mexican Hispanic patients with HED.
Male and female patients (35 families) from different geographical regions of Mexico with features suggestive of HED were enrolled in the study (Fig. 1). Index cases and their parents were screened for missing or malformed teeth, thin or sparse hair, and nail changes; all subjects answered questions about sweating, heat intolerance, fever, seizures, and family history of siblings deceased due to unknown feve
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