525 research outputs found
Characterizing Volcanic Eruptions on Venus: Some Realistic (?) Scenarios
When Pioneer Venus arrived at Venus in 1978, it detected anomalously high concentrations of SO2 at the top of the troposphere, which subsequently declined over the next five years. This decline in SO2 was linked to some sort of dynamic process, possibly a volcanic eruption. Observations of SO2 variability have persisted since Pioneer Venus. More recently, scientists from the Venus Express mission announced that the SPICAV (Spectroscopy for Investigation of Characteristics of the Atmosphere of Venus) instrument had measured varying amounts of SO2 in the upper atmosphere; VIRTIS (Visible and Infrared Thermal Imaging Spectrometer) measured no similar variations in the lower atmosphere (ESA, 4 April, 2008). In addition, Fegley and Prinn stated that venusian volcanoes must replenish SO2 to the atmosphere, or it would react with calcite and disappear within 1.9 my. Fegley and Tremain suggested an eruption rate on the order of approx 1 cubic km/year to maintain atmospheric SO2; Bullock and Grinspoon posit that volcanism must have occurred within the last 20-50 my to maintain the sulfuric acid/water clouds on Venus. The abundance of volcanic deposits on Venus and the likely thermal history of the planet suggest that it is still geologically active, although at rates lower than Earth. Current estimates of resurfacing rates range from approx 0.01 cubic km/yr to approx 2 cubic km/yr. Demonstrating definitively that Venus is still volcanically active, and at what rate, would help to constrain models of evolution of the surface and interior, and help to focus future exploration of Venus
Global Roughness Texture of the Moon and Mars
Statistical measures of patterns (textures) in surface roughness are used to quantitatively differentiate regional geomorphic units on the Moon and Mars (e.g. cratered highlands, volcanic terrains and planar lowlands). The existence of vastly distinct crustal types on Mars and the Moon is well established [e.g. 1, 2, 3, & 4]. Here, a new methodology developed for differentiating terrestrial volcanic deposits using ~1 m resolution topography data [5], is tested on two global data sets where roughness pixels are much larger (1/4 of a degree)
Spatial and Alignment Analyses for a field of Small Volcanic Vents South of Pavonis Mons Mars
The Tharsis province of Mars displays a variety of small volcanic vent (10s krn in diameter) morphologies. These features were identified in Mariner and Viking images [1-4], and Mars Orbiter Laser Altimeter (MOLA) data show them to be more abundant than originally observed [5,6]. Recent studies are classifying their diverse morphologies [7-9]. Building on this work, we are mapping the location of small volcanic vents (small-vents) in the Tharsis province using MOLA, Thermal Emission Imaging System, and High Resolution Stereo Camera data [10]. Here we report on a preliminary study of the spatial and alignment relationships between small-vents south of Pavonis Mons, as determined by nearest neighbor and two-point azimuth statistical analyses. Terrestrial monogenetic volcanic fields display four fundamental characteristics: 1) recurrence rates of eruptions,2 ) vent abundance, 3) vent distribution, and 4) tectonic relationships [11]. While understanding recurrence rates typically requires field measurements, insight into vent abundance, distribution, and tectonic relationships can be established by mapping of remotely sensed data, and subsequent application of spatial statistical studies [11,12], the goal of which is to link the distribution of vents to causal processes
Evidence for Water Ie on the Moon: Results for Anomalous Polar Craters from the LRO Mini-RF Imaging Radar
The Mini-RF radar instrument on the Lunar Reconnaissance Orbiter spacecraft mapped both lunar poles in two different RF wavelengths (complete mapping at 12.6 cm S-band and partial mapping at 4.2 cm X-band) in two look directions, removing much of the ambiguity of previous Earth- and spacecraft-based radar mapping of the Moon's polar regions. The poles are typical highland terrain, showing expected values of radar cross section (albedo) and circular polarization ratio (CPR). Most fresh craters display high values of CPR in and outside the crater rim; the pattern of these CPR distributions is consistent with high levels of wavelength-scale surface roughness associated with the presence of block fields, impact melt flows, and fallback breccia. A different class of polar crater exhibits high CPR only in their interiors, interiors that are both permanently dark and very cold (less than 100 K). Application of scattering models developed previously suggests that these anomalously high-CPR deposits exhibit behavior consistent with the presence of water ice. If this interpretation is correct, then both poles may contain several hundred million tons of water in the form of relatively "clean" ice, all within the upper couple of meters of the lunar surface. The existence of significant water ice deposits enables both long-term human habitation of the Moon and the creation of a permanent cislunar space transportation system based upon the harvest and use of lunar propellant
Developmental delay in Rett syndrome: data from the natural history study
Background: Early development appears normal in Rett syndrome (OMIM #312750) and may be more apparent than real. A major purpose of the Rett Syndrome (RTT) Natural History Study (NHS) was to examine achievement of developmental skills or abilities in classic and atypical RTT and assess phenotype-genotype relations in classic RTT. Methods: Developmental skills in four realms, gross and fine motor, and receptive and expressive communication from initial enrollment and longitudinal assessments for up to 7 years, were assessed from 542 females meeting criteria for classic RTT and 96 females with atypical RTT divided into two groups: 50 with better and 46 with poorer functional scores. Data were analyzed for age at acquisition and loss of developmental features and for phenotype-genotype effects. Acquired, lost, and retained skills were compared between classic RTT and atypical RTT with better or poorer functional scores using Fisher's Exact test. To examine if the mean total score from the Motor Behavioral Assessment during follow-up differed for acquiring a skill, we used a generalized estimating equation assuming compound symmetry correlation structure within a subject. A general linear model was used to examine whether the mean age of acquisition or loss of a developmental skill differed by mutation type. P values <0.05 were considered significant and were two-sided without adjustment for multiple testing. Statistical analyses utilized SAS 9.3 (SAS Institute, Cary, NC, USA). Results: Early developmental skills or abilities were often acquired albeit later than normal. More complex motor and communication acquisitions were delayed or absent. Clinical severity was less in those achieving the respective skill. Individuals with R133C, R294X, and R306C point mutations and 3′ truncations tended to have better developmental outcomes. Conclusions: Early developmental skills were acquired by many, but clear differences from normal emerged, particularly in skills expected after age 6 months. When comparing clinical severity, greater acquisition of specific skills was associated with specific mutations, confirming the impression that these mutations confer milder developmental abnormalities. These data may serve for planning and interpretation of early intervention studies in RTT. Trial registration This NHS study, clinicaltrials.gov (NCT00296764), represents the largest group of RTT participants assessed repeatedly by direct examination
Evidence for Water Ice on the Moon: Results for Anomalous Polar Craters from the LRO Mini-RF Imaging Radar
The Mini-RF radar instrument on the Lunar Reconnaissance Orbiter spacecraft mapped both lunar poles in two different RF wavelengths (complete mapping at 12.6 cm S-band and partial mapping at 4.2 cm X-band) in two look directions, removing much of the ambiguity of previous Earth- and spacecraft-based radar mapping of the Moon's polar regions. The poles are typical highland terrain, showing expected values of radar cross section (albedo) and circular polarization ratio (CPR). Most fresh craters display high values of CPR in and outside the crater rim; the pattern of these CPR distributions is consistent with high levels of wavelength-scale surface roughness associated with the presence of block fields, impact melt flows, and fallback breccia. A different class of polar crater exhibits high CPR only in their interiors, interiors that are both permanently dark and very cold (less than 100 K). Application of scattering models developed previously suggests that these anomalously high-CPR deposits exhibit behavior consistent with the presence of water ice. If this interpretation is correct, then both poles may contain several hundred million tons of water in the form of relatively "clean" ice, all within the upper couple of meters of the lunar surface. The existence of significant water ice deposits enables both long-term human habitation of the Moon and the creation of a permanent cislunar space transportation system based upon the harvest and use of lunar propellant
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Shiva target irradiation facility
The first laser/plasma studies performed with the Shiva laser system will be two sided irradiations extending the data obtained by other LLL lasers to higher powers. The twenty approximately 1 TW laser pulses will reach the target simultaneously from above and below in nested pentagonal clusters. The upper and lower clusters of ten beams each are radially polarized so that they strike the target in p-polarization and maximize absorption. This geometry introduces laser system isolation problems which will be briefly discussed. The layout and types of target diagnostics will be described and a brief status report on the facility given
Reunifying from behind bars: A quantitative study of the relationship between parental incarceration, service use, and foster care reunification
Incarcerated parents attempting to reunify with their children in foster care can find it difficult to complete the activities on their court-ordered case plans, such as drug treatment services and visitation with children. Although much has been written regarding the obstacles that are likely to interfere with reunification for incarcerated parents, very little quantitative research has examined the topic. This study uses secondary data to examine the incarceration experiences and reunification outcomes of a sample of 225 parents in one large urban California county. In multivariate analysis controlling for problems and demographics, incarcerated parents were less likely to reunify with their children; however, service use appeared to mediate this relationship, as the negative association between incarceration and reunification did not persist when service use was included as a variable in the model. Suggestions are made for policy and practice changes to improve reunification outcomes for this population of parents.
Natural Changes in Brain Temperature Underlie Variations in Song Tempo during a Mating Behavior
The song of a male zebra finch is a stereotyped motor sequence whose tempo varies with social context – whether or not the song is directed at a female bird – as well as with the time of day. The neural mechanisms underlying these changes in tempo are unknown. Here we show that brain temperature recorded in freely behaving male finches exhibits a global increase in response to the presentation of a female bird. This increase strongly correlates with, and largely explains, the faster tempo of songs directed at a female compared to songs produced in social isolation. Furthermore, we find that the observed diurnal variations in song tempo are also explained by natural variations in brain temperature. Our findings suggest that brain temperature is an important variable that can influence the dynamics of activity in neural circuits, as well as the temporal features of behaviors that some of these circuits generate
Development of trofinetide for the treatment of Rett syndrome: from bench to bedside
Rett syndrome (RTT) is rare neurodevelopmental disorder caused by mutations in the MECP2 gene that encodes methyl-CpG-binding protein 2 (MeCP2), a DNA-binding protein with roles in epigenetic regulation of gene expression. Functional loss of MeCP2 results in abnormal neuronal maturation and plasticity, characterized by loss of verbal communication and loss of fine and gross motor function, among others. Trofinetide, a synthetic analog of glycine-proline-glutamate, was approved by the US Food and Drug Administration for the treatment of RTT in adult and pediatric patients aged 2Â years and older. Here, we present the development of trofinetide from bench research to clinical studies and emphasize how the collaboration between academia, the pharmaceutical industry, and patient advocacy led to the recent approval. The bench-to-bedside development of trofinetide underscores the value of collaboration between these groups in the development and approval of treatments for rare diseases
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