514 research outputs found

    Gas hydrate occurrences along the Haida Gwaii margin - Constraints on the geothermal regime and implications for fluid flow

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    Seismic-reflection data along the Haida Gwaii margin collected from 1967 to 2013 were used to identify gas hydrate–related bottom-simulating reflectors (BSRs). The BSRs occur along the Queen Charlotte Terrace only, within more strongly folded and tectonically deformed sedimentary ridges. The BSRs are absent within well-bedded and sediment-filled minibasins. The BSR is modeled as the base of the phase boundary of the methane hydrate (structure I) stability zone and is used to estimate geothermal gradients. The P-wave velocity structure required to convert observed depths of the BSR in two-way time to meters below seafloor was constrained from ocean-bottom seismometers. The BSR-derived gradients are lower than data from heat-probe deployments in the region, as well as predicted values from previous modeling of the large-scale tectonic thermal regime. Lower values of the BSR-derived thermal gradients may be due to topographic effects across the ridges where BSRs were observed. The previously identified landward decrease in thermal gradients across the terrace was also identified to a lesser extent from the BSRs, in accordance with the effects of oblique convergence of the Pacific plate with the North American plate. Geothermal gradients decreased from south to north by a factor of two, which is likely an effect of plate cooling due to an increase in age of the underlying plate (ca. 8 Ma off southern Haida Gwaii to ca. 12 Ma at Dixon Entrance) as well as the fact that sediments triple in thickness over the same distance. This may be due to downward flexure of the underlying crust during transpression and/or a high flux of sediments through Dixon Entrance

    Review of NASA In-Space Propulsion Technology Program Inflatable Decelerator Investments

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    The NASA In-Space Propulsion Technology (ISPT) Program is managed by the NASA Headquarters Science Mission Directorate and is implemented by the Marshall Space Flight Center in Huntsville, Alabama. The ISPT objective is to fund development of promising in- space propulsion technologies that can decrease flight times, decrease cost, or increase delivered payload mass for future science missions. Before ISPT will invest in a technology, the Technology Readiness Level (TRL) of the concept must be estimated to be at TRL 3. A TRL 3 signifies that the technical community agrees that the feasibility of the concept has been proven through experiment or analysis. One of the highest priority technology investments for ISPT is Aerocapture. The aerocapture maneuver uses a planetary atmosphere to reduce or alter the speed of a vehicle allowing for quick, propellantless (or using very little propellant) orbit capture. The atmosphere is used as a brake, transferring the energy associated with the vehicle s high speed into thermal energy. The ISPT Aerocapture Technology Area (ATA) is currently investing in the development of advanced lightweight ablative thermal protection systems, high temperature composite structures, and heat-flux sensors for rigid aeroshells. The heritage of rigid aeroshells extends back to the Apollo era and this technology will most likely be used by the first generation aerocapture vehicle. As a second generation aerocapture technology, ISPT is investing in three inflatable aerodynamic decelerator concepts for planetary aerocapture. They are: trailing ballute (balloon-parachute), attached afterbody ballute, and an inflatable aeroshell. ISPT also leverages the NASA Small Business Innovative Research Program for additional inflatable decelerator technology development. In mid-2004 ISPT requested an independent review of the three inflatable decelerator technologies funded directly by ISPT to validate the TRL and to identify technology maturation concerns. An independent panel with expertise in advanced thin film materials, aerothermodynamics, trajectory design, and inflatable structures was convened to assess the ISPT investments. The panel considered all major technical subsystems including materials, aerothermodynamics, structural dynamics, packaging, and inflation systems. The panel assessed the overall technology readiness of inflatable decelerators to be a 3 and identified fluid-structure interaction, aeroheating, and structural adhesives to be of highest technical concern

    Conformational comparisons of Pasteurella multocida types B and E and structurally related capsular polysaccharides

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    Pasteurella multocida, an encapsulated gram-negative bacterium, is a significant veterinary pathogen. The P. multocida is classified into 5 serogroups (A, B, D, E, and F) based on the bacterial capsular polysaccharide (CPS), which is important for virulence. Serogroups B and E are the primary causative agents of bovine hemorrhagic septicemia that is associated with significant yearly losses of livestock worldwide, primarily in low- and middle-income countries. The P. multocida disease is currently managed by whole-cell vaccination, albeit with limited efficacy. CPS is an attractive antigen target for an improved vaccine: CPS-based vaccines have proven highly effective against human bacterial diseases and could provide longer-term protection against P. multocida. The recently elucidated CPS repeat units of serogroups B and E both comprise a N-acetyl-ÎČ-D-mannosaminuronic acid/N-acetyl-ÎČ-D-glucosamine disaccharide backbone with ÎČ-D-fructofuranose (Fruf) side chain, but differ in their glycosidic linkages, and a glycine (Gly) side chain in serogroup B. Interestingly, the Haemophilus influenzae types e and d CPS have the same backbone residues. Here, comparative modeling of P. multocida serogroups B and E and H. influenzae types e and d CPS identifies a significant impact of small structural differences on both the chain conformation and the exposed potential antibody-binding epitopes (Ep). Further, Fruf and/or Gly side chains shield the immunogenic amino-sugar CPS backbone—a possible common strategy for immune evasion in both P. multocida and H. influenzae. As the lack of common epitopes suggests limited potential for cross-reactivity, a bivalent CPS-based vaccine may be necessary to provide adequate protection against P. multocida types B and E

    Evaluation of Mobile Advanced Road Weather Information Sensor (MARWIS) by Lufft for Indiana Winter Road Operations

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    The students of the Field Infrastructure Assessment course evaluated the Mobile Advanced Road Weather Information Sensor by Lufft on behalf of the Indiana Department of Transportation. The device is mounted on a vehicle, takes roadway condition measurements 100 times per second, and aggregates the measurements into one-second intervals. The data is transmitted real-time to the cloud. The class specifically evaluated the following measurements: road condition, surface temperature, and friction. It was found that the MARWIS temperature reading was systematically 4˚F lower than the probe readings. Skid test empirical results were consistent with the MARWIS friction readings. It was also found, using two devices on the back of the test vehicle, that the friction in the wheel track was greater than the friction in the center of the lane, as expected. Lastly, the “chemically wet” road condition was not consistently observed by MARWIS where expected

    Prenatal Phthalate Exposures and Childhood Fat Mass in a New York City Cohort

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    Background:Experimental animal studies and limited epidemiologic evidence suggest that prenatal exposure to phthalates may be obesogenic, with potential sex-specific effects of phthalates having anti-androgenic activity.Objectives:We aimed to assess associations between prenatal phthalate exposures and childhood fat mass in a prospective cohort study.Methods:We measured phthalate metabolite concentrations in third-trimester maternal urine in a cohort of women enrolled in New York City between 1998 and 2002 (n = 404). Among 180 children (82 girls and 98 boys), we evaluated body composition using a Tanita scale at multiple follow-up visits between ages 4 and 9 years (363 total visits). We estimated associations of standard deviation differences or tertiles of natural log phthalate metabolite concentrations with percent fat mass using linear mixed-effects regression models with random intercepts for repeated outcome measurements. We assessed associations in multiple metabolite models and adjusted for covariates including prepregnancy body mass index, gestational weight gain, maternal smoking during pregnancy, and breastfeeding.Results:We did not observe associations between maternal urinary phthalate concentrations and percent body fat in models examining continuous exposures. Fat mass was 3.06% (95% CI: –5.99, –0.09%) lower among children in the highest tertile of maternal urinary concentrations of summed di(2-ethylhexyl) phthalate (ΣDEHP) metabolites than in children in the lowest tertile. Though estimates were imprecise, there was little evidence that associations between maternal urinary phthalate concentrations and percent fat mass were modified by child’s sex.Conclusions:Prenatal phthalate exposures were not associated with increased body fat among children 4–9 years of age, though high prenatal DEHP exposure may be associated with lower fat mass in childhood.Citation:Buckley JP, Engel SM, Mendez MA, Richardson DB, Daniels JL, Calafat AM, Wolff MS, Herring AH. 2016. Prenatal phthalate exposures and childhood fat mass in a New York City cohort. Environ Health Perspect 124:507–513; http://dx.doi.org/10.1289/ehp.150978

    A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda Galaxy

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    Dwarf satellite galaxies are thought to be the remnants of the population of primordial structures that coalesced to form giant galaxies like the Milky Way. An early analysis noted that dwarf galaxies may not be isotropically distributed around our Galaxy, as several are correlated with streams of HI emission, and possibly form co-planar groups. These suspicions are supported by recent analyses, and it has been claimed that the apparently planar distribution of satellites is not predicted within standard cosmology, and cannot simply represent a memory of past coherent accretion. However, other studies dispute this conclusion. Here we report the existence (99.998% significance) of a planar sub-group of satellites in the Andromeda galaxy, comprising approximately 50% of the population. The structure is vast: at least 400 kpc in diameter, but also extremely thin, with a perpendicular scatter <14.1 kpc (99% confidence). Radial velocity measurements reveal that the satellites in this structure have the same sense of rotation about their host. This finding shows conclusively that substantial numbers of dwarf satellite galaxies share the same dynamical orbital properties and direction of angular momentum, a new insight for our understanding of the origin of these most dark matter dominated of galaxies. Intriguingly, the plane we identify is approximately aligned with the pole of the Milky Way's disk and is co-planar with the Milky Way to Andromeda position vector. The existence of such extensive coherent kinematic structures within the halos of massive galaxies is a fact that must be explained within the framework of galaxy formation and cosmology.Comment: Published in the 3rd Jan 2013 issue of Nature. 19 pages, 4 figures, 1 three-dimensional interactive figure. To view and manipulate the 3-D figure, an Adobe Reader browser plug-in is required; alternatively save to disk and view with Adobe Reade

    The AFHSC-Division of GEIS Operations Predictive Surveillance Program: a multidisciplinary approach for the early detection and response to disease outbreaks

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    The Armed Forces Health Surveillance Center, Division of Global Emerging Infections Surveillance and Response System Operations (AFHSC-GEIS) initiated a coordinated, multidisciplinary program to link data sets and information derived from eco-climatic remote sensing activities, ecologic niche modeling, arthropod vector, animal disease-host/reservoir, and human disease surveillance for febrile illnesses, into a predictive surveillance program that generates advisories and alerts on emerging infectious disease outbreaks. The program’s ultimate goal is pro-active public health practice through pre-event preparedness, prevention and control, and response decision-making and prioritization. This multidisciplinary program is rooted in over 10 years experience in predictive surveillance for Rift Valley fever outbreaks in Eastern Africa. The AFHSC-GEIS Rift Valley fever project is based on the identification and use of disease-emergence critical detection points as reliable signals for increased outbreak risk. The AFHSC-GEIS predictive surveillance program has formalized the Rift Valley fever project into a structured template for extending predictive surveillance capability to other Department of Defense (DoD)-priority vector- and water-borne, and zoonotic diseases and geographic areas. These include leishmaniasis, malaria, and Crimea-Congo and other viral hemorrhagic fevers in Central Asia and Africa, dengue fever in Asia and the Americas, Japanese encephalitis (JE) and chikungunya fever in Asia, and rickettsial and other tick-borne infections in the U.S., Africa and Asia
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