789 research outputs found

    Subsonic sting interference on the aerodynamic characteristics of a family of slanted-base ogive-cylinders

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    Support interference free drag, lift, and pitching moment measurements on a range of slanted base ogive cylinders were made using the NASA Langley 13 inch magnetic suspension and balance system. Typical test Mach numbers were in the range 0.04 to 0.2. Drag results are shown to be in broad agreement with previous tests with this configuration. Measurements were repeated with a dummy sting support installed in the wind tunnel. Significant support interferences were found at all test conditions and are quantified. Further comparison is made between interference free base pressures, obtained using remote telemetry, and sting cavity pressures

    Imaging X-ray spectrometer

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    An X-ray spectrometer for providing imaging and energy resolution of an X-ray source is described. This spectrometer is comprised of a thick silicon wafer having an embedded matrix or grid of aluminum completely through the wafer fabricated, for example, by thermal migration. The aluminum matrix defines the walls of a rectangular array of silicon X-ray detector cells or pixels. A thermally diffused aluminum electrode is also formed centrally through each of the silicon cells with biasing means being connected to the aluminum cell walls and causes lateral charge carrier depletion between the cell walls so that incident X-ray energy causes a photoelectric reaction within the silicon producing collectible charge carriers in the form of electrons which are collected and used for imaging

    Testing the Hydrogen Peroxide-Water Hypothesis for Life on Mars with the TEGA instrument on the Phoenix Lander

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    Since Viking has conducted its life detection experiments on Mars, many missions have enhanced our knowledge about the environmental conditions on the Red Planet. However, the Martian surface chemistry and the Viking lander results remain puzzling. Non-biological explanations that favor a strong inorganic oxidant are currently favored (e.g., Mancinelli, 1989; Quinn and Zent, 1999; Klein, 1999, Yen et al., 2000), but problems remain regarding the life time, source, and abundance of that oxidant to account for the Viking observations (Zent and McKay, 1994). Alternatively, a hypothesis favoring the biological origin of a strong oxidizer has recently been advanced (Houtkooper and Schulze-Makuch, 2007). Here, we report about laboratory experiments that simulate the experiments to be conducted by the Thermal and Evolved Gas Analyzer (TEGA) instrument of the Phoenix lander, which is to descend on Mars in May 2008. Our experiments provide a baseline for an unbiased test for chemical versus biological responses, which can be applied at the time the Phoenix Lander transmits its first results from the Martian surface.Comment: 11 pages and 3 figure

    Update of High Resolution (e,e'K^+) Hypernuclear Spectroscopy at Jefferson Lab's Hall A

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    Updated results of the experiment E94-107 hypernuclear spectroscopy in Hall A of the Thomas Jefferson National Accelerator Facility (Jefferson Lab), are presented. The experiment provides high resolution spectra of excitation energy for 12B_\Lambda, 16N_\Lambda, and 9Li_\Lambda hypernuclei obtained by electroproduction of strangeness. A new theoretical calculation for 12B_\Lambda, final results for 16N_\Lambda, and discussion of the preliminary results of 9Li_\Lambda are reported.Comment: 8 pages, 5 figures, submitted to the proceedings of Hyp-X Conferenc

    Dialogue Design for a Robot-Based Face-Mirroring Game to Engage Autistic Children with Emotional Expressions

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    We present design strategies for Human Robot Interaction for school-aged autistic children with limited receptive language. Applying these strategies to the DE-ENIGMA project (large EU project addressing emotion recognition in autistic children) supported development of a new activity for in facial expression imitation whereby the robot imitates the child’s face to encourage the child to notice facial expressions in a play-based game. A usability case study with 15 typically-developing children aged 4–6 at an English-language school in the Netherlands was performed to observe the feasibility of the setup and make design revisions before exposing the robot to autistic children

    Lithostratigraphic investigation of a Late Devonian carbonate-evaporite sequence; the Duperow Formation, Williston Basin, North Dakota

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    The Duperow Formation of northwestern North Dakota is a cyclical carbonate evaporite unit deposited on a shallow marine shelf during the early part of the Late Devonian (Frasnian). The formation forms the lower part of the Jefferson Group and lithostratigraphic review permits three informal members to be recognized: lower, middle, and upper. Petrographic, lithologic, and well log examination of drill cores and thin sections allows the identification of seven lithofacies within the three members. Lithofacies include; bioclastic wackestone/packstone (LF1), stromatoporoid boundstone/floatstone (LF2), Amphipora boundstone/floatstone (LF3), peloidal wackestone (LF4), dolomitic mudstone (LF5), microbially laminated dolowackestone (LF6), and anhydrite (Lf7). Lithofacies are further grouped into five lithofacies associations (LFA I to LFA V) which correspond to five depositional settings during accumulation of Duperow strata. Lithofacies were deposited within normal marine subtidal, stromatoporoid bank or mound, intertidal slightly restricted, intertidal more restricted, and supratidal conditions. Rocks of the Duperow were typically deposited in a transition from subtidal to supratidal environments, preserving several shallowing upward successions. Nine short term (1-2 million years) third order cycles are recorded by the rocks of the Duperow which represent two transgressive phases and one regressive phase. Diagenetic features within the Duperow enhance porosity and establish units with appreciable amounts of reservoir characteristics. The main diagenetic features observed are micrite enveloping and micritization, calcite cementation, dolomitization, compaction, dissolution, and anhydrite cementation. Only dolomitization and dissolution increase porosity in the rocks of the Duperow. Dolomitization is fabric selective, as only the stromatoporoid boundstone/floatstone and microbially laminated dolowackestone lithofacies contain large amounts of dolomite and well developed intercrystalline porosity. These lithofacies are traceable and correlated throughout the entire study area and extend away from the known producing regions along the Nesson and Billings anticlines. The high degrees of dolomitization observed are the result of active fracture and fault systems acting as conduits for dolomitizing fluids. Paleostructural highs and lows allow for the migration of fluids into the highly susceptible carbonates of the Duperow Formation

    An Electron Fixed Target Experiment to Search for a New Vector Boson A' Decaying to e+e-

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    We describe an experiment to search for a new vector boson A' with weak coupling alpha' > 6 x 10^{-8} alpha to electrons (alpha=e^2/4pi) in the mass range 65 MeV < m_A' < 550 MeV. New vector bosons with such small couplings arise naturally from a small kinetic mixing of the "dark photon" A' with the photon -- one of the very few ways in which new forces can couple to the Standard Model -- and have received considerable attention as an explanation of various dark matter related anomalies. A' bosons are produced by radiation off an electron beam, and could appear as narrow resonances with small production cross-section in the trident e+e- spectrum. We summarize the experimental approach described in a proposal submitted to Jefferson Laboratory's PAC35, PR-10-009. This experiment, the A' Experiment (APEX), uses the electron beam of the Continuous Electron Beam Accelerator Facility at Jefferson Laboratory (CEBAF) at energies of ~1-4 GeV incident on 0.5-10% radiation length Tungsten wire mesh targets, and measures the resulting e+e- pairs to search for the A' using the High Resolution Spectrometer and the septum magnet in Hall A. With a ~1 month run, APEX will achieve very good sensitivity because the statistics of e+e- pairs will be ~10,000 times larger in the explored mass range than any previous search for the A' boson. These statistics and the excellent mass resolution of the spectrometers allow sensitivity to alpha'/alpha one to three orders of magnitude below current limits, in a region of parameter space of great theoretical and phenomenological interest. Similar experiments could also be performed at other facilities, such as the Mainz Microtron.Comment: 19 pages, 12 figures, 2 table

    Preservation of micro-architecture and angiogenic potential in a pulmonary acellular matrix obtained using intermittent intra-tracheal flow of detergent enzymatic treatment

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    Tissue engineering of autologous lung tissue aims to become a therapeutic alternative to transplantation. Efforts published so far in creating scaffolds have used harsh decellularization techniques that damage the extracellular matrix (ECM), deplete its components and take up to 5 weeks to perform. The aim of this study was to create a lung natural acellular scaffold using a method that will reduce the time of production and better preserve scaffold architecture and ECM components. Decellularization of rat lungs via the intratracheal route removed most of the nuclear material when compared to the other entry points. An intermittent inflation approach that mimics lung respiration yielded an acellular scaffold in a shorter time with an improved preservation of pulmonary micro-architecture. Electron microscopy demonstrated the maintenance of an intact alveolar network, with no evidence of collapse or tearing. Pulsatile dye injection via the vasculature indicated an intact capillary network in the scaffold. Morphometry analysis demonstrated a significant increase in alveolar fractional volume, with alveolar size analysis confirming that alveolar dimensions were maintained. Biomechanical testing of the scaffolds indicated an increase in resistance and elastance when compared to fresh lungs. Staining and quantification for ECM components showed a presence of collagen, elastin, GAG and laminin. The intratracheal intermittent decellularization methodology could be translated to sheep lungs, demonstrating a preservation of ECM components, alveolar and vascular architecture. Decellularization treatment and methodology preserves lung architecture and ECM whilst reducing the production time to 3 h. Cell seeding and in vivo experiments are necessary to proceed towards clinical translation

    Effect of Absent Tactile Sensation on Multi-digit Coordination Underlying Hand Control

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    We investigated the effect of anesthesia, causing absent tactile sensation feedback, on multi-digit coordination underlying hand control. The purpose of the study is to expand our understanding on the essential role of tactile sensation feedback in the sensorimotor integration process by examining the motor coordination patterns during multi-digit forces production tasks. We hypothesized that absent tactile sensation feedback would interrupt the force sharing pattern at local and non-local digits. Twelve participants were utilized for data collection and statistical analysis (25.6 ± 4.1 years old, 6 males and 6 females), right-handed (according to their preferred hand use for writing and eating) and had no significant hand injury within the last five years. All participants performed a maximal voluntary contraction (MVC), ramp, and step task, pre- and post-anesthesia. In general, participants presented lower maximal force production in all MVC conditions after anesthesia, total MVC force was not distributed evenly among individual digits, and when sensory function of the MVC involved digits are uniformly absent or intact, force sharing pattern across the individual digits would be maintained. When the instructed finger (master finger) was index, other fingers (enslaved fingers) barely produced force. However, other enslaved fingers showed relatively higher forces when the master finger was ring or little finger. When required force level increased, performance error was increased accordingly. The findings from the current study confirmed our hypothesis that absent tactile sensation feedback (somatosensory feedback) will not only affect force production at local digits, but also at non-local digits as well

    Recombinant activated factor VII (rFVIIa) as salvage treatment for intractable hemorrhage

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    BACKGROUND: Recently, there has been an increased use of recombinant activated factor VII (rFVIIa) to promote hemostasis in various hemorrhagic conditions. The objective of this study was to determine the outcome of patients treated with rFVIIa who had intractable bleeding associated with cardiac surgery (CSP) or as a result of other causes (OBP). METHODS: The medical records of 40 consecutive patients treated with rFVIIa were retrospectively reviewed for blood product use before and after treatment. In all patients, rFVIIa was given only after all other measures to stop bleeding had failed. The number of transfused units of red cells (R), platelets (P), fresh frozen plasma (F), and cryoprecipitate (C) were determined both before and after administration of rFVIIa, and the results compared. Mortality at 4 hours and 30 days was assessed. Patients dying within 4 hours of rFVIIa administration were not evaluable for response. Patient characteristics were also assessed as risk factors for mortality. RESULTS: Twelve of 24 CSP survived for more than 4 hours. These 12 patients required an average of 17 units (U) of R, 18 U of P, 18 U of F and 15 U of C pre-treatment compared to an average of 6 U, 10 U, 9 U and 4 U of R, P, F and C respectively, post-treatment. These differences were statistically significant. For the OBP, 11 of 16 survived more than four hours. These 11 patients required an average of 10 U of R, 11 U of P, 14 U of F and 10 U of C pretreatment compared to an average of 1 U, 2 U, 2 U and 0 U of R, P, F, and C respectively, post-treatment. With the exception of C, there was a statistically significant decrease in blood product use following treatment with rFVIIa. Of the survivors in each group, 6 of 12 CSP and 2 of 11 OBP died between 3 and 30 days post-treatment from causes other than bleeding. Mortality at 30 days for CSP and OBP survivors was 50% and 18% respectively, whereas overall 30 day mortality was 75% for CSP and 44% for OBP. CONCLUSIONS: rFVIIa is effective in decreasing blood product use and promoting hemostasis in patients with intractable bleeding associated with cardiac surgery and a variety of other causes
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