725 research outputs found
A guidance and control assessment of three vertical landing options for RLV
The National Aeronautics and Space Administration is considering a vertical lander as a candidate concept for a single-stage-to-orbit reusable launch vehicle (RLV). Three strategies for guiding and controlling the inversion of a reentering RLV from a nose-first attitude to a vertical landing attitude are suggested. Each option is simulated from a common reentry state to touchdown, using a common guidance algorithm and different controllers. Results demonstrate the characteristics that typify and distinguish each concept and help to identify peculiar problems, level of guidance and control sophistication required, feasibility concerns, and areas in which stringent subsystem requirements will be imposed by guidance and control
Ion-channel-like behavior in lipid bilayer membranes at the melting transition
It is well known that at the gel-liquid phase transition temperature a lipid
bilayer membrane exhibits an increased ion permeability. We analyze the
quantized currents in which the increased permeability presents itself. The
open time histogram shows a "-3/2" power law which implies an open-closed
transition rate that decreases like as time evolves. We
propose a "pore freezing" model to explain the observations. We discuss how
this model also leads to the noise that is commonly observed in
currents across biological and artificial membranes.Comment: 5 pages, 4 figure
Interpersonal violence in peacetime Malawi.
Background: The contribution of interpersonal violence (IPV) to trauma burden varies greatly by region. The high rates of IPV in sub-Saharan Africa are thought to relate in part to the high rates of collective violence. Malawi, a country with no history of internal collective violence, provides an excellent setting to evaluate whether collective violence drives the high rates of IPV in this region.
Methods: This is a retrospective review of a prospective trauma registry from 2009 through 2016 at Kamuzu Central Hospital in Lilongwe, Malawi. Adult (\u3e16 years) victims of IPV were compared with non-intentional trauma victims. Log binomial regression determined factors associated with increased risk of mortality for victims of IPV.
Results: Of 72 488 trauma patients, 25 008 (34.5%) suffered IPV. Victims of IPV were more often male (80.2% vs. 74.8%; p
Discussion: Even in a sub-Saharan country that never experienced internal collective violence, IPV injury rates are high. Public health efforts to measure and address alcohol use, and studies to determine the role of mob justice, poverty, and intimate partner violence in IPV, in Malawi are needed.
Level of evidence: Level III
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EM 14 - Bubbleless Gas Transfer Technology for the In Situ Remediation of Chlorinated Hydrocarbons
The primary objective of this project is to demonstrate the ability of hydrogen to supply reducing equivalents for the reductive dehalogenation of PCE. This objective will be accomplished by two types of activities. First, laboratory experiments will compare the kinetics of hydrogen-mediated dehalogenation with natural routes of loss (hydrolysis and natural attenuation). Secondly, bench-scale column experiments will be performed to demonstrate hydrogen-mediated reductive dehalogenation in aquifer sediments
The olfactory system of migratory adult sea lamprey (Petromyzon marinus) is specifically and acutely sensitive to unique bile acids released by conspecific larvae.
Mechanisms of Groucho-mediated repression revealed by genome-wide analysis of Groucho binding and activity
Antibody validation (A) Chromatin isolated and sheared exactly as for the ChIP-seq analysis was subjected to immunoprecipitation with the indicated amounts (in μl) of affinity purified antibody against the Gro GP domain used for the ChIP-seq analysis, and then probed in a western blot with both an anti-Gro monoclonal antibody (mAb) or the anti-GP antibody. The band indicated by the asterisk is a cross-reacting protein that is recognized in the western blot but that is not efficiently immunoprecipitated by the anti-GP antibody. Ab HC – antibody heavy chain. (B) Heat map showing overlap (Jacard similarity coefficient [96]) between the peaks called in the duplicate ChIP-seq experiments at each time point. (C) Representative genome browser tracts comparing duplicate ChIP-seq experiments. (D and E) Comparison of Gro binding patterns obtained by ChIP-seq using our anti-GP antibody with that obtained by ChIP-chip (0–12 hr embryos; modENCODE #597) and ChIP-seq (white pre-pupae; modENCODE #4981) using independently derived antibodies [40]. (PDF 588 kb
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Measurements of actinides in soil, sediments, water and vegetation in Northern New Mexico
This study was undertaken during 1991 - 1998 to identify the origin of plutonium uranium in northern New Mexico Rio Grande and tributary stream sediments. Isotopic fingerprinting techniques help distinguish radioactivity from Los Alamos National Laboratory (LANL) and from global fallout or natural sources. The geographic area covered by the study extended from the headwaters of the Rio Grande in southern Colorado to Elephant Butte Reservoir in southern New Mexico. Over 100 samples of stream channel and reservoir bottom sediments were analyzed for the atom ratios of plutonium and uranium isotopes using thermal ionization mass spectrometry (TIMS). Comparison of these ratios against those for fallout or natural sources allowed for quantification of the Laboratory impact. Of the seven major drainages crossing LANL, movement of LANL plutonium into the Rio Grande can only be traced via Los Alamos Canyon. The majority of sampled locations within and adjacent to LANL have little or no input of plutonium from the Laboratory. Samples collected upstream and distant to L A N show an average (+ s.d.) fallout 240Pu/239Pauto m ratio of 0.169 + 0.012, consistent with published worldwide global fallout values. These regional background ratios differ significantly from the 240Pu/239Pu atom ratio of 0.015 that is representative of LANL-derived plutonium entering the Rio Grande at Los Alamos Canyon. Mixing calculations of these sources indicate that the largest proportion (60% to 90%) of the plutonium in the Rio Grande sediments is from global atmospheric fallout, with an average of about 25% from the Laboratory. The LANL plutonium is identifiable intermittently along the 35-km reach of the Rio Grande to Cochiti Reservoir. The source of the LANL-derived plutonium in the Rio Grande was traced primarily to pre-1960 discharges of liquid effluents into a canyon bottom at a distance approximately 20 km upstream of the river. Plutonium levels decline exponentially with distance downstream after mixing with cleaner sediments, yet the LANL isotopic fingerprint remains distinct for at least 55 km from the effluent source. Plutonium isotopes in Rio Grande and Pajarito Plateau sediments are not at levels known to adversely affect public health. Activities of 239+240pwui thin this sample set ranged from 0.001- 0.046 pCUg in the Rio Grande to 3.7 pCi/g near the effluent discharge point. Levels in the Rio Grande are usually more than 1000 times. lower than prescribed cleanup standards. Uranium in stream and reservoir sediments is predominantly within natural concentration ranges and is of natural uranium isotopic composition. None of the sediments from the Rio Grande show identifiable Laboratory uranium, using the isotopic ratios. These results suggest that the mass of Laboratory-derived uranium entering the Rio Grande is small relative to the natural load carried with river sediments
Consequences of centralised blood bank policies in sub-Saharan Africa
Safe and reliable transfusion services remain largely unavailable to the world’s poorest populations, particularly in sub-Saharan Africa. WHO responded to this crisis with a strategy focused on centralising blood transfusion services, the exclusive use of volunteer donors, donor blood testing, and transfusion stewardship. On the basis of our experience in Malawi, we think that this policy has unintentionally decreased the availability of blood products for patients with acute haemorrhage
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