187,163 research outputs found
Computer program FPIP-REV calculates fission product inventory for U-235 fission
Computer program calculates fission product inventories and source strengths associated with the operation of U-235 fueled nuclear power reactor. It utilizes a fission-product nuclide library of 254 nuclides, and calculates the time dependent behavior of the fission product nuclides formed by fissioning of U-235
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Structure of the novel membrane-coating material in proton-secreting epithelial cells and identification as an H+ATPase.
Specialized proton-secreting cells known collectively as mitochondria-rich cells are found in a variety of transporting epithelia, including the kidney collecting duct (intercalated cells) and toad and turtle urinary bladders. These cells contain a population of characteristic tubulovesicles that are believed to be involved in the shuttling of proton pumps (H+ATPase) to and from the plasma membrane. These transporting vesicles have a dense, studlike material coating the cytoplasmic face of their limiting membranes and similar studs are also found beneath parts of the plasma membrane. We have recently shown that this membrane coat does not contain clathrin. The present study was performed to determine the structure of this coat in rapidly frozen and freeze-dried tissue, and to determine whether the coat contains a major membrane protein transported by these vesicles, a proton pumping H+ATPase. The structure of the coat was examined in proton-secreting, mitochondria-rich cells from toad urinary bladder epithelium by rapidly freezing portions of apical membrane and associated cytoplasm that were sheared away from the remainder of the cell using polylysine-coated coverslips. Regions of the underside of these apical membranes as large as 0.2 micron2 were decorated by studlike projections that were arranged into regular hexagonal arrays. Individual studs had a diameter of 9.5 nm and appeared to be composed of multiple subunits arranged around a central depression, possibly representing a channel. The studs had a density of approximately 16,800 per micron2 of membrane. Similar arrays of studs were also found on vesicles trapped in the residual band of cytoplasm that remained attached to the underside of the plasma membrane, but none were seen in adjacent granular cells. To determine whether these arrays of studs contained H+ATPase molecules, we examined a preparation of affinity-purified bovine medullary H+ATPase, using the same technique, after incorporation of the protein eluted from a monoclonal antibody affinity column into phospholipid liposomes. The affinity-purified protein was shown to be capable of ATP-dependent acidification. In such preparations, large paracrystalline arrays of studs identical in appearance to those seen in situ were found. The dimensions of the studs as well as the number per square micrometer of membrane were identical to those of toad bladder mitochondria-rich cells: 9.5 nm in diameter, 16,770 per micron2 of membrane.(ABSTRACT TRUNCATED AT 400 WORDS
Out-of-pocket health care expenditure in Turkey: analysis of the household budget surveys 2002-2008
This paper analyses the prevalence of ‘catastrophic’ out-of-pocket health expenditure in Turkey and identifies the factors which are associated with its risk using the Turkish Household Budget Surveys from 2002 to 2008. A sample selection approach based on Sartori (2003) is adopted to allow for the potential selection problem which may arise if poor households choose not to seek health care due to concerns regarding its affordability. The results suggest that poor households are less likely to seek health care as compared to non-poor households and that a negative relationship between poverty and experiencing catastrophic health expenditure remains even after allowing for such selection bias. Our findings, which may assist policy-makers concerned with health care system reforms, also highlight factors such as insurance coverage, which may protect households from the risk of incurring catastrophic health expenditure
Nitrogen superfractionation in dense cloud cores
We report new calculations of interstellar 15N fractionation. Previously, we
have shown that large enhancements of 15N/14N can occur in cold, dense gas
where CO is frozen out, but that the existence of an NH + N channel in the
dissociative recombination of N2H+ severely curtails the fractionation. In the
light of recent experimental evidence that this channel is in fact negligible,
we have reassessed the 15N chemistry in dense cloud cores. We consider the
effects of temperatures below 10 K, and of the presence of large amounts of
atomic nitrogen. We also show how the temporal evolution of gas-phase isotope
ratios is preserved as spatial heterogeneity in ammonia ice mantles, as
monolayers deposited at different times have different isotopic compositions.
We demonstrate that the upper layers of this ice may have 15N/14N ratios an
order of magnitude larger than the underlying elemental value. Converting our
ratios to delta-values, we obtain delta(15N) > 3,000 per mil in the uppermost
layer, with values as high as 10,000 per mil in some models. We suggest that
this material is the precursor to the 15N `hotspots' recently discovered in
meteorites and IDPsComment: accepted by MNRA
Ground winds for Kennedy Space Center, Florida (1978 version)
Ground level runway wind statistics are presented for the Kennedy Space Center, Florida area. Crosswind, headwind, tailwind, and headwind reversal percentage frequencies are given with respect to month and hour for the Kennedy Space Center Space Shuttle runway. This document supersedes NASA CR-128995 and should be used in place of it
Phonographic neighbors, not orthographic neighbors, determine word naming latencies
The orthographic neighborhood size (N) of a word—the number of words that can be formed from that word by replacing one letter with another in its place—has been found to have facilitatory effects in word naming. The orthographic neighborhood hypothesis attributes this facilitation to interactive effects. A phonographic neighborhood hypothesis, in contrast, attributes the effect to lexical print-sound conversion. According to the phonographic neighborhood hypothesis, phonographic neighbors (words differing in one letter and one phoneme, e.g., stove and stone) should facilitate naming, and other orthographic neighbors (e.g., stove and shove) should not. The predictions of these two hypotheses are tested. Unique facilitatory phonographic N effects were found in four sets of word naming mega-study data, along with an absence of facilitatory orthographic N effects. These results implicate print-sound conversion—based on consistent phonology—in neighborhood effects rather than word-letter feedback
Impact of Rotation on the Evolution of Low-Mass Stars
High precision photometry and spectroscopy of low-mass stars reveal a variety
of properties standard stellar evolution cannot predict. Rotation, an essential
ingredient of stellar evolution, is a step towards resolving the discrepancy
between model predictions and observations. The first rotating stellar model,
continuously tracing a low-mass star from the pre-main sequence onto the
horizontal branch, is presented. The predicted luminosity functions of stars of
globular clusters and surface rotation velocities on the horizontal branch are
discussed.Comment: 5 pages, 4 figures. Oral contrubution. Proceedings of the workshop
"XXI Century challenges for stellar evolution", held in Cefalu' (Sicily,
Italy), August 29 - September 2, 2007; S. Cassisi and M. Salaris Eds. To be
published in Mem. SAIt Vol. 79 No.
Temporal and Spatial Turbulent Spectra of MHD Plasma and an Observation of Variance Anisotropy
The nature of MHD turbulence is analyzed through both temporal and spatial
magnetic fluctuation spectra. A magnetically turbulent plasma is produced in
the MHD wind-tunnel configuration of the Swarthmore Spheromak Experiment (SSX).
The power of magnetic fluctuations is projected into directions perpendicular
and parallel to a local mean field; the ratio of these quantities shows the
presence of variance anisotropy which varies as a function of frequency.
Comparison amongst magnetic, velocity, and density spectra are also made,
demonstrating that the energy of the turbulence observed is primarily seeded by
magnetic fields created during plasma production. Direct spatial spectra are
constructed using multi-channel diagnostics and are used to compare to
frequency spectra converted to spatial scales using the Taylor Hypothesis.
Evidence for the observation of dissipation due to ion inertial length scale
physics is also discussed as well as the role laboratory experiment can play in
understanding turbulence typically studied in space settings such as the solar
wind. Finally, all turbulence results are shown to compare fairly well to a
Hall-MHD simulation of the experiment.Comment: 17 pages, 17 figures, Submitted to Astrophysical Journa
SpinLink: An interconnection system for the SpiNNaker biologically inspired multi-computer
SpiNNaker is a large-scale biologically-inspired multi-computer designed to model very heavily distributed problems, with the flagship application being the simulation of large neural networks. The project goal is to have one million processors included in a single machine, which consequently span many thousands of circuit boards. A computer of this scale imposes large communication requirements between these boards, and requires an extensible method of connecting to external equipment such as sensors, actuators and visualisation systems. This paper describes two systems that can address each of these problems.Firstly, SpinLink is a proposed method of connecting the SpiNNaker boards by using time-division multiplexing (TDM) to allow eight SpiNNaker links to run at maximum bandwidth between two boards. SpinLink will be deployed on Spartan-6 FPGAs and uses a locally generated clock that can be paused while the asynchronous links from SpiNNaker are sending data, thus ensuring a fast and glitch-free response. Secondly, SpiNNterceptor is a separate system, currently in the early stages of design, that will build upon SpinLink to address the important external I/O issues faced by SpiNNaker. Specifically, spare resources in the FPGAs will be used to implement the debugging and I/O interfacing features of SpiNNterceptor
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