510 research outputs found
Alkali metal-refractory metal biphase electrode for AMTEC
An electrode having increased output with slower degradation is formed of a film applied to a beta-alumina solid electrolyte (BASE). The film comprises a refractory first metal M.sup.1 such as a platinum group metal, suitably platinum or rhodium, capable of forming a liquid or a strong surface adsorption phase with sodium at the operating temperature of an alkali metal thermoelectric converter (AMTEC) and a second refractory metal insoluble in sodium or the NaM.sup.1 liquid phase such as a Group IVB, VB or VIB metal, suitably tungsten, molybdenum, tantalum or niobium. The liquid phase or surface film provides fast transport through the electrode while the insoluble refractory metal provides a structural matrix for the electrode during operation. A trilayer structure that is stable and not subject to deadhesion comprises a first, thin layer of tungsten, an intermediate co-deposited layer of tungsten-platinum and a thin surface layer of platinum
Thin metal electrode for AMTEC
An electrode having higher power output is formed of a thin, porous film (less than 1 micrometer) applied to a beta-alumina solid electrolyte (BASE). The electrode includes an open grid, current collector such as a series of thin, parallel, grid lines applied to the thin film and a plurality of cross-members such as loop of metal wire surrounding the BASE tube. The loops are electrically connected by a bus wire. The overall impedance of the electrode considering both the contributions from the bulk BASE and the porous electrode BASE interface is low, about 0.5 OHM/cm.sup.2 and power densities of over 0.3 watt/cm.sup.2 for extended periods
Methane Post-Processing and Hydrogen Separation for Spacecraft Oxygen Loop Closure
State-of-the-art life support oxygen recovery technology on the International Space Station is based on the Sabatier reaction where only about half of the oxygen required for the crew is recovered from metabolic carbon dioxide (CO2). The Sabatier reaction produces water as the primary product and methane as a byproduct. Oxygen recovery is constrained by both the limited availability of reactant hydrogen from water electrolysis and Sabatier methane (CH4) being vented as a waste product resulting in a continuous loss of reactant hydrogen. Post-processing methane with the Plasma Pyrolysis Assembly (PPA) to recover this hydrogen has the potential to substantially increase oxygen recovery and thus dramatically reduce the logistical challenges associated with oxygen resupply. The PPA decomposes methane into predominantly hydrogen and acetylene. A purification system is necessary to purify hydrogen before it is recycled back to the Sabatier reactor. Testing and evaluation of acetylene removal systems and PPA system architectures are presented and discussed
Evolution of the Major Moss Lineages: Phylogenetic Analyses Based on Multiple Gene Sequences and Morphology
The relationship between commercial cotton cultivars with varying Meloidogyne incognita resistance genes and yield
Recycling Argon through Metamorphic Reactions: the Record in Symplectites
The 40Ar/39Ar ages of metamorphic micas that crystallized at high temperatures are commonly interpreted as cooling ages, with grains considered to have lost 40Ar via thermally-driven diffusion into the grain boundary network. Recently reported laser-ablation data suggest that the spatial distribution of Ar in metamorphic micas does not always conform to the patterns predicted by diffusion theory and that despite high metamorphic temperatures, argon was not removed efficiently from the local system during metamorphic evolution. In the Western Gneiss Region (WGR), Norway, felsic gneisses preserve microtextural evidence for the breakdown of phengite to biotite and plagioclase symplectites during near isothermal decompression from c. 20–25 to c. 8–12 kbar at ~700°C. These samples provide an ideal natural laboratory to assess whether the complete replacement of one K-bearing mineral by another at high temperatures completely ‘resets’ the Ar clock, or whether there is some inheritance of 40Ar in the neo-crystallized phase. The timing of the high-temperature portion of the WGR metamorphic cycle has been well constrained in previous studies. However, the timing of cooling following the overprint is still much debated. In-situ laser ablation spot dating in phengite, biotite-plagioclase symplectites and coarser, texturally later biotite yielded 40Ar/39Ar ages that span much of the metamorphic cycle. Together these data show that despite residence at temperatures of ~700°C, Ar is not completely removed by diffusive loss or during metamorphic recrystallization. Instead, Ar released during phengite breakdown appears to be partially reincorporated into the newly crystallizing biotite and plagioclase (or is trapped in fluid inclusions in those phases) within a close system. Our data show that the microtextural and petrographic evolution of the sample being dated provides a critical framework in which local 40Ar recycling can be tracked, thus potentially allowing 40Ar/39Ar dates to be linked more accurately to metamorphic history
Hydrogen Purification and Recycling for an Integrated Oxygen Recovery System Architecture
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Nature and mental health: An ecosystem service perspective
A growing body of empirical evidence is revealing the value of nature experience for mental health. With rapid urbanization and declines in human contact with nature globally, crucial decisions must be made about how to preserve and enhance opportunities for nature experience. Here, we first provide points of consensus across the natural, social, and health sciences on the impacts of nature experience on cognitive functioning, emotional well-being, and other dimensions of mental health. We then show how ecosystem service assessments can be expanded to include mental health, and provide a heuristic, conceptual model for doing so
Extensive optical and near-infrared observations of the nearby, narrow-lined type Ic SN 2007gr: days 5 to 415
We present photometric and spectroscopic observations at optical and
near-infrared wavelengths of the nearby type Ic SN 2007gr. These represent the
most extensive data-set to date of any supernova of this sub-type, with
frequent coverage from shortly after discovery to more than one year
post-explosion. We deduce a rise time to B-band maximum of 11.5 \pm 2.7 days.
We find a peak B-band magnitude of M_B=-16.8, and light curves which are
remarkably similar to the so-called 'hypernova' SN 2002ap. In contrast, the
spectra of SNe 2007gr and 2002ap show marked differences, not least in their
respective expansion velocities. We attribute these differences primarily to
the density profiles of their progenitor stars at the time of explosion i.e. a
more compact star for SN 2007gr compared to SN 2002ap. From the
quasi-bolometric light curve of SN 2007gr, we estimate that 0.076 0.010
Msun of 56Ni was produced in the explosion. Our near-infrared (IR) spectra
clearly show the onset and disappearance of the first overtone of carbon
monoxide (CO) between ~70 to 175 days relative to B-band maximum. The detection
of the CO molecule implies that ionised He was not microscopically mixed within
the carbon/oxygen layers. From the optical spectra, near-IR light curves, and
colour evolution, we find no evidence for dust condensation in the ejecta out
to about 400 days. Given the combination of unprecedented temporal coverage,
and high signal-to-noise data, we suggest that SN 2007gr could be used as a
template object for supernovae of this sub-class.Comment: A&A accepted; 26 pages & 16 figure
Acute Severe Pain Is a Common Consequence of Sexual Assault
Sexual assault (SA) is common, but the epidemiology of acute pain after SA has not previously been reported. We evaluated the severity and distribution of pain symptoms in the early aftermath of SA among women receiving sexual assault nurse examiner (SANE) care, and the treatment of pain by SANE nurses. Severe pain (≥7 on a 0–10 numeric rating scale) was reported by 53/83 women sexual assault survivors (64% [95% CI, 53%–74%]) at the time of SANE evaluation and 43/83 women (52% [95% CI, 41%–63%]) one week later. Pain in four or more body regions was reported by 44/83 women (53% [95% CI, 42%–64%]) at the time of initial evaluation and 49/83 women (59% [95% CI, 48%–70%]) at one week follow-up. Among survivors with severe pain at the time of initial post-assault evaluation, only 7/53 (13% [95% CI, 6%–26%]) received any pain medication at the time of initial SANE treatment. These findings suggest that pain is common in SA survivors in the early post-assault period, but rarely treated
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