27,210 research outputs found
Hydrogen-fueled engine
A hydrogen-oxygen fueled internal combustion engine is described, which utilizes an inert gas, such as argon, as a working fluid to increase the efficiency of the engine, eliminate pollution, and facilitate operation of a closed cycle energy system. In a system where sunlight or other intermittent energy source is available to separate hydrogen and oxygen from water, the oxygen and inert gas are taken into a diesel engine into which hydrogen is injected and ignited. The exhaust is cooled so that it contains only water and the inert gas. The inert gas in the exhaust is returned to the engine for use with fresh oxygen, while the water in the exhaust is returned to the intermittent energy source for reconversion to hydrogen and oxygen
Angle-resolved photoemission spectroscopy of band tails in lightly doped cuprates
We amend ab initio strongly-correlated band structures by taking into account
the band-tailing phenomenon in doped charge-transfer Mott-Hubbard insulators.
We show that the photoemission from band tails accounts for sharp
"quasi-particle" peaks, rapid loss of their intensities in some directions of
the Brillouin zone ("Fermi-arcs") and high-energy "waterfall" anomalies as a
consequence of matrix-element effects of disorder-localised states in the
charge-transfer gap of doped cuprates.Comment: 4 pages, 4 figure
Are the Nuclei of Seyfert 2 Galaxies Viewed Face-On?
We show from modeling the Fe Kalpha line in the ASCA spectra of four X-ray
bright narrow emission line galaxies (Seyfert types 1.9 and 2) that two equally
viable physical models can describe the observed line profile. The first is
discussed by Turner et al. (1998) and consists of emission from a nearly
pole-on accretion disk. The second, which is statistically preferred, is a
superposition of emission from an accretion disk viewed at an intermediate
inclination of about 48 degrees and a distinct, unresolved feature that
presumably originates some distance from the galaxy nucleus. The intermediate
inclination is entirely consistent with unified schemes and our findings
challenge recent assertions that Seyfert 2 galaxies are preferentially viewed
with their inner regions face-on. We derive mean equivalent widths for the
narrow and disk lines of =60 eV and = 213 eV, respectively. The
X-ray data are well described by a geometry in which our view of the active
nucleus intersects and is blocked by the outer edges of the obscuring torus,
and therefore do not require severe misalignments between the accretion disk
and the torus.Comment: 19 pages, 3 postscript figures. Accepted for publication in ApJ
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Splanchnic metabolism of nutrients and hormones in steers fed alfalfa under conditions of increased absorption of ammonia and L-arginine supply across the portal-drained viscera
Effects of increased ammonia and/or arginine
absorption on net splanchnic (portal-drained viscera
[PDV] plus liver) metabolism of nonnitrogenous
nutrients and hormones in cattle were examined. Six
Hereford à Angus steers (501 ± 1 kg BW) prepared with
vascular catheters for measurements of net flux across
the splanchnic bed were fed a 75% alfalfa:25% (as-fed
basis) corn and soybean meal diet (0.523 MJ of ME/[kg
BW0.75.d]) every 2 h without (27.0 g of N/kg of DM) and
with 20 g of urea/kg of DM (35.7 g of N/kg of DM) in a
split-plot design. Net flux measurements were made
immediately before and after a 72-h mesenteric vein
infusion of L-arginine (15 mmol/h). There were no treatment
effects onPDVor hepaticO2 consumption. Dietary
urea had no effect on splanchnic metabolism of glucose
or L-lactate, but arginine infusion decreased net hepatic
removal of L-lactate when urea was fed (P < 0.01). Net PDV appearance of n-butyrate was increased by arginine
infusion (P < 0.07), and both dietary urea (P <
0.09) and arginine infusion (P < 0.05) increased net
hepatic removal of n-butyrate. Dietary urea also increased
total splanchnic acetate output (P < 0.06),
tended to increase arterial glucagon concentration (P
< 0.11), and decreased arterial ST concentration (P <
0.03). Arginine infusion increased arterial concentration
(P < 0.07) and net PDV release (P < 0.10) and
tended to increase hepatic removal (P < 0.11) of insulin,
as well as arterial concentration (P < 0.01) and total
splanchnic output (P < 0.01) of glucagon. Despite
changes in splanchnic N metabolism, increased ammonia
and arginine absorption had little measurable effect
on splanchnic metabolism of glucose and other nonnitrogenous
components of splanchnic energy metabolism
Implications of the X-ray Variability for the Mass of MCG-6-30-15
The bright Seyfert 1 galaxy \mcg shows large variability on a variety of time
scales. We study the \aproxlt 3 day time scale variability using a set of
simultaneous archival observations that were obtained from \rxte and the {\it
Advanced Satellite for Cosmology and Astrophysics} (\asca). The \rxte\
observations span nearly sec and indicate that the X-ray Fourier Power
Spectral Density has an rms variability of 16%, is flat from approximately
10^{-6} - 10^{-5} Hz, and then steepens into a power law
with \alpha\aproxgt 1. A further steepening to occurs
between 10^{-4}-10^{-3} Hz. The shape and rms amplitude are comparable to what
has been observed in \ngc and \cyg, albeit with break frequencies that differ
by a factor of 10^{-2} and 10^{4}, respectively. If the break frequencies are
indicative of the central black hole mass, then this mass may be as low as
. An upper limit of ks for the relative lag
between the 0.5-2 keV \asca band compared to the 8-15 keV \rxte band was also
found. Again by analogy with \ngc and \cyg, this limit is consistent with a
relatively low central black hole mass.Comment: 5 pages, 3 figures, LaTeX, uses emulateapj.sty and apjfonts.sty,
revised version, accepted for publication in ApJ Letter
NuSTAR Observations of G11.2â0.3
We present in this paper the hard X-ray view of the pulsar wind nebula in G11.2â0.3 and its central pulsar powered pulsar J1811â1925 as seen by NuSTAR. We complement the data with Chandra for a more complete picture and confirm the existence of a hard, power-law component in the shell with photon index Î = 2.1 ± 0.1, which we attribute to synchrotron emission. Our imaging observations of the shell show a slightly smaller radius at higher energies, consistent with Chandra results, and we find shrinkage as a function of increased energy along the jet direction, indicating that the electron outflow in the PWN may be simpler than that seen in other young PWNe. Combining NuSTAR with INTEGRAL, we find that the pulsar spectrum can be fit by a power law with Î = 1.32 ± 0.07 up to 300 keV without evidence of curvature
Imaging topographic growth by long-lived postseismic afterslip at Sefidabeh, east Iran
This paper describes observations and models of the postseismic deformation following the 1994 Sefidabeh earthquake sequence in east Iran, which shed light on the nature of the earthquake cycle and the mechanisms of topographic growth in the region. Interferometric synthetic aperture radar observations show creeping fault motion (âpostseismic afterslipâ) on an array of faults. Some of these faults probably represent the extensions of those that ruptured in the blind thrust-faulting earthquakes in 1994, and cut through the entire seismogenic layer, while others are shallow and break up the hanging walls of the coseismic faults. The postseismic slip accommodates at least part of the vertical displacement gradient resulting from the buried coseismic slip, which was concentrated at depths of greater than âŒ5âkm. The postseismic afterslip is visible for over 16 years following the earthquakes. Agreement between the areas of postseismic uplift and indications of long-term motion preserved in the geomorphology suggest that shallow fault slip during seismic cycles similar to the one we have observed governs the development of the landscape in the region. Slip on an array of shallow faults provides a mechanism for the development of short-wavelength topography and geological structures above active thrust faults and has important implications for the interpretation of shallow geological features produced in regions experiencing similar seismic cycles to that at Sefidabeh.This study forms part of the NERC- and ESRC-funded project âEarthquakes without Frontiers.âThis is the final published version of an article which originally appeared in Tectonics. It is also available from the journal's website at http://onlinelibrary.wiley.com/doi/10.1002/2013TC003462/abstract. © 2014 American Geophysical Unio
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