14,875 research outputs found
Collapsible pistons for light-gas guns
Moving and expandable parts of gun consist of pump-tube diaphragm, piston, launch-tube diaphragm, and saboted projectile. As a result of improved piston design, pressure cycle has been significantly improved by smoother buildup, increasing muzzle velocities up to 50%
Metabolism of ticagrelor in patients with acute coronary syndromes.
© The Author(s) 2018Ticagrelor is a state-of-the-art antiplatelet agent used for the treatment of patients with acute coronary syndromes (ACS). Unlike remaining oral P2Y12 receptor inhibitors ticagrelor does not require metabolic activation to exert its antiplatelet action. Still, ticagrelor is extensively metabolized by hepatic CYP3A enzymes, and AR-C124910XX is its only active metabolite. A post hoc analysis of patient-level (n = 117) pharmacokinetic data pooled from two prospective studies was performed to identify clinical characteristics affecting the degree of AR-C124910XX formation during the first six hours after 180 mg ticagrelor loading dose in the setting of ACS. Both linear and multiple regression analyses indicated that ACS patients presenting with ST-elevation myocardial infarction or suffering from diabetes mellitus are more likely to have decreased rate of ticagrelor metabolism during the acute phase of ACS. Administration of morphine during ACS was found to negatively influence transformation of ticagrelor into AR-C124910XX when assessed with linear regression analysis, but not with multiple regression analysis. On the other hand, smoking appears to increase the degree of ticagrelor transformation in ACS patients. Mechanisms underlying our findings and their clinical significance warrant further research.Peer reviewedFinal Published versio
Half-Megasecond Chandra Spectral Imaging of the Hot Circumgalactic Nebula around Quasar Mrk 231
A deep 400-ksec ACIS-S observation of the nearest quasar known, Mrk 231, is
combined with archival 120-ksec data obtained with the same instrument and
setup to carry out the first ever spatially resolved spectral analysis of a hot
X-ray emitting circumgalactic nebula around a quasar. The 65 x 50 kpc X-ray
nebula shares no resemblance with the tidal debris seen at optical wavelengths.
One notable exception is the small tidal arc 3.5 kpc south of the nucleus where
excess soft X-ray continuum emission and Si XIII 1.8 keV line emission are
detected, consistent with star formation and its associated alpha-element
enhancement, respectively. An X-ray shadow is also detected at the location of
the 15-kpc northern tidal tail. The hard X-ray continuum emission within 6 kpc
of the center is consistent with being due entirely to the bright central AGN.
The soft X-ray spectrum of the outer (>6 kpc) portion of the nebula is best
described as the sum of two thermal components with T~3 and ~8 million K and
spatially uniform super-solar alpha element abundances, relative to iron. This
result implies enhanced star formation activity over ~10^8 yrs accompanied with
redistribution of the metals on large scale. The low-temperature thermal
component is not present within 6 kpc of the nucleus, suggesting extra heating
in this region from the circumnuclear starburst, the central quasar, or the
wide-angle quasar-driven outflow identified from optical IFU spectroscopy on a
scale of >3 kpc. Significant azimuthal variations in the soft X-ray intensity
are detected in the inner region where the outflow is present. The soft X-ray
emission is weaker in the western quadrant, coincident with a deficit of Halpha
and some of the largest columns of neutral gas outflowing from the nucleus.
Shocks created by the interaction of the wind with the ambient ISM may heat the
gas to high temperatures at this location. (abridged)Comment: 43 pages, 11 figures, accepted for publication in the Astrophysical
Journa
Quantum Walks on Trees with Disorder: Decay, Diffusion, and Localization
Quantum walks have been shown to have impressive transport properties
compared to classical random walks. However, imperfections in the quantum walk
algorithm can destroy any quantum mechanical speed-up due to Anderson
localization. We numerically study the effect of static disorder on a quantum
walk on the glued trees graph. For small disorder, we find that the dominant
effect is a type of quantum decay, and not quantum localization. For
intermediate disorder, there is a crossover to diffusive transport, while a
localization transition is observed at large disorder, in agreement with
Anderson localization on the Cayley tree.Comment: 12 pages, 13 figure
Evaluation of a light-gas gun hypervelocity augmentation technique Final report
Interior ballistics of constant base pressure hypervelocity gu
Interplay between structure and magnetism in nanowires
We investigate the equilibrium geometry and electronic structure of
MoSI nanowires using ab initio Density Functional
calculations. The skeleton of these unusually stable nanowires consists of
rigid, functionalized Mo octahedra, connected by flexible, bi-stable sulphur
bridges. This structural flexibility translates into a capability to stretch up
to approximate 20% at almost no energy cost. The nanowires change from
conductors to narrow-gap magnetic semiconductors in one of their structural
isomers.Comment: 4 pages with PRL standards and 3 figure
- …