11,312 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%
Regression Depth and Center Points
We show that, for any set of n points in d dimensions, there exists a
hyperplane with regression depth at least ceiling(n/(d+1)). as had been
conjectured by Rousseeuw and Hubert. Dually, for any arrangement of n
hyperplanes in d dimensions there exists a point that cannot escape to infinity
without crossing at least ceiling(n/(d+1)) hyperplanes. We also apply our
approach to related questions on the existence of partitions of the data into
subsets such that a common plane has nonzero regression depth in each subset,
and to the computational complexity of regression depth problems.Comment: 14 pages, 3 figure
Evaluation of Dual-Activity Opioid-NPFF Ligands for Antinociception
Opioids have become a staple in the medical world as an analgesic used to treat acute and chronic pain. However, there are many issues associated with the frequent use of opioids including tolerance, constipation, and opioid-induced hyperalgesia. Fortunately, recent discoveries of neuropeptide FF (NPFF) antagonists, have led to the understanding that tolerance and hyperalgesia caused by opioids can be greatly reduced. This discovery eventually led to the creation of dual ligands with both opioid agonist and NPFF antagonist activity. These dual ligands have been shown to prevent tolerance and opioid-induced hyperalgesia while maintain analgesic qualities in mice. However, these studies have involved injecting the drug directly into the brain due to their inability to cross the blood brain barrier, which makes them unfit to be converted into drugs fit for clinical use. Intravenous or intraperitoneal injection routes can be used but, oral administration would be the best option for therapeutic use. With this goal in mind, we are met with the task of having the drug penetrate the blood-brain barrier so that it may reach the appropriate recepetors. In this study, we had modified the lead small molecule (non-4,5α-epoxymorphinan derived) designated multiple ligands to hopefully have such blood-brain barrier penetration capabilities. We will evaluate the antinociception of these compounds to determine if they have successfully reached their target receptors from peripheral administration. These compounds tested represent only a portion of the compounds created by our lab
Evaluation of Dual-Activity Opioid-NPFF Ligands for Antinociception
Opioids have become a staple in the medical world as an analgesic used to treat acute and chronic pain. However, there are many issues associated with the frequent use of opioids including tolerance, constipation, and opioid-induced hyperalgesia. Fortunately, recent discoveries of neuropeptide FF (NPFF) antagonists, have led to the understanding that tolerance and hyperalgesia caused by opioids can be greatly reduced. This discovery eventually led to the creation of dual ligands with both opioid agonist and NPFF antagonist activity. These dual ligands have been shown to prevent tolerance and opioid-induced hyperalgesia while maintain analgesic qualities in mice. However, these studies have involved injecting the drug directly into the brain due to their inability to cross the blood brain barrier, which makes them unfit to be converted into drugs fit for clinical use. Intravenous or intraperitoneal injection routes can be used but, oral administration would be the best option for therapeutic use. With this goal in mind, we are met with the task of having the drug penetrate the blood-brain barrier so that it may reach the appropriate recepetors. In this study, we had modified the lead small molecule (non-4,5α-epoxymorphinan derived) designated multiple ligands to hopefully have such blood-brain barrier penetration capabilities. We will evaluate the antinociception of these compounds to determine if they have successfully reached their target receptors from peripheral administration. These compounds tested represent only a portion of the compounds created by our lab
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
Evaluation of a light-gas gun hypervelocity augmentation technique Final report
Interior ballistics of constant base pressure hypervelocity gu
A Chandra X-Ray Survey of Ultraluminous Infrared Galaxies
We present results from Chandra observations of 14 ultraluminous infrared
galaxies (ULIRGs; log(L_IR/L_Sun) >= 12) with redshifts between 0.04 and 0.16.
The goals of the observations were to investigate any correlation between
infrared color or luminosity and the properties of the X-ray emission and to
attempt to determine whether these objects are powered by starbursts or active
galactic nuclei (AGNs). The sample contains approximately the same number of
high and low luminosity objects and ``warm'' and ``cool'' ULIRGs. All 14
galaxies were detected by Chandra. Our analysis shows that the X-ray emission
of the two Seyfert 1 galaxies in our sample are dominated by AGN. The remaining
12 sources are too faint for conventional spectral fitting to be applicable.
Hardness ratios were used to estimate the spectral properties of these faint
sources. The photon indices for our sample plus the Chandra-observed sample
from Ptak et al.(2003) peak in the range of 1.0-1.5, consistent with
expectations for X-ray binaries in a starburst, an absorbed AGN, or hot
bremsstrahlung from a starburst or AGN. The values of photon index for the
objects in our sample classified as Seyferts (type 1 or 2) are larger than 2,
while those classified as HII regions or LINERs tend to be less than 2. The
hard X-ray to far-infrared ratios for the 12 weak sources are similar to those
of starbursts, but we cannot rule out the possibility of absorbed, possibly
Compton-thick, AGNs in some of these objects. Two of these faint sources were
found to have X-ray counterparts to their double optical and infrared nuclei.Comment: 40 pages, 5 tables, 14 figures, accepted by Ap
Genetic recombination during coinfection of two mutants of human respiratory syncytial virus
Recombination between coinfecting viruses had not been documented previously for a nonsegmented negative-strand RNA virus (mononegavirus). We investigated the potential of intermolecular recombination by respiratory syncytial virus (RSV) by coinfecting HEp-2 cells with two recombinant RSV (rRSV) mutants lacking either the G gene (DeltaG/HEK) or the NS1 and NS2 genes (DeltaNS1/2). These viruses replicate inefficiently and form pinpoint plaques in HEp-2 cells. Therefore, potential recombined viruses with a growth and/or plaque formation advantage should easily be identified and differentiated from the two parental viruses. Further identification of potential recombinants was aided by the inclusion of point mutation markers in the F and L genes of DeltaG/HEK and the design of reverse transcription-PCR (RT-PCR) primers capable of detecting these markers. Independent coinfections and control single infections by these two rRSV mutants were performed. In one of six coinfections, an RSV variant was identified that produced plaques slightly larger than those of wild-type RSV in HEp-2 cells. RT-PCR and sequencing provided evidence that this variant was a recombined RSV (rec-RSV). The rec-RSV appeared to have been generated by a polymerase jump from the DeltaG/HEK genome to that of DeltaNS1/2 and back again in the vicinity of the SH-G-F genes. This apparently involved nonhomologous and homologous recombination events, respectively. The recombined genome was identical to that of the DeltaG/HEK mutant except that all but the first 12 nucleotides of the SH gene were deleted and replaced by an insert consisting of the last 91 nucleotides of the G gene and its downstream intergenic region. This insert could have come only from the coinfecting DeltaNS1/2 virus. This resulted in the formation of a short chimeric SH:G gene. Northern and Western blot analysis confirmed that the rec-RSV did not express the normal SH and G mRNAs and proteins but did express the aberrant SH:G mRNA. This provides an experimental demonstration of intermolecular recombination yielding a viable, helper-independent mononegavirus. However, the isolation of only a single rec-RSV under these optimized conditions supports the idea that RSV recombination is rare indeed
Elliptical Galaxy in the Making: The Dual Active Galactic Nuclei and Metal-enriched Halo of Mrk 273
A systematic analysis of the X-ray emission from the nearby ultraluminous
infrared galaxy Mrk 273 was carried out by combining new 200 ksec Chandra data
with archived 44 ksec data. The active galactic nucleus (AGN) associated with
the Southwest nucleus is confirmed by the new data, and a secondary hard X-ray
(4-8 keV) point source is detected, coincident with the Northeast nucleus at a
projected distance of 0.75 kpc from the Southwest nucleus. The hard X-ray
spectrum of the Northeast nucleus is consistent with a heavily absorbed AGN,
making Mrk 273 another example of a dual AGN in a nearby galaxy merger.
Significant 1-3 keV emission is found along the ionization cones and outflowing
gas detected in a previous study. The data also map the giant X-ray nebula
south of the host galaxy with unprecedented detail. This nebula extends on a
scale of 40 kpc 40 kpc, and is not closely related to the
well-known tidal tail seen in the optical. The X-ray emission of the nebula is
best described by a single-temperature gas model, with a temperature of
7 million K and a super-solar /Fe ratio. Further analysis suggests that
the southern nebula has most likely been heated and enriched by multiple
galactic outflows generated by the AGN and/or circumnuclear starburst in the
past, on a time scale of 0.1 Gyr, similar to the merger event itself.Comment: 25 pages, 22 figures, 4 tables, accepted for publication in the
Astrophysical Journa
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