316 research outputs found
Assessing molecular outflows and turbulence in the protostellar cluster Serpens South
Molecular outflows driven by protostellar cluster members likely impact their
surroundings and contribute to turbulence, affecting subsequent star formation.
The very young Serpens South cluster consists of a particularly high density
and fraction of protostars, yielding a relevant case study for protostellar
outflows and their impact on the cluster environment. We combined CO
observations of this region using the Combined Array for Research in
Millimeter-wave Astronomy (CARMA) and the Institut de Radioastronomie
Millim\'{e}trique (IRAM) 30 m single dish telescope. The combined map allows us
to probe CO outflows within the central, most active region at size scales of
0.01 pc to 0.8 pc. We account for effects of line opacity and excitation
temperature variations by incorporating CO and CO data for the
and transitions (using Atacama Pathfinder Experiment and
Caltech Submillimeter Observatory observations for the higher CO transitions),
and we calculate mass, momentum, and energy of the molecular outflows in this
region. The outflow mass loss rate, force, and luminosity, compared with
diagnostics of turbulence and gravity, suggest that outflows drive a sufficient
amount of energy to sustain turbulence, but not enough energy to substantially
counter the gravitational potential energy and disrupt the clump. Further, we
compare Serpens South with the slightly more evolved cluster NGC 1333, and we
propose an empirical scenario for outflow-cluster interaction at different
evolutionary stages.Comment: 26 pages, 15 figures, accepted for publication in the Astrophysical
Journa
Toward a Better Benchmark: Assessing the Utility of Not-at-Fault Traffic Crash Data in Racial Profiling Research
As studies on racial profiling and biased policing have begun to proliferate, researchers are debating which benchmark is most appropriate for comparison with police traffic stop data. Existing benchmark populations, which include populations estimated from census figures, licensed drivers, arrestees, reported crime suspects, and observed drivers and traffic violators, all have significant limitations. This article offers a new, alternative benchmark for police traffic stops, a benchmark that has not been previously applied or tested in a racial profiling research setting. The analysis presented compares traffic observation data, gathered at selected, high volume intersections during an ongoing racial profiling study in Miami-Dade County, Florida, to not-at-fault driver demographic data from two-vehicle crashes at those same intersections. Findings indicate that non-responsible drivers in two-vehicle crashes appear to represent a reasonably accurate estimate of the racial composition of drivers on the roadways at selected intersections and within areas of varying racial composition. The implications of this finding for racial profiling research are discussed, and suggested areas for future inquiry are identified
Revealing The Millimeter Environment of the New FU Orionis Candidate HBC722 with the Submillimeter Array
We present 230 GHz Submillimeter Array continuum and molecular line
observations of the newly discovered FUor candidate HBC722. We report the
detection of seven 1.3 mm continuum sources in the vicinity of HBC722, none of
which correspond to HBC722 itself. We compile infrared and submillimeter
continuum photometry of each source from previous studies and conclude that
three are Class 0 embedded protostars, one is a Class I embedded protostar, one
is a Class I/II transition object, and two are either starless cores or very
young, very low luminosity protostars or first hydrostatic cores. We detect a
northwest-southeast outflow, consistent with the previous detection of such an
outflow in low-resolution, single-dish observations, and note that its axis may
be precessing. We show that this outflow is centered on and driven by one of
the nearby Class 0 sources rather than HBC722, and find no conclusive evidence
that HBC722 itself is driving an outflow. The non-detection of HBC722 in the
1.3 mm continuum observations suggests an upper limit of 0.02 solar masses for
the mass of the circumstellar disk. This limit is consistent with typical T
Tauri disks and with a disk that provides sufficient mass to power the burst.Comment: 12 pages, 7 figures, accepted by Ap
ALMA Cycle 1 Observations of the HH46/47 Molecular Outflow: Structure, Entrainment and Core Impact
We present ALMA Cycle 1 observations of the HH46/47 molecular outflow using
combined 12m array and ACA observations. The improved angular resolution and
sensitivity of our multi-line maps reveal structures that help us study the
entrainment process in much more detail and allow us to obtain more precise
estimates of outflow properties than previous observations. We use 13CO(1-0)
and C18O(1-0) emission to correct for the 12CO(1-0) optical depth to accurately
estimate the outflow mass, momentum and kinetic energy. This correction
increases the estimates of the mass, momentum and kinetic energy by factors of
about 9, 5 and 2, respectively, with respect to estimates assuming optically
thin emission. The new 13CO and C18O data also allow us to trace denser and
slower outflow material than that traced by the 12CO maps, and they reveal an
outflow cavity wall at very low velocities (as low as 0.2km/s with respect to
the cores central velocity). Adding with the slower material traced only by
13CO and C18O, there is another factor of 3 increase in the mass estimate and
50% increase in the momentum estimate. The estimated outflow properties
indicate that the outflow is capable of dispersing the parent core within the
typical lifetime of the embedded phase of a low-mass protostar, and that it is
responsible for a core-to-star efficiency of 1/4 to 1/3. We find that the
outflow cavity wall is composed of multiple shells associated with a series of
jet bow-shock events. Within about 3000AU of the protostar the 13CO and C18O
emission trace a circumstellar envelope with both rotation and infall motions,
which we compare with a simple analytic model. The CS(2-1) emission reveals
tentative evidence of a slowly-moving rotating outflow, which we suggest is
entrained not only poloidally but also toroidally by a disk wind that is
launched from relatively large radii from the source.Comment: Accepted for publication in ApJ. 26 pages, 20 figure
SMA and Spitzer Observations of Bok Glouble CB17: A Candidate First Hydrostatic Core?
We present high angular resolution SMA and Spitzer observations toward the
Bok globule CB17. SMA 1.3mm dust continuum images reveal within CB17 two
sources with an angular separation of about 21" (about 5250 AU at a distance of
250 pc). The northwestern continuum source, referred to as CB17 IRS, dominates
the infrared emission in the Spitzer images, drives a bipolar outflow extending
in the northwest-southeast direction, and is classified as a low luminosity
Class0/I transition object (L_bol ~ 0.5 L_sun). The southeastern continuum
source, referred to as CB17 MMS, has faint dust continuum emission in the SMA
1.3mm observations (about 6 sigma detection; ~3.8 mJy), but is not detected in
the deep Spitzer infrared images at wavelengths from 3.6 to 70 micron. Its
bolometric luminosity and temperature, estimated from its spectral energy
distribution, are less than 0.04 L_sun and 16 K, respectively. The SMA CO(2-1)
observations suggest that CB17 MMS may drive a low-velocity molecular outflow
(about 2.5 km/s), extending in the east-west direction. Comparisons with
prestellar cores and Class0 protostars suggest that CB17 MMS is more evolved
than prestellar cores but less evolved than Class0 protostars. The observed
characteristics of CB17 MMS are consistent with the theoretical predictions
from radiative/magneto hydrodynamical simulations of a first hydrostatic core,
but there is also the possibility that CB17 MMS is an extremely low luminosity
protostar deeply embedded in an edge-on circumstellar disk. Further
observations are needed to study the properties of CB17 MMS and to address more
precisely its evolutionary stage.Comment: 33 pages, 11 figures, to be published by Ap
The redox-active drug metronidazole and thiol-depleting garlic compounds act synergistically in the protist parasite Spironucleus vortens
Spironucleus vortens is a protozoan parasite associated with significant mortalities in the freshwater angelfish, Pterophyllum scalare. Control of this parasite is especially problematic due to restrictions on the use of the drug of choice, metronidazole (MTZ), on fish farms. Use of garlic (Allium sativum) is undergoing a renaissance following experimental validations of its antimicrobial efficiency. Ajoene ((E,Z)-4,5,9-trithiadodeca-1,6,11-triene 9-oxide), is a stable transformation product of allicin, the primary biologically active component of garlic. In the current study, an ajoene oil crude extract had a minimum inhibitory concentration (MIC) of 40 μg/ml against S. vortens. GC-MS and NMR spectroscopy revealed this ajoene extract contained a mixture of the (E) and (Z)-ajoene isomers along with diallyl disulphide (DADS) and diallyl trisulphide (DATS). The only component of the ajoene crude oil found to substantially inhibit S. vortens growth by optical density monitoring (Bioscreen C Reader) was (Z)-ajoene (MIC 16 μg/ml). Ajoene oil acted in synergy with MTZ in vitro, reducing the individual MIC of this drug (4 μg/ml) by 16-fold, and that of ajoene oil by 200-fold with a fractional inhibitory concentration (FIC) index of 0.263. This synergistic interaction was confirmed in vivo. S. vortens-infected P. scalare angelfish dosed orally with 0.5% (v/w) MTZ combined with 0.05% (v/w) ajoene displayed a significant reduction in faecal trophozoite count, whilst those fed on 0.5% MTZ flakes (half the recommended oral dose) alone did not. This study demonstrates for the first time the synergistic interaction between the synthetic drug MTZ and natural ajoene oil both in vitro and in vivo. Future work should evaluate the potential synergy of ajoene and MTZ against MTZ-resistant bacteria and protists
Metal clad aramid fibers for aerospace wire and cable
High strength light weight metal clad aramid fibers can provide significant weight savings when used to replace conventional metal wire in aerospace cable. An overview of metal clad aramid fiber materials and information on performance and use in braided electrical shielding and signal conductors is provided
Studying the Outflow-Core Interaction with ALMA Cycle 1 Observations of the HH46/47 Molecular Outflow
We present preliminary analysis of ALMA cycle 1 12m array ^(12)CO /^(13)CO /C^(18)O data of the HH 46/47 molecular outflow. ^(13)CO and C^(18)O trace relatively denser outflow material than ^(12)CO and allow us to trace the outflow to lower velocities than what it possible using only the ^(12)CO emission. Interestingly, the cavity wall of the red lobe can be seen at velocity as low as 0.2 km/s. Using C^(18)O, we are now able to estimate the optical depth of ^(13)CO, and then use the corrected ^(13)CO emission to further and better correct the ^(12)CO emission and estimate the mass, momentum, and kinetic energy of the outflow. Moreover, C^(18)O reveals a flattened rotational structure at the center, likely to be a rotational envelope infalling onto an inner Keplerian disk
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