1,071 research outputs found
SPITZER observations of dust destruction in the Puppis A supernova remnant
The interaction of the Puppis A supernova remnant (SNR) with a neighboring molecular cloud provides a unique
opportunity to measure the amount of grain destruction in an SNR shock. Spitzer Space Telescope MIPS imaging
of the entire SNR at 24, 70, and 160 μm shows an extremely good correlation with X-ray emission, indicating
that the SNR’s IR radiation is dominated by the thermal emission of swept-up interstellar dust, collisionally
heated by the hot shocked gas. Spitzer IRS spectral observations targeted both the Bright Eastern Knot (BEK)
of the SNR where a small cloud has been engulfed by the supernova blast wave and outlying portions of the
associated molecular cloud that are yet to be hit by the shock front. Modeling the spectra from both regions
reveals the composition and the grain size distribution of the interstellar dust, both in front of and behind the
SNR shock front. The comparison shows that the ubiquitous polycyclic aromatic hydrocarbons of the interstellar
medium are destroyed within the BEK, along with nearly 25% of the mass of graphite and silicate dust grains
Potential anti-inflammatory and anti-cancer properties of farnesol
© 2018 by the authors. Farnesol, an acyclic sesquiterpene alcohol, is predominantly found in essential oils of various plants in nature. It has been reported to exhibit anti-cancer and anti-inflammatory effects, and also alleviate allergic asthma, gliosis, and edema. In numerous tumor cell lines, farnesol can modulate various tumorigenic proteins and/or modulates diverse signal transduction cascades. It can also induce apoptosis and downregulate cell proliferation, angiogenesis, and cell survival. To exert its anti-inflammatory/anti-oncogenic effects, farnesol can modulate Ras protein and nuclear factor kappa-light-chain-enhancer of activated B cells activation to downregulate the expression of various inflammatory mediators such as cyclooxygenase-2, inducible nitric oxide synthase, tumor necrosis factor alpha, and interleukin-6. In this review, we describe the potential mechanisms of action underlying the therapeutic effects of farnesol against cancers and inflammatory disorders. Furthermore, these findings support the clinical development of farnesol as a potential pharmacological agent in clinical studies
Aerothermal Design of a Common Probe for Multiple Planetary Destinations
Estimate the mass of the Thermal Protection System (TPS) for a single design construct of an atmospheric entry probe with a rigid aeroshell, which could be used at five destinations, i.e. Venus, Saturn, Uranus, Neptune, and perhaps, Jupiter. The entry mass of the probe is 400 kg with a ballistic coefficient of 216 kg/m2. Process: The 3DoF trajectory simulation program Traj, coupled with the TPS response program FIAT was used for simulation and design. The assumed atmospheric models were VIRA (Venus-GRAM) for Venus, the Julianne Moses' model for Saturn, a NASA Ames engineering model for Uranus, Neptune-GRAM for Neptune, and Galileo Probe (Al Seiff's) result for Jupiter
Time Evolution of the Reverse Shock in SN 1006
The Schweizer-Middleditch star, located behind the SN 1006 remnant and near
its center in projection, provides the opportunity to study cold, expanding
ejecta within the SN 1006 shell through UV absorption. Especially notable is an
extremely sharp red edge to the Si II 1260 Angstrom feature, which stems from
the fastest moving ejecta on the far side of the SN 1006 shell--material that
is just encountering the reverse shock. Comparing HST far-UV spectra obtained
with COS in 2010 and with STIS in 1999, we have measured the change in this
feature over the intervening 10.5-year baseline. We find that the sharp red
edge of the Si II feature has shifted blueward by 0.19 +/- 0.05 Angstroms,
which means that the material hitting the reverse shock in 2010 was moving
slower by 44 +/- 11 km/s than the material that was hitting it in 1999, a
change corresponding to - 4.2 +/- 1.0 km/s/yr. This is the first observational
confirmation of a long-predicted dynamic effect for a reverse shock: that the
shock will work its way inward through expanding supernova ejecta and encounter
ever slower material as it proceeds. We also find that the column density of
shocked Si II (material that has passed through the reverse shock) has
decreased by 7 +/- 2% over the ten-year period. The decrease could indicate
that in this direction the reverse shock has been ploughing through a dense
clump of Si,leading to pressure and density transients.Comment: 8 pages, includes 5 figure
A High-Resolution X-Ray and Optical Study of SN1006: Asymmetric Expansion and Small-Scale Structure in a Type Ia Supernova Remnant
We introduce a deep (670 ks) X-ray survey of the entire SN 1006 remnant from the Chandra X-Ray Observatory, together with a deep H image of SN 1006 from the 4 m Blanco telescope at CTIO. Comparison with Chandra images from 2003 gives the first measurement of the X-ray proper motions around the entire periphery, carried out over a 9 yr baseline. We find that the expansion velocity varies significantly with azimuth. The highest velocity of approx.7400 km/s (almost 2.5 times that in the northwest (NW)) is found along the southeast (SE) periphery, where both the kinematics and the spectra indicate that most of the X-ray emission stems from ejecta that have been decelerated little, if at all. Asymmetries in the distribution of ejecta are seen on a variety of spatial scales. Si-rich ejecta are especially prominent in the SE quadrant, while O and Mg are more uniformly distributed, indicating large-scale asymmetries arising from the explosion itself. Neon emission is strongest in a sharp filament just behind the primary shock along the NWrim, where the pre-shock density is highest. Here the Ne is likely interstellar, while Ne within the shell may include a contribution from ejecta. Within the interior of the projected shell we find a few isolated "bullets" of what appear to be supernova ejecta that are immediately preceded by bowshocks seen in H, features that we interpret as ejecta knots that have reached relatively dense regions of the surrounding interstellar medium, but that appear in the interior in projection. Recent three-dimensional hydrodynamic models for Type Ia supernovae display small-scale features that strongly resemble the ones seen in X-rays in SN 1006; an origin in the explosion itself or from subsequent hydrodynamic instabilities both remain viable options. We have expanded the search for precursor X-ray emission ahead of a synchrotron-dominated shock front, as expected from diffusive shock acceleration theory, to numerous regions along both the northeast and southwest rims of the shell. Our data require that a precursor be thinner than about 3, and fainter than about 5% of the post-shock peak. These limits suggest that the magnetic field is amplified by a factor of seven or more in a narrow precursor region, promoting diffusive particle acceleration
Isospin splitting in heavy baryons and mesons
A recent general analysis of light-baryon isospin splittings is updated and
extended to charmed baryons.
The measured and splittings stand out as being difficult
to understand in terms of two-body forces alone.
We also discuss heavy-light mesons; though the framework here is necessarily
less general, we nevertheless obtain some predictions that are not strongly
model-dependent.Comment: 12 pages REVTEX 3, plus 4 uuencoded ps figures, CMU-HEP93-
Report on the Third Workshop on Sustainable Software for Science: Practice and Experiences (WSSSPE3)
This report records and discusses the Third Workshop on Sustainable Software
for Science: Practice and Experiences (WSSSPE3). The report includes a
description of the keynote presentation of the workshop, which served as an
overview of sustainable scientific software. It also summarizes a set of
lightning talks in which speakers highlighted to-the-point lessons and
challenges pertaining to sustaining scientific software. The final and main
contribution of the report is a summary of the discussions, future steps, and
future organization for a set of self-organized working groups on topics
including developing pathways to funding scientific software; constructing
useful common metrics for crediting software stakeholders; identifying
principles for sustainable software engineering design; reaching out to
research software organizations around the world; and building communities for
software sustainability. For each group, we include a point of contact and a
landing page that can be used by those who want to join that group's future
activities. The main challenge left by the workshop is to see if the groups
will execute these activities that they have scheduled, and how the WSSSPE
community can encourage this to happen
Recommended from our members
Electronic interactions between gold nanoclusters in constrainedgeometries
Misfit-dislocation generation by dissociated dislocations in quantum-well heterostructures
The mechanisms whereby 60° misfit dislocations are generated from dissociated threading dislocations in quantum-well heterostructures are considered. The two partial dislocations experience different misfit stresses, resulting in each partial having a different critical thickness. As a consequence, a number of different dislocation configurations are predicted, including the possibility of producing stacking faults of infinite width. © 1994 The American Physical Societ
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