6,195 research outputs found
The Class 0 Protostar BHR71: Herschel Observations and Dust Continuum Models
We use Herschel spectrophotometry of BHR71, an embedded Class 0 protostar, to
provide new constraints on its physical properties. We detect 645 (non-unique)
spectral lines amongst all spatial pixels. At least 61 different spectral lines
originate from the central region. A CO rotational diagram analysis shows four
excitation temperature components, 43 K, 197 K, 397 K, and 1057 K. Low-J CO
lines trace the outflow while the high-J CO lines are centered on the infrared
source. The low-excitation emission lines of H2O trace the large-scale outflow,
while the high-excitation emission lines trace a small-scale distribution
around the equatorial plane. We model the envelope structure using the dust
radiative transfer code, Hyperion, incorporating rotational collapse, an outer
static envelope, outflow cavity, and disk. The evolution of a rotating
collapsing envelope can be constrained by the far-infrared/millimeter SED along
with the azimuthally-averaged radial intensity profile, and the structure of
the outflow cavity plays a critical role at shorter wavelengths. Emission at
20-40 um requires a cavity with a constant-density inner region and a power-law
density outer region. The best fit model has an envelope mass of 19 solar mass
inside a radius of 0.315 pc and a central luminosity of 18.8 solar luminosity.
The time since collapse began is 24630-44000 yr, most likely around 36000 yr.
The corresponding mass infall rate in the envelope (1.2x10 solar mass
per year) is comparable to the stellar mass accretion rate, while the mass loss
rate estimated from the CO outflow is 20% of the stellar mass accretion rate.
We find no evidence for episodic accretion.Comment: Accepted for publication in ApJ. 33 pages; 34 figures; 4 table
Situating the Georgia Performance Standards in the Social Studies Debate: An Improvement for Social Studies Classrooms or Continuing the Whitewash
After approximately two decades of using the Quality Core Curriculum, in 2005 the State of Georgia began the process of implementing the new Georgia Performance Standard. In this article the authors examine the strengths and weaknesses of this new curriculum, along with the proposed model of implementation. In this examination, the authors will attempt to situate both the standards and their implementation within the current political struggle over curriculum in the United States
Crude Protein, and other Chemical Constituents of Corn Hybrids Evaluated in the 1994 Kentucky Hybrid Corn Performance Tests
Grain samples have been collected each year since 1990 from three locations of the Kentucky Hybrid Corn Performance Test and analyzed for crude protein (CP). The objective was to provide an unbiased comparative evaluation of the CP concentration of com hybrids sold in Kentucky. The results indicate that while management and environment at each test location may have significant influences, CP does differ among hybrid genotypes. The feeding value of specific hybrid genotypes based on their protein concentration may have significant influence in diet formulation for non-ruminant animals due to the amount of supplement needed to properly balance the diet, and may be an important economic factor in animal production. Previous summaries of annual results have been published (I, 2, 3). CP data for hybrids tested in 1994 plus multiple year means derived from data collected in three previous years are included in this report. Annual data are averaged over locations
An Unusual Combination of Neurological Manifestations and Sudden Vision Loss in a Child with Familial Hyperphosphatemic Tumoral Calcinosis
Hyperphosphatemia in the absence of renal failure is an unusual occurrence, particularly in children, but is a common primary feature of familial hyperphosphatemic tumor calcinosis. We report a child with hyperphosphatemia who presented with multiple episodes of neurologic dysfunction involving lower motor neuron facial nerve palsy along with sequential visual loss. He also had an episode of stroke. There was an extensive metastatic calcification of soft tissue and vasculature. Hyperphosphatemia with normal serum alkaline phosphatase, calcium, parathyroid hormone, and renal function was noted. He was managed with hemodialysis and sevelamer (3 months) without much success in reducing serum phosphate level, requiring continuous ambulatory peritoneal dialysis (3 years). Intact fibroblast growth factor 23 (FGF23) was undetectable, with C-terminal FGF23 fragments significantly elevated (2575 RU/ml, normal A (p.N162K) mutation in FGF23 exon 3, confirming the diagnoses of primary FGF23 deficiency, the first case to be reported from India
Comparison between hybrid and fully kinetic models of asymmetric magnetic reconnection: coplanar and guide field configurations
Magnetic reconnection occurring in collisionless environments is a
multi-scale process involving both ion and electron kinetic processes. Because
of their small mass, the electron scales are difficult to resolve in numerical
and satellite data, it is therefore critical to know whether the overall
evolution of the reconnection process is influenced by the kinetic nature of
the electrons, or is unchanged when assuming a simpler, fluid, electron model.
This paper investigate this issue in the general context of an asymmetric
current sheet, where both the magnetic field amplitude and the density vary
through the discontinuity. A comparison is made between fully kinetic and
hybrid kinetic simulations of magnetic reconnection in coplanar and guide field
systems. The models share the initial condition but differ in their electron
modeling. It is found that the overall evolution of the system, including the
reconnection rate, is very similar between both models. The best agreement is
found in the guide field system, which confines particle better than the
coplanar one, where the locality of the moments is violated by the electron
bounce motion. It is also shown that, contrary to the common understanding,
reconnection is much faster in the guide field system than in the coplanar one.
Both models show this tendency, indicating that the phenomenon is driven by ion
kinetic effects and not electron ones.Comment: 11 pages, 8 figures, accepted in Physics of Plasma
Kinematically Cold Populations at Large Radii in the Draco and Ursa Minor Dwarf Spheroidals
We present projected velocity dispersion profiles for the Draco and Ursa
Minor (UMi) dwarf spheroidal galaxies based on 207 and 162 discrete stellar
velocities, respectively. Both profiles show a sharp decline in the velocity
dispersion outside ~30 arcmin (Draco) and ~40 arcmin (UMi). New, deep
photometry of Draco reveals a break in the light profile at ~25 arcmin. These
data imply the existence of a kinematically cold population in the outer parts
of both galaxies. Possible explanations of both the photometric and kinematic
data in terms of both equilibrium and non-equilibrium models are discussed in
detail. We conclude that these data challenge the picture of dSphs as simple,
isolated stellar systems.Comment: 5 pages, accepted for publication in ApJ Letter
Three-coordinate iron(II) expanded ring N-heterocyclic carbene complexes
A sterically demanding seven-membered expanded ring N-heterocyclic carbene (NHC) ligand allows access to rare examples of three-coordinate iron(II)-NHC complexes incorporating only halide coligands of the general formula [Fe(NHC)X 2 ] (NHC = 7-DiPP; X = Br (1) Cl (2)). Reducing the steric influence of the ancillary NHC ligand through modulation of the N-aryl substituents leads to either four- or three-coordinate complexes of the general formula [Fe(NHC)Br 2 (THF)] (3) or [Fe(NHC)Br 2 ] (4) (NHC = 7-Mes), dependent upon the solvent of recrystallization. The further reduction of NHC steric influence results in four-coordinate geometries at iron in the form of the dimeric species [Fe(NHC)Br(μ-Br)] 2 (5) or [Fe(NHC)Br 2 (THF)] (6) (NHC = SDiPP), again dependent upon the solvent of recrystallization. Compounds 1-6 have been analyzed by 1 H NMR spectroscopy, X-ray crystallography, elemental microanalysis, Mössbauer spectroscopy (for 1 and 3-5), and Evans method magnetic susceptibility. In addition to these measurements the three-coordinate species 1 and 4 have been further analyzed by SQUID magnetometry and CASSCF calculations, which show significant magnetic anisotropy that is extremely sensitive to the coordination geometry
Differential Responses of Human and Mouse Lung Epithelial Cells in Inducible Resistance to Viral Infection
https://openworks.mdanderson.org/sumexp21/1240/thumbnail.jp
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