266 research outputs found
Nonlinear Hodge maps
We consider maps between Riemannian manifolds in which the map is a
stationary point of the nonlinear Hodge energy. The variational equations of
this functional form a quasilinear, nondiagonal, nonuniformly elliptic system
which models certain kinds of compressible flow. Conditions are found under
which singular sets of prescribed dimension cannot occur. Various degrees of
smoothness are proven for the sonic limit, high-dimensional flow, and flow
having nonzero vorticity. The gradient flow of solutions is estimated.
Implications for other quasilinear field theories are suggested.Comment: Slightly modified and updated version; tcilatex, 32 page
Myopericarditis diagnosed by a 64-slice coronary CT angiography "triple rule out" protocol
We report a case of myopericarditis in a 30-year-old male complaining of shortness of breath. In an emergency department (ED) setting, the symptoms of myopericarditis may overlap with many disease entities and can be a challenging diagnosis to make. However, with the use of a 64-section coronary CT angiography in a “triple rule out” (TRO) protocol, we were able to detect a large pericardial effusion surrounding the heart and moderate global hypokinesis in the setting of normal-sized heart chambers and normal coronary arteries. We were further able to exclude pulmonary embolism and thoracic dissection. This is the first reported case of diagnosing myopericarditis using a TRO protocol. It demonstrates the usefulness of TRO in making an emergent diagnosis of myopericarditis while excluding other life-threatening diseases that can lead to earlier appropriate ED disposition and care
Molecular Evolution in Collapsing Prestellar Cores
We have investigated the evolution and distribution of molecules in
collapsing prestellar cores via numerical chemical models, adopting the
Larson-Penston solution and its delayed analogues to study collapse. Molecular
abundances and distributions in a collapsing core are determined by the balance
among the dynamical, chemical and adsorption time scales. When the central
density n_H of a prestellar core with the Larson-Penston flow rises to 3 10^6
cm^{-3}, the CCS and CO column densities are calculated to show central holes
of radius 7000 AU and 4000 AU, respectively, while the column density of N2H+
is centrally peaked. These predictions are consistent with observations of
L1544. If the dynamical time scale of the core is larger than that of the
Larson-Penston solution owing to magnetic fields, rotation, or turbulence, the
column densities of CO and CCS are smaller, and their holes are larger than in
the Larson-Penston core with the same central gas density. On the other hand,
N2H+ and NH3 are more abundant in the more slowly collapsing core. Therefore,
molecular distributions can probe the collapse time scale of prestellar cores.
Deuterium fractionation has also been studied via numerical calculations. The
deuterium fraction in molecules increases as a core evolves and molecular
depletion onto grains proceeds. When the central density of the core is n_H=3
10^6 cm^{-3}, the ratio DCO+/HCO+ at the center is in the range 0.06-0.27,
depending on the collapse time scale and adsorption energy; this range is in
reasonable agreement with the observed value in L1544.Comment: 21 pages, 17 figure
Capacitive Beam Position Monitor for NDCX-II
This note describes the design, fabrication and calibration of the NDCX-II capacitive beam position monitor
New Panoramic View of CO and 1.1 mm Continuum Emission in the Orion A Molecular Cloud. I. Survey Overview and Possible External Triggers of Star Formation
We present new, wide and deep images in the 1.1 mm continuum and the
CO (=1-0) emission toward the northern part of the Orion A Giant
Molecular Cloud (Orion-A GMC). The 1.1 mm data were taken with the AzTEC camera
mounted on the Atacama Submillimeter Telescope Experiment (ASTE) 10 m telescope
in Chile, and the CO (=1-0) data were with the 25 beam receiver
(BEARS) on the NRO 45 m telescope in the On-The-Fly (OTF) mode. The present
AzTEC observations are the widest (\timeform{1.D7}
\timeform{2.D3}, corresponding to 12 pc 17 pc) and the
highest-sensitivity (9 mJy beam) 1.1 mm dust-continuum imaging of
the Orion-A GMC with an effective spatial resolution of 40\arcsec. The
CO (=1-0) image was taken over the northern \timeform{1D.2}
\times\timeform{1D.2} (corresponding 9 pc 9 pc) area with a
sensitivity of 0.93 K in , a velocity resolution of 1.0 km
s, and an effective spatial resolution of 21\arcsec. With these data,
together with the MSX 8 m, Spitzer 24 m and the 2MASS data, we have
investigated the detailed structure and kinematics of molecular gas associated
with the Orion-A GMC and have found evidence for interactions between molecular
clouds and the external forces that may trigger star formation. Two types of
possible triggers were revealed; 1) Collision of the diffuse gas on the cloud
surface, particularly at the eastern side of the OMC-2/3 region, and 2)
Irradiation of UV on the pre-existing filaments and dense molecular cloud
cores. Our wide-field and high-sensitivity imaging have provided the first
comprehensive view of the potential sites of triggered star formation in the
Orion-A GMC.Comment: 32 pages, 20 figures, accepted for publication in PAS
Galaxy clusters at z~1 imaged by ALMA with the Sunyaev-Zel'dovich effect
We present high angular-resolution measurements of the thermal
Sunyaev-Zel'dovich effect (SZE) toward two galaxy clusters, RCS J2319+0038 at
z=0.9 and HSC J0947-0119 at z=1.1, by the Atacama Large
Millimeter/submillimeter Array (ALMA) in Band 3. They are supplemented with
available Chandra X-ray data, optical data taken by Hyper Suprime-Cam on
Subaru, and millimeter-wave SZE data from the Atacama Cosmology Telescope.
Taking into account departures from spherical symmetry, we have reconstructed
non-parametrically the inner pressure profile of two clusters as well as
electron temperature and density profiles for RCS J2319+0038. This is one of
the first such measurements for an individual cluster at . We
find that the inner pressure profile of both clusters is much shallower than
that of local cool-core clusters. Our results consistently suggest that RCS
J2319+0038 hosts a weak cool core, where radiative cooling is less significant
than in local cool cores. On the other hand, HSC J0947-0119 exhibits an even
shallower pressure profile than RCS J2319+0038 and is more likely a
non-cool-core cluster. The SZE centroid position is offset by more than 140
kpc from the peaks of galaxy distribution in HSC J0947-0119,
suggesting a stronger influence of mergers in this cluster. We conclude that
these distant clusters are at a very early stage of developing the cool cores
typically found in clusters at lower redshifts.Comment: 26 pages, 13 figures, 8 tables, submitted to PAS
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