148 research outputs found
CO-0.30-0.07: A Peculiar Molecular Clump with an Extremely Broad Velocity Width
The high velocity dispersion compact cloud CO-0.30-0.07 is a peculiar
molecular clump discovered in the central moleculr zone of the Milky Way, which
is characterized by its extremely broad velocity emissions () despite the absence of internal energy sources. We present new
interferometric maps of the cloud in multiple molecular lines in frequency
ranges of 265--269 GHz and 276--280 GHz obtained using the Sumbmillimeter
Array, along with the single-dish images previously obtained with the ASTE 10-m
telescope. The data show that the characteristic broad velocity emissions are
predominantly confined in two parallel ridges running through the cloud center.
The central ridges are tightly anti-correlated with each other in both space
and velocity, thereby sharply dividing the entire cloud into two distinct
velocity components (+15 km s and +55 km s). This morphology is
consistent with a model in which the two velocity components collide with a
relative velocity of 40 at the interface defined by the
central ridges, although an alternative explanation with a highly inclined
expanding-ring model is yet to be fully invalidated. We have also unexpectedly
detected several compact clumps (pc in radius) likely formed by
shock compression. The clumps have several features in common with typical
star-forming clouds: high densities (), rich
abundances of hot-core-type molecular species, and relatively narrow velocity
widths apparently decoupled from the furious turbulence dominating the cloud.
The cloud CO-0.30-0.07 is possibly at an early phase of star formation activity
triggered by the shock impact.Comment: 29 pages, 10 figures, accepted for publication in Ap
Physical Conditions of Molecular Gas in the Galactic Center
We estimated physical conditions of molecular gas in the central molecular
zone (CMZ) of the Galaxy, using our CO J=3-2 data obtained with the Atacama
Submillimeter Telescope Experiment (ASTE) in conjunction with J=1-0 12CO and
13CO data previously observed with the NRO 45m telescope. The large velocity
gradient (LVG) approximation was employed. Distributions of gas density,
kinetic temperature, and CO column density are derived as functions of position
and velocity for the entire coverage of the CO J=3-2 data. We fairly determined
physical conditions for 69 % of data points in the CMZ with >= 1 sigma CO
detections. Kinetic temperature was found to be roughly uniform in the CMZ,
while gas density is higher in the 120-pc star forming ring than in the outer
dust lanes. Physical conditions of high J=3-2/J=1-0 features are also
discussed.Comment: 8 pages, 6 figures, to appear in PAS
Sepsis-associated neuroinflammation in the spinal cord
Septic patients commonly present with central nervous system (CNS) disorders including impaired consciousness and delirium. Today, the main mechanism regulating sepsis-induced cerebral disorders is believed to be neuroinflammation. However, it is unknown how another component of the CNS, the spinal cord, is influenced during sepsis. In the present study, we intraperitoneally injected mice with lipopolysaccharide (LPS) to investigate molecular and immunohistochemical changes in the spinal cord of a sepsis model. After LPS administration in the spinal cord, pro-inflammatory cytokines including interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha mRNA were rapidly and drastically induced. Twenty-four-hour after the LPS injection, severe neuronal ischemic damage spread into gray matter, especially around the anterior horns, and the anterior column had global edematous changes. Immunostaining analyses showed that spinal microglia were significantly activated and increased, but astrocytes did not show significant change. The current results indicate that sepsis induces acute neuroinflammation, including microglial activation and pro-inflammatory cytokine upregulation in the spinal cord, causing drastic neuronal ischemia and white matter edema in the spinal cord
Time-delayed collective flow diffusion models for inferring latent people flow from aggregated data at limited locations
The rapid adoption of wireless sensor devices has made it easier to record location information of people in a variety of spaces (e.g., exhibition halls). Location information is often aggregated due to privacy and/or cost concerns. The aggregated data we use as input consist of the numbers of incoming and outgoing people at each location and at each time step. Since the aggregated data lack tracking information of individuals, determining the flow of people between locations is not straightforward. In this article, we address the problem of inferring latent people flows, that is, transition populations between locations, from just aggregated population data gathered from observed locations. Existing models assume that everyone is always in one of the observed locations at every time step; this, however, is an unrealistic assumption, because we do not always have a large enough number of sensor devices to cover the large-scale spaces targeted. To overcome this drawback, we propose a probabilistic model with flow conservation constraints that incorporate travel duration distributions between observed locations. To handle noisy settings, we adopt noisy observation models for the numbers of incoming and outgoing people, where the noise is regarded as a factor that may disturb flow conservation, e.g., people may appear in or disappear from the predefined space of interest. We develop an approximate expectation-maximization (EM) algorithm that simultaneously estimates transition populations and model parameters. Our experiments demonstrate the effectiveness of the proposed model on real-world datasets of pedestrian data in exhibition halls, bike trip data and taxi trip data in New York City
The Connection between Gamma-Ray Bursts and Extremely Metal-Poor Stars: Black Hole-forming Supernovae with Relativistic Jets
Long-duration gamma-ray bursts (GRBs) are thought to be connected to luminous
and energetic supernovae (SNe), called hypernovae (HNe), resulting from the
black-hole (BH) forming collapse of massive stars. For recent nearby
GRBs~060505 and 060614, however, the expected SNe have not been detected. The
upper limits to the SN brightness are about 100 times fainter than
GRB-associated HNe (GRB-HNe), corresponding to the upper limits to the ejected
Ni masses of . SNe with a small
amount of Ni ejection are observed as faint Type II SNe. HNe and faint
SNe are thought to be responsible for the formation of extremely metal-poor
(EMP) stars. In this Letter, a relativistic jet-induced BH forming explosion of
the 40 star is investigated and hydrodynamic and nucleosynthetic
models are presented. These models can explain both GRB-HNe and GRBs without
bright SNe in a unified manner. Their connection to EMP stars is also
discussed. We suggest that GRBs without bright SNe are likely to synthesize
\Mni\sim 10^{-4} to or .Comment: 7 pages, 3 figures. Accepted for publication in the Astrophysical
Journal Letters (10 March 2007, v657n2 issue
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