1,097 research outputs found
SiO Emission in the Multi-Lobe Outflow associated with IRAS 16293-2422
We have mapped the thermal emission line of SiO (v = 0; J = 2-1) associated
with the quadrupolar molecular outflow driven by the very cold far-infrared
source IRAS 16293-2422. The SiO emission is significantly enhanced in the
northeastern red lobe and at the position ~50" east of the IRAS source. Strong
SiO emission observed at ~50" east of the IRAS source presents evidence for a
dynamical interaction between a part of the eastern blue lobe and the dense
ambient gas condensation, however, such an interaction is unlikely to be
responsible for producing the quadrupolar morphology. The SiO emission in the
northeastern red lobe shows the spatial and velocity structure similar to those
of the CO outflow, suggesting that the SiO emission comes from the molecular
outflow in the northeastern red lobe itself. The observed velocity structure is
reproduced by a simple spatio-kinematic model of bow shock with a shock
velocity of 19-24 km/s inclined by 30-45 deg from the plane of the sky. This
implies that the northeastern red lobe is independent of the eastern blue lobe
and that the quadrupolar structure is due to two separate bipolar outflows.
The SiO emission observed in the western red lobe has a broad pedestal shape
with low intensity. Unlike the SiO emission in the northeastern red lobe, the
spatial extent of the SiO emission in the western red lobe is restricted to its
central region. The spatial and velocity structures and the line profiles
suggest that three different types of the SiO emission are observed in this
outflow; the SiO emission arises from the interface between the outflowing gas
and the dense ambient gas clump, the SiO emission coming from the outflow lobe
itself, and the broad SiO emission with low intensity observed at the central
region of the outflow lobe.Comment: 14 pages, 6 figures (figures 1 and 4 are color), gzipped tar file, To
appear in the Ap
The ortho-to-para ratio of ammonia in the L1157 outflow
We have measured the ortho-to-para ratio of ammonia in the blueshifted gas of
the L1157 outflow by observing the six metastable inversion lines from (J, K) =
(1, 1) to (6, 6). The highly excited (5, 5) and (6, 6) lines were first
detected in the low-mass star forming regions. The rotational temperature
derived from the ratio of four transition lines from (3, 3) to (6, 6) is
130-140 K, suggesting that the blueshifted gas is heated by a factor of ~10 as
compared to the quiescent gas. The ortho-to-para ratio of the NH3 molecules in
the blueshifted gas is estimated to be 1.3--1.7, which is higher than the
statistical equilibrium value. This ratio provides us with evidence that the
NH3 molecules have been evaporated from dust grains with the formation
temperature between 18 and 25 K. It is most likely that the NH3 molecules on
dust grains have been released into the gas phase through the passage of strong
shock waves produced by the outflow. Such a scenario is supported by the fact
that the ammonia abundance in the blueshifted gas is enhanced by a factor of ~5
with respect to the dense quiescent gas.Comment: 16 pages, including 3 PS figures. To appear in the ApJ (Letters).
aastex macro
Synthesizing Diverse Lung Nodules Wherever Massively: 3D Multi-Conditional GAN-Based CT Image Augmentation for Object Detection
Accurate Computer-Assisted Diagnosis, relying on large-scale annotated
pathological images, can alleviate the risk of overlooking the diagnosis.
Unfortunately, in medical imaging, most available datasets are
small/fragmented. To tackle this, as a Data Augmentation (DA) method, 3D
conditional Generative Adversarial Networks (GANs) can synthesize desired
realistic/diverse 3D images as additional training data. However, no 3D
conditional GAN-based DA approach exists for general bounding box-based 3D
object detection, while it can locate disease areas with physicians' minimum
annotation cost, unlike rigorous 3D segmentation. Moreover, since lesions vary
in position/size/attenuation, further GAN-based DA performance requires
multiple conditions. Therefore, we propose 3D Multi-Conditional GAN (MCGAN) to
generate realistic/diverse 32 X 32 X 32 nodules placed naturally on lung
Computed Tomography images to boost sensitivity in 3D object detection. Our
MCGAN adopts two discriminators for conditioning: the context discriminator
learns to classify real vs synthetic nodule/surrounding pairs with noise
box-centered surroundings; the nodule discriminator attempts to classify real
vs synthetic nodules with size/attenuation conditions. The results show that 3D
Convolutional Neural Network-based detection can achieve higher sensitivity
under any nodule size/attenuation at fixed False Positive rates and overcome
the medical data paucity with the MCGAN-generated realistic nodules---even
expert physicians fail to distinguish them from the real ones in Visual Turing
Test.Comment: 9 pages, 6 figures, accepted to 3DV 201
Coupling biochemistry and mechanics in cell adhesion: a model for inhomogeneous stress fiber contraction
Biochemistry and mechanics are closely coupled in cell adhesion. At sites of
cell-matrix adhesion, mechanical force triggers signaling through the
Rho-pathway, which leads to structural reinforcement and increased
contractility in the actin cytoskeleton. The resulting force acts back to the
sites of adhesion, resulting in a positive feedback loop for mature adhesion.
Here we model this biochemical-mechanical feedback loop for the special case
when the actin cytoskeleton is organized in stress fibers, which are
contractile bundles of actin filaments. Activation of myosin II molecular
motors through the Rho-pathway is described by a system of reaction-diffusion
equations, which are coupled into a viscoelastic model for a contractile actin
bundle. We find strong spatial gradients in the activation of contractility and
in the corresponding deformation pattern of the stress fiber, in good agreement
with experimental findings.Comment: Revtex, 35 pages, 13 Postscript figures included, in press with New
Journal of Physics, Special Issue on The Physics of the Cytoskeleto
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