348 research outputs found
Very Long Baseline Interferometry imaging of H2O maser emission in the nearby radio galaxy NGC 4261
We report dual-frequency very long baseline interferometry (VLBI)
observations at 22 and 43 GHz toward the nucleus of a nearby radio galaxy NGC
4261. In particular, we present a VLBI image of the 22 GHz H2O maser line and
its location in the circumnuclear region of NGC 4261. H2O maser emission is
marginally detected above the three times the rms level within a velocity range
of approximately 2250-2450 km/s, slightly red-shifted with respect to the
systemic velocity. H2O maser emission is located approximately 1 milliarcsecond
(mas) east of the brightest continuum component at 22 GHz, where the continuum
spectrum is optically thick, that is at the free-free absorbed receding jet by
ionized gas. A positional coincidence between H2O maser emission and an ionized
gas disk implies that the H2O maser emission arises from the near side of the
disk, amplifying continuum emission from the background receding jet. If the
disk axis is oriented 64 degree relative to the line of sight, the H2O maser
emission is expected to be at a mean radius of 0.3 pc in the disk. The broad
line width of the H2O maser emission can be attributed to complex kinematics in
the immediate vicinity of the supermassive black hole (SMBH), including ongoing
gas infall onto the SMBH, turbulence, and outflow. This is analogous to the
multi-phase circumnuclear torus model in the nearest radio-loud H2O megamaser
source NGC 1052. An alternative explanation for H2O maser association is the
shock region between the jet and the ambient molecular clouds. However, this
explanation fails to describe the explicit association of H2O maser emission
only with the free-free absorbed receding jet.Comment: 10 pages, 5 figures, submitted to PAS
Improving Tracking Performance of Predictive Functional Control Using Disturbance Observer and Its Application to Table Drive Systems
A practical approach for improving tracking performance of the predictive functional control (PFC) is proposed. The disturbance observer is utilized to nominalize the actual plant and to reduce the predicted output error in the PFC algorithm by canceling not only constant but also high-order disturbances. The proposed control scheme is experimentally validated on a single axis table drive system and is compared with the standard PFC and the industrial cascade control. The experimental results prove the effectiveness of the proposed disturbance observer-based PFC scheme
Effect of Oligomers Derived from Biodegradable Polyesters on Eco- and Neurotoxicity
Biodegradable polymers are eco-friendly materials and have attracted attention for use in a sustainable society because they are not accumulated in the environment. Although the characteristics of biodegradable polymers have been assessed well, the effects of their degradation products have not. Herein, we comprehensively evaluated the chemical toxicities of biodegradable polyester, polycaprolactone (PCL), and synthetic oligocaprolactones (OCLs) with different degrees of polymerization. While the PCL did not show any adverse effects on various organisms, high levels of shorter OCLs and the monomer (1 μg/mL for freshwater microorganisms and 1 mg/mL for marine algae and mammalian cells) damaged the tested organisms, including freshwater microorganisms, marine algae, and mammalian cells, which indicated the toxicities of the degradation products under unnaturally high concentrations. These results highlight the need for a further understanding of the effects of the degradation products resulting from biodegradable polyesters to ensure a genuinely sustainable society
VERA monitoring of the radio jet 3C 84 during 2007--2013: detection of non-linear motion
We present a kinematic study of the subparsec-scale radio jet of the radio
galaxy 3C 84/NGC 1275 with the VLBI Exploration of Radio Astrometry (VERA)
array at 22 GHz for 80 epochs from 2007 October to 2013 December. The averaged
radial velocity of the bright component "C3" with reference to the radio core
is found to be between 2007 October and 2013 December. This
constant velocity of C3 is naturally explained by the advancing motion of the
head of the mini-radio lobe. We also find a non-linear component in the motion
of C3 with respect to the radio core. We briefly discuss possible origins of
this non-linear motion.Comment: 11 pages, 7 figures, 8 tables (table 1 - 5 are supplementaries),
accepted for publication on PAS
Interferometric 12CO(J=2-1) image of the Nuclear Region of Seyfert 1 Galaxy NGC 1097
We have mapped the central region of the Seyfert 1 galaxy NGC 1097 in
12CO(J=2-1) with the Submillieter Array (SMA). The 12CO(J=2-1) map shows a
central concentration and a surrounding ring, which coincide respectively with
the Seyfert nucleus and a starburst ring. The line intensity peaks at the
nucleus, whereas in a previously published 12CO(J=1-0) map the intensity peaks
at the starburst ring. The molecular ring has an azimuthally averaged
12CO(J=2-1)/(J=1-0) intensity ratio (R21) of about unity, which is similar to
those in nearby active star forming galaxies, suggesting that most of the
molecular mass in the ring is involved in fueling the starburst. The molecular
gas can last for only about 1.2\times10^8 years without further replenishment
assuming a constant star formation rate and a perfect conversion of gas to
stars. The velocity map shows that the central molecular gas is rotating with
the molecular ring in the same direction, while its velocity gradient is much
steeper than that of the ring. This velocity gradient of the central gas is
similar to what is usually observed in some Seyfert 2 galaxies. To view the
active nucleus directly in the optical, the central molecular gas structure can
either be a low-inclined disk or torus but not too low to be less massive than
the mass of the host galaxy itself, be a highly-inclined thin disk or clumpy
and thick torus, or be an inner part of the galactic disk. The R21 value of
~1.9 of the central molecular gas component, which is significantly higher than
the value found at the molecular gas ring, indicates that the activity of the
Seyfert nucleus may have a significant influence on the conditions of the
molecular gas in the central component.Comment: 22 pages, 4 figures, accepted by Ap
Insulin receptor cleavage induced by estrogen impairs insulin signaling
Introduction: Soluble insulin receptor (sIR), which is the ectodomain of insulin receptor (IR), is present in human plasma. Plasma sIR levels are positively correlated with blood glucose levels and negatively correlated with insulin sensitivity. An in vitro model of IR cleavage shows that extracellular calpain 2 directly cleaves IR, which generates sIR, and sequential cleavage of the IRβ subunit by γ-secretase impairs insulin signaling in a glucose concentration-dependent manner. Nevertheless, sIR levels vary among subjects with normal glucose levels.
Research design and methods: We examined sIR levels of pregnant women throughout gestation. Using an in vitro model, we also investigated the molecular mechanisms of IR cleavage induced by estradiol.
Results: In pregnant women, sIR levels were positively correlated with estrogen levels and significantly increased at late pregnancy independent of glucose levels. Using an in vitro model, estrogen elicited IR cleavage and impaired cellular insulin signaling. Estradiol-induced IR cleavage was inhibited by targeting of calpain 2 and γ-secretase. Estrogen exerted these biological effects via G protein-coupled estrogen receptor, and its selective ligand upregulated calpain 2 expression and promoted exosome secretion, which significantly increased extracellular calpain 2. Simultaneous stimulation of estrogen and high glucose levels had a synergic effect on IR cleavage. Metformin prevented calpain 2 release in exosomes and restored insulin signaling impaired by estrogen.
Conclusions: Estradiol-induced IR cleavage causes cellular insulin resistance, and its molecular mechanisms are shared with those by high glucose levels. sIR levels at late pregnancy are significantly elevated along with estrogen levels. Therefore, estradiol-induced IR cleavage is preserved in pregnant women and could be part of the etiology of insulin resistance in gestational diabetes mellitus and overt diabetes during pregnancy
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