150 research outputs found
Very Long Baseline Array Imaging of Parsec-scale Radio Emissions in Nearby Radio-quiet Narrow-line Seyfert 1 Galaxies
We conducted Very Long Baseline Array (VLBA) observations of seven nearby
narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz (18cm) with milli-arcsecond
resolution. This is the first systematic very long baseline interferometry
(VLBI) study focusing on the central parsec-scale regions of radio-quiet NLS1s.
Five of the seven were detected at a brightness temperature of >~5x10^6 K and
contain radio cores with high brightness temperatures of >6x10^7 K, indicating
a nonthermal process driven by jet-producing central engines as is observed in
radio-loud NLS1s and other active galactic nucleus (AGN) classes. VLBA images
of MRK 1239, MRK 705, and MRK 766 exhibit parsec-scale jets with clear linear
structures. A large portion of the radio power comes from diffuse emission
components that are distributed within the nuclear regions (<~300 pc), which is
a common characteristic throughout the observed NLS1s. Jet kinetic powers
limited by the Eddington limit may be insufficient to allow the jets escape to
kiloparsec scales for these radio-quiet NLS1s with low-mass black holes of
<~10^7 M_sun.Comment: 12 pages, 3 figures, 3 tables, accepted for publication in Ap
Bigradient Phase Referencing
We propose bigradient phase referencing (BPR), a new radio-observation
technique, and report its performance using the Japanese
very-long-baseline-interferometry network (JVN). In this method, a weak source
is detected by phase-referencing using a primary calibrator, in order to play a
role as a secondary calibrator for phase-referencing to a weak target. We will
be given the opportunity to select a calibrator from lots of milli-Jansky
sources, one of which may be located at the position closer to the target. With
such a smaller separation, high-quality phase-referencing can be achieved.
Furthermore, a subsequent more-sophisticated calibration can relocate array's
focus to a hypothetical point much closer to the target; a higher quality of
phase referencing is available. Our demonstrative observations with strong
radio sources have proved the capabilities of BPR in terms of image dynamic
ranges and astrometric reproducibility. The image dynamic range on a target has
been improved with a factor of about six compared to that of normal
phase-referencing; the resultant position difference of target's emission
between two epochs was only 62+-50 micro-arcsecond, even with less than 2300-km
baselines at 8.4 GHz and fast-switching of a target-calibrator pair of a
2.1-degree separation.Comment: 10 pages, 4 figures, accepted for publication in PAS
Short-Term Variability of PKS1510-089
We searched a short-term radio variability in an active galactic nucleus PKS
1510-089. A daily flux monitoring for 143 days at 8.4 GHz was performed, and
VLBI observations at 8.4, 22, and 43 GHz were carried out 4 times during the
flux monitoring period. As a result, variability with time scale of 20 to 30
days was detected. The variation patterns were well alike on three frequencies,
moreover those at 22 and 43 GHz were synchronized. These properties support
that this short-term variability is an intrinsic one. The Doppler factor
estimated from the variability time scale is 47. Since the Doppler factor is
not extraordinary large for AGN, such intrinsic variability with time scale
less than 30 days would exist in other AGNs.Comment: 14 pages, 4 figure
On the Characteristic Difference of Neoclassical Bootstrap Current and Its Effects on MHD Equilibria between CHS Heliotron/Torsatron and CHS-qa Quasi-Axisymmetric Stellarator
The characteristic difference of neoclassical bootstrap current and its effects on MHD equilibria are described for the CHS heliotron/torsatron and the CHS-qa quasi-axisymmetric stellarator. The direction of bootstrap current strongly depends on collisionality in CHS, whereas it does not in CHS-qa because of quasi-axisymmetry. In the CHS configuration, it appears that enhanced bumpy (Bs1) and sideband components of helical ripple (By1) play an important role in reducing the magnetic geometrical factor, which is a key factor in evaluating the value of bootstrap cuffent, and determining its polarity. The bootstrap current in CHS-qa is theoretically predicted to be larger than that in CHS and produces significant effects on the resulting rotational transform and magnetic shear. In the finite B plasmas, the magnetic well becomes deeper in both CHS and CHS-qa and its region is expanded in CHS. The existence of co-flowing bootstrap current makes the magnetic well shallow in comparison with that in currentless equilibrium
VLBI Monitoring of 3C 84 (NGC 1275) in Early Phase of the 2005 Outburst
Multi-epoch Very Long Baseline Interferometry (VLBI) study of the sub-pc
scale jet of 3C 84 is presented. We carried out 14-epoch VLBI observations
during 2006-2009 with the Japanese VLBI Network (JVN) and the VLBI Exploration
of Radio Astrometry (VERA), immediately following the radio outburst that began
in 2005. We confirmed that the outburst was associated with the central ~1 pc
core, accompanying the emergence of a new component. This is striking evidence
of the recurrence of jet activity. The new component became brighter during
2008, in contrast to the constant gamma-ray emission that was observed with the
Fermi Gamma-ray Space Telescope during the same time. We found that the
projected speed of the new component is 0.23c from 2007/297 (2007 October 24)
to 2009/114 (2009 April 24). The direction of movement of this component
differs from that of the pre-existing component by ~40 degree. This is the
first measurement of kinematics of a sub-pc jet in a gamma-ray active phase.
Possible detection of jet deceleration and the jet kinematics in connection
with the gamma-ray emission is discussed.Comment: 5 pages, 3 figures. Accepted for publication in PAS
Improved Path Planning of the Blade for an Automatic Spinach Harvester
ArticleIFAC-PapersOnLine. 53(2): 15816-15823. (2020)journal articl
Thioredoxin interacting protein protects mice from fasting induced liver steatosis by activating ER stress and its downstream signaling pathways
Under normal conditions, fasting results in decreased protein disulfide isomerase (PDI) activity and accumulation of unfolded proteins, leading to the subsequent activation of the unfolded protein response (UPR)/autophagy signaling pathway to eliminate damaged mitochondria. Fasting also induces upregulation of thioredoxin-interacting protein (TXNIP) expression and mice deficient of this protein (TXNIP-KO mice) was shown to develop severe hypoglycemia, hyperlipidemia and liver steatosis (LS). In the present study, we aimed to determine the role of TXNIP in fasting-induced LS by using male TXNIP-KO mice that developed LS without severe hypoglycemia. In TXNIP-KO mice, fasting induced severe microvesicular LS. Examinations by transmission electron microscopy revealed mitochondria with smaller size and deformities and the presence of few autophagosomes. The expression of beta-oxidation-associated genes remained at the same level and the level of LC3-II was low. PDI activity level stayed at the original level and the levels of p-IRE1 and X-box binding protein 1 spliced form (sXBP1) were lower. Interestingly, treatment of TXNIP-KO mice with bacitracin, a PDI inhibitor, restored the level of LC3-II after fasting. These results suggest that TXNIP regulates PDI activity and subsequent activation of the UPR/autophagy pathway and plays a protective role in fasting-induced LS
Development of LiDAR Based Navigation System for Automation of Tree Harvesting Process
This study focuses on an autonomous moving system for the automation of the harvesting process by high-performance machines in the forestry. Many fatal accidents occur due to the harvesting process. In this research, a navigation system has been developed to enable autonomous travel between accumulation sites and trees to be harvested to improve productivity and safety. A 3D map is generated by LiDAR observation, and harvester moves autonomously towards the tree as specified by the operator. A test of the harvesting process was performed in an experimental environment. The evaluation focused on the required time of the autonomous movement in the process. The effectiveness of the system was confirmed in operations such as row thinning by the results.The 2021 International Conference on Artificial Life and Robotics (ICAROB 2021), January 21-24, 2021, Higashi-Hiroshima (オンライン開催に変更
Cancer Cell-Derived Granulocyte-Macrophage Colony-Stimulating Factor Is Dispensable for the Progression of 4T1 Murine Breast Cancer
We previously reported that 4T1 murine breast cancer cells produce GM-CSF that up-regulates macrophage expression of several cancer promoting genes, including Mcp-1/Ccl2, Ccl17 and Rankl, suggesting a critical role of cancer cell-derived GM-CSF in cancer progression. Here, we attempted to define whether 4T1 cell-derived GM-CSF contributes to the expression of these genes by 4T1tumors, and their subsequent progression. Intraperitoneal injection of anti-GM-CSF neutralizing antibody did not decrease the expression of Mcp-1, Ccl17 or Rankl mRNA by 4T1 tumors. To further examine the role of cancer cell-derived GM-CSF, we generated GM-CSF-deficient 4T1 cells by using the Crisper-Cas9 system. As previously demonstrated, 4T1 cells are a mixture of cells and cloning of cells by itself significantly reduced tumor growth and lung metastasis. By contrast, GM-CSF-deficiency did not affect tumor growth, lung metastasis or the expression of these chemokine and cytokine genes in tumor tissues. By in-situ hybridization, the expression of Mcp-1 mRNA was detected in both F4/80-expressing and non-expressing cells in tumors of GM-CSF-deficient cells. These results indicate that cancer cell-derived GM-CSF is dispensable for the tuning of the 4T1 tumor microenvironment and the production of MCP-1, CCL17 or RANKL in the 4T1 tumor microenvironment is likely regulated by redundant mechanisms
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