34 research outputs found
Astrometry of Water Maser Sources in Nearby Molecular Clouds with VERA - II. SVS 13 in NGC 1333
We report on the results of multi-epoch VLBI observations with VERA (VLBI
Exploration of Radio Astrometry) of the 22 GHz H2O masers associated with the
young stellar object SVS 13 in the NGC 1333 region. We have carried out
phase-referencing VLBI astrometry and measured an annual parallax of the maser
features in SVS 13 of 4.25+/-0.32 mas, corresponding to the distance of
235+/-18 pc from the Sun. Our result is consistent with a photometric distance
of 220 pc previously reported. Even though the maser features were detectable
only for 6 months, the present results provide the distance to NGC 1333 with
much higher accuracy than photometric methods. The absolute positions and
proper motions have been derived, revealing that the H2O masers with the LSR
(local standard of rest) velocities of 7-8 km s-1 are most likely associated
with VLA4A, which is a radio counterpart of SVS 13. The origin of the observed
proper motions of the maser features are currently difficult to attribute to
either the jet or the rotating circumstellar disk associated with VLA4A, which
should be investigated through future high-resolution astrometric observations
of VLA4A and other radio sources in NGC 1333.Comment: 9 pages, 5 figures. PASJ, in press (2008, Vol. 60, No. 1
Astrometry of Galactic Star Forming Region Sharpless 269 with VERA : Parallax Measurements and Constraint on Outer Rotation Curve
We have performed high-precision astrometry of H2O maser sources in Galactic
star forming region Sharpless 269 (S269) with VERA. We have successfully
detected a trigonometric parallax of 189+/-8 micro-arcsec, corresponding to the
source distance of 5.28 +0.24/-0.22 kpc. This is the smallest parallax ever
measured, and the first one detected beyond 5 kpc. The source distance as well
as proper motions are used to constrain the outer rotation curve of the Galaxy,
demonstrating that the difference of rotation velocities at the Sun and at S269
(which is 13.1 kpc away from the Galaxy's center) is less than 3%. This gives
the strongest constraint on the flatness of the outer rotation curve and
provides a direct confirmation on the existence of large amount of dark matter
in the Galaxy's outer disk.Comment: 7 pages and 4 figures, Accepted by PASJ (Vol. 59, No. 5, October 25,
2007 issue
Distance to Orion KL Measured with VERA
We present the initial results of multi-epoch VLBI observations of the 22 GHz
H2O masers in the Orion KL region with VERA (VLBI Exploration of Radio
Astrometry). With the VERA dual-beam receiving system, we have carried out
phase-referencing VLBI astrometry and successfully detected an annual parallax
of Orion KL to be 2.29+/-0.10 mas, corresponding to the distance of 437+/-19 pc
from the Sun. The distance to Orion KL is determined for the first time with
the annual parallax method in these observations. Although this value is
consistent with that of the previously reported, 480+/-80 pc, which is
estimated from the statistical parallax method using proper motions and radial
velocities of the H2O maser features, our new results provide the much more
accurate value with an uncertainty of only 4%. In addition to the annual
parallax, we have detected an absolute proper motion of the maser feature,
suggesting an outflow motion powered by the radio source I along with the
systematic motion of source I itself.Comment: 7 pages, 3 figures. PASJ, in press (Vol. 59, No. 5, October 25, 2007
issue
Absolute Proper Motions of H2O Masers Away from the Galactic Plane Measured with VERA in the "Superbubble" Region NGC 281
We report on absolute proper-motion measurements of an H2O maser source in
the NGC 281 West molecular cloud, which is located ~320 pc above the Galactic
plane and is associated with an HI loop extending from the Galactic plane. We
have conducted multi-epoch phase-referencing observations of the maser source
with VERA (VLBI Exploration of Radio Astrometry) over a monitoring period of 6
months since May 2006. We find that the H2O maser features in NGC 281 West are
systematically moving toward the southwest and further away from the Galactic
plane with a vertical velocity of ~20-30 km/s at its estimated distance of
2.2-3.5 kpc. Our new results provide the most direct evidence that the gas in
the NGC 281 region on the HI loop was blown out from the Galactic plane, most
likely in a superbubble driven by multiple or sequential supernova explosions
in the Galactic plane.Comment: 10 pages, 5 figures, PASJ in press (Vol. 59, No. 4; August 25, 2007
issue
VLBI Astrometry of AGB Variables with VERA -- A Semiregular Variable S Crateris --
We present a distance measurement for the semiregular variable S Crateris (S
Crt) based on its annual parallax. With the unique dual beam system of the VLBI
Exploration for Radio Astrometry (VERA) telescopes, we measured the absolute
proper motion of a water maser spot associated with S Crt, referred to the
quasar J1147-0724 located at an angular separation of 1.23. In
observations spanning nearly two years, we have detected the maser spot at the
LSR velocity of 34.7 km s, for which we measured the annual parallax of
2.330.13 mas corresponding to a distance of 430 pc. This
measurement has an accuracy one order of magnitude better than the parallax
measurements of HIPPARCOS. The angular distribution and three-dimensional
velocity field of maser spots indicate a bipolar outflow with the flow axis
along northeast-southwest direction. Using the distance and photospheric
temperature, we estimate the stellar radius of S Crt and compare it with those
of Mira variables.Comment: 9 pages, 4 figures, accepted for publication in PASJ (Vol.60, No.5,
October 25, VERA special issue
Allosteric regulation by cooperative conformational changes of actin filaments drives mutually exclusive binding with cofilin and myosin
Heavy meromyosin (HMM) of myosin II and cofilin each binds to actin filaments cooperatively and forms clusters along the filaments, but it is unknown whether the two cooperative bindings are correlated and what physiological roles they have. Fluorescence microscopy demonstrated that HMM-GFP and cofilin-mCherry each bound cooperatively to different parts of actin filaments when they were added simultaneously in 0.2 μM ATP, indicating that the two cooperative bindings are mutually exclusive. In 0.1 mM ATP, the motor domain of myosin (S1) strongly inhibited the formation of cofilin clusters along actin filaments. Under this condition, most actin protomers were unoccupied by S1 at any given moment, suggesting that transiently bound S1 alters the structure of actin filaments cooperatively and/or persistently to inhibit cofilin binding. Consistently, cosedimentation experiments using copolymers of actin and actin-S1 fusion protein demonstrated that the fusion protein affects the neighboring actin protomers, reducing their affinity for cofilin. In reciprocal experiments, cofilin-actin fusion protein reduced the affinity of neighboring actin protomers for S1. Thus, allosteric regulation by cooperative conformational changes of actin filaments contributes to mutually exclusive cooperative binding of myosin II and cofilin to actin filaments, and presumably to the differential localization of both proteins in cells
Distance to VY Canis Majoris with VERA
We report astrometric observations of H2O masers around the red supergiant VY
Canis Majoris (VY CMa) carried out with VLBI Exploration of Radio Astrometry
(VERA). Based on astrometric monitoring for 13 months, we successfully measured
a trigonometric parallax of 0.88 +/- 0.08 mas, corresponding to a distance of
1.14 +0.11/-0.09 kpc. This is the most accurate distance to VY CMa and the
first one based on an annual parallax measurement. The luminosity of VY CMa has
been overestimated due to a previously accepted distance. With our result, we
re-estimate the luminosity of VY CMa to be (3 +/- 0.5) x 10^5 L_sun using the
bolometric flux integrated over optical and IR wavelengths. This improved
luminosity value makes location of VY CMa on the Hertzsprung-Russel (HR)
diagram much closer to the theoretically allowable zone (i.e. the left side of
the Hayashi track) than previous ones, though uncertainty in the effective
temperature of the stellar surface still does not permit us to make a final
conclusion.Comment: 7 pages, 4 figures, accepted for publication in PASJ, VERA special
issu
Astrometry of HO Masers in Nearby Star-Forming Regions with VERA. III. IRAS 22198+6336 in L1204G
We present results of multi-epoch VLBI observations with VERA (VLBI
Exploration of Radio Astrometry) of the 22 GHz HO masers associated with
a young stellar object (YSO) IRAS 22198+6336 in a dark cloud L1204G. Based on
the phase-referencing VLBI astrometry, we derive an annual parallax of IRAS
22198+6336 to be 1.3090.047 mas, corresponding to the distance of
76427 pc from the Sun. Although the most principal error source of our
astrometry is attributed to the internal structure of the maser spots, we
successfully reduce the errors in the derived annual parallax by employing the
position measurements for all of the 26 detected maser spots. Based on this
result, we reanalyze the spectral energy distribution (SED) of IRAS 22198+6336
and find that the bolometric luminosity and total mass of IRAS 22198+6336 are
450 and 7, respectively. These values are consistent with
an intermediate-mass YSO deeply embedded in the dense dust core, which has been
proposed to be an intermediate-mass counterpart of a low-mass Class 0 source.
In addition, we obtain absolute proper motions of the HO masers for the
most blue-shifted components. We propose that the collimated jets aligned along
the east-west direction are the most plausible explanation for the origin of
the detected maser features.Comment: 15 pages, 7 figures, accepted for publication in PASJ (Vol.60, No.5,
October 25, VERA special issue
DOCK2 is involved in the host genetics and biology of severe COVID-19
「コロナ制圧タスクフォース」COVID-19疾患感受性遺伝子DOCK2の重症化機序を解明 --アジア最大のバイオレポジトリーでCOVID-19の治療標的を発見--. 京都大学プレスリリース. 2022-08-10.Identifying the host genetic factors underlying severe COVID-19 is an emerging challenge. Here we conducted a genome-wide association study (GWAS) involving 2, 393 cases of COVID-19 in a cohort of Japanese individuals collected during the initial waves of the pandemic, with 3, 289 unaffected controls. We identified a variant on chromosome 5 at 5q35 (rs60200309-A), close to the dedicator of cytokinesis 2 gene (DOCK2), which was associated with severe COVID-19 in patients less than 65 years of age. This risk allele was prevalent in East Asian individuals but rare in Europeans, highlighting the value of genome-wide association studies in non-European populations. RNA-sequencing analysis of 473 bulk peripheral blood samples identified decreased expression of DOCK2 associated with the risk allele in these younger patients. DOCK2 expression was suppressed in patients with severe cases of COVID-19. Single-cell RNA-sequencing analysis (n = 61 individuals) identified cell-type-specific downregulation of DOCK2 and a COVID-19-specific decreasing effect of the risk allele on DOCK2 expression in non-classical monocytes. Immunohistochemistry of lung specimens from patients with severe COVID-19 pneumonia showed suppressed DOCK2 expression. Moreover, inhibition of DOCK2 function with CPYPP increased the severity of pneumonia in a Syrian hamster model of SARS-CoV-2 infection, characterized by weight loss, lung oedema, enhanced viral loads, impaired macrophage recruitment and dysregulated type I interferon responses. We conclude that DOCK2 has an important role in the host immune response to SARS-CoV-2 infection and the development of severe COVID-19, and could be further explored as a potential biomarker and/or therapeutic target