409 research outputs found
Astrometry of HO Masers in Nearby Star-Forming Regions with VERA --- IV. L1448C
We have carried out multi-epoch VLBI observations with VERA (VLBI Exploration
of Radio Astrometry) of the 22~GHz HO masers associated with a Class 0
protostar L1448C in the Perseus molecular cloud. The maser features trace the
base of collimated bipolar jet driven by one of the infrared counter parts of
L1448C named as L1448C(N) or L1448-mm A. We detected possible evidences for
apparent acceleration and precession of the jet according to the
three-dimensional velocity structure. Based on the phase-referencing VLBI
astrometry, we have successfully detected an annual parallax of the HO
maser in L1448C to be 4.310.33~milliarcseconds (mas) which corresponds to
a distance of 23218~pc from the Sun. The present result is in good
agreement with that of another HO maser source NGC~1333 SVS13A in the
Perseus molecular cloud, 235~pc. It is also consistent with the photometric
distance, 220~pc. Thus, the distance to the western part of the Perseus
molecular cloud complex would be constrained to be about 235~pc rather than the
larger value, 300~pc, previously reported.Comment: 15 pages, 5 figures, accepted for publication in PAS
Copper-catalyzed site-selective direct arylation of triptycene
A site-selective direct CH arylation protocol for the triptycene skeleton is developed using copper catalyst and diaryliodonium reagents. With the aid of directing groups, C₃-symmetric trisubstituted triptycenes are selectively synthesized, and the structure was determined by X-ray diffraction analysis. Further derivatization of the installed bromo functionalities is also described
Electrophilic substitution of asymmetrically distorted benzenes within triptycene derivatives
Herein we disclose a unique directing effect of 9-substituted triptycenes in electrophilic substitution to achieve the regioselective functionalization of the triptycene core. The Hirshfeld population analysis was adopted to predict the selectivity in electrophilic substitution. TMS and t-Bu groups were found to considerably accelerate the reaction at C2 positions to produce C3-symmetric isomers. Correlation between distortion and charge distribution within benzene rings was systematically examined.Ueno K., Nishii Y., Miura M.. Electrophilic substitution of asymmetrically distorted benzenes within triptycene derivatives. Organic Letters. 23(9), 3552-3556, (2021), 7 May 2021; ©2021 American Chemical Society. https://doi.org/10.1021/acs.orglett.1c00970
H2O maser motions and the distance of the star forming region G192.16-3.84
We present the results of astrometic observations of H2O masers associated
with the star forming region G192.16-3.84 with the VLBI Exploration of Radio
Astrometry (VERA). The H2O masers seem to be associated with two young stellar
objects (YSOs) separated by \sim1200 AU as reported in previous observations.
In the present observations, we successfully detected an annual parallax of
0.66 \pm 0.04 mas for the H2 O masers, which corresponds to a distance to
G192.16-3.84 of D = 1.52 \pm 0.08 kpc from the Sun. The determined distance is
shorter than the estimated kinematic distance. Using the annual parallax
distance and the estimated parameters of the millimeter continuum emission, we
estimate the mass of the disk plus circumstellar cloud in the southern young
stellar object to be 10.0+4.3M\cdot. We also estimate the galactocentric
distance and the peculiar motion -3.6 of G192.16-3.84, relative to a circular
Galactic rotation: R\star = 9.99 \pm 0.08 kpc, Z\star = -0.10 \pm 0.01 kpc, and
(U\star,V\star,W\star)=(-2.8\pm1.0,-10.5\pm0.3,4.9\pm2.7)[kms-1]respectively.
The peculiar motion of G192.16-3.84 is within that typically found in recent
VLBI astrometric results. The angular distribution and three-dimensional
velocity field of H2O maser features associated with the northern YSO indicate
the existence of a bipolar outflow with a major axis along the
northeast-southwest direction.Comment: 9 pages, 2 figures and 4 tables. Accepted for publication on PAS
Focal Myasthenia Gravis in Two Dogs
Two dogs were presented with history of regurgitation. Both dogs were diagnosed with focal myasthenia gravis (FMG). Thoracic radiography was consisted with megaesophagus. Acetylcholine receptors (AChRs) antibody titer was positive. Both dogs were treated with pyridostigmine bromide as sole treatment. One case rapidly resolved with the recovery of the esophagus, while the other case even the AChRs antibody titer was normalized after 60 days but the clinical remission was occurred after long time. This report suggested that clinical signs of FMG were resolved, but we can’t predict the time required, additionally, pyridostigmine bromide might be effective for palliation of symptoms
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