59 research outputs found
First detection of 22 GHz H2O masers in TX Camelopardalis
Simultaneous time monitoring observations of HO , SiO
= 1--0, 2--1, 3--2, and SiO = 0, = 1--0 lines were carried
out in the direction of the Mira variable star TX Cam with the Korean VLBI
Network single dish radio telescopes. For the first time, the HO maser
emission from TX Cam was detected near the stellar velocity at five epochs from
April 10, 2013 ( = 3.13) to June 4, 2014 ( = 3.89) including
minimum optical phases. The intensities of HO masers are very weak
compared to SiO masers. The variation of peak antenna temperature ratios among
SiO = 1, = 1--0, = 2--1, and = 3--2 masers is investigated
according to their phases. The shift of peak velocities of HO and SiO
masers with respect to the stellar velocity is also investigated according to
observed optical phases. The HO maser emission occurs around the stellar
velocity during our monitoring interval. On the other hand, the peak velocities
of SiO masers show a spread compared to the stellar velocity. The peak
velocities of SiO = 2--1, and = 3--2 masers show a smaller spread with
respect to the stellar velocity than those of SiO = 1--0 masers. These
simultaneous observations of multi-frequencies will provide a good constraint
for maser pumping models and a good probe for investigating the stellar
atmosphere and envelope according to their different excitation conditions.Comment: 10 page
Selective inference for clustering with unknown variance
In many modern statistical problems, the limited available data must be used
both to develop the hypotheses to test, and to test these hypotheses-that is,
both for exploratory and confirmatory data analysis. Reusing the same dataset
for both exploration and testing can lead to massive selection bias, leading to
many false discoveries. Selective inference is a framework that allows for
performing valid inference even when the same data is reused for exploration
and testing. In this work, we are interested in the problem of selective
inference for data clustering, where a clustering procedure is used to
hypothesize a separation of the data points into a collection of subgroups, and
we then wish to test whether these data-dependent clusters in fact represent
meaningful differences within the data. Recent work by Gao et al. [2022]
provides a framework for doing selective inference for this setting, where a
hierarchical clustering algorithm is used for producing the cluster
assignments, which was then extended to k-means clustering by Chen and Witten
[2022]. Both these works rely on assuming a known covariance structure for the
data, but in practice, the noise level needs to be estimated-and this is
particularly challenging when the true cluster structure is unknown. In our
work, we extend this work to the setting of noise with unknown variance, and
provide a selective inference method for this more general setting. Empirical
results show that our new method is better able to maintain high power while
controlling Type I error when the true noise level is unknown
Simultaneous VLBI Astrometry of H2O and SiO Masers toward the Semiregular Variable R Crateris
We obtained, for the first time, astrometrically registered maps of the 22.2
GHz H2O and 42.8, 43.1, and 86.2 GHz SiO maser emission toward the semiregular
b-type variable (SRb) R Crateris, at three epochs (2015 May 21, and 2016
January 7 and 26) using the Korean Very-long-baseline Interferometry Network.
The SiO masers show a ring-like spatial structure, while the H2O maser shows a
very asymmetric one-side outflow structure, which is located at the southern
part of the ring-like SiO maser feature. We also found that the 86.2 GHz SiO
maser spots are distributed in an inner region, compared to those of the 43.1
GHz SiO maser, which is different from all previously known distributions of
the 86.2 GHz SiO masers in variable stars. The different distribution of the
86.2 GHz SiO maser seems to be related to the complex dynamics caused by the
overtone pulsation mode of the SRb R Crateris. Furthermore, we estimated the
position of the central star based on the ring fitting of the SiO masers, which
is essential for interpreting the morphology and kinematics of a circumstellar
envelope. The estimated stellar coordinate corresponds well to the position
measured by Gaia
Asymmetric distributions of H2O and SiO masers towards V627 Cas
We performed simultaneous observations of the H2O 6(1,6) - 5(2,3) (22.235080
GHz) and SiO v= 1, 2, J = 1 - 0, SiO v = 1, J = 2 - 1, 3 - 2 (43.122080,
42.820587, 86.243442, and 129.363359 GHz) masers towards the suspected D-type
symbiotic star, V627 Cas, using the Korean VLBI Network. Here, we present
astrometrically registered maps of the H2O and SiO v = 1, 2, J = 1 - 0, SiO v =
1, J = 2 - 1 masers for five epochs from January 2016 to June 2018.
Distributions of the SiO maser spots do not show clear ring-like structures,
and those of the H2O maser are biased towards the north-north-west to west with
respect to the SiO maser features according to observational epochs. These
asymmetric distributions of H2O and SiO masers are discussed based on two
scenarios of a bipolar outflow and the presence of the hot companion, a white
dwarf, in V627 Cas. We carried out ring fitting of SiO v = 1, and v = 2 masers
and estimated the expected position of the cool red giant. The ring radii of
the SiO v = 1 maser are slightly larger than those of the SiO v = 2 maser, as
previously known. Our assumption for the physical size of the SiO maser ring of
V627 Cas to be the typical size of a SiO maser ring radius (\sim4 au) of red
giants yields the distance of V627 Cas to be \sim1 kpc.Comment: 7 pages, 4 figures, 1 table, Published in MNRA
Role of kif2c, A Gene Related to ALL Relapse, in Embryonic Hematopoiesis in Zebrafish
Relapse of acute lymphoblastic leukemia (ALL) is dangerous and it worsens the prognosis of patients; however, prognostic markers or therapeutic targets for ALL remain unknown. In the present study, using databases such as TARGET, GSE60926 and GSE28460, we determined that KIF2C and its binding partner, KIF18B are overexpressed in patients with relapsed ALL compared to that in patients diagnosed with ALL for the first time. As 50% of the residues are exactly the same and the signature domain of KIF2C is highly conserved between human and zebrafish, we used zebrafish embryos as a model to investigate the function of kif2c in vivo. We determined that kif2c is necessary for lymphopoiesis in zebrafish embryos. Additionally, we observed that kif2c is not related to differentiation of HSCs; however, it is important for the maintenance of HSCs as it provides survival signals to HSCs. These results imply that the ALL relapse-related gene KIF2C is linked to the survival of HSCs. In conclusion, we suggest that KIF2C can serve as a novel therapeutic target for relapsed ALL
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