27 research outputs found
Satellite-based In-situ Monitoring of Space Weather:
Many recent satellites have mission periods longer than 10 years; thus, satellite-based local space weather monitoring
is becoming more important than ever. This article describes the instruments and data applications of the Korea Space
wEather Monitor (KSEM), which is a space weather payload of the GeoKompsat-2A (GK-2A) geostationary satellite. The
KSEM payload consists of energetic particle detectors, magnetometers, and a satellite charging monitor. KSEM will provide
accurate measurements of the energetic particle flux and three-axis magnetic field, which are the most essential elements of
space weather events, and use sensors and external data such as GOES and DSCOVR to provide five essential space weather
products. The longitude of GK-2A is 128.2° E, while those of the GOES satellite series are 75° W and 135° W. Multi-satellite
measurements of a wide distribution of geostationary equatorial orbits by KSEM/GK-2A and other satellites will enable the
development, improvement, and verification of new space weather forecasting models. KSEM employs a service-oriented
magnetometer designed by ESA to reduce magnetic noise from the satellite in real time with a very short boom (1 m), which
demonstrates that a satellite-based magnetometer can be made simpler and more convenient without losing any performance
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As part of the next-generation Compact Advanced Satellite 500 (CAS500) project, CAS500-4 is scheduled to be launched in 2025 focusing on the remote sensing of agriculture and forestry. To obtain quantitative information on vegetation from satellite images, it is necessary to acquire surface reflectance through atmospheric correction. Thus, it is essential to develop an atmospheric correction method suitable for CAS500-4. Since the absorption and scattering characteristics in the atmosphere vary depending on the wavelength, it is needed to analyze the sensitivity of atmospheric correction parameters such as aerosol optical depth (AOD) and water vapor (WV) considering the wavelengths of CAS500-4. In addition, as CAS500-4 has only five channels (blue, green, red, red edge, and near-infrared), making it difficult to directly calculate key parameters for atmospheric correction, external parameter data should be used. Therefore, this study performed a sensitivity analysis of the key parameters (AOD, WV, and O3) using the simulated images based on Sentinel-2 satellite data, which has similar wavelength specifications to CAS500-4, and examined the possibility of using the products of GEOKOMPSAT-2A (GK2A) as atmospheric parameters. The sensitivity analysis showed that AOD was the most important parameter with greater sensitivity in visible channels than in the near-infrared region. In particular, since AOD change of 20% causes about a 100% error rate in the blue channel surface reflectance in forests, a highly reliable AOD is needed to obtain accurate surface reflectance. The atmospherically corrected surface reflectance based on the GK2A AOD and WV was compared with the Sentinel-2 L2A reflectance data through the separability index of the known land cover pixels. The result showed that two corrected surface reflectance had similar Seperability index (SI) values, the atmospheric corrected surface reflectance based on the GK2A AOD showed higher SI than the Sentinel-2 L2A reflectance data in short-wavelength channels. Thus, it is judged that the parameters provided by GK2A can be fully utilized for atmospheric correction of the CAS500-4. The research findings will provide a basis for atmospheric correction of the CAS500-4 in the future. ?? This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited
The shadow knows: using shadows to investigate the structure of the pretransitional disk of HD 100453
We present GPI polarized intensity imagery of HD 100453 in Y-, J-, and K1
bands which reveals an inner gap ( au), an outer disk ( au) with
two prominent spiral arms, and two azimuthally-localized dark features also
present in SPHERE total intensity images (Wagner 2015). SED fitting further
suggests the radial gap extends to au. The narrow, wedge-like shape of the
dark features appears similar to predictions of shadows cast by a inner disk
which is misaligned with respect to the outer disk. Using the Monte Carlo
radiative transfer code HOCHUNCK3D (Whitney 2013), we construct a model of the
disk which allows us to determine its physical properties in more detail. From
the angular separation of the features we measure the difference in inclination
between the disks 45, and their major axes, PA = 140 east
of north for the outer disk and 100for the inner disk. We find an
outer disk inclination of from face-on in broad agreement
with the Wagner 2015 measurement of 34. SPHERE data in J- and H-bands
indicate a reddish disk which points to HD 100453 evolving into a young debris
disk
Beclin 1 functions as a negative modulator of MLKL oligomerisation by integrating into the necrosome complex
Necroptosis is a form of regulated cell death caused by formation of the necrosome complex. However, the factors modulating this process and the systemic pathophysiological effects of necroptosis are yet to be understood. Here, we identified that Beclin 1 functions as an anti-necroptosis factor by being recruited into the necrosome complex upon treatment with TNF alpha, Smac mimetic, and pan-caspase inhibitor and by repressing MLKL oligomerisation, thus preventing the disruption of the plasma membrane. Cells ablated or knocked-out for Beclin 1 become sensitised to necroptosis in an autophagy-independent manner without affecting the necrosome formation itself. Interestingly, the recruitment of Beclin 1 into the necrosome complex is dependent on the activation and phosphorylation of MLKL. Biochemically, the coiled-coil domain (CCD) of Beclin 1 binds to the CCD of MLKL, which restrains the oligomerisation of phosphorylated MLKL. Finally, Beclin 1 depletion was found to promote necroptosis in leukaemia cells and enhance regression of xenografted-tumour upon treatment with Smac mimetics and caspase inhibitors. These results suggest that Beclin 1 functions as a negative regulator in the execution of necroptosis by suppressing MLKL oligomerisation
Near-Infrared Imaging Polarimetry of Inner Region of GG Tau A Disk
By performing non-masked polarization imaging with Subaru/HiCIAO, polarized
scattered light from the inner region of the disk around the GG Tau A system
was successfully detected in the band with a spatial resolution of
approximately 0.07\arcsec, revealing the complicated inner disk structures
around this young binary. This paper reports the observation of an arc-like
structure to the north of GG Tau Ab and part of a circumstellar structure that
is noticeable around GG Tau Aa extending to a distance of approximately 28 AU
from the primary star. The speckle noise around GG Tau Ab constrains its disk
radius to <13 AU. Based on the size of the circumbinary ring and the
circumstellar disk around GG Tau Aa, the semi-major axis of the binary's orbit
is likely to be 62 AU. A comparison of the present observations with previous
ALMA and near-infrared (NIR) H emission observations suggests that the
north arc could be part of a large streamer flowing from the circumbinary ring
to sustain the circumstellar disks. According to the previous studies, the
circumstellar disk around GG Tau Aa has enough mass and can sustain itself for
a duration sufficient for planet formation; thus, our study indicates that
planets can form within close (separation 100 AU) young binary
systems.Comment: Accepted for publication in AJ, 12 pages, 5 figure
A Substellar Companion to Pleiades HII 3441
We find a new substellar companion to the Pleiades member star, Pleiades HII
3441, using the Subaru telescope with adaptive optics. The discovery is made as
part of the high-contrast imaging survey to search for planetary-mass and
substellar companions in the Pleiades and young moving groups. The companion
has a projected separation of 0".49 +/- 0".02 (66 +/- 2 AU) and a mass of 68
+/- 5 M_J based on three observations in the J-, H-, and K_S-band. The spectral
type is estimated to be M7 (~2700 K), and thus no methane absorption is
detected in the H band. Our Pleiades observations result in the detection of
two substellar companions including one previously reported among 20 observed
Pleiades stars, and indicate that the fraction of substellar companions in the
Pleiades is about 10.0 +26.1/-8.8 %. This is consistent with multiplicity
studies of both the Pleiades stars and other open clusters.Comment: Main text (14 pages, 4 figures, 4 tables), and Supplementary data (8
pages, 3 tables). Accepted for Publications of Astronomical Society of Japa
Identification of MYC as an antinecroptotic protein that stifles RIPK1-RIPK3 complex formation
The underlying mechanism of necroptosis in relation to cancer is still unclear. Here, MYC, a potent oncogene, is an antinecroptotic factor that directly suppresses the formation of the RIPK1-RIPK3 complex. Gene set enrichment analyses reveal that the MYC pathway is the most prominently down-regulated signaling pathway during necroptosis. Depletion or deletion of MYC promotes the RIPK1-RIPK3 interaction, thereby stabilizing the RIPK1 and RIPK3 proteins and facilitating necroptosis. Interestingly, MYC binds to RIPK3 in the cytoplasm and inhibits the interaction between RIPK1 and RIPK3 in vitro. Furthermore, MYC-nick, a truncated form that is mainly localized in the cytoplasm, prevented TNF-induced necroptosis. Finally, down-regulation of MYC enhances necroptosis in leukemia cells and suppresses tumor growth in a xenograft model upon treatment with birinapant and emricasan. MYC-mediated suppression of necroptosis is a mechanism of necroptosis resistance in cancer, and approaches targeting MYC to induce necroptosis represent an attractive therapeutic strategy for cancer
High-contrast Polarimetry Observation of T Tau Circumstellar Environment
We conducted high-contrast polarimetry observations of T Tau in the H-band,
using the HiCIAO instrument mounted on the Subaru Telescope, revealing
structures as near as 0.\arcsec1 from the stars T Tau N and T Tau S. The
whole T Tau system is found to be surrounded by nebula-like envelopes, and
several outflow-related structures are detected in these envelopes. We analyzed
the detailed polarization patterns of the circumstellar structures near each
component of this triple young star system and determined constraints on the
circumstellar disks and outflow structures. We suggest that the nearly face-on
circumstellar disk of T Tau N is no larger than 0.\arcsec8, or 117 AU, in the
northwest, based on the existence of a hole in this direction, and no larger
than 0.\arcsec27, or 40 AU, in the south. A new structure "N5" extends to
about 0.\arcsec42, or 59 AU, on the southwest of the star, believed to be
part of the disk. We suggest that T Tau S is surrounded by a highly inclined
circumbinary disk with a radius of about 0.\arcsec3, or 44 AU, with a
position angle of about 30, that is misaligned with the orbit of the T
Tau S binary. After analyzing the positions and polarization vector patterns of
the outflow-related structures, we suggest that T Tau S should trigger the
well-known E-W outflow, and is also likely to be responsible for a southwest
precessing outflow "coil" and a possible south outflow.Comment: 12 pages, 6 figures, accepted by The Astrophysical Journa