393 research outputs found
EFSO at different geographical locations verified with observing-system experiments
ひとつひとつの観測データが気象予測に与える影響を簡易に評価する手法を確認 --北極の観測データは7日先の北米気象予測の改善に貢献することも明らかに--. 京都大学プレスリリース. 2021-04-30.An ensemble-based forecast sensitivity to observations (EFSO) diagnosis has been implemented in an atmospheric general circulation model–ensemble Kalman filter data assimilation system to estimate the impacts of specific observations from the quasi-operational global observing system on weekly short-range forecasts. It was examined whether EFSO reasonably approximates the impacts of a subset of observations from specific geographical locations for 6-hour forecasts, and how long the 6-hour observation impacts can be retained during the 7-day forecast period. The reference for these forecasts was obtained from 12 data denial experiments in each of which a subset of three radiosonde observations launched from a geographical location was excluded. The 12 locations were selected from three latitudinal bands comprising (i) four Arctic regions, (ii) four midlatitude regions in the Northern Hemisphere, and (iii) four tropical regions during the Northern Hemisphere winter of 2015/16. The estimated winter-averaged EFSO-derived observation impacts well corresponded to the 6-hour observation impacts obtained by the data denials and EFSO could reasonably estimate the observation impacts by the data denials on short-range (6-hour to 2-day) forecasts. Furthermore, during the medium-range (4-day to 7-day) forecasts, it was found that the Arctic observations tend to seed the broadest impacts and their short-range observation impacts could be projected to beneficial impacts in Arctic and midlatitude North American areas. The midlatitude area located just downstream of dynamical propagation from the Arctic toward the midlatitudes. Results obtained by repeated Arctic data-denial experiments were found to be generally common to those from the non-repeated experiments
Rayleigh-Taylor Instabilities in Type Ia Supernova Remnants undergoing Cosmic-Ray Particle Acceleration - Low Adiabatic Index Solutions
This study investigates the evolution of Rayleigh-Taylor (R-T) instabilities
in Type Ia supernova remnants that are associated with a low adiabatic index
gamma, where gamma < 5/3, which reflects the expected change in the supernova
shock structure as a result of cosmic-ray particle acceleration. Extreme cases,
such as the case with the maximum compression ratio that corresponds to
gamma=1.1, are examined. As gamma decreases, the shock compression ratio rises,
and an increasingly narrow inter shock region with a more pronounced initial
mixture of R-T unstable gas is produced. Consequently, the remnant outline may
be perturbed by small-amplitude, small-wavelength bumps. However, as the
instability decays over time, the extent of convective mixing in terms of the
ratio of the radius of the R-T fingers to the blast wave does not strongly
depend on the value of gamma for gamma >= 1.2. As a result of the age of the
remnant, the unstable gas cannot extend sufficiently far to form metal-enriched
filaments of ejecta material close to the periphery of Tycho's supernova
remnant. The consistency of the dynamic properties of Tycho's remnant with the
adiabatic model gamma=5/3 reveals that the injection of cosmic rays is too weak
to alter the shock structure. Even with very efficient acceleration of cosmic
rays at the shock, significantly enhanced mixing is not expected in Type Ia
supernova remnants.Comment: 11 pages, 10 figures, MNRAS, accepte
Impact of radiosonde data over the Arctic Ocean on atmospheric circulation at high latitudes
第3回極域科学シンポジウム/特別セッション「これからの北極研究」11月28日(水) 国立極地研究所 2階大会議
SOD1 Is Essential for the Viability of DT40 Cells and Nuclear SOD1 Functions as a Guardian of Genomic DNA
Reactive oxygen species (ROSs) are produced during normal cellular metabolism, particularly by respiration in mitochondria, and these ROSs are considered to cause oxidative damage to macromolecules, including DNA. In our previous paper, we found no indication that depletion of mitochondrial superoxide dismutase, SOD2, resulted in an increase in DNA damage. In this paper, we examined SOD1, which is distributed in the cytoplasm, nucleus, and mitochondrial intermembrane space. We generated conditional SOD1 knockout cells from chicken DT40 cells and analyzed their phenotypes. The results revealed that SOD1 was essential for viability and that depletion of SOD1, especially nuclear SOD1, increased sister chromatid exchange (SCE) frequency, suggesting that superoxide is generated in or near the nucleus and that nuclear SOD1 functions as a guardian of the genome. Furthermore, we found that ascorbic acid could offset the defects caused by SOD1 depletion, including cell lethality and increases in SCE frequency and apurinic/apyrimidinic sites
Non-thermal emission from old supernova remnants
We study the non-thermal emission from old shell-type supernova remnants
(SNRs) on the frame of a time-dependent model. In this model, the
time-dependent non-thermal spectra of both primary electrons and protons as
well as secondary electron/positron () pairs can be calculated
numerically by taking into account the evolution of the secondary
pairs produced from proton-proton (p-p) interactions due to the accelerated
protons collide with the ambient matter in an SNR. The multi-wavelength photon
spectrum for a given SNR can be produced through leptonic processes such as
electron/positron synchrotron radiation, bremsstrahlung and inverse Compton
scattering as well as hadronic interaction. Our results indicate that the
non-thermal emission of the secondary pairs is becoming more and more
prominent when the SNR ages in the radiative phase because the source of the
primary electrons has been cut off and the electron synchrotron energy loss is
significant for a radiative SNR, whereas the secondary pairs can be
produced continuously for a long time in the phase due to the large energy loss
time for the p-p interaction. We apply the model to two old SNRs, G8.70.1
and G23.30.3, and the predicted results can explain the observed
multi-wavelength photon spectra for the two sources.Comment: 11 pages, 7 figures, accepted for publication in MNRA
Methodology for Analyzing Coupling Mechanisms in RFI Problems based on PEEC
In This Article, a Method for Analyzing Coupling Mechanisms in Radio Frequency Interference (RFI) Problems is Proposed. the Partial Element Equivalent Circuit (PEEC) Method is First Used to Derive the Retarded Inductances and Capacitances between Different Mesh Cells. with the Introduction of a Novel Partitioning Algorithm, the Capacitive Coupling and Inductive Coupling between Arbitrary Layout Parts Can Be Quantified based on the Magnitude of the Displacement Current and Induced Voltage Drop. the Accuracy of the PEEC Models is Validated by Comparison with Different Commercial Tools. the Proposed Coupling Mechanism Analysis Flow Provides a Useful Prelayout Tool for RFI Risk Analysis
Expression of leptin receptors in hepatic sinusoidal cells
Emerging evidence has suggested a critical role of leptin in hepatic inflammation and fibrogenesis, however, the precise mechanisms underlying the profibrogenic action of leptin in the liver has not been well elucidated. Therefore, the present study was designed to investigate the expression and functions of leptin receptors (Ob-R) in hepatic sinusoidal cells. Hepatic stellate cells (HSCs), Kupffer cells and sinusoidal endothelial cells (SECs) were isolated from rat livers by in situ collagenase perfusion followed by differential centrifugation technique, and expression of Ob-Ra and Ob-Rb, short and long Ob-R isoforms, respectively, were analyzed by RT-PCR. Ob-Ra mRNA was detected ubiquitously in HSCs and SECs. In contrast, Ob-Rb was detected clearly only in SECs and Kupffer cells, but not in 7-day cultured HSCs. Indeed, tyrosine-phosphorylation of STAT-3, a downstream event of Ob-Rb signaling, was observed in SECs, but not in HSCs, 1 hr after incubation with leptin. Further, leptin increased AP-1 DNA binding activity and TGF-beta 1 mRNA levels in Kupffer cells and SECs, whereas leptin failed to increase TGF-beta 1 mRNA in HSCs. These findings indicated that SECs and Kupffer cells, but not HSCs, express functional leptin receptors, through which leptin elicits production of TGF-beta 1. It is hypothesized therefore that leptin, produced systemically from adipocytes and locally from HSCs, up-regulates TGF-beta 1 thereby facilitate tissue repairing and fibrogenesis in the sinusoidal microenvironment
Neutrino emission of Fermi supernova remnants
The Fermi -ray space telescope reported the observation of several
Galactic supernova remnants recently, with the -ray spectra well
described by hadronic collisions. The possible neutrino emissions from
these Fermi detected supernova remnants are discussed in this work, assuming
the hadronic origin of the -ray emission. The muon event rates induced
by the neutrinos from these supernova remnants on typical km neutrino
telescopes, such as the IceCube and the KM3NeT, are calculated. The results
show that for most of these supernova remnants the neutrino signals are too
weak to be detected by the on-going or up-coming neutrino experiment. Only for
the TeV bright sources RX J1713.7-3946 and possibly W28 the neutrino signals
can be comparable with the atmospheric background in the TeV region, if the
protons can be accelerated to very high energies. The northern hemisphere based
neutrino telescope might detect the neutrinos from these two sources.Comment: 16 pages with elsarticle style, 4 figures, 1 table. Minor revisions,
accepted for publication in Astroparticle Physic
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