温帯の散孔材樹種における道管サイズの季節変化と水分条件との関係

Vessel lumen area and leaf water potential (ψleaf) at predawn and midday were measured periodically to reveal seasonal variations in the vessel sizes of diffuse-porous species and to determine the factors that cause this variation. Two deciduous species (Cercidiphyllum japonicum and Liriodendron tulipifera) and one evergreen species (Quercus glauca) were studied. In most of the samples, mean vessel lumen area (MVLA) initially increased then eventually decreased after a period, but this period varied among species. In C. japonicum, the decrease in MVLA coincided with a decrease in predawn ψleaf. In contrast, MVLA variations in most samples of L. tulipifera and Q. glauca did not show such a relationship. However, one of the L. tulipifera samples had an earlier decrease in MVLA that coincided with a lower predawn ψleaf. There was no clear relationship between the variation in vessel size and midday ψleaf, because midday ψleaf showed daily variation depending on vapor pressure deficit, which had less seasonality. Thus, we concluded that there are species-specific annual patterns in vessel size variation that are likely determined by internal factors. Low water availability is one of the external factors inducing the formation of narrower vessels.散孔材における道管サイズの季節変化, およびその変化を引き起こす要因を明らかにするため, 道管形成の観察と夜明け前と日中の葉の水ポテンシャル (ψleaf)の測定を定期的に行った. 試料には落葉樹のカツラとユリノキ, 常緑樹のアラカシを用いた. 全ての樹種で道管サイズは一年の成長の始めに増加し, ある時期から減少していた. 減少が始まる時期は樹種によって異なっており, カツラでは夜明け前のψleaf の低下と対応が見られた. 一方でユリノキとアラカシでは, 道管サイズと夜明け前のψleaf の対応は見られなかった. ただし夜明け前のψleaf が他よりも低下していた個体では道管サイズの減少が早く始まっていたため, 乾燥ストレスの影響が示唆された. 日中のψleaf は日変動が大きく, 道管サイズとの明確な関連性は見られなかった. したがって, 年輪内の道管サイズの変化は主に内的要因によって決まっており, 乾燥ストレスは外部要因として道管サイズを減少させると考えられた

X-ray Observation of Mars with Suzaku at Solar Minimun

Mars was observed in X-rays during April 3-5 2008 for 82 ksec with the Japanese Suzaku observatory. Mars has been known to emit X-rays via the scattering of solar X-rays and via the charge exchange between neutral atoms in the exosphere and solar wind ions. Past theoretical studies suggest that the exospheric neutral density may vary by a factor of up to 10 over the solar cycle. To investigate a potential change of the exospheric charge exchange emission, Mars was observed with Suzaku at solar minimum. Significant signals were not detected at the position of Mars in the energy band of 0.2-5 keV. A 2 sigma upper limit of the O VII line flux in 0.5-0.65 keV was 4.3$\times10^{-5}$ ph cm$^{-2}$ s$^{-1}$. Comparing this upper limit to the past Chandra and XMM-Newton observations conducted near solar maximum, it was found that the exospheric density at solar minimum does not exceed that near solar maximum by more than 6-70 times.Comment: 17 pages, 7 figures, accepted for publication in PAS

Enhancement of Terrestrial Diffuse X-ray Emission Associated With Coronal Mass Ejection and Geomagnetic Storm

We present an analysis of a Suzaku observation taken during the geomagnetic storm of 2005 August 23-24. We found time variation of diffuse soft X-ray emission when a coronal mass ejection hit Earth and caused a geomagnetic storm. The diffuse emission consists of fluorescent scattering of solar X-rays and exospheric solarwind charge exchange. The former is characterized by a neutral oxygen emission line due to strong heating of the upper atmosphere during the storm time, while the latter is dominated by a sum of C V, C VI, N VI, N VII, O VII, and O VIII emission lines due to the enhanced solar wind flux in the vicinity of the exosphere. Using the solar wind data taken with the ACE and WIND satellites,a time correlation between the solar wind and the strong O VII line flux were investigated. We estimated necessary column densities for the solar X-ray scattering and exospheric SWCX. From these results, we argue that a part of the solar wind ions enter inside the magnetosphere and cause the SWCX reaction.Comment: 33 pages, 16 figures, accepted for publication in PAS

Detection of Excess Hard X-ray Emission from the Group of Galaxies HCG62

From the group of galaxies HCG62, we detected an excess hard X-ray emission in energies above $\sim 4$ keV with \A SCA. The excess emission is spatially extended up to $\sim10'$ from the group center, and somewhat enhanced toward north. Its spectrum can be represented by either a power-law of photon index 0.8-2.7, or a Bremsstrahlung of temperature $>6.3$ keV. In the 2-10 keV range, the observed hard X-ray flux, $(1.0\pm0.3)\times10^{-12}$ erg cm$^{-2}$ s$^{-1}$, implies a luminosity of $(8.0\pm2.0)\times10^{41}$ erg s$^{-1}$ for a Hubble constant of 50 km s$^{-1}$ Mpc$^{-1}$. The emission is thus too luminous to be attributed to X-ray binaries in the memb er galaxies. We discuss possible origin of the hard X-ray emission.Comment: 6 pages, 3 Postscript figures, uses emulateapj.sty. Accepted for publication in the Astrophysical Journal Letter

Radial and vertical distributions of radiocesium in tree stems of Pinus densiflora and Quercus serrata 1.5 y after the Fukushima nuclear disaster.

The radial and vertical distributions of radiocesium in tree stems were investigated to understand radiocesium transfer to trees at an early stage of massive contamination from the Fukushima nuclear disaster. A conifer species (Japanese red pine) and a broad-leaved species (Japanese konara oak) were selected to determine whether the radiocesium contamination pattern differs between species. Stem disks were collected at several heights and separated into outer bark, inner bark, and wood. The radiocesium concentration was the highest in the outer bark, followed by that in the inner bark and wood. The vertical distribution of the radiocesium concentration at each stem part differed between the species. The difference between species in radiocesium concentration of the outer bark could be explained by presence or absence of leaves at the time of the disaster. However, the reasons for the differences between species in the radiocesium concentration of the inner bark and wood are unclear. The radial distribution in the wood of the studied species showed a common pattern across stem disk heights and species. However, the radiocesium concentration ratio between sapwood and inner bark was significantly different between species. Although the radial contamination pattern in the wood was similar in the studied species during the early stage of contamination, the radiocesium transport pathway and allocation would be different between the species, and the contamination pattern will likely be different between the species at later stages. Continued investigations are important for understanding the radiocesium cycle and the accumulation of radiocesium in the tree stems of each species

A new adrenal computer imaging technique using dual-radioisotopes.

Computer processed adrenal imaging using dual-radioisotopes, 6 beta-iodomethyl-19-nor-cholest-5(10)-en-3 beta-ol-131I and 99mTc-phytate was performed in 12 patients with primary aldosteronism and 4 with Cushing's syndrome due to adrenocortical tumor. Adreno-photoscanning and hepato-photoscanning were performed in the same position 2-4 days following intravenous administration of radiocholesterol. The scintigraphic information was stored on cassettes and scan subtraction and a digital-computer method for data smoothing were performed on an oscilloscope. The tumor site could be determined in all cases until day 4 by this computer processed image.</p

A modular approach to large-signal modeling of an interconnected AC/MTDC system

Y. Susuki, N. Kawamoto, Y. Ohashi, A. Ishigame, T. Funaki and S. D’Arco, "A Modular Approach to Large-Signal Modeling of an Interconnected AC/MTDC System," 2020 IEEE PES Innovative Smart Grid Technologies Europe (ISGT-Europe), The Hague, Netherlands, 2020, pp. 945-949, doi: 10.1109/ISGT-Europe47291.2020.9248890