We have investigated the characteristics of radiation damage to charge coupled devices (CCDs) in the space environment. The X-ray astronomy satellite ASCA launched on February 20, 1993 in low Earth ...orbit carries CCDs specially developed for soft X-ray detection. We have traced the performance of the CCDs for 3 years. We have observed both the gradual decrease of charge transfer efficiency (CTE) and the increase of dark current. These are phenomenologically explained by the increase of charge traps due to irradiation by high energy charged particles. However, some of the effects of the radiation damage in the CCD are quite non-uniform over the chip on various scales. We discuss characteristics of the charge traps and possible origins of the non-uniformity.
The performance of the charge coupled devices on-board the ASCA satellite has been traced for five years after the launch. We found the gradual increase of the dark current and the decrease of the ...charge transfer efficiency. These changes may be explained by charge traps due to the radiation damage. The nature of the radiation damage is investigated in detail using various methods.
The minimum solute concentration in alpha -dendrite arms and the amount of crystallized compounds were measured in Al--6.5% Mg alloys with small amounts of Fe, Mn and Ti, solidified uni- and ...nondirectionally. In the alloys solidified unidirectionally the minimum Mg concentration increases with the increase in average cooling rate during solidification; in the alloys solidified nondirectionally the opposite phenomenon is obtained. In the alloys solidified nondirectionally the nonequilibrium eutectic phase beta crystallizes and the amount of beta increases with the increase in cooling rate. The amount of nonequilibrium eutectic phase beta increases with the increase in Mn concentration and the amount of crystallized compound Al(Fe,Mn) increases with the increase in Fe concentration. The minimum Fe concentration in the alloys solidified nondirectionally increases and the minimum Mn concentration is not affected by the increase in cooling rate. The minimum Fe concentration decreases with increase in Mn concentration and markedly with Ti addition. 10 ref.--AA
Charge coupled devices (CCDs) optimized for soft X-ray detection were utilized for the solid-state imaging spectrometers (SIS) onboard the ASCA satellite, and have been in operation since its launch ...in 1993. We have been carefully monitoring the change in performance of SIS due to radiation damage over three years since launch. Both an increase of dark current and a decrease of charge transfer efficiency are observed, as expected from experiments in the laboratory, but their characteristics are somewhat different from those predicted before launch. This is the first detailed analysis of radiation damage to CCDs actually operated in the space environment and gives important information for the development of similar detectors for space applications.
Two new Exobasidium species on Vaccinium spp. in Japan are described and discussed. Exobasidium kishianum, which causes Exobasidium leaf blight on V. hirtum var. pubescens and V. smallii, is ...characterized by its ellipsoid to ovoid basidiospores with (0–)1–3 septa. Its systemic infection is also observed. Exobasidium inconspicuum, causing Exobasidium leaf blister on V. hirtum var. pubescens, is characterized by its obovoid or ellipsoid to oval basidiospores with 0–4 septa. Mode of germination of the basidiospores is by germ tube in both species.
Witches' broom on Rhododendron wadanum has been observed since 1994 in Nagano Pref. and recently, in 2000, it was found at Mt. Tsukuba, Ibaraki Pref., Japan. In comparison with the morphology, the ...mode of germination of basidiospores and the cultural characteristics of the 99 validly described taxa, this fungus was considered as a new species and named Exobasidium nobeyamense.
The clinical usefulness of diffusion-weighted echo planar imaging (DW-EPI) was studied in 55 patients with acute brain ischemia. Ischemic lesions were identified on DW-EPI as hyperintense regions in ...all patients before changes were detected by conventional magnetic resonance imaging techniques in 12 cases studied earlier than 6 hours after onset. The earliest case was verified on DW-EPI at 50 minutes after onset. The ultra-fast imaging technique took less than 2 minutes to perform even for restless patients. Three patients had cardioembolic middle cerebral artery occlusion, and emergent percutaneous transluminal recanalization was carried out. Chronological changes in the signal of brain ischemia on DW-EPI depended on the site and size of the lesion, lacunar infarct of basal ganglia, and/or massive infarct due to major vessel occlusion, and were affected by associated hemorrhagic events. Coronal DW-EPI could more easily demarcate ischemia in the brainstem and/or cerebellum than axial scans when susceptibility artifacts were present. Coronal scans also demonstrated the site and direction of the pyramidal tract and its anatomical correlation with the lesions. DW-EPI has potential for the diagnostic and therapeutic planning of patients with acute brain ischemia.
Two Exobasidium species causing Exobasidium leaf blister on Rhododendron spp. are described. An Exobasidium leaf blister on Rhododendron yedoense var. yedoense f. yedoense has been recognized in ...Hokkaido Prefecture, Japan, since the first report was issued in 1950. The causal fungus is identified with Exobasidium dubium from the morphology of its hymenial structure and mode of germination of the basidiospores. Another Exobasidium leaf blister on Rhododendron dauricum has been observed in Hokkaido Prefecture, Japan. In comparison with morphology based on hymenial structure and mode of germination of the basidiospores of the 100 validly described taxa, this fungus differs from those known taxa in the size of basidia and basidiospores, the numbers of sterigmata and septa of basidiospores, and the mode of germination of basidiospores. Thus, a new species, Exobasidium miyabei, is established and illustrated.
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