ホクリクムヨウランに関する細胞学的知見

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Relaminarization of accelerated turbulent boundary layer under favorable pressure gradient with sink flow type (Coherent structure and two-point statistics)

The relaminarization process of a turbulent boundary layer under a sink flow was investigated experimentally. The boundary layer was accelerated because of the contraction of the flow area. The mean and fluctuating velocity components were measured using a hot-wire anemometer. With relaminarization, the fluctuating velocity, which was normalized by the free-stream velocity, decreased. The degree of decrease differed between the streamwise and wall-normal components, depending on the distance from the wall. The conditional probabilities that two hot-wire probes separated in the spanwise direction simultaneously observed turbulent and nonturbulent flows were obtained. A spanwise-wide turbulent region was spread near the wall, but its width decreased as the distance from the wall increased. When the layer was relaminarized, this decrease in the spanwise width started near the wall. The low-speed streak spacing of the coherent structure was obtained from the lateral correlation coefficient of the streamwise fluctuating velocity and average spanwise spectra, and both parameters were somewhat consistent. Both the spanwise spacing of the streaks and the vertical scale of the coherent structure increased because of relaminarization. The conditional lateral correlation coefficient of the streamwise fluctuating velocity based on turbulence or nonturbulence was calculated. The streak spacing was slightly wider under nonturbulent conditions. This trend is consistent with the spreading behavior of the streak spacing, owing to relaminarization. With relaminarization, coherent structures became less frequent

準絶滅危惧種ワカサハマギクの減少要因とレッドリストの再評価: 個体群の約30 年後の追跡調査から

Chrysanthemum wakasaense （Asteraceae） is a perennial herb, distributed over the Japan Sea side areas of Tottori, Hyogo, Kyoto and Fukui prefectures, as well as calcareous mountains in Shiga prefecture and adjacent areas. The species is treated as an endangered plant of Japan （Environmental Agency of Japan 2007） and of some prefectures, however, the rank and criteria of categories differ nationally and between the prefectures. In 2008, a follow-up survey after 30 years was conducted on the 59 coastal populations of C. wakasaense in the four prefectures in order to evaluate its threatened status. Among them, 14 populations （23.7%） had become extinct, another 14 populations （23.7%） exhibited size-reduction, 28 populations （47.5%） had maintained their original population sizes, and two populations （3.3%） showed exceptional size-enlargements. In the four prefectures, a marked difference was recognized in the conditions; extinction and reduction were predominant in Tottori, Kyoto, and Fukui Prefectures, while no extinction was found in Hyogo Prefecture. The main factors for extinction of the species were presumed to be natural succession and roadworks. Cultivated garden chrysanthemums, which can cause genetic pollution in wild chrysanthemums, were observed in 21 populations （47.7% of the present populations）, which were neighboring places with garden flowers and/or cemeteries or stone statues of Jizo with offerings of flowers. In actual fact, the natural hybrids between C. wakasaense and garden chrysanthemum were observed in 6 populations （13.6%）. Re-evaluations to the rank of C. wakasaense as an endangered plant of Japan and of related prefectures, and suggestions for conservation of the species were presented here