Ultrafast Control of Crystal Structure in a Topological Charge-Density-Wave Material

Optical control of crystal structures is a promising route to change physical properties including topological nature of a targeting material. Time-resolved X-ray diffraction measurements using the X-ray free-electron laser are performed to study the ultrafast lattice dynamics of VTe$_2$, which shows a unique charge-density-wave (CDW) ordering coupled to the topological surface states as a first-order phase transition. A significant oscillation of the CDW amplitude mode is observed at a superlattice reflection as well as Bragg reflections. The frequency of the oscillation is independent of the fluence of the pumping laser, which is prominent to the CDW ordering of the first-order phase transition. Furthermore, the timescale of the photoinduced 1$T^{\prime\prime}$ to 1$T$ phase transition is independent of the period of the CDW amplitude mode

Biological significance of unmethylated DNA in human testicular cancer.

科学研究費補助金研究成果報告書研究種目: 基盤研究(C)研究期間: 2003～2004課題番号: 15591682研究代表者: 成田 充弘（滋賀医科大学・医学部・助手）研究代表者: 川上 享弘（滋賀医科大学・医学部・助手）研究分担者: 岡本 圭生（滋賀医科大学・医学部・助手）研究分担者: 岡田 裕作（滋賀医科大学・医学部・教授）研究分担者: 杉原 洋行（滋賀医科大学・医学部・助教授）研究分担者: 坂野 祐司（滋賀医科大学・医学部・助手

Prolactin and Upstream Migration of the Amphidromous Teleost, Ayu Plecoglossus altivelis

Changes in mRNA levels of prolactin (PRL) during the upstream migration were examined in fry of the amphidromous fish, ayu Plecoglossus altivelis. Quantification of mRNA has been done with real-time PCR and expressed as whole body or pituitary contents depending the body size of fry. PRL mRNA levels of ayu caught in seawater of the coastal area remained low during early spring. Prior to the start of the upstream migration, the fish caught in the coastal area in mid spring showed increased levels of PRL mRNA. There were further increases in PRL levels in the fish caught in the river. Analysis of proportions revealed that there were significant differences among PRL mRNA in the fish caught in different environmental salinities. Body weight showed a positive relation with PRL mRNA in ayu caught in seawater. A landlocked population of ayu, which migrates from lake to river, showed no significant change in PRL mRNA levels before and after upstream migration. Results in this study indicate the importance of up-regulation of PRL gene expression of ayu during the upstream migration from seawater to fresh water. There is a possible relationship between body size and PRL in the early developmental stage of ayu in seawater, but not in the fish in fresh water

Annual variation in biomass and the community structure of crustacean zooplankton over 5 years in Lake Toya, Japan

Biomass and population dynamics of crustacean zooplankton were investigated in Lake Toya, oligotrophic caldera lake in Japan, during five years from 1992 to 1997. Zooplankton biomass increased in summer with increasing water temperature every year, and varied annually even if temperature and food conditions did not change so much. In 1992 and 1993, zooplankton biomass reached up to > 4 g dry-wt m^[-2], while it declined below 1 g dry-wt m^[-2] after 1994. This extreme change of the zooplankton biomass depends on succession of three dominant species from large ones, such as Daphnia longispina and Cyclops cf. sibiricus, to small ones, such as Eubosmina longispina and Bosmina longirostris. Analyzing population dynamics of the dominant crustaceans demonstrates that the year-to-year variation in the abundance is related to the death rate but not birth rate. Since chlorophyll a concentrations within the euphotic zone and the birth rates of each species were rather higher in low zooplankton biomass years, the higher death rates after 1994 is not considered to be attributed to food shortage. Two planktivorous fish, lacustrine sockeye salmon (Oncorhynchus nerka) and pond smelt (Hypomesus transpacificus nipponensis), were artificially introduced every year for the sake of commercial fisheries in the lake. Although the two fishes are expected to be the most important predator for the large crustaceans, D. longispina and C. cf. sibiricus, which are actually fed on by the two fishes, the annual catch of the fishes was positively correlated to the average biomass of the crustaceans during summer season. This conflicting result is considered to be attributed to less catch of the fishes with fishing regulation for a gill net used by fishermen due to lowering the growth rate of the fishes in the low zooplankton biomass years. Proliferation of young and/or small fishes, including young-of-the-year pond smelt, which cannot be caught with the gill net may play an important role for eliminating the large crustaceans. Our results suggest that excessively artificial introduction of planktivorous fish, especially pond smelt, limits the zooplankton production in oligotrophic lake such as Lake Toya, subsequently decreasing the growth rate of the fish, and that this negative feed-back finally enhances lowering the annual fish catch