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排序方式: 共有209条查询结果,搜索用时 275 毫秒
201.
Kei’ichiro?IguchiEmail author Katsutoshi?Watanabe Mutsumi?Nishida 《Fisheries Science》2005,71(2):308-313
An increasing demand for stocking of hatchery-reared ayu, Plecoglossus altivelis, has aroused concerns about their genetic status which has an effect on their post-stocking performance and the conservation
of native biodiversity. Instead of costly analysis, fluctuating asymmetry (FA) was examined to test its suitability as an
indirect measure of genetic diversity. Two bilateral traits, pectoral and pelvic fin rays, were targeted, and two wild and
four hatchery populations of ayu were sampled for comparison. Frequency of FA in soft-rays was not similar between specimens
in both pelvic and pectoral fins. The wild populations did not show FA incidences lower than the hatchery populations, suggesting
a considerable degree of environmental stress operating in the wild populations. Comparison between the hatchery populations
showed overall increasing FA incidence with the decrease in genetic diversity, although the correlation was not complete in
detail. In conclusion, FA can be used as a convenient tool to compare genetic status, but quantified evaluation is rather
limited to monitoring changes in the genetic variation within a hatchery population. 相似文献
202.
Ryuya Takanashi Wataru Ishihara Kei Sawata Yuzou Sano Tomonori Azuma Mitsunori Mori Akio Koizumi Yoshihisa Sasaki Takuro Hirai 《Journal of Wood Science》2014,60(3):186-193
In order to investigate shear failure surface of decayed wood, wood pieces of ezomatsu (Picea jezoensis) were exposed to brown-rot fungus (Fomitopsis palustris), and standard shear test in radial plane was conducted. The failure surfaces were examined by scanning electron microscopy and surface roughness measurements were also conducted. Transwall failure that the crack elongated parallel to the tracheid axis was observed in the earlywood region through all phases of decay. Intrawall failure principally occurred in the latewood region on the early phase of decay. When decay progressed considerably, transwall failure that the crack elongated perpendicularly to the tracheid axis occurred. And transwall failure was also dominant failure morphology in the latewood region. Fragments of tracheids which were partly peeled out from S2 layers were observed in some specimens. Size and appearance frequency of fragments of tracheid were smaller and lower when decay progressed. Arithmetic average roughness, which was the index of fragment size and appearance frequency, had positive correlation to shear strength ratio. Especially, line surface roughness of radial direction, which was measured across the radial files of tracheid, had the highest correlation to the shear strength ratio. The surface roughness would be a good indicator to evaluate the decay degree. 相似文献
203.
Koji MISUMI Yuri HIRAYAMA Sachiko EGAWA Shoko YAMASHITA Hiroyoshi HOSHI Kei IMAI 《The Journal of reproduction and development》2013,59(6):520-524
This study was conducted to clarify the feasibility of newly developed vitrification
techniques for porcine embryos using the micro volume air cooling (MVAC) method
without direct contact with liquid nitrogen (LN2). Expanded blastocysts
were vitrified in a solution containing 6 M ethylene glycol, 0.6 M trehalose and 2%
(wt/vol) polyethylene glycol in 10% HEPES-buffered PZM-5. The blastocysts were
collected from gilts and vitrified using the new device (MVAC) or a Cryotop (CT).
Blastocysts were stored in LN2 for at least 1 month. After warming,
cryoprotective agents were removed using a single step. Survival of the embryos was
assessed by in vitro culture (Experiment 1) and by embryo transfer
to recipients (Experiment 2). In Experiment 1, the embryos vitrified by the MVAC or
CT and fresh embryos without vitrification (Control) were used. The survival rates of
embryos in the MVAC, CT and Control groups were 88.9% (32/36), 91.7% (33/36) and 100%
(34/34), respectively, after 48 h culture, and the hatching rates of embryos after 48
h incubation were 69.4% (25/36), 63.9% (23/36) and 94.1% (32/34), respectively. In
Experiment 2, 64 vitrified embryos were transferred to 5 recipient gilts, and 8
healthy piglets were produced from 3 recipients in the MVAC group. Similarly, 66
vitrified embryos were transferred to 5 recipient gilts, and 9 healthy piglets were
produced from 2 recipients in the CT group. These results indicated that porcine
expanded blastocysts can be cryopreserved using the MVAC method without potential
pathogen contamination from LN2. 相似文献
204.
Murakami M Hirose K Yurimoto H Nakashima S Takafuji N 《Science (New York, N.Y.)》2002,295(5561):1885-1887
Secondary ion mass spectrometry measurements show that Earth's representative lower mantle minerals synthesized in a natural peridotitic composition can dissolve considerable amounts of hydrogen. Both MgSiO3-rich perovskite and magnesiowüstite contain about 0.2 weight percent (wt%) H2O, and CaSiO3-rich perovskite contains about 0.4 wt% H2O. The OH absorption bands in Mg-perovskite and magnesiowüstite were also confirmed with the use of infrared microspectroscopic measurements. Earth's lower mantle may store about five times more H2O than the oceans. 相似文献
205.
Post-perovskite phase transition in MgSiO3 总被引:2,自引:0,他引:2
In situ x-ray diffraction measurements of MgSiO3 were performed at high pressure and temperature similar to the conditions at Earth's core-mantle boundary. Results demonstrate that MgSiO3 perovskite transforms to a new high-pressure form with stacked SiO6-octahedral sheet structure above 125 gigapascals and 2500 kelvin (2700-kilometer depth near the base of the mantle) with an increase in density of 1.0 to 1.2%. The origin of the D" seismic discontinuity may be attributed to this post-perovskite phase transition. The new phase may have large elastic anisotropy and develop preferred orientation with platy crystal shape in the shear flow that can cause strong seismic anisotropy below the D" discontinuity. 相似文献
206.
Water normally exists in hydrogen-bonded environments, but a single molecule of H(2)O without any hydrogen bonds can be completely isolated within the confined subnano space inside fullerene C(60). We isolated bulk quantities of such a molecule by first synthesizing an open-cage C(60) derivative whose opening can be enlarged in situ at 120°C that quantitatively encapsulated one water molecule under the high-pressure conditions. The relatively simple method was developed to close the cage and encapsulate water. The structure of H(2)O@C(60) was determined by single-crystal x-ray analysis, along with its physical and spectroscopic properties. 相似文献
207.
Ohta K Onoda S Hirose K Sinmyo R Shimizu K Sata N Ohishi Y Yasuhara A 《Science (New York, N.Y.)》2008,320(5872):89-91
Recent discovery of a phase transition from perovskite to post-perovskite suggests that the physical properties of Earth's lowermost mantle, called the D' layer, may be different from those of the overlying mantle. We report that the electrical conductivity of (Mg0.9Fe0.1)SiO3 post-perovskite is >10(2) siemens per meter and does not vary greatly with temperature at the conditions of the D' layer. A post-perovskite layer above the core-mantle boundary would, by electromagnetic coupling, enhance the exchange of angular momentum between the fluid core and the solid mantle, which can explain the observed changes in the length of a day on decadal time scales. Heterogeneity in the conductivity of the lowermost mantle is likely to depend on changes in chemistry of the boundary region, not fluctuations in temperature. 相似文献
208.
日本柑橘黄龙病病原体电镜观察及PCR检测 总被引:3,自引:3,他引:0
对日本柑橘黄龙病病原体的形态结构进行了电镜观察,结果发现柑橘黄龙病病菌日本株系绝大多数是球形和短椭圆形,极少观察到棒状形态,直径为100~500nm,外被一层胶状物质包围,厚约10~50nm,这与其他地区发现的柑橘黄龙病病原体形态不同.PCR检测表明,以硅藻土法提取的DNA为模板,利用Ready-To-Go^TM PCR bead法可以得到理想结果。 相似文献
209.
Kousuke Yatsuya Yukio Matsumoto Kei Sasaki Norio Shirafuji Daisuke Muraoka 《Fisheries Science》2017,83(6):939-946
The kelp Saccharina japonica is a dominant seaweed along the Sanriku coast where fisheries for sea urchin and abalone are among the most prosperous in Japan. We investigated the phenology of the kelp at depths of 6, 9 and 12 m from March 2015 to March 2016. The sea urchin Mesocentrotus nudus, a dominant herbivore off the coast, was also monitored with respect to its gonads for fishery use. Juvenile kelp appeared in March and rapidly elongated until May. Weight of the kelp significantly increased from April to July. Sori formation commenced from September and ceased in December. Density and biomass of the kelp were higher in the shallower sites than in the deeper one throughout the year. The highest biomasses recorded between July and October were 3773, 1939 and 501 g dry weight m?2 at depths of 6, 9 and 12 m, respectively. No regrowth of kelp blades was observed, indicating that S. japonica in this region has an annual life cycle. The gonad index of the sea urchin in the 12-m site was lower than that in the 6- and 9-m sites, indicating the close relation of the gonad index with the biomass of the kelp. 相似文献