排序方式: 共有15条查询结果,搜索用时 15 毫秒
1.
The hydrographic observations in the vicinity of a seamount, the Tosa-Bae, southeast of Shikoku have been carried out two times in summer of 1991 and 1992. The temperature, salinity fields are observed by CTD and velocity fields are measured by ADCP. Results of these observation are presented in this paper. It is shown that salinity maximum water at a depth of 100 m is confined to a southeastern are of the Tosa-Bae, however, salinity minimum water is found in northern side of the Tosa-Bae. This indicates the westward intrusion of less saline water over northern slope. A positive correlation is detected between the estimated Rossby height (fL/N) and the observed height of Taylor Column estimated from the vertical change in the isotherms and isohalines. Almost both heights give smaller value than representative depth of bottom topography of the Tosa-Bae, it is indicated that the topographic effect of the Tosa-Bae is not fully reached to the surface. From the correlations between the vertical difference of geostrophic flow and that of ADCP velocity, ageostrophic flow component is detected. 相似文献
2.
Mitsuhiko Hayashi Ichiro Tamura Osamu Shimomura Hiroshi Sawamoto Haruki Kawamura 《Physics and Chemistry of Minerals》1987,14(4):341-344
Néel temperature (Tm N of α-Fe2SiO4 (fayalite) was measured as a function of pressure by means of Mössbauer spectroscopy in the pressure range 0–16 Gpa. High pressure was generated using a clamp-type miniature diamond anvil cell which was inserted into a cryostat. The Néel temperature increased linearly with increasing pressure at a rate of dT N /dp=2.2±0.2 K/GPa. The result is discussed on the basis of the model proposed for the magnetic structure of fayalite by Santoro et al. (1966). The observed dT N /dp suggests that the superexchange interactions vary as the ?10/3 power of the volume while the volume dependence of the direct exchange interactions is positive and small. 相似文献
3.
Genki I. Matsumoto Yukinori Tani Koji Seto Tomoko Tazawa Masumi Yamamuro Takahiro Watanabe Toshio Nakamura Tetsuo Takemura Satoshi Imura Hiroshi Kanda 《Journal of Paleolimnology》2010,44(2):677-693
Antarctic climate changes influence environmental changes at both regional and local scales. Here we report Holocene paleolimnological
changes in lake sediment core Sk4C-02 (length 378.0 cm) from Lake Skallen Oike in the Soya Kaigan region of East Antarctica
inferred from analyses of sedimentary facies, a range of organic components, isotope ratios of organic carbon and nitrogen,
and carbon-14 dating by Tandetron accelerator mass spectrometry. The sediment core was composed of clayish mud (378.0–152.5 cm)
overlain by organic sediments (152.5 cm-surface). The age of the surface and the core bottom were 150 (AD1950-1640) and ca.
7,030 ± 73 calibrated years before present (cal BP), respectively, and the mean sedimentation rate was estimated to be 0.55 mm/year.
Multi-proxy analyses revealed that the principal environmental change in the core is a transition from marine to lacustrine
environments which occurred at a depth of 152.5 cm (ca. 3,590 cal BP). This was caused by relative sea level change brought
about by ongoing retreat of glaciers during the mid-Holocene warming of Antarctica, and ongoing isostatic uplift which outpaced
changes in global (eustatic) sea level. The mean isostatic uplift rate was calculated to be 2.8 mm/year. The coastal marine
period (378.0–152.5 cm, ca. 7,030–3,590 cal BP) was characterized by low biological production with the predominance of diatoms.
During the transition period from marine to freshwater conditions (152.5-approximately 135 cm, ca. 3,590–3,290 cal BP) the
lake was stratified with marine water overlain by freshwater, with a chemocline and an anoxic (sulfidic) layer in the bottom
of the photic zone. Green sulfur bacteria and Cryptophyta were the major photosynthetic organisms. The Cryptophyta appeared
to be tolerant of the moderate salinity and stratified water conditions. The lacustrine period (approximately 135 cm-surface,
ca. 3,290 cal BP-present) was characterized by high biological production by green algae (e.g. Comarium clepsydra and Oedegonium spp.) with some contributions from cyanobacteria and diatoms. Biological production during this period was 8.7 times higher
than during the coastal marine period. 相似文献
4.
The effect of topography on moss vegetation is examined to clarify the processes that affect the colonization of polar deserts on continental Antarctica. Data on the presence of the mosses Bryum pseudotriquetrum and Pottia heimii, and relative altitude were recorded. The altitude measurements were used to infer the underlying topographical attributes of the substrate in the study plots. Specifically, the local distribution of moss plants was clarified using the topographical attributes to construct generalized linear mixed models (GLMMs). The models suggested that steep slopes and convex microhabitats within areas of concave general relief (at the plot scale 4 × 4 m) promoted the establishment of moss. This correspondence to general relief was more apparent for B. pseudotriquetrum than for P. heimii. Among the study plots, general relief was found to be an important determinant of the precise spatial distribution of B. pseudotriquetrum. The standard surface estimated using the robust methods presented in this study is shown to be more accurate for describing moss distribution than the prevailing least-squares method. 相似文献
5.
于1992~1994年 ,在中国水科院黄海水产研究所小麦岛试验基地(青岛)进行的“中日合作真鲷增殖放流项目”执行期间 ,对真鲷饵料生物———眼点拟微绿藻 (Nannochloropsisoculata)和L型褶皱臂尾轮虫 (Branchionus plicatilis)进行了大量培养。眼点拟微绿藻的平均接种密度为1211.3×104个/ml,经5~6d的室内或室外露天培养即可达到平均为2341.0×104 个/ml的收获密度 ;采用眼点拟微绿藻和新鲜面包酵母作为混合饵料 ;褶皱臂尾轮虫 (L型 )培养3~4d即可由接种时平均密度148.0个/ml,增长至平均216.8个/ml的采收密度。眼点拟微绿藻和轮虫的日间增殖密度分别是12.8 %和26.6 %。每生产108个褶皱臂尾轮虫需要消耗0.73m3眼点拟微绿藻 (密度为2000×104/ml)和790.8g 鲜面包酵母。采用此法 ,作者连续3a成功地为每年百万尾以上真鲷苗种提供了足够的生物饵料。总结3a苗种培育和生物饵料培养之间的关系 ,作者认为 ,大规模稳定生产海水鱼类苗种时,育苗与饵料生物培养 (褶皱臂尾轮虫和眼点拟微绿藻 )水体的合理比例应为1∶1~1.5∶3。 相似文献
6.
Shuro?YoshikawaEmail author Toshiya?Kanamatsu Kazuhisa?Goto Izumi?Sakamoto Masatoshi?Yagi Mikio?Fujimaki Riichirou?Imura Kenji?Nemoto Hide?Sakaguchi 《Geo-Marine Letters》2015,35(4):315-328
Ongoing geological research into processes operating on the nearshore continental shelf and beyond is vital to our understanding of modern tsunami-generated sediment transport and deposition. This paper investigates the southern part of Sendai Bay, Japan, by means of high-resolution seismic surveys, vibracoring, bathymetric data assimilation, and radioisotope analysis of a core. For the first time, it was possible to identify an erosional surface in the shallow subsurface, formed by both seafloor erosion and associated offshore-directed sediment transport caused by the 2011 Tohoku-oki tsunami. The area of erosion and deposition extends at least 1,100 m offshore from the shoreline down to water depths of 16.7 m. The tsunami-generated sedimentological signature reaches up to 1.2 m below the present seafloor, whereas bathymetric changes due to storm-related reworking over a period of 3 years following the tsunami event have been limited to the upper ~0.3 m, despite the fact that the study area is located on an open shelf facing the Pacific Ocean. Tsunami-generated erosion surfaces may thus be preserved for extended periods of time, and may even enter the rock record, because the depth of tsunami erosion can exceed the depth of storm erosion. This finding is also important for interpretation of modern submarine strata, since erosion surfaces in shallow (depths less than ~1 m) seismic records from open coast shelves have generally been interpreted as storm-generated surfaces or transgressive ravinement surfaces. 相似文献
7.
Abstract Illite crystallinity (IC) and illite b, lattice spacing were measured across the Cretaceous Shimanto Belt, Kii Peninsula, Southwest Japan. For the IC survey, 103 samples of argillaceous rocks were analyzed from the central area and the western area of the belt. Values of IC (Kubler Index) vary between 0.28 and 0.71 Δ°2θ and indicate diagenetic and anchizone metamorphism respectively. The IC distribution reveals two contrasting patterns of thermal maturity. The Hanazono Formation, exposed in the northern area of the belt, generally dips north, but IC values increase systematically from 0.28 Δ°2θ in the north to 0.54 Δ°2θ in the south and indicate an inverted thermal structure. Values in other formations vary widely in the southern area of the belt ranging between 0.45 and 0.71 Δ°2θ, but the values do not show any systematic change from north to south and on average remain almost constant. Illite bo , lattice spacing values for 56 samples vary between 9.006 and 9.041 Å corresponding to intermediate pressure conditions of the metamorphic facies. These values, combined with paleotemperatures estimated from IC, indicate paleogeothermal gradients of 22 and 31°C/km for the northern and southern areas of the belt, respectively. The inverted thermal structure of the Hanazono Formation, together with a lower paleogeothermal gradient, possibly is a result of the subduction of a relatively cold oceanic plate during the Late Cretaceous. The higher geothermal gradient could be a product of late thermal overprinting caused by the later subduction of a comparatively younger and hotter oceanic plate during the Eocene. 相似文献
8.
9.
There are many experimental approaches,field investigations and numerical calculations for movements of woods in a clear water and debris flow.However,kinematic conditions for accumulated logs and the interactions between a main flow and logs have not been fully evaluated.Mitigations for woods need taking into account the characteristics of tree species such as conifer and broad-leaf trees and of shapes such as root swells and crown.In the present study,we focus on the differences in specific weight of conifer and broad-leaf trees with some moisture in a sediment-water mixture flow with narrow flow width,and consider that conifer and broad-leaf tree are floating and submerged solid phase,respectively.Flume tests are conducted in steady flow of clear and debris flow over a rigid bed in order to evaluate conifer and broad-leaf tree movement in clear water and debris flow.Experimental data indicates that dimensionless transverse diffusion coefficient can be 0.1 to 0.4 and 0.3 to 0.9 in flow direction.Those diffusive characteristics seem to be independent of Reynolds number and Froude number,but dependent of bed slope,i.e.,gravity,though detailed considerations are needed to discuss about flow characteristics such as spatial eddy structures,momentum transfer induced by interactions of logs and so on. 相似文献
10.
Tatsuyuki Yamamoto Hideo Akiyoshi Keisuke Yoshikiyo Tetsuya Takahashi Yukiko Tanabe Sakae Kudoh Satoshi Imura Naoyuki Yamamoto 《地学前缘(英文版)》2013,4(6):647-653
A study on the effect of the solar ultra-violet radiation on the human skin fibroblast cells revealed that the production of matrix metalloproteinase-2 was inhibited by the radiation.A CO2 incubator connected by optical fibers to a reflector telescope for collecting the solar light was built at Syowa station by the 49th Japanese Antarctica Research Expedition.The direction of the telescope was continuously controlled by a sun-tracker to follow the movement of the Sun automatically.The intensity of the collected light was monitored by a portable spectrophotometer housed inside.The human skin fibroblast cells were incubated in the CO2 chamber to investigate the effect of the solar radiation at Syowa station and were compared with those reference experiments at a laboratory in Japan.The results showed cell damage by strong UV radiation.The production of matrix metalloproteinase-2 was prompted by the moderate UV-B,but was inhibited by the strong UV-B radiation,as studied under laboratory conditions in Japan.The effect of strong solar radiation at Syowa station involving the radiation of UV-B region was estimated to be of the same extent of the radiation caused by an artificial UV-B light with the intensity more than 50 mJ/cm2. 相似文献