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41.
Masao SAKAMOTO Arnold GUCSIK Hirotsugu NISHIDO Kiyotaka NINAGAWA Tasuku OKUMURA Shin TOYODA 《Meteoritics & planetary science》2010,45(1):32-42
Abstract– Planar deformation features (PDFs) and planar fractures (PFs) have been found and confirmed by optical microscope observations and microRaman spectroscopy in quartz grains from Mt. Oikeyama (Akaishi Mountains, Central Japan), for which the semicircular topographic feature of the ridge suggests a crater formed by an impact event. According to the optical microscope observations, a low shock pressure (8–10 GPa) is estimated by the occurrence of basal or ω PDFs leading to lack of multiple sets of PDFs. In addition, a new type of planar microstructure was found in several quartz grains. The microRaman characteristics of PDFs in quartz from Mt. Oikeyama show the amorphous state indicating the presence of weak broad bands at 400 and 800 cm?1 peak positions. These characteristics are indicative of PDFs that are limited to shocked quartz. This indicates an impact origin for distinct planar microstructures in quartz from Mt. Oikeyama. 相似文献
42.
43.
High(C2/c)-low(P21/c) phase transition in clinoenstatite and pigeonite was successfully observed in situ at high temperatures for the first time under a transmission electron microscope. The phase transition was revealed to possess the characteristics of a first-order transition, due to the coexistence of both phases separated by the sharp interfaces and the nucleation-growth process. The diffusionless and time-independent reaction suggests that the transition occurs athermal-martensitically. Furthermore, the small or even negative thermal hysteresis and the interface motion suggest that the transition is not a typical type but a thermoelastic type of the martensitic transformation. This type of the transformation, studied extensively in metallurgy in relation to shape memory effect, is first recognized in rock-forming minerals. 相似文献
44.
45.
Naoto Ebuchi Yasushi Fukamachi Kay I. Ohshima Kunio Shirasawa Masao Ishikawa Toru Takatsuka Takaharu Daibo Masaaki Wakatsuchi 《Journal of Oceanography》2006,62(1):47-61
Three High Frequency (HF) ocean radar stations were installed around the Soya/La Perouse Strait in the Sea of Okhotsk in order
to monitor the Soya Warm Current (SWC). The frequency of the HF radar is 13.9 MHz, and the range and azimuth resolutions are
3 km and 5 deg., respectively. The radar covers a range of approximately 70 km from the coast. The surface current velocity
observed by the HF radars was compared with data from drifting buoys and shipboard Acoustic Doppler Current Profilers (ADCPs).
The current velocity derived from the HF radars shows good agreement with that observed using the drifting buoys. The root-mean-square
(rms) differences were found to be less than 20 cm s−1 for the zonal and meridional components in the buoy comparison. The observed current velocity was also found to exhibit reasonable
agreement with the shipboard ADCP data. It was shown that the HF radars clearly capture seasonal and short-term variations
of the SWC. The velocity of the Soya Warm Current reaches its maximum, approximately 1 m s−1, in summer and weakens in winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately
40 km. The surface transport by the SWC shows a significant correlation with the sea level difference along the strait, as
derived from coastal tide gauge records at Wakkanai and Abashiri.
Deceased. 相似文献
46.
Masao Fukasawa 《Journal of Oceanography》1983,39(1):15-21
Data from XBT observations in the vicinity of the shoal, Kokushô-sone (30°00′N, 128°30′E) which is located in the current zone of the Kuroshio in the East China Sea, are analysed to show the distribution of isothermal layers. Isothermal layers are found in abundance in and near a cold water region along the slope of the shoal where the existence of upwelling is suggested. It is found that there is a good spatial correlation between the distribution of isothermal layers and that of cold waters along the slope, and that the distribution of isothermal layers is a helpful indicator for elucidating the nature of oceanic structures in the vicinity of the shoal. 相似文献
47.
Yukio Fujinawa Yoshinobu Tsuji Isao Watabe Ken Sasaki Masao Nomoto Toshiaki Hara Yoshito Tsuji 《Journal of Oceanography》1980,36(5):253-258
The results of laboratory and field experiments on a CTD measuring unit attached to a controllable towed body is described. It was verified that the three-dimensional distribution of salinity and temperature could be observed with sufficient accuracy (to 0.03 in salinity and to 0.01°C in temperature if proper correction is adopted) while cruising at up to 4 knots. A double integrated A/D converter is used to compensate for effects of extraneous environmental changes. 相似文献
48.
The Algal Growth Potential (AGP) of water samples collected off Gamagori in Mikawa Bay was measured from May 1978 through February 1979, and the limiting nutrient was determined using regression analysis and enrichment bioassays. The surface and bottom water samples had AGP that produced increments of chemical oxygen demand (COD) of 2.1 mg l–1 and 3.1 mg l–1, respectively, on average. These values ofCOD correspond to 46% and 97% of the average COD values of the raw water samples at the surface and bottom, respectively. Seasonal changes of AGP showed a close correlation with those of dissolved inorganic nitrogen (DIN) concentration. Enrichment bioassays showed that DIN was the most deficient nutrient. The DIN:phosphate-phosphorus (PO4
3–-P) ratios and DIN: dissolved phosphorus (DP) ratios in the water samples were below the cellular N:P ratios of the natural algal populations. These results suggest that AGP was mainly limited by DIN concentration. 相似文献
49.
Keiji Horikawa Masao Minagawa Yoshihisa Kato Masafumi Murayama Seiya Nagao 《Journal of Oceanography》2006,62(4):427-439
N2 fixation is an important biological process that adds new nitrogen to oceans and plays a key role in modulating the oceanic
nitrate inventory. However, it is not known how, when, and where N2 fixation rates have varied in response to past climate changes. This study presents a new record of nitrogen isotopic composition
(δ15N) over the last 83 kyr from a sediment core (KH02-4 SUP8) taken in the Sulu Sea in the western equatorial Pacific region;
data allow the N2 fixation variability in the sea to be reconstructed. Sediments, sinking, and suspended particulate organic matter (POM) all
have lighter isotopic values compared to the δ15N values of substrate nitrate (av. 5.8‰) in North Pacific Intermediate Water. These lighter δ15N values are regarded as reflecting N2 fixation in the Sulu Sea surface water. A δ15N mass balance model shows that N2 fixation rates were significantly enhanced during 54–34 kyr in MIS-3 and MIS-2. It has been speculated that higher interglacial
denitrification rates in the Arabian Sea and the eastern tropical Pacific would have markedly decreased the global oceanic
N inventory and contributed to the increase in N2 fixation in oligotrophic regions, but such a model was not revealed by our study. It is possible that changes in N2 fixation rates in the Sulu Sea were regional response, and accumulation of phosphate in the surface waters due to enhanced
monsoon-driven mixing is thought to have stimulated enhancements of N2 fixation during MIS-3 and MIS-2. 相似文献
50.
Vertical profiles of210Pb and230Th in the deep water were analyzed by using a simple one-dimensional model. Both nuclides are considered to settle down with the velocity of 1×10–4 cm/sec. The diameter of particle corresponding to the velocity is calculated to be 5, while only about 10 % of the nuclides can be collected on filter paper with a pore size of 0.5. It is supposed that the nuclides exist in particulate materials which is changeable in size. This suggestion is supported from the following evidences. (1) The directly observed behavior of marine snow and the size distribution of particles observed with a coulter counter. (2) The existence of many chemical elements of which residence time is about 150 years. (3) Their possible existence as eutectic solid phases in the seawater. (4) The consistency of the observed accumulation rate of pelagic sediments with that estimated from the settling velocity. (5) The consistency of the decomposition rate of organic matter in the deep water estimated from the oxygen comsumption with that from the settling velocity. 相似文献