Comparison of Internal Structures of Marine Manganese Deposits of Hydrogenetic, Diagenetic and Hydrothermal Origins     

Yumi HAT TA  Makoto WATANABE  Kenichi HOSHINO  Akira USUI 《Resource Geology》1999,49(1):49-54

Abstract: Detailed microscopic observation, combined with X-ray diffraction and EPMA analyses of samples from marine manganese deposits of three different origins, suggests that characteristic internal structures are inherent in each manganse mineral; vernadite (δ–MnO₂), buserite (10Å–manganate) and todorokite (10Å–manganate).  相似文献   

Direct measurements of submarine groundwater discharge (SGD) over a fractured rock aquifer in Flamengo Bay Brazil   总被引：1，自引：0，他引：1  

Henry Bokuniewicz  Makoto Taniguchi  Tomotoshi Ishitoibi  Matthew Charette  Matthew Allen  Evgeny A. Kontar 《Estuarine, Coastal and Shelf Science》2008

Measurements of submarine groundwater discharge (SGD) along the South American coast and over fractured rock aquifers are rare. The rate and distribution of SGD was measured using three types of vented benthic chambers on the floor of Flamengo Bay located at the southeast coast of Brazil. Discharge rates were found up to almost 400 cm day⁻¹, although typically less than 100 cm d⁻¹. Large variations in SGD rates were seen over distances of a few meters which are attributed to the geomorphologic features of the fracture rock aquifer underlying a thin blanket of coastal sediments; clustering of fractures and the topography of the rock–sediment interface might be focusing or dispersing the discharge of groundwater. SGD was modulated by the tides with the highest values occurring at times of low tide, but the interaction was non-linear and, the correlation was weak at tidal ranges less than 1 m. The effect was masked by devices that integrated the SGD, but detected on continuously recording devices.  相似文献   

Orbital evolution of giant comet-like objects     

Tsuko Nakamura  Makoto Yoshikawa 《Celestial Mechanics and Dynamical Astronomy》1993,57(1-2):113-121

We investigated by numerical integrations the long-term orbital evolution of four giant comets or comet-like objects. They are Chiron, P/Schwassmann-Wachmann 1 (SW1), Hidalgo, and 1992AD (5145), and their orbits were traced for 100–200 thousand years (kyr) toward both the past and the future. For each object, 13 orbits were calculated, one for the nominal orbital elements and other 12 with slightly modified elements based on the rms residual of the orbit determination and on the number of observations. As past studies indicate, their orbital evolution is found to be very chaotic, and thus can be described only in terms of probability. Plots of the semi-major axis (a) and perihelion distance (q) of the objects treated here seem to cross each other frequently, suggesting a possibility of their common evolutionary paths. About a half of all the calculated orbits showedq- ora-decreasing evolution. This indicates that, at least on the time scale in question, the giant comet-like objects are possibly on a dynamical track that can lead to capture from the outer solar system. We could hardly find the orbits with perihelia far outside the orbit of Saturn (q>15 AU). This is perhaps because the evolution of the orbits beyond Saturn is so slow that substantial orbital changes do not take place within 100–200 kyr.  相似文献   

A simple analytical model for the secular resonance ν6 in the asteroidal belt     

Makoto Yoshikawa 《Celestial Mechanics and Dynamical Astronomy》1987,40(3-4):233-272

When asteroids are in the secular resonance ₆, the variation of the eccentricity becomes very large. In this paper, the dynamics of this secular resonance ₆ is investigated by a simple analytical model, in which the third degree terms of the eccentricity and inclination are taken into account. The eccentricity variations of asteroids located near this resonance are represented clearly by the diagrams of equi-Hamiltonian curves on the plane of versuse ( the longitude of perihelion of asteroids and Saturn,e: the eccentricity of asteroids). These diagrams predict that the eccentricity of these asteroids suffers a large increase or decrease, and that the secular resonance argument librates about 0° and 180°. In order to confirm these predictions, numerical integrations are carried out over one million years. By these integrations, it is found that the eccentricity of secular resonant asteroids becomes more than 0.8, and that the libration about 0° also exists, as well as the libration about 180°. The strongly depopulated region in the asteroidal belt, which corresponds to the position of the secular resonance ₆, is also explained well by this analytical model.  相似文献   

GMS proton flux observation during February 1978     

Tsugunobu Nagai  Masaynki Kuwashima  Makoto Kawamura  Tsuyoshi Kohno 《Planetary and Space Science》1979,27(7):1035-1037

It is suggested that the drop out of the 1.2–4 MeV proton flux, observed by the geostationary satellite GMS, was due to the Earthward shift of the particle boundary in all local time. The particle boundary motions are associated with substorm activities.  相似文献   

Nitrate and phosphate uptake kinetics ofChattonella antiqua grown in light/dark cycles     

Yasuo Nakamura  Makoto M. Watanabe 《Journal of Oceanography》1983,39(4):167-170

Nitrate and phosphate uptake kinetics ofChattonella antiqua were examined under light and dark conditions. The uptake kinetics ofC. antiqua followed the Michaelis-Menten equation. The maximal uptake rates (V _max) of nitrate and phosphate in the dark were 86 and 93% of those in the light, respectively. The half-saturation constants (K ₈ ) were not significantly affected by illumination and were comparable to those of other phytoplankton. However, specific maximal uptake rates ofC. antiqua for these substrates were much smaller than those of other phytoplankton.  相似文献   

TIDICS—Control of tidal residual circulation and tidal exchange in a channel-basin system     

Makoto Kashiwai 《Journal of Oceanography》1985,41(1):1-10

A self-excited oscillation of tidal flow occurs in a tidal channel-basin system with a narrow and high speed inflowing tidal jet. The mechanism of this oscillation was examined through hydraulic experiments. Results show that the oscillation is caused by alternation in the strength of asymmetric residual circulation caused by a biased supply of vorticity by asymmetric tidal vortex pairs, and that the mechanism of alternation also depends on negative feed-back between the residual circulation and the vorticity supply.The unstable state of the flow suggested the possibility of controlling the tidal current and tidal exchange in the channel-basin system and this was confirmed experimentally. Under fixed tidal conditions and with fixed basin dimensions, the tidal residual circulation was controlled to form two strong clockwise and anticlockwise circulations or a single circulation by changing the shape of the bay entrance.  相似文献   

History and present status of the fishery of Sergestes lucens (Penaeidea, Decapoda, Crustacea) in Suruga Bay, Japan     

Omori  Makoto; Konagaya  Teruo; Noya  Kazuo 《ICES Journal of Marine Science》1973,35(1):61-77

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Productivity of zooplankton in the sea: Problems in relation to study on Sergestes lucens in Suruga Bay     

Makoto Omori 《Journal of Oceanography》1970,26(4):242-252

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Temporal and spatial variations in the spawning activity of the micronektonic shrimp,Sergia lucens (hansen) in Suruga Bay,Japan     

Gretchen H. Bishop  Makoto Omori  Fumio Muranaka 《Journal of Oceanography》1989,45(4):243-250

Temporal and spatial variations in the spawning activity ofSergia lucens were investigated in relation to some environmental conditions of Suruga Bay. The daily egg abundance varied considerably with the coefficient of variation from 81% to 269% in July. The spawning activity was most clearly affected by temperature, but the relationship to lunar period and content of chlorophylla were not obvious. Timing of the July spawning is predictable with increase of the surface temperature to 24°C and strong vertical movements of the 18°C isotherm depth; it is also related to modal length of the shrimp in June. It is suggested that intrusion of cold water at 20–50 m affects reproduction of the shrimps and vertical distribution of eggs and larvae. The shrimp population seemed to relate principally to two spawning grounds,i.e. the head part and the western part of the bay. The timing of spawning is not always synchronous throughout the bay. The spawning is sporadic and the distribution of eggs is patchy. This may reflect a recent decrease in the population of the shrimp due to increased fishing pressure.A part of the present paper is based on the thesis submitted by G. H. B. in partial fulfilment of the requirements for her degree of Master of Science at the Tokyo University of Fisheries in 1986.  相似文献