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191.
192.
Synthetic clinoenstatite (MgSiO3) has been converted to a single phase with the perovskite structure in complete reactions at approx. 300 kbar in experiments that utilize the laser-heated diamond-anvil pressure apparatus. The structure of this phase after quenching was determined by powder X-ray diffraction intensity measurement to be similar to that of the distorted rare-earth, orthoferrite-type, orthorhombic perovskites, but it is suggested that such distortion from ideal cubic perovskite would diminish at high pressure. The unit cell dimensions and density of perovskite-type MgSiO3 at ambient conditions (1 bar, 25°C) are a=4.780(1) Å, b=4.933(1) Å, c=6.902(1) Å, V=162.75 Å3, and ρ=4.098(1) g/cm3. This phase is 3.1% denser than the isochemical oxide mixture [periclase (MgO)+stishovite (SiO2)]. The small crystal-field stabilization energy of the cation site in the perovskite structure may play an important role in limiting the high-pressure stability field of perovskites that contain transition metal cations. Approximate calculations of the crystal-field effects indicate that perovskite of pure FeSiO3 composition may become stable at 400–600 kbar; pressures greater than 800 kbar would be required to stabilize CoSiO3 or NiSiO3 perovskite. 相似文献
193.
Prof.Dr. Atsushi Watanabe 《Aquatic Sciences - Research Across Boundaries》1970,32(2):566-569
Summary The paper gives a survey of the blue-green algae found in Japan and used as food, medicine and nitrogenous fertilizer.
Since time immemorial four kinds (Aphanothece sacrum, Nostoc verrucosum, Nostoc commune, Blachytrichia quoyi) have been used for cooking purposes; yet it is only now that man is trying to cultivate a species, theAphanothece sacrum. Recently a bluegreen alga (Spirulina maxima), which is particularly rich in protein and vitamins and has always been eaten by the natives, became known in Africa.
The medicinal effects of linolenic acid was examined connection with the circulation of fatty acid. Only two of the species
analysed (Spirulina platensis, Arthrospira sp.) produce relatively large quantities of γ-linolenic acid.
The effects of the nitrogen-producing blue-green algaTolypothrix tenuis were observed in over 40 rice fields in various regions in Japan. In some places a considerable increase in the yield was
noticed, but this was never as high as in India. Presumably the difference can be traced back to 3 main factors: air temperature,
alkalinity of the water and the amount of nitrogen fertilizer.
Zusammenfassung Das Referat gibt eine übersicht über essbare, medizinisch wirksame und stickstoffdüngende Blaualgen speziell aus Japan. Vier Arten (Aphanothece sacrum, Nostoc verrucosum, Nostoc commune, Blachytrichia quoyi) werden seit alter Zeit als Zugabe zu den Mahlzeiten gebraucht, wobei man erst heute eine Art (Aphanothece sacrum) zu kultivieren versucht. Kürzlich wurde in Afrika eine Blaualge (Spirulina maxima), bekannt, die einen besonders hohen Gehalt an Eiweiss und Vitaminen aufweist und seit jeher von den Eingeborenen gegessen wird. Im Zusammenhang mit dem Kreislauf der Fetts?uren wurde die medizinische Wirkung der Linols?ure geprüft. Nur zwei der analysierten Arten (Spirulina platensis, Arthrospira sp.) bilden relativ grosse Mengen Linols?ure. In gut 40 Reisfeldern verschiedener Regionen in Japan wurde die Wirkung der stickstoff-bindenden BlaualgeTolypothrix tenuis beobachtet. Es konnten zum Teil betr?chtliche Steigerungen erzielt werden, doch nie so hohe wie in Indien. Vermutlich sind die Unterschiede haupts?chlich auf drei Faktoren: Lufttemperatur, Alkalinit?t des Wassers und Menge an Stickstoffdünger zurückzuführen.相似文献
194.
The northern Ryukyu Arc has active backarc rift, neutral-stress forearc, and active accretionary prism. The Okinawa Trough has been shaped by the episodic rifting in the backarc. Paleostresses were inferred in this study from mesoscale faults in Neogene forearc sediments called the Miyazaki Group, southeast Kyushu in the northern Ryukyu Arc. The forearc stress changed from compressional to extensional from the latest Miocene through Early Pliocene time. The stress history is concordant with the transition in tectonic regime from folding to rifting in the backarc. The transition in the stress state occurred simultaneously also with trenchward movement of the volcanic front. These phenomena suggest that the subducting slab under southern Kyushu became steeper in the Early Pliocene. Extensional tectonics ceased sometime in the late Pliocene or early to mid-Pleistocene, concordant with the counterclockwise change of subducting direction of the Philippine Sea Plate. 相似文献
195.
Atsushi Saotome Ryunoshin YoshinakaMasahiko Osada Hiroyasu Sugiyama 《Engineering Geology》2002,64(1):1-17
Volcanic breccia is a representative heterogeneous rock. As a preliminary study for determining its mechanical properties in laboratory and field experiments, its material properties and structural features were described. Three-dimensional clast-size distribution was also estimated for the study site using the theory of stereology. With this distribution determined, a numerical simulation was performed to investigate the relationship between the volumetric proportion of clasts in a sample and the areal proportion and maximum length of clasts on a lateral surface of the sample. The following observations were made: (1) coefficients of variation for volumetric proportion are dependent on the size of the sample, and became large when the size of the sample is small; (2) samples with a small coefficient of variation can be selected at any size if a restriction is placed on the ratio, Dmax/D0, of the maximum length of clasts to the size of the sample; and (3) the volumetric proportion of clasts in each sample can be estimated from the observed areal proportions within an error range that depends on the whole volumetric proportion. 相似文献
196.
197.
Abstract Upper Paleozoic to Mesozoic sedimentary sequences of chert (Liminangcong Formation), clastics (Guinlo Formation) and a number of limestone units (Coron Formation, Minilog Formation and Malajon Limestone) constitute the accretionary complex of the North Palawan block, Philippines. Based on chert-to-clastic transitions from different stratigraphic sequences around the Calamian Islands, three accretionary belts are delineated: the Northern Busuanga Belt (NBB), the Middle Busuanga Belt (MBB) and the Southern Busuanga Belt (SBB). The accretion events of these belts along the East Asian accretionary complex, indicated by their sedimentary transitions, began with the Middle Jurassic NBB accretion, followed by the Late Jurassic MBB accretion and the Early Cretaceous SBB accretion. Several limestone blocks that formed over the seamounts became juxtaposed with chert–clastic sequences during accretion. During the Late Cretaceous, accretion-subduction along the East Asian margin subsided bringing tectonic stability to the region. The seafloor spreading during the mid-Oligocene disconnected the entire North Palawan block from the Asian mainland and then migrated southward. The collision between the North Palawan block and the Philippine Island Arc system in the middle Miocene generated a megafold structure in the Calamian Islands as a result of the clockwise turn of the accretionary belts in the eastern Calamian from originally northeast–southwest to northwest–southeast. 相似文献
198.
Manabu Kanda Atsushi Inagaki Marcus Oliver Letzel Siegfried Raasch Tsutomu Watanabe 《Boundary-Layer Meteorology》2004,110(3):381-404
The spatial representativeness of heat fluxes on the basis of single-tower measurements, and the mechanism of the so-called energy imbalance problem, are investigated through numerical experiments using large-eddy simulation (LES). LES experiments are done for the daytime atmospheric boundary layer heated over a flat surface, as a best-case scenario completely free of sensor errors and the uncertainties of field conditions. Imbalance is defined as the deviation of the `turbulent' heat flux at a grid point from the horizontally averaged `total' heat flux. Both the theoretical and numerical results of the present study suggest the limitation of single-tower measurements and the necessity of horizontally-distributed observation networks.The temporally averaged `turbulent' flux based on a point measurement systematically underestimates the `total' flux (negative imbalance). This is attributed to local advection effects caused by the existence of turbulent organized structures (TOS), whose time scale is much longer than that of thermal plumes. The temporal and spatial change of TOS patterns causes low-frequency trends in the velocity and temperature data resulting in large scatter of the flux estimates. The influences of geostrophic wind speed, averaging time, observation height, computational domain size and resolution on tower-measured fluxes are also discussed. Finally, it is suggested that a weak inhomogenity in surface heating may reduce the negative bias of flux estimates. 相似文献
199.
Stable carbon and oxygen isotope measurements of biogenic carbonate provide information for reconstructing past oceanic environments. In particular, 18O/16O ratios correlate with the temperature and salinity of seawater and 13C/12C is a proxy for dissolved inorganic carbon in seawater and symbiont photosynthesis. Here, we report 13C/12C and 18O/16O values for skeletons of corals (genus Porites) with various growth rates. In faster-growing corals, 13C/12C and 18O/16O showed out-of-phase annual fluctuations. In slower-growing corals, the isotopes fluctuated in phase. We developed a simple vector notation to show two patterns of 13C/12C annual fluctuation, each with a different offset in relation to 18O/16O annual fluctuation. The phase offset between 13C/12C and 18O/16O annual fluctuations depends on the relative intensities of kinetic isotope effects on calcification and metabolic isotope effects such as photosynthesis. This model might improve our ability to infer past climate and oceanographic conditions from coral skeletons. 相似文献
200.