Evaporation metamorphism of primitive dust material in the early solar nebula

An evaporation experiment on matrix material of the Murchison (C2) meteorite up to 1900°C in vacuo has revealed the evaporation sequence of primitive dust material and the associated evolution of residual solid phases from hydrous silicates through magnesium silicates and iron-metal to calcium-aluminum oxides. The comparison with primitive meteorites suggests that the evaporation metamorphism coupled with the re-condensation may have played an important role in the generation of diverse primitive meteorites in the early solar nebula.     

A note on stilpnomelane mineralogy

Stilpnomelane analyses are classified into two separate groups of ferro- and ferristilpnomelanes on the H₂O(+)-Fe₂O₃/(Fe₂O₃+FeO) diagram. The relation is not comparable with that of oxyhornblende.     

Robust active vibration suppression control with constraint on the control signal: application to flexible structures

A unified mathematical framework, sustained by experimental results, is presented for robust controller design taking into account the constraint on the control signal. The design procedure is exemplified for an active vibration suppression control problem with applications to flexible structures. The considered experimental set‐up is a three‐storey flexible structure with an active mass driver placed on the last storey. First, the considered flexible structure is identified and the model's parametric uncertainties are deduced. Next, control constraints are presented for the robust control design problem, taking into account the restriction imposed on the control signal. Finally, the effectiveness of the control system is tested through experiments, when the input disturbance is assumed to be a sinusoidal one as well as a historical earthquake record (1940 El Centro record). Copyright © 2003 John Wiley & Sons, Ltd.     

Variation of the distribution coefficients of rare earth elements in modern coral-lattices: species and site dependencies

Rare earth element (REE) concentrations in the carbonate lattice of four species of coral have been analyzed and compared with the dissolved REE in ambient seawaters. The corals were from two areas of different salinity, marine (34-34.5) and bay (33-34). The measurement of REE in coral was carried out with inductively coupled plasma mass spectrometry (ICP-MS) after meticulous washing of coral samples, digestion with acetic acid and preconcentration of REE. The concentrations of REE in the two ambient seawaters were quite different, being ten-times higher in the bay area and enriched in light REE. However, the average distribution coefficients (D’s) were almost identical in the two areas. Substantial distribution coefficient differences were observed among the four coral species and the magnitude of inter-species variation in D was also species-dependent. Theoretical calculations imply that pH variation could cause variations in D large enough to account for the small differences between the two areas.     

3-D Modelling of Plate Interfaces and Numerical Simulation of Long-term Crustal Deformation in and around Japan

— We developed a 3-D simulation model for long-term crustal deformation due to steady plate subduction in and around Japan by incorporating viscoelastic slip-response functions into a realistic 3-D plate interface model, constructed on the basis of the topography of ocean floors and hypocenter distributions of earthquakes. The lithosphere-asthenosphere system is modelled by an elastic surface layer overlying a Maxwellian viscoelastic half-space. Kinematic interaction at plate interfaces is rationally represented by the increase of tangential displacement discontinuity (fault slip) across the interfaces. With this model, giving the steady slip rates at plate interfaces calculated from NUVEL-1A, we simulated long-term crustal deformation due to steady plate subduction in and around Japan. The simulated crustal deformation pattern is characterized by steep uplift at island arcs, sharp subsidence at ocean trenches and gentle uplift at outer rises. The numerical results show the strong dependence of the deformation pattern on the 3-D geometry of plate interfaces.     

The characterization and distribution of aerosol and gaseous species in the winter monsoon over the western pacific ocean

During the winters of 1981 and 1982, measurements were taken on two Japanese islands of the aerosol and gaseous species which had been carried by northwesterly monsoons over the Pacific Ocean. The aerosols were characterized as sea-salt particles; soil particles, and as particles of sulfate, nitrate, organics and elemental carbon. At Chichi-jima island, which is about 800 km away from the main islands of Japan, it was found that the level of the anthropogenic components of the aerosols was considerably higher than their background level. The mean concentrations of the species on the islands are given in tabular forms. According to a survey made on board a ferry boat, the aerosol and gaseous species were fairly uniformly distributed along the southern coast of the main Japanese islands.     

Mapping method of rainfall-induced landslide hazards by infiltration and slope stability analysis

Landslides - By utilizing the Green-Ampt infiltration equation and the infinite slope stability model, a method for analyzing shallow slope failures caused by rainfall is developed. With rainfall...     

Standing stocks and production rates of phytoplankton and abundance of bacteria in the Seto Inland Sea, Japan

Standing stocks and production rates of phytoplankton and abundance of bacteria were investigated at 39 stations in the Seto Inland Sea, Japan during four crulses in October 1993, January, April and June 1994. Primary productivity was measured by the¹³C tracer method. Photosynthetic rate varied from 0.41 to 32.1 μgC/1/h with an average value of 4.67 μgC/l/h. Annual primary production was estimated to be 218 gC/m²/year. Annual primary production in this study was 1.8 times as high as the values which were previously reported at same area. The reason for the disagreement between our primary production value and previous values is not thought to be due to the difference of methods used for measuring primary production or the different Chl.a concentrations but to the method of estimating the primary production in the euphotic zone from thein vitro measurements. The distribution of bacterial cells in surface seawater was examined during the same cruises. Bacterial cell density ranged from 0.32 to 3.4×10⁶ cells/ml. The density was relatively high in the eutrophic regions of Hiroshima Bay and Osaka Bay In addition, a high density of bacteria was also observed in an area within Suo Nada where Chl.a was relatively low. The disparity between Chla and bacterial density in Suo Nada suggests that bacterial abundance can be controlled by the availability of substrates other than phytoplankton exudate.     

Primary productivity and solar radiation off Sanriku in May 1997

We measured the in situ primary production at four stations from the surface to 80 m off Sanriku in late May 1997. The depth-integrated daily primary production in the upper 80 m was estimated to be 391, 468, and 855 mgC m⁻²d⁻¹ in water from the Oyashio, and 336 mgC m⁻²d⁻¹ in the warm-core ring. The variation in the primary production was primarily due to the variation in phytoplankton activity (chlorophyll α-specific primary production). A combination of previous and present studies in water from the Oyashio and the warm-core ring suggested that phytoplankton activity is proportional to light intensity between 12 and 50 Ein m⁻²d⁻¹ which is close to the usual light condition (61–75 Ein m⁻²d⁻¹) off Sanriku in May and June. Light may be a limiting factor for phytoplankton off Sanriku in late spring and early summer.     

Origin of the early Cenozoic belt boundary thrust and Izanagi–Pacific ridge subduction in the western Pacific margin

The belt boundary thrust within the Cretaceous–Neogene accretionary complex of the Shimanto Belt, southwestern Japan, extends for more than ~ 1 000 km along the Japanese islands. A common understanding of the origin of the thrust is that it is an out of sequence thrust as a result of continuous accretion since the late Cretaceous and there is a kinematic reason for its maintaining a critically tapered wedge. The timing of the accretion gap and thrusting, however, coincides with the collision of the Paleocene–early Eocene Izanagi–Pacific spreading ridges with the trench along the western Pacific margin, which has been recently re‐hypothesized as younger than the previous assumption with respect to the Kula‐Pacific ridge subduction during the late Cretaceous. The ridge subduction hypothesis provides a consistent explanation for the cessation of magmatic activity along the continental margin and the presence of an unconformity in the forearc basin. This is not only the case in southwestern Japan, but also along the more northern Asian margin in Hokkaido, Sakhalin, and Sikhote‐Alin. This Paleocene–early Eocene ridge subduction hypothesis is also consistent with recently acquired tomographic images beneath the Asian continent. The timing of the Izanagi–Pacific ridge subduction along the western Pacific margin allows for a revision of the classic hypothesis of a great reorganization of the Pacific Plate motion between ~ 47 Ma and 42 Ma, illustrated by the bend in the Hawaii–Emperor chain, because of the change in subduction torque balance and the Oligocene–Miocene back arc spreading after the ridge subduction in the western Pacific margin.