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31.
The low energy effective theory for the Randall-Sundrum two-brane system is investigated with an emphasis on the role of the
non-linear radion in the brane world. It is shown that the gravity on the brane world is described by a quasi-scalar-tensor
theory with a specific coupling function.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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33.
Electromagnetometry at the sea floor has been developed over the last two decades taking advantage of the progress of positioning
and acoustic technology in marine region. In spite of its risks and costs, electromagnetometry at the sea floor has significantly
contributed to the study of conductivity anomalies through direct observations of electromagnetic variations at the sea floor.
Some of the fruitful results of the ocean bottom observations around Japan as well as data processing of sea floor electromagnetic
measurements are reviewed. Future problems in electromagnetometry at the sea floor are also discussed. In conclusion, the
importance of establishing semipermanent electromagnetic observatories at the sea floor is emphasized. 相似文献
34.
Fumito Shiraishi Yuki Eno Yuki Nakamura Yusaku Hanzawa Jiro Asada Anelize Manuela Bahniuk 《Sedimentology》2019,66(2):459-479
The relative influences of biotic and abiotic processes on travertine fabrics are still not well understood, despite increasing interest in the last decade to better understand the record of ancient microbial life and sedimentary fabrics in microbial hydrocarbon reservoirs. This study examines travertines at Satono‐yu hot spring in Japan (the temperature of water flowing over the travertine was ca 35°C), to better understand the interaction between depositional, hydrochemical and microbial parameters at different flow settings. Characteristics of the bulk hydrochemistry, mineralogy (exclusively aragonite) and the driving force for precipitation (primarily abiotic CO2 degassing with some photosynthetic microbial contribution) were similar among all of the flow settings. Conversely, the increase in flow velocity suppressed the influence of photosynthesis and enhanced the abiotic precipitation due to the thinner diffusive boundary layer at the travertine surface–water interface. Additionally, the increase in flow velocity changed the microbial composition and decreased the bacterial diversity by reflecting their adhesion efficiency on the travertine substrate. The acidity of the cyanobacterial sheaths controls the aragonite nucleation rate and the resulting calcification, even at significantly high equilibrium CO2 partial pressure (ca 22 to 28 matm), high dissolved inorganic carbon concentration (ca 35 to 38 mmol l?1), and elevated aragonite saturation state (ca 20‐fold to 34‐fold). Therefore, the increase in flow velocity suppresses the microbial influence with respect to the increase in the saturation state, the nucleation site supply and pore space generation. Overall, this results in the predominance of abiotic precipitation under high flow velocities. Consequently, a sparse‐micritic fabric with abundant interlamina porosity forms under lower flow velocity where the microbial influence is effective, while a dense‐sparitic fabric with little inter‐crystalline porosity forms under higher flow velocity where abiotic precipitation prevails. These findings provide an essential base for assessing the formation processes of ancient travertines and comparable deposits from petrological fabrics. 相似文献
35.
Kenichiro Tani Richard S. Fiske Yoshihiko Tamura Yukari Kido Jiro Naka Hiroshi Shukuno Rika Takeuchi 《Bulletin of Volcanology》2008,70(5):547-562
Sumisu volcano was the site of an eruption during 30–60 ka that introduced ∼48–50 km3 of rhyolite tephra into the open-ocean environment at the front of the Izu-Bonin arc. The resulting caldera is 8 × 10 km
in diameter, has steep inner walls 550–780 m high, and a floor averaging 900 m below sea level. In the course of five research
cruises to the Sumisu area, a manned submersible, two ROVs, a Deep-Tow camera sled, and dredge samples were used to study
the caldera and surrounding areas. These studies were augmented by newly acquired single-channel seismic profiles and multi-beam
seafloor swath-mapping. Caldera-wall traverses show that pre-caldera eruptions built a complex of overlapping dacitic and
basaltic edifices, that eventually grew above sea level to form an island about 200 m high. The caldera-forming eruption began
on the island and probably produced a large eruption column. We interpret that prodigious rates of tephra fallback overwhelmed
the Sumisu area, forming huge rafts of floating pumice, choking the nearby water column with hyperconcentrations of slowly
settling tephra, and generating pyroclastic gravity currents of water-saturated pumice that traveled downslope along the sea
floor. Thick, compositionally similar pumice deposits encountered in ODP Leg 126 cores 70 km to the south could have been
deposited by these gravity currents. The caldera-rim, presently at ocean depths of 100–400 m, is mantled by an extensive layer
of coarse dense lithic clasts, but syn-caldera pumice deposits are only thin and locally preserved. The paucity of syn-caldera
pumice could be due to the combined effects of proximal non-deposition and later erosion by strong ocean currents. Post-caldera
edifice instability resulted in the collapse of a 15° sector of the eastern caldera rim and the formation of bathymetrically
conspicuous wavy slump structures that disturb much of the volcano’s surface. 相似文献
36.
Following the oil spill from the Russian tanker Nakhodka in 1997 in the Sea of Japan, polycyclic aromatic hydrocarbons (PAH) were monitored for three years in some molluscs from the Mikuni-cho shore in Japan. Total PAH concentrations in marine organisms except for spiny top shell, ranged from 5.3 to 32.7 ng/g wet weight, but no trends were evident. Total PAH concentration in spiny top shell (Turbo cornutus) was 44 ng/g w.w. in the first month after the oil spill. However, it rapidly decreased to less than 5.4 ng/g w.w. from the second month. Spiny top shell, which was exposed to dietary Nakhodka heavy fuel oil, concentrated benzo(a)pyrene to 17.1 ng/g w.w. after two weeks of exposure and then rapidly eliminated it during an elimination phase. These results suggest that spiny top shell accumulates PAHs because of their low ability to metabolize PAH, but it can excrete parent PAHs rapidly when removed from the source of contamination. Thus it is suitable as an indicator organism in monitoring oil contamination. It can also be inferred from these field and laboratory investigations that, in three years, organisms from the Mikuni-cho shore seem to have adequately recovered from the Nakhodka oil spill contamination. 相似文献
37.
Shoji?AraiEmail author Jiro?Uesugi Ahmed?H.?Ahmed 《Contributions to Mineralogy and Petrology》2004,147(2):145-154
A new type of podiform chromitite was found at Wadi Hilti in the northern Oman ophiolite. It is within a late-intrusive dunite body, possibly derived from olivine-rich crystal mush, between the sheeted dike complex and upper gabbro. This chromitite forms small (<30 cm in thickness) pods with irregular to lenticular shapes. Neither layering nor graded bedding is observed within the pods. The chromitite is in the upper crust, by far shallower in ophiolite stratigraphy than the other podiform chromitites that have ever been found in the Moho transition zone to the upper mantle. It is distributed along a small felsic to gabbroic melt pool within the dunite body, which was formed by melting of gabbroic blocks captured by the mush. Chromian spinel was precipitated due to mixing of two kinds of melt, a basaltic interstitial melt from the mush and an evolved, possibly felsic, melt formed by the melting of gabbro blocks. The podiform chromitite reported here is strikingly similar in petrography and spinel chemistry to the stratiform chromitite from layered intrusions. The former contains plagioclase and clinopyroxene as matrix silicates instead of olivine as well as includes euhedral and fine spinel with solid mineral inclusions. Chromian spinel of the upper crustal podiform chromitite from Oman has relatively low content of (Cr2O3 + Al2O3), the Cr/(Cr + Al) atomic ratio of around 0.6, and the relatively high TiO2 content ranging from 1 to 3 wt%. We conclude that assimilation of relatively Si-rich materials (crustal rocks or mantle orthopyroxene) by olivine-spinel saturated melts can explain the genesis of any type of chromitite.Editorial responsibility: V. Trommsdorff 相似文献
38.
Dynamical properties of an anchorage of South Bisan-seto Suspension Bridge are determined by means of in situ measurement of the ambient vibrations. This anchorage, being located in the sea, is tall and slender; its natural frequencies are expected to be low. On the other hand, the elasticity of the ground estimated from the conventional geological data is highly dispersed. It even suggests the possibility of resonance between the towers and this anchorage. It is therefore necessary to know its natural frequencies precisely. Seismic motions and microtremors are acquired and used properly. The observation is repeated every year during the period of construction of the anchorage so that its inertial properties change significantly. First modes of the longitudinal and the transversal vibrations of the anchorage are identified and their frequencies determined. The elasticity modulus estimated from these natural frequencies is about five times as large as that of the geological survey while it is consistent with that obtained from the velocity of the elastic waves of the ground. 相似文献