An emission pathway for stabilization at 6?Wm?2 radiative forcing

Representative Concentration Pathway 6.0 (RCP6) is a pathway that describes trends in long-term, global emissions of greenhouse gases (GHGs), short-lived species, and land-use/land-cover change leading to a stabilisation of radiative forcing at 6.0 Watts per square meter (Wm^?2) in the year 2100 without exceeding that value in prior years. Simulated with the Asia-Pacific Integrated Model (AIM), GHG emissions of RCP6 peak around 2060 and then decline through the rest of the century. The energy intensity improvement rates changes from 0.9% per year to 1.5% per year around 2060. Emissions are assumed to be reduced cost-effectively in any period through a global market for emissions permits. The exchange of CO₂ between the atmosphere and terrestrial ecosystem through photosynthesis and respiration are estimated with the ecosystem model. The regional emissions, except CO₂ and N₂O, are downscaled to facilitate transfer to climate models.     

Numerical simulations of pulsationally unstable accretion disks around supermassive black holes

The innermost region of slim accretion disks with standard viscosity is unstable against axisymmetric radial inertial acoustic perturbations under certain conditions. Numerical simulations are performed in order to demonstrate behaviors of such unstable disks. It is shown that oscillations with the period of 10^–3 (M _BH/M ) s can be excited near the inner edge of the disks, whereM _BH is the mass of the central object. This kind of unstable disks is a possible origin of the periodic X-ray time variabilities with period of 10⁴s observed in a Seyfert galaxy NGC 6814.     

Experimental investigation of the α-β transformation of San Carlos olivine single crystal

Single crystalline San Carlos olivine (1 mm cube) was transformed to (Mg,Fe)₂SiO₄β-phase at 13.5–15 GPa, 1030–1330 °C for 0–600 min using a multi-anvil high pressure apparatus. The α-β transformation occurred by incoherent surface nucleation and interface-controlled growth and recovered partially transformed samples showed sharply defined reaction rim. The growth rate of the β-phase rim significantly decreased with time and the growth eventually ceased. TEM observations revealed that many dislocations were created in both the relict olivine just near the α-β interface and the β-phase in the rim, which show evidence for deformation caused by interfacial stresses associated with the misfit elastic strain of the transformation. The observed tangled dislocation texture in β-phase suggested that the β-phase rim was hardened and relaxation of the interfacial stress was retarded. This probably caused a localized pressure drop in the relict olivine and decreased the growth rate. Time-dependent growth rates of β-phase is possibly controlled by the rheology of β-phase, which must be considered for the prediction of the olivine metastability in the subducting slabs. Received: 24 January 1997 / Revised, accepted: 24 July 1998     

Geotraverse across the Sikhote Alin — The Sea of Japan — The Honshu Island — The Pacific

The paper presents the results of geological-geophysical research carried out during the Soviet-Japanese cooperative study of the structure and dynamics of the Earth's crust and upper mantle in the transition zone from the Pacific Ocean to the Asian continent. The 300 km deep geological-geophysical section of the tectonosphere (geotraverse) has been compiled on the basis of combined interpretations of seismic, geological, petrographic, gravimetric, magnetometric, electromagnetic and heat flow measurements. Estimates were made of deep temperatures along the geotraverse and of the depths of the partial melting level that can be identified with the upper boundary of the asthenosphere.     

Giant Megamullion in the Parece Vela Backarc Basin

We present results of high-resolution bathymetric studies of the extinct intermediate-spreading Parece Vela Basin in the northwestern Pacific, where we have identified an extremely large mullion structure, here termed a giant megamullion. We find that the giant megamullion is nearly an order of magnitude larger than the similar structures in the slow-spreading Mid-Atlantic Ridge (`megamullions'). The giant megamullion has slightly elevated mantle Bouguer anomaly, and yields serpentinized peridotites and gabbros, suggesting that they are exposing oceanic crust and upper mantle. An off-axis rugged `chaotic terrain' was also identified in the Parece Vela Basin. The terrain consists of isolated and elevated blocks capped by corrugated axis-normal lineations, and associated deeps. We thus interpret it as analogues to the Mid-Atlantic Ridge megamullions. We propose that amagmatic tectonics producing the giant megamullion and the chaotic terrain occupied a significant part in crustal construction in the Parece Vela Basin evolution.     

Variability of the central region in active galactic nuclei

Summary We review implications of the observed optical and X-ray variability (periodicities and light-curves), relevant for the understanding of physical conditions in the deep interiors of active galactic nuclei. We discuss in detail kinematical, hydrodynamical, thermal and radiative transfer effects which may be responsible for observed variability patterns. We put emphasis on theoretical options which can predict basic accretion parameters, such as the mass of the central black hole, the accretion rate and the inclination angle, in terms of observable quantities. Closed analytical results are given whenever available.     

A Paleogene magmatic overprint on Cretaceous seamounts of the western Pacific

The West Pacific Seamount Province (WPSP) represents a series of short-lived Cretaceous hotspot tracks. However, no intraplate volcanoes in advance of petit-spot volcanism erupted near a trench have been identified after the formation of the WPSP on the western Pacific Plate. This study reports new ages for Paleogene volcanic edifices within the northern WPSP, specifically the Ogasawara Plateau and related ridges, and Minamitorishima Island. These Paleogene ages are the first reported for basaltic rocks on western Pacific seamounts, in an area that has previously only yielded Cretaceous ages. The newly found Paleogene volcanisms overprint the Early–middle Cretaceous volcanic edifices, because the seamount or paleo-island material-covered reefal limestone caps on these edifices are uniformly older than the Paleogene volcanism identified in this study. This study outlines several possible causative factors for the Paleogene volcanism overprinting onto existing Cretaceous seamounts, including volcanism related to lithospheric stress, or a younger hotspot track within the northern part of the WPSP that records magmatism from ~60 Ma.     

Fine-scale chemostratigraphy of cross-sectioned hydrogenous ferromanganese nodules from the western North Pacific

A broad area densely covered by ferromanganese nodules was recently discovered around Minamitorishima (Marcus) Island, representing a high-potential metal resource, particularly for Co, Ni, Mo, and W. We studied 16 nodule samples from nodule fields around Minamitorishima Island. To define the fine-scale chemostratigraphy of the nodules, polished cross-sections of the samples were analyzed by microfocus X-ray fluorescence. Our results show that a general pattern of compositional variation was common throughout the growth history of the nodules in all the regions we studied. Chemical mapping clarified changes in the chemical signature and proportion of five lithological components throughout the growth history: Mn represented columnar δ-MnO₂; Fe represented layered amorphous FeOOH*xH₂O; Ti represented TiO₂*2H₂O intergrown with an amorphous FeOOH phase; P, Ca and Y represented particles of biogenic calcium phosphate; and Si, Al, K, Cu, and Ni represented pelagic sediment infills. We proposed a method for a creating a multi-dimensional compositional map of the fine-scale chemostratigraphy observed in the ferromanganese oxide layers on the basis of merging the mapped Mn, Fe, Ti, P, Si and Cu intensities. Multi-dimensional compositional mapping of the sampled nodules from the western North Pacific revealed two fundamental findings: (1) previously recognized first-order Fe–Mn layers, L0, L1, and L2, were further divided into two, three, and four sublayers, respectively, and (2) a delayed supply of material to be nuclei of nodule or a growth hiatus of Fe–Mn layer(s), leading to missing sublayers in the layers L0 and L2, regulated the nodule size. In contrast, layer L1, which does not have any missing sublayers, was commonly observed in the samples for this study and has been reported in studies of other regions in the western Pacific. We propose, therefore, that the layer L1 is a key facies for examining chemostratigraphic correlations with other areas of seafloor.     

考虑系统柔度影响的水压致裂法测量深部岩石应力

为了有效测量水压致裂方法中的重张压力,必须使用具有足够小柔度的试验设备,否则无法从重张压力估计垂直钻孔平面的最大水平应力.仅通过替换水压致裂系统中的某一部件来大幅度降低系统柔度是很难的.但如果流量计尽可能安装在靠近跨接式封隔器隔离出的钻孔测试区.那么系统柔度就会大大降低.为此,我们研制出配有井下流量计的试验系统,并在野...