Metabolism and chemical composition of marine pelagic amphipods: synthesis toward a global bathymetric model

Respiration and ammonia excretion data and chemical composition data [water content, ash, carbon (C), nitrogen (N) and C:N ratios] of 18–32 amphipods (hyperiids and gammarids) from the epipelagic through bathypelagic zones of the world’s oceans were compiled. The independent variables including body mass, habitat temperature and mid-sampling depth were all significant predictors of respiration, accounting for 65–83 % of the variance in the data, while the former two variables were significant predictors of ammonia excretion, accounting for 64–77 % of the variance. Atomic O:N ratios (respiration:ammonia excretion) ranged from 11 to 74 (median 21.5). C composition was negatively correlated with habitat temperature, but water contents, ash, N, and the C:N ratio were uncorrelated with the three independent variables. As judged by C:N ratios, protein was considered to be the major organic component of most pelagic amphipods. However, some amphipods from >500 m depth exhibited high C:N ratios (>10) suggesting a large deposition of lipids in the body. Comparison of the present results with global bathymetric models of euphausiids and pelagic copepods revealed that respiration rates of the pelagic amphipods were near-equal to the rates of euphausiids but greater than the rates of pelagic copepods, reflecting taxon-specific body morphology and swimming behavior among the three taxa. As a marked feature of body chemical composition, the pelagic amphipods exhibited extremely high ash content (mean 25 % of DM) due to their possession of a robust exoskeleton.     

Seasonal Variations of Plankton Food Web Structure in the Coastal Water off Usujiri Southwestern Hokkaido,Japan

The planktonic food web structure in the subarctic coastal water off Usujiri south-western Hokkaido, Japan was investigated from June 1997 to June 1999, based on seasonal biomass data of pico- (<2 µm), nano- (2–10 µm), micro- (10–200 µm) and mesoplankton (>200 µm), and path analysis using the structural equation model (SEM). In spring, microphytoplankton predominated due to diatom bloom, while pico- and nanophytoplankton predominated in the other seasons, except November and December 1997. The seasonal change in size distribution of heterotrophic plankton was almost similar to that of phytoplankton, and mesozooplankton biomass was high in spring. The path analyses suggest that the main channel in the microbial food web could vary according to phytoplankton size composition, indicating not only the classical food chain (microphytoplankton - copepods) but also the indirect route (microphytoplankton - naked dinoflagellates - copepods).     

Multiple generations of forearc mafic–ultramafic rocks in the Timor–Tanimbar ophiolite, eastern Indonesia

We investigated mafic–ultramafic rocks distributed in the Timor–Tanimbar region as a possible modern analogue for the Mediterranean-type ophiolites in the Tethyan system. The geological occurrence suggests that the buoyant subduction of Australian continent uplifted the fragments of newly formed mantle–crust section, which extends to the neighboring preemplaced forearc marginal basins. However, we recognized a large variety of igneous features, which is consistent with the lack of complete succession and the presence of abundant crosscutting structures. All peridotite masses in Timor (Mutis, Atapupu and Dili) are mostly fertile (lherzolitic) in compositions. In addition, we found depleted harzburgite, highly refractory dunite and olivine websterite to occur as minor constituents, which display compositional contrast to those of the lherzolites. Structurally overlying Ocussi volcanics resemble island–arc tholeiite in terms of trace element characteristics, apparently inconsistent with genetic relationship with Timor lherzolite masses. In eastern small islands (Moa and Dai), all types of ophiolitic rocks display varying degrees of island–arc affinities. Cumulate origin of wehrlite and gabbroic rocks in Dai is marked by early crystallization of clinopyroxene and common occurrence of high-calcic plagioclase. Dikes cutting the gabbro sequence have weak island–arc signatures relative to those of Ocussi volcanics. Mildly depleted lherzolite–harzburgite in Moa was intruded by high-Mg andesitic magma, which crystallized hornblende gabbro containing high-Mg orthopyroxene. These petrological and geochemical variations can be best explained by the combination of (1) a temporal change of igneous activity possibly associated with development of forearc basin and (2) the emplacement of spatially different forearc regions in each locality. Unusual occurrence of fertile lherzolite in the forearc setting, generation of high-Mg andesite magmatism, inverted metamorphic grade recorded from associated metamorphic rocks, and formation of marginal basins may be linked to the injection of high-temperature asthenospheric materials into the mantle wedge.     

Bulk parameterization for a vegetated surface and its application to a simulation of nocturnal drainage flow

Two simple models are presented for describing the surface energy budget above vegetated surfaces. One is the traditional single-source model that includes only one energy budget equation for the entire canopy-soil system, and the other is the double-source model that includes separate energy budget equations for the vegetation canopy and the underlying soil surface. In both models, the bulk transfer coefficients needed to solve the energy budget equations are parameterized as functions of leaf area index, leaf transfer coefficients, and soil surface roughnesses to obtain the best fit to values calculated by a standard multilayer-canopy model. The validity of these models was tested by comparing their performance with that of the multilayer-canopy model for simulation of the surface energy balance and nocturnal drainage flow above vegetation. Results show that the double-source model gives reliable estimations for all cases ranging from sparse to dense vegetation covers; the single-source model is only applicable to dense, fully-covered vegetation. It is also shown that sparse vegetation weakens nocturnal drainage flow, since it isolates the cool underlying soil surface from the atmosphere above the canopy. This phenomenon cannot be described by a traditional single-source model incorporated commonly in many atmospheric models; however, the double-source model adequately describes this process.     

Cyclic analysis and capacity prediction of concrete‐filled steel box columns

Concrete‐filled steel columns have been widely used in civil and architectural constructions throughout the world in recent years. This study is concerned with the cyclic elastoplastic analysis and capacity prediction of concrete‐filled steel columns having thick‐ and thin‐walled stiffened box‐shaped sections. An analytical procedure for determining the ultimate state of the concrete‐filled steel column is proposed based on the fiber analysis technique. Strength and ductility predictions are made by means of a new failure criterion. This is proposed based on the average failure strain of concrete and steel at critical regions. A recently developed monotonic stress–strain relation for confined concrete is modified so that it can be used in the analysis of thin‐ or thick‐walled section columns with stiffeners. A simple cyclic rule is introduced into this model in order to be used in cyclic analysis. Material non‐linearity of steel is represented by the modified two surface model developed at Nagoya University. The predictions are then compared with the existing experimental results and found to exhibit satisfactory agreement. Both small‐ and large‐scaled columns are considered in the comparisons. Copyright © 2001 John Wiley & Sons, Ltd.     

Propagation Speed of a Magnetic Flux-tube Soliton with Electric Current

We present some results of a magnetic flux-tube soliton propagating along a current loop surrounded by a weakly ionized plasma, by using a 3-D Neutral-MHD simulation code. When the velocity of mass flows outside the current loop exceeds about 0.6_A, the magnetic pulse behaves as an isolated string wave which is called a curved soliton, propagating with a velocity less than that one of exterior mass flow. The propagation speed of the magnetic flux-tube soliton is studied by changing the intensity of the electric current along the flux tube, which usually cannot be observed directly. It is found that the soliton speed decreases proportionally to the increment of the electric current, and the speed is independent of the direction of the electric current. We can estimate the current intensity inside a magnetic flux-tube soliton by observations of the soliton speed and the external plasma flow velocity. These results should be compared with recent high-resolution observations of moving magnetic features (MMFs) observed near sunspots.     

Strong ground motion during the largest aftershock (Mw=5.8) of the 1999 Izmit earthquake, Turkey

We present a preliminary study of strong ground motion during the largest aftershock (M_w 5.8) of the 1999 Izmit earthquake (M_w 7.4), Turkey, at 11:55 on 13 September 1999. The peak ground acceleration observed near the epicentre of this aftershock was in agreement with that predicted by standard empirical prediction equations. Its spectral source parameters of the largest aftershock are also typical for a M_w 5.8 earthquake. At greater epicentral distances, there is an order-of-magnitude in scatter in peak ground acceleration values for this aftershock, which is attributed to site effects. The presence of thick layers of low-velocity sediments caused significant amplification of S-waves in the Avcılar district of Istanbul, at frequencies of 1 Hz, explaining the observed concentration of damage there as a result of the Izmit mainshock.     

Formation of intermediate-mass black holes as primordial black holes in the inflationary cosmology with running spectral index

Formation of primordial black holes (PBHs) on astrophysical mass scales is a natural consequence of inflationary cosmology, if the primordial perturbation spectrum has a large and negative running of the spectral index as observationally suggested today because double inflation is required to explain it and fluctuations on some astrophysical scales are enhanced in the field-oscillation regime in between. It is argued that PBHs thus produced can serve as intermediate-mass black holes (IMBHs), which act as the observed ultraluminous X-ray sources (ULXs) by choosing appropriate values of the model parameters in their natural ranges. Our scenario can be observationally tested in near future because the mass of PBHs is uniquely determined once we specify the values of the amplitude of the curvature perturbation, spectral index and its running on large scales.