Year-to-year change in water exchange characteristics in a semi-enclosed bya,Lake Hamana

The year-to-year change in characteristics of water exchange between Lake Hamana, a semi-enclosed bya, and the adjacent open sea is investigated.The destruction of the bay mouth by a typhoon in 1953 and subsequent stabilization work on the bay mouth from 1954 to 1973 resulted in an increase in the tidal prism volume of the bay (Mazda, 1983). In the present paper, a simple model has been constructed in which the magnitude of water exchange depends on the tidal prism, and using this model, the year-to-year increase in salinity of the bay water after 1953 can be well explained. Consequently, it can be said that the salinity increase after 1953 is a result of a progressive increase in water exchange caused by successive changes in topography of the bay mouth.The extent of water exchange in Lake Hamana, which varies seasonally, has increased gradually since 1953, and became stable after about 1967. For instance, at present the turnover time of the bay for exchange with open sea water reaches a maximum (2.9 months) in January and a minimum (0.9 month) in October, while in 1955 it is estimated to have been about 2.5 times that at the present time.     

Searching for novel CYP members using cDNA library from a minke whale liver

The contaminant-induced cytochrome P450 (CYP) members in minke whale (Balaenoptera acutorostrata) can be potential biomarkers of the contaminant exposure and toxic effects. In this study, we constructed a cDNA library from the liver of minke whale from the North Pacific, and further screened a total of 6930 clones randomly selected in the library for the isolation of cDNA clones encoding novel members of CYP superfamily. The screening revealed the isolation of six novel CYP cDNA clones that are classified into CYP1A, CYP2C, CYP2E, CYP3A, CYP4, and CYP4A subfamilies. The BLAST homology search using the partial cDNA fragments of four CYP subfamilies (CYP1A, CYP2C, CYP2E and CYP4A) demonstrated that the minke whale CYPs were most closely related to pig CYPs (81-91%). Identification of multiple CYP genes in marine mammal species such as minke whale will provide new insights into the metabolic or toxicological functions of individual CYP members.     

Detailed Observation of Spatial Abundance of Clam Larva Ruditapes philippinarum in Tokyo Bay, Central Japan

The spatial distribution of the larval abundance of the clam Ruditapes philippinarum has been investigated at 65 stations throughout Tokyo Bay on August 2, 2001. The large number of small D-shaped larvae that were found shortly after hatching in the waters around the Banzu, Futtu, and Sanmaizu-Haneda areas indicates that spawning populations in these areas probably contribute greatly to the larval supply in the bay. Small larvae also occurred abundantly around the Yokohama and Ichihara port areas, suggesting that these port regions play a role in the transport of larvae into Tokyo Bay. This revised version was published online in July 2006 with corrections to the Cover Date.     

Flocculation and particle size analysis of expansive clay sediments affected by biological, chemical, and hydrodynamic factors

Expansive clay sediments are abundant in riverine and estuarine waters and bottom beds, and their particle size distributions (PSD) are important for the analysis of sediment transport. This paper presents an experimental study to evaluate, using a laser particle size analyzer under varying flow conditions, the intrinsic PSD of two expansive clays, a Ca- and a Na-montmorillonite and the influence of biological, chemical, and hydrodynamic factors on their flocculation and PSD. The considered biological factor consists of three extracellular polymeric substances of varying polarity, including xanthan gum, guar gum, and chitosan; the chemical factor is the salinity; and the hydrodynamic factor is the types of flow indicated by the Reynolds number and shear rate. The intrinsic PSD of both clays show a multimodal lognormal distribution with sizes ranging from 0.2 to 50 μm. All three biopolymers, xanthan gum, guar gum, and chitosan, can facilitate flocculation through long-range polymer bridging and short-range ion-dipole interaction, hydrogen bonding, and Coulomb force. The influence of salinity is different for the two clays: the particle size of the Na-montmorillonite increases with salinity, which is caused by flocculation resulting from the suppressed electrical double layer, while that of the Ca-montmorillonite is slightly reduced owing to the decreased basal spacing and cation exchange. For different hydrodynamic conditions, higher shear rate promotes the flocculation of Ca-montmorillonite, but breaks the Na-montmorillonite flocs. The significance of understanding the flocculation and PSD of expansive clays is also discussed in terms of sediment transport under different aquatic environments.     

Submarine flank eruption preceding caldera subsidence during the 2000 eruption of Miyakejima Volcano, Japan

During the early part of a seismic swarm preceding eruption and caldera formation at Miyakejima Volcano, discoloured sea surfaces were observed 1.5 km off the western coast of Miyakejima on 27 June 2000. A later survey of the area using a multi-beam side scan sonar and a remotely operated small submarine revealed four craters of 20–30 m diameter aligned east-west in a 100×10–30 m area on the seafloor, with hot water at 140°C being released from one of the centres. Each crater consists of submarine spatter overlain in part by scoria lapilli. Dredged spatter from the craters was fresh, and there was no evidence of activity of marine organisms on the spatter surface, indicating that the discoloured sea surface resulted from magmatic eruption on the seafloor. This eruption occurred when a westward-propagating seismic swarm, initiated beneath Miyakejimas summit, passed through the area. Finding new magma on the seafloor demonstrates that this seismic swarm was associated with intruding magma, moving outward from beneath Miyakejima. Submarine spatter shows flattened shapes with a brittle crust formed by cooling in water, and its composition is aphyric andesite of 54 wt% SiO₂. The spatter is similar in whole rock and mineral composition to spatter erupted in 1983. However, the wide range of Cl in melt inclusions in plagioclase of the 27 June submarine spatter shows that it is not simply a remnant of the 1983 magma, which has only high Cl melt inclusions in plagioclase. The mixed character of melt inclusions suggests involvement of a magma with low Cl melt inclusions. The magma erupted explosively on 18 August from Miyakejimas summit, considered as the second juvenile magma in this eruption, contains low Cl melt inclusions in plagioclase. Based on these observations and the eruption sequence, we present the following model: (1) A shallow magma chamber was filled with a remnant of 1983 magma that had evolved to a composition of 54–55 wt% SiO₂. (2) Injection of the 18 August magma into this chamber generated a mixed magma having a wide range of Cl in melt inclusions contained plagioclase. The magma mixing might have occurred shortly before the submarine eruption and could have been a trigger for the initiation of the removal of magma from the chamber as an extensive dyke, which eventually led to caldera subsidence.Editorial responsibility: S Nakada, T Druitt     

Damper placement optimization in a shear building model with discrete design variables: a mixed‐integer second‐order cone programming approach

Supplemental damping is known as an efficient and practical means to improve seismic response of building structures. Presented in this paper is a mixed‐integer programming approach to find the optimal placement of supplemental dampers in a given shear building model. The damping coefficients of dampers are treated as discrete design variables. It is shown that a minimization problem of the sum of the transfer function amplitudes of the interstory drifts can be formulated as a mixed‐integer second‐order cone programming problem. The global optimal solution of the optimization problem is then found by using a solver based on a branch‐and‐cut algorithm. Two numerical examples in literature are solved with discrete design variables. In one of these examples, the proposed method finds a better solution than an existing method in literature developed for the continuous optimal damper placement problem. Copyright © 2013 John Wiley & Sons, Ltd.     

Recycling of Coal Fly Ash and Paper Waste to Improve Low Productive Red Soil in Okinawa,Japan

Coal fly ash (CFA) and paper waste (PW) related environmental problems and its recycling techniques have been a major challenge to society. Therefore, it is of crucial importance to develop new recycling methods for CFA and PW. This work proposes a potential new way of developing synthetic aggregates (SA) using CFA, PW, starch waste and ammonium sulfate (AS) as a granular nitrogen fertilizer medium, and their utilization as a soil amendment to improve crop production in the low productive acidic red soil of Okinawa, Japan. Three types of SA with three different nitrogen (N) percentages were produced and used to amend acidic red soil in a pot experiment for the cultivation of Komatsuna, which is also called as Japanese mustard spinach (Brassica rapa var. pervidis). SA had a low bulk density (0.58–0.62 g/cm³), high water holding capacity (0.60–0.64 kg/kg), high saturated hydraulic conductivity (2.34·10^–2 cm/s), high mean weight diameter (MWD) (4.32–4.48 mm), alkaline pH (8.58–8.61), high electrical conductivity (EC) (82.18–84.35 mS/m) and high carbon (C) content (68.71–70.07 g/kg) in comparison with the acidic red soil. The trace element concentrations of the developed SA were below the maximum pollutant concentration of individual metals for land application of sewage sludge given by the US Environmental Protection Agency. Scanning electron microscopic (SEM) studies showed the higher structural surface area of SA, where round shaped CFA particles were embedded into the fibrous PW matrix. Incorporation of SA into the acidic red soil not only enhanced soil fertility but also improved the physical and chemical properties of the soil compared to soil without SA addition. SA addition to the acidic red soil significantly increased the growth and yield parameters of Komatsuna compared to soil without SA addition.     

Multi-approach characterization of shallow-water carbonates off Minamitorishima and their depositional settings/history

Sedimentological, geochemical, and chronological analyses were carried out on 18 carbonate rock samples collected at depths of 938, 1085, and 3354 m on the western slope of Minamitorishima (Marcus Island), which is located near the western margin of the Pacific Plate. Four groups of carbonate rocks were distinguished: a mollusk-rich limestone, a coral-rich dolomite, a foraminiferal-nannofossil packstone, and a phosphatized mudstone/wackestone. The mollusk-rich limestone is characterized by the dominance of bivalves (including rudists) and gastropod shells. Strontium isotope ratios (⁸⁷Sr/⁸⁶Sr) and Mesorbitolina ex gr. texana (a large benthic foraminifer) indicate that the shallow-water carbonates were deposited during the late Aptian–early Albian (ca. 123–111 Ma). The coral-rich dolomite is characterized by abundant scleractinian corals and nongeniculate coralline algae associated with encrusting acervulinid foraminifers. The biotic composition is similar to that of the Oligocene–Pleistocene carbonates reported from other seamounts in the northwestern Pacific. Geochemical data show that the coral-rich carbonates were dolomitized at 9.5–6.8 Ma (Tortonian–Messinian) and that normal seawater was the most likely parent fluid. The foraminiferal-nannofossil packstone is a semi-consolidated foraminiferal-nannofossil ooze and was deposited during the Pleistocene (0.99–0.45 Ma). The phosphatized mudstone/wackestone is marked by the absence of macrofossils and the presence of traces of planktic foraminifers. Although its depositional age is not constrained, the Sr isotope ratios indicate that the phosphatization occurred at 33.2–28.9 Ma. After the deposition of the Cretaceous shallow-water carbonates, including the mollusk-rich limestone, Minamitorishima was drowned and its top was covered with a pelagic cap, represented by the mudstone/wackestone. The late Eocene–early Oligocene volcanism (40.2–33.2 Ma) caused episodic uplift and returned the top of Minamitorishima to a shallow-water environment. After the early Oligocene phosphatization of the pelagic cap, coral reefs flourished on the top of this island. The reef limestone was dolomitized during the Tortonian–Messinian.     

慢地震与深部不连续颤动和慢滑事件同时发生

我们对日本西南部南海俯冲板块界面过渡带发生的超低频地震进行报道。由矩震级为3.1～3.5的超低频地震引起的地震波显示其卓越长周期约为20s。超低频地震活动伴随深源低频颤动和慢滑事件同时发生,并随之移动。慢地震一直被认为会增加向上倾斜的大型逆冲地震断裂带上的应力,而这3种现象的同时发生提高了人们对慢地震的探测和特性鉴定水平。