Evidence of microphytobenthic roles on coastal shallow water of the Seto Inland Sea,Japan

This study describes the temporal variation of microphytobenthic biomass and its controlling factors, as well as the impact of microphytobenthic activities on coastal shallow sediment in the eastern Seto Inland Sea, Japan. The chlorophyll a (Chl a), phaeopigments and sedimentary biophilic element (C, N, P and Si) contents in surface sediments, as well as nutrient concentrations at the sediment-water interface (overlying water and pore water) were observed monthly during November 2003 to May 2005 at one site in Shido Bay (water depth ca. 7 m) and at one site in Harima-Nada (35 m). No correlation was observed between the sedimentary biophilic elements and other parameters. The maximum chlorophyll a content of 48.2 μg g^–1 was found in surface sediments under the photon flux reaching the seafloor of 537 μmol photon m^–2 s^–1 during the winter period when water transparency was the highest at station S (Shido Bay). Our results suggest that higher chlorophyll a content in surface sediment was due to the fresh microphytobenthic biomass (mainly benthic diatom). We also found a significant negative correlation between Chl a and inorganic nutrients in pore water during the low temperature period, especially silicic acid. This result suggests that the silicic acid was assimilated largely during the increase of microphytobenthic biomass in surface sediment. This study suggests that the microphytobenthic roles may have a great effect on nutrient budgets during the large supply of irradiance (winter periods) for their photosynthetic growth in shallow coastal waters.     

Axially-symmetric explosion with thermal radiation

A point explosion with thermal radiation in an axially symmetric inhomogeneous medium is investigated by generalizing the method of Laumbach and Probstein to include the effects of radiative cooling. As an example, a point explosion in the plane stratified transparent medium with exponential density distribution is calculated. It is shown that the focusing effect along the symmetry axis is enhanced by radiative cooling effect. Explosion models of extragalactic double radio sources are briefly discussed.     

Gravelly spit deposits in a transgressive systems tract: the Pleistocene Higashikanbe Gravel, central Japan

The Pleistocene Higashikanbe Gravel, which crops out along the Pacific coast of the Atsumi Peninsula, central Japan, consists of well‐sorted, pebble‐ to cobble‐size gravel beds with minor sand beds. The gravel includes large‐scale foreset beds (5–10 m high) and overlying subhorizontal beds (0·5–3 m thick), showing foreset and topset structure, from which the gravel has previously been interpreted as deposits of a Gilbert‐type delta. However, (1) the gravel beds lack evidence of fluvial activity, such as channels in the subhorizontal beds; (2) the foresets incline palaeolandwards; (3) the gravels fill a fluvially incised valley; and (4) the gravels overlie low‐energy deposits of a restricted environment, such as a bay or an estuary. The foresets generally dip towards the inferred palaeoshoreline, indicating landward accretion of gravel. Reconstruction of the palaeogeography of the peninsula indicates that the Higashikanbe Gravel was deposited as a spit similar to that developed at the western tip of the present Atsumi Peninsula, rather than as a delta. According to the new interpretation, the large‐scale foreset beds are deposits on the slopes of spit platforms and accreted in part to the sides of small islets that are fragments of the submerging spit during relative sea‐level rise. The subhorizontal beds include nearshore deposits on the spit platform topsets and deposits of gravel shoals or bars, which are reworked sediments of the spit beach gravels during a transgression. The lack of spit beach facies in the subhorizontal beds results from truncation by shoreface erosion. Dome structure, which is a cross‐sectional profile of a recurved gravel spit at its extreme point, and sandy tidal channel deposits deposited between the small islets were also identified in the Higashikanbe Gravel. The Higashikanbe Gravel fills a fluvially incised valley and occupies a significant part of a transgressive systems tract, suggesting that gravelly spits are likely to be well developed during transgressions. The large‐scale foreset beds and subhorizontal beds of gravelly spits in transgressive systems tracts contrast with the foreset and topset beds of deltas, characteristic of highstand, lowstand and shelf‐margin systems tracts.     

Hinode Flare Catalogue

We describe a catalogue of solar flares observed by the three instruments (SOT, XRT, EIS) onboard the Hinode satellite. From the launch of the Hinode satellite in September 2006 until late 2011, about 5000 solar flares (larger than A-class in the GOES classification) occurred during the five-year period of Hinode observations, and more than half of them were captured by the Hinode telescopes. Observation information for RHESSI and Nobeyama Radioheliograph are also included in the catalogue. This catalogue is distributed to users through the Internet. It will be useful and helpful for scientists in surveying flares to be analyzed, facilitate access to Hinode data, and help advance data analysis activities among the world solar community.     

Experimental studies on debris flow with logs focusing on specific weight difference of log species

There are many experimental approaches,field investigations and numerical calculations for movements of woods in a clear water and debris flow.However,kinematic conditions for accumulated logs and the interactions between a main flow and logs have not been fully evaluated.Mitigations for woods need taking into account the characteristics of tree species such as conifer and broad-leaf trees and of shapes such as root swells and crown.In the present study,we focus on the differences in specific weight of conifer and broad-leaf trees with some moisture in a sediment-water mixture flow with narrow flow width,and consider that conifer and broad-leaf tree are floating and submerged solid phase,respectively.Flume tests are conducted in steady flow of clear and debris flow over a rigid bed in order to evaluate conifer and broad-leaf tree movement in clear water and debris flow.Experimental data indicates that dimensionless transverse diffusion coefficient can be 0.1 to 0.4 and 0.3 to 0.9 in flow direction.Those diffusive characteristics seem to be independent of Reynolds number and Froude number,but dependent of bed slope,i.e.,gravity,though detailed considerations are needed to discuss about flow characteristics such as spatial eddy structures,momentum transfer induced by interactions of logs and so on.     

Seismic response control using electromagnetic inertial mass dampers

This paper presents a new type of electromagnetic damper with rotating inertial mass that has been developed to control the vibrations of structures subjected to earthquakes. The electromagnetic inertial mass damper (EIMD) consists of a ball screw that converts axial oscillation of the rod end into rotational motion of the internal flywheel and an electric generator that is turned by the rotation of the inner rod. The EIMD is able to generate a large inertial force created by the rotating flywheel and a variable damping force developed by the electric generator. Device performance tests of reduced‐scale and full‐scale EIMDs were undertaken to verify the basic characteristics of the damper and the validity of the derived theoretical formulae. Shaking table tests of a three‐story structure with EIMDs and earthquake response analyses of a building with EIMDs were conducted to demonstrate the seismic response control performance of the EIMD. The EIMD is able to reduce story drifts as well as accelerations and surpasses conventional types of dampers in reducing acceleration responses. Copyright © 2013 John Wiley & Sons, Ltd.     

Negligible effect of the benthic fauna on measuring the nutrient upward fluxes from coastal sediments

Although the influence of benthic fauna on estimating the nutrient upward fluxes from the coastal sediments are a concern, there are few comprehensive studies. We conducted monthly observations in a coastal embayment to examine the effect of benthic fauna on measuring the nutrient flux. Nutrient fluxes were measured by the core incubation method and the densities of organisms in benthic communities were also measured. Numerical composition of benthic communities, according to taxonomic group, was dominated by Polychaeta composed of a few Capitellida and Spionidae species. A negligible effect of the benthic communities on measuring nutrient fluxes was demonstrated.     

Geotechnical sealing material for coastal disposal facility for soils and wastes contaminated by radioactive cesium

Safe disposal of wastes produced due to the process of decontamination in and around Fukushima No. 1 nuclear power plant is an urgent requirement. The purpose of this study was to develop a sealing material which can be used as an engineered barrier for a final disposal facility for the soils and wastes contaminated by radioactive cesium. The analyses conducted based on 4-m-thick sealing layer revealed that the hydraulic conductivity of the sealing material needs to be kept below 5.0?×?10^?10?m/s to avoid the seepage of contaminants below the environmentally safe limits. Sealing material was developed using marine clay–bentonite mixture and the engineering characteristics were examined. The results of laboratory experiments showed that, with the addition of bentonite, the hydraulic conductivity equal to or less than 5.0?×?10^?10?m/s was achieved when the effective consolidation stress is equal to or more than 27?kPa. From the tests for adsorption properties for cesium, it was found that the sealing material showed the significant capacity of adsorption for cesium in seawater. It was concluded that the construction of waste disposal facility on the sandy seafloor is feasible using the sealing layer proposed in this study.     

Sealevel history recorded in the Pleistocene carbonate sequence in IODP Hole 310‐M0005D,off Tahiti

Material cored during the Integrated Ocean Drilling Program (IODP) Expedition 310 ‘Tahiti Sea Level’ revealed that the fossil reef systems around Tahiti are composed of two major stratigraphic sequences: (i) a last deglacial sequence; and (ii) an older Pleistocene sequence. The older Pleistocene carbonate sequence is composed of reef deposits associated with volcaniclastic sediments and was preserved in Hole 310‐M0005D drilled off Maraa. Within an approximately 70‐m‐thick older Pleistocene sequence (33.22–101.93 m below seafloor; 92.85–161.56 m below present sealevel) in this hole, 11 depositional units are defined by lithological changes, sedimentological features, and paleontological characteristics and are numbered sequentially from the top of the hole downward (Subunits P1–P11). Paleowater depths inferred from nongeniculate coralline algae, combined with those determined by using corals and larger foraminifers, suggest two major sealevel rises during the deposition of the older Pleistocene sequence. Of these, the second sealevel rise is associated with an intervening sealevel drop. It is likely that the second sealevel rise corresponds to that during Termination II (TII, the penultimate deglaciation, from Marine Isotope Stages 6 to 5e). Therefore, the intervening sealevel drop can be correlated with that known as the ‘sealevel reversal’ during TII. Because there are limited data on the Pleistocene reef systems in the tropical South Pacific Ocean, this study provides important information about Pleistocene sealevel history, the evolution of coral reef ecosystems, and the responses of coral reefs to Quaternary climate changes.