Geochemistry of hydroxy acids in sediments—I. Some freshwater and brackish water lakes in Japan

Series of α, β, ω and (ω-1) hydroxy fatty acids (FAOHs) were determined in several freshwater and brackish water lacustrine sediments in Japan. Analytical procedure used was digestion of the solvent-extracted sediment with HF/HCl followed by solvent and saponification extraction of the residue. Abundances of α/β and ω-FAOH determined by this procedure were 2–3 times higher than those obtained by single alkaline saponification and of the same order with those provided by HCl hydrolysis. Major portion of α/β-FAOH was obtained by solvent extraction of the acid-treated sediments, while subsequent alkaline saponification was needed for the majority of ω-FAOH to be recovered. Thus determined FAOHs comprised 33–61% (Av. = 42%) of the “bound” acid constituents in the lacustrine surface sediments. The α/β and ω-FAOH composition was principally the same among the samples examined, except for relative proportions of the iso to anteiso C₁₅ and C₁₇ ß(α)-FAOH, which showed significant variations in the ranges of 0.30–1.1 and 0.46–1.5, respectively. In the holomictic lakes, the ratios together with the same ratios of the “bound” branched monocarboxylic acids tended to decrease with increasing water depth of the lakes, suggesting that the ratios may indicate an extent of the early diagenetic alteration of the bacteria-derived lipids either in water column or in surface sediment.     

Great earthquake at 7.3 ka inferred from tsunami deposits in the Sukumo Bay area,Southwestern Japan

Tsunami deposits in Kyushu Island, Southwestern Japan, have been attributed to the 7.3 ka Kikai caldera eruption, but their origin has not been confirmed. We analyzed an 83-cm-thick Holocene event deposit in the SKM core, obtained from incised valley fill in the coastal lowlands near Sukumo Bay, Southwestern Shikoku Island. We confirmed that the event deposit contains K-Ah volcanic ash from the 7.3 ka eruption. The base of the event deposit erodes the underlying inner-bay mud, and the deposit contains material from outside the local terrestrial and marine environment, including angular quartz porphyry from a small inland exposure, oyster shell debris, and a coral fragment. Benthic foraminifers and ostracods in the deposit indicate various habitats, some of which are outside Sukumo Bay. The sand matrix contains low-silica volcanic glass from the late stage of the Kikai caldera eruption. We also documented the same glass in an event deposit in the MIK1 core, from the incised Oyodo River valley in the Miyazaki Plain on Southeastern Kyushu. These two 7.3 ka tsunami deposits join other documented examples that are widely distributed in Southwestern Japan including the Bungo Channel and Beppu Bay in Eastern Kyushu, Tachibana Bay in Western Kyushu, and Zasa Pond on the Kii Peninsula as well as around the caldera itself. The tsunami deposits near the caldera have been divided into older and younger 7.3 ka tsunami deposits, the younger ones matching the set of widespread deposits. We attribute the younger 7.3 ka tsunami deposits to a large tsunami generated by a great interplate earthquake in the Northern part of the Ryukyu Trench and (or) the Western Nankai Trough just after the late stage of the Kikai caldera eruption and the older 7.3 ka tsunami deposits to a small tsunami generated by an interplate earthquake or Kikai caldera eruption.     

A discrete thermodynamic approach for anisotropic plastic–damage modeling of cohesive‐frictional geomaterials

A discrete plastic–damage model is developed for cohesive‐frictional geomaterials subjected to compression‐dominated stresses. Macroscopic plastic strains of material are physically generated by frictional sliding along weakness planes. The evolution of damage is related to the evolution of weakness planes physically in connection with the propagation of microcracks. A discrete approach is used to account for anisotropic plastic flow and damage evolution, by introducing two stress invariants and one plastic hardening variable for each family of sliding weakness planes. Plastic flow in each family is coupled with damage evolution. The proposed model is applied to typical geomaterials and comparisons between numerical predictions and experimental data are presented. Copyright © 2009 John Wiley & Sons, Ltd.     

Sulfur stable isotopes indicate the source of sinking materials in a coastal bay: Otsuchi Bay,Sanriku, Japan

Through 2004 and 2005, δ ³⁴S of sinking material from Otsuchi Bay was measured at the center and rocky shore of the bay. At the center of the bay δ ³⁴S was high (18∼21‰) in the material collected from April to November. However, δ ³⁴S was low (9∼14‰) in the material collected from December to March. The increase in δ ³⁴S in April was attributed to an increase in phytoplankton biomass because marine phytoplanktonic δ ³⁴S is high. When δ ³⁴S of sinking material was low, input of riverine material or bottom sediment resuspension were considered as the probable causes, because their δ ³⁴S is low. Marine sulfur was always high (more than 70%) at both stations. The difference between the δ ³⁴S of sinking material collected from the different sampling stations indicates that marine macroalgae contribute to sinking material near the shore when phytoplankton is scarce. In conclusion, the relative influence of different material sources to sinking materials could be successfully estimated using δ ³⁴S.     

A GPU based real-time GPS software receiver

Off-the-shelf graphics processing units provide low-cost massive parallel computing performance, which can be utilized for the implementation of a GPS software receiver. In order to realize a real-time capable system the crucial stages of the receiver should be optimized to suit the requirements of a parallel processor. Moreover, the receiver should be capable to provide wider correlation functions and provide easy access to the spectral domain of the signals. Thus, the most suitable correlation algorithm, which forms the core part of each receivers should be chosen and implemented on the graphics processor. Since the sampling rate of the received signal limits the real-time capabilities of the software radio it is necessary to determine an optimum value, considering that the precision of the observable varies with sampling bandwidth. We are going to discuss details and present our single frequency multi-channel implementation, which is capable of operating in real-time mode. Our implementation differs from other solutions by the wideness of the correlation function and allows simple handling of data in the spectral domain. Comparison with output from a commercial hardware receiver, which shares the antenna with the software radio, confirms the consistency and accuracy of our development.     

Wind Fields over Funka Bay and Their Effect on Water Circulation in the Bay

Horizontal wind fields over Funka Bay during cold air outbreaks were simulated using a 3-D meso-scale atmospheric model. The simulated wind fields over the bay have a positive curl in the north and a negative curl in the south. These wind fields were used to simulate the current in Funka Bay using a barotropic ocean model. The simulated current pattern was composed of two vortices—one with anti-clockwise vorticity in the north and the other with clockwise vorticity in the south—and was in the opposite direction to that simulated by the uniform wind fields. This is because the wind stress curl effect on the vorticity production in Funka Bay opposes and overwhelms the bathymetry torque effect during cold air outbreaks. These results show that the non-uniformity of the wind fields caused by the land topography around a shallow lake or bay cannot be neglected in simulating its currents.     

Comparative Late Pleistocene Paleoceanographic Changes in the Mid Latitude Boreal and Austral Western Pacific

Middle latitudes of the northern and southern hemispheres of the western Pacific are the sensitive areas for the climatic change. We reconstruct the variation in primary productivity to evaluate the shift of the transition zone between the central water mass and cold water in the both hemispheres. In cores S2612 and LH3166, which are located around boreal and austral 35 degree, the mean C_Organic/N atomic ratios are 7.8 and 7.2, respectively. Therefore it is suggested that organic matter is mainly of marine origin (excluding the middle Stage 6 to Stage 7 with the high C_Organic/N atomic ratios in core LH3166). Primary productivities estimated from these cores in the middle latitudes of the western Pacific during the late Pleistocene demonstrate similar profiles. Maxima are observed at late Stage 2, late Stage 4 (middle Stage 4 for L3187) and late Stage 6 while minimum values were observed at Stage 5. Mass accumulation rates of organic carbon and biogenic opal also show similar profiles in these cores. These results and paleontological evidence show that the transition zone between Subtropical and subarctic waters almost synchronously migrated along the latitudinal transection during the last 150 kyr.     

Nonlinear hydrodynamical models of stellar convective zones

Large-eddy simulation (LES) of turbulent convection is discussed in various versions (mixing-length theory, modal theory and spectral theory) in respect to the application to stellar convective zones. For the model construction, the non-local mixing-length formalism is suitable. However, for the determination of basic flow patterns and of mixing-length, the quasi-linear and nonlinear modal theories are useful. The eddy diffusivities are essential in these theories, and the nonlinear treatment of convection consistent with turbulent diffusivities (of effective Reynolds number of about 20 and Prandtl number of 0.4) offers a simple method of constructing stellar models without the use of the mixing-length.Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September–6 October, 1984.     

Numerical study on the bulk heat transfer coefficient for a variety of vegetation types and densities

The relationship between the geometrical structure of a canopy layer and the bulk transfer coefficient was investigated using a numerical canopy model. The following results were obtained:

1. The bulk transfer coefficients for momentum and heat, C _M and C _H , change with non-dimensional canopy density C _* each has a maximum.
2. The value of C _M is always larger than the value of C _H for a canopy with c _m > c _h , c _m and c _h being the drag coefficient and the heat transfer coefficient of an individual canopy element, respectively.
3. The value of C _* at which C _H has its maximum value is larger than the value of C _* at which C _M has its maximum. Therefore, the reciprocal of the sublayer Stanton number b _h ^?1 ranges between 50 and 65 for C _* around 0.1 while it ranges between 0 and 30 for C _* < 10^?2 and C _* > 2 (when c _m = 0.5).
4. The value of B _H ^?1 in the present study is consistent with most available observations, except for canopies of medium density (when C _* is around 0.1) for which no observational value has been obtained.