Decomposition characteristics of particulate organic matter in hiroshima bay     

Tohru Seiki  Etsuji Date  Hirofumi Izawa 《Journal of Oceanography》1991,47(5):207-220

The decomposition characteristics of particulate organic matter (POM) sampled with plankton nets in Hiroshima Bay were investigated under aerobic conditions in a laboratory experiment.The POM derived from plankton consisted of both a labile fraction (70–80 % of the whole) and a refractory fraction (20–30%). The labile fraction was completely decomposed within 40 days at 20°C. Although the concentrations of particulate organic carbon (POC) decreased gradually with time, an apparent lag phase was recognized in the decomposition of particulate phosphorus (PP) at an early stage, which might result from a specific uptake of dissolved inorganic phosphorus (DIP) by bacteria. A comparison of the metabolic activity between dissolved organic matter (DOM) and POM by measuring ATP contents showed that the former was one order of magnitude larger than the latter.On the other hand, there was no significant difference among the decomposition rates of POM collected at various depths. The change of the first-order rate constant (k) for the POM decomposition by temperature was expressed ask=0.0329 exp(0.0644T), and the Q₁₀ value was 1.94. There were fairly large variances ink values obtained from the various plankton species. Thek values averaged 0.144 day^–1 and ranged from 0.078 to 0.20 day^–1 at 20°C.  相似文献   

Kinematic interpretation of remnant en-echelon rift segments of the southwestern Japan Sea     

J. V. Smith  S. Yamauchi 《Tectonophysics》1994,230(3-4):143-150

The southwestern Japan Sea and the margin of southwestern Japan feature parallel elongate extensional sub-basins and grabens. These structures are oblique to the trend of southwestern Japan and are interpreted as the remnant of an en-echelon array. Such a right-stepping remnant en-echelon pattern indicates sinistral rifting of the southwestern Japan block from Asia. The major extensional fault trends are parallel over a distance of 600 km. Infinitesimal kinematic relations show that it is unlikely that these faults initiated in response to rotation about the nearby pole determined from paleomagnetic studies. Rather, an earlier stage of rifting about a distant pole is indicated. The rotational pole of this early rifting was probably located at least 6000 km away from the rift and the pole of rotation was offset from the rift trend by a similar distance. Rifting about this distant rotational pole loosened the southwestern Japan continental block from the Asian mainland making it susceptible to a large rotation about a nearby pole.  相似文献   

Seepage and consolidation of bentonite saturated with pure- or salt-water by the method of unified molecular dynamics and homogenization analysis     

Y. Ichikawa  K. Kawamura  M. Nakano  K. Kitayama  T. Seiki  N. Theramast 《Engineering Geology》2001,60(1-4):127-138

Bentonite clay is a micro-inhomogeneous material, which consists of clay minerals (mainly montmorillonite), macro-grains (mainly quartz), water, air and others. Properties of the saturated bentonite clay are essentially characterized by the montmorillonite and water (i.e. montmorillonite hydrate). We analyze the molecular behavior of sodium montmorillonite hydrate Na_1/3Al₂[Si_11/3Al_1/3]O₁₀(OH)₂·nH₂O by applying a molecular dynamics (MD) simulation method. And by using the MD results we calculate the swelling property of the montmorillonite hydrate, and compare with an experimental result. Next, by using the same MD procedure we treat a montmorillonite mineral with a large number of external water molecules to check the properties of the water. Here we treat pure- and salt-water. Then we calculate the diffusivity and viscosity of water molecules and Na⁺ and Cl⁻ ions.

For extending the microscopic characteristics of constituent materials to a macroscopic seepage behavior of the micro-inhomogeneous material we apply a homogenization analysis (HA). That is, starting with the Navier–Stokes equation with distributed viscosity that is calculated by the former MD procedure we determine macroscopic permeability characteristics of bentonite for both cases of pure- and salt-water. Then, by using the permeability property we calculate long-term consolidation behavior of buffering clay, which is planed to be used for high-level radioactive waste (HLRW) management. Here the deformation is treated under the well-defined Cam clay model.  相似文献   

Differences in abundance and distribution of Alexandrium cysts in Sendai Bay,northern Japan,before and after the tsunami caused by the Great East Japan Earthquake     

Takashi Kamiyama  Hiroyuki Yamauchi  Satoshi Nagai  Mineo Yamaguchi 《Journal of Oceanography》2014,70(2):185-195

The tsunami caused by the Great East Japan Earthquake on 11 March 2011 greatly influenced the coastal benthic environment on the northern Pacific coast of Japan. We used the direct count method to investigate changes in the abundance and distribution of Alexandrium (Alexandrium tamarense and Alexandrium catenella) cysts before and after the tsunami in Sendai Bay. Densities of Alexandrium cysts in sediments collected in summer 2011 ranged from 0 to 8,190 cysts cm^?3. In the western part of the bay, the density increased greatly after the tsunami, the highest density being approximately 10 times the density recorded in 2005. Molecular identification of single cysts with multiplex polymerase chain reaction (PCR) showed that Alexandrium tamarense dominated the cyst population in the southwestern part of the bay in 2011. Furthermore, accumulation of cysts on the surface sediment after disturbance of the sediment was confirmed by a laboratory experiment. The main factor causing the drastic changes in abundance and distribution of Alexandrium cysts after the earthquake was considered to be vertical and horizontal redistribution of the cysts in sediments after the tsunami.  相似文献   

ISRM Suggested Method for the Needle Penetration Test   总被引：1，自引：0，他引：1  

Resat Ulusay  Ömer Aydan  Zeynal A. Erguler  Dominique J. M. Ngan-Tillard  Takafumi Seiki  Wim Verwaal  Yasuhito Sasaki  Akira Sato 《Rock Mechanics and Rock Engineering》2014,47(3):1073-1085

  相似文献   

ENA detection in the dayside of Mars: ASPERA-3 NPD statistical study     

A. Mura  S. Orsini  E. Kallio  S. Barabash  A. Grigoriev  H. Andersson  M. Yamauchi  N. Krupp  K. Asamura  C.C. Curtis  B.R. Sandel  M. Grande  J.U. Kozyra  S. McKenna-Lawlor  R. D’Amicis  S. Massetti  P.C. Brandt  R.A. Frahm 《Planetary and Space Science》2008,56(6):840-845

The Analyzer of Space Plasma and EneRgetic Atoms (ASPERA-3) on board Mars Express is designed to study the interaction between the solar wind and the atmosphere of Mars and to characterize the plasma and neutral gas environment in near-Mars space. Neutral Particle Detectors (NPD-1 and 2), which form part of the ASPERA-3 instrument suite, are Energetic Neutral Atom (ENA) detectors which use the time-of-flight (ToF) technique to resolve the energy of detected particles. In the present study, we perform a statistical analysis of NPD ToF data collected between 14 March 2004 and 17 June 2004 when Mars Express was located at the dayside of Mars looking toward the planet. After pre-processing and removal of UV contamination, the ToF spectra were fitted with simple analytical functions so as to derive a set of parameters. The behavior of these parameters, as a function of spacecraft position and attitude, is compared with a model, which describes ENA generation by charge exchange between shocked solar wind protons and extended Martian exosphere. The observations and the model agree well, indicating that the recorded signals are charge-exchanged shocked solar wind.  相似文献   

The Venusian induced magnetosphere: A case study of plasma and magnetic field measurements on the Venus Express mission     

E. Kallio  T.L. Zhang  R. Jarvinen  P. Janhunen  J.-A. Sauvaud  J.-J. Thocaven  H. Andersson  K. Brinkfeldt  M. Holmström  M. Yamauchi  W. Baumjohann  A.J. Coates  D.O. Kataria  K.C. Hsieh  M. Grande  T. Säles  P. Riihelä  N. Krupp  J.G. Luhmann  S. Orsini  A. Mura  M. Maggi  P. Brandt  K. Szego  R.A. Frahm  J.R. Sharber  P. Bochsler 《Planetary and Space Science》2008,56(6):796-801

Plasma and magnetic field measurements made onboard the Venus Express on June 1, 2006, are analyzed and compared with predictions of a global model. It is shown that in the orbit studied, the plasma and magnetic field observations obtained near the North Pole under solar minimum conditions were qualitatively and, in many cases also, quantitatively in agreement with the general picture obtained using a global numerical quasi-neutral hybrid model of the solar wind interaction (HYB-Venus). In instances where the orbit of Venus Express crossed a boundary referred to as the magnetic pileup boundary (MPB), field line tracing supports the suggestion that the MPB separates the region that is magnetically connected to the fluctuating magnetosheath field from a region that is magnetically connected to the induced magnetotail lobes.  相似文献   

The magnetic field near Mars: A comparison between a hybrid model, Mars Global Surveyor and Mars Express observations     

H. Frilund  M. Yamauchi  P. Janhunen  J.-A. Sauvaud 《Planetary and Space Science》2008,56(6):828-831

Mars Express (MEX) does not carry its own magnetometer which complicates interpretation of ASPERA-3/MEX ion measurements. The direction of the interplanetary magnetic field (IMF) is especially important because it, among other things, determines the direction of the convective electric field and orientation of the cross tail current sheet and tail lobes. In this paper we present a case study to show the properties of the magnetic field near Mars in a quasi-neutral hybrid (QNH) model at the orbits where the Mars Global Surveyor (MGS) has made measurements, present a method to derive the IMF clock angle by comparing fields in a hybrid model and the direction of the magnetic field measured by MGS by deriving the IMF clock angle. We also use H⁺ ring velocity distribution observations upstream of the bow shock measured by the IMA/ASPERA-3 instrument on board MEX spacecraft. These observations are used to indirectly provide the orientation of the IMF. We use a QNH model (HYB-Mars) where ions are modeled as particles while electrons form a mass-less charge neutralizing fluid. We found that the direct MGS and non-direct IMA observations of the orientation magnetic field vectors in non-crustal magnetic field regions are consistent with the global magnetic field draping pattern predicted by the global model.  相似文献   

The Kellwasser events in the Upper Devonian Frasnian to Famennian transition in the Toc Tat Formation,northern Vietnam     

Toshifumi Komatsu  Ryota Urakawa  Toshitaka Inada  Kazuki Yamauchi  Takumi Maekawa  Reishi Takashima  Mark Williams  Phong D. Nguyen  Hung D. Doan  Minh T. Nguyen  Shuji Niko  Gengo Tanaka  Tatsuhiko Yamaguchi 《Island Arc》2019,28(1)

Upper Devonian carbonates of the Toc Tat Formation in the Si Phai Pass area of Dong Van District, northern Vietnam were deposited in carbonate platform, slope, and basin environments. These carbonates yield abundant conodonts indicative of the Palmatolepis nasuta, Pa. linguiformis and Pa. triangularis zones, the Frasnian–Famennian stage boundary being identified by the first occurrence of Pa. triangularis. Two positive carbon isotope excursions are recognized, the lower excursion peaking in the interval of the lower to middle Pa. nasuta Zone, whilst the upper excursion peaks just above the local Frasnian–Famennian boundary. Based on the biostratigraphy, these excursions equate to the Lower and Upper Kellwasser events. Locally, tentaculitoid taxa (Nowakia, Styliolina, Homoctenus, and Metastyliolina?) are abundant in the interval of the Pa. nasuta Zone, but show a drastic decline in abundance before the Lower Kellwasser Event, and only two taxa survived into the Famennian.  相似文献   

东京都的地震防灾对策   总被引：1，自引：0，他引：1  

笹井洋一 《国际地震动态》2005,(3):28-32

造成死亡和失踪人数超过14万重大人员损失的关东大地震距今已有80年了。每年在关东大地震发生的9月1日举行大规模的防灾训练也已成为惯例。东京都在市区和多摩地区轮流(每年一交换)设置主训练场,2003年设在今野市,共有28500人参加了训练。当然,各区市町村的自主防灾组织也会在各自的社区举办消防训练。1995年阪神大震灾最宝贵的经验就是灾民自己行动起来相互救助,保全了许多人的性命。  相似文献