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Search Results: 1 - 10 of 3736 matches for " Tokiyuki Sato "
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Reconstruction of Paleoceanography Significance in the Western Pacific and Atlantic Oceans during the Neogene Based on Calcareous Nannofossil Productivity and Size Variations, Related to the Global Tectonic Events  [PDF]
Santi Dwi Pratiwi, Tokiyuki Sato
Open Journal of Geology (OJG) , 2016, DOI: 10.4236/ojg.2016.68070
Abstract: We investigated the calcareous nannofossils in the western Pacific and Bahama Bank of Caribbean Sea to reconstruct the paleoceanography and correlate with the global events. The absolute abundant of coccolith (number/g) are gradually increased from NN6 throughout NN19 Zone, while the relative abundance of Discoaster is decreased at Sites 782 in the western Pacific Ocean. The changes of the modal and maximum size of Reticulofenestra which are strongly reflected the collapse of sea surface stability, show four times in 8.8 Ma, 6.4 Ma, 5.4 Ma and 3.75 Ma at Site 782. On the basis of relationship between the changes of maximum sizes of Reticulofenestra and nutrient condition, these eutrophication events are clearly traceable to the western Pacific, Bahama Bank, northwestern Pacific Ocean and to the Indian Ocean. Two paleoceanographic events found in 8.8 Ma and 3.75 Ma are interpreted as change to high nutrient condition resulted in the intensification of Asian Monsoon and closure of Panama Isthmus.
Sea-Surface Dynamics Changes in the Subpolar North Atlantic Ocean (IODP Site U1314) during Late Pliocene Climate Transition Based on Calcareous Nannofossil Observation  [PDF]
Resti Samyati Jatiningrum, Tokiyuki Sato
Open Journal of Geology (OJG) , 2017, DOI: 10.4236/ojg.2017.710103
Abstract: Calcareous nannofossils were observed to reconstruct the surface water conditions during late Pliocene climate transition (2.55 to 2.88 Ma) from the southern Gardar Drift, in the subpolar North Atlantic IODP Site U1314 (56°21.9’1N, 27°53.3’W). A total of 24 species from 14 genera were identified by polarizing microscope observation. The coccolith assemblages are dominated by species belonging to genus Reticulofenestra with different (size-defined) morphotype. Hence, changes in paleoceanographic condition are shown by the size variation of Reticulofenstraspecimens. Before ~2.76 Ma, the studied interval is characterized by the presence of an abundant larger Reticulofenstra group. It indicates warm oligotrophic and stable surface waters. At ~2.76 Ma the abundance of large Reticulofenstra decreased abruptly and alternated with small Reticulofenstra, suggesting collapse of sea surface stability with strong mixing condition. This event coeval with the final closure of the Central American Seaway (CAS) and the onset of intensified North Hemisphere Glaciation (NHG). Subsequently, the size variation of Reticulofenestra specimens exhibits a sequential pattern that is somewhere consistent with the interglacial-glacial cycle. The pattern begins with a gradual increase in size upward during interglacial suggesting warm oligotrophic and stable condition, and ends with an abrupt decrease in coccolith size during glacial suggesting eutrophic or strong mixing condition and destabilized sea surface waters.
Miocene to Pliocene Paleoceanography of the Western Equatorial Pacific Ocean Based on Calcareous Nannofossils, ODP Hole 805B  [PDF]
Meutia Farida, Ryo Imai, Tokiyuki Sato
Open Journal of Geology (OJG) , 2012, DOI: 10.4236/ojg.2012.22008
Abstract: We describe in detail the Miocene to Quaternary paleoceanography of the western equatorial Pacific Ocean based on calcareous nannofossils of Hole 805B. The relative abundance of Discoaster which lived in the lower photic zone under the stable sea with nutricline and thermocline, decreased step by step at NN5/NN6 and NN10/NN11 boundaries. Al- though the size of Reticulofenestra which is strongly influenced by nutrient, increased five times throughout the section, it drastically decreased in NN4-5 zone, NN10, NN12, and in NN15/NN16 boundary. On the basis of the relationship between Discoaster abundance and Reticulofenestra size change, collapse of the stability of the sea surface in the west- ern equatorial Pacific Ocean progressed step by step throughout the Miocene to Quaternary.
IODP Expeditions 303 and 306 Monitor Miocene- Quaternary Climate in the North Atlantic
James E.T. Channell,Tokiyuki Sato,Toshiya Kanamatsu,Rüdiger Stein
Scientific Drilling , 2006, DOI: 10.2204/iodp.sd.2.01.2006
Abstract: Introduction The IODP Expeditions 303 and 306 drilling sites were chosen for two reasons: (1) to capture Miocene-Quaternary millennial-scale climate variability in sensitive regions at the mouth of the Labrador Sea and in the North Atlantic icerafted debris (IRD) belt (Ruddiman et al., 1977), and (2) to provide the sedimentary and paleomagnetic attributes, including adequate sedimentation rates, for constructinghigh-resolution isotopic and magnetic stratigraphies.High accumulation rates, reaching 20 cm ky-1, permit the study of millennial-scale variations in climate and in the Earth's magnetic fi eld over the past several million years, when the amplitude and frequency of climate variability changed substantially. Shipboard logging and scanning data (magnetic susceptibility and remanence, density, natural gamma radiation, digital images and color refl ectance) and post-expedition x-ray fl uorescence (XRF) scanning datahave revealed that the sediment cores recovered on Expeditions 303 and 306 contain detailed histories of millennial-scale climate and geomagnetic fi eld variability throughout the late Miocene to Quaternary epochs. The climate proxies will be integrated with paleomagnetic data to place the records of millennial-scale climate change into a high resolution stratigraphy based on oxygen isotope andrelative paleomagnetic intensity (RPI). The paleomagnetic record of polarity reversals, excursions and RPI in these cores is central to the construction of the stratigraphic template and will provide detailed documentation of geomagnetic fi eld behavior.
On Supersymmetry of the Covariant 3-Algebra Model for M-Theory  [PDF]
Matsuo Sato
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.311226
Abstract: We examine a natural supersymmetric extension of the bosonic covariant 3-algebra model for M-theory proposed in [1]. It possesses manifest SO(1,10) symmetry and is constructed based on the Lorentzian Lie 3-algebra associated with the U(N) Lie algebra. There is no ghost related to the Lorentzian signature in this model. It is invariant under 64 supersymmetry transformations although the supersymmetry algebra does not close. From the model, we derive the BFSS matrix theory and the IIB matrix model in a large N limit by taking appropriate vacua.
Analysis of the Tracer Diffusion Phenomena through Cracks in the Porous Media by Means of X-Ray CT  [PDF]
Akira Sato
Materials Sciences and Applications (MSA) , 2013, DOI: 10.4236/msa.2013.48A003

The migration process of contamination materials in the porous rock mass was visualized and analyzed by X-ray CT image data. In this study, Kimachi sandstone, which had approximately 26% porosity, was used as a rock sample. Here two cases of diffusion phenomena were analyzed. One is the case that solute diffuses into the porous rock mass from the crack surfaces, and it simulates the contamination process of rock mass. Another is the case that the solute diffuses out of the porous rock mass, and it simulates the process that the contamination materials spread from highly contaminated sources. It was found that the diffusion phenomena were clearly visualized by X-ray CT method. By introducing the parameter, coefficient of tracer density increment α, quantitative analysis of tracer density became possible, and the relation between the density distribution of tracer and the crack apertures and the relation between the density distribution and porosity distribution became clear.

Zariski 3-Algebra Model of M-Theory  [PDF]
Matsuo Sato
Journal of Modern Physics (JMP) , 2013, DOI: 10.4236/jmp.2013.44A006

We review on Zariski 3-algebra model of M-theory. The model is obtained by Zariski quantization of a semi-light-cone supermembrane action. The model has manifest N=1 supersymmetry in eleven dimensions and its relation to the supermembrane action is clear.

Factors Affecting Minimum Foot Clearance in the Elderly Walking: A Multiple Regression Analysis  [PDF]
Keizo Sato
Open Journal of Therapy and Rehabilitation (OJTR) , 2015, DOI: 10.4236/ojtr.2015.34015
Abstract: Because falls among the elderly can cause serious injury leading to a bedridden state, methods to maintain motor function in the elderly and prevent falls are important. Among falls by the elderly are tripping falls, in which the forefoot gets caught on the floor to cause the fall. Minimum foot clearance (MFC), the smallest distance between the floor and the foot during the swing phase of gait, has been given attention as a cause of tripping falls, as elderly people at risk of falling have been reported to have low MFC. No research has been done, however, to examine what geriatric factors determine MFC. In this study, various measurements were taken on muscle strength, joint angles, and other characteristics as factors possibly influencing the height of MFC, a multiple regression analysis was performed with MFC as the dependent variable, and those factors with high degrees of influence were extracted. The results revealed that the height of MFC is highly influenced by strength of the hip flexors and angle of ankle dorsiflexion. The results of this study should be taken into consideration when having elderly people do fall prevention training.
Structure Analysis for Hydrate Models of Ethyleneimine Oligomer by Quantum Chemical Calculation  [PDF]
Minoru Kobayashi, Hisaya Sato
Pharmacology & Pharmacy (PP) , 2010, DOI: 10.4236/pp.2010.12009
Abstract: Structure analyses for hydrate models of ethyleneimine oligomer (5-mer as model of PEI) were investigated by quantum chemical calculations. Conformation energies and structures optimized for hydrate models of (ttt)5 and (tgt)5 conformers were examined. Hydrate ratio, h [h = H2O/N (mol)], was set from 0.5 to 2. In anhydrates, (tg+t)5 conformer was more stable (?1.8 kcal/m.u.) than (ttt)5. In hydrates, (ttt)5 conformers were more stable (?0.7 - ?4.3) than (tg+t)5. These results corresponded to experimental results that anhydrous linear PEI crystal changes from double helical to single planar chain in hydration process. Structures calculated for (ttt)5 agreed in those observed for hydrates of PEI. In all (tg+t)5 conformers, O???H bonds between waters were found with the decreases of N???H bonds between imino group and water. The O???H bonds in (tg+t)5 conformer resulted in its high chain torsion, and strongly related with instability and structure change (large swelling).
A Theoretical Study on Van Der Pauw Measurement Values of Inhomogeneous Compound Semiconductor Thin Films  [PDF]
Toru Matsumura, Yuichi Sato
Journal of Modern Physics (JMP) , 2010, DOI: 10.4236/jmp.2010.15048
Abstract: The influence of intermixing heterogeneous regions that have different electrical properties from the base materials on van der Pauw measurement values was theoretically studied by computer simulation using the finite-element method. The measurement samples selected were thin films of inhomogeneous semiconductors. Calculated electrical properties, such as resistivity, carrier density, and mobility of the thin films, varied in predictable ways when heterogeneous regions were dispersed in wide ranges over the samples. On the other hand, the mobility of the thin films showed a different change when heterogeneous regions were locally concentrated in the measurement samples.
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