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Expanding-contracting Earth

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Geoscience Frontiers 2013年第3期4卷 341-347页

作者： Taku Tsuchiya Kenji kawai Shigenori Maruyama Geodynamic Research Center Ehime UniversityMatsuyamaEhime 790-8577Japan Department of Earth and Planetary Sciences Tokyo Institute of TechnologyMeguroTokyo 152-8551Japan Department of Earth Science University of CaliforniaSanta Barbara 93106CAUSA

The Earth was born from a giant impact at 4.56 Ga. It is generally thought that the Earth subsequently cooled, and hence shrunk, over geologic time. However, if the Earth＇s convection was double-layered, there must have been a peak of expansion during uni-directional cooling. We computed the expansion- contraction effect using first principles mineral physics data. The result shows a radius about 120 km larger than that of the present Earth immediately after the consolidation of the magma-ocean on the surface, and subsequent shrinkage of about 110 km in radius within about 10 m.y., followed by gradual expansion of 11 km in radius due to radiogenic heating in the lower mantle in spite of cooling in the upper mantle in the Archean. This was due to double-layered convection in the Archean with final collapse of overturn with contraction of about g km in radius, presumably by the end of the Archean. Since then, the Earth has gradually cooled down to reduce its radius by around 12 km. Geologic evidence supports the late Archean mantle overturn ca. 2.6 Ga, such as the global distribution of super-liqnidus flood basalts on nearly all cratonic fragments （〉35 examples）. If our inference is correct, the surface environment of the Earth must have undergone extensive volcanism and emergence of local landmasses, because of the thin ocean cover （3-5 km thickness）. Global unconformity appeared in cratonic fragments with stromatolite back to 2.9 Ga with a peak at 2.6 Ga. The global magmatism brought extensive crustal melting to yield explosive felsic volcanism to transport volcanic ash into the stratosphere during the catastrophic mantle overturn. This event seems to be recorded by sulfur mass-independent fractionation （SMIF） at 2.6 Ga. During the mantle overturn, a number of mantle plumes penetrated into the upper mantle and caused local upward doming of by ca. 2-3 km which raised local landmasses above sea-level. The consequent increase of atmospheric oxygen enabled life evolutio

关键词： Mantle overturn Expanding Earth Global unconformity Nutrients Eukaryotes

The second continent:Existence of granitic continental materials around the bottom of the mantle transition zone

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Geoscience Frontiers 2013年第1期4卷 1-6页

作者： Kenji kawai Shinji Yamamoto Taku Tsuchiya Shigenori Maruyama Department of Earth Science University of CaliforniaSanta BarbaraCA 93106USA Department of Earth and Planetary Sciences Tokyo Institute of TechnologyOokayama 2-12-1MeguroTokyo 152-8551Japan Department of Earth and Planetary Sciences Tokyo Institute of TechnologyOokayama 2-12-1MeguroTokyo 152-8551.Japan Department of Earth Science and Astronomy Graduate School of Arts and SciencesThe University of TokyoKomaba 3-8-1MeguroTokyo 153-8902Japan Geodynamics Research Center Ehime University.Bunkyo-cho 2-5MatsuyamaEhime 790-8577Japan

It has been thought that granitic crust, having been formed on the surface, must have survived through the Earth＇s evolution because of its buoyancy. At subduction zones continental crust is predominantly created by arc magmatism and is returned to the mantle via sediment subduction, subduction erosion, and continental subduction. Granitic rocks, the major constituent of the continental crust, are lighter than the mantle at depths shallower than 270 km, but we show here, based on first principles calcu- lations, that beneath 270 km they have negative buoyancy compared to the surrounding material in the upper mantle and transition zone, and thus can be subducted in the depth range of 270-660 km. This suggests that there can be two reservoirs of granitic material in the Earth, one on the surface and the other at the base of the mantle transition zone （MTZ）. The accumulated volume of subducted granitic material at the base of the MTZ might amount to about six times the present volume of the continental crust. Our calculations also show that the seismic velocities of granitic material in the depth range from 270 to 660 km are faster than those of the surrounding mantle. This could explain the anomalous seismic-wave velocities observed around 660 km depth. The observed seismic scatterers and reported splitting of the 660 km discontinuity could be due to jadeite dissociation, chemical discontinuities between granitic material and the surrounding mantle, or a combination thereof.

关键词： Continental growthGraniteFirst principlesMantle transition zoneTectonicsGeodynamics

Future Strategy of Breeding:Learn by Two Important Genes of Miracle Rice

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Molecular Plant 2020年第6期13卷 823-824页

作者： Kyosuke kawai Miyako Ueguchi-Tanaka Makoto Matsuoka Bioscience and Biotechnology Center Nagoya University464-8601 NagoyaJapan

In the"Analects of Confucius",there is a classic sentence that"too much is as bad as too little".The work by Wang et al.(2020)published in this issue reminds us that crop breeders should bear this sentence in mind whe... 详细信息

关键词： breed Learn she

Essential cellular modules for the proliferation of the primitive cell

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Geoscience Frontiers 2018年第4期9卷 1155-1161页

作者： Koichi Higashi Yoshikazu kawai Tomoya Baba Ken Kurokawa Taku Oshima Genome Evolution Laboratory National Institute of Genetics Centre for Bacterial Cell Biology Institute for Cell and Molecular BiosciencesMedical SchoolNewcastle University Advanced Genomics Center National Institute of Genetics Earth-Life Science Institute Tokyo Institute of Technology Graduate School of Biological Sciences Nara Institute of Science and Technology

Bacteria appeared early in the evolution of cellular life on planet Earth, and therefore the universally essential genes or biological pathways found across bacterial domains may represent fundamental genetic or cellular systems used in early life. The essential genes and the minimal gene set required to support bacterial life have recently been experimentally and computationally identified. It is, however,still hard to estimate the ancient genes present in primitive cells compared to the essential genes in contemporary bacteria, because we do not know how ancestral primitive cells lived and proliferated, and therefore cannot directly evaluate the essentiality of the genes in ancestral primitive cells. The cell wall is normally essential for bacterial proliferation and cellular division of walled bacterial cells is normally highly controlled by the essential FtsZ cell division machinery. But, bacteria are capable of reverting to their cell wall deficient ancestral form, called the ＂L-form＂. Unlike ＂normal＂ cells, L-forms divide by a simple physical mechanism based on the effects of membrane dynamics, suggesting a mode of primitive proliferation before the appearance of the cell wall. In this review, we summarize the experimental and computational investigations of minimal gene sets and discuss the minimal cellular modules required to support the proliferation of primitive cells, based on L-form proliferation.

关键词： L-form Essential genes Minimal gene set KEGG module Bacteria

Detecting MoS2 and MoSe2 with optical contrast simulation

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Progress in Natural Science:Materials International 2019年第6期29卷 667-671页

作者： Xiaohe Zhang Hiroyo kawai jing Yang Kuan Eng johnson Goh Victoria junior College Institute of Materials Research and Engineering A*STAR (Agency for Science Technology and Research) Department of Physics Faculty of Science National University of Singapore

Optical imaging is a promising method to identify and locate 2D materials efficiently and non-invasively. By putting a 2D material on a substrate, the nanolayer will add to an optical path and create a contrast to the case when the nanolayer is absent. This optical contrast imaging can be used to identify the 2D material and its number of layers. To make the optical imaging process in the laboratories an effective tool, Fresnel Law as a model was used to simulate the optical imaging results of 2D materials(graphene, Mo S2 and MoSe2) on top of different thickness of SiO2and Si wafer in the present investigation. The results provide the details of the optimal conditions(optimal light wavelength and optimal SiO2thickness) to identify and locate single to few 2D nanolayers, which can be used directly in laboratories. The optical contrasts of 1–5 layers of molybdenum disulfide(MoS2) and molybdenum diselenide(MoSe2) were simulated. To the best of our knowledge, it is the first time that the optical contrast results of MoSe2have been reported. In particular, this work highlights the sensitivity of the model on the accuracy of the refractive indices used. It is demonstrated that through computational modeling that optical contrast can allow effective determination of number of layers in few layer 2D materials.

关键词： 2D materials Optical imaging Substrate Fresnel law

Production analysis of functionally distributed machines for underground mining

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International journal of Mining Science and Technology 2016年第3期26卷 477-485页

作者： Fukui Rui Kusaka Kouhei Nakao Masayuki Kodama Yuichi Uetake Masaaki kawai Kazunari Department of Mechanical Engineering The University of Tokyo Komatsu Ltd.

Recent years, underground mining method is becoming popular because of its potentially high productivity and efficiency. In this method, a mining machinery; load haul dump(LHD), is used as both an excavator and a transporter of ore. This paper proposes a distributed system that realizes the excavation and transport functions with separated vehicles, an excavator and a transporter. In addition, this research proposes a mining map and configurations suitable for the proposed distributed system. To evaluate the productivity of the proposed system, a simulation environment has been developed. Analysis using the simulator reveals what performance factors of the excavator and the transporter have large impacts on the productivity. Simulation results also demonstrate the difference of potential between LHD system and the distributed system that can be explained based on their functions allocation.

关键词： Underground mining Mining machinery Autonomous system design Distributed system System configuration

High-pressure phase transitions of anorthosite crust in the Earth's deep mantle

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Geoscience Frontiers 2018年第6期9卷 1859-1870页

作者： Masayuki Nishi Steeve Gréaux Shigehiko Tateno Yasuhiro Kuwayama Kenji kawai Tetsuo Irifune Shigenori Maruyama Geodynamics Research Centre Ehime UniversityEhime 790-8577Japan Earth-Life Science Institute Tokyo Institute of TechnologyTokyo 152-8550Japan Institute for Planetary Materials Okayama UniversityMisasaTottori 682-0193Japan Department of Earth Planetary Science School of ScienceUniversity of Tokyo113-0033 Hongo 7-3-1BunkyoTokyoJapan Novosibirsk State University Pirogova 1630090Russia

We investigated phase relations, mineral chemistry, and density of lunar highland anorthosite at conditions up to 125 GPa and 2000 K. We used a multi-anvil apparatus and a laser-heated diamond-anvil cell for this purpose. In-situ X-ray diffraction measurements at high pressures and composition analysis of recovered samples using an analytical transmission electron microscope showed that anorthosite consists of garnet,CaAl_4Si_2O_(11)-rich phase(CAS phase), and SiO_2 phases in the upper mantle and the mantle transition *** lower mantle conditions, these minerals transform to the assemblage of bridgmanite, Ca-perovskite,corundum, stishovite, and calcium ferrite-type aluminous phase through the decomposition of garnet and CAS phase at around 700 km depth. Anorthosite has a higher density than PREM and pyrolite in the upper mantle, while its density becomes comparable or lower under lower mantle conditions. Our results suggest that ancient anorthosite crust subducted down to the deep mantle was likely to have accumulated at660-720 km in depth without coming back to the Earth's surface. Some portions of the anorthosite crust might have circulated continuously in the Earth's deep interior by mantle convection and potentially subducted to the bottom of the lower mantle when carried within layers of dense basaltic rocks.

关键词： Anorthosite Phase transformation Multi-anvil apparatus Diamond-anvil cell Mantle dynamics

The life of animals in japanese art

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The life of animals in Japanese art

Gamete Dialogs in Green Lineages

作者： edited by Robert T. Singer kawai Masatomo

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Molecular Plant 2015年第10期8卷 1442-1454页

作者： Toshiyuki Mori Hiroko kawai-Toyooka Tomoko Igawa Hisayoshi Nozaki Department of Biological Sciences Graduate School of Science The University of Tokyo 7-3-1 Hongo Bunkyo-ku Tokyo 113-0033 Japan Graduate School of Horticulture Chiba University 648 Matsudo Matsudo Chiba 271-8510 Japan

Gamete fusion is a core process of sexual reproduction and, in both plants and animals, different sex gametes fuse within species. Although most of the molecular factors involved in gamete interaction are still unknown in various sex-possessing eukaryotes, reports of such factors in algae and land plants have been increasing in the past decade. In particular, knowledge of gamete interaction in flowering plants and green algae has increased since the identification of the conserved gamete fusion factor GENERATIVE CELL SPECIFIC 1/HAPLESS 2 （GCS1/HAP2）. GCSl was first identified as a pollen generative cell-specific transmembrane protein in the lily （Lilium Iongiflorum）, and was then shown to function not only in flowering plant gamete fusion but also in various eukaryotes, including unicellular protists and metazoans. In addition, although initially restricted to Chlamydomonas, knowledge of gamete attachment in flowering plants was also acquired. This review focuses on recent progress in the study of gamete interaction in volvocine green algae and flowering plants and discusses conserved mechanisms of gamete recognition, attachment, and fusion leading to zygote formation.

关键词： sexual reproduction gamete fusion flowering plants green algae evolution