Biological production in meso-scale eddies caused by frontal disturbances of the Kuroshio Extension   总被引：1，自引：0，他引：1  

Kimura  Shingo; Nakata  Hideaki; Okazaki  Yuji 《ICES Journal of Marine Science》2000,57(1):133-142

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Nanophase magnetite in matrix of anomalous EL3 chondrite Northwest Africa (NWA) 8785     

M. K. Weisberg  M. E. Zolensky  M. Kimura  K. T. Howard  D. S. Ebel  M. L. Gray  C. M. O'D. Alexander 《Meteoritics & planetary science》2023,58(12):1693-1706

NWA 8785 is a remarkable EL3 chondrite with a high abundance (~34 vol%) of an Fe-rich matrix. This is the highest matrix abundance known among enstatite chondrites (ECs) and more similar to the matrix abundances in some carbonaceous and Rumuruti chondrites. X-ray diffraction and TEM data indicate that the fine-grained portion of the NWA 8785 matrix consists of nanoscale magnetite mixed with a noncrystalline silicate material and submicron-sized enstatite and plagioclase grains. This is the first report of magnetite nanoparticles in an EL3. The Si content of the metal (0.7 wt%), presence of ferroan alabandite, and its O isotopic composition indicate NWA 8785 is EL3-related. Having more abundant matrix than in other ECs, and that the matrix is rich in magnetite nanoparticles, which are not present in any other EC, suggest classification as an EL3 anomalous. Although we cannot completely exclude any of the mechanisms or environments for formation of the magnetite, we find a secondary origin to be the most compelling. We suggest that the magnetite formed due to hydrothermal activity in the meteorite parent body. Although ECs are relatively dry and likely formed within the nebular snow line, ices may have drifted inward from just beyond the snow line to the region where the EL chondrites were accreting, or more likely the snow line migrated inward during the early evolution of the solar system. This may have resulted in the condensation of ices and provided an ice-rich region for accretion of the EL3 parent body. Thus, the EL3 parent body may have had hydrothermal activity and if Earth formed near the EC accretion zone, similar bodies may have contributed to the Earth's water supply. NWA 8785 greatly extends the range of known characteristics of ECs and EC parent body processes.  相似文献   

A practical model to estimate photosynthetically active radiation using general meteorological elements in a temperate humid area and comparison among models     

Yasuko Mizoguchi  Yukio Yasuda  Yoshikazu Ohtani  Tsutomu Watanabe  Yuji Kominami  Katsumi Yamanoi 《Theoretical and Applied Climatology》2014,115(3-4):583-589

Although accurately evaluating photosynthetically active radiation is important, much effort is required to measure this radiation using a quantum sensor. We develop a new model that makes estimates using only general meteorological data—solar radiation, atmospheric pressure, air temperature, and relative humidity. Root mean square deviations for eight datasets at five sites in Japan were smaller than 5.2 %, similar to error in other studies and to individual differences of quantum sensors. Most root mean square deviations of nine previous models and our eight datasets are larger than that of the new estimation model, which performed well. This suggests that the model is useful for estimating photosynthetically active radiation in a temperate, humid area of Japan.  相似文献   

Biotic response of benthic foraminifera in Aso-kai lagoon,central Japan,to changes in terrestrial climate and ocean conditions (~AD 700–1600)     

Hiroyuki Takata  Satoshi Tanaka  Koji Seto  Saburo Sakai  Katsumi Takayasu  Boo-Keun Khim 《Journal of Paleolimnology》2014,51(3):421-435

We investigated responses of shallow-water benthic foraminifera to changes in climate and ocean conditions, using sediment core ASC2 from Aso-kai lagoon, central Japan. Six AMS ¹⁴C dates reveal that the studied interval corresponds to sediments deposited from ~AD 700 to 1600. Sulfur content of the bulk sediment and multi-dimensional scaling (MDS) axis 1 of fossil benthic foraminifera indicate that the composition of the benthic foraminifera community was closely related to dissolved oxygen (DO) concentration in the hypolimnion. The sulfur content and MDS axis 1 also revealed two shifts over the 900-year interval. In the first phase (~AD 700–1250), the Shannon–Wiener Index (H′), E (S₂₀₀), evenness and rank abundance curve (RAC) kurtosis indicate a gradual deterioration in structure of the benthic foraminifera community. In that period, there are statistically significant correlations between the faunal composition (MDS axis 1) and faunal structure [Shannon–Wiener (H′), E (S₂₀₀), evenness and RAC kurtosis]. In the second phase (~AD 1250–1600), however, faunal composition and structure show no marked correspondence. Instead, abundance of benthic foraminifera fluctuated on a scale of ~200 years. Thus, a shift in the biotic response of benthic foraminifera in Aso-kai lagoon occurred in ca. AD 1250. Gradual deterioration of benthic foraminifera, with taxonomic losses, is consistent with declining DO in the first phase, possibly associated with the increasing influence of the Tsushima Warm Current. The possibility that closure of Aso-kai lagoon and development of the sand bar affected benthic foraminifera cannot, however, be ruled out. No corresponding response was observed in the second phase, during which there was no distinct taxonomic loss. Large variations in abundance, however, were a consequence of strength of the East Asian summer and winter monsoons. The shift in the biotic response of benthic foraminifera in Aso-kai lagoon during the period AD 700–1600 was apparently a result of changes in climate and ocean conditions on the East Asian continental margin.  相似文献   

Seasonal variation of carbon dioxide fluxes over irrigated soybean (Glycine max L.)     

Levent Şaylan  Reiji Kimura  Erdenebayar Munkhtsetseg  Makio Kamichika 《Theoretical and Applied Climatology》2011,105(1-2):277-286

In this study, variations in carbon dioxide (CO₂) fluxes resulting from gross primary production (GPP), net ecosystem exchange (NEE), and respiration (R _e) of soybean (Glycine max L.) were investigated by the Eddy Covariance method during the growing period from June to November 2005 on an irrigated sand field at the Arid Land Research Center, Tottori University in Tottori, Japan. Although climatic conditions were humid and temperate, the soybeans required frequent irrigation because of the low water holding capacity of the sandy soil at the field site. Finally, it has been found that the accumulated NEE, GPP, and R _e fluxes of soybean over 126 days amount to ?93, 319, and 226 gC m^?2, respectively. Furthermore, the average ratio of GPP to R _e was 1.4 and the average ratio of NEE to GPP was about ?0.29 for the growth period of soybean. Daily maximum NEE of ?3.8 gC m^?2 occurred when LAI was 1.1.  相似文献   

The ultra-low-frequency associated with magnetic disturbances earthquakes     

Masashi Hayakawa  Yasuhide Hobara  Kenji Ohta  Katsumi Hattori 《地震学报(英文版)》2011,(6):523-534

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Evidences of increasing primary production in the ocean by Stommel's perpetual salt fountain     

Shigenao Maruyama  Takashi YabukiTetsuya Sato  Koutaro TsubakiAtsuki Komiya  Mikihito WatanabeHiroshi Kawamura  Katsumi Tsukamoto 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(5):567-574

The American physical oceanographer Henry Stommel and co-workers proposed “the perpetual salt fountain” and suggested the possibility of upwelling deep seawater without an energy source. In the open ocean, deep seawater containing rich nutrients becomes a source of primary production. Previously, we have tested Stommel's hypothesis by numerical simulations and in ocean experiments, and confirmed the upwelling of a perpetual salt fountain. In the present study, we conducted an open-ocean experiment in the Philippines Sea, and succeeded to demonstrate an increase in chlorophyll concentration. The chlorophyll concentration at the pipe outlet was much greater than that in the surrounding seawater. Satellite ocean-color image around the pipe was analyzed, and the signal of artificial upwelling is investigated. Composite analysis of satellite chlorophyll image indicates an increased surface chlorophyll distribution in the vicinity of pipe position, in which the increasing signal is much larger than the expected production based on nutrient supply. Although the problem must be further discussed, this increased signal is shown to be statistically significant. This mechanism may contribute to effective utilization of fishery resources in subtropical oligotrophic region.  相似文献   

Agricultural risk management policies under climate uncertainty   总被引：1，自引：0，他引：1  

Jesús Antón  Andrea Cattaneo  Shingo Kimura  Jussi Lankoski 《Global Environmental Change》2013,23(6):1726-1736

Climate change is forecasted to increase the variability of weather conditions and the frequency of extreme events. Due to potential adverse impacts on crop yields it will have implications for demand of agricultural risk management instruments and farmers’ adaptation strategies. Evidence on climate change impacts on crop yield variability and estimates of production risk from farm surveys in Australia, Canada and Spain, are used to analyse the policy choice between three different types of insurance (individual, area-yield and weather index) and ex post payments. The results are found to be subject to strong uncertainties and depend on the risk profile of different farmers and locations; the paper provides several insights on how to analyse these complexities. In general, area yield performs best more often across our countries and scenarios, in particular for the baseline and marginal climate change (without increases in extreme events). However, area yield can be very expensive if farmers have limited information on how climate change affects yields (misalignment in expectations), and particularly so under extreme climate change scenarios. In these more challenging cases, ex post payments perform well to increase low incomes when the risk is systemic like in Australia; Weather index performs well to reduce the welfare costs of risks when the correlation between yields and index is increased by the extreme events. The paper also analyses the robustness of different instruments in the face of limited knowledge of the probabilities of different climate change scenarios; highlighting that this added layer of uncertainty could be overcome to provide sound policy advice under uncertainties introduced by climate change. The role of providing information to farmers on impacts of climate change emerges as a crucial result of this paper as indicated by the significantly higher budgetary expenditures occurring across all instruments when farmers’ expectations are misaligned relative to actual impacts of climate change.  相似文献   

Demonstration of crystalline forsterite grain formation due to coalescence growth of Mg and SiO smoke particles     

C. Kaito  Y. Ojima  K. Kamitsuji  O. Kido  Y. Kimura  H. Suzuki  T. Sato  T. Nakada  Y. Saito  C. Koike 《Meteoritics & planetary science》2003,38(1):49-57

Abstract— Experimental studies of coalescence between Mg grains and SiO grains in smoke reveal the direct production of crystalline forsterite grains. The present results also show that different materials can be produced by grain‐grain collisions, which have been considered one of the models of grain formation in the interstellar medium. The fundamentals of coalescence growth in smoke, which have been developed in our series of experiments, are presented in this paper. Mg₂Si polyhedral grains were obtained in a Mg grain‐rich atmosphere. Mg₂SiO₄ polyhedral grains were obtained in a SiO grain‐rich atmosphere. The IR spectra of the resultant grains showed the characteristics of crystalline forsterite.  相似文献   

A survey of emission-line stars in the perseus dark cloud     

Liu Cai-pin  Zhang Chun-sheng  Kimura Hiroshi 《Chinese Astronomy and Astrophysics》1981,5(3):276-281

The results of an objective prism survey of H_α emission-line stars in a 5° × 5° region around NGC 1333 are presented. We have identified 25 stars as having H_α -line in emission, of which 11 have been discovered in the Lick H_α-survey. The limiting magnitude of the present survey is about 16.7 mag. in blue. These are suspected to be mainly T Tauri stars. Based on the UGR(Kiso) multiexposure plates, we have found that, on the [(G - U), (R - G)]-diagram, the domain of H_α emission line stars is fairly well delineated and separate from other stars. Some interesting features in their space distribution are also discussed briefly.  相似文献