DYNAMICS OF INHIBITORY PULSE-COUPLED OSCILLATORS

この論文は国立情報学研究所の電子図書館事業により電子化されました。A complete classification of dynamics of a population of a inhibitory pulse-coupled oscillators is presented. The model is based on the work of Mirollo and Strogatz, but our model has an inhibitory coupling between oscillators which makes a sharp contrast with the dynamics of the above authors' model. The main result is that for a large class of initial conditions, the population approaches a periodic state in which all the oscillators keep finite size of phase difference (we call it "phase locking solution" here). For the remaining class of initial data except for nongeneric ones, it evolves to a periodic state with a cluster or a synchronous state depending on a size of cluster. The criterion for the classification is explicitly given and can be judged easily only by the initial condition

Analysis of a rare-earth sample, Didym by ion chromatography/neutron activation analysis and isotachophoresis/particle induced X-ray emission method

希土類元素の発見史において, 当時単元素と考えられていたジジム (Didym) はBraunerにより現在のPr, Ndに分離され原子量が測定されている (1882年). 本研究では, 実際の分離過程で使用された酸化物試料中の希土類元素の組成を二つの結合分析法を用いて分析した. 中性子放射化分析法 (NAA) では, 40μgの試料で四つの元素が測定されたのに対して, イオンクロマトグラフ分離 (IC) を組み合わせたIC/NAAを用いた分析では, 100μgのジジムを分析したとき, 0.004重量%のYbなど13種の希土類元素を定量することが可能であった. 一方, 等速電気泳動分離/粒子励起X線分析法 (ITP/PIXE) では12種の希土類元素が定量できた. 二つの結合分析法による測定結果はよく一致しており, セル石 (Cerite) から分離されたジジムには, CeはほとんどなかったがLaが多量に含まれており, 今回分析した試料はLaを分離する前の試料と推察された.In the history of the discovery of rare-earth elements, two elements, Pr and Nd were isolated by Brauner (1882) from a rare-earth sample (Didym) which was considered to be mono-element and their atomic numbers were also determined. In this study, the oxide sample employed in the separation processes was analyzed using two coupled analytical methods, ion chromatography/neutron activation analysis (IC/NAA) and isotachophoresis/particle induced X-ray emission method (ITP/PIXE). Four rare-earth elements were only determined by NAA of 40 μg of Digym. Whereas for IC/NAA with preseparation process, 13 rare-earth elements containing 0.004 mass% Yb were determined when 100 μg of Didym was analyzed. For ITP/PIXE, 12 rare-earth elements were determined. The results obtained by the coupled analytical methods agreed with each other. Although the content of Ce in the sample (Didym) obtained from Cerite was very small, that of La was large, suggesting that chemical treatments to remove La had not been achieved

Enhanced chemical weathering as a geoengineering strategy to reduce atmospheric carbon dioxide, supply nutrients, and mitigate ocean acidification

Chemical weathering is an integral part of both the rock and carbon cycles and is being affected by changes in land use, particularly as a result of agricultural practices such as tilling, mineral fertilization, or liming to adjust soil pH. These human activities have already altered the chemical terrestrial cycles and land-ocean flux of major elements, although the extent remains difficult to quantify. When deployed on a grand scale, Enhanced Weathering (a form of mineral fertilization), the application of finely ground minerals over the land surface, could be used to remove CO2 from the atmosphere. The release of cations during the dissolution of such silicate minerals would convert dissolved CO2 to bicarbonate, increasing the alkalinity and pH of natural waters. Some products of mineral dissolution would precipitate in soils or taken up by ecosystems, but a significant portion would be transported to the coastal zone and the open ocean, where the increase in alkalinity would partially counteract “ocean acidification” associated with the current marked increase in atmospheric CO2. Other elements released during this mineral dissolution, like Si, P or K, could stimulate biological productivity, further helping to remove CO2 from the atmosphere. On land, the terrestrial carbon-pool would likely increase in response to Enhanced Weathering in areas where ecosystem growth rates are currently limited by one of the nutrients that would be released during mineral dissolution. In the ocean, the biological carbon pumps (which export organic matter and CaCO3 to the deep ocean) may be altered by the resulting influx of nutrients and alkalinity to the ocean. This review merges current interdisciplinary knowledge about Enhanced Weathering, the processes involved, and the applicability as well as some of the consequences and risks of applying the method