排序方式： 共有16条查询结果，搜索用时 31 毫秒
1.
Yoshiaki Yamaguchi Junji Akai Katsutoshi Tomita 《Contributions to Mineralogy and Petrology》1978,66(3):263-270
Porphyroclastic diopside in garnet lherzolite from Alpe Arami, Bellinzona, Switzerland includes optically-visible clinoamphibole lamellae with a composition intermediate between pargasite and edenite. X-ray and electron microscopic observations show that the diopside crystal contains sub-microscopic thin clinoamphibole lamellae parallel to (010), which have coherent interfaces to the host. A kind of planar defect parallel to (010) in clinopyroxene structure, as suggested by Chisholm (1973), is shown here to correspond to intercalation of a 9 Å lattice fringe of double-chain structure in the electron micrograph of the diopside. The thin clinoamphibole lamellae are observed to be segregated domains consisting of two and more 9 Å fringes.From the chemical characteristics and textural relations of the development of such clinoamphiboles, the chemical change required to form them is considered to have been caused principally by decreasing solubility of atoms such as Na, Al and Cr in clinopyroxene structure during the retrogressive reequilibration. Also, a possibility of finite solid solution of clinoamphibole in clinopyroxene is discussed. 相似文献
2.
3.
Nobuki Kawashima Kazunori Akai Yukio Murasato Susumu Sasaki 《Astrophysics and Space Science》1984,106(1):117-123
In an electron beam emission experiment on board the EXOS-B (JIKIKEN) satellite (200 V, 1 mA-maximum), several types of waves are strongly excited by the beam such as plasma frequency, upper hybrid frequency, electron cyclotron frequency, their harmonics and nonlinear coupling of these waves. Measurements of these waves give information on local plasma density and magnetic field strength and it is revealed that the electron beam emission from the spacecraft is a powerful diagnostic tool in the magnetosphere. A long term observation in this electron beam experiment has provided us with the average plasma density profile in the magnetosphere. It is also useful for the detection of the plasmapause. Plasma density measurements down to the order of 10 cm–3 are possible. The instrument itself is very simple and compact, so that it will be a powerful plasma diagnostic tool in future magnetospheric and planetary explorations. 相似文献
4.
Junji Akai 《Contributions to Mineralogy and Petrology》1982,80(2):117-131
Clinopyroxene transforms to triple chain silicate, double chain silicate (amphibole) and sheet silicate (talc) in the metasomatic process of the Akatani ore deposit. The triple chain silicate is contained in fibrous amphibole-like phase (“amphibole”). It is of electron microscopic size of 1,000 Å at maximum width in b-direction, and is a calciferous analogue of clinojimthompsonite. Various kinds of fine textures formed in metasomatic reaction process were found in clinopyroxenes. A large amount of triple chains and a small amount of double chains were transformed from single chains in the host clinopyroxene, maintaining topotactic relation. The kinetics of the structural change of biopyriboles at the Akatani ore deposit was discussed from the viewpoint of the mode of occurrence of triple and double chain silicates. The nucleation of triple chain structure slab with one triple chain width is apt to occur rather than the nucleation of double chain structure slab with width of two double chains in clinopyroxene host. Various fine textures in clinopyroxenes and amphibole-like phase were interpreted as corresponding to the propagation of metasomatic reactions. 相似文献
5.
H. Anawar K. Komaki J. Akai J. Takada T. Ishizuka T. Takahashi T. Yoshioka K. Kato 《Environmental Geology》2002,41(7):816-825
A stratigraphic profile of solid phase As was measured to investigate the diagenetic cycling of arsenic and related elements in fluvial sediments of the Meghna River delta plain. The distributions of Fe, Mn, and Al are typically characterized by surficial solid phase enrichment, and As is distributed down to 36.6 m showing similar alternate layers of maxima and minima with Fe, Mn and TOC, which reflects the diagenetic remobilization and periodical differences in source materials of As. Lithological characteristics and geochemical data suggest that elevated levels of As are found in organic-matter-rich clay and silty sand rather than sand samples, with occasionally enriched As content in iron-oxyhydroxide-coated sand grains. Arsenic demonstrates a positive and significant co-variation with total organic carbon in sediments, which suggests the important role of particulate and colloidal organic matter and biological activity in controlling the distribution of arsenic in the Bengal delta. However, the concentrations of Fe and Mn weakly correlate with As contents, whereas Al contents show no relationship with As. The results of this study suggest that reactive oxides or hydroxides of Fe and Mn, rather than Fe and Mn with other minerals, might control arsenic distribution. 相似文献
6.
7.
S. Endo T. Akai Y. Akahama M. Wakatsuki T. Nakamura Y. Tomii K. Koto Y. Ito M. Tokonami 《Physics and Chemistry of Minerals》1986,13(3):146-151
Single crystal stishovite with a square prismatic habit and maximum length 0.8 mm was grown from α-quartz at 120 kbar and ～1,300° C. Li2WO4, chosen as a result of a previous experiment in growing coesite, was also successful as flux for stishovite. Single crystal X-ray structure analysis of the crystals thus obtained has been carried out at high temperatures under ambient pressure. Lattice constant measurements give a larger thermal expansion coefficient along the a-axis than along the c-axis. The bond distances and bond angles show a decreasing distortion of the SiO6 octahedron with increasing temperature. The increasing amplitude of thermal vibrations of oxygen atoms with increasing temperature results in increasing O-O repulsion in the basal plane, which explains the observed crystallographic changes. 相似文献
8.
Summary A mobile RASS (Radio Acoustic Sounding System), which can be loaded onto a truck along with all the other equipment, including
the power supply, was developed for atmospheric temperature measurement. Also, since it is necessary to avoid noise pollution
in surrounding areas when conducting observations with the mobile RASS, a new method that allows measurement of the temperature
profile up to about 200 m using a single acoustic pulse was devised. We discuss the development of a truck-mounted mobile
RASS and the results of the first mobile observation conducted at various locations in the Tokyo area.
Received November 3, 1998 Revised June 16, 1999 相似文献
9.
Masami Izuho Yuichi Nakazawa Fumito Akai Tsutomu Soda Hirotaka Oda 《Geoarchaeology》2009,24(4):492-517
In order to better understand modern human behavioral variability in Hokkaido, Japan, we consider the geoarchaeology of the Kamihoronai‐Moi site in terms of its geochronology, stratigraphy, depositional environments, and post‐depositional disturbances. A Paleolithic component is stratigraphically situated between the Eniwa‐a (15,000–17,000 14C yr B.P.) and the Tarumae‐d (8000–9000 14C yr B.P.) tephras. Moreover, six AMS 14C ages on charcoal from a Pleistocene‐aged hearth feature are between 14,400 and 14,800 14C yr B.P. Quantitative examinations of patterns in artifact distributions show a low degree of vertical and horizontal displacement of chipped‐stone artifacts, suggesting that post‐depositional movement of the cultural material was insufficient to disrupt the original pattern of artifact distribution. © 2009 Wiley Periodicals, Inc. 相似文献
10.
Influence of microbial photosynthesis on tufa stromatolite formation and ambient water chemistry, SW Japan 总被引：1，自引：0，他引：1
Photosynthetic influences on tufa stromatolite formation and ambient water chemistry were investigated at two well-studied streams depositing tufa in Southwestern Japan (Shirokawa and Shimokuraida). The tufa stromatolites in both streams are composed of fine-grained calcite crystals showing annual lamination, and colonized by a number of filamentous cyanobacteria as well as non-phototrophic bacteria. Microelectrode measurements of pH, O2, and Ca2+ near the stromatolite surface (the diffusive boundary layer; DBL) revealed that the investigated tufa stromatolites are formed by photosynthesis-induced CaCO3 precipitation (PCP): cyanobacterial photosynthesis induces calcite precipitation under light conditions, while respiration of cyanobacteria and non-phototrophic bacteria inhibits precipitation in the dark. The bulk water chemistry at the lower sites of the investigated streams showed the daytime decreases of Ca2+ concentration and alkalinity that was expected for significant influence of PCP, while the other expected change, increased pH, was not observed. In order to examine this discrepancy, a novel approach using semi-in situ microelectrode measurements was applied to perform precise quantitative calculations. The calculation results demonstrated that the observed Ca2+ concentration and alkalinity decreases were caused by PCP, and that the concomitant pH increase was expected to be under the detection level of a conventional pH meter. Although the amount of PCP is supposed to be significantly affected by light intensity, observations in Shimokuraida revealed that the amount of PCP on cloudy day nonetheless accounted for about 80% of that on sunny day. Despite the significant role of PCP for tufa stromatolite formation, PCP accounted for only about 10% of the precipitated calcite in the investigated streams, which indicates that tufa stromatolites, the characteristic deposits in the streams, are responsible for only a small portion of calcite precipitation, and the rest is considered to precipitate inorganically at biofilm-free substrates. 相似文献