排序方式: 共有29条查询结果,搜索用时 31 毫秒
1.
2.
Steven Emerson Susan Kalhorn Lucinda Jacobs Bradley M Tebo Kenneth H Nealson Reinhardt A Rosson 《Geochimica et cosmochimica acta》1982,46(6):1073-1079
A simple mass balance for dissolved manganese(II) in waters containing low levels of oxygen in Saanich Inlet indicates that the residence time for Mn(II) removal to the solid phase is on the order of a few days. The average oxidation state of Mn in particulate material sampled from the region of Mn removal was 2.3–2.7, and electron micrographs revealed structures characteristic of bacterially formed Mn precipitates. Radiotracer experiments utilizing 54Mn(II) indicated that removal of Mn from solution in the region of active uptake was substantially blocked by a poison mixture, demonstrating that Mn(II) binding to particulates is catalyzed by bacteria in this environment. 相似文献
3.
In this rebuttal to G. Levin's critique of our previous publication, we claim again that iron(VI) is a very good candidate as a martian oxidant. Our experiments cannot be explained as a result of microbial activities, as we showed that Fe(VI) could be used as a sterilizing agent for destroying microorganisms, nucleic acids, and proteins. 相似文献
4.
The Al–Mg-rich granulites from the In Ouzzal craton, Algeria, show a great diversity of mineral reactions which correspond to continuous equilibria as predicted by phase relationships in the FeO–MgO–Al2O3–SiO2 system. The sequence of mineral reactions can be subdivided into three distinct stages: (1) a high-P stage characterized by the growth of coarse mineral assemblages involving sapphirine and the disappearance of early corundum and spinel-bearing assemblages; (2) a high-T stage characterized by the development of Sa–Qz-bearing assemblages; and (3) a later stage, in which garnet-bearing assemblages are replaced by more or less fine symplectites involving cordierite. During the course of early mineral reactions, the distribution coefficient, Kd, between the various ferromagnesian phases decreased significantly whereas Al2O3 in pyroxene increased concomitantly. These observations, when combined with topological constraints, clearly indicate that the high-P stage 1 was accompanied by a significant rise in temperature (estimated at 150 ± 50° C) under near isobaric conditions, in agreement with the reaction textures. By stage 2, pressure and temperature were extreme as evidenced by the low Kd value between orthopyroxene and garnet (Kd= 2.06–1.99), the high alumina content in pyroxene (up to 11.8%) and the high magnesium content in garnet [100 Mg/(Mg + Fe) = 60.6]. Mineral thermometry based on Fe–Mg exchange between garnet and pyroxene and on Al-solubility in pyroxene gives temperatures close to 970 ± 70° C at 10 ± 1.5 kbar. These results are in agreement with the development of Sa–Qz assemblages on a local scale. Late mineral reactions have been produced during a decompression stage from about 9 to 6 kbar. Except for local re-equilibration of Mg and Fe at grain boundaries, there is no evidence for further reactions below 700° C. We interpreted the whole set of mineral reactions as due to changes in pressure and temperature during a tectonic episode located at c. 2 Ga. Because of the lack of evidence for further uplift after the thermal relaxation which occurred at c. 6 kbar, it is possible however that the exhumation of this granulitic terrane occurred in a later tectonic event unrelated to its formation. 相似文献
5.
H. M. Tovmassian R. Kh. Hovhanessian R. A. Epremian D. Huguenin S. I. Serova V. G. Titov M. KH. Manarov 《Astrophysics and Space Science》1990,174(2):297-302
The results of UV-observations at 1640 Å of the regions of stellar associations Per OB1, Sco OB1, and Cyg OB1 made with the space telescope Glazar are presented. Respectively, 42, 22, and 30 hot stars brighter than 10m at 1640 Å were detected and measured in the mentioned stellar associations. A few of them are suspected to be variable in far UV. 相似文献
6.
7.
In an effort to elucidate the mechanism of formation and accretion of ferromanganese nodules, transverse sections of undisturbed botryoid surfaces of nodules from the abyssal central North Pacific were examined by X-ray analyses both by multiple replicate sample transects and mapping. Surface concentrations of Mn and Fe were found of the size and shape of microorganisms. Abundant microorganism-like objects covering the surface and the apparent absence of Si (i.e. no sediment) with the Mn and Fe concentrations suggests microorganisms may be involved either in the selective accretion or removal of these metals. If metal accretion was simply physicochemical, one would expect a more or less even distribution of Mn and Fe on the botryoid surfaces.The replicate X-ray sample transects showed that Mn and Fe have a distribution corresponding to botryoid zonation. Areas of high Mn X-ray intensity were found associated with the cap and equatorial zones of the botryoid. Most of the valley zone of the botryoid show a more or less even Mn distribution and an increase in Fe X-ray intensity. At the base of the botryoid both metals apparently precipitously decrease. 相似文献
8.
Pure cultures of Chlorella sp. catalyzed the oxidation of soluble Mn(II) to particulate, extracellular, manganic oxides. Manganese oxidation was dependent on photosynthetic activity: no oxidation was observed in the dark when cells were grown heterotrophically on glucose, or in the light when photosystem II was inhibited by the addition of DCMU. Manganates were not formed when media were buffered below pH 8.0, suggesting that an important driving force for manganese oxidation was the high pH resulting from photosynthesis. Field studies with minielectrodes in Oneida Lake, New York, demonstrated steep gradients of O2 and pH and the presence of particulate manganic oxides associated with pelagic aggregates of the cyanobacterium Microcystis sp. The manganese oxidation reaction apparently occurs only when photosynthesizing algae are present as dense populations that can generate microenvironments of high (>9.0) pH, either as aggregates in the pelagic zone or concentrated cell cultures in the laboratory. A large-scale transition from soluble to particulate manganese was measured in the surface waters of Oneida Lake throughout summer 1986. Removal of Mn(II) was correlated with the presence of aggregate-forming cyanobacteria that oxidize Mn(II) by the mechanism described above. 相似文献
9.
10.
介绍了如何将互联网技术应用于石油行业的局域网或广域网中,在服务器端提供图形信息数据库的服务,并在客户端利用浏览器进行图形信息的查询,实现勘探开发图形信息的共享。 相似文献