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1.
Susumu Sakata John M. Hayes Michel Rohmer Alan B. Hooper Myriam Seemann 《Organic Geochemistry》2008,39(12):1725
For the ammonia-oxidizing bacterium Nitrosomonas europaea, grown autotrophically using semicontinuous culturing, average biomass was depleted in 13C relative to CO2 dissolved in the medium by ca. 20‰ and the total-lipid extract was depleted in 13C relative to biomass by 3.7‰. The n-alkyl lipids (weighted average of fatty acids) and isoprenoid lipids (weighted average of hopanoids) were both depleted in 13C relative to biomass by about 9‰. The large depletion in the isoprenoid lipids seems to indicate that isotopic fractionations associated with the biosynthesis of methylerythritol phosphate (MEP) affected at least two carbon positions in each isoprene unit. Among the fatty acids, trans-9-hexadecenoic acid was most depleted (13.0‰ relative to biomass), followed by cis-9- hexadecenoic acid (9.6‰) and hexadecanoic acid (6.9‰). Isotopic relationships between the three acids suggest that significant isotope effects were associated with the desaturation and cis to trans isomerization of fatty acids. Given these observations, hopanoids produced by ammonia-oxidizing bacteria growing in natural waters are likely to be depleted in 13C by 26–30‰ relative to dissolved CO2. Since CO2 at aquatic oxyclines is often depleted in 13C, the range of δ values expected for hopanoids is ca. −34‰ to −55‰. The δ values of geohopanoids observed in numerous studies and attributed to unspecified chemoautotrophs fall within this range. 相似文献
2.
Myriam Sibuet Luc Floury Anne-Marie Alayse-Danet Andr Echardour Tanguy LeMoign Roger Perron 《Progress in Oceanography》1990,24(1-4)
In order to make progress in the study of processes in deep-sea ecosystems, we have developed a strategy for the use of submersibles in conjunction with free vehicles. The BIOCYAN programme, which was conducted by French oceanographers at a permanent station in the Bay of Biscay, involved the use of submersibles for benthic ecological studies. It lead to the development of a variety of equipment for sampling and experimental studies. The submersible Cyana has a limited equipment workload, so the initial step was to develop a free vehicle which could function as a shuttle to act as an independent transport for equipment to be used from the submersible. Two other devices have been developed for sampling with precision the surficial layers of the sediment, one of which can be used in conjunction with an injection module to measure rates of processes in situ by incubations, following injection with labelled substrates. These devices, the free-lift shuttle, tube corers, a blade box corer and the associated injection module are described. 相似文献
3.
Jean-Marie Auzende Eiichi Honza Xavier Boespflug Satendra Deo Jean-Philippe Eissen Jun Hashimoto Philippe Huchon Junichiro Ishibashi Yo Iwabuchi Philip Jarvis Masato Joshima Kiyoyuki Kisimoto Yasuto Kuwahara Yves Lafoy Tsuyoshi Matsumoto Jean-Pierre Maze Kiyohiko Mitsuzawa Hiroyasu Monma Takeshi Naganuma Yukihiro Nojiri Suguru Ohta Kiyoshi Otsuka Yoshihisa Okuda Hélène Ondreas Akira Otsuki Etienne Ruellan Myriam Sibuet Manabu Tanahashi Takeo Tanaka Tetsuro Urabe 《Marine Geophysical Researches》1990,12(4):269-283
The aim of the Japanese-French Kaiyo 87 cruise was the study of the spreading axis in the North Fiji Basin (SW Pacific). A
Seabeam and geophysical survey allowed us to define the detailed structure of the active NS spreading axis between 16° and
22° S and its relationships with the left lateral motion of the North Fiji Fracture Zone. Between 21° S and 18°10′ S, the
spreading axis trends NS. From 18°10 S to 16°40 S the orientation of the spreading axis changes from NS to 015°. North of
16°40′ S the spreading axis trends 160°. These two 015° and 160° branches converge with the left lateral North Fiji fracture
zone around 16°40′ S to define an RRFZ triple junction. Water sampling, dredging and photo TV deep towing give new information
concerning the hydrothermal activity along the spreading axis. The discovery of hydrothermal deposits associated with living
communities confirms this activity. 相似文献
4.
5.
Neo-rural populations and their relations with local decision makers in rural Québec: collaboration or conflict? 总被引:1,自引:0,他引:1
The socio-demographic recomposition of the countryside is affecting local interactions and power relations. Understanding these relationships remains a challenge, as the studies to date are often limited to conflicts between neo-rural populations (newcomers) and long-time country residents over partial issues, without including decision makers. To go beyond this conflictual and fragmentary perspective, the objective of this article is to present an overall picture of both cooperative and oppositional relations between four groups, namely, newcomers, long-time rural residents, leaders of local organizations and municipal officials, in regard to all the issues that concern them. The data are based on interviews with these various actors in two contrasting rural areas of Québec (Canada). After looking at the newcomers’ mixed assessment of their participation in community life, we concentrate on areas of collaboration and/or conflict between all the actors regarding demographic, economic, sociocultural, political, environmental and agricultural issues. Three main trends emerge, revealing unexpected ways of interacting, complex power relations and antagonistic conceptions of rural spaces and their future development. 相似文献
6.
Bouaida Jihad Witam Omar Ibnoussina Mounsif Delmaki Abd El Fettah Benkirane Myriam 《Natural Hazards》2021,105(2):1835-1859
Natural Hazards - Despite the controversy regarding their use, school buildings are often assigned as emergency evacuation shelters, temporary accommodation and aid distribution hubs following... 相似文献
7.
Transport properties of rocks from statistics and percolation 总被引:7,自引:0,他引:7
Two simplified microstructural models that account for permeability and conductivity of low-porosity rocks are compared. Both models result from statistics and percolation theory. The first model assumes that transport results from the connection of 1D objects or pipes; the second model assumes that transport results from the connection of 2D objects or cracks. In both cases, statistical methods permit calculation of permeability k and conductivity , which are dependent on three independent microvariables: average pipe (crack) length, average pipe radius (crack aperture), and average pipe (crack) spacing. The degree of connection is one aspect of percolation theory. Results show that use of the mathematical concept of percolation and use of the rock physics concept of tortuosity are equivalent. Percolation is used to discuss k and near the threshold where these parameters vanish. Relations between bulk parameters (permeability, conductivity, porosity) are calculated and discussed in terms of microvariables. 相似文献
8.
On the basis of two assumptions i.e. (1) plastic and anelastic behaviour of the upper mantle can be approximated by the behaviour of the dominant mineral olivine, and (2) the behaviour of natural olivine and synthetic forsterite are similar, we have investigated the flow laws and the flow microstructures of forsterite single crystals. The results obtained between 1400–1650°C and 10–100 MPa suggest a model of climb controlled creep in which the a edge dislocations are dominant. The activation energy measured in that regime is 4.7 eV, close to that of Si self-diffusion and the flow law is , where σ is in MPa. Extrapolation of these results to the upper mantle would imply very low stresses (i.e. ?10 MPa) in the asthenosphere. However the effect of pressure and grain size are unknown and extrapolation to very low stresses is not straightforward. 相似文献
9.
Spectra of internal friction between 2 and 8 Hz were studied in a single crystal of enstatite, in a polycrystal of synthetic forsterite and in several samples of natural peridotite. Measurements of Q?1 and μ were performed in vacuum (10?6 torr), from room temperature up to 1100°C. For these experimental conditions no peak was observed in the polycrystalline undeformed forsterite, but the background attenuation irregularly increased from 5 · 10?3 to 10?2.A peak Q?1 = 7 · 10?2 appears in a deformed peridotite at 930°C. It is reduced of 60% after 5 h of annealing at 1100°C. But the background attenuation persists. In the single crystal of enstatite, a peak is observed at 760°C (Q?1 = 6 · 10?2). A mechanism involving dislocations is suggested as a possible explanation for the peak obtained with the peridotite samples. If this hypothesis is right, the observed effect would be diffusion controlled so that one can expect pressure to translate it towards higher temperature. This mechanism could therefore appear in the upper mantle. Background attenuation could be the result of intergranular thermal losses. 相似文献
10.