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TL;DR: In this paper, the abundance and distribution of glycerol dialkyl glycerolic tetraethers (GDGTs) were compared in two contrasting environments: a temperate podzol located 40 km north of Paris (France) and a tropical pzol from the Amazon Basin (Brazil).
41 citations
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TL;DR: In this article, a series of controlled abiotic synthesized magnetite nanocrystals were carried out to explore the possibility of using morphological criteria, crystal size distributions, and shape ratio as tools for identifying magnetite that would be specifically produced by magnetotactic bacteria.
Abstract: A series of controlled abiotic syntheses of magnetite nanocrystals were carried out to explore the possibility of using morphological criteria, crystal size distributions, and shape ratio as tools for identifying nanocrystals that would be specifically produced by magnetotactic bacteria. High-quality magnetite crystals synthesized with various controlled total iron concentrations were shown to have cubo-octahedral shapes and sizes varying from 4 to 24 nm. The mean particle size of the population was found to be 10.5 ± 0.7 nm and no significant effect of the total iron concentration on the particle size was observed. Systematical analyses of size and morphology also allowed for the determination of crystal size and shape ratio distributions. Crystal sizes were observed to follow log-normal distributions. Shape factors are bounded by one, with maxima between 0.80 to 1.00. Their distributions are asymmetric, with a cut off toward the high values. Crystal morphologies and shape factors appear not to be a powerful diagnostic tool for the differentiation of abiotic vs. biotic particles. However, crystal size distributions of abiotic crystals are significantly different from those of biotic populations. Indeed, opposite asymmetry of the size distributions from biogenic and non biogenic crystals was observed, with cut off toward larger sizes for biogenic nanocrystals and with cut off toward smaller sizes for abiogenic nanocrystals. This therefore constitutes a potential diagnostic tool for deciphering magnetite origin.
41 citations
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31 May 2009TL;DR: The physical and engineering challenges in scaling fiber lasers toward 10kW include avoiding nonlinear thresholds, particularly SRS, obtaining sufficient pump brightness, and overcoming thermal issues as discussed by the authors, and the methods to overcome these barriers are reviewed and results > 6kW SM are provided.
Abstract: The physical and engineering challenges in scaling fiber lasers toward 10kW include 1) avoiding non-linear thresholds, particularly SRS, 2) obtaining sufficient pump brightness, and 3) overcoming thermal issues. The methods to overcome these barriers are reviewed and results >6kW SM are provided. Article not available.
41 citations
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TL;DR: In this article, a segment of the Interandean Depression of Ecuador between Ambato and Quito is characterized by an uppermost Pliocene-Quaternary basin, which is located between two N-S trending reverse basement faults: the Victoria Fault and the Pisayambo Fault.
Abstract: SUMMARY The segment of the Interandean Depression of Ecuador between Ambato and Quito is characterized by an uppermost Pliocene-Quaternary basin, which is located between two N-S trending reverse basement faults: the Victoria Fault to the west, and the Pisayambo Fault to the east. The clear evidence of E-W shortening for the early Pleistocene (between 1.85 and 1.21 Ma) favours a compressional basin interpretation. The morphology (river deviations, landslides, folded and flexure structures) demonstrates continuous shortening during the late Quaternary. The late Pliocene-Quaternary shortening reached 3400 f 600 m with a rate of 1.4 f 0.3 mm yr-'. The E-W shortening is kinematically consistent with the current right-lateral reverse motion along the NE-SW trending Pallatanga Fault. The Quito-Ambato zone appears to act as a N-S restraining bend in a system of large right-lateral strike-slip faults. The compressive deformation. which affects the Interandean Depression during the Pliocene is apparently coeval to the beginning subduction of very young oceanic lithosphere north of the Gulf of Guayaquil. The relatively buoyant new crust may have significantly increased the mechanical coupling in the subduction zone from Pliocene to Present.
41 citations
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TL;DR: In this paper, the authors consider the factors that create a habitable planet at all scales, from planetary inventories to micro-habitats in soft sediments and intangibles such as habitat linkage.
Abstract: The factors that create a habitable planet are considered at all scales, from planetary inventories to micro-habitats in soft sediments and intangibles such as habitat linkage. The possibility of habitability first comes about during accretion, as a product of the processes of impact and volatile inventory history. To create habitability water is essential, not only for life but to aid the continual tectonic reworking and erosion that supply key redox contrasts and biochemical substrates to sustain habitability. Mud or soft sediment may be a biochemical prerequisite, to provide accessible substrate and protection. Once life begins, the habitat is widened by the activity of life, both by its management of the greenhouse and by partitioning reductants (e.g. dead organic matter) and oxidants (including waste products). Potential Martian habitats are discussed: by comparison with Earth there are many potential environmental settings on Mars in which life may once have occurred, or may even continue to exist. The long-term evolution of habitability in the Solar System is considered.
41 citations
Authors
Showing all 903 results
Name | H-index | Papers | Citations |
---|---|---|---|
Claude J. Allègre | 106 | 327 | 35092 |
Paul Tapponnier | 99 | 294 | 42855 |
Francesco Mauri | 85 | 352 | 69332 |
Barbara Romanowicz | 67 | 284 | 14950 |
Geoffrey C. P. King | 64 | 157 | 17177 |
Yi-Gang Xu | 64 | 271 | 14292 |
Jérôme Gaillardet | 63 | 199 | 14878 |
François Guyot | 61 | 292 | 12444 |
Georges Calas | 60 | 266 | 10901 |
Ari P. Seitsonen | 59 | 212 | 45684 |
Michele Lazzeri | 58 | 140 | 57079 |
Bernard Bourdon | 58 | 118 | 9962 |
Gianreto Manatschal | 56 | 200 | 10063 |
Nikolai M. Shapiro | 56 | 154 | 15508 |
Guillaume Morin | 55 | 156 | 7218 |