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131.
Iron isotope fractionation and the oxygen fugacity of the mantle 总被引:3,自引:0,他引:3
Williams HM McCammon CA Peslier AH Halliday AN Teutsch N Levasseur S Burg JP 《Science (New York, N.Y.)》2004,304(5677):1656-1659
The oxygen fugacity of the mantle exerts a fundamental influence on mantle melting, volatile speciation, and the development of the atmosphere. However, its evolution through time is poorly understood. Changes in mantle oxidation state should be reflected in the Fe3+/Fe2+ of mantle minerals, and hence in stable iron isotope fractionation. Here it is shown that there are substantial (1.7 per mil) systematic variations in the iron isotope compositions (delta57/54Fe) of mantle spinels. Spinel delta57/54Fe values correlate with relative oxygen fugacity, Fe3+/sigmaFe, and chromium number, and provide a proxy of changes in mantle oxidation state, melting, and volatile recycling. 相似文献
132.
Véronique Bernier Gosselin Marie Babkine Sylvain Nichols André Desrochers 《The Canadian veterinary journal. La revue veterinaire canadienne》2012,53(8):849-854
An ultrasonographic approach for the tympanic bulla in calves is described. Ultrasound evaluation was performed through a lateral approach on 7 fetuses, 2 newborn calves, and 4 living calves of various ages. The probe was positioned caudal to the vertical mandibular ramus, ventral to the base of the ear. Three different positions of the probe were used. The tympanic bulla and adjacent structures were successfully identified and their ultrasonographic appearance described. Fluid within the tympanic bulla was visualized in 12 bullae in the cadavers and in 6 bullae in live calves. Ultrasound imaging has been shown to be useful but its diagnostic value remains to be studied in clinical cases of otitis media in calves. 相似文献
133.
Chamaillard S Fichot R Vincent-Barbaroux C Bastien C Depierreux C Dreyer E Villar M Brignolas F 《Tree physiology》2011,31(10):1076-1087
The ongoing global change could be an additional threat to the establishment and the long-term survival of Populus nigra L., an emblematic European riparian species. With the general aim of gaining insights into the adaptive potential of this species, we (i) quantified variations within and among three French P. nigra populations for key physiological attributes, i.e., water-use efficiency (assessed from bulk leaf carbon isotope discrimination, Δ(13)C), growth performance and related leaf traits, (ii) examined genotype and population by environment interactions, and (iii) explored the relationship between Δ(13)C and growth. Thirty genotypes were sampled in each of three naturally established populations and grown in two different sites, Orléans (ORL) and Guémené-Penfao (GMN). In ORL, two similar plots were established and different watering regimes were applied in order to test for the drought response. Significant variations were observed for all traits within and among populations irrespective of site and watering. Trait variation was larger within than among populations. The effect of drought was neither genotype- nor population-dependent, contrary to the effect of site. The population ranking was maintained in all sites and watering regimes for the two most complex traits: Δ(13)C and growth. Moreover, these two traits were unrelated, which indicates that (i) water-use efficiency and growth are largely uncoupled in this species, and (ii) the environmental factors driving genetic structuration for Δ(13)C and growth act independently. The large variations found within populations combined with the consistent differences among populations suggest a large adaptive potential for P. nigra. 相似文献
134.
In a 4-year study, we investigated changes in leaf physiology, crown morphology and whole-tree biomass allocation in seedlings and saplings of shade-tolerant sugar maple (Acer saccharum Marsh.) and intermediate shade-tolerant yellow birch (Betula alleghaniensis Britt.) growing in natural understory light (0.5 to 35% of full sunlight) or in understory light reduced by 50% with shade nets to simulate the effect of gap closure. Leaf physiological parameters were mainly influenced by the light gradient, whereas crown morphological and whole-tree allocational parameters were mainly influenced by tree size. No single physiological, morphological or allocational trait was identified that could explain the difference in shade tolerance between the species. Yellow birch had higher growth rates, biomass allocation to branches and leaf physiological plasticity and lower crown morphological plasticity in unmodified understory light than sugar maple. Sugar maple did not display significant physiological plasticity, but showed variation with tree size in both crown morphology and whole-tree biomass allocation. When sugar maple was small, a greater proportion of whole-tree biomass was allocated to roots. However, physiological differences between the species decreased with decreasing light and most morphological and allocational differences tended to disappear with increasing tree size, suggesting that many species differences in shade-tolerance are expressed mainly during the seedling stage. Understory trees of both species survived for 4 years under shade nets, possibly because of higher plasticity when small and the use of stored reserves when taller. 相似文献
135.
Molinari F Rio M Meskenaite V Encha-Razavi F Augé J Bacq D Briault S Vekemans M Munnich A Attié-Bitach T Sonderegger P Colleaux L 《Science (New York, N.Y.)》2002,298(5599):1779-1781
A 4-base pair deletion in the neuronal serine protease neurotrypsin gene was associated with autosomal recessive nonsyndromic mental retardation (MR). In situ hybridization experiments on human fetal brains showed that neurotrypsin was highly expressed in brain structures involved in learning and memory. Immuno-electron microscopy on adult human brain sections revealed that neurotrypsin is located in presynaptic nerve endings, particularly over the presynaptic membrane lining the synaptic cleft. These findings suggest that neurotrypsin-mediated proteolysis is required for normal synaptic function and suggest potential insights into the pathophysiological bases of mental retardation. 相似文献
136.
Aboriginal peoples living a traditional lifestyle are potentially exposed to contaminants, such as methylmercury (MeHg), which bioaccumulate in aquatic ecosystems. A preliminary analysis of testing of Canadian indigenous people for MeHg from 1970 to 1992 is outlined. By December 1992,71,842 tests of 38,571 individuals had been carried out in 514 native communities across Canada. Of these, 8,847 individuals (23%) had blood, or blood equivalent, MeHg levels greater than 20 μg/l and 608 (1.6%) had levels over 100 μg/l. Clinical examinations were offered to all with levels greater than 100 μg/l in blood, but were unable to produce a definitive diagnosis. In an attempt to ascertain fetal exposure, 2,405 umbilical cord blood samples were taken. In about half of these cases the samples were paired with maternal levels. Of the cord samples 523 (21.8%) were found to have levels greater than 20 μg/l, and the highest level was 224 μg/l. The highest maternal level found was 86 μg/l. A discussion of the assessment of risk from exposure to MeHg in this population is presented as are the initial results of the 20 year retrospective analysis including seasonal exposure patterns and trends in exposure levels. Probable future intiatives based on this analysis are noted. 相似文献
137.
Manhattan Lebrun Florie Miard Nour Hattab-Hambli Sylvain Bourgerie Domenico Morabito 《Water, air, and soil pollution》2018,229(5):163
With the development of the industrial era, environmental pollution by organic and inorganic pollutants increased and became a worldwide issue. Particularly, former industrial sites often present high concentrations of metal(loid)s. These pollutions have adverse effects not only on the environment but also to human health, as pollutants can enter the food chain. Therefore, contaminated sites need rehabilitation. Phytoremediation is a clean and low-cost solution to remediate such sites. However, vegetation establishment can be difficult on such extreme soils from both a physical and a chemical point of view. Consequently, amendments, like biochar and garden soil, must be applied. Biochar, product of biomass pyrolysis under low-oxygen conditions, showed beneficial effects on soil fertility and plant growth, as well as metal(loid) sorption properties. The aims of this study were to investigate the effects of two organic amendments, biochar and garden soil, alone or combined, on the physico-chemical properties of a post-industrial soil and the growth of two Salix species (Salix alba and Salix viminalis) and evaluate the phytostabilizing capacities of the two Salix species. In this goal, a greenhouse experiment was performed, using garden soil at 50% (v/v) and/or biochar at 2 or 5% (w/w). The results showed that biochar did not improve soil physico-chemical properties, neither did it affect plant parameters (dry weight, organ metal(loid)s concentrations). Moreover, higher metal(loid) concentrations were found in the roots compared to the upper parts. Finally, S. alba presented lower metal(loid) concentrations in the aboveground parts compared to S. viminalis, associated with a good growth, which make it a better candidate for phytostabilization of the studied soil. 相似文献
138.
Jan Gielen Tineke Ultzen Sylvain Bontems Wouter Loots Alie van Schepen Annemarie Westerbroek Peter de Haan Mart van Grinsven 《Euphytica》1996,88(2):139-149
Summary Cucumber mosaic virus (CMV) infections rank among the most devastating diseases in the commercial culture of tomato (Lycopersicon esculentum Mill.), for which suitable sources of natural resistance are not available. The concept of pathogen-derived resistance, however, offers an alternate approach to combat plant viral diseases by transformation of crops with nucleotide sequences derived from the viral genome. This report demonstrates the successful application of such a pathogen-derived resistance gene comprising the CMV coat protein (CP) gene, to generate protection to CMV infections in cultivated tomato. Transformation of an inbred tomato line with the CMV CP gene isolated from a subgroup I strain, engendered high levels of protection to various CMV strains, including a virulent strain causing lethal necrosis and a typical subgroup II strain. Moreover, when challenged by natural infection through aphid vectors in open field, levels of protection were largely maintained in hemizygous hybrids. In all, these results demonstrate that synthetic resistance genes based on the CMV CP gene make excellent sources of broad spectrum resistance to CMV infections for introgression into tomato breeding programs. 相似文献
139.
Sylvain Massuel Guillaume Favreau Marc Descloitres Yann Le Troquer Yves Albouy Bernard Cappelaere 《CATENA》2006
In semiarid southwestern Niger, most of the groundwater recharge is indirect and occurs through endoreic ponds. Elsewhere in the landscape, there is no evidence of deep infiltration, with a possible exception for gullies and alluvial fans on sandy slopes. In order to verify this hypothesis, a detailed geophysical and geochemical survey was conducted on a large, representative mid-slope fan (6 ha). At this site, distributed hydrological modelling conducted over the encompassing endoreic catchment (190 ha) showed high losses of runoff water by infiltration. Electromagnetic mapping and 2-D electrical imaging survey were used to investigate the 35 m deep vadose zone; in addition, 8 boreholes were drilled following the geophysical survey to constrain the interpretation. Variations in apparent electrical conductivity measured in boreholes appear to be mainly linked with changes in the soil solution mineralization. An extrapolation throughout the area shows that apparent electrical conductivity of the ground is systematically lower below channels; this suggests localised leaching through the unsaturated zone. A physically-based, 2-D distributed hydrologic model was used to estimate the amount of surface water loss by infiltration for the 1992–2002 period. Depending on year, infiltrated volumes range from 1000 to 24 000 m3. This represents between 5% and 16% of the runoff that reaches the final outlet of the basin, an endoreic valley bottom pond where recharge to the aquifer has been shown to occur. Because leaching of the vadose zone is observed down to a depth of 10 m below channels, episodic groundwater recharge through sandy mid-slope fans is highly probable during rainy years. 相似文献
140.
Philippe Bataillard Sylvain Grangeon Paul Quinn Fred Mosselmans Abdeltif Lahfid Guillaume Wille Catherine Joulian Fabienne Battaglia-Brunet 《Journal of Soils and Sediments》2014,14(3):615-629