Köppen–Geiger Climate Classification for Europe Recaptured via the Hölder Regularity of Air Temperature Data     

Adrien Deliège  Samuel Nicolay 《Pure and Applied Geophysics》2016,173(8):2885-2898

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Application of trichloroacetic acid (TCA) to extraction of soft body for the determination of tissue Cd, Cu, Pb and Zn in the prosobranch Hydrobia ulvae (Pennant)     

Sokolowski A  Richard P  Fichet D  Radenac G  Guyot T 《Marine pollution bulletin》2003,46(10):1326-1333

The application of trichloroacetic acid (TCA) as a shell extractant for preparation of soft body parts with reference to tissue metal concentrations (Cd, Cu, Pb, Zn) in shellfish has been evaluated on the example of the mud snail Hydrobia ulvae, a small marine prosobranch densely present in rocky and soft-bottom habitats of the eastern Atlantic. A solution of 0.1 M TCA was tested on individuals treated according to two different protocols: (1) thawed after freezing ("non-dried") and (2) thawed and air-dried to a constant weight ("dried"). Two points were investigated in detail to improve the method: individual soft tissue dry weight and tissue metal concentration following a standard digestion method. In both instances, the results were compared with those from manually dissected snails. Conditions for total shell decalcification of 60 individuals (3-4 mm long) were 5.5 h in 20 ml of 0.1 M TCA.No differences in individual soft tissue weight were observed between the treatments, indicating good efficiency of the TCA extraction with respect to weight of soft body parts. In contrast, tissue metal concentrations varied among treatments. The TCA extraction of the dried animals had a good recovery for Cd, most likely due to the lower solubility of Cd vital cellular components (proteins and mineral concretions) from the dried tissue. Satisfactory recoveries of the tissue concentrations of Cu and Pb were obtained for the non-dried individuals. This might be related to the specific distribution of metals in the organism (namely in the digestive glands and gonads) and their different chemical reactivity with TCA after the tissue was dried. Limited susceptibility of Zn-bearing protein bindings to complexing with TCA also accounts for significantly lower concentrations of Zn in the mud snail's soft tissue that was extracted. The 0.1 M TCA solution is therefore recommended for extraction of the shells of Hydrobia ulvae for tissue determination of Cd, Cu and Pb; however the treatment protocol does affect metal recovery and thus a consistent procedure should be followed.The extracted metals from the soft tissues and shells of the mud snails (on the basis of both metal concentrations and contents) were ranked in order of increasing contribution of soft body parts to the total (shell+tissue): Pb相似文献   

Contrasting regional discharge evolutions in the Amazon basin (1974–2004)   总被引：1，自引：0，他引：1  

Jhan Carlo Espinoza Villar  Jean Loup Guyot  Josyane Ronchail  Grard Cochonneau  Naziano Filizola  Pascal Fraizy  David Labat  Eurides de Oliveira  Juan Julio Ordoez  Philippe Vauchel 《Journal of Hydrology》2009,375(3-4):297-311

Former hydrological studies in the Amazon Basin generally describe annual discharge variability on the main stem. However, the downstream Amazon River only represents the mean state of the Amazonian hydrological system. This study therefore uses a new data set including daily discharge in 18 sub-basins to analyze the variability of regional extremes in the Amazon basin, after recalling the diversity of the hydrological annual cycles within the Amazon basin. Several statistical tests are applied in order to detect trends and breaks in the time series. We show that during the 1974–2004 period, the stability of the mean discharge on the main stem in Óbidos is explained by opposite regional features that principally involve Andean rivers: a decrease in the low stage runoff, particularly important in the southern regions, and an increase in the high stage runoff in the northwestern region. Both features are observed from the beginning of the nineties. These features are also observed in smaller meridian sub-basins in Peru and Bolivia. Moreover we show that the changes in discharge extremes are related to the regional pluriannual rainfall variability and the associated atmospheric circulation as well as to tropical large-scale climatic indicators.  相似文献   

Bacteria in the Tatahouine meteorite: nanometric-scale life in rocks.     

P h Gillet  J A Barrat  T h Heulin  W Achouak  M Lesourd  F Guyot  K Benzerara 《Earth and Planetary Science Letters》2000,175(3-4):161-167

We present a study of the textural signature of terrestrial weathering and related biological activity in the Tatahouine meteorite. Scanning and transmission electron microscopy images obtained on the weathered samples of the Tatahouine meteorite and surrounding soil show two types of bacteria-like forms lying on mineral surfaces: (1) rod-shaped forms (RSF) about 70-80 nm wide and ranging from 100 nm to 600 nm in length; (2) ovoid forms (OVF) with diameters between 70 and 300 nm. They look like single cells surrounded by a cell wall. Only Na, K, C, O and N with traces of P and S are observed in the bulk of these objects. The chemical analyses and electron diffraction patterns confirm that the RSF and OVF cannot be magnetite or other iron oxides, iron hydroxides, silicates or carbonates. The sizes of the RSF and OVF are below those commonly observed for bacteria but are very similar to some bacteria-like forms described in the Martian meteorite ALH84001. All the previous observations strongly suggest that they are bacteria or their remnants. This conclusion is further supported by microbiological experiments in which pleomorphic bacteria with morphology similar to the OVF and RSF objects are obtained from biological culture of the soil surrounding the meteorite pieces. The present results show that bacteriomorphs of diameter less than 100 nm may in fact represent real bacteria or their remnants.  相似文献   

Arsenite sorption at the magnetite-water interface during aqueous precipitation of magnetite: EXAFS evidence for a new arsenite surface complex   总被引：2，自引：0，他引：2  

Yuheng Wang  Georges Ona-Nguema  Farid Juillot  François Guyot  Gordon E. Brown Jr. 《Geochimica et cosmochimica acta》2008,72(11):2573-2586

The interaction of aqueous As(III) with magnetite during its precipitation from aqueous solution at neutral pH has been studied as a function of initial As/Fe ratio. Arsenite is sequestered via surface adsorption and surface precipitation reactions, which in turn influence the crystal growth of magnetite. Sorption samples were characterized using EXAFS spectroscopy at the As K-edge in combination with HRTEM observations, energy dispersive X-ray analysis at the nanoscale, electron energy loss spectroscopy at the Fe L₃-edge, and XRD-Rietveld analyses of reaction products. Our results show that As(III) forms predominantly tridentate hexanuclear As(III)O₃ complexes (³C), where the As(III)O₃ pyramids occupy vacant tetrahedral sites on {1 1 1} surfaces of magnetite particles. This is the first time such a tridentate surface complex has been observed for arsenic. This complex, with a dominant As-Fe distance of 3.53 ± 0.02 Å, occurs in all samples examined except the one with the highest As/Fe ratio (0.33). In addition, at the two highest As/Fe ratios (0.133 and 0.333) arsenite tends to form mononuclear edge-sharing As(III)O₃ species (²E) within a highly soluble amorphous As(III)-Fe(III,II)-containing precipitate. At the two lowest As/Fe ratios (0.007 and 0.033), our results indicate the presence of additional As(III) species with a dominant As-Fe distance of 3.30 ± 0.02 Å, for which a possible structural model is proposed. The tridentate ³C As(III)O₃ complexes on the {1 1 1} magnetite surface, together with this additional As(III) species, dramatically lower the solubility of arsenite in the anoxic model systems studied. They may thus play an important role in lowering arsenite solubility in putative magnetite-based water treatment processes, as well as in natural iron-rich anoxic media, especially during the reductive dissolution-precipitation of iron minerals in anoxic environments.  相似文献   

Climate policies as a hedge against the uncertainty on future oil supply   总被引：2，自引：2，他引：0  

Julie Rozenberg  Stéphane Hallegatte  Adrien Vogt-Schilb  Olivier Sassi  Céline Guivarch  Henri Waisman  Jean-Charles Hourcade 《Climatic change》2010,101(3-4):663-668

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High-temperature properties of geikielite (MgTiO3-ilmenite) from high-temperature high-pressure Raman spectroscopy — Some implications for MgSiO3-ilmenite     

B. Reynard  F. Guyot 《Physics and Chemistry of Minerals》1994,21(7):441-450

The Raman spectra of geikielite (MgTiO₃-ilmenite) have been recorded at high pressure (up to 27 GPa) and at high temperature (up to 1820 K). No phase transitions could be evidenced in both cases. In particular, no cation disordering can be evidenced from the high temperature spectra. The observed Raman wavenumber shifts with pressure and with temperature are used to calculate the intrinsic mode anharmonic parameters. The low absolute values of these parameters indicate that geikielite has a nearly quasi-harmonic behaviour, at least to moderate temperatures. However, systematics and the temperature evolution of Raman linewidths suggest that the absolute values of the anharmonic parameters increase at high temperatures. Anharmonic corrections are applied to Kieffer modelling of the constant volume heat capacity of geikielite. They amount to +4 J · mol^-1 · K^-1 at 1800 K, i.e. are much lower than those inferred for, for instance, olivine and garnet structures. These results are used to discuss some implications on the phase relations of the high-pressure MgSiO₃-ilmenite, and the factors controlling the occurence of order-disorder transitions in ilmenite structures.  相似文献   

Pressure-induced structural modifications in Mg2GeO4-olivine: A Raman spectroscopic study     

Bruno Reynard  Pierre-Emmanuel Petit  François Guyot  Philippe Gillet 《Physics and Chemistry of Minerals》1994,20(8):556-562

Raman spectra of Mg₂GeO₄-olivine were obtained from ambient pressure up to 34 GPa at ambient temperature. Under quasi-hydrostatic pressure conditions, the following modifications in the Raman spectra occur as pressure increases: 1) near 11 GPa, two sharp extra bands appear in the 600–700 cm^?1 frequency range, and increase in intensity with respect to the olivine bands; 2) above 22 GPa, these two bands become very intense, and the number, position and relative intensity of the other vibrational bands drastically change; 3) the intensity of sharp bands progressively decreases above 25 GPa. The transformation occurs at lower pressures under non-hydrostatic conditions. During decompression to atmospheric pressure, the high-pressure phase partially reverts to olivine. These observations can be interpreted as the progressive metastable transformation from the olivine structure to a crystalline phase with four-fold coordinated Ge, in which the GeO₄ tetrahedra are polymerized. We propose that the metastable high-pressure phase is a structurally disordered spinelloid close to the hypothethical ω- or ?^*-phase, and forms by a shear mechanism assisted by the development of a dynamical instability in the olivine structure. Implications for the transformations undergone by olivines under far-from-equilibrium conditions (e.g. in subducting lithospheric slabs and in shocks) are discussed.  相似文献   

High-temperature heat capacity and phase transitions of CaTiO3 perovskite     

F. Guyot  P. Richet  Ph. Courtial  Ph. Gillet 《Physics and Chemistry of Minerals》1993,20(3):141-146

Drop-calorimetry measurements performed on CaTiO₃ perovskite between 400 and 1800 K have shown the occurrence of two overlapping phase transitions at 1384 and 1520 K. The 1384 K transition shows a λ-type C _p variation with a very sharp C _p decrease after the transition; in contrast, the 1520 K transition exhibits a unusual λ shape with a long high-temperature tail spanning more than 400 K. By comparison with previous structural studies, we suggest that the 1384 K transition may be due to an orthorhombic Pbnm to orthorhombic Cmcm transition and that the peak centered at 1520 K represents the effects of overlapping orthorhombic to tetragonal and tetragonal to cubic phase transitions. The large anomaly of specific heat above 1520 K suggests that the cubic phase produced may be strongly disordered up to the melting point.  相似文献   

Phase changes and thermodynamic properties of CaTiO3. Spectroscopic data,vibrational modelling and some insights on the properties of MgSiO3 perovskite     

Philippe Gillet  François Guyot  Geoffrey D. Price  Benoit Tournerie  Andrée Le Cleach 《Physics and Chemistry of Minerals》1993,20(3):159-170

The effect of pressure (up to 21 GPa at room temperature) and temperature (up to 1570 K at room pressure) on the Raman spectrum of CaTiO₃ is presented. No significant changes, which could be attributed to a major structural change, are observed in the spectra up to 22 GPa. The pressure shifts of the Raman modes can be related to a significant compression of the Ti-O bond. Discontinuous changes in the spectra upon heating may be related to phase changes observed by calorimetry and X-ray diffraction. The important temperature shifts of some low-frequency modes can be related to an increase in the Ti-O-Ti angle in agreement with the X-ray data showing a decrease of the structural distortion with increasing temperature. These data are compared to those available for MgSiO₃-perovskite and show that CaTiO₃ is a good structural analogue for MgSiO₃-perovskite. The present spectroscopic data are used to calculate the specific heat and entropy of CaTiO₃. The role of the low frequency modes in the calculations is emphasized. Good agreement is observed between calculated and experimentally determined values in the 0–1300 K temperature range. A similarly defined model is proposed for MgSiO₃-perovskite. It is found that the entropy lies between 57 and 64 J/mol/K at 298 K and between 190 and 200 J/mol/K at 1000 K in agreement with the values inferred from experimental equilibrium data. Finally we briefly discuss the values of the Grüneisen parameters of both perovskites inferred from macroscopic and microscopic data.  相似文献