Attenuation of Rayleigh waves across the volcanic area of the Massif Central,France

Rayleigh wave attenuation is investigated for periods ranging from 20 to 90 s, along a 450 km-long profile following the Oligocene tensile zone of the French Massif Central. A model is deduced by inversion, assuming that the S-wave intrinsic quality factor Q_β is frequency-independent, and yields a mean value Q_β = 43 ± 10 for the first 100 km in the upper mantle. This value, far lower than the mean value obtained in Eurasia, is close to those obtained in other recent tensile areas, e.g., the western United States or mid-oceanic ridges.A velocity-depth model for S-waves, deduced in a previous study from surface-wave propagation, has been corrected for the attenuation effect. We find a discrepancy between the corrected S-model and P-wave residuals in the same area, implying that Q_β must be frequency-dependent. This can be a clue for partial melting in the upper mantle beneath this region.     

Geoid anomalies over Gorringe Ridge,North Atlantic Ocean

Gorringe Ridge is a strong uplifted block of oceanic crust and upper mantle lying at the eastern end of the Azores-Gibraltar plate boundary. The geoid over this structure derived from Seasat altimeter data exhibits a 9-m height anomaly with a north-south lateral extension smaller than 200 km. An attempt is made to interpret this geoid together with the gravity anomalies and with the seismicity, which has been compiled as a function of depth.It is first shown that the flexure of the oceanic lithosphere due to the ridge loading does not provide a good fit of the geoid anomalies and probably should be discarded, as it assumes a continuous unfractured elastic plate.Models involving local heterogeneities are then tested. The comparison of the observed geoid anomalies with the anomalies due to the uncompensated relief indicates that the topographic high has no shallow compensation.Uncompensated models, previously proposed to explain the gravity anomalies, are tested using the geoid. One model (Purdy and Bonnin, in Bonnin [11]), which involves an uplift of upper mantle material at depth, generates too strong geoid anomalies and must be discarded. Another model, which represents a nascent subduction zone (Le Pichon et al. [25]), fits both the gravity and geoid anomalies, but leads to difficulties in explaining the deep seismicity north of Gorringe Ridge.A model in isostatic equilibrium is also able to fit both gravity and geoid anomalies. This model involves a deep root of density 3.0 g cm^?3, as has been previously proposed for many oceanic ridges and plateaus. This model is compatible with the deep seismicity, but the origin of this low-density material at great depth is up to now an unresolved question.More likely, dynamical models taking into account the forces induced by the convection related to the slow plate convergence in this area will have to be considered.     

De l'emploi des methodes chimiques et spectrographiques pour l'etude des poteries antiques

Résumé Le but de mon travail est de vérifier dans quelle mesure l'analyse chimique et spectrographique des poteries antiques peut permettre de différencier entre elles ces poteries, et apporter des élémentes susceptibles de résoudre certains problèmes archéologiques de localisation.J'ai analysé un certain nombre échantillons de poteries antiques — 300 échantillons environ — qui ont été mis à ma disposition par MonsieurVallet, professeur à la Faculté des Lettres de Clermont-Ferrand. Ces échantillons sont de provenance diverse: France, Italie, Sicile, Grèce propre et îles grecques, Asie Mineure, Afrique du Nord.L'analyse chimique a porté sur les éléments suivants: Fer, Titane et Manganèse. L'analyse spectrographique porte sur les oligoéléments métalliques suivants: Plomb, Etain, Argent, Cuivre, Chrome, Nickel et Cobalt.Les teneurs en Titane, Plomb, Etain et Argent ne montrent pas de différences significatives. Par contre, les teneurs en Fer, Manganèse d'une part, Cuivre, Chrome, Nickel et Cobalt d'autre part, apportent des éléments de différenciation.

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The aim of this study is to verify to what extent chemical and spectrochemical analysis can distinguish among sherds from various localities and to give new data to solve some of the archaeological problems about location.About 300 sherds have been analysed; I got them from D.Vallet, Professor at the Faculté des Lettres in Clermont-Ferrand, Auvergne — These samples come from various countries, namely from: France, Italy, Greece, Greek Islands, Asia Minor, North Africa.The chemical analysis was for: Iron, Titanium and Manganese. The determination of trace elements such as: Lead, Tin, Silver, Copper, Chronium, Nickel, Cobalt, is now being carried out by means of spectrochemical analysis.The amount of Titanium, Lead, Tin and Silver shows no significant differences — On the contrary the amount of Iron, Manganese, Copper, Chronium, Nickel and Cobalt, give a good criterion for comparing and contrasting sherds of different provenance.

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Zusammenfassung Das Ziel meiner Arbeit ist, zu untersuchen, in welchem Maße es die chemische und spektrographische Analyse von antiken Tonwaren erlaubt, zwischen diesen Tonwaren zu unterscheiden und Lösungen für archäologische Ortsprobleme zu finden.Ich habe eine bestimmte Anzahl von antiken Tonwaren — ungefähr 300 Proben — analysiert die mir M.Vallet, Professor an der Geisteswissenschaftlichen Fakultät von Clermont-Ferrand, zur Verfügung gestellt hat. Diese Proben sind verschiedener Herkunft: Frankreich, Italien, Sizilien, Griechisches Festland, Griechische Inseln, Kleinasien und Nordafrika.Die chemische Analyse betraf die folgenden Elemente: Eisen, Titan, Mangan. Durch die spektrographische Analyse wurden die folgenden Elemente untersucht: Blei, Zink, Silber, Kupfer, Chrom, Nickel und Kobalt.Der Gehalt an Titan, Blei, Zink und Silber der einzelnen Proben zeigte keine wesentlichen Differenzen. Im Gegensatz dazu schwankte der Gehalt an Eisen und Mangan einerseits und Kupfer, Chrom, Nickel und Kobalt anderseits.

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Galactic evolution and star counts in the milky way

A model of population synthesis for our Galaxy is used to estimate the constraints imposed by photometric and astrometric star counts. We construct a statistical method to compute the degree of compatibility of the model with the data in the form of a multidimensional functionf(V, B-V, U-B, ). We apply the method to the determination of the star formation history in the Galaxy from Schmidt plates towards the anticentre. Although the presently available data do not allow us to draw firm conclusions, we show that the same kind of data with a slightly better photometric accuracy and with proper motions would give new constraints on the past star formation rate of the Galaxy.     

The seismological picture of the inner core: structure and rotation

This paper presents a review of recent results concerning the structure and the rotation of the inner core, as inferred from seismological observations. We first focus on the apparent hemispherical pattern of the inner core structure, observed in both the anisotropy and the heterogeneity of the uppermost layers, whereas isotropic velocities seem to be homogeneous in a broad wavelength domain. Then we present results on the radial variations of the attenuation and its possible anisotropy, for which viscoelasticity and wave scattering provide complementary explanations. Linked to these results is a discussion about the detection of the PKJKP phase, which propagates as S-wave inside the inner core. Finally, the seismological observations of a possible inner core rotation are discussed; recent results seem to favour rotation rates below 0.2° yr^?1.     

Chemical and biological characterization of particles by flow cytometry in the Krka estuary, Croatia

Flow cytometry was used to characterize suspended particles in the Krka estuary (Croatia). This technique allows a rapid characterization and quantification of individual particles; it is based on the simultaneous measurement of the light scatter and natural or induced fluorescence. The relative size of the particles was determined by light scatter signals and by a calibration with fluorescent beads.The determination of organic particles was carried out by staining with fluorescein isothiocyanate (FITC). The autofluorescence of photosynthetic pigments (chlorophyll and phycoerythrin) present in the phytoplankton population was measured. The carbohydrates (galactose and glucose-mannose) were stained by lectins conjugated to FITC. The abundance of organic coatings or mineral particles and detritus was obtained from the difference between the total number of particles stained by specific carbohydrate fluorochromes and living cells.Results show that the Krka estuary is characterized by the occurrence of very small particles. About 80% of suspended particles are organic, most of these particles being living cells. The only exception is the Guduca River, a small tributary.     

7-ethylresorufin O-deethylase activity and level of DNA-adducts in trout treated with benzo(a)pyrene

In fish, as well as in mammals, it is well known that the cytochrome P450-dependent oxidative metabolism of xenobiotics can generate DNA-reactive species. Moreover, this metabolism is known to be inducible by several compounds of environmental significance, such as polychlorobiphenyls, polycyclic aromatic hydrocarbons (PAHs) and dioxins. Consequently, we studied the relationship between the degree of induction of the cytochrome P4501A, expressed as that of 7-ethylresorufin O-deethylase (EROD) activity, and the level of DNA-adducts, using the post-labelling assay, in the liver of rainbow trout exposed to benzo(a)pyrene (a representative PAH). The results showed a significant 2- to 4-fold increase in EROD activity 2, 4 and 8 days after treatment, paralleled by an increase in DNA-adduct levels. This work further emphasizes the involvement of cytochrome P4501A in the metabolism of benzo(a)pyrene into genotoxic metabolites in rainbow trout.     

Aquifer Discharge Drives Microbial Community Change in Karst Estuaries

Karst estuaries are unique systems governed by freshwater inputs that flow directly to the sea through karst conduits and/or matrices. Because they are found at the interface between terrestrial and marine environments, they can act as sentinels to climate change and as indicators of aquifer health. The physical and geochemical gradients formed in karst estuaries are a direct result of the interactions between inland hydrological conditions and sea level. To examine the influence these gradients have on microbial communities in the water column and sediment of a karst estuary, we studied the spring-fed Double Keyhole Karst Estuary in west central Florida for a 2-year period. Four sites were monitored within this system starting at the Double Keyhole Spring Conduit extending 2 km west through the estuary toward the Gulf of Mexico. Water column and sediment samples were collected quarterly at all sites from September 2011 through September 2013. Archaeal, bacterial, and microbial eukaryote communities were analyzed using quantitative PCR and length-heterogeneity PCR. The biological communities were analyzed in the context of hydrological, physical, and geochemical parameters in order to determine which factor(s) governed the observed changes of microbial abundance and richness. The major finding of this study was that microbial community change in this karst estuary was primarily driven by the volume of aquifer discharge and associated physical gradients, and less by the geochemical fluctuations within the system.