Search results for "Mineral"
showing 10 items of 2711 documents
Biogenic Fenton process - A possible mechanism for the mineralization of organic carbon in fresh waters.
2020
To explore the mechanisms that mineralize poorly bioavailable natural organic carbon (OC), we measured the mineralization of OC in two lake waters over long-term experiments (up to 623 days) at different pH and iron (Fe) levels. Both the microbial and photochemical mineralization of OC was higher at pH acidified to 4 than at the ambient pH 5 or an elevated pH 6. During 244 days, microbes mineralized up to 60% of OC in the 10-mu m filtrates of lake water and more than 27% in the 1-mu m filtrates indicating that large-sized microbes/grazers enhance the mineralization of OC. A reactivity continuum model indicated that the acidification stimulated the microbial mineralization of OC especially i…
Sunlit surface waters : exploring the photochemical reactivity of dissolved organic carbon
2017
In surface waters, solar radiation can photochemically mineralise the dissolved organic carbon (DOC, a measure of dissolved organic matter, DOM) to dissolved inorganic carbon (DIC). This DIC photoproduction constitutes an essential yet vague flux in the aquatic carbon cycling. The present thesis is based on the empirical assessment of the DOC photochemical reactivity, which was determined as the spectral apparent quantum yields (AQY) for DIC photoproduction. First, AQYs were determined in DOM solutions to quantify the impact of pH and DOM-associated iron. Then boreal lake waters were used for assessing the alteration of DOC photoreactivity due to water quality and catchment property. By sim…
Biochemical characteristics of the soluble organic matrix from the shell of three recent terebratulid brachiopod species.
2008
7 pages; International audience; To build their shells, brachiopods secrete a mixture of proteins and polysaccharides, collectively called the organic matrix. This matrix mediates the calcification process by allowing crystal nucleation followed by elongation and finally by stopping the crystal growth. Ultimately, the matrix controls the different microstructures formed. Brachiopod shells are composites with both organic and inorganic constituents intimately associated. This work represents an attempt to characterize the matrices using two combined approaches: (1) scanning electron microscopy for localization within the shell, (2) analysing extracted matrices at the molecular level to deter…
Ultrasound measurements in bone using an array transducer
2014
Halogens and trace metal emissions from the ongoing 2008 summit eruption of Kīlauea volcano, Hawai`i
2012
Volcanic plume samples taken in 2008 and 2009 from the Halemàumàu eruption at Kīlauea provide new insights into Kīlauea's degassing behaviour. The Cl, F and S gas systematics are consistent with syn-eruptive East Rift Zone measurements suggesting that the new Halemàumàu activity is fed by a convecting magma reservoir shallower than the main summit storage area. Comparison with degassing models suggests that plume halogen and S composition is controlled by very shallow (<3m depth) decompression degassing and progressive loss of volatiles at the surface. Compared to most other global volcanoes, Kīlauea's gases are depleted in Cl with respect to S. Similarly, our Br/S and I/S ratio measurem…
Le pavimentazioni musive di Piazza Sett’Angeli - Palermo. Caratterizzazione mineralogico-petrografica dei materiali litoidi (tessere e malte di allet…
2016
Nel presente contributo sono illustrati i risultati di un indagine mineralogico-petrografica finalizzata alla caratterizzazione dei materiali litoidi (tessere e malte di alletamento), impiegati nella pavimentazione musiva romana di epoca imperiale sita a Palermo in Piazza Sett’Angeli. Campioni rappresentativi di ciascuna tipologia di materiale sono stati analizzati scegliendo le tecniche analitiche più idonee in base alla loro natura: microscopia ottica su sezione sottile (PLM) e diffrattometria ai raggi X (XRD) nel caso delle tessere lapidee e delle malte; microscopia elettronica a scansione con spettrometro a dispersione di energia (SEMEDS) nel caso delle tessere vitree. L’indagine minera…
Les marbres et jaspes siciliens utilisés dans la pratique décorative à "marmi mischi".
2013
STUDIO MINERALOGICO-PETROGRAFICO E PROBLEMI CONSERVATIVI
2011
Il capitolo illustra le risultanze dello studio delle problematiche conservative e della caratterizzazione mineralogico petrografica dei materiali lapidei del teatro ellenistico di Morgantina (Enna). Tale attività è stata finalizzata alla definizione dell'intervento conservativo del teatro. The chapter illustrates the results of the study of conservation issues and petrographic mineralogical characterization of the stone materials of the Hellenistic theater of Morgantina (Enna). This activity was aimed at defining the conservative intervention of the theatre.
Archaeometric Characterisation of Decorated Pottery from the Archaeological Site of Villa dei Quintili (Rome, Italy): Preliminary Study
2019
This work focused on the study of decorated pottery dated back to the 16th century from the Roman archaeological site of Villa dei Quintili, a monumental complex located in the south-eastern part of Rome (Italy). A minero-petrographic and geochemical study was undertaken to analyse five archaeological samples in order to define textural features and raw materials used for their production, along with the chemical and physical composition of the superficial decorative glazed coatings. For this purpose, different analytical methods were used, such as polarising optical microscope (POM), X-ray diffraction (XRD), micro-Raman spectroscopy, X-Ray fluorescence (XRF), and electron microprobe analys…
Perception of mineral character in Sauvignon blanc wine: inter-individual differences
2014
Revue non indexée dans le JCR.; Of the descriptors employed to characterize wine organoleptically, minerality is arguably one of the most enigmatic. The aim of the work described in this article was to delineate the nature of perceived minerality in Sauvignon wine, specifically its sensorial reality for experienced wine professionals from France and New Zealand. Participants evaluated 16 Sauvignon blanc wines (8 French; 8 New Zealand) under three conditions, ortho-nasal olfaction, palate only (Nose-clip condition), and by full tasting (global perception). Data from the global condition only are reported here. Key results include: i) that although there were quantitative differences in perce…