Geochimica et Cosmochimica Acta Supplement, Jul 1, 2008
Mineral-solution reactions such as nucleation, particle growth, crystallisation and biomineralisa... more Mineral-solution reactions such as nucleation, particle growth, crystallisation and biomineralisation occur in a wide variety of low-temperature geochemical systems including soils, sediments and contaminated land environments (eg permeable reactive barriers). Studying these processes in situ can be challenging, as many of these reactions occur in suboxic or anoxic environments, on fast time-scales (secondsminutes), or are mediated by microorganisms. Synchrotron-based scattering techniques have been used to ...
Vivianite (Fe3(PO4)2·8H2O) has been reported to form as a secondary mineralization product during... more Vivianite (Fe3(PO4)2·8H2O) has been reported to form as a secondary mineralization product during the microbial reduction of phosphate-containing Fe(III) minerals [1 – 3]. The phosphate-rich nature of vivianite makes it a suitable sink for phosphorus, which is a scarce and irreplaceable resource, and a major contributor to eutrophication in surface water bodies. There is, therefore, interest in synthesizing vivianite by Fe(III) reducing bacteria such as Geobacter sulfurreducens and Shewanella putrefaciens, to treat phosphate-rich waters, recovering the phosphate for re-use in agriculture. In this study, factors including the presence and absence of phosphate and electron shuttle, the buffer system, pH, microbial load, and the type of Fe(III)-reducing bacteria that influence the formation of vivianite under laboratory batch systems have been investigated. The rate of Fe(II) production, and its interaction with the residual Fe(III) and other oxyanions (e.g., PO43-, CO32-) was found to...
the growth solution, 7Li/6Li isc3x lower in calcite andc11x lower in aragonite, with no relations... more the growth solution, 7Li/6Li isc3x lower in calcite andc11x lower in aragonite, with no relationship to salinity for either mineral. Similar isotope fractionation to these inorganic experiments are observed for biogenically produced calcite (foraminifera) and aragonite (corals). This suggests little biological control during Li incorporation into biogenic calcium carbonates. The difference in fractionation between calcite and aragonite is consistent with an equilibrium isotope fractionation reflecting different incorporation mechanisms for Li into the two minerals. Four samples of the benthic foraminifera Uvigerina, precipitated over a temperature range of 14 8C, have Li/Ca ranging from 18.5 to 13.1 Amol/mol. The ratio is inversely related to temperature with a sensitivity of 2.5F0.8 % per 8C. This sensitivity is similar to that observed in a previous study of foraminiferal Li/Ca, but about half that observed during inorganic calcite growth. The large variability in both Li/Ca and t...
This catalogue presents a selection of 135 images - most of which have never before been publishe... more This catalogue presents a selection of 135 images - most of which have never before been published - of Marilyn Monroe - the famous star, the myth and the icon of the 20th century. It also includes portraits of other iconic stars, such as Marlon Brando, Mia Farrow, Ursula Andress, Sophia Loren, Judy Garland, Anthony Quinn, Woody Allen and Sean Connery. The photographs recreate a certain magic and charm, providing a journey of discovery, drawing one into Marilyn's private circle. The photographers responsible for the images are Sam Shaw and his son Larry. Sam had his first contact with the world of the cinema in 1950, and met Marilyn in 1951 and from then never abandoned her. It was from him that we received the legendary image of Marilyn on the set of Seven Year Itch, her white dress blown up by the hot air from a grate. This collection is a perfect example of a family archive that bears witness to the spirit of an epoch, both in Hollywood and in Paris. A third of the shots are ...
River currents, wind, and waves drive bed-load transport, in which sediment particles collide wit... more River currents, wind, and waves drive bed-load transport, in which sediment particles collide with each other and Earth's surface. A generic consequence is impact attrition and rounding of particles as a result of chipping, often referred to in geological literature as abrasion. Recent studies have shown that the rounding of river pebbles can be modeled as diffusion of surface curvature, indicating that geometric aspects of impact attrition are insensitive to details of collisions and material properties. We present data from fluvial, aeolian, and coastal environments and laboratory experiments that suggest a common relation between circularity and mass attrition for particles transported as bed load. Theory and simulations demonstrate that universal characteristics of shape evolution arise because of three constraints: (i) Initial particles are mildly elongated fragments, (ii) particles collide with similarly-sized particles or the bed, and (iii) collision energy is small enoug...
Geochimica et Cosmochimica Acta Supplement, Jul 1, 2008
Mineral-solution reactions such as nucleation, particle growth, crystallisation and biomineralisa... more Mineral-solution reactions such as nucleation, particle growth, crystallisation and biomineralisation occur in a wide variety of low-temperature geochemical systems including soils, sediments and contaminated land environments (eg permeable reactive barriers). Studying these processes in situ can be challenging, as many of these reactions occur in suboxic or anoxic environments, on fast time-scales (secondsminutes), or are mediated by microorganisms. Synchrotron-based scattering techniques have been used to ...
Vivianite (Fe3(PO4)2·8H2O) has been reported to form as a secondary mineralization product during... more Vivianite (Fe3(PO4)2·8H2O) has been reported to form as a secondary mineralization product during the microbial reduction of phosphate-containing Fe(III) minerals [1 – 3]. The phosphate-rich nature of vivianite makes it a suitable sink for phosphorus, which is a scarce and irreplaceable resource, and a major contributor to eutrophication in surface water bodies. There is, therefore, interest in synthesizing vivianite by Fe(III) reducing bacteria such as Geobacter sulfurreducens and Shewanella putrefaciens, to treat phosphate-rich waters, recovering the phosphate for re-use in agriculture. In this study, factors including the presence and absence of phosphate and electron shuttle, the buffer system, pH, microbial load, and the type of Fe(III)-reducing bacteria that influence the formation of vivianite under laboratory batch systems have been investigated. The rate of Fe(II) production, and its interaction with the residual Fe(III) and other oxyanions (e.g., PO43-, CO32-) was found to...
the growth solution, 7Li/6Li isc3x lower in calcite andc11x lower in aragonite, with no relations... more the growth solution, 7Li/6Li isc3x lower in calcite andc11x lower in aragonite, with no relationship to salinity for either mineral. Similar isotope fractionation to these inorganic experiments are observed for biogenically produced calcite (foraminifera) and aragonite (corals). This suggests little biological control during Li incorporation into biogenic calcium carbonates. The difference in fractionation between calcite and aragonite is consistent with an equilibrium isotope fractionation reflecting different incorporation mechanisms for Li into the two minerals. Four samples of the benthic foraminifera Uvigerina, precipitated over a temperature range of 14 8C, have Li/Ca ranging from 18.5 to 13.1 Amol/mol. The ratio is inversely related to temperature with a sensitivity of 2.5F0.8 % per 8C. This sensitivity is similar to that observed in a previous study of foraminiferal Li/Ca, but about half that observed during inorganic calcite growth. The large variability in both Li/Ca and t...
This catalogue presents a selection of 135 images - most of which have never before been publishe... more This catalogue presents a selection of 135 images - most of which have never before been published - of Marilyn Monroe - the famous star, the myth and the icon of the 20th century. It also includes portraits of other iconic stars, such as Marlon Brando, Mia Farrow, Ursula Andress, Sophia Loren, Judy Garland, Anthony Quinn, Woody Allen and Sean Connery. The photographs recreate a certain magic and charm, providing a journey of discovery, drawing one into Marilyn's private circle. The photographers responsible for the images are Sam Shaw and his son Larry. Sam had his first contact with the world of the cinema in 1950, and met Marilyn in 1951 and from then never abandoned her. It was from him that we received the legendary image of Marilyn on the set of Seven Year Itch, her white dress blown up by the hot air from a grate. This collection is a perfect example of a family archive that bears witness to the spirit of an epoch, both in Hollywood and in Paris. A third of the shots are ...
River currents, wind, and waves drive bed-load transport, in which sediment particles collide wit... more River currents, wind, and waves drive bed-load transport, in which sediment particles collide with each other and Earth's surface. A generic consequence is impact attrition and rounding of particles as a result of chipping, often referred to in geological literature as abrasion. Recent studies have shown that the rounding of river pebbles can be modeled as diffusion of surface curvature, indicating that geometric aspects of impact attrition are insensitive to details of collisions and material properties. We present data from fluvial, aeolian, and coastal environments and laboratory experiments that suggest a common relation between circularity and mass attrition for particles transported as bed load. Theory and simulations demonstrate that universal characteristics of shape evolution arise because of three constraints: (i) Initial particles are mildly elongated fragments, (ii) particles collide with similarly-sized particles or the bed, and (iii) collision energy is small enoug...
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