Formic Acid Synthesis in a Water–Mineral System: Major Role of the Interface

Mineral surfaces are known for their catalytic properties, as they lower kinetic bar- riers to reactions, and modify chemical equilibria. Using ab-initio molecular dynamics and enhanced sampling methods we predict that the MgO(001)/water interface ther- modynamically favours the formation of formic acid from carbon monoxide and water. This occurs despite the lack of direct participation from the surface atoms, the reac- tion taking place beyond the first adsorbed layer. Furthermore, the application of an external electric field on the reaction in bulk water shows a similar effect. We propose that formic acid may be stabilised by the surface electric field, by direct comparison with the equilibrium in bulk water with and without an external electric field applied, and at the MgO(001)/water interface

Immuno-detection of Staphylococcus aureus biofilm on a cochlear implant

Abstract : Case presentation: : A 46-year-old man suffering from progressive deafness since childhood received a Clarion 90 K cochlear implant with the HiRes® preformed electrode in his left ear in October 2006. A persistent Staphylococcus aureus infection failed to be treated with corticoids, amoxicillin/ clavulanate, ciprofloxaxin, and rifampin. The processor was removed on July 2007. Interventions: : The removed cochlear implant processor was treated with different reagents, with the aim of detecting a S. aureus and S. aureus biofilm: (1) fluorescein-coupled Fc of anti-human serum, (2) polyclonal anti-polysaccharide intercellular adhesion antibodies coupled to Alexa Fluor 568 goat anti-rabbit immunoglobulin (Ig)G, (3) crystal violet, (4) methylene blue, (5) acridine orange, (6) Gram stain, and (7) live/dead fluorescent stain. Results: : S. aureus and the major constituent of the S. aureus biofilm, the polysaccharide intercellular adhesion, were detected on the surface of the implant. S. aureus was isolated after a simple contact between the implant and a solid growth medium. The ability of the isolated S. aureus strain to produce biofilm in vitro was confirmed. Interpretation: : S. aureus biofilm was documented on the implant. Initial bacterial colonization could be related to the pocket of the removable magnet. Colonies of S. aureus without biofilm were found attached to the electrode wire. Conclusion: : We report one case of a S. aureus biofilm infection documented on a cochlear implant, as assessed by immuno-microscopy. The biofilm was likely responsible for the persistent infection which manifested for many months after the implant surgery and could explain the unusual bacterial phenotypic resistance against administered antimicrobial agent

Ex-situ mineral carbonation: resources, process and environmental assessment (Carmex project)

This article presents the main results of the Carmex project (2009-2012), whose purpose was to review the feasibility of ex-situ mineral carbonation in terms of resource availability, performance of the aqueous mineral carbonation process and life cycle analysis criteria. This collaborative project looked at a wide range of generic issues about this CO2 mitigation option, with particular views on assessing its potential in the context of New-Caledonia. Indeed, insularity and local abundance of 'carbonatable' rocks and industrial wastes (i.e. rich in MgO, CaO, if not Fe(II)O), coupled with significant GHG emissions from first-class nickel pyrometallurgical industries, make it a potential candidate for application of ex-situ mineral carbonation. The project conducted a worldwide analysis of the potential of ex-situ mineral carbonation using a dedicated SIG-based tool. Using a variety of materials the project also reviewed a number of critical issues associated with the aqueous mineral carbonatation process itself, with promising perspectives. Finally, through life cycle analysis of the system as a whole, ex-situ mineral carbonation was compared to mainstream CSC solutions. It was concluded that the viability of this CO2 storage option is located at the level of the process itself and lies with the optimisation of its operating conditions

Spi-1, Fli-1 and Fli-3 (miR-17-92) Oncogenes Contribute to a Single Oncogenic Network Controlling Cell Proliferation in Friend Erythroleukemia

Clonal erythroleukemia developing in susceptible mice infected by Friend virus complex are associated with highly recurrent proviral insertions at one of three loci called Spi-1, Fli-1 or Fli-3, leading to deregulated expression of oncogenic Spi-1 or Fli-1 transcription factors or miR-17-92 miRNA cluster, respectively. Deregulated expression of each of these three oncogenes has been independently shown to contribute to cell proliferation of erythroleukemic clones. Previous studies showed a close relationship between Spi-1 and Fli-1, which belong to the same ETS family, Spi-1 activating fli-1 gene, and both Spi-1 and Fli-1 activating multiple common target genes involved in ribosome biogenesis. In this study, we demonstrated that Spi-1 and Fli-1 are also involved in direct miR-17-92 transcriptional activation through their binding to a conserved ETS binding site in its promoter. Moreover, we demonstrated that physiological re-expression of exogenous miR-17 and miR-20a are able to partially rescue the proliferation loss induced by Fli-1 knock-down and identified HBP1 as a target of these miRNA in erythroleukemic cells. These results establish that three of the most recurrently activated oncogenes in Friend erythroleukemia are actually involved in a same oncogenic network controlling cell proliferation. The putative contribution of a similar ETS-miR-17-92 network module in other normal or pathological proliferative contexts is discussed

Análisis de la evolución hidrogeoquímica y diagnóstico de procesos de biomineralización controlada en agua subterránea : caso Pozo UPTC, Sogamoso

1 recurso en línea (103 páginas) : ilustraciones color, figuras, tablas.Geomicrobiology has special interest in the role played by microorganisms in chemical cycles of chemical elements, including iron. Therefore, the incidence of bacteria in the absorption and reduction of elements of interest has been studied; Experimental studies have also been carried out on the use of catabolic processes of different bacteria as a bioremediation technique during the treatment of groundwater. However, the design of a formulation for the purification of this type of water, it is advisable to know the dynamics of the flow and the great part of the rock-water interaction processes that have influenced the chemical tool of the underground resource. In accordance with the above, it was pointed out the hydrogeochemical processes that have intervened in the evolution of the groundwater captured in the UPTC well, Sogamoso, and the iron and manganese removal capacity in the well water samples was evaluated from the exploitation of bacterial biomineralization processes. To do this, the sampling of eleven (11) samples of groundwater was carried out for the analysis of physicochemical parameters and the determination of the concentrations of the ionic content of interest. The processing of the information was done through hydrogeochemical diagrams (Piper, Stiff and Schoeller-Berkaloff) and some binary graphs that provide information on local conditions; and in a complementary manner, two (2) multivariate statistical methods were applied to quantitatively verify the results obtained through the hydrogeochemical analysis. In a complementary manner, the isotopic content of four (4) of the samples was analyzed to identify the possible recharge zones and, in this way, the preliminary hydrogeological model was constructed for the study area. The integration of this information allowed to define part of the natural and exogenous constituents to the dynamics of the underground flow. Additionally, an experimental method of bioremediation based on the biomineralization mechanisms, typical of the Magnetotactic Bacteria (MTB's) was tested, from which it was possible to eliminate part of the high content of Fe and Mn in the well waters. For this, it was required of the prospection of MTB at regional level, the isolation, the characterization and the verification of the magnetic response of the microorganisms, to finally, perform a process of inoculation of samples enriched with MTB in well water samples. This research for the opening to the future development of methodologies that include the use of microorganisms with magnetic properties and the use of bacterial biomineralization processes for the removal of medical crystals during the treatment of groundwater.La geomicrobiología tiene especial interés en el papel que desempeñan los microorganismos en los ciclos biológicos de los elementos químicos, entre ellos el hierro. Por ello, se ha estudiado la incidencia de bacterias en la absorción y reducción de elementos de interés; asimismo se han realizado estudios experimentales acerca de la utilización de los procesos catabólicos de diferentes bacterias como técnica de biorremediación durante el tratamiento de aguas subterráneas. No obstante, previo a cualquier formulación para la depuración de este tipo de aguas, es recomendable conocer la dinámica del flujo y gran parte de los procesos de interacción roca-agua que han incidido en la composición química del recurso subterráneo. Conforme a lo anterior, se analizaron los procesos hidrogeoquímicos que han intervenido en la evolución del agua subterránea captada en el pozo UPTC, Sogamoso, y se evaluó la capacidad de remoción de hierro y manganeso en muestras de agua del pozo a partir del aprovechamiento de los procesos de biomineralización bacteriana. Para ello, se realizó la toma de once (11) muestras de agua subterránea para el análisis de parámetros fisicoquímicos y la determinación de las concentraciones del contenido iónico de interés. El procesamiento de la información se realizó a través de diagramas hidrogeoquímicos (Piper, Stiff y Schoeller-Berkaloff) y algunos gráficos binarios que aportaran información de las condiciones locales; y de manera complementaria, se aplicaron dos (2) métodos estadísticos multivariantes para comprobar cuantitativamente los resultados obtenidos a través del análisis hidrogeoquímico. De manera complementaria, se analizó el contenido isotópico de cuatro (4) de las muestras, para identificar las posibles zonas de recarga y de esta manera construir el modelo hidrogeológico preliminar para el área de estudio. La integración de esta información permitió definir parte de los constituyentes naturales y exógenos a la dinámica del flujo subterráneo. Adicionalmente, se ensayó un método experimental de biorremediación basado en los mecanismos de biomineralización, propios de las bacterias Magnetotácticas (MTB’s), a partir del cual se logró remover parte del alto contenido de Fe y Mn en las aguas del pozo. Para ello, se requirió de la prospección de MTB’s a nivel regional, el aislamiento, la caracterización y la comprobación de la respuesta magnética de los microorganismos, para finalmente, realizar un proceso de inoculación de muestras enriquecidas con MTB´s en muestras de agua del pozo. Esta investigación da apertura al futuro desarrollo de metodologías que incluyan la utilización de microorganismos con propiedades magnéticas y el uso de procesos de biomineralización bacteriana para la remoción de elementos metálicos durante el tratamiento de aguas subterráneas.Bibliografía y webgrafía: páginas 94-103.PregradoIngeniero Geólog

Multiple plasmon resonances in naturally-occurring multiwall nanotubes: infrared spectra of chrysotile asbestos

Chrysotile asbestos is formed by densely packed bundles of multiwall hollow nanotubes. Each wall in the nanotubes is a cylindrically wrapped layer of $Mg_3 Si_2 O_5 (OH)_4$. We show by experiment and theory that the infrared spectrum of chrysotile presents multiple plasmon resonances in the Si-O stretching bands. These collective charge excitations are universal features of the nanotubes that are obtained by cylindrically wrapping an anisotropic material. The multiple plasmons can be observed if the width of the resonances is sufficiently small as in chrysotile.Comment: 4 pages, 5 figures. Revtex4 compuscript. Misprint in Eq.(6) correcte

About the foundations of direct aqueous carbonation with dissolution enhancing organic salts

Direct aqueous carbonation is a promising mineral carbonation route. Under mildly acidic conditions, this single-step carbonation process aims to simultaneously dissolve Ca/Mg-bearing silicates or wastes and precipitate Ca/Mg carbonates. By and large, since mineral dissolution is rate limiting due to the lack of protons at near-neutral pH, research has mainly been concerned with the issue of enhancing dissolution. By analysing the liquid phase, it has been established that polyacid organic salts can significantly enhance silicate dissolution under such unfavourable conditions. Comparatively little attention has been paid to the investigation of the very basis of the whole process, i.e. the concomitance of silicate dissolution and carbonate precipitation. By taking a close look at the solid phases in lizardite and olivine slurries, this work confirms the co-occurrence of magnesium silicate dissolution and magnesite precipitation inside a stirred reactor operating at 120°C, 20 bar of CO2 and 0.1M disodium oxalate, thereby bringing indisputable evidence that supports the foundation of direct aqueous carbonation with organic salts

Synchrotron-based speciation of chromium in an Oxisol from New Caledonia: Importance of secondary Fe-oxyhydroxides

abstract In New Caledonia, the weathering of ultamafic rocks under a tropical climate has led to the residual accumulation of trace elements in lateritic soils widely dominated by Fe-oxyhydroxides. The speciation of trace elements, such as Cr, Ni, and Co, in these Oxisols remains a major subject of interest regarding mining and environmental issues. We have assessed the speciation of chromium in the upper part of an Oxisol, by combining bulk and spatially resolved chemical analyses (EPMA and SEM-EDS) with synchrotron-based spectroscopic data (EXAFS and XANES). EPMA indicates that the main hosts for chromium in the bedrock sample are the silicates forsterite, enstatite, and lizardite. Hosting of chromium in these easily weatherable mineral species could lead to a significant loss of this element upon weathering. However, total analyses of major elements indicate only a slight depletion of Cr, together with an immobility of Fe and Al and drastic losses of Si and Mg, after the weathering of the bedrock. Such a low mobility of chromium is likely related to its significant incorporation in goethite and hematite formed after the weathering of Fe 2+ -bearing primary silicates. This efficiency of secondary Fe-oxyhydroxides at immobilizing chromium is demonstrated by quantitative analysis of EXAFS data that indicates that these mineral species host between 67 and 75 wt% of total Cr (compared to the 18 to 22 wt% of total Cr hosted by chromite). In addition, SEM observation and SEM-EDS analyses performed on the Oxisol samples also show some evidence for chemical weathering of chromite. Chromite could then represent a past and/or present source of chromium upon extended tropical weathering of the studied Oxisol, rather than a stable host. These results emphasize the importance of secondary Fe-oxyhydroxides, compared to Cr-spinels, on chromium hosting in Oxisols developed upon tropical weathering of ultramafic rocks. Although the trapping mechanism of chromium mainly corresponds to incorporation within the structural network of goethite and hematite, sorption reactions at the surface of these mineral species could also be involved in such a process. In addition, considering their potential oxidative reactivity that can generate Cr 6+ or enhance the chemical weathering of chromite, the occurrence of Mn oxides could significantly modify the behavior of chromium upon weathering. These considerations indicate that further studies are needed to assess the actual potential of chromium release from Oxisols developed upon weathering of ultramafic rocks under a tropical climate

Comprehensive analysis of direct aqueous mineral carbonation using dissolution enhancing organic additives.

Direct aqueous mineral carbonation using organic anions has been presented by many as a promising strategy for mineral carbonation, on the basis that additives such as oxalate increase the rate and extent of dissolution of magnesium silicates several folds. Through geochemical modelling and detailed solid characterization, this paper discusses and extends our current understanding of this process. The role of disodium oxalate as a dissolution enhancing agent for olivine is thoroughly examined through experiments in which all phases are carefully analysed. We show that under 20 bar of CO2 pressure formation of strong oxalate-magnesium complexes in solution and precipitation of MgC2O4,2H2O (glushinskite) impede any chance of obtaining significant amounts of magnesium carbonate. Other promising ligands from a dissolution perspective, namely citrate and EDTA salts, are also investigated. Contrary to oxalate, these ligands do not form any solid by-products with magnesium, and yet they do not produce better carbonation results, thereby casting strong doubts on the possibility of developing a direct aqueous mineral carbonation process using organic salts. Geochemical modelling permits successful simulation of the dissolution kinetics of magnesium silicate using a shrinking particle model that accounts for the precipitation of glushinskite, amorphous silica and a magnesium phyllosilicate at advanced stages of the dissolution process