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Colmenares J.C.,Polish Academy of Sciences | Luque R.,University of Cordoba, Spain
Chemical Society Reviews | Year: 2014

Heterogeneous photocatalysis has become a comprehensively studied area of research during the past three decades due to its practical interest in applications including water-air depollution, cancer therapy, sterilization, artificial photosynthesis (CO2 photoreduction), anti-fogging surfaces, heat transfer and heat dissipation, anticorrosion, lithography, photochromism, solar chemicals production and many others. The utilization of solar irradiation to supply energy or to initiate chemical reactions is already an established idea. Excited electron-hole pairs are generated upon light irradiation of a wide-band gap semiconductor which can be applied to solar cells to generate electricity or in chemical processes to create/degrade specific compounds. While the field of heterogeneous photocatalysis for pollutant abatement and mineralisation of contaminants has been extensively investigated, a new research avenue related to the selective valorisation of residues has recently emerged as a promising alternative to utilise solar light for the production of valuable chemicals and fuels. This tutorial review will focus on the potential and applications of solid photonanocatalysts for the selective transformation of biomass-derived substrates. This journal is © The Royal Society of Chemistry. Source

Tadesse H.,U.S. Environmental Protection Agency | Luque R.,University of Cordoba, Spain
Energy and Environmental Science | Year: 2011

Petroleum is currently being used as a major source for chemicals, materials, and fuels, but poses major concerns in terms of its future utilisation due to resource limitation, increasing costs and associated environmental issues. An alternative raw material for chemicals and biofuels production is lignocellulosic biomass. The conversion of biomass to biofuels begins with biomass pretreatment in which chemical and/or physical treatments are utilised to remove or weaken the tight linkages among cell-wall components, making biomass easier to degrade. The use of ionic liquids-salts (mixtures of cations and anions that melt below 100 °C) has been described as a new potentially viable development in this area due to the increasing interest in the use of such compounds to pretreat lignocellulosic materials and to catalyse the dissolution of cellulose. This manuscript aims to provide an overview on the major representative progress and development of the use of ionic liquids systems for biomass pretreatment and cellulose dissolution. A comparison of the environmental impact of different ionic liquids for the conversion of carbohydrates into useful biofuel intermediates will be described, with their inherent advantages for biomass valorisation processes in terms of unique and tuneable physico-chemical properties. © 2011 The Royal Society of Chemistry. Source

Lucena R.,University of Cordoba, Spain
Analytical and Bioanalytical Chemistry | Year: 2012

Extraction techniques, which focus on selectivity and sensitivity enhancement by isolation and preconcentration of target analytes, are essential in many analytical methods. Because many extraction techniques occur under diffusion-controlled conditions, stirring of the sample solution is required to accelerate the extraction by favoring diffusion of the analytes from the bulk solution to the extractant phase. This stirring may be performed by use of an external device or by integrating extraction and stirring in the same device. This review focuses on the latter techniques, which are promising methods for sample treatment. First, stir-bar-sorptive extraction, the most widely used method, is considered, paying special attention to the development of new coatings. Finally, a general overview of novel integrated techniques in both solid-phase and liquid-phase microextraction is presented; their main characteristics and marked trends are reported. © Springer-Verlag 2012. Source

This review article addresses recent methodological and instrumental innovations in MEKC with emphasis on practical aspects. Like its predecessors, this review is intended to provide an updated overview covering work on the most salient methodological contributions to enhancing sensitivity and resolution in MEKC-based determinations published over the past two years. The most widespread approaches to enhancing sensitivity, which include improving "classical" online sample concentration techniques, combinations of on- and off-line sample concentration protocols and recent developments are discussed, and so are modifications of existing MEKC systems with various micellar phases, the use of BGE additives (organic modifiers, chiral selectors, gold nanoparticles) and coated capillaries, and the implementation of 2D separations and chemometric methods to enhance resolution. Instrumental approaches such as MS and LIF are also discussed, and proposals for overcoming the problems typically encountered in directly coupling MEKC with MS, and the recent inception of quantum dots with a great potential for LIF detection in MEKC, are also dealt with. Finally, foreseeable developments on potential future directions are also expressed. © 2012. Source

Magnesium reduces vascular smooth muscle cell (VSMC) calcification in vitro but the mechanism has not been revealed so far. This work used only slightly increased magnesium levels and aimed at determining: a) whether inhibition of magnesium transport into the cell influences VSMC calcification, b) whether Wnt/β-catenin signaling, a key mediator of osteogenic differentiation, is modified by magnesium and c) whether magnesium can influence already established vascular calcification. Human VSMC incubated with high phosphate (3.3 mM) and moderately elevated magnesium (1.4 mM) significantly reduced VSMC calcification and expression of the osteogenic transcription factors Cbfa-1 and osterix, and up-regulated expression of the natural calcification inhibitors matrix Gla protein (MGP) and osteoprotegerin (OPG). The protective effects of magnesium on calcification and expression of osteogenic markers were no longer observed in VSMC cultured with an inhibitor of cellular magnesium transport (2-aminoethoxy-diphenylborate [2-APB]). High phosphate induced activation of Wnt/β-catenin pathway as demonstrated by the translocation of β-catenin into the nucleus, increased expression of the frizzled-3 gene, and downregulation of Dkk-1 gene, a specific antagonist of the Wnt/β-catenin signaling pathway. The addition of magnesium however inhibited phosphate-induced activation of Wnt/β-catenin signaling pathway. Furthermore, TRPM7 silencing using siRNA resulted in activation of Wnt/β-catenin signaling pathway. Additional experiments were performed to test the ability of magnesium to halt the progression of already established VSMC calcification in vitro. The delayed addition of magnesium decreased calcium content, down-regulated Cbfa-1 and osterix and up-regulated MGP and OPG, when compared with a control group. This effect was not observed when 2-APB was added. In conclusion, magnesium transport through the cell membrane is important to inhibit VSMC calcification in vitro. Inhibition of Wnt/β-catenin by magnesium is one potential intracellular mechanism by which this anti-calcifying effect is achieved. Source

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