Electrodeposición de vanadio y níquel de los asfaltenos de crudos pesados

(Eng) Heavy metals are present in porphyrins in oil asphaltenes. High content of V and Ni could be attractive to produce high value metal oxides. These metals are undesirable due to corrosion issues and catalyst contamination in cracking processes. The purpose of this project was to prepare an electrochemical cell, with graphite work electrode, wire Ag counterelectrode and a Ag/AgNO3 reference electrode, in order to evaluate and make the electrochemical characterization and deposition of V and Ni content in resin asphaltene concentrate and pure asphaltenes obtained from Colombian heavy oils. High resolution analytics before and after the deposition was done: elemental analysis, FT-IR, and atomic absorption. The variables as work potential, reaction time and electrode materials during the electro-reduction was evaluated by cyclic voltammetry and chronoamperommeter in two solutions: (I) Tetrahydrofuran and LiClO4 at 0.02 M, and (II) 20% CH3OH, 0.5 % H3PO4, 0.1 M LiClO4 in acetonitrile. Results are discussed compared with traditional method of demetallization by acid digestion.(Spa) La presencia de metales en los asfaltenos, especialmente del vanadio y níquel, puede ser una fuente de productos de valor agregado, pero representan una desventaja en las refinerías ya que no solo contaminan los productos sino que envenenan los catalizadores durante el proceso de craqueo catalítico. El objetivo de este proyecto fue el montaje de una celda electroquímica (donde se utilizó una barra de grafito como electrodo de trabajo, un alambre de Pt como contraelectrodo y un electrodo de Ag/AgNO3 como electrodo de referencia) para la caracterización y electrodeposición de V y Ni contenidos en los extractos resino-asfaltenicos y asfaltenos purificados de los crudos pesados. Los análisis de alta resolución antes y después de la deposición fueron: análisis elemental, FT-IR y absorción atómica. El efecto de las variables electroquímicas como potencial de trabajo, tiempo de reacción y material del electrodo en el proceso de electroreducción se evaluó por voltametría cíclica (VC) y cronoamperometría en dos medios: (I) Tetrahidrofurano y LiClO4 al 0.02 M, (II) 20% de CH3OH, 0.5 % de H3PO4, 0.1 M de LiClO4 en acetonitrilo. Los resultados obtenidos se discuten comparándolos con los obtenidos por el método tradicional de desmetalización en ambientes de digestión ácida

Visualization of single molecules building a viral capsid protein lattice through stochastic pathways

Direct visualization of pathways followed by single molecules while they spontaneously self-assemble into supramolecular biological machines may provide fundamental knowledge to guide molecular therapeutics and the bottom-up design of nanomaterials and nanodevices. Here, high-speed atomic force microscopy is used to visualize self-assembly of the bidimensional lattice of protein molecules that constitutes the framework of the mature human immunodeficiency virus capsid. By real-time imaging of the assembly reaction, individual transient intermediates and reaction pathways followed by single molecules could be revealed. As when assembling a jigsaw puzzle, the capsid protein lattice is randomly built. Lattice patches grow independently from separate nucleation events whereby individual molecules follow different paths. Protein subunits can be added individually, while others form oligomers before joining a lattice or are occasionally removed from the latter. Direct real-time imaging of supramolecular selfassembly has revealed a complex, chaotic process involving multiple routes followed by individual molecules that are inaccessible to bulk (averaging) technique

Spinal cord metabolic signatures in models of fast- and slow-progressing SOD1G93A Amyotrophic Lateral Sclerosis

The rate of disease progression in amyotrophic lateral sclerosis (ALS) is highly variable, even between patients with the same genetic mutations. Metabolic alterations may affect disease course variability in ALS patients, but challenges in identifying the preclinical and early phases of the disease limit our understanding of molecular mechanisms underlying differences in the rate of disease progression. We examined effects of SOD1G93A on thoracic and lumbar spinal cord metabolites in two mouse ALS models with different rates of disease progression: the transgenic SOD1G93A-C57BL/6JOlaHsd (C57-G93A, slow progression) and transgenic SOD1G93A-129SvHsd (129S-G93A, fast progression) strains. Samples from three timepoints (presymptomatic, disease onset, and late stage disease) were analyzed using Gas Chromatography-Mass Spectrometry metabolomics. Tissue metabolome differences in the lumbar spinal cord were driven primarily by mouse genetic background, although larger responses were observed in metabolic trajectories after the onset of symptoms. The significantly affected lumbar spinal cord metabolites were involved in energy and lipid metabolism. In the thoracic spinal cord, metabolic differences related to genetic background, background-SOD1 genotype interactions, and longitudinal SOD1G93A effects. The largest responses in thoracic spinal cord metabolic trajectories related to SOD1G93A effects before onset of visible symptoms. More metabolites were significantly affected in the thoracic segment, which were involved in energy homeostasis, neurotransmitter synthesis and utilization, and the oxidative stress response. We find evidence that initial metabolic alterations in SOD1G93A mice confer disadvantages for maintaining neuronal viability under ALS-related stressors, with slow-progressing C57-G93A mice potentially having more favorable spinal cord bioenergetic profiles than 129S-G93A. These genetic background-associated metabolic differences together with the different early metabolic responses underscore the need to better characterize the impact of germline genetic variation on cellular responses to ALS gene mutations both before and after the onset of symptoms in order to understand their impact on disease development

Visualization of Single Molecules Building a Viral Capsid Protein Lattice through Stochastic Pathways

Direct visualization of pathways followed by single molecules while they spontaneously self-assemble into supramolecular biological machines may provide fundamental knowledge to guide molecular therapeutics and the bottom-up design of nanomaterials and nanodevices. Here, high-speed atomic force microscopy is used to visualize self-assembly of the bidimensional lattice of protein molecules that constitutes the framework of the mature human immunodeficiency virus capsid. By real-time imaging of the assembly reaction, individual transient intermediates and reaction pathways followed by single molecules could be revealed. As when assembling a jigsaw puzzle, the capsid protein lattice is randomly built. Lattice patches grow independently from separate nucleation events whereby individual molecules follow different paths. Protein subunits can be added individually, while others form oligomers before joining a lattice or are occasionally removed from the latter. Direct real-time imaging of supramolecular self-assembly has revealed a complex, chaotic process involving multiple routes followed by individual molecules that are inaccessible to bulk (averaging) techniques

Carbon monoxide oxidation on Pt-Ru electrocatalysts supported on high surface area carbon

This find is registered at Portable Antiquities of the Netherlands with number PAN-0000787

Development of a Passive Mini-Direct Ethanol Fuel Cell: Effect of Mea Assembly Parameters by Hot Pressure

This paper presents preliminary results on the design, construction and evaluation of a passive mini direct ethanol fuel cell (DEFC), capillary fed with 2 mol l-1 aqueous ethanol, at a rate of 2.03 μL min-1, and air oxygen in the cathode through an air vent. Parameters such as pressure, temperature and time of manufacturing a membrane-electrode assembly (MEA) by hot-pressure were evaluated. As the electrode holder used a 0.25 cm2 carbon tissue which was deposited on the catalytic layer (C. L.) for both the anode (0.8 mg cm-2of PtRu/C) and the cathode (0.8 mg cm -2of Pt/C), Nafi on® 115 membranes were used as the electrolyte. The results show, an average power density of 302 μWcm2 under the best conditions used, a catalytic layer with a Nafi on percentage of 50% at 25 °C. A temperature of 125 °C, a pressure of 49.2 Kg/cm2, and 90 seconds duration were used to obtain the MEA