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Pinilla J.L.,CSIC - Institute of Carbochemistry | Lazaro M.J.,CSIC - Institute of Carbochemistry | Suelves I.,CSIC - Institute of Carbochemistry | Moliner R.,CSIC - Institute of Carbochemistry | Palacios J.M.,Campus University Autonoma
Chemical Engineering Journal | Year: 2010

Carbon nanofibers (CNFs) production in the range of hundreds of grams per day has been achieved in a fluidized bed reactor (FBR) by methane decomposition using a nickel based catalyst. The characterization of the carbon produced at different operating conditions (temperature, space velocity and the ratio of gas flow velocity, uo, to the minimum fluidization velocity, umf) has been accomplished by means of X-ray diffraction (XRD), N2 adsorption, temperature-programmed oxidation (TPO), scanning electron microscope (SEM) and transmission electron microscopy (TEM). It has been concluded that the structural and textural properties of the CNFs obtained in the FBR are analogous to the ones obtained in a fixed bed reactor at a production scale two orders of magnitude lower. Thus, FBR can be envisaged as a promising reaction configuration for the catalytic decomposition of methane (CDM), allowing the production of high quantities of CNFs with desirable structural and textural properties. © 2009 Elsevier B.V. All rights reserved.

Pinilla J.L.,CSIC - Institute of Carbochemistry | Suelves I.,CSIC - Institute of Carbochemistry | Lazaro M.J.,CSIC - Institute of Carbochemistry | Moliner R.,CSIC - Institute of Carbochemistry | Palacios J.M.,Campus University Autonoma
International Journal of Hydrogen Energy | Year: 2010

CO2-free production of hydrogen via catalytic decomposition of methane (CDM) was studied in a fluidized bed reactor (FBR) using a NiCu/Al 2O3 catalyst. A parametric study of the effects of some process variables, including catalyst particle size, reaction temperature, space velocity and the ratio of gas flow velocity to the minimum fluidization velocity (uo/umf), was undertaken. A mean particle size of 150 μm allows optimization of results in terms of hydrogen production without agglomeration problems. The operating conditions strongly affect the catalyst performance: hydrogen production was enhanced by increasing operating temperature and lowering space velocity. However, increases in operating temperature, space velocity and the ratio uo/umf provoked increases in the catalyst deactivation rate. At 700 °C, carbon was deposited as carbon nanofibers, while higher temperatures promoted the formation of encapsulating carbon, which led to rapid catalyst deactivation. © 2010 Published by Elsevier Ltd on behalf of Professor T. Nejat Veziroglu.

Breton-Romero R.,Campus University Autonoma | Lamas S.,Campus University Autonoma
Redox Biology | Year: 2014

Redox signaling is implicated in different physiological and pathological events in the vasculature. Among the different reactive oxygen species, hydrogen peroxide (H2O2) is a very good candidate to perform functions as an intracellular messenger in the regulation of several biological events.In this review, we summarize the main physiological sources of H2O2 in the endothelium and the molecular mechanisms by which it is able to act as a signaling mediator in the vasculature. © 2014 The Authors.

Bezbradica D.I.,University of Belgrade | Mateo C.,Campus University Autonoma | Guisan J.M.,Campus University Autonoma
Journal of Molecular Catalysis B: Enzymatic | Year: 2014

Immobilization of enzymes on glutaraldehyde-activated supports has been largely used on supports previously activated with amine groups. Therefore, the supports are positively charged hence usually the immobilization is promoted through a two step mechanism: in a first step the enzyme is adsorbed on the support via an anionic exchange mechanism and then, the covalent immobilization occurs. In this paper a new glutaraldehyde activated support without a net charge is presented and characterized in immobilizations of trypsin, penicillin acylase G, lipase and E. coli BL21 cell extract. Immobilization mechanism was studied and this was produced without an adsorption step. This support promoted initially a reversible immobilization, converting into irreversible after incubation of the enzyme-support for several days or after a reduction step. In addition the stability of glutaraldehyde groups was studied retaining around 50 and 25% of its immobilization capacity for 24 h at pH 7 and 10 respectively. This fact allows the incubation of the enzyme with the support even at alkaline pH promoting an extra stabilization factor for trypsin on this support. © 2014 Elsevier B.V.

Breton-Romero R.,Campus University Autonoma | Gonzalez De Orduna C.,Campus University Autonoma | Romero N.,University of the Republic of Uruguay | Sanchez-Gomez F.J.,Campus University Autonoma | And 5 more authors.
Free Radical Biology and Medicine | Year: 2012

Laminar shear stress (LSS) is a protective hemodynamic regulator of endothelial function and limits the development of atherosclerosis and other vascular wall diseases related to pathophysiological generation of reactive oxygen species. LSS activates several endothelial signaling responses, including the activation of MAPKs and eNOS. Here, we explored the mechanisms of activation of these key endothelial signaling pathways. Using the cone/plate model we found that LSS (12 dyn/cm2) rapidly promotes endothelial intracellular generation of superoxide and hydrogen peroxide (H 2O2). Physiological concentrations of H2O 2 (flux of 0.1 nM/min and 15 μM added extracellularly) significantly activated both eNOS and p38 MAPK. Pharmacological inhibition of NADPH oxidases (NOXs) and specific knockdown of NOX4 decreased LSS-induced p38 MAPK activation. Whereas the absence of eNOS did not alter LSS-induced p38 MAPK activation, pharmacological inhibition and knockdown of p38α MAPK blocked H2O2- and LSS-induced eNOS phosphorylation and reduced •NO levels. We propose a model in which LSS promotes the formation of signaling levels of H2O2, which in turn activate p38α MAPK and then stimulate eNOS, leading to increased •NO generation and protection of endothelial function. © 2012 Elsevier Inc. All rights reserved.

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