Single-site and nanosized Fe-Co electrocatalysts for oxygen reduction: Synthesis, characterization and catalytic performance

The impregnation of Ketjen Black (C) with iron and cobalt phthalocyanines (MPc) taken one by one or as a 1:1 stoichiometric mixture, followed by heat treatment at 600 °C under inert atmosphere, gave materials containing arrays of single metal ions coordinated by four nitrogen atoms (M-N₄ units). Increasing the pyrolysis temperature to 800° resulted in the formation of carbon-supported, nanosized metal particles. A key role of the carbon support in determining the material structure at either temperature investigated was demonstrated by TPD, EXAFS, XANES and XRPD studies. These also showed that a Fe-Co alloy is obtained at 800 °C when the impregnation of Ketjen Black involves a mixture of FePc and CoPc. Electrodes coated with the different Fe, Co and Fe-Co materials, containing ca. 3 wt% metal loadings, were scrutinized for the oxygen reduction reaction (ORR) in alkaline media by linear sweep voltammetry. For comparative purposes, two Pt electrocatalysts containing 3 and 20 wt% metal were investigated. The electrochemical activity of all materials was analyzed by Tafel and Koutecky-Levich plots as well as chronopotentiometry. The Fe-containing electrocatalysts have been found to be highly active for the ORR in alkaline media with convective limiting currents as high as 600 A g Fe⁻¹ at room temperature and onset potentials as high as 1.02 V vs. RHE. It has been found that (i) the ORR mass activity of the Pc-derived electrocatalysts is superior to that of the Pt catalysts investigated; (ii) the activity of FePc and FePc-CoPc/C, heat treated at either 600 or 800 °C, is superior to that of the corresponding Co materials; (iii) the electrocatalysts obtained at 600 °C are fairly more active than those obtained at 800 °C.     

An Intelligent Transportation System to control air pollution and road traffic in cities integrating CEP and Colored Petri Nets

Neural Computing and Applications - Air pollution generated by road traffic in large cities is a great concern in today’s society since pollution has an important impact on human health, even...     

Reversal left diastolic ventriculo-atrial flow induced by asynchronism in a patient with dilated cardiopathy and VVI pacemaker]

Current therapy for glioma is suboptimal. The transfer of apoptosis genes to tumors constitutes one of the most promising strategies for cancer gene therapy. We have previously shown that massive apoptosis occurs when wild-type p53 or E2F-1 expression is induced in glioma. However, the mechanism of action and the efficiency in inducing apoptosis of these two proteins are not similar. Adenovirus-mediated p53 gene transfer is ineffective in causing apoptosis in glioma cells that retain wild-type p53 genotype or overexpress the p21 protein. The p16/Rb/E2F pathway is the most frequent target of genetic alterations in gliomas, and therefore constitutes a suitable target for gene therapy strategies. However, the transfer of either the p16 or Rb gene to glioma cells results in cytostatic effect. The E2F-1 protein is able to induce generalized apoptosis in gliomas independently of the p53, p16 or Rb status. In addition, p21- or p16-mediated growth arrest did not protect glioma cells from E2F-1-mediated apoptosis. The apoptotic molecule bax is induced in p53-mediated apoptosis, but bax is not induced in E2F-1-mediated apoptosis in glioma cells. Careful selection of patients may be necessary before designing therapeutic strategies using either p53 or E2F-1 as a therapeutic tools for glioma patients.     

Parallel solvers for discrete-time algebric Riccati equations

We investigate the numerical solution of discrete-time algebraic Riccati equations on a parallel distributed architecture. Our solvers obtain an initial solution of the Riccati equation via the disc function method, and then refine this solution using Newton's method. The Smith iteration is employed to solve the Stein equation that arises at each step of Newton's method. The numerical experiments on an Intel Pentium-II cluster, connected via a Myrinet switch, report the performance and scalability of the new algorithms. Copyright © 2001 John Wiley & Sons, Ltd.     

Grafting of cyclodextrins onto polypropylene nonwoven fabrics for the manufacture of reactive filters. II. Characterization

A novel method for the preparation of immobilized α, β, or γ‐cyclodextrins on polypropylene nonwoven supports has been previously presented. The obtained new materials were prepared by graft‐polymerization of glycidyl methacrylate onto polypropylene after activation of the support by the electron beam technique, followed by the coupling of cyclodextrins with the epoxide groups. The structure of the resulting materials is characterized in detail using Fourier transform infrared spectroscopy, solid state nuclear magnetic resonance analysis, differential scanning calorimetry, thermogravimetric analysis, and optical microscopy. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 2166–2173, 2000     

Peimine,an Anti-Inflammatory Compound from Chinese Herbal Extracts,Modulates Muscle-Type Nicotinic Receptors

Fritillaria bulbs are used in Traditional Chinese Medicine to treat several illnesses. Peimine (Pm), an anti-inflammatory compound from Fritillaria, is known to inhibit some voltage-dependent ion channels and muscarinic receptors, but its interaction with ligand-gated ion channels remains unexplored. We have studied if Pm affects nicotinic acetylcholine receptors (nAChRs), since they play broad functional roles, both in the nervous system and non-neuronal tissues. Muscle-type nAChRs were incorporated to Xenopus oocytes and the action of Pm on the membrane currents elicited by ACh (I_AChs) was assessed. Functional studies were combined with virtual docking and molecular dynamics assays. Co-application of ACh and Pm reversibly blocked I_ACh, with an IC₅₀ in the low micromolar range. Pm inhibited nAChR by: (i) open-channel blockade, evidenced by the voltage-dependent inhibition of I_Ach, (ii) enhancement of nAChR desensitization, revealed by both an accelerated I_ACh decay and a decelerated I_ACh deactivation, and (iii) resting-nAChR blockade, deduced from the I_ACh inhibition elicited by Pm when applied before ACh superfusion. In good concordance, virtual docking and molecular dynamics assays demonstrated that Pm binds to different sites at the nAChR, mostly at the transmembrane domain. Thus, Pm from Fritillaria bulbs, considered therapeutic herbs, targets nAChRs with high affinity, which might account for its anti-inflammatory actions.     

Manganese ferrite nanoparticles synthesized through a nanocasting route as a highly active Fenton catalyst

Spinel ferrite MnFe₂O₄ nanoparticles were synthesized by means of a nanocasting technique using a low-cost mesoporous silica gel as a hard template. The magnetic nanoparticles, of <10 nm diameter and with a surface area of around 100 m²/g, were tested as a heterogeneous Fenton catalyst for the decomposition of hydrogen peroxide under neutral and basic conditions. This catalyst shows a much higher activity than previous heterogeneous catalysts reported in the literature, which is mainly ascribed to its small particle size. Furthermore, the magnetic catalyst can be easily separated from the reaction medium by means of an external magnetic field. The effects of residual silica and the purity of the catalyst (hematite formation) on catalytic activity have been studied and correlated. The results obtained show this catalyst to be a suitable candidate for the removal of pollutants in wastewaters by means of the Fenton heterogeneous reaction.