Synthesis and Evaluation of Voltage-Gated Sodium Channel Blocking Pyrroline Derivatives Endowed with Both Antiarrhythmic and Antioxidant Activities

Under the hypothesis that cardioprotective agents might benefit from synergism between antiarrhythmic activity and antioxidant properties, a small series of mexiletine analogues were coupled with the 2,2,5,5-tetramethylpyrroline moiety, known for its antioxidant effect, in order to obtain dual-acting drugs potentially useful in the protection of the heart against post-ischemic reperfusion injury. The pyrroline derivatives reported herein were found to be more potent as antiarrhythmic agents than mexiletine and displayed antioxidant activity. The most interesting tetramethylpyrroline congener, a tert-butyl-substituted analogue, was at least 100 times more active as an antiarrhythmic than mexiletine.     

Influence of the Cooling Temperature on the Mechanical Behavior of an Oxidized Self-Healing Ceramic Matrix Composite

Composites made of ceramic for both fibers and matrix are aimed at being used in aerospace applications, which means being submitted to mechanical stresses at high temperatures in oxidizing and corrosive environments for long durations. The oxidation/corrosion resistance of these materials is linked to their ability to self-heal by creating an oxide phase which can restrict the access of the oxygen into the bulk of the material. During thermomechanical cycles, the distribution of O₂ inside the material as well as the distribution and the state of the liquid oxides will undergo some modifications. A specific test has been conceived and performed in order to evidence the influence of the viscosity of this oxide on the mechanical properties of the material. Results have shown that the stiffening which is observed seems to be proportional to the increase in the viscosity of the sealing oxide, in conjunction with the decrease in the temperature.     

A new modeling approach of pressure waves at the inlet of internal combustion engines

This paper presents a new model used to describe the propagation of pressure waves at the inlet systems of internal combustion engine. In the first part, an analogy is made between the compressible air in a pipe and a mechanical ideal mass damper spring system. A new model is then presented and the parameters of this model are determined by the use of an experimental setup (shock tube test bench). With this model, a transfer function is defined in order to link directly the pressure and the air mass flow rate. In the second part, the model is included into an internal combustion engine simulation code. The results obtained with this code are compared to experimental ones which are measured on a one-cylinder engine test bench. This last one is driven by an electric motor in order to study only the effect of the pressure waves on the engine behavior. A good agreement is obtained between the experimental results and the numerical ones and the new approach is an alternative method for modeling the pressure wave phenomena in an internal combustion engine manifold.     

Exposure of several Belgian consumer groups to pesticide residues through fresh fruit and vegetable consumption

The output of a pesticide surveillance program (detection frequency and number of exceeding measures) can lead to unnecessary concern among consumers since they lack information concerning the actual exposure. In this study, the exposure to pesticide residues through fruit and vegetable consumption is evaluated based on the 2008 surveillance data of the Belgian Federal Agency for the Safety of the Food Chain (FASFC).Results (deterministic and probabilistic approach) demonstrate that the chronic exposure of the adult population (>15 years) is generally under control, even at high or frequent consumption of fruit and vegetables. For most of the pesticide residues studied, the exposure is one hundred times lower than the ‘acceptable daily intake’ or ADI. With regard to children (2–5 years) who consume regularly or large amounts of fruit and vegetables, there are however, indications that for some pesticides the ADI can be exceeded. Nevertheless, due to the large uncertainty in these calculations, a more detailed study is required for this vulnerable group of consumers. In addition, it was demonstrated that washing and peeling of fruit and vegetables result in an exposure that is probably five to six times lower.     

High nutrient loading and climatic parameters influence the dominance and dissimilarity of toxigenic cyanobacteria in northern bays of Lake Victoria

Eutrophication of Lake Victoria led to changes in its phytoplankton communities. However, different levels of eutrophication exist in the open lake and the bays, and between embayments. This study utilized spatial and temporal sampling of Napoleon Gulf and Murchison Bay, exhibiting different trophic conditions. Over one year, we investigated phytoplankton biomass, richness, diversity and dissimilarity, and related the dynamics of the dominant species to the limnological and climatic conditions. The results confirmed that Napoleon Gulf and Murchison Bay showed large differences in eutrophication status, with lower nutrient concentrations in Napoleon Gulf than in Murchison Bay, where a strong gradient was observed from inshore to offshore areas. These nutrient dynamics resulted in a 4 to 10 fold higher chlorophyll-a in Murchison Bay than in Napoleon Gulf. From the embayments, 135 phytoplankton taxa were recorded with no significant differences in alpha diversity. However, high dissimilarity in community structure was observed in beta diversity, mostly due to a turnover among the dominant toxigenic species. Thus, from a similar species pool, there was a shift in the dominant toxigenic cyanobacteria from Microcystis flos-aquae and M. aeruginosa in Murchison Bay, Dolichospermum circinale and Planktolyngbya circumcreta in Napoleon Gulf to D. circinale in the offshore stations. These cyanobacteria are toxigenic taxa with known health hazards. Using partial least square models, we showed that both climatic variables (e.g. wind, solar radiation) and levels of inorganic dissolved nutrients (e.g. SRP, NO₃^–, and NH₄⁺) are the main drivers of differences and dominance in cyanobacteria communities in northern Lake Victoria.     

Solid/Liquid Separation of Pig Manure by Biological Flotation: Pilot-Scale Study

Many problems are associated with pig manure production like high biochemical oxygen demand, chemical oxygen demand, nitrogen, and phosphorus contents. Manure produces may be used in land spreading for agricultural purposes. Over application of liquid manure or runoff caused by precipitation contribute notably to surface or overland flow of phosphorus. In this study, the LISOX process is proposed for use in medium size farms, namely a 2,000-head swine farm. The LISOX process uses biological passive flotation, without any gas addition, to enable the flocs to rise to the surface. Results show that this technology is able to considerably reduce the solids content in the final effluent to 1.1±0.3% and reached solids content of 17.9±2.6% in the combined solid manure obtained at the end of the LISOX process. Total phosphorus (Pt) concentrations have been reduced from 1,234±428?mg/L to 146±46?mg/L in the final effluent, while a value of Pt of 20.6±7.9?g/kg has been obtained in the final solid fraction of the treated manure. The initial ammonium ion/total phosphorus ratio of 2.3±1.0 has been increased to respectively 16.4±4.6 and 17.6±5.4 after the primary and the secondary flotation, which is clearly much higher than the target value (NH4/Pt>7).     

Learning eigenfunctions links spectral embedding and kernel PCA

In this letter, we show a direct relation between spectral embedding methods and kernel principal components analysis and how both are special cases of a more general learning problem: learning the principal eigenfunctions of an operator defined from a kernel and the unknown data-generating density. Whereas spectral embedding methods provided only coordinates for the training points, the analysis justifies a simple extension to out-of-sample examples (the Nystr?m formula) for multidimensional scaling (MDS), spectral clustering, Laplacian eigenmaps, locally linear embedding (LLE), and Isomap. The analysis provides, for all such spectral embedding methods, the definition of a loss function, whose empirical average is minimized by the traditional algorithms. The asymptotic expected value of that loss defines a generalization performance and clarifies what these algorithms are trying to learn. Experiments with LLE, Isomap, spectral clustering, and MDS show that this out-of-sample embedding formula generalizes well, with a level of error comparable to the effect of small perturbations of the training set on the embedding.     

Study of the oxidation kinetics of finely-divided magnetites. II - Influence of chromium substitution

The oxidation kinetics of magnetites substituted by chromium (Fe²⁺Fe³⁺_2?xCr³⁺_x)O^2?₄ (0 < x < 2) into γ(Fe³⁺_1?yCr³⁺_y)₂O^2?₃, (x = 3y), which is a metastable phase, was found out to be ruled by the law of diffusion, under variable working conditions, of vacancies generated at the surface. The chemical diffusion coefficient is a function of the substitution ratio, crystallite size and the number of vacancies in the spinel lattice. Contrary to magnetites substituted by aluminum, the activation energy varies irregularly with the substitution ratio.     

Synthesis of poly(methyl methacrylate)-g-poly(dimethyl siloxane) graft copolymers via a miniemulsion process

Summary In this article, we describe the synthesis of a PMMA-g-PDMS graft copolymer via a miniemulsion process. A highly hydrophobic PDMS macromonomer was copolymerized in the presence of MMA. Latex particles were obtained with a high yield and a complete incorporation of the macromonomer by using AIBN as initiator, SDS as a surfactant and a PMMA-b-PEO block copolymer as a cosurfactant, with a given amount of methanol in order to reduce the interfacial tension. The characterization of the resulting latex by ¹H NMR and QELS evidenced the interest of such a process in order to copolymerize monomers with very different solubilities and to obtain directly a graft copolymer in aqueous dispersion. Received: 12 March 2001/ Revised version: 15 September 2001/ Accepted: 15 September 2001