Supported gold catalysis in the hydrogenation of canola oil

The catalytic activity of gold supported on silica orγ-alumina has been studied in the hydrogenation of canola oil. In the hydrogenation of butadiene and pentene using these catalysts, high stability, low yield oftrans-isomers and high monoene selectivity have been reported in the literature. Catalysts containing 1% and 5% Au w/w on porous silica andγ-alumina were active in hydrogenating canola oil in the range of 150 to 250 C and 3550 to 5620 kPa. The activity level of these catalysts was about 30 times lower than that shown by the standard AOCS Ni catalyst based on the concentration of metal (g Au/L oil). Up to 91% monoene content was obtained using these catalysts in comparison with a maximum of 73% for the AOCS standard Ni catalysts. Gold catalysts can be recovered easily by filtration and reused several times without a decrease in activity. The hydrogenated oil was nearly colorless. No gold was detectable in the oil. Contrary to claims in the patent literature, the gold catalyst produces higher concentrations oftrans-isomers than does nickel. However, using gold catalysts the complete reduction of linolenic acid in canola oil can be achieved at a lowertrans-isomer content in the products than that obtained by using the AOCS standard nickel catalyst.     

Technical note The application of selective principal components analysis (SPCA) to a Thematic Mapper (TM) image for the recognition of geomorphologic features configuration

Selective principal components analysis (SPCA) has been applied to highly- and/or little-correlated subgroups of bands. Its usefulness was demonstrated in two ways. First, the final result is a false colour composition based on the first order principal component of each highly correlated subgroup of bands, the resulting image containing more than 95 per cent of the total variance of the six TM bands used. Secondly, the second order principal component of pairs of little-correlated bands will show the information that is unique for each band. Both types of analysis have been applied to characterize the geomorphological units at a site in SW Spain. Both methodologies have demonstrated to be very useful in a difficult to access area, with high vegetation diversity covering quite different geomorphic features.     

A Coarse-Grained Parallel Algorithm for the All-Substrings Longest Common Subsequence Problem

Given two strings A and B of lengths n_a and n_b, respectively, the All-substrings Longest Common Subsequence (ALCS) problem obtains, for any substring B' of B, the length of the longest string that is a subsequence of both A and B'. The sequential algorithm for this problem takes O(n_a n_b) time and O(n_b) space. We present a parallel algorithm for the ALCS problem on the Coarse-Grained Multicomputer (BSP/CGM) model with p < √n_a processors, that takes O(n_a n_b/p) time, O(log p) communication rounds and O(n_b √n_a) space per processor. The proposed algorithm also solves the basic Longest Common Subsequence (LCS) problem that finds the longest string (and not only its length) that is a subsequence of both A and B. To our knowledge, this is the best BSP/CGM algorithm in the literature for the LCS and ALCS problems.     

Recent advances in cancer therapy

The treatment of cancer has developed substantially from its conception in the first years of the 20th century. Since the introduction of alkylating agents during second World War, the oncology specialty has markedly grown. In the recent years, new drugs have been approved for the treatment of cancer. Such examples include the taxanes (Docetaxel and Paclitaxel), Vinorelbine, Irinotecan, Topotecan, Gemcitabine and Gliadel. We will discuss these new chemotherapuetic agents, their pharmacology, indications, toxicity and appropriate dosing. There is no doubt that further clinical research is needed to determine the optimal use of these agents.     

Confined melting in deformable porous media: A first attempt to explain the graphite/salt composites behaviour

This paper deals with phase change in composite materials made of graphite and a phase-change material (PCM). The composites are manufactured by compressing a solid mixture of salt and graphite particles. In previous works, the interest of such materials for thermal energy storage at high temperature has been highlighted. They are characterized by quite high energy storage capacity as well as high thermal conductivity. However, first melting/crystallization of these composites could lead to significant salt leakage and shows some a priori unexpected features like melting over a range of temperature instead of at constant temperature and significant loss of heat storage capacity. A poro-thermo-elastic analysis is carried out in this paper for understanding salt melting within the graphite matrices and for proposing reliable ways for composite materials improvement. An intentionally simple think-model, based on mass and energy conservation equations, pressure-dependent liquid–crystal equilibriums, linear elasticity laws and Poiseuille-like flow, is proposed. In spite of the simplicity, the model turns out to be apt to explain main macroscopic features of materials melting as observed in calorimetric tests. The influence on melting dynamics of parameters like the heating rate, the pore-wall rigidity and thickness, the salt volume expansion and the pore connectivity is investigated and several ways for composite materials improvements are discussed.     

Damage by eutectic particle cracking in aluminum casting alloys A356/357

The strain dependence of particle cracking in aluminum alloys A356/357 in the T6 temper has been studied in a range of microstructures produced by varying solidification rate and Mg content, and by chemical (Sr) modification of the eutectic silicon. The damage accumulates linearly with the applied strain for all microstructures, but the rate depends on the secondary dendrite arm spacing and modification state. Large and elongated eutectic silicon particles in the unmodified alloys and large π-phase (Al₉FeMg₃Si₅) particles in alloy A357 show the greatest tendency to cracking. In alloy A356, cracking of eutectic silicon particles dominates the accumulation of damage while cracking of Fe-rich particles is relatively unimportant. However, in alloy A357, especially with Sr modification, cracking of the large π-phase intermetallics accounts for the majority of damage at low and intermediate strains but becomes comparable with silicon particle cracking at large strains. Fracture occurs when the volume fraction of cracked particles (eutectic silicon and Fe-rich intermetallics combined) approximates 45 pct of the total particle volume fraction or when the number fraction of cracked particles is about 20 pct. The results are discussed in terms of Weibull statistics and existing models for dispersion hardening.     

A micro-mechanics damage approach for fatigue of composite materials

A new model for fatigue damage evolution of polymer matrix composites (PMC) is presented. The model is based on a combination of an orthotropic damage model and an isotropic fatigue evolution model. The orthotropic damage model is used to predict the orthotropic damage evolution within a single cycle. The isotropic fatigue model is used to predict the magnitude of fatigue damage accumulated as a function of the number of cycles. This approach facilitates the determination of model parameters since the orthotropic damage model parameters can be determined from available data from quasi-static-loading tests. Then, limited amount of fatigue data is needed to adjust the fatigue evolution model. The combination of these two models provides a compromise between efficiency and accuracy. Decomposition of the state variables down to the constituent scale is accomplished by micro-mechanics. Phenomenological damage evolution models are then postulated for each constituent and for the micro-structural interaction among them. Model parameters are determined from available experimental data. Comparison between model predictions and additional experimental data is presented.     

A micromechanics approach for damage modeling of polymer matrix composites

A new model for damage evolution in polymer matrix composites is presented. The model is based on a combination of two constituent-level models and an interphase model. This approach reduces the number of empirical parameters since the two constituent-level models are formulated for isotropic materials, namely fiber and matrix. Decomposition of the state variables down to the micro-scale is accomplished by micromechanics. Phenomenological damage evolution models are then postulated for each constituent. Determination of material parameters is made from available experimental data. The required experimental data can be obtained with standard tests. Comparison between model predictions and additional experimental data is presented.