Microstructural Evolution in Liquid-Phase-Sintered SiC: Part I, Effect of Starting Powder

The effect of starting SiC powder (β-SiC or α-SiC), with simultaneous additions of Al₂O₃ and Y₂O₃, on the microstructural evolution of liquid-phase-sintered (LPS) SiC has been studied. When using α-SiC starting powder, the resulting microstructures contain hexagonal platelike α-SiC grains with an average aspect ratio of 1.4. This anisotropic coarsening is consistent with interface energy anisotropy in α-SiC. When using β-SiC starting powder, the β→α phase transformation induces additional anisotropy in the coarsening of platelike SiC grains. A strong correlation between the extent of β→α phase transformation, as determined using quantitative XRD analysis, and the average grain aspect ratio is observed, with the maximum average aspect ratio reaching 3.8. Based on these observations and additional SEM and TEM characterizations of the microstructures, a model for the growth of these high-aspect-ratio SiC grains is proposed.     

Adsorption of 4-chlorophenol by inexpensive sewage sludge-based adsorbents

Sewage sludge was used as precursor to develop a potential inexpensive adsorbent by both simple drying and pyrolysis. The resulting materials were evaluated as adsorbents for the removal of 4-chlorophenol (4-CP) from aqueous solution. The dried biosolids showed a BET surface area lower than 3 m²/g, which yield a maximum adsorption capacity of 0.73 mmol 4-CP/g at pH 5.0 and 15 °C. The carbonization of biosolids under relatively mild conditions allowed obtaining materials with BET surface area up to 45 m²/g, which led to a significant increase of the maximum adsorption capacity (1.36 mmol 4-CP/g). The high ash content of the starting material (23%, d.b.) limits the development of porosity on a total dry-weight basis. Adsorption data were well fitted to the Redlich–Peterson isotherm equation whereas the most commonly used Langmuir and Freundlich equations were less satisfactory probably because of the occurrence of summative adsorption phenomenon. A thermodynamic study of the adsorption showed the spontaneous and exothermic nature of the process. Thus, simple drying and carbonization provide two ways of valorization of sewage sludge through its conversion into inexpensive low-rank adsorbents potentially useful for the removal of some hazardous water pollutants, like chlorophenols and related compounds.     

Changes in the milk and cheese fat composition of ewes fed commercial supplements containing linseed with special reference to the CLA content and isomer composition

A study was carried out to increase the CLA contents in ewes’ milk fat under field conditions by dietary means and to investigate the extent of the changes and consequences for milk processing and cheese quality. During a 3-mon period, ewes’ bulk milk samples were collected every week from two different herds. For the first 4 wk the ewes were fed a conventional diet. Then the following 6 wk a supplement enriched in α-linolenate (whole linseed) was incorporated into the ovine diet. Finally, in the last 3 wk the feeding was the same as in the first 4 wk. The FA profile in milk fat was monitored by GC, and the distribution of CLA isomers was thoroughly tested by combining GC-MS of 4,4-dimethyloxazoline derivatives (DMOX) with silver ion-HPLC (Ag⁺-HPLC) of FAME. Reconstructed mass spectral profiles of CLA characteristic ions from DMOX were used to identify positional isomers, and Ag⁺-HPLC was used to quantify them. An increase in total CLA in milk fat was observed, and total CLA remained elevated during the weeks of enriched α-linolenate feeding. In our experimental conditions there was a linear relationship between trans-vaccenic acid (trans-11-octadecenoic acid; trans-11 18∶1) and 9-cis, 11-trans CLA in ewes’ milk fat. Concerning the CLA isomer profile, increases in the 11,13- and 12,14–18∶2 positional isomers were considerable when linseed was included in the diet. Organoleptic characteristics of cheeses made with CLA-enriched milk did not substantially differ from those made with nonsupplemented ewes’ milk. CLA total content and isomer profile did not change during ripening.     

Use of an environmental specimen bank for evaluating the impact of the Prestige oil spill on the levels of trace elements in two species of Fucus on the coast of Galicia (NW Spain)

In the present study we investigated possible contamination by trace elements due to the oil slick caused by the shipwreck of the Prestige oil tanker, in two species of brown macroalgae (Fucus vesiculosus and Fucus ceranoides) collected from the coastal area most severely affected by the spill (Galicia, NW Spain). The oil slick apparently did not cause significant increases in the concentrations of the trace elements studied, except vanadium. It appears that the magnitude of terrestrial inputs to coastal waters is sufficiently high to mask the inputs of trace elements from the fuel. The observed exception of V suggests that bioaccumulation of this element by the two species of Fucus may be used to indicate exposure to petrochemical products similar to the Prestige fuel. The findings of the study are another example of the importance of the existence of Environmental Specimen Banks for studies of this type.     

Hot corrosion behaviour of 7YSZ + Gd2O3 nano-composites in molten salts prepared by spark plasma sintering

This study compares the hot corrosion performance of yttria-stabilised zirconia (7YSZ), and 7YSZ?+?Gd₂O₃ composite samples in the presence of molten mixture of Na₂SO₄?+?V₂O₅ at 1150°C. For 7YSZ, the reaction between NaVO₃ and Y₂O₃ produces YVO₄ and leads the transformation of tetragonal ZrO₂ to monoclinic ZrO₂. A high-density in sintered 7YSZ?+?Gd₂O₃ samples, led minor amounts of monoclinic ZrO₂ and tetragonal GdVO₄ as the hot corrosion products with only traceable amounts of YVO₄, and a stable corroded layer was formed. Due to the synergic effect of doping of zirconia with Gd₂O₃, the 7YSZ?+?Gd₂O₃ sample has a much better hot corrosion crack resistance than 7YSZ.     

Water-Based Graphene Oxide–Silicon Hybrid Nanofluids—Experimental and Theoretical Approach

In the current paper, a new hybrid nanofluid based on graphene oxide sheets and silicon nanoparticles is proposed for thermal applications. GO sheets and Si nanoparticles with different mixture ratios are dispersed in distilled water. Dynamic viscosity is measured at temperatures within the range 20–50 °C and the values are compared to the results available in the literature. The results indicated that the viscosity increases with increasing the mixture ratio of graphene oxide. A new correlation for the dynamic viscosity based on the experimental findings is proposed. Finally, the criteria for the performance of new hybrid nanofluid for thermal applications are analyzed.     

Uncalibrated visual servoing using the fundamental matrix

This paper describes a new algorithm for visual control of an uncalibrated 3 DOF joint system, using two weakly calibrated fixed cameras. The algorithm estimates on-line the Image Jacobian, a matrix which linearly relates joint velocity and image feature velocity. In our experiments we prove that by using the fundamental matrix, robustness of the estimation in the presence of noise is significantly increased with respect to already existing algorithms in specialized literature.     

Multi‐phosphorylation of the Intrinsically Disordered Unique Domain of c‐Src Studied by In‐Cell and Real‐Time NMR Spectroscopy

Intrinsically disordered regions (IDRs) are preferred sites for post‐translational modifications essential for regulating protein function. The enhanced local mobility of IDRs facilitates their observation by NMR spectroscopy in vivo. Phosphorylation events can occur at multiple sites and respond dynamically to changes in kinase–phosphatase networks. Here we used real‐time NMR spectroscopy to study the effect of kinases and phosphatases present in Xenopus oocytes and egg extracts on the phosphorylation state of the “unique domain” of c‐Src. We followed the phosphorylation of S17 in oocytes, and of S17, S69, and S75 in egg extracts by NMR spectroscopy, MS, and western blotting. Addition of specific kinase inhibitors showed that S75 and S69 are phosphorylated by CDKs (cyclin‐dependent kinases) differently from Cdk1. Moreover, although PKA (cAMP‐dependent protein kinase) can phosphorylate S17 in vitro, this was not the major S17 kinase in egg extracts. Changes in PKA activity affected the phosphorylation levels of CDK‐dependent sites, thus suggesting indirect effects of kinase–phosphatase networks. This study provides a proof‐of‐concept of the use of real‐time in vivo NMR spectroscopy to characterize kinase/phosphatase effects on intrinsically disordered regulatory domains.     

Optimal and heuristic solution methods for a multiprocessor machine scheduling problem

This paper deals with the scheduling of operations on a multiprocessor machine in the context of shoe manufacturing. Multiprocessor machines are composed of several parallel processors. Unlike parallel machines, the entire machine needs to be stopped whenever a single processor needs a setup. Our industrial partner, one of the major winter-shoe manufacturers in Canada, offers a relatively large variety of models. For each of these models, all the sizes proposed by this manufacturer must be produced in various quantities. Our objective is to schedule the production of the required sizes on the machine's different processors in order to minimize the global makespan, which includes both the production time and the set up time. We first present a mathematical formulation of the problem. Then, we introduce a decomposition procedure based on the mathematical model, and we demonstrate that this procedure is very efficient for small- and medium-size instances. We also propose two construction heuristics and two improvement heuristics for larger problems, and we report the results of our extensive computational experiments to demonstrate the quality of the proposed heuristics in terms of reducing production time and computational effort.