Homogeneous Catalysis for the Production of Fine Chemicals. Palladium- and Nickel-Catalysed Aromatic Carbon–Carbon Bond Formation

In this article we describe our recent efforts in the area of palladium- and nickel-catalysed aromatic substitution reactions. Main focus is on low cost and low waste production methods. The use of aromatic carboxylic anhydrides in the Heck reaction leads to a waste-free protocol. In addition these reactions are easy to work up as no ligands or bases are used. For Heck reactions where substrates or products do not tolerate high temperatures we found that use of a bulky phosphoramidite (13b) as ligand for palladium leads to a very fast reaction at low temperatures. Recycle of palladium in ligand-free Heck and Suzuki reactions is easily accomplished by treating the palladium black that precipitates at the end of the reaction on a carrier material with a small excess of I₂ prior to its re-use in the next run. Use of aryl chlorides in the palladium- and nickel-catalysed formation of biaryls can be accomplished by using the nickel-catalysed coupling with arylzinc chlorides. Better still, it was possible to make use of the arylgrignard and use a catalytic amount of ZnCl₂. Whereas the strength of these aromatic substitution reactions lies in their broad tolerance of functional groups, one exception was the Sonogashira reaction on 3-bromoaniline. The problem was solved by making use of in situ catalytic protection of the NH₂ group with benzaldehyde.     

Effect of Silica‐Coated Poly(butyl methacrylate)‐block‐poly(methyl methacrylate) Double‐Shell Particles on the Mechanical Properties of PMMA Composites

Silica nanoparticles with an average diameter of 12 nm are grafted with PBMA‐b‐PMMA double shells through typical sequential ATRP from bromoisobutyrate initiators anchored at the silica surface using an epoxysilane. A commercially available PMMA homopolymer is used for the preparation of composites with unmodified, silane‐modified and double‐shell‐modified silica particles. Good mechanical properties are obtained for silica double shell containing systems. The silica content in double shell particle systems is varied from 0 to 2.5 wt%. A significant improvement in impact properties is observed. The surface‐modified silica particles are characterized by ATR‐FTIR, NMR, GPC, and thermal analyses. TEM analysis is used to analyze the nature of dispersion of particles in the composites.

     

Morphology and thermomechanical properties of recycled PET–organoclay nanocomposites

Recycled PET/organoclay nanocomposites were prepared by melt intercalation process with several amounts (1, 3, and 5 wt %) of clay modified with quaternary ammonium salt (DELLITE 67G) dispersed in a recycled poly(ethylene terephthalate) (rPET) matrix. The resultant mechanical properties (modulus and yield strength) of the nanocomposites were found to be different from those of rPET. Wide angle X‐ray scattering (WAXS) and Transmission Electron Microscopy (TEM) measurements have shown that although complete exfoliation was not achieved, delaminated clay platelets could be observed. Thermal analysis did not show significant changes in the thermal properties from those of recycled PET. Mechanical testing showed that nanocomposite properties were superior to the recycled PET in terms of strength and elasticity modulus. This improvement was attributed to nanoscale effects and strong interaction between the rPET matrix and the clay interface, as revealed by WAXS and TEM. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1839–1844, 2007     

拼焊板方盒件拉延实验研究

对相同材料不同厚度，不同材料相同厚度，不同材料不同厚度的拼焊板方盒件进行了拉深实验研究，得到了盒底部焊缝向厚板侧移动，侧壁处焊缝向薄板侧移动的焊缝移动规律，分析了压边力，材料强度对焊缝移动距离的影响，分析了法兰区的起皱和局部过度减薄等工艺缺陷。     

Cr(VI) removal from synthetic and real wastewaters: The use of the invasive biomass Sargassum muticum in batch and column experiments

The macroalgae Sargassum muticum was selected for the treatment of solutions containing Cr(VI). Very acidic pH values were established as optimal for Cr(VI) reduction. Algae chemical modification reduced equilibrium time to 4 h. First order kinetic model was used to describe the reduction kinetic of Cr(VI). A column experiment allowed to distinguish the processes occurring during Cr(VI) elimination: its reduction to Cr(III) and the subsequent adsorption of this species formed. Under the selected conditions the biomass was capable of reducing all the incoming Cr(VI) during 77 h. Industrial wastewaters from chrome plating industry were also tested for chromium removal.     

Effects of genomic selection on genetic improvement, inbreeding, and merit of young versus proven bulls

Genomic selection has the potential to revolutionize dairy cattle breeding because young animals can be accurately selected as parents, leading to a much shorter generation interval and higher rates of genetic gain. The aims of this study were to assess the effects of genomic selection and reduction of the generation interval on the rate of genetic gain and rate of inbreeding. Furthermore, the merit of proven bulls relative to young bulls was studied. This is important for breeding organizations as it determines the relative importance of progeny testing. A closed nucleus breeding scheme was simulated in which 1,000 males and 1,000 females were born annually, 200 bulls were progeny tested, and 20 sires and 200 dams were selected to produce the next generation. In the “proven” (PROV) scenario, only cows with own performance records and progeny-tested bulls were selected as parents. The proportion of the genetic variance that was explained by simulated marker information (M) was varied from 0 to 100%. When M increased from 0 to 100%, the rate of genetic gain increased from 0.238 to 0.309 genetic standard deviations (σ) per year (+30%), whereas the rate of inbreeding reduced from 1.00 to 0.42% per generation. Alternatively, when young cows and bulls were selected as parents (YNG scenario), the rate of genetic gain for M = 0% was 0.292 σ/yr but the corresponding rate of inbreeding increased substantially to 3.15% per generation. A realistic genomic selection scheme (YNG with M = 40%) gave 108% higher rate of genetic gain (0.495 σ/yr) and approximately the same rate of inbreeding per generation as the conventional system without genomic selection (PROV with M = 0%). The rate of inbreeding per year, however, increased from 0.18 to 0.52% because the generation interval in the YNG scheme was much shorter. Progeny-testing fewer bulls reduced the rate of genetic gain and increased the rate of inbreeding for PROV, but had negligible effects for YNG because almost all sires were young bulls. In scenario YNG with M = 40%, the best young bulls were superior to the best proven bulls by 1.27 σ difference in genomic estimated breeding value. This superiority increased even further when fewer bulls were progeny tested. This stochastic simulation study shows that genomic selection in combination with a severe reduction in the generation interval can double the rate of genetic gain at the same rate of inbreeding per generation, but with a higher rate of inbreeding per year. The number of progeny-tested bulls can be greatly reduced, although this will slightly affect the quality of the proven bull team. Therefore, it is important for breeding organizations to predict the future demand for proven bull semen in light of the increasing superiority of young bulls.     

Explaining the variation in the shear force of lamb meat using sarcomere length, the rate of rigor onset and pH

The temperature when the pH=6.0 (temp@pH6) impacts on the tenderness and eating quality of sheep meat. Due to the expense, sarcomere length is not routinely measured as a variable to explain variation in shear force, but whether measures such as temp@pH6 are as useful a parameter needs to be established. Measures of rigor onset in 261 carcases, including the temp@pH6, were evaluated in this study for their ability to explain some of the variation in shear force. The results show that for 1 day aged product combinations of the temp@pH6, the pH at 18 °C and the pH at 24 h provided a larger reduction (almost double) in total shear force variation than sarcomere length alone, with pH at 24 h being the single best measure. For 5 day aged product, pH at 18 °C was the single best measure. Inclusion of sarcomere length did represent some improvement, but the marginal increase would not be cost effective.