Ion-release, dissolution and buffering by zinc phosphate dental cements

The interaction of zinc phosphate dental cement with aqueous solutions has been studied in order to elucidate the relationship between pH change and ion release (dissolution). For each storage medium (deionized water, lactic acid at pH 2.7 and lactate buffer at pH 2.2) five cylindrical specimens of zinc phosphate cement (6 mm diameter×12 mm height) were prepared and weighed. They were stored individually in 8 cm³ of solution for a week, then the pH was determined and the specimens reweighed. The solutions were replaced and the specimens stored for a further week, then the pH and the weight were again measured. This was repeated for four weeks. For each storage solution at each time interval, the concentration of ions leached (Na, Mg, Al, Zn and P) were determined using ICP-OES. The lactate buffer was particularly erosive and reduced specimens to 4.1% (±0.9%) of their original mass after 4 weeks. The lactic acid was also erosive, but in water, specimens showed no significant mass change after 4 weeks. In all media, Na, Al, Mg, Zn and P ions were released, with mole ratios varying at each time interval. In all cases, the pH shifted towards neutral, but the relationship between ion release and solution pH was not straightforward. From the mole ratios of ions, estimates could be made of the relative proportions of attack at matrix to attack at filler, and this showed attack at filler predominated in most solutions at most time intervals.     

Epoxidation of cyclohexene on Nb-containing meso- and macroporous materials

Various niobium-containing meso- and macroporous materials were prepared and characterised by means of XRD and H₂-TPR techniques, scanning electron microscopy (SEM), and sorption measurements. They were tested in the liquid phase oxidation of cyclohexene to epoxide with hydrogen peroxide. The effect of various parameters such as a nature of solvent, material structure, atmosphere on the activity and selectivity of the reaction was studied. NbMCM-41 and NbSM-2 materials are highly active in the epoxidation.     

使用高场非对称波形离子迁移谱（FAIMS）技术提高液相色谱-质谱（LC-MS）分析的选择性

对一些审查严格的应用领域,如制药工业等,方法的选择性至关重要.高场非对称波形离子迁移谱(FAIMS)技术可以有效提高方法的选择性.本文描述了这种与色谱和质谱正交的技术,并显示了在LC-MS流程中它能够显著提高实验室的产出率.     

Ultra-extensible solvent-free elastomers based on nanocomposite poly(2-methoxyethylacrylate)/clay xerogels

Physically cross-linked solvent-free supramolecularly assembled nanocomposite elastomers were prepared, which displayed exceptionally high extensibility (up to 6000%), besides generally high mechanical properties (G' in rubber region between 1.5 and 40 MPa). The nanocomposites are based on linear poly(2-methoxyethylacrylate) (polyMEA) and montmorillonite clay (physical cross-linker), and were obtained via free-radical polymerization of the monomer in the presence of the exfoliated nanofiller dispersed in water. The mechanical properties of the studied products were varied in a very wide range by changing the concentrations of the radical redox co-initiator pair, at given constant nanofiller loadings. The latter in turn also strongly altered the product properties. This applied synthesis approach, aimed at obtaining longer elastic chains, made possible to increase the elongation at break up to six times, and also to tremendously and simultaneously increase the toughness (effect of entanglements), as well as to shift the tensile curves between “plastic-like elastomer” and “simple elastomer.” In all cases, however, the nanocomposite samples displayed a highly efficient recovery, even after very high deformations. The structure–property relationships were deeper elucidated by thermo-mechanical analysis (DMTA), TGA (thermal stability, elastic chains' immobilization), TEM and X-ray diffraction.     

Oxidation of ethanol over supported manganese catalysts—effect of the carrier

MnO_x catalysts supported on alumina, titania or yttria-stabilised zirconia were studied in ethanol oxidation. Catalysts were characterized by determining their XRD, TPR, TPD-O₂ and TPD-NH₃ properties and light-off behavior. The effect of kind of carrier on activity in the ethanol oxidation and on selectivity to acetaldehyde (ACA) was determined. Relation between the TPR properties of the catalysts and their activity in ethanol conversion is suggested. The maximum of selectivity to ACA appears in the same sequence of temperatures as the first peak of oxygen desorption from supported MnO_x catalysts.     

The selective catalytic oxidation of methane to methyl bisulfate at ambient pressure

The selective catalytic oxidation of methane in 25 wt.% oleum to methyl bisulfate at ambient pressure in presence of PtCl₄ catalyst was investigated. The reaction between methane and sulfuric acid took place at atmospheric pressure if the mass transfer between gas and liquid was sufficient. The process was carried out at 130–220 °C in absorption reactor packed with glass balls 1.5–7 mm in diameter.     

Organosilicon sulfides as co-initiators in photoinduced free radical polymerization

Summary Three sulfur-containing silanes (organosilicon sulfides) were investigated as electron donors in photoinduced free radical polymerization, in conjunction with xanthene dye (5,7-diiodo-3-butoxy-6-fluorone, DIBF) as sensitizer. The results were compared with the nonsulfur-containing silane, N-((trimethylsilyl)methyl)aniline (K1) and thiophenoxyacetic acid (TPAA). The kinetic studies clearly showed that the DIBF-organosilicon sulfides exhibit a significant increase in the efficiency of free radical polymerization of TMPTA compared to nonsulfur-containing silane and that the efficiency of all tested electron donors is only slightly dependent on the structure of the sulfur-containing co-initiators.     

Dietary fish oil dose- and time-response effects on cardiac phospholipid fatty acid composition

Fish consumption is associated with reduced cardiovascular mortality, and elevated myocardial long-chain n−3 polyunsaturated FA (PUFA) content is implicated in this cardioprotection. This study examined the dose and time responses for incorporation of n−3 PUFA into cellular membranes in rats fed fish oil (FO)-containing diets. For the time course study, rats were fed a 10% FO diet for periods ranging from 0 to 42 d, after which myocardial and erythrocyte membrane fatty acid composition was determined. For the dose response study, rats (n=3) were fed 0, 1.25, 2.5, 5, or 10% FO for 4 wk, with myocardial, erythrocyte, and skeletal muscle membrane FA determined. Myocardial DHA (22∶6n−3) levels doubled in 2 d, stabilizing at levels ≈200% higher than control after 28 d feeding with 10% FO. By comparison, DHA levels doubled after 4 wk of 1.25% FO feeding. In myocardium and skeletal muscle, EPA (20∶5n−3) levels remained low, but in erythrocytes EPA levels reached 50% of DHA levels. The n−3 PUFA were incorporated at the expense of n−6 PUFA in myocardium and skeletal muscle, whereas erythrocytes maintained arachidonic acid levels, and total n−3 PUFA incorporation was lower. This study shows that low doses of FO produce marked changes in myocardial DHA levels; maximal incorporation takes up to 28 d to occur; and while erythrocytes are a good indicator of tissue n−3 incorporation in stable diets, they vary greatly in their time course and pattern of incorporation.