Al2O3/Yttria‐Stabilized Zirconia Hollow‐Fiber Membrane Incorporated with Iron Oxide for Pb(II) Removal

Removal by absorptive ceramic membranes can simultaneously absorb and separate metal ions from water. Alumina/yttria‐stabilized zirconia (Al₂O₃/YSZ) hollow‐fiber membranes, fabricated using phase inversion and sintering process, were deposited with iron oxide by an in‐situ hydrothermal process. The results showed that α‐Fe₂O₃ was produced and incorporated across the membranes. A reduction in flux was recorded with the deposition of α‐Fe₂O_3. However, it improved the adsorption capacity for heavy metal adsorption. The adsorption‐separation test demonstrated that the optimized membrane is able to completely remove Pb(II) ions after two hours.     

Transesterification of Palm-based Methyl Palmitate into Esteramine Catalyzed by Calcium Oxide Catalyst

The technology for transesterification reactions between methyl esters and alcohols is well established by using classical homogeneous alkaline catalysts, which provide high conversion of methyl esters to specialty or nonindigenous esters. However, in certain products where the purity of the esters is of concern, the removal of homogeneous catalysts after the completion of the reaction is a challenge in terms of production cost and water footprint. Therefore, a study to investigate the potential of heterogeneous catalysts was conducted on reactions between methyl palmitate and triethanolamine. The degree of basicity and active surface area of calcium oxide (CaO), zinc oxide (ZnO), and magnesium oxide (MgO) were first characterized by using temperature-programmed desorption (TPD-CO₂) and Brunauere–Emmett–Teller (BET), respectively. Among the metal oxides investigated, the CaO catalyst showed the best catalytic activity toward the transesterification process as it gave the highest conversion of methyl palmitate and yielded fatty esteramine compositions similar to the conventional homogeneous catalyst. The optimum transesterification condition by using the CaO catalyst utilized a lower vacuum system of approximately 200 mbar, which could minimize a considerable amount of energy consumption. Furthermore, low CaO dosage of 0.1% was able to give a conversion of 94.5% methyl ester and formed esteramine at 170 °C for 2 h. Therefore, the production of esterquats from esteramine may become more economically feasible through the methyl ester route by using the CaO catalyst, which can be recycled three times.     

Study of the effect of BDMA catalyst in the epoxy novolac curing process by isothermal DSC

Epoxy novolac/anhydride cure kinetics has been studied by differential scanning calorimetry under isothermal conditions. The system used in this study was an epoxy novolac resin (DEN431), with nadic methyl anhydride as hardener and benzyldimethylamine as accelerator. Kinetic parameters including the reaction order, activation energy and kinetic rate constants, were investigated. The cure reaction was described with the catalyst concentration, and a normalized kinetic model developed for it. It is shown that the cure reaction is dependent on the cure temperature and catalyst concentration, and that it proceeds through an autocatalytic kinetic mechanism. The curing kinetic constants and the cure activation energies were obtained using the Arrhenius kinetic model. A suggested kinetic model with a diffusion term was successfully used to describe and predict the cure kinetics of epoxy novolac resin compositions as a function of the catalyst content and temperature. Copyright © 2003 Society of Chemical Industry     

基于谐振原理的硅微机械加速度计

基于力学振动原理 ,导出敏感梁类谐振振动的微分方程 ,给出了振梁型加速度计的设计原理。指出了加速度计谐振梁频率的相对变化量与梁的厚度无关 ;为避免输出非线性频率信号 ,频率的相对变化率和激励振动的振幅都不宜太大     

晶须取向对SiCw/6061Al复合材料热压缩变形行为的影响

采用SEM 和 Magiscan-2A 图像分析系统研究了晶须取向对SiCw/6061Al复合材料在300℃压缩变形行为的影响.结果表明:晶须取向影响着晶须折断程度和转动角度; 随着晶须取向角的增加,晶须转动和折断行为所导致的软化效果下降.同时晶须取向也影响复合材料的热压缩应力-应变曲线的形状.在热压缩变形过程中,晶须取向角为0°和30°的复合材料表现出明显应变软化现象, 晶须取向角为45°的复合材料无明显软化现象.晶须取向角为90℃的复合材料表现出应变硬化现象.     

Continuous-wave quantum yields of various cobalamins are influenced by competition between geminate recombination and cage escape

Quantum yields of photolysis of the cobalt-carbon bond for three cobalamin compounds were measured with a continuous-wave laser at 442 nm under both aerobic and anaerobic conditions. Aerobically, the initial homolysis product, Co(II) cobalamin, is trapped by oxygen to form aquocobalamin. Use of an excess of the radical trapping reagent 2,2,6,6-tetramethyl-1-piperidinyloxyl, under anaerobic conditions, scavenges the carbon radical and allows detection of the cobalt(II) photoproduct. Quantum yields measured under anaerobic conditions for 5'-deoxyadenosylcobalamin (phi (Co-C alpha),442 = 0.20 +/- 0.03) and methylcobalamin (phi (Co-C alpha),442 = 0.35 +/- 0.03) are in agreement with the values obtained under aerobic conditions (phi (Co-C alpha),442 = 0.19 +/- 0.04 and phi (Co-C alpha),442 = 0.36 +/- 0.04, respectively). Additionally, the quantum yield values for 5'-deoxyadenosylcobalamin and its base-off derivative (phi (Co-C alpha),442 = 0.045 +/- 0.015) match those obtained on a nanosecond time scale [Chen, E., & Chance, M. R. (1990) J. Biol. Chem. 256, 12987-12994]. A comparison of quantum yields obtained anaerobically for 5'-deoxyadenosylcobalamin and methylcobalamin in H2O versus ethylene glycol shows a 4-fold decrease for the former cobalamin and no change for the latter. These quantum yields are evaluated in terms of time-independent radical separation distances.     

声光效应拉曼-内斯方程矩阵级数解法及声光调制器优化设计

提出一种求解正常声光相互作用拉曼 内斯 (Raman Nath)方程的矩阵级数解法 ,该解法直观方便且具有普遍性。计算结果表明 ,对Q =4 1π ,Bragg衍射的效率只有 97 5 % ;对非对称入射 ,以往的Raman Nath近似解误差较大 ;指出提高Bragg衍射效率的有效途径在于提高声光频率比并给出计算声光器件最优长度的计算公式。     

Spontaneous rise of fetal platelet counts despite increasing anti-HPA-5b antibodies

A 47-year-old woman with seronegative polyarthritis, diarrhea, and photosensitivity dermatitis was found to have Crohn's disease and pellagra. The presence of high values of 5-hydroxyindolacetic acid in the urine began the exhaustive investigations and finally enterotomy. No mass lesion was found. Argyrophilic cells were not increased in areas of inflamed intestinal mucosa or the normal mucosa. The disagreement between biochemical and histologic findings was attributed to sampling error. Antiinflammatory treatment for Crohn's disease was given and the gastrointestinal and articular symptoms improved, excretion of 5-hydroxyindolacetic acid returned to normal and there was no relapse of pellagra. Pellagra as a complication of Crohn's disease has been described in 4 cases; malnutrition and intestinal malabsorption were the proposed mechanisms for the niacin deficiency and pellagra of those patients. In the current case, the pathogenesis of pellagra may be accounted to wastage of tryptophan by an increased pool of intestinal argyrophilic cells, suggested by increased urinary excretion of 5-hydroxyindolacetic acid.     

Improved atrial function in bicaval versus standard orthotopic techniques in cardiac transplantation

Atrial geometry is preserved in the bicaval technique of cardiac transplantation. Using Doppler echocardiography, we investigated the impact of this technique on preservation of atrial function and found that echocardiographic indexes of atrial function are improved in bicaval cardiac transplants versus the standard orthotopic transplants.