Axial impeller selection for anchorage dependent animal cell culture in stirred bioreactors: Methodology based on the impeller comparison at just-suspended speed of rotation

Animal cells, which are nowadays essential for the industrial production of proteinic compounds, are commonly cultivated inside stirred tank bioreactors. In case of anchorage dependent cells, they are usually fixed on microcarriers. The choice of agitation conditions (impeller type, rotational speed…) in this type of process is not an easy task as it has to fulfil three potentially conflicting goals: (1) maintaining microcarriers in complete suspension, (2) homogenizing the culture medium, and (3) limiting mechanical constraints generated by the hydrodynamics on the cells. The aim of this study is to present an original methodology to select the most appropriate axial impeller for this specific application. Seven propellers are preselected on basis of their characteristics available in the literature. Instead of comparing impellers at a given rotational speed or a given power input, they are compared at their respective minimum impeller rotational speed that leads to a complete microcarrier suspension, i.e. at their respective just-suspended speed N_js. They are then compared at higher rotational speeds N, expressed as multiples of N_js. The impeller classification is based on the intensity of mechanical constraints they produced, evaluated from: (1) the macro-shear rate quantified by the spatial derivative of time average velocity fields measured by P.I.V., (2) the micro-shear rate characterized by the ratio between the microcarrier diameter to the average Kolmogorov scale computed from power input measurements, and (3) the impact of microcarrier collisions on cells described via the turbulent collision severity index also computed from power input measurements. Results show that the 125 mm diameter TTP impeller (Mixel) and the 150 mm diameter Elephant Ear impeller (Applikon) produce the smallest mechanical constraints at their just-suspended speed (50 and 20 rpm, respectively). Moreover, the mechanical constraints they produce increase more slowly with the N/N_js ratio than the mechanical constraints produced by other impellers. These propellers are thus even more advantageous if rotational speeds higher than the just-suspended speed have to be used.     

厚堆积层中大型竖井的开挖施工技术

一座水电站的大型出线竖井深度488.5 m,断面直径14.0 m,采用矿井法正向开挖方案,施工的关键是做好井口防护,控制爆破,监测井壁土层的变形,及时用锚杆加固及注浆,再衬砌井壁混凝土。     

Levels of essential and toxic elements in Porphyra columbina and Ulva sp. from San Jorge Gulf, Patagonia Argentina

Baseline concentration levels of As, B, Ca, Cd, Cr, Cu, Co, Fe, Mg, Mn, Mo, Ni, P, Pb, Se, V, and Zn were determined for Porphyra columbina and Ulva sp. collected from three locations along San Jorge Gulf, in Patagonia Argentina. Elements were quantified by inductively coupled plasma-optical emission spectrometry, with the exception of lead and cadmium in some samples which were determined by electrothermal atomic absorption spectrometry. Three stations with different exposure degree to human activities, Bahía Solano, the mouth of Arroyo La Mata stream and Punta Maqueda, were selected as sampling points. The results showed a wide range of metal retention capacity between the two studied species. Regarding the levels of pollutants found in the researched sites, Punta Maqueda seemed to be less influenced by anthropogenic activities than the other two sites except for Cd. Taking into account their toxicities seasonal variations in Pb and Cd levels were studied in both algae in Punta Maqueda. Maximum concentrations of Cd (9.8 microg g(-1) dry wt.) were observed in P. columbina during winter, and maximum levels of Pb (0.82 microg g(-1) dry wt.) were detected in Ulva sp. during summer. Legislative and health safety aspects were evaluated for Cd and Pb.     

基于挥发性成分分析的葡萄酒产地及品种鉴别研究进展

随着葡萄酒市场的日渐繁荣,消费者越来越注重对葡萄酒品质的追求。葡萄酒的原产地及品种是决定葡萄酒品质的重要因素,而挥发性成分在表征某一特定产地或某一品种葡萄酒中起着重要作用,因此,利用挥发性成分鉴别葡萄酒产地及品种有重要意义。本文介绍了葡萄酒挥发性成分分析方法的研究进展,总结了利用挥发性成分鉴别葡萄酒产地及品种的研究现状,以期促进对葡萄酒挥发性成分的深入研究,为保障葡萄酒的品质和真实性,以及建立更加完善的葡萄酒挥发性指纹图谱提供理论参考。     

闪蒸对昌黎产区‘马瑟兰’葡萄酒单体酚类物质的影响

以欧亚种酿酒葡萄‘马瑟兰’为试材,研究闪蒸处理对葡萄酒发酵及陈酿过程中单体酚类物质和CIELab色泽参数的影响。结果表明,与传统浸渍发酵（对照组）相比,闪蒸有利于提高发酵过程中多数单体花色苷的质量浓度,但不利于保持陈酿过程中各单体花色苷质量浓度。闪蒸增加了葡萄酒发酵及陈酿过程中槲皮素-3-O-葡萄糖苷、儿茶素、反式白藜芦醇及白藜芦醇葡萄糖苷等非花色苷单体酚类物质的质量浓度,但降低了槲皮素、杨梅酮、酚酸类单体酚、顺式白藜芦醇及白皮杉醇等酚类物质的质量浓度。闪蒸处理可降低葡萄酒亮度L*、黄蓝度b*值和色调角hab,显著增加红绿度a*、色度Cab*值,使葡萄酒颜色更红、更深、更耐陈酿,两组葡萄酒间颜色差异明显。结论：闪蒸有利于增加‘马瑟兰’葡萄酒单体酚总质量浓度及葡萄酒颜色的稳定性。     

橡皮布打孔机凹凸模的研究与设计

着重探讨了模架的静力学仿真分析和凹凸模的结构设计,并在此基础上设计制作了橡皮布打孔机.此设备的应用改变了原有的打孔模式,提高了打孔的质量和精度,大幅提高了打孔效率及装卡成功率.     

激光辅助热喷涂NiCoCrAlYTa/ZrO2/BaF2·CaF2涂层的组织及性能∗

高温耐磨涂层是航空发动机关键摩擦副可靠使用的重要保障,鉴于其服役环境日益严苛复杂,进一步提高涂层的高温耐磨性能是十分必要的。利用激光辅助热喷涂技术制备 NiCoCrAlYTa / ZrO₂ / BaF₂·CaF₂ 高温耐磨涂层,利用 SEM、EDS 分析高温耐磨涂层的横截面微观组织及化学成分,研究 ZrO₂ / BaF₂·CaF₂质量分数、激光功率及扫描速度对耐磨涂层微观组织、力学性能及高温耐磨性能的影响。结果表明：激光辅助处理可以诱导耐磨涂层表面形成具有树枝状结构的 ZrO₂陶瓷层; 当激光功率为 80 W,扫描速度为 8 mm / s,喷涂粉末为 75 wt.% NiCoCrAlYTa+25 wt.% ZrO₂ / BaF₂·CaF₂时,制备涂层的微观组织、综合力学性能及高温耐磨性能达到最好;在此工艺参数下,涂层顶部的 ZrO₂ 陶瓷层最为致密均匀,其平均纳米硬度为 13.6 GPa,平均弹性模量为 182.5 GPa,800 ℃时的磨损率为 2.7×10^?5 mm³ ·N^?1 ·m^?1 。将高温耐磨涂层的组分设计与激光辅助热喷涂工艺相结合,可为提高涂层综合性能的提供解决途径。     

用于医疗器械快速灭菌的低温等离子体装置研究

现有低温等离子体技术存在放电范围小、放电电压高等局限性,不适用于大尺寸医疗器械的消毒灭菌。 本文研制了一 种灭菌装置,在较低击穿电压下(大气压氦气 325 V,大气压空气 585 V)产生了大面积等离子体,且创新性地在印刷电路板上实 现了气体放电。 通过 COMSOL 等离子体仿真以及实际放电实验,同时实现了低气压与大气压环境下的均匀辉光放电,放电实 验结果表明:相对气压在-70~ -50 kPa 范围内,击穿电压值最低。 通过灭菌实验,验证了此灭菌装置产生等离子体的灭菌效 能,并对影响灭菌效果的因素进行了探究,灭菌实验结果表明:电源频率是影响灭菌效果的最关键因素,灭菌时间其次,氦气气 压对灭菌效果影响最小。 对于一定浓度的大肠杆菌,6 min 即可达到完全灭菌。     

考虑实时SOC与动态循环效率的电池损耗评估及储能定容策略

笔者提出一种高精度电池寿命损耗评估模型,该模型能充分挖掘厂家提供数据中的有效信息,从而建立起动态循环效率、放电深度（DOD）与实时荷电状态（SOC）应力等因素之间的映射关系。同时,针对采用更精细化的储能模型所引入的非线性项,提出一种基于滚动McCormick松弛方法的优化求解算法,该算法可将原本包含混合整数非线性规划问题转化为混合整数线性规划问题,从而实现优化问题的数值化求解。最后,通过算例证明所提出的精细化电池寿命模型与滚动McCormick求解算法的合理性和优越性。