Preparation and in vitro studies of microencapsulated cells releasing human tissue inhibitor of metalloproteinase-2

Objective: To prepare microencapsulated cells releasing human tissue inhibitor of metalloproteinase-2 (TIMP-2), and investigate their biological characteristics in vitro. Methods: Chinese hamster ovary (CHO) cells were stably transfected with a human TIMP-2 expression vector, encapsulated in barium alginate microcapsules and cultured in vitro. Morphological appearance of the microcapsules was observed under a light microscope. Cell viability was assessed using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Enzyme linked immunosorbent assay (ELISA) and reverse zymography were used to confirm the release of biologically active TIMP-2 from the microcapsules. Cryopreservation study of the microencapsulated cells was carried out using dimethyl sulfoxide (DMSO) as preservative agent. Results: The microcapsules appeared like a sphere with diameter of 300–600 μm. The surface of the capsule wall was clearly smooth. The microencapsulated cells survived well and kept proliferating over the 6 weeks observed. No significant difference in TIMP-2 secretion was found between encapsulated and unencapsulated cells. Reverse zymography confirmed the bioactivity of MMP (matrix metalloproteinase) inhibition of TIMP-2. The cryopreservation process did not damage the microcapsule morphology nor the viability of the cells inside. Conclusion: Microencapsulated engineered CHO cells survive at least 6 weeks after preparation in vitro, and secrete bioactive TIMP-2 freely from the microcapsules.     

双作用叶片泵定子内表面曲线的分析与改进

本文针对目前使用的双作用叶片泵定子内表面存在的缺点进行分析,提出新的解决办法,即用新型的改进型梯形过渡曲线代替传统的等加速等减速过渡曲线.     

不可逆回热斯特林热泵的生态学优化研究

应用有限时间热力学理论，探讨热阻及回热损失对一类斯特林热泵的生态学优化性能的影响，所得结论可为斯特林热泵的研制和设计提供新的理论指导。     

变频调速在供水系统中的应用

本文介绍了在供水系统中选择变频调速的原因;分析了一种变频调速供水装置的主电路、控制电路、工作原理及应用效果。     

地表水源热泵系统水体初始温度分布模型

以滞留水体为地表水源热泵系统为研究对象,进行水温初始温度分布分析.根据水温控制方程和水流控制方程建立了二维初始水温模型,求得了水体初始水温的数值分布,并对计算结果和实际测试数据进行了对比分析.该温度分布模型可以应用于地表水源热泵初始水体的适应性研究,为动态负荷下水体水温变化规律的研究奠定了基础.     

离心泵的机械密封技术改造

文章对泵传统轴封泄漏成因进行了分析,结合生产实际情况,采用成熟的技术成果对循环水泵的密封实施改造,实现了节约成本又方便检修维护的目的。     

大学生心泵功能现状特点及体育锻炼对策

采用实验测试方法对１１２６名大学生８项心泵功能指标进行纵向对比，分析大学生心泵功能现状特点、发展趋势及与体育锻炼的关系。研究结果表明：１）目前在校四个年级男大学生心功能各项指标呈持续增长趋势，而高年级女大学生的心功能明显下降；２）入学时来自农村的大学生功能优于来自城市的大学生，而在大学高年级则呈相反趋势；３）将两次测试的心泵功能指标对比发现，入学时心泵功能水平男学生１９９５年比１９９１年要高，但大学四年级毕业时大多数指标１９９５年比１９９１年差；４）大学生心泵功能检测结果大多数指标显示大学生高年级有所下降，据此提出了体育锻炼对策     

计算机在抽油机井间抽制度优选中的应用

本文给出了抽油机井间歇抽油时,间抽时间的确定方法,并用Deiphi语言编制了相应的实用软件.经过大庆采油一厂14口井的使用,具有方便、快捷、实用等优点,日节电7028kwh,泵效提高17%,对低产井开采具有较强的实用价值.     

脯酰肽内切酶抑制剂的研究进展

介绍了国内外对脯酰肽内切酶(PEP)抑制剂的最新研究进展．     

Experimental performance of moderate and high temperature heat pump charged with refrigerant mixture BY-3

Theoretical and experimental analysis of a new refrigerant mixture BY-3 was conducted based on a single-stage vapor compression refrigeration system. The water-water heat pump system used BY-3 to produce hot water when the low temperature was 20 ℃. The following results were obtained: the highest temperature at the condenser outlet reached about 85 ℃; when the difference between the water temperatures at the condenser outlet and the evaporator inlet was less than 40 ℃, the coefficient of performance (COP) was larger than 4; when the difference reached 55 ℃, the COP still kept 3; the discharge temperature of BY-3 was lower than 100 ℃, and the refrigerant vapor pressure kept lower than 1.8 MPa. When the water temperature at the condenser outlet reached over 85 ℃, nearly a 5 ℃ superheating temperature was maintained.