Collagen-coated Ba(2+)-alginate microcarriers for the culture of anchorage-dependent mammalian cells

Several types of microcarriers suitable for large-scale cultivation of mammalian cells are commercially available. However, many of these carriers have disadvantages, e.g., the need for enzymatic digestion for cell harvesting, size limitations and insufficient biocompatibility. These limitations have been overcome by the development of collagen-coated Ba(2+)-alginate microcarriers. Ba(2+)-alginate microspheres, made with the air-jet droplet generator technique, were collagen-coated by incubation in a 0.5% collagen solution, with subsequent gelling of the collagen layer around the alginate microspheres. Human chang liver (CCL-13) and mouse fibroblast (L929) cell lines were cultivated in stationary, unstirred cultures as model systems. After a lag phase of nearly 24 h, the cells grew rapidly on these microcarriers and reached confluence after 3 days. The microcarrier cultures were stable for an additional 4-9 days and longer. Cells were harvested either by trypsinization or by dissolution of the alginate matrix using 5 mM EDTA. The main advantages of this new microcarrier system are that the preparation procedure is easy and can be accomplished on demand with standard laboratory equipment.     

对可持续城镇的探索——一个不可能实现的梦想？

本论文讨论的问题是,为什么在中央和地方政府投入大量资金,而且有规划专家参与的情况下,挪威“可持续城镇”的试验仍然失败了?本论文的主要数据来自国家和地方政府的评估报告,以及作者在《1945~1995:克里斯蒂安桑的规划、实施与结果分析》一文中所作的早期研究。     

The effect of degree of branching on the rheological and thermal properties of hyperbranched aliphatic polyethers

A series of hyperbranched aliphatic polyethers with different degree of branching (DB) and molecular weights have been studied with respect to their rheological and thermal properties. The DB was shown to affect the ability of the polymers to crystallize and thereby also the rheological properties of the polymers. A low DB resulted in semi-crystalline polymers with melting points between 100 and 130°C. The polymers with a higher DB were essentially amorphous and behaved as non-entangled Newtonian liquids in the molten state.     

Clusterwise linear least absolute deviations regression

A FORTRAN subroutine implementation for this purpose is given.     

Nonvolatile reaction products of heat-induced degradation of α-glucans Part II: Analysis of short-chain α-glucans by gas chromatography/mass spectrometry

 By means of model systems, the thermal behaviour of short-chain α-glucans (degree of polymerization, 1–4) as well as that of 1,6-anhydro-β-d-glucopyranose at 180  °C in quasi-waterfree systems was investigated. The main aim was to identify anhydrosugars, isomeric products and other products which cannot be degraded by amylolysis. Using the techniques described it was possible to detect 1,6-anhydrodisaccharides with different linkages, as well as glucobioses and their homologues. Maltulopyranose and its homologues were detected for the first time during thermolysis of the α-glucans, but free fructose has yet to be detected during their thermolysis. A possible mechanism for the formation of maltulopyranose is proposed. Besides these results, the formation of 1,2-anhydrosaccharides as reactive intermediates of thermolysis of α-glucans is reported. Received: 21 November 1997/Revised version: 12 January 1998     

符合ZigBee协议的RF解决方案的实现

IEEE802.15,4/ZigBee是针对无线监测和控制系统的需求而设计的射频标准.设计者可以利用符合ZigBee标准的开发平台,进行ZigBee产品的开发,该平台由硬件和软件组成.这将大大缩短产品上市时间,并减少系统设计及ZigBee认证所需的费用.