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We demonstrate a highly integrated microfluidic chip with the function of DNA amplification. The integrated chip combines giant electrorheological-fluid actuated micromixer and micropump with a microheater array, all formed using soft lithography. Internal functional components are based on polydimethylsiloxane (PDMS) and silver∕carbon black-PDMS composites. The system has the advantages of small size with a high degree of integration, high polymerase chain reaction efficiency, digital control and simple fabrication at low cost. This integration approach shows promise for a broad range of applications in chemical synthesis and biological sensing∕analysis, as different components can be combined to target desired functionalities, with flexible designs of different microchips easily realizable through soft lithography. 相似文献
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In order to determine the role of time limits on both test performance and test validity, we asked approximately 300 volunteers–prospective graduate students–to each write two essays–one in a 40-minute time period and the other in 60 minutes. Analyses revealed that, on average, test performance was significantly better when examinees were given 60 minutes instead of 40. However, there was no interaction between test-taking style (fast vs. slow) and time limits. 'That is', examinees who described themselves as slow writers/test takers did not benefit any more (or any less) from generous time limits than did their quicker counterparts. In addition, there was no detectable effect of different time limits on the meaning of essay scores, as suggested by their relationship to several nontest indicators of writing ability. 相似文献
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This paper addresses a neglected topic in the knowledge management literature: how the size of a network of actors affects the nature of intra-network social relations and knowledge processes. It makes a theoretical contribution to developing understanding in this area drawing on a range of literatures including practice-based perspectives on knowledge, the literature on the embeddedness of social relations, and relevant knowledge management literature. The central focus of this paper is on the relationship between network size, network density, and how these variables affect intra-network knowledge processes. It suggests that as network size increases network density is likely to decrease (as it becomes problematic for the actors in such networks to retain strong ties with a significant proportion of the network's members), which it will be suggested has significant ramifications for intra-network knowledge processes. This paper concludes by reflecting on the implications of the ideas developed for network-based forms of organizing, and innovation processes. 相似文献
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