Control systems, technically complex activities

The complexities of protocols for fluorescent and chromogenic in situ hybridization necessarily entail careful attention to controls. In particular, the possibility of native enzyme activity or the presence of endogenous biotin in the experimental tissue should be considered, though this can be addressed by exposing control tissue to the detection system in the absence of probe. The relative merits of digoxigenin versus biotin, and some of the technical problems associated with each, have been previously discussed (Chevalier et al., 1997 Luo and jackson, 1999). 

Control of stereoselectivity is easier with homogeneous than with heterogeneous catalysts. On the other hand, these soluble catalysts are more difficult to separate and to handle than the technically well-established heterogeneous catalysts. A promising strategy to combine the best properties of the two catalyst types is the heterogenization or immobilization of active metal complexes on insoluble supports or carriers [1, 2, 3]. Besides easy separation, immobilization opens opportunities like, e.g., the use of continuous flow reactors [4,5,6], site isolation [7], or the tuning of the catalyst environment [8,9,10] which in some cases can lead to improved catalytic performance. On the other hand, immobilization increases the complexity and the costs of the catalytic system. 

System safety is an approach to accident prevention that involves the detection of deficiencies in system components that have a potential for failure or an accident. Some component deficiencies lead to failures for the entire system. System safety is the application of technical and managerial skills to the systematic, forward-looking identification and control of hazards throughout the life cycle of a system project, program or activity. People developed system safety methods especially for complex systems. 

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