Feature-level evolution

Budding on the general wafer removal models of the previous section, this section considers models related to how wafer surface material is planarized. These include models for feature-level evolution, and die-level models for planarization as functions of layout, pad, and asperity properties. Again, our goal is not to provide a comprehensive survey of existing CMP models instead, our purpose is to present models that demonstrate how key physical effects in planarization can be predicted. 

Feature-level models considering local topography evolution... 

All the four essential features of the active site of chymotrypsin are thus also present in subtilisin. Furthermore, these features are spatially arranged in the same way in the two enzymes, even though different framework structures bring different loop regions into position in the active site. This is a classical example of convergent evolution at the molecular level. 

David Turnbull, in his illuminating Commentary on the Emergence and Evolution of Materials Science (Turnbull 1983), defined materials science broadly as the characterisation, understanding, and control of the structure of matter at the ultramolecular level and the relating of this structure to properties (mechanical, magnetic, electrical, etc.). That is, it is Ultramolecular Science . In professional and educational practice, however, he says that materials science focuses on the more complex features of behaviour, and especially those aspects controlled by crystal... 

The evolution of antiviral resistance for viruses discussed in this chapter (HIV, HBV, HCV, and Influenza virus) shares some common features. Replication in vivo results in the generation of viral variation and selection of preexisting viruses from the population occurs under particular conditions. This will only happen when the escaping viruses have a sufficient level of both resistance and RC. In most cases, the resistance level subsequently increases further by the gradual acquisition of further mutations. Additional compensatory mutations then accumulate that help to restore full RC in the third stage. 

From the atomic to the macroscopic level chirality is a characteristic feature of biological systems and plays an important role in the interplay of structure and function. Originating from small chiral precursors complex macromolecules such as proteins or DNA have developed during evolution. On a supramolecular level chirality is expressed in molecular organization, e.g. in the secondary and tertiary structure of proteins, in membranes, cells or tissues. On a macroscopic level, it appears in the chirality of our hands or in the asymmetric arrangement of our organs, or in the helicity of snail shells. Nature usually displays a preference for one sense of chirality over the other. This leads to specific interactions called chiral recognition. 

In the last 20 years, a new problem, the evolutionary origin of levels of organization, or evolutionary transition, has been added to those celebrated since Darwin (Buss, 1987). In their recent book, The Major Transitions in Evolution, Maynard Smith and Szathmary (1995, p. 6) identified what they considered to be eight major originations of new levels of organization (Table 11.1). For most of these, they claimed a common feature . .. entities that were capable of independent replication before the transition... 

In recent years no truly new basic principles have been introduced for the detection of luminescence. However, the technical evolution in the field of microelectronics and optoelectronics, charge coupled device (CCD) detectors, fiberoptics, assembly techniques, and robotics resulted in the introduction on the market of new generations of instruments with increased performance, speed, and ease of handling. In this chapter, some of their typical features will be reviewed. To keep this presentation at a concrete level and to illustrate some specific item, instruments of different makes will be referred to. However, this does not imply they are better than those not cited. It is more a matter of availability of recent documentation at the time of writing. Note that numerical values cited typically relate what can be done today and may vary from one instrument to another from the same company. 

Successful molecular evolution that puts strict demands on accurate transfer of molecular information executed by highly precise control of size, shape, topology, flexibility, and surface chemistry at the molecular level. The latter five features have been dubbed critical molecular design parameters. 

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