Build-up approach

The petrochemical industry typically works on a build-up approach where the base oil feedstock is fractionated, and complex materials are built up from simpler ones, producing a wide array of materials in the process, for a range of market outlets. The future exploitation of plant materials is seen in a somewhat similar fashion, although in contrast to the petrochemical industry, there will typically be an initial breaking up of more complex materials into simpler building blocks that can then be utilised and built on with the support of chemical, biochemical and catalytic processes, to produce more complex products synonymous with those produced by today s petrochemical industry. This whole crop approach to industrial use of plant-derived material is typically termed biorefining (see Chapter 1). 

The build-up approach has also been used to predict DNA structures. The number of degrees of torsional freedom is much greater for the nucleic acid subunits than for amino acids and currently requires access to supercomputer resources in order to surmount the vast combinatorial explosion. The building blocks used in the reported work are the 16 deoxydinucleoside monophosphates (Figure 6), which were combined to give a variety of molecules, the largest of which was a d(CG)6 d(CG)e dodecamer. In this case the lowest energy structures were the B and Z forms. 

Recently developed techniques for the fabrication of thin-film metal phosphates and phosphonates provide another method for the preparation of layered solids at surfaces. Layers of precisely controlled thickness can be built up by alternate immersion of a suitably pretreated surface in aqueous solutions of a soluble phosphate or phosphonate followed by an appropriate metal salt. This leads to the sequential build-up of thin metal containing films at the surface [72, 214] (see figure 6.18). The method is quite flexible and can be used to build up mixed microporous films on the surface which show molecular sieving properties [215, 216]. This building up approach looks very attractive for the systematic development of thin, selective films. 

Recognizing the efficiencies of the petroleum refinery in producing a large variety of products simultaneously, conventional thought is that the most effective plan for conversion of bioresources will be through a biorefinery process. In the petrorefinery process based on a build-up approach, feedstocks such as crude oil... 

There is some uncertainty connected with testing techniques, errors of characteristic measurements, and influence of fectors that carmot be taken into account for building up a model. As these factors cannot be evaluated a priori and their combination can bring unpredictable influence on the testing results it is possible to represent them as additional noise action [4], Such an approach allows to describe the material and testing as a united model — dynamic mathematical model. 

Figure 2 4 uses electrostatic potential maps to show this build up of electron den sity m the region between two hydrogen atoms as they approach each other closely enough for their orbitals to overlap... 

Nanaomycin A 103 and deoxyfrenolicin 108 are members of a group of naphthoquinone antibiotics based on the isochroman skeleton. The therapeutic potential of these natural products has attracted considerable attention, and different approaches towards their synthesis have been reported [65,66]. The key step in the total synthesis of racemic nanaomycin A 103 is the chemo-and regioselective benzannulation reaction of carbene complex 101 and allylacety-lene 100 to give allyl-substituted naphthoquinone 102 after oxidative workup in 52% yield [65] (Scheme 47). The allyl functionality is crucial for a subsequent intramolecular alkoxycarbonylation to build up the isochroman structure. However, modest yields and the long sequence required to introduce the... 

Nanotechnology is the branch of engineering that deals with the manipulation of individual atoms, molecules, and systems smaller than 100 nanometers. Two different methods are envisioned for nanotechnology to buUd nanostructured systems, components, and materials. One method is the top-down approach and the other method is called the bottom-up approach. In the top-down approach the idea is to miniaturize the macroscopic structures, components, and systems toward a nanoscale of the same. In the bottom-up approach the atoms and molecules constituting the building blocks are the starting point to build the desired nanostmcture [96-98]. 

The bottom-up approach contains two distinct stages. First, by successive backpropagation steps one builds a decision policy. Then, this uncovered policy is evaluated and refined, and its expected benefits confirmed before any implementation actually takes place. This two-stage process is conceptually similar to dynamic programming solution strategies, where first a decision policy is constructed by backward induction, and then one finds a realization of the process for the given policy, in order to check its expected performance (Bradley et al., 1977). 

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