Reduction artificial processes

Overhead costs, artificial Overhead costs become direct costs Overhead value analysis Overhead cost reduction Business processes Smoothing factor Alpha Primary data... 

Figure 20. Artificial muscle under work. In reduction (A) electrons are injected into the polymer chains. Positive charges are annihilated. Counter-ions and water molecules are expelled. The polymer shrinks and compaction stress gradients appear at each point of the interface of the two polymers. The free end of the bilayer describes an angular movement toward the left side. (B) Opposite processes and movements occur under oxidation. (Reprinted from T. F. Otero and J. Rodriguez, in Intrinsically Conducting Polymers An Emerging Technology, M. Aldissi, ed., pp. 179-190, Figs. 1,2. Copyright 1993. Reprinted with kind permission of Kluwer Academic Publishers.)...

Much interest has recently been shown in artificial photosynthesis. Photosynthesis is a system for conversion or accumulation of energy. It is also interesting that some reactions occur simultaneously and continuously. Fujishima et al. [338] pointed out that a photocatalytic system resembles the process of photosynthesis in green plants. They described that there are three important parts of the overall process of photosynthesis (1) oxygen generation by the photolysis of water, (2) photophosphorylation, which accumulates energy, and (3) the Calvin cycle, which takes in and reduces carbon dioxide. The two reactions, reduction of C02 and generation of 02 from water, can occur simultaneously and continuously by a sonophotocatalytic reaction. 

A separate class of experimental evaluation methods uses biological mechanisms. An artificial neural net (ANN) copies the process in the brain, especially its layered structure and its network of synapses. On a very basic level such a network can learn rules, for example, the relations between activity and component ratio or process parameters. An evolutionary strategy has been proposed by Miro-datos et al. [97] (see also Chapter 10 for related work). They combined a genetic algorithm with a knowledge-based system and added descriptors such as the catalyst pore size, the atomic or crystal ionic radius and electronegativity. This strategy enabled a reduction of the number of materials necessary for a study. 

Aprotic solvents mimic the hydrophobic protein interior. However, a functional artificial receptor for flavin binding under physiological conditions must be able to interact with the guest even in competitive solvents. As found by spectroscopic measurements with phenothiazene-labeled cyclene, the coordinative bond between flavin and Lewis-acidic macrocyclic zinc in methanol was strong enough for this function. Stiochiometry of the complex was proved by Job s plot analysis. Redox properties of the assemblies in methanol were studied by cyclic voltammetry which showed that the binding motif allowed interception of the ECE reduction mechanism and stabilisation of a flavosemiquinone radical anion in a polar solvent. As a consequence, the flavin chromophore switched from a two-electron-one-step process to a two-step-one-electron-each by coordination. 

Deactivation of an excited species can proceed through radiation or radiationless decays, energy transfer quenching, or electron transfer routes. The operation of artificial photosynthetic devices relies mainly on electron-transfer (ET) processes induced by an excited species [16, 17]. Two general mechanisms can be involved in the ET process of an excited species Reductive ET quenching of an excited species, S, by an electron donor D, results in the redox products S- and D+ (Fig. 4 a). Alternatively, oxidative quenching of the excited species by an electron acceptor, A, can occur (Fig. 4b), resulting in the electron transfer products S+ and A-. 

Fig. 7. General scheme of an artificial photosynthetic device S — photosensitizer, A — electron acceptor, D — electron donor, and P2 — reactants (substrates) for the reduction and oxidation processes, respectively...

Table 1 summarizes several redox transformations that can be accomplished in artificial photosynthetic assemblies including the photolysis of water, carbon dioxide reduction, and nitrogen fixation processes. The endoergicities of these transformations, and the number of electrons involved in the reduction processes, are also indicated in the table. It is evident that the energy per electron to drive the various transformations are met by visible light quanta. 

C1-reduction products and certainly to higher oligomerized reduced products. Also, reduction of C02 in an aqueous medium is anticipated to be accompanied by the competitive reduction of water (H2 evolution), see Eq. (25). Thus, the intermediary redox species generated in an ET process could yield a mixture of products. Catalysts could play a central role in inducing selectivity and in controlling a desired specific route that utilizes the ET products. Thus, one can define three complementary functions of catalysts in artificial photosynthetic devices ... 

For a bulk macroscopic electrode, where reduction (or oxidation) of a solution species occurs, the limiting current i, is given by Eq. (26), where Z is the number of electrons participating in the redox process, F is the Faraday constant, D0 and C0 are the diffusion coefficient and concentration of the solution species respectively, and is the width of the diffusion layer [81]. In an artificial photosynthetic... 

---