Evolutionary modification

The classic flowsheet for the production of acetates was unsuitable for adoption for methyl acetate. However, the flowsheet generated by the conventional conceptual process design approach using literature schemes and standard patterns seems especially complicated for such simple chemistry involving so few components. This first flowsheet is a candidate for evolutionary modification. 

One evolutionary strategy is to search for thermodynamic inefficiencies to attack, for example, through exergy analysis. Another strategy is to search for structural inefficiencies including design redundancies. In our first flowsheet, both flash columns have similar feed compositions, both overheads go to the same decanter, and both underflows go to wastewater treatment. Therefore, these 

The relative performances of the original and evolved designs can be determined only by analysis. The evolved design has fewer columns, but has the added complication of either refrigeration or membranes, and the amount of acetic acid which must be separated from water is much increased. The results 

If the hierarchical means-ends analysis synthesis procedure is applied to the methyl acetate problem, the task identification, task integration, and equipment design stages are kept completely separate. Following the property-difference hierarchy, an identity-changing reaction task (Task A) is identified first, as before. When examining the differences between the result of this reaction task application and the product methyl acetate and by-product water destinations, 

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Once acceptable flow sheet is generated, consider evolutionary modification. 

Moderate evolutionary modification of mafic melts during emplacement, with some fractional crystallisation, crustal assimilation (e.g. at Torre Alfina) and unmixing of felsic residual melts at Montecatini Val di Cecina. 

Ps via the intermediate production of Ins(l,4,5,6)P4. Sequence comparisons of the yeast Ins(l,4,5)P3 3/6-kinase with the mammalian Ins(l,4,5)P3 3-kinases demonstrated them to be part of a closely related family and suggested the Ins(l,4,5)P3 3-kinases were merely a recent evolutionary modification and specialization of this catalyticaUy versatile kinase family (24). The cloning... 

There appears to be three fundamental approaches to the synthesis of chemical process flowsheets. The first, systematic generation, builds the flowsheet from smaller, more basic components strung together in such a way that raw materials eventually become transformed into the desired product. The second, evolutionary modification, starts with an existing flowsheet for the same or a similar product and then makes modifications as necessary to adopt the design to meet the objectives of the specific case at hand. The third, superstructure optimization, views synthesis as a mathematical optimization over structure this approach starts with a larger superflowsheet that contains embedded within it many redundant alternatives and interconnections and then systematically strips the less desirable parts of the superstructure away. 

Although much (perhaps most) conceptual process design is in fact done by the evolutionary modification of whole or partial existing flowsheets, it is sometimes necessary to generate a flowsheet from scratch. 

Procedures for the actual synthesis of heat-exchanger networks are somewhat less well developed however, all of the standard process synthesis approaches— including systematic generation, evolutionary modification, and superstructure... 

Algorithmic and/or Heuristic Evolutionary Modification of Fbwsheet Superstructure... 

Orthologous sequences are homologous sequences in different species that have common origin and whose distinctions come about by gradual evolutionary modifications from the common ancestor. Orthologous sequences tend to have the same function in different species. 

Trichome PPO appears to be an example of an evolutionary modification of an existing plant enzyme for use as an insect defense mechanism. PPO enzymes, of molecular weight 45,000, are localized in the thylakoid and are nearly ubiquitous in tissues of plants (12,18.). Unlike other known nuclear encoded chloroplast proteins, the 45 kD thylakoid PPO, whose function is unknown, is translated at its mature size of 45 kD, and does not possess a transit peptide sequence (19). In contrast, the 5 9 kD trichome PPO is translated as a 67 kD precursor and localized in the leucoplasts of trichome and outer epidermal cells. Immunological and primary sequence similarities between the 59 kD trichome PPO and the 45 kD thylakoid PPO underscore the close evolutionary relationship between these two proteins. The apparent advantage of the very high concentration of PPO in the trichome is the high initial rate of catalysis which results upon trichome rupture, facilitating the entrapment of mobile insects. 

The immunochemical cross-reactivity revealed by quantitative precipitin reaction of 22 primate serum albumins with anti-HSA was consistent with the presumed phylogenetic relationships to man on the assumption that the evolutionary modification of protein structure has been... 

The Thylox process is no longer used commercially, while the arsenic-based version of the Giammarco-Vetrocoke process is still supported by the licensor in countries where the use of arsenical solutions is permitted. A non-arsenic, evolutionary modification of the G-V process is currently being offered for CO2 removal, and is claimed to be very competitive. This form of the process can not be classified as a liquid redox process, and is discussed in Chapter 5. 

Jemvall, J., Kerynen, S.V.E., and Thesleff, I. (2000) Quantifying evolutionary modification of development in mammalian molar topography. American Zoologist, 40 1076-1077. 

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