Optimization obstacles

In subsequent chapters we will examine these obstacles and discuss some ways of mitigating such difficulties in performing optimization, but you should be aware these difficulties cannot always be alleviated. 

It is not surprising that multistep synthesis of challenging and complex target molecules is an engine for the discovery of new synthetic principles and novel methodology which may have very broad application. Just as each component of structural complexity can signal a strategy for synthesis, each obstacle to the realization of a chemical synthesis presents an opportunity for scientific discovery. 5.10 Optimization of a Synthetic Sequence... 

Only a few years ago it was widely accepted that the cofactor regeneration problem represented a serious obstacle with respect to the commercial viability of enzymatic redox processes. Hopefully it is clear from the preceding discussion that there is no longer a cofactor regeneration problem anymore than there is an enzyme problem . The number of readily available enzymes has increased dramatically in the last decade and advances in in vitro evolution have made it possible to routinely optimize the performance of enzymes. The coupling of enzymes in multi-enzyme cascade processes is an attractive way to regenerate cofactors, shift equilibria towards products and remove intermediate products that cause inhibition. Hence, we expect that multi-enzyme cascade processes will become much more common in the future. 

External excitatory and inhibitory stimuli for acceptance or rejection of food are modified by the internal condition of the insect (e.g., hunger). This modification can cause a given stimulus to produce different responses, depending upon the internal condition of the insect. After host acceptance, there are still obstacles that the insect must overcome in order to survive, grow, and reproduce. These hurdles include allelochemicals that block nutrient availability, defenses of susceptible plants, poor balance of essential nutrients, and less than optimal water content. Neonate larvae may be far more sensitive to some of these obstacles than older ones. 

For oxide CMP at PMD and ILD levels, a pilot wafer must be run to estimate the optimal polish time, prior to processing a whole lot. This not only wastes precious production time but also adds a human factor into the process control, a major obstacle that hinders CMP from becoming a true mass-production tool in Si processing. In addition, due to the fact that the polish rate may vary from wafer to wafer in CMP, the final remaining PMD... 

The use of simulation tools (e.g., computer programs) to calculate curing conditions is an area of great interest and is increasingly used to optimize cure for several processes including LCM [32,35] however, there are some obstacles to the use of this advanced route, such as the need of ... 

This condensation helps one understand why the yield of pyrroles from ketoximes and acetylene is reduced in some cases and consequently allows a more directed search for ways to overcome this obstacle. Optimization of this side reaction would make possible a one-pot preparation of valuable dipyrroles with cyclopropyl or vinyl substituents, such as 98a,c for example. 

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