Available in abundance

Hydrogen (H2) is the simplest molecule and its properties are fully understood. Because this clean resource is available in abundance at a very low cost, catalytic hydrogenation is a core... 

Solar energy is available in abundant supply and nonpolluting. It is an extremely attractive means to convert solar energy to chemical energy. 

The example of HK and GK quoted earlier illustrates how a cell can adapt to relatively sudden (minutes to hours time frame) fluctuations in its environment or physiological circumstances. Suppose, however, that the stimulus to change was more prolonged (hours to days), or that a particular substrate previously absent, becomes available in abundance. Perhaps a preferred substrate becomes unavailable and the cell has to adapt to use an alternative, or a toxin needs to be metabolized quickly. In such circumstances it makes sense to change the concentration of the enzyme itself in order to cope with the new substrate load. 

Glucose is taken up into liver cells when available in abundance in blood, eg, after a meal. 

Optically active aldehydes are available in abundance from amino and hydroxy acids or from carbohydrates, thereby providing a great variety of optically active nitrile oxides via the corresponding oximes. Unfortunately, sufficient 1,4- or 1,3-asymmetric induction in cycloaddition to 1-alkenes or 1,2-disubstituted alkenes has still not been achieved. This represents an interesting problem that will surely be tackled in the years to come. On the other hand, cycloadditions with achiral olefins lead to 1 1 mixtures of diastereoisomers, that on separation furnish pure enantiomers with two or more stereocenters. This process is, of course, related to the separation of racemic mixtures, also leading to both enantiomers with 50% maximum yield for each. There has been a number of applications of this principle in synthesis. Chiral nitrile oxides are stereochemicaUy neutral, and consequently 1,2-induction from achiral alkenes can fully be exploited (see Table 6.10). 

Reactions with alkali feldspars do not provide divalent cations for the precipitation of carbonate minerals and initially were thought to be of little significance for mineral trapping (Gunter et al. 1997). However, more recent work indicates that dissolution of alkali feldspars contributes to the fixing of C02 as the sodium alumino-carbonate mineral dawsonite, NaAlC03(0H)2 (Johnson et al. 2001). In this case, the Na necessary for dawsonite precipitation is available in abundance in the brine, but dissolution of alkali feldspar provides a source of aluminum and neutralizes the acidic C02 according to (Johnson et al. 2001) ... 

At present, HpNC is significantly easier to make than ONC, which is an expensive explosive and also difficult to make. Research is now focused on finding an economical synthetic route and to make it directly by tetramerization of dinitro-acetylene (a compound not yet known). By exploiting the property of TNC (of highly acidic nature) and use of interfacial nitration, TNC is converted to PNC [261]. Acetylene (parent hydrocarbon of dinitroacetylene and a cheap starting material available in abundance) is acidic in nature and therefore, it is speculated that acetylene may be converted to dinitroacetylene by following the approach of conversion of TNC to PNC, followed by its tetramerization resulting in the formation of ONC. 

The raw materials used should be cheap, available in abundance and the process of manufacture should be easy, rapid and safe in all respects. 

In-vitro approach Data are available in abundance concerning metal effects on isolated chloroplasts (for a review, see Clijsters and Van Assche, 1985). All the metals studied were found to be potential inhibitors of photosystem 2 (PS 2) photosystem 1 (PS 1) was reported to be less sensitive. From the in-vitro experiments, at least two potential metal-sensitive sites can be derived in the photosynthetic electron transport chain the water-splitting enzyme at the oxidising side of PS 2, and the NADPH-oxido-reductase (an enzyme with functional SH-groups) at the reducing side of PS 1 (Clijsters and Van Assche, 1985). Moreover, in vitro, non cyclic photophosphorylation was very sensitive to lead (Hampp et al., 1973 b) and mercury (Honeycutt and Korgmann, 1972). Both cyclic and non-cyclic photophosphorylation were proven to be inhibited by excess of copper (Uribe and Stark, 1982) and cadmium (Lucero et al, 1976). 

Nitrogen is a component of amino acids that make up proteins chlorophyll (the molecule that captures the sun s energy) enzymes and the genetic material, nucleic acids. Therefore, this nutrient is required in large amounts by all plants and forms one of three primary nutrients. Although nitrogen is available in abundance... 

On the other hand, onium salts based in N (or S or P) are commercially available in abundance. Extended by introducing a variety of alkyl and aryl groups, they present a large variety of properties, being all liquid electrolytes. 

Because of the individual nature of the problems encountered, we have made no attempt to present detailed methodological information on site-specific modification. This is available in abundance in the books and reviews cited in ch. 1. 

Ethylene glycol was available in abundant quantities because it was derived from ethylene, a by-product in the cracking of petroleum. Ethylene, treated with chlorine water, yields ethylene chlorhydrin, which is converted to ethylene glycol when heated with a mild alkali such as sodium carbonate or calcium hydroxide. 

Polyvinyl chloride, alcohol, acetate, and their copolymers are used to a limited extent for fibre production. They are cheap because the monomers are easily prepared from ethylene or acetylene, both of which are available in abundance. The fibres have not been used much for textiles, however, because they soften at temperatures varying between 50 and 100°C, according to the composition of the polymer. 

Off-the-shelf. Most sundry items, such as laboratory equipment, stationary supplies, etc. are available off-the-shelf. Some raw materials, too, are available off-the-shelf those that are available in abundance and for which there is room to negotiate terms of supply are lavender, citrus oils and peppermint. Climatic or political changes can alter raw materials from readily available to difficult to find, a fact that will increase price dramatically. 

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