Hostile environment concept

Environmental contamination usually consists of a mixture of pollutants and their partially degraded derivatives. Such an ill-defined chemical mixture will eventually lead to the formation of an ecosystem of microbes. The individual member species cannot survive in the toxic and hostile environment. Effective bioremediation technologies should therefore invoke a mixture of microorganisms forming synergistic consortia. Any realistic bioremediation concept is based on the recognition that it is the concerted action of various species, which may bring about the desired clean-up effect. 

On the basis of the experience with Tazerka and units installed in other pans of the world, we believe that the concept of a floating production, storage, and offloading system offers an excellent possibility for the development of a marginal field and/or for application as an early production facility. We also believe that the good results obtained in relatively mild environments (the Mediterranean. Santa Barbara Channel, and the Philippines) and the successful operation of a floating storage unit in the North Sea justify the statement that an FPSU could be applied successfully in more hostile environments such as the North Sea and other comparable areas. 

This concept is illustrated in Fig. 8.11 for a poly(ethylene terephthalate) substrate and a mild steel (ferric oxide) substrate with, in both cases, water as the hostile environment. Values of y and yl of the various adhesives may be measured, as described in Chapter 2, or extracted from the literature (see Table 2.3) for example, considering a styrene-butadiene rubbery adhesive the values are 27.8 and 1.3 mJ/m, respectively, and for a typical epoxy adhesive they are 41.2 and 5.0 mJ/m, respectively. Hence, it is evident that these (and most other) adhesives will form an environmentally water-stable interface with the poly(ethylene terephthalate) substrate but an unstable interface with mild steel. Indeed, the data confirm that if only secondary molecular forces are acting across the interface then water will virtually always desorb organic adhesives, which typically have low surface free energies of less than about 60 mJ/m, from a metal oxide surface. Hence, for such interfaces, stronger intrinsic adhesion forces must be forged which are more resistant to rupture by water. 

It is already over two decades since the first concepts of the use of fiber optic techniques for sensor purposes were discussed. The initial drive for the development of fiber optic sensors came from their potential use in military and aerospace applications where the cost factors of the introduction of new technology were less rigid and the working environment more hostile than is experienced with other areas of application. 

Various formulation concepts have been introduced as potential ways to protect peptide and protein drugs from the hostile GI environment to increase their oral absorption such as use particulate drug carriers (microspheres, lipo-somes, and lectins), coadministration of enzyme inhibitors and absorption enhancers, use of chemical modification (prodrug), and site-specific delivery to the colon or rectum. Some of these approaches are discussed later. 

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