Dissolved oxygen choice

It has been shown that various small scale models consisting of idealized reactor types can be used to simulate large scale fermentation processes, with respect to dissolved oxygen inhomogeneities. The reaction kinetic expressions, material balances on substrates, and products have to be formulated and solved in the context of the combined model network. The choice of the model configuration depends on (1) the system that has to be simulated, (2) knowledge of the hydrodynamics of the system, and (3) the equipment available and financial resources. 

Henry s law makes a strange standard state, because its f° = Hi does not correspond to the behavior of pure i but rather to the behavior of i in the solution as x,- —> 0.00. This is one of the reasons it says in Chapter 7 that is sometimes chosen to correspond to the fugacity of pure i at this temperature and pressure and sometimes not. For dissolved oxygen in liquid water at 68°F there is no pure state of pure liquid oxygen, because oxygen cannot exist as a liquid at this temperature. The fact that Henry s law leads to this strange value off seems to have no practical consequences, and is pointed out here only to remind the reader that we make several choices for f°, some of them not very intuitive. (Some authors make much of this unimportant distinction, under the name unsymmetrical standard states.)... 

Any chemical species that tends to prohibit photopolymerization reactions, even in small concentrations, is called quencher. Oxygen is just one of many choices of quencher [154-156]. By attentively adding prescribed quenchers into resin solution, it is much easier to control polymerization than use of dissolved oxygen. Figure 22 shows line structures of 100 nm width that were two-photon photopolymerized with the same resin, SCR 500, except for an additional quencher. It is believed that by properly choosing quencher species and optimizing their concentration, a further decrease of polymerized voxel size is possible. 

At elevated temperatures where titanium alloys could be the adherend of choice, a different failure mechanism becomes important. The solubility of oxygen is very high in titanium at high temperatures (up to 25 at.%), so the oxygen in a CAA or other surface oxide can and does dissolve into the metal (Fig. 12). This diffusion leaves voids or microcracks at the metal-oxide interface and embrittles the surface region of the metal (Fig. 13). Consequently, bondline stresses are concentrated at small areas at the interface and the joint fails at low stress levels [51,52]. Such phenomena have been observed for adherends exposed to 600°C for as little as 1 h or 300°C for 710 h prior to bonding [52] and for bonds using... 

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