Oxygen conditions

Probably the most significant control technology breakthrough came m 1977, when Volvo released a computer-controlled, fuel-mjected vehicle equipped with a three-way catalyst. The new catalytic converters employed platinum, palladium, and rhodium to simultaneously reduce NO and oxidize CO and HC emissions under carefully controlled oxygen conditions. The new Bosch fuel injection system on the vehicle provided the precise air/fuel control necessary for the new catalyst to perform effectively. The combined fuel control and three-way catalyst system served as the foundation for emissions control on the next generation of vehicles. 

Nickel-iron alloys fully immersed in sea-water may suffer localised corrosion which can be severe under conditions where oxygen is constantly renewed at the surface and the formation of protective corrosion products is hindered, e.g. in fully-aerated flowing sea-water. In quieter, less oxygenated conditions, average corrosion rates of Fe-36Ni are low and well below those for mild steel, as exemplified in the data given in Table 3.33 . However the resistance to localised attack is not improved to the same extent. 

Mixed conditioning has also been used. In this, one part of the circuit (usually the low-pressure system) is dosed conventionally, e.g. with hydrazine/ammonia, whilst the high-pressure system is subjected to oxygenated conditions. 

Figure 9.30. Steady-state effect of catalyst potential, Urhe, on the rate enhancement ratios, Ph2 = fH2 / r 2 and po = ro /Iq and on the corresponding consumption rates of hydrogen and oxygen. Conditions as in Fig. 9.26.35 Reproduced by permission of The Electrochemical Society.

GP 2] [R 2] New microstructured silver platelets have no initial activity for ethylene oxide formation [26, 40]. After treatment with the OAOR process, a small increase in activity was observed. After 1000 h of operation under oxygen conditions, larger amounts of ethylene oxide were produced. 

There are examples in which base radicals undergo reaction with adjacent base residues. The 5-(2 -deoxyuridinyl)methyl radical (63, Scheme 8.30) can forge an intrastrand cross-link with adjacent purine residues. Cross-link formation is favored with a guanine residue on the 5 -side of the pyrimidine radical and occurs under low-oxygen conditions. A mechanism was not proposed for this process, but presumably the reaction involves addition of the nucleobase alkyl radical to the C8-position of the adjacent purine residue. Molecular oxygen likely inhibits crosslink formation by trapping the radical 63, as shown in Scheme 8.24. The radical intermediate 89 must undergo oxidation to yield the final cross-linked product 90,... 

Under low oxygen conditions, C5 -sugar radicals can react with the base residue on the same nucleotide. In purine nucleotides, the carbon-centered radical 91 can add to the C8-position of the nucleobase (Scheme 8.31). Oxidation of the intermediate nucleobase radical 92 yields the 8,5 -cyclo-2 -deoxypurine lesion 93197,224,225,230-233 Similarly, in pyrimidine nucleotides, the C5 -radical can add to the C6-position of nucleobase. Reduction of the resulting radical intermediate yields the 5, 6-cyclo-5,6-dihydro-2 -deoxypyrimidine lesion 94,234-236... 

In our study we used commercial microorganisms mixtures especially suited to utilisation of hydrocarbons. The pure strain of Pseudomonas pseudoalcaligenes No 10086, one of the most effective PCBs congeners degrades was used in experiment to check the process effects in both (with and without oxygen) conditions in presence of waste transformer oil. 

As a result of the highly reduced state of petroleum hydrocarbons, the preferred and most thermodynamically terminal electron acceptor for microbial processes is oxygen. The inverse relationship between the concentrations of BTEX and dissolved oxygen within a plume is indicative of the extent of microbial metabolism of this class of contaminant. Data from various sites indicate that the natural attenuation of BTEX proceeds at higher rates under oxygenated conditions. The biodegradation of... 

Despite the fact that dibenzothiophene can be readily oxidized with peracetic acid, it is generally resistant to milder oxidative conditions. It is, for example, stable to heating in an inert solvent at 150° in the presence of bronze and oxygen, conditions under which both biphenyl sulfide and dibenzyl sulfide gave insoluble precipitates. It is not surprising, therefore, that dibenzothiophene has been reported to have little or no antioxidant properties and more recent work has generally confirmed this. Octahydrodibenzothiophene has, however, been reported to be useful as an oil antioxidant. ... 

Compounds tested in a more physiological 3-D environment show increased predictability of in vivo responses and help to span the gap between 2-D tissue culture and animal models. There is also evidence that 3-D cultures can identify active compounds that would fail to show their potential in 2-D (56, 57). The complexity of 3-D cultures can be increased by the addition of one or more cell types (fibroblasts, endothelial cells) and/or culture with different media, substrates, or oxygenation conditions. However, a disadvantage is that there is still a lack of simple, standardized, and reliable 3-D protocols that allow their incorporation into the pre-clinical high-throughput validation and drug evaluation process, although there have been several advances in this area in recent years (30, 58-61). 

Hartmans, K. J. (1993). Influence of low oxygen conditions on dormancy and sprout growth of six seed potato cultivars. Proceedings 12 EAPR Conference, pp 89-90. Paris, France EAPR. 

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