Effect-additive design, mixture studies

The current study deals with experiments designed to investigate specially prepared compositions with mutual contamination between Sn02 and M0O3. The conclusion is, that the contamination, in any form, if formed in the mixture, cannot account for the synergistic effects. Additional experiments conducted with the S ime catalysts in the... 

As mentioned previously, in the AMD retina iron metabolism is compromised (He et al., 2007 Wong et al., 2007). Thus, it is of interest to determine the effects of potential antioxidants in the presence of iron. In an in vitro study of ARPE-19 cells, addition of a lipophilic iron complex led to about a ninefold increase in the photosensitized yield of 7a,(3-cholesterol hydroperoxides (Wrona et al., 2004). In the presence of the iron, ascorbate exerted pro-oxidant effects, while the effects of a-tocopherol, zeaxanthin, or their combination were still protective (Wrona et al., 2004). Thus, it appears that the effects of potential antioxidants are strongly dependent on the sources of oxidative damage. The same antioxidant may be protective under certain conditions and exert deleterious effects when the conditions are changed. Therefore a detailed understanding of the sources of the oxidative damage is required in order to design an adequate antioxidant mixture. 

Some enzymes have been found to be capable of conversion of the polyaromatic sulfur heterocycles in mixtures of an aqueous phase containing buffer+water-miscible solvent and a water-immiscible solvent. For example, conversion of thiophenes and sulfides was demonstrated in an aqueous system with 20% acetonitrile in contact with 0.2% diesel. A process for sulfur removal was designed based on this reaction [394], Additional details were given in Section 4.2.1. In a subsequent study effect of this system on PAH... 

Because there are various options to account for possible combined effects, including concentration addition alone, response addition alone, or concentration addition and response addition in concert, and motives from study quality, assessment endpoint, mechanistic features, and statistical characteristics and biases, there should be a way to logically choose amongst methods for mixture extrapolation. The logical and pragmatic way to choose amongst alternative approaches is to design and follow a tiered approach (see Chapter 1). 

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