Combinations in general

Increased effectiveness of organic acids may be achieved when used in lower concentrations, but in combination with additional inhibitors. For example, combining nisin with reduced organic acid concentrations may decrease potential flavor flaws in meat products (Samelis et al., 2005). Citric and ascorbic acids, in combination, are effective in inhibiting growth and toxin production of C. botulinum type B in vacuum-packed foodstuffs (Barbosa-Canovas et al., 2003 Samelis et al., 2005). In other studies, a combination of equal amounts of ascorbic acid and citric acid did not have additional benefits, compared with using ascorbic acid alone (Mancini et al., 2007). 

A combination of fumaric acid (0.15%) and sodium benzoate (0.05%) was more effective against E. coli 0157 H7 than a combination of fumaric acid (0.15%) and potassium sorbate (0.05%). This combination has been found to possess even more potent antimicrobial activity than sodium benzoate (0.05%) plus potassium benzoate, which is a common commercial practice (Comes and Beelman, 2002). 

Chill-wash combined with citric acid and followed by low-temperature incubation with or without the presence of nisin, is also useful in the poultry industry for raw poultry products (Phillips and Duggan, 2002). Hot water washings, followed by an organic acid rinse have been widely evaluated on beef carcasses. The inclusion of organic acid rinses further reduces the bacterial populations. The greatest reductions in E. coli populations are found when combining hot water and acid treatment (Eggenberger-Solorzano et al., 2002). 

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The resolution of the y-camera is determined by both the collimator and the crystal/photomultipher tube combination. In general, the resolution is significantly poorer than that of other modaUties such as magnetic resonance imaging (mri) and x-ray computerized tomography (ct). For single-photon... 

Combining techniques introduces new considerations and new problems. If two purification techniques each give 10-fold enrichment for the desired protein when executed independently on a crude extract, it does not mean that they give 100-fold enrichment when combined. In general, they give somewhat less. As a rule, purification techniques that combine most effectively usually are based on different properties of the protein. For example, a technique based on size fractionation is more effectively combined with a technique based on charge than with another technique based on size fractionation. 

An analysis similar to those just presented can be done for other possible coupling combinations. In general,... 

The effort to obtain a clear understanding of the nature of valence and of chemical combination in general has led in recent years to the dissociation of the concept of valence into several new concepts—/onic valence, oxidation number, covalence, coordination ni/mber—corresponding to different modes of interaction of the atoms. These new concepts are discussed in later sections. 

Figure 2.6. Idealized glass-rubber transition behavior of incompatible two-polymer combinations. In general, both glass-rubber transitions will be observed. ...

However, as in all technique combinations one should carefully weigh the advantages of combining experiments against the (slight) loss in data quality that is intrinsic to these technique combinations. In general the synergy of simultaneously obtained data sets is only useful in the case of faster time-resolved experiments or in special cases where there is only a limited amount of sample material available. 

Selection of stationary phases is, therefore, limited for these preparative techniques. The only materials which can be used are those for which an additional amount of binder endows the necessary stability and does not impair the separation these can be silica, kieselguhr, alumina, plaster of Paris (76), and their combinations. In general, silica gel of TLC quality (15 pm average particle size) with gypsum binder is used with additional binder, 3.5% calcium sulfate hemihydrate. If other types of silica without binder are used, approximately 20% of the binder must be added. It is reconunended that several layers be prepared together and stored in a safe place. They can be activated before use. Precoated glass rotors (1,2, or 4 mm layer thickness) are available from Analtech (Newark, Delaware, USA). 

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