Very high interactions

If the precipitation takes place, an opaque product is obtained, whereas a transparent appearance denotes a material having a very high interaction of the sites of the opposite character. Many solvents cause opacity, but the resin produced may still completely lack the desired ion-exchange properties. Most of solvents have a very weak influence, but an exception arises in the case of aliphatic acids. Possibly, the solvent competes with the acidic monomer for the amine hydrochloride, thus minimizing the association of the acidic and basic monomers. 

Thus, it would be expected that at least a small fraction of Ni-Cu intermetallic compound may be formed. In fact, theoretical studies carried out on Ni-Cu systems indicate that the formation of bimetallic Ni-Cu clusters with an important surface nickel enrichment is very likely [14]. Taking into account the peculiar characteristics of the starting oxide precursor, in which a very high interaction between Ni and Cu cations exists, and the TPR results, we suggest that the formation of some Ni-Cu bimetallic clusters in the Ni-Cu-Zn-Al system could be possible In other words, since the catalytic behaviour of the Ni-Zn-Al system is significantly modified by the addition of Cu, it is very likely that some kind of interaction between Ni and Cu exists. It is probable, then, that the Ni-Cu-Zn-Al catalyst is constituted by monometallic nickel and copper clusters strongly interacting, and/or bimetallic Ni-Cu clusters. 

A similar study of the nitration of 2,5-dichloro- and 2,5-dibromo-nitrobenxene under a variety of conditions has been made. At the very high acidities in oleum the o /)-ratio for nitration was less than unity. It increased with decreasing acidity of the medium and became greater than unity at roughly the acidity represented by 89-90 % sulphuric acid. The results were interpreted in terms of the interaction between the nitronium ion and the nitro group, but the results are complicated and the interpretation not compelling. 

The term chiral recognition refers to a process m which some chiral receptor or reagent interacts selectively with one of the enantiomers of a chiral molecule Very high levels of chiral recognition are common m biological processes (—) Nicotine for exam pie IS much more toxic than (+) nicotine and (+) adrenaline is more active than (—) adrenaline m constricting blood vessels (—) Thyroxine an ammo acid of the thyroid gland that speeds up metabolism is one of the most widely used of all prescription... 

There is assumed to be no interaction between the superfluid and normal components, thus the superfluid component can diffuse very rapidly to a heat source where it absorbs energy by reverting to the normal state. It thereby produces the very high effective thermal conductivity observed in helium II. 

At very high dopant concentrations, transport occurs direcdy between the dopant molecules. The polymer acts only as a binder in most cases. Taking TPD-doped PVK as an example, at low TPD concentrations the hole mobihty first decreases from 3 x 10 cm /Vs to 10 cm /Vs with increasing TPD concentration, because TPD molecules act as hole traps (48,49). At higher TPD concentrations, new direct transport channels between the TPD molecules open up and the hole mobihty increases to lO " cm /Vs for ca 60% TPD doping (Table 1, entries 9—11) (48,49). In this case, there is no evidence for unusual interaction between TPD and PVK that affects the hole transport process. 

Adhesion to Metals. For interaction between coating and substrate to occur, it is necessary for the coating to wet the substrate (107). Somewhat oversimplified, the surface tension of the coating must be lower than the surface tension of the substrate. In the case of metal substrates, clean metal surfaces have very high surface tensions and any coating wets a clean metal substrate. 

In contrast, the alkane chains on the polymeric phase cannot collapse in an environment of water as they are rigidly held in the polymer matrix. Thus, the retention of the solute now continuously falls as the methanol concentration increases as shown in Figure 4. It should be pointed out that if the nature of the solutestationary phase interactions on the surface of a bonded phase is to be examined in a systematic manner with solvents having very high water contents, then a polymeric phase should be used and brush type reversed phases avoided if possible. 

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