Contact hypothesis

Proponents of the contact hypothesis contend that inter-group contact between people of equal status in harmonious circumstances will cause them to become less prejudiced and to abandon previously held racial stereotypes. They point... 

Dixon, J., Durrheim, K, Tredoux, C. (2005). Beyond the optimal contact strategy A reality check for the contact hypothesis. American Psychologist, 60, 697-711. 

These polymers by virtue of their chemistry self assemble in aqueous media,driven by the entropy gain associated with the liberation of water bounding the previously unassociated hydrophobic entities — the so called hydrophobic association. Self assembly yields extremely stable entities with critical micellar concentrations in the iM range, compared to the mM range seen for surfactants such as Triton-X 100 and the pluronic block copolymers. This exceptional stability stems from the ability of each amphiphilic molecule to engage in multiple hydrophobic associations proof of this multiple hydrophobic contact hypothesis is provided by evidence that more stable micelles (with a... 

It was concluded33,34 these gelation phenomena are consistent with the segment-segment contact hypothesis of Frenkel et al. O We now extend this conclusion to include the earlier "cold spot" hypothesis of Ueberreiter. 30... 

Correlations of nucleation rates with crystallizer variables have been developed for a variety of systems. Although the correlations are empirical, a mechanistic hypothesis regarding nucleation can be helpful in selecting operating variables for inclusion in the model. Two examples are (/) the effect of slurry circulation rate on nucleation has been used to develop a correlation for nucleation rate based on the tip speed of the impeller (16) and (2) the scaleup of nucleation kinetics for sodium chloride crystalliza tion provided an analysis of the role of mixing and mixer characteristics in contact nucleation (17). Pubhshed kinetic correlations have been reviewed through about 1979 (18). In a later section on population balances, simple power-law expressions are used to correlate nucleation rate data and describe the effect of nucleation on crystal size distribution. 

Komatsu [478] has put forward the hypothesis that reaction in many powder mixtures is initiated only at interparticle contact and that product formation occurs by diffusion through these contact zones. Here, one of the participating reactants is not covered with a coherent product layer. Quantitative consideration of this model leads to a modified Jander equation. 

The mechanism by which these solutes exert their influence on protein stability is uncertain. The phenomenon has been extensively studied by Timasheff and his colleagues and their conclusion is that all of the protein structure-stabilising compounds are preferentially excluded from contact with the surface of the protein (Timasheff, 1982). This explanation is rather different from that invoked in the water replacement hypothesis. 

Based on this hypothesis we reversed the order in which the reactants are brought into contact. Consequently, we added an aqueous solution of BPA, sodium hydroxide, and phase transfer catalyst into a well-stirred solution of cyanogen bromide in carbon tetrachloride. Under these conditions poly(iminocarbonates) of high molecular weight were readily obtained (Fig. 8.)... 

The central hypothesis of the knowledge-based approach [16, 17] is that pairwise contacts follow an exponential Boltzmann-like distribution [33] according to its interaction energy... 

Among MC lattice models of the double layer, it is also worth mentioning the work of Nazmutdinov et al. (1988), who used a lattice model involving two mono-layers of water molecules on the surface of an electrode, forming a hexagonal close-packed array. The interaction of each water molecule in contact with the metal surface (assumed to be Hg) was taken from quantum-mechanical calculations. Information was obtained concerning the relative numbers of molecules with different numbers of hydrogen bonds, and it was concluded that the hypothesis of an icelike state of water in a monolayer on Hg is rather unlikely. 

A hypothesis that edge and corner sites work as active sites can explain why turn over frequency (TOF), which is defined as the reaction rate per one active site, in the case of metal catalysts, per surface exposed metal atom, increases with a decrease in the diameter of gold particles. However, it fails to explain the significant contribution of support materials and the contact structure of gold NPs. It seems to be reasonable that those edges and corners act as the sites for adsorption of one of the reactants, for example, CO in its oxidation. 

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