Two-component concept

Much of the research pursued by the authors of this paper and by their associates has involved studies of the catalytic hydrogenation of coals in the absence of solvent. The technique has been used to elucidate the mechanisms of catalytic coal liquefaction and to provide simultaneously some insight into the structure of coals. Peter Given was directly instrumental in providing the incentive for this research which has extended since 1983. Previous findings were disseminated through several publications (4-8. In this paper, some of the earlier data have been collated with more recent results (9) to provide an account of the relevance of these studies to the two-component concept. 

The field-density concept is especially usefiil in recognizing the parallelism of path in different physical situations. The criterion is the number of densities held constant the number of fields is irrelevant. A path to the critical point that holds only fields constant produces a strong divergence a path with one density held constant yields a weak divergence a path with two or more densities held constant is nondivergent. Thus the compressibility Kj,oi a one-component fluid shows a strong divergence, while Cj in the one-component fluid is comparable to (constant pressure and composition) in the two-component fluid and shows a weak... 

The Dehye-Hbckel theory of electrolytes based on the electric field surrounding each ion forms the basis for modern concepts of electrolyte behavior (16,17). The two components of the theory are the relaxation and the electrophoretic effect. Each ion has an ion atmosphere of equal opposite charge surrounding it. During movement the ion may not be exacdy in the center of its ion atmosphere, thereby producing a retarding electrical force on the ion. 

Blocked isocyanate, for our purposes, will refer to the reaction product of a diisocyanate or isocyanate-terminated prepolymer in which the isocyanate functionality has been reacted with a blocking agent . Once blocked , the diisocyanate can be added to polyols or certain chain extenders, and these materials will not react at room temperature. The concept is shown in the sixth item of Fig. 1. An adhesive formulated with a blocked isocyanate is basically a two-component adhesive that does not react until heated to the activation temperature. When an adhesive is made with a blocked isocyanate together with hydroxyl-containing curatives, the adhesive has a good long shelf life at room temperature. However, once heated... 

Of course, LC is not often carried out with neat mobile-phase fluids. As we blend solvents we must pay attention to the phase behavior of the mixtures we produce. This adds complexity to the picture, but the same basic concepts still hold we need to define the region in the phase diagram where we have continuous behavior and only one fluid state. For a two-component mixture, the complete phase diagram requires three dimensions, as shown in Figure 7.2. This figure represents a Type I mixture, meaning the two components are miscible as liquids. There are numerous other mixture types (21), many with miscibility gaps between the components, but for our purposes the Type I mixture is Sufficient. 

In studying two-component polymerization catalysts, beginning with Feldman and Perry (161), a radioactive label was introduced into the growing polymer chain by quenching the polymerization with tritiated alcohols. The use of these quenching agents is based on the concept of the anionic coordination mechanism of olefin polymerization occurring... 

The conclusion may be drawn that the data obtained of comparative studies of olefin polymerization by the one-component catalyst (TiCl2) and two-component systems (TiCl2 + AlEtxCl ) confirm the concept of monometallic active centers on the surface of titanium chlorides developed by Cossee and Arlman (170-173). 

Because of its motor, i.e., activating effect on vascular smooth muscle and its inhibitory effect on intestinal smooth muscle, the sympathetic nervous system has been cast into the role of the component of the nervous system that executes control of visceral function in times of physical emergency for the organism. The phrase fight or flight has been often used to describe the circumstances in which the adrenergic transmitters of the sympathetic system are dominant over the cholinergic parasympathetic system. This concept is perhaps oversimplified but it has the utility of a first approximation of how the two components of the ANS interact in the periphery. Sensory inputs which lead to increased blood pressure, for example, activate the sympathetic pathways. 

The concept of clinical synergism, which m be extremely difficult to demonstrate convincingly. Even with trimethoprim plus sulphamethoxazole, where tme synergism occurs in vitro, the optimum ratio of the two components may not always be present in vivo, i.e. at the site of infection in a particular tissue. 

The concept of supercriticality is more complex if a two-component fluid is used. For most mixtures used, SFE must be carried out above a certain pressure to ensure that the fluid is in one phase. For MeOH-C02 mixtures at 50 °C the fluid is in one phase and can be described as supercritical above 95 bar, whatever the composition [284]. Compounds may also be added to the supercritical phase as a reactant rather than as a simple modifier. 

To exploit the concept of PMF to represent solvent in free energy calculations, practical approximations must be constructed. A common approach is to treat the two components Z H/"P(X) and Z lYelec(X) separately. Approximations for the nonpolar term are usually derived from geometric considerations, as in scaled particle theory, for example [62], The electrostatic contribution is usually derived from continuum electrostatics. We consider these two contributions in turn. 

The concept of segregation and its meaning to chemical reactors was first described by Danckwerts (1953). The intensity or degree of segregation is given the symbol I, which varies between one and zero. Shown in Fig. 1 is a tank with two components, A and B, which are separated into volume fractions, qA and l-qA this condition represents complete initial segregation (1 = 1). Stirring or... 

More than 93.5 percent of the variance is explained by the first two components, which tells us that two degrees of freedom describe most of the natural isotopic variation with the five chronometers. This observation has led to the concept of the Mantle Plane of Zindler et al. (1982), since a plane is defined by only two independent variables, and has been extensively discussed by Allegre et al. (1987). 

As a comment to the atomic dimensions concept, two rules , Vegard s andBiltz-Zen s rules, formulated for solid solutions, and to a certain extent for ordered compounds can be mentioned here. These rules, mutually incompatible, are very seldom obeyed they may however be useful either as approximations or for defining reference behaviours. The first one, Vegard s rule (1921), corresponds to an additivity rule for interatomic distances (or lattice parameters or average atomic diameters). For a solid solution (x = atomic fraction) between two components of... 

CNT-based inorganic hybrid materials are part of carbon-based inorganic hybrid materials as anodic electrodes in LIBs. The concept has been proven to be successful at least at laboratory scale, and is promising as a potential alternative to replace graphite-based anodes. However, little is known about the interface structure between CNT and the supported active materials, and thus the electron transfer between the two components. More detailed fundamental research on the interface and interaction between CNTs and active materials at atomic level is needed for a better understanding of the abovementioned improvement. 

There are several directions along which one can generalize the concept of spurious cooperativity discussed in Section 3.5. (1) Instead of equal mole fractions = o = l/2, one can start with any composition of the two components. 

The solid polymer electrolyte approach provides enhanced safety, but the poor ambient temperature conductivity excludes their use for battery applications. which require good ambient temperature performance. In contrast, the liquid lithium-ion technology provides better performance over a wider temperature range, but electrolyte leakage remains a constant risk. Midway between the solid polymer electrolyte and the liquid electrolyte is the hybrid polymer electrolyte concept leading to the so-called gel polymer lithium-ion batteries. Gel electrolyte is a two-component system, viz., a polymer matrix... 

The concept of countercurrent extraction was then introduced, and it was shown how the minimum phase ratio for a given degree of extraction was determined. Countercurrent extraction could yield both high recoveries and concentrated extracts, but studies on two-component extractions soon showed that product purity suffered. 

---