Detour factor

The diffusion coefficient will be lower, the greater the distance the gas must travel in traversing the membrane. Thus bulky monomeric units, fillers, and crystalline regions lower diffusion coefficients (detour factor). The more flexible the chains of the membrane material, the less activation energy will be needed for the diffusion, and the greater also will be the diffusion coefficient. 

In this section, we provide a brief introduction to the field of display engineering and the human-factors issues which dictate display design. We then assess how OLEDs measure up to the criteria necessary to achieve a commercially successful display technology. But first, we take a short detour to lay out the language used by display engineers and to provide a means of translating from the scientific units that wc have used up to now. 

Although the structure of haptens exerts an important influence on catalysis by antibodies, stabilization of the transition state by catalytic antibodies cannot always and cannot fully explain all observations. Sometimes, in analogy to the evolution of enzyme function, antibodies can take mechanistically unexpected detours. As an example, the corresponding antibody catalyzes the hydrolysis of arylamides according to Figure 18.3 by a factor of 2.5 x 105 over background. 

Secondly, even if a reaction looks good on paper and even if thermodynamic factors are favorable (going downhill in free energy), there still must exist a realistic mechanism by which the reaction can occur. No such reaction channel is available for the direct conversion of methane and carbon dioxide into acetic acid. Yet there are ways of going around these apparently insurmountable obstacles. For example, in the present case the following stepwise detour can be proposed ... 

So the key fundamental question here is the following Which precursor-and/or process-driven factors are responsible for this detour from fiat to curved sp structures In competition with the well-documented tendency of (fused) benzene rings to stack parallel to each other and thus retain planarity and resist curvature, there is an apparently effective mechanism for the elimination of pentagons at graphene edges. It is summarized in Table 1.2 and Figure 1.7 and is discussed in some detail below. 

Three of the factors that are crucial to the success of femtochemistry experiments are as follows. First, each laser pulse must last no longer than a few femtoseconds, otherwise there would be unacceptable uncertainty in identifying the moment at which a reaction is started or the time at which a spectrum is recorded. Second, perhaps obviously, the probe pulse must reach the sample within a few tens of femtoseconds after the arrival of the pump pulse. This is achieved by using mirrors to create a detour in the path of each laser beam, with the detour being longer for the probe pulse than for the pump pulse. 

First, we will first discuss the "bulk" molecular devices which have been popular, even though they are molecular devices only in the larger sense (i.e. because of the band structure of the solids, or because of phase change properties, or other bulk effects). Second, a small detour is made to discuss electron transfer within the primary reaction center in photosynthesis, and the controlling factors in intramolecular electron transfer. Third, we will concentrate on the truly unimolecular devices. Fourth and last, a discussion on molecular "wires" and connectors is given. 

The study of atomic structure in Chapter 6 provided an interesting detour into modern physics, and there s no doubt that the paradoxes of quantum mechanics are intellectually intriguing. But quite apart from pure scientific curiosity, the concepts we developed for atomic structure offer important insights into some of the most fundamental questions in chemistry. How and why do atoms combine to form molecules What do those molecules actually look like, and which factors determine their shapes In our technological society, the answers to these seemingly abstract questions can have tremendous practical and economic importance. Knowing how to control or selectively exploit the formation of chemical bonds has played a crucial role in the development of many new materials and devices. 

Nielsen (1967) developed a simple model to describe the permeability of filled-poly-mers on the basis of tortusity argnment. In an ideal case where clay particles are fully exfoliated and uniformly dispersed along a preferred orientation (0 = 0°) in a polymer matrix, the tortuous factor x (defined as the ratio of the detour distance d to the thickness d of the specimen) becomes ... 

The path taken by an ion from one electrode to the other will not be a straight one, as it has to evade the solid structures by making detours. The ratio of the mean actual path in comparison with the direct distance is called the tortuosity factor T. For plastic bodies consisting essentially of spherical, interconnected particles with voids in between, with a porosity of about 60%, this value is roughly 1.3 for higher porosities it decreases to approach a value of 1.0 at very high porosities. 

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