Polarization configuration, ideal

The competition between the polar and steric dipoles of molecules may also lead to internal frustration. In this case, the local energetically ideal configuration cannot be extended to the whole space, but tends to be accomodated by the appearance of a periodic array of defects. For example, the presence of the strong steric dipole at the head of a molecule forming bilayers will induce local curvature. As the size of the curved areas increases, an increase in the corresponding elastic energy makes energetically preferable the... 

The location of the acyl chain is of primary importance in the binding process because of its size. Due to the movement of lid during interfacial activation, a hydrophobic trench is created between the lid and enzyme surface. The trench size is ideal to accommodate the acyl chain. Interactions between the non-polar residues of the trench and the non-polar acyl chain stabilize the coupling. It has been postulated that the configuration of the trench is responsible for substrate specificity. This hypothesis seems plausible since lipases usually discriminate against certain acyl chain lengths, degrees of unsaturation, and location of double bonds in the chain. Any of these factors could affect the interaction between the acyl chain and the trench. 

A very interesting application of the classical current interruption technique has been reported by Lorenz and Eichkom [67], who showed that by adopting the galvanostatic configuration it is possible to evaluate the importance of the ohmic drop realistically, point by point, and obtain polarization curves with a trend very close to the ideal one. In fact, it can be experimentally demonstrated that the value of R, is not constant but is influenced by the mass transfer when the current flowing in the electrolytic cell is sufficiently high. In other words, it cannot be excluded a priori that the quantity R, depends on the electrode overvoltage. 

The stationary arrangement of components used in EDXRF is ideally suited for geometrical configurations that exploit polarization phenomena to reduce background and thereby improve signal-to-noise ratios. 

Major improvements in predicting wetting and wettability of polymer systems need major advances in two specific areas a) the molecular configuration at the solid/ liquid boundary especially for relatively polar materials and, b), the wettability of non-ideal (heterogeneous) surfaces. The reader is recommended to two reviews that discuss very recent advances in these and related areas. 

Important electrical characteristics of an electrode/tissue system are determined solely by the geometrical configuration. To clarify this important function, the systems to be treated in Chapter 6 are simple models suited for basic analysis and mathematical treatment as well as computational approaches such as finite element analysis (Section 6.5). In bioimpedance systems, the biomaterial is usually an ionic wet conductor, and the current carrying electrodes are polarized. However, in fliis chapter, the models are idealized in several ways. Biomaterial is considered homogeneous and isotropic. An electrode is considered isoelectric (superconducting metal). Only DC systems without polarization phenomena and frequency dependence are considered. Then a potential difference between two points in tissue space is equal to the voltage difference found between two circuit wires connected to the same two points,... 

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