Lateral electron transport, effect

As the prospective systems for spintronics, two-dimensional semiconducting electron structures where electrons are localized in the -direction and free in the lateral ones, are assumed. High mobilities of electrons (n > I (P cm2/(Vs)) achievable there make the electron transport easy. In order to discuss the possible effects of SO coupling we will consider three types of structures shown in Fig.l. In these structures, the electron states are extended along... 

Very little is known about the motions of lipid bilayers at elevated pressures. Of particular interest would be the effect of pressure on lateral diffusion, which is related to biological functions such as electron transport and some hormone-receptor interactions. Pressure effects on lateral diffusion of pme lipid molecules and of other membrane components have yet to be carefully studied, however. Figure 9 shows the pressure effects on the lateral self diffusion coefficient of sonicated DPPC and POPC vesicles [86]. The lateral diffusion coefficient of DPPC in the liquid-crystalline (LC) phase decreases, almost exponentially, with increasing pressure from 1 to 300 bar at 50 °C. A sharp decrease in the D-value occurs at the LC to GI phase transition pressure. From 500 bar to 800 bar in the GI phase, the values of the lateral diffusion coefficient ( IT0 cm s ) are approximately constant. There is another sharp decrease in the value of the lateral diffusion coefficient at the GI-Gi phase transition pressure. In the Gi phase, the values of the lateral diffusion coefficient ( 1-10"" cm s ) are again approximately constant. 

Phototaxis in Rb. sphaeroides is triggered by the effects of the photosynthetic machinery on the rate of electron transfer (9). Thus, in contrast to the situation in H. salinarum, phototaxis in Rb. sphaeroides does not involve a dedicated photosensor. The rate of electron transfer is presumably sensed by an as yet unidentified receptor, and relayed into the complex set of Che proteins in Rb. sphaeroides (Fig. 1). Thus, phototaxis responses in Rb. sphaeroides can be regarded as a form of redox taxis and are modulated by factors affecting electron transport, such as the presence or absence of oxygen (19). The Rb. sphaeroides encodes nine transmembrane chemoreceptors (MCPs) and four putative cytoplasmic MCPs, four CheA proteins, and six CheY proteins (20). A number of proteins from this Che system have been shown to be required for phototaxis in Rb. sphaeroides, showing that the signal transduction chains for phototaxis and chemotaxis converge at this level (21). A similar situation holds for phototaxis and chemotaxis in R. centenum (see later). 

The conceptual model followed is the simple three step process where a photon enters the solid causing a transition, the excited electron transports to the surface, and exits. It is assumed that relatively little of interest to a discussion of the excited state (two-peak) structure occurs in the transport so all attention is focussed on the transition. No consideration is given to resonance effects as they are assumed to be a modulation in the driving rate that will cancel out in the energetics. As will be discussed later, in the case that one restricts consideration solely to the two primary channels, one is basically studying the poorly screened and fully screened model (Fuggle et al. 1980) that has been used successfully to interpret the data for the lanthanides (Gudat et al. 1982). 

An SECM feedback response to an electroactive polymer film can be controlled either by ET kinetics at the film-solution interface or by film conductivity. The contribution of lateral film conductivity to the effective ET rate measured by SECM was addressed in the recent study of polyaryl multilayers attached with ferrocenes [65] or ferrocene-terminated dendrimers [69] on unbiased carbon electrodes. In the latter study, the dependence of apparent ET rate constant, feei. on the generation of dendrimers (Table 6.2) was ascribed to the different efficiencies of electron transport inside and between dendrimers (Figure 6.22). Interestingly, the theory of the aforementioned triple potential step method predicts its potential to separately determine heterogeneous ET rate and lateral conductivity for a thin polymer film coated on an insulating surface [70]. 

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