Microscopic conductivity

Fast VG, Kleber AG Microscopic conduction in cultured strands of neonatal rat heart cells measured with voltage sensitive dyes. Circ Res 1993 73 914-925. 

The process of ATP-vesicle fusion with the cell membrane was visualized using a freeze-fracture electron microscope, conducted by NanoAnalytical Laboratories in San Francisco, CA. An example of one ATP-vesicle beginning to morph with the cell is shown in Fig. 1 (see Note 4). 

In other PANl systems protonated with HBF [266], HCl [261,278] and H2SO4 [303], temperature-independent susceptibility is observed. In PANI-CSA the electrical conductivity tr behaves as a metal, that is, a oc /T, above 200 K [304] and in PANl-HCI the microscopic conductivity obtained from the spin dynamics showed the semiconductor-to-metal transition around 150K [305,306]. Furthermore, the metallic optical absoiption was found in PANI-HBF, [280]. Then the temperature-independent susceptibility could be assigned to the Pauli susceptibility in these systems. 

However, PANI-H2SO4 indicates a semiconducting behaviour not only in the dc conductivity, but also in the microscopic conductivity up to 300 K obtained by... 

Figure 6.49. The protonation level dependence of the diffusion rates D// along and across the chains, together with the dc electrical conductivity a and the microscopic conductivity < for PANl-HCl [263,345], Note the small dependence of Dy on v and the similarity of to a. (after [263])...

The metallic state of the conducting polymers has been confirmed by optical measurements and thermoelectric power, but only above 200 C by dc conductivity because of semiconducting transport betw een the metallic regions. The intrinsic anisotropy of such a metallic conduction that could specify dimensionality of the electronic states, is rather difficult to measure by dc conductivity for the same reason. The spin dynamic techniques might be a powerful tool to characterize microscopic conduction of charge carriers with spin. Such studies were recently reported for several systems with ESR and NMR as a function of frequency. This... 

It has been shown that a pressed polypyrrole/ polycarbonate composite gives rise to microscopic conduction phenomena, and its conductivity is stable up to 200 C. Results obtained with a composite containing 20% of PPY in polycarbonate, pressed under 2000 bars up to 280°C, show that the material is still conductive (2 S/cm) and can be used as absorbing material having stable microwave properties. 

D. Xu and R. Davis, Atomic force microscope conductivity measurements of single ferritin molecules. Thesis, Brigham Young University, 2004. 

Impedance spectra of such crystals, reported by Bonanos and Lilley [1981], displayed only bulk and electrode arcs. The same data plotted in the modulus plane (Figure 4.1.45) revealed two overlapping arcs a low frequency arc ascribed to the matrix and a high frequency one ascribed to the dispersed phase. Using the Maxwell-Wagner effective medium relation (Eq. 20), the modulus spectra were modeled and the microscopic conductivities of the two phases were evaluated for... 

Figure 1. (a) The density of states of a-SiHv after Fritzsche s synthesis of the experimental data. (d) A sketch of the microscopic conductivities and mobilities for the conduction and valence bands. 

In Fig. (lb) are shown the corresponding microscopic conductivities and mobilities. However, to complete the correspondence between... 

The metallic temperature dependence of S(T) observed at surprisingly low concentrations of PANI-CSA indicates that the microscopic conduction mechanism is not changed as PANI-CSA is diluted in PMMA. Although ai T) is strongly dependent on the mean free path and the number of connected pathways, S(T) is rather insensitive to the change in the number of pathways once the connected paths are formed above the percolation threshold. 

Table 5.4 Spin Diffusion Rates and Microscopic Conductivities, cTj and for Four Polythiophene Family Compounds...

Fourier s model of heat conduction applies to certain regimes or scales of dimensions, times, and temperature regimes. The applicability of microscopic conduction model can be described based on the following criteria (a) space scale, (b) time scales, and (c) temperature regimes. 

Polyaniline in its emeraldine-base form (PANb) was fabricated in LB multilayer as a mixture with stearic acid. In the LB film, PANb was phase separated needle-like stearic acid microcrystals were observable under an optical microscope. Conductivities as high as 1 S/cm were achieved by doping in a HCl solution... 

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