Electrical excitation structural properties

What is most interesting about many of the new solid state materials are their electrical and magnetic properties. Chemists have to learn to measure these properties, not only to make the new materials and determine their structures. The history of the compounds that are at the center of today s exciting developments in high-temperature superconductivity makes this point very well. Chemists must be able to reason intelligendy about the electronic structure of the compounds they make in order to understand how these properties and structures may be tuned. In a similar way, the study of surfaces must perforce involve a knowledge of the electronic structure of... 

The development of the concept of ionic channel started with the realisation by Bernstein that cellular excitability was a property of the membrane. The starting point at the experimental level was the observation by Cole and Curtis that, concomitant with a propagated electrical impulse (manifestation of cellular electrical excitability) in the squid giant nerve fibre, a decrease in the electrical resistance took place with no detectable change in the membrane capacitance. This result lent strong support to Bernstein s concept and clearly indicated that the most plastic components of the axolemma, the proteins, underwent structural transitions leading to a transient increase in ionic fluxes. 

In these oxides, the 6s and 5d and, to a lesser extent, the 4f electrons of the rare earth atom are mainly responsible for electrical transport and structural properties, whereas the localized 4f electrons govern the magnetic properties. X-ray absorption spectroscopy (XAS) offers the important advantage of simultaneously probing the 4f and the ds conduction states in these oxides. In XAS, the dipole selection rules are strictly obeyed and this facilitates the identification of the spectral features. Generally, the 3d—>4f (Mjv-v) or 4d—>4f (Niv-v) absorption transitions are studied. In these absorption processes the excited 4f electron participates directly in the transition. The resulting multiplet structure is observed to provide a finger-print of the 4f population of the rare earth atom. The modification in the valence band electron distribution introduced by the delocalization of a 4f electron is probed by the transition of a 2p (Ln-m) electron in the vacant sd conduction states. In this case the 4f electron does not participate direct in the transition. 

The propeller polymer (R)-54 bears the similar structural feature of 56 which may lead to interesting NLO property. The work of Persoons and co-workers [55] shows that the chirality of materials can also contribute significantly to the second-order NLO effect. Because of the potentially useful optical and electrical properties and the exciting structures, we have synthesized and characterized (R)-54 and other propeller polymers of similar structure. 

In contrast to magnetic properties, the theory of electric-field-like properties is much easier to cast into a set of working equations. One of them has attracted particular interest, and that is the electric field gradient (EFG). This property is of decisive importance to Mossbauer spectroscopy, i.e., to the spectroscopy of excited nuclear states whose energies are modulated by the molecular structure (the chemical environment ). In order to see how this property arises, we study the electrostatic electron-nucleus interaction of extended, not spherically symmetric charge distributions. For this we apply a multipole expansion in order to generate the properties term by term. 

BNNTs have a structure similar to CNTs and promise exciting electrical and mechanical properties beyond what can be obtained with CNTs. BNNTs are semiconductors with a tunable band gap of 5.5 with high tensile strength and high... 

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