Electrochemical capacitors (ultracapacitors) are one approach to meeting the high power requirements for the energy storage system in an electric vehicle. Energy is stored in an electrochemical capacitor by charge separation in the double layer formed in the micropores of a very high surface area electrode material, which does not undergo chemical change as in a battery. Consequently, the material requirements for capacitors are very different from those of batteries. In the last several years, a number of promising material technologies have been identified for use in electrochemical capacitors. These include activated carbon fibers, foams, and composites, doped conducting polymers, and mixed metal oxides. The most important material property is its specific capacitance (F/gm or F/cm3). Carbon materials with specific capacitances of 100 to 300 F/gm have been developed. Doped polymer materials having specific capacitances of 300 to 400 F/gm are also being studied. In addition to high specific capacitance, the electrode material must also have a low electronic resistivity ( < 0.1 Ω-cm) in order that charge can be distributed with minimum voltage drop in the electrode. Electrochemical capacitor cells have been fabricated using the various material technologies with both aqueous and organic electrolytes. Tests of the cells have shown near ideal charge/discharge characteristics — that is, the voltage versus time curves are nearly linear for constant current tests. The energy densities of 1 V cells, using aqueous electrolytes, are 1 to 1.5 W-h/kg and those of 3 V cells, using organic electrolytes are 7 to 10 W-h/kg. Most of the cells have high power densities of 1 to 3 kW/kg. Numerous new materials for electrochemical capacitors have been identified, processed, and tested in electrodes and cells in recent years and progress is rapid in this relatively new field of research.

In order to investigate the structure−property relationship of nonlinear optical materials, a series of organometallic chromophores were synthesised utilising the [Fe 2 (η-C 5 H 5 ) 2 (CO) 2 (µ-CO)(µ-C−)] + electron-accepting moiety and the ferrocenyl group, Fc, as the electron donor. The π-linker between these two termini was systematically modified and the mutual electronic communication between them was determined using IR, NMR, and electronic absorption spectroscopy. An X-ray structure determination of [Fe 2 (η-C 5 H 5 ) 2 (CO) 2 (µ-CO)(µ-C−CH=CH−CH=C(Cl)−Fc)][BF 4 ] confirmed the strong electronic interaction between the donor and the acceptor with reduced π-bridge bond-length alternation. The nonlinear optical properties of these complexes were examined using the hyper Rayleigh scattering technique. The experimental first hyperpolarisabilities are some of the highest obtained for ferrocenyl chromophores and, significantly, no enhancement

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From the tensorial point of view, the essential characteristic of a semisimple lie algebra A is the non-singularity of the Killing form, since this enables one to construct a system of Cartesian tensors over A. That system is the subject of this paper.