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A symmetric lithium cell Li/P(EO) 20 LiTFSI/Li has been studied at 80°C by confocal Raman microspectrometry while current densities of up to 0.5 mA cm -2 are passed through the cell. The Raman observation is performed on the edge of the cell along a line of points extending from one electrode to the other at a depth of about 20 μm within the electrolyte. Local salt concentration is measured in the electrolyte as a function of time, current density I, and electrolyte thickness L (90 and 160 μm). When the steady-state regime is reached, linear and symmetric salt concentration gradients are observed. They are proportional to I and L as expected from the theoretical predictions for a binary electrolyte containing a fully dissociated salt with negligible ionic associations. In addition, preliminary results have been obtained concerning the establishment and relaxation of the steady state. From these data, it is shown that salt diffusion coefficient and ionic transport numbers can be determined with a reasonable precision. Confocal Raman microspectrometry can therefore be considered as a new and powerful spectroelectrochemical method to study transport properties in polymer electrolytes.

Confocal Raman Microspectrometry is shown to be a powerful technique to study electrochemical devices under working conditions with a spatial resolution of about l μm3. This is first illustrated on a Li/P(EO)20, LiTFSI/Li symmetrical cell where salt concentration gradients in the polymer electrolyte are measured as a function of current density and time. These data give access to transport properties of the polymer electrolyte, namely transport numbers and diffusion coefficients. A second example is provided by electrostatic supercapacitors using activated carbon fabrics of high specific surface area and proton conducting liquid electrolytes. A mapping of a carbon fiber and of the surrounding electrolyte is recorded for ± IV polarizations. The relative intensity and the frequencies of the D and G Raman lines of carbon are found to be very sensitive to the carbon charge.

GTP-binding proteins regulate a wide variety of intracellular signalling pathways in eukaryotic cells. The Ras GTP-binding proteins have received a great deal of attention since they were found to be modified by amino acid substitutions in a large number of cancers. It is now clear that Ras plays an essential role in regulating normal cell growth and differentiation, although how this is achieved biochemically is not known. The cellular concentration of Ras bound to GTP appears to be the limiting factor for signalling, and, not suprisingly, it is tightly controlled by both positive and negative regulators. There is now convincing evidence that the loss of one of these negative regulators of Ras, neurofibromin, can contribute to the development of malignancy; thus, neurofibromin behaves as a tumour suppressor gene product.