Using photoacoustic laser spectroscopy, the noninvasive determination of blood constituents like hemoglobin and glucose is feasible. The aim of our investigations is the development of a sensor which is suitable for continuously noninvasive monitoring of blood glucose concentrations in diabetic patients. For this purpose a photoacoustic sensor head was developed and coupled via an optical fiber bundle to an array of 8 laser diodes emitting at various wavelengths in the near infrared region. Applying a special modulation scheme, the tiny changes of the absorption coefficient of whole blood caused by the variations of blood glucose concentrations could be measured. A resolution of 70 mg/dl was achieved, a value which is already close to the clinical requirements for a continuously working glucose sensor.

The Pacific Northwest Laboratory evaluated the potential feasibility of using chemical energy storage at the Solar Electric Generating System (SEGS) power plants developed by Luz International. Like sensible or latent heat energy storage systems, chemical energy storage can be beneficially applied to solar thermal power plants to dampen the impact of cloud transients, extend the daily operating period, and/or allow a higher fraction of power production to occur during high-valued peak demand periods. Higher energy storage densities make chemical energy storage a potentially attractive option. The results of the evaluation indicated that a system based on the reversible reaction, CaO + H2O = Ca(OH)2, could be technically and economically feasible for this application, but many technical and economic issues must be resolved.

Pulsed photoacoustic laser spectroscopy was used for depth-resolved analysis of artificial tissue models. The technique was applied to investigate the spatial resolution capabilities of a fiber-optical-coupled photoacoustic sensor head. The time-resolved measurements confirmed the theoretical predictions of a depth resolution of 0.1 mm. In an adapted skin model, a strongly absorbing target could be detected up to a layer depth of 14 mm. At a layer depth of 5 mm, a lateral resolution of 3.5 mm was achieved. Because of the depth-resolving capability, this method is well suited as a complementary approach for two-dimensional imaging techniques.

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