A general theory of Rayleigh scattering due to composition fluctuations in multi-component systems is developed with the aid of the grand canonical ensemble of Gibbs. It reduces to the usual expression for systems of two components, but contains previously neglected terms arising from thermodynamic interactions between solutes in systems of more than two components. The theory is used to interpret the turbidity measurements of polystyrene in benzene-methanol mixtures of Ewart, Roe, Debye, and McCartney.

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Surveys estimate that 1.8 to 3.6 percent of workers in the U.S. labor force suffer from major depression. Depression has a significant impact on vocational functioning. Seventeen to 21 percent of the workforce experiences short-term disability during any given year, and 37 to 48 percent of workers with depression experience short-term disability. Studies indicate that treating workplace depression provides favorable cost offsets for employers, although a number of methodological issues have influenced the interpretation of these findings. In addition to disability costs, cost analyses need to include lost wages and indirect costs to employers, such as the costs of hiring and training new employees. In general, employers are not aware of the extent of the indirect costs of untreated depression. They have mistaken assumptions about the availability of effective treatment, and they are unaware of how often depression contributes to worker disability. The workers' compensation system and the courts have been slow to recognize depression as a work-related disability, and as a result employers have few incentives to treat and prevent workplace depression.

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In medical ultrasound imaging, 2-D array transducers have become essential to implement dynamic focusing and phase-correction in the elevation dimension as well as real-time volumetric scanning. Unfortunately, the small size of a 2-D array element results in a small clamped capacitance and a large electrical impedance near resonance. These elements have poor sensitivity because their impedance is much higher than the electrical impedance of the transmit and receive circuitry. Sensitivity can be improved by using an N layer structure of PZT ceramic with the layers connected acoustically in series and electrically in parallel. For the multilayer ceramic (MLC), the damped capacitance is multiplied by a factor of N(2) and the electrical impedance by 1/N(2) compared to a single layer element of the same dimensions. A 3x43 phased-array transducer has been fabricated using 3 layer PZT-5H material. Each element had a thickness of 0.66 mm and an area of 0.37x3.5 mm. The MLC was manufactured using thick film technology with plated-through vias to electrically interconnect the electrode layers. The completed transducer was compared to a single layer control array of similar dimensions. With a light epoxy backing and a lambda/4 matching layer, the MLC array elements had an impedance of 100 Omega at series resonance of 2.25 MHz, compared to 800 Omega for the control elements. The lower impedance of the MLC elements resulted in a minimum round-trip insertion loss of 24.0 dB, compared to an 34.1 dB for the control array elements. These results were consistent with KLM modeling. B-scan images were made of cysts in a tissue-mimicking phantom and of the left kidney in vivo. The images clearly showed a higher signal-to-noise ratio for the MLC array compared to the control. As a result, 2-D arrays made of multilayer ceramics can be used to form images at a higher frequency and greater range than single layer arrays.