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Abstract:  Ultrasonic imaging techniques play an important role in endoscopic pre-operative staging and post operative follow-up of tumour patients as well as for the assessment of cardiac insufficiency. However, cancerous lesions offer only low-contrast targets. Therefore, high sensitivity systems with good contrast as well as flexible and robust handling are required to obtain diagnostic accuracy and confidence. We developed a radial scanning ultrasonic catheter with a total diameter of 2.3 mm, which makes use of a LIGA geared micromotor to turn an ultrasonic transducer directly at the tip of the catheter. Connector rings fitted on a shaft as well as sliding contacts transmit the 20/30 MHz signals from the transmitter/receiver of an ultrasound monitor system (Kretz Technik AG, Austria) to/from the rotating transducer. Due to its excellent performance and easy handling the scanner module will be applied in a number of ultrasonic diagnostic applications.

The generalized Gaussian formalism is applied to praseodymium-doped fluoride fibre amplifiers to obtain accurate analytic expressions for the small signal gain. The effect of confining the dopant to a central portion of the core is investigated. We find that dopant confinement improves the efficiency of these fibre amplifiers. The optimum cutoff wavelength for fibres with confined dopant is longer than that for fibres with fully doped cores.

In this paper a statistical ensemble of laser light is defined. The lasing field is treated as a classical variable, the spontaneous emission is considered phenomenally by using a random function. Special attention is paid to the transverse mode behaviour. To calculate the ensemble elements, an approach based on Fresnel integration has been developed. Theoretical investigations into some stripe stable resonators have been carried out. Some results for the intensity, the mode spectrum, the correlation between transverse modes, the beam quality, and the spectra of the intensity and the output power fluctuation are presented and discussed.

Based on average intensity distributions at two axial positions, an experimental approach to determine the mode coherence coefficients was developed. Using this approach, investigations were carried out for a CO2 laser with a stripe resonator. The power partitions of, and cross-correlations between, modes at different aperture widths and the dependence of the beam quality on the aperture width were studied. The measuring principle, an iterative fit method, and some experimental results are presented and discussed.

Taking the modal behaviours of the laser field into account, the coherence properties of laser light can be characterized by mode coherence functions (MCFs) and mode coherence coefficients (MCCs). Changes in laser light properties due to optical operations can be described by transformation laws for the MCFs and the MCCs. The transformation laws as well as transformation matrices for propagation in free space, phase transformations, spatial amplitude modulations and aperturizing are given. Furthermore, intensity distributions and intensity moments in the spatial and in the spatial frequency domains are expressed in terms of the MCCs. General expressions for the beam quality factors,M2s, obtained using the intensity moments and some useful expressions for intensity moments of higher order are discussed.

The dynamics and the structure of the plasma layer in a 1.3 kJ plasma focus were investigated by means of the Schlieren technique. A mode-locked dye laser provides a repetitively pulsed illumination source, which is used for stroboscopic recordings of the plasma sheath. During the rundown phase the plasma layer attains a minimum thickness at a finite distance from the surface of the centre electrode. The observed broadening of the plasma sheath near the centre electrode surface indicates reduced temperatures due to plasma heat losses to the electrode. During the collapse phase the evolution of periodic density modulations of the plasma sheath was observed in the gradient region of the layer adjacent to the zone of the magnetic field. The corresponding wave vector is parallel to the direction of the current. From the Schlieren images the sheath parameters, including electron density, electron density gradient and the growth rates of hydrodynamic instabilities, were determined.

In 85 patients, breast augmentation mammaplasty (often bilateral) was performed in the course of 5 1/2 years when the breast was too small or after subcutaneous mastectomy. In two women, a very painful deformation and pronounced hardening of the breast clinically simulating cancer and a foreign body reaction of irregular density appeared histologically in association with severe capsular fibrosis. In two further women, enlarged lymph nodes simulating metastases were observed in the axilla with a similar foreign body reaction. Prior performance of lymphography could be excluded with certainty in each case. In one of these cases, a scirrhous carcinoma on the implant capsule occurred in the residual parenchyma after subcutaneous mastectomy.

Ohne Zusammenfassung:

Abstract: The laser-tube stray capacity and the time dependent spark resistances of the pulsing system influence the operation of a N2-laser. Their analysis with experimental and analog-computer methods yields an optimum value of the stray capacity. In the case of a 40 kV pulse from a 2-gap Marx generator with a 0.4 J energy input we obtain 120 kW laser output with 2.5 ns halfwidth at an optimum stray capacity of 120 pF. A substantially reduced threshold value and increased laser output were observed with a fast single-gap transmission line pulser of the “Nanolite” type.