No abstract

In view of the limited availability of fossil fuels and the necessity to reduce the output of emissions of greenhouse gases in the long term, the transport sector needs efficient, environmentally compatible drive solutions. Hydrogen, as a clean and sustainable fuel, offers a high implementation potential and can be used both in internal combustion engines and in fuel cells. In urban deployment the fuel cell drive has specific advantages and is suitable for use in city buses. Integration of high‐power energy storage systems improves fuel consumption and can reduce the costs of the drive system. In May 2000 MAN presented its first fuel cell bus, which was successfully deployed in passenger transport in various cities. The next FC‐bus, using hybrid fuel cell propulsion, is planned under the framework of the Bavarian hydrogen project at Munich Airport and will be tested from spring 2004 on. The first deployment of pre‐series bus fleets with fuel cells using hydrogen as fuel can be expected from the end of this decade onwards.

Our investigations in human specimens and animal experiments show that prostheses with a spongy metal surface can become fixed by bony ingrowth to varying degrees. After consistent clinical and radiological follow-up over 12-65 months (mean 34 months) in a prospective study of 100 consecutive patients in whom 106 cementless total hip replacements had been carried out, we were able to show that after 1 year 82% of patients were pain-free with the prosthesis fixed by bony ingrowth, 8% were pain-free with the prosthesis fixed by dense fibrous tissue and 10% were not pain-free, but did not want revision surgery. Thigh pain decreased steadily from 53% 3 months postoperatively to 6.6% 15 months after operation. We believe that, when the implantation technique is exact, a high percentage of cementless spongy metal prostheses are fixed by bony ingrowth, and that a cementless prosthesis should be implanted only in patients under 60 years of age without osteoporosis.

In an in vitro study of the sheep's meniscus, the possibilities to reduce the thermal tissue necrosis caused by high-frequency electrosurgery of the meniscus were studied. Under standardized conditions, machine-made sections through the meniscus were cut using electrodes of various thicknesses and different settings of the electric generator. The thermal tissue necrosis near the cut through the meniscus was determined using light microscopy and image analysis on the specimen stained according to Masson-Goldner. With a constant voltage of 250 V tissue necrosis was significantly less for electrodes of a diameter of 0.5 mm than for 1.5-mm electrodes (187.3 microns as compared with 368.0 microns). For electrosections carried out using a commercially available electrode with a low voltage of 250 V as well as with a power-controlled generator, tissue necrosis was also significantly less than with a constant high voltage of 395 V (181.4 microns and 210.2 microns as compared with 325.0 microns). Thus, an effective reduction of thermal tissue necrosis in arthroscopic partial meniscectomy is possible when thin electrodes and power-controlled generators are used.