Rate of occupational accidents in the mining industry since 1950--a successful approach to prevention policy

This paper deals with the decrease in the rate of accident insurance claims in the German mining industry over the last five decades. It intends to show that this process is above all the result of a prevention policy where companies and the body responsible for the legal accident insurance in the mining industry, the Bergbau-Berufsgenossenschaft (BBG), work hand in hand. A system like the German accident insurance scheme, combining prevention, rehabilitation, and compensation, enables successful and modern safety and health measures.     

Biodegradation behavior and material properties of aliphatic/aromatic polyesters of commercial importance

Copolyesters of aliphatic monomers with a defined amount of terephthalic acid recently have been shown to be biodegradable. This group of plastic materials exhibits very interesting material properties with regard to their technical application potential. A tensile strength of 25 N/mm² combined with elongations at break up to 1500% was achieved for BTA materials. Melting points varied from 80 to 140‡C. Biodegradation rate under compositing conditions were determined, showing typical erosion rates of films, in the range of 5 to 10 Μm/week. The material properties and the degradation rate as well can be adjusted by the copolymer composition. Stretching of the polymer in the cold state leads to 10-fold higher mechanical strength of the material. The polyester chain can be extended to high molar masses, resulting in melt viscosities suitable, e.g., for melt below extrusion.     

Pigeon homing: new airbag experiments to assess the role of olfactory information for pigeon navigation

Summary In three series of experiments we assessed the effects of olfactory and non-olfactory information collected en route or at the release site on the initial orientation of homing pigeons. In the first experiment, pigeons were transported in open crates to two sites located in opposite directions from the home loft. They were left at the site for 1 h, then put into airtight containers filled with air from that site and brought back to the loft. From there, controls were transported back to the original site. Experimentals were transported to the opposite site. Upon arrival at the site, the olfactory mucosae of both groups were anesthetized with Gingicain. Thus in this experiment, control and experimental pigeons were exposed to different olfactory as well as to different non-olfactory information during displacement and at the site. In the second series, controls and experimentals were treated as in the first experiment, except that they were enclosed in the airtight containers at the very beginning of the experiment and were ventilated with synthetic air until arrival at the final release site. This treatment excluded the possibility to perceive olfactory information en route or at the site. In this series, the two groups differed only with respect to non-olfactory information perceived during displacement and/or at the release site. In the third series, we exposed pigeons at the loft to air collected either at the later release site (controls) or to air collected at a site located in opposite direction of the home loft (experimentals). Here the two groups differed only with respect to their exposure to air of different origin. In all three series, the pooled controls showed a directional preference that was statistically indistinguishable from the home direction. All three experimental groups were disoriented. In the first two series, the differences in the initial orientation of control and experimental pigeons were highly significant. In the third experiment, there was only very weak statistical evidence for a difference between controls and experimentals. These results suggest that more than one factor is involved in the pigeons' navigation system. According to the present experiment with synthetic air, pigeons probably gather and process non-olfactory information during the first part of their transport from the home loft to the release site. Thus, some kind of, in this case non-olfactory, route reversal seems to be involved in the homing process. In addition, the experiment involving only manipulations of airborne information indicated some olfactory component. Previous experiments at our loft did not result in disorientation of the pigeons if either only the access to airborne information had been removed or when otherwise unmanipulated pigeons had been transported in detours to the final release site. Therefore, we assume that our pigeons' navigation system relies on several cues. Deletion of one cue can be compensated by other information. Often the initial orientation of our pigeons is disturbed only when at least one cue is removed and another one provides false information.