Azolla filiculoides has been an ephemeral plant in Poland since the end of the 20th century. In the last 15 years this species appeared in 5 locations in south-west Poland. Habitat and plants of two populations became destroyed, three other still exist. A. filiculoides occurs in eutrophic or even polluted water where it forms dense mats, up to 10 cm thick. It stays sterile and propagates only in a vegetative manner. Frost resistance of Lower Silesia populations is higher than reported so far; fern may winter and rebuild the population after frost reaching 22^oC. Size of the populations is changeable during the vegetation season. A. filiculoides occurs in water habitats and plant communities in which it substitutes Lemna minor

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AbstractThe article presents the tests that were conducted to examine the possibility of the fuel filter shank’s thread shearing under the impact of hydrostatic pressure. Increased wear due to friction was confirmed on the threads of the titanium shanks that were tested, together with significantly reduced wear of the mating threads and steel sleeves. Shearing tests confirmed that to shear a thread that is worn to a degree similar to the threads that were tested, it is necessary to apply eight times more static pressure than the maximum pressure in the filter. A comparison of the shape of the coils of the thread that was subjected to the pressure test with the thread from the damaged filter demonstrated a significant difference in the wearing of these elements due to friction.

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