The disruption of the endocrine systems of gastropod molluscs and consequential physiological changes (imposex and intersex) are used as biomarkers for environmental contamination by tributyltin compounds. The first international laboratory performance study on the determination of imposex and intersex in neogastropod molluscs, Nucella lapillus and Littorina littorea has been undertaken by the QUASIMEME (Quality Assurance of Information for Marine Environmental Monitoring in Europe) project. Samples of live gastropods were distributed and participants were asked to record shell height and sex, together with penis length and vas deferens sequence stage (VDS) in Nucella or the intersex stage (IS) and prostate length in Littorina. Calculations were made of vas deferens sequence index (VDSI) and the relative penis size index (RPSI) in Nucella and of intersex stage index (ISI) and the average female prostate length (FPrL) in Littorina. Thirteen (87%) of the 15 participating laboratories returned data. The remaining two laboratories asked to participate in later exercises. For Nucella, seven laboratories reported sex ratios significantly different from the reference laboratory data. Differences in penis length measurements between laboratories were largely random, although there were indications of systematic errors affecting the data from three laboratories. Seven laboratories reported satisfactory data (Z-score magnitude of Z < 2) for VDSI. The inclusion of a high proportion of sub-adults in the Nucella samples may have made separation of the sexes more difficult than in mature adults. The sub-adults will have had smaller pene than mature adults in the same population, and therefore any errors (random or systematic) in the measurement of penis length or observation of reproductive organs would have a potentially greater impact on the final reported values of the summary imposex indices. The Littorina sample did not show a high degree of intersex (ISI = 0.41). The laboratories could determine the sex of Littorina reliably and only one laboratory reported data significantly different from the reference laboratory. All except two laboratories reported satisfactory data for ISI.
SummaryTests have been made to examine the dynamic response of representative heliport structures to helicopter landing loads. The loads applied by an S.5S helicopter were measured by British European Airways and the corresponding strains, reactions and deflections occurring in the instrumented test platform were recorded by the Building Research Station.This paper describes the specially designed recording equipment fitted to the helicopter and discusses the data obtained from over 400 heavy landings. It is concluded that:—(a)The tyre deflection method used to measure applied load was better than the others considered.(b) Overall accuracy achieved was in the order of ± 10 to 15 percent.(c) Accuracy could have been improved if more time had been available to eliminate the effects of follower bounce and to establish the exact degree of sideloading present on the mainwheels.(d) There was inconsistency in oleo performance which had a marked effect on the time-history of load application.(e) The time-history of load application also depended on whether or not the rotor was running and providing lift.(f) In very few of the landings from a low hover and in none of the 30 or so run-on landings did all four wheels touch together; this is the most critical loading of the structure.(g) Despite the large number of heavy landings earlier in the trial the undercarriage finally failed at 19 fps which was considerably in excess of its design velocity.
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