Summary Galinsoga quadriradiata (hairy galinsoga) and Galinsoga parviflora (smallflower galinsoga, gallant soldier) are very troublesome weeds in many vegetable row crops in Europe. To optimise management strategies for Galinsoga spp. control, an in‐depth study of germination biology was performed. Germination experiments were conducted to evaluate the impact of light and alternating temperatures on germination of a large set of Galinsoga populations. Seedling emergence was investigated by burying seeds at different depths in a sandy and sandy loam soil. Dormancy of fresh seeds harvested in autumn was evaluated by studying germination response in light at 25/20°C with and without nitrate addition. Seed longevity was investigated in an accelerated ageing experiment by exposing seeds to 45°C and 100% relative humidity. Galinsoga spp. seeds required light for germination; light dependency varied among populations. Seedling emergence decreased drastically with increasing burial depth. Maximum depth of emergence varied between 4 and 10 mm depending on soil type and population. In a sandy soil, emergence percentages were higher and seedlings were able to emerge from greater depths than in a sandy loam soil. Freshly produced G. parviflora seeds, harvested in autumn, showed a varying but high degree of primary dormancy and were less persistent than G. quadriradiata seeds that lack primary dormancy. Lack of primary dormancy of freshly harvested G. quadriradiata seeds and light dependency for germination may be used to optimise and develop Galinsoga management strategies.
This paper summarizes the differences in the design approaches for tensile surface structures between the earliest structures in the 1950s and today’s practice. Current software tools allow more refined and advanced calculations. Nevertheless, a basic hand calculation can clarify the process in a few pages and provide the appropriate key data. A transparent setup allows the form‐finding and structural analysis to be redone. The calculation of the cable net for the bandstand by André Paduart (1958) is analysed in this paper as a case study. Both the hand calculation (19 pages) and the numerical simulation are summarized and the design context of the initial and current calculations are described. The approximations made by Paduart resulted in a remarkably intelligible and coherent evaluation of the cable net structure. The historical approach can still be applied for a first verification of a pretensioned cable net or for a membrane structure as the simplified calculation method is similar.
No other exhibition has more references in the history of engineering than Expo 58, the first post-war world fair (Brussels). The contemporary specialist press labelled the exhibition a ‘festival of structures’ and focused on its widespread application of hanging roofs. This paper engages in complex analyses of three hanging roofs at Expo 58: the Marie Thumas pavilion, the pavilion of France and the US pavilion. Three fields of influence added to the enthusiasm for hanging roofs: the context of the fair, the post-war developments in engineering and the contemporary unease with functionalism among architects. In all three fields, hanging roofs were considered promissory of future developments: light and efficient in material use, of a radical new shape and illustrative of the benefits of a closer collaboration between architects and engineers. Nevertheless, the analyses also demonstrate the tensions between the preconditions of the contexts and their rhetoric on innovation and experiment. The research presented stems from an interdisciplinary approach and is based mainly on archival material and contemporary sources.
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