SCIENCE AT WORK SPECIAL FOCUS REPORT LAB PROFILE WATCH PORTFOLIO OPINION Applied Physics BY BRETT KRAABEL Stop the Screech Illustration showing how different peeling angles (top) cause stick-slip instability in the tape (bottom). Plant Biology Gone with the Smell of Roses BY LÉA GALANOPOULO 8 CNRS INTERNATIONAL MAGAZINE Customers in florist shops tend to agree: roses seem to have lost their scent. “By only selecting blooms that can survive longer than ten days in a vase, the world’s most popular cut flower has lost its fragrance,” explains Jean-Claude Caissard.1 Like other scientists, this plant biology specialist has been trying to solve the mystery of roses. “The Romans were the first to domesticate them,” he explains, “but this practice was abandoned during the Middle Ages, when roses were only used for their pharmaceutical properties.” However, in the 19th century, with the advent of the English garden, they were all the rage in France. “Growers therefore bred new varieties to meet increasing demand,” points out Blandine Veith,2 a sociologist specialized in the commoditization and patrimonialization of ornamental plants. There are now more than 30,000 rose varieties: “Breeders try to obtain blossoms that are increasingly large and colorful, on plants that can flower all year round,” adds Caissard. “In nature, however, a rose only blooms one or two weeks a year.” Yet hybridization is not the only culprit in this loss of perfume, which has always been a fragile trait. “Among the descendants of a specific rose line, 90% will not have the scent of their parents. In 10% of cases, the rose will keep a fragrance, but not necessarily the desired one: some may smell of pineapple, for example,” says the researcher who, with his team, has set out to map the genes that give roses their scent. “Fragrant roses sometimes have fragile petals, which makes them difficult to ship by air,” explains Veith. 1. Laboratoire de biotechnologies végétales appliquées aux plantes aromatiques et médicinales (Université Jean Monnet). 2. Laboratoire dynamiques sociales et recomposition des espaces (CNRS / Université Paris Ouest). The scent of roses is an extremely fragile trait that is difficult to preserve from one flower to another. © J.-C. CAISSARD There is no mistaking the screech of adhesive tape being removed from a substrate. This sound in fact indicates an instability in the peeling process that not only damages the adhesive, but also produces unacceptable noise levels in industry. In medical applications, this instability can cause pain or even additional injuries when removing bandages. To help the adhesive industry overcome this problem, researchers from three CNRS laboratories1 have conducted an extensive study2 with the support of the French National Research Agency (ANR). They analyzed how the speed and angle at which tape is peeled from its substrate affects stability, and found that the latter significantly decreases at large peeling angles. The resulting instability is called “stick-slip instability,” where the speed at which the strip separates from the substrate alternates rapidly between fast and slow. The precise characteristics of this instability, explains co-author of the study Marie-Julie Dalbe, “depend on factors such as the velocity applied to the free end of the ribbon, the properties of the glue, the elasticity of the tape, its inertia, and the angle of separation.” By using a custom-made device 1. Laboratoire de physique (ENS de Lyon / CNRS / Université de Lyon); Institut lumière matière (CNRS / Université Claude Bernard Lyon-I); Laboratoire Fluides, automatique et systèmes thermiques (CNRS / Université Paris-Sud). 2. M.-J. Dalbe et al., “Peeling-angle dependence of the stick-slip instability during adhesive tape peeling ,” Soft Matter, 2014. 10 (48): 9637–43.
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