No abstract

Ocean acidification (OA) and the associated changes in seawater carbonate chemistry pose a threat to calcifying organisms. This is particularly serious for shelled molluscs, in which shell growth and microstructure has been shown to be highly sensitive to OA. To improve our understanding of the responses of abalone to OA, this study investigated the effects of CO 2 -induced ocean acidification on extra-cellular acid-base parameters in the European abalone Haliotis tuberculata. Three-year-old adult abalone were exposed for 15 days to three different pH levels (7.9, 7.7, 7.4) representing current and predicted near-future conditions. Haemolymph pH and total alkalinity were measured at different time points during exposure and used to calculate the carbonate parameters of the extracellular fluid. Total protein content was also measured to determine whether seawater acidification influences the composition and buffer capacity of haemolymph. Extracellular pH was maintained at seawater pH 7.7 indicating that abalones are able to buffer moderate acidification (-0.2 pH units). This was not due to an accumulation of HCO 3 -ions but rather to a high haemolymph protein concentration. By contrast, haemolymph pH was significantly decreased after 5 days of exposure to pH 7.4, indicating that abalone do not compensate for higher decreases in seawater pH. Total alkalinity and dissolved inorganic carbon were also significantly decreased after 15 days of low pH exposure. It is concluded that changes in the acid-base balance of the haemolymph might be involved in deleterious effects recorded in adult H.2 tuberculata facing severe OA stress. This would impact both the ecology and aquaculture of this commercially important species.

Purpose Robotic friction stir welding (RFSW) is an innovative process which enables solid-state welding of aluminum parts using robots. A major drawback of this process is that the robot joints undergo elastic deformation during the welding, because of the high forces induced by the process. This leads to tool deviation and incorrect orientation. There is currently no computer-aided manufacturing/computer-aided design (CAD) software for generating off-line paths which integrates robot deflections, and the main purpose of this study is to propose an off-line methodology to plan a path for RFSW with the integration of the deflections. Design/methodology/approach The approach is divided into two steps. The first step consists of extracting position and orientation data from CAD models of the workpieces and adding the deflections calculated with a deflection model to generate a suitable path for performing RFSW. The second step consists of the smooth fitting of the suitable path using Bézier curves. Findings The method is experimentally validated by welding a curved workpiece using a Kuka KR500-2MT robot. A suitable tool position and orientation were calculated to perform this welding, an experimental procedure was set up, a defect-free weld was performed and a high accuracy was achieved in terms of position and orientation. Practical implications This method can help manufacturers to easily perform RFSW for three-dimensional workpieces regardless of the lateral tool deviation, loss of the right orientation and control force stability. Originality/value The originality of this method lies in compensating for robot deflections without using expensive sensors, which is the most commonly used method for compensating for robot deflection. This off-line method can lead to a reduction in programming time in comparison with teach programming method and leads to reduced investment costs in comparison with commercial off-line programming packages.