Acceleration of conducting polymer-coated latex particles as projectiles in hypervelocity impact experiments

A series of sterically-stabilized polystyrene latex particles in the size range 0.1-5.0 mu m have been coated with ultrathin (1 km s(-1)) using a Van de Graaff accelerator. These coated latexes have two main advantages compared to the sterically-stabilize polypyrrole particles of 0.1-0.3 mu m diameter reported previously. First, a wider particle size range can be accessed. Second, the particle size distributions of the coated latexes are much narrower than those of the pure polypyrrole particles reported earlier. Preliminary studies confirm that, after charging and acceleration, these conducting polymer-coated latex particles have very similar mass-velocity profiles to those reported for colloidal iron particles in the hypervelocity literature. The hypervelocity impact generated ionization has been measured for latex spheres impacting copper targets. This is compared to previous work for impact ionization by iron particles, thus demonstrating the ability to study the dependence of impact ionization on widely different projectile materials

First report of black rot caused by Xanthomonas nasturtii on watercress in Spain and Portugal

Xanthomonas nasturtii was first identified as the cause of black rot of watercress (Nasturtium officinale) on plants grown in Florida, USA (Vicente et al., 2017). Similar symptoms had been reported earlier in Hawaii (McHugh & Constantinides, 2004) and an unidentified Xanthomonas sp. was isolated in Portugal in 2003 from wild watercress (Cruz et al., 2017). Since 2017, watercress crops in southern Spain have occasionally exhibited small yellow leaf lesions around the hydathodes, leaf spots, V-shaped leaf lesions, wilt, distortion and senescence (Fig. 1). Symptoms were more frequent during mild and humid periods from November to February, reducing yields by up to 60% and leading to rejection of some crops (Lascelles, 2019). In 2021, symptoms were seen on watercress produced in Portugal and sold in the UK