Investigation of an optically induced superstrate plasma for tuning microstrip antennas

Optically induced electron-hole plasmas in silicon are used to perform radiation pattern tuning. The antenna is a slot loaded microstrip patch and the effect of illumination is shown to produce beam switching in the radiation patterns of certain modes while other modes are left unaffected. The structure is specifically designed to make the best use of currently available miniature laser sources to form a compact tunable package. Modelled and measured results for tuning of the radiation patterns and frequency response are presented. The effect of the losses incurred by the plasma along with the losses in the optically transparent ground plane are quantified in both simulation and measurement. This forms the basis for designing other types of optically tunable miniature antennas based on the structure presented

Antifouling activity of Celastroids isolated from Maytenus Species, natural and sustainable alternatives for marine coatings

A group of celastroids, quinone-methide nortriterpenes isolated from Maytenus vitis-idaea and Maytenus spinosa were assayed for their antifouling activity. Toxicity assays were performed on Balanus amphitrite nauplii, and the most promising compounds were then incorporated in soluble-matrix antifouling paints, which were tested in the ocean. The results obtained after a 45 day-field trial of the paints indicated in all cases promising antifouling potencies. Although all compounds showed antifouling activity on a wide range of organisms, tingenone and celastrol were the most effective inhibitors of the settlement of fouling organisms. The effect of these substances on nauplii in laboratory tests was temporary instead of toxic, with a high recovery rate, which may avert a potentially adverse ecological damage on the benthic community. These results may provide a more environmentally friendly alternative for the control of biofouling, replacing toxic additives actually in use in marine paints.Fil: Perez, Miriam Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Tecnología de Pinturas (i); Argentina. Universidad Nacional de La Plata; ArgentinaFil: Sánchez, Marianela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos Aplicados A la Química Orgánica (i); ArgentinaFil: Stupak, Mirta Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Tecnología de Pinturas (i); ArgentinaFil: García, Mónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Tecnología de Pinturas (i); ArgentinaFil: Rojo de Almeida, Maria T.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos Aplicados A la Química Orgánica (i); Argentina. Universidade Federal Da Santa Catarina; BrasilFil: Oberti, Juan Carlos María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Instituto Multidisciplinario de Biología Vegetal (p); ArgentinaFil: Palermo, Jorge Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos Aplicados A la Química Orgánica (i); ArgentinaFil: Blustein, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Centro de Investigación y Desarrollo En Tecnología de Pinturas (i); Argentina. Universidad Nacional de La Plata; Argentin