Fabrication of MEMS Directional Acoustic Sensors for Underwater Operation

The article of record as published may be found at https://doi.org/10.3390/s20051245In this work, microelectromechanical systems (MEMS)-based directional acoustic sensors operating in an underwater environment are explored. The studied sensors consist of a free-standing single wing or two wings pivoted to a substrate. The sensors operate in a narrow frequency band determined by the resonant frequency of the mechanical structure. The electronic readout of the mechanical response is obtained using interdigitated comb finger capacitors attached to the wings. The characteristics of MEMS sensors immersed in silicone oil are simulated using finite element modeling. The performance of the sensors is evaluated both in air and underwater. For underwater testing and operation, the sensors are packaged in a housing containing silicone oil, which was specially developed to present near unity acoustic transmission. The measurements show that the resonant frequency of the sensors obtained in air shifts to a lower frequency when immersed in silicone oil, which is primarily due to the mass loading of the liquid. The peak sensitivity of the MEMS sensors is approximately 6 mV/Pa or −165 dB re 1 V/μPa, and the directional response shows a dipole pattern. The signal-to-noise ratio was found to be about 200 or 23 dB at 1 Pa incident sound pressure. The results show the potential of MEMS sensors to be used in underwater applications for sound source localization

Overall evaluation of artichoke leftovers: Agricultural measurement and bioactive properties assessed after green and low-cost extraction methods

Globe artichoke is rich in nutrients and phenolic compounds. However, nearly 85% of its biomass is discarded following harvest. To propose a scalable and economically attractive process for the revalorization of this material, a holistic analysis of the leftovers (bracts, stems and leaves) of three Argentine cultivars (Sampedrino, Gallego and Gringo) was proposed. Agricultural studies revealed differences for the crop yield of each variety and that bracts accounted for 65% of the overall waste biomass. Differences were also found for morphological features (aspect evaluation and color in the L*, a* and b* values). For the recovery of phenolic compounds, low-cost, green, and industrially applicable extraction methods were proposed and regardless of the water-based variations employed, stems extracts showed the highest values for biological activity. Among varieties, Sampedrino had the highest phenolic compounds concentration and antioxidant capacity for stems extracts (4.3 ± 0.2 mgGA/gFW for total phenolic compounds, 1.21 ± 0.01 mgGA/gFW for ABTS.+ scavenging capacity and 0.73 ± 0.02 mgGA/gFW for Ferric reducing antioxidant power). HPLC-MS confirmed the presence of 5-O-caffeoylquinic acid and dicaffeoylquinic acids in all samples, and a flavonoid with medical applications, kaempferol-3-O-glucoside, in leaves of all varieties. High concentrations of anthocyanins were also found in stems of all varieties. Here we propose friendly extractions using aqueous solvents for the recovery of health-promoting phenolic bioactive compounds that present great feasibility and transferability to the food industry for added-value products.EEA San PedroFil: Zazzali, Ignacio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Orgánica y Departamento de Industrias; ArgentinaFil: Zazzali, Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR); ArgentinaFil: Zazzali, Ignacio. Universidad de Buenos Aires. Centro de Investigaciones en Hidratos de Carbono (CIHIDECAR); ArgentinaFil: Gabilondo, Julieta. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria San Pedro; ArgentinaFil: Peixoto Mallmann, Luana. Universidade Federal do Río Grande do Sul. Instituto de Ciência e Tecnologia de Alimentos; Brasil.Fil: Rodrigues, Eliseu. Universidade Federal do Río Grande do Sul. Instituto de Ciência e Tecnologia de Alimentos; Brasil.Fil: Perullini, Mercedes. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Perullini, Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Química Física de Los Materiales, Medio Ambiente y Energía (INQUIMAE); ArgentinaFil: Perullini, Mercedes. Universidad de Buenos Aires. Instituto de Química Física de Los Materiales, Medio Ambiente y Energía (INQUIMAE); Argentin