Silicon as resistance inducer to control black apphid Aphis craccivora Koch, 1854 in cowpea beans [Vigna unguiculata (L)] Walp

The black aphid Aphis craccivora (Koch, 1854) stands out between the bugs considered cowpea pests. The objective of this study was to evaluate the effects of silicon application on the resistance induction of cowpea plants to the black aphid A. craccivora. The experiment was conducted in the Entomology Laboratory of the Phytosanitary sector of the Centro de Ciências Agrárias at the Universidade Federal do Piauí. The effects of the application of silicon on biological aspects were evaluated using a completely randomized design, with four treatments and 40 repetitions, being: silicon in soil (T1), silicon in soil + leaf (T2), silicone leaf (T3), and control (T4). The following biological variables were evaluated: generation period, reproductive period, fecundity, and daily average of nymphs per female. The silicon and lignin contents were also evaluated in the plants. The silicic acid was applied in a 1% solution around the stem of the plants (soil), 15 days after emergence, by diluting 2 g of the product in 200 mL of water. However, the leaf application was carried out with sprayer five days after application in soil. The non-preference of A. craccivora on bean was also evaluated. The evaluations were performed after 24, 48 and 72 hours of infestation by counting nymphs at 24, 48 and 72 hours and adults at each leaf session. The application of silicon promotes the reduction of the production of nymphs, interfering in the biological aspects of A. craccivora, and has potential to be used in a cowpea pest management program in cowpea.

Deposição de hidreto de silício sobre a zircônia em diferentes tempos: análise química, microestrutural e durabilidade da união ao cimento resinoso / Deposition of silicon hydride on the zirconia in different times: chemical, microstructural analyses and bond strenght with resin cement

O objetivo deste estudo foi avaliar a Deposição Química na Fase Vapor Assistido por Plasma (PECVD) com hidreto de silício (SiH4) em zircônia VITA YZ HT em diferentes tempos, bem como os seus efeitos nas características superficiais do material e na união ao cimento resinoso antes e após a termociclagem. Blocos de zircônia Vita YZ HT foram obtidos, polidos, sinterizados e divididos em 5 grupos, de acordo com o tempo de PECVD (n = 31): Zr-30 (30s), Zr-60 (60s), Zr-120 (120s) e Zr-300 (300s). O grupo controle (Zr-0) não recebeu deposição. Análises de DRX, FTIR, EDS, FE-SEM, XPS, goniometria e perfilometria foram utilizadas para caracterização química e topográfica. O silano Monobond N foi aplicado na superfície e um cilindro de cimento resinoso (Variolink N) foi confeccionado (3 × 3 mm). Metade dos espécimes de cada grupo foi armazenada por 24 h ou submetida à termociclagem (6 × 10³ ciclos). Teste de resistência ao cisalhamento (SBS) foi realizado. Os resultados foram submetidos aos testes one-way Anova e Tukey (α = 0,05). Para os grupos experimentais, o XPS mostrou que a formação de ligações Si-O contribuiu para o aumento da Energia Livre de Superfície (ELS). MEV-FEG e EDS mostraram que quanto maior o tempo de deposição, maior a quantidade de silício na superfície, apresentando apenas fase tetragonal. Zr-60 e Zr-300 apresentaram maior e menor rugosidade superficial, respectivamente. O silício penetrou na microestrutura, causando maior concentração de tensão. A resistência de união ao cimento resinoso foi melhorada após todos os tempos de deposição da PECVD. Portanto, a técnica de PECVD com o composto químico SiH4 associada ao tratamento químico com primer universal baseado em metacrilato de silano é uma alternativa promissora para a manutenção da ligação entre cimento resinoso e zircônia HT(AU)

The aim of this study was to evaluate the effect of Plasma-enhanced Chemical Vapor Deposition (PECVD) with silicon hydride (SiH4) on VITA YZ HT zirconia at different times, as well as its effects on material surface characteristics and bonding to resin cement before and after thermocycling. Blocks of VITA YZ HT zirconia were obtained, polished, sintered, and divided into five groups, according to PECVD time (n = 31): Zr-30 (30 s), Zr-60 (60 s), Zr-120 (120 s), and Zr-300 (300 s). The control group (Zr-0) did not receive deposition. XRD, FTIR, EDS, FE-SEM, XPS, goniometry, and profilometry analyses were used for chemical and topographic characterization. Monobond N silane was applied to the surface, and a cylinder of resin cement (Variolink N) was made (3 × 3 mm). Half of the specimens of each group were stored for 24 h or subjected to thermocycling (6 × 10³ cycles). A shear bond strength (SBS) test was performed. Results were subjected to one-way ANOVA and Tukey's tests (α = 0.05). For experimental groups, XPS showed that formation of Si-O bonds contributed to increased Surface Free Energy (SFE). FE-SEM and EDS showed that the longer the deposition time, the greater the amount of silicon on the surface, presenting only a tetragonal phase. Zr-60 and Zr-300 presented higher and lower surface roughnesses, respectively. The silicon penetrated the microstructure, causing higher stress concentrations. The bond strength to resin cement was improved after all PECVD deposition times. Thus, the PECVD technique with the chemical compound SiH4, associated with chemical treatment with universal primer based on silane methacrylate, is a promising alternative for maintaining bonding between resin cement and HT zirconia(AU)