RESUMO Testes de toxicidade anaeróbia foram realizados com corantes aromáticos azo (tetra-azo Direct Black 22 — DB22 e di-azo Direct Orange 4 — DO4) e antraquinônico (Reactive Blue 19 — RB19), com o objetivo de verificar a influência dos diferentes grupos químicos desses compostos na inibição da atividade metanogênica. Para o corante DB22, foram realizados dois testes com concentrações de corante de 0,03, 0,06, 0,09, 0,12 e 0,24 mmol·L−1 (TTADB22) e 0,3, 0,6, 0,9; ,,2 e 2,4 mmol·L−1 (TTADB22Adap, com lodo adaptado). Para os corantes DO4 (TTADO4) e RB19 (TTARB19), as concentrações utilizadas foram 0,5, 1, 2, 3, e 4 mmol·L−1. Os resultados indicaram que ambos os grupamentos químicos azo e antraquinônico podem ser inibidores da metanogênese. Cada corante resultou em um potencial tóxico diferente, dependendo da natureza do corante, das concentrações utilizadas e dos subprodutos gerados. O corante antraquinônico RB19 apresentou taxa de inibição da metanogênese duas vezes maior que o azocorante DO4, sugerindo maior tolerância dos microrganismos metanogênicos ao azocorante do que ao corante antraquinônico. Entre os azocorantes, as maiores taxas de inibição foram verificadas para o DB22 (48%), que possui maior número de grupos sulfônicos em sua estrutura que o DO4. Em geral, maiores percentuais de remoção de corante foram obtidos para menores concentrações de corante aplicadas.

ABSTRACT Anaerobic toxicity tests were performed using aromatic azo dyes (tetra-azo Direct Black 22 — DB22 and diazo Direct Orange 4 — DO4) and an anthraquinone dye (Reactive Blue 19 — RB19), aiming to verify the influence of the different chemical groups of these dyes on the inhibition of methanogenic activity. For DB22 dye, two tests were performed with dye concentrations of 0.03; 0.06; 0.09; 0.12; and 0.24 mmol·L−1 (TTABD22) and 0.3; 0.6; 0.9; 1.2; and 2.4 mmol·L−1 (TTADB22Adap, with adapted sludge). For DO4 (TTADO4) and RB19 (TTARB19) dyes, the concentrations used were 0.5; 1.0; 2.0; 3.0; and 4.0 mmol·L−1. The results indicated that both azo and anthraquinone chemical groups may be inhibitors for methanogenesis. Each dye resulted in a different toxic potential, depending on the nature of the dye, the concentrations used, and the by-products generated. Anthraquinone dye RB19 showed an inhibition rate of methanogenesis twice as high as azo dye DO4, indicating greater tolerance of methanogenic microorganisms to azo dye than to anthraquinone dye. Among the azo dyes, the highest inhibition rates were verified for DB22 (48%), which has a greater number of sulfonic groups in its structure than DO4. In general, higher percentages of dye removal were obtained for lower dye concentrations.

ABSTRACT. Brachiaria brizantha is the most economically important forage grass in Brazil and is propagated through sowing. Producing high-quality seeds has been a constant challenge due to their uneven maturation. The development and application of precise and non-destructive methods for identifying internal damages to seeds, such as the X-ray test, which quickly indicates the quality of the lots, is of fundamental importance for the seed industry. In this work, the quality of Brachiaria brizantha seeds was analyzed based on the morphological characteristics observed in X-ray images that were related to viability using a mixture model under a Bayesian approach, with the following objectives: i) verify the adequacy of the Bayesian modeling used in the data analysis; ii) associate the efficiency of using radiographs as a way to assess the viability of the seeds; and iii) relate the classifications carried out by evaluators with the probability of originating normal or abnormal seedlings. The methodology applied for the analysis proved to be adequate. Further, the Bayesian estimates for parameters related to internal morphology were established with associated levels of uncertainty, which represents an advantage over usual frequentist methods. Based on the model's estimates, seeds evaluated as potentially unviable by three evaluators had practically no probability of germination and did not germinate in the test applied later. Seeds classified as potentially viable had a high probability of developing into normal seedlings, while 73.27% showed this property in the germination test.

Abstract Water deficit stress is the abiotic factor with the highest impact on crop yield. The objective of this study was to evaluate grain yield (GY), the anthesis-silking interval (ASI) and drought tolerance indices in maize hybrids. We evaluated GY and the ASI of 86 hybrids under two moisture levels (normal irrigation and water stress) for three consecutive years. The stress susceptibility index, water stress tolerance, drought resistance coefficient, drought resistance index, stress tolerance index and harmonic mean were evaluated. There were significant hybrid x environment interactions for GY and the ASI. Differences in the ASI among environments ranged from 0 to 5 days. The hybrids P3862, 1I873, 1I923, 1I862 and 1J1211 showed high GY, associated with the highest drought tolerance indices. The stress tolerance index and harmonic mean indices can be used to identify higher-yielding maize hybrids in environments with and without water restriction.

ABSTRACT. Maize breeding programs conduct multi-environment trials every year to assess the performance of new cultivars in pre-releasing tests. The data are combined across sites and seasons to perform a joint analysis in order to obtain information that will help breeders to select the best cultivars for different environments. Beyond this, it is essential to understand the different factors that can hamper the selection and genetic progress (i.e., genetic variability, selection intensity and genotype-by-environment interactions). In this study, the genetic progress (GP) was estimated and the adaptability and stability of 81 maize genotypes were evaluated in a series of trials for the value of cultivation and use (VCU) between the 2010/11 and 2014/15 growing seasons. The genotypes were composed of open-pollinated varieties, topcross hybrids, intervarietal hybrids, and single, double and three-way cross hybrids and were assessed in 117 environments in the central region of Brazil, from which 22 presented environmental stresses. For grain yield, an annual GP of 331.5 kg ha-1 was observed, thus showing efficiency in the selection of superior cultivars. Additionally, it was observed that some low-cost seed cultivars showed yield potential, adaptability and stability estimates that were compatible with commercial hybrids, thus making them quite attractive for cultivation in environments with or without abiotic stresses.

This work presents a density functional theory study of the norbornene ROMP metathesis reactions. The energies have been calculated in a Grubbs catalyst model Cl2(PH3)2Ru=CH2. The geometries and energy profile are similar to the Grubbs metilydene (Cl2(PCy3)2Ru=CH2 real model. It was found that the metathesis reaction proceeds via associative mechanism (catalyst-norbonene) followed by dissociative substitution of a phosphine ligand with norbonene, giving a monophosphine complex. The results are in reasonable agreement with the available experimental data. The dissociation energy of the phosphines is predicted to be 23.2 kcal mol-1.