Differential effects of aging on spatial contrast sensitivity to linear and polar sine-wave gratings

Changes in visual function beyond high-contrast acuity are known to take place during normal aging. We determined whether sensitivity to linear sine-wave gratings and to an elementary stimulus preferentially processed in extrastriate areas could be distinctively affected by aging. We measured spatial contrast sensitivity twice for concentric polar (Bessel) and vertical linear gratings of 0.6, 2.5, 5, and 20 cycles per degree (cpd) in two age groups (20-30 and 60-70 years). All participants were free of identifiable ocular disease and had normal or corrected-to-normal visual acuity. Participants were more sensitive to Cartesian than to polar gratings in all frequencies tested, and the younger adult group was more sensitive to all stimuli tested. Significant differences between sensitivities of the two groups were found for linear (only 20 cpd; P<0.01) and polar gratings (all frequencies tested; P<0.01). The young adult group was significantly more sensitive to linear than to circular gratings in the 20 cpd frequency. The older adult group was significantly more sensitive to linear than to circular gratings in all spatial frequencies, except in the 20 cpd frequency. The results suggest that sensitivity to the two kinds of stimuli is affected differently by aging. We suggest that neural changes in the aging brain are important determinants of this difference and discuss the results according to current models of human aging

Dinâmica de transposição de herbicida através de palha de aveia-preta utilizando diferentes pontas de pulverização Dynamics of herbicide crossing through black oat straw by using different nozzle models

A transposição da palha por herbicidas aplicados em pré ou pós-emergência durante a aplicação é determinante na sua eficiência, dinâmica e impacto ambiental. O experimento foi conduzido no Núcleo de Pesquisas Avançadas em Matologia - FCA/UNESP, campus de Botucatu-SP, tendo como objetivo avaliar o desempenho de diferentes modelos de pontas de pulverização na transposição em quantidades crescentes de palha de aveia-preta (Avena strigosa). Os tratamentos foram constituídos pelo monitoramento do traçador corante Azul Brilhante (FDC-1) a 3.000 ppm, pulverizado com as pontas de pulverização XR11002-VS, TJ60-11002VS, FL-5VS, DG11002-VS, TXVK-8, TT11002-VP e AI11002-VS, utilizando, respectivamente, as pressões de trabalho de 1,4; 2,0; 1,5; 2,0; 4,9; 3,0 e 3,0 kgf cm² e volume de calda de 200, 200, 428, 200, 213 e 270 L ha-1 sobre quantidades de 0, 1, 2, 4, 6, 8, 10 e 12 t ha-1 de palha de aveia-preta. O delineamento utilizado foi o inteiramente casualizado, com sete tratamentos e cinco repetições, as quais foram constituídas de caixas plásticas com palha acondicionada sobre um fundo falso de área conhecida, sendo este lavado após as aplicações, para posterior quantificação do traçador em espectrofotometria. O modelo de Mitscherlich simplificado (Y = 10 &#094; (2 - (C*X))) mostrou ajuste satisfatório para os dados originais de traçador que transpôs a palha, apresentando coeficientes de determinação (R²) elevados, oscilando entre 0,9782 e 0,9971. Todos os modelos de pontas de pulverização mostraram-se similares na transposição da palha pelo traçador. As porcentagens médias de transposição foram de 43,00; 18,77; 3,73; 0,78; 0,17; 0,04 e 0,01% para as quantidades de 1, 2, 4, 6, 8, 10 e 12 t ha-1 de palha, respectivamente.<br>Straw crossing by pre- or post-emergence herbicide application determines its effectiveness, dynamics and environmental impact. The trial was carried out at NuPAM - FCA/UNESP, Botucatu Campus, São Paulo, Brazil, to evaluate the performance of different nozzle models in crossing increasing amounts of black oat (Avena strigosa) straw. The treatments consisted of monitoring Brilliant Blue (FDC-1) tracer dye at 3.000 ppm, sprayed with nozzles XR11002-VS; TJ60-11002VS; FL-5VS; DG11002-VS; TXVK-8; TT11002-VP and AI11002-VS, at work pressures 19.9; 28.4; 21.3; 28.4; 69.7; 42.7 and 42.7 PSI, respectively; and mix volumes 200; 200; 428; 200; 213 and 270 L ha-1; on 0, 1, 2, 4, 6, 8, 10 and 12 t ha-1 of black oat straw. The experimental design was entirely randomized with seven treatments and five replications, constituted by plastic boxes packed with straw over a fake bottom of known area, washed after the applications, for posterior tracer quantification by spectrophotometry. The Simplified Mitscherlich model (Y = 10 &#094; (2 - (C*X))) showed a satisfactory adjustment for the tracer original data crossing the straw, presenting high determination coefficients (R²) between 0.9782 and 0.9971. The nozzle models were similar in relation to straw crossing by the tracer. The mean crossing percentages were 43.00; 18.77; 3.73; 0.78; 0.17; 0.04 and 0.01% for the amounts 1, 2, 4, 6, 8, 10 and 12 t ha¹ of black oat straw, respectively

Associação do herbicida tebuthiuron com a cobertura de palha no controle de plantas daninhas no sistema de cana-crua

O objetivo da presente pesquisa foi verificar a eficácia do herbicida tebuthiuron no controle de plantas daninhas quando associadas à presença de palha de cana-de-açúcar. Para isso, conduziu-se um experimento em condições controladas em casa de vegetação, utilizando-se vasos com quatro repetições, onde, além das testemunhas com e sem palha, o tebuthiuron foi aplicado em diferentes situações: sobre 5 t de palha ha-1; sobre o solo posteriormente recoberto com 5 t de palha ha-1; sobre o solo sem cobertura de palha; e com ou sem simulação de distintas quantidades de chuva aplicada antes ou após a aplicação do produto. A dose de Combine 500 SC (tebuthiuron) aplicada foi de 1.000 g i.a. ha-1, com consumo de calda equivalente a 200 L ha-1. As plantas daninhas presentes no experimento foram Brachiaria plantaginea, Brachiaria decumbens e Ipomoea grandifolia. Avaliou-se a porcentagem de controle das plantas daninhas aos 7, 14, 21, 28, 35, 42, 49 e 56 DAA nos tratamentos em que o tebuthiuron foi aplicado em pré-emergência e aos 3, 10, 17, 24, 31 e 38 DAA, quando o herbicida foi aplicado em pós-emergência; e a biomassa seca aos 56 ou 38 DAA. Verificou-se que, independentemente da planta daninha avaliada, os maiores índices de controle foram alcançados quando o tebuthiuron foi aplicado sobre a palha, simulando-se em seguida precipitação correspondente a 2,5 ou 30 mm de chuva, e nos tratamentos em que o herbicida foi aplicado diretamente no solo desnudo ou recoberto com palha. Dessa forma, para I. grandifolia, B. plantaginea e B. decumbens, os índices mais elevados de controle foram alcançados quando o tebuthiuron atingiu o solo, tanto aplicado diretamente como quando lixiviado da palha pela chuva simulada após a aplicação.The objective of this work was to evaluate the effectiveness of tebuthiuron associated with sugar cane straw to control weed under different conditions. Thus, an experiment was carried out in pots with four replications where, besides being applied with and without straw, tebuthiuron was applied on 5 t straw ha-1; on soil recently covered with 5 t straw ha-1;and on soil without straw cover and with and without simulation of different amounts of rain applied before or after herbicide application. The rate of Combine 500 SC (tebuthiuron) applied was 1,000 g a.i. ha -1 with 200 L ha-1 of spray volume application. The weeds used were Brachiaria plantaginea, Brachiaria decumbens and Ipomoea grandifolia. Weed control percentage was evaluated at 7, 14, 21, 28, 35, 42, 49 and 56 days after application (DAA) when tebuthiuron was applied in pre-emergence; and at 3, 10, 17, 24, 31 and 38 DAA when applied in post-emergence; dry matter weight was evaluated at 56 and 38 DAA, respectively. Regardless of the weed assessed, it was verified that the highest control rates were reached when tebuthiuron was applied on the straw, after rainfall simulation corresponding to 2.5 or 30 mm or for the treatments where the herbicide was applied directly on bare soil or covered with straw. Thus, for I. grandifolia, B. plantaginea and B. decumbens, the highest control levels were obtained when the herbicide reached the soil directly as well as leached through the straw by simulated rainfall after application