A thorough analysis of the short- and mid-term activity-related variations in the solar acoustic frequencies

The frequencies of the solar acoustic oscillations vary over the activity cycle. The variations in other activity proxies are found to be well correlated with the variations in the acoustic frequencies. However, each proxy has a slightly different time behaviour. Our goal is to characterize the differences between the time behaviour of the frequency shifts and of two other activity proxies, namely, the area covered by sunspots and the 10.7cm flux. We define a new observable that is particularly sensitive to the short-term frequency variations. We then compare the observable when computed from model frequency shifts and from observed frequency shifts obtained with the Global Oscillation Network Group (GONG) for cycle 23. Our analysis shows that on the shortest time-scales the variations in the frequency shifts seen in the GONG observations are strongly correlated with the variations in the area covered by sunspots. However, a significant loss of correlation is still found. We verify that the times when the frequency shifts and the sunspot area do not vary in a similar way tend to coincide with the times of the maxima of the quasi-biennial variations seen in the solar seismic data. A similar analysis of the relation between the 10.7cm flux and the frequency shifts reveals that the short-time variations in the frequency shifts follow even more closely those of the 10.7cm flux than those of the sunspot area. However, a loss of correlation between frequency shifts and 10.7cm flux variations is still found around the same times.Comment: 7 pages, 6 figures, accepted for publication in MNRA

On the relation between activity-related frequency shifts and the sunspot distribution over the solar cycle 23

The activity-related variations in the solar acoustic frequencies have been known for 30 years. However, the importance of the different contributions is still not well established. With this in mind, we developed an empirical model to estimate the spot-induced frequency shifts, which takes into account the sunspot properties, such as area and latitude. The comparison between the model frequency shifts obtained from the daily sunspot records and those observed suggests that the contribution from a stochastic component to the total frequency shifts is about 30%. The remaining 70% is related to a global, long-term variation. We also propose a new observable to investigate the short- and mid-term variations of the frequency shifts, which is insensitive to the long-term variations contained in the data. On the shortest time scales the variations in the frequency shifts are strongly correlated with the variations in the total area covered by sunspots. However, a significant loss of correlation is still found, which cannot be fully explained by ignoring the invisible side of the Sun when accounting for the total sunspot area. We also verify that the times when the frequency shifts and the sunspot areas do not vary in a similar way tend to coincide with the times of the maximum amplitude of the quasi-biennial variations found in the seismic data.Comment: 4 pages, 2 figures, proceedings of the Joint TASC2 - KASC9 Workshop - SPACEINN - HELAS8 Conference "Seismology of the Sun and the Distant Stars 2016: Using Today's Successes to Prepare the Future". To be published by the EPJ Web of Conference

Metodologias empregadas em estudos de avaliação da atividade alelopática em condições de laboratório: revisão crítica.

Nas últimas décadas, tem proliferado a formação de grupos de pesquisa dedicados aos estudos na área de alelopatia, em diferentes partes do mundo. O Brasil não ficou imune a essa tendência; prova disso são os números cada vez maiores de artigos científicos publicados em periódicos nacionais e internacionais. O fato de a alelopatia ser uma ciência relativamente jovem, podendo ser considerada em sua fase juvenil de desenvolvimento, tem propiciado a proliferação de técnicas de estudos diversificadas e muitas vezes carentes de embasamento. Adicionalmente, essa peculiaridade dificulta o entendimento das grandezas expressas e do valor biológico que os resultados apresentados podem significar. Uniformizar os procedimentos é, sem dúvida alguma, ponto de partida quando se pensa na dimensão que a alelopatia pode representar em futuro próximo. Neste trabalho, foram revisados criticamente os protocolos pertinentes aos processos empregados nos bioensaios desenvolvidos para caracterizar as propriedades alelopáticas de extratos brutos e de substâncias químicas. Ao mesmo tempo, os pontos fortes e as limitações de cada procedimento são apresentados

Quasivariational solutions for first order quasilinear equations with gradient constraint

We prove the existence of solutions for an evolution quasi-variational inequality with a first order quasilinear operator and a variable convex set, which is characterized by a constraint on the absolute value of the gradient that depends on the solution itself. The only required assumption on the nonlinearity of this constraint is its continuity and positivity. The method relies on an appropriate parabolic regularization and suitable {\em a priori} estimates. We obtain also the existence of stationary solutions, by studying the asymptotic behaviour in time. In the variational case, corresponding to a constraint independent of the solution, we also give uniqueness results

Produtividade e desempenho de cana soca cultivada em diferentes espaçamentos e doses de adubação nitrogenada em cobertura.

RESUMO: A cana-de-açúcar é atualmente uma das culturas mais importantes no cenário socioeconômico brasileiro, por ser a principal matéria-prima utilizada pela indústria sucroalcooleira para a produção de açúcar e etanol, com poucos estudos dedicados a cana soca. O trabalho foi conduzido com objetivo de avaliar o desenvolvimento e a produtividade da cana-soca, plantada em espaçamentos entrelinhas de 1,0 e 1,5 m, submetida a diferentes doses de adubação nitrogenada de cobertura. O experimento foi conduzido em campo, no município de Presidente Prudente, SP. Utilizou-se o delineamento experimental em blocos completos ao acaso, com quatro repetições, no esquema fatorial 4x2, com parcelas sub-divididas, em que nas parcelas foram instalados os espaçamentos entre sulcos de 1,0 e 1,5 m e nas sub-parcelas a adubação nitrogenada de cobertura na cana-soca com 0, 50, 100 e 200 kg ha-1de nitrogênio sendo aplicado aos 60 dias após o corte (DAC). Foram realizadas análises de produtividade e o Brix aos nove e aos doze meses após o corte. Os resultados foram submetidos à análise de variância e analisados pelo teste Tukey a 5% de probabilidade. Conclui-se que a adubação nitrogenada não influenciou o desenvolvimento e a produtividade da cana soca (segundo corte), tendo o espaçamento entrelinhas de 1,0 m apresentado produtividade superior ao de 1,5 m. ABSTRACT: The sugarcane is currently one of the most important crops in the Brazilian economic scenario may be the main raw material used by the industry for the production of sugar and ethanol, with few studies dedicated to ratoon. The objective of this study was to evaluate the growth and yield of ratoon cane (variety RB 867515), planted in row widths of 1.0 and 1.5 m, subjected to different doses of nitrogen fertilization. The experiment was conducted in the field, in the city of Presidente Prudente-SP. The experimental design was randomized in split-plot, with four replications, in a 4x2 factorial, in which the plots were installed spacings of 1.0 and 1.5 m in the sub-plots the nitrogen applied in the sugarcane with 0, 50, 100 and 200 kg N ha-1at 60 days after cutting (DAC). Productivity and o Brix analyses at nine and twelve months after the cut. The results were submitted to ANOVA and Tukey test (5% probability). Nitrogen fertilization didn?t influence the development and productivity of sugarcane ratoon. The ratoon cane yield was greater in spacing of 1.0 m in relation to 1.5 m