254 research outputs found
Phase Diagram of the Heisenberg Spin Ladder with Ring Exchange
We investigate the phase diagram of a generalized spin-1/2 quantum
antiferromagnet on a ladder with rung, leg, diagonal, and ring-exchange
interactions. We consider the exactly soluble models associated with the
problem, obtain the exact ground states which exist for certain parameter
regimes, and apply a variety of perturbative techniques in the regime of strong
ring-exchange coupling. By combining these approaches with considerations
related to the discrete Z_4 symmetry of the model, we present the complete
phase diagram.Comment: 17 pages, 10 figure
Evaluation of inoculum potential of pathogens in seeds: relation to physiological quality and DNA quantification by qPCR
Detection of Sclerotinia sclerotiorum in soybean seeds by conventional and quantitative PCR techniques
Anatomia foliar, morfologia e aspectos ecológicos das espécies da família Amaranthaceae da Reserva Particular do Patrimônio Natural Cara Preta, em Alto Paraíso, GO, Brasil
Physical properties and particle-size fractions of soil organic matter in crop-livestock integration
Generating fuzzy rules by learning from olive tree transpiration measurement - An algorithm to automatize Granier sap flow data analysis
The present study aims at developing an intelligent system of automating data analysis and prediction
embedded in a fuzzy logic algorithm (FAUSY) to capture the relationship between environmental variables
and sap flow measurements (Granier method). Environmental thermal gradients often interfere
with Granier sap flow measurements since this method uses heat as a tracer, thus introducing a bias in
transpiration flux calculation. The FAUSY algorithm is applied to solve measurement problems and provides
an approximate and yet effective way of finding the relationship between the environmental variables
and the natural temperature gradient (NTG), which is too complex or too ill-defined for precise
mathematical analysis. In the process, FAUSY extracts the relationships from a set of input–output environmental
observations, thus general directions for algorithm-based machine learning in fuzzy systems
are outlined. Through an iterative procedure, the algorithm plays with the learning or forecasting via a
simulated model. After a series of error control iterations, the outcome of the algorithm may become
highly refined and be able to evolve into a more formal structure of rules, facilitating the automation
of Granier sap flow data analysis. The system presented herein simulates the occurrence of NTG with reasonable
accuracy, with an average residual error of 2.53% for sap flux rate, when compared to data processing
performed in the usual way. For practical applications, this is an acceptable margin of error given
that FAUSY could correct NTG errors up to an average of 76% of the normal manual correction process. In
this sense, FAUSY provides a powerful and flexible way of establishing the relationships between the
environment and NTG occurrencesinfo:eu-repo/semantics/publishedVersio
Estímulo no crescimento e na hidrólise de atp em raízes de alface tratadas com humatos de vermicomposto: ii - efeito da fonte de vermicomposto.
Um dos fatores mais limitantes para a produção de vermicomposto é a disponibilidade de esterco. Neste trabalho, foi avaliado o efeito da substituição parcial do esterco por bagaço de cana e por resíduos de leguminosa (Gliricidia sepium) na vermicompostagem sobre a qualidade do vermicomposto e sobre a bioatividade dos humatos, avaliadas por meio da análise do crescimento radicular e da atividade das bombas de H+ isoladas de raízes de alface. A substituição do esterco por bagaço de cana e por resíduos de leguminosas não acarretou prejuízo às características químicas dos vermicompostos. No entanto, os humatos isolados
dos diferentes vermicompostos apresentaram características químicas distintas,tais como: acidez e propriedades óticas distintas. Os humatos produzidos a partir de esterco de bovino e da mistura esterco bovino + bagaço proporcionaram maiores estímulos no crescimento radicular das plantas de alface, sendo os mais indicados para uso na forma solúvel. A inclusão de resíduos de leguminosas no processo de vermicompostagem produziu humatos sem efeito sobre o desenvolvimento das raízes de alface
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