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The growth curves of animals, in general, have an “S” shape, also known as sigmoidal curves. This type of   curve is well fitted by nonlinear regression models, including von Bertalanffy’s model, which has been widely  applied in several areas, being presented in literature through different parameterizations, which in practice, can complicate its understanding, affect nonlinearity measures and inferences about parameters. To quantify  the nonlinearity present in a Bates and Watts model, a geometric concept of curvature has been used. The aim of this work was to analytically develop three parameterizations of the von Bertalanffy’s nonlinear model  referring to its nonlinearity, implications for inferences and to establish relationships between parameters in the different ways of expressing the models. These parameterizations were adjusted to the growth data of sheep. For each parameterization, the intrinsic and parametric curvature measurements described by Bates and Watts were calculated. The parameterization choice affects nonlinearity measures, consequently, influences the reliability and inferences about estimated parameters. The forms most used in literature showed the greatest deviations from linearity, showing the importance of analyzing these measures in any growth curve study. Parameterization should be used in which the b estimate represents the abscissa of the inflection point, as it presents minor linearity deviations and direct biological interpretation for all parameters.

A COVID-19 é uma infecção causada pelo coronavírus SARS-CoV-2, sendo que seus primeiros registros foram na cidade chinesa de Wuhan em dezembro de 2019, e foi considerada pela Organização Mundial da Saúde (OMS) uma pandemia mundial em março de 2020.  No Brasil, a COVID-19 se espalhou atingindo as 27 unidades federativas (UFs). Com isso, as tomadas de decisões para diminuir a velocidade de transmissão foram baseadas nas recomendações da OMS, onde a principal é isolamento social. Entretanto, devido a heterogeneidade da população em cada uma das UFs, a pandemia se difundiu de forma distinta.  Deste modo, é interessante fazer o agrupamento das UFs por similaridade devido algumas características, e assim, observar as medidas de combate a COVID-19 realizadas em cada um desse grupos. O objetivo deste estudo foi agrupar as UFs usando análise de cluster pelo método não-hierárquico k-means considerando os coeficientes epidemiológicos como incidência, prevalência e letalidade. Os dados foram obtidos do site do Ministério da Saúde do Brasil e foi constituído pelas variáveis número de casos e óbitos novos e acumulados nas UFs, além da população em risco.  Para análise de cluster a base de dados foi dividida em três períodos cronológicos para os três coeficientes em estudo. Com a análise de cluster foi possível verificar a estratificação da UFs conforme suas similaridades em relação a COVID-19. Assim, a estratificação da incidência, prevalência e letalidade por UFs pode se apresentar como um recurso adicional para sinalizar quais locais e quais medidas deverão ser adotadas e onde essas medidas foram eficazes.

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Doru luteipes (Scudder, 1876) is an omnivorous predator that finds different food resources in the corn plant: eggs of Spodoptera frugiperda (J.E. Smith, 1797), uredospores of Puccinia polysora (Underw, 1897), and pollen. Knowing the survival and food preferences of this predator is essential to define its relevance as a biological control agent. We hypothesize that the foraging behavior and predatory capacity of D. luteipes may be affected when several food resources, especially eggs of S. frugiperda, uredospores of P. polysora, and pollen are concurrently in the same plant. The survival of D. luteipes in the nymph stage and their preference among food resources, often available in corn plants, were determined. To verify the survival of D. luteipes, newly hatched nymphs were fed exclusively with 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- a combination of uredospores + eggs, and 5- artificial diet (control). In another experiment, nymphs and adults of D. luteipes with 24 and 48 hours of fasting were individually released in the center of a container with four diets: 1- uredospores of P. polysora, 2- eggs of S. frugiperda, 3- corn pollen, 4- artificial diet, and maintained for 10 minutes, to evaluate the food choice and feeding time. The exclusive feeding with S. frugiperda eggs caused low nymph survival (8%), but the combination of P. polysora uredospores + S. frugiperda eggs allowed 58.3% survival. D. luteipes preferred feeding during the nighttime and the most significant proportions of choices by nymphs and adults were for pollen and diet, with adults spending more time eating pollen. These findings indicate that the trophic choices of D. luteipes are relevant to understand its contribution as an agent to control pest insects and fungal diseases in corn.

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