Silvio Sandoval Zocchi

Discrete triangular distributions and non-parametric estimation for probability mass function

Abstract Discrete triangular distributions are introduced, in order to serve as kernels in the non-parametric estimation for probability mass function. They are locally symmetric around every point of estimation. Their variances depend on the smoothing bandwidth and establish a bridge between Dirac and discrete uniform distributions. The boundary bias related to the discrete triangular kernel estimator is solved through a modification of the kernel near the boundary. The mean integrated squared errors and then the optimal bandwidth are investigated. We also study the adequate bandwidth for excess zeros. The performance of the discrete triangular kernel estimator is illustrated using simulated count data. An application to count data from football is described and compared with a binomial kernel estimator.

Propriedades de barreira e solubilidade de filmes de amido de ervilha associado com goma xantana e glicerol

The aim of this work was to evaluate the barrier properties and solubility of biofilms made from wrinkled pea starch with high amylose content in association with xanthan gum and glycerol. Filmogenic solution (FS) with different levels of pea starch (3, 4 and 5%), xanthan gum (0, 0.05 and 0.1%) and glycerol (glycerol-starch 1:5 W/W) were tested. FS was obtained by boiling (5 minutes), autoclaving for 1 hour at 120 oC and the films were prepared by casting. The increased concentration of starch and glycerol in the composition caused increases in thickness of the films and in their solubility in water. The plasticizer also generated higher coefficients of water vapor and oxygen permeabilities to water vapor and to oxygen. The increasing concentration of xanthan gum did not interfere in the properties studied. Biofilms produced with wrinkled pea starch, with or without xanthan gum and glycerol, showed better barrier to oxygen and water vapor and low solubility in water, in comparison with films of yellow pea starch and other starch sources.

Distribution of aflatoxin contamination in maize samples

The distribution of the aflatoxin contamination was studied among four maize fractions, separated according to Brazilian grading rules for maize. The fraction that contained fermented, moldy, heated and sprouted grains normally had the highest levels of aflatoxin. However, the fraction contribution to the whole sample contamination level took into account the contamination fraction level and its weight to the whole sample. Considering this, the fraction that contained insect damaged, hollow, up to ¼ fermented and grains damaged by other causes was normally the fraction responsible for the total contamination level in the samples. Nevertheless, the fraction contributions were variable from sample to sample. Therefore, in conclusion, it was not possible to establish a standard behavior for grain fraction-type contribution for different maize lots. The Brazilian grading by qualitative types applied to samples did not show statistic correlation with aflatoxin contamination levels (P<0.05). Two type-1 samples (the best quality type) presented contamination of 380 and 146ng/g. The number of samples with contamination levels above those allowed by Brazilian law (20ng/g) was the same for qualitative types 2, 3, and BS (Below Standard).

Uso de peróxido de hidrogênio e ácido cítrico na conservação de cogumelos Pleurotus sajor-caju in natura

The mushrooms Pleurotus sajor-caju are usually avaliable in natura and according to the storage conditions, its shelf life varies from 3 to 7 days. The objectives of this study were to evaluate the increase of fresh mushroomsshelf life by immersion into citric acid solution, hydrogen peroxide solutions and distilled water. Fresh mushrooms were immersed in these solutions for 2 minutes, dried, packed in trays and kept under refrigeration (4°C) for 10 days. Color, texture and loss mass of the mushrooms were evaluated in the first, fifth and tenth days. A yellowish colour in the mushrooms appeared and their texture and mass decreased. The global aspect of the immersed mushrooms had no difference compared to the control; thus the process of immersion into different solutions did not extend the shelf life of fresh mushrooms.

On General Continuous Triangular and Two-sided Power Distributions

In this article, we directly introduce the continuous version of the general discrete triangular distributions (Kokonendji and Zocchi, 2010). It is bounded and, in general, unimodal with pike. It contains thus a very useful class of two-sided power distributions (van Dorp and Kotz, 2002a,b, 2003). Moments, particular cases, limit distributions, and relations between parameters are straightforwardly derived.

Phenotypic plasticity and local adaptation favor range expansion of a Neotropical palm

Abstract One of the most intriguing questions in plant ecology is which evolutionary strategy allows widely distributed species to increase their ecological range and grow in changing environmental conditions. Phenotypic plasticity and local adaptations are major processes governing species range margins, but little is known about their relative contribution for tree species distribution in tropical forest regions. We investigated the relative role of phenotypic plasticity and local adaptation in the ecological distribution of the widespread palm Euterpe edulis in the Brazilian Atlantic Forest. Genetic sampling and experiments were performed in old‐growth remnants of two forest types with higher (Seasonal Semideciduous Forests vs. Submontane Rainforest) and lower biogeographic association and environmental similarities (Submontane Rainforest vs. Restinga Forest). We first assessed the molecular genetic differentiation among populations, focusing on the group of loci potentially under selection in each forest, using single‐nucleotide polymorphism (SNPs) outliers. Further, we looked for potential adaptive divergence among populations in a common garden experiment and in reciprocal transplants for two plant development phases: seedling establishment and sapling growth. Analysis with outlier loci indicated that all individuals from the Semideciduous Forest formed a single group, while another group was formed by overlapping individuals from Submontane Rainforest and Restinga Forest. Molecular differentiation was corroborated by reciprocal transplants, which yielded strong evidence of local adaptations for seedling establishment in the biogeographically divergent Rainforest and Semideciduous Forest, but not for Restinga Forest and Submontane Rainforest. Phenotypic plasticity for palm seedling establishment favors range expansion to biogeographically related or recently colonized forest types, while persistence in the newly colonized ecosystem may be favored by local adaptations if climatic conditions diverge over time, reducing gene flow between populations. SNPs obtained by next‐generation sequencing can help exploring adaptive genetic variation in tropical trees, which impose several challenges to the use of reciprocal transplants.

Reconciling the Mitscherlich’s law of diminishing returns with Liebig’s law of the minimum. Some results on crop modeling

Reliable fertilizer recommendations depend on the correctness of the crop production models fitted to the data, but generally the crop models are built empirically, neglecting important physiological aspects related with response to fertilizers, or they are based in laws of plant mineral nutrition seen by many authors as conflicting theories: the Liebigs Law of the Minimum and Mitscherlichs Law of Diminishing Returns. We developed a new approach to modelling the crop response to fertilizers that reconcile these laws. In this study, the Liebigs Law is applied at the cellular level to explain plant production and, as a result, crop models compatible with the Law of Diminishing Returns are derived. Some classical crop models appear here as special cases of our methodology, and a new interpretation for Mitscherlichs Law is also provided.

Planning Herbicide Dose-Response Bioassays Using the Bootstrap

Dose response herbicide bioassays generally demand large amounts of time and resources. The choice of doses to be used is thus critical. For a given model, optimum design theory can be used to generate optimum designs for parameter estimation. However, such designs depend on the parameter values and in general do not have enough support points to detect lack of fit. This work describes the use of bootstrap methods to generate an empirical distribution of the optimum design points, based on the results of a previous experiment, and suggests designs based on this distribution. These designs are then compared to the Bayesian D-optimum designs