Self-Similarity and Lamperti Convergence for Families of Stochastic Processes

We define a new type of self-similarity for one-parameter families of stochastic processes, which applies to a number of important families of processes that are not self-similar in the conventional sense. This includes a new class of fractional Hougaard motions defined as moving averages of Hougaard L\'evy process, as well as some well-known families of Hougaard L\'evy processes such as the Poisson processes, Brownian motions with drift, and the inverse Gaussian processes. Such families have many properties in common with ordinary self-similar processes, including the form of their covariance functions, and the fact that they appear as limits in a Lamperti-type limit theorem for families of stochastic processes.Comment: 23 pages. IMADA preprint 2010-09-0

Some discrete exponential dispersion models : poisson-tweedie and hinde-demétrio classes

In this paper we investigate two classes of exponential dispersion models (EDMs) for overdispersed count data with respect to the Poisson distribution. The first is a class of Poisson mixture with positive Tweedie mixing distributions. As an approximation (in terms of unit variance function) of the first, the second is a new class of EDMs characterized by their unit variance functions of the form µ + µp, where p is a real index related to a precise model. These two classes provide some alternatives to the negative binomial distribution (p = 2) which is classically used in the framework of regression models for count data when overdispersion results in a lack of fit of the Poisson regression model. Some properties are then studied and the practical usefulness is also discussed

The new class of Kummer beta generalized distributions

Ng and Kotz (1995) introduced a distribution that provides greater flexibility to extremes.We define and study a new class of distributions called the Kummer beta generalized family to extend the normal, Weibull, gamma and Gumbel distributions, among several other well-known distributions. Some special models are discussed. The ordinary moments of any distribution in the new family can be expressed as linear functions of probability weighted moments of the baseline distribution. We examine the asymptotic distributions of the extreme values. We derive the density function of the order statistics, mean absolute deviations and entropies. We use maximum likelihood estimation to fit the distributions in the new class and illustrate its potentiality with an application to a real data set

Hierarchical models with normal and conjugate random effects : a review

Molenberghs, Verbeke, and Demétrio (2007) and Molenberghs et al. (2010) proposed a general framework to model hierarchical data subject to within-unit correlation and/or overdispersion. The framework extends classical overdispersion models as well as generalized linear mixed models. Subsequent work has examined various aspects that lead to the formulation of several extensions. A unified treatment of the model framework and key extensions is provided. Particular extensions discussed are: explicit calculation of correlation and other moment-based functions, joint modelling of several hierarchical sequences, versions with direct marginally interpretable parameters, zero-inflation in the count case, and influence diagnostics. The basic models and several extensions are illustrated using a set of key examples, one per data type (count, binary, multinomial, ordinal, and time-to-event)

Aplicação de alguns herbicidas na cultura da couve-flor (Brassica oleracea var. botrytis)

An experiment about herbicide use on cauliflower (Brassica oleracea var. botrytis) crop was conducted in the Experimental Field of Horticulture Section DAH-ESALQ, Piracicaba, Brazil. It was tested Dacthal (DCPA), Tenoran (chloroxuron), Afalon (linuron) and Ramrod (propachlor). Dacthal, Ramrod and Tenoran were not fitotoxic to cauliflower, and Afa-lon was very toxic. The herbicide that gave the best results to cauliflower was Ramrod.Foi conduzido na Área Experimental do Setor de Horticultura, DAH-ESALQ, Piracicaba, um experimento sobre o uso de alguns herbicidas na cultura da couve-flor (Brassica oleracea var. botrytis). Os herbicidas foram Dacthal (DCPA), Tenoran (cloroxuron), Afalon (linuron) e Ramrod (propacloro). O Dacthal, Ramrod, e o Tenoran não foram fitotóxicos à couve-flor, enquanto que o Afalon foi muito fitotóxico. O herbicida que melhor resultado apresentou para a couve-flor foi o Ramrod

Qualidade fisiológica e comportamento de sementes de soja (Glycine max (L.) Merrill) no armazenamento e no campo

Soybean, seeds (Glycine mas (L.) Merrill) of 'IAC-Foscarin 31' (Group VI) and 'IAC-8' (group VIII) were harvested weekly in field plots planted in 1981, 1982 and 1983; after harvests, seeds were stored under normal environment conditions, dry chamber (35% RH) and cold chamber (10°C + 80% RH) during six months at the Seed Laboratory of the Escola Superior de Agricultura "Luiz de Queiroz", Universidade de São Paulo, Brasil. The behavior of seeds during storage was evaluated bimonthly by germination, accelerated aging, electrical conductivity and seedling emergence tests; plat performance was studied in field experiments planted in 1982, 1983 and 1984. Results showed that all laboratory tests were related to field emergence, but electrical conductivity was found to be the most efficient test to characterize physiological quality and field emergence potential. Seeds of 'IAC-8' showed better quality than 'IAC-Foscarin 31', but this fact was related to environmental conditions during maturation and harvest time. Storability was determined by environmental relative humidity and initial quality of seeds.A presente pesquisa, conduzida, entre 1981 e 1985 no Departamento de Agricultura e Horticultura da Escola Superior de Agricultura "Luiz de Queiroz" - USP, constou de colheita, em diferentes épocas, de campos de sementes dos cultivares IAC-Foscarin 31 (precoce) e IAC-8 (semi-tardio). Os materiais coletados foram, em seguida, armazenados em câmara seca, câmara fria e ambiente normal; periodicamente, com intervalos bimestrais, conduziram-se testes de germinação, envelhecimento acelerado, conduti-vidade elétrica e emergência das plântuIas, além de ensaios de campo instalados em época normal de semeadura para a cultura da soja. Observou-se que os testes realizados em laboratório, com destaque para o de condutividade elétrica, mostraram-se eficientes para diferenciar níveis de qualidade fisiológica e estimar o potencial de emergência das plântulas; sementes do cultivar precoce apresentaram qualidade fisiológica inferior às do semi-tardio, fato atribuído às condições climáticas adversas predominantes durante o final do ciclo das plantas. A umidade relativa do ambiente e a qualidade fisiológica inicial constituiram-se em fatores preponderantes no potencial de conservação das sementes