Growth curve based on scale mixtures of skew-normal distributions to model the age-length relationship of Cardinalfish (Epigonus Crassicaudus)

Our article presents a robust and flexible statistical modeling for the growth curve associated to the age-length relationship of Cardinalfish (Epigonus Crassicaudus). Specifically, we consider a non-linear regression model, in which the error distribution allows heteroscedasticity and belongs to the family of scale mixture of the skewnormal (SMSN) distributions, thus eliminating the need to transform the dependent variable into many data sets. The SMSN is a tractable and flexible class of asymmetric heavy-tailed distributions that are useful for robust inference when the normality assumption for error distribution is questionable. Two well-known important members of this class are the proper skew-normal and skew-t distributions. In this work emphasis is given to the skew-t model. However, the proposed methodology can be adapted for each of the SMSN models with some basic changes. The present work is motivated by previous analysis about of Cardinalfish age, in which a maximum age of 15 years has been determined. Therefore, in this study we carry out the mentioned methodology over a data set that include a long-range of ages based on an otolith sample where the determined longevity is higher than 54 years.Comment: 16 pages, 6 figure

Non-Gaussian Geostatistical Modeling using (skew) t Processes

We propose a new model for regression and dependence analysis when addressing spatial data with possibly heavy tails and an asymmetric marginal distribution. We first propose a stationary process with $t$ marginals obtained through scale mixing of a Gaussian process with an inverse square root process with Gamma marginals. We then generalize this construction by considering a skew-Gaussian process, thus obtaining a process with skew-t marginal distributions. For the proposed (skew) $t$ process we study the second-order and geometrical properties and in the $t$ case, we provide analytic expressions for the bivariate distribution. In an extensive simulation study, we investigate the use of the weighted pairwise likelihood as a method of estimation for the $t$ process. Moreover we compare the performance of the optimal linear predictor of the $t$ process versus the optimal Gaussian predictor. Finally, the effectiveness of our methodology is illustrated by analyzing a georeferenced dataset on maximum temperatures in Australi

Skewed Factor Models Using Selection Mechanisms

Traditional factor models explicitly or implicitly assume that the factors follow a multivariate normal distribution; that is, only moments up to order two are involved. However, it may happen in real data problems that the first two moments cannot explain the factors. Based on this motivation, here we devise three new skewed factor models, the skew-normal, the skew-t, and the generalized skew-normal factor models depending on a selection mechanism on the factors. The ECME algorithms are adopted to estimate related parameters for statistical inference. Monte Carlo simulations validate our new models and we demonstrate the need for skewed factor models using the classic open/closed book exam scores dataset

Ideology and Etiology in the Treatment of Edward Bliss Emerson\u27s Pulmonary Consumption

Although Edward Bliss Emerson’s life had unusual promise, his death was quite ordinary: he died of pulmonary consumption, which accounted for one in five deaths in the 1830s. He went to the West Indies in search of a more healthful climate, and sought it in St. Croix and Puerto Rico. But his quest was short-lived, and he died in 1834 at the age of 29. Because there was no consensus on the cause of consumption, treatment for the condition varied widely, and included a number of nostrums and therapies that may be considered “self-care.” Edward adopted a series of practices that he documented in his journal, therefore providing us with the range of lifestyle interventions and other therapies that were seen as desirable, and the belief systems informing these at the time. These practices ranged from the medically-sanctioned to the highly personal and idiosyncratic, and suggest a variety of holistic approaches to addressing an illness for which there was no “magic bullet.

Vegetable protein isolates

This chapter discusses the importance of vegetable proteins as functional ingredients in food formulations. It provides an overview of the main chemical components, world production, history and food applications of the main vegetable protein sources (legumes, cereals, oilseeds, roots and green leaves), with special emphasis on soybean, pea, and wheat. The chapter includes a description of the composition and structure of the main protein fractions, and a general approach to protein extraction, purification and processing technology to prepare protein meals, concentrates and isolates. In addition, the technologically important functional properties of vegetable protein preparations are described. Finally, nutritional and health effects, as well as the regulatory status of vegetable protein products are examined.Spanish Ministry of Science and Innovation.Peer reviewe