Laplace approximation and natural gradient for Gaussian process regression with heteroscedastic student-t model

Statistics and Computing - We propose the Laplace method to derive approximate inference for Gaussian process (GP) regression in the location and scale parameters of the student- $$ {t}$$...     

The evolutionary diversity of urban forests depends on their land-use history

Urban Ecosystems - Urbanization leads to strong modifications of landscape structure and ecosystem functioning, and urban areas are spreading rapidly. The aim of this study was to investigate how...     

The Clinical Correlates of Reported Childhood Sexual Abuse: An Association Between Age at Trauma Onset and Severity of Depression and PTSD in Adults

This study investigated the relationship between the age of -self‐reported sexual abuse occurrence and the development of post-traumatic stress disorder and/or depressive symptoms in adulthood. Subjects were evaluated for the presence of post-traumatic stress disorder and/or depressive symptoms as well as for a self-reported history of sexual abuse before the age of 18. Results found that relative risk of having severe post-traumatic stress disorder symptoms was 10 times higher in patients reporting sexual abuse after age 12 than in those reporting sexual abuse before age 12. Relative risk of having severe depressive symptoms was higher for those abused before the age of 12 than for those abused after the age of 12. Findings suggest that the impact of reported sexual abuse at different stages of development may lead to distinct psychiatric symptoms in adulthood.     

The impact of AIDS on income and human capital

This paper studies the impact of HIV/AIDS on per capita income and education. It explores two channels on how HIV/AIDS affects income that have not been sufficiently stressed by previous literature: the reduction of the incentives to stay in school due to shorter expected longevity and the reduction in productivity of experienced workers. In the model, individuals live for three periods, may get infected in the second period, and with some probability die of AIDS before reaching the third period of their lives. Parents care for the welfare of the future generations so that they will maximize lifetime utility of their dynasty. The simulations predict that the most affected countries in Sub-Saharan Africa in the future will be, on average, 30% poorer than they would be without AIDS. Schooling will decline in some cases by 40%. These figures are dramatically reduced with widespread medical treatment, as it increases the survival probability and productivity of infected individuals.     

Market Rationality Inside Voluntary Sector: An Analysis of Five Organizations in Rio de Janeiro,Brazil

What we now understand as rational and logical in today’s world provides a mental scheme to take action, based on a framework of premises and values. These rules aim to maximize the utility of consequences, despite of any subjective value. Weber (Economy and Society, 1978) classified this scheme as an “instrumental rationality”, characterized by being guided by the goals, means, and consequence of the action. On the other hand, he also defined “substantive rationality”, postulated on the values of the subject, and not guided by any consequences of action. This study acknowledges that NGOs (non-governmental organizations) must belong to a field other than that of economic businesses, because they are based on different rationalities, especially when they encompass the observation in organizations that work for social transformation. A field study was made with five nonprofit organizations whose stated goals were social transformation, seeking to identify influences that the adoption of instrumental rationality imposes on accomplishing the expected objectives for these organizations. Contingencies were found that benefit from using instrumentality in such organizations, such as the need for self-subsistence, the area where they work, size of the organization, influence of the leader and so on. The conclusion is that the lack of consciousness of the market’s influence on them very often causes them to uncritically and bluntly absorb the typical organizational dynamics of economic business, which has strong potential to corrupt their conceptual motivations, when guiding them strategically through the consequences of actions.     

A new geometric INAR(1) process based on counting series with deflation or inflation of zeros

In this paper, we introduce a new non-negative integer-valued autoregressive time series model based on a new thinning operator, so called generalized zero-modified geometric (GZMG) thinning operator. The first part of the paper is devoted to the distribution, GZMG distribution, which is obtained as the convolution of the zero-modified geometric (ZMG) distributed random variables. Some properties of this distribution are derived. Then, we construct a thinning operator based on the counting processes with ZMG distribution. Finally, an INAR(1) time series model is introduced and its properties including estimation issues are derived and discussed. A small Monte Carlo experiment is conducted to evaluate the performance of maximum likelihood estimators in finite samples. At the end of the paper, we consider an empirical illustration of the introduced INAR(1) model.     

A Bernoulli autoregressive moving average model applied to rainfall occurrence

Abstract

In this article, we propose a new model for binary time series involving an autoregressive moving average structure. The proposed model, which is an extension of the GARMA model, can be used for calculating the forecast probability of an occurrence of an event of interest in cases where these probabilities are dependent on previous observations in the near term. The proposed model is used to analyze a real dataset involving a series that contains only data 0 and 1, indicating the absence or presence of rain in a city located in the central region of São Paulo state, Brazil.     

Some simple estimators for the two-parameter gamma distribution

ABSTRACT

In this paper, we propose two new simple estimation methods for the two-parameter gamma distribution. The first one is a modified version of the method of moments, whereas the second one makes use of some key properties of the distribution. We then derive the asymptotic distributions of these estimators. Also, bias-reduction methods are suggested to reduce the bias of these estimators. The performance of the estimators are evaluated through a Monte Carlo simulation study. The probability coverages of confidence intervals are also discussed. Finally, two examples are used to illustrate the proposed methods.     

Alternative Procedures to Discriminate Non Nested Multivariate Linear Regression Models

ABSTRACT

This article builds classical and Bayesian testing procedures for choosing between non nested multivariate regression models. Although there are several classical tests for discriminating univariate regressions, only the Cox test is able to consistently handle the multivariate case. We then derive the limiting distribution of the Cox statistic in such a context, correcting an earlier derivation in the literature. Further, we show how to build alternative Bayes factors for the testing of nonnested multivariate linear regression models. In particular, we compute expressions for the posterior Bayes factor, the fractional Bayes factor, and the intrinsic Bayes factor.     

Major Chemical Accidents in Industrializing Countries: The Socio-Political Amplification of Risk

Accidents in the chemical industry, such as those that took place in Seveso (1976) and Bhopal (1984), may kill or injure thousands of people, cause serious health hazards and irreversible environmental damage. The aim of this paper is to examine the ever-increasing risk of similar accidents becoming a frequent ocurrence in the so-called industrializing countries. Using figures from some of the worst chemical accidents in the last decades, data on the Bhopal disaster, and Brazil's social and institutional characteristics, we put forward the hypothesis that present social, political and economic structures in industrializing countries make these countries much more vulnerable to such accidents and create the type of setting where–if and when these accidents occur–they will have even more catastrophic consequences. The authors argue that only the transformation of local structures, and stronger technical cooperation between international organizations, industrialized and industrializing countries could reduce this vulnerability.