A Influência da publicidade na segurança rodoviária

Dissertação apresentada à Escola Superior de Comunicação Social para obtenção de grau de mestre em Publicidade e Marketing.

From weak Allee effect to no Allee effect in Richards’ growth models

Population dynamics have been attracting interest since many years. Among the considered models, the Richards’ equations remain one of the most popular to describe biological growth processes. On the other hand, Allee effect is currently a major focus of ecological research, which occurs when positive density dependence dominates at low densities. In this chapter, we propose the dynamical study of classes of functions based on Richards’ models describing the existence or not of Allee effect. We investigate bifurcation structures in generalized Richards’ functions and we look for the conditions in the (β, r) parameter plane for the existence of a weak Allee effect region. We show that the existence of this region is related with the existence of a dovetail structure. When the Allee limit varies, the weak Allee effect region disappears when the dovetail structure also disappears. Consequently, we deduce the transition from the weak Allee effect to no Allee effect to this family of functions. To support our analysis, we present fold and flip bifurcation curves and numerical simulations of several bifurcation diagrams.

Main causes of death in Dande, Angola: results from verbal autopsies of deaths occurring during 2009–2012

bACKGROUND - The Dande Health and Demographic Surveillance System (HDSS) located in Bengo province, Angola, covers nearly 65,500 residents living in approximately 19,800 households. This study aims to describe the main causes of deaths (CoD) occurred within the HDSS, from 2009 to 2012, and to explore associations between demographic or socioeconomic factors and broad mortality groups (Group I-Communicable diseases, maternal, perinatal and nutritional conditions; Group II-Non-communicable diseases; Group III-Injuries; IND-Indeterminate). Methods - Verbal Autopsies (VA) were performed after death identification during routine HDSS visits. Associations between broad groups of CoD and sex, age, education, socioeconomic position, place of residence and place of death, were explored using chi-square tests and fitting logistic regression models. Results - From a total of 1488 deaths registered, 1009 verbal autopsies were performed and 798 of these were assigned a CoD based on the 10th revision of the International Classification of Diseases (ICD-10). Mortality was led by CD (61.0%), followed by IND (18.3%), NCD (11.6%) and INJ (9.1%). Intestinal infectious diseases, malnutrition and acute respiratory infections were the main contributors to under-five mortality (44.2%). Malaria was the most common CoD among children under 15 years old (38.6%). Tuberculosis, traffic accidents and malaria led the CoD among adults aged 15–49 (13.5%, 10.5 % and 8.0% respectively). Among adults aged 50 or more, diseases of the circulatory system (23.2%) were the major CoD, followed by tuberculosis (8.2%) and malaria (7.7%). CD were more frequent CoD among less educated people (adjusted odds ratio, 95% confidence interval for none vs. 5 or more years of school: 1.68, 1.04–2.72). Conclusion - Infectious diseases were the leading CoD in this region. Verbal autopsies proved useful to identify the main CoD, being an important tool in settings where vital statistics are scarce and death registration systems have limitations.