I love shopping but what am I going to buy? Social interaction and consumption choices.

In the present work, we analyze the emergence of fashion cycles and complex phenomena in a discrete time dynamic model in which a population is divided into two groups, bandwagoners and snobs. Both groups react differently to the aggregate demand for goods in the previous period and, in particular, bandwagoners imitate the consumption styles prevailing in society, while snobs try to distinguish themselves from them. We consider a first specification of the model in which the structure of the population is fixed and we show how in the case of polymorphic population it is possible to observe cyclical behaviors in collective consumption and the onset of chaotic regimes. We further propose an extension of the model in which we investigate the interdependence between the evolution of collective consumption choices and the evolution of the structure of the groups in a framework in which individuals may change the structure of preferences and then switch between being of one type or another. In the extension, we analyze how both consumption cycles (and then fashion cycles) and the evolution of the groups may lead to the emergence of chaotic dynamics, as well as the coexistence of attractors.

Clinical and Laboratory Features of 184 Italian Pediatric Patients Affected with Selective IgA Deficiency (SIgAD): a Longitudinal Single-Center Study.

PURPOSE: Selective IgA deficiency (SIgAD) is the most common humoral primary immunodeficiency. Long-term follow-up data in large cohort of pediatric patients are scarce. METHODS: We report on a single-center cohort of 184 pediatric patients affected with selective IgA deficiency and describe the characteristics at diagnosis and during follow-up. RESULTS: Respiratory infections were the most common clinical finding leading to the initial diagnosis (62%). Positive family history for antibody deficiencies (selective IgA deficiency, common variable immunodeficiency) led to SIgAD diagnosis in 16% of cases. During follow-up, while the incidence of respiratory infections was not particularly high, gastrointestinal symptoms were reported in 27% of patients. Allergic manifestations were found in 23% at diagnosis and an additional 16% of patients during follow-up, leading to a prevalence of atopy of 39% among SIgAD patients. Autoimmune manifestations, excluding celiac disease, were found in 9% of affected patients during follow-up. Celiac disease was found in a high prevalence (14%). Increase of serum IgA levels to partial deficiency (9%) and normal serum levels for age (4%) was observed during follow-up. A small percentage of patients (2%) progressed to common variable immunodeficiency (CVID). CONCLUSIONS: In conclusion, this is the first study to describe a large single-center pediatric cohort of patients affected with SIgAD, revealing that overall most patients do well with regard to infections. Many develop CD, at a rate much higher than the general population. A few normalize their IgA levels. A few progress to CVID. Thus, careful follow-up is suggested to diagnose and treat potential complications earlier for avoiding potential morbidities.

Local environmental quality and heterogeneity in an OLG agent-based model with spatial externalities.

Most of the theoretical contributions on the relationship between economy and environment assume the environment as a good distributed homogeneously among agents. The aim of this work is to relax this hypothesis and to consider that the environment can have a local character even if conditioned through externalities by the choices made at the global level. In this article, we adapt the classical framework introduced in John and Pecchenino (Econ J 104(427):1393-1410, 1994) to analyze the dynamic relationship between environment and economic process, and we propose an OLG agent-based model where each agent perceives her own level of environmental quality determined by her own decisions, and by the decisions of those living around her. Despite the attention devoted to local environmental aspects, network externalities (determined through the scheme of Moore neighborhoods) play a fundamental role in defining environmental dynamics and they may induce the emergence of cyclical dynamics. The occurrence of oscillations in the local environmental quality is partially mitigated by the presence of heterogeneity in individuals' preferences. Finally, when a centralized planner is introduced, the dynamics converge to stationary values regardless of the assumption on heterogeneity of agents.