Modeling stylized features in default rates.

We propose a stochastic model for the probability of default based on diffusions with given marginal distribution and autocorrelation function. The model tries to capture stylized features observed in historical default rates and is analytically tractable. Estimation procedures and expressions for analysis and prediction are provided.

Characteristic function estimation of non-Gaussian Ornstein-Uhlenbeck processes.

Continuous non-Gaussian stationary processes of the OU-type are becoming increasingly popular given their flexibility in modelling stylized features of financial series such as asymmetry, heavy tails and jumps. The use of non-Gaussian marginal distributions makes likelihood analysis of these processes unfeasible for virtually all cases of interest. This paper exploits the self-decomposability of the marginal laws of OU processes to provide explicit expressions of the characteristic function which can be applied to several models as well as to develop e±cient estimation techniques based on the empirical characteristic function. Extensions to OU-based stochastic volatility models are provided.Ornstein-Uhlenbeck process; Lévy process; self-decomposable distribution; characteristic function; estimation

The use of Mean Residual Life in testing departures from Esxponentiality.

vita media residua; test di esponenzialità; processo di wiener; processo di quantili

Il Prometheus Vinctus di Jean Dorat: qualche stravaganza congetturale

Aeschylus’ Prometheus Bound edited by Jean Dorat (Io. Auratus) in 1548 presents corrections of many printing errors of the Aldine (Venetiis 1518), i.e. the only source of Dorat, and different emendations ope ingenii. The aim of this paper is to discuss and contextualize three odd and arbitrary conjectures advanced by the ‘poëta regius’ Dorat at PV 41, 77 and 746

Overdenture sobre implantes em pacientes idosos

Um dos grandes desafios da Medicina Dentária moderna está relacionado com a necessidade de um atendimento diferenciado e multidisciplinar voltado para os cuidados com a saúde bucal da população idosa e pela promoção de um envelhecimento saudável. O médico dentista precisa estar atento às mudanças e particularidades advindas do envelhecimento, dada a inter-relação entre saúde oral e saúde geral do paciente. A perda dos dentes, que constitui um dos problemas mais comuns a nível mundial, resulta em diversos prejuízos funcionais, tais como: reabsorção óssea, desconforto, instabilidade, diminuição da capacidade proprioceptiva e mastigatória, afetando, assim, a qualidade de vida desses pacientes devido à grande insatisfação com a reabilitação oral tradicional. Com o surgimento dos implantes osteointegrados, estes aspectos foram melhorados, pela possibilidade de novas opções de tratamento como as sobredentaduras ou overdentures, que comprovaram ampla margem de indicação a esses pacientes que buscam melhoria funcional de suas peças protéticas. Deste modo, o presente trabalho tem como objetivo apresentar uma alternativa de tratamento aos pacientes idosos através de reabilitações orais com as sobredentaduras ou overdentures, restabelecendo a saúde do sistema estomatognático e o equilíbrio biopsicossocial do paciente idoso. Foi realizada uma pesquisa bibliográfica online entre Dezembro de 2015 e Março de 2016, com o objetivo de fazer uma revisão bibliográfica acerca do tema. Foi estabelecido um limite temporal entre 1995 e 2015, entretanto algumas outras publicações relevantes com datas anteriores foram consideradas.One of the great challenges of a modern dentistry is associated with the necessity to need a differentiated and multidisciplinary assistance focused on the care of the oral health of the elderly population and the promotion of healthy aging. The dentist needs to be aware of changes and circumstances arising from aging, given the interrelationship between oral health and general health of the patient. Loss of teeth, which is one of the most common problems worldwide, results in several functional limitations, such as bone reabsorption, discomfort, instability, masticatory capacity and proprioceptive decreased, thus affecting the quality of life of patients due to high dissatisfaction with traditional oral rehabilitation. With the advent of dental implants, these aspects have been improved by the possibility of new treatment options as overdentures, which proved wide margin of indication to those patients seeking functional improvement of their prosthetic devices. Therefore, this study intends to present an alternative treatment to elderly patients through oral rehabilitations with overdentures, restoring the health of the stomatognathic system and biopsychosocial balance of the elderly. We have done an on-line literature search between December 2015 and March 2016, in order to make a literature review about the subject. A time limit was established, between 1995 and 2015, however some other relevant publications backdating were considered

Characteristic function estimation of Ornstein-Uhlenbeck-based stochastic volatility models.

Continuous-time stochastic volatility models are becoming increasingly popular in finance because of their flexibility in accommodating most stylized facts of financial time series. However, their estimation is difficult because the likelihood function does not have a closed-form expression. In this paper we propose a characteristic function-based estimation method for non-Gaussian Ornstein-Uhlenbeck-based stochastic volatility models. After deriving explicit expressions of the characteristic functions for various cases of interest we analyze the asymptotic properties of the estimators and evaluate their performance by means of a simulation experiment. Finally, a real-data application shows that the superposition of two Ornstein-Uhlenbeck processes gives a good approximation to the dependence structure of the process.ornstein-uhlenbeck process; lévy process; stochastic volatility; characteristic function estimation