Long memory in the R/US / US exchange rate: A robust analysis

This article shows that the evidence of long memory for the daily R$/US$ exchange rate series after the implementation of the Real Plan is not robust when we analyze the existence of structural breaks in this series. We demonstrate that the long memory observed is caused by changes in the structure of variance, captured by a Markov Switching model in all the parameters. A Monte Carlo study shows that the long memory structure can be induced by changes in the unconditional variance parameters, and that the data generating mechanism is a short memory process.Neste artigo mostramos que a evidência de memória longa para a série de taxas de câmbio diárias R$/US$ após a implementação do Plano Real não é robusta quando analisamos a existência de quebras estruturais nesta série. Demonstramos que a memória longa encontrada é causada por mudanças na estrutura da variância, capturadas por um modelo de Mudança Markoviana em todos os parâmetros. Um estudo de Monte Carlo mostra que a estrutura de memória longa é induzida por mudanças nos parâmetros da variância incondicional, e o mecanismo gerador dos dados é um processo de memória curta

Bayesian Inference Applied to Dynamic Nelson-Siegel Model with Stochastic Volatility

In this article we propose to estimate a dynamic model for the term structure of interest rates considering two alternative specifications of the Nelson and Siegel (1987) model, generalizing several models found in literature. At first, we consider the weights of factors time-varying with conditional heteroskedasticity using a stochastic volatility model with common factors. In the second case, we consider a model where the latent factors individually follow autoregressive processes with stochastic volatility, including the possibility of leverage effects. The so-called volatility factorsseek to capture the uncertainty over time associated with the level, slope and curvature of the yield curve. The estimation is performed using Bayesian inference using Monte Carlo Markov Chain methods. The results for the term structure of DI futures and U.S. Treasuries used in this studyshow that the volatility factors are highly persistent, and also indicate that the use of stochastic volatility lead to better in-sample fits to the observed yield curve

Colorectal video-assisted surgery in Uruguay, after 106 cases

Marcelo Viola Malet: Clínica Quirúrgica “B”. Facultad de Medicina. Universidad de la República, Uruguay.-- Marcelo Laurini: Clínica Quirúrgica “3”. Facultad de Medicina. Universidad de la República, Uruguay.-- Justino Zeballos: Clínica Quirúrgica “B”. Facultad de Medicina. Universidad de la República, Uruguay.-- Nicolás Muniz: Clínica Quirúrgica “B”. Facultad de Medicina. Universidad de la República, Uruguay.-- Pablo Rodríguez Goñi: Clínica Quirúrgica “F”. Facultad de Medicina. Universidad de la República, Uruguay.-- Fernando Castelli: . Clínica Quirúrgica “A”. Facultad de Medicina. Universidad de la República, Uruguay.-- Gustavo Sánchez: Clínica Quirúrgica “2”. Facultad de Medicina. Universidad de la República, Uruguay.-- César Canessa: Clínica Quirúrgica “B”. Facultad de Medicina. Universidad de la República, Uruguay.-- Humberto Viola: Departamento de Cirugía, MUCAM, Montevideo, Uruguay. Contacto: Marcelo Viola Malet. E-mail: [email protected] advenimiento de la cirugía laparoscópica ha tenido un gran impacto en la cirugía gastrointestinal en los últimos 20 años. En particular la cirugía laparoscópica colorrectal es sin dudas el desarrollo técnico más importante en la cirugía de colon y recto de los últimos 15 años, y probablemente tendrá un impacto significativo en la formación quirúrgica y en los resultados de esta cirugía. En este trabajo intentamos reflejar nuestra experiencia en la cirugía laparoscópica colorrectal refiriéndonos a los aspectos fundamentalmente técnicos, el instrumental y nuestros resultados a corto y mediano plazo con este tipo de abordaje para la patología colorrectal. Contamos con experiencia en 106 casos de cirugía colorrectal laparoscópica, 63 hombres y 43 mujeres, desde noviembre de 2007 hasta marzo de 2014. En los últimos 4 años se operaron un promedio de 22 pacientes por año. Nuestra serie presentó un índice de falla de sutura del 4.72% y una mortalidad operatoria del 3.7%. El seguimiento promedio de los pacientes fue de 22 meses, con un mínimo de 1 y un máximo de 59 meses. La sobrevida global de la serie fue de 96.9%, con una media de sobrevida de 56.8 meses (IC: 54.3 – 59.2 meses); y una sobrevida libre de enfermedad de 90.7%, con una media de tiempo libre de la enfermedad de 52.2 meses (IC: 48.2 -56.3 meses). La cirugía laparoscópica colorrectal es factible y segura, con cifras de morbimortalidad similares a las presentadas en series a nivel mundial, tanto en cirugía laparoscópica como laparotómica, así como en la radicalidad oncológica de las resecciones.The advent of laparoscopic surgery has had a huge impact on gastrointestinal surgery in the past 20 years. Laparoscopic colorectal surgery is undoubtedly the most important technical development of the past 15 years, and will very likely have a significant impact on surgical training and on the results of this surgery. In recent years, significant events have happened in the history of surgery that have led us to develop new concepts, new terms, and different ways of performing the same techniques. In this paper we try to show our experience in laparoscopic colorectal surgery, mainly referring to the technical aspects, tools and our results in the short and medium term with this type of approach for colorectal disease. We have done 106 laparoscopic colorectal surgeries, 63 men and 43 women were operated since November 2007 to March 2014. In the last 4 years an average of 22 patients were operated per year. Our series presents a suture failure rate of 4.72% and an operative mortality of 3.7%. The average patient follow-up was 22 months, with a minimum of 1 and a maximum of 59 months. Overall survival in the series was 96.9%, with a median survival of 56.7 months (CI: 54.3 to 59.2 months) and disease free survival of 90.7% with a half off due to illness 52.2 months (CI: 48.2 to 56.3 months). Laparoscopic colorectal surgery is feasible and safe, with figures similar to those presented in series worldwide, both in laparotomic and laparoscopic surgery, as well as in cancer morbidity radical resections

Hemorragia Digestiva Alta en el Hospital Maciel. Estudio prospectivo descriptivo

Prospective descriptive study of patientshospitalized with high digestive haemorrhage(HDH) in the Emergency Unit of Maciel Hospitalbetween April 2000 and October 2001.The most frequent cause of HDH was theexistence of peptic gastroduodenal lesions and thispopulation is taken as the center for statisticalanalysis.Los autores realizan un estudio prospectivodescriptivo de los pacientes que ingresaron conhemorragia digestiva alta (HDA) en el Departamentode Emergencia del Hospital Maciel entreabril del año 2000 y octubre del 2001.La causa más frecuente de HDA fueron laslesiones pépticas gastroduodenales y se toma estapoblación como centro del análisis estadístico

Constrained smoothing B-splines for the term structure of interest rates

The constrained smoothing B-splines (COBS) is proposed as a nonparametric approach to estimate the term structure of interest rate. Compared to the existing methods in the literature, COBS' main innovation lies in its incorporation of important constraints imposed by no-arbitrage, such as monotonically decreasing and boundary conditions for the discount function, positive forward and spot rates. In addition, by estimating the conditional median function, COBS is less sensible to outliers in reduced samples than other common methods in the literature. Estimation for high and low liquidity markets together with simulation exercises puts COBS in an intermediate position between usual parametric and nonparametric methods in the literature. It has more flexibility than parametric methods and, compared to other nonparametric methods, satisfies no-arbitrage constraints and generates parsimonious shapes of the term structure of interest rates.Term structure No-arbitrage Interpolation Smoothing splines