Option-implied preferences adjustments, density forecasts, and the equity risk premium

The main objective of this paper is to analyse the value of information contained in prices of options on the IBEX 35 index at the Spanish Stock Exchange Market. The forward looking information is extracted using implied risk-neutral density functions estimated by a mixture of two lognormals and several alternative risk adjustments: the power, exponential and habit inspired based stochastic discount factors. Moreover, by allowing additional flexibility in the shape of the stochastic discount factor, two other ad hoc time varying risk aversion adjustments are also employed. Our results show that, between October 1996 and March 2000, we can reject the hypothesis that the risk neutral densities provide accurate predictions of the distributions of future realisations of the IBEX 35 index at four and eight week horizons. When forecasting through risk adjusted densities the performance of this period is statistically improved and we no longer reject that hypothesis. Somehow surprisingly, all risk adjusted densities generate similar forecasting statistics. Finally, from October 1996 to December 2004, the ex ante risk premium perceived by investors and that are embedded in option prices is between 12 and 18 percent higher than the premium required to compensate the same investors for the realised volatility in stock market returns. [resumen de autor

Testing the forecasting performance of IBEX 35 option-implied risk neutral densities

The main objective of this paper is to test whether the risk neutral densities (RNDs) implied in the prices of the future options contract on the Spanish IBEX 35 index accurately predict the distribution of future outcomes of the underlying asset. We estimate RNDs using both parametric and nonparametric procedures. We find that between 1996 and 2003 we cannot reject the hypothesis that the RNDs provide accurate predictions of the distributions of future realisations of the IBEX 35 index at four week horizon. However, this result is not robust by subperiods. In particular, from October 1996 to February 2000, we find that RNDs are not able to consistently predict the actual realisations of returns. In this period, option prices assign a low risk neutral probability to large rises compared with realisations. Tests based on the tails of the distribution show that RNDs significantly understate the right tail of the distribution for both the whole period and the first subperiod.[resumen de autor

Impact of the historical introduction of exotic fishes on the chironomid community of Lake Azul (Azores Islands)

Little is known about the effect of top predator introduction in historically fishless communities, especially on remote islands. This issue is important because it might strongly affect climate reconstructions derived from biota assemblages such as chironomids. Head capsule larval remains of chironomids have been studied in a 660 years lacustrine sedimentary sequence from Lake Azul (Sao Miguel Island, Azores archipelago) to assess the extent and timescale of the effect of the predator introduction occurring in this historically fishless lake. Analysis of similarity showed that the chironomid assemblage was statistically different before and after predator introduction (R = 0.78; p < 0.001). Abundance of chironomids was about 40% greater in the fishless lake period compared to the period in the presence of predator. Results show major change in chironomid assemblage coinciding with the first time of goldfish introduction (around 1790 CE), followed by carp (1890 CE) and pike (1979 CE) introductions. The composition of feeding group guilds changed following a pattern characterized by a decrease in abundance of detritivorous and predaceous taxa and an increase in abundance of grazing chironomid taxa. This study suggests that predator introduction was the most important factor affecting the chironomid assemblages in this natural, Azorean fishless lake, but predators did not affect all chironomid species. Other external forcings like major climate oscillations, anthropogenic activities in the catchment basin, and volcanic eruptions seem to play an additional role. The latest stage of the warm and arid Medieval Climate Anomaly (1000–1300 CE) favoured the occurrence of some warm-adapted chironomid taxa, which were absent through the Little Ice Age (ca. 1450–1850 CE) cool period.Azores. Fundo Regional da Ciência e Tecnologia; M3.1.7/F/009/2011Ministerio de Ciencia e Innovación; CGL2010-15767Ministerio de Ciencia e Innovación; CGL2013-40608-RPortugal. Fundação para a Ciência e Tecnologia; SFRH/BPD/99461/2014Portugal. Fundação para a Ciência e Tecnologia; SFRH/BPD/79923/2011Portugal. Fundação para a Ciência e Tecnologia; UID/BIA/50027/2013Portugal. Fundação para a Ciência e Tecnologia; POCI-01-0145-FEDER-00682

Atypical presentation of immunoglobulin G4-related disease as subglottic stenosis: a case-based review

Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory pathology that has been reported to affect principally the retroperitoneum, hepatobiliary system, salivary glands, orbital structures or lymph nodes. However, IgG4-RD with laryngeal involvement is a very rare entity. Our aims were to describe a case of subglottic stenosis as first and only manifestation of IgG4-RD and review the literature. A patient with IgG4-RD affecting the larynx that presented as subglottic stenosis is described. A MEDLINE database search of IgG4-RD cases with laryngopharyngeal manifestations was also conducted. A 30-year-old Caucasian woman was referred to a tertiary care hospital for dyspnea on exertion, which had been increasing for the last 4 months. Medical and surgical procedures revealed a subglottic stenosis, with a histological finding of IgG4 positive plasma cell infiltration. There was no evidence of other organ involvement. She was successfully treated with oral glucocorticoids and rituximab infusions. Glucocorticoids were rapidly tapered and the rituximab regimen was optimized, with no evidence of relapses. In the literature review, we found a total of 12 reported cases with laryngopharyngeal involvement, two of them with subglottic stenosis. IgG4-RD of the larynx is rare but should be considered after excluding more common disorders

Prótesis parcial obturatriz paralelizada, en paciente oncológico

Al enfrentarnos a casos que tienen relación con tumores de cabeza y cuello, hay que tener en cuenta la gran diversidad de presentaciones de las neoplasias, histopatología y topografía anatómica de las mismas. Sumado a esto intervendrán factores etiológicos o de riesgo, que darán distintas características epidemiológicas, sintomatológicas, tanto en la forma de progresión de la enfermedad, como en su pronóstico y plan de tratamiento. En este trabajo los autores presentan un caso clínico de una paciente femenino de 25 años con una maxilectomia, por mixoma odontogénico, en su variable histológica de Fibromixoma Odontogénico, ubicado en el seno maxilar derecho. El tratamiento rehabilitador protésico, se realiza con una prótesis obturatriz esquelética, preparando los pilares paralelizados, con los principios de un eje único y preciso de inserción y retiro

Variación y cambio lingüístico en el aula: nuevas propuestas pedagógicas para acercar sincronía y diacronía

Memoria ID-0070. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2014-2015

Impact of the historical introduction of exotic fishes on the chironomid community of Lake Azul (Azores Islands)

Little is known about the effect of top predator introduction in historically fishless communities, especially on remote islands. This issue is important because it might strongly affect climate reconstructions derived from biota assemblages such as chironomids. Head capsule larval remains of chironomids have been studied in a 660 years lacustrine sedimentary sequence from Lake Azul (Sao Miguel Island, Azores archipelago) to assess the extent and timescale of the effect of the predator introduction occurring in this historically fishless lake. Analysis of similarity showed that the chironomid assemblage was statistically different before and after predator introduction (R = 0.78; p < 0.001). Abundance of chironomids was about 40% greater in the fishless lake period compared to the period in the presence of predator. Results show major change in chironomid assemblage coinciding with the first time of goldfish introduction (around 1790 CE), followed by carp (1890 CE) and pike (1979 CE) introductions. The composition of feeding group guilds changed following a pattern characterized by a decrease in abundance of detritivorous and predaceous taxa and an increase in abundance of grazing chironomid taxa. This study suggests that predator introduction was the most important factor affecting the chironomid assemblages in this natural, Azorean fishless lake, but predators did not affect all chironomid species. Other external forcings like major climate oscillations, anthropogenic activities in the catchment basin, and volcanic eruptions seem to play an additional role. The latest stage of the warm and arid Medieval Climate Anomaly (1000-1300 CE) favoured the occurrence of some warm-adapted chironomid taxa, which were absent through the Little Ice Age (ca. 1450-1850 CE) cool period