Outliers and misleading leverage effect in asymmetric GARCH-type models

This paper illustrates how outliers can affect both the estimation and testing of leverage effect by focusing on the TGARCH model. Three estimation methods are compared through Monte Carlo experiments: Gaussian Quasi-Maximum Likelihood, Quasi-Maximum Likelihood based on the Student-t likelihood and Least Absolute Deviation method. The empirical behavior of the t-ratio and the Likelihood Ratio tests for the significance of the leverage parameter is also analyzed. Our results put forward the unreliability of Gaussian Quasi-Maximum Likelihood methods in the presence of outliers. In particular, we show that one isolated outlier could hide true leverage effect whereas two consecutive outliers bias the estimated leverage coefficient in a direction that crucially depends on the sign of the first outlier and could lead to wrongly reject the null of no leverage effect or to estimate asymmetries of the wrong sign. By contrast, we highlight the good performance of the robust estimators in the presence of one isolated outlier. However, when there are patches of outliers, our findings suggest that the sizes and powers of the tests as well as the estimated parameters based on robust methods may still be distorted in some cases. We illustrate these results with two series of daily returns.Generalitat Valenciana, Funder Id: http://dx.doi.org/10.13039/501100003359, Grant Number: AICO/2019/295. Consejería de Educación, Junta de Castilla y León, Funder Id: http://dx.doi.org/10.13039/501100008431, Grant Number: VA148G18. Spanish Government, Grant Number: ECO2017-87069-P and ECO2016-77900-P

Identification of asymmetric conditional heteroscedasticity in the presence of outliers

The identification of asymmetric conditional heteroscedasticity is often based on sample cross-correlations between past and squared observations. In this paper we analyse the effects of outliers on these cross-correlations and, consequently, on the identification of asymmetric volatilities. We show that, as expected, one isolated big outlier biases the sample cross-correlations towards zero and hence could hide true leverage effect. Unlike, the presence of two or more big consecutive outliers could lead to detecting spurious asymmetries or asymmetries of the wrong sign. We also address the problem of robust estimation of the cross-correlations by extending some popular robust estimators of pairwise correlations and autocorrelations. Their finite sample resistance against outliers is compared through Monte Carlo experiments. Situations with isolated and patchy outliers of different sizes are examined. It is shown that a modified Ramsay-weighted estimator of the cross-correlations outperforms other estimators in identifying asymmetric conditionally heteroscedastic models. Finally, the results are illustrated with an empirical application.Financial support from the Spanish Government under project ECO2014-58434-P by the first author and under project ECO2012-32401 by the second and third authors, is gratefully acknowledged. The first and second authors also acknowledge financial support from Generalitat Valenciana under project PROMETEO/2013/037 and from Comunidad de Castilla y León under project VA066U13, respectively

Antonio León Ortega, un escultor de frontera

La obra de Antonio León Ortega se muestra como alternativa a los cánones preestablecidos en la escultura religiosa de España y Portugal desde el SXVII, y sin renunuciar a estos, aporta una visión personal, bañada de nuevas propuestas plásticas aprendidas en el ambiente del Madrid del primer cuarto de SXX.The work of Antonio León Ortega is shown as an alternative to the canons preset in religious sculpture of Spain and Portugal from the XVII, and not renouncing to theese, brings a personal, bathed vision of new proposed plastic learned in the atmosphere in Madrid in the first quarter of XX.

Comparison of particulate matter emission and soluble matter collected from combustion cigarettes and heated tobacco products using a setup designed to simulate puffing regimes

An experimental setup was designed and optimized to collect particulate matter suspended in cigarettes smoke or in the aerosol generated during the use of heated tobacco products (HTPs). The setup is mainly based on a gas washing flask containing water where particulate matter and soluble compounds can be trapped, resembling interaction in the body. This system allows to perform puffing experiments in conditions similar to those of the Health Canada Intense puffing regime. In the study, cigarettes and Heets (in IQOS heater) from Philip Morris Products were used. Complementary characterization of this particulate matter has been extracted from experiments on a gas washing flask containing isopropanol. Total organic carbon analysis, laser diffraction, UV-vis spectrophotometry and transmission electron microscopy measurements have shown that cigarette smoke contains a large number and content of compounds soluble in water and isopropanol, together with solid particles generated during combustion. In contrast, negligible presence of non-combustion related particles was detected in Heets aerosol samples. These facts, together with the higher amount of water soluble compounds and higher number of polyaromatic hydrocarbons detected in the cigarettes smoke, allow to conclude that HTPs are less harmful than combusted cigarettes.The research described in this study was funded by Philip Morris Products S.A., Switzerland (part of Philip Morris International group of companies)

TiO2 and TiO2-Carbon Hybrid Photocatalysts for Diuron Removal from Water

TiO2 and TiO2-activated carbon (AC) photocatalysts have been prepared (by sol-gel synthesis), characterized, and tested in the removal of diuron from water under simulated solar light. The preparation variables of the two series of catalysts are: (i) heat-treatment temperature of bare TiO2 (350, 400, 450 and 500 °C) and (ii) activated carbon content (0.5, 1, 5, and 10 wt.%) in TiO2-AC samples heat-treated at 350 °C. The activated carbon was previously prepared by hydrothermal carbonization of saccharose and has spherical shape. The heat-treatment temperature does not determine the efficiency of TiO2 for diuron photocatalytic degradation but clearly influences the diuron adsorption capacity. The capacity of TiO2-AC samples for diuron removal increases with the carbon content and it is the result of combined diuron adsorption and photodegradation. Thus, the sample with highest carbon content (10 wt.% nominal) leads to the highest diuron removal. The TiO2-AC photocatalysts have proved to be capable of degrading diuron previously adsorbed in dark conditions, which allows their regeneration.This research was funded by the Spanish Ministry of Science, Innovation and Universities, MICIU, and Fondo Europeo de Desarrollo Regional, FEDER, (RTI2018-095291-B-I00), by Generalitat Valenciana and FEDER (GV/FEDER (PROMETEO/2018/076)) and by the University of Alicante (VIGROB-136)

The stellar content of giant H II regions in NGC 7714

This is an electronic version of an article published in The Astrophysical Journal. García-Vargas, M.L., González-Delgado, R.M., Pérez, E., Alloin, D., Díaz, A. and E. Terlevich. The stellar content of giant H II regions in NGC 7714. The Astrophysical Journal 478 (1997): 112-12

Conservative management of dentigerous cysts in children

Purpose and Introduction: Dentigerous cysts are epithelial in origin and are the most commonly found cyst in children. The majority of these lesions are usually a radiological finding and are capable of quite large before being diagnosed. The standard treatment for these cysts is the enucleation and the extraction of the affected tooth. However, if the patient is a child and the affected tooth is not developed, a more conservative attitude should be considered. Material and Methods: (Clinical case): A 7-year-old patient is presented with an eruptive backlog of the lower permanent first molars. Radiological examination reveals two radiolucid lesions in relation to them, which are compatible with a dentigerous cyst, and in relation to the inferior aveolar nerve and various germs. A partial enucleation is carried out, maintaining all the dental germs related to the cyst in mouth and monitoring the patient until the case study is over. Results and Discussion: Diagnosis and early treatment of these lesions in children is of great importance, especially in cases where the lesions enclose permanent teeth. Conclusions: Whenever possible, a conservative attitude should be taken, one that allows for the maintenance of the dentition and treatment of the associated cyst in order to not compromise either the occlusion or the mental state of these patients

Fieldtrip manual for Plant Biodiversity

Plant Biodiversity is a subject taught during the second year of the Undergraduate Degree in Biology at the University of Alicante. The main principles about the diversity and morphology of the plants are mostly given during the theoretical classes. This fieldtrip practical manual, together with the laboratory sessions, gives the students an opportunity to see our most common wild plant species. Their direct observations allow them to identify properly the main botanical families, genera and species of our wild flora. This Fieldtrip manual for Plant Biodiversity has been written to enhance the understanding of plant diversity and to identify the different ecological conditions for plant species. Students have to understand that “plants do not grow everywhere”. Most of our natural flora, and specially the endemic one, requires specific environmental conditions to grow. So, the objectives of these fieldtrips are to identify wild flora and to recognise the ecological habitats where many of the identified plant species live