Growth curve based on scale mixtures of skew-normal distributions to model the age-length relationship of Cardinalfish (Epigonus Crassicaudus)

Our article presents a robust and flexible statistical modeling for the growth curve associated to the age-length relationship of Cardinalfish (Epigonus Crassicaudus). Specifically, we consider a non-linear regression model, in which the error distribution allows heteroscedasticity and belongs to the family of scale mixture of the skewnormal (SMSN) distributions, thus eliminating the need to transform the dependent variable into many data sets. The SMSN is a tractable and flexible class of asymmetric heavy-tailed distributions that are useful for robust inference when the normality assumption for error distribution is questionable. Two well-known important members of this class are the proper skew-normal and skew-t distributions. In this work emphasis is given to the skew-t model. However, the proposed methodology can be adapted for each of the SMSN models with some basic changes. The present work is motivated by previous analysis about of Cardinalfish age, in which a maximum age of 15 years has been determined. Therefore, in this study we carry out the mentioned methodology over a data set that include a long-range of ages based on an otolith sample where the determined longevity is higher than 54 years.Comment: 16 pages, 6 figure

Dephasing-assisted transport in linear triple quantum dots

Environmental noise usually hinders the efficiency of charge transport through coherent quantum systems; an exception is dephasing-assisted transport (DAT). We show that linear triple quantum dots in a transport configuration and subjected to pure dephasing exhibit DAT if the coupling to the drain reservoir exceeds a threshold. DAT occurs for arbitrarily weak dephasing and the enhancement can be directly controlled by the coupling to the drain. Moreover, for specific settings, the enhanced current is accompanied by a reduction in relative shot noise. We identify the quantum Zeno effect and long-distance tunnelling as underlying dynamical processes involved in dephasing-assisted and -suppressed transport. Our analytical results are obtained by using the density matrix formalism and the characteristic polynomial approach to full counting statistics.Comment: To appear in New Journal of Physics, 20 pages, 5 figure

Spatial dispersion in Casimir forces: A brief review

We present the basic principles of non-local optics in connection with the calculation of the Casimir force between half-spaces and thin films. At currently accessible distances $L$, non-local corrections amount to about half a percent, but they increase roughly as 1/L at smaller separations. Self consistent models lead to corrections with the opposite sign as models with abrupt surfaces.Comment: Proceedings of QFEXT05, Barcelona, Sept. 5-9, 200

Variable stars in the globular cluster M28 (NGC 6626)

We present a new search for variable stars in the Galactic globular cluster M28 (NGC 6626). The search is based on a series of BVI images obtained with the SMARTS Consortium's 1.3m telescope at Cerro Tololo Inter-American Observatory, Chile. The search was carried out using the ISIS v2.2 image subtraction package. We find a total of 25 variable stars in the field of the cluster, 9 being new discoveries. Of the newly found variables, 1 is an ab-type RR Lyrae star, 6 are c-type RR Lyrae, and 2 are long-period/semi-regular variables. V22, previously classified as a type II Cepheid, appears as a bona-fide RRc in our data. In turn, V20, previously classified as an ab-type RR Lyrae, could not be properly phased with any reasonable period. The properties of the ab-type RR Lyrae stars in M28 appear most consistent with an Oosterhoff-intermediate classification, which is unusual for bona-fide Galactic globulars clusters. However, the cluster's c-type variables do not clearly support such an Oosterhoff type, and a hybrid Oosterhoff I/II system is accordingly another possibility, thus raising the intriguing possibility of multiple populations being present in M28. Coordinates, periods, and light curves in differential fluxes are provided for all the detected variables.Comment: A&A, in pres

Paisajes culturales agrarios del estado Mérida,Venezuela

Este trabalho aborda a interpretação das paisagens culturais agrárias no estado de Mérida, na Cordilheira dos Andes venezuelanos, adaptado a uma classificação dos tipos bioclimáticos. No "Andar SubAndino", acima de 400m de altitude, domina a paisagem com banana, árvores de fruto, e criação de gado (para produção de carne e leite), enquanto que entre 400 e 1700m a paisagem predominante é café sob sombra em ambientes úmidos e campos de cana de açúcar em ambientes secos. No "Andar Andino", entre 1700 e 2300m predomina uma produção intensiva de hortaliças e tubérculos (principalmente de batatas) em ambientes húmidos, enquanto ambientes secos apresentam uma paisagem relíquia de antigos campos de trigo. O sector da pecuária é dominado por gado de leite. Elevações de 2300 a 3000m são dominadas pela agricultura comercial intensiva dos pequenos e médios produtores de legumes, batatas e flores; assim como a pecuária leiteira e piscicultura de truta. No "Andar AltiAndino" existem culturas intensivas e extensivas, e criação de gado de leite entre 3000 e 4000m, enquanto acima de 4000m há uma pastagem básica muito extensa.En este trabajo se aborda la interpretación de los paisajes culturales agrarios del estado Mérida, en los Andes venezolanos, utilizando una clasificación por pisos bioclimáticos. En el “Piso Subandino”, hasta los 400m de elevación, predomina el paisaje con plátano (banana), árboles frutales, y ganadería vacuna extensiva (producción de carne y leche), mientras que entre los 400 y 1700m el paisaje predominante es el de cafetales bajo sombra en ambientes húmedos y de caña de azúcar en ambientes más secos. En el “Piso Andino”, entre los 1700 y 2300m predomina la producción intensiva de hortalizas, papa y ajo en ambientes húmedos, mientras que en ambientes secos queda un paisaje relicto del cultivo del trigo de épocas pretéritas. En el sector pecuario predomina la ganadería de altura para producción láctea. En elevaciones de 2300 a 3000m predomina una agricultura de tipo comercial e intensiva de pequeños y medianos productores de hortalizas, papas y flores; así como ganadería de altura y piscicultura de truchas. En el “Piso Altiandino” hay cultivos intensivos y extensivos, y ganadería extensiva entre 3000 y 4000m, mientras que en las tierras por sobre 4000m existe un pastoreo básico muy extensivo.This work deals with the interpretation of agrarian cultural landscapes in Mérida State, in the Venezuelan Andes, adapted to a classification of bioclimatic belts. In the "SubAndean bealt", up to 400m of elevation, the landscape with banana, fruit trees and cattle ranching (for meat and milk production) dominates, while between 400 and 1700m the predominant landscape is coffee plantations under shade in moist environments and sugarcane fields in dry environments. In the "Andean bealt", between 1700 and 2300m predominates an intensive production of vegetables and tubercles (mainly potatoes) in humid environments, while the dry environments exhibit a relict landscape of past wheat fields. The livestock sector is dominated by dairy-cattle ranching. Elevations of 2300 to 3000m are dominated by intensive commercial agriculture of small and medium producers of vegetables, potatoes and flowers, as well as dairy-cattle ranching and trout fish-farming. In the "HighAndean bealt" there are intensive and extensive crops, and cattle ranching between 3000 and 4000m, while above 4000m there is a very basic extensive-grazing