Empirical likelihood confidence intervals for complex sampling designs

We define an empirical likelihood approach which gives consistent design-based confidence intervals which can be calculated without the need of variance estimates, design effects, resampling, joint inclusion probabilities and linearization, even when the point estimator is not linear. It can be used to construct confidence intervals for a large class of sampling designs and estimators which are solutions of estimating equations. It can be used for means, regressions coefficients, quantiles, totals or counts even when the population size is unknown. It can be used with large sampling fractions and naturally includes calibration constraints. It can be viewed as an extension of the empirical likelihood approach to complex survey data. This approach is computationally simpler than the pseudoempirical likelihood and the bootstrap approaches. The simulation study shows that the confidence interval proposed may give better coverages than the confidence intervals based on linearization, bootstrap and pseudoempirical likelihood. Our simulation study shows that, under complex sampling designs, standard confidence intervals based on normality may have poor coverages, because point estimators may not follow a normal sampling distribution and their variance estimators may be biased.<br/

Holomorphic Parafermions in the Potts model and SLE

We analyse parafermionic operators in the Q-state Potts model from three different perspectives. First, we explicitly construct lattice holomorphic observables in the Fortuin-Kasteleyn representation, and point out some special simplifying features of the particular case Q=2 (Ising model). In particular, away from criticality, we find a lattice generalisation of the massive Majorana fermion equation. We also compare the parafermionic scaling dimensions with known results from CFT and Coulomb gas methods in the continuum. Finally, we show that expectation values of these parafermions correspond to local observables of the SLE process which is conjectured to describe the scaling limit of the Q-state Potts model.Comment: 18 pages. v2: references to related work clarified. v3: minor corrections, version accepted for publication in JSTA

Small-scale vortical motions in cool stellar atmospheres

Aims: Our aim is to study the presence and properties of small-scale swirls in numerical simulations of the atmospheres of cool main-sequence stars. Our particular focus is on understanding the variations in these properties for different stellar types and their sensitivity to the surface magnetic field. Furthermore, we aim to investigate the role of these events in the energy transport within the simulated atmospheres. Methods: We analyze three-dimensional, radiative-magnetohydrodynamic, box-in-a-star, numerical simulations of four main-sequence stars of spectral types K8V, K2V, G2V, and F5V. These simulations include a surface small-scale dynamo responsible for amplifying an initially weak magnetic field. Thus, we can study models characterized by very weak, or, magnetic fields in near equipartition. To identify small-scale vortices in horizontal layers of the simulations, we employ the automated algorithm SWIRL. Results: Small-scale swirls are abundant in the simulated atmospheres of all the investigated cool stars. The characteristics of these events appear to be influenced by the main properties of the stellar models and by the strength of the surface magnetic field. In addition, we identify signatures of torsional Alfv\'enic pulses associated with these swirls, which are responsible for a significant vertical Poynting flux in the simulated stellar photospheres. Notably, this flux is particularly significant in the K8V model, suggesting a possible link to the enhanced basal \ion{Ca}{ii} H and K fluxes observed in the range of $B-V$ color index $1.1 \leq B - V \leq 1.4$. Finally, we present a simple analytical model, along with an accompanying scaling relation, to explain a peculiar result of the statistical analysis that the rotational period of surface vortices increases with the effective temperature of the stellar model

Description of the Tadpole of \u3cem\u3eAtelopus tricolor\u3c/em\u3e

Tadpoles of Atelopus belong to the gastromyzophorous guild of exotrophic larvae (Altig and Johnston, 1989), and are characterized by the presence of a conspicuous abdominal sucker and an expanded oral disc. The larvae of several Atelopus species have been described previously: A. varius (Starrett, 1967); A. certus, A. ignescens, and A. spumarius (Duellman and Lynch, 1969); A. cruciger (Mebs, 1980); A. flavescens (Lescure, 1981); A. peruensis (Gray and Cannatella, 1985); and A. subornatus (Lynch, 1986). These represent about 15% of the known species in the genus (Frost, 1985; Duellman, 1993). Although Atelopus tricolor was originally described at the beginning of the century (Boulenger, 1902), it is a poorly known species. It has been reported from only a few localities from southern Peru (type locality: Marcapata Valley, Departamento Cuzco), to Departamento Cochabamba, Bolivia (Fugler, 1984; De la Riva, 1990; Reynolds and Foster, 1992), at elevations of 600-2100 m (Duellman, 1979). Herein we characterize and illustrate the tadpole of Ate/opus tricolor

The Distress Calls of \u3cem\u3eLeptodactylus chaquensis\u3c/em\u3e Cei, 1950 and \u3cem\u3eLeptodactylus elenae\u3c/em\u3e Heyer, 1978 (Anura: Leptodactylidae)

We describe the distress calls of Leptodactylus chaquensis and Leptodactylus elenae. They each consist of a single, long, tonal sound with complex harmonic structure and complex frequency modulation. The distress calls of both species are different from their respective advertisement calls. Moreover, there are also clear interspecific differences. Harmonic frequencies in L. elenae are higher, there are fewer emphasized harmonics and the call is shorter and repeated at a higher rate (sometimes paired) than the call of L. chaquensis. Call duration, call rate, and position of the dominant harmonic change with the strength of the stimulus that the individuals are under; therefore, they are more variable than their respective advertisement calls

Excitons and charged excitons in semiconductor quantum wells

A variational calculation of the ground-state energy of neutral excitons and of positively and negatively charged excitons (trions) confined in a single-quantum well is presented. We study the dependence of the correlation energy and of the binding energy on the well width and on the hole mass. The conditional probability distribution for positively and negatively charged excitons is obtained, providing information on the correlation and the charge distribution in the system. A comparison is made with available experimental data on trion binding energies in GaAs-, ZnSe-, and CdTe-based quantum well structures, which indicates that trions become localized with decreasing quantum well width.Comment: 9 pages, 11 figure

Caracterización de los sistemas de producción de leche en la cuenca noreste de la Provincia de Córdoba, Argentina

91-97La cuenca lechera noreste es una de las principales regiones de mayor producción e industrialización de leche en la provincia de Córdoba. Sin embargo, no se dispone de una correcta caracterización de los sistemas de producción. Para ello se analizaron las diferencias en la composición de las dietas, la superficie de los establecimientos, la distancia al pavimento, el nivel de equipamiento, las mejoras de capital y la composición del rodeo en tambos con distinto nivel de producción. El objetivo de este estudio fue determinar las características de los tambos en la cuenca noreste de Córdoba a través de la estructura de producción, la base forrajera y la composición del rodeo. Se trabajó con una base de datos de 2070 tambos de los 3253 existentes en la provincia. Se establecieron dos categorías M1 y M2 que representan tambos de menor y mayor escala. A su vez, se subdividieron en alta y baja producción, resultando en cuatro modelos productivos. Esta cuenca se asienta en establecimientos con sistemas productivos con una alta heterogeneidad entre ellos que confiere una gran variabilidad en la zona. El modelo de tambos pequeños y de menor producción presenta una base forrajera compuesta principalmente por forraje alfalfa. El modelo de tambos pequeños y de alta producción presenta una estructura productiva con mayores mejoras y un alto porcentaje de alfalfa y silo. El modelo de tambos grandes y de baja producción se caracteriza por utilizar una dieta con baja participación de forraje silo y concentrados