Two-level interacting boson models beyond the mean field

The phase diagram of two-level boson Hamiltonians, including the Interacting Boson Model (IBM), is studied beyond the standard mean field approximation using the Holstein-Primakoff mapping. The limitations of the usual intrinsic state (mean field) formalism concerning finite-size effects are pointed out. The analytic results are compared to numerics obtained from exact diagonalizations. Excitation energies and occupation numbers are studied in different model space regions (Casten triangle for IBM) and especially at the critical points.Comment: 14 pages, 13 figure

Perovskite-like LaNiO3-δ as oxygen electrode material for solid oxide electrolysis cells

Perovskite-like LaNiO3-δ was evaluated as potential oxygen electrode material for solid oxide electrolysis cells. Compared to the Ruddlesden-Popper Lan+1NinO3n+1 (n = 1,2,3) counterparts, LaNiO3-δ exhibits higher p-type metallic-like conductivity under oxidizing conditions (450 S×cm-1 at 800°C for highly porous ceramics) together with a moderate thermal expansion coefficient (13.7 ppm×K-1 in air at 25-800°C) compatible with common solid electrolytes. The measured electrode polarization resistance (Rη) in contact with YSZ, CGO and LSGM solid electrolytes was 1.4, 0.77 and 0.22 Ω×cm2 at 800°C, and 208, 123 and 7.1 Ω×cm2 at 600°C, respectively, under zero-current conditions in air. Surface modification of via PrOx infiltration resulted in lower values of Rη (0.024 Ω×cm2 at 800°C and 0.76 Ω×cm2 at 600°C) and low anodic overpotentials (20 mV at 800°C and 500 mA×cm-2) in contact with LSGM.publishe

Propiedades psicométricas del Cuestionario de Aceptación y Acción-II en adultos ecuatorianos

Objetivo. Analizar las propiedades psicométricas del AAQ-II en población adulta ecuatoriana con tomas presenciales, aumentando la fiabilidad de la muestra. Método. En este estudio se evaluaron las propiedades psicométricas de la Acceptance and Action Questionnaire-II (AAQ-II) en población ecuatoriana. Participaron 450 personas entre 18 y 53 años, de las cuales un 46.7% fueron mujeres y un 53.3% hombres. Resultados. En el análisis factorial confirmatorio se encontró una estructura de tres dimensiones: evitación de recuerdos, evitación emocional y falta de autodominio. Un análisis de invarianza reveló que la escala es invariante entre hombres y mujeres. Se encontró que la escala presenta buena consistencia interna (α = .90). Se discute la validez de la AAQ-II como una herramienta para evaluar la evitación experiencial en población adulta ecuatoriana

Phylo‐biogeographical distribution of whitefly Bemisia tabaci (Insecta: Aleyrodidae) mitotypes in Ecuador

Abstract The Bemisia tabaci complex in Ecuador was studied with respect to phylogenetic relationships and eco‐geographical distribution. Whitefly samples were collected from natural and agricultural environments in nine provinces of Ecuador (latitude, 2° N–5° S; longitude, 78°–81° W). Mitotypes were identified based on phylogenetic analysis of the 3′‐mtCOI‐tRNAleu region (832 bp) and corrected pairwise distance analysis. The distribution of mitotypes was modeled using MaxEnt, and their predicted niches were characterized according to environmental gradients. Four B. tabaci mitotypes were identified, of which three are endemic, herein ECU1–3, and the other is the introduced B mitotype. Mitotypes ECU1 (44%), ECU2 (0.74%), and ECU3 (1.47%) grouped in the American Tropics (AMTROP) species and diverged by as much as 10%, which was higher than previous estimates for the AMTROP clade of 7–8.6%. Although haplotypes of ECU1 and ECU2 are known from the American Tropics, this is the first report of the ECU3 mitotype, which may possibly be restricted to southern Ecuador. The distribution of the three ECU‐endemic mitotypes spanned the high‐altitude niches of the western slope of the Andes, rich in microclimates with variable temperature and humidity conditions. The non‐endemic B mitotype (47%) occurred only in the irrigated cropping systems located in hot and/or dry‐tropical ecological niches. Of the endemic mitotypes, ECU1 occupied the most ecological niches. Among variables contributing to ECU1 and B mitotype niche range assignments, the most significant to influence ecological range was rainfall. The B. tabaci endemic to Ecuador were more diverse with respect to mtCOI‐tRNAleu sequence than previously known, and occupied distinct microclimate niches suggestive of ecological resilience

Mixed Ionic-Electronic Conductivity, Redox Behavior and Thermochemical Expansion of Mn-Substituted 5YSZ as an Interlayer Material for Reversible Solid Oxide Cells

Manganese-substituted 5 mol.% yttria-stabilized zirconia (5YSZ) was explored as a prospective material for protective interlayers between electrolyte and oxygen electrodes in reversible solid oxide fuel/electrolysis cells. [(ZrO2)0.95(Y2O3)0.05]1−x[MnOy]x (x = 0.05, 0.10 and 0.15) ceramics with cubic fluorite structure were sintered in air at 1600 °C. The characterization included X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), thermogravimetry and dilatometry in controlled atmospheres, electrical conductivity measurements, and determination of oxygen-ion transference numbers by the electromotive force (EMF) technique. Mn-substituted 5YSZ solid solutions exhibit variable oxygen nonstoichiometry with manganese cations in a mixed 2+/3+ oxidation state under oxidizing conditions. Substitution by manganese gradually increases the extent of oxygen content variation on thermal/redox cycling, chemical contribution to thermal expansion and dimensional changes on reduction. It also deteriorates oxygen-ionic conductivity and improves p-type electronic conductivity under oxidizing conditions, leading to a gradual transformation from predominantly ionic to prevailing electronic transport with increasing x. Mn2+/3+→Mn2+ transformation under reducing atmospheres is accompanied by the suppression of electronic transport and an increase in ionic conductivity. All Mn-substituted 5YSZ ceramics are solid electrolytes under reducing conditions. Prolonged treatments in reducing atmospheres, however, promote microstructural changes at the surface of bulk ceramics and Mn exsolution. Mn-substituted 5YSZ with 0.05 ≤ x < 0.10 is considered the most suitable for the interlayer application, due to the best combination of relevant factors, including oxygen content variations, levels of ionic/electronic conductivity and thermochemical expansion

Recurrence of floor of the mouth dysontogenic cyst in childhood

The dysontogenic cysts of the floor of the mouth, which probably derive from pluripotent ectodermal cells entrapped during midline fusion of the branchial arches, include three histological subtypes: epidermoid, dermoid, and teratoid. The teratoid cyst, composed of ectodermal, endodermal, and mesodermal structures, is rare, with 26 cases reported in the English literature, most of them detected during childhood. We present a case of a teratoid cyst of the floor of the mouth in an 8-month-old boy, which was initially operated on the suspicion of ranula. A year after the operation a recurrent teratoid cyst was detected, with a sinus tract to the floor of the mouth. A recurrent dysontogenic cyst is very rare, with only five cases reported, and only one during childhood. The presence of tracts or adhesions not identified during the primary excision could explain the recurrence.Keywords: children, dysontogenic cyst, floor of the mouth, recurrence, teratoid cys

Estudio preliminar de la capacidad de dos especies de áfidos para transmitir el virus del mosaico de la calabaza (sqmv) en melón bajo condiciones de invernadero e identificación de sus enemigos naturales.

Se estudió de forma preliminar la capacidad de dos especies de pulgones para transmitir el virus del mosaico de la calabaza (SqMV) y se identificaron sus enemigos naturales. El estudio se realizó en las localidades de Pedro Carbo, Virgen de Fátima y Pechiche. Se corroboró la identidad del virus mediante la prueba de ELISA-DAS y se mantuvo la fuente de inóculo en plantas de Cucumis melo y Cucurbita pepo. Para la identificación de los pulgones se observaron estructuras de la cabeza, corniculos y cauda y se instalaron colonias de Aphis gossypii sobre plantas de melón y de Myzus persicae sobre pimiento. Para los ensayos de transmisión se emplearon cinco minutos en los periodos de adquisición e inoculación, previo a una hora de ayuno. La identificación de los enemigos naturales se realizó utilizando bases de datos y colecciones sinópticas internacionales. Se comprobó la presencia del virus del mosaico de la calabaza en las zonas de Pedro Carbo y Pechiche; además, en los ensayos preliminares realizados, la transmisión con A. gossypii resultó positiva en un porcentaje de 10, 84% ± 0,031, no así con M. persicae. La transmisión en los controles fue nula. Se identificaron 12 depredadores, un parasitoide y dos entomopatógenos; se destaca la infección de pulgones por Nomuraea rileyi –hospederos que se reportan por primera vezESPO