Spectral density of an interacting dot coupled indirectly to conducting leads

We study the spectral density of electrons rho in an interacting quantum dot (QD) with a hybridization lambda to a non-interacting QD, which in turn is coupled to a non-interacting conduction band. The system corresponds to an impurity Anderson model in which the conduction band has a Lorentzian density of states of width Delta2. We solved the model using perturbation theory in the Coulomb repulsion U (PTU) up to second order and a slave-boson mean-field approximation (SBMFA). The PTU works surprisingly well near the exactly solvable limit Delta2 -> 0. For fixed U and large enough lambda or small enough Delta2, the Kondo peak in rho(omega) splits into two peaks. This splitting can be understood in terms of weakly interacting quasiparticles. Before the splitting takes place the universal properties of the model in the Kondo regime are lost. Using the SBMFA, simple analytical expressions for the occurrence of split peaks are obtained. For small or moderate Delta2, the side bands of rho(omega) have the form of narrow resonances, that were missed in previous studies using the numerical renormalization group. This technique also has shortcomings for describing properly the split Kondo peaks. As the temperature is increased, the intensity of the split Kondo peaks decreases, but it is not completely suppressed at high temperatures.Comment: 13 pages, 13 figures, accepted in Phys. Rev.

Fruit characteristics and cuticle triterpenes as related to postharvest quality of highbush blueberries

Chilean fresh blueberries take 20-50 days to arrive by boat to the Northern hemisphere, softening and dehydration being the main defects upon arrival. The effect of maturity at harvest (75% blue, 100% blue, and overripe) on cuticular triterpene content, and the possible associated impacts on firmness and weight loss after cold storage were explored for 'Duke' and 'Brigitta' fruit, both non-bagged or bagged in macroperforated low-density polyethylene bags. Softening and weight loss varied with cultivar and maturity stage: 'Duke' fruit softened faster and were more prone to dehydration than 'Brigitta' samples, whereas overripe fruit were less firm after storage. This is the first report characterizing the triterpenoid fraction in cuticles of fresh blueberries, which may play a role in their postharvest behavior. Weight loss and softening rates were highly correlated to ursolic acid contents at harvest; further research will be required for a better understanding of these relationships.Fruit samples were provided by AMS Family, Maule Region, Chile. We thank Irene Manríquez, Instituto de Química de Recursos Naturales, Universidad de Talca, for her skillful technical work. In Chile, this work was supported by the National Commission for Scientific and Technological Research CONICYT (FONDECYT 11130539) and PCHA/Doctorado Nacional/2013-63130042, the research programs “Adaptation of Agriculture to Climate Change (A2C2)”, “PIEI-QUIM-BIO”, “Fondo Proyectos de Investigación” and “Núcleo Científico Multidisciplinario”, Universidad de Talca. In Spain this work was partially supported by “Fundación Carolina” and “Programa de Doctorado en Ciencia y Tecnología Agraria y Alimentaria”, Universitat de Lleida

Manipulating Majorana Fermions in Quantum Nanowires with Broken Inversion Symmetry

We study a Majorana-carrying quantum wire, driven into a trivial phase by breaking the spatial inversion symmetry with a tilted external magnetic field. Interestingly, we predict that a supercurrent applied in the proximate superconductor is able to restore the topological phase and therefore the Majorana end-states. Using Abelian bosonization, we further confirm this result in the presence of electron-electron interactions and show a profound connection of this phenomenon to the physics of a one-dimensional doped Mott-insulator. The present results have important applications in e.g., realizing a supercurrent assisted braiding of Majorana fermions, which proves highly useful in topological quantum computation with realistic Majorana networks.Comment: 5 pages, 3 figures, Supplementary Material is adde

Firmness at harvest impacts postharvest fruit softening and internal browning development in mechanically damaged and non-damaged highbush blueberries (Vaccinium corymbosum L.)

Fresh blueberries are very susceptible to mechanical damage, which limits postharvest life and firmness. Softening and susceptibility of cultivars 'Duke' and 'Brigitta' to developing internal browning (IB) after mechanical impact and subsequent storage was evaluated during a 2-year study (2011/2012, 2012/2013). On each season fruit were carefully hand-picked, segregated into soft (<1.60 N), medium (1.61-1.80 N), and firm (1.81-2.00 N) categories, and then either were dropped (32 cm) onto a hard plastic surface or remained non-dropped. All fruit were kept under refrigerated storage (0ºC and 85-88% relative humidity) to assess firmness loss and IB after 7, 14, 21, 28, and 35 days. In general, regardless of cultivar or season, high variability in fruit firmness was observed within each commercial harvest, and significant differences in IB and softening rates were found. 'Duke' exhibited high softening rates, as well as high and significant r2 between firmness and IB, but little differences for dropped vs. non-dropped fruit. 'Brigitta,' having lesser firmness rates, exhibited almost no relationships between firmness and IB (especially for non-dropped fruit), but marked differences between dropping treatments. Firmness loss and IB development were related to firmness at harvest, soft and firm fruit being the most and least damaged, respectively. Soft fruit were characterized by greater IB development during storage along with high soluble solids/acid ratio, which could be used together with firmness to estimate harvest date and storage potential of fruit. Results of this work suggest that the differences in fruit quality traits at harvest could be related to the time that fruit stay on the plant after turning blue, soft fruit being more advanced in maturity. Finally, the observed differences between segregated categories reinforce the importance of analyzing fruit condition for each sorted group separately.In Chile, this work was supported by the National Commission for Scientific and Technological Research CONICYT (FONDECYT 11130539) and the Universidad de Talca (research programs “Adaptation of Agriculture to Climate Change (A2C2)”, “Fondo Proyectos de Investigación” and “Núcleo Científico Multidisciplinario”). In Spain, this work was partially supported by “Fundación Carolina” and “Programa de Doctorado en Ciencia y Tecnología Agraria y Alimentaria”, Universitat de Lleida

Evaluación del grado de queratinización y el recuento de AgNORs en citología exfoliativa de mucosa oral normal de individuos fumadores y no fumadores

Objetivos. En individuos fumadores con mucosa oral clínicamente sana, se han observado cambios citológicos como una mayor queratinización, existiendo también reportes de un mayor grado de actividad nucleolar. En estos estudios, las células para frotis se han obtenido por medio de espátula de madera. Nuestro objetivo es evaluar la profundidad de muestras citológicas de mucosa oral obtenidas con cepillo para frotis (endobrush) y comparar el grado de queratinización y la actividad nucleolar en pacientes fumadores y no fumadores. Diseño del estudio. Se obtuvieron frotis de mucosa oral de borde de lengua clínicamente normal de 30 individuos fumadores y 30 no fumadores, utilizando espátula de madera y endobrush. Las muestras fueron teñidas con Papanicolaou y con la tinción AgNORs. Resultados. Con la espátula de madera se obtuvo un mayor porcentaje de células epiteliales superficiales anucleadas (P= 0.016) y con el endobrush se obtuvieron células más profundas (tipo intermedias) (P= 0.035). Los individuos fumadores presentaron un mayor porcentaje de células superficiales anucleadas con ambas técnicas, diferencia que fue estadísticamente significativa con la técnica endobrush (P=0.005). El promedio de AgNORs en las células nucleadas fue mayor en los individuos fumadores (3.83) que en los no fumadores (2.79) (P= 0.003). Conclusiones. El endobrush permite obtener células de estratos más profundos. Los individuos fumadores con mucosa clínicamente normal presentan un mayor porcentaje de células queratinizadas y una mayor actividad nucleolar, sugiriendo que el consumo de cigarrillo influye en la actividad celular de la mucosa del borde de lengua.Objetive.In smokers with clinically normal buccal mucosa, cytological changes such as increased keratinization, and higher nucleolar activity have been observed. In these studies the cells for cytological smears were obtained with a wooden spatula. Our objectives were to evaluate the depth of cytological smears of oral mucosa obtained with both a brush (endobrush) and a wooden spatula, and to compare the degree of keratinization and the nucleolar activity in smokers and non-smokers. Design. We obtained cytological smears of clinically normal lateral tongues of 30 smokers and 30 non-smokers using both a wooden spatula and endobrush. The samples were dyed with Papanicolaou and the AgNORs. Results. With the wooden spatula we found a greater percentage of enucleated superficial epithelial cells (P = 0.016) and deeper cells were obtained with an endobrush (intermediate cells) (P =0.035). The smokers showed a greater percentage of enucleated superficial cells with both techniques, however this difference was significantly greater with Endobrush (P=0.005). The average of AgNORs in the nucleated cells was greater in smokers (3.83) than in non-smokers (2.79) (P=0.003). Conclusion. The Endobrush allows the clinician to obtain deeper cells of buccal mucosa. Smokers with clinically normal mucosa show a greater percentage of keratinized cells and a greater nucleolar activity, suggesting that cigarette smoking influences the cellular activity of the mucosa of the lateral tongue

One- and many-body effects on mirages in quantum corrals

Recent interesting experiments used scanning tunneling microscopy to study systems involving Kondo impurities in quantum corrals assembled on Cu or noble metal surfaces. The solution of the two-dimensional one-particle Schrodinger equation in a hard wall corral without impurity is useful to predict the conditions under which the Kondo effect can be projected to a remote location (the quantum mirage). To model a soft circular corral, we solve this equation under the potential W*delta(r-r0), where r is the distance to the center of the corral and r0 its radius. We expand the Green's function of electron surface states Gs0 for r<r0 as a discrete sum of contributions from single poles at energies epsilon_i-I*delta_i. The imaginary part delta_i is the half-width of the resonance produced by the soft confining potential, and turns out to be a simple increasing function of epsilon_i. In presence of an impurity, we solve the Anderson model at arbitrary temperatures using the resulting expression for Gs0 and perturbation theory up to second order in the Coulomb repulsion U. We calculate the resulting change in the differential conductance Delta dI/dV as a function of voltage and space, in circular and elliptical corrals, for different conditions, including those corresponding to recent experiments. The main features are reproduced. The role of the direct hybridization between impurity and bulk, the confinement potential, the size of the corral and temperature on the intensity of the mirage are analyzed. We also calculate spin-spin correlation functions.Comment: 13 pages, 12 figures, accepted for publication in Phys. Rev. B. Calculations of spin correlations within an additional approximation adde

Straight to the Point: How people encode linear discontinuations

Spatial discontinuations, as those found in cities and buildings, are everyday events. But, how do we encode and classify such misalignments? This is the topic of this paper. Twenty participants were asked to classify a total of 51 icons showing an upward-moving line being misaligned to the right, left and straight down. The results show that subjects were very sensitive to slight discontinuations occurring to vertical lines and that there was not exact symmetry between the left and right axis, meaning that the pieces slightly misaligned to the left were encoded differently than those misaligned to the right.Fil: Mora, Rodrigo I.. Universidad Diego Portales; ChileFil: Lobos, Alejandro. Universidad Diego Portales; ChileFil: Ibañez, Agustin Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto de Neurología Cognitiva; Argentina. Universidad Diego Portales; Chil

Evaluation of potential nirs to predict pastures nutritive value

This paper describes the capability of near infra-reflectance (NIRS) to predict the nutritional quality of pastures from southern Chile (39°-40°S). A Fourier transformed near-infrared (FT-NIR) method for rapid determination of dry matter (DM), crude protein (CP), in vitro digestibility (IVD) and metabolizable energy (ME) was used. Calibration models were developed between chemical and NIRS spectral data using partial least squares (PLS) regression and external validation. The coefficients of determination in calibration (R2c) were high varying between 0.89-0.99 and the root mean square errors of calibration (RMSEC) were low, ranging between 0.46-2.55 for the parameters analysed. The Residual Prediction Deviation (RPD) was higher than 2.5. Our results confirmed the convenience of using a wide range of samples applicability in the calibration set. Data also showed that the use of an independent set of samples for external validation increases the robustness of the models to predict unknown samples. Our results indicated RPD values higher than 2.5 which is the minimum recommended for this type of prediction. Thus, the result showed that NIRS was useful to estimate the nutritional quality of permanent pastures, and has a great potential to be used as a rapid decision tool for the studied analysis.Thanks the Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT) post-doc grant n°3120069.info:eu-repo/semantics/publishedVersio

Towards electrical domain-wall control in polyacetylene-based electronic nanodevices

We theoretically propose a polymer-based nano-device consisting of a single trans-polyacetylene (tPA) molecule capacitively coupled to external voltage gates. We model the integrated device using a Su-Schrieffer-Heeger (SSH)-like Hamiltonian, and we demonstrate the emergence of localized domain walls (DWs) with quantized charges (i.e., soliton excitations) localized at the gates. Interestingly, by increasing the applied voltage, multiple discrete charges can be accumulated, which may be useful for potential technological applications. Exploiting the topological character of the solitonic excitations of tPA, this device can be considered as an organic-based quantum dot with a very large and robust quantized charge.Comment: 16 pages, 5 figure

Determinación de los índices de salud nutricional de la leche fresca de bovino mediante espectroscopía de infrarrojo cercano

Bovine milk is one of the most complete foods that exist. During the last decades, milk FA have shown to improve human health due to the reduction in risk of cardiovascular disease and related pathologies. The aim of this study was to evaluate the feasibility of near infrared spectroscopy (NIRS) reflectance analysis to predict the nutritional value, fatty acid (FA) composition, and health index of fresh milk from dairy cows of pastoral systems. The prediction of Atherogenicity and Thrombogenicity indexes, along with other FA ratios in fresh milk samples by NIRS were precise and accurate. In addition, the calibration model obtained by NIRS provides an opportunity for the routine quantification of milk’s healthy FA such as omega-3 and conjugated linoleic acid (CLA), with applications in the dairy industry for food labeling, and at the farm level for management of the dairy cow’s diet.La leche bovina es uno de los alimentos más completos que existe. Durante la última década, se ha demostrado que los ácidos grasos de la leche pueden mejorar la salud humana, a través de la reducción del riesgo de enfermedades cardiovasculares y patologías asociadas. El objetivo de este estudio fue evaluar la factibilidad del análisis de reflectancia NIRS para predecir valor nutricional, composición de ácidos grasos e índices de salud de leche fresca de vacas de sistemas lecheros pastoriles. La predicción por NIRS del índice aterogénico y trombogénico, de ácidos grasos en muestras de leche fresca, fueron precisos. Por tanto, el modelo de calibración obtenido por NIRS representa una oportunidad para la cuantificación rutinaria de los ácidos grasos saludables de la leche como omega-3 y CLA, con aplicaciones en la industria lechera para el etiquetado nutricional y a nivel de lechería para el manejo de la alimentación de las vacas