Chemical abundances of late-type pre-main sequence stars in the σ\sigma-Orionis cluster

The young $\sigma$-Orionis cluster is an important location for understanding the formation and evolution of stars, brown dwarfs, and planetary-mass objects. Its metallicity, although being a fundamental parameter, has not been well determined yet. We present the first determination of the metallicity of nine young late-type stars in $\sigma$-Orionis. Using the optical and near-infrared broadband photometry available in the literature we derive the effective temperatures for these nine cluster stars, which lie in the interval 4300--6500 K (1--3 \Msuno). These parameters are employed to compute a grid of synthetic spectra based on the code MOOG and Kurucz model atmospheres. We employ a $\chi^2$-minimization procedure to derive the stellar surface gravity and atmospheric abundances of Al, Ca, Si, Fe, Ni and Li, using multi-object optical spectroscopy taken with WYFFOS+AF2 at at the William Herschel Telescope ($\lambda/\delta\lambda\sim7500$). The average metallicity of the $\sigma$-Orionis cluster is [Fe/H] $= -0.02\pm0.09\pm0.13$ (random and systematic errors). The abundances of the other elements, except lithium, seem to be consistent with solar values. Lithium abundances are in agreement with the "cosmic" $^7$Li abundance, except for two stars which show a $\log \epsilon(\mathrm{Li})$ in the range 3.6--3.7 (although almost consistent within the error bars). There are also other two stars with $\log \epsilon(\mathrm{Li})\sim 2.75$. We derived an average radial velocity of the $\sigma$-Orionis cluster of $28\pm4$km/s. The $\sigma$-Orionis metallicity is roughly solar.Comment: Accepted for publication in Astronomy and Astrophysic

Nuclear effects in neutrino and antineutrino CCQE scattering at MINERvA kinematics

We compare the charged-current quasielastic neutrino and antineutrino observables obtained in two different nuclear models, the phenomenological SuperScaling Approximation and the Relativistic Mean Field approach, with the recent data published by the MINERvA Collaboration. Both models provide a good description of the data without the need of an ad hoc increase in the mass parameter in the axial-vector dipole form factor. Comparisons are also made with the MiniBooNE results where different conclusions are reached.Comment: 6 pages, 7 figures, Accepted for publication in Physical Review

Accurate and Efficient Design of Double Post Substrate Integrated Waveguide Filters Using Simulators Based on Open Space Modal Expansions

© 2012 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.An Agressive Space Mapping (ASM) strategy for efficiently and accurately designing passive filters in substrate integrated waveguide (SIW) technology is presented and successfully validated for the double post topology. Full-wave simulators based on open space modal expansions are used in both the coarse and fine models of this strategy.Díaz Caballero, E.; Morro, JV.; Esteban González, H.; Boria Esbert, VE.; Belenguer Martínez, Á. (2012). Accurate and Efficient Design of Double Post Substrate Integrated Waveguide Filters Using Simulators Based on Open Space Modal Expansions. IEEE. doi:10.1109/APS.2012.6348982

Neutral current (anti)neutrino scattering: Relativistic mean field and superscaling predictions

We evaluate the neutral current quasi-elastic neutrino cross section within two nuclear models: the SuSA model, based on the superscaling behavior of electron scattering data, and the RMF model, based on relativistic mean field theory. We also estimate the ratio (νp→νp)/(νN→νN) and compare with the MiniBooNE experimental data, performing a fit of the parameters MA and gA(s) within the two models. Finally, we present our predictions for antineutrino scatteringFondos FEDER FIS2011-28738-C02-01Spanish Consolider-Ingenio 2000 program CPAN CSD2007-0004

Effect of dietary macronutrients on the expression of cholecystokinin, leptin, ghrelin and neuropeptide Y in gilthead sea bream (Sparus aurata)

Endocrine factors released from the central nervous system, gastrointestinal tract, adipose tissue and other peripheral organs mediate the regulation of food intake. Although many studies have evaluated the effect of fed-to-starved transition on the expression of appetite-related genes, little is known about how the expression of appetite-regulating peptides is regulated by the macronutrient composition of the diet. The aim of the present study was to examine the effect of diet composition and nutritional status on the expression of four peptides involved in food intake control in gilthead sea bream (Sparus aurata): neuropeptide Y (NPY), ghrelin, cholecystokinin (CCK) and leptin. Quantitative real-time RT-PCR showed that high protein/low carbohydrate diets stimulated the expression of CCK and ghrelin in the intestine and leptin in the adipose tissue, while downregulation of ghrelin and NPY mRNA levels was observed in the brain. Opposite effects were found for the expression of the four genes in fish fed low protein/high carbohydrate diets or after long-term starvation. Our findings indicate that the expression pattern of appetite-regulating peptides, particularly CCK and ghrelin, is modulated by the nutritional status and diet composition in S. aurata

Synthesis and luminescence properties of electrodeposited ZnO Films

ZnO films have been grown on gold (111) by electrodeposition using two different OH- sources, nitrate and peroxide, in order to obtain a comparative study between these films. The morphology, structural and optical characterization of the films were investigated depending on the solution used (nitrate and peroxide) and the applied potential. Scanning Electron Microscopy pictures show different morphologies in each case. X-Ray Diffraction confirms that the films are pure ZnO oriented along the (0002) direction. ZnO films have been studied by photoluminescence to identify the emission of defects in the visible range. A consistent model that explains the emissions for the different electrodeposited ZnO films is proposed. We have associated the green and yellow emissions to a transition from the donor OH- to the acceptor zinc vacancies (VZn-) and to interstitial oxygen (Oi0), respectively. The orange-red emission is probably due to transitions from the conducting band to Oi- and OZn 0 defects and the infrared emission to transition from these Oi -/2- and OZn 0/- defects to the valence band.Comment: 17 pages, 1 Table and 10 figure

Electrical conductivity measurements of films

Póster presentado en la 12th European Conference on Thermoelectrics (ECT2014), celebrada en Madrid del 24 al 26 de septiembre de 2014.The characterization of the electrical conductivity of thin films is mandatory in all materials but particularly in thermoelectricity, its measurement is crucial in order to be able to determine the power factor and the figure of merit. A technique that could be used to carry out electrical measurements on thin films is the four probe technique. However, the spreading of the current due to the electrical field or the influence of the electrical contact resistances complicate the determination and analysis of the electrical conductivity of the film. In order to overcome these problems, we carried out a mesa attack on Bi2Te3 films grown by electrodeposition technique, which are hold on a Si substrate with a gold layer of 150nm. The goal is fabricating pillars whose later film resistivity analysis could approach to the 1D electrical model, which cannot be taken into account when dealing with a big film area. For that purpose, a lithography process was done on films with different thicknesses, which consist of a pattern of disks with different diameters ranging between 120µm and 60µm diameter. After the lithography, we evaporated 100nm of gold on top of the disks that would act as the top electrode. Then, we removed the photoresist and we performed a mesa attack with diluted nitric acid (1:2.5). As a result, we obtained pillars as the ones showed in Figure 1. On these pillars, I-V curves with the four probe technique were taken and the resistances of the pillars were determined. Representing the resistance of the pillars versus the inverse of the area of the pillar, the total resistivity of the films, which includes the contact resistances between the electrodes and the pillar, is obtained. Finally, to determine the electrical contact resistance and obtain the pure electrical resistivity of the film, these measurements were performed on different pillar thicknesses. The experimental results have been double-checked with COMSOL simulations of the four probe experiments carried out here, observing a good agreement between them.Peer Reviewe

Optimization of bismuth telluride films and nano-wire arrays via electrodeposition for thermoelectric applications

Comunicación presentada en el 3rd Early Stage Researchers Workshop in Nanoscience, celebrado en Madrid el 27 y 28 de junio de 2013.Due to the current world’s demand for energy, there is a great interest in thermoelectricity, which offers the possibility of increasing the sustainability of our electrical system. Thermoelectric materials can convert heat into electricity and vice versa, and thus they offer a way of recovering wasted heat produced in engines, industrial processes and others into usable power. However, one of the main problems for their actual use is their low efficiency in this conversion. This efficiency is directly related with what is called the thermoelectric figure of merit, described by ZT=(S2·σ·T)/κ ,where S, σ, κ, and T stand for the Seebeck coefficient, electrical and thermal conductivities, and the absolute temperature, respectively. Given that in classical physics S, σ, and κ, are correlated, the improvement of the efficiency is not straightforward. Nevertheless, in 1993 a theoretical work suggested that the efficiency could be greatly enhanced by reducing the dimensionality of the structures under studied and working in the nano-scale. Therefore, much experimental effort has been done to achieve these kind of structures and in some cases, an enhancement of the ZT value has been achieved, although this has not been due to the quantum confinement to the charge carriers, as it was theoretically predicted, but to an increase of the κ due to the increased number of interface boundaries in nanostructures. Among the most efficient thermoelectric materials used for applications at room temperature, bismuth telluride (Bi2Te3) and its different alloys stand out, with a ZT for Bi2Te3of around 1 at RT [2]. We present here an optimized method of obtaining films and nanowire arrays via electrochemical deposition in a conventional three-electrode cell. Different ways of improving the quality of the obtained films have been studied (working electrode, constant and pulsed potentials, different chemical baths, etc.) in order to obtain highly oriented (110) films, which are the most favorable for out-of-plane applications. Then, nanostructuration has been achieved by changing the working electrode to porous alumina templates and realizing the electrochemical deposition inside the pores. The samples produced have been characterized using SEM, EDX, AFM, XRD, and Raman spectrometry, and in the case of the films, their transport properties have also been measured.Peer Reviewe

Charged-current inclusive neutrino cross sections in the SuperScaling model

SuperScaling model (SuSA) predictions to neutrino-induced charged-current π+ production in the Δ-resonance region are explored under MiniBooNE experimental conditions. The SuSA charged-current π+ results are in good agreement with data on neutrino flux-averaged double-differential cross sections. The SuSA model for quasielastic scattering and its extension to the pion production region are used for predictions of charged-current inclusive neutrino- nucleus cross sections. The contribution of two-particle-two-hole vector meson-exchange current excitations is also considered within a fully relativistic model. Results are compared with the T2K experimental data for inclusive scattering.España, DGI y Fundación FEDER FIS2011-28738-C02-01, FPA2013-41267Junta de Andalucía CSD2007-0004