Interferometric observations of SiO thermal emission in the inner wind of M-type AGB stars IK Tauri and IRC+10011

Context. AGB stars go through a process of strong mass-loss that involves pulsations of the atmosphere, which extends to a region where the conditions are adequate for dust grains to form. Radiation pressure acts on these grains which, coupled to the gas, drive a massive outflow. The details of this process are not clear, including which molecules are involved in the condensation of dust grains. Aims. To study the role of the SiO molecule in the process of dust formation and mass-loss in M-type AGB stars. Methods. Using the IRAM NOEMA interferometer we observed the $^{28}$SiO and $^{29}$SiO $J=3-2$, $v=0$ emission from the inner circumstellar envelope of the evolved stars IK Tau and IRC+10011. We computed azimuthally averaged emission profiles to compare the observations to models using a molecular excitation and ray-tracing code for SiO thermal emission. Results. We observed circular symmetry in the emission distribution. We also found that the source diameter varies only marginally with radial velocity, which is not the expected behavior for envelopes expanding at an almost constant velocity. The adopted density, velocity, and abundance laws, together with the mass-loss rate, which best fit the observations, give us information on the chemical behavior of the SiO molecule and its role in the dust formation process. Conclusions. The results indicate that there is a strong coupling between the depletion of gas phase SiO and gas acceleration in the inner envelope. This could be explained by the condensation of SiO into dust grains

Una herramienta web para el cálculo y simulación de estructuras caché

Versión electrónica de la ponencia presentada en V Congreso de Tecnologías Aplicadas a la Enseñanza de la Electrónica, celebrado en Las Palmas de Gran Canaria en 2002La herramienta presentada facilita la resolución de problemas sencillos relacionados con el tamaño en bits de los campos en la palabra de direccionamiento, así como con el tamaño de la propia estructura de la unidad de memoria cache. Además permite la simulación del modo de operación de una memoria cache con unas características previamente seleccionadas. El objetivo es ayudar al alumno en la compresión del funcionamiento de la memoria cache y disponer de una herramienta que facilita el calculo de los parámetros asociados a su estructura. La aplicación se ha desarrollado en Java para que sea accesible desde la página web de la asignatura Arquitectura e Ingeniería de Computadores impartida en la E.T.S de Informática de la UAM

Rapid thermal annealing behavior of amorphous SiC layers deposited by electron cyclotron resonance plasma

The archival version of this work was published in Journal of the electrochemical society 143.1 (1996): 271-277Hydrogenated amorphous silicon carbide, a‐SiC:H, has been deposited by electron cyclotron resonance plasmas. Operating in methane excess (Formula flow ratios between 2 and 4) and at high enough microwave powers, the deposited SiC films are close to stoichiometric. In these SiC layers, only small traces of the Formula and Formula stretching bands can be detected. Rapid thermal annealing leads to nearly complete dehydrogenation of the SiC layers deposited under these conditions as deduced from ellipsometric and infrared spectroscopy

Uncorrelated scattering approximation for the scattering and break-up of weakly bound nuclei on heavy targets

The scattering of a weakly bound (halo) projectile nucleus by a heavy target nucleus is investigated. A new approach, called the Uncorrelated Scattering Approximation, is proposed. The main approximation involved is to neglect the correlation between the fragments of the projectile in the region where the interaction with the target is important. The formalism makes use of hyper-spherical harmonics, Raynal-Revay coefficients and momentum-localized wave functions to expand projectile channel wave functions in terms of products of the channel wave function of the individual fragments. Within this approach, the kinetic energy and angular momentum of each fragment is conserved during the scattering process. The elastic, inelastic and break-up S-matrices are obtained as an analytic combination involving the bound wave function of the projectile and the product of the S-matrices of the fragments. The approach is applied to describe the scattering of deuteron on $^{58}$Ni at several energies. The results are compared with experimental data and continuum-discretized coupled-channels calculations.Comment: 34 pages, 5 figures, accepted for publication in Nucl. Phys.

Erosión en olivar ecológico. Manual de campo: diagnóstico y recomendaciones

Es una guía práctica para el reconocimiento del riesgo de erosión en olivare ecológicos y su prevención. No obstante, gran parte de las mismas, se puede aplicar a casi cualquier tipo de olivares no ecológicos.Peer reviewe

Effect of different drying systems for the conservation of olive leaves on their nutritive value for ruminants

Leaves obtained from olive trees (Olea europaea L.) were stored under various conditions for periods up to 42 months. Duration of storage had a marked effect on crude protein digestibility of leaves when fed to sheep. Protein appeared to be unavailable to animals fed leaves stored for 24 months or longer. The effect of storage on organic matter digestibility was less dramatic and due largely to the loss of soluble cell contents (r = 0.97). As a result, the proportion of water-insoluble dry matter and lignin present in leaves increased with duration of storage while the proportion of water or acetone-water (60:30 v/v) soluble material decreased. Despite being unavailable in vivo, cellulase digestion released protein from the water-insoluble residues of stored leaves in greater amounts than that released from freshly-dried leaves. It appears likely that protein released from stored leaves was in the form of a complex and remained unavailable to the animal. Hydrolysable and condensed tannins were not detected in fresh or dried leaves and could not have acted as complexing agents. The seco-iridoid glycoside oleuropein was found in fresh tissue (69.9 g kg(-1)) but concentrations decreased on storage in parallel with the observed decrease in crude protein digestibility (r = 0.80). ((C) Elsevier/Inra)

Super-poissonian photon statistics and correlations between pump and probe fields in Electromagnetically Induced Transparency

We have measured the photon statistics of pump and probe beams after interaction with Rb atoms in a situation of Electromagnetically Induced Transparency. Both fields present super-poissonian statistics and their intensities become correlated, in good qualitative agreement with theoretical predictions in which both fields are treated quantum-mechanically. The intensity correlations measured are a first step towards the observation of entanglement between the fields.Comment: 4 pages, two-column, 4 figures, first submitted to PRL on Aug. 6, 200

Labo-micro: entorno de test para la verificación de microprocesadores experimentales sobre circuitos FPGA.

Versión electrónica de la ponencia presentada en V Congreso de Tecnologías Aplicadas a la Enseñanza de la Electrónica, celebrado en Las Palmas de Gran Canarias en 2002En este documento se presenta un entorno de verificación que permite comprobar el funcionamiento de un microprocesador diseñado en VHDL para ser implementado en un circuito reconfigurable del tipo FPGA. Se ha desarrollado un conjunto de herramientas que permiten a) volcar el diseño en la FPGA, b) utilizar un microcontrolador externo para cargar el programa de prueba y c) observar los resultados de su ejecución a través de una memoria de doble puerto situada entre la FPGA y el microcontrolador