Giant Anisotropic Magneto-Resistance in ferromagnetic atomic contacts

Magneto-resistance is a physical effect of great fundamental and industrial interest since it is the basis for the magnetic field sensors used in computer read-heads and Magnetic Random Access Memories. As device dimensions are reduced, some important physical length scales for magnetism and electrical transport will soon be attained. Ultimately, there is a strong need to know if the physical phenomena responsible for magneto-resistance still hold at the atomic scale. Here, we show that the anisotropy of magneto-resistance is greatly enhanced in atomic size constrictions. We explain this physical effect by a change in the electronic density of states in the junction when the magnetization is rotated, as supported by our ab-initio calculations. This stems from the "spin-orbit coupling" mechanism linking the shape of the orbitals with the spin direction. This sensitively affects the conductance of atomic contacts which is determined by the overlap of the valence orbitals.Comment: latex AAMR.tex, 6 files, 5 figures, 4 pages (http://www-drecam.cea.fr/spec/articles/S06/011

The Coronal Structure of AB Doradus

We perform a numerical simulation of the corona of the young, rapidly rotating K0 dwarf AB Doradus using a global MHD model. The model is driven by a surface map of the radial magnetic field constructed using Zeeman-Doppler Imaging. We find that the global structure of the stellar corona is dominated by strong azimuthal tangling of the magnetic field due to the rapid rotation. The MHD solution enables us to calculate realistic Alfv\'en surfaces and we can therefore estimate the stellar mass loss rate and angular momentum loss rate without making undue theoretical simplifications. We consider three cases, parametrized by the base density of the corona, that span the range of possible solutions for the system. We find that overall, the mass and angular-momentum loss rates are higher than in the solar case; the mass loss rates are 10 to 500 times higher, and the angular momentum loss rate can be up to $3\times{10}^4$ higher than present day solar values. Our simulations show that this model can be use to constrain the wide parameter space of stellar systems. It also shows that an MHD approach can provide more information about the physical system over the commonly used potential field extrapolation.Comment: 13 pages, 7 figure

Fully relativistic calculation of magnetic properties of Fe, Co and Ni adclusters on Ag(100)

We present first principles calculations of the magnetic moments and magnetic anisotropy energies of small Fe, Co and Ni clusters on top of a Ag(100) surface as well as the exchange-coupling energy between two single adatoms of Fe or Co on Ag(100). The calculations are performed fully relativistically using the embedding technique within the Korringa-Kohn-Rostoker method. The magnetic anisotropy and the exchange-coupling energies are calculated by means of the force theorem. In the case of adatoms and dimers of iron and cobalt we obtain enhanced spin moments and, especially, unusually large orbital moments, while for nickel our calculations predict a complete absence of magnetism. For larger clusters, the magnitudes of the local moments of the atoms in the center of the cluster are very close to those calculated for the corresponding monolayers. Similar to the orbital moments, the contributions of the individual atoms to the magnetic anisotropy energy strongly depend on the position, hence, on the local environment of a particular atom within a given cluster. We find strong ferromagnetic coupling between two neighboring Fe or Co atoms and a rapid, oscillatory decay of the exchange-coupling energy with increasing distance between these two adatoms.Comment: 8 pages, ReVTeX + 4 figures (Encapsulated Postscript), submitted to PR

Influencia de la personalidad en la salud y en la participación social de las personas mayores: el papel de la extraversión y del optimismo.

Health and social participation are two fundamental pillars of active aging thus it is important to understand variables that might affect them. The aim of this study was to analyze the relationship between extraversion, optimism, health status and social participation. The sample comprised 406 community-dwelling older adults (M=74.88, SD= 6.75) from urban areas of Granada. It was found that extraversion and optimism positively correlated with perceived health status and with social participation and negatively correlated with number of illnesses. The association between personality  and social participation was stronger than the one between personality and health. This study highlights the relevance that personality has for older adults’ health and social participation thus it is important to consider personality in active aging models.La salud y la participación son dos pilares fundamentales del envejecimiento activo por lo que es importante entender las variables que los afectan. El objetivo del presente estudio fue analizar la relación entre extraversión, optimismo y salud y participación social en personas mayores. La muestra estuvo compuesta por 406 personas mayores (M=74.88, DT= 6.75) que vivían en Granada capital. La extraversión y el optimismo correlacionaban positivamente con el estado percibido de salud y con la participación social y negativamente con el número de enfermedades. La asociación entre personalidad y participación social eran más fuerte que la asociación entre personalidad y salud. El presente estudio destaca la importancia de la personalidad para la salud y la participación social de las personas mayores por tanto es relevante tener en cuenta la personalidad en los modelos de envejecimiento activo

Coronagraphic near-IR photometry of AB Dor C

Observations of low-mass companions for which the dynamical masses are well constrained help to improve the calibration of evolutionary models. Such observations thereby provide more confidence in the estimation of the mass of a companion using the photometric methods expected for the next generation of planet finder instruments. The commissioning of a new coronagraph at the Very Large Telescope (VLT) was the occasion to test the performance of this technique on the well-known object AB Dor A and its 0.09$M_\odot$ companion AB Dor C. The purpose of this paper is to refine the photometric analysis on this object and to provide an accurate photometric error budget. In addition to coronagraphy, we calibrated the residual stellar halo with a reference star. We used standard techniques for photometric extraction. The companion AB Dor C is easily detected at 0.185" from the primary star, and its magnitudes in H and Ks are in agreement with an M5.5 object, as already known from spectroscopic observations. However, these new measurements make the earlier J-band photometry less reliable. Finally, the comparison with evolutionary models supports an age of (75\pm 25) Myr, contrary to previous analyses. These observations demonstrate that coronagraphic observations can be more efficient than direct imaging, not only to improve contrast, but also to provide a better photometric estimation as long as a good calibration of the stellar halo is achieved.Comment: Research Note to appear in Astronomy and Astrophysic

Promoción del envejecimiento activo en la atención gerontológica: el papel de la educación social

Active ageing is being studied from different professional perspectives, strengthening the action for the elderly people in order to promote their autonomy, and improve their quality of life. This focus since a lot of social organizations is forgotten in nursing homes because of absence of innovative projects that introduce the features of the changes that have occurred in the profile of the elderly people. New requirements that are not solved by the stagnation suffered since 2003 in this kind of treatments. The inclusion of Social Education and innovative projects can be the solution to this problem, that will be affect a large percentage of the population in the near future.El Envejecimiento Activo es objeto de estudio desde distintas perspectivas profesionales, fortaleciendo la acción dirija a las personas mayores para la promoción de su autonomía y la mejora de su calidad de vida. Esta atención prestada por muchos organismos sociales, queda olvidada en los complejos geriátricos debido a la ausencia de programas innovadores que introduzcan las características de los cambios que se han dado en el perfil de las personas mayores. Nuevas demandas que no quedan suplidas por el estancamiento sufrido desde el año 2003, en las funciones profesionales ejercidas dentro de las residencias. La inclusión de la Educación Social y de proyectos innovadores puede ser la solución a esta problemática que afectará al bienestar de un gran porcentaje de la población próximamente

Three years in the coronal life of AB Dor. I. Plasma emission measure distributions and abundances at different activity levels

The young active star AB Dor (K1 IV-V) has been observed 16 times in the last three years with the XMM-Newton and Chandra observatories, totalling 650 ks of high-resolution X-ray spectra. The XMM/RGS observations with the highest and lowest average emission levels have been selected to study the coronal properties of AB Dor in two different activity levels. We compare the results based on the XMM data with those obtained from a higher resolution Chandra/HETG spectrum, using the same line-based analysis technique. We have reconstructed the plasma Emission Measure Distribution vs. temperature (EMD) in the range log T(K) ~ 6.1-7.6, and we have determined the coronal abundances of AB Dor, obtaining consistent results between the two instruments.The overall shape of the EMD is also consistent with the one previously inferred from EUVE data. The EMD shows a steep increase up to the peak at log T (K) ~ 6.9 and a substantial amount of plasma in the range log T (K) ~ 6.9-7.3. The coronal abundances show a clear trend of increasing depletion with respect to solar photospheric values, for elements with increasing First Ionization Potential (FIP), down to the Fe value ([Fe/H]=-0.57), followed by a more gradual recovery of the photospheric values for elements with higher FIP. He-like triplets and Fe XXI and Fe XXII lines ratios indicate electron densities log ne~10.8 cm^-3 at log T(K) ~ 6.3 and log ne ~ 12.5 at log T(K) ~ 7, implying plasma pressures steeply increasing with temperature. These results are interpreted in the framework of a corona composed of different families of magnetic loop structures, shorter than the stellar radius and in isobaric conditions, having pressures increasing with the maximum plasma temperature, and which occupy a small fraction (f ~ 10^-4 - 10^-6) of the stellar surface.Comment: Accepted by A&

La importancia de mantenerse activo en la vejez

Activities engagement is one of the three pillars of successful aging, along with health and high cognitive and physical functioning. The importance of participation lies in its influence on other variables such as wellbeing, physical and mental health. The objective of this study was to analyze the impact of participation on psychological wellbeing, depression and health and to determine if there are differences according to the type of activity performed. A sample of 139 people aged 55 to 94 from Granada (49 men and 90 women) was used. Participants were asked about their participation in a list of 16 activities classified as formative, physical or craft, they were asked to rate their subjective health and they were applied the Psychological Wellbeing Scales and the abbreviated version of the Geriatric Depression Scale (GDS). The results indicate gender differences in participation but not in the other variables analyzed. The total participation in activities was related and was predictor of psychological wellbeing, subjective health and depression but differences were observed according to the type of activity performed. Formative activities relate to personal growth, manual activities with environmental mastery and health, and physical activities with positive relations with others, health and depression. These results highlight the importance of achieving an integral participation in different activities if we are to promote the successful aging of the elderly.La participación es uno de los tres pilares del envejecimiento con éxito, junto con la salud y el alto funcionamiento cognitivo y físico. La importancia de la participación radica en su influencia sobre otras variables como el bienestar, la salud física y mental. El objetivo de este estudio fue analizar el impacto de la participación sobre el bienestar, depresión y salud y determinar si existen diferencias según el tipo de actividad realizada. Para ello se utilizó una muestra de 139 personas de entre 55 y 94 años de la provincia de Granada (49 hombres y 90 mujeres). A los participantes se les preguntó sobre su participación en una lista de 16 actividades clasificadas como formativas, físicas o de manualidades, se les pidió que valoraran su salud subjetiva y se les aplicaron las Escalas de Bienestar Psicológico y la versión abreviada de la Escala de Depresión Geriátrica (GDS). Los resultados indican diferencias de género en la participación pero no en las otras variables analizadas. La participación total en actividades se relacionaba y fue predictor del bienestar psicológico, la salud subjetiva y la depresión pero se observaron diferencias según el tipo de actividad realizada. Las actividades formativas se relacionan con el crecimiento personal, las actividades manuales con el dominio del entorno y la salud y las actividades físicas con las relaciones personales, salud y depresión. Estos resultados resaltan la importancia de lograr una participación integral en diferentes actividades si queremos potenciar el envejecimiento exitoso de las personas mayores

Femtosecond laser microstructuring of zirconia dental implants

This study evaluated the suitability of femtosecond laser for microtexturizing cylindrical zirconia dental implants surface. Sixty-six cylindrical zirconia implants were used and divided into three groups: Control group (with no laser modification), Group A (microgropored texture), and Group B (microgrooved texture). Scanning electron microscopy observation of microgeometries revealed minimal collateral damage of the original surface surrounding the treated areas. Optical interferometric profilometry showed that ultrafast laser ablation increased surface roughness (Ra, Rq, Rz, and Rt) significantly for both textured patterns from 1.2× to 6×-fold when compared with the control group (p Group B 8.4% ± 0.42% > Group A 1.6% ± 0.35%) and aluminum (Control 4.3% ± 0.9% > Group B 2.3% ± 0.3% > Group A 1.16% ± 0.2%) in the laser-treated surfaces (p Group A 1.94% > Group B 1.72%) as the surfaces were processed with ultrashort laser pulses. We concluded that femtosecond laser microstructuring offers an interesting alternative to conventional surface treatments of zirconia implants as a result of its precision and minimal damage of the surrounding areas