Magnetic Domains and Surface Effects in Hollow Maghemite Nanoparticles

In the present work, we investigate the magnetic properties of ferrimagnetic and noninteracting maghemite (g-Fe2O3) hollow nanoparticles obtained by the Kirkendall effect. From the experimental characterization of their magnetic behavior, we find that polycrystalline hollow maghemite nanoparticles are characterized by low superparamagnetic-to-ferromagnetic transition temperatures, small magnetic moments, significant coercivities and irreversibility fields, and no magnetic saturation on external magnetic fields up to 5 T. These results are interpreted in terms of the microstructural parameters characterizing the maghemite shells by means of an atomistic Monte Carlo simulation of an individual spherical shell model. The model comprises strongly interacting crystallographic domains arranged in a spherical shell with random orientations and anisotropy axis. The Monte Carlo simulation allows discernment between the influence of the structure polycrystalline and its hollow geometry, while revealing the magnetic domain arrangement in the different temperature regimes.Comment: 26 pages, 8 figures. In press in Phys. Rev.

Broadband distortion modeling in Lyman-α\alpha forest BAO fitting

In recent years, the Lyman-$\alpha$ absorption observed in the spectra of high-redshift quasars has been used as a tracer of large-scale structure by means of the three-dimensional Lyman-$\alpha$ forest auto-correlation function at redshift $z\simeq 2.3$, but the need to fit the quasar continuum in every absorption spectrum introduces a broadband distortion that is difficult to correct and causes a systematic error for measuring any broadband properties. We describe a $k$-space model for this broadband distortion based on a multiplicative correction to the power spectrum of the transmitted flux fraction that suppresses power on scales corresponding to the typical length of a Lyman-$\alpha$ forest spectrum. Implementing the distortion model in fits for the baryon acoustic oscillation (BAO) peak position in the Lyman-$\alpha$ forest auto-correlation, we find that the fitting method recovers the input values of the linear bias parameter $b_{F}$ and the redshift-space distortion parameter $\beta_{F}$ for mock data sets with a systematic error of less than 0.5\%. Applied to the auto-correlation measured for BOSS Data Release 11, our method improves on the previous treatment of broadband distortions in BAO fitting by providing a better fit to the data using fewer parameters and reducing the statistical errors on $\beta_{F}$ and the combination $b_{F}(1+\beta_{F})$ by more than a factor of seven. The measured values at redshift $z=2.3$ are $\beta_{F}=1.39^{+0.11\ +0.24\ +0.38}_{-0.10\ -0.19\ -0.28}$and$b_{F}(1+\beta_{F})=-0.374^{+0.007\ +0.013\ +0.020}_{-0.007\ -0.014\ -0.022}$(1$\sigma$, 2$\sigma$and 3$\sigma$ statistical errors). Our fitting software and the input files needed to reproduce our main results are publicly available.Comment: 28 pages, 15 figures, matches the published versio

Democracy in the Digital Communication Environment: A Typology Proposal of Political Monitoring Processes

The digital environment creates new opportunities for citizen political participation. Among these, the monitoring of political and economic power centers stands out. This includes public scrutiny of the management of public funds and the activities of the public and economic systems, thus denouncing dysfunctional features. This article aims to describe, differentiate, and classify the various forms that monitoring can take in current democracies. The results indicate that three major monitoring fields exist: governmental monitoring, shared monitoring, and civic monitoring. This study focuses on the last by specifying its four types: watchdog function, extraction and filtration of secret information, expansion of issues through alternative journalism, and extension of representation beyond parliaments

The Role of Face Parts in Gender Recognition

This paper evaluates the discriminant capabilities of face parts in gender recognition. Given the image of a face, a number of subimages containing the eyes, nose, mouth, chin, right eye, internal face (eyes, nose, mouth, chin), external face (hair, ears, contour) and the full face are extracted and represented as appearance-based data vectors. A greater number of face parts from two databases of face images (instead of only one) were considered with respect to previous related works, along with several classification rules. Experiments proved that single face parts offer enough information to allow discrimination between genders with recognition rates that can reach 86%, while classifiers based on the joint contribution of internal parts can achieve rates above 90%. The best result using the full face was similar to those reported in general papers of gender recognition (>95%). A high degree of correlation was found among classifiers as regards their capacity to measure the relevance of face parts, but results were strongly dependent on the composition of the database. Finally, an evaluation of the complementarity between discriminant information from pairs of face parts reveals a high potential to define effective combinations of classifiers

The 15-M Movement and the new media: A case study of how new themes were introduced into Spanish political discourse

The 15-M movement, driven by mass mobilisations calling for the regeneration of the political system in May 2011, has had a profound impact on Spanish political discourse. This paper analyses the changes in news production and distribution resulting from the example set by this social movement. The introduction of news using social media outside the boundaries established by the journalistic and political elites represents an innovative strategy to bring the movement’s demands onto the mainstream media agenda and to instigate monitoring processes

On the Complementarity of Face Parts for Gender Recognition

This paper evaluates the expected complementarity between the most prominent parts of the face for the gender recognition task. Given the image of a face, five important parts (right and left eyes, nose, mouth and chin) are extracted and represented as appearance-based data vectors. In addition, the full face and its internal rectangular region (excluding hair, ears and contour) are also coded. Several mixtures of classifiers based on (subsets of) these five single parts were designed using simple voting, weighted voting and other learner as combiners. Experiments using the FERET database prove that ensembles perform significantly better than plain classifiers based on single parts (as expected)

Comportamiento biológico intraarticular de distintos aloinjertos tendinosos: estudio experimental

Se ha efectuado un estudio experimental comparativo, con valoración macro y microscópica, de la supervivencia, dentro de la articulación de la rodilla del conejo, de tendones flexores sobre extensores y dentro de estos, entre tendones conservados en fresco, congelados, liofilizados y fijados en solución de glutaraldehido al 0,2%. Los tendones se mantuvieron libres en la articulación receptora durante periodos distintos de tiempo. Entre los resultados destaca la pérdida de volumen, en el tiempo, de la masa tendinosa (18% de despariciones totales, con un 28% de pérdida final global). Los tendones fijados en glutaraldehido fueron los que presentaron menor pérdida de volumen. Los tendones implantados en fresco y los congelados presentaron una mayor tasa de infección. La mejor respuesta de supervivencia se detectó en los tendones conservados en glutaraldehido y los congelados. Así mismo, tenían más posibilidades de sobrevivir los flexores que los extensores. Desde el punto de vista histológico, los tendones conservados en fresco desencadenaron una mayor respuesta inflamatoria, con gran alteración estructural. Desde el punto de vista microscópico no se han hallado diferencias significativas entre flexores y extensores.Different groups of flexor and extensor tendons have been compared in their abitihty survive within the rabbit knee joint. Tendons were grouped and compared according four different storage procedures like freezing, lyophylization and fixation in 0,2% glutaraldehid. Some of them were used in fresh. All tendons have been kept inside the joint as free graft. All specimens lost weight along the study (18% of total loosing of specimen, and 28% of global loosing). Tendons fixed in disclosed less loosing of volume. Allograft infection was related to the method o glutaraildehid of storage, relationship being statistically significant (fresh tendons and frozen tendons were infected more easily). The best survival was found in both frozen and glutaraldehid fixed tendons. Flexor tendons show more chances of survival than extensors tendons. Histologically, fresh tendons disclosed the greatest inflammatory reaction. Opposite to the macroscopic findings, there were no significant differences between flexors and extensors tendons in the microscopical study