Dipole–dipole interaction in superparamagnetic nanocrystalline Fe63.5Cr10Si13.5B9Cu1Nb3

Cr-substituted Finemet-type nanocrystalline alloy (Fe63.5Cr10Si13.5B9Cu1Nb3) has been studied by differential scanning calorimetry, x-ray diffraction, Mo¨ssbauer spectroscopy, and magnetic measurements. The Curie temperature of the remaining amorphous phase decreases as the crystalline volume fraction increases, reaching values below room temperature. This feature makes the alloy adequate for studying the magnetic decoupling of the ~Fe,Si! nanocrystals at moderated temperatures and, in particular, the superparamagnetic relaxation in broad temperature and crystalline fraction ranges. It was shown that the anomalous dependence of the coercive field on the annealing temperature can be satisfactorily explained assuming a dipolar-type interaction between the crystallites.DGES del Gobierno español-PB97-1119-CO2-01Fondo de investigación del gobierno húngaro-OTKA T-030753Academia de Ciencias de Hungría-AKP 98-25 2,

Exploring the S-Matrix of Massless Particles

We use the recently proposed generalised on-shell representation for scattering amplitudes and a consistency test to explore the space of tree-level consistent couplings in four-dimensional Minkowski spacetime. The extension of the constructible notion implied by the generalised on-shell representation, i.e. the possibility to reconstruct at tree level all the scattering amplitudes from the three-particle ones, together with the imposition of the consistency conditions at four-particle level, allow to rediscover all the known theories and their algebra structure, if any. Interestingly, this analysis seems to leave room for high-spin couplings, provided that at least the requirement of locality is weakened. We do not claim to have found tree-level consistent high-spin theories, but rather that our methods show signatures of them and very likely, with a suitable modification, they can be a good framework to perform a systematic search.Comment: 44 pages, 1 figur

Study of Professional Profiles in Social Education. The Final Degree Project, an opportunity for applied research

Els últims anys s’han caracteritzat per avenços importants en la professionalització de l’educació social, que han suposat un increment gradual del reconeixement i la contractació de llocs de treball específics. Tot i això, una de les majors inquietuds de l’educació social és la seva professionalització. Aquesta realitat ens ha portat a iniciar una línia d’investigació que es desenvolupa en els TFG (Treball Fi de Grau) de la titulació universitàriade Grau en Educació Social de la Universitat de Vigo, el disseny del qual es descriu en aquest article.Los últimos años han venido caracterizados por importantes avances en la profesionalización de la educación social, que han supuesto un incremento paulatino del reconocimiento ycontratación de puestos específicos. A pesar de ello, una de las mayores inquietudes de la educación social es su profesionalización.Esta realidad nos ha llevado a iniciar una línea de investigación que se viene desarrollando en los TFG (Trabajo Fin de Grado) de la titulación universitaria de Grado en Educación Social de la Universidad de Vigo, cuyo diseño se describe en este artículo.The last few years have been characterized by significant progress in the professionalization of social education, which have resultedin a gradual increase in recognition and in recruitment to fill specific posts. At the same time, the issue of professionalization is one ofthe major concerns of social education. This state of affairs has led us to start work on a line of research that is developed in the FinalProject of the degree in Social Education at the University of Vigo, the design of which is described in this article

La animación sociocultural, un ámbito transversal a otros ámbitos de la educación social

Definir l’espai professional de l’educació social és una empresa en construcció. Un dels àmbits proposats, juntament amb d’altres, el constitueix l’animació sociocultural. Tanmateix, la pràctica professional de l’educació social és complexa, fet que es reflecteix en les interrelacions entre les diferents àrees d’intervenció atès que no hi ha unes fronteres clares entre elles. Aquest article recull, a partir de les opinions (qüestionaris semiestructurats) de professionals de l’educació social, les interconnexions de l’animació sociocultural en àrees tan diverses com centres de menors, toxicòmans, persones grans, discapacitats, etc. Els resultats indiquen que, en aquests contextos, l’animació sociocultural és un recurs per a la integració i promoció de col·lectius que viuen situacions de marginació, tot afavorint una major equitat per a tots. En conclusió, posen en evidència que, en la praxi de l’educació social, l’animació sociocultural s’ha incorporat a l’àmbit de l’educació especialitzada.Delimiting the professional niche of social education is an ongoing endeavour. One of the proposed fields is sociocultural animation. However, the professional practice of social education is complex, a condition that is reflected in the interrelationships among the different areas of intervention, which have no clear boundaries between them. Though the opinions of social education professionals (via semi-structured questionnaires) the article examines the interconnections of sociocultural animation in such varied contexts as centres for young people, drug addiction, the elderly and people with disabilities. The results indicate that in these settings sociocultural animation is being used as a resource for the integration and promotion of marginal groups into society, fostering greater equality for all. In conclusion, they highlight the fact that in the praxis of social education, sociocultural animation is now integrated fully into specialized education.Definir el espacio profesional de la educación social es una empresa en construcción. Uno de los ámbitos propuestos, junto a otros, lo constituye la animación sociocultural. Sin embargo, la práctica profesional de la educación social es compleja, lo que se refleja en las interrelaciones entre las distintas áreas de intervención, no existiendo unas fronteras claras entre las mismas. Este artículo recoge, a partir de las opiniones (cuestionarios semiestructurados) de profesionales de la educación social, las interconexiones de la animación sociocultural en áreas tan diversas como centros de menores, toxicómanos, personas mayores, discapacitados, etc. Los resultados indican que, en estos contextos, la animación sociocultural es un recurso para la integración y promoción de colectivos que viven situaciones de marginación, favoreciendo mayor equidad para todos. En conclusión, ponen en evidencia que, en la praxis de la educación social, la animación sociocultural se ha incorporado al ámbito de la educación especializada

Eclipsing Binaries Showing Light Time Effect

Four eclipsing binaries, which show apparent changes of period, have been studied with respect to a possible presence of the light time effect. With a least squares method we calculated new light elements of these systems, the mass function of the predicted third body, and its minimum mass. We discuss the probability of the presence of such bodies in terms of mass function, changes in radial velocity and third light in solution of light curves.Comment: 4 pages, 4 figures, 1 table, conference proceeding

How far do they go? The outer structure of dark matter halos

We study the density profiles of collapsed galaxy-size dark matter halos with masses 1e11-5e12 Msun focusing mostly on the halo outer regions from the formal virial radius Rvir up to 5-7Rvir. We find that isolated halos in this mass range extend well beyond Rvir exhibiting all properties of virialized objects up to 2-3Rvir: relatively smooth density profiles and no systematic infall velocities. The dark matter halos in this mass range do not grow as one naively may expect through a steady accretion of satellites, i.e., on average there is no mass infall. This is strikingly different from more massive halos, which have large infall velocities outside of the virial radius. We provide accurate fit for the density profile of these galaxy-size halos. For a wide range (0.01-2)Rvir of radii the halo density profiles are fit with the approximation rho=rho_s exp(-2n[x^{1/n}-1])+rho_m, where x=r/r_s, rho_m is the mean matter density of the Universe, and the index n is in the range n=6-7.5. These profiles do not show a sudden change of behavior beyond the virial radius. For larger radii we combine the statistics of the initial fluctuations with the spherical collapse model to obtain predictions for the mean and most probable density profiles for halos of several masses. The model give excellent results beyond 2-3 formal virial radii.Comment: 15 pages, 10 figures, submitted to Ap

Magnetocaloric effect in Mn-containing Hitperm-type alloys.

The magnetocaloric effect of Fe60−xMnxCo18Nb6B16 x=0,2,4 is studied. Mn addition decreases the Curie temperature of the alloys but also reduces the peak entropy change and the refrigerant capacity of the material. The estimated adiabatic temperature change, for a maximum applied field of 15 kOe, is 1.3 K. Obtained values are comparable to those of some Nanoperm-type alloys. The magnetic entropy change, SM, of the studied samples follows a master curve, which is the same for all of them. The exponent controlling the field dependence of SM scales with reduced temperature in the same way as the master curve does

Towards Prediction of Financial Crashes with a D-Wave Quantum Computer

Prediction of financial crashes in a complex financial network is known to be an NP-hard problem, i.e., a problem which cannot be solved efficiently with a classical computer. We experimentally explore a novel approach to this problem by using a D-Wave quantum computer to obtain financial equilibrium more efficiently. To be specific, the equilibrium condition of a nonlinear financial model is embedded into a higher-order unconstrained binary optimization (HUBO) problem, which is then transformed to a spin-$1/2$ Hamiltonian with at most two-qubit interactions. The problem is thus equivalent to finding the ground state of an interacting spin Hamiltonian, which can be approximated with a quantum annealer. Our experiment paves the way to study quantitative macroeconomics, enlarging the number of problems that can be handled by current quantum computers

The Clumping Transition in Niche Competition: a Robust Critical Phenomenon

We show analytically and numerically that the appearance of lumps and gaps in the distribution of n competing species along a niche axis is a robust phenomenon whenever the finiteness of the niche space is taken into account. In this case depending if the niche width of the species $\sigma$ is above or below a threshold $\sigma_c$, which for large n coincides with 2/n, there are two different regimes. For $\sigma > sigma_c$ the lumpy pattern emerges directly from the dominant eigenvector of the competition matrix because its corresponding eigenvalue becomes negative. For $\sigma </- sigma_c$ the lumpy pattern disappears. Furthermore, this clumping transition exhibits critical slowing down as $\sigma$ is approached from above. We also find that the number of lumps of species vs. $\sigma$ displays a stair-step structure. The positions of these steps are distributed according to a power-law. It is thus straightforward to predict the number of groups that can be packed along a niche axis and it coincides with field measurements for a wide range of the model parameters.Comment: 16 pages, 7 figures; http://iopscience.iop.org/1742-5468/2010/05/P0500