Quantum dynamics of crystals of molecular nanomagnets inside a resonant cavity

It is found that crystals of molecular nanomagnets exhibit enhanced magnetic relaxation when placed inside a resonant cavity. A strong dependence of the magnetization curve on the geometry of the cavity has been observed, providing indirect evidence of the coherent microwave radiation by the crystals. A similar dependence has been found for a crystal placed between the Fabry-Perot superconducting mirrors.

Microwave absorption and magnetization tunneling in Mn12-acetate molecular clusters

In this paper we study the effect of microwave absorption on the quantum relaxation rate of Mn12 molecular clusters. We have determined first the resonant frequencies of a microwave resonator containing a single crystal of Mn12-Acetate and measured initial isothermal magnetization curves while microwave power was put into the resonator. We have found that the tunneling rate changes one order of magnitude for certain frequencies. This suggests that the microwave shaking of the nuclear spin and molecular vibrational degrees of freedom is responsible for the huge increasing of the tunneling rate.

Crystal defects and spin tunneling in single crystals of Mn12 clusters

The question addressed in this paper is that of the influence of the density of dislocations on the spin tunneling in Mn12 clusters. We have determined the variation in the mosaicity of fresh and thermally treated single crystals of Mn12 by analyzing the widening of low angle x-ray diffraction peaks. It has also been well established from both isothermal magnetization and relaxation experiments that there is a broad distribution of tunneling rates which is shifted to higher rates when the density of dislocations increases.

Observation of phonon-induced magnetic deflagration in manganites

Very fast magnetic avalanches in (La, Pr)-based manganites are the signature of a phase transition from an insulating blocked charge-ordered antiferromagnetic state to a charge-delocalized ferromagnetic (CD-FM) state. We report here the experimental observation that this transition does not occur either simultaneously or randomly in the whole sample but there is instead a spatial propagation with a velocity of the order of tens of m/s. Our results show that avalanches originate from the inside of the sample, move to the outside, and occur at values of the applied magnetic field that depend on the CD-FM fraction in the sample. Moreover, upon application of surface acoustic waves at constant magnetic fields, we are able to trigger avalanches at very well-determined values of the temperature and magnetic field. Due to the interaction with the acoustic waves, the number of isolated ferromagnetic clusters in La0.225Pr0.40Ca0.375MnO3 starts to grow across the entire sample in the same way as if it were a magnetic deflagration.

Topological magnetic irreversibility in superconducting Pb samples of various shapes

The magnetic-field dependence of the magnetization of cylinders, disks, and spheres of pure type-I superconducting lead was investigated by means of isothermal measurements of first magnetization curves and hysteresis cycles. Depending on the geometry of the sample and the direction and intensity of the applied magnetic field, the intermediate state exhibits different irreversible features that become particularly highlighted in minor hysteresis cycles. The irreversibility is noticeably observed in cylinders and disks only when the magnetic field is parallel to the axis of revolution and is very subtle in spheres. When the magnetic field decreases from the normal state, the irreversibility appears at a temperature-dependent value whose distance to the thermodynamic critical field depends on the sample geometry. The irreversible features in the disks are altered when they are submitted to an annealing process. These results agree well with very recent high-resolution magneto-optical experiments in similar materials that were interpreted in terms of transitions between different topological structures for the flux configuration in the intermediate state. A discussion of the relative role of geometrical barriers for flux entry and exit and pinning effects as responsible for the magnetic irreversibility is given.

Projecte d’una xarxa de distribució elèctrica de mitja tensió, centres de transformació i instal·lacions d'enllaç d’un polígon industrial

Disseny d’una xarxa de distribució d’alta tensió de tercera categoria de 25 kV subterrània, a partir d’ara mitja tensió (MT), amb deu centres de transformació i distribució de 1000 kVA cadascun. La reforma d’un centre de transformació i distribució de 630 kVA i el disseny de la xarxa de baixa tensió. Amb la finalitat de donar subministrament d’energia elèctrica a les industries d’un polígon del terme municipal de Torroella de Montgrí (GIRONA) i obtenir l’autorització administrativa per la posterior posada en servei d’aquesta instal•lació. No queda inclòs en aquest projecte la instal•lació d’enllumenat públic

Escoletes de Menorca : qu?? ho ha fet i ho fa possible?. 'Escuelas infantiles de Menorca : ??qu?? lo ha hecho y lo hace posible?''

Resumen tomado de la publicaci??n. Incluye gr??ficas y tablas de datos

Evaluación integral de programas, rehabilitación integral de barrios : la experiencia de Palma de Mallorca.

Resumen tomado de la publicación. Los dos primeros autores son miembros de la Universitat de les Illes Baleares y el tercero pertenece al Ajuntament de Palma

Seminari de recerca d'adreces a Internet útils per a la classe de medi a primària. 'Seminario de búsqueda de direcciones en internet útiles para la clase de medio en primaria'.

El profesorado del CP Alcúdia entró a formar parte del proyecto Xarxipèlag y, en este sentido, se introdujo a los alumnos una hora de enseñanza asistida por ordenador y se organizó para el profesorado un curso avanzado sobre las Tecnologías de la Información (TIC) y un Seminario de Aplicación en el Aula de las TIC. En el curso 2001-2002 han realizado un seminario de estudio sobre las posibilidades del uso de Internet en el aula. Se han repasado los diversos tipos de búsquedas, incidiendo en aquellas útiles para la clase de primaria, y se ha planteado un sistema de organización y categorización.

Projecte lingüístic de ciutat. 'Proyecto lingüístico de ciudad'.

Documento electrónico de 17 páginas en formato PDF. El autor era concejal del área de educación y política lingüística del Ayuntamiento de Ciutadella (Menorca) Menorca)

Mòdul del Full de càlcul Excel. 'Módulo de la hoja de cálculo Excel'.

Resumen tomado de la publicación. Incluye capturas de pantalla de ordenador de dicho editor de cálculo y ficheros para la realización de las actividades prácticas

Mòdul de Word avançat. 'Módulo de Word avanzado'.

Resumen tomado de la publicación. Incluye imágenes de capturas de pantalla del ordenador que refuerzan las explicaciones del curso