Electrical conduction and magnetic properties of nanoconstrictions and nanowires created by focused electron/ion beam and of Fe3O4 thin films

La tesis se centra en la fabricación y estudio de las propiedades eléctricas y magnéticas de nanoestructuras con aplicaciones potenciales en nanoelectrónica. Se estudian las propiedades de magnetotransporte de películas epitaxiales de Fe3O4. Se desarrolla un método para fabricar constricciones de tamaño atómico en metales usando un haz focalizado de iones. Y se examinan diferentes tipos de nanohílos fabricados mediante deposición usando un haz focalizado de electrones/iones: los de Pt presentan una transición metal-aislante, los de W son superconductores por debajo de 5 K y los de Co son fuertemente magnético

Brief communication: Residence time of energy in the atmosphere

In atmospheric chemistry, a parameter called residence time is defined for each gas as T D M=F, where M represents the mass of the gas in the atmosphere and F is the total average influx or outflux, which in time averages are equal. In this brief communication, we extend this concept from matter to energy which is also a conservative quantity and estimate the average residence time of energy in the atmosphere, which amounts to about 58 d. A similar estimation for the residence time of energy in the Sun is of the order of 107 years, which agrees with the Kelvin-Helmholtz timescale

Brief communication: lower-bound estimates for residence time of energy in the atmospheres of Venus, Mars and Titan

The residence time of energy in a planetary atmosphere, tau, which was recently introduced and computed for the Earth''s atmosphere (Osacar et al., 2020), is here extended to the atmospheres of Venus, Mars and Titan. tau is the timescale for the energy transport across the atmosphere. In the cases of Venus, Mars and Titan, these computations are lower bounds due to a lack of some energy data. If the analogy between tau and the solar Kelvin-Helmholtz scale is assumed, then tau would also be the time the atmosphere needs to return to equilibrium after a global thermal perturbation

Launching a new dimension with 3D magnetic nanostructures

The scientific and technological exploration of three-dimensional magnetic nanostructures is an emerging research field that opens the path to exciting novel physical phenomena, originating from the increased complexity in spin textures, topology, and frustration in three dimensions. One can also anticipate a tremendous potential for novel applications with those systems in a magnetic sensor and information processing technologies in terms of improved energy efficiency, processing speed, functionalities, and miniaturization of future spintronic devices. These three-dimensional structures are distinct from traditional bulk systems as they harness the scientific achievements of nanomagnetism, which aimed at lowering the dimensions down to the atomic scale, but expand those now in a tailored and designed way into the third dimension. This research update provides an overview of the scientific challenges and recent progress with regard to advances in synthesis approaches and state-of-the-art nanoscale characterization techniques that are prerequisite to understand, realize, and control the properties, behavior, and functionalities of three-dimensional magnetic nanostructures

The negative binomial distribution as a renewal model for the recurrence of large earthquakes

The negative binomial distribution is presented as the waiting time distribution of a cyclic Markov model. This cycle simulates the seismic cycle in a fault. As an example, this model, which can describe recurrences with aperiodicities between 0 and 0.5, is used to fit the Parkfield, California earthquake series in the San Andreas Fault. The performance of the model in the forecasting is expressed in terms of error diagrams and compared with other recurrence models from literature

Time to failure of dynamic local load-sharing fiber bundle models in 1 to 3 dimensions

Extensive Monte Carlo simulations are carried out in one, two and three dimensions for dynamic local load-sharing fiber bundle models following a power-law breaking rule with exponent . This exponent controls the degree of disorder of the bundle. The results are obtained using two methods of introducing disorder in the simulations. In the standard, or classical, Monte Carlo method the disorder is quenched; in the second, or radioactive method the disorder is annealed. Both methods give identical mean time-to-failure values for systems of the same size. However, the radioactive method proves to be more efficient due to the smaller standard deviation of the probability distribution function of the time-to-failure. We take advantage of this efficiency to compute the asymptotic mean time-to-failure of large systems as a function of the degree of disorder, as parameterized by . Based on these extensive simulations, conclusions are drawn regarding the upper critical dimension of time-dependent local load-sharing fiber bundle models

Seguimiento de las medidas de gases traza y partículas de los servicios municipales del Ayuntamiento de Zaragoza y de otras redes

La importancia de cuidar la calidad del aire repercute directamente en la salud de las personas, sobre todo en las zonas urbanas. Es por ello que, desde hace varias décadas, son muchas las medidas legislativas que han impulsado la reducción de las emisiones contaminantes y que han establecido los límites seguros de inmisión, es decir, del aire que respiramos. Para asegurar que se cumplen estas medidas y para avisar a la población frente a episodios de alta polución, en los últimos años han aumentado y mejorado las redes de observación de la calidad del aire a nivel europeo y, en particular, en Aragón y en la ciudad de Zaragoza. Gracias a ello, el número de muertes prematuras causadas por la contaminación atmosférica ha disminuido en las últimas décadas, pero todavía representa una parte importante de la mortalidad a nivel nacional e internacional.<br /

Three-dimensional nanomagnetism

Magnetic nanostructures are being developed for use in many aspects of our daily life, spanning areas such as data storage, sensing and biomedicine. Whereas patterned nanomagnets are traditionally two-dimensional planar structures, recent work is expanding nanomagnetism into three dimensions; a move triggered by the advance of unconventional synthesis methods and the discovery of new magnetic effects. In three-dimensional nanomagnets more complex magnetic configurations become possible, many with unprecedented properties. Here we review the creation of these structures and their implications for the emergence of new physics, the development of instrumentation and computational methods, and exploitation in numerous applications

Layer-by-layer growth of complex-shaped three-dimensional nanostructures with focused electron beams

The fabrication of three-dimensional (3D) nanostructures is of great interest to many areas of nanotechnology currently challenged by fundamental limitations of conventional lithography. One of the most promising direct-write methods for 3D nanofabrication is focused electron beam-induced deposition (FEBID), owing to its high spatial resolution and versatility. Here we extend FEBID to the growth of complex-shaped 3D nanostructures by combining the layer-by-layer approach of conventional macroscopic 3D printers and the proximity effect correction of electron beam lithography. This framework is based on the continuum FEBID model and is capable of adjusting for a wide range of effects present during deposition, including beam-induced heating, defocussing and gas flux anisotropies. We demonstrate the capabilities of our platform by fabricating free-standing nanowires, surfaces with varying curvatures and topologies, and general 3D objects, directly from standard stereolithography (STL) files and using different precursors. Real 3D nanoprinting as demonstrated here opens up exciting avenues for the study and exploitation of 3D nanoscale phenomena

Estudio de un modelo tipo autómata celular para simular la dinámica de empresas en el mercado.

Hemos diseñado un modelo tipo autómata celular para simular la dinámica de empresas en el mercado. Este modelo está inspirado en los de Incendios Forestales que cumplen el paradigma de Criticidad Auto-organizada. Las simulaciones se han llevado a cabo en retículos de distinta dimensionalidad para comparar eventualmente con resultados reales obtenidos de datos publicados en diferentes países