The economic effects of exogenous fiscal shocks in Spain: a SVAR approach

This paper estimates the effects of exogenous fiscal policy shocks in Spain in a VAR framework. Government expenditure expansionary shocks are found to have positive effects on output in the short-term at the cost of higher inflation and public deficits and lower output in the medium and long term. Tax increases are found to drag economic activity in the medium term while entailing an only temporary improvement of the public budget balance. The application of these results to the analysis of fiscal policy in Spain since the mid-nineties points to the conclusion that the consolidation process does not seem to have involved costs in terms of output growth. Moreover, the stance of fiscal policy has become more counter-cyclical in that period. JEL Classification: E62, H30Fiscal multipliers, Fiscal shocks, VAR

Environmental Costs Account: a base for measuring sustainability in transport plans.

Each city need to develop sustainable transport plans according to its fu-ture developments. This means identifying the best policy package of transport measures that could produce more sustainable future scenarios: lowest environmental impact, but also better social standards and at mini-mum cost. To that end, it is necessary to measure the environmental and social costs of each alternative transport mode. This paper proposes a me-thodology to calculate those costs in different city contexts: city centre and metropolitan suburbs. It provides a measure of the following environmen-tal costs: pollution, noise, green house gasses and land taken. Then the so-cial costs as congestion and accident costs. These two cost categories are calculated for each mean of transport: metro, bus, private car and taxi. The methodology has been applied to Madrid Region through modeling its mobility demand in 2004. The outputs are costs per passenger-km in each mode and Area: city centre and metropolitan ring. Therefore it is possible to assign monetary costs to environmental and social costs of each trans-port option; for example, car environmental costs are four times higher than buses on average, but it differs a lot from city centre to outskirt areas. Finally, some guidelines can be extracted to develop a more sustainable transport policy for Madrid Region

Processes with Long Memory: Regenerative Construction and Perfect Simulation

We present a perfect simulation algorithm for stationary processes indexed by Z, with summable memory decay. Depending on the decay, we construct the process on finite or semi-infinite intervals, explicitly from an i.i.d. uniform sequence. Even though the process has infinite memory, its value at time 0 depends only on a finite, but random, number of these uniform variables. The algorithm is based on a recent regenerative construction of these measures by Ferrari, Maass, Mart{\'\i}nez and Ney. As applications, we discuss the perfect simulation of binary autoregressions and Markov chains on the unit interval.Comment: 27 pages, one figure. Version accepted by Annals of Applied Probability. Small changes with respect to version

Contribución al conocimiento de la secuencia arqueológica y el hábitat del Holoceno inicial en el Maestrazgo

Se presenta el estudio de un total de cinco yacimientos localizados en el tramo superior del Riu de les Coces (Alt Maestral, Castellón). Partiendo de los problemas derivados de la naturaleza de la información manejada se aborda su contextualización en el marco de la secuencia arqueológica y del hábitat del Holoceno inicial en el Maestrazgo y en el contexto regional. Los resultados obtenidos permiten por un lado, relativizar la idea de una secuencia local continua e ininterrumpida desde el Magdaleniense superior hasta el Mesolítico Reciente, y por otro. la sucesión de dos modelos diferentes de ocupación del territorio

Virtual divide, Bologna education model and geographic information technologies

RESUMEN. El presente artículo reflexiona acerca del impacto que el desarrollo tecnológico tiene en nuestras sociedades. A lo largo del primer apartado se señala la importancia que la segregación digital tiene en la actual sociedad de la información, confirmándose posteriormente el hecho de que la formación es la única respuesta válida para evitarla. En ese sentido, se enfatiza la oportunidad histórica que la Unión Europea tiene de cara a integrar en su nuevo Espacio de Educación Superior (EEES) soluciones que minimicen este impacto. Las tecnologías de la información geográfica (TIG) son presentadas como un ejemplo de tecnologías que puede generar este tipo de segregación en el futuro próximo, planteándose la necesidad de una reflexión seria acerca del modo en que deben de ser diseñados los programas de futuros cursos postgrado relativos a las TIG.ABSTRACT. The following report deals with the concept of digital divide. It is pointed out the importance of this type of segregation in the information society we live and it is showed how education and training has been considered the unique way to avoid it. In this sense, it is also emphasized the chance that the European Union has to face this coming trouble at this particular time. The definition of a new education system at the European Higher Education Area (EHEA) based on lifelong learning philosophy and the Bologna principles give us a new educative context. Geographic Information Technologies (GIT) are presented as an example of expertise that can generate digital segregation in the nearest future making a final point about how the new postgraduate courses related to GIT should be define at the European universities

Contributions to nanophotonics: linear, nonlinear and quantum phenomena

(English) Nanophotonics can be defined as the science and technology studying the control optical fields at the nanoscale and their interaction with matter. In order to spatially control such fields we would need structures with characteristic dimensions of the order of the wavelength, bringing us to the nanoscale. A way to control optical fields at this scale is the use of nanoantennas, optical equivalent of radio-antennas. They provide efficient interfaces between near-fields generated by light sources and radiative channels. After a brief Introduction, Chapter 2 describes interaction between single photon emitters and nanoantennas. We start the chapter introducing a method to numerically simulate the interaction. A key concept to solving Maxwell equations is that of the Green function. I show how this function relates to the emission rate of optical emitters in a nanophotonic environment. I then describe an our efforts to build a lifetime-imaging near-field scanning optical microscope. Using this rig we are able to measure changes changes in the emission rate of single emitters that interact with resonant optical antennas. A complementary way to control optical field in the nanoscale is using dielectric confinement. Chapter 3 introduces hybrid structures combining nanoantennas and dielectric waveguides. I generalize the Green function formalism introduced in Chapter 2, and show how this is related to the energy transfer rate between a donor and an acceptor. I use this numerical method to calculate the energy transfer rate in a hybrid structure. An increase of orders of magnitude is found at distances of the order of the wavelengths of the transferred photons. This chapter finishes by discussing the role that the local density of optical states has on the energy transfer efficiency. Nanoantennas increase near-field by orders of magnitude. In these conditions, nonlinear optical effects start to play a role. Chapter 4 is devoted to these nonlinear interactions mediated by nanoantennas. I explore nonlinear interactions in resonant nanoantennas, in particular SHG. First I introduce a method to numerically compute the contributions to SHG generated by the metal in nanoantennas. Both surface and bulk contributions to SHG are considered. I use the numerical method to show that narrowings within the antenna shape are sources of increased SHG. The increase in SHG is attributed to increase of the local field gradients, that increase to the bulk contribution to SHG. We numerically validate our results by performing SHG measurements at the single resonant antenna level. Optical fields are functions of space, but also of time. The development of broadband femtosecond lasers and pulse shaping techniques allows control of optical field down to the femtosecond timescale. Chapter 5 explores the control of optical fields in time. Using phase shaping methods we optimize the two-photon absorption process in single QDs. I introduce a new optimization algorithm, that allows us to perform the optimization using as feedback signal the luminesce from single QDs. We then compare our results with standard phase shaping techniques. Based on their success to effectively control all kinds of optical fields, plasmon supporting nanoantennas are being actively researched in the field of quantum optics. In Chapter 6 I describe a quantum eraser experiment mediated by structures supporting surface plasmon resonances. I first explain the details and subtleties of a quantum eraser experiment. I then detail our efforts to reproduce previously reported results about how to fabricate elliptical bullseye antennas behaving as quarter waveplates. Quarter waveplates are a required part for the quantum eraser effect to take place. An additional key component of our experiment is a bright, state-of-the-art entangle polarization entangle photon source that is described at length. We then perform a quantum eraser experiment mediated by plasmons.(Español) La nanofotónica es el conjunto de ciencia y tecnologías que estudian el control de campos ópticos en la nanoescala y la interacción de estos con la materia. Para controlar estos campos, necesitamos estructuras con dimensiones características del orden la su longitud de onda, lo que nos lleva a la nanoescala. Una forma de controlar campos ópticos a estas escalas es mediante el uso de nanoantenas, los equivalentes a frecuencias ópticas de las antenas de radio. Las nanoantenas proporcionan interfaces entre los campos cercanos generados por emisores ópticos y modos de radiación. Tras una breve introducción, el capítulo 2 describe la interacción entre emisores de fotones individuales y nanoantennas. El capitulo comienza introduciendo un método numérico de simulación que nos permite calcular la función de Green y su relación con la tasa de emisión de fotones de emisores ópticos en entornos nanofotónicos. Describo a continuación la construcción de un microscopio óptico de campo cercano capaz de medir el tiempo de vida de las tasas de emisión de emisores de fotones individuales que interactúan con nanoantenas. Un método complementario para controlar campos ópticos es la utilización del confinamiento dialéctico. El capítulo 3 introduce estructuras híbridas que combinan nanoantenas y guías de onda. Generalizo el formalismo de las funciones de Green del capitulo 1, y muestro como las nuevas funciones están relacionadas con la transferencia de energía entre un donor y un aceptor. Seguidamente, calculo la tasa de transferencia de fotones mediada por la estructura híbrida. Observamos un incremento de ordenes de magnitud en la tasa de transferencia a distancias comparables con las longitudes de onda de los fotones transmitidos. El capitulo finaliza discutiendo el papel que la densidad local de estado ópticos juega en la eficiencia de la transferencia de energía. Las nanoantenas incrementan el campo cercano órdernes de magnitud. En estas condiciones los efectos no-linearles comienzan a entrar en juego. El capitulo 4 está dedicado a estas interacciones no lineales mediadas por nanoantenas, en particular la generación de segundo armónico (SHG). Primeramente, introduzco un método numérico para calcular las contribuciones superficiales y volumétricas a SHG. Estrecheces introducidas a lo largo de las nanoantenas incrementan las emisiones de SHG. Este incremento es atribuido al incremento de gradientes de campo, que contribuyen mayoritariamente a un incremento de la parte volumétrica. Finalmente validamos nuestros resultados numérico experimentalmente. Los campos ópticos son funciones del espacio, pero también del tiempo. El desarrollo de láseres de femtosegundo de banda ancha, unido a las técnicas de formación de pulsos permiten el control de la luz a escalada de femtosegundos. El capítulo 5 explora este control de los campos en el tiempo. Utilizando técnicas de formación de pulsos optimizamos los procesos de absorción de dos fotones en puntos cuánticos de semiconductores. Introduzco un nuevo algoritmo de optimización que nos permite utilizar como señal de retroalimentación la señal de luminiscencia de puntos cuánticos individuales. Debido al éxito en el control de todo tipo de campos ópticos, las nanoantenas basadas en resonancias de plasmones están siendo activamente investigadas en el campo de la óptica cuántica. En el capitulo 6 describo un experimento de borrado cuántico mediado por estructuras basadas en resonancias plasmónicas. Primeramente describo los detalles y sutilezas de este tipo de experimentos. Seguidamente detallo nuestros esfuerzos para reproducir resultados previos acerca de la fabricación antenas elípticas de diana que se comportan como retardados de cuarto de onda. Estos retardadores de cuarto de onda son necesarios para que el efecto de borrado cuántico pueda darse. Otro ingrediente clave de nuestro experimento es una fuente brillante de fotones ...Postprint (published version

An Empirical Study of Real-World SPARQL Queries

Understanding how users tailor their SPARQL queries is crucial when designing query evaluation engines or fine-tuning RDF stores with performance in mind. In this paper we analyze 3 million real-world SPARQL queries extracted from logs of the DBPedia and SWDF public endpoints. We aim at finding which are the most used language elements both from syntactical and structural perspectives, paying special attention to triple patterns and joins, since they are indeed some of the most expensive SPARQL operations at evaluation phase. We have determined that most of the queries are simple and include few triple patterns and joins, being Subject-Subject, Subject-Object and Object-Object the most common join types. The graph patterns are usually star-shaped and despite triple pattern chains exist, they are generally short.Comment: 1st International Workshop on Usage Analysis and the Web of Data (USEWOD2011) in the 20th International World Wide Web Conference (WWW2011), Hyderabad, India, March 28th, 201