Composition and Inversion of Schema Mappings

In the recent years, a lot of attention has been paid to the development of solid foundations for the composition and inversion of schema mappings. In this paper, we review the proposals for the semantics of these crucial operators. For each of these proposals, we concentrate on the three following problems: the definition of the semantics of the operator, the language needed to express the operator, and the algorithmic issues associated to the problem of computing the operator. It should be pointed out that we primarily consider the formalization of schema mappings introduced in the work on data exchange. In particular, when studying the problem of computing the composition and inverse of a schema mapping, we will be mostly interested in computing these operators for mappings specified by source-to-target tuple-generating dependencies

Analysis of judgmental adjustments in the presence of promotions

Sales forecasting is increasingly complex due to many factors, such as product life cycles that have become shorter, more competitive markets and aggressive marketing. Often, forecasts are produced using a Forecasting Support System that integrates univariate statistical forecasts with judgment from experts in the organization. Managers add information to the forecast, like future promotions, potentially improving accuracy. Despite the importance of judgment and promotions, the literature devoted to study their relationship on forecasting performance is scarce. We analyze managerial adjustments accuracy under periods of promotions, based on weekly data from a manufacturing company. Intervention analysis is used to establish whether judgmental adjustments can be replaced by multivariate statistical models when responding to promotional information. We show that judgmental adjustments can enhance baseline forecasts during promotions, but not systematically. Transfer function models based on past promotions information achieved lower overall forecasting errors. Finally, a hybrid model illustrates the fact that human experts still added value to the transfer function models

Los restos humanos de la Cueva de la Carigüela (Píñar, Granada) y el destino de los últimos neandertales

Se aborda el estudio de los restos óseos de los Neandertales de la Cueva de la Carigüela y a partir del mismo se plantea el tema del final de los Neandertales.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Cryptocurrency Mining Games with Economic Discount and Decreasing Rewards

In the consensus protocols used in most cryptocurrencies, participants called miners must find valid blocks of transactions and append them to a shared tree-like data structure. Ideally, the rules of the protocol should ensure that miners maximize their gains if they follow a default strategy, which consists on appending blocks only to the longest branch of the tree, called the blockchain. Our goal is to understand under which circumstances are miners encouraged to follow the default strategy. Unfortunately, most of the existing models work with simplified payoff functions, without considering the possibility that rewards decrease over time because of the game rules (like in Bitcoin), nor integrating the fact that a miner naturally prefers to be paid earlier than later (the economic concept of discount). In order to integrate these factors, we consider a more general model where issues such as economic discount and decreasing rewards can be set as parameters of an infinite stochastic game. In this model, we study the limit situation in which a miner does not receive a full reward for a block if it stops being in the blockchain. We show that if rewards are not decreasing, then miners do not have incentives to create new branches, no matter how high their computational power is. On the other hand, when working with decreasing rewards similar to those in Bitcoin, we show that miners have an incentive to create such branches. Nevertheless, this incentive only occurs when a miner controls a proportion of the computational power which is close to half of the computational power of the entire network

La función social de las ciencias del pasado. Stephen Jay Gould in memorian

Eudald CARBONELL ; Robert SALA, Planeta humano. Josep CORBELLA ; Eudald CARBONELL ; Salvador MOYÀ ; Robert SALA, Sapiens. El largo camino de los homínidos hacia la inteligencia. Jaume BERTRANPETIT ; Cristina JUNYENT, Viaje a los orígenes. Una historia biológica del ser humano

Fundamentals and Applications of Surface-Enhanced Raman Spectroscopy (SERS)

When a molecule is adsorbed on some metallic nanostructured surfaces such as silver, copper or gold, it can undergo an enormous enhancement of the Raman signal giving rise to the so called Surface-Enhanced Raman Scattering (SERS). The high sensitivity of this effect allows an accurate structural study of adsorbates at very low concentrations. The SERS effect has historically been associated with the substrate roughness on two characteristic length scales. Surface roughness on the 10 to 100 nm length scale supports localized plasmon resonances which are considered as the dominant enhancement mechanism of SERS (Electromagnetic Enhancement Mechanism: SERS-EM). It is usually accepted that these electromagnetic resonances can increase the scattered intensity by an average factor of ca. 104 to 107. A secondary mechanism often thought to require atomic scale roughness is referred to as Charge Transfer (CT) Enhancement Mechanism (SERS-CT). This mechanism involves the photoinduced transfer of an electron from the metal to the adsorbate or vice versa and involves new electronic excited CT states which result from adsorbate–substrate chemical interactions. It is also estimated that such SERS-CT mechanism can enhance the scattering cross-section by a factor of ca. 10 to 102. These two mechanisms can operate simultaneously, depending on the particular systems and experimental conditions, making difficult to recognize each one and to estimate their relative magnitude in a particular spectrum.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Vegetación perenne en taludes de carretera: condicionantes para su establecimiento y oportunidades para la conservación y restauración de ecosistemas

Las carreteras producen muchos impactos ambientales negativos sobre el territorio que atraviesan. Pero hay estudios que apuntan que los márgenes de las carreteras pueden ser interesantes para la conservación de la biodiversidad y la mejora de servicios ecosistémicos debilitados en territorios agrícolas intensivos y altamente fragmentado. En la actualidad, los trabajos de restauración y manejo de los taludes de carretera se centran en objetivos técnicos (controlar la erosión de los taludes o mejorar la integración paisajística) a corto plazo. En esta tesis doctoral se ha profundizado en la base de conocimientos que permite desarrollar medidas de restauración, manejo y gestión de los márgenes de carretera con objetivos a medio y largo plazo, como pueden ser la conservación de la biodiversidad o el fortalecimiento de los servicios ecosistémicos debilitados. Los estudios realizados para esta tesis se han focalizado en la vegetación perenne y a escalas amplias: dos estudios a escala regional considerando especies leñosas y dos a escala de paisaje considerando la comunidad de plantas perennes. Con esta tesis se han permitido conocer los condicionantes para el establecimiento de la vegetación perenne en márgenes de carretera, así como analizar las potencialidades de dichos márgenes en la oferta de servicios ecosistémicos en entornos agrícolas fragmentados y de alto interés para la conservación, concretamente en territorios con suelos de yeso. A lo largo de toda esta tesis se ha demostrado que prácticamente todas las especies de plantas perennes son capaces de llegar y establecerse en los márgenes de las carreteras, aunque llegan de manera diferencial dependiendo del tipo de dispersión, y además generan comunidades diferentes dependiendo de las características propias de cada margen de carretera. Para las especies de dispersión por animales es importante la estructura del paisaje y la presencia de árboles cerca de los taludes, así como la edad de los propios taludes. Por su parte, las especies de dispersión por viento no tienen limitaciones aparentes para llegar a los márgenes de las carreteras y sus limitaciones son a escala de micrositio favorable para la germinación y establecimiento. También se ha demostrado que los márgenes de las carreteras son excelentes reservorios de diversidad, incluyendo especies protegidas, endémicas o raras. Por ultimo, pese a demostrar la existencia de flujos ecológicos perpendiculares a la vía, no se ha encontrado un efecto de la distancia de carretera sobre las remanentes de hábitat cercanos a la carretera. Los resultados de esta tesis permiten afirmar que la colonización natural, o restauración pasiva, es una poderosa herramienta de restauración ecológica de los márgenes de las carretera, siempre que se den las condiciones idóneas tanto en el propio margen como en el entorno cercano. Además, esta restauración pasiva tiene la capacidad de mejorar la conservación de la diversidad biológica en ambientes agrícolas, ya que mantiene el pool regional de especies y permite que se establezcan flujos ecológicos entre los márgenes de las carreteras y sus entornos