Nondiffracting Accelerating Waves: Weber waves and parabolic momentum

Diffraction is one of the universal phenomena of physics, and a way to overcome it has always represented a challenge for physicists. In order to control diffraction, the study of structured waves has become decisive. Here, we present a specific class of nondiffracting spatially accelerating solutions of the Maxwell equations: the Weber waves. These nonparaxial waves propagate along parabolic trajectories while approximately preserving their shape. They are expressed in an analytic closed form and naturally separate in forward and backward propagation. We show that the Weber waves are self-healing, can form periodic breather waves and have a well-defined conserved quantity: the parabolic momentum. We find that our Weber waves for moderate to large values of the parabolic momenta can be described by a modulated Airy function. Because the Weber waves are exact time-harmonic solutions of the wave equation, they have implications for many linear wave systems in nature, ranging from acoustic, electromagnetic and elastic waves to surface waves in fluids and membranes.Comment: 10 pages, 4 figures, v2: minor typos correcte

It remains to be seen whether recent reforms can reverse Mexico’s decline in electoral integrity

Mexico has a chequered history when it comes to elections, with its electoral integrity occasionally coming under question. Here, Miguel Angel Lara Otaola assesses Mexico against the Perceptions of Electoral Integrity Index and analyses recent elections as well as the recent problems faced by the country from the disappearance of 43 students last year to the recent escape from prison by the top drug lord in the country

Brexit and the tragedy of Europe

Is the EU in danger of collapse following the UK’s decision to leave? Miguel Angel Lara Otaola writes that Brexit represents a key challenge for Europe’s post-war system of open markets, cooperation between nations, stability, and peace. He argues that both the UK and the rest of the EU will need to be constructive in their negotiations if they are to avoid aggravating tensions and divisions

Perception is key in explaining when election results are, and aren’t, accepted by voters

Is it sufficient for elections merely to have been conducted fairly for the result to be accepted? Drawing on research conducted on 28 separate elections, Miguel Angel Lara Otaola argues that elections not only need to be conducted fairly, but that they have to be perceived as such. If this does not happen, the risk of violence and other kinds of instability is heightened considerably

Caracterización hidrodinámica de praderas naturales de macrófitos bentónicos en fondos someros afectados por mareas

Mención europeaThe inner water body of Cadiz bay is a shallow and tide-dominated lagoon, affected by episodic wind-storms and profusely inhabited by marine macrophytes (> 90% covering). These macrophytes are key to the functioning and productivity of this system and their interactions with hydrodynamics affects important ecological processes such as resources uptake and availability, bed stability and sedimentation. To understand the physical settings controlling such processes, the main objective of this PhD thesis was to study the effects of the marine macrophytes on the spatial patterns of current velocity and turbulence, and their potential consequences for sedimentary and nutrients dynamics. For this propose, hydrodynamic gradients along natural canopies, as well as the influence of some benthic landscape elements (i.e. microtopography, benthic transitions and patches fragmentation) were analysed with a combination of in situ measurements (e.g. acoustic Doppler velocimeter (ADV) and dye tracer measurements) and flume tank experiments. Main results revealed that (1) the flow accelerates over the canopies, being partially explained by submergence conditions, (2) fragmentation of intertidal patches augments horizontal turbulent diffusivity of solutes, whereas their retention time remains unaffected, and (3) the leading edge is the most active sedimentation zone on a seagrass meadow. Microtopography seems to promote the benthic macrophyte interactions only on cases affected by high flow events. Overall, diffusive limited- rather than mechanical stress- conditions dominate during no windy spring tide periods. Present study provides important keys to understand the role of marine macrophytes as ecosystem engineers from the inner Cadiz bay.*Beca de Formación del Personal Investigador del Ministerio de Educación y Ciencia (2006-2010), asociada al proyecto del Plan Nacional de I+D+i “Estudio integrado del efecto de las variables físico-químicas sobre la ecología de la praderas de macrófitos marinos del Parque Natural Bahía de Cádiz. Aplicaciones para la gestión” (CTM2005-00395)196 página

Detecting and Monitoring Hate Speech in Twitter

Social Media are sensors in the real world that can be used to measure the pulse of societies. However, the massive and unfiltered feed of messages posted in social media is a phenomenon that nowadays raises social alarms, especially when these messages contain hate speech targeted to a specific individual or group. In this context, governments and non-governmental organizations (NGOs) are concerned about the possible negative impact that these messages can have on individuals or on the society. In this paper, we present HaterNet, an intelligent system currently being used by the Spanish National Office Against Hate Crimes of the Spanish State Secretariat for Security that identifies and monitors the evolution of hate speech in Twitter. The contributions of this research are many-fold: (1) It introduces the first intelligent system that monitors and visualizes, using social network analysis techniques, hate speech in Social Media. (2) It introduces a novel public dataset on hate speech in Spanish consisting of 6000 expert-labeled tweets. (3) It compares several classification approaches based on different document representation strategies and text classification models. (4) The best approach consists of a combination of a LTSM+MLP neural network that takes as input the tweet’s word, emoji, and expression tokens’ embeddings enriched by the tf-idf, and obtains an area under the curve (AUC) of 0.828 on our dataset, outperforming previous methods presented in the literatureThe work by Quijano-Sanchez was supported by the Spanish Ministry of Science and Innovation grant FJCI-2016-28855. The research of Liberatore was supported by the Government of Spain, grant MTM2015-65803-R, and by the European Union’s Horizon 2020 Research and Innovation Programme, under the Marie Sklodowska-Curie grant agreement No. 691161 (GEOSAFE). All the financial support is gratefully acknowledge

Explanatory Factors for Public Transportation Financing Needs in Spain

Public transport financing in Spain has generated interest due to the absence of a governing regulatory framework. There is a need for rules that help allocate public subsidies to guarantee the system’s financial sustainability. Without explicit regulation, the current system for assigning and distributing public funding among Spanish cities has become unbalanced. Our goal is to identify the principal factors that explain why urban transport services in different cities require varying levels of public financing. Our results show that variables such as the “passengers,” “number of vehicles,” “number of employees,” “autonomous community deficit”, and “population density” are influencing factors for the needs of public subsidies. Document type: Articl

Nematodos de la subfamilia Criconematinae (Nematoda: Criconematidae) en la España peninsular

Se realiza un estudio de las caracteristicas morfológicas y morfométricas de los nematodos de la subfamilia Criconematinae encontrados en España peninsular, se describen machos de Seriespinula allieri y se incluye una clave para la identificación de las especies encontradas.Se han encontrado trece especies pertenecientes a los géneros Criconema, Croserinema, Crossonema, Ogma y Seriespinula. Las especies de la subfamilia Criconematinae aparecen con mayor frecuencia en los ecosistemas naturales que en los cultivos. Crossonema menzeli sólo se ha encontrado en hayedos, C. multisquamatum aparece en cítricos y Criconema mutabile en cultivos horticolas del sur peninsular y en frutales en la mitad norte peninsular.A morphological and morphometrical study of the nematodes from subfamily Criconematinae in Peninsular Spain is carried out, male of Seriespinula allieri is reported and a key for identification of species found is provided. Thirteen species have been found belonging to the genera Criconema, Croserinema, Crossonema, Ogma and Seriespinula. The species of Criconematinae appear mostly in natural ecosistems. Crossonema menzeli has been found only in beech forests, C. multisquamatum in citrus orchards and Criconema mutabile in vegetables crops in Southern Spain and in fruit orchards in the half Northern of Spain

A flexible model for Web service discovery

Also published online by CEUR Workshop Proceedings (CEUR-WS.org, ISSN 1613-0073) Proceedings of the 1st International Workshop on Semantic Matchmaking and Resource Retrieval, SMR 06The advent of the SOA paradigm is expected to cause an increase in the number of available Web services. In this setting, advanced facilities for the discovery of Web services that provide a given functionality are required so that this increase does not create a bottleneck for the exploitation of services in an SOA. In this paper, we present a model for the discovery of Web services which relies on alternative views of Web service functional capabilities, allowing for different trade-offs between the accuracy of discovery results and the efficiency of the discovery process. Up to three filtering steps, with increasing complexity, can be successively applied in order to refine discovery results. Furthermore, the use of taxonomies of functional categories, close to the intuition of average users, is introduced by our model with a two-fold purpose: a) supporting the user in the description of goals and Web services, and b) allowing for a coarse-grained but highly efficient discovery. Due to its flexibility, the model proposed is expected to cover a wide range of use cases