Interest communities and flow roles in directed networks: the Twitter network of the UK riots

Directionality is a crucial ingredient in many complex networks in which information, energy or influence are transmitted. In such directed networks, analysing flows (and not only the strength of connections) is crucial to reveal important features of the network that might go undetected if the orientation of connections is ignored. We showcase here a flow-based approach for community detection in networks through the study of the network of the most influential Twitter users during the 2011 riots in England. Firstly, we use directed Markov Stability to extract descriptions of the network at different levels of coarseness in terms of interest communities, i.e., groups of nodes within which flows of information are contained and reinforced. Such interest communities reveal user groupings according to location, profession, employer, and topic. The study of flows also allows us to generate an interest distance, which affords a personalised view of the attention in the network as viewed from the vantage point of any given user. Secondly, we analyse the profiles of incoming and outgoing long-range flows with a combined approach of role-based similarity and the novel relaxed minimum spanning tree algorithm to reveal that the users in the network can be classified into five roles. These flow roles go beyond the standard leader/follower dichotomy and differ from classifications based on regular/structural equivalence. We then show that the interest communities fall into distinct informational organigrams characterised by a different mix of user roles reflecting the quality of dialogue within them. Our generic framework can be used to provide insight into how flows are generated, distributed, preserved and consumed in directed networks.Comment: 32 pages, 14 figures. Supplementary Spreadsheet available from: http://www2.imperial.ac.uk/~mbegueri/Docs/riotsCommunities.zip or http://rsif.royalsocietypublishing.org/content/11/101/20140940/suppl/DC

Clasificación multicriterio: una regla simple para tratar problemas complejos

Complex problems require new approaches to be addressed, and these approaches require new operational instruments. It describes multicriteria classification --a comprehensive generalisation of the traditional enumeration and sorting in row-- as a method that allows the simultaneous handling of multiple criteria or dimensions of value for an objective accounting from which, without paradox, arises the need for a subjective decision, showing that the final priority must lie on the processes and not on the objects. It also examines its role in the new foundation of historical systems science (or Natural History)

The 'who' and 'what' of #diabetes on Twitter

Social media are being increasingly used for health promotion, yet the landscape of users, messages and interactions in such fora is poorly understood. Studies of social media and diabetes have focused mostly on patients, or public agencies addressing it, but have not looked broadly at all the participants or the diversity of content they contribute. We study Twitter conversations about diabetes through the systematic analysis of 2.5 million tweets collected over 8 months and the interactions between their authors. We address three questions: (1) what themes arise in these tweets?, (2) who are the most influential users?, (3) which type of users contribute to which themes? We answer these questions using a mixed-methods approach, integrating techniques from anthropology, network science and information retrieval such as thematic coding, temporal network analysis, and community and topic detection. Diabetes-related tweets fall within broad thematic groups: health information, news, social interaction, and commercial. At the same time, humorous messages and references to popular culture appear consistently, more than any other type of tweet. We classify authors according to their temporal 'hub' and 'authority' scores. Whereas the hub landscape is diffuse and fluid over time, top authorities are highly persistent across time and comprise bloggers, advocacy groups and NGOs related to diabetes, as well as for-profit entities without specific diabetes expertise. Top authorities fall into seven interest communities as derived from their Twitter follower network. Our findings have implications for public health professionals and policy makers who seek to use social media as an engagement tool and to inform policy design.Comment: 25 pages, 11 figures, 7 tables. Supplemental spreadsheet available from http://journals.sagepub.com/doi/suppl/10.1177/2055207616688841, Digital Health, Vol 3, 201

Location Aided Cooperative Detection of Primary User Emulation Attacks in Cognitive Wireless Sensor Networks Using Nonparametric Techniques

Primary user emulation (PUE) attacks are a major security challenge to cognitive wireless sensor networks (CWSNs). In this paper, we propose two variants of the PUE attack, namely, the relay and replay attacks. Such threats are conducted by malicious nodes that replicate the transmissions of a real primary user (PU), thus making them resilient to many defensive procedures. However, we show that those PUE attacks can be effectively detected by a set of cooperating secondary users (SUs), using location information and received signal strength (RSS) measurements. Two strategies for the detection of PUE relay and replay attacks are presented in the paper: parametric and nonparametric. The parametric scheme is based on the likelihood ratio test (LRT) and requires the existence of a precise path loss model for the observed RSS values. On the contrary, the nonparametric procedure is not tied to any particular propagation model; so, it does not require any calibration process and is robust to changing environmental conditions. Simulations show that the nonparametric detection approach is comparable in performance to the LRT under moderate shadowing conditions, specially in case of replay attacks

Caracterización estructural de anticlinales en el extremo sur de la Cordillera Oriental, provincia de Salta, Argentina

Tesis presentada para optar al Grado de Doctor en Ciencias NaturalesFil: Hernández, Mariano. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentin

Pseudoaneurismas femorales en fracturas de cadera. ¿Se puede evitar?

Aunque la aparición de un pseudoaneurisma femoral es infrecuente en el contexto del tratamiento de fracturas pertrocantéreas, debido a su extrema gravedad y a su posible implicación en las causas de mortali - dad, es necesario realizar un diagnóstico temprano y un tratamiento adecuado. Presentamos 3 casos en los que se produjo una lesión de la arteria femoral superficial, y 2 de la arteria femoral profunda, tratados los 3 casos con stents recubiertos. Conclusiones . Se debe tomar en consideración, recti fi car la aducción y rotación interna de la extremidad fracturada una vez colocado el implante, el uso de brocas cortas o con un tope para el momento del en - cerrojado distal, longitud adecuada de los tornillos, controlar el desplazamiento del trocánter menor, o una correcta colocación de los cerclajes femorales, para poder disminuir la incidencia de este tipo de lesiones.Although the appearance of a femoral pseudoaneurysm is uncommon in the context of treatment of trochanteric fractures, due to their extreme gravity and its possible involvement in the causes of death, it is ne - cessary for early diagnosis and appropriate treatment. We report 3 cases in which an injury occurred superficial femoral artery, and 2 of the deep femoral artery, 3 cases treated with stents. Conclusions. It should be taken into consideration, correct adduction and internal rotation of the fractured limb once fitted the implant, the use of short bits or a cap on the distal locking time, proper length screws, control the displacement of the lesser trochanter , or the correct placement of the femoral cerclage, to decrease the incidence of these injuries

Editorial: Clínica y ciencia.

Sin resumen

A note to baroque vestiges and news of St. Mark’s Church (Salamanca)

El presente artículo realiza una aproximación a la topografía devocional de la iglesia salmantina de San Marcos en época barroca. A través de noticias bibliográficas y relatos figurativos se reconstruye su aspecto original y se rastrea el paradero de los desaparecidos retablos tras la reforma violetiana de 1967, identificando piezas perdidas actualmente descontextualizadas.In this paper is made an approach to the missing baroque altarpieces of the St. Mark’s church in Salamanca (Spain), discovering their appearance and offering clues to its present location after the reform of 1967. Also pieces currently decontextualized are identified.peerReviewe