Where are my followers? Understanding the Locality Effect in Twitter

Twitter is one of the most used applications in the current Internet with more than 200M accounts created so far. As other large-scale systems Twitter can obtain enefit by exploiting the Locality effect existing among its users. In this paper we perform the first comprehensive study of the Locality effect of Twitter. For this purpose we have collected the geographical location of around 1M Twitter users and 16M of their followers. Our results demonstrate that language and cultural characteristics determine the level of Locality expected for different countries. Those countries with a different language than English such as Brazil typically show a high intra-country Locality whereas those others where English is official or co-official language suffer from an external Locality effect. This is, their users have a larger number of followers in US than within their same country. This is produced by two reasons: first, US is the dominant country in Twitter counting with around half of the users, and second, these countries share a common language and cultural characteristics with US

Analysis of searching mechanisms in hierarchical p2p based overlay networks

Proceedings of: The 6th Annual Mediterranean Ad Hoc Networking Workshop (Med Hoc Net 2007. (Corfu, Greece), June 2007This work presents a study of searching mechanisms in Peer-to-Peer (p2p) networks. The aim of this research line is to analyse cross-searching mechanisms that will allow the hierarchical interconnection of p2p networks. A set of relevant metrics for interconnection scenarios are defined to evaluate scalability, robustness and routing latency.This work has been partially supported by the European Union under the IST Content (FP6-2006-IST-507295) project and by the Madrid regional government under the Biogridnet (CAM, S-0505/TIC-0101) project.Publicad

After the Footsteps of the King: the Spatial and Chronological Structure of the Crónica de Fernando IV as a Key Gateway to the Text History

La Crónica de Fernando IV acarrea un desajuste cronológico que se vuelve mayor a medida que avanza la historia. La comparación de la información cronológica y espacial del relato con los datos ofrecidos por la documentación de la cancillería real permite, no sólo comprobar la exactitud del itinerario del rey dibujado por la crónica, o localizar con mayor precisión cronológica los acontecimientos históricos descritos en la narración, sino plantear algunas conclusiones acerca del proceso compositivo del texto. Así, desde una perspectiva diferente, se aplica la metodología y estudio de los intinerarios regios a la resolución de preguntas relacionadas con la crítica genética. Este último aspecto constituye el objetivo esencial del trabajo.The Crónica de Fernando IV carries a chronological mistake which increases as the story moves forward. The comparison between the chronological and spatial information of the chronicle and the data provided by the documents from the chancellery let us not only check the accuracy of the king’s itinerary or the precise dating of the events that the chronicle tells about, but also to come up with some conclusions about the writing process of the text. So, a new perspective is used to apply the metodology and study of royal itineraries to solve relevant issues concerning genetic criticism. The analysis of the later aspect is the major aim of this work

Riesgos biológicos en el personal sanitario

Este trabajo es un revisión bibliográfica de los riesgos biológicos a los que se ve sometido el personal sanitario, y abarca varios aspectos relacionados con él, como son definición de riesgo biológico , vías de entrada , tipos de agentes patógenos ,cómo se puede reducir el riesgo , medidas preventivas ,vacunación del personal sanitario, tipos de sistemas de seguridad de los que disponemos en nuestro medio de trabajo , protocolo de actuación frente a un riesgo biológico , obligaciones del empresario frente a amenazas de riesgo biológico que afecten a sus trabajadores y cómo se notifica a la autoridades competentes

P2P Based Architecture for Global Home Agent Dynamic Discovery in IP Mobility

Mobility in packet networks has become a critical issue in the last years. Mobile IP and the Network Mobility Basic Support Protocol are the IETF proposals to provide mobility. However, both of them introduce performance limitations, due to the presence of an entity (Home Agent) in the communication path. Those problems have been tried to be solved in different ways. A family of solutions has been proposed in order to mitigate those problems by allowing mobile devices to use several geographically distributed Home Agents (thus making shorter the communication path). These techniques require a method to discover a close Home Agent, among those geographically distributed, to the mobile device. This paper proposes a peer-topeer based solution, called Peer-to-Peer Home Agent Network, in order to discover a close Home Agent. The proposed solution is simple, fully global, dynamic and it can be developed in IPv4 and IPv6.No publicad

Is Content Publishing in BitTorrent Altruistic or Profit-Driven

BitTorrent is the most popular P2P content delivery application where individual users share various type of content with tens of thousands of other users. The growing popularity of BitTorrent is primarily due to the availability of valuable content without any cost for the consumers. However, apart from required resources, publishing (sharing) valuable (and often copyrighted) content has serious legal implications for user who publish the material (or publishers). This raises a question that whether (at least major) content publishers behave in an altruistic fashion or have other incentives such as financial. In this study, we identify the content publishers of more than 55k torrents in 2 major BitTorrent portals and examine their behavior. We demonstrate that a small fraction of publishers are responsible for 66% of published content and 75% of the downloads. Our investigations reveal that these major publishers respond to two different profiles. On one hand, antipiracy agencies and malicious publishers publish a large amount of fake files to protect copyrighted content and spread malware respectively. On the other hand, content publishing in BitTorrent is largely driven by companies with financial incentive. Therefore, if these companies lose their interest or are unable to publish content, BitTorrent traffic/portals may disappear or at least their associated traffic will significantly reduce

Benefits on using H-P2PSIP in mobile environments

Proceeding of: VIII Jornadas de Ingeniería Telemática (JITEL '09), Universidad Politécnica de Cartagena, Cartagena, Murcia, 15-17 de septiembre de 2009The use of peer-to-peer technologies is increasing everyday and the improvement of mobility technologies is a reality. Now, it is expected that peer-to-peer applications run on mobile devices, but the conjunction of these two technologies is an open research issue. The user mobility impacts on the churn suffered by peer-to-peer networks and consequently it impacts on their performance. Therefore, some mechanisms are necessary to minimize this undesirable effect. Our proposal tries to solve this problem by using a Hierarchical P2PSIP architecture where different overlays are used for different peer mobility behaviours and they are interconnected between them through an interconnection overlay. In this way it is possible for peers that share the same behaviour to choose a certain protocol or to optimize some functionality that suits best with their mobility situation, while maintaining connectivity with all peers.This research work is being supported by the European Commission under the IST Content Network of Excellence3 (FP6-2006-IST-038423), by the Regional Government of Madrid under the BioGridNet4 project (CAM, S-0505/TIC- 0101) and by the Ministry of Science and Innovation under the CONPARTE project (MEC, TEC2007-67966-C03-03/TCM).No publicad

H-P2PSIP: Interconnection of P2PSIP domains for Global Multimedia Services based on a Hierarchical DHT Overlay Network

The IETF P2PSIP WG is currently standardising a protocol for distributed mul- timedia services combining the media session functionality of SIP and the decentralised distribution and localisation of resources in peer-to-peer networks. The current P2PSIP scenarios only consider the infrastructure for the connectivity inside a single domain. This paper proposes an extension of the current work to a hierarchical multi-domain scenario: a two level hierarchical peer-to-peer overlay architecture for the interconnection of different P2PSIP domains. The purpose is the creation of a global decentralised multimedia services in enterprises, ISPs or community networks. We present a study of the Routing Performance and Routing State in the particular case of a two-level Distributed Hash Table Hierarchy that uses Kademlia. The study is supported by an analytical model and its validation by a peer-to-peer simulator.En prens

Gasification technology assessment of sterile coal to clean electrical power generation.

Sterile coal is a low-value residue associated to the coal extraction and mining activity. According to the type and origin of the coal bed configuration, sterile coal production can mainly vary on quantity, calorific value and presence of sulphur compounds. In addition, the potential availability of sterile coal within Spain is apparently high and its contribution to the local power generation would be of interest playing a significant role. The proposed study evaluates the availability and deployment of gasification technologies to drive clean electricity generation from waste coal and sterile rock coal, incorporating greenhouse gas emission mitigation systems, like CO2, H2S and NOx removal systems. It establishes the target facility and its conceptual basic design proposal. The syngas obtained after the gasification of sterile coal is processed through specific conditioning units before entering into the combustion chamber of a gas turbine. Flue gas leaving the gas turbine is ducted to a heat recovery steam generation boiler; the steam produced within the boilerdrives a steam turbine. The target facility resembles a singular Integrated Gasification in Combined Cycle (IGCC) power station. The evaluation of the conceptual basic design according to the power output set for a maximum sterile contribution, established that rates over 95% H2S and 90% CO2 removal can be achieved. Noticeable decrease of NOx compounds can be also achieved by the use of commercial technology. A techno-economic approach of the conceptual basic design is made evaluating the integration of potential unitsand their implementation within the target facility aiming toachieve clean power generation. The criterion to be compliant with the most restrictive regulation regarding environmental emissions is setting to carry out this analysis