Tetraspanins interweave EV secretion, endosomal network dynamics and cellular metabolism

Tetraspanin proteins organize membrane nanodomains related to cell adhesion and migration. An essential feature conserved along the superfamily is their cone-shaped tertiary structure, which allows tetraspanins to be enriched in highly curved membrane structures. Their conical shape, together with their ability to associate to transmembrane receptors and to bind to cystoskeletal and signaling scaffolds, are key in their ability to regulate endosomal network dynamics and Extracellular Vesicle biogenesis and cargo selection. Recent evidence suggests that tetraspanins have a relevant impact in mitochondria turnover and regulation of cellular metabolism. In this review we highlight those reports that point to tetraspanins as key regulators in the communication between the endosomal network, EVs and the cellular metabolismWe thank Dr. Cabañas for critical reading of the manuscript. This work has been supported by grants BIO2017-86500-R, PID2020- 119627GB-I00, and RED2018-102411-T TeNTaCLES from Ministerio Español de Ciencia e Innovación (Spain) to MY-M. VT is supported by an FPI-UAM predoctoral fellowshi

Energy vulnerability and self-imposed austerity: An ethnographic approach to adaptation strategies to extreme heat among older adults in Madrid

This article analyses local practices concerning energy saving in the context of summer heat. It argues that the analysis of people's thermal regulation activities in a situation of energy marginalization is central to understanding the social dynamics of energy vulnerability. The research combines architectural/urban and ethnographic perspectives to investigate the adaptive capacities of users and how external factors and regulations influence local practices concerning energy saving. Older adults are one of the most vulnerable groups to summer heat, as well as most prone to suffering energy vulnerability. The article examines how adults over 65 years of age in Madrid experience heat stress and adapt to extreme temperatures through the analysis of a collaborative documentary film, ‘The Wave’ (30′), written and designed by research participants to show the ways in which they experience summer heat. It explores older adults' adaptation practices and the various external factors influencing their use of energy dependent adaptation strategies, including climate change (rising temperatures), existing conditions (urban, cultural, and social) and policies/economy (energy prices). The article highlights how these factors govern citizens' energy consumption and how they are negotiated locally through embodied, environmental, and social adjustments.The research leading to these results was funded by the EEA Financial Mechanism 2014 - 2021 through the National Science Centre in Poland (grant no. 2019/35/J/HS6/03992). Co-author Daniel Torrego Gómez is funded by the European Union - NextGenerationEU, Margarita Salas Grants, and Universidad de Alicante

Providing service guarantees in 802.11e EDCA WLANs with legacy stations

Although the EDCA access mechanism of the 802.11e standard supports legacy DCF stations, the presence of DCF stations in the WLAN jeopardizes the provisioning of the service guarantees committed to the EDCA stations. The reason is that DCF stations compete with Contention Windows (CWs) that are predefined and cannot be modified, and as a result, the impact of the DCF stations on the service received by the EDCA stations cannot be controlled. In this paper, we address the problem of providing throughput guarantees to EDCA stations in a WLAN in which EDCA and DCF stations coexist. To this aim, we propose a technique that, implemented at the Access Point (AP), mitigates the impact of DCF stations on EDCA by skipping with a certain probability the Ack reply to a frame from a DCF station. When missing the Ack, the DCF station increases its CW, and thus, our technique allows us to have some control over the CWs of the legacy DCF stations. In our approach, the probability of skipping an Ack frame is dynamically adjusted by means of an adaptive algorithm. This algorithm is based on a widely used controller from classical control theory, namely a Proportional Controller. In order to find an adequate configuration of the controller, we conduct a control-theoretic analysis of the system. Simulation results show that the proposed approach is effective in providing throughput guarantees to EDCA stations in presence of DCF stations.European Community's Seventh Framework ProgramPartly funded by the Ministry of Science and Innovation of Spain, under the QUARTET project (TIN2009-13992-C02-01)Publicad

Estrategias de configuración de redes WLAN IEEE 802.11e EDCA

Las redes inalámbricas de área local (WLANs) se han convertido en una solución muy común para proporcionar acceso a Internet. El principal mecanismo usado a nivel MAC (Medium Access Control) para las WLANs es el definido por el estándar IEEE 802.11. Recientemente, el grupo de trabajo (Working Group) 802.11 ha aprobado un nuevo estándar, denominado 802.11e, que extiende dicho mecanismo para suministrar calidad de servicio (QoS). Este nuevo estándar se basa en una serie de parámetros a configurar, tema aún pendiente de ser resuelto pues si bien se proporcionan unos valores recomendados para dichos parámetros, estos valores son estáticos por lo que su idoneidad no está garantizada. La presente tesis aborda el diseño de estrategias de configuración que optimicen el uso del mecanismo EDCA del estándar 802.11e. A tal efecto, se distinguen dos escenarios WLAN bien diferentes, cada uno definiendo una diferente estrategia de configuración para los mencionados parámetros: En el primer escenario, denominado WLAN abierta, se supone un entorno abierto como, por ejemplo, un hot-spot. En dicho escenario no se puede confiar en la caracterización del tráfico y los requisitos de servicio que pudiesen proporcionar los usuarios, dado que estos bien pueden declarar unos valores diferentes a los reales para obtener más recursos de la red. Dichos usuarios pueden incluso saturar su acceso inalámbrico (esto es, tener siempre un paquete en proceso de ser transmitido)para obtener recursos adicionales. Para este escenario se propone una configuración que garantice un rendimiento óptimo incluso en presencia de posibles usuarios saturando sus interfaces. Dada la naturaleza abierta de este escenario, adicionalmente se desarrolla un mecanismo que detecta comportamientos no ajustados a una determinada configuración. En el segundo escenario, denominado WLAN cerrada, los usuarios son dignos de confianza. Un ejemplo de dicho escenario puede ser un entorno de oficinas, donde sólo los empleados pueden conectarse a la red. En este caso, tanto la caracterización declarada del tráfico, así como los requisitos de servicio, pueden ser utilizados con objeto de calcular la configuración óptima que proporciona el mejor rendimiento. Nótese que, en este escenario, dado que se dispone de más información, sí que es posible escoger la configuración que mejor atiende los requisitos y características de las fuentes de tráfico. Las principales contribuciones de la presente tesis se resumen a continuación: para el escenario de la WLAN abierta, en primer lugar se analiza el rendimiento de una red saturada,a partir del cual se propone un algoritmo de configuración que optimiza el rendimiento global de la red, tanto en el modo básico como en el modo multirate. También se propone un algoritmo para detectar usuarios maliciosos en la red. Para el caso de la WLAN cerrada, se presentan algoritmos para caracterizar el comportamiento del retardo (valor medio, desviación típica y función de distribución) de la red en condiciones de no saturación. Con base en estos resultados, se presenta un algoritmo que calcula la configuración óptima para un caso de uso de Voz sobre IP. Por último, se describen resultados experimentales centrados también en este caso de uso. ____________________________________________Nowadays Wireless LANs (WLANs) have become a very popular technology for Internet access. The Medium Access Control algorithm used by today’s WLANs is the one defined by the IEEE 802.11 standard. Recently, the IEEE 802 Working Group has approved a new standard called 802.11e that extends the basic 802.11 algorithm with Quality of Service capabilities. This new standard is based on a number of open parameters the configuration of which is yet an unsolved research issue. Although the standard includes some recommendations for the parameters configuration, these recommendations are statically set and do no guarantee optimized performance. This thesis takes up the issue of designing optimal configuration guidelines for 802.11e EDCA. To this aim, in this thesis two different WLAN scenarios are considered, each scenario driving to a different configuration strategy for the setting of the parameters: In the first scenario, which we call open WLAN, an open scenario like e.g. a hot-spot is assumed. In such scenario, the network cannot rely on the traffic characterization and requirements declared by the users, as users could potentially declare different values than the real ones thereby gaining additional resources from the network. Such users could even saturate their wireless access (i.e. by having always packets ready for transmission) in order to obtain extra resources. For this scenario, we propose an optimal configuration that guarantees optimal operation even in the presence of users saturating their channel. Given the untrusted nature of this scenario, mechanisms that detect malicious behaviours are devised. In the second scenario, the closed WLAN, users’behaviour can be trusted. An example of such a scenario could be an office setting in which only trusted employees are allowed to connect to the network. In this case, the source behaviour declared by the users, as well as their Quality of Service requirements, can be used in order to compute an optimal configuration that optimizes the behaviour given this information. Note that with this scenario, given that more information is known, it is possible to choose a parameter configuration that better meets the requirements and characteristics of the sources. The main contributions of this thesis are summarized as follows. For the open WLAN scenario, we first analyze the performance of a saturated WLAN and then, based on this analysis, we propose configuration algorithms that optimize the overall network performance both in the basic and multirate modes.We also propose an algorithm to detect malicious users in this scenario. For the closed WLAN scenario, we present novel algorithms to compute the delay performance (average delay, typical deviation and delay distribution) of a nonsaturated WLAN. Next, based on these analysis, we present an algorithm for computing the optimal configuration for the use case of VoIP traffic. Finally, we present some experimental results for this use case

Optimal configuration of a resource-on-demand 802.11 WLAN with non-zero start-up times

Resource on Demand in 802.11 Wireless LANs is receiving an increasing attention, with its feasibility already proved in practice and some initial analytical models available. However, while these models have assumed that access points (APs) start up in zero time, experimentation has showed that this is hardly the case. In this work, we provide a new model to account for this time in the simple case, of a WLAN formed by two APs where the second AP is switched on/off dynamically to adapt to the traffic load and reduce the overall power consumption, and show that it significantly alters the results when compared to the zero start-up time case, both qualitatively and quantitatively. Our findings show that having a non-zero start up time modifies significantly the trade-offs between power consumption and performance that appears on Resource on Demand solutions. Finally, we propose an algorithm to optimize the energy consumption of the network while guaranteeing a given performance bound.The work of J. Ortín was partly supported by the Centro Universitario de la Defensa through project CUD2013-05, Gobierno de Aragon (research group T98) and the European Social Fund (ESF). The work of P. Serrano and C. Donato was partly supported by the European Commission under grant agreement H2020-ICT-2014-2-671563 (Flex5Gware) and by the Spanish Ministry of Economy and Competitiveness under grant agreement TEC2014-58964-C2-1-R (DRONEXT)

A control theoretic approach for throughput optimization in IEEE 802.11e EDCA WLANs

The MAC layer of the 802.11 standard, based on the CSMA/CA mechanism, specifies a set of parameters to control the aggressiveness of stations when trying to access the channel. However, these parameters are statically set independently of the conditions of the WLAN (e.g. the number of contending stations), leading to poor performance for most scenarios. To overcome this limitation previous work proposes to adapt the value of one of those parameters, namely the CW, based on an estimation of the conditions of the WLAN. However, these approaches suffer from two major drawbacks: i) they require extending the capabilities of standard devices or ii) are based on heuristics. In this paper we propose a control theoretic approach to adapt the CW to the conditions of the WLAN, based on an analytical model of its operation, that is fully compliant with the 802.11e standard. We use a Proportional Integrator controller in order to drive the WLAN to its optimal point of operation and perform a theoretic analysis to determine its configuration. We show by means of an exhaustive performance evaluation that our algorithm maximizes the total throughput of the WLAN and substantially outperforms previous standard-compliant proposals.European Community's Seventh Framework ProgramThe work described in this article has been partially supported by the European Community’s Seventh Framework Programme under the ICT FP7 Integrated Project CARMEN (INFSO-ICT-214994) and by the Spanish Government under the POSEIDON project (TSI2006-12507-C03).Publicad

Experimenting with commodity 802.11 hardware: overview and future directions

The huge adoption of 802.11 technologies has triggered a vast amount of experimentally-driven research works. These works range from performance analysis to protocol enhancements, including the proposal of novel applications and services. Due to the affordability of the technology, this experimental research is typically based on commercial off-the-shelf (COTS) devices, and, given the rate at which 802.11 releases new standards (which are adopted into new, affordable devices), the field is likely to continue to produce results. In this paper, we review and categorise the most prevalent works carried out with 802.11 COTS devices over the past 15 years, to present a timely snapshot of the areas that have attracted the most attention so far, through a taxonomy that distinguishes between performance studies, enhancements, services, and methodology. In this way, we provide a quick overview of the results achieved by the research community that enables prospective authors to identify potential areas of new research, some of which are discussed after the presentation of the survey.This work has been partly supported by the European Community through the CROWD project (FP7-ICT-318115) and by the Madrid Regional Government through the TIGRE5-CM program (S2013/ICE-2919).Publicad

Excavaciones en el conjunto funerario de época hispano-visigoda de la Cabeza (La Cabrera, Madrid)

La presencia visigoda en la actual Comunidad de Madrid está ampliamente constatada a través de las innumerables necrópolis conocidas. El pequeño conjunto funerario de la Cabeza, excavado con carácter de urgencia, ofrece una serie de características que le hacen particularmente interesante: número de tumbas, situación geográfica, ubicación topográfica, tipología del conjunto, etc. Tanto por su arquitectura funeraria como, y sobre todo, por el material hallado, hemos fechado el conjunto dentro del siglo VII