Response threshold models and stochastic learning automata for self-coordination of heterogeneous multi-task distribution in multi-robot systems.

This paper focuses on the general problem of coordinating multiple robots. More specifically, it addresses the self-selection of heterogeneous specialized tasks by autonomous robots. In this paper we focus on a specifically distributed or decentralized approach as we are particularly interested in a decentralized solution where the robots themselves autonomously and in an individual manner, are responsible for selecting a particular task so that all the existing tasks are optimally distributed and executed. In this regard, we have established an experimental scenario to solve the corresponding multi-task distribution problem and we propose a solution using two different approaches by applying Response Threshold Models as well as Learning Automata-based probabilistic algorithms. We have evaluated the robustness of the algorithms, perturbing the number of pending loads to simulate the robot’s error in estimating the real number of pending tasks and also the dynamic generation of loads through time. The paper ends with a critical discussion of experimental results.

Contribution to flexible service coordination in mobile prosumer environments

Este trabajo de Tesis se desarrolla en el marco de los escenarios de ejecución distribuida de servicios móviles y contribuye a la definición y desarrollo del concepto de usuario prosumer. El usuario prosumer se caracteriza por utilizar su teléfono móvil para crear, proveer y ejecutar servicios. Este nuevo modelo de usuario contribuye al avance de la sociedad de la información, ya que el usuario prosumer se transforma de creador de contenidos a creador de servicios (estos últimos formados por contenidos y la lógica para acceder a ellos, procesarlos y representarlos). El objetivo general de este trabajo de Tesis es la provisión de un modelo de creación, distribución y ejecución de servicios para entorno móvil que permita a los usuarios no programadores (usuarios prosumer), pero expertos en un determinado dominio, crear y ejecutar sus propias aplicaciones y servicios. Para ello se definen, desarrollan e implementan metodologías, procesos, algoritmos y mecanismos adaptables a dominios específicos, para construir entornos de ejecución distribuida de servicios móviles para usuarios prosumer. La provisión de herramientas de creación adaptadas a usuarios no expertos es una tendencia actual que está siendo desarrollada en distintos trabajos de investigación. Sin embargo, no se ha propuesto una metodología de desarrollo de servicios que involucre al usuario prosumer en el proceso de diseño, desarrollo, implementación y validación de servicios. Este trabajo de Tesis realiza un estudio de las metodologías y tecnologías más innovadoras relacionadas con la co‐creación y utiliza este análisis para definir y validar una metodología que habilita al usuario para ser el responsable de la creación de servicios finales. Siendo los entornos móviles prosumer (mobile prosumer environments) una particularización de los entornos de ejecución distribuida de servicios móviles, en este trabajo se tesis se investiga en técnicas de adaptación, distribución, coordinación de servicios y acceso a recursos identificando como requisitos las problemáticas de este tipo de entornos y las características de los usuarios que participan en los mismos. Se contribuye a la adaptación de servicios definiendo un modelo de variabilidad que soporte la interdependencia entre las decisiones de personalización de los usuarios, incorporando mecanismos de guiado y detección de errores. La distribución de servicios se implementa utilizando técnicas de descomposición en árbol SPQR, cuantificando el impacto de separar cualquier servicio en distintos dominios. Considerando el plano de comunicaciones para la coordinación en la ejecución de servicios distribuidos hemos identificado varias problemáticas, como las pérdidas de enlace, conexiones, desconexiones y descubrimiento de participantes, que resolvemos utilizando técnicas de diseminación basadas en publicación subscripción y algoritmos Gossip. Para lograr una ejecución flexible de servicios distribuidos en entorno móvil, soportamos la adaptación a cambios en la disponibilidad de los recursos, proporcionando una infraestructura de comunicaciones para el acceso uniforme y eficiente a recursos. Se han realizado validaciones experimentales para evaluar la viabilidad de las soluciones propuestas, definiendo escenarios de aplicación relevantes (el nuevo universo inteligente, prosumerización de servicios en entornos hospitalarios y emergencias en la web de la cosas). Abstract This Thesis work is developed in the framework of distributed execution of mobile services and contributes to the definition and development of the concept of prosumer user. The prosumer user is characterized by using his mobile phone to create, provide and execute services. This new user model contributes to the advancement of the information society, as the prosumer is transformed from producer of content, to producer of services (consisting of content and logic to access them, process them and represent them). The overall goal of this Thesis work is to provide a model for creation, distribution and execution of services for the mobile environment that enables non‐programmers (prosumer users), but experts in a given domain, to create and execute their own applications and services. For this purpose I define, develop and implement methodologies, processes, algorithms and mechanisms, adapted to specific domains, to build distributed environments for the execution of mobile services for prosumer users. The provision of creation tools adapted to non‐expert users is a current trend that is being developed in different research works. However, it has not been proposed a service development methodology involving the prosumer user in the process of design, development, implementation and validation of services. This thesis work studies innovative methodologies and technologies related to the co‐creation and relies on this analysis to define and validate a methodological approach that enables the user to be responsible for creating final services. Being mobile prosumer environments a specific case of environments for distributed execution of mobile services, this Thesis work researches in service adaptation, distribution, coordination and resource access techniques, and identifies as requirements the challenges of such environments and characteristics of the participating users. I contribute to service adaptation by defining a variability model that supports the dependency of user personalization decisions, incorporating guiding and error detection mechanisms. Service distribution is implemented by using decomposition techniques based on SPQR trees, quantifying the impact of separating any service in different domains. Considering the communication level for the coordination of distributed service executions I have identified several problems, such as link losses, connections, disconnections and discovery of participants, which I solve using dissemination techniques based on publish‐subscribe communication models and Gossip algorithms. To achieve a flexible distributed service execution in mobile environments, I support adaptation to changes in the availability of resources, while providing a communication infrastructure for the uniform and efficient access to resources. Experimental validations have been conducted to assess the feasibility of the proposed solutions, defining relevant application scenarios (the new intelligent universe, service prosumerization in hospitals and emergency situations in the web of things).

Contribution to integration and coordination mechanisms for mobile distributed services in publish/subscribe networks

Esta tesis doctoral está enmarcada en dos diferentes pero complementarias áreas de investigación: las redes de Publicación/Subscripción y los servicios móviles distribuidos. Con el paso de los años las redes de Publicación/Subscripción han ido ofreciendo el soporte de comunicaciones desacopladas y ligeras que a su vez, han mejorado la distribución de la información en muchos escenarios de aplicación como lo son la ejecución de servicios distribuidos en entornos fijos. Los servicios móviles distribuidos han de ser desplegados en ambientes inalámbricos en donde los dispositivos móviles deben confiar en las mismas características que las redes de Publicación/Subscripción han estado ofreciendo a sus contrapartes fijos. En este contexto, una de las líneas de investigación pendientes consiste en cómo tomar ventaja de estas características, y cómo avanzar hacia nuevas soluciones no existentes con el fin de mejorar la integración entre los dispositivos fijos y móviles, y la ejecución de los servicios móviles distribuidos. En esta tesis doctoral se pretende avanzar en los mecanismos de integración y coordinación de los servicios móviles distribuidos en el contexto de las redes de Publicación/Subscripción. Los objetivos específicos de esta disertación están enfocados en lograr la integración de los sistemas de Publicación/Suscripción fijos y móviles, y la pro-visión de una versión de red de Publicación/Subscripción específica y uniforme que cuente con mecanismos de coordinación que mejoren la ejecución de los servicios móviles distribuidos. Los resultados de esta tesis doctoral están enmarcados en una versión específica de una red de Publicación/Subscripción que integra brokers fijos y móviles, y permite una coordinación totalmente desacoplada y mejorada entre dispositivos móviles que ejecutan fragmentos de servicios. Las contribuciones específicas son las siguientes: una nueva arquitectura de broker móvil que he llamado Rendezvous Mobile broker, un modelo abstracto de servicios móviles distribuidos coordinados sobre una red de Publicación/Subscripción, mejoras en los mecanismos de enrutamiento epidémicos para diseminar eventos de control producidos por fragmentos de servicios, una solución para soportar servicios altamente fragmentados y geográficamente dispersos, y finalmente una solución de interconexión entre dos dominios de red basados en Publicación/Subscripción: una red basada en el protocolo PubSubHubbub y otro en una red basada en el Publish/Subscribe Internet Routing Paradigm (PSIRP). Los experimentos llevados a cabo confirman que la versión específica de red de Pu-blicación/Subscripción propuesta incrementa el rendimiento de la red en términos de tiempo de espera entre nodos finales, permite una coordinación de los servicios móviles distribuidos más resistente a interrupciones y un mejor uso de los recursos de red, y finalmente logra exitosamente, con variaciones mínimas en el rendimiento de las comunicaciones, la interconexión entre estos dominios de Publicación/Subscripción diferentes. ABSTRACT This dissertation is made up of two different but complementary research areas: Publish/Subscribe networks and mobile distributed services. Over the years, Publish/Subscribe networks have been offering the lightweight and decoupled communication characteristics to improve the information distribution in several application domains such as the execution of distributed services. Mobile distributed services are set to be deployed in wireless environments where mobile devices must rely on the same features Publish/Subscribe networks can offer; so one of the pending research directions consists of how to take advantage of these features and further advance to-wards new un-existing solutions that enhance the integration between mobile and fixed systems and the execution of mobile distributed services. This dissertation seeks to advance the integration and coordination mechanisms of mobile distributed services in the context of Publish/Subscribe networks. The specific objectives aim to enable the integration of mobile and fixed Publish/Subscribe systems and provide a uniform and specific version of a Publish/Subscribe network with new coordination mechanisms that improve the execution of mobile distributed services. The results of this dissertation are enclosed in one specific version of a Publish/Subscribe network that integrates mobile and fixed brokers and coordinates the execution of mobile distributed services. These specific contributions are: a new architecture of a mobile broker I called Rendezvous Mobile Broker, an abstract model for coordinating mobile distributed services executions using a Publish/Subscribe net-work, new gossip routing solutions to disseminate events of services, mechanisms to support highly partitioned and geographically dispersed services and finally, an inter-networking solution between two Publish/Subscribe domains: a PubSubHubbub-based network and the Publish/Subscribe Internet Routing Paradigm (PSIRP)-based network. The experimental efforts confirm that the specific version of the Publish/Subscribe proposed in this dissertation improves the performance of the overall network in terms of end-to-end delay, enables a more resilience execution of mobile distributed services, a better usage of the existing network resources, and finally successfully achieves, with minor variations in the network performance, the internetworking between two different Publish/Subscribe domains.

The Role of Multilateral Coordination in Transport Policy: The Case of the Maghreb Countries

El WCTR es un congreso de reconocido prestigio internacional en el ámbito de la investigación del transporte y aunque las actas publicadas están en formato digital y sin ISSN ni ISBN, lo consideramos lo suficientemente importante como para que se considere en los indicadores. This paper aims at describing how multilateral cooperation policies are influencing national transport policies in developing countries. It considers the evolution of national transport policies and institutional frameworks in Algeria, Morocco and Tunisia in the last 10 years, and analyses the influence that EU cooperation programmes (particularly those within the Euromed programme initiative) and international coordination activities have played in the evolution towards efficient, sustainable transport systems in those countries. Notwithstanding the significant socioeconomic, political and institutional differences among the three countries, three major traits are common to the transport policy framework in all cases: a focus on megaprojects; substitution of traditional ministerial services by ad hoc public agencies to develop those megaprojects, and progressive involvement of international private players for the operation (and eventually the design and construction) of new projects, focusing on know-how transfer rather than investment needs. The hypotheses is that these similarities are largely due to the influence of the international cooperation promoted by the European Union since the mid- 1990s. The new decision making situation is characterized by the involvement of two new relevant stakeholders, the EU and a limited number of global transport operators. The hierarchical governance model evolves towards more complex structures, which explain the three common traits mentioned above. International coordination has been crucial for developing national transport visions, which are coherent with a regional, transnational system.

Coordination mechanisms and software in industrial networks - a literature review

This paper groups recent supply chain management research focused on organizational design and its software support. The classification encompasses criteria related to research methodology and content. Empirical studies from management science focus on network types and organizational fit. Novel planning algorithms and innovative coordination schemes are developed mostly in the field of operations research in order to propose new software features. Operations and production management realize cost-benefit analysis of IT software implementations. The success of software solutions for network coordination depends strongly on the fit of three dimensions: network configuration, coordination scheme and software functionality. This paper concludes with proposals for future research on unaddressed issues within and among the identified research streams.

Multi-UAV Coordination and Control Interface

The interest in missions with multiple Unmanned Aerial Vehicles (UAVs) has increased significantly in last years. These missions take advantage of the use of fleets instead of single UAVs to ensure the success, reduce the duration or increase the goals of the mission. In addition, they allow performing tasks that require multiple agents and certain coordination (e.g. surveillance of large areas or transport of heavy loads). Nevertheless, these missions suppose a challenge in terms of control and monitoring. In fact, the workload of the operators rises with the utilization of multiple UAVs and payloads, since they have to analyze more information, make more decisions and generate more commands during the mission. This work addresses the operator workload problem in multi-UAV missions by reducing and selecting the information. Two approaches are considered: a first one that selects the information according to the mission state, and a second one that selects it according to the operator preferences. The result is an interface that is able to control the amount of information and show what is relevant for mission and operator at the time.

Energetic considerations of ciliary beating and the advantage of metachronal coordination

The internal mechanism of cilia is among the most ancient biological motors on an evolutionary scale. It produces beat patterns that consist of two phases: during the effective stroke, the cilium moves approximately as a straight rod, and during the recovery stroke, it rolls close to the surface in a tangential motion. It is commonly agreed that these two phases are designed for efficient functioning: the effective stroke encounters strong viscous resistance and generates thrust, whereas the recovery stroke returns the cilium to starting position while avoiding viscous resistance. Metachronal coordination between cilia, which occurs when many of them beat close to each other, is believed to be an autonomous result of the hydrodynamical interactions in the system. Qualitatively, metachronism is perceived as a way for reducing the energy expenditure required for beating. This paper presents a quantitative study of the energy expenditure of beating cilia, and of the energetic significance of metachronism. We develop a method for computing the work done by model cilia that beat in a viscous fluid. We demonstrate that for a single cilium, beating in water, the mechanical work done during the effective stroke is approximately five times the amount of work done during the recovery stroke. Investigation of multicilia configurations shows that having neighboring cilia beat metachronally is energetically advantageous and perhaps even crucial for multiciliary functioning. Finally, the model is used to approximate the number of dynein arm attachments that are likely to occur during the effective and recovery strokes of a beat cycle, predicting that almost all of the available dynein arms should participate in generating the motion.

Design and characterization of α-melanotropin peptide analogs cyclized through rhenium and technetium metal coordination

α-Melanocyte stimulating hormone (α-MSH) analogs, cyclized through site-specific rhenium (Re) and technetium (Tc) metal coordination, were structurally characterized and analyzed for their abilities to bind α-MSH receptors present on melanoma cells and in tumor-bearing mice. Results from receptor-binding assays conducted with B16 F1 murine melanoma cells indicated that receptor-binding affinity was reduced to approximately 1% of its original levels after Re incorporation into the cyclic Cys4,10, d-Phe7–α-MSH4-13 analog. Structural analysis of the Re–peptide complex showed that the disulfide bond of the original peptide was replaced by thiolate–metal–thiolate cyclization. A comparison of the metal-bound and metal-free structures indicated that metal complexation dramatically altered the structure of the receptor-binding core sequence. Redesign of the metal binding site resulted in a second-generation Re–peptide complex (ReCCMSH) that displayed a receptor-binding affinity of 2.9 nM, 25-fold higher than the initial Re–α-MSH analog. Characterization of the second-generation Re–peptide complex indicated that the peptide was still cyclized through Re coordination, but the structure of the receptor-binding sequence was no longer constrained. The corresponding 99mTc- and 188ReCCMSH complexes were synthesized and shown to be stable in phosphate-buffered saline and to challenges from diethylenetriaminepentaacetic acid (DTPA) and free cysteine. In vivo, the 99mTcCCMSH complex exhibited significant tumor uptake and retention and was effective in imaging melanoma in a murine-tumor model system. Cyclization of α-MSH analogs via 99mTc and 188Re yields chemically stable and biologically active molecules with potential melanoma-imaging and therapeutic properties.

Kinesin’s processivity results from mechanical and chemical coordination between the ATP hydrolysis cycles of the two motor domains

Kinesin is a processive motor protein: A single molecule can walk continuously along a microtubule for several micrometers, taking hundreds of 8-nm steps without dissociating. To elucidate the biochemical and structural basis for processivity, we have engineered a heterodimeric one-headed kinesin and compared its biochemical properties to those of the wild-type two-headed molecule. Our construct retains the functionally important neck and tail domains and supports motility in high-density microtubule gliding assays, though it fails to move at the single-molecule level. We find that the ATPase rate of one-headed kinesin is 3–6 s−1 and that detachment from the microtubule occurs at a similar rate (3 s−1). This establishes that one-headed kinesin usually detaches once per ATP hydrolysis cycle. Furthermore, we identify the rate-limiting step in the one-headed hydrolysis cycle as detachment from the microtubule in the ADP⋅Pi state. Because the ATPase and detachment rates are roughly an order of magnitude lower than the corresponding rates for two-headed kinesin, the detachment of one head in the homodimer (in the ADP⋅Pi state) must be accelerated by the other head. We hypothesize that this results from internal strain generated when the second head binds. This idea accords with a hand-over-hand model for processivity in which the release of the trailing head is contingent on the binding of the forward head. These new results, together with previously published ones, allow us to propose a pathway that defines the chemical and mechanical cycle for two-headed kinesin.

Selenium redox biochemistry of zinc–sulfur coordination sites in proteins and enzymes

Selenium has been increasingly recognized as an essential element in biology and medicine. Its biochemistry resembles that of sulfur, yet differs from it by virtue of both redox potentials and stabilities of its oxidation states. Selenium can substitute for the more ubiquitous sulfur of cysteine and as such plays an important role in more than a dozen selenoproteins. We have chosen to examine zinc–sulfur centers as possible targets of selenium redox biochemistry. Selenium compounds release zinc from zinc/thiolate-coordination environments, thereby affecting the cellular thiol redox state and the distribution of zinc and likely of other metal ions. Aromatic selenium compounds are excellent spectroscopic probes of the otherwise relatively unstable functional selenium groups. Zinc-coordinated thiolates, e.g., metallothionein (MT), and uncoordinated thiolates, e.g., glutathione, react with benzeneseleninic acid (oxidation state +2), benzeneselenenyl chloride (oxidation state 0) and selenocystamine (oxidation state −1). Benzeneseleninic acid and benzeneselenenyl chloride react very rapidly with MT and titrate substoichiometrically and with a 1:1 stoichiometry, respectively. Selenium compounds also catalyze the release of zinc from MT in peroxidation and thiol/disulfide-interchange reactions. The selenoenzyme glutathione peroxidase catalytically oxidizes MT and releases zinc in the presence of t-butyl hydroperoxide, suggesting that this type of redox chemistry may be employed in biology for the control of metal metabolism. Moreover, selenium compounds are likely targets for zinc/thiolate coordination centers in vivo, because the reactions are only partially suppressed by excess glutathione. This specificity and the potential to undergo catalytic reactions at low concentrations suggests that zinc release is a significant aspect of the therapeutic antioxidant actions of selenium compounds in antiinflammatory and anticarcinogenic agents.

Impaired motor coordination and persistent multiple climbing fiber innervation of cerebellar Purkinje cells in mice lacking Gαq

Mice lacking the α-subunit of the heterotrimeric guanine nucleotide binding protein Gq (Gαq) are viable but suffer from ataxia with typical signs of motor discoordination. The anatomy of the cerebellum is not overtly disturbed, and excitatory synaptic transmission from parallel fibers to cerebellar Purkinje cells (PCs) and from climbing fibers (CFs) to PCs is functional. However, about 40% of adult Gαq mutant PCs remain multiply innervated by CFs because of a defect in regression of supernumerary CFs in the third postnatal week. Evidence is provided suggesting that Gαq is part of a signaling pathway that is involved in the elimination of multiple CF innervation during this period.

Stimulation of human 8-oxoguanine-DNA glycosylase by AP-endonuclease: potential coordination of the initial steps in base excision repair

8-Oxoguanine-DNA glycosylase 1 (OGG1), with intrinsic AP lyase activity, is the major enzyme for repairing 7,8-dihydro-8-oxoguanine (8-oxoG), a critical mutagenic DNA lesion induced by reactive oxygen species. Human OGG1 excised the damaged base from an 8-oxoG·C-containing duplex oligo with a very low apparent kcat of 0.1 min–1 at 37°C and cleaved abasic (AP) sites at half the rate, thus leaving abasic sites as the major product. Excision of 8-oxoG by OGG1 alone did not follow Michaelis–Menten kinetics. However, in the presence of a comparable amount of human AP endonuclease (APE1) the specific activity of OGG1 was increased ∼5-fold and Michaelis–Menten kinetics were observed. Inactive APE1, at a higher molar ratio, and a bacterial APE (Nfo) similarly enhanced OGG1 activity. The affinity of OGG1 for its product AP·C pair (Kd ∼ 2.8 nM) was substantially higher than for its substrate 8-oxoG·C pair (Kd ∼ 23.4 nM) and the affinity for its final β-elimination product was much lower (Kd ∼ 233 nM). These data, as well as single burst kinetics studies, indicate that the enzyme remains tightly bound to its AP product following base excision and that APE1 prevents its reassociation with its product, thus enhancing OGG1 turnover. These results suggest coordinated functions of OGG1 and APE1, and possibly other enzymes, in the DNA base excision repair pathway.

How amoeboids self-organize into a fruiting body: Multicellular coordination in Dictyostelium discoideum

When individual amoebae of the cellular slime mold Dictyostelium discoideum are starving, they aggregate to form a multicellular migrating slug, which moves toward a region suitable for culmination. The culmination of the morphogenesis involves complex cell movements that transform a mound of cells into a globule of spores on a slender stalk. The movement has been likened to a “reverse fountain,” whereby prestalk cells in the upper part form a stalk that moves downwards and anchors to the substratum, while prespore cells in the lower part move upwards to form the spore head. So far, however, no satisfactory explanation has been produced for this process. Using a computer simulation that we developed, we now demonstrate that the processes that are essential during the earlier stages of the morphogenesis are in fact sufficient to produce the dynamics of the culmination stage. These processes are cAMP signaling, differential adhesion, cell differentiation, and production of extracellular matrix. Our model clarifies the processes that generate the observed cell movements. More specifically, we show that periodic upward movements, caused by chemotactic motion, are essential for successful culmination, because the pressure waves they induce squeeze the stalk downwards through the cell mass. The mechanisms revealed by our model have a number of self-organizing and self-correcting properties and can account for many previously unconnected and unexplained experimental observations.