834 resultados para IT Security, Internet, Personal Firewall, Security Mechanism, Security System, Security Threat, Security Usability, Security Vulnerability
Resumo:
Los dispositivos mviles modernos disponen cada vez de ms funcionalidad debido al rpido avance de las tecnologas de las comunicaciones y computaciones mviles. Sin embargo, la capacidad de la batera no ha experimentado un aumento equivalente. Por ello, la experiencia de usuario en los sistemas mviles modernos se ve muy afectada por la vida de la batera, que es un factor inestable de difcil de control. Para abordar este problema, investigaciones anteriores han propuesto un esquema de gestion del consumo (PM) centrada en la energa y que proporciona una garanta sobre la vida operativa de la batera mediante la gestin de la energa como un recurso de primera clase en el sistema. Como el planificador juega un papel fundamental en la administracin del consumo de energa y en la garanta del rendimiento de las aplicaciones, esta tesis explora la optimizacin de la experiencia de usuario para sistemas mviles con energa limitada desde la perspectiva de un planificador que tiene en cuenta el consumo de energa en un contexto en el que sta es un recurso de primera clase. En esta tesis se analiza en primer lugar los factores que contribuyen de forma general a la experiencia de usuario en un sistema mvil. Despus se determinan los requisitos esenciales que afectan a la experiencia de usuario en la planificacin centrada en el consumo de energa, que son el reparto proporcional de la potencia, el cumplimiento de las restricciones temporales, y cuando sea necesario, el compromiso entre la cuota de potencia y las restricciones temporales. Para cumplir con los requisitos, el algoritmo clsico de fair queueing y su modelo de referencia se extienden desde los dominios de las comunicaciones y ancho de banda de CPU hacia el dominio de la energa, y en base a sto, se propone el algoritmo energy-based fair queueing (EFQ) para proporcionar una planificacin basada en la energa. El algoritmo EFQ est diseado para compartir la potencia consumida entre las tareas mediante su planificacin en funcin de la energa consumida y de la cuota reservada. La cuota de consumo de cada tarea con restricciones temporales est protegida frente a diversos cambios que puedan ocurrir en el sistema. Adems, para dar mejor soporte a las tareas en tiempo real y multimedia, se propone un mecanismo para combinar con el algoritmo EFQ para dar preferencia en la planificacin durante breves intervalos de tiempo a las tareas ms urgentes con restricciones temporales.Las propiedades del algoritmo EFQ se evaluan a travs del modelado de alto nivel y la simulacin. Los resultados de las simulaciones indican que los requisitos esenciales de la planificacin centrada en la energa pueden lograrse. El algoritmo EFQ se implementa ms tarde en el kernel de Linux. Para evaluar las propiedades del planificador EFQ basado en Linux, se desarroll un banco de pruebas experimental basado en una sitema empotrado, un programa de banco de pruebas multihilo, y un conjunto de pruebas de cdigo abierto. A travs de experimentos especficamente diseados, esta tesis verifica primero las propiedades de EFQ en la gestin de la cuota de consumo de potencia y la planificacin en tiempo real y, a continuacin, explora los beneficios potenciales de emplear la planificacin EFQ en la optimizacin de la experiencia de usuario para sistemas mviles con energa limitada. Los resultados experimentales sobre la gestin de la cuota de energa muestran que EFQ es ms eficaz que el planificador de Linux-CFS en la gestin de energa, logrando un reparto proporcional de la energa del sistema independientemente de en qu dispositivo se consume la energa. Los resultados experimentales en la planificacin en tiempo real demuestran que EFQ puede lograr de forma eficaz, flexible y robusta el cumplimiento de las restricciones temporales aunque se d el caso de aumento del el nmero de tareas o del error en la estimacin de energa. Por ltimo, un anlisis comparativo de los resultados experimentales sobre la optimizacin de la experiencia del usuario demuestra que, primero, EFQ es ms eficaz y flexible que los algoritmos tradicionales de planificacin del procesador, como el que se encuentra por defecto en el planificador de Linux y, segundo, que proporciona la posibilidad de optimizar y preservar la experiencia de usuario para los sistemas mviles con energa limitada. Abstract Modern mobiledevices have been becoming increasingly powerful in functionality and entertainment as the next-generation mobile computing and communication technologies are rapidly advanced. However, the battery capacity has not experienced anequivalent increase. The user experience of modern mobile systems is therefore greatly affected by the battery lifetime,which is an unstable factor that is hard to control. To address this problem, previous works proposed energy-centric power management (PM) schemes to provide strong guarantee on the battery lifetime by globally managing energy as the first-class resource in the system. As the processor scheduler plays a pivotal role in power management and application performance guarantee, this thesis explores the user experience optimization of energy-limited mobile systemsfrom the perspective of energy-centric processor scheduling in an energy-centric context. This thesis first analyzes the general contributing factors of the mobile system user experience.Then itdetermines the essential requirements on the energy-centric processor scheduling for user experience optimization, which are proportional power sharing, time-constraint compliance, and when necessary, a tradeoff between the power share and the time-constraint compliance. To meet the requirements, the classical fair queuing algorithm and its reference model are extended from the network and CPU bandwidth sharing domain to the energy sharing domain, and based on that, the energy-based fair queuing (EFQ) algorithm is proposed for performing energy-centric processor scheduling. The EFQ algorithm is designed to provide proportional power shares to tasks by scheduling the tasks based on their energy consumption and weights. The power share of each time-sensitive task is protected upon the change of the scheduling environment to guarantee a stable performance, and any instantaneous power share that is overly allocated to one time-sensitive task can be fairly re-allocated to the other tasks. In addition, to better support real-time and multimedia scheduling, certain real-time friendly mechanism is combined into the EFQ algorithm to give time-limited scheduling preference to the time-sensitive tasks. Through high-level modelling and simulation, the properties of the EFQ algorithm are evaluated. The simulation results indicate that the essential requirements of energy-centric processor scheduling can be achieved. The EFQ algorithm is later implemented in the Linux kernel. To assess the properties of the Linux-based EFQ scheduler, an experimental test-bench based on an embedded platform, a multithreading test-bench program, and an open-source benchmark suite is developed. Through specifically-designed experiments, this thesis first verifies the properties of EFQ in power share management and real-time scheduling, and then, explores the potential benefits of employing EFQ scheduling in the user experience optimization for energy-limited mobile systems. Experimental results on power share management show that EFQ is more effective than the Linux-CFS scheduler in managing power shares and it can achieve a proportional sharing of the system power regardless of on which device the energy is spent. Experimental results on real-time scheduling demonstrate that EFQ can achieve effective, flexible and robust time-constraint compliance upon the increase of energy estimation error and task number. Finally, a comparative analysis of the experimental results on user experience optimization demonstrates that EFQ is more effective and flexible than traditional processor scheduling algorithms, such as those of the default Linux scheduler, in optimizing and preserving the user experience of energy-limited mobile systems.
Resumo:
La Tesis decodifica una seleccin de veinte proyectos representativos de Sejima-SANAA, desde su primer proyecto construido, la Casa Platform I, 1987, hasta el Centro Rolex, 2010, ao en que Sejima y Nishizawa SANAA- reciben el Premio Pritzker. De los veinte proyectos once son de Sejima: Casa Platform I, Casa Platform II, Residencia de Mujeres, Casa N, Pachinco Parlor I, Villa en el Bosque, Comisara en Chofu, Casa Y, Apartamentos en Gifu, Edificio de equipamientos en la Expo Tokio 96, Pachinko Parlor III; y nueve de SANAA: edificio Multimedia en Oogaki, estudio de viviendas metropolitanas,Park Caf en Koga, De Kunstlinie en Almere, Museo de Kanazawa, Pabelln de Toledo, Escuela de Zollverein, Casa Flor y Centro Rolex. La decodificacin lee la obra de Sejima-SANAA a la inversa para reconstruir, en un ejercicio de simulacin ficticia, una versin verosmil y coherente de los que podran haber sido sus procesos proyectuales; podran, porque los verdaderos son imposibles de dilucidar. Los que se proponen se pretenden exclusivamente verosmiles y plausibles. Con ello se pretende contribuir al entendimiento y comprensin de la arquitectura de Sejima-SANAA y, tangencialmente y en menor medida, a la teora sobre el ejercicio proyectual arquitectnico. La decodificacin se centra en dos aspectos concretos: la forma arquitectnica y el papel proyectual de la estructura portante. Ambas decodificaciones se extienden inevitablemente a otros aspectos relacionados, como, por ejemplo, la naturaleza del espacio arquitectnico. El procedimiento de investigacin parti de una descripcin objetiva y pormenorizada de los significantes formales y estructurales de cada proyecto desde su propia configuracin fsica y geomtrica. Esa descripcin objetiva, llevada al lmite, permiti que afloraran estructuras conceptuales y lgicas subyacentes de cada proyecto. Unida a interpretacin crtica, mediante su relacin y confrontacin con otras arquitecturas y otros modos de hacer conocidos- permiti trazar la reconstitucin ficticia que persigue la decodificacin. Ese trabajo se materializ en veinte ensayos crticos y se acompa de un conjunto de otros textos sobre temas sugeridos o reclamados por el proceso de investigacin. El conjunto de todos esos textos constituye el material de trabajo de la tesis. A partir de ah, con una visin de conjunto, la tesis identifica una trayectoria de estrategias formales y una trayectoria de estrategias proyectuales relacionadas con lo portante. Juntas conforman el grueso de la tesis que se expone en los cuatro captulos centrales. Los precede un captulo introductorio que expone el recorrido biogrfico de K. Sejima y la trayectoria profesional de Sejima-SANAA; y los siguen de unos textos transversales sobre forma, lugar y espacio. La tesis termina con una sntesis de sus conclusiones. Las estrategias formales se exponen en tres captulos. El primero, Primeras estrategias formales agrupa proyectos de la primera etapa de Sejima. El segundo captulo est dedicado enteramente al proyecto de los apartamentos en Gifu, 1994-98, que segn esta tesis, supuso un importante punto de inflexin en la trayectoria de Sejima; tanto el tercer captulo lleva por nombre Estrategias formales despus de Gifu y recoge los proyectos que le siguieron. Las Primeras estrategias formales, varias y balbucientes, se mueven en general en torno a dos modos o procedimientos de composicin, bien conocidos: por partes y sistemtico. ste ltima inicia en la trayectoria de SANAA un aspecto que va a ser relevante de aqu en adelante: entender el proyecto como propuesta genrica en la que, ms all de su realidad especfica y tangible, subyace una lgica, en cada proyecto la suya, extrapolable a otros lugares, otras dimensiones, incluso otros programas: cada proyecto podra dar lugar a otros proyectos de la misma familia. La composicin sistemtica incluye, entre otros, la Casa Platform II, basada en la definicin de un elemento constructivo, y la formulacin de unas leyes de repeticin y de posibles modos de agrupacin. Incluye tambin la Residencia de Mujeres Saishunkan Seiyaku- proyecto que lanz a Sejima a la fama internacional-, que tambin sera un sistema, pero distinto: basado en la repeticin regular de una serie de elementos a lo largo de una directriz generando un hipottico contenedor infinito del que el proyecto sera tan solo un fragmento. La estrategia formal del edificio de Gifu ahondara en la voluntad genrica del proyecto, adoptando la lgica de un juego. El proyecto sera una partida del juego, pero no la nica posible, podran jugarse otras. Esta hiptesis del juego est verificada en El Juego de Gifu que - tras formular el juego identificando sus elementos (tablero y fichas), reglas y procedimientos- juega una partida: la que habra dado lugar al edificio proyectado por Sejima. Gifu extiende el concepto de repetir un elemento constructivo a la de repetir un patrn espacial, lo que conlleva: la desvinculacin entre forma y funcin; y un nuevo concepto de flexibilidad, que deja de referirse al uso flexible del edificio construido para pertenecer al momento proyectual en que se asignan funciones especficas a los patrones espaciales. Esta tesis propone que esa asignacin de funciones sera uno de los ltimos eslabones del proceso proyectual, algo opuesto a la premisa moderna de la forma sigue a la funcin. Las estrategias formales Despus de Gifu tienen tambin lgicas de juego, pero cada estrategia responde a un juego distinto, como dejan entrever sus nombres: Tableros de Juego, que con distintos grados de madurez estara presente en varios proyectos; Elementos de Catlogo en el Museo de Kanazawa; Forma apriorstica, en la Casa Flor y Repeticin de una situacin topolgica, en el Centro Rolex. Todas esas estrategias, o juegos, mantienen aspectos comunes relativos a la forma arquitectnica, precisamente los aspectos Gifu: la repeticin aplicada al patrn espacial, y lo que conlleva: desvinculacin entre forma y funcin y la nueva acepcin de flexibilidad. Tableros de Juego consiste en configurar cada sistema de proyecto (estructura, cerramientos, particiones y mobiliario) eligiendo elementos ofrecidos por una geometra de base, en cada proyecto la suya, en general reticular: intersecciones, lneas, mdulos. Cada sistema se configura, en principio, sin relacin de subordinacin con cualquiera de los dems; cuando esa subordinacin es ineludible, el juego determina que el sistema portante no puede materializar el orden geomtrico de base, lo que se traduce en que no ejerce el papel dominante. Por lo tanto, Tableros de Juego transgrede la lgica de la planta libre moderna: la estructura ni refleja ni revela el orden de base y los sistemas no respetan las relaciones de subordinacin jerrquica y encadenada que aquella determinaba. Esta estrategia de Tableros de juego deriva en soluciones y proyectos formales muy distintos: los proyectos de Oogaki y Park Caf, que presentaran Tableros de Juego incipientes; De Kunstlinie en Almere y la Escuela de Zollverein, que presentaran una consolidacin de esta estrategia; y el Pabelln de Vidrio de Toledo que resultara de la subversin de la estrategia. Este ltimo proyecto, adems, lleva el concepto de repeticin ms all del elemento constructivo y del patrn espacial (que en este caso tiene forma de burbuja) parar acabar afectando a la propia experiencia del espectador, que est donde est, siempre tiene la sensacin de estar en el mismo sitio. Esta tesis denomina a ese espacio repetitivo como espacio mantra. La estrategia Elementos de Catlogo se ilustra con el Museo de Kanazawa. Su lgica parte de la definicin de una serie de elementos, muy pocos, y se basa en el ingente nmero de posibles combinaciones entre s. Gifu habra anunciado el catalogo de elementos en la caracterizacin de sus patrones espaciales. La estrategia Forma Apriorstica se ilustra con la Casa Flor. La decisin sobre el tipo de forma -en este caso la de una ameba- estara al principio del proceso proyectual, lo que no quiere decir que sea una forma arbitraria: la forma de la ameba lleva implcita la repeticin de un patrn espacial (el seudpodo) y una apoteosis del concepto de repeticin que, alcanzando la experiencia espacial, da lugar a un espacio repetitivo o mantra. El Espacio Mantra es uno de los leitmotivs, que se emplean como argumento en la ltima estrategia formal que la Tesis decodifica: el Centro Rolex. Con respecto a la estructura portante, la tesis identifica y traza una trayectoria de cinco estrategias proyectuales: preeminencia, ocultacin, disolucin, desaparicin y desvirtuacin. --Ocultacin, reduce el papel dominante de la estructura. Al principio es una ocultacin literal, casi un tapado de los elementos estructurales, como en Gifu; luego se hace ms sofisticada, como la ocultacin por camuflaje o la paradjica ocultacin por multiplicacin de Park Caf. --La disolucin merma la condicin dominante de la estructura que en lugar de configurarse como sistema unitario u homogneo se fragmenta en varios subsistemas. --La desaparicin se refiere a estructuras que desaparecen como sistemas propios y autnomos, a proyectos en los que la funcin portante es desempeada por otros sistemas como el de las particiones. La desaparicin culmina con la Casa Flor, cuyo permetro ejerce la funcin portante y adems es transparente, est desmaterializado: la estructura se ha hecho invisible, ha desaparecido. --La desvirtuacin se refiere a estructuras que s se presentan como sistemas propios y autnomos, pero dejan de tener un papel preeminente por cuanto no materializan el orden de base: esta estrategia es correlativa a la estrategia formal Tableros de juego. Las conclusiones de la tesis estn en la propia organizacin de la tesis: la identificacin de las estrategias. An as, y como eplogos, se exponen seis. Las dos primeras subrayan el hilo conductor del trabajo realizado, que radica en la cualidad genrica de las estrategias proyectuales en Sejima-SANAA. Las cuatro siguientes dilucidan hasta qu punto hay, en sus proyectos, rasgos o significantes formales y/o estructurales que sean a su vez seales caractersticas del panorama arquitectnico contemporneo; y plantean la pregunta estrella: hay algunos que, apuntando ms lejos, supongan aportaciones originales? --Como aportaciones originales la tesis destaca: la identificacin entre el ideal genrico y proyecto concreto; y la propuesta de un espacio nuevo, hbrido, una suerte de estadio intermedio entre el espacio subdividido y compartimentado de la tradicin y el continuo moderno. --Como sntomas de contemporaneidad se destacan: respecto de la forma, la traslacin de la especificidad formal de la parte al conjunto; y respecto de la estructura, la tendencia contempornea a hacer estructuras cada vez ms ligeras y livianas, que tienden a lo evanescente. sta ltima, la tendencia al evanescencia estructural, podra tener la condicin de aportacin original, no en vano la desaparicin de la estructura lleva la evanescencia hacia sus ltimas consecuencias, y en el caso de estructuras con presencia fsica, hace que dejen de ser el sistema ordenador orquestador del proceso proyectual. ABSTRACT The Thesis decodes a selection of twenty representative Sejima-SANAA projects, from the first one built, the Platform I House in 1987, to the Rolex Center in 2010, year in which Sejima and Nishizawa SANAA- received the Pritzker Prize. Eleven projects are from Sejima: Platform I, Platform II, Saishunkan Seiyaku Womens Dormitory, N- House, Pachinco Parlor I, Villa in the Forest, Policy Box at Chofu Station, Y-House, Gifu Kitigata Apartment, World City Expo 96 Facilities Building, Pachinko Parlor III; and nine from SANAA: Multimedia Workshop in Ogaki, Metropolitan Housing Studies, Park Caf in Koga, De Kunstlinie in Almere, Kanazawa Museum, Glass Pavilion at the Toledo Museum of Art, Zollverein School, Flower House and the Rolex Center. This decoding reads the Sejima-SANAAs projects inversely aiming to reconstruct', in a fictitious simulation exercise, a likely and coherent version of what her/their projectual processes could have been; could, because the true ones are impossible to explain. The ones proposed here pretend only to be likely and reasonable. By so doing the Thesis tries to contribute to the understanding and comprehension of Sejima-SANAA architecture and, tangentially and to a lesser extent, to the theory of architectural projects exercise. Decoding centers in two specific aspects: architectural form, and projectual role of the load bearing structure. Both decodes inevitably extend to other related aspects such as, for example, the nature of space. The research procedure begun by carrying out an objective and detailed description of the formal and structural signifiers of each project; looking at them from their physical and geometric configuration. Taken to the limit, the objective descriptions allowed the conceptual structures and underlying logics of each project to arise. Together with critical interpretations, which related and confronted them with other architectures and well-known projectual working ways, it became possible to outline and trace the intended fictitious reconstruction decodes. The descriptive analytical work materialized in twenty critical essays, and was accompanied by a set of other essays on subjects suggested or demanded by the research process. Together, all those texts were the material basis on which thesis work was built. Looking at the whole and taking it from there, the thesis identifies two related projectual trajectories: a trajectory of formal strategies and a trajectory of strategies having to do with structural systems and components. Both, together, constitute the bulk of the thesis, as presented in the four central chapters. Preceding them there is an introductory chapter outlining the biographical path of Kazuyo Sejima and the professional trajectory of Sejima-SANAA. And following them there is another one containing transversal texts on form, place and space. The thesis ends with a synthesis on conclusions. The formal strategies are displayed in three chapters. The first one, `Early formal strategies' groups the first phase projects by Sejima. The second one, Formal strategies of Gifus paradigm, is entirely dedicated to the Gifu apartments project, 1994-98, which according to this thesis meant an important inflexion point in Sejimas trajectory; so much so that the third chapter is named `Formal strategies after Gifu' and gathers the selected projects that followed it. The Early formal strategies', diverse and tentative, move in general around two well-known projectual composition methods composition by parts, and systematic composition. This last one systematic composition- begins and leads in SANAAs trajectory an aspect which will remain relevant from here on: the understanding of the project as if it were an specific instance of a generic proposal in which -below and beyond the project tangible reality- there lays a logic that could be applicable at other places, for other dimensions, even with other programs; from each project, other projects of the same family could rise. The set of projects using this systematic composition method include, among others, the Platform II House, based on the definition of a constructive element and of rules having to do with its replicas and their possible groupings. It also includes the Saishunkan Seiyaku Women Residence -project that launched Sejima to international fame- that could also be seen as a system, but of a different kind: a system based on the regular repetition of a series of elements along a directive line, thus generating a hypothetical infinite container of which the project would be only a fragment. The formal strategy of the Gifu apartments building would push further towards the generic project concept, adopting the logic of a game. The project would be a bout, a round, one play, but not the only possible one; others could be played. The thesis confirms this game hypothesis -after having formulated `The Game of Gifu' and identified its elements (board, chips, rules and procedures)- playing the one play from which the building as projected by Sejima would have raised. Gifu extends the concept of repeating a constructive element to that of repeating a space pattern element, and to what it implies: the decoupling of form and function, leading to a new concept of flexibility that no longer refers to the flexible use of the constructed building but to the projectual moment at which the specific functions are assigned to the space patterns. This thesis proposes that this allocation of functions would be one of the last steps in projectual process, quite opposite from the modern premise: form follows function. The Formal strategies after Gifu do also have a game logic; but, as their names reveal, each strategy responds to a different game: Game Boards, present with different maturity levels in several projects; Elements from a Catalogue, in the Kanazawa Museum; Aprioristic Form, in the Flower House; and Repetition of a topologic situation', in the Rolex Center. All of these strategies, or games, maintain common aspects having to do with architectural form; aspects that were already present, precisely, in Gifu: repetition of space pattern units, uncoupling of form and function, and a new meaning of flexibility. -`Game Boards consists on setting up a base geometry -each project his, generally reticular- and give form to each project system (structure, closings, partitions and furniture) by choosing elements -intersections, lines, modules- it offers. Each project system is formed, in principle, with no subordinated relation with any of the others; when subordination is unavoidable, the game rules determine that the load bearing structural system may not be the one to materialize the base geometric order, which means that it does not exert the dominant role. Therefore, Game Boards' transgresses the Modern logic, because the structure neither reflects nor reveals the base order, and because the systems do not respect any of the hierarchic and chained subordination relations that the free plan called for. Game Boards' leads to quite different solutions and formal projects: the Oogaki and Park Coffee projects show incipient Game Boards; The Almere Kunstlinie and the Zollverein School present consolidations of this strategy; and the Toledos Glass Pavilion results from subverting the strategy. In addition, the Toledo project takes the repetition concept beyond that of using a constructive element and a space pattern element (in this case with a bubble form) to end up affecting the personal experience of the spectator, who, wherever he is, feels to always be in the same place. This thesis denominates that repetitive space as Mantra space '. -Elements from a Catalogue is shown with the Kanazawa Museum. Its logic starts from the definition of a series of elements, very few, and it is based on the huge number of possible combinations among them. The Elements from a Catalogue approach was announced in the Gifu project when characterizing its space pattern elements. -Aprioristic Form' is illustrated by the Flower House. The decision on the type of form -in this case the form of an amoeba- would be the beginning of the projectual process, but it does not mean it is arbitrary form: the amoeba form implies repeating a space pattern (pseudopodia) and an apotheosis of the repetition concept: embracing the space experience, it gives rise to a repetitive or mantra space. Mantra Space is one of leitmotivs used as an argument in the last formal strategy Thesis decodes: the Rolex Center. With respect to the Projectual strategies of the load bearing structure, the thesis finds and traces a trajectory of five projectual strategies: preeminence, concealment, dissolution, disappearance and desvirtuacin. --Preeminence is present in Sejimas first works in which she resorts to structures which have a dominant preeminent role in the project in so far as they impersonate the greater scale and/or materialize the base geometric order. In later works that preeminence will be inverted, the projects aiming towards its opposite: lighter, slighter, smaller structures. -Concealment reduces the dominant role of the structure. At the outset concealment is literal, almost hiding the structural elements, as in Gifu; soon it will become more sophisticated, such as the concealment by camouflage or the paradoxical concealment by multiplication in the Koga Park Caf. -Dissolution diminishes the dominant condition of the structure: instead of its being configured as unitary or homogenous system is fragmented in several subsystems. -Disappearance talks about structures that fade away as self referred and independent systems; projects in which the load bearing function is carried out by other systems such as the set of partitions. Disappearance reaches its zenith at the Flower House, whose perimeter functions structurally being, in addition, transparent, immaterial: its structure has become invisible, has disappeared. -Desvirtuacin talks about structures that do appear like independent self-systems, but which that do not longer have a preeminent paper, inasmuch as they do not materialize the base order. This strategy correlates with the Game Boards formal strategy. The thesis conclusions are show by the organization of the thesis itself: its identification of the different strategies. Even so, as epilogues, the thesis exposes six Conclusions. The first two emphasize the leading thread of the work done, rooted in the generic quality of the Sejima-SANAA projectual strategies. The following four expound to what extent their projects show features, or formal and/or structural signifiers, which also are or can be read as characteristic signals of the contemporary architectonic panorama, and raise the key question: aiming farther, may some of them be taken as original contributions? -As original contributions the conclusions highlight: the identification between the generic ideal and the concrete project; and the proposal of a new, hybrid space, kind of an intermediate stage between the traditional subdivided compartmented space and the continuous modern. -As symptoms of contemporaneousness: in relation to the form it highlights the transferring of the formal specificity from the part to the whole; and in relation to the structure, it underscore the contemporary tendency towards lighter and growingly slimmer structures, tending to the evanescent. This last one, the tendency towards structural evanescence, could have condition of being an original contribution, not in vain it carries the structural disappearance towards its last consequences; and in the case of structures with physical presence, it makes them to cease being the ordering system orchestrating the projectual process.
Resumo:
La Arquitectura de la Red de las Cosas (IoT) hace referencia a una red de objetos cotidianos interconectados digitalmente. Gracias a IoT, no slo podemos almacenar, analizar e intercambiar informacin y datos con dichos objetos, sino que adems ellos pueden tener la capacidad de interactuar entre ellos de forma autnoma. Para ellos, los objetos cotidianos disponen de actuadores y sensores que permiten modificar su comportamiento y conocer su estado y propiedades, respectivamente. La gestin de IoT combina todas las funcionalidades necesarias para coordinar un sistema con una Arquitectura de la Red de las Cosas. Una buena gestin del sistema puede reducir costes, mejorar la asistencia a problemas de uso inesperado, corregir fallos y permitir la escalabilidad del sistema permitindole la incorporacin de nuevos mdulos y funcionalidades. En este Proyecto Fin de Grado se realizar primero un anlisis de los aspectos de IoT relacionados con la gestin de dispositivos integrados en la Arquitectura de la Red de las Cosas. Despus se proceder a realizar la especificacin y el diseo de plataforma de gestin. Y finalmente se desarrollarn un caso de uso que permita validar algunos elementos de la plataforma diseada. Se realizarn distintas pruebas para comprobar una correcta gestin de los dispositivos como el correcto funcionamiento del diseo previamente establecido, por medio, entre otras, de las siguientes operaciones: listar los elementos conectados, posibilidad de obtener y/o modificar dichos elementos (su configuracin y su estado) o presentar informes y comprobar el estado en el que se encuentran los dispositivos: operativos o no operativos. De tal forma, en esta memoria se plasma como se ha desarrollado la gestin de dispositivos integrados en un sistema con Arquitectura de la Red de las Cosas utilizando tanto plataformas Intel Galileo como Arduino. ABSTRACT. The Architecture of the Internet of Things (IoT) refers to a network of digitally interconnected everyday objects. With IoT, not only we can store, analyze and exchange information and data with objects, but they can also autonomously interact among them. To accomplish that, the everyday objects are made of actuators and sensors that let us act on their behavior and know their state and properties, respectively. Management of IoT combines all the functionalities needed for coordinating a system with an Architecture of the Internet of Things. A good management system can reduce faults, improve assistance to reduce unexpected problems, correct errors and allow the scalability of the system, allowing the addition of new modules and functionalities. In this Degree Final Project, an analysis about aspects of IoT related to the management of devices integrated into the Architecture of the Internet of things is carried out first. Then, the specification and the design of the management platform is made. Finally, a use case will be developed to validate some elements of the designed platform. Several tests will be run to check the correct management of the devices such as the proper functioning of the design previously established, requesting, among others, the following set of operations: list the connected elements, possibility to obtain or modify these elements (their configuration and their state) or reporting and checking which devices are operating or non-operating. So, in this memory it is explained how it has been carried out the management of devices integrated in a system with an Architecture of the Internet of Things (IoT), based on the Intel Galileo and Arduino platforms.
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Los sistemas empotrados son cada da ms comunes y complejos, de modo que encontrar procesos seguros, eficaces y baratos de desarrollo software dirigidos especficamente a esta clase de sistemas es ms necesario que nunca. A diferencia de lo que ocurra hasta hace poco, en la actualidad los avances tecnolgicos en el campo de los microprocesadores de los ltimos tiempos permiten el desarrollo de equipos con prestaciones ms que suficientes para ejecutar varios sistemas software en una nica mquina. Adems, hay sistemas empotrados con requisitos de seguridad (safety) de cuyo correcto funcionamiento depende la vida de muchas personas y/o grandes inversiones econmicas. Estos sistemas software se disean e implementan de acuerdo con unos estndares de desarrollo software muy estrictos y exigentes. En algunos casos puede ser necesaria tambin la certificacin del software. Para estos casos, los sistemas con criticidades mixtas pueden ser una alternativa muy valiosa. En esta clase de sistemas, aplicaciones con diferentes niveles de criticidad se ejecutan en el mismo computador. Sin embargo, a menudo es necesario certificar el sistema entero con el nivel de criticidad de la aplicacin ms crtica, lo que hace que los costes se disparen. La virtualizacin se ha postulado como una tecnologa muy interesante para contener esos costes. Esta tecnologa permite que un conjunto de mquinas virtuales o particiones ejecuten las aplicaciones con unos niveles de aislamiento tanto temporal como espacial muy altos. Esto, a su vez, permite que cada particin pueda ser certificada independientemente. Para el desarrollo de sistemas particionados con criticidades mixtas se necesita actualizar los modelos de desarrollo software tradicionales, pues estos no cubren ni las nuevas actividades ni los nuevos roles que se requieren en el desarrollo de estos sistemas. Por ejemplo, el integrador del sistema debe definir las particiones o el desarrollador de aplicaciones debe tener en cuenta las caractersticas de la particin donde su aplicacin va a ejecutar. Tradicionalmente, en el desarrollo de sistemas empotrados, el modelo en V ha tenido una especial relevancia. Por ello, este modelo ha sido adaptado para tener en cuenta escenarios tales como el desarrollo en paralelo de aplicaciones o la incorporacin de una nueva particin a un sistema ya existente. El objetivo de esta tesis doctoral es mejorar la tecnologa actual de desarrollo de sistemas particionados con criticidades mixtas. Para ello, se ha diseado e implementado un entorno dirigido especficamente a facilitar y mejorar los procesos de desarrollo de esta clase de sistemas. En concreto, se ha creado un algoritmo que genera el particionado del sistema automticamente. En el entorno de desarrollo propuesto, se han integrado todas las actividades necesarias para desarrollo de un sistema particionado, incluidos los nuevos roles y actividades mencionados anteriormente. Adems, el diseo del entorno de desarrollo se ha basado en la ingeniera guiada por modelos (Model-Driven Engineering), la cual promueve el uso de los modelos como elementos fundamentales en el proceso de desarrollo. As pues, se proporcionan las herramientas necesarias para modelar y particionar el sistema, as como para validar los resultados y generar los artefactos necesarios para el compilado, construccin y despliegue del mismo. Adems, en el diseo del entorno de desarrollo, la extensin e integracin del mismo con herramientas de validacin ha sido un factor clave. En concreto, se pueden incorporar al entorno de desarrollo nuevos requisitos no-funcionales, la generacin de nuevos artefactos tales como documentacin o diferentes lenguajes de programacin, etc. Una parte clave del entorno de desarrollo es el algoritmo de particionado. Este algoritmo se ha diseado para ser independiente de los requisitos de las aplicaciones as como para permitir al integrador del sistema implementar nuevos requisitos del sistema. Para lograr esta independencia, se han definido las restricciones al particionado. El algoritmo garantiza que dichas restricciones se cumplirn en el sistema particionado que resulte de su ejecucin. Las restricciones al particionado se han diseado con una capacidad expresiva suficiente para que, con un pequeo grupo de ellas, se puedan expresar la mayor parte de los requisitos no-funcionales ms comunes. Las restricciones pueden ser definidas manualmente por el integrador del sistema o bien pueden ser generadas automticamente por una herramienta a partir de los requisitos funcionales y no-funcionales de una aplicacin. El algoritmo de particionado toma como entradas los modelos y las restricciones al particionado del sistema. Tras la ejecucin y como resultado, se genera un modelo de despliegue en el que se definen las particiones que son necesarias para el particionado del sistema. A su vez, cada particin define qu aplicaciones deben ejecutar en ella as como los recursos que necesita la particin para ejecutar correctamente. El problema del particionado y las restricciones al particionado se modelan matemticamente a travs de grafos coloreados. En dichos grafos, un coloreado propio de los vrtices representa un particionado del sistema correcto. El algoritmo se ha diseado tambin para que, si es necesario, sea posible obtener particionados alternativos al inicialmente propuesto. El entorno de desarrollo, incluyendo el algoritmo de particionado, se ha probado con xito en dos casos de uso industriales: el satlite UPMSat-2 y un demostrador del sistema de control de una turbina elica. Adems, el algoritmo se ha validado mediante la ejecucin de numerosos escenarios sintticos, incluyendo algunos muy complejos, de ms de 500 aplicaciones. ABSTRACT The importance of embedded software is growing as it is required for a large number of systems. Devising cheap, efficient and reliable development processes for embedded systems is thus a notable challenge nowadays. Computer processing power is continuously increasing, and as a result, it is currently possible to integrate complex systems in a single processor, which was not feasible a few years ago.Embedded systems may have safety critical requirements. Its failure may result in personal or substantial economical loss. The development of these systems requires stringent development processes that are usually defined by suitable standards. In some cases their certification is also necessary. This scenario fosters the use of mixed-criticality systems in which applications of different criticality levels must coexist in a single system. In these cases, it is usually necessary to certify the whole system, including non-critical applications, which is costly. Virtualization emerges as an enabling technology used for dealing with this problem. The system is structured as a set of partitions, or virtual machines, that can be executed with temporal and spatial isolation. In this way, applications can be developed and certified independently. The development of MCPS (Mixed-Criticality Partitioned Systems) requires additional roles and activities that traditional systems do not require. The system integrator has to define system partitions. Application development has to consider the characteristics of the partition to which it is allocated. In addition, traditional software process models have to be adapted to this scenario. The V-model is commonly used in embedded systems development. It can be adapted to the development of MCPS by enabling the parallel development of applications or adding an additional partition to an existing system. The objective of this PhD is to improve the available technology for MCPS development by providing a framework tailored to the development of this type of system and by defining a flexible and efficient algorithm for automatically generating system partitionings. The goal of the framework is to integrate all the activities required for developing MCPS and to support the different roles involved in this process. The framework is based on MDE (Model-Driven Engineering), which emphasizes the use of models in the development process. The framework provides basic means for modeling the system, generating system partitions, validating the system and generating final artifacts. The framework has been designed to facilitate its extension and the integration of external validation tools. In particular, it can be extended by adding support for additional non-functional requirements and support for final artifacts, such as new programming languages or additional documentation. The framework includes a novel partitioning algorithm. It has been designed to be independent of the types of applications requirements and also to enable the system integrator to tailor the partitioning to the specific requirements of a system. This independence is achieved by defining partitioning constraints that must be met by the resulting partitioning. They have sufficient expressive capacity to state the most common constraints and can be defined manually by the system integrator or generated automatically based on functional and non-functional requirements of the applications. The partitioning algorithm uses system models and partitioning constraints as its inputs. It generates a deployment model that is composed by a set of partitions. Each partition is in turn composed of a set of allocated applications and assigned resources. The partitioning problem, including applications and constraints, is modeled as a colored graph. A valid partitioning is a proper vertex coloring. A specially designed algorithm generates this coloring and is able to provide alternative partitions if required. The framework, including the partitioning algorithm, has been successfully used in the development of two industrial use cases: the UPMSat-2 satellite and the control system of a wind-power turbine. The partitioning algorithm has been successfully validated by using a large number of synthetic loads, including complex scenarios with more that 500 applications.
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El crecimiento demogrfico y el proceso de urbanizacin que ha experimentado el planeta en el ltimo siglo se ha traducido, en contextos de pobreza, en la generacin de tugurios y en el aumento de la poblacin viviendo en condiciones de habitabilidad precaria (HaP) fruto de la urbanizacin informal. Situacin que, segn las estimaciones de Naciones Unidas continuar teniendo lugar en las prximas dcadas, especialmente en las ciudades de las regiones menos desarrolladas. Este ha sido el problema especfico que se ha querido atender con el presente trabajo: la bsqueda de un instrumento urbano que incida en la reduccin de las tasas de precariedad habitacional urbana futuras, la bsqueda de instrumentos que eviten que ese aumento de la urbanizacin se traduzca en aumento de poblacin condenada a vivir en tugurios durante dcadas. Dicha bsqueda ha tenido lugar en el marco de la teora de la Habitabilidad Bsica (HaB) desarrollada por el ICHaBCtedra UNESCO de Habitabilidad Bsica de la UPM. Una HaB que consiste en la satisfaccin de las necesidades fundamentales de habitabilidad pero, a su vez, o ms importante an, en una esperanza de mejora y progreso paulatino de esas condiciones elementales entendida como herramienta de desarrollo y lucha contra la pobreza. Como herramienta bsica, no se trata de ofrecer las condiciones ideales, sino de brindar un camino razonable, que se considera posible, para que miles de millones de personas que viven en HaP o parecen condenadas a tener que hacerlo, puedan acceder a mejores condiciones de vida en tiempos ms cortos. Entre las polticas habitacionales no convencionales puestas en marcha desde Hbitat I en 1976, las de habilitacin urbana progresiva, y ms en particular, la Ocupacin Guiada, resultan ser en contextos de escasez econmica, el mejor instrumento para hacer frente a la urbanizacin informal, un instrumento paradigmtico mnimo preferente de implantacin ex novo de HaB. Lo es, por la atencin prestada en la eleccin del suelo y la parcelacin, las dos etapas cabecera del proceso, as como por los mecanismos implementados para atender la etapa de urbanizacin en su fase provisional, y por dejar la ltima etapa, la de la edificacin de las viviendas, en manos de la poblacin. El proceso de urbanizacin que se favorece es parecido al de los tugurios y ocupaciones ilegales en lo referente a las etapas y mecanismos de crecimiento. Sin embargo, la diferencia est en las condiciones en las que se produce, en los niveles de salubridad y de seguridad, y en la proyeccin de futuro. El Programa de Ocupacin Guiada 'Alto Trujillo' (POG), puesto en marcha por la municipalidad de Trujillo (Per) entre 1995 y 2006 fue concebido para hacer frente a los procesos de urbanizacin informal que estaban teniendo lugar en la ciudad y ha demostrado ser un mecanismo adecuado para garantizar el acceso regulado al suelo, las infraestructuras, los servicios bsicos y la vivienda en condiciones de fuerte restriccin econmica mediante un cogestin acertada entre municipalidad, poblacin y dems actores del proceso. El POG eligi un suelo no vulnerable y en continuidad con el tejido urbano, con la parcelacin estableci el orden geomtrico del asentamiento y reserv los espacios pblicos destinados a equipamientos, zonas verdes y viario, y fij las dimensiones de las parcelas, acompa a la poblacin en el proceso de ocupacin guiada de las mismas, as como en el posterior desarrollo progresivo del asentamiento haciendo una fuerte apuesta por lo pblico, relegando la construccin de las viviendas al esfuerzo de los pobladores. Los POG municipales resultan ser un instrumento replicable siempre que se den cinco condiciones: la existencia de un marco institucional adecuado que contemple la descentralizacin de competencias, que haya inters y continuidad poltica en el gobierno local, acceso a suelo urbano disponible y voluntad de co-gestin con la poblacin. El anlisis del POG ha permitido elaborar una propuesta de replicabilidad del POG basada en la experiencia de soluciones ya implementadas, que han sido contrastadas empricamente y analizadas para aprender de sus fortalezas, oportunidades, debilidades y amenazas, as como de sus aciertos y errores. La estrategia de replicabilidad del POG se plantea como alternativa a la urbanizacin informal con mecanismos mejorados para que las ciudades se desarrollen siguiendo unos parmetros mnimos de HaB y no a travs de asentamientos informales que dificulten el progreso futuro de las familias que los habitan y de las mismas ciudades de las que forman parte. Esta propuesta de replicabilidad, que precisa ser adaptada a cada contexto, tena una clara vocacin: intentar ser instrumento en la regin del planeta donde, segn las estimaciones, en los prximos treinta aos el crecimiento demogrfico y el proceso de urbanizacin sern ms fuertes: frica Subsahariana. Por ello, con el apoyo de expertos mozambiqueos en temas de habitabilidad, se estudi la replicabilidad en Mozambique incorporando las medidas necesarias que daran respuesta a los condicionantes particulares del pas. ABSTRACT The demographic growth and the urbanisation process that the planet has experienced in the last century has turned into the generation of slums and in the increase of population living in conditions of precarious habitability (HaP) result of the informal urbanisation, in contexts of poverty. According to the United Nations estimations, this situation will continue taking place in the next decades, especially in the cities of the least developed regions. The present work has wanted to attend this specific problem by the search of an urban instrument that has an impact on the reduction of the urban future precarious housing rates, a search of instruments that prevent that this urbanisation spread become an increase of population doomed to live in slums during decades. The above mentioned search has taken place in the frame of the Basic Habitability theory (HaB) developed by the ICHaB-Ctedra UNESCO of Basic Habitability of the UPM. HaB consists of the satisfaction of the fundamental habitability needs but, in turn, or still more important, it is the hope of improvement and gradual progress of these elementary conditions. The HaB is understood as a tool of development and fight against poverty. As a basic tool, it does not offer the ideal conditions, but it offers a reasonable way, which is considered to be possible, so that thousands of million persons who live in HaP or that seem to be doomed to have to do it, could gain access to better living conditions in shorter times. Between the non conventional housing policies started up from Habitat I in 1976, those of urban progressive fitting out, and more especially, the Guided Occupation, has turned out to be, in contexts of economic shortage, the best instrument to face the informal urbanisation, a preferential and minimum paradigmatic instrument of ex-novo HaB implementation. It is so due to the attention given to the appropriate site selection and the land allotment, both headboard stages of the process, as well as to the mechanisms implemented to attend the urbanisation stage in its provisional phase, and to leave the last stage, the building process, in population hands. The urbanisation process that is favored is similar to that of the slums and squatting in what concerns the stages and mechanisms of growth. Nevertheless, the difference is in the conditions in which it takes place, in the levels of health and safety, and in the future projection. The Program of Guided Occupation 'Alto Trujillo' (PGO), turned on by the Provincial City Hall of Trujillo (Peru) between 1995 and 2006, was conceived to face the processes of informal urbanisation that took place in the city and it has demonstrated to be a mechanism adapted to guarantee the regulated access to soil, infrastructures, basic services and housing in conditions of strong economic restriction by means of a succeeded co-management between municipality, population and other process actors. The PGO chose a non vulnerable soil in continuity with the urban fabric, with the land allotment established the settlement geometric order, reserved the public spaces allocated for urban facilities, green spaces and streets, and fixed the plot dimensions, accompanied the population in the plot guided occupation process, as well as in the later progressive settlement development betting strongly for the public components, relegating the housing construction to the settlers effort. The municipal PGO turn out to be a replicable instrument under five conditions: the existence of an institutional suitable frame that contemplates the decentralization competitions, interest and political continuity in the local government, access to urban available soil and will of co-management with the population. The PGO analysis has allowed to elaborate a replicability proposal of the PGO based on the experience of the already implemented solutions, which have been empirically confirmed and analyzed to learn of its strengths, opportunities, weaknesses and threats, as well as of its successes and mistakes. The replicability strategy of the PGO is considered an alternative to the informal urbanisation with improved mechanisms in order that the cities can develop following a few HaB's minimal parameters, but not through informal settlements that would make difficult the families future progress and that of the cities where they live. This replicability proposal, that needs to be adapted to every context, had a clear vocation: try to be an instrument in the region of the planet where, according to the estimations, in the next thirty years the demographic growth and the urbanisation process will be stronger: Sub-Saharan Africa. Therefore, with the support of Mozambican experts in habitability topics, the replicability was studied in Mozambique incorporating the necessary measures that would give response to the country's determinants.
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The replication system of bacteriophage T4 uses a trimeric ring-shaped processivity clamp (gp45) to tether the replication polymerase (gp43) to the template-primer DNA. This ring is placed onto the DNA by an ATPase-driven clamp-loading complex (gp44/62) where it then transfers, in closed form, to the polymerase. It generally has been assumed that one of the functions of the loading machinery is to open the clamp to place it around the DNA. However, the mechanism by which this occurs has not been fully defined. In this study we design and characterize a double-mutant gp45 protein that contains pairs of cysteine residues located at each monomer-monomer interface of the trimeric clamp. This mutant protein is functionally equivalent to wild-type gp45. However, when all three monomer-monomer interfaces are tethered by covalent crosslinks formed (reversibly or irreversibly) between the cysteine pairs these closed clamps can no longer be loaded onto the DNA nor onto the polymerase, effectively eliminating processive strand-displacement DNA synthesis. Analysis of the individual steps of the clamp-loading process shows that the ATPase-dependent interactions between the clamp and the clamp loader that precede DNA binding are hyperstimulated by the covalently crosslinked ring, suggesting that binding of the closed ring induces a futile, ATP-driven, ring-opening cycle. These findings and others permit further characterization and ordering of the steps involved in the T4 clamp-loading process.
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The mechanism of proton transfer from the bulk into the membrane protein interior was studied. The light-induced reduction of a bound ubiquinone molecule QB by the photosynthetic reaction center is accompanied by proton trapping. We used kinetic spectroscopy to measure (i) the electron transfer to QB (at 450 nm), (ii) the electrogenic proton delivery from the surface to the QB site (by electrochromic carotenoid response at 524 nm), and (iii) the disappearance of protons from the bulk solution (by pH indicators). The electron transfer to QB and the proton-related electrogenesis proceeded with the same time constant of 100 s (at pH 6.2), whereas the alkalinization in the bulk was distinctly delayed ( 400 s). We investigated the latter reaction as a function of the pH indicator concentration, the added pH buffers, and the temperature. The results led us to the following conclusions: (i) proton transfer from the surface-located acidic groups into the QB site followed the reduction of QB without measurable delay; (ii) the reprotonation of these surface groups by pH indicators and hydronium ions was impeded, supposedly, because of their slow diffusion in the surface water layer; and (iii) as a result, the protons were slowly donated by neutral water to refill the proton vacancies at the surface. It is conceivable that the same mechanism accounts for the delayed relaxation of the surface pH changes into the bulk observed previously with bacteriorhodopsin membranes and thylakoids. Concerning the coupling between proton pumps in bioenergetic membranes, our results imply a tendency for the transient confinement of protons at the membrane surface.
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Ascorbate (vitamin C) recycling occurs when extracellular ascorbate is oxidized, transported as dehydroascorbic acid, and reduced intracellularly to ascorbate. We investigated microorganism induction of ascorbate recycling in human neutrophils and in microorganisms themselves. Ascorbate recycling was determined by measuring intracellular ascorbate accumulation. Ascorbate recycling in neutrophils was induced by both Gram-positive and Gram-negative pathogenic bacteria, and the fungal pathogen Candida albicans. Induction of recycling resulted in as high as a 30-fold increase in intracellular ascorbate compared with neutrophils not exposed to microorganisms. Recycling occurred at physiologic concentrations of extracellular ascorbate within 20 min, occurred over a 100-fold range of effector/target ratios, and depended on oxidation of extracellular ascorbate to dehydroascorbic acid. Ascorbate recycling did not occur in bacteria nor in C. albicans. Ascorbate did not enter microorganisms, and dehydroascorbic acid entry was less than could be accounted for by diffusion. Because microorganism lysates reduced dehydroascorbic acid to ascorbate, ascorbate recycling was absent because of negligible entry of the substrate dehydroascorbic acid. Because ascorbate recycling occurs in human neutrophils but not in microorganisms, it may represent a eukaryotic defense mechanism against oxidants with possible clinical implications.
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Several microbial systems have been shown to yield advantageous mutations in slowly growing or nongrowing cultures. In one assay system, the stationary-phase mutation mechanism differs from growth-dependent mutation, demonstrating that the two are different processes. This system assays reversion of a lac frameshift allele on an F plasmid in Escherichia coli. The stationary-phase mutation mechanism at lac requires recombination proteins of the RecBCD double-strand-break repair system and the inducible error-prone DNA polymerase IV, and the mutations are mostly 1 deletions in small mononucleotide repeats. This mutation mechanism is proposed to occur by DNA polymerase errors made during replication primed by recombinational double-strand-break repair. It has been suggested that this mechanism is confined to the F plasmid. However, the cells that acquire the adaptive mutations show hypermutation of unrelated chromosomal genes, suggesting that chromosomal sites also might experience recombination protein-dependent stationary-phase mutation. Here we test directly whether the stationary-phase mutations in the bacterial chromosome also occur via a recombination protein- and pol IV-dependent mechanism. We describe an assay for chromosomal mutation in cells carrying the F lac. We show that the chromosomal mutation is recombination protein- and pol IV-dependent and also is associated with general hypermutation. The data indicate that, at least in these male cells, recombination protein-dependent stationary-phase mutation is a mechanism of general inducible genetic change capable of affecting genes in the bacterial chromosome.
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Earlier we have shown that oscillations with a long period ("supercycles") may arise in two-locus systems experiencing cyclical selection with a short period. However, this mode of complex limiting behavior appeared to be possible for narrow ranges of parameters. Here we demonstrate that a multilocus system subjected to stabilizing selection with cyclically moving optimum can generate ubiquitous complex limiting behavior including supercycles, T-cycles, and chaotic-like phenomena. This mode of multilocus dynamics far exceeds the potential attainable under ordinary selection models resulting in simple behavior. It may represent a novel evolutionary mechanism increasing genetic diversity over long-term time periods.
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RNA-RNA interactions govern a number of biological processes. Several RNAs, including natural sense and antisense RNAs, interact by means of a two-step mechanism: recognition is mediated by a loop-loop complex, which is then stabilized by formation of an extended intermolecular duplex. It was proposed that the same mechanism holds for dimerization of the genomic RNA of human immunodeficiency virus type 1 (HIV-1), an event thought to control crucial steps of HIV-1 replication. However, whereas interaction between the partially self-complementary loop of the dimerization initiation site (DIS) of each monomer is well established, formation of the extended duplex remained speculative. Here we first show that in vitro dimerization of HIV-1 RNA is a specific process, not resulting from simple annealing of denatured molecules. Next we used mutants of the DIS to test the formation of the extended duplex. Four pairs of transcomplementary mutants were designed in such a way that all pairs can form the loop-loop "kissing" complex, but only two of them can potentially form the extended duplex. All pairs of mutants form heterodimers whose thermal stability, dissociation constant, and dynamics were analyzed. Taken together, our results indicate that, in contrast with the interactions between natural sense and antisense RNAs, no extended duplex is formed during dimerization of HIV-1 RNA. We also showed that 55-mer sense RNAs containing the DIS are able to interfere with the preformed HIV-1 RNA dimer.
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When NMR hydrogen exchange was used previously to monitor the kinetics of RNase A unfolding, some peptide NH protons were found to show EX2 exchange (detected by base catalysis) in addition to the expected EX1 exchange, whose rate is limited by the kinetic unfolding process. In earlier work, two groups showed independently that a restricted two-process model successfully fits published hydrogen exchange rates of native RNase A in the range 0-0.7 M guanidinium chloride. We find that this model predicts properties that are very different from the observed properties of the EX2 exchange reactions of RNase A in conditions where guanidine-induced unfolding takes place. The model predicts that EX2 exchange should be too fast to measure by the technique used, whereas it is readily measurable. Possible explanations for the contradiction are considered here, and we show that removing the restriction from the earlier two-process model is sufficient to resolve the contradiction; instead of specifying that exchange caused by global unfolding occurs by the EX2 mechanism, we allow it to occur by the general mechanism, which includes both the EX1 and EX2 cases. It is logical to remove this restriction because global unfolding of RNase A is known to give rise to EX1 exchange in these unfolding conditions. Resolving the contradiction makes it possible to determine whether populated unfolding intermediates contribute to the EX2 exchange, and this question is considered elsewhere. The results and simulations indicate that moderate or high denaturant concentrations readily give rise to EX1 exchange in native proteins. Earlier studies showed that hydrogen exchange in native proteins typically occurs by the EX2 mechanism but that high temperatures or pH values above 7 may give rise to EX1 exchange. High denaturant concentrations should be added to the list of variables likely to cause EX1 exchange.
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The conditioning of culture medium by the production of growth-regulatory substances is a well-established phenomenon with eukaryotic cells. It has recently been shown that many prokaryotes are also capable of modulating growth, and in some cases sensing cell density, by production of extracellular signaling molecules, thereby allowing single celled prokaryotes to function in some respects as multicellular organisms. As Escherichia coli shifts from exponential growth to stationary growth, many changes occur, including cell division leading to formation of short minicells and expression of numerous genes not expressed in exponential phase. An understanding of the coordination between the morphological changes associated with cell division and the physiological and metabolic changes is of fundamental importance to understanding regulation of the prokaryotic cell cycle. The ftsQA genes, which encode functions required for cell division in E. coli, are regulated by promoters P1 and P2, located upstream of the ftsQ gene. The P1 promoter is rpoS-stimulated and the second, P2, is regulated by a member of the LuxR subfamily of transcriptional activators, SdiA, exhibiting features characteristic of an autoinduction (quorum sensing) mechanism. The activity of SdiA is potentiated by N-acyl-homoserine lactones, which are the autoinducers of luciferase synthesis in luminous marine bacteria as well as of pathogenesis functions in several pathogenic bacteria. A compound(s) produced by E. coli itself during growth in Luria Broth stimulates transcription from P2 in an SdiA-dependent process. Another substance(s) enhances transcription of rpoS and (perhaps indirectly) of ftsQA via promoter P1. It appears that this bimodal control mechanism may comprise a fail-safe system, such that transcription of the ftsQA genes may be properly regulated under a variety of different environmental and physiological conditions.
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The small hardcover volume contains excerpts copied by John Winthrop beginning at the age of thirteen as a freshman at Harvard College. Winthrops own description of this book as a book of Extracts from many Authors is accurate, as it includes neither personal information about Winthrop nor reflections on what he read. With the exception of occasional notations indicating the date he finished reading particular books, the volume consists of passages he copied from a wide range of sources. It begins with an index of the various sections of the book (History, Poetry, Miscellanies, Geography, Divinity, History, Philosophy, Philosophy, Miscellanies, Poetry, Divinity, Philosophy) and ends with an index of the extracts' authors.
Resumo:
The start of accession negotiations between Ankara and the EU is vital for the future of both Turkey and the Union, including Poland as its member state, as well as for the geopolitical situation in Eurasia (the Black Sea region, Caucasus, Central Asia and the Middle East). Appreciating the significance of these issues, the Centre for Eastern Studies in early 2005 decided to launch a project entitled "Turkey after the start of negotiations with the European Union - foreign relations and the domestic situation". The goal of this project is to present, within the context of accession negotiations, Turkey's greatest internal challenges as well as Ankara's relations with its neighbour regions, the EU and the USA. This Report is the first of three which will be published as part of the project. The Report includes texts on Turkish-US relations since 2003, major political and social challenges on Turkey's path towards the EU and the current condition of the Turkish economy. The Report was developed between July 2005 and November 2006, over which time CES workers and associates searched for publicly available materials in Poland, Turkey and EU countries, and went on three research trips to Turkey, where they met local researchers, analysts, politicians and officials. The authors of the Report would like to express their gratitude to everyone who have shared their opinions with them, and to the Polish Embassy in Ankara, especially to Ambassador Grzegorz Michalski and Minister Andrzej Ananicz for their expert support and assistance in the authors' work on this Report. This Report does not present the official stance of the Polish government on the issues discussed therein; instead it reflects the personal views of its authors, who have made their best efforts to ensure that their work is reliable.
