14,982 research outputs found
Consent and the Construction of the Volunteer: Institutional Settings of Experimental Research on Human Beings in Britain during the Cold War
This study challenges the primacy of consent in the history of human experimentation and argues that privileging the cultural frameworks adds nuance to our understanding of the construction of the volunteer in the period 1945 to 1970. Historians and bio-ethicists have argued that medical ethics codes have marked out the parameters of using people as subjects in medical scientific research and that the consent of the subjects was fundamental to their status as volunteers. However, the temporality of the creation of medical ethics codes means that they need to be understood within their historical context. That medical ethics codes arose from a specific historical context rather than a concerted and conscious determination to safeguard the well-being of subjects needs to be acknowledged. The British context of human experimentation is under-researched and there has been even less focus on the cultural frameworks within which experiments took place. This study demonstrates, through a close analysis of the Medical Research Council's Common Cold Research Unit (CCRU) and the government's military research facility, the Chemical Defence Experimental Establishment, Porton Down (Porton), that the `volunteer' in human experiments was a subjective entity whose identity was specific to the institution which recruited and made use of the subject. By examining representations of volunteers in the British press, the rhetoric of the government's collectivist agenda becomes evident and this fed into the institutional construction of the volunteer at the CCRU. In contrast, discussions between Porton scientists, staff members, and government officials demonstrate that the use of military personnel in secret chemical warfare experiments was far more complex. Conflicting interests of the military, the government and the scientific imperative affected how the military volunteer was perceived
Embodying entrepreneurship: everyday practices, processes and routines in a technology incubator
The growing interest in the processes and practices of entrepreneurship has
been dominated by a consideration of temporality. Through a thirty-six-month
ethnography of a technology incubator, this thesis contributes to extant
understanding by exploring the effect of space. The first paper explores how
class structures from the surrounding city have appropriated entrepreneurship
within the incubator. The second paper adopts a more explicitly spatial analysis
to reveal how the use of space influences a common understanding of
entrepreneurship. The final paper looks more closely at the entrepreneurs within
the incubator and how they use visual symbols to develop their identity. Taken
together, the three papers reject the notion of entrepreneurship as a primarily
economic endeavour as articulated through commonly understood language and
propose entrepreneuring as an enigmatic attractor that is accessed through the
ambiguity of the non-verbal to develop the ‘new’. The thesis therefore contributes
to the understanding of entrepreneurship and proposes a distinct role for the non-verbal in that understanding
Walking with the Earth: Intercultural Perspectives on Ethics of Ecological Caring
It is commonly believed that considering nature different from us, human beings (qua rational, cultural, religious and social actors), is detrimental to our engagement for the preservation of nature. An obvious example is animal rights, a deep concern for all living beings, including non-human living creatures, which is understandable only if we approach nature, without fearing it, as something which should remain outside of our true home. “Walking with the earth” aims at questioning any similar preconceptions in the wide sense, including allegoric-poetic contributions. We invited 14 authors from 4 continents to express all sorts of ways of saying why caring is so important, why togetherness, being-with each others, as a spiritual but also embodied ethics is important in a divided world
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Effect of Prior Plastic Strain on the High Temperature Creep Deformation and Damage Response of Type 316H Stainless Steel
Creep damage in ductile alloys is associated with creep deformation, crack growth and starts with the nucleation and growth of cavities. Under sustained high temperature and stress conditions, growing cavities can start to coalesce leading to microcracking and ultimate failure of a component. This mechanism can limit the lifetime of power plant components operating at high temperature. Many engineering components enter service in a cold-worked or prestrained condition as a result of manufacturing processes such as bending, forging, welding etc. Such pre-conditioning alters the creep resistance of the material significantly. Its effect on the creep deformation properties of a structure during service, and creep damage response can be advantageous for some materials but disadvantageous for others. Hence it is crucial to understand the effects of prior plastic strain when assessing the lifetime and safety of power plant components, for example in the context of nuclear power generation. The research set out in this thesis aims to examine the effect of prior plastic strain on subsequent creep deformation behaviour and development of damage in AISI Type 316H austenitic stainless steel, a material widely used in the fleet of Advanced Gas Cooled reactors operated by EDF Energy in the UK.
A novel cylindrical hourglass-shaped test specimen was designed for the research where a constant applied load provided a variation in uniaxial stress and associated creep strain rate along the hourglass gauge length. A further innovation in this PhD work involved exploiting the potential of 3D digital image correlation (3D-DIC) for measuring spatially resolved creep deformation along the hourglass gauge section over long duration creep tests at a high temperature of 550◦C. The scope of testing included load-controlled creep tests carried out on 5 samples where 0, 4, 8, 12 and 16% of prior tensile plastic strain was introduced at room temperature. The prestraining was carried out on cylindrical samples before the hourglass shape was machined, ensuring a uniform level of prior plastic strain was present along the gauge section prior to creep experiments. It was found that prior plastic strain increased the creep resistance of the as-received material. Increasing plastic strain decreased the creep strain rate and creep ductility. On the other hand, it resulted in an increase in time to failure.
After creep failure at the maximum stress location, small-angle neutron scattering (SANS) was utilised to investigate changes in creep cavitational damage as a function of applied stress, level of creep strain and prior plastic strain at room temperature. Two sets of experiments were performed using the D11 instrument at the ILL reactor source (France) and the SANS2D instrument at the ISIS spallation source (UK). Very similar scattering results were obtained from the two instruments. Furthermore, SANS data from the instruments were analysed using two independent analysis routes; a maximum entropy method (MAXE) and a Monte Carlo algorithm (McSAS). Since SANS is an indirect method for measuring creep cavitation, the microstructure of the specimens was also investigated using qualitative scanning electron microscopy (SEM) in order to interpret and verify the SANS cavitation observations. The SANS investigations revealed a strong correlation between the volume fraction and number density of creep cavities with applied stress and creep strain. Furthermore, an increasing number density of small creep cavities as a function of prior plastic strain was observed and verified by qualitative SEM studies. This is new evidence that prior plastic strain, induced at room temperature, introduces specific cavitational damage in Type 316H stainless steel. The macroscopic damage calculation based on the stress modified ductility exhaustion model revealed that the majority of damage for the series of prestrained specimens is caused by plastic hole growth as a consequence of inducing prior plastic strain rather than due to creep related diffusion processes
Smart-antenna techniques for energy-efficient wireless sensor networks used in bridge structural health monitoring
Abstract: It is well known that wireless sensor networks differ from other computing platforms in that 1- they typically require a minimal amount of computing power at the nodes; 2- it is often desirable for sensor nodes to have drastically low power consumption. The main benefit of the this work is a substantial network life before batteries need to be replaced or, alternatively, the capacity to function off of modest environmental energy sources (energy harvesting). In the context of Structural Health Monitoring (SHM), battery replacement is particularly problematic since nodes can be in difficult to access locations. Furthermore, any intervention on a bridge may disrupt normal bridge operation, e.g. traffic may need to be halted. In this regard, switchbeam smart antennas in combination with wireless sensor networks (WSNs) have shown great potential in reducing implementation and maintenance costs of SHM systems. The main goal of implementing switch-beam smart antennas in our application is to reduce power consumption, by focusing the radiated energy only where it is needed. SHM systems capture the dynamic vibration information of a bridge structure in real-time in order to assess the health of the structure and to predict failures. Current SHM systems are based on piezoelectric patch sensors. In addition, the collection of data from the plurality of sensors distributed over the span of the bridge is typically performed through an expensive and bulky set of shielded wires which routes the information to a data sink at one end of the structure. The installation, maintenance and operational costs of such systems are extremely high due to high power consumption and the need for periodic maintenance. Wireless sensor networks represent an attractive alternative, in terms of cost, ease of maintenance, and power consumption. However, network lifetime in terms of node battery life must be very long (ideally 5–10 years) given the cost and hassle of manual intervention. In this context, the focus of this project is to reduce the global power consumption of the SHM system by implementing switched-beam smart antennas jointly with an optimized MAC layer. In the first part of the thesis, a sensor network platform for bridge SHM incorporating switched-beam antennas is modelled and simulated. where the main consideration is the joint optimization of beamforming parameters, MAC layer, and energy consumption. The simulation model, built within the Omnet++ network simulation framework, incorporates the energy consumption profiles of actual selected components (microcontroller, radio interface chip). The energy consumption and packet delivery ratio (PDR) of the network with switched-beam antennas is compared with an equivalent network based on omnidirectional antennas. In the second part of the thesis, this system model is leveraged to examine two distinct but interrelated aspects: Gallium Arsenide (GaAs) based solar energy harvesting and switched-beam antenna strategies. The main consideration here is the joint optimization of solar energy harvesting and switchedbeam directional antennas, where an equivalent network based on omnidirectional antennas acts as a baseline reference for comparison purposes.Il est bien connu que les réseaux de capteurs sans fils diffèrent des autres plateformes informatiques
étant donné 1- qu’ils requièrent typiquement une puissance de calcul minimale aux
noeuds du réseau ; 2- qu’il est souvent désirable que les noeuds capteurs aient une consommation
d’énergie dramatiquement faible. La principale retombée de ce travail réside en la durée
de vie allongée du réseau avant que les piles ne doivent être remplacées ou, alternativement,
la capacité de fonctionner indéfiniment à partir de modestes sources d’énergie ambiente (glânage
d’énergie). Dans le contexte du contrôle de la santé structurale (CSS), le remplacement de
piles est particulièrement problématique puisque les noeuds peuvent se trouver en des endroits
difficiles d’accès. De plus, toute intervention sur un pont implique une perturbation de l’opération
normale de la structure, par exemple un arrêt du traffic. Dans ce contexte, les antennes
intelligentes à commutation de faisceau en combinaison avec les réseaux de capteurs sans fils
ont démontré un grand potentiel pour réduire les coûts de réalisation et d’entretien de systèmes
de CSS. L’objectif principal de l’intégration d’antennes à commutation de faisceau dans notre
application réside dans la réduction de la consommation énergétique, réalisée en concentrant
l’énergie radiée uniquement là où elle est nécessaire. Les systèmes de CSS capturent l’information
dynamique de vibration d’une structure de pont en temps réel de manière à évaluer la santé
de la structure et prédire les failles. Les systèmes courants de CSS sont basés sur des senseurs
piézoélectriques planaires. De plus, la collecte de données à partir de la pluralité de senseurs
distribués sur l’étendue du pont est typiquement effectuée par le biais d’un ensemble coûteux
et encombrant de câbles blindés qui véhiculent l’information jusqu’à un point de collecte à une
extremité de la structure. L’installation, l’entretien, et les coûts opérationnels de tels systèmes
sont extrêmement élevés étant donné la consommation de puissance élevée et le besoin d’entretien
régulier. Les réseaux de capteurs sans fils représentent une alternative attrayante, en termes
de coût, facilité d’entretien et consommation énergétique. Toutefois, la vie de réseau en termes
de la durée de vie des piles doit être très longue (idéalement de 5 à 10 ans) étant donné le coût
et les problèmes liés à l’intervention manuelle. Dans ce contexte, ce projet se concentre sur la
réduction de la consommation de puissance globale d’un système de CSS en y intégrant des
antennes intelligentes à commutation de faisceau conjointement avec une couche d’accès au
médium (couche MAC) optimisée. Dans la première partie de la thèse, une plateforme de réseau
de capteurs sans fils pour le CSS d’un pont incorporant des antennes à commutation de faisceaux
est modélisé et simulé, avec pour considération principale l’optimisation des paramètres
de sélection de faisceau, de la couche MAC et de la consommation d’énergie. Le modèle de
simulation, construit dans le logiciel de simulation de réseaux Omnet++, incorpore les profils
de consommation d’énergie de composants réels sélectionnés (microcontrôleur, puce d’interface
radio). La consommation d’énergie et le taux de livraison de paquets du réseau avec antennes
à commutation de faisceau est comparé avec un réseau équivalent basé sur des antennes omnidirectionnelles.
Dans la deuxième partie de la thèse, le modèle système proposé est mis à
contribution pour examiner deux aspects distrincts mais interreliés : le glânage d’énergie à partir
de cellules solaire à base d’arséniure de Gallium (GaAs) et les stratégies liées aux antennes
à commutation de faisceau. La considération principale ici est l’optimisation conjointe du glânage d’énergie et des antennes à commutation de faisceau, en ayant pour base de comparaison
un réseau équivalent à base d’antennes omnidirectionnelles
Spaces in-between: a transitional inquiry into transitionality
Working between the philosophy of Deleuze and Guattari and the psychoanalysis of
Winnicott, through stories and creative writing, I create new concepts and understandings of
the notion of assemblages. This thesis is a playful exploration of experiences, thinking with
theory, making a creative-relational inquiry.
Moving between the refrain and the transitional object, I work with the idea of a transitional
inquiry: between the internal and external, between the conscious and unconscious,
producing something-in-the-world. Even though it is personal, this type of inquiry de-centres
the notion of the subject to include objects, machines, and the creation of territories as
fundamental aspects to understand human processes.
One of the main contributions of working with Deleuze, Guattari, and Winnicott is to think
the transitional object together with the refrain and propose a holding-machine to help other
machines develop and process assemblages. This concept emerges while working with stories
of trauma, understanding them as moments where the subject cannot process events and
affects.
This exploration is about spaces in-between, spaces that are not entirely what they are, as
they move between the created and the discovered, between the intensities and extensions,
fantasy, and reality
Preparación de fibras y otros materiales de carbono para adsorción de CO2 en post-combustión
Finalmente, otro carbón activo, GAL, y una tela de carbón activada, CAD, se sintetizaron por activación química con ácido fosfórico de lignina y tela vaquera. Los distintos materiales se han caracterizado utilizando diversas técnicas y procedimientos, tales como adsorción-desorción de N2 a -196 ºC, adsorción de CO2 a 0 ºC, XPS, DTP y SEM. Para la evaluación de los materiales en la aplicación de interés se han realizado experimentos de adsorción, en equilibrio y en columna lecho fijo, en un rango amplio de condiciones experimentales e incluyendo las temperaturas, presiones y composiciones típicas de los procesos de post-combustión. También se ha estudiado el potencial de regeneración de varios de los materiales mediante ciclos de adsorción-desorción.
Los resultados obtenidos han sido muy prometedores, alcanzándose capacidades de adsorción y selectividades comparables a las de otros materiales complejos incluso a temperaturas elevadas. Cabe destacar, además, que la presencia de H2Ov, o bien no afecta de manera significativa al rendimiento de los materiales analizados; o bien, podría actuar de forma sinérgica y mejorar su capacidad de adsorción. Por otro lado, se ha conseguido profundizar y establecer relaciones muy interesantes entre las características estructurales del material (porosidad, química superficial, morfología, etc.) y la capacidad de adsorción en diferentes condiciones; y se han calculado diversos parámetros termodinámicos y cinéticos importantes para futuras etapas de diseño.La adsorción de CO2 sobre sólidos porosos en sistemas de post-combustión constituye una de las alternativas prioritarias para reducir y estabilizar su concentración a los niveles exigidos. Entre los adsorbentes estudiados, los materiales de carbono resultan especialmente interesantes debido al carácter hidrofóbico (mayor estabilidad en presencia de humedad) y menor calor de adsorción (facilidad de regeneración) que generalmente presentan. En el contexto de desarrollo sostenible, su obtención a partir de residuos biomásicos conllevaría beneficios sinérgicos adicionales, al capturarse CO2 y valorizarse un residuo simultáneamente. Sin embargo, las condiciones típicas de las corrientes de post-combustión suponen un verdadero reto y sus capacidades de adsorción y selectividades aún deben ser mejoradas para su implementación real. Ambos parámetros están intrínsecamente relacionados con las propiedades fisicoquímicas y estructurales del material, por lo que los esfuerzos se están orientando a clarificar su influencia, así como a desarrollar nuevos materiales carbonosos con las características óptimas.
En esta línea, el objetivo principal de esta Tesis Doctoral ha sido caracterizar y evaluar una serie de materiales de carbono diferentes como adsorbentes de CO2 en condiciones de post-combustión. En concreto, se han preparado seis materiales de carbón a partir de cuatro tipos de residuos lignocelulósicos con alto potencial de valorización, abundantes y de bajo coste: fibras de carbón por electrospinning, FCL, y un carbonizado granular, GCL, a partir de lignina Alcell®; dos carbones activos, GAS y GAWBa, por activación física de hueso de aceituna y residuo de aglomerado de madera, respectivamente. GAWBa fue, además, impregnado con acetato de bario en una etapa posterior para dotarlo de un cierto número de grupos básicos superficiales
Investigating interactions between influenza A virus and respiratory syncytial virus during coinfection
Respiratory viruses are the cause of significant disease burden and coinfections with more than one virus constitute between 10-30% of viral respiratory infections. Interactions among respiratory viruses are recognised for their importance in influencing viral dynamics, however direct virus-virus interactions are poorly understood. Influenza A virus (IAV) and respiratory syncytial virus (RSV) are important respiratory pathogens that share epidemiological characteristics, including timing of seasonal peaks of infections, and biological characteristics, including cellular tropism within the respiratory tract.
To characterise interactions between IAV and RSV during coinfection, we developed an in vitro model in A549 cells, a cell line derived from the human lung. Analysis of viral growth kinetics and viral dynamics by live cell imaging showed that, while IAV replication appears unaffected by coinfection with RSV, RSV replication is significantly decreased in coinfection. Imaging of coinfected cells stained for IAV and RSV nucleoproteins and glycoproteins show that they localise to the same regions of the plasma membrane, suggesting there may be opportunity for viral interactions during viral assembly. To further explore this hypothesis, virus particles budding from coinfected cells were examined using super-resolution confocal microscopy. Filamentous structures extended from coinfected cells, that incorporated glycoproteins from both viruses in distinct patches along the filament. The ultra-structure of these filaments, determined by cryo-electron tomography, revealed the formation of chimeric viral particles (CVPs) that contained genomes and structural features from both IAV and RSV. Additionally, coinfection by IAV and RSV generated pseudotyped RSV filaments that incorporate IAV glycoproteins. Functional assays using a sialidase showed that CVPs can facilitate entry of IAV into cells that were stripped of IAV entry receptors, demonstrating CVPs possess expanded receptor tropism.
To determine the likelihood for CVP formation in the airway epithelium, we coinfected primary differentiated human bronchial epithelial cell (hBEC) cultures at air-liquid interface. We observed that IAV and RSV infect ciliated epithelial cells and identified foci of coinfection. IAV and RSV proteins both localised at the apical surface of coinfected cells, providing opportunity for interactions to occur during viral assembly. Additionally, IAV and RSV replication kinetics and cytopathic effect in hBEC cultures reflected trends observed in the in vitro cell model, suggesting that viral interactions may be conserved between simplified and representative airway models.
Overall, this project characterises interactions between IAV and RSV during coinfection and we show that coinfection by IAV and RSV results in formation of a novel class of viral particles. By expanding viral tropism, formation of CVPs may alter viral dissemination within the respiratory tract, potentially impacting disease outcomes for a coinfected individual. Further, by defining a previously unknown source of viral interaction with implications on viral structure, we contribute more widely to the understanding of the properties of IAV and RSV, and their infection biology as a whole
Toward Efficient Organic Photovoltaics: From Formulation and Novel Materials to Device Architectures
Organic photovoltaic (OPV) offer unique advantages such as molecular engineering, flexibility and roll-to-roll manufacturing that can significantly reduce production costs. However, their efficiencies still lag behind inorganic PVs. It has been demonstrated that morphology control and recombination mechanisms play a key role in the efficiency. In this way, methods to enhance the performance by enabling morphology tuneability to further optimise OPVs are needed. To this end, this thesis introduces three novel approaches that can be utilised to improve the efficiency in OPVs.
In the first part of this work, a formulation approach is investigated by examining OPVs in which the morphology is optimised by ternary blends. Particularly, donor polymers P3HT, PTB7 and fullerene acceptors PC71BM and ICBA were systematically characterised. It is shown that different combinations of ternary blends outperformed binary controls. Results demonstrated that depending on the donor material used, the molecular intermixing of the constituents was different, yielding varied impacts on the performance and thus determining whether ternary blends offer a benefit or not.
The second approach reviewed consisted in the study of charge transport in novel materials, specifically non-fullerenes (NFA), hybrid fullerenes and fullerenes. For the first time, electron mobility was probed, which can be a limiting factor of the efficiency. It was demonstrated that NFA realised higher electron mobilities (closer to benchmark PCBM) in contrast to hybrid fullerenes, which yielded low mobilities. It was shown that the synthetic approach utilised to fabricate these compounds and its resulting morphology had a profound impact in their capability to mediate electron transport.
For the third method, device architectures were simulated in the form of multi junction OPVs termed as tandems. In such devices, a current matching between photoactive layers is generally required to maximise the performance. Through advanced modelling, it was shown that devices with unbalanced current matching are dominated by recombination losses of charges in the layer doing most of the absorption. It was demonstrated that changing the transport properties of the layer performing least of the absorption could assist alleviating these losses. It is also shown that different illumination conditions can further reduce the performance in tandem OPVs and that one can mitigate these reductions by suitable materials selection
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