Dissertations / Theses on the topic 'Gaia hypothesis'

Marine aerosols have a large potential to influence the Earth¿s climate through their effects on cloud properties. The CLAW hypothesis goes further, and suggests that marine aerosols formed by the sulphur cycle of the ocean and the atmosphere act as a mechanism for regulating the Earth's climate. This effect is produced through the influence of plankton emissions of sulphur compounds on cloud formation. Phytoplankton produces dimethylsulphide (DMS), a highly volatile sulphur compound. Once in the atmosphere, DMS is oxidized and becomes the main source of natural atmospheric sulphates. These sulphates act as condensation nuclei, particles that are essential for the formation of clouds. Those marine particles in the atmosphere play an important role in the Earth's radiation budget. Indirectly they produce a greater amount of cloud droplets. Higher cloud condensation nuclei imply smaller cloud droplets. The efficiency of smaller droplets in reflecting incident solar radiation is greater, resulting in an increase in cloud albedo, producing a cooling effect on the Earth's surface. To properly study the marine aerosols we need accurate knowledge of the global seawater distribution of the aerosol precursors. Our work focused on the ocean-to-atmosphere emissions of DMS and other biogenic gases that can have an impact on cloud microphysics. During the thesis we updated the monthly global DMS climatology taking advantage of the three-fold increased size and better resolved distribution of the observations available in the DMS database. The emerging patterns found with the previous versions of the database and climatology were explored with the updated version. The statistical relationships between the seasonalities of DMS concentrations and solar radiation doses and chlorophyll a concentrations were here re-examined. Analyses of nine years of satellite data suggested that there is a natural inverse correlation between the spatial cover of low marine clouds and the cloud droplet size, which is related to the presence of small aerosols. This coupled seasonality pushes cloud albedo to contribute higher negative radiative forcing in summer and lower in winter. This relation is disrupted in the marine atmosphere regions heavily impacted by anthropogenic aerosols. Consequently, the potential influence the aerosol precursors have on marine clouds was next analysed over unpolluted and polluted ocean, separately. The 9 years of global satellite data and ocean climatologies were used to derive parameterizations of the production fluxes of secondary aerosols formed by oxidation of DMS and other biogenic organic volatiles. Further, the emission fluxes of biogenic primary organic and sea salt aerosols ejected by wind action on sea surface were also globally studied. Series of weekly estimates of these fluxes were correlated to series of cloud droplet effective radius. The outcome of the statistical analyses indicated that sulphur and organic secondary aerosols might be important in seeding cloud nucleation and droplet activation over mid and high latitude unpolluted oceanic regions. Conversely, primary aerosols (organic and sea salt) showed that, despite contributing to large shares of the marine aerosol mass, they do not seem to be major drivers of the variability of cloud microphysics. Our results provide partial support for the feasibility of the CLAW hypothesis at the seasonal scale. Despite that DMS has drawn much of the attention on the links between marine biota and climate regulation, the implication of other biogenic precursors on cloud formation provides and suggests a wider scope on the formulation of such hypothesis.
Los aerosoles marinos tienen un gran potencial para influir en el clima de la Tierra a través de sus efectos en las propiedades de las nubes. La hipótesis de CLAW va más allá y sugiere que los aerosoles marinos formados por el ciclo del azufre en océanos y atmósfera actúan como un mecanismo para la regulación del clima de la Tierra. Este efecto se produce a través de la influencia de las emisiones de plancton de compuestos de azufre en la formación de nubes. El fitoplancton produce sulfuro de dimetilo (DMS), un compuesto de azufre altamente volátil. Una vez en la atmósfera, el DMS se oxida y se convierte en la principal fuente de sulfatos naturales atmosféricos. Estos sulfatos actúan como núcleos de condensación, partículas esenciales para la formación de nubes. Estas partículas presentes en la atmósfera marina juegan un papel importante en el ciclo radiativo de la Tierra. Indirectamente, producen una mayor cantidad de gotas de las nubes. Mayor número de núcleos de condensación en las nubes implica gotas de nubes más pequeñas. La eficacia de las pequeñas gotas en reflejar la radiación solar incidente es mayor, lo que resulta en un aumento del albedo de las nubes, produciendo un efecto de enfriamiento en la superficie de la Tierra. Para estudiar adecuadamente los aerosoles marinos necesitamos tener un correcto conocimiento de la distribución oceánica global de los precursores de aerosoles. Nuestro trabajo se ha centrado en las emisiones del océano a la atmósfera de DMS y otros gases biogénicos que puede tener un impacto en la microfísica de nubes. Durante la tesis se ha actualizado la climatología mensual global de DMS, aprovechando el aumento en tres veces del número de observaciones y una mejor distribución global de las mismas, en la base de datos de DMS. Los patrones emergentes encontrados con las versiones anteriores de la base de datos y de la climatología se han re-evaluado con la versión actualizada. Las relaciones estadísticas encontradas entre la evolución temporal de las concentraciones de DMS y las dosis de radiación solar y concentraciones de clorofila han sido re-examinadas. Los análisis de nueve años de datos de satélite sugieren que existe una correlación inversa entre la cubierta espacial de nubes marinas bajas y el tamaño de las gotas de nubes, relacionado con la presencia de aerosoles pequeños. Esta estacionalidad acoplada conduce al albedo de las nubes a contribuir a un forzamiento radiativo negativo superior en verano, y más bajo en invierno. Esta relación se interrumpe en las regiones de la atmósfera marina con un alto impacto de los aerosoles antropogénicos. En consecuencia, la posible influencia de los precursores de aerosoles marinos en las nubes se ha analizado en una atmósfera marina limpia y contaminada, por separado. Los 9 años de datos satelitales globales y climatologías oceánicas se han utilizado para derivar las parametrizaciones de los flujos de producción de aerosoles secundarios, formados por la oxidación de DMS, y otros compuestos volátiles orgánicos biogénicos. Además, los flujos de emisiones biogénicas de aerosoles primarios orgánicos y aerosoles de sal marina expulsados por acción del viento sobre la superficie del mar se ha estudiado también a nivel global. Las series semanales de las estimaciones de estos flujos se han correlacionado con las series temporales de los radios de las gotas de nubes. El resultado de los análisis estadísticos ha indicado que el azufre orgánico y otros aerosoles secundarios pueden ser importantes en la nucleación y la activación de sus gotas sobre las regiones oceánicas no contaminadas en latitudes medias y altas. Por el contrario, aerosoles primarios (orgánico y la sal del mar) han mostrado que, a pesar de que contribuyen a una gran proporción de la masa de aerosol marino, no parecen ser los principales motores de la variabilidad de la microfísica de nubes. Nuestros resultados proporcionan un apoyo parcial a la viabilidad de la hipótesis de CLAW a escala estacional. A pesar de que el DMS ha llamado mucho la atención sobre los vínculos entre la biota marina y la regulación del clima, la implicación de otros precursores biogénicos en la formación de nubes ofrece y sugiere un mayor alcance en la formulación de esta hipótesis.

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To build a sustainable future is humanity's great mission in a world characterized by deep social inequalities and environmental changes. Saint-Exupéry said: "The future is not a place where we are going, but a place we are creating. The path to it is not found but built and the act of doing so transforms both the creator and his destiny". Man has the competence to begin its construction, however, must transform himself to make it happen. The purpose of this thesis, elaborated in the form of an essay, is to explore possibilities to build this auspicious future, committed to future generations without under valuating the forces that defend the continuity of our way of life. Three fundamental questions ground this work: where do we come from, what are we and where are we going to, that are structured in three human journeys: past, present and future. In the first we find the lessons and learnings of the evolution process, essential for understanding the present and planning the future. The second journey depicts both the human capacity to transform the planet, adapting it to its needs and desires, as the resistance of those who stand against the continuity of the capitalist world system and defy humanity to metamorphose into a meta system rich in possibilities or to sink in a generalized insignificance. On the last journey, the future, it is approached a vision of the complexity of the world and the human psychic nature, which feed discussions about the individual and collective transformations that must occur to generate a desired future. Man has before him uncertainties, bifurcations and dilemmas, which can result in catastrophe or well-being. The social and climatic deterioration, perverse by itself, can also be good, taking the humanity off passivity, leading it to an overall transformation. A plausible path is a new civilizing context grounded in holistic and ecological educational reform, and structured through a truly global society: the World-Society. There is a great challenge ahead. What will happen, however, only the future will show
Construir um futuro sustentável é a grande missão da humanidade em um mundo assinalado por desigualdades sociais enraizadas e mudanças ambientais profundas. Saint-Exupéry disse: “O futuro não é um lugar para onde estamos indo, mas um lugar que estamos criando. O caminho para ele não é encontrado, mas construído e o ato de fazê-lo transforma tanto o realizador quando o destino”. O homem tem competência para iniciar sua construção, mas deverá se transformar para concretizá-lo. Com esta tese, elaborada na forma de um ensaio, exploram-se possibilidades para se construir esse futuro auspicioso, comprometido com as gerações futuras, sem desprezar as forças que defendem a continuidade do nosso modo de vida. Três questões fundamentais a embasam: de onde viemos, quem somos e para onde vamos, que na tese são abordadas na forma de jornadas humanas: passada, presente e futura. Da primeira extraem-se as lições e aprendizados da história evolutiva, imprescindíveis para se compreender o presente e planejar o futuro. A segunda jornada retrata tanto as profundas transformações que o homem produziu no planeta, adequando-o às suas necessidades e desejos, como as reações dos se posicionam contra a continuidade do sistema mundo capitalista e convidam a humanidade a metamorfosear-se em um metassistema rico em possibilidades ou sucumbir no abismo da insignificância generalizada. Na última jornada, a futura, são abordados conhecimentos sobre a complexidade do mundo e sobre a natureza psíquica humana, que alimentam discussões sobre as transformações individuais e coletivas que devem ocorrer para que se possa engendrar um futuro desejado. O homem tem diante de si incertezas, bifurcações e dilemas, que podem conduzi-lo à catástrofe ou ao bem-estar. A deterioração social e climática, perversa por si, pode ser também um bem e tirar a humanidade da passividade, conduzindo a uma mudança abrangente. Um caminho plausível é um novo contexto civilizatório embasado em uma reforma educacional holística e ecológica, e estruturado através de uma sociedade realmente global: uma Sociedade-Mundo. Há um grande desafio à frente. O que acontecerá, entretanto, só o futuro dirá

Cette thèse est une enquête d'histoire et de philosophie des sciences sur l'hypothèse Gaïa (HG) proposée par Lovelock et Margulis dans les années 1970. L'examen historique de l'élaboration d'HG et de sa très riche réception dans diverses disciplines scientifiques (climatologie, biogéochimie, géochimie, biologie de l'évolution, écologie et sciences de la complexité) et au sein des mouvements environnementalistes nous conduit à montrer qu'une ambiguïté majeure sur le statut d'HG grève la littérature : qu'est-ce qu'HG ? Nous montrons qu'HG a été considérée tantôt comme une hypothèse, tantôt comme une théorie, tantôt comme un programme de recherche, tantôt comme une philosophie de la nature. Chacune de ces lectures est ensuite examinée. Nous proposons une caractérisation épistémologique et historique d'HG montrant qu'HG ne doit pas être interprétée comme une hypothèse devant être confrontée de manière directe aux faits, mais comme une théorie élaborée avec des modèles. Nous clarifions alors le rôle et le statut méthodologique des modèles et théories d'HG ainsi que les concepts et hypothèses fondamentales qui les sous-tendent. La reconnaissance de Gaïa comme un système constitué des vivants et de l'environnement avec lequel ils interagissent a été l'origine de la constitution d'un nouveau programme de recherche: les sciences du système Terre. Nous proposons une histoire et une caractérisation de ce programme, repérons les déplacements philosophiques qu'il a opérés à propos des concepts de vie, d'environnement et de nature puis analysons les liens entre les conceptions que Lovelock a de Gaïa et les prescriptions environnementales qu'il a prononcées au nom de Gaïa
The Gaia hypothesis (GH) proposed in the 1970's by Lovelock and Margulis is here analyzed from a history and philosophy of science perspective. The historical analysis of GH's elaboration and rich reception across various disciplines (climatology, biogeochemistry, geochemistry, evolutionary biology, ecology and complexity sciences) and within environmentalist movements leads me to argue that a major ambiguity plagues the relevant literatures: what is GH? I show that GH has been considered as a hypothesis, as a theory, as a research program, or as a philosophy of nature. Each of these interpretations is then analyzed. An epistemological and historical characterisation of GH shows that GH should not be interpreted as a hypothesis which ought to be confronted directly to empirical facts, but as a theory elaborated with models. I elucidate the methodological role and status of GH's models and theories before clarifying the concepts and expliciting the fundamental hypotheses underlying these models and theories. The recognition of Gaia as a system constituted of living organisms and the environment with which they internet led to the constitution of a new research program: the Earth system sciences. I offer a history and a characterisation of this research program, specify the philosophical shifts it brought about concepts such as life, the environment and nature and I analyze the relationships between Lovelock's conceptions of Gaia and the environmental prescriptions he pronounced in the name of Gaia

Obesity is a significant public health concern, with implications for the health and well being of millions of people in the United States and world. The purpose of this thesis is to explore the relationship between obesity, segment biomechanics in the form of joint stress and restricted range of motion, and cardiorespiratory fitness. In three studies, anatomical modeling using three dimensional infrared motion capture system was used to calculate joint stresses and range of motion limitations. The results are applied to better understand the impact that obesity has on biomechanics, taking into consideration factors of fitness and fatigue, during walking and common rehabilitation exercises. The first study compared the biomechanical differences between ten obese and ten normal weight adults while performing squat and lunge exercises and found significant increases in lower limb moments in obese females. Increased moments suggest that obese individuals experience higher biomechanical stress than normal weight individuals and may have less flexibility in selecting movement strategies while performing basic rehabilitation exercises. The second study examined how walking, a commonly prescribed exercise to combat obesity, may impact an obese individual's joint biomechanics. While the results of this study, comparing joint stress in ten obese and ten normal weight females, did not observe significant differences between the obese and normal weight groups, stronger relationships were present between moments and VO2 max, rather than BMI, suggesting the importance of fitness in context of developing walking programs. The final study explicitly addressed the relationship between obesity, fitness and biomechanics. Walking and jogging biomechanics was reported in 30 boys and girls, aged 8-11, before and after a fatigue protocol. Hip and knee moments were moderately associated with cardiorespiratory fitness and showed significant increase after cardiorespiratory fatigue. Including measures of adiposity and strength improved the associations between fitness and moments. This thesis concludes that the relationship between biomechanics and obesity, observed in adults and children, should be understood in the larger framework of the reverse causation hypothesis. The reverse causation hypothesis describes obesity as a positive feedback loop, in which certain factors are related to obesity in a bi-directional manner: both causing, but also amplified by, the presence of excess adipose tissue. While further study is required to clarify these relationships, these associations may have implications for participation in physical activities and long-term effects on the musculoskeletal system, thus illustrating the positive feedback loop of the reverse causation hypothesis.

In der Literatur wird von einem kontinuierlichen, weltweiten Anstieg der Inzidenz des Typ 1 Diabetes mellitus unter Kindern und jungen Erwachsenen, insbesondere in der Altersgruppe der unter 20-Jährigen, berichtet. Die multizentrische Studie EURODIAB untersuchte in den Jahren 1989-2003 die Inzidenz des Typ 1 Diabetes in 17 europäischen Ländern und bestätigte mit deren Ergebnissen diese weltweite Tendenz. Die Akzelerator Hypothese von Wilkin aus dem Jahr 2001 sieht die Ursache hierfür durch einen übermäßigen Gewichtsanstieg bedingt, da auch die Inzidenz übergewichtiger Kinder innerhalb der letzten Jahre zugenommen hat. Demnach sei die Anzahl Betroffener insgesamt gleich, jedoch in jungen Jahren (bis 15 Jahre) erhöht. Folglich sei Übergewicht mit Insulinresistenz ein Triggerfaktor für eine raschere Progression der Erkrankung und würde zu einem vorzeitigen klinischen Ausbruch des Typ-1-Diabetes beitragen. Im Rahmen dieser Dissertation verglichen wir anthropometrische Geburtsdaten von 1.117 Kindern mit Typ 1 Diabetes mellitus, deren Erstmanifestation zwischen 1988 und April 2013 lag, mit einer Kontrollgruppe, die bezüglich Geschlecht, Alter und Schwangerschaftswoche angepasst wurde (n=54.344). Des Weiteren wurden die Kinder mit Diabetes entsprechend ihres Alters bei Manifestation bestimmten Gruppen zugeordnet: G1:0-4,9 Jahre; G2:5 9,9 Jahre; G3:10-20 Jahre. Diese Unterteilung wurde vorgenommen, um festzustellen, ob Kinder, bei denen eine Diabetes Erkrankung früher klinisch manifest wird, zur Geburt bzw. zum Zeitpunkt der Diagnosestellung einen höheren Gewichts SDS aufweisen als Kinder, welche erst in späteren Jahren betroffen sind. Zusätzlich wurden Verlaufsdaten des BMI SDS von 540 Studienkindern vor, zu und nach Manifestation ermittelt und mit einer gesunden Kontrollpopulation (n=134.249) verglichen. Hierbei zeigten Kinder und Jugendliche mit Typ 1 Diabetes im Vergleich zu Stoffwechselgesunden signifikant erhöhte Geburtsgewicht SDS Werte. Es konnte jedoch keine signifikante Abhängigkeit zwischen einer vorzeitigen Diabetes-Manifestation und einem erhöhten Geburtsgewichts bzw. einem erhöhten BMI SDS zum Zeitpunkt der Manifestation gezeigt werden. Ebenso blieb der laut Wilkin zu erwartende Gewichtsanstieg 4 Jahre vor Ausbruch der Erkrankung aus. Kinder mit Diabetes verlieren, wie erwartet, zur Manifestation an Gewicht und erreichen nach ungefähr einem Jahr ihr Ausgangsgewicht. In den Folgejahren sind Kinder mit Typ 1 Diabetes signifikant schwerer als die Kontrollgruppe. Aufgrund dieser Ergebnisse müssen wir die von Wilkin postulierte „Akzelerator Hypothese“ widerlegen.

Hipóteses precisas são características naturais das teorias econômicas de determinação do valor ou preço de ativos financeiros. Nessas teorias, a precisão das hipóteses assume a forma do conceito de equilíbrio ou da não arbitragem. Esse último possui um papel fundamental nas teorias de finanças. Sob certas condições, o Teorema Fundamental do Apreçamento de Ativos estabelece um sistema único e coerente para valorização dos ativos em mercados não arbitrados, valendo-se para tal das formulações para processos de martingal. A análise da distribuição estatística desses ativos financeiros ajuda no entendimento de como os participantes se comportam nos mercados, gerando assim as condições para se arbitrar. Nesse sentido, a tese defendida é a de que o estudo da hipótese de não arbitragem possui contrapartida científica, tanto do lado teórico quanto do empírico. Utilizando-se do modelo estocástico Variância Gama para os preços dos ativos, o teste Bayesiano FBST é implementado com o intuito de se verificar a existência da arbitragem nos mercados, potencialmente expressa nos parâmetros destas densidades. Especificamente, a distribuição do Índice Bovespa é investigada, com os parâmetros risco-neutros sendo estimados baseandose nas opções negociadas no Segmento de Ações e no Segmento de Derivativos da BM&FBovespa. Os resultados aparentam indicar diferenças estatísticas significantes em alguns períodos de tempo. Até que ponto esta evidência é a expressão de uma arbitragem perene nesses mercados ainda é uma questão em aberto.
Precise hypotheses are natural characteristics of the economic theories for determining the value or prices of financial assets. Within these theories the precision is expressed in terms of equilibrium and non-arbitrage hypotheses. The former concept plays an essential role in the theories of finance. Under certain conditions, the Fundamental Theorem of Asset Pricing establishes a coherent and unique asset pricing framework in non-arbitraged markets, grounded on martingales processes. Accordingly, the analysis of the statistical distributions of financial assets can assist in understanding how participants behave in the markets, and may or may not engender conditions to arbitrage. On this regard, the dissertation proposes that the study of non-arbitrage hypothesis has a scientific counterparty, theoretically and empirically. Using a variance gamma stochastic model for prices, the Bayesian test FBST is conducted to verify the presence of arbitrage potentially incorporated on these densities parameters. Specifically, the Bovespa Index distribution is investigated, with risk neutral parameters estimated based on options traded in the Equities Segment and the Derivatives Segment at the BM&FBovespa Exchange. Results seem to indicate significant statistical differences at some periods of time. To what extent this evidence is actually the expression of a perennial arbitrage between the markets still is an open question.

Indoor localization remains an open problem in geolocation research, and once this is solved the localization enables counting and tracking of building occupants. This information is vital in an emergency, enables occupancy-optimized heating or cooling, and assists smart buildings in tailoring services for occupants. Unfortunately, two prevalent technologies---GPS and cellular-based positioning---perform poorly indoors due to attenuation and multipath from the building. To address this issue, the research community devised many alternatives for indoor localization (e.g., beacons, RFID tags, Wi-Fi fingerprinting, and UWB to cite just a few examples). A drawback with most is the requirement for those being located to carry a properly-configured device at all times. An alternative based on computer vision techniques poses significant privacy concerns due to cameras recording building occupants. By contrast, ILoViT research makes novel use of accelerometers already present in some buildings. These sensors were originally intended to monitor structural health or to study structural dynamics. The key idea is that when a person's footstep-generated floor vibrations can be detected and located then it becomes possible to locate persons moving within a building. Vibration propagation in buildings has complexities not encountered by acoustic or radio wave propagation in air; thus, conventional localization algorithms are inadequate. ILoVIT algorithms account for these conditions and have been demonstrated in a public building to provide sub-meter accuracy. Localization provides the foundation for counting and tracking, but providing these additional capabilities confronts new challenges. In particular, how does one determine the correct association of footsteps to the person making them? The ILoViT research created two methods for solving the data association problem. One method only provides occupancy counting but has modest, polynomial time complexity. The other method draws inspiration from prior work in the radar community on the multi-target tracking problem, specifically drawing from the multiple hypothesis tracking strategy. This dissertation research makes new enhancements to this tracking strategy to account for human gait and characteristics of footstep-derived multilateration. The Virginia Polytechnic Institute and State University's College of Engineering recognized this dissertation research with the Paul E. Torgersen Graduate Student Research Excellence Award.
Ph. D.

The multi-target tracking problem essentially involves the recursive joint estimation of the state of unknown and time-varying number of targets present in a tracking scene, given a series of observations. This problem becomes more challenging because the sequence of observations is noisy and can become corrupted due to miss-detections and false alarms/clutter. Additionally, the detected observations are indistinguishable from clutter. Furthermore, whether the target(s) of interest are point or extended (in terms of spatial extent) poses even more technical challenges. An approach known as random finite sets provides an elegant and rigorous framework for the handling of the multi-target tracking problem. With a random finite sets formulation, both the multi-target states and multi-target observations are modelled as finite set valued random variables, that is, random variables which are random in both the number of elements and the values of the elements themselves. Furthermore, compared to other approaches, the random finite sets approach possesses a desirable characteristic of being free of explicit data association prior to tracking. In addition, a framework is available for dealing with random finite sets and is known as finite sets statistics. In this thesis, advanced signal processing techniques are employed to provide enhancements to and develop new random finite sets based multi-target tracking algorithms for the tracking of both point and extended targets with the aim to improve tracking performance in cluttered environments. To this end, firstly, a new and efficient Kalman-gain aided sequential Monte Carlo probability hypothesis density (KG-SMC-PHD) filter and a cardinalised particle probability hypothesis density (KG-SMC-CPHD) filter are proposed. These filters employ the Kalman- gain approach during weight update to correct predicted particle states by minimising the mean square error between the estimated measurement and the actual measurement received at a given time in order to arrive at a more accurate posterior. This technique identifies and selects those particles belonging to a particular target from a given PHD for state correction during weight computation. The proposed SMC-CPHD filter provides a better estimate of the number of targets. Besides the improved tracking accuracy, fewer particles are required in the proposed approach. Simulation results confirm the improved tracking performance when evaluated with different measures. Secondly, the KG-SMC-(C)PHD filters are particle filter (PF) based and as with PFs, they require a process known as resampling to avoid the problem of degeneracy. This thesis proposes a new resampling scheme to address a problem with the systematic resampling method which causes a high tendency of resampling very low weight particles especially when a large number of resampled particles are required; which in turn affect state estimation. Thirdly, the KG-SMC-(C)PHD filters proposed in this thesis perform filtering and not tracking , that is, they provide only point estimates of target states but do not provide connected estimates of target trajectories from one time step to the next. A new post processing step using game theory as a solution to this filtering - tracking problem is proposed. This approach was named the GTDA method. This method was employed in the KG-SMC-(C)PHD filter as a post processing technique and was evaluated using both simulated and real data obtained using the NI-USRP software defined radio platform in a passive bi-static radar system. Lastly, a new technique for the joint tracking and labelling of multiple extended targets is proposed. To achieve multiple extended target tracking using this technique, models for the target measurement rate, kinematic component and target extension are defined and jointly propagated in time under the generalised labelled multi-Bernoulli (GLMB) filter framework. The GLMB filter is a random finite sets-based filter. In particular, a Poisson mixture variational Bayesian (PMVB) model is developed to simultaneously estimate the measurement rate of multiple extended targets and extended target extension was modelled using B-splines. The proposed method was evaluated with various performance metrics in order to demonstrate its effectiveness in tracking multiple extended targets.

abstract: This thesis examines the use of the earth goddess figure in John Varley's Gaean Trilogy (1979-1984). In the figure of Gaea (Varley's alien goddess villain), the reader is presented with a host of popular culture feminine archetypes with connotations connected to the long-standing tradition of associating femininity and materiality, and Varley's literary examination, operating through the exaggeration of these archetypes, displays their essential flaws. The ultimate antagonistic functions of these archetypal figures, relative to the human characters occupying the world underwritten by them, suggests that Varley uses such figural archetypes to deconstruct, via their varied failures, both the archetypes themselves and the evocative symbolic contexts associated with them, therein demonstrating their inherent limitations and providing a cautionary tale that highlights the fallibility of projective archetypal construction-even seemingly positive ones. By examining these archetypes as performances of gender, the thesis illustrates Varley's integration, at the end of the 1970's, of second-wave feminist theoretical ideals into science fiction (a genre with a long history dedicated to the experimental examination of all social typology) initially sets up and then subsequently breaks down the archetypal villain, thus pursuing a political dimension as well. The narrative experiment in typology promotes a turning away from the ancient symbolic associations of femininity to explore a new kind of goddess, one not reliant on pre-existing archetypes but one more attuned to the emergence of "gender" itself as a construct used to define the feminine itself.
Dissertation/Thesis
M.A. English 2012

Text in Afrikaans
This research deals with the artist's contribution towards the current process of ecological purification through which mankind's attention are brought to the destructive maintenance of the planet. The alchemical artist uses purification as a means to make social comments on the lifestyle of the contemporary person, through the aestheticism of objects. The different manifestations of ceo-feministic thought within environmental activism are explored to make the reader aware of the diversity of ceo-feministic thought. Eco-feminism in general, tries to promote the importance of the earth as a life supporting system by respecting her needs, cycles, energies and eco-systems. As a result of this process, the public are invited to take part in recycle-art through which a change in attitude towards purification and the survival of the planet, are being accomplished
Art History, Visual Arts & Musicology
M.A. (Visual Arts)

Increased tripping frequency and the associated risk of falling is an international health problem in older adult populations. The average distance between the toe and the ground surface is approximately 1.3cm at the event where the toe reaches a minimum clearance height during leg swing of walking (Winter 1991, Begg et al. 2007). Little is known about how the lower limbs are controlled and coordinated to perform safe (risk-averse) toe-to-ground clearance. This thesis investigates the kinematic interactions of the lower limbs during unperturbed walking with a specific emphasis on examining the cooperative interactions of the stance and swing limb.