Le travail de cette thèse a consisté à concevoir, réaliser et optimiser un montage expérimental de Polarisation Dynamique Nucléaire multi-échantillons pour des applications biomédicales en Imagerie Spectroscopique par Résonance Magnétique. Ce montage est constitué d'un aimant à fort champ magnétique (3,35T), dans lequel se place un système cryog&nique à bain d'hélium (He4) liquide pompé pouvant atteindre des températures infèrieures à 1,2K. Un ensemble d'inserts permet d'effectuer les différentes étapes du processus PDN dont l'irradiation des échantillons par un champ micro-onde (f=94GHz et P=50mW) et le suivi de leur polarisation par Résonance Magnétique Nucléaire. Ce système permet de polariser jusqu'à trois échantillons, de volume proche de 1mL, à des taux de polarisation de quelques pourcents. Il présente une forte autonomie supérieure à quatre heures, autorisant ainsi la polarisation de molécules à longues constantes de temps de polarisation. La possibilité de disposer quasi-simultanèment, après dissolution, de plusieurs échantillons fortement polarisés ouvre la voie à de nouvelles applications dans le domaine de l'imagerie biomédicale.

The gravity model for international trade is one of the most successful empirical models in trade literature. There is a long tradition to log-linearise the multiplicative model and to estimate the parameters of interest by least squares. But this practice is inappropriate for several reasons. First of all, bilateral trade flows are frequently zero and disregarding countries that do not trade with each other produces biased results. Second, log-linearisation in the presence of heteroscedasticity leads to inconsistent estimates in general. In recent years, the Poisson gravity model along with pseudo maximum likelihood estimation methods have become popular as a way of dealing with such econometric issues as arise when dealing with origin-destination flows. But the standard Poisson model specification is vulnerable to problems of overdispersion and excess zero flows. To overcome these problems, this paper presents zero-inflated extensions of the Poisson and negative binomial specifications as viable alternatives to both the log-linear and the standard Poisson specifications of the gravity model. The performance of the alternative model specifications is assessed on a real world example, where more than half of country-level trade flows are zero. (authors' abstract) / Series: Working Papers in Regional Science

This paper proposes a new panel data structural gravity approach for estimating the trade and welfare effects of Brexit. The suggested Constrained Poisson Pseudo Maximum Likelihood Estimator exhibits some useful properties for trade policy analysis and allows to obtain estimates and confidence intervals which are consistent with structural trade theory. Assuming different counterfactual post-Brexit scenarios, our main findings suggest that UKs (EUs) exports of goods to the EU (UK) are likely to decline within a range between 7.2% and 45.7% (5.9% and 38.2%) six years after the Brexit has taken place. For the UK, the negative trade effects are only partially offset by an increase in domestic goods trade and trade with third countries, inducing a decline in UKs real income between 1.4% and 5.7% under the hard Brexit scenario. The estimated welfare effects for the EU are negligible in magnitude and statistically not different from zero. / Series: Department of Economics Working Paper Series

The dissertation investigates the design of an electronic-waste material recovery facility in the north western precinct of the inner city of Tshwane. It aims to explore the re-configuration of the industrial typology within a contemporary network society, and make apparent it’s changing role and form, influenced by a globalized industrial paradigm that is increasingly decentralized, immaterial and knowledge intensive. It suggests a hybridity of type and process, where value in terms of the local and the material is investigated as an expression of the new industrial ethos of innovation, information access, collaboration and transparency. / Dissertation MArch(Prof)--University of Pretoria 2013 / Architecture / MArch(Prof) / Unrestricted

This dissertation explores the potential of new public landscapes developed in small scale lost, or latent spaces within the urban fabric of Pretoria, in order to change the CBD into a living city that encourages urban regeneration through tactical intervention. The urban voids of Pretoria will be mapped and a site developed using a series of tactical interventions. The exploration of current pop-up trends and guerilla urbanism as a vehicle for urban renewal provides the basis for the phasing process. C13/4/48 / Dissertation ML(Prof)--University of Pretoria, 2012. / Architecture / ML(Prof) / Unrestricted

The purpose of this dissertation was to explore how a landscape architect may help to address environmental decay and the threat of food scarcity that are the results of rapid urban growth. For this urban renewal scheme, it is proposed that the underutilized open spaces within the city are reclaimed and interconnected in order to maximize their potential, forming a continuous landscape network. It is believed that this landscape network needs to function beyond mere beautification in order to be successful and productive. A multifunctional strategy is thus brought forward, as emphasis is placed upon providing for food security and realizing the city’s wasted resources. Along with related economic and ecological advantages, ways in which open space may be more sustainably managed are explored. Acknowledging the sheer lack of municipal funds, community involvement is believed to be the catalyst of this vision. Surrounding neighbourhoods are hence proposed to be the maintainers of their surrounding open spaces, decreasing the monetary pressures on the authorities. Emphasis is placed on ways in which communities may be incorporated through designing for flexibility, pride of ownership and sense of belonging. A new identity that ties in with the original genius of place is ultimately promoted through this meaningful utility parkland. An abandoned stretch of land along the Walker Spruit between Pretoria’s Sunnyside East and Clydesdale suburbs served as a model for testing the hypothesis of a spatially continuous, linear and productive community park. / Dissertation ML(Prof)--University of Pretoria, 2012. / Architecture / Unrestricted

Many urban poor are living lifestyles prescient of a future with little to no accessible fossil fuels, a future lacking easy access to electricity, flowing water, and food security. Scientists such as David Holmgren warn that the rest of society may face a similar scenario. According to the Association for the Study of Peak Oil and Gas (ASPO 2008), the peak of oil discovery happened in the 1960’s. In 1981 the world started using more than what was found in new fields and since then the gap between discovery and production has been ever widening, many countries have already passed their peak, which indicates that a global peak is imminent. This dissertation investigates a new typology for urban living. An area south of Marabastad, in the north-western quadrant of the city of Pretoria is selected as the wasted landscape for testing the hypothesis that a drosscape has the potential to be designed and developed into an agrarian conservancy to support a society in need of sustainable, innovative places. Part One of the dissertation investigates agriculture as a method for returning the site to some utilitarian efficiency. However, landscapes contain the potential to be more than functional tracts of land with no meaning. Thus Part Two of the dissertation investigates the fact that a creative approach to the implementation of city farming in the Steenovenspruit drosscape can ingrain in the modern industrial city a place with which the inhabitants can identify, where form does not only follow function but also enhances and expresses the celebration of man’s working relationship with the land, as well as celebrating the historic traces evident on the landscape. A palimpsest emerges out of the faint residue of past uses, displaying traces of the character the site once had. The dissertation proposes that by capturing the essence of these past layers of productive use and further enriching the palimpsest by introducing traces of farming and gardens, meaning and experiential use of the land will be returned to the people of Marabastad. The dissertation also proposes that through this experiential use the community is once again able to leave traces on the landscape and lift the site out of limbo and once again into the process of place-making, or refounding. A conservancy is proposed for the Steenovenspruit drosscape which combines the concept of palimpsest and the poetic nature of farming across a number of city blocks, connecting Marabastad and the CBD. The conservancy encapsulates a variety of land uses including residential and gathering traces, however the core of the conservancy centres around a historical city block which formed part of the old Pretoria townlands and which morphs once again into productive landscape. / Dissertation ML(Prof)--University of Pretoria, 2012. / Architecture / ML(Prof) / Unrestricted

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