Master of Arts / Department of Economics / Peri da Silva / Rose (2004) reports that GATT/WTO membership produces no positive effects on international trade. This is a remarkable determination given the widespread belief in academic and policy circles that the WTO successfully promotes trade flows by reducing barriers to international trade. Empirical literature measuring the GATT/WTO trade effects has produced notably diverse results since Rose's (2004) paper. This report introduces the history of GATT/WTO and describes the GATT/WTO’s aim to promote trade using multilateral rounds of trade negotiations. It confirms that the efforts toward trade liberalization made by the GATT/WTO are partially achieved by tariff reductions and other trade obligations. In discussing the literature related to Rose’s surprising results, we argue that the gravity model employed by Rose (2004) is not theoretically sound since it omits multilateral resistance terms and fails to capture unobserved bilateral heterogeneity. However, we find that even an accurate specification gravity model that controls multilateral resistance, unobserved bilateral heterogeneity, and individual regional trade agreement effect cannot fully account for Rose’s GATT/WTO trade effects findings. The present report suggests that a new approach, specifically the nonparametric method used by Chang and Lee (2011), may offer sound guidance for future research attempting to understand Rose’s mysterious findings.

Doctor of Philosophy / Department of Agricultural Economics / Glynn Tonsor / Few things facing the U.S. meat industry in recent years have garnered more attention of economic researchers than food safety events, policies, and mitigation efforts. This dissertation has two main essays and themes focusing on both domestic and international food safety issues. Contributing new insights to this situation, the impacts of FSIS (Food Safety Inspection Service) recalls on consumer meat demand in the United States are estimated by a series of Rotterdam models in the first study using monthly grocery-scanner data. Multiple model specifications are employed to further assess effects across meat products and geographic regions. Recall variables are constructed separately as beef E. coli recall, beef non-E. coli recall, pork recall, and poultry recall variables to facilitate finer assessment of demand impacts. Results suggest beef E. coli recalls significantly reduce the demand for ground beef contemporaneously among most, but not all, regions in the United States. The ultimate finding of food safety effects neither being fully homogeneous nor entirely heterogeneous warrants appreciation. In order to protect domestic consumers and meat industries from potential food safety hazards, some member countries of the WTO implement sanitary and phytosanitary (SPS) measures as non-tariff barriers. The second study focuses on investigating the determinants of red meat trade patterns and associated impacts of SPS regulations. This analysis uses multiple product-level gravity equation models and PPML (Poisson Pesudo Maximum-likelihood estimators to overcome sample selection bias and heteroscedasticity and examine the trade relationship among other factors. Results indicate that, trade values of frozen beef and pork are significantly reduced by the implementation of SPS measures. Also, the spillover effects across meat products on trade were detected which provides essential information to the meat industry, policy makers, and trade representatives.

This thesis presents searches for evidence for Weakly Interacting Massive Particles (WIMPs) and Extra Dimensions in proton-proton collisions recorded by the ATLAS experiment at the CERN Large Hadron Collider (LHC). The WIMP is one of the main candidates to constitute the particle content of Dark Matter. Extra Dimensions are introduced in several theories in order to explain the apparent weakness of gravity when compared to the other interactions in Nature. Theories with WIMPs as well as Extra Dimensions can manifest themselves at the LHC, with experimental signatures characterized by an energetic hadronic jet associated with large missing momentum. These signatures are known as monojet signatures, and are investigated in this thesis.  The first analysis is performed using L = 20.3 fb-1 of proton-proton collisions at √s = 8 TeV recorded in the ATLAS Run 1. The second analysis is performed using L = 3.2 fb-1 of proton-proton collisions at √s = 13 TeV recorded in the ATLAS Run 2. No significant excess over the expected background is found in either of the analyses. New exclusion limits are set at 95% confidence level on Dark Matter particle production. New limits are also set on graviton production in the so-called ADD scenario with Extra Dimensions.

The aim of the thesis is to introduce the current economic situation of Italy, is macroeconomical characteristics and features. Gravitz model of international trade is introduced here and applied to analyse trade relations of Italy with its major business partners. Recommendations and ways to improve its trade balance by increasing exports are presented in the thesis.

Recently it has been shown that N = 4 super Yang-Mills theory is integrable in the planar limit. Past arguments suggest the integrability is only present in the planar limit. However, this conclusion was shown to be incorrect. Two speci c classes of operators were studied in the O(N) sector. The rst were labelled by Young diagrams having two long columns. The second were labelled by Young diagrams having two long rows. This result was then generalized to p long rows or columns with p xed to be O(1) as N ! 1. For this case, the non-planar limit was found to be integrable. In this dissertation, we extend this work by considering p to be O(N). We have calculated the dilation operator for the case with two impurities.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. March 2013. / In the past decade, the gauge/gravity duality has been extensively explored in the large N limit. In particular, the spectrum of anomalous dimensions have been compared with the energy spectrum of the dual string theory showing remarkable agreement. In this limit, for operators with a bare dimension of order 1, planar diagrams give the leading contribution to the anomalous dimension. To obtain the anomalous dimensions, one needs to diagonalize the dilatation operator. One of the methods used to accomplish this is integrability. This allows an exact computation of the spectrum of the anomalous dimensions. There is by now a great deal of evidence that N = 4 supersymmetric Yang-Mills (SYM) theory and N = 6 superconformal Chern Simons (ABJ(M)) theory are integrable in the planar limit. In this thesis we probe the gauge gravity duality at finite N using novel tools developed from the representation theory of symmetric and unitary groups. We start by studying the action of the nonplanar dilatation operator of N = 4 SYM theory and ABJ(M) theory. The gauge invariant operators we consider are the restricted Schur polynomials. In the case of N = 4 SYM theory, we obtain the spectrum of the anomalous dimension beyond the SU(2) sector at one loop, and in the SU(2) sector at two loops. In both cases, we obtain the spectrum at arbitrary (finite) N. We then obtain the spectrum of anomalous dimensions in the SU(2) sector of ABJ(M) theory at two loops. The class of gauge invariant operators we consider have classical dimension of order O(N). In both theories, the spectrum of the anomalous dimensions reduces to a set of decoupled harmonic oscillators at large N. This indicates, for the first time, that N = 4 SYM theory and ABJ(M) theory exhibit nonplanar integrability. We expect to recover non-perturbative quantum gravity effects, from the gauge/gravity duality, when N is finite. The non-planar integrability we discover here may play an important role in finite N studies of the gauge/gravity duality, and hence may play an important role in understanding non-perturbative string stringy physics. In addition, we study various classes of correlators in ABJ(M) theory. In this context, we derive extremal n-point correlators in ABJ(M) theory and we probe the giant graviton dynamics in these theories.

A dissertation submitted to the University of the Witwatersrand, Faculty of Science in ful lment of the academic requirements of the degree of Master of Science. Johannesburg, 2015. / The gauge/gravity correspondence is a conjectured exact duality between quantum eld theories and theories of quantum gravity. A very simple gauge/string duality, claims an equivalence between the Gaussian matrix model and the topological A-model string theory on P1. In this dissertation we study this duality, proposing concrete operators in the matrix model that are dual to gravitational descendants of the puncture operator of the topological string theory. We test our proposal by showing that a large number of matrix model correlators are in complete agreement with correlators in the dual topological string theory. Contact term interactions, as proposed by Gopakumar and Pius, play an interesting and non-trivial role in the duality.

Le désir de comprendre l'origine de la Terre, son évolution et sa composition, le futur de notre planète et les événements géologiques comme les séismes et les désastres qu'ils provoquent, ainsi que la curiosité de l'esprit humain font que les chercheurs étudient l'évolution tectonique et la structure actuelle de la Terre. Entre les paramètres clé pour une meilleure compréhension se trouvent la profondeur de la limite croûte-manteau (Moho) et celle de la limite entre la lithosphère et l'asthénosphère (LAB). Le but de cette thèse était de modéliser la limite lithosphère-asthénosphère (LAB) et l'épaisseur crustale sous l'Alborz central, le block sud-caspien et les régions environnantes. Dans cette étude, nous utilisions une méthode d'imagerie de la lithosphère, basée sur l'interprétation de données gravimétriques et de la topographie en équilibre isostatique local. Nous appliquons des algorithmes 1D et 2D de modélisation avant de présenter un nouvel algorithme d'inversion 3D. Nous présentons d'abord une inversion conjointe 1D de données de géoïde et de topographie. Le second pas est la modélisation 2D le long de trois profils par l'interprétation conjointe de géoïde, gravité (air libre et Bouguer), de topographie et de flux de chaleur à la surface. Finalement, nous performons une inversion 3D conjointe de données de géoïde, gravité (air libre) et de topographie. L'application des trois différentes méthodes à la région d'étude nous donne comme résultats principaux une croûte épaisse sous la chaine d'Alborz et sous l'Apsheron-Balkan Sill à la limite septentrionale du bassin sud-caspien. Des fortes variations de l'épaisseur de la lithosphère ont été obtenues, où la lithosphère la plus mince est localisée sous l'Iran central et NW, surtout dans des régions de volcanisme Cénozoïque. Les régions d'épaisseur maximale de la lithosphère se trouvent sous l'Apsheron-Balkan Sill, indiquant en combinaison avec un épaississement parallèle de la croûte une subduction de la lithosphère sud-caspienne vers le nord sous la lithosphère eurasienne. / The wish to understand the Earth's origin, evolution and composition, curiosity of the human to comprehend our planet's future evolution plus the geological needs compel researchers to investigate tectonic evolution and their present day structure and behavior. Some key parameters to better understand these subjects are depth of the Moho (the boundary between crust and mantle) and of the lithosphere-asthenosphere boundary (LAB). The targeted area of this research includes the Alborz Mountains in northern Iran and the South Caspian Basin. The Alborz Mountains separate the South Caspian Basin from Central Iran. For our research, the definition of the LAB is an isotherm and we try to calculate the temperature distribution in the lithosphere. We also consider local isostasy to be valid for our modeling. Gravity, geoid, topography and surface heat flow data are used in this research to model the Moho and LAB discontinuities. Potential field data are sensitive to the lateral density variations which happen across these two boundaries but at different depth. In this research 1D, 2D and 3D modeling has been conducted in our targeted area. In 1D modeling, our data are topography and geoid undulations. The method is a 1D inversion based on a two-layered model comprising crust and lithospheric mantle. Using gravity, geoid, topography and surface heat flow data, we have modeled 2D distributions of the density and temperature in the lithosphere along three profiles crossing Iran in SW-NE direction from the Arabian foreland in the SW to the South Caspian Basin and the Turan Platform to the NE. Finally, a 3D algorithm has been developed and tested to obtain the density structure of the lithosphere from joint inversion of free air gravity, geoid and topography data based on a Bayesian approach with Gaussian probability density function. The algorithm delivers the crustal and lithospheric thicknesses and the average crustal density. The results show crustal root under the Alborz Mountains and a thin crust under the southernmost South Caspian Basin thickening northward until the Apsheron-Balkan Sill. Regarding LAB, the results show thick lithosphere under the South Caspian Basin compared to thin lithosphere of Central Iran.

Em função da rapidez e precisão na obtenção de coordenadas, o Global Positioning System (GPS) revolucionou o posicionamento espacial. Entretanto, a maior necessidade em aplicações nas áreas de Geodésia, Geofísica e Engenharia, em termos de altitude, é voltada para a altitude ortométrica e não para a elipsoidal (determinada por GPS). Um modelo de ondulação geoidal mais acurado possibilitaria tranformar altitudes elipsoidais em ortométricas, mantendo o mesmo nível de precisão da determinação GPS. Neste trabalho foram gerados modelos geoidais gravimétricos para o Brasil, GEOIDE2005 e STOKES2005, por meio da técnica 'remover-calcular-repor' em conjunto com a modificação do núcleo da integral de Stokes proposta por Featherstone, no caso do cálculo por FFT, e a proposta por Vanicek e Kleusberg, para o cálculo por integração numérica. As informações gravimétricas utilizadas no cálculo, provenientes de diversas instituições brasileiras e sul-americanas, foram compiladas, validadas e homogeneizadas de modo a gerar uma malha de 10' x 10' de anomalias médias de gravidade de Helmert, em continente, e ar-livre, nas áreas oceânicas. A contribuição dos longos comprimentos de onda do geóide, relativa à área externa à calota de integração, é fornecida por um modelo de geopotencial. A escolha desse modelo foi feita a partir de comparações de diferentes modelos de geopotencial para identificar o que melhor se ajusta ao país. O modelo digital de terreno foi selecionado a partir de estudos detalhados e foi utilizado para gerar valores de altitudes médias, reconstituir anomalias Bouguer em Helmert, calcular correção de terreno e efeito indireto. Foram organizadas e analisadas informações sobre estações que possuíam altitude elipsoidal, determinada por levantamentos GPS, e altitude ortométrica, obtidas por meio de nivelamento geométrico. A diferença entre essas duas altitudes forneceu as ondulações geoidais utilizadas para avaliação dos modelos de geopotencial e dos modelos geoidais aqui apresentados. Ao final, são relacionados os resultados das comparações, relatadas conclusões, levantadas as perspectivas futuras e sugeridas recomendações para futuros trabalhos. / The Global Positoning System (GPS) generated a revolutionon on coordinates acquisition, considering quickness and precision. However, the major need in Geodesy, Geophysics and Engineering areas, regarding heights, is directed to orthometric height, not to ellipsoidal (determined by GPS). A more accurate geoid undulation model would allow the transformation of ellipsoidal to orthometric heights, keeping the same precision level of GPS determinations. This work generated gravity geoid models to Brasil, GEOIDE2005 and STOKES2005, using the “remove-restore" technique together with the modification of Stokes integral kernel proposed by Featherstone, in FFT computation, and the Vanicek and Kleusberg proposal, in numerical integration computation. The gravimetric informations used in the computations, from several Brazilian and South American organizations, were compiled, validated and homogenized to generate a 10’x 10’Helmert mean gravity grid, on terrestrial areas, and free-air, on ocean. The geoid long wavelength contribution, related to integration cap’s external area, is provided by a geopotential model. The choice of this model was done from comparisons of different geopotential models in order to identify the one that best fits to the country. The digital terrain model was selected from detailed studies and was used to generate mean height values, reconstitute Helmert anomalies from Bouguer, compute terrain correction and indirect effect. Informations about stations with ellipsoidal height, determined by GPS surveys, and orthometric height, obtained by spirit levelling,, were organized and analyzed. The differences between these two heights provided the geoid undulations used to evaluate geopotential models and geoid models presented here. At the end, the results from comparisons and conclusions are informed, future perspectives are raised and recommendations are suggested.

A madeira tem aplicações já difundidas em diversos setores, no entanto, muitas vezes é utilizada sem o conhecimento de suas propriedades. A caracterização de espécies de madeira consiste em determinar suas propriedades físicas, de resistência e rigidez através de ensaios normalizados. O inconveniente de grande parte desses ensaios é a utilização de equipamentos de alto custo e grande porte, disponíveis apenas em centros de pesquisa. Porém, o ensaio de densidade aparente é de fácil determinação por utilizar equipamentos simples na sua execução. Sendo assim, neste trabalho são determinadas as correlações entre a densidade aparente e as propriedades físicas, de resistência e de rigidez da madeira, de quarenta espécies nativas brasileiras, do grupo dicotiledôneas. Através de análise estatística, foram obtidas expressões matemáticas que permitem estimar, a partir da densidade aparente, grande parte das propriedades de resistência e rigidez da madeira. Tais expressões são apresentadas como proposta para a utilização na caracterização de espécies menos conhecidas, o que viabiliza o adequado emprego de espécies nativas nas mais variadas aplicações para as quais a madeira é indicada. Apresentam-se também aferições das expressões propostas pela norma brasileira NBR 7190, que permitem a caracterização simplificada das resistências da madeira de espécies usuais a partir dos ensaios de resistência à compressão paralela às fibras. / Wood has diffused applications in several sections, however, a lot of times it is used without the knowledge of its properties. The characterization of wood species consists of determining its physical, strength and stiffness properties, through normalized tests. The inconvenience of many of those tests is the use of equipments of high cost and great load, available just in research centers. Even so, the test of specific gravity is of easy determination for using simple equipments in its execution. Being like this, in this study the correlations between the specific gravity, physical and mechanical properties of wood from forty brazilian native species of hardwoods are determined. The mathematical expressions obtained through this study, permit estimate most wood properties of strength and stiffness, based on their specific gravity. Such expressions are proposed as means of characterizing less-known species, what makes possible the appropriate employment of native species in most varied applications for which wood is the indicated material. Furthermore, it is presented the calibration of the expressions proposed by the brazilian code NBR 7190, being these a simplified method of characterizing mechanical properties of common species of wood by means of tests of strength in compression parallel to the grain.