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abstract: Excessive gestational weight gain (EGWG) affects 50% of US pregnant women and may be an important contributor to obesity in both the mother and child. Novel strategies to prevent EGWG are needed to reduce the risk of adverse health outcomes for the mother and child. This dissertation presents three manuscripts that 1) propose a novel model to explain how prenatal yoga may prevent EGWG through behavioral, psychological/emotional, and physical factors, 2) test the feasibility and preliminary efficacy of a prenatal yoga intervention to prevent EGWG compared to a pregnancy education comparison group, and 3) qualitatively investigate pregnant women’s experiences participating in a prenatal yoga intervention to prevent EGWG. In manuscript two, 49 women were recruited and randomized to a 12-week prenatal yoga intervention (n=23) or a time-matched pregnancy education comparison group (n=26). A satisfaction survey was administered at post-intervention to assess feasibility outcomes (e.g., acceptability, demand). Mindfulness, emotion regulation, self-awareness, sleep quality, depression, anxiety, and perceived stress were assessed at baseline and post-intervention (12-weeks) and GWG was assessed weekly. Linear mixed models were used to analyze pre-post changes in primary (i.e., GWG during pregnancy) and secondary (i.e., mindfulness, emotion regulation, self-awareness, sleep quality, depression, anxiety, and stress) outcomes. In manuscript three, interviews were conducted with pregnant women who participated in the prenatal yoga intervention (n=13). Interview responses were summarized using an inductive approach to thematic analysis. Findings in manuscript two suggest that prenatal yoga was a feasible method to prevent EGWG with high enjoyment and satisfaction reported among participants. The average number of prenatal yoga sessions attended was 8.84 (SD = 3.85). There was no significant group differences on the rate of GWG or total GWG throughout the intervention and a significant group x time interaction effect for stress (p=.03). In manuscript three, twelve themes were identified among the data and were organized into the following categories (three themes each): 1) experiences of prenatal yoga, 2) prenatal yoga and weight, 3) barriers to prenatal yoga, and 4) facilitators of prenatal yoga. This initial evidence suggests that prenatal yoga has potential as a strategy to prevent EGWG in pregnant women. / Dissertation/Thesis / Embargo form / Doctoral Dissertation Exercise and Nutritional Sciences 2019

Potato production requires high phosphorus (P) application with potential negative environmental or nutritional consequences for potato as well as for subsequent crops. Impacts of high available P on yield and plant nutrition of species in potato cropping rotations are inadequately understood, and could result in antagonistic interactions with cationic micronutrients such as zinc (Zn) and manganese (Mn). Three hydroponic experiments were conducted with Russet Burbank potato to elucidate P and Zn relationships and associated interactions with other nutrients. In the first experiment, P solution concentration was constant at 256 µM while Zn concentration varied: 0.1, 2, 6, 18, 54, 162 and 456 µM Zn. In the second, Zn solution concentration was constant at 6 µM while P concentration varied: 32, 64, 128, 256, 512, 1024 and 2048 µM P. In the third, three levels of P and Zn varied in all possible combinations: 32, 128 and 1024 µM P and 0.1, 54 and 486 µM Zn. As expected, Zn increased in all plant parts with increasing old shoots while root P increased. This suggests a P-Zn complex formation in roots preventing movement of P to the shoots of plants under high Zn. This was confirmed under variable P and Zn. Contrary to expectations, a direct impact of increased solution P on Zn uptake or distribution in potato was not observed except at 486 µM Zn in the third experiment. Increased solution P at low Zn levels resulted in a steep increase of P in new and old shoot growth and an accumulation of Mn in potato roots—factors that might indirectly impact Zn nutrition in potato. Although high P levels in potato did not directly reduce Zn content or cause Zn deficiency, excessive P accumulation with insufficient Zn may reduce the activity of Zn by interacting with other micronutrients such as Mn.

No description available.

No description available.

A travers ce projet de recherche nous avons exploré différents aspects d’une dérégulation du système dopaminergique sur les troubles du repos, en prenant pour exemple deux maladies neurologiques : la maladie de Willis-Ekbom (MWE) et la maladie de Parkinson (MP). La MWE est une maladie neurologique sensorimotrice caractérisée par des douleurs dans les membres inférieurs, s’accompagnant d’un besoin irrépressible de bouger et ce, suivant un profil circadien. Ainsi, le premier volet de ces travaux s’est appliqué à reproduire chez le macaque, les principales altérations du métabolisme du fer et de celui de la dopamine reportées dans la MWE. Tout d’abord, nous avons établit les bases physiologiques des variations circadiennes des concentrations du fer et de ses biomarqueurs au niveau central et périphérique. Puis, nous avons développé un protocole simple, uniquement basé sur des prélèvements sanguins répétés, permettant d’induire efficacement une déplétion en fer sérique et de ses protéines associées. Finalement, ce protocole nous a permis d’explorer les liens entre l’altération de l’homéostasie du fer au niveau du système nerveux central, les perturbations neurochimiques dans différentes structures cérébrales ainsi que les modifications locomotrices qui en résultent. Le second volet de cette thèse a testé l’impact des agonistes des récepteurs dopaminergiques de type D1 (SKF38393) et D2 (quinpirole), sur les troubles du sommeil dans un modèle macaque de la MP, à l’aide d’enregistrements polysomnographiques. Pour cela, nous avons évalué les effets de ces agents pharmacologiques sur l’émergence de la somnolence diurne et sur l’altération du sommeil paradoxal, induits par une intoxication au MPTP. Nos résultats mettent en évidence que le quinpirole est inefficace pour restaurer les niveaux de base de ces deux paramètres. En revanche, le SKF38393 permet une diminution notable de la somnolence diurne ainsi qu’une restauration du sommeil paradoxal. Finalement, les perturbations monoaminergiques liées à la déplétion en fer ouvrent de multiples perspectives de recherche sur la physiopathologie de la MWE. De même, l’amélioration des troubles veille-sommeil par l’agoniste des récepteurs D1, offre de nouvelles pistes thérapeutiques quant à la prise en charge des troubles du repos dans la MP. L’ensemble de nos résultats apporte un niveau de compréhension supplémentaire quant au rôle de la dopamine dans les altérations du repos. / During this thesis project we explored several aspects of the impact of a dopaminergic system dysregulation on the rest alterations, through two neurological diseases: the Willis-Ekbom’s disease (WED) and Parkinson’s diseases (PD). The WED is a neurological sensorimotor disorder mainly characterized by pain in lower limbs. It preferentially appears in the evening and transiently and partially is alleviated by motor activity. Thus, the first part of this work aimed at reproducing the main dysfunctions of the iron and dopaminergic metabolisms observed in WED, in the macaque monkey. We first established the circadian variations of iron-indicator concentrations in serum and cerebrospinal fluid. Then we developed a rapid protocol based on repeated blood withdrawals, allowing to efficiently induce serum iron depletion. Finally, this protocol enabled us to investigate the relationship between iron metabolism dysfunctions, neurochemical alterations and the subsequent locomotor behavioural changes. In the second part, of this research project we examined the impact of selective D1 (SKF38393) and D2 (quinpirole) receptor agonists on the sleep impairments in a macaque model of PD using the polysomnographic recording technique. Thus we investigated the effects of these two pharmacological compounds on the daytime sleepiness and on the paradoxical sleep induced by MPTP intoxication. Our results demonstrated the inefficacy of quinpirole to restore these two altered sleep parameters. By contrast, SKF38393 significantly decreased daytime napping and substantially restored paradoxical sleep. Finally, the monoaminergic dysregulations, induced by iron depletion, may offer multiple perspectives to unravel the WED pathophysiology. In the same line, the beneficial effects exhibited by the D1 receptor agonist bring new therapeutic avenues to treat sleep-wake disorders in PD. Together, the global results bring new insights in the underlying mechanisms of sleep impairment involving dopamine.

L’objet de cette thèse est d’étudier dans un contexte de financiarisation des marchés de matières premières, certaines stratégies adoptées par les investisseurs et leurs impacts sur la volatilité et le co-mouvement excessif entre les marchés énergétiques et financiers. Pour ce faire, trois études sont proposées. La première fait appel aux modèles à changement de régime (MS-VAR) appliqués sur un ensemble des produits énergétiques et couvre la période 1992-2017. Les résultats obtenus suggèrent qu’en période de forte volatilité, les agents commerciaux (agents de couverture) jouent un rôle crucial dans la découverte des prix du marché du gaz. Cependant, ces agents de couverture affectent le bon fonctionnement des autres marchés (pétrole, essence, fioul) et amplifient leur volatilité. La deuxième étude traite les modèles GARCH ADCC versus GARCH DCC sur un échantillon de 17 pays et sur la période 1997-2016. Cette étude met en avant l’effet asymétrique des chocs pétroliers sur les corrélations conditionnelles des marchés asiatiques et africains, qui s’expliquent notamment par les activités d’arbitrage et les comportements hétérogènes des investisseurs. La troisième étude porte sur les modèles autorégressifs à retards échelonnés (ARDL) et révèle qu’après la crise financière, et au-delà des fondamentaux macro-économiques et financiers, l’indice de la spéculation excessive explique, aussi bien à long terme qu’à court terme, la corrélation entre le marché pétrolier et les marchés financiers de certains pays. Ceci génère un phénomène de co-mouvement excessif, et donc un effet de financiarisation sur ces marchés. Enfin, nous concluons les éléments suivantes : premièrement, en période de forte volatilité, le marché du gaz constitue une valeur refuge pour les investisseurs financiers ; deuxièmement, le comportement de l’investisseur explique l’effet de co-mouvement excessif entre le marché pétrolier et certains marchés financiers ; troisièmement, ce phénomène de co-mouvement excessif limite les avantages de la diversification internationale des portefeuilles notamment au moment des turbulences financières. / The object of this thesis is to study in a context of financialization of commodity markets, some strategies adopted by investors and their impact on volatility and excess co-movement between energy markets and financial markets. To this end, three studies are proposed. The first study uses the approach VAR with Switching Regime (MS-VAR) applied to energy markets during the period 1992-2017. The results suggest that during high volatility period, commercial agents (hedging agents) play a crucial role in the discovery of gas market prices. However, these agents affect the efficiency of other markets (crude oil, gasoline, heating oil) and amplify their volatilities. The second study employs GARCH ADCC versus GARCH DCC models for a sample of 17 countries and covering the period 1997-2016. This study highlights the asymmetric effect of oil shocks on the conditional correlations of the Asian and African markets, which can be explained in particular by the arbitrage activities and the heterogeneous behavior of investors. The third study focuses on Autoregressive Distributed Lag models (ARDL) and reveals that after the financial crisis, and beyond the macroeconomic and financial fundamentals, the index of excessive speculation, explains in long term as well as in short term, the correlation between oil market and some financial markets. This generates a phenomenon of excess co-movement, and therefore a financializing effect on these markets. Finally, we can conclude that : firstly, during high volatility period, gas market is a safe haven for financial investors ; secondly, the behavior of the investor explains the effect of excess co-movement between the oil market and some financial markets ; thirdly, this phenomenon of excess co-movement limits the benefits of international portfolio diversification especially during financial turbulences.

Base erosion in the form of profit shifting has become an increasing concern internationally as well as in South Africa. A significant type of base erosion in South Africa is in the form of excessive interest deductions where income is effectively shifted to a no-tax or low-tax jurisdiction. One of the key developments affecting the South African tax laws was the introduction of provisions that target base erosion and profit shifting. Included in these provisions is section 23M, which limits the deduction of interest paid to persons in whose hands the interest received is not subject to tax in South Africa. It was, however, identified that section 23M may target the same interest risks that the new section 31 thin capitalisation provisions address. Section 23M was said to be the enactment of thin capitalisation. Although one of the purposes of tax treaties is to encourage international trade and investment, there is also discriminatory taxation, which runs counter to that purpose and therefore the prevention of such discrimination is important when dealing with tax treaties. The Organisation for Economic Cooperation and Development’s (OECD) Model Tax Convention contains a handful of special criteria in article 24, which must not lead to different or less favourable treatment with regard to taxation. It was found that the non-discrimination article, in particular articles 24(4) and 24(5), may prevent the application of a thin capitalisation regime if the provisions are in contrast with the OECD non-discrimination provisions. Article 24(4) and article 24(5), however, contain an exception that the non-discrimination provisions would not be applicable provided that the thin capitalisation regimes are compatible with the arm’s length principles of article 9. If section 23M was therefore found to be an arm’s length transaction, the article 24(4) and (5) non-discrimination provisions would without further consideration, not be applicable. It was, however, found that section 23M does not consider the factors that should be considered when an arm’s length transaction is applicable, but merely applies the same formula to each company regardless of the size of the company or the industry sector. As a result of this, it appears as if section 23M is arbitrary in nature and therefore would not represent an arm’s length transaction. The exception would not be applicable and would therefore increase the potential non-compliance with the non-discrimination provision. The objective of this study was to determine whether any aspect of section 23M would be contrary to the OECD guidelines relevant to thin capitalisation and in particular the non-discrimination provisions. It was, however, found that although it appears as if section 23M’s primary focus is on cross-border transactions, the provisions do not directly discriminate on the basis of residence. As a result of the discrimination being indirect discrimination and the fact that the cause of section 23M being applicable is not foreign ownership, but rather due to the creditor not being subject to tax, it was concluded that the OECD non-discrimination provisions would not be applicable to section 23M. / MCom (South African and International Tax), North-West University, Potchefstroom Campus, 2015

Base erosion in the form of profit shifting has become an increasing concern internationally as well as in South Africa. A significant type of base erosion in South Africa is in the form of excessive interest deductions where income is effectively shifted to a no-tax or low-tax jurisdiction. One of the key developments affecting the South African tax laws was the introduction of provisions that target base erosion and profit shifting. Included in these provisions is section 23M, which limits the deduction of interest paid to persons in whose hands the interest received is not subject to tax in South Africa. It was, however, identified that section 23M may target the same interest risks that the new section 31 thin capitalisation provisions address. Section 23M was said to be the enactment of thin capitalisation. Although one of the purposes of tax treaties is to encourage international trade and investment, there is also discriminatory taxation, which runs counter to that purpose and therefore the prevention of such discrimination is important when dealing with tax treaties. The Organisation for Economic Cooperation and Development’s (OECD) Model Tax Convention contains a handful of special criteria in article 24, which must not lead to different or less favourable treatment with regard to taxation. It was found that the non-discrimination article, in particular articles 24(4) and 24(5), may prevent the application of a thin capitalisation regime if the provisions are in contrast with the OECD non-discrimination provisions. Article 24(4) and article 24(5), however, contain an exception that the non-discrimination provisions would not be applicable provided that the thin capitalisation regimes are compatible with the arm’s length principles of article 9. If section 23M was therefore found to be an arm’s length transaction, the article 24(4) and (5) non-discrimination provisions would without further consideration, not be applicable. It was, however, found that section 23M does not consider the factors that should be considered when an arm’s length transaction is applicable, but merely applies the same formula to each company regardless of the size of the company or the industry sector. As a result of this, it appears as if section 23M is arbitrary in nature and therefore would not represent an arm’s length transaction. The exception would not be applicable and would therefore increase the potential non-compliance with the non-discrimination provision. The objective of this study was to determine whether any aspect of section 23M would be contrary to the OECD guidelines relevant to thin capitalisation and in particular the non-discrimination provisions. It was, however, found that although it appears as if section 23M’s primary focus is on cross-border transactions, the provisions do not directly discriminate on the basis of residence. As a result of the discrimination being indirect discrimination and the fact that the cause of section 23M being applicable is not foreign ownership, but rather due to the creditor not being subject to tax, it was concluded that the OECD non-discrimination provisions would not be applicable to section 23M. / MCom (South African and International Tax), North-West University, Potchefstroom Campus, 2015

Le but de la présente thèse a été d'approfondir la compréhension de la relation entre l'anxiété et l'épuisement professionnel en vérifiant la présence de liens entre d'une part, des composantes cognitives anxieuses, soient la tendance à s'inquiéter, l'intolérance à l'incertitude, l'attitude négative face aux problèmes, le perfectionnisme et le sentiment de responsabilité excessive et, d'autre part, les dimensions d'épuisement professionnel, soient l'exténuation, le cynisme et le sentiment d'inefficacité professionnelle. Également, le lien entre la présence d'un TAG et le niveau d'épuisement professionnel a été vérifié. Des corrélations partielles, des analyses de régressions et des analyses de covariance univariées amènent à confirmer partiellement les hypothèses de l'étude en montrant que chacune des composantes cognitives anxieuses s'avère significativement reliée à au moins une composante de l'épuisement professionnel. De plus, les gens présentant un TAG démontrent un niveau d'exténuation significativement plus élevé que les gens ne présentant pas les critères du trouble. Ce résultat vient en appui au modèle du TAG selon lequel les inquiétudes et l'anxiété pourraient précéder l'épuisement.