Deep HI observations of nearby late-type galaxies

This thesis makes use of sensitive Hi observations to map the distribution and kinematics of the low column density neutral hydrogen in late-type nearby mostly isolated galaxies and in the nearby M81 group. Using the KAT-7, GBT and MeerKAT AR1 telescopes, we present in the second chapter a survey of the Hi in a sample of twenty nearby, mostly isolated galaxies down to low column density levels. This provided a new Hi view of some of these galaxies, which allowed to derive their kinematics out to unprecedented extents. Despite the short spacings of KAT-7 and MeerKAT AR1, and the large size of the single-dish GBT that make these telescopes ideal for detecting faint structures, the observations revealed no clear detection of low column density Hi clouds down to a typical sensitivity of ∼2.2 × 1018 cm−2 that could be associated to gas accretion in the observed galaxies. However, we do not discard the existence of such structures that, we note, could be in the form of discrete clouds smaller than the beam size of the telescopes. In the third chapter, we use the DRAO telescope to perform a sensitive survey of the Hi in a 5 ◦ × 5 ◦ area of the M81 group. Similarly to previous observations, we find that the three major and interacting galaxies of the group – M81, M82 and NGC 3077 – are connected through Hi bridges and intergalactic Hi clouds. One of the major findings of the survey is the more complete map of the western Hi arm connecting the three galaxies to the dwarf galaxy NGC 2976. These observations offer enough resolution to map the structure of the arm, and reveal a complex of small clouds filling the space between the arm and the Hi forming “main body” of the interacting galaxies. Using a tilted-ring model, we also construct a large-scale rotation curve of the system formed by the interacting galaxies. Consistently with the large-scale velocity field, we observe a flat trend for the rotation velocity of the system from 20 kpc out to 80 kpc, well beyond the outskirts of the M81 disk, although with asymmetries like a wiggle at the vicinity of M82. The fourth chapter focuses on a subset of the M81 survey containing the dwarf galaxy IC 2574 and the Hi complex HIJASS J1021+68. In this chapter we perform a thorough analysis of the distribution and kinematics of the Hi in the two systems, and thanks to the high sensitivity we are able to detect a substantially large amount of low column density Hi around IC 2574, in the form of an Hi envelope, and in two large concentrations around the galaxy. We find evidence that HIJASS J1021+68 – which is found to be connected to IC 2574 through a filament of discrete clouds – is not a dark galaxy as previously suggested, but is instead a complex of clouds either stripped from, or falling onto the primordial Hi envelope of IC 2574. The kinematical analysis of IC 2574 using a 3D tilted-ring model brings us to derive its rotation curve out to a larger extent than previous works and allows us to constrain its Dark Matter halo parameters, which we find consistent with the literature. Overall, the different results presented in this work prove that the Hi content of local galaxies is higher than what current observations reveal, and new sensitive telescopes such as MeerKAT and the upcoming SKA will unveil a new Hi view of galaxies

Protection des dénominations géographiques dans l'Union Européenne : effectivité et analyse des effets sur le commerce

La protection des dénominations géographiques (DG) est un enjeu controversé, autant à l’OMC que dans les accords bilatéraux, tel que constaté lors de l’accord de libre-échange Canada et l’UE. En général, les pays nord-américains protègent les DG comme des marques de commerce. Ces gouvernements considèrent qu’il est possible de répliquer dans un pays autre que leur lieu d’origine les méthodes de production associées aux marques. Par exemple, du fromage « Parmesan » et du jambon « de Parme » sont fabriqués et commercialisés au Canada sous ces désignations. L’UE privilégie une approche de terroir, appliquant une protection sui generis, qui soutient que seuls les producteurs localisés dans une région donnée peuvent se prévaloir du terme géographique associé à cette région pour désigner leurs produits. Mais, plus de 20 ans après l’adoption de son premier règlement sur les DG en 1992, l’usage du système DG par les États membres de l’Union s’avère mitigée. La présente thèse tente de comprendre les facteurs qui expliquent cette situation, et analyse les implications des DG sur les échanges intra-européens. Nos recherches sur les facteurs explicatifs font ressortir deux points essentiels liés à la conception du droit européen sur les DG : la question des conflits potentiels entre les marques géographiques et les AOP/IGP, et celle de la dégénérescence des DG. En plus, elles notent une relative confusion des consommateurs entre produits DG et produits biologiques, et un faible intérêt des petits producteurs étant donné les coûts assez dissuasifs de la mise en place et le suivi-contrôle des DG. Nos résultats sur les implications de la protection européenne indiquent que le commerce entre pays détenant des produits protégés par une DG s’accroît de 0,76%, après avoir contrôlé les effets des autres déterminants pouvant influencer le commerce. Toutefois, des effets de détournement de commerce sont aussi constatés lorsque le pays importateur ne produit pas de DG. De plus, on observe que le système européen de protection des DG a un effet de renforcement des frontières nationales dans l’Union. Une approche par produit confirme que la protection de certains produits-DG aurait plus d’implications commerciales que dans d’autres.The protection of geographical indications (GIs) is a very controversial subject at the World Trade Organization as well as in the negotiations of bilateral trade agreements like the Canada/European Union Trade Agreement (CETA). This is mainly because different countries have very different views on how to go about protecting GIs. North American countries favor trademarks because they believe that the “know-how” can be transferred across geographical boundaries and that it is possible to replicate or even improve on ancestral production processes developed in a given region. “Parmesan” cheese and “Parma” ham are examples of products manufactured and marketed under these names in Canada. The European Union (EU) promotes a « terroir » approach, applying a sui generis protection, which grants a monopoly of the GI to producers located in a specific region. The first European regulation of GIs was adopted in 1992. But more than 20 years later, the effectiveness of GIs in the EU Member States appears mixed. Our thesis attempts to explain reasons for this situation and analyzes the trade-impact of GI protection considering trade within the European Union. Our research on reasons highlights two key issues related to the European GI regulation: potential conflicts between geographical marks (containing geographical names or terms) and sign of GIs (IGP/PDO), and the degeneration of GIs. In addition, we note that consumers are comparatively confused between GIs products and organic products, and small potential producers are rather deterred by the costs of GIs implementation, monitoring and control. Our findings suggest that the protection of GIs creates trade when the importing and exporting countries have GI-protected products. Trade increased by 0.76% when both exporting and importing countries have protected products, after controlling for the effects of others determinants of trade. There is also empirical evidence regarding a trade-diverting effect when the importing country does not have GIs. In addition, our results note a border enlargement effect arising from European GI-protection. An analysis by sector of production indicates that the trade-impact of protecting GIs in some sectors is more important than other sectors

Solid-state synthesis and physico-chemical characterization of modified smectites using natural clays from Burkina Faso

Solid-state intercalation was applied to prepare organo-smectites using cationic surfactants and natural clays containing smectite at various surfactant/smectite ratios. The surfactants enter the interlayers of smectites causing a swelling of the clays. The used clays were collected in Siétougou and Diabari villages located in the eastern part of Burkina Faso. The solid-state intercalation was successful for all four surfactants applied, n-dodecyltrimethylammonium bromide, (n-C12H25(CH3)3NBr), n-tetradecyltrimethylammonium bromide, (n-C14H29(CH3)3NBr), n-hexadecyltrimethylammonium bromide (n-C16H33(CH3)3NBr) and di-n-dodecyldimethyl­ammonium bromide ((n-C12H25)2(CH3)2NBr) at different levels of the cation exchange capacity (CEC). The synthesized organo-smectites were characterized regarding relative density, structural and textural properties. XRPD data showed a systematic increase of the basal spacing of the unit cell of the smectite up to >38 Å at 2.0-CEC loading of the surfactant. This increase indicates that the surfactants penetrated into the smectite interlayers with the surfactants being arranged parallel to the layers at low concentrations and almost perpendicular at high ones. FTIR spectra of the organo-smectites showed a decrease in the intensities of the water bands at around 1630 cm-1 and 3400 cm-1, and new specific bands close to 2920 cm-1 and 2850 cm-1 were assigned to the asymmetric and symmetric stretching of CH2 groups of the surfactants, respectively.                     KEY WORDS: Smectite, Organo-smectite, Surfactant, Intercalation   Bull. Chem. Soc. Ethiop. 2021, 35(1), 43-59. DOI: https://dx.doi.org/10.4314/bcse.v35i1.

RTAs’ Proliferation and Trade-diversion effects: Evidence of the “Spaghetti Bowl” Phenomenon

This paper investigates the trade-diversion effects of regional trade agreements (RTAs), so-called “Spaghetti bowl” Phenomenon (SBP), in multilateral trade. The SBP is due to the proliferation of RTAs. Thus, we investigate the relationship between the number of RTAs concluded by a country and the additional trade value attributed to an RTA. The main finding reveals a negative trade-effect between them, confirming the existence of SBP multilateral trade. However, results could not conclude evidence of a negative effect of overlapping RTAs, involving the existence of SBP, within North-North, North-South or South-South trade. But, the additional trade value attributed to an RTA concluded with EU countries or US seems to confirm significantly a trade-diversion effect because of the number of RTAs signed by these countries

Solid-state synthesis and physico-chemical characterization of modified smectites using natural clays from Burkina Faso

Solid-state intercalation was applied to prepare organo-smectites using cationic surfactants and natural clays containing smectite at various surfactant/smectite ratios. The surfactants enter the interlayers of smectites causing a swelling of the clays. The used clays were collected in Sietougou and Diabari villages located in the eastern part of Burkina Faso. The solid-state intercalation was successful for all four surfactants applied, n-dodecyltrimethylammonium bromide, (n-C12H25(CH3)(3)NBr), n-tetradecyltrimethylammonium bromide, (n-C14H29(CH3)(3)NBr), n-hexadecyltrimethylammonium bromide (n-C16H33(CH3)(3)NBr) and di-n-dodecyldimethylammonium bromide ((n-C12H25)(2)(CH3)(2)NBr) at different levels of the cation exchange capacity (CEC). The synthesized organo-smectites were characterized regarding relative density, structural and textural properties. XRPD data showed a systematic increase of the basal spacing of the unit cell of the smectite up to >38 angstrom at 2.0-CEC loading of the surfactant. This increase indicates that the surfactants penetrated into the smectite interlayers with the surfactants being arranged parallel to the layers at low concentrations and almost perpendicular at high ones. FTIR spectra of the organo-smectites showed a decrease in the intensities of the water bands at around 1630 cm(-1) and 3400 cm(-1), and new specific bands close to 2920 cm(-1) and 2850 cm(-1) were assigned to the asymmetric and symmetric stretching of CH2 groups of the surfactants, respectively

Observing galaxies in the Southern Filament of the Virgo Cluster with KAT-7 and WSRT

To date, our understanding of the formation and evolution of galaxies attributes a very important role to the neutral hydrogen (HI) gas since it constitutes the reservoir of fuel out of which galaxies form stars. In their evolution, galaxies interact with each other and with their environment, and very often these interactions leave fingerprints in the HI distribution. The extended HI envelopes of galaxies are sensitive tracers of those tidal interactions. In the present study, we map the HI distribution of galaxies in a ~1.5° X 2.5° region of the Virgo cluster using the Karoo Array Telescope (KAT-7) and the Westerbork Synthesis Radio Telescope (WSRT). With a total observing time of ~78 hours with the KAT-7 and 48 hours with the WSRT, we search for low HI column density features in the region. Despite the different observing time and beam size of the two telescopes, we reach similar column density sensitivities of NHI ~1 X 10¹⁸ atoms cm⁻² over 16.5kms⁻¹. With a new approach, we combine the two observations to map both the large and small scale structures. We detect, out to an unprecedented extent, an HI tail of ~60 kpc being stripped off NGC 4424, a peculiar spiral galaxy. The properties of the galaxy, together with the shape of the tail, suggests that NGC 4424 is a post-merger galaxy undergoing a ram pressure stripping as it falls into the centre of the Virgo Cluster along a filamentary structure. We also give the HI parameters of the galaxies detected

NUTRItion and CLIMate (NUTRICLIM): investigating the relationship between climate variables and childhood malnutrition through agriculture, an exploratory study in Burkina Faso

Malnutrition remains a leading cause of death in children in low- and middle-income countries; this will be aggravated by climate change. Annually, 6.9 million deaths of children under 5 were attributable directly or indirectly to malnutrition. Although these figures have recently decreased, evidence shows that a world with a medium climate (local warming up to 3–4 °C) will create an additional 25.2 million malnourished children. This proof of concept study explores the relationships between childhood malnutrition (more specifically stunting), regional agricultural yields, and climate variable through the use of remote sensing (RS) satellite imaging along with algorithms to predict the effect of climate variability on agricultural yields and on malnutrition of children under 5. The success of this proof of purpose study, NUTRItion and CLIMate (NUTRICLIM), should encourage researchers to apply both concept and tools to study of the link between weather variability, crop yield, and malnutrition on a larger scale. It would also allow for linking such micro-level data to climate models and address the challenge of projecting the additional impact of childhood malnutrition from climate change to various policy relevant time horizons