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See detailDynamique et composition des atmosphères supérieures de Mars et Vénus observées par les spectrographes ultraviolets à bord de Mars Express et Vénus Express
Stiepen, Arnaud ULg

Doctoral thesis (2014)

Venus has a dense CO2-dominated atmosphere. Above 50 km, the atmospheric circulation is composed of two dominants patterns: the Retrograde Superrotating Zonal (RSZ) circulation up to 65 km and the ... [more ▼]

Venus has a dense CO2-dominated atmosphere. Above 50 km, the atmospheric circulation is composed of two dominants patterns: the Retrograde Superrotating Zonal (RSZ) circulation up to 65 km and the subsolar to antisolar (SSAS) circulation beyond 120 km. The SSAS is caused by the temperature gradient between the day and the night hemispheres and it generates a global flow from the dayside to the nightside. Between 65 and 120 km, the circulation is complex as it is the superposition of the two main components. I have used the nightglow emitted by the NO* molecule (180-300 nm) produced by recombination of N(4S) and O(3P) atoms. These atoms are created by photodissociation of N2 and CO2 molecules on the dayside and carried to the nightside by the SSAS circulation. I analyze the full set of measurements of the NO δ and γ bands measured by the SPICAV instrument on board the ESA Venus Express spacecraft. I discuss the altitude and brightness of the emission peak (60 kR at 115 km) and show that the emission profile exhibits a secondary peak in ~10% of the cases. This additional peak is probably caused by upward-moving gravity waves propagating from below. I have developed an inversion method of the observed limb profiles to compare the results with a chemical-diffusive model of the atmosphere of Venus and constrain the vertical fluxes of N and O. On the basis of an extended statistical analysis, I characterize the presence of a bright spot of the nightglow of NO shifted from the antisolar point and located around 0230LT, 10°S. I use the vast SPICAV airglow database to statistically demonstrate that the NO nightglow is highly variable, both temporally and spatially. Mars experiences seasons as its rotation axis is inclined from its spin axis. Its upper atmospheric dynamics is dominated by summer-to-winter global transport. I study the upper atmosphere of Mars using nightglow observations performed by the SPICAM instrument on board ESA’s Mars Express spacecraft. I analyze the δ and γ bands of molecule NO in the nightside mesosphere to confirm, on statistical basis, the peak brightness and altitude of the NO UV emission (5 kR at 72 km). I show that the NO nightglow is located following the relation Latitude = -80xsin(Solar Longitude), in agreement with results based on stellar occultations and from the LMD model, which simulates the photochemistry and dynamics of the Mars atmosphere. I have performed a detailed study of the CO Cameron band (170 to 270 nm) and CO2+ doublet (290 nm) dayglow. I have developed a method to deduce the temperature profile around 150 km, an important study as the distribution of the temperature in the Mars atmosphere is poorly known. I showed that the temperature at high altitude is only weakly correlated with the solar EUV flux. This result suggests that the variability of the upper atmosphere may include internal processes. Comparisons with the Mars Global Ionosphere Thermosphere Model show that the model can reproduce the observation for high solar conditions but predicts lower temperature for low to moderate solar conditions. Further study will therefore be necessary to identify and understand the mechanisms that govern the temperature variability. [less ▲]

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See detailDynamique et perspectives de la filière cotonnière du Burundi
Gahungu, Antoine ULg

Doctoral thesis (2012)

Cotton cultivation was introduced in Burundi in 1919 under the Belgian mandate with the objective to monetize the rural economy and open the country to international trade. After independence (1962), the ... [more ▼]

Cotton cultivation was introduced in Burundi in 1919 under the Belgian mandate with the objective to monetize the rural economy and open the country to international trade. After independence (1962), the cotton crop continued to flourish as a vertically integrated chain from upstream to downstream in pursuing the objectives of job creation, import substitution and maximizing the added value generated by various cotton products. Since 1993, the cotton is in perpetual decline due to various factors both endogenous and exogenous to reach in 2009 the lowest level in its history. Its competitiveness is challenged by instability of the global market of cotton fiber, policies (subsidies) of large producers (China, India, USA, Pakistan, ...), competition from synthetic textile industry, the prices of agricultural inputs (fertilizers and phytosanitary products) and raw materials for industries, competition for food crops production factors which are already scarce and especially less remunerative producer prices. Survey work on a sample of 120 farms during three seasons (2007/2008, 2008/2009, 2009/2010) as well as interviews with various agents involved in the cotton sector have been conducted to understand the reasons of the decline of the cotton sector and see the adaptation mechanisms implemented in the segment "producers - COGERCO." It appears from these investigations that the cotton is not competitive with food crops. The price paid to growers is not motivating, production costs are expensive and factors of production become increasingly restrictive. COGERCO however, continues to subsidize cotton without benefit. In this context the majority of cotton producers combine beans or cowpeas with cotton to take advantage of subsidies (inputs, management, ...) and other benefits (loans, fields ...) that the company offers to producers without benefit to the company. The latter is in chronic deficit due to poor sector governance which is under pressure of privatization already imposed on other agro-industrial crops of the country (coffee, tea). [less ▲]

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See detailDynamique et pluralisme culturel dans l’ensemble bruxellois
Martiniello, Marco ULg

in Galissot, R. (Ed.) Pluralisme culturel en Europe : Culture(s) européenne(s) et culture(s) des diasporas (1993)

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See detailDynamique et pluralisme culturels dans l'ensemble Bruxellois
Martiniello, Marco ULg

in Social Sciences Information = Information sur les Sciences Sociales (1992), 31(2), 293-309

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See detailDynamique et production printanière du Mysidacé Leptomysis lingvura en baie de Calvi
Dauby, Patrick ULg

in Annales de la Société Royale Zoologique de Belgique (1984), 114((suppl. 1)), 196

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See detailLa dynamique fluviale d’un cours d’eau de marge passive : le Chassezac (Cévennes, France)
Jacob, N.; Gob, F.; Bravard, J. P. et al

in Géomorphologie : Relief, Processus, Environnement (2006)

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See detailDynamique forestière et enrichissements forestiers. Rapport n° 1.
Doucet, Jean-Louis ULg; Djohnhou, Olivier; Obama, Engelbert et al

Report (2008)

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 2.
Doucet, Jean-Louis ULg; Djohnhou, Olivier; Geam, Marie et al

Report (2009)

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 3.
Doucet, Jean-Louis ULg; Lagoute, Paul; Mebouomb, Elvis et al

Report (2009)

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 4.
Doucet, Jean-Louis ULg; Mebouomb, Elvis; Mouzome, Joselin et al

Report (2010)

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 5.
Doucet, Jean-Louis ULg; Mebouomb, Elvis; Mouzome, Joselin et al

Report (2010)

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 6.
Doucet, Jean-Louis ULg; Mebouomb, Elvis; Mouzome, Joselin et al

Report (2011)

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 7.
Doucet, Jean-Louis ULg; Amandé, Jean; Essik, Jean-Marie et al

Report (2011)

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 8.
Doucet, Jean-Louis ULg; Amandé, Jean; Bracke, Charles et al

Report (2012)

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See detailDynamique forestière et enrichissements forestiers. Site de Mbang. Rapport n° 9.
Doucet, Jean-Louis ULg; Amandé, Jean; Bracke, Charles et al

Report (2012)

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See detailDynamique forestière sous l’effet de lisière au Parc National de la Kibira (Burundi)
Bararunyeretse, P; Bogaert, Jan ULg; Nzigidahera, B et al

in Bulletin Scientifique de l'Institut National pour l'Environnement et la Conservation de la Nature (INECN) (2012), 10

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See detailDynamique non-linéaire de la molécule d’ADN : modélisation de sa dénaturation
Sacré, Pierre ULg

Master's dissertation (2008)

L’ADN est une molécule fabuleuse et essentielle dont la structure et la fonction sont en étroite relation. Elle est un centre d’intérêt important à la fois pour les biologistes, les chimistes et les ... [more ▼]

L’ADN est une molécule fabuleuse et essentielle dont la structure et la fonction sont en étroite relation. Elle est un centre d’intérêt important à la fois pour les biologistes, les chimistes et les physiciens. Ce travail s’intéresse à la dynamique non-linéaire de la molécule d’ADN et en particulier à l’étude de sa dénaturation. La modélisation a pour but de compléter les résultats expérimentaux pour mieux comprendre les mécanismes sous-jacents. Après une revue des propriétés biologiques de la molécule et des différents modèles proposés dans la littérature scientifiques, nous présentons le modèle de Peyrard-Bishop-Dauxois qui s’intéresse à la dynamique d’étirement transversal des paires de bases. Ce modèle donne comme solutions des excita- tions non-linéaires localisées, breathers, qui décrivent les ouvertures fluctuantes observées pendant le processus de transcription mais aussi dans l’ADN au repos. Nous nous intéressons à leur propagation et aux mécanismes d’interactions avec des inhomogénéités dans la chaîne à la base de leur croissance. Nous analysons la dénaturation thermique en utilisant des outils de physique statistique standard et des simulations numériques de dynamique moléculaire. Le modèle simple est cependant extrêmement riche du point de vue physique car il exhibe un comportement non-linéaire complexe. Il est également très pertinent pour décrire les mouvements de respiration interne de l’ADN et les mécanismes de leur formation et de leur croissance. L’importance de l’ADN et de ses fonctions demande encore de nombreuses investigations. Les directions les plus prometteuses sont l’étude de modèles non-linéaires inhomogènes et des interactions entre l’ADN et son environnement dans le but de faire un pont entre la physique non-linéaire de l’ADN et la médecine. [less ▲]

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See detailLa dynamique paradoxale de l'EEE
Younes, Nathalie; Rege Colet, Nicole; Detroz, Pascal ULg et al

in Vantourout, Marc; Douasdé, R; Romaiville, Marc (Eds.) Evaluation et enseignement supérieur (2013)

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