Instabilités transverses et auto-organisation dans un nuage d’atomes froids. Gap labelling dans les quasi-cristaux bidimensionnels.

In this thesis, I report the results of studies performed during these last three years at Institut Non Linéaire de Nice.First, I present our feedback experiment leading to the spontaneous formation of patterns in the cross section of a laser beam passing through a cloud of cold 87 Rb atoms and retro-reflected by a mirror. In these experiments we were able to identify three mechanisms of nonlinearity : the spin nonlinearity associated with the Zeeman degrees of freedom, the electronic nonlinearity due to the saturation of a two-level atom and the optomechanical nonlinearity due to the spatial bunching of atoms by the dipole force. The instabilities corresponding to each nonlinear mechanism occurs in different range of the experimental parameters and can be selected and studied independently. The experimental observations are compared with various theoretical models.In the second part of the thesis, I present our study of the integrated density of states (IDOS) and the local density of states (LDOS) of the bands of a two-dimensional quasicrystal. In an experiment conducted at Laboratoire de Physiquede la Matière Condensée (LPMC), we realized quasicrystals by disposing dielectric resonators operating in the microwave regime on 2D Penrose tiling. A numerical model including experimental parameters is used to compare to the experimental findings.Dans cette mémoire de thèse, je rapporte les résultats des études réaliséesdurant ces trois dernière années à l’Institut Non Linéaire de Nice.D’une part, je présente nos expériences de miroir de rétro-action condui-sant à la formation spontanée de patterns dans la section transversale d’unfaisceau laser (pompe) traversant le centre d’un nuage d’atomes froids de87Rb et rétro-réfléchi par un miroir placé à une distance d du nuage. Dansces expériences nous discernons trois types de mécanismes de nonlinéari-tés : la nonlinéarité de spin qui est liée au pompage Zeeman, la nonlinéaritéélectronique existant pour un atome à deux niveaux et la nonlinéarité opto-mécanique qui est liée à la force dipolaire. Ces mécanismes dépendant des paramètres du MOT et de la pompe (intensité, désaccord, durée) sont étudiés séparément en jouant sur ces paramètres. Ces études expérimentales sont comparés avec des résultats obtenus avec des modèles théoriques.D’autre part, je présente nos observation concernant la densité d’état intégrée et les la densité d’états locale des bandes d’un quasi-cristal bidimensionnel. Dans cette expérience réalisé au Laboratoire de Physique de la Matière Condensée, nous avons réalisé des quasi-cristaux en disposant des résonateurs diélectriques agissant dans le domaine micro-onde sur des pavages de Penrose 2D. Un modèle numérique prenant en compte les paramètresexpérimentales est utilisé pour comparer les résultats obtenus

Réhabilitation et Valorisation d'Anciens Sites Miniers en Champ de Tomate : Cas de l'Ancienne Carrière de Hamdallaye dans la Commune Rurale de Sangarédi, Préfecture de Boké, République de Guinée

Les activités agricoles occupent 64% de la population Guinéenne, qui y tire 80% de ses revenus (FIDA, 2020). Les femmes qui représentent 52% de la population sont actives tout au long de la chaine de production, elles comptent pour 53,3% de la main d’œuvre et y dévouent 80% de leur temps (UN, 2012). Cependant, la plupart peinent à posséder la terre (PAM, 2019).  Par ailleurs, malgré la contribution appréciable des compagnies minières au développement économique des pays, pas ou très peu d’efforts sont consentis pour la réhabilitation des anciennes carrières en domaines agricoles. La richesse du sous-sol guinéen, l’intensification de l’exploitation minière et leurs corolaires en Guinée en général et dans la zone de Boké en particulier, qui est une zone de production agricole, font que les domaines cultivables sont sous pressions anthropiques et climatiques (MIPPP, 2022). Par conséquent, la réhabilitation et la valorisation des anciennes carrières à des fins agricoles s’imposent comme une nécessité. L’objectif de l’étude est de réhabiliter un ancien site minier à Hamdallaye en un champ de tomate. Après la fermeture des excavations et l’aménagement grossier du site par la compagnie minière, nous avons procédé au retrait des blocs de pierres et à l’étalement d’une couche d’environ 25 cm d’argile surmontée de 25cm de terre. Puis, le site a été mis en jachère pendant 15 mois après avoir été nivelé. Par la suite, une analyse agro pédologique du sol viabilisé a été réalisée dont les résultats sont les suivants : Texture : limono-argilo-sableuse ; pH : moyennement acide ; Matière organique : bien présente ; Azote : bien présent ; Phosphore : très faible ; Potassium : teneur élevée ; Capacité d’échange cationique : moyennement faible. En plus, un test de comportement a montré que le meilleur résultat est obtenu à partir de la combinaison des engrais organiques et minéraux. Conséquemment, des apports en fiente et NPK ont été faits lors de la production de la tomate. Malgré les difficultés rencontrées, les résultats de la production sont plutôt satisfaisants, ils démontrent la possibilité de réhabiliter une ancienne carrière en champ de tomate.   Agricultural activities occupy 64% of the Guinean population, who derive 80% of their income from it (IFAD, 2020). Women, who represent 52% of the population, are active throughout the production chain, accounting for 53.3% of the workforce and devoting 80% of their time to it (UN, 2012). However, most struggle to own land (WFP, 2019).  Furthermore, despite the significant contribution made by mining companies to the economic development of countries, little or no effort is made to rehabilitate former quarries into agricultural estates. The richness of the Guinean subsoil, the intensification of mining and its corollaries in Guinea in general and in the Boké area in particular, which is an agricultural production zone, mean that cultivable land is under anthropic and climatic pressure (MIPPP, 2022).  Consequently, the rehabilitation and development of former quarries for agricultural purposes is a necessity. The aim of the study is to rehabilitate a former mining site in Hamdallaye into a tomato field. Once the excavations had been closed and the site roughly landscaped by the mining company, we proceeded to remove the stone blocks and spread a layer of around 25 cm of clay topped with 25 cm of soil. The site was then leveled and left to lie fallow for 15 months. An agro-pedological analysis of the serviced soil was then carried out, with the following results: Texture: silty-clay-sandy; pH: moderately acidic; Organic matter: present; Nitrogen: present; Phosphorus: very low; Potassium: high; Cation exchange capacity: moderately low. In addition, a behavioral test showed that the best results were obtained from the combination of organic and mineral fertilizers. Consequently, manure and NPK inputs were made during tomato production. Despite the difficulties encountered, the production results are quite satisfactory, demonstrating the possibility of rehabilitating an old quarry into a tomato field

Increase of malaria attacks among children presenting concomitant infection by Schistosoma mansoni in Senegal

Helminthic infections concomitant with malaria are common in inter-tropical areas. A recent study showed that mice co-infected with Schistosoma mansoni and Plasmodium chabaudi develop higher P. chabaudi parasitaemia and had a higher mortality rate. This important observation deserved to be further investigated among human populations. Malaria attacks were recorded in 512 children aged 6–15 years living in Richard Toll (Northern Senegal) among whom 336 were infected by S. mansoni, and 175 were not. The incidence rate of malaria attacks was significantly higher among S. mansoni-infected individuals, particularly those carrying the highest worm loads, as compared to uninfected subjects (26.6% versus 16,4 %). In contrast, the rate of malaria attacks was lower, without reaching significance, in medium grade S. mansoni infections. Thus, infection by S. mansoni affects susceptibility to malaria, but this can vary according to the intensity of parasite load. The immunological mechanisms underlying this dual effect need to be further explored

The Middle Stone Age of Atlantic Africa: A critical review

Evidence of early Homo sapiens populations at the Atlantic coast of Africa remains relatively poorly known in relation to other regions of the continent. Nevertheless, available data across the continent provides a good starting point for current and future research investigations. The many sites known, documented and studied contribute in an increasingly way to the global understanding of the human emergence, including evidence of human evolutionary and technological advances, specific adaptations to diverse environments, the diffusion of Homo species and how humans interacted with each other from the “Early Stone Age (ESA)” through to the Middle Stone Age (MSA) from northern and southern Africa to the West. The differences of knowledge between the Atlantic coast in regard to other regions might be attributed to a number of reasons including but not limited to the history of scientific interest, site formation processes or economic, institutional and political constraints. However, the region received a renewed attention and funds that, combined with new methods and techniques, has been allowing an increased training of new researchers and the acquisition of high-resolution archaeological, paleoenvironmental and chronological data. Together, these inputs will reduce the differences of knowledge between the Atlantic coast and the Northern, Southern and Eastern Africa regions. The African Atlantic Coast represents more than 40% of the continent's perimeter, covering all Africa's climate zones, the hot arid environments, mountainous regions, and tropical rainforest could become relevant barriers for human mobility, but the shallow continental platform, and the great number of river basins allowed mobility between north and south coastal biomes into the continental interiors. These may have provided predictable patchy clusters of resources allowing human populations to thrive, enabling greater mobility and consequent diffusion of cultural traits, resources, and DNA. In this paper we review the record about the prehistory, paleoenvironments and paleoanthropological visibility and potentiality of Atlantic Africa

Maternal and Child Health Services in the Context of the Ebola Virus Disease: Health Care Workers’ Knowledge, Attitudes and Practices in Rural Guinea

The objective of this study was to document maternal and child health care workers‘ knowledge, attitudes and practices on service delivery before, during and after the 2014 EVD outbreak in rural Guinea. We conducted a descriptive cross-sectional study in ten health districts between October and December 2015, using a standardized self-administered questionnaire. Overall 299 CHWs (94% response rate) participated in the study, including nurses/health technicians (49%), midwives (23%), managers (16%) and physicians (12%). Prior to the EVD outbreak, 87% of CHWs directly engaged in managing febrile cases within the facility, while the majority (89% and 63%) referred such cases to another facility and/or EVD treatment centre during and after the EVD outbreak, respectively. Compared to the period before the EVD outbreak when approximately half of CHWs (49%) reported systematically measuring body temperature prior to providing any care to patients, most CHWs reported doing so during (98%) and after the EVD outbreak (88%). The main challenges encountered were the lack of capacity to screen for EVD cases within the facility (39%) and the lack of relevant equipment (10%). The majority (91%) of HCWs reported a decrease in the use of services during the EVD outbreak while an increase was reported by 72% of respondents in the period following the EVD outbreak. Infection prevention and control measures established during the EVD outbreak have substantially improved self-reported provider practices for maternal and child health services in rural Guinea. However, more efforts are needed to maintain and sustain the gain achieved.Key words: Maternal and child health, practices, Ebola, Guine

The response is like a big ship': community feedback as a case study of evidence uptake and use in the 2018-2020 Ebola epidemic in the Democratic Republic of the Congo.

INTRODUCTION: The 2018-2020 Ebola outbreak in the Democratic Republic of the Congo (DRC) took place in the highly complex protracted crisis regions of North Kivu and Ituri. The Red Cross developed a community feedback (CF) data collection process through the work of hundreds of Red Cross personnel, who gathered unprompted feedback in order to inform the response coordination mechanism and decision-making. AIM: To understand how a new CF system was used to make operational and strategic decisions by Ebola response leadership. METHODS: Qualitative data collection in November 2019 in Goma and Beni (DRC), including document review, observation of meetings and CF activities, key informant interviews and focus group discussions. FINDINGS: The credibility and use of different evidence types was affected by the experiential and academic backgrounds of the consumers of that evidence. Ebola response decision-makers were often medics or epidemiologists who tended to view quantitative evidence as having more rigour than qualitative evidence. The process of taking in and using evidence in the Ebola response was affected by decision-makers' bandwidth to parse large volumes of data coming from a range of different sources. The operationalisation of those data into decisions was hampered by the size of the response and an associated reduction in agility to new evidence. CONCLUSION: CF data collection has both instrumental and intrinsic value for outbreak response and should be normalised as a critical data stream; however, a failure to act on those data can further frustrate communities

Exploring experiences of HIV care to optimize patient-centred care in Conakry, Guinea: a qualitative study

IntroductionStudies on the organisation of care and the power dynamic between providers and patients with HIV in sub-Saharan Africa are rare. This study aims to describe the patient-provider relationship and explore the challenges to optimal and patient-centred care for HIV patients.MethodsThis was a qualitative exploratory descriptive study using in-depth individual interviews and focus group discussions. In total, 17 individual interviews and 5 focus group discussions were conducted. This was conducted in four urban health facilities in Conakry, the capital of Guinea. Three group of participants were included in this study namely patients with HIV; health providers including facilities and services managers; and psychosocial counsellors. Psychosocial counsellors provide emotional and psychosocial support to HIV patients. Their role in the organization care in Guinea is new and they contribute to strengthening adherence of patients with HIV to ARV treatment.ResultsPatients with HIV, health providers, and psychosocial counsellors have a positive perception of the patient-provider relationship. This relationship was characterized essentially by maintaining confidentiality of HIV status disclosure, caring attitudes towards patients (being available, adjusting locations for accessing ART, based on patients’ preferences), and participating in HIV patient’s social life. However, scolding and miscommunication about the interpretation of viral load tests were reported. The shortage of human resources, low salaries of health staff, poor infrastructure, and the financial burden borne by patients with HIV impede the implementation of optimal patient-centred care.ConclusionIntegrating psychosocial counsellors in HIV care organization, improving access to ARV, infrastructure, increasing human resources, and removing the financial burden for HIV patients are needed to optimal patient-centred care in Guinea