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

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

Analyse comparative des initiatives One Health en Guinée et en République Démocratique du Congo: Un appel à l’opérationnalisation

La Guinée et la République Démocratique du Congo (RDC) sont deux pays confrontés à des maladies zoonotiques (ré)émergentes, lesquelles représentent de graves menaces pour la santé publique et pour l’économie. Cela renforce l’importance de mettre l'accent sur les approches interdisciplinaires pour la prévention, la détection et l’atténuation des maladies infectieuses afin de mettre en place des systèmes de réponses adéquats. Dans les dernières années, des efforts ont été fournis dans les deux pays pour la conception, la mise en œuvre et la promotion de l’approche “Une Seule Santé” (One Health) qui offre des solutions à l’interface homme-animal-plante-écosystèmes. Cependant, dans ces pays, il n’existe pas une approche systémique “Une Seule Santé” qui soit réellement opérationnelle. Ainsi, cet article vise à faire une analyse comparative des initiatives « One Health » (OH) en Guinée et en RDC. Les résultats suggèrent qu'il existe un engagement fort de la part du gouvernement guinéen à signer un ordre conjoint de collaboration entre les trois départements clés, mais la coopération et la collaboration entre les différents secteurs et disciplines font défaut. En RDC, trois plateformes existent, mais leurs actions ne sont pas coordonnées, ce qui démontre les lacunes dans la vision globale que devrait avoir l’approche OH. Le défi majeur dans ces deux pays est d'adopter une approche holistique pour dépasser les structures et les paradigmes organisationnels et disciplinaires pour développer une véritable coopération entre tous les secteurs directement ou indirectement touchés par les maladies à potentiel épidémique.   Guinea and the Democratic Republic of Congo (DRC) are two countries facing (re)emerging zoonotic diseases, which pose serious threats to public health and the economy. This reinforces the importance of emphasizing interdisciplinary approaches for the prevention, detection, and mitigation of infectious diseases to put in place adequate response systems. In recent years, efforts have been made in both countries for the design, implementation, and promotion of the “One Health” (OH) approach which offers solutions at the human-animal-animal-plant-ecosystems interface. However, in these countries, there is no operational OH systemic approach. Thus, this article aims to make a comparative analysis of the OH initiatives in Guinea and the DRC. Findings suggest there is a strong commitment on the part of the government of Guinea to sign a joint order of collaboration between the three key departments, but cooperation and collaboration between different sectors and disciplines is lacking. In the DRC, three platforms exist but are not coordinated, which shows gaps in the overall vision that OH should be in the country. The major challenge in these two countries is to adopt a holistic approach to go beyond organizational and disciplinary structures and paradigms to develop real coordination and cooperation between all the sectors directly or indirectly affected by diseases with epidemic potential

Anopheles gambiae s.l. swarms trapping as a complementary tool against residual malaria transmission in eastern Gambia

Malaria remains a major health problem and vector control is an essential approach to decrease its burden, although it is threatened by insecticide resistance. New approaches for vector control are needed. The females of Anopheles gambiae s.l. mate once in their life and in the swarms formed by males. Trapping swarms of Anopheles gambiae s.l. males is a potential new intervention for vector control, alternative to the use of insecticides, as it would disrupt mating . The proof-of-concept pilot study aiming at investigating swarm trapping as a potential vector control intervention, was carried out in 6 villages as in eastern Gambia. Swarms of Anopheles gambiae s.l. were identified and their size, height, and duration determined during the baseline year. Swarm trapping by local volunteers was implemented the following transmission season in 4 villages while the other 2 villages were taken as controls. Entomological outcomes were monitored by Human Landing Catches and Pyrethrum Spray Catches. A cross-sectional survey to determine malaria prevalence was carried out at the peak of the malaria transmission season for two consecutive years. At baseline, 23 swarming sites of Anopheles gambiae s.l. were identified. Before the intervention, mean indoor resting density per house and malaria prevalence were similar between control and intervention villages. Following the intervention, Anopheles gambiae s.l. indoor resting density was 44% lower in intervention than in control villages (adj IRR: 0.0.56; 95% CI 0.47-0.68); the odds of malaria infections were 68% lower in intervention than in control villages (OR: 0.32; 95% CI 0.11-0.97). Swarm trapping seems to be a promising, community-based vector control intervention that could reduce malaria prevalence by reducing vector density. Such results should be further investigated and confirmed by larger cluster-randomized trials

Antibiotic susceptibility profile of Streptococcus pneumoniae isolated from acute respiratory infection in Dakar: a cross sectional study

Streptococcus pneumoniae is a pathogen causing pneumonia, meningitis, otitis and bacteraemia. Nowadays, S. pneumoniae is developing antibacterial resistance, particularly for those with reduced susceptibility to penicillin. The objective of this study was to assess the susceptibility profile of S. pneumoniae strains isolated from acute respiratory infections (ARIs) in children younger than 5 years of age in Dakar, Senegal. S. pneumoniae strains were isolated from broncho-alveolar lavages (BALs), nasopharyngeal swabs, and middle ear secretion from children in the Paediatric Department of Abass Ndao University Teaching Hospital and Paediatric Department of Roi Baudouin Hospital in Dakar, Senegal. The strains were cultivated on Columbia agar supplemented with 5% of horse blood and gentamicin (6 mg/L). Antibiotic susceptibility testing was performed using E-test method. A total of 34 strains of S. pneumoniae were isolated and identified in this study, among them 7 strains (20.58%) showed penicillin-resistance. Antibiotics such as amoxicillin/clavulanic acid (MIC90=0.036 μg/mL), cefuroxim (MIC90=0.38 μg/mL), cefixim (MIC90=1.5 μg/mL), as well as macrolides (azithromycin MIC90=1.5 μg/mL, clarithromycin MIC90=0.125 μg/mL) and fluoroquinolone (levofloxacin MIC90=1 μg/mL, ofloxacin MIC90=2 μg/mL) were mostly active. However, all S. pneumoniae strains were resistant to sulfamethoxazole/trimethoprim (MIC90: 32 μg/mL). Except of S. pneumoniae strains penicillin-resistance or reduced susceptibility, most strains were susceptible to β-lactams antibiotics commonly used in ARI treatment. Continuous surveillance of antimicrobial resistance patterns of pneumococcus strains is still crucial for effective control of ARIs in children