Transports actifs et stratégies d'accès à l'emploi des populations des quartiers périphériques dans les villes africaines : le cas de Ouagadougou

Cette thèse interroge la mobilité des populations précaires qui se déplacent pour le motif de l'emploi, entre les quartiers périphériques considérés comme étant des zones de génération des déplacements et les autres quartiers ainsi que les quartiers centraux, qui sont des zones d'attraction ou de destination des mobilités domicile-travail. Pour se rendre à leur lieu d'emploi, ces populations adoptent une mobilité active et se déplacent à pied ou à vélo. L'approche proposée dans notre thèse s'articule sur l'analyse des différentes stratégies adoptées par ces populations précaires, sachant que ces stratégies ne sont pas exclusives, mais se complètent, il s'agit de l'intermodalité, le recours aux réseaux sociaux et le choix des emplois de proximité/éloignement. Dans le cas des villes du Sud, il est nécessaire de redéfinir la mobilité des actifs précaires comme étant une « mobilité de survie ». Ils sont « mobiles malgré tout » à cause de l'adaptabilité de leurs pratiques de mobilité, dont la pénibilité est caractérisée selon notre approche par les seuils de mobilité et dépend finalement d'une combinaison de facteurs centrés sur les conditions de déplacement qui sont marquées par les contraintes extérieures sociales, politiques, économiques et environnementales. La question des mobilités éprouvantes dans notre approche confirme l'étroitesse du lien qui se dégage entre « pratiques de mobilité » et « survie des actifs précaires ». Ce lien mérite d'être analysé et nous abordons cette question à la fois sous l'angle des stratégies de mobilité et sous l'angle de la pénibilité en lien avec la mobilité de survie. L'objectif de notre thèse consiste à explorer et à documenter les différentes stratégies de mobilité adoptées par les actifs précaires à Ouagadougou au Burkina Faso en tenant compte du contexte de leur ancrage résidentiel dans les quartiers périphériques. Notre population cible est constituée par les actifs précaires âgés de 40 à 55 ans. Pour réaliser cette exploration, nous utilisons l'approche espace-temps-activités, car les besoins de déplacement s'expriment à la fois dans le temps et dans l'espace et varient selon : la position sociale de l'individu, l'âge et les modes de vie. Aussi, la mobilité des populations précaires peut être vécue de manière différente suivant le niveau de pénibilité, le contexte professionnel et le niveau des revenus. Nos hypothèses de travail prennent en compte les effets induits par les amplitudes de déplacement qui sont de proximité ou d'éloignement, sur les stratégies de mobilité. Ensuite, nous abordons la question des réseaux sociaux d'entraide qui sont « des refuges ou des exutoires » dans les pratiques de mobilité et face aux situations imprévues que nous qualifions « d'amplificateurs de pénibilité ». Le capital social constitué par ces réseaux sociaux représente un facteur décisif à la pérennisation de la situation de mobilité. Il se dégage que l'apport des réseaux sociaux d'amis et de voisinage présente un enjeu aussi considérable que celui des réseaux de famille. Nous explorons enfin la manière dont les stratégies adoptées améliorent les conditions de vie des populations. Cette thèse a également pour but d'éclairer la relation entre deux quartiers périphériques situés à des distances différentes, mais qui vivent une même intensité quant à leurs flux de mobilité par rapport aux quartiers centraux. L'un des apports majeurs de notre thèse a été l'analyse des trajectoires de vie des actifs précaires et à travers nos analyses, il se dégage qu'un événement ou une situation imprévue peuvent reconfigurer les conditions de vie et les seuils de mobilité d'un individu ou d'un ménage qui sont : la mobilité de survie, la mobilité de subsistance, la mobilité d'épargne et la mobilité d'investissement. Les différents facteurs qui peuvent contribuer à fragiliser les stratégies de mobilité sont : les facteurs de motilité (accessibilité, compétences, appréhension des opportunités) ainsi que d'autres facteurs tels que la distance des déplacements et les emplois occupés, les situations imprévues, l'aspect genre et l'aspect institutionnel à travers les politiques publiques mises en place. Nos résultats montrent qu'une harmonisation entre les stratégies et les facteurs de mobilité favorise l'amélioration des conditions de vie des ménages.\ud ______________________________________________________________________________ \ud MOTS-CLÉS DE L’AUTEUR : Mobilités urbaines, mobilités actives, mobilité de survie, trajectoires de vie, quartiers périphériques, stratégies de mobilité et seuils de mobilité

Electrical Performance of Zinc Oxide Thin Films Transistors

The capacitive properties and performance of ZnO (TFT) thin film transistors prepared at 100°C were studied. The ZnO thin films were deposited by rf magnetron sputtering on silicon substrates. The frequency dependence of the conductivity and the capacity of the ZnO thin films was studied in the frequency range from 5 kHz to 13 MHz. Shown that total conductivity increases with frequency and decreases with temperature. This shows that the thermally activated conduction mechanism maintains the correlated barrier of the charge carrier on the localized states as a function of the experimental data. Activation energy is in the range of literature. ZnO-based transistors (TFTs) show non-linearities in both the current voltage and the transfer characteristics which are explained due to the presence of trap states. These traps cause a reversible threshold voltage change as revealed by low frequency capacitance voltage measurements in metal insulating semiconductor (MIS) capacitors. Thermal degradation experiments in heterojunctions confirm the presence of a trap state at 0.32 eV

Cases of Impaired Oxidative Burst in HIV-Exposed Uninfected Infants’ Neutrophils—A Pilot Study

An increased risk of serious bacterial infections in HIV-exposed uninfected (HEU) infants has been demonstrated. Although neutrophils are essential for the protection of infants against bacterial infections, no study has investigated their profile in HEU infants to date. In this study, we assessed the function of neutrophils in HEU infants using the nitroblue tetrazolium reduction test. Among 25 HEU infants, 9 (36%) showed a reduced ability of their neutrophils to produce reactive oxygen species upon stimulation with bacteria. No alteration of total neutrophil counts was noted in the blood of HEU infants indicating that the alteration observed in the 36% of HEU infants may only be functional. Conclusively, impaired neutrophil function could be a factor of vulnerability in HEU infants

Potential of Host Markers Produced by Infection Phase-Dependent Antigen-Stimulated Cells for the Diagnosis of Tuberculosis in a Highly Endemic Area

CITATION: Chegou, N. N. et al. 2012. Potential of host markers produced by infection phase-dependent antigen-stimulated cells for the diagnosis of tuberculosis in a highly endemic area. PLoS ONE, 7(6): e38501, doi:10.1371/journal.pone.0038501.The original publication is available at http://journals.plos.org/plosoneBackground: Recent interferon gamma (IFN-γ)-based studies have identified novel Mycobacterium tuberculosis (M.tb) infection phase-dependent antigens as diagnostic candidates. In this study, the levels of 11 host markers other than IFN-γ, were evaluated in whole blood culture supernatants after stimulation with M.tb infection phase-dependent antigens, for the diagnosis of TB disease. Methodology and Principal Findings: Five M.tb infection phase-dependent antigens, comprising of three DosR-regulon-encoded proteins (Rv2032, Rv0081, Rv1737c), and two resucitation promoting factors (Rv0867c and Rv2389c), were evaluated in a case-control study with 15 pulmonary TB patients and 15 household contacts that were recruited from a high TB incidence setting in Cape Town, South Africa. After a 7-day whole blood culture, supernatants were harvested and the levels of the host markers evaluated using the Luminex platform. Multiple antigen-specific host markers were identified with promising diagnostic potential. Rv0081-specific levels of IL-12(p40), IP-10, IL-10 and TNF-α were the most promising diagnostic candidates, each ascertaining TB disease with an accuracy of 100%, 95% confidence interval for the area under the receiver operating characteristics plots, (1.0 to 1.0). Conclusions: Multiple cytokines other than IFN-γ in whole blood culture supernatants after stimulation with M.tb infection phase-dependent antigens show promise as diagnostic markers for active TB. These preliminary findings should be verified in well-designed diagnostic studies employing short-term culture assays. © 2012 Chegou et al.http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0038501Publisher's versio

Potential of novel Mycobacterium tuberculosis infection phase-dependent antigens in the diagnosis of TB disease in a high burden setting

<p>Abstract</p> <p>Background</p> <p>Confirming tuberculosis (TB) disease in suspects in resource limited settings is challenging and calls for the development of more suitable diagnostic tools. Different <it>Mycobacterium tuberculosis (M.tb) </it>infection phase-dependent antigens may be differentially recognized in infected and diseased individuals and therefore useful as diagnostic tools for differentiating between <it>M.tb </it>infection states. In this study, we assessed the diagnostic potential of 118 different <it>M.tb </it>infection phase-dependent antigens in TB patients and household contacts (HHCs) in a high-burden setting.</p> <p>Methods</p> <p>Antigens were evaluated using the 7-day whole blood culture technique in 23 pulmonary TB patients and in 19 to 21 HHCs (total n = 101), who were recruited from a high-TB incidence community in Cape Town, South Africa. Interferon-gamma (IFN-γ) levels in culture supernatants were determined by ELISA.</p> <p>Results</p> <p>Eight classical TB vaccine candidate antigens, 51 DosR regulon encoded antigens, 23 TB reactivation antigens, 5 TB resuscitation promoting factors (rpfs), 6 starvation and 24 other stress response-associated TB antigens were evaluated in the study. The most promising antigens for ascertaining active TB were the rpfs (Rv0867c, Rv2389c, Rv2450c, Rv1009 and Rv1884c), with Areas under the receiver operating characteristics curves (AUCs) between 0.72 and 0.80. A combination of <it>M.tb </it>specific ESAT-6/CFP-10 fusion protein, Rv2624c and Rv0867c accurately predicted 73% of the TB patients and 80% of the non-TB cases after cross validation.</p> <p>Conclusions</p> <p>IFN-γ responses to TB rpfs show promise as TB diagnostic candidates and should be evaluated further for discrimination between <it>M.tb </it>infection states.</p

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Development of immune-based TB tests suitable for resource limited settings

Thesis (PhD)--Stellenbosch University, 2014.ENGLISH ABSTRACT: - Background - Tuberculosis (TB) is still one of the leading causes of death in poor socio-economic settings. This situation is encouraged by the lack of simple and rapid tests suitable for rapid diagnosis. The newly developed Interferon-gamma Release assays (IGRAs) can detect Mycobacterium tuberculosis (M.tb) infection but fail to discriminate active TB from latently infected individuals. - Objectives - The present thesis aims to develop a rapid and simple test for the diagnosis of active TB disease. This objective was divided into four sub-objectives: 1) identification of potential M.tb antigens and host markers suitable for a TB test using a 7-day whole blood assay (WBA), 2) validate the promising results in an overnight WBA for a rapid, albeit not ex vivo, test, 3) evaluate the diagnostic utility of a two colour ELISpot test, 4) use an unbiased approach to discover multiple new host markers with diagnostic utility using mass spectrometry. - Methods and results - Participants were recruited from the Ravensmead/Uitsig community and day clinics. Stimulated and unstimulated analyte levels in 7-day and overnight WBA supernatants from active TB cases were compared to analyte levels in controls. The results of these experiments showed that Rv0081-stimulated levels of IP-10, IL-12p40, TNF-α and IL-10 were the most promising diagnostic markers in the long term assay as they could correctly classify 100% of the study participants in this assay. Acute phase proteins mainly CRP and SAA were the best diagnostic antigens in the short term assay. The diagnostic utility of these markers was greater in Quantiferon Nil supernatants compared to the stimulated samples. IFN-γ and IL-2 ELISpot was performed where it was found that single cytokine measures could not discriminate active TB to latent infection. When single and double secreting cell populations were taken into consideration, a combination model of ESAT6/CFP10-stimulated single IFN-γ, single IL-2 and IFN-γ/IL-2 double secreting cells could classify participants into their clinical groups with good accuracy. In a pilot study for future discovery of diagnostic markers by mass spectrometry, three depletion methods (ProteoSpin column, Heparin column and ProteoPrep 20) were assessed to identify the most appropriate depletion method for high abundant proteins from serum. The depleted serum samples were analysed in Orbitrap Velos. The antibody based method, ProteoPrep 20, was the best depletion method as it led to the visualisation of a larger number of proteins on Orbitrap. - Conclusion - M.tb antigen-stimulated host markers hold promises in diagnosis of active TB disease. The excellent accuracy observed in the long term assay could not be repeated in the short term assay. Acute phase proteins are the most promising but perform better in unstimulated than in stimulated supernatants and should be evaluated in ex vivo samples like serum or plasma. However, it is likely that further unbiased proteomic approaches, like mass spectrometry, will identify additional promising markers that will allow the development of ex vivo, accurate, pointof- care tests for TB.AFRIKAANSE OPSOMMING: - Agtergrond - Tuberkulose (TB) is steeds die hoof oorsaak van meeste sterftes in behoeftige gebiede wêreldwyd. Hierdie situasie word aangemoedig deur die gebrek aan ʼn eenvoudige en vinnige diagnostiese toets wat spesifiek toepaslik is vir hierdie gebiede. Die nuut ontwikkelde ʽInterferon Gamma-Release’ (IGRA) toetse kan met uitstekende akkuraatheid ʼn Mycobacterium tuberkulose (M.tb) infeksie opspoor, maar is ondoeltreffend om tussen aktiewe TB en sluimerende M.tb infeksie in die mens te onderskei. - Objektiewe - Die huidige tesis het ten doel om 'n vinnige en eenvoudige toets vir die diagnose van aktiewe TB te ontwikkel. Hierdie doelwit is in vier sub-doelwitte verdeel: 1) identifikasie van potensiële M.tb antigene en gasheer merkers wat geskik vir 'n TB-toets deur gebruik te maak van ʼn 7-dag vol bloed toets (WBA), 2) evaluasie van die toepaslikheid van hierdie potensiële merkers en antigene in ʼn oornag WBA, vir die ontwerp van in 'n direkte toets, 3) beoordeling van die diagnostiese waarde van die twee-kleur ELISpot, 4) Assessering van die diagnostiese doeltreffendheid van verskeie gasheer merkers deur gebruik te maak van massaspektrometrie. - Metodes en Resultate - Deelnemers is gewerf vanuit die Ravensmead / Uitsig gemeenskap en klinieke. Gestimuleerde en ongestimuleerde analiet vlakke in 7-dag- en oornag WBA supernatante van aktiewe TB-pasiënte is vergelyk met analiet vlakke in ooreenstemmende kontrole groepe. Resultate van hierdie eksperiment het getoon dat vlakke van IP-10, IL-12p40, TNF-α en IL-10 in antigeen Rv0081 gestimuleerde supernatante, die mees belowende diagnostiese merkers in die lang termyn toets is. Hierdie merkers kon met 100% akkuraatheid die studie deelnemers klassifiseer. Akute fase proteïene, hoofsaaklik CRP en SAA, is aangewys as die beste diagnostiese merkers in die kort termyn toets. Die diagnostiese waarde van hierdie merkers was meer omvangryk in Quantiferon Nil supernatante in vergelyking met dié van WBAs. IFN-γ/IL-2 twee-kleur ELISpot is uitgevoer volgens die vervaardiger se instruksies. Direkte vergelyking het aangetoon dat die kol-vormende eenhede vanaf individuele sitokien produserende selle, nie kan diskrimineer tussen aktiewe TB te latente M.tb infeksie nie. Alhoewel, indien beide enkel-en dubbel sitokien produserende sel populasies in ag geneem word, kan 'n kombinasie van die model ESAT6/CFP10-stimuleerde enkel IFN-γ, enkel IL-2 en IFN- γ/IL-2 dubbel produserende selle, deelnemers klassifiseer in hul kliniese groepe met goeie akkuraatheid. Drie metodes (ProteoSpin kolom Heparien kolom en ProteoPrep 20) is gebruik om oorvloedige serum proteïene te vernietig, waarna die diagnostiese nut van sirkulerende serum merkers deur middel van massaspektrometrie bepaal is. Analise van die serum monsters met behulp van die Orbitrap Velos, het aangetoon dat die teenliggaam metode, ProteoPrep 20, die mees suksesvolle metode is, aangesien dit gelei tot die visualisering van 'n groter aantal proteïene op die Orbitrap. - Gevolgtrekking - M.tb antigeen gestimuleerde gasheer merkers toon groot potensiaal in die diagnose aktiewe TB. Die uitstekende diagnostiese akkuraatheid wat waargeneem is in die lang termyn toets kon egter nie met dieselfde graad van akkuraatheid in die kort termyn toets herhaal word nie. Akute fase proteïene is bewys as die mees belowende ongestimuleerde merkers in die kort termyn toets. Daarbenewens verhoog die diagnostiese waarde van akute fase proteïne aansienlik wanneer gemeet word in Quantiferon supernatant in vergelyking met vol bloed supernatant

"Time-varying electric field induced transmembrane potential of a core-shell model of biological cells"

International audienc

"Simulation of a toy model of cylindrical cells submitted to nonionizing electromagnetic field: effect of membrane cell disruption

International audienc