Etude des cellules mémoires résistives RRAM à base de HfO2 par caractérisation électrique et simulations atomistiques

Among non-volatile memory technologies, NAND Flash represents a significant portion in the IC market and has benefitted from the traditional scaling of semiconductor industry allowing its high density integration. However, this scaling seems to be problematic beyond the 22 nm node. In an effort to go beyond this scaling limitation, alternative memory solutions are proposed among which Resistive RAM (RRAM) stands out as a serious candidate for NAND Flash replacement. Hence, in this PhD thesis we try to respond to many open questions about RRAM devices based on hafnium oxide (HfO2), in particular, by addressing the lack of detailed physical comprehension about their operation and reliability. The impact of scaling, the role of electrodes, the process of defects formation and diffusion are investigated. The impact of alloying/doping HfO2 with other materials for improved RRAM performance is also studied. Finally, our study attempts to provide some answers on the conductive filament formation, its stability and possible composition.La mémoire NAND Flash représente une part importante dans le marché des circuits intégrés et a bénéficié de la traditionnelle miniaturisation de l’industrie des sémiconducteurs lui permettant un niveau d’intégration élevé. Toutefois, cette miniaturisation semble poser des sérieux problèmes au-delà du noeud 22 nm. Dans un souci de dépasser cette limite, des solutions mémoires alternatives sont proposées parmi lesquelles la mémoire résistive (RRAM) se pose comme un sérieux candidat pour le remplacement de NAND Flash. Ainsi, dans cette thèse nous essayons de répondre à des nombreuses questions ouvertes sur les dispositifs RRAM à base d’oxyde d’hafnium (HfO2) en particulier en adressant le manque de compréhension physique détaillée sur leur fonctionnement et leur fiabilité. L’impact de la réduction de taille des RRAM, le rôle des électrodes et le processus de formation et de diffusion des défauts sont étudiés. L’impact de l’alliage/dopage de HfO2 avec d’autres matériaux pour l’optimisation des RRAM est aussi abordé. Enfin, notre étude tente de donner quelques réponses sur la formation du filament conducteur, sa stabilité et sa possible composition

Factor of Adoption of Organic Cotton in Southern Mali in the Villages of Kolodieba and Yanfolila

Organic cotton has started in 2004 in Mali in the context of a serious crisis in the conventional cotton   production system. It is all the more important for developing countries like Mali where agriculture, one of the pillars of the economy, remains heavily dependent on chemical pesticides. The aim of this study is to analyze the adoption of organic cotton production in the villages of Kolondieba and Yanfolila in southern Mali. Our survey involved 114 people including 48 organic cotton producers and 67 conventional cotton producers. Data were collected through individual interviews based on questionnaires. The analysis of the adoption of organic cotton carried out using a logistic regression model showed that the socio-economic characteristics of producers as well as the sex and education of producers are the main factors influencing their choice of production or not organic cotton. Women prefer organic production more than conventional production. This allows them not to depend on their husbands for inputs but also to have their own fields. Producers who have a very large number of people in the family, producers with schooling, as well as producers with a lot of beef are more apt to adopt organic cotton. Keywords: Adoption, Socio-economic factors, Organic cotton DOI: 10.7176/JESD/12-10-03 Publication date:May 31st 202

Evaluation de l’impact de l’utilisation du diammonium phosphate sur la disponibilité du zinc dans un sol rizicole au Mali

L’utilisation des fertilisants chimiques dans l’agriculture s’est fortement accentuée ce dernier temps au Mali. En effet l’apport régulier du diammonium phosphate (DAP) peut influencer la mobilité du zinc, car les phosphates fixent cet élément. L’étude a pour but d’évaluer l’impact de l’utilisation de ce fertilisant phosphaté sur la disponibilité du zinc. Ainsi pour la caractérisation, l’échantillon est analysé par plusieurs méthodes physico-chimiques : la diffraction des rayons X et la microscopie électronique à balayage. Des essais d’absorption ont été réalisés avec cinq pots numérotés (P0, P1, P2, P3, P4) contenant chacun 1 kg d’échantillon auxquels a été ajouté respectivement 0 ; 2 ; 4 ; 8 et 10 g du fertilisant. D’autres essais ont été conduits avec 3 g d’échantillons prélevés dans le pot P4, auxquels ont été appliqué respectivement 150 ppm, 300 ppm, 450 ppm et 600 ppm de zinc. Il ressort de ce travail que la quantité de Zn retenu est proportionnelle à celle du DAP et que la limite (rétention en 21 jours) = 499,9993 ppm > limite (rétention en 15 jours) = 499,9991 ppm > limite (rétention en 7 jours) = 499,9990 ppm > limite (rétention en 1 jour) = 499,9980 ppm. Cette étude a montré que le diammonium phosphate retient le zinc et influence donc sa biodisponibilité.Mots clés : Sol rizicole, Pana au Mali, rétention du zinc, impact de l’utilisation, Diammonium phosphate. English Title: Estimate the impact of phosphate diammonium usage on the availability of zinc in a rice producing soil in Mali The use of chemical fertilizers in agriculture has highly increased this last time in Mali. In fact the regular contribution of DAP can influence the mobility of zinc, because the phosphate fix this element. The object of this study is to estimate the impact of this phosphate fertilizer on the availability of zinc. So for the characterization, the sample is analysed through several physico-chemical methods: the X rays diffraction and the sweeping electronic microscopy. Some absorbing tests have been carried out with five numbered pots (P0, P1, P2, P3, P4) containing each 1 kg of sample to which has been added respectively 0; 2; 4; 8 and 10 g of the fertilizer. Other tests have conducted with 3 g samples removed from the pot P4, to which has been applied respectively 150 ppm, 300 ppm, 450 ppm and 600 ppm of zinc. As a result of the work the quantity of zinc retained is proportional to the one of DAP and the limit (retention in 21 days) = 499.9993 ppm > limit (retention in 15 days) = 499.9991 ppm > limit (retention in 7 days) = 499.9990 ppm > limit (retention in 1 day) = 499.9980 ppm. This study has shown that the phosphate diammonium retains the zinc and influences in this case its bioavailability.Keywords: Rice producing soil, Pana in Mali, zinc retention, the impact of the usage, phosphate diammonium

Empirical analysis of the relationship between Supply Chain Management and business performance: Case of companies in the cotton sector in Mali.

As part of a national policy favoring the local processing of agricultural products, several companies have been created in the cotton sector in Mali. According to the 2014 report of the National Council of the Malian Patronage, several Malian companies have difficulties in terms of performance. The reasons for this insufficiency are: (difficult access to financing, poor management, poor quality of products, lack of information, etc.). We can summarize this situation by a lack of practices in Supply Chain Management. The objective of this section was to empirically evaluate the impact of supply chain management on the performance of companies operating in the cotton sector in Mali. We favored an approach that links four SCM practices across a variety of dimensions of performance. In our methodology, we used an econometric regression analysis. At the end of this study, it should be remembered that the practices of the management of the supplier relationship and the exchange and sharing of information constitute the two most productive supply chain management practices in the cotton sector in Mali. In addition, among the dimensions of performance considered, financial performance and customer satisfaction are the two most sensitive variants of SCM practices. Key words: the company, Performance, Supply Chain Management, information, customer, cotton sector

Primary squamous cell carcinoma of the kidney in southern Senegal (Ziguinchor): case report and review of the literature

The kidney's primary squamous cell carcinoma is a rare tumor, representing 0.5-0.8% of malignant renal tumors and 4% of upper urinary tract tumors. This pathology often occurs after a long past history of renal lithiasis and repeated untreated or poorly treated urinary tract infections. The delay in diagnosis resulting from an insidious symptomatology, without specific signs, often leads to a pejorative development, especially in poor countries. A seventy-nine-year-old Senegalese woman, with no past history of lithiasis nor recurrent urinary tract infection and urinary schistosomiasis, was received for a recurrent total hematuria associated with left lumbar pain. Clinical examination revealed a mobile tender left lumbar mass, with lumbar contact and renal sloshing. The left renal tumor´s diagnosis was retained on clinical and scannographic arguments, justifying an enlarged left total nephrectomy, by laparotomy. The anatomopathological examination of the surgical sample made it possible to make the diagnosis of primary invasive squamous cell carcinoma of the left kidney and to find foci of carcinoma in-situ on squamous metaplasia in the calyxes. Unlike the typical case of primary squamous cell carcinoma of the kidney, our patient did not have a long past history of renal lithiasis nor untreated or poorly treated recurrent urinary tract infections and urinary schistosomiasis. Primary squamous cell carcinoma of the kidney may not be related to a past history of recurrent urinary tract infections and lithiasis, but to any other cause of squamous metaplasia of the urothelium. Surgery remains the best option for this entity

L’entrepreneuriat féminin au Mali : Enjeux et perspectives

Today access to employment in the public services in Mali constitutes a major challenge for the active population, in particular women. This constraint results in a dominance of informal employment. This type of employment exists in all institutional sectors and in all regions and regardless of background and sex. Female entrepreneurship has taken on increasing importance for decades in most industrialized countries but also in developing countries with specific characteristics (micro-enterprises). International organizations see women's entrepreneurship as an important means of combating poverty and promoting the women’s development. It is in this context that the article discusses the issues and in order to decide the future prospects of this entrepreneurship on the labor market. In a theoretical context, without modeling aspect, the methodological research focuses on the documentary review, the exploration of available data produced by the statistical information structures of public administrations in Mali. The analyzes of these data are contrasted with the various socio-demographic determinants. The results showed that female entrepreneurship is topical in Mali through different forms of organizations, especially in the informal sector in small businesses such as agribusiness. It emerges from these results that the difficulties or constraints are multiple, for which support measures are requested by women entrepreneurs.     Classification JEL : J64 Paper type : Empirical ResearchL'accès à l'emploi dans les fonctions publiques de l’État constitue aujourd’hui au Mali un défi majeur pour la population active, en particulier les femmes. Cette contrainte se traduit par une dominance de l'emploi informel Ce type d'emploi existe dans tous les secteurs institutionnels et dans toutes les régions et quel que soit le milieu et le sexe. L’entrepreneuriat féminin a pris depuis des décennies une importance croissante dans la plupart des pays industrialisés, mais aussi dans les pays en voie de développement avec des caractéristiques spécifiques (micro entreprises). Les organisations internationales voient l’entrepreneuriat féminin comme un important moyen de lutte contre la pauvreté et de l’épanouissement de la femme. C’est dans ce contexte que cet article évoque les enjeux et opine les perspectives d’avenir de cet entrepreneuriat sur le marché du travail. Dans un contexte théorique, sans aspect de modélisation, la méthodologie de la recherche porte sur la revue documentaire, l’exploration des données disponibles produites par les structures d’informations statistiques des administrations publiques du Mali. Les analyses de ces données sont contrastées aux divers déterminants sociodémographiques. Les résultats ont montré que l’entrepreneuriat féminin est à l’actualité au Mali à travers différentes formes d’organisations surtout dans le secteur informel dans de petites entreprises comme les agroalimentaires. Il ressort de ces résultats que les difficultés ou les contraintes sont multiples dont des mesures d’accompagnement sont sollicitées par les femmes entrepreneures.     Classification JEL : J64 Type de papier : Recherche empiriqu

Interethnic Differences in Antigen-Presenting Cell Activation and TLR Responses in Malian Children during Plasmodium falciparum Malaria

The Fulani ethnic group from West Africa is relatively better protected against Plasmodium falciparum malaria as compared to other sympatric ethnic groups, such as the Dogon. However, the mechanisms behind this lower susceptibility to malaria are largely unknown, particularly those concerning innate immunity. Antigen-presenting cells (APCs), and in particular dendritic cells (DCs) are important components of the innate and adaptive immune systems. Therefore, in this study we investigated whether APCs obtained from Fulani and Dogon children exhibited differences in terms of activation status and toll-like receptor (TLR) responses during malaria infection. Lower frequency and increased activation was observed in circulating plasmacytoid DCs and BDCA-3+ myeloid DCs of infected Fulani as compared to their uninfected counterparts. Conversely, a higher frequency and reduced activation was observed in the same DC subsets obtained from peripheral blood of P. falciparum-infected Dogon children as compared to their uninfected peers. Moreover, infected individuals of both ethnic groups exhibited higher percentages of both classical and inflammatory monocytes that were less activated as compared to their non-infected counterparts. In line with APC impairment during malaria infection, TLR4, TLR7 and TLR9 responses were strongly inhibited by P. falciparum infection in Dogon children, while no such TLR inhibition was observed in the Fulani children. Strikingly, the TLR-induced IFN-γ release was completely abolished in the Dogon undergoing infection while no difference was seen within infected and non-infected Fulani. Thus, P. falciparum infection is associated with altered activation status of important APC subsets and strongly inhibited TLR responses in peripheral blood of Dogon children. In contrast, P. falciparum induces DC activation and does not affect the innate response to specific TLR ligands in Fulani children. These findings suggest that DCs and TLR signalling may be of importance for the protective immunity against malaria observed in the Fulani

PD-1 Co-inhibitory and OX40 Co-stimulatory Crosstalk Regulates Helper T Cell Differentiation and Anti-Plasmodium Humoral Immunity

SummaryThe differentiation and protective capacity of Plasmodium-specific T cells are regulated by both positive and negative signals during malaria, but the molecular and cellular details remain poorly defined. Here we show that malaria patients and Plasmodium-infected rodents exhibit atypical expression of the co-stimulatory receptor OX40 on CD4 T cells and that therapeutic enhancement of OX40 signaling enhances helper CD4 T cell activity, humoral immunity, and parasite clearance in rodents. However, these beneficial effects of OX40 signaling are abrogated following coordinate blockade of PD-1 co-inhibitory pathways, which are also upregulated during malaria and associated with elevated parasitemia. Co-administration of biologics blocking PD-1 and promoting OX40 signaling induces excessive interferon-gamma that directly limits helper T cell-mediated support of humoral immunity and decreases parasite control. Our results show that targeting OX40 can enhance Plasmodium control and that crosstalk between co-inhibitory and co-stimulatory pathways in pathogen-specific CD4 T cells can impact pathogen clearance

Memory CD8 + T cell compartment associated with delayed onset of Plasmodium falciparum infection and better parasite control in sickle‐cell trait children

Study of individuals with protection from Plasmodium falciparum (Pf) infection and clinical malaria, including individuals affected by the sickle-cell trait (HbAS), offers the potential to identify cellular targets that could be translated for therapeutic development. We previously reported the first involvement of cellular immunity in HbAS-associated relative protection and identified a novel subset of memory-activated NK cells that was enriched in HbAS children and associated with parasite control. We hypothesised that other memory cell subsets might distinguish the baseline profile of HbAS children and children with normal haemoglobin (HbAA). Subsets of memory T cells and NK cells were analysed by flow cytometry in paired samples collected from HbAS and HbAA children, at baseline and during the first malaria episode of the ensuing transmission season. Correlations between cell frequencies and features of HbAS-mediated protection from malaria were determined. HbAS children displayed significantly higher frequency of memory CD8+ T cells at baseline than HbAA children. Baseline frequency of memory CD8+ T cells correlated with features of HbAS-mediated protection from malaria. Exploration of memory CD8+ T cell subsets revealed that central memory CD8+ T cell frequency was higher in HbAS children than in HbAA children. This study shows that HbAS children develop a larger memory CD8+ T cell compartment than HbAA children, and associates this compartment with better control of subsequent onset of infection and parasite density. Our data suggest that central memory CD8+ T cells may play an important role in the relative protection against malaria experienced by HbAS individuals, and further work to investigate this is warranted

A Positive Correlation between Atypical Memory B Cells and Plasmodium falciparum Transmission Intensity in Cross-Sectional Studies in Peru and Mali

transmission intensity correlates with atypical memory B cell expansion.. In Peru, the mean level of atypical memory B cells, as a percent of total B cells, was higher than U.S. adults (Peru mean: 5.4% [95% CI: 3.61–7.28]; U.S. mean: 1.4% [95% CI: 0.92–1.81]; p<0.0001) but lower than Malian adults (Mali mean 13.1% [95% CI: 10.68–15.57]; p = 0.0001). In Peru, individuals self-reporting ≥1 prior malaria episodes had a higher percentage of atypical memory B cells compared to those reporting no prior episodes (≥1 prior episodes mean: 6.6% [95% CI: 4.09–9.11]; no prior episodes mean: 3.1% [95% CI: 1.52–4.73]; p = 0.028). infection could contribute to our understanding of naturally-acquired malaria immunity