Ultrathin Oxide Films by Atomic Layer Deposition on Graphene

In this paper, a method is presented to create and characterize mechanically robust, free standing, ultrathin, oxide films with controlled, nanometer-scale thickness using Atomic Layer Deposition (ALD) on graphene. Aluminum oxide films were deposited onto suspended graphene membranes using ALD. Subsequent etching of the graphene left pure aluminum oxide films only a few atoms in thickness. A pressurized blister test was used to determine that these ultrathin films have a Young's modulus of 154 \pm 13 GPa. This Young's modulus is comparable to much thicker alumina ALD films. This behavior indicates that these ultrathin two-dimensional films have excellent mechanical integrity. The films are also impermeable to standard gases suggesting they are pinhole-free. These continuous ultrathin films are expected to enable new applications in fields such as thin film coatings, membranes and flexible electronics.Comment: Nano Letters (just accepted

Mechanical properties of freely suspended atomically thin dielectric layers of mica

We have studied the elastic deformation of freely suspended atomically thin sheets of muscovite mica, a widely used electrical insulator in its bulk form. Using an atomic force microscope, we carried out bending test experiments to determine the Young's modulus and the initial pre-tension of mica nanosheets with thicknesses ranging from 14 layers down to just one bilayer. We found that their Young's modulus is high (190 GPa), in agreement with the bulk value, which indicates that the exfoliation procedure employed to fabricate these nanolayers does not introduce a noticeable amount of defects. Additionally, ultrathin mica shows low pre-strain and can withstand reversible deformations up to tens of nanometers without breaking. The low pre-tension and high Young's modulus and breaking force found in these ultrathin mica layers demonstrates their prospective use as a complement for graphene in applications requiring flexible insulating materials or as reinforcement in nanocomposites.Comment: 9 pages, 5 figures, selected as cover of Nano Research, Volume 5, Number 8 (2012

Fc gamma receptor IIa-H131R polymorphism and malaria susceptibility in sympatric ethnic groups, Fulani and Dogon of Mali.

It has been previously shown that there are some interethnic differences in susceptibility to malaria between two sympatric ethnic groups of Mali, the Fulani and the Dogon. The lower susceptibility to Plasmodium falciparum malaria seen in the Fulani has not been fully explained by genetic polymorphisms previously known to be associated with malaria resistance, including haemoglobin S (HbS), haemoglobin C (HbC), alpha-thalassaemia and glucose-6-phosphate dehydrogenase (G6PD) deficiency. Given the observed differences in the distribution of FcγRIIa allotypes among different ethnic groups and with malaria susceptibility that have been reported, we analysed the rs1801274-R131H polymorphism in the FcγRIIa gene in a study of Dogon and Fulani in Mali (n = 939). We confirm that the Fulani have less parasite densities, less parasite prevalence, more spleen enlargement and higher levels of total IgG antibodies (anti-CSP, anti-AMA1, anti-MSP1 and anti-MSP2) and more total IgE (P < 0.05) compared with the Dogon ethnic group. Furthermore, the Fulani exhibit higher frequencies of the blood group O (56.5%) compared with the Dogon (43.5%) (P < 0.001). With regard to the FcγRIIa polymorphism and allele frequency, the Fulani group have a higher frequency of the H allele (Fulani 0.474, Dogon 0.341, P < 0.0001), which was associated with greater total IgE production (P = 0.004). Our findings show that the FcγRIIa polymorphism might have an implication in the relative protection seen in the Fulani tribe, with confirmatory studies required in other malaria endemic settings

Perceptions and Adaptation Practices of Agropastoralists to Rainfall and Temperature Changes in Mali

Many people in African countries derive their livelihoods from agriculture and livestock. Therefore, unfavourable environmental and climatic conditions render them more vulnerable to increasing food insecurity and poverty rates. However, few studies have investigated how farmers’ adaptation strategies affect farm productivity and household food security in the Sahelian region, notably Mali. This study aims to examine the impacts of climate change agro-pastoralists and to analyse the adaptation strategies in Mali. For this purpose, an analysis of daily rainfall and temperature data from 1960 to 2020 over Bamako, Ségou and Sikasso station was carried out using Instat+ v3.36, Rstudio, XLSTAT and Rclimdex software. Field surveys were conducted among 355 agropastoralists in three regions of Mali to assess the impacts and adaptation strategies of agropastoralists. The analysis of climate data showed a downward trend in overall rainfall. As for the temperature, it shows an upward trend over the series from 1960 to 2020 at the station of Ségou, Sikasso and Bamako. Agropatoralists use adaptation strategies such as organic fertilizers, changing planting dates and growing of short duration maize varieties to mitigate against the negative effects of climate change. The use of organic fertilizers and short-duration use of improved varieties promotes agricultural productivity and food security. We conclude that building agropastoralists adaptive capacity tends to reduce their vulnerability to climate change by increasing crop yields and food security

Effect of hydrogen implantation on the mechanical properties of AlN throughout ion-induced splitting

The ability to transfer bulk quality III-N thin layers onto foreign platforms is a powerful strategy to enable high-efficiency and low-cost optoelectronic devices. Ion-cut using sub-surface defect engineering has been an effective process to split and transfer a variety of semiconductors. With this perspective, hydrogen-implanted AlN samples were annealed in air at temperatures ranging from 300°C to 600°C for 5 min to study the influence of pre-layer splitting treatments on the nanomechanical properties. There is a clear dependence of the hardness on implanted hydrogen implantation fluence. We observe that the as-implanted hardness increased from 18 GPa for the virgin reference sample to ∼25 GPa for the highest fluence of 3 × 1017 H cm-2 prior to annealing. In the case of reference single crystalline Si samples, a significant drop in the hardness and elastic modulus is observed in the H implantation-induced damage zone subsequent to thermal annealing , while for crystalline epitaxial AlN samples with 0.5 × 1017 and 2.0 × 1017 H implant fluences, the hardness increases and peaks until the thermal annealing temperature reaches 350°C and subsequently begins to drop thereafter for higher annealing temperatures. However, for the 1.0 × 1017 H implantation fluence the hardness continues to increase with increasing thermal annealing temperature

Treatment of Posterior Urethral Valves with the Forgarty Catheter: Experience of the Pediatric Surgery

Background. Posterior urethral valves are membranous folds that obstruct urine output. The treatment is multidisciplinary. Aim: To describe the results of valves destruction using the Fogarty catheter. Patients and Methods: This was a retrospective and descriptive study ranging from January 1st, 2014 to December 31th, 2020 in all boys admitted for posterior urethral valves confirmed by retrograde urethrocystography and treated in the department of pediatric surgery by Fogarty valve destruction technique. After the treatment the patients were followed for a period of 6 months with an ultrasound and serum creatinine level. The chi square test was used to discuss the results with a significance threshold of p≤ 0.05 Results: In 7 years we managed 82 cases of posterior urethral valves. The average age of our patients was 9.1± 14.73 months (1 day and 72 months). The mean serum creatinine level was 97.38 ±133.35 μmol/L.&nbsp; A vesico-ureteral reflux was associated with the urethral valves in 29.3% and a vesical diverticulum in 32.9%. Bilateral ureterohydronephrosis was noted in 61%. After 3 months of follow-up the serum creatinine level remained high in 13.4% and a vesico-ureteral reflux persisted in 18.3% of cases. The mean time to valve destruction was 57 ±4.15 days (1 and 660 days). During six months of survey our success rate was 70.7%. Urinary tract infection was noted in 19.5%, and the mortality rate was 9.76%. Conclusion: Although an alternative method, valves destruction technique by the Fogarty probe can give satisfactory results. The rapid diagnosis and treatment of valves will help to improve the prognosis

Human candidate polymorphisms in sympatric ethnic groups differing in malaria susceptibility in Mali.

Malaria still remains a major public health problem in Mali, although disease susceptibility varies between ethnic groups, particularly between the Fulani and Dogon. These two sympatric groups share similar socio-cultural factors and malaria transmission rates, but Fulani individuals tend to show significantly higher spleen enlargement scores, lower parasite prevalence, and seem less affected by the disease than their Dogon neighbours. We have used genetic polymorphisms from malaria-associated genes to investigate associations with various malaria metrics between the Fulanai and Dogon groups. Two cross sectional surveys (transmission season 2006, dry season 2007) were performed. Healthy volunteers from the both ethnic groups (n=939) were recruited in a rural setting. In each survey, clinical (spleen enlargement, axillary temperature, weight) and parasitological data (malaria parasite densities and species) were collected, as well as blood samples. One hundred and sixty six SNPs were genotyped and 5 immunoassays (AMA1, CSP, MSP1, MSP2, total IgE) were performed on the DNA and serum samples respectively. The data confirm the reduced malaria susceptibility in the Fulani, with a higher level of the protective O-blood group, and increased circulating antibody levels to several malaria antigens (p<10(-15)). We identified SNP allele frequency differences between the 2 ethnic groups in CD36, IL4, RTN3 and ADCY9. Moreover, polymorphisms in FCER1A, RAD50, TNF, SLC22A4, and IL13 genes were correlated with antibody production (p-value<0.003). Further work is required to understand the mechanisms underpinning these genetic factors