31 research outputs found

    The influence of sulfate in aluminum coagulation of water

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    Aluminum salts are the most common coagulants used in water treatment to remove contaminants. The objectives of this research was to provide an understanding of some aspects of the influence of sulfate in aluminum coagulation chemistry of natural water. Al(III) solutions were titrated with base to study the role of sulfate in the hydrolysis/precipitation of aluminum. Jar tests were conducted to treat water samples containing varying concentrations of aquatic humic substances (AHS), sulfate and pH. The kinetics and adsorption isotherms of sulfate and aquatic humic substances on aluminum precipitate were developed in adsorption experiments using aluminum precipitate adsorbents. The application of a sensor for Al(III) based on immobilized morin was investigated. Aluminum chloride and aluminum nitrate had similar hydrolysis/precipitation characteristics. Aluminum precipitation occurred at a lower formation function ratio r = (OH) \sb{b}/ (Al) \sb{t} for aluminum sulfate than for aluminum chloride or aluminum nitrate. The aluminum sulfate precipitate was presumed to be an Al-OH-SO\sb4 solid. Equilibrium calculation (ALCHEMI) predicted jurbanite for similar conditions. The addition of sulfate to aluminum chloride solutions resulted in titration curves similar to that of aluminum sulfate. Acidification of the sample prior to titration did not impact the titration curves. An aluminum speciation scheme was presented showing the predominance of monomers at low r ratios, followed by polymers, and Al(OH)\sb4\sp- at high r ratios. pH had the most influence in the coagulation of the water samples treated. The impact of sulfate and AHS additions varied depending on the pH. Turbidity and AHS removal were greater at pH4 than at pH7. Maximum removals were obtained at pH5.5. The formation function fell within the range measured in the Al(III) titration experiments. Higher aluminum precipitates were measured at pH7. The adsorption data of aquatic humic substances (AHS) on aluminum chloride and aluminum sulfate precipitates fitted the Freundlich isotherm best. More AHS adsorbed to the aluminum sulfate precipitate. Little difference existed between the AHS absorbed to either aluminum chloride or aluminum sulfate at pH5.5 and 7. AHS adsorbed to aluminum precipitates formed with AHS. Sulfate adsorption on aluminum precipitates increased with decreasing pH and fitted the Langmuir isotherm best. The competition between AHS and sulfate for the adsorption sites of the aluminum precipitates favored AHS. Inconsistent results were obtained with the sensor based on immobilized morin. Modifications to the procedure and the use of other ligands were recommended in lieu of morin

    THE INVLUENCE OF SULFATE IN ALUMINUM COAGULATION OF WATER

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    The Role of the African Union and Regional Economic Communities as Impetus for Peace and Security: A Case Study of the Economic Community of West African States

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    This paper aims to analyse the link between the African Union (AU), as the premier regional institution whose mandate is mainly to provide peace and security on the continent, and Regional Economic Communities (RECS) in maintenance of peace and security. The article, other than providing a brief background of the international security system, attempts to analyse the conceptual, theoretical, and normative aspects of security within the context of mainly the role of African Union, and RECs, and connects it to the broader international system, where the United Nation(UN) remains a central actor on issues of global peace security. To anchor the debate on the role of the AU and RECs on peace and security the paper uses the Economic Community of West African States (ECOWAS) as a case study for empirical analysis. This is due to the greater similarity between ECOWAS and the AU peace and security architecture that continues to play a complimentary role in ensuring peace and security in the ECOWAS sub- region as evidenced by its numerous intervention with full support of the AU. The article concludes by reiterating the need for institutionalising further the various norms and legal frameworks that should mirror RECs and AU’s collective stand in ensuring peace and security. RECs should also be at the forefront in ensuring peace and security as they are closer to the conflict, which impacts their national interest more than the AU or UN which in most cases seems far flung and do not bear the immediate negative impact of the conflict

    Field experiments of Anopheles gambiae attraction to local fruits/seedpods and flowering plants in Mali to optimize strategies for malaria vector control in Africa using attractive toxic sugar bait methods

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    <p>Abstract</p> <p>Background</p> <p>Based on recent studies in Israel demonstrating that attractive toxic sugar bait (ATSB) methods can be used to decimate local anopheline and culicine mosquito populations, an important consideration is whether the same methods can be adapted and improved to attract and kill malaria vectors in Africa. The ATSB approach uses fruit or flower scent as an attractant, sugar solution as a feeding stimulant, and an oral toxin. The ATSB solutions are either sprayed on vegetation or suspended in simple bait stations, and the mosquitoes ingesting the toxic solutions are killed. As such, this approach targets sugar-feeding female and male mosquitoes. This study examines the attractiveness of African malaria vectors to local fruits/seedpods and flowering plants, key biological elements of the ATSB approach for mosquito control.</p> <p>Methods</p> <p>Three field experiments were conducted at sites in Mali. The attraction of <it>Anopheles gambiae </it>s.l. to 26 different local fruits and seedpods was determined at a site in the semi-arid Bandiagara District of Mali. Wire mesh glue traps with fruits/seedpods suspended on skewers inside were set along a seasonal lagoon. Seven replicates of each fruit/seedpod species were tested, with a water-soaked sponge and a sugar-soaked sponge as controls. The attraction of <it>An. gambiae </it>s.l. to 26 different types of flowering plants was determined at a site near Mopti in Mali. The flowering plants held in a water-filled buried container were tested using the same glue traps, with controls including water only and sugar solution. Six replicates of each selected plant type were tested on transects between rice paddies. Additional studies using CDC light traps were done to determine the relative densities and periodicity of <it>An. gambiae </it>s.l. attraction to branches of the most highly attractive flowering plant, branches without flowers, human odor, and candescent light.</p> <p>Results</p> <p>Of the 26 fruits and seedpods tested, 6 were attractive to <it>An. gambiae </it>s.l. females and males, respectively. Guava (<it>Psidium guajava</it>) and honey melon (<it>Cucumis melo</it>) were the two most attractive fruits for both females and males. Of the 26 flowering plants tested, 9 were significantly attractive for females, and 8 were attractive for males. <it>Acacia macrostachya </it>was the most attractive flowering plant. Periodicity studies using this plant showed peaks of <it>An. gambiae </it>s.l. attraction between 1930 and 2200 h and 0400-0500 h, which differed considerably from the response to human odors, which expectedly peaked at around midnight.</p> <p>Conclusion</p> <p>These field experiments in Mali highlight that female and male <it>An. gambiae </it>s.l. have pronounced differences in attraction for diverse types of indigenous fruits/seedpods and flowering plants. The identification of attractive fruits and seedpods shows that a variety of indigenous and locally abundant natural products could potentially be used as juices to make ATSB solution for mosquito control. As well, the simple methods used to identify the most attractive flowering plants provide valuable insights into the natural history of sugar feeding for <it>An. gambiae </it>s.l. These observations can be used to guide future strategies for employing ATSB methods for malaria vector control in Africa. They also provide a basis for subsequent chemical analysis and development of attractive baits for mosquito control.</p

    Apport des moyens endoscopiques dans la dilatation des sténoses caustiques de l’oesophage

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    Introduction: The aim of this work was to present the contribution of the endoscopy in the management of esophageal dilatation for caustic esophageal stenosis (CES). Methods: This was a descriptive and prospective study in the thoracic surgery department at the Hospital of Mali. A total of 46 cases of CES is recorded and divided into 4 groups according to the topography of the esophageal lesions. For the different methods of dilatation the number of performed endoscopic support was determined to understand the contribution of endoscopic means in the success of dilatation for CES. The outcome, complications and mortality in the two methods were compared. Results: Fibroscopy was used in 41.30% of patients with Savary Guillard dilators and in 47.82% of patients with Lerut dilators. Video laryngoscopy was used in 58.69% of patients who underwent dilatation with Lerut dilators. The passage of the guide wire was performed in 39.13% under video laryngoscopy and 58.68% under fibroscopy. In comparison of the two methods, there is a significant difference in the occurrence of complications (p = 0.04075), general anesthesia (p = 0.02287), accessibility (p = 0.04805) and mortality (p = 0.00402). Conclusion: The CES is a serious disease and under evaluated in Mali. The endoscopies contribute significantly to the success of esophageal dilatation for caustic stenosis in the different methods we used.Keywords: Esophagus, caustic stenosis, dilatation, endoscopicPan African Medical Journal 2016; 2

    Differential infectivity of gametocytes after artemisinin-based combination therapy of uncomplicated falciparum malaria

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    Background: Most malaria-endemic countries use artemisinin-based combination therapy (ACT) as their first-line treatment. ACTs are known to be highly effective on asexual stages of the malaria parasite. Malaria transmission and the spread of resistant parasites depend on the infectivity of gametocytes. The effect of the current ACT regimens on gametocyte infectivity is unclear. Objectives: This study aimed to determine the infectivity of gametocytes to Anopheles gambiae following ACT treatment in the field. Methods: During a randomised controlled trial in Bougoula-Hameau, Mali, conducted from July 2005 to July 2007, volunteers with uncomplicated malaria were randomised to receive artemether-lumefantrine, artesunate-amodiaquine, or artesunate-sulfadoxine/pyrimethamine. Volunteers were followed for 28 days, and gametocyte carriage was assessed. Direct skin feeding assays were performed on gametocyte carriers before and after ACT administration. Results: Following artemether-lumefantrine treatment, gametocyte carriage decreased steadily from Day 0 to Day 21 post-treatment initiation. In contrast, for the artesunate-amodiaquine and artesunate-sulfadoxine/pyrimethamine arms, gametocyte carriage increased on Day 3 and remained constant until Day 7 before decreasing afterward. Mosquito feeding assays showed that artemether-lumefantrine and artesunate-amodiaquine significantly increased gametocyte infectivity to Anopheles gambiae sensu lato (s.l.) (p < 10−4), whereas artesunate-sulfadoxine/pyrimethamine decreased gametocyte infectivity in this setting (p = 0.03). Conclusion: Different ACT regimens could lead to gametocyte populations with different capacity to infect the Anopheles vector. Frequent assessment of the effect of antimalarials on gametocytogenesis and gametocyte infectivity may be required for the full assessment of treatment efficacy, the potential for spread of drug resistance and malaria transmission in the field

    Different Plasmodium falciparum clearance times in two Malian villages following artesunate monotherapy.

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    BACKGROUND: Artemisinin resistance described as increased parasite clearance time (PCT) is rare in Africa. More sensitive methods such as qPCR might better characterize the clearance phenotype in sub-Saharan Africa. METHODS: PCT is explored in Mali using light microscopy and qPCR after artesunate for uncomplicated malaria. In two villages, patients were followed for 28 days. Blood smears and spots were collected respectively for microscopy and qPCR. Parasitemia slope half-life was calculated after microscopy. Patient residual parasitemia were measured by qPCR. RESULTS: Uncorrected adequate clinical and parasitological responses (ACPR) observed in Faladje and Bougoula-Hameau were 78% and 92%, respectively (p=0.01). This reached 100% for both after molecular correction. Proportions of 24H microscopy positive patients in Faladje and Bougoula-Hameau were 97.2% and 72%, respectively (p<0.0001). Slope half-life was 2.8h in Faladje vs 2H in Bougoula-Hameau (p<0.001) and Proportions of 72H patients with residual parasitemia were 68.5% and 40% in Faladje and Bougoula-Hameau, respectively (p=0.003). The mean residual parasitemia was 2.9 in Faladje vs. 0.008 in Bougoula-Hameau (p=0.002). Although artesunate is efficacious in Mali, the longer parasite clearance time with submicroscopic parasitemia observed may represent early signs of developing P. falciparum resistance to artemisinins

    Successful field trial of attractive toxic sugar bait (ATSB) plant-spraying methods against malaria vectors in the Anopheles gambiae complex in Mali, West Africa

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    <p>Abstract</p> <p>Background</p> <p>Based on highly successful demonstrations in Israel that attractive toxic sugar bait (ATSB) methods can decimate local populations of mosquitoes, this study determined the effectiveness of ATSB methods for malaria vector control in the semi-arid Bandiagara District of Mali, West Africa.</p> <p>Methods</p> <p>Control and treatment sites, selected along a road that connects villages, contained man-made ponds that were the primary larval habitats of <it>Anopheles gambiae </it>and <it>Anopheles arabiensis</it>. Guava and honey melons, two local fruits shown to be attractive to <it>An. gambiae </it>s.l., were used to prepare solutions of Attractive Sugar Bait (ASB) and ATSB that additionally contained boric acid as an oral insecticide. Both included a color dye marker to facilitate determination of mosquitoes feeding on the solutions. The trial was conducted over a 38-day period, using CDC light traps to monitor mosquito populations. On day 8, ASB solution in the control site and ATSB solution in the treatment site were sprayed using a hand-pump on patches of vegetation. Samples of female mosquitoes were age-graded to determine the impact of ATSB treatment on vector longevity.</p> <p>Results</p> <p>Immediately after spraying ATSB in the treatment site, the relative abundance of female and male <it>An. gambiae </it>s.l. declined about 90% from pre-treatment levels and remained low. In the treatment site, most females remaining after ATSB treatment had not completed a single gonotrophic cycle, and only 6% had completed three or more gonotrophic cycles compared with 37% pre-treatment. In the control site sprayed with ASB (without toxin), the proportion of females completing three or more gonotrophic cycles increased from 28.5% pre-treatment to 47.5% post-treatment. In the control site, detection of dye marker in over half of the females and males provided direct evidence that the mosquitoes were feeding on the sprayed solutions.</p> <p>Conclusion</p> <p>This study in Mali shows that even a single application of ATSB can substantially decrease malaria vector population densities and longevity. It is likely that ATSB methods can be used as a new powerful tool for the control of malaria vectors, particularly since this approach is highly effective for mosquito control, technologically simple, inexpensive, and environmentally safe.</p

    Expanding Research Capacity in Sub-Saharan Africa Through Informatics, Bioinformatics, and Data Science Training Programs in Mali

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    Bioinformatics and data science research have boundless potential across Africa due to its high levels of genetic diversity and disproportionate burden of infectious diseases, including malaria, tuberculosis, HIV and AIDS, Ebola virus disease, and Lassa fever. This work lays out an incremental approach for reaching underserved countries in bioinformatics and data science research through a progression of capacity building, training, and research efforts. Two global health informatics training programs sponsored by the Fogarty International Center (FIC) were carried out at the University of Sciences, Techniques and Technologies of Bamako, Mali (USTTB) between 1999 and 2011. Together with capacity building efforts through the West Africa International Centers of Excellence in Malaria Research (ICEMR), this progress laid the groundwork for a bioinformatics and data science training program launched at USTTB as part of the Human Heredity and Health in Africa (H3Africa) initiative. Prior to the global health informatics training, its trainees published first or second authorship and third or higher authorship manuscripts at rates of 0.40 and 0.10 per year, respectively. Following the training, these rates increased to 0.70 and 1.23 per year, respectively, which was a statistically significant increase (p &lt; 0.001). The bioinformatics and data science training program at USTTB commenced in 2017 focusing on student, faculty, and curriculum tiers of enhancement. The program’s sustainable measures included institutional support for core elements, university tuition and fees, resource sharing and coordination with local research projects and companion training programs, increased student and faculty publication rates, and increased research proposal submissions. Challenges reliance of high-speed bandwidth availability on short-term funding, lack of a discounted software portal for basic software applications, protracted application processes for United States visas, lack of industry job positions, and low publication rates in the areas of bioinformatics and data science. Long-term, incremental processes are necessary for engaging historically underserved countries in bioinformatics and data science research. The multi-tiered enhancement approach laid out here provides a platform for generating bioinformatics and data science technicians, teachers, researchers, and program managers. Increased literature on bioinformatics and data science training approaches and progress is needed to provide a framework for establishing benchmarks on the topics

    Differential Plasmodium falciparum infection of Anopheles gambiae s.s. molecular and chromosomal forms in Mali

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    BACKGROUND: Anopheles gambiae sensu stricto (s.s.) is a primary vector of Plasmodium falciparum in sub-Saharan Africa. Although some physiological differences among molecular and chromosomal forms of this species have been demonstrated, the relative susceptibility to malaria parasite infection among them has not been unequivocally shown. The objective of this study was to investigate P. falciparum circumsporozoite protein infection (CSP) positivity among An. gambiae s.s. chromosomal and molecular forms. METHODS: Wild An. gambiae from two sites Kela (n = 464) and Sidarebougou (n = 266) in Mali were screened for the presence of P. falciparum CSP using an enzyme-linked immunosorbent assay (ELISA). Samples were then identified to molecular form using multiple PCR diagnostics (n = 713) and chromosomal form using chromosomal karyotyping (n = 419). RESULTS: Of 730 An. gambiae sensu lato (s.l.) mosquitoes, 89 (12.2%) were CSP ELISA positive. The percentage of positive mosquitoes varied by site: 52 (11.2%) in Kela and 37 (13.9%) in Sidarebougou. Eighty-seven of the positive mosquitoes were identified to molecular form and they consisted of nine Anopheles arabiensis (21.4%), 46 S (10.9%), 31 M (12.8%), and one MS hybrid (14.3%). Sixty of the positive mosquitoes were identified to chromosomal form and they consisted of five An. arabiensis (20.0%), 21 Savanna (15.1%), 21 Mopti (30.4%), 11 Bamako (9.2%), and two hybrids (20.0%). DISCUSSION: In this collection, the prevalence of P. falciparum infection in the M form was equivalent to infection in the S form (no molecular form differential infection). There was a significant differential infection by chromosomal form such that, P. falciparum infection was more prevalent in the Mopti chromosomal forms than in the Bamako or Savanna forms; the Mopti form was also the most underrepresented in the collection. Continued research on the differential P. falciparum infection of An. gambiae s.s. chromosomal and molecular forms may suggest that Plasmodium – An. gambiae interactions play a role in malaria transmission
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