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Open Journal of Geology 2017年第11期7卷 1724-1738页

作者： germain Marie Monespérance Mboudou Kennedy Folepai Fozao olivier Annoh Njoh Christopher Mbaringong Agyingi Economic Geology Unit Department of Geology University of Buea Buea Cameroon Sedimentology and Petroleum Geolgy/Engineering Unit Department of Geology University of Buea Buea Cameroon

Field studies (location Au pits, sampling of different layers of sedimentary sequences filling the pits, panning of sediments), litho-stratigraphic investigations, grain size analysis and outlining of depositional conditions revealed a characteristic fining upward sequence in all the sections of 08 Au-pits within the Betare Oya basin. A typical profile is 2.5 to 4.5 m thick and is composed of a 30 to 50 cm organic topsoil layer, underlain by a 1.5 m thick reddish brownish gold free saprolite, which is underlain by 1.5 m sandy section. From litho-stratigraphic investigations and grain size analysis results a quartz dominated gravelly 1.4 m thick layer consisting in boulders (275 mm), cobbles (2-−0.0148x2 + 1.2187x + 2.0344, R2 = 0.6929 (sandy layer);2) y = 0.0617x2 + 1.0849x + 0.8097, R2 = 0.8694 (gravelly layer);and y > R2 is satisfied in both cases. This implies that Au recovery from these layers could be effective through gravity separation using sieves mounted on classifiers of 7 cm (sandy layer) and 10 cm (gravelly layer) diameter.

关键词： Betare Oya Aspect Ratios Au Grains Yield Alluvial Sediments Pull-Apart Basin

Water quality and water-use conflicts in Lake Taabo(Ivory Coast)

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Open Journal of Ecology 2012年第1期2卷 38-47页

作者： Noel Groga Allassane Ouattara Sebastino Da Costa Alain Dauta olivier Beauchard Jacques Moreau germain Gourene Pascal Laffaille Laboratoire d’Ecologie et de Biologie Aquatique(LEBA)UFR des Sciences et de Gestion de l’Environnement Universite d’Abobo-Adjame AbidjanAbidjanFrance Universite de Toulouse ToulouseFrance Centre National de Recherche Agronomique(CNRA)Projet Challenge Programm BP AbidjanFrance CNRS UMR 5245 Laboratoire Ecologie Fonctionnelle et EnvironnementToulouseFrance Ecosystem Management Research Group-Universiteitsplein Department of BiologyCampus Drie EikenUniversity of AntwerpWilrijkBelgium Institut National Polytechique de Toulouse Universite Paul SabatierToulouseFrance Ecole Nationale Superieur Agronomique de Toulouse ToulouseFrance

The Lake Taabo (Ivory Coast, Africa) results of the construction of the Taabo dam on the Bandama River. The changes in the water level of the 69-km2 lake depend on 1) the rainfall linked to alternating dry/wet seasons;2) the extraction of water for human uses;3) the discharge of water from the upstream dam and the volumes turbined by the Kossou dam;4) the various anthropic effects (discharge of untreated waste water from towns and industries, and leaching from agricultural land). The average concentrations of nutrients (NH4-N: 1.1 mg/L, NO3-N: 1.62 mg/L, PO4-P: 10 mg/L, SiO2: 15 mg/L) and chlo- rophyll a (from 4.8 to 16.5 μg/L, average 11.4 μg/L) indicates some degree of eutrophication. The cumulated effects that threaten the ecosystem (degradation of water quality and eutrophication) are such that they are likely to interfere with various water uses. In a context of growing health and environmental concerns in Africa, this study demonstrates conflicts between different uses of this water resource and the urgent need for an appropriate policy including specific monitoring of lake water quality, wastewater control, and a programme to reduce agricultural fertilizers.

关键词： Conflicts over Water Use Pollution Tropical Lake Lake Structure

Carbonate Enrichment in Volcanic Debris and Its Relationship with Carbonate Dissolution Signatures of Springs in the Sabga-Bamessing, North West, Cameroon

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International Journal of Geosciences 2014年第1期5卷 107-121页

作者： Raymond Beri Verla germain M. M. Mboudou olivier Njoh Gilles Nyuyki Ngoran Aloysius Ngambu Afahnwie 1Department of Geology Faculty of science University of Buea Buea Cameroon 2Explorers 33 Consultants Yaounde Cameroon 1Explorers 33 Consultants Yaounde Cameroon 2Ministry of Mines Yaounde Cameroon Department of Geology Faculty of science University of Buea Buea Cameroon

Sabga-Bamessing is a part of the Bamenda Mountains, an extinct volcanic center of the West Cameroon Highlands along the Cameroon Volcanic Line (CVL). The pristine volcanic rocks of the Sabga area are alkali mafic to felsic (basanites, phonolites, trachytes and rhyolites). Some weathered sections of a heterolithologic debris flow with a suppositious primary chemistry of the original volcanic rocks prior to weathering have shown significant calcium carbonate enrichment. CaO and LOI values of up 61.31% and 41.72% respectively show corresponding enrichment of 16.54 and 10.88, when compared with average fresh volcanic rocks. Na+ normalized molar ratios computed from the chemistry of springs and rivers show carbonate dissolution signature which is contrary to silicate dissolution expected in acid volcanic rocks. Saturation indices (SI) calculated with PHREEQC reveal that brackish to saline springs are supersaturated with Calcite (CaCO3), Aragonite (CaCO3), Dolomite (CaMg(CO3)2 and Hydroxyl apatite (Ca5(PO4)3OH). Recharging contributions to spring water chemistry deviate from those produced by rock weathering, precipitation and evaporation/crystallization. An enrichment process is therefore predicted as a recharging contributor to water chemistry.

关键词： Cameroon Volcanic Line (CVL) Carbonate Enrichment Carbonate Dissolution Weathering

Polyester-supported Chitosan-Poly(vinylidene fluoride)-Inorganic-Oxide-Nanoparticles Composites with Improved Flame Retardancy and Thermal Stability

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Chinese Journal of Polymer Science 2020年第1期38卷 84-91,I0007页

作者： Ahmed Abed Nabil Bouazizi Stephane Giraud Ahmida El Achari Christine Campagne olivier Thoumire Reddad El Moznine Omar Cherkaoui Julien Vieillard Abdelkrim Azzouz ENSAIT GEMTEX-Laboratoire de Genie et Materiaux TextilesF-59000 LilleFrance Laboratory LPMC Faculty of Science El JadidaChouaib Doukkali UniversityEl JadidaMorocco Laboratory REMTEX ESITHRouted'EI Jadidakm8BP 7731-OulfaCasablancaMorocco Normandie Univ. UNIROUENCNRSPBS(UMR 6270)55 rue Saint Germain27000 EvreuxFrance Normandie Univ. UNI ROUENINSA RouenCNRSCOBRA(UMR 6014)55 rue Saint Germain27000 EvreuxFrance Nanoqam Department of ChemistryUniversity of Quebec at MontrealQCCanada

Polyester(PET) was pre-activated by atmospheric air plasma and coated by various inorganic oxide nanoparticles(MOx) such as titanium dioxide(TiO2), zinc oxide(ZnO), and silicon oxide(SiO2), using poly(vinylidene fluoride)(PVDF) and chitosan(CT) as binders. The resulting PET-PVDF-MOx-CT composites were thermally compressed and then characterized by scanning electron microscopy, Fourier infrared spectroscopy, thermal gravimetric analysis, and flame retardancy(FR) ability tests. PET modifications resulted in more thermally stable and less harmful composites with weaker hazardous gas release. This was explained in terms of structure compaction that blocks pyrolysis gas *** incorporation was found to reduce the material susceptibility to oxidation. This judicious procedure also allowed improving flame retardancy ability, by lengthening the combustion delay and slowing the flame propagation. Chitosan also turned out to contribute to a possible synergy with the other polymers present in the synthesized materials. These results provide valuable data that allow understanding the FR phenomena and envisaging low-cost high FR materials from biodegradable raw materials.

关键词： Polyester nonwovens Composite PVDF Flame retardancy Material oxides Chitosan

An Ischemic Stroke in a Sub-Saharan African Patient Revealing a Carotid Web: A Case Report and a Systematic Literature Review

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World Journal of Neuroscience 2022年第3期12卷 144-152页

作者： Léhleng Agba Donissongui Soro Awissoba Awidina-Ama Liliane Ngoudjo Hugo Yaïche olivier Heinzlef Neurology Department Centre Hospitalier Intercommunal de Poissy/Saint-Germain-En-Laye Poissy France Neurology Department CHU-Kara Université de Kara Kara Togo

One third of ischemic strokes have no known cause, and basic understanding of the mechanisms of these “cryptogenic” strokes is lacking. However, observational studies are increasingly bringing to light an etiology that has long remained hidden, the carotid web. The authors report a case of carotid web in a 32-year-old patient, gardener, from sub-Sharan Africa, with no medical history or known cerebrovascular risk factors. Indeed, due to a sudden weakness of his left limbs, the MRI was performed and revealed an ischemic stroke positive on diffusion-weighted within the territory of the right middle cerebral artery. FLAIR sequences were normal, while T2* sequences revealed an M1 thrombus ipsilateral to the brain lesion. After thrombolysis and thrombectomy, the patient’s weakness improved significantly. Digital subtraction angiography of supra-aortic trunks revealed the carotid web, which was incriminated as the etiology of this ischemic stroke in the absence of any abnormality on the other ancillary examinations that were performed. To prevent a recurrence, the patient was given Aspegic 250 mg/day and received physical therapy. The clinical course was improved and at 3 months, there was no new cerebrovascular event and his Rankin score was 1.

关键词： Carotid Web Ischemic Stroke Sub-Saharan Africa