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Search Results: 1 - 10 of 10908 matches for " Kamgang Pierre "
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Spinel-Bearing Lherzolite Xenoliths from Hosséré Garba (Likok, Adamawa-Cameroon): Mineral Compositions and Geothermobarometric Implications  [PDF]
Nguihdama Dagwai, Chazot Gilles, Kamgang Pierre, Mbowou Gbambié Isaac Bertrand, Ngounouno Isma?la
International Journal of Geosciences (IJG) , 2014, DOI: 10.4236/ijg.2014.512117
Abstract: Spinel-bearing lherzolite xenoliths from the Hossere Garba (1272 m.a.s.l) volcano on the Adamawa Plateau, is located in Likok village, at about 35 km to WSW of Ngaoundere. These xenoliths (~11 cm size) have been sampled into the host basaltic lava flows from the NE flank of the Hossere Garba volcano. These xenoliths characterized by porphyroclastic texture consisted of olivine (~55 vol.%), orthopyroxene (~19 vol.%) and clinopyroxene (~21 vol.%) crystals. Spinel crystals (~5 vol.%) are red brown and interstitial between the crystals of olivine and pyroxenes. CaO contents are low (<0.08 wt%) in olivine and similar to those estimated (CaO: 0.05 - 0.1 wt%) for the mantle origin. The values of AlVI/AlIV ratio range between 1.1 and 1.3 for the Cr-diopside crystals from Hossere Garba xenoliths. The constant value of the volumes V(Cell) and V(M1) for clinopyroxene compositions, indicates the similar pressures. Hossere Garba represents a residual sequence issued from partial melting of a mantle source. Similar compositions have been recorded in minerals of ultramafic xenoliths from other ultramafic xenoliths domains of the Cameroon Line and the Adamawa Plateau.
Study of Multi-Origin Hazards and Assessment of Associated Risks in the Lefo Caldera (Bamenda Volcano, Cameroon Line)  [PDF]
Zangmo Tefogoum Ghislain, Nkouathio David Guimolaire, Kagou Dongmo Armand, Gountie Dedzo Merlin, Kamgang Pierre
International Journal of Geosciences (IJG) , 2014, DOI: 10.4236/ijg.2014.511107
Abstract: The Bamenda Volcano (BV) (2621 m) is a stratovolcano situated in the Cameroon Line (CL). BV includes Mount Lefo (2534 m) which is situated on its southern slopes and contains one elliptical caldera (3 × 4 km). This caldera is propitious to farming and breeding activity. Despite these profitable assets, Lefo caldera (LC) is an amphitheater of the occurrence of multi-origin hazards that have direct or indirect impacts on the biodiversity and human patrimony. The most present hazards are those of meteorological origin. Numerous combined factors (steepest slopes, heavy rainfalls, weathered state of volcanic products…) rule these hazards. These factors gave rise to the occurrence of landslides, gullies erosion and rock falls which occur precisely on caldera northern and eastern rims. Hazards of anthropogenic origin are based on the destruction of the vegetation cover by the population for dealing, firewood and building issues. Moreover, during the breeding activity, the cattle covers the caldera throughout the day; this unevens the topography and destroys the meadow. Hazards of volcanological origin are not yet occurring in LC; but the recent Lake Monoun (1984) and Nyos (1986) CO2 eruptions, mount Cameroon eruptions (1999 and 2000) and mount Oku Lake event (2011) which are close to the BV and, the age of 0 Myr of basalt, constitutes a subject of controversy toward the reactivation of the Cameroonian hotspot faults. The assessment of risks in LC was based on the average income of breeding activity and house investment. The economy of LC is valued at about US$527472.527. The level of such risk will be important in case of loss of human beings and the destruction of geomorphosites’ values. In order to reduce the level of looses in this zone, hazard and risks maps are provided in this paper as well as some recommendations.
Evidence of Dengue Virus Transmission and Factors Associated with the Presence of Anti-Dengue Virus Antibodies in Humans in Three Major Towns in Cameroon
Maurice Demanou ,Régis Pouillot,Marc Grandadam,Pascal Boisier,Basile Kamgang,Jean Pierre Hervé,Christophe Rogier,Dominique Rousset,Christophe Paupy
PLOS Neglected Tropical Diseases , 2014, DOI: 10.1371/journal.pntd.0002950
Abstract: Background Dengue is not well documented in Africa. In Cameroon, data are scarce, but dengue infection has been confirmed in humans. We conducted a study to document risk factors associated with anti-dengue virus Immunoglobulin G seropositivity in humans in three major towns in Cameroon. Methodology/Principal Findings A cross sectional survey was conducted in Douala, Garoua and Yaounde, using a random cluster sampling design. Participants underwent a standardized interview and were blood sampled. Environmental and housing characteristics were recorded. Randomized houses were prospected to record all water containers, and immature stages of Aedes mosquitoes were collected. Sera were screened for anti-dengue virus IgG and IgM antibodies. Risk factors of seropositivity were tested using logistic regression methods with random effects. Anti-dengue IgG were found from 61.4% of sera in Douala (n = 699), 24.2% in Garoua (n = 728) and 9.8% in Yaounde (n = 603). IgM were found from 0.3% of Douala samples, 0.1% of Garoua samples and 0.0% of Yaounde samples. Seroneutralization on randomly selected IgG positive sera showed that 72% (n = 100) in Douala, 80% (n = 94) in Garoua and 77% (n = 66) in Yaounde had antibodies specific for dengue virus serotype 2 (DENV-2). Age, temporary house walls materials, having water-storage containers, old tires or toilets in the yard, having no TV, having no air conditioning and having travelled at least once outside the city were independently associated with anti-dengue IgG positivity in Douala. Age, having uncovered water containers, having no TV, not being born in Garoua and not breeding pigs were significant risk factors in Garoua. Recent history of malaria, having banana trees and stagnant water in the yard were independent risk factors in Yaounde. Conclusion/Significance In this survey, most identified risk factors of dengue were related to housing conditions. Poverty and underdevelopment are central to the dengue epidemiology in Cameroon.
Regolith Geochemistry and Mineralogy of the Mbalam Itabirite-Hosted Iron Ore District, South Eastern Cameroon  [PDF]
M. T. Nforba, V. Kamgang Kabeyene, C. E. Suh
Open Journal of Geology (OJG) , 2011, DOI: 10.4236/ojg.2011.12003
Abstract: Mbalam is a major emerging iron ore district in Cameroon. The regolith over the Mbalam itabirite, consists of relict, erosion and depositional units. Itabirite rock fabric is preserved in the relict regolith, the erosion unit is marked by erosion of the carapace cap regolith, with the depositional unit dominated by canga (loose fragments of hematite and/or itabirite cemented by goethite) or loose scree. Fe concentration increases from average of 46.18 wt% in the depositional soil material to as much as 79.08 wt% in the relict regolith regime with variation due to supergene weathering. Fe is the least mobile of the major elements, and the Fe oxides become significant phases and control the distributions of many elements. Absorption of P by iron oxides or oxyhydroxides appears to be the major mechanism of P retention in the different regolith environment. Au dispersion in the weathering profile occurs by two possible mechanisms (mechanical and hydromorphic) and it distribution is sporadic. Zr maintains a positive correlation with Al and Ti indicating extensive chemical weathering in the source area and resulting in a relative concentration of those residual elements. The weathered material show relatively high ΣREE; this is due to upward remobilisation from the lower primary itabirite, and the downward leaching of the upper mineralisation horizons by the descending epigenetic solutions.
Modeling the Dynamics of Malaria Transmission with Bed Net Protection Perspective  [PDF]
Jean Claude Kamgang, Vivient Corneille Kamla, Stéphane Yanick Tchoumi
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.519298
Abstract: We propose and analyze an epidemiological model to evaluate the effectiveness of bed nets as a prophylactic measure in malaria-endemic areas. The main purpose in this work is the modeling of the aggressiveness of anopheles mosquitoes relative to the way humans use to protect themselves against bites of mosquitoes. This model is a system of several differential equations: the number of equations depends on the particular assumptions of the model. We compute the basic reproduction number\"\", and show that if\"\", the disease free equilibrium (DFE) is globally asymptotically stable on the non-negative orthant. If\"\", the system admits a unique endemic equilibrium (EE) that is globally and asymptotically stable. Numerical simulations are presented corresponding to scenarios typical of malaria-endemic areas, based on data collected in the literature. Finally, we discuss the relative effectiveness of different kinds of bed nets.
An Explanation of the Black Color of River Nyong Water’s and Associated Alluviums (Cameroon)  [PDF]
Samba Assomo Philippe, Chi Cheyneysu Emmanuel Toussaints, Kamgang Kabeyene Beyala Veronique
International Journal of Geosciences (IJG) , 2015, DOI: 10.4236/ijg.2015.64030
Abstract: The River Nyong is situated in Akonolinga (central-south of Cameroon). In order to search for raw materials in ceramic use, samples of alluvium obtained from the deposits in the Nyong River clays have been studied. The results obtained show that, the samples contain important quantity of organic matter and the soil is acidic .These two parameters are necessary to understand the origin of the characteristic color of alluvium and water of the River Nyong.
Backward Bifurcation and Control in Transmission Dynamics of Arboviral Diseases
Hamadjam Abboubakar,Jean Claude Kamgang,Daniel Tieudjo
Quantitative Biology , 2015,
Abstract: In this paper, we derive and analyze a compartmental model for the control of arboviral diseases which takes into account an imperfect vaccine combined with individual protection and some vector control strategies already studied in the literature. After the formulation of the model, a qualitative study based on stability analysis and bifurcation theory reveals that the phenomenon of backward bifurcation may occur. The stable disease-free equilibrium of the model coexists with a stable endemic equilibrium when the reproduction number, R 0 , is less than unity. Using Lyapunov function theory, we prove that the trivial equilibrium is globally asymptotically stable; When the disease-- induced death is not considered, or/and, when the standard incidence is replaced by the mass action incidence, the backward bifurcation does not occur. Under a certain condition , we establish the global asymptotic stability of the disease--free equilibrium of the full model. Through sensitivity analysis, we determine the relative importance of model parameters for disease transmission. Numerical simulations show that the combination of several control mechanisms would significantly reduce the spread of the disease, if we maintain the level of each control high, and this, over a long period.
Global Stability of a SVEIR Epidemic Model: Application to Poliomyelitis Transmission Dynamics  [PDF]
L. N. Nkamba, J. M. Ntaganda, H. Abboubakar, J. C. Kamgang, Lorenzo Castelli
Open Journal of Modelling and Simulation (OJMSi) , 2017, DOI: 10.4236/ojmsi.2017.51008
Abstract: The lack of treatment for poliomyelitis doing that only means of preventing is immunization with live oral polio vaccine (OPV) or/and inactivated polio vaccine (IPV). Poliomyelitis is a very contagious viral infection caused by poliovirus. Children are principally attacked. In this paper, we assess the impact of vaccination in the control of spread of poliomyelitis via a deterministic SVEIR (Susceptible-Vaccinated-Latent-Infectious-Removed) model of infectious disease transmission, where vaccinated individuals are also susceptible, although to a lesser degree. Using Lyapunov-Lasalle methods, we prove the global asymptotic stability of the unique endemic equilibrium whenever \"\"?. Numerical simulations, using poliomyelitis data from Cameroon, are conducted to approve analytic results and to show the importance of vaccinate coverage in the control of disease spread.
Industrial Potentiality of Alluvial Clays Deposits from Cameroon: Influence of Lateritic Clayey Admixture for Fired Bricks Production  [PDF]
Aubin Nzeugang Nzeukou, Véronique Kabeyene Kamgang, Robert Eko Medjo, Uphie Chinje Melo, André Njoya, Patrick Ninla Lemougna, Nathalie Fagel
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2013, DOI: 10.4236/jmmce.2013.15037
Abstract: The cartography and characterization of an alluvial clay deposit from Ebebda (Central region of Cameroon) were carried out in order to assess its suitability for the production of fired clay bricks. The clayey area investigated is ~ 50,000 m2 with an average thickness of the exploitable layer of 2.2 m, suggesting a deposit of about ~2.2 × 105 tonnes of clay. Mineralogy, physico-chemical and thermal analyses as well as firing properties were performed on representative clay samples. Kaolinite and quartz are the major minerals associated to illite. Upon heating to 900℃ - 1200℃, the linear shrinkage varies from 1.5% to 15%, the water absorption from 1.5% to 24% and the bending strength from 2 to 12 MPa. The admixture of lateritic clays (widely available) at 50%, 60%, 70% and 80% allow to decrease the shrinkage and bending strength, and to increase the water absorption. Overall, properties were satisfying the requirement for fired brick with 70% of laterite in the mixture.
Effets des extraits totaux aqueux de mallotus oppositifolium et de euphorbia hirta (euphorbiaceae) sur l’activite contractile intestinale du rat
R Kamgang, R Zintchem, T Dimo, MP Yewah
African Journal of Science and Technology , 2001,
Abstract: Effects of total aqueous extracts of Mallotus oppositifolium and Euphorbia hirta (Euphorbiaceae) on intestinal contractile activity of the rat. - The contractile activity of the total aqueous extract of Mallotus oppositifolium (Mo) and Euphorbia hirta (Eh) leaves was investigated. Mo extracts (1.32 mg/mL) demonstrated inhibiting effect on the stimulation of rat ileal contractions by acetylcholine (-9 mm) and potassium chloride (-7 mm). Administrated before the magnesium sulfate (6 g/kg), Mo extracts reduce the faeces quantity (- 11g, p<1 %). Eh activated the stimulation of rat ileal contractions by acetylcholine (+148 %) and potassium chloride (+381 %). Administrated before the magnesium sulfate, the Eh aqueous extract reduced the quantity of faeces (-12 g, p<5 %). The results suggest that on the contractile activity of the rat intestine, total aqueous extracts of Mallotus oppositifolium could have antispasmodic effect, while Euphorbia hirta extracts could have spasmogenic effect in vitro and antidiarrhoeic effects in vivo
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