Pheochromocytoma (PHEO) is a rare endocrine tumor from the chromaffin cells in the adrenomedullary gland and sympathetic/parasympathetic ganglia, secreting one or more catecholamines. It is frequently associated with ...Pheochromocytoma (PHEO) is a rare endocrine tumor from the chromaffin cells in the adrenomedullary gland and sympathetic/parasympathetic ganglia, secreting one or more catecholamines. It is frequently associated with hypertension and described in the literature as a cause of secondary diabetes mellitus. In patients with known persistent uncontrolled diabetes, PHEO is rarely mentioned as the cause of uncontrolled diabetes. The authors report a rare case of PHEO diagnosed in a 64-year-old female patient treated for 10 years with type 2 diabetes mellitus and hypertension. She was treated using a combination of insulin (2 injections) and Metformin 1000 mg twice a day. The glycemic control was poor (HbA1c-11%), and persistent High Blood Pressure (HBP). She presented with unexplained weight loss associated with permanent hyperhidrosis (sweating), affecting her quality of life and diffuse abdominal pain. The investigations confirmed the diagnosis of PHEO, which resection led to improvement of glycemic control and hypertension.展开更多
The digital transformation in Cameroon presents critical cybersecurity challenges that demand immediate attention and strategic intervention. This comprehensive analysis examines the evolving cybersecurity landscape i...The digital transformation in Cameroon presents critical cybersecurity challenges that demand immediate attention and strategic intervention. This comprehensive analysis examines the evolving cybersecurity landscape in Cameroon from 2020 to 2023, during which cyber-attacks increased by 156% and financial losses from digital fraud exceeded $45 million. This research identifies significant vulnerabilities in Cameroon’s cybersecurity ecosystem through a rigorous assessment of national infrastructure, policy frameworks, and institutional capacities. Recent data indicates that while digital service adoption has grown exponentially, with internet penetration reaching 35.2% in 2023, cybersecurity measures have lagged significantly behind international standards. This analysis draws on comprehensive data from multiple sectors, including financial services, government institutions, and telecommunications, incorporating findings from the National Cybersecurity Assessment Program and the Digital Infrastructure Security Report. The research reveals that 73% of organizations lack dedicated security teams, while response times to cyber incidents average 72 hours—three times than the global standard. Based on these findings, this paper proposes evidence-based solutions for enhancing digital resilience, including policy modernization, capacity-building initiatives, and technical infrastructure development. The recommendations encompass short-term tactical responses, medium-term strategic improvements, and long-term structural changes, providing a comprehensive roadmap for strengthening Cameroon’s national cybersecurity frameworks.展开更多
In order to contribute to a better understanding of the biodiversity of local chicken populations, this study focused on the description of the essential qualitative parameters in the phenotypic characterization of lo...In order to contribute to a better understanding of the biodiversity of local chicken populations, this study focused on the description of the essential qualitative parameters in the phenotypic characterization of local species. Conducted in 6 localities in the Far North Region of Cameroon (Doukoula, Yagoua, Guidiguis, Dziguilao, Maroua 3rd and Méri), a population of 240 local chickens, including 172 hens and 68 cocks were characterized in family farms. The choice of localities was made on the basis of their strong potential local chicken flocks in the region. To this end, each animal was the subject of a qualitative description based on the identification of the sex of the animal, the description of the colorations of the plumage and extremities, and the description of the types of format, plumage and crests. All observations were made with the naked eye and in daylight and then photographed. The main results show that the plumage colors are multiple and dominated by the White-Pied-Black (21.7%) and the Mille-fleur (20.8%);the wattles are dominated by the red (60%) and the pink (35.4%);the tarsi are dominated by the white (43.8%) and the black (32.08%);the white skin (92.5%) dominates over the pink skin (7.5%);the “Smooth-uniform” feather is dominant (97.08%), followed by the smooth-crested type (2.08%) and the fries type (0.82%);the medium size of the chickens is dominant (86.66%), followed by the dwarf size (9.58%) and the large size (3.75%). The results of this study demonstrate that there is a strong phenotypic diversity within the local chicken population. This diversity can serve as a basis for the development of selection, conservation and genetic potential improvement programs based on rational exploitation of the local chicken.展开更多
Existing knowledge on degraded mountain landscapes does not shed sufficient light on the socio-economic and ecological opportunities essential for successful restoration initiatives.To address this knowledge lacuna,a ...Existing knowledge on degraded mountain landscapes does not shed sufficient light on the socio-economic and ecological opportunities essential for successful restoration initiatives.To address this knowledge lacuna,a study was conducted on the Bamboutos Mountains landscape in Cameroon with the main objective being to analyse the opportunities for restoring this landscape in line with local,national and international development goals and to minimise the negative effects of land-use decisions.Following the Restoration Opportunity Assessment Methodology(ROAM)approach,five participatory reflection workshops were organized in the five target clusters of the landscape for data collection.The results of the study led to the development of a restoration map that presents five interventions:grassland management on an area of 4,720 ha currently occupied by shrub savannah;the practice of fruit-based agroforestry on 3,221 ha of agricultural fields;the planting of riparian forests on 451 ha of degraded watercourses;the revegetation and conservation of the Bamboutos Mountains forest reserve,sacred forests and relics of degraded forests on 435 ha of area;and the revegetation of 6 ha of degraded water sources.The carbon stocks vary from 2.66 to 345.15 tC/ha depending on the type of restoration intervention with a total carbon stock of 247,367.45 tC/ha on the 8,834 ha of area to be restored.This presents a very satisfactory economic cost-benefit,because for an investment of USD 5,991,269.84,a gain of USD 100,439,519.13 could be achieved after 20 years,i.e.,an estimated profit of USD 94,448,249.29.These results provide an understanding of the types of restoration interventions possible in this landscape,a solid basis for planning a restoration initiative.The results equally provide guidance on priority areas from a social,economic,and ecological perspective.展开更多
BACKGROUND The global prevalence of diabetes among adults aged 29-79 years was found to be 10.5%.It is a global public health threat with a rising trend in morbidity and mortality.Poor glycemic control(GC)among patien...BACKGROUND The global prevalence of diabetes among adults aged 29-79 years was found to be 10.5%.It is a global public health threat with a rising trend in morbidity and mortality.Poor glycemic control(GC)among patients with type 2 diabetes mellitus(T2DM)is a major determinant of diabetes-related complications.There are limited data on GC and associated factors among patients with T2DM in South West Region,Cameroon.AIM To assess GC and identify contributing factors among patients with T2DM in a regional hospital in South West Region,Cameroon.METHODS A cross-sectional study was conducted from February 2022 to July 2022 among 131 participants in Limbe Regional Hospital who were selected by convenience.Glycated hemoglobin(HbA1c)was measured by ion-exchange chromatography.Sociodemographic,clinical,and lifestyle data were collected,entered into Excel,and exported to Statistical Package for Social Sciences version 22 for analysis.A multivariate logistic regression analysis was conducted to assess the association between explanatory variables and GC.The level of significance was set at P<0.05.RESULTS The mean age was 56±5.1 years.Eighty-eight(67.2%)patients were female.The mean HbA1c was 8.8%±1.8%.Poor GC(HbA1c≥7%)was registered in 106(80.9%;95%confidence interval:73.1%-87.3%)participants.Lack of self-monitoring of blood glucose at home was associated with poor GC(adjusted odds ratio:3.858,95%confidence interval:1.262-11.800;P=0.018).CONCLUSION The majority of patients with T2DM had poor GC.Absence of self-monitoring of blood glucose at home was the main contributing factor for poor GC.展开更多
Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon...Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon stocks in the sacred forests of Bandrefam and Batoufam (western Cameroon). The floristic inventory and the stand structures were carried out in 25 m × 25 m plots for individuals with diameters greater than 10 cm;5 m × 5 m for individuals with diameters less than 10 cm. Carbon stocks were estimated using the non-destructive method and allometric equations. The floristic inventory identified 65 species divided into 57 genera and 30 families in the Bandrefam sacred forest and 45 species divided into 42 genera and 27 families in the Batoufam sacred forest. In the Bandrefam, the most important families are Phyllanthaceae (53.98%), Moraceae (21.69%), Lamiaceae (20.15%). At Batoufam, the most important families are Phyllanthaceae (39.73%), Fabaceae (28.47%), Araliaceae (23.77%). Malacantha alnifolia (55.14%), Vitex grandifolia (18.43%), Bosqueia angolensis (15.06%) were the most important species in Bandrefam. Otherwise, Malacantha alnifolia (28%), Polyscias fulva (22.73%), Psychotria sp. (21.28%) were the most important in Batoufam. The Bandrefam sacred forest has the highest tree density (2669 stems/ha). Total carbon stock is 484.88 ± 2.28 tC/ha at Batoufam and 313.95 ± 0.93 tC/ha at Bandrefam. The economic value varies between 5858.04 ± 27.62 USD/ha in Batoufam sacred forest and 3788.51 ± 11.26 USD/ha in Bandrefam sacred forest. The number of individuals and small-diameter trees has little influence on the carbon stocks in the trees. Medium-diameter trees store the most carbon, and very large-diameter trees, which are very poorly represented, store less carbon. In another way, wood density and the basal areas influence the carbon storage of the trees.展开更多
Invariably, it is the poorest of the poor who are mostly affected by perverse disasters, policies and laws. A major concern in disaster research is to explore the relationship between shock experiences and victims＇ p...Invariably, it is the poorest of the poor who are mostly affected by perverse disasters, policies and laws. A major concern in disaster research is to explore the relationship between shock experiences and victims＇ perceptions of risk, as well as their possible effect on victims＇ behavior for resilience and adaptation. We explore this relationship on victimized households of the 1986 Lake Nyos disaster, employing a quasi-experimental design. Matching was done with non-affected households. Both groups affected and non-affected households were of adequate size, and subject to the same questionnaire. Selection of （470） test and matching households was purposely limited to nine of the ten towns accommodating both survivors and non survivors of the examined disaster. A list constructed with traditional rulers in each village allowed for random sampling of non victims for comparative analysis. We then compare households affected by the disaster with those who were not. The results reveal differentiated perceptions of risk and management behavior contingent on whether households experienced the shock or not. However, solidarity and reciprocity remained extremely high and not significantly different amongst both household types, suggesting resilience of endogenous, informal risk response mechanisms to natural shocks. The article concludes that analyzing risk perceptions can help explain why some individuals, households or communities may be resilient to shocks and others not. We argue for a combination of subjective perceptions and objective shock analysis, especially if the analyst hopes to influence policy.展开更多
A study on the validity of volume equations currently used for three timber species, Entandrophragma cylindricum, Erythrophleum ivorensis and Pericopsis elata （Sapelli, Tali and Assamela respectively） in south east ...A study on the validity of volume equations currently used for three timber species, Entandrophragma cylindricum, Erythrophleum ivorensis and Pericopsis elata （Sapelli, Tali and Assamela respectively） in south east Cameroon, was conducted between the months of July and September, 2007 to evaluate their suitability for the site. Twenty-two percent sampling intensity was conducted within annual allowable cuts and diameter readings taken on standing trees with the aid of a wide band Relascope. A non linear regression equation model was employed to compute volume equations and the student＇s t-test for the analysis of the existing models. Based on individual tree volumes within stands, new equations for the three species were constructed. A comparison was made between the new equations and those that were being used at the site. Results indicated a total standing volume of 0.007 m3/ha obtained for the three species （Sapelli 0.003 m3/ha, Tali 0.002 m3/ha and Assamela 0.002 m3/ha）. Two new volume equation models [B] and [C] were retained for their goodness-of-fit with [B] for Assamela and [C] for Sapelli and Tali. Results also showed that a total volume of 0.005 m3/ha was underestimated for the three species （Sapelli 0.002 m3/ha, Tali 0.001 m3/ha and Assamela 0.002 m3/ha） when existing volume equations were applied. It is imperative to construct new volume equations that are compatible with the ecological characteristics of the site using representative samples. Setting-up appropriate methods for their validation shall also serve as checks to future management errors.展开更多
In order to reduce the increase of fuel prices,and improve the living conditions of the population,a study was carried out by Convention No.1/IRAD/PCS ESA2-SDCC in the region of Garoua in Cameroon.The study aimed to c...In order to reduce the increase of fuel prices,and improve the living conditions of the population,a study was carried out by Convention No.1/IRAD/PCS ESA2-SDCC in the region of Garoua in Cameroon.The study aimed to characterize the behaviour ofJ.curcas associated with V.unguiculata in marginal soils in the Sahel region in order to improve the livelihoods of the farmers and promote its domestication in rural areas.It also aimed at pointing out the influence of two implantation techniques of d.curcas on the germination,the different quantities of NPK and cow dung,planting techniques and association with V.unguiculata var.lori on growth parameters of development and yield of J.curcas on the degraded marginal soils in the region.The experimental design was a completely randomized block with five levels of fertilization(F0:control;FI:50 g;F2:100 g of NPK 15-20-15;F3:1 kg and 2 kg of cow dung)per plant.Two types of establishment propagator(Ge)and direct seedling(Se)with three replications were used.Data were analysed by Stratigraphic+and XLSTAT.Results showed that the propagator germination was higher than the direct seeding,95%and 40%respectively.The Principal Component Analysis(PCA)of the parameters of growths and yield of J.curcas showed high correlation between the production of the leaves and the length of the leaves(R=0.861;P〈0.001).These parameters were correlated with the Biplot(F1 and F2)to 53.24%.It was opposed to the positives and imperfect correlation between the height and the recover parameters(R=0.486;P〈0.05).The treatments 100 g of NPK per plant and 2 kg of cow dung per plant induced strongly the development and yield ofJ.curcas and V.unguiculata adapted to marginal soils.展开更多
Iron, zinc and vitamin A deficiencies co-exist in Cameroon in all age groups. However, natural sources of vitamin A are available and could be used to meet the need of the whole population in association with iron and...Iron, zinc and vitamin A deficiencies co-exist in Cameroon in all age groups. However, natural sources of vitamin A are available and could be used to meet the need of the whole population in association with iron and zinc supplementation. This study aims at assessing the serum levels of zinc and iron after 11 days of supplementation. The study enrolled 26 men 08-33 years）, distributed into five groups. From the first day, they were supplemented with 20 mg of zinc and iron, taken each alone, both either together or at two different times. The five last days, participants were put on free vitamin A diets. Serums were obtained at day l, day 5 and day 11 for Zn and Fe levels determination by atomic absorption spectrophotometry. The highest serum iron and zinc concentrations were observed in groups either supplemented with zinc or with iron given alone. In those two groups, serum Zn concentrations increased from 0.69 μg/mL ±0.02μg/mL to 0.95 μg/mL ± 0.13 μg/mL （group 2）, from 0.48 μg/mL ± 0.06 μg/mL to 0.97 μg/mL ± 0.11 μg/mL （group 3）; and serum Fe concentrations from 1.49 μg/mL ± 0.54 μg/mL to 3.49 μg/mL ± 1.01 μg/mL （group 2）; and from 1.42 μg/mL ± 0.45 μg/mL to 3.41 μg/mL ± 0.81 μg/mL （group 3）, respectively. Supplementation with Fe or Zn alone increased both Fe and Zn serum levels of participants. Serum levels of iron and zinc when given together or at different time were not significantly different. Further studies on a larger population are necessary to confirm that supplementation with zinc or with iron alone could raise both zinc and iron levels in serum simultaneously.展开更多
A study was carried out in the Northern region of Cameroon to assess the influence of fertilizers （chemical fertilizer NPK （15-20-15 w/w/w） or cow dung） on the growth and yield ofJatropha curcas from four origins ...A study was carried out in the Northern region of Cameroon to assess the influence of fertilizers （chemical fertilizer NPK （15-20-15 w/w/w） or cow dung） on the growth and yield ofJatropha curcas from four origins namely Cameroon, Senegal, Tanzania and Mozambique. The experimental design was factorial with 4 origins×3 fertilizers×8 month durations. After planting, growth parameters and dendrometric measurements were carried out monthly during eight months. Data were analyzed using a Statgraphics program and Duncan test. The results showed that plant of Tanzania and Mozambique origin had higher germination rate in field 75% and 69.5%, respectively. The survival rate of transplants was 100% for Cameroon origin and 98.48% for Senegal origin. NPK and cow dung significantly （P 〈 0.05） increased the growth parameters height, diameter, number of ramifications, leaves and fruits of Jatropha curcas. In addition Jatropha from Cameroon origin exhibited the highest growing conditions and high fruit yield, then highlighting its potential for the biofuel program of the country. But significant improvement needs to be done, particularly on the level of fertilizer needed.展开更多
Food safety is to be a vital component of food security, with mycotoxin contamination, a major contributing factor. In linewith this, this study aimed at investigating the effect of maize maturity at harvest, and proc...Food safety is to be a vital component of food security, with mycotoxin contamination, a major contributing factor. In linewith this, this study aimed at investigating the effect of maize maturity at harvest, and processing techniques on the aflatoxin andfumonisin levels in maize and maize products. Three maize maturity stages （80, 85, and 90 days after sowing）, two drying processes（sun and barn drying）, three storage periods （one, two and three months） and subsequent maize derivatives under these conditionswere sampled. These were analysed for total aflatoxins and total fumonisins using quantitative ELISA and samples with totalaflatoxins and total fumonisins exceeding regulated levels were analyzed by liquid chromatography-tandem mass spectrometry（LC-MS/MS） to determine the sub-types of toxins present. Results obtained showed that all analyzed samples were contaminatedwith total aflatoxins （range： 0.8 to 20 μg/kg） and total fumonisins （range： 10 to 5990 μg/kg）. Sun or barn drying for one weekfollowed by one month usual storage resulted in significant total fumonisins contamination, emphasizing the need of at least twoweeks of drying maize. It was also observed that processing techniques partly reduced the levels of toxins, mainly in maize productsthat have a sieving step.展开更多
The REE signature of banded iron formations (BIF) and martite-goethite mineralization of the Njweng ridge (South Cameroon) are used here to decipher the nature of the ocean during the period of BIF precipitation. The ...The REE signature of banded iron formations (BIF) and martite-goethite mineralization of the Njweng ridge (South Cameroon) are used here to decipher the nature of the ocean during the period of BIF precipitation. The textures of typical BIF categories are also presented as the only sedimentary feature. Two types of BIF facies are present at Njweng: the oxide and silicate facies. These facies show two stages of phase transformations. The first is the transformation of the original magnetite mineral into martite by oxidation resulting in trellis texture;the second is a simultaneous transformation by hydration into goethite and dehydration into martite. The samples typically show LREE depleted patterns relative to HREE, a characteristic similar to that of modern seawater. Also the strong positive Eu anomalies from the samples indicate the involvement of hydrothermal plumes of volcanic origin such as at mid ocean ridges (MOR). Yttrium (Y) has a strong positive anomaly pointing to the transportation of REEs as aqueous complexes within these ancient seas. The BIF samples have no positive Ce anomalies, suggesting that the oceans at that time were more reducing with no Ce fractionation than in present day oceans. The martite-goethite mineralization rather shows a positive Ce anomaly that derived from the enrichment in REE during the weathering of REE-bearing minerals. These results are integrated into existing literature on REE in BIFs worldwide and provide new insights into these heretofore unstudied BIFs of the northern edge of the Congo Craton.展开更多
Three monogenetic cones in the Baossi–Warack area, Ngaoundéré, Adamawa Plateau forming part of the Cameroon Volcanic Line(CVL) are documented in this study. Basaltic lavas(<1 km^3) scattered around these...Three monogenetic cones in the Baossi–Warack area, Ngaoundéré, Adamawa Plateau forming part of the Cameroon Volcanic Line(CVL) are documented in this study. Basaltic lavas(<1 km^3) scattered around these vents and restricted volcaniclastic deposits were emplaced by Hawaiian and mild strombolian style eruptions. The lavas are porphyritic, mainly composed of olivine(chrysolite) and clinopyroxene(diopside and augite) phenocrysts and plagioclase(andesine) microphenocrysts. Accessory minerals include titano-magnetite and titano-hematite, nepheline,apatite and amphibole xenocrysts. Sanidine occurs in some samples and sodi-potassic albite in others. Some olivines and clinopyroxenes exhibit resorbed margins and thin reaction rims while plagioclase displays oscillatory zoning, and sieved textures as a result of magma mixing. Whole-rock geochemistry data indicates that the lavas are silica-undersaturated, composed of basanites and basalts, showing little compositional variations(SiO_2: 39.20 wt.%–48.01 wt.%,MgO: 5.29 wt.%–9.70 wt.%). Trace elements patterns of these lavas suggest they are enriched in LILE including Pb,probably due to crustal contamination. REE patterns suggest cogenetic magmas below Baossi 1 and Baossi 2 volcanoes,and distinct sources below Warack volcano and nearby lavas.The lavas studied show affinity to high-μ(HIMU), enriched type Ⅰ(EM1) and Oceanic Island Basalt(OIB)-like mantle signatures and thus indicate a heterogeneous mantle source underneath the vents as noted at other monogenetic and polygenetic volcanoes along the CVL. Primary melts derived from low degrees of partial melting(0.5%–2%) and encountered low rates of fractionation, and crustal contamination coupled with magma mixing. These melts evolved independently through structural weaknesses in the basement.展开更多
Exploration for primary gold in tropical settings is often problematic because of deep weathering and the development of a thick soil cover. In this paper we present the results of both chargeability and resistivity s...Exploration for primary gold in tropical settings is often problematic because of deep weathering and the development of a thick soil cover. In this paper we present the results of both chargeability and resistivity surveys carried out over the Belikombone hill gold prospect (14?00' - 14?25'E, 5?25' - 6?00'N) in the Betare Oya area (eastern Cameroon), where previous soil sampling had identified gold anomalies. The geophysical data were obtained using Syscal Junior 48 resistivity meter and the Schlumberger configuration array for both the vertical electrical soundings (VES) and horizontal profiling. These data were further built into a GIS framework and the continuity of favourable gold-bearing structures at depth modeled using WINSEV, RED2INV and SURFER extensions softwares. IP (Induced Polarization)-chargeability and resistivity data combined, have identified irregular anomalous zones trending NE-SW. This trend is consistent with the attitude of most auriferous quartz veins exposed in artisanal pits and parallel to the regional shear zone system and foliations. The high resistivity anomalies correspond to quartz veins while the relatively high IP anomalies correspond to low sulphide ± gold concentrations in the quartz veins. Modeling IP-chargeability and resistivity data prepared as contours and 3D maps, culminated to the development of an inferred, irregular and discontinuous mineralized body at depths of up to 95 m. The size and shape of this mineralized body can only later be tested by drilling to ascertain the resource.展开更多
We used the Earth Gravitational Model （EGM2008） data sets to analyze the regional gravity anoma- lies and to study the underground structures in Cameroon. We first created a high-resolution Free-Air anomaly database...We used the Earth Gravitational Model （EGM2008） data sets to analyze the regional gravity anoma- lies and to study the underground structures in Cameroon. We first created a high-resolution Free-Air anomaly database, then corrected the gravity field of the topographic effect by using ETOPO1 DEM with a resolution of 0.01~ to obtain the Bouguer anomaly, then applied a multi-scale wavelet-analysis technique to separate the gravity-field components into different parts of shallow-to-deep origins, and finally used the logarithmic power spectrum technique to obtain detailed images and corresponding source depths as well as certain lateral inho- mogeneity of structure density. The anomalies of shallow origin show successive elongated gravity ＂highs＂ and ＂lows＂ attributable to subsurface Tertiary and lower Cretaceous undulations. Our results are in good agreement with previous investigations.展开更多
Bioko Island（3008 m a.s.l） is located in the presently more active volcanic zone of the Cameroon Line and composed essentially of alkaline basalts and hawaiites, and lesser mugearites. The rocks show microlitic porp...Bioko Island（3008 m a.s.l） is located in the presently more active volcanic zone of the Cameroon Line and composed essentially of alkaline basalts and hawaiites, and lesser mugearites. The rocks show microlitic porphyritic texture with phenocrysts of olivine（83% 〈 Fo 〈 87%） and clinopyroxene in a matrix of plagioclase, clinopyroxene and oxides. Hawaiites and mugearites also include phenocrysts of plagioclase（An62-67Ab35-32Or3-1）. Major element variation diagrams show an increase in Si O2, Al2O3, Na2 O and K2 O with increasing Mg O for the studied rock groups. The rocks are characterized by low（^86Sr/^87Sr）i ratios（0.70320e0.70406）, high 3Nd（t） values（2.56e4.33） and high（^206Pb/^204Pb）i ratios（20.032e20.035） values.Basalts are enriched in LILE and LREE, and have（Hf/Sm）N= 0.57e1.16. These geochemical signatures are similar to those of the Mount Cameroon rocks, and might be attributed to low degrees of partial melting from a garnet-amphibole-bearing mantle source. The trace elements and isotopic compositions suggest that the parental magma source might have involved HIMU- and EM1-components.展开更多
Geophysical and geotechnical surveys were conducted in the Western Cameroon (Kekem area) following a landslide on argillaceous material in order to understand the triggering processes and mechanisms of this landslide ...Geophysical and geotechnical surveys were conducted in the Western Cameroon (Kekem area) following a landslide on argillaceous material in order to understand the triggering processes and mechanisms of this landslide and to assess the stability of the slope. The geophysical soundings consisting of vertical electrical soundings with the Schlumberger electrode array configuration were carried out to monitor the behaviour of electrical resistivity in the landslide. Geoelectrical data showed a zone of low resistivity values identified as a clayey sand-filled aquifer. This aquifer played an important role in the triggering process of the landslide. Geotechnical soundings showed that the aquifer had a thickness of 7.0 m. The depth from the landslide crest level to the failure surface reached 3.0 m and 20.6 m. Laboratory tests were then carried out in order to evaluate the cohesion of the soil and the angle of internal friction, and to calculate the safety factor in view of making a stability analysis. The laboratory results exhibited a soil with low consistency, almost doughy. The mean value of the safety factor (1.4) been lower than the slope stability coefficient (1.5), revealed that the slope is unstable, likely to know at any moment a reactivation of the slide. This study showed that electrical soundings coupled with geotechnical surveys are useful tools for the characterization of landslides.展开更多
Mapping and documentation of lithological varieties and their corresponding geochemistry at the Kitongo uranium mineralization were concerned. The Kitongo U occurrence is hosted by granitic rocks that include interlea...Mapping and documentation of lithological varieties and their corresponding geochemistry at the Kitongo uranium mineralization were concerned. The Kitongo U occurrence is hosted by granitic rocks that include interleaved sequences of metasedimentary and metavolcanic rocks of the collectively termed Poli Group. U-mineralization and Na-metasomatism are related and structurally controlled. The most promising uraniferous bodies are intimately related to intersections between the ductile ENE-trending faults and the brittle conjugate R' faults postdating the shearing event. The con- centration of uranium at fault intersections rather than along individual faults suggests that these zones that are dilatational in nature were also highly permeable and therefore the hydrothermal fluids ponded there could readily precipitate U therein. A two-stage albitization has altered the foliated granitic host rock and the second albitization that has over-printed the first one is more effective at fault intersections. Whole rock geochemistry was performed by using ICP-MS and ICP-AES respectively for major oxides, trace and REE. The U-bearing rock suite exhibits restricted range in SiO2 concentration (62.89% - 70.91%) and Al2O3 (13.16% - 18.59%) and it is poor in MgO (0.02% - 1.03%), CaO (0.24% - 1.88%) and K2O (0.08% - 5.32%). The mineralized rocks are however comparatively richer in Na2O (4.33% - 10.92%) compared to their barren counterparts. The host granite and associated granodioritic rocks in the area are weakly metaluminous, peralkaline, and are calc-alkaline. They are moderately to strongly fractionated and have tholeiitic and shoshonitic affinities with moderate to high HFSE (high field strength elements) and LILE (large ion lithophile elements) enrichment. The Rb/Sr, Rb/Ba and Sr/Ba ratios are 0.31, 0.14 and 1.48, respectively. U content in the mineralized granite is up to 651 ppm while the non-mineralized rock has only 2.4 ppm U. The REE patterns of the granite show LREE enrichment and strong Eu negative anomalies (Eu/Eu* = 0.03 to 0.48). The main mineralization stage characterized by local U, Na, Pb, Zn, Ga, Hf, Sr, Fe, Al, P and Zr enrichments is related to the second albitization event and could probably be associated in time with the calcite-uranium stage. The identification of fault segments favorable for uranium mineralization in northern Cameroon (Poli area) is important for understanding the genesis of hydrothermal ore deposits within continental strike-slip faults and therefore has great implications for exploration strategies.展开更多
In Douala, economic capital of Cameroon, annual rainfall and temperature from its meteorological station (latitude: 4o00'N;longitude: 9o43'E;elevation: 5.0 m) were obtained and analysed to investigate the impa...In Douala, economic capital of Cameroon, annual rainfall and temperature from its meteorological station (latitude: 4o00'N;longitude: 9o43'E;elevation: 5.0 m) were obtained and analysed to investigate the impact of climate variability on groundwater recharge. The climate shows a strong evidence of changes towards persistent weather conditions. The region is mainly characterized by a mean inter-annual temperature of 27.4oC and influenced by the mount Cameroon (4095 m in elevation). A recent decrease in mean annual rainfall occurred since 1982. The average annual rainfall which was 4200 mm with about 220 days of rainfall from 1917 to 1937 has moved to 4049 mm for the period 1937-1957, to 3826 mm for the period 1968-1988 and to 3619 mm for the period 1971-2001. Between, 1997 and 2007, the total number of days of rainfall has not exceeded 220 (193 days of rainfall in 1998 and 216 days of rainfall in 1999). By using Gauss law on 31 years (1971-2001) of annual rainfall, one note that the value 2850 mm has 20% of luck to be not observed and the value 4219 mm has 20% of luck to be exceeded. Douala already suffers from water shortage not because of decrease of rainfall but due to quality of underground water and salty taste of the main river catched for water supply. Moreover, precipitation is considered as the main replenishment source of all water resources in the study area (watershed of Besseke). The calculated interannual groundwater recharge rate (potential recharge, not necessarily real) is about 9% compared to the interannual total precipitation received by this area located closer the Atlantic Ocean (Gulf of Guinea). Groundwater discharge from the aquifer occurs between November and March.展开更多
文摘Pheochromocytoma (PHEO) is a rare endocrine tumor from the chromaffin cells in the adrenomedullary gland and sympathetic/parasympathetic ganglia, secreting one or more catecholamines. It is frequently associated with hypertension and described in the literature as a cause of secondary diabetes mellitus. In patients with known persistent uncontrolled diabetes, PHEO is rarely mentioned as the cause of uncontrolled diabetes. The authors report a rare case of PHEO diagnosed in a 64-year-old female patient treated for 10 years with type 2 diabetes mellitus and hypertension. She was treated using a combination of insulin (2 injections) and Metformin 1000 mg twice a day. The glycemic control was poor (HbA1c-11%), and persistent High Blood Pressure (HBP). She presented with unexplained weight loss associated with permanent hyperhidrosis (sweating), affecting her quality of life and diffuse abdominal pain. The investigations confirmed the diagnosis of PHEO, which resection led to improvement of glycemic control and hypertension.
文摘The digital transformation in Cameroon presents critical cybersecurity challenges that demand immediate attention and strategic intervention. This comprehensive analysis examines the evolving cybersecurity landscape in Cameroon from 2020 to 2023, during which cyber-attacks increased by 156% and financial losses from digital fraud exceeded $45 million. This research identifies significant vulnerabilities in Cameroon’s cybersecurity ecosystem through a rigorous assessment of national infrastructure, policy frameworks, and institutional capacities. Recent data indicates that while digital service adoption has grown exponentially, with internet penetration reaching 35.2% in 2023, cybersecurity measures have lagged significantly behind international standards. This analysis draws on comprehensive data from multiple sectors, including financial services, government institutions, and telecommunications, incorporating findings from the National Cybersecurity Assessment Program and the Digital Infrastructure Security Report. The research reveals that 73% of organizations lack dedicated security teams, while response times to cyber incidents average 72 hours—three times than the global standard. Based on these findings, this paper proposes evidence-based solutions for enhancing digital resilience, including policy modernization, capacity-building initiatives, and technical infrastructure development. The recommendations encompass short-term tactical responses, medium-term strategic improvements, and long-term structural changes, providing a comprehensive roadmap for strengthening Cameroon’s national cybersecurity frameworks.
文摘In order to contribute to a better understanding of the biodiversity of local chicken populations, this study focused on the description of the essential qualitative parameters in the phenotypic characterization of local species. Conducted in 6 localities in the Far North Region of Cameroon (Doukoula, Yagoua, Guidiguis, Dziguilao, Maroua 3rd and Méri), a population of 240 local chickens, including 172 hens and 68 cocks were characterized in family farms. The choice of localities was made on the basis of their strong potential local chicken flocks in the region. To this end, each animal was the subject of a qualitative description based on the identification of the sex of the animal, the description of the colorations of the plumage and extremities, and the description of the types of format, plumage and crests. All observations were made with the naked eye and in daylight and then photographed. The main results show that the plumage colors are multiple and dominated by the White-Pied-Black (21.7%) and the Mille-fleur (20.8%);the wattles are dominated by the red (60%) and the pink (35.4%);the tarsi are dominated by the white (43.8%) and the black (32.08%);the white skin (92.5%) dominates over the pink skin (7.5%);the “Smooth-uniform” feather is dominant (97.08%), followed by the smooth-crested type (2.08%) and the fries type (0.82%);the medium size of the chickens is dominant (86.66%), followed by the dwarf size (9.58%) and the large size (3.75%). The results of this study demonstrate that there is a strong phenotypic diversity within the local chicken population. This diversity can serve as a basis for the development of selection, conservation and genetic potential improvement programs based on rational exploitation of the local chicken.
基金the material and logistical support provided by the Environmental Geomatics Laboratory of the Forestry Department of the University of Dschang
文摘Existing knowledge on degraded mountain landscapes does not shed sufficient light on the socio-economic and ecological opportunities essential for successful restoration initiatives.To address this knowledge lacuna,a study was conducted on the Bamboutos Mountains landscape in Cameroon with the main objective being to analyse the opportunities for restoring this landscape in line with local,national and international development goals and to minimise the negative effects of land-use decisions.Following the Restoration Opportunity Assessment Methodology(ROAM)approach,five participatory reflection workshops were organized in the five target clusters of the landscape for data collection.The results of the study led to the development of a restoration map that presents five interventions:grassland management on an area of 4,720 ha currently occupied by shrub savannah;the practice of fruit-based agroforestry on 3,221 ha of agricultural fields;the planting of riparian forests on 451 ha of degraded watercourses;the revegetation and conservation of the Bamboutos Mountains forest reserve,sacred forests and relics of degraded forests on 435 ha of area;and the revegetation of 6 ha of degraded water sources.The carbon stocks vary from 2.66 to 345.15 tC/ha depending on the type of restoration intervention with a total carbon stock of 247,367.45 tC/ha on the 8,834 ha of area to be restored.This presents a very satisfactory economic cost-benefit,because for an investment of USD 5,991,269.84,a gain of USD 100,439,519.13 could be achieved after 20 years,i.e.,an estimated profit of USD 94,448,249.29.These results provide an understanding of the types of restoration interventions possible in this landscape,a solid basis for planning a restoration initiative.The results equally provide guidance on priority areas from a social,economic,and ecological perspective.
文摘BACKGROUND The global prevalence of diabetes among adults aged 29-79 years was found to be 10.5%.It is a global public health threat with a rising trend in morbidity and mortality.Poor glycemic control(GC)among patients with type 2 diabetes mellitus(T2DM)is a major determinant of diabetes-related complications.There are limited data on GC and associated factors among patients with T2DM in South West Region,Cameroon.AIM To assess GC and identify contributing factors among patients with T2DM in a regional hospital in South West Region,Cameroon.METHODS A cross-sectional study was conducted from February 2022 to July 2022 among 131 participants in Limbe Regional Hospital who were selected by convenience.Glycated hemoglobin(HbA1c)was measured by ion-exchange chromatography.Sociodemographic,clinical,and lifestyle data were collected,entered into Excel,and exported to Statistical Package for Social Sciences version 22 for analysis.A multivariate logistic regression analysis was conducted to assess the association between explanatory variables and GC.The level of significance was set at P<0.05.RESULTS The mean age was 56±5.1 years.Eighty-eight(67.2%)patients were female.The mean HbA1c was 8.8%±1.8%.Poor GC(HbA1c≥7%)was registered in 106(80.9%;95%confidence interval:73.1%-87.3%)participants.Lack of self-monitoring of blood glucose at home was associated with poor GC(adjusted odds ratio:3.858,95%confidence interval:1.262-11.800;P=0.018).CONCLUSION The majority of patients with T2DM had poor GC.Absence of self-monitoring of blood glucose at home was the main contributing factor for poor GC.
文摘Sacred forests play a valuable role in the conservation of local biodiversity and provide numerous ecosystem services in Cameroon. The aim of this study was to estimate floristic diversity, stand structures and carbon stocks in the sacred forests of Bandrefam and Batoufam (western Cameroon). The floristic inventory and the stand structures were carried out in 25 m × 25 m plots for individuals with diameters greater than 10 cm;5 m × 5 m for individuals with diameters less than 10 cm. Carbon stocks were estimated using the non-destructive method and allometric equations. The floristic inventory identified 65 species divided into 57 genera and 30 families in the Bandrefam sacred forest and 45 species divided into 42 genera and 27 families in the Batoufam sacred forest. In the Bandrefam, the most important families are Phyllanthaceae (53.98%), Moraceae (21.69%), Lamiaceae (20.15%). At Batoufam, the most important families are Phyllanthaceae (39.73%), Fabaceae (28.47%), Araliaceae (23.77%). Malacantha alnifolia (55.14%), Vitex grandifolia (18.43%), Bosqueia angolensis (15.06%) were the most important species in Bandrefam. Otherwise, Malacantha alnifolia (28%), Polyscias fulva (22.73%), Psychotria sp. (21.28%) were the most important in Batoufam. The Bandrefam sacred forest has the highest tree density (2669 stems/ha). Total carbon stock is 484.88 ± 2.28 tC/ha at Batoufam and 313.95 ± 0.93 tC/ha at Bandrefam. The economic value varies between 5858.04 ± 27.62 USD/ha in Batoufam sacred forest and 3788.51 ± 11.26 USD/ha in Bandrefam sacred forest. The number of individuals and small-diameter trees has little influence on the carbon stocks in the trees. Medium-diameter trees store the most carbon, and very large-diameter trees, which are very poorly represented, store less carbon. In another way, wood density and the basal areas influence the carbon storage of the trees.
文摘Invariably, it is the poorest of the poor who are mostly affected by perverse disasters, policies and laws. A major concern in disaster research is to explore the relationship between shock experiences and victims＇ perceptions of risk, as well as their possible effect on victims＇ behavior for resilience and adaptation. We explore this relationship on victimized households of the 1986 Lake Nyos disaster, employing a quasi-experimental design. Matching was done with non-affected households. Both groups affected and non-affected households were of adequate size, and subject to the same questionnaire. Selection of （470） test and matching households was purposely limited to nine of the ten towns accommodating both survivors and non survivors of the examined disaster. A list constructed with traditional rulers in each village allowed for random sampling of non victims for comparative analysis. We then compare households affected by the disaster with those who were not. The results reveal differentiated perceptions of risk and management behavior contingent on whether households experienced the shock or not. However, solidarity and reciprocity remained extremely high and not significantly different amongst both household types, suggesting resilience of endogenous, informal risk response mechanisms to natural shocks. The article concludes that analyzing risk perceptions can help explain why some individuals, households or communities may be resilient to shocks and others not. We argue for a combination of subjective perceptions and objective shock analysis, especially if the analyst hopes to influence policy.
文摘A study on the validity of volume equations currently used for three timber species, Entandrophragma cylindricum, Erythrophleum ivorensis and Pericopsis elata （Sapelli, Tali and Assamela respectively） in south east Cameroon, was conducted between the months of July and September, 2007 to evaluate their suitability for the site. Twenty-two percent sampling intensity was conducted within annual allowable cuts and diameter readings taken on standing trees with the aid of a wide band Relascope. A non linear regression equation model was employed to compute volume equations and the student＇s t-test for the analysis of the existing models. Based on individual tree volumes within stands, new equations for the three species were constructed. A comparison was made between the new equations and those that were being used at the site. Results indicated a total standing volume of 0.007 m3/ha obtained for the three species （Sapelli 0.003 m3/ha, Tali 0.002 m3/ha and Assamela 0.002 m3/ha）. Two new volume equation models [B] and [C] were retained for their goodness-of-fit with [B] for Assamela and [C] for Sapelli and Tali. Results also showed that a total volume of 0.005 m3/ha was underestimated for the three species （Sapelli 0.002 m3/ha, Tali 0.001 m3/ha and Assamela 0.002 m3/ha） when existing volume equations were applied. It is imperative to construct new volume equations that are compatible with the ecological characteristics of the site using representative samples. Setting-up appropriate methods for their validation shall also serve as checks to future management errors.
文摘In order to reduce the increase of fuel prices,and improve the living conditions of the population,a study was carried out by Convention No.1/IRAD/PCS ESA2-SDCC in the region of Garoua in Cameroon.The study aimed to characterize the behaviour ofJ.curcas associated with V.unguiculata in marginal soils in the Sahel region in order to improve the livelihoods of the farmers and promote its domestication in rural areas.It also aimed at pointing out the influence of two implantation techniques of d.curcas on the germination,the different quantities of NPK and cow dung,planting techniques and association with V.unguiculata var.lori on growth parameters of development and yield of J.curcas on the degraded marginal soils in the region.The experimental design was a completely randomized block with five levels of fertilization(F0:control;FI:50 g;F2:100 g of NPK 15-20-15;F3:1 kg and 2 kg of cow dung)per plant.Two types of establishment propagator(Ge)and direct seedling(Se)with three replications were used.Data were analysed by Stratigraphic+and XLSTAT.Results showed that the propagator germination was higher than the direct seeding,95%and 40%respectively.The Principal Component Analysis(PCA)of the parameters of growths and yield of J.curcas showed high correlation between the production of the leaves and the length of the leaves(R=0.861;P〈0.001).These parameters were correlated with the Biplot(F1 and F2)to 53.24%.It was opposed to the positives and imperfect correlation between the height and the recover parameters(R=0.486;P〈0.05).The treatments 100 g of NPK per plant and 2 kg of cow dung per plant induced strongly the development and yield ofJ.curcas and V.unguiculata adapted to marginal soils.
文摘Iron, zinc and vitamin A deficiencies co-exist in Cameroon in all age groups. However, natural sources of vitamin A are available and could be used to meet the need of the whole population in association with iron and zinc supplementation. This study aims at assessing the serum levels of zinc and iron after 11 days of supplementation. The study enrolled 26 men 08-33 years）, distributed into five groups. From the first day, they were supplemented with 20 mg of zinc and iron, taken each alone, both either together or at two different times. The five last days, participants were put on free vitamin A diets. Serums were obtained at day l, day 5 and day 11 for Zn and Fe levels determination by atomic absorption spectrophotometry. The highest serum iron and zinc concentrations were observed in groups either supplemented with zinc or with iron given alone. In those two groups, serum Zn concentrations increased from 0.69 μg/mL ±0.02μg/mL to 0.95 μg/mL ± 0.13 μg/mL （group 2）, from 0.48 μg/mL ± 0.06 μg/mL to 0.97 μg/mL ± 0.11 μg/mL （group 3）; and serum Fe concentrations from 1.49 μg/mL ± 0.54 μg/mL to 3.49 μg/mL ± 1.01 μg/mL （group 2）; and from 1.42 μg/mL ± 0.45 μg/mL to 3.41 μg/mL ± 0.81 μg/mL （group 3）, respectively. Supplementation with Fe or Zn alone increased both Fe and Zn serum levels of participants. Serum levels of iron and zinc when given together or at different time were not significantly different. Further studies on a larger population are necessary to confirm that supplementation with zinc or with iron alone could raise both zinc and iron levels in serum simultaneously.
文摘A study was carried out in the Northern region of Cameroon to assess the influence of fertilizers （chemical fertilizer NPK （15-20-15 w/w/w） or cow dung） on the growth and yield ofJatropha curcas from four origins namely Cameroon, Senegal, Tanzania and Mozambique. The experimental design was factorial with 4 origins×3 fertilizers×8 month durations. After planting, growth parameters and dendrometric measurements were carried out monthly during eight months. Data were analyzed using a Statgraphics program and Duncan test. The results showed that plant of Tanzania and Mozambique origin had higher germination rate in field 75% and 69.5%, respectively. The survival rate of transplants was 100% for Cameroon origin and 98.48% for Senegal origin. NPK and cow dung significantly （P 〈 0.05） increased the growth parameters height, diameter, number of ramifications, leaves and fruits of Jatropha curcas. In addition Jatropha from Cameroon origin exhibited the highest growing conditions and high fruit yield, then highlighting its potential for the biofuel program of the country. But significant improvement needs to be done, particularly on the level of fertilizer needed.
文摘Food safety is to be a vital component of food security, with mycotoxin contamination, a major contributing factor. In linewith this, this study aimed at investigating the effect of maize maturity at harvest, and processing techniques on the aflatoxin andfumonisin levels in maize and maize products. Three maize maturity stages （80, 85, and 90 days after sowing）, two drying processes（sun and barn drying）, three storage periods （one, two and three months） and subsequent maize derivatives under these conditionswere sampled. These were analysed for total aflatoxins and total fumonisins using quantitative ELISA and samples with totalaflatoxins and total fumonisins exceeding regulated levels were analyzed by liquid chromatography-tandem mass spectrometry（LC-MS/MS） to determine the sub-types of toxins present. Results obtained showed that all analyzed samples were contaminatedwith total aflatoxins （range： 0.8 to 20 μg/kg） and total fumonisins （range： 10 to 5990 μg/kg）. Sun or barn drying for one weekfollowed by one month usual storage resulted in significant total fumonisins contamination, emphasizing the need of at least twoweeks of drying maize. It was also observed that processing techniques partly reduced the levels of toxins, mainly in maize productsthat have a sieving step.
文摘The REE signature of banded iron formations (BIF) and martite-goethite mineralization of the Njweng ridge (South Cameroon) are used here to decipher the nature of the ocean during the period of BIF precipitation. The textures of typical BIF categories are also presented as the only sedimentary feature. Two types of BIF facies are present at Njweng: the oxide and silicate facies. These facies show two stages of phase transformations. The first is the transformation of the original magnetite mineral into martite by oxidation resulting in trellis texture;the second is a simultaneous transformation by hydration into goethite and dehydration into martite. The samples typically show LREE depleted patterns relative to HREE, a characteristic similar to that of modern seawater. Also the strong positive Eu anomalies from the samples indicate the involvement of hydrothermal plumes of volcanic origin such as at mid ocean ridges (MOR). Yttrium (Y) has a strong positive anomaly pointing to the transportation of REEs as aqueous complexes within these ancient seas. The BIF samples have no positive Ce anomalies, suggesting that the oceans at that time were more reducing with no Ce fractionation than in present day oceans. The martite-goethite mineralization rather shows a positive Ce anomaly that derived from the enrichment in REE during the weathering of REE-bearing minerals. These results are integrated into existing literature on REE in BIFs worldwide and provide new insights into these heretofore unstudied BIFs of the northern edge of the Congo Craton.
基金financially supported by the Ministry of Higher Education, Cameroon, through the Special Allocation for the Modernization of Research (SAMR) granted to the first author
文摘Three monogenetic cones in the Baossi–Warack area, Ngaoundéré, Adamawa Plateau forming part of the Cameroon Volcanic Line(CVL) are documented in this study. Basaltic lavas(<1 km^3) scattered around these vents and restricted volcaniclastic deposits were emplaced by Hawaiian and mild strombolian style eruptions. The lavas are porphyritic, mainly composed of olivine(chrysolite) and clinopyroxene(diopside and augite) phenocrysts and plagioclase(andesine) microphenocrysts. Accessory minerals include titano-magnetite and titano-hematite, nepheline,apatite and amphibole xenocrysts. Sanidine occurs in some samples and sodi-potassic albite in others. Some olivines and clinopyroxenes exhibit resorbed margins and thin reaction rims while plagioclase displays oscillatory zoning, and sieved textures as a result of magma mixing. Whole-rock geochemistry data indicates that the lavas are silica-undersaturated, composed of basanites and basalts, showing little compositional variations(SiO_2: 39.20 wt.%–48.01 wt.%,MgO: 5.29 wt.%–9.70 wt.%). Trace elements patterns of these lavas suggest they are enriched in LILE including Pb,probably due to crustal contamination. REE patterns suggest cogenetic magmas below Baossi 1 and Baossi 2 volcanoes,and distinct sources below Warack volcano and nearby lavas.The lavas studied show affinity to high-μ(HIMU), enriched type Ⅰ(EM1) and Oceanic Island Basalt(OIB)-like mantle signatures and thus indicate a heterogeneous mantle source underneath the vents as noted at other monogenetic and polygenetic volcanoes along the CVL. Primary melts derived from low degrees of partial melting(0.5%–2%) and encountered low rates of fractionation, and crustal contamination coupled with magma mixing. These melts evolved independently through structural weaknesses in the basement.
文摘Exploration for primary gold in tropical settings is often problematic because of deep weathering and the development of a thick soil cover. In this paper we present the results of both chargeability and resistivity surveys carried out over the Belikombone hill gold prospect (14?00' - 14?25'E, 5?25' - 6?00'N) in the Betare Oya area (eastern Cameroon), where previous soil sampling had identified gold anomalies. The geophysical data were obtained using Syscal Junior 48 resistivity meter and the Schlumberger configuration array for both the vertical electrical soundings (VES) and horizontal profiling. These data were further built into a GIS framework and the continuity of favourable gold-bearing structures at depth modeled using WINSEV, RED2INV and SURFER extensions softwares. IP (Induced Polarization)-chargeability and resistivity data combined, have identified irregular anomalous zones trending NE-SW. This trend is consistent with the attitude of most auriferous quartz veins exposed in artisanal pits and parallel to the regional shear zone system and foliations. The high resistivity anomalies correspond to quartz veins while the relatively high IP anomalies correspond to low sulphide ± gold concentrations in the quartz veins. Modeling IP-chargeability and resistivity data prepared as contours and 3D maps, culminated to the development of an inferred, irregular and discontinuous mineralized body at depths of up to 95 m. The size and shape of this mineralized body can only later be tested by drilling to ascertain the resource.
基金supported by CAS-TWAS under grant FR 3240267248the National Natural Science Foundation of China(41021003)the Research Project of State Key Laboratory of Geodesy and Earth's Dynamics(SKLGED2013-4-1-Z)
文摘We used the Earth Gravitational Model （EGM2008） data sets to analyze the regional gravity anoma- lies and to study the underground structures in Cameroon. We first created a high-resolution Free-Air anomaly database, then corrected the gravity field of the topographic effect by using ETOPO1 DEM with a resolution of 0.01~ to obtain the Bouguer anomaly, then applied a multi-scale wavelet-analysis technique to separate the gravity-field components into different parts of shallow-to-deep origins, and finally used the logarithmic power spectrum technique to obtain detailed images and corresponding source depths as well as certain lateral inho- mogeneity of structure density. The anomalies of shallow origin show successive elongated gravity ＂highs＂ and ＂lows＂ attributable to subsurface Tertiary and lower Cretaceous undulations. Our results are in good agreement with previous investigations.
基金financially supported by the Ministère des Affaires Economiques (Project SGB/ NAT 91-98)
文摘Bioko Island（3008 m a.s.l） is located in the presently more active volcanic zone of the Cameroon Line and composed essentially of alkaline basalts and hawaiites, and lesser mugearites. The rocks show microlitic porphyritic texture with phenocrysts of olivine（83% 〈 Fo 〈 87%） and clinopyroxene in a matrix of plagioclase, clinopyroxene and oxides. Hawaiites and mugearites also include phenocrysts of plagioclase（An62-67Ab35-32Or3-1）. Major element variation diagrams show an increase in Si O2, Al2O3, Na2 O and K2 O with increasing Mg O for the studied rock groups. The rocks are characterized by low（^86Sr/^87Sr）i ratios（0.70320e0.70406）, high 3Nd（t） values（2.56e4.33） and high（^206Pb/^204Pb）i ratios（20.032e20.035） values.Basalts are enriched in LILE and LREE, and have（Hf/Sm）N= 0.57e1.16. These geochemical signatures are similar to those of the Mount Cameroon rocks, and might be attributed to low degrees of partial melting from a garnet-amphibole-bearing mantle source. The trace elements and isotopic compositions suggest that the parental magma source might have involved HIMU- and EM1-components.
文摘Geophysical and geotechnical surveys were conducted in the Western Cameroon (Kekem area) following a landslide on argillaceous material in order to understand the triggering processes and mechanisms of this landslide and to assess the stability of the slope. The geophysical soundings consisting of vertical electrical soundings with the Schlumberger electrode array configuration were carried out to monitor the behaviour of electrical resistivity in the landslide. Geoelectrical data showed a zone of low resistivity values identified as a clayey sand-filled aquifer. This aquifer played an important role in the triggering process of the landslide. Geotechnical soundings showed that the aquifer had a thickness of 7.0 m. The depth from the landslide crest level to the failure surface reached 3.0 m and 20.6 m. Laboratory tests were then carried out in order to evaluate the cohesion of the soil and the angle of internal friction, and to calculate the safety factor in view of making a stability analysis. The laboratory results exhibited a soil with low consistency, almost doughy. The mean value of the safety factor (1.4) been lower than the slope stability coefficient (1.5), revealed that the slope is unstable, likely to know at any moment a reactivation of the slide. This study showed that electrical soundings coupled with geotechnical surveys are useful tools for the characterization of landslides.
文摘Mapping and documentation of lithological varieties and their corresponding geochemistry at the Kitongo uranium mineralization were concerned. The Kitongo U occurrence is hosted by granitic rocks that include interleaved sequences of metasedimentary and metavolcanic rocks of the collectively termed Poli Group. U-mineralization and Na-metasomatism are related and structurally controlled. The most promising uraniferous bodies are intimately related to intersections between the ductile ENE-trending faults and the brittle conjugate R' faults postdating the shearing event. The con- centration of uranium at fault intersections rather than along individual faults suggests that these zones that are dilatational in nature were also highly permeable and therefore the hydrothermal fluids ponded there could readily precipitate U therein. A two-stage albitization has altered the foliated granitic host rock and the second albitization that has over-printed the first one is more effective at fault intersections. Whole rock geochemistry was performed by using ICP-MS and ICP-AES respectively for major oxides, trace and REE. The U-bearing rock suite exhibits restricted range in SiO2 concentration (62.89% - 70.91%) and Al2O3 (13.16% - 18.59%) and it is poor in MgO (0.02% - 1.03%), CaO (0.24% - 1.88%) and K2O (0.08% - 5.32%). The mineralized rocks are however comparatively richer in Na2O (4.33% - 10.92%) compared to their barren counterparts. The host granite and associated granodioritic rocks in the area are weakly metaluminous, peralkaline, and are calc-alkaline. They are moderately to strongly fractionated and have tholeiitic and shoshonitic affinities with moderate to high HFSE (high field strength elements) and LILE (large ion lithophile elements) enrichment. The Rb/Sr, Rb/Ba and Sr/Ba ratios are 0.31, 0.14 and 1.48, respectively. U content in the mineralized granite is up to 651 ppm while the non-mineralized rock has only 2.4 ppm U. The REE patterns of the granite show LREE enrichment and strong Eu negative anomalies (Eu/Eu* = 0.03 to 0.48). The main mineralization stage characterized by local U, Na, Pb, Zn, Ga, Hf, Sr, Fe, Al, P and Zr enrichments is related to the second albitization event and could probably be associated in time with the calcite-uranium stage. The identification of fault segments favorable for uranium mineralization in northern Cameroon (Poli area) is important for understanding the genesis of hydrothermal ore deposits within continental strike-slip faults and therefore has great implications for exploration strategies.
文摘In Douala, economic capital of Cameroon, annual rainfall and temperature from its meteorological station (latitude: 4o00'N;longitude: 9o43'E;elevation: 5.0 m) were obtained and analysed to investigate the impact of climate variability on groundwater recharge. The climate shows a strong evidence of changes towards persistent weather conditions. The region is mainly characterized by a mean inter-annual temperature of 27.4oC and influenced by the mount Cameroon (4095 m in elevation). A recent decrease in mean annual rainfall occurred since 1982. The average annual rainfall which was 4200 mm with about 220 days of rainfall from 1917 to 1937 has moved to 4049 mm for the period 1937-1957, to 3826 mm for the period 1968-1988 and to 3619 mm for the period 1971-2001. Between, 1997 and 2007, the total number of days of rainfall has not exceeded 220 (193 days of rainfall in 1998 and 216 days of rainfall in 1999). By using Gauss law on 31 years (1971-2001) of annual rainfall, one note that the value 2850 mm has 20% of luck to be not observed and the value 4219 mm has 20% of luck to be exceeded. Douala already suffers from water shortage not because of decrease of rainfall but due to quality of underground water and salty taste of the main river catched for water supply. Moreover, precipitation is considered as the main replenishment source of all water resources in the study area (watershed of Besseke). The calculated interannual groundwater recharge rate (potential recharge, not necessarily real) is about 9% compared to the interannual total precipitation received by this area located closer the Atlantic Ocean (Gulf of Guinea). Groundwater discharge from the aquifer occurs between November and March.
