Modeling Daily Average Temperatures in a Coastal Site of Central Africa: An Analysis of Seasonal Divisions

The seasonality and day-to-day variation of near-surface temperature patterns can greatly control nearly all physical and biological processes though temperature predictions at such scales remain challenging. This paper implements a simple analytical approach in order to generate daily average temperatures which implicitly accounts for surface heating and drivers through a comprehensive representation of station-based temperature records on a universal standard calendar propagated by the earth’s dynamics features. The modeled and observed pattern of daily temperatures exhibits a close agreement with the level of strength agreement exceeding 0.56. The extreme high and low values of the observed temperature patterns are equally well captured although model underestimates the probability of temperatures around the two modal peaks (~25.6℃ and 27.5℃). Additionally, a theoretical thermal-based division led to the identification of six seasons, including two hot and cold periods along with two pairs of mixed hot-cold. The theoretical division proposed here appears to be a good approximation for the understanding of rainfall seasonality in this area.

Evaluation of the Fetal-Maternal Radiation Doses in CT-Pelvimetry and Estimation of the Fetal Radiation Risks in 03 Radiology Departments in Douala-Cameroon

Background: CT in pregnant patients requires careful consideration of the radiation dose and corresponding radiation risks from ionizing radiation to the unborn child. The determination of foetal dose in diagnostic radiology is of interest as a basis for risk estimates from medical exposure of the pregnant patient. Objective: To evaluate the foetal-maternal radiation doses delivered during the CT-Pelvimetry procedure and to estimate the risk to the unborn child to develop a cancer in childhood and hereditary disease. Materials and Methods: We investigate the foetal-maternal radiation doses during CT-scan Pelvimetry in Douala (Cameroon). Data of 194 helical acquisition CT-Pelvimetry were collected between May 2017 and May 2019. An average DLP for the examination was established and the average effective dose was evaluated. The fetal dose was calculated and the FetDose V5 program was used for risk estimations. Results: The average dose length product (DLP) was 56.17 mGy·cm (range: 51.69 - 59.21 mGy·cm). The average effective dose received by women pregnant was 0.78 mSv. The mean individual fetal dose was 1.5 mGy (range: 0.76 - 1.87 mGy). The risk of Childhood Cancer calculated was: range 1 in 16,000 to 1 in 10,000 and 1 in 260,000 to 1 in 106,000 to the risk of Hereditary Disease, respectively. Conclusion: This study shows that the foetal-maternal doses delivered during CT-Pelvimetry examinations are very low and the risks of childhood cancers and hereditary diseases are derisory, the technology should be further investigated to ensure its full potential for optimal diagnostic accuracy.

Measurement of Natural Radioactivity in Lagoon Sands Used in Construction in the District of Abidjan, Côte d’Ivoire

Sand is an important natural material for the construction of houses, work buildings and other public spaces. This work, which is one of the first contributions to the environmental quality of construction materials, concerns the measurement of natural radioactivity in the lagoon sands collected in the district of Abidjan. Nineteen (19) samples of these sands are analyzed by gamma-ray spectrometry equipped with HPGe detector. The mean values obtained for 226Ra, 232Th and 40K are respectively 7.76 ± 1.84 Bq·kg-1, 5.21 ± 1.36 Bq·kg-1, and 217.31 ± 5.03 Bq·kg-1. The estimated average value of radium equivalent (Raeq) is 31.94 Bq·kg-1. The results show that the average values obtained are far lower than the global limits of 35, 30, and 400 Bq·kg-1 for the concentrations of 226Ra, 232Th and 40K, respectively, and 370 Bq·kg-1 for the equivalent radium established by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Therefore, the use of the analyzed lagoon sand samples in the different construction sectors should not cause serious radiological effects on the populations living in the District of Abidjan. Our results provide new data on building materials radioactivity in Côte d’Ivoire and all over the World. They can also be used as a reference for future work.

The Relationship between Global Solar Radiation and Sunshine Durations in Cameroon

Based on the well-known modified Angstrom formula on the relationship between the sunshine duration and the global solar radiation, this paper aimed to estimate the value of the constant a and b in Cameroon. Only five cities (Maroua, Garoua, NGaoundéré, Yaoundé and Douala) had the both available in-situ data recorded during the period of eleven years (1996-2006) beside which four others cities (Dschang, Koundja, Yoko and Manfé) had only the in-situ sunshine duration available data recorded during the period of twenty years (1986-2006). The 9 cities were grouped in 3 different climate regions. Based on the data of the 5 first cities belonging the 3 regions, the follow constant values a1 = -0.05, a2 = -0.02, a3 = -0.14 and b1 = 0.94, b2 = 0.74, b3 = 1.12 were obtained. The Root Mean Square Error (RMSE) Mean Bias Error (MBE) and correlation coefficient (r) were also determined. Then we used these values to estimate the global solar radiation for the other four remain cities. The constants a and b obtained values are in accordance with those of the West Africa region which Cameroon belongs to. So they can be employed in estimating global solar radiation of location in Cameroon paying attention only to the geographical location information.

Atmospheric Dispersion Modeling of the Emissions from the Logbaba Thermal Power Plant, Douala-Cameroon

Air quality in the vicinity of the thermal power plant of Logbaba in the town of Douala was investigated in this study using data collected in a 5-year period (2008-2012). The distribution of pollutants such as SO2, NOx, CO and the particle matter PM2.5 was analyzed using numerical modeling, based on physical and thermal characteristics, as well as the operating periods of the power plant. The American Environmental Regulator Model (AERMOD) that is an atmospheric dispersion model was used for simulation. The wind rose and others National Oceanic Atmospheric Administration (NOAA) in-situ data were used for the validation of the model. The pollutants distribution was evaluated at two locations: the exit of the power plant, considered as reference point, and at 330 m away from the exit where the first houses appeared. The results show that the relative concentration for each contaminant at the exit of the power plant is 7.2% for the PM2.5 during 24 hours of emission, 46.0% for CO over 8 hours of emission, and 17.5% for SO2 over one hour. The NOx is the highest pollutant with 259.1% over an hour of emission and 51.0% over one year. Beyond 330 m of the power plant, only NOx keeps a polluting character with a relative rate of 100%. These results show that the pollution level of the power plant is over the threshold for air quality set by the World Health Organization. Moreover, among all pollutants investigated, NOx appears to be the most critical for the population in the vicinity of the Logbaba thermal power plant. This information is therefore important for policy and decision makers in preventing the vulnerability of the population to air pollutants from such industrial settings.

Front-Face Fluorescence Using UV-LED Coupled to USB Spectrometer to Discriminate between Virgin Olive Oil from Two Cultivars

A simple setup using a 365 nm LED coupled to a USB spectrometer through an optical fibre, in a front-face fluorescence configuration, was used to investigate the ability of fluorescence spectroscopy technique to discriminate between varieties of olive oil. To achieve this task, Virgin Olive Oils (VOO) from two major Tunisian olive cultivars known as Chetoui and Chemlali were used. Spectral analysis showed a clear separation between these two VOO varieties. A one-way ANOVA attests that this discrimination is significant. The Principal Components Analyses (PCA) showed that the normalized fluorescence intensities are the good parameters for this discrimination. This observation strengthens the potential of our spectral parameters to perform reliable analysis.

Control of malaria and other vector-borne protozoan diseases in the tropics: enduring challenges despite considerable progress and achievements

Vector-borne protozoan diseases represent a serious public health challenge,especially in the tropics where poverty together with vector-favorable climates are the aggravating factors.Each of the various strategies currently employed to face these scourges is seriously inadequate.Despite enormous efforts,vaccines-which represent the ideal weapon against these parasitic diseases—are yet to be sufficiently developed and implemented.Chemotherapy and vector control are therefore the sole effective attempts to minimize the disease burden.Nowadays,both strategies are also highly challenged by the phenomenon of drug and insecticide resistance,which affects virtually all interventions currently used.The recently growing support from international organizations and governments of some endemic countries is warmly welcome,and should be optimally exploited in the various approaches to drug and insecticide research and development to overcome the burden of these prevalent diseases,especially malaria,leishmaniasis,Human African Trypanosomiasis(HAT),and Chagas disease.