Biological nitrogen fixation in Crotalaria species estimated using the 15N isotope dilution method

A greenhouse experiment was conducted to measure nitrogen fixation in three Crotalaria species : C. ochroleuca, C. perrottetii and C. retusa growing in Senegal by using 15N direct isotope dilution technique. Two non-fixing plants, Senna obtusifolia and Senna occidentalis served as reference plants. The amount of nitrogen fixed two months after planting was obtained using the average of the two reference plants. The atom % 15N excess in the Crotalaria species was significantly lower than that of the reference plants, indicating that significant nitrogen fixation occurred in the three plants. Significant differences were observed between the Crotalaria species; C. ochroleuca yielded more dry matter weight and total nitrogen than did C. perrottetti and C. retusa. The % nitrogen derived from atmosphere (%Ndfa) in leaves and stems was also higher in C. ochroleuca. There was no significant difference in %Ndfa in the whole plant between the three Crotalaria species (47% to 53%). In contrast, interspecific variability was observed based on the %Ndfa. C. ochroleuca significantly exhibited the higher amount of total nitrogen fixed, equivalent to 83 kg of nitrogen fixed per hectare. Based on these data, it was concluded that C. ochroleuca could be used in multiple cropping systems in Senegal for making more nitrogen available to other plants. (African Journal of Biotechnology: 2002 1(1): 17-22

Complexes soufrés du Mercure (II) et du Plomb (II) pour l’optique non linéaire

Date du colloque : 02/2011</p

A sensitivity study on the role of the swamps of southern Sudan in the summer climate of North Africa using a regional climate model

We used the regional climate model RegCM3 to investigate the role of the swamps of southern Sudan in affecting the climate of the surrounding region. Towards this end, we first assessed the performance of a high resolution version of the model over northern Africa. RegCM3 shows a good skill in simulating the climatology of rainfall and temperature patterns as well as the related circulation features during the summer season, outperforming previous coarser resolution applications of the model over this region. Sensitivity experiments reveal that, relative to bare soil conditions, the swamps act to locally modify the surface energy budget primarily through an increase of surface latent heat flux. Existence of the swamps leads to lower ground temperature (up to 2 °C), a larger north–south temperature gradient, and increased local rainfall (up to 40 %). Of particular importance is the impact on rainfall in the surrounding regions. The swamps have almost no impact on the rainfall over the source region of the Nile in Ethiopia or in the Sahel region; however, they favor wetter conditions over central Sudan (up to 15 %) in comparison to the bare desert soil conditions.Abdus Salam International Centre for Theoretical Physics (Earth System Physics)International Atomic Energy AgencySTEP progra

Consistency of projected drought over the Sahel with changes in the monsoon circulation and extremes in a regional climate model projections

As a step toward an increased understanding of climate change over West Africa, in this paper we analyze the relationship between rainfall changes and monsoon dynamics in high-resolution regional climate model experiments performed using the Regional Climate Model (RegCM3). Multidecadal simulations are carried out for present-day and future climate conditions under increased greenhouse gas forcing driven by the global climate model European Center/Hamburg 5 (ECHAM5). Compared to the present day, the future scenario simulation produces drier conditions over the Sahel and wetter conditions over orographic areas. The Sahel drying is accompanied by a weaker monsoon flow, a southward migration and strengthening of the African Easterly Jet, a weakening of the Tropical Easterly Jet, a decrease of the deep core of ascent between the jets, and reduced African Easterly Wave activity. These circulation changes are characteristics of dry periods over the Sahel and are similar to the conditions found in the late twentieth century observed drought over the region. Changes in extreme events suggest that the drier conditions over the Sahel are associated with more frequent occurrences of drought periods. The projected drought over the Sahel is thus physically consistent with changes in the monsoon circulation and the extreme indices (maximum dry spell length and 5 day precipitation)

On the structural, morphological, optical and electrical properties of sol–gel deposited ZnO:In films

Indium-doped zinc oxide thin films deposition was performed by the sol–gel technique using homogeneous and stable solutions of zinc acetate 2-hydrate and indium chloride in ethanol. Films were spin coated onto glass substrates. After drying and after a heat treatment at 450 °C, highly transparent (80%–90%) films were obtained. The effect on the structural, morphological, optical and electrical thin films properties of the dopant concentration was investigated. The temperature dependencies of the electrical conductivity under vacuum and in open atmosphere were analysed and discussed

Implementation of active management of the third period of childbirth for the prevention of immediate post-partum bleeding in four regional maternity hospitals of Conakry, Guinea

Background: The objective of this study was to determine the frequency, skills level of health care service providers; to identify complications and difficulties related to the implementation of AMTPC/GATPA.Methods: It was about prospective study, descriptive of 6 months (1st March to 31st August 2014) carried out in the maternity hospitals of Faranah, Kindia, Mamou and Nzérékoré. It concerned the parturient women who had recently given birth and the personnel that carried out AMTPC/GATPA in these hospitals.Results: During the study period of 1,254 out of 1,305 births had benefited of AMTPC/GATPA, a frequency of 96.1%. The midwives were the most represented personnel in the implementation of GATPA (44.1%). In 46.4% of the cases, the health care service providers acquired this competence from the initial training. The release was obtained in the first trial in 64.9% cases. The duration of implementation of GATPA was less than 5 minutes in 72.6% cases. The different stages were respected in 91.5% cases. Complications were dominated by retention of placental fragments (10.2%). Lack of oxytocin was the main difficulty (36.6%).Conclusions: The sustainability of this achievement would depend on the systematic and correct implementation of AMTPC/GATPA at all childbirth attendants and the effective management of oxytocin

Hodgkin Lymphoma at the Paediatric Oncology Unit of Gabriel Touré Teaching Hospital, Bamako, Mali: 5-Year Experience

Introduction. The aim of this retrospective, unicentric study over 5 years is to describe the epidemiologic, pathologic, clinic and therapeutic aspects of children treated for Hodgkin lymphoma in our paediatric oncology unit. Patients and Methods. From January 2005 to December 2009, all children under 18 years of age, with Hodgkin lymphoma were included in this study. The treatment protocol was the GFAOP (Groupe Franco—Africain d'Oncologie Pédiatrique) Hodgkin lymphoma treatment protocol. Results. During the study period, 217 cancer cases were diagnosed in our centre. Of these cases, 7 were Hodgkin Lymphoma (LH) (0.04%). The mean age was 11.7 years. The sex-ratio was 6/1. 4% (5/7) of patients were stage IIB and 28.6% (2/7) stage IIIB of Ann-Arbor classification. There were 3 cases (42.8%) of sclero-nodular subtype, 2 cases (28.6%) of lymphocyte-rich classical HL subtype, 1 case (14.3%) of mixed cellularity and 1 case (14.3%) of lymphocyte depleted subtype. With a median followup of 37 months, 5 patients (71.4%) are alive, and 2 patients (28.6%) died. Conclusion. Broader multicentric studies are needed for more accurate data on this malignancy

Uptake of Soil and Water Conservation Technologies in West Africa: A Case Study of the Office de la Haute Vallée du Niger (OHVN) in Mali

This report provides a descriptive analysis of the uptake of Soil and Water Conservation (S&WC) technologies based on a survey undertaken in a degraded area of Mali, the Office de la Haute Valeé du Niger (OHVN). A total of 531 rural households were interviewed from 26 villages, with the objective of characterizing, identifying and evaluating potential environmental, socioeconomic, institutional and technological constraints to uptake of S&WC technologies, comparing users and nonusers of the technologies at the village, household and plot levels. The study revealed that 40% of the households were using S&WC technologies in the OHVN zone. A range of factors such as endowments in livelihood assets and transforming structures such as markets and institutions, access to roads, suitability of soil for cotton, prevalence of input product markets, access to fertilizers on credit and others were the drivers of uptake. Adoption was concentrated in the southern part of the OHVN zone, where OHVN’s Natural Resource Management Program had been involved in disseminating technologies. At the household level, users of S&WC technologies were found to have more livelihood assets than nonusers. Most farmers reported high productivity gains ranging from 20% to 60% from these technologies. Overall, 75% of the user households were reported to have accumulated more assets and become more food secure

Sensitivity study of the regional climate model RegCM4 to different convective schemes over West Africa

Abstract. The latest version of RegCM4 with CLM4.5 as a land surface scheme was used to assess the performance and sensitivity of the simulated West African climate system to different convection schemes. The sensitivity studies were performed over the West African domain from November 2002 to December 2004 at a spatial resolution of 50 km × 50 km and involved five convective schemes: (i) Emanuel; (ii) Grell; (iii) Emanuel over land and Grell over ocean (Mix1); (iv) Grell over land and Emanuel over ocean (Mix2); and (v) Tiedtke. All simulations were forced with ERA-Interim data. Validation of surface temperature at 2 m and precipitation were conducted using data from the Climate Research Unit (CRU), Global Precipitation Climatology Project (GPCP) and the Tropical Rainfall Measurement Mission (TRMM) during June to September (rainy season), while the simulated atmospheric dynamic was compared to ERA-Interim data. It is worth noting that the few previous similar sensitivity studies conducted in the region were performed using BATS as a land surface scheme and involved less convective schemes. Compared with the previous version of RegCM, RegCM4-CLM also shows a general cold bias over West Africa whatever the convective scheme used. This cold bias is more reduced when using the Emanuel convective scheme. In terms of precipitation, the dominant feature in model simulations is a dry bias that is better reduced when using the Emanuel convective scheme. Considering the good performance with respect to a quantitative evaluation of the temperature and precipitation simulations over the entire West African domain and its subregions, the Emanuel convective scheme is recommended for the study of the West African climate system