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Sample records for west african dwarf

  1. Reproductive Parameters of the West African Dwarf Bucks Raised in ...

    African Journals Online (AJOL)

    DR Ezihe

    2Department of Animal Production, University of Agriculture, Makurdi ... Thirty West African Dwarf (WAD) bucks were evaluated for reproductive ... human consumption in the third world. ... animals. Testicular size and scrotal circumference are closely related to each other ... separately using a ''Diamond MCT 500'' model.

  2. growth and physiological performance of west african dwarf goats

    African Journals Online (AJOL)

    user

    2014-09-02

    Sep 2, 2014 ... Department of Animal Science and ** Department of Crop Science. Faculty of ... production of small ruminants such as sheep ... JOURNAL OF RESEARCH IN FORESTRY, WILDLIFE AND .... African Dwarf Goat project.

  3. Thermorespiratory Response of West African Dwarf Does to Progestagen Injection

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    Ogundana, FA.

    2005-01-01

    Full Text Available The physiological responses in terms of respiration rate (RR and rectal temperature (RT of 30 West African Dwarf (WAD does were monitored after a single im injection of different doses of progestagens meant for synchronising oestrus. The treatments involved im injection of 1 2 ml of sterile water (Control; 2 25 mg Medroxy Progesterone Acetate, MPA; 3 50 mg MPA; 4 50 mg Progesterone and 5 100 mg progesterone. The RR and RT of each animal were measured at 9:00, 13:00 and 17:00 h for 21 days after each injection. In all the treatment groups the RT did not change significantly (P> 0.05 during the weeks following treatment. On the contrary the RR was significantly higher (P< 0.05 in the week after injection than in the pre-injection period. Both the RR and the RT were higher at 13:00 h and 17:00 h than at 9:00 h. The RR was more influenced by the animal body size than the RT, while the ambient temperature and humidity affected both the animal's RT and RR. These results indicate that the thermorespiratory function of WAD does under their native humid environment is not negatively affected by injecting ≤ 100 mg progesterone or ≤ 50 mg MPA to synchronize oestrus.

  4. The interaction between nutrition and metabolism in West African Dwarf goats, infected with trypanosomes.

    NARCIS (Netherlands)

    Dam, van J.T.P.

    1996-01-01

    In a series of experiments the interaction between nutrition and energy- and nitrogen metabolism of West African Dwarf goats, infected with trypanosomes was studied. Animals were injected with trypanosomes, and feed intake, energy and nitrogen balance and blood metabolites and hormones were measured

  5. The interaction between nutrition and metabolism in West African dwarf goats, infected with trypanosomes

    NARCIS (Netherlands)

    Dam, van J.T.P.

    1996-01-01

    In a series of experiments the interaction between nutrition and energy- and nitrogen metabolism of West African Dwarf goats, infected with trypanosomes was studied. Animals were injected with trypanosomes, and feed intake, energy and nitrogen balance and blood metabolites and hormones were measured

  6. Effectiveness Evaluation of Levamisole, Albendazole, Ivermectin, and Vernonia amygdalina in West African Dwarf Goats

    OpenAIRE

    Adediran, Oyeduntan A.; Uwalaka, Emmanuel C.

    2015-01-01

    Anthelmintic drug resistance has led to the search for alternatives in controlling helminth infections. Fifty West African Dwarf goats without history of anthelmintic treatment were divided equally into five groups. Group A was treated with ivermectin injection subcutaneously, group B with levamisole subcutaneously, group C with albendazole orally, and group D with aqueous extract of Vernonia amygdalina and group E was untreated control. Faecal samples were collected before treatment from eac...

  7. Trypanosomiasis in Red Sokoto and West African Dwarf Goats at Ikpa Abattoir, Nsukka, Enugu State, Nigeria

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    Okafor Obioma Juliet

    2013-10-01

    Full Text Available Goat serves as a major investment to most homes in Nigeria, mainly for provision of animal protein and income. The output of this animal is disturbed by Tsetse infestation which is the primary vector of Trypanosome. A survey of Trypanosomiasis of goat in Ikpa abattoir Nsukka, Enugu State, Nigeria was carried out between September and October 2010. This was aimed at determining the species of Trypanosome prevalent in the area and their infection rates among breeds of goat. 106 goats were sampled, among which 15(14.1% were positive for Trypanosome infection. The infection rates among the goat breeds were; Sokoto red (10.4% and West African Dwarf Goat (50.0%. The species of Trypanosome encountered were Trypanosoma vivax(66.7% and Trypanosoma brucei (33.3%. In the infection by sex, this was common among female goats in the various breeds examined and this stood as follows; 9.4% in Sokoto red and 4.7% in West African Dwarf goat. Considering the overall infection rate of Trypanosome in the breeds of goat in the study area, this was relatively high when compared with similar results in related areas; chemo prophylactic and insect control measures should be put in place to rescue the area.

  8. Inclusion of Tithonia diversifolia in multinutrient blocks for WestAfrican dwarf goats fed Brachiaria straw.

    Science.gov (United States)

    Tendonkeng, Fernand; Fogang Zogang, Bienvenu; Sawa, Camara; Boukila, Benoît; Pamo, Etienne Tedonkeng

    2014-08-01

    Recent investigations suggest that the development of multinutrient feed blocks with inclusion of tree and shrub leaves could improve the nutritive value and digestibility of straw. In order to test these possibilities, three types of multinutrient blocks (MNB) namely: MNB0 (wheat bran = 100%; Tithonia diversifolia leaf = 0%), MNB50 (wheat bran = 50%; T. diversifolia leaf = 50%) and MNB100 (wheat bran = 0%; T. diversifolia leaf = 100%) were fed for 15 days in a 3 × 3 Latin square arrangement to West African dwarf goats consuming Brachiaria ruziziensis straw. The blocks presented a good cohesion and a good hardness. The inclusion of T. diversifolia improved levels of crude protein, mineral, feed unit for milk production (UFL) and feed unit for meat production (UFV), but decreased palatability. The effects on the digestibility of B. ruziziensis straw were evaluated in nine West African dwarf goats fed individually with MNB0 + straw, MNB50 + straw and MNB100 + straw. The dry matter, organic matter and crude fibre digestibility of B. ruziziensis straw increased slightly with increasing level of inclusion of T. diversifolia. The apparent digestibility of nitrogen was comparable for all diets independent of the level of inclusion of T. diversifolia. This study showed that the inclusion of T. diversifolia leaves in the MNBs can be recommended to improve the feeding of goats during periods of drought.

  9. Haemonchotolerance in West African Dwarf goats: contribution to sustainable, anthelmintics-free helminth control in traditionally managed Nigerian dwarf goats.

    Science.gov (United States)

    Chiejina, Samuel N; Behnke, Jerzy M; Fakae, Barineme B

    2015-01-01

    West African Dwarf (WAD) goats are extremely important in the rural village economy of West Africa, but still little is known about their biology, ecology and capacity to cope with gastrointestinal nematode (GIN) infections. Here, we summarise the history of this breed and explain its economic importance in rural West Africa. We review recent work showing that Nigerian WAD goats are highly trypanotolerant and resist infections with Haemonchus contortus more effectively than other breeds of domestic goat (haemonchotolerance). We believe that haemonchotolerance is largely responsible for the generally low level GIN infections and absence of clinical haemonchosis in WADs under field conditions, and has contributed to the relatively successful and sustainable, anthelmintics-free, small-scale system of goat husbandry in Nigeria's humid zone, and is immunologically based and genetically controlled. If haemonchotolerance can be shown to be genetically controlled, it should be possible to exploit the underlying genes to improve GIN resistance among productive fibre and milk producing breeds of goats, most of which are highly susceptible to nematode infections. Genetic resistance to GIN and trypanosome infections would obviate the need for expensive chemotherapy, mostly unaffordable to small-holder farmers in Africa, and a significant cost of goat husbandry in more developed countries. Either introgression of resistance alleles into susceptible breeds by conventional breeding, or transgenesis could be used to develop novel parasite-resistant, but highly productive breeds, or to improve the resistance of existing breeds, benefitting the local West African rural economy as well as global caprine livestock agriculture. © S.N. Chiejina et al., published by EDP Sciences, 2015.

  10. Comparative Response of the West African Dwarf Goats to Experimental Infections with Red Sokoto and West African Dwarf Goat Isolates of Haemonchus contortus

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    Lucas Atehmengo Ngongeh

    2015-01-01

    Full Text Available Response of the West African Dwarf (WAD goats to two different isolates of Haemonchus contortus, the Red Sokoto (RS goat isolate (RSHc and the WAD goat isolate (WADHc (isolated from WAD goats, was studied by experimental infections of 4–6-month-old male WAD goat kids. Group 1 and Group 2 goats were each infected with 4500 infective larvae (L3 of RSHc and WADHc, respectively. Group 3 animals served as uninfected control. Prepatent period (PPP, faecal egg counts (FEC, worm burden (WB, body weight (BW, packed cell volume (PCV, and body condition score (BCS were determined. WAD goats infected with RSHc isolate and the ones infected with WADHc isolate had mean PPP of 19.63±0.26 and 19.50±0.19, respectively. Goats infected with WADHc isolate had significantly higher FEC (P=0.004 and WB (P=0.001. BW were significantly higher (P=0.004 both in the controls and in Group 2 goats infected with WADHc isolate than in Group 1 goats infected with the RSHc isolate. BCS of animals in both infected groups dropped significantly (P=0.001. There was a significant drop in PCV (P=0.004 of both infected groups in comparison. Both isolates of H. contortus were pathogenic to the host.

  11. Trypanotolerance in Djallonke sheep and West African Dwarf goats : Importance of trypanosomosis, nutrition, helminth infections and management factors

    NARCIS (Netherlands)

    Osaer, S.; Goossens, B.

    1999-01-01

    The main breeds of sheep and goats in The Gambia, the Djallonke sheep and West African Dwarf goats are trypanotolerant. The Djallonke sheep, however, have a higher degree of trypanotolerance than the WAD goats. This trait is genetically linked although the mechanism of trypanotolerance is different

  12. Changes in liver and fat depots of West African dwarf goats (Capra aegagus hircus) after an infection with T. vivax.

    NARCIS (Netherlands)

    Hamminga, B.J.; Wensing, Th.; Zwart, D.

    1996-01-01

    Nine West African dwarf goats (Capra aegagus hircus) were each infected experimentally with 3 x 107 Trypanosoma vivax parasites. The changes in the plasma concentration of nonesterified fatty acids (NEFA) were monitored during the infection and the level of hepatic triacylglycerols and glycogen was

  13. Trypanotolerance in Djallonke sheep and West African Dwarf goats : Importance of trypanosomosis, nutrition, helminth infections and management factors

    NARCIS (Netherlands)

    Osaer, S.; Goossens, B.

    1999-01-01

    The main breeds of sheep and goats in The Gambia, the Djallonke sheep and West African Dwarf goats are trypanotolerant. The Djallonke sheep, however, have a higher degree of trypanotolerance than the WAD goats. This trait is genetically linked although the mechanism of trypanotolerance is different

  14. Changes in liver and fat depots of West African dwarf goats (Capra aegagus hircus) after an infection with T. vivax.

    NARCIS (Netherlands)

    Hamminga, B.J.; Wensing, Th.; Zwart, D.

    1996-01-01

    Nine West African dwarf goats (Capra aegagus hircus) were each infected experimentally with 3 x 107 Trypanosoma vivax parasites. The changes in the plasma concentration of nonesterified fatty acids (NEFA) were monitored during the infection and the level of hepatic triacylglycerols and glycogen was

  15. The unique resistance and resilience of the Nigerian West African Dwarf goat to gastrointestinal nematode infections

    Science.gov (United States)

    2011-01-01

    Background West African Dwarf (WAD) goats serve an important role in the rural village economy of West Africa, especially among small-holder livestock owners. They have been shown to be trypanotolerant and to resist infections with Haemonchus contortus more effectively than any other known breed of goat. Methods In this paper we review what is known about the origins of this goat breed, explain its economic importance in rural West Africa and review the current status of our knowledge about its ability to resist parasitic infections. Conclusions We suggest that its unique capacity to show both trypanotolerance and resistance to gastrointestinal (GI) nematode infections is immunologically based and genetically endowed, and that knowledge of the underlying genes could be exploited to improve the capacity of more productive wool and milk producing, but GI nematode susceptible, breeds of goats to resist infection, without recourse to anthelmintics. Either conventional breeding allowing introgression of resistance alleles into susceptible breeds, or transgenesis could be exploited for this purpose. Appropriate legal protection of the resistance alleles of WAD goats might provide a much needed source of revenue for the countries in West Africa where the WAD goats exist and where currently living standards among rural populations are among the lowest in the world. PMID:21291550

  16. The unique resistance and resilience of the Nigerian West African Dwarf goat to gastrointestinal nematode infections

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    Chiejina Samuel N

    2011-02-01

    Full Text Available Abstract Background West African Dwarf (WAD goats serve an important role in the rural village economy of West Africa, especially among small-holder livestock owners. They have been shown to be trypanotolerant and to resist infections with Haemonchus contortus more effectively than any other known breed of goat. Methods In this paper we review what is known about the origins of this goat breed, explain its economic importance in rural West Africa and review the current status of our knowledge about its ability to resist parasitic infections. Conclusions We suggest that its unique capacity to show both trypanotolerance and resistance to gastrointestinal (GI nematode infections is immunologically based and genetically endowed, and that knowledge of the underlying genes could be exploited to improve the capacity of more productive wool and milk producing, but GI nematode susceptible, breeds of goats to resist infection, without recourse to anthelmintics. Either conventional breeding allowing introgression of resistance alleles into susceptible breeds, or transgenesis could be exploited for this purpose. Appropriate legal protection of the resistance alleles of WAD goats might provide a much needed source of revenue for the countries in West Africa where the WAD goats exist and where currently living standards among rural populations are among the lowest in the world.

  17. Concentration of trace element in milk of West African dwarf goats affected by state of lactation

    Energy Technology Data Exchange (ETDEWEB)

    Akinsoyinu, A.O.; Tewe, O.O.; Mba, A.U.

    1979-06-01

    Ten adult West African dwarf (Fouta djallon) does about 2 yr old and weighing from 22 to 28 kg were kept for two lactations with 18 wk per lactation. During these periods the does were handmilked twice daily, and the daily samples were bulked for each animal for subsequent chemical analysis. Each goat was fed Cynodon nlemfuensis ad libitum and 1 kg of dairy concentrate mixture daily. Colostrum contained (mg/liter) much higher iron, 2.46 +- .27; copper, 3.14 +- .12; manganese, .20 +- .03; zinc, 14.11 +- .45; and iodine, 319.69 +- 14.13 mg/liter than the corresponding values in mature milk which were .43 +- .12; .28 +- .20; .5 +- .04; 4.01 +- .51, and 108.52 +- 28.25. These elements in the colostrum approached normal values between the 5th and 6th day after parturition. The concentration decreased with advance in lactation except for zinc.

  18. A survey of West African Dwarf (WAD goats enterprises in Lafia area, Nasarawa State, Nigeria

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    Hassan Ishaq Ibrahim

    2011-01-01

    Full Text Available West African Dwarf (WAD Goat enterprises were studied using data collected from 120 households where goats are kept. The result revealed that majority of the households heads were male and married, with an average of 46 years and had up to eight years experience in goat production. A very few were members of cooperative societies. Contact with extension agents by the respondents was also minimal, while 40% rear goats for both home consumption and income generation. Goats were kept by the respondents under semi intensive and extensive feeding systems. The average number of goats kept per household was 12. Majority of the respondents sell their goats at home and the selling price was determined by the prevailing market price or by reproductive value. Feed shortage was the major constraint militating against goat production in the study area. There is a high potential to increase the productivity of goats if the technical and managerial constraints can be solved by providing better quality feeds and improved extension service delivery.

  19. Biochemical Effects of Xylazine, Propofol, and Ketamine in West African Dwarf Goats

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    Ukwueze Celestine Okwudili

    2014-01-01

    Full Text Available Anaesthesia was induced in West African Dwarf (WAD goats using different combinations of propofol (P, xylazine (X, and ketamine (K, and the biochemical effect of the drugs determined. Twenty male (WAD goats were randomly assigned to five treatment groups viz. Control (C (2.5 mL IV normal saline; group K + X (5 mg/kg IV ketamine + 0.05 mg/kg IV xylazine, group P + X (5 mg/kg IV propofol + 0.05 mg/kg IV xylazine, group P + K (propofol 5 mg/kg IV + ketamine 5 mg/kg IV, and group P + K + X (propofol 2.5 mg/kg IV + ketamine 2.5 mg/kg IV + xylazine 0.05 mg/kg IV, respectively. There was increase (P0.05 in serum creatinine. These biochemical changes were transient. P + K + X would be the best drug combinations considering the biochemical parameter measured. However, data on blood glucose, ALT, BUN, and cortisol levels in an anaesthsized goat should be interpreted with caution in order to avoid erroneous interpretation in these animals.

  20. Effectiveness Evaluation of Levamisole, Albendazole, Ivermectin, and Vernonia amygdalina in West African Dwarf Goats.

    Science.gov (United States)

    Adediran, Oyeduntan A; Uwalaka, Emmanuel C

    2015-01-01

    Anthelmintic drug resistance has led to the search for alternatives in controlling helminth infections. Fifty West African Dwarf goats without history of anthelmintic treatment were divided equally into five groups. Group A was treated with ivermectin injection subcutaneously, group B with levamisole subcutaneously, group C with albendazole orally, and group D with aqueous extract of Vernonia amygdalina and group E was untreated control. Faecal samples were collected before treatment from each animal and larval culture was carried out. Faecal egg count reduction (FECR) test was carried out for each group and the data analysed using FECR version 4 to calculate percent reduction in faecal egg count. Predominant helminth infections from larval culture were Haemonchus contortus (70%), Trichostrongylus spp. (61%), and Oesophagostomum spp. (56%). Mixed infection was present in all the animals. From the FECR test Vernonia amygdalina extract was more effective against helminths (100%), compared to ivermectin 96%, levamisole 96%, and albendazole 99%. The lower 95% confidence limit was 89 for ivermectin and levamisole and 91 for albendazole. There is low resistance to ivermectin and levamisole and susceptibility to albendazole while V. amygdalina has great potentials that could be explored for the treatment of helminth diseases in goats.

  1. UTILIZATION OF MEXICAN SUNFLOWER LEAF MEAL-BASED DIETS BY PRE WEANED WEST AFRICAN DWARF LAMBS

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    Anthony Henry Ekeocha

    2012-06-01

    Full Text Available Studies were conducted using 16 West African Dwarf (WAD lambs selected from 16 ewes brought to heat (Oestrus by synchronization and served by 2 rams. The experimental animals were placed at 6 weeks of age and were fed with Panicum maximum plus concentrate diet mixture of Mexican Sunflower Leaves (MSL and Wheat Bran (WB such that 0, 15, 30 and 45% of wheat bran was replaced by weight with MSL gravimetrically in diets A, B, C and D respectively. The experiment lasted for seven weeks. Feed and water were provided ad libitum and routine vaccination and medication were administered. Parameters measured were weight gain, dry matter intake, weaning weight and Feed Conversion Ratio (FCR. The Dry Matter Intake - DMI (g/day was highest for lambs on diet C (156.94 followed by B (156.53, A (154.29 and D (152.04 g/day respectively. This increase was numerically higher than observed values for animals on treatments A and B but statistically significant (P0.05. Results from this study showed that 30% MSLM-based diet was acceptable to the pre-weaned lambs as it supported dry matter intake, optimum weight gain, weaning weight and feed conversion ratio before diminishing return sets in.

  2. Effectiveness Evaluation of Levamisole, Albendazole, Ivermectin, and Vernonia amygdalina in West African Dwarf Goats

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    Oyeduntan A. Adediran

    2015-01-01

    Full Text Available Anthelmintic drug resistance has led to the search for alternatives in controlling helminth infections. Fifty West African Dwarf goats without history of anthelmintic treatment were divided equally into five groups. Group A was treated with ivermectin injection subcutaneously, group B with levamisole subcutaneously, group C with albendazole orally, and group D with aqueous extract of Vernonia amygdalina and group E was untreated control. Faecal samples were collected before treatment from each animal and larval culture was carried out. Faecal egg count reduction (FECR test was carried out for each group and the data analysed using FECR version 4 to calculate percent reduction in faecal egg count. Predominant helminth infections from larval culture were Haemonchus contortus (70%, Trichostrongylus spp. (61%, and Oesophagostomum spp. (56%. Mixed infection was present in all the animals. From the FECR test Vernonia amygdalina extract was more effective against helminths (100%, compared to ivermectin 96%, levamisole 96%, and albendazole 99%. The lower 95% confidence limit was 89 for ivermectin and levamisole and 91 for albendazole. There is low resistance to ivermectin and levamisole and susceptibility to albendazole while V. amygdalina has great potentials that could be explored for the treatment of helminth diseases in goats.

  3. Effect of source and sex on blood protein fractions of West African Dwarf Goats (WADG

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    J. C. Okonkwo,

    2011-03-01

    Full Text Available Source and sex effects on the total blood protein and its various fractions were studied using juvenile West African Dwarf goats derived from Southern Nigeria. The goats were sourced from three distinct towns in the humid tropics namely, South-East (Umuahia, South-South (Ugheli and South-West (Akure at the rate of 6 males and 18 females per location. The mean values of the total blood plasma protein and its fractions obtained for the WADGs from different zones are 10.01±0.07 g/100ml, 10.07±0.08 g/100ml and 10.16±0.35 g/100ml (total plasma protein; 9.62±0.10 g/100ml, 9.68±0.08 g/100ml and 9.68±0.09 g/100ml (total serum protein, 0.38±0.03 g/100ml, 0.39±0.01 g/100ml, and 0.38±0.04 g/100ml (plasma fibrinogen, 5.62±0.23 g/100ml, 5.78±0.24 g/100ml and 5.45±0.26 g/100ml (serum albumin, 4.00±0.19 g/100ml, 3.89±0.29 g/100ml, and 4.12±0.25 g/100ml (serum globulin, and 1.41±0.27, 1.49±0.15 and 1.34±0.12 (albumin/globulin ratio for the goats from South-East (Umuahia, South-South (Ugheli and South-West (Akure respectively. The studies also indicate that albumin accounts for 53-58% of the total serum protein; globulin accounts for 42-47% serum protein, and the plasma fibrinogen 3.6-4% of the total plasma protein. sex and source interaction had no significant (P>0.05 effects on serum proteins; plasma fibrinogen is sex dependent, and the source of goat affects the proportions of the serum albumin, globulin, and albumin/globulin ratio characteristics of the experimental goats.

  4. Determination of Browse Intake and Nutrient Digestibility of Grazing West African Dwarf (WAD) Goats Fed Varying Levels of Gmelina arborea Leaves as Supplements in Delta State Nigeria

    OpenAIRE

    O. Okpara; P.O. Akporhuarho; G.O. Okagbare

    2014-01-01

    The Research was carried out to assess the browse intake and nutrient digestibility of grazing West African Dwarf (WAD) goats fed varying levels of Gmelina arborea leaves as supplement. Which produces appreciable amount of forage even at the peak of the dry season in the tropics, thereby ensuring all year round supply of follage and fodder. Thirty growing West Africa Dwarf (WAD) goats were used to dertermine the level of browse intake and nutrient diggestibility by goats fed verying levels Gm...

  5. Correlates of resistance to gastrointestinal nematode infection in Nigerian West African dwarf sheep

    Institute of Scientific and Technical Information of China (English)

    IK Idika; SN Chiejina; LI Mhomga; PA Nnadi; LA Ngongeh

    2012-01-01

    ABSTRACT Objective:To investigate correlates of resistance toGI nematode infection inNigerianWest African dwarf(WAD) sheep.Methods:Thirty three sheep were randomly assigned to two groups, A(n=27) which were used for experimental infections, andB(n=6) which served as uninfected control.Each infected animal received weekly escalating infections with infective larvae(60%Haemonchus contortus (H. contortus) and40%Trichostrongylus colubriformis (T. colubriformis) for4 weeks.The responses of all the infected and control sheep were assessed by faecal egg count(FEC), worm burden(Wb), packed cell volume(PCV), body weight(Bwt), and body condition score(BCS).On the basis of their individual faecal egg output,Lambs in groupA with epg≤1 000 on any sampling day were classified as low faecal egg count(LFEC) phenotype(n =16), those with epg between1000 and10000 as intermediate(n=5) and lambs with epg >10000 as high feacal egg count(HFEC) phenotype(n=6).Results:The difference between theFEC classes was highly significant(P=0.001).TheBCS and weight gained at the end of the experiment by the control andLFEC sheep was significantly higher(P≤0.05) than those of the intermediate and HFEC phenotypes.There was a significant and negative correlation between the parasitological measures and the trio ofBCS,PCV andBwt of sheep.Conclusions:The result of the study indicated that theFEC, weight gain,PCV, andBCS are correlates and potential selection criteria ofGI nematode resistantWAD sheep.

  6. Studies on the development of omasum in West African dwarf goats (Capra hircus).

    Science.gov (United States)

    Nwaogu, Chima Innocent; Ezeasor, Nwagbo Daniel

    2008-10-01

    This work studied the sequential morphological changes of omasum in foetuses, neonates and adult West African Dwarf (WAD) goats by gross and light microscopic methods. The mean omasal volume was 1.37 +/- 0.36, 4.2 +/- 0.4, 8.7 +/- 6.9 and 60.1 +/- 8.6 ml for gestation day 87 and 146 foetuses, neonates and adults respectively. Grossly the mucosa exhibited longitudinally oriented primary, secondary, tertiary and quartnery laminae with smooth surface in foetuses and numerous papillae in the adults. Microscopically it was lined by stratified squamous epithelium which was divided into larger lighter luminal and smaller darker basal zones in gestation day 60 foetuses. The core of the laminae contained extension of the inner muscular tunic. The basal zone developed lateral evaginations (corial papillae) into the lighter zone of the laminae in gestation day 106 foetuses. By term these corial papillae approached the luminal surface. The papillae emerged above the luminal surface in 4 week old neonates. The papillae were fully developed in adult goats. The mean papillary height and width were -205.1 +/- 34.0, 67.0 +/- 9.6; 235.0 +/- 86.5, 185.0 +/- 42.3 and 570.3 +/- 60.0, 290.1 +/- 66.3 microm for foetuses, neonates and adult goats. The inner circular layer was thicker than the outer longitudinal layer of the muscular tunic. The central muscular layer of the laminae originated from the inner circular layer with attachment to the outer muscular layer in adults. This attachment could be adaptation for better anchorage and muscular contraction of the laminae in WAD goats.

  7. Nitrogen balance of lactating West African dwarf ewe fed Mexican sunflower leaf meal based diets

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    A. H. Ekeocha

    2012-08-01

    Full Text Available Fifteen days prior to weaning, sixteen West African dwarf (WAD ewes (Initial BW 19.13±1.53kg on a basal diet of Panicum maximum were allotted into 4 treatment groups A, B, C and D of 4 replicates each. The mexican sunflower leaf (MSL replaced wheat bran (WB gravimetrically at 0, 15, 30 and 45%. Treatment A served as control. The experiment lasted for one week. Digestibility was determined using a 6-d total fecal collection. The 16 ewes were previously lambed 10 weeks before the commencement of this study and tagged to their respective treatments. Parameters measured were nitrogen intake, nitrogen balance, nitrogen apparent digestibility and nitrogen retention. Data were analyzed using descriptive statistics and ANOVA. Animals on treatment B had the highest N-intake (18.1g/d, N faecal (1.7 g/d, N absorbed (16.4 g/d and N balance (16.3 g/d and this was significant (P. Urinary nitrogen g/d was significantly higher (P with increasing inclusion of MSLM in the ration while protein retention increased from treatment A (0% MSLM to treatment B (15% MSLM (89.8 – 90.3% and subsequently decreased from treatment B (15%MSLM to D (45% MSLM (90.3 - 84.4%. Nitrogen balance was positively related to DM intake and N intake. The overall regression were nitrogen balance (NB =2.50+0.067 DMI; R2 = 0.9372, (P=0.3937 and NB= 0.75+0.9066 NI; R2 = 0.9957, (P=0.1401. Inclusion of up to 30% MSLM in the diets of lactating ewe appeared most beneficial to sheep as it had no negative effects on nitrogen intake.

  8. Pathogenicity of local isolates of Mycoplasma ovipneumoniae and Mycoplasma arginini in experimental West African Dwarf goats

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    Chinedu Adive Akwuobu

    2016-09-01

    Full Text Available Objective: This study was carried out to assess the pathogenicity of local isolates of Mycoplasma ovipneumoniae and M. arginini in West African dwarf goats (kids in Nigeria. Materials and methods: A total of 22 goats aged less than 1-year were purchased from markets. The goats were divided into six groups comprising of four experimental groups (EG; 4 in each and two control groups (CG; 3 in each. The goats were fed ad libitum with standard diets and safe water. Groups EG1 and EG2 were infected with M. ovipneumoniae through trans-tracheal (TT and intravenous (IV routes, respectively, while those in groups EG3 and EG4 were infected with M. arginini through the same routes. Goats in groups CG1 and CG2 were inoculated with sterile Mycoplasma broth through TT and IV routes, respectively. In all cases, the amount of bacteria inoculated was 1.5x108 cells/mL. After the onset of the disease in goats, re-isolation of Mycoplasma was performed by culturing on mycoplasma agar supplemented with mycoplasma supplement G. The goats were monitored for 14 days post-infection (PI to observe respiratory signs and mortality. Post-mortem (PM examination was performed on each animal that died, while one surviving goat from each of the groups was sacrificed at 14 days PI for PM. After PM, histopathology was performed to observe the changes in tissues. Results: Cough and nasal discharges were observed in all the experimentally infected goats seven days PI. Mortalities were recorded in goats in EG1 (two goats, EG2 (one goats, EG3 (two goats and EG4 (one goat. At PM, pneumonic lesions were observed in the lungs of all the experimentally infected goats. Conclusion: This study provides evidence that the local isolates of M. ovipneumoniae and M. arginini strains are pathogenic for goats in Nigeria. [J Adv Vet Anim Res 2016; 3(3.000: 242-251

  9. Haematological and serum biochemical parameters of West African Dwarf goats fed dried cassava leaves-based concentrate diets.

    Science.gov (United States)

    Oni, Adebayo Olusoji; Arigbede, Oluwasanmi Moses; Sowande, Olusiji Sunday; Anele, Uchenna Young; Oni, Oluwakemi Oluremilekun; Onwuka, Chryss Friday Ijeoma; Onifade, Olufemi Sunday; Yusuf, Kafayat Omowumi; Dele, Peter Aniwe; Aderinboye, Ronke Yemisi

    2012-03-01

    The study was conducted to investigate the effects of feeding different levels of dried cassava leaves at 0%, 20%, 40% and 60%, respectively, using guinea grass as basal feed, on the haematological and serum biochemical parameters of West African Dwarf (WAD) goats. The study lasted for 116 days during which haematological and serum biochemical parameters were monitored in 40 male goats before and after, using a completely randomized design. At the start of the experiment, packed cell volume (PCV) ranged from 21.5% to 25.5% while haemoglobin concentration (Hb) and RBC significantly (P diets. At the end of the trial, there was a slight increase in the values of PCV and Hb in the diets (P > 0.05). Lymphocyte reduced significantly (P diets. Neutrophils, however, increased (P > 0.05) at the 0% to 40% levels and reduced at the 60% level of dried cassava leaves inclusion. At the start of the experiment, values for glucose significantly (P diets. The study revealed that inclusion of dried cassava leaves in the diets of West African Dwarf goats had no deleterious effects on the haematological and serum biochemical parameters of WAD goats and could therefore be included in ruminant diets up to 60%.

  10. PREDICTION OF LIVE BODY WEIGHT FROM LINEAR BODY MEASUREMENTS OF WEST AFRICAN LONG-LEGGED AND WEST AFRICAN DWARF SHEEP IN NORTHERN GHANA

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    P.T. BIRTEEB

    2012-09-01

    Full Text Available The knowledge of live weight of animals is so important in the livestock production and marketing practices that this study was undertaken to develop models for predicting the weight of sheep at market ages. Data comprising of the weight and linear body measurements were collected on the West African Long-Legged (WALL and the West African Dwarf (WAD sheep from Pong-Tamale and subjected to regression analyses. The results revealed that heart girth was the best predictor of liveweight, with prediction accuracies of 92.36% for two years old WALL sheep and 81.20% for one year old WAD sheep, while wither height was the second most important trait in liveweight prediction, in simple linear models. The quadratic models of the single-trait models also had heart girth as the best predictor of liveweight, recording 92.92% accuracy for one year old WALL sheep. Only two traits were mostly required for weight estimation in the multiple-trait models, and the best model was obtained from two years old WALL where heart girth and body length accounted for about 95.53% in prediction accuracy. The multiple-trait quadratic models were generally better in liveweight prediction compared to the respective linear models. Clearly, weight estimation was more accurate among the WALL than the WAD sheep, and also among the younger sheep regardless of the breed. The variations in the models suggest that breed and age of sheep had influence on the type of models required to predict their live body weight.

  11. Leucaena and dried poultry waste improve the performance of West African Dwarf sheep on a grass diet.

    Science.gov (United States)

    Agbor, Euphresia Besongtakor; Ndamukong, Kenneth Jacob Ngoh; Pamo, Etienne Tendonkeng

    2013-04-01

    This study investigated the effects on digestibility and growth when West African Dwarf (WAD) sheep were fed a basal diet of Tripsacum laxum with Leucaena leucocephala or dried poultry waste as supplement. Fifteen WAD sheep (12 rams and 3 ewes) were randomly allocated to three dietary treatments of 5 animals each, namely T1-basal diet of chopped T. laxum (control), T2-basal diet plus dried poultry waste, and T3-basal diet plus L. leucocephala. Animals had access to drinking water and a mineral mix ad libitum. They were weighed weekly after a 2-week adaptation period, for a duration of 12 weeks. At the end of the feeding trial, three rams randomly selected from each treatment group were used for the digestibility study. Results revealed that average daily intake of L. leucocephala (350.0 ± 0.3 g/animal) was higher than that of dried poultry waste (260.0 ± 0.1 g/animal). The supplemented groups, T2 and T3, gained 21.4 and 31.0 g daily respectively, while animals of the control group (T1) lost 6.0 g daily. There was a significant difference (P<0.01) in dry matter intake between the control and supplemented groups, with T2 recording the highest intake. Organic matter intake of treatment 3 was significantly (P<0.01) higher than that of T1 and T2. The differences in crude fibre (CF) ingestion between T2 and T1 as well as T3 and T1 were significant (P<0.01), with the highest ingestion of CF occurring in T1. The dry matter digestibility of the supplemented groups was significantly higher (P<0.05) than that of the control. The organic matter digestibility of T2 and T3, as well as T1 and T3 were significantly different (P<0.05), being highest in T3 (77.0 ± 2.1 %) and lowest in T2 (58.1 ± 1.0 %) It was concluded from the study that T. laxum can be better utilized in West African Dwarf sheep when supplemented with dried poultry waste or L. leucocephala.

  12. Semen characteristics and sperm morphological studies of the West African Dwarf Buck treated with Aloe vera gel extract

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    Oyeyemi Matthew Olugbenga

    2011-01-01

    Full Text Available Background: Aloe vera (Aloe barbadensis miller is an evergreen perennial plant widely used in modern herbal practice and is often available in proprietary herbal preparations.Objective: This study was designed to investigate the semen picture and spermatozoa morphology of West African Dwarf (WAD bucks treated with Aloe vera extract.Materials and Methods: Twelve sexually matured WAD bucks, weighing between 11 and 15 kg, were used for the study. The bucks were first used as control (pre-treatment and later as two groups of six animals each. The first six bucks received 10 mls of the 3% extract while the other six received 10 mls of the 4% of the extract for a 7 day period. Semen was collected from both the 3 and 4% extract treated bucks for the control (pre-treatment, on days eight (first week post-treatment and fifteen (second week post-treatment in each case using the electroejaculation method. The spermiogram of the bucks were investigated using standard procedures. Data obtained were analyzed using two way ANOVA and significance reported at p<0.05.Results: The continuous administration of Aloe vera extract significantly (p<0.05 reduced sperm concentration, motility and percentage livability and resulted in increased sperm abnormalities in the WAD buck.Conclusion: Aloe vera adversely affected the spermiogram of bucks. The plant can reduce fertility in male animals and is therefore not recommended for medicinal purpose in male animals especially those used for breeding.

  13. Studies on Zinc and Copper Ion in Relation to Wound Healing in Male and Female West African Dwarf Goats.

    Science.gov (United States)

    Olaifa, A K; Fadason, S T

    2017-03-06

    Wound healing remains a challenging clinical problem for which precise and efficient management is essential in order to curtail morbidity and mortality. Wound healing has been shown to depend upon the availability of appropriate trace elements like copper and zinc which serve as enzyme cofactors and structural components in tissue repair. This study aims at evaluating the distribution of zinc and copper found in the hair as well as skin during epidermal wound healing. Adult and healthy West African dwarf (WAD) goats of both sexes fed with concentrate, grass, cassava peel and water ad libitum were used. The animals were housed for three weeks before commencement of the experiments. Epidermal wounds were created on the trunks of all the goats using cardboard template of 1cm². Progressive changes in wound contraction were monitored grossly by placing clean and sterile venier calliper on the wound margin. Hair and skin elemental (copper and zinc) analyses were done using atomic absorption spectroscopy (AAS). Significant increases in Cu level were observed in the female hair compared with that of males. There were significant increases in the Zn levels of the females' hair compared with the males. The wound healed faster in female goat compared with the males. The ratio of copper to zinc is clinically more important than the concentration of either of these trace metals. The pattern of distribution between zinc and copper concentration in the skin and hair of the male and female goats observed in this study could be added factor responsible for early wound healing in female. Therefore, our findings suggest that the distribution in the Cu and Zinc level in skin and hair of both male and female goats could also be a factor for wound healing in the animals.

  14. Performance of West African dwarf goats fed Guinea grass-Verano stylo mixture, N-fertilized and unfertilized Guinea grass.

    Science.gov (United States)

    Bamikole, M A.; Ezenwa, I; Akinsoyinu, A O.; Arigbede, M O.; Babayemi, O J.

    2001-02-01

    The supplementary values of Verano stylo in a mixed Guinea grass (Panicum maximum cv. Ntchisi)-Verano stylo (Stylosanthes hamata cv. Verano) diet from a sown grass-legume mixture and N fertilized grass were compared in West African dwarf (WAD) goats. Liveweight (LW) gain, feed intake, digestibility and N utilization were determined using 15 goats in two trials lasting for 98 days. Goats were fed Guinea grass-Verano stylo mixture (GSM), N-fertilized (NFG) and unfertilized grass (UFG). The goats were divided into three groups of five animals each and randomly allocated to the dietary treatments in a randomized complete block design. Total DM and OM intakes of the goats did not vary significantly among the forage diets and averaged 55.1 and 50.4gkg(-1)W(0.75) per day, respectively. CP intake (gkg(-1)W(0.75) per day) was highest with NFG (5.6) followed by GSM (4.8) and the UFG (3.5). Total N excreted followed the same trend as the CP intake. There was no significant difference between N-retention of GSM and NFG (28.5 and 26.7%), but goats on UFG had a negative N balance (-9.16%). Animals on GSM had significantly higher liveweight gain (31.9g per day) than those of NFG (25.1g per day) and UFG (21.9g per day) which also differed significantly. The digestibilities of total DM, OM, CP, NDF were higher with GSM than NFG or UFG. It is concluded that growing Verano stylo in mixture with Guinea grass is a better option for improving the feed quality of forage diets for goats than direct application of inorganic fertilizer at 200kgNha(-1) to the pure grass.

  15. Effect of Tree Leaves on Rumen Fermentation, Microbial Count and Blood Urea Nitrogen of West African Dwarf Goats

    Directory of Open Access Journals (Sweden)

    Adelusi, O. O.

    2016-12-01

    Full Text Available This experiment was carried out to assess the effect of Azadirachta indica, Newbouldia laevis and Spondias mombin leaves on rumen fermentation, microbial count and blood urea nitrogen (BUN of West African Dwarf (WAD goats. Sixteen WAD bucks (11.6 ? 0.9 kg in body weight were allocated to 4 treatments: 1 Control and 2 40 g/day of Azadirachta indica, 3 40 g/day of Newbouldia laevis and 4 40 g/day of Spondias mombin leaves arranged in a completely randomised design. The ground leaves were included in concentrate diets served on dry matter basis at 2% of body weight while Panicum maximum was fed ad libitum. The control diet had no tree leaves. Data were collected on chemical composition, rumen fermentation and microbial ecology, and BUN. Saponin was highest (P < 0.05 in S. mombin (8.14% while A. indica and N. laevis had 5.78% and 1.56%, respectively. Rumen ammonia nitrogen was least (P < 0.05 in goats fed A. indica (8.35 mg/dL while the highest (P < 0.05 total volatile fatty acid (TVFA was obtained from goats fed S. mombin with 125.51 mM. Goats fed N. laevis yielded the highest (P < 0.05 acetate with 70.65 mol/100 mol while propionate production was highest (P < 0.05 in the rumen of goats fed S. mombin (27.15 mol/100 mol. Viable bacteria count was lowest (P < 0.05 in rumen of goats fed A. indica (3.95?1012 cfu/ml while the least (P < 0.05 protozoa population was obtained from the rumen of bucks fed S. mombin (4.18?109 cfu/ml. All goats in the treatments containing tree leaves had higher (P < 0.05 and a rapid increase in BUN between 0 and 6 h post feeding when compared with the Control. It is concluded that feeding ground leaves of S. mombin to goats increases rumen total volatile fatty acid and propionate production and reduces the protozoa population.

  16. The effect of the quality of roughage on the course of Trypanosoma vivax infection in West African dwarf goats: II. Metabolic profile, packed cell volume, and pathology of disease.

    NARCIS (Netherlands)

    Dam, van J.T.P.; Heide, van der D.; Ingh, van den T.S.G.A.M.; Wensing, T.; Zwart, D.

    1998-01-01

    Effects of trypanosome infection and feed quality on the metabolism of trypanotolerant West African Dwarf goats were measured. Goats were allotted to either a diet of lucerne pellets (Crude protein level = 172 g/kg DM; n = 14) or a diet of chopped grass straw (Crude protein level = 68 g/kg DM; n =

  17. Assessment of Common Anaesthetic and Clinical Indices of Multimodal Therapy of Propofol, Xylazine, and Ketamine in Total Intravenous Anaesthesia in West African Dwarf Goat

    Directory of Open Access Journals (Sweden)

    Ukwueze Celestine Okwudili

    2014-01-01

    Full Text Available The assessment of anaesthetic and clinical indices of multimodal therapy of propofol, xylazine, and ketamine was done in West African Dwarf (WAD goat. Sixteen healthy male WAD goats were assigned into four treatment groups, namely, control (group A (ketamine 5 mg/kg + xylazine 0.05 mg/kg, group B (propofol 5 mg/kg + xylazine 0.05 mg/kg, group C (propofol 5 mg/kg + ketamine 5 mg/kg, and group D (propofol 2.5 mg/kg + ketamine 2.5 mg/kg + xylazine 0.05 mg/kg. All drugs were administered intravenously. The multimodal therapy decreased significantly (P<0.05 the heart rate in groups A, B, and D. Also respiratory rate significantly (P<0.05 decreased in groups A, B, and D but significantly (P<0.05 increased at 20 min after induction in group C. However, temperature significantly (P<0.05 decreased in groups A, B, and C. The induction was good and smooth in groups B and D. Surgical anaesthetic time was longer in groups B and D and shorter in group C. The quality of recovery was good in groups B and D. Side effects such as salivation and apnoea were observed in all groups. In conclusion, the multimodal therapy could be used successfully. However, group D could be the best combination considering the parameters measured.

  18. Effects of species and season on chemical composition and ruminal crude protein and organic matter degradability of some multi-purpose tree species by West African dwarf rams.

    Science.gov (United States)

    Arigbede, O M; Anele, U Y; Südekum, K-H; Hummel, J; Oni, A O; Olanite, J A; Isah, A O

    2012-04-01

    Seasonal chemical composition and ruminal organic matter (OM) and crude protein (CP) degradabilities were determined in four tropical multi-purpose tree species (MPTS) namely; Pterocarpus santalinoides, Grewia pubescens, Enterolobium cyclocarpum and Leucaena leucocephala. Three West African dwarf (WAD) rams fitted with permanent rumen cannula were used for the degradability trials. Foliage samples were collected four times to represent seasonal variations as follows: January--mid dry; April--late dry; July--mid rainy and October--late rainy seasons. Leaf samples were randomly collected from the trees for estimation of dry matter (DM) and chemical composition. Ruminal in sacco OM and CP degradabilities were estimated from residues in nylon bags. All samples had high CP (161-259 g/kg DM) and moderate fibre concentrations [neutral detergent fibre (without residual ash], 300-501 g/kg DM; acid detergent fibre (without residual ash), 225-409 g/kg DM and acid detergent lignin, 87-179 g/kg DM across seasons. Interaction effects of species and season on chemical composition were highly significant (p = 0.001) except for trypsin inhibitor (p = 0.614). The MPTS recorded more than 60% OM and CP degradability at 24 h, which implied that they were all highly degradable in the rumen. Their incorporation into ruminant feeding systems as dry season forage supplements is therefore recommended.

  19. Effects of Low Plane of Nutrition on the Development of Lean Muscle, Bone and Fat in the West African Dwarf Goats of Nigeria

    Directory of Open Access Journals (Sweden)

    Awah, AA.

    1997-01-01

    Full Text Available Thirty West African Dwarf goat kids were raised on low plane of nutrition from 5 days old to 52 weeks of age. They were serially slaughtered at 2, 8, 12, 24 and 52 weeks old to study changes in liveweight and the development of lean muscle, bone and fat. Lean muscle and fat expressed as the percentage of empty body weight (E.B.W. increased from 32.5 % and 3.5 % at 2 weeks to 42.0 % and 9.4 % at 52 weeks respectively. These increases at 52 weeks old represented about 544.9 % and 1093.3 % over their respective weights at 2 weeks old. The bone tissue increased to about 307.3 % at 52 weeks old over its weight at 2 weeks of age, but decreased from 15.4 % E.B.W. at 2 weeks to 10.9 % E.B.W. at 52 weeks of age. Lean muscle was consistently the largest carcass tissue from 2 weeks to 52 weeks of age followed by the bone tissue, while fat was the least. Female goat kids entered the rapid fattening phase at about 38 weeks of age (6.9 kg liveweight, but the males did not enter the rapid fattening phase, even at 52 weeks of age (11.8 kg. liveweight.

  20. Effects of supplementing cassava peels with cassava leaves and cowpea haulms on the performance, intake, digestibility and nitrogen utilization of West African Dwarf goats.

    Science.gov (United States)

    Abatan, Oluwayemisi; Oni, Adebayo Olusoji; Adebayo, Kolawole; Iposu, Shamusideen; Sowande, Olusiji Sunday; Onwuka, Chryss Friday Ijeoma

    2015-01-01

    A 16-week experiment was conducted to determine the utilization of ratios of cassava leaf meal, cassava peel and cowpea haulms by West African Dwarf (WAD) goats. Thirty WAD bucks aged 8 ± 1.3 months with body weights of 6-6.5 ± 0.12 kg were divided into five groups of six animals and each group randomly assigned to one of the treatments in a completely randomized design. The five dietary treatments were formulated to contain cassava peels, leaves and cowpea haulms at different proportions of 700:100:175 (T1), 500:200:275 (T2), 300:300:375 (T3) and 100:400:475 (T4) g/kg dry matter (DM), respectively. A standard diet formulated to meet the nutrient requirement of the animals with no cassava and cowpea haulms was used as the control diet (T5). DM intake ranged from 316.16 to 458.73 g/day and significantly increased (linear (L), quadratic (Q), cubic (C): P cassava peels reduced and cassava leaves and cowpea haulms increased in the diets. The crude protein (CP) intake significantly increased (L, Q, C: P cassava peels reduced and cassava leaves and cowpea haulms increased in the diets. Growth rate values significantly (L: P cassava leaves and cowpea haulms increased and reduced cassava peels in the diets. The highest N intake of 14.75 g/day obtained in T4 was significantly (L: P cassava peels, leaves and cowpea haulms in the proportion of 100:400:475 g/kg DM improved the growth and digestibility of WAD goats and can therefore be used to sustain animal performance during the dry season in a total mixed ration.

  1. Feeding potential of cassava (Manihot esculenta Crantz) peels ensiled with Leucaena leucocephala and Gliricidia sepium assessed with West African dwarf goats.

    Science.gov (United States)

    Oduguwa, Bamidele Omonuwa; Oni, Adebayo Olusoji; Arigbede, Oluwasanmi Moses; Adesunbola, Julius Olukunle; Sudekum, Karl Heinz

    2013-08-01

    Cassava peels (CaPe) were ensiled in mixtures with Gliricidia sepium and Leucaena leucocephala, and the utilization of the mixed silages by West African dwarf (WAD) goats was assessed. Five silages were composed, comprising of 100% ensiled CaPe (control), CaPe + G. sepium 2:1 (w/w; 2CGS), CaPe + G. sepium 1:1 (w/w; CGS), CaPe + L. leucocephala 2:1 (w/w; 2CLL) and CaPe + L. leucocephala 1:1 (w/w; CLL). All diets were supplemented with molasses (40 g/kg) before ensiling which lasted 3 months. Fifteen WAD goats (8.01 ± 0.12 kg body weight) were fed one of the experimental diets (50 g/kg body weight) for 8 weeks. The control had the lowest hydrocyanic acid content (0.05 mg/kg DM), while others ranged from 6.2 to 81.3 mg/kg. Condensed tannin concentration ranged from 1.7 to 8.4 mg/kg DM, while mimosine levels were 11.6 and 12.4 mg/kg DM in 2CLL and CLL, respectively. After fermentation, all silages showed low pH (<4.5) and were different (P < 0.05) in the lactic, acetic and butyric acid concentrations. Ratio of foliage supplementation influenced DM intake (P < 0.05). Daily weight gains ranged from 17 (CLL) to 24 g/day in control. The digestibility coefficients of nutrients and fibre fractions differed (P < 0.05) among diets. The values for packed cell volume, haemoglobin, red blood cells, neutrophils, lymphocytes and monocytes were also different (P < 0.05) across the dietary treatments. Ensiling CaPe with foliages of G. sepium and L. leucocephala can be recommended for feeding WAD goats especially during the dry spells when there is little or no available forage for the animals.

  2. The Development Of Lean Muscle, Bone And Fat In The West African Dwarf Goat Of Nigeria Maintained On Good Plane Of Nutrition

    Directory of Open Access Journals (Sweden)

    Awah, AA.

    1994-01-01

    Full Text Available Thirty West African Dwarf goat kids were raised on good diets intensively from 5 days to 52 weeks of age. Six animals (3 males and 3 females were serially slaughtered at 2, 8, 12, 24 and 52 weeks of age to study changes in liveweight and the development of lean muscle, bone and fat. Lean muscle and fat expressed as the percentage of empty body weight (E.B.W. increased from 31.8 % and 3.8 % at 2 weeks to 43.2 % and 14.2 % at 52 weeks respectively. These increases at 52 weeks old were about 673.2 % and 2090.8 %> over their respective weights at 2 weeks old. The bone tissue also increased to about 220.7 %, at 52 weeks old over the weight at 2 weeks of age, but decreased from 17.4 % E.B.W. at 2 weeks to 9.8 % E.B.W. at 52 weeks of age. At 2 weeks old, muscle was the largest tissue, followed by bone, while fat was the least. The bone grew at a low impetus rate, muscle at intermediate rate and fat at high impetus rate so that at 52 weeks of age, fat became the second largest tissue and bone the least. Male goat kids entered the rapid fattening phase later in life (about 43 weeks of age and at heavier liveweight (about 12 kg liveweight than the female goat kids (about 28 weeks of age and 9 kg liveweight respectively.

  3. Performance and Parasitology of Semi-intensively Managed West African Dwarf Sheep Exposed to Gastrointestinal Helminth Infect-ed Paddocks and Varied Protein-energy Feeds

    Directory of Open Access Journals (Sweden)

    Adekayode Olarinwaju SONIBARE

    2016-12-01

    Full Text Available Background: The performance and parasitology of semi-intensively managed West African dwarf (WAD lambs were evaluated following exposure to gastrointestinal helminth infected paddock and varied protein-energy feeds.Methods: Twenty four lambs obtained from the Department of Animal Breeding and Genetics and brought to Directorate of University farm (DUFARM of Federal University of Agriculture Abeokuta, Ogun state, Nigeria, where the research was carried out in 2014, were grouped into four each containing six animals based on different energy-protein feed combination thus; group 1(G1 low energy low protein, group 2 (G2 low energy high protein, group 3 (G3 high energy low protein and group 4 (G4 high energy high protein. Experimental animals were supplemented with concentrate feed after grazing on daily in a nematode infected paddock. Clinical signs of infection were monitored. Live weight, faecal egg count (FEC, worm counts, packed cell volume (PCV, haemoglobin concentration (Hb and red blood cell count (RBC were determined using standard methods.Results: Anorexia and intermittent diarrhea were the observed signs. Worm counts did not differ significantly (P=0.309 among the groups. The weight and FEC differed significantly (P˂0.05 across the days and among the groups, while haematological parameters increased significantly (P˂0.05 across the days and among the groups.Conclusion: Lambs in G2 followed by G4 showed improved parameters and superior performance when compared to the other groups. It is therefore recommended that feed high in protein content is capable of mitigating deleterious effect of gastrointestinal helminth parasitism.

  4. Resistance and resilience of traditionally managed West African Dwarf goats from the savanna zone of northern Nigeria to naturally acquired trypanosome and gastrointestinal nematode infections.

    Science.gov (United States)

    Behnke, J M; Chiejina, S N; Musongong, G A; Nnadi, P A; Ngongeh, L A; Abonyi, F O; Fakae, B B

    2011-03-01

    A survey was conducted of gastrointestinal nematode infections and trypanosomosis in Nigerian West African Dwarf (WAD) goats from the savanna region of the country. Animals were screened at two markets, Gboko and Akpagher, from the beginning of April until the end of September, coinciding with the end of the dry season and the first 5 months of the wet season. Of 1054 goats that were examined, 80.5% carried gastrointestinal (GI) nematodes belonging to the genera Haemonchus (61.0%), Oesophagostomum (21.0%) and Trichostrongylus (17.9%). Faecal egg counts (FEC) increased very slowly but significantly from April to maximum levels in September, and varied marginally between the two market sources. The majority of goats (68.8 and 70.1% at the two markets) had low FEC not exceeding 50 eggs/g (epg). FEC did not differ significantly between the sexes or between age classes. Packed cell volume (PCV) also declined significantly with month of the study, but was affected by host sex (a significant month x sex interaction) being generally higher in male animals throughout the period. There was a highly significant negative correlation between log₁₀(FEC+1) and PCV, when all other factors had been taken into account. Body condition scores (BCS) also declined with month of the study, but there was a marked difference between the two sexes, with male animals generally showing a greater stability of BCS across the months compared with females. Trypanosome infections were found in only 4% of the goats and only during the rainy season. Most infections (92.86%) were caused by Trypanosoma brucei alone although T. vivax and T. congolense were occasionally detected. Overall, the majority of goats sampled each month maintained generally good body condition (BCS 3.0-5.0), normal or slightly reduced PCV, even when concurrently infected with trypanosomes and GI nematodes. However, four concurrently infected goats showed signs of overt anaemia during periods of peak infection, during the

  5. Species-level diversification of African dwarf crocodiles (Genus Osteolaemus): a geographic and phylogenetic perspective.

    Science.gov (United States)

    Eaton, Mitchell J; Martin, Andrew; Thorbjarnarson, John; Amato, George

    2009-03-01

    The taxonomy of the African dwarf crocodile (genus Osteolaemus) has been disputed since a novel morphotype was discovered in the early 20th Century. Because this poorly-known reptile is widely hunted throughout the forests of Central and West Africa, resolving the existence and extent of taxonomic units has important management and conservation implications. Lack of molecular data from individuals of known origin and historical disagreement on diagnostic morphological characters have hindered attempts to settle one of the most important taxonomic questions in the Crocodylia. In an effort to clarify the evolutionary relationships among dwarf crocodiles, we sequenced three mitochondrial and two nuclear genes using a large sample of dwarf crocodiles from known localities across major drainage basins of forested Africa. Concordant results from Bayesian, maximum likelihood, maximum parsimony and population aggregation analytical methods support a previously recognized division of the dwarf crocodile into a Congo Basin form (O. osborni) and a West African form (Osteolaemus tetraspis), but also reveal a third diagnosable lineage from West Africa warranting recognition as an separate taxonomic unit. Corrected genetic distances between geographic regions ranged from 0.2% to 0.6% in nuclear fragments and 10.0 to 16.2% in mitochondrial COI. Population aggregation, using fixed and alternate character (nucleotide) states to cluster or divide populations, recovered 232 such molecular characters in 4286 bp of sequence data and unambiguously aggregated populations into their respective geographic clade. Several previously recognized morphological differences coincide with our molecular analysis to distinguish Congo Basin crocodiles from the Ogooué Basin and West Africa. Discrete morphological characters have not yet been documented between the latter two regions, suggesting further work is needed or molecular data may be required to recognize taxonomic divisions in cases where

  6. ANAESTHESIA IN WEST-AFRICAN DWARF GOAT

    African Journals Online (AJOL)

    The mean heart rate (HR) in XK and L group were significantly ( P < 0.05) higher between 10-30 minutes post ... side effects were salivation (100%) in all experimental animals. Urination .... Additional drugs were administered at one- third the ...

  7. Glucose intolerance in the West African Diaspora

    DEFF Research Database (Denmark)

    Nielsen, Jannie; Christensen, Dirk Lund

    2011-01-01

    In the United States, Black Americans are largely descendants of West African slaves; they have a higher relative proportion of obesity and experience a higher prevalence of diabetes than White Americans. However, obesity rates alone cannot explain the higher prevalence of type 2 diabetes. Type 2...

  8. Wildlife resources of the West African savanna

    NARCIS (Netherlands)

    Bie, de S.

    1991-01-01

    The wild fauna in Africa is a renewable resource and its overexploitation has led to the depletion of animal populations. This thesis focusses on the ecological characterization of the ungulate community of the West African savanna, with special reference to the Biosphere Reserve 'Boucle du

  9. West African spatial patterns of economic activities

    DEFF Research Database (Denmark)

    Walther, Olivier; Howard, Allen; Retaillé, Denis

    2015-01-01

    Over the last 30 years, two different bodies of literature developed by both US historians and francophone geographers have moved toward similar conclusions regarding West African economic spatial patterns. Despite their different backgrounds, both the ‘spatial factor’ approach promoted...

  10. West African International Summer School for Young Astronomers

    Science.gov (United States)

    Strubbe, Linda E.; Okere, Bonaventure

    2016-10-01

    The West African International Summer School for Young Astronomers (WAISSYA) is a week-long program for university science students and teachers from West Africa to develop their interest in astronomy. The first summer school was held in Abuja, Nigeria, in 2013; the second Summer School was held in Nsukka, Nigeria, in July 2015. West Africa has a large number of students interested in science, but a paucity of facilities or interest from funding bodies in developing West African astronomy. Our broad goals for the WAISSYA program are: (1) to introduce West African students to astronomy; (2) to exchange ideas about teaching and learning in West Africa and abroad; and (3) to continue building a sustained astronomy partnership between West Africa and Canada. We now briefly describe three defining aspects of WAISSYA 2015.

  11. West African Journal of Pharmacology and Drug Research ...

    African Journals Online (AJOL)

    West African Journal of Pharmacology and Drug Research. ... related topics including chemotherapy and toxicology will be considered for publication. ... Introduction: This should begin on a new page and should contain a brief account of the ...

  12. West African Journal of Industrial and Academic Research: Editorial ...

    African Journals Online (AJOL)

    West African Journal of Industrial and Academic Research: Editorial Policies ... computers, mathematics, control and information technology, physics, industrial electronics, management sciences and engineering, industry chemistry, general technology rocketry, space and astronomy, earth sciences, ... Peer Review Process.

  13. West African colonial civil servants in the nineteenth century : African participation in British colonial expansion in West Africa

    NARCIS (Netherlands)

    Arhin, K.

    1985-01-01

    From the 1850's to mid 1890's Africans were employed in top positions in the embryonic West African colonial services. This book contains the biographies of three of them: Ferguson on the Gold Coast, Lawson in Sierra Leone and Payne in Nigeria. All three had in common that they believed in British r

  14. Iridovirus disease in two ornamental tropical freshwater fishes: African lampeye and dwarf gourami.

    Science.gov (United States)

    Sudthongkong, Chaiwud; Miyata, Masato; Miyazaki, Teruo

    2002-04-05

    Many species of ornamental freshwater fishes are imported into Japan from all over the world. We found African lampeye Aplocheilichthys normani and dwarf gourami Colisa lalia suffering from an iridovirus infection just after being imported by tropical fish wholesalers from Singapore. African lampeye were cultured on the Indonesian Island of Sumatra and dwarf gourami were cultured in Malaysia before export. Diseased fishes displayed distinct histopathological signs of iridovirus infection: systemic appearance of inclusion body-bearing cells, and necrosis of splenocytes and hematopoietic cells. Electron microscopy revealed viral particles (African lampeye:180 to 200 nm in edge to edge diameter; dwarf gourami: 140 to 150 nm in diameter) in an inclusion body within the cytoplasm of inclusion body-bearing cells as well as in the cytoplasm of necrotized cells. Experimental infection with an iridovirus isolate from African lampeye (ALIV) revealed pathogenicity of ALIV to African lampeye and pearl gourami Trichogaster leeri. Polymerase chain reaction (PCR) products from ALIV and an iridovirus isolate from dwarf gourami (DGIV) using iridovirus-specific primers were indistinguishable. The nucleotide sequence of PCR products derived from ALIV (696 base pairs) and DGIV (701 base pairs) had 95.3% identity. These results indicate that ALIV and DGIV have a single origin.

  15. Translating West African Strategy with Airpower Means: A Qualitative Comparison of Tactical Airlift Shaping Operations

    Science.gov (United States)

    2016-06-10

    TRANSLATING WEST AFRICAN STRATEGY WITH AIRPOWER MEANS: A QUALITATIVE COMPARISON OF TACTICAL AIRLIFT SHAPING OPERATIONS A thesis...Translating West African Strategy with Airpower Means: A Qualitative Comparison of Tactical Airlift Shaping Operations 5a. CONTRACT NUMBER 5b. GRANT...ABSTRACT TRANSLATING WEST AFRICAN STRATEGY WITH AIRPOWER MEANS: A QUALITATIVE COMPARISON OF TACTICAL AIRLIFT SHAPING OPERATIONS , by Maj Matthew C

  16. Genetic relationships among West African okra (Abelmoschus caillei ...

    African Journals Online (AJOL)

    STORAGESEVER

    2008-05-16

    May 16, 2008 ... Key words: West African okra, genetic relationship, Abelmoschus caillei, ... has long been a major goal in evolutionary biology. Infor- ... management as a quick, cost-effective and reliable ... affected by environment (Staub et al., 1997). ... Supernatant containing DNA was transferred into a new 2 ml U –.

  17. Agriculture, livelihoods and climate change in the West African Sahel

    NARCIS (Netherlands)

    Sissoko, K.; Keulen, van H.; Verhagen, A.; Tekken, V.; Battaglini, A.

    2011-01-01

    The West African Sahel is a harsh environment stressed by a fast-growing population and increasing pressure on the scarce natural resources. Agriculture is the main source of livelihood of the majority of the people living in the area. Increases in temperature and/or modifications in rainfall quanti

  18. Body measurement characteristics of the West African Dwarf (WAD ...

    African Journals Online (AJOL)

    STORAGESEVER

    2008-07-18

    Jul 18, 2008 ... 2Faculty of Agriculture, Department of Animal Science, University of Ibadan, Nigeria. Accepted 24 June ... in fundamental research and a potential store of unique genes, which ... MATERIALS AND METHODS. The study was ...

  19. Contribution of "Women's Gold" to West African livelihoods

    DEFF Research Database (Denmark)

    Pouliot, Mariéve

    2012-01-01

    Contribution of ``Women's Gold'' to West African Livelihoods: The Case of Shea ( Vitellaria paradoxa ) in Burkina Faso. This paper (i) quantifies the contribution that Vitellaria paradoxa makes to the total income of rural households belonging to different economic groups in two areas of Burkina ...... not be considered as a remedy to poverty but instead as a way for households to diversify their livelihood strategy and decrease their vulnerability to food insecurity and climate variability....

  20. Challenging the Woodfuel Crisis in West African Woodlands

    DEFF Research Database (Denmark)

    Hansfort, Sofie Louise; Mertz, Ole

    2011-01-01

    —have been produced by the government of Mali to prove the impacts of woodfuel consumption in Bamako on surrounding woodlands. This study evaluates the methodology and data used to describe this woodfuel crisis through a comparison with regional and historical data. The results of the energy gap analyses...... of West African woodlands and urban consumption are needed to avoid misinterpretations of the impacts of woodfuel harvesting on woody resources....

  1. Characterization of the casein gene complex in West African goats and description of a new alpha(s1)-casein polymorphism.

    Science.gov (United States)

    Caroli, A; Chiatti, F; Chessa, S; Rignanese, D; Ibeagha-Awemu, E M; Erhardt, G

    2007-06-01

    The analysis of casein polymorphisms was carried out in West Africa goat populations: Red Sokoto (n = 57), West African Dwarf Nigeria (n = 27), West African Dwarf Cameroon (n = 39), and Borno (n = 37). The 4 casein genes alpha(s1) (CSN1S1), beta (CSN2), alpha(s2) (CSN1S2), and kappa (CSN3) were typed at the DNA level. No null alleles were found in any of the genes analyzed. A PCR single-strand conformation polymorphism method was implemented for the identification of CSN1S1*F allele simultaneously with A/0(1), B/E, N and the new allele. The allele differed from CSN1S1*B by a synonymous transversion TCG-->TCT in the codon corresponding to Ser(66) of the mature protein. The new allele, named CSN1S1*B', occurred at a high frequency in all the populations, ranging from 0.295 (West African Dwarf Cameroon) to 0.405 (Borno). A greater frequency was found for alleles associated with high alpha(s1)-casein quantity, as has already been observed in the goat populations from the Mediterranean area. The intermediate E allele occurred only in the Red Sokoto and at a low frequency. The faint F allele occurred in 3 populations at frequencies lower than 0.03. Linkage disequilibrium occurred in all the populations, with highly significant differences in Borno, Red Sokoto, and West Africa Dwarf Nigeria, and significant differences in West Africa Dwarf Cameroon. Only 10 haplotypes showed frequencies > or =0.05 in at least 1 of the 4 populations considered, and the overall frequency was >0.1 only for 4 haplotypes: BAAB, B'ACA, ACAB, and BACA (in the order CSN1S1-CSN2-CSN1S2-CSN3). Haplotype BAAB, postulated as an ancestral haplotype in previous studies, was the most common haplotype in all breeds except Borno, where B'ACA was predominant. The results obtained are of considerable significance given that very little information exists on the subject for African goats. The high frequency of strong alleles in the calcium-sensitive caseins as well as the high linkage disequilibrium found

  2. The West African Health Organization's experience in improving the health research environment in the ECOWAS region

    National Research Council Canada - National Science Library

    Aidam, Jude; Sombié, Issiaka

    2016-01-01

    The West African Health Organization (WAHO) implemented a research development program in West Africa during 2009-2013 using the Knowledge for Better Health Research Capacity Development Framework, developed by Pang et al...

  3. Characterization of Serum Phospholipase A2 Activity in Three Diverse Species of West African Crocodiles

    Directory of Open Access Journals (Sweden)

    Mark Merchant

    2011-01-01

    Full Text Available Secretory phospholipase A2, an enzyme that exhibits substantial immunological activity, was measured in the serum of three species of diverse West African crocodiles. Incubation of different volumes of crocodile serum with bacteria labeled with a fluorescent fatty acid in the sn-2 position of membrane lipids resulted in a volume-dependent liberation of fluorescent probe. Serum from the Nile crocodile (Crocodylus niloticus exhibited slightly higher activity than that of the slender-snouted crocodile (Mecistops cataphractus and the African dwarf crocodile (Osteolaemus tetraspis. Product formation was inhibited by BPB, a specific PLA2 inhibitor, confirming that the activity was a direct result of the presence of serum PLA2. Kinetic analysis showed that C. niloticus serum produced product more rapidly than M. cataphractus or O. tetraspis. Serum from all three species exhibited temperature-dependent PLA2 activities but with slightly different thermal profiles. All three crocodilian species showed high levels of activity against eight different species of bacteria.

  4. Will elephants soon disappear from West African savannahs?

    Directory of Open Access Journals (Sweden)

    Philippe Bouché

    Full Text Available Precipitous declines in Africa's native fauna and flora are recognized, but few comprehensive records of these changes have been compiled. Here, we present population trends for African elephants in the 6,213,000 km² Sudano-Sahelian range of West and Central Africa assessed through the analysis of aerial and ground surveys conducted over the past 4 decades. These surveys are focused on the best protected areas in the region, and therefore represent the best case scenario for the northern savanna elephants. A minimum of 7,745 elephants currently inhabit the entire region, representing a minimum decline of 50% from estimates four decades ago for these protected areas. Most of the historic range is now devoid of elephants and, therefore, was not surveyed. Of the 23 surveyed elephant populations, half are estimated to number less than 200 individuals. Historically, most populations numbering less than 200 individuals in the region were extirpated within a few decades. Declines differed by region, with Central African populations experiencing much higher declines (-76% than those in West Africa (-33%. As a result, elephants in West Africa now account for 86% of the total surveyed. Range wide, two refuge zones retain elephants, one in West and the other in Central Africa. These zones are separated by a large distance (∼900 km of high density human land use, suggesting connectivity between the regions is permanently cut. Within each zone, however, sporadic contacts between populations remain. Retaining such connectivity should be a high priority for conservation of elephants in this region. Specific corridors designed to reduce the isolation of the surveyed populations are proposed. The strong commitment of governments, effective law enforcement to control the illegal ivory trade and the involvement of local communities and private partners are all critical to securing the future of elephants inhabiting Africa's northern savannas.

  5. Will elephants soon disappear from West African savannahs?

    Science.gov (United States)

    Bouché, Philippe; Douglas-Hamilton, Iain; Wittemyer, George; Nianogo, Aimé J; Doucet, Jean-Louis; Lejeune, Philippe; Vermeulen, Cédric

    2011-01-01

    Precipitous declines in Africa's native fauna and flora are recognized, but few comprehensive records of these changes have been compiled. Here, we present population trends for African elephants in the 6,213,000 km² Sudano-Sahelian range of West and Central Africa assessed through the analysis of aerial and ground surveys conducted over the past 4 decades. These surveys are focused on the best protected areas in the region, and therefore represent the best case scenario for the northern savanna elephants. A minimum of 7,745 elephants currently inhabit the entire region, representing a minimum decline of 50% from estimates four decades ago for these protected areas. Most of the historic range is now devoid of elephants and, therefore, was not surveyed. Of the 23 surveyed elephant populations, half are estimated to number less than 200 individuals. Historically, most populations numbering less than 200 individuals in the region were extirpated within a few decades. Declines differed by region, with Central African populations experiencing much higher declines (-76%) than those in West Africa (-33%). As a result, elephants in West Africa now account for 86% of the total surveyed. Range wide, two refuge zones retain elephants, one in West and the other in Central Africa. These zones are separated by a large distance (∼900 km) of high density human land use, suggesting connectivity between the regions is permanently cut. Within each zone, however, sporadic contacts between populations remain. Retaining such connectivity should be a high priority for conservation of elephants in this region. Specific corridors designed to reduce the isolation of the surveyed populations are proposed. The strong commitment of governments, effective law enforcement to control the illegal ivory trade and the involvement of local communities and private partners are all critical to securing the future of elephants inhabiting Africa's northern savannas.

  6. Future of West African Monsoon in A Warming Climate

    Science.gov (United States)

    Raj, Jerry; Kunhu Bangalath, Hamza; Stenchikov, Georgiy

    2016-04-01

    West Africa is the home of more than 300 million people whose agriculture based economy highly relies on West African Monsoon (WAM), which produces a mean annual rainfall of 150 - 2,500 mm and variability and change of which have devastating impact on the local population. The observed widespread drought in West Africa during the 1970s and 1980s was the most significant drought at regional scale during the twentieth century. In this study, a high resolution AGCM, High Resolution Atmospheric Model (HiRAM), is used to study the effects of anthropogenic greenhouse warming on WAM. HiRAM is developed at GFDL based on AM2 and employs a cubed-sphere finite volume dynamical core and uses shallow convective scheme (for moist convection and stratiform cloudiness) instead of deep convective parameterization. Future projections are done using two representative concentration pathways, RCP 4.5 and RCP 8.5 from 2007 to 2050 at C360 (~25 km) resolution. Both RCP 4.5 and RCP 8.5 scenarios predict warming over West Africa during boreal summer, especially over Western Sahara. Also, both scenarios predict southward shift in WAM rainfall pattern and drying over Southern Sahara, while RCP 8.5 predicts enhanced rainfall over Gulf of Guinea. The intensification of rainfall over tropical latitudes is caused by increased low level winds due to warm SST over Gulf of Guinea.

  7. Lassa fever in West African sub-region: an overview

    Directory of Open Access Journals (Sweden)

    O. Ogbu

    2007-01-01

    Full Text Available Lassa fever is an acute viral zoonotic illness caused by Lassa virus, an arenavirus known to beresponsible for a severe haemorrhagic fever characterised by fever, muscle aches, sore throat, nausea,vomiting and, chest and abdominal pain. The virus exhibits persistent, asymptomatic infection withprofuse urinary virus excretion in the ubiquitous rodent vector, Mastomys natalensis. Lassa fever isendemic in West Africa and has been reported from Sierra Leone, Guinea, Liberia, and Nigeria. Somestudies indicate that 300,000 to 500,000 cases of Lassa fever and 5000 deaths occur yearly across WestAfrica. Studies reported in English, that investigated Lassa fever with reference to West Africa wereidentified using the Medline Entrez-PubMed search and were used for this review. The scarcity ofresources available for health care delivery system and the political instability that characterise theWest African countries would continue to impede efforts for the control of Lassa fever in the sub-region.There is need for adequate training of health care workers regarding diagnostics, intensive care ofpatients under isolation, contact tracing, adequate precautionary measures in handling infectiouslaboratory specimens, control of the vector as well as care and disposal of infectious waste.

  8. Lassa fever in West African sub-region: an overview.

    Science.gov (United States)

    Ogbu, O; Ajuluchukwu, E; Uneke, C J

    2007-03-01

    Lassa fever is an acute viral zoonotic illness caused by Lassa virus, an arenavirus known to be responsible for a severe haemorrhagic fever characterised by fever, muscle aches, sore throat, nausea, vomiting and, chest and abdominal pain. The virus exhibits persistent, asymptomatic infection with profuse urinary virus excretion in the ubiquitous rodent vector, Mastomys natalensis. Lassa fever is endemic in West Africa and has been reported from Sierra Leone, Guinea, Liberia, and Nigeria. Some studies indicate that 300,000 to 500,000 cases of Lassa fever and 5000 deaths occur yearly across West Africa. Studies reported in English, that investigated Lassa fever with reference to West Africa were identified using the Medline Entrez-PubMed search and were used for this review. The scarcity of resources available for health care delivery system and the political instability that characterise the West African countries would continue to impede efforts for the control of Lassa fever in the sub-region. There is need for adequate training of health care workers regarding diagnostics, intensive care of patients under isolation, contact tracing, adequate precautionary measures in handling infectious laboratory specimens, control of the vector as well as care and disposal of infectious waste.

  9. Genetic structure in four West African population groups.

    Science.gov (United States)

    Adeyemo, Adebowale A; Chen, Guanjie; Chen, Yuanxiu; Rotimi, Charles

    2005-06-24

    Africa contains the most genetically divergent group of continental populations and several studies have reported that African populations show a high degree of population stratification. In this regard, it is important to investigate the potential for population genetic structure or stratification in genetic epidemiology studies involving multiple African populations. The presences of genetic sub-structure, if not properly accounted for, have been reported to lead to spurious association between a putative risk allele and a disease. Within the context of the Africa America Diabetes Mellitus (AADM) Study (a genetic epidemiologic study of type 2 diabetes mellitus in West Africa), we have investigated population structure or stratification in four ethnic groups in two countries (Akan and Gaa-Adangbe from Ghana, Yoruba and Igbo from Nigeria) using data from 372 autosomal microsatellite loci typed in 493 unrelated persons (986 chromosomes). There was no significant population genetic structure in the overall sample. The smallest probability is associated with an inferred cluster of 1 and little of the posterior probability is associated with a higher number of inferred clusters. The distribution of members of the sample to inferred clusters is consistent with this finding; roughly the same proportion of individuals from each group is assigned to each cluster with little variation between the ethnic groups. Analysis of molecular variance (AMOVA) showed that the between-population component of genetic variance is less than 0.1% in contrast to 99.91% for the within population component. Pair-wise genetic distances between the four ethnic groups were also very similar. Nonetheless, the small between-population genetic variance was sufficient to distinguish the two Ghanaian groups from the two Nigerian groups. There was little evidence for significant population substructure in the four major West African ethnic groups represented in the AADM study sample. Ethnicity

  10. Copula Deletion and West African Languages: A Source for Covert Norms in American Black English.

    Science.gov (United States)

    Donahue, Thomas S.

    The loss of the copula in Black English Vernacular (BEV) is demonstrably traceable to norms of pidginization that have their roots in West African languages and in contact among those languages. An extensive examination of the verb systems of a number of West African languages reveals that in every case a variety of verbal forms serves the many…

  11. Spatial air pollution modelling for a West-African town

    Directory of Open Access Journals (Sweden)

    Sirak Zenebe Gebreab

    2015-11-01

    Full Text Available Land use regression (LUR modelling is a common approach used in European and Northern American epidemiological studies to assess urban and traffic related air pollution exposures. Studies applying LUR in Africa are lacking. A need exists to understand if this approach holds for an African setting, where urban features, pollutant exposures and data availability differ considerably from other continents. We developed a parsimonious regression model based on 48-hour nitrogen dioxide (NO2 concentrations measured at 40 sites in Kaédi, a medium sized West-African town, and variables generated in a geographic information system (GIS. Road variables and settlement land use characteristics were found to be important predictors of 48-hour NO2 concentration in the model. About 68% of concentration variability in the town was explained by the model. The model was internally validated by leave-one-out cross-validation and it was found to perform moderately well. Furthermore, its parameters were robust to sampling variation. We applied the model at 100 m pixels to create a map describing the broad spatial pattern of NO2 across Kaédi. In this research, we demonstrated the potential for LUR as a valid, cost-effective approach for air pollution modelling and mapping in an African town. If the methodology were to be adopted by environmental and public health authorities in these regions, it could provide a quick assessment of the local air pollution burden and potentially support air pollution policies and guidelines.

  12. Monogeneans of West African cichlid fish: evolution and cophylogenetic interactions.

    Directory of Open Access Journals (Sweden)

    Monika Mendlová

    Full Text Available The goals of this paper were to investigate phylogenetic and evolutionary patterns of cichlid fish from West Africa and their Cichlidogyrus and Scutogyrus monogenean parasites, to uncover the presence of host-parasite cospeciation and to assess the level of morphological adaptation in parasites. This required the following steps, each one representing specific objectives of this paper: (1 to build phylogenetic trees for Cichlidogyrus and Scutogyrus species based on ribosomal DNA sequences, (2 to investigate phylogenetic relationships within West African cichlid fish based on the analysis of mitochondrial cytochrome b DNA sequences, (3 to investigate host-parasite cophylogenetic history to gain clues on parasite speciation process, and (4 to investigate the link between the morphology of the attachment apparatus and parasite phylogeny. Phylogenetic analyses supported the monophyletic origin of the Cichlidogyrus/Scutogyrus group, and suggested that Cichlidogyrus is polyphyletic and that Scutogyrus is monophyletic. The phylogeny of Cichlidae supported the separation of mouthbrooders and substrate-brooders and is consistent with the hypothesis that the mouthbrooding behavior of Oreochromis and Sarotherodon evolved from substrate-brooding behavior. The mapping of morphological characters of the haptor onto the parasite phylogenetic tree suggests that the attachment organ has evolved from a very simple form to a more complex one. The cophylogenetic analyses indicated a significant fit between trees using distance-based tests, but no significant cospeciation signal using tree-based tests, suggesting the presence of parasite duplications and host switches on related host species. This shed some light on the diversification process of Cichlidogyrus species parasitizing West African cichlids.

  13. Morphological Characterization of African Bush Mango trees (Irvingia species) in the Dahomey Gap (West Africa)

    NARCIS (Netherlands)

    Vihotogbe, R.; Berg, van den R.G.; Sosef, M.S.M.

    2013-01-01

    The variation of the morphological characters of bitter and sweet African bush mango trees (Irvingia species) was investigated in the Dahomey Gap which is the West African savannah woodland area separating the Upper and the Lower Guinean rain forest blocks. African bush mangoes have been rated as th

  14. Noma: experiences with a microvascular approach under West African conditions.

    Science.gov (United States)

    Giessler, Goetz A; Schmidt, Andreas B

    2003-09-15

    Noma (cancrum oris) is a serious ulcerating disease that generally begins in the gingival sulcus of children. One of the main areas of prevalence today is West Africa. If noma is survived, it results in disfiguring midfacial defects and intense scarring. Oral incompetence is often combined with trismus resulting from scar formation or bony fusion between the maxilla and the mandible. Reconstructive approaches with pedicled flaps from the head or shoulder area for closure of the outer defects have been prone to donor-site complications or have not properly addressed the trismus, leading to high recurrence rates. During three West African Interplast missions, a single-stage procedure was developed for reconstruction of the inner and outer linings of the oral, nasal, and paranasal cavities, with restoration of jaw function. The procedure consists of radical scar excision, placement of an external distractor for mouth opening, and primary closure of the defect with a folded free parascapular flap for full-thickness coverage. Twenty-three patients with various noma-related defects were treated with this procedure; two cases are described in detail. This combined treatment can be a safe successful procedure for patients with noma, especially those with severe soft-tissue destruction and profound trismus, even under demanding surgical conditions.

  15. Simulation of West African air pollution during the DACCIWA experiment with the GEOS-Chem West African regional model.

    Science.gov (United States)

    Morris, Eleanor; Evans, Mathew

    2017-04-01

    Pollutant emissions from West African cities are forecast to increase rapidly in future years because of extensive economic and population growth, together with poorly regulated industrialisation and urbanisation. Observational constraints in this region are few, leading to poor understanding of present-day air pollution in this region. To increase our understanding of the processes controlling air pollutants over the region, airborne observations were made from three research aircraft based out of Lomé, Togo during the DACCIWA field campaign in June-July 2016. A new 0.25x0.3125 degree West Africa regional version of the GEOS-Chem offline chemical transport model has also been developed to explore the processes controlling pollutants over the region. We evaluate the model using the aircraft data and focus on primary (CO, SO2, NOx, VOCs) and secondary pollutants (O3, aerosol). We find significant differences between the model and the measurements for certain primary compounds which is indicative of significant uncertainties in the base (EDGAR) emissions. For CO (a general tracer of pollution) we evaluate the role of different emissions sources (transport, low temperature combustion, power generation) in determining its concentration in the region. We conclude that the leading cause of uncertainty in our simulation is associated with the emissions datasets and explore the impact of using differing datasets.

  16. West African immigrant families from Mauritania and Senegal in Cincinnati: a cultural primer on children's health.

    Science.gov (United States)

    Vaughn, Lisa M; Holloway, Miranda

    2010-02-01

    Similar to many cities in the US, the Greater Cincinnati area has recently had an increase in immigrants from other countries. In particular, there is a small but growing population of West African immigrants especially from Senegal and Mauritania. In order to better understand children's health of West African families in the Cincinnati area, in-depth, in-home narrative interviews were conducted with ten West African immigrant parents from Senegal and Mauritania. Four salient themes about cultural information related to children's health were derived from the qualitative analysis: (1) health care practice and expectations including barriers; (2) cultural values and identity; (3) health beliefs and traditions/customs; and (4) quality of life. It is essential that health care providers understand the nuances of working with West African immigrants including cultural differences, strengths, challenges and perceptions in order to provide these individuals with the most effective health care services.

  17. West African Power Pool: Planning and Prospects for Renewable Energy

    Energy Technology Data Exchange (ETDEWEB)

    Miketa, Asami [IRENA, Bonn (Germany); Merven, Bruno [Energy Research Centre, Univ. of Cape Town (South Africa)

    2013-06-25

    With the energy systems of many African countries dominated by fossil-fuel sources that are vulnerable to global price volatility, regional and intra-continental power systems with high shares of renewable energy can provide least-cost option to support continued economic growth and address the continent’s acute energy access problem. Unlocking Africa’s huge renewable energy potential could help to take many people out of poverty, while ensuring the uptake of sustainable technologies for the continent’s long-term development. The report examines a ''renewable scenario'' based on a modelling tool developed by IRENA and tested with assistance from the Economic Community of West African States (ECOWAS). Initial results from the ECOWAS Renewable Energy Planning (EREP) model for continental ECOWAS countries show that the share of renewable technologies in the region could increase from the current 22% of electricity generation to as much as 52% in 2030, provided that the cost of these technologies continues to fall and fossil fuel prices continue to rise. In this scenario, nearly half of the envisaged capacity additions between 2010 and 2030 would be with renewable technologies. Analysis using EREP – along with a similar model developed for Southern Africa – can provide valuable input for regional dialogue and energy projects such as the East and Southern Africa Clean Energy Corridor and the Programme for Infrastructure and Development in Africa (PIDA). IRENA, together with partner organisations, has started plans to set up capacity building and development support for energy system modelling and planning for greater integration of renewables in Africa. IRENA is also completing a similar model and study for East Africa and intends to extend this work to Central and North Africa.

  18. Multiresolution quantification of deciduousness in West Central African forests

    Directory of Open Access Journals (Sweden)

    G. Viennois

    2013-04-01

    Full Text Available The characterization of leaf phenology in tropical forests is of major importance and improves our understanding of earth-atmosphere-climate interactions. The availability of satellite optical data with a high temporal resolution has permitted the identification of unexpected phenological cycles, particularly over the Amazon region. A primary issue in these studies is the relationship between the optical reflectance of pixels of 1 km or more in size and ground information of limited spatial extent. In this paper, we demonstrate that optical data with high to very-high spatial resolution can help bridge this scale gap by providing snapshots of the canopy that allow discernment of the leaf-phenological stage of trees and the proportions of leaved crowns within the canopy. We also propose applications for broad-scale forest characterization and mapping in West Central Africa over an area of 141 000 km2. Eleven years of the Moderate Resolution Imaging Spectroradiometer (MODIS Enhanced Vegetation Index (EVI data were averaged over the wet and dry seasons to provide a dataset of optimal radiometric quality at a spatial resolution of 250 m. Sample areas covered at a very-high (GeoEye and high (SPOT-5 spatial resolution were used to identify forest types and to quantify the proportion of leaved trees in the canopy. The dry season EVI was positively correlated with the proportion of leaved trees in the canopy. This relationship allowed the conversion of EVI into canopy deciduousness at the regional level. On this basis, ecologically important forest types could be mapped, including young secondary, open Marantaceae, Gilbertiodendron dewevrei and swamp forests. We show that in west central African forests, a large share of the variability in canopy reflectance, as captured by the EVI, is due to variation in the proportion of leaved trees in the upper canopy, thereby opening new perspectives for biodiversity and carbon-cycle applications.

  19. Living Beyond Boundaries: West African Servicemen in French Colonial Conflicts, 1908-1962

    OpenAIRE

    2011-01-01

    Living Beyond Boundaries: West African Servicemen in French Colonial Conflicts, 1908-1962, is a history of French West African colonial soldiers who served in French Empire. Known by the misnomer tirailleurs sénégalais, these servicemen contributed to the expansion, maintenance, and defense of France's presence on several continents. The complex identity and shifting purpose of this institution were directly linked to French colonialism, but determined by numerous actors and settings. The...

  20. Critical Postcolonial Dance Pedagogy: The Relevance of West African Dance Education in the United States

    Science.gov (United States)

    Cruz Banks, Ojeya

    2010-01-01

    This dance ethnography examines work conducted by the Dambe Project--a nonprofit organization that specializes in African performing arts education and mentorship. The study focuses on the implications of the organization's dance pedagogy in light of its postcolonial context and the importance of West African dance education in the United States.…

  1. Does a ruderal strategy dominate the endemic flora of the West African forests?

    NARCIS (Netherlands)

    Holmgren, M.; Poorter, L.

    2007-01-01

    Aim To understand the distribution pattern of endemic plant species in West African rain forests, one of the global priority areas for biodiversity conservation. Location Upper Guinean forests, West Africa (Senegal, Guinea-Bissau, Guinea, Sierra Leone, Liberia, Côte d'Ivoire, Ghana and Togo). Method

  2. Fire Regime and Stability of the West African Tropical Forest

    Science.gov (United States)

    Dwomoh, F. K.; Wimberly, M. C.

    2014-12-01

    Ecological discussions concerning alternative stable states theory suggest that tropical forest ecosystems could shift to qualitatively different alternative states upon catastrophic disturbances which exceed forest resilience. In this regard, it is expected that changes in the fire regime facilitated by climate and land use alterations could lead to rapid forest cover loss, creating conditions likely to push tropical forests to tipping points, beyond which forest resilience is lost. However, there is a dearth of empirical examples of fire-driven alternative stable states involving tropical forests. Key among the constraints for this scarcity are the requirements for large scale disturbances and long-term data, both of which are scarce. However, in the West African tropical forest (referred to as the Upper Guinean forest, UGF) a number of protected areas were impacted by large fire events during the 1980s El Niño-driven droughts, providing an opportunity for testing hypotheses concerning alternative stable states in tropical forest ecosystems. This paper aims to demonstrate fire-driven alternative stable states in the deciduous forest zone of the UGF by analyzing fire activity and forest recovery in fire-impacted forest reserves. We analyzed historical Landsat and MODIS imagery to map and quantify vegetation cover change, fire frequency and fire severity patterns. Our analyses suggest that the historic fires in the 1980s were catastrophic enough to remove forest canopy, thereby triggering a landscape-scale alternative stable states. Forest cover declined substantially becoming replaced by a novel ecosystem with low tree density. Our results also indicate the establishment of a positive fire-vegetation feedback effect, such that the new vegetation which displaced severely burned forests is more pyrogenic and maintained through frequent burns. This study expands our knowledge on the vulnerability of tropical forest ecosystems to state transitions in response to fire

  3. The turbulence underside of the West African Monsoon

    Science.gov (United States)

    Lothon, M.; Lohou, F.; Saïd, F.; Campistron, B.; Canut, G.; Couvreux, F.; Durand, P.; Kalapureddy, M. C.; Lee, Y.; Madougou, S.; Serça, D.

    2009-09-01

    We present an experimental analysis of the sahelian Planetary Boundary Layer (PBL) processes in the context of the AMMA (African Monsoon Multidisciplinary Analysis) program and its extensive observational deployment in 2006. From May to October, two opposite flows are interacting in the first 5 thousands m over surface in Sahel: the moist southerly monsoon flow and the overlying northeasterly Saharan Air Layer (SAL) in which the African Easterly Jet (AEJ) is developing, generated by the contrast of surface moisture and temperature between Sahara and the Gulf of Guinea. Until the monsoon onset in mid-July, the low troposphere is slowly moistening through advection from the Guinea Gulf by the monsoon flow, especially during the night. During the day, the dry convection occurring within the PBL vertically redistributes part of the water vapour. After the onset, deep convection occurs much more frequently and the role played by the PBL completely changes. The relative position of the interface between monsoon and SAL and the PBL top inversion is crucial for the nature of the interaction and its impact on scalars, especially water vapour. We consider the role of the PBL processes in this context, and focus on four main aspects: (1) the diurnal cycle of the low troposphere, (2) the interaction between the PBL and the AEJ, (3) the entrainment at the PBL top (4) the impact of the PBL processes at surface. We base our analysis on long term profilers, radiosondes, and surface flux data, short term aircraft turbulence measurements made during the Special Observing Periods and Large Eddy Simulation. The network of wind profilers enables us to study the large scale circulation and highlight the consistence and extent of the nocturnal jet, and the importance of the diurnal cycle of the low troposphere for the West African Monsoon. During daytime, both the wind within the monsoon flow and the AEJ windspeed in the overlying SAL decrease, due to turbulent mixing within the PBL and

  4. Ozone budget in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis campaign

    Directory of Open Access Journals (Sweden)

    M. Saunois

    2009-03-01

    Full Text Available A bi-dimensional latitudinal-vertical meterological model coupled with O3-NOx-VOC chemistry is used to reproduce the distribution of ozone and precursors in the boundary layer over West Africa during the African Monsoon Multidisciplinary Analysis (AMMA campaign as observed on board the Facility for Airborne Atmospheric Measurements (FAAM BAe 146 Atmospheric Research Aircraft. The model reproduces the increase of ozone mixing ratios in the boundary layer observed between the forested region south of 13° N and the Sahelian area northward. Sensitivity and budget analysis reveals that the intertropical convergence zone is a moderate source of O3 rich-air in the boundary layer due to convective downdrafts. Dry deposition drives the ozone minimum over the vegetated area. The combination of high NOx emissions from soil north of 13° N and northward advection by the monsoon flux of VOC-enriched air masses contributes to the ozone maximum simulated at higher latitudes. Simulated OH exhibit a well marked latitudinal gradient with minimum concentrations over the vegetated region where the reactions with biogenic compounds predominate. The model underestimates the observed OH mixing ratios, however this model discrepancy has slight effect on ozone budget and does not alter the conclusions.

  5. Review of Recent Developments and the Future Prospective in West African Atmosphere/Land Interaction Studies

    Directory of Open Access Journals (Sweden)

    Yongkang Xue

    2012-01-01

    Full Text Available This paper reviews West African land/atmosphere interaction studies during the past decade. Four issues are addressed in this paper: land data development, land/atmosphere interactions at seasonal-interannual scales, mesoscale studies, and the future prospective. The development of the AMMA Land Surface Model Intercomparison Project has produced a valuable analysis of the land surface state and fluxes which have been applied in a number of large-scale African regional studies. In seasonal-interannual West African climate studies, the latest evidence from satellite data analyses and modeling studies confirm that the West African region has a climate which is particularly sensitive to land surface processes and there is a strong coupling between land surface processes and regional climate at intraseasonal/seasonal scales. These studies indicate that proper land surface process representations and land status initialization would substantially improve predictions and enhance the predictability of West African climate. Mesoscale studies have revealed new understanding of how soil moisture heterogeneity influences the development of convective storms over the course of the diurnal cycle. Finally, several important issues regarding the future prospective are briefly addressed.

  6. Characteristics and phylogeny of Bacillus cereus strains isolated from Maari, a traditional West African food condiment

    DEFF Research Database (Denmark)

    Thorsen, Line; Kando, Christine Kere; Sawadogo, Hagrétou

    2015-01-01

    light on the succession and pathogenic potential of B. cereus species in traditional West African food condiment and clarifies their phylogenetic relatedness to B. cereus biovar anthracis. Future implementation of GMP and HACCP and development of starter cultures for controlled Maari fermentations......Maari is a spontaneously fermented food condiment made from baobab tree seeds in West African countries. This type of product is considered to be safe, being consumed by millions of people on a daily basis. However, due to the spontaneous nature of the fermentation the human pathogen Bacillus...

  7. Effects of parity on blood pressure among West African Dogon women.

    Science.gov (United States)

    Taylor, Jacquelyn Y; Sampson, Deborah A; Anderson, Cindy M; Caldwell, Dennis; Taylor, Andre D

    2012-01-01

    This study examined the effect of parity on blood pressure (BP) readings and BMI among rural West African Dogon women. Correlational research design. Sangha, West Africa 133 West African Dogon Women Demographic survey including age, number of children, history of hypertension, and village affiliation. BP readings were taken in accordance with JNC-7 guidelines. BMI was calculated from height and weight. Women with BP readings diagnostic of hypertension were typically older (M = 55.72 years) than those who were normotensive (M = 42.40). However, BMI, on average, was within normal range for both groups (22.81 and 22.15, respectively). A statistically significant difference was found between number of children and systolic BP (SBP), P = .015, with those having 5 or more children with higher SBP than those with one to three children. A statistically significant difference, P = .001, was found between hypertension and normotensive diagnostic groups. This study shows that increased parity of five or more children may contribute to West African Dogon women's risk factors for hypertension in terms of increased SBP. Because BMI was within normal range for both groups of women, it was not shown to be an independent risk factor for hypertension in this sample. Further studies, with larger samples followed throughout their childbearing years (before, during, and after each pregnancy), are needed before more definitive conclusions can be made regarding the effects of parity on BMI and BP among rural West African Dogon women.

  8. Pan-African Paleostresses and Reactivation of the Eburnean Basement Complex in Southeast Ghana (West Africa

    Directory of Open Access Journals (Sweden)

    Mahaman Sani Tairou

    2012-01-01

    Full Text Available This faulting tectonics analysis concerns the southernmost segment of the Dahomeyide Orogen and the West-African craton eastern margin in southeast Ghana. The analysis of strike-slip faults in the frontal units of the Dahomeyide Belt indicates that four distinct compressive events (NE-SW, ENE-WSW to E-W, ESE-WNW to SE-NW and SE-NW to SSE-NNW originated the juxtaposition of the Pan-African Mobile Zone and the West-African craton. These paleostress systems define a clockwise rotation of the compressional axis during the structuring of the Dahomeyide Orogen (650–550 Ma. The SE-NW and SSE-NNW to N-S compressional axes in the cratonic domain and its cover (Volta Basin suggest that the reactivation of the eastern edge of the West African craton is coeval with the last stages of the Pan-African tectogenesis in southeast Ghana. An extensional episode expressed as late normal faulting is also recorded in this study. This E-W to SE-NW extension, which is particular to the southernmost part of the Dahomeyide Belt, appears to be post-Pan-African. This extension probably contributed to the formation of a major Jurassic rifting zone that originated the Central Atlantic and the Benue Trough.

  9. Energy Generation Potential of West African Ocean Current ...

    African Journals Online (AJOL)

    PROF. OLIVER OSUAGWA

    2015-12-01

    Dec 1, 2015 ... Department of Marine Engineering, Faculty of Technology, Federal University of Petroleum Resources, P.M.B. 1221 ... West Africa in a streamed regular supply. ... system; Design of ocean current generating system whose efficiency relies .... Offloading Liquefied Natural Gas Facility for Offshore West Africa.

  10. activities of the ap leventis, the west african foremost ornithological ...

    African Journals Online (AJOL)

    Administrator

    This may be because of their high mobility, which make it easy for ... postgraduate students at Masters level have so far graduated, and are now ... Garden Warbler Sylvia borin migration in sub-Saharan West Africa: Phenology and body mass.

  11. Shaping Futures and Feminisms: Qur'anic Schools in West African Francophone Fiction

    Science.gov (United States)

    Edwin, Shirin

    2011-01-01

    This article examines the representation of female education in Qur'anic schools in a selection of West African francophone novels. I argue that in being the earliest form of education for most Muslim women and also a neglected topic of scholarly interest, the Qur'anic school shapes their feminisms in more significant ways than has been…

  12. Shaping Futures and Feminisms: Qur'anic Schools in West African Francophone Fiction

    Science.gov (United States)

    Edwin, Shirin

    2011-01-01

    This article examines the representation of female education in Qur'anic schools in a selection of West African francophone novels. I argue that in being the earliest form of education for most Muslim women and also a neglected topic of scholarly interest, the Qur'anic school shapes their feminisms in more significant ways than has been…

  13. A comparative history of commercial transition in three West African slave trading economies, 1630 to 1860

    NARCIS (Netherlands)

    Dalrymple-Smith, Angus

    2017-01-01

    The nineteenth century ‘commercial transition’ from export economies based on slaves to ones dominated by commodities like palm oil has been a central theme in West African history. However, most studies have tended to focus on the impact of the change and assumed that its causes were

  14. Experimental clinical and pathologic characterization of West African Newcastle disease viruses

    Science.gov (United States)

    Newcastle disease is a very significant disease of commercial and backyard poultry in Africa, and has been reported in numerous African countries. Recent analysis of strains from West Africa has revealed the emergence of at least one novel genetic lineage that differs from the previously-characteriz...

  15. The West African sports official : an insider's view of sports administration

    NARCIS (Netherlands)

    Beek, van W.E.A.

    2013-01-01

    Using my own experience as a sports administrator, I describe and analyse the organisational culture of West African sports. As a cultural anthropologist and draughts player, I have been President of the Fédération Mondiale du Jeu de Dames for eleven years, followed by four years as Executive Vice-P

  16. West African pholcid spiders: an overview, with descriptions of five new species (Araneae, Pholcidae

    Directory of Open Access Journals (Sweden)

    Bernhard A. Huber

    2013-10-01

    Full Text Available This paper summarizes current knowledge about West African pholcids. West Africa is here defined as the area south of 17°N and west of 5°E, including mainly the Upper Guinean subregion of the Guineo-Congolian center of endemism. This includes all of Senegal, The Gambia, Guinea Bissau, Guinea, Sierra Leone, Liberia, Ivory Coast, Ghana, Togo and Benin. An annotated list of the 14 genera and 38 species recorded from this area is given, together with distribution maps and an identification key to genera. Five species are newly described: Anansus atewa sp. nov., Artema bunkpurugu sp. nov., Leptopholcus kintampo sp. nov., Spermophora akwamu sp. nov., and S. ziama sp. nov. The female of Quamtana kitahurira is newly described. Additional new records are given for 16 previously described species, including 33 new country records. Distribution patterns of West African pholcids are discussed, as well as possible explanations for relatively low West African pholcid species diversity as compared to Central and East Africa.

  17. familiarity with modern health management trends by west african ...

    African Journals Online (AJOL)

    2010-09-09

    Sep 9, 2010 ... professionals to accept that all clinical decisions have ... subscribe to the power sharing (1). ... professional organisations, have become important ... was administered to a sample of surgeons at a ..... should be an asset to their management skills. ... research systems in ten countries of the WHO African.

  18. The extinction of the West African lion: whose responsibility?

    NARCIS (Netherlands)

    Nollkaemper, A.

    2014-01-01

    A recently published study showed that the lion in West Africa is now critically endangered and faces extinction. From one angle, this would be just one of the large (though unknown) number of species that has previously faced extinction or has even become extinct. But the risk of extinction of some

  19. The extinction of the West African lion: whose responsibility?

    NARCIS (Netherlands)

    A. Nollkaemper

    2014-01-01

    A recently published study showed that the lion in West Africa is now critically endangered and faces extinction. From one angle, this would be just one of the large (though unknown) number of species that has previously faced extinction or has even become extinct. But the risk of extinction of some

  20. Outcome of Radioiodine Therapy in a West African Population

    NARCIS (Netherlands)

    Onimode, Yetunde A; Ankrah, Alfred; Adedapo, Kayode S

    2016-01-01

    Hyperthyroidism continues to be a pressing public health concern in West Africa. Its prevalence in Africa has been quoted as 1.2%-9.9%, with Graves' disease as its most common cause. Radioiodine-131 (RAI) therapy of hyperthyroidism recently commenced in two government hospitals in Ghana and Nigeria.

  1. Mixed farming : scope and constraints in West African savanna

    NARCIS (Netherlands)

    Slingerland, M.

    2000-01-01

    Since colonial times the crop livestock integration concept has been a leading development model in francophone West Africa. So far, it has failed in certain aspects, such as cultivation of fodder crops, intensification of cereal production through animal traction, and sedentarisation of

  2. Mixed farming : scope and constraints in West African Savannah

    NARCIS (Netherlands)

    Slingerland, M.A.

    2000-01-01

    Since colonial times the crop livestock integration concept has been a leading development model in francophone West Africa. So far, it has failed in certain aspects, such as cultivation of fodder crops, intensification of cereal production through animal traction, and sedentarisation of mobile live

  3. Toward a Historical Archaeology of West African Borderlands

    African Journals Online (AJOL)

    user

    there is the dearth of the comparative analysis of these sources in tandem with the ... to yield new insights into the dynamics of the region's modern history. Keywords: ... The comparative study of archaeological and historical data in the reconstruction of ... trade as well as intra-regional East-West trade patterns (2001, p. 4).

  4. Mixed farming : scope and constraints in West African savanna

    NARCIS (Netherlands)

    Slingerland, M.

    2000-01-01

    Since colonial times the crop livestock integration concept has been a leading development model in francophone West Africa. So far, it has failed in certain aspects, such as cultivation of fodder crops, intensification of cereal production through animal traction, and sedentarisation of mo

  5. West-African trypanosomiasis in a returned traveller from Ghana: an unusual cause of progressive neurological decline.

    Science.gov (United States)

    Elliott, Ivo; Patel, Trupti; Shah, Jagrit; Venkatesan, Pradhib

    2014-08-14

    West-African trypanosomiasis caused by Trypanosoma brucei gambiense is a rare imported infection presenting with somnolence, lymphadenopathy and wide-ranging neurological symptoms. A 67-year-old Caucasian man presented with a 10-month history of cognitive deterioration, ataxic gait, somnolence and urinary incontinence. His symptoms had progressed more rapidly over the course of a month prior to admission. Serological testing confirmed a diagnosis of West-African trypanosomiasis. The patient was successfully treated with eflornithine and made a good recovery. West-African trypanosomiasis should be considered in the differential diagnosis of unexplained cognitive decline in those with a relevant travel history. If left untreated, the condition is universally fatal.

  6. Tropical Atlantic Hurricanes, Easterly Waves, and West African Mesoscale Convective Systems

    Directory of Open Access Journals (Sweden)

    Yves K. Kouadio

    2010-01-01

    Full Text Available The relationship between tropical Atlantic hurricanes (Hs, atmospheric easterly waves (AEWs, and West African mesoscale convective systems (MCSs is investigated. It points out atmospheric conditions over West Africa before hurricane formation. The analysis was performed for two periods, June–November in 2004 and 2005, during which 12 hurricanes (seven in 2004, five in 2005 were selected. Using the AEW signature in the 700 hPa vorticity, a backward trajectory was performed to the African coast, starting from the date and position of each hurricane, when and where it was catalogued as a tropical depression. At this step, using the Meteosat-7 satellite dataset, we selected all the MCSs around this time and region, and tracked them from their initiation until their dissipation. This procedure allowed us to relate each of the selected Hs with AEWs and a succession of MCSs that occurred a few times over West Africa before initiation of the hurricane. Finally, a dipole in sea surface temperature (SST was observed with a positive SST anomaly within the region of H generation and a negative SST anomaly within the Gulf of Guinea. This SST anomaly dipole could contribute to enhance the continental convergence associated with the monsoon that impacts on the West African MCSs formation.

  7. Vector competence in West African Aedes aegypti Is Flavivirus species and genotype dependent.

    Directory of Open Access Journals (Sweden)

    Laura B Dickson

    2014-10-01

    Full Text Available Vector competence of Aedes aegypti mosquitoes is a quantitative genetic trait that varies among geographic locations and among different flavivirus species and genotypes within species. The subspecies Ae. aegypti formosus, found mostly in sub-Saharan Africa, is considered to be refractory to both dengue (DENV and yellow fever viruses (YFV compared to the more globally distributed Ae. aegypti aegypti. Within Senegal, vector competence varies with collection site and DENV-2 viral isolate, but knowledge about the interaction of West African Ae. aegypti with different flaviviruses is lacking. The current study utilizes low passage isolates of dengue-2 (DENV-2-75505 sylvatic genotype and yellow fever (YFV BA-55 -West African Genotype I, or YFV DAK 1279-West African Genotype II from West Africa and field derived Ae. aegypti collected throughout Senegal to determine whether vector competence is flavivirus or virus genotype dependent.Eight collections of 20-30 mosquitoes from different sites were fed a bloodmeal containing either DENV-2 or either isolate of YFV. Midgut and disseminated infection phenotypes were determined 14 days post infection. Collections varied significantly in the rate and intensity of midgut and disseminated infection among the three viruses.Overall, vector competence was dependent upon both viral and vector strains. Importantly, contrary to previous studies, sylvatic collections of Ae. aegypti showed high levels of disseminated infection for local isolates of both DENV-2 and YFV.

  8. Recent climatological trend of the Saharan heat low and its impact on the West African climate

    Science.gov (United States)

    Lavaysse, Christophe; Flamant, Cyrille; Evan, Amato; Janicot, Serge; Gaetani, Marco

    2016-12-01

    The Saharan heat low (SHL) plays a pivotal role in the West African monsoon system in spring and summer. The recent trend in SHL activity has been analysed using two sets of numerical weather prediction (NWP) model reanalyses and Atmospheric Models Intercomparison Project simulations from 15 climate models performed in the framework of the 5th Coupled Models Intercomparison Project (CMIP5) exercise. A local increase of temperature in the Sahara during the 90s is found in the two sets of NWP models temperature. This increase is stronger within the SHL region than over the surrounding areas. Using different temporal filters (under 25 days, 25-100 days and above 300 days), we show that this is accompanied by a slight but widespread increase of temperature, and a change in the filtered signal under 25 days during the transition period of the 90s. We also show that SHL pulsations occurring at different time scales impact the West Africa climate on a variety of spatial scales, from the regional scale (for the high band pass) to the synoptic scale (for the low band pass signal). Despite a large variability in the temporal trends for 15 climate models from the CMIP5 project, the warming trend in the 90s is observed in the models ensemble mean. Nevertheless, large discrepancies are found between the NWP models reanalyses and the climate model simulations regarding the spatial and temporal evolutions of the SHL as well as its impact on West African climate at the different time scales. These comparisons also reveal that climate models represent the West African monsoon interactions with SHL pulsations quite differently. We provide recommendations to use some of them depending on the time scales of the processes at play (synoptic, seasonal, interannual) and based on key SHL metrics (location, mean intensity, global trend, interaction with the West African monsoon dynamics).

  9. Comparative Analysis of Breast Cancer Phenotypes in African American, White American, and West Versus East African patients: Correlation Between African Ancestry and Triple-Negative Breast Cancer.

    Science.gov (United States)

    Jiagge, Evelyn; Jibril, Aisha Souleiman; Chitale, Dhananjay; Bensenhaver, Jessica M; Awuah, Baffour; Hoenerhoff, Mark; Adjei, Ernest; Bekele, Mahteme; Abebe, Engida; Nathanson, S David; Gyan, Kofi; Salem, Barbara; Oppong, Joseph; Aitpillah, Francis; Kyei, Ishmael; Bonsu, Ernest Osei; Proctor, Erica; Merajver, Sofia D; Wicha, Max; Stark, Azadeh; Newman, Lisa A

    2016-11-01

    Triple-negative breast cancer (TNBC) is more common among African American (AA) and western sub-Saharan African breast cancer (BC) patients compared with White/Caucasian Americans (WA) and Europeans. Little is known about TNBC in east Africa. Invasive BC diagnosed 1998-2014 were evaluated: WA and AA patients from the Henry Ford Health System in Detroit, Michigan; Ghanaian/west Africans from the Komfo Anokye Teaching Hospital in Kumasi, Ghana; and Ethiopian/east Africans from the St. Paul's Hospital Millennium Medical College in Addis Ababa, Ethiopia. Histopathology and immunohistochemistry for estrogen receptor (ER), progesterone receptor (PR), and HER2/neu expression was performed in Michigan on formalin-fixed, paraffin-embedded samples from all cases. A total of 234 Ghanaian (mean age 49 years), 94 Ethiopian (mean age 43 years), 272 AA (mean age 60 years), and 321 WA (mean age 62 years; p = 0.001) patients were compared. ER-negative and TNBC were more common among Ghanaian and AA compared with WA and Ethiopian cases (frequency ER-negativity 71.1 and 37.1 % vs. 19.8 and 28.6 % respectively, p < 0.0001; frequency TNBC 53.2 and 29.8 % vs. 15.5 and 15.0 %, respectively, p < 0.0001). Among patients younger than 50 years, prevalence of TNBC remained highest among Ghanaians (50.8 %) and AA (34.3 %) compared with WA and Ethiopians (approximately 16 % in each; p = 0.0002). This study confirms an association between TNBC and West African ancestry; TNBC frequency among AA patients is intermediate between WA and Ghanaian/West Africans consistent with genetic admixture following the west Africa-based trans-Atlantic slave trade. TNBC frequency was low among Ethiopians/East Africans; this may reflect less shared ancestry between AA and Ethiopians.

  10. Serum 25-hydroxyvitamin D in a West African population of tuberculosis patients and unmatched healthy controls

    DEFF Research Database (Denmark)

    Wejse, Christian; Olesen, Rikke; Rabna, Paulo;

    2007-01-01

    BACKGROUND: Little is known regarding vitamin D deficiency (VDD) in African populations and in tuberculosis (TB) patients. VDD has been shown to be associated with TB. OBJECTIVE: We aimed to compare the degree of vitamin D insufficiency (VDI) and VDD in TB patients and healthy adult controls in a...... in a West African population. DESIGN: An unmatched case-control study was performed at a Demographic Surveillance Site in Guinea-Bissau. Serum 25-hydroxyvitamin D(3) [25(OH)D(3)] concentrations were measured in 362 TB patients and in 494 controls. RESULTS: Hypovitaminosis D [25(OH)D(3)...

  11. Serum 25-hydroxyvitamin D in a West African population of tuberculosis patients and unmatched healthy controls

    DEFF Research Database (Denmark)

    Wejse, Christian; Olesen, Rikke; Rabna, Paulo

    2007-01-01

    BACKGROUND: Little is known regarding vitamin D deficiency (VDD) in African populations and in tuberculosis (TB) patients. VDD has been shown to be associated with TB. OBJECTIVE: We aimed to compare the degree of vitamin D insufficiency (VDI) and VDD in TB patients and healthy adult controls...... in a West African population. DESIGN: An unmatched case-control study was performed at a Demographic Surveillance Site in Guinea-Bissau. Serum 25-hydroxyvitamin D(3) [25(OH)D(3)] concentrations were measured in 362 TB patients and in 494 controls. RESULTS: Hypovitaminosis D [25(OH)D(3) Udgivelsesdato: 2007...

  12. Response to habitat modifcation by foraging Dark-chanting Goshawks Melierax metabates in a West African savanna

    NARCIS (Netherlands)

    Dietz, Mauritia; Komdeur, Jan; Buij, Ralph; van Dorst, Nikkie; Salomons, Henriette; Croes, Barbara

    2015-01-01

    Anthropogenic habitat alteration has probably contributed significantly to the decrease of raptor populations in West African savannas. To evaluate the impact of habitat degradation on foraging by sedentary Afrotropical raptors, we investigated the differences in microhabitat selection, foraging eff

  13. Response to habitat modification by foraging dark-chanting goshawks Melierax metabates in a West African savanna

    NARCIS (Netherlands)

    Buij, Ralph; Van Dorst, Nikie; Salomons, Henriette F.; Croes, Barbara M.; Dietz, Maurine W.; Komdeur, Jan

    2015-01-01

    Anthropogenic habitat alteration has probably contributed significantly to the decrease of raptor populations in West African savannas. To evaluate the impact of habitat degradation on foraging by sedentary Afrotropical raptors, we investigated the differences in microhabitat selection, foraging eff

  14. Response to habitat modification by foraging Dark-chanting Goshawks Melierax metabates in a West African savanna

    NARCIS (Netherlands)

    Buij, Ralph; Dorst, Van Nikie; Salomons, Henriëtte F.; Croes, Barbara M.; Dietz, Maurine W.; Komdeur, Jan

    2015-01-01

    Anthropogenic habitat alteration has probably contributed significantly to the decrease of raptor populations in West African savannas. To evaluate the impact of habitat degradation on foraging by sedentary Afrotropical raptors, we investigated the differences in microhabitat selection, foraging

  15. Response to habitat modification by foraging Dark-chanting Goshawks Melierax metabates in a West African savanna

    NARCIS (Netherlands)

    Buij, Ralph; Dorst, Van Nikie; Salomons, Henriëtte F.; Croes, Barbara M.; Dietz, Maurine W.; Komdeur, Jan

    2015-01-01

    Anthropogenic habitat alteration has probably contributed significantly to the decrease of raptor populations in West African savannas. To evaluate the impact of habitat degradation on foraging by sedentary Afrotropical raptors, we investigated the differences in microhabitat selection, foraging

  16. The Role of Credit Access in Improving Cocoa Production in West African Countries

    OpenAIRE

    Nyemeck, J.B.; Gockowski, James; Nkamleu, Guy Blaise

    2008-01-01

    This study uses survey data to examine the role of access to credit on cocoa production, in West African cocoa production countries under conditions of agricultural policy liberalization. The study specifies and estimates econometric models to simulate the counterfactual of what cocoa production would be in the absence of credit facilities. The survey results show that about 54% of cocoa farmers have access to credit in Nigeria, and respectively 37% in Cameroon, while in Ghana and Côte d’Ivoi...

  17. Understanding the mechanisms behind the West African Monsoon northward extension during Mid-Holocene

    Science.gov (United States)

    Gaetani, Marco; Messori, Gabriele; Zhang, Qiong; Flamant, Cyrille; Evan, Amato T.; Pausata, Francesco S. R.

    2016-04-01

    Understanding the West African monsoon (WAM) dynamics in the mid-Holocene (MH) is a crucial issue in climate modelling, because numerical models typically fail to reproduce the extensive precipitation suggested by proxy evidence. This discrepancy is largely due to unrealistic imposed land surface cover and aerosols. Numerical experiments are conducted by imposing a "green Sahara", along with a reduced dust concentration in the atmosphere, coherently with the MH environment in the region, and the atmospheric dynamics response and impact on precipitation are investigated. The response of the WAM system to the imposed conditions shows a dramatic augmentation of the precipitation across West Africa up to the Mediterranean coast. This follows a substantial reorganization of the regional circulation, with some monsoonal circulation features (Saharan heat low, African easterly jet, African easterly waves) weakened in favour of deep convection development over land. The simulated response is dominated by land cover changes, and the reduction in dust concentration further enhances the changes induced by the "green Sahara". The intensity and meridional extent of the WAM is fully consistent with proxy evidence. The results for the MH WAM present important implications for understanding future climate scenarios in the region, in the perspective of projected wetter conditions in West Africa.

  18. A multi-model approach to the Atlantic Equatorial mode: impact on the West African monsoon

    Energy Technology Data Exchange (ETDEWEB)

    Losada, T.; Rodriguez-Fonseca, B. [Universidad Complutense de Madrid, Madrid (Spain); Janicot, S.; Gervois, S. [LOCEAN/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Chauvin, F. [GAME/CNRM, Meteo-France/CNRS, Toulouse (France); Ruti, P. [Progetto Speciale Clima Globale, Ente Nazionale per le NuoveTecnologie, Rome (Italy)

    2010-07-15

    This paper is focused on the West African anomalous precipitation response to an Atlantic Equatorial mode whose origin, development and damping resembles the observed one during the last decades of the XXth century. In the framework of the AMMA-EU project, this paper analyses the atmospheric response to the Equatorial mode using a multimodel approach with an ensemble of integrations from 4 AGCMs under a time varying Equatorial SST mode. The Guinean Gulf precipitation, which together with the Sahelian mode accounts for most of the summer West African rainfall variability, is highly coupled to this Equatorial Atlantic SST mode or Atlantic Nino. In a previous study, done with the same models under 1958-1997 observed prescribed SSTs, most of the models identify the Equatorial Atlantic SST mode as the one most related to the Guinean Gulf precipitation. The models response to the positive phase of equatorial Atlantic mode (warm SSTs) depicts a direct impact in the equatorial Atlantic, leading to a decrease of the local surface temperature gradient, weakening the West African Monsoon flow and the surface convergence over the Sahel. (orig.)

  19. Comparison of different pretreatment strategies for ethanol production of West African biomass.

    Science.gov (United States)

    Thomsen, Sune Tjalfe; Londoño, Jorge Enrique González; Schmidt, Jens Ejbye; Kádár, Zsófia

    2015-03-01

    Pretreating lignocellulosic biomass for cellulosic ethanol production in a West African setting requires smaller scale and less capital expenditure compared to current state of the art. In the present study, three low-tech methods applicable for West African conditions, namely Boiling Pretreatment (BP), Soaking in Aqueous Ammonia (SAA) and White Rot Fungi pretreatment (WRF), were compared to the high-tech solution of hydrothermal pretreatment (HTT). The pretreatment methods were tested on 11 West African biomasses, i.e. cassava stalks, plantain peelings, plantain trunks, plantain leaves, cocoa husks, cocoa pods, maize cobs, maize stalks, rice straw, groundnut straw and oil palm empty fruit bunches. It was found that four biomass' (plantain peelings, plantain trunks, maize cobs and maize stalks) were most promising for production of cellulosic ethanol with profitable enzymatic conversion of glucan (>30 g glucan per 100 g total solids (TS)). HTT did show better results in both enzymatic convertibility and fermentation, but evaluated on the overall ethanol yield the low-tech pretreatment methods are viable alternatives with similar levels to the HTT (13.4-15.2 g ethanol per 100 g TS raw material).

  20. The relationship between the Guinea Highlands and the West African offshore rainfall maximum

    Science.gov (United States)

    Hamilton, H. L.; Young, G. S.; Evans, J. L.; Fuentes, J. D.; Núñez Ocasio, K. M.

    2017-01-01

    Satellite rainfall estimates reveal a consistent rainfall maximum off the West African coast during the monsoon season. An analysis of 16 years of rainfall in the monsoon season is conducted to explore the drivers of such copious amounts of rainfall. Composites of daily rainfall and midlevel meridional winds centered on the days with maximum rainfall show that the day with the heaviest rainfall follows the strongest midlevel northerlies but coincides with peak low-level moisture convergence. Rain type composites show that convective rain dominates the study region. The dominant contribution to the offshore rainfall maximum is convective development driven by the enhancement of upslope winds near the Guinea Highlands. The enhancement in the upslope flow is closely related to African easterly waves propagating off the continent that generate low-level cyclonic vorticity and convergence. Numerical simulations reproduce the observed rainfall maximum and indicate that it weakens if the African topography is reduced.

  1. Investigating the zoonotic origin of the West African Ebola epidemic

    Science.gov (United States)

    Marí Saéz, Almudena; Weiss, Sabrina; Nowak, Kathrin; Lapeyre, Vincent; Zimmermann, Fee; Düx, Ariane; Kühl, Hjalmar S; Kaba, Moussa; Regnaut, Sebastien; Merkel, Kevin; Sachse, Andreas; Thiesen, Ulla; Villányi, Lili; Boesch, Christophe; Dabrowski, Piotr W; Radonić, Aleksandar; Nitsche, Andreas; Leendertz, Siv Aina J; Petterson, Stefan; Becker, Stephan; Krähling, Verena; Couacy-Hymann, Emmanuel; Akoua-Koffi, Chantal; Weber, Natalie; Schaade, Lars; Fahr, Jakob; Borchert, Matthias; Gogarten, Jan F; Calvignac-Spencer, Sébastien; Leendertz, Fabian H

    2015-01-01

    The severe Ebola virus disease epidemic occurring in West Africa stems from a single zoonotic transmission event to a 2-year-old boy in Meliandou, Guinea. We investigated the zoonotic origins of the epidemic using wildlife surveys, interviews, and molecular analyses of bat and environmental samples. We found no evidence for a concurrent outbreak in larger wildlife. Exposure to fruit bats is common in the region, but the index case may have been infected by playing in a hollow tree housing a colony of insectivorous free-tailed bats (Mops condylurus). Bats in this family have previously been discussed as potential sources for Ebola virus outbreaks, and experimental data have shown that this species can survive experimental infection. These analyses expand the range of possible Ebola virus sources to include insectivorous bats and reiterate the importance of broader sampling efforts for understanding Ebola virus ecology. PMID:25550396

  2. The West African species of Caenis Stephens (Insecta: Ephemeroptera

    Directory of Open Access Journals (Sweden)

    Malzacher, P.

    Full Text Available The present paper is the result of the examination of several thousand specimens of the genus Caenis Stephens, 1835 (Ephemeroptera which were collected in West Africa in more than 200 light trap samples from 32 rivers in Guinea, Mali, Ivory Coast, Togo and Ghana. Five new species are described: Caenis vermifera n. sp. (Ivory Coast, Guinea, C. nigricola n. sp. (Mali, Guinea, C. jinjanoides n. sp. (Guinea, Ivory Coast, C. kohli n. sp. (Guinea, and C. orthostilata n. sp. (Mali. The extensive materials allow to add distributional data to previously known species. C. elouardi, C. cibaria kunda, C. gilliesi, C. jinjana, C. antelucana, C. brevipes, C. berneri, and C. pallida are redescribed. The eggs of most of the treated species are described based on SEM pictures. Several questions concerning supposed species relationships are discussed. The subspecies rank of C. brevipes occidentalis Malzacher, 1993 ist rejected.

  3. Investigating the zoonotic origin of the West African Ebola epidemic.

    Science.gov (United States)

    Marí Saéz, Almudena; Weiss, Sabrina; Nowak, Kathrin; Lapeyre, Vincent; Zimmermann, Fee; Düx, Ariane; Kühl, Hjalmar S; Kaba, Moussa; Regnaut, Sebastien; Merkel, Kevin; Sachse, Andreas; Thiesen, Ulla; Villányi, Lili; Boesch, Christophe; Dabrowski, Piotr W; Radonić, Aleksandar; Nitsche, Andreas; Leendertz, Siv Aina J; Petterson, Stefan; Becker, Stephan; Krähling, Verena; Couacy-Hymann, Emmanuel; Akoua-Koffi, Chantal; Weber, Natalie; Schaade, Lars; Fahr, Jakob; Borchert, Matthias; Gogarten, Jan F; Calvignac-Spencer, Sébastien; Leendertz, Fabian H

    2014-12-30

    The severe Ebola virus disease epidemic occurring in West Africa stems from a single zoonotic transmission event to a 2-year-old boy in Meliandou, Guinea. We investigated the zoonotic origins of the epidemic using wildlife surveys, interviews, and molecular analyses of bat and environmental samples. We found no evidence for a concurrent outbreak in larger wildlife. Exposure to fruit bats is common in the region, but the index case may have been infected by playing in a hollow tree housing a colony of insectivorous free-tailed bats (Mops condylurus). Bats in this family have previously been discussed as potential sources for Ebola virus outbreaks, and experimental data have shown that this species can survive experimental infection. These analyses expand the range of possible Ebola virus sources to include insectivorous bats and reiterate the importance of broader sampling efforts for understanding Ebola virus ecology.

  4. Prioritizing West African medicinal plants for conservation and sustainable extraction studies based on market surveys and species distribution models.

    NARCIS (Netherlands)

    Andel, van T.R.; Croft, S.; Loon, van E.E.; Quiroz Villarreal, D.K.; Towns, A.M.; Raes, N.

    2015-01-01

    Sub-Saharan African human populations rely heavily on wild-harvested medicinal plants for their health. The trade in herbal medicine provides an income for many West African people, but little is known about the effects of commercial extraction on wild plant populations. Detailed distribution maps

  5. Prioritizing West African medicinal plants for conservation and sustainable extraction studies based on market surveys and species distribution models

    NARCIS (Netherlands)

    van Andel, T.R.; Croft, S.; van Loon, E.E.; Quiroz, D.; Towns, A.M.; Raes, N.

    2015-01-01

    Sub-Saharan African human populations rely heavily on wild-harvested medicinal plants for their health. The trade in herbal medicine provides an income for many West African people, but little is known about the effects of commercial extraction on wild plant populations. Detailed distribution maps

  6. Association between consumption of black tea and iron status in adult Africans in the North West Province: The THUSA study

    NARCIS (Netherlands)

    Hogenkamp, P.S.; Jerling, J.C.; Hoekstra, T.; Boonstra, A.; MacIntyre, U.E.

    2008-01-01

    The association between black tea consumption and iron status was investigated in a sample of African adults participating in the cross-sectional THUSA (Transition and Health during Urbanization of South Africans) study in the North West Province, South Africa. Data were analysed from 1605 apparentl

  7. Prioritizing West African medicinal plants for conservation and sustainable extraction studies based on market surveys and species distribution models.

    NARCIS (Netherlands)

    Andel, van T.R.; Croft, S.; Loon, van E.E.; Quiroz Villarreal, D.K.; Towns, A.M.; Raes, N.

    2015-01-01

    Sub-Saharan African human populations rely heavily on wild-harvested medicinal plants for their health. The trade in herbal medicine provides an income for many West African people, but little is known about the effects of commercial extraction on wild plant populations. Detailed distribution maps a

  8. Prioritizing West African medicinal plants for conservation and sustainable extraction studies based on market surveys and species distribution models

    NARCIS (Netherlands)

    van Andel, T.R.; Croft, S.; van Loon, E.E.; Quiroz, D.; Towns, A.M.; Raes, N.

    2015-01-01

    Sub-Saharan African human populations rely heavily on wild-harvested medicinal plants for their health. The trade in herbal medicine provides an income for many West African people, but little is known about the effects of commercial extraction on wild plant populations. Detailed distribution maps a

  9. Surface response to rain events throughout the West African monsoon

    Directory of Open Access Journals (Sweden)

    F. Lohou

    2013-07-01

    Full Text Available This study analyses the response of the continental surface to a rain event, taking advantage of the long-term near-surface measurements over different vegetation covers at different latitudes, acquired during the African Monsoon Multidisciplinary Analysis (AMMA experiment. The simulated surface response by nine land surface models involved in AMMA Land Model Intercomparison Project (ALMIP, is compared to the observations. The surface response, described via the evaporative fraction, evolves in two steps: the immediate surface response and the surface recovery. The immediate surface response corresponds to an increase in the evaporative fraction occurring immediately after the rain. For all the experimental sites, the immediate surface response is strongest when the surface is relatively dry. From the simulation point of view, this relationship is highly model and latitude dependent. The recovery period, characterized by a decrease of the evaporative fraction during several days after the rain, follows an exponential relationship whose rate is vegetation dependent: from 1 day over bare soil to 70 days over the forest. Land surface models correctly simulate the decrease of EF over vegetation covers whereas a slower and more variable EF decrease is simulated over bare soil.

  10. The EU Migration Regime and West African Clandestine Migrants

    Directory of Open Access Journals (Sweden)

    Hannah M. Cross

    2009-08-01

    Full Text Available This article examines the relationship between the EU migration regime and clandestine migration from West Africa to Europe. A review of the development of EU border and immigration policy reveals significant and sustained moves towards securitisation of migrants and the externalisation of border controls to countries of origin and transit. This emphasis on repression limits the scope of cooperation with ‘third countries’ (those outside Europe in co-development, labour mobility, sea patrols and repatriation, which are examined separately as deterrents to uncontrolled emigration. This paper then analyses the motivations and intentions of Senegalese youth around the Cap Vert peninsula. This analysis includes the role of emigration in development and more recently, the impact of human losses and repatriations resulting from the clandestine journey by pirogue (open fishing boat to the Canary Islands. This article argues that in this case, youth are excluded both from labour and asylum policies and instead are managed as a security threat, contradicting the factors driving this journey.

  11. Human Adaptation of Ebola Virus during the West African Outbreak.

    Science.gov (United States)

    Urbanowicz, Richard A; McClure, C Patrick; Sakuntabhai, Anavaj; Sall, Amadou A; Kobinger, Gary; Müller, Marcel A; Holmes, Edward C; Rey, Félix A; Simon-Loriere, Etienne; Ball, Jonathan K

    2016-11-03

    The 2013-2016 outbreak of Ebola virus (EBOV) in West Africa was the largest recorded. It began following the cross-species transmission of EBOV from an animal reservoir, most likely bats, into humans, with phylogenetic analysis revealing the co-circulation of several viral lineages. We hypothesized that this prolonged human circulation led to genomic changes that increased viral transmissibility in humans. We generated a synthetic glycoprotein (GP) construct based on the earliest reported isolate and introduced amino acid substitutions that defined viral lineages. Mutant GPs were used to generate a panel of pseudoviruses, which were used to infect different human and bat cell lines. These data revealed that specific amino acid substitutions in the EBOV GP have increased tropism for human cells, while reducing tropism for bat cells. Such increased infectivity may have enhanced the ability of EBOV to transmit among humans and contributed to the wide geographic distribution of some viral lineages. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  12. Outbreaks-of Ebola virus disease in the West African sub-region.

    Science.gov (United States)

    Osungbade, K O; Oni, A A

    2014-06-01

    Five West African countries, including Nigeria are currently experiencing the largest, most severe, most complex outbreak of Ebola virus disease in history. This paper provided a chronology of outbreaks of Ebola virus disease in the West African sub-region and provided an update on efforts at containing the present outbreak. Literature from Pubmed (MEDLINE), AJOL, Google Scholar and Cochrane database were reviewed. Outbreaks of Ebola, virus disease had frequently occurred mainly in Central and East African countries. Occasional outbreaks reported from outside of Africa were due to laboratory contamination and imported monkeys in quarantine facilities. The ongoing outbreak in West Africa is the largest and first in the sub-region; the number of suspected cases and deaths from this single current outbreak is already about three times the total of all cases and deaths from previous known outbreaks in 40 years. Prevention and control efforts are hindered not only by lack of a known vaccine and virus-specific treatment, but also by weak health systems, poor sanitation, poor personal hygiene and cultural beliefs and practices, including myths and misconceptions about Ebola virus disease--all of which are prevalent in affected countries. Constrained by this situation, the World Health Organisation departed from the global standard and recommended the use of not yet proven treatments to treat or prevent the disease in humans on ethical and evidential grounds. The large number of people affected by the present outbreak in West Africa and the high case-fatality rate calls for accelerated evaluation and development of the investigational medical interventions for life saving and curbing the epidemic. Meanwhile, existing interventions such as early detection and isolation, contact tracing and monitoring, and adherence to rigorous procedures of infection prevention and control should be intensified.

  13. Optical Spectra of Ultracool Dwarfs with the Southern African Large Telescope

    CERN Document Server

    Koen, C; Väisänen, P; Koen, T

    2016-01-01

    New spectra of 81 ultracool dwarfs (spectral types M7 and later) are discussed. Spectral classifications of 49 objects are available in the literature, while 32 objects are newly classified. The known spectral types were used to test an automated classification scheme, which relies primarily on template fitting, supplemented by matching of spectral indices calibrated against the template spectra. An attempt was made to quantify the uncertainty in the spectral types, which is generally better than two subclasses. Objects for which spectral types differ by more than one subclass from the literature classifications are discussed individually. Discrepancies between automated classifications based on respectively template fitting and spectral index matching, may be useful for flagging objects with unusual spectra. Aside from the 32 first-time classifications, alternative classifications are presented for 32 previously classified dwarfs. Very large (equivalent width greater than 130 \\AA) H$\\alpha$ flares are report...

  14. Optical spectra of ultracool dwarfs with the Southern African Large Telescope

    Science.gov (United States)

    Koen, C.; Miszalski, B.; Väisänen, P.; Koen, T.

    2017-03-01

    New spectra of 81 ultracool dwarfs (spectral types M7 and later) are discussed. Spectral classifications of 49 objects are available in the literature, while 32 objects are newly classified. The known spectral types were used to test an automated classification scheme, which relies primarily on template fitting, supplemented by matching of spectral indices calibrated against the template spectra. An attempt was made to quantify the uncertainty in the spectral types, which is generally better than two subclasses. Objects for which spectral types differ by more than one subclass from the literature classifications are discussed individually. Discrepancies between automated classifications based on, respectively, template fitting and spectral index matching, may be useful for flagging objects with unusual spectra. Aside from the 32 first-time classifications, alternative classifications are presented for 32 previously classified dwarfs. Very large (equivalent width greater than 130 Å) Hα flares are reported for the known ultracool dwarf binary 2MASS J15200224-4422419; curiously, the object does not appear to have quiescent emission lines. Non-zero equivalent-width measurements are listed for a further 29 objects.

  15. Glucose intolerance in the West African Diaspora: a skeletal muscle fibre type distribution hypothesis.

    Science.gov (United States)

    Nielsen, J; Christensen, D L

    2011-08-01

    In the United States, Black Americans are largely descendants of West African slaves; they have a higher relative proportion of obesity and experience a higher prevalence of diabetes than White Americans. However, obesity rates alone cannot explain the higher prevalence of type 2 diabetes. Type 2 diabetes is characterized by insulin resistance and beta-cell dysfunction. We hypothesize that the higher prevalence of type 2 diabetes in African Americans (as compared to White Americans) is facilitated by an inherited higher percentage of skeletal muscle fibre type II and a lower percentage of skeletal muscle fibre type I. Skeletal muscle fibre type II is less oxidative and more glycolytic than skeletal muscle fibre type I. Lower oxidative capacity is associated with lower fat oxidation and a higher disposal of lipids, which are stored as muscular adipose tissue in higher amounts in Black compared to White Americans. In physically active individuals, the influence of muscle fibre composition will not be as detrimental as in physically inactive individuals. This discrepancy is caused by the plasticity in the skeletal muscle fibre characteristics towards a higher activity of oxidative enzymes as a consequence of physical activity. We suggest that a higher percentage of skeletal muscle fibre type II combined with physical inactivity has an impact on insulin sensitivity and high prevalence of type 2 diabetes in Blacks of West African ancestry.

  16. Circulating Adiponectin Is Associated with Renal Function Independent of Age and Serum Lipids in West Africans

    Directory of Open Access Journals (Sweden)

    A. P. Doumatey

    2012-01-01

    Full Text Available Adiponectin, a protein secreted by adipose tissue, has been associated with renal dysfunction. However, these observations have not been adequately investigated in large epidemiological studies of healthy individuals in general and in African populations in particular. Hence, we designed this study to evaluate the relationship between adiponectin and renal function in a large group of nondiabetic West Africans. Total adiponectin was measured in 792 participants. MDRD and Cockroft-Gault (CG- estimated GFR were used as indices of renal function. Linear and logistic regression models were used to determine the relationship between adiponectin and renal function. Adiponectin showed an inverse relationship with eGFR in univariate (BetaMDRD=-0.18, BetaCG=-0.26 and multivariate (BetaMDRD=-0.10, BetaCG=-0.09 regression analyses. The multivariate models that included age, sex, BMI, hypertension, smoking, HDL-C, LDL-C, triglycerides, and adiponectin explained 30% and 55.6% of the variance in GFR estimated by MDRD and CG methods, respectively. Adiponectin was also a strong predictor of moderate chronic kidney disease (defined as eGFR < 60 mL/min/1.73 m2. We demonstrate that adiponectin is associated with renal function in nondiabetic West Africans. The observed relationship is independent of age and serum lipids. Our findings suggest that adiponectin may have clinical utility as a biomarker of renal function.

  17. Observations of Coastally Transitioning West African Mesoscale Convective Systems during NAMMA

    Directory of Open Access Journals (Sweden)

    Bradley W. Klotz

    2012-01-01

    Full Text Available Observations from the NASA 10 cm polarimetric Doppler weather radar (NPOL were used to examine structure, development, and oceanic transition of West African Mesoscale Convective Systems (MCSs during the NASA African Monsoon Multidisciplinary Analysis (NAMMA to determine possible indicators leading to downstream tropical cyclogenesis. Characteristics examined from the NPOL data include echo-top heights, maximum radar reflectivity, height of maximum radar reflectivity, and convective and stratiform coverage areas. Atmospheric radiosondes launched during NAMMA were used to investigate environmental stability characteristics that the MCSs encountered while over land and ocean, respectively. Strengths of African Easterly Waves (AEWs were examined along with the MCSs in order to improve the analysis of MCS characteristics. Mean structural and environmental characteristics were calculated for systems that produced TCs and for those that did not in order to determine differences between the two types. Echo-top heights were similar between the two types, but maximum reflectivity and height and coverage of intense convection (>50 dBZ are all larger than for the TC producing cases. Striking differences in environmental conditions related to future TC formation include stronger African Easterly Jet, increased moisture especially at middle and upper levels, and increased stability as the MCSs coastally transition.

  18. Genetic and BMI risks for predicting blood pressure in three generations of West African Dogon women.

    Science.gov (United States)

    Taylor, Jacquelyn Y; Sampson, Deborah; Taylor, Andre D; Caldwell, Dennis; Sun, Yan V

    2013-01-01

    The study of genetic polymorphisms and body mass index (BMI) among African women in Africa and in the United States contributes to our understanding of the genetic and environmental risk factors for hypertension. African American women have the highest prevalence of hypertension and obesity compared to other ethnic groups in the United States. Using a cross-sectional research design, we examined the effects of genetic and environmental risks of single nucleotide polymorphisms (SNPs) and BMI on blood pressure (BP) among three generations of West African Dogon women (N = 199). We genotyped six SNPs located in the candidate genes known to be related to hypertension. We tested the associations between these SNPs and systolic BP (SBP) and diastolic BP (DBP) with Fisher's exact tests, chi-square tests for independence, and multivariable linear mixed models. The SNP rs8179526 (SLC4A5) was significantly associated with SBP adjusted for age, age(2), and BMI (p = .02). The "C" allele variant of rs8179526 (allele frequency of 0.445) was associated with higher SBP. This SNP did not deviate from the Hardy-Weinberg equilibrium (HWE) with p value of .772. The SNP × BMI interaction effects associated with SBP and DBP were not significant. rs8179526 is located on the SLC4A5 gene on chromosome 2. SLC4A5 encodes a protein that transports sodium and bicarbonate across cell membranes while regulating cellular pH and contains several SNPs linked to elevated BP. Knowledge of the SNP's effect on hypertension among West African women can help health practitioners educate their patients about genetic risks of developing hypertension.

  19. Instrumental evidence of an unusually strong West African Monsoon in the 19th century

    Science.gov (United States)

    Gallego, David; Ordoñez, Paulina; Ribera, Pedro; Peña-Ortiz, Cristina; Garcia-Herrera, Ricardo; Vega, Inmaculada; Gomez, Francisco de Paula

    2016-04-01

    The precipitation in the Sahel -which is mainly controlled by the dynamics of the West African Monsoon-, has been in the spot of the climate community for the last three decades due to the persistence of the drought period that started in the 1970s. Unfortunately, reliable meteorological series in this area are only available since the beginning of the 20th Century, thus limiting our understanding of the significance of this period from a long term perspective. Currently, our knowledge of what happened in times previous to the 20th Century essentially relies in documentary or proxy sources. In this work, we present the first instrumental evidence of a 50 year-long period characterised by an unusually strong West African monsoon in the19th Century. Following the recent advances in the generation of climatic indices based on data from ship's logbooks, we used historical wind observations to compute a new index (the so-called ASWI) for characterising the strength of the West African Monsoon. The ASWI is based in the persistence of the southwesterly winds in the [29°W-17°W;7°N-13°N] area and it has been possible to compute it since 1790 for July and since 1839 for August and September. We show that the ASWI is a reliable measure of the monsoon's strength and the Sahelian rainfall. Our new series clearly shows the well-known drought period starting in the 1970s. During this dry period, the West African Monsoon was particularly weak and interestingly, we found that since then, the correlations with different climatic patterns such as the Pacific and Atlantic "El Niño" changed significantly in relation to those of the previous century. Remarkably, our results also show that the period 1839-1890 was characterised by an unusually strong and persistent monsoon. Notwithstanding, two of the few dry years within this period were concurrent with large volcanic eruptions in the Northern Hemisphere. This latter result supports the recently suggested relationship between major

  20. An assessment of West African seahorses in fisheries catch and trade.

    Science.gov (United States)

    Cisneros-Montemayor, A M; West, K; Boiro, I S; Vincent, A C J

    2016-02-01

    This study provides the first assessment of a heavily traded West African seahorse species, Hippocampus algiricus, and the first information on short-snouted seahorse Hippocampus hippocampus biology in Africa. A total of 219 seahorses were sampled from fisher catch in Senegal and The Gambia, with estimated height at reproductive activity for H. algiricus (161 mm) larger than mean ± S.D. catch height (150 ± 31 mm). Catch composition, height at reproductive activity and potential biases in fishery retention are discussed with regard to the current Convention on International Trade of Endangered Species (CITES) guidelines.

  1. On the mathematical analysis of Ebola hemorrhagic fever: deathly infection disease in West African countries.

    Science.gov (United States)

    Atangana, Abdon; Goufo, Emile Franc Doungmo

    2014-01-01

    For a given West African country, we constructed a model describing the spread of the deathly disease called Ebola hemorrhagic fever. The model was first constructed using the classical derivative and then converted to the generalized version using the beta-derivative. We studied in detail the endemic equilibrium points and provided the Eigen values associated using the Jacobian method. We furthered our investigation by solving the model numerically using an iteration method. The simulations were done in terms of time and beta. The study showed that, for small portion of infected individuals, the whole country could die out in a very short period of time in case there is not good prevention.

  2. Channa andrao, a new species of dwarf snakehead from West Bengal, India (Teleostei: Channidae).

    Science.gov (United States)

    Britz, Ralf

    2013-10-30

    Channa andrao, new species, from Lefraguri swamp, West Bengal, India, differs from all its congeners except, C. asiatica, C. bleheri and C. burmanica and the recently described C. hoaluensis and C. ninhbinhensis by the absence of pelvic fins. It can be distinguished from all other pelvic fin-less species of snakeheads by its colour pattern, and differs further in its number of vertebrae, dorsal- and anal-fin rays, and lateral-line scales from individual snakehead species in this complex. Channa andrao raises the number of snakehead species endemic to the Eastern Himalaya biodiversity hotspot to ten, representing almost one third of the known species in the genus.

  3. Productivity assessments in small ruminants improvement programmes. A case study of the West African Dwarf Goat.

    NARCIS (Netherlands)

    Bosman, H.

    1995-01-01

    Livestock production in the tropics is characterised by a high degree of variability in terms of composition, setting and aims. A good understanding of these characteristics is a prerequisite for the planning of a successful improvement programme. A frequently used criterion to assess the suitabilit

  4. Productivity assessments in small ruminant improvement programmes : a case study of the West African dwarf goat

    NARCIS (Netherlands)

    Bosman, H.G.

    1995-01-01

    Livestock production in the tropics is characterised by a high degree of variability in terms of composition, setting and aims. A good understanding of these characteristics is a prerequisite for the planning of a successful improvement programme. A frequently used criterion to assess the

  5. Interdecadal variation of the West African summer monsoon during 1979-2010 and associated variability

    Energy Technology Data Exchange (ETDEWEB)

    Li, Huanlian [Chinese Academy of Sciences, Nansen-Zhu International Research Centre, Institute of Atmospheric Physics, Beijing (China); Graduate University of Chinese Academy of Sciences, Beijing (China); Chinese Academy of Sciences, Climate Change Research Center, Beijing (China); Wang, Huijun [Chinese Academy of Sciences, Nansen-Zhu International Research Centre, Institute of Atmospheric Physics, Beijing (China); Chinese Academy of Sciences, Climate Change Research Center, Beijing (China); Yin, Yizhou [Tsinghua University, Center for Earth System Science, Beijing (China)

    2012-12-15

    This paper addresses the interdecadal variation of the West African summer monsoon (WASM) along with its background of atmospheric circulation and possible physical mechanism over the past 32 years (1979-2010). It is indicated that the WASM starts to strengthen from 1998 as the rainfall begins to increase over western West Africa on the whole, which shows a new interdecadal variation. In this interdecadal variation, the strengthened ascending motion corresponding to enhanced divergence (convergence) movement on the upper (lower) troposphere is prone to develop the local circulation of the monsoon. Moreover, the strengthened southwestern (eastern) wind on the lower (upper) level leads to more moisture from the Atlantic and the Gulf of Guinea transported to the West African continent. In addition, the summer subtropical high over the north Atlantic and western West Africa is strong and northward, and the tropical east wind is also strong. Statistically, the weaker (stronger) the spring North Atlantic Oscillation (NAO) is, the stronger (weaker) the tropical easterly is, and then the WASM is also stronger. But the effect of the NAO on the decadal variation of the WASM is not so significant from the north Atlantic anomaly sensitivity simulation with a single model. This is also an indication that the relationship between the WASM and NAO is complicated in an interdecadal time scale and is needed further study. In terms of sea surface temperature (SST) variation, the tendency is toward warming in the subtropical north Pacific, the south Pacific and north Atlantic. Numerical simulation experiments and data analysis show that the SST variation in the north Pacific plays an important role in the latest interdecadal strengthening of the WASM during the past 32 years, while the influences of the south Pacific and the north Atlantic SST anomalies are not so significant to the associated atmospheric circulation changes. (orig.)

  6. Functional Characterization of Adaptive Mutations during the West African Ebola Virus Outbreak.

    Science.gov (United States)

    Dietzel, Erik; Schudt, Gordian; Krähling, Verena; Matrosovich, Mikhail; Becker, Stephan

    2017-01-15

    The Ebola virus (EBOV) outbreak in West Africa started in December 2013, claimed more than 11,000 lives, threatened to destabilize a whole region, and showed how easily health crises can turn into humanitarian disasters. EBOV genomic sequences of the West African outbreak revealed nonsynonymous mutations, which induced considerable public attention, but their role in virus spread and disease remains obscure. In this study, we investigated the functional significance of three nonsynonymous mutations that emerged early during the West African EBOV outbreak. Almost 90% of more than 1,000 EBOV genomes sequenced during the outbreak carried the signature of three mutations: a D759G substitution in the active center of the L polymerase, an A82V substitution in the receptor binding domain of surface glycoprotein GP, and an R111C substitution in the self-assembly domain of RNA-encapsidating nucleoprotein NP. Using a newly developed virus-like particle system and reverse genetics, we found that the mutations have an impact on the functions of the respective viral proteins and on the growth of recombinant EBOVs. The mutation in L increased viral transcription and replication, whereas the mutation in NP decreased viral transcription and replication. The mutation in the receptor binding domain of the glycoprotein GP improved the efficiency of GP-mediated viral entry into target cells. Recombinant EBOVs with combinations of the three mutations showed a growth advantage over the prototype isolate Makona C7 lacking the mutations. This study showed that virus variants with improved fitness emerged early during the West African EBOV outbreak. The dimension of the Ebola virus outbreak in West Africa was unprecedented. Amino acid substitutions in the viral L polymerase, surface glycoprotein GP, and nucleocapsid protein NP emerged, were fixed early in the outbreak, and were found in almost 90% of the sequences. Here we showed that these mutations affected the functional activity of

  7. Desertification and a shift of forest species in the West African Sahel

    Science.gov (United States)

    Gonzalez, P.

    2001-01-01

    Original field data show that forest species richness and tree density in the West African Sahel declined in the last half of the 20th century. Average forest species richness of areas of 4 km2 in Northwest Senegal fell from 64 ?? 2 species ca 1945 to 43 ?? 2 species in 1993, a decrease significant at p changes have shifted vegetation zones toward areas of higher rainfall at an average rate of 500 to 600 m yr-1. Arid Sahel species have expanded in the north, tracking a concomitant retraction of mesic Sudan and Guinean species to the south. Multivariate analyses identify latitude and longitude, proxies for rainfall and temperature, as the most significant factors explaining tree and shrub distribution. The changes also decreased human carrying capacity to below actual population densities. The rural population of 45 people km-2 exceeded the 1993 carrying capacity, for firewood from shrubs, of 13 people km-2 (range 1 to 21 people km-2). As an adaptation strategy, ecological and socioeconomic factors favor the natural regeneration of local species over the massive plantation of exotic species. Natural regeneration is a traditional practice in which farmers select small field trees that they wish to raise to maturity, protect them, and prune them to promote rapid growth of the apical meristem. The results of this research provide evidence for desertification in the West African Sahel. These documented impacts of desertification foreshadow possible future effects of climate change.

  8. West African Youth Initiative: outcome of a reproductive health education program.

    Science.gov (United States)

    Brieger, W R; Delano, G E; Lane, C G; Oladepo, O; Oyediran, K A

    2001-12-01

    To describe the implementation and evaluation of an adolescent reproductive health peer education program in West Africa. The program, known as the West African Youth Initiative (WAYI), was developed to improve knowledge of sexuality and reproductive health, and promote safer sex behaviors and contraceptive use among sexually active adolescents in Nigeria and Ghana. Between November 1994 and April 1997, two organizations, the Association for Reproductive and Family Health (ARFH), based in Nigeria, and Advocates for Youth, based in Washington D.C., supported community-based youth-serving organizations in the two countries to implement peer education projects. Consultants from the African Regional Health Education Centre (ARHEC) in Nigeria provided technical assistance in designing and conducting a quasi-experimental process and outcome evaluation of the projects. There were significant differences over time and between intervention and control groups concerning reproductive health knowledge, use of contraceptives in the previous 3 months, willingness to buy contraceptives, and self-efficacy in contraceptive use. Overall, the project provides evidence that peer education is most effective at improving knowledge and promoting attitudinal and behavior change among young people in school settings.

  9. A new perspective on West African hydroclimate during the last deglaciation

    Science.gov (United States)

    Parker, Andrew O.; Schmidt, Matthew W.; Jobe, Zane R.; Slowey, Niall C.

    2016-09-01

    Widespread drought characterized the Heinrich 1 and Younger Dryas cold periods of the last deglaciation throughout much of Africa, causing large increases in dust emissions from the Sahara and Sahel. At the same time, increases in wind strength may have also contributed to dust flux, making it difficult to interpret dust records alone as reflecting changes in rainfall over the region. The Niger River has the third largest drainage basin in Africa and drains most of the Sahara and Sahel and thus preserves and propagates climatic signals. Here, we present new reconstructions of Niger Delta sea surface salinity and Niger River discharge for the last 20,000 years in order to more accurately reconstruct the onset of the Western African Monsoon system. Based on calculated δ18OSEAWATER (δ18OSW) and measured Ba/Ca ratios in planktonic foraminifera, these new records reflect changes in sub-Saharan precipitation across the Niger River Basin in West Africa and reveal that the West African Monsoon system began to intensify several thousand years after the equatorial Monsoon system in Central Africa. We also present new records of primary productivity in the Niger Delta that are related to wind-driven upwelling and show that productivity is decoupled from changes in Niger River discharge. Our results suggest that wind strength, rather than changes in monsoon moisture, was the primary driver of dust emissions from the Sahara and Sahel across the last deglaciation.

  10. Geographical assessment of body measurements and qualitative traits in West African cattle.

    Science.gov (United States)

    Traoré, Amadou; Koudandé, Delphin Oloronto; Fernández, Iván; Soudré, Albert; Granda, Víctor; Álvarez, Isabel; Diarra, Siaka; Diarra, Fousseyni; Kaboré, Adama; Sanou, Moumouni; Tamboura, Hamidou Hamadou; Goyache, Félix

    2015-12-01

    A total of 1015 adult cows belonging to nine West African cattle breeds were assessed for 16 body measurements and 18 qualitative traits to ascertain the existence of geographical patterns of variation. Sampling was carried out in 29 different provinces of Mali, Burkina Faso and Benin. For body measurements, taurine breeds took lower average values than the zebu breeds. Sanga cattle took intermediate values. Qualitative traits did not allow to differentiate among cattle groups (taurine, zebu or sanga) or breeds. Principal component analysis identified two factors explaining 56.4 and 9.2 % of the variance for body measurements, respectively. Two correspondence analysis dimensions computed on qualitative traits explained a small proportion of the variability (20.8 and 13.5 %, respectively). Contour plots were constructed using the eigenvalues computed for each individual and either factor or dimension identified; confidence regions calculated confirmed that body measurements clearly differentiated zebu and taurine cattle breeds while qualitative traits did not. Factor 1 was projected on a geographical map, using provinces as nodes, to assess breed-free variation for body measurements. A pattern of continuous variation from the Sahel area southwards was identified. Probably, breeding decisions promoting the crosses between zebu-like and taurine cattle are underlying this geographical pattern of variation. The implementation of selection strategies aiming at the increase of the productivity of native West African taurine cattle breeds while avoiding looses in trypanotolerant ability would be highly advisable.

  11. Outcome of left heart mechanical valve replacement in West African children - A 15-year retrospective study

    Directory of Open Access Journals (Sweden)

    Tamatey Martin

    2011-04-01

    Full Text Available Abstract Background The West African sub-region has poor health infrastructure. Mechanical valve replacement in children from such regions raises important postoperative concerns; among these, valve-related morbidity and complications of lifelong anticoagulation are foremost. Little is known about the long-term outcome of mechanical valve replacement in West Africa. We sought to determine the outcome of mechanical valve replacement of the left heart in children from this sub-region. Method We conducted a retrospective review of all consecutive left heart valve replacements in children ( Results One hundred and fourteen patients underwent mitral valve replacement (MVR, aortic valve replacement (AVR or mitral and aortic valve replacements (MAVR. Their ages ranged from 6-18 years (13.3 ± 3.1 years. All patients were in NYHA class III or IV. Median follow up was 9.1 years. MVR was performed in 91 (79.8% patients, AVR in 13 (11.4% and MAVR in 10 (8.8% patients. Tricuspid valve repair was performed concomitantly in 45 (39.5% patients. There were 6 (5.3% early deaths and 6 (5.3% late deaths. Preoperative left ventricular dysfunction (ejection fraction Conclusion Mechanical valve replacement in West African children has excellent outcomes in terms of mortality, valve-related events, and reoperation rate. Preoperative left ventricular dysfunction is the primary determinant of mortality within the first 2 years of valve replacement. The risk of valve-related complications is acceptably low. Anticoagulation is well tolerated with a very low risk of bleeding even in this socioeconomic setting.

  12. Macro-habitat preferences by the African manatee and crocodiles – ecological and conservation implications

    OpenAIRE

    L. Luiselli; Akani, G. C.; N. Ebere; Angelici, F.M.; Amori, G.; Politano, E.

    2012-01-01

    African manatees (Trichechus senegalensis) and crocodiles are threatened species in parts of their range. In West Africa, crocodiles may constitute the main predators for manatees apart from humans. Here, we explore the macro-habitat selection of manatees and two species of crocodiles (West African crocodiles Crocodylus suchus and dwarf crocodile Osteolaemus tetraspis) in the Niger Delta (Nigeria), testing the hypotheses that (i) manate...

  13. Mode of production and population patterns: policy implications for West African development.

    Science.gov (United States)

    Franke, R W

    1981-01-01

    Recent developments in population theory have made possible a re-examination of demographic evidence from West Africa which suggests that population growth and migration are primarily responses to changes in the nature of the production system. Precolonial, colonial, and independence period data provide a series of correlations consistent with the approach and suggest a possible new synthesis of the West African data. The poorest countries of West Africa are those bordering on the Sahara Desert, known as the "Sahel" region. In response to the drought and famine in that region from 1968-1974, numerous proposals have been made for increased attention to reducing population growth. The analysis presented in this paper leads to the conclusion that population policies other than those attempting to lower the birth rate are called for. These would include relocation of populations previously displaced by colonial labor migrations and the re-integration of herding and farming production systems, both of which policies should be considered as population policies. Data are presented from specific projects underway in Senegal, Mauritania, and Mali, to illustrate the argument.

  14. The Impact of Desert Dust Aerosol Radiative Forcing on Global and West African Precipitation

    Science.gov (United States)

    Jordan, A.; Zaitchik, B. F.; Gnanadesikan, A.; Dezfuli, A. K.

    2015-12-01

    Desert dust aerosols exert a radiative forcing on the atmosphere, influencing atmospheric temperature structure and modifying radiative fluxes at the top of the atmosphere (TOA) and surface. As dust aerosols perturb radiative fluxes, the atmosphere responds by altering both energy and moisture dynamics, with potentially significant impacts on regional and global precipitation. Global Climate Model (GCM) experiments designed to characterize these processes have yielded a wide range of results, owing to both the complex nature of the system and diverse differences across models. Most model results show a general decrease in global precipitation, but regional results vary. Here, we compare simulations from GFDL's CM2Mc GCM with multiple other model experiments from the literature in order to investigate mechanisms of radiative impact and reasons for GCM differences on a global and regional scale. We focus on West Africa, a region of high interannual rainfall variability that is a source of dust and that neighbors major Sahara Desert dust sources. As such, changes in West African climate due to radiative forcing of desert dust aerosol have serious implications for desertification feedbacks. Our CM2Mc results show net cooling of the planet at TOA and surface, net warming of the atmosphere, and significant increases in precipitation over West Africa during the summer rainy season. These results differ from some previous GCM studies, prompting comparative analysis of desert dust parameters across models. This presentation will offer quantitative analysis of differences in dust aerosol parameters, aerosol optical properties, and overall particle burden across GCMs, and will characterize the contribution of model differences to the uncertainty of forcing and climate response affecting West Africa.

  15. Evidence of common signatures of selection in the genomes of West African cattle and the Yoruba human population

    Science.gov (United States)

    In 1954, Allison found that the sickle-cell anemia mutation in the beta hemoglobin gene was highly prevalent in West African people because it is protective against malaria, so carriers would thrive and leave offspring in spite of the genetic disease. This is one of the earliest evidences of an envi...

  16. Breeding performance of the Grasshopper Buzzard (Butastur rufipennis) in a natural and a human-modified West African savanna

    NARCIS (Netherlands)

    Buij, R.; Kortekaas, K.; Krimpen, R.R.D.; Wijk, van H.J.; Zanden, S.; Iongh, de H.H.; Heitkonig, I.M.A.; Snoo, de G.R.; Komdeur, J.

    2013-01-01

    Few studies have examined raptor reproduction in response to land-use change in sub-Saharan Africa, hampering conservation efforts to address regional declines. To further our understanding of mechanisms underlying the dramatic declines of West African raptors, we examined the relationship between

  17. Exploring the Interplay of Cultural Capital, "Habitus," and Field in the Life Histories of Two West African Teacher Candidates

    Science.gov (United States)

    Park, Gloria; Rinke, Carol; Mawhinney, Lynnette

    2016-01-01

    This paper captures the life histories of two West African pre-service teachers pursuing their education in the United States. Based on a larger study examining the life histories of 45 undergraduate pre-service teachers, these narratives focus specifically on international student experiences in the US. Grounded in Bourdieu's theory of…

  18. PTSD symptom structure among West African war trauma survivors living in African refugee camps: a factor-analytic investigation.

    Science.gov (United States)

    Vinson, Gregory A; Chang, Zoua

    2012-04-01

    We examined the factor structure of measured posttraumatic stress disorder (PTSD) symptoms in a sample of West African civilian refugees who had fled the civil war in Sierra Leone between 2001 and 2006. Given that such war-affected populations are common but understudied in trauma research, our objective was to examine the similarities and differences in this factor structure compared to prevailing models of PTSD symptom structure. As part of treatment services provided in refugee camps, refugees (2,140 women, 1,662 men, 1 unknown) from Sierra Leone, Liberia, and Guinea completed the 17 symptoms portion of the Posttraumatic Stress Diagnostic Scale (PDS). We used exploratory and confirmatory factor analyses to investigate whether there was a factor structure unique to this population, and made comparisons with the numbing, dysphoria, and aroused intrusion models. Results from the confirmatory analyses showed that the dysphoria model best fit the data (root mean square error of approximation [RMSEA] = .062); however, exploratory analyses revealed that 3 items loaded differently than theoretically expected. Psychological distress cross-loaded on reexperiencing and avoidance factors and physiological reactivity loaded on the avoidance factor instead of the reexperiencing factor. The sleep difficulties item was not well explained, generally; the highest loading (λ = .22) was on the dysphoria factor. Copyright © 2012 International Society for Traumatic Stress Studies.

  19. T-lymphocyte subsets in West African children: impact of age, sex, and season

    DEFF Research Database (Denmark)

    Lisse, I M; Aaby, P; Whittle, H

    1997-01-01

    OBJECTIVE: There has been no reference material for T-lymphocyte subsets for normal children in developing countries. We therefore used T-lymphocyte subset determinations among children in three different studies in Guinea-Bissau to construct age-related reference material and to examine possible...... determinants of T-lymphocyte subset levels. METHODS: A total of 803 healthy West African children younger than 6 years were included in the three community studies of T-lymphocyte subsets among twins and singletons, after measles infection and after measles immunization. We used the immunoalkaline phosphatase...... method to determine T-lymphocyte subsets. RESULTS: We found differences by age, sex, and season, whereas there were no significant differences by birth order, twinning, or ethnic group. The CD4+ percentage declined from birth to age 2 years, at which time it started to increase to higher levels at age 4...

  20. The complex vaginal flora of West African women with bacterial vaginosis.

    Science.gov (United States)

    Pépin, Jacques; Deslandes, Sylvie; Giroux, Geneviève; Sobéla, François; Khonde, Nzambi; Diakité, Soumaila; Demeule, Sophie; Labbé, Annie-Claude; Carrier, Nathalie; Frost, Eric

    2011-01-01

    The spectrum of bacteria associated with bacterial vaginosis (BV) has recently expanded through taxonomic changes and the use of molecular methods. These methods have yet to be used in large-scale epidemiological studies in Africa where BV is highly prevalent. An analysis of samples obtained during a clinical trial of the management of vaginal discharge in four West African countries. Samples were available from 1555 participants; 843 (54%) had BV. Nucleic acids of 13 bacterial genera or species potentially associated with BV were detected through the polymerase chain reaction. The associations between various components of the vaginal flora were complex. Excluding Lactobacillus, the other 12 micro-organisms were all associated with each other at the p≤0.001 level. The prevalence of various bacterial genera or species varied according to age, sexual activity and HIV status. In multivariate analysis, the presence of Gardnerella vaginalis, Bifidobacterium, Megasphaera elsdenii, Dialister, Mycoplasma hominis, Leptotrichia, and Prevotella were independently associated with BV as was the absence of Lactobacillus and Peptoniphilus. However, Mobiluncus, Atopobium vaginae, Anaerococcus, and Eggerthella were not independently associated with BV. Unexpectedly, after treatment with a regimen that included either metronidazole or tinidazole, the proportion of patients with a complete resolution of symptoms by day 14 increased with the number of bacterial genera or species present at enrolment. Numerous bacterial genera or species were strongly associated with each other in a pattern that suggested a symbiotic relationship. BV cases with a simpler flora were less likely to respond to treatment. Overall, the vaginal flora of West African women with BV was reminiscent of that of their counterparts in industrialized countries.

  1. The complex vaginal flora of West African women with bacterial vaginosis.

    Directory of Open Access Journals (Sweden)

    Jacques Pépin

    Full Text Available BACKGROUND: The spectrum of bacteria associated with bacterial vaginosis (BV has recently expanded through taxonomic changes and the use of molecular methods. These methods have yet to be used in large-scale epidemiological studies in Africa where BV is highly prevalent. METHODS: An analysis of samples obtained during a clinical trial of the management of vaginal discharge in four West African countries. Samples were available from 1555 participants; 843 (54% had BV. Nucleic acids of 13 bacterial genera or species potentially associated with BV were detected through the polymerase chain reaction. RESULTS: The associations between various components of the vaginal flora were complex. Excluding Lactobacillus, the other 12 micro-organisms were all associated with each other at the p≤0.001 level. The prevalence of various bacterial genera or species varied according to age, sexual activity and HIV status. In multivariate analysis, the presence of Gardnerella vaginalis, Bifidobacterium, Megasphaera elsdenii, Dialister, Mycoplasma hominis, Leptotrichia, and Prevotella were independently associated with BV as was the absence of Lactobacillus and Peptoniphilus. However, Mobiluncus, Atopobium vaginae, Anaerococcus, and Eggerthella were not independently associated with BV. Unexpectedly, after treatment with a regimen that included either metronidazole or tinidazole, the proportion of patients with a complete resolution of symptoms by day 14 increased with the number of bacterial genera or species present at enrolment. CONCLUSIONS: Numerous bacterial genera or species were strongly associated with each other in a pattern that suggested a symbiotic relationship. BV cases with a simpler flora were less likely to respond to treatment. Overall, the vaginal flora of West African women with BV was reminiscent of that of their counterparts in industrialized countries.

  2. Anti-Toxoplasma activity of vegetal extracts used in West African traditional medicine

    Directory of Open Access Journals (Sweden)

    Benoit-Vical F.

    2000-03-01

    Full Text Available Both Toxoplasma gondii and Plasmodium are Apicomplexan protozoa that share common metabolic pathways and potential drug targets. The objective of this study was to examine the anti- Toxoplasma activity of nine West African plants with known activity against P. falciparum. The extracts were obtained from parts of plant commonly used, by most traditional healers, in the form of infusion or as water decoction. The in vitro activity of plant extracts on T. gondii was assessed on MRC5 tissue cultures and was quantified by enzyme-linked immunoassay. Aqueous extracts from Vernonia colorata were found to be inhibitory for Toxoplasma growth at concentrations > 10 mg/L, with an IC50 of 16.3 mg/L. A ten-fold gain in activity was obtained when organic solvents such as dichloromethane, acetone or ethanol were used to extract V. colorata's active principles. These extracts were inhibitory at concentrations as low as 1 mg/L, with IC50 of 1.7, 2.6 and 2.9 mg/L for dichloromethane, acetone and ethanol extracts respectively. These results indicate a promising source of new anti-Toxoplasma drugs from V. colorata and African medicinal plants.

  3. Tracking cashew economically important diseases in the West African region using metagenomics

    Directory of Open Access Journals (Sweden)

    Filipa eMonteiro

    2015-06-01

    Full Text Available During the last decades, agricultural land-uses in West Africa were marked by dramatic shifts in the coverage of individual crops. Nowadays, cashew (Anacardium occidentale L. is one of the most export-oriented horticulture crops, notably in Guinea-Bissau. Relying heavily on agriculture to increase their income, developing countries have been following a strong trend of moving on from traditional farming systems towards commercial production. Emerging infectious diseases, driven either by adaptation to local conditions or inadvertent importation of plant pathogens, are able to cause tremendous cashew production losses, with economic and social impact of which, in developing countries is often underestimated. Presently, plant genomics with metagenomics as an emergent tool, presents an enormous potential to better characterize diseases by providing extensive knowledge on plant pathogens at a large scale. In this perspective, we address metagenomics as a promising genomic tool to identify cashew fungal associated diseases as well as to discriminate the causal pathogens, aiming at obtaining tools to help design effective strategies for disease control and thus promote the sustainable production of cashew in West African region.

  4. Model Simulations of Complex Dust Emissions over the Sahara during the West African Monsoon Onset

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    Carolina Cavazos-Guerra

    2012-01-01

    Full Text Available The existing limitations in ground-based observations in remote areas in West Africa determine the dependence on numerical models to represent the atmospheric mechanisms that contribute to dust outbreaks at different space-time scales. In this work, the ability of the Weather Research and Forecasting model coupled with the Chemistry (WRF-Chem model using the GOCART dust scheme is evaluated. The period comprises the West African Monsoon onset phase (the 7th to 12th of June, 2006 coinciding with the AMMA Special Observing Period (SOP. Different features in the horizontal and vertical dynamical structure of the Saharan atmosphere are analyzed with a combination of satellite and ground-based observations and model experimentation at 10 and 30 km model resolution. The main features of key Saharan dust processes during summer are identifiable, and WRF-CHEM replicates these adequately. Observations and model analyses have shown that cold pools (haboobs contributed a substantial proportion of total dust during the study period. The comparative analysis between observations and WRF-Chem simulations demonstrates the model efficiency to simulate the spatial and 3D structure of dust transport over the Sahara and Sahel. There is, therefore, a strong basis for accurate forecasting of dust events associated with synoptic scale events when model dust emission parameterization is suitably calibrated.

  5. Genome-Wide Divergence in the West-African Malaria Vector Anopheles melas

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    Kevin C. Deitz

    2016-09-01

    Full Text Available Anopheles melas is a member of the recently diverged An. gambiae species complex, a model for speciation studies, and is a locally important malaria vector along the West-African coast where it breeds in brackish water. A recent population genetic study of An. melas revealed species-level genetic differentiation between three population clusters. An. melas West extends from The Gambia to the village of Tiko, Cameroon. The other mainland cluster, An. melas South, extends from the southern Cameroonian village of Ipono to Angola. Bioko Island, Equatorial Guinea An. melas populations are genetically isolated from mainland populations. To examine how genetic differentiation between these An. melas forms is distributed across their genomes, we conducted a genome-wide analysis of genetic differentiation and selection using whole genome sequencing data of pooled individuals (Pool-seq from a representative population of each cluster. The An. melas forms exhibit high levels of genetic differentiation throughout their genomes, including the presence of numerous fixed differences between clusters. Although the level of divergence between the clusters is on a par with that of other species within the An. gambiae complex, patterns of genome-wide divergence and diversity do not provide evidence for the presence of pre- and/or postmating isolating mechanisms in the form of speciation islands. These results are consistent with an allopatric divergence process with little or no introgression.

  6. Changes in the interannual SST-forced signals on West African rainfall. AGCM intercomparison

    Energy Technology Data Exchange (ETDEWEB)

    Mohino, Elsa [LOCEAN/IPSL, Universite Pierre et Marie Curie, Paris Cedex 05 (France); Universidad de Sevilla, Sevilla (Spain); Rodriguez-Fonseca, Belen [Universidad Complutense de Madrid, Dpto. Geofisica y Meteorologia, Madrid (Spain); Instituto de Geociencias (CSIC-UCM), Madrid (Spain); Losada, Teresa [Universidad Complutense de Madrid, Dpto. Geofisica y Meteorologia, Madrid (Spain); Gervois, Sebastien [LOCEAN/IPSL, Universite Pierre et Marie Curie, Paris Cedex 05 (France); Janicot, Serge [LOCEAN/IPSL, IRD, Universite Pierre et Marie Curie, Paris (France); Bader, Juergen [Bjerknes Centre for Climate Research, Bergen (Norway); Ruti, Paolo [Progetto Speciale Clima Globale, Ente Nazionale per le Nuove Tecnologie, l' Energia e l' Ambiente, Rome (Italy); Chauvin, Fabrice [GAME/CNRM, Meteo-France/CNRS, Toulouse (France)

    2011-11-15

    Rainfall over West Africa shows strong interannual variability related to changes in Sea Surface Temperature (SST). Nevertheless, this relationship seem to be non-stationary. A particular turning point is the decade of the 1970s, which witnessed a number of changes in the climatic system, including the climate shift of the late 1970s. The first aim of this study is to explore the change in the interannual variability of West African rainfall after this shift. The analysis indicates that the dipolar features of the rainfall variability over this region, related to changes in the Atlantic SST, disappear after this period. Also, the Pacific SST variability has a higher correlation with Guinean rainfall in the recent period. The results suggest that the current relationship between the Atlantic and Pacific El Nino phenomena is the principal responsible for these changes. A fundamental goal of climate research is the development of models simulating a realistic current climate. For this reason, the second aim of this work is to test the performance of Atmospheric General Circulation models in simulating rainfall variability over West Africa. The models have been run with observed SSTs for the common period 1957-1998 as part of an intercomparison exercise. The results show that the models are able to reproduce Guinean interannual variability, which is strongly related to SST variability in the Equatorial Atlantic. Nevertheless, problems in the simulation of the Sahelian interannual variability appear: not all models are able to reproduce the observed negative link between rainfall over the Sahel and El Nino-like anomalies in the Pacific, neither the positive correlation between Mediterranean SSTs and Sahelian rainfall. (orig.)

  7. Incidence of pregnancy following antiretroviral therapy initiation and associated factors in eight West African countries

    Science.gov (United States)

    Burgos-Soto, Juan; Balestre, Eric; Minga, Albert; Ajayi, Samuel; Sawadogo, Adrien; Zannou, Marcel D.; Leroy, Valériane; Ekouevi, Didier K.; Dabis, François; Becquet, Renaud

    2014-01-01

    Introduction This study aimed at estimating the incidence of pregnancy after antiretroviral therapy (ART) initiation in eight West African countries over a 10-year period. Methods A retrospective analysis was conducted within the international database of the IeDEA West Africa Collaboration. All HIV-infected women aged <50 years and starting ART for their own health between 1998 and 2011 were eligible. Pregnancy after ART initiation was the main outcome and was based on clinical reporting. Poisson regression analysis accounting for country heterogeneity was computed to estimate first pregnancy incidence post-ART and to identify its associated factors. Pregnancy incidence rate ratios were adjusted on country, baseline CD4 count and clinical stage, haemoglobin, age, first ART regimen and calendar year. Results Overall 29,425 HIV-infected women aged 33 years in median [Inter Quartile Range: 28–38] contributed for 84,870 women-years of follow-up to this analysis. The crude incidence of first pregnancy (2,304 events) was 2.9 per 100 women-years [95% confidence interval [CI]: 2.7–3.0], the highest rate being reported among women aged 25–29 years: 4.7 per 100 women-years; 95% CI: 4.3–5.1. The overall Kaplan-Meier probability of pregnancy occurrence by the fourth year on ART was 10.9% (95% CI: 10.4–11.4) and as high as 28.4% (95% CI: 26.3–30.6) among women aged 20–29 years at ART initiation. Conclusion The rate of pregnancy occurrence after ART initiation among HIV-infected women living in the West Africa region was high. Family planning services tailored to procreation needs should be provided to all HIV-infected women initiating ART and health consequences carefully monitored in this part of the world. PMID:25216079

  8. West African monsoon decadal variability and surface-related forcings: second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II)

    Science.gov (United States)

    Xue, Yongkang; De Sales, Fernando; Lau, William K.-M.; Boone, Aaron; Kim, Kyu-Myong; Mechoso, Carlos R.; Wang, Guiling; Kucharski, Fred; Schiro, Kathleen; Hosaka, Masahiro; Li, Suosuo; Druyan, Leonard M.; Sanda, Ibrah Seidou; Thiaw, Wassila; Zeng, Ning; Comer, Ruth E.; Lim, Young-Kwon; Mahanama, Sarith; Song, Guoqiong; Gu, Yu; Hagos, Samson M.; Chin, Mian; Schubert, Siegfried; Dirmeyer, Paul; Ruby Leung, L.; Kalnay, Eugenia; Kitoh, Akio; Lu, Cheng-Hsuan; Mahowald, Natalie M.; Zhang, Zhengqiu

    2016-12-01

    The second West African Monsoon Modeling and Evaluation Project Experiment (WAMME II) is designed to improve understanding of the possible roles and feedbacks of sea surface temperature (SST), land use land cover change (LULCC), and aerosols forcings in the Sahel climate system at seasonal to decadal scales. The project's strategy is to apply prescribed observationally based anomaly forcing, i.e., "idealized but realistic" forcing, in simulations by climate models. The goal is to assess these forcings' effects in producing/amplifying seasonal and decadal climate variability in the Sahel between the 1950s and the 1980s, which is selected to characterize the great drought period of the last century. This is the first multi-model experiment specifically designed to simultaneously evaluate such relative contributions. The WAMME II models have consistently demonstrated that SST forcing is a major contributor to the twentieth century Sahel drought. Under the influence of the maximum possible SST forcing, the ensemble mean of WAMME II models can produce up to 60 % of the precipitation difference during the period. The present paper also addresses the role of SSTs in triggering and maintaining the Sahel drought. In this regard, the consensus of WAMME II models is that both Indian and Pacific Ocean SSTs greatly contributed to the drought, with the former producing an anomalous displacement of the Intertropical Convergence Zone before the WAM onset, and the latter mainly contributes to the summer WAM drought. The WAMME II models also show that the impact of LULCC forcing on the Sahel climate system is weaker than that of SST forcing, but still of first order magnitude. According to the results, under LULCC forcing the ensemble mean of WAMME II models can produces about 40 % of the precipitation difference between the 1980s and the 1950s. The role of land surface processes in responding to and amplifying the drought is also identified. The results suggest that catastrophic

  9. Pattern of skin infections in black Africans of Sierra Leone (West Africa

    Directory of Open Access Journals (Sweden)

    Bari Arfan ul

    2007-01-01

    Full Text Available Background: Physical differences among human populations may lead to variable prevalence of skin disorders in different ethnicities. Skin infections are one of the important curable and largely preventable categories of skin disorders in the communities. Aim: The purpose of the study was to see the patterns of skin infections in black Africans of Sierra Leone and to compare with other ethnic populations. Materials and Methods: Local blacks of all age groups presenting in Dermatology out patient department of Pak Field Hospital (established as a part of UN peacekeeping mission in Sierra Leone were included (from Nov 2004 to Oct 2005. Relevant clinical history and physical examination was done. Laboratory investigations were carried out when indicated. Skin diseases were broadly classified into two major categories i.e., infective and noninfective. Among infective, sexually transmitted infections were again separated. Nonblack settlers in the area and UN troops were not included in the study. Data was recorded and analyzed by Microsoft Excel program. Results: 3011 patients belonging to different local tribes having a variety of skin disorders were seen. Patients were of all ages and both sexes ranging from one month to 73 years of age. The Infective skin disorders were seen in 61.7% patients and most prevalent were superficial fungal infections (41.2% followed by, sexually transmitted infections (9.9% and parasitic infections (6.5%. Bacterial and viral infections were rare and so was the scabies. More than 90% parasitic infections were onchocerciasis with full spectrum of cutaneous manifestations. Conclusion: Pattern of skin infections in blacks varies considerably from other ethnic races. Environmental factors, geographical location and free existence of vector for onchocerciasis in West African region, possibly have a significant influence in this variable prevalence.

  10. Association between age at antiretroviral therapy initiation and 24-month immune response in West-African HIV-infected children

    DEFF Research Database (Denmark)

    Desmonde, Sophie; Dicko, Fatoumata; Koueta, Fla

    2014-01-01

    OBJECTIVE: We describe the association between age at antiretroviral therapy (ART) initiation and 24-month CD4 cell response in West African HIV-infected children. METHODS: All HIV-infected children from the IeDEA paediatric West African cohort, initiating ART, with at least two CD4 cell count...... measurements, including one at ART initiation (baseline) were included. CD4 cell gain on ART was estimated using a multivariable linear mixed model adjusted for baseline variables: age, CD4 cell count, sex, first-line ART regimen. Kaplan-Meier survival curves and a Cox proportional hazards regression model...... compared immune recovery for age within 24 months post-ART. RESULTS: Of the 4808 children initiated on ART, 3014 were enrolled at a median age of 5.6 years; 61.2% were immunodeficient. After 12 months, children at least 4 years at baseline had significantly lower CD4 cell gains compared with children less...

  11. Blindness and Visual Impairment in an Urban West African Population: The Tema Eye Survey

    Science.gov (United States)

    Budenz, Donald L.; Bandi, Jagadeesh R.; Barton, Keith; Nolan, Winifred; Herndon, Leon; Whiteside-de Vos, Julia; Hay-Smith, Graham; Kim, Hanna; Tielsch, James

    2012-01-01

    Objective To determine the prevalence, etiologies, and risk factors of blindness and visual impairment among persons age 40 years and older residing in an urban West African location. Design Population-based cross-sectional study. Participants Five thousand six hundred and three participants residing in Tema, Ghana. Methods Proportionate random cluster sampling was used to select participants age 40 and over living in the city of Tema. Presenting distance visual acuity was measured at 4 and 1 meters using a reduced Logarithm of the Minimum Angle of Resolution (logMAR) tumbling E chart and then with trial frame based on autorefraction. A screening examination was performed in the field on all participants. Complete clinical examination by an ophthalmologist was performed on participants with best corrected visual acuity visual acuity in the better eye of visual impairment (visual acuity in the better eye of visual impairment was 17.1% and blindness was 1.2%. After refraction and spectacle correction, the prevalence of visual impairment and blindness decreased to 6.7% and 0.75% respectively, suggesting that refractive error is the major correctable etiology of visual impairment and blindness in this population. Of 65 subjects having visual acuity visual impairment, and one to normal. The remaining 43 (66%) had underlying pathology (19 cataract, 9 glaucoma, 3 non-glaucomatous optic neuropathy, 3 corneal opacities, 3 retinal disease, 5 undetermined) that prevented refractive correction. Increased age was a significant risk factor for blindness and visual impairment. Conclusions There is a high prevalence of blindness and visual impairment among those aged ≥40 years in Tema, Ghana, West Africa. Refractive error is a major cause of blindness and visual impairment in this population, followed by cataract, glaucoma, and corneal disease. PMID:22677425

  12. Estimation of freshwater availability in the West African sub-continent using the SWAT hydrologic model

    Science.gov (United States)

    Schuol, Jürgen; Abbaspour, Karim C.; Srinivasan, Raghavan; Yang, Hong

    2008-04-01

    SummaryAccurate knowledge of freshwater availability is indispensable for water resources management at regional or national level. This information, however, has historically been very difficult to obtain because of lack of data, difficulties in the aggregation of spatial information, and problems in the quantification of distributed hydrological processes. The currently available estimates of freshwater availability by a few large international organizations such as FAO and UNESCO are often not sufficient as they only provide aggregated rough quantities of river discharge and groundwater recharge (blue water) at a national level and on a yearly basis. This paper aims to provide a procedure to improve the estimations of freshwater availability at subbasin level and monthly intervals. Applying the distributed hydrological model "Soil and Water Assessment Tool" (SWAT), the freshwater availability is quantified for a 4-million km 2 area covering some 18 countries in West Africa. The procedure includes model calibration and validation based on measured river discharges, and quantification of the uncertainty in model outputs using "Sequential Uncertainty Fitting Algorithm" (SUFI-2) The aggregated results for 11 countries are compared with two other studies. It was seen that for most countries, the estimates from the other two studies fall within our calculated prediction uncertainty ranges. The uncertainties are, in general, within reasonable ranges but larger in subbasins containing features such as dams and wetlands, or subbasins with inadequate climate or landuse information. As the modelling procedure in this study proved quite successful, its application for quantification of freshwater availability at a global scale is already underway. There are, however, two limitations in the West African model: (1) not all the components of the water balance model such as soil moisture or deep aquifer recharge could be directly calibrated because of lack of data and (2) the

  13. Impact of climate change on vegetation dynamics in a West African river basin

    Science.gov (United States)

    Sawada, Y.; Koike, T.

    2012-12-01

    Future changes in terrestrial biomass distribution under climate change will have a tremendous impact on water availability and land productivity in arid and semi-arid regions. Assessment of future change of biomass distribution in the regional or the river basin scale is strongly needed. An eco-hydrological model that fully couples a dynamic vegetation model (DVM) with a distributed biosphere hydrological model is applied to multi-model assessment of climate change impact on vegetation dynamics in a West African river basin. In addition, a distributed and auto optimization system of parameters in DVM is developed to make it possible to model a diversity of phonologies of plants by using different parameters in the different model grids. The simple carbon cycle modeling in a distributed hydrological model shows reliable accuracy in simulating the seasonal cycle of vegetation on the river basin scale. Model outputs indicate that generally, an extension of dry season duration and surface air temperature rising caused by climate change may cause a dieback of vegetation in West Africa. However, we get different seasonal and spatial changes of leaf area index and different mechanisms of the degradation when we used different general circulation models' outputs as meteorological forcing of the eco-hydrological model. Therefore, multi-model analysis like this study is important to deliver meaningful information to the society because we can discuss the uncertainties of our prediction by this methodology. This study makes it possible to discuss the impact of future change of terrestrial biomass on climate and water resources in the regional or the river basin scale although we need further sophistications of the system. Performance of the eco-hydrological model (WEB-DHM+DVM) in Volta River Basin, with basin-averaged leaf area index from model (blue solid line) and AVHRR satellite-derived product (red rectangles).

  14. Securing Security Governance in Post-conflict Situation : A Framework of Conflict Prevention through ECOWARN in West African Region

    OpenAIRE

    Yamane, Tatsuo

    2013-01-01

    This article focuses on an analytical approach of “security governance” in light of post-conflict situation and aims to examine a system of conflict prevention in the West African region from a viewpoint of the approach. The security governance initially developed security studies of International Relations especially for the regional governance in the field of European security. On that basis of making and developing the new perspective for the region, it currently goes to expand the subject...

  15. Analysis of Science Process Skills in West African Senior Secondary School Certificate Physics Practical Examinations in Nigeria

    OpenAIRE

    A.O. Akinbobola; F. Afolabi

    2010-01-01

    This study analyzes the science process skills in West African senior secondary school certificate physics practical examinations in Nigeria for a period of 10 years (1998-2007). Ex-post facto design was adopted for the study. The 5 prominent science process skills identified out of the 15 used in the study are: manipulating (17%), calculating (14%), recording (14%), observing (12%) and communicating (11%). The results also show high percentage rate of basic (lower order) science process skil...

  16. A Drumming Dance: A Study on the Effects of West African Dance on Motor Performance and Motivation among Collegiate Dancers

    OpenAIRE

    Wajid-Ali, Darlisa Gloria

    2016-01-01

    Changes in cardiovascular health, balance, agility, and motivation were assessed during a 6-week West African dance and live drumming intervention with collegiate dancers. The study measured cardiovascular health with the Accelerated 3-Minute Step test, balance with the m/r Star Excursion Balance test, and agility with the Illinois Agility test. Motivation was measured using the Classroom Life Measure, Motivated Strategies Learning Questionnaire, and the Rosenberg Self-Esteem Scale. The inter...

  17. How Does Gender Affect Sustainable Intensification of Cereal Production in the West African Sahel? Evidence from Burkina Faso

    OpenAIRE

    Theriault, Veronique; Smale, Melinda; Haider, Hamza

    2017-01-01

    Summary Better understanding of gender differences in the adoption of agricultural intensification strategies is crucial for designing effective policies to close the gender gap while sustainably enhancing farm productivity. We examine gender differences in adoption rates, likelihood and determinants of adopting strategy sets that enhance yields, protect crops, and restore soils in the West African Sahel, based on analysis of cereal production in Burkina Faso. Applying a multivariate probit m...

  18. Strengthening malaria prevention and control: integrating West African militaries' malaria control efforts. The inaugural meeting of the West African Malaria Task Force, April 24-26, 2013, Accra, Ghana.

    Science.gov (United States)

    McCollum, Jeffrey T; Hanna, Refaat; Halbach, Alaina C; Cummings, James F

    2015-01-01

    From April 24 to 26, 2013, the Armed Forces Health Surveillance Center and the U.S. Africa Command cosponsored the inaugural meeting of the West Africa Malaria Task Force in Accra, Ghana. The meeting's purpose was to identify common challenges, explore regional and transcontinental collaborations, and to share knowledge about best practices in the fight against malaria in West Africa. Military representatives from Benin, Burkina Faso, Ghana, Liberia, Niger, Nigeria, Senegal, and Togo participated in the Task Force; various U.S. Government agencies were also represented, including the Department of Defense, the Centers for Disease Control and Prevention, and the Agency for International Development. African nation participants presented brief overviews of their military's malaria prevention and control measures, surveillance programs, diagnostic capabilities, and treatment regimens emphasizing gaps within existing programs. Representatives from U.S. agencies discussed activities and capabilities relevant for the region, challenges and lessons learned regarding malaria, and highlighted opportunities for enhanced partnerships to counter malaria in West Africa. This article summarizes the major conclusions of the Task Force meeting, identifies relevant focus areas for future Task Force activities, and outlines opportunities for further inclusion of West African militaries to improve regional malaria surveillance and control efforts.

  19. Determinants of suboptimal complementary feeding practices among children aged 6-23 months in four anglophone West African countries.

    Science.gov (United States)

    Issaka, Abukari I; Agho, Kingsley E; Page, Andrew N; Burns, Penelope L; Stevens, Garry J; Dibley, Michael J

    2015-10-01

    Suboptimal complementary feeding practices have a detrimental impact on a child's growth, health and development in the first two years of life. They lead to child malnutrition, which contributes to the high prevalence of stunting (38%) and underweight (28%) reported for children feeding practices in four anglophone West African countries (Ghana, Liberia, Nigeria and Sierra Leone) using the most recent Demographic and Health Surveys. The study covered 12 623 children aged 6-23 months from four anglophone West African countries (Ghana: 822 children: Liberia: 1458 children, Nigeria: 8786 children and Sierra Leone: 1557 children). Four complementary feeding indicators were examined against a set of individual-, household- and community-level factors, using multiple regression analysis. Multivariate analyses found that lack of post-natal contacts with health workers, maternal illiteracy and geographical region were common determinants of delayed introduction of solid, semi-solid or soft foods across all four countries. Predictors for minimum dietary diversity, minimum meal frequency and minimum acceptable diet included children aged 6-11 months, administrative/geographical region, poorer household income and limited access to media. The authors recommend that the four anglophone West African countries studied should prioritise efforts to improve complementary feeding practices in order to reduce child morbidity and mortality. Interventional studies on complementary feeding should target those from poor and illiterate households.

  20. Population structure of clinical Pseudomonas aeruginosa from West and Central African countries.

    Directory of Open Access Journals (Sweden)

    Pascal Cholley

    Full Text Available Pseudomonas aeruginosa (PA has a non-clonal, epidemic population with a few widely distributed and frequently encountered sequence types (STs called 'high-risk clusters'. Clinical P. aeruginosa (clinPA has been studied in all inhabited continents excepted in Africa, where a very few isolates have been analyzed. Here, we characterized a collection of clinPA isolates from four countries of West and Central Africa.184 non-redundant isolates of clinPA from hospitals of Senegal, Ivory Coast, Nigeria, and Central African Republic were genotyped by MLST. We assessed their resistance level to antibiotics by agar diffusion and identified the extended-spectrum β-lactamases (ESBLs and metallo-β-lactamases (MBLs by sequencing. The population structure of the species was determined by a nucleotide-based analysis of the entire PA MLST database and further localized on the phylogenetic tree (i the sequence types (STs of the present collection, (ii the STs by continents, (iii ESBL- and MBL-producing STs from the MLST database.We found 80 distinct STs, of which 24 had no relationship with any known STs. 'High-risk' international clonal complexes (CC155, CC244, CC235 were frequently found in West and Central Africa. The five VIM-2-producing isolates belonged to CC233 and CC244. GES-1 and GES-9 enzymes were produced by one CC235 and one ST1469 isolate, respectively. We showed the spread of 'high-risk' international clonal complexes, often described as multidrug-resistant on other continents, with a fully susceptible phenotype. The MBL- and ESBL-producing STs were scattered throughout the phylogenetic tree and our data suggest a poor association between a continent and a specific phylogroup.ESBL- and MBL-encoding genes are borne by both successful international clonal complexes and distinct local STs in clinPA of West and Central Africa. Furthermore, our data suggest that the spread of a ST could be either due to its antibiotic resistance or to features

  1. Exploring child prostitution in a major city in the West African region.

    Science.gov (United States)

    Hounmenou, Charles

    2016-09-01

    The study explored the characteristics of child prostitution in a major city in the West African region. A convenience sample of children in prostitution, specifically girls below age 18 (n=243), were recruited on 83 prostitution sites identified in Ouagadougou, the capital city of Burkina Faso. A survey instrument, consisting of 71 closed-ended question items, was used to explore various variables including profile of children in prostitution, factors of vulnerability to prostitution; prostitution practices, compensations and related issues in child prostitution. The findings show that most children in prostitution in the city were from Burkina Faso (63%) and Nigeria (30%), two countries that do not share borders. Most native respondents practiced prostitution for survival and to support their families. In contrast, all the respondents from Nigeria practiced prostitution as victims of international sex trafficking. An important finding was that 77% of the children in prostitution surveyed were educated. Among the respondents, there were similarities in the major life events that contributed to their situation of prostitution. These life events include early separation with parents, sexual abuse, foster care, and forced marriage. Implications for policy, practice and research are discussed.

  2. Instrumental Learning and Sustainability Indicators: Outputs from Co-Construction Experiments in West African Biosphere Reserves

    Directory of Open Access Journals (Sweden)

    Harold Levrel

    2008-06-01

    Full Text Available Co-adaptive management of biodiversity is largely based on a collective learning process. This collective learning concerns "instrumental policy learning," "social policy learning," and "political learning." This paper focuses on instrumental policy learning that has been launched in four West African biosphere reserves. It is based on a MAB-UNESCO/UNEP-GEF programme concerning the co-construction of interaction indicators (between development and conservation, inspired by the Integrated Natural Resource Management (INRM methodology. Using this process, we were able to test conventional Pressure-State-Response indicators, highlight their limitations, and develop new indicators starting from stakeholders' stories and perceptions. These new indicators can also be tested through collective restitutions and simulations. We also discuss: a proposed framework for producing interaction indicators that are relevant to all stakeholders and enjoy a certain legitimacy; the importance of an ecosystem services approach to support discussions on biodiversity conservation; opportunities for using the indicators in an interactive, decentralized way at the ecosystem scale through simulation models; the costs of collecting, processing, and maintaining these interaction indicators, and how these costs may be offset using local knowledge.

  3. Evolution of a Paleoproterozoic “weak type” orogeny in the West African Craton (Ivory Coast)

    Science.gov (United States)

    Vidal, M.; Gumiaux, C.; Cagnard, F.; Pouclet, A.; Ouattara, G.; Pichon, M.

    2009-11-01

    The Paleoproterozoic domain of the Ivory Coast lies in the central part of the West African Craton (WAC) and is mainly constituted by TTG, greenstones, supracrustal rocks and leucogranites. A compilation of metamorphic and radiometric data highlights that: i) metamorphic conditions are rather homogeneous through the domain, without important metamorphic jumps, ii) HP-LT assemblages are absent and iii) important volumes of magmas emplaced during the overall Paleoproterozoic orogeny suggesting the occurrence of long-lived rather hot geotherms. Results of the structural analysis, focused on three areas within the Ivory Coast, suggest that the deformation is homogeneous and distributed through the Paleoproterozoic domain. In details, results of this study point out the long-lived character of vertical movements during the Eburnean orogeny with a two folds evolution. The first stage is characterized by the development of "domes and basins" geometries without any boundary tectonic forces and the second stage is marked by coeval diapiric movements and horizontal regional-scale shortening. These features suggest that the crust is affected by vertical movements during the overall orogeny. The Eburnean orogen can then be considered as an example of long-lived Paleoproterozoic "weak type" orogen.

  4. West African Squall-Line Thermodynamic Structure Retrieved from Dual-Doppler Radar Observations.

    Science.gov (United States)

    Roux, Frank; Testud, Jacques; Payen, Marc; Pinty, Bernard

    1984-11-01

    Pressure and temperature fields within a West African squall line, retrieved from dual-Doppler radar data collected during the `COPT 81' (Convection Profonde Tropicale) experiment are presented. The method for derivation of thew results is approximately similar to that proposed by Gal-Chen, based on the anelastic equation of motion.Comparisons between pressure and temperature fields deduced from radar data at the lowest levels and surface network measurements show good agreement. The inferred thermodynamic structure displays the influence of a low-level frontward flow which is mainly due to a density current of cold air, generated in the stratiform region of the squall line and resulting from a mesoscale downdraft. This frontward flow contributes to initiate and maintain a frontal updraft through both nonhydrostatic pressure perturbation and temperature difference between entering air and colder frontward flow. At higher altitudes, mixing with the environment reduces buoyancy in the frontal updraft, while weaker convective updrafts develop in the inner region.Comparisons between these results and the kinematic and thermodynamic structures deduced from a previous observation (Le Mone, 1983) display different types of dynamics of organized convective systems.

  5. Analysis of farmers’ adaptation to weather extremes in West African Sudan Savanna

    Directory of Open Access Journals (Sweden)

    David Boansi

    2017-06-01

    Full Text Available There have been recent incidences of weather extremes in the West African Sudan Savanna and farmers have responded through implementation of relevant adaptation strategies. For a deeper insight into farmers’ adaptation to climatic shocks, this study documents farmers’ perception of recent changes in the local climate, and identifies factors that influence the number and choice of strategies implemented. Interdependencies among strategies are explored and joint and marginal probabilities of adoption estimated. Upper East Ghana and Southwest Burkina Faso are used as the case study regions. These regions were selected due to extreme reliance of inhabitants on agriculture for sustenance, and their recent exposure to weather extremes. Through estimation of a Poisson regression and multivariate probit model to identify the major factors that influence the number and choice of strategies adopted, we discover that, limited access to credit, markets, and extension services, smaller cropland area, and low level of mechanization could impede effective adaptation to weather extremes. To enhance farmers’ adaptive capacity, policy makers and various stakeholders need to contribute towards improving farmers’ access to credit, markets, and extension services, and implement measures to promote mechanization.

  6. The West African Monsoon simulated by global and regional climate models

    Science.gov (United States)

    Nikulin, Grigory; Jones, Colin; Kjellström, Erik; Gbobaniyi, Emiola

    2013-04-01

    We present results from two ensembles of global and regional climate simulations with a focus on the West African Monsoon (WAM). The first ensemble includes eight coupled atmosphere ocean general circulation models (AOGCMs) from the CMIP5 project, namely: CanESM2, CNRM-CM5, HadGEM2-ES, NorESM1-M, EC-EARTH, MIROC5, GFDL-ESM2M and MPI-ESM-LR. The second ensemble consists of corresponding downscaling of all 8 AOGCMs by a regional climate model - RCA4 produced at the Rossby Centre (SMHI) in the Africa-CORDEX activities. Spatial resolution varies from about 1° to 3° in the AOGCM ensemble while all regional simulations are at the same 0.44° resolution. To see what added value higher resolution can provide ability of the eight AOGCMs and the downscaled RCA4(AOGCMs) to simulate the key characteristics of the WAM rainy season are evaluated and then inter-compared between the global and regional ensembles. The main focus in our analysis is on the WAM rainy season onset, cessation, length, total precipitation, its mean intensity and intraseasonal variability. Future climate projections under the RCP45 and RCP85 scenarios are analyzed and again inter-compared for both ensembles in order to assess uncertainties in the future projections of the WAM rainy season from the global and regional ensembles.

  7. Effect of feeding some West African browse foliages on growth and carcass composition in sheep.

    Science.gov (United States)

    Ouédraogo-Koné, Salifou; Kaboré-Zoungrana, Chantal Y; Ledin, Inger

    2009-10-01

    The effect of feeding foliage from Afzelia africana, Pterocarpus erinaceus or Khaya senegalensis on growth performance was evaluated using 32 West African Djallonké rams of about 8 months of age and with a mean initial body weight (BW) of 16.1 kg. The animals were randomly assigned to four groups of 8 animals and the experiment lasted for 13 weeks. All the animals received the same amount of hay from Andropogon gayanus and maize bran (200 g/day each) and dried foliage ad libitum. The control group was fed cottonseed cake in restricted amounts. The animals were able to consume higher amounts of A. africana than of P. erinaceus and K. senegalensis. There was no significant difference in growth rate between sheep offered A. africana or P. erinaceus, 62.9 and 58.8 g/d, respectively, but sheep offered K. senegalensis had a lower average daily gain, 48 g/day (P < 0.05) due to lower consumption of both energy and crude protein. Animals in the control group had the highest growth rate, 95.8 g/day. Sheep offered P. erinaceus and K. senegalensis had similar carcass characteristics and dressing percentage but lower fasted BW, empty BW, carcass weight and dressing percentage (P < 0.05) than sheep offered A. africana. These tree species can provide valuable feed during periods of feed shortage in the humid and sub-humid zones.

  8. Stratospheric variability of wave activity and parameters in equatorial coastal and tropical sites during the West African monsoon

    Science.gov (United States)

    Kafando, P.; Chane-Ming, F.; Petitdidier, M.

    2016-12-01

    Recent numerical studies in stratospheric dynamics and its variability as well as climate, have highlighted the need of more observational analyses to improve simulation of the West African monsoon (WAM). In this paper, activity and spectral characteristics of short-scale vertical waves (wavelengths tropical lower stratosphere during the WAM. A first detailed description of such waves over West Africa is derived from high-resolution vertical profiles of temperature and horizontal wind obtained during Intensive Observation Period of the African Monsoon Multidisciplinary Analyses (AMMA) Campaign 2006. Monthly variation of wave energy density is revealed to trace the progression of the inter-tropical convergence zone (ITCZ) over West Africa. Mesoscale inertia gravity-waves structures with vertical and horizontal wavelengths of 1.5-2.5 and 400-1100 km respectively and intrinsic frequencies of 1.1-2.2 f or periods tropical LS with intense activity during July and August when the WAM is installed over the tropical West Africa. Over equatorial region, gravity waves with intrinsic frequencies of 1.4-4 f or periods tropical stations.

  9. African Sub-Regional Organizations in Peacekeeping and Peacemaking: The Economic Community of West African State (ECOWAS)

    Science.gov (United States)

    2005-03-01

    West Africa.18 At the advent of the Liberian crisis ECOWAS attempted to move quickly from dealing with economic to security 17 Confort Ero and A...www.reliefweb.int/w/rwb.ns> (8 February 2005). Confort Ero and A, Ndinga-Muvumba, "Small Arms, Light Weapons", in Adekeye Adebajo and Ismail Rashid, West

  10. Above ground biomass estimation from lidar and hyperspectral airbone data in West African moist forests.

    Science.gov (United States)

    Vaglio Laurin, Gaia; Chen, Qi; Lindsell, Jeremy; Coomes, David; Cazzolla-Gatti, Roberto; Grieco, Elisa; Valentini, Riccardo

    2013-04-01

    The development of sound methods for the estimation of forest parameters such as Above Ground Biomass (AGB) and the need of data for different world regions and ecosystems, are widely recognized issues due to their relevance for both carbon cycle modeling and conservation and policy initiatives, such as the UN REDD+ program (Gibbs et al., 2007). The moist forests of the Upper Guinean Belt are poorly studied ecosystems (Vaglio Laurin et al. 2013) but their role is important due to the drier condition expected along the West African coasts according to future climate change scenarios (Gonzales, 2001). Remote sensing has proven to be an effective tool for AGB retrieval when coupled with field data. Lidar, with its ability to penetrate the canopy provides 3D information and best results. Nevertheless very limited research has been conducted in Africa tropical forests with lidar and none to our knowledge in West Africa. Hyperspectral sensors also offer promising data, being able to evidence very fine radiometric differences in vegetation reflectance. Their usefulness in estimating forest parameters is still under evaluation with contrasting findings (Andersen et al. 2008, Latifi et al. 2012), and additional studies are especially relevant in view of forthcoming satellite hyperspectral missions. In the framework of the EU ERC Africa GHG grant #247349, an airborne campaign collecting lidar and hyperspectral data has been conducted in March 2012 over forests reserves in Sierra Leone and Ghana, characterized by different logging histories and rainfall patterns, and including Gola Rainforest National Park, Ankasa National Park, Bia and Boin Forest Reserves. An Optech Gemini sensor collected the lidar dataset, while an AISA Eagle sensor collected hyperspectral data over 244 VIS-NIR bands. The lidar dataset, with a point density >10 ppm was processed using the TIFFS software (Toolbox for LiDAR Data Filtering and Forest Studies)(Chen 2007). The hyperspectral dataset, geo

  11. The taxonomic status of two West African Leptopelis species: L. macrotis Schiøtz, 1967 and L. spiritusnoctis Rödel, 2007 (Amphibia: Anura: Arthroleptidae

    Directory of Open Access Journals (Sweden)

    Mark-Oliver Roedel

    2014-03-01

    Full Text Available We herein examine the taxonomic status of two West African forest-dwelling Leptopelis species. The small L. spiritusnoctis, described from the Upper Guinean forests of West Africa, was recently synonymized with L. aubryi, described from Gabon. The large L. macrotis, known from Ghana to Sierra Leone, was downgraded to a subspecies of L. millsoni, ranging from the Niger Delta to eastern Democratic Republic of Congo. These taxonomic decisions are in contrast to the general biogeographic pattern of African forest anurans and we consequently tested if the morphologically similar taxon pairs are indeed conspecifics by applying acoustic and molecular techniques. Both techniques confirmed that populations from West Africa differ significantly from their Central African morphological equivalents. Consequently, we herein resurrect L. spiritusnoctis as a valid species. The acoustic data indicate that L. aubryi may comprise a complex of cryptic species. We further advocate using the name L. macrotis for West African and L. millsoni for Central African populations of these larger arboreal frogs. However, we had neither genetic nor acoustic data from the type locality of L. millsoni available and could not clarify if these frogs belong to the more western or eastern taxon or even represent a Nigerian endemic. Thus, it is possible that West African populations need to be termed L. millsoni in the future. For populations east of the Cross River, Nigeria, the name L. guineensis would be available.

  12. A historical overview of Moroccan magmatic events along northwest edge of the West African Craton

    Science.gov (United States)

    Ikenne, Moha; Souhassou, Mustapha; Arai, Shoji; Soulaimani, Abderrahmane

    2017-03-01

    Located along the northwestern edge of the West African Craton, Morocco exhibits a wide variety of magmatic events from Archean to Quaternary. The oldest magmatic rocks belong to the Archean Reguibat Shield outcrops in the Moroccan Sahara. Paleoproterozoic magmatism, known as the Anti-Atlas granitoids, is related to the Eburnean orogeny and initial cratonization of the WAC. Mesoproterozoic magmatism is represented by a small number of mafic dykes known henceforth as the Taghdout mafic volcanism. Massive Neoproterozoic magmatic activity, related to the Pan-African cycle, consists of rift-related Tonian magmatism associated with the Rodinia breakup, an Early Cryogenian convergent margin event (760-700 Ma), syn-collisional Bou-Azzer magmatism (680-640 Ma), followed by widespread Ediacaran magmatism (620-555 Ma). Each magmatic episode corresponded to a different geodynamic environment and produced different types of magma. Phanerozoic magmatism began with Early Cambrian basaltic (rift?) volcanism, which persisted during the Middle Cambrian, and into the Early Ordovician. This was succeeded by massive Late Devonian and Carboniferous, pre-Variscan tholeiitic and calc-alkaline (Central Morocco) volcanic flows in basins of the Moroccan Meseta. North of the Atlas Paleozoic Transform Zone, the Late Carboniferous Variscan event was accompanied by the emplacement of 330-300 Ma calc-alkaline granitoids in upper crustal shear zones. Post-Variscan alkaline magmatism was associated with the opening of the Permian basins. Mesozoic magmatism began with the huge volumes of magma emplaced around 200 Ma in the Central Atlantic Magmatic Province (CAMP) which was associated with the fragmentation of Pangea and the subsequent rifting of Central Atlantic. CAMP volcanism occurs in all structural domains of Morocco, from the Anti-Atlas to the External Rif domain with a peak activity around 199 Ma. A second Mesozoic magmatic event is represented by mafic lava flows and gabbroic intrusions in

  13. Characteristics and phylogeny of Bacillus cereus strains isolated from Maari, a traditional West African food condiment.

    Science.gov (United States)

    Thorsen, Line; Kando, Christine Kere; Sawadogo, Hagrétou; Larsen, Nadja; Diawara, Bréhima; Ouédraogo, Georges Anicet; Hendriksen, Niels Bohse; Jespersen, Lene

    2015-03-02

    Maari is a spontaneously fermented food condiment made from baobab tree seeds in West African countries. This type of product is considered to be safe, being consumed by millions of people on a daily basis. However, due to the spontaneous nature of the fermentation the human pathogen Bacillus cereus occasionally occurs in Maari. This study characterizes succession patterns and pathogenic potential of B. cereus isolated from the raw materials (ash, water from a drilled well (DW) and potash), seed mash throughout fermentation (0-96h), after steam cooking and sun drying (final product) from two production sites of Maari. Aerobic mesophilic bacterial (AMB) counts in raw materials were of 10(5)cfu/ml in DW, and ranged between 6.5×10(3) and 1.2×10(4)cfu/g in potash, 10(9)-10(10)cfu/g in seed mash during fermentation and 10(7) - 10(9) after sun drying. Fifty three out of total 290 AMB isolates were identified as B. cereus sensu lato by use of ITS-PCR and grouped into 3 groups using PCR fingerprinting based on Escherichia coli phage-M13 primer (M13-PCR). As determined by panC gene sequencing, the isolates of B. cereus belonged to PanC types III and IV with potential for high cytotoxicity. Phylogenetic analysis of concatenated sequences of glpF, gmk, ilvD, pta, pur, pycA and tpi revealed that the M13-PCR group 1 isolates were related to B. cereus biovar anthracis CI, while the M13-PCR group 2 isolates were identical to cereulide (emetic toxin) producing B. cereus strains. The M13-PCR group 1 isolates harboured poly-γ-D-glutamic acid capsule biosynthesis genes capA, capB and capC showing 99-100% identity with the environmental B. cereus isolate 03BB108. Presence of cesB of the cereulide synthetase gene cluster was confirmed by PCR in M13-PCR group 2 isolates. The B. cereus harbouring the cap genes were found in potash, DW, cooking water and at 8h fermentation. The "emetic" type B. cereus were present in DW, the seed mash at 48-72h of fermentation and in the final product

  14. Effects of the environment on fish juvenile growth in West African stressful estuaries

    Science.gov (United States)

    Diouf, K.; Guilhaumon, F.; Aliaume, C.; Ndiaye, P.; Chi, T. Do; Panfili, J.

    2009-06-01

    The knowledge of juvenile fish growth in extreme environmental conditions is a key to the understanding of adaptive responses and to the relevant management of natural populations. The juvenile growth of an extreme euryhaline tilapia species, Sarotherodon melanotheron (Cichlidae), was examined across a salinity gradient (20-118) in several West African estuarine ecosystems. Juveniles were collected during the reproduction period of two consecutive years (2003 and 2004) in six locations in the Saloum (Senegal) and Gambia estuaries. Age and growth were estimated using daily otolith microincrements. For each individual, otolith growth rates showed three different stages (slow, fast, decreasing): around 4 ± 0.5 μm d -1 during the first five days, 9 ± 0.5 μm d -1 during the next 15 days and 4 ± 0.50 μm d -1 at 60 days. Growth modelling and model comparisons were objectively made within an information theory framework using the multi-model inference from five growth models (linear, power, Gompertz, von Bertalanffy, and logistic). The combination of both the model adjustment inspection and the information theory model selection procedure allowed identification of the final set of models, including the less parameterised ones. The estimated growth rates were variable across spatial scales but not across temporal scales (except for one location), following exactly the salinity gradient with growth decrease towards the hypersaline conditions. The salinity gradient was closely related to all measured variables (condition factor, mean age, multi-model absolute growth rate) demonstrating the strong effect of hypersaline environmental conditions—induced by climate changes—on fish populations at an early stage.

  15. A 1700-year history of West African multidecadal sea surface temperature and rainfall variability

    Science.gov (United States)

    Kuhnert, Henning; Stefan, Mulitza; Gesine, Mollenhauer

    2010-05-01

    Tropical Atlantic sea surface temperatures (SST) exert a major influence on the latitudinal position and intensity of the West African Monsoon and the tropical rainbelt. The impact of the Atlantic Multidecadal Oscillation (AMO) in particular has previously been demonstrated, but little information is available beyond the instrumental time period. We have reconstructed summer-fall SST and relative changes in the discharge of the Senegal River from a sediment core off southern Mauritania. Time series of SST and seawater-d18O (a measure of salinity and hence discharge) were estimated from planktonic foraminiferal Mg/Ca and d18O. The records are sufficiently resolved to infer multidecadal variability over the past 1700 years and centennial variability over the past 3300 years. River discharge increases slightly over the entire time series. This can be brought into agreement with the general Sahel drying trend indicated by previous studies, when we assume a southward migration of the rainbelt that leads to locally enhanced rainfall over the southernmost Senegal River catchment area in Guinea. SST cooled by 1-1.5 °C between AD 1250 and 1500, more pronounced and somewhat earlier compared with the North Atlantic mean. Spectral analysis reveals several multidecadal periods (38, ~45 and ~62 years) where SST and Senegal River discharge are tightly coupled and are driven by the AMO. The exception is a 30-year periodicity in discharge that has no counterpart in SST, and is potentially linked to meridional tropical SST gradient anomalies. AMO signatures are present throughout the past 1700 years, but vary in amplitude. The most recent and persistent phase of enhanced AMO variability commences around AD 1250 contemporaneous with the transition from the Medieval Climate Anomaly to the Little Ice Age.

  16. Fire Patterns and Drivers of Fires in the West African Tropical Forest

    Science.gov (United States)

    Dwomoh, F. K.; Wimberly, M. C.

    2015-12-01

    The West African tropical forest (referred to as the Upper Guinean forest, UGF), is a global biodiversity hotspot providing vital ecosystem services for the region's socio-economic and environmental wellbeing. It is also one of the most fragmented and human-modified tropical forest ecosystems, with the only remaining large patches of original forests contained in protected areas. However, these remnant forests are susceptible to continued fire-mediated degradation and forest loss due to intense climatic, demographic and land use pressures. We analyzed human and climatic drivers of fire activity in the sub-region to better understand the spatial and temporal patterns of these risks. We utilized MODIS active fire and burned area products to identify fire activity within the sub-region. We measured climatic variability using TRMM rainfall data and derived indicators of human land use from a variety of geospatial datasets. We used a boosted regression trees model to determine the influences of predictor variables on fire activity. Our analyses indicated that the spatial and temporal variability of precipitation is a key driving factor of fire activity in the UGF. Anthropogenic effects on fire activity in the area were evident through the influences of agriculture and low-density populations. These human footprints in the landscape make forests more susceptible to fires through forest fragmentation, degradation, and fire spread from agricultural areas. Forested protected areas within the forest savanna mosaic experienced frequent fires, whereas the more humid forest areas located in the south and south-western portions of the study area had fewer fires as these rainforests tend to offer some buffering against fire encroachment. These results improve characterization of UGF fire regime and expand our understanding of the spatio-temporal dynamics of tropical forest fires in response to human and climatic pressures.

  17. WASCAL - West African Science Service Center on Climate Change and Adapted Land Use Regional Climate Simulations and Land-Atmosphere Simulations for West Africa at DKRZ and elsewhere

    Science.gov (United States)

    Hamann, Ilse; Arnault, Joel; Bliefernicht, Jan; Klein, Cornelia; Heinzeller, Dominikus; Kunstmann, Harald

    2014-05-01

    Changing climate and hydro-meteorological boundary conditions are among the most severe challenges to Africa in the 21st century. In particular West Africa faces an urgent need to develop effective adaptation and mitigation strategies to cope with negative impacts on humans and environment due to climate change, increased hydro-meteorological variability and land use changes. To help meet these challenges, the German Federal Ministry of Education and Research (BMBF) started an initiative with institutions in Germany and West African countries to establish together a West African Science Service Center on Climate Change and Adapted Land Use (WASCAL). This activity is accompanied by an establishment of trans-boundary observation networks, an interdisciplinary core research program and graduate research programs on climate change and related issues for strengthening the analytical capabilities of the Science Service Center. A key research activity of the WASCAL Competence Center is the provision of regional climate simulations in a fine spatio-temporal resolution for the core research sites of WASCAL for the present and the near future. The climate information is needed for subsequent local climate impact studies in agriculture, water resources and further socio-economic sectors. The simulation experiments are performed using regional climate models such as COSMO-CLM, RegCM and WRF and statistical techniques for a further refinement of the projections. The core research sites of WASCAL are located in the Sudanian Savannah belt in Northern Ghana, Southern Burkina Faso and Northern Benin. The climate in this region is semi-arid with six rainy months. Due to the strong population growth in West Africa, many areas of the Sudanian Savannah have been already converted to farmland since the majority of the people are living directly or indirectly from the income produced in agriculture. The simulation experiments of the Competence Center and the Core Research Program are

  18. Phylogeography of the Afromontane Prunus africana reveals a former migration corridor between East and West African highlands.

    Science.gov (United States)

    Kadu, C A C; Schueler, S; Konrad, H; Muluvi, G M M; Eyog-Matig, O; Muchugi, A; Williams, V L; Ramamonjisoa, L; Kapinga, C; Foahom, B; Katsvanga, C; Hafashimana, D; Obama, C; Geburek, T

    2011-01-01

    Scattered populations of the same tree species in montane forests through Africa have led to speculations on the origins of distributions. Here, we inferred the colonization history of the Afromontane tree Prunus africana using seven chloroplast DNA loci to study 582 individuals from 32 populations sampled in a range-wide survey from across Africa, revealing 22 haplotypes. The predominant haplotype, HT1a, occurred in 13 populations of eastern and southern Africa, while a second common haplotype, HT1m, occurred in populations of western Uganda and western Africa. The high differentiation observed between populations in East Africa was unexpected, with stands in western Uganda belonging with the western African lineage. High genetic differentiation among populations revealed using ordered alleles (N(ST) = 0.840) compared with unordered alleles (G(ST) = 0.735), indicated a clear phylogeographic pattern. Bayesian coalescence modelling suggested that 'east' and 'west' African types likely split early during southward migration of the species, while further more recent splitting events occurred among populations in the East of the continent. The high genetic similarity found between western Uganda and west African populations indicates that a former Afromontane migration corridor may have existed through Equatorial Africa.

  19. The West African monsoon: Contribution of the AMMA multidisciplinary programme to the study of a regional climate system.

    Science.gov (United States)

    Lebel, T.; Janicot, S.; Redelsperger, J. L.; Parker, D. J.; Thorncroft, C. D.

    2015-12-01

    The AMMA international project aims at improving our knowledge and understanding of the West African monsoon and its variability with an emphasis on daily-to-interannual timescales. AMMA is motivated by an interest in fundamental scientific issues and by the societal need for improved prediction of the WAM and its impacts on water resources, health and food security for West African nations. The West African monsoon (WAM) has a distinctive annual cycle in rainfall that remains a challenge to understand and predict. The location of peak rainfall, which resides in the Northern Hemisphere throughout the year, moves from the ocean to the land in boreal spring. Around the end of June there is a rapid shift in the location of peak rainfall between the coast and around 10°N where it remains until about the end of August. In September the peak rainfall returns equatorward at a relatively steady pace and is located over the ocean again by November. The fact that the peak rainfall migrates irregularly compared to the peak solar heating is due to the interactions that occur between the land, the atmosphere and the ocean. To gain a better understanding of this complex climate system, a large international research programme was launched in 2002, the biggest of its kind into environment and climate ever attempted in Africa. AMMA has involved a comprehensive field experiment bringing together ocean, land and atmospheric measurements, on timescales ranging from hourly and daily variability up to the changes in seasonal activity over a number of years. This presentation will focus on the description of the field programme and its accomplishments, and address some key questions that have been recently identified to form the core of AMMA-Phase 2.

  20. Phylogeographic reconstruction of African yellow fever virus isolates indicates recent simultaneous dispersal into east and west Africa.

    Directory of Open Access Journals (Sweden)

    Andrew Beck

    Full Text Available Yellow fever virus (YFV is a mosquito-borne flavivirus that is a major public health problem in tropical areas of Africa and South America. There have been detailed studies on YFV ecology in West Africa and South America, but current understanding of YFV circulation on the African continent is incomplete. This inadequacy is especially notable for East and Central Africa, for which the unpredictability of human outbreaks is compounded by limitations in both historical and present surveillance efforts. Sparse availability of nucleotide sequence data makes it difficult to investigate the dispersal of YFV in these regions of the continent. To remedy this, we constructed Bayesian phylogenetic and geographic analyses utilizing 49 partial genomic sequences to infer the structure of YFV divergence across the known range of the virus on the African continent. Relaxed clock analysis demonstrated evidence for simultaneous divergence of YFV into east and west lineages, a finding that differs from previous hypotheses of YFV dispersal from reservoirs located on edges of the endemic range. Using discrete and continuous geographic diffusion models, we provide detailed structure of YFV lineage diversity. Significant transition links between extant East and West African lineages are presented, implying connection between areas of known sylvatic cycling. The results of demographic modeling reinforce the existence of a stably maintained population of YFV with spillover events into human populations occurring periodically. Geographically distinct foci of circulation are reconstructed, which have significant implications for studies of YFV ecology and emergence of human disease. We propose further incorporation of Bayesian phylogeography into formal GIS analyses to augment studies of arboviral disease.

  1. Comparative study of potential transfer of natural and anthropogenic cadmium to plankton communities in the North-West African upwelling

    Energy Technology Data Exchange (ETDEWEB)

    Auger, P.A., E-mail: pierreamael.auger@gmail.com [Laboratoire de Physique des Océans (LPO), UMR-CNRS 6523/IFREMER/IRD/UBO, BP70, 29280 Plouzané (France); Machu, E.; Gorgues, T.; Grima, N. [Laboratoire de Physique des Océans (LPO), UMR-CNRS 6523/IFREMER/IRD/UBO, BP70, 29280 Plouzané (France); Waeles, M. [Université de Bretagne Occidentale (UBO), Laboratoire de l' Environnement Marin (LEMAR), UMR-CNRS 6539/IRD/UBO, place N. Copernic, 29280 Plouzané (France)

    2015-02-01

    A Lagrangian approach based on a physical–biogeochemical modeling was used to compare the potential transfer of cadmium (Cd) from natural and anthropogenic sources to plankton communities (Cd-uptake) in the North-West African upwelling. In this region, coastal upwelling was estimated to be the main natural source of Cd while the most significant anthropogenic source for marine ecosystem is provided by phosphate industry. In our model experiment, Cd-uptake (natural or anthropogenic) in the North-West African upwelling is the result of an interplay between the Cd dispersion (by advection processes) and the simulated biological productivity. In the Moroccan waters, advection processes limit the residence time of water masses resulting in a low natural Cd-uptake by plankton communities while anthropogenic Cd-uptake is high. As expected, the situation is reversed in the Senegalo-Mauritanian upwelling where natural Cd-uptake is higher than anthropogenic Cd-uptake. Based upon an estimate of Cd sources, our modeling study shows, unexpectedly, that the anthropogenic signal of potential Cd-bioaccumulation in the Moroccan upwelling is of the same order of magnitude as the natural signal mainly present in the Senegalo-Mauritanian upwelling region. A comparison with observed Cd levels in mollusk and fishes, which shows overall agreement with our simulations, is confirming our estimates. - Highlights: • We model the physical–biogeochemical dynamics in the North-West African upwelling. • We model the transport of cadmium from natural and anthropogenic sources. • We derive proxies of potential cadmium absorption and bioaccumulation in the plankton food chain. • The anthropogenic signal off Morocco at least equals the natural upwelling signal off Mauritania. • We compare our results with observed cadmium levels in mollusks and fishes.

  2. Transversal analysis of public policies on user fees exemptions in six West African countries

    Directory of Open Access Journals (Sweden)

    Ridde Valéry

    2012-11-01

    Full Text Available Abstract Background While more and more West African countries are implementing public user fees exemption policies, there is still little knowledge available on this topic. The long time required for scientific production, combined with the needs of decision-makers, led to the creation in 2010 of a project to support implementers in aggregating knowledge on their experiences. This article presents a transversal analysis of user fees exemption policies implemented in Benin, Burkina Faso, Mali, Niger, Togo and Senegal. Methods This was a multiple case study with several embedded levels of analysis. The cases were public user fees exemption policies selected by the participants because of their instructive value. The data used in the countries were taken from documentary analysis, interviews and questionnaires. The transversal analysis was based on a framework for studying five implementation components and five actors’ attitudes usually encountered in these policies. Results The analysis of the implementation components revealed: a majority of State financing; maintenance of centrally organized financing; a multiplicity of reimbursement methods; reimbursement delays and/or stock shortages; almost no implementation guides; a lack of support measures; communication plans that were rarely carried out, funded or renewed; health workers who were given general information but not details; poorly informed populations; almost no evaluation systems; ineffective and poorly funded coordination systems; low levels of community involvement; and incomplete referral-evacuation systems. With regard to actors’ attitudes, the analysis revealed: objectives that were appreciated by everyone; dissatisfaction with the implementation; specific tensions between healthcare providers and patients; overall satisfaction among patients, but still some problems; the perception that while the financial barrier has been removed, other barriers persist; occasionally a

  3. Allometric models and aboveground biomass stocks of a West African Sudan Savannah watershed in Benin.

    Science.gov (United States)

    Chabi, Adéyèmi; Lautenbach, Sven; Orekan, Vincent Oladokoun Agnila; Kyei-Baffour, Nicholas

    2016-12-01

    The estimation of forest biomass changes due to land-use change is of significant importance for estimates of the global carbon budget. The accuracy of biomass density maps depends on the availability of reliable allometric models used in combination with data derived from satellites images and forest inventory data. To reduce the uncertainty in estimates of carbon emissions resulting from deforestation and forest degradation, better information on allometric equations and the spatial distribution of aboveground biomass stocks in each land use/land cover (LULC) class is needed for the different ecological zones. Such information has been sparse for the West African Sudan Savannah zone. This paper provides new data and results for this important zone. The analysis combines satellite images and locally derived allometric models based on non-destructive measurements to estimate aboveground biomass stocks at the watershed level in the Sudan Savannah zone in Benin. We compared three types of empirically fitted allometric models of varying model complexity with respect to the number of input parameters that are easy to measure at the ground: model type I based only on the diameter at breast height (DBH), type II which used DBH and tree height and model type III which used DBH, tree height and wood density as predictors. While for most LULC classes model III outperformed the other models even the simple model I showed a good performance. The estimated mean dry biomass density values and attached standard error for the different LULC class were 3.28 ± 0.31 (for cropland and fallow), 3.62 ± 0.36 (for Savanna grassland), 4.86 ± 1.03 (for Settlements), 14.05 ± 0.72 (for Shrub savanna), 45.29 ± 2.51 (for Savanna Woodland), 46.06 ± 14.40 (for Agroforestry), 94.58 ± 4.98 (for riparian forest and woodland), 162 ± 64.88 (for Tectona grandis plantations), 179.62 ± 57.61 (for Azadirachta indica plantations), 25.17 ± 7.46 (for Gmelina arborea plantations

  4. Small reservoirs in the West African savanna: Usage, monitoring and impact (Invited)

    Science.gov (United States)

    Van De Giesen, N.; Liebe, J. R.; Annor, F.; Andreini, M.

    2013-12-01

    The West African savanna is dotted with thousands of small reservoirs. These reservoirs were primarily built for irrigation purposes, supplying supplementary irrigation in the rainy season and full irrigation in the dry season. Some reservoirs were specifically constructed for watering cattle. Most reservoirs, however, now fulfill a multitude of functions in addition to irrigation and cattle watering, such as fishing, bathing, household water, supply of construction materials, and recreation. In the framework of the Small Reservoirs Project (www.smallreservoirs.org), extensive research has been undertaken over the past ten years that addresses the functioning of these reservoirs and the development of new monitoring methods. This presentation will give a general overview of our findings with respect to history, usage, and hydrological impact of small reservoirs in West Africa. In general, no comprehensive databases are available to local and national governments that contain all reservoirs and their attributes. Remote sensing, therefore, offers an interesting alternative to produce inventories of small reservoirs in a cost effective way. The most straightforward application is the mapping of small reservoirs with the aid of optical satellite images. Open water tends to stand out clearly from its surroundings in such images, allowing for relatively accurate determination of the location and surface area of the reservoirs. An important early discovery was that within a given geomorphological region, there is a very good correlation between surface area and storage volume. Once this correlation is established through a small sub-sample of the reservoirs, all volumes can be calculated on the basis of surfaces as determined through remote sensing. In turn, this opens up the opportunity to monitor water storage over the year by means of satellite images. Optical images are usually not available during large parts of the year due to cloud cover. This holds especially true

  5. Analysis and Prediction of West African Moist Events during the Boreal Spring of 2009

    Science.gov (United States)

    Mera, Roberto Javier

    Weather and climate in Sahelian West Africa are dominated by two major wind systems, the southwesterly West African Monsoon (WAM) and the northeasterly (Harmattan) trade winds. In addition to the agricultural benefit of the WAM, the public health sector is affected given the relationship between the onset of moisture and end of meningitis outbreaks. Knowledge and prediction of moisture distribution during the boreal spring is vital to the mitigation of meningitis by providing guidance for vaccine dissemination. The goal of the present study is to (a) develop a climatology and conceptual model of the moisture regime during the boreal spring, (b) investigate the role of extra-tropical and Convectively-coupled Equatorial Waves (CCEWs) on the modulation of westward moving synoptic waves and (c) determine the efficacy of a regional model as a tool for predicting moisture variability. Medical reports during 2009, along with continuous meteorological observations at Kano, Nigeria, showed that the advent of high humidity correlated with cessation of the disease. Further analysis of the 2009 boreal spring elucidated the presence of short-term moist events that modulated surface moisture on temporal scales relevant to the health sector. The May moist event (MME) provided insight into interplays among climate anomalies, extra-tropical systems, equatorially trapped waves and westward-propagating synoptic disturbances. The synoptic disturbance initiated 7 May and traveled westward to the coast by 12 May. There was a marked, semi-stationary moist anomaly in the precipitable water field (kg m-2) east of 10°E through late April and early May, that moved westward at the time of the MME. Further inspection revealed a mid-latitude system may have played a role in increasing the latitudinal amplitude of the MME. CCEWs were also found to have an impact on the MME. A coherent Kelvin wave propagated through the region, providing increased monsoonal flow and heightened convection. A

  6. Representation of the West African Monsoon System in the aerosol-climate model ECHAM6-HAM2

    Science.gov (United States)

    Stanelle, Tanja; Lohmann, Ulrike; Bey, Isabelle

    2017-04-01

    The West African Monsoon (WAM) is a major component of the global monsoon system. The temperature contrast between the Saharan land surface in the North and the sea surface temperature in the South dominates the WAM formation. The West African region receives most of its precipitation during the monsoon season between end of June and September. Therefore the existence of the monsoon is of major social and economic importance. We discuss the ability of the climate model ECHAM6 as well as the coupled aerosol climate model ECHAM6-HAM2 to simulate the major features of the WAM system. The north-south temperature gradient is reproduced by both model versions but all model versions fail in reproducing the precipitation amount south of 10° N. A special focus is on the representation of the nocturnal low level jet (NLLJ) and the corresponding enhancement of low level clouds (LLC) at the Guinea Coast, which are a crucial factor for the regional energy budget. Most global climate models have difficulties to represent these features. The pure climate model ECHAM6 is able to simulate the existence of the NLLJ and LLC, but the model does not represent the pronounced diurnal cycle. Overall, the representation of LLC is worse in the coupled model. We discuss the model behaviors on the basis of outputted temperature and humidity tendencies and try to identify potential processes responsible for the model deficiencies.

  7. The social ecology of resolving family conflict among West African immigrants in New York: a grounded theory approach.

    Science.gov (United States)

    Rasmussen, Andrew; Chu, Tracy; Akinsulure-Smith, Adeyinka M; Keatley, Eva

    2013-09-01

    The current study employs a grounded theory approach to examine West African immigrants' resolution of parent-child conflict and intimate partner conflict. Data from 59 participants present an interactive social ecological framework, where a lack of resolution at one level results in attempts to resolve problems at higher levels. Four levels are identified within West African immigrants' problem solving ecology, each with specific actors in positions of authority: individual/dyadic (parents and spouses), extended family (which includes distant relatives and relatives living in home countries), community leadership (non-family elders and religious leaders), and state authorities. From participants' descriptions of family challenges emerged a picture of a social ecology in flux, with traditional, socially conservative modes of resolving family conflict transposed across migration into the more liberal and state-oriented familial context of the United States. This transposition results in a loss spiral for the traditional social ecology, differentially affecting individual actors within families. Implications for helping professionals working with new immigrant communities include identifying variability in openness to adapting structures that are not working well (e.g., patriarchal protection of abusive husbands) and supporting structures known to be associated with well being (e.g., collective monitoring of youth).

  8. Chloroplast DNA phylogeography suggests a West African centre of origin for the baobab, Adansonia digitata L. (Bombacoideae, Malvaceae).

    Science.gov (United States)

    Leong Pock Tsy, Jean-Michel; Lumaret, Roselyne; Mayne, Diana; Vall, Abdallahi Ould Mohamed; Abutaba, Yahia I M; Sagna, Maurice; Rakotondralambo Raoseta, Soaharin'ny Ony; Danthu, Pascal

    2009-04-01

    The African baobab (Adansonia digitata L.) is an emblematic, culturally important, and physically huge tropical tree species whose natural geographical distribution comprises most of tropical Africa, but also small patches of southern Arabia, and several Atlantic and Indian Ocean islands surrounding the African continent, notably including Madagascar. We analysed the polymerase chain reaction-restriction fragment length polymorphism of five chloroplast DNA fragments obtained from 344 individuals of A. digitata collected from 74 populations covering the entire extant distribution range of the species. Our goal was to reconstruct the phylogeographical history of the species and, if possible, to identify its centre of origin, which has been a subject of controversy for many decades. We identified five haplotypes whose distribution is clearly geographically structured. Using several species of Adansonia and of closely related genera as outgroups, the haplotypes showed a clear phylogeographical pattern of three groups. Two are phylogenetically related to the outgroup taxa, and are distributed in West Africa. The third group is substantially more differentiated genetically from outgroup species, and it corresponds to southern and eastern Africa, Arabia and the Indian Ocean islands, including Madagascar. According to our results, the tetraploid A. digitata, or its diploid progenitor, probably originated in West Africa and migrated subsequently throughout the tropical parts of that continent, and beyond, by natural and human-mediated terrestrial and overseas dispersal.

  9. Impact of GCM boundary forcing on regional climate modeling of West African summer monsoon precipitation and circulation features

    Science.gov (United States)

    Kebe, Ibourahima; Sylla, Mouhamadou Bamba; Omotosho, Jerome Adebayo; Nikiema, Pinghouinde Michel; Gibba, Peter; Giorgi, Filippo

    2017-03-01

    In this study, the latest version of the International Centre for Theoretical Physics Regional Climate Model (RegCM4) driven by three CMIP5 Global Climate Models (GCMs) is used at 25 km grid spacing over West Africa to investigate the impact of lateral boundary forcings on the simulation of monsoon precipitation and its relationship with regional circulation features. We find that the RegCM4 experiments along with their multimodel ensemble generally reproduce the location of the main precipitation characteristics over the region and improve upon the corresponding driving GCMs. However, the provision of different forcing boundary conditions leads to substantially different precipitation magnitudes and spatial patterns. For instance, while RegCM4 nested within GFDL-ESM-2M and HadGEM2-ES exhibits some underestimations of precipitation and an excessively narrow Intertropical Convergence Zone, the MPI-ESM-MR driven run produces precipitation spatial distribution and magnitudes more similar to observations. Such a superior performance originates from a much better simulation of the interactions between baroclinicity, temperature gradient and African Easterly Jet along with an improved connection between the Isentropic Potential Vorticity, its gradient and the African Easterly Waves dynamics. We conclude that a good performing GCM in terms of monsoon dynamical features (in this case MPI-ESM-MR) is needed to drive RCMs in order to achieve a better representation of the West Africa summer monsoon precipitation.

  10. Life in the spray zone – overlooked diversity in West African torrent-frogs (Anura, Odontobatrachidae, Odontobatrachus

    Directory of Open Access Journals (Sweden)

    Michael Barej

    2015-07-01

    Full Text Available West African torrent-frogs of the genus Odontobatrachus currently belong to a single species: Odontobatrachus natator (Boulenger, 1905. Recently, molecular results and biogeographic separation led to the recognition of five Operational Taxonomic Units (OTUs thus identifying a species-complex. Based on these insights, morphological analyses on more than 150 adult specimens, covering the entire distribution of the family and all OTUs, were carried out. Despite strong morphological congruence, combinations of morphological characters made the differentiation of OTUs successful and allowed the recognition of five distinct species: Odontobatrachus natator, and four species new to science: Odontobatrachus arndti sp. n., O. fouta sp. n., O. smithi sp. n. and O. ziama sp. n. All species occur in parapatry: Odontobatrachus natator is known from western Guinea to eastern Liberia, O. ziama sp. n. from eastern Guinea, O. smithi sp. n. and O. fouta sp. n. from western Guinea, O. arndti sp. n. from the border triangle Guinea-Liberia-Côte d’Ivoire. In addition, for the first time the advertisement call of a West African torrent-frog (O. arndti sp. n. is described.

  11. Paleoproterozoic Greenstone-Granite Belts in Northern Brazil and the Former Guyana Shield - West African Craton Province

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    Ian McReath

    2006-03-01

    Full Text Available The mainly meta-volcano-sedimentary Vila Nova Group and associated granites constitute separate belts, which formpart of a large paleoproterozoic (mainly rhyacian province in the Guyana Shield of which northern Brazil forms a part, andthe West African Craton. In Brazil the southwestern Serra do Ipitinga and Serra Tumucumaque-Serra do Navio belts have noobvious geometrical extensions in the Guyanas or Venezuela, and may represent deposits formed at penecontemporaneouspassive continental margins and ocean floor spreading centres. To the Northeast the Serra Lombarda-Tartarugalzinho andOiapoque belts are continuations of Guianese belts. In the former the igneous rocks have geochemical characteristics ofsuprasubduction environments. Belts in the Guyana Shield and West African Craton have many similar features. Themegaprovince evolved in a number of stages, which may have started at about 2.3 Ga, and continued with diminished activityafter 2.11 Ga. Both major juvenile additions and (possibly minor reworking of earlier crust contributed to the growth of theprovince. The major transcurrent deformation, responsible for the present structure of the belts, probably occurred duringthe later stages of evolution of the province, but metamorphism and deformation are registered even in the oldest rocks.

  12. Very high CO2 exchange fluxes at the peak of the rainy season in a West African grazed semi-arid savanna ecosystem

    DEFF Research Database (Denmark)

    Tagesson, Håkan Torbern; Ardoe, Jonas; Guiro, Idrissa;

    2016-01-01

    Africa is a sink of carbon, but there are large gaps in our knowledge regarding the CO2 exchange fluxes for many African ecosystems. Here, we analyse multi-annual eddy covariance data of CO2 exchange fluxes for a grazed Sahelian semi-arid savanna ecosystem in Senegal, West Africa. The aim of the ...... response to climate change.......Africa is a sink of carbon, but there are large gaps in our knowledge regarding the CO2 exchange fluxes for many African ecosystems. Here, we analyse multi-annual eddy covariance data of CO2 exchange fluxes for a grazed Sahelian semi-arid savanna ecosystem in Senegal, West Africa. The aim...

  13. Analysis of West African Drug Trafficking: The Dynamics of Interdiction and State Capacity

    Science.gov (United States)

    2011-03-01

    Illegal drug trafficking through West Africa has grown dramatically in the last decade, capturing the attention of U.S., European, and U.N...policymakers. Most countries in West Africa have struggled to adapt to the challenges drug trafficking has presented. A few countries, like Ghana, have made a

  14. The nocturnal low-level jet in theWest African Sahel from observations, analyses, and conceptual models

    Science.gov (United States)

    Bessardon, Geoffrey; Brooks, Barbara; Marsham, John; Ross, Andrew

    2017-04-01

    There is a strong diurnal cycle in the West African monsoon (WAM) and the nocturnal low-level jet (NLLJ) is a key component of the nocturnal monsoon flow, transporting heat, moisture, and aerosols. Shear beneath the NLLJ has been linked to cloud formation and daytime mixing of NLLJ momentum to the surface is a key process for dust uplift. This study presents a comparison between observations from the WestnAfrican Sahel, reanalyses and two conceptual models of the NLLJ inertial oscillation. Past studies have identified inertial oscillations as the main cause of NLLJs at midlatitudes, but this study provides a novel quantitative test of conceptual models for the NLLJ at a monsoonal latitude. A comparison of 18 cases observed during the African Monsoon Multidisciplinary Analysis (AMMA) shows that an inertial oscillation is the main mechanism behind the NLLJ in the summertime Sahel. The inclusion of friction is essential for a realistic jet evolution. A simple conceptual model with friction captures the NLLJ strength, but gives too rapid rotation, likely due to the assumption of a constant equilibrium wind, when there are significant changes in geostrophic wind overnight. Reanalyses give a realistic rotation rate, but too weak NLLJ, with too strong winds at low-levels, due to too much mixing. This leads to substantial biases in reanalysed moisture transport.

  15. HLA-DRB1 and -DQB1 loci in three west African ethnic groups: genetic relationship with sub-Saharan African and European populations.

    Science.gov (United States)

    Lulli, Patrizia; Mangano, Valentina D; Onori, Annamaria; Batini, Chiara; Luoni, Gaia; Sirima, Bienvenu S; Nebie, Issa; Chessa, Luciana; Petrarca, Vincenzo; Modiano, David

    2009-11-01

    The Fulani of west Africa have been shown to be less susceptible to malaria and to mount a stronger immune response to malaria than sympatric ethnic groups. The analysis of HLA diversity is useful for the assessment of the genetic distance between the Fulani and sympatric populations, which represents the necessary theoretical background for the investigation of genetic determinants of susceptibility to malaria. We assessed the polymorphism of HLA-DRB1 and -DQB1 loci and analyzed the distribution of alleles/haplotypes in Fulani, Mossi, and Rimaibé from Burkina Faso. We then investigated the genetic relationship of these three ethnic groups with other sub-Saharan African populations as well as with Europeans. We confirmed that the Fulani from Burkina Faso are genetically distinct from sympatric Mossi and Rimaibé. Furthermore the Fulani from Burkina Faso are close to those from The Gambia and, intriguingly, share the distribution of specific alleles with east African populations (Amhara and Oromo). It is noteworthy that the HLA-DRB1*04 and -DQB1*02 alleles, which are implicated in the development of several autoimmune diseases, are present at high frequency in the Fulani, suggesting their potential involvement in the enhanced immune reactivity observed in this population.

  16. Tropospheric ozone production related to West African city emissions during the 2006 wet season AMMA campaign

    Directory of Open Access Journals (Sweden)

    G. Ancellet

    2010-11-01

    Full Text Available During the African Monsoon Multidisciplinary Analyses (AMMA airborne measurements of ozone, CO and nitrogen oxides by the French and German falcon aircraft took place near three cities in West Africa (Cotonou, Niamey and Ouagadougou. Significant ozone production (O3 increase of 40–50 ppbv took place during two specific events: one near Cotonou on the coast of the Guinea Gulf, and the other near Niamey in the Sahel region. In both cases a high level of NOx (>3 ppbv is related to the ozone production. The ozone production is mainly driven by the Lagos-Cotonou anthropogenic emissions in Cotonou. In Niamey the combined effect of advection of VOC emissions from the forest and stagnation over the city area and the poorly vegetated soils recently wetted by convected systems is needed to achieve a similar level of ozone precursors. In Ouagadougou no ozone plume is found because of the absence of a pause in the convective activity and of the larger vegetated area around the city which prevented ozone plume formation during the wet season.

    To discuss the ozone increase near Cotonou two different approaches have been implemented: a FLEXPART simulation to quantify the probability of transport from the SH compared to air mass stagnation over the emission area and a simulation of the BOLAM mesoscale model with two different tracers for the anthropogenic emission (RETRO inventory for 2000 and the biomass burning. The BOLAM model shows a good agreement with the meteorological observations of the aircraft and allows to identify the key influence of the anthropogenic emissions in the first 3 km while the biomass burning plume remains above this altitude.

    The day to day variability of the ozone and CO in Niamey and Ouagadougou is discussed using FLEXPART simulations of the air mass stagnation in the 12° N–14° N latitude band and northward advection of air masses from the vegetated areas influenced by the biogenic

  17. West African Journal of Applied Ecology - Vol 24, No 2 (2016)

    African Journals Online (AJOL)

    Table of Contents. Articles. Arsenic Intensity Risk Assessment at AngloGold Obuasi Goldmine, Ghana, West ... with urine in comparison with other organic and inorganic soil amendments · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT

  18. Micronutrient density and stability in West African pearl millet – potential for biofortification

    DEFF Research Database (Denmark)

    Bürger, Anna; Jensen, Henning Høgh; Gondah, Jadah

    2014-01-01

    Pearl millet (Cenchrus americanus (L.) Morrone) is one of the most important cereals in West and Central Africa (WCA). Human populations in WCA are strongly affected by micronutrient deficiencies. Biofortification, the development of pearl millet varieties with enhanced micronutrient levels...

  19. Genetic and phenotypic parameters of body weight in West African Dwarf goat and Djallonké sheep

    NARCIS (Netherlands)

    Bosso, N.A.; Cissé, M.F.; Waaij, van der E.H.; Fall, A.; Arendonk, van J.A.M.

    2007-01-01

    The International Trypanotolerance Centre's small ruminant breeding programme was initiated in 1995. The aim was to increase the efficiency of meat production and the trypanotolerance of the animals (sheep and goat). To achieve that goal, selection was based on estimated breeding values for daily we

  20. Geochemistry of Archean Mafic Amphibolites from the Amsaga Area, West African Craton, Mauritania: Occurrence of Archean oceanic plateau

    Science.gov (United States)

    El Atrassi, Fatima; Debaille, Vinciane; Mattielli, Nadine; Berger, Julien

    2015-04-01

    While Archean terrains are mainly composed of a TTG (Tonalite-trondhjemite-granodiorite) suite, more mafic lithologies such as amphibolites are also a typical component of those ancient terrains. Although mafic rocks represent only ~10% of the Archean cratons, they may provide key evidence of the role and nature of basaltic magmatism in the formation of the Archean crust as well as the evolution of the Archean mantle. This study focuses on the Archean crust from the West African craton in Mauritania (Amsaga area). The Amsaga Archean crust mainly consists of TTG and thrust-imbricated slices of mafic volcanic rocks, which have been affected by polymetamorphic events from the amphibolite to granulite facies. We report the results of a combined petrologic, Sm-Nd isotopic, major element and rare earth element (REE) study of the Archean amphibolites in the West African craton. This study was conducted in order to characterize these rocks, to constrain the time of their formation and to evaluate their tectonic setting and their possible mantle source. Our petrological observations show that these amphibolites have fine to medium granoblastic and nematoblastic textures. They are dominated by amphibolite-facies mineral assemblages (mainly amphibole and plagioclase), but garnet and clinopyroxene occur in a few samples. These amphibolites have tholeiitic basalt composition. On a primitive mantle-normalized diagram, they display fairly flat patterns without negative anomalies for either Eu or Nb-Ta. We have shown using Sm-Nd whole rock isotopic data that these amphibolites formed at 3.3 ±0.075 Ga. They have positive ɛNdi values (+5.2 ± 1.6). These samples show isotopically juvenile features, which rule out the possibility of significant contamination of the protolith magmas by ancient continental crust. Based on these geochemical data we propose that the tholeiitic basalts were formed in an oceanic plateau tectonic setting from a mantle plume source and that they have a

  1. Clinical profile and containment of the Ebola virus disease outbreak in two large West African cities, Nigeria, July–September 2014

    Directory of Open Access Journals (Sweden)

    Chima Ohuabunwo

    2016-12-01

    Conclusion: The EVD outbreak in Nigeria was characterized by the severe febrile gastroenteritis syndrome typical of the West African outbreak, better outcomes, rapid containment, and no infection among EVD care-providers. Early case detection, an effective incident management system, and prompt case management with on-site mobilization and training of local professionals were key to the outcome.

  2. Weeding method and pre-sowing tillage effects on weed growth and pearl millet yield in a sandy soil of the West African Sahelian zone.

    NARCIS (Netherlands)

    Klaij, M.C.; Hoogmoed, W.B.

    1996-01-01

    Weed control for the West African Sahel rainfed crops is done mainly manually, resulting in high labor requirements. Because of the seasonality of rainfed farming, weed control is often late and incomplete, resulting in considerable losses in crop yield. We examined the case of weed control in conti

  3. Characterization of African Bush Mango trees with emphasis on the differences between sweet and bitter trees in the Dahomey Gap (West Africa)

    NARCIS (Netherlands)

    Vihotogbe, R.

    2012-01-01

     African bush mango trees (ABMTs) are economically the most important species within the family of Irvingiaceae. They are priority trees producing non-timber forest products (NTFPs) and widely distributed in the humid lowland forests of West and Central Africa. To boost their production and dev

  4. Weakening and Shifting of the Saharan Heat Low Circulation During Wet Years of the West African Monsoon

    CERN Document Server

    Shekhar, Ravi

    2016-01-01

    The correlation between increased West African monsoon rainfall and anomalously low surface pressure over the Sahara is well established in observations and global climate models, and has been interpreted as a strengthening of the Saharan Heat Low (SHL) during wet monsoon years. This study uses two atmospheric reanalysis datasets to examine interannual variability of Sahel rainfall and the shallow Saharan Heat Low circulation, which consists of the near surface SHL and the Saharan High in the lower mid-troposphere. During wet Sahel years, the SHL circulation shifts poleward, producing a drop in low-level geopotential height and surface pressure over the Sahara. Statistically removing the effect of the poleward shift from the low-level geopotential eliminates significant correlations between this geopotential and Sahel precipitation. As the SHL circulation shifts poleward, its mid-tropospheric divergent outflow decreases, indicating a weakening of its overturning mass flux. The poleward shift and weakening of ...

  5. Leukocyte transcript alterations in West-African girls following a booster vaccination with diphtheria-tetanus-pertussis vaccine

    DEFF Research Database (Denmark)

    Orntoft, Nikolaj W; Thorsen, Kasper; Benn, Christine S;

    2013-01-01

    Background. Observational studies from low-income countries have shown that the vaccination against diphtheria, tetanus and pertussis (DTP) is associated with excess female mortality due to infectious diseases. Methods. To investigate possible changes in gene expression after DTP vaccination, we...... identified a group of nine comparable West African girls, from a biobank of 356 children, who were due to receive DTP booster vaccine at age 18 months. As a pilot experiment we extracted RNA from blood samples before, and 6 weeks after, vaccination to analyze the coding transcriptome in leukocytes using...... expression microarrays, and ended up with information from eight girls. The data was further analyzed using dedicated array pathway and network software. We aimed to study whether DTP vaccination introduced a systematic alteration in the immune system in girls. Results. We found very few transcripts to alter...

  6. Discovery and Description of Ebola Zaire Virus in 1976 and Relevance to the West African Epidemic During 2013-2016.

    Science.gov (United States)

    Breman, Joel G; Heymann, David L; Lloyd, Graham; McCormick, Joseph B; Miatudila, Malonga; Murphy, Frederick A; Muyembé-Tamfun, Jean-Jacques; Piot, Peter; Ruppol, Jean-François; Sureau, Pierre; van der Groen, Guido; Johnson, Karl M

    2016-10-15

     In 1976, the first cases of Ebola virus disease in northern Democratic Republic of the Congo (then referred to as Zaire) were reported. This article addresses who was responsible for recognizing the disease; recovering, identifying, and naming the virus; and describing the epidemic. Key scientific approaches used in 1976 and their relevance to the 3-country (Guinea, Sierra Leone, and Liberia) West African epidemic during 2013-2016 are presented.  Field and laboratory investigations started soon after notification, in mid-September 1976, and included virus cell culture, electron microscopy (EM), immunofluorescence antibody (IFA) testing of sera, case tracing, containment, and epidemiological surveys. In 2013-2016, medical care and public health work were delayed for months until the Ebola virus disease epidemic was officially declared an emergency by World Health Organization, but research in pathogenesis, clinical presentation, including sequelae, treatment, and prevention, has increased more recently.  Filoviruses were cultured and observed by EM in Antwerp, Belgium (Institute of Tropical Medicine); Porton Down, United Kingdom (Microbiological Research Establishment); and Atlanta, Georgia (Centers for Disease Control and Prevention). In Atlanta, serological testing identified a new virus. The 1976 outbreak (280 deaths among 318 cases) stopped in 2 years. Transmission indices (R0) are higher in all 3 countries than in 1976.  An international commission working harmoniously in laboratories and with local communities was essential for rapid success in 1976. Control and understanding of the recent West African outbreak were delayed because of late recognition and because authorities were overwhelmed by many patients and poor community involvement. Despite obstacles, research was a priority in 1976 and recently. Published by Oxford University Press for the Infectious Diseases Society of America 2016. This work is written by (a) US Government employee(s) and is

  7. Diversity and species composition of West African ungulate assemblages: effects of fire, climate and soil

    NARCIS (Netherlands)

    Klop, L.F.; Prins, H.H.T.

    2008-01-01

    Aim Anthropogenic fires are a major component of the ecology of rangelands throughout the world. To assess the effects of these fires on the diversity patterns of herbivores, we related gradients in fire occurrence, climate and soil fertility to patterns in alpha and beta diversity of African ungula

  8. Seed systems for African food security: linking molecular genetic analysis and cultivator knowledge in West Africa

    NARCIS (Netherlands)

    Richards, P.; Bruin-Hoekzema, de M.; Hughes, S.G.; Kudadjie, C.Y.; Offei, S.K.; Struik, P.C.

    2009-01-01

    A challenge for African countries is how to integrate new sources of knowledge on plant genetics with knowledge from farmer practice to help improve food security. This paper considers the knowledge content of farmer seed systems in the light of a distinction drawn in artificial intelligence researc

  9. a literary analysis of the west africans' reaction to the introduction of ...

    African Journals Online (AJOL)

    mycl

    analyzed based on two Francophone novels: Camara Laye's The. African Child and ... Education System. One trait ... This feeling of nostalgia concerns the time prior to the Western school, and ..... The Anglophones' target is to present the real face of their society to ...... Emerging from all sides, from deep valleys of shadow ...

  10. Should I stay or should I go? Dispersal and population structure in small, isolated desert populations of West African crocodiles.

    Science.gov (United States)

    Velo-Antón, Guillermo; Godinho, Raquel; Campos, João Carlos; Brito, José Carlos

    2014-01-01

    The maintenance of both spatial and genetic connectivity is paramount to the long-term persistence of small, isolated populations living in environments with extreme climates. We aim to identify the distribution of genetic diversity and assess population sub-structuring and dispersal across dwarfed desert populations of Crocodylus suchus, which occur in isolated groups, usually less than five individuals, along the mountains of Mauritania (West Africa). We used both invasive and non-invasive sampling methods and a combination of mitochondrial DNA (12 S and ND4) and microsatellite markers (32 loci and a subset of 12 loci). Our results showed high genetic differentiation and geographic structure in Mauritanian populations of C. suchus. We identified a metapopulation system acting within four river sub-basins (high gene flow and absence of genetic structure) and considerable genetic differentiation between sub-basins (FST range: 0.12-0.24) with rare dispersal events. Effective population sizes tend to be low within sub-basins while genetic diversity is maintained. Our study suggests that hydrographic networks (temporal connections along seasonal rivers during rainy periods) allow C. suchus to disperse and maintain metapopulation dynamics within sub-basins, which attenuate the loss of genetic diversity and the risk of extinction. We highlight the need of hydrographic conservation to protect vulnerable crocodiles isolated in small water bodies. We propose C. suchus as an umbrella species in Mauritania based on ecological affinities shared with other water-dependent species in desert environments.

  11. Should I stay or should I go? Dispersal and population structure in small, isolated desert populations of West African crocodiles.

    Directory of Open Access Journals (Sweden)

    Guillermo Velo-Antón

    Full Text Available The maintenance of both spatial and genetic connectivity is paramount to the long-term persistence of small, isolated populations living in environments with extreme climates. We aim to identify the distribution of genetic diversity and assess population sub-structuring and dispersal across dwarfed desert populations of Crocodylus suchus, which occur in isolated groups, usually less than five individuals, along the mountains of Mauritania (West Africa. We used both invasive and non-invasive sampling methods and a combination of mitochondrial DNA (12 S and ND4 and microsatellite markers (32 loci and a subset of 12 loci. Our results showed high genetic differentiation and geographic structure in Mauritanian populations of C. suchus. We identified a metapopulation system acting within four river sub-basins (high gene flow and absence of genetic structure and considerable genetic differentiation between sub-basins (FST range: 0.12-0.24 with rare dispersal events. Effective population sizes tend to be low within sub-basins while genetic diversity is maintained. Our study suggests that hydrographic networks (temporal connections along seasonal rivers during rainy periods allow C. suchus to disperse and maintain metapopulation dynamics within sub-basins, which attenuate the loss of genetic diversity and the risk of extinction. We highlight the need of hydrographic conservation to protect vulnerable crocodiles isolated in small water bodies. We propose C. suchus as an umbrella species in Mauritania based on ecological affinities shared with other water-dependent species in desert environments.

  12. AFRICAN TEXTILES

    African Journals Online (AJOL)

    West African textiles form an important aspect of African art. Their uniqueness in ... more improvised, fluid effect that plays with de- ... on the off-beat in African music, notions of re- ... also named after perceived visual similarities .... of palm leaf serves as a brush and the resist paint .... has begun to be seriously investigated.

  13. Analysis of a grid ionospheric vertical delay and its bounding errors over West African sub-Saharan region

    Science.gov (United States)

    Abe, O. E.; Otero Villamide, X.; Paparini, C.; Radicella, S. M.; Nava, B.

    2017-02-01

    Investigating the effects of the Equatorial Ionization Anomaly (EIA) ionosphere and space weather on Global Navigation Satellite Systems (GNSS) is very crucial, and a key to successful implementation of a GNSS augmentation system (SBAS) over the equatorial and low-latitude regions. A possible ionospheric vertical delay (GIVD, Grid Ionospheric Vertical Delay) broadcast at a Ionospheric Grid Point (IGP) and its confidence bounds errors (GIVE, Grid Ionospheric Vertical Error) are analyzed and compared with the ionospheric vertical delay estimated at a nearby user location over the West African Sub-Saharan region. Since African sub-Saharan ionosphere falls within the EIA region, which is always characterized by a disturbance in form of irregularities after sunset, and the disturbance is even more during the geomagnetically quiet conditions unlike middle latitudes, the need to have a reliable ionospheric threat model to cater for the nighttime ionospheric plasma irregularities for the future SBAS user is essential. The study was done during the most quiet and disturbed geomagnetic conditions on October 2013. A specific low latitude EGNOS-like algorithm, based on single thin layer model, was engaged to simulate SBAS message in the study. Our preliminary results indicate that, the estimated GIVE detects and protects a potential SBAS user against sampled ionospheric plasma irregularities over the region with a steep increment in GIVE to non-monitored after local sunset to post midnight. This corresponds to the onset of the usual ionospheric plasma irregularities in the region. The results further confirm that the effects of the geomagnetic storms on the ionosphere are not consistent in affecting GNSS applications over the region. Finally, this paper suggests further work to be investigated in order to improve the threat integrity model activity, and thereby enhance the availability of the future SBAS over African sub-Saharan region.

  14. Factors controlling the distribution of ozone in the West African lower troposphere during the AMMA (African Monsoon Multidisciplinary Analysis wet season campaign

    Directory of Open Access Journals (Sweden)

    M. Saunois

    2009-08-01

    Full Text Available Ozone and its precursors were measured on board the Facility for Airborne Atmospheric Measurements (FAAM BAe 146 Atmospheric Research Aircraft during the monsoon season 2006 as part of the African Monsoon Multidisciplinary Analysis (AMMA campaign. One of the main features observed in the west African boundary layer is the increase of the ozone mixing ratios from 25 ppbv over the forested area (south of 12° N up to 40 ppbv over the Sahelian area. We employ a two-dimensional (latitudinal versus vertical meteorological model coupled with an O3-NOx-VOC chemistry scheme to simulate the distribution of trace gases over West Africa during the monsoon season and to analyse the processes involved in the establishment of such a gradient. Including an additional source of NO over the Sahelian region to account for NO emitted by soils we simulate a mean NOx concentration of 0.7 ppbv at 16° N versus 0.3 ppbv over the vegetated region further south in reasonable agreement with the observations. As a consequence, ozone is photochemically produced with a rate of 0.25 ppbv h−1 over the vegetated region whilst it reaches up to 0.75 ppbv h−1 at 16° N. We find that the modelled gradient is due to a combination of enhanced deposition to vegetation, which decreases the ozone levels by up to 11 pbbv, and the aforementioned enhanced photochemical production north of 12° N. The peroxy radicals required for this enhanced production in the north come from the oxidation of background CO and CH4 as well as from VOCs. Sensitivity studies reveal that both the background CH4 and partially oxidised VOCs, produced from the oxidation of isoprene emitted from the vegetation in the south, contribute around 5–6 ppbv to the ozone gradient. These results suggest that the northward transport of trace gases by the monsoon flux, especially during nighttime, can have a significant, though secondary

  15. The Impact of the Atlantic Cold Tongue on West African Monsoon Onset in Regional Model Simulations for 1998-2002

    Science.gov (United States)

    Druyan, Leonard M.; Fulakeza, Matthew B.

    2014-01-01

    The Atlantic cold tongue (ACT) develops during spring and early summer near the Equator in the Eastern Atlantic Ocean and Gulf of Guinea. The hypothesis that the ACT accelerates the timing of West African monsoon (WAM) onset is tested by comparing two regional climate model (RM3) simulation ensembles. Observed sea surface temperatures (SST) that include the ACT are used to force a control ensemble. An idealized, warm SST perturbation is designed to represent lower boundary forcing without the ACT for the experiment ensemble. Summer simulations forced by observed SST and reanalysis boundary conditions for each of five consecutive years are compared to five parallel runs forced by SST with the warm perturbation. The article summarizes the sequence of events leading to the onset of the WAM in the Sahel region. The representation of WAM onset in RM3 simulations is examined and compared to Tropical Rainfall Measuring Mission (TRMM), Global Precipitation Climatology Project (GPCP) and reanalysis data. The study evaluates the sensitivity of WAM onset indicators to the presence of the ACT by analysing the differences between the two simulation ensembles. Results show that the timing of major rainfall events and therefore theWAM onset in the Sahel are not sensitive to the presence of the ACT. However, the warm SST perturbation does increase downstream rainfall rates over West Africa as a consequence of enhanced specific humidity and enhanced northward moisture flux in the lower troposphere.

  16. Future changes in the West African Monsoon: A COSMO-CLM and RCA4 multimodel ensemble study

    Science.gov (United States)

    Anders, Ivonne; Gbobaniyi, Emiola

    2014-05-01

    In this multi-model multi-ensemble study, we intercompare results from two regional climate simulation ensembles to see how well they reproduce the known main features of the West African Monsoon (WAM). Each ensemble was created under the ongoing CORDEX-Africa activities by using the regional climate models (RCA4 and COSMO-CLM) to downscale four coupled atmosphere ocean general circulation models (AOGCMs), namely, CNRM-CM5, HadGEM2-ES, EC-EARTH, and MPI-ESM-LR. Spatial resolution of the driving AOGCMs varies from about 1° to 3° while all regional simulations are at the same 0.44° resolution. Future climate projections from the RCP8.5 scenario are analyzed and inter-compared for both ensembles in order to assess deviations and uncertainties. The main focus in our analysis is on the projected WAM rainy season statistics. We look at projected changes in onset and cessation, total precipitation and temperature toward the end of the century (2071-2100) for different time scales spanning seasonal climatologies, annual cycles and interannual variability, and a number of spatial scales covering the Sahel, the Gulf of Guinea and the entire West Africa. Differences in the ensemble projections are linked to the parameterizations employed in both regional models and the influence of this is discussed.

  17. Bacillus anthracis Diversity and Geographic Potential across Nigeria, Cameroon and Chad: Further Support of a Novel West African Lineage.

    Science.gov (United States)

    Blackburn, Jason K; Odugbo, Moses Ode; Van Ert, Matthew; O'Shea, Bob; Mullins, Jocelyn; Perreten, Vincent; Perrenten, Vincent; Maho, Angaya; Hugh-Jones, Martin; Hadfield, Ted

    2015-01-01

    Zoonoses, diseases affecting both humans and animals, can exert tremendous pressures on human and veterinary health systems, particularly in resource limited countries. Anthrax is one such zoonosis of concern and is a disease requiring greater public health attention in Nigeria. Here we describe the genetic diversity of Bacillus anthracis in Nigeria and compare it to Chad, Cameroon and a broader global dataset based on the multiple locus variable number tandem repeat (MLVA-25) genetic typing system. Nigerian B. anthracis isolates had identical MLVA genotypes and could only be resolved by measuring highly mutable single nucleotide repeats (SNRs). The Nigerian MLVA genotype was identical or highly genetically similar to those in the neighboring countries, confirming the strains belong to this unique West African lineage. Interestingly, sequence data from a Nigerian isolate shares the anthrose deficient genotypes previously described for strains in this region, which may be associated with vaccine evasion. Strains in this study were isolated over six decades, indicating a high level of temporal strain stability regionally. Ecological niche models were used to predict the geographic distribution of the pathogen for all three countries. We describe a west-east habitat corridor through northern Nigeria extending into Chad and Cameroon. Ecological niche models and genetic results show B. anthracis to be ecologically established in Nigeria. These findings expand our understanding of the global B. anthracis population structure and can guide regional anthrax surveillance and control planning.

  18. Bacillus anthracis Diversity and Geographic Potential across Nigeria, Cameroon and Chad: Further Support of a Novel West African Lineage.

    Directory of Open Access Journals (Sweden)

    Jason K Blackburn

    Full Text Available Zoonoses, diseases affecting both humans and animals, can exert tremendous pressures on human and veterinary health systems, particularly in resource limited countries. Anthrax is one such zoonosis of concern and is a disease requiring greater public health attention in Nigeria. Here we describe the genetic diversity of Bacillus anthracis in Nigeria and compare it to Chad, Cameroon and a broader global dataset based on the multiple locus variable number tandem repeat (MLVA-25 genetic typing system. Nigerian B. anthracis isolates had identical MLVA genotypes and could only be resolved by measuring highly mutable single nucleotide repeats (SNRs. The Nigerian MLVA genotype was identical or highly genetically similar to those in the neighboring countries, confirming the strains belong to this unique West African lineage. Interestingly, sequence data from a Nigerian isolate shares the anthrose deficient genotypes previously described for strains in this region, which may be associated with vaccine evasion. Strains in this study were isolated over six decades, indicating a high level of temporal strain stability regionally. Ecological niche models were used to predict the geographic distribution of the pathogen for all three countries. We describe a west-east habitat corridor through northern Nigeria extending into Chad and Cameroon. Ecological niche models and genetic results show B. anthracis to be ecologically established in Nigeria. These findings expand our understanding of the global B. anthracis population structure and can guide regional anthrax surveillance and control planning.

  19. Measuring pesticide ecological and health risks in West African agriculture to establish an enabling environment for sustainable intensification.

    Science.gov (United States)

    Jepson, P C; Guzy, M; Blaustein, K; Sow, M; Sarr, M; Mineau, P; Kegley, S

    2014-04-01

    We outline an approach to pesticide risk assessment that is based upon surveys of pesticide use throughout West Africa. We have developed and used new risk assessment models to provide, to our knowledge, the first detailed, geographically extensive, scientifically based analysis of pesticide risks for this region. Human health risks from dermal exposure to adults and children are severe enough in many crops to require long periods of up to three weeks when entry to fields should be restricted. This is impractical in terms of crop management, and regulatory action is needed to remove these pesticides from the marketplace. We also found widespread risks to terrestrial and aquatic wildlife throughout the region, and if these results were extrapolated to all similar irrigated perimeters in the Senegal and Niger River Basins, they suggest that pesticides could pose a significant threat to regional biodiversity. Our analyses are presented at the regional, national and village levels to promote regulatory advances but also local risk communication and management. Without progress in pesticide risk management, supported by participatory farmer education, West African agriculture provides a weak context for the sustainable intensification of agricultural production or for the adoption of new crop technologies.

  20. Nutrient flows in urban and peri-urban agroecosystems in three West African cities

    NARCIS (Netherlands)

    Abdulkadir, A.

    2012-01-01

    Key words: Sustainability, CATPCA, two-step cluster analysis, farm types, nutrient balances, West Africa, gross margin, NUTMON/MONQI. Urban and peri-urban agriculture (UPA) is defined as the cultivation of crops and keeping livestock within and around cities. In addition to providing the cities&rsq

  1. Options for carbon sequestration in West African soils: an exploratory study with special focus on Senegal

    NARCIS (Netherlands)

    Batjes, N.H.

    2001-01-01

    The organic matter content of many soils in West Africa has been depleted due to overgrazing, agricultural mismanagement, deforestation and overexploitation of the natural resources. Degraded agro(eco)systems can be managed to increase carbon sinks in vegetation and soil, and to reduce carbon emissi

  2. Surface runoff scale effects in West African watersheds: Modeling and management options

    NARCIS (Netherlands)

    Giesen, van de N.C.; Stomph, T.J.; Ridder, de N.

    2005-01-01

    Measurements of surface runoff from uniform slopes of different lengths in West Africa have shown that longer slopes tend to have less runoff per unit of length than short slopes. The main reason for this scale effect is that once the rain stops, water on long slopes has more opportunity time to inf

  3. Restoring and maintaining the productivity of West African soils: key to sustainable development

    NARCIS (Netherlands)

    Mokwunye, A.U.; Jager, de A.; Smaling, E.M.A.

    1996-01-01

    This report highlights the alarming situation as to low soil fertility and its continued decline in West Africa. Through literature review, a description is given of farming systems and soil fertility in the three major agro-ecological zones: the Equatorial Forest Zone, the Guinea Savanna Zone, and

  4. Nutrient flows in urban and peri-urban agroecosystems in three West African cities

    NARCIS (Netherlands)

    Abdulkadir, A.

    2012-01-01

    Key words: Sustainability, CATPCA, two-step cluster analysis, farm types, nutrient balances, West Africa, gross margin, NUTMON/MONQI. Urban and peri-urban agriculture (UPA) is defined as the cultivation of crops and keeping livestock within and around cities. In addition to providing the

  5. Biogeographical and anthropogenic determinants of landscape-scale patterns of raptors in West African savannas

    NARCIS (Netherlands)

    Buij, Ralph; Croes, Barbara M.; Komdeur, Jan

    2013-01-01

    Strong raptor population declines have recently been reported in sub-Saharan West Africa, where the pressure on wildlife and their supporting habitats is particularly high. This makes it imperative to understand the role of land-use on landscape-scale patterns of raptors and to define priority areas

  6. Change and Variation in Family Religious Language Policy in a West African Muslim Community

    Science.gov (United States)

    Moore, Leslie C.

    2016-01-01

    This article examines variation in family religious language policy in a Muslim community in West Africa. Taking an ethnographically grounded case study approach, I situate families' choices with regards to their children's religious (language) education within the larger linguistic, social, and cultural context, focusing on new influences on…

  7. Dyed and Printed Textiles: Javanese Batik [and] Dutch Wax Prints [and] West African Adire. Third Edition.

    Science.gov (United States)

    Burke, Sue

    Three booklets focusing on dyed and printed textile techniques of Java, West Africa, and the Netherlands describe historical and ethnographic materials as well as the development of particular technical traditions. Each section may be used alone or with either or both of the others. When used together, these booklets illustrate the…

  8. The role of the Indian monsoon onset in the West African monsoon onset: observations and AGCM nudged simulations

    Energy Technology Data Exchange (ETDEWEB)

    Flaounas, Emmanouil [LATMOS/IPSL, Universite Pierre et Marie Curie, Paris cedex 05 (France); Janicot, Serge [LOCEAN/IPSL, IRD, Universite Pierre et Marie Curie, Paris (France); Bastin, Sophie [LATMOS/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Roca, Remy [LMD/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Mohino, Elsa [LOCEAN/IPSL, CNRS, Universite Pierre et Marie Curie, Paris (France); Universidad de Sevilla, Sevilla (Spain)

    2012-03-15

    In spring the inland penetration of the West African Monsoon (WAM) is weak and the associated rainband is located over the Guinean coast. Then within a few days deep convection weakens considerably and the rainband reappears about 20 days after over the Sahel, where it remains until late September signalling the summer rainy season. Over the period 1989-2008 a teleconnection induced by the Indian monsoon onset is shown to have a significant impact on the WAM onset, by performing composite analyses on both observational data sets and atmospheric general circulation model simulations ensembles where the model is nudged to observations over the Indian monsoon sector. The initiation of convective activity over the Indian subcontinent north of 15 N at the time of the Indian monsoon onset results in a westward propagating Rossby wave establishing over North Africa 7-15 days after. A back-trajectory analysis shows that during this period, dry air originating from the westerly subtropical jet entrance is driven to subside and move southward over West Africa inhibiting convection there. At the same time the low-level pressure field over West Africa reinforces the moisture transport inland. After the passage of the wave, the dry air intrusions weaken drastically. Hence 20 days after the Indian monsoon onset, convection is released over the Sahel where thermodynamic conditions are more favourable. This scenario is very similar in the observations and in the nudged simulations, meaning that the Indian monsoon onset is instrumental in the WAM onset and its predictability at intraseasonal scale. (orig.)

  9. Tobacco use and its determinants in HIV-infected patients on antiretroviral therapy in West African countries

    Science.gov (United States)

    Jaquet, Antoine; Ekouevi, Didier-Koumavi; Aboubakrine, Maiga; Bashi, Jules; Messou, Eugène; Maiga, Moussa; Traore, Hamar-Alassane; Zannou, Marcel; Guehi, Calixte; Ba-Gomis, Franck-Olivier; Minga, Albert; Allou, Gérard; Eholie, Serge-Paul; Dabis, Francois; Bissagnene, Emmanuel; Sasco, Annie-Jeanne

    2009-01-01

    INTRODUCTION Tobacco smoking is common in HIV-infected patients from industrialized countries. In West Africa, few data exist concerning tobacco consumption. METHODS A cross-sectional survey was conducted within the International epidemiological Database to Evaluate AIDS (IeDEA) network in West Africa. Health workers administered to patients receiving antiretroviral treatment a questionnaire assessing tobacco and cannabis consumption. Regular smokers were defined as present smokers who smoked >1 cigarette per day for ≥1 year. RESULTS Overall, 2920 patients were enrolled in three countries. The prevalence of ever smokers and present smokers were 46.2% (95% CI 42.8–49.5) and 15.6% (95% CI 13.2–18.0) in men and 3.7% (95% CI 2.9–4.5) and 0.6% (95% CI 0.3–0.9) in women, respectively. Regular smoking was associated being from Côte d’Ivoire or Mali compared to Benin (OR 4.6; 95% CI 2.9–7.3 and 7.7; 95% CI 4.4–13.6), a severely impaired immunological status at HAART initiation (OR 1.5; 95% CI 1.1–2.2) and a history of tuberculosis (OR 1.8; 95% CI 1.1–3.0). CONCLUSION Marked differences of smoking prevalence exist between these West African countries. This survey approach also provides evidences concerning the association between cigarette smoking and tuberculosis in HIV-infected patients, a major public health issue in this part of the world. PMID:19861019

  10. Health-Needs Assessment for West African Immigrants in Greater Providence, RI.

    Science.gov (United States)

    Adu-Boahene, Akosua Boadiwaa; Laws, Michael Barton; Dapaah-Afriyie, Kwame

    2017-01-06

    African immigrants in the United States may experience barriers to health-care access and effectiveness. This mixed-methods study used paper-based surveys of people (N=101) in the target population from Nigeria, Ghana, and Liberia, recruited through convenience and snowball sampling. Semi-structured interviews were conducted with 3 clergy members who pastor churches with large Nigerian, Ghanaian, and Liberian populations, respectively; and five physicians and a clinical pharmacist who serve African immigrants. Length of stay in the United States was associated with the health status of refugee children. Undocumented immigration status was associated with lack of health insurance. Cardiovascular diseases, uterine fibroids and stress-related disorders were the most prevalent reported conditions. Regardless of English fluency, many immigrants are unfamiliar with medical terminology. African immigrants in the state of Rhode Island need more health education and resources to navigate the US health-care system. [Full article available at http://rimed.org/rimedicaljournal-2017-01.asp].

  11. Institutional development: from legal pluralism to institutional bricolage in West African pastoralism.

    Science.gov (United States)

    Fokou, G; Bonfoh, B

    2016-11-01

    Pastoralists in Africa are increasingly vulnerable to the effects of globalisation, climate change and changes in land use. They are confronted with problems related to access to scarce natural resources and their regulation, the management of mobility, and too little investment in health systems, livestock production and social service delivery. However, this paper focuses on positive trends and vital innovations in pastoral societies. These rely on robust institutions and policy frameworks that contribute to economically secure, politically stable, and environmentally sustainable livelihoods for African pastoral societies. The authors analyse ways in which internal and external efforts can improve the economic viability and social aspects of pastoralism. The institutions that manage natural resources and their effects on livelihoods and access to social services must be critically reviewed. The authors suggest that a new model for the economic and social development of African pastoralism should be positioned between donor- or governmentdriven development (in other words, 'seeing like a state') and the autonomous development goals of pastoralists ('seeing like a pastoralist'). Pastoralists are resourceful, entrepreneurial and innovative people, fully able to support new institutional systems and services which recognise their way of life and production systems. It seems evident that African pastoralism will maintain its vitality and creativity through a process of 'bricolage', with institutional and policy innovations based on a constant renegotiation of norms, the reinvention or transformation of tradition, the importance of legitimate authority and the role of the people themselves in shaping such arrangements.

  12. [Pattern of systemic lupus erythematosus in Benin and West African patients].

    Science.gov (United States)

    Zomalheto, Zavier; Assogba, Michee; Agbodande, Anthelme; Atadokpede, Felix; Gounongbe, Marcelle; Avimadje, Martin

    2014-12-01

    To describe the clinical features, laboratory characteristics and the treatment of systemic lupus erythematosus (SLE) among Benin people and West Africa people. This is a part of a retrospective study which initially concerned patients seen in the rheumatology, dermatology and internal medicine departments of National Hospital University of Cotonou during January 2000 to March 2013 (14 years). Patients included in the study were all older than 16 years and fulfilling at least four of ACR criteria 1997 for Systemic lupus erythematosus. In a second step, we collect the data of the countries of West Africa where the work on the systemic lupus erythematosus have been published through a literature review including all articles published in the local, regional and international journals. Demographic, clinical and outcomes data were analyzed. 33 cases of lupus were diagnosed in 14 years in Cotonou. The sex ratio was 32/1 and means age 28.76 ± 8.01 [16-51]. The mean delay before diagnosis was 15 months [1- 84 months]. Polyarthralgia/ polyarthritis were the most common presentations (94.3 %) followed by systemic manifestations (78.9 %). Nineteen (19) patients achieved serological profiles. The anti- ds DNA were positive in 15 cases, anti- Sm in 10 cases and anti -SSA in 5 cases. Anti - phospholipids and lupus anticoagulant were absent. Treatment modalities were: corticosteroids (n = 21) antimalarials (n=15) , methotrexate (n = 4) , body corticosteroids (n=5), clinical monitoring without treatment (n = 3). Outcome was satisfactory in 25 cases. Eight (8) patients developed complications, 4 cases of death were observed and 8 patients lost to follow. These data are congruent with those published in the countries of West Africa. SLE seems rare in Benin. In general, in West Africa, the diagnosis is difficult because the clinical polymorphism by misdiagnosis and access serological profiles difficulty. However, the disease appears to be well controlled by treatment dominated by

  13. Biogeographical and anthropogenic determinants of landscape-scale patterns of raptors in West African savannas

    OpenAIRE

    2013-01-01

    Strong raptor population declines have recently been reported in sub-Saharan West Africa, where the pressure on wildlife and their supporting habitats is particularly high. This makes it imperative to understand the role of land-use on landscape-scale patterns of raptors and to define priority areas for conservation. We examine landscape-scale community patterns of raptors in biogeographical zones with different degrees of anthropogenic land-use and assess the role of protected areas in maint...

  14. Molecular evolution of Azagny virus, a newfound hantavirus harbored by the West African pygmy shrew (Crocidura obscurior in Côte d'Ivoire

    Directory of Open Access Journals (Sweden)

    Kang Hae Ji

    2011-07-01

    Full Text Available Abstract Background Tanganya virus (TGNV, the only shrew-associated hantavirus reported to date from sub-Saharan Africa, is harbored by the Therese's shrew (Crocidura theresae, and is phylogenetically distinct from Thottapalayam virus (TPMV in the Asian house shrew (Suncus murinus and Imjin virus (MJNV in the Ussuri white-toothed shrew (Crocidura lasiura. The existence of myriad soricid-borne hantaviruses in Eurasia and North America would predict the presence of additional hantaviruses in sub-Saharan Africa, where multiple shrew lineages have evolved and diversified. Methods Lung tissues, collected in RNAlater®, from 39 Buettikofer's shrews (Crocidura buettikoferi, 5 Jouvenet's shrews (Crocidura jouvenetae, 9 West African pygmy shrews (Crocidura obscurior and 21 African giant shrews (Crocidura olivieri captured in Côte d'Ivoire during 2009, were systematically examined for hantavirus RNA by RT-PCR. Results A genetically distinct hantavirus, designated Azagny virus (AZGV, was detected in the West African pygmy shrew. Phylogenetic analysis of the S, M and L segments, using maximum-likelihood and Bayesian methods, under the GTR+I+Γ model of evolution, showed that AZGV shared a common ancestry with TGNV and was more closely related to hantaviruses harbored by soricine shrews than to TPMV and MJNV. That is, AZGV in the West African pygmy shrew, like TGNV in the Therese's shrew, did not form a monophyletic group with TPMV and MJNV, which were deeply divergent and basal to other rodent- and soricomorph-borne hantaviruses. Ancestral distributions of each hantavirus lineage, reconstructed using Mesquite 2.74, suggested that the common ancestor of all hantaviruses was most likely of Eurasian, not African, origin. Conclusions Genome-wide analysis of many more hantaviruses from sub-Saharan Africa are required to better understand how the biogeographic origin and radiation of African shrews might have contributed to, or have resulted from, the evolution

  15. Trends and Variability in Pastoral Resources in the West African Sahel

    Science.gov (United States)

    Hanan, N. P.

    2014-12-01

    The geography of water and nutrients in the savannas of West Africa has shaped the development of a system of migratory cattle movements ("transhumance") in which herds travel north during the rainy season to graze the nutritious grasslands of the Sahel and return south in the dry season to graze in fallow lands and on agricultural residue. Cattle in this system gain most of their body mass while grazing in the Sahel and frequently lose mass on their dry season range. The Sahel is, therefore, at the heart of extensive livestock production systems in West Africa. However, there is increasing concern regarding how climate change will impact the region, while human population growth and economic development require increased agricultural and livestock production. The future for pastoral production systems in West Africa is, therefore, uncertain. This presentation combines remote sensing of vegetation structure and phenology with a watershed-scale tree-grass ecohydrology model, to explore how key resources for Sahelian pastoralist communities (forage and surface water for livestock, woody biomass for fuel) respond to climate variability and extreme events, conditioned by human management of grazing, fire and fuel-wood harvest. Mortality of woody species and loss of herbaceous cover during the Sahelian droughts of the 1970's and 1980's significantly perturbed vegetation dynamics and ecohydrological interactions, perturbations from which the region is still recovering. The re-greening and reforestation of the Sahel reported by many authors is, in part, an expression of this recovery. Future trajectories of change in pastoral resources in the Sahel, in particular forage availability and drinking water, are explored using climate change ensembles.

  16. Statistical modeling of the abundance of vectors of West African Rift Valley fever in Barkedji, Senegal.

    Directory of Open Access Journals (Sweden)

    Cheikh Talla

    Full Text Available Rift Valley fever is an emerging mosquito-borne disease that represents a threat to human and animal health. The exophilic and exophagic behavior of the two main vector in West Africa (Aedes vexans and Culex poicilipes, adverse events post-vaccination, and lack of treatment, render ineffective the disease control. Therefore it is essential to develop an information system that facilitates decision-making and the implementation of adaptation strategies. In East Africa, RVF outbreaks are linked with abnormally high rainfall, and can be predicted up to 5 months in advance by modeling approaches using climatic and environmental parameters. However, the application of these models in West Africa remains unsatisfactory due to a lack of data for animal and human cases and differences in the dynamics of the disease emergence and the vector species involved in transmission. Models have been proposed for West Africa but they were restricted to rainfall impact analysis without a spatial dimension. In this study, we developed a mixed Bayesian statistical model to evaluate the effects of climatic and ecological determinants on the spatiotemporal dynamics of the two main vectors. Adult mosquito abundance data were generated from July to December every fortnight in 2005-2006 at 79 sites, including temporary ponds, bare soils, shrubby savannah, wooded savannah, steppes, and villages in the Barkédji area. The results demonstrate the importance of environmental factors and weather conditions for predicting mosquito abundance. The rainfall and minimum temperature were positively correlated with the abundance of Cx. poicilipes, whereas the maximum temperature had negative effects. The rainfall was negatively correlated with the abundance of Ae. vexans. After combining land cover classes, weather conditions, and vector abundance, our model was used to predict the areas and periods with the highest risks of vector pressure. This information could support decision

  17. Extreme flooding in the West African cities of Dakar and Ouagadougou - atmospheric dynamics and implications for flood risk assessments

    Science.gov (United States)

    Engel, Thomas; Fink, Andreas; Knippertz, Peter

    2017-04-01

    In this study, two extreme, high-impact events of heavy rainfall and severe floods in West African urban areas (Ouagadougou in 2009, Dakar in 2012) are investigated in terms of their atmospheric causes and statistical return periods. In terms of the synoptic-convective dynamics, the Ouagadougou case is truly exceptional. A succession of two strong and temporarily slow-moving African Easterly Waves (AEWs) caused record-breaking values of tropospheric moisture and low-level relative vorticity, thereby providing the synoptic forcing for the nighttime genesis of Mesoscale Convective Systems (MCSs). Ouagadougou was hit by two successive MCSs, the latter being possible due to the rotation and swift moisture refuelling by the strong convergence in the AEW-related vortex. It is speculated that this case may allow a glimpse of a new type of extreme Sahelian rainstorms. Similarly to the Ouagadougou case, an AEW was instrumental in the overnight development of an MCSs to the east of Dakar, but neither the AEW vortex nor the tropospheric moisture content was as exceptional as in the Ouagadougou case. The Return Value (RV) analysis suggests that TRMM 3B42 data appears to be suitable to estimate centennial RVs using the "peak-over-threshold" approach with a GPD fit, though the good performance might be a result of errors in estimating extreme rainfall over the arid Sahel. On the contrary PERSIANN-CDR is inappropriate for this purpose, despite having a twice as long observational period. The Ouagadougou event also shows that highly unusual dynamical developments can create extreme situations well outside of any RV estimates from century-long daily rainfall observations.

  18. West African monsoon intraseasonal activity and its daily precipitation indices in regional climate models: diagnostics and challenges

    Science.gov (United States)

    Poan, E. D.; Gachon, P.; Dueymes, G.; Diaconescu, E.; Laprise, R.; Seidou Sanda, I.

    2016-11-01

    The West African monsoon intraseasonal variability has huge socio-economic impacts on local populations but understanding and predicting it still remains a challenge for the weather prediction and climate scientific community. This paper analyses an ensemble of simulations from six regional climate models (RCMs) taking part in the coordinated regional downscaling experiment, the ECMWF ERA-Interim reanalysis (ERAI) and three satellite-based and observationally-constrained daily precipitation datasets, to assess the performance of the RCMs with regard to the intraseasonal variability. A joint analysis of seasonal-mean precipitation and the total column water vapor (also called precipitable water— PW) suggests the existence of important links at different timescales between these two variables over the Sahel and highlights the relevance of using PW to follow the monsoon seasonal cycle. RCMs that fail to represent the seasonal-mean position and amplitude of the meridional gradient of PW show the largest discrepancies with respect to seasonal-mean observed precipitation. For both ERAI and RCMs, spectral decompositions of daily PW as well as rainfall show an overestimation of low-frequency activity (at timescales longer than 10 days) at the expense of the synoptic (timescales shorter than 10 days) activity. Consequently, the effects of the African Easterly Waves and the associated mesoscale convective systems are substantially underestimated, especially over continental regions. Finally, the study investigates the skill of the models with respect to hydro-climatic indices related to the occurrence, intensity and frequency of precipitation events at the intraseasonal scale. Although most of these indices are generally better reproduced with RCMs than reanalysis products, this study indicates that RCMs still need to be improved (especially with respect to their subgrid-scale parameterization schemes) to be able to reproduce the intraseasonal variance spectrum adequately.

  19. Preparing for Ebola Virus Disease in West African countries not yet affected: perspectives from Ghanaian health professionals.

    Science.gov (United States)

    Nyarko, Yaw; Goldfrank, Lewis; Ogedegbe, Gbenga; Soghoian, Sari; de-Graft Aikins, Ama

    2015-02-26

    The current Ebola Virus Disease (EVD) epidemic has ravaged the social fabric of three West African countries and affected people worldwide. We report key themes from an agenda-setting, multi-disciplinary roundtable convened to examine experiences and implications for health systems in Ghana, a nation without cases but where risk for spread is high and the economic, social and political impact of the impending threat is already felt. Participants' personal stories and the broader debates to define fundamental issues and opportunities for preparedness focused on three inter-related themes. First, the dangers of the fear response itself were highlighted as a threat to the integrity and continuity of quality care. Second, healthcare workers' fears were compounded by a demonstrable lack of societal and personal protections for infection prevention and control in communities and healthcare facilities, as evidenced by an ongoing cholera epidemic affecting over 20,000 patients in the capital Accra alone since June 2014. Third, a lack of coherent messaging and direction from leadership seems to have limited coordination and reinforced a level of mistrust in the government's ability and commitment to mobilize an adequate response. Initial recommendations include urgent investment in the needed supplies and infrastructure for basic, routine infection control in communities and healthcare facilities, provision of assurances with securities for frontline healthcare workers, establishment of a multi-sector, "all-hazards" outbreak surveillance system, and engaging directly with key community groups to co-produce contextually relevant educational messages that will help decrease stigma, fear, and the demoralizing perception that the disease defies remedy or control. The EVD epidemic provides an unprecedented opportunity for West African countries not yet affected by EVD cases to make progress on tackling long-standing health systems weaknesses. This roundtable discussion

  20. Unmet reproductive health needs among women in some West African countries: a systematic review of outcome measures and determinants.

    Science.gov (United States)

    Ayanore, Martin Amogre; Pavlova, Milena; Groot, Wim

    2016-01-16

    Identifying relevant measures of women's reproductive health needs is critical to improve women's chances of service utilization. The study aims to systematically review and analyze the adequacy of outcome measures and determinants applied in previous studies for assessing women reproductive health needs across West Africa. Evidence on outcomes and determinants of unmet reproductive health needs among women of childbearing age in diverse multicultural, religious, and ethnic settings in West African countries was systematically reviewed. The review included recent English language publications (from January 2009 - March 2014). Clinical studies particularly on obstetric care services and reproductive services in relation to HIV/AIDS were excluded. We acknowledge the possibility to have excluded non-English publications and yet-to-be-published articles related to the study aim and objectives. Outcomes and determinants were assessed and defined at three main levels; contraceptive use, obstetric care, and antenatal care utilization. Results show increasing unmet need for women's reproductive health needs. Socio-cultural norms and practices resulting in discontinuation of service use, economic constraints, travel distance to access services and low education levels of women were found to be key predictors of service utilization for contraception, antenatal and obstetric care services. Outcome measures were mainly assessed based on service utilization, satisfaction, cost, and quality of services available as core measures across the three levels assessed in this review. Evidence from this review indicates that currently applied measures of women's reproductive health needs might be inadequate in attaining best maternal outcomes since they appear rather broad. More support and research for developing and advancing context-related measures may help to improve women's maternal health.

  1. Numerical Simulation of Surface Energy and Water Balances over a Semiarid Grassland Ecosystem in the West African Savanna

    Directory of Open Access Journals (Sweden)

    Emmanuel Quansah

    2017-01-01

    Full Text Available To understand surface energy exchange processes over the semiarid regions in West Africa, numerical simulations of surface energy and water balances were carried out using a one-dimensional multilayer atmosphere-SOil-VEGetation (SOLVEG model for selected days of the dry and rainy seasons over a savanna grassland ecosystem in Sumbrungu in the Upper East region of Ghana. The measured Bowen ratio was used to partition the residual energy into the observed sensible heat flux (H and latent heat flux (LE in order to investigate the impact of the surface energy closure on model performance. The results showed that the model overall reproduced the diurnal changes in the observed energy fluxes, especially the net radiation (Rn, compared to half-hourly eddy covariance flux measurements, for the study periods. The performance measure in terms of the correlation coefficient (R, centred root mean square error (RMSE, and normalized standard deviation (σ between the simulated H and LE and their corresponding uncorrected observed values ranged between R = 0.63–0.99 and 0.83–0.94, RMSE = 0.88–1.25 and 0.88–1.92, and σ = 0.95–2.23 and 0.13–2.82 for the dry and rainy periods respectively, indicating a moderate to good model performance. The partitioning of H and LE by SOLVEG was generally in agreement with the observations during the dry period but showed clear discrepancies during the rainy period, particularly after rainfall events. Further sensitivity tests over longer simulation periods (e.g., 1 year are required to improve model performance and to investigate seasonal exchanges of surface energy fluxes over the West African Savanna ecosystems in more details.

  2. Genome-wide search for susceptibility genes to type 2 diabetes in West Africans: potential role of C-peptide.

    Science.gov (United States)

    Chen, Guanjie; Adeyemo, Adebowale; Zhou, Jie; Chen, Yuanxiu; Huang, Hanxia; Doumatey, Ayo; Lashley, Kerrie; Agyenim-Boateng, Kofi; Eghan, Benjamin A; Acheampong, Joseph; Fasanmade, Olufemi; Johnson, Thomas; Okafor, Godfrey; Oli, Johnnie; Amoah, Albert; Rotimi, Charles

    2007-12-01

    C-peptide is a substance that the pancreas releases into the circulation in equimolar amounts to insulin and has demonstrated important physiological effects which relate to the vascular field, in particular the microcirculation. For this analysis, we included 321 full and 36 half sibling pairs affected with type 2 diabetes (T2D) from West Africa. A genome-wide panel of 390 tri-nucleotide and tetra-nucleotide repeats with an average distance of 8.9 cM was performed on a total of 691 persons. Variance components based on multipoint linkage approach as implemented in SOLAR were performed for log C-peptide. Significant linkage evidences were observed on 10q23 at D10S2327 with a LOD score of 4.04 (nominal p-value=0.000008, empirical p-value=0.0004); and on 4p15 at D4S2632 with a LOD score of 3.48 (nominal p-value=0.000031, empirical p-value=0.0013). Other suggestive evidence of linkage were observed on 15q14 at D15S659 with a LOD score 2.41 (nominal p-value=0.000435, empirical p-value=0.0068), and on 18p11 near D18S976 with a LOD score 2.18 (nominal p-value=0.000771 and empirical p-value=0.0094). Interestingly, five positional candidate genes for diabetes and related complications are located in our linkage region (the pituitary adenylate cyclase activating polypeptide (PACAP in 18p11); the peroxisome proliferator-activated receptor gamma coactivator 1 (PPARGC1 in 4p15); PTEN, PPP1R5, and IDE located in 10q23. In conclusion, we identified four major genetic loci (10q23, 4p15, 15q14, and 18p11) influencing C-peptide concentration in West Africans with T2D.

  3. Sahel megadrought during Heinrich Stadial 1: evidence for a three-phase evolution of the low- and mid-level West African wind system

    Science.gov (United States)

    Bouimetarhan, Ilham; Prange, Matthias; Schefuß, Enno; Dupont, Lydie; Lippold, Jörg; Mulitza, Stefan; Zonneveld, Karin

    2012-12-01

    Millennial-scale dry events in the Northern Hemisphere monsoon regions during the last Glacial period are commonly attributed to southward shifts of the Intertropical Convergence Zone (ITCZ) associated with an intensification of the northeasterly (NE) trade wind system during intervals of reduced Atlantic meridional overturning circulation (AMOC). Through the use of high-resolution last deglaciation pollen records from the continental slope off Senegal, our data show that one of the longest and most extreme droughts in the western Sahel history, which occurred during the North Atlantic Heinrich Stadial 1 (HS1), displayed a succession of three major phases. These phases progressed from an interval of maximum pollen representation of Saharan elements between ˜19 and 17.4 kyr BP indicating the onset of aridity and intensified NE trade winds, followed by a millennial interlude of reduced input of Saharan pollen and increased input of Sahelian pollen, to a final phase between ˜16.2 and 15 kyr BP that was characterized by a second maximum of Saharan pollen abundances. This change in the pollen assemblage indicates a mid-HS1 interlude of NE trade wind relaxation, occurring between two distinct trade wind maxima, along with an intensified mid-tropospheric African Easterly Jet (AEJ) indicating a substantial change in West African atmospheric processes. The pollen data thus suggest that although the NE trades have weakened, the Sahel drought remained severe during this time interval. Therefore, a simple strengthening of trade winds and a southward shift of the West African monsoon trough alone cannot fully explain millennial-scale Sahel droughts during periods of AMOC weakening. Instead, we suggest that an intensification of the AEJ is needed to explain the persistence of the drought during HS1. Simulations with the Community Climate System Model indicate that an intensified AEJ during periods of reduced AMOC affected the North African climate by enhancing moisture

  4. North African dust deposition and hydroclimate over the last 60 ka: A combined view from the east and west of the continent

    Science.gov (United States)

    Kinsley, C. W.; McGee, D.; Bradtmiller, L. I.; Tierney, J. E.; Winckler, G.; Stuut, J. B. W.; deMenocal, P. B.

    2014-12-01

    Past changes in atmospheric circulation and hydroclimate over North Africa can be explored by reconstructing eolian dust accumulation in both East and West African margin sediments. Recent high-resolution reconstructions of dust deposition from West Africa (1) indicate dramatic changes in North African dust emissions over the last 20 ka, with comparable results to those found in the terrigenous accumulation rates at nearby ODP Hole 658C (2). A high-resolution record of aridity from East Africa using δDwax indicates dramatic changes in hydroclimate over the past 40 ka (3). The records show similar trends with arid conditions/high dust emissions seen during the Last Glacial Maximum, the Younger Dryas and Heinrich Event 1 (H1), and the wettest conditions of the past 40,000 years with accompanying low dust emissions during the African Humid Period. This study has two goals: 1) Extend the dust flux and terrigeneous accumulation records from West Africa back to 35 ka and 60 ka respectively, to provide quantitative estimates of the magnitude of eolian deposition changes associated with previous Heinrich Stadials (H2 to H6) and summer insolation minima/maxima; 2) Construct a high-resolution record of eolian dust accumulation rates off the East African margin over the past 20 ka using the same sample material as (3) allowing quantitative estimates of the magnitude of dust flux changes associated with abrupt changes in hydroclimate and provide a direct comparison of dust flux and δDwax. The combination of these study areas from both sides of the African continent, and comparison of the dust and leaf wax proxies promises to provide a more complete picture of hydroclimate changes accompanying orbital- and millennial-scale climate changes in North Africa over the last 60,000 years. 1. EPSL 371-372, 163-176. 2. Paleoceanography 21, PA4203. 3. Science 342, 843-846.

  5. Statistical ensemble postprocessing for precipitation forecasting during the West African Monsoon

    Science.gov (United States)

    Vogel, Peter; Gneiting, Tilmann; Knippertz, Peter; Fink, Andreas H.; Schlüter, Andreas

    2017-04-01

    Precipitation forecasts for one up to several days are of high socioeconomic importance for agriculturally dominated societies in West Africa. In this contribution, we evaluate the performance of operational European Centre for Medium-Range Weather Forecasts (ECWMF) raw ensemble and statistically postprocessed against climatological precipitation forecasts for accumulation periods of 1 to 5 days for the monsoon periods (May to mid-October) from 2007 to 2014. We use Bayesian Model Averaging (BMA) and Ensemble Model Output Statistics (EMOS) as state-of-the-art postprocessing methods and verify against station and gridded Tropical Rainfall Measuring Mission (TRMM) observations. Based on a subset of past forecast—observation-pairs, statistical postprocessing corrects ensemble forecasts for biases and dispersion errors. For the midlatitudes, statistical postprocessing has demonstrated its added value for a wide range of meteorological quantities and this contribution is the first to apply it to precipitation forecasts over West Africa, where the high degree of convective organization at the mesoscale makes precipitation forecasts particularly challenging. The raw ECMWF ensemble predictions of accumulated precipitation are poor compared to climatological forecasts and exhibit strong dispersion errors and biases. For the Guinea Coast, we find a substantial wet bias of the ECMWF ensemble and more than every second ensemble forecast fails to capture the verifying observation within its forecast range. Postprocessed forecasts clearly outperform ECMWF raw ensemble forecasts by correcting for biases and dispersion errors, but disappointingly reveal only slight, if any, improvements compared to climatological forecasts. These results hold across verification regions and years, for 1 to 5-day accumulated precipitation forecasts, and for station and gridded observations. We investigate different spatial accumulation sizes from 0.25 x 0.25° to 5 x 2° longitude

  6. Identification of a Pertinent Referential Period for Drought Definition in the West African Soudano-Sahelian Zone from Precipitation

    Science.gov (United States)

    Ibrahim, B.; Wisser, D.; Barry, B.

    2014-12-01

    Many studies have been undertaken on climate variability analysis in West Africa since the drastic drought recorded at the beginning of the 1970s. The variability highlighted by these studies relies in many cases on different baseline periods chosen with regard to the data available or to the reference periods defined by the World Meteorological Organization (WMO). However, the significance of the change in a time series for a given period is determined from some statistical tests. We develop in this study a statistical method to identify a pertinent reference period for rainfall and temperature variability analysis in the West African Soudano-Sahelian zone. The method is based on an application of three tests of homogeneity in time series and three tests of shift detection in time series. The pertinent reference period is defined as a period of more than 20 years and homogeneous with regard to the main climate parameters (rainfall and temperature). The application of the method on four different gridded climate data from 1901 to 2012 shows that the 1945-1970 period is the longest homogeneous period with regard to the annual rainfall amount. An assessment of the significance of the difference between the confidence interval at the level of 95% around the average during this period and the annual rainfall amounts time series shows that the normal amount is between -10% and +10% of that average. Thus, with regard to that referential period, a wet (dry) year is defined with a surplus (gap) of 10% in the annual rainfall amount above (below) this average. The decadal proportions of wet and dry years reveal that the 1971-1980 period presents the most important number of significant dry years with 1984 as the driest year over the whole 1901-2012 period. The drought periods recorded in the region are mainly characterized by segments of consecutive dry years that had severe impacts on crop production and livestock. Key words: climate variability; climate change; drought

  7. Crustal evolution and the eclogite to granulite phase transition in xenoliths from the West African Craton

    Science.gov (United States)

    Haggerty, S. E.; Hills, D. V.; Toft, P. B.

    1988-01-01

    A suite of eclogite and granulite facies xenoliths from kimberlite pipes in the Archean Man Shield of West Africa is described. The xenoliths include lithologies ranging in composition from komatiite to anorthosite and appear to be geochemically, petrologically, and geophysically related. The suite may represent fractionation of felsic material separated from ancient mantle and added to early Archean crust. The samples can be used to define a xenolith geotherm, which may represent an ancient episode of high heat flow. The samples also imply that the crust-mantle boundary is a gradational and possibly interlayered geochemical, mineralogical, and seismic transition. It is speculated that the depleted subcontinental mantle required by diamond bearing coalescence of smaller depletion cells formed by extraction of ancient crustal components. These depleted zones are surrounded by fertile asthenospheric mantle, which may have given rise to later flood basalts such as the Karroo and Parana Provinces.

  8. Small businesses performance in West African border regions: Do social networks pay off?

    DEFF Research Database (Denmark)

    Kuepié, Mathias; Tenikué, Michel; Walther, Olivier

    on economic performances in Niger and Benin than in Nigeria, where average profit is much higher. Experience is more closely correlated with profit in the region where traders have developed re-export trade activities than where petty trade is the dominant form of business.......This paper studies the link between economic performance and social networks in West Africa. Using first-hand data collected on 358 small-scale traders in five border markets between Niger, Nigeria and Benin, we are particularly interested in testing whether the most well-connected actors of trade...... networks are also the most successful in terms of monthly sales and profit. The paper shows that the overall economic performance of traders is affected by the socio-professional position of the actors with whom they are connected. While social ties with local religious leaders have no effect...

  9. Social networks and small businesses performance in West African border regions

    DEFF Research Database (Denmark)

    Kuépié, Mathias; Tenikue, Michel; Walther, Olivier

    2016-01-01

    burden that leads to a negative economic impact. Testing the effect of social networks between small traders and three categories of actors, we find that the most well-connected actors are also the most successful in terms of monthly profit. The effects of social networks are, however, dependent...... with traditional religious leaders has a negative effect on economic performance. Our work has two implications: first, collecting data on social networks remains challenging due to endogeneity. Second, network-enhancing policies should aim at improving both the internal connectivity of economic actors......This paper studies the link between economic performance and social networks in West Africa. Using data collected about 358 small-scale traders in five border markets, we show that social network can simultaneously be a resource which positively contributes to labor market outcomes and a social...

  10. Social networks and small businesses performance in West African border regions

    DEFF Research Database (Denmark)

    Kuépié, Mathias; Tenikue, Michel; Walther, Olivier

    2016-01-01

    on the type of persons with whom traders are connected. We show that support received from state representatives and politicians is converted into economic performance, while the impact of law enforcement officers on the monthly profits of traders is not significant. We also find that interacting......This paper studies the link between economic performance and social networks in West Africa. Using data collected about 358 small-scale traders in five border markets, we show that social network can simultaneously be a resource which positively contributes to labor market outcomes and a social...... burden that leads to a negative economic impact. Testing the effect of social networks between small traders and three categories of actors, we find that the most well-connected actors are also the most successful in terms of monthly profit. The effects of social networks are, however, dependent...

  11. Long‐term spatio‐temporal changes in a West African bushmeat trade system

    Science.gov (United States)

    McNamara, J.; Kusimi, J. M.; Rowcliffe, J. M.; Cowlishaw, G.; Brenyah, A.; Milner‐Gulland, E. J.

    2015-01-01

    Abstract Landscapes in many developing countries consist of a heterogeneous matrix of mixed agriculture and forest. Many of the generalist species in this matrix are increasingly traded in the bushmeat markets of West and Central Africa. However, to date there has been little quantification of how the spatial configuration of the landscape influences the urban bushmeat trade over time. As anthropogenic landscapes become the face of rural West Africa, understanding the dynamics of these systems has important implications for conservation and landscape management. The bushmeat production of an area is likely to be defined by landscape characteristics such as habitat disturbance, hunting pressure, level of protection, and distance to market. We explored (SSG, tense) the role of these four characteristics in the spatio‐temporal dynamics of the commercial bushmeat trade around the city of Kumasi, Ghana, over 27 years (1978 to 2004). We used geographic information system methods to generate maps delineating the spatial characteristics of the landscapes. These data were combined with spatially explicit market data collected in the main fresh bushmeat market in Kumasi to explore the relationship between trade volume (measured in terms of number of carcasses) and landscape characteristics. Over time, rodents, specifically cane rats (Thryonomys swinderianus), became more abundant in the trade relative to ungulates and the catchment area of the bushmeat market expanded. Areas of intermediate disturbance supplied more bushmeat, but protected areas had no effect. Heavily hunted areas showed significant declines in bushmeat supply over time. Our results highlight the role that low intensity, heterogeneous agricultural landscapes can play in providing ecosystem services, such as bushmeat, and therefore the importance of incorporating bushmeat into ecosystem service mapping exercises. Our results also indicate that even where high bushmeat production is possible, current harvest

  12. Long-term spatio-temporal changes in a West African bushmeat trade system.

    Science.gov (United States)

    McNamara, J; Kusimi, J M; Rowcliffe, J M; Cowlishaw, G; Brenyah, A; Milner-Gulland, E J

    2015-10-01

    Landscapes in many developing countries consist of a heterogeneous matrix of mixed agriculture and forest. Many of the generalist species in this matrix are increasingly traded in the bushmeat markets of West and Central Africa. However, to date there has been little quantification of how the spatial configuration of the landscape influences the urban bushmeat trade over time. As anthropogenic landscapes become the face of rural West Africa, understanding the dynamics of these systems has important implications for conservation and landscape management. The bushmeat production of an area is likely to be defined by landscape characteristics such as habitat disturbance, hunting pressure, level of protection, and distance to market. We explored (SSG, tense) the role of these four characteristics in the spatio-temporal dynamics of the commercial bushmeat trade around the city of Kumasi, Ghana, over 27 years (1978 to 2004). We used geographic information system methods to generate maps delineating the spatial characteristics of the landscapes. These data were combined with spatially explicit market data collected in the main fresh bushmeat market in Kumasi to explore the relationship between trade volume (measured in terms of number of carcasses) and landscape characteristics. Over time, rodents, specifically cane rats (Thryonomys swinderianus), became more abundant in the trade relative to ungulates and the catchment area of the bushmeat market expanded. Areas of intermediate disturbance supplied more bushmeat, but protected areas had no effect. Heavily hunted areas showed significant declines in bushmeat supply over time. Our results highlight the role that low intensity, heterogeneous agricultural landscapes can play in providing ecosystem services, such as bushmeat, and therefore the importance of incorporating bushmeat into ecosystem service mapping exercises. Our results also indicate that even where high bushmeat production is possible, current harvest levels may

  13. The Pan-African orogenic belt of southern Mauritanides and northern Rokelides (southern Senegal and Guinea, West Aftica): gravity evidence for a collisional suture

    Science.gov (United States)

    Ponsard, J. F.; Roussel, J.; Villeneuve, M.; Lesquer, A.

    The geological history in southern Senegal and Guinea results in the existence, on the western margin of the West African craton, of a Pan-African orogenic belt which is capped in part with late Proterozoic and Paleozoic terranes. In addition to geological features, the gravity signature and deduced crustal model bear evidence of an eastern crustal block corresponding to the old rigid craton and a denser and thicker western block related to the reactivated basement province. The discontinuity in density between both is interpreted as the Pan-African suture which dips westward beneath the reactivated block. The short wavelength gravity highs superimposed to the gravity gradient in the central domain are interpreted as west-dipping wedge-shaped dense bodies squeezed at depth along the suture. These may reflect either remains of oceanic crust or granulite facies rocks derived from the crustal overthrusting process. Finally using both geological and geophysical materials, the Pan-African belt of southern Mauritanides and northern Rokelides appears to be consistent with a continental collision-basement reactivation model.

  14. Assessing the potential of multi-seasonal WorldView-2 imagery for mapping West African agroforestry tree species

    Science.gov (United States)

    Karlson, Martin; Ostwald, Madelene; Reese, Heather; Bazié, Hugues Roméo; Tankoano, Boalidioa

    2016-08-01

    High resolution satellite systems enable efficient and detailed mapping of tree cover, with high potential to support both natural resource monitoring and ecological research. This study investigates the capability of multi-seasonal WorldView-2 imagery to map five dominant tree species at the individual tree crown level in a parkland landscape in central Burkina Faso. The Random Forest algorithm is used for object based tree species classification and for assessing the relative importance of WorldView-2 predictors. The classification accuracies from using wet season, dry season and multi-seasonal datasets are compared to gain insights about the optimal timing for image acquisition. The multi-seasonal dataset produced the most accurate classifications, with an overall accuracy (OA) of 83.4%. For classifications based on single date imagery, the dry season (OA = 78.4%) proved to be more suitable than the wet season (OA = 68.1%). The predictors that contributed most to the classification success were based on the red edge band and visible wavelengths, in particular green and yellow. It was therefore concluded that WorldView-2, with its unique band configuration, represents a suitable data source for tree species mapping in West African parklands. These results are particularly promising when considering the recently launched WorldView-3, which provides data both at higher spatial and spectral resolution, including shortwave infrared bands.

  15. Pathogenesis of fulminant monkeypox with bacterial sepsis after experimental infection with West African monkeypox virus in a cynomolgus monkey.

    Science.gov (United States)

    Nagata, Noriyo; Saijo, Masayuki; Kataoka, Michiyo; Ami, Yasushi; Suzaki, Yuriko; Sato, Yuko; Iwata-Yoshikawa, Naoko; Ogata, Momoko; Kurane, Ichiro; Morikawa, Shigeru; Sata, Tetsutaro; Hasegawa, Hideki

    2014-01-01

    The pathogenesis of severe human monkeypox, which causes systemic and fulminant infections, is not clear. This study presents a case repot of fulminant monkeypox with bacterial sepsis after experimental infection with monkeypox virus in a cynomolgus monkey (Macaca fascicularis). In our previous study (Saijo et al., 2009, J Gen Virol), two cynomolgus monkeys became moribund after experimental infection with monkeypox virus Liberia strain, West African strain. One exhibited typical monkeypox-related papulovesicular lesions. The other monkey presented fulminant clinical symptoms with a characteristic flat red rash similar to that found in smallpox, which is associated with extremely high fatality rates. In this study, we found that the monkey with flat red rash had high levels of viremia and neutropenia, as well as high plasma levels of pro-inflammatory cytokines and chemokines compared with the other monkey. Monkeypox virus replicates in epithelial cells and macrophages in various organs. Sepsis due to Gram-positive cocci was confirmed histopathologically in the monkey with flat red rash. The lack of inflammatory response in the lesion suggested that the monkey with sepsis experienced strong immune suppression during the viral infection. The neutropenia and excessive inflammatory cytokine responses indicate that neutrophils play key roles in the pathogenesis of systemic and fulminant human monkeypox virus infections with sepsis.

  16. The impact of the goitrogen 6-propylthiouracil (PTU) on West-African clawed frog (Xenopus tropicalis) exposed during metamorphosis.

    Science.gov (United States)

    Carlsson, Gunnar; Norrgren, Leif

    2007-04-20

    This study investigated the suitability of using tadpoles of the West-African clawed frog (Xenopus tropicalis) for studying adverse effects on the thyroid hormone system after chemical exposure. Tadpoles were exposed to the thyroxine synthesis inhibitor 6-propylthiouracil (PTU) at concentrations between 2-75mg/L during 14 days. After 5 and 14 days of exposure the developmental stage, hind limb length, body length and weight were measured. Moreover, histological measurements of the thyroid glands were performed after 14 days of exposure. These measurements included maximum thyroid cross-section area, follicular area and epithelial cell height. Tadpoles in the 75mg/L treatment were less developed and had shorter hind limb length than the control group after 14 days of exposure. No effects were recorded on these parameters at lower PTU concentrations. The histological measurements revealed clear dose-response relationships in both follicular cross-section area and epithelial cell height, with lowest observed effect concentrations (LOECs) recorded at 2 and 5mg/L, respectively. This study shows that X. tropicalis is a suitable species for detection of thyroid disrupting chemicals. Further, histopathological measurements of thyroid glands are more sensitive parameters compared with apical endpoints when studying adverse effects on thyroid hormone system caused by PTU exposure in X. tropicalis.

  17. Psychological strengths, coping and suicide ideation in the South African Police Services In The North West Province

    Directory of Open Access Journals (Sweden)

    S. Rothmann

    2002-10-01

    Full Text Available Relatively high numbers of suicides occur in the South African Police Services. The objective of this research was to determine the relationship between sense of coherence, generalised self-efficacy, locus of control and coping on the one hand and suicide ideation among police personnel on the other hand. The study population (N = 287 consisted of uniformed police personnel in the North West Province. The results showed that sense of coherence and generalised self-efficacy are related to suicide ideation of police members. A discriminant analysis showed that sense of coherence, coping strategies and medical status correctly classified 81,48% of participants who scored high on suicide ideation. Opsomming ‘n Relatiewe hoë getal selfmoorde kom in die Suid-Afrikaanse Polisiediens voor. Die doelstelling van hierdie navorsing was om die verband tussen koherensiesin, algemene selfdoeltreffendheid, lokus van beheer en coping enersyds en selfmoorddenkbeeldvorming van polisiepersoneel andersyds te bepaal. Die studiepopulasie (N = 287 het bestaan uit polisiepersoneel in die Noordwes-Provinsie. Die resultate het aangetoon dat koherensiesin en algemene selfdoeltreffendheid verband hou met selfmoorddenkbeeldvorming by polisieper-soneel. ‘n Diskriminantontleding het aangetoon dat koherensiesin, coping-strategieë en mediese toestand 81,48% van die deelnemers met hoë tellings ten opsigte van selfmoorddenkbeeldvorming korrek geklassifiseer het.

  18. The impact of IMF conditionality on government health expenditure: A cross-national analysis of 16 West African nations.

    Science.gov (United States)

    Stubbs, Thomas; Kentikelenis, Alexander; Stuckler, David; McKee, Martin; King, Lawrence

    2017-02-01

    How do International Monetary Fund (IMF) policy reforms-so-called 'conditionalities'-affect government health expenditures? We collected archival documents on IMF programmes from 1995 to 2014 to identify the pathways and impact of conditionality on government health spending in 16 West African countries. Based on a qualitative analysis of the data, we find that IMF policy reforms reduce fiscal space for investment in health, limit staff expansion of doctors and nurses, and lead to budget execution challenges in health systems. Further, we use cross-national fixed effects models to evaluate the relationship between IMF-mandated policy reforms and government health spending, adjusting for confounding economic and demographic factors and for selection bias. Each additional binding IMF policy reform reduces government health expenditure per capita by 0.248 percent (95% CI -0.435 to -0.060). Overall, our findings suggest that IMF conditionality impedes progress toward the attainment of universal health coverage. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Comparison of West African and Congo Basin monkeypox viruses in BALB/c and C57BL/6 mice.

    Directory of Open Access Journals (Sweden)

    Christina L Hutson

    Full Text Available Although monkeypox virus (MPXV studies in wild rodents and non-human primates have generated important knowledge regarding MPXV pathogenesis and inferences about disease transmission, it might be easier to dissect the importance of virulence factors and correlates of protection to MPXV in an inbred mouse model. Herein, we compared the two clades of MPXV via two routes of infection in the BALB/c and C57BL/6 inbred mice strains. Our studies show that similar to previous animal studies, the Congo Basin strain of MPXV was more virulent than West African MPXV in both mouse strains as evidenced by clinical signs. Although animals did not develop lesions as seen in human MPX infections, localized signs were apparent with the foot pad route of inoculation, primarily in the form of edema at the site of inoculation; while the Congo Basin intranasal route of infection led to generalized symptoms, primarily weight loss. We have determined that future studies with MPXV and laboratory mice would be very beneficial in understanding the pathogenesis of MPXV, in particular if used in in vivo imaging studies. Although this mouse model may not suffice as a model of human MPX disease, with an appropriate inbred mouse model, we can unravel many unknown aspects of MPX pathogenesis, including virulence factors, disease progression in rodent hosts, and viral shedding from infected animals. In addition, such a model can be utilized to test antivirals and the next generation of orthopoxvirus vaccines for their ability to alter the course of disease.

  20. Production of autoinducer-2 by aerobic endospore-forming bacteria isolated from the West African fermented foods.

    Science.gov (United States)

    Qian, Yang; Kando, Christine Kere; Thorsen, Line; Larsen, Nadja; Jespersen, Lene

    2015-11-01

    Autoinducer-2 (AI-2) is a quorum-sensing (QS) molecule which mediates interspecies signaling and affects various bacterial behaviors in food fermentation. Biosynthesis of AI-2 is controlled by S-ribosylhomocysteine lyase encoded by the luxS gene. The objective of this study was to investigate production of AI-2 by aerobic endospore-forming bacteria (AEB) isolated from the West African alkaline fermented seed products Mantchoua and Maari. The study included 13 AEB strains of Bacillus subtilis, B. cereus, B. altitudinis, B. amyloliquefaciens, B. licheniformis, B. aryabhattai, B. safensis, Lysinibacillus macroides and Paenibacillus polymyxa. All the tested strains harbored the luxS gene and all strains except for P. polymyxa B314 were able to produce AI-2 during incubation in laboratory medium. Production of AI-2 by AEB was growth phase dependent, showing maximum activity at the late exponential phase. AI-2 was depleted from the culture medium at the beginning of the stationary growth phase, indicating that the tested AEB possess a functional AI-2 receptor that internalizes AI-2. This study provides the evidences of QS system in Bacillus spp. and L. macroides and new knowledge of AI-2 production by AEB. This knowledge contributes to the development of QS-based strategies for better control of alkaline fermentation.

  1. Macro-habitat preferences by the African manatee and crocodiles – ecological and conservation implications

    Directory of Open Access Journals (Sweden)

    L. Luiselli

    2012-07-01

    Full Text Available African manatees (Trichechus senegalensis and crocodiles are threatened species in parts of their range. In West Africa, crocodiles may constitute the main predators for manatees apart from humans. Here, we explore the macro-habitat selection of manatees and two species of crocodiles (West African crocodiles Crocodylus suchus and dwarf crocodile Osteolaemus tetraspis in the Niger Delta (Nigeria, testing the hypotheses that (i manatees may avoid crocodiles in order to minimize risks of predation, and (ii the two crocodile species do compete. The study was carried out between 1994 and 2010 with a suite of different field techniques. We observed that the main macro-habitat types were freshwater rivers and coastal lagoons for manatees, mangroves for West African crocodiles, and rivers and creeks for dwarf crocodiles, with (i the three species differing significantly in terms of their macro-habitat type selection, and (ii significant seasonal influence on habitat selection of each species. Null models for niche overlap showed a significantly lower overlap in macro-habitat type use between manatee and crocodiles, whereas the two crocodiles were relatively similar. Null model analyses did not indicate any competitive interactions between crocodiles. On the other hand, manatees avoided macro-habitats where crocodiles, and especially West African crocodiles, are abundant.

  2. Large scale prediction of soil properties in the West African yam belt based on mid-infrared soil spectroscopy

    Science.gov (United States)

    Baumann, Philipp; Lee, Juhwan; Paule Schönholzer, Laurie; Six, Johan; Frossard, Emmanuel

    2016-04-01

    Yam (Dioscorea sp.) is an important staple food in West Africa. Fertilizer applications have variable effects on yam tuber yields, and a management option solely based on application of mineral NPK fertilizers may bear the risk of increased organic matter mineralization. Therefore, innovative and sustainable nutrient management strategies need to be developed and evaluated for yam cultivation. The goal of this study was to establish a mid-infrared soil spectroscopic library and models to predict soil properties relevant to yam growth. Soils from yam fields at four different locations in Côte d'Ivoire and Burkina Faso that were representative of the West African yam belt were sampled. The project locations ranged from the humid forest zone (5.88 degrees N) to the northern Guinean savannah (11.07 degrees N). At each location, soils of 20 yam fields were sampled (0-30 cm). For the location in the humid forest zone additional 14 topsoil samples from positions that had been analyzed in the Land Degradation Surveillance Framework developed by ICRAF were included. In total, 94 soil samples were analyzed using established reference analysis protocols. Besides soils were milled and then scanned by fourier transform mid-infrared spectroscopy in the range between 400 and 4000 reciprocal cm. Using partial least squares (PLS) regression, PLS1 calibration models that included soils from the four locations were built using two thirds of the samples selected by Kennard-Stones sampling algorithm in the spectral principal component space. Models were independently validated with the remaining data set. Spectral models for total carbon, total nitrogen, total iron, total aluminum, total potassium, exchangeable calcium, and effective cation exchange capacity performed very well, which was indicated by R-squared values between 0.8 and 1.0 on both calibration and validation. For these soil properties, spectral models can be used for cost-effective, rapid, and accurate predictions

  3. Evidence of cretaceous to recent West African intertropical vegetation from continental sediment spore-pollen analysis

    Science.gov (United States)

    Salard-Cheboldaeff, M.; Dejax, J.

    The succession of spore-pollen assemblages during the Cretaceous and Tertiary, as defined in each of the basin from Senegal to Angola, gives the possibility to consider the intertropical African flora evolution for the past 120 M.a. During the Early Cretaceous, xeric-adapted gymnosperms and various ferns were predominant the flora which nevertheless comprises previously unknown early angiosperm pollen. During the Middle Cretaceous, gymnospers were gradually replaced by angiosperms; these became more and more abundant, along with the diversification of new genera and species. During the Paleocene, the radiation of the monocotyledons (mainly that of the palm-trees) as well as a greater diversification among the dicotyledons and ferms are noteworthy. Since gymnosperms had almost disappeared by the Eocene, the diversification of the dicotyledons went on until the neogene, when all extinct pollen types are already present. These important modifications of the vegetation reflect evolutionary trends as well as climatic changes during the Cretaceous: the climate, firstly hot, dry and perhaps arid, did probably induced salt deposition, and later became gradually more humid under oceanic influences which arose in connection with the Gondwana break-up.

  4. Uncovering cryptic species diversity of a termite community in a West African savanna.

    Science.gov (United States)

    Hausberger, Barbara; Kimpel, Dorothea; van Neer, Abbo; Korb, Judith

    2011-12-01

    To uncover the termite species diversity of a natural African savanna ecosystem, we combined morphological analyses and sequencing of three gene fragments (cytochrome oxidase I, cytochrome oxidase II and 28SrDNA, total length about 2450 bp) to infer putative species from phylogenetic trees. We identified 18 putative species clusters with high support values and which we retrieved consistently. Samples from two genera (Ancistrotermes and Microcerotermes) were excluded from the mitochondrial phylogenetic analyses as they might represent nuclear mitochondrial sequences (NUMTs). In total, our data suggest a species richness of at least 20 species, all but one belonging to the Termitidae (higher termites), and among them the fungus-growing Macrotermitinae were most prevalent with at least nine putative species. Within the fungus-growers the most species-rich genus was Microtermes and its four putative species were all cryptic species. Their abundance in the samples suggests that they play an important ecological role which is completely unstudied also due to the lack of reliable identification means. Our study shows that morphological traits are unreliable means of species identification for several termite taxa. Yet reliable and consistent identification is necessary for studying the functional role of termites in ecosystem and global processes.

  5. Nauclea latifolia: biological activity and alkaloid phytochemistry of a West African tree.

    Science.gov (United States)

    Boucherle, Benjamin; Haudecoeur, Romain; Queiroz, Emerson Ferreira; De Waard, Michel; Wolfender, Jean-Luc; Robins, Richard J; Boumendjel, Ahcène

    2016-09-25

    Covering up to 2016Nauclea latifolia (syn. Sarcocephalus latifolius, Rubiaceae), commonly called the African pincushion tree, is a plant widely used in folk medicine in different regions of Africa for treating a variety of illnesses, including malaria, epilepsy and pain. N. latifolia has not only drawn the interest of traditional healers but also of phytochemists, who have identified a range of bioactive indole alkaloids in its tissue. More recently, following up on the traditional use of extracts in pain management, a bio-guided purification from the roots of the tree led to the identification of the active ingredient as tramadol, available as a synthetic analgesic since the 1970s. The discovery of this compound as a natural phytochemical was highlighted worldwide. This review focuses on the correlation between extracted compounds and pharmacological activities, paying special attention to infectious diseases and neurologically-related disorders. A critical analysis of the data reported so far on the natural origin of tramadol and its proposed biosynthesis is also presented.

  6. Vertical structure of aerosols and water vapor over West Africa during the African monsoon dry season

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    S.-W. Kim

    2009-10-01

    Full Text Available We present observations of tropospheric aerosol and water vapor transport over West Africa and the associated meteorological conditions during the AMMA SOP-0 dry season experiment, which was conducted in West Africa in January–February 2006. This study combines data from ultra-light aircraft (ULA-based lidar, airborne in-situ aerosol and gas measurements, standard meteorological measurements, satellite-based aerosol measurements, airmass trajectories, and radiosonde measurements. At Niamey (13.5° N, 2.2° E the prevailing surface wind (i.e. Harmattan was from the northeast bringing dry dusty air from the Sahara desert. High concentrations of mineral dust aerosol were typically observed from the surface to 1.5 or 2 km associated with the Saharan airmasses. At higher altitudes the prevailing wind veered to the south or southeast bringing relatively warm and humid airmasses from the biomass burning regions to the Sahel (<10° N. These elevated layers had high concentrations of biomass burning aerosol and were typically observed between altitudes of 2–5 km. Meteorological analyses show these airmasses were advected upwards over the biomass burning regions through ascent in Inter-Tropical Discontinuity (ITD zone. Aerosol vertical profiles obtained from the space-based lidar CALIOP onboard CALIPSO during January 2007 also showed the presence of dust particles (particle depolarization (δ~30%, lidar Ångström exponent (LAE<0, aerosol backscatter to extinction ratio (BER: 0.026~0.028 sr−1 at low levels (<1.5 km and biomass burning smoke aerosol (δ<10%, LAE: 0.6~1.1, BER: 0.015~0.018 sr−1 between 2 and 5 km. CALIOP data indicated that these distinct continental dust and biomass burning aerosol layers likely mixed as they advected further south over the tropical Atlantic Ocean, as indicated an intermediate values of δ (10~17%, LAE (0.16~0.18 and BER (0.0021~0.0022 sr−1.

  7. Comparing model ensembles in an event attribution study of 2012 West African rainfall

    Science.gov (United States)

    Parker, Hannah; Lott, Fraser C.; Cornforth, Rosalind J.

    2016-04-01

    In 2012, heavy rainfall resulted in flooding and devastating impacts across West Africa. With many people highly vulnerable to such events in this region, here we investigate whether anthropogenic climate change has influenced such heavy precipitation events. We use a probabilistic event attribution approach to assess the contribution of anthropogenic greenhouse gas emissions, by comparing the probability of such an event occurring in climate model simulations with all known climate forcings to those where natural forcings only are simulated. An ensemble of simulations from 10 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) is compared to two much larger ensembles of atmosphere-only simulations, from the Met Office model HadGEM3-A and from climateprediction.net (a regional version of HadAM3P). These are used to assess whether the choice of model ensemble influences the attribution statement that can be made. Results show that anthropogenic greenhouse gas emissions have decreased the probability of high precipitation, although the magnitude and confidence intervals of the decrease depend on the model ensemble used. The influences of significant teleconnections are then removed from the CMIP5 ensemble to see how this influences the results and compares with the atmosphere-only ensembles.

  8. Did Neoliberalizing West African Forests Produce a New Niche for Ebola?

    Science.gov (United States)

    Wallace, Robert G; Kock, Richard; Bergmann, Luke; Gilbert, Marius; Hogerwerf, Lenny; Pittiglio, Claudia; Mattioli, Raffaele; Wallace, Rodrick

    2016-01-01

    A recent study introduced a vaccine that controls Ebola Makona, the Zaire ebolavirus variant that has infected 28,000 people in West Africa. We propose that even such successful advances are insufficient for many emergent diseases. We review work hypothesizing that Makona, phenotypically similar to much smaller outbreaks, emerged out of shifts in land use brought about by neoliberal economics. The epidemiological consequences demand a new science that explicitly addresses the foundational processes underlying multispecies health, including the deep-time histories, cultural infrastructure, and global economic geographies driving disease emergence. The approach, for instance, reverses the standard public health practice of segregating emergency responses and the structural context from which outbreaks originate. In Ebola's case, regional neoliberalism may affix the stochastic "friction" of ecological relationships imposed by the forest across populations, which, when above a threshold, keeps the virus from lining up transmission above replacement. Export-led logging, mining, and intensive agriculture may depress such functional noise, permitting novel spillovers larger forces of infection. Mature outbreaks, meanwhile, can continue to circulate even in the face of efficient vaccines. More research on these integral explanations is required, but the narrow albeit welcome success of the vaccine may be used to limit support of such a program.

  9. Zoogeography of the bottom Foraminifera of the West-African coast

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    V. Mikhalevich

    2008-03-01

    Full Text Available The sediment samples from the continental shelf of West-Equatorial Africa (from the Strait of Gibraltar to the Niger estuary, depths ranging from 0 to 69 m were found to contain 176 bottom foraminiferal species. For the majority of them (126 species, their areas of occurrences were mapped and the peculiar features of the geographical range and distribution were studied. The species natural habitats were established based on the taxonomical revision of the species in study all over the World Ocean based on the collections of the Zoological Institute RAS and wide literary data. The method of perforated cards was used to mark the geographical locations of all of the species studied. In order to establish the species geographic zonal distribution (together with their depth habitat the five characteristic groups of the species were separated: 1. pan-oceanic (cosmopolitan, 2. widely spread tropical-boreal, 3. tropical-law boreal, 4. tropical-subtropical, 5. tropical. The percent of the species of each group among the species composition was established for the fauna of each station and for the whole region.

  10. Global health security: the wider lessons from the west African Ebola virus disease epidemic.

    Science.gov (United States)

    Heymann, David L; Chen, Lincoln; Takemi, Keizo; Fidler, David P; Tappero, Jordan W; Thomas, Mathew J; Kenyon, Thomas A; Frieden, Thomas R; Yach, Derek; Nishtar, Sania; Kalache, Alex; Olliaro, Piero L; Horby, Peter; Torreele, Els; Gostin, Lawrence O; Ndomondo-Sigonda, Margareth; Carpenter, Daniel; Rushton, Simon; Lillywhite, Louis; Devkota, Bhimsen; Koser, Khalid; Yates, Rob; Dhillon, Ranu S; Rannan-Eliya, Ravi P

    2015-05-09

    The Ebola virus disease outbreak in West Africa was unprecedented in both its scale and impact. Out of this human calamity has come renewed attention to global health security--its definition, meaning, and the practical implications for programmes and policy. For example, how does a government begin to strengthen its core public health capacities, as demanded by the International Health Regulations? What counts as a global health security concern? In the context of the governance of global health, including WHO reform, it will be important to distil lessons learned from the Ebola outbreak. The Lancet invited a group of respected global health practitioners to reflect on these lessons, to explore the idea of global health security, and to offer suggestions for next steps. Their contributions describe some of the major threats to individual and collective human health, as well as the values and recommendations that should be considered to counteract such threats in the future. Many different perspectives are proposed. Their common goal is a more sustainable and resilient society for human health and wellbeing.

  11. Harmattan, Saharan heat low, and West African monsoon circulation: modulations on the Saharan dust outflow towards the North Atlantic

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    K. Schepanski

    2017-09-01

    Full Text Available The outflow of dust from the northern African continent towards the North Atlantic is stimulated by the atmospheric circulation over North Africa, which modulates the spatio-temporal distribution of dust source activation and consequently the entrainment of mineral dust into the boundary layer, as well as the transport of dust out of the source regions. The atmospheric circulation over the North African dust source regions, predominantly the Sahara and the Sahel, is characterized by three major circulation regimes: (1 the harmattan (trade winds, (2 the Saharan heat low (SHL, and (3 the West African monsoon circulation. The strength of the individual regimes controls the Saharan dust outflow by affecting the spatio-temporal distribution of dust emission, transport pathways, and deposition fluxes.This study aims at investigating the atmospheric circulation pattern over North Africa with regard to its role favouring dust emission and dust export towards the tropical North Atlantic. The focus of the study is on summer 2013 (June to August, during which the SALTRACE (Saharan Aerosol Long-range TRansport and Aerosol-Cloud interaction Experiment field campaign also took place. It involves satellite observations by the Spinning Enhanced Visible and InfraRed Imager (SEVIRI flying on board the geostationary Meteosat Second Generation (MSG satellite, which are analysed and used to infer a data set of active dust sources. The spatio-temporal distribution of dust source activation frequencies (DSAFs allows for linking the diurnal cycle of dust source activations to dominant meteorological controls on dust emission. In summer, Saharan dust source activations clearly differ from dust source activations over the Sahel regarding the time of day when dust emission begins. The Sahara is dominated by morning dust source activations predominantly driven by the breakdown of the nocturnal low-level jet. In contrast, dust source activations in the Sahel are

  12. The representation of low-level clouds during the West African monsoon in weather and climate models

    Science.gov (United States)

    Kniffka, Anke; Hannak, Lisa; Knippertz, Peter; Fink, Andreas

    2016-04-01

    The West African monsoon is one of the most important large-scale circulation features in the tropics and the associated seasonal rainfalls are crucial to rain-fed agriculture and water resources for hundreds of millions of people. However, numerical weather and climate models still struggle to realistically represent salient features of the monsoon across a wide range of scales. Recently it has been shown that substantial errors in radiation and clouds exist in the southern parts of West Africa (8°W-8°E, 5-10°N) during summer. This area is characterised by strong low-level jets associated with the formation of extensive ultra-low stratus clouds. Often persisting long after sunrise, these clouds have a substantial impact on the radiation budget at the surface and thus the diurnal evolution of the planetary boundary layer (PBL). Here we present some first results from a detailed analysis of the representation of these clouds and the associated PBL features across a range of weather and climate models. Recent climate model simulations for the period 1991-2010 run in the framework of the Year of Tropical Convection (YOTC) offer a great opportunity for this analysis. The models are those used for the latest Assessment Report of the Intergovernmental Panel on Climate Change, but for YOTC the model output has a much better temporal resolution, allowing to resolve the diurnal cycle, and includes diabatic terms, allowing to much better assess physical reasons for errors in low-level temperature, moisture and thus cloudiness. These more statistical climate model analyses are complemented by experiments using ICON (Icosahedral non-hydrostatic general circulation model), the new numerical weather prediction model of the German Weather Service and the Max Planck Institute for Meteorology. ICON allows testing sensitivities to model resolution and numerical schemes. These model simulations are validated against (re-)analysis data, satellite observations (e.g. CM SAF cloud and

  13. A comparison of model ensembles for attributing 2012 West African rainfall

    Science.gov (United States)

    Parker, Hannah R.; Lott, Fraser C.; Cornforth, Rosalind J.; Mitchell, Daniel M.; Sparrow, Sarah; Wallom, David

    2017-01-01

    In 2012, heavy rainfall resulted in flooding and devastating impacts across West Africa. With many people highly vulnerable to such events in this region, this study investigates whether anthropogenic climate change has influenced such heavy precipitation events. We use a probabilistic event attribution approach to assess the contribution of anthropogenic greenhouse gas emissions, by comparing the probability of such an event occurring in climate model simulations with all known climate forcings to those where natural forcings only are simulated. An ensemble of simulations from 10 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) is compared to two much larger ensembles of atmosphere-only simulations, from the Met Office model HadGEM3-A and from weather@home with a regional version of HadAM3P. These are used to assess whether the choice of model ensemble influences the attribution statement that can be made. Results show that anthropogenic greenhouse gas emissions have decreased the probability of high precipitation across most of the model ensembles. However, the magnitude and confidence intervals of the decrease depend on the ensemble used, with more certainty in the magnitude in the atmosphere-only model ensembles due to larger ensemble sizes from single models with more constrained simulations. Certainty is greatly decreased when considering a CMIP5 ensemble that can represent the relevant teleconnections due to a decrease in ensemble members. An increase in probability of high precipitation in HadGEM3-A using the observed trend in sea surface temperatures (SSTs) for natural simulations highlights the need to ensure that estimates of natural SSTs are consistent with observed trends in order for results to be robust. Further work is needed to establish how anthropogenic forcings are affecting the rainfall processes in these simulations in order to better understand the differences in the overall effect.

  14. Development and validation of risk profiles of West African rural communities facing multiple natural hazards.

    Science.gov (United States)

    Asare-Kyei, Daniel; Renaud, Fabrice G; Kloos, Julia; Walz, Yvonne; Rhyner, Jakob

    2017-01-01

    West Africa has been described as a hotspot of climate change. The reliance on rain-fed agriculture by over 65% of the population means that vulnerability to climatic hazards such as droughts, rainstorms and floods will continue. Yet, the vulnerability and risk levels faced by different rural social-ecological systems (SES) affected by multiple hazards are poorly understood. To fill this gap, this study quantifies risk and vulnerability of rural communities to drought and floods. Risk is assessed using an indicator-based approach. A stepwise methodology is followed that combines participatory approaches with statistical, remote sensing and Geographic Information System techniques to develop community level vulnerability indices in three watersheds (Dano, Burkina Faso; Dassari, Benin; Vea, Ghana). The results show varying levels of risk profiles across the three watersheds. Statistically significant high levels of mean risk in the Dano area of Burkina Faso are found whilst communities in the Dassari area of Benin show low mean risk. The high risk in the Dano area results from, among other factors, underlying high exposure to droughts and rainstorms, longer dry season duration, low caloric intake per capita, and poor local institutions. The study introduces the concept of community impact score (CIS) to validate the indicator-based risk and vulnerability modelling. The CIS measures the cumulative impact of the occurrence of multiple hazards over five years. 65.3% of the variance in observed impact of hazards/CIS was explained by the risk models and communities with high simulated disaster risk generally follow areas with high observed disaster impacts. Results from this study will help disaster managers to better understand disaster risk and develop appropriate, inclusive and well integrated mitigation and adaptation plans at the local level. It fulfills the increasing need to balance global/regional assessments with community level assessments where major decisions

  15. Biodiversity and probiotic potential of yeasts isolated from Fura, a West African spontaneously fermented cereal.

    Science.gov (United States)

    Pedersen, Line Lindegaard; Owusu-Kwarteng, James; Thorsen, Line; Jespersen, Lene

    2012-10-01

    Fura is a spontaneously fermented pearl millet product consumed in West Africa. The yeast species involved in the fermentation were identified by pheno- and genotypic methods to be Candida krusei, Kluyveromyces marxianus, Candida tropicalis, Candida rugosa, Candida fabianii, Candida norvegensis and Trichosporon asahii. C. krusei and K. marxianus were found to be the dominant species. Survival in pH 2.5 or in the presence of bile salts (0.3% (w/v) oxgall) and growth at 37°C were independently determined as indicators of the survival potential of the isolates during passage through the human gastrointestinal tract. Selected yeast species isolates were assessed for their probiotic potential. All of the examined yeast isolates survived and grew at human gastrointestinal conditions in pH 2.5, 0.3% (w/v) oxgall at 37°C. The effect on the transepithelial electrical resistance (TEER) across polarized monolayers of intestinal epithelial cells of human (Caco-2) and porcine (IPEC-J2) origin, were determined. The Caco-2 cells and IPEC-J2 cells displayed clearly different relative TEER results. The strains of C. krusei, K. marxianus, C. rugosa and T. asahii were able to increase the relative TEER of Caco-2 monolayers after 48h. In comparison, the relative TEER of IPEC-J2 monolayers decreased when exposed to the same yeasts, even though T. asahii did not differ significantly from Saccharomyces cerevisiae var. boulardii which is used as a human probiotic. C. tropicalis resulted in the largest relative TEER decrease for both the human and the porcine cell model assays. Hyphal growth was observed for C. albicans and C. tropicalis after 48h of incubation with polarized Caco-2 monolayers, whereas this was not the case for the remaining yeast species. In the present study new yeast strains with potential probiotic properties have been isolated to be used potentially as starter cultures for fura production.

  16. The socio-economic drivers of bushmeat consumption during the West African Ebola crisis

    Science.gov (United States)

    Arandjelovic, Mimi; Boesch, Lukas; Gatiso, Tsegaye; Grimes, Trokon; Kuehl, Hjalmar S.; Lormie, Menladi; Stephens, Colleen; Tweh, Clement; Junker, Jessica

    2017-01-01

    Bushmeat represents an important source of animal protein for humans in tropical Africa. Unsustainable bushmeat hunting is a major threat to wildlife and its consumption is associated with an increased risk of acquiring zoonotic diseases, such as Ebola virus disease (EVD). During the recent EVD outbreak in West Africa, it is likely that human dietary behavior and local attitudes toward bushmeat consumption changed in response to the crisis, and that the rate of change depended on prevailing socio-economic conditions, including wealth and education. In this study, we therefore investigated the effects of income, education, and literacy on changes in bushmeat consumption during the crisis, as well as complementary changes in daily meal frequency, food diversity and bushmeat preference. More specifically, we tested whether wealthier households with more educated household heads decreased their consumption of bushmeat during the EVD crisis, and whether their daily meal frequency and food diversity remained constant. We used Generalized Linear Mixed Models to analyze interview data from two nationwide household surveys across Liberia. We found an overall decrease in bushmeat consumption during the crisis across all income levels. However, the rate of bushmeat consumption in high-income households decreased less than in low-income households. Daily meal frequency decreased during the crisis, and the diversity of food items and preferences for bushmeat species remained constant. Our multidisciplinary approach to study the impact of EVD can be applied to assess how other disasters affect social-ecological systems and improve our understanding and the management of future crises. PMID:28282378

  17. Distinct lineages of Ebola virus in Guinea during the 2014 West African epidemic.

    Science.gov (United States)

    Simon-Loriere, Etienne; Faye, Ousmane; Faye, Oumar; Koivogui, Lamine; Magassouba, Nfaly; Keita, Sakoba; Thiberge, Jean-Michel; Diancourt, Laure; Bouchier, Christiane; Vandenbogaert, Matthias; Caro, Valérie; Fall, Gamou; Buchmann, Jan P; Matranga, Christan B; Sabeti, Pardis C; Manuguerra, Jean-Claude; Holmes, Edward C; Sall, Amadou A

    2015-08-06

    An epidemic of Ebola virus disease of unprecedented scale has been ongoing for more than a year in West Africa. As of 29 April 2015, there have been 26,277 reported total cases (of which 14,895 have been laboratory confirmed) resulting in 10,899 deaths. The source of the outbreak was traced to the prefecture of Guéckédou in the forested region of southeastern Guinea. The virus later spread to the capital, Conakry, and to the neighbouring countries of Sierra Leone, Liberia, Nigeria, Senegal and Mali. In March 2014, when the first cases were detected in Conakry, the Institut Pasteur of Dakar, Senegal, deployed a mobile laboratory in Donka hospital to provide diagnostic services to the greater Conakry urban area and other regions of Guinea. Through this process we sampled 85 Ebola viruses (EBOV) from patients infected from July to November 2014, and report their full genome sequences here. Phylogenetic analysis reveals the sustained transmission of three distinct viral lineages co-circulating in Guinea, including the urban setting of Conakry and its surroundings. One lineage is unique to Guinea and closely related to the earliest sampled viruses of the epidemic. A second lineage contains viruses probably reintroduced from neighbouring Sierra Leone on multiple occasions, while a third lineage later spread from Guinea to Mali. Each lineage is defined by multiple mutations, including non-synonymous changes in the virion protein 35 (VP35), glycoprotein (GP) and RNA-dependent RNA polymerase (L) proteins. The viral GP is characterized by a glycosylation site modification and mutations in the mucin-like domain that could modify the outer shape of the virion. These data illustrate the ongoing ability of EBOV to develop lineage-specific and potentially phenotypically important variation.

  18. Characterization of the Fire Regime and Drivers of Fires in the West African Tropical Forest

    Science.gov (United States)

    Dwomoh, F. K.; Wimberly, M. C.

    2016-12-01

    The Upper Guinean forest (UGF), encompassing the tropical regions of West Africa, is a globally significant biodiversity hotspot and a critically important socio-economic and ecological resource for the region. However, the UGF is one of the most human-disturbed tropical forest ecosystems with the only remaining large patches of original forests distributed in protected areas, which are embedded in a hotspot of climate stress & land use pressures, increasing their vulnerability to fire. We hypothesized that human impacts and climate interact to drive spatial and temporal variability in fire, with fire exhibiting distinctive seasonality and sensitivity to drought in areas characterized by different population densities, agricultural practices, vegetation types, and levels of forest degradation. We used the MODIS active fire product to identify and characterize fire activity in the major ecoregions of the UGF. We used TRMM rainfall data to measure climatic variability and derived indicators of human land use from a variety of geospatial datasets. We employed time series modeling to identify the influences of drought indices and other antecedent climatic indicators on temporal patterns of active fire occurrence. We used a variety of modeling approaches to assess the influences of human activities and land cover variables on the spatial pattern of fire activity. Our results showed that temporal patterns of fire activity in the UGF were related to precipitation, but these relationships were spatially heterogeneous. The pattern of fire seasonality varied geographically, reflecting both climatological patterns and agricultural practices. The spatial pattern of fire activity was strongly associated with vegetation gradients and anthropogenic activities occurring at fine spatial scales. The Guinean forest-savanna mosaic ecoregion had the most fires. This study contributes to our understanding of UGF fire regime and the spatio-temporal dynamics of tropical forest fires in

  19. Recent Trends in the Regime of Extreme Rainfall in the West African Sahel

    Science.gov (United States)

    Lebel, T.; Panthou, G.; Vischel, T.; Quantin, G.

    2015-12-01

    West Africa is known for having experienced an extreme drought starting at the end of the 1960s that is recognized to be the greatest climatic signal at regional scale since the beginning of meteorological measurements. Despite a moderate recovery of the annual precipitations since the 1990s in the Central and Eastern Sahel, rainfall over the last two decades remains lower by 15% than during the period 1950-1970. Paradoxically these persisting dry conditions have been accompanied by a dramatic increase of flood fatalities especially over the recent 10 years. Using a homogeneous dataset of 41 daily rainfall series covering the period 1950-2010, an integrated regional approach based on the statistical extreme value theory was then used to reduce the local sampling effects and to provide robust estimates of intense rainfall distributions to be analyzed in conjunction with the annual rainfall series. This led to identify some key rainfall regime characteristics related to the decadal scale rainfall variability over the region. The main factor of the rainfall deficit during the great 1970-2000 drought was a lower occurrence of rainy days, extreme rainy days being the most affected. Over the last ten years, the Sahelian rainfall regime is characterized by a lasting deficit of the number of rainy days, while at the same time the extreme rainfall occurrence is on the rise. As a consequence the proportion of annual rainfall associated with extreme rainfall has increased from 17% in the 1970-1990 years to 19% in the 1991-2000 years and to 22% in the 2001-2010 years. This tends to support the idea that a more extreme climate has been observed over the last 10 years, with a persisting deficit of the occurrence of rainfall associated with an increase of the occurrence of extreme daily rainfall. Our results also suggest that the intensification of the precipitation regime has likely contributed to the aggravation of the hydrological risks in the Sahel.

  20. Agricultural Production, Land-use/cover Change and the Desertification Debate in the West African Savannah: An Adapted Political Ecology Approach

    Directory of Open Access Journals (Sweden)

    Peter Kojo Boateng

    2013-10-01

    Full Text Available In the semi-arid tropics of West Africa where farming is the major livelihood source, it is claimed that African farmers are degrading their land: first because of shifting cultivation, later because population growth brought about “over-cultivation” or farm expansion and the scattering of more farms on the landscape.  In response to these issues, West African governments have emphasised the need and rolled out programmes for modernisation of smallholder agriculture through promotion of capital-intensive and market-driven strategies. Implicit in this modernisation policy orientation is the idea that the way production is organised by peasants in the semi-arid environments have to change; meaning poor peasants, regarded as perpetuators of land degradation, who may not produce for the market need to be modernised in line with the state’s vision of agricultural development and environmental management. However, new perspectives being generated from several local level studies of agricultural production and land-use/cover change in the semi-arid savannah regions of West Africa offer departure points from those dominant narratives of increasing degradation and desertification. This paper discusses this emerging paradigmatic revolution by reviewing the literature on 3 highly polarised issues around land-use/cover change in the West African savannah – (a discourses of environmental degradation; (b human-environment interactions and agricultural production; and (c mapping of land cover changes in drylands. Within these reviews, the paper highlights ways it move beyond currently contrasting views, before advancing an adapted political ecology framework deemed suited for exploring the complex relationships between agricultural production and land-use/cover change.

  1. Standardising visual control devices for tsetse flies: Central and West African species Glossina palpalis palpalis.

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    Dramane Kaba

    Full Text Available BACKGROUND: Glossina palpalis palpalis (G. p. palpalis is one of the principal vectors of sleeping sickness and nagana in Africa with a geographical range stretching from Liberia in West Africa to Angola in Central Africa. It inhabits tropical rain forest but has also adapted to urban settlements. We set out to standardize a long-lasting, practical and cost-effective visually attractive device that would induce the strongest landing response by G. p. palpalis for future use as an insecticide-impregnated tool in area-wide population suppression of this fly across its range. METHODOLOGY/PRINCIPAL FINDINGS: Trials were conducted in wet and dry seasons in the Ivory Coast, Cameroon, the Democratic Republic of Congo and Angola to measure the performance of traps (biconical, monoconical and pyramidal and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a practical enumerator at these remote locations to compare landing efficiencies of devices. Independent of season and country, both phthalogen blue-black and blue-black-blue 1 m(2 targets covered with adhesive film proved to be as good as traps in phthalogen blue or turquoise blue for capturing G. p. palpalis. Trap efficiency varied (8-51%. There was no difference between the performance of blue-black and blue-black-blue 1 m(2 targets. Baiting with chemicals augmented the overall performance of targets relative to traps. Landings on smaller phthalogen blue-black 0.25 m(2 square targets were not significantly different from either 1 m(2 blue-black-blue or blue-black square targets. Three times more flies were captured per unit area on the smaller device. CONCLUSIONS/SIGNIFICANCE: Blue-black 0.25 m(2 cloth targets show promise as simple cost effective devices for management of G. p. palpalis as they can be used for both control when impregnated with insecticide and for

  2. Standardising Visual Control Devices for Tsetse Flies: Central and West African Species Glossina palpalis palpalis

    Science.gov (United States)

    Kaba, Dramane; Zacarie, Tusevo; M'Pondi, Alexis Makumyaviri; Njiokou, Flobert; Bosson-Vanga, Henriette; Kröber, Thomas; McMullin, Andrew; Mihok, Steve; Guerin, Patrick M.

    2014-01-01

    Background Glossina palpalis palpalis (G. p. palpalis) is one of the principal vectors of sleeping sickness and nagana in Africa with a geographical range stretching from Liberia in West Africa to Angola in Central Africa. It inhabits tropical rain forest but has also adapted to urban settlements. We set out to standardize a long-lasting, practical and cost-effective visually attractive device that would induce the strongest landing response by G. p. palpalis for future use as an insecticide-impregnated tool in area-wide population suppression of this fly across its range. Methodology/Principal Findings Trials were conducted in wet and dry seasons in the Ivory Coast, Cameroon, the Democratic Republic of Congo and Angola to measure the performance of traps (biconical, monoconical and pyramidal) and targets of different sizes and colours, with and without chemical baits, at different population densities and under different environmental conditions. Adhesive film was used as a practical enumerator at these remote locations to compare landing efficiencies of devices. Independent of season and country, both phthalogen blue-black and blue-black-blue 1 m2 targets covered with adhesive film proved to be as good as traps in phthalogen blue or turquoise blue for capturing G. p. palpalis. Trap efficiency varied (8–51%). There was no difference between the performance of blue-black and blue-black-blue 1 m2 targets. Baiting with chemicals augmented the overall performance of targets relative to traps. Landings on smaller phthalogen blue-black 0.25 m2 square targets were not significantly different from either 1 m2 blue-black-blue or blue-black square targets. Three times more flies were captured per unit area on the smaller device. Conclusions/Significance Blue-black 0.25 m2 cloth targets show promise as simple cost effective devices for management of G. p. palpalis as they can be used for both control when impregnated with insecticide and for population sampling when

  3. Late Cretaceous Turbidite Reservoirs Along the Equatorial West African Margin: An Industry Perspective on Source-to-Sink Relationships

    Science.gov (United States)

    Wilson, Jonathan; Kohlmann, Fabian; Nicoll, Graeme

    2017-04-01

    The source-to-sink mindset provides an important framework for the exploration geologist. It enables an integrated understanding of hinterland and basin, and can lead to subsurface risk mitigation, particularly with respect to predicting reservoir location and quality. Despite the numerous benefits associated with source-to-sink analysis, such studies are time-consuming to generate, encompassing a large array of disciplines and data, and are not routinely performed within the hydrocarbon industry. The discovery of several significant hydrocarbon fields along the equatorial West African margin has been followed by a series of expensive failures throughout the last decade associated with reservoir quality/presence. This paper discusses a case study focused on the equatorial West African margin, demonstrating how three well-known but effective approaches can be integrated to reconstruct source-to-sink relationships in an ancient sedimentary system, helping de-risk exploration efforts. The first step is to characterize the hinterland. To do this, detailed information was collected for two separate but interlinked datasets—mineral deposits and hard rock geochronology. Combined, these two datasets allow an understanding of the timing and nature of an areas tectonic evolution to be easily developed. The data can be used alongside stratigraphic data and geodynamic information from a plate tectonic model to reconstruct topography and bathymetry of the earth at different episodes of geological time. Paleo digital elevation models (PDEMs) give a first-order approximation of hinterland topography and therefore allow possible sediment source areas to be identified and potential sediment transport pathways to be visualized by means of the digital reconstruction of paleo-drainage networks and their attendant watersheds. This integrated global dataset of hinterland geochronology provides useful "source" information complemented by "sink" information contained within a detrital

  4. Coconut genome size determined by flow cytometry: Tall versus Dwarf types.

    Science.gov (United States)

    Freitas Neto, M; Pereira, T N S; Geronimo, I G C; Azevedo, A O N; Ramos, S R R; Pereira, M G

    2016-02-11

    Coconuts (Cocos nucifera L.) are tropical palm trees that are classified into Tall and Dwarf types based on height, and both types are diploid (2n = 2x = 32 chromosomes). The reproduction mode is autogamous for Dwarf types and allogamous for Tall types. One hypothesis for the origin of the Dwarf coconut suggests that it is a Tall variant that resulted from either mutation or inbreeding, and differences in genome size between the two types would support this hypothesis. In this study, we estimated the genome sizes of 14 coconut accessions (eight Tall and six Dwarf types) using flow cytometry. Nuclei were extracted from leaf discs and stained with propidium iodide, and Pisum sativum (2C = 9.07 pg DNA) was used as an internal standard. Histograms with good resolution and low coefficients of variation (2.5 to 3.2%) were obtained. The 2C DNA content ranged from 5.72 to 5.48 pg for Tall accessions and from 5.58 to 5.52 pg for Dwarf accessions. The mean genome sizes for Tall and Dwarf specimens were 5.59 and 5.55 pg, respectively. Among all accessions, Rennel Island Tall had the highest mean DNA content (5.72 pg), whereas West African Tall had the lowest (5.48 pg). The mean coconut genome size (2C = 5.57 pg, corresponding to 2723.73 Mbp/haploid set) was classified as small. Only small differences in genome size existed among the coconut accessions, suggesting that the Dwarf type did not evolve from the Tall type.

  5. The impact of convection in the West African monsoon region on global weather forecasts - explicit vs. parameterised convection simulations using the ICON model

    Science.gov (United States)

    Pante, Gregor; Knippertz, Peter

    2017-04-01

    The West African monsoon is the driving element of weather and climate during summer in the Sahel region. It interacts with mesoscale convective systems (MCSs) and the African easterly jet and African easterly waves. Poor representation of convection in numerical models, particularly its organisation on the mesoscale, can result in unrealistic forecasts of the monsoon dynamics. Arguably, the parameterisation of convection is one of the main deficiencies in models over this region. Overall, this has negative impacts on forecasts over West Africa itself but may also affect remote regions, as waves originating from convective heating are badly represented. Here we investigate those remote forecast impacts based on daily initialised 10-day forecasts for July 2016 using the ICON model. One set of simulations employs the default setup of the global model with a horizontal grid spacing of 13 km. It is compared with simulations using the 2-way nesting capability of ICON. A second model domain over West Africa (the nest) with 6.5 km grid spacing is sufficient to explicitly resolve MCSs in this region. In the 2-way nested simulations, the prognostic variables of the global model are influenced by the results of the nest through relaxation. The nest with explicit convection is able to reproduce single MCSs much more realistically compared to the stand-alone global simulation with parameterised convection. Explicit convection leads to cooler temperatures in the lower troposphere (below 500 hPa) over the northern Sahel due to stronger evaporational cooling. Overall, the feedback of dynamic variables from the nest to the global model shows clear positive effects when evaluating the output of the global domain of the 2-way nesting simulation and the output of the stand-alone global model with ERA-Interim re-analyses. Averaged over the 2-way nested region, bias and root mean squared error (RMSE) of temperature, geopotential, wind and relative humidity are significantly reduced in

  6. Geochemistry of Archean Mafic Amphibolites from the Amsaga Area, West African Craton, Mauritania: What Is the Message?

    Science.gov (United States)

    El Atrassi, F.; Debaille, V.; Mattielli, N. D. C.; Berger, J.

    2014-12-01

    While Archean terrains are mainly composed of a TTG (Tonalite-trondhjemite-granodiorite) suite, more mafic lithologies such as amphibolites are also a typical component of those ancient terrains. Although mafic rocks represent only ~10% of the Archean cratons, they may provide key evidence of the role and nature of basaltic magmatism in the formation of the Archean crust as well as the evolution of the Archean mantle. This study focuses on the Archean crust from the West African Craton in Mauritania (Amsaga area). The Amsaga Archean Crust mainly consists of TTG and thrust-imbricated slices of mafic volcanic rocks, which have been affected by polymetamorphic events from the amphibolite to granulite facies. Our main objectives aim to the identification of the mafic lithology origin and a better understanding of their role in the continental crust emplacement. Our petrological observations show that these amphibolites have fine to medium granoblastic and nematoblastic textures. The amphibolites are dominated by amphibolite-facies mineral assemblages (mainly amphibole and plagioclase), but garnet and clinopyroxene occur in a few samples. Two groups are distinct in their geochemical characteristics (major and trace elements), although both have tholeiitic basalt composition. The first group show LREE-enriched patterns and negative Nb-Ta anomalies. The second group is characterized by near-flat LREE patterns and flat HREE patterns. This second group clearly shows no Nb-Ta anomalies. The first group could be related to arc-like basalts, as it is many similarities with some Archean amphibolites probably formed in a supra-subduction zone, for instance the volcanic rocks from the southern edge of the Isua Supracrustal Belt. On the contrary, the second group has a MORB-like signature which is more unusual during the Archean. Different scenarios will be discussed regards to the Archean geodynamics.

  7. Comparison of a flow assay for brucellosis antibodies with the reference cELISA test in West African Bos indicus.

    Directory of Open Access Journals (Sweden)

    Barend M deC Bronsvoort

    Full Text Available Brucellosis is considered by the Food and Agricultural Organisation and the World Health Organisation as one of the most widespread zoonoses in the world. It is a major veterinary public health challenge as animals are almost exclusively the source of infection for people. It is often undiagnosed in both human patients and the animal sources and it is widely acknowledged that the epidemiology of brucellosis in humans and animals is poorly understood, particularly in sub-Saharan Africa. It is therefore important to develop better diagnostic tools in order to improve our understanding of the epidemiology and also for use in the field for disease control and eradication. As with any new diagnostic test, it is essential that it is validated in as many populations as possible in order to characterise its performance and improve the interpretation of its results. This paper describes a comparison between a new lateral flow assasy (LFA for bovine brucellosis and the widely used cELISA in a no gold standard analysis to estimate test performance in this West African cattle population. A Bayesian formulation of the Hui-Walter latent class model incorporated previous studies' data on sensitivity and specificity of the cELISA. The results indicate that the new LFA is very sensitive (approximately 87% and highly specific (approximately 97%. The analysis also suggests that the current cut-off of the cELSIA may not be optimal for this cattle population but alternative cut-offs did not significantly change the estimates of the LFA. This study demonstrates the potential usefulness of this simple to use test in field based surveillance and control which could be easily adopted for use in developing countries with only basic laboratory facilities.

  8. Variability and Predictability of West African Droughts. A Review in the Role of Sea Surface Temperature Anomalies

    Science.gov (United States)

    Rodriguez-Fonseca, Belen; Mohino, Elsa; Mechoso, Carlos R.; Caminade, Cyril; Biasutti, Michela; Gaetani, Marco; Garcia-Serrano, J.; Vizy, Edward K.; Cook, Kerry; Xue, Yongkang; Polo, Irene; Losada, Teresa; Druyan, Leonard M.; Fontaine, Bernard; Bader, Juergen; Doblas-Reyes, Francisco J.; Goddard, Lisa; Janicot, Serge; Arribas, Alberto; Lau, William; Colman, Andrew; Vellinga, M.; Rowell, David P.; Kucharski, Fred; Voldoire, Aurore

    2015-01-01

    The Sahel experienced a severe drought during the 1970s and 1980s after wet periods in the 1950s and 1960s. Although rainfall partially recovered since the 1990s, the drought had devastating impacts on society. Most studies agree that this dry period resulted primarily from remote effects of sea surface temperature (SST) anomalies amplified by local land surface-atmosphere interactions. This paper reviews advances made during the last decade to better understand the impact of global SST variability on West African rainfall at interannual to decadal time scales. At interannual time scales, a warming of the equatorial Atlantic and Pacific/Indian Oceans results in rainfall reduction over the Sahel, and positive SST anomalies over the Mediterranean Sea tend to be associated with increased rainfall. At decadal time scales, warming over the tropics leads to drought over the Sahel, whereas warming over the North Atlantic promotes increased rainfall. Prediction systems have evolved from seasonal to decadal forecasting. The agreement among future projections has improved from CMIP3 to CMIP5, with a general tendency for slightly wetter conditions over the central part of the Sahel, drier conditions over the western part, and a delay in the monsoon onset. The role of the Indian Ocean, the stationarity of teleconnections, the determination of the leader ocean basin in driving decadal variability, the anthropogenic role, the reduction of the model rainfall spread, and the improvement of some model components are among the most important remaining questions that continue to be the focus of current international projects.

  9. Assessment of the petroleum, coal and geothermal resources of the economic community of West African States (ECOWAS) Region

    Energy Technology Data Exchange (ETDEWEB)

    Mattick, Robert E. [U.S. Geological Survey, Boulder, CO (United States); Spencer, Frank D. [U.S. Geological Survey, Boulder, CO (United States); Zihlman, Frederick N. [U.S. Geological Survey, Boulder, CO (United States)

    1982-01-01

    Approximately 85 percent of the land area of the ECOWAS (Economic Community of West African States) region is covered by basement rocks (igneous and highly metamorphosed rocks) or relatively thin layers of Paleozoic, Upper Precambrian, and Continental Intercalaire sedimentary rocks. These areas have little or no petroleum potential. The ECOWAS region can be divided into 13 sedimentary basins on the basis of analysis of the geologic framework of Africa. These 13 basins can be further grouped into 8 categories on the basis of similarities in stratigraphy, geologic history, and probable hydrocarbon potential. The author has attempted to summarize the petroleum potential within the geologic framework of the region. The coal discoveries can be summarized as follows: the Carboniferous section in the Niger Basin; the Paleocene-Maestrichtian, Maestrichtian, and Eocene sections in the Niger Delta and Benin; the Maestrichtian section in the Senegal Basin; and the Pleistocene section in Sierra Leone. The only proved commercial deposits are the Paleocene-Maestrichtian and Maestrichtian subbituminous coal beds of the Niger Delta. Some of the lignite deposits of the Niger Delta and Senegal Basin, however, may be exploitable in the future. Published literature contains limited data on heat-flow values in the ECOWAS region. It is inferred, however, from the few values available and the regional geology that the development of geothermal resources, in general, would be uneconomical. Exceptions may include a geopressured zone in the Niger Delta and areas of recent tectonic activity in the Benue Trough and Cameroon. Development of the latter areas under present economic conditions is not feasible.

  10. Hierarchical multi-species modeling of carnivore responses to hunting, habitat and prey in a West African protected area.

    Directory of Open Access Journals (Sweden)

    A Cole Burton

    Full Text Available Protected areas (PAs are a cornerstone of global efforts to shield wildlife from anthropogenic impacts, yet their effectiveness at protecting wide-ranging species prone to human conflict--notably mammalian carnivores--is increasingly in question. An understanding of carnivore responses to human-induced and natural changes in and around PAs is critical not only to the conservation of threatened carnivore populations, but also to the effective protection of ecosystems in which they play key functional roles. However, an important challenge to assessing carnivore communities is the often infrequent and imperfect nature of survey detections. We applied a novel hierarchical multi-species occupancy model that accounted for detectability and spatial autocorrelation to data from 224 camera trap stations (sampled between October 2006 and January 2009 in order to test hypotheses about extrinsic influences on carnivore community dynamics in a West African protected area (Mole National Park, Ghana. We developed spatially explicit indices of illegal hunting activity, law enforcement patrol effort, prey biomass, and habitat productivity across the park, and used a Bayesian model selection framework to identify predictors of site occurrence for individual species and the entire carnivore community. Contrary to our expectation, hunting pressure and edge proximity did not have consistent, negative effects on occurrence across the nine carnivore species detected. Occurrence patterns for most species were positively associated with small prey biomass, and several species had either positive or negative associations with riverine forest (but not with other habitat descriptors. Influences of sampling design on carnivore detectability were also identified and addressed within our modeling framework (e.g., road and observer effects, and the multi-species approach facilitated inference on even the rarest carnivore species in the park. Our study provides insight for the

  11. West African equatorial ionospheric parameters climatology based on Ouagadougou ionosonde station data from June 1966 to February 1998

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    F. Ouattara

    2009-06-01

    Full Text Available This study is the first which gives the climatology of West African equatorial ionosphere by using Ouagadougou station through three solar cycles. It has permitted to show the complete morphology of ionosphere parameters by analyzing yearly variation, solar cycle and geomagnetic activity, seasonal evolution and diurnal development. This work shows that almost all ionospheric parameters have 11-year solar cycle evolution. Seasonal variation shows that only foF2 exhibits annual, winter and semiannual anomaly. foF2 seasonal variation has permitted us to identify and characterize solar events effects on F2 layer in this area. In fact (1 during quiet geomagnetic condition foF2 presents winter and semiannual anomalies asymmetric peaks in March/April and October. (2 The absence of winter anomaly and the presence of equinoctial peaks are the most visible effects of fluctuating activity in foF2 seasonal time profiles. (3 Solar wind shock activity does not modify the profile of foF2 but increases ionization. (4 The absence of asymmetry peaks, the location of the peaks in March and October and the increase of ionization characterize recurrent storm activity. F1 layers shows increasing trend from cycle 20 to cycle 21. Moreover, E layer parameters seasonal variations exhibit complex structure. It seems impossible to detect fluctuating activity effect in E layer parameters seasonal variations but shock activity and wind stream activity act to decrease E layer ionization. It can be seen from Es layer parameters seasonal variations that wind stream activity effect is fairly independent of solar cycle. E and Es layers critical frequencies and virtual heights diurnal variations let us see the effects of the greenhouse gases in these layers.

  12. Late-life depression: Burden, severity and relationship with social support dimensions in a West African community.

    Science.gov (United States)

    Olagunju, Andrew Toyin; Olutoki, Michael Olasunkanmi; Ogunnubi, Oluseun Peter; Adeyemi, Joseph Dada

    2015-01-01

    The occurrence of depression in old age is often linked with grave consequences. The purpose of this study is to investigate the burden of depression and its relationship with perceived social support among the elderly in a West African community setting. In this cross-sectional study, participants made up of 350 elders aged 60 years and above were selected through multi-stage random sampling technique. All participants were interviewed with designed questionnaire, multidimensional scale of perceived social support (MSPSS) and Geriatric Depression Scale (GDS) to elicit socio-demographic profile, social support and depressive psychopathology respectively. The participants were largely females (52.9%) and their mean age was 68.8±7.3 years. A little above one-quarter (26.4%) had depressive episode, and mild severity was preponderant. Low level of social support was associated with depression (χ(2)=8.418, p=0.004); especially low social supports from significant others (χ(2)=3.989, p=0.046) and family members (χ(2)=4.434, p=0.035). Similarly, severity of depression in the elderly correlated negatively with availability of social support from significant others (χ(2)=5.495, p=0.019) and family members (χ(2)=5.149, p=0.023). Considering the burden of depression in this elderly population and the influential roles of social support especially from family and significant others on depression; strengthening of informal social support and formal social support for the elders is advocated. In addition, design of community based geriatric mental health with social services and articulation of public policy to address old age needs are implied. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  13. Human activities and microbial geographies. An anthropological approach to the risk of infections in West African hospitals.

    Science.gov (United States)

    d'Alessandro, Eugénie

    2015-07-01

    In hospital care, management of the risk of infection represents a crucial issue. Nevertheless, this question remains a neglected area in anthropological research, especially in African countries. To shed new light on this question, we conducted an anthropological investigation in the infectious disease department of a hospital in Niger. Daily observation of the work of the hospital staff for a total period of 6 months was spread out over 2008 and 2009. During our prolonged stay, we also collected 64 in-depth interviews of health care workers and attendants in the department. This study method made it possible to describe many of the practices and discourses related to the issues of medical and personal care and hospital hygiene and to compare the practices observed to standard principles for preventing hospital-acquired infections. Our ethnographic attention to the behavior of the actors showed the absence of formal spatial segmentations between different activities. The care provided by the untrained relatives serving as personal attendants introduced territorial enclaves governed by home hygiene standards into the interior of technical spaces. At the same time, privatizing equipment and space for their diverse activities, the medical staff disrupted technical chains and generated the recurrent crossing of microbial geographies. These results allow us to offer two principal guidelines for improving the quality of care and the management of risks of infection in hospitals in West Africa: (1) the essential role of the attendants in the care provided to hospital inpatients must be officially taken into account, especially by including them in the organization of medical hygiene procedures; (2) the different overlapping technical activities and social activities in the work space must be limited by their geographic and architectural segmentation.

  14. How Does Gender Affect Sustainable Intensification of Cereal Production in the West African Sahel? Evidence from Burkina Faso.

    Science.gov (United States)

    Theriault, Veronique; Smale, Melinda; Haider, Hamza

    2017-04-01

    Better understanding of gender differences in the adoption of agricultural intensification strategies is crucial for designing effective policies to close the gender gap while sustainably enhancing farm productivity. We examine gender differences in adoption rates, likelihood and determinants of adopting strategy sets that enhance yields, protect crops, and restore soils in the West African Sahel, based on analysis of cereal production in Burkina Faso. Applying a multivariate probit model to a nationally representative household panel, we exploit the individual plot as unit of analysis and control for plot manager characteristics along with other covariates. Reflecting the socio-cultural context of farming combined with the economic attributes of inputs, we find that female managers of individual cereal fields are less likely than their male counterparts to adopt yield-enhancing and soil-restoring strategies, although no differential is apparent for yield-protecting strategies. More broadly, gender-disaggregated regressions demonstrate that adoption determinants differ by gender. Plot manager characteristics, including age, marital status, and access to credit or extension services do influence adoption decisions. Furthermore, household resources influence the probability of adopting intensification strategy sets differently by gender of the plot manager. Variables expressing the availability of household labor strongly influence the adoption of soil-restoring strategies by female plot managers. By contrast, household resources such as extent of livestock owned, value of non-farm income, and area planted to cotton affect the adoption choices of male plot managers. Rectifying the male bias in extension services along with improving access to credit, income, and equipment to female plot managers could contribute to sustainable agricultural intensification.

  15. Synergy in efficacy of fungal entomopathogens and permethrin against West African insecticide-resistant Anopheles gambiae mosquitoes.

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    Marit Farenhorst

    Full Text Available BACKGROUND: Increasing incidences of insecticide resistance in malaria vectors are threatening the sustainable use of contemporary chemical vector control measures. Fungal entomopathogens provide a possible additional tool for the control of insecticide-resistant malaria mosquitoes. This study investigated the compatibility of the pyrethroid insecticide permethrin and two mosquito-pathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, against a laboratory colony and field population of West African insecticide-resistant Anopheles gambiae s.s. mosquitoes. METHODOLOGY/FINDINGS: A range of fungus-insecticide combinations was used to test effects of timing and sequence of exposure. Both the laboratory-reared and field-collected mosquitoes were highly resistant to permethrin but susceptible to B. bassiana and M. anisopliae infection, inducing 100% mortality within nine days. Combinations of insecticide and fungus showed synergistic effects on mosquito survival. Fungal infection increased permethrin-induced mortality rates in wild An. gambiae s.s. mosquitoes and reciprocally, exposure to permethrin increased subsequent fungal-induced mortality rates in both colonies. Simultaneous co-exposure induced the highest mortality; up to 70.3+/-2% for a combined Beauveria and permethrin exposure within a time range of one gonotrophic cycle (4 days. CONCLUSIONS/SIGNIFICANCE: Combining fungi and permethrin induced a higher impact on mosquito survival than the use of these control agents alone. The observed synergism in efficacy shows the potential for integrated fungus-insecticide control measures to dramatically reduce malaria transmission and enable control at more moderate levels of coverage even in areas where insecticide resistance has rendered pyrethroids essentially ineffective.

  16. Does a wife's education influence spousal agreement on approval of family planning?: Random-effects Modeling using data from two West African Countries.

    Science.gov (United States)

    Hossain, Mian; Ahmed, Saifuddin; Rogers, Laurencia

    2014-05-01

    Spousal approval of family planning is critical for contraceptive use. Both contraceptive use rates and women's education are low in many West-African countries and this study examines the role of wives' education in spousal agreement on approval of family planning in two sub-Saharan West African countries. We used couples' data from Demographic Health Surveys in Senegal and in Niger, conducted in 2005 and 2006, respectively. Multiple logistic regression results using multilevel modeling show that the odds of spousal agreement on approval of family planning were slightly over three times [OR: 3.16; 95% CI: 1.32 to 7.57] in Senegal and were about three times [OR: 3.07; 95% CI: 1.64 to 5.76] in Niger higher for women with more than primary education. Findings suggest that improvement in women's education could lead to spousal agreement on approval of family planning, which may lead to use of family planning in sub-Saharan African countries.

  17. Characterization of West African Jet Streams and Their Association to ENSO Events and Rainfall in ERA-Interim 1979–2011

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    Churchill Okonkwo

    2014-01-01

    Full Text Available The interannual variability of West African jet streams and their association with rainfall are reexamined using European Reanalysis ERA-Interim 1979–2011. The objective of the study is to characterize their climatology and role in rainfall variability in western Sahel. Wavelet analysis was used on wind speed data and implications to ENSO were discussed subsequently. Our results show that while the low-level African Westerly Jet (AWJ correlates well with rainfall south of the equator in boreal winter months, the Tropical Easterly Jet (TEJ and African Easterly Jet (AEJ correlate better with rainfall north of the equator in the boreal summer months. Results of interannual-to-decadal variability in 200 mb, 600 mb, and 850 mb of zonal wind reveal that there is enhanced variability in the 2–8 year band. Also, the TEJ, AEJ, and AWJ fluctuations are coupled with variations in southern oscillation. Further analysis suggests a statistically significant association between TEJ and the El Niño events of the 1980s that led to intense drought in the Sahel region of West Africa. The 2007 moderate La Niña shows a statistically significant coherence with the 500 mb, 600 mb, and 850 mb jets. These associations are also phase locked, suggesting that the association may be more than by chance.

  18. Geology of the world-class Kiaka polyphase gold deposit, West African Craton, Burkina Faso

    Science.gov (United States)

    Fontaine, Arnaud; Eglinger, Aurélien; Ada, Koumangdiwè; André-Mayer, Anne-Sylvie; Reisberg, Laurie; Siebenaller, Luc; Le Mignot, Elodie; Ganne, Jérôme; Poujol, Marc

    2017-02-01

    The Kiaka gold deposit is a major resource in West Africa, with measured and indicated resources of 124 Mt at 1.09 g/t Au (3.9 Moz) and inferred resources of 27 Mt at 0.83 g/t Au (0.8 Moz). Located within the Manga-Fada N'Gourma greenstone and plutonic belt in south of the Burkina Faso, the deposit is hosted by a metamorphosed volcano-sedimentary sequence of lithic-, quartz-biotite metagreywackes, aluminosilicate-bearing metapelites and garnet-orthopyroxene-bearing schists and volcanic units. Structural observations indicate four local deformation events: DK1, DK2 and DK3 and DK4. Respectively, these events are linked to regional D1 E-W compression, D2 NW-SE compression and lastly, D3- and D4-related reactivations along D2 shear zones. The S2 foliation and D2 shear zones are developed during lower amphibolite facies metamorphism whereas retrogression occurs during D3-4 reactivations along these shear zones at upper greenschist facies conditions. The emplacement of a dioritic intrusion, dated at 2140 ± 7 Ma (Concordia U-Pb age on magmatic zircon), is interpreted to be contemporaneous with sinistral displacement along mineralized, NE-trending D2 shear zones. The intersection of these shears zones and the Markoye shear zone (dextral-reverse D1 and sinistral-reverse D2 reactivations) controlled the final geometry of the host rocks and the ore zones. Four subparallel elongated ore bodies are mainly hosted within D2-related shear zones and some are developed in an apparent axial plane of a F2 isoclinal fold. Detailed petrographic studies have identified two main types of hydrothermal alteration associated with two stages of gold mineralization. The stage (1) corresponds to replacement zones with biotite and clinozoisite during the D2 event associated with pyrrhotite ± pyrite, chalcopyrite (disseminated gold stage). The stage (2) occurs during reactivations of the D2-related auriferous shear zones (vein stage) and is characterized by diopside ± actinolite D3 veins and

  19. Why do global climate models struggle to represent low-level clouds in the West African summer monsoon?

    Science.gov (United States)

    Knippertz, Peter; Hannak, Lisa; Fink, Andreas H.; Kniffka, Anke; Pante, Gregor

    2017-04-01

    Climate models struggle to realistically represent the West African monsoon (WAM), which hinders reliable future projections and the development of adequate adaption measures. Low-level clouds over southern West Africa (5-10°N, 8°W-8°E) during July-September are an integral part of the WAM through their effect on the surface energy balance and precipitation, but their representation in climate models has so far received little attention. These clouds usually form during the night near the level of the nocturnal low-level jet ( 950 hPa), thicken and spread until the mid-morning ( 09 UTC), and then break up and rise in the course of the day, typically to about 850 hPa. The low thermal contrast to the surface and the frequent presence of obscuring higher-level clouds make detection of the low-level clouds from space rather challenging. Here we use 30 years of output from 18 models participating in the Coupled Model Intercomparison Project Phase 5 (CMIP5) as well as 20 years of output from 8 models participating in the Year of Tropical Convection (YoTC) experiments to identify cloud biases and their causes. A great advantage of the YoTC dataset is the 6-hourly output frequency, which allows an analysis of the diurnal cycle, and the availability of temperature and moisture tendencies from parameterized processes such as convection, radiation and boundary-layer turbulence. A comparison to earlier analyses based on CMIP3 output reveals rather limited improvements with regard to the represenation of low-level cloud and winds. Compared to ERA-Interim re-analyses, which shows satisfactory agreement with surface observations, many of the CMIP5 and YoTC models still have large biases in low-level cloudiness of both signs and a tendency to too high elevation and too weak diurnal cycles. At the same time, these models tend to have too strong low-level jets, the impact of which is unclear due to concomitant effects on temperature and moisture advection as well as turbulent

  20. Disagreements between Moisture Distribution in (Re)Analysis Products associated with Surges of the West African Monsoon

    Science.gov (United States)

    Roberts, Alex; Knippertz, Peter; Marsham, John

    2014-05-01

    Reanalysis and operational analysis products are routinely used as the best estimates of the atmospheric state for climatological studies, to initialise operational forecasts or simulations for research, or to drive chemistry transport models. Differences between the models employed, assimilation methods and assimilated datasets can lead to substantial differences between (re)analysis products. Here we analyse such differences in the distribution of low-level water vapour to estimate the zonal mean position of the leading edge of the West African Monsoon (the Intertropical Discontinuity, ITDΦ). We do this for 11 monsoon seasons (April-September, 2000-2010) in 7 (re)analysis products: (1) NCEP-NCAR, (2) NCEP-DOE, (3) MERRA, (4) CFSR, (5) ERA-Interim, (6) GFS operational analysis and (7) ECMWF operational analysis. Long-term biases and inter-annual and seasonal patterns of disagreement between the different (re)analysis products are identified, together with particular periods with extreme disagreement . Composites of the extreme disagreement events show that they coincide with northward excursions of the ITDΦ and the production of rainfall in the Sahel and Sahara. Tropical Rainfall Measuring Mission (TRMM) 3B42 V7 rainfall retrievals are used to illustrate the presence of precipitating clouds north of the ITDΦ one to four days before peak disagreement. TRMM retrievals are compared with outgoing longwave radiation (OLR) from the products which produce the greatest and smallest range of movement of ITDΦ. The product with the greatest range which also stays north longest compares well with TRMM and has a much greater coverage of cold cloud compared to the product which produces the smallest and shortest lived northward surge. The largest disagreement occurs during the retreat of the ITDΦ. The sparse nature of observations over much of West Africa mean that the ITD in (re)analysis products is poorly constrained, particularly if ITDΦ is far north. Therefore, it is

  1. Nature and evolution of Neoproterozoic ocean-continent transition: Evidence from the passive margin of the West African craton in NE Mali

    Science.gov (United States)

    Renaud, Caby

    2014-03-01

    The Timétrine massif exposed west of the Pan-African suture zone in northeastern Mali belongs to the passive margin of the West African craton facing to the east intra-oceanic arc assemblages and 730 Ma old pre-collisional calc-alkaline plutons. The Timétrine lithologic succession includes from the base to the top Mesoproterozoic cratonic to passive margin formations overlain by deep-sea Fe-Mg schists. Submarine metabasalts and two ultramafic massifs of serpentinized mantle peridotites are inserted as olistoliths towards the top whereas turbidites of continental origin represent the younger unit. Field and petrological data have revealed a distinct metasedimentary sequence attached to the serpentinized peridotites. It essentially consists of impure carbonates, Fe jaspers and polymictic breccias containing altered blocks of mantle peridotites, most rocks being enriched in detrital chromite. This association is interpreted as reworked chemical and detrital sediments derived from the alteration of mafic-ultramafic rocks. It is argued that mantle exhumation above sea floor took place during the Neoproterozoic rifting and crustal thinning period under possible tropical conditions, as suggested by the large volume of silicified serpentinites. In spite of greenschist facies metamorphic overprint characterized by widespread Fe-rich blue amphiboles that are not diagnostic of high-pressure conditions, it is possible to reconstruct a former ocean-continent transition similar to that evidenced for the Mesozoic period, followed by the deposition of syn-to post rift terrigeneous turbidites roughly coeval with ocean spreading some time before 800 Ma. It is concluded that the serpentinite massifs were tectonically emplaced first in an extensional setting, then incorporated within deep-sea sediments as olistoliths and finally transported westward during late Neoproterozoic collisional tectonics onto the West African craton.

  2. A comparison of phenotypic traits related to trypanotolerance in five west african cattle breeds highlights the value of shorthorn taurine breeds.

    Directory of Open Access Journals (Sweden)

    David Berthier

    Full Text Available Animal African Trypanosomosis particularly affects cattle and dramatically impairs livestock development in sub-Saharan Africa. African Zebu (AFZ or European taurine breeds usually die of the disease in the absence of treatment, whereas West African taurine breeds (AFT, considered trypanotolerant, are able to control the pathogenic effects of trypanosomosis. Up to now, only one AFT breed, the longhorn N'Dama (NDA, has been largely studied and is considered as the reference trypanotolerant breed. Shorthorn taurine trypanotolerance has never been properly assessed and compared to NDA and AFZ breeds.This study compared the trypanotolerant/susceptible phenotype of five West African local breeds that differ in their demographic history. Thirty-six individuals belonging to the longhorn taurine NDA breed, two shorthorn taurine Lagune (LAG and Baoulé (BAO breeds, the Zebu Fulani (ZFU and the Borgou (BOR, an admixed breed between AFT and AFZ, were infected by Trypanosoma congolense IL1180. All the cattle were genetically characterized using dense SNP markers, and parameters linked to parasitaemia, anaemia and leukocytes were analysed using synthetic variables and mixed models. We showed that LAG, followed by NDA and BAO, displayed the best control of anaemia. ZFU showed the greatest anaemia and the BOR breed had an intermediate value, as expected from its admixed origin. Large differences in leukocyte counts were also observed, with higher leukocytosis for AFT. Nevertheless, no differences in parasitaemia were found, except a tendency to take longer to display detectable parasites in ZFU.We demonstrated that LAG and BAO are as trypanotolerant as NDA. This study highlights the value of shorthorn taurine breeds, which display strong local adaptation to trypanosomosis. Thanks to further analyses based on comparisons of the genome or transcriptome of the breeds, these results open up the way for better knowledge of host-pathogen interactions and

  3. Note on the seasonal use of lowland and highland habitats by the West African Chimpanzee Pan troglodytes verus (Schwarz, 1934 (Primates: Hominidae: Implications for its conservation

    Directory of Open Access Journals (Sweden)

    P.I. Ndiaye

    2013-02-01

    Full Text Available The West African Chimpanzee Pan troglodytes verus is endangered. In order to gain insight into the survival potential of this subspecies in Senegal (West Africa, we investigated relationships between this primate and its habitat, particularly from a novel perspective: the influence of the topography on the seasonality of its distribution within its habitat. In Senegal chimpanzees are rarely seen in the wild, particularly outside of protected areas, which is where the present study was conducted on the basis of nest census findings (N=436. According to our observations between March 1998 and March 2000, we established that chimpanzees nested in the gallery forest during the dry season and higher areas (hills and plateaus, plateau edge gallery forests during the rainy season. Valley flooding during the rainy season may be the major reason for chimpanzees to nest in the highlands. The results can help conservation managers to protect the species.

  4. High-resolution measurements of atmospheric molecular hydrogen and its isotopic composition at the West African coast of Mauritania

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    S. Walter

    2013-05-01

    Full Text Available Oceans are a net source of molecular hydrogen (H2 to the atmosphere, where nitrogen (N2 fixation is assumed to be the main biological production pathway followed by photochemical production from organic material. The sources can be distinguished using isotope measurements because of clearly differing isotopic signatures of the produced hydrogen. Here we present the first ship-borne measurements of atmospheric molecular H2 mixing ratio and isotopic composition at the West African coast of Mauritania (16–25° W, 17–24° N. This area is one of the biologically most active regions of the world's oceans with seasonal upwelling events and characterized by strongly differing hydrographical/biological properties and phytoplankton community structures. The aim of this study was to identify areas of H2 production and distinguish H2 sources by isotopic signatures of atmospheric H2. For this more than 100 air samples were taken during two cruises in February 2007 and 2008. During both cruises a transect from the Cape Verde Islands towards the Mauritanian Coast was sampled to cover differing oceanic regions such as upwelling and oligotrophic regimes. In 2007, additionally, four days were sampled at high resolution of one sample per hour to investigate a possible diurnal cycle of atmospheric H2. Our results indicate the influence of local sources and suggest the Banc d'Arguin as a pool for precursors for photochemical H2 production, whereas oceanic N2 fixation could not be identified as a source for atmospheric H2 during these two cruises. The variability in diurnal cycles is probably influenced by released precursors for photochemical H2 production and also affected by a varying origin of air masses. This means for future investigations that only measuring the mixing ratio of H2 is insufficient to explain the variability of an atmospheric diurnal cycle and support is needed, e.g. by isotopic measurements. Nevertheless, measurements of atmospheric H2

  5. Mat-related sedimentary structures in Neoproterozoic peritidal passive margin deposits of the West African Craton (Anti-Atlas, Morocco)

    Science.gov (United States)

    Bouougri, E.; Porada, H.

    2002-11-01

    Proterozoic inliers in the central Anti-Atlas mountains expose predominantly siliciclastic sedimentary successions deposited in peritidal zones along the Neoproterozoic continental margin of the West African Craton (WAC). The low-grade metamorphic and modestly deformed sediments contain a wealth of sedimentary structures related to the former presence and activities of microbial mats and respective physicobiological processes. The well-preserved structures include wrinkle structures, erosion marks, microbial sand chips, spindle-shaped and subcircular microbial shrinkage cracks, and possibly gas domes and cabbage-head structures. Thin sections exhibit mat fragments and dispersed grains of hematite/limonite after pyrite in fine-grained quartzitic storm deposits. Post-storm layers frequently consist of matrix-supported sand-sized to silt-sized grains and are overlain by argillaceous veneers including isolated silt-sized grains and black carbonaceous laminae. The muddy veneers are considered to represent compacted stacks of microbial mats (biolaminites), which colonized and biostabilized storm and post-storm layers, and thus prevented them from eroding. In the absence of grazing and burrowing organisms and at suitable depositional and hydrodynamic conditions, it may be expected that Proterozoic microbial mats extensively grew from the supratidal to the intertidal zones and occasionally, e.g. behind protective barriers, in the subtidal zone and beyond. Mat-related structures, however, need specific conditions for their formation and preservation: Wrinkle structures, erosion marks, and microbial sand chips require tractional currents and soon deposition and burial, respectively. Such conditions are preferably met in intertidal and supratidal zones. Spindle-shaped and subcircular cracks require mat shrinkage due to either desiccation or "syneresis". Crack propagation implies progressive shrinkage, while superposition of crack generations indicates repeated alternation

  6. The Guiana and the West African Shield Palaeoproterozoic grouping: new palaeomagnetic data for French Guiana and the Ivory Coast

    Science.gov (United States)

    Nomade, Sébastien; Chen, Yan; Pouclet, André; Féraud, Gilbert; Théveniaut, Hervé; Daouda, Bertin Yao; Vidal, Max; Rigolet, Cécile

    2003-09-01

    The aim of this study is to document the Palaeoproterozoic palaeomagnetic database for the Guiana and West African Shields in order to better understand the paleogeographic evolution of these two cratons. A total of 59 sites were sampled (33 in French Guiana and 26 in the Ivory Coast) in granites and metavolcanic rocks. Magnetic, petrographic and palaeomagnetic investigations were carried out on these rocks. Magnetic experiments and petrographic observations show that undeformed magnetite is the main magnetic remanent carrier in granites of French Guiana and both magnetite and haematite in rocks from the Ivory Coast. Both thermal and magnetic alternating-field demagnetizations were applied to the rocks. Four high-temperature magnetic remanent directions were isolated in French Guiana and the Ivory Coast. These directions are distinct from the present Earth's field and to the local Early Jurassic palaeomagnetic components. Reversal and contact tests were obtained for the collection from French Guiana. Based on these arguments and mineralogical investigations, we propose that the magnetic remanence represent a Palaeoproterozoic magnetization. Four virtual palaeomagnetic poles were calculated: GUI1, GUI2 for French Guiana; IC1 and IC2 for the Ivory Coast with their corresponding coordinates: GUI1: λGUI1=-62°N, φGUI1= 61°E, k= 18, A95= 10°, N= 15; GUI2: λGUI2=-5°N, φGUI2= 50°E, k= 26, A95= 18°, N= 5; IC1: λIC1=-82°N, φIC1= 292°N, k= 28, A95= 13°, N= 6; IC2: λIC2=-25°N, φIC2= 83°E, k= 11, A95= 16°, N= 9. The magnetization age ranged from 2.04 to 1.97 Ga for the French Guiana poles (40Ar/39Ar) and between 2.10 to 2.00 Ga for the Ivory Coast poles (startigraphic ages). Combining these new palaeomagnetic poles and previously published data, two apparent polar wander paths were proposed for these two shields. The comparison of these two Palaeoproterozoic paths seems to indicate that the two cratons belonged to the same block at about 2.00 Ga but

  7. Sensitivity of the southern West African mean atmospheric state to variations in low-level cloud cover as simulated by ICON

    Science.gov (United States)

    Kniffka, Anke; Knippertz, Peter; Fink, Andreas

    2017-04-01

    This contribution presents first results of numerical sensitivity experiments that are carried out in the framework of the project DACCIWA (Dynamics-Aerosol-Chemistry-Cloud Interactions in West Africa). DACCIWA aims to investigate the impact of the drastic increase in anthropogenic emissions in West Africa on the local weather and climate, for example through cloud-aerosol interactions or impacts on radiation and stability. DACCIWA organised a major international field campaign in West Africa in June-July 2016 and involves a wide range of modelling activities. Several studies have shown - and first results of the DACCIWA campaign confirm - that extensive ultra-low stratus clouds form in the southern parts of West Africa (8°W-8°E, 5-10°N) at night in connection with strong nocturnal low-level jets. The clouds persist long after sunrise and have therefore a substantial impact on the surface radiation budget and consequently on the diurnal evolution of the daytime, convectively mixed boundary layer. The objective of this study is to investigate the sensitivity of the West African monsoon system and its diurnal cycle to the radiative effects of these low clouds. The study is based on a series of daily 5-day sensitivity simulations using ICON, the operational numerical weather prediction model of the German Weather Service during the months July - September 2006. In these simulations, low clouds are made transparent, by artificially lowering the optical thickness information passed on to the model's radiation scheme. Results reveal a noticeable influence of the low-level cloud cover on the atmospheric mean state of our region of interest and beyond. Also the diurnal development of the convective boundary layer is influenced by the cloud modification. In the transparent-cloud experiments, the cloud deck tends to break up later in the day and is shifted to a higher altitude, thereby causing a short-lived intensification around 11 LT. The average rainfall patterns are

  8. Prostate cancer disparities in Black men of African descent: a comparative literature review of prostate cancer burden among Black men in the United States, Caribbean, United Kingdom, and West Africa

    Directory of Open Access Journals (Sweden)

    Reams R Renee

    2009-02-01

    Full Text Available Abstract Background African American men have the highest prostate cancer morbidity and mortality rates than any other racial or ethnic group in the US. Although the overall incidence of and mortality from prostate cancer has been declining in White men since 1991, the decline in African American men lags behind White men. Of particular concern is the growing literature on the disproportionate burden of prostate cancer among other Black men of West African ancestry in the Caribbean Islands, United Kingdom and West Africa. This higher incidence of prostate cancer observed in populations of African descent may be attributed to the fact that these populations share ancestral genetic factors. To better understand the burden of prostate cancer among men of West African Ancestry, we conducted a review of the literature on prostate cancer incidence, prevalence, and mortality in the countries connected by the Transatlantic Slave Trade. Results Several published studies indicate high prostate cancer burden in Nigeria and Ghana. There was no published literature for the countries Benin, Gambia and Senegal that met our review criteria. Prostate cancer morbidity and/or mortality data from the Caribbean Islands and the United Kingdom also provided comparable or worse prostate cancer burden to that of US Blacks. Conclusion The growing literature on the disproportionate burden of prostate cancer among other Black men of West African ancestry follows the path of the Transatlantic Slave Trade. To better understand and address the global prostate cancer disparities seen in Black men of West African ancestry, future studies should explore the genetic and environmental risk factors for prostate cancer among this group.

  9. Three West African Countries

    African Journals Online (AJOL)

    of variance for fresh yield, all main effects were significant. First order interaction ... A plot of environmental mean yields against coefficient of variation (CV) per cent judged genotype. 82/00942 as ..... have low stability. By Shukla's definition,.

  10. West African Waterworlds

    DEFF Research Database (Denmark)

    Olwig, Mette Fog; Rasmussen, Laura Vang

    2015-01-01

    encountering a narrative of desertification with little mention of floods and saw that the narrative influenced both local everyday life agendas and global policy agendas. We here discuss how and why water’s absence has remained the dominant environmental narrative, eclipsing the increasingly relevant problem...... of water’s excess. We suggest that the emerging climate change narrative might prove powerful enough to change the desertification narrative’s dominance....

  11. WEST AFRICAN JOURNAL, OFMEDICINE

    African Journals Online (AJOL)

    kttttt 疹了邯 Chirurgié diu kk TertidrettiiVigéridiº 铨 Lg Í 3 Z: i fi! :) i titi i v zroiirtoo o aj Tot; w og o 23 i l'I: Jo id zog; arit til 'to ?.0 `` i to ti : b : 1 a 1 lib A izq it-tlo zil! i ...

  12. West African Antislavery Movements

    DEFF Research Database (Denmark)

    Hahonou, Eric Komlavi; Pelckmans, Lotte

    2011-01-01

    -slavery movements had raised awareness, this political emergence was even easier. Indeed the fight against ‘slave mentalities’ was everywhere a major challenge and a crucial step to mobilize groups of slave status under a united force. As this article argues changes in political structures and changes in political...

  13. Determinants of Early Introduction of Solid, Semi-Solid or Soft Foods among Infants Aged 3–5 Months in Four Anglophone West African Countries

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    Abukari I. Issaka

    2014-07-01

    Full Text Available This study was conducted to explore and identify factors associated with the practice of early introduction of solid, semi-solid or soft foods among infants aged 3–5 months in four Anglophone West African countries. Data sources for the analyses were the latest Demographic and Health Survey datasets of the 4 countries, namely Ghana (GDHS, 2008, Liberia (LDHS, 2007, Nigeria (NDHS, 2013 and Sierra Leone (SLDHS, 2008. Multiple logistic regression methods were used to analyze the factors associated with early introduction of solid, semi-solid or soft foods among infants aged 3–5 months, using individual-, household- and community-level determinants. The sample consisted of 2447 infants aged 3–5 months from four Anglophone West African countries: 166 in Ghana, 263 in Liberia, 1658 in Nigeria and 360 in Sierra Leone. Multivariable analyses revealed the individual factors associated with early introduction of solid, semi-solid or soft foods in these countries. These included increased infant’s age, diarrhea, acute respiratory infection and newborns perceived to be small by their mothers. Other predictors of early introduction of solid, semi-solid or soft foods were: mothers with no schooling, young mothers and fathers who worked in an agricultural industry. Public health interventions to improve exclusive breastfeeding practices by discouraging early introduction of solid, semi-solid or soft foods are needed in all 4 countries, targeting especially mothers at risk of introducing solid foods to their infants early.

  14. Endangered West African Chimpanzees Pan troglodytes verus (Schwarz, 1934 (Primates: Hominidae in Senegal prefer Pterocarpus erinaceus, a threatened tree species, to build their nests: implications for their conservation

    Directory of Open Access Journals (Sweden)

    P.I. Ndiaye

    2013-12-01

    Full Text Available The West African Chimpanzee Pan troglodytes verus is Endangered (A4cd ver 3.1 in Senegal (Humle et al. 2008, mainly due to habitat fragmentation and destruction. We gathered qualitative and quantitative data on the tree species preferences of the West African Chimpanzee for nest building in order to gain insight into habitat dependence. Between March 1998 and Febrary 2000 we identified tree species in which a sample of 1790 chimpanzee nests had been built, and ranked species in preference order. We compared this sample to the relative abundance of tree species in the chimpanzee habitat to determine whether particular species were chosen for nesting. We observed that about a quarter (25.42% of nests were built in Pterocarpus erinaceus, which is considerably greater than would be expected from the abundance of this species in the habitat (6.35%, indicating a strong preference by chimpanzees. We examined the physical traits of the most-used tree species and concluded that height and wood hardness may be key choice features. P. erinaceus is threatened in Senegal due to extensive cutting, which may endanger chimpanzees living outside the boundaries of protected areas. In the current anthropogenic setting our results provide conservation managers with information on how to protect a key aspect of the chimpanzee natural environment.

  15. The hopes of West African refugees during resettlement in northern Sweden: a 6-year prospective qualitative study of pathways and agency thoughts

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    Anjum Tanvir M

    2012-01-01

    Full Text Available Abstract Background Little is known about how positive phenomena can support resettlement of refugees in a new country. The aim of this study was to examine the hopeful thinking in a group of West African quota refugees at arrival and after 6 years in Sweden and compare these thoughts to the views of resettlement support professionals. Method The primary study population comprised 56 adult refugees and 13 resettlement professionals. Qualitative data were collected from the refugees by questionnaires on arrival and 6 years later. Data were collected from the resettlement professionals by interview about 3 years after arrival of the refugees. Snyder's cognitive model of hope was used to inform the comparative data analyses. Results Hopes regarding education were in focus for the refugees shortly after arrival, but thoughts on family reunion were central later in the resettlement process. During the later stages of the resettlement process, the unresponsiveness of the support organization to the family reunion problem became as issue for the refugees. The professionals reported a complex mix of "silent agency thoughts" underlying the local resettlement process as a contributing reason for this unresponsiveness. Conclusion Hopes regarding education and family reunion were central in the resettlement of West African refugees in Sweden. These thoughts were not systematically followed up by the support organization; possibly the resources for refugees were not fully released. More studies are needed to further investigate the motivational factors underpinning host community support of refugees' hopes and plans.

  16. Strangelet dwarfs

    CERN Document Server

    Alford, Mark G; Reddy, Sanjay

    2011-01-01

    If the surface tension of quark matter is low enough, quark matter is not self bound. At sufficiently low pressure and temperature, it will take the form of a crystal of positively charged strangelets in a neutralizing background of electrons. In this case there will exist, in addition to the usual family of strange stars, a family of low-mass large-radius objects analogous to white dwarfs, which we call "strangelet dwarfs". Using a generic parametrization of the equation of state of quark matter, we calculate the mass-radius relationship of these objects.

  17. Impacts of warm and cold situations in the Mediterranean basins on the West African monsoon: observed connection patterns (1979-2006) and climate simulations

    Energy Technology Data Exchange (ETDEWEB)

    Fontaine, Bernard; Roucou, Pascal; Sijikumar, Sivarajan [CNRS/University of Burgundy, Centre de Recherches de Climatologie, Dijon (France); Garcia-Serrano, Javier; Rodriguez-Fonseca, Belen; Losada, Teresa [Universidad Complutense de Madrid, Madrid (Spain); Chauvin, Fabrice [CNRS/Meteo-France, Centre National de Recherches Meteorologiques, Toulouse (France); Gervois, Sebastien; Janicot, Serge [CNRS/IRD/Paris VI, Institut Pierre-Simon Laplace/LOCEAN, Paris (France); Ruti, Paolo [Environmental and Energy Research Institute, Rome (Italy)

    2010-07-15

    Using both empirical and numerical ensemble approaches this study focuses on the Mediterranean/West African relationship in northern summer. Statistical analyses utilize skin temperature, sea surface temperature, in situ and satellite rainfall, outgoing longwave radiation (OLR) observations and reanalyzed data winds and specific humidity on isobaric surfaces. Numerical investigations are based on a large set of sensitivity experiments performed on four atmospheric general circulation models (AGCM): ARPEGE-Climat3, ECHAM4, LMDZ4 and UCLA7.3. Model outputs are compared to observations, discussed model by model and with an ensemble (multi-model) approach. As in previous studies the anomalous Mediterranean warm events are associated with specific impacts over the African monsoon region, i.e., a more intense monsoon, enhanced flux convergence and ascendances around the ITCZ, a strengthening of low level moisture advection and a more northward location of ascending motion in West Africa. The results show also new features (1) thermal variability observed in the two Mediterranean basins has unalike impacts, i.e. the western Mediterranean covaries with convection in Gulf of Guinea, while the eastern Mediterranean can be interpreted as Sahelian thermal-forcing; (2) although observations show symmetry between warming and cooling, modelling evidences only support the eastern warming influence; (3) anomalous East warm situations are associated with a more northward migration of the monsoon system accompanied by enhanced southwertely flow and weakened northeasterly climatological wind; (4) the multi-model response shows that anomalous East warm surface temperatures generate an enhancement of the overturning circulation in low and high levels, an increase in TEJ (Tropical Eeasterly Jet) and a decrease in AEJ (African Eeasterly Jet). (orig.)

  18. The first phylogeographic population structure and analysis of transmission dynamics of M. africanum West African 1--combining molecular data from Benin, Nigeria and Sierra Leone.

    Directory of Open Access Journals (Sweden)

    Florian Gehre

    Full Text Available Mycobacterium africanum is an important cause of tuberculosis (TB in West Africa. So far, two lineages called M. africanum West African 1 (MAF1 and M. africanum West African 2 (MAF2 have been defined. Although several molecular studies on MAF2 have been conducted to date, little is known about MAF1. As MAF1 is mainly present in countries around the Gulf of Guinea we aimed to estimate its prevalence in Cotonou, the biggest city in Benin. Between 2005-06 we collected strains in Cotonou/Benin and genotyped them using spoligo- and 12-loci-MIRU-VNTR-typing. Analyzing 194 isolates, we found that 31% and 6% were MAF1 and MAF2, respectively. Therefore Benin is one of the countries with the highest prevalence (37% of M. africanum in general and MAF1 in particular. Moreover, we combined our data from Benin with publicly available genotyping information from Nigeria and Sierra Leone, and determined the phylogeographic population structure and genotypic clustering of MAF1. Within the MAF1 lineage, we identified an unexpected great genetic variability with the presence of at least 10 sub-lineages. Interestingly, 8 out of 10 of the discovered sub-lineages not only clustered genetically but also geographically. Besides showing a remarkable local restriction to certain regions in Benin and Nigeria, the sub-lineages differed dramatically in their capacity to transmit within the human host population. While identifying Benin as one of the countries with the highest overall prevalence of M. africanum, this study also contains the first detailed description of the transmission dynamics and phylogenetic composition of the MAF1 lineage.

  19. Combatting African Animal Trypanosomiasis (AAT) in livestock: The potential role of trypanotolerance.

    Science.gov (United States)

    Yaro, M; Munyard, K A; Stear, M J; Groth, D M

    2016-07-30

    African Animal Trypanosomiasis (AAT) is endemic in at least 37 of the 54 countries in Africa. It is estimated to cause direct and indirect losses to the livestock production industry in excess of US$ 4.5 billion per annum. A century of intervention has yielded limited success, owing largely to the extraordinary complexity of the host-parasite interaction. Trypanotolerance, which refers to the inherent ability of some African livestock breeds, notably Djallonke sheep, N'Dama cattle and West African Dwarf goats, to withstand a trypanosomiasis challenge and still remain productive without any form of therapy, is an economically sustainable option for combatting this disease. Yet trypanotolerance has not been adequately exploited in the fight against AAT. In this review, we describe new insights into the genetic basis of trypanotolerance and discuss the potential of exploring this phenomenon as an integral part of the solution for AAT, particularly, in the context of African animal production systems.

  20. White dwarf-red dwarf binaries in the Galaxy

    NARCIS (Netherlands)

    Besselaar, E.J.M. van den

    2007-01-01

    This PhD thesis shows several studies on white dwarf - red dwarf binaries. White dwarfs are the end products of most stars and red dwarfs are normal hydrogen burning low-mass stars. White dwarf - red dwarf binaries are both blue (white dwarf) and red (red dwarf). Together with the fact that they are

  1. Impacts of the diversity of traditional uses and potential economic value on food tree species conservation status: case study of African bush mango trees (Irvingiaceae) in the Dahomey Gap (West Africa).

    NARCIS (Netherlands)

    Vihotogbé, R.; Kakai, R.G.; Bongers, F.; Andel, van T.; Berg, van den R.G.; Sinsin, B.; Sosef, M.S.M.

    2014-01-01

    Background and aims – Bitter and sweet African bush mango trees belong to the family Irvingiaceae and produce valuable non-timber forest products in humid lowland areas of West and Central Africa. The bitter and sweet types are treated as distinct taxa at the variety or species level. They have not

  2. Impacts of the diversity of traditional uses and potential economic value on food tree species conservation status: case study of African bush mango trees (Irvingiaceae) in the Dahomey Gap (West Africa).

    NARCIS (Netherlands)

    Vihotogbé, R.; Kakai, R.G.; Bongers, F.; Andel, van T.; Berg, van den R.G.; Sinsin, B.; Sosef, M.S.M.

    2014-01-01

    Background and aims – Bitter and sweet African bush mango trees belong to the family Irvingiaceae and produce valuable non-timber forest products in humid lowland areas of West and Central Africa. The bitter and sweet types are treated as distinct taxa at the variety or species level. They have not

  3. Petrochemical and petrophysical characterization of the lower crust and the Moho beneath the West African Craton, based on Xenoliths from Kimberlites

    Science.gov (United States)

    Haggerty, Stephen E.; Toft, Paul B.

    1988-01-01

    Additional evidence to the composition of the lower crust and uppermost mantle was presented in the form of xenolith data. Xenoliths from the 2.7-Ga West African Craton indicate that the Moho beneath this shield is a chemically and physically gradational boundary, with intercalations of garnet granulite and garnet eclogite. Inclusions in diamonds indicate a depleted upper mantle source, and zenolith barometry and thermometry data suggest a high mantle geotherm with a kink near the Moho. Metallic iron in the xenoliths indicates that the uppermost mantle has a significant magnetization, and that the depth to the Curie isotherm, which is usually considered to be at or above the Moho, may be deeper than the Moho.

  4. The state of the research for health environment in the ministries of health of the Economic Community of the West African States (ECOWAS).

    Science.gov (United States)

    Sombié, Issiaka; Aidam, Jude; Konaté, Blahima; Somé, Télesphore D; Kambou, Stanislas Sansan

    2013-09-11

    An assessment of the state of the Research for Health (R4H) environment can provide relevant information about what aspects of national health research systems needs strengthening, so that research output can be relevant to meet national priorities for decision-making. There is limited information on the state of the R4H environment in the Economic Community of West African States (ECOWAS). This article describes the state of the R4H environment within the Ministries of Health of the ECOWAS member states and outlines of some possibilities to strengthen health research activities within the ECOWAS region. Information on the national-level R4H environment (governance and management; existence of a national policy; strategic and research priorities documents; ethics committees; research funds; coordination structures; monitoring and evaluation systems; networking and capacity building opportunities) was collected from the Ministries of Health research units in 14 ECOWAS countries using self-administered questionnaires. A workshop was held where country report presentations and group discussions were used to review and validate responses. Data from the discussions was transcribed using Nvivo, and strengths, weaknesses, opportunities and threats (SWOT) analysis of the functioning of the units was done using Robert Preziosi's organisational diagnosis tool. The findings indicate that as of January 2011, 50% of ECOWAS countries had established directorates for health research with defined terms of reference. The existing funding mechanisms were inadequate to support the research structures within and outside the MoHs, and for building the capacity of researchers. Networking and monitoring activities were weak and only 7% of the directors of research units were trained in research management. The majority (85.7%) of countries had broader national health policies, and 57% of the countries had some form of policy or strategic document for research development. Half of the

  5. Persistence of full-length caspase-12 and its relation to malaria in West and Central African populations.

    NARCIS (Netherlands)

    McCall, M.B.B.; Ferwerda, B.; Hopman, J.; Ploemen, I.H.J.; Maiga, B.; Daou, M.; Dolo, A.; Hermsen, C.C.; Doumbo, O.K.; Bedu-Addo, G.; Meer, J.W.M. van der; Troye-Blomberg, M.; Ven, A.J.A.M. van der; Schumann, R.R.; Sauerwein, R.W.; Mockenhaupt, F.P.; Netea, M.G.

    2010-01-01

    BACKGROUND: The full-length (L-) variant of caspase-12 is believed to predispose to sepsis. It has been replaced in the genome of most human populations by the (S-) variant, which leads to premature termination of translation. Strikingly, the L-allele is still widely prevalent in African populations

  6. Occurrence, distribution and health risk from polycyclic aromatic compounds (PAHs, oxygenated-PAHs and azaarenes) in street dust from a major West African Metropolis.

    Science.gov (United States)

    Bandowe, Benjamin A Musa; Nkansah, Marian Asantewah

    2016-05-15

    Scientific evidence suggests that the burden of disease on urban residents of sub-Saharan African Countries is increasing, partly as a result of exposure to elevated concentrations of toxic environmental chemicals. However, characterization of the levels, composition pattern and sources of polycyclic aromatic compounds (PACs) in environmental samples from African cities is still lacking. This study measured the PAHs, oxygenated-PAHs (OPAHs) and azaarene (AZAs) content of street dusts collected from Kumasi, Ghana (a major metropolis located in the tropical forest zone of West Africa). The ∑Alkyl+parent-PAHs, ∑OPAHs and ∑AZAs concentration in street dust averaged 2570 ng g(-1) (range: 181-7600 ng g(-1)), 833 ng g(-1) (57-4200 ng g(-1)) and 73 ng g(-1) (3.3-240 ng g(-1)), respectively. The concentrations of ∑Alkyl+parent-PAHs were strongly correlated (n=25) with ∑OPAHs (r=0.96, p10(-6) indicating high risk of contracting cancer from exposure to street dust from Kumasi. The contribution of OPAHs, AZAs, and alkyl-PAHs in street dust to cancer risk could not be quantified because of lack of toxicity equivalency factors for these compounds; however this could be significant because of their high concentration and known higher toxicity of some polar PACs and alkyl-PAHs than their related parent-PAHs.

  7. Linking the sub-Saharan and West Eurasian gene pools: maternal and paternal heritage of the Tuareg nomads from the African Sahel.

    Science.gov (United States)

    Pereira, Luísa; Cerný, Viktor; Cerezo, María; Silva, Nuno M; Hájek, Martin; Vasíková, Alzbeta; Kujanová, Martina; Brdicka, Radim; Salas, Antonio

    2010-08-01

    The Tuareg presently live in the Sahara and the Sahel. Their ancestors are commonly believed to be the Garamantes of the Libyan Fezzan, ever since it was suggested by authors of antiquity. Biological evidence, based on classical genetic markers, however, indicates kinship with the Beja of Eastern Sudan. Our study of mitochondrial DNA (mtDNA) sequences and Y chromosome SNPs of three different southern Tuareg groups from Mali, Burkina Faso and the Republic of Niger reveals a West Eurasian-North African composition of their gene pool. The data show that certain genetic lineages could not have been introduced into this population earlier than approximately 9000 years ago whereas local expansions establish a minimal date at around 3000 years ago. Some of the mtDNA haplogroups observed in the Tuareg population were involved in the post-Last Glacial Maximum human expansion from Iberian refugia towards both Europe and North Africa. Interestingly, no Near Eastern mtDNA lineages connected with the Neolithic expansion have been observed in our population sample. On the other hand, the Y chromosome SNPs data show that the paternal lineages can very probably be traced to the Near Eastern Neolithic demic expansion towards North Africa, a period that is otherwise concordant with the above-mentioned mtDNA expansion. The time frame for the migration of the Tuareg towards the African Sahel belt overlaps that of early Holocene climatic changes across the Sahara (from the optimal greening approximately 10 000 YBP to the extant aridity beginning at approximately 6000 YBP) and the migrations of other African nomadic peoples in the area.

  8. Energy partitioning over the West African savanna: multi-year evaporation and surface conductance measurements in Eastern Burkina Faso

    NARCIS (Netherlands)

    Bagayoko, F.; Yonkeu, S.; Elbers, J.A.; Giesen, van de N.

    2007-01-01

    Seasonal variability of the energy partitioning was analyzed with a combination of eddy fluxes of sensible and latent heat and weather data on intensely farmed land in the savanna area of Eastern Burkina Faso, West Africa. The analysis covers two rainy seasons (May-October 2003 and 2004), one dry se

  9. The role of risk perception in willingness to respond to the 2014-2016 West African Ebola outbreak

    DEFF Research Database (Denmark)

    Gee, Stephanie; Skovdal, Morten

    2017-01-01

    Background: The 2014–2016 West Africa Ebola Virus Disease (EVD) outbreak was an unprecedented public health event, and in addition to claiming over 11,000 lives, it resulted in the deaths of more healthcare workers than any outbreak in recent history. While a cadre of willing and able health...

  10. The Paternal Landscape along the Bight of Benin – Testing Regional Representativeness of West-African Population Samples Using Y-Chromosomal Markers

    Science.gov (United States)

    Larmuseau, Maarten H. D.; Vessi, Andrea; Jobling, Mark A.; Van Geystelen, Anneleen; Primativo, Giuseppina; Biondi, Gianfranco; Martínez-Labarga, Cristina; Ottoni, Claudio; Decorte, Ronny; Rickards, Olga

    2015-01-01

    Patterns of genetic variation in human populations across the African continent are still not well studied in comparison with Eurasia and America, despite the high genetic and cultural diversity among African populations. In population and forensic genetic studies a single sample is often used to represent a complete African region. In such a scenario, inappropriate sampling strategies and/or the use of local, isolated populations may bias interpretations and pose questions of representativeness at a macrogeographic-scale. The non-recombining region of the Y-chromosome (NRY) has great potential to reveal the regional representation of a sample due to its powerful phylogeographic information content. An area poorly characterized for Y-chromosomal data is the West-African region along the Bight of Benin, despite its important history in the trans-Atlantic slave trade and its large number of ethnic groups, languages and lifestyles. In this study, Y-chromosomal haplotypes from four Beninese populations were determined and a global meta-analysis with available Y-SNP and Y-STR data from populations along the Bight of Benin and surrounding areas was performed. A thorough methodology was developed allowing comparison of population samples using Y-chromosomal lineage data based on different Y-SNP panels and phylogenies. Geographic proximity turned out to be the best predictor of genetic affinity between populations along the Bight of Benin. Nevertheless, based on Y-chromosomal data from the literature two population samples differed strongly from others from the same or neighbouring areas and are not regionally representative within large-scale studies. Furthermore, the analysis of the HapMap sample YRI of a Yoruban population from South-western Nigeria based on Y-SNPs and Y-STR data showed for the first time its regional representativeness, a result which is important for standard population and forensic genetic applications using the YRI sample. Therefore, the uniquely

  11. The Paternal Landscape along the Bight of Benin - Testing Regional Representativeness of West-African Population Samples Using Y-Chromosomal Markers.

    Directory of Open Access Journals (Sweden)

    Maarten H D Larmuseau

    Full Text Available Patterns of genetic variation in human populations across the African continent are still not well studied in comparison with Eurasia and America, despite the high genetic and cultural diversity among African populations. In population and forensic genetic studies a single sample is often used to represent a complete African region. In such a scenario, inappropriate sampling strategies and/or the use of local, isolated populations may bias interpretations and pose questions of representativeness at a macrogeographic-scale. The non-recombining region of the Y-chromosome (NRY has great potential to reveal the regional representation of a sample due to its powerful phylogeographic information content. An area poorly characterized for Y-chromosomal data is the West-African region along the Bight of Benin, despite its important history in the trans-Atlantic slave trade and its large number of ethnic groups, languages and lifestyles. In this study, Y-chromosomal haplotypes from four Beninese populations were determined and a global meta-analysis with available Y-SNP and Y-STR data from populations along the Bight of Benin and surrounding areas was performed. A thorough methodology was developed allowing comparison of population samples using Y-chromosomal lineage data based on different Y-SNP panels and phylogenies. Geographic proximity turned out to be the best predictor of genetic affinity between populations along the Bight of Benin. Nevertheless, based on Y-chromosomal data from the literature two population samples differed strongly from others from the same or neighbouring areas and are not regionally representative within large-scale studies. Furthermore, the analysis of the HapMap sample YRI of a Yoruban population from South-western Nigeria based on Y-SNPs and Y-STR data showed for the first time its regional representativeness, a result which is important for standard population and forensic genetic applications using the YRI sample

  12. Thriving public-private partnership to fortify cooking oil in the West African Economic and Monetary Union (UEMOA) to control vitamin A deficiency: Faire Tache d'Huile en Afrique de l'Ouest.

    Science.gov (United States)

    Sablah, Mawuli; Klopp, Jennifer; Steinberg, Douglas; Touaoro, Zaoro; Laillou, Arnaud; Baker, Shawn

    2012-12-01

    In sub-Saharan Africa, more than 42% of children are at risk for vitamin A deficiency, and control of vitamin A deficiency will prevent more than 600,000 child deaths annually. In the West African Economic and Monetary Union (UEMOA), an estimated 54.3% of preschool-age children are vitamin A deficient and 13% of pregnant women have night blindness. To project the achievements of this West African coalition. This article documents the achievements, challenges, and lessons learned associated with the development of a public-private partnership to fortify vegetable oil in West Africa through project reports and industry assessments. National-level food consumption surveys identified cooking oil as a key vehicle for vitamin A. Stakeholders therefore advocated for the production of fortified vegetable oil at large scale, supported industrial assessments, and reinforced the capacity of cooking oil industries to implement vitamin A fortification through effective coordination of public and private partnerships tied with standards, regulations, and social marketing. Strong alliances for food fortification were established at the regional and national levels. Stakeholders also developed policies, adopted directives, built capacity, implemented social marketing, and monitored quality enforcement systems to sustain fortification for maximum public health impact. The synergy created resulted from the unique and complementary core competencies of all the partners under effective coordination. The initiative began with the 8 UEMOA member countries and now includes all 15 countries of the Economic Community of West African States (ECOWAS), plus Cameroon, Tanzania, and Mozambique, forming a sub-Saharan Africa-wide initiative on food fortification. All members of the Professional Association of Cooking Oil Industries of the West African Economic and Monetary Union (AIFO-UEMOA) now fortify edible oil with vitamin A. Through multisector cooperation, an estimated 70% of the population

  13. Impacts of the Sahel-Sahara Interface Reforestation on West African Climate: Intraseasonal Variability and Extreme Precipitation Events

    Directory of Open Access Journals (Sweden)

    Ibrahima Diba

    2016-01-01

    Full Text Available This study aims to evaluate the impacts of the Sahel-Sahara interface reforestation on spatiotemporal variability of the summer rainfall and extreme precipitation events over West Africa using the RegCM4 model. The land surface scheme of RegCM4 was modified to incorporate an East-West reforested zone (15°N and 20°N. Two runs were performed using the standard version of RegCM4 and the modified one of the same model taking into account the incorporated forest. The reforestation significantly modifies rainfall signal over West Africa by increasing it over the reforested zone and the Fouta Jallon highlands (FJH. This rainfall increase is associated with a strengthening of the atmospheric moisture over the reforested area. This atmospheric moisture content increase associated with the wind dynamic may explain the spatiotemporal change of the rainfall and extreme precipitation events. The analysis of the impacts of the reforestation on some rainfall indices shows an increase of the 90th, 95th, and 99th percentiles over the reforested zone and off the FJH. This reforestation also causes an increase of the maximum length of the consecutive wet days over and off FJH and a decrease of the maximum length of the consecutive dry days over the northern Sahel and the reforested zone.

  14. Naming Disney's Dwarfs.

    Science.gov (United States)

    Sidwell, Robert T.

    1980-01-01

    Discusses Disney's version of the folkloric dwarfs in his production of "Snow White" and weighs the Disney rendition of the dwarf figure against the corpus of traits and behaviors pertaining to dwarfs in traditional folklore. Concludes that Disney's dwarfs are "anthropologically true." (HOD)

  15. SUPPLEMENTARY VALUE OF TEPHROSIA BRACTEOLATA, TEPHROSIA CANDIDA, LEUCAENA LEUCOCEPHALA AND GLIRICIDIA SEPIUM HAY FOR WEST AFRICAN DWARF GOATS KEPT ON RANGE

    Directory of Open Access Journals (Sweden)

    Jacob BABAYEMI

    2006-12-01

    Full Text Available Supplementary values of unconventional browse Tephrosia bracteolata (TB and Tephrosia candida (TC and commonly utilized browse plants Gliricidia sepium (GS and Leucaena leucocephala (LL were studied in goats grazed on a rangeland in the dry season. Crude protein (g/Kg DM content of TC (19.25 compared favourably to those of GS (19.78 and that of LL (19.91 while that of TB was low (14.25. Total cell wall content, neutral detergent fi bre (NDF, g/Kg DM was lower in both TB (56.03 and TC (59.11 than in GS (61.20 and LL (37.50. Dry matter intake (g/d of TB (87.39 was signifi cantly higher than that of TC (76.49 while similar values were recorded in GS (63.81 and LL (63.31. Improved daily weight gain (g/d of 14.88, 17.86, 14.88 and 17.86 were obtained when goats were fed TB, TC, GS and LL browse supplements responsively compared to the daily gain of 11.90 from the unsuplemented goats. The digestibility of CP, NDF and ADF in both TB and TC compared favourably to those of GS and LL. The fi ndings from this study have shown that Tephrosia bracteolata and Tephrosia candida can be used as alternative browse supplement for goats grazing on natural grassland in the dry season to achieve improved weight gain. This will translate to a reduction in the pressure on the commonly use browse like Gliricidia sepium and Leucaena leucocephala.

  16. Brown Dwarf Companions to White Dwarfs

    CERN Document Server

    Burleigh, M R; Dobbie, P D; Farihi, J; Napiwotzki, R; Maxted, P F L; Barstow, M A; Jameson, R F; Casewell, S L; Gänsicke, B T; Marsh, T R

    2011-01-01

    Brown dwarf companions to white dwarfs are rare, but recent infra-red surveys are slowly reveal- ing examples. We present new observations of the post-common envelope binary WD0137-349, which reveals the effects of irradiation on the ~ 0.05M* secondary, and new observations of GD 1400 which show that it too is a close, post-comon envelope system. We also present the lat- est results in a near-infrared photometric search for unresolved ultracool companions and to white dwarfs with UKIDSS. Twenty five DA white dwarfs were identified as having photometric excesses indicative of a low mass companion, with 8-10 of these having a predicted mass in the range asso- ciated with brown dwarfs. The results of this survey show that the unresolved (< 2") brown dwarf companion fraction to DA white dwarfs is 0.3 \\leq fWD+BD \\leq 1.3%.

  17. Mitigation of Disasters Due to Severe Climate Events: from Policy to Practice,the West African Coastal Region Experience

    Science.gov (United States)

    Ediang, Okuku

    2016-07-01

    The distributive pattern of disaster due to severe climate events over the coast of West Africa especially Nigeria was examined using yearly mean disaster due to severe climatic events for the period of 30 years (1981-2010) from the marine stations in the coastal region of Nigeria. Graphical and isohyetal analyses were used to look into the patter of severe weather events over the area considered and to see if the severe weather events is increasing or not in the coast of West Africa especially the Nigerian coast and how to mitigate ,were policy relating to severe weather events are discussed. The paper conclude that due to the nature of coast of West Africa and Nigeria in particular, it enjoys longer severe weather events season than dry during the wet season, it is common to observe periods of enhanced or suppressed convective activity to persist over the wide areas for somedays. This paper also contributes to the wealth of knowledge already existing on Indigenous people play major roles in preserving the ecosystem especially during severe weather events . This has resulted in the recent calls for the integration of indigenous knowledge systems into global knowledge system strategies. Until now, integrating local knowledge systems into severe weather events and climate change concerns is not a completely new idea. A comprehensive review of literature using electronic and non-electronic databases formed the methodology. The paper conclude also by drawing the attention that by targeting Promoting indigenous people's participation in severe weather events and climate change issues is an important initiative towards adaptation and sustainable development in Africa and around the world. It is increasingly realized that the global knowledge system has dominated research, policies and programmes that address current severe weather events and climate change's challenges,mitigation and adaptation strategies.

  18. Recruitment patterns of young-of-the-year mugilid fishes in a West African estuary impacted by climate change

    Science.gov (United States)

    Trape, Sébastien; Durand, Jean-Dominique; Guilhaumon, François; Vigliola, Laurent; Panfili, Jacques

    2009-11-01

    With the persistence of the sub-Saharan drought since the 1970s, the Sine Saloum estuary (Senegal) - the second largest coastal Biosphere Reserve of West-Africa - has become an "inverse estuary" and hypersaline (salinity > 60) in its upstream part. A one-year survey was conducted from April 2007 to March 2008 at eight sites distributed along the salinity gradient, to investigate the recruitment patterns of young-of-the-year mugilids in such an impacted ecosystem. Fishes were sampled monthly with a conical net and a beach seine in salinities ranging from 31 to 104. Samples were identified to the species level. For the smallest individuals (changing environmental conditions.

  19. The influence of biomass burning and transport on tropospheric composition over the tropical Atlantic Ocean and Equatorial Africa during the West African monsoon in 2006

    Directory of Open Access Journals (Sweden)

    J. E. Williams

    2010-10-01

    Full Text Available Biomass burning (BB in southern Africa is the largest emission source of CO and O3 precursors within Africa during the West African Monsoon (WAM between June and August. The long range transport and chemical processing of such emissions thus has the potential to exert a dominant influence on the composition of the tropical troposphere over Equatorial Africa (EA and the Tropical Atlantic Ocean (TAO. We have performed simulations using a three-dimensional global chemistry-transport model (CTM to quantify the effect that continental transport of such BB plumes has on the EA region. BB emissions from southern Africa were found to exert a significant influence over the TAO and EA between 10° S–20° N. The maximum concentrations in CO and O3 occur between 0–5° S near the position of the African Easterly Jet – South as placed by the European Centre for Medium range Weather Forecasts (ECMWF meteorological analysis data. By comparing co-located model output with in-situ measurements we show that the CTM fails to capture the tropospheric profile of CO in southern Africa near the main source region of the BB emissions, as well as the "extreme" concentrations of both CO and O3 seen between 600–700 hPa over EA around 6° N. For more northerly locations the model exhibits high background concentrations in both CO and O3 related to BB emissions from southern Africa. By altering both the temporal resolution and the vertical distribution of BB emissions in the model we show that changes in temporal resolution have the largest influence on the transport of trace gases near the source regions, EA, and in the outflow towards the west of Central Africa. Using a set of trajectory calculations we show that the performance of the CTM is heavily constrained by the ECMWF meteorological fields used to drive the CTM, which transport biomass burning plumes from southern Africa into the lower troposphere of the TAO rather

  20. Detection of the East and West African kdr mutation in Anopheles gambiae and Anopheles arabiensis from Uganda using a new assay based on FRET/Melt Curve analysis

    Directory of Open Access Journals (Sweden)

    Backeljau Thierry

    2006-02-01

    Full Text Available Abstract Background Appropriate monitoring of vector resistance to insecticides is an integral component of planning and evaluation of insecticide use in malaria control programmes. The malaria vectors Anopheles gambiae s.s. and Anopheles arabiensis have developed resistance to pyrethroid insecticides as a result of a mechanism conferring reduced nervous system sensitivity, better known as knockdown resistance (kdr. In An. gambiae s.s. and An. arabiensis, two different substitutions in the para-type sodium channel, a L1014F substitution common in West Africa and a L1014S replacement found in Kenya, are linked with kdr. Two different allele-specific polymerase chain reactions (AS-PCR are needed to detect these known kdr mutations. However, these AS-PCR assays rely on a single nucleotide polymorphism mismatch, which can result in unreliable results. Methods Here, a new assay for the detection of knockdown resistance in An. gambiae s.s. and An. arabiensis based on Fluorescence Resonance Energy Transfer/Melt Curve analysis (FRET/MCA is presented and compared with the existing assays. Results The new FRET/MCA method has the important advantage of detecting both kdr alleles in one assay. Moreover, results show that the FRET/MCA is more reliable and more sensitive than the existing AS-PCR assays and is able to detect new genotypes. By using this technique, the presence of the East African kdr mutation (L1014S is shown for the first time in An. arabiensis specimens from Uganda. In addition, a new kdr genotype is reported in An. gambiae s.s. from Uganda, where four An. gambiae s.s. mosquitoes possess both, the West (L1014F and East (L1014S African kdr allele, simultaneously. Conclusion The presence of both kdr mutations in the same geographical region shows the necessity of a reliable assay that enables to detect both mutations in one single assay. Hence, this new assay based on FRET/MCA will improve the screening of the kdr frequencies in An. gambiae s

  1. Association analysis of photoperiodic flowering time genes in west and central African sorghum [Sorghum bicolor (L. Moench

    Directory of Open Access Journals (Sweden)

    Bhosale Sankalp U

    2012-03-01

    Full Text Available Abstract Background Photoperiod-sensitive flowering is a key adaptive trait for sorghum (Sorghum bicolor in West and Central Africa. In this study we performed an association analysis to investigate the effect of polymorphisms within the genes putatively related to variation in flowering time on photoperiod-sensitive flowering in sorghum. For this purpose a genetically characterized panel of 219 sorghum accessions from West and Central Africa was evaluated for their photoperiod response index (PRI based on two sowing dates under field conditions. Results Sorghum accessions used in our study were genotyped for single nucleotide polymorphisms (SNPs in six genes putatively involved in the photoperiodic control of flowering time. Applying a mixed model approach and previously-determined population structure parameters to these candidate genes, we found significant associations between several SNPs with PRI for the genes CRYPTOCHROME 1 (CRY1-b1 and GIGANTEA (GI. Conclusions The negative values of Tajima's D, found for the genes of our study, suggested that purifying selection has acted on genes involved in photoperiodic control of flowering time in sorghum. The SNP markers of our study that showed significant associations with PRI can be used to create functional markers to serve as important tools for marker-assisted selection of photoperiod-sensitive cultivars in sorghum.

  2. The West African monsoon onset in 2006: sensitivity to surface albedo, orography, SST and synoptic scale dry-air intrusions using WRF

    Energy Technology Data Exchange (ETDEWEB)

    Flaounas, Emmanouil [Universite Pierre et Marie Curie (UPMC), LATMOS/IPSL, Paris cedex 05 (France); Janicot, Serge [UPMC, LOCEAN/IPSL, IRD, Paris (France); Bastin, Sophie [UPMC, LATMOS/IPSL, CNRS, Paris (France); Roca, Remy [UPMC, LMD/IPSL, CNRS, Paris (France)

    2012-02-15

    In order to test the sensitivity of the transitional phase of the 2006 West African monsoon (WAM) onset to different mechanisms, weather research and forecasting (WRF) model simulations have been carried out addressing the role of the Saharan heat low (SHL) and its sensitivity to the albedo field and to the northern Africa orography, and the role of the sea surface temperature (SST) in the eastern tropical Atlantic and Mediterranean. Lowering albedo over the desert region induces a northward location of the inter-tropical convergence zone (ITCZ), while removing mountains in North Africa reduces rainfall over West Africa. Shifting SST forward by 15 days leads to a northward location of the ITCZ before the WAM onset. However none of these factors modifies the timing of the WAM onset in 2006. The transitional phase of the 2006 WAM onset has been examined in more detail. The enhancement of SHL intensity, combined with the development of the oceanic cold tongue in the Guinea gulf, leads to low-level moisture flux divergence in the ITCZ reducing rainfall and increasing low-level humidity over the Sahel. However, weakening of convection can be clearly attributed to dry-air intrusions in mid-levels, originating from the subtropical westerly jet and associated with Rossby wave pattern over North Africa. Sensitivity tests on the synoptic scale forcing outside of the WRF model domain confirm the dominating role of large-scale dynamics to control the transitional phase of the WAM onset and its timing. However it is shown that the regional factors can modulate this larger scale forcing. (orig.)

  3. Land use scenarios development and impacts assessment on vegetation carbon/nitrogen sequestration in the West African Sudan savanna watershed, Benin

    Science.gov (United States)

    Chabi, A.

    2015-12-01

    ackground: Reduced Emissions from Deforestation and Degradation (REDD+), being developed through the United Nations Framework Convention on Climate Change (UNFCCC) requires information on the carbon/nitrogen stocks in the plant biomass for predicting future climate under scenarios development. The development of land use scenarios in West Africa is needed to predict future impacts of change in the environment and the socio-economic status of rural communities. The study aims at developing land use scenario based on mitigation strategy to climate change as an issue of contributing for carbon and nitrogen sequestration, the condition 'food focused' as a scenario based crop production and 'financial investment' as scenario based on an economic development pathway, and to explore the possible future temporal and spatial impacts on vegetation carbon/nitrogen sequestration/emission and socio-economic status of rural communities. Preliminary results: BEN-LUDAS (Benin-Land Use DyNamic Simulator) model, carbon and nitrogen equations, remote sensing and socio-economic data were used to predict the future impacts of each scenario in the environment and human systems. The preliminary results which are under analysis will be presented soon. Conclusion: The proposed BEN-LUDAS models will help to contribute to policy decision making at the local and regional scale and to predict future impacts of change in the environment and socio-economic status of the rural communities. Keywords: Land use scenarios development, BEN-LUDAS, socio-economic status of rural communities, future impacts of change, assessment, West African Sudan savanna watershed, Benin

  4. Views of West African surgeons on how well their educational and professional backgrounds may have prepared them for health leadership roles

    Directory of Open Access Journals (Sweden)

    Abdulraheem O. Mahmoud

    2010-12-01

    Full Text Available Background: Because of the appalling health indices in West Africa, Physicians there need to be at the forefront of the organizational challenge in managing and improving health systems. Aim: To collate the views of West African surgeons on how well their educational and professional backgrounds may have prepared them for leadership and managerial roles in health care, and draw appropriate policy implications. Material and Methods: Filled structured questionnaires from 110 surgeons that were attending an annual conference were analyzed. The respondents’ bio data, professional, educational, health administrative backgrounds were probed. Their views on justifications for physicians’ involvement in health managerial roles, probable influence of some physicians’ characteristic traits and professional attributes on health leadership roles, and suggestions for improvement were also collated. Results: 71.8% of the respondents had held or were then holding health-related administrative posts; 90% had attended different varieties of management courses; 95.4% identified physicians as the inherent leaders of the health care team; but only 28.4% adjudged their health management role “strongly important” (28.4% among their multi-faceted roles; and they largely agreed that some stated professional and characteristic traits of physicians tend to make them poor leaders and managers. Conclusions: Our findings suggest that the preparations that the respondents got from their formal and professional education for leadership and managerial roles in health care were not optimal. We recommend for a paradigm shift for physicians on health leadership issue which is to be facilitated by a well-focused short time duration health management course for all physicians, particularly specialists.

  5. Views of West African surgeons on how well their educational and professional backgrounds may have prepared them for health leadership roles

    Directory of Open Access Journals (Sweden)

    Abdulraheem O Mahmoud

    2010-01-01

    Full Text Available Background: Because of the appalling health indices in West Africa, Physicians there need to be at the forefront of the organizational challenge in managing and improving health systems. Aim: To collate the views of West African surgeons on how well their educational and professional backgrounds may have prepared them for leadership and managerial roles in health care, and draw appropriate policy implications. Material and Methods: Filled structured questionnaires from 110 surgeons that were attending an annual conference were analyzed. The respondents′ bio data, professional, educational, health administrative backgrounds were probed. Their views on justifications for physicians′ involvement in health managerial roles, probable influence of some physicians′ characteristic traits and professional attributes on health leadership roles, and suggestions for improvement were also collated. Results: 71.8% of the respondents had held or were then holding health-related administrative posts; 90% had attended different varieties of management courses; 95.4% identified physicians as the inherent leaders of the health care team; but only 28.4% adjudged their health management role "strongly important" (28.4% among their multi-faceted roles; and they largely agreed that some stated professional and characteristic traits of physicians tend to make them poor leaders and managers. Conclusions: Our findings suggest that the preparations that the respondents got from their formal and professional education for leadership and managerial roles in health care were not optimal. We recommend for a paradigm shift for physicians on health leadership issue which is to be facilitated by a well-focused short time duration health management course for all physicians, particularly specialists.

  6. Duffy negative antigen is no longer a barrier to Plasmodium vivax--molecular evidences from the African West Coast (Angola and Equatorial Guinea.

    Directory of Open Access Journals (Sweden)

    Cristina Mendes

    2011-06-01

    Full Text Available BACKGROUND: Plasmodium vivax shows a small prevalence in West and Central Africa due to the high prevalence of Duffy negative people. However, Duffy negative individuals infected with P. vivax have been reported in areas of high prevalence of Duffy positive people who may serve as supply of P. vivax strains able to invade Duffy negative erythrocytes. We investigated the presence of P. vivax in two West African countries, using blood samples and mosquitoes collected during two on-going studies. METHODOLOGY/FINDINGS: Blood samples from a total of 995 individuals were collected in seven villages in Angola and Equatorial Guinea, and 820 Anopheles mosquitoes were collected in Equatorial Guinea. Identification of the Plasmodium species was achieved by nested PCR amplification of the small-subunit rRNA genes; P. vivax was further characterized by csp gene analysis. Positive P. vivax-human isolates were genotyped for the Duffy blood group through the analysis of the DARC gene. Fifteen Duffy-negative individuals, 8 from Equatorial Guinea (out of 97 and 7 from Angola (out of 898, were infected with two different strains of P. vivax (VK210 and VK247. CONCLUSIONS: In this study we demonstrated that P. vivax infections were found both in humans and mosquitoes, which means that active transmission is occurring. Given the high prevalence of infection in mosquitoes, we may speculate that this hypnozoite-forming species at liver may not be detected by the peripheral blood samples analysis. Also, this is the first report of Duffy negative individuals infected with two different strains of P. vivax (VK247 and classic strains in Angola and Equatorial Guinea. This finding reinforces the idea that this parasite is able to use receptors other than Duffy to invade erythrocytes, which may have an enormous impact in P. vivax current distribution.

  7. Two new species, including one representing a new genus, of the West African millipede family Campodesmidae (Diplopoda: Polydesmida

    Directory of Open Access Journals (Sweden)

    Didier VandenSpiegel

    2015-09-01

    Full Text Available A new genus, Campodesmoides gen. nov., is described to only encompass C. corniger sp. nov., from Cameroon. This genus and species is distinguished from the few known species of the small western African family Campodesmidae, all currently in Campodesmus, by the much longer antennae and legs, the normal pore formula with ozopores borne on porosteles, and the suberect and distally twisted gonopod, coupled with peculiar horns on a few anterior postcollum segments. A new Campodesmus is also described, C. alobatus sp. nov., from Ivory Coast, which differs from congeners primarily in the lack of a dorsal/lateral lobe on the otherwise usual and strongly subcircular gonopod telopodite, albeit the latter is not directed mesad, but held subparallel to the main body axis.

  8. Atmospheres of Brown Dwarfs

    CERN Document Server

    Helling, Christiane

    2014-01-01

    Brown Dwarfs are the coolest class of stellar objects known to date. Our present perception is that Brown Dwarfs follow the principles of star formation, and that Brown Dwarfs share many characteristics with planets. Being the darkest and lowest mass stars known makes Brown Dwarfs also the coolest stars known. This has profound implication for their spectral fingerprints. Brown Dwarfs cover a range of effective temperatures which cause brown dwarfs atmospheres to be a sequence that gradually changes from a M-dwarf-like spectrum into a planet-like spectrum. This further implies that below an effective temperature of < 2800K, clouds form already in atmospheres of objects marking the boundary between M-Dwarfs and brown dwarfs. Recent developments have sparked the interest in plasma processes in such very cool atmospheres: sporadic and quiescent radio emission has been observed in combination with decaying Xray-activity indicators across the fully convective boundary.

  9. Specific and generic stem biomass and volume models of tree species in a West African tropical semi-deciduous forest

    DEFF Research Database (Denmark)

    Goussanou, Cédric A.; Guendehou, Sabin; Assogbadjo, Achille E.

    2016-01-01

    The quantification of the contribution of tropical forests to global carbon stocks and climate change mitigation requires availability of data and tools such as allometric equations. This study made available volume and biomass models for eighteen tree species in a semi-deciduous tropical forest...... in West Africa. Generic models were also developed for the forest ecosystem, and basic wood density determined for the tree species. Non-destructive sampling approach was carried out on five hundred and one sample trees to analyse stem volume and biomass. From the modelling of volume and biomass...... predictive ability for biomass. Given tree species richness of tropical forests, the study demonstrated the hypothesis that species-specific models are preferred to generic models, and concluded that further research should be oriented towards development of specific models to cover the full range...

  10. Episode-specific risk factors for progression of acute diarrhoea to persistent diarrhoea in west African children

    DEFF Research Database (Denmark)

    Sodemann, Morten; Jakobsen, M S; Mølbak, Kare

    2013-01-01

    The aim of the present study, carried out in Guinea-Bissau, West Africa, was to identify episode-specific risk factors for persistent diarrhoea (PD) related to clinical observations and management efforts. We followed 319 episodes of childhood diarrhoea by repeated household interviews until...... prior (OR = 6.52 (95% CI 1.69-25.1)), mother had to force breast feeding (OR = 8.01 (2.99-21.5)) and current infection with Cryptosporidium (OR = 5.53 (2.10-14.6)) were the most important independent risk factors for the development of PD. Late consultation (> 48 h) was associated with PD, reflecting....... We were unable to identify management factors with a significant influence on the risk of developing PD....

  11. Genetics, Morphology, Advertisement Calls, and Historical Records Distinguish Six New Polyploid Species of African Clawed Frog (Xenopus, Pipidae) from West and Central Africa.

    Science.gov (United States)

    Evans, Ben J; Carter, Timothy F; Greenbaum, Eli; Gvoždík, Václav; Kelley, Darcy B; McLaughlin, Patrick J; Pauwels, Olivier S G; Portik, Daniel M; Stanley, Edward L; Tinsley, Richard C; Tobias, Martha L; Blackburn, David C

    2015-01-01

    African clawed frogs, genus Xenopus, are extraordinary among vertebrates in the diversity of their polyploid species and the high number of independent polyploidization events that occurred during their diversification. Here we update current understanding of the evolutionary history of this group and describe six new species from west and central sub-Saharan Africa, including four tetraploids and two dodecaploids. We provide information on molecular variation, morphology, karyotypes, vocalizations, and estimated geographic ranges, which support the distinctiveness of these new species. We resurrect Xenopus calcaratus from synonymy of Xenopus tropicalis and refer populations from Bioko Island and coastal Cameroon (near Mt. Cameroon) to this species. To facilitate comparisons to the new species, we also provide comments on the type specimens, morphology, and distributions of X. epitropicalis, X. tropicalis, and X. fraseri. This includes significantly restricted application of the names X. fraseri and X. epitropicalis, the first of which we argue is known definitively only from type specimens and possibly one other specimen. Inferring the evolutionary histories of these new species allows refinement of species groups within Xenopus and leads to our recognition of two subgenera (Xenopus and Silurana) and three species groups within the subgenus Xenopus (amieti, laevis, and muelleri species groups).

  12. Genetics, Morphology, Advertisement Calls, and Historical Records Distinguish Six New Polyploid Species of African Clawed Frog (Xenopus, Pipidae from West and Central Africa.

    Directory of Open Access Journals (Sweden)

    Ben J Evans

    Full Text Available African clawed frogs, genus Xenopus, are extraordinary among vertebrates in the diversity of their polyploid species and the high number of independent polyploidization events that occurred during their diversification. Here we update current understanding of the evolutionary history of this group and describe six new species from west and central sub-Saharan Africa, including four tetraploids and two dodecaploids. We provide information on molecular variation, morphology, karyotypes, vocalizations, and estimated geographic ranges, which support the distinctiveness of these new species. We resurrect Xenopus calcaratus from synonymy of Xenopus tropicalis and refer populations from Bioko Island and coastal Cameroon (near Mt. Cameroon to this species. To facilitate comparisons to the new species, we also provide comments on the type specimens, morphology, and distributions of X. epitropicalis, X. tropicalis, and X. fraseri. This includes significantly restricted application of the names X. fraseri and X. epitropicalis, the first of which we argue is known definitively only from type specimens and possibly one other specimen. Inferring the evolutionary histories of these new species allows refinement of species groups within Xenopus and leads to our recognition of two subgenera (Xenopus and Silurana and three species groups within the subgenus Xenopus (amieti, laevis, and muelleri species groups.

  13. Clinical profile and containment of the Ebola virus disease outbreak in two large West African cities, Nigeria, July-September 2014.

    Science.gov (United States)

    Ohuabunwo, Chima; Ameh, Celestine; Oduyebo, Oyin; Ahumibe, Anthony; Mutiu, Bamidele; Olayinka, Adebola; Gbadamosi, Wasiu; Garcia, Erika; Nanclares, Carolina; Famiyesin, Wale; Mohammed, Abdulaziz; Nguku, Patrick; Koko, Richard I; Obasanya, Joshua; Adebayo, Durojaye; Gbadegesin, Yemi; Idigbe, Oni; Oguntimehin, Olukayode; Nyanti, Sara; Nzuki, Charles; Abdus-Salam, Ismail; Adeyemi, Joseph; Onyekwere, Nnanna; Musa, Emmanuel; Brett-Major, David; Shuaib, Faisal; Nasidi, Abdulsalami

    2016-12-01

    The Ebola virus disease (EVD) outbreak in Nigeria began when an infected diplomat from Liberia arrived in Lagos, the most populous city in Africa, with subsequent transmission to another large city. First-, second-, and third-generation contacts were traced, monitored, and classified. Symptomatic contacts were managed at Ebola treatment centers as suspected, probable, and confirmed EVD cases using standard operating procedures adapted from the World Health Organization EVD guidelines. Reverse transcription PCR tests confirmed EVD. Socio-demographic, clinical, hospitalization, and outcome data of the July-September 2014 Nigeria EVD cohort were analyzed. The median age of the 20 EVD cases was 33 years (interquartile range 26-62 years). More females (55%), health workers (65%), and persons outbreak in Nigeria was characterized by the severe febrile gastroenteritis syndrome typical of the West African outbreak, better outcomes, rapid containment, and no infection among EVD care-providers. Early case detection, an effective incident management system, and prompt case management with on-site mobilization and training of local professionals were key to the outcome. Copyright © 2016. Published by Elsevier Ltd.

  14. PTCH-1 and MDM2 expression in ameloblastoma from a West African sub-population: implication for chemotherapeutics.

    Science.gov (United States)

    Udeabor, Samuel Ebele; Adisa, Akinyele Olumuyiwa; Lawal, Ahmed Oluwatoyin; Barbeck, Mike; Booms, Patrick; Sader, Robert Alexander; Ghanaati, Shahram

    2015-01-01

    Ameloblastoma is a slow growing, painless odontogenic swelling which can attain sizes that result in severe deformities of the craniofacial complex. It is the most commonly encountered odontogenic tumor in Nigeria. Surgical intervention is currently the method of treatment; however identification of altered molecular pathways may inform chemotherapeutic potential. The Protein Patched homolog 1 (PTCH-1) is overexpressed in ameloblastoma. Also, mutation in the MDM2 gene can reduce the tumor suppressor function of p53 and promote ameloblastoma growth. No study however has characterized the molecular profile of African cases of ameloblastoma with a view to developing chemotherapeutic alternatives. The objective was to characterize the PTCH-1 genetic profile of Ameloblastoma in Nigerian patients as a first step in investigating its potential for chemotherapeutic intervention. Twenty-eight FFPE blocks of ameloblastoma cases from Nigerian patients were prepared for antibody processing to PTCH-1 (Polyclonal Anti-PTCH antibody ab39266) and MDM2 (Monoclonal Anti-MDM2 antibody (2A10) ab16895). Cytoplasmic brown staining was considered as positive for PTCH while nuclear staining was positive for MDM2. Moderate and strong expressions for PTCH in ameloblast and stellate reticulum were 78.6% and 60.7% respectively. Only 3 (10.7%) cases expressed MDM2. The importance of our study is that it supports, in theory, anti-PTCH/SHH chemotherapeutics for Nigerian ameloblastoma cases and also infers the possible additional use of anti-p53 agents.

  15. Seed dispersal and movement patterns in two species of Ceratogymna hornbills in a West African tropical lowland forest.

    Science.gov (United States)

    Holbrook, Kimberly M; Smith, Thomas B

    2000-10-01

    We studied two species of Ceratogymna hornbills, the black-casqued hornbill, C. atrata, and the white-thighed hornbill, C. cylindricus, in the tropical forests of Cameroon, to understand their movement patterns and evaluate their effectiveness as seed dispersers. To estimate hornbill contribution to a particular tree species' seed shadow we combined data from movements, determined by radio-tracking, with data from seed passage trials. For 13 individuals tracked over 12 months, home range varied between 925 and 4,472 ha, a much larger area than reported for other African avian frugivores. Seed passage times ranged from 51 to 765 min, with C. atrata showing longer passage times than C. cylindricus, and larger seeds having longer gut retention times than smaller seeds. Combining these data, we estimated that seed shadows were extensive for the eight tree species examined, with approximately 80% of seeds moved more than 500 m from the parent plant. Maximum estimated dispersal distances for larger seeds were 6,919 and 3,558 m for C. atrata and C. cylindricus, respectively. The extent of hornbill seed shadows suggests that their influence in determining forest structure will likely increase as other larger mammalian dispersers are exterminated.

  16. On the data-driven inference of modulatory networks in climate science: an application to West African rainfall

    Science.gov (United States)

    González, D. L., II; Angus, M. P.; Tetteh, I. K.; Bello, G. A.; Padmanabhan, K.; Pendse, S. V.; Srinivas, S.; Yu, J.; Semazzi, F.; Kumar, V.; Samatova, N. F.

    2015-01-01

    Decades of hypothesis-driven and/or first-principles research have been applied towards the discovery and explanation of the mechanisms that drive climate phenomena, such as western African Sahel summer rainfall~variability. Although connections between various climate factors have been theorized, not all of the key relationships are fully understood. We propose a data-driven approach to identify candidate players in this climate system, which can help explain underlying mechanisms and/or even suggest new relationships, to facilitate building a more comprehensive and predictive model of the modulatory relationships influencing a climate phenomenon of interest. We applied coupled heterogeneous association rule mining (CHARM), Lasso multivariate regression, and dynamic Bayesian networks to find relationships within a complex system, and explored means with which to obtain a consensus result from the application of such varied methodologies. Using this fusion of approaches, we identified relationships among climate factors that modulate Sahel rainfall. These relationships fall into two categories: well-known associations from prior climate knowledge, such as the relationship with the El Niño-Southern Oscillation (ENSO) and putative links, such as North Atlantic Oscillation, that invite further research.

  17. Air pollution from gas flaring: new emission factor estimates and detection in a West African aerosol remote-sensing climatology

    Science.gov (United States)

    MacKenzie, Rob; Fawole, Olusegun Gabriel; Levine, James; Cai, Xiaoming

    2016-04-01

    Gas flaring, the disposal of gas through stacks in an open-air flame, is a common feature in the processing of crude oil, especially in oil-rich regions of the world. Gas flaring is a prominent source of volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAH), CO, CO2, nitrogen oxides (NOx), SO2 (in "sour" gas only), and soot (black carbon), as well as the release of locally significant amounts of heat. The rates of emission of these pollutants from gas flaring depend on a number of factors including, but not limited to, fuel composition and quantity, stack geometry, flame/combustion characteristics, and prevailing meteorological conditions. Here, we derive new estimated emission factors (EFs) for carbon-containing pollutants (excluding PAH). The air pollution dispersion model, ADMS5, is used to simulate the dispersion of the pollutants from flaring stacks in the Niger delta. A seasonal variation of the dispersion pattern of the pollutant within a year is studied in relation to the movements of the West Africa Monsoon (WAM) and other prevailing meteorological factors. Further, we have clustered AERONET aerosol signals using trajectory analysis to identify dominant aerosol sources at the Ilorin site in West Africa (4.34 oE, 8.32 oN). A 10-year trajectory-based analysis was undertaken (2005-2015, excluding 2010). Of particular interest are air masses that have passed through the gas flaring region in the Niger Delta area en-route the AERONET site. 7-day back trajectories were calculated using the UK Universities Global Atmospheric Modelling Programme (UGAMP) trajectory model which is driven by analyses from the European Centre for Medium-Range Weather Forecasts (ECMWF). From the back-trajectory calculations, dominant sources are identified, using literature classifications: desert dust (DD); Biomass burning (BB); and Urban-Industrial (UI). We use a combination of synoptic trajectories and aerosol optical properties to distinguish a fourth source

  18. Undetectable plasma viral load predicts normal survival in HIV-2-infected people in a West African village

    Directory of Open Access Journals (Sweden)

    Ricard Dominique

    2010-05-01

    Full Text Available Abstract Background There have been no previous studies of the long-term survival and temporal changes in plasma viral load among HIV-2 infected subjects. Methods 133 HIV-2 infected and 158 HIV-uninfected subjects from a rural area in North-west Guinea-Bissau, West Africa were enrolled into a prospective cohort study in 1991 and followed-up to mid-2009. Data were collected on four occasions during that period on HIV antibodies, CD4% and HIV-2 plasma viral load. Results Median age (interquartile range [IQR] of HIV-2 infected subjects at time of enrollment was 47 (36, 60 years, similar to that of HIV-uninfected control subjects, 49 (38, 62 (p = 0.4. Median (IQR plasma viral load and CD4 percentage were 347 (50, 4,300 copies/ml and 29 (22, 35 respectively. Overall loss to follow-up to assess vital status was small, at 6.7% and 6.3% for HIV-2 infected and uninfected subjects respectively. An additional 17 (12.8% and 16 (10.1% of HIV-2 infected and uninfected subjects respectively were censored during follow-up due to infection with HIV-1. The mortality rate per 100 person-years (95% CI was 4.5 (3.6, 5.8 among HIV-2 infected subjects compared to 2.1 (1.6, 2.9 among HIV-uninfected (age-sex adjusted rate ratio 1.9 (1.3, 2.8, p Viral load measurements were available for 98%, 78%, 77% and 61% HIV-2 infected subjects who were alive and had not become super-infected with HIV-1, in 1991, 1996, 2003 and 2006 respectively. Median plasma viral load (RNA copies per ml (IQR did not change significantly over time, being 150 (50, 1,554; n = 77 in 1996, 203 (50, 2,837; n = 47 in 2003 and 171 (50, 497; n = 31 in 2006. Thirty seven percent of HIV-2 subjects had undetectable viraemia ( Conclusions A substantial proportion of HIV-2 infected subjects in this cohort have stable plasma viral load, and those with an undetectable viral load (37% at study entry had a normal survival rate. However, the sequential laboratory findings need to be interpreted with caution given

  19. Large-scale impacts of climate change on tropical West African ecosystems over the past ~540,000 years

    Science.gov (United States)

    Gosling, William; Miller, Charlotte; Kemp, David; Coe, Angela; Gilmour, Iain

    2016-04-01

    A paucity of empirical non-marine data means that uncertainty surrounds the impact of climate change on terrestrial ecosystems in tropical regions. The sedimentary-fill of the Bosumtwi impact crater (Ghana) provides the longest Quaternary terrestrial archive of environmental change in Africa, spanning the last ~540,000 years. Here we present a reconstruction of vegetation biomes and moisture availability in tropical West Africa for the past ~540,000 years using pollen analysis and the nitrogen isotope composition of bulk organic matter preserved in sediments from Lake Bosumtwi. Variations in grass pollen abundance (0-99%) indicate abrupt transitions between savannah and woodland biomes. Coeval variations in the nitrogen isotopic composition of organic matter indicate that intervals of savannah expansion coincided with minimum lake-levels and low regional moisture availability. The observed changes responded to orbitally paced global climate variations on both glacial-interglacial and shorter timescales. Importantly, the magnitude and abruptness of ecosystem change revealed by our data exceeds that previously determined from marine records, demonstrating for the first time the true sensitivity of tropical regions to Quaternary climate change.

  20. Visible and infrared properties of unaltered to weathered rocks from Precambrian granite-greenstone terrains of the West African Craton

    Science.gov (United States)

    Metelka, Václav; Baratoux, Lenka; Jessell, Mark W.; Naba, Séta

    2015-12-01

    In situ and laboratory 0.35 μm-2.5 μm spectra of rocks from a Paleoproterozoic granite-greenstone terrain along with its Neoproterozoic sedimentary cover and derived regolith materials were examined in western Burkina Faso. The reflectance spectra show the influence of typical arid to semi-arid weathering with the formation of desert varnish, iron films, and dust coatings. Fe and Mg-OH absorption features related to chlorite, amphibole, pyroxene, epidote, and biotite are observable in the mafic and intermediate meta-volcanic rocks as well as in the granodiorites and tonalites. Al-OH absorption caused by kaolinite, smectite, illite/muscovite are typical for meta-volcano-sedimentary schists, Tarkwaian-type detrital meta-sediments, sandstones of the Taoudeni basin, all of the weathered surfaces and regolith materials. Ferric and ferrous iron absorptions related to both primary rock-forming minerals and secondary weathering minerals (goethite, hematite) were observed in most of the sampled materials. The results show that although weathering alters the spectral signature of the fresh rock, indicative absorption features located in the short wave infrared region remain detectable. In addition, spectra of soils partially reflect the mineral composition of the weathered rock surfaces. The analysis of the hyperspectral data shows the potential of differentiating between the sampled surfaces. The library presents a primary database for the geological and regolith analysis of remote sensing data in West Africa.

  1. Patterning and predicting aquatic insect richness in four West-African coastal rivers using artificial neural networks

    Directory of Open Access Journals (Sweden)

    Edia E.O.

    2010-10-01

    Full Text Available Despite their importance in stream management, the aquatic insect assemblages are still little known in West Africa. This is particularly true in South-Eastern Ivory Coast, where aquatic insect assemblages were hardly studied. We therefore aimed at characterising aquatic insect assemblages on four coastal rivers in South-Eastern Ivory Coast. Patterning aquatic insect assemblages was achieved using a Self-Organizing Map (SOM, an unsupervised Artificial Neural Networks (ANN method. This method was applied to pattern the samples based on the richness of five major orders of aquatic insects (Diptera, Ephemeroptera, Coleoptera, Trichoptera and Odonata. This permitted to identify three clusters that were mainly related to the local environmental status of sampling sites. Then, we used the environmental characteristics of the sites to predict, using a multilayer perceptron neural network (MLP, trained by BackPropagation algorithm (BP, a supervised ANN, the richness of the five insect orders. The BP showed high predictability (0.90 for both Diptera and Trichoptera, 0.84 for both Coleoptera and Odonata, 0.69 for Ephemeroptera. The most contributing variables in predicting the five insect order richness were pH, conductivity, total dissolved solids, water temperature, percentage of rock and the canopy. This underlines the crucial influence of both instream characteristics and riparian context.

  2. West African paleoclimates during the last climatic cycle inferred from an Atlantic deep-sea pollen record

    Science.gov (United States)

    Lezine, Anne-Marie

    1991-05-01

    Pollen studies of marine sediments from Atlantic deep-sea core V22-196 (13°50' N-18°57' W; 3728-m water depth) are used to reconstruct paleoclimates of north tropical west Africa since 140,000 yr B.P. High concentration of pollen, mainly from Saharan and arid littoral zones suggests a strengthened tradewind circulation since ca. 60,000 yr B.P. that became even stronger after 40,000 yr B.P. and reached a maximum 17,000 yr B.P. Periods of eolian transport of pollen to the Atlantic occurred about 94,000 and 105,000 yr B.P. and during Termination II. Conversely, high relative values of pollen from Sudanian and Guinean zones and from Mangrove and freshwater vegetation, coincident with maxima of dinocyst concentration, are interpreted as reflecting both strong fluvial inputs and the expansion of humid vegetation on the adjacent continent during wet periods dated between 140,000 and 118,000, 105,000 and 96,000, 92,000 and 73,000, 52,000 and 44,000 yr B.P. and 12,000 yr B.P. and the Holocene. The strong correlation of these results from the eastern tropical Atlantic with those from the Arabian Sea corroborates fluctuations of monsoon climate.

  3. Aerosol patterns and aerosol-cloud-interactions off the West African Coast based on the A-train formation

    Science.gov (United States)

    Fuchs, Julia; Bendix, Jörg; Cermak, Jan

    2013-04-01

    In this study, spatial and temporal aerosol patterns off the Western African coast are characterized and related to cloud properties, based on satellite data Atmospheric aerosols play a key role in atmospheric processes and influence our environmental system in a complex way. Their identification, characterization, transport patterns as well as their interactions with clouds pose major challenges. Especially the last aspect reveals major uncertainties in terms of the Earth's radiation budget as reported in the IPCC's Fourth Assessment Report (IPCC, 2007). Western and Southern Africa are dominated by two well-known source types of atmospheric aerosols. First, the Saharan Desert is the world's largest aeolian dust emitting source region. Second, biomass burning aerosol is commonly transported off-shore further south (Kaufman et al., 2005). Both aerosol types influence Earth's climate in different manners and can be detected by the MODIS (MODerate resolution Imaging Spectrometer) sensor onboard the EOS platforms as they propagate to the Central and Southern Atlantic. The motivation of this study was to reveal the seasonal pattern of the Saharan dust transport based on an observation period of 11 years and trying to explain the meteorological mechanisms. North African dust plumes are transported along a latitude of 19°N in July and 6°N in January. The seasonally fluctuating intensities adapt to the annual cycle of wind and precipitation regimes. A strong relationship is found between the spatial shift of the Azores High and the Saharan dust load over the middle Atlantic Ocean. Monthly Aerosol Optical Thickness products of Terra MODIS and NCEP-DOE (National Centers for Environmental Predictions) Reanalysis II data are used for this purpose. The relationship between aerosol and cloud droplet parameters is blurred by high sensitivities to aerosol size and composition (Feingold, 2003; McFiggans et al., 2006) as well as meteorological context (Ackerman et al., 2004

  4. The stable hydrogen isotopic composition of sedimentary plant waxes as quantitative proxy for rainfall in the West African Sahel

    Science.gov (United States)

    Niedermeyer, Eva M.; Forrest, Matthew; Beckmann, Britta; Sessions, Alex L.; Mulch, Andreas; Schefuß, Enno

    2016-07-01

    Various studies have demonstrated that the stable hydrogen isotopic composition (δD) of terrestrial leaf waxes tracks that of precipitation (δDprecip) both spatially across climate gradients and over a range of different timescales. Yet, reconstructed estimates of δDprecip and corresponding rainfall typically remain largely qualitative, due mainly to uncertainties in plant ecosystem net fractionation, relative humidity, and the stability of the amount effect through time. Here we present δD values of the C31n-alkane (δDwax) from a marine sediment core offshore the Northwest (NW) African Sahel covering the past 100 years and overlapping with the instrumental record of rainfall. We use this record to investigate whether accurate, quantitative estimates of past rainfall can be derived from our δDwax time series. We infer the composition of vegetation (C3/C4) within the continental catchment area by analysis of the stable carbon isotopic composition of the same compounds (δ13Cwax), calculated a net ecosystem fractionation factor, and corrected the δDwax time series accordingly to derive δDprecip. Using the present-day relationship between δDprecip and the amount of precipitation in the tropics, we derive quantitative estimates of past precipitation amounts. Our data show that (a) vegetation composition can be inferred from δ13Cwax, (b) the calculated net ecosystem fractionation represents a reasonable estimate, and (c) estimated total amounts of rainfall based on δDwax correspond to instrumental records of rainfall. Our study has important implications for future studies aiming to reconstruct rainfall based on δDwax; the combined data presented here demonstrate that it is feasible to infer absolute rainfall amounts from sedimentary δDwax in tandem with δ13Cwax in specific depositional settings.

  5. Ethno-botanical study of the African star apple (Chrysophyllum albidum G. Don in the Southern Benin (West Africa

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    Houessou Laurent G

    2012-10-01

    Full Text Available Abstract Background In addition to plant species biology and ecology, understanding the folk knowledge systems related to the use of plant species and how this knowledge system influences the conservation of plant species is an important issue in the implementation of sustainable strategies of biodiversity conservation programs. This study aimed at providing information on the use and local knowledge variation on Chrysophyllum albidum G. Don a multipurpose tree species widely used in southern Benin. Methods Data was collected through 210 structured interviews. Informants were randomly selected from ten villages. The fidelity level and use value of different plant parts of C. albidum were estimated. The variation in ethnobotanical knowledge was assessed by comparing the use value between ethnic, gender and age groups. In order to assess the use pattern of the different plant parts in folk medicine, a correspondence analysis was carried out on the frequency citation of plant parts. Results Four categories of use (food, medicine, firewood and timber were recorded for C. albidum. With respect to the different plant parts, the fleshy pulp of the African star apple fruit showed high consensus degree as food among the informants. Fifteen diseases were reported to be treated by the different parts of C. albidum in the region. Correspondence analysis revealed the specificity of each part in disease treatment. There was no significant difference among ethnic groups regarding the ethno-botanical use value of C. albidum. However, significant difference existed between genders and among age groups regarding the knowledge of the medical properties of this species. Conclusions C. albidum is well integrated in the traditional agroforestry system of the southern Benin. Despite its multipurpose character, this species remains underutilized in the region. Considering the current threat of habitat degradation, action is needed in order to ensure the long term

  6. Future Water Resources Assessment for West African River Basins Under Climate Change, Population Growth and Irrigation Development

    Science.gov (United States)

    Wisser, D.; Ibrahim, B.; Proussevitch, A. A.

    2014-12-01

    West Africa economies rely on rain-fed agriculture and are extremely vulnerable to changes in precipitation. Results from the most recent generation of regional climate models suggest increases in rainy season rainfall variability (delayed rainy season onset, increased probability of dry spells, shorter rainy season duration) despite a moderate increase in rainy season total precipitation. These changes could potentially have detrimental effects on crop yield and food security. Additional pressures on water resources come from increased demand as a result of high population growth rates (~3% per year). Increased water storage and irrigation can help improve crop yields but future assessments of water resources are needed to prioritize irrigation development as an adaptation option. Increased water abstraction, in turn can impact water availability in downstream regions so that an integrated assessment of future water availability and demand is needed. We use a set of 15 RCM outputs from the CORDEX data archive to drive WBMplus, a hydrological model and simulate water availability under climate change. Based on estimated water constraints, we develop scenarios to expand irrigated areas (from the current 1% of all croplands) and calculate the effects on water scarcity, taking into account increased demand for domestic consumption and livestock water demand, at a spatial resolution of 10 km. Results around the 2050's indicate large potential to develop irrigated areas on ground and surface water and increase local water storage without increasing water scarcity downstream for many river basins in the region that could help alleviate pressures on the cropping systems and thereby increase food security.

  7. At-Risk Serum Cholesterol Profile at Both Ends of the Nutrition Spectrum in West African Adults? The Benin Study

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    Jean-Pierre Després

    2013-04-01

    Full Text Available Low HDL-cholesterol (HDL-C, using as cut-offs 1.03 mmol/L in men and 1.29 mmol/L in women, was observed in more than 25% apparently healthy adults (n = 541 in a cross-sectional study on nutrition transition and cardiometabolic risk factors (CMRF in Benin, West Africa. Both overweight/obesity (35.3% and underweight (11.3% were present, displaying the double burden of malnutrition. We examined in more depth the association of low HDL-C with nutrition and with other CMRF. Metabolic syndrome components were assessed, plus the ratio of total cholesterol (TC/HDL-C and serum homocysteine. Insulin resistance was based on Homeostasis Model Assessment. We also measured BMI and body composition by bio-impedance. Dietary quality was appraised with two non-consecutive 24 h recalls. Low HDL-C was associated with much higher TC/HDL-C and more abdominal obesity in men and women and with more insulin resistance in women. The rate of low HDL-C was highest (41.9% among the overweight/obese subjects (BMI ≥ 25, but it also reached 31.1% among the underweight (BMI < 18.5, compared with 17.3% among normal-weight subjects (p < 0.001. Lower dietary micronutrient adequacy, in particular, in vitamins A, B3, B12, zinc and calcium, was associated with low HDL-C when controlling for several confounders. This suggests that at-risk lipoprotein cholesterol may be associated with either underweight or overweight/obesity and with poor micronutrient intake.

  8. A One-Year Study of the Diurnal Cycle of Meteorology, Clouds, and Radiation in the West African Sahel Region

    Energy Technology Data Exchange (ETDEWEB)

    Marquardt-Collow, Allison; Ghate, Virendra P.; Miller, Mark A.; Trabachino, Lynne

    2016-01-09

    The diurnal cycles of meteorological and radiation variables are analyzed during the wet and dry seasons over the Sahel region of West Africa during 2006 using surface data collected by the Atmospheric Radiation Measurement (ARM) program’s Mobile Facility, satellite radiation measurements from the Geostationary Earth Radiation Budget (GERB) instrument aboard Meteosat 8, and reanalysis products from the National Center for Environmental Prediction (NCEP). The meteorological analysis builds upon past studies of the diurnal cycle in the region by incorporating diurnal cycles of lower tropospheric wind profiles, thermodynamic profiles, integrated water vapor and liquid water measurements, and cloud radar measurements of frequency and location. These meteorological measurements are complemented by 3-hour measurements of the diurnal cycles of the TOA and surface shortwave (SW) and longwave (LW) radiative fluxes and cloud radiative effects (CREs), and the atmospheric radiative flux divergence (RFD) and atmospheric CREs. Cirrus cloudiness during the dry season is shown to peak in coverage in the afternoon, while convective clouds during the wet season are shown to peak near dawn and have an afternoon minimum related to the rise of the Lifting Condensation Level into the Saharan Air Layer. The LW and SW RFDs and CREs exhibit diurnal cycles during both seasons, but there is a relatively small difference in the LW cycles during the two seasons (10-30 Wm^(-2) depending on the variable and time of day). Small differences in the TOA CREs during the two seasons are overwhelmed by large differences in the surface SW CREs, which exceed 100 Wm^(-2). A significant surface SW CRE during the wet season combined with a negligible TOA SW CRE produces a diurnal cycle in the atmospheric CRE that is modulated primarily by the SW surface CRE, peaks at midday at ~150 Wm^(-2), and varies widely from day to day.

  9. Investigating Dwarf Spiral Galaxies

    Science.gov (United States)

    Weerasooriya, Sachithra; Dunn, Jacqueline M.

    2017-01-01

    Several studies have proposed that dwarf elliptical / spheroidal galaxies form through the transformation of dwarf irregular galaxies. Early and late type dwarfs resemble each other in terms of their observed colors and light distributions (each can often be represented by exponential disks), providing reason to propose an evolutionary link between the two types. The existence of dwarf spirals has been largely debated. However, more and more recent studies are using the designation of dwarf spiral to describe their targets of interest. This project seeks to explore where dwarf spirals fit into the above mentioned evolutionary sequence, if at all. Optical colors will be compared between a sample of dwarf irregular, dwarf elliptical, and dwarf spiral galaxies. The dwarf irregular and dwarf elliptical samples have previously been found to overlap in both optical color and surface brightness profile shape when limiting the samples to their fainter members. A preliminary comparison including the dwarf spiral sample will be presented here, along with a comparison of available ultraviolet and near-infrared data. Initial results indicate a potential evolutionary link that merits further investigation.

  10. Anaemia and zidovudine-containing antiretroviral therapy in paediatric antiretroviral programmes in the IeDEA Paediatric West African Database to evaluate AIDS

    Directory of Open Access Journals (Sweden)

    Lorna A Renner

    2013-09-01

    Full Text Available Introduction: There is a risk of anaemia among HIV-infected children on antiretroviral therapy (ART containing zidovudine (ZDV recommended in first-line regimens in the WHO guidelines. We estimated the risk of severe anaemia after initiation of a ZDV-containing regimen in HIV-infected children included in the IeDEA West African database. Methods: Standardized collection of data from HIV-infected children (positive PCR<18 months or positive serology ≥18 months followed up in HIV programmes was included in the regional IeDEA West Africa collaboration. Ten clinical centres from seven countries contributed (Benin, Burkina Faso, Côte d'Ivoire, Gambia, Ghana, Mali and Senegal to this collection. Inclusion criteria were age <16 years and starting ART. We explored the data quality of haemoglobin documentation over time and the incidence and predictors of severe anaemia (Hb<7g/dL per 100 child-years of follow-up over the duration of first-line antiretroviral therapy. Results: As of December 2009, among the 2933 children included in the collaboration, 45% were girls, median age was five years; median CD4 cell percentage was 13%; median weight-for-age z-score was−2.7; and 1772 (60.4% had a first-line ZDV-containing regimen. At baseline, 70% of the children with a first-line ZDV-containing regimen had a haemoglobin measure available versus 76% in those not on ZDV (p≤0.01: the prevalence of severe anaemia was 3.0% (n=38 in the ZDV group versus 10.2% (n=89 in those without (p<0. 01. Over the first-line follow-up, 58.9% of the children had ≥1 measure of haemoglobin available in those exposed to ZDV versus 60.4% of those not (p=0.45. Severe anaemia occurred in 92 children with an incidence of 2.47 per 100 child-years of follow-up in those on a ZDV-containing regimen versus 4.25 in those not (p≤0.01. Adjusted for age at ART initiation and first-line regimen, a weight-for-age z-score ≤−3 was a strong predictor associated with a 5.59 times risk of

  11. Overcoming Phosphorus Deficiency in West African Pearl Millet and Sorghum Production Systems: Promising Options for Crop Improvement.

    Science.gov (United States)

    Gemenet, Dorcus C; Leiser, Willmar L; Beggi, Francesca; Herrmann, Ludger H; Vadez, Vincent; Rattunde, Henry F W; Weltzien, Eva; Hash, Charles T; Buerkert, Andreas; Haussmann, Bettina I G

    2016-01-01

    West Africa (WA) is among the most food insecure regions. Rapid human population growth and stagnating crop yields greatly contribute to this fact. Poor soil fertility, especially low plant available phosphorus (P) is constraining food production in the region. P-fertilizer use in WA is among the lowest in the world due to inaccessibility and high prices, often unaffordable to resource-poor subsistence farmers. This article provides an overview of soil P-deficiency in WA and opportunities to overcome it by exploiting sorghum and pearl millet genetic diversity. The topic is examined from the perspectives of plant breeding, soil science, plant physiology, plant nutrition, and agronomy, thereby referring to recent results obtained in a joint interdisciplinary research project, and reported literature. Specific objectives are to summarize: (1) The global problem of P scarcity and how it will affect WA farmers; (2) Soil P dynamics in WA soils; (3) Plant responses to P deficiency; (4) Opportunities to breed for improved crop adaptation to P-limited conditions; (5) Challenges and trade-offs for improving sorghum and pearl millet adaptation to low-P conditions in WA; and (6) Systems approaches to address soil P-deficiency in WA. Sorghum and pearl millet in WA exhibit highly significant genetic variation for P-uptake efficiency, P-utilization efficiency, and grain yield under P-limited conditions indicating the possibility of breeding P-efficient varieties. Direct selection under P-limited conditions was more efficient than indirect selection under high-P conditions. Combining P-uptake and P-utilization efficiency is recommendable for WA to avoid further soil mining. Genomic regions responsible for P-uptake, P-utilization efficiency, and grain yield under low-P have been identified in WA sorghum and pearl millet, and marker-assisted selection could be possible once these genomic regions are validated. Developing P-efficient genotypes may not, however, be a sustainable

  12. Overcoming Phosphorus Deficiency in West African Pearl Millet and Sorghum Production Systems: Promising Options for Crop Improvement

    Science.gov (United States)

    Gemenet, Dorcus C.; Leiser, Willmar L.; Beggi, Francesca; Herrmann, Ludger H.; Vadez, Vincent; Rattunde, Henry F. W.; Weltzien, Eva; Hash, Charles T.; Buerkert, Andreas; Haussmann, Bettina I. G.

    2016-01-01

    West Africa (WA) is among the most food insecure regions. Rapid human population growth and stagnating crop yields greatly contribute to this fact. Poor soil fertility, especially low plant available phosphorus (P) is constraining food production in the region. P-fertilizer use in WA is among the lowest in the world due to inaccessibility and high prices, often unaffordable to resource-poor subsistence farmers. This article provides an overview of soil P-deficiency in WA and opportunities to overcome it by exploiting sorghum and pearl millet genetic diversity. The topic is examined from the perspectives of plant breeding, soil science, plant physiology, plant nutrition, and agronomy, thereby referring to recent results obtained in a joint interdisciplinary research project, and reported literature. Specific objectives are to summarize: (1) The global problem of P scarcity and how it will affect WA farmers; (2) Soil P dynamics in WA soils; (3) Plant responses to P deficiency; (4) Opportunities to breed for improved crop adaptation to P-limited conditions; (5) Challenges and trade-offs for improving sorghum and pearl millet adaptation to low-P conditions in WA; and (6) Systems approaches to address soil P-deficiency in WA. Sorghum and pearl millet in WA exhibit highly significant genetic variation for P-uptake efficiency, P-utilization efficiency, and grain yield under P-limited conditions indicating the possibility of breeding P-efficient varieties. Direct selection under P-limited conditions was more efficient than indirect selection under high-P conditions. Combining P-uptake and P-utilization efficiency is recommendable for WA to avoid further soil mining. Genomic regions responsible for P-uptake, P-utilization efficiency, and grain yield under low-P have been identified in WA sorghum and pearl millet, and marker-assisted selection could be possible once these genomic regions are validated. Developing P-efficient genotypes may not, however, be a sustainable

  13. Overcoming Phosphorus Deficiency in West African Pearl Millet and Sorghum Production Systems: Promising Options for Crop Improvement

    Directory of Open Access Journals (Sweden)

    Dorcus C. GEMENET

    2016-09-01

    Full Text Available West Africa (WA is among the most food insecure regions. Rapid human population growth and stagnating crop yields greatly contribute to this fact. Poor soil fertility, especially low plant available phosphorus (P is constraining food production in the region. P-fertilizer use in WA is among the lowest in the world due to inaccessibility and high prices, unaffordable to resource-poor farmers. This article provides an overview of soil P-deficiency in WA and opportunities to overcome it by exploiting sorghum and pearl millet genetic diversity. The topic is examined from the perspectives of plant breeding, soil science, plant physiology, plant nutrition, and agronomy, thereby referring to recent results obtained in a joint interdisciplinary research project, and reported literature. Specific objectives are to summarize: (1 The global problem of P scarcity and how it will affect WA farmers; (2 Soil P dynamics in WA soils; (3 Plant responses to P deficiency; (4 Opportunities to breed for improved crop adaptation to P-limited conditions; (5 Challenges and trade-offs for improving sorghum and pearl millet adaptation to low-P conditions in WA; and (6 Systems approaches to addressing soil P-deficiency in WA.Sorghum and pearl millet in WA exhibit highly significant genetic variation for P-uptake efficiency, P-utilization efficiency, and grain yield under P-limited conditions indicating the possibility of breeding P-efficient varieties. Direct selection under P-limited conditions was more efficient than indirect selection under high-P conditions. Combining P-uptake and P-utilization efficiency is recommendable for WA to avoid further soil mining. Genomic regions responsible for P-uptake, P-utilization efficiency, and grain yield under low-P have been identified in WA sorghum and pearl millet, and marker-assisted selection could be possible once these genomic regions are validated. Developing P-efficient genotypes may not however be a sustainable solution in

  14. Genetic Diversity of the Hepatitis B Virus Strains in Cuba: Absence of West-African Genotypes despite the Transatlantic Slave Trade.

    Directory of Open Access Journals (Sweden)

    Licel A Rodríguez Lay

    Full Text Available Cuba is an HBsAg low-prevalence country with a high coverage of anti-hepatitis B vaccine. Its population is essentially the result of the population mix of Spanish descendants and former African slaves. Information about genetic characteristics of hepatitis B virus (HBV strains circulating in the country is scarce. The HBV genotypes/subgenotypes, serotypes, mixed infections, and S gene mutations of 172 Cuban HBsAg and HBV-DNA positive patients were determined by direct sequencing and phylogenetic analysis. Phylogenetic analysis of HBV S gene sequences showed a predominance of genotype A (92.4%, subgenotype A2 (84.9% and A1 (7.6%. Genotype D (7.0% and subgenotype C1 (0.6% were also detected but typical (subgenotypes of contemporary West-Africa (E, A3 were conspicuously absent. All genotype A, D, and C strains exhibited sequence characteristics of the adw2, ayw2, and adrq serotypes, respectively. Thirty-three (19.1% patients showed single, double, or multiple point mutations inside the Major Hydrophilic domain associated with vaccine escape; eighteen (10.5% patients had mutations in the T-cell epitope (amino acids 28-51, and there were another 111 point mutations downstream of the S gene. One patient had an HBV A1/A2 mixed infection. This first genetic study of Cuban HBV viruses revealed only strains that were interspersed with strains from particularly Europe, America, and Asia. The absence of genotype E supports previous hypotheses about an only recent introduction of this genotype into the general population in Africa. The presence of well-known vaccine escape (3.5% and viral resistance mutants (2.9% warrants strain surveillance to guide vaccination and treatment strategies.

  15. Genetic Diversity of the Hepatitis B Virus Strains in Cuba: Absence of West-African Genotypes despite the Transatlantic Slave Trade.

    Science.gov (United States)

    Rodríguez Lay, Licel A; Corredor, Marité B; Villalba, Maria C; Frómeta, Susel S; Wong, Meilin S; Valdes, Lidunka; Samada, Marcia; Sausy, Aurélie; Hübschen, Judith M; Muller, Claude P

    2015-01-01

    Cuba is an HBsAg low-prevalence country with a high coverage of anti-hepatitis B vaccine. Its population is essentially the result of the population mix of Spanish descendants and former African slaves. Information about genetic characteristics of hepatitis B virus (HBV) strains circulating in the country is scarce. The HBV genotypes/subgenotypes, serotypes, mixed infections, and S gene mutations of 172 Cuban HBsAg and HBV-DNA positive patients were determined by direct sequencing and phylogenetic analysis. Phylogenetic analysis of HBV S gene sequences showed a predominance of genotype A (92.4%), subgenotype A2 (84.9%) and A1 (7.6%). Genotype D (7.0%) and subgenotype C1 (0.6%) were also detected but typical (sub)genotypes of contemporary West-Africa (E, A3) were conspicuously absent. All genotype A, D, and C strains exhibited sequence characteristics of the adw2, ayw2, and adrq serotypes, respectively. Thirty-three (19.1%) patients showed single, double, or multiple point mutations inside the Major Hydrophilic domain associated with vaccine escape; eighteen (10.5%) patients had mutations in the T-cell epitope (amino acids 28-51), and there were another 111 point mutations downstream of the S gene. One patient had an HBV A1/A2 mixed infection. This first genetic study of Cuban HBV viruses revealed only strains that were interspersed with strains from particularly Europe, America, and Asia. The absence of genotype E supports previous hypotheses about an only recent introduction of this genotype into the general population in Africa. The presence of well-known vaccine escape (3.5%) and viral resistance mutants (2.9%) warrants strain surveillance to guide vaccination and treatment strategies.

  16. Genetic Diversity of the Hepatitis B Virus Strains in Cuba: Absence of West-African Genotypes despite the Transatlantic Slave Trade

    Science.gov (United States)

    Rodríguez Lay, Licel A.; Corredor, Marité B.; Villalba, Maria C.; Frómeta, Susel S.; Wong, Meilin S.; Valdes, Lidunka; Samada, Marcia; Sausy, Aurélie; Hübschen, Judith M.; Muller, Claude P.

    2015-01-01

    Cuba is an HBsAg low-prevalence country with a high coverage of anti-hepatitis B vaccine. Its population is essentially the result of the population mix of Spanish descendants and former African slaves. Information about genetic characteristics of hepatitis B virus (HBV) strains circulating in the country is scarce. The HBV genotypes/subgenotypes, serotypes, mixed infections, and S gene mutations of 172 Cuban HBsAg and HBV-DNA positive patients were determined by direct sequencing and phylogenetic analysis. Phylogenetic analysis of HBV S gene sequences showed a predominance of genotype A (92.4%), subgenotype A2 (84.9%) and A1 (7.6%). Genotype D (7.0%) and subgenotype C1 (0.6%) were also detected but typical (sub)genotypes of contemporary West-Africa (E, A3) were conspicuously absent. All genotype A, D, and C strains exhibited sequence characteristics of the adw2, ayw2, and adrq serotypes, respectively. Thirty-three (19.1%) patients showed single, double, or multiple point mutations inside the Major Hydrophilic domain associated with vaccine escape; eighteen (10.5%) patients had mutations in the T-cell epitope (amino acids 28-51), and there were another 111 point mutations downstream of the S gene. One patient had an HBV A1/A2 mixed infection. This first genetic study of Cuban HBV viruses revealed only strains that were interspersed with strains from particularly Europe, America, and Asia. The absence of genotype E supports previous hypotheses about an only recent introduction of this genotype into the general population in Africa. The presence of well-known vaccine escape (3.5%) and viral resistance mutants (2.9%) warrants strain surveillance to guide vaccination and treatment strategies. PMID:25978398

  17. What drives the spatial variability of primary productivity and matter fluxes in the north-west African upwelling system? A modelling approach

    Science.gov (United States)

    Auger, Pierre-Amaël; Gorgues, Thomas; Machu, Eric; Aumont, Olivier; Brehmer, Patrice

    2016-11-01

    A comparative box analysis based on a multi-decadal physical-biogeochemical hindcast simulation (1980-2009) was conducted to characterize the drivers of the spatial distribution of phytoplankton biomass and production in the north-west (NW) African upwelling system. Alongshore geostrophic flow related to large-scale circulation patterns associated with the influence of coastal topography is suggested to modulate the coastal divergence, and then the response of nutrient upwelling to wind forcing. In our simulation, this translates into a coastal upwelling of nitrate being significant in all regions but the Cape Blanc (CB) area. However, upwelling is found to be the dominant supplier of nitrate only in the northern Saharan Bank (NSB) and the Senegalo-Mauritanian (SM) regions. Elsewhere, nitrate supply is dominated by meridional advection, especially off Cape Blanc. Phytoplankton displays a similar behaviour with a supply by lateral advection which equals the net coastal phytoplankton growth in all coastal regions except the Senegalo-Mauritanian area. Noticeably, in the Cape Blanc area, the net coastal phytoplankton growth is mostly sustained by high levels of regenerated production exceeding new production by more than twofold, which is in agreement with the locally weak input of nitrate by coastal upwelling. Further offshore, the distribution of nutrients and phytoplankton is explained by the coastal circulation. Indeed, in the northern part of our domain (i.e. Saharan Bank), the coastal circulation is mainly alongshore, resulting in low offshore lateral advection of nutrients and phytoplankton. Conversely, lateral advection transports coastal nutrients and phytoplankton towards offshore areas in the latitudinal band off the Senegalo-Mauritanian region. Moreover, this latter offshore region benefits from transient southern intrusions of nutrient-rich waters from the Guinean upwelling.

  18. West African monsoon dynamics and precipitation: the competition between global SST warming and CO2 increase in CMIP5 idealized simulations

    Science.gov (United States)

    Gaetani, Marco; Flamant, Cyrille; Bastin, Sophie; Janicot, Serge; Lavaysse, Christophe; Hourdin, Frederic; Braconnot, Pascale; Bony, Sandrine

    2016-04-01

    Climate variability associated with the West African monsoon (WAM) has important environmental and socio-economic impacts in the region. However, state-of-the-art climate models still struggle in producing reliable climate predictions. An important cause of this low predictive skill is the sensitivity of climate models to different forcings. In this study, the mechanisms linking the WAM dynamics to the CO2 forcing are investigated, by comparing the effect of the CO2 direct radiative effect with its indirect effect mediated by the global sea surface warming. The July-to-September WAM variability is studied in climate simulations extracted from the Coupled Model Intercomparison Project Phase 5 archive, driven by prescribed sea surface temperature (SST). The individual roles of global SST warming and CO2 atmospheric concentration increase are investigated through idealized experiments simulating a 4 K warmer SST and a quadrupled CO2 concentration, respectively. Results show opposite and competing responses in the WAM dynamics and precipitation. A dry response (-0.6 mm/day) to the SST warming is simulated in the Sahel, with dryer conditions over western Sahel (-0.8 mm/day). Conversely, the CO2 increase produces wet conditions (+0.5 mm/day) in the Sahel, with the strongest response over central-eastern Sahel (+0.7 mm/day). The associated responses in the atmospheric dynamics are also analysed, showing that the SST warming affects the Sahelian precipitation through modifications in the global tropical atmospheric dynamics, reducing the importance of the regional drivers, while the CO2 increase reinforces the coupling between precipitation and regional dynamics. A general agreement in model responses demonstrates the robustness of the identified mechanisms linking the WAM dynamics to the CO2 direct and indirect forcing, and indicates that these primary mechanisms are captured by climate models. Results also suggest that the spread in future projections may be caused by

  19. Effects of waste water irrigation on soil properties and soil fauna of spinach fields in a West African urban vegetable production system.

    Science.gov (United States)

    Stenchly, Kathrin; Dao, Juliane; Lompo, Désiré Jean-Pascal; Buerkert, Andreas

    2017-03-01

    The usage of inadequately processed industrial waste water (WW) can lead to strong soil alkalinity and soil salinization of agricultural fields with negative consequences on soil properties and biota. Gypsum as a soil amendment to saline-sodic soils is widely used in agricultural fields to improve their soil physical, chemical and hence biological properties. This study aimed at analysing the effects of intensive WW irrigation on the structure and composition of soil-dwelling arthropods on spinach fields (Spinacia oleracea L.) in a West African urban vegetable production system. We used gypsum as a soil amendment with the potential to alleviate soil chemical stress resulting in a potentially positive impact on soil arthropods. A total of 32 plots were established that showed a gradient in soil pH ranging from slight to strong soil alkalinity and that were irrigated with WW (n = 12) or clean water (CW; n = 20), including eight plots into which gypsum was incorporated. Our study revealed a high tolerance of soil-dwelling arthropods for alkaline soils, but spinach fields with increased soil electrical conductivity (EC) showed a reduced abundance of Hymenoptera, Diptera and Auchenorrhyncha. Arthropod abundance was positively related to a dense spinach cover that in turn was not affected by WW irrigation or soil properties. Gypsum application reduced soil pH but increased soil EC. WW irrigation and related soil pH affected arthropod composition in the investigated spinach fields which may lead to negative effects on agronomical important arthropod groups such as pollinators and predators. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Factors Associated with Early Introduction of Formula and/or Solid, Semi-Solid or Soft Foods in Seven Francophone West African Countries

    Directory of Open Access Journals (Sweden)

    Abukari I. Issaka

    2015-01-01

    Full Text Available The aim of this study was to identify factors associated with early introduction of formula and/or solid, semi-solid or soft foods to infants aged three to five months in seven Francophone West African countries. The sources of data for the analyses were the most recent Demographic and Health Survey datasets of the seven countries, namely Benin (BDHS, 2012, Burkina Faso (BFDHS, 2010, Cote d’Ivoire (CIDHS, 2011–2012, Guinea (GDHS, 2012, Mali (MDHS, 2012–2013, Niger (NDHS, 2012 and Senegal (SDHS, 2010. The study used multiple logistic regression methods to analyse the factors associated with early introduction of complementary feeding using individual-, household- and community-level determinants. The sample was composed of 4158 infants aged between three and five months with: 671 from Benin, 811 from Burkina Faso, 362 from Cote d’Ivoire, 398 from Guinea, 519 from Mali, 767 from Niger and 630 from Senegal. Multiple analyses indicated that in three of the seven countries (Benin, Guinea and Senegal, infants who suffered illnesses, such as diarrhoea and acute respiratory infection, were significantly more likely to be introduced to formula and/or solid, semi-solid or soft foods between the age of three and five months. Other significant factors included infants who: were born in second to fourth position (Benin, whose mothers did not attend any antenatal clinics (Burkina Faso and Niger, were male (Cote d’Ivoire and Senegal, lived in an urban areas (Senegal, or were delivered by traditional birth attendants (Guinea, Niger and Senegal. Programmes to discourage early introduction of formula and/or solid, semi-solid or soft foods in these countries should target the most vulnerable segments of the population in order to improve exclusive breastfeeding practices and reduce infant mortality.

  1. West African monsoon dynamics and precipitation: the competition between global SST warming and CO2 increase in CMIP5 idealized simulations

    Science.gov (United States)

    Gaetani, Marco; Flamant, Cyrille; Bastin, Sophie; Janicot, Serge; Lavaysse, Christophe; Hourdin, Frederic; Braconnot, Pascale; Bony, Sandrine

    2017-02-01

    Climate variability associated with the West African monsoon (WAM) has important environmental and socio-economic impacts in the region. However, state-of-the-art climate models still struggle in producing reliable climate predictions. An important cause of this low predictive skill is the sensitivity of climate models to different forcings. In this study, the mechanisms linking the WAM dynamics to the CO2 forcing are investigated, by comparing the effect of the CO2 direct radiative effect with its indirect effect mediated by the global sea surface warming. The July-to-September WAM variability is studied in climate simulations extracted from the Coupled Model Intercomparison Project Phase 5 archive, driven by prescribed sea surface temperature (SST). The individual roles of global SST warming and CO2 atmospheric concentration increase are investigated through idealized experiments simulating a 4 K warmer SST and a quadrupled CO2 concentration, respectively. Results show opposite and competing responses in the WAM dynamics and precipitation. A dry response (-0.6 mm/day) to the SST warming is simulated in the Sahel, with dryer conditions over western Sahel (-0.8 mm/day). Conversely, the CO2 increase produces wet conditions (+0.5 mm/day) in the Sahel, with the strongest response over central-eastern Sahel (+0.7 mm/day). The associated responses in the atmospheric dynamics are also analysed, showing that the SST warming affects the Sahelian precipitation through modifications in the global tropical atmospheric dynamics, reducing the importance of the regional drivers, while the CO2 increase reinforces the coupling between precipitation and regional dynamics. A general agreement in model responses demonstrates the robustness of the identified mechanisms linking the WAM dynamics to the CO2 direct and indirect forcing, and indicates that these primary mechanisms are captured by climate models. Results also suggest that the spread in future projections may be caused by

  2. Calorific value of Prosopis africana and Balanites aegyptiaca wood: Relationships with tree growth, wood density and rainfall gradients in the West African Sahel

    Energy Technology Data Exchange (ETDEWEB)

    Montes, Carmen Sotelo; Weber, John C. [World Agroforestry Centre (ICRAF), Sahel Office, B.P. E 5118 Bamako (Mali); Silva, Dimas Agostinho da; Bolzon de Muniz, Graciela Ines [Universidade Federal do Parana (UFPR), Av. Lothario Meissner, 900, CEP.: 80270-170-Curitiba (Brazil); Garcia, Rosilei A. [Universidade Federal Rural do Rio de Janeiro (UFRRJ), Instituto de Florestas, Departamento de Produtos Florestais, BR 465, km 07, 23890-000, Seropedica, Rio de Janeiro (Brazil)

    2011-01-15

    Prosopis africana and Balanites aegyptiaca are native tree species in the West African Sahel and provide wood for fuel, construction and other essential products. A provenance/progeny test of each species was established at one relatively dry site in Niger, and evaluated at 13 years. Gross calorific value of the wood was determined for a random sample of trees in each test: gross CV and CVm{sup 3} = gross calorific value in MJ kg{sup -1} and MJ m{sup -3}, respectively. The major objectives were to determine if gross CV was positively correlated with wood density and tree growth, and if gross CV and/or CVm{sup 3} varied with rainfall gradients in the sample region. Provenances were grouped into a drier and more humid zone, and correlations were computed among all trees and separately in each zone. Results indicated that gross CV was not significantly correlated with density in either species. Gross CV was positively correlated with growth of P. africana (but not B. aegyptiaca) only in the drier zone. Gross CVm{sup 3} was positively correlated with growth of both species, and the correlations were stronger in the drier zone. Multiple regressions with provenance latitude, longitude and elevation indicated that provenance means for gross CV increased, in general, from the drier to the more humid zones. Regressions with gross CVm{sup 3} were not significant. Results are compared with earlier research reports from the provenance/progeny tests and with other tropical hardwood species; and practical implications are presented for tree improvement and conservation programs in the region. (author)

  3. Addressing diarrhea prevalence in the West African Middle Belt: social and geographic dimensions in a case study for Benin.

    Science.gov (United States)

    Pande, Saket; Keyzer, Michiel A; Arouna, Aminou; Sonneveld, Ben G J S

    2008-04-23

    In West Africa, the Northern Sahelian zone and the coastal areas are densely populated but the Middle Belt in between is in general sparsely settled. Predictions of climate change foresee more frequent drought in the north and more frequent flooding in the coastal areas, while conditions in the Middle Belt will remain moderate. Consequently, the Middle Belt might become a major area for immigration but there may be constraining factors as well, particularly with respect to water availability. As a case study, the paper looks into the capacity of the Middle Belt zone of Benin, known as the Oueme River Basin (ORB), to reduce diarrhea prevalence. In Benin it links to the Millennium Development Goals on child mortality and environmental sustainability that are currently farthest from realization. However, diarrhea prevalence is only in part due to lack of availability of drinking water from a safe source. Social factors such as hygienic practices and poor sanitation are also at play. Furthermore, we consider these factors to possess the properties of a local public good that suffers from under provision and requires collective action, as individual actions to prevent illness are bound to fail as long as others free ride. Combining data from the Demographic Health Survey with various spatial data sets for Benin, we apply mixed effect logit regression to arrive at a spatially explicit assessment of geographical and social determinants of diarrhea prevalence. Starting from an analysis of these factors separately at national level, we identify relevant proxies at household level, estimate a function with geo-referenced independent variables and apply it to evaluate the costs and impacts of improving access to good water in the basin. First, the study confirms the well established stylized fact on the causes of diarrhea that a household with access to clean water and with good hygienic practices will, irrespective of other conditions, not suffer diarrhea very often. Second

  4. Addressing diarrhea prevalence in the West African Middle Belt: social and geographic dimensions in a case study for Benin

    Directory of Open Access Journals (Sweden)

    Arouna Aminou

    2008-04-01

    Full Text Available Abstract Background In West Africa, the Northern Sahelian zone and the coastal areas are densely populated but the Middle Belt in between is in general sparsely settled. Predictions of climate change foresee more frequent drought in the north and more frequent flooding in the coastal areas, while conditions in the Middle Belt will remain moderate. Consequently, the Middle Belt might become a major area for immigration but there may be constraining factors as well, particularly with respect to water availability. As a case study, the paper looks into the capacity of the Middle Belt zone of Benin, known as the Oueme River Basin (ORB, to reduce diarrhea prevalence. In Benin it links to the Millennium Development Goals on child mortality and environmental sustainability that are currently farthest from realization. However, diarrhea prevalence is only in part due to lack of availability of drinking water from a safe source. Social factors such as hygienic practices and poor sanitation are also at play. Furthermore, we consider these factors to possess the properties of a local public good that suffers from under provision and requires collective action, as individual actions to prevent illness are bound to fail as long as others free ride. Methods Combining data from the Demographic Health Survey with various spatial data sets for Benin, we apply mixed effect logit regression to arrive at a spatially explicit assessment of geographical and social determinants of diarrhea prevalence. Starting from an analysis of these factors separately at national level, we identify relevant proxies at household level, estimate a function with geo-referenced independent variables and apply it to evaluate the costs and impacts of improving access to good water in the basin. Results First, the study confirms the well established stylized fact on the causes of diarrhea that a household with access to clean water and with good hygienic practices will, irrespective of

  5. Assessing the impact of climate change on water resources in a tropical West African catchment using an ensemble of CORDEX climate simulations (Dano, Burkina Faso)

    Science.gov (United States)

    Yira, Yacouba; Diekkrüger, Bernd; Steup, Gero; Yaovi Bossa, Aymar

    2016-04-01

    This study assesses the potential impact of climate change on water resources in the Dano catchment (Burkina Faso, West Africa). There is now essential consensus on the importance of performing multi (climate)-model assessments in order to estimate the response of the West African climate to global change. Taking advantage of the results of the COordinated Regional climate Downscaling Experiment (CORDEX-Africa) project, this study evaluates climate change impacts on water resources using an ensemble of six Regional Climate Models (RCMs) in a catchment that is potentially vulnerable to climate change and presents a low adaptive capacity. The ensemble of RCMs was first evaluated to get an estimate of the historical simulated rainfall for the catchment by comparing RCM-based simulated historical rainfall to the observed rainfall data provided by the National Meteorological Service (DGM). In general, the simulated historical rainfall agrees within some degree of variability with the observed rainfall in regard to the mean annual cycle of precipitation. However, significant biases such as a double-peaked rainy season as well as the timing of the rainy season were exhibited by individual RCMs. A statistical bias correction (Quantile mapping) was then applied to the RCM-based simulated daily rainfall for the overlapping period of 1971-2000. The results confirm the effectiveness of the applied bias correction method for rainfall. Temperature and bias corrected rainfall data from the ensemble of RCMs was used as input for the Water flow and balance Simulation Model (WaSiM) to simulate river discharge, soil moisture, evapotranspiration and groundwater depth. To take into account the concern of the potential alteration of the climate change signal due to bias correction, uncorrected climate data for a single RCM was also applied to the hydrological model. The simulated hydrological variables show a similar behavior under observed and bias corrected climate data for the

  6. Ebola exposure, illness experience, and Ebola antibody prevalence in international responders to the West African Ebola epidemic 2014-2016: A cross-sectional study.

    Directory of Open Access Journals (Sweden)

    Catherine F Houlihan

    2017-05-01

    Full Text Available Healthcare and other front-line workers are at particular risk of infection with Ebola virus (EBOV. Despite the large-scale deployment of international responders, few cases of Ebola virus disease have been diagnosed in this group. Since asymptomatic or pauci-symptomatic infection has been described, it is plausible that infections have occurred in healthcare workers but have escaped being diagnosed. We aimed to assess the prevalence of asymptomatic or pauci-symptomatic infection, and of exposure events, among returned responders to the West African Ebola epidemic 2014-2016.We used snowball sampling to identify responders who had returned to the UK or Ireland, and used an online consent and questionnaire to determine their exposure to EBOV and their experience of illness. Oral fluid collection devices were sent and returned by post, and samples were tested using an EBOV IgG capture assay that detects IgG to Ebola glycoprotein. Blood was collected from returnees with reactive samples for further testing. Unexposed UK controls were also recruited. In all, 300 individuals consented, of whom 268 (89.3% returned an oral fluid sample (OFS. The majority had worked in Sierra Leone in clinical, laboratory, research, and other roles. Fifty-three UK controls consented and provided samples using the same method. Of the returnees, 47 (17.5% reported that they had had a possible EBOV exposure. Based on their free-text descriptions, using a published risk assessment method, we classified 43 (16% as having had incidents with risk of Ebola transmission, including five intermediate-risk and one high-risk exposure. Of the returnees, 57 (21% reported a febrile or diarrhoeal illness in West Africa or within 1 mo of return, of whom 40 (70% were not tested at the time for EBOV infection. Of the 268 OFSs, 266 were unreactive. Two returnees, who did not experience an illness in West Africa or on return, had OFSs that were reactive on the EBOV IgG capture assay, with

  7. Construction and compression of Dwarf

    Institute of Scientific and Technical Information of China (English)

    XIANG Long-gang; FENG Yu-cai; GUI Hao

    2005-01-01

    There exists an inherent difficulty in the original algorithm for the construction of Dwarf, which prevents it from constructing true Dwarfs. We explained when and why it introduces suffix redundancies into the Dwarf structure. To solve this problem, we proposed a completely new algorithm called PID. It bottom-up computes partitions of a fact table, and inserts them into the Dwarf structure. Ifa partition is an MSV partition, coalesce its sub-Dwarf; otherwise create necessary nodes and cells. Our performance study showed that PID is efficient. For further condensing of Dwarf, we proposed Condensed Dwarf, a more compressed structure, combining the strength of Dwarf and Condensed Cube. By eliminating unnecessary stores of "ALL" cells from the Dwarf structure, Condensed Dwarf could effectively reduce the size of Dwarf, especially for Dwarfs of the real world, which was illustrated by our experiments. Its query processing is still simple and, only two minor modifications to PID are required for the construction of Condensed Dwarf.

  8. Briefing : West Africa and its oil

    NARCIS (Netherlands)

    Ellis, S.D.K.

    2003-01-01

    The US war on terrorism and preparations for war against Iraq have enormously increased the strategic value of West African oil reserves. This comes at a time when there have been massive new discoveries in offshore waters. This article focuses on the increased US interests in West African oil. It e

  9. Tropical convective systems life cycle characteristics from geostationary satellite and precipitating estimates derived from TRMM and ground weather radar observations for the West African and South American regions

    Science.gov (United States)

    Fiolleau, T.; Roca, R.; Angelis, F. C.; Viltard, N.

    2012-12-01

    In the tropics most of the rainfall comes in the form of individual storm events embedded in the synoptic circulations (e.g., monsoons). Understanding the rainfall and its variability hence requires to document these highly contributing tropical convective systems (MCS). Our knowledge of the MCS life cycle, from a physical point of view mainly arises from individual observational campaigns heavily based on ground radar observations. While this large part of observations enabled the creation of conceptual models of MCS life cycle, it nevertheless does not reach any statistically significant integrated perspective yet. To overcome this limitation, a composite technique, that will serve as a Day-1 algorithm for the Megha-Tropiques mission, is considered in this study. this method is based on a collocation in space and time of the level-2 rainfall estimates (BRAIN) derived from the TMI radiometer onboard TRMM with the cloud systems identified by a new MCS tracking algorithm called TOOCAN and based on a 3-dimensional segmentation (image + time) of the geostationary IR imagery. To complete this study, a similar method is also developed collocating the cloud systems with the precipitating features derived from the ground weather radar which has been deployed during the CHUVA campaign over several Brazilian regions from 2010 up to now. A comparison of the MCSs life cycle is then performed for the 2010-2012 summer seasons over the West African, and South American regions. On the whole region of study, the results show that the temporal evolution of the cold cloud shield associated to MCSs describes a symmetry between the growth and the decay phases. It is also shown that the parameters of the conceptual model of MCSs are strongly correlated, reducing thereby the problem to a single degree of freedom. At the system scale, over both land and oceanic regions, rainfall is described by an increase at the beginning (the first third) of the life cycle and then smoothly decreases

  10. Early upper digestive tract side effects of zidovudine with tenofovir plus emtricitabine in West African adults with high CD4 counts

    Directory of Open Access Journals (Sweden)

    Eric Ouattara

    2013-04-01

    Full Text Available Introduction: Tenofovir (TDF with emtricitabine (FTC and zidovudine (ZDV is a recognized alternate first-line antiretroviral (ART regimen for patients who cannot start treatment with non-nucleoside reverse transcriptase inhibitors (NNRTIs. Clinical studies comparing TDF+FTC+ZDV to other regimens are lacking. Methods: Participants in a trial of early ART in Côte d'Ivoire (Temprano ANRS 12136 started treatment with TDF/FTC plus either efavirenz (EFV or ZDV (HIV-1+2 dually infected patients and women refusing contraception or previously treated with nevirapine. We compared rates of upper digestive serious adverse events (sAEs between TDF/FTC+EFV and TDF/FTC+ZDV patients during the first six months of treatment. sAEs were defined as either grade 3–4 AEs or persistent grade 1–2 AEs leading to drug discontinuation. Results: A total of 197 patients (76% women, median CD4 count 395/mm3 started therapy with TDF/FTC, 126 with EFV and 71 with ZDV. During the first six months of ART, 94 patients had digestive AEs (nausea/vomiting of any grade (EFV 36/126, 29%; ZDV 58/71, 82%, p<0.0001, including 20 sAEs (EFV 3/126, 5%; ZDV 17/71, 24%, p<0.0001. In-patients on TDF/FTC+ZDV with digestive AEs, the median time to the first symptom was two days (IQR: 1–4. Plasma ZDV (Cmax distributions and pill ZDV dosages were normal. Patients with digestive AEs had higher haemoglobin levels and tended to have higher body mass indices and more frequent past histories of cotrimoxazole (CTX prophylaxis. Conclusions: We observed an unexpectedly high rate of digestive sAEs in West African adults, mostly women, who started a 3-nuc ART with TDF/FTC+ZDV in Côte d'Ivoire. These adults were participating in a trial of early ART and had much higher CD4 counts than those who currently routinely start ART in sub-Saharan Africa. They all received CTX concomitantly with ZDV. We suggest that further early prescriptions of TDF+XTC+ZDV should be carefully monitored and that whenever

  11. Salinity-related variation in gene expression in wild populations of the black-chinned tilapia from various West African coastal marine, estuarine and freshwater habitats

    Science.gov (United States)

    Tine, Mbaye; McKenzie, David J.; Bonhomme, François; Durand, Jean-Dominique

    2011-01-01

    This study measured the relative expression of the genes coding for Na +, K +-ATPase 1α(NAKA), voltage-dependent anion channel (VDAC), cytochrome c oxidase-1 (COX), and NADH dehydrogenase (NDH), in gills of six wild populations of a West African tilapia species, acclimatised to a range of seasonal (rainy or dry) salinities in coastal, estuarine and freshwater sites. Previous laboratory experiments have demonstrated that these genes, involved in active ion transport, oxidative phosphorylation, and intra-cellular ATP transport, are relatively over-expressed in gill tissues of this species acclimated to high salinity. Positive correlations between relative expression and ambient salinity were found for all genes in the wild populations (Spearman rank correlation, p < 0.05), although for some genes these were only significant in either the rainy season or dry season. Most significantly, however, relative expression was positively correlated amongst the four genes, indicating that they are functionally interrelated in adaptation of Sarotherodon melanotheron to salinity variations in its natural environment. In the rainy season, when salinity was unstable and ranged between zero and 37 psu across the sites, overall mean expression of the genes was higher than in the dry season, which may have reflected more variable particularly sudden fluctuations in salinity and poorer overall water quality. In the dry season, when the salinity is more stable but ranged between zero and 100 psu across the sites, NAKA, NDH and VDAC expression revealed U-shaped relationships with lowest relative expression at salinities approaching seawater, between 25 and 45 psu. Although it is not simple to establish direct relationship between gene expression levels and energy requirement for osmoregulation, these results may indicate that costs of adaptation to salinity are lowest in seawater, the natural environment of this species. While S. melanotheron can colonise environments with extremely

  12. Increasing nutrient use efficiency in West-African agriculture: the impact of micro-topography on nutrient leaching from cattle and sheep manure

    NARCIS (Netherlands)

    Brouwer, J.; Powell, J.M.

    1998-01-01

    In African agriculture, availability of nutrients for crop production can be increased using external inputs such as mineral fertiliser. However, for many African farmers the large scale use of external inputs will remain beyond reach for the foreseeable future. There is, therefore, also a need for

  13. WEST AFRICAN JOURNAL OF MEDICINE

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    clinical improvement was sustained on .... confirmed from studies are referred to as ... transcutaneous oxygen saturation, a ... panniculitis, fat necrosis and vascular ... and mortality associated with calci- ... (ucMGP) as a biomarker for cardio-.

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    Prevention of Dental Caries: Knowledge, Practice and Opinion of. Paediatricians in Lagos ... health education programme for paediatricians, referral of related cases to .... following were the inclusion criteria: specialisation in .... (AAP) in 2003 released a policy calling .... centers in Kubeng Kerian, Malaysia: A preliminary ...

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    We have tried various modes of treatment for this ... hencc advances and treatment modalities available only to .... Figure l: Ahhc Internal Medicine Unit: Pain Severity in Sickle Cell Disease. Pain is scored ... nature 01' sickle cell disease in the.

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    Departments of †Obstetrics and Gynaecology and Department of Medicine, Royal Alexandra Hospital Paisley and ‡Obstetrics and ... Current treatment and foetal ..... prednisolone has been tried.48, ... chronic nature of the disease and the fact.

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    METHODS: Chorionic villi obtained from 10 women in transabdominal ... manual dissection of visible blood clots. The aim is to ... demonstrate the application of boiling- based method of .... automated Rapid Method of Extracting. Genomic DNA ...

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    en place le premier système médical d'urgences au Nigeria en 2001. .... Ambulance Training School and Israel in ..... choices. Health care establishments should be categorized into levels of injury care ... cultural determinants of an emergency.

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    health problem in developing countries. ... newly diagnosed and managed in the Hospital over a five-year ... missed abortion or for renioval ofretained placenta .... government policy that wi11 enable ... theràpeutic equipment is also' necessàry.

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    College Hospital, Ibadan, Oyo State, Nigeria. §College of ... Characteristics of Inflammatory Bowel Disease in Three Tertiary Health. Centers in ..... of relapses, these patients missed schools or work frequently. DISCUSSION ... personnel with appropriate equipment to make such .... should be made by the government to.

  1. WEST AFRICAN JOURNAL OF MEDICINE

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    systematic random sampling procedure over a four-week period, ... des standards plus élevés de soins. ... technological advances, shifting ... effect of 2 to limit effect of clustering and ..... Lab. Personnel. Figure 2: Attitude of Health Workers toward Clients. Table 5: Views of Clients on ..... preferences in the measurement of.

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    increasing worldwide, while the outcomes remain poor and treatment cost high. ... diagnosis by assessing utility of estimated glomerular filtration rate (eGFR) in Nigerians and .... hypertensive kidney disease accounted for 37.5%, chronic ...

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    intermittent fever of 4days duration and worsened dysuria. ... some other unknown factors protect. Nigerians ... origin. Asinobi et al reported sustained hypertension in 4.8 % of boys with PUV.12 ... and Lorenzo review of 10 cases of PUV.13.

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    Dyslipidaemia among Nigerian Oil Workers with Type 2 Diabetes Mellitus. Dyslipidémie chez les ... several reports on lipid profile in type 2 DM among Nigerians. (non-oil workers) in ..... Diabetes Mellitus and its Complication. Report of a WHO ...

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    Effectiveness of Interventions to Reduce Coronary Heart Disease Risk. Efficacité des Interventions ... as dietary and lifestyle modifications on some risk factors of. CHD were studied .... mean values for age, fasting blood glucose, cholesterol ...

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    Presence of Mycoplasma and Ureaplasma Species in theVagina of Women of Reproductive Age. .... expensive and time-consuming nature of its isolation ... media. Suspected colonies were seen with. "fried-egg" appearance when examined.

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    significantly higher IAUGC than the fruits (orange, pineapple, mango, pawpaw .... eight min at 12 500g at room temperature. Plasma was .... effect of the ripeness of banana in increasing its ... orange juice was similar to that of whole oranges.

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    in Parkinson's Disease Patients at the Lagos University Teaching Hospital .... and other distant states within Nigeria. ... estimated from samples drawn after an overnight fast (> 12 hours). The blood ... level ± SD for the cases on low dose ... mainly to variations in the cut-off value .... evaluated (e.g. folate and vitamin B12.

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    Anthropometric Predictors of Elevated Prostate Specific Antigen among. Rural and ... BACKGROUND: Obesity has been assoeiated with incidence ... Hospital, Warri, Delta State, Nigeria; Ëlioward University Cancer Center, Washington DC.

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    and Department of Surgery, College of Medicine, University of Ibadan, Ibadan. ' Correspondence: ... The sensitivity and specificity of this antibody for the ... 4) The effect of disease progression was ..... relevance in human breast cancer. British.

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    size and spleen size in children with sickle cell disease and the factors that influence them. METHODS: This was a retrospective study of children with ..... America is such that recurrent infarction ... observed that the frequency of bone pain.

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    Aripiprazole appears effective in its treatment. WAJM 2011; ... épileptiques réfractaires est difficile à éviter pour les médecins .... could be a good alternative to flunarazine. She started the drug in ..... Burris KD, Molski TF, Xu C Ryan E,. Tottori K ...

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    METHODS: A bacteriological survey of all eye surgical procedures between September ... hands of surgeons and conjunctivae of patients. Running water .... latex gloves, and face masks were available in both .... nurses association. Revised ...

  14. WEST AFRICAN JOURNAL OF MEDICINE

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    were studies of whom 372 presented with alarm symptoms. ... benign diseases of peptic ulcer, gastric ulcer and gastritis showed strong similarity in ... These guidelines require the .... Table 1: Age and Sex of Patients in Relation to Indications for Endoscopy and the. Commonest ..... results of biopsies could help define the.

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    BACKGROUND: Maternal death and disability remain significant problems in ... delivery, length of labour, difficult delivery of placenta, lacerations .... Review Board (NYIT IRB) and questionnaire were ... women who fit the inclusion criteria from.

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    †Nigerian Institute of Medical Research, Lagos, Nigeria, ‡Federal Medical Center Owerri, Imo State, Eastern Nigeria, ... à améliorer recherche des cas, en particulier chez hard-to-atteindre les .... questions for participants on their health,.

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    avec une épilepsie (PVE) et leurs soignants dans la recherche de traitement. SCHÉMA ... sur la maladie obtenues de sources surtout non médicales. WAJM 2013; 32(1): 26–30. .... questions during all the phases of the survey. Statistical ...

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    Yield is improved by adherence to the ASGE guidelines but its accuracy as a screening tool for OGD at. Korle Bu Teaching Hospital is too low to recommend it for adoption. ... Patients for elective therapeutic OGD, less than .... wall obesity.

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    Twin Reversed Arterial Perfusion Sequence in a Triplet Natural Pregnancy: Case Report from ... delivery at the labour ward four years ago in the same hospital but the underlying .... pump twin for signs of cardiac failure and facilitate delivery ...

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    where iodine deficiency have been corrected the histological pattern of goitre ... inadequate.Near total thyroidectomy is recommended as the .... regular intake of iodized salt was sought from all the ..... tissue as much as is practically possible.

  1. WEST AFRICAN JOURNAL OF MEDICINE

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    Department of †Paediatrics, ‡Community Medicine and Primary Care, Olabisi Onabanjo University, Sagamu, Nigeria. *Correspondence: Dr. ... Nutritional Status of Semi-Urban Nigerian School Children using the 2007 ... ORIGINAL ARTICLE ...

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    Department of Oral and Maxillofacial Surgery University of Benin Teaching Hospital, Benin City, Edo ... RESULTS: Acute dental abscess, trauma, bleeding and pain in ... treatment when indicated. ... during implant procedure27 or third molar.

  3. Juvenile Ultracool Dwarfs

    CERN Document Server

    Rice, Emily L; Cruz, Kelle; Barman, Travis; Looper, Dagny; Malo, Lison; Mamajek, Eric E; Metchev, Stanimir; Shkolnik, Evgenya L

    2011-01-01

    Juvenile ultracool dwarfs are late spectral type objects (later than ~M6) with ages between 10 Myr and several 100 Myr. Their age-related properties lie intermediate between very low mass objects in nearby star-forming regions (ages 1-5 Myr) and field stars and brown dwarfs that are members of the disk population (ages 1-5 Gyr). Kinematic associations of nearby young stars with ages from ~10-100 Myr provide sources for juvenile ultracool dwarfs. The lowest mass confirmed members of these groups are late-M dwarfs. Several apparently young L dwarfs and a few T dwarfs are known, but they have not been kinematically associated with any groups. Normalizing the field IMF to the high mass population of these groups suggests that more low mass (mainly late-M and possibly L dwarf) members have yet to be found. The lowest mass members of these groups, along with low mass companions to known young stars, provide benchmark objects with which spectroscopic age indicators for juvenile ultracool dwarfs can be calibrated and...

  4. Dwarf-Galaxy Cosmology

    CERN Document Server

    Schulte-Ladbeck, Regina; Brinks, Elias; Kravtsov, Andrey

    2010-01-01

    Dwarf galaxies provide opportunities for drawing inferences about the processes in the early universe by observing our "cosmological backyard"-the Local Group and its vicinity. This special issue of the open-access journal Advances in Astronomy is a snapshot of the current state of the art of dwarf-galaxy cosmology.

  5. Database for West Africa

    African Journals Online (AJOL)

    Such database can prove an invaluable source of information for a wide range of agricultural and ... national soil classification systems around the world ... West African Journal of Appl ied Ecology, vol. .... SDB FAO-ISRIC English, French, Spanish Morphology and analytical ..... Furthermore, it will enhance the state of soil.

  6. Coupled marine productivity and salinity and West African monsoon variability over the last 30,000 years in the eastern equatorial Atlantic Ocean

    Science.gov (United States)

    Marret, F.; Kim, S.-Y.; Scourse, J.; Kennedy, H.

    2009-04-01

    Marine cores collected off west equatorial Africa have highlighted transfer of terrigenous material in the close ocean that have had a deep influence on the marine productivity for the last 30,000 years. The strength of the West African Monsoon has varied though time, from weak during glacial periods to strong during interglacials. In consequence, the amount of precipitation on the continent had drastic effect on the vegetation cover and soil erosion. Studies of marine cores have enabled the observation of changes in vegetation cover, from extended equatorial rainforest to expansion of savannahs. In association with open grassland association, soil is open to erosion, although precipitation is less; conversely, during periods of extended rainforest in a context of strong monsoon, soil erosion is minimised to the presence of trees. In both cases, terrigenous material is flushed out to the adjacent marine domain and has a profound influence on the marine biota. Three marine cores were studied from a north south transect, from Cameroon to Angola (off Sanaga, off Ogouée, and off Congo rivers), for their palynomorph contents. All cores contain a robust chronology based on radiocarbon dates and two have stable isotope data, allowing comparison. Dinoflagellate cysts were studied for retracing sea-surface conditions such as temperature, salinity and productivity whereas pollen were used to assess changes in the vegetation on the close continent for the last 30,000 years (1). A number of pollen records from terrestrial sequences from equatorial central Africa document the dynamics of the lowland rainforest and savannah in relation to climatic changes during the Holocene. Prior to the Holocene, continental records are scarce in this vast region and/or only allow reconstruction of the local vegetation. In our records, terrestrial proxies (pollen, spores, and charred grass cuticles) signal changes in the expansion/regression of the lowland rainforest which we relate to the

  7. Irradiated brown dwarfs

    CERN Document Server

    Casewell, S L; Lawrie, K A; Maxted, P F L; Dobbie, P D; Napiwotzki, R

    2014-01-01

    We have observed the post common envelope binary WD0137-349 in the near infrared $J$, $H$ and $K$ bands and have determined that the photometry varies on the system period (116 min). The amplitude of the variability increases with increasing wavelength, indicating that the brown dwarf in the system is likely being irradiated by its 16500 K white dwarf companion. The effect of the (primarily) UV irradiation on the brown dwarf atmosphere is unknown, but it is possible that stratospheric hazes are formed. It is also possible that the brown dwarf (an L-T transition object) itself is variable due to patchy cloud cover. Both these scenarios are discussed, and suggestions for further study are made.

  8. Dwarfs in ancient Egypt.

    Science.gov (United States)

    Kozma, Chahira

    2006-02-15

    Ancient Egypt was one of the most advanced and productive civilizations in antiquity, spanning 3000 years before the "Christian" era. Ancient Egyptians built colossal temples and magnificent tombs to honor their gods and religious leaders. Their hieroglyphic language, system of organization, and recording of events give contemporary researchers insights into their daily activities. Based on the record left by their art, the ancient Egyptians documented the presence of dwarfs in almost every facet of life. Due to the hot dry climate and natural and artificial mummification, Egypt is a major source of information on achondroplasia in the old world. The remains of dwarfs are abundant and include complete and partial skeletons. Dwarfs were employed as personal attendants, animal tenders, jewelers, and entertainers. Several high-ranking dwarfs especially from the Old Kingdom (2700-2190 BCE) achieved important status and had lavish burial places close to the pyramids. Their costly tombs in the royal cemeteries and the inscriptions on their statutes indicate their high-ranking position in Egyptian society and their close relation to the king. Some of them were Seneb, Pereniankh, Khnumhotpe, and Djeder. There were at least two dwarf gods, Ptah and Bes. The god Ptah was associated with regeneration and rejuvenation. The god Bes was a protector of sexuality, childbirth, women, and children. He was a favored deity particularly during the Greco-Roman period. His temple was recently excavated in the Baharia oasis in the middle of Egypt. The burial sites and artistic sources provide glimpses of the positions of dwarfs in daily life in ancient Egypt. Dwarfs were accepted in ancient Egypt; their recorded daily activities suggest assimilation into daily life, and their disorder was not shown as a physical handicap. Wisdom writings and moral teachings in ancient Egypt commanded respect for dwarfs and other individuals with disabilities.

  9. Effect of Age at Antiretroviral Therapy Initiation on Catch-up Growth Within the First 24 Months Among HIV-infected Children in the IeDEA West African Pediatric Cohort

    DEFF Research Database (Denmark)

    Jesson, Julie; Koumakpaï, Sikiratou; Diagne, Ndeye R

    2015-01-01

    BACKGROUND: We described malnutrition and the effect of age at antiretroviral therapy (ART) initiation on catch-up growth over 24 months among HIV-infected children enrolled in the International epidemiologic Databases to Evaluate Aids West African paediatric cohort. METHODS: Malnutrition...... 2001 and 2012, 2004 HIV-infected children ART initiation, 51% were underweight, 48% were stunted and 33% were wasted. The 24-month adjusted estimates for catch-up growth were 69% [95% confidence interval (CI): 57-80], 61% (95% CI: 47-70) and 90% (95% CI: 76......-95) for WAZ, HAZ and WHZ/BAZ, respectively. Adjusted catch-up growth was more likely for children ART initiation compared with children ≥5 years for WAZ, HAZ (P children is an additional burden that has to be urgently...

  10. Genetic diversity and difference within and between bitter and sweet African bush mango trees (Irvingia spp., Irvingiaceae) in West and Central Africa

    NARCIS (Netherlands)

    Vihotogbé, R.; Berg, van den R.G.; Missinhoun, A.A.; Sinsin, B.; Sosef, M.S.M.

    2015-01-01

    Economically important food tree species in sub-Saharan Africa should be domesticated to enhance their production within agro forestry systems. The African bush mango trees (Irvingia species) are highly preserved and integrated in agro forestry systems in tropical Africa. However, the taxonomic

  11. Increasing nutrient use efficiency through improved feeding and manure manegement in urban and peri-urban livestock units of a West African city: A scenario analysis

    NARCIS (Netherlands)

    Diogo, V.; Schlecht, E.; Buerkert, A.; Rufino, M.C.; Wijk, van M.T.

    2013-01-01

    In many African cities urban and peri-urban agriculture (UPA) plays a major role in creating jobs and contributing to food security. However, many small-scale UPA systems are characterised by excessive nutrient inputs to the livestock unit and poor handling of manure. To assess the impact of improve

  12. El auge y el declive de las culturas del África Occidental (o Atlántica / The Rise and Fall of West (or Atlantic African Cultures

    Directory of Open Access Journals (Sweden)

    Justo Bolekia Boleká

    2014-12-01

    Full Text Available Cada uno de los pueblos negro-africanos presenta un perfil cultural que le hace ser singular y esencialmente semejante a otros, como parte importante de un todo cultural, algunas veces difícil de determinar explícitamente.  Los procesos que definían a los negro-africanos experimentaron una acelerada transformación debido al choque cultural que vivieron durante casi cinco siglos de su historia. Este choque debilitó sus estructuras culturales, creando Estados con lenguas extranjeras oficiales,  religiones de importación, escuelas desvernacularizadas, etc., y desplazando los tradicionales sistemas sociopolíticos negro-africanos. Esta fuerte aculturación del África negra se ve fortalecida por la dominancia de la cultura exógena, que impide la reconfiguración etnocultural de sus habitantes y sociedades. Este es el gran reto de su futuro: fortalecer sus diversidades y enseñar a sus habitantes a aprender a ser africanos.Each black African peoples presents a cultural identity that makes it unique and essentially similar to others, as an important element of a whole culture, sometimes difficult to determine. The processes that defined black Africans experienced a accelerated transformation due to the culture shock lived for five centuries of their history. This shock weakened their cultural structures, creating states with official foreign languages, imported religions, acculturated schools, etc., and replacing the traditional black-African socio-political systems with Western models. This strong acculturation of black Africa was strengthened by the exogenous culture dominance; avoiding the ethno-cultural reconfiguration of its people and societies. This is the great challenge of their future: to strengthen African diversities and to teach the people to learn to be Africans.

  13. A comparison between legume technologies and fallow, and their effects on maize and soil traits, in two distinct environments of the West African savannah

    NARCIS (Netherlands)

    Franke, A.C.; Laberge, G.; Oyewole, B.D.; Schulz, S.; Tobe, O.

    2008-01-01

    Legume¿maize rotation and maize nitrogen (N)-response trials were carried out simultaneously from 1998 to 2004 in two distinct agro-ecological environments of West Africa: the humid derived savannah (Ibadan) and the drier northern Guinea savannah (Zaria). In the N-response trial, maize was grown

  14. Indigenous West African plants as novel sources of polysaccharide degrading enzymes: application in the reduction of the viscosity of cereal porridges

    NARCIS (Netherlands)

    Dicko, M.H.; Hilhorst, M.H.; Traore, A.S.

    2005-01-01

    Ethnobotanical and biochemical surveys revealed that some local plants from West Africa are novel sources of polysaccharide degrading enzymes such as amylases and glucanases. The study shows that these enzymes could be used for various biotechnological applications. In a crude extract of Curculigo p

  15. Raptors in changing West African savannas : the impact of anthropogenic land transformation on populations of Palearctic and Afrotropical raptors in northern Cameroon

    NARCIS (Netherlands)

    Buij, Ralph

    2013-01-01

    Raptors in West Africa’s savannas have strongly declined the past four decades and many species now survive only in a few pockets of intact habitat, mostly inside protected areas, while some species are on the brink of extinction. Little is known about the processes that sustain raptor populations w

  16. Indigenous West African plants as novel sources of polysaccharide degrading enzymes: application in the reduction of the viscosity of cereal porridges

    NARCIS (Netherlands)

    Dicko, M.H.; Hilhorst, M.H.; Traore, A.S.

    2005-01-01

    Ethnobotanical and biochemical surveys revealed that some local plants from West Africa are novel sources of polysaccharide degrading enzymes such as amylases and glucanases. The study shows that these enzymes could be used for various biotechnological applications. In a crude extract of Curculigo

  17. White Dwarf Mass Distribution

    CERN Document Server

    Kepler, S O; Romero, Alejandra Daniela; Ourique, Gustavo; Pelisoli, Ingrid

    2016-01-01

    We present the mass distribution for all S/N > 15 pure DA white dwarfs detected in the Sloan Digital Sky Survey up to Data Release 12, fitted with Koester models for ML2/alpha=0.8, and with Teff > 10 000 K, and for DBs with S/N >10, fitted with ML2/alpha=1.25, for Teff > 16 000 K. These mass distributions are for log g > 6.5 stars, i.e., excluding the Extremely Low Mass white dwarfs. We also present the mass distributions corrected by volume with the 1/Vmax approach, for stars brighter than g=19. Both distributions have a maximum at M=0.624 Msun but very distinct shapes. From the estimated z-distances, we deduce a disk scale height of 300 pc. We also present 10 probable halo white dwarfs, from their galactic U, V, W velocities.

  18. Nitrogen Oxide biogenic emissions from soils: impact on NOx and ozone formation in West Africa during AMMA (African Monsoon Multidisciplinary Analysis)

    OpenAIRE

    2007-01-01

    International audience; Nitrogen Oxide biogenic emissions from soils are driven by soil and environmental parameters. The relationship between these parameters and NO fluxes is highly non linear. A new algorithm, based on a neural network calculation, is used to reproduce the NO biogenic emissions in West Africa during the AMMA campaign, in August 2006. It has been coupled in the surface scheme of a coupled chemistry dynamics model to estimate the impact of the NO emissions on NOx and O3 form...

  19. Axions and White Dwarfs

    CERN Document Server

    Isern, J; Garcia-Berro, E; Salaris, M; Torres, S

    2010-01-01

    White dwarfs are almost completely degenerate objects that cannot obtain energy from the thermonuclear sources and their evolution is just a gravothermal process of cooling. The simplicity of these objects, the fact that the physical inputs necessary to understand them are well identified, although not always well understood, and the impressive observational background about white dwarfs make them the most well studied Galactic population. These characteristics allow to use them as laboratories to test new ideas of physics. In this contribution we discuss the robustness of the method and its application to the axion case.

  20. Region 2 of 8q24 is associated with the risk of aggressive prostate cancer in Caribbean men of African descent from Guadeloupe (French West Indies)

    Institute of Scientific and Technical Information of China (English)

    Geraldine CancelTassin; Marc Romana; Cecile Gaffory; Pascal Blanchet; Olivier Cussenot; Luc Multigner

    2015-01-01

    Multiple regions of the genome have been associated with the risk of prostate cancer in Caucasians, particularly including several polymorphisms located at 8q24. Region 2 of 8q24 has been repeatedly found to be associated with the risk of prostate cancer among men of African descent, although one study performed in the Caribbean island of Jamaica did not report this finding. In this study, the single nucleotide polymorphism rs16901979, located in region 2 of 8q24, was genotyped in 498 cases of histologically confirmed prostate cancer and 541 controls from the French Caribbean islands of Guadeloupe, where the population is largely of African descent. The AA genotype and the A allele at rs16901979 were associated with elevated risks of prostate cancer (odds ratios [ORs] = 1.84, 95% confidence interval [95% CI] = 1.26–2.69, P = 0.002 and OR = 1.36, 95% CI = 1.13–1.64, P = 0.001, respectively). Following stratification of the patients by disease aggressiveness, as defined by the Gleason score, the pooled genotypes AC + AA were associated with a higher risk of a Gleason score ≥7 at diagnosis (OR = 1.79, 95% CI = 1.17–2.73, P = 0.007). In summary, the A allele at rs16901979 was associated with the risk of prostate cancer in the Caribbean population of Guadeloupe, confirming its involvement in populations of African descent. Moreover, our study provides the first evidence of an association between this variant and the risk of aggressive prostate cancer.

  1. White Dwarfs in Globular Clusters

    CERN Document Server

    Möhler, S

    2008-01-01

    We review empirical and theoretical findings concerning white dwarfs in Galactic globular clusters. Since their detection is a critical issue we describe in detail the various efforts to find white dwarfs in globular clusters. We then outline the advantages of using cluster white dwarfs to investigate the formation and evolution of white dwarfs and concentrate on evolutionary channels that appear to be unique to globular clusters. We also discuss the usefulness of globular cluster white dwarfs to provide independent information on the distances and ages of globular clusters, information that is very important far beyond the immediate field of white dwarf research. Finally, we mention possible future avenues concerning globular cluster white dwarfs, like the study of strange quark matter or plasma neutrinos.

  2. HLA-E coding and 3' untranslated region variability determined by next-generation sequencing in two West-African population samples.

    Science.gov (United States)

    Castelli, Erick C; Mendes-Junior, Celso T; Sabbagh, Audrey; Porto, Iane O P; Garcia, André; Ramalho, Jaqueline; Lima, Thálitta H A; Massaro, Juliana D; Dias, Fabrício C; Collares, Cristhianna V A; Jamonneau, Vincent; Bucheton, Bruno; Camara, Mamadou; Donadi, Eduardo A

    2015-12-01

    HLA-E is a non-classical Human Leucocyte Antigen class I gene with immunomodulatory properties. Whereas HLA-E expression usually occurs at low levels, it is widely distributed amongst human tissues, has the ability to bind self and non-self antigens and to interact with NK cells and T lymphocytes, being important for immunosurveillance and also for fighting against infections. HLA-E is usually the most conserved locus among all class I genes. However, most of the previous studies evaluating HLA-E variability sequenced only a few exons or genotyped known polymorphisms. Here we report a strategy to evaluate HLA-E variability by next-generation sequencing (NGS) that might be used to other HLA loci and present the HLA-E haplotype diversity considering the segment encoding the entire HLA-E mRNA (including 5'UTR, introns and the 3'UTR) in two African population samples, Susu from Guinea-Conakry and Lobi from Burkina Faso. Our results indicate that (a) the HLA-E gene is indeed conserved, encoding mainly two different protein molecules; (b) Africans do present several unknown HLA-E alleles presenting synonymous mutations; (c) the HLA-E 3'UTR is quite polymorphic and (d) haplotypes in the HLA-E 3'UTR are in close association with HLA-E coding alleles. NGS has proved to be an important tool on data generation for future studies evaluating variability in non-classical MHC genes.

  3. Eastern Spruce Dwarf Mistletoe

    Science.gov (United States)

    F. Baker; Joseph O' Brien; R. Mathiasen; Mike Ostry

    2006-01-01

    Eastern spruce dwarf mistletoe (Arceuthobium pusillum) is a parasitic flowering plant that causes the most serious disease of black spruce (Picea mariana) throughout its range. The parasite occurs in the Canadian provinces of Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland; in the Lake States of Minnesota,...

  4. Lodgepole Pine Dwarf Mistletoe

    Science.gov (United States)

    Frank G. Hawksworth; Oscar J. Dooling

    1984-01-01

    Lodgepole pine dwarf mistletoe (Arceuthobium americanum Nutt. ex Engelm.) is a native, parasitic, seed plant that occurs essentially throughout the range of lodgepole pine in North America. It is the most damaging disease agent in lodgepole pine, causing severe growth loss and increased tree mortality. Surveys in the Rocky Mountains show that the parasite is found in...

  5. A first-language-first multilingual model to meet the quality imperative in formal basic education in three `francophone' West African countries

    Science.gov (United States)

    Nikièma, Norbert

    2011-12-01

    This paper documents the new trend towards a first-language-first multilingual model in formal education in three former French colonies of West Africa, namely Burkina Faso, Mali and Niger. It compares the sociolinguistic situations, the conditions of the development of multilingual education and the achievements of mother-tongue-medium education in all three countries. The evidence is that, contrary to common discourse in francophonie, a strong first-language-first model in formal education is the best guarantee of a good mastery of French and, more generally, of quality education in francophone countries.

  6. The importance of baobab (Adansonia digitata L.) in rural West African subsistence--suggestion of a cautionary approach to international market export of baobab fruits.

    Science.gov (United States)

    Buchmann, Christine; Prehsler, Sarah; Hartl, Anna; Vogl, Christian R

    2010-01-01

    The European Commission recently authorized the import of baobab (Adansonia digitata L.) fruit pulp as a novel food. In rural West Africa the multipurpose baobab is used extensively for subsistence. Three hundred traditional uses of the baobab were documented in Benin, Mali, and Senegal across 11 ethnic groups and 4 agroecological zones. Baobab fruits and leaves are consumed throughout the year. The export of baobab fruits could negatively influence livelihoods, including reduced nutritional intake, change of power relations, and access rights. Capacity building and certification could encourage a sustainable and ethical trade of baobab fruits without neglecting baobab use in subsistence.

  7. POTENTIAL EFFECTS OF LIBERALIZATION OF THE WORLD AGRICULTURAL TRADE FOR THE AGRI-FOOD SECTOR OF ECONOMIC COMMUNITY OF WEST AFRICAN STATES (ECOWAS

    Directory of Open Access Journals (Sweden)

    Karolina Pawlak

    2014-06-01

    Full Text Available The state of agri-food trade in two selected trade blocs from the African region was presented in the paper. Moreover, the possibilities of development of trade, production, demand and prices in agri-food sector of ECOWAS countries in view of changes caused by further liberalization of the world agricultural trade were discussed. A general equilibrium model Global Trade Analysis Project was used in the research to make the projections. The results of the analysis showed that a greater degree of liberalization of the world agricultural trade could cause an increase in the value of export and import of certain plant origin products, as well as may contribute to the decline in production and prices for these products. 

  8. Logical Features of African History of Colonial Period Compiled by the West%西方编纂殖民时期非洲史之逻辑特征

    Institute of Scientific and Technical Information of China (English)

    马燕坤

    2013-01-01

    The dindustrial revolution impacted Africa greatly. The west considers its own expression of history as classics, which makes African history or Africa in history westinized. Bureaucratism is mixed with colonization in Africa, which produces a false impression that Africa has no history before colonists came. As African countries became independent, influenced by new economic factors and political structure, African history has gone through a change, entering a time of stock-taking.%西方工业革命的启动,使其将触角伸向了非洲。同时也将自己对历史的表述方式视作经典,最终使非洲的历史或史学中的非洲成了西方魂魄的附身。西方对非洲史的编纂,尽管从辩证唯物主义体系中确实可以导出一些革命性的原则,也可挖掘出某些能动性机制,但是在整个过程中却不乏西方以杂色的观点为非洲史提供标准的尝试。非洲史官僚化与殖民化计划搅合在一起,造成了在殖民者把历史引入非洲之前其是没有历史的错觉,最终塑造了西方史学对非洲历史文化产生影响的事实。随着非洲的纷纷独立,在新的经济因素与政治结构的影响下,西方的非洲史学经历了一次转变,进入了清点存货的时代。

  9. Usefulness of Noninvasive Predictors of Oesophageal Varices in Black African Cirrhotic Patients in Côte d'Ivoire (West Africa

    Directory of Open Access Journals (Sweden)

    Alassan Kouamé Mahassadi

    2012-01-01

    Full Text Available Aims. To determine the usefulness of platelet count (PC, spleen diameter (SD and platelet count/spleen diameter ratio (PC/SD ratio for the prediction of oesophageal varices (OV and large OV in black African patients with cirrhosis in Côte d’Ivoire. Materials and Methods. Study was conducted in a training sample (111 patients and in a validation sample (91 patients. Results. Factors predicting OV were sex: (OR=0.08, P=0.0003, PC (OR = 12.4, P=0.0003, SD (OR = 1.04, P=0.002 in the training sample. The AUROCs (±SE of the model (cutoff ≥ 0.6, PC (cutoff 140 and PC/SD ratio (cutoff ≤ 868 were, respectively; 0.879 ± 0.04, 0.768 ± 0.06, 0.679 ± 0.06, 0.793 ± 0.06. For the prediction of large OV, the model’s AUROC (0.850 ± 0.05 was superior to that of PC (0.688 ± 0.06, SD (0.732 ± 0.05 and PC/SD ratio (0.752 ± 0.06. In the validation sample, with PC, PC/SD ratio and the model, upper digestive endoscopy could be obviated respectively in 45.1, 45.1, and 44% of cirrhotic patients. Prophylactic treatment with beta blockers could be started undoubtedly respectively in 36.3, 41.8 and 28.6% of them as having large OV. Conclusion. Non-invasive means could be used to monitor cirrhotic patients and consider treatment in African regions lacking endoscopic facilities.

  10. Timing and tectonic implications of the Pan-African Bangangte syenomonzonite, West Cameroon: Constraints from in-situ zircon U-Pb age and Hf-O isotopes

    Science.gov (United States)

    Tchouankoue, Jean Pierre; Li, Xian-Hua; Belnoun, Rose Noel Ngo; Mouafo, Lucas; Ferreira, Valderez Pinto

    2016-12-01

    The Bangangte pluton is a SW-NE elongated (5 × 20 km) massif located in the southeastern part of the Pan-African North Equatorial Fold Belt in Cameroon, consisting of two units with dominant monzonites in the south and syenites in the north. SIMS U-Pb zircon dating yields consistent emplacement ages of 585 ± 4 Ma and 583 ± 4 Ma for the southern unit and the northern unit, respectively. The Bangangte rocks display typical shoshonitic compositions characterized by Na2O + K2O > 5 wt%, K2O/Na2O ∼2, enrichment in LILE and LREE, but depletion in HFSE. Rocks from both units have similar O-Hf isotopes, with the monzonite zircons from the southern unit showing slightly higher δ18O (7.0 ± 0.4‰) but lower εHf(t) (-15.3 ± 1.4) value than the syenite zircons from southern unit (δ18O = 6.0 ± 0.4‰; εHf(t) = -14.0 ± 2.0). They were generated by partial melting of an enriched mantle source metasomatized by previous subduction processes, accompanied by crystal fractionation of pyroxene, Ti-Fe oxides and apatite, as well as crustal contamination to varying degrees. These rocks display a transitional geochemical feature of the subduction-related and within-plate shoshonites, suggesting that they were most likely emplaced in a post-collisional setting at the waning stage of the Pan-African orogeny.

  11. The white dwarf luminosity function

    Science.gov (United States)

    García-Berro, Enrique; Oswalt, Terry D.

    2016-06-01

    White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for ∼ 10 Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks the essential observational tools are the luminosity and mass functions of white dwarfs, whereas the theoretical tools are the evolutionary sequences of white dwarf progenitors, and the corresponding white dwarf cooling sequences. In particular, the observed white dwarf luminosity function is the key manifestation of the white dwarf cooling theory, although other relevant ingredients are needed to compare theory and observations. In this review we summarize the recent attempts to empirically determine the white dwarf luminosity function for the different Galactic populations. We also discuss the biases that may affect its interpretation. Finally, we elaborate on the theoretical ingredients needed to model the white dwarf luminosity function, paying special attention to the remaining uncertainties, and we comment on some applications of the white dwarf cooling theory. Astrophysical problems for which white dwarf stars may provide useful leverage in the near future are also discussed.

  12. M Dwarf Mysteries

    Science.gov (United States)

    Henry, Todd J.; Jao, Wei-Chun; Irwin, Jonathan; Dieterich, Sergio; Finch, Charlie T.; Riedel, Adric R.; Subasavage, John P.; Winters, Jennifer; RECONS Team

    2017-01-01

    During RECONS' 17-year (so far) astrometry/photometry program at the CTIO/SMARTS 0.9m, we have observed thousands of the ubiquitous red dwarfs in the solar neighborhood. During this reconnaissance, a few mysterious characters have emerged ...The Case of the Mercurial Stars: One M dwarf has been fading steadily for more than a decade, at last measure 6% fainter than when it was first observed. Another has grown brighter by 7% over 15 years. Are these brightness changes part of extremely long stellar cycles, or something else entirely?The Case of Identical Stellar Twins that Aren't: Two M dwarfs seem at first to be identical siblings traveling together through the Galaxy. They have virtually identical spectra at optical wavelengths and identical colors throughout the VRIJHK bands. Long-term astrometry indicates that they are, indeed, at the same distance via parallax measurements, and their proper motions match precisely. Yet, one of the twins is FOUR times brighter than the other. Followup work has revealed that the brighter component is a very close spectroscopic double, but no other stars are seen. So, the mystery may be half solved, but why do the close stars remain twice as bright as their widely-separated twin?The Case of the Great Kaboom!: After more than 1000 nights of observing on the reliable 0.9m telescope, with generally routine frames reading out upon the screen, one stellar system comprised of five red dwarfs flared in stunning fashion. Of the two distinct sources, the fainter one (an unresolved double) surpassed the brightness of the brighter one (an unresolved triple), increasing by more than three full magnitudes in the V filter. Which component actually flared? Is this magnificent outburst an unusual event, or in fact typical for this system and other M dwarfs?At the AAS meeting, we hope to probe the cognoscenti who study the Sun's smaller cousins to solve these intriguing M Dwarf Mysteries.This effort has been supported by the NSF through grants

  13. International employees' concerns during serious disease outbreaks and the potential impact on business continuity: Lessons identified from the 2014-15 West African Ebola outbreak.

    Science.gov (United States)

    Cole, Jennifer; Watkins, Chris

    This paper presents the findings of research carried out into the information-seeking behaviour, and information requirements of a small sample of international workers stationed in West Africa during the Zaire Ebola virus outbreak of 2014-15. The research study under which these results were obtained was part of exploratory research for a PhD focused on the use, and potential uses, of social media platforms during serious disease outbreaks that might be used to inform policy planning for public health and emergency response interventions. Thus, the findings from this study may provide valuable insights to business continuity managers and emergency planners in making future decisions about information exchange and crisis decision-making during future serious disease outbreaks.

  14. African Journals Online: Browse Alphabetically -- letter D

    African Journals Online (AJOL)

    The journal publishes original research, case report/case series, letter to the editor, reviews of health ... Democracy & Development: Journal of West African Affairs ... Civic organisations and the new and innovative programmes, activities, and ...

  15. The white dwarf luminosity function

    CERN Document Server

    García-Berro, Enrique

    2016-01-01

    White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for $\\sim 10$ Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks the essential observational tools are the luminosity and mass functions of white dwarfs, whereas the theoretical tools are the evolutionary sequences of white dwarf progenitors, and the corresponding white dwarf cooling sequences. In particular, the observed white dwarf luminosity function is the key manifestation of the white dwarf cooling theory, although other...

  16. Dwarf Spheroidals in MOND

    CERN Document Server

    Angus, Garry W

    2008-01-01

    We take the line of sight velocity dispersions as functions of radius for 8 Milky Way dwarf spheroidal galaxies and use Jeans analysis to calculate the mass-to-light ratios (M/L) in Modified Newtonian Dynamics (MOND). Using the latest structural parameters, distances and variable velocity anisotropy, we find 6/8 dwarfs have sensible M/L using only the stellar populations. Sextans and Draco, however, have M/L=9.2_{-3.0}^{+5.3} and 43.9_{-19.3}^{+29.0} respectively, which poses a problem. Apart from the need for Sextans' integrated magnitude to be reviewed, we propose tidal effects intrinsic to MOND, testable with numerical simulations, but fully orbit dependant, which are disrupting Draco. The creation of the Magellanic Stream is also re-addressed in MOND, the scenario being the stream is ram pressure stripped from the SMC as it crosses the LMC.

  17. Searching for Brown Dwarf Outflows

    CERN Document Server

    Whelan, E T; Bacciotti, F; Randich, S; Natta, A

    2009-01-01

    As outflow activity in low mass protostars is strongly connected to ac- cretion it is reasonable to expect accreting brown dwarfs to also be driving out- flows. In the last three years we have searched for brown dwarf outflows using high quality optical spectra obtained with UVES on the VLT and the technique of spectro-astrometry. To date five brown dwarf outflows have been discovered. Here the method is discussed and the results to date outlined.

  18. Dwarf Dark Matter Halos

    CERN Document Server

    Colin, Pierre; Valenzuela, O; Gottlöber, S

    2003-01-01

    We use N-body simulations to study properties of dwarf halos with virial masses in the range 10^7-10^9 Msun/h. Unlike recent reported results, we find that the density profiles of relaxed dwarf halos are well fitted by the NFW profile and do not have cores. We estimate the distribution of concentrations for halos in mass range that covers six orders of magnitude from 10^7 Msun/h to 10^13 Msun/h, and find that the data are well reproduced by the model of Bullock et al. (2001). We predict that present-day isolated dwarf halos should have a very large median concentration of ~ 35. For halos with masses that range from 4.6 x 10^9 Msun/h to 10^13 Msun/h we measure the subhalo circular velocity function and find that they are similar when normalized to the circular velocity of the parent halo. We compute the halo mass function and the halo spin parameter distribution and find that the former is very well reproduced by the Sheth and Tormen model while the latter is well fitted by a lognormal distribution with lambda...

  19. Re-testing and misclassification of HIV-2 and HIV-1&2 dually reactive patients among the HIV-2 cohort of The West African Database to evaluate AIDS collaboration

    Directory of Open Access Journals (Sweden)

    Boris K Tchounga

    2014-08-01

    Full Text Available Introduction: West Africa is characterized by the circulation of HIV-1 and HIV-2. The laboratory diagnosis of these two infections as well as the choice of a first-line antiretroviral therapy (ART is challenging, considering the limited access to second-line regimens. This study aimed at confirming the classification of HIV-2 and HIV-1&2 dually reactive patients followed up in the HIV-2 cohort of the West African Database to evaluate AIDS collaboration. Method: A cross-sectional survey was conducted from March to December 2012 in Burkina Faso, Côte d’Ivoire and Mali among patients classified as HIV-2 or HIV-1&2 dually reactive according to the national HIV testing algorithms. A 5-ml blood sample was collected from each patient and tested in a single reference laboratory in Côte d’Ivoire (CeDReS, Abidjan with two immuno-enzymatic tests: ImmunoCombII® (HIV-1&2 ImmunoComb BiSpot – Alere and an in-house ELISA test, approved by the French National AIDS and hepatitis Research Agency (ANRS. Results: A total of 547 patients were included; 57% of them were initially classified as HIV-2 and 43% as HIV-1&2 dually reactive. Half of the patients had CD4≥500 cells/mm3 and 68.6% were on ART. Of the 312 patients initially classified as HIV-2, 267 (85.7% were confirmed as HIV-2 with ImmunoCombII® and in-house ELISA while 16 (5.1% and 9 (2.9% were reclassified as HIV-1 and HIV-1&2, respectively (Kappa=0.69; p<0.001. Among the 235 patients initially classified as HIV-1&2 dually reactive, only 54 (23.0% were confirmed as dually reactive with ImmunoCombII® and in-house ELISA, while 103 (43.8% and 33 (14.0% were reclassified as HIV-1 and HIV-2 mono-infected, respectively (kappa= 0.70; p<0.001. Overall, 300 samples (54.8% were concordantly classified as HIV-2, 63 (11.5% as HIV-1&2 dually reactive and 119 (21.8% as HIV-1 (kappa=0.79; p<0.001. The two tests gave discordant results for 65 samples (11.9%. Conclusions: Patients with HIV-2 mono-infection are

  20. 57Fe Mössbauer spectroscopy investigations of iron oxidation states in the Harmattan dust nutrient contribution to West African soils

    Science.gov (United States)

    Adetunji, Jacob

    2014-12-01

    A variety of investigations have been carried out on Harmattan dust over many decades demonstrating the continuing importance of the Harmattan dust phenomenon. The investigations have included elemental enrichment factors, mineralogical nutrient input through dust deposition on the soil, meteorological studies, etc. Harmattan dust is important, not only for its impact on radio communication and low visibility in the shipping lanes over the Atlantic, but also on the livelihood and health of people living in countries over which the dust-laden Harmattan wind blows. However, so far, the aspect of nutrient mineral deposition on the soil has not been thoroughly investigated and requires attention, since the majority of people living in West Africa rely heavily on agriculture. It is therefore relevant to know the useful nutrients in the Harmattan dust deposited on soils of the region. This study is therefore aimed at determining the ferric-ferrous ratio of the iron-bearing minerals contained in the Harmattan dust, so their nutritional contribution can be considered. The Mössbauer technique is a powerful tool for studying the ferric-ferrous ratio and has therefore been used, for the first time, to determine the oxidation states of iron in the dust samples. The results of the analysis show that the Harmattan dust is seriously deficient in ferrous iron, which is the more soluble Fe-ion, needed in the soil for healthy crops and plants in general.

  1. Osmoregulatory strategies in natural populations of the black-chinned tilapia Sarotherodon melanotheron exposed to extreme salinities in West African estuaries.

    Science.gov (United States)

    Lorin-Nebel, Catherine; Avarre, Jean-Christophe; Faivre, Nicolas; Wallon, Sophie; Charmantier, Guy; Durand, Jean-Dominique

    2012-08-01

    The effect of salinity was studied in natural populations of the black-chinned tilapia (Sarotherodon melanotheron) from West Africa. This euryhaline species colonizes nearly all coastal environments from bays to lagoons characterized by salinities ranging from fresh water to hypersaline water over 100 ‰. Individuals were sampled during the dry season at several locations characterized by different levels of salinity (3-102 ‰). Their osmotic status and their gills were analyzed. The branchial mitochondria-rich cells (MRC), localized at the basis of the filaments and along the lamellae in fish taken from the saline stations, showed a wide plasticity with significant differences in their number and size. The most striking results were a significant larger area (≈3x) and a higher number (≈55x) of MRC at high salinity (102 ‰) compared to low salinity (3 ‰). The major ion transporters and channels were localized by immunocytochemistry and different expression patterns have been recorded between stations. Despite an increased Na⁺/K⁺-ATPase (NKA) α-subunit expression and NKA activity, pointing to an increased monovalent ion excretion, a severe osmotic imbalance was recorded in animals living in hypersaline environments.

  2. Hemoglobin C associated with protection from severe malaria in the Dogon of Mali, a West African population with a low prevalence of hemoglobin S.

    Science.gov (United States)

    Agarwal, A; Guindo, A; Cissoko, Y; Taylor, J G; Coulibaly, D; Koné, A; Kayentao, K; Djimde, A; Plowe, C V; Doumbo, O; Wellems, T E; Diallo, D

    2000-10-01

    The malaria hypothesis proposes a survival advantage for individuals with hemoglobin variants in areas of endemic Plasmodium falciparum malaria. Hemoglobin C (HbC) is a possible example in West Africa, where this hemoglobin has a centric distribution with high frequencies among certain populations including the Dogon ethnic group. To test whether HbC is associated with protection from malaria, we performed a case-control study in the Dogon of Bandiagara, Mali. HbC was present in 68 of 391 (17.4%) of uncomplicated malaria control cases, whereas it was detected in only 3 of 67 cases (4.5%) of severe malaria (odds ratio [OR], 0.22; P =. 01). Further, HbC was present in only 1 of 34 cases (2.9%) with cerebral manifestations, the most common presentation of severe malaria in this population (OR, 0.14; P =.03). Episodes of uncomplicated malaria and parasitemias (4800-205 050/microL) were identified in cases of homozygous HbC (HbCC), which indicates that P falciparum parasites are able to efficiently replicate within HbCC erythrocytes in vivo. These findings suggest that HbC does not protect against infection or uncomplicated malaria but can protect against severe malaria in the Dogon population of Bandiagara, Mali. The data also suggest that the protective effect associated with HbC may be greater than that of HbS in this population.

  3. Comparison of multi-temporal NOAA-AVHRR and SPOT-XS satellite data for mapping land-cover dynamics in the West African Sahel

    Science.gov (United States)

    Marsh, S. E.; Walsh, J. L.; Lee, C. T.; Beck, L. R.; Hutchinson, C. F.

    1992-01-01

    Multi-resolution and multi-temporal remote sensing data (SPOT-XS and AVHRR) were evaluated for mapping local land-cover dynamics in the Sahel of West Africa. The aim of this research was to evaluate the agricultural information that could be derived from both high and low spatial resolution data in areas where there is very often limited ground information. A combination of raster-based image processing and vector-based geographical information system mapping was found to be effective for understanding both spatial and spectral land-cover dynamics. The SPOT data proved useful for mapping local land-cover classes in a dominantly recessive agricultural region. The AVHRR-LAC data could be used to map the dynamics of riparian vegetation, but not the changes associated with recession agriculture. In areas where there was a complex mixture of recession and irrigated agriculture, as well as riparian vegetation, the AVHRR data did not provide an accurate temporal assessment of vegetation dynamics.

  4. Terrestrial ecology in South Africa and South West Africa – project abstracts for 1979

    CSIR Research Space (South Africa)

    Ecosystems Programmes, Cooperative Scientific Programmes

    1981-05-01

    Full Text Available Brief descriptions of over 200 research projects undertaken during 1979 in South African and South West African terrestrial ecosystems are presented. The abstracts are arranged alphabetically according to author name and a keyword index is provided...

  5. The South African pleuronectiform ichthyofauna is diverse ...

    African Journals Online (AJOL)

    spamer

    African coast, from the South African Cape west coast to the Arabian Sea, on predominantly sandy substrata at depths of 30–430 .... Port Elizabeth. Study area ... Ovary larger, becoming orange-red, with a grainy appearance due to visible eggs. Testes whitish ...... species of the Eastern Cape coast of South Africa, with notes.

  6. Nitrogen Oxide biogenic emissions from soils: impact on NOx and ozone formation in West Africa during AMMA (African Monsoon Multidisciplinary Analysis

    Directory of Open Access Journals (Sweden)

    J.-P. Chaboureau

    2007-10-01

    Full Text Available Nitrogen Oxide biogenic emissions from soils are driven by soil and environmental parameters. The relationship between these parameters and NO fluxes is highly non linear. A new algorithm, based on a neural network calculation, is used to reproduce the NO biogenic emissions in West Africa during the AMMA campaign, in August 2006. It has been coupled in the surface scheme of a coupled chemistry dynamics model to estimate the impact of the NO emissions on NOx and O3 formation in the lower troposphere. Four different simulations on the same domain and at the same period are compared: CTRL run (without soil NO emissions, YL95 run (with NO emissions inventory, at low time and space resolution, SOILNOx run (with NO emissions from neural network and ALLNOx run (with NO from neural network. The influence of NOx from lightning is assessed, and is limited to the upper troposphere. Compared to parameterisations generally used at the global and regional scales, the neural network parameterisation can give higher NOx (up to +380 ppt and ozone (up to +7ppb, closer to the ones measured in aircrafts during the AMMA field campaign. The NO emission from soils calculated with neural network responds to changes in soil moisture giving enhanced emissions over the wetted soil, as observed by aircraft measurements after the passing of a convective system, well reproduced by the model. Consecutive enhancement of NOx and ozone is limited to the lowest layers of the atmosphere in modelling, whereas measurements show higher levels above 500 m. This equation allows an immediate response of fluxes to environmental parameters, on the contrary to fixed emission inventories. The annual cycle of emissions from this algorithm will be simulated in a future work

  7. Nitrogen Oxide biogenic emissions from soils: impact on NOx and ozone formation in West Africa during AMMA (African Monsoon Multidisciplinary Analysis)

    Science.gov (United States)

    Delon, C.; Reeves, C. E.; Stewart, D. J.; Serça, D.; Dupont, R.; Mari, C.; Chaboureau, J.-P.; Tulet, P.

    2007-10-01

    Nitrogen Oxide biogenic emissions from soils are driven by soil and environmental parameters. The relationship between these parameters and NO fluxes is highly non linear. A new algorithm, based on a neural network calculation, is used to reproduce the NO biogenic emissions in West Africa during the AMMA campaign, in August 2006. It has been coupled in the surface scheme of a coupled chemistry dynamics model to estimate the impact of the NO emissions on NOx and O3 formation in the lower troposphere. Four different simulations on the same domain and at the same period are compared: CTRL run (without soil NO emissions), YL95 run (with NO emissions inventory, at low time and space resolution), SOILNOx run (with NO emissions from neural network) and ALLNOx run (with NO from neural network). The influence of NOx from lightning is assessed, and is limited to the upper troposphere. Compared to parameterisations generally used at the global and regional scales, the neural network parameterisation can give higher NOx (up to +380 ppt) and ozone (up to +7ppb), closer to the ones measured in aircrafts during the AMMA field campaign. The NO emission from soils calculated with neural network responds to changes in soil moisture giving enhanced emissions over the wetted soil, as observed by aircraft measurements after the passing of a convective system, well reproduced by the model. Consecutive enhancement of NOx and ozone is limited to the lowest layers of the atmosphere in modelling, whereas measurements show higher levels above 500 m. This equation allows an immediate response of fluxes to environmental parameters, on the contrary to fixed emission inventories. The annual cycle of emissions from this algorithm will be simulated in a future work

  8. The Archean kalsilite-nepheline syenites of the Awsard intrusive massif (Reguibat Shield, West African Craton, Morocco) and its relationship to the alkaline magmatism of Africa

    Science.gov (United States)

    Haissen, Faouziya; Cambeses, Aitor; Montero, Pilar; Bea, Fernando; Dilek, Yildirim; Mouttaqi, Abdellah

    2017-03-01

    More than 40% of the known alkaline complexes are reported from Africa. Most are ring complexes composed of syenites and associated or not, lithotypes as carbonatites, granites and mafic rocks. Radiometric dating indicates the presence of alkaline complexes with ages spanning from Precambrian to the present. In terms of outcrops, alkaline complexes are reported from cratonic zones and from belts embedded between cratonic areas. Because of the high economic potential for associated REE deposits, these alkaline complexes have received much attention from Earth scientists. These studies aim mainly to constrain the role of the mantle and the crust (and the interaction between them) in the genesis of this peculiar magmatism, and also to explain the variability observed in lithotypes and geotectonic settings. Among those alkaline complexes, Precambrian occurrences are rare. Up-to-date only a few Proterozoic examples were cited in Africa. The recently studied Awsard complex in Southern Morocco is a peculiar one with a crystallization age of 2.46 Ga and an unusual rock assemblages. This paper is a first approximation to a comparison of geochemical and isotopic fingerprints of the Awsard magmatism (as the oldest one) with other known different ages African complexes from different geotectonic settings, aiming to detect if there is any evolution in this alkaline magmatism through time. A first conclusion is that magma sources for this alkaline magmatism has been probably evaluating over geological time, from parental magmas compositions close to that of primitive mantle in these early geological time to compositions holding more and more depleted mantle and continental crust components. However, to go further in this debate more modern isotopic, geochemical and geochronological data from all these complexes are needed. Nevertheless, this comparison highlighted the peculiar character of the Awsard magmatism with an isotopic composition very close to that of Primitive mantle

  9. Axion cooling of white dwarfs

    CERN Document Server

    Isern, J; Garcia--Berro, E; Salaris, M; Torres, S

    2013-01-01

    The evolution of white dwarfs is a simple gravothermal process. This process can be tested in two ways, through the luminosity function of these stars and through the secular variation of the period of pulsation of those stars that are variable. Here we show how the mass of the axion can be constrained using the white dwarf luminosity function.

  10. In-situ measurements of tropical cloud properties in the West African monsoon: upper tropospheric ice clouds, mesoscale convective system outflow, and subvisual cirrus

    Science.gov (United States)

    Frey, W.; Borrmann, S.; Kunkel, D.; Weigel, R.; de Reus, M.; Schlager, H.; Roiger, A.; Voigt, C.; Hoor, P.; Curtius, J.; Krämer, M.; Schiller, C.; Volk, C. M.; Homan, C. D.; Fierli, F.; di Donfrancesco, G.; Ulanovsky, A.; Ravegnani, F.; Sitnikov, N. M.; Viciani, S.; D'Amato, F.; Shur, G. N.; Belyaev, G. V.; Law, K. S.; Cairo, F.

    2011-01-01

    In-situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 ''Geophysica'' with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two or three modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionate more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3, and satellite images clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow (developing MCS) ice crystal number concentrations of up to 8.3 cm-3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m-3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm-3, an ice water content of 2.3 × 10-4 g m-3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm-3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10-4 g m-3. All known in-situ measurements of subvisual tropopause cirrus are compared and an

  11. In situ measurements of tropical cloud properties in the West African Monsoon: upper tropospheric ice clouds, Mesoscale Convective System outflow, and subvisual cirrus

    Science.gov (United States)

    Frey, W.; Borrmann, S.; Kunkel, D.; Weigel, R.; de Reus, M.; Schlager, H.; Roiger, A.; Voigt, C.; Hoor, P.; Curtius, J.; Krämer, M.; Schiller, C.; Volk, C. M.; Homan, C. D.; Fierli, F.; di Donfrancesco, G.; Ulanovsky, A.; Ravegnani, F.; Sitnikov, N. M.; Viciani, S.; D'Amato, F.; Shur, G. N.; Belyaev, G. V.; Law, K. S.; Cairo, F.

    2011-06-01

    In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS) clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100) and a Cloud Imaging Probe (CIP) operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS). Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6) cm-3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m-3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm-3, an ice water content of 2.3 × 10-4 g m-3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm. Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm-3 with maximum particle sizes of 130 μm, and the mean ice water content was about 1.4 × 10-4 g m-3. All known in situ measurements of subvisual tropopause cirrus are compared

  12. Obtaining land cover changes information from multitemporal analysis of Landsat-TM images: results from a case study in West African dryland

    Science.gov (United States)

    Nutini, F.; Boschetti, M.; Brivio, P. A.; Antoninetti, M.

    2012-04-01

    The Sahelian belt of West Africa is a semiarid region characterized by wide climate variations, which can in turn affect the livelihood of local populations particularly in rangeland areas, as happens during the dramatic food crisis in the 70-80s caused by rainfall scarcity. The monitoring of natural resources and rainfed agricultural activities, with the aim to provide information to support Sahelian food security action, needs the production of detailed thematic maps as emphasized by several scientific papers. In this framework, a study was conducted to develop a method to exploit time series of remote sensed satellite data to 1) provide reliable land cover (LC) map at local scale in a dry region and 2) obtain a LC change (LCC) map that contribute to identify the plausible causes of local environmental instability. Satellite images used for this work consist in a time series of Landsat Thematic Mapper (TM) (path row 195-50) acquired in the 2000 (6 scenes) and 2007 (9 scenes) from February (Dry season) to September (end of wet season). The study investigates the different contribution provided by spectra information of a single Landsat TM image and by time series of derived NDVI. Different tests have been conducted with different combination of data set (spectral and temporal)in order to identify the best approach to obtain a LC map in five classes of interest: Shrubland, Cultivated Land, Water body, Herbaceous vegetation and Bare soil. The best classification approach is exposed and applied on two years in the last decade. The comparison between this two LC results in land cover change map, that displays the changes of vegetation patterns that have been characterized the area. The discussed results show a largely stable dryland region, but locally characterized by hot-spot of decreasing in natural vegetation inside the rangelands and an increasing of cultivations along fossil valleys where human activities are slightly intense. The discussion shows that this hot

  13. IGOB131, a novel seed extract of the West African plant Irvingia gabonensis, significantly reduces body weight and improves metabolic parameters in overweight humans in a randomized double-blind placebo controlled investigation

    Directory of Open Access Journals (Sweden)

    Mbofung Carl MF

    2009-03-01

    Full Text Available Abstract Background A recent in vitro study indicates that IGOB131, a novel seed extract of the traditional West African food plant Irvingia gabonensis, favorably impacts adipogenesis through a variety of critical metabolic pathways including PPAR gamma, leptin, adiponectin, and glycerol-3 phosphate dehydrogenase. This study was therefore aimed at evaluating the effects of IGOB131, an extract of Irvingia gabonensis, on body weight and associated metabolic parameters in overweight human volunteers. Methods The study participants comprised of 102 healthy, overweight and/or obese volunteers (defined as BMI > 25 kg/m2 randomly divided into two groups. The groups received on a daily basis, either 150 mg of IGOB131 or matching placebo in a double blinded fashion, 30–60 minutes before lunch and dinner. At baseline, 4, 8 and 10 weeks of the study, subjects were evaluated for changes in anthropometrics and metabolic parameters to include fasting lipids, blood glucose, C-reactive protein, adiponectin, and leptin. Results Significant improvements in body weight, body fat, and waist circumference as well as plasma total cholesterol, LDL cholesterol, blood glucose, C-reactive protein, adiponectin and leptin levels were observed in the IGOB131 group compared with the placebo group. Conclusion Irvingia gabonensis administered 150 mg twice daily before meals to overweight and/or obese human volunteers favorably impacts body weight and a variety of parameters characteristic of the metabolic syndrome. This is the first double blind randomized placebo controlled clinical trial regarding the anti-obesity and lipid profile modulating effects of an Irvingia gabonensis extract. The positive clinical results, together with our previously published mechanisms of gene expression modulation related to key metabolic pathways in lipid metabolism, provide impetus for much larger clinical studies. Irvingia gabonensis extract may prove to be a useful tool in dealing with the

  14. Effect of Age at Antiretroviral Therapy Initiation on Catch-Up Growth within the First 24 Months among HIV-Infected Children in the IeDEA West African Pediatric Cohort

    Science.gov (United States)

    Jesson, Julie; Koumakpaï, Sikiratou; Diagne, Ndeye R.; Amorissani-Folquet, Madeleine; Kouéta, Fla; Aka, Addi; Lawson-Evi, Koko; Dicko, Fatoumata; Kouakou, Kouadio; Pety, Touré; Renner, Lorna; Eboua, Tanoh; Coffie, Patrick A.; Desmonde, Sophie; Leroy, Valériane

    2015-01-01

    Background We described malnutrition and the effect of age at antiretroviral therapy (ART) initiation on catch-up growth over 24 months among HIV-infected children enrolled in the IeDEA West African paediatric cohort (pWADA). Methods Malnutrition was defined at ART initiation (baseline) by a Z-score <-2 SD, according to three anthropometric indicators: Weight-for-age (WAZ) for underweight, Height-for-age (HAZ) for stunting, and Weight-for-Height/BMI-for-age (WHZ/BAZ) for wasting. Kaplan-Meier estimates for catch-up growth (Z-score ≥-2 SD) on ART, adjusted for gender, immunodeficiency and malnutrition at ART initiation, ART regimen, time period and country, were compared by age at ART initiation. Cox proportional hazards regression models determined predictors of catch-up growth on ART over 24 months. Results Between 2001 and 2012, 2004 HIV-infected children < 10 years of age were included. At ART initiation, 51% were underweight, 48% were stunted and 33% were wasted. The 24-month adjusted estimates for catch-up growth were 69% (95% confidence interval [CI]: 57;80), 61% (95%CI: 47;70), and 90% (95%CI: 76;95) for WAZ, HAZ, and WHZ/BAZ, respectively. Adjusted catch-up growth was more likely for children <5 years of age at ART initiation compared to children ≥5 years for WAZ, HAZ (P<0.001), and for WHZ/BAZ (P = 0.026). Conclusions Malnutrition among these children is an additional burden that has to be urgently managed. Despite a significant growth improvement after 24 months on ART, especially in children <5 years, a substantial proportion of children still never achieved catch-up growth. Nutritional care should be part of the global healthcare of HIV-infected children in sub-Saharan Africa. PMID:25955835

  15. In situ measurements of tropical cloud properties in the West African Monsoon: upper tropospheric ice clouds, Mesoscale Convective System outflow, and subvisual cirrus

    Directory of Open Access Journals (Sweden)

    W. Frey

    2011-06-01

    Full Text Available In situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100 and a Cloud Imaging Probe (CIP operated aboard the Russian high altitude research aircraft M-55 Geophysica with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS. Two to four modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionately more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3 and satellite images, clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow from a developing MCS ice crystal number concentrations of up to (8.3 ± 1.6 cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm.

    Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130

  16. In-situ measurements of tropical cloud properties in the West African monsoon: upper tropospheric ice clouds, mesoscale convective system outflow, and subvisual cirrus

    Directory of Open Access Journals (Sweden)

    W. Frey

    2011-01-01

    Full Text Available In-situ measurements of ice crystal size distributions in tropical upper troposphere/lower stratosphere (UT/LS clouds were performed during the SCOUT-AMMA campaign over West Africa in August 2006. The cloud properties were measured with a Forward Scattering Spectrometer Probe (FSSP-100 and a Cloud Imaging Probe (CIP operated aboard the Russian high altitude research aircraft M-55 ''Geophysica'' with the mission base in Ouagadougou, Burkina Faso. A total of 117 ice particle size distributions were obtained from the measurements in the vicinity of Mesoscale Convective Systems (MCS. Two or three modal lognormal size distributions were fitted to the average size distributions for different potential temperature bins. The measurements showed proportionate more large ice particles compared to former measurements above maritime regions. With the help of trace gas measurements of NO, NOy, CO2, CO, and O3, and satellite images clouds in young and aged MCS outflow were identified. These events were observed at altitudes of 11.0 km to 14.2 km corresponding to potential temperature levels of 346 K to 356 K. In a young outflow (developing MCS ice crystal number concentrations of up to 8.3 cm−3 and rimed ice particles with maximum dimensions exceeding 1.5 mm were found. A maximum ice water content of 0.05 g m−3 was observed and an effective radius of about 90 μm. In contrast the aged outflow events were more diluted and showed a maximum number concentration of 0.03 cm−3, an ice water content of 2.3 × 10−4 g m−3, an effective radius of about 18 μm, while the largest particles had a maximum dimension of 61 μm.

    Close to the tropopause subvisual cirrus were encountered four times at altitudes of 15 km to 16.4 km. The mean ice particle number concentration of these encounters was 0.01 cm−3 with maximum particle sizes of 130 μm, and the mean

  17. Habitability of planets around red dwarf stars.

    Science.gov (United States)

    Heath, M J; Doyle, L R; Joshi, M M; Haberle, R M

    1999-08-01

    Recent models indicate that relatively moderate climates could exist on Earth-sized planets in synchronous rotation around red dwarf stars. Investigation of the global water cycle, availability of photosynthetically active radiation in red dwarf sunlight, and the biological implications of stellar flares, which can be frequent for red dwarfs, suggests that higher plant habitability of red dwarf planets may be possible.

  18. Magnetized White Dwarfs

    CERN Document Server

    Terrero, D Alvear; Martínez, A Pérez

    2016-01-01

    The purpose of this thesis is to obtain more realistic equations of state to describe the matter forming magnetized white dwarfs, and use them to solve its structure equations. The equations of state are determined by considering the weak magnetic field approximation $Bdwarfs. Also, we consider the energy and pressure correction due to the Coulomb interaction of the electron gas with the ions located in a crystal lattice. Moreover, spherically symmetric Tolman-Oppenheimer-Volkoff structure equations are solved independently for the perpendicular and parallel pressures, confirming the necessity of using axisymmetric structure equations, more adequate to describe the anisotropic system. Therefore, we study the solutions in cylindrical coordinates. In this case, the mass per longitude unit is obtained instead of the total mass of the whit...

  19. Throwing Icebergs at White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-08-01

    Where do the metals come from that pollute the atmospheres of many white dwarfs? Close-in asteroids may not be the only culprits! A new study shows that distant planet-size and icy objects could share some of the blame.Pollution ProblemsArtists impression of rocky debris lying close around a white dwarf star. [NASA/ESA/STScI/G. Bacon]When a low- to intermediate-mass star reaches the end of its life, its outer layers are blown off, leaving behind its compact core. The strong gravity of this white dwarf causes elements heavier than hydrogen and helium to rapidly sink to its center in a process known as sedimentation, leaving an atmosphere that should be free of metallic elements.Therefore its perhaps surprising that roughly 2550% of all white dwarfs are observed to have atmospheric pollution by heavy elements. The short timescales for sedimentation suggest that these elements were added to the white dwarf recently but how did they get there?Bringing Ice InwardIn the generally accepted theory, pre-existing rocky bodies or an orbiting asteroid belt survive the stars evolution, later accreting onto the final white dwarf. But this scenario doesnt explain a few observations that suggest white dwarfs might be accreting larger planetary-size bodies and bodies with ices and volatile materials.Dynamical evolution of a Neptune-like planet (a) and a Kuiper belt analog object (b) in wide binary star systems. Both have large eccentricity excitations during the white dwarf phase. [Stephan et al. 2017]How might you get large or icy objects which would begin on very wide orbits close enough to a white dwarf to become disrupted and accrete? Led by Alexander Stephan, a team of scientists at UCLA now suggest that the key is for the white dwarf to be in a binary system.Influence of a CompanionIn the authors model, the white-dwarf progenitor is orbited by both a distant stellar companion (a common occurrence) and a number of large potential polluters, which could have masses between that

  20. PROPERTIES OF THE COOLEST DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    SAUMON, DIDIER [Los Alamos National Laboratory; LEGGETT, SANDY K. [NON LANL; FREEDMAN, RICHARD S. [NON LANL; GEBALLE, THOMAS R. [NON LANL; GOLIMOWSKI, DAVID A. [NON LANL; LODIEU, NICOLAS [NON LANL; MARLEY, MARK S. [NON LANL; STEPHENS, DENISE [NON LANL; PINFIELD, DAVID J. [NON LANL; WARREN, STEPHEN J. [NON LANL

    2007-01-18

    Eleven years after the discovery of the first T dwarf, we have a population of ultracool L and T dwarfs that is large enough to show a range of atmospheric properties, as well as model atmospheres advanced enough to study these properties in detail. Since the last Cool Stars meeting, there have been observational developments which aid in these studies. they present recent mid-infrared photometry and spectroscopy from the Spitzer Space Telescope which confirms the prevalence of vertical mixing in the atmospheres of L and T dwarfs. Hence, the 700 K to 2200 K L and t dwarf photspheres require a large number of parameters for successful modeling: effective temperature, gravity, metallicity, grain sedimentation and vertical mixing efficiency. They also describe initial results of a search for ultracool dwarfs in the UKIRT Infrared Deep Sky Survey, and present the latest T dwarf found to date. They conclude with a discussion of the definition of the later-than-T spectral type, the Y dwarf.