African Journal of Science and Technology最新文献_第6页

Effets des extraits totaux aqueux de mallotus oppositifolium et de euphorbia hirta (euphorbiaceae) sur l’activite contractile intestinale du rat 大戟科(大戟科)和大戟科(大戟科)总水提取物对大鼠肠道收缩活性的影响

African Journal of Science and Technology Pub Date : 2009-07-28 DOI: 10.4314/AJST.V2I2.44664

R. Kamgang, R. Zintchem, T. Dimo, Mp Yewah

引用次数: 9

Risque d’inondation dans la vallee de nyos 尼奥斯山谷有洪水风险

African Journal of Science and Technology Pub Date : 2009-07-28 DOI: 10.4314/AJST.V2I2.44671

M. Tchindjang, Ni Konfor

{"title":"Risque d’inondation dans la vallee de nyos","authors":"M. Tchindjang, Ni Konfor","doi":"10.4314/AJST.V2I2.44671","DOIUrl":"https://doi.org/10.4314/AJST.V2I2.44671","url":null,"abstract":"The maar Nyos, situated at latitude 6°26’78”N and 10°17’76”E along the Cameroon Volcanic Line is well known for its stratification from bottom to top. It lies on a granitic topography at 1100 m above sea level. The granitic cliff exposed to the west of the lake rises 100m above the water level. The lake waters are held behind to the north by a natural pyroclastic dam on which water overflows creating semi giant potholes. The overflow forms a waterfall of about 30-40m. This dam is highly and densely fractured (13 fractures of 23-40m long). The breakdown of this dam can create floods that will drawn over 10.000 people in both Cameroon and Nigeria (according to McKIE, 2000). The lake contains 3 billions m3 of water. At the bottom, the concentration of carbon dioxide is 85m/10m3 of water. The dam remains a great potential danger to the population, aggravated by the high concentration of carbon dioxide in the lake emanating from the mantle which can lead to another gas disaster. The tectonic instability or ever a slight earth tremors can break the dam and cause floods downstream. A volcanic eruption might even worsen the situation. This paper presents the results of a recent research carried out on the lake after the onset of the first phase of the degassing project.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77455238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 5

Effect of accel on the vase life and post harvest quality of alstroemeria (alstroemeria aurantiaca l.) cut flowers 加速剂对桃金娘切花花瓶寿命及采后品质的影响

African Journal of Science and Technology Pub Date : 2009-07-28 DOI: 10.4314/AJST.V2I1.44650

T. M. Mutui, V. Emongor, M. Hutchinson

{"title":"Effect of accel on the vase life and post harvest quality of alstroemeria (alstroemeria aurantiaca l.) cut flowers","authors":"T. M. Mutui, V. Emongor, M. Hutchinson","doi":"10.4314/AJST.V2I1.44650","DOIUrl":"https://doi.org/10.4314/AJST.V2I1.44650","url":null,"abstract":"Freshly cut flowering stems of Alstroemeria ‘Yellow King’ and ‘Marina’ were placed in glass jars containing solutions of Accel at 0, 25, 50, 75 and 100 mg/litre BA equivalent and arranged in a completely randomised design with 3 replicates. The effect of Accel on the vase life and quality of Alstroemeria was investigated. Flowers held in Accel at 25 or 50 mg/litre BA equivalent consistently increased the number of days to full opening of primary florets and delayed the onset of flower senescence as measured by days to 50 % petal fall and days to 50 % leaf yellowing. Accel at 25mg/ litre BA equivalent significantly increased the leaf nitrogen and chlorophyll content of Alstroemeria cut flowers. High Accel concentrations of 50, 75 and 100 mg/litre BA equivalent reduced significantly the leaf water content of Alstroemeria cut flowers. Accel at 75 and 100 mg/litre BA equivalent increased leaf dry weight of Alstroemeria cut flowers. Our results indicate that Accel at 25 mg/litre BA equivalent has the potential to be used as a commercial cut flower preservative solution for delaying flower senescence, prolonging the vase life and enhancing post harvest quality of Alstroemeria cut flowers","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"834 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73842411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 38

Insecticidal activity of extracts derived from different parts of the mangrove tree rhizophora mucronata (rhizophoraceae) lam. Against three arthropods 红树根茎不同部位提取物的杀虫活性。对抗三只节肢动物

African Journal of Science and Technology Pub Date : 2009-07-28 DOI: 10.4314/AJST.V2I2.44668

J. Kabaru, L. Gichia

{"title":"Insecticidal activity of extracts derived from different parts of the mangrove tree rhizophora mucronata (rhizophoraceae) lam. Against three arthropods","authors":"J. Kabaru, L. Gichia","doi":"10.4314/AJST.V2I2.44668","DOIUrl":"https://doi.org/10.4314/AJST.V2I2.44668","url":null,"abstract":"The insecticidal and antifeedant activity of extracts derived from different parts of the mangrove tree Rhizophora mucronata (Rhizophoraceae) Lam. is reported. The 70% ethanol extracts of leaves, bark, stem wood and pith were tested for toxicity against adults of the desert locust Schistocerca gregaria (Forskal), the 2nd instar larvae of Aedes aegypti (L.) and the 1st instar larvae of the brine shrimp Artemia salina (Leach). Antifeedant activity of the extracts was assessed through tests conducted on S. gregaria adults by the paper feeding protection bioassay. In tests carried out on A. aegypti mosquito larvae, bark and pith extracts showed high toxicity with 48 hour LC50’s of 157.4 ppm and 168.3 ppm respectively. Stem wood extracts had low activity with an LC50 of 1003.4 ppm while leaf extracts did not exhibit toxic effects at a concentration of 1000 ppm. A similar trend in activity was observed with antifeedant tests conducted on the desert locust S. gregaria and on toxicity tests carried out on A. salina larvae. The bulk of the active compounds are sequestered in the bark, pith and stem wood with the least being found in the leaves. The results indicate that R.mucronata is a potential source of botanical insecticides(s).","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"73 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83626716","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 90

SEISMOTECTONICS OF ZIMBABWE 津巴布韦地震构造学

African Journal of Science and Technology Pub Date : 2009-07-27 DOI: 10.4314/AJST.V1I4.44622

Jh Dumisani

引用次数: 4

Comparative effectiveness of animal manures on soil chemical properties, yield and root growth of amaranthus (amaranthus cruentus l.) 动物粪便对苋菜(amaranthus cruentus l.)土壤化学性质、产量和根系生长的影响比较

African Journal of Science and Technology Pub Date : 2009-07-27 DOI: 10.4314/AJST.V1I4.44623

A. Maerere, GG Kimbi, Dlm Nonga

{"title":"Comparative effectiveness of animal manures on soil chemical properties, yield and root growth of amaranthus (amaranthus cruentus l.)","authors":"A. Maerere, GG Kimbi, Dlm Nonga","doi":"10.4314/AJST.V1I4.44623","DOIUrl":"https://doi.org/10.4314/AJST.V1I4.44623","url":null,"abstract":"Pot and field experiments were conducted to compare the effects of dairy cow, goat and poultry manures on soil available levels of N and P and amaranths yield and root growth. The three amendments were applied on Oxisols at 100, 150 and 170 kg N/ha in a split plot design and replicated three times. Pot experiment lasted for one month whereas field experiment was conducted over three monthly crop cycles. Results of both experiments indicated that applications of the three manures significantly (P from the three manures revealed that for all the parameters evaluated the trend was; Poultry manure > goat manure > dairy cow manure. This was largely attributed to differences in total N, total P, C/N and C/P ratios of the amendments. Field experiment results revealed that responses were highest after the third crop harvest suggesting that mineralization of organic N and P increased with time. Based on fertilizer recommendations of N and P for Southern highlands of Tanzania and the highest rate used in this study (170 kg N/ha), applications of 5.8 tons/ha, 9.8 tons/ha and 13.4 tons/ha of poultry, goat and dairy cow manure will suffice the equirement of 40 kg N/ha and 20 kg P/ha recommended for most field crops.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"6 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79788055","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 84

Variable structure unit vector control of electric power generation 发电变结构单位矢量控制

African Journal of Science and Technology Pub Date : 2009-07-27 DOI: 10.4314/AJST.V1I4.44627

F. Okafor

引用次数: 6

Analysis of NO x reduction in diesel engines by air injection using stochastic 用随机方法分析柴油机喷气对nox的影响

African Journal of Science and Technology Pub Date : 2009-07-27 DOI: 10.4314/AJST.V1I4.44624

I. Mkilaha, G. John

{"title":"Analysis of NO x reduction in diesel engines by air injection using stochastic","authors":"I. Mkilaha, G. John","doi":"10.4314/AJST.V1I4.44624","DOIUrl":"https://doi.org/10.4314/AJST.V1I4.44624","url":null,"abstract":"Combustion phenomena have been found to be dependent on the turbulence of the air/gas and fuel in the cylinder. By enhancing turbulent mixing of fuel in the combustion chamber it is possible to improve combustion process. Based on the stochastic nature of turbulence of combustion processes as occurring in an IDI internal combustion engine, a model was developed based on these principles when compressed air was injected into the engine. The air injection was carried out in order to control the emission of NOx and soot simultaneously. In the present model, the mechanism of NOx formation is modeled using the thermal NOx principles while the soot emission is modeled using the global combustion model, which considered combustion as heat addition. Obtained results show close agreement with the experimental ones. The Zeldovich model used has been found model closely IDI engine processes also for the case of air injection as is case of a normal engine. This is due to the microscopic treatment of the mixing process, which involved over-simplification of HC combustion chemistry. It is shown that although there is no substantial temperature drop when compressed air was injected into the chamber, at microscopic scales, the mixing process that occur lead to local temperature drop. It is these local areas of temperature quenching that enhance the suppression of the formation of NOx. At high loads, however, particulate and HC are increased due to the enrichment of fuel in the local areas where the temperatures have substantially been reduced.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89594187","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Optimisation of the baluba east ore treatment 巴鲁巴东矿石处理的优化

African Journal of Science and Technology Pub Date : 2009-07-27 DOI: 10.4314/AJST.V1I4.44621

C. Chabuka, L. Witika

{"title":"Optimisation of the baluba east ore treatment","authors":"C. Chabuka, L. Witika","doi":"10.4314/AJST.V1I4.44621","DOIUrl":"https://doi.org/10.4314/AJST.V1I4.44621","url":null,"abstract":"The Baluba east concentrator is part of the Roan Antelope Mining Corporation (RAMCO) which is a unit of the Binani Group of Companies. It treats an ore which is a mixture of sulphide and oxide copper minerals. In the flotation of mixed sulphide - oxide ores, the sulphide minerals are floated first, then followed by a sulphidisation step of the oxide minerals to effect their flotation. This test work was carried out because of a decrease in the grades and recoveries obtainable during the period of January 1998 up to around September 1998. This was so despite having an above average head grade of 1.91%Tcu. The optimum mesh of grind was found to be 65% passing 75 im using release analysis and the conclusions were drawn on the basis of flotation kinetics. The optimisation of reagents addition was done using a FACTORIAL DESIGN of experiments to improve the reliability of the result and Analysis of Variance(ANOVA) and the F-test were used to draw meaningful conclusions. Dosages of 120g/t collector (SIPX) and 100 g/t conditioner (NaHS) were obtained as the optimum reagent levels. The associated concentrate grade was 6.10%TCu (without a cleaning stage) at a recovery of 90.16%TCu. This adjustment in reagent consumption rates, if effected, would introduce a 10% reduction in collector consumption and a 50% reduction in conditioner consumption, which clearly indicates a significant reduction in the overall costs of reagents per tonne ore treated.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"44 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83252972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 4

Determination of the isostatic compensation mechanism of the region of the Adamawa dome, West Central Africa using the admittance technique of gravity data. 利用重力资料导纳技术确定中非西部Adamawa巨蛋区域的均衡补偿机制。

African Journal of Science and Technology Pub Date : 2009-07-27 DOI: 10.4314/AJST.V1I4.44626

J. M. Nnange, Y. Djomani, J. Fairhead, C. Ebinger

{"title":"Determination of the isostatic compensation mechanism of the region of the Adamawa dome, West Central Africa using the admittance technique of gravity data.","authors":"J. M. Nnange, Y. Djomani, J. Fairhead, C. Ebinger","doi":"10.4314/AJST.V1I4.44626","DOIUrl":"https://doi.org/10.4314/AJST.V1I4.44626","url":null,"abstract":"The Adamawa dome in Central Cameroon represents a post-Cretaceous uplifted region, paralled to a Precambrian Foumban Shear Zone, and characterised by Tertiary-Recent volcanic centres of the Cameroon Volcanic Line, and a long negative Bouguer anomaly similar in shape and amplitude to those of other African domes. Using the Admittance Technique of gravity data, the present study aims at computing the Isostatic Compensation Mechanism of the region of the Adamawa dome. The results show that the dome is overcompensated and fits models involving density contrasts beneath the elastic plate and the consequent upwarping of the plate above low density material at depths. A comparison of the Adamawa admittance to the East African and Ethiopian plateau shows that a dynamic compensation mechanism may not be ruled out entirely for the Adamawa dome. Le dome de l’Adamaoua, au centre du Cameroun, est caracterise par des volcans datant du Tertiaire au Recent et appartenant a la ligne volcanique du Cameroun. Ce dome est parallele a une zone cisaillee precambrienne et a une longue anomalie de Bouguer, il ressemble aux autres domes africains par sa forme et son etendue. Dans cette etude, l’admittance ou la fonction de reponse isostatique du dome de l’Adamaoua determinee a partir des donnees gravimetriques montre que le dome est exagerement compense et est comparable aux modeles qui presentent des contrastes de densite entre la plaque elastique et l’escarpement subsequent de la plaque situee au-dessus des couches moins denses des profondeurs. En comparant l’admittance du dome de l’Adamaoua avec des plateaux de l’Afrique de l’Est et d’Ethiopie, on constate qu’un mecanisme de compensation dynamique est aussi une hypothese envisageable dans ce contexte.","PeriodicalId":7641,"journal":{"name":"African Journal of Science and Technology","volume":"52 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2009-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83794369","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 18