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15 results on '"Kamau, G. N."'

1. Rice Husk Ash Cement – An alternative pozzolana cement for Kenyan building Industry

Author

Waswa-Sabuni, B., Syagga, P. M, Dulo, S. O, and Kamau, G. N

Abstract

A survey was carried out to assess the quantities of rice husks at the rice milling plants in the country. Mwea, Ahero, West Kano and Bunyala rice growing areas were visited. Large deposits of husks exist at rice milling plants in these areas with Mwea leading. Samples of rice husks from Mwea Rice Mills were used to confirm the pozzolanic properties of rice husk ash (RHA). Chemical analysis of the ash showed high silica (SiO2) content (more than 50%) which is a requirement for a good pozzolanic material. The engineering properties of the cement resulting from a mixture of OPC plus RHA and lime plus RHA were satisfactory with addition of up to 50% RHA. The RHA improved greatly the compressive strength of lime. The cost of producing RHA was considered in pricing the resulting binder and it showed that the use of RHA to supplement OPC and lime reduced the overall cost of the binder. (Journal of Civil Engineering, JKUAT: 2002 8: 13-26)

Published
2004

3. Letters and Viewpoints Potentials of Using Waste Burnt Clay as a Pozzolanic Material in Kenya

Author

Syagga, P. M., Kamau, G. N., Waswa-Sabuni, B., and Dulo, S. O.

Subjects
waste burnt clay, pozzolanic material, masonry clement, building standards
Abstract

Samples of waste burnt clay were collected from various parts of the country to study their pozzolanic properties. The samples were ground into fine powder and taken for chemical tests. Results from the chemical tests on all the samples showed high silica content. In fact the combined percentages of Silica (SiO2), Alumina (Al2O3) and Iron Oxide (Fe2O3) was more than 70%, a requirement by the Kenyan standard for a suitable pozzolanic material. One sample from a major factory (being a large quantity) was mixed with various proportions of Ordinary Portland cement (OPC) and used for physical tests. Results showed compressive strengths way above the recommended for masonry cement when up to 50% OPC was replaced with burnt clay. For masonry works 50% OPC replacement with burnt clay will still give satisfactory results and reduce cost of binder by at least 20%. Discovery and Innovation Vol. 13 no. 3/4 December (2001) pp. 114-118 KEY WORDS: waste burnt clay, pozzolanic material, masonry clement, building standards

Published
2001

7. Distribution, Fate, and Effects of 14C-DDT in Model Ecosystems Simulating Tropical Kenyan Freshwater Environments.

Author

Wandiga, S. O., Yebiyo, B. T., Lalah, J. O., and Kamau, G. N.

Subjects
DDT (Insecticide), INSECTICIDES, PESTICIDES, BIODEGRADATION, BIOTIC communities, FRESHWATER ecology
Abstract

This article investigates the distribution, bioaccumulation, depuration, degradation and acute toxicity of DDT in model tropical fresh water ecosystems in Kenya. Acute toxicity of DDT to the fish Tilapia zilli was studied in a stabilized aquarium containing fresh lakewater. The rate of elimination of the pesticide through diffusion decreased as the difference between the concentration of the pesticide in fish and water decreased. The primary metabolites of DDT were detected in the fresh water sediments as early as 24 hours after spiking.

Published
2005
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8. Myoglobin Coadsorbed on Electrodes from Microemulsions Provides Reversible Electrochemistry and Tunable Electrochemical Catalysis

Author

Kamau, G. N., Guto, M. P., Munge, B., Panchagnula, V., and Rusling, J. F.

Abstract

The iron heme protein myoglobin (Mb) coadsorbs with surfactant onto glassy carbon, pyrolytic graphite, and platinum electrodes from microemulsions of sodium dodecyl sulfate or cetyltrimethylammonium bromide, water, oil, and pentanol. Adsorbates on all electrodes gave reversible heme FeIII/FeII voltammetry for Mb, which spectroscopy showed to be in near-native conformation. The nature of the adsorbed films was highly dependent on the electrode material. The carbon electrodes gave nonideal thin-film voltammetry, but Pt electrode voltammetry was more consistent with thick films featuring in-film diffusion of protein. Mb films on all electrodes supported electrochemical catalytic reduction of 1,2-dibromocyclohexane (DBCH) and trichloroacetic acid (TCA). Results on carbon electrodes were consistent with Michaelis−Menten enzyme kinetics. The catalytic rate and binding of reactant to Mb were more efficient for DBCH in microemulsions than in aqueous buffer but were more efficient for TCA in aqueous buffer. Microemulsions exerted a tuning effect on the reactivity of these reactants according to their hydrophobicity. The more hydrophobic DBCH had better access to Mb in the surfactant films and reacted at a faster rate, while the hydrophilic TCA had poor access to the catalyst in the film.

Published
2003

9. Enhanced Rates of Organic Dehalogenations in a Microemulsion Using Adsorbed Metal Phthalocyanines on Electrodes

Author

Kamau, G. N. and Rusling, J. F.

Abstract

Copper and nickel phthalocyanines and their tetrasulfonates adsorbed onto carbon electrodes were used for electrochemical catalytic reduction of 1,2-dibromobutane (DBB), trans-1,2-dibromocyclohexane (DBCH), and trichloroacetic acid (TCA) in a bicontinuous microemulsion made from didodecyldimethylammonium bromide (DDAB), dodecane, and water and in homogeneous acetonitrile/water. Square wave voltammetry was used to obtain apparent pseudo-first-order rate constants (k‘) for the rate-determining step (rds) involving reaction of organohalides with catalysts reduced by two electrons. Reductions of DBCH and DBB gave larger k‘ values in the microemulsion than in homogeneous solvent. For reduction of TCA, larger k‘ values were found in the homogeneous solvent. Results suggest that DBCH and DBB give higher reaction rates in the microemulsion because of preconcentration of the relatively nonpolar organohalides into a surfactant film on the MPCTS-coated electrode. TCA may be partly rejected from the film, decreasing its reaction rate. Thus, when using electrodes with adsorbed catalysts in microemulsions, reactant concentration in an adsorbed film on the electrode appears to be an important rate-controlling factor.

Published
1996

11. COMPARATIVE ASSESSMENT OF TOTAL PHENOLIC CONTENT IN SELECTED MEDICINAL PLANTS.

Author

Johnson CE, Oladeinde FO, Kinyua AM, Michelin R, Makinde JM, Jaiyesimi AA, Mbiti WN, Kamau GN, Kofi-Tsekpo WM, Pramanik S, Williams A, Kennedy A, Bronner Y, Clarke K, Fofonoff P, and Nemerson D

Abstract

This study was to compare the total phenolic (TP) content in extracts from eleven plant materials collected at different geographical locations in Kenya, Nigeria, and USA. These plants have been selected because the majority of them are highly pigmented, from yellow to purple, and would therefore have economic value in industries for producing antioxidants and surfactants. Two of them were collected from the industrial and domestic waste outlets. Each analysis was achieved using the Folin-Ciocalteau technique. The order of decreasing phenolic acid content as gallic acid concentration (mg/g dry weight) was Prunus africana (55.14) > Acacia tortilis (42.11) > Khaya grandifoliola (17.54) > Curcuma longa (17.23) > Vernonia amygdalina (14.9)> Russelia equisetiformis (14.03) > Calendula officinalis (7.96) >Phragmites australis (control) (7.09) > Rauwolfia vomitoria (6.69) > Phragmites australis (industrial) (6.21) > Cnidoscolus aconitifolius (5.6). The TP contents of Spartina alterniflora species were below the detection limit.

Published
2008
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12. Distribution, fate, and effects of 14C-DDT in model ecosystems simulating tropical Kenyan freshwater environments.

Author

Wandiga SO, Yebiyo BT, Lalah JO, and Kamau GN

Subjects
Animals, Carbon Radioisotopes, DDT analysis, DDT pharmacokinetics, Ecosystem, Kenya, Longevity drug effects, Nymphaea chemistry, Nymphaea metabolism, Toxicity Tests, Acute, Water Pollutants, Chemical analysis, Water Pollutants, Chemical pharmacokinetics, DDT toxicity, Fresh Water chemistry, Geologic Sediments chemistry, Nymphaea drug effects, Tilapia metabolism, Water Pollutants, Chemical toxicity
Published
2005
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13. Potential antitermite compounds from Juniperus procera extracts.

Author

Kinyanjui T, Gitu PM, and Kamau GN

Subjects
Animals, Chromatography, Thin Layer, Gas Chromatography-Mass Spectrometry, Insect Control, Plant Extracts chemistry, Isoptera drug effects, Juniperus chemistry, Plant Extracts toxicity
Abstract

Thin layer chromatography (TLC) analysis revealed that destructive distillation of Juniperus procera tree gave ten major components, whereas Croton megalocarpus tree yielded five components. This was confirmed by gas chromatography (GC). The components were isolated by column chromatography and analysed using infrared, ultra-violet, visible and mass spectroscopy (MS) techniques. The whole extract was about 30.3% of the starting material (sawdust) and consisted of 77.5% water and 22.5% oily reddish-brown layer. The extracts had alcoholic and phenolic compounds together with acids. Cedrol, a tertiary tricyclic alcohol, was found to be in the greatest proportion in the oily layer. IR spectra with a peak beyond 3000 cm(-1), UV-VIS absorption maxima at 230 nm and mass spectra with m/e 204 suggested the presence of cedrene in the extract.

Published
2000
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14. Films formed by oxidation of ferrocene at platinum electrodes.

Author

Kamau GN, Saccucci TM, Gounili G, Nassar AE, and Rusling JF

Subjects
Electrochemistry, Metallocenes, Microelectrodes, Oxidation-Reduction, Platinum, Ferrous Compounds chemistry, Organometallic Compounds chemistry
Abstract

Oxidation of ferrocene in acetonitrile resulted in films on Pt electrodes under voltammetric conditions. Films were more readily formed with tetrabutylammonium tetrafluoroborate as the electrolyte than with perchlorate salts. No films were detected when ferrocene was oxidized in aqueous 0.05 M cetyltrimethylammonium bromide (CTAB). Analysis of the films by FT-IR and Auger spectroscopy confirmed iron-containing oxidation products on Pt, presumably from chemical reactions of ferricinium ions. Oxidation of 50-100 mM ferrocene in acetonitrile on Pt yielded insoluble precipitates. Analyses by MS, FT-IR, and UV-visible (water extract), suggested a mixture of oligomeric material and a small fraction of ferricinium ions. Film formation had much less influence on voltammograms on 12.5-micron-radius Pt microdisks than on 0.5-mm-radius Pt. This is consistent with the smaller sensitivity of microelectrodes to chemical reactions following charge transfer. The smaller apparent heterogeneous rate constants (k zero') found for ferrocene on macroelectrodes than on microelectrodes could possibly be influenced by film formation on larger Pt electrodes. Correlations between macro- and microelectrode kinetic data suggest that macroelectrode k zero' values may be valid in a relative sense when ohmic drop is negligible. Bias in k zero's on conventional-sized electrodes should be small in solutions giving minimal film formation, such as micellar CTAB.

Published
1994
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