Mlewa C.M.,Pwani University
African Journal of Ecology | Year: 2013
The taxonomy of the two established barbus species: Barbus neumayeri and Barbus pellegrini has presented problems due to their close relationship and pronounced character variation within and between their populations. In this study, morphomeristic methods were used to investigate Barbus specimens from several populations in the Lake Kivu - Lake Edward area. Meristic and morphometric data on specimens in the RMAC collection from lakes Kivu and Edward, and the Nyabarongo and Mpanga river systems were analysed using principal component analysis in the PAST software programme. The results revealed additional morphomeristic characters useful in distinguishing the two closely related barbus species; hence, both B. pellegrini and B. neumayeri are redescribed incorporating additional characters to their respective original descriptions. Specimens from Nyabarongo river system were significantly different to warrant recognition as new species; thus, a new species B. new species is proposed and described. Meristically, the B. new species and the two established species are distinguished by lateral line scale counts; while predorsal length, head length and body depth at operculum, expressed as percentage of standard length, are the most diagnostic morphometric characters. © 2013 Blackwell Publishing Ltd.
Olwendo O.J.,Pwani University |
Cesaroni C.,Italian National Institute of Geophysics and Volcanology
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2016
NeQuick 2 is an ionospheric electron density model which provides electron density for a given location. Its output depends on solar activity expressed by 12-month running average sunspot number (R12) or solar radio flux (F10.7). To improve the model capabilities to reproduce electron density, data ingestion techniques have been implemented which replace the standard solar activity indices input with effective parameters that allow adapting a model to a certain data sets. In regions like the Sub-Saharan Africa where few observational data were available until recently, the performance of the ingested model needs some validation. This study investigates the performance of NeQuick 2 in the Kenya region. , a low latitude region by assisting the model with total electron content measurement from a single GNSS station. These measurements are used to calculate effective ionization level parameters, which enable the difference between the measured and modeled TEC over the station to be less or equal to 0.5 TECU. The results show that by using computed effective parameters values as inputs in nearby stations, the model performance is greatly improved for both the low and moderate solar activity. This work has also demonstrated the capability of the model to describe spatial distribution of the total electron content in the low- latitude ionosphere. © 2016 Elsevier Ltd.
Kelvin K.,Kenya Industrial Research and Development Institute KIRDI |
Tole M.,Pwani University
Water, Air, and Soil Pollution | Year: 2011
Constructed wetlands have recently received considerable attention as low cost and efficient means of cleaning up many different types of wastewaters at secondary and tertiary levels. This is an environmentally sound method of wastewater treatment that does not use hazardous chemicals, and is based on the high productivity and nutrient removal capability of the wetland that strongly relies on its intricate ecosystem structure and function. Research work was conducted on a tropical constructed wetland to establish its capability to treat wastewater during the dry season. A comparison of its efficacy with that of conventional wastewater treatment plants was made on the basis of the measured water quality parameters. Temperature, pH, dissolved oxygen, and conductivity were measured in situ. Total suspended solids (TSS), total dissolved solids (TDS), biochemical oxygen demand (BOD5), chemical oxygen demand (COD), phosphorus, ammonia, and nitrites were analyzed in the laboratory. Fecal coliforms were enumerated and Escherichia coli counts were determined. The TSS values reduced from a mean of 102 mg/l at the influent point to 16 mg/l at the effluent point, depicting a reduction of 84.3%. Influent TDS averaged 847 mg/l, while the effluent averaged 783 mg/l. Dry season BOD5 levels were reduced from an average of 286 at the inlet point to 11 mg/l at the outlet representing a reduction efficiency of 96.2%. COD levels were reduced from a mean of 2,002.5 to 47.5 mg/l depicting a removal efficiency of 97.6%. Phosphorus was reduced from a mean of 14 to 11 mg/l representing a percentage removal of 21.4%. Levels of ammonia reduced from a mean of 61 at the influent point to 36 mg/l at the effluent point representing a percent reduction of 41.0%. There was a 99.99% reduction for both the fecal coliforms and E. coli counts. Conductivity of wastewater increased from 1.08 to 1.98 mS, while the pH increased from 6.23 at the inlet point to 7.99 at the outlet of the system. Temperature and dissolved oxygen measurements showed a diurnal variation. The dry season wastewater heavy metal concentrations were in the following ranges: Pb (0.7-6.9 ppm), Cr (0.2-0.5 ppm), Zn (0.1-2.3 ppm), Ni (0.1-1.3 ppm) with Cd and Cu not being detected in the wastewater streams. Overall, tropical constructed wetlands are effective in treating wastewater streams and they perform a lot better than the popularly used waste stabilization ponds. This paper recommends that they can be widely used within the tropics. © 2010 Springer Science+Business Media B.V.
Baluku T.K.,Pwani University |
Hellberg M.A.,University of KwaZulu - Natal
Physics of Plasmas | Year: 2015
Using a kinetic theory approach, dust ion acoustic (DIA) waves are investigated in an unmagnetized collisionless plasma with kappa-distributed electrons and ions, and Maxwellian dust grains of constant charge. Both analytical and numerical results, the latter following from the full solution of the associated dispersion relation, are presented, and a comparison is made. The effects of the ion and electron spectral indices, as well as the species' density (ne/ni) and temperature (Te/Ti) ratios, on the dispersion and damping of the waves are considered. In the long wavelength regime, increases in both the electron spectral index (κe) and the dust density fraction (reduced f=ne/ni) lead to an increase in phase velocity. The range in wavelength over which modes are weakly damped increases with an increase in Te/Ti. However, the ion spectral index, κi, does not have a significant effect on the dispersion or damping of DIA waves. © 2015 AIP Publishing LLC.
Olwendo O.J.,University of Nairobi |
Olwendo O.J.,Pwani University |
Baki P.,University of Nairobi |
Mito C.,University of Nairobi |
Doherty P.,Boston College
Journal of Atmospheric and Solar-Terrestrial Physics | Year: 2012
The ionosphere Total Electron Content (TEC), derived by analyzing dual frequency signals from the Global Positioning System (GPS) recorded from two stations in the Kenyan region is studied. We present the mean diurnal, monthly, seasonal, and annual variation in the ionospheric TEC during the lowest solar activity phase for the periods of 2009-2010. Seasonal variations in daytime TEC show a semiannual periodicity, with minimum in June solstice and maxima in March equinox and December solstice. Using mean hourly monthly TEC, we found semiannual variation with two maxima occurring in months of April-March, and September-October. Seasonal variations in the nighttime TEC reveal semiannual periodicity with high background levels observed in the equinoctial months and low background levels in solstice. Results of seasonal variations and month-to-month variations in TEC have been compared with the TEC derived from the IRI-2007 model using the NeQuick option for the topside electron density. The IRI-TEC is too high for all the seasons except for the March equinox where there seems to be good agreement between observation and model. The model is in good agreement with the monthly variation but overestimates for the months of May, June, July, August and September for all the years studied. The minimum monthly mean is lowest in the model for all the months by about 3-5 TECU in comparison to the GPS-TEC. We attribute this to the fact that the model excludes TEC from the plasmasphere while the overestimation of TEC has been associated to overestimation of the equatorial ion fountain effect and also the inability of the model to predict localized (regional) ionospheric effects arising from electromagnetic forcing at the low latitude. © 2012 Elsevier Ltd.