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Catalytic Properties of Luminescent Tris-Homoleptic Cyclometalated Iridium(III) Complexes in the Oxidation of Morin in Visible Light
Full text linkThe photo-oxidation of Morin, 2′,3,4′,5,7-pentahydroxyflavone by six luminescent homoleptic tris-cyclometalated iridium(III) complexes was investigated with the aim of evaluating the catalytic properties of the complexes. The Iridium complexes were synthesized using 2-(1-naphthyl)-pyridine (npy) ligand and its derivatives such as npy-OMe, npy-CF3 and npy-Me to form Tris-homoleptic cyclometalated complexes; Ir(npy)3, Ir(npy-OMe)3, Ir(npy-CF3)3, Ir(npy-Me)3, Ir(Me-npy-Me)3, and Ir(Me-npy)3 with substitution at para position relative to nitrogen. The ligand substitution positions were found to influence the excited state lifetimes, where the complexes exhibited long lifetimes, τ, 1.4 – 3.6 μs, ensuring time for substrates to react before relaxation to ground state. All the six complexes displayed reversible or pseudo reversible redox processes with ground state oxidation potential range of 0.57 to 0.93V compared to Standard Calomel Electrode in CH2Cl2. The complexes degraded morin with rate constants kobs between 0.023-0.036 s -1 within a timescale of 12 minutes. The Ir(npy-Me)3 complex was found to have a high degradation with a rate constant of kobs = 0.036 s -1. Degradation reactions using all the six Iridium (III) complexes photoredox catalysts were found to follow first order kinetics and ca. 10-fold faster compared to similar oxidative reactions
Artificial Neural Network for Prediction of Pollution Load of Lead, Copper, and Cadmium in a Water Resource: A case Study of River Sosiani, Eldoret Municipality, Kenya
Full text linkThis study aimed at predicting the pollution load of Lead, Copper, and Cadmium in river Sosiani using the Artificial Neural Network, based on parameters, Physico-chemical; turbidity, Electrical Conductivity, and Chemical Oxygen Demand, and Chemical; fluoride and phosphate. The Atomic Absorption Spectrophotometer, Ultra Violet-Visible Spectrophotometer, Ion Selective electrodes and Redox-titration methods were used for analysis in from six sample sites, S1 to S6. A total of 78 datasets from the experimental results were used and divided into three, training 60%, testing 20%, and holdout 20%. The model used the IBM SPSS statistics 20 software, and performances evaluated using Pearson’s correlation coefficient. The mean pollution loads from laboratory analysis were 0.615±0.293, 0.037±0.027, and 0.096±0.030 mg/L while those from ANN were 0.615±0.293, 0.032±0.023, and 0.073±0.033 mg/L for Pb, Cu, and Cd, respectively. The correlation coefficients between the ANN and the observed values for Pb, Cu, and Cd were 0.9999, 0.9910, and 0.9965, respectively. The ANN was able to predict the pollution load of Pb, Cu, and Cd in the river
A Simplified Method for Parameter Determination of a Photovoltaic Module using Manufacturer’s data
Full text linkAccurate and fast modelling and simulation of Photovoltaic module requires careful determination and identification of the unknown parameters required in fitting the voltage-current and power-voltage curves to replicate an actual system. The main objective of this study is to determine ideality factor (A), saturation current (Io), photocurrent (Iph), series resistance (Rs) and shunt resistance (Rsh), the five unknown parameters using Isc, Impp, Vmpp, and Voc available from manufacturer's datasheet. A single diode equivalent circuit has been used to formulate a simple method for evaluating ideality factor (A), saturation current (Io) and photocurrent (Iph) by first assuming that the photovoltaic array has negligible series resistance (Rs) and infinite parallel resistance (Rsh). Additional analysis of series and parallel resistance have been carried out for fine tuning the voltage-current and power-voltage curves to fit the experimental data. The model presented in this work has been simulated using the GNU Octave open-source software. The photovoltaic modules with International Electrotechnical Commission (IEC) 61215 standards have been selected from Solarex-MSX60, BP- SX150 and Kyocera-KK280P. The extracted parameters produced results for the output power with an error of less than 0.5% for all the modules
Electrocatalytic reduction and characterization of Tetrachlorvinphos in acetonitrile-water (1:1) media in presence of cyanocobalamin
Full text linkThis work investigates a possible electrocatalytic degradation of tetrachlorvinphos pesticide in acetonitrile-water media using cyanocobalamin as the catalyst. The catalyst and its derivatives are employed in some organic synthesis due to their ability to form and selectively cleave Co-C bonds. There is inadequate data from previous related works. This study explores possible electrocatalytic route for degradation of tetrachlorvinphos using the catalyst at temperature of 24 ± 1° by cyclic voltammetry method. Tetrachlorvinphos exhibited two consecutive reduction peaks at ~-0.710 ± 0.004 V and ~ -1.096 ± 0.029 V Versus Ag/AgCl. The second reduction peak registered a diffusion coefficient value of 3.68 x 10-5 cm2s-1 and current density of be 5.83 x 10-5 A/cm2. The reduction potential for tetrachlorvinphos in presence of cyanocobalamin was observed to be -0.923 ± 0.03 V versus Ag/AgCl. The diffusion coefficient and current density value was reported at 3.37 x 10-5 cm2s-1 and 2.56 X 10-5 A/cm2 respectively for an electro-reduction process. This implies that, catalytic reduction of the pesticide occurred at a significantly lower potential compared to direct reduction. The over potential saving of about 0.168 V is an indication of the catalyst efficiency on the pesticide degradation
Extending usability of old terrestrial fibre optic cables in Third-World Economic Zones
Full text linkCommunication Fibre Optic Cables (FOC) experience mechanical perturbations while in service thereby deforming their cylindrical shape and increasing birefringence. This leads to Polarization Mode Dispersion (PMD). This work investigated PMD fluctuations in cables that have been buried underground for more than 10 years in a semi-arid climatic region in Kenya. PMD was measured using EXFO-FTB5700 analyzer at hourly intervals in the target cables for 2,480 hours. PMD coefficient of 0.215 √⁄ was recorded. Outage margin () of 2.13 for the 10 Gbps system running an On-Off Keying Non-Return-to-Zero (OOK-NRZ) scheme (with 10ps receiver tolerance) was obtained. Similar analysis for the 100 Gbps system running a Dual Polarization Quadrature Phase-Shift Keying (DPQPSK) scheme (with 30 ps receiver tolerance), revealed an outage margin of 6.38. The availability of 99.29 % (corresponding to a downtime of 53.44 hours per year) revealed that, the cable under test could not sustain PMD limitations in a Dense Wavelength Division Multiplexing (DWDM) system that is deployed with a 10 Gbps transponder in a non-regenerated fibre span exceeding 450 km. 100 Gbps DWDM systems proved more resilient when using DP-QPSK than 10Gbps when using OOK-NRZ. The outage of 53.44 hours per year in a high capacity traffic system can translate to a substantial amount of losses in terms of credit notes to customers for not meeting the standard service level agreement of 99.999 % service availability. To overcome this limitation, it is recommended that 10 Gbps transponders that use OOK-NRZ channel modulation technique be replaced with 100 Gbps that uses DP QPSK technique to mitigate dispersion related outages in the links. This would also effectively provide a lot of idle capacity that can accelerate digitization of institutions and villages
The Synergy between the Comprehensive Nuclear Test-Ban Treaty Organization and the Kenya National Data Centre: Insights from Analysis of Chyulu Earthquake using Seismic and Infrasound Technologies
Full text linkChyulu hills is located on an off-rift volcano in the southwestern Kenya and has been seismically active. On 24th March 2019, Chyulu hills experienced one of the strongest earthquake in Kenya in recent times. The body wave seismic phases, surface wave seismic phase as well as the focal depth was used to analyse the seismic events. The propagation velocity of the seismic wave signal detection through infrasound station I32KE was also used. The seismic and infrasound data were processed using Geotool and DTK-GPMCC softwares provided to member states. The results showed that the seismic event was a natural earthquake by virtue of its focal depth of about 9.1 km and seismic wave velocity of 6.2 km/s. The infrasound station to source azimuth of 139.63o further complemented the epicentre of the seismic event as being in the southwestern Kenya near Chyulu hills
INFLUENCE OF STRATEGY TYPOLOGY ON PERFORMANCE OF FREIGHT FORWARDING COMPANIES IN KENYA
Full text linkStrategic management scholars have argued that firms in the same industryhave varying performance outcome attributed to several aspects such asthose registering exemplary performance embracing strategy typologies inthe face of intense market demands and rapidly changing competition tosurvive and maintain superior performance. The aim of this study was toestablish the influence of strategy typology on performance of freightforwarding companies in Kenya. The research was based on the industrialorganizational economic theory. Positivism research philosophy anddescriptive cross-sectional survey were used. Stratified random sampling wasapplied to derive a study sample of 120 freight forwarding firms. Primarydata was collected using semi-structured questionnaires. Data was analyzedusing regression analysis. The results of the study showed that there was asignificant influence of strategy typology on organizational performance. Thefinding supported the arguments that industrial organization economictheory assumed that an organization’s performance and ultimate survivaldepend on its ability to adapt to industry forces, even though theorganization has limited control. The study is set to enable management tomake informed decisions while planning for their medium and long-termstrategies. Strategies that are appropriately implemented enable theorganization to compete and record improved performance. The researcherrecommended replication of the study in different sectors and countries toenhance understanding of the relationship between strategy typology andorganizational performance
STRATEGY TYPOLOGY, ORGANIZATIONAL FACTORS AND PERFORMANCE OF FREIGHT FORWARDING COMPANIES IN KENYA
Full text linkThe aim of this study was to determine whether organizational factors hadan intervening effect on the relationship between strategy typology andorganizational performance. Organizational factors which comprise ofshared values, skills and systems enable companies to adapt the correctstrategy and direct the conduct of their business to achieve superiorperformance. The research was based on Resource based theory whichpostulates that firm resources consist of assets, capabilities, competences anddefinitive techniques among other organizational factors. The firm resourcesenable the firm to formulate and implement strategies that are aimed atenhancing organizational performance. Positivism research philosophy anddescriptive cross-sectional survey were used in this study. Stratified randomsampling was applied to obtain a study sample of 120 freight forwardingfirms. Primary data was collected using semi-structured questionnaires. Datawas analyzed using regression analysis. The results of the study showed thatthere was a significant influence of strategy typology on organizationalperformance. However, the study found that organizational factors have nosignificant intervening influence on the relationship between strategytypology and organizational performance. This indicates that themanagement should consider enhancing skills of their human resources andinstill the virtues of shared values across various organizational functions.Also, develop systems that are endowed with technology that would ensureseamless flow of communication that enhances firm performance
An artificial neural network model for predicting maize prices in Kenya
Full text linkIn the current globalization era, food security management in developing countries like Kenya that consider agriculture as a dominant economic activity require efficient and reliable food price forecasting models more than ever. Due to rare data availability and data time lag in developing agricultural dominated economies, normally needs reliance on time series forecasting models. Artificial Neural Network (ANN) modelling methodology gives a possible potential price forecasting method in developing countries based on available data. This study demonstrated the superiority of ANN over linear model methodology based on Root Mean Squared Error (RMSE) and Mean Absolute Deviation (MAD) performance metrics. Lower comparative RMSE value would imply a better prediction while results with lower MAD were more close to actual values. Empirical study showed that an ANN model is able to capture adequate number of directions of monthly price change as compared to the linear models. It has also been observed that feeding the model with lagged observation of the same variable leads to more accurate forecasts than its performance in its multivariate form. Models reviewed during this study, showed little effort in development of research tools, therefore we purposed to develop a user- friendly ANN prototype based on the proposed model
People living with HIV on atazanavir-based second line regimens are not highly adherent to therapy; a report from a tertiary referral hospital in Kenya
Full text linkBackground: Adherence to antiretroviral therapy is a necessity for the attainment of favorable treatment outcomes. Several factors are known to influence adherence levels among different cohorts of patients. These factors are likely to be different for patients on second line therapies and knowing them might improve the quality of care provided and generally raise adherence levels. Objective: To determine adherence levels and their determinants in people living with HIV on second line therapy. Methods: A cross-sectional study was undertaken in a HIV clinic within Kenyatta National Hospital in October, 2017. Data were collected through interviews and adherence was assessed by oral interview of past medication use and then analyzed in R. Results: One hundred and ten patients were enrolled; 46 (41.8%) of whom were males. The mean age was 39.8 years (± 11.8). Most participants, 96 (87.3%), were moderately adherent while 14 (12.7%) had low adherence. None were highly adherent. Age (aOR = 1.10, 95% CI; 1.04, 1.19) and depression (aOR =0.17, 95% CI 0.04, 0.64) were independently associated with adherence. Conclusion: None of the patients on second line regimens were highly adherent to therapy. Younger patients and those with depression require additional adherence counselling. Key words: People Living With HIV, Antiretroviral Therapy, Adherenc