Search

In order to enable the solar activity of ZnO and to reduce the rate of recombination of the electron–hole in the use of Ca ferrite for photoredox reaction, heterojunction composite of these two semiconductors was prepared and characterized. The solar activity of the heterojunction was determined in two separate synthetic waste waters containing Rhodamine B (RhB) and Cr (VI). The underlying mechanisms of the RhB decolourization/mineralization and Cr (VI) reduction to Cr (III) were elucidated. Within the calcination temperature and precursors combination ratios (i.e. Ca Ferrite and ZnO ratio) studied, the optimum photoredox efficiency was achieved at 500 °C and precursors combination ratio of 1:1. The SEM analysis and elemental mapping showed an even dispersion of the precursors mix. The presence of Ca Ferrite conferred solar activity and narrowed the band gap of the heterojunction. The photoluminescence spectra and electro impedance spectra showed that the recombination rate of the heterojunction was lowered than that of any of the precursors. The fitting of the time–concentration profiles of the RhB decolourization/mineralization and Cr(VI) reduction to the pseudo first order kinetic equation showed that the values of the rate constants greatly depended on the initial pollutant concentrations. While all the generated reactive species were found to be responsible for the decolourization/mineralization of RhB, the superoxide was the sole reactive species ascertained for the Cr (VI) reduction to Cr (III).

The anti-bacterial properties of aqueous and ethanol extracts of the calyces of Hibiscus sabdariffa on five bacteria genera, namely, Escherichia coli, Staphylococcus aureus, Salmonella typhi, Shigella dysenteriae and Streptococcus mutans were evaluated using agar well and disc diffusion methods. Six bioactive compounds were identified from phytochemical analysis of the juice extract of H. sabdariffa. Analysis revealed the presence of the following in the water and ethanol extracts: saponins (1.46%), alkaloids (0.09%), tannins (0.19%), total phenols (0.07%), flavonoids (2.41%) and glycosides (0.13%). The results revealed that both water and ethanol extracts had significant anti-bacterial effects (P ≤ 0.05) against the tested pathogenic bacteria genera with the ethanol extract of Roselle having higher anti-bacterial effects against all the pathogens. S. aureus and E. coli were the most sensitive to Roselle juice extract (47.9 and 45. 8 mm zones of inhibition, respectively). The minimum inhibitory concentration (MIC) for the ethanol extract of H. sabdariffa was between 0.26 and 1.03 mg/ml. The results observed in this study contribute to scientific baseline data on the anti-bacterial activities of H. sabdariffa juice extract. Key words: Antimicrobial activity, minimum inhibitory concentration, pathogenic bacteria, phytochemical, Hibiscus sabdariffa.

Sclerotium rolfsii Sacc. is an important fungal pathogen affecting the production of tomato (Lycopersicon esculentum Mill.). Conventional control methods using chemicals are expensive, which constitute environmental hazards. This has necessitated the search for alternatives in botanicals. Ethanol and supernatant solution of fermented maize slurry extracts from Ocimum gratissimum, Cymbopogon citratus, Xylopia aethiopica, Aframomum melegueta and Allium sativum were evaluated. In vitro test was carried out at 1, 2, 3, 4 and 5% concentrations against the pathogen. Mycelial growth was significantly reduced in the following descending order: O. gratissimum > A. melegueta > A. sativum > X. aethiopica > C. citratus. Supernatant solution extracts of O. gratissimum and A. melegueta at 5% concentration gave highest mycelial reduction (0.00 mm), respectively, while O. gratissimum ethanol extract recorded highest mycelial reduction (0.23 mm) among the ethanol extracts. Supernatant solution of fermented maize slurry ex...

Water is one of the indispensable resources for the continued existence of all living things including man. Government has failed to adequately provide safe, pipe-borne water for the increasing population in Nigeria and this has encouraged the sale of drinking water by private enterprises that have little knowledge about good manufacturing practices. This study investigated the bacteriological quality of commercial sachet-packed drinking water at point-of-sale in south-western Nigeria with emphasis on pathogenic bacteria in 108 samples tested, in order to evaluate the contribution of this popular product to the increasing incidence of typhoid fever and related illnesses. Ten-fold serial dilution of water samples and the pour plate technique were used to investigate the presence of Salmonella and indicator coliform Escherichia coli in sachet-packed water samples. Aerobic and total coliforms were also enumerated. Characterization of isolates was by in-vitro cultural, morphological and biochemical characteristics. Results showed that 87% of the sachet-packed water samples examined contained Salmonella and/or Escherichia coli, indicative of fecal contamination and inadequate water treatment or no treatment at all. The study also showed that about 65% of the polythene sachets used was not of food-grade quality and imparted polyester taste in the water samples. High aerobic colony counts in the order of 6.0 log CFU/ml was recorded from 93% of water samples examined. E. coli counts used as indicator of hygiene criteria were present in the range of 98 and 106 cfu/100ml of water sample, while Salmonella counts used as food safety criteria were between 2.12x101 and 2.20x101. These mean values were greater than the international guidelines for drinking water quality. The findings of this study indicate that sachet-packed water samples examined do not meet microbiological standards for drinking water quality. National surveillance agencies need to monitor and enforce compliance with microbiological safety standards of sachet-packed water being sold to the public.

The intractable problem of tuberculosis (TB) control despite advances in chemotherapy requires additional research effort to unravel the pertinent factors that make the disease preponderant in developing countries. The present study examined the pattern of TB morbidity in Lagos metropolis with the aim of identifying the explanatory factors. Data on reported cases of pulmonary TB were collected from five DOTS centres (1997 to 2002). Moreover, 120 TB patients were sampled from the DOTS centres so as to provide additional information. Results showed significant variation in the morbidity pattern of TB between residential areas in Lagos metropolis (p < 0.05). Furthermore, TB cases showed a rapid increase between 1997 and 2002. About 58% of TB cases were reported by males, age groups 21-30 and 31-40 accounted for 61.8% while 55.8% of the patients earn below N10,000 monthly. From the regression model, house quality accounted for 67.3% of the morbidity pattern of TB.