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Tropospheric radio wave signals experience loss due to multipath effect, scattering and other forms of attenuation through the atmospheric medium, primarily due to variations in weather conditions with time. The knowledge of surface... more
Tropospheric radio wave signals experience loss due to multipath effect, scattering and other forms of attenuation through the atmospheric medium, primarily due to variations in weather conditions with time. The knowledge of surface refractivity profile is important for optimal planning of Very High Frequency/Ultra High Frequency (VHF/UHF) terrestrial radio links in a region. The study of surface refractivity (Ns) over the North-Central Nigeria was carried out using meteorological data from seven locations in North-Central zone of Nigeria. The seasonal variations of Ns were also derived using the monthly summaries of surface data obtained from Nigerian Meteorological Agency (NIMET) over seven stations of Abuja, Lafia, Lokoja, Makurdi, Jos, Minna and Ilorin between 2005 and 2010.The results indicated that the monthly averages of radio refractivity during the rainy season months (April to October) are greater than the Ns values during the dry season months (November to March) for all ...
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The knowledge of good refractivity profile is vital for proper planning of terrestrial communication links; surface refractivity profile of a station is particularly required for enhanced planning and prediction of performance of... more
The knowledge of good refractivity profile is vital for proper planning of terrestrial communication links; surface refractivity profile of a station is particularly required for enhanced planning and prediction of performance of terrestrial radio links especially in tropical regions where International Telecommunication Union Recommendations (ITU-R) has called for such local propagation data. The diurnal surface radio refractivity Ns over Sokoto was investigated for a period of three years (2008-2010). High values of Ns were recorded in the early morning hours while low values were recorded during afternoon hours. The least mean hourly Ns varied between 270-280 N-units in January (a typical dry season month in Sokoto) while the mean maximum was recorded between 345-360 N- units in July (a typical rainy season month). Also, average seasonal variation of Ns was 356-440 N-units in rainy season and 270-285 N-units in dry season. The result of this investigation also showed that relativ...
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Fumonisins are toxic and carcinogenic compounds produced by fungi that can be readily found in maize. The establishment of maximum limits for fumonisins requires the development of scientifically based sampling plans to detect fumonisin... more
Fumonisins are toxic and carcinogenic compounds produced by fungi that can be readily found in maize. The establishment of maximum limits for fumonisins requires the development of scientifically based sampling plans to detect fumonisin in maize. As part of an International Atomic Energy Agency effort to assist developing countries to control mycotoxin contamination, a study was conducted to design sampling plans to detect fumonisin in maize produced and marketed in Nigeria. Eighty-six maize lots were sampled according to an experimental protocol in which an average of 17 test samples, 100 g each, were taken from each lot and analyzed for fumonisin B1 by using liquid chromatography. The total variability associated with the fumonisin test procedure was measured for each lot. Regression equations were developed to predict the total variance as a function of fumonisin concentration. The observed fumonisin distribution among the replicated-sample test results was compared with several ...
Research Interests: Mathematics, Algorithms, Analytical Chemistry, Performance, Nigeria, and 15 moreMedicine, Food Analysis, Regression Analysis, Plants, Fruit, High Performance Liquid Chromatography, High Pressure Liquid Chromatography, Fumonisin, Gramineae, Mycotoxin, Lot, Reproducibility of Results, Food Contamination, Food Sciences, and Fumonisins
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Seventy-one (71) food samples were analyzed for the mycotoxin fumonisin by a monoclonal antibody based competitive enzyme-linked immunosorbent assay (ELISA). Fumonisins were detected primarily in corn-based products with 7/12, 2/2 and 1/3... more
Seventy-one (71) food samples were analyzed for the mycotoxin fumonisin by a monoclonal antibody based competitive enzyme-linked immunosorbent assay (ELISA). Fumonisins were detected primarily in corn-based products with 7/12, 2/2 and 1/3 and 1/7 yellow cornmeal, blue cornmeal, corn muffin mix, and mixed grain cereal samples yielding positive results, respectively. When the positive samples and randomly selected negative samples were assessed by other methods, correlations (r values) between ELISA and gas chromatography-mass spectrometry (GC-MS), ELISA and high-pressure liquid chromatography (HPLC) and GC-MS and HPLC were 0.478 (p < 0.05), 0.512 (p < 0.05), and 0.946 (p < 0.01), respectively. The results suggested that although the immunoassay could be used for screening of fumonisin in food samples, higher estimates were attained by ELISA than by the other two methods particularly in the more contaminated samples. These observations may result from differences in sample pr...
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The performance of an experimental polyclonal antibody (PAb)-based competitive direct enzyme-linked immunosorbent assay (CD-ELISA) developed for the analysis of fumonisins in corn was assessed by comparison with an established... more
The performance of an experimental polyclonal antibody (PAb)-based competitive direct enzyme-linked immunosorbent assay (CD-ELISA) developed for the analysis of fumonisins in corn was assessed by comparison with an established high-performance liquid chromatography (HPLC) method. The comparative study was conducted using a series of 20 corn samples naturally contaminated with combined fumonisin levels ranging from <0.05 to >5 μg/g (ppm). Linear regression analysis between the results generated by HPLC and CD-ELISA provided correlation coefficients (r) and regression slopes (b) of r = 0.960, b = 1.493 (P < 0.001); r = 0.865, b = 3.903 (P < 0.001); and r = 0.832, b = 0.107 (P < 0.001) for the individual fumonisins B1 (FB1), B2 (FB2) and B3 (FB3), respectively, while corresponding values of r = 0.967, b = 1.059 (P < 0.001) were obtained for the combined FB1, FB2, and FB3 concentrations. In 3 of 18 fumonisin-positive corn samples, combined fumonisin levels determined b...
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The only way to achieve a more precise estimate of the true lot concentration is to reduce the total variability of the mycotoxin test procedure. The total variability of the test procedure can be reduced by reducing the variability... more
The only way to achieve a more precise estimate of the true lot concentration is to reduce the total variability of the mycotoxin test procedure. The total variability of the test procedure can be reduced by reducing the variability associated with each step of the mycotoxin test procedure. Increasing the size of the laboratory sample can reduce the sampling variability. The sample preparation variability can be reduced either by increasing the size of the test portion and/or by increasing the degree of comminuting (increasing the number of particles per unit mass in the test portion). The analytical variance can be reduced by either increasing the number of aliquots quantified by the analytical method and/or using a more precise quantification method (e.g. using HPLC instead of TLC). If the variability associated with one or more of these steps can be reduced, then the total variability associated with a mycotoxin test result can be reduced (Eq. 8.1).
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It is important to be able to detect and quantify the mycotoxin concentration in foods and feeds destined for human and animal consumption. In research, quality assurance, and regulatory activities, correct decisions concerning the fate... more
It is important to be able to detect and quantify the mycotoxin concentration in foods and feeds destined for human and animal consumption. In research, quality assurance, and regulatory activities, correct decisions concerning the fate of commercial lots can only be made if the mycotoxin concentration in the lot can be estimated with a high degree of accuracy and precision. The mycotoxin concentration of a lot is usually estimated by measuring the mycotoxin concentration in a small representative sample taken from the lot, called the laboratory sample(Fig. 2.1).
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Once the mycotoxin concentration is quantified, the concentration value is used to estimate the true lot concentration or is compared to an accept/reject limit (ARL). The ARL is a predefined threshold concentration, usually equal to a... more
Once the mycotoxin concentration is quantified, the concentration value is used to estimate the true lot concentration or is compared to an accept/reject limit (ARL). The ARL is a predefined threshold concentration, usually equal to a legal limit used in regulatory applications. If the mycotoxin concentration in a test portion taken from a laboratory sample is less than or equal to the ARL, the lot is accepted, otherwise the lot is rejected.
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A survey has been carried out in Italy on the natural occurrence of fumonisins B1 (FB1) and B2 (FB2) in corn kernels from regional distributors and corn genotypes from breeding stations as well as in commercially available corn-based food... more
A survey has been carried out in Italy on the natural occurrence of fumonisins B1 (FB1) and B2 (FB2) in corn kernels from regional distributors and corn genotypes from breeding stations as well as in commercially available corn-based food products. All corn samples were fumonisin positive at levels up to 5310 ng/g for FB1 and up to 1480 for FB2. In corn-based foods, the highest fumonisin contamination levels were recorded in puffed (extruded) corn containing up to 6100 ng/g of FB1 and up to 520 ng/g of FB2. Levels ranging from 420 to 3760 ng/g FB1 and from 80 to 910 ng/g FB2 were detected in corn grits, corn flour or polenta (a sort of thick porridge made with corn flour). All sweet corn samples examined were positive for FB1, at levels varying from 60 to 790 ng/g FB1, but negative for FB2. Lower levels of fumonisins were found in other commodities, such as popcorn (up to 60 ng/g FB1 and 20 ng/g FB2), tortilla chips (up to 60 ng/g FB1 and 10 ng/g FB2), and corn flakes (10 ng/g FB1). These findings indicate a high degree of human exposure to fumonisins in Italy through the ingestion of commercially available corn-based foodstuffs.
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The effect of gamma-irradiation on fumonisin B1 (FB1) and fumonisin B2 (FB2) occurring in maize materials has been investigated together with the stability of fumonisins in gamma-irradiated maize stored at different temperatures (-18 to... more
The effect of gamma-irradiation on fumonisin B1 (FB1) and fumonisin B2 (FB2) occurring in maize materials has been investigated together with the stability of fumonisins in gamma-irradiated maize stored at different temperatures (-18 to +40 degrees C) for different periods (2, 4, 13 and 26 weeks). Fifteen KGy gamma-irradiation was required to sterilize efficiently maize flour. This process caused a decrease in fumonisin content of about 20%. The stability studies showed that fumonisins are stable in gamma-irradiated maize for at least 6 months at 25 degrees C or at least 4 weeks at 40 degrees C. These data indicate that gamma-irradiation is an appropriate technique for obtaining sterilized maize materials to be used for intercomparison studies on analytical procedures for the measurement of the fumonisin content.
Research Interests: Engineering, Chemistry, Gamma Rays, Medicine, Maize, and 14 moreTemperature, Sterilization, High Pressure Liquid Chromatography, CHEMICAL SCIENCES, Fumonisin, Zea mays, Irradiation, Food Contamination, Carboxylic Acids, Drug Stability, Gamma Irradiation, Fumonisins, drug storage, and Medical and Health Sciences
The results of an intercomparison study for the analysis of fumonisin B1 (FB1) and fumonisin B2 (FB2) in a contaminated maize material (Maize B, containing approximately 2 micrograms/g FB1 and 1 micrograms/g FB2) and its... more
The results of an intercomparison study for the analysis of fumonisin B1 (FB1) and fumonisin B2 (FB2) in a contaminated maize material (Maize B, containing approximately 2 micrograms/g FB1 and 1 micrograms/g FB2) and its &#39;blank&#39; counterpart (Maize A, containing less than 20 ng/g FB1 and FB2) are reported. Maize materials were distributed in 60 g sachets, submitted to gamma-irradiation at 15 kGy, and distributed to participating laboratories. The study was carried out by 24 European laboratories, most of which have national or international responsibilities for food/feed quality control. Participants used basically one method with some modifications, based on clean-up through SAX minicolumn and reversed phase HPLC with fluorescence detection of the OPA-fumonisin derivatives. The intercomparison study generated data (after correction for recoveries) with repeatability and reproducibility levels of: RSDr = 10% and RSDR = 11% for FB1; RSDr = 11% and RDSR = 13% for FB2. The recoveries obtained by most participants were considered low (70% for FB1 and 69% for FB2), being considerably affected by the extraction mode. Average recoveries for laboratories using blending were 62% and 60%, whereas for laboratories using shaking they were 85% and 86% for FB1 and FB2, respectively. The day-to-day- data showed a between-day, within-laboratory repeatability lower than 15% (CV &lt; 15%) for FB1 for all laboratories, whereas only three laboratories obtained a between-day, within-laboratory reproducibility higher than 15% (CV &gt; 15%) for FB2.
Research Interests: Engineering, Chemistry, Analytical Chemistry, Chromatography, Medicine, and 15 moreQuality Control, European Commission, Europe, Maize, Animal Feed, High Pressure Liquid Chromatography, CHEMICAL SCIENCES, Fumonisin, Mycotoxin, Food Contamination, Carboxylic Acids, Liver cancer, Fumonisins, Pulmonary Edema, and Medical and Health Sciences
Because of the variability among laboratory sample test results, two types of mistakes are associated with any mycotoxin-sampling plan. First, good lots (lots with a concentration less than or equal to the legal limit) will test bad and... more
Because of the variability among laboratory sample test results, two types of mistakes are associated with any mycotoxin-sampling plan. First, good lots (lots with a concentration less than or equal to the legal limit) will test bad and be rejected by the sampling plan. The chances of making this type of mistake is often called the seller’s risk (false positives or type I, α error) since these lots will be rejected at an unnecessary cost to the seller of the product. Secondly, bad lots (lots with a concentration greater than the legal limit) will test good and be accepted by the sampling program. The chances of making this type of mistake is called the buyer’s risk (false negatives, or type II, β error) since contaminated lots will be processed into feed or food causing possible health problems and/or economic loss to the buyer of the product.