AJOL: Global Journal of Pure and Applied Sciences: Volume 7 No 1 January 2001 Abstracts

POST-HARVEST DETERIORATION OF IRISH POTATO (Solanum tuberosum L) BY MICRO-ORGANISMS
N. A. ONUNKA, and U. N. EKWENYE

Post harvest dterioration of Irish potato (Solanum tuberosum) (L) under storage was investigated in the laboratory and found to be caused by fusarium solani. This fungus is a primary invader of the tubers and entry is through wounds arising from harvesting and handling. A range of growth media were used and potato dextrose broth supported the growth of the organism better than potato carrot broth and Czapek dox broth. The least growth was observed in Czapek dox broth.

Growth of this fungus was maximum at temperature of 30 ºC and relative humidity of 90% while 4 ºC was found to be best storage temperature for the crop. A pH range of 2 – 10 supported the growth of the fungus with maximum growth occurring at pH of 4.

RESPONSE OF WATER LEAF VEGETABLE (Talinum Trangulare Jacq) TO NITROGEN AND ORGANIC FERTILIZERS IN CALABAR AREA OF SOUTHEAST NIGERIA
U. C. AMALU, and B. F. D. OKO

Investigations were carried out to determine the growth and yield responses of waterleaf (Talinum traingulare Jacq), a vegetable crop, to different sources and levels of nitrogen and organic fertilizers at the Teaching and Research Farm of the University of Calabar in a high rainfall area of Southeast Nigeria. The results showed as expected, that yield performance was better in manured than in control plots. Responses varied very widely with sources of maures in terms of vegetative growth and yields. Effects of the compound fertilizer (NPK) were superior to single fertilizer (urea) and organic manure (cowdung) in that order. Average cumulative fresh weight of waterleaf under the different manurial regimes were 1.89 kg, 1.65 kg and 0.89 kg for NPK, urea and cowdung, respectively. Studies are, however, continuing to enable us elucidate current fertilizer rates as well as develop optimum fertilizer formulae for intensive Talinum cultivation in the zone.

CYTOTOXICITY OF CELL FREE FILTRATES OF CAMPYLOBACTER JEJUNI ISOLATED IN LAGOS, NIGERIA
J. EPOKE, and A. O. COKER

Culture filtrates of Campylobacter jejuni strains isolated from clinical specimens in Lagos Nigeria were tested for toxic activity. Two out of five filtrates tested manifested cytopathic effect on BHK cells. The effects were mainly cytotoxic and cytotonic. Toxic activity of C. jejuni filtrates was much lower than toxic activity elicited by a known toxigenic Vibrio cholerae strain. The reduced potency of C. jejuni culture filtrate may thus account for lower volume of diarrhoea seen in C. jejuni enteritis as compared with classical cholera “rice water stool”.

MOULTING CYCLE AND GROWTH IN THE AFRICAN RIVER PRAWN Macrobrachium vollenhovenii (Herklots 1857) (Decapoda, Palaemonidae)

The moult cycle in adults and juveniles of Macrobrachium vollenhovenii was investigated. Increase in length at moult calculated as growth factor (% increment in length) was 1.06 (21%) and 0.86 (12%) for juveniles and adults, respectively. Limb regeneration was found to accelerate the moulting process in the species. The aquacultural implications of these results are discussed.

OBSERVATIONS ON THE HELMINTH PARASITES OF WILD AND CULTURED TILAPIA IN THE OKIGWE AREA OF IMO STATE, NIGERIA

A total of 449 specimen of Tilapia comprising Tilapia nilotica (Oreochromis), Tilapia zilli and Tilapia galilea (Sarotherodon) collected from the Federal and State Fish ponds, Okigwe and from the Imo River were examined for helminth infections. Out of these, only 5 (1.1%) fish were infected. These came from the wild. Tilapia zilli had the highest rate of infection (66.6%) while the prevalence rate of infection of Tilapia observed was 50.0%. Parasites recovered included Enclinostomum heterostomum (14.3%), Paracamallanus cyathopharynx (14.3%) and Caryophylleus sp (42.8%). Comparing the infection rates of the fish from the ponds (cultured) with the fish from the open natural water system (wild), the wild fish recorded a high rate of infection (50.0%) as opposed to no infection recorded for the cultural fish from the two fish farms. Only the males were infected among the infected fish.

INTER-RELATIONSHIP BETWEEN MAJOR IONS, TOTAL DISSOLVED SOLIDS AND CONDUCTIVITY IN SOME TROPICAL FISH PONDS

Major ions, total dissolved solids (T. D. S.), conductivity and their inter-relationships were investigated in eight fish ponds located in Ile-Ife, Nigeria. Chloride concentrations were the least of all the measured. Sulphate and magnesium concentrations were highest in station 7 while other parameters (potassium, chloride, calcium, alkalinity, conductivity and total dissolved solids (T. D. S.)) were highest in station 6. The ponds belong to class 1 of the African waters since they all have electrical conductance of less than 600 ms cm^-1. Highest conductivity values were recorded between March and May and thereafter values dropped gradually until the end of the investigation in August. Very high positive correlations existed between the summation of the total cations and anions, suggesting a direct relationship between the measured ions. Similarly, high and positive correlations existed between the total ions and electrical conductance and between total dissolved solids (T. D. S.) and conductivity of the pond waters, also suggesting that increase in total ions still results in the increasing level of total dissolved solids (T. D. S.) and electrical conductance. These inter-relationships are used to explain the contributive role of each ion to the total dissolved solids (T. D. S.) and conductivity levels of a tropical fish pond.

EFFECTS OF EARLY STARVATION ON THE DEVELOPMENT AND SURVIVAL OF Macrobrachium vollenhovenii (Herklots, 1857) LARVAE REARED IN THE LABORATORY

Macrobrachium vollenhovenii (Herklots) has been identified as a crustacean species with great culture potential. The effects of starvation on development and survival of early larval stages of the African river prawn M. vollenhovenii were investigated.

As an aspect of the ongoing effort to determine the culturability of the species, the time of first need for exogenous food by the larvae was examined in relation to larval development and survival.

Larvae required external food 2 to 3 days from hatching. This time corresponded with the period of transformation of the first larval stages into stage II larvae. Larvae starved at this stage of development cannot moult into subsequent instars and soon die.

TECHNICAL AND ALLOCATIVE EFFICIENCIES OF SMALL SCALE CASSAVA GROWERS IN FIVE SELECTED GOVERNMENT AREAS OF CROSS RIVER STATE

In this paper, the single equation estimation technique using the ordinary least square (OLS) multiple approach was used to estimate the relationship between farm size and such factors as Capital, Labour and Education of Small Scale Cassava growers in five Local Government Areas of Cross River State. In addition, technical and allocative efficiencies as well as resource elasticities were estimated based on the results of the specified production functions.

The R2 (which is the explanatory power) for the production was .71. For the estimated marginal value product functions, the R2 ranged from .29 to .40. Two of the explanatory variables in the production function, land and labour were significant at the 95% confidence level. The results of the marginal value products functions indicated an inverse relationship between productivity and farm size while technical and allocative efficiencies for land, show that the relatively smaller farm sizes were more efficient. Resource elasticities were also found to be inelastic implying that strategies aimed at decreasing resource prices to improve productivity of cassava growers would have minimal effect.

THE MICROBIOLOGY AND DETERIORATION OF SOFT DRINKS SUBJECTED TO TWO DIFFERENT MARKETING CONDITIONS

The microbial quality and successional changes in two brands (A and B) of soft drinks held under two marketing conditions (ambient ca 28 ºC and open air ca 34 ºC) were investigated using spread-plate technique. Heterogeneous flora was isolated from the two brands but varied with brand. Pediococcus spp. occurred in brand A but not in brand B. Much higher incidence (30%) of Staphylococcus spp. was observed in brand B as compared with 10% in brand A. Bacillus spp. were the most predominant bacterial group found in both brands while Aspergillus spp. and Cladosporium spp. dominated the two brands. Incidence of Bacillus spp. in samples held in open-air was remarkably increased by approximately 103% in brand A but tended to remain unchanged in brand B. Exposure of samples to the two conditions resulted in about 2-fold increase in Lactobacillus spp. in brand B on day 14 and decreased thereafter but decrease occurred in brand A after initial increase. Initial increase in Staphylococcus spp. occurred in both brands but became non-detectable in samples held under ambient condition as opposed to low incidences in samples subjected to open-air. Dramatic changes also occurred in the mycoflora; Arthrinium spp. were not isolated until day 14 and higher incidences occurred in samples held in open-air. Saccharomyces spp. were undetected in the samples until day 21. Approximately 13- and 9-fold increases in total aerobic bacterial counts were observed in brands A and B samples held in at 34 ºC respectively. Higher fungal populations occurred in both brands subjected to open-air with brand B samples showing the higher population. The diversity of the microbial flora and the phenomenal changes in incidences of Bacillus spp. coupled with prevalence of Aspergillus spp. in the open-air-held samples could pose health risks. Adoption of adequate quality control measures and distribution practices would likely reduce the microbial diversity and deterioration (characterized by sedimentation) due probably to Bacillus spp. and Saccharomyces spp. Consumption of these products is not advised after 14 days of exposure to the marketing conditions studied in this work.

Beef, pork and chicken meat were used in this study. Heat treatments were carried out at 115 ºC in stationary and rotating autoclaves, 125 ºC in stationary and rotating autoclaves, 125 ºC in stationary and 125 ºC but higher Fo value in stationary and rotating autoclaves.

The results of the analysis showed higher protein values in the range of 20.54% to 23.92% (autoclaved) and 20.25% to 20.85% (raw) beef; those of pork samples were from 19.12% to 21.68% (autoclaved), 19.19% to 19.83% (raw) while chicken samples were from 22.00% to 24.76% (autoclaved) and raw sample is 20.75% respectively. In the case of fat content, autoclaved beef samples showed higher values than the raw samples in the range of 3.0% to 4.5% (autoclaved), 1.0% to 1.5% (raw), while the reverse was the case with pork and chicken where the range for pork was from 2.5% to 5.0% (autoclaved), 5.0% to 5.5% (raw), and chicken from 0.5% to 2.0% (autoclaved) and 2.5% (raw) samples respectively. The ash content of autoclaved beef and pork samples showed lower values than their raw samples and were in the range of 1.13% to 1.53% (autoclaved) and 1.01% to 1.74% (raw) for beef and 1.20% to 1.62% (autoclaved), 1.14% to 1.68% for raw pork samples while autoclaved chicken samples showed higher values than the raw sample in the range of 1.20% to 1.62% (autoclaved) and 1.02% raw samples respectively. Apart from two autoclaved pork samples SA3 (stationary) and SF5 (rotating) that showed higher moisture content than their raw samples other pork samples (SAI, BF2, SA4) beef and chicken samples showed lower values. The moisture content of pork sample (SA3) was 76.5% (autoclaved) 72.0% (raw) SF5 samples was 75.0% (autoclaved) and 73.0% (raw) respectively.

Amino acid content of the sample also showed that by far a higher effect exists with the behaviour of individual amino acid of the raw material than the parameters of heat treatment. In all product samples cystein and tryptophan contents of autoclaved samples were lower than those of the raw samples.

The amino acid range for beef was from 99.24 g to 99.98 g (autoclaved). 100.00 g to 103.90 g (raw); pork samples 102.24 g (raw); chicken samples 99.99 g to 100.01 g (autoclaved) and 100.01 g for raw samples respectively. Thiamine retention was higher in canned beef than other canned meat. More thiamine was retained in autoclaved pork in rotation than in autoclaved stationary treatment. Thiamine in beef ranged from 0.85 g to 1.20 mg (autoclaved), 1.86 mg to 2.50 mg (raw samples); pork 0.44 mg to 0.81 mg (autoclaved) and 1.19 mg to 1.80 mg (raw); chicken 0.06 mg to 0.10 mg (autoclaved) and 1.25 mg for raw sample respectively. The result on thiamine retention showed that, that of canned chicken was more sensitive to heat treatment than other canned meat samples.

On the whole, the results of this study showed that products heating largely by conduction-stationary heat treatment resulted in acceptable quality meat products.

THE EFFECT OF CLIMATIC FACTORS ON THE OCCURRENCE AND GROSS PATHOLOGICAL LESIONS IN BACTERIAL PNEUMONIA OF OVINE AND CAPRINE HOSTS IN ZARIA, NIGERIA

The bacterial agents of ovine and caprine pneumonia and associated gross pathological lesions were studied for a period of ten years (1985-1995). Bacteriological data were obtained from the necropsy report books of the Microbiology and Pathology Dagnostic units of the Department of Vetinary Pathology and Microbiology, Ahmadu Bello University, Zaria, on 283 Pathologic lung samples. The major bacterial agents isolated from affected ovine lungs were E. Coli 24.7%; Pasteurella multocida 17.3%; Arcanobacterium pyogenes 14.9%; Streptococcus pyogenes 6.9%; and Neiseria catarrhalis 5.7% and from caprine lungs were E. Coli 26.6%; Pasteurella multocida 13.8%; Staphylococcus aureus 16.5%; Aracanobacterium pyogenes 11.9%; Streptococcus pyogenes 8.2%; and Proteus vulgaris 5.5%. There were more cases of ovine pneumonia (61.5%) than caprine (38.5%). In both sheep and goat, more cases of pneumonia were recorded during the dry season, with the highest monthly average value for both occurring in January. Annual distribution of ovine Pneumonia was highest in 1990 (24.7%), followed by 1987 (21.8%), while caprine pneumonia was highest in 1990 (22.9%) followed by 1998 (21.1%). The findings of this study suggest a high susceptibility of small ruminants in Zaria to bacterial pneumonia during the early dry season and early rainy season. It is recommended that adequate management measures should be instituted to protect stock during these periods of high vulnerability.

A COMPARATIVE STUDY OF THE TRIGLYCERIDE AND FATTY ACID COMPOSITIONS OF PALM OILS FROM PLANTATIONS IN SOUTH-EASTERN NIGERIA

Triglyceride and fatty acid composition were determined for palm oils from three different oil palm plantations in South-Eastern Nigeria. Each of the plantations belong to slightly different vegetation belts. The red fruits if the Tenera variety exhibited significant variations (P < 0.5) across the locations. Much of the variations occurred in triglycerides with two or more unsaturated fatty acids in their molecules (P00,000 and OLL) with P00 showing greater differences than the others. Most of the constituent unsaturated fatty acids were observed to vary in their concentrations across locations. Both the locations and varietal source appear to affect the mean total unsaturation of the oil samples.

THE ESTIMATION OF MODIFIED NON-SPECIFIC SOLUBILITY PARAMETER OF LIQUIDS BY CORRELATION WITH REFRACTIVE INDEX AND MOLAR ENERGIES OF VAPORIZATION

For apolar liquids, the modified non-specific solubility parameter d’ has been correlated with a form of the Lorentz-Lorenz refractive index function and the molar energy of vaporization per unit volume, and two expressions have been developed. Using one form of these expressions, and by introducing the contribution of dipole moment per unit molar volume, expressions for the estimation of modified non-specific solubility parameter of polar liquids have emerged. These expressions however, have different values of the constants C and K for different families of liquids in order to yield estimated modified non-specific solubility parameter d’_est; not significantly different from the experimental values, d’_exp, for liquids. The K values obtained from a consideration of energy of vaporization per unit molar volume, for polar, associated liquids (alcohols) and polar non-associated liquids seem to lend support for the proposition of structural differences in these groups of liquids.

Photolysis of nickel hydroxy azide at 380 ºK is compared with that of nickel azide under similar considerations. Nickel azide sample was prepared by adapting the method of Brauer while nickel hydroxy azide was obtained by dehydrating the dihydrate of nickel azide crystals (Ni(N₃)₂.2H₂O) and exposing to atmospheric moisture. The rate of evolution of nitrogen at constant temperature and different intensities, decreases with time. The pressure of nitrogen produced with time varies directly as at all intensities. The rate of photolysis at constant temperature at intervals of time varies with intensity. Absence of photoconduction in the region reveals that excitons are the main reactants which get trapped in adjacent azide ions. This is evident in the linear dependence of the rate of photolysis on the intensity. The rate of photolysis of Ni(OH)N₃ is observed to be lower than that of Ni(N₃)₂ by about a factor of 10.

SYNTHESIS AND X-RAY DIFFRACTION STUDIES OF g-AL₂O₃ USING ALUMINUM ACETYLACETONATE (AAA) PRECURSOR VIA A NOVEL SOL-GEL ROUTE

Crystalline powder of g-Al₂O₃ has been successfully synthesized by employing aluminum acetylacteonate-methanol-ethylene glycol-water system via a novel sol-gel route. The crystalline particles of the powder obtained were examined by X-ray diffraction, scanning electron microscopy and transmission electron microscopy, while the surface area of the oxide powder was obtained by nitrogen adsorption BET surface area measurement. The result obtained indicated that the g-Al₂O₃ is cubic with a = b = c = 7.5911A⁰, the mean particle diameter is 85 nm and the BET surface area is 120 m²/g. The result showed that the product obtained is a pure g-Al₂O₃ with a nanocrystalline structure. The oxide powder could be very important in catalysis and gas sensing of hydrocarbons.

THE GEOCHEMISTRY, TECTONIC SETTING AND ORIGIN OF THE MASSIVE MELANOCRATIC AMPHIBOLITE IN THE ILESHA SCHIST BELT, SOUTHWESTERN NIGERIA

A massive melanocratic amphibolite, (MMA) occurs in Ilesha schist belt within a series of muscovite schists and amphibolite gneiss. Though metamorphosed, MMA shows no obvious textural deformation. Actinolite, tremolite, hornblende and boitite constitute the major minerals in MMA. Minor minerals in MMA include calcite, plagioclase and pyroxene while monazite, zircon and apatite form the accessory minerals. Chemical studies revealed that MMA contains low K₂O and Na₂O. Its Mg¹, Cr and Ni contents are considerably lower than those of similar basalts derived from purely primitive mantle. Enrichment of LREE, negative Eu/Eu* anomaly and occurrence of monazite in its mineralogy are all indications that the precursor magma of MMA contains a sedimentary input. The plots of immobile trace (Zr, Ti, Nb, Y) and rare earth elements during the greenschist-amphibolite metamorphic grade for MMA show that it was derived from a low-K-Tholeiitic magma in a volcanic geotectonic setting (back arc basin).

POROSITY AND COMPACTION TREND IN OKAN FIELD (WESTERN NIGER DELTA) BASED ON WELL LOG DATA

Porosity and compaction trends in Okan Field have been highlighted based on the interpretation of well log data within the productive interval of 5000 to 10,000 ft. Six Porosity Zones have been delineated based on the interpretation of gamma – ray log from the representative wells. The zones that occurred between 5000 ft. and 8000 ft. appeared to be tectonically controlled whereas the deeper zones result mainly from diagenetic changes associated with the burial history of the sediments. Regionally, these zones represent from bottom to top, cyclic deposition of clays and sands which become increasingly sandy upward through the sequence. Porosity values are in the range of 15 and 25% and this is good enough to enhance hydrocarbon accumulation in the area. Sedimentation pattern is normal in most parts of the field except for a local zone of overpressure observed at a depth of 8300 ft. in the northeastern section of the field. The main hydrocarbon trap results from vertical stacking of porous reservoirs sands while the stratigraphic trap is evident from reservoir Pinchouts.

GEOPHYSICAL EXPLORATION FOR GROUNDWATER IN A SEDIMENTARY ENVIRONMENT: A CASE STUDY FROM NANKA OVER NANKA FORMATION IN ANMABRA BASIN, SOUTHEASTERN NIGERIA

The interpretation of live resistivity curves over Nanka town within geologic terrain often referred to as Nanka Formation in Anambra Basin, south-eastern Nigeria indicates that the area has a great groundwater potential. A correlation of the curves with the lithologic log from a nearby borehole suggests that the major lithologic units penetrated by the sounding curves are Laterite, Clay Sandstone and clay.

The sandstone unit which is the aquiferous zone has a resistivity range of between 500 ohm.m and 960 ohm.m and thickness in excess of 200 m. The depth to the water table is at least 100 m.

ORGANIC MATTER EVALUATION OF THE NKPORO SHALE, ANAMBRA BASIN, FROM WIRELINE LOGS

A modified form of Schmoker’s formation density log technique has been used in evaluating the total organic carbon content TOC of the continuous shale sections of the Nkporo Shale in three exploratory wells (Alade – 1, Anambra River – 1, and Anambra River – 3) in the Anambra Basin. Weight percent TOC was found to range from 0.2 – 4.9%; with an average of 2.8% in Alade – 1 well; 0.2 – 4.3%, with an average of 1.8% in the Anambra River – 1 well; and 0.2 – 5.3%, with an average of 3% in the Anambra River – 3 well. The average TOC values obtained in this study are similar to the average TOC values obtained from organic geochemical analysis of the Nkporo Shale in the Anambra Basin, the Afikpo Syncline, and the Calabar Flank.

Crossplots of the formation density and the gamma ray logs show a generally positive correlation between them; although a few intervals have high gamma ray values corresponding with low formation density. The positive correlation between the formation density and the gamma ray logs suggests a dominantly terrestrial source for the organic matter. Intervals with low formation density (high TOC) corresponding with high gamma ray values are interpreted as source beds with significant marine organic matter.

ALTERNATIVE MODELS FOR THE INTERPRETATION OF AEROMAGNETIC DATA IN AREAS AROUND THE MAGNETIC EQUATOR

Four interpretational models are recognized in areas around the magnetic equator. They are point pole, line of poles, point dipole and line of dipoles. Point pole models are recognized by adjacent circular contours of magnetic high and low, while line of poles models are identified by elliptical contours of magnetic high and low adjacent to each other. When magnetic contours are simply circular or nearly circular, the source is approximated as point dipole and contours of line of dipole model are always elliptical in shape. A decision between dipolar and monopolar model is made using the shape of magnetic signature. When a magnetic signature has completely dominant low, the correct model will be a dipole. While a magnetic high flanked by low is approximated as point pole/line of pole (monopole). Magnetic signature that does not assume any of these shapes is a pointer to remanent magnetization. The four interpretational models have close relationship with half-width of magnetic anomalies and are therefore valuable for depth determination. The four interpretational models have been employed to analyse aeromagnetic data from crystalline basement and sedimentary areas of Nigeria.

DESIGN, CONSTRUCTION AND TESTING OF AN OPTICAL DEVICE FOR THE DETERMINATION OF EGG FERTILITY

This study reports the design, construction and testing of an optical device to determine the fertility of poultry egg at early age. The device consists of optical components such as condenser lens, objective lens, eyepiece lens and a source of light, all encased in a wooden frame. It has a total length of about 1m and produces an inverted image with a magnification of 5.02. The internal structure of the egg could be viewed with the naked eye through the eye piece. The device was tested using ten (10) incubated eggs for 7 days. Result showed that the device could detect fertile eggs within the first three days of incubation. This device therefore has an advantage over the conventional candler which could detect fertile eggs between the fifth and seventh day and is recommended for egg candling in the poultry industry.

EFFECTS OF CLAY RESISTIVITY INDEX THIN BED: CASE STUDY FROM WESTERN NIGER DELTA

Certain clays produce micro-porosities that retain a relatively thick water layer and enhance the path for conductivity of electric currents through capillary forces. Saturation exponent (n) in clay-rich fields is less than the value of 2, usually assumed in well-logging. Accurately determined clay-corrected saturation exponent (“n”) and resistivity index are needed for better reserve estimation.

A clay inclusion study of saturation-resistivity relationships from thin and laminated beds is carried out in the laboratory. Saturation exponents (n) are measured on a number of core samples from several wells in a Niger Delta field Cation exchange capacity (CEC) technique is used to detect clay in the rocks CEC values are in the ranges of 0.0278 and 0.0078 for the interval 5456 - 5574 ft. and 0.0025 – 0.0166 for 8600 to 8695 ft. A correlation of the resistivity index and saturation indicates deviations, from ‘normal’, caused by the effect of clay minerals such as kaolinite, montmorillonite and smectite. Clay presence produces a curve towards low saturation point. The average field “n” is 1.83 and acceptable CEC tolerance in heterogeneous formations is within a depth of 0.2 ft. The larger the CEC, the greater the suppression of downhole resistivity and active clays such as montmorillonites have greater influence on log response than kaolinite.

ELECTRICAL RESISTIVITY SOUNDINGS TO DETERMINE SUBSURFACE CONTAMINATION IN THE VICINITY OF REFUSE DUMP

Four Wenner apparent pseudosections and a vertical electrical sounding were made at the Orita Aperin refuse dump site, Ibadan, South West Nigeria, to map the gross layered structure of the refuse as well as the extent of groundwater contamination. Wood, leaves, newspaper, cloth, polythene bags, plastics, glass and metal refuse interspersed with soil exhibited resistivity of 11.6 ohm-m and layer thickness of 0.7 m as obtained from the inversion of the sounding. The unsaturated layer has a resistivity of 6.8 ohm-m and thickness of 0.6 m while leachate-saturated is characterized by low resistivity of 2.9 ohm-m; 1.2 m thickness.

The fractured layer exhibited resistivity of 49.6 ohm-m. The accurate determination of the refuse thickness in geoelectrical model is primarily due to a strong resistivity contrast between the leachate saturated (2.9 ohm-m) and underlying saturated fractured rock (49.6 ohm-m). Despite this contrast, models generated from electrical resistivity soundings are reasonably accurate in their depictions of internal structure of the dump site. The hydrochemical analysis of the surface and groundwater samples collected within the vicinity of the dump site were analysed for physico-chemical parameters. The results produced higher concentration of TDS, total hardness, Cl^-, NO₃^-, Mg²⁺, Na⁺, K⁺ and pH value for water collected at close locations to the dump site than those far away from the site: an evidence for a quantitative assessment of groundwater contamination.

TEMPERATURE VARIABILITY AND OUTBREAK OF MENINGITIS AND MEASLES IN YOLA, NIGERIA

The influence of temperature on temporal variations of outbreak of meningitis and measles in Yola, Nigeria was examined. Data on monthly maximum temperature and reported cases of the two diseases for a period of 13 years were collected and analysed. The report shows that the reported cases of the two diseases are high between January and April when temperatures are also high. Correlation analysis indicates that the reported cases of the two diseases are positively and significantly related to temperature. Regression analysis suggests that 53% and 79% of the variations in the outbreak of meningitis and measles respectively can be attributed to temperature. Housing conditions in the city also aggravate the effect of temperature. Appropriate measures were suggested to minimise the effects of temperature in the study area.

TEMPERATURE VARIATIONS IN THE NIGER DELTA SUBSURFACE FROM CONTINUOUS TEMPERATURE LOGS

Continuous temperature data from 126 wells allowed to attain a state of thermal equilibrium for several months and 134 wells (stabilisation within thirty days) were used to determine the variations in temperature in the Niger Delta.

At about 8,000 ftss., high temperatures of 80 - 120 ºC exist in the Northern and Ughellis depobelts, low temperatures of 46 – 88 ºC are recorded in the Central and Coastal depobelts, moderate temperatures 80 – 100 ºC are seen in the Offshore depobelt. At 6,000 and 4,000 ftss. similar trends are also evident.

Regional geothermal gradients range from 1.5 – 2.5 ºC/100 m in the Coastal depobelt and Offshore regions and increases northward to 4.5 ºC/100 m. Vertical geothermal gradients show a continuous but non linear function with depth and increases with diminishing sand percentage from less than 1.0 ºC/100 m in the continental sands through 2.5 ºC/100 m in the paralic section to 5.0 ºC/100 m in the continuous shaly section. Higher gradients are associated with shaly formations primarily because of low thermal conductivity.

EFFECT IF BILIRUBIN CONCENTRATION ON RADIATION ABSORBED DOSE EQUIVALENT USING LiF (TLD – 100) CHIPS

N. O. EGBE, B. F. OLISEMEKE, A. F. NNEOYI-EGBE, M. U. ETUNG, E. U. EYONG and R. R. ETTARH

The effect of bilirubin concentration on dose equivalent of absorbed radiation was investigated in vitro in this study. Different concentrations of bilirubin were exposed to a fixed dose equivalent x-ray irradiation from an R501 x-ray generator. The fraction of radiation transmitted and the fraction absorbed were measured using LiF (TLD 100) chips as detectors, and the radiation absorbed by bilirubin was computed. Results indicate that at low concentrations (25 mmol/L to 76 mmol/L) absorbed doses decreased with increase in bilirubin concentration. At higher bilirubin concentrations (76 mmol/L to 460 mmol/L) and beyond, there was an increase in absorption with a strong positive correlation (r = 0.92) between dose absorbed and bilirubin concentration. The possible applications of this property of bilirubin as a modifier at high concentrations--- to enhance radiation effect on diseased tissue during radiotherapy, and the danger inherent presenting neonates for radiodiagnostic examinations are discussed.

THE EFFECTS OF g-IRRADIATION ON THE OPTICAL AND ELECTRICAL PROPERTIES OF BUFFER SOLUTION CROWN CdS THIN FILMS

Pure and aluminum doped (0.001 wt %Al) CdS thin films were deposited on microscope glass slides using buffer solution growth technique based on CdSO₄ as the cadmium source, thiourea as the sulphur source, and (NH₄)₂ SO₄ as a buffer. The effects of gamma radiation on the optical and electrical properties of the CdS films have been investigated by measuring their optical absorbance and electrical conductivities before and after irradiation by different doses of g – radiation in the range 7.27 × 10² to 2.04 × 10⁵ Gy.

The absorbance was found to be dependent on film’s thickness (and aluminum dopant concentration) and g – radiation doses. CdS films (pure and doped) g – irradiated at high doses (2.6 × 10⁶ Gy) have the lowest absorbance. Gamma – irradiation induced dark electrical conductivity in CdS films, which was dependent on absorbed g – radiation dose rate. The conductivity was permanent at high g – radiation dose (2.04 × 10⁵ Gy) and transitory below this dose.

Generally, the optical band gap values if unirradiated and g – irradiated CdS : Al films were lower than that of pure CdS films. The band gaps and electrical conductivities of pure and CdS : Al films, unirradiated and irradiated at low g – radiation doses (≤ 1.45 × 10⁴ Gy) are the same i. e., 2.43 ± 0.02 eV and 0.068 ± 0.005 (W-cm)^-1, and 2.31 ± 0.02 eV and 0.69 ± 0.05 (W-cm)^-1 for pure and CdS : Al films respectively. At high g – radiation doses, the band gaps decreased to 2.30 eV and below 2.30 eV for pure and CdS : Al films respectively, accompanied by increase in the dark electrical conductivties.

A method is developed for the deduction of a transition metal ion potential from a knowledge of the phase-shift. The method used is based the distorted plane – wave scattering approximation for the deduction of non singular potentials from scattering phase shifts in an inverse scattering approach. The resulting electron – ion potential obtained is a finite Dirichlet series sum of short-range exponential functions. The Fourier transform of the potential is obtained for applications to the transition metals.

A SIMPLE METHOD FOR ESTIMATING THERMAL RESPONSE OF BUILDING MATERIALS IN TROPICAL CLIMATIC ZONES

This paper develops a simple method for estimating the thermal response of building materials in the tropical climatic zone using the basic heat equation. The efficacy of the developed model has been tested with data from three West African cities, namely Kano (lat. 12.1 ºN) Nigeria, Ibadan (lat. 7.4 ºN) Nigeria and Cotonou (lat. 6.4 ºN) Republic of Benin, by considering a reference building with a flat ceiling option. Results show that the interior air temperature obtained as a direct response to the fluctuations of the outside air temperature indicate daily temperature reductions of varying magnitudes, depending on the building insulation, material thickness used and also on property value of the material adopted. It is concluded from the model’s estimates that interior temperatures for thermal comfort can be realized through the appropriate application of passive systems.

ON MEAN STATE OF THE ATMOSPHERE AT THE END OF RAINY SEASON IN SOUTHWEST NIGERIA DURING THE MOSOSCALE EXPERIMENT I FROM 28^TH SEPTEMBER – 9^TH OCTOBER, 1991

For a long time upper air data Nigeria had been fragmentary. Poor operational upper air network had therefore been responsible for the poor products users get from the forecast office.

This paper describes the wind information obtained during a specifically designed meteorological experiment tagged “Mesoscale Experiment I” to monitor the pattern of wind flow at low-levels during the occurrence of squall lines systems at the end of rainy season in three locations in Southwest Nigeria from 28^th Sept/9^th Oct 1991. Analysis of both the zonal and meridional wind components showed that the southerlies were favourable for bad weather. The winds were found to be generally weak southerlies at the end of the rainy season.

THE COMPUTATION OF LINEAR TRIANGULAR SYSTEM MATRICES IN THE FINITE ELEMENT METHOD

An algorithm is developed for generating the system matrices for the Finite Element Method of solving some classes of second order partial differential equations problems using the linear triangular elements. This algorithm reduces the complexity normally associated with the finite element approximation and makes the powerful technique accessible to more people even on personal computers.

A THEORETICAL MARKOV CHAIN MODEL FOR EVALUATING CORRECTIONAL METHODS APPLIED TO PEOPLE WITH CRIMINAL TENDENCIES

In this paper a stochastic method is applied in the study of the long time effect of confinement in a correctional institution on the behaviour of a person with criminal tendencies. The approach used is Markov chain, which uses past history to predict the state of a system in the future. A model is developed for comparing the effect of different correctional practices on people with criminal tendencies. The statistics for this comparison is the number of people whose criminal tendencies are completely destroyed at the end of their confinement. The model so developed is applied to a simulated data on deviants of the same criminal offence. The number of them who permanently recover and those who permanently remain unrecovered were obtained.

ON FINDING THE NON-ISOMORPHISM CLASSES OF THE (n × n) / k SEMI-LATIN SQUARES

We give and prove group-theoretic lemmas which would enable one to find the non-isomorphism classes of the (n × n) / k semi-Latin squares. These lemmas are most useful when the sizes and number of semi-Latin squares under consideration are large, and the computing method via the ‘nauty package’ for finding their isomorphism classes, given by Bailey and Chigbu, is not readily available.

A SIMULATION OF ALLOCATION OF DOCTORS TO SHIFTS IN AN EMERGENCY TREATMENT ROOM

This paper modifies Vassilacopoulos approach of solving problem of allocating doctors to shifts in Accident and Emergency Department of Hospitals by assuming that the feasible solution of the problem can be obtained if number of available doctor hours after a doctor has been assigned per hour of the week is proportional to the average of the lengths of the shifts for the week. A computer program is developed to solve a dynamic programming problem of allocating doctors, the optimal solution of which provides solution to another dynamic programming problem of allocating doctors to shifts.

KEY WORDS: Emergency, waiting – time, queue – size, arrival – rate, shift.

African Journals Online Global Journal of Pure and Applied Sciences

Volume 7 No 1 January 2001

African Journals Online
Global Journal of Pure and Applied Sciences