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  • Author or Editor: I. Essien x
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Abstract  

The239,240Pu/238U ratios in nature determined by previous and present workers have been used to evaluate the extent of plutonium and uranium fallout contamination on the earth's surface. The contamination of the earth's surface due to radioactive fallout of plutonium and uranium varies between 0.01 and 24%. The overall results show that the whole globe is affected by the fallout, thus explaining the high239,240Pu/238U ratios found in our environment today.

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Abstract  

The -recoil effect of239Pu has been observed in environmental samples and theN 5 P /N5 ratio in these samples has been calculated. This ratio in atmospheric samples is in the range between 10–5 and 10–4 (atom/atom). For other contemporary terrestrial samples it is in the range between 10–7 and 10–6 (atom/atom), while that of uranium mineral is about 10–10 (atom/atom). The results further explain the radioactive fallout contamination of our environment by uranium and plutonium isotopes.

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Abstract  

A series of leaching experiments with HF, HCl, HNO3 were carried out on samples of uranium minerals (uraninite and carnotite samples). Anomalously high234U/238U ratios were observed in some uranium fractions. The observed234U/238U activity ratios varied between the values of 1.019±0.155 and 6.210±0.504 (Ci/Ci), while the bulk carnotite sample had an activity ratio of 1.010±0.005 (Ci/Ci). These results are interpreted as due to alpha-recoil effect and changes in oxidation state of uranium.

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Abstract  

A survey of the environmental radioactivity in Uyo /5° N, 7° 50 E/, Nigeria has been done for the period 1981 to 1986. An overall average of 8.5±0.5 pCi is the environmental radioactivity for the surrounding air and 8.2±0.4 pCi for the top soil. Airborne -particles were also measured using CR-39 plastic detectors. The University Campus in Uyo had an overall average -activity of 75.3±0.8 fmCi while other sectors of the town had an average of 95.2±1.1 fmCi. Our results show a non-uniform distribution of - and other radioactivity in Uyo.

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Abstract  

A survey of the environmental radioactivity in the Eastern States of Nigeria, consisting of Akwa Ibom and Corss River States has been done and that of Uyo (5°N, 7°50E), Nigeria, has been updated for the period of 1981 to 1991. An overall average of 329.7±13.3 mBq is the environmental radioactivity for the surrounding air in Akwa Ibom State, while 348.5±13.7 mBq is the activity for the air in Cross River State. There has been a marked increase of average environmental radioactivity in Uyo from 293.0±12.6 mBq to 373.7±14.8 mBq in recent years with a yearly mean of 324.1±13.7 mBq.

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Abstract  

A marked increase in the concentration of238U in rain was observed at Fayetteville (36 °N, 94 °W), Arkansas, after the 18 May 1980 eruption of Mount St. Helens. The fallout of natural uranium observed during the summer months of 1980 can be attributed to the 18 May 1980 events, which ejected an amount of ash material on the order of 4 km3 or about 8·1015 grams into the atmosphere.234U and235U were found to be highly enriched relative to238U in several rain samples collected at Fayetteville, Arkansas, prior to the volcanic eruption. The anomalous uranium seems to have originated from the Soviet satellite Cosmos-954, which fell over Canada, on 24 January 1978. The effect of the 25th Chinese nuclear test, which occurred on 16 October 1980, on the concentrations of uranium isotopes in rain appears to have been insignificant.

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Abstract  

Radiochemical measurements of the concentrations of thorium, uranium and plutonium isotopes were carried out for the samples of Arkansas River collected at six locations in the states of Colorado and Oklahoma. The uranium to thorium ratios in the river samples were found to be highly variable and generally much greater than the ratios found in soils and in rainwater. An attempt has been made to determine the apparent230Th ages (or the times which elapsed since the last major disruption of the radioactive equilibria) from the observed230Th/232Th and234U/232Th ratios in the water samples.

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Abstract  

Marked increases in the concentrations of thorium and uranium isotopes observed in rain samples collected at Fayetteville (36° N, 94° W), Arkansas, during 1983 are attributed to the fallout from the 1982 eruption of El chichón volcano in Mexico.

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The incidence and heat resistance of conidiospores produced by dermatophytes isolated from athlete’s kits (canvasses, stockings and spike shoes) stored in Nigerian University Sport’s Centre were investigated. Epidermophyton floccosum, Microsporum oudouinii, Microsporum canis, Trichophyton concentricum, Trichophyton mentagrophytes and Trichophyton rubrum were isolated and their incidence on the athlete’s kits varied with the species and type of kits. Among the isolates T. mentagrophytes, T. rubrum and E. floccosum with 25%, 23% and 20% prevalence rates respectively, were the most common isolates, and are often associated with tinea pedis (athletes foot). Canvasses with the highest incidence of dermatophytes (25 out of 34 fungal isolates) were the most contaminated kits and could serve as effective articles for the transmission of tinea pedis among athletes in Nigeria. The common etiological agents screened, produced asexual spores (conidiospores) that exhibited high resistance to heat treatment at 80 °C. Of the three isolates, E. floccosum , with a decimal reduction time ( D -value) of D 80 = 4.4 min was the most resistant followed by T. mentagrophytes with D 80 = 4.0 min and then T. rubrum with D 80 = 3.2 min. The spores elimination pattern indicates that increasing the heating duration would decrease the decimal reduction time and possibly denature the fungal propagules but may damage the skin during treatment with hot water compresses. The findings have shown that the use of hot water compresses is palliative but heat treatment especially vapour-heat treatment offers adequate preventive measures if applied for periodic treatment of contaminated kits. However, determining the correct condition for effective decontamination will require detailed understanding of the heat resistance of fungal spores. Otherwise treatment of kits with detergent and chaotropic agent such as urea and guanidinium salt is preferred to heat treatment.

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