Coupling source term, mineral reactivity and flow in radionuclide transport

Part of this study has been published in Applied Geochemistry. Another publication is in line in Environmental Science & Technology.The focus of this work is to investigate the dissolution of MW25, a non-radioactive simulant of UK high-level nuclear waste borosilicate glass, and to predict its performance in the near field of a geological repository. A single-pass flow-through (SPFT) experimental system was used to measure the forward dissolution rates of MW25. Experiments were conducted in two parts. Experiment Part 1 considers the dissolution of the waste glass in deionised water at 40 and 90 oC and circum-neutral pH. Experiment Part 2 considers the dissolution of the waste glass in simulant groundwaters, with similar compositions to groundwaters of Callovo-Oxfordian clay (lower-strength sedimentary rock (LSSR)) and Borrowdale Volcanic Group rocks (higher-strength rock (HSR)), at 40 oC and pH 7. The forward dissolution rate measured in deionised water was found to be approximately one order of magnitude higher at 90 oC than at 40 oC. A similar release was observed for Si, Mg and Al at 40 oC and 90 oC, whereas the B, Cs, Na, Li and Mo showed an order of magnitude increase when the temperature was increased from 40 to 90 oC for low q/S values. The activation energy (Ea) of the reactions shows that the dissolution process is a surface phenomenon. At 90 oC the net effect of the processes governing MW25 dissolution led to the preferential release of boron and alkali metals relative to the release of Si during the transient dissolution stage, accompanied by an increase in the concentration of silicic acid. This suggests that the solution activity of silicic acid at a higher temperature has a weak influence on the release of the mobile elements. The forward dissolution rate measured in LSSR simulant groundwater was found to be slightly higher than that measured in HSR simulant groundwater. The dissolution behaviour of MW25 in both groundwaters is consistent with its behaviour in deionised water at 40 oC, with the dissolution rates of elements increasing as flow rates were increased. However, forward dissolution rates measured in the simulant groundwaters were lower than the forward dissolution rates measured in deionised water under these experimental conditions. This is attributable to the interaction of the components of the simulant groundwaters with the glass, as revealed by post-reaction surface analyses, and a consequential lower alkalinity of the leachates collected in the experiments with simulant groundwater than in deionised water. Reactive chemical transport simulations of waste glass dissolution and radionuclide release in a hypothetical near field were conducted over a time span of a million years with GoldSim. The results showed that enclosing the waste glass in a steel canister covered by a copper canister and emplacing the waste package in a granite host rock is optimal for the long-term isolation of the radionuclides. The waste glass was found to play a significant role in the overall performance of the near field. This study features a new method for estimating the surface area of reacted glass powder more accurately than the geometric surface area estimate, which is the preferred standard method among researchers.Cambridge Trust and Islamic Development Bank (IDB

Inflammation: the foundation of diseases and disorders. A review of phytomedicines of South African origin used to treat pain and inflammatory conditions.

Great interest in herbal medicine as a potential source of phytopharmaceuticals has created the need to review common factors responsible for major diseases and body disorders. This review shows one such common factor in inflammation and the role herbal medicine can play. Traditional medicinal herbal remedies in the southern African region have long been used to treat various pain- or inflammation-related symptoms. Although the precise mechanisms of action of many herbal drugs have yet to be determined, some of them have been shown to exert anti-inflammatory and/or antioxidant effects in a variety of cells in the human and animal bodies. There is increasing evidence toindicate that both peripheral and central nervous system cells play a prominent role in the chronic inflammatory responses in the body system and anti-inflammatory herbal medicine and its constituents are being proved to be a potent protector against various pro-inflammatory mediators in diseases and disorders. These mediators have therefore been suspected of being the functional basis of diseases and disorders. The structural diversity of these medicinal herbs makes them a valuable source of novel lead compounds against the therapeutic molecular targets, cytokines and mediators, that have been newly discovered by the platforms of genomics, proteomics, metabolomics and highthroughput technologies. This article reviews the basic mechanisms of inflammation and the potential of 123 southern African plant species to be effective as chronic inflammatory disease preventive agents. With one third of these species there are no indications of the chemical composition, indicating possible subjects for further research

Antipyretic, analgesic, anti-inflammatory and cytotoxic effects of four derivatives of salicylic acid and anthranilic acid in mice and rats

Four-Substituted derivatives of salicylic and anthranilic acids: 2-hydroxy-5-azidosulfonylbenzoic acid (HASBA, 1), 2-acetyloxy-5- azidosulfonylbenzoic acid (AASBA, 2), 2-acetamido-5- azidosulfonylbenzoic acid (AMASBA, 3) and 2-acetamido-5-sulfonamidobenzoic acid (AMSABA, 4) were synthesized and evaluated for their analgesic, antipyretic, anti-inflammatory and cytotoxic activities. HASBA, AASBA and AMASBA showed higher analgesic activity than aspirin (ASA) at 100 mg/kg dose, while AMSABA showed the least analgesic property. AMASBA exhibited higher antipyretic activity than paracetamol (PCM), while HASBA, AASBA and AMSABA also showed antipyretic effects which were of equal potency to that of PCM. The order of anti-inflammatory effects of the four compounds is: AASBA > AMASBA > HASBA > AMSABA. The effects of the substituents on the biological activities of the synthesized compounds are discussed. Key Words: Salicylic acid derivatives, anthranilic acid, analgesic, anti-inflammatory, antipyretic, cytotoxicity. African Journal of Biotechnology Vol.3(8) 2004: 426-43

Assessing the effect of radioactive waste glass dissolution on early-stage radionuclide migration using simplified geological repository Monte Carlo transport models

AbstractThe vitrification of radioactive waste within glass and subsequent disposal within a geological disposal facility (GDF) requires a comprehensive understanding of the effect of glass dissolution on GDF performance. This paper aims to analyse the effect of both high-level and intermediate-level waste (HLW and ILW) glass dissolution source terms on radionuclide release into the geosphere just above the disposal vault (the ‘crown’). Radionuclide migration was simulated in GoldSim for HLW in either granite or clay host rocks with a bentonite buffer using carbon steel or copper canisters, whereas ILW simulations considered either granite or clay host rocks, in either bentonite buffer or cement backfill, using concrete or cast-iron canisters. Glass dissolution source terms were varied by coupling GoldSim and MATLAB to modify the initial, residual, and resumption dissolution rates of the glass or by applying the analytical GRAAL model to glass dissolution. HLW glass results indicate no preference of granite over clay host rocks for a given canister type but that a copper canister is preferable to steel. ILW results suggest that a granite–bentonite–cast-iron environment yields lowest crown activities with cast-iron preferable to concrete as the canister, bentonite preferable to cement as the buffer/backfill, and granite preferable to clay as the host rock. Varying glass dissolution source terms (initial, residual, and resumption dissolution rates) had an understood effect on radionuclide migration, although changes were arguably insignificant considering peak crown activity for both HLW and ILW.</jats:p

Effect of stem - bark ofErythrophleum suaveolens (Guill. & Perri.) saponin on fresh water snail (Lanistes lybicus) tissues

The study investigated the activity of saponin from ethanolic extract of Erythrophleum suaveolens stem bark against freshwater snail, Lanistes lybicus. The crude saponin (4 g) was separated by silica gel using gradient elution with dichloromethane in methanol (100:0 to 0:100) followed by thin layer chromatography using precoated silica gel 60 F254. Fractionated saponins (90:10, 80:20 and 70:30) were employed for snail toxicity using fresh water snails, L. lybicus. The biochemical changes were evaluated in haemolymph, muscle, intestine and hepatopancreas of fresh water snails exposed to sublethal dose of fractionated saponins. Elevation of activities of acid and alkaline phosphatase in the intestine and hepatopancreas, haemolymph and total protein level were observed. The activity ofacetylcholinesterase was inhibited in the haemolymph, muscle, hepatopancreas and intestine of the snails. The activity of saponin was observed to be dose dependent as mortality increased with relativeincrease in the saponin concentrations. The study provides considerable scope in exploiting local indigenous plant resources for control of fresh water snails and monitor water pollution.Key words: Erythrophleum suaveolens, saponin, molluscicidal activity, Lanistes lybicus, pollution, hepatopancreas

Effects of aqueous Anaphe venata extract on fecal pellet output in mice

The consumption of Silkworm, Anaphe venata has been reported to be associated with a high incidence of seasonal ataxia in some parts of Nigeria. Injection of some doses of Aqueous Anaphe venata extract (AAV) by intraperitoneal route into mice has been reported to cause some behavioral changes associated with ataxia. We administered some doses of the extract (50&#8211;300 mg/kg) to mice orally in view of finding its effects on their fecal pellet output and elucidating the mechanism of action of the extract in the intestine of the mice. The extract caused a significant increase in fecal pellet weight and intestinal transit which was not dose-dependent. Doses of 200 and 300 mg/kg of the extract caused more significant reversal of loperamide-induced constipation than castor oil. Chlorpheniramine nifedipine and promethazine (1 mg/kg) blocked the increased fecal pellet output induced by the extract, while atropine and hexamethonium (1 mg/kg) did not block this effect of the extract. We concluded that AAV increased fecal pellet output of mice by increasing the peristaltic waves in their intestine via stimulation of H1 receptors and opening of L-type calcium channels and not through the cholinergic receptors.Keywords: H1 receptors, L-type calcium channels, intestinal transit, peristalsi

Improving growth performance of fingerlings of Clarias anguillaris through intraspecific hybridization

The development of aquaculture in Africa has been very slow due to lack of feeds and high quality seed (fingerlings). Hybridization is employed to combine desirable characteristics from one species to another to improve the genetic quality of parental stock with respect to fast growth, high percentage survival, resistance against unfavourable environment and diseases. This study was conducted to evaluate the growth performance of three strains of local Clarias anguillaris obtained from Onitsha (Rain forest), Makurdi (Guinea Savanna) and Maiduguri (Sahel Sananna) in Nigeria through intraspecific hybridization. The three strains were hybridized and the percentage survival, weight and length parameters were determined. The percentage survival was significantly higher in parental and intraspecific mating combinations. The mean values of initial and final weight at indoor rearing showed no significant differences (P&gt;0.05) between the parental and intraspecific mating combinations. However, the mean values of final weight at the outdoor rearing showed significant differences (P&lt;0.05) between the parental and intraspecific mating combinations. The initial length revealed significant differences (P&lt;0.05), while the final length are not. The Maiduguri parental strain recorded highest length gain of 8.97cm and Onitsha strain hybridized with Maiduguri strain recorded 7.93cm. However, Onitsha strain hybridized with Maiduguri strain showed superiority in growth performance in both indoor (16.05 g) and outdoor (1127.43 g) experiment. This could be further propagated to mass produce fingerlings for farmers.Keywords: Hybridization, Clarias anguillaris, growth performance, fingerling

Neuropharmacological effects of Alchornea cordifolia (Schumach. & Thonn.) Mull. Arg. (Euphorbiaceae) in mice

Alchornea cordifolia (Euphorbiaceae) is a common plant, which has featured prominently in traditional medicinal practice. It has been reported that the decoction of the leaves is taken as central nervous system stimulant. This work was therefore undertaken to examine the central nervous system effects. The neuropharmacological profile of the plant was determined in mice to which the plant extract had been orally administered at respective doses of 250, 500 and 1,000 mg/kg. The behavioral models used included noveltyinduced behaviors (locomotion, rearing and grooming), holeboard and elevated plus maze (anxiolytic) and forced swimming (antidepressant). The Y-maze was used for the investigation of the plant extract on locomotion, learning and memory. The results obtained showed that both locomotor and rearing activities were significantly decreased at the highest dose of 1000 mg/kg orally, while grooming behavior was significantly decreased at all the doses administered. In the hole board experiment, the frequency of head-dips was decreased significantly at 1000 mg/kg, while there was no significant effect observed in the elevated plus maze. Y-maze model results showed that it had no significant effect on spatial memory. There was no significant difference in the immobility duration due to administration of the extract in the forced swimming test. In conclusion, the present study showed that although the ethanolic leaf extract of A. cordifolia exhibited some central inhibitory effect, it is devoid of anxiolytic, antidepressant activities and has no significant effect on learning and memory in mice.Keyword: A. cordifolia, locomotion, grooming, mice, anxiolytic, antidepressant, mic

Improving breeding performance of fingerlings of Clarias gariepinus through intraspecific hybridization

The scarcity of genetically improved fish seed is a major constraint to rapid development of aquaculture in Nigeria due to inbreeding. The study was conducted to monitor breeding indices from intra-specific mating combinations of wild stocks of Clarias gariepinus. Broodstock of C. gariepinus were collected from Lokoja (LK), Makurdi (MK), Agenebode (AG) and Onitsha (ON) and compared with domesticated strain. 16 mating combinations of parental and intraspecific mating combinations were conducted in triplicates. Results were subjected to one way analysis of variance (ANOVA) (α= 0.05). The results showed collection from Onitsha had highest values of fertilization (95.2%), hatchability (87.6 %) and survival (66.0 %), followed by crosses from female from Onitsha : ♀ON X ♂LK, ♀ON X  ♂MK and ♀ON X  ♂AG having 95.8 %, 91.1 % and 88.8 % (fertilization), 68.7 %, 61.9 % and 60.7 % (hatchability) and 61 %, 57 % and 63 % (survival) respectively. Domesticated strain had least values (81.9 %, 59.4 % and 51 %) fertilization, hatchability and survival respectively. ANOVA (α&lt; 0.05) showed variation in fertilization, hatchability and survival. The better performing strains could be explored for genetic development. However, protein and gene profiling of these natural populations may be necessary to identify the proteins and genes responsible for these variations in breeding performances.Key Words: Breeding, performance, Clarias gariepinus, hybridizatio

Effects of artemether on the plasma and urine concentrations of some electrolytes in rats

This study was carried out to determine the changes in the urine levels of sodium (Na+), potassium (K+), and calcium (Ca2+) of rats during a week of intramuscular administration of artemether (12.5 to 50.0 mg/kg/day), another one week thereafter and their concentrations in the plasma at the end of the study. At 12.5 and 25.0 mg/kg of artemether, urine Na+ concentration was significantly increased throughout the study (p &lt; 0.05), except on Day 7 (at 12.5 mg/kg) and Day 11 (at 25.0 mg/kg), when it was not significantly different from the control. At 12.5 mg/kg of the drug, urine K+ concentration was significantly increased throughout the study (p &lt; 0.05). Artemether caused no significant changes in urine Ca2+ concentration in the control rats as well as those that received 12.5 and 25.0 mg/kg of artemether. Progressive and significant reductions in the urine concentrations of all the electrolytes at 50.0 mg/kg of artemether were observed. Their concentrations in the plasma were also significantly reduced at this dose of the drug. A dose-dependent degeneration of the renal tissue of all the experimental rats was also observed. We concluded that high doses of artemether caused progressive degeneration of the renal tissue of rats, inability of the damaged kidneys to concentrate urine, which manifested as excessive water loss and electrolyte depletion.Key words: Artemether, electrolytes in plasma, urine concentrations, rats