1,721,058 research outputs found
Effect of uranium uptake on oxidative stress reactions for Phaseolus vulgaris
No full textThe present study aims to analyze the biological effects induced by bioaccumulation of uranium by Phaseolus vulgaris. Following a 1 week exposure, plant development and the capacity of enzymes involved in the anti-oxidative defense mechanism of the plant were analyzed.uranium; oxidative stress; Phaseolus vulgaris; uptake; hydroponic
Effect of uranium uptake on oxidative stress reactions for Phaseolus vulgaris
No full textThe present study aims to analyze the biological effects induced by bioaccumulation of uranium by Phaseolus vulgaris. Following a 1 week exposure, plant development and the capacity of enzymes involved in the anti-oxidative defense mechanism of the plant were analyzed.uranium; oxidative stress; Phaseolus vulgaris; uptake; hydroponic
Interception of radionuclides by planophile crops: A simple semi-empirical modelling approach in case of nuclear accident fallout
No full textShortly after an atmospheric release, the interception of radionuclides by crop canopies represents the main uptake pathway leading to food chain contamination. The food chain models currently used in European emergency decision support systems require a large number of input parameters, which inevitably leads to high model complexity. In this study, we have established a new relationship for wet deposited radionuclides to simplify the current modelling approaches. This relationship is based on the hypothesis that the stage of plant development is the key factor governing the interception of radionuclides by crops having horizontally oriented leaves (planophile crops). The interception fraction (f) and the leaf area index normalized (f(LAI)) and mass normalized (f(B)) interception fractions were assessed for spinach (Spinacia oleracea) and radish (Raphanus sativus) at different stages of plant development and for different contamination treatments and plant densities. A database of 191 f values for Cs-137 and Th-229 was built and complemented with existing literature covering various radionuclides and crops with similar canopy structure. The overall f increased with the plant growth, while the reverse was observed for f(B). The f(LAI) significantly decreased by doubling the contaminated rainfall deposited. Fitting a multiple linear regression to predict the f value as a function of the standing biomass (B), and the radionuclide form (anion and cation) led to a better estimation of the interception (R-2 = 81%) than the ECOSYS-87 model (R-2 = 35%). Hence, the simplified modelling approach here proposed seems to be a suitable risk assessment tool as fewer parameters will minimize the model complexity and facilitate the decision-making procedures in case of emergencies, when countermeasures need to be identified and implemented promptly. (C) 2020 Elsevier Ltd. All rights reserved.The authors wish to thank dr. Gerard Prohl (International € Atomic Energy Agency) for proof reading the article, dr. Ella Roelant (University of Antwerp) for providing statistical and modelling assistance, dr. Diederik Jacques (SCK CEN) for his contribution to modeling the speciation of radionuclides, the lab-technicians Axel Van Gompel and Robin Nauts (Biosphere Impact Study, SCK CEN) for helping during laboratory activities, and the ing. Leen Verheyen
(Low-level Radiactivity Measurements, SCK CEN), expert in gamma spectrometry. This work was funded by the Belgian Nuclear Research Centre (SCK CEN) as PhD grant for Antonella CristinaCristina, A (corresponding author), Belgian Nucl Res Ctr SCK CEN, Fdn Publ Util, Biosphere Impact Studies, B-2400 Mol, Belgium ; Univ Antwerp, Dept Biosci Engn, Groenenborgerlaan 171, B-2020 Antwerp, Belgium.
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Effect of uranium and cadmium uptake on oxidative stress reactions for Phaseolus vulgaris
No full textBean seedlings were grown under controlled conditions on a Hoagland solution. Ten-day-old seedlings were exposed to 0, 0.1, 1, 10, 100 and 1000 µM U or 0.5 and 1 µM Cd. Following 7 days’ exposure, plants were sampled for determination of contaminant uptake, biometric parameters (shoot and root length, area of primary leaves, weight of shoot, root and primary leaves) and activity of enzymes involved in the plant’s anti-oxidative defense mechanisms. Generally we did not observe a significant difference in plant development between control and treated plants based on biometric parameters. Enzyme activities in roots were stimulated with increasing contaminant concentrations (though generally not significantly). However, for roots exposed to 1000 µM U, enzyme activity was generally significantly reduced. In shoots no significant difference in the defense mechanism between the treatments was observed
Can we predict uranium bioavailability based on soil parameters? Part 1: Effect of soil parameters on soil solution uranium concentration
No full textPresent study aims to quantify the influence of soil parameters on soil solution uranium concentration for U-238 spiked soils. Eighteen soils collected under pasture were selected such that they covered a wide range for those parameters hypothesised as being potentially important in determining U sorption. Maximum soil solution uranium concentrations were observed at alkaline pH, high inorganic carbon content and low cation exchange capacity, organic matter content, clay content, amorphous Fe and phosphate levels. Except for the significant correlation between the solid-liquid distribution coefficients (K-d, L kg(-1)) and the organic matter content (R-2 = 0.70) and amorphous Fe content (R-2 = 0.63), there was no single soil parameter significantly explaining the soil solution uranium concentration (which varied 100-fold). Above pH = 6, log(K-d) was linearly related with pH [log(K-d) = -1.18 pH + 10.8, R-2 = 0.65]. Multiple linear regression analysis did result in improved predictions of the soil solution uranium concentration but the model was complex. (c) 2006 Elsevier Ltd. All rights reserved
Study of biological effects and oxidative stress related responses in gamma irradiated Arabidopsis thaliana plants
No full textThis study aimed at investigating biological effects in Arabidopsis thaliana leaves and roots irradiated for 72 h with 3.5 Gy or 30 Gy of gamma radiation, and to unravel oxidative stress related responses to achieve a better understanding of the importance of the cellular redox balance as a modulator in gamma radiation stress. A. thaliana performs like a rather radioresistant plant species as no alterations on growth and only minor alterations in the nutrient profile were observed. Gamma irradiation did not seem to induce an NADPH mediated oxidative burst and lipid peroxidation appeared to be directly induced by ionizing radiation rather than mediated through LOX activity. As ionizing radiation can cause indirect damage via water radiolysis, H2O2 is hypothesized to be an important reactive oxygen species under radiation stress. Although most H2O2-scavenging enzymes remained unchanged, important alterations were observed for CAT1, CAT2 and CAT3 expression
Onderzoek naar de mogelijkheden voor het berekenen van scheepsvoortstuwingsinstallaties m.b.v. een kennisysteem
No full textEen kennissysteem is een intelligent computerprogramma dat een kennis en redeneermechanisme gebruikt voor het oplossen van complexe problemen. Het trekken van conclusies uit de aanwezige kennis gebeurt door het van de kennisbank gescheiden redeneersysteem. De scheiding van kennis en redeneren is in feite een scheiding tussen WAT en HOE. Voor presentatie van kennis zijn verschillende methoden ontwikkeld. Dergelijke presentaties zijn voor de computer van belang om efficiënt en effectief te kunnen redeneren. De meest toegepaste zijn produktie-regels, semantische netwerken en frames. Het ontwikkelen van kennissystemen kan op vele niveaus plaatsvinden, van een complete ontwikkelomgeving op speciale voor Al-toepassing ontwikkelde hardware tot en met Basic op een PC. Quaestor is een "Rule Based Expert system" en in feite een intelligente programmagenerator. Een probleem gedefinieerd door de gebruiker wordt opgelost door het genereren van vergelijkin (Yen, gevormd door relaties die geselecteerd zijn uit een database of "knowledge base". De gebruiker heeft een belangrijke rol in dit proces door het verzorgen van "meta-knowledge". Dit is informatie over hoe de kennis in de database moet worden gebruikt voor het bereiken van een oplossing van een specifiek probleem. Het te ontwerpen kennissysteem van de scheepsvoortstuwingsinstallatie zal geïmplementeerd worden in het softwarepakket Quaestor. Van de voortstuwingsinstallatie zal hiertoe een parametrisch model worden gemaakt van de verschillende componenten van de voortstuwingsinstallatie. Voor het model zal het schip in een aantal submodellen worden verdeeld. De hoofdindeling van het schip zal bestaan uit zeven submodellenMechanical, Maritime and Materials EngineeringMarine and Transport TechnologyShip Design, Production and Operatio
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