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[en] In 1994, the substances and risks sector of the National Institute of Public Health and the Environment (RIVM) decided to strengthen its research into risk assessment methodology strategically. To further this goal, this report describes the area of RIVM research dealing with the prediction of human exposure. A representative selection of the models used to predict human exposure to both chemical substances and radiation is analysed. The analysis considers aspects of the models such as the aims, basic principles, the extent to which the models have been analysed and values of default parameters. For comparison purposes, a model used to assess human exposure to micro-organisms is also included. All models are being, or are about to be, used operationally to produce risk assessments in the substances and risks sector and also in the public health and environmental research sectors. All the models discussed have a defined area of application and are directly available in support of policy implementation. Comparison of areas of research dealing with exposure assessment for substances and radiation reveals many methodological similarities. However, at the level of models and parameters, an in-depth analysis of these similarities and explained or unexplained differences is lacking. A first attempt is made in this report. Detailed examination of organisational aspects and RIVM-models for human exposure prediction reveals that all relevant areas of interest are covered. The range of methodology for the prediction of actual risks and exposures is great, for all exposure routes. The coverage is more uniform for radiation than for chemical substances, however. For both areas the prediction and recording of emissions could be improved. The development of risk assessment systems and related harmonisation projects have been underway for many years (for example CSOIL, USES, RIBRON). The methodology for the prediction of actual exposures and risks still requires further development and projects to this end are proposed. Analysis of the models also shows that few models have completed all stages of model development from concept to analysis and validation. Many models are still under development and this implies that the data requirements for these models often cannot yet be fulfilled. As regards the overall objective, this report concludes that the RIVM requires a broad, up to date range of instruments for exposure prediction and must be actively involved in all kinds of nationally and internationally relevant networks. The RIVM should also continue to be involved in the development and evaluation of methodology and in discussions concerning harmonisation between sectors. The expertise required is available. Good internal co-ordination is essential. As regards the objectives of this RIVM management project, it was concluded that, in view of the many fruitful discussions which took place between researchers in the laboratories of sectors 2, 4 and 5, an important aim of this project, i.e. to further internal harmonisation and communication in the area of human exposure prediction, had been achieved. (author)
[en] No abstract prepared. See title.18 refs
[nl]In de voorgaande artikelen in NVS Nieuws over de blootstelling van de Nederlandse bevolking aan ioniserende straling is ingegaan op de blootstelling van patienten aan ioniserende straling door medisch diagnostische toepassingen, de blootstelling aan radon en de blootstelling aan externe straling vanuit de omgeving. In dit artikel wordt - in volgorde van relatief aandeel - ingegaan op de overige bronnen van ioniserende straling. Evenals in de voorgaande artikelen wordt de stralingsbelasting uitgedrukt als gemiddelde effectieve dosis per bron. Dit is de collectieve dosis per bron, gedeeld door het aantal leden van de bevolking, ongeacht de werkelijke groepsgrootte en de variatie in de ontvangen dosis over de Nederlandse bevolking. 18 refs
[en] Radioiodinated m-iodobenzylguanidine (MIBG), an analogue of the neurotransmitter norepinephrine (NE), is increasingly used in the diagnosis and treatment of neural crest tumors. Active uptake and subsequent retention of MIBG and NE was studied in human neuroblastoma SK-N-SH cells. Neuron-specific uptake of [125I]MIBG and [3H]NE saturated at extracellular concentration of 10(-6) M and exceeded by 20-30-fold that by passive diffusion alone. A minimum of 50% of accumulated MIBG remained permanently stored but the SK-N-SH cells were incapable of retaining recaptured [3H]NE. [125I]MIBG was displaced from intracellular binding sites by unlabeled MIBG with 10-fold higher potency than by unlabeled NE. MIBG stored in SK-N-SH cells was insensitive to depletion by the inhibitor of granular uptake reserpine (RSP) and was not precipitated in a granular fraction by differential centrifugation. Only few electron-dense granules were found in these cells by electron microscopy. In contrast, MIBG storage in PC-12 pheochromocytoma cells which contained many storage granules, was sensitive to RSP and part of accumulated drug was recovered in a granular fraction. Accordingly, storage of MIBG in the SK-N-SH neuroblastoma cells is predominantly extravesicular and thus essentially different from that of biogenic amines in normal adrenomedullary tissue or in pheochromocytoma tumors, while sharing with these tissues a common mechanism of active uptake
[en] High-precision measurements of total solar irradiance, made by the active cavity radiometer irradiance monitor on the Solar Maximum Mission satellite, show the irradiance to have been variable throughout the first 153 days of observations. The corrected data resolve orbit-to-orbit variations with uncertainties as small as 0.001 percent. Irradiance fluctuations are typical of a band-limited noise spectrum with high-frequency cutoff near 0.15 day-1; their amplitudes about the mean value of 1368.31 watts per square meter approach +- 0.05 percent. Two large decreases in irradiance of up to 0.2 percent lasting about 1 week are highly correlated with the development of sunspot groups. The magnitude and time scale of the irradiance variability suggest that considerable energy storage occurs within the convection zone in solar active regions
[en] We demonstrate that network models for wave mechanical systems with quenched disorder cover the physics of mesoscopic electrons. The models are constructed as a network of random scattering matrices connecting incoming to outgoing wave amplitudes. The corresponding wave dynamics is given by a discrete unitary time evolution operator. We report on three different universality classes: two-dimensional, spinless, non-chiral electrons with (O2NC) and without time reversal symmetry (U2NC), and two-dimensional, non-chiral electrons with time reversal symmetric spin-scattering (S2NC). We determine the phase diagram in the parameter space of scattering strengths. The O/U2NC models show strong localization. We find symmetry factors in localization lengths as well as multifractal exponents in agreement with theoretical predictions. The S2NC model displays a localization-delocalization transition. We determine the critical exponent of the localization length and the multifractal scaling exponent of the order parameter to he ν ∼ 2.4 and α0∼2.18, respectively. (Copyright (1998) World Scientific Publishing Co. Pte. Ltd)
[en] This paper discussed the barriers and drivers for the implementation of biorefinery technology in the forestry industry. A multi-criteria decision making (MCDM) methodology was used by a panel of industry experts. The objective, drivers and barriers, and the decision structure and weighting procedure were established during a pre-panel phase. An analytic hierarchy process (AHP) was then applied to compare qualitative criteria. Pair-wise criteria were used to determine the importance of each driver and barrier. Drivers for the implementation of biorefineries included the opportunity to ensure short-term profitability; the provision of raw materials at competitive prices; potential financial incentives; and the opportunity to transform the forestry business model and increase its market value. Barriers included uncertainty in relation to government policies for biorefineries; high technology risks; the need for partnerships; and the fact that many industry members favour short-term decision-making. Results of the study showed that the most significant barrier was related to risk. 5 refs., 3 tabs., 3 figs.
[en] The concentrations of potassium, stable cesium, calcium and ammonium in soil, and pH are known to affect the uptake of 134Cs from soil. Uncertain is whether this is a direct effect on the uptake (e.g. through competition for binding sites) or an indirect effect through a changing distribution of 134Cs between the solid and liquid phase of the soil. The uptake of 134Cs by earthworms from solution and soil has been studied to investigate these effects. The effects of potassium and stable cesium expressed per mmol added, were comparable: 134Cs accumulation decreases with potassium and stable cesium concentration in solution. No significant effects from varying pH or calcium and ammonium concentrations on 134Cs uptake from liquid medium were observed. 134Cs concentrations in the earthworms increased with temperature, which could mainly be explained by earthworm-related factors such as increased metabolism or feeding rate. Addition of calcium, potassium, ammonium and organic matter to soil increased the amount of 134Cs in soil solution significantly. However, the overall effects of additions of K+, Ca++, NH4+ and organic matter on the 134Cs concentrations in earthworms were non-significant. Based on the experiments in liquid medium increasing the concentration of potassium in soil solution showed to be most effective and most realistic in reducing 134Cs uptake. The results in soil indicate that the effect of potassium will depend on other soil characteristics as well
[en] This article provided a literature review of emerging technologies for ethanol production in Canada. A multi-criteria decision making (MCDM) panel was used to weigh critical metrics for evaluating the potential of emerging forest biorefinery technologies for bio-ethanol production. The 3-step methodology identified key factors for evaluating technology pathways. Key factors were applied to a group of selected technologies in order to collect data. All previous criteria were weighted through the MCDM panel in order to rank the technologies, which included biochemical pathway and thermochemical pathway production processes. Criteria included return on investment; feedstock flexibility; technology risk; energy and integration; products and revenue diversification; potential for additional products; and potential environmental impact. The study showed that techno-economic criteria are the most important barriers to the implementation of ethanol biorefineries. While thermochemical processes are economically feasible and provide greater flexibility, biochemical refining processes may provide for the development of other value-added products. 21 refs., 3 tabs., 7 figs.
[en] Since 2002 five annual auctions of gasoline service stations along the national road network have been held. In each auction 7-20 gasoline service stations were auctioned one after the other. The objective of this evaluation is to learn lessons from the results of the past five auctions and use them to organize future auctions. What needs to be kept in mind is the fact that the main objective of the auctions, as an important part of the MDW trajectory gasoline, is to create a sufficiently competitive market along the national road network. [mk]
[de]Sinds 2002 hebben vijf jaarlijkse veilingen van benzinestations langs het rijkswegennet plaatsgevonden. Bij elke veiling werden 7-20 benzinestations 1 voor 1 na elkaar geveild. Het doel van deze evaluatie is om uit de resultaten van de afgelopen vijf veilingen lessen te trekken die gebruikt kunnen worden voor de wijze waarop toekomstige veilingen gehouden worden. Hierbij moet in het oog gehouden worden dat het hoofddoel van de veilingen, als belangrijk onderdeel van het MDW-traject Benzine, het creeren van een voldoende concurrerende markt langs het hoofdwegennet is