Development of mechanistic models for the description of radionuclide retention onto calcareous gravels.

The retention capacity of natural calcareous gravels used as a filling material between the packages containing radioactive waste materials in the disposal cells was evaluated for Sr, U, Ni, Ag, 14C, 99Tc, 239Pu, 228Th and 152Eu. The thermodynamic calculations performed considering repository conditions indicated that the chemistry of most of these elements was dominated by neutral or cationic species, this is the case of 238Pu 152Eu, 228Th, Ni and Ag. The studied gravels presented high sorption capacities for these cationic or neutral species, but they are not efficient on retaining anionic species as in the case of 99Tc or Sr, which is already present in the composition of the studied gravels. For those elements where the predominant species are carbonated (14C and U) low distribution coefficients were obtained. A preliminary mechanistic sorption model was developed for each radionuclide considering carbonate (>CO3H) and calcium hydroxide (>CaOH) sites. Our preliminary model allowed to successfully reproduce the experimental trend of the data obtained in this work.

The issue of Cs-137 in firewood and biomass combustion: a review.

In large parts of Europe, the Chernobyl accident of 1986 caused fallout of Cs-137. This led to the uptake of Cs-137 in trees or other materials used for bioenergy production or as firewood for domestic purposes. This Cs-137 may concentrate in the ashes of the combustion process in such a way that the clearance level of 100 Bq per kg, defined in Directive 2013/59/Euratom (EU BSS), may consequently be exceeded. There is currently no clear consensus in Europe regarding the regulatory approach to this issue: should the import and use of Cs-137 contaminated biomass and its ashes be considered as a planned exposure situation or rather as an existing exposure situation? If considered as an existing exposure situation, which reference level should be applied? We compare the approaches in various European countries, such as Finland, Norway, Sweden, Belgium and the Netherlands. Results of a recent measurement campaign performed in Belgium on firewood imported from Belarus, Ukraine and other countries show a quite large range of Cs-137 activity concentration in firewood. Analysis of samples from biomass combustion confirms that the clearance level of 100 Bq per kg Cs-137 may be exceeded even when the activity concentration in the initial pellet is trivial. A review of dose-assessment studies performed by STUK and from the literature is presented. The general context of biomass energy production is sketched: for instance, in the Netherlands, 40 large biomass firing plants (capacity > 10 MW) are operational and some 20 more are already planned. The fly ashes from the biomass combustion may be a valuable resource for the construction industry, and the issue of Cs-137 contamination is connected with the requirements of the EU BSS regarding the natural radioactivity of building materials. Assessing the impact of Cs-137 contamination and clarifying regulations in the frame of a graded approach are important elements in this context.

Quality evaluation of patient educational resources for catheter ablation treatment of atrial fibrillation.

AIMS: The prevalence of atrial fibrillation (AF) is increasing rapidly with the growing utilization of catheter ablation (CA) as a treatment strategy. Education for individuals undertaking this procedure is diverse, with varying degrees of information provided and little standardization. Many individuals utilize the internet as an educational resource. However, there is limited regulation of online patient information. To evaluate the quality of web-based patient education resources for patients undergoing CA for AF. METHODS AND RESULTS: A cross-sectional observational study was performed to obtain all freely accessible online educational resources about CA for AF from inception until 1 October 2019. Search engines used: Google, Yahoo!, and Bing. The Patient Education Materials Assessment Tool (PEMAT) was used to evaluate the quality of web-based patient education materials and printable tools. The PEMAT score objectively measures both the understandability and actionability of educational material. A total of 17 websites and 15 printable sources were included in the analysis. Non-government organizations developed 19% of materials and 75% were created by private or university hospitals. Nineteen sources (59.4%) were rated as highly understandable: 9 websites (52.9%) and 10 printable tools (66.7%). Seven sources (21.9%) were rated as highly actionable: 6 (35.3%) websites and 1 (6.7%) printable tool. CONCLUSION: The overall understandability of educational CA material was high, whilst improvement of actionability is warranted. The addition of summaries, visual aids, and tools, such as checklists may improve quality. These findings have significant implications for the development of patient educational material for CA in AF.

Effect of monovalent cations on the kinetics of hypoxic conformational change of mitochondrial complex I.

Mitochondrial complex I is a large, membrane-bound enzyme central to energy metabolism, and its dysfunction is implicated in cardiovascular and neurodegenerative diseases. An interesting feature of mammalian complex I is the so-called A/D transition, when the idle enzyme spontaneously converts from the active (A) to the de-active, dormant (D) form. The A/D transition plays an important role in tissue response to ischemia and rate of the conversion can be a crucial factor determining outcome of ischemia/reperfusion. Here, we describe the effects of alkali cations on the rate of the D-to-A transition to define whether A/D conversion may be regulated by sodium. At neutral pH (7-7.5) sodium resulted in a clear increase of rates of activation (D-to-A conversion) while other cations had minor effects. The stimulating effect of sodium in this pH range was not caused by an increase in ionic strength. EIPA, an inhibitor of Na(+)/H(+) antiporters, decreased the rate of D-to-A conversion and sodium partially eliminated this effect of EIPA. At higher pH (>8.0), acceleration of the D-to-A conversion by sodium was abolished, and all tested cations decreased the rate of activation, probably due to the effect of ionic strength. The implications of this finding for the mechanism of complex I energy transduction and possible physiological importance of sodium stimulation of the D-to-A conversion at pathophysiological conditions in vivo are discussed.