De productie en moleculaire verschijningsvorm van radiotoxisch Po-210 in kernfusie- en splijtingsreactoren = The Production and Molecular Occurrence of Radiotoxic Po-210 in Nuclear Fusion and Fission Reactors

In order to counter the climate change, there is a need for a radical revolution in the global energy supply. One of the most realistic scenarios is a substantial shift towards renewable energy sources, supported by a flexible baseload from carbon-free nuclear energy. The main requirements for this new generation of nuclear reactors are intrinsic safety, high fuel efficiency and a minimum amount of (long-lived) radioactive waste. A promising candidate for the near future is the lead (alloy) cooled fast fission reactor. An ideal long-term solution are nuclear fusion reactors, which produce only a small amount of short-lived radioactive waste. A problem that occurs in both these reactor types is the undesired production of the highly radiotoxic polonium-210 isotope. In this PhD thesis, the total production of this isotope in a nuclear fusion reactor is determined using neutron transport and inventory calculations. Next, quantum chemical calculations are performed to predict the molecular form in which Po-210 will occur in both discussed reactor types. Combining both aspects allows to estimate the risk associated with the presence of Po-210 in a nuclear reactor and can help to design efficient Po-210 extraction systems

Newly discovered populations of the Ethiopian endemic and endangered Afrixalus clarkei Largen, implications for conservation

Knowledge of the Ethiopian amphibian fauna is limited and Southwest Ethiopia remains understudied. This part of Ethiopia, where most of the country’s remaining natural forest is situated, is known to harbour the only populations of Afrixalus clarkei (Largen), an endemic banana frog, worldwide. This species is under great threat of extinction and is therefore classified as endangered on the IUCN red list. We surveyed different potential habitats for this species outside its known range and found several new populations extending its known habitat preference, and the geographical and altitudinal range of the species. We here show that Afrixalus clarkei is more common than previously thought

Po-containing molecules in fusion and fission reactors

Fission and fusion reactors can only play a role in the future energy landscape if they are inherently safe by design. For some reactor concepts, a major remaining issue is the undesired production of radiotoxic Po-210. To filter out the volatile Po species, information on their molecular composition is needed. An experimental characterization is very challenging due to the large required amount of radioactive Po. An alternative quantum chemistry approach was taken to predict the temperature-dependent stability of relevant diatomic Po-containing molecules. Experimental data on lighter analogue molecules was used to establish a well-founded methodology. The relative occurrence of the Po species was estimated in the cover gas of (i) the lead-bismuth eutectic coolant in the accelerator-driven MYRRHA fission reactor and (ii) the Pb-Li eutectic tritium breeder in the DEMO fusion reactor. In both systems, Po is found to occur mainly as PbPo molecules and atomic Po

Methodology to assess the reliability behavior of RF-MEMS

This paper reports on the investigation of the main phenomenon which limits the lifetime of capacitive RF MEMS : dielectric charging. To understand this effect, we have developed specific test set which measures the electrical (at both low and microwave frequencies) and electromechanical performances of RF MEMS to investigate their reliability. Several experiments have thus been performed such as DC bias stress and cycling under different actuation waveforms and environment conditions. These tests have shown that the dielectric charging creates a drift of the threshold voltages and we propose an appropriate figure of merit regarding the lifetime of capacitive RF-MEMS and a key parameter to determine the type of the failure which occurs

Biodiversity Express Survey Salonga National Park DRC December 2022

Abstract: Salonga National Park is positioned in the central Congo Basin, covering a vast area in excess of 3.5 million ha of lowland Guinea-Congolian rainforest. It comprises the largest rainforest reserve in Africa, and second largest in the world. The principal aim of the project was to undertake a multiple taxa biodiversity assessment, with special attention to biological communities that have received relatively little attention. We undertook fieldwork at three study sites in Salonga from 25 November \u2013 15 December 2022, collecting standardised data on birds, amphibians, reptiles, fish and selected invertebrate groups (spiders, ants, butterflies, hawkmoths, dragonflies, ground beetles and various other groups). Collectively, we recorded 160 species of birds, 32 species of herpetofauna, 32 fish and over 400 species of invertebrates. Our findings include several species of conservation concern on the IUCN RedList such as Grey Parrot (Endangered), Congo Peacock (Near Threatened), Crowned Eagle (Near Threatened) and Forest Hinge-back Tortoise (Data Deficient). We discovered new species of virtually any taxonomic group studied including a shrew, frog, fish, spiders, ant, dragonfly, bugs and many more are expected as the material is studied in more detail. We also identified several range extensions of varying significance including Barred Long-tailed Cuckoo (identification pending confirmation) which would be the first record for the Guinea-Congo Basin biome. This biodiversity express survey revealed high species diversity and richness considering the short sampling time. The large number of new species to science reflects how poorly studied this region is, and also how much more is likely to be present. More and more long-term studies across a broader spread of floral and faunal groups are required to better understand the biodiversity of Salonga

Galectin-9 and CXCL10 as biomarkers for disease activity in juvenile dermatomyositis : a longitudinal cohort study and multi-cohort validation

Objective: Objective evaluation of disease activity is challenging in patients with juvenile dermatomyositis (DM) due to a lack of reliable biomarkers, but it is crucial to avoid both under- and overtreatment of patients. Recently, we identified 2 proteins, galectin-9 and CXCL10, whose levels are highly correlated with the extent of juvenile DM disease activity. This study was undertaken to validate galectin-9 and CXCL10 as biomarkers for disease activity in juvenile DM, and to assess their disease specificity and potency in predicting the occurrence of flares. Methods: Levels of galectin-9 and CXCL10 were measured by multiplex immunoassay in serum samples from 125 unique patients with juvenile DM in 3 international cross-sectional cohorts and a local longitudinal cohort. The disease specificity of both proteins was examined in 50 adult patients with DM or nonspecific myositis (NSM) and 61 patients with other systemic autoimmune diseases. Results: Both cross-sectionally and longitudinally, galectin-9 and CXCL10 outperformed the currently used laboratory marker, creatine kinase (CK), in distinguishing between juvenile DM patients with active disease and those in remission (area under the receiver operating characteristic curve [AUC] 0.86–0.90 for galectin-9 and CXCL10; AUC 0.66–0.68 for CK). The sensitivity and specificity for active disease in juvenile DM was 0.84 and 0.92, respectively, for galectin-9 and 0.87 and 1.00, respectively, for CXCL10. In 10 patients with juvenile DM who experienced a flare and were prospectively followed up, continuously elevated or rising biomarker levels suggested an imminent flare up to several months before the onset of symptoms, even in the absence of elevated CK levels. Galectin-9 and CXCL10 distinguished between active disease and remission in adult patients with DM or NSM (P = 0.0126 for galectin-9 and P < 0.0001 for CXCL10) and were suited for measurement in minimally invasive dried blood spots (healthy controls versus juvenile DM, P = 0.0040 for galectin-9 and P < 0.0001 for CXCL10). Conclusion: In this study, galectin-9 and CXCL10 were validated as sensitive and reliable biomarkers for disease activity in juvenile DM. Implementation of these biomarkers into clinical practice as tools to monitor disease activity and guide treatment might facilitate personalized treatment strategies