Halomonas desiderata as a bacterial model to predict the possible biological nitrate reduction in concrete cells of nuclear waste disposals

After closure of a waste disposal cell in a repository for radioactive waste, resaturation is likely to cause the release of soluble species contained in cement and bituminous matrices, such as ionic species (nitrates, sulfates, calcium and alkaline ions, etc.), organic matter (mainly organic acids), or gases (from steel containers and reinforced concrete structures as well as from radiolysis within the waste packages). However, in the presence of nitrates in the near-field of waste, the waste cell can initiate oxidative conditions leading to enhanced mobility of redox-sensitive radionuclides (RN). In biotic conditions and in the presence of organic matter and/or hydrogen as electron donors, nitrates may be microbiologically reduced, allowing a return to reducing conditions that promote the safety of storage. Our work aims to analyze the possible microbial reactivity of nitrates at the bitumen – concrete interface in conditions as close as possible to radioactive waste storage conditions in order (i) to evaluate the nitrate reaction kinetics; (ii) to identify the by-products (NO2−, NH4+, N2, N2O, etc.); and (iii) to discriminate between the roles of planktonic bacteria and those adhering as a biofilm structure in the denitrifying activity. Leaching experiments on solid matrices (bitumen and cement pastes) were first implemented to define the physicochemical conditions that microorganisms are likely to meet at the bitumen-concrete interface, e.g. highly alkaline pH conditions (10 < pH < 11) imposed by the cement matrix. The screening of a range of anaerobic denitrifying bacterial strains led us to select Halomonas desiderata as a model bacterium capable of catalyzing the reaction of nitrate reduction in these particular conditions of pH. The denitrifying activity of H. desiderata was quantified in a batch bioreactor in the presence of solid matrices and/or leachate from bitumen and cement matrices. Denitrification was relatively fast in the presence of cement matrix (<100 h) and 2–3 times slower in the presence of bituminous matrix (pH 9.7). The maximal rate of denitrification was approximately 0.063 mM h−1 and some traces of nitrite were detected for a few hours (<2%). Overall, the presence of solid cement promoted the kinetics of denitrification. The inspection of the solid surfaces at the end of the experiment revealed the presence of a biofilm of H. desiderata on the cement paste surface. These attached bacteria showed a comparable denitrifying activity to planktonic bacterial culture. However, no colonization of bitumen was observed either by SEM or by epifluorescence microscopy

Reactivity of nitrate and organic acids at the concrete–bitumen interface of a nuclear waste repository cell

This study investigates the fate of nitrate and organic acids at the bitumen–concrete interface within repository cell for long-lived, intermediate-level, radioactive wastes. The interface was simulated by a multiphase system in which cementitious matrices (CEM V cement paste specimens) were exposed to bitumen model leachates consisting of nitrates and acetic acid with and without oxalic acid, chemical compounds likely to be released by bitumen. Leaching experiments were conducted with daily renewal of the solutions in order to accelerate reactions. The concentrations of anions (acetate, oxalate, nitrate, and nitrite) and cations (calcium, potassium) and the pH were monitored over time. Mineralogical changes of the cementitious matrices were analysed by XRD. The results confirmed the stability of nitrates in the abiotic conditions of the experiments. The action of acetic acid on the cementitious matrix was similar to that of ordinary leaching in the absence of organic acids (i.e. carried out with water or strong acids); no specific interaction was detected between acetate and cementitious cations. The reaction of oxalic acid with the cementitious phases led to the precipitation of calcium oxalate salts in the outer layer of the matrix. The concentration of oxalate was reduced by 65% inside the leaching medium

Altered cortical and subcortical connectivity due to infrasound administered near the hearing threshold – Evidence from fMRI

In the present study, the brain’s response towards near- and supra-threshold infrasound (IS) stimulation (sound frequency < 20 Hz) was investigated under resting-state fMRI conditions. The study involved two consecutive sessions. In the first session, 14 healthy participants underwent a hearing threshold—as well as a categorical loudness scaling measurement in which the individual loudness perception for IS was assessed across different sound pressure levels (SPL). In the second session, these participants underwent three resting-state acquisitions, one without auditory stimulation (no-tone), one with a monaurally presented 12-Hz IS tone (near-threshold) and one with a similar tone above the individual hearing threshold corresponding to a ‘medium loud’ hearing sensation (supra-threshold). Data analysis mainly focused on local connectivity measures by means of regional homogeneity (ReHo), but also involved independent component analysis (ICA) to investigate inter-regional connectivity. ReHo analysis revealed significantly higher local connectivity in right superior temporal gyrus (STG) adjacent to primary auditory cortex, in anterior cingulate cortex (ACC) and, when allowing smaller cluster sizes, also in the right amygdala (rAmyg) during the near-threshold, compared to both the supra-threshold and the no-tone condition. Additional independent component analysis (ICA) revealed large-scale changes of functional connectivity, reflected in a stronger activation of the right amygdala (rAmyg) in the opposite contrast (no-tone > near-threshold) as well as the right superior frontal gyrus (rSFG) during the near-threshold condition. In summary, this study is the first to demonstrate that infrasound near the hearing threshold may induce changes of neural activity across several brain regions, some of which are known to be involved in auditory processing, while others are regarded as keyplayers in emotional and autonomic control. These findings thus allow us to speculate on how continuous exposure to (sub-)liminal IS could exert a pathogenic influence on the organism, yet further (especially longitudinal) studies are required in order to substantialize these findings

Physico-chemical interactions at the concrete-bitumen interface of nuclear waste repositories

This study investigates the fate of nitrate and organic acids at the bitumenconcrete-steel interface within a repository storage cell for long-lived, intermediatelevel, radioactive wastes. The interface was simulated by a multiphase system in which cementitious matrices (CEM V paste specimens) were exposed to bitumen model leachates consisting of nitrates and acetic acid with and without oxalic acid, chemical compounds likely to be released by bitumen. Leaching experiments were conducted with daily renewal of the solutions in order to accelerate reactions. C-steel chips, simulating the presence of steel in the repository, were added in the systems for some experiments. The concentrations of anions (acetate, oxalate, nitrate, and nitrite) and cations (calcium, potassium, ammonium) and the pH were monitored over time. Mineralogical changes of the cementitious matrices were analysed by XRD. The results confirmed the stability of nitrates in the absence of steel, whereas, reduction of nitrates was observed in the presence of steel (production of NH4+). The action of acetic acid on the cementitious matrix was similar to that of ordinary leaching; no specific interaction was detected between acetate and cementitious cations. The reaction of oxalic acid with the cementitious phases led to the precipitation of calcium oxalate salts in the outer layer of the matrix. The concentration of oxalate was reduced by 65% inside the leaching medium

Catalyse biotique et abiotique de la réduction des nitrates en milieu alcalin dans le contexte du stockage profond des déchets radioactifs

Cette étude explore la réactivité des nitrates à l’interface bitume-béton dans une alvéole de stockage de déchets radioactifs de moyenne activité et à vie longue dans la perspective de déterminer les conditions redox qui s’y développeront. La première partie du travail visait à identifier, en conditions abiotiques (sans bactéries), les interactions entre deux composants du système : le béton (introduit sous forme de pâtes de ciment) et le bitume (simulé par des lixiviats modèles constitués de solutions d’acides organiques et de nitrates). La seconde partie de l’étude a été conduite en conditions biotiques avec deux espèces de bactéries hétérotrophes dénitrifiantes (Pseudomonas stutzeri – Ps et Halomonas desiderata – Hd) et avait pour but d’analyser la réaction de réduction des nitrates (cinétiques, sous-produits, rôle de la matière organique) en conditions de pH neutre à alcalin (caractéristiques de l’environnement chimique imposé par le béton). Les résultats ont montré que des interactions fortes se produisaient entre la matrice cimentaire et les acides organiques, acétique et oxalique, interactions susceptibles de réduire la biodisponibilité de cette matière organique (pour l’oxalate en particulier), et ont confirmé la stabilité des nitrates dans ces conditions. En conditions biotiques, les nitrates ont été réduits par Ps et Hd selon la voie métabolique de dénitrification anaérobie. Les cinétiques de réduction étaient plus élevées avec Ps mais les réactions étaient inhibées pour pH > 9. Hd était en revanche capable de réaliser la dénitrification jusqu’à pH 11 au moins

Cyclosporiasis Outbreak in Germany Associated with the Consumption of Salad

This outbreak is the first foodborne cyclosporiasis outbreak reported from central Europe. The illness was reported in 34 persons who attended luncheons at a German restaurant. The overall attack rate was 85% (34/40). The only foods associated with significant disease risk were two salad side dishes prepared from lettuce imported from southern Europe and spiced with fresh green leafy herbs (p=0.0025)

Controlling Magnonic Spin Current through Magnetic Anisotropy and Gilbert Damping

The magnon propagation length, (MPL) of a ferro/ferrimagnet (FM) is one of the key factors that controls the generation and propagation of thermally-driven spin current in FM/heavy metal (HM) bilayer based spincaloritronic devices. Theory predicts that for the FM layer, MPL is inversely proportional to the Gilbert damping (alpha) and the square root of the effective magnetic anisotropy constant (K_eff). However, direct experimental evidence of this relationship is lacking. To experimentally confirm this prediction, we employ a combination of longitudinal spin Seebeck effect (LSSE), transverse susceptibility, and ferromagnetic resonance experiments to investigate the temperature evolution of MPL and establish its correlation with the effective magnetic anisotropy field, H_K^eff (proportional to K_eff) and alpha in Tm3Fe5O12 (TmIG)/Pt bilayers. We observe concurrent drops in the LSSE voltage and MPL below 200 K in TmIG/Pt bilayers regardless of TmIG film thickness and substrate choice and attribute it to the noticeable increases in H_K^eff and alpha that occur within the same temperature range. This study not only highlights the ability to manipulate MPL by controlling H_K^eff and alpha in FM/HM based spincaloritronic nanodevices, but also shows that the tuning of alpha is more effective than H_K^eff in controlling MPL and, hence, the spincaloritronic efficiency.Comment: 5 main text figure

Cooperative report of #vBIB20 – the virtual conference of BIB and TIB about library topics (May 26-28 2020)

Nach der Covid-19-bedingten Absage des 109. Deutschen Bibliothekartags, der von 26. bis 29. Mai 2020 in Hannover stattfinden hätte sollen, wurde vom Berufsverband Information Bibliothek (BIB) und von TIB – Leibniz-Informationszentrum Technik und Naturwissenschaften und Universitätsbibliothek mit #vBIB20 zwischen 26. und 28. Mai 2020 kurzfristig eine virtuelle Konferenz rund um bibliothekarische Themen organisiert. Im vorliegenden kooperativen Bericht werden Vorträge zu den Themenbereichen Publikationswesen, Open Access, Forschungsdatenmanagement, Bibliothekstatistik und NS-Provenienzforschung vorgestellt.After the cancellation of the 109. Deutscher Bibiothekartag (109th German Librarian Day), which should have taken place in Hannover from Mai 26th to 29th 2020, the Berufsverband Infromation Bibliothek (BIB) and the TIB – Leibniz Information Centre for Science and Technology University Library – together with #vBIB20 organised at short notice a virtual conference about library topics from May 26th to 28th 2020. In this cooperative report lectures are presented about publication system, Open Access, research data management, library statistics and provenance research