Non-contact in situ multi-diagnostic NMR/dielectric spectroscopy

Introduction of a dielectric material in an NMR probe head modifies the frequency response of the probe circuit, a phenomenon revealed by the detuning of the probe. For NMR spectroscopy, this detuning is corrected for by tuning and matching the probe head prior to the NMR measurement. The magnitude of the probe detuning - the dielectric shift - provides direct access to the dielectric properties of the sample, enabling NMR spectrometers to simultaneously perform both dielectric and NMR spectroscopy. By measuring sample permittivity as function of frequency, permittivity spectroscopy can be performed using the new methodology. As a proof concept, this was evaluated on methanol, ethanol, 1-propanol, 1-pentanol and 1-octanol using a commercial CPMAS NMR probe head. The results accurately match literature data collected by standard dielectric spectroscopy techniques. Subsequently, the method was also applied to investigate the solvent-surface interactions of water confined in the micropores of an MFI-type, hydrophilic zeolite with Si/Al ratio of 11.5. In the micropores, water adsorbs to Br{\o}nsted acid sites and defect sites, resulting in a drastically decreased dielectric permittivity of the nano-confined water. A theoretical background for the new methodology is provided using an effective electric circuit model of a CPMAS probe head with solenoid coil, describing the detuning resulting from insertion of dielectric samples in the probe head

The rockerverse : packages and applications for containerisation with R

The Rocker Project provides widely used Docker images for R across different application scenarios. This article surveys downstream projects that build upon the Rocker Project images and presents the current state of R packages for managing Docker images and controlling containers. These use cases cover diverse topics such as package development, reproducible research, collaborative work, cloud-based data processing, and production deployment of services. The variety of applications demonstrates the power of the Rocker Project specifically and containerisation in general. Across the diverse ways to use containers, we identified common themes: reproducible environments, scalability and efficiency, and portability across clouds. We conclude that the current growth and diversification of use cases is likely to continue its positive impact, but see the need for consolidating the Rockerverse ecosystem of packages, developing common practices for applications, and exploring alternative containerisation software

Technetium interaction with natural organic matter: complexation versus colloid/colloid association

The redox-sensitive fission product technetium-99 (Tc) is of great interest in nuclear waste disposal studies because of its potential for contaminating the geosphere due to its very long half-life (2.13105 year) and high mobility under oxidising conditions, where technetium forms pertechnetate (TcO4-). Under suitable reducing conditions, e.g. in the presence of an iron(II) containing solid phase which can act as an electrondonor, the solubility can be limited by the reduction of pertechnetate followed by the formation of a surface precipitate.1 However, by association with mobile humic substances (HS) or other associating/complexing species, the solubility of reduced Tc species may be drastically enhanced.2 Detailed multiple scattering analysis of EXAFS data of Tc(IV)/pyrogallol solutions based on DFT modeled reference structures has demonstrated the existence of a stable Tc-pyrogallol complex which is readily formed at pH 11 and remains stable towards technetium colloid or precipitate formation both as function of pH and time in the pH range between 11 and 4.3 The occurrence of stable, readily formed Tc-complexes with pyrogallol, a humic substance model compound, is a strong indication for the existence of similar complexes in natural systems containing dissolved organic matter. The formation of such complexes indicates an extra potential for migration of Tc(IV) in systems containing natural organic matter, in addition to the previously discovered Tc(IV) eigencolloids stabilized by dissolved HS through colloid-colloid interactions.2 The formation of stable Tc(IV)-NOM complexes was investigated as function of pH using dissolved Boom Clay organic matter. Pertechnetate was pre-reduced in supernatant solutions containing natural BC organic matter at different pH. After the pre-reduction and re-setting of the supernatant pH to pH 8.2, the predominant pH in the Boom Clay system, the supernatant solutions were contacted with the Boom Clay solid phases. Comparison of these systems with reference Boom Clay batch systems allows to evaluate the competition between the sorption of technetium on the BC solid phase and the formation of stable Tc(IV)-BC organic matter complexes and Tc(IV)-BC organic matter colloid/colloid associations. 1Cui, D. Q. and T. E. Eriksen (1996). "Reduction of pertechnetate in solution by heterogeneous electron transfer from Fe(II)-containing geological material." ES&T 30(7): 2263-2269. 2Maes, A., K. Geraedts, C. Bruggeman, J. Vancluysen, A. Roßberg and H. Hennig (2004). "Evidence for the Formation of Technetium Colloids in Humic Substances by X-Ray Absorption Spectroscopy." ES&T 38(7): 2044-2051. 3Breynaert, E., Maes, A. (2007). Structure elucidation of Tc(IV) Pyrogallol Complexes. Migration Conference, Munichstatus: publishe

ESRF Experimental report 26-01 798 - Selenium solid phase speciation in Boom Clay batch conditions

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Interaction of Se with Boom Clay: XAS solid phase speciation

INTERACTION OF SE WITH BOOM CLAY: XAS SOLID PHASE SPECIATION ERIC BREYNAERT1*, DIRK DOM1, JACQUELINE VANCLUYSEN1, ANDREAS SCHEINOST2, ANDRÉ MAES1 1Center for surface Chemistry and Catalysis (M2S, KULeuven), B-3001Leuven,, Belgium 2Forschungszentrum Dresden-Rossendorf, 01314 Dresden, Germany *[email protected] The Boom Clay formation mainly consists of mixed clay minerals (illite, interstratified illite-smectite), pyrite and immobile and dissolved natural organic matter. Within the geological repository concept, the Boom clay formation itself is considered the primary barrier against radionuclide migration. It provides good sorption capacities, very low permeability, and chemically reducing conditions due to the presence of pyrite (FeS2) Since the mobility and consequently also the dose contribution is highly related to the speciation of selenium, the knowledge on its behaviour in the far field of the Boom Clay formation is very important for the safety case of the future Belgian high level waste disposal program. In all previous studies, the interpretation of the behaviour of Se in Boom Clay conditions has always been based on circumstantial evidence such as solubility measurements or comparison with the spectroscopically identified speciation of Se in model systems [1-3]. Since pyrite (FeS2) is one of the main minerals governing the redox conditions of the Boom Clay solid phases, it is expected that selenite will be reduced to Se0 in the Boom Clay system, thereby effectively limiting the solution concentration to the solubility of Se0, provided that there is no interaction with the mobile Boom Clay organic matter. Selenite was equilibrated with Boom Clay for 1 month, before phase separation into 4 size fractions (clay-rich, pyrite-rich, organic matter-rich, supernatant) was achieved using centrifugation. For the first time the solid phase reaction products for the interaction of selenite with the Boom Clay solid phase have been spectroscopically identified. Based on the XANES/EXAFS analysis, selenite is reduced to Se0 on all solid phase size fractions of the Boom Clay, confirming the reduction of selenite to metallic selenium in the Boom Clay system. Despite of the low equilibrium concentration in the supernatant solution (5x10-6M of Se) XANES measurements were possible and unexpectedly indicated the presence of a selenide phase (FeSe or an organic selenide), although Se0 was observed on the respective solid phase fractions. 1. Bruggeman C., Maes A., Vancluysen J. and Vandemussele P. (2005). Selenite reduction in Boom clay: effect of FeS2, clay minerals and dissolved organic matter. Env. Poll., 137: 209-221. 2. Scheinost A.C. and Charlet L. (2008). Selenite reduction by mackinawite, magnetite and siderite: XAS characterization of nanosized redox products. ES&T, 42(6): 1984-1989. 3. Breynaert, E., Bruggeman C. and Maes A. (2008) XANES-EXAFS analysis of se solid-phase reaction products formed upon contacting Se(IV) with FeS2 and FeS. ES&T, 42(10): 3595-3601. Keywords: EXAFS/XANES, selenium, solid phase speciation.status: publishe

Selenium liquid phase speciation in Boom Clay conditions - 1st progress report

In this first report the experimental strategy and conditions used to obtain relevant and representative samples for XAS analysis will be explained in detail. XAS results are shown for representative liquid phase samples. Due the presence of unexpectedly high concentration of dissolved species that could not be identified as any of the available references, a new pyrite-based reduction mechanism is presented. Based on this mechanism, hypothesis was put forward about the identity of the unknown dissolved species. In addition, the new mechanism allows explaining all current experimental observations, more specifically the presence of this currently non-identified dissolved species and the unexpected relation between Se(IV) reduction and pH as observed by (7).status: publishe

Progress report M2S-LCC-R.2008-01/02 - Technetium Boom Clay HS Complex Formation - Structure elucidation of Tc(IV)-pyrogallol complexes

Progress report for topics - "Technetium Boom Clay HS Complex Formation" and "Structure elucidation of Tc(IV)-pyrogallol complexes"nrpages: 30status: publishe

ESRF Experimental report 20-01 677 - Selenium solid phase speciation in Boom Clay conditions

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