Papers by Daniel Grolimund
"Damascening, defined in this context as the inlay of one metal into a different metal base, is a... more "Damascening, defined in this context as the inlay of one metal into a different metal base, is a rare decorative technique in the Early Bronze Age, known only from seven bronze artefacts found north of the Alps. This paper reports on the first thorough scientific examination of one such find, the axe from Thun-Renzenbühl grave no. 1. This interdisciplinary project involving several institutions in Germany and Switzerland investigated the axe by means of neutron radiographic imaging and X-ray microprobe methods, supported by microscopic examination. The result is an attempt to reconstruct the fabrication and decoration process and to reconsider the enigmatic question of the origins of the damascene technique north of the Alps.
Le damasquinage, défini dans ce contexte comme étant un enchâssement de métal dans une base faite d’un métal différent, est une technique décorative rare au début de l’âge de bronze, connue seulement grâce à sept objets en bronze trouvés dans le Nord des Alpes. Cet article relate le premier examen scientifique approfondi d’une découverte de ce type, la hache de la tombe n° 1 de Thun-Renzenbühl. Ce projet interdisciplinaire, auquel participent plusieurs établissements allemands et suisses, a etudié cette hache au moyen de l’imagerie neutronique et de la microsonde de Castaing, complétées par un examen au microscope. Il en a résulté une tentative de reconstituer la fabrication et la décoration, ainsi qu’un réexamen de la question énigmatique portant sur les origines de la technique du damasquinage dans le Nord des Alpes."
Scientific reports, Feb 7, 2024
The long-term safe disposal of radioactive waste corresponds to a challenging responsibility of p... more The long-term safe disposal of radioactive waste corresponds to a challenging responsibility of present societies. Within deep geological waste disposal concepts, host rocks correspond to the ultimate safety barrier towards the environment. To assess the performance of such barriers over extended time scales, mechanistic information on the interaction between the radiotoxic, long-lived radionuclides like plutonium and the host rock is essential. Chemical imaging based on synchrotron microspectroscopic techniques was used to visualize undisturbed reactive transport patterns of Pu within pristine Opalinus Clay rock material. Pu +V is shown to be progressively reduced along its diffusion path to Pu +IV and Pu +III due to interaction with redox-active clay rock constituents. Experimental results and modeling emphasize the dominant role of electron-transfer reactions determining the mobility of Pu in reactive barrier systems. The effective migration velocity of Pu is controlled by the kinetic rates of the reduction to Pu +IV and Pu +III and the redox capacity of the involved electron donor pools. To advance our predictive capabilities further, an improved understanding of the nature and capacity of redox-active components of the reactive barrier material is fundamental. The findings represent an essential contribution to the evaluation of the long-term safety of potential nuclear waste repositories and have implications regarding the development of effective geological disposal strategies. The long-term safe disposal of radioactive waste corresponds to a challenging responsibility of present societies. Concepts based on a multi-barrier repository in deep geological formations represent a promising class of disposal strategies 1-4. Within these concepts, the host rock corresponds to the ultimate safety barrier towards the environment. To assess the performance of such final barriers, detailed information on the interaction between the different radiotoxic, long-lived radionuclides and the host rock is essential. Furthermore, to allow for reliable long-term predictions concerning the spreading of long-lived radionuclides, it is fundamental to identify and understand the physico-chemical reactive (solute) transport mechanisms along the entire transport paths through all the different barriers. Based on inventories and their long half-lives, plutonium (Pu) and other actinides are the major contributors to the radiotoxicity of spent nuclear fuel in a deep geological repository after a storage period of several hundred years 5,6. After its discovery in the 1940s, Pu was found to be a distinctive chemical element. Twenty Pu isotopes have been identified. Concerning wastes arising from nuclear power generation, the isotopes 239 Pu and 242 Pu with half-lives of 2.41 × 10 4 years and 3.75 × 10 5 years, respectively, are the most important ones due to their high radiological toxicities and long-term persistence in the environment. Considering its chemical properties, Pu is a highly redox-sensitive element with a resulting complex chemical behavior. Under conditions relevant to waste repositories as well as to near-surface environments, Pu can exist in aqueous solutions in several oxidation states simultaneously 7,8. The electronic states and chemical speciation are strongly dependent on the local chemical conditions such as pH, Eh, complexing ligands, and ionic strength. This ability to exist in multiple oxidation states stems from similarities in reduction potentials and disproportionation 9-11. Based on its complex geochemistry, the mobility of Pu in natural subsurface systems is potentially controlled by a broad range of geochemical reactions, including sorption reactions, precipitation, redox reactions, complexation, as well as the formation of poly-nuclear and colloidal species 12. However, the corresponding reaction rates and equilibrium states differ significantly between the different oxidation states 13. Accordingly, the oxidation state
Physical Review Letters, Feb 2, 2007
Structural changes of the iron(II)-tris-bipyridine (Fe II bpy 3 2) complex induced by ultrashort ... more Structural changes of the iron(II)-tris-bipyridine (Fe II bpy 3 2) complex induced by ultrashort pulse excitation and population of its short-lived (0:6 ns) quintet high spin state have been detected by picosecond x-ray absorption spectroscopy. The structural relaxation from the high spin to the low spin state was followed over the entire lifetime of the excited state. A combined analysis of the x-rayabsorption near-edge structure and extended x-ray-absorption fine structure spectroscopy features delivers an Fe-N bond elongation of 0.2 Å in the quintet state compared to the singlet ground state.
Applied Optics, Oct 17, 2018
Macromolecular crystallography often requires focused high-intensity x-ray beams for solving chal... more Macromolecular crystallography often requires focused high-intensity x-ray beams for solving challenging protein structures from micrometer-sized crystals using current synchrotron radiation sources. The design of optical focusing schemes for hard x-rays showing high efficiency and flexibility in beam size is therefore continuously pursued. Here, we present an innovative solution based on a two-stage demagnification of the undulator source for photon energies from 6 keV to 19 keV, commissioned at the X10SA beamline of the Swiss Light Source, where a secondary source is imaged by two crossed silicon kinoform x-ray diffractive lenses with 75 nm outermost zone width. A source-size limited spot with a size of 4.8 μm×1.7 μm(h×v,FWHM) and flux of 7.5×10 photons/s at 12.4 keV is demonstrated at the sample position.
Journal of Environmental Quality, Mar 1, 1999
The assessment of elemental release processes in soils are of large interest in soil research. A ... more The assessment of elemental release processes in soils are of large interest in soil research. A technique is presented where the advantages of a flow-through reactor are combined with a specific infinite sink. Between the two reactors an electrolyte solution (pH 6) acting as a transport carrier was circulated continuously in a closed-loop setup. To demonstrate the capability of the new technique, phosphate desorpfion kinetics from different synthetic Fe and Mn hydroxides coated on silica sand were studied. The relative amount of P desorbed increased in the order ferrihydrite (10% of the initially sorbed P) goethite (20%) << hematite (65%) < Mn dioxide (80%). We suggest that this technique can also be adapted to other issues, for example, desorption of other anions and cations from solid phases (soils and sediments) because the composition of the infinite sink is variable.
Water Resources Research, Mar 1, 2001
We present an extensive experimental data set of particle release from natural porous media satur... more We present an extensive experimental data set of particle release from natural porous media saturated with monovalent cations. The generation process of mobile colloidal particles is studied by means of leaching of saturated laboratory columns packed with a noncalcareous soil material with various monovalent electrolytes and by analyzing the colloids in the effluent over typically 1000 pore volumes. The concentration of released particles cannot be modeled with simple first-order kinetics but can be rationalized in terms of a distribution of release rate coefficients k. The experimentally observed effluent concentration often decays with time as a power law c cr t-(s+ 1) for long times, suggesting a distribution of release rate coefficients p(k) cr k •-1 for small k. The observed values of exponent a range between 0.01 and 0.8. The composition of the pore water is found to have a profound influence on the particle release characteristics. With decreasing salt concentration the rate for particle release increases. Anionic organic and inorganic ligands have a major effect on the release process. For the ligands studied, the amount of released particles decreases in the sequence malonate, chloride, phtalate, and azide.
Scientific Reports, Oct 6, 2015
Review of Scientific Instruments, Dec 22, 2003
We present a setup which allows the measurement of time-resolved x-ray absorption spectra with pi... more We present a setup which allows the measurement of time-resolved x-ray absorption spectra with picosecond temporal resolution on liquid samples at the Advanced Light Source at Lawrence Berkeley National Laboratories. The temporal resolution is limited by the pulse width of the synchrotron source. We characterize the different sources of noise that limit the experiment and present a single-pulse detection scheme.
Environmental Science & Technology, Jun 21, 2005
Materials today advances, Jun 1, 2023
AGU Fall Meeting Abstracts, Dec 1, 2017
Environmental Science: Processes & Impacts, 2020
Correction for 'Multimodal X-ray microanalysis of a UFeO 4 particle: evidence for the environment... more Correction for 'Multimodal X-ray microanalysis of a UFeO 4 particle: evidence for the environmental stability of ternary U(V) oxides from depleted uranium munitions testing' by Daniel E. Crean et al., Environ. Sci.:
European Microscopy Congress 2016: Proceedings, Dec 20, 2016
Journal of physics, May 1, 2016
X-ray absorption spectroscopy is employed to study the local structure of pure and Cr-doped UO2 a... more X-ray absorption spectroscopy is employed to study the local structure of pure and Cr-doped UO2 at 300 K. The U L3-edge EXAFS spectrum is interpreted within the multiplescattering (MS) theory using the results of the classical and ab initio molecular dynamics simulations, allowing us to validate the accuracy of theoretical models. The Cr K-edge XANES is simulated within the full-multiple-scattering formalism considering a substitutional model (Cr at U site). It is shown that both unrelaxed and relaxed structures, produced by ab initio density functional theory (DFT) calculations, fail to describe the experiment.
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Papers by Daniel Grolimund
Le damasquinage, défini dans ce contexte comme étant un enchâssement de métal dans une base faite d’un métal différent, est une technique décorative rare au début de l’âge de bronze, connue seulement grâce à sept objets en bronze trouvés dans le Nord des Alpes. Cet article relate le premier examen scientifique approfondi d’une découverte de ce type, la hache de la tombe n° 1 de Thun-Renzenbühl. Ce projet interdisciplinaire, auquel participent plusieurs établissements allemands et suisses, a etudié cette hache au moyen de l’imagerie neutronique et de la microsonde de Castaing, complétées par un examen au microscope. Il en a résulté une tentative de reconstituer la fabrication et la décoration, ainsi qu’un réexamen de la question énigmatique portant sur les origines de la technique du damasquinage dans le Nord des Alpes."
Le damasquinage, défini dans ce contexte comme étant un enchâssement de métal dans une base faite d’un métal différent, est une technique décorative rare au début de l’âge de bronze, connue seulement grâce à sept objets en bronze trouvés dans le Nord des Alpes. Cet article relate le premier examen scientifique approfondi d’une découverte de ce type, la hache de la tombe n° 1 de Thun-Renzenbühl. Ce projet interdisciplinaire, auquel participent plusieurs établissements allemands et suisses, a etudié cette hache au moyen de l’imagerie neutronique et de la microsonde de Castaing, complétées par un examen au microscope. Il en a résulté une tentative de reconstituer la fabrication et la décoration, ainsi qu’un réexamen de la question énigmatique portant sur les origines de la technique du damasquinage dans le Nord des Alpes."