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33403 Publications

Observation of charge density waves in free-standing 1T-TaSe2 monolayers by transmission electron microscopy

Börner, P. C.; Kinyanjui, M. K.; Björkman, T.; Lehnert, T.; Krasheninnikov, A. V.ORC; Kaiser, U.
While bulk 1T-TaSe2 is characterized by a commensurate charge density wave (CCDW) state below 473K, the stability of the CCDW state in a 1T-TaSe2 monolayer, although theoretically predicted, has not been experimentally confirmed so far. As charge density waves and periodic lattice distortions (PLDs) always come together, we evaluate the PLD in a 1T-TaSe2 monolayer from low-voltage aberration-corrected high-resolution transmission electron microscopy experiments. To prevent fast degradation of 1T-TaSe2 during exposure to the electron-beam, a 1T-TaSe2/graphene heterostructure was prepared. We also perform the image simulations based on atom coordinates obtained using density functional theory calculations. From the agreement between the experimental and simulated images, we confirm the stability of the CCDW/PLD in a monolayer 1T-TaSe2/graphene heterostructure at room temperature in the form of a 13 13 superstructure. At the same time, we find that in comparison to multi-layer structures, the superstructure is less pronounced.
Keywords: 1T-TaSe2, graphene, TEM, first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-28260
Publ.-Id: 28260


Reversible superdense ordering of lithium between two graphene sheets

Kühne, M.; Börrnert, F.; Fecher, S.; Ghorbani-Asl, M.ORC; Biskupek, J.; Samuelis, D.; Krasheninnikov, A. V.ORC; Kaiser, U.; Smet, J. H.
Many carbon allotropes can act as host materials for reversible lithium uptake1,2, thereby laying the foundations for existing and future electrochemical energy storage. However, insight into how lithium is arranged within these hosts is difficult to obtain from a working system. For example, the use of in situ transmission electron microscopy3–5 to probe light elements (especially lithium)6,7 is severely hampered by their low scattering cross-section for impinging electrons and their susceptibility to knock-on damage8. Here we study the reversible intercalation of lithium into bilayer graphene by in situ low-voltage transmission electron microscopy, using both spherical and chromatic aberration correction9 to enhance contrast and resolution to the required levels. The microscopy is supported by electron energy-loss spectroscopy and density functional theory calculations. On their remote insertion from an electrochemical cell covering one end of the long but narrow bilayer, we observe lithium atoms to assume multi-layered close-packed order between the two carbon sheets. The lithium storage capacity associated with this superdense phase far exceeds that expected from formation of LiC6, which is the densest configuration known under normal conditions for lithium intercalation within bulk graphitic carbon10. Our findings thus point to the possible existence of distinct storage arrangements of ions in two-dimensional layered materials as compared to their bulk parent compounds.
Keywords: Li storage, graphene, TEM, first-principles caclulations

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Permalink: https://www.hzdr.de/publications/Publ-28259
Publ.-Id: 28259


Epitaxial Mn5Ge3 (100) layer on Ge (100) substrates obtained by flash lamp annealing

Xie, Y.; Yuan, Y.; Wang, M.; Xu, C.; Hübner, R.; Grenzer, J.; Zeng, Y.; Helm, M.; Zhou, S.; Prucnal, S.
Mn5Ge3 thin films have been demonstrated as promising spin-injector materials for germanium-based spintronic devices. So far, Mn5Ge3 has been grown epitaxially only on Ge (111) substrates. In this letter, we present the growth of epitaxial Mn5Ge3 films on Ge (100) substrates. The Mn5Ge3 film is synthetized via sub-second solid-state reaction between Mn and Ge upon flash lamp annealing for 20 ms at the ambient pressure. The single crystalline Mn5Ge3 is ferromagnetic with a Curie temperature of 283 K. Both the c-axis of hexagonal Mn5Ge3 and the magnetic easy axis are parallel to the Ge (100) surface. The millisecond-range flash epitaxy provides a new avenue for the fabrication of Ge-based spin-injectors fully compatible with CMOS technology.
Keywords: Mn5Ge3, epitaxial thin film, ferromagnetism, spintronic devices

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Permalink: https://www.hzdr.de/publications/Publ-28258
Publ.-Id: 28258


First Series of Tetravalent Thorium-, Uranium- and Neptunium-Amidinate Complexes

Schöne, S.ORC; Kaden, P.ORC; Patzschke, M.ORC; Roesky, P. W.ORC; Stumpf, T.; März, J.ORC
Actinides (An) can possess a variety of different oxidation states, which typically range from +III to +VI for the early actinides Th-Cm. They have unique electronic properties originating from the 5f-orbitals, what makes their coordination chemistry a fascinating area of research for both, the nuclear engineering but also for fundamental chemistry. Thorium (Th), uranium (U), neptunium (Np) and plutonium (Pu) can form highly charged cations with the oxidation state of four (An4+), which is the dominant one under reductive conditions. Furthermore, An(IV) are of particular interest for the coordination chemistry because of their strong interaction with ligands.
Hence, the overall aim of our investigations is a deep understanding of the interaction mechanisms between tetravalent An (An(IV)) and ligands bearing soft donor atoms, such as nitrogen (N). Thus, we focused on the synthesis and characterization of a series of An(IV) complexes with the N-donor ligand N,N’-Diisopropylbenzamidine (iPr2BA) both in solution and in solid state.
The structures of the synthesised complex series were determined by single-crystal X-ray diffraction (SC-XRD), showing the An(IV) coordinated by three iPr2BA molecules and one chloro ligand in a monocapped octahedral coordination geometry. This is the very first example of an An(IV) complex series including Np(IV) as a transuranium element with an amidinate ligand. The isostructural complexes allow a direct comparison of the binding situation of the An(IV) across the series. Quantum chemical calculation strongly supported the experimental results to to further study the electronic structure of the complexes.
NMR-spectroscopic investigations of the dissolved complexes in toluene-d8 showed significant chemical shifts due to considerable effects of the paramagnetic metal centres U(IV) and Np(IV) compared to the diamagnetic reference [Th(iPr2BA)3Cl].
Keywords: actinide, amidinate, coordination chemistry, thorium, uranium, neptunium, NMR, SC-XRD
  • Invited lecture (Conferences)
    10th International Conference on f-Elements (ICFE-10), 03.-07.09.2018, Lausanne, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-28257
Publ.-Id: 28257


Coordination Chemistry of Tetravalent Actinides: Series & Trends

Schöne, S.ORC; Radoske, T.ORC; Kloditz, R.; Köhler, L.; Kaden, P.ORC; Patzschke, M.ORC; Roesky, P. W.ORC; Stumpf, T.; März, J.ORC
The coordination chemistry of actinides (An) using model ligands helps to deeply understand their bonding situation on a molecular level. However, the basic An chemistry is still little explored. Characteristic of An is a huge variety of possible oxidation states, typically ranging from II to VII for early An. A suitable approach to explore the fundamental phico-chemical properties of An is to study a series of isostructural An compounds in the same oxidation state. Observed changes in e.g. the binding situation or magnetic effects among the An series could deliver insight into their unique electronic properties mainly origination from the f-electrons. A question still remaining in An chemistry is the degree of "covalency". However, studies covering TRU elements are rather scarce. Against this background, we are strongly motivated to perform a systematic comparison of isostructural An complexes (Th, U and Np).
In this study we investigate the coordination chemistry of tetravalent actinides (An(IV)) for two major reasons: a) the series of An(IV) is the largest accessible one within the early actinides, and b) the tetravalent state is the dominant one particularly under anoxic conditions. The ligands used in this study range from hard- (oxygen) and medium- (nitrogen) to pure soft-donor (carbon) character, according to Pearsons's HSAB concept. Due to the expected changes in orbital overlap between the metal and ligand, the formed complexes could further provide us a deep insight into the electronic situation of the actinides.
The An(IV) complexes are characterised in solution by NMR-, IR- and UV-vis spectroscopy as well as in the solid-state by SC_XRD. The acquired experimental results are further supported by quantum chemical calculations with a focus on the electronic structure of the complexes.
Keywords: actinide, coordination chemistry, thorium, uranium, neptunium
  • Invited lecture (Conferences)
    ISNSC - 10th International Symposium on Nano and Supramolecular Chemistry 2018, 08.-13.07.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28256
Publ.-Id: 28256


Synthesis and Characterization of U(IV) Imidazol-2-ylidene Complexes

Köhler, L.; März, J.ORC; Patzschke, M.ORC; Kaden, P.ORC; Monkowius, U.ORC
In the field of actinide coordination chemistry, it is assumed that ligands bearing soft donor atoms, according to Pearson’s hard-soft-acid-base concept, such as sulphur, phosphorous or carbon lead to stable complexes. Furthermore, due to the expected strong orbital overlap between the metal and ligand, the formed complexes would provide us a deep insight into the electronic situation of the actinides. However, the majority of published actinide compounds still focusses on complexes with hard donor atoms such as oxygen.
A few examples of actinide-carbene complexes reported in the literature emphasise the remarkable strong σ donor properties of the carbon donor ligands, making the complexes e.g. excellent catalysts in organic synthesis1. Of particular interest are N-heterocyclic carbenes (NHCs) based on an imidazole-2-ylidene backbone, also known as “Arduengo carbenes”. For instance, the stability and electronic properties of these ligands can be easily tuned by synthetic introduction of suitable substituents at the nitrogen atoms.
The aim of this study is the synthesis of tetravalent actinide (An(IV)) complexes with soft-donor carbene ligands according to Figure 1 and the characterisation of the formed complexes in solution by NMR-, IR- and UV-vis spectroscopy as well as the solid-state characterisation with the help of single crystal X-ray diffraction. The acquired experimental results are further supported by quantum chemical calculations to further study the electronic structure of the complexes.
Keywords: actinide, coordination chemistry, carbene, uranium
  • Poster
    ISNSC - 10th International Symposium on Nano and Supramolecular Chemistry 2018, 08.-12.07.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28255
Publ.-Id: 28255


Coordination Chemistry of Uranium (U(IV) and -(VI)) with Bidentate N-donor Ligands

März, J.ORC; Schöne, S.ORC; Radoske, T.ORC; Patzschke, M.ORC; Stumpf, T.; Ikeda-Ohno, A.ORC
The bidentate N-donor ligands 2,2’-bipyridine (bipy) and 1,10-phenanthroline (phen) have attracted considerable attention in the field of coordination chemistry over the last decades because of their remarkable stability towards a wide variety of transition metals1. The coordination chemistry of uranium (U) has been explored with these N-donor ligands as well with a primary focus on its hexavalent state (U(VI) as UO₂2+). To the contrary, much less attention has been paid for the lower oxidation states, such as a tetravalent state (U(IV)). Here we present a systematic study on the coordination chemistry of U(IV) and -(VI) with bipy and phen under different chemical conditions, such as different solvents and changing the metal / ligand ratio.

In this study we succeeded to obtain a series of U(IV) complexes with U:ligand ratios of 1:1 and 1:2, all of which show an eight-fold coordinated uranium centre. In addition to the ligand, chloro and methanolato ligands are coordinating to the metal centre for charge compensation. Interestingly, the complexation between U(IV) and the ligand does occur even in protic solvents, in which the ligand is expected to be protonated. We also obtained another series of U(VI) complexes with both bipy and phen, underlining the versatile coordination chemistry of uranyl (UO22+). That is, the coordination between uranyl and the ligand depends strongly on the pH of the solvent used. For instance, in media with lower pH mononuclear complexes are formed, showing the uranyl unit in an unusually bent geometry.3 On the other hand, dinuclear uranyl arrangements with hydroxo-brinding are dominated in the media with higher pH, as shown in the right of Fig. 1. As illustrated in Fig. 1, bipy and phen are forming isostructural complexes both with U(IV) and- (VI).
Keywords: uranium, coordination chemistry, N-donor ligand, bipyridine, phenanthroline
  • Lecture (Conference)
    RadChem 2018, 13.-18.05.2018, Mariánské Lázně, Tschechien

Permalink: https://www.hzdr.de/publications/Publ-28254
Publ.-Id: 28254


Recovery of gallium from wafer fabrication industry wastewaters by Desferrioxamine B and E using reversed-phase chromatography approach

Jain, R.; Fan, S.; Kaden, P.; Tsushima, S.; Foerstendorf, H.; Barthen, R.; Lehmann, F.; Pollmann, K.
Gallium (Ga) is a critical element in developing renewable energy generation and energy efficient systems. The supply of Ga is at risk and needed recycling technologies for its availability in future. This study demonstrated the recovery of Ga3+ from low gallium concentrated wafer fabrication industry wastewaters using the siderophores desferrioxamine B (DFOB) and desferrioxamine E (DFOE). The complexation of Ga3+ by DFOB and DFOE was through hydroxamate group as demonstrated by infrared spectroscopy, nuclear magnetic resonance and density functional theory calculations. The high selectivity of DFOB/E towards Ga3+ was observed due to the formation of highly stable complex. Indeed, due to the formation of such high stability complex, the DFOB and DFOE were able to successfully complex 100% Ga in the two different wastewater from wafer fabrication industry. For the recovery of the siderophores, a high rate of decomplexation of Ga (>90%) was achieved upon addition of 6 times excess of ethylenediaminetetraacetic acid (EDTA) at pH of 3.5. More than 95% of Ga-DFOB and Ga-DFOE complex were recovered with purity (% of Ga moles in comparison to total moles of metals) of 70.4 and 94.9%, respectively by application of a C18 reversed-phase chromatography column. A preliminary cost-calculation demonstrated that acetonitrile consumption and desferrioxamines are major cost input for the technology. This study, for the first time, demonstrated a technical solution to the recovery of Ga3+ from the low concentrated wastewater based on siderophores and reversed-phase chromatography. A German patent application had been filed for this technology.
Keywords: Metal recovery, recycling, resource efficiency, cost-benefit, wastewater

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Permalink: https://www.hzdr.de/publications/Publ-28253
Publ.-Id: 28253


Pulsating dissolution of crystalline matter

Fischer, C.; Lüttge, A.
Fluid-solid reactions result in dissolution or precipitation reactions. The prediction of the related material flux
from or to the reacting surface, its variations and changes with time are of interest to a wide array of disciplines.
Reaction rate maps that are derived from sequences of topography maps illustrate the spatial distribution of
reaction rates across the crystal surface [1]. Here we present dissolution rate maps that reveal the existence
of rhythmic pulses of the material flux from the crystal surface. This observation leads to a change in our
understanding of the way crystalline matter dissolves. Rhythmic fluctuations of the reactive surface site density
and potentially concomitant oscillations in the fluid saturation imply spatial and temporal variability in surface
reaction rates. Knowledge of such variability could aid attempts to upscale microscopic rates and predict reactive
transport through changing porous media.
[1] Fischer, C., Luttge, A., 2017. Beyond the conventional understanding of water–rock reactivity. Earth and
Planetary Science Letters 457, 100-105.
  • Lecture (Conference)
    EGU 2018 - European Geosciences Union General Assembly 2018, 08.-13.04.2018, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-28252
Publ.-Id: 28252


Dissolution rate variability of sandstone calcite cement

Pedrosa, E. T.; Fischer, C.; Lüttge, A.
For a holistic understanding of the long-term usage and safety analysis of reservoir rocks it is crucial to understand the fundamental mineral reactions and its control mechanisms. Kinetic quantification of the processes involved with fluid-rock interactions are especially important for predicting the evolution of pore space in rocks subjected to fluid injection, such as in CO2-sequestration and hydrocarbon exploration techniques.
The calcite cement selected for this study belongs to a fluvial-aeolian Rotliegend succession exposed near Bebertal (Flechtinge High, Germany) that was deposited in the same conditions as those that form the prolific gas reservoirs of the Southern Permian Basin1,2. Optical microscopy, SEM-BSE images and Cathodoluminescence analysis of the unreacted samples showed that two types of cement were present, although the calcite cement patches were composed of single crystals. We hypothesized that these different types of cement would react differently to fluid input. We used polished thick-sections of plug samples for dissolution experiments in a flow-through cell using a 2 mmol Na2CO3 solution (pH = 8.6, T≈ 21°C), for 7 reaction intervals (3 to 32 hours). Before and after each experiment the sample’s topography changes were mapped using a vertical scanning interferometer (VSI). High-resolution surface maps are subsequently used to calculate surface dissolution rates3.
After experiments, VSI images revealed an increase of the surface roughness in the cement patches. Detailed analysis of the rate dissolution variability in between the calcite cement patches and the intravariability of each cement patch related to chemical composition variability in the samples will be presented.
1Fischer, C., Gaupp, R., Dimke, M., Sill, O., 2007. A 3D high resolution model of bounding surfaces in aelian-fluvial deposits: An outcrop analogue study from the Permian Rotliegend, Northern Germany. Journal of Petroleum Geology, 30(3), 257–273.
2Fischer, C.; Dunkl, I.; von Eynatten, H.; Wijbrans, J. R.; Gaupp, R., 2012. Products and timing of diagenetic processes in Upper Rotliegend sandstones from Bebertal (North German Basin, Parchim Formation, Flechtingen High, Germany). Geological Magazine, 149 (5), 827-840.
3Luttge, A., and Bolton, E., 1999. An interferometric study of the dissolution kinetics of anorthite : The role of reactive surface area. American Journal of Science, 299, 652–678.
  • Lecture (Conference)
    GeoBonn 2018, 02.-06.09.2018, Bonn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28251
Publ.-Id: 28251


Precipitation and dissolution of cement minerals in sandstone: Opportunities and limitations of pore and plug scale flow analysis for reactive transport modelling approaches

Kulenkampff, J.; Karimzadeh, L.; Fischer, C.
Reservoir properties of sandstones are controlled by precipitation and dissolution reactions at the pore walls. Both, the formation and dissolution of cement minerals are responsible for the complex pattern formation of porosity and permeability in reservoir rocks.
At the scale of drilled core sections (plugs), experimental and analytical approaches utilize positron emission tomography (PET) with radiotracers (Kulenkampff et al. 2016). Resulting spatiotemporal concentration distributions provide quantitative insight into fluid flow and diffusion parameters. The sensitivity is in the picomolar range of the utilized radiotracers and the spatial resolution is about 1 mm. Thus, mechanistically-important surface features such as etch pits or growth hillocks and their evolution during reaction are not yet part of the direct analysis of the flow field.
Here, we present an approach based on existing information about the complex crystal surface morphology and rate evolution (Fischer& Luttge 2017). We utilize artificial materials that are produced by 3D printing capabilities. Such an approach using PET analysis of sequences of machined surfaces in flow-through experiments provides quantitative insight into the local stability vs. temporal heterogeneity of fluid flow close to reacting surfaces. The measured flow velocity data from PET are implemented into reactive transport models and compared to existing small-scale calculations. We discuss the resulting size and complexity of surface rate patterns.

Fischer, C. and A. Luttge (2017). Beyond the conventional understanding of water–rock reactivity. Earth and Planetary Science Letters, 457: 100-105
J. Kulenkampff, M. Gründig, A. Zakhnini and J. Lippmann-Pipke (2016): Geoscientific process monitoring with positron emission tomography (GeoPET). Solid Earth, 7: 1217-1231
  • Lecture (Conference)
    Interpore 2018, 14.-17.05.2018, New Orleans, USA

Permalink: https://www.hzdr.de/publications/Publ-28250
Publ.-Id: 28250


Surface-Functionalized Mesoporous Nanoparticles as Heterogeneous Supports To Transfer Bifunctional Catalysts into Organic Solvents for Tandem Catalysis

Zhang, N.; Hübner, R.; Wang, Y.; Zhang, E.; Zhou, Y.; Dong, S.; Wu, C.
The combination of chemo- and biocatalysts offers a powerful platform to address synthetic challenges in chemistry, particularly in synthetic cascades. However, transferring both catalysts into organic solvents remains technically difficult because of the enzyme inactivation and catalyst precipitation. Herein, we designed a facile approach using functionalized mesoporous silica nanoparticles (MSN) to transfer chemo- and biocatalysts into a variety of organic solvents. As a proof-of-concept, two distinct catalysts, palladium nanoparticles (Pd NPs) and Candida antarctica lipase B (CalB), were stepwise loaded into separate locations of the mesoporous structure, which not only provided catalysts with heterogeneous supports for the recycling but also avoided their mutual inactivation. Moreover, mesoporous particles were hydrophobized by surface alkylation, resulting in a tailor-made particle hydrophobicity, which allowed bifunctional catalysts to be dispersed in eight organic solvents. Eventually, these attractive material properties provided the MSN-based bifunctional catalysts with remarkable catalytic performance for cascade reaction synthesizing benzyl hexanoate in toluene. With a broader perspective, the success of this study opens new avenues in the field of multifunctional catalysts where a plethora of other chemo- and biocatalysts can be incorporated into surface-functionalized materials ranging from soft matters to porous networks for synthetic purposes in organic solvents.
Keywords: multifunctional biocatalyst, mesoporous silica nanoparticles (MSN), palladium nanoparticles, lipase CalB, cascade reaction

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Permalink: https://www.hzdr.de/publications/Publ-28249
Publ.-Id: 28249


Strong Variation Of Electronic Properties Of MoS2 And WS2 Nanotubes In Presence Of External Electric Fields

Zibouche, N.; Philipsen, P.; Kuc, A.
Transition-metal dichalcogenides attracted a huge international research focus from the point of two-dimensional materials. These materials exist also as nanotubes, how- ever, they have been mostly studied for their lubricant properties. Despite their inter- esting electronic properties, quite similar to their 2D counterparts, nanotubes remain much less explored. Like in 2D materials, electronic properties of nanotubes can be strongly modulated by external means, such as strain or electric field. Here, we report on the effect of external electric fields on the electronic properties of MoS2 and WS2 nanotubes, using density functional theory. We show that the electric field induces a strong polarization in these nanotubes, what results in a nearly linear decrease of the band gaps with the field strength and eventually in a semiconductor-metal transi- tion. In particular for large tube diameters, this transition can occur for field strengths between 1 - 2 V nm−1. This is an order of magnitude weaker than fields required to close the band gaps in the corresponding 2D mono- and bilayers of transition-metal dichalcogenides. We also observe splittings of the degenerate valence and conduction band states due to the Stark effect. Accordingly, such nanotubes could be used in na- noelectronics as logical switches, even at moderate field strengths that can be achieved experimentally, for example, by applying a gate voltage.

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Permalink: https://www.hzdr.de/publications/Publ-28248
Publ.-Id: 28248


Trace element geochemistry of sphalerite in contrasting hydrothermal fluid systems of the Freiberg district, Germany: insights from LA-ICP-MS analysis, near-infrared light microthermometry of sphalerite-hosted fluid inclusions, and sulfur isotope geochemistry

Bauer, M. E.; Burisch, M.; Ostendorf, J.; Krause, J.; Frenzel, M.ORC; Seifert, T.; Gutzmer, J.
The historic silver mining district of Freiberg (Germany) comprises hydrothermal vein-style mineralization of Permian and Cretaceous age. We compare sphalerite compositions with associated ore-forming fluids and constrain the behavior of critical metals such as In, Ge, and Ga in contrasting hydrothermal environments. Fluid inclusion studies reveal that the Permian veins formed due to boiling and cooling of a low-salinity (0 to 6% eq. w[NaCl]) magmatic-hydrothermal fluid at 350 to 230 °C. In contrast, Cretaceous veins formed by mixing of highly saline (17 to 24% eq. w[NaCl + CaCl2] and variable Na/(Na + Ca) ratios) brines at low temperatures (~ 120 °C). Sulfides of the Permian ore stage have a narrow range of δ34SVCDT from − 2.3 to + 0.9‰, while the sulfides of the Cretaceous stage have a large scatter and significantly more negative δ34SVCDT values (− 30.9 to − 5.5‰), supporting the different nature of the hydrothermal systems. Contrasting fluid systems and ore-forming mechanisms correspond to markedly different trace element systematics in sphalerite. Permian sphalerite is significantly enriched in In (up to 2500 μg/g In) relative to two sphalerite generations of Cretaceous veins. The latter have higher Ge (up to 2700 μg/g Ge) and Ga (up to 1000 μg/g Ga) concentrations. The observed trace element systematics of different sphalerite generations imply that In is enriched in high-temperature, low- to intermediate-salinity fluids with a significant magmatic-hydrothermal fluid component, while Ge and Ga are more concentrated in low-temperature, high-salinity crustal fluids with no obvious magmatic-hydrothermal affiliation.
Keywords: Sphalerite, Indium, Germanium, Gallium, Critical metals, EPMA, LA-ICP-MS, Fluid inclusions, Near-infrared light microthermometry, Sulfur isotopes, Geothermometer, Erzgebirge

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Permalink: https://www.hzdr.de/publications/Publ-28247
Publ.-Id: 28247


Indium and selenium distribution in the Neves-Corvo deposit, Iberian Pyrite Belt, Portugal

Carvalho, J. R. S.; Relvas, J. M. R. S.; Pinto, A. M. M.; Frenzel, M.; Krause, J.; Gutzmer, J.; Pacheco, N.; Fonseca, R.; Santos, S.; Caetano, P.; Reis, T.; Goncalves, M.
High concentrations of indium (In) and selenium (Se) have been reported in the Neves-Corvo volcanic-hosted massive sulfide deposit, Portugal. The distribution of these ore metals in the deposit is complex as a result of the combined effects of early ore-forming processes and late tectonometamorphic remobilization. The In and Se contents are higher in Cu-rich ore types, and lower in Zn-rich ore types. At the deposit scale, both In and Se correlate positively with Cu, whereas their correlations with Zn are close to zero. This argues for a genetic connection between Cu, In and Se in terms of metal sourcing and precipitation. However, re-distribution and re-concentration of In and Se associated with tectonometamorphic deformation are also processes of major importance for the actual distribution of these metals throughout the whole deposit. Although minor roquesite and other In-bearing phases were recognized, it is clear that most In within the deposit is found incorporated within sphalerite and chalcopyrite. When chalcopyrite and sphalerite coexist, the In content in sphalerite (avg. 1400 ppm) is, on average, 2–3 times higher than in chalcopyrite (avg. 660 ppm). The In content in stannite (avg. 1.3 wt.%) is even higher than in sphalerite, but the overall abundance of stannite is subordinate to either sphalerite or chalcopyrite. Selenium is dispersed widely between many different ore minerals, but galena is the main Se-carrier. On average, the Se content in galena is ~50 times greater than in either chalcopyrite (avg. 610 ppm) or sphalerite (avg. 590 ppm). The copper concentrate produced at Neves-Corvo contains very significant In (+Se) content, well above economic values if the copper smelters recovered it. Moreover, the high In content of sphalerite from some Cu-Zn ores, or associated with shear structures, could possibly justify, in the future, a selective exploitation strategy for the production of an In-rich zinc concentrate.
Keywords: Neves-Corvo, indium, selenium

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Permalink: https://www.hzdr.de/publications/Publ-28246
Publ.-Id: 28246


A spectroscopic study of trivalent cation (Cm3+ and Eu3+) sorption on monoclinic zirconia (ZrO2)

Eibl, M.ORC; Virtanen, S.; Pischel, F.; Bok, F.; Lönnrot, S.; Shaw, S.ORC; Huittinen, N.ORC
Hypothesis:
Zirconia (ZrO2) formed by corrosion of zircalloy, can immobilize radioactive contaminants (e.g. actinides) in repositories for spent nuclear fuel (SNF). The presence of organic and inorganic carbon at the highly reactive ZrO2 surface impacts the adsorption of these metal ions and their surface speciation.
Experiments:
Sorption of Eu3+ and Cm3+ on zirconia was studied in batch-sorption experiments, and via laser spectroscopy (TRLFS). Two zirconia solids with varying carbon content were utilized. The influence of carbon impurities on the ZrO2 surface charge was investigated via zeta-potential measurements. Batch data was collected for various Eu3+ concentrations, while the pH-dependent Cm3+ surface speciation was studied with TRLFS. The spectroscopic sorption data was modeled using the Diffuse Double Layer (DDL) model.
Findings:
The ZrO2 surface charge measurements yielded a pHIEP of 6 which was influenced by the presence of inorganic and organic carbon species. The pH-dependent sorption of Eu3+ showed a maximum sorption above pH 5.5, with no impact of the carbon concentration. The speciation of the trivalent metal, however, was different in the presence of intrinsic organic carbon in the sample, resulting in the formation of an organic Cm3+-complex on the surface. The sorption data was well described by our DDL model.
Keywords: Cm3+, Eu3+, zirconia (ZrO2), organic impurity, laser spectroscopy (TRLFS), sorption, surface complexation modeling

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  • Secondary publication expected from 01.09.2020

Permalink: https://www.hzdr.de/publications/Publ-28245
Publ.-Id: 28245


Bestimmung der Input Funktion für das kinetische Modelling von (+)-[18F]Flubatine

Patt, M.; Tiepolt, S.; Sattler, B.; Hoepping, A.; Smits, R.; Deuther-Conrad, W.; Becker, G. A.; Steinbach, J.; Brust, P.; Sabri, O.
Der Abstract wird nachgereicht.
  • Lecture (Conference)
    56. Jahrestagung der DGN, 18.-21.04.2018, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 56(2018), V10

Permalink: https://www.hzdr.de/publications/Publ-28244
Publ.-Id: 28244


C-11 Markierung von zwei neuen Liganden für den Alpha7-Subtyp des nikotinischen Acetylcholinrezeptor (nAChR)

Patt, J. T.; Deuther-Conrad, W.; Peters, D.; Barthel, H.; Brust, P.; Sabri, O.; Patt, M.
Abstract wird nachgereicht.
  • Lecture (Conference)
    56. Jahrestagung der DGN, 18.-21.04.2018, Bremen, Deutschland
  • Abstract in refereed journal
    Nuklearmedizin 56(2018), V24

Permalink: https://www.hzdr.de/publications/Publ-28243
Publ.-Id: 28243


On Development and Validation of subcooled nucleate models for OpenFOAM Foundation Release

Peltola, J.; Bainbridge, W.; Lehnigk, R.; Schlegel, F.; Pättikangas, T. J. H.
Subcooled nucleate boiling capability based on [1] was introduced to OpenFOAM 4.0 [2] within multiphase framework called reactingEulerFoam that supports two- and multiphase simulations. Since then the capability has been further refined and extended in subsequent releases 5.0 and 6. The present implementation - available in OpenFOAM Foundation development release [3] - includes the RPI wall boiling model [4] with run time selectable nucleation site density and bubble departure diameter and frequency models. Runtime selectable wall heat transfer models for distribution of wall heat flux between gas and liquid phases are also included for non-equilibrium phase change simulations. Interfacial heat transfer and phase change are calculated with two-resistance approach and interface temperature using user selectable heat transfer models and saturation temperature model. For turbulence modelling, single-phase models available in the release can be selected and there are also specialized k-ε and k-ω two-phase models available. For bubble diameter modelling algebraic [5], IATE [6] and inhomogeneous class method models are available [7, 8].

The present paper compares simulation results obtained with different model combinations to publicly available experimental data from DEBORA and other experiments. The implications of the choices of the models and model parameters on accuracy and performance are discussed and practical recommendations are given for those that intend to use this publicly available resource for further research.

[1] Peltola, J., & Pättikangas, T.J.H. (2012). CFD4NRS-4, paper 59.
[2] OpenFOAM Foundation, OpenFOAM 4.0, (2016) https://openfoam.org/version/4.0/
[3] OpenFOAM Foundation, OpenFOAM-dev, (2014-2018) https://openfoam.org/version/dev/
[4] N. Kurul and M.Z. Podowski, 27th National Heat Transfer Conference, Minneapolis, USA, July 28–31, 1991.
[5] Anglart, H., Nylund, O., Kurul, N., & Podowski, M. Z. (1997). Nuc. Engineering and Design, 177(1-3), 215-228.
[6] Ishii, M., Kim, S., & Kelly, J. (2005). Nuclear Engineering and Technology, 37(6), 525-536.
[7] Kumar, S., & Ramkrishna, D. (1996). Chemical Engineering Science, 51(8), 1311-1332.
[8] Liao, Y., Oertel, R., Kriebitzsch, S., Schlegel, F., & Lucas, D. (2018). Int. J. Num. Meth. Fluids, 87(4), 202-215
  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
  • Contribution to proceedings
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
    Proceedings of NURETH-18

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Permalink: https://www.hzdr.de/publications/Publ-28242
Publ.-Id: 28242


Compact high-brightness X-ray sources for ultrafast probing of explosively driven solid-density materials by Travelling-Wave Thomson-Scattering

Steiniger, K.; Bussmann, M.; Loeser, M.; Albach, D.; Debus, A.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Debus, A.
The Traveling-Wave Thomson-Scattering geometry is introduced and the possibility to realize optical free-electron lasers with it explained. An example setup for a TWTS OFEL providing 1 Angström radiation is shown and its application to the probing of the ion dynamics in a laser driven cryogenic hydrogen slab presented.
  • Lecture (Conference)
    EUCALL Joint Foresight Topical Workshop: Theory and Simulation of Photon-Matter Interaction, 02.-05.07.2018, Szeged, Hungary

Permalink: https://www.hzdr.de/publications/Publ-28241
Publ.-Id: 28241


Two-bubble class approach based on measured bubble size distribution for bubble columns with and without internals

Möller, F.; Kipping, R.; Lavetty, C.; Hampel, U.; Schubert, M.
The complex flow patterns in bubble columns can be phenomenologically described by the two-bubble class approach. For the first time, this approach is applied to bubble columns with dense internals. Internals of square and triangular pitch tube patterns of two tube sizes (8×10-3 and 13×10-3 m) with flat and U-tube bottom design and cross-sectional occupation of ~25% were inserted in a bubble column of 0.1 m diameter and 2 m height. Contrary to the well-known gas disengagement technique, dual-plane ultrafast X-ray computed tomography data have been used for the bubble class allocation. Experiments were performed at superficial gas velocities ranging from 0.02 m s-1 to 0.20 m s-1 to cover homogeneous and heterogeneous flow conditions. The contributions of small and large bubble classes on total holdup, flow structure and bubble rise velocities were determined. Furthermore, the regime transition onset was determined based on the two-bubble class approach. Eventually, new correlations for regime transition, small and large bubble rise velocity, large bubble holdup as well as total holdup are proposed based on sub-channel area, sub-channel hydraulic diameter and occlusion area.
Keywords: Bubble column, heat exchanger internals, two-bubble class approach, bubble size distribution, gas holdup, bubble rise velocity, ultrafast X-ray tomography

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Permalink: https://www.hzdr.de/publications/Publ-28240
Publ.-Id: 28240


Compact, high-yield incoherent and coherent X-ray sources by Traveling-Wave Thomson-Scattering

Steiniger, K.; Loeser, M.; Albach, D.; Pausch, R.; Roeser, F.; Schramm, U.; Siebold, M.; Bussmann, M.; Debus, A.
In Traveling-Wave Thomson-Scattering pulse-front tilted, petawatt class laser pulses are scattered off relativistic electrons to realize compact optical free-electron lasers or brilliant incoherent X-ray sources with state-of-the-art electron accelerators and high-power laser systems. Example setups of TWTS OFELs providing ultraviolet radiation are presented together with an optical setup to compensate laser dispersion.
  • Invited lecture (Conferences)
    Visions on Future Laser-based X-ray Science and Technology, 19.-20.11.2018, Castelldefels, Spain

Permalink: https://www.hzdr.de/publications/Publ-28239
Publ.-Id: 28239


Irradiation tests at HZDR

Müller, S. E.ORC; Ferrari, A.ORC
Irradiation tests at HZDR in the framework of the MUSE project are presented
  • Lecture (Conference)
    MUSE meeting, 22.10.2018, Fermilab, USA

Permalink: https://www.hzdr.de/publications/Publ-28238
Publ.-Id: 28238


FLUKA simulations for the Mu2e experiment

Müller, S. E.; Ferrari, A.
FLUKA simulations for the Mu2e experiment are presented
  • Lecture (Conference)
    MU2E collaboration meeting, 18.10.2018, 18.10.2018, Fermilab, USA

Permalink: https://www.hzdr.de/publications/Publ-28237
Publ.-Id: 28237


Laser-driven plasma pinching in e−e+ cascade

Efimenko, E. S.; Bashinov, A. V.; Gonoskov, A. A.; Bastrakov, S. I.; Muraviev, A. A.; Meyerov, I. B.; Kim, A. V.; Sergeev, A. M.
The cascaded production and dynamics of electron-positron plasma in ultimately focused laser fields of extreme intensity are studied by 3D particle-in-cell simulations with the account for the relevant processes of quantum electrodynamics (QED). We show that, if the laser facility provides a total power above 20 PW, it is possible to trigger not only a QED cascade but also pinching in the produced electron-positron plasma. The plasma self-compression in this case leads to an abrupt rise of the peak density and magnetic (electric) field up to at least 10^28 cm^−3 and 1/20 (1/40) of the Schwinger field, respectively. Determining the actual limits and physics of this process might require quantum treatment beyond the used standard semiclassical approach. The proposed setup can thus provide extreme conditions for probing and exploring fundamental physics of the matter and vacuum.

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Permalink: https://www.hzdr.de/publications/Publ-28236
Publ.-Id: 28236


Unconventional trace elements in sphalerite – Clues to fluid origin?

Frenzel, M.ORC; Slattery, A.; Wade, B.; Gilbert, S.; Ciobanu, C. C.; Cook, N. J.; Voudouris, P.
It is well known that the trace element content of sphalerite correlates with the conditions of ore formation (T, fS2). However, the suite of trace elements analysed in geological studies is generally restricted to the chalcophile and siderophile elements (Ag, As, Cd, Co, Fe, Ga, Ge, In, Mn, Sb, Se etc.). This may limit the inferences that can be made about the chemistry of the ore-forming fluids.

We used an integrated analytical approach consisting of electron probe micro-analysis, laser-ablationinductively coupled plasma-mass spectrometry, scanning electron microscopy and transmission electron microscopy to investigate the incorporation of the halogens Cl and Br, as well as the alkali metals Na and K into natural sphalerite from a range of deposits. This allowed us to study element distribution at length scales from >1 mm down to ~1 nm.

We found that Cl, Br, Na and K occur in measurable concentrations (100s to 1000s of ppm) in samples from several deposits. Chlorine occurs as either atomic substitutions in the sphalerite lattice or as a mixture of substitution and nano-inclusions. Unfortunately, analytical limitations mean that an investigation of the nanoscale distribution of Br, Na and K was not possible. However, concentrations of these elements (determined by LA-ICP-MS) correlate with Cl concentrations suggesting that they may be present together
with Cl in the sphalerite lattice.

The levels of trace elements present as atomic substitutions are generally related to the chemistry of the oreforming fluids. Therefore, our findings raise the possibility to measure Cl concentrations as well as Cl/Br ratios in natural sphalerite, and use these measurements to constrain fluid salinity and origin. However, more work will be required to constrain the relevant thermodynamic relationships and improve the detection limits of Cl and Br before such measurements can become a standard tool in economic geology.
  • Lecture (Conference)
    SEG 2018 conference, Keystone, 24.09.2018, Keystone, Colorado, United States of America

Permalink: https://www.hzdr.de/publications/Publ-28235
Publ.-Id: 28235


Criticality - What makes a raw material critical?

Frenzel, M.; Kullik, J.; Reuter, M. A.; Gutzmer, J.
A key to the current debate on the supply security of mineral raw materials is the concept of 'criticality'. This presentation provides a brief review of the criticality concept, as well as the methodologies used in its assessment, including a critical evaluation of their validity. Furthermore, it discusses several risks present in global raw materials markets that are not captured by most criticality assessments. The key result is that current assessments of raw material criticality are fundamentally flawed in several ways. This is mostly due to a lack of adherence to risk theory, and highly limits their applicability. Many of the raw materials generally identified as critical may not be critical, meaning that new assessments are urgently required.

While these are important results for policy makers, it is not necessarily clear what their implications are for geoscientific research on critical element deposits, the topic of this session. Therefore, this question will briefly be explored in the second part of the presentation.
  • Invited lecture (Conferences)
    GeoBonn, 05.09.2018, Bonn, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28233
Publ.-Id: 28233


Investigation of 18F-labelled pyrazolo[2,3-d]pyrimidines for molecular imaging of the adenosine A2A receptor with positron emission tomography (PET)

Lai, T. H.; Moldovan, R.-P.; Brust, P.
Objectives: The adenosine A2A receptor (A2AR) is a promising target for the development of PET radiotracers for molecular imaging of neurodegenerative diseases and cancer. Based on binding-affinities the 4 and 2-fluorobenzyl derivatives 1 (Ki(hA2A) = 5.3 nM) and 2 (Ki(hA2A) = 2.1 nM) were chosen for radiofluorination. Methods: Three different strategies for the synthesis of [18F]1 have been investigated. The first two are using [18F]fluorobenzaldehyde, which was applied either in a reductive amination or in a reduction followed by an Appel and benzylation reaction. The third strategy is based on a one-step radiolabelling starting from a boronic acid pinacol ester precursor employing [18F]TBAF and Cu(OTf)2(py)4 in n-BuOH/DMA. The specific binding of [18F]1 and [18F]2 on mice brain slices was evaluated by in vitro autoradiography. Results: The two- and four-step labelling strategies resulted in a radiochemical yield (RCY) of only 1.4% or 10% [18F]1 (non-isolated). Thus, [18F]1 and [18F]2 were prepared by a one-step procedure with a RCY of 52+7 or 9+1% (EOB), a molar activity of 135+64 or 132 GBq/µmol (EOS) and a radiochemical purity of >98%. In vitro autoradiography performed with [18F]2 demonstrated high binding to the striatum, a brain region with high density of A2AR, which could be blocked by selective A2A ligands. Conclusions: An efficient copper-mediated one-step radiolabelling procedure was established for two new highly affine A2A radiotracers. The first in vitro study with [18F]2 demonstrated excellent potential for the imaging of adenosine A2AR. Current work focuses on further in vitro and in vivo investigations.
Keywords: adenosine A2A, PET, radiotracer, 18F
  • Poster
    15th Research Festival Leipzig 2019, 18.01.2019, Leipzig, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-28232
Publ.-Id: 28232


The geometallurgical assessment of by-products - Geochemical proxies for the complex mineralogical deportment of indium at Neves-Corvo, Portugal

Frenzel, M.ORC; Bachmann, K.; Carvalho, J. R. S.; Relvas, J. M. R. S.; Pacheco, N.; Gutzmer, J.
Many by-productmetals are classified as critical.However, they are only ofmarginal interest tomanymining companies and are rarely part of detailed resource statements or geometallurgical assessments. As a result, there is a general lack of reliable quantitative data on the mineralogy and spatial distribution of these metals in ore deposits—hampering assessments of future availability.We propose here an innovative approach to integrate by-product metals into geometallurgical assessments. As an example, we use the distribution and deportment of indium at Neves-Corvo, a major European base-metal mine (Cu + Zn), and one of the largest and richest volcanichosted massive sulfide (VHMS) deposits in the world. Based on a combination of bulk-ore geochemistry and mineralogical and microanalytical data, this study is the first to develop a quantitativemodel of indium deportment inmassive sulfide ores, demonstrating how regularities in indium partitioning between different minerals can be used to predict its mineralogical deportment in individual drill-core samples. Bulk-ore assays of As, Cu, Fe, Pb, S, Sb, Sn, Zn, and In are found to be sufficient for reasonably accurate predictions. The movement of indium through the ore processing plants is fully explained by its mineralogical deportment, allowing for specific mine and process planning. The novel methodologies implemented in this contribution for (1) the assessment of analytical uncertainties, (2) the prediction of complex mineralogical deportments from bulk geochemical data, and (3) the modeling of byproduct recoveries from individual mining blocks, are of general applicability to the geometallurgical assessment of many other byproduct metals in polymetallic sulfide ores, including Ga, Ge, Mo, Re, Se, Te, as well as the noble metals.
Keywords: Geometallurgy; By-products; Trace elements; Automated mineralogy; Mineral balances; VMS deposits; VHMS deposits

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Permalink: https://www.hzdr.de/publications/Publ-28231
Publ.-Id: 28231


Simulation-based exergy, thermo-economic and environmental footprint analysis of primary copper production

Abadías Llamas, A.; Reuter, M. A.; Valero Capilla, A.; Torres Cuadra, C.; Peltomäki, M.; Stelter, M.; Valero Delgado, A.; Roine, A.; Hultgren, M.
The transition from a Linear to Circular Economy has become a societal challenge to be tackled. However, the increasing complexity of materials and products increases also the sophistication of the circular economy systems required to deal with them. These systems are very resource consuming, therefore, a rigorous evaluation of the impact of every “actor” in circular economy must be done at design and operation stages to ensure the sustainability of the metal-production value chain.

A circular economy system implies, among others, low consumption of energy and material resources and low production of wastes or pollutant emissions. Its sustainability cannot therefore be evaluated just with one indicator. In this paper, we integrate indicators such as recovery rates, environmental impact indicators, as well as the quantities and qualities of the flows, losses and emissions, quantified through exergy. These must all be considered and evaluated simultaneously to perform a rigorous sustainability analysis.

The challenges of achieving a circular processing system and society are illustrated using a unique copper flowsheet that covers the complete processing chain from ore to refined metal including among others minor elements refining, scrap recycling, residue processing, steam utilization, sulphur capture and power generation in 129 unit operations linked by 289 streams and all the compositional and thermochemical detail. Using a simulation-based approach, two scenarios have been studied and compared: (i) a representative primary copper flowsheet and (ii) excluding all waste treatment processes. This unique simulated flowsheet permits a complete evaluation of various scenarios of all copper related processing options (while any additional unit operations can also be added) and also rigorously permits an allocation of impacts of all flows, products, residues etc. as a function of the complete mineral composition.

This approach to evaluating systems shows how to estimate the true losses from a system and will be a key approach to evaluate the true circularity of the circular economy system.
Keywords: Circular economy Metallurgical process simulation Thermoeconomics Exergy Copper production Life Cycle Assessment (LCA) System design

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Permalink: https://www.hzdr.de/publications/Publ-28230
Publ.-Id: 28230


Application of Layered Double Hydroxides for 99Tc remediation

Daniels, N.; Franzen, C.; Kvashnina, K.; Petrov, V.; Torapava, N.; Bukaemskiy, A.; Kowalski, P.; Hölzer, A.; Walther, C.
The present study investigates possible use of Layered Double Hydroxides (LDH) for Tc(VII) remediation. Mg/Al- and Mg/Fe-LDH were obtained by a hydrothermal route and thermally activated at 450°C, which was shown to significantly improve the Tc(VII) removal efficiency. Based on XRD investigation of Tc-LDH phases, the Tc(VII) uptake follows the restoring of an LDH structure. X-ray absorption spectroscopy demonstrates that Tc ions interact solely via the Tc-O bond, leaving no evidences of farther atomic interactions with, e.g., layers of LDH. The presence of competing anions, like NO3-, or CO32- in the solution decreases Tc(VII) uptake by LDH. Presently investigated thermally activated Mg0.67/Al0.33-LDH revealed a maximum uptake capacity of up to 1.27 mol/kg (or 20 wt.%), which is higher than that of the Mg0.75/Fe0.25-LDH (0.9 mol/kg). In agreement with these findings, theoretical simulations predicted incorporation energies for Mg0.67/Al0.33-LDH and Mg0.75/Fe0.25-LDH of -128 kJ/mol and -110 kJ/mol, respectively. Investigation of Tc-LDH in different leaching media demonstrated a rather high Tc(VII) stability in LDH in contact with diluted solutions containing Cl- and OH-, however, in a high saline solution, like Q-brine a rather fast release of TcO4- occurs due to anionic exchange with Cl-.
Keywords: Technetium, Layered Double Hydroxides, uptake, disposal

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  • Secondary publication expected from 19.04.2020

Permalink: https://www.hzdr.de/publications/Publ-28229
Publ.-Id: 28229


Developments in the estimation of tensile strength by small punch testing

Holmström, S.; Simonovski, I.; Baraldi, D.; Bruchhausen, M.; Altstadt, E.ORC; Delville, R.
The Small Punch (SP) test is a relatively simple test well suited for material ranking and material property estimation in situations where standard testing is not possible or considered too material consuming. The material tensile properties, e.g. the ultimate tensile strength (Rm) and proof strength (Rp02) are usually linearly correlated to the force-deflection behaviour of a SP test. However, if the test samples and test set-up dimensions are not according to standardized dimensions or the material ductility does not allow the SP sample to deform to the pre-defined displacements used in these correlations, the standard formulations can naturally not be used. Also, in cases where no supporting Rm data is available the applied correlation factors cannot be verified. In this paper a formulation is proposed that enables the estimation of Rm without supporting uniaxial tensile strength data for a range of materials, both for the soon to be standardized flat samples as well as for curved (tube section) samples. The proposed equations are based on the classical and recent SP and Small Punch Creep (SPC) formulations. It is claimed that the both equivalent stress in small punch creep and tensile strength can be robustly estimated with the same type of equations at least for ductile and semi-ductile ferritic/martensitic and austenitic steels. It is also shown that the same equations can be applied on non-standard test samples and test set-ups. The tensile strength of semi-ductile materials such as 46% cold worked 15-15Ti cladding steel tubes are successfully estimated by correcting the correlations for the curvature of the samples. The usability of the SP testing and assessment method for estimating tensile strength of engineering steels in general and for nuclear claddings in specific has been verified.
Keywords: small punch testing, tensile strength, models, fuel claddings

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Permalink: https://www.hzdr.de/publications/Publ-28228
Publ.-Id: 28228


Dancing performance of organic droplets in aqueous surfactant solutions

Cejkova, J.; Schwarzenberger, K.; Eckert, K.; Tanaka, S.
Droplet systems remain the subject of a constant fascination in science and technology. Here we focus on organic droplets floating on the surface of aqueous surfactant solutions. These droplets can exhibit intriguing interactions. Recently we have found independently in two laboratories that we can observe almost the same complex collective behaviour in two different droplet systems. The aim of this paper is to compare both droplets systems, present their differences and show their similar oscillatory behaviour. The first system consists of decanol droplets floating on sodium decanoate solution. In the second one, the droplets consist of a mixture of ethyl salicylate and liquid paraffin and they are placed on the surface of aqueous sodium dodecyl sulphate solution. Although the mechanism of these spatio-temporal interactions of droplets is not fully understood yet, we believe that this behaviour is based on the same phenomena.

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Permalink: https://www.hzdr.de/publications/Publ-28227
Publ.-Id: 28227


Materials research in high magnetic fields

Wosnitza, J.
  • Invited lecture (Conferences)
    12th Annual Matsurf Seminar, 05.11.2018, Turku, Finnland

Permalink: https://www.hzdr.de/publications/Publ-28226
Publ.-Id: 28226


FFLO states in organic superconductors − Modulated order parameter

Wosnitza, J.
  • Invited lecture (Conferences)
    Workshop on “Emergent Phenomena in Strongly Correlated Quantum Matter”, 26.-31.08.2018, Natal, Brasilien

Permalink: https://www.hzdr.de/publications/Publ-28225
Publ.-Id: 28225


"Superconductivity under Extreme Conditions” (Discussion Leader of this Session)

Wosnitza, J.
  • Invited lecture (Conferences)
    Gordon Research Conference on Conductivity and Magnetism in Molecular Materials, 12.-17.08.2018, Smithfield, USA

Permalink: https://www.hzdr.de/publications/Publ-28224
Publ.-Id: 28224


Spin-imbalanced superconductivity in layered organic superconductors

Wosnitza, J.
  • Invited lecture (Conferences)
    International Conference on Science and Technology of Synthetic Metals 2018 (ICSM 2018), 01.-06.07.2018, Busan, Korea

Permalink: https://www.hzdr.de/publications/Publ-28223
Publ.-Id: 28223


Frustrated and low-dimensional magnets in high magnetic fields

Wosnitza, J.
  • Invited lecture (Conferences)
    12th International Conference on Research in High Magnetic Fields (RHMF 2018), 24.-28.06.2018, Santa Fe, USA

Permalink: https://www.hzdr.de/publications/Publ-28222
Publ.-Id: 28222


Kinetic concepts for quantitative prediction of fluid-solid interactions

Lüttge, A.; Arvidson, R. S.; Fischer, C.; Kurganskaya, I.
In a unique “perspectives” format that examines both past and future, we appraise the field of crystal dissolution kinetics, showing how the last century’s strong progress in experimental discovery has both driven, and been driven by, the tandem evolution of basic theory. To provide context for examining the current state-of-the-art in this critical field, we highlight the key milestones that have punctuated our progress in understanding the dynamics of crystalline surfaces. For crystal growth, these are the energy relations between kinks on stepped surfaces, and the phenomena of screw dislocations sustaining steady state growth at low thermodynamic overstep. For crystal dissolution, the corresponding recognition is the tie between defects, hollow cores, and macroscopic etch pits. These latter relationships have been more recently formalized in the stepwave model, incorporating etch pit nucleation, step generation, and global retreat of the crystal surface: the total dissolution rate. All these conceptual advances contain an assertion of a link, fundamental but often implicit, between mass action and kinetics, where chemical potential is the primary driver of rates of physical process. This link is inherent in many “classical” rate equations, whose parameterization is often the endgame of laboratory observations.
Today, this extant framework serves as the conceptual basis for organizing the data available from a sophisticated suite of analytical and experimental instrumentation. These resources permit ever-increasing resolution of reacting surfaces in breathtaking detail, often under in situ conditions. These direct observations are now further enhanced by powerful computer-driven simulation and numerical modeling, allowing the virtual exploration of complex reaction systems, ranging from isolated single crystals to porous, multiphase networks. Despite the exhilarating breadth and detail of these accomplishments, it is also becoming increasingly apparent that we are moving further, not closer, from the goal of predictive understanding, a goal that is an increasingly vital social responsibility of our science. A major source of this divergence reflects the fact that at key intersecting points of study, our prowess in technical observation has effectively outpaced our theoretical understanding. In confronting the daunting complexity of these systems, we must be careful to first identify major vacancies in theory. Until we resolve these deficits, more observations may be of only limited utility.
In assessing this problem, a major uncertainty is how to properly reconcile thermodynamics, by its very nature a macroscopic formalism, with our current focus on atomic scales of reaction. This may be a problem unique to crystalline materials and their interactions with phases whose components are otherwise mobile. Detailed balancing and related microscopic reversibility, the implicit link referred to above, is often used to form a mechanistic bridge between the macroscopic distribution of energy and microscopic heterogeneity of events in crystal surfaces, but its employment creates two problems: spatial and temporal. First, reaction mechanism is truly atomic in dimension, involving actual, nondegenerate collisions at crystal surface sites, whereas 〖∆G〗_r or ∆μ is macroscopic. Second, the rate at which a crystal surface dissolves reflects both the chemical composition of the ambient fluid and the distribution of surface energy. Reaction towards “equilibrium”, involving the typically slow redistribution of surface energy, may thus inherit topography inconsistent with the computed “driving force”. This reactivity mismatch yields surfaces that evolve over time, producing a heterogeneous distribution of rates. This distribution can be efficiently characterized by rate spectra: the span of non-steady-state rates reflecting diversity of reactive sites established under previous 〖∆G〗_r regimes. We use these spectra as a basic compact variable: a signal that encodes the complex link between site-specific surficial energy distributions, solution and surface chemistry, and the cumulative rate that results. Because this encoding is efficiently captured by numerous surface analytical microscopies (VSI, AFM), this approach permits the testing of hypotheses regarding the probabilistic nature of rate distributions, a process we hope the community will embrace, serving ultimately as a key step forward in establishing useful predictive approaches. We illustrate this potential with a series of case studies that target a range of composition, space, and time scales.

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Permalink: https://www.hzdr.de/publications/Publ-28221
Publ.-Id: 28221


Neutronic analyses of the FREYA experiments in support of the ALFRED LFR core design and licensing

Sarotto, M.; Firpo, G.; Kochetkov, A.; Krása, A.; Fridman, E.; Cetnar, J.; Domanska, G.
During the EURATOM FP7 project FREYA, a number of experiments was performed in a critical core assembled in the VENUS-F zero-power reactor able to reproduce the ALFRED lead-cooled fast reactor spectrum in a dedicated island. The experiments dealt with the measurements of integral and local neutronic parameters, such as: the core criticality, the control rod and the lead void reactivity worth, the axial distributions of fission rates for the nuclides of major interest in a fast spectrum, the spectral indices of important actinides (U238, Pu239, Np237) respect to U235. With the main aim to validate the neutronic codes adopted for the ALFRED core design, the VENUS-F core and its characterisation measurements were simulated with both deterministic (ERANOS) and stochastic (MCNP, SERPENT) codes, by adopting different nuclear data libraries (JEFF, ENDF/B, JENDL, TENDL). This paper summarises the main results obtained and points out a general agreement between measurements and simulations, with few discrepancies for some parameters that are here discussed. Additionally, a sensitivity and uncertainty analysis was performed with deterministic methods for the core reactivity: it clearly indicates that the calculation accuracy of the different codes/libraries resulted to be lower than the uncertainties due to nuclear data.
Keywords: FREYA EU FP7 project; ALFRED LFR, VENUS-F reactor; Measurements of neutronic parameters; ERANOS deterministic code; MNCP and SERPENT stochastic codes.
  • Journal of Nuclear Engineering and Radiation Science 6(2020)1, 011402
    DOI: 10.1115/1.4044000

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  • Secondary publication expected from 13.06.2020

Permalink: https://www.hzdr.de/publications/Publ-28219
Publ.-Id: 28219


Wasserstoffbrennen in der Sonne: Die 12C(p,γ)13N-Reaktion und die Radiofrequenz-Ionenquelle für den Felsenkeller-Beschleuniger

Reinicke, S.
Die Reaktion 12C(p,γ)13N bestimmt die Rate des Bethe-Weizsäcker-Zyklus in der anfänglichen Entwicklungsphase von Sternen und am äußeren Rand der Sonne. Eine genaue Kenntnis der Reaktionsrate ist somit für die Entwicklung von stellaren Modellen erforderlich. Über das Verhältnis der Raten von den Protoneneinfangreaktionen von 12C und 13C kann außerdem das entsprechende Isotopenverhältnis in Sternen bestimmt werden. Eine Revision der Rate von 12C(p,γ)13N könnte damit einen unerwartet hohen Isotopenanteil von 13C erklären, der in verschiedenen Meteoriteneinschlüssen gemessen wurde und mit den existierenden stellaren Modellen nicht hinreichend in Konsistenz gebracht werden kann.
Für den S-Faktor der Reaktion existieren im Energiebereich unterhalb von 190 keV nur Messdaten aus den 1950er Jahren. Bei der Untersuchung von ähnlichen Reaktionen des Wasserstoffbrennens wurden die mit der verwendeten Messtechnik erlangten Messdaten durch moderne Experimente teilweise um einen Faktor zwei oder höher revidiert.
Ziel der gegenwärtigen Arbeit war das Messen von S-Faktor-Werten in einem weiten Energiebereich von 130 keV bis 450 keV zur Überprüfung der alten Messdaten und um eine zukünftige präzisere Extrapolation zu astrophysikalisch relevanten Energien hin zu ermöglichen. Dabei wurde eine Messung in inverser Kinematik, eine Methode, für die bisher keine publizierten Daten zu der Reaktion existieren, am HZDR 3 MV Tandetron Beschleuniger durchgeführt mit TiH2-Proben, die mit 12C2+-Ionen bestrahlt wurden. Die Reaktion wurde mittels Gammaspektrometrie ausgewertet und die Proben durch die Methode der Nuklearen Resonanz-Reaktionsanalyse charakterisiert.
Die neuen Messdaten sind im Energiebereich von 130 keV bis 170 keV im Mittel etwa 20 % höher als die Werte eines existierenden Fits an die bestehenden Messdaten, im Rahmen der Messunsicherheiten aber mit diesen konsistent. Im Energiebereich der Resonanz oberhalb von 420 keV wurde eine Diskrepanz zu den alten Messwerten festgestellt. Die neuen Werte liegen in diesem Bereich systematisch bis zu 50 % unterhalb der alten Messwerte.
Als weiteres Ziel dieser Arbeit wurde mithilfe von ionenoptischen Simulationen mit SIMION 8.1 ein elektrostatischer Deflektor und eine Einzellinse für eine RadiofrequenzIonenquelle entwickelt, die im Inneren des Hochspannungsterminals des Felsenkeller Beschleunigers eingesetzt werden soll. Durch die Erkenntnisse der Simulationen konnte ein Deflektor gebaut und getestet werden, der unter den Bedingungen auf dem Beschleuniger-Terminal funktionsfähig ist und zusammen mit der Ionenquelle einen intensiven Strahl von Wasserstoff oder Helium in die Beschleunigungsstrecke umlenken kann. Die Simulationen sagen Strahlverluste von maximal 10 % für Wasserstoff und 1.5 % für Helium voraus, womit, basierend auf den Messungen an einem Vakuumteststand und den Angaben des Herstellers der Ionenquelle, Strahlströme von 80 µA für 4He+ und über 100 µA für Protonen nach Verlassen des Beschleunigers zu erwarten sind. Der Untertage-Beschleuniger am Felsenkeller und die Radiofrequenz-Ionenquelle können zu einer weiteren Messung der Reaktion 12C(p,γ)13N mit besserer Statistik und einem zu niedrigeren Energien erweiterten Messbereich verwendet werden.

The reaction 12C(p,γ)13N determines the rate of the Bethe-Weizsäcker cycle in the initial development phase of stars and near the surface of the Sun. An exact knowledge of the reaction rate is thus required for the development of precise stellar models. In addition, the ratio of the rates of the proton capture reactions of 12C and 13C is used to determine the corresponding isotopic ratio in stars. A revision of the rate of 12C(p,γ)13N might help to explain an unexpectedly high isotopic abundance of 13C, which was measured in presolar grains and cannot be sufficiently explained with the existing stellar models.
For the S-factor of 12C(p,γ)13N in an energy range below 190 keV, the only existing data were measured in the 1950s. For similar reactions of hydrogen burning, data obtained with these measuring techniques were revised by a factor of two or higher by modern experiments.
The aim of the present thesis was to measure S-factor data in a wide energy range from 130 keV to 450 keV in order to verify the old data and to allow a more precise extrapolation towards astrophysically relevant energies in the future. A measurement in inverse kinematics, a method for which no published data on the reaction exist, was performed at the HZDR 3 MV Tandetron accelerator with a 12C2+ ion beam and the use of TiH2 targets. Gamma spectroscopy was used to measure the yield and the targets were characterized with nuclear resonant reaction analysis (NRRA).
In the energy range from 130 keV to 170 keV, the new values are on average about 20 % higher than the values of a recent fit to the old data, but they are consistent within uncertainties. In the energy range of the resonance above 420 keV, a discrepancy to the old data was found. The new values in this region are up to 50 % lower than the values from previous measurements.
Another goal of this work was the development of an electrostatic deflector and an einzel lens for a radio frequency ion source inside the high voltage terminal of the Felsenkeller accelerator. For this purpose, ion-optics simulations with SIMION 8.1 were performed, which lead to a design choice for the deflector allowing the transmission of intensive beams through the accelerator. The simulation predicts beam losses of less than 10 % for hydrogen and less than 1.5 % for helium, which based on easurements with a vacuum test chamber leads to expected beam currents of 80 µA for 4He+ at the exit of the acceleration tube. According to the data sheet of the radio frequency ion source, proton beams of more than 100 µA are to be expected.
The Felsenkeller underground accelerator and its radio frequency ion source can be used to perform further measurements of the reaction 12C(p,γ)13N with improved statistical uncertainties and an extension of the energy region towards lower energies.
  • Doctoral thesis
    TU Dresden, 2018
    Mentor: Prof. Dr. Kai Zuber, PD Dr. Daniel Bemmerer
    171 Seiten
  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-094 2019

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Publ.-Id: 28218


Physical and electrical properties of nitrogen-doped hydrogenated amorphous carbon films

Fenker, M.; Julin, J.ORC; Petrikowski, K.; Richter, A.
Nitrogen-doped hydrogenated amorphous carbon films (a-C:H:N) have been prepared by a plasma-activated chemical vapor deposition technique (PACVD) by using a plasma beam source (PBS). The properties of the a-C:H:N films were changed by varying the total pressure, the substrate temperature (100 °C, 300 °C) and nitrogen partial pressure p(N₂) by adding nitrogen to the precursor acetylene (C₂H₂). For the investigations, a-C:H:N films have been deposited onto glass slides and doped silicon wafers. The deposition rate decreased with increasing nitrogen content in the N₂/C₂H₂ gas mixture and with decreasing total pressure. The elemental composition of two sample series (300 °C) has been analyzed with Elastic Recoil Detection Analysis (ERDA). The highest N content and N/C ratio was estimated to be 16 at.% and 0.25 at the highest p(N₂), respectively. Microhardness measurements showed that the hardness decreased with increasing p(N₂). Electrical resistance of the a-C:H:N films was measured by 4-point probe. Electrically conductive coatings have been obtained by nitrogen-doped a-C:H films at higher substrate temperature (300 °C). The electrical resistance of the a-C:H:N films also decreases with ecreasing total pressure, with the lowest value being about 1 Ohm cm. The film density was determined by means of X-ray reflectometry (XRR).
Keywords: PACVD; DLC; carbon films; carbon nitride films; XRR; electrical conductivity

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Measurement of the prompt fission γ-ray spectrum of 242Pu

Urlass, S.; Beyer, R.ORC; Junghans, A. R.ORC; Kögler, T.ORC; Schwengner, R.ORC; Wagner, A.ORC
The prompt γ-ray spectrum of fission fragments is important in understanding the dynamics of the fission process, as well as for nuclear engineering in terms of predicting the γ-ray heating in nuclear reactors. The γ-ray spectrum measured from the fission fragments of the spontaneous fission of 242Pu will be presented here. A fission chamber containing in total 37mg of 242Pu was used as active sample. The γ-quanta were detected with high time- and energy-resolution using LaBr3 and HPGe detectors, respectively, in coincidence with spontaneous fission events detected by the fission chamber.
The acquired γ-ray spectra were corrected for the detector response using the spectrum stripping method. About 70 million fission events were detected which results in a very low statistical uncertainty and a wider energy range covered compared to previous measurements. The prompt fission γ-ray spectrum measured with the HPGe detectors shows structures that allow conclusions about the nature of γ-ray transitions in the fission fragments. The average photon multiplicity of 8.2 and the average total energy release by prompt photons per fission event of about 6.8 MeV were determined for both detector types.
Keywords: nELBE, prompt fission, gamma-rays, plutonium, 242Pu, fission chamber

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Calcium molybdate, CaMoO₄: a promising target material for 99m-Tc and its potential applications in nuclear medicine and nuclear waste disposal

Johnstone, E. V.; Czerwinski, K. R.; Hartmann, T.; Poineau, F.; Bailey, D. J.; Hyatt, N. C.; Mayordomo, N.; Nuñez, A.; Tsang, F. Y.; Sattelberger, A. P.; German, K. E.; Mausolf, E. J.
Calcium molybdate (CaMoO₄ ) is a robust, inorganic material known for its favorable physicochemical properties making it ideal for a wide scope of applications concerning optics (i.e., phosphors, scintillators, laser hosts, etc.), nuclear waste encapsulation and disposal, corrosion inhibition, etc. Calcium molybdate occurs in nature as the mineral Powellite, and the compound adopts the scheelite (CaWO₄ ) structure-type with Mo fully oxidized in the +6-oxidation state. This Mo-containing ceramic phase exhibits limited insoluble in aqueous environments and relative thermal stability at elevated temperatures. In the laboratory, CaMoO₄ can be synthesized straightforward from the stoichiometric solid-state reaction MoO₃ with the respective calcium oxide or carbonate, e.g., CaO or CaCO₃, at elevated temperatures, or alternatively via co-precipitation, sol-gel, or mechanochemical methods. Depending on synthetic conditions, single phase nano-powders to monoliths can be generated and tailored for its successive application. Likewise, the scheelite structure type can incorporate different doping elements into the host lattice, such as Pb2+ or elements arising from the lanthanoid series, which are used for applications with phosphors. , ,
On the periodic table, Mo (Z = 42) is located on the 5th row within the transition metals and precedes the lightest, inherently radioactive element, technetium (Tc, Z = 43). Molybdenum is characterized by an assortment of naturally occurring isotopes (i.e., 92Mo 14.53%, 94Mo 9.16%, 95Mo 15.84%, 96Mo 16.67%, 97Mo 9.60%, 98Mo 24.39%, and 100Mo 9.82%) making it a suitable starting material for the transmutation to an array of different Tc isotopes depending on isotope enrichment, particle beam type (e.g., proton, deuteron, electron, neutron, photon, etc.), and beam energy. One of the most recognized Mo-Tc radionuclidic parent-daughter couples is 99Mo-99mTc, where the daughter isotope 99mTc has been notoriously branded as the workhorse of the nuclear diagnostic imaging industry used worldwide in 30 to 40 million procedures annually, i.e., ~ 9,000 6-day Ci at end of processing (EOP) per week. As the international geopolitical attitude towards using highly enriched uranium (HEU) for the production of 99Mo begins to shift, the use of non-fission sources for the production of 99mTc is becoming increasingly more vital, and new methods for production and separation are desperately being sought. For example, the United States of America currently has no domestic supply in place for the production of 99mTc, although it is responsible for half of the world’s usage.
When considering both, the isotopic and physicochemical composition and properties of Mo and CaMoO₄, strong arguments can be made to pursue the better understanding of CaMoO₄ and its relationship as a host material for direct transmutation of Mo → Tc and / or post-processing integration of Tc, specifically 99mTc at the atomistic level to weight percentages in its fundamental structure for applications such as nuclear waste disposal and radiopharmaceuticals. In this work, the synthesis and irradiation of CaMoO₄ using a modular, fusion-based neutron source and its successive characterizations are reported. Further discussions are presented considering these empirical data and their context with potential applications in the realms of nuclear medicine and materials.
Keywords: technetium, waste disposal encapsulation, molybdate, ceramics, post-irradiation
  • Contribution to proceedings
    10th Symposium on Technetium and Rhenium science and application, 03.-06.10.2018, Moscow, Russia
    10th Symposium on Technetium and Rhenium science and application, 978-5-9933-0132-7
  • Lecture (Conference)
    10th Symposium on Technetium and Rhenium science and application, 03.-06.10.2018, Moscow, Russia

Permalink: https://www.hzdr.de/publications/Publ-28215
Publ.-Id: 28215


Effects of gamma-alumina nanoparticles on strontium sorption in smectite: additive model approach

Mayordomo, N.; Alonso, U.; Missana, T.
Strontium sorption was analysed in binary mixtures of smectite and γ-alumina nanoparticles under different pH, ionic strength and Sr concentration. The aims were to verify if γ-alumina nanoparticles enhance Sr sorption in smectite and to analyse whether a component additive model satisfactorily described Sr sorption in the mixtures.
In smectite, Sr sorption mainly occurs by cation exchange but surface complexation was also accounted for. In both solids, surface complexation was described with a non-electrostatic model.
The addition of γ-Al₂O₃ nanoparticles to smectite improved Sr uptake under alkaline pH and high ionic strength, and the additive model successfully reproduced experimental data. In contrast, under acid pH and low ionic strength, no sorption improvement was observed upon adding the nanoparticles and the additive model overestimated Sr sorption. The competition of Al(III) ions, coming from γ-Al₂O₃ dissolution, partially explained the differences between data and model. Nevertheless, surface interactions between alumina particles and smectite layers may be shielding the charge, hindering contaminant access to exchangeable sites in smectite.
Keywords: Strontium, smectite, alumina, nanoparticles, sorption modelling, additive model

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Publ.-Id: 28214


Is It Here/There Yet? - Real Life Experiences of Generating/Evaluating Extreme Data Sets Around the World

Juckeland, G.ORC; Huebl, A.ORC; Bussmann, M.ORC

Large scale simulations easily produce vast amounts of data that cannot always be evaluated in-situ. At that point parallel file systems come into play, but their per node performance is essentially limited to about the speed of a USB 2.0 thumb drive (e.g. the Spider file system at OLCF provides over 1 TB/s write bandwidth, but with 18000+ nodes of Titan writing simultaneously, this number is reduced to about 50 MB/s per node). Making the most out of such a limited resource requires I/O libraries that actually scale. In addition such libraries also offer on the fly data transformations (e.g. compression) to better utilize the raw I/O bandwidth, albeit, opening a new can of worms by trading compression throughput with compression ratios for performance. We will present a detailed study of I/O performance and various compression techniques at OLCF and compare them against smaller local I/O installations, demonstrating the highest achieved I/O performance for real world applications at OLCF. Furthermore, we demonstrate that the best performing I/O setup can be determined prior to starting the job based on hardware characteristics.
Now that you have your data on disk the clock starts ticking and you are fighting against the deadline until your data will be purged, since most centers only offer the high performing storage spaces on a temporary basis. Extracting all valuable information out of a petabyte sized data set requires parallel processing as well and induces wait times until the resources are available and quite naturally a lot of trial-and-error for the evaluation. The time constraint for keeping the temporary data becomes even more troublesome when trying to compare multiple large simulations that naturally have a delay of multiple days until they are scheduled and write their results. And ideally analysis could embrace the data of multiple simulations of a quarterly accounted, yet year-long computing campaign. Another challenge for actually conducting scientific discoveries comes when utilizing multiple compute sites. This seems to be rather usual for research groups as they will use all the compute clock cycles they
can get wherever that may be. For comparative studies the data sets now need to be available at the same time for analysis, e.g. via archiving solutions or transfer to one location. The achievable transfer bandwidth between data centers is in our experience still much lower than expected. The talk will also present on the experiences of evaluating petabyte sized data sets in such a diverse environment.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-09-18
    DOI: 10.14278/rodare.70
    License: CC-BY-4.0

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Publ.-Id: 28213


Cross section and neutron angular distribution measurements of neutron scattering on natural iron

Pirovano, E.ORC; Beyer, R.ORC; Dietz, M.; Junghans, A. R.ORC; Müller, S. E.; Nolte, R.; Nyman, M.; Plompen, A. J. M.; Röder, M.; Szücs, T.; Takacs, M. P.
New measurements of the neutron scattering double differential cross section of iron were carried out at the neutron time-of-flight facilities GELINA and nELBE. A neutron spectrometer consisting of an array of up to 32 liquid organic scintillators was employed, which was designed to measure the scattering differential cross section at eight scattering angles and to simultaneously determine the integral cross section via numerical quadrature. The separation of elastic from inelastic scattering was achieved by analysing the time-of-flight dependent light-output distributions to determine the scattered neutron energy. The method was validated by studying elastic scattering on carbon and it was proved to work well for the determination of the elastic cross section. Here, the possibility to extend it to inelastic scattering was investigated too. For these experiments a sample of natural iron was used and the results cover the incident neutron energy range from 2 to 6~MeV. Both the differential and the integral elastic cross sections were produced for Fe, while for inelastic scattering, partial angular distributions for scattering from the first excited level of Fe could be determined.
Keywords: GELINA, nELBE, fast neutron scattering, cross section, angular distribution, iron
Related publications
Measurements of neutron scattering angular distributions … (Id 26138) HZDR-primary research data are used by this publication

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Radiosynthesis and preliminary biological evaluation of a novel 18F-labeled MCT1/MCT4 inhibitor for tumor imaging by PET

Sadeghzadeh, M.; Moldovan, R.-P.; Wenzel, B.; Deuther-Conrad, W.; Toussaint, M.; Fischer, S.; Ludwig, F.-A.; Teodoro, R.; Kranz, M.; Spalholz, T.; Gurrapu, S.; Steinbach, J.; Drewes, L. R.; Brust, P.
Aim: Monocarboxylate transporters (MCTs) are integral plasma membrane proteins that bi-directionally transport lactate and ketone bodies and are highly expressed in non-hypoxic regions of human colon, brain, breast, lung and other tumors.[1] Transporter inhibition leads to intracellular lactate accumulation, acidosis and cell death especially in glioma cell lines.[2] Accordingly, MCT1/MCT4 inhibitors are regarded to be of potential clinical use. In the current study a new 18F-labeled MCT1/MCT4 inhibitor was developed for in vivo PET imaging of MCT1/MCT4-overexpressing brain tumors.

Methods: (E)-2-Cyano-3-{4-[(3-fluoropropyl)(propyl)amino]-2-methoxyphenyl}acrylic acid (CAPAA) was synthesized from m-anisidine in three consecutive steps with 50% overall yield. Similar strategy was carried out to synthesize the mesylated precursor for radiosynthesis. Radiosynthesis of [18F]CAPAA was achieved by a two-step reaction, starting with the nucleophilic substitution of fluorine-18 on the alkyl chain using [18F]TBAF followed by removal of the protecting group by TFA at room temperature. [18F]CAPAA was isolated by semi-preparative HPLC eluting with 46% CH3CN/aq. 20 mM NH4HCO2 (Reprosil-Pur C18-AQ column, 250 × 10 mm), purified via Sep-Pak® C18 light cartridge and formulated in 10% EtOH/saline solution. LogD was assessed by the shake-flask method. The average IC50 values for MCT1 and MCT4 were evaluated via [14C]lactate uptake assay on the rat brain cerebrovascular endothelial cell line RBE4. The apparent affinity of [18F]CAPAA (KD) was determined using brain homogenate obtained from female CD1 mouse. The radiotracer metabolism was investigated in female CD1 mice by radio-HPLC of plasma and brain samples obtained at 30 min p.i. Plasma obtained at 60 min p.i. was used to measure the in vivo plasma free fraction.

Results: During radiosynthesis, a radiolabeled intermediate was obtained by an optimized procedure (CH3CN, 50µl of TBAHCO3-, 2-5 GBq of K[18F]F, 100 ̊C, 15 min) with 55-70% yield (n=8, non-isolated) determined by radio-HPLC analysis. Deprotection of tert-Bu group was accomplished with TFA in acetonitrile at r.t. for 15 min with 65-73% yield (n=10, radio-HPLC, non-isolated). The radiotracer was obtained in 42-65% radiochemical yield (RCY) with >98% radiochemical purity (RCP). The radioligand was highly stable in saline and PBS (>95%) up to 60 min. LogD was determined as 0.42 which reveals the tracer has moderate lipophilicity. CAPAA showed high MCT1 and MCT4 inhibition activity (IC50 = 11 and 6.4 nM respectively). [18F]CAPAA binds with an apparent KD value of ~30 nM in a saturable manner to a binding site in the brain of healthy mice. In vivo studies showed >99% of intact tracer in plasma at 30 min p.i. and a free fraction in plasma of ~3% at 60 min p.i.

Conclusions: [18F]CAPAA was achieved in high RCY and RCP and showed considerable in vitro and in vivo stability. Accordingly, the newly developed MCT1/MCT4 radioligand is anticipated to be a useful agent for imaging of tumors by PET. Animal PET imaging on healthy and brain tumor-bearing mice is currently performed.
Keywords: Radiofluorination, MCT1, Tumor imaging
  • Contribution to proceedings
    26. Jahrestagung Arbeitsgemeinschaft Radiochemie und Radiopharmazie (AGRR2018), 20.-22.09.2018, Aachen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28210
Publ.-Id: 28210


Paramagnetic NMR investigations of metal-organic complexes of soft donor ligands and the tetravalent actinides

Schöne, S.ORC; Radoske, T.; Felsner, B.; Köhler, L.; Patzschke, M.ORC; März, J.ORC; Kaden, P.ORC
NMR spectroscopy of metal-organic complexes of the f-element metal ions is often challenging due to additional chemical shifts and enhanced relaxation close to the paramagnetic metal center. These effects originate from electronic interactions between metal and ligand and often result in large additional NMR chemical shifts, compared to isostructural diamagnetic complexes, ob-served on the resonances of the ligands’ nuclei. The major two contributors to these paramag-netic chemical shifts are Fermi-contact shifts (FCS) and pseudo-contact shifts (PCS). FCS are due to delocalization of unpaired electron density in molecular orbitals involving both metal and ligand orbitals and thus report on the bond properties. PCS are originating from distance- and angle-dependent dipolar coupling of electron spins through space and are therefore bearing structural information.

The paramagnetic contributions can be mathematical separated provided that a suitable diamag-netic reference is available in order to subtract non-paramagnetic contributions. For the trivalent actinides no diamagnetic reference in the same series is available in milligram scale. Further-more, all available theories behind mathematical disentangling of contributions to the paramag-netic chemical shift, even for the lanthanide series, omit the influence of spin-orbit effects that might have a sizeable contribution as well. [1,2] Comparing studies of isostructural diamagnetic complexes of both f-element series of tetravalent metal ions (Ce(IV) and Th(IV)) allow for an es-timation of additional influences to the chemical shifts and the effect of contributions usually omitted by commonly used mathematical theories.

With Th(IV) as a diamagnetic reference in the same series, studying paramagnetic metal-organic complexes of the tetravalent actinides (An(IV)) allows to assess the chemical bonding situation via the influences on NMR chemical shifts (via FCS) and additionally allows to exploit the geo-metrical information which can be extracted from dipolar interactions (via PCS). These structural properties of the complexes as derived from PCS contributions can be compared to single crys-tal X-ray diffraction structures enabling a comparison of solution state and solid state structure of the metal-organic complexes under investigation. Herein we report the first results of investiga-tions of N- and N,O-donor ligand complexes of the An(IV) series (Th(IV), U(IV) and Np(IV)).
Keywords: NMR, actinides, paramagnetic, metal organic, Th, U, Np, Pu, Thorium, Uranium, Neptunium, Plutonium, diamagnetic
  • Lecture (Conference)
    ATAS - 4th International Workshop on Advanced Techniques in Actinide Spectroscopy, 06.-09.11.2018, Nice, France

Permalink: https://www.hzdr.de/publications/Publ-28209
Publ.-Id: 28209


Development of the first 18F-labeled MCT1/MCT4 lactate transport inhibitor: Radiosynthesis and preliminary in vivo evaluation in mice

Sadeghzadeh, M.; Moldovan, R.-P.; Wenzel, B.; Kranz, M.; Deuther-Conrad, W.; Toussaint, M.; Fischer, S.; Ludwig, F.-A.; Teodoro, R.; Gurrapu, S.; Drewes, L. R.; Brust, P.
Objectives: Although, lactate is occasionally considered as a waste in physiological cell metabolism, it is also known as an important substrate that fuels the oxidative metabolism of oxygenated tumor cells. Therefore, tumor cells express a set of plasma membrane transporters for lactate. Those monocarboxylate transporters (MCTs) are regarded as functional biomarkers for the metabolic symbiosis between glycolytic and oxidative tumor cells [1]. Overexpression of MCT1 and MCT4 has been shown for a variety of human cancers (e.g. colon, brain, breast, and kidney) [2]. Experimentally, inhibition of MCT1/MCT4 resulted in intracellular lactate accumulation, acidosis and cell death. In the current study, the first 18F-labeled MCT1/MCT4 inhibitor was developed for potential in vivo imaging of MCT expression in cancer.
Methods: Fluorinated α-CHC derivatives (FACH and tert-Bu-FACH) were synthesized and the inhibitory activity of FACH towards MCT1 and MCT4 was estimated by [14C]lactate uptake assays using an immortalized rat brain endothelial cell line (RBE4). For the radiosynthesis of [18F]FACH, a protected mesylate precursor was developed to prevent any possible effect on the labeling reaction. [18F]FACH was produced via a two-step radiosynthesis approach, starting with the nucleophilic substitution on the alkyl chain using [18F]TBAF followed by removal of the protecting group by trifluoroacetic acid (TFA) at room temperature (Figure 1A).
Isolation of [18F]FACH was performed by semi-preparative HPLC (Reprosil-Pur C18-AQ column, 250 × 10 mm, 46% CH3CN/aq. 20 mM NH4HCO2, pH = 4-5, flow 3.5 mL/min). The tracer was finally purified via solid-phase extraction (Sep-Pak® C18 light cartridge) and formulated in 10% EtOH/saline solution. In vitro stability tests were performed in pig plasma, saline, PBS and n-octanol. The LogD value was assessed by the shake-flask method. The in vivo metabolism of the radiotracer was investigated in female CD-1 mice at 30 min p.i. The biodistribution of [18F]FACH and the inhibitory effects of FACH and α-CHC were investigated by dynamic PET imaging (60 min, nanoScan® PET/MRI, MEDISO, Budapest, Hungary) of female CD-1 mice (Figure 1B).
Results: FACH showed strong inhibition of MCT1 and MCT4 (IC50 = 11 and 6.4 nM respectively). The intermediate [18F]tert-Bu-FACH was obtained by an optimized procedure (CH3CN, 3.75 µmol of TBAHCO3, 2-5 GBq of K[18F]F, 100 ̊C, 15 min) with 55-85% radiochemical yield (n = 10, non-isolated). [18F]FACH was obtained after deprotection of [18F]tert-Bu-FACH with TFA in acetonitrile at room temperature for 15 min. After purification and formulation, the novel radiotracer could be achieved with a RCY of 39 ± 3% (n = 10, EOB), molar activity of 42-100 GBq/µmol (EOS), and RCP >98%. The measured logD value (0.42) reveals moderate lipophilicity of the radiotracer. [18F]FACH was highly stable in saline (>98%) up to 60 min. In vivo metabolite studies showed >98% of intact tracer in plasma, brain, liver and kidney at 30 min p.i. Beside [18F]FACH, a few polar metabolites were also found in urine after 30 min p.i. The organ distribution pattern of [18F]FACH in healthy mice corresponds to the specific expression of MCT1 and MCT4 in kidney, lung, pancreas and liver. In these tissues, a moderate to high reduction of uptake was observed after after pre-injection of FACH and α-CHC, respectively.
Conclusions: The high uptake of [18F]FACH in kidney and other peripheral MCT-expressing organs together with the strong inhibition by specific drugs provide evidence that the new MCT1/MCT4-targeting radiotracer could be proven in ongoing studies to be useful for imaging of solid tumors with PET.
Keywords: Monocarboxylate transporter, Radiofluorination, PET, [18F]FACH
  • Contribution to proceedings
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS2019), 26.-31.05.2019, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-28208
Publ.-Id: 28208


The Unofficial "Green HPCG"

Huebl, A.ORC

An unofficial list of HPC systems, compiled from the HPCG Benchmark and TOP500 in order to explore an alternative metric for the Green500.

Keywords: hpc; manycore; top500; computing; hardware; energy efficiency
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2018-11-18
    DOI: 10.14278/rodare.68
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-28207
Publ.-Id: 28207


FMR Linewidth Variation with Distance from Lateral Antiferromagnet/Ferromagnet Interfaces

Usami, T.; Bali, R.; Lindner, J.; Itoh, M.; Taniyama, T.
B2-ordered FeRh alloys show a fascinating first-order magnetic phase transition from the antiferromagnetic (AFM) to the ferromagnetic (FM) state at around 380 K[1]. Recently, the AFM/FM phase transition and its related phenomena have been extensively studied; the transition temperature can be manipulated by substituting ions[2], introducing disorder via ion irradiation[3], injecting a spin-polarized current[4], and applying an electric field[5]. These experimental demonstrations would provide a fundamental basis for the use of FeRh in practical novel spintronic applications such as magnetic recordings, AFM memory resistors, and magnonic devices. Also, we have shown a long-range propagation of spin waves in a ferromagnetic Fe60Rh40 thin wire, demonstrating that FeRh has its potential of an alternative material for magonics [6]. In this study, we report ferromagnetic resonance (FMR) in the proximity of lateral AFM/FM FeRh interfaces that are generated by Ne+ ion irradiation. From the FMR measurements, we find a unique dependence of linewidth of the FMR spectra as a function of distance between the rf-antenna and the AFM/FM interface.
  • Poster
    Magnetics and Optics Research International Symposium 2018, 07.-10.01.2018, New York, United States of America

Permalink: https://www.hzdr.de/publications/Publ-28206
Publ.-Id: 28206


The role of fluid flow in heat and mass transport in Liquid Metal Batteries

Personnettaz, P.; Landgraf, S.; Nimtz, M.; Weber, N.; Weier, T.
Liquid metal batteries (LMBs) are suggested as a promising energy storage technology. An LMB is a three liquid layers concentration cell: two liquid metal electrodes are divided by a molten salt electrolyte. The relatively simple composition and geometry, the occurrence of multi-physics phenomena and the completely liquid nature of the active material have made the LMB an interesting candidate for continuum mechanics studies, ranging from magnetohydrodynamics to transport phenomena, such as Marangoni convection. The cell is in fact subject to a simultaneous transport of charge, heat, mass and momentum together with electrochemical reactions. The fluid flow can be beneficial if it is able to enhance the mixing at the electrolyte interfaces, thereby preventing the formation of intermetallic solid phases. However, a vigorous flow can also be detrimental to the safe operation of the battery, leading to short circuit induced by the rupture of the thin electrolyte layer. In our work the attention is focused on the role of fluid flow in heat and mass transport.
Thermally driven convection is investigated in a three layer Li||Bi LMB with an extended version of the VOF solver multiphaseInterFOAM. A relevant flow is discovered in the pure negative electrode, however it is too weak to deform the liquid interface. Moreover mass transfer is studied in the positive electrode with a single-phase CFD solver. The presence of solutal convection is numerically confirmed during the charge of the cell. The flow structures and the effects on cell efficiency are presented, the modeling limitations and the future developments are discussed.
Keywords: LMB, mass transport, heat transfer, openFoam, CFD
  • Poster
    MHD Days and GDRI Dynamo Meeting, 26.-28.11.2018, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-28204
Publ.-Id: 28204


Ion induced ferromagnetism combined with self-assembly for large area magnetic modulation of thin films

Krupinski, M.; Bali, R.; Mitin, D.; Sobieszczyk, P.; Gregor-Pawlowski, J.; Zarzycki, A.; Böttger, R.; Albrecht, M.; Potzger, K.; Marszałek, M.
A highly versatile and scalable path to obtain buried magnetic nanostructures within alloy thin films, while maintaining a flat topography, is described. A magnetic pattern of nanoscale periodicity is generated over ∼cm 2 areas by employing a B2 → A2 structural transition in the prototype Fe 60 Al 40 thin alloy films. The phase transition was induced in the confined regions via ion-irradiation through self-assembled nanosphere masks. In this way, large area patterns of a hexagonal symmetry of ferromagnetic nanostructures embedded within a paramagnetic Fe 60 Al 40 thin film are realized. The depth and lateral distribution of the induced magnetization was investigated by magnetometry and microscopy methods. Magnetic contrast imaging as well as simulations shows that the obtained magnetic structures are well defined, with the magnetic behavior tunable via the mask geometry.
Keywords: self-assembly; magnetic nanostructures; chemical disorder; magnetic patterning; ion irradiation

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Permalink: https://www.hzdr.de/publications/Publ-28203
Publ.-Id: 28203


Identical pion intensity interferometry in central Au+Au collisions at 1.23A GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Kühn, W.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K. N.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.
For the first time, identical pion HBT intensity interferometry is investigated for a large heavy ion collision system in the energy region of 1 GeV per nucleon. High-statistics π−π− and π+π+ data are presented for central Au+Au collisions at 1.23A GeV, measured with HADES at SIS18/GSI. The radius parameters, derived from the correlation function depending on relative momenta in the longitudinal-comoving system and parametrized as three-dimensional Gaussian distribution, are studied as function of transverse momentum. A substantial charge-sign difference of the source radii is found, particularly pronounced at low transverse momentum. The extracted Coulomb-corrected source parameters agree well with a smooth extrapolation of the center-of-mass energy dependence established at higher energies, extending the corresponding excitation functions down towards a very low energy. Our data would thus rather disfavour any strong energy dependence of the radius parameters in the low energy region.

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Permalink: https://www.hzdr.de/publications/Publ-28202
Publ.-Id: 28202


High-field ESR in low-dimensional spin systems

Zvyagin, S.ORC
Electron spin resonance (ESR) is traditionally recognized as one of the most sensitive tools for probing magnetic excitations in strongly-correlated spin systems. Among other exchange-coupled spin systems, low-dimensional magnets serve as almost ideal paradigmatic models in quantum magnetism, exhibiting highly unusual ground-state properties and spin dynamics. Here, I review results of our recent high-field ESR studies of some low-dimensional magnets, including quantum spin chains [1], quantum antiferromagnets on triangular lattice [2], Heisenberg spin ladders [3], and quasi-two-dimensional magnets on a honeycomb lattice [4]. In addition, I will give a brief introduction into the high-field ESR facilities at the Dresden High Magnetic Field Laboratory, which allows for multi-frequency ESR experiments in a very broad frequency range (ca 50 GHz - 9 THz) in magnetic fields up to 60 T and above.
  • Invited lecture (Conferences)
    Third Joint Conference of the Asia-Pacific EPR/ESR Society and The International EPR (ESR) Society (IES) Symposium, 23.-27.09.2018, Brisbane, Australia

Permalink: https://www.hzdr.de/publications/Publ-28200
Publ.-Id: 28200


TEM investigation of irradiation-induced defects in an ion-irradiated Fe-9Cr ODS steel

Vogel, K.; Duan, B.; Heintze, C.; Bergner, F.
Oxide dispersion strengthened (ODS) steels are promising candidate materials for structural components in nuclear power generators. Here we report on our preliminary results of TEM investigations of irradiation-induced defects in an ion-irradiated Fe-9Cr ODS steel. A cross-sectional TEM sample prepared by focused ion beam (FIB) was studied in a FEI Talos F200X transmission electron microscope by imaging under various diffraction conditions in bright- and dark-field mode. The TEM micrographs show a defect-rich band of about 400 nm width. The band is aligned parallel to the specimen surface and its position corresponds to the position of the peaks in the damage and/or injected interstitials profiles. Therefore we conclude that the defects within the band are caused by the ion irradiation. In higher magnified images of the band we observe a large number of defects, which appear as "black dots" showing a high contrast under kinematic bright-field conditions. We assume that these defects are interstitial loops, however this assumption has to be proved by further investigations. Additionally we observe some strongly curved dislocation segments, which will also be a subject of our further TEM studies.
Keywords: Transmission Electron Microscopy, Irradiation-induced defects
  • Poster
    Microscopy of Radiation Damage 2018, 21.-23.03.2018, Oxford, United Kingdom

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Permalink: https://www.hzdr.de/publications/Publ-28199
Publ.-Id: 28199


Effect of Tb for Gd substitution on magnetic and magnetocaloric properties of melt-spun (Gd1-xTbx)3Co alloys

Shishkin, D. A.; Volegov, A. S.; Ogloblichev, V. V.; Mikhalev, K. N.; Gerasimov, E. G.; Terentev, P. B.; Gaviko, V. S.; Gorbunov, D. I.; Baranov, N. V.
The melt-spun (Gd1-xTbx)3Co alloys (0≤x≤1) have been obtained and studied by X-ray diffraction, ac-susceptibility, magnetization in steady and pulse magnetic fields, and NMR measurements. A comparison of the results obtained on melt-spun alloys with their crystalline analogs has revealed a strong impact of amorphization on the magnetic state and magnetocaloric properties. The Gd-rich amorphous (Gd1-xTbx)3Co alloys (x≤0.1) exhibit increased magnetic ordering temperatures in comparison with the crystalline compounds, which is attributed to the appearance of a magnetic moment on Co atoms. The substitution of Tb for Gd results in the growth of the ratio of local anisotropy to exchange. The melt quenching of the (Gd1-xTbx)3Co alloys allows improving their magnetocaloric properties in the temperature range from 80 K up to 170 K.

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Permalink: https://www.hzdr.de/publications/Publ-28198
Publ.-Id: 28198


Cm complexation with aqueous phosphates at elevated temperatures

Huittinen, N.; Jordan, N.; Demnitz, M.; Lösch, H.; Starke, S.; Brendler, V.
Orthophosphate ions (H2PO4-, HPO42-, and PO43-) are ubiquitous in the environment and may originate from the natural decomposition of rocks and minerals (e.g. monazite or apatite), agricultural runoff, or from wastewater treatment plants. Furthermore, the potential use of monazite (LnPO4) ceramics for the immobilization of specific actinide-containing waste streams may become an important source of phosphates in the future [1–2]. Among the inorganic ligands, phosphates are strong complexants and can be expected to influence the speciation of dissolved radioactive contaminants when present in solution. However, very little data is available on the complexation of especially actinides with aqueous phosphates, even though these complexation reactions precede any aqueous synthesis of monazite ceramics and are expected to occur in natural waters as well as in the proximity of monazite-containing high-level waste repositories. The existing data also suffers from an almost systematic absence of independent spectroscopic validation of the stoichiometry of the proposed complexes.
In the present work, time-resolved laser fluorescence spectroscopy (TRLFS) has been employed to study the complexation of the actinide Cm3+ (5×10-7 M) as a function of total phosphate concentration (0–0.5 M Σ(PO4)) in the temperature regime 25–80°C, using NaClO4 as a background electrolyte (0.5–2.1 M). The studies have been conducted in the acidic pH-range ( log[H+] = 1–2.5) to avoid precipitation of solid Cm rhabdophane (CmPO4×nH2O). Under these experimental conditions, the trivalent actinide cation was found to form a complex with the anionic H2PO4- species, i.e. CmH2PO42+ and Cm(H2PO4)2+, depending on the solution pH and the total phosphate concentration, Figure 1.
The complexation reaction occurs at lower total phosphate concentration when increasing the ionic strength or the temperature. Using specific ion interaction theory (SIT) and the Van’t Hoff equation, obtained conditional constants at varying ionic strengths and temperatures have been extrapolated to infinite dilution (logβ0) and values for the enthalpy ΔRH° (assumed constant between 25 to 80 °C) and entropy ΔRS° of reaction have been acquired. The results of the extrapolations are shown exemplarily for the CmH2PO42+ species in Figure 2.
The new thermodynamic data derived in this fundamental study will contribute to a fundamental process understanding necessary to critically assess the environmental fate of actinides in the environment.
  • Lecture (Conference)
    Radiation in the environment – scientific achievements and challenges for the society, 16.-17.04.2018, Helsinki, Finland

Permalink: https://www.hzdr.de/publications/Publ-28197
Publ.-Id: 28197


Spectroscopic investigations of Cm3+ incorporation in lanthanide orthophosphates

Huittinen, N.; Scheinost, A. C.; Ji, Y.; Kowalski, P. M.; Arinicheva, Y.; Neumeier, S.
Monazites (LnPO4) are envisioned as potential immobilization matrices for high-level radioactive wastes produced e.g. during the nuclear fuel cycle [1–2]. Hydrated rhabdophane (LnPO4×0.67H2O) is a precursor phase during monazite synthesis and a potential solubility-limiting solid phase under nuclear waste storage conditions [3–4]. Thus, for a reliable long-term safety assessment of nuclear waste repositories for conditioned radioactive waste, a fundamental understanding of the radionuclide incorporation process in both the pristine monazite ceramics and their alteration products is required.
In the present study [5] we have combined two spectroscopic methods, (1) time-resolved laser fluorescence spectroscopy (TRLFS) and (2) extended x-ray absorption fine structure spectroscopy (XAFS) with density functional theory-based ab initio calculations to investigate the incorporation of the actinide curium (Cm) in (La,Gd)PO4 monazite and rhabdophane solid phases. Spectroscopic methods allow for direct probing of the dopant and its local environment in host matrices, providing a better understanding of potential lattice defect formations, lattice strain or disordering phenomena, and site population deviances with regard to the composition of the host structure, which may occur in the solid phase upon introduction of the dopant. Ab initio calculations can further deliver descriptions and explanations for spectroscopic findings, thus, contributing to a better understanding of the incorporation processes on a molecular level.
The solid phases were synthesized by addition of phosphoric acid to a solution containing La3+ and Gd3+ in desired relative concentrations and a small amount of the actinide (248Cm), until a white precipitate of La1-xGdxPO4 rhabdophane doped with approximately 50 ppm Cm3+ was obtained. An aliquot of the obtained solid phase was thereafter sintered at 1450°C to acquire the crystalline monazite ceramic. Structural refinement of collected XRD data for both rhabdophane and monazite solids show a linear dependency of lattice parameters as a function of Gd3+ substitution according to Vegard’s law.
Our combined spectroscopic results show that Cm3+ is incorporated in the monazite end-members (LaPO4 and GdPO4) on one specific, highly ordered lattice site. In the intermediate solid solution compositions, an increasing disorder around the Cm3+ dopant can be seen as a result of a broader distribution of possible Cm∙∙∙O bond-lengths in comparison to the end-member compositions with very well-defined nearest neighbour distances. Despite this local structural disordering, homogenous solid solutions were obtained for all synthesized monazite compositions without the formation of dopant clusters that could potentially hamper the performance of the monazite ceramics for the immobilization of minor actinide containing wastes.
The hydrated rhabdophane lattice comprises two different site types that could accommodate the actinide dopant: a 9-coordinated “hydrated” site amounting to two thirds (2/3) of the total number of lanthanide sites in the solid structure, where one coordinating oxygen atom originates from a water molecule, and an 8-fold coordinated “non-hydrated” site (1/3 of available Ln sites) where all oxygen atoms are provided by phosphate groups [4]. Based on our laser spectroscopic investigations, curium incorporation on both site types can be confirmed, however, the site occupancy is not in agreement with the hydrated rhabdophane structure. In contrast, a preferential incorporation of curium on non-hydrated lattice sites can be seen, especially for the La-rich rhabdophane compositions, implying that structural substitution reactions cannot be predicted based on the structure of the host matrix only.
  • Lecture (Conference)
    4th International Workshop on Advanced Techniques in Actinide Spectroscopy (ATAS), 06.-09.11.2018, Nice, France

Permalink: https://www.hzdr.de/publications/Publ-28196
Publ.-Id: 28196


Inverted hysteresis and negative remanence in a homogeneous antiferromagnet

Opherden, L.; Billitewski, T.; Hornung, J.; Herrmannsdörfer, T.; Samartzis, A.; Islam, A. T. M. N.; Anand, V. K.; Lake, B.; Moessner, R.; Wosnitza, J.
Magnetic remanence—found in bar magnets or magnetic storage devices—is probably the oldest and most ubiquitous phenomenon underpinning the technological applications of magnetism. It is a macroscopic nonequilibrium phenomenon: A remanent magnetization appears when a magnetic field is applied to an initially unmagnetized ferromagnet, and then taken away. Here, we present an inverted magnetic hysteresis loop in the pyrochlore compound Nd2Hf2O7: The remanent magnetization points in a direction opposite to the applied field. This phenomenon is exquisitely tunable as a function of the protocol in field and temperature, and it is reproducible as in a quasiequilibrium setting.

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Permalink: https://www.hzdr.de/publications/Publ-28195
Publ.-Id: 28195


Quantitative Modelling and Assessment for Circular Economy Systems

Bartie, N.; Fröhling, M.; Reuter, M. A.
Minerals and metals required to produce renewables and everyday electric and electronic technologies are extracted from both geological (primary) and urban (secondary, recycling) mines. Extraction and recycling process complexity is often neglected in impact assessments. Treatment of interconnected components in isolation is physically impossible, and should be reflected in impact assessments. Claims of completely closed loops neglect irreversible losses governed by the thermodynamics. Aggregation of complex processes into average “black boxes” reduces resolution, removing the ability to allocate impacts and optimise circular economy systems that are often geographically and temporally dispersed. We aim to expand and integrate existing frameworks, models and tools, including fundamental thermochemistry, process simulation, life cycle inventory and impact assessment, costing and thermoeconomics, and to utilise multi-criteria optimisation to conduct holistic assessments and optimisation of resource efficiency, losses and impacts of entire circular economies at high resolution. This will benefit stakeholders from operational through to policy-making levels.
Keywords: Life cycle, Recycling, Metals, Exergy, Thermodynamics, Holistic analysis
  • Poster
    Sustainable Minerals 2018, 14.-15.06.2018, Windhoek, Namibia

Permalink: https://www.hzdr.de/publications/Publ-28194
Publ.-Id: 28194


HILIC - A simple method to determine [18F]fluoride in plasma and tissue samples

Wenzel, B.; Moldovan, R.; Teodoro, R.; Deuther-Conrad, W.; Brust, P.
Objectives: The investigation of the metabolism of 18F-labeled radiotracers is a crucial step in the development process. Most often radio-defluorination as well as O- and N-dealkylation are observed resulting in the formation of very polar radiometabolites such as [18F]fluoride, [18F]fluoroethanol or [18F]fluoroacetic acid. Due to their high polarity these compounds are not easy to separate and analyze by the routinely used reversed phase HPLC. In a recent study we were faced with the problem of finding a high fraction of a very polar radiometabolite in brain samples of mice obtained after injection of a newly developed radiotracer, which seemed to be [18F]fluoride. However, as [18F]fluoride is not able to penetrate the blood-brain barrier to a considerable amount, we were interested to investigate the identity of this radiometabolite in the brain samples.

Methods: Hydrophilic interaction chromatography (HILIC) was selected as HPLC method since the elution order is more or less the reverse of the elution order in RP-HPLC. This is achieved by the use of a polar stationary phase and an aqueous mobile phase with a high content of organic solvent. In the present study, the retention and elution profile of [18F]fluoride was investigated by using a Nucleodur HILIC column (250 × 4.6 mm; Macherey-Nagel GmbH, Germany) and modifying the following parameters: i) organic solvent (e.g. CH3CN, CH3OH, THF), ii) pH value of the eluent, iii) concentration and nature of buffer additives (e.g. ammonium acetate, ammonium formate) and iv) isocratic and gradient mode. Typical investigated conditions comprised eluent compositions of 86-70% organic solvent/14-30% water, buffer concentrations ranging from 5 to 100 mM and acid concentrations of 0.05%.

Results:
The type of the organic solvent strongly influenced the retention of [18F]fluoride. Best results could be achieved with CH3CN, while with CH3OH almost no retention could be obtained. Also the pH value of the eluent played a crucial role. By using 0.05% trifluoroacetic acid (pH ~2) or formic acid (pH ~3) in the eluent, [18F]fluoride strongly retained on the stationary phase and eluted only at long retention times as very broad peak. The use of buffer systems at pH 6 to 8 improved the retention and the peak shape. Comparing ammonium formate and ammonium acetate the latter gave so far the best results. For example, under isocratic conditions at 74% CH3CN/20 mM NH4OAcaq, [18F]fluoride eluted at a retention time of 14 min while more lipophilic compounds such as typical 18F-labeled radiotracers elute close to the dead time of the column (A in Figure 1). Subsequently, this method was used to investigate homogenates of ex vivo brain samples of our newly developed P2Y1 receptor radiotracer [18F]1 (1-{2-[2-(tert-butyl)phenoxy]pyridin-3-yl}-3-[4-[18F](2-fluoroethyl)phenyl]urea) [1], and it could be demonstrated that the main radiometabolite observed in the brain after 30 min p.i. is indeed [18F]fluoride (B in Figure 1).

Figure 1: A) HILIC radio-chromatogram of a mixture of [18F]1 and [18F]fluoride, B) HILIC radio-chromatogram of a mouse brain sample at 30 min p.i. of [18F]1; conditions: Nucleodur HILIC, 250 x 4.6 mm, 74% CH3CN/20 mM NH4OAcaq, flow 1.0 mL/min.

Conclusions:
Hydrophilic interaction chromatography is a simple and useful method to determine [18F]fluoride in biological samples such as plasma and brain homogenates. Further investigation is ongoing to further improve the retention profile and to use this method also for other typical polar radiometabolites such as [18F]fluoroacetic acid and [18F]fluoroethanol.

References: [1] Moldovan et al. Eur. J. Med. Chem. (in revision) "Studies towards the development of a PET radiotracer for imaging of the P2Y1 receptors in the brain: synthesis, 18F labeling and preliminary biological evaluation".
  • Lecture (Conference)
    ISRS 2019, 26.05.-01.06.2019, Beijing, China

Permalink: https://www.hzdr.de/publications/Publ-28193
Publ.-Id: 28193


Association of Eu(III) and Cm(III) onto an extremely halophilic archaeon

Bader, M.; Moll, H.ORC; Steudtner, R.; Lösch, H.; Drobot, B.; Stumpf, T.; Cherkouk, A.ORC
Regarding the final storage of high-level radioactive waste in a deep geological repository next to geological, geochemical and geophysical also microbial aspects have to be taken into account. Rock salt is a potential host rock formation for the repository. One in rock salt common indigenous microorganism is the halophilic archaeon Halobacterium noricense DSM15987T, which was used in our study to investigate its interactions with the trivalent actinide curium and its inactive analogue europium as function of time and concentration. Time-resolved laser-induced fluorescence spectroscopy was applied to characterize formed species in the µM europium concentration range. An extended evaluation of the data with parallel factor analysis revealed the association of Eu(III) to a phosphate compound released by the cells (F2/F1 ratio: 2.50) and a solid species (F2/F1 ratio: 1.80). The association to an aqueous phosphate species and a solid species could be proven with the site-selective TRLFS. Experiments with Cm(III) in the nM concentration range showed a time- and pCH+-dependent species distribution. These species were characterized by red shifted emission maxima, 600 – 602 nm, in comparison to the free Cm(III) aqueous ion, 593.8 nm. After 24 h 40 % of the luminescence intensity was measured on the cells corresponding to 0.18 µg Cm(III)/gDBM. Our results demonstrate that Halobacterium noricense DSM15987T interacts with Eu(III) by the formation of phosphate species, whereas for Cm(III) also a complexation with carboxylic functional groups was observed.

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Permalink: https://www.hzdr.de/publications/Publ-28192
Publ.-Id: 28192


Experimental investigation on the buoyancy-induced flow in a model of the Czochralski crystal growth process

Pal, J.; Franke, S.; Eckert, S.; Gerbeth, G.
Within this paper we present a model experiment focusing on investigations of the flow field in a Czochralski puller. Low melting point liquid metals as GaInSn are an important tool to investigate the flow structure for such industrial processes. The topology of the prevailing thermally-driven convection might be very complex and is mainly determined by the aspect ratio of the liquid volume and the strength of the convection described by the characteristic dimensionless Grashof number. The measurements of the fluid flow have been conducted by means of the ultrasound Doppler velocimetry (UDV) with and without the influence of external magnetic fields. Two kinds of sensor configurations were used to investigate the flow. Firstly, measurements of the radial velocity component by means of single UDV transducers were carried out shortly below the melt surface across the entire diameter of the cylindrical liquid column at various azimuthal angles. Secondly, a vertically arranged UDV array was applied at the side of the cylinder to obtain more detailed information about the radial velocities in the covered meridional plane. The results reveal the complex flow structure of natural convection in a Czochralski crucible which gains in complexity with applied external magnetic fields.
Keywords: Czochralski crystal growth process
  • Lecture (Conference)
    Electromagnetic Processing of Materials 2018, 14.-18.10.2018, Awaji, Japan
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 424(2018), 012011
    DOI: 10.1088/1757-899X/424/1/012011

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Publ.-Id: 28191


The challenge of digitalising lead smelting with technology elements

Schalkwyk, R. F. Van; Reuter, M. A.; Stelter, M.
Technology elements (e.g. Te, Se, Ge) are crucial to the creation of complex products, e.g. photovoltaic cells, which also drive the circular economy. However, these elements introduce complexity when the waste materials (slags, flue dusts or electronic wastes) that contain them are treated in lead smelters. This strategy of treating wastes in lead smelters is followed to utilise existing infrastructure as far as possible. In order to address the complex metallurgy, a dynamic model of the furnaces that are operative in lead metallurgy is required. This project focuses on the laboratory measurements of thermodynamic and kinetic parameters that will be used to create a dynamic model of a Top Submerged Lance furnace.
Keywords: Top Submerged Lance furnace, Kinetics, Technology Elements, Modeling
  • Lecture (Conference)
    GDMB Lead Experts Meeting, 26.04.2018, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28190
Publ.-Id: 28190


Digitalizing the circular economy: Behaviour of technology elements during lead smelting

Schalkwyk, R. F. Van; Reuter, M. A.; Stelter, M.
Lead pyrometallurgical infrastructure plays an important role in the circular economy, due to the application of existing lead infrastructure and smelters for processing of secondary materials (e.g. electronics, flue dusts and waste slags). However, as the proportion of non-traditional secondary feed materials to smelters increases, so does the complexity. Better understanding is required of non-traditional and minor elements in lead metallurgy, e.g. Se.
During direct lead smelting, molten metal and slag phases form and minor elements are distributed amongst these. Se typically reports to the lead bullion and is removed from the bullion during refining stages. It is important to determine the metal/slag distribution in order to understand downstream process impacts and to avoid contamination of the final product.
Equilibration experiments are carried out in a laboratory furnace to determine slag/metal distributions of minor elements. At thermodynamic equilibrium, the distribution is affected by the temperature, slag composition, oxygen potential and interactions between elements in the melt. Results from equilibrium measurements and process implications will be discussed.
Keywords: Lead, Equilibrium, Selenium, Technology Elements, Circular Economy
  • Poster
    Sustainable Minerals, 14.-15.06.2018, Namibia, Namibia

Permalink: https://www.hzdr.de/publications/Publ-28189
Publ.-Id: 28189


Two-dimensional Pd3P2S8 Semiconductors as Photocatalysts for Solar Oxygen Evolution Reaction: A Theoretical Investigation

Jing, Y.; Heine, T.
On the basis of first principles calculations, we propose Pd3P2S8 monolayer and bilayer, two-dimensional semiconductors, whose layered bulk parent crystals are experimentally reported, as promising photocatalysts for the solar-driven oxygen evolution reaction. The monolayer is kinetically and thermodynamically stable and shows a small cleavage energy of 0.35 J m−2, suggesting that it can be prepared by exfoliation from its bulk material, and exhibits a direct band gap of 2.98 eV, which can be engineered by applying strain. The Pd3P2S8 bilayer is an indirect band gap semiconductor with a slightly smaller band gap of 2.83 eV. The photoexcited holes generate favorable driving forces for promoting the specific solar-driven O2 evolution reaction. The extraordinary electronic properties, pronounced light harvesting capability in the visible and ultraviolet regions and active surface sites render the Pd3P2S8 monolayer and bilayer as compelling 2D materials with interesting application potential for photocatalytic and photoelectrocatalytic water splitting.

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Permalink: https://www.hzdr.de/publications/Publ-28188
Publ.-Id: 28188


Cavitation energies can outperform dispersion interactions

He, S.; Biedermann, F.; Vankova, N.; Zhechkov, L.; Heine, T.ORC; Hoffman, R. E.; de Simone, A.; Duignan, T. T.; Nau, W. M.
In this work we prepare Langmuir–Blodgett monolayers with a trifunctional amphiphilic anthraphane monomer. Upon spreading at the air/water interface, the monomers self-assemble into 1 nm-thin monolayer islands, which are highly fluorescent and can be visualized by the naked eye upon excitation. In situ fluorescence spectroscopy indicates that in the monolayers, all the anthracene units of the monomers are stacked face-to-face forming excimer pairs, whereas at the edges of the monolayers, free anthracenes are present acting as edge groups. Irradiation of the monolayer triggers [4 + 4]-cycloadditions among the excimer pairs, effectively resulting in a two-dimensional (2D) polymerization. The polymerization reaction also completely quenches the fluorescence, allowing to draw patterns on the monomer monolayers. More interestingly, after transferring the monomer monolayer on a solid substrate, by employing masks or the laser of a confocal scanning microscope, it is possible to arbitrarily select the parts of the monolayer that one wants to polymerize. The unpolymerized regions can then be washed away from the substrate, leaving 2D macromolecular monolayer objects of the desired shape. This photolithographic process employs 2D polymerizations and affords 1 nm-thin coatings.
Keywords: 2D polymerization; air/water interface; anthracene; fluorescence; photolithography; self-assembled monolayers

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Publ.-Id: 28187


PtTe Monolayer: Two-Dimensional Electrocatalyst with High Basal Plane Activity toward Oxygen Reduction Reaction

Wang, Y.; Li, Y.; Heine, T.
PtTe is a layered bulk material that was discovered in 1897. According to first-principles calculations, it is one of the few layered materials that maintains structure and metallic character when thinned down to the monolayer. Interlayer energy is small enough to allow for chemical exfoliation techniques. Our calculations show that monolayer PtTe is a candidate to substitute Pt electrodes, and we computationally studied its catalytic performance in the oxygen reduction reaction (ORR). Remarkably, the basal plane of a PtTe monolayer exhibits excellent catalytic activity toward ORR, with a positive half-wave potential (∼0.90 V) and a high four-electron reduction pathway selectivity. These characteristics suggest that it outperforms Pt electrodes as catalyst, has a reduced Pt content, high Pt utilization, and a high surface area, and is a promising candidate for fuel cell components.

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Publ.-Id: 28186


Target volumes in adaptive treatment of NSCLC show large discrepancies among experts

Apolle, R.; Appold, S.; Bussink, J.; Faivre-Finn, C.; Khalifa, J.; Lievens, Y.; de Ruysscher, D.; van Elmpt, W.; Troost, E. G. C.
Purpose or Objective
Target volume delineation is subject to inter-observer variability (IOV) and thus a major source of uncertainty in radiation treatment planning. IOV in the context of treatment adaptation is largely unknown. We analysed IOV of the primary gross tumour volume (GTV) and clinical target volume (CTV) in locally advanced NSCLC delineated by experts in the pre- and mid-treatment (PT and MT) setting.

Material and Methods
Five patients from routine clinical practice, who underwent repeat imaging, were selected such that a variety of features likely to prompt adaptation, e.g. atelectasis, central primary tumour, was included. Brief case reports and CT imaging data were sent to six observers, supplemented with FDG-PET studies in two cases at PT and three at MT. Observers received PT and MT imaging data at least one week apart and were asked to delineate the GTV and CTV in their own treatment planning system and to comment on their delineation process, i.e. on how GTV to CTV expansion and adaptation were performed. Delineations were rasterised on a 1mm³ grid and their compatibility assessed with the Generalised Conformity Index (CIgen). Differences in IOV between PT and MT were probed with Wilcoxon signed-rank tests and the correlation between GTV and CTV IOV evolution with Spearman rank correlation. While it is respectively impossible and very difficult for these tests to show two-sided α=0.05 significance at n=5, more powerful parametric alternatives cannot credibly be employed.

Results
A total of 109/120 delineations were received and analysed. Figure 1 shows an overview of IOV in terms of volume overlap. All but one case saw a reduction of CIgen when transitioning from PT to MT (p=0.125 for both GTVs and CTVs). Agreement in corresponding GTV and CTV delineations was generally comparable at individual time points, and there was a trend of a correlation between GTV and CTV CIgen changes (ρ=0.9, p=0.083). This behaviour is consistent with almost all observers adopting an isotropic GTV to CTV expansion of 5 mm with rare editing for anatomical boundaries at either time point. MT GTV delineations were only occasionally adopted from PT after image registration (9/28 analysed observers and cases), the remainder contoured anew. Post-transfer adaptation to changed anatomy was performed by one observer, and inclusion of PT GTV in MT CTV by two. Figure 2 shows the two cases demonstrating the most extreme changes in IOV (improvement and deterioration). In both cases large volumes of consolidated lung lead to increased IOV, but at different time points. Shortcomings of this in silico contouring challenge were incomplete FDG-PET availability and a lack of contrast-enhanced CT, both current clinical standard. Modern MRI would also have been welcomed by many.

Conclusion
Differing approaches of reacting to intra-therapeutic changes further increase IOV in target volume delineation in the adaptive setting. Consensus guidelines and in-depth analysis of per-treatment tumour shrinkage patterns are urgently needed.
Keywords: Delineation
  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Mailand, Italien

Permalink: https://www.hzdr.de/publications/Publ-28185
Publ.-Id: 28185


Target volume delineation for adaptive treatment in HNSCC is highly variable among experts

Apolle, R.; Bijl, H. P.; Blanchard, P.; Laprie, A.; Madani, I.; Ruffier, A.; van Elmpt, W.; Troost, E. G. C.
Purpose or Objective
Inter-observer variability (IOV) in target volume delineation is a well-documented phenomenon and a major source of uncertainty in radiation treatment (RT) planning. The increasing adoption of adaptive RT adds a dynamic component to IOV, which is largely unknown. We analysed IOV in the pre- and mid-treatment (PT and MT) setting using expert primary gross tumour volume (GTV) and clinical target volume (CTV) delineations in locally advanced HNSCC.

Material and Methods
Five patients from routine clinical practice, who underwent repeat imaging, were selected such that a variety of features likely to prompt adaptation were included. Brief case reports and CT imaging data were sent to five observers, the latter supplemented with pre-therapeutic FDG-PET in four cases. Observers received PT and MT imaging data at least one week apart and were asked to delineate the GTV and CTV in their own treatment planning system and to comment on their delineation process, i.e. on how GTV to CTV expansion and adaptation were performed. Delineations were rasterised on a 1mm³ grid and their compatibility assessed with the Generalised Conformity Index (CIgen). Differences in IOV between PT and MT were probed with Wilcoxon signed-rank tests and the correlation between GTV and CTV IOV evolution with Spearman rank correlation. While it is respectively impossible and very difficult for these tests to show two-sided α=0.05 significance at n=5, more powerful parametric alternatives cannot credibly be employed. Delineations were processed with ITK and statistical analyses performed in R.

Results
A total of 82/100 delineations were received and analysed. Figure 1 shows an overview of IOV in terms of volume overlap. All cases and volumes suffered a reduction of CIgen when transitioning from PT to MT (p=0.063 for both CTVs and GTVs). There was generally better agreement in CTV than GTV delineations at individual time points, and the correlation between GTV and CTV CIgen changes was very weak (ρ=0.5, p=0.45). This comparative robustness of CTV delineations might stem from GTV to CTV expansion practices, which overwhelmingly employed sizeable isotropic margins (mean: 7.6 mm) and additional editing for anatomical boundaries at both time points. Figure 2 shows a case in which CIgen for CTVs remains stable despite deteriorating IOV in the primary GTV. MT GTV delineations were often based on PT delineations after image registration (14/24 analysed observers and cases), the remainder contoured de novo. Post-transfer adaptation to changed anatomy was performed by two observers and inclusion of the PT GTV in the MT CTV by one. Shortcomings of this contouring challenge are a lack of MRI and contrast-enhanced CT at both time points.

Conclusion
IOV in target volume delineation increases during treatment, where a disparity in institutional adaptation practices adds to the static causes of IOV. Consensus guidelines are urgently needed and should recommend scope, frequency, and quality of MT imaging alongside adaptation strategies.
Keywords: Delineation
  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Mailand, Italien

Permalink: https://www.hzdr.de/publications/Publ-28184
Publ.-Id: 28184


Correction of Geometrical Effects of a Knife-Edge Slit Camera for Prompt Gamma-Based Range Verification in Proton Therapy

Petzoldt, J.; Janssens, G.; Nenoff, L.; Richter, C.; Smeets, J.
Prompt gamma (PG) based range verification can potentially reduce the safety margins in proton therapy. A knife-edge slit camera has been developed in this context using analytical PG simulations as reference for absolute range verification during patient treatment. Geometrical deviations between measurement and simulation could be observed and have to be corrected for in order to improve the range retrieval of the system. A geometrical correction model is derived from Monte Carlo simulations in water. The influence of different parameters is tested and the model is validated in a dedicated benchmark experiment. We found that the geometrical correction improves the agreement between measured and simulated PG profiles resulting in an improved range retrieval and higher accuracy for absolute range verification. An intrinsic offset of 1.4 mm between measurement and simulation is observed in the experimental data and corrected in the PG simulation. In summary, the absolute range verification capabilities of a PG camera have been improved by applying a geometrical correction model.

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Permalink: https://www.hzdr.de/publications/Publ-28183
Publ.-Id: 28183


Rare-Earth orthophosphates from atomistic simulations

Ji, Y.; Kowalski, P. M.; Kegler, P.; Huittinen, N.; Marks, N.; Vinograd, V.; Arinicheva, Y.; Neumeier, S.; Bosbach, D.
Lanthanide phosphates (LnPO4 ) are considered as a potential nuclear waste form for immobilization of Pu and minor actinides (Np, Am and Cm). In that respect, in the recent years we have applied advanced atomistic simulation methods to investigate various properties of these materials on the atomic scale. In particular, we computed several structural, thermochemical, thermodynamic and radiation damage related parameters. From a theoretical point of view, these materials turn out to be excellent systems for testing quantum mechanics-based computational methods for strongly correlated electronic systems. On the other hand, by conducting joint atomistic modeling and experimental research, we have been able to obtain enhanced understanding of the properties of lanthanide phosphates. Here we discuss joint initiatives directed at understanding the thermodynamically driven long-term performance of these materials, including long-term stability of solid solutions with actinides and studies of structural incorporation of f elements into these materials. In particular, we discuss the maximum load of Pu into the lanthanide-phosphate monazites. We also address the importance of our results for applications of lanthanide-phosphates beyond nuclear waste applications, in particular the monazite-xenotime systems in geothermometry. For this we have derived a stateof-the-art model of monazite-xenotime solubilities. Last but not least, we discuss the advantage of usage of atomistic simulations and the modern computational facilities for understanding of behavior of nuclear waste-related materials.
Keywords: Rare-earth phosphates, Atomistic simulations, Monazite, Xenotime, nuclear waste management, Ceramics, Thermodynamics, solid solutions

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Permalink: https://www.hzdr.de/publications/Publ-28182
Publ.-Id: 28182


Experimental Analysis of the effect of column feed pipe configurations on the flow morphology

Döß, A.ORC; Schubert, M.; Hampel, U.
Droplets entrained by the vapor phase can drastically reduce the separation capacity of distillation columns and cause severe corrosion problems, process instabilities as well as higher emissions due to droplet carry-over into the downstream process units.
Intensive interactions between vapor and liquid phases favor droplet formation. Feed pipe and feed inlet are prone positions for such droplet formation, depending on flow rates, phase change and pipe geometry resulting in characteristic morphologies.
Several models are available to predict the flow regime for known liquid and vapor flow rates. However, these models and flow maps are often restricted to fully developed flows in straight pipes of small diameter only and do not account for the effects of various entrance lengths, larger diameters as well as bends found in industry. Thus, an experimental analysis is performed to study the effect of column feed pipe configurations on the evolving flow regime using the wire-mesh sensor technique (Fig. 1). Wire-mesh sensors visualize the dynamic flow structure in the pipe cross-section at high spatiotemporal resolution (1 to 3 mm, up to 10,000 Hz). This work is supported by the Federal Ministry for Economic Affairs and Energy (BMWi) based on a decision by the German Bundestag (FKZ 03ET1395D).
Keywords: Two-phase flow morphology, Horizontal feed pipe, Wire-mesh sensor, Pipe configuration
  • Poster
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-13.09.2018, Aachen, Deutschland
    DOI: 10.1002/cite.201855425

Permalink: https://www.hzdr.de/publications/Publ-28181
Publ.-Id: 28181


Dynamic Aeration for Improved Oxygen Mass Transfer in the Wastewater Treatment Process

Herrmann-Heber, R.; Reinecke, S. F.; Hampel, U.
Wastewater treatment is responsible for about 1% of the total electric energy consumption in developed countries. The dynamic aeration method, which applies oscillations to the gas flow, shows a high potential for increase of oxygen mass transfer and energy efficiency of the biological wastewater treatment process. We investigated the mass transfer of pulsed aeration modes in comparison to constant flow aeration in a test geometry in a numerical study. The effects of flow rate, pulsation frequency, bubble size and injection depth on mass transfer were studied. Gas was pulsated with a square wave pattern in on/off mode for the application in aeration basins of wastewater treatment plants. A geometry with up to 4 m aeration depth was investigated. The air supply was pulsed with frequencies in the range of 0.1 to 4 Hz. An increase of oxygen mass transfer rate by up to 24% is determined compared to continuous aeration. Moreover, comparable mass transfer rates are achieved for lower gas mass flow rates during pulsation. Thus, air demand in compression and energy consumption can be reduced when dynamic aeration is applied.
Keywords: Wastewater aeration; pulsed aeration; oxygen mass transfer; CFD

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Permalink: https://www.hzdr.de/publications/Publ-28180
Publ.-Id: 28180


Flow morphology in feed pipes: theoretical analysis and experimental investigation

Döß, A.ORC; Schubert, M.; Hampel, U.; Schleicher, E.; Geipel, C.; Mehringer, C.; Flegiel, F.
Efficient separation in distillation columns driven by the thermodynamic non-equilibrium between vapor and liquid phase is achieved by high turbulence as well as large interfacial area. At the same time, intensive interactions between vapor and liquid phases result in the formation of droplets, whose entrainment by the vapor phase may drastically reduce the separation capacity. The feed pipe is a prone position for such droplet formation. Besides the flash evaporation, the evolving flow morphology in the feed pipe is decisive for the droplet generation.The flow morphology in pipes depends on fluid flow rates and properties as well as on the pipe geometry. Several models and flow regime maps for fully developed flows in small pipe diameters exist, relating operating conditions and flow morphology. However, industrial feed pipe configurations with larger diameters and bends are so far not studied.
Thus, an experimental study in feed pipes of 50 mm and 200 mm diameter is performed using the wire-mesh sensor technique (Fig. 1). The wire-mesh sensor visualizes the dynamic flow structure in the pipe cross-section at high spatiotemporal resolution (1 to 3 mm, up to 10,000 Hz). The obtained data are compared with the
state-of the art models to assess their applicability for feed pipes. This project is supported by the Federal Ministry for Economic Affairs and Energy (BMWi) based on a decision by the German Bundestag (FKZ 03ET1395D).
Keywords: Two-phase flow morphology, Horizontal feed pipe, Wire-mesh sensor
  • Lecture (Conference)
    ACHEMA 2018, Session: TERESA – Droplet entrainment and droplet reduction in mass transfer devices, 11.-15.06.2018, Fankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28179
Publ.-Id: 28179


PREFACE: American Journal of Science, Vol. 318, November, 2018

Fischer, C.; Arvidson, R. S.; (Editors)
Research in fluid-solid interaction processes has expanded tremendously over the past few decades, with key fronts ranging from fundamental understanding of reaction kinetics to detailed predictions involving the release, migration, and retention of environmentally important components. This special issue of AJS showcases the diversity and progress of this research in a series of invited papers that also illustrate core problems and solutions.
A central theme is the challenge involved in the integration of reaction processes over length and time scales that span many orders of magnitude. At one end of this spectrum, both theoretical and modeling approaches have evolved to describe the very brief interactions at the molecular scale, allowing key insights into details of reaction mechanism. At the other, modeling approaches have focused on the longer reaction times and lengths that characterize macroscopic systems. Experimental and analytical observations are also now able to map the dynamics and reactivity of reacting surfaces at the pore scale and above, providing these modeling approaches with essential feedbacks towards validation of predictions and identification of aspects where improvement is needed.
The strong coupling between the two “worlds” of experimental and simulation approaches is perhaps the most important result of the last years of research in our field. A primary motivation for this special issue was to highlight this productive interaction. A second motivation was to mark the 60th birthday of Professor Andreas Lüttge. Starting his scientific work at Tübingen University, followed by appointments at Yale University, Rice University, and now at the University of Bremen, he has continued to pursue the productive synergy of these two activities via pioneering work combining kinetic Monte Carlo simulations with complementary observations of reacting mineral surfaces.

This special issue is published in two parts. This first part begins with theoretical work by Bender and Becker, involving the kinetics of interactions between redox-sensitive plutonyl species, iron, and hydroxyl radical. This work nicely illustrates a divide-and-conquer approach, elucidating the stepwise reaction sequence involved in the formation and configuration of various complexes. In so doing, it also provides a potential framework for approaching related problems in the context of interactions at mineral surfaces. The second contribution, by Churakov and Prasianakis, combines thermodynamic calculations and kinetic simulations. Here the authors use the scale of the pore itself as a central connector to elegantly link the atomistic description of mineral surface reactivity with structural and compositional heterogeneities of real materials. The third contribution, by Kim, Marcano, Ellis, and Becker, presents experimental data on the photocatalytic role of TiO2 nanoparticles in uranyl reduction, using a diverse array of organic ligands as electron donors. This study demonstrates the importance of understanding the environmental specificity of reactions at surfaces, documenting the sensitivity of reduction efficiency to both ligand and UV wavelength. The last paper in this special issue’s first part, by Gebauer, Raiteri, Gale, and Cölfen, provides insight into current discussions concerning the birth of crystal nuclei during homogeneous precipitation in solution. They provide a nice summary of the ongoing debate, and stimulate further examination of true nature of these processes, arguing that the “critical” aspect of these clusters lies not in their size, but in their dynamics.
This last point also bears on a larger fundamental problem: how to resolve our new and increasing knowledge of the kinetics of these microscopic interactions, with the conventional thermodynamic framework that has long guided our interpretations of interactions at the mineral-fluid interface, but which is also largely macroscopic in origin. In the near future, we will announce the second part of this special issue, with a specific focus on new experimental results that challenge conventional model predictions.
  • Book (Editorship)
    New Haven, Connecticut: American Journal of Science, Yale University, 2018
    DOI: 10.2475/09.2018.01

Permalink: https://www.hzdr.de/publications/Publ-28178
Publ.-Id: 28178


Use of immobilizing individual abdominal corset in patients with upper-GI tumors treated with proton beam irradiation

Thiele, J.; Schneider, S.; Valentini, C.; Lohaus, F.; Stefanowicz, S.; Haak, D.; Krause, M.; Hoffmann, A. L.; Troost, E. G. C.
Purpose/Objective: The irradiation of tumors, which are subject to respiration-induced motion is challenging for pencil beam scanning (PBS) based proton therapy due to the interplay effect and the temporally varying tissue densities along the beam path. Here, we report on the feasibility, tolerability and setup reproducibility of an individualized immobilization device for patients with tumors in the upper abdomen, who are treated with PBS.

Material/Methods: Since January 2018, nine patients with tumors in the upper abdomen (pancreas, liver and gall bladder) have been treated with PBS at our department. All patients eligible for this study underwent the following procedure within 10-days: (1) intra-tumoral implantation of three fiducial markers for target localization, (2) design of an individualized abdominal corset for motion reduction by abdominal compression, (3) abdominal MRI scan with intravenous contrast agent (c.a.) for target volume definition and tumor motion quantification, and (4) 4D-CT scan with c.a. for treatment planning. CT simulation and irradiation was performed with a vacuum mattress (Fig.1). Before each treatment fraction, the position of the target volume was verified with orthogonal X-ray imaging. First, a 2D/2D match with the DRRs was performed and then the position of the fiducial markers was verified (tolerance level: 3-5mm). In case this tolerance level was exceeded, a CT scan was performed in-room and the dose distribution was recalculated for plan comparison; in case of clinically relevant changes in the dose distribution, a new plan was calculated.

Result: All patients tolerated the marker implantation, the abdominal corset and the treatment well with no treatment interruptions. In 4 out of the 300 applied fractions (1,3%) the tolerance level of the fiducial markers was exceeded. For these fractions, the recalculated dose distribution nevertheless showed sufficient target coverage (Fig. 2). The entire treatment fraction (including patient positioning, setup verification and dose delivery) did not exceed the standard time slot of 30 minutes.

Conclusion: This study demonstrates that PBS-based proton therapy with an abdominal corset to reduce breathing motion of GI-tumors is feasible, well-tolerated by patients and provides a reproducible setup without prolonging the daily treatment time.

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Permalink: https://www.hzdr.de/publications/Publ-28177
Publ.-Id: 28177


Implementation of CT-based attenuation maps of RT positioning devices in PET/MRI - online vs offline

Täubert, L.; Pfaffenberger, A.; Berker, Y.; Beuthien-Baumann, B.; Hoffmann, A. L.; Troost, E. G. C.; Koerber, S. A.; Kachelrieß, M.; Gillmann, C.
Purpose or Objective
Integrating PET/MR hybrid imaging into radiation treatment (RT) planning has great potential to improve tumor delineation and dose prescription. Since these scans must be acquired under treatment conditions, attenuation correction of RT positioning devices is necessary. Attenuation maps can be implemented either online (directly at the PET/MRI scanner) or offline (at another PC). In this study, we compare both methods and assess their impact on PET image quality using a CT-based user-generated attenuation map of an RT table overlay.
Material and Methods
CT images of an RT table overlay (in-house construction) were acquired on a stand-alone CT (Somatom Definition Flash, Siemens Healthineers, Erlangen, Germany) at 120 kV and 360 mAs. Based on the CT images, an attenuation map of the RT table overlay was calculated via the bilinear approach [1]. The RT table overlay was then mounted onto the patient table of the PET/MRI (Biograph mMR, Siemens Healthineers) and two sets of PET-measurements were taken using an active 68Ge phantom (32 MBq, 10 min scan time). The phantom was scanned with the RT table overlay (RT scan), and without the RT table overlay (reference scan). PET reconstructions of the phantom scans were performed online at the PET/MRI scanner and offline using the e7tools (Version VA20, Siemens Healthineers) with identical reconstruction parameters. For the PET-reconstructions of the RT scan, the attenuation map of the RT table overlay was implemented. Attenuation correction accuracy was evaluated by comparing PET activities between RT and reference scans in 10 ROIs placed every 10 slices along the phantom in longitudinal direction, both for the online and the offline reconstruction methods.
Results
The RT table overlay attenuation map was successfully added to the hardware attenuation maps produced online and offline. Table 1 compares measured PET activities. For the online reconstruction, a mean percentage difference of 0.7% was found between the reference and the RT scan. For the offline reconstruction, a mean percentage difference of 1.4% was found. A systematic difference of around 500 Bq/ml was found between the online and offline reconstructions.
Conclusion
For the integration of PET/MRI in RT planning, attenuation correction of RT positioning devices is viable. The online reconstruction seems to be more accurate, but it has the disadvantage that the attenuation map must be removed from the system after every RT measurement to prevent an incorrect reconstruction of patient data that were not scanned in RT setup. Alternatively, offline reconstruction can be implemented at any PC via e7tools, and the reconstruction could be automated, thereby diminishing human error. The cause of the systematic signal difference in online and offline reconstruction needs to be investigated further.

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Permalink: https://www.hzdr.de/publications/Publ-28176
Publ.-Id: 28176


Development of an anthropomorphic multimodality pelvis phantom for PET/MRI- and CT-based RT planning

Homolka, N.; Pfaffenberger, A.; Beuthien-Baumann, B.; Mann, P.; Schneider, V.; Johnen, W.; Runz, A.; Echner, G.; Hoffmann, A. L.; Troost, E. G. C.ORC; Koerber, S. A.; Seco, J.; Gillmann, C.
Purpose
The aim of the study is the further development of an anthropomorphic multimodality pelvis phantom (ADAM, [1]) for the integration of PSMA-PET/MRI-based treatment planning of prostate cancer patients.
Materials/Methods
CT and 3T-MRI characteristics of different tissue types are mimicked using agarose gels (Agarose NEEO Ultra-Qualität Carl Roth GmbH + Co. KG, Germany) mixed with different concentrations of Gadolinium (Gd, MultiHance® 0.5 M, Bracco Imaging Deutschland GmbH) and sodium fluoride (NaF, Carl Roth GmbH + Co. KG). Gels were scanned using a 3T PET/MRI (Biograph mMR, Siemens Healthineers, Erlangen, Germany) using a saturation recovery sequence with multiple inversion times and a spin-echo sequence with multiple echo times. Based on the resulting images, T1- and T2-relaxation times were determined using in-house written software. CT scans of the agarose mixtures were performed on a stand-alone CT scanner (Somatom Definition Flash, Siemens Healthineers) at 120kV and 390 mAs.
The gels can be doped with radioactive tracers to simulate tumors in PET. Agarose mixtures that agreed best with reference values derived from literature data [2-4] were subsequently doped with patient-specific activity concentrations of 18F and 68Ga (e.g. 3kBq/ml 68Ga and 11kBq/ml 18F for the primary tumor). Organ shells (prostate with two intraprostatic lesions,
ESTRO abstract Noa Homolka, Physics Track lymph nodes and bone metastases) were printed using a 3D printer (Stratasys Objet 300 Connex 3, print material: VeroClear). The doped, liquid agarose gels were filled into the organ shells where they solidified within seconds. Organ shells were scanned at the 3T PET/MRI scanner (PET acquisition time: 10 min, MRI: T2-weighted morphological sequence).
Results
The final compositions of agarose gels are the following (given as mass fractions of agarose/NaF/Gd): Prostate (1.35%/3.2%/0.011%), tumor (2.25%/3.2%/0.0085%), lymph nodes (3.2%/1.4%/0.025%).
T1- and T2-relaxation times and CT numbers of the developed agarose gels fit well to reference values (Figure 1). Exemplary PET- and MR-images of a prostate with two intraprostatic lesions doped with 11 kBq/mL 18F are shown in Figure 2. The PET signal can be detected and the tumors appear hypointense on T2-weighted MRI.
Conclusion
Agarose gel mixtures with organ-specific MR-relaxation times at 3T and CT numbers have been developed and doped with radioactive tracers. The gels will be used in the pelvis phantom which will be central to simulate and optimize the technical workflow for the integration of PSMA-PET/MRI-based RT planning of prostate cancer patients.

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Permalink: https://www.hzdr.de/publications/Publ-28175
Publ.-Id: 28175


Modelling of Complex Flow Sheets

van den Boogaart, K. G.; Kern, M.; Schach, E.; Krupko, N.; Hannula, J.; Menzel, P.; Prior, A.; Tolosana Delgado, R.
Complex multi-element ores, like the skarn ores from the AFK project and the Tellerhäuser pilot plant, are difficult to process due to their complex and fine-grained mineralogy. The valuable elements are enriched in various scales. The deposit hosts a very large, high-grade tin orebody, which is challenging to process because of the high energy consumption during grinding and the very fine-grained tin mineralisation. Traditional way of processing such ores would consist of a milling to desired liberation size, followed by a separation of cassiterite based on density or floatability properties. As it has been done historically due to the specific properties of the ore this approach however requires a selection between very intensive grinding with lots of fines, or less grinding with insufficient liberation, both approaches essentially leading to low final concentrate grades.
Unlike many other deposits, the Tellerhäuser skarn ore has a much more complex structure, which can be exploited with more advanced flow sheets. Additionally to the tin mineralization there is a substantial enrichment in multiple potential by-products. The fine-grained tin mineralization itself is locatedin lithologies (units of consistent geometallurgical, mineralogical and physical characteristics) dominated by tin free minerals. Despite a background concentration of unrecoverable tin as a trace element in the whole skarn body, the cassiterite mineralisation is localized within the ore body at mining block scale. It is thus possible to reject gangue material at various scales: Exploration based on mineralogical information allows distinguishing processable ore from gangue. A separation based on mineral groups allows to reject unmineralized skarns at various scales and to enrich preconcentrates for various by-products before cassiterite is liberated.
Applied in the right way, automated mineralogy data allows characterizing the spatial and mineralogical structure and physical properties of particles at various scales from mining blocks (selective processing), through cm-scale (sensor sorting), sub mm-scale (physical processing) down to µm scale (ultra-fine processing). This allows the prediction of potential separation behaviour of complex processing chains and thus to infer optimal separation criteria, separation thresholds, milling targets, mass streams, savings potential and environmental properties of all processing steps from mine to final concentrate.
In this way, the detailed understanding of the deposit and ore structure allows to model the different processing steps in an optimal scale and detail, combined to one flowsheet. The effect of imperfect processing behaviour can be quantified and understood in particle-level detail and used to determine suitable processing equipment.
Keywords: Automated Mineralogy, Particle Based Simulation
  • Invited lecture (Conferences)
    FAME Closure Conference, 05.-06.12.2018, London, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-28174
Publ.-Id: 28174


Microbial diversity in an arid, naturally saline environment

Bachran, M.; Kluge, S.; Lopez-Fernandez, M.; Cherkouk, A.
The Arava Valley in Israel is a rock desert within the Great African Rift valley. Soil from this area is covered with a salt crust. Here, we report microbial diversity from arid, naturally saline samples collected near Ein Yahav from the Arava Valley by culture-independent as well as culture-dependent analysis. High-throughput sequencing of the hypervariable region V4 of the 16S rRNA gene revealed that the microbial community consists of halophiles from the domain Bacteria as well as Archaea. Bacterial diversity was mainly represented by the genus Salinimicrobium of the order Flavobacteriales within the phylum Bacteroidetes, from the gammaproteobacterial orders Alteromonadales and Oceanospirillales as well as representatives from the order Bacillales of the phylum Firmicutes. Archaeal diversity was dominated by euryarchaeal Halobacteria from the orders Halobacteriales, Haloferacales and Natrialbales. But more than 40 % of the sequences affiliated with Archaea were assigned to unknown or unclassified archaea. Even if taxonomic resolution of the 16S rRNA gene V4 region for Archaea is limited, this study indicates the need of further and more detailed studies of Archaea. By using culture-dependent analysis bacteria of the order Bacillales as well as archaea from all three halobacterial orders Halobacteriales, Haloferacales and Natrialbales including potentially novel species from the genera Halorubrum and Haloparvum were isolated.

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Permalink: https://www.hzdr.de/publications/Publ-28173
Publ.-Id: 28173


Ultrasonic measurements of the flow field in foam and froth

Heitkam, S.; Nauber, R.; Richter, T.; Büttner, L.; Czarske, J.; Eckert, K.
In this work, the non-invasive Ultrasound-Doppler velocimetry has been used to measure the velocity distribution inside a liquid foam bulk for the first time. The foam flows upward in a transparent channel. Optical correlation algorithms and conductivity measurement provide reference data. An array of ultrasound transducers is mounted within the channel, sending bursts along the main flow axis and receiving the echoes. The penetration depth equals up to 0.2 meters. With purposely designed flows it is demonstrated, that the velocity uncertainty is below 15 percent and the spatial resolution better than 1 cm. In static experiments, the applicability to particle laden foam and froth has been estimated. These parameters allow for monitoring of industrial processes as well as scientific investigation of three-dimensional foam and froth flow on medium scales.
Keywords: Ultrasound Doppler Velocimetry, Foam flow
  • Lecture (Conference)
    ISUD 11 - 11th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 06.09.2018, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-28171
Publ.-Id: 28171


Neutron Imaging of Foam and Froth

Heitkam, S.; Lappan, T.; Rudolph, M.; Trtik, P.; Eckert, S.; Eckert, K.
The present contribution reports on the investigation of particle movement and drainage in unsteady foam and froth using Neutron Imaging (NI) (S. Heitkam et al. "Neutron imaging of froth structure and particle motion." Minerals Engineering, vol. 119, pp. 126-129, 2018.)

Froth flotation is one of the major separation processes in mining. Billions of tons per year of ore are treated by flotation worldwide. Despite the industrial relevance, measurement techniques for the observation of particle movement and liquid distribution inside the froth are limited.

In this situation, NI can reveal new insights on the mechanisms in froth flotation. NI is similar to radiography, but X-rays are replaced by neutrons. The neutrons pass through the measurement object, being partially attenuated. Then they hit a scintillator, generating photons that are observed by a high-speed camera. The advantage of NI in froth research is, that some materials (e.g. gadolinium) offer extremely high attenuation of neutrons. And also water attenuates neutrons about 30 times stronger than X-rays.
Keywords: Neutron Imaging, Foam, Froth
  • Lecture (Conference)
    EUFOAM, 10.07.2018, Liege, Belgium

Permalink: https://www.hzdr.de/publications/Publ-28170
Publ.-Id: 28170


Ultrasonic measurements of the velocity distribution inside foam

Heitkam, S.; Nauber, R.; Büttner, L.; Czarske, J.; Eckert, K.
The flowing behavior of liquid foam and froth is not yet well investigated. One reason for that is, that adequate measurement techniques are scarcely available. Also, industrial foam applications could be improved by monitoring the foam flow in the process.

In this work, the ultrasound Doppler velocimetry is used to measure the velocity distribution inside liquid foam. (Nauber et al. “Ultrasonic measurements of the bulk flow field in foams.”, Physical Review E, vol. 97 (1), pp 013113, 2018). To that end, an array of five ultrasound transducers is positioned inside a foam channel. One transducer sends pulses into the foam and the others receive the echoes. Sound pulses are reflected at moving particles and air-liquid interfaces. The echoes reveal the longitudinal velocity distribution along the beam axis. Multiplexing of the array allows for 2D-1C measurement.
Keywords: Ultrasound Doppler Velocimetry, Foam flow
  • Lecture (Conference)
    EUFOAM, 10.07.2018, Liege, Belgium

Permalink: https://www.hzdr.de/publications/Publ-28169
Publ.-Id: 28169


Phase-resolving simulation of dense bubble clusters under periodic shear

Heitkam, S.ORC; Fröhlich, J.
The paper studies the response of a cluster of bubbles to osmotic pressure, and steady and oscillatory shearing by resolved numerical simulations. In contrast to other investigations, the movement of the interstitial fluid is fully resolved. To that end, an immersed-boundary method is employed, yielding the trajectory of each bubble and the flow and pressure field of the fluid. Additionally, a physically motivated collision model ensures realistic bubble interactions. Furthermore, a suitable numerical configuration is proposed which allows imposing osmotic pressure and shear in a way that integrates well into the simulation without generating artefacts. This method allows for the realistic investigation of the compression of bubbles across the jamming limit, demonstrating the influence of the inertia of the interstitial fluid. Applying oscillatory shearing with varying osmotic pressure, shear stress and frequency, the occurrence of shear bands is demonstrated and the influence on rheometric measurements is discussed.
Keywords: Bubbles, Simulation, Rheology, Foam

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Permalink: https://www.hzdr.de/publications/Publ-28168
Publ.-Id: 28168


Improving the range accuracy in particle therapy: Wrap up of the workshop

Richter, C.
Summary of the workshop results
  • Lecture (Conference)
    2ND ESTRO PHYSICS WORKSHOP - SCIENCE IN DEVELOPMENT, 26.-27.10.2018, Malaga, España

Permalink: https://www.hzdr.de/publications/Publ-28167
Publ.-Id: 28167


Improving range accuracy in particle therapy: Introduction of the workshop

Richter, C.
Introduction of the workshop
  • Lecture (Conference)
    2ND ESTRO PHYSICS WORKSHOP - SCIENCE IN DEVELOPMENT, 26.-27.10.2018, Malaga, España

Permalink: https://www.hzdr.de/publications/Publ-28166
Publ.-Id: 28166


Hochpräzisions-Strahlentherapie: Mit Protonen gegen Krebs

Richter, C.
Überblicksvortrag
  • Invited lecture (Conferences)
    50. Kraftwerkstechnisches Kolloquium, 23.-24.10.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28165
Publ.-Id: 28165


Dual-energy CT for automatic organ at risk segmentation in brain tumor patients using a multi-atlas and deep-learning approach

van der Heyden, B.; Wohlfahrt, P.; Troost, E.; Terhaaf, K.; Eekers, D.; Richter, C.; Verhaegen, F.
In radiotherapy, computed tomography (CT) datasets are frequently used to calculate radiation treatment plans to interpret dose evaluation metrics in healthy surrounding organs that need to be spared, the organs at risk (OARs). Based on CT scan and/or magnetic resonance images, the OARs have to be delineated by hand which is one of the most time-consuming tasks in the clinical radiotherapy workflow. Recent multi-atlas (MA) or deep learning (DL) based methods aim to improve the clinical workflow by automatically segment the OARs on a CT dataset. However, no studies investigated the performance of these MA or DL methods on dual-energy CT datasets which have been shown to improve the image quality compared to 120 kVp single-energy CT. In this study, the in-house developed MA method and the DL method (two-step three dimensional U-net) are described first. Then, the performance of both approaches (MA and DL) was quantitatively and qualitatively evaluated on various dual-energy CT datasets, more specifically on pseudo-monoenergetic CT dataset that were generated between 40 keV and 170 keV.

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Permalink: https://www.hzdr.de/publications/Publ-28164
Publ.-Id: 28164


Log file based dose reconstruction and accumulation for 4D adaptive pencil beam scanned proton therapy in a clinical treatment planning system: Implementation and proof-of-concept

Meijers, A.; Jakobi, A.; Stützer, K.; Marmitt, G.; Both, S.; Langendijk, J.; Richter, C.; Knopf, A.
Background and Purpose
Motion induced uncertainties hamper the clinical implementation of pencil beam scanning proton therapy (PBS-PT). Prospective pre-treatment evaluations only provide multi-scenario predictions without giving a clear conclusion for the actual treatment. Therefore, in this proof-of-concept study we present a methodology for a fraction-wise retrospective 4D dose reconstruction and accumulation aiming at the evaluation of treatment quality during and after treatment.
Material and Methods
We implemented an easy-to-use, script-based 4D dose assessment of PBS-PT for patients with moving tumours in a commercially available treatment planning system. This 4D dose accumulation uses treatment delivery log files and breathing pattern records of each fraction as well as weekly repeated 4D-CT scans acquired during the treatment course. The approach was validated experimentally and was executed for an exemplary data set of a lung cancer patient.
Results
The script-based 4D dose reconstruction and accumulation was implemented successfully, requiring minimal user input and a reasonable processing time (around 10 minutes for a fraction dose assessment). An experimental validation using a dynamic CIRS thorax phantom confirmed the precision of the 4D dose reconstruction methodology. In a proof-of-concept study, the accumulation of 33 reconstructed fraction showed a linear increase of D98 values. Projected treatment course D98 values revealed a CTV under dosage after fraction 25. This loss of target coverage was confirmed in a DVH comparison of the nominal, the projected (after 16 fractions) and the accumulated (after 33 fractions) dose distribution.
Conclusions
The presented method allows for the assessment of the conformity between planned and delivered dose as the treatment course progresses. The implemented approach considers the influence of changing patient anatomy and variations in the breathing pattern. This facilitates treatment quality evaluation and supports decisions regarding plan adaptation. In a next step, this approach will be applied to a larger patient cohort to investigate its capability as 4D quality control and decision support tool for treatment adaptation.

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Permalink: https://www.hzdr.de/publications/Publ-28163
Publ.-Id: 28163


Large refrigerant capacity induced by table-like magnetocaloric effect in amorphous Er0.2Gd0.2Ho0.2Co0.2Cu0.2 ribbons

Li, L.; Xu, C.; Yuan, Y.; Zhou, S.
The microstructure, magnetism, and magnetocaloric properties in melt-spun Er0.2Gd0.2Ho0.2Co0.2 Cu0.2 ribbons were reported. The ribbons are fully amorphousized and all the constituent elements are distributed uniformly. The large table-like magnetocaloric effect (MCE) from 25 to 75 K has been observed, resulting in a large value of refrigerant capacity (RC). With the magnetic field change (μ0H) of 0–5 T, the values of maximum magnetic entropy change (−Smax M ) reaches 11.1 J/kg K, and the corresponding value of RC are as large as 806 J/kg, make the amorphous Er0.2Gd0.2Ho0.2Co0.2Cu0.2 ribbons extremely attractive for cryogenic magnetic refrigeration.
Keywords: Table-like magnetocaloric effect; Er0.2Gd0.2Ho0.2Co0.2Cu0.2 amorphous ribbons; large refrigeration capacity

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Permalink: https://www.hzdr.de/publications/Publ-28162
Publ.-Id: 28162


Dual-energy computed tomography for improved delineation in postoperative brain-tumor patients

Wohlfahrt, P.; Agolli, L.; Pilz, K.; Richter, C.; Troost, E.
Purpose/Objective:
The clinical use of dual-energy CT (DECT) contributes to an improved accuracy in proton treatment planning compared to single-energy CT (SECT) as demonstrated in recent studies. A precise delineation of tumor volumes and organs at risk (OARs) is essential in particular for emerging high-conformal treatment techniques. Since DECT provides additional tissue information and allows for the generation of various tissue contrasts, we assessed its influence on the intra- and inter-observer delineation variability.
Material/Methods:
Two cohorts of 10 postoperative brain-tumor patients each, receiving either a 120kVp SECT or 80/140kVp DECT scan with identical total dose, were evaluated. Pseudo-monoenergetic CT (MonoCT) datasets of 50, 60, 70 and 79keV, representing several tissue contrasts, were derived from DECT scans processed in syngo.via (Siemens Healthineers). Three radiation oncologists with different levels of experience in neuro-oncology delineated the postoperative tumor bed volume (TBV) and OARs (brainstem, parotid and lacrimal glands, eyes, lenses, optic nerves, and chiasm) on each dataset, at least two-weeks apart per patient. Relevant image information was blinded. The delineations on SECT datasets were repeated once to assess the intra-observer variability. Finally, the delineation was also performed on T1/T2 MR scans as clinical reference.
The contour conformity was quantified by the Jaccard index (JI) and Hausdorff distance (HD) between the intersection and union of the respective contours (Fig. 1).
Results:
The median inter-observer TBV conformity (Fig. 2A) was almost independent from the CT dataset (HD=6-9mm, JI=61-66%) and comparable to MR scans (HD=6-7mm, JI = 66-67%). The consistency of brainstem contours (Fig. 2B) was best at the lowest energy of MonoCT datasets (median HD=2.8mm, JI=81%). In contrast, the contour conformity of the parotid glands (Fig. 2C) gained slightly from an increased energy (median HD reduction of 0.6mm, JI increase of 1%) and also led to better results as MR scans. For these OARs, using the most suitable MonoCT instead of SECT resulted in smaller interobserver variations. No relevant differences between SECT and MonoCT were determined for the other OARs, potentially due to their small volume.
The intra-observer TBV variability obtained on SECT did not depend on clinical experience. However, the contouring of less experienced clinicians is more affected by different image contrasts introduced by MonoCT of different energies (Fig. 2D).
Conclusion:
For postoperative brain-tumor patients, DECT-derived MonoCT datasets can improve the intra- and inter-observer delineation conformity compared to the currently used SECT. Moreover, they in part led to similar or better results as the gold standard MR. The most suitable image contrast to meet individual delineation requirements of anatomical structures can be chosen after CT acquisition. Future studies need to show whether the advantages can also be translated to other tumor entities and body regions.
  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Milano, Italia
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 133(2019), S559-S560
    DOI: 10.1016/S0167-8140(19)31432-X

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Permalink: https://www.hzdr.de/publications/Publ-28161
Publ.-Id: 28161


Glassy formation ability, magnetic properties and magnetocaloric effect in Al27Cu18Er55 amorphous ribbon

Li, L.; Xu, C.; Yuan, Y.; Zhou, S.
In this work, we have fabricated the Al27Cu18Er55 amorphous ribbon with good glassy formation ability by melt-spinning technology. A broad paramagnetic (PM) to ferromagnetic (FM) transition (second ordered) together with a large reversible magnetocaloric effect (MCE) in Al27Cu18Er55 amorphous ribbon was observed around the Curie temperature TC 11 K. Under the magnetic field change (DH of 0–7 T, the values of MCE parameter of the maximum magnetic entropy change (DSM max) and refrigerant capacity (RC) for Al27Cu18Er55 amorphous ribbon reach 21.4 J/kg K and 599 J/kg, respectively. The outstanding glass forming ability as well as the excellent magneto-caloric properties indicate that Al27Cu18Er55 amorphous could be a good candidate for low temperature magnetic refrigeration.
Keywords: Al27Cu18Er55 amorphous ribbon, Magnetocaloric effect, Magnetic properties, Magnetic refrigeration

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Permalink: https://www.hzdr.de/publications/Publ-28160
Publ.-Id: 28160


Range verification in proton therapy: Can prompt-gamma imaging identify the source of deviation?

Khamfongkhruea, C.; Janssens, G.; Petzoldt, J.; Smeets, J.; Pausch, G.; Richter, C.
Purpose/ Objective
In-vivo prompt-gamma imaging (PGI) is a promising method for directly assessing deviations in the proton range during proton therapy. However, several effects that can cause range shifts in patients need to be distinguished, e.g. global errors in CT conversion to stopping power ratio (SPR), variations in patient setup, and changes in the patient anatomy. Here, we evaluate if the source of range deviation in proton pencil-beam scanning (PBS) can be distinguished based on PGI information using a slit camera [1].
Material and Methods
For a virtual head-and-neck tumor in an anthropomorphic head phantom, a PBS treatment plan with simultaneous integrated boost (3 beams, 70Gy and 57Gy in 33 fractions) was generated. For all PBS spots in the investigated beam, PGI profiles were simulated using a verified analytical model of the slit camera [2, 3] for the reference scenario as well as for different error scenarios: SPR change of ±1.0, ±2.0 and ±3.5%, setup error in beam direction of ±1mm and ±3mm, and 10 scenarios of realistic anatomical changes (Fig. 1). A decision-tree approach was proposed to classify different groups of error sources. This included preceding filtering of PBS spots containing reliable PGI information for range verification. For simplification and better hypothesis generation, the head phantom was first overridden with water density. Afterwards, the real phantom anatomy including all heterogeneities was analyzed. It was evaluated whether the different error scenarios could be classified correctly.

Results
An automated filter to identify reliable PBS spots was developed, e.g. assuring that the spot position is within the effective field of view (FOV) of the camera and that the fall-off of the PGI profile is completely included in the FOV – even in case of range shifts. For subsequent decision-tree-based error source classification (Fig. 2), the following parameters were selected: The coefficient of determination (R2), the slope and intercept of the linear regression between range shift and penetration depth as well as the 2D range shift map. With this approach, 27 of 30 error scenarios could be identified correctly. However, the three error scenarios with anatomical changes in the nasal cavity could not be identified because the automated filtering approach had removed most relevant spots in this region.
Conclusion
An automated classification approach was introduced to identify the source for range deviation solely from prompt-gamma information. Based on phantom data, including simulation of realistic anatomical variation, the results are promising. Further refinement of this initial approach might be beneficial. An extension of the validation with patient CT data is in preparation. In the future, an application of the approach on clinically measured PGI data is planned. Also other classification methods could be evaluated.
  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Milano, Italia
  • Open Access Logo Abstract in refereed journal
    Radiotherapy and Oncology 133(2019), S296-S297
    DOI: 10.1016/S0167-8140(19)30986-7

Permalink: https://www.hzdr.de/publications/Publ-28159
Publ.-Id: 28159


Neutronen-Imaging von partikelbeladenen Schäumen

Heitkam, S.; Rudolph, M.; Lappan, T.; Sarma, M.; Eckert, S.; Trtik, P.; Lehmann, E.; Vontobel, P.; Eckert, K.
Die Flotation ist ein Trennverfahren mit großer industrieller Bedeutung, beispielsweise in der Gewinnung von Elementen aus Erzen. Dabei werden die Erze gemahlen und in Wasser suspendiert. Durch Zugabe geeigneter oberflächenaktiver Substanzen werden die gewünschten Partikel selektiv hydrophobisiert. Dadurch haften sie an eingebrachten Gasblasen an, werden an die Oberfläche transportiert und dort in sich bildenden Schaum eingelagert. Der Schaum wird abgezogen und man erhält gewünschte Partikel in hoher Konzentration.
Keywords: Neutron Imaging, Froth flotation
  • Lecture (Conference)
    Dechema Jahrestreffen, 06.03.2018, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28158
Publ.-Id: 28158


p-type co-doping effect in (Ga,Mn)As: Mn lattice location and magnetic phase transition

Xu, C.; Yuan, Y.; Wang, M.; Zhou, S.; Helm, M.
III-Mn-V based diluted magnetic semiconductors offer an opportunity to explore various aspects of carrier transport in the presence of cooperative phenomena [1]. In this work, we demonstrate the efficiency of an alternative approach to control the carrier state through involving one magnetic impurity Mn and one electrically active dopant Zn. Mn-doped and Zn co-doped GaAs films have been prepared by combining ion implantation and pulsed laser melting, followed by a systematic investigation on the magnetic and transport properties of (Ga,Mn)As by varying Mn concentration as well as by Zn co-doping. Changes of electrical, magnetic and magneto-transport behavior of the investigated (Ga,Mn)As were observed after co-doping with Zn. The changes are caused by interstitial Mn atoms which are transferred from substitutional sites or formation of Mn-Zn dimers.
Keywords: Dilute ferromagnetic semiconductor, ion implantation, co-doping, magnetic properties
  • Lecture (Conference)
    Deutsche Physikalische Gesellschaft 2018, 11.-16.03.2018, Berlin, Deutschland
  • Lecture (Conference)
    Ion Implantation and other Applications of Ions and Electrons 2018, 18.06.-21.11.2018, Kazimierz Dolny, Poland

Permalink: https://www.hzdr.de/publications/Publ-28157
Publ.-Id: 28157


Tracking of particles in froth using neutron imaging

Heitkam, S.; Lappan, T.; Eckert, S.; Trtik, P.; Eckert, K.
In this study, neutron imaging is employed to investigate the movement of hydrophobic particles in a rising froth column. A cylindrical batch-flotation cell is mounted to a rotary stage, allowing for three-dimensional analysis. Gadolinium particles of 200 μm diameter are hydrophobized and floated by means of small air bubbles. The generated froth is investigated by neutron imaging. Using particle-tracking and a reconstruction algorithm for the third dimension, the movement of particles in the froth is analyzed. Varying the concentration of the frother sodium oleate, different froth stabilities are compared. It has been found, that with decreasing froth stability bubble rupture leads to higher horizontal diffusion of particles and to higher agglomeration of particles.
Keywords: Froth, Particle laden Foam, Particle Tracking, Neutron Radiography, Neutron Imaging

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  • Secondary publication expected from 17.04.2020

Permalink: https://www.hzdr.de/publications/Publ-28156
Publ.-Id: 28156


All-optical structuring of laser-driven proton beam profiles

Obst-Hübl, L.ORC; Ziegler, T.ORC; Brack, F.-E.; Branco, J.; Bussmann, M.; Cowan, T. E.; Curry, C. B.; Fiuza, F.; Garten, M.; Gauthier, M.; Göde, S.; Glenzer, S. H.; Huebl, A.; Irman, A.; Kim, J. B.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Pausch, R.; Prencipe, I.; Rehwald, M.; Rödel, C.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.
Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact MeV proton accelerators with unique bunch characteristics. Yet, direct control of the proton beam profile is usually not possible. Here we present a readily applicable all-optical approach to imprint detailed spatial information from the driving laser pulse onto the proton bunch. In a series of experiments, counter-intuitively, the spatial profile of the energetic proton bunch was found to exhibit identical structures as the fraction of the laser pulse passing around a target of limited size.
Such information transfer between the laser pulse and the naturally delayed proton bunch is attributed to the formation of quasi-static electric fields in the beam path by ionization of residual gas. Essentially acting as a programmable memory, these fields provide access to a higher level of proton beam manipulation.
Keywords: laser plasma interaction, laser particle acceleration, novel accelerator concepts, high performance computing, high power lasers
Related publications
All-optical structuring of laser-driven proton beam … (Id 28136) HZDR-primary research data are used by this publication
  • Open Access Logo Nature Communications 9(2018), 5292
    DOI: 10.1038/s41467-018-07756-z
  • Lecture (Conference)
    Advanced Accelerator Concepts Workshop 2018, 13.-17.08.2018, Breckenridge, USA
  • Poster
    Advanced Accelerator Concepts Workshop 2018, 13.-17.08.2018, Breckenridge, USA
  • Lecture (Conference)
    Matter and Technologies Annual Meeting, 12.-14.06.2018, Berlin, Deutschland
  • Lecture (Conference)
    Matter and Technology Meeting, 06.03.2019, Jena, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-28155
Publ.-Id: 28155


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