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34118 Publications

Expression of ecto-nucleoside triphosphate diphosphohydrolases-2 and -3 by the enteric nervous system impacts inflammation in experimental colitis and Crohn’s disease

Feldbrügge, L.; Moss, A. C.; Yee, E. U.; Csizmadia, E.; Mitsuhashi, S.; Longhi, M. S.; Stephan, H.; Wu, Y.; Cheifetz, A. S.; Müller, C. E.; Sevigny, J.; Robson, S. C.; Jiang, Z. G.

Abstract
Background & Aims: Recent studies have suggested that the enteric nervous system can modulate gut immunity. Ecto-nucleoside triphosphate diphosphohydrolases (E-NTPDases) of the CD39 family regulate purinergic signaling by sequential phosphohydrolysis of extracellular ATP, a pro-inflammatory signaling molecule. Herein, we test the hypothesis that E-NTPDases modulate neuro-immune crosstalk in gut inflammation.
Methods: We determined expression patterns of NTPDase-2 and NTPDase-3 in murine and human colon. Experimental colitis was induced by dextran sodium sulfate (DSS) in mice deficient in NTPDase-2 or NTPDase-3. We compared plasma ADPase activity from Crohn’s patients to healthy controls, and correlated levels of ADPase activity with Crohn’s disease activity.
Results: NTPDase-2 and 3 were mainly expressed in cells of the enteric nervous system in both murine and human colon. When compared to wild type, DSS-induced colitis was exacerbated in NTPDase-2 null mice, as measured by both clinical disease activity and histology, while NTPDase-3 null mice merely developed more severe anemia. Colonic macrophages isolated from NTPDase-2 null mice displayed a more pro-inflammatory phenotype compared to wild type. Crohn’s patients had decreased plasma ADPase activity when compared to healthy controls. The enzyme activity sensitive to an inhibitor against NTPDase-2 and NTPDase-3 showed the most striking difference and was inversely correlated with Crohn’s disease activity.
Conclusions: NTPDase-2 and 3 are ecto-enzymes expressed in the enteric nervous system in both murine and human colon, and are protective against gut inflammation in experimental colitis and exhibit alterations in human Crohn’s disease. These observations suggest that purinergic signaling modulated by non-CD39 NTPDases governs neuro-immune interactions that are relevant in Crohn’s disease.

Keywords: Crohn’s disease; ectonucleotidase; CD39; NTPDase-2 (CD39L1); NTPDase-3 (CD39L3)

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Permalink: https://www.hzdr.de/publications/Publ-25398
Publ.-Id: 25398


Speciation of uranium(VI) in the presence of cellulose degradation products

Brinkmann, H.; Moll, H.

Low and intermediate level waste contain cellulosic material in considerable amounts. In a repository nuclear waste is often surrounded by cementitious backfill material. If water ingresses a hyperalkaline environment will be established. Since cellulose will be relatively fast degraded under alkaline conditions, there is a high risk that small organic, water soluble molecules will be formed. These molecules can act as complexing agents for radionuclides and thereby affecting their sorption behavior and solubility adversely. Therefore the focus of current investigations is on the interaction of uranium (VI) with Isosaccharinic acid (ISA) as main degradation product of cellulose first in the acidic pH range. The progress and results of these studies within the MIND project (work package 1) will be presented.

Keywords: Cellulose; Isosaccharinic acid; Uranium; Speciation

  • Lecture (others)
    MIND Project Annual Meeting 2017, 03.-05.05.2017, Prague, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-25397
Publ.-Id: 25397


The redistribution of platinum-group elements and platinum-group minerals in the weathered chromitites of the Lower and Middle Group chromitites of the Bushveld Complex and the mineralogical siting of Ru

Junge, M.; Bachmann, K.; Kotzé, E.; Oeser-Rabe, M.

The chromitite seams of the Lower Group (LG) and Middle Group (MG) of the Bushveld Complex in South Africa contain elevated Pt and Pd concentrations. So far, only limited work has been done on the distribution of platinum-group elements (PGE) and platinum-group minerals (PGM) in these ores. In particular, the knowledge about the effects of weathering of PGM and the redistribution of PGE in these ores are rare. Previous studies showed that the main PGM are PGE-sulfides (cooperite-braggite, malanite, laurite), followed by PGE-sulfarsenides, sperrylite and Pt-Fe alloys. During weathering PGM are largely destroyed and only relict PGM are observed. Platinum-group minerals are weathered along small cracks and neo-formation of PGM may take place. Additionally, the mineralogical siting of Ru within chromitites is studied here. It was shown by LA-ICP-MS work that chromite can host some 100s-ppb of Ru.

  • Contribution to proceedings
    14th Biennial SGA Meeting, 20.-23.08.2017, Québec City, Canada
    SGA Québec 2017 Mineral Resources to Discover

Permalink: https://www.hzdr.de/publications/Publ-25396
Publ.-Id: 25396


Synthesis and in vitro evaluation of 5-substituted benzovesamicol analogs containing N-substituted amides as potential positron emission tomography tracers for the vesicular acetylcholine transporter

Roslin, S.; de Rosa, M.; Deuther-Conrad, W.; Eriksson, J.; Odell, L. R.; Antoni, G.; Brust, P.; Larhed, M.

Herein, new ligands for the vesicular acetylcholine transporter (VAChT), based on a benzovesamicol scaffold, are presented. VAChT is acknowledged as a marker for cholinergic neurons and a positron emission tomography tracer for VAChT could serve as a tool for quantitative analysis of cholinergic neuronal density. With an easily accessible triflate precursor, aminocarbonylations were utilized to evaluate the chemical space around the C5 position on the tetrahydronaphthol ring. Synthesized ligands were evaluated for their affinity and selectivity for VAChT. Small, preferably aromatic, N-substituents proved to be more potent than larger substituents. Of the fifteen compounds synthesized, benzyl derivatives (±)-7i and (±)-7l had the highest affinities for VAChT. Compound (±)-7i was chosen to investigate the importance of stereochemistry for binding to VAChT and selectivity toward the σ1 and σ2 receptors. Enantiomeric resolution gave (+)-7i and (-)-7i, and the eutomer showed seven times better affinity. Although racemate (±)-7i was initially promising, the affinity of (-)-7i for VAChT was not better than 56.7nM which precludes further preclinical evaluation. However, the nanomolar binding together with the ready synthesis of [11C]-(±)-7i shows that (-)-7i can serve as a scaffold for future optimizations to provide improved 11C-labelled VAChT PET tracers.

Keywords: Vesicular acetylcholine transporter; VAChT; PET tracer; Aminocarbonylation; 11C-labeling

Permalink: https://www.hzdr.de/publications/Publ-25395
Publ.-Id: 25395


Evaluation of hemodynamic impairments in unilateral high-grade carotid artery stenosis patients and healthy age-matched participants

Kaczmarz, S.; Göttler, J.; Griese, V.; Petr, J.; Zimmer, C.; Sorg, C.; Preibisch, C.

Objectives:
Internal carotid-artery stenosis (ICAS) is a major public health issue, as it accounts for approximately 20% of all strokes1. However, related complex hemodynamic impairments are not well understood2. We therefore propose a multimodal MRI-protocol. The major aims were to evaluate its reliability and investigate physiological changes.
Methods:
In the ongoing clinical study, 52 subjects (29 healthy controls: 70.3±4.7y, 13 males; 23 patients with asymptomatic unilateral ICAS, NASCET>70%: 70.5±6.8y, 15 males) underwent MRI on a Philips 3T-Ingenia. We propose a combination of three different MR-based methods, accounting for cerebrovascular reactivity (CVR) by breathhold-fMRI (voxelsize 3x3x3mm3, 38 slices, TE/TR=30ms/1200ms, acq.time=5:48min), CBF by pCASL (3D-readout, voxelsize 2.7x2.8x6mm3, 16 slices, TE/TR=7.4ms/4403ms, label duration=1800ms, PLD=2000ms, acq.time 5:43min) and relative oxygen extraction fraction (rOEF) by a multi-parametric quantitative-BOLD approach3 (voxelsize 2x2x3mm3, 30 slices). For each participant, individual masks of watershed areas were defined for both hemispheres in grey-matter and mean values of all three modalities were compared.
Results:
In healthy participants, our results show no significant lateralization of all three modalities on a group level. For ICAS-patients, regionally reduced CVR (p=0.003) as well as hypoperfusion (p< 0.001) were found ipsilateral to the stenosis (figure). In accordance with the literature, we did not find ICAS-induced changes in oxygen extraction on a group level (p=0.310).4 Even though focal rOEF increases could be suspected in single patients.
Conclusions:
The presented preliminary results thus imply successful application of our multimodal-MRI approach and are highly promising with respect to gaining a deeper insight into ICAS-related physiological changes. Further investigations of the relations between the parameters are currently in progress.

  • Open Access Logo Contribution to proceedings
    28rd International Symposium on Cerebral Blood Flow, Metabolism and Function, 01.04.2017, Berlin, Germany
    Proceedings of the 28rd International Symposium on Cerebral Blood Flow, Metabolism and Function, 498
  • Poster
    28rd International Symposium on Cerebral Blood Flow, Metabolism and Function, 01.04.2017, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-25394
Publ.-Id: 25394


The Common Data Acquisition Platform in the Helmholtz Association

Kaever, P.; Balzer, M.; Kopmann, A.; Zimmer, M.; Rongen, H.

Various centres of the German Helmholtz Association (HGF) started in 2012 to develop a modular data acquisition (DAQ) platform, covering the entire range from detector readout to data transfer into parallel computing environments. This platform integrates generic hardware components like the multi-purpose HGF-Advanced Mezzanine Card or a smart scientific camera framework, adding user value with Linux drivers and board support packages. Technically the scope comprises the DAQ-chain from FPGA-modules to computing servers, notably frontend-electronics-interfaces, microcontrollers and GPUs with their software plus high-performance data transmission links. The core idea is a generic and component-based approach, enabling the implementation of specific experiment requirements with low effort. This so called DTS-platform will support standards like MTCA.4 in hard- and software to ensure compatibility with commercial components. Its capability to deploy on other crate standards or FPGA-boards with PCI express or Ethernet interfaces remains an essential feature. Competences of the participating centres are coordinated in order to provide a solid technological basis for both research topics in the Helmholtz Programme "Matter and Technology", "Detector Technology and Systems" and "Accelerator Research and Development". The DTS-platform aims at reducing costs and development time and will ensure access to latest technologies for the collaboration. Due to its flexible approach, it has the potential to be applied in other scientific programs.

Keywords: Data acquisition concepts; Software architectures (event data models, frameworks and databases); Detector control systems (detector and experiment monitoring and slow-control systems, architecture, hardware, algorithms, databases); Image reconstruction in medical imaging

  • Contribution to proceedings
    Topical Workshop on Electronics for Particle Physics (TWEPP2016), 26.-30.09.2016, Karlsruhe, Deutschland
    Journal of Instrumentation 12(2017),C04004: IOPscience
    DOI: 10.1088/1748-0221/12/04/C04004

Permalink: https://www.hzdr.de/publications/Publ-25393
Publ.-Id: 25393


Electronic Structure Simulation of Thin Silicon Layers: Impact of Orientation, Confinement, and Strain

Joseph, T.; Fuchs, F.; Schuster, J.; Schulz, S. E.

Fully Depleted Silicon on Insulator transistors (FDSOI) are a promising approach for further scaling. The device features a fully depleted body which is isolated by an insulator box. This introduces better electrostatics, lower leakage current and thus better channel control. The device performance is heavily influenced by the orientation, confinement and strain in the ultra-thin body. In this work the electronic structure of ultra-thin silicon layers is investigated using Density Functional Theory (DFT). The simulation parameters for the model system were calibrated to reproduce the experimental band gap of bulk silicon. This ensures that the model describes the electronic structure of ultra-thin silicon layers accurately. Our study demonstrates the impact of confinement, orientation and strain on material dependent transport properties and their influence on the device performance. For this purpose our results will be used as an input for device simulations using Synopsys Sentaurus TCAD.
We find that the band gap of the silicon layer increases with decreasing slab thickness which is a clear indication of quantum confinement. From the simulation, the band gap for the {100} confinement is found to be higher than {110} and {111} scenarios. Band gap is one of the factors which influence the intrinsic carrier in the semiconductor and thereby the transport. Another important factor for the transport is lattice strain. Strain is a useful method for modulating band structures. One good example is the transformation of direct band gap in {100} confined silicon slab to indirect band gap with 2 % biaxial compression. In our presentation we will discuss the influence of the effective mass as well. Furthermore, the strain dependence of the electronic structure and its impact on device properties is analyzed systematically.

Keywords: silicon; confinement; density functional theory; FDSOI; strain engineering

  • Poster
    Material for Advanced Metallization (MAM), 26.-29.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25392
Publ.-Id: 25392


Simulation of Reconfigurable Field-effect Transistors: Impact of the NiSi2-Si Interfaces, Crystal Orientation, and Strain

Fuchs, F.; Schuster, J.; Gemming, S.

Reconfigurable transistors (RFETs) can be switched between electron and hole current by changing the polarity of the gate potential. This allows a much higher functionality and hence, logic operations can be realized with fewer transistors. The device performance of such a transistor is strongly dominated by the contact physics.
In this work, the electron transport across the NiSi 2 -Si interface is studied using the NEGF formalism and density functional theory, which allows us to consider the atomic structure of the interface. A new model is then presented which relates the electron transport through the interface to the transfer characteristic of an RFET. The model is compared to experimental data, which shows very good agreement, especially with respect to the ratio between electron and hole current (left figure).
Based on the model, different structure variations at the interface and their consequences on the device performance are discussed. It is demonstrated that best symmetry between electron and hole current is achieved for the <110> crystal orientation, which is much worse for <100> orientation (right figure). This makes the <110> orientation advantageous for RFETs. Also the influence of strain generated parallel to the interface plane is investigated (right figure). It is shown that strain can be used to tune the symmetry in case of <110> crystal orientation even further. This is entirely different for the <100> crystal orientation, where the highest electron currents are observed for all strain states. In this state, the electron currents are about three orders of magnitude higher than the hole currents. A detailed discussion of these differences based on work function and band structure analysis will be given in our contribution.

Keywords: reconfigurable transistor; RFET; density functional theory; metal-semiconductor interface

  • Lecture (Conference)
    Material for Advanced Metallization (MAM), 26.-29.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25391
Publ.-Id: 25391


NiSi2-Si interfaces as building blocks for reconfigurable field-effect transistors: from the atomic structure to device characteristics

Fuchs, F.; Schuster, J.; Gemming, S.

The electron transport across metal-semiconductor interfaces is crucial for the functionality of reconfigurable field-effect transistors, which can be switched between electron and hole current. Devices were already fabricated experimentally, however, a profound understanding of the underlaying mechanism is not yet available.
This study focuses on the NiSi2-Si interface, which is studied using the NEGF formalism. Based on the calculated transmission spectra, the transfer characteristic of a reconfigurable transistor is obtained using a simplified approach. Even though this model strongly simplifies the electrostatic environment in a transistor, very good agreement with experimental devices is demonstrated. The impact of strain on the device characteristic is studied as well. It is shown that the magnitude of electron and hole current can be altered successfully. They can also be tuned to be symmetric, which fits to experimental observations. Finally, new insight into the device functionality is gained based on our calculations of the work functions and effective masses of the isolated NiSi 2 and Si.

Keywords: reconfigurable transistor; RFET; density functional theory; metal-semiconductor interface

  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25390
Publ.-Id: 25390


Phage display – a new tool for the recovery of valuable metals from primary and secondary resources

Matys, S.; Lederer, F.; Schönberger, N.; Braun, R.; Lehmann, F.; Flemming, K.; Bachmann, S.; Curtis, S.; Macgillivray, R.; Pollmann, K.

The development of effective and ecofriendly processes for the recovery of critical elements poses a challenge for scientists all over the world. A novel approach is the generation of highly specific peptides that bind with high affinity to individual elements of interest. The peptides are selected by phage surface display (PSD) technology. In this study PSD technology has been applied in two different approaches. The focus of the first approach was the identification of peptides that bind specifically to special particles of interest that are part of electronic scrap aiming towards the development of new recycling processes. In the second approach metal ion binding peptides were isolated via PSD to use them for the targeted removal and enrichment of these elements from complex leaching solutions or from industrial waters. To address the economic production of peptides, the development of a new expression system is also part of this study.

Keywords: bacteriophage; biosorption; bioflotation; fluorescent phosphors; Ga-; Co-; Ni-ions; heterologous peptide expression

  • Open Access Logo Solid State Phenomena 262(2017), 443-446
    DOI: 10.4028/www.scientific.net/SSP.262.443
  • Lecture (Conference)
    22. International Biohydrometallurgy Symposium, 24.-27.09.2017, Freiberg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-25389
Publ.-Id: 25389


PET imaging of α7 nicotinic acetylcholine receptors in a heterotopic xenograft model of brain cancer

Deuther-Conrad, W.; Neuber, C.; Teodoro, R.; Kranz, M.; Belter, B.; Peters, D.; Pietzsch, J.; Brust, P.

Objectives
Molecular imaging by means of PET supports both the molecular profiling of tumors and the validation of corresponding targeted therapies in cancer treatment. The intracellular pathways triggered by nicotinic acetylcholine receptors (nAChR) mediate carcinogenic effects related to tobacco-derived compounds as well as autocrine and paracrine stimulation. In particular the α7 nAChR is of significance for the pathogenesis of cancers and may have potential for novel therapeutic concepts. Accordingly, we investigated with the in-house developed α7 nAChR-specific radioligand [18F]NS10743 the expression of α7 nAChR in the heterotopic U87-MG xenograft mouse model of glioblastoma.
Methods
Subcutaneous U87-MG tumor xenografts were generated in female NMRI nu/nu mice. [18F]NS10743 was obtained by automated radiosynthesis [1]. All animals were scanned in a nanoScan® PET/MRI system for 60 min post injection of [18F]NS10743 under control (n=5) and blocking (n=4) conditions (2 mg/kg NS6740 i.p. 15 min before the radioligand) on two consecutive days. Volumes of interest (VOI) were identified from the co-registered MR images (brain, tumor, and muscle) or from the first frame of the PET images (vena cava). Data analysis was based on the calculation of standardized uptake values (SUVs) and the shape of the time-activity curves (TACs). Intratumoral heterogeneity has been addressed by an additional VOI using a 75%-SUVmax isocontour in the control scans. Perfusion was assessed by Hoechst 33342, and autoradiography, fluorescence microscopy, and immunohistochemistry studies were performed ex vivo.
Results
Within 3-4 weeks after implantation of U87-MG cells, the longest axis of the tumor xenograft reached 5-10 mm. Dynamic PET scans, performed after i.v. administration of 6-12 MBq [18F]NS10743 (7-65 GBq/µmol at time of injection), revealed moderate uptake in the tumor with SUVmax of 0.91±0.16 at 40 min p.i. and tumor-to-muscle ratios of 0.93±0.08 at 60 min p.i. The individual tumor TACs are consistent regarding shape with relatively slow increase in the uptake of activity. NS6740 pre-blocking significantly reduced the activity uptake in the tumor (SUVmax=0.65±0.10; p<0.05).
Conclusions
Dynamic PET with [18F]NS10743 was able to detect α7 nAChR in the subcutaneous U87-MG mouse xenograft model of glioblastoma. The suitability of this approach for detection of α7 nAChR-expressing tumors in the brain remains to be investigated.
References
[1] R. Teodoro et al., Appl Radiat Isot, 2014, 95c,76-84

Keywords: molecular characterisation; glioblastoma; xenograft; U87; alpha7 nicotinic acetylcholine receptor; molecular imaging; PET; [18F]NS10743; microPET; sequential PET/MRI

  • Poster
    22nd International Symposium on Radiopharmaceutical Sciences, 14.-19.05.2017, Dresden, Deutschland
  • Open Access Logo Abstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 60(2017)1, 165
    DOI: 10.1002/jlcr.3508

Permalink: https://www.hzdr.de/publications/Publ-25388
Publ.-Id: 25388


Engineering the Electronic Properties of Two-Dimensional Transition Metal Dichalcogenides by Introducing Mirror Twin Boundaries

Komsa, H.-P.; Krasheninnikov, A. V.

Grain boundaries in 2D materials can have marked influence on the material properties. The effects can be not only detrimental, but also beneficial in transition metal dichalcogenides (TMDs), so that controlling the density and type of the boundaries in these systems should be important for engineering their properties. However, this is often possibly only during the growth stage. Molybdenum and tungsten dichalcogenides feature a particular set of 60° mirror twin boundaries, which are reported to occur upon merging of the growing flakes, to appear during growth to accommodate for the nonstoichiometry of the sample, or to be produced a posteriori by electron irradiation or thermal annealing. Furthermore, different preparation conditions lead to different atomic structure of the boundary, which consequently exhibit different electronic properties. This has obviously garnered interest for the ability to control grain boundary types and densities. In this progress report, the recent experimental and theoretical work related to the characterization of mirror twin boundaries is reviewed. A consistent set of formation energies for the mirror twin boundaries is provided, which then allows a coherent picture on the formation mechanisms under different conditions to be drawn. Finally, the electronic structure of these boundaries is analyzed and their potential applications are discussed.

Keywords: 2D materials; first principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-25387
Publ.-Id: 25387


Atomic defects and doping of monolayer NbSe2

Nguyen, L.; Komsa, H.-P.; Khestanova, E.; Kashtiban, R.; Peters, J. P.; Lawlor1, S.; Sanchez, A. M.; Sloan, J.; Gorbachev, R.; Grigorieva, I.; Krasheninnikov, A. V.; Haigh, S. J.

We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

Keywords: graphene; 2D materials; TEM; first-principles calculations

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Permalink: https://www.hzdr.de/publications/Publ-25386
Publ.-Id: 25386


EDTA and DTPA as scaffolds for successful Ln3+/An3+ separations from spent nuclear fuel

Langford-Paden, M. H.; Andrews, M. B.; Swinburn, A. N.; Alker, A.; Beal, K.; Anuar, N. S. B. K.; Knight, M. E.; Jones, J. E.; Beele, B.; Adam, C.; Panak, P.; Geist, A.; Kaden, P.; Natrajan, L. S.

Multi-dentate ligands are instrumental to extraction and separations chemistry associated with nuclear fuel reprocessing. Specifically, the TALSPEAK (Trivalent Actinide Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexations) process utilises DTPA to facilitate the separation of minor actinides, MA3+ (Am3+ and Cm3+), from Ln3+ and Y3+, allowing the MA3+ to be reprocessed further by transmutation. The TALSPEAK process involves the preferential extraction of the major component (Ln3+) into the organic phase using HDEHP, while the DTPA-derived ligands remain in the aqueous phase coordinating MA3+ which favour soft donor interactions. The process requires the use of lactic acid as a buffer to maintain pH 3.6 in order to prevent the precipitation of DTPA complexes at low pH, commonly experienced during the processing cycle. Amino acid conjugates derived from EDTA and DTPA present ideal candidates as self-buffering DTPA/EDTA ligands, therefore removing the need for lactic acid in the TALSPEAK process. The ligands (right) produce an internal buffer pH 1.5-2.5 at μM to mM concentrations. The synthesis, coordination chemistry, photophysical properties and separation behaviour of these new ligands and stability towards ionising radiation is presented.

Keywords: Lanthanide(III); Actinide(III); amino acids; DTPA

  • Poster
    ThUL School in Actinide chemistry 2016, 19.-23.09.2016, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25385
Publ.-Id: 25385


Two-dimensional MoS2 under ion irradiation: from controlled defect production to electronic structure engineering

Ghorbani-Asl, M.; Kretschmer, S.; Spearot, D. E.; Krasheninnikov, A. V.

Two-dimensional (2D) transition metal dichalcogenides (TMDs), like MoS2, have unique electronic and optical properties, which can further be tuned using ion bombardment and post-synthesis ion-beam mediated methods combined with exposure of the irradiated sample to precursor gases. The optimization of these techniques requires a complete understanding of the response of 2D TMDs to ion irradiation, which is affected by the reduced dimensionality of the system. By combining analytical potential molecular dynamics with first-principles calculations, we study the production of defects in free-standing MoS2 sheets under noble gas ion irradiation for a wide range of ion energies when nuclear stopping dominates, and assess the probabilities for different defects to appear. We show that depending on the incident angle, ion type and energy, sulfur atoms can be sputtered away predominantly from the top or bottom layers, creating unique opportunities for engineering mixed MoSX compounds where X are chemical elements from group V or VII. We study the electronic structure of such systems, demonstrate that they can be metals, and finally discuss how metal/semiconductor/metal junctions, which exhibit negative differential resistance, can be designed using focused ion beams combined with the exposure of the system to fluorine.

Keywords: Two-dimensional materials; ion irradiation; atomistic simulations; defects

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Permalink: https://www.hzdr.de/publications/Publ-25384
Publ.-Id: 25384


Radiosynthesis of (S)-[18F]T1: The first PET radioligand for molecular imaging of α3β4 nicotinic acetylcholine receptors

Sarasamkan, J.; Fischer, S.; Deuther-Conrad, W.; Ludwig, F.-A.; Scheunemann, M.; Arunrungvichian, K.; Vajragupta, O.; Brust, P.

Recent pharmacologic data revealed the implication of α3β4 nicotinic acetylcholine receptors (nAChRs) in nicotine and drug addiction. To image α3β4 nAChRs in vivo, we aimed to establish the synthesis of a [18F]-labelled analog of the highly affine and selective α3β4 ligand (S)-3-(4-(4-fluorophenyl)-1H-1,2,3-triazol-1-yl)quinuclidine ((S)-T1). (S)-[18F]T1 was synthesized from ethynyl-4-[18F]fluorobenzene ([18F]5) and (S)-azidoquinuclidine by click reaction.
After a synthesis time of 130 min (S)-[18F]T1 was obtained with a radiochemical yield (non-decay corrected) of 4.3 ± 1.3%, a radiochemical purity of > 99% and a molar activity of > 158 GBq/µmol. The brain uptake and the brain-to-blood ratio of (S)-[18F]T1 in mice at 30 min post injection were 2.02 (SUV) and 6.1, respectively.
According to an ex-vivo analysis, the tracer remained intact (> 99%) in brain. Only one major radiometabolite was detected in plasma and urine samples. In-vitro autoradiography on pig brain slices revealed binding of (S)-[18F]T1 to brain regions associated with the expression of α3β4 nAChRs, which could be reduced by the α3β4 nAChR selective drug AT-1001. These findings make (S)-[18F]T1 a potential tool for the non-invasive imaging of α3β4 nAChRs in the brain by PET.

Keywords: α3β4 Nicotinic acetylcholine receptor; Click reaction; Drug addiction; Positron emission tomography; [18F]-Radioligand (S)-[18F]T1; Radiofluorination

Permalink: https://www.hzdr.de/publications/Publ-25383
Publ.-Id: 25383


Heating, Ionization and Magnetic Instability in Short Pulse High Power Laser-Solid Target Interactions

Huang, L. G.; Kluge, T.; Schlenvoigt, H.-P.; Metzkes, J.; Cowan, T.

During short pulse high power laser solid matter interactions, a significant fraction of laser pulse energy is absorbed to generate an intense beam of fast electrons with relativistic kinetic energies near the critical density surface. The transport of the intense fast beam into the solid target is of fundamental importance to many complex dynamics such as plasma oscillation, heating, ionization, instability, electric field and magnetic field generation, photon emission and so on. In the talk, we will present the ultrafast plasma dynamics for ion heating in buried layer targets[1], bulk electron heating [2], collisional ionization [2,3], transport instability and quasistatic magnetic generation from PIC simulations.
In order to connect the complex plasma dynamics seen in PIC simulations with experiments, we will discuss the role of insitu synthetic diagnostics that mimic experimental diagnostics. As one key example we propose to use XRay Free Electron Lasers for probing the density modulations in the bulk target by small angle Xray scattering which allows for femtosecond and nanometer resolution of transient plasma processes. We will also discuss the feasibility to probe selfgenerated MegaGauss magnetic fields associated with the transport instability of the laser accelerated hot electrons using Faraday rotation method. With these techniques, probing fundamental plasma properties will allow for direct comparison to simulations, challenging state of the art theoretical modeling of collisions, ionizations and so on.
[1] L. G. Huang, M. Bussmann, T. Kluge, A. L. Lei, W. Yu, and T. E. Cowan, Phys. Plasmas 20, 093109 (2013).
[2] L. G. Huang, T. Kluge, and T. E. Cowan, Phys. Plasmas 23, 063112 (2016).
[3] T. Kluge, M. Bussmann, H.K.Chung, C. Gutt, L. G. Huang, M. Zacharias, U. Schramm, and T. E. Cowan, Phys.Plasmas 23, 033103 (2016).

Keywords: high power laser; XFEL; solid target; heating; ionization; magnetic instability

  • Lecture (Conference)
    Workshop: High Intensity Laser Matter Science at the HED Instrument at the European XFEL, 05.-06.04.2017, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-25382
Publ.-Id: 25382


Coordination Chemistry of Uranium (U(IV) and -(VI)) with Bidentate N-donor Ligands, 2,2’-Bipyridine and 1,10-Phenanthroline

März, J.; Schöne, S.; Radoske, T.; Patzschke, M.; Stumpf, T.; Ikeda-Ohno, A.

Because of their remarkable stability towards a wide variety of transition metals1, 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. The coordination chemistry of uranium (U) with these N-donor ligands has been also explored primarily for its hexavalent state (U(VI) as UO22+), whilst much less attention has been paid for the lower oxidation states, such as tetravalent (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.
We succeeded to obtain a series of U(IV) complexes with the U:ligand ratio of 1:1 and 1:2, all showing the eight-fold coordination geometry of the uranium centre. In addition to the ligand, chloro and methanolato ligands are also 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, as shown in the right of Fig. 1, dinuclear uranyl arrangements with hydroxo-brinding are dominated in the media with higher pH. As illustrated in Fig. 1, bipy and phen are forming isostructural complexes both with U(IV) and- (VI). The electronic structure of the complexes is further studied by quantum chemical calculations.

Keywords: Coordination chemistry; Actinides; Uranium; N-donor ligands

  • Lecture (Conference)
    Actinides, 09.-14.07.2017, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-25381
Publ.-Id: 25381


Interaction of Tetravalent Actinides (An(IV)) with Mixed N/O-Donor Imine Type Ligands

Radoske, T.; März, J.; Kaden, P.; Walter, O.; Weigand, J. J.; Stumpf, T.; Ikeda-Ohno, A.

Because of their unique electronic properties originating from 5f-orbitals, the coordination chemistry of actinides (An) is still an attractive research field in terms not only of nuclear engineering but also of basic chemistry. In particular, the early An show profound complex chemistry due to a wide variety of possible oxidation states ranging from +II to +VII, which is in contrast to the dominant trivalent state for their chemical analog of lanthanides. The aim of our research activities is to gain knowledge about the interaction of An with a variety of hard- and soft-donor ligands, eventually providing a comprehensive understanding of the electronic nature of actinide compounds. To this end, the focus of this study lies on the characterization of Th(IV) and U(IV) complexes with the imine ligand salen and its derivative (Figure 1). The ligands possess both O- (i.e. hard) and N-donor (soft) groups in the structure, which could be also considered as a simplified model of naturally relevant organic O-/N-donor ligands.

Results and Discussion
A series of single crystals of the U(IV)-salen complexes were obtained as a function of M:L ratio and pH by liquid-liquid diffusion methods. SC-XRD measurements on the obtained crystals revealed the new crystal structures, all showing the eight-fold coordination of the U centre with a trigonal dodecahedral geometry with the ligands on the primary coordination sphere of U.
UV-visible absorption measurements of U(IV)-salen solution as a function of M:L ratio indicate the existence of two independent solution species in the system, assigning as the U(IV)-salen complexes with the M:L ratios of 1:1 and 1:2. 1H-NMR spectra of the dissolved complex [UIV(Le)2] and the pure ligand in solution were recorded. All expected multiplets of the complex can be clearly identified and confirm complexation. The spectra also showed a significant high-field shift due to proximity of the paramagnetic uranium(IV) centre, indicating that the metal is positioned at the centre of the coordination polyhedron formed by the two ligand molecules.

Keywords: Actinides; Uraniun; Thorium; Salen; Imine; Ligand; Complex

  • Lecture (Conference)
    Actinides 2017, 09.-14.07.2017, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-25380
Publ.-Id: 25380


Uranium(V) incorporation mechanisms and stability in Fe(II)/Fe(III) iron (oxyhydr)oxides

Roberts, H. E.; Morris, K.; Law, G. T. W.; Mosselmans, J. F. W.; Bots, P.; Kvashnina, K.; Shaw, S.

Understanding the interactions between radionuclides and mineral phases underpins site environmental clean-up and waste management in the nuclear industry. The transport and fate of radionuclides in many subsurface environmental systems are controlled by adsorption, redox and mineral incorporation processes. Interactions of iron (oxyhydr)oxides with uranium have been extensively studied due to both the abundance of uranium as an environmental contaminant and the ubiquity of iron (oxyhydr)oxides in engineered and natural environments. Despite this, detailed mechanistic information regarding the incorporation of uranium into Fe(II) bearing magnetite and green rust is sparse. Here, we present a co-precipitation study where U(VI) was reacted with environmentally relevant iron(II/III) (oxyhydr)oxide mineral phases. Based on diffraction, microscopic and spectroscopic evidence, we propose the reduction of U(VI) via a one electron transfer to U(V) and stabilisation of the U(V) by incorporation during co-precipitation with iron (oxyhydr)oxides. U(V) was stable in both magnetite and green rust structures and incorporated via substitution for octahedrally coordinated Fe in a uranate-like coordination environment. As the Fe(II)/Fe(III) ratio increased, a proportion of U(IV) was also precipitated as surface associated UO2. These novel observations have significant implications for the behaviour of uranium within engineered and natural environments.

Keywords: Uranium; Magnetite; Green Rust; Incorporation; Environmental fate

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Permalink: https://www.hzdr.de/publications/Publ-25379
Publ.-Id: 25379


Vortex dynamics in disks with tailored magnetisations: from single frequency to multiple frequencies

Ramasubramanian, L.; Fowley, C.; Kákay, A.; Yildirim, O.; Matthes, P.; Lindner, J.; Fassbender, J.; Gemming, S.; Schulz, S. E.; Deac, A. M.

The fundamental oscillation mode of magnetic vortices in thin-film elements has recently been proposed for designing spin-torque-driven nano-oscillators [1]. Commercial applications require tuning of the output frequency by external parameters, such as applied fields or spin-polarized currents. However, the tunability of vortex-based devices is limited, since the gyrotropic frequency is specific to the individual sample design. Indeed, the fundamental frequency is known to be determined by the saturation magnetisation, M_s , as well as the geometrical confinement of the magnetisation e.g. the diameter and height of a magnetic disk [2, 3]. Micromagnetic simulations [4] have shown that if regions with different saturation magnetisation can be induced in a magnetic disk, multiple precession frequencies can be generated. Ion implantation is a promising method to fabricate such devices [5].
To study the formation of magnetic vortices with respect to size and thickness, disks with different radii- 0.5 µm to 4 µm and thicknesses- 25 nm and 30 nm were prepared using electron beam lithography followed by electron beam evaporation. Moreover, to allow for electrical measurements, the single disks were contacted by gold leads to study the interaction of spin polarized current on the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect (MOKE), X-ray magnetic circular dichroism (XMCD) and magnetotransport measurements.
The magnetic field dependence can be tuned by the disk size as shown by XMCD (Figure 1 (a)). Higher magnetic stability due to larger annihilation fields can be achieved by smaller disk diameters whereas larger field sensitivity is present in larger disks (Figure 1 (b)).
Magnetotransport measurements on electrically contacted disks (Figure 2 (a)) show the presence of anisotropic magnetoresistance (AMR) in different disks with varying thickness (Figure 2 (b)). Additionally, to the shown static DC measurements, AC measurements are accessible by a lock-in technique and the resonance frequencies measured for 3 µm and 4 µm radii disks with 25 nm permalloy are 40.9 MHz and 29.5 MHz respectively. In order to alter the saturation magnetisation within defined volumes and to achieve two different oscillation frequencies, a concentric region is irradiated within the actual disk (Figure 2 (c)). After ion irradiation, modified magnetic vortex dynamics are investigated by ac-magnetotransport measurements and the results are supported by micromagnetic simulations.
Acknowledgements:
This work is supported by the Helmholtz Young Investigator Initiative Grant No. VH-N6-1048. Support of the Nanofabrication Facilities of Rossendorf at the Ion Beam Centre is gratefully acknowledged (Dr. Artur Erbe, Bernd Scheumann).

Keywords: magnetic vortex; electrical detection; dynamics

  • Lecture (Conference)
    INTERMAG, 24.-28.04.2017, Dublin, Ireland

Permalink: https://www.hzdr.de/publications/Publ-25378
Publ.-Id: 25378


Electrically detected magnetic vortex dynamics in Permalloy disks

Ramasubramanian, L.; Fowley, C.; Kákay, A.; Yildirim, O.; Matthes, P.; Lindner, J.; Fassbender, J.; Gemming, S.; Schulz, S. E.; Deac, A. M.

The magnetic “vortex” is a potential candidate for future spintronic devices, like frequency sensors [S. Kasai, et al. PRL 97, 107204 (2006)] [R. Moriya, et al. Nat. Phys. 4:368 (2008)], spin torque oscillators [V. S. Pribiag, et al. Nat. Phys. 3:498 (2007)], and tunable magnonic crystals [J. Shibata, et al. PRB 67, 224404 (2003)]. The fundamental frequency is determined by the saturation magnetisation, as well as the geometrical confinement of the magnetisation i.e. the diameter and height of a magnetic disk. In this study, Permalloy disks (with diameters ranging from 1µm to 8µm) are patterned and contacted to study the interaction of spin polarized current on the magnetic vortex. The presence of vortex is verified by magneto optic Kerr effect, X-ray photoemission electron microscopy and magnetotransport measurements. The resonance frequency is measured using a lock-in technique based on the anisotropic magnetoresistance effect. Modification of the resonance frequency by ion irradiation will be presented.

Keywords: magnetic vortex; dynamics; electrical detection

  • Lecture (Conference)
    DPG-Frühjahrstagung 2017, 19.-24.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-25377
Publ.-Id: 25377


Thermally Induced Spin Transfer Torque on MgO-based magnetic tunnel junctions using microstrip based resonator

Cansever, H.; Fowley, C.; Narkowicz, R.; Kowalska, E.; Aleksandrov, Y.; Yildirim, O.; Titova, A.; Lenz, K.; Lindner, J.; Fassbender, J.; Deac, A. M.

Magnetic tunnel junctions have been commonly used in spintronics applications, such as magnetic random access memory (M-RAM), spin transfer torque RAM (STT-RAM) and hard disc drive (HDD) because of high storage capacity. A spin polarized current flowing through a ferromagnetic layer can exert spin-transfer-torque (STT) on the local magnetization. When we apply thermal gradient across the junction we can induce what is called thermal spin transfer torque (T-STT). In this study, the microresonator FMR technique is used in order to analyze how the ferromagnetic resonance signal corresponding to the free layer of an in-plane MgO-based tunnel junction device is modified in the presence of a temperature gradients across the barrier. Details of resonator fabrication and preliminary measurements are presented. This work is supported by DFG-SPP1538.

Keywords: spin transfer torque; microresonator; thermal gradient

  • Lecture (Conference)
    DPG-Frühjahrstagung 2017, 19.-24.03.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-25376
Publ.-Id: 25376


Synthesis and characterization of the first chiral benzamidinate complexes of tetravalent actinides (An(IV))

Schöne, S.; März, J.; Kaden, P.; Weigand, J. J.; Roesky, P. W.; Stumpf, T.; Ikeda-Ohno, A.

In contrast to the dominant trivalent state for the lanthanides (Ln(III)), a wide variety of oxidation states (from +II to +VII) of actinides (An) makes their chemistry intricate but attractive. Especially the early An of thorium (Th), uranium (U), neptunium (Np) and plutonium (Pu) form highly charged cations with the oxidation state four (An4+), which are of particularly interest for the coordination chemistry due to their strong interaction with organic ligands. The focus of our investigations lies in the comprehensive characterization of tetravalent An (An(IV)) complexes with soft ligand donor atoms, such as nitrogen. The present study focuses particularly on the interaction of An(IV) with benzamidinate ligands, which could be considered as a simplified model of naturally occurring N-donor organic compounds.
Recently, the lanthanide complexes with the chiral benzamidine, (S,S)-N,N-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA), have been successfully synthesized by the group of Prof. Roesky1,2. The present study is inspired by these precedent studies to synthesize a new series of benzamidine compounds with An(IV).

  • Lecture (Conference)
    Actinides 2017, 09.-14.07.2017, Sendai, Japan
  • Lecture (Conference)
    10th International Symposium on Nano and Supramolecular Chemistry, 10.07.2018, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25375
Publ.-Id: 25375


Magnetic properties of HoFe₆Al₆ with a compensation point near absolute zero: A theoretical and experimental study

Sabdenov, C. K.; Davydova, M. D.; Zvezdin, K. A.; Zvezdin, A. K.; Andreev, A. V.; Gorbunov, D. I.; Tereshina, E. A.; Skourski, Y.; Sebek, J.; Tereshina, I. S.

Ferrimagnet HoFe6Al6 (tetragonal ThMn12-type crystal structure) has a compensation point for the Ho and Fe magnetic sublattices at a temperature close to absolute zero. The experimental study was carried out in fields up to 60 T. H-T phase diagrams and a full magnetization process along the principal crystallographic directions of a single-crystalline sample are obtained theoretically by using a model of a f-d ferrimagnet with two anisotropic sublattices, coupled by weak exchange interaction. The two first-order phase transitions, found experimentally along the [110] and [100] axes, were explained theoretically. The transition along the [110] direction occurs between noncollinear and collinear phases, it starts at the compensation point and ends at a tricritical point around 60 T. The transition along the [100] direction goes also from the point of compensation to the point of the liquid-vapor type at 40 T. This transition was shown to occur between two distinct noncollinear phases. The crucial role of the strong rare-earth anisotropy for the positions of the obtained critical points was revealed.

Permalink: https://www.hzdr.de/publications/Publ-25374
Publ.-Id: 25374


Uniaxial-stress tuned large magnetic-shape-memory effect in Ni-Co-Mn-Sb Heusler alloys

Salazar Mejia, C.; Küchler, R.; Nayak, A. K.; Felser, C.; Nicklas, M.

Combined strain and magnetization measurements on the Heusler shape-memory alloys Ni45Co5Mn38Sb12 and Ni44Co6Mn38Sb12 give evidence for strong magneto-structural coupling. The sample length changes up to 1% at the martensitic transformation, between a ferromagnetic, austenitic phase at high temperatures and a weakly magnetic, low-symmetry martensitic phase at lower temperatures. Under moderate uniaxial stress, the change in the sample length increases to and saturates at about 3%, pointing to stabilization of a single martensitic variant. A reverse martensitic transformation can also be induced by applying magnetic field: we find that within the temperature range of thermal hysteresis of the martensitic transformation, applying a field can induce a metastable expansion of the sample, while at slightly lower temperatures, the field response is reversible. These findings provide key information for future use of Ni(Co)-Mn-Sb-based Heusler compounds in, e.g., actuators and mechanical switches.

Permalink: https://www.hzdr.de/publications/Publ-25373
Publ.-Id: 25373


Analysis of the exclusive final state npe+e in quasi-free np reaction

Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gill, K.; Golubeva, M.; Guber, F.; Gumberidze, M.; Harabasz, S.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kotte, R.; Krása, A.; Krebs, E.; Kuc, H.; 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.; Maurus, S.; Mangiarotti, A.; Markert, J.; Metag, V.; Michel, J.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petousis, V.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Sellheim, P.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Wendisch, C.; Wirth, J.; Zanevsky, Y.; Zumbruch, P.

We report on the investigation of dielectron production in tagged quasi-free neutron-proton collisions by using a deuteron beam of kinetic energy 1.25 GeV/u inpinging on a liquid hydrogen target. Our measurements with HADES confirm a significant excess of e+e− pairs above the π0 mass in the exclusive channel dp→npe+e−(pspect) as compared to the exclusive channel ppe+e− measured in proton-proton collisions at the same energy. That excess points to different bremsstrahlung production mechanisms. Two models were evaluated for the role of the charged pion exchange between nucleons and double-Δ excitation combined with intermediate ρ-meson production. Differential cross sections as a function of the e+e− invariant mass and of the angles of the virtual photon, proton and electrons provide valuable constraints and encourage further investigations on both experimental and theoretical side.

Permalink: https://www.hzdr.de/publications/Publ-25372
Publ.-Id: 25372


Thermal anemometry grid sensor for spatially-resolved measurement of gas phase temperature and velocity in fuel element subchannels

Arlit, M.; Schleicher, E.; Hampel, U.

Since the Fukushima accident the spent fuel pool has gained some special focus in nuclear safety research, since it is potentially endangered by a longer persisting station black-out or a loss of the coolant due to a leakage in the pool liner. Behind this background the German national joint project SINABEL (SIcherheit NAsslager BrennElement Lagerbecken) has been launched, which targets an experimental investigation and an improved modelling of the thermal hydraulics in fuel element mock-up in the spent fuel pool under accident scenario conditions. The goal is to develop validated simulation tools for the prediction of temperature courses and the support of the emergency management.
Experimental investigations within the project are performed in a mock-up of a 10 x 10 boiling water reactor fuel element. Surface temperatures of the electrical heated rods are measured by means of 134 thermocouples at different locations. Another parameter of interest is the steam flow velocity in the sub-channels. For this purpose no commercial measurement technique is applicable due to limited accessibility and high temperatures. For this reasons a special thermal anemometry grid sensor has been developed. It consists of a grid of thermal resistors in the bundle cross-section with one resistor in each sub-channel. Via the resistors fluid temperature as well as flow velocity can be obtained. Applied measurement techniques are resistance thermometry and thermal anemometry respectively. The measurements are obtained simultaneously by sampling the data with a special multiplexed excitation scheme. Our contribution gives a brief description of the thermal anemometry grid sensor along with first results from studies on a potential natural circulation in the completely dried state.

Keywords: Thermal anemometry grid sensor; Temperature grid sensor; Spent fuel pool; Thermal hydraulics

  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi´an, China

Permalink: https://www.hzdr.de/publications/Publ-25371
Publ.-Id: 25371


Neutron Noise Observations in German KWU Built PWR and Analyses with the Reactor Dynamics Code DYN3D

Rohde, U.; Seidl, M.; Kliem, S.; Bilodid, Y.

Low-frequency neutronic noise with a bandwidth of up to ten percent of the reactor power has been observed in Konvoi-type PWRs in Germany in the last years. Several attempts were made to identify the reasons for increased magnitudes of the neutronic fluctuations in comparison with pre-Konvoi reactors, and various hypotheses have been created to explain this effect.
In this paper, results of noise simulations performed with use of the reactor dynamics code DYN3D are presented. Both fluctuations of the coolant inlet temperature and mass flow rate were considered. Besides of un-correlated fluctuations, correlated temperature fluctuations were simulated. The correlations between fluctuations in the individual fuel assemblies were obtained based on an experimentally validated coolant mixing model. However, the features of the neutronic noise found in the simulations do not correspond to the measurements.
Obviously, more complex mechanisms than only temperature and/or mass flow fluctuations have to be considered. Simulated fluctuations of the local moderator density, independently from thermal hydraulics, indicate that potentially deformations or vibrations of the fuel rod lattice leading to variations of the local moderator content might be responsible for the observed neutronic noise. Advanced models coupling neutronics, thermal hydraulics, turbulence and mechanical modelling have to be developed.

Keywords: PWR; KWU; Neutron noise; DYN3D

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Permalink: https://www.hzdr.de/publications/Publ-25370
Publ.-Id: 25370


Field induced phase transition in the few photon regime

Panferov, A. D.; Smolyansky, S. A.; Titov, A. I.; Kämpfer, B.; Otto, A.; Blaschke, D. B.; Juchnowski, L.

Some features of the field induced phase transition accompanied by the vacuum creation of an electron-positron plasma (EPP) in strong time-dependent electric fields have been discussed in the work [1] in the domain of the tunneling mechanism (ω ≪ m, where ω is the characteristic frequency of the external field and m is the electron mass). In the present contribution the features of this process will be considered in the few photon domain where ω ~ m. We observe a narrowing of the transient domain of the quickly oscillations and, mainly, a considerable growth of the effectiveness of the EPP production. Under these circumstances, we see an increase of the effectiveness of the EPP creation in the particular case of a bifrequent excitation, where both mechanisms (tunneling and few photon) act simultaneously [2, 3].

Permalink: https://www.hzdr.de/publications/Publ-25369
Publ.-Id: 25369


Proton radiography for integrating positioning and treatment planning of small animals at an experimental proton beam

Müller, J.; Neubert, C.; von Neubeck, C.; Krause, M.; Enghardt, W.; Bütof, R.; Dietrich, A.; Lühr, A.

Integrated small animal X-ray imaging and irradiation devices have facilitated image-guided pre-clinical radiooncological experiments. Here, a proton-based radiography method is proposed for in-line small animal treatment planning and positioning verification at an experimental proton beamline.
A double-scattered 125 MeV proton beam (10 x 10 cm² field size) and a flat-panel, scintillation-based dose detector (Lynx, IBA Dosimetry) were used to obtain planar scans of deceased mice positioned in a closed multi-modality bed. Two modes of image acquisition were used: absorption and scattering. In absorption mode, slabs of plastic with a water equivalent path length (WEPL) of 7.08 g/cm² were placed between object and Lynx detector. In scattering mode, all plastic slabs were removed. Digital, pixel-wise image processing was applied to combine the information. A WEPL calibration curve was obtained using plastic slices of known WEPL as objects. For verification, planar X-ray images of the same objects were acquired.
The proposed radiography technique allowed for detection of contours (e.g., mouse body, bed and background) and reliable automated (rigid) registration of proton radiography images to planar X-ray scans. Planar 2D radiological thickness maps of mice were obtained. Specific structures could be visualized with a spatial resolution of less than 1 mm, especially regions with high local density differences including lung, hind leg, jaws and skull.
The method appears suitable to position small animals for precise irradiation of subcutaneous (hind leg) and orthotopic (lung, brain) tumor models. Currently extended image analysis may enhance visualization of the animal’s internal structure to facilitate in-line treatment planning.

Keywords: Radiography; Imaging; proton therapy; Preclinical research; Cancer

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25368
Publ.-Id: 25368


Year-round record of bulk and size-segregated aerosol composition in central Antarctica (Concordia site) Part 2: Biogenic sulfur (sulfate and methanesulfonate) aerosol

Legrand, M.; Preunkert, S.; Weller, R.; Zipf, L.; Elsässer, C.; Merchel, S.; Rugel, G.; Wagenbach, D.

Multiple year-round (2006-2015) records of the bulk and size-segregated composition of aerosol were obtained at the inland site of Concordia located in East Antarctica. The well-marked maximum of non-sea-salt sulfate (nssSO4) in January (84 ± 25 ng m-3 against 4.4 ± 2.3 ng m-3 in July) is consistent with observations made at the coast (280 ± 78 ng m-3 in January against 16 ± 9 ng m-3 in July at Dumont d’Urville, for instance). In contrast, the well-marked maximum of MSA at the coast in January (60 ± 23 ng m-3 at Dumont d’Urville) is not observed at Concordia (4.6 ± 2.4 ng m-3 in January). Instead, the MSA level at Concordia peaks in October (5.6 ± 1.9 ng m-3) and March (13.2 ± 6.1 ng m-3).
As a result, a surprisingly low MSA to nssSO4 ratio (RMSA) is observed at Concordia in midsummer (0.05 ± 0.02 in January against 0.25 ± 0.09 in March). We find that the low value of RMSA in mid-summer at Concordia is mainly driven by a drop of MSA levels that takes place in submicron aerosol (0.3 μm diameter). The drop of MSA coincides with periods of high photochemical activity as indicated by high ozone levels, strongly suggesting the occurrence of an efficient chemical destruction of MSA over the Antarctic plateau in mid-summer. The relationship between MSA and nssSO4 levels is examined separately for each season and indicates that concentration of non-biogenic sulfate over the Antarctic plateau does not exceed 1 ng m-3 in fall and winter and remains below 5 ng m-3 in spring. This weak non-biogenic sulfate level is discussed in the light of radionuclides (210Pb, 10Be, and 7Be) also measured on bulk aerosol samples collected at Concordia. The findings highlight the complexity in using MSA in deep ice cores extracted from inland Antarctica as a proxy of past DMS emissions from the southern ocean.

Keywords: Methanesulfonate; MSA to non-sea-salt sulfate ratio; DMS emissions; sea-salt aerosol; 210Pb; 10Be and 7Be; Chemistry(chemical composition and reactions)

Permalink: https://www.hzdr.de/publications/Publ-25367
Publ.-Id: 25367


Influence of FeII on the retention mechanisms of NpO2+ by montmorillonite

Marques Fernandes, M.; Scheinost, A. C.; Baeyens, B.

For the safety case for high-level radioactive waste repositories, redox phenomena play an important role for radionuclide retention. In the near field, the corrosion of steel canisters will release large amounts of ferrous iron and in addition produce H2 with a strong influence on the “in situ” redox potential (Eh). This combination of high {FeII} and low (Eh) in the interstitial waters of the engineered barrier system (bentonite, consisting predominantly of the phyllosilicate montmorillonite) is expected to have a strong impact on the retention of redox sensitive radionuclides like Tc, Se and the early actinides U, Np, and Pu, all of high relevance for safety of radioactive waste repositories.
In the present work we investigated by X-ray absorption spectroscopy (XAS) the influence of FeII on the retention of the redox sensitive NpV by montmorillonite. Since natural montmorillonite always contains structural Fe, we made use of a synthetic iron-free montmorillonite (IFM) [1] to discriminate the influence of sorbed FeII from that of structural iron. For FeII loadings below 40 mmol·kg-1, sorbed Fe had no effect, with Np showing the typical sorption behaviour of the pentavalent aquo-ion by forming comparatively weak inner-sphere sorption complexes at the edge sites of montmorillonite. For FeIIsorb above 40 mmol·kg-1, however, we observed an increasing reduction of NpV to NpIV, with a complete reduction for FeIIsorb  80 mmol·kg-1. In spite of the low solubility of NpO2, we did not observe precipitation of this phase, but formation of mononuclear innersphere sorption complexes (Fig. 1-A). The influence of structural FeII was investigated using citrate-dithionite–bicarbonate (CDB) reduced SWy montmorillonite (i.e. structural FeIII fully reduced to FeII). XAS showed that Np is present only as NpIV on the clay surface (Fig. 1-B).
Our study demonstrates that both structural and adsorbed FeII on montmorillonite lead to a surface mediated reduction of NpV, thereby increasing the retention by more than two orders of magnitude.

Keywords: montmorillonite; iron; neptunium; EXAFS; XANES; sorption modeling

  • Lecture (Conference)
    AnXAS 2017: 8th Workshop on Speciation, Techniques, and Facilities for Radioactive Materials at Synchrotron Light Sources, 11.-13.04.2017, Oxford, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-25366
Publ.-Id: 25366


Technetium interaction with Fe(II)-minerals analysed by spectroscopy and thermodynamics

Yalcintas, E.; Scheinost, A. C.; Gaona, X.; Altmaier, M.; Geckeis, H.

Technetium–99 is a β–emitting fission product which needs to be analysed for the safety assessment of repositories for radioactive waste disposal due to its significant inventory in spent nuclear fuel and its long half-life (t½ ~211.000 a). Although several oxidation states of Tc are reported in the literature, Tc(VII) and Tc(IV) are the prevailing redox states in the absence of any complexing ligand under non-reducing and reducing conditions, respectively. Tc(VII) is the most stable oxidation state of Tc in suboxic/oxidising environments. It is found as the highly mobile TcO4– anion over the entire pH range and shows very high solubility and weak sorption properties. Under reducing conditions, Tc(IV) forms sparingly soluble hydrous oxides TcO2∙xH2O(s) and is usually sorbed strongly onto mineral surfaces. Because of the large differences in the aquatic chemistry of Tc(VII) and Tc(IV), an accurate knowledge of Tc redox chemistry is necessary for an appropriate assessment of Tc retention/mobilization processes.
In the present work, the mechanisms for the reduction and uptake of Tc by magnetite (Fe3O4) and mackinawite (FeS) are investigated using X-ray absorption spectroscopy, in combination with thermodynamic calculations of the Tc/Fe systems and accurate characterization of the solution properties (pHm, pe, [Tc]). Batch sorption experiments were performed under strictly anoxic conditions using freshly prepared magnetite and mackinawite in 0.1 M NaCl solutions with varying initial Tc(VII) concentrations (2·10–5 and 2·10–4 M) and Tc loadings (400–900 ppm). EXAFS data evaluation shows that the mechanisms of Tc(IV) retention by magnetite and mackinawite are strongly dependent on the loading, [Tc]0 and pHm. The results provide key inputs for the understanding of the mechanisms driving the reduction and retention of Tc by magnetite and mackinawite under repository-relevant conditions, whilst highlighting the need of coupling classical wet-chemistry techniques, thermodynamic calculations and advanced spectroscopic methods when investigating complex processes or systems such as redox and mineral interfaces.

Keywords: technetium; EXAFS; XANES; mackinawite; magnetite; redox

  • Invited lecture (Conferences)
    Goldschmidt 2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25365
Publ.-Id: 25365


Monothioarsenate transformation kinetics determines arsenic mobility in sulfidic and organic-rich systems

Besold, J.; Biswas, A.; Suess, E.; Scheinost, A. C.; Rossberg, A.; Mikutta, C.; Kretzschmar, R.; Gustafsson, J. P.; Planer-Friedrich, B.

Peatlands play an important role in arsenic sequestration. In such carbon-rich and sulfidic environments the dominant species is generally assumed to be arsenite for which recent X-ray absorption spectroscopy (XAS)-based studies showed that it can strongly bind to natural organic matter (NOM) via reduced sulfur bridges [1]. However, in sulfidic solutions, arsenite can also react with sulfide or elemental sulfur to form thioarsenates. Thioarsenates are often overlooked due to a lack of suitable analytical methods [2] and their mobility in organic-rich systems is unknown. Porewater analysis of an arsenic-rich, minerotrophic peatland (Gola di Lago, Switzerland) showed that thioarsenates actually accounted for up to 70 % of total porewater arsenic, with monothioarsenate (MTA) being the dominant species. To investigate the extent, kinetics, and mechanisms of MTA binding to NOM, MTA was incubated with sulfurized peat at pH 4.5, 7.0, and 8.5. While MTA was stable for 41 days at pH 8.5, it was completely transformed to arsenite at pH 4.5, following acid-catalyzed and sulfide-dependent redox transformation kinetics. Total arsenic sorption was lowest at pH 8.5 and highest at pH 4.5 (7 and 32 μmol As/mol C, respectively). XAS revealed that in this sulfidic system, arsenic was bound to NOM as previously reported via reduced sulfur bridges as arsenite and additionally via oxygen as arsenite at low to neutral pH or as arsenate and low amounts of arsenite via oxygen at high pH. MTA did not bind to sulfurized NOM at all. The results demonstrate that the mobility of arsenic in sulfidic, organic-rich systems strongly depends on the pH, the sulfide-to-arsenic and the sulfide-to-carbon ratios which govern thioarsenate formation in solution, their transformation to arsenite and finally its sorption kinetics.
[1] Langner et al. (2012) Nat. Geosci. 5, 66-73. [2] Planer-Friedrich et al. (2015) Environ. Sci. Technol. 49, 6554-6563.

Keywords: arsenic; sorption; thioarsenite; EXAFS; XANES; peat

  • Lecture (Conference)
    Goldschmidt 2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25364
Publ.-Id: 25364


Sorption of U and Eu on illite: influence of accessory minerals

Marques Fernandes, M.; Scheinost, A. C.; Baeyens, B.

The interaction of radio(-contaminants) at water-mineral interfaces is a key process in retarding their migration in the environment. Therefore, elucidation of the processes involved, and the development of sorption models accounting for these processes, is crucial for a reliable risk assessment. This task can realistically only be tackled, if for a given multimineralic soil or rock the most relevant minerals can be identified. Only for these, the sorption processes need to be determined and modelled, and the sorption by the soil/rock entity is then predictable by summing up the sorption of these few minerals according to their fraction in the soil or rock.
Here we show that this procedure can already be hampered at the level of a presumably pure mineral. Sorption experiments conducted with purified illite du Puy showed under certain conditions (pH, concentration, dissolved carbonate) an unexpected enhancement of the retention of UVI and EuIII. EXAFS and TRLF spectroscopies revealed that this effect is due to the interaction with phosphate groups not expected at the illite surface. Only after a severe acid treatment of the illite, sorption and surface complexation approached that expected for pure illite. The release of Ca and P during the severe acid treatment suggest dissolution of an apatite-type accessory mineral. The mineral itself is difficult to identify with common analytical methods such as XRD or TEM due to i.e. low concentration and/or amorphous nature of the accessory phase, low electron density of its constituent elements. Our results demonstrate that accessory phases might substantially contribute to the sorption of a bulk mineral phase.

Keywords: Ilite; uranium; europium; sorption modeling; EXAFS; TRLFS

  • Lecture (Conference)
    Goldschmidt 2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25363
Publ.-Id: 25363


In-house reference materials for the determination of low titanium concentration in SiO2 by secondary ion mass spectrometry (SIMS)

Ziegenrücker, R.; Belokonov, G.; Böttger, R.; Couffignal, F.; Munnik, F.; Renno, A.; Wiedenbeck, M.; Wu, H. S.

SIMS (Secondary Ion Mass Spectrometry) is a routinely used analytical technique for geochemical and mineralogical applications. Nevertheless, quantification is still the major challenge of this method. Due to the fact, that each analysed matrix needs its own matrix-matched reference material (RM), the list of available reference materials is short compared to the needs of the analysts. A current evaluation of the GeoReM database [1] shows a strong focus on using the well-known NIST SRM 610-617 glasses for trace element analysis and several zircons for isotope analysis.

One approach for the production of suitable RMs is the use of ion implantation to introduce a known amount of an isotope into a matrix-matched material. This approach is widely-used for SIMS applications in materials science, but rarely used for geochemical problems. Bumett et al. (2014) [2] demonstrated the principal appropriateness of this method and ways to calibrate nominal implant fluence. We choose the more elaborate way of implanting a box profile to allow a homogeneous distribution of the respective isotope in all three dimensions.

The mineralogical and chemical “simple” SiO2 system entails many interesting scientific challenges like the Ti-in-quartz geothermometer [3, 4]. We implanted 47Ti respectively 48Ti into synthetic ultra-high purity silica glass. Several box profiles with concentrations between 10 and 1000 ppm and a maximum depth of homogeneous 47/48Ti distribution between 200 and 500 nm were produced at the Ion Beam Center in Dresden-Rossendorf. The single implantation steps with different ion-energies and -doses were simulated with the SRIM (Stopping and Range of Ions in Matter) software [5] and optimized to the necessary concentrations, implantation-depths and limits of the implanter. After the implantations, the surface-roughness of the implanted glasses was measured using atomic force microscopy (AFM). The roughness is still in the range necessary for SIMS measurements.

We characterized several implanted test-samples with different concentrations and maximum implantation-depths by means of SIMS and other analytical techniques. It has been shown, that Ti is dissolved in the glass structure. The homogeneity of the Ti-concentration is within ± 5% uncertainty in all 3 dimensions.


[1] http://georem.mpch-mainz.gwdg.de
[2] Bumett, D.S., et al. (2014). Ion Implants as Matrix-Appropriate Calibrators for Geochemical Ion Probe Analyses. Geostandards and Geoanalytical Research, 39(3), 265-276.
[3] Wark, D. A., Watson E. B. (2006). TitaniQ: a titanium-in-quartz geothermometer. Contributions to Mineralogy and Petrology, 152(6), 743-754.
[4] Thomas, J. B., Watson E. B., et al. (2010). TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz. Contributions to Mineralogy and Petrology, 160(5), 743–759.
[5] Ziegler J. F. (2004). SRIM-2003. Nuclear Instruments and Methods in Physics Research Section B, 219-220, 1027-1036.

Keywords: SIMS; reference materials; titanium; quartz; implantation

  • Poster
    2nd International Conference on Applied Mineralogy & Advanced Materials and 13th International Conference on Applied Mineralogy, 05.-09.06.2017, Castellaneta Marina- Taranto, Italy

Permalink: https://www.hzdr.de/publications/Publ-25362
Publ.-Id: 25362


Bubble Generation by Solid Membrane Spargers for Activated Sludge Wastewater Treatment Application

Mohseni, E.; Herrmann-Heber, R.; Reinecke, S.; Hampel, U.

Current endeavor experimentally studies the initial bubble size distribution from the stainless steel diffusers and needle spargers with very fine orifice diameters range from 30 to 200 µm. To evaluate the performance of these spargers, the results where compared with four industrial rubber membranes in terms of Sauter mean diameter, pressure drop and frequency of bubble formation. Outcomes of current study showed that, the stainless steel perforated plates impose their superiority over the flexible membranes, by generating 50% smaller bubbles, and 70% higher bubble generation frequency at 60% less pressure drop. Moreover, the perforated stainless steel plates are able to produce bubble sizes in the same class as needles at 40% of the pressure drop caused by needle spargers and average of 60% higher bubble generation frequency.

Keywords: Bubble Generation; Activated Sludge; Aeration; Biological Wastewater Treatment; Multiphase Flow

  • Contribution to proceedings
    The 9th Eastern European Young Water Professionals Conference, 24.-27.05.2017, Budapest, Hungary
    Proceedings of the 9th Eastern European Young Water Professionals Conference
  • Lecture (Conference)
    The 9th Eastern European Young Water Professionals Conference, 24.-27.05.2017, Budapest, Hungary

Permalink: https://www.hzdr.de/publications/Publ-25361
Publ.-Id: 25361


Terahertz spectroscopy of semiconductor nanostructures with a free-electron laser

Schneider, H.

In this talk I will present our recent experimental investigations on carrier dynamics in graphene studied via nonlinear laser spectroscopy, on time-resolved photoluminescence dynamics of single InAs/GaAs quantum dots under pulsed inter-sublevel excitation, and on sub-diffraction limited terahertz imaging by a GaAs-based superlens studied by scattering near-field optical microscopy. The experiments have been carried out using the mid-infrared/terahertz free-electron laser facility FELBE in Dresden, Germany.

Keywords: terahertz; free-electron laser; graphene; quantum dots; superlens

  • Lecture (others)
    Seminarvortrag, University of Wollongong, 02.03.2017, Wollongong, Australia

Permalink: https://www.hzdr.de/publications/Publ-25360
Publ.-Id: 25360


Chancen und Grenzen einer Circular Economy

Reuter, M. A.

  • Invited lecture (Conferences)
    Tag der Metallurgie, 02.-04.03.2016, Goslar, Deutschland
  • Invited lecture (Conferences)
    Berliner Recycling- und Rohstoffkonferenz, 06.-07.03.2016, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25359
Publ.-Id: 25359


Towards a simplified TALSPEAK process using DTPA-amino acid conjugates

Jones, J. E.; Adam, C.; Kaden, P.; Martin, L. R.; Geist, A.; Natrajan, L. S.; Sharrad, C. A.

The TALSPEAK process [1] was developed at Oak Ridge National Laboratory in the 1960’s to separate trivalent actinide ions, An(III), from the chemically similar lanthanide ions, Ln(III), by solvent extraction. The idea was to use an extracting agent unselective for An(III) over Ln(III) and add a complexing agent to the aqueous phase to infer selectivity [2]. Despite the simplicity of this concept, TALSPEAK is actually a rather complex system, with numerous equilibria involved. The original TALSPEAK system consisted of HDEHP (bis-2-ethylhexyl phosphoric acid) as the extracting agent, DTPA (diethylenetriamine pentaacetic acid) as the An(III)-selective complexing agent and lactic acid as buffering agent. Constantly improving TALSPEAK by substituting the components of the original system, ALSEP [3] and Advanced TALSPEAK [4, 5] have been developed.
We have pursued a concept which differs in two aspects, (a) using amino acids (AA) as buffering agent [6] and (b) linking them to the complexing agent. This way, only a single molecule is added to the aqueous phase and the system is expected to behave more simply. Several DTPA-AA conjugates were synthesised, DTPA-Arg, DTPA-His, DTPA-Ser and DTPA-Ala. These were tested in solvent extraction experiments. Organic phase was 0.2 mol/L HDEHP in kerosene, aqueous phases were solutions containing 50 mmol/L DTPA-AA conjugate, Am(III) and Ln(III) (Y; La–Lu). pH was adjusted by adding HNO3 or NaOH.
The lowest pH at which separation was achieved (i.e., Am(III) distribution ratio < 1 and all Ln(III) distribution ratios > 1) was in the range of 1.1–1.5. Separation factors for Eu(III) over Am(III) were ≈ 100 and the minimum separation factors between Am(III) and the least extracted Ln(III), being Nd(III) in all cases, were 30–40.
The coordination chemistry was studied by luminescence and NMR. Photophysical studies of the Eu(III)-DTPA-AA complexes demonstrated characteristic Eu(III) emission, with associated lifetime decay profiles confirming 1:1 coordination. 1H NMR studies were performed with Am(III), confirming successful complexation.
In conclusion, an improved TALSPEAK system is reported which compares favourably to known TALSPEAK systems.
1. Weaver, B.; Kappelmann, F. A., USAEC report ORNL-3559, Oak Ridge National Laboratory, USA: 1964.
2. Nilsson, M.; Nash, K. L., Solvent Extr. Ion Exch. 2007, 25 (6), 665–701.
3. Gelis, A. V.; Lumetta, G. J., Ind. Eng. Chem. Res. 2014, 53 (4), 1624–1631.
4. Braley, J. C.; Grimes, T. S.; Nash, K. L., Ind. Eng. Chem. Res. 2010, 51 (2), 629–638.
5. Lumetta, G. J.; Casella, A. J.; Rapko, B. M.; Levitskaia, T. G.; Pence, N. K.; Carter, J. C.; Niver, C. M.; Smoot, M. R., Solvent Extr. Ion Exch. 2015, 33 (3), 211–223.
6. Grimes, T. S.; Tillotson, R. D.; Martin, L. R., Solvent Extr. Ion Exch. 2014, 32 (4), 378–390.

Keywords: TALSPEAK; amino acids; actinide(III); lanthanide(III)

  • Lecture (Conference)
    41st Annual Actinide Separations Conference, 23.-25.05.2017, Lemont, IL, United States

Permalink: https://www.hzdr.de/publications/Publ-25358
Publ.-Id: 25358


THz spectroscopy of solids with a free electron laser

Helm, M.

THz spectroscopy of solids with a free electron laser

Keywords: terahertz; free electron laser; spectroscopy

  • Invited lecture (Conferences)
    2nd German THz Conference, 29.-31.03.2017, Bochum, Germany

Permalink: https://www.hzdr.de/publications/Publ-25356
Publ.-Id: 25356


Quantification of MRI visibility and artefacts at 3T of BioXmark® fiducial marker in a pancreas tissue mimicking phantom

Schneider, S.; Jølck, R. I.; Troost, E. G. C.; Hoffmann, A. L.

Purpose: X-ray based position verification of the target volume in image-guided radiation therapy (IGRT) of patients with pancreatic ductal adenocarcinoma (PDAC) is currently performed on rigid fiducial markers that are implanted under endoscopic ultrasonography. A new biodegradable liquid fiducial marker has recently been introduced. To assess its potential use for magnetic resonance imaging (MRI) guided radiotherapy of PDAC, the MRI visibility and artefacts of this marker were quantified and compared against rigid gold markers.

Material and Methods: Different spherical volumes (10 µL, 25 µL, 50 µL and 100 µL) of BioXmark® (Nanovi Radiotherapy A/S) as well as four differently oriented Gold Anchor™ (Naslund Medical AB; Ø 0.28 mm, 1 cm and 2 cm length) and three VisiCoil™ (IBA Dosimetry; Ø 0.35 mm, 5 mm and 10 mm length) were implanted in a spherical gel phantom mimicking the proton spin relaxation properties of healthy pancreatic tissue at 3 Tesla. MR relaxometry was performed to quantify the size and magnitude of the decrease in T¬2* relaxation time and relative proton density ρ(H) as a measure of visibility, and to quantify the size and magnitude of the increase in magnetic field inhomogeneity ΔB_0 as a measure of signal artefacts. The phantom was scanned in a 3.0 T Philips Ingenuity TF PET/MR scanner with an 8-channel head coil. For T2*- and ΔB_0-mapping a spoiled 3D multi-echo gradient echo sequence (GRE) was performed. ρ(H)-mapping was based on the signal intensity at TE = 0 ms relative to ultrapure water extrapolated from the T2-decay curve deduced from a spin echo sequence with different echo times. The signal was corrected for its T1 decay and B1- field inhomogeneity, for which an inversion-recovery spin echo sequence with multiple inversion times and a gradient echo sequence with different repetition times was utilized respectively.

Results: The rigid markers showed a direct linear relationship between size of visibility and artefact. BioXmark® showed a tendency towards larger size of visibility at smaller artefacts. BioXmark® markers up to 100 µL created volumes of visibility comparable to the size of visibility of VisiCoil™ and Gold Anchor™ markers. The magnitude of visibility was the highest for BioXmark® from 25µL – 100µL showing no correlation with the magnitude of artefact. The rigid markers show a non-linear correlation between magnitude of visibility and artefact where Gold Anchor™ induce the strongest artefacts.

Conclusion: BioXmark® causes signal voids on MRI due to its low proton density without strongly affecting the magnetic field in the surrounding tissue. The latter was found to be the main effect leading to the visibility of the rigid markers especially in GRE sequences. Hence, especially when a low level of image distortion is required, MRI characteristics of the BioXmark® surpass those of rigid gold markers currently being used for IGRT of PDAC.

Keywords: fiducial marker; MRI; visibility; artefacts; image-guided radiation therapy

Permalink: https://www.hzdr.de/publications/Publ-25355
Publ.-Id: 25355


Establishment of a small animal setup for multimodal imaging and irradiation

Neubert, C.; Müller, J.; Bütof, R.; Lühr, A.; von Neubeck, C.; Schürer, M.; Beyreuther, E.; Tillner, F.; Krause, M.; Dietrich, A.

For preclinical cancer research, dedicated small animal imaging and irradiation devices are increasingly gaining importance to examine experimental tumors and normal tissue models. We designed a special small animal bed, which is intended to be used for multimodal imaging (e.g. MRI, CT, PET) and image-guided treatment with different radiation types (e.g. photons, protons). The multimodality small animal bed was constructed with CAD software and produced with a 3D printer using the fused deposition modeling procedure. The bed is made of thin acrylonitrile butadiene styrene (ABS), which is fully compatible with magnetic fields, barely influence radiation and is chemically resistant against most frequently used disinfectants. To facilitate proper positioning and alignment of the animal, the bed contains a tooth bar and ear pins for cranial fixation as well as a detachable distal foot holder for the hind leg. For inhalation anesthesia, a respective mask is integrated. To avoid hypothermia, the bed is supplied with a controllable stream of HEPA-filtered warm air. Furthermore, the respiration of the animal can be monitored during the experiment using a respiratory cushion. Suitability of the prototype was tested for photon and proton irradiation as well as CT imaging and proton radiography. In conclusion, the designed multimodality bed enables standardized positioning of small animals and provides integrated solutions for their anesthesia, warming and monitoring. Ist use for multimodal monitoring and image-guided irradiation of experimental tumors will simplify the workflow and image analyses for preclinical radiooncological investigations.

Keywords: Preclinical research; cancer; proton therapy; imaging

  • Poster
    Jahrestagung/Dreiländertagung Deutsche Gesellschaft für Medizinische Physik, 10.-13.09.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25354
Publ.-Id: 25354


Indium-bearing sulphides from the Hämmerlein polymetallic skarn deposit, Germany – Evidence for late stage diffusion of indium into sphalerite

Bauer, M. E.; Seifert, T.; Krause, J.; Burisch, M.; Richter, N.; Gutzmer, J.

The Hämmerlein skarn deposit, located in the western Erzgebirge (Germany), consists of a cassiterite-dominated Sn mineralization associated with minor Zn-Cu-In sulphide mineralization. In this contribution, we describe the nature of the sulphide-associated In mineralization based on underground mapping, mineralogical methods (microscopy, SEM-based MLA studies and EPMA X-ray element maps) and mineral chemistry data (quantitative EPMA data).
In-bearing sphalerite and roquesite [CuInS2] are closely associated with paragenetically late In-bearing chalcopyrite (average 0.15 wt% In). Sphalerite contains up to 20 wt% In as well as elevated Cu contents. The highest In concentrations occur exclusively at rims and along cracks of sphalerite grains. The appearance resembles diffusion profiles, suggesting that In enrichment is due to an hydrothermal overprint that postdates the formation of sphalerite. Detailed textural observations show that the diffusion fronts in sphalerite grains are thicker where they are in contact to anhedral masses of hematite and magnetite that are regarded as product of decomposition of of In-bearing chalcopyrite. Hematite and magnetite have In concentrations below the detection limit (EPMA). Indium and Cu, released by the decomposition of In-bearing chalcopyrite, were incorporated into sphalerite along grain boundaries and cracks.. EPMA element distribution maps indicate that the In enrichment in sphalerite is related to the coupled substitution of Cu+ + In3+ ↔ 2 Zn2+ [1].

[1] Johan (1988) Mineralogy and Petrology 39, 211–229.

  • Open Access Logo Contribution to proceedings
    Goldschmidt Conference 2017, 13.-18.08.2017, Paris, France
    Goldschmidt Conference Archive, Paris: Geochemical Society and European Association of Ge
  • Lecture (Conference)
    Goldschmidt Conference 2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25353
Publ.-Id: 25353


Mineral Systems Analysis of Variscan ore deposits: The need for geochemical data

Gutzmer, J.; Burisch, M.; Frenzel, M.; Ostendorf, J.; Haschke, S.; Seifert, T.; Markl, G.

Mineral Systems Analysis aims to provide a holistic understanding of geological processes required to form and preserve ore deposits at all scales [1]. Detailed knowledge of the ore-forming process alone does thus not suffice. Instead, comprehensive knowledge is required, taking into consideration all drivers of a given mineral system, including geodynamic setting and crustal architecture, crustal fertility (metal source), metal transport mechanism, processes of local concentration (trap) as well as postdepositonal alteration and preservation. Robust conceptual models are the result of Mineral Systems Analysis; these models are used to efficiently identify exploration targets or target regions [2].
Mineral Systems Analysis has generally not been applied to the Variscan Orogen, despite its exceptional endowment in mineral deposits. This is attributable to a severe lack of modern geoscientific data for most of the known mineral deposits many of which have ceased production decades ago. As a direct consequence, our understanding of the mineral system of the Variscan Orogen is rather tentative. We illustrate the state of knowledge on selected examples and illustrate how the use of state-of-the-art geochemical data, combined with current regional geotectonic understanding, vastly improve our understanding – and enable us to carry out Mineral Systems Analysis. This, in turn, will provide a suitable foundation for future exploration targeting.

  • Open Access Logo Contribution to proceedings
    Goldschmidt Conference 2017, 13.-18.08.2017, Paris, France
    Goldschmidt Conference Archive, Paris: Geochemical Society and European Association of Ge
  • Lecture (Conference)
    Goldschmidt Conference 2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25352
Publ.-Id: 25352


Insights into oncoidal morphology and sedimentology of a Mesoarchean granular iron formation from southern Africa using 3D X-ray computed tomography (µXCT)

Smith, A. J. B.; Beukes, N. J.; Gutzmer, J.; Johnson, C. M.; Czaja, A. D.; de Beer, F. C.

The oldest known granular iron formation (GIF) occurs in the ca. 2.96¬–2.92 Ga Mozaan Group of the Pongola Supergroup of southern Africa. The GIF comprises stacked beds interbedded with deeper water facies iron formation. The chert granules are marked by irregular rims composed of magnetite and calcite and can be defined as oncoids. Initial geochemical studies showed that the calcite is isotopically light, suggesting an organic carbon source for CO2, and that the Fe isotope characteristics of shallower water GIF are decoupled from those in the deeper water iron formation. Due to the complexity of the oncoidal rim morphologies, traditional petrography is complicated by the bias inherent to 2D intersections of the samples. However, the different mineral densities allow successful µXCT application revealing that rim morphologies are fairly homogenous consisting of multiple, multi-directional, micro-scale chert, magnetite and calcite domes surrounding the granule cores. The chert cores of the granules and domes suggest continuous chert precipitation in a wave-reworked environment. A surprising result was that calcite was not limited to the granule rims, and that some granules contain abundant calcite in their cores, indicating that calcite formation is not linked to that of magnetite. Ferric iron can therefore not be the organic carbon oxidant. 3D reconstruction of granules and samples shows that the GIF contains multiple upward fining beds, with granules decreasing in size, followed by granule and rim fragments, terminating in an Fe-rich clay layer. Granule rims can also be seen to have been broken off. These characteristics support deposition from storm surge currents.

  • Open Access Logo Contribution to proceedings
    Goldschmidt Conference 2017, 13.-18.08.2017, Paris, France
    Goldschmidt Archive, Paris: Geochemical Society
  • Lecture (Conference)
    Goldschmidt Conference 2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25351
Publ.-Id: 25351


Modified DTPA ligand systems for simplified trivalent actinide-lanthanide separations based on the TALSPEAK process

Jones, J. E.; Langford, M. H.; Geist, A.; Panak, P. J.; Kaden, P.; Adam, C.; Adam, N.; Sharrad, C. A.; Martin, L.; Natrajan, L. S.

The necessity to reprocess spent nuclear fuel has arisen from increasing volumes of highly active and long-lived radionuclides associated with nuclear fission alongside increasing environmental impact concerns. In particular, one major challenge is the separation of the long-lived trivalent minor actinides (here, AmIII and CmIII) from the trivalent lanthanides in order to allow the future transmutation of the actinides into shorter lived radionuclides for the purpose of reducing the long-term radiotoxicity of the waste and the volume build up in storage. There are currently a number of different processes under development world-wide, all of which rely on the coordination chemistry and selective extraction of the minor actinides from the trivalent lanthanides using solvent partitioning. Of these, The TALSPEAK process (Trivalent Actinide Lanthanide Separation by Phosphorus reagent Extraction from Aqueous Komplexations) has showed great promise in separating the trivalent lanthanides from the minor actinides. The process uses DTPA (diethylenetriamine pentaacetic acid) as the chelating holdback reagent, HDEHP (bis-2-ethylhexyl phosphoric acid) as the extracting ligand and lactic acid as the buffer to prevent precipitation of DTPA that occurs at below pH 3.6. However, despite the considerable separation factors obtainable, and the fact the process exhibits promising radiolysis resistance, the process operates at sub optimal pH values. To overcome these limitations, we have developed a family of DTPA-amino acid conjugates that operate under TALSPEAK-like conditions over a much lower pH range of 1.5-2.5. Additionally, these ligands show comparable selectivity to the TALSPEAK process and are also relatively resistant to radiolysis. We will discuss the coordination chemistry of these ligands with the lanthanides and minor actinides using a combination of luminescence and NMR spectroscopies.

Keywords: DTPA; amino acids; actinides(III); lanthanides(III)

  • Lecture (Conference)
    253rd ACS National Meeting & Exposition, 02.-06.04.2017, San Francisco, CA, United States

Permalink: https://www.hzdr.de/publications/Publ-25350
Publ.-Id: 25350


Assessment of thermal phenomena in Li||Bi liquid metal batteries through analytical and numerical models

Personnettaz, P.

Liquid Metal Batteries (LMBs) are a promising electrical energy storage technology, built as a stable density stratification of two liquid metals separated by a molten salt. Their operation has been proved only for small prototypes, in order to transfer it to the industrial scale full knowledge of the different phenomena occurring in LMBs is required. In this work, done at Helmholtz-Zentrum Dresden-Rossendorf, we focus our attention on the thermal phenomena that appear inside Li||Bi LMBs . The system is first analyzed in the framework of the electrochemistry, a simple voltage model is developed and the heat generation terms are estimated. The geometrical and operating parameters are fully defined from multi-physics considerations. Then LMBs are studied with the continuum mechanics approach and all possible thermal phenomena are discussed. In the hypothesis of pure heat conduction, the first assessment of the effects of the reversible heat generation was done. Moreover the multiphase solver multiphaseInterFOAM is extended in order to take into account the thermal convection inside the cell. The results of our solver are compared to the one of a pseudo-spectral code. Finally some simulation results of thermal convection in LMBs are proposed.

  • Master thesis
    Politecnico di Torino, 2017

Permalink: https://www.hzdr.de/publications/Publ-25349
Publ.-Id: 25349


Smart Kd-values as realistic distribution coefficients

Stockmann, M.; Britz, S.; Flügge, J.; Fricke, J.; Becker, D.; Noseck, U.; Brendler, V.

One important natural process retarding the transport of contaminants is sorption onto mineral surfaces. A respective process understanding and realistic geochemical modelling of sorption is thus of high relevance in safety assessments of radioactive waste repositories. Further application areas are groundwater protection, environmental remediation or e.g. disposal of chemotoxic hazardous waste. Most often conventional concepts with constant distribution coefficients (Kd-values) are applied in reactive transport simulations, with the advantage to be simple and computationally fast, but not reflecting changes in geochemical conditions. Here, the smart Kd concept (www.smartkd-concept.de), a mechanistic approach mainly based on surface complexation models, is applied in geochemical modelling and has been further developed to calculate more realistic distribution coefficients for a wide range of important environmental parameters, e.g. pH, ionic strenght, competing cations and complexing ligands [1, 2] using PHREEQC, UCODE and RepoSUN/SimLab [3, 4, 5]. The philosophy behind this approach is to compute a-priori multidimensional smart Kd matrices which are available for subsequent transport simulations. We could demonstrate that constant Kd-values (e.g. for U(VI) [6], see Fig. 1) used so far are too crude an assumption but they rather range over several orders of magnitude. For considering worst case scenarios much smaller Kd-values have to be use than in conventional concepts. Similar results will be presented for Am and Np.

Keywords: Distribution coefficient; Radionuclides; Sorption; Safety assessment

  • Lecture (Conference)
    Goldschmidt2017 Konferenz, 13.-18.08.2017, Paris, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-25348
Publ.-Id: 25348


The code system AC2 for the simulation of advanced reactors within the frame of the German EASY project

Buchholz, S.; Klein-Heßling, W.; Bonfigli, G.; Kaczmarkiewicz, N.; Neukam, N.; Schäfer, F.; Wagner, T.

The reliable simulation of all relevant phenomena occurring during accidents in nuclear power plants (NPP) is an ongoing challenge for the development of computer codes. New generation reactor designs are using more and more passive type systems within their safety systems to cope with accidents. System codes such as the code system AC2 consisting of the modules ATHLET, ATHLET/CD and COCOSYS used in licensing procedures and for safety analyses have to be further developed and validated to be able to simulate such passive systems behaviour.
One aim of the German project EASY is the enhancement and validation of AC2 towards its use for reliable analysis of the behaviour of passive safety systems in nuclear power plants (NPP).
In this paper the work related on the extended coupling between the modules ATHLET and COCOSYS and first results showing the extended capability of the new design of coupling will be presented.
For that the coupling of both codes had to be extended to allow the simulation of the interaction between passive components linked to the primary system with interaction to the containment behaviour. The new coupling concept, using a full interlinked data network and an advanced data transfer between both modules, has in addition an user interface to implement additional modules into ATHLET code. Here new technologies are used to couple both codes improving the modular structure and maintainability.

Keywords: Coupling of code systems; passive systems; operational and accident behavior

  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi’an, China
    Proceedings of NURETH-17
  • Lecture (Conference)
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi’an, China

Permalink: https://www.hzdr.de/publications/Publ-25347
Publ.-Id: 25347


Evidence of design basis accidents mitigation solely with passive safety systems within the frame of the German EASY project

Buchholz, S.; Schaffrath, A.; Bonfigli, G.; Kaczmarkiewicz, N.; Neukam, N.; Schäfer, F.; Wagner, T.

Advanced reactor concepts such as Generation III, III+ and also SMR provide passive safety systems to cope with design basis accidents like loss of coolant accident or loss of main heat sink. In order to be able to assess the controllability of such DBA with passive systems only, computer codes are needed which are able to simulate the behaviour of these passive systems and which are well validated. In the German EASY project the coupled code system AC2 –mainly composed of the system code ATHLET-(CD) and the containment code COCOSYS –is currently being enhanced and validated for such applications on the basis of the KERENA reactor concept of AREVA.
Beyond the implementation of a suitable and effective coupling of the two codes ATHLET and COCOSYS, code development is done for modelling the behaviour of a passive flooding valve and enhancing the ATHLET 3D-model for large water pools.
Validation of the codes is done in two ways: Firstly, single effect tests, performed at the INKA facility in Karlstein, are used to validate the codes for the passive components used in the KERENA design. Secondly, the coupled code system is validated by simulating several integral tests which will be performed at the INKA facility during EASY. These integral tests represent design basis accidents such as SB-LOCA, LB-LOCA and SBO.
Finally, an uncertainty and sensitivity analyses of two integral tests will be performed since the behaviour of passive safety systems is affected strongly by the respective boundary conditions of the system.

Keywords: EASY; Passive Safety Systems; Validation; Code Coupling; AC2

  • Contribution to proceedings
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi’an, China
    Proceedings of NURETH-17
  • Lecture (Conference)
    17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-17), 03.-08.09.2017, Xi’an, China

Permalink: https://www.hzdr.de/publications/Publ-25346
Publ.-Id: 25346


Modelling of NTCP for acute side effects in patients with prostate cancer or brain tumours receiving proton therapy

Dutz, A.; Agolli, L.; Troost, E. G. C.; Krause, M.; Baumann, M.; Lühr, A.; Löck, S.

The purpose of this study was to identify patients who likely benefit most from proton therapy (PT), based on the potential reduction of normal tissue complication probability (NTCP) compared to photon therapy. The NTCP models required for this comparison were developed using clinical data on acute side effects of prostate cancer and brain tumour patients having received PT.
In this study, 113 patients with primary brain tumours and 30 patients with adenocarcinoma of the prostate who had received PT were included. For the brain tumour patients, the radiation-induced acute side effects alopecia, erythema, pain and fatigue were considered. For prostate cancer patients, several gastrointestinal and genitourinary side effects were investigated. The occurrence of these side effects was correlated with different dose-volume parameters of associated organs at risk (OARs), such as skin and brain or rectum and bladder. The respective NTCPs were modelled by logistic regression. For every patient a volumetric modulated arc therapy (VMAT) photon treatment plan was retrospectively created. Differences in dosimetric parameters and NTCP between PT and VMAT plans were evaluated.
Significant correlations were found between acute side effects and dose to OARs. For example, occurrence of alopecia grade 2 and erythema grade ≥2 depended on dose-volume parameters in the high dose region of the skin (p<0.001). Proton plans showed significantly reduced low to intermediate dose volumes in all investigated OARs compared to VMAT plans (p<0.001). In the more relevant high dose volumes smaller differences between proton and photon treatment were found.
We found significant correlations between the occurrence of acute side effects and dose-volume parameters of associated OARs for patients with primary brain tumours or prostate cancer receiving PT. After inclusion of late side effects and validation in an external dataset, these NTCP models may be used to identify patients likely to benefit most from PT.

Keywords: Proton therapy; NTCP-models

  • Lecture (Conference)
    Jahrestagung der Biomedizinischen Technik und Dreiländertagung der Medizinischen Physik 2017, 10.-13.09.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25345
Publ.-Id: 25345


PRONTOX – A prospective randomized clinical trial for the treatment of lung cancer patients at the University Proton Therapy Dresden

Jakobi, A.; Stützer, K.; Thiele, J.; Makocki, S.; Troost, E. G. C.; Richter, C.

Patients with advanced lung cancer have a low overall survival despite treatment. Radiotherapy treatment is often lim-ited by the toxicity in the surrounding healthy tissue of the lung, oesophagus, spinal cord and heart. The prospective randomized clincial trial PRONTOX (NCT02731001) aims on the analyses of toxicities in patients treated for advanced lung cancer with either photon therapy or proton therapy. Only patients with tumor motion <10 mm are included. Photon and proton treatment plans are created based on time-resolved computed tomography (4D CT) imaging. Both plans are independently evaluated by experienced physicians for their applicability. If both treatments are deemed acceptable in terms of dosimetric parameters, randomization is executed. The dosimetric analysis includes the evaluation of the individual tumour motion and the uncertainties in range (3.5 %) and set-up (±3 mm) for the proton therapy treatment. End of March 2017, three patients were included, of which 2 had already finished their treatment getting double-scattered proton therapy. For the three patients, tumour motion was negligible and had only small effects on the dose distribution. The additional uncertainty analyses revealed the robustness of the generated proton therapy plans against the individual motion (maximum motion amplitude < 2 mm) as well as range and set-up uncertainties. During the treatment, respiratory surrogate signals were recorded for evaluation of breathing variabilities. In addition, control 4D CT were acquired once a week during treatment according to the trial protocol. Based on this imaging, changes in the patient anatomy and tumour motion were assessed. For the two patients who already completed treatment, the effect of anatomical changes and tumour motion changes on the fractional and accumulated dose distribution was small. No intervention e.g. a treatment plan adaptation was required in any case. Follow-up showed no recurrence and no side effects for these two patients so far.

Keywords: proton therapy; trial; lung cancer

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland
    DOI: 10.1515/bmt-2017-5036
  • Open Access Logo Abstract in refereed journal
    Biomedical Engineering / Biomedizinische Technik 62(2017)s1, P145
    DOI: 10.1515/bmt-2017-5036

Permalink: https://www.hzdr.de/publications/Publ-25343
Publ.-Id: 25343


Influence of anatomical changes in robust optimized proton plans for bilateral head and neck cancer targets

Cubillos Mesías, M.; Baumann, M.; Troost, E. G. C.; Lohaus, F.; Agolli, L.; Rehm, M.; Richter, C.; Stützer, K.

Robust optimization in proton therapy considers uncertainties in patient setup and particle range during the optimization process. However, anatomical changes that may occur during the treatment course are neglected. The aim of this study was to quantify the influence of anatomical changes on the dose distributions for head and neck cancer (HNC) patients scheduled for bilateral neck irradiation.

Datasets from eight bilateral HNC patients, consisting of a planning computed tomography (CT) and weekly control CTs, were used. Intensity-modulated proton therapy plans were calculated with minimax robust optimization, account-ing 3 mm and 3.5% for setup and range uncertainty, respectively. The dose to the low- and high-risk clinical target vol-umes (CTV) consisted of 57 and 70 Gy(RBE), respectively, in 33 fractions. Organs at risk, e.g. spinal cord, brainstem, parotid glands, larynx, pharyngeal constrictor and esophageal inlet muscle, were considered for plan optimization and analysis. The cumulative dose during 33 fractions was checked weekly taking the anatomy of the control CTs into ac-count, and compared with the nominal plan.

Nominal plans fulfilled the clinical specifications of D98 ≥ 95% of the prescribed dose to the CTVs (range: 95.8-98.8% for low-risk CTV and 96.2-98.9% for high-risk CTV). During the treatment course, anatomical changes lead to reduced D98 values in five patients, with minimum of 87.3% in the low-risk CTV and 91.3% in the high-risk CTV. Maximum doses to spinal cord and brainstem remained below 45 Gy and 54 Gy, respectively. Mean doses to the contralateral pa-rotid gland remained below 26 Gy, except in one patient (maximum mean dose = 27.2 Gy).

For some patients, robust optimization prior to treatment initiation is insufficient to account for anatomical changes occurring during the treatment course. The results for a total cohort of 17 patients, including robustness analysis and plan adaptation strategies will be presented.

Keywords: Head-and-neck cancer; Proton therapy; Robust optimization; Adaptation

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25342
Publ.-Id: 25342


Biosynthesis of magnetic nanoparticles by human mesenchymal stem cells following transfection with the magnetotactic bacterial gene mms6

Elfick, A.; Rischitor, G.; Mouras, R.; Azfer, A.; Lungaro, L.; Uhlarz, M.; Herrmannsdörfer, T.; Lucocq, J.; Gamal, W.; Bagnaninchi, P.; Semple, S.; Salter, D. M.

The use of stem cells to support tissue repair is facilitated by loading of the therapeutic cells with magnetic nanoparticles (MNPs) enabling magnetic tracking and targeting. Current methods for magnetizing cells use artificial MNPs and have disadvantages of variable uptake, cellular cytotoxicity and loss of nanoparticles on cell division. Here we demonstrate a transgenic approach to magnetize human mesenchymal stem cells (MSCs). MSCs are genetically modified by transfection with the mms6 gene derived from Magnetospirillum magneticum AMB-1, a magnetotactic bacterium that synthesises single-magnetic domain crystals which are incorporated into magnetosomes. Following transfection of MSCs with the mms6 gene there is bio-assimilated synthesis of intracytoplasmic magnetic nanoparticles which can be imaged by MR and which have no deleterious effects on cell proliferation, migration or differentiation. The assimilation of magnetic nanoparticle synthesis into mammalian cells creates a real and compelling, cytocompatible, alternative to exogenous administration of MNPs.

Permalink: https://www.hzdr.de/publications/Publ-25341
Publ.-Id: 25341


DTPA-amino acid conjugates, complexing agent and buffer in a single molecule: towards a simplified TALSPEAK process

Jones, J. E.; Geist, A.; Kaden, P.; Martin, L. R.; Natrajan, L. S.

1. Introduction
The TALSPEAK process [1] was developed at Oak Ridge National Laboratory in the 1960’s to separate trivalent actinide ions, An(III), from chemically similar lanthanide ions, Ln(III) by solvent extraction. The idea was using an extracting agent unselective for An(III) over Ln(III) and adding a complexing agent to the aqueous phase to infer selectivity [2]. Despite the simplicity of this concept, TALSPEAK is actually a rather complex system, with numerous equilibria involved. The original TALSPEAK system consisted of HDEHP (bis-2-ethylhexyl phosphoric acid) as the extracting agent, DTPA (diethylenetriamine pentaacetic acid) as the An(III)-selective complexing agent and lactic acid as buffering agent. Constantly improving TALSPEAK by substituting the components of the original system, ALSEP [3] and Advanced TALSPEAK [4, 5] have been developed.
We have pursued a concept which differs in two aspects, (a) using amino acids (AA) as buffering agent and (b) linking them to the complexing agent. This way, only a single molecule is added to the aqueous phase and the system is expected to behave more simply.
2. Results and Discussion
Several DTPA-AA conjugates were synthesised, DTPA-Arg, DTPA-His, DTPA-Ser and DTPA-Ala. These were tested in solvent extraction experiments. Organic phase was 0.2 mol/L HDEHP in kerosene, aqueous phases were solutions containing 50 mmol/L DTPA-AA conjugate, Am(III) and Ln(III) (Y; La–Lu). pH was adjusted by adding HNO3 or NaOH.
The lowest pH at which separation was achieved (i.e., Am(III) distribution ratio < 1 and all Ln(III) distribution ratios > 1) was in the range of 1.1–1.5. Separation factors for Eu(III) over Am(III) were ≈ 100 and the minimum separation factors between Am(III) and the least extracted Ln(III), being Nd(III) in all cases, were 30–40.
The coordination chemistry was studied by luminescence and NMR. Photophysical studies of the Eu(III)-DTPA-AA complexes demonstrated characteristic Eu(III) emission, with associated lifetime decay profiles confirming 1:1 coordination. 1H NMR studies were performed with Am(III), confirming successful complexation.
In conclusion, an improved TALSPEAK system is reported which compares favourably to known TALSPEAK systems.

Key words: TALSPEAK, amino acids, actinides(III), lanthanides(III)

1. Weaver, B.; Kappelmann, F. A., USAEC report ORNL-3559, Oak Ridge National Laboratory, USA: 1964.
2. Nilsson, M.; Nash, K. L., Solvent Extr. Ion Exch. 2007, 25 (6), 665–701.
3. Gelis, A. V.; Lumetta, G. J., Ind. Eng. Chem. Res. 2014, 53 (4), 1624–1631.
4. Braley, J. C.; Grimes, T. S.; Nash, K. L., Ind. Eng. Chem. Res. 2010, 51 (2), 629–638.
5. Lumetta, G. J.; Casella, A. J.; Rapko, B. M.; Levitskaia, T. G.; Pence, N. K.; Carter, J. C.; Niver, C. M.; Smoot, M. R., Solvent Extr. Ion Exch. 2015, 33 (3), 211–223.

Keywords: TALSPEAK; Aminosäuren Actinide(III); Lanthanide(III)

  • Poster
    ISEC 2017 – The 21st International Solvent Extraction Conference, 05.-09.11.2017, Miyazaki, Japan

Permalink: https://www.hzdr.de/publications/Publ-25340
Publ.-Id: 25340


MLA-based detection of organic matter with iodized epoxy resin – An alternative to carnauba

Rahfeld, A.; Gutzmer, J.

Solid organic matter is an important constituent not only in coal, but also in black shale-hosted ore deposits. The reliable recognition and quantification of organic carbon – as well as its microfabric relation to associated inorganic minerals - plays a crucial role in characterization by scanning electron microscopy-based image analysis. However, the use of conventional epoxy resin in the preparation of grain mounts does not allow for recognition of solid organic carbon compounds. In this study we illustrate that the use of iodized epoxy resin readily overcomes this bottleneck. Best results are obtained with an addition of 15 wt% iodoform to the epoxy resin. With process samples of black shale-hosted polymetallic Kupferschiefer-type ore as a case study it is shown that recognition and quantification of solid organic carbon is easily achieved and that tangible parameters such as particle and grain sizes, association and liberation for ore and gangue minerals can be determined in the presence of solid organic matter. Due to the inherent uncertainty of the exact chemical composition of the kerogen contained in Kupferschiefer it was not possible to attain exact comparability between chemical Corg assays and assays calculated from MLA data. However, the results are still found to closely agree with one another. The strength of iodized resin lies in its ability to distinguish organic matter with high hydration ratios in addition to the easy integration in sample preparation. It could therefore be an attractive supplement in the analyses of other raw materials containing complex organic-matter.

Keywords: SEM-based image analysis; epoxy resin; iodoform; organic matter; Kupferschiefer

Permalink: https://www.hzdr.de/publications/Publ-25339
Publ.-Id: 25339


Ion Irradiation Induced Cobalt/Cobalt Oxide Heterostructures: From Materials to Devices

Hilliard, D.; Yildirim, O.; Fowley, C.; Kanth Arekapudi, S. S. P. K.; Cansever, H.; Böttger, R.; Hlawacek, G.; Hellwig, O.; Lindner, J.; Fassbender, J.; Deac, A. M.; Perzanowski, M.

Spintronic devices are often patterned from continuous films into micro- or nanostructures. Fabrication of those nano-devices is self-limited and depends on the lateral resolution of the chosen fabrication method. Ion irradiation offers an alternative route to introduce smaller magnetic patterns limited by the size of the ion beam. Irradiation of oxide materials can cause chemical reduction and lead to the local formation of metallic species. By using the oxide family of ferromagnets (e.g., Fe, Ni and Co), reduction leads to the formation of ferromagnetic and conducting volumes limited by the size of the ion irradiated area that are embedded into a non-magnetic and insulating matrix. On the other hand, the physical mechanism behind ion irradiation-induced oxide reduction could not be explained. Therefore, our studies focus on ion (H, He, Ne, O) irradiated cobalt-oxide (CoO or Co3O4) systems in order to explain the physics behind the process. Also, the knowledge is being exploited to tune exchange-bias direction, prepare nano contacts for synchronized spin torque oscillators, and to form topographically stabilized magnetic skyrmions.

Keywords: Cobalt oxide; Ion irradiation; Oxygen reduction; Ferromagnetic

  • Lecture (Conference)
    INTERMAG Dublin 2017, 24.-28.04.2017, Dublin, Ireland
  • Poster
    DPG-Frühjahrstagung (DPG Spring Meeting), 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25338
Publ.-Id: 25338


Model driven SAXS reconstruction

Zacharias, M.; Garten, M.; Rödel, M.; Kluge, T.; Bussmann, M.; Cowan, T.; Garcia, A. L.; Gutt, C.; Hartley, N.; Kraus, D.; Mcbride, E.; Pelka, A.; Prencipe, I.; Rödel, C.; Schramm, U.

We present an approach for reconstructing real space information from small angle x-ray scattering images that utilizes reduced models to describe the scattering distribution. This implies a massive reduction of the reconstruction space dimensionality. First reconstruction results for experimental data are shown.

Keywords: SAXS; reconstruction; phase retrieval; LN04

  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25337
Publ.-Id: 25337


Ab initio thermodynamic study of proton conductivity in BaZrO3

Raja, N.; Murali, D.; Posselt, M.; Satyanarayana, S. V. M.

BaZrO3 (BZO) is a potential candidate material for electrode in solid oxide fuel cells (SOFL) because of its excellent reported proton conductivity [1, 2]. It is suggested that presence of intrinsic point defects such as O vacancies act as sinks for O atoms produced upon hydrogenation of water molecule and promote proton conductivity. For this, the formation energy of O atom should be lower and its migration should be suppressed [3]. Since these materials are used at high temperature, it is very important to consider effects of phonons on the defect chemistry [4, 5, 6]. In this work, first, we identify thermodynamically favorable conditions for the formation of BZO by free energy calculations of bulk phases using Density Functional Theory. Next, we study the free energy of formation of both neutral and charged O vacancies of stable BZO phase and discuss significance of these results for experimental growth conditions. Initial results show that phonon contributions to free formation energy of charged vacancy is significantly high compared to neutral vacancy due to large lattice distortion and negative formation entropy for charged vacancy. Studies also show that acceptor doping both at A and B site lowers the formation energy of O vacancy in the vicinity of dopant atoms resulting in increase of proton conductivity [7, 8]. In order to understand the mechanism of this enhancement, we study the free energy of formation of O clusters in reducing conductions for acceptor doping at A and B sites.

References

[1] K. D. Kreuer, Annu. Rev. Mater. Res. 2003, 33:333–59.
[2] K. D. Kreuer, ed. T. Ishihara, Springer, 2009, pp. 261–271.
[3] Emile B´ evillon, Guilhem Dezanneau, and Gr´ egory Geneste, Physical Review B 2011, 83,
174101.
[4] Jessica Hermet, Francois Bottin, Guilhem Dezanneau, and Gregory Geneste Physical Review
B 2012, 85, 205137.
[5] Denis Gryaznov, Evgeny Blokhin, Alexandre Sorokine, Eugene A. Kotomin, Robert A.
Evarestov, Annette Bussmann-Holder, and Joachim Maier J. Phys. Chem. C 2013, 117,
13776−13784.
[6] Tor S. Bjørheim, Marco Arrigoni, Denis Gryaznov, Eugene Kotomin and Joachim Maier
Phys. Chem. Chem. Phys. 2015, 17, 20765.
[7] Marten E. Bjorketun, Per G. Sundell, and Goran Wahnstrom Physical Review B, 2007,
76, 054307.
[8] Andreas Løken, Sarmad W. Saeed, Marit N. Getz, Xin Liu and Tor S. Bjørheim, J. Mater.
Chem. A, 2016, 4, 9229.

Keywords: DFT; proton conductivity; solid oxide fuel cells

  • Lecture (Conference)
    International Conference on Advances in Functional Materials, 06.-08.01.2017, Chennai, Madras, India

Permalink: https://www.hzdr.de/publications/Publ-25336
Publ.-Id: 25336


New results for the structure of certain warm dense matter states

Vorberger, J.

The dynamic and static structure factors contain a wealth of information about the state and properties of a physical system. The structure of a system relates directly to its equation of state, collective modes, stopping power and relaxation processes.
Since x-ray and particle scattering are extremely important experimental tools to diagnose warm dense matter, theoretical predictions of the structure have become one of the best modes of comparison between theory and experiment in the warm dense matter regime.
We give an overview of state of the art theoretical methods to calculate the structure of warm dense matter in equilibrium and non-equilibrium. Results are given for such states as created in recent experiments. Limits of the current theories and possible future developments are discussed.

Keywords: warm dense matter; x-ray scattering; structure; non-equilibrium; dissociation; ionisation; strong coupling

  • Lecture (Conference)
    Workshop on Science of "From Matter to Materials and Life", 19.-20.10.2017, Hamburg, Deutschland
  • Lecture (Conference)
    Workshop on Science of "From Matter to Materials and Life", 15.-16.12.2016, Hamburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25335
Publ.-Id: 25335


The structure and its role in uncovering the physics of warm dense matter

Vorberger, J.

Warm dense matter states in the transition region from high pressure solids to high temperature plasmas are found in terrestrial planets, giant planets, and exoplanets. Such states are created in the laboratory during interaction of lasers or shock waves with matter. The intention is usually to obtain direct experimental access to equilibrium or nonequilibrium warm dense matter states or it might be an intermediate state on the way to fusion plasmas states or laser-plasma acceleration experiments.
Studying warm dense matter, one faces several challenges. The first is the determination of a full set of basic parameter like density, charge state, temperature, or the momentum distribution function that fixes the state of matter in the phase space. Only then is it meaningful to investigate important quantities like the equation of state, phase transitions, structure, collective excitations, relaxation processes, or the stopping power.
Here, we present recent developments and results in warm dense matter physics. The close interplay between theory and experiment via x-ray scattering and first principle simulations is highlighted. The dynamic structure factor containing a wealth of information serves as the connection between measurements and calculations. Results are given for a number of elements like aluminium, carbon, or iron, and materials like plastic.

Keywords: warm dense matter; dynamic structure; x-ray scattering; non-equilibrium; equilibrium; ionisation; strong coupling; giant planets; ICF

  • Invited lecture (Conferences)
    DPG Frühjahrstagung Bremen, 13.-17.03.2017, Bremen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25334
Publ.-Id: 25334


The non-equilibrium structure in warm dense matter

Vorberger, J.

Powerful femtosecond pump lasers and femtosecond x-ray probe beams created by free electron lasers make it possible to create and diagnose strongly correlated states of matter in which the electron and ion Wigner distribution functions are of a strongly non-equilibrium type.
We therefore present a quantum theory for the dynamic structure factors in just such non-equilibrium, correlated, two-component systems.
To make our theory applicable for x-ray scattering as in equilibrium, a generalized Chihara decomposition for the total electron structure factor in non-equilibrium is derived. Examples are given and the influence of correlations and exchange on the structure and the x-ray scattering spectrum are discussed for a model non-equilibrium distribution, as often encountered during laser heating of materials, as well as for two-temperature systems.

Keywords: warm dense matter; structure; x-ray scattering; dynamic structure; non-equilibrium

  • Lecture (Conference)
    37th International Workshop on High Energy Density Physics with Intense Ion and Laser Beams, 29.01.-03.02.2017, Hirschegg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-25333
Publ.-Id: 25333


Studying laser ion acceleration with overdense hydrogen ribbon targets by PIC code simulation

Branco, J.; Zeil, K.; Obst, L.; Schramm, U.; Kluge, T.; Bussmann, M.

We present simulation results on laser ion acceleration using hydrogen ribbon targets irradiated by ultra-intense, ultra-short laser pulses. These targets promise to produce pure proton beams applicable for cancer therapy at high repetition rates. We address critical issues concerning the acceleration process that potentially hinders the application of these beams in a clinical scenario.

For achieving proton energies suitable for the treatment of deep seated tumors it is important to increase the laser intensity. At high laser intensities, plasma instabilities both at the target surfaces and target bulk can create electron filaments which result in non-uniform proton beams, detrimental for delivering uniform dose distributions.

By varying the laser contrast it is possible to change the preplasma scale length to influence the formation of instabilities. Other means of controlling proton beams are either changing target geometry (e.g. going from planar ribbon targets to spherical droplet targets) or the polarization. We present results of 2D3V particle-in-cell simulations at realistic densities that show the influence on the plasma dynamics and final beam properties and discuss their relevance regarding applications of solid hydrogen targets for laser-driven proton tumor therapy.

Keywords: Ion acceleration; cryogenic hydrogen; PIC simulation; proton therapy; preplasma; intensity; filamentation

  • Lecture (Conference)
    New Accelerator Concepts I, 20.03.2017, TU Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-25332
Publ.-Id: 25332


Role of Oxygen Vacancy on the Hydrophobic Behavior of TiO2 Nanorods on Chemically Etched Si Pyramids

Saini, C. P.; Barman, A.; Das, D.; Satpati, B.; Bhattacharyya, S. R.; Kanjilal, D.; Ponomaryov, A.; Zvyagin, S.; Kanjilal, A.

Oxygen vacancy (OV) controlled hydrophobicity of self-assembled TiO2 nanorods (NRs) on chemically etched Si pyramids is investigated by irradiating with 50 keV Ar-ions at room temperature. Apparent contact angle (CA) is found to increase from 122° to 141° up to a fluence of 1 × 1015 ions/cm2, followed by a gradual reduction to 130° at 1 × 1017 ions/cm2. However, the drop in apparent CA is found to be associated with the decrease in fractional surface area via transformation of NRs to an amorphous layer above 1 × 1015 ions/cm2, though it is still higher than that of as-grown one. Detailed X-ray photoelectron spectroscopy and electron paramagnetic resonance measurements suggest that the control of hydrophobic behavior is related to the suppression of surface free energy via migration of OVs into the voids in TiOx layers.

Permalink: https://www.hzdr.de/publications/Publ-25331
Publ.-Id: 25331


Coordination chemistry of tetravalent neptunium with aromatic polycarboxylate ligands

Volkringer, C.; Martin, N. P.; März, J.; Hennig, C.; Ikeda-Ohno, A.; Loiseau, T.

Coordination polymers are organic-inorganic complexes built up from the association of metallic centers with O- or N-donor ligands. In the particular case of actinides (An), previous literature mainly has reported the synthesis of solid networks bearing U(VI) or Th(IV). Trans-uranium elements have been much less studied due to their high radiotoxicity and limited amount of the material source. Among the possible oxidation states of An, the tetravalent state has been investigated most actively and large polynuclear oxo-clusters have been isolated for U1,2 or Pu3. In contrast, there are very few data concerning Np(IV) compounds. In 2012, Takao et al.4 reported the formation of Np(IV) hexanuclear cluster in an aqueous solution. The knowledge of the formation of such polynuclear An(IV) species could be of significant importance for the fate of An in contaminated soils containing O-donor ligands, such as humic acids or organic pollutants.
In this work, we studied the crystallization of Np(IV) with various aromatic polycarboxylate ligands in different solvents and analyzed their crystal structures. In water, an infinite chain of Np2O2(H2O)2(1,2-bdc)2 were isolated in the presence of phthalate.5 This compound crystallizes as orange aggregates, whereas the analogue compound with uranium is obtained as green crystals. With mellitic acid the oxidation of Np(IV) to Np(V) was observed and led to large green plates, involving layers of {NpO7H2O0-2} units linked to each other via trans-dioxo neptunyl bonds.
The use of other solvents allowed the crystallization of large polynuclear discrete Np(IV) clusters. For example, using DMF, the hexanuclear unit of [Np6O4(OH)4] has been obtained with different dicarboxylic ligands and is the basic building unit to form an open-framework structure (Figure 1, left). The corresponding structures revealed the isolation of the hexanuclear cluster An6O8 with Np(IV), the first example of hexanuclear Np(IV) complex characterized in the solid state. These clusters are linked by the ligand creating tetrahedral and octahedral voids in the structure. The formation of larger neptunium-based polyoxo clusters will be also presented.

Keywords: actinides; neptunium; coordination; carboxylate; metal-organic framework; polymers; tetravalent; single crystal structure

  • Lecture (Conference)
    Actinides 2017, 13.-14.07.2017, Sendai, Japan

Permalink: https://www.hzdr.de/publications/Publ-25330
Publ.-Id: 25330


Eco-efficiency indicator framework implemented in the metallurgical industry: part 2-a case study from the copper industry

Reuter, M. A.; Ronnlund, I.; Horn, S.; Aho, J.; Aho, M.; Paallysaho, M.; Ylimaki, L.; Pursula, T.

Purpose Sustainability differentiation has become an important issue for companies throughout the value chain. There is thus a need for detailed and credible analyses, which show the current status and point out where improvements can be done and how. The study describes how a comprehensive product-centric eco-efficiency indicator framework can be used to evaluate, benchmark, and communicate the sustainability of a copper production value chain. The indicator framework, together with the suggested data collection and simulation methods, aims at evaluating the whole system, while still enabling a focus on scopes of different width. The status of the environment, current production technologies, locationspecific and process-specific issues all play a role in achieving sustainable development.
Methods Copper cathode production from copper ore was chosen to exemplify the developed framework. Data sets from a simulation tool were used when available and LCI databases and LCA software were utilized for the remaining steps. The value chain is analyzed and the benchmark for each indicator built according to the new Gaia Refiner indicator framework. This method enables analysis of specific production steps with a higher degree of accuracy.
Results and discussion The case study shows how some important environmental sustainability issues in copper production can be analyzed and benchmarked within a product group. Benchmark data is collected and used in the analysis for the selected system scope. Data availability is still an issue and the example shows which areas require more information in this context so that products and value chains can be benchmarked in the future on a more consistent basis. The energy mix, chemical use, and land use contribute to potential environmental sustainability risks within the product benchmarking group, while emissions control shows competitive environmental sustainability advantages for the case study.
Conclusions The methodology is shown to work well in highlighting the sustainability advantages and risks of value chains in copper production with the selected system scope in a visualmanner through the Sustainability Indicator "Flower" The importance of a baseline is clear.
The effect of the metal ore grade on the results shows that the scalability of the analysis system is very important. Scaling the system scope up will show the differences in varying value chains and scaling the system scope down will show efficiency differences between more similar value chains, thus visualizing where innovation has the biggest impact.

Keywords: Benchmarking; Circular economy; Eco-efficiency; Footprint; Indicator; Metallurgy; Process and system simulation; Resource efficiency; Sustainability

Permalink: https://www.hzdr.de/publications/Publ-25329
Publ.-Id: 25329


Radiochronology of Abyssal Sediments with 10Be and 26Al - Advantages and Obstacles

Feige, J.; Wallner, A.; Bourlès, D.; Fifield, L. K.; Golser, R.; Rugel, G.; Merchel, S.; Steier, P.; Winkler, S. R.

The long-lived radionuclides 10Be (t1/2=1.4 Myr) and 26Al (t1/2=0.7 Myr) are widely used for dating applications, e.g. determination of surface exposure durations of terrestrial quartz or meteorites to cosmic rays. Stratigraphic chronologies of marine reservoirs such as sediments, deep-sea crusts and nodules are often obtained via 10Be /9Be ratios, while 26Al/27Al ratios are only scarcely used.

The deep-ocean floor is shielded from cosmic rays by several km of water, preventing direct cosmogenic production. In marine reservoirs, inputs of 10Be and 26Al occur due to their production in the atmosphere, in which 10Be is however ~500 times more abundant than 26Al. The freshly produced radionuclides settle onto the open ocean floor within ~100 (26Al) and ~1000 (10Be) years. An additional source may be the production via the 23Na(alpha,n)26Al reaction induced by alpha-particles originating from decay of U and Th.

We analyzed 85 samples from four deep-sea sediment cores from the Indian Ocean and 21 from two manganese nodules from the Atlantic Ocean. The isotope ratios of 26Al/27Al and 10Be/9Be were measured by AMS at the VERA facility (University of Vienna, Austria) and at the DREAMS facility (HZDR, Dresden, Germany). Due to the low 26Al/27Al ratios, i.e. ~10-14 vs. 10Be/9Be: ~10-11, the measurement of 26Al is much more time consuming. However, as stable 27Al is naturally enough abundant in sediments (in contrast to stable 9Be), the work without addition of a carrier and stable isotope measurements reduces potential error sources.

Our results indicate that 10Be/9Be and 26Al/27Al are both valuable tools for dating deep-sea sediments up to 3-5 Myr. Beyond these limits in-situ production of 26Al becomes significant. The nodule in-situ production of 26Al is clearly dominating the atmospheric production.

Keywords: AMS; deep-sea

  • Lecture (Conference)
    14th International Conference on Accelerator Mass Spectrometry (AMS-14), 14.-18.08.2017, Ottawa, Canada

Permalink: https://www.hzdr.de/publications/Publ-25328
Publ.-Id: 25328


Micrometeorites from Rooftops of Physics Buildings - Origin and Cosmic Ray Exposure

Feige, J.; Gaertner, A.; Klingner, N.; Merchel, S.; Patzer, A. B. C.

Each year, about 30,000 tons of extraterrestrial solid material falls onto the Earth's surface. A non-negligible fraction of these materials are micrometeorites (MMs); small (1 µm up to 1 mm), mostly spherical, particles that predominantly originate from the asteroid belt between Mars and Jupiter.

As soon as MMs are released in space, they are affected by the radiation pressure of the Sun causing them to spiral inwards. While travelling towards the Sun, the particles are irradiated by solar and galactic cosmic rays, producing cosmogenic nuclides such as 10Be (t1/2=1.4 Myr) and 26Al (t1/2=0.7 Myr).

In urban areas MMs are accumulating on the rooftops of buildings [1]. They can be easily collected from roofs of high buildings, where anthropogenic influences like pollution (e.g. from traffic) are reduced.

We have taken samples using a simple magnet from the rooftops of three physics buildings of the northern and southern hemisphere: the physics building of the Berlin Institute of Technology (~45 m above street level, Berlin, Germany), the accelerator buildings of the ANU in Canberra (44 m, Australia), and the accelerator building at HZDR, Dresden, Germany (24 m).

The magnetic fraction is investigated non-destructively by SEM-EDX to allow for enrichment of potential magnetic MM particles (~50–200 μm). Proof of extraterrestrial origin will be achieved by the determination of minor elements such as Ni from the interior of the spherules after cutting. We will then perform a radiochemical separation from individual samples and measure 10Be and 26Al by AMS at the DREAMS facility (HZDR [2]).

The experimental concentrations of those radionuclides will be compared with theoretical production rates [3] to deduce exposure ages and the potential origin of the samples.

[1] Genge et al., Geol., doi:10.1130/G38352.1 (2016)
[2] Rugel et al., NIMB, 370, 94 (2016)
[3] Trappitsch & Leya, Meteorit. Planet. Sci., 48, 195 (2013)

Keywords: AMS; meteorite

  • Poster
    14th International Conference on Accelerator Mass Spectrometry (AMS-14), 14.-18.08.2017, Ottawa, Canada

Permalink: https://www.hzdr.de/publications/Publ-25327
Publ.-Id: 25327


Fate of biological selenium(0) nanoparticles at elevated temperature

Fischer, S.; Jain, R.; Tsushima, S.; Jordan, N.

Selenium is toxic and thus its fate in the environment has to be ascertained. The bio-transformation of Se oxyanions by microorganisms will affect its (bio)availability in the environment. The microorganisms are known to reduce Se oxyanions to biological Se(0) nanoparticles (BioSe-Nanospheres) or biological Se(0) nanorods (BioSe-Nanorods) under mesophilic (30 °C) and thermophilic (55 °C) conditions, respectively. Though both types exhibit a coating of extracellular polymeric substances, their colloidal properties differs, leading to a different mobility in environmental waters. [1] Consequently, understanding the underlying mechanisms of the formation of amorphous BioSe-Nanospheres and trigonal BioSe-Nanorods is essential to understand the fate of selenium in the environment.
This study identified BioSe-Nanospheres produced by various microorganisms behaving differently when exposed to thermophilic conditions (55 °C). The bacteria strain E.coli K12 and the anaerobic granular sludge from a full scale Upflow Anaerobic Sludge Bioreactor were used to produce BioSe-Nanospheres at 30 °C. After purification (to separate the particles from the cells) the BioSe-Nanospheres were heated for 7 days at 55 °C with shaking. The Raman and Scanning Electron Microsocpy data evidenced a transformation of the anaerobic granular sludge Se(0) particles to trigonal BioSe-Nanorods upon heating, while the BioSe-Nanospheres of the bacteria strain E.coli K12 remained spherical and amorphous.
The CD-Spectrosopy data revealed that the proteins coating the anaerobic granular sludge BioSe-Nanospheres gets unstable during a heating time of 23 hours, suggesting a denaturating process. Such a behavior was not observed for particles produced via E. coli. Unravelling the differences in particles coating and selenium allotropy which results in changes of mobility and toxicity will further increase the knowledge on the environmental fate of selenium.
[1] Jain, R. et al., Environ. Sci.: Nano, 2017.

Keywords: selenium nanoparticles; selenium nanorods; E.coli K12; Anaerobic granular sludge

  • Lecture (Conference)
    Goldschmidt Conference, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25326
Publ.-Id: 25326


Preparation of a novel radiotracer targeting the EphB4 receptor via radiofluorination using spiro azetidinium salts as precursor

Wiemer, J.; Steinbach, J.; Pietzsch, J.; Mamat, C.

The visualization of Eph receptors, which are overexpressed in various tumor entities, using selective small molecule Eph inhibitors by means of PET is a promising approach for tumor imaging. Indazolylpyrimidineamines represent a class of compounds, which are known to have high affinity especially for the EphB4 receptor. Radiofluorination of these compounds could provide a highly specific imaging agent and was investigated using a classical nucleophilic introduction of [18F]fluoride as well as a less common nucleophilic ring opening reaction of azetidinium salts. In the past, radiofluorinations using azetidinium precursors were demonstrated to result in high radiochemical yields in short periods of time. For this purpose, an azetidinium precursor based on the indazolylpyrimidineamine lead compound was developed and radiofluorination was successfully accomplished. The respective [18F]radiotracer was quickly prepared with high radiochemical purity >97% and in a radiochemical yield of 34%.

Keywords: EphB4 ligand; spiro salts; N-(pyrimidyl)indazolamine

  • Open Access Logo Journal of Labelled Compounds and Radiopharmaceuticals 60(2017), 489-498
    DOI: 10.1002/jlcr.3526

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-25325
Publ.-Id: 25325


Development of a Thermodynamic Database for Europium

Jordan, N.; Huittinen, N.; Lösch, H.; Barkleit, A.; Bok, F.; Heller, A.; Brendler, V.

Due to their wide-spread application of Rare Earth Elements (REE) in high technological products, their separation from one another is mandatory. The optimization of physico-chemical conditions for the design of any effective extraction and recycling processes relies on accurate, consolidated, internationally recognized and reliable thermodynamic data, which are so far not available for REE.

This study aims at providing such a critically-assessed and internally consistent data base for europium. An evaluation of all available primary literature sources for Eu(III) complexation constants (log β) and solubility products (log Ksp) with inorganic ligands (OH−, Cl−, NO3−, SO42−, PO43−, and CO32−), evidenced several critical issues i) inconsistencies between different sources, ii) lack of accurate activity coefficient treatment in case of the formation of weak complexes, and iii) absence of independent spectroscopic validation of the stoichiometry of the proposed complexes.

Thus, several actions have been undertaken:
a) recalculation of the log β of weak complexes (Cl−, NO3−) by using an hypothetical reference state (at trace ligand concentration) [1].
b) in case of PO43− complexation, Time-resolved Laser-induced Fluorescence Spectroscopy was used to monitor the speciation evolution of Eu at micromolar concentrations and to identify the prevailing species as well as their stoichiometries. The respective complexation constants were derived from the spectroscopic data sets.
c) the conditional log β and log Ksp were extrapolated to standard conditions (I = 0 M, T = 298.15 K) using the Specific Ion Interaction Theory.

[1] Spahiu, K. et al. (1998) Radiochim. Acta 82, 413-419.

  • Contribution to proceedings
    Goldschmidt 2017, 13.-18.08.2017, Paris, France
  • Lecture (Conference)
    Goldschmidt 2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25324
Publ.-Id: 25324


The action of cellulose-based and conventional flotation reagents under dry and wet conditions correlating inverse gas chromatography to microflotation studies

Hartmann, R.; Rudolph, M.; Ämmälä, A.; Illikainen, M.

The fundamental formation of the three phase contact in flotation is an intensively and controversially discussed phenomenon and the contact angle method is usually employed to characterise the wettability of solid surfaces. A more recent technique to explore the hydrophobicity of solid particulate phases is inverse gas chromatography (iGC) which is used to quantify the wettability of solid surfaces through thermodynamic parameters. In this article, the recently introduced net free energy of interaction between particles and bubbles immersed in water ΔGpwb is derived from the surface free energy analysis and its correlation to the flotability of solid phases is evaluated. At the same time, a more detailed analysis on the action of flotation reagents is presented performing iGC measurements under dry and flotation experiments under aqueous conditions. In general, flotation reagents have to satisfy required features to adsorb selectively, render the solid surface wetting property sufficiently, and comply current regulations concerning the preservation of the environment. Consequently, many conventional reagents are increasingly subjected to restrictions. One potential alternative candidate is nanocellulose due to the versatile chemical composition and functionality. The synthesis of cellulose nanocrystals (CNCs) includes different mechanical and chemical modification routes to lower the crystal sizes and integrate specific functional groups and organic components into the cellulose structure. This study is concentrated on the investigation of aminated CNCs for the flotation of quartz in comparison to conventional reagents. The employment of CNCs as a renewable and sustainable alternative to conventional chemicals is challenging due to the more complex structure of cellulose crystals and leads to new perspectives regarding the action of flotation reagents at the interface of a mineral under dry and wet environments.

Keywords: flotation; inverse gas chromatography; cellulose-based reagent; surface free energy

Permalink: https://www.hzdr.de/publications/Publ-25323
Publ.-Id: 25323


Ultra-robust high-field magnetization plateau and supersolidity in bond-frustrated MnCr2S4

Tsurkan, V.; Zherlitsyn, S.; Prodan, L.; Felea, V.; Cong, P. T.; Skourski, Y.; Wang, Z.; Deisenhofer, J.; Krug Von Nidda, H.-A.; Wosnitza, J.; Loidl, A.

Frustrated magnets provide a promising avenue for realizing exotic quantum states of matter, such as spin liquids and spin ice or complex spin molecules. Under an external magnetic field, frustrated magnets can exhibit fractional magnetization plateaus related to definite spin patterns stabilized by field-induced lattice distortions. Magnetization and ultrasound experiments in MnCr2S4 up to 60 T reveal two fascinating features: an extremely robust magnetization plateau with an unusual spin structure and two intermediate phases, indicating possible realizations of supersolid phases. The magnetization plateau characterizes fully polarized chromium moments, without any contributions from manganese spins. At 40 T, the middle of the plateau, a regime evolves, where sound waves propagate almost without dissipation. The external magnetic field exactly compensates the Cr–Mn exchange field and decouples Mn and Cr sublattices. In analogy to predictions of quantum lattice-gas models, the changes of the spin order of the manganese ions at the phase boundaries of the magnetization plateau are interpreted as transitions to supersolid phases.

Permalink: https://www.hzdr.de/publications/Publ-25322
Publ.-Id: 25322


Chlorine measurements at the 5MV French AMS national facility ASTER: Associated external uncertainties and comparability with the 6MV DREAMS facility

Braucher, R.; Keddadouche, K.; Aumaître, G.; Bourlès, D. L.; Arnold, M.; Pivot, S.; Baroni, M.; Scharf, A.; Rugel, G.; Bard, E.

After 6 years of 36Cl routine operation, more than 6000 unknown samples have been measured at the 5 MV French AMS national facility ASTER (CEREGE, Aix en Provence). This paper presents the long term behavior of ASTER through the analysis of the measurements of the most used chlorine standards and reference materials, KNSTD1600, SM-Cl-12 and SM-Cl-13 over a 46 months’ time period.
Comparison of measured chlorine concentrations (both 35Cl and 36Cl ) from ice samples on two AMS facilities operating at 5MV (ASTER) and 6MV (DREAMS, Helmholtz-Zentrum Dresden-Rossendorf ) and normalizing to two different reference materials agree within uncertainties making both reference materials (SM-Cl-12 and KNSTD1600) suitable for 36Cl measurement at ASTER.

Keywords: Accelerator mass spectrometry; Chlorine; Standard; Cosmogenic nuclides

Permalink: https://www.hzdr.de/publications/Publ-25321
Publ.-Id: 25321


Sulphide vein mineralization of the shallow eastern stock work zone and its genetic relation to the massive sulphide mineralization at the Sakatti Cu-Ni-PGE deposit, Finland

Fröhlich, F.; Gutzmer, J.; Siikaluoma, J.; Osbahr, I.

he Sakatti Cu-Ni-PGE deposit is situated in northern Finland and was discovered by Anglo American Exploration in 2009 (Halkoaho 2014). It is said to be one of the most significant discoveries in Finland for more than a generation (Maier et al. 2015). The mineralization comprises massive, disseminated and vein sulphides. A stockwork is formed by the sulphide veins, which contains exceptionally high grades of Cu, platinum-group elements (PGE) and Au in the shallow eastern part of the deposit. In contrast to the massive and disseminated sulphide mineralization, the mineralogy, mineral paragenesis and petrography of the stockwork zone is relatively poorly uninvestigated, and this study aimed at increasing knowledge of it.
Traditional light microscopy and automated scanning electron microscope (SEM)- based image analyses using a mineral liberation analyser (MLA) on 20 samples from 11 drill holes revealed a classic magmatic sulphide assemblage of chalcopyrite ± pyrrhotite, pentlandite and pyrite. Additionally, 1,133 platinum-group mineral (PGM) particles belonging almost exclusively to the moncheite (PtTe2) – merenskyite (PdTe2) – melonite (NiTe2) solid solution series were discovered (Fig. 1 a, b). Notably, almost two-thirds of the PGE-bearing phases consist of melonite. Some of the PGM particles contain inclusions of electrum (AgAu2) and muthmannite (AgAuTe2), which possess an average of 0.25 wt% Au. For the first time at Sakatti, one particle of irarsite (IrAsS) was encountered. The PGM display a trimodal particle area distribution, which is a result of an increasing mineralogical complexity of the particles relative to their sizes. Most of the PGM are hosted in inclusions (76%) (mainly in chalcopyrite), whereas minor amounts are located at grain boundaries (19%) and in cracks (5%).
An enrichment of PPGE relative to IPGE was recognized in the sulphide veins, which is in line with data on the massive and disseminated sulphide mineralization at Sakatti (Ahvenjärvi 2015). However, the di erence between maximum and minimum enrichments is more pronounced for the sulphide veins.
Element ratios calculated from geochemical data obtained by ICP-MS/OE analyses and displayed in various plots (e.g. Cu/Ir vs. Ni/Pd, Rh vs. Rh/Cu (Fig. 2)) indicate that the Cu-rich sulphide veins represent the magmatic crystallization products of a highly fractionated Cu-rich sulphide liquid enriched in Pt, Pd, Au, Ag, As, Bi, Pb, Se, Te and Zn, which separated from monosulphide solid solution (mss). Intermediate solid solution (iss) solidi ed from the Cu-rich sulphide liquid, exsolving chalcopyrite at <550 °C. Simultaneously, small volumes of intercumulus residual melt mainly contained the precious metals Bi and Te due to their incompatibility in iss. Solitary and composite PGM, as well as Au minerals crystallized rst from the residual melt (<600 °C), followed by a succession of various Bi, Ag and Pb tellurides (~540 °C), and nally sphalerite (ZnS) and galena (PbS). However, melonite crystallized in two stages: as large, solitary grains directly exsolved from Ni-bearing iss (~600 °C) shortly after the formation of moncheite and merenskyite from the residual melt, and during subsolidus exsolution (<600 °C) with precipitation on the surfaces of earlier formed PGM. Finally, slight remobilization of the PGM occurred at temperatures <300 °C, veri ed by minor amounts of Cl-bearing minerals and ragged particle shapes. Surprisingly, the geochemical data (Fig. 2), petrography and genetic concept of the sulphide veins at Sakatti proved to be very similar to the Cu-rich footwall veins at the McCreedy East deposit in Sudbury (Canada) (Naldrett et al. 1999, Dare et al. 2014).

  • Open Access Logo Contribution to proceedings
    3rd Finnish National Colloquium of Geosciences, 15.-16.03.2017, Espoo, Finland
    Abstract Book, 3rd Finnish National Colloquium of Geosciences, Espoo: Geological Survey of Finland, ISBN 978-952-217-376-8, 26-27
  • Lecture (Conference)
    3rd Finnish National Colloquium of Geosciences, 15.-16.03.2017, Espoo, Finland

Permalink: https://www.hzdr.de/publications/Publ-25320
Publ.-Id: 25320


Monte Carlo simulation and experimental validation of magnetic field effects on proton dose distributions

Schellhammer, S. M.; Lühr, A.; Gantz, S.; Oborn, B.; Zarini, O.; Wohlfahrt, P.; Zeil, K.; Bussmann, M.; Hoffmann, A. L.

Given the physical properties and the sensitivity to morphological variations of proton therapy, it could greatly benefit from integration with magnetic resonance (MR) imaging. Such integration raises several challenges, as both systems mutually interact with each other. The problem of magnetic field induced dose distortions has been predicted by Monte Carlo (MC) simulation in previous studies, but no experimental validation has been performed yet. We present and compare simulated and measured dose distributions in a realistic magnet setup.

2D dose distributions of proton pencils beams (80-180MeV) traversing the field of a 1T NdFeB permanent magnet while depositing energy in a PMMA slab phantom were simulated using the Geant4 toolkit and measured using EBT3 radiochromic films. The Geant4 model was validated against depth-dose measurements performed with a multi-layer ionisation chamber. The magnetic vector field was calculated using finite-element modelling and validated experimentally using a Hall probe. Deflected beam trajectories and depth-dose curves were extracted from the 2D dose distributions and compared. Demagnetization and radioactivation of the magnet material were simulated and monitored during measurement.

The range predicted by the MC model agreed with the Giraffe measurements within 0.5mm, and calculated and measured magnetic field data agreed within 2%. The lateral beam deflection was clearly visible on EBT3 films and ranged from 1mm to 10mm for 80MeV and 180MeV, respectively. Simulated and measured range and deflection agreed within 1mm for all studied energies. Demagnetization and radioactivation effects were negligible.

For the first time, MC simulations of magnetically deflected proton beams inside tissue-equivalent material have been experimentally validated with dose measurements. The results indicate that the magnetic field induced proton beam deflection is both measurable and accurately predictable. This demonstrates the feasibility of accurate dose calculation as well as measurement within the framework of MR-integrated proton therapy.

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25319
Publ.-Id: 25319


Studying a new LWFA scheme that produces electron bunches of several hundred picocoulombs using PIConGPU

Pausch, R.; Debus, A.; Steiniger, K.; Garten, M.; Couperus, J.; Köhler, A.; Burau, H.; Huebl, A.; Irman, A.; Schramm, U.; Bussmann, M.

We present recent simulation studies of laser wake eld acceleration that match experiments performed at HZDR which produce quasi mono-energetic electron bunches of several hundred picocoulombs charge. The talk focuses on the dynamics of this new acceleration scheme and required code improvements to study it using the 3D3V particle-in-cell code PIConGPU. We discuss in detail the influence of various ionization mechanisms and laser implementations on the plasma dynamics. Furthermore, we present computation constrains and implementation challenges that these new methods entail. On top of discussing the acceleration scheme, we predict experimental observables using PIConGPU’s in-situ synthetic radiation diagnostics. It allows predicting spectra from infrared to x-rays and provides the capability to determine the temporal and spatial origin of the radiation. These radiation simulations give valuable spectral signatures that allow conclusions on the micrometer femtosecond electron dynamics occurring in experiments. As an example of such a signature, simu- lated betatron spectra will be compared to experimentally measured spectra in order to determine the spatial extent of the electron bunch.

Keywords: PIConGPU; GPU; radiation; LWFA; acceleartion; electrons

  • Lecture (Conference)
    DPG-Frühjahrstagung, 19.-24.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25318
Publ.-Id: 25318


Actinide Incorporation Into Pristine and Stabilized Zirconia Phases

Eibl, M.; Huittinen, N.; Stumpf, T.

In the present study the stabilizing effect of the actinide analogue ion Eu3+ on zirconia in dependency of the molar fraction and the influence of the trivalent stabilizer cation radius on zirconia solids in a series of Ln3+ (Ln3+ = La, Sm, Gd, Tb, Lu) co-doped with Eu3+ is investigated using a combination of x-ray powder diffraction (PXRD) and time-resolved laser fluorescence spectroscopy (TRLFS). PXRD is employed to gain an insight into the zirconia crystal structure in the presence of Eu3+ and/or Ln3+ and to identify the various zirconia phases (m, t, and c).
For the material with 2% Eu3+ mainly the monoclinic structure is to be seen in the PXRD pattern. A sample with 8% Eu3+ can be assigned to the tetragonal structure while at an incorporation percentage of 22% Eu3+ the cubic phase is predominant. The broadness of the TRLFS emission peaks of the sample with 2% Eu3+ speaks for a poorly ordered solid or Eu3+ incorporation on a very distorted host cation site. The 7F1 as well as the 7F2 band show a strong band splitting which correlates to low crystal symmetry. The band splitting of both samples with higher europium content is reduced because of a higher symmetry as could be seen in the XRD pattern. To prove the transferability of the lanthanide to actinides selected samples will be prepared and studied using Cm3+ as dopant.
The effect of different stabilizers on the nucleation process has been studied using a combination of the crystal truncation diffraction (CTR) and the resonant anomalous x-ray scattering techniques (RAXR) using synchrotron radiation at the European synchrotron radiation facility (ESRF) in Grenoble.
The results of these ongoing investigations will be presented in detail at the conference.

  • Poster
    16th International Conference on the Chemistry and Migration Behaviour of Actinides and Fission Products in the Geosphere, 10.-15.09.2017, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-25317
Publ.-Id: 25317


Spectroscopic identification of Np(V) sorption complexes on birnessite

Müller, K.; Simon, B.; Bok, F.; Rossberg, A.

Mn oxide minerals are ubiquitous in soils and sediments and participate in a variety of chemical reactions that affect groundwater and bulk soil composition. Even at tracer concentrations they play a decisive role in regulating the mobility of contaminants due to their high sorption and redox capacity and scavenging capability [1]. Due to its long half-life and its toxicity, Np-237 is considered as a major contaminant of the ecosystem in the long-term safety assessment of nuclear waste repositories. The pentavalent state is environmentally most relevant [2].
In this work, Np(V) sorption on amorphous birnessite (Bs) is investigated using a combination of ATR FT-IR and EXAFS spectroscopy on a molecular level with thermodyanamic modelling of batch sorption studies.
For the first time, in-situ Np(V) sorption is comparatively studied on the oxyhydroxides of Fe and Mn by ATR FT-IR spectroscopy under a variety of environmentally relevant sorption conditions, e.g. micromolar Np concentrations, low acidic to neutral pH, moderate ionic strength [3]. From the results, the formation of single inner-sphere complexes can be derived. In addition, time resolved spectra provide kinetic information on the surface reactions. Complementary EXAFS measurements evidence mononuclear bidentate edge-sharing Np(V) complexes on the Bs surface.

Keywords: ATR FT-IR; EXAFS; Actinides; manganese oxides

  • Lecture (Conference)
    Goldschmidt Conference, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25316
Publ.-Id: 25316


Multimetallic Hierarchical Aerogels: Shape Engineering of the Building Blocks for Efficient Electrocatalysis

Cai, B.; Dianat, A.; Hübner, R.; Liu, W.; Wen, D.; Benad, A.; Sonntag, L.; Gemming, T.; Cuniberti, G.; Eychmüller, A.

A new class of multimetallic hierarchical aerogels composed entirely of interconnected Ni-PdxPty nano-building-blocks with in situ engineered morphologies and compositions is demonstrated. The underlying mechanism of the galvanic shape-engineering is elucidated in terms of nanowelding of intermediate nanoparticles. The hierarchical aerogels integrate two levels of porous structures, leading to improved electrocatalysis performance.

Permalink: https://www.hzdr.de/publications/Publ-25315
Publ.-Id: 25315


Experiments on Gas-Liquid Flow in Vertical Pipes

Lucas, D.; Beyer, M.; Szalinski, L.

A comprehensive database on upward two-phase flows in vertical pipes was obtained using the wire-mesh sensor technologies for gas-liquid flows in vertical pipes. The investigations were done for different pipe diameter as well as for flows with and without phase transfer. Wire-mesh sensors provide detailed information on the structure of the gas-liquid interphase. Basic characteristics of gas-liquid flows can be observed in such experiments and are discussed in this chapter. The quantitative results obtained in the measurements as radial volume fraction profiles, radial gas velocity profiles, bubble size distributions, distributions of interfacial area density, and others are valuable data for the development and validation of Computational fluid dynamics (CFD) codes for multiphase flows.

Keywords: Gas-liquid flow; Pipe flow; Bubble size distribution; Phase transfer; Experiment; Database

  • Book chapter
    G.H. Yeoh: Handbook of Multiphase Flow Science and Technology, Singapore: Springer, 2017, 978-981-4585-86-6
    DOI: 10.1007/978-981-4585-86-6_15-1

Permalink: https://www.hzdr.de/publications/Publ-25314
Publ.-Id: 25314


Oxidation state and local structure of technetium reacted with siderite

Schmeide, K.; Rossberg, A.; Weiss, S.; Brendler, V.; Scheinost, A. C.

99Tc is a long-lived (t1/2 = 2.1 × 105 years) β-emitter formed during the fission of U and is of major concern for radioactive waste disposal. Its environmental mobility is primarily governed by the oxidation states VII and IV, with TcVII forming the highly mobile TcO4 aquo anion, whereas TcIV is rather immobile due to the low solubility of its hydrolysis products. Redox processes, which are able to convert TcVII into TcIV, are hence of paramount importance for the safety of radioactive waste repositories. FeII-bearing minerals, ubiquitous in nature and also forming as corrosion products of the carbon steel canisters foreseen as a possible first enclosure of radioactive waste, play a vital role in these redox reactions due to their high redox reactivity and high sorption capacity, as has been shown not only for Tc, but also for Se, U, Np and Pu.
Here we focus on the retention of TcVII by a typical FeII mineral in carbonate-rich environments, siderite (FeCO3), which we studied in the relevant pH range (7 – 12.6) under anoxic conditions by means of batch sorption experiments and by X-ray absorption spectroscopy. Sorption experiments showed that Tc retention by siderite is fast (within minutes) and efficient (log Rd ~5) across the investigated pH range and independent of ionic strength (0.1 – 1 M NaCl). Tc K-edge X-ray absorption near-edge structure (XANES) data confirmed that the Tc immobilization is due to the surface-mediated reduction of TcVII to TcIV. The local structure of TcIV as probed by extended X-ray absorption fine-structure (EXAFS) spectroscopy revealed two different species: in the pH range 7.8 to 11.5, TcO2-dimers form inner-sphere sorption complexes at the surface of siderite or of an FeII,III (hydr)oxide potentially formed during the redox reaction. At pH 11.8 to 12.6, the retention proceeds through the (near-surface) incorporation of TcIV by siderite.
In conclusion, siderite contributes effectively to the retention of Tc in the near-field of nuclear waste repositories.

Keywords: Technetium; siderite; reduction; adsorption; incorporation; technetium carbonate; X-ray absorption spectroscopy

  • Contribution to proceedings
    Goldschmidt 2017, 13.-18.08.2017, Paris, France
  • Lecture (Conference)
    Goldschmidt 2017, 13.-18.08.2017, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-25313
Publ.-Id: 25313


Efficient solution of 3D electromagnetic eddy-current problems within the finite volume framework of OpenFOAM

Beckstein, P.; Galindo, V.; Vukcevic, V.

Eddy-current problems occur in a wide range of industrial and metallurgical applications where conducting material is processed inductively. Motivated by realising coupled multi-physics simulations, we present a new method for the solution of such problems in the finite volume framework of foam-extend, an extended version of the very popular OpenFOAM software. The numerical procedure involves a semi-coupled multi-mesh approach to solve Maxwell’s equations for non-magnetic materials by means of the Coulomb gauged magnetic vector potential A and the electric scalar potential φ. The concept is further extended on the basis of the mpressed and reduced magnetic vector potential and its usage in accordance with Biot-Savart’s law to achieve a very efficient overall modeling even for complex three-dimensional geometries. Moreover, we present a special discretisation scheme to account for possible discontinuities in the electrical conductivity. To complement our numerical method, an extensive validation is completing the paper, which provides insight into the behaviour and the potential of our approach.

Keywords: eddy-currents; induction processing; potential formulation; Maxwell’s equations; finite volume method; block-coupling; OpenFOAM; foam-extend

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Permalink: https://www.hzdr.de/publications/Publ-25312
Publ.-Id: 25312


Microfluidic experiments on enrichment of paramagnetic metal ions in aqueous solutions by applying inhomogeneous magnetic fields

Mutschke, G.; Yang, X.; Wojnicki, M.; Femerling, M.; Zabinski, P.

Magnetic separation is a well-established technology for separating magnetic particles from solutions. The magnetic gradient force scales with the magnetization density and the volume of the particle. The magnetic moment of paramagnetic metal ions in solution could be utilized as well for separating ions from solutions in strong magnetic fields of large spatial gradients. This idea dates back to early work of Noddack et al [1], where firstly separation effects were found for rare earth metal ions in aqueous solutions. However, the effect is limited, as the ratio of magnetic to thermal energy is small. Recently, distinct separation effects of paramagnetic ions in inhomogeneous magnetic fields were reported in gel [2] and in various aqueous solutions [3,4,5].
Triggered by these findings, microfluidic experiments were performed. The setup consists of a small reactor printed by 3D technology where a spiral pipe flow is exposed to an inhomogeneous magnetic field created by an iron wire, the spiral of which is close to the pipe, and which is magnetized in an external magnetic field, thus creating strong gradients near the pipe. Flow experiments were performed for different salt solutions. At the outflow, the flow volume was separated into a near-magnet and a far-magnet half, the concentrations of which were analyzed by UV/VIS spectrophotometry and by ICP-MS. The absorption spectrum of 0.1 M HoCl3 solution is shown in Fig.1. According to Beer-Lambert's law, the absorbance in selected peaks can be used as a measure of the ion concentration. The concentration difference from the two outlets of the reactor was measured, and the effects of the magnetic field gradient and the flow rate were studied.
Acknowledgement:
This work is supported by the German Federal Ministry of Education and Research, Grant No. 01DS16007.
References
[1] Noddack, W., Noddack, I. and Wicht, E., Berichte der Bunsengesellschaft für physikalische Chemie 62 (1958): 77-85.
[2] Franczak, A., Binnemans, K., & Fransaer, J., Phys. Chem. Chem. Phys. 18 (2016): 27342-27350.
[3] Kolczyk, K., Kutyla, D., Wojnicki, M., Cristofolini, A., Kowalik, R., & Zabinski, P., Magnetohydrodynamics 52 (2016): 541-547.
[4] Yang, X., Tschulik, K., Uhlemann, M., Odenbach, S., & Eckert, K., J. Phys. Chem. Lett. 3 (2012): 3559-3564.
[5] Bing, J., Ping, W., Han, R., Shiping, Z., Abdul, R., & Li, W., Chin. Phys. B 25 (2016) 074704.

  • Lecture (Conference)
    68th Annual Meeting of the International Society of Electrochemistry, 27.08.-01.09.2017, Providence, RI, USA

Permalink: https://www.hzdr.de/publications/Publ-25311
Publ.-Id: 25311


Entropy Evolution in the Magnetic Phases of Partially Frustrated CePdAl

Lucas, S.; Grube, K.; Huang, C.-L.; Sakai, A.; Wunderlich, S.; Green, E. L.; Wosnitza, J.; Fritsch, V.; Gegenwart, P.; Stockert, O.; von Löhneysen, H.

In the heavy-fermion metal CePdAl, long-range antiferromagnetic order coexists with geometric frustration of one-third of the Ce moments. At low temperatures, the Kondo effect tends to screen the frustrated moments. We use magnetic fields B to suppress the Kondo screening and study the magnetic phase diagram and the evolution of the entropy with B employing thermodynamic probes. We estimate the frustration by introducing a definition of the frustration parameter based on the enhanced entropy, a fundamental feature of frustrated systems. In the field range where the Kondo screening is suppressed, the liberated moments tend to maximize the magnetic entropy and strongly enhance the frustration. Based on our experiments, this field range may be a promising candidate to search for a quantum spin liquid.

Permalink: https://www.hzdr.de/publications/Publ-25310
Publ.-Id: 25310


Analytical balance-based Faraday magnetometer

Riminucci, A.; Uhlarz, M.; de Santis, R.; Herrmannsdörfer, T.

We introduce a Faraday magnetometer based on an analytical balance in which we were able to apply magnetic fields up to 0.14 T. We calibrated it with a 1mm Ni sphere previously characterized in a superconducting quantum interference device (SQUID) magnetometer. The proposed magnetometer reached a theoretical sensitivity of 3x 10-8 Am2. We demonstrated its operation on magnetic composite scaffolds made of poly(e-caprolactone)/iron-doped hydroxyapatite. To confirm the validity of the method, we measured the same scaffold properties in a SQUID magnetometer. The agreement between the two measurements was within 5% at 0.127 T and 12% at 24mT. With the addition, for a small cost, of a permanent magnet and computer controlled linear translators, we were thus able to assemble a Faraday magnetometer based on an analytical balance, which is a virtually ubiquitous instrument. This will make simple but effective magnetometry easily accessible to most laboratories, in particular, to life sciences ones, which are increasingly interested in magnetic materials.

Permalink: https://www.hzdr.de/publications/Publ-25309
Publ.-Id: 25309


Predicting SAXS images beyond single scattering

Garten, M.; Grund, A.; Huebl, A.; Burau, H.; Widera, R.; Kluge, T.; Fortmann-Grote, C.; Bussmann, M.

We present a scalable GPU-based software framework for simulating photon scattering processes of X-ray beams in matter using Monte-Carlo methods. These simulations enable us to predict SAXS signals for experiments at upcoming superlative research facilities like the European XFEL. Often the expected outcome of SAXS experiments is produced by a Fourier Transform of a static 2D electron density distribution. Our new framework provides the opportunity to simulate the probing of femtosecond timescale 3D3V electron dynamics with single and multiple scattering and is extendable by more complex physics processes like laser absorption, atomic excitation and de-excitation to further enhance its predictive capability. As a foundation we use libPMacc, a powerful particle-mesh accelerator library that is also used by PIConGPU, the reportedly fastest fully-relativistic 3D3V particle-in-cell code in the world.

Keywords: XFEL; scattering; SAXS; pump-probe; GPU; HPC; simulation

  • Lecture (Conference)
    DPG Frühjahrstagung Dresden 2017, 23.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25308
Publ.-Id: 25308


Enhancing atomic physics modeling in PIConGPU

Garten, M.; Huebl, A.; Burau, H.; Grund, A.; Widera, R.; Zacharias, M.; Kluge, T.; Bussmann, M.

In laser-generated plasmas the free electron density is a crucial parameter for plasma dynamics. Therefore, to model its spatial and temporal evolution the adequate treatment of ionization is vital. This poster presents the work in progress on numerical field ionization methods implemented in the world's fastest 3D3V electromagnetic particle-in-cell code PIConGPU. Thus, computing a value for the systematic error via repeating simulations with varying ionization schemes is in reach. With high performance computing we can give a range of validity for predictions of pump-probe experiments with high power lasers and X-ray free electron lasers.

Keywords: laser-particle acceleration; field ionization; particle-in-cell; HPC

  • Poster
    DPG Frühjahrstagung 2017 Dresden, 22.03.2017, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25307
Publ.-Id: 25307


A new wettability Parameter based on iGC to characterize the Flotation process for the Separation of fine Mineral particles

Rudolph, M.; Babel, B.; Hartmann, R.; Leistner, T.; Graebe, K.

Flotation is a heterocoagulation based separation process for fine particles in aqueous dispersions (size range approx. 5 µm < x <200 µm). It is used in large extent and with billions of tons of particles processed per year in the mining industry to separate valuable mineral particles from worthless ones. The main principle of separation is the particles’ differences in wettability. This wettability is influenced by controlled selective adsorption of amphiphilic molecules rendering most typically the valuable containing minerals hydrophobic. Usually the particle property “wettability” is being quantified with a water contact angle. However, this value is not only difficult to assess for particles but furthermore through Young’s equation a function of the surface free energy, which is a complex parameter as a result of various interatomic/intermolecular interactions. Using iGC we are able to characterize these complex wettability properties of particles assessing the heterogeneity of disperse and acid base specific surface free energies. These complex values are used in accordance to an approach by van Oss to formulate a new wettability parameter for flotation which is the specific free energy of interaction between a particle and a gas bubble immersed in water. We are presenting the general approach and results from various mineral collector systems and give insights to the boundary conditions and the general calculation scheme.

Keywords: inverse gas chromatography; minerals; flotation; surface free energy; collectors; surfactants; separation

  • Invited lecture (Conferences)
    IGC Symposium 2017, 20.06.2017, Köln, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25306
Publ.-Id: 25306


Angular Distribution Measurement of Gamma Rays from Inelastic Neutron Scattering on Fe-56 at the nELBE Time-of-Flight Facility

Dietz, M.; Bemmerer, D.; Beyer, R.; Gohl, S.; Junghans, A. R.; Kögler, T.; Massarczyk, R.; Müller, S. E.; Schwengner, R.; Szücs, T.; Takacs, M. P.; Wagner, A.; Wagner, L.

Inelastic neutron scattering from 56 Fe was studied at the nELBE time-of-flight facility. The incoming neutron energy ranges from 100keV to 10MeV in the fast neutron spectrum, where high precision nuclear data are needed. A detector setup has been installed to investigate the γ-ray angular distributions. It contains five HPGe and five LaBr 3 detectors positioned at 30, 55, 90, 125 and 150 degrees relative to the beam axis. The intrinsic and the neutron induced background from the setup was subtracted by cyclical measurements with and without the natural Fe-target. Corrections for extended source efficiency and gamma-self-absorption, inside the target, were done using GEANT4 simulations.
The angular distributions measured with the HPGe detectors are compared with earlier data. High neutron energy resolution up to a few keV was obtained with the LaBr 3 detectors due to their much better time resolution.

Keywords: gamma-ray angular distribution; inelastic neutron scattering 56Fe(n; n'g)

  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology (ND2016), 11.-16.09.16, Bruges, Belgium
    European Physical Journal - Web of Conferences
    DOI: 10.1051/epjconf/201714611040

Permalink: https://www.hzdr.de/publications/Publ-25305
Publ.-Id: 25305


Measurements with neutrons and photons at nELBE

Beyer, R.; Dietz, M.; Frotscher, A.; Görres, J.; Junghans, A. R.; Kögler, T.; Nolte, R.; Oberlack, U.; Pirovano, E.; Plompen, A.; Reifarth, R.; Schwengner, R.; Urlaß, S.; Wagner, A.

The neutron time-of-flight facility nELBE at Helmholtz-Zentrum Dresden-Rossendorf features the first photo-neutron source at a superconducting electron accelerator, which provides a very precise time structure, high repetition rate and favorable background conditions due to the low instantaneous flux and the absence of any moderating materials. The neutron energy spectrum ranges from about 100 keV up to 10 MeV. The resulting very flexible beam properties at nELBE enable a broad range of nuclear physics experiments. Examples for the versatility of nELBE will be presented: Total neutron cross section measurements to look for unknown nuclear levels relevant for the astrophysical s-process, determination of the photon angular distribution after inelastic neutron scattering, determination of the detector response of a Dark Matter detector based on liquid Xe, or determination of the neutron induced fission cross section of 242Pu.

Keywords: nELBE; neutron time-of-flight; neutron inelastic scattering; neutron transmission; neutron induced fission; dark matter; liquid Xe

  • Lecture (Conference)
    81. Jahrestagung der DPG und DPG-Frühjahrstagung, 27.-31.03.2017, Münster, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-25304
Publ.-Id: 25304


Methods for investigating Australia's former nuclear test sites

Johansen, M. P.; Caffrey, E. A.; Child, D. P.; Collins, R. N.; Harrison, J. J.; Hotchkis, M. A. C.; Howard, D. L.; Howell, N.; Payne, T. E.; Mokhber Shahin, L.; Ikeda-Ohno, A.; Thiruvoth, S.

The radiological residues at the former weapons testing sites in Australia at Maralinga, Emu and the Montebello Islands are of ongoing interest in terms of environmental fate, transport, and uptake into the biosphere1. The physical and chemical characteristics of these residues affect their mobility and availability for uptake into living organisms2. At the Taranaki site, Maralinga, substantial body burdens of Pu were observed in mammals, likely due to the presence of respirable particles. Actinides often occur in particulate forms that, for characterisation, require advanced techniques including Accelerator Mass Spectrometry (AMS)3, Scanning electron microscopy and synchrotron X-ray fluorescence microscopy (XFM). Many nuclear test site particles have core-shell, or inhomogenous structures where the surface is dominated by lighter elements sourced from local soils and the Pu concentrated in the interior4. Modelling results suggest that for respirable-sized Pu-containing particles (that can be inhaled and lodged in the lung), most of the alpha emissions escape the particle and are deposited in the surrounding tissue.4 For larger particles, (e.g. >7 µm), which typically do not lodge in the lung but could be ingested, most of the alpha emissions do not escape the particle, but are instead captured within the particle itself (self-shielding) therefore decreasing the effective dose. We are currently using advanced techniques to compare the radionuclide forms from the inland sites (Maralinga and Emu) with the marine site (Montebello Islands).

Keywords: Actinides; radionuclides; environmental radioactivity; radioecology; environmental science; nuclear tests

  • Lecture (Conference)
    Annual Congress of the Royal Australian Chemical Institute (RACI) 2017, 23.-28.07.2017, Melbourne, Australia

Permalink: https://www.hzdr.de/publications/Publ-25303
Publ.-Id: 25303


Radiation hard ceramic RPC development

Akindinov, A.; Dreyer, J.; Fan, X.; Kämpfer, B.; Kiselev, S.; Kotte, R.; Laso Garcia, A.; Malkevich, D.; Naumann, L.; Nedosekin, A.; Plotnikov, V.; Stach, D.; Sultanov, R.; Voloshin, K.

We report recent advances in R&D; on the Beam Fragmentation and T0 Counter (BFTC) for the CBM experiment, based on RPCs with floating electrodes made of resistive ceramic material. An optimal value of the ceramics bulk resistivity has been determined to be about 5·109 Ω·cm. RPCs with such electrodes show even characteristics and stable operation under particle fluxes of up to 150 kHz/cm2, with the detection efficiency above 90%.

Permalink: https://www.hzdr.de/publications/Publ-25302
Publ.-Id: 25302


In situ RBS, Raman spectroscopy, and ellipsometry study of nickel-catalyzed graphitization of thin amorphous carbon films

Janke, D.; Wenisch, R.; Lungwitz, F.; Munnik, F.; Hulman, M.; Gemming, S.; Rafaja, D.; Krause, M.

Metal-induced crystallization (MIC) with and without layer exchange (LE) is a method to decrease the crystallization temperature of amorphous group 14 elements by up to several hundred degrees. In situ experiments are expected to provide new insights into thin film evolution and elementary process steps of MIC and to improve existing models of this type of phase transformation. In this contribution in situ Rutherford backscattering spectrometry (RBS), Raman spectroscopy and spectroscopic ellipsometry studies were performed during annealing of amorphous carbon/nickel (a-C/Ni) layer stacks at temperatures up to 750°C.
LE was observed independently of the initial stacking sequence, while transformation rate and temperature differ significantly. The positions of the G, D and 2D Raman lines as well as the I(D)/I(G) ratio changed during the LE process. These were assigned in agreement with the Three-Stage-Model [1], confirming the transformation of a-C to nc-graphite. In situ RBS measurements demonstrated an opposite shift of the C- and Ni- related backscattering energies, proving that LE and graphitization occur simultaneously.
[1] Ferrari et al., Phys. Rev. B 61 (2000) 14095

Keywords: Metal-induced crystallization; in situ RBS; in situ Raman spectroscopy

  • Poster
    International Winterschool on Electronic Properties of Novel Materials, 04.-11.03.2017, Kirchberg in Tirol, Österreich

Permalink: https://www.hzdr.de/publications/Publ-25301
Publ.-Id: 25301


High-resolution study of the 113 Cd(n,γ γ) spectrum by statistical decay model with discrete levels and transitions

Belgya, T.; Szentmiklósi, L.; Massarczyk, R.; Schwengner, R.; Junghans, A. R.; Grosse, E.

The gamma-ray spectrum and the decay scheme of 114 Cd obtained from a radiative neutron capture experiment on 113 Cd samples are modelled in the framework of extreme statistical model. The unfolding of the experimental spectrum with proper normalization yields a total capture cross section of 21640 b and an average gamma-ray multiplicity of 4.1. Using the extreme statistical model the development of the low energy decay scheme of 114 Cd is in progress. In the model the constant-temperature level density is used, where the temperature parameter was very sensitive to the shape of the modelled gamma-ray spectrum. Using this sensitivity T=0.64 MeV was obtained with the constraint of good description of low energy level density and the level density at the binding energy. This is in full agreement with our earlier publication. For the description of the continuum shape of the unfolded spectrum the inclusion of low energy enhancement for the photon strength function was an important new addition.

Keywords: neutron radiative capture; 113Cd(n; gamma); capture gamma-ray spectrum; photon strength function

  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology, 11.-16.09.16, Bruges, Belgium
    European Physical Journal - Web of Conferences
    DOI: 10.1051/epjconf/201714605009

Permalink: https://www.hzdr.de/publications/Publ-25300
Publ.-Id: 25300


Neutron Transmission Measurement for Natural W at nELBE

Song, T.-Y.; Kim, J. W.; Kim, H. I.; Yang, S.-C.; Lee, C. W.; Lee, Y.-O.; Junghans, A. R.; Beyer, R.; Kögler, T.; Schwengner, R.; Hannaske, R.; Wagner, L.; Leinhardt, T. P.; Takacs, M. P.; Massarczyk, R.; Müller, S.; Ferrari, A.; Schmidt, K.; Röder, M.; Bemmerer, D.; Szücs, T.; Wagner, A.

Korea has developed a Helium Cooled Ceramic Reflector Test Blanket Module (Ko HCCR TBM) related to the ITER project. Tungsten is considered as a prime candidate for the plasma facing materials in fusion reactors, and for the structure material of Ko HCCR TBM. KAERI (Korea Atomic Energy Research Institute) has been evaluating neutron cross sections of tungsten isotopes for neutron energy of up to 150 MeV based on nuclear reaction codes and available measurement data. New experimental data were measured at nELBE of HZDR (Helmholtz-Zentrum Dresden-Rossendorf) for a comparison with the evaluated and existing measurement data. The neutron source nELBE adopts a 40 MeV superconducting electron linac and a liquid Pb target for time-of-flight measurements. The nELBE neutron source uses no moderator and provides fast neutrons. An electron bunch length of 5 ps and a compact target provide a good neutron energy resolution with a relatively short flight length compared to other time-of-flight neutron sources. Transmission data of a natural tungsten sample were measured with a flight path length of 852.1 cm and a repetition rate of 101.56 kHz. The neutron total cross section of natural tungsten was obtained for an energy range of 100 keV to 10 MeV.

Keywords: neutron total cross section; W; fast neutron transmission measurement; nELBE time-of-flight facility

  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology, 11.-16.09.16, Bruges, Belgium
    European Physical Journal - Web of Conferences
    DOI: 10.1051/epjconf/201714611044

Permalink: https://www.hzdr.de/publications/Publ-25299
Publ.-Id: 25299


FDG uptake in normal tissues assessed by PET during treatment has prognostic value for treatment results in head and neck squamous cell carcinomas undergoing radiochemotherapy

Zschaeck, S.; Löck, S.; Leger, S.; Haase, R.; Bandurska-Luque, A.; Appold, S.; Kotzerke, J.; Zips, D.; Richter, C.; Gudziol, V.; Schreiber, A.; Zöphel, K.; Baumann, M.; Krause, M.

Background and purpose: Pronounced early side effects have been suggested to be a positive prognostic factor in patients undergoing chemo-radio-therapy (CRT) for head and neck squamous cell carcinomas (HNSCC). We assessed the utility of positron emission tomography (PET) during treatment to analyze the correlation of 18F-fluorodeoxyglucose (FDG) uptake in off target structures within the irradiated volume with outcome.
Material and methods: Two independent cohorts of patients with locally advanced HNSCC, both treated within prospective clinical imaging trials with curatively intended CRT were retrospectively analyzed.
The exploratory cohort included 50, the independent validation cohort 26 patients. Uptake of FDG in mucosa and submucosal soft tissues (MST) as well as in other structures was assessed at week 4 during treatment. Considered endpoints were local tumor control (LC) and overall survival (OS). The prognostic value of FDG uptake on the endpoints was measured by the concordance index (ci) using univariate and multivariate Cox regression analyses based on the continuous variables of the exploratory cohort.
Results: In the exploratory cohort FDG uptake in MST was prognostic for LC (hazard ratio HR = 0.23, p = 0.025) and OS (HR = 0.30, p = 0.003) in univariate analyses. These findings remained significant upon multivariate testing (LC HR = 0.14, p = 0.011; OS HR = 0.20, p = 0.001) and were confirmed in the validation cohort for LC (HR = 0.15, p = 0.034) and OS (HR = 0.17, p = 0.003). Also the SUVmean threshold of MST that was generated within the exploratory cohort (2.375) yielded significant differences in OS (p = 0.006) and a statistical trend for LC (p = 0.078) when applied to the validation cohort.
Conclusions: FDG uptake in normal tissues within the irradiated volume measured by PET during treatment has significant prognostic value in HNSCC. This effect may potentially be of use for personalized treatment adaptation.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-25298
Publ.-Id: 25298


Breaking of axial symmetry in excited nuclei as identified in experimental data

Junghans, A.; Grosse, E.; Massarczyk, R.

A phenomenological prediction for radiative neutron capture is presented and compared to recent compilations of Maxwellian averaged cross sections and average radiative widths. Photon strength functions and nuclear level densities near the neutron separation energy are extracted from data without the assumption of axial symmetry – at variance to common usage. A satisfactory description is reached with a small number of global parameters when theoretical predictions on triaxiality (from constrained HFB calculations with the Gogny D1S interaction) are inserted into conventional calculations of radiative neutron capture. The photon strength is parametrized using the sum of three Lorentzians (TLO) in accordance to the dipole sum rule. The positions and widths are accounted for by the droplet model with surface dissipation without locally adjusted parameters. Level densities are influenced strongly by the significant collective enhancement based on the breaking of axial symmetry. With the less stringent requirement of invariance against rotation by 180° a global set of parameters which allows to describe the photon strength function and the level densities in the nuclear mass range from mass number 50 < A < 250 is found.

Keywords: nuclear structure; axial symmetry breaking; photon strength function; GDR; neutron capture

  • Open Access Logo Contribution to proceedings
    International Conference on Nuclear Data for Science and Technology 2016, 11.-16.09.16, Bruges, Belgium
    European Physical Journal - Web of Conferences
    DOI: 10.1051/epjconf/201714605007

Permalink: https://www.hzdr.de/publications/Publ-25297
Publ.-Id: 25297


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