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35836 Publications

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

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

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

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

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.

[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

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

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

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

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

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

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

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

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

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

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

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

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

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 (, 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

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

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

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

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

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

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.

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

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

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

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

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.


[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,
[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,
[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

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

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

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

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

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.

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

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

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

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

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

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
    Online First (2017) DOI: 10.1002/jlcr.3526


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

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

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.

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

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

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

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

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

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

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.

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

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

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


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.
This work is supported by the German Federal Ministry of Education and Research, Grant No. 01DS16007.
[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

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.

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.

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

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

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

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

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

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

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%.

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

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

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

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.

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

Publ.-Id: 25297

THEREDA – Thermodynamic Reference Database

Moog, H. C.; Altmaier, M.; Bok, F.; Brendler, V.; Gaona, X.; Marquardt, C.; Montoya, V.; Richter, A.; Scharge, T.; Thoenen, T.; Voigt, W.; Yalçintaş, E.

Thermodynamic data are necessary for the estimation of the maximum likely solubility of hazardous contaminants such as radio nuclides in aqueous solutions. Such assessments are done within the frame of long term safety analysis for repositories of radioactive waste. For this purpose various databases exist in the world. But they are poorly comparable and furthermore reflect the needs of the respective national disposal programme.
Not only activities related to the identification of a suitable site for disposal, for the construction of a repository, its operation and finally its closure, but also the establishment of reliable thermodynamic data is a time-consuming, expensive and long-term effort which spans generations of scientists. It is necessary to store the results of many research projects, national and international, in a way that ensures internal consistency, allows for easy access, and allows for an easy application in thermodynamic equilibrium calculations with some of the most popular codes. Therefore, the establishment of such a database is a national task and an important part for a long-term knowledge management.
To meet this demand a project was launched in 2006 to create a common, mutually agreed and web-based Thermodynamic Reference Database – THEREDA (Moog et al. 2015). The database is run by the following institutions:

  • GRS: Gesellschaft für Anlagen- und Reaktorsicherheit mbH, Abteilung Prozessanalyse, Theodor-Heuss-Straße 4, D-38122 Braunschweig, Germany
  • KIT-INE: Karlsruhe Institute of Technology, Institute for Nuclear Waste Disposal, P.O. Box 3640, D-76021 Karlsruhe, Germany
  • HZDR-IRC: Helmholtz-Zentrum Dresden-Rossendorf, Institute of Radiochemistry, Bautzner Landstraße 400, D-01328 Dresden, Germany
  • TU-BAF: Technische Universität Bergakademie Freiberg, Fakultät für Chemie und Physik, Institut für Anorganische Chemie, Leipziger Straße 29, 09596 Freiberg, Germany
  • PSI-LES: Paul Scherrer Institut, Laboratory for Waste Management, Villigen, Switzerland
In the initial phase of the project the participating institutions agreed upon quality objectives:
  • Transparency: all data should be traceable to a publicly available reference.
  • Consistency: all data should be stored in a way which ensures internal consistency between data directly entered and other data, which are internally calculated from the former ones.
  • Comprehensiveness: the database should cover the whole range of possible applications with regard to safety assessments for nuclear disposal sites. Where data are missing, appropriate estimates should be added.
  • Uncertainties: wherever possible, uncertainties of data were to be captured.
  • Data assessment: the referenced source, the data quality and the way in which every particular datum was derived should be captured in terms of pre-defined identifiers. Thus, data of poor quality and estimates, which were added to meet the objective "comprehensiveness", are marked accordingly for the user.
Criteria for the quality of thermodynamic data were largely adopted from a database established by OECD-NEA. However, provisions had to be met for additional parameters needed to cover the specific conditions in northern German deep geologic strata as they are likely to occur in clay or rock salt formations.
The development of recommended thermodynamic data follows an internal scheme for quality assurance. Additional documentation is available about the selection of data, but also about technical specifications of the databank to enable future users the maximum possible benefit of today’s work.
In technical terms stored data are managed in ways to keep them accessible as long as possible. This includes the use of open source rather than proprietary software. The data structure was designed to be flexible to cover potential future needs in safety assessment. Databases are issued in plain text files which can be processed as long as computers exist. Internal project communication as well as public access to the database is realized by a graphical user interface accessible over the world wide web:
This project was and is jointly funded by the Federal Ministry of Education and Reearch (BMBF) (GRS: 02C1426/02C1628, FZD: 02C1436, TU-BAF: 02C1446), the Federal Ministry of Economics and Technology (BMWi) (FZK/KIT: 02E10126/02E1067, FZD: 02E10136, GRS: 02E10146, TU-BAF: 02E10709), and the Federal Office for Radiation Protection (BfS ) with funds from the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU).
H. C. Moog et al., Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem. (55), 72-84 (2015).

Keywords: THEREDA; Thermodynamische Referenzdatenbank; Thermodynamic Reference Database; Pitzer

  • Lecture (Conference)
    ENTRIA Conference, 26.-28.09.2017, Braunschweig, Deutschland

Publ.-Id: 25296

Inductive measurement of the free surface of liquid metals

Zürner, T.; Ratajczak, M.; Wondrak, T.; Eckert, S.

A novel measurement system to determine the surface position and topology of liquid metals is presented. It is based on the induction of eddy currents by a time-harmonic magnetic field and the subsequent measurement of the resulting secondary magnetic field using gradiometric induction coils. The system is validated experimentally for static and dynamic surfaces of the low-melting liquid metal alloy gallium-indium-tin in a narrow vessel. It is shown that a precision below 1 mm and a time resolution of at least 20 Hz can be achieved.

Keywords: Inductive measurement; liquid metal; surface topology


Publ.-Id: 25295

In-situ XAFS characterization of PtPd nanoparticles synthesized by galvanic replacement

Tymen, S.; Scheinost, A. C.; Friebe, C.; Schubert, U. S.

Platinum-palladium nanoparticles are synthesized and characterized with regard to their application in fuel cells due to their high (electro)catalytic activity. Different preparation times are applied leading to different structures, from Pd cubic to core-shell PtPd concave, and different chemical compositions. The resulting particles are studied via TEM and in-situ XAFS measurements. The latter allows the investigation of the oxygen reduction reaction following the variations with varying applied potentials by analysis using ITFA and the creation of a two-component system that consists of metallic Pt-Pd and the related oxide. With the used model, the different concentrations of the oxide are linked to the consecutive chemical steps of the oxygen reduction reaction.
Finally, the catalytic activity of the particles is determined via linear scanning voltammetry and reveals a dependence on the shape and the composition of the particles.

Keywords: Pt; Pd; nanoparticles; catalysis; EXAFS; TEM; fuel cell

  • Open Access Logo Advances in Nanoparticles 6(2017), 75-91
    DOI: 10.4236/anp.2017.62007
  • Invited lecture (Conferences)
    Ninth Joint BER II and BESSY II User Meeting, 13.-15.12.2017, Berlin, Germany

Publ.-Id: 25294

Simple Formulas for Porosity and Specific Surface of the Cherry-Pit Model

Stoyan, D.; Hermann, H.; Elsner, A.

The cherry-pit or penetrable concentric-shell model is an important, very successful stochastic model for random porous media with open pores. It is based on a random system of hard spheres (the ‘pits’), which are dilated in order to get open pores. The exact determination of porosity _phi_ and specific surface s is a problem obviously too difficult for the contemporary mathematics. Already in the 1980ies approximations were found which are presented in the book by Torquato (2002). Since 2009 these formulas have been refined by the authors, by combination of simulation and ideas of stochastic geometry. This includes the study of the poly-disperse case of pits with random radii, which was mastered by means of correction factors. In the present paper the true nature of these factors is explained, which leads to simple and elegant formulas in which only the first three moments of the radius distribution appear.

Keywords: cherry-pit model; specific surface; sphere packings; stochastic geometry

Publ.-Id: 25293

CT imaging during treatment improves radiomic predictions for patients with locally advanced head and neck cancer

Leger, L.; Zwanenburg, A.; Pilz, K.; Baumann, M.; Troost, E.; Richter, C.; Löck, S.

Introduction: Radiomics applies machine learning algorithms to characterize the tumor phenotype and to predict clinical outcome based on quantitative imaging data. It has been applied using pre-treatment computed tomography (CT) scans but only few studies have assessed radiomics on imaging acquired during radiotherapy. Therefore, we compared the performance of radiomic models based on the pre-treatment CT with that based on CT imaging during treatment.
Material/Methods: Two datasets of patients with advanced stage head and neck squamous cell carcinoma (HNSCC) were used as an exploratory and a validation cohort (47 and 30 patients, respectively). All patients received primary radio-chemotherapy (RCT) and underwent a non-contrast-enhanced CT scan pre-treatment and in week 2 (W2) of treatment. 1610 image features were extracted from the gross tumour volume, delineated on the baseline CT and the W2 CT. Radiomic models were built to predict loco-regional tumour control (LRC). Different feature selection methods (mutual information maximization (MIM), random forest variable importance (RFVI)) and learning algorithms (Cox regression (COX), random forest (RF)) were evaluated using the concordance index (CI) as performance measure.
Results: On the W2 CT both FS methods combined with the RF algorithm achieved a higher performance (CI=0.71) than on the baseline CT (CI<0.65), which was also observed using the Cox regression model (W2 CT: CI=0.66, baseline CT: CI=0.51).
Conclusions: CT scans from the second week of RCT for patients with locally advanced HNSCC improved the performance of radiomic prediction models compared to baseline CT scans. The incorporation of during-treatment imaging is a promising way to improve radiomic models for clinical treatment adaption.

  • Lecture (Conference)
    15th Acta Oncologica conference on biology-guided adaptive radiotherapy - BIGART 2017, 14.-16.06.2017, Aarhus, Danmark

Publ.-Id: 25292

Development of an experimental setup for the integration of multi-modality imaging and photon/proton irradiation for preclinical cancer research with small animals

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

In this abstract, we present an experimental setup that allows for multi-modal, cross-platform imaging of small animals as well as image-guided proton- and photon irradiation under laboratory conditions.
The setup consists of two units: A primary bedding unit which holds the animal and which is equipped with a breathing mask for inhalation anesthesia, an inlet for warm air and a breathing sensor. The primary unit was designed to meet the demands of the various imaging (magnetic resonance imaging, positron emission tomography, computed tomography, proton radiography,) and treatment modalities (photon- and proton irradiation). The bedding unit can be mounted inside a container, which is designed to maintain pathogen-free conditions outside designated animal laboratory facilities.
The second, peripheral unit comprises a heating module, several sensors and read-out electronics to control and monitor temperature as well as vital signs. Moreover, it allows for remote emergency intervention (e.g. oxygen flush) during the animal’s anesthesia.
The setup has currently been tested for proton irradiation in an experimental area. A method was implemented to perform on-line position verification by proton radiography.
The presented setup features multiple advantages for combined, multi-modal treatment which is of special importance for the monitoring and treatment planning of experimental tumor models. In particular, orthotopic tumors which require accurate imaging – the modality of which can be chosen based upon tissue and treatment – and treatment planning. It satisfies the various modalities’ requirements, hence allowing for one combined workflow. Moreover, image analysis is strongly simplified as multi-modal images can be co-registered without sophisticated techniques.

Keywords: Preclinical research; cancer; proton therapy; imaging

  • Lecture (Conference)
    15th Acta Oncologica conference on biology-guided adaptive radiotherapy - BiGART 2017, 13.-16.06.2017, Aarhus, Dänemark

Publ.-Id: 25291

ATHLET model development for the passive pressure pulse transmitter as part of the passive safety systems of a nuclear reactor within the frame of the German EASY project

Sporn, M.; Neukam, N.; Schuster, C.; Hurtado, A.; Hampel, U.; Schäfer, F.

In nuclear power plants, various kinds of active safety systems are installed to control reactor power and to ensure safe and stable core cooling for a wide spectrum of transients and accidents. The safety concept is complemented by inherent safety features and, especially for new reactor designs, by innovative passive safety systems. These systems are based on a change in the thermodynamic equilibrium established at steady-state conditions, enabling them to function without electric power supply. An important part of the passive safety systems of the KERENA© reactor, an evolutionary boiling-water reactor concept jointly developed by AREVA and PreussenElectra (formerly E.ON), is the passive pressure pulse transmitter (PPPT). In case of an accident with decreasing reactor water level, the PPPT serves as an alternative trigger to activate reactor scram, containment isolation or automatic depressurization of the reactor cooling system. Investigations on the interaction of the various components of the KERENA© passive safety concept (e.g. PPPT, emergency condenser and containment cooling condenser) are being performed for the EASY project. Using the system code ATHLET an input deck of the PPPT has been developed and successfully validated. Additionally, an ATHLET input deck for the complete passive heat-removal system has been developed to simulate hypothetical accident transients, which will be experimentally investigated at the INKA test facility in Karlstein. In this paper, the results of the simulations for the PPPT and a simulation for a hypothetical loss-of-coolant accident are presented.

Keywords: Passive pressure pulse transmitter; passive systems; ATHLET; KERENA; INKA; EASY

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

Publ.-Id: 25290

Does the UO2(CH3COO)3-complex really exist: a spectroscopic study

Brinkmann, H.; Moll, H.; Stumpf, T.

The coordination chemistry of radionuclides (RN) with organic components is of great interest since latter can affect the mobility as well as the sorption behavior adversely. Acetate (AcO-) can be a biotic or abiotic degradation product of organic material present in nuclear waste. Additionally it is often declared as model compound for more complex organic structures. A large number of studies is available which investigated the speciation of uranium(VI) in the presence of acetate under acidic conditions. From potentiometric titrations it seems to be very clear that three uranyl-acetate species are formed under acidic conditions: UO2AcO+ (1:1), UO2(AcO)2 (1:2) and UO2(AcO)3- (1:3).
Spectroscopic methods (e.g. IR and EXAFS) provide no certainty whether the 1:3 complex exists or not. TRLFS and UV-vis spectroscopy were mainly applied to characterize the formation of the 1:1 complex. In this study TRLFS, ATR-FT-IR and UV-vis spectroscopy were applied to determine the speciation of uranium(VI) in the presence of acetate and to fill the gap of missing spectroscopic data for the other formed species. Experimental conditions were chosen so that all three previous identified species should be formed. Data evaluation was performed on the basis of factor analysis resulting in single component spectra and stability constants. The findings led us to the conclusion that the 1:3 complex was not formed. In addition the detailed evaluation of ATR-FT-IR spectra show that an approximation used in potentiometric studies should be treated with caution. All these indications reinforce the doubts with respect to the existence of the UO2(AcO)3- species.

Keywords: Acetate; Uranyl; TRLFS; UV-vis; ATR-FT-IR

  • Poster
    GDCh-Wissenschaftsforum Chemie 2017, 10.-14.09.2017, Berlin, Deutschland

Publ.-Id: 25289

Canola cell (Brassica napus) responses to europium(III) exposure: a spectroscopic study

Moll, H.; Sachs, S.; Geipel, G.

Rare earth elements (REE, e.g. lanthanides) and radionuclides are released in the environment. Hence, detailed knowledge of the fate of these elements in the ecosphere including the food chain is required for a reliable assessment of the resulting risk potential for humans and wildlife. Our aim is to explore the complex processes of trivalent actinides with plant cells on a molecular level using europium(III) as an analogue for trivalent actinides. Callus cell cultures are suitable models for studying cell metabolism processes in plants. They retain the ability to form metabolites characteristic of intact tissues for an adaptation to stress conditions, in this case europium.
We studied the response of Brassica napus cells to europium(III) exposure (30 µM and 200 µM). Time-resolved laser-induced fluorescence spectroscopy (TRLFS) was used as direct speciation technique to explore the Eu(III) speciation on callus cells and cell compartments after cell fractionation. The possible release of plant cell metabolites (e.g. phenolic compounds) promoted due to the cell contact with Eu(III) was investigated.
After an exposure time of 42 days and at 200 µM Eu(III) the growth of the calli was inhibited by ca. 50 % compared to 30 µM Eu(III) and the control. This correlates with increased amounts of secreted phenolic compounds. Callus cells accumulated 7.2 to 100 µg Eu/gwhet cells depending on [Eu(III)]initial. Cell fractionation studies revealed that 98 % of the Eu(III) was located on large cell fragments and 2 % was found in the cytoplasm. TRLFS studies showed a different Eu(III) speciation on callus cells (active uptake) compared to those found on suspension cell cultures (bioassociation).
This knowledge contributes to an improved understanding of REE/radionuclide interactions with plants on a molecular level.

Keywords: plants; europium; metabolism; TRLFS

  • Contribution to proceedings
    Goldschmidt2017, 13.-18.08.2017, Paris, France
  • Lecture (Conference)
    Goldschmidt2017, 13.-18.08.2017, Paris, France

Publ.-Id: 25288

Recent and present activities in THEREDA

Moog, H. C.; Altmaier, M.; Brendler, V.; Bok, F.; Gaona, X.; Marquardt, C.; Richter, A.; Scharge, T.; Thoenen, T.; Voigt, W.

THEREDA is the acronym for “Thermodynamic Reference Database”, a multi-institutional, national joint project to create a mutually accepted database for the geochemical modeling of solubilities in the near field of an underground repository for high-level waste in a rock salt formation (Moog et al. 2015).
As of April 2010 THEREDA became operative in the world wide web, and since 30th of June 2011 ready-to-use parameterfiles for EQ3/6, Geochemist’s Workbench, PHREEQC, and ChemApp are released. During the following years the team issued altogether eleven data releases. Each release covers data for particular subsystems only.
Data releases
During the last two years three data releases were issued. Each release was qualified and documented with test calculations. Apart from ChemApp the releases are accompanied by code-specific scripts which enable the user to reproduce our calculations.
R-09 covered the systems

  • U(IV) – (Na, K) – HCO3 – H2O
  • U(IV) – Na – Cl – H2O
  • U(VI) – (Na, K, Ca) – Cl – H2O
R-10 covered the systems
  • Na - Cl - Tc(IV) / Tc(VII) - OH,
  • Mg - Cl - Tc(IV) - OH,
  • Ca - Cl - Tc(IV) - OH
R-11 covered the systems
  • Sr – (Na, K, Mg, Ca) – Cl – H2O
  • Sr - Na – SO4 – H2O
R-10 was the first release to cover a redox reaction. Our efforts to produce parameter files for different codes which deliver the same result posed unexpected difficulties and revealed differences on how the different codes tackle redox transitions.
Extension of internal calculation
THEREDA features a system of internal calculations of dependent data from independent data (the latter ones directly entered). It has been extended to provide for temperature extrapolations from standard reaction data and for the calculation of the latter from temperature functions of equilibrium constants of standard molar Gibbs free enthalpies of reaction.
Data releases
The following data releases are in preparation and have priority for 2017.
  • Solubility of oxygen in pure water and high saline solutions
  • Na, K – Cl,SO4 – (PO43-, HPO42-, H2PO4-) –H2O (binary, ternary, and some quaternary systems tested)
  • This will lead to an upgrade of R-09 covering uranium solubility in phosphate bearing solutions
  • Merge of R-01 (Na, K, Mg, Ca – Cl, SO4 – H2O polythermal) and R-03 (Na, K, Mg, Ca – Cl, SO4 – HCO3/CO2(g) – H2O 298.15K only) with an upgrade of the latter for elevated temperatures.
As a side product, the release on the oxygen solubilities will lead to a re-evaluation of logK-values for the reactions
2H2O(l) ⇌ O2(aq) + 2H2(g)
2H2O(l) ⇌ O2(g) + 2H2(g)
1. H. C. MOOG et al., Disposal of Nuclear Waste in Host Rock formations featuring high-saline solutions - Implementation of a Thermodynamic Reference Database (THEREDA). Appl. Geochem. (55), 72-84 (2015).
E. Yalçintaş et al., Thermodynamic description of Tc(IV) solubility and hydrolysis in dilute to concentrated NaCl, MgCl2 and CaCl2 solutions, Dalton Transactions (45), 8916-8936 (2016). -> [YAL/GAO2016]
2. J. B. Macaskill et al., Isopiestic measurements on aqueous Mixtures of Sodium Chloride and Strontium Chloride. J. Solution Chem. (7), 339-347 (1978). -> [MAC/WHI1978]
3. V. K. Filippov et al., Thermodynamics of phase equilibria in the potassium, strontium, sodium, chloride, water (K+,Sr2+|| Cl--H2O, Na+,Sr2+|| Cl--H2O and Na+,K+,Sr2+|| Cl--H2O) systems at 25°, Russ. J. Gen. Chem. (60), 427-431 (1990). -> [FIL/FED1990]
4. J. A. Rard and D. G. Miller, Isopiestic determination of the osmotic and activity coefficients of aqueous mixtures of sodium chloride and strontium chloride at 25° C, J. Chem. Eng. Data (27), 342-346 (1982). -> [RAR/MIL1982b]
5. S. L. Clegg et al., Isopiestic Determination of the Osmotic and Activity Coefficients of NaCl + SrCl2 + H2O at 298.15 K and Representation with an Extended Ion-Interaction Model, J. Chem. Eng. Data (50), 1162-1170 (2005). -> [CLE/RAR2005]
6. M. Kydynov et al., Solubility in the quaternary system consisting of lithium, sodium and strontium chlorides and water at 25 °C, J. Appl. Chem. (London) (4), 736-739 (1969). -> [KYD/LOM1969]

Keywords: THEREDA; Thermodynamic Reference Database; Pitzer

  • Lecture (Conference)
    Actinide Brine Chemistry (ABC-Salt V Workshop 2017), 26.-28.03.2017, Ruidoso, USA

Publ.-Id: 25287

60Fe and 244Pu in deep-sea archives - a link to nearby supernova activity and r–process sites

Wallner, A.; Kinoshita, N.; Feige, J.; Froehlich, M.; Hotchkis, M.; Fifield, L. K.; Golser, R.; Honda, M.; Linnemann, U.; Matsuzaki, H.; Merchel, S.; Paul, M.; Rugel, G.; Schumann, D.; Tims, S. G.; Steier, P.; Yamagata, T.; Winkler, S. R.

The Interstellar Medium (ISM) is continuously fed with new nucleosynthetic products. The solar system moves through the ISM and collects dust particles. Therefore, direct detection of freshly produced radionuclides on Earth, i.e. before decaying, provide insight into recent and nearby nucleosynthetic activities [1,2]. Indeed, a pioneering work at TU Munich [3,4], which applied the ultra-sensitive single atom counting technique of accelerator mass spectrometry (AMS) to an ocean crust-sample, showed an enhanced 60Fe signal possibly of extraterrestrial origin. Within an international collaboration [5-7] we have continued to search for ISM radionuclides incorporated in terrestrial archives. We have analyzed several deep-sea sediments, crusts and nodules for extraterrestrial 60Fe (t1/2=2.6 Myr), 26Al (t1/2=0.7 Myr) and 244Pu (t1/2=81 Myr) [5-8] which are complemented by independent work at TU Munich [9-11]. All the data demonstrate a clear global 60Fe influx that is interpreted as exposure of Earth to recent (≤10 Myr) supernova explosions. Furthermore, the low concentrations measured for 244Pu suggest an unexpectedly low abundance of interstellar 244Pu [5]. This finding signals a rarity of actinide r–process nucleosynthesis which is incompatible with the rate and expected yield of standard core collapse supernovae as the predominant actinide-producing sites. In this talk I will also present additional new results for 60Fe and 244Pu measured with unprecedented sensitivity. These data provide new insights into their concomitant influx and their ISM concentrations over a time period of the last 11 million years.
[1] J. Ellis et al., ApJ. 470, 1227 (1996).
[2] G. Korschinek et al., Radiocarbon 38, 68 (1996); abstract.
[3] K. Knie et al., Phys. Rev. Lett. 83, 18 (1999).
[4] K. Knie et al., Phys. Rev. Lett. 93, 171103 (2004).
[5] A. Wallner et al., Nature Comm. 6, 5956 (2015).
[6] J. Feige et al., EPJ Web of Conf. 63, 3003 (2013).
[7] A. Wallner et al., Nature 532, 69 (2016).
[8] M. Paul M. et al. Astrophys. J. Lett. 558, L133L135 (2001).
[9] C. Wallner et al. New Astron. Rev. 48, 145150 (2004).
[10] L. Fimiani et al., Phys. Rev. Lett. 116, 151104 (2016).
[11] P. Ludwig et al., PNAS 113, 9232 (2016).

Keywords: accelerator mass spectrometry; AMS; supernova

  • Lecture (Conference)
    Nuclear Physics in Astrophysics 8 (NPA8), 18.-23.06.2017, Catania, Italia

Publ.-Id: 25286

Entwicklung und Validierung von Bildauswertealgorithmen zur Charakterisierung der Gas-Flüssigkeits-Strömung in Anstaupackungen

Litzka, A.

Am Helmholtz-Zentrum Dresden Rossendorf wird die Fluiddynamik von Anstaupackungen untersucht, einer neuen Form von Einbauten für Trennkolonnen. Für die Auswertung der Messungen mithilfe der ultraschnellen Röntgentomographie werden Algorithmen benötigt, welche die Ermittlung der Phasenverteilung in den Packungen ermöglichen.
In dieser Arbeit wurde untersucht, ob dies mithilfe von Bildsegmentierung erfolgen kann. Die Segmentierung muss in Gas, Flüssigkeit und Titanblech erfolgen. Es wurden geeignete Messphantome erstellt, anhand derer die Implementierung der Algorithmen erfolgte. Für die Validierung der Ergebnisse wurden Referenzmessungen mit Röntgen-Mikrotomographie eingesetzt.
Aufgrund der mangelnden Bildqualität der rekonstruierten Daten ist zunächst nur Identifikation der Gasphase in den Phantomen möglich. Der Ansatz die Feststoffstruktur mithilfe der Referenzmessung lokalisieren zu können, scheiterte an einer Verzerrung der abgebildeten Geometrien durch die ultraschnelle Röntgentomographie infolge der Bildrekonstruktion.
Des Weiteren wurde versucht mithilfe einer Dekonvolution die Bildqualität zu verbessern und so die Voraussetzung für eine Segmentierung in drei Phasen zu schaffen. Im entfalteten Bild ist es für eine der drei Strömungsformen möglich, in lokalen Bereichen Schwellwerte für eine Segmentierung in drei Phasen zu ermitteln. Offen ist, ob sich dies auf die anderen Strömungsformen übertragen lässt und eine Optimierung der Auswertealgorithmen eine ausreichende Genauigkeit der Anteilsbestimmung ermöglicht.

  • Study thesis
    TU Dresden, 2017
    Mentor: J. Sohr, M. Schubert, U. Hampel

Publ.-Id: 25285

Site-specific binding affinity of Eu(III) towards Ca-binding protein calmodulin: A combined spectroscopic and theoretical study

Tsushima, S.; Samsonov, S.; Drobot, B.; Raff, J.; Komeiji, Y.; Mochizuki, Y.

Molecular modelling of actinide interaction with large biomolecules by quantum chemical calculations is restricted by request for huge computational resources. We challenged this problem by applying Fragment Molecular Orbital (FMO) method. In FMO, the molecular system is partitioned into small fragments and each fragment and fragment pair is subjected to self-consistent field calculations which drastically reduces computational cost.1 We are upgrading FMO program Abinit-MP 2 to implement f orbitals. Here, interaction of Eu3+ with Ca-binding protein calmodulin (CaM) was studied. Calculations were performed in the following way. Using the crystal structure of Ca2+-bound CaM, all four Ca2+ ions were replaced by Eu3+, protonation state of Eu-CaM was adjusted, and 12 Na+ were added for neutralization. The structure was immersed in a TIP3P water bath of 8 Å thickness around Eu-CaM and submitted to 100 ns molecular dynamics (MD) run. Structure at each 1 ns was collected (100 samples), waters were stripped off to 4 Å coverage, and the structures were used in FMO calculations at MP2 level. The statistical average of inter-fragment interaction energy (IFIE) was calculated. Average coordination number of Eu in Eu-CaM during 100 ns MD run is between 8.9 and 9.1. Eu sits in the same binding site as Ca but with increased bidentate coordination. Additionally, increased water coordination is observed. In EF Hand 1, 2, and 4, there is an average of 1.7 to 1.9 coordinating waters to Eu whereas in Hand 3 there is an average of 2.9 waters. This result perfectly matches with previous spectroscopic findings where 2 waters was found at sites 1 and 2 and at either site 3 or site 4, with 3 waters at the remaining site.3 When we compare four metal-binding sites in Eu-CaM, the IFIE between Eu3+ and the corresponding binding site are overall similar among three of the four binding sites, namely EF Hand 1, 2, and 4. On the other hand the IFIE for Hand 3 is clearly smaller pointing to that Hand 3 is the weakest binding site. The reason for this is clear; EF Hand 3 carries only three negatively charged residues, whereas the other motifs have four of them. Consequently, Eu binding in EF Hand 3 exhibits relatively larger fluctuations compared to other binding sites which causes structural disorder to Eu-CaM. We also performed titration and Eu luminescence lifetime measurements which are found to be consistent with MD and FMO results.

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

Publ.-Id: 25284

Untersuchung heterogener Strömungsmuster in Anstaupackungen mittels ultraschneller Röntgentomographie: Methode und Validierung

Sohr, J.; Litzka, A.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.

Die Kombination von strukturierten Packungen unterschiedlicher geometrischer Oberflächen in Anstaupackungen (s. Abb. 1) führt zu einem axial verteilten Strömungsprofil bestehend aus Blasenströmung, Sprudelschicht und Filmströmung. Die Strömungsmorphologie variiert dabei in den einzelnen Strömungsbereichen sehr stark, sodass durch integrale Hold-up-Messungen kaum Rückschlüsse auf die individuellen Flüssigkeitsinhalte und Phasengrenzflächen gezogen werden können. Zeitlich und örtlich hochaufgelöste bildgebende Messverfahren, wie die ultraschnelle Röntgentomographie, können hier neue Erkenntnisse zur Fluiddynamik liefern [1].
Im Rahmen eines durch die DFG geförderten Projekts sind umfangreiche Fluiddynamikstudien mittels ultraschneller Röntgentomographie geplant. In einem ersten Schritt wird die ultraschnelle Röntgentomographie für die Untersuchung der unterschiedlichen Strömungsmorphologien validiert. Dazu werden mittels Micro-Computertomographie exakt charakterisierte statische Messphantome eingesetzt und Methoden zur Erfassung und Bewertung von Hold-up, Phasenverteilung und Phasengrenzflächen entwickelt. Die Validierung dieser Methoden ist Gegenstand dieses Beitrags.
[1] Janzen, A., Schubert, M., Barthel, F., Hampel, U., Kenig, E.Y., Chem. Eng. Process, (2013), 66, 20-26.

  • Lecture (Conference)
    Jahrestreffen der ProcessNet Fachgruppen Mechanische Flüssigkeitsabtrennung, Kristallisation, Phytoextrakte, Adsorption, Extraktion, Fluidverfahrenstechnik und Membrantechnik, 06.-10.03.2017, Köln, Deutschland

Publ.-Id: 25283

A highly-parallel Monte-Carlo-Simulation of X-Ray-Scattering using a Particle-Mesh-Code on GPUs

Grund, A.

Im Rahmen dieser Arbeit wurde eine Softwarelösung entwickelt, welche die Streuung von Röntgenstrahlung in Materie mit einem Monte-Carlo-Ansatz simuliert. Dazu wurde die Anwendung der Röntgen-Kleinwinkelstreuung (SAXS) zur Untersuchung der komplexen Prozesse bei der Interaktion intensiver kurzer Laserpulse mit Festkörpern als Motivation verwendet und beschrieben, wie Fouriertransformationen zur Näherung dieser Streuung verwendet werden können. Darauf aufbauend wurde einerseits die schnelle Fouriertransformation (FFT) als effiziente Implementierung für Computer vorgestellt und andererseits wurde auf die Limitierung dieses Ansatzes zur Beschreibung der Streuprozesse eingegangen. Um diese Limitierungen zu umgehen, wurde ein Modell entwickelt, das die Röntgenstrahlung mittels photonenähnlicher Teilchen beschreibt. Da für eine gute Abbildung der physikalischen Prozesse Milliarden solcher Teilchen benötigt werden, wurde die auf diesem Modell basierende Simulation von Anfang an auf die hoch parallele Struktur moderner Grafikprozessoren ausgelegt, welche es ermöglicht, sehr viele Teilchen gleichzeitig zu simulieren. Der implementierte Algorithmus wurde detailliert beschrieben, wobei gezielt auf die Besonderheiten von Grafikprozessoren eingegangen wurde. Da die richtige Wahl der Datentypen wesentlich für die Geschwindigkeit und Präzision des Algorithmus ist, wurde in einer umfassenden theoretischen Analyse und Tests der numerischen Genauigkeit der Implementation gezeigt, dass sogar mit Berechnungen in geringer Genauigkeit Ergebnisse erzielt werden, die keine wesentlichen Abweichungen von denen der exakten Berechnung aufzeigen. Dadurch können für typische Anwendungen kleinere Datentypen gewählt werden, was die Durchführung umfangreicherer Simulationen auf einer gegebenen Hardware erlaubt. Abschließend konnte die Korrektheit für ausgewählte Beispiele sowie eine gute Skalierbarkeit nachgewiesen werden.

English abstract:
In this thesis a software solution was developed that simulates the scattering of X-rays in matter using a Monte Carlo approach. The application of small-angle X-ray scattering in the studies of the complex processes occurring during the interaction of short intense laser pulses in solid matter provides the motivation for this work. Therefore this technique is described and it is shown how Fourier transformation can be used for approximating the scattering results. It is shown how they can be efficiently implemented in computers using the fast Fourier transform (FFT) and why this approach has limitations when describing scattering processes. To circumvent these, a model was developed that uses photon-like particles to describe the X-rays. Billions of such particles are required to provide a good approximation of the physical processes involved, which is why the simulation algorithm described in this work was designed from the ground up to support the massively parallel structure of modern graphic processing units (GPUs) allowing to simulate many particles at once. The implemented algorithm is described focusing on the special methods required to make the most use out of GPUs. As the choice of the appropriate data types is vital for the correctness and precision of the algorithm a comprehensive analysis and test of the numerical accuracy was deployed. It is shown that even reduced precision provides results that are accurate enough for a wide range of applications. Therefore, smaller data types can be used allowing to simulate much larger experiments on a given hardware. Finally the correctness and good scalability of the parallel algorithm are demonstrated.

Keywords: HPC; Exascale; Monte-Carlo; Photons; Scattering; SAXS

  • Diploma thesis
    TU Dresden, 2016
    Mentor: Prof. Dr. W. Nagel, Dr. T. Kluge, Dr. M. Bussmann, Dr. A. Knüpfer

Publ.-Id: 25282

Holography at QCD-Tc

Zöllner, R.; Kämpfer, B.

Within an extended soft wall model, we study the temperature dependence of the lowest vector meson states. Scales are adjusted by using as input the ρ meson mass in vacuum and the velocity of sound from lattice QCD which displays a minimum at Tc. The melting of the ρ meson occurs at temperatures O(Tc).

Publ.-Id: 25280

The photoluminescence response to structural changes of Yb implanted ZnO crystals subjected to non-equilibrium processing

Ratajczak, R.; Prucnal, S.; Guziewicz, E.; Mieszczynski, C.; Snigurenko, D.; Stachowicz, M.; Skorupa, W.; Turos, A.

In this paper, we present the detailed study of optical and structural properties of Yb implanted single ZnO crystals. Hydrothermally grown wurtzite (0001) ZnO crystals were implanted with 150 keV Yb ions to fluencies of 5e14 and 1e15 at/cm2. After ion implantation, two different types of annealing were performed: rapid thermal annealing (RTA) and millisecond range flash lamp annealing (FLA). Crystalline quality, damage recovery, and Yb lattice site location were evaluated by the Channeling Rutherford Backscattering Spectrometry (RBS/c). It is shown that independent of the used annealing technique, defects formed in ZnO during ion implantation can be removed. Upon RTA performed at the temperature higher than 800C, strong out-diffusion of implanted Yb atoms and precipitation on the surface takes place. Consequently, the degradation of the photoluminescence (PL) efficiency is observed. The diffusion of implanted Yb during millisecond range FLA does not occur for such experimental conditions. Moreover, FLA treatment for 20 ms leads to the formation of single crystalline ZnO layer with Yb incorporated in the substitutional lattice sites. According to RBS/c and PL data, Yb atoms substituted in the Zn sublattice are predominantly in the 2þ oxidation state. The most intensive PL has been observed after annealing at 800C for 20 min which is accompanied with the reduction of Yb substitutional fraction and formation of octahedron Yb-oxygen clusters within ZnO.

Keywords: ZnO; ion implantation; FLA; Yb; photoluminescence; RBS

Publ.-Id: 25279

Application of a single wire-mesh sensor in a parabolic trough facility with direct steam generation

Hoffmann, A.; Schleicher, E.; Keller, L.; Leon Alonso, J.; Pitz-Paal, R.

The direct steam generation process can contribute to increase the cost-effectiveness of line-focused solar thermal power plants. The current research focuses on the once-through mode as very promising option for large-scale commercial plants. However, the existing pool of knowledge about the steam–water flow in the horizontal receiver pipes reveals knowledge gaps. The present contribution aims to experimentally investigate the two-phase flow in the receiver pipes of the DISS test facility at the Plataforma Solar de Almer´ıa, Spain, by an invasive measurement device for the first time. Therefore a conductance wire-mesh sensor is employed in the low-quality evaporation section of the DISS test facility. This measurement device measures the local instantaneous void fraction that is used to describe the prevailing flow pattern under different pressures and mass flow rates. The results show slug flow, roll waves, wavy flow, and stratified-wavy flow in the horizontal receiver pipes within pressures of 30 to 80 bar. The probability of slug flow or large-amplitude waves decreases with higher pressures. The findings provide a valuable knowledge about the flow structure within the receiver pipes and confirm the proof of function of the wire-mesh sensor under conditions of the direct steam generation process.

Keywords: Wire-mesh sensor; flow pattern; experiment; direct steam generation; parabolic trough; two-phase flow

Publ.-Id: 25278

Accelerator based Light Source Activities in Germany

Michel, P.

Accelerator based light sources for investigation of matter and materials are highly interesting tools in basic research and applied science. Wavelength ranges from microwaves to hard Gamma rays with extremely high photon fluxes and high average beam power can be generated. In most cases, accelerator based light sources are tunable and provide extremely short and high intensity light pulses. For many applications accelerator based sources offer clear advantages in comparison with other light sources, and can also be synchronized to with external laser based sources. Sophisticated accelerator technologies, such as superconducting RF technology, has pushed this trend during the last decade.
In Germany, an extended program to develop new accelerator technologies has been established in the framework of the Helmholtz Association. More than 200 million Euro will be invested from 2016-2019 within this publicly funded program. Against this background, a number of accelerator projects have been realized or started, in particular for generating light beams for research. This talk will give an overview about the largest existing accelerator facilities and projects for light generation reaching from THz up to x-Rays.
Flash and XFEL at DESY, FLUTE and the former THz project TBONE at KIT Karlsruhe, BESSY VSR and bERLinPro at HZB Berlin and ELBE and a potential follow up project at HZDR will be presented.

Keywords: Accelerator; THz; X-rays; XFEL; FLUTE; FLASH; BESSY VSR; BERLINPRO; ELBE

  • Invited lecture (Conferences)
    IX International Workshop on Advanced Generation of THz and Compton X-rays (AGTaX) using Compact Electron Accelerators, 06.-07.03.2017, New Delhi, India

Publ.-Id: 25277

Brillant Light from Cutting Edge Technologies

Michel, P.

Coherent sources of light such as Free Electron Lasers (FELs) are now modern microscopes in science. With the help of the extremely brilliant light that FELs can produce over a wide range of wavelengths, some of the most elusive scientific questions can be effectively answered. These important questions cover matter and novel materials, artificial quantum structures, semiconductor devices, as well as organic and biological samples related to the environment or drug discovery. With special technologies like near field techniques it is possible to overcome fixed measuring limits such as the diffraction limit according to Abbe and to explore some of the smallest building blocks of the world. By means of hard X-rays from X-ray FELs, the chemical structure of complex molecules, e.g. Proteins, can be determined. With the extreme electric fields of long-wave THz rays, the electronic states of solids can be examined or altered, or, for example, the signals of nerves through the membranes of neurons can be investigated. Furthermore, the ultrashort pulses of FEL light can probe the dynamics of fundamental physical and chemical processes with unprecedented resolution. To this extent, accelerator research facilities play a decisive role in science. In addition, such advanced technologies as accelerator systems and free electron lasers provide many other benefits beyond the applications for basic scientific research these technologies and research facilities are the sources of knowledge and training for young students and scientists. Building an accelerator can also benefit the national and local industry. For example, the development of new technologies and methods often also lead to industrial applications and in the process, many personnel are trained. In Dresden-Rossendorf, an accelerator center was built after the reunification of Germany, and in 2001, the ELBE superconducting accelerator went into operation with a variety of secondary sources, including FELs. Today, ELBE is a globally recognized facility drawing scientists and engineers from around the world. More than 70 user groups carry out experiments annually in basic and applied research. Hundreds of publications and scientific contributions to conferences and workshops were held in many areas of science. ELBE is an extremely positive example of how the ambitious establishment of a complicated accelerator facility drives the success of a scientific research center.

Keywords: Brillant; FEL; Synchrotron; accelereator

  • Invited lecture (Conferences)
    IX International Workshop on Advanced Generation of THz and Compton X-rays (AGTaX) using Compact Electron Accelerators, 06.-07.03.2017, New Delhi, India

Publ.-Id: 25276

Production and purification of no-carrier-added 89Zr at the Leipzig cyclotron for extraction studies with a calix[4]arene

Mansel, A.; Franke, K.

Zirconium is one of the main contaminants in important lanthanide ores. To study the separation of tetravalent zirconium from the trivalent lanthanides by means of calixarene liquid-liquid extraction, the radiotracer technique was used [89Zr (T1/2=78.4 h, Eγ=909 keV, 99%)]. The production of this radionuclide was performed at the Leipzig cyclotron CYCLONE 18/9® by using the nuclear reaction 89Y(p,n)89Zr. An yttrium foil (natural abundance 100% 89Y; 80 mg) was irradiated with 14 MeV protons at a current of 22 µA for one hour. The irradiated target was stored for one hour for the decay of the short-lived 89mZr (T1/2=4.2 min) and was then dissolved in conc. HNO3. After dissolution of the residue with 9 M HNO3, UTEVA-Spec® was used to adsorb 89Zr and elute Y3+ with 9 M HNO3 from the resin. 89Zr was washed from the resin by complexation with 0.1 M oxalic acid. The oxalic acid complex was decomposed by fuming with conc. H2SO4. The no-carrier-added 89Zr was dissolved in 1 M H2SO4 with a radiochemical yield of 101% ± 8%. An activity of ~400 MBq was achieved 5 hours after end of bombardment with a detection limit of 7 fM (0.6 pg/L) for no-carrier-added 89Zr.
Liquid-liquid extraction was performed with a calixarene/chloroform system from acidic aqueous solutions with pH values from 1 to 5. A calix[4]arene, exhibiting phosphonate ester and carboxylic groups, was used. A solution containing ~5 MBq/L 89Zr and 10 µM non-radioactive zirconium carrier was shaken with a tenfold excess of the calixarene at the desired pH for one hour. After separation of the organic and the aqueous phases, the content of 89Zr was measured by γ-counting in both phases. An extraction yield of >95% was reached for zirconium at pH 4. In previous studies with 152Eu, less than 5% of this lanthanide were extracted at pH 4, while >98% of the 152Eu were extracted at pH 8.
In future studies, 89Zr could be used for radiolabelling ZrO2-nanoparticles in environmental sciences as a surrogate for long-lived ThO2-nanoparticles.

Keywords: Zirconium; Cyclotron; Yttrium; Proton induced nuclear reaction; Calixarene; Solvent extraction

  • Lecture (Conference)
    5th International Nuclear Chemistry Congress - INCC, 27.08.-02.09.2017, Gothenburg, Sweden

Publ.-Id: 25275

Uranium (VI) complexation with aqueous silicates under elevated temperatures

Lösch, H.; Huittinen, N.; Stumpf, T.

For the safety assessment of high-level nuclear waste repositories in deep geological formations, a sound understanding on the migration behavior of mobilized radionuclides from the spent nuclear fuel (SNF) is required. In recent decades, the solution chemistry of actinides, including hydrolysis and complexation with inorganic ligands such as silicates and carbonates, as well as the interactions of actinides at interfaces present in the geo- and biosphere, have been intensely investigated. These studies are, however, often conducted at ambient temperatures (20-30°C), which hampers the prediction of actinide migration in the environment of heat generating high-level nuclear waste repositories. It is estimated that maximum temperatures in the near field of a SNF repository could reach 100°C, depending on the waste form and host rock under consideration. Thus, for a reliable safety assessment of future SNF repositories, already existing thermodynamic data at 25°C (logK(T), ΔrH, ΔrS, ΔrG) should be expanded to higher temperatures [1, 2].
Silicon is ubiquitous in natural waters as ionic or colloidal species, as a result of weathering of amorphous silica or silicate minerals. U(VI) complexation with silicates in solution has been already subject in previous studies, but only in the temperature range between 20-25°C. For the U(VI)-silicate complexation reaction presented below, a log10*K° between (-1.44) - (-2.65) has been reported [3-4].

UO22+ + Si(OH)4(aq) ↔ UO2SiO(OH)3+ + H+

In the present study, we investigate the complexation of U(VI) with aqueous silicates at temperatures between 0-60°C, thus, allowing the extraction of complexation constants at elevated temperatures as well as thermodynamic parameters for the identified species.
The complexation of U(VI) with dissolved silicates will be investigated as a function of temperature, silicate concentration and pH. The U(VI) concentration will be fixed at 5*10-6 M and the silicate concentration will be varied between 3*10-4 - 2*10-3 M. The complexation will be analyzed with a combination of time-resolved laser-induced fluorescence (TRLFS) and UV-vis absorption spectroscopy to extract the complexation constants at elevated temperatures and subsequent determination of thermodynamic constants (ΔH, ΔS, ΔG). Slope analysis is used to calculate the complex formation constants, which are recalculated to standard conditions with the van´t Hoff equation and the SIT model.
The complexation constants, thermodynamic data and potential solubility products will be included in a thermodynamic database. Thermodynamic speciation modelling of the U(VI) silicate complexation behavior will be done based on the experimental data. Here, comparisons using existing data for ambient conditions can be directly made to estimate the influence of elevated temperatures on the complexation behavior and phase equilibria of U(VI) in the presence of silicates.
Results from the U(VI)-silicate complexation study at elevated temperatures will be presented at the conference.

[1] Warwick P., Hall A., Zhu J., Dimmock P.W., Robbins R., Carlsen L., Lassen P., (1997), Chemosphere, 35, 2471-2477
[2] Rao L., Jiang J., Zanonato P., Bernardo P., Bismondo A., Garnov A.Y., (2002), Radiochim. Acta, 90, 581-588
[3] Guillaumont, R., Fanghänel, T., Neck, V., Fuger, J., Palmer, D.A., Grenthe, I., Rand, M.H., (2003), “Update on the Chemical Thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium, Chemical Thermodynamics 5”, Nuclear Energy Agency, Elsevier Science Publisher
[4] Moll H., Geipel G., Brendler V., Bernhard G. and Nitsche H., (1998), J. Alloys Compounds 271–273, 765–768.

Keywords: Uranium (VI); silicates; complexation; aqueous system; elevated temperatures

  • Poster
    Migration 2017, 10.-15.09.2017, Barcelona, Spanien

Publ.-Id: 25274

Impact of dynamic geochemical conditions on plutonium and americium mobility at a legacy trench disposal site

Payne, T. E.; Kinsela, A. S.; Ikeda-Ohno, A.; Vazquez-Campos, X.; Waite, T. D.; Harrison, J. J.; Bligh, M. W.; Johansen, M. P.; Thiruvoth, S.; Wilsher, K. L.

Low-level radioactive wastes were disposed by burial in closely-spaced unlined trenches in clay-rich surface layers at the Little Forest Site on the southern periphery of Sydney, Australia, between 1960 and 1968. A previous paper [1] gave a general description of the site and described the distribution of plutonium in soils and groundwaters. A process known as the ‘bath-tub’ effect, in which the former trenches become filled to the ground surface with water during intense periodic rainfall events, was implicated in the mobilisation and dispersion of actinides in the surface soils.
A follow-up study investigated the chemical speciation of Pu and Am in water obtained from a sampler within one of the former trenches. The presence of readily detected amounts of Pu and Am provided a unique opportunity to study their aqueous speciation in this environment. The predominant oxidation state of dissolved Pu species was found to be Pu(IV), however the pH-Eh conditions of the groundwater were very close to the transition with Pu (III), suggesting that small changes in chemical conditions could alter its oxidation state [2]. Large proportions of both Pu and Am were associated with mobile colloids in the submicron size range. However, it was clear from ongoing studies at the site that the distribution of dissolved, colloidal and particulate forms of actinides was very variable, and sensitively dependent on the preceding conditions. These included the interval elapsed since the most recent rainfall event at the time of sampling, the initial state of water-saturation of the site when significant rainfall occurred, the intensity of rainfall, and the length of time between rainfall events.
The geochemical form of plutonium was found to be strongly affected by the changes in the redox state and groundwater chemistry during influxes of rainfall-derived water. The cycling of iron, including its precipitation in response to redox changes, is of particular importance, given its potential role as an actinide-sorbing phase. Following rainfall events, the chemical forms of Pu and Am transition from a particle-associated phase immediately after the initial rainwater pulse, to a progressively more soluble form as reducing conditions become re-established.
The formation of strongly sorbing Fe-oxyhydroxide particles is therefore a key process in the cycling of actinides in the system. Simulations in the laboratory using trench-derived water samples showed that increasing concentrations of dissolved silicate progressively retarded Fe(II) oxidation kinetics in the relevant pH range. Furthermore, with increasing Si, the primary Fe(III) oxidation product transitioned from lepidocrocite to a ferrihydrite / silica-ferrihydrite composite [3]. It was inferred that the presence of silicate restricts Fe-polymerization and consequently inhibits Fe(III) solid-phase particle growth. The presence of silicate may therefore significantly retard Fe(II) oxidation rates and facilitate transport of trace concentrations of plutonium and americium, which would otherwise adsorb to the Fe(III) oxide resulting from Fe(II) oxidation.
Microbial analyses demonstrated that oxygen-laden rainwater rapidly altered the redox balance in the trench water, strongly impacting the speciation of radionuclides and microbial functioning. When water levels were lowest, more reducing conditions prevailed, with the microbial community exhibiting a higher representation of dissimilatory sulfate reduction and methanogenesis pathways [4]. When water levels are low in the trenches, the Fe is predominantly present in soluble reduced forms.
In summary, the behaviour of actinides at the site is strongly influenced by a number of hydrological, geochemical and microbial factors and has a strong cyclic variation triggered by episodic rainfall events. Our results have important implications for the ongoing management of this site and are of relevance to other near-surface environmental systems in which redox cycling occurs. In the case of near-surface legacy radioactive waste sites, consideration should be given to the major consequential impact of these fluctuations on the mobility of disposed actinides and other radionuclides.
[1] Payne, T.E., Harrison, J.J., Hughes, C.E., Johansen, M.P., Thiruvoth, S., Wilsher, K.L., Cendón, D.I., Hankin, S.I., Rowling, B. and Zawadzki, A. (2013). Trench ‘Bathtubbing’ and Surface Plutonium Contamination at a Legacy Radioactive Waste Site. Environmental Science & Technology, 47: 13284-13293.
[2] Ikeda-Ohno, A., Harrison, J.J., Thiruvoth, S., Wilsher, K., Wong, H.K.Y., Johansen, M.P., Waite, T.D. and Payne, T.E. (2014). Solution Speciation of Plutonium and Americium at an Australian Legacy Radioactive Waste Disposal Site. Environmental Science & Technology, 48: 10045-10053.
[3] Kinsela, A.S., Jones, A.M., Bligh, M.W., Pham, A.N., Collins, R.N., Harrison, J.J., Wilsher, K.L., Payne, T.E., and Waite, T.D (2016). Influence of Dissolved Silicate on Rates of Fe(II) Oxidation Environmental Science & Technology. 50: 11663−11671
[4] Vazquez-Campos, X, Kinsela, A.S., Bligh, M.W., Harrison, J.J., Payne, T.E., and Waite, T.D., Response of microbial community function to fluctuating geochemical conditions within a legacy radioactive waste trench environment. Submitted to Applied and Environmental Microbiology, 2017.

Keywords: actinides; plutonium. americium; migration; geochemistry; nuclear waste disposal; surface water; speciation; minerals

  • Lecture (Conference)
    Migration 2017, 10.-15.09.2017, Barcelona, Spain

Publ.-Id: 25273

Chloride Ion Battery Review: Theoretical Calculations, State of the Art, Safety, Toxicity and an outlook towards future developments

Gschwind, F.; Euchner, H.; Rodriguez-Garcia, G.

Batteries using chloride ions as shuttles have only been under investigation for a few years, but already several publications have dealt with this topic. In this review, we extensively report for the first time the state of the art, along with theoretical screening and calculations and an analysis of safety and toxicity. At the end, possible future approaches are evaluated.

  • Open Access Logo European Journal of Inorganic Chemistry 2017(2017)21, 2784-2799
    Online First (2017) DOI: 10.1002/ejic.201700288


Publ.-Id: 25272

An Eulerian-Eulerian Computational Approach for Simulating Descending Gas-Liquid Flows in Reactors with Solid Foam Internals

Subramanian, K.; Zalucky, J.; Schubert, M.; Lucas, D.; Hampel, U.

Chemical reactors with new types of packings, such as metallic and ceramic open-pore foams, have become of subjects of scientific and engineering interest in the past decades. For so-called trickle bed reactors the new packing types provide favorable conditions, such as a high specific surface area and low pressure drop, which are believed to contribute to an intensification of mass and heat transfer. While a number of experimental studies have been recently been reported in literature, hydrodynamic modelling and simulation, particularly at the full reactor scale, is still in its infancy due to the complexity of two-phase flow in such non-regular packings.
In this work, an attempt has been made to model and predict flow pattern and liquid distribution in a trickle bed reactor with solid foams using computational fluid dynamics. A three-dimensional model based on the relative permeability approach was adopted, where gas and liquid phases flow co-currently downwards through a reactor with SiSiC ceramic foams as internals. The influence of both mechanical and capillary dispersion is included and studied in detail for foams of two different pore densities. The simulation results are validated against experimental data. In particular, the effects of gas and liquid superficial velocities and pore density on liquid holdup and two-phase pressure drop were studied in detail.

Keywords: Computational fluid dynamics; liquid holdup; multiphase flow pattern; relative permeability concept; Solid foams

Publ.-Id: 25271

Architecture and mineral potential of the Paleoproterozoic Karrat Group, West Greenland: Results of the 2016 Season

Rosa, D.; Dewolfe, M.; Guarnieri, P.; Kolb, J.; Laflamme, C.; Partin, C. A.; Salehi, S.; Sørensen, E. V.; Thaarup, S.; Thrane, K.; Zimmermann, R.

This report presents the preliminary results of the second field season of a joint project be- tween the Geological Survey of Denmark and Greenland (GEUS) and the Ministry of Min- eral Resources of Greenland (MMR) focusing on the Paleoproterozoic Karrat Group. The motivation for the expedition stems from an evaluation of the mineral potential along with understanding the stratigraphic architecture of the Karrat Group and aims to address stra- tigraphy, structure, and economic geology. Field work extended to northern Karrat Group outcrops, between Upernavik and Kullosuaq, and allowed further studies of the southern Karrat Group outcrops between Svartenhuk and Maarmorilik. The relationship between the Karrat Group and the Prøven Igneous Complex (PIC), emplaced between these two areas, was also assessed. The 2016 field season was aided by oblique aerial photography (“pho- toflying”), and hyperspectral techniques. Hyperspectral scenes were collected along cliff faces in the areas with the most prospective mineral potential, including Kangerluarsuk Fjord and Maarmorilik. These studies have built on the observations made in 2015, and have led either to the consolidation or to the revision of interpretations suggested after that season.
The exposed Karrat Group extends from ~71° to ~75°N and is composed of five formations: the Qeqertarssuaq (Lower Karrat Group), Qaarsukassak, Mârmorilik, Kangilleq, and Nûkavsak formations (Upper Karrat Group), of which the Qaarsukassak amd Kangilleq formations are informal. The lower and upper Karrat Group are separated by a regional erosional unconformity, which represents a revision to the Karrat stratigraphy established during the 2015 field season. The Karrat Group has not been differentiated north of Uper- navik due to the high metamorphic grade and polyphase deformation. Major goals of the field work included delineating contact relationships between units, documenting sedimen- tary structures that can define depositional environment(s), mapping the lateral extent and nature of extrusive mafic volcanism and volcaniclastic rocks in the upper Karrat Group (Kangilleq Formation), and determining the relative age relationships between units, which is elusive since several units are not in contact with one another. Integrated stratigraphy, sedimentology, volcanology, and ongoing geochronology will lead to a better understanding of the basin tectonic setting(s) in which the Karrat Group was deposited.
The deformation history of the area put forward after the 2015 season has been reviewed, and this succession is suggested: a NW-vergent D1 north of the Prøven Igneous Complex and channel flow in an orogen-scale NW-SE compression; D2 is characterised by E-W extension near Archean orthogneiss at Kangiusap Kuua and distal compression further to the E (previously assigned to D4); D3 is represented by structuring of the Kigarsima nappe overprinting all the other structures on Karrat Island and the peninsula to the SE (formerly described as D2); and, finally, a NW-SE compression, documented in the Maarmorilik area, is now relabeled as D4 (previously assigned to D3).
The time-stratigraphic horizon above and laterally to the Kangilleq Formation volcanism represents a period of VMS-formation on (or just below) the seafloor. Sampling of massive sulfides has yielded anomalous base metal concentrations (typically <0.3% Cu+Pb+Zn). However, because it is known that massive sulfide horizons can display zonations from low-grade to gold- and/or base metal-rich zones, these horizons potentially constitute tar- gets for future base metal and/or gold exploration in the Karrat region.
A Mississippi-Valley Type (MVT) origin is suggested for the Zn-Pb mineralisation in the Qaarsukassak Formation (RTZ Discovery), which might therefore have formed at the same time as the mineralisation in the Mârmorilik Formation. This is based on proximity of the Qaarsukassak Formation mineralisation to Archean rocks and the association of its distri- bution with marble and chert horizons. The possible role of evaporites and their diapirism in the mineralising process has been highlighted in the Mârmorilik Formation, by establishing the proximity of the known Lower Mârmorilik Formation showings to what can be interpret- ed to have been an evaporite horizon (now a “mottled pelite”). From this horizon, evaporites possibly ascended and were emplaced, as diapirs, within the Upper Mârmorilik Formation, underneath the pelites that would have acted as cap rock (where the Black Angel deposit is). Diapirism was likely triggered by deformation, during which evaporites flowed along thrust planes, as has been tentatively documented through the hyperspectral survey.
Possible silicate-silicate liquid immiscibility accompanied by silicate-sulfide immisciblity, occurred in a gabbro complex identified on the eastern side of Nutaarmiut island, to the southeast of Upernavik. The degree of PGE-Au enrichment in the sulfide has not been tested yet, but could potentially be of economic significance.

  • Other report
    København: GEUS Geological Survey of Denmark and Greenland, 2017
    112 Seiten

Publ.-Id: 25270

Proton modulated arc therapy for the treatment of left-sided breast cancer

Delso, N.; Stützer, K.; Kirk, M.; Huang, S.; Sanchez-Parcerisa, D.; Lin, L.; Freedman, G.; Metz, J.; Abel, E.; Carabe, A.

Current proton techniques for left-sided breast cancer use an anterior or lateral anterior oblique (LAO) proton beam which places the distal edge of the beam immediately against the ipsilateral lung and the cardiac structures. Tangential proton modulated arc therapy (tPMAT) would place the distal edge within the target, reducing the dose and linear energy transfer (LET) to the lung, the heart or the left anterior descending (LAD) artery.

Six patients treated with a single LAO proton beam (sLAO), were re-planned using a tPMAT beam extending from the left lateral to the mediastinal side of the patient. The plans consisted of fifty mono-energetic beams, separated by 2o each. A custom wedge was devised for each patient to enable full target coverage. Dose and volume constraints for PTV, heart, lung, LAD in both treatment modalities were reported, and the statistical significance of their difference was determined using the t-test. LET distributions were calculated and reported for all patients. The robustness of both plan modalities were tested by calculating perturbed doses with isocenter shiftsof 3mm in all 6 principal directions and considering ±3.5% range uncertainty.

tPMAT showed equal or better capacity to cover the target with 95% of the dose while maintaining the dose below prescription for the organs at risk (OARs). The use of tPMAT reduces the LET in the OARs compared to the sLAO. tPMAT is also more robust to isocenter shifts and range uncertainties. A universal wedge can be used in tPMAT without changing the dosimetric or biophysical properties of the plan.

tPMAT provides robust dosimetric and biophysical benefits over the current sLAO technique. The possibility of using universal wedges indicates the possibility of doing tPMAT without altering the current fast turnaround of PBS planning and delivery.

Keywords: PMAT; breast cancer; uncertainty; proton therapy; LET

  • Lecture (Conference)
    Annual Meeting of the American Association for Physicists in Medicine 2017, 30.07.-03.08.2017, Denver, Colorado, USA

Publ.-Id: 25269

Thermoelectric Properties of Natural Chalcopyrite from Zacatecas, Mexico

Wyżga, P.; Bobnar, M.; Hennig, C.; Leithe-Jasper, A.; Mori, T.; Gumeniuk, R.

The phase and chemical compositions of the mineral chalcopyrite from the sulphide footwall vein in La Cantera (Zacatecas, Mexico) is examined by powder x-ray diffraction, energy dispersive x-ray spectroscopy and chemical ICP-OES analyses. The influence of the detected impurities on the thermoelectric parameters (i.e. thermopower, electrical and thermal conductivities) is discussed. Thermoelectric figure of merit ZT of the studied natural minerals is found to be of the same order of magnitude (~ 10-3) as reported for CuFeS2 synthesized in the laboratory.

Keywords: chalcopyrite; powder x-ray diffraction; energy dispersive x-ray spectroscopy; ICP-OES

  • Zeitschrift für Anorganische und Allgemeine Chemie 643(2017)13, 858-863
    Online First (2017) DOI: 10.1002/zaac.201700074

Publ.-Id: 25268

Surface charge and particle size determine the metabolic fate of dendritic polyglycerols

Pant, K.; Pufe, J.; Zarschler, K.; Bergmann, R.; Steinbach, J.; Reimann, S.; Haag, R.; Pietzsch, J.; Stephan, H.

Dendritic polyglycerols (dPG) are water soluble, polyether-based nanomaterials which hold great potential in diagnostic as well as therapeutic applications. In order to translate them for in vivo applications, a systematic assessment regarding their cell and tissue interactions as well as their metabolic fate in vivo is a crucial step. Herein, we explore the structure-activity relationship of three different sizes (ca. 3, 5, and 10 nm) of neutral dendritic polyglycerol (dPG) and their corresponding negatively charged sulfate analogs (dPGS) on their in vitro and in vivo characteristics. Cellular metabolic activity was studied in A431 and HEK293 cells. Biomolecular corona formation was determined using electrophoretic mobility shift assay, which showed an increased protein binding of the dPGS even with serum concentrations as low as 20%. An in situ technique, microscale thermophoresis, was employed to address the binding affinities of these nanomaterials with serum proteins such as serum albumin, apo-transferrin, and fibrinogen. In addition, nanoparticle-cell interactions were studied in differentiated THP-1 cells which showed a charge dependent scavenger receptor-mediated uptake. In line with this data, detailed biodistribution and small animal PET imaging studies in Wistar rats using 68Ga-labeled dPG-/dPGS-NOTA conjugates showed that the neutral dPG-NOTA conjugates were quantitatively excreted via the kidneys with a subsequent hepatobiliary excretion with an increase in their size, whereas the polysulfated analogs (dPGS-NOTA) were sequestered preferentially in the liver and kidneys irrespective of their size. Taken together, this systematic study accentuates that the pharmacokinetics of dPGs is critically dependent on the overall size and charge and can be ‚fine-tuned’ for the intended requirements in nano-theranostics.

Publ.-Id: 25267

Experimental Investigation of Two-Phase Pipe Flow with Ultrafast X-ray Tomography and comparison with state-of-the-art CFD simulation

Banowski, M.; Hampel, U.; Krepper, E.; Beyer, M.; Lucas, D.

In this paper, we report on experimental investigations of air/water two-phase flow in a vertical pipe, which is a benchmark experiment for the development and validation of two-phase CFD models and codes. We conducted experiments for co-current upward and downward flow as well as counter-current flow at ambient temperature and pressure conditions. As measurement technique, we employed ultrafast X-ray tomography, which gives two-dimensional cross-sectional images of the gas-liquid distribution in two planes up to 2500 Hz scanning speed. In this paper, we briefly explain this technique, introduce essential data processing steps and discuss the findings of the study.

Keywords: Two-phase flow; ultrafast X-ray tomography; pipe flow; gas holdup measurement; image processing; bubble size measurement; CFD code validation

Publ.-Id: 25266

A novel fuzzy-logic based method for determination of individual bubble velocity and size from dual-plane ultrafast X-ray tomography data of two-phase flow

Banowski, M.; Patmonoaji, A.; Lucas, D.; Hampel, U.

Ultrafast X-ray tomography enables non-invasive imaging of gas-liquid flows with high spatial and temporal resolution. While it is relatively straightforward to extract e.g. gas fraction profiles from cross-sectional tomographic images, the extraction of bubble and gas-liquid interface information requires advanced image processing techniques. Thereby it is an important necessity to transform the temporal scale in the scanned sequences into a corresponding length scale for obtaining correct volumetric information. For bubbly flows this means that the velocity of the dispersed phase, i.e. the gas bubbles, has to be determined from dual-plane scans. A common and widely applied method to obtain gas phase velocities is cross-correlating the image sequences of the two scanning planes. This gives an averaged velocity for each position in the cross-section. In the present work, a new method is introduced, which determines the velocity of individual gas bubbles. This new method is termed as “bubble twinning method”, because it tries to identify twin-bubbles in both scanning planes. The developed algorithm compares essential bubble parameters, that is, volume, position and residence time in the slice, by applying a fuzzy-logic based membership function approach. The algorithm was tested for bubbly flow as well as slug flow conditions. Results are compared with established theoretical predictions as well as the cross-correlation method.

Keywords: Ultrafast X-ray tomography; image processing; bubbly flow; bubble velocity; bubble size

Publ.-Id: 25265

The uranium citric acid system and its sorption onto hematite

Steudtner, R.; Müller, K.; Schmeide, K.; Brendler, V.

The determination and verification of thermodynamic and kinetic parameters of complexation, redox and sorption processes will improve the safety assessment of nuclear waste disposal sites. On one side, this study focusses on uranium complexation and redox reactions in aqueous citric acid solution as a function of reaction parameters (pH, c, T, atm.) and visible light irradiation. To evaluate the impact of these reaction parameters on the uranium – citric acid – water system i we used UV-Vis, ATR FT-IR and TRLF spectroscopy. In all systems the uranium citrate complexes were detected as dissolved species. We identified and characterized the formed complexes for uranium(VI) – (UO2)2(cit)22–, (UO2)2(cit)2(OH)3–, (UO2)2(cit)2(OH)24– and (UO2)3(cit)3(OH)55– as well as for uranium(IV) – U(H2cit)3+, U(Hcit)20 (aq.) and U(cit)22– and determined the corresponding complex formation constants. The determination and verification of thermodynamic and kinetic parameters of complexation and redox processes were consequently applied to the uranium sorption on hematite in the presence of citric acid.
The uranium reactions at the iron mineral − water interface were comprehensively investigated by in situ vibrational spectroscopy and classical batch sorption experiments. The uranium retention on hematite depends on pH value and citric acid concentration. By infrared spectroscopy, we observe a typical chemical binding of uranium by formation of an inner-sphere sorption complex in absence of citric acid. In presence of citric acid the sorption process is suppressed due to simultaneous complex formation in aqueous solution.

  • Lecture (Conference)
    GDCh-Wissenschaftsforum Chemie 2017, 11.-14.09.2017, Berlin, Deutschland

Publ.-Id: 25264

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