Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

"Online First" included
Without submitted and only approved publications
Only approved publications

35836 Publications

Effects of Magnetic Field on Hydrogen Bubble Detachment during Water Electrolysis

Yang, X.; Mutschke, G.; Margitta, U.; Eckert, K.

Water electrolysis is a promising option for hydrogen production from renewable resources. One main challenge in making water electrolysis economically competitive is to raise its efficiency by decreasing the cell voltage. In this respect, electrode coverage by gas bubbles is one of the key sources which creates undesired overpotential.

Better understanding of the fundamentals of bubble nucleation, growth, and detachment in detail might bring new ideas in such effective manipulating of bubbles and substantially accelerate a way toward advanced electrolysis. Despite extensive efforts in the past, important aspects of bubble dynamics, such as the interaction/coalescence of bubbles significantly affecting their evolution or different growth modes of the bubbles themselves, are not yet fully understood. To provide that necessary information on the bubble shape profile, including the contact angle, the contact line the bubble forms with the electrode [1], the Marangoni convection[2], we use a micro electrode to produce single hydrogen bubbles. Water electrolysis was carried out under potentiostatic conditions in a 1 M H2SO4 solution in a small electrochemical cell ([2], [3], [4]). The behavior of a single hydrogen bubble evolving on a microelectrode (100 µm in diameter) was analyzed by measurements of the current transient as well as by microscopic high speed imaging. Tracer particles were additionally added to the solution to measure the flow in the vicinity of the bubble.

The contribution will present experimental results of the hydrogen bubble release size and the bubble growing mechanism at two different magnetic field orientations and at different field intensities. As shown in Fig.1, the bubble departure size decreased with increase of the magnetic field intensity when the magnetic field was applied parallel to the electrode surface. However, an increase of the departure size was observed when the field was applied perpendicular to the electrode surface. The effects were further explained by the MHD convection around the bubble. A comparison of the flow field by measurements and numerical simulation will be presented.

  • Lecture (Conference)
    The 8th International Conference on Magneto-Science, 10.-14.10.2019, Hefei, China

Permalink: https://www.hzdr.de/publications/Publ-29792
Publ.-Id: 29792


The effect of hypoxia on the induction of strand breaks in plasmid DNA by alpha-, beta- and Auger electron-emitters 223Ra, 188Re, 99mTc and DNA-binding 99mTc-pyrene

Reissig, F.; Wunderlich, G.; Runge, R.; Freudenberg, R.; Lühr, A.; Kotzerke, J.

Radiation-induced DNA damage occurs as a consequence of both direct and indirect effects of ionizing radiation. The induction mechanism of DNA damage is mainly influenced by the physical characteristics of the radiation quality, especially the linear energy transfer. In general, hypoxia reduces the effect of irradiation treatment in tumor cells and leads to poor patient outcomes. Emitters with high linear energy transfer (alpha- or Auger-electron-emitters) can overcome this obstacle. Our aim is to demonstrate the influence of hypoxia on the interaction between different radiation qualities with DNA by using a cell free plasmid model modulated by the free radical scavenger dimethyl sulfoxide (DMSO).
Plasmid DNA was irradiated with 223Ra, 188Re, 99mTc and DNA-binding 99mTc-pyrene in the absence or presence of DMSO and either under normoxic or hypoxic conditions. The resulting DNA damage in form of single- (SSB) and double strand breaks (DSB) was analyzed by agarose gel electrophoresis. Applied radiation doses of up to 200 Gy of 223Ra, 188Re or 99mTc or 60 Gy of 99mTc-pyrene led to maximal yields of SSB (80%) in plasmid DNA. Irradiation with 223Ra, 188Re or 99mTc at 200 Gy induced 30%, 28% and 32% linear plasmid conformations, respectively, which are associated with DSB. Hypoxia had a minor effect on SSB and DSB induction from 223Ra but a small enhancement in DSB for 188Re and 99mTc. DMSO could prevent DSB completely and SSB DNA damage from the three “free” radionuclides to comparable levels. DNA-binding 99mTc-pyrene induced less SSB and DSB compared to free 99mTcO4- due to its own radical scavenging properties. However, an additional incubation of DMSO could prevent the SSB and DSB induction only to a minor extent. Direct insults of Auger-electrons from 99mTc-pyrene are more effective than high-energy electrons or alpha particles due to the minimal distance between the radionuclide and the DNA.
We conclude that hypoxia does not limit DNA damage in plasmids induced by 223Ra, 188Re, 99mTc and 99mTc-pyrene. Dose-dependent radiation effects were comparable for alpha-emitters and both high- and low-energy electron emitters. The radioprotection by DMSO was not influenced by hypoxia. Overall, the results indicate the contribution of mainly indirect radiation effects for 99mTc, 188Re and 223Ra. 99mTc-pyrene caused direct DNA damages. The direct participation of oxygen in cell-free plasmid DNA damage induction was not proven.

Keywords: hypoxia; plasmid DNA; α-emitter; Auger-electrons; DMSO

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29791
Publ.-Id: 29791


Shrinking-field concept spars the periventricular region in proton therapy of gliomas

Eulitz, J.; Hahn, C.; Raschke, F.; Karpowitz, C.; Enghardt, W.; Troost, E. G. C.; Krause, M.; Lühr, A.

Recent findings suggest an increased radiosensitivity of the cerebral periventricular region (PVR; Eulitz 2019, Harrabi 2019) in primary brain tumor patients. Shrinking-field concepts (SFC) are used in proton therapy, e.g. of the brain, to spare normal brain tissue. Since there is a correlation between treatment associated brain injury and dose / LET (Peeler 2019), the evaluation of the impact of SFC in PVR dose and LET sparing is necessary. We compared observed radiation-induced brain injuries after proton therapy for glioma patients treated either conventional (CC) or with SFC, and introduce an approach for PVR-adapted proton treatment planning.

All grade II and III glioma patients treated between 2014 and 2018 with (adjuvant) proton radio(chemo)therapy to a total dose (D) of 54-60 Gy(RBE) were considered for analysis. 33% of the patients received SFC (with sequential- or simultaneously-integrated proton boost (SIB)) with a prescribed dose reduction of 6-10 Gy(RBE) in the outer part of the target volume. Contrast enhancements (CE) on follow-up MRI (fuMRI) diagnosed as treatment-related brain injury lesions (symptomatic or clinically silent) were traced back to the fuMRI of first appearance, delineated and deformably co-registered to the planning CT. The distance between CE lesions to the cerebral ventricles was determined. The PVR was estimated as a 4 mm band around the segmented cerebral ventricles. The PVR volume VX% receiving more than X% of prescribed dose as well as D and LET within the CE lesions were calculated. Brain injury-free survival (in/outside PVR) was derived in a Kaplan-Meyer analysis. For a SIB patient with a CE lesion 10 months after proton therapy, PVR sparing treatment planning was performed.

For the SFC and UD patient cohort, the observed CE lesions clustered in direct proximity to the cerebral ventricles with median distances of 2.6 mm and 2.3 mm, respectively. Mean dose at the CE lesion was 54.4±3.5 Gy(RBE) and 56.4±4.3 Gy(RBE) and the corresponding LET value 2.7±0.4 keV/µm and 3.2±0.9 keV/µm, respectively. The SFC reduced V100% and V90% in the PVR by 11.3% and 35.3%, respectively. No significant difference was found in one-year symptomatic (p = 0.15) and asymptomatic (p = 0.75) injury free survival. An average CE lesion dose of 55 Gy(RBE) was derived within PVR tissue for all patients and used as PVR tolerance dose. Incorporating the PVR as OAR in treatment plan optimization reduced the V55Gy within the CE lesion and PVR contour by 19.1% and 2.0%, respectively, without compromising target coverage, plan robustness or clinical dose constrains (Fig. 1).

For both treatment concepts, late brain injury showed a remarkably similar proximity to the cerebral ventricles and dependence on dose and LET. The SFC spares parts of the PVR from high dose and has the potential to improve treatment outcome. However, significant reduction of brain toxicity may require a dedicated PVR dose sparing planning strategy minimizing V55Gy.

Keywords: Proton therapy; Gliomas; Normal brain tissue toxicity

  • Contribution to proceedings
    ESTRO 39, 03.-07.04.2020, Vienna, Austria
    ESTRO39 abstract book

Permalink: https://www.hzdr.de/publications/Publ-29790
Publ.-Id: 29790


Engineering Self-Supported Noble Metal Foams Toward Electrocatalysis and Beyond

Du, R.; Jin, X.; Hübner, R.; Fan, X.; Hu, Y.; Eychmüller, A.

Noble metals, despite their expensiveness, display irreplaceable roles in widespread fields. To acquire novel physicochemical properties and boost the performance-to-price ratio for practical applications, one core direction is to engineer noble metals into nanostructured porous networks. Noble metal foams (NMFs), featuring self-supported, 3D interconnected networks structured from noble-metal-based building blocks, have drawn tremendous attention in the last two decades. Inheriting structural traits of foams and physicochemical properties of noble metals, NMFs showcase a variety of interesting properties and impressive prospect in diverse fields, including electrocatalysis, heterogeneous catalysis, surface-enhanced Raman scattering, sensing and actuation, etc. A number of NMFs have been created and versatile synthetic approaches have been developed. However, because of the innate limitation of specific methods and the insufficient understanding of formation mechanisms, flexible manipulation of compositions, structures, and corresponding properties of NMFs are still challenging. Thus, the correlations between composition/structure and properties are seldom established, retarding material design/optimization for specific applications. This review is devoted to a comprehensive introduction of NMFs ranging from synthesis to applications, with an emphasis on electrocatalysis. Challenges and opportunities are also included to guide possible research directions in this field and promote the interest of interdisciplinary scientists.

Permalink: https://www.hzdr.de/publications/Publ-29789
Publ.-Id: 29789


Identical pion intensity interferometry at sqrt(s_NN)=2.4 GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Mangiarotti, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Piasecki, K.; Pietraszko, J.; Przygoda, W.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rosier, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Siebenson, J.; Silva, L.; Sobolev, Y. G.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Wójcik, D.; Zanevsky, Y.; Zumbruch, P.

High-statistics π−π− and π+π+ femtoscopy data are presented for Au+Au collisions at sqrt(s_NN)=2.4 GeV, measured with HADES at SIS18/GSI. The experimental correlation functions allow the determination of the space-time extent of the corresponding emission sources via a comparison to models. The emission source, parametrized as three-dimensional Gaussian distribution, is studied in dependence on pair transverse momentum, azimuthal emission angle with respect to the reaction plane, collision centrality and beam energy. For all centralities and transverse momenta, a geometrical distribution of ellipsoidal shape is found in the plane perpendicular to the beam direction with the larger extension perpendicular to the reaction plane. For large transverse momenta, the corresponding eccentricity approaches the initial eccentricity. The eccentricity is smallest for most central collisions, where the shape is almost circular. The magnitude of the tilt angle of the emission ellipsoid in the reaction plane decreases with increasing centrality and increasing transverse momentum. All source radii increase with centrality, largely exhibiting a linear rise with the number of participants, irrespective of transverse momentum. A substantial charge-sign difference of the source radii is found, appearing most pronounced at low transverse momentum. The extracted source parameters are consistent with the extrapolation of their energy dependence down from higher energies.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-29788
Publ.-Id: 29788


Versatile Bispidine-based Bifunctional Chelators for 64CuII-Labelling of Biomolecules

Singh, G.; Zarschler, K.; Hunoldt, S.; Santana Martinez, I. I.; Rühl, C.; Matterna, M.; Bergmann, R.; Mathe, D.; Hegedüs, N.; Bachmann, M.; Comba, P.; Stephan, H.

Bifunctional chelators as parts of modular metal-based radiopharmaceuticals are responsible for stable complexation of the radiometal ion and for covalent linkage between the complex and the targeting vector. To avoid loss of complex stability, the bioconjugation strategy should not interfere with the radiometal chelation by occupying coordinating groups. The C9 position of the very stable CuII chelator 3,7-diazabicyclo[3.3.1]nonane (bispidine) is virtually predestined to introduce functional groups for facile bioconjugation as this functionalisation does not disturb the metal binding centre. We describe the preparation and characterisation of a set of novel bispidine derivatives equipped with suitable functional groups for diverse bioconjugation reactions, including common amine coupling strategies (bispidine-isothiocyanate) and the Cu-free strain promoted alkyne-azide cycloaddition. We demonstrate their functionality and versatility in an exemplary way by conjugation to an antibody-based biomolecule and validate the obtained conjugate in vitro and in vivo.

Keywords: bispidines; bifunctional chelator; site-specific labelling; imaging; EGFR

Permalink: https://www.hzdr.de/publications/Publ-29787
Publ.-Id: 29787


Ultrasmall silicon nanoparticles as a promising platform for multimodal imaging

Singh, G.; Ddungu, J. L. Z.; Licciardello, N.; Bergmann, R.; de Cola, L.; Stephan, H.

Bimodal systems for nuclear and optical imaging are currently being intensively investigated due to their comparable detection sensitivity and complementary information they provide. In this perspective, we have implemented both modalities on biocompatible ultrasmall silicon nanoparticles (Si NPs). Such nanoparticles are particularly interesting since highly biocompatible, covalent surface functionalization and demonstrated a very fast body clearance. We prepared monodisperse citrate-stabilized Si NPs (2.4 ± 0.5 nm) with more than 40 accessible terminal amino groups per particle and, for the first time, simultaneously a near-infrared dye (IR800-CW) and a radiolabel (64Cu-NOTA = 1,4,7-triazacyclononane-1,4,7-triacetic acid) have been covalently linked to the surface of such Si NPs. The obtained nanomaterials have been fully characterized them by HR-TEM, XPS, UV-Vis and FT-IR spectroscopy. These dual-labelled particles do not exhibit any cytotoxicity in vitro. In vivo studies employing both positron emission tomography (PET) and optical imaging (OI) techniques revealed a rapid renal clearance of dual-labelled Si NPs from mice.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29786
Publ.-Id: 29786


Updates on the FLUKA geometry for the MU2E experiment

Müller, S.; Ferrari, A.; Rachamin, R.

Presentation at Mu2e Collaboration Meeting 16.10.2019

Keywords: Mu2e; FLUKA; Monte Carlo; CLFV

  • Lecture (Conference)
    Mu2e Collaboration Meeting, 16.-19.10.2019, Fermilab, Batavia, USA

Permalink: https://www.hzdr.de/publications/Publ-29784
Publ.-Id: 29784


Synthesis and cyclooxygenase inhibition of sulfonamide-substituted (dihydro)pyrrolo[3,2,1-hi]indoles and their potential prodrugs

Laube, M.; Gassner, C.; Knieß, T.; Pietzsch, J.

Non-invasive imaging of cyclooxygenase-2 (COX-2) by radiolabeled ligands is attractive for the diagnosis of cancer and novel highly affine leads with optimized pharmacokinetic profile are of high interest for future developments. Recent findings have shown that methylsulfonyl-substituted (dihydro)pyrrolo[3,2,1-hi]indoles represent highly potent and selective COX-2 inhibitors but possess unsuitable pharmacokinetic properties for radiotracer applications. Based on these results, we herein present the development and evaluation of a second series of sulfonamide-substituted (dihydro)pyrrolo[3,2,1-hi]indoles and their conversion into the respective more hydrophilic N-propionamide-substituted analogs. In comparison to the methylsulfonyl-substituted leads, COX inhibition potency and selectivity was retained in the sulfonamide-substituted compounds; however, the high lipophilicity might hinder their future use. The N-propionamide-substituted analogs showed a significantly decreased lipophilicity and, as expected, lower or no COX-inhibition potency. Hence, the N-(sulfonyl)propionamides can be regarded as potential prodrugs, which represents a potential approach for more sophisticated radiotracer developments.

Keywords: Cancer; Imaging; Inflammation; Lipophilicity; McMurry cyclization; Structure-Activity-Relationship

Permalink: https://www.hzdr.de/publications/Publ-29783
Publ.-Id: 29783


Characterization of Tissue Transglutaminase as a Potential Biomarker for Tissue Response toward Biomaterials

Hauser, S.; Wodtke, R.; Tondera, C.; Wodtke, J.; Neffe, A. T.; Hampe, J.; Lendlein, A.; Löser, R.; Pietzsch, J.

Tissue transglutaminase (TGase 2) is proposed to be important for biomaterial−tissue interactions due to its
presence and versatile functions in the extracellular environment. TGase 2 catalyzes the cross-linking of proteins through its Ca2+-dependent acyltransferase activity. Moreover, it enhances the interactions between fibronectin and integrins, which in turn mediates the adhesion, migration, and motility of the cells. TGase 2 is also a key player in the pathogenesis of fibrosis. In this study, we investigated whether TGase 2 is present at the biomaterial−tissue interface and might serve as an informative biomarker for the visualization of tissue response toward gelatin-based biomaterials. Two differently cross-linked hydrogels were used, which were obtained by the reaction of gelatin with lysine diisocyanate ethyl ester. The overall expression of TGase 2 by endothelial cells, macrophages, and granulocytes was partly influenced by contact to the hydrogels or their degradation products, although no clear correlation was evidenced. In contrast, the secretion of TGase 2 differed remarkably between the different cells, indicating that it might be involved in the cellular reaction toward gelatin-based hydrogels. The hydrogels were implanted subcutaneously in immunocompetent, hairless SKH1-Elite mice. Ex vivo immunohistochemical analysis of tissue sections over 112 days revealed enhanced expression of TGase 2 around the hydrogels, in particular at days 14 and 21 post-implantation. The incorporation of fluorescently labeled cadaverine derivatives for the detection of active TGase 2 was in accordance with the results of the expression analysis. The presence of an irreversible inhibitor of TGase 2 led to attenuated incorporation of the cadaverines, which verified the catalytic action of TGase 2. Our in vitro and ex vivo results verified TGase 2 as a potential biomarker for tissue response toward gelatin-based hydrogels. In vivo, no TGase 2 activity was detectable, which is mainly attributed to the unfavorable physicochemical properties of the cadaverine probe used.

Keywords: extracellular matrix modifying enzymes; gelatin-based hydrogels; biomaterial−tissue interface; polyamines; optical imaging

Downloads:

  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-29782
Publ.-Id: 29782


Accuracy and robustness of 4D logfile-based dose reconstruction

Spautz, S.; Peters, N.; Meijers, A.; Jakobi, A.; Knopf, A.; Troost, E. G. C.; Richter, C.; Stützer, K.

Introduction: We plan to use 4D logfile-based dose reconstruction for daily monitoring and potential intervention in PBS treatments of non-small cell lung cancer patients, restricted to limited motion (≤5mm). Here, we assessed the validity of reconstructed doses and their sensitivity to selected disturbed input parameters by dedicated phantom experiments.
Material/Methods: Quasi-monoenergetic proton fields were delivered to a dynamic thorax phantom (G.C. Technology, Germany) equipped with a 3cm soft-tissue target intersected by a radiochromic film. The surrogate signal (AZ733-V, ANZAI Medical Co.,Ltd, Japan) of the motion patterns (cos/cos4, period: 5s, peak-to-peak amplitude: 5mm and 30mm) was recorded in synchronization with the machine logfiles. 4D reconstructions with 1mm/3mm dose grid resolution were performed using 4DCTs of 12 amplitude-sorted phases and either ground truth or automatically generated deformation vector fields. Characteristic 1D profiles of the reconstructed and measured doses were compared by gamma index analyses (2mm, 2%). Maximum dose deviations due to simulated offsets between motion and machine logfiles (±1/±5/±25/±250ms) were assessed for quasi-monoenergetic and 4D optimized plans.
Results: Characteristic dose patterns were well reproduced (Fig.1). Gamma pass rates were >98% under static conditions. For 5mm motion, the pass rate of 94.2% for an ideal reconstruction with 1mm³ dose voxels dropped to 93.0% with clinically used voxel sizes (3×3×3mm³), 83.6% when using automated DIR and 78.2% for the combination of both, respectively. For the 30mm motion, the CT artifacts and residual motion were predominant and lead for 3mm dose grids to gamma pass rates of approximately 84%, irrespective of chosen DIR. Fig.2 depicts the effect of simulated logfile asynchrony.
Conclusions: The implemented method is robust against disturbed input parameters for the small, clinically aimed motion amplitudes. Reconstruction accuracy decreases with deformation-related inaccuracies and increasing 4DCT artifacts for large motion. Consistent breathing and regular control CTs are compulsory for meaningful 4D logfile-based dose reconstructions.

  • Poster
    4D Treatment Workshop for Particle Therapy 2019, 22.-23.11.2019, Kraków, Polska

Permalink: https://www.hzdr.de/publications/Publ-29781
Publ.-Id: 29781


Search for beta-delayed proton emission from ¹¹Be

Riisager, K.; Borge, M. J. G.; Briz, J. A.; Carmona-Gallardo, M.; Forstner, O.; Fraile, L. M.; Fynbo, H. O. U.; Garzon Camacho, A.; Johansen, J. G.; Jonson, B.; Lund, M. V.; Lachner, J.; Madurga, M.; Merchel, S.; Nacher, E.; Nilsson, T.; Steier, P.; Tengblad, O.; Vedia, V.

We report on an attempt to reproduce the observation of beta-minus-delayed proton emission from ¹¹Be through detection of the final state nucleus ¹⁰Be with accelerator mass spectrometry. Twelve samples were collected at the ISOLDE facility at CERN at different separator settings, allowing tests of different sources of contamination to be carried out. The observed amounts of ¹⁰Be per collected ¹¹Be rule out several contamination sources, but do not agree internally. Formation of BeH molecular ions in the ion source may explain our data, in which case an upper limit of the beta p branching ratio of 2.2 x10-6 can be derived.

Keywords: beta-decay; AMS

Permalink: https://www.hzdr.de/publications/Publ-29780
Publ.-Id: 29780


A Simulation-Based Study on Reprocessing of Phosphate Tailings for Recovering Pyrochlore and Monazite

Vicino Pacheco De Aquino, T.; Pereira, L.; Hassanzadehmahaleh, A.; Belo Fernandes, I.; Rudolph, M.; Mischo, H.; Barakos, G.

The present study aims to investigate possibilities for improving the recovery of pyrochlore ((Na, Ca)₂Nb₂O₆) and monazite ((Ce, La, Th, Sm)PO4) as by-products from a phosphate mine with current niobium (Nb) production from geometallurgical perspectives. With this purpose, process mineralogy of Nb- and REE-bearing minerals together with operating properties of the concentration plant are examined using respectively mineral liberation analyzer (MLA) and the HSC® Chemistry 9 simulation module. A plant-site sampling campaign was performed and key operating parameters such as throughputs and pulp densities for individual streams were measured. The results obtained by MLA analyses as the base of mineral mass balances were compared and validated by commonly used chemical characterization techniques i.e. X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma–optical emission spectroscopy (ICP-OES). Simulation results showed that the combination of Nb flotation rougher and scavenger cells into one single rougher bank plus the addition of a new scavenger bank (4x1.4 m³ cells) can increase pyrochlore recovery in the silica/niobium flotation circuit from approximately 31% to 44%. This cell configuration improves the ultimate pyrochlore’s plant recovery from 27% to 38% leading to a substantial enhancement in final concentrate throughput from 540 to 740 kg/h. Future studies on this topic include the use of wet high intensity magnetic separation (WHIMS) and froth flotation respectively for the pre-concentration and concentration of monazite.

Keywords: Pyrochlore; phosphate deposit; rare earth elements (REE); HSC Sim®; process simulation

  • Contribution to proceedings
    International Mineral Processing Conference Eurasia (IMPC 2019), 31.10.-02.11.2019, Antalya, Turkey
    Proceedings of IMPC 2019

Permalink: https://www.hzdr.de/publications/Publ-29779
Publ.-Id: 29779


⁹⁹Tc immobilization by aluminum solids containing Fe(II) moieties

Mayordomo, N.; Rodriguez Hernandez, D. M.; Molodtsov, K.; Johnstone, E. V.; Roßberg, A.; Heim, K.; Foerstendorf, H.; Schild, D.; Brendler, V.; Müller, K.

The immobilization of ⁹⁹Tc is predominantly mediated by the reduction of Tc(VII) to Tc(IV), primarily due to the fact that [Tc(VII)O₄] ⁻ interactions with solid interfaces are limited, whereas Tc(IV)O₂ is a hardly soluble solid [1]. Tc reduction is facilitated by Fe²⁺, particularly when it is present as a sorbed species or a constituent mineral phase [2].
The present work analyzes the ⁹⁹Tc aqueous removal by two aluminum solids containing Fe(II) moieties: γ-Al₂O₃ with sorbed Fe²⁺ and Fe(II)-Al(III) layered double hydroxide (LDH). Batch contact experiments demonstrate that both solids are effective Tc scavengers, yielding a complete removal for pH > 6.5 and from pH 3.5 to 10.5, respectively. Characterization via XPS, XAS, and in situ ATR FT-IR spectroscopy provided information of the Tc speciation and uptake mechanism. Secondary Fe-minerals (hematite, magnetite, ferrihydrite) formed in the reduction were also identified by Raman microscopy.

Bibliography
[1] Meena, A. H.; Arai, Y. Env. Chem Lett 2017, 15, 241–263.
[2] Cui, D.; Eriksen, T. E. Environ. Sci. Technol. 1996, 30 (7), 2259–2262.

  • Lecture (Conference)
    The 43th symposium on scientific basis for nuclear waste management, 21.-24.10.2019, Viena, Austria

Permalink: https://www.hzdr.de/publications/Publ-29778
Publ.-Id: 29778


Some microbial issues regarding the storage of high-level radioactive waste

Matschiavelli, N.; Kluge, S.; Dressler, M.; Cherkouk, A.

The talk summerizes bio-geochemical results regarding the potential geo-technical barrier bentonite in a repositors of high-level radioactive waste.

  • Lecture (others)
    18th bilateral meeting HZDR/IRE - PSI/LES, 28.-29.10.2019, HZDR, IRE, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29777
Publ.-Id: 29777


Nonstoichiometric Phases of Two-Dimensional Transition-Metal Dichalcogenides: From Chalcogen Vacancies to Pure Metal Membranes

Joseph, T.; Ghorbani Asl, M.; Kvashnin, A. G.; Larionov, K. V.; Popov, Z. I.; Sorokin, P. B.; Krasheninnikov, A.

Two-dimensional (2D) membranes consisting of a single layer of Mo atoms were recently manufactured [ Adv. Mater. 2018, 30, 1707281] from MoSe2 sheets by sputtering Se atoms using an electron beam in a transmission electron microscope. This is an unexpected result as formation of Mo clusters should energetically be more favorable. To get microscopic insights into the energetics of realistic Mo membranes and nonstoichiometric phases of transition-metal dichalcogenides (TMDs) MaXb, where M = Mo and W and X = S, Se, and Te, we carry out first-principles calculations and demonstrate that the membranes, which can be referred to as metallic quantum dots embedded into a semiconducting matrix, can be stabilized by charge transfer. We also show that an ideal neutral 2D Mo or W sheet is not flat but a corrugated structure, with a square lattice being the lowest-energy configuration. We further demonstrate that several intermediate nonstoichiometric phases of TMDs are possible as they have lower formation energies than pure metal membranes. Among them, the orthorhombic metallic 2D M4X4 phase is particularly stable. Finally, we study the properties of this phase in detail and discuss how it can be manufactured by the top-down approaches.

Keywords: 2D; non-stoichiometric phases; Transition-Metal Dichalcogenides; DFT; metal membrane

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29776
Publ.-Id: 29776


Thickness of polyelectrolyte layers of separately confined bacteria alters key physiological parameters on a single cell level

Rybkin, I.; Gorin, D.; Sukhorukov, G.; Lapanje, A.

Confinement of bacterial cells in matrix or capsules is an integral part of many biotechnological applications. Here, it is adopted the well-known layer-by-layer method of deposition of a few nanometer thick polyelectrolyte layers to confine separated bacterial cells in permeable and physically durable shells. Due to the physical properties of such a confinement, here it is found that this method enables investigation of effects of physical barrier against the mass gain and cell division. Using the method of time-lapse confocal microscopy, it is observed a prolonged lag phase, dependent on the number of polyelectrolyte layers. In the confinement, both the GFP fluorescent signal from the leaking T7 promoter and cell size, were increased by more than five and two times, respectively. This creates paradigm shift that enables using mechanical entrapment for control of bacterial cell physiology which opens possibilities of controlling the division rate as well as gene expression. These effects can be attributed to the perturbation of the sensing of the cell size, which results in disproportional synthesis of cell envelope against the intracellular material and compels cells to grow rapidly. In addition, the charged surface of cells enabled longer intercellular physical interaction resulting in spherically shaped microcolonies.

Keywords: time-lapse confocal microscopy; polyelectrolytes; layer-by-layer encapsulation; electrostatic interactions; cell surface modification

Permalink: https://www.hzdr.de/publications/Publ-29775
Publ.-Id: 29775


M4F - Materials Modelling For Fusion and Fission Materials - Domain 1

Heintze, C.; Olsson, P.; Konstantinovic, M.; Caturla, M.-J.

The talk provides on overview on the objectives, activities and first results of Domain 1 of the H2020/EU project M4F. It aims at providing a broader scientific motivation and background for the benefit of the PhD students and post-docs participating in the project.

  • Lecture (others)
    M4F PhD and post-doc event, 23.-25.06.2019, Miraflores de la Sierra, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-29774
Publ.-Id: 29774


Behaviour of C, Ni, Si, P under ion irradiation at different doses in model FeCr(Ni, Si, P) alloys

Gueye, P.-M.; Gomez-Ferrer, B.; Heintze, C.; Pareige, C.

Ferritic-martensitic steels with high chromium content are considered as promising candidates as structural materials in Gen-IV reactors because of their low swelling value for operating conditions and low ductile-brittle transition temperature (DBTT) shift under irradiation. Nevertheless, they tend to harden and embrittle under irradiation at low temperatures (350°C). Impurities as Ni, Si and P are known to increase hardening in these steels by creating solute-rich clusters (SRCs) [1-4].
In order to understand the role of each impurity on the formation of SRCs under irradiation, FeCr (NiSiP) alloys with different concentrations in Ni, Si and P have been ion irradiated with 5 MeV Fe2+ ions up to 0.1, 0.5 and 2.5 dpa at 300°C. The evolution of the solute distribution has been investigated by atom probe tomography (APT).
The results reveal the tendency to cluster of Ni, Si and P under irradiation from 0.1 dpa. Moreover, differences on the solutes distributions between materials containing one low-alloying element (Ni, Si or P) and the alloy containing Ni, Si and P, suggest a synergetic effect between these species. Results show the major role of P on the formation of the SRCs. The influence of C on the formation of SRCs will also be discussed.

References
[1] F. Garner, M. Toloczko, B. Sencer, J. Nucl. Mater. 276 (2000) 123.
[2] R. L. Klueh, A. T. Nelson, J. Nucl. Mater. 371 (2007) 37-52.
[3] A. Kohyama, A. Hishinuma, D. S. Gelles, R. L. Klueh, W. Dietz, K. Ehrlich, J. Nucl. Mater. 233-237 (1996) 138-147.
[4] B. Gomez-Ferrer, C. Heintze, C. Pareige, J. Nucl. Mater. 515 (2019) 35-44.

  • Lecture (others)
    M4F PhD and post-doc event, 23.-25.06.2019, Miraflores de la Sierra, Madrid, Spain

Permalink: https://www.hzdr.de/publications/Publ-29773
Publ.-Id: 29773


On the role of Ni, Si and P on the nanostructural evolution of FeCr alloys under irradiation – link with hardening

Pareige, C.; Gómez-Ferrer, B.; Heintze, C.; Oñorbe, E.; Hernandez-Mayoral, M.; Desgardin, P.; Malerba, L.

High-chromium ferritic-martensitic (F-M) steels are promising candidates for structural components in Gen-IV reactors because of their excellent swelling resistance and good thermal properties. However, the operating window of these steels is constrained by irradiation hardening at low temperature (<350°C). This issues has been addressed within the FP7/MatISSE project.
After neutron irradiation of Fe-Cr alloys of low purity (model alloys of F-M steels), impurities as P, Ni and Si have been shown to create solute clusters which significantly contribute to hardening and might be associated with small invisible dislocation loops1. In order to understand the role of each impurity on the formation of the nano-features formed under irradiation and the eventual synergies between the different species, FeCr(SiNiP) alloys of different composition has been ion irradiated and characterized using transmission electron microscopy, atom probe tomography, positron annihilation and nano-indentation. Combination of these techniques enabled to study the influence of these impurities on the concentration of vacancy defects, formation of solute clusters and dislocation loops and to make the link with irradiation hardening.

  • Lecture (Conference)
    SMINS 5 - NEA International Workshop on Structural Materials for Innovative Nuclear Systems, 08.-11.07.2019, Kyoto, Japan

Permalink: https://www.hzdr.de/publications/Publ-29772
Publ.-Id: 29772


Influence of impurities in microstructural evolution of FeCr alloys under ion irradiation – link with hardening

Pareige, C.; Gómez-Ferrer, B.; Heintze, C.; Onorbe, E.; Hernándet Mayoral, M.; Gueye, P.-M.; Malerba, L.

After neutron irradiation of Fe-Cr alloys of low purity (model alloys of F-M steels), impurities as P, Ni and Si have been shown to create solute clusters which significantly contribute to hardening and might be associated with small dislocation loops. In order to understand the role of each impurity on the formation of the nano-features formed under irradiation and the eventual synergies between the different species, FeCr(SiNiP) alloys of different composition have been ion irradiated and characterized using transmission electron microscopy, atom probe tomography and nano-indentation. Combination of these techniques enabled to study the influence of these impurities on the formation of solute clusters and dislocation loops and to make the link with irradiation hardening. Influence of C atoms on the nanostructure evolution will also be discussed.

  • Lecture (Conference)
    MINES - Materials in Nuclear Energy Systems, 06.-10.10.2019, Baltimore, Maryland, USA

Permalink: https://www.hzdr.de/publications/Publ-29771
Publ.-Id: 29771


Neutron irradiated microstructure of FeCr alloys investigated by TEM

Hernández Mayoral, M.; Onorbe, E.; Gómez-Ferrer, B.; Heintze, C.; Malerba, L.; Gueye, P.-M.; Pareige, C.

Different parameters have been observed to influence the nature and evolution of the neutron radiation induced features, which are responsible of the mechanical behavior of FeCr-based alloys. In this work, the experimental conditions were selected so as to focus on the effect of both, composition and irradiation temperature. The study has been performed in the framework of collaborative European funded projects, where a combination of advanced characterization techniques was applied to a set of alloys of varying composition and initial microstructure, which were irradiated together under different conditions of temperature, dose and also dose-rate. The characterization of dislocation loops has been performed on the basis of Transmission Electron Microscopy (TEM), while the solute redistribution has been studied by Atom Probe Tomography (APT). The results, that show how the involved variables affect the neutron irradiated microstructure, will be presented and discussed.

  • Lecture (Conference)
    MINES - Materials in Nuclear Energy Systems, 06.-10.10.2019, Baltimore, Maryland, USA

Permalink: https://www.hzdr.de/publications/Publ-29770
Publ.-Id: 29770


Hyperspectral outcrop models for palaeoseismic studies

Kirsch, M.; Lorenz, S.; Zimmermann, R.; Andreani, L.; Tusa, L.; Pospiech, S.; Jackisch, R.; Unger, G.; Khodadadzadeh, M.; Ghamisi, P.; Middleton, M.; Ojala, A.; Mattila, J.; Nordbäck, N.; Palmu, J.-P.; Ruskeeniemi, T.; Sutinen, R.; Tiljander, M.; Heikkilä, P.; Gloaguen, R.

The traditional study of palaeoseismic trenches, involving logging, stratigraphic and structural interpretation, can be time consuming and affected by biases and inaccuracies. To overcome these limitations, a new workflow is presented that integrates infrared hyperspectral and photogrammetric data to support field-based palaeoseismic observations. As a case study, this method is applied on two palaeoseismic trenches excavated across a post-glacial fault scarp in northern Finnish Lapland. The hyperspectral imagery (HSI) is geometrically and radiometrically corrected, processed using established image processing algorithms and machine learning approaches, and co-registered to a structure-from-motion point cloud. HSI-enhanced virtual outcrop models are a useful complement to palaeoseismic field studies as they not only provide an intuitive visualisation of the outcrop and a versatile data archive, but also enable an unbiased assessment of the mineralogical composition of lithologic units and a semi-automatic delineation of contacts and deformational structures in a 3D virtual environment.

Keywords: palaeoseismology; SfM photogrammetry; hyperspectral imaging; geology; remote sensing; outcrop models

  • Open Access Logo The Photogrammetric Record 34(2019)168, 385-407
    Online First (2019) DOI: 10.1111/phor.12300

Permalink: https://www.hzdr.de/publications/Publ-29768
Publ.-Id: 29768


Neutron Transmission Measurements at nELBE

Junghans, A.; Beyer, R.; Claußner, J.; Kögler, T.; Urlaß, S.; Bemmerer, D.; Ferrari, A.; Schwengner, R.; Wagner, A.; Dietz, M.; Frotscher, A.; Grieger, M.; Hensel, T.; Koppitz, M.; Ludwig, F.; Turkat, S.; Nolte, R.; Pirovano, E.; Kopecky, S.; Nyman, M.; Plompen, A.; Schillebeeckx, P.; Borris, E.; Reifarth, R.; Veltum, D.; Weigand, M.; Glorius, J.; Görres, J.; Oberlack, U.; Wenz, D.

Neutron total cross sections are an important source of experimental data in the evaluation of neutroninduced cross sections. The sum of all neutron-induced reaction cross sections can be determined with a precision of a few per cent in a relative measurement. The neutron spectrum of the photoneutron source nELBE extends in the fast region from about 100 keV to 10 MeV and has favourable conditions for transmission measurements due to the low instantaneous flux of neutrons and low gamma-flash background. Several materials of interest (in part included in the CIELO evaluation or on the HPRL of OECD/NEA) have been investigated: 197Au [1, 2], natFe [2], natW [2], 238U, natPt, 4He, natO, natNe, natXe. For gaseous targets high pressure gas cells with flat end-caps have been built that hold up to 200 bar pressure. The experimental setup will be presented including results from several transmission experiments and the data analysis leading to the total cross sections will be discussed

Keywords: neutron total cross sections; He; Ne; O; Xe; Pt; 238U; nELBE time of flight faciltiy; transmission measurement

Permalink: https://www.hzdr.de/publications/Publ-29767
Publ.-Id: 29767


Direct Synthesis of Large-Scale Multilayer TaSe2 on SiO2/Si Using Ion Beam Technology

Tsai, H.-S.; Liu, F.-W.; Liou, J.-W.; Chi, C.-C.; Tang, S.-Y.; Wang, C.; Ouyang, H.; Chueh, Y.-L.; Liu, C.; Zhou, S.; Woon, W.-Y.

The multilayer 1T-TaSe2 is successfully synthesized by annealing a Se-implanted Ta thin film on the SiO2/Si substrate. Material analyses confirm the 1T (octahedral) structure and the quasi-2D nature of the prepared TaSe2. Temperaturedependent resistivity reveals that the multilayer 1T-TaSe2 obtained by our method undergoes a commensurate charge-density wave (CCDW) transition at around 500 K. This synthesis process has been applied to synthesize MoSe2 and HfSe2 and expanded for synthesis of one more transition-metal dichalcogenide (TMD) material. In addition, the main issue of the process, that is, the excess metal capping on the TMD layers, is solved by the reduction of thickness of the as-deposited metal thin film in this work.

Keywords: TaSe2; charge-density wave; ion beam; synthesis

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29766
Publ.-Id: 29766


Production of the amphiphilic siderophore Marinobactin for the application as froth flotation reagent. 

Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.

The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work presents interaction studies and flotation experiments of different scales, including “Bubble pick up test”, Halimond tube tests and one-liter flotation experiments of iron, copper and PGM containing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.

Keywords: Marinobactin; Marinobacter; amphiphilic; Siderophores froth flotation

  • Lecture (Conference)
    23. International Biohydrometallurgy Symposium, 20.10.2019, Fukuoka, Japan

Permalink: https://www.hzdr.de/publications/Publ-29765
Publ.-Id: 29765


Amphiphilic Siderophores – A group of complexing surfactant bioreagents for the application in froth flotation separation

Schrader, S.; Kutschke, S.; Hartmann, S.; Pollmann, K.; Rudolph, M.

The consumption of metallic raw materials is constantly increasing. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, new approaches will have to be developed, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in conventional froth flotation processes. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to selectively form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate functional groups, is responsible for the selective binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same and even more selective functional groups are highly potential as ecofriendly collector molecules for flotation and should generally be interesting for the surfactant industry. The molecule’s tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work includes also interaction studies and flotation experiments of different scales, including bubble pick-up tests, Halimond tube microflotation and batch lab flotation experiments of iron and copper bearing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.

Keywords: Marinobactin; Marinobacter; amphiphilic; Siderophores froth flotation

  • Poster
    Jahrestreffen der ProcessNet-Fachgruppen Zerkleinern und Klassieren, Kristallisation und Grenzflächenbestimmte Systeme und Prozesse, 12.-13.03.2019, Bamberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29764
Publ.-Id: 29764


Integriertes Management und Publikation von wissenschaftlichen Artikeln, Software und Forschungsdaten am Helmholtz-Zentrum Dresden-Rossendorf (HZDR)

Reschke, E.; Konrad, U.

Mit dem Ziel, das Publizieren von Artikeln, Forschungsdaten und wissenschaftlicher Software gemäß den FAIR-Prinzipien (https://www.go-fair.org/fair-principles/) zu unterstützen, wurde am HZDR ein integriertes Publikationsmanagement aufgebaut. Insbesondere Daten- und Softwarepublikationen erfordern die Entwicklung bedarfsgerechter organisatorischer und technischer Strukturen ergänzend zu bereits sehr gut funktionierenden Services im Publikationsmanagement. In der Zusammenarbeit mit Wissenschaftlern des HZDR und internationalen Partnern in ausgewählten Projekten wurde der Bedarf an Unterstützung im Forschungsdatenmanagement analysiert. Darauf aufbauend wurde schrittweise ein integriertes System von Infrastrukturen und Services entwickelt und bereitgestellt. In einer seit Mai 2018 gültigen Data Policy wurden die Rahmenbedingungen und Regelungen sowohl für wissenschaftliche Mitarbeiter als auch für externe Messgäste definiert. Im Vortrag wird auf die Erfahrungen im integrierten Publikationsmanagement für Artikel, Forschungsdaten und Forschungssoftware eingegangen und daraus resultierend werden die nächsten Aufgaben und Ziele entwickelt.

Keywords: Open Access; Research Data; Rodare; Robis; Research Infrastructure

  • Open Access Logo Invited lecture (Conferences)
    „Forschungsdaten in Sachsen: Planen – Organisieren – Nachnutzen“ – 1. sächsische FDM-Tagung, 19.09.2019, Dresden, Deutschland

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29763
Publ.-Id: 29763


Production of the amphiphilic siderophore marinobactin and the application as froth flotation reagent

Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.

The consumption of metallic raw materials increased in the last years. The coverage of demand is getting more difficult, because both primary and secondary raw materials become more and more complex. To find a solution, some new ways have to be gone, like the combination of biotechnology with classic processing methods.
The idea of this work is the biotechnological production of siderophores for the application as a reagent in the classic froth flotation process. Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants. Especially the group of amphiphilic siderophores are very interesting. The hydrophilic part, carrying hydroxamate groups, is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubble and spares additional chemicals and further working steps for making the target mineral particles hydrophobic.
Besides the biotechnological production of these amphiphilic siderophores, this work presents interaction studies and flotation experiments of different scales, including “Bubble pick up test”, Halimond tube tests and one-liter flotation experiments of iron, copper and PGM containing ores.
The application of amphiphilic siderophores as biochemicals in the froth flotation process can change the classic processing method in a more sustainable process – the Bioflotation process. This will reduce the usage of other chemical agents. Moreover, the specific metal binding of siderophores changes flotation in a more purposeful and efficient process and is an important enrichment for the field of Biohydrometallurgy.

Keywords: Marinobactin; Marinobacter; amphiphilic; Siderophores froth flotation

  • Poster
    4th Green & Sustainable Chemistry Conference, 05.-08.05.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29762
Publ.-Id: 29762


Simulation-Based Exergy and LCA Analysis of Aluminum Recycling: Linking Predictive Physical Separation and Re-melting Process Models with Specific Alloy Production

Hannula, J. O.; Da Assuncao Godinho, J. R.; Abadias Llamas, A.; Luukkanen, S.; Reuter, M.

Recycling and process metallurgy are the main enablers of Circular Economy (CE). To assess the circularity of CE, a detailed understanding of the limits of the current recycling infrastructure is required. For this paper, a predictive physical separation model for Eddy Current Separator was developed using 3D particle-level detail acquired by Computed Tomography. The developed model was combined with re-melting and alloying models to create an aluminum recycling flowsheet in a simulation platform HSC Sim. Different simulation scenarios were considered, and the impact of the physical separation stage to resource efficiency was quantified by measuring the required additional resources to produce specific alloy types. The resource efficiency and environmental impacts were estimated through exergy analysis and Life Cycle Assessment based on the detailed physical and thermochemistry simulation models. The paper demonstrates how digitalization and exergy analysis allow more efficient use of resources in the sense of CE.

Keywords: Aluminum Recycling; Modeling; Simulation; Exergy; Circular Economy

Permalink: https://www.hzdr.de/publications/Publ-29761
Publ.-Id: 29761


Impact of range uncertainty on clinical distributions of linear energy transfer and biological effectiveness in proton therapy

Hahn, C.; Eulitz, J.; Peters, N.; Wohlfahrt, P.; Enghardt, W.; Richter, C.; Lühr, A.

In proton radiotherapy, range uncertainties can lead to differences between the clinically approved dose and that delivered to the patient. Likewise, the linear energy transfer (LET), which drives the relative biological effectiveness (RBE), is affected by range uncertainties. Clinical robust dose optimization ensures the delivery of the prescribed dose but not of a specific LET. In this study, the impact of range uncertainties on LET distributions in clinically robust dose-optimized treatment plans was quantified and potential biological implications in patients were assessed.
For each of six cancer patients (two brain, head-and-neck and prostate), two nominal treatment plans in pencil beam scanning mode were robustly dose-optimized using single- and multi-field optimization, respectively. Scenarios with range uncertainty of ± 3.5% were achieved by global rescaling of stopping-power ratios. Dose and LET distributions were recalculated using the nominal beam parameters and used to estimate the probability of radiation-induced toxicity.
The optimization technique had a minor impact on the results. For all patients, LET distributions in the target volume were rather homogeneous with average LET below 3.2 keV/µm and only a weak impact of range uncertainty was found. In contrast, LET hotspots (> 7 keV/µm) occurred in several organs at risk (OARs). Elevated and inhomogeneous LET distributions were organ- and patient-specific for OARs susceptible to range uncertainties. The observed changes in the probability for radiation-induced toxicity depended on OAR location and range uncertainty scenario.
Range uncertainties can substantially change LET values in OARs while the observed LET variation among all patients and scenarios was small in the CTV. The present findings support a constant RBE prescription in the CTV. However, unforeseen toxicity may occur in normal tissue due to elevated and inhomogeneous LET distributions caused by range uncertainty. We encourage LET-related objectives in robust optimization and consideration of range uncertainty in RBE assessment based on patient follow-up datasets.

Keywords: proton therapy; range uncertainties; linear energy transfer (LET); biological effectiveness

  • Open Access Logo Medical Physics 47(2020)12, 6151-6162
    Online First (2020) DOI: 10.1002/mp.14560

Permalink: https://www.hzdr.de/publications/Publ-29760
Publ.-Id: 29760


Design and Evaluation of a STM-FPGA-DAQ-HLS-Template for the Mu2e Experiment

Knodel, O.

Overview and status of the STM-FPGA-DAQ-HLS-Template for the Mu2e Experiment located Fermilab.

Keywords: Data Management; DAQ; FPGA; Mu2e

  • Invited lecture (Conferences)
    STM-Working Group Meeting, 09.10.2019, Batavia, United States

Permalink: https://www.hzdr.de/publications/Publ-29759
Publ.-Id: 29759


HZDR Data Management Strategy — An Overview

Knodel, O.; Müller, S.

Overview of the HZDR data management strategy, hosted services for collaborative work and a (planned) technical realization.

Keywords: Data Management

  • Invited lecture (Conferences)
    Meeting with the Scientific Computing Division at Fermilab, 08.10.2019, Batavia, United States

Permalink: https://www.hzdr.de/publications/Publ-29758
Publ.-Id: 29758


Recent progress in application of computational chemistry to actinide interaction with biomolecules

Tsushima, S.

Thanks to rapid advancement in computing technology, computer chemistry is becoming increasingly important in the field of biology. This approach is nowadays a common tool for drug discovery or for studying diseases such as HIV. In this talk, I will present several examples in which computer chemistry was applied for studying potential health risk of accidental ingestion of actinides and lanthanides. The new approach called “fragment molecular orbital method” has been implemented to drastically reduce computing time, which made it possible to calculate interactions of actinide/lanthanide with large biological molecules such as DNA and protein using full quantum mechanical description. In one example, how uranium ingestion could damage DNA in a molecular scale will be presented.

  • Invited lecture (Conferences)
    Engineering Physics Seminar Series at the Department of Engineering Physics of the McMaster University, 04.10.2019, Hamilton, Canada

Permalink: https://www.hzdr.de/publications/Publ-29757
Publ.-Id: 29757


Crystallization of Anhydrous Proton from Acidic Aqueous Solution with Diamide Building Block

Kazama, H.; Tsushima, S.; Takao, K.

Although H+ has the largest hydration enthalpy amongst all the monovalent cations, we have demonstrated that anhydrous H+ can be crystallized together with selected diamide building block (L) and NO3− even in acidic aqueous solutions, which were confirmed in 3 different structures. One of these anhydrous H+ adducts constitutes of H+-involved hydrogen bond polymers [L···H+]n, which are coupled with another H+ adduct [O2NO−···H+···O−NO2]− as a counteranion unit. The anhydrous H+ can also be trapped between L and NO3− to form heteroleptic O···H+···O hydrogen bonds observed in two different crystal structures. DFT calculations revealed that there is no energetic barrier in these O···H+···O hydrogen bonds, having so-called a single-well hydrogen bond.

Permalink: https://www.hzdr.de/publications/Publ-29756
Publ.-Id: 29756


Re-mining of mine wastes in Germany: Challenges and opportunities

Büttner, P.; Nühlen, J.; Meima, J.; Gutzmer, J.

The Fraunhofer Institute for Environmental, Safety, and Energy Technology and the Helmholtz Institute Freiberg for Resource Technology (HIF) have together compiled a mine waste cadaster for Germany on behalf of the Federal Institute for Geosciences and Natural Resources (BGR). For this purpose, a wide variety of data sources was evaluated with the aim to create a national database able to provide an overview about the content of critical raw materials (CRM) in mine waste repositories in Germany. Yet, even though mine wastes containing economically significant amounts of CRM, re-mining these anthropogenic “ore bodies” faces considerable technical and non-technical challenges.

Mine wastes often create environmental problems, such as acid rock drainage with associated high sulfate and heavy metal concentrations. This creates societal pressure for remediation. Remediation, however, is usually achieved by covering the surface with a water impermeable layer, an approach that is not sustainable, because of the required follow-up care and the inaccessibility of the resources that remain contained in the mine wastes. Besides that, legislative barriers are in conflict with recovering CRM and other metals and minerals from historic mine wastes. Many sites have essentially been abandoned since mining ceased in the 20th century. High metal contents and acidity released during sulfide oxidation has facilitated the establishment of a very specific flora and fauna. Species on these sites are often rare and strictly protected by environmental legislation. Metal recovery is all but impossible from such sites, despite the fact that acid rock drainage from these sites leads to environmental degradation downstream from the mine waste site.

Another important aspect is the general lack of suitable beneficiation and metallurgical infrastructure in Germany. Large capital investment would thus be necessary to enable the recovery of strategic metals from historic mine waste. Even if high metal concentrations are present in some mine wastes, small volumes will render the set-up of large, stationary plants unfeasible. Instead, flexible and semi-mobile small-scale technologies need to be developed. Such technologies are, at present, not available on the market.

To work at the intersection of society, legislation, remediation and re-mining is the aim of the new rECOmine partnership. This partnership is funded by the Federal Ministry of Education and Research (BMBF) for the next five years within the WIR! Program. It will be coordinated by HIF and build up three test sites in Saxony to develop combined remediation and re-mining technologies under real conditions with local partners.

Keywords: Re-Mining; Mine Waste; Resource; Tailing; Feasilbility; MLA

  • Lecture (Conference)
    GeoMünster 2019, 22.-25.09.2019, Münster, Germany

Permalink: https://www.hzdr.de/publications/Publ-29755
Publ.-Id: 29755


Dynamically Pre-Compressed Hydrocarbons Studied by Self-Impedance Mismatch

Hartley, N.; Zhang, C.; Duan, X.; Huang, L.; Jiang, S.; Li, Y.; Yang, L.; Pelka, A.; Wang, Z.; Yang, J.; Kraus, D.

Using the SG-III prototype laser at CAEP, Mianyang, we irradiated polystyrene samples with a thermal radiation drive, reaching conditions on the principal Hugoniot up to P~1 TPa (10 Mbar), and away from the Hugoniot up to P~300 GPa (3 Mbar). The response of the samples was measured with a velocity interferometry diagnostic to determine the material and shock velocity, and hence the conditions reached, and the reflectivity of the sample, from which changes in the conductivity can be inferred. By applying the self-impedance mismatch technique with the measured velocities, the pressure and density of thermodynamic points away from the principal Hugoniot were determined. Our results show an unexpectedly large reflectivity at the highest shock pressures, while the off-Hugoniot points agree with previous work suggesting that CH conductivity, at least at the shock front, is primarily temperature-dependent.

Keywords: Polymers; Shock compression; Optical properties; Thermodynamic states and processes; Planetary interiors; Shock waves; Hydrodynamics simulations; Metallization process

Permalink: https://www.hzdr.de/publications/Publ-29754
Publ.-Id: 29754


⁶⁰Fe deposition during the late Pleistocene and the Holocene echoes supernova activity

Wallner, A.; Feige, J.; Fifield, K.; Froehlich, M. B.; Golser, R.; Hotchkis, M. A. C.; Koll, D.; Leckenby, G.; Martschini, M.; Merchel, S.; Panjkov, S.; Pavetich, S.; Rugel, G.; Tims, S. G.

Nuclides synthesized in massive stars are ejected into space via their stellar winds and in supernova explosions. The Solar System moves through the interstellar medium and collects some of these nucleosynthesis products. One such product is ⁶⁰Fe, a radionuclide with 2.6 million years half-life, that is predominantly produced in massive stars and ejected in supernova explosions. Extraterrestrial ⁶⁰Fe has been found on Earth, suggesting close-by supernova explosions ~2–3 and ~6 million years ago. Here, we report on the detection of a continuous interstellar ⁶⁰Fe-influx on Earth over the past ~33,000 years. This time period coincides with passage of our Solar System through such interstellar clouds, which have a significantly larger particle density compared to the local average interstellar medium embedding our Solar System for the past few million years. The interstellar ⁶⁰Fe was extracted from five deep-sea sediment samples and accelerator mass spectrometry was used for single atom counting. Despite the low number of 19 detected atoms, owing to a low influx, the ⁶⁰Fe-deposition rate does not indicate large variations over the 33,000 years. The measured approximately constant ⁶⁰Fe-time profile does not seem to reflect any large changes in the interstellar particle density during Earth’s passage through local interstellar clouds, that could be expected if the local cloud represented an isolated remnant of the most recent Supernova ejecta that traversed the Earth ~2–3 million years ago. The identified ⁶⁰Fe influx may signal a late echo of some million-year old supernovae with the ⁶⁰Fe-bearing dust particles still permeating the interstellar medium.

Keywords: AMS; supernova

  • Proceedings of the National Academy of Sciences of the United States of America 117(2020)36, 21873-21879
    Online First (2020) DOI: 10.1073/pnas.1916769117

Permalink: https://www.hzdr.de/publications/Publ-29752
Publ.-Id: 29752


Delayed arrival of arterial blood in cortex is associated with decreased CSF levels of amyloid beta in predementia Alzheimer's disease

Palhaugen, L.; Selnes, P.; Tecelao, S.; Lysvik, E. K.; Ingala, S.; Petr, J.; Bjornerud, A.; Mutsaerts, H. J.; Fladby, T.

Delayed arrival of arterial blood in cortex is associated with decreased CSF levels of amyloid beta in predementia Alzheimer's disease

  • Open Access Logo Contribution to proceedings
    Congress of the European Academy of Neurology, 29.06.2019, Oslo, Norway
  • Poster
    Congress of the European Academy of Neurology, 29.06.2019, Oslo, Norway

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29751
Publ.-Id: 29751


Scalable particle-in-cell simulations on many-core hardware with the free and open source code PIConGPU

Steiniger, K.; Bastrakov, S.; Cowan, T.; Debus, A.; Garten, M.; Göthel, I.; Hübl, A.; Juckeland, G.; Kelling, J.; Kluge, T.; Koßagk, S.; Matthes, A.; Pausch, R.; Schramm, U.; Starke, S.; Widera, R.; Worpitz, B.; Bussmann, M.

Exploring new regimes, optimizing experimental setups, or quantifying sensitivity of final beam parameters on experimental parameters, represent current challenges for simulations of laser plasma accelerators. Time-to-solution and scalability are key parameters for codes to minimize turnaround times in order to scan e.g. tens of parameters such as the laser leading edge, resolve solid density target physics and run full-scale start-to-end simulations. PIConGPU reaches unprecedented performance by accelerating 100% of its computations on many-core architectures and leveraging next-generation scalable I/O. High-resolution, full-geometry studies on top-ten listed supercomputers decisively enhance predictive capabilities. PIConGPU's design allows for utilizing various compute architectures, including modern X86 and ARM CPUs and GPUs with a single, adaptable code base. Users can now run PIConGPU on almost any machine, either by easy recompiling or using predefined Docker images, and everybody can download, use and contribute to the code without extensive knowledge in compute architectures. We highlight latest additions to PIConGPU such as scalable file I/O via a new openPMD-API including ADIOS2 support for on the fly loosely coupled data analysis, live visualization with particle and field rendering, non-standard Gaussian laser pulses via Laguerre modes, in-situ X-ray scattering image generation, and an pythonic simulation setup interface.

Keywords: PIConGPU; Manycore; Scalable I/O; Alpaka; openPMD

  • Open Access Logo Lecture (Conference)
    4th European Advanced Accelerator Concepts Workshop (EAAC2019), 15.-20.09.2019, La Biodola Bay - 57037 Portoferraio Isola d’Elba, Repubblica Italiana

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29750
Publ.-Id: 29750


Origin of the butterfly magnetoresistance in a Dirac nodal-line system

Chiu, Y.-C.; Chen, K.-W.; Schönemann, R.; Quito, V. L.; Sur, S.; Zhou, Q.; Graf, D.; Kampert, W. A. G.; Förster, T.; Yang, K.; Mccandless, G. T.; Chan, J. Y.; Baumbach, R. E.; Johannes, M. D.; Balicas, L.

We report a study on the magnetotransport properties and on the Fermi surfaces (FS) of ZrSi(Se,Te) semimetals. Density-functional theory (DFT) calculations, in absence of spin orbit coupling (SOC), reveal that both the Se and the Te compounds display Dirac nodal lines (DNL) close to the Fermi level εF at symmorphic and nonsymmorphic positions, respectively. We find that the geometry of their FSs agrees well with DFT predictions. ZrSiSe displays low residual resistivities, pronounced magnetoresistivity, high carrier mobilities, and a butterflylike angle-dependent magnetoresistivity (AMR), although its DNL is not protected against gap opening. As in Cd3As2, its transport lifetime is found to be 102 to 103 times larger than its quantum one. ZrSiTe, which possesses a protected DNL, displays conventional transport properties. Our evaluation indicates that both compounds most likely are topologically trivial. Nearly angle-independent effective masses with strong angle-dependent quantum lifetimes lead to the butterfly AMR in ZrSiSe.

Permalink: https://www.hzdr.de/publications/Publ-29749
Publ.-Id: 29749


The tremendous influence of hydrogenation on magnetism of NdMnGe

Ovchenkova, I. A.; Tereshina, I. S.; Bogdanov, A. E.; Tereshina-Chitrova, E. A.; Paukov, M. A.; Gorbunov, D.; Nikitin, S. A.

The hydride NdMnGeH with the tetragonal ZrSiCuAs-type of structure (P4/nmm, N129, tP8) was obtained by hydrogen absorption at 523 K and 1 MPa from the NdMnGe intermetallic compound with a the tetragonal CeFeSi crystal structure (P4/nmm, N129, tP6). Measurements of magnetization in high magnetic fields up to 60 T and heat capacity measurements reveal pronounced changes in the magnetic properties of NdMnGe after hydrogenation. The Nd sublattice changes its ordering type from ferromagnetic to the antiferromagnetic one with a more than twofold decrease of and its magnetic ordering temperature (from 199 to 84 K). We explain the observed effects by the altered exchange interactions within the Nd sublattice resulting from the changed Nd–Nd interplane distances by interstitial atoms. The results are compared with data obtained previously for the NdMn1- xTixGe compounds, where the Ti substitution also changes significantly the magnetic properties.

Permalink: https://www.hzdr.de/publications/Publ-29748
Publ.-Id: 29748


Noble gases and radionuclides in Washington County iron meteorite

Ott, U.; Vogt, M.; Merchel, S.; Hopp, J.; Koll, D.; Lachner, J.; Trieloff, M.; Wallner, A.

The Washington County iron meteorite is unique in that it contains solar-type noble gases (He and Ne). We report additional noble gas analyses, supplemented by radionuclide data obtained at ANU (Canberra) and VERA (Univ. Vienna). Activities in dpm/kg measured on two specimens taken close to those analyzed for noble gases are: 5.15/5.40 (¹⁰Be); 3.46/2.66 (²⁶Al); 23.7/22.2 (³⁶Cl); 425/448 (⁵³Mn). ⁶⁰Fe is 1.09/1.29 dpm/kg Ni. Both cosmogenic noble gases and radionuclides indicate a preatmospheric radius of at most 15 cm. The ³⁶Cl-³⁶Ar cosmic ray exposure age of ~120 Ma agrees well with that of [1] based on noble gases only and is in disagreement with the much longer age (575 Ma) obtained by [2] using the ⁴¹K/⁴⁰K method. The new noble gas data further confirm that the solar noble gases are volume-correlated, an inference being that the Earth’s iron core may constitute a potential source reservoir for the solar-type Ne observed in terrestrial mantle materials.
We thank S. Beutner for ICP-MS analyses.
[1] Vogt, M. (2018), PhD Diss., Univ. Heidelberg. [2] Voshage, H. (1967) Z. Naturforsch 22a, 477–506.

Keywords: meteorite; AMS

  • Lecture (Conference)
    Paneth Kolloquium, 29.-31.10.2019, Nördlingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29747
Publ.-Id: 29747


The effect of long-range order on intermolecular interactions in organic semiconductors: zinc octaethyl porphyrin molecular thin film model systems.

Kumar, A.; Naumenko, D.; Rossi, G.; Magnano, E.; Nappini, S.; Bondino, F.; Segoloni, E.; Amidani, L.; D’Acapito, F.; Boscherini, F.; Barba, L.; Pace, E.; Benfatto, M.; Casassa, S.; Pedio, M.

In order to optimize the performance of devices based on porphyrin thin films it is of great importance to gain a physical understanding of the various factors which affect their charge transport and lightharvesting properties. In this work, we have employed a multi-technique approach to study vacuum deposited zinc octaethyl porphyrin (ZnOEP) thin films with different degrees of long-range order as model systems. An asymmetrical stretching of the skeletal carbon atoms of the porphyrin conformer has been observed and attributed to ordered molecular stacking and intermolecular interactions. For ordered films, a detailed fitting analysis of the X-ray absorption near edge structure (XANES) using the MXAN code establishes a symmetry reduction in the molecular conformer involving the skeletal carbon atoms of the porphyrin ring; this highlights the consequences of increased p–p stacking of ZnOEP molecules adopting the triclinic structure. The observed asymmetrical stretching of the p conjugation network of the porphyrin structure can have significant implications for charge transport and light harvesting, significantly influencing the performance of porphyrin based devices.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29746
Publ.-Id: 29746


THz relaxation dynamics and nonlinear optics in graphene

Helm, M.

Graphene, because of its peculiar linear band structure, shows some fascinating effects in the relaxation processes of excited electrons. Due to the zero band gap, many of those processes are best investigated at low energies, in the THz region. By linearly polarized pump-probe measurements we show that fast thermalization occurs only with respect to energy, but not to momentum, i.e. the electron distribution remains anisotropic for more than 5 ps (Phys. Rev. Lett. 117, 087401 (2016)). Applying a magnetic field splits the bands into non-equidistant Landau levels. This gives rise to a situation, where strong pumping of a Landau level actually leads to its depletion, due to strong Auger type electron-electron scattering (Nat. Phys. 11, 75 (2015)). In the same system, a large, resonant third-order optical nonlinearity is demonstrated via degenerate four-wave mixing (Nano Lett. 17, 2184 (2017)). All experiments were performed with a THz free-electron laser at frequencies around 20 THz, in collaboration with M. Mittendorff, J. König-Otto, S. Winnerl, A. Pashkin H. Schneider, with theory support by F. Wendler, T. Winzer, F. Kadi, E. Malic, A. Knorr, Y. Wang, A. Belyanin, and samples from W. de Heer and C. Berger.

Keywords: free electron laser; graphene; terahertz; relaxation; nonlinear optics

  • Invited lecture (Conferences)
    2D Materials 2019, 30.09.-04.10.2019, Sochi, Russia

Permalink: https://www.hzdr.de/publications/Publ-29745
Publ.-Id: 29745


Challenges for MR integrated Particle Therapy (MRiPT)

Lühr, A.

The increasing interest for particle therapy (PT) builds on its unique depth-dose characteristics, which are exploited to achieve a significant reduction in normal-tissue dose deposition proximal and distal to the tumor volume. At the same time, this feature makes PT more susceptible to morphological variations (i.e. anatomical changes and organ motion) and patient set-up uncertainties than conventional high-energy X-ray therapy (XT).
The integration of magnetic resonance (MR) imaging and PT (MRiPT) at treatment isocenter would offer an opportunity to fully exploit the dosimetric benefit of PT and realize its true clinical potential, especially for moving tumors in the thorax and abdomen. The unparalleled soft-tissue contrast and real-time imaging capabilities provided by MR imaging allow for online tumor tracking and plan adaptation. Given the steep dose gradients of PT, its targeting accuracy is expected to benefit even more from MR-guidance than XT performed with hybrid MR-linear accelerator systems. Therefore, as a next step in the technological development of image-guided radiation therapy, the concept of integrating real-time MR image guidance with PT has gained significant interest in the scientific community over the past few years.
In this presentation, a number of technological challenges will be discussed that need to be overcome before patient treatment with MRiPT can safely be realized. These challenges include the following aspects: (a) distortion of the proton dose distribution by the magnetic fields of the MR scanner, (b) impact on the MR image quality by the static and dynamic electromagnetic fields of a PT facility, and (c) integration of the MR and PT systems for online adaptive treatment. Furthermore, the current status of a first functional proof-of-concept system for in-beam MR imaging at a PT research beam line installed at OncoRay in Dresden, Germany will be presented.

  • Invited lecture (Conferences)
    ESTRO meets Asia 2019, 06.-08.12.2019, Singapore, Singapore

Permalink: https://www.hzdr.de/publications/Publ-29744
Publ.-Id: 29744


Signatures of Technetium Oxidation States: A New Approach

Bauters, S.; Scheinost, A.; Schmeide, K.; Weiß, S.; Dardenne, K.; Rothe, J.; Mayordomo, N.; Steudtner, R.; Stumpf, T.; Abram, U.; Butorin, S.; Kvashnina, K.

A general strategy for the determination of Tc oxidation state by new approach involving X-ray absorption near edge spectroscopy (XANES) at the Tc L₃ edge is shown. A comprehensive series of ⁹⁹Tc compounds, ranging from oxidation states I to VII, was measured and subsequently simulated within the framework of crystal-field multiplet theory. The observable trends in absorption edge energy shift in combination with the spectral shape allow for a deeper understanding of complicated Tc coordination chemistry. This approach can be extended to numerous studies of Tc systems as this method is one of the most sensitive methods for accurate Tc oxidation state and ligand characterization.

Keywords: Technetium L₃ edge XANES; Technetium oxidation states; Electronic structure; Crystal-field multiplet calculations

Permalink: https://www.hzdr.de/publications/Publ-29743
Publ.-Id: 29743


Basic verification of a numerical framework applied to a morphology adaptive multi-field two-fluid model considering bubble motions

Meller, R.; Schlegel, F.; Lucas, D.

A morphology adaptive modeling framework is derived that is able to handle computationally efficiently dispersed as well as resolved interfacial structures coexisting in the computational domain with the same set of equations. The Eulerian multi-field two-fluid model is combined with the compact momentum interpolation method for multiple phases, which has been proposed in the literature as an extension to the Rhie-Chow pressure-velocity coupling. Additionally to the interfacial drag force, the virtual mass force is consistently accounted for in the model. Utilizing a specialized interfacial drag formulation, large interfacial structures can be described with the presented method in a volume-of-fluid-like manner, additionally to the disperse description. The strong phase coupling due to the drag closure model in interfacial regions is resolved with a partial elimination algorithm, which is adapted to work in an approximate manner for more than two phases via a sum formulation. The presented model is implemented in the C++ library OpenFOAM and solver performance is compared to results obtained with the homogeneous model approach in two cases of a single rising gas bubble for two- and three-dimensional space, respectively. Additionally, for both three-dimensional cases, the results are compared to experimental data. Finally, the presented method’s capability of representing dispersed and resolved interfacial structures at the same time is demonstrated with two test cases: a two-dimensional gas bubble, rising in a liquid, which is laden with micro gas bubbles, and a two-dimensional stagnant stratification of water and oil, sharing a large-scale interface, which is penetrated by micro gas bubbles.

Keywords: Finite volume method; Multiphase flow; Multi-field two-fluid model; Eulerian-Eulerian model; Momentum interpolation; Partial elimination algorithm

Related publications

  • Open Access Logo International Journal for Numerical Methods in Fluids 93(2021)3, 748-773
    Online First (2020) DOI: 10.1002/fld.4907

Permalink: https://www.hzdr.de/publications/Publ-29742
Publ.-Id: 29742


Infrared nanospectroscopy at cryogenic temperatures and on semiconductor nanowires

Lang, D.

This PhD thesis concentrates on scattering scanning near-field infrared microscopy (s-SNIM) which utilizes the radiation from the free-electron laser (FEL) at the Helmholtz-Zentrum Dresden-Rossendorf. The FEL is an intense, narrow-band radiation source, tunable from the mid- to far-infrared spectral range (5 meV to 250 meV). The s-SNIM technique enables infrared microscopy and spectroscopy with a wavelength-independent spatial resolution of about 10nm. The first part demonstrates the extension of s-SNIM at the FEL towards cryogenic temperatures as low as 5K. To this end, we show the functionality of our low-temperature s-SNIM apparatus on different samples such as Au, structured Si/SiO2, as well as the multiferroic material gallium vanadium sulfide (GaV4S8). The latter material recently attracted a lot of interest since it hosts a Néel-type skyrmion lattice – a periodic array of spin vortices. Below T = 42K, GaV4S8 undergoes a structural phase transition and then forms ferroelectric domains, which we can map out by low-tempererature s-SNIM. Notably, we found a strong impact on the ferroelectric domains upon infrared irradiation, which we further utilize to calibrate the local heat contribution of the focused infrared beam beneath the s-SNIM probe.
The second part of this thesis contains comprehensive s-SNIM investigations of high-quality semiconductor nanowires (NWs) rown by molecular beam epitaxy. Such NWs are promising building blocks for fast (opto-)electronic nanodevices, amongst thers due to their high carrier mobility. We have examined highly doped GaAs/InGaAs core/shell NWs and observed a strong and spectrally sharp plasmonic resonance at about hw = 125 meV, using a continuous wave CO2 laser for probing. If we probe the same NWs utilizing the intense, pulsed FEL radiation, we observe a pronounced redshift to hw < 100 meV and a broading of the plasmonic response. This nonlinear response is most likely induced by heating of the electron gas upon irradiation by the strong FEL pulses. Our observations open up the possibility to actively induce and observe non-equilibrium states in s-SNIM directly by the mid-infrared beam. Beside the nonlinear effect, we prepared and measured cross sections of both homogeneously-doped and modulation-doped core/shell NWs.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-105 2019
    ISSN: 2191-8708, eISSN: 2191-8716

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29741
Publ.-Id: 29741


A study on the relationship between upstream and downstream conditions in swirling two-phase flow

Sahovic, B.; Atmani, H.; Wiedemann, P.; Schleicher, E.; Legendre, D.; Climent, E.; Zamanski, R.; Pedrono, A.; Hampel, U.

Inline fluid separation is a concept, which is used in the oil and gas industry. Inline fluid separators typically have a static design and hence changing inlet conditions lead to less efficient phase separation. For introducing flow control into such a device, additional information is needed about the relationship of upstream and downstream conditions. This paper introduces a study on this relationship for gas/liquid two-phase flow. The downstream gas core development was analyzed for horizontal device installation in dependence of the inlet gas and liquid flow rates. A wire-mesh sensor was used for determining two-phase flow parameters upstream and a high-speed video camera to obtain core parameters downstream the swirling device. For higher accuracy of the calculated void fraction, a novel method for wire-mesh sensor data analysis has been implemented. Experimental results have shown that void fraction data of the wire-mesh sensor can be used to predict the downstream behavior for a majority of the investigated cases. Additionally, the upstream flow pattern has an impact on the stability of the gas core downstream which was determined by means of experimental data analysis.

Keywords: Gas-liquid flow; inline fluid separation; swirling element; wire-mesh sensor; digital image processing; high-speed camera

Permalink: https://www.hzdr.de/publications/Publ-29740
Publ.-Id: 29740


Reducible contributions to quantum electrodynamics in external fields

Ahmadiniaz, N.; Edwards, J. P.; Ilderton, A.

We consider one-particle reducible (1PR) contributions to QED and scalar QED processes in external fields, at one-loop and two-loop order. We investigate three cases in detail: constant crossed fields, constant magnetic fields, and plane waves. We find that 1PR tadpole contributions in plane waves and constant crossed fields are non-zero, but contribute only divergences to be renormalised away. In constant magnetic fields, on the other hand, tadpole contributions give physical corrections to processes at one-loop and beyond. Our calculations are exact in the external fields and we give strong and weak field expansions in the magnetic case.

Permalink: https://www.hzdr.de/publications/Publ-29739
Publ.-Id: 29739


Compton-like scattering of a scalar particle with N photons and one graviton

Ahmadiniaz, N.; Balli, F. M.; Corradini, O.; Dávila, J. M.; Schubert, C.

Tree-level scattering amplitudes for a scalar particle coupled to an arbitrary number N of photons and a single graviton are computed. We employ the worldline formalism as the main tool to compute the irreducible part of the amplitude, where all the photons and the graviton are directly attached to the scalar line, then derive a tree replacement rule to construct the reducible parts of the amplitude which involve irreducible pure N-photon two-scalar amplitudes where one photon line emits the graviton. We test our construction by verifying the on-shell gauge and diffeomorphism Ward identities, at arbitrary N.

Keywords: Scattering amplitudes; gravitons; Ward identities

Permalink: https://www.hzdr.de/publications/Publ-29738
Publ.-Id: 29738


Compliant magnetic field sensors for flexible electronics

Makarov, D.

I will review our recent activities on compliant magnetic field sensors.

Keywords: flexible electronics; shapeable magnetoelectronis

  • Invited lecture (Conferences)
    FFlexCom Meeting 2019; DFG Priority Programme “High Frequency Flexible Bendable Electronics for Wireless Communication Systems”, SPP 1796, 07.10.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29737
Publ.-Id: 29737


Helium interactions with (Y, Ti, O) nanoclusters in bcc Fe

Vallinayagam, M.; Posselt, M.; Faßbender, J.

Nanometer size (Y, Ti, O) clusters in nanostructured ferritic/martensitic Fe-Cr alloys can act as sinks for the transmutation product helium. In this manner irradiation swelling can be retarded significantly. Many details of He storage in or near the clusters are still not understood. In this work interactions of He with (Y, Ti, O) clusters in bcc Fe are investigated by density functional theory (DFT) calculations. Four different cluster structures studied in our previous work [1] are considered: Cage-type clusters with (i) 6 O atoms, 9 vacancies (v) and 6 Y atoms, and (ii) with 7 O, 9 v, 3 Y, and 3 Ti, as well as clusters with O in the center containing (iii) 6 O, 9 v, 6 Y, and (iv) 7 O, 9 v, 3 Y, 3 Ti. It is found that the most stable position of He is in the center of the cluster, followed by the interfacial substitutional site and other interstitial positions between metal or oxygen atoms, and sites away from the cluster. This shows the He trapping may be nearly irrespective of cluster morphology and mainly depend on cluster composition. Adding a second He atom to the cluster structure is investigated for selected cases. Furthermore, barriers for possible jumps between different sites at the rim of the cluster and the center are determined. First results show that these barriers are higher if the cluster contains Ti and that there is a strong dependence on the particular position at the rim. For the discussion of the results also the DFT data obtained from studies on the interaction of He with single O, Y, and Ti atoms as well as with a single vacancy are used.

[1] Vallinayagam et.al. Investigation of structural models for O-Y and O-Y-Ti clusters in bcc Fe: A DFT study J. Phys.: Condens. Matter (2018) https://doi.org/10.1088/1361-648X/aaf9cd

Keywords: DFT; ODS; He storage

  • Lecture (Conference)
    EUROMAT-2019 Conference, 01.-05.09.2019, Stockholm, Sweden

Permalink: https://www.hzdr.de/publications/Publ-29736
Publ.-Id: 29736


Validating the Predictive Power of Statistical Models in Retrieving Leaf Dry Matter Content of a Coastal Wetland from a Sentinel-2 Image

Ali, A. M.; Darvishzadeh, R.; Rafiezadeh Shahi, K.; Skidmore, A.

Leaf dry matter content (LDMC), the ratio of leaf dry mass to its fresh mass, is a key plant trait, which is an indicator for many critical aspects of plant growth and survival. Accurate and fast detection of the spatiotemporal dynamics of LDMC would help understanding plants' carbon assimilation and relative growth rate, and may then be used as an input for vegetation process models to monitor ecosystems. Satellite remote sensing is an effective tool for predicting such plant traits non-destructively. However, studies on the applicability of remote sensing for LDMC retrieval are scarce. Only a few studies have looked into the practicality of using remotely sensed data for the prediction of LDMC in a forest ecosystem. In this study, we assessed the performance of partial least squares regression (PLSR) plus 11 widely used vegetation indices (VIs), calculated based on different combinations of Sentinel-2 bands, in predicting LDMC in a coastal wetland. The accuracy of the selected methods was validated using LDMC, destructively measured in 50 randomly distributed sample plots at the study site in Schiermonnikoog, the Netherlands. The PLSR applied to canopy reflectance of Sentinel-2 bands resulted in accurate prediction of LDMC (coefficient of determination (R-2) = 0.71, RMSE = 0.033). PLSR applied to the studied VIs provided an R-2 of 0.70 and RMSE of 0.033. Four vegetation indices (enhanced vegetation index(EVI), specific leaf area vegetation index (SLAVI), simple ratio vegetation index (SRVI), and visible atmospherically resistant index (VARI)) computed using band 3 (green) and band 11 of the Sentinel-2 performed equally well and achieved a good measure of accuracy (R-2 = 0.67, RMSE = 0.034). Our findings demonstrate the feasibility of using Sentinel-2 surface reflectance data to map LDMC in a coastal wetland.

Keywords: LDMC; PLSR; vegetation indices; Sentinel-2; wetland

Permalink: https://www.hzdr.de/publications/Publ-29735
Publ.-Id: 29735


First principles calculations of the thermodynamic stability of Ba, Zr, and O vacancies in BaZrO3

Nadarajan, R.; Devaraj, M.; Satyanarayana, S. V. M.; Posselt, M.

The temperature dependence of the stability of bulk BaZrO3 (BZO) and of the vacancies in this material is investigated by considering phonon contributions to the free energy. The stability diagram of BZO is determined for different chemical environments. With increasing temperature the stability region becomes smaller which is particularly caused by the strong temperature dependence of the chemical potential of gaseous oxygen. The free formation energy of Ba, Zr, and O vacancies in BZO is calculated for all possible charge states and for different atomic reservoirs. While the free formation energy of Zr vacancies is strongly influenced by temperature a weaker dependence is found for Ba and O vacancies. This has also an effect on the charge transition levels at different temperatures. Present results demonstrate that O poor reservoir conditions and a Fermi level close to the valence band maximum favour a high concentration of doubly positively charged O vacancies which is a prerequisite to get a large number of protonic defects and a good proton conductivity. In such a chemical environment the amount of Ba and Zr vacancies is low so that Ba and Zr deficiencies are not an important issue and BZO stays sufficiently stable.

Keywords: DFT; Barium Zirconate; thermodynamic stability; vacancies

Permalink: https://www.hzdr.de/publications/Publ-29734
Publ.-Id: 29734


Comparison of Eulerian QBMM and classical Eulerian – Eulerian method for the simulation of polydisperse bubbly flows

Li, D.; Marchisio, D.; Hasse, C.; Lucas, D.

The spatial gas distribution of poly-disperse bubbly flows depends greatly on the bubble size. To reflect the resulting polycelerity, more than two momentum balance equations (typically for the gas and liquid phases) have to be considered, as done in the multifluid approach. The inhomogeneous multiple-size group model follows this approach, also combined with a population balance model. As an alternative, in a previous work, an Eulerian quadrature-based moments method (E-QBMM) was implemented in OpenFOAM; however, only the drag force was included. In this work, different nondrag forces (lift, wall lubrication, and turbulent dispersion) are added to enable more complex test cases to be simulated. Simulation results obtained using E-QBMM are compared with the classical E – E method and validated against experimental data for different test cases. The results show that there is good agreement between E-QBMM and E – E methods for mono-disperse cases, but E-QBMM can better simulate the separation and segregation of small and large bubbles.

Keywords: bubbly flow; E – E method; E-QBMM; non-drag forces; wall peak

Permalink: https://www.hzdr.de/publications/Publ-29733
Publ.-Id: 29733


Radio- and photosensitization of plasmid DNA by DNA binding ligand propidium iodide: Investigation of Auger electron induction and detection of Cherenkov-emission

Kotzerke, J.; Runge, R.; Gotze, P.; Wunderlich, G.; Enghardt, W.; Freudenberg, R.

Purpose We investigated whether propidium iodide (PI) enhances DNA damaging effects of ionizing and non-ionizing radiation species (X-rays, alpha-, beta-, auger electron emission and light of various wavelengths, respectively). This biophysical experimental setting allowed us, furthermore, to investigate whether Cherenkov emission can be detected by photodynamic effects and increased DNA damage.
Material and methods Conformation changes of plasmid DNA were detected and quantified by gelelectrophoresis and fluorescence imaging. Hydrogen peroxide, stannous dichloride, and dimethylsulfoxide were used as chemical modulators, Tc-99m, Re-188, Ra-223, and x-ray (32 kV and 200 kV) reflected radiotoxicity and light (lambda = 254 nm, 366 nm and 530-575 nm) induced phototoxicity.
Results Radiotracers and x-rays induced dose dependent DNA damage. PI did not serve as radiosensitizer in radioisotopes, while a low effect was detected in X-rays. The phototoxicity was dependent on the wavelengths of light. Light with a wavelength range of 530-575 nm in combination with PI resulted in direct DNA damage. The yield of Cherenkov emission was far below the photon emission of light irradiation and not distinguishable from general radiotoxicity.
Conclusions PI binds to plasmid DNA, is not chemotoxic, and increases radiotoxicity only to minor extent. Phototoxicity and its stimulation by PI is dependent on the wavelength of the light. No kind of energy deposition was capable of inducing an Auger electron cascade.
Furthermore, no increase in DNA damage induced by photodynamic effects from Cherenkov emission was detectable.

Keywords: Probidium Iodide; Plasmid DNA; Auger Electrons; Cherenkov Emission

Permalink: https://www.hzdr.de/publications/Publ-29732
Publ.-Id: 29732


Radioresistance of KRAS/TP53-mutated lung cancer can be overcome by radiation dose escalation or EGFR tyrosine kinase inhibition in vivo

Gurtner, K.; Kryzmien, Z.; Koi, L.; Wang, M.; Benes, C.; Hering, S.; Willers, H.; Baumann, M.; Krause, M.

Recent clinical data have linked KRAS/TP53 comutation (mut) to resistance to radiotherapy (RT), but supporting laboratory in vivo evidence is lacking. In addition, the ability of different radiation doses, with/without epidermal growth factor receptor (EGFR)-directed treatment, to achieve local tumor control as a function of KRAS status is unknown. Here, we assessed clonogenic radiation survival of a panel of annotated lung cancer cell lines. KRASmut/TP53mut was associated with the highest radioresistance in nonisogenic and isogenic comparisons. To validate these findings, isogenic TP53mut NCI-H1703 models, KRASmut or wild-type (wt), were grown as heterotopic xenografts in nude mice. A clinical RT schedule of 30 fractions over 6 weeks was employed. The dose that controlled 50% of tumors (TCD50) was calculated. The TCD50 for KRASwt/TP53mut xenografts was 43.1 Gy whereas KRASmut/TP53mut tumors required a 1.9-fold higher TCD50 of 81.4 Gy. The EGFR inhibitor erlotinib radiosensitized KRASmut but not KRASwt cells and xenografts.
The TCD50 associated with adding erlotinib to RT was 58.8 Gy for KRASmut, that is, a 1.4-fold dose enhancement. However, the EGFR antibody cetuximab did not have a radiosensitizing effect. In conclusion, we demonstrate for the first time that KRASmut in a TP53mut background confers radioresistance when studying a clinical RT schedule and local control rather than tumor growth delay. Despite the known unresponsiveness of KRASmut tumors to EGFR inhibitors, erlotinib radiosensitized KRASmut tumors. Our data highlight KRAS/TP53 comutation as a candidate biomarker of radioresistance that can be at least partially reversed by dose escalation or the addition of a targeted agent.

Permalink: https://www.hzdr.de/publications/Publ-29731
Publ.-Id: 29731


Comparable radiation response of ex vivo and in vivo irradiated tumor samples determined by residual γH2AX

Rassamegevanon, T.; Löck, S.; Baumann, M.; Krause, M.; von Neubeck, C.

Purpose: a) To investigate if an ex vivo cultured and irradiated tumor biopsy reflects and predicts the radiation response of the corresponding in vivo irradiated tumor measured with the DNA double strand break marker γH2AX foci. Materials and methods: Five human head and neck squamous cell carcinoma (hHNSCC) xenograft models were used. Fine needle biopsies were taken from anesthetized tumor-bearing NMRI nude mice prior to in vivo single dose irradiation (0, 2, 4, or 8 Gy) under ambient blood flow. Biopsies were ex vivo reoxygenated and irradiated with equivalent doses. Tumors and biopsies were fixed 24 h post irradiation, and γH2AX foci were assessed in oxygenated tumor regions. Results: Linear regression analysis showed comparable slopes of the residual γH2AX foci dose–response curves in four out of five hHNSCC models when in vivo and ex vivo cohorts were compared. The slopes from ex vivo biopsies and in vivo tumors could classify the respective tumor model as sensitive or resistant according to the intrinsic radiation sensitivity (TCD50). Conclusion: The ability of ex vivo irradiated tumor biopsies to reflect and predict the intrinsic radiation response of in vivo tumors increases the translational potential of the ex vivo γH2AX foci assay as a diagnostic tool for clinical practice. © 2019 Elsevier B.V.

Keywords: Intrinsic radiation sensitivity; Predictive biomarker; Radiation therapy; γH2AX foci

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29730
Publ.-Id: 29730


Lift Forces on Solid Spherical Particles in Wall-bounded Flows

Shi, P.; Rzehak, R.

The present work is concerned with the lift forces acting on particles immersed in a wall-bounded fluid. Conditions where the particle translates in a fluid at rest and in a linear shear flow are considered. Likewise, non-rotating particles and particles in free rotation driven solely by the flow are considered. Furthermore, situations where the wall lies in the inner region and in the outer region of the flow disturbance produced by the particle are distinguished. The focus is on solid spherical particles at Reynolds numbers up to O(〖10〗^2 ) which are relevant for particulate flows in chemical and minerals engineering. A comprehensive review of existing results from analytical, experimental, and direct numerical simulation studies is given. The available correlations are critically assessed by comparison to data from these studies. Based on the comparison recommendations are given which correlations to use, including some new proposals, and gaps in the data are identified.

Keywords: lift force; particles; wall-bounded flow; particle rotation; inner / outer region; correlation

Permalink: https://www.hzdr.de/publications/Publ-29729
Publ.-Id: 29729


Au incorporation into various ZnO crystallographic cuts realised by ion implantation – ZnO damage characterization

Mackova, A.; Malinsky, P.; Jagerova, A.; Miksova, R.; Nekvindova, P.; Cajzl, J.; Böttger, R.; Akhmadaliev, S.

Non-polar surfaces, such as a-plane (11–20) and m-plane (10-10), for ZnO have become more attractive as numerous efforts have recently been made to grow non-polar ZnO facets for applications in nanoscale photonic devices. Noble-metal incorporation into transparent semiconductors such as ZnO has been investigated because of the non-linear optical response of such structures. This paper presents a study of defect evolution in various ZnO crystallographic cuts caused by Au implantation. The investigation has focused on ZnO structure characterisation, Au distribution and the interior morphology of the a-, m- and c-planes ZnO single crystals implanted with 400 keV Au+ ions at the ion fluences of 5 × 1014 and 1 × 1015 cm−2 and subsequently annealed at 600 °C in O2. The structure modification was studied using Rutherford backscattering spectrometry (RBS) in the channelling mode (RBS/C) and Raman spectroscopy. After the ion-implantation process, low surface damage was observed in all ZnO orientations unlike deep structural damage. Deep structural damage grew with increased Au-ion fluence and Au did not exhibit strong out-diffusion from the depth to the surface during the post-implantation annealing. Small but noticeable differences were observed between different ZnO orientations. RBS measurements during ion implantation revealed more progressive deep-damage formation in the c- and m-planes than in the a-plane ZnO. Simultaneously, the smallest Zn sub-lattice disorder deduced from RBS/C measurements was observed in the a-plane ZnO. During post-implantation annealing, a slight structure recovery (about 4%) was observed in all orientations. Raman spectroscopy confirmed the increasing structure disorder with the enhanced ion fluence for all as-implanted ZnO orientations and a partial reconstruction of the ZnO structure during annealing, when the intensity of E2 phonons was increased and that of longitudinal optical (LO) phonons was suppressed because of the disorder recovery. E2 (high) and E1(LO) Raman phonon modes connected with oxygen sub-lattice ordering/disordering have been investigated in detail – they show a significant modification mainly in the m-plane. The cause of the different behaviour of ZnO planes as well as the differences in the incorporation and movement of Au and Er atoms in the ZnO structure are discussed in the work.

Permalink: https://www.hzdr.de/publications/Publ-29728
Publ.-Id: 29728


Entwicklung des Gesamtsystems - Stand der Modellierungs- und Simulationsarbeiten

Fogel, S.

Entwicklung eines tubularen Dampf-Elektrolyseurs mit integrierter Kohlenwasserstoffsynthese (DELTA)

  • Lecture (others)
    5. Projekttreffen DELTA, 25.04.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29727
Publ.-Id: 29727


3. Zwischenbericht DELTA

Fogel, S.

Entwicklung eines tubularen Dampf-Elektrolyseurs mit integrierter Kohlenwasserstoffsynthese (DELTA)

  • Other report
    Dresden: HZDR, 2019
    27 Seiten

Permalink: https://www.hzdr.de/publications/Publ-29726
Publ.-Id: 29726


Single Cell and System Modeling of Tubular Proton Conducting Solid Oxide Steam Electrolyzers for Intermittent Operation

Fogel, S.; Kryk, H.; Hampel, U.

Due to the constantly growing utilization of wind and solar energy, the demand for technologies for temporal and spatial decoupling of energy provision and consumption is steadily increasing. The application of proton-conducting solid oxide electrolysis cells (H-SOEC) has been a main concern in recent research activities since they offer an environmentally friendly and efficient technique for the conversion of excess energy into hydrogen. As renewables occur intermittently, SOEC designs and all employed materials have to be capable of withstanding large electrical transients and therefore harsh operating conditions. Tubular cell designs of SOEC received increased attention in recent years due to their inherent advantages. They offer rapid startup capabilities as well as high resistance to heat, thermal cycling, thermal stresses and high-pressure application capabilities. Since the knowledge of the dynamic behavior of SOECs is key to their future application, this work aims to study the transient behavior of a single, proton conducting SOEC during rapid load variations and of multi-tubular stacks on a system scale under high-pressure operation. The use of different load variation speeds is discussed with respect to cell control.

Keywords: SOEC; load variation; transient operation; tubular cell; proton conduction

  • Lecture (Conference)
    12th European Congress of Chemical Engineering ECCE, 15.-19.09.2019, Florence, Italy

Permalink: https://www.hzdr.de/publications/Publ-29725
Publ.-Id: 29725


Transient Operation of Tubular H-SOECs for Hydrogen Production in CCU Processes

Fogel, S.; Kryk, H.; Hampel, U.

Since the utilization of wind and solar energy is constantly growing, the demand for technologies for temporal and spatial decoupling of energy provision and consumption is steadily increasing. The application of proton-conducting solid oxide electrolysis cells (H-SOECs) has been a main concern of recent research activities since they offer an environmentally friendly and efficient technique for the conversion of excess energy and steam into hydrogen. An appropriate coupling of stationary carbon dioxide (CO2) emitters and consumers offers a promising option for chemical energy storage and the production of valuable chemicals (e.g. methanol). Using electrolytic hydrogen production together with suitable downstream syntheses units as combined power-to-liquid technologies, a promising method for the recycling of carbon dioxide (CCU) can be provided. Since renewables occur intermittently, SOECs have to be capable of withstanding harsh operating conditions and the knowledge of their dynamic behavior is crucial for their future system application. This work studies the transient behavior of a single tubular, proton conducting SOEC during rapid load variations through 2D-FEM single cell and quasi-2D system scale simulations and evaluates the usability of the cell in combination with fluctuating loads.

Keywords: SOEC; dynamic operation; CCU; hydrogen; proton conduction; renewable energy

  • Poster
    17th International Conference on Carbon Dioxide Utilization ICCDU 2019, 23.-27.06.2019, Aachen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29724
Publ.-Id: 29724


Transient behavior of tubular solid oxide electrolyzer cells under fast load variations

Fogel, S.; Kryk, H.; Hampel, U.

Solid oxide electrolyzer cells (SOEC) pose a promising technology for the production of hydrogen gained from renewables, such as wind and PV. Due to the fluctuating nature of these sources, the transient behavior of SOEC under various load cases plays a crucial role in terms of their long-time stability, degradation behavior, conver-sion efficiency and application. As a consequence of the intermittent occurrence of renewables, SOEC designs and all employed materials have to be capable of with-standing harsh operating conditions, leading to strict demands regarding process control and the overall cell design. Tubular cell designs of SOECs received in-creased attention in recent years due to their inherent advantages. They offer rapid startup capabilities as well as high resistance to heat and thermal stresses. Further-more, tubular cells are characterized by significantly smaller sealing lengths in com-parison to planar cells, enabling a high-pressure application. Operating SOECs at elevated pressures poses beneficial opportunities for their future system application, since the produced hydrogen does not need to be compressed using a separate compressor stage or the electrolyzer can be combined with promising downstream synthesis units (e.g. methanol synthesis). Dynamic simulations can be used to de-termine the transient behavior of SOECs during operation with harsh load-transients. This simulation work aimed to study the transient behavior of a single, proton conducting SOEC during rapid load variations under high-pressure opera-tion. For this purpose, a two-dimensional model of a tubular SOEC was developed and different load steps and their influence on crucial operational parameters, such as temperature profiles, cell potential and species concentrations were investigated. The feasibility of the cell design regarding harsh transient load variations was stud-ied. Various load-pulse shapes and durations, different flow configurations and steam mass flow rates have been investigated and their influence on the short-term transient behavior of the cell were examined. With the aid of the aforementioned simulations, limiting operational states of the cell (e.g. steam starvation and tempera-ture hot-spots) as well as beneficial process parameter combinations for an im-proved cell operational behavior were ought to be identified with respect to advanc-es in cell control strategies.

Keywords: SOEC; dynamic operation; proton conduction

  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe Energieverfahrenstechnik, 06.-07.03.2019, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29723
Publ.-Id: 29723


Analog of cosmological particle creation in electromagnetic waveguides

Lang, S.; Schützhold, R.

We consider an electromagnetic waveguide with a time-dependent propagation speed v(t) as an analog for cosmological particle creation. In contrast to most previous studies which focus on the number of particles produced, we calculate the corresponding two-point correlation function. For a small steplike variation delta v(t), this correlator displays characteristic signatures of particle pair creation. As another potential advantage, this observable is of first order in the perturbation delta v(t), whereas the particle number is second order in delta v(t) and thus more strongly suppressed for small delta v(t).

Permalink: https://www.hzdr.de/publications/Publ-29722
Publ.-Id: 29722


Update the MUSIG model in ANSYS CFX for reliable modelling of bubble coalescence and breakup

Liao, Y.

The MUSIG (Multiple Size Group) model in the commercial CFD code ANSYS CFX is a population balance approach for describing binary bubble coalescence and breakup events. It is widely used in the simulation of poly-dispersed bubble flows. The purpose of this work is to identify some inconsistencies in the discrete method that applied for the solution of the population balance equation in MUSIG, and propose an improved one for discretising the source and sink terms that result from bubble coalescence and breakup. The new formulation is superior to the existing ones in preserving both mass and number density of bubbles, allowing arbitrary discretisation schemes and free of costly numerical integrations. The numerical results on the evolution of bubble size distributions in bubble flows reveal that the inconsistency in the original MUSIG regarding bubble breakup is non-negligible in both academic and practical cases. The updates presented in this work are necessary and important for calibration of bubble coalescence and breakup models using the MUSIG approach.

Keywords: MUSIG; ANSYS CFX; Coalescence and breakup; Method of classes; Discrete formulation; Population balance equation

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29721
Publ.-Id: 29721


Synthesis, Structural Characterisation, and Cytotoxicity Studies of Bi, W, and Mo containing Homo- and Hetero-bimetallic Polyoxometalates

Senevirathna, D.; Werrett, M.; Kubeil, M.; Stephan, H.; Andrews, P.

Three new and different homo- and hetero-bimetallic polyoxometalate (POM) species have been synthesised by simple one-pot synthetic methods utilising naturally occurring bismite (Bi2O3) (or Bi(NO3)3·5H2O) and aryl sulfonic acids. The POM species isolated are {(NH4)14[Bi2W22O76]·14H2O} (1·14H2O), {NH4[Bi(DMSO)7][Mo8O26]·H2O} (2·H2O) and {[(NH4)4(Mo36O108(OH)4·16H2O)]·45H2O} (3·45H2O). The compounds have been characterised by X-ray crystallography, energy dispersive X-ray spectroscopy (EDX), powdered X-ray diffraction (PXRD), mass spectrometry (ESI-MS), Raman spectroscopy, thermogravimetric (TGA) and ICP analyis. In vitro cytoxicity and proliferation studies conducted on 1 and 3, highlight the low toxicity of these species.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29719
Publ.-Id: 29719


Effect of nozzle geometry on pressure drop in submerged gas injection

Xiao, J.; Yan, H.-J.; Schubert, M.; Unger, S.; Liu, L.; Schleicher, E.; Hampel, U.

Submerged gas injection into liquid leads to complex multiphase flow, in which nozzle geometries are crucial important for the operational expenditure in terms of pressure drop. The influence of the nozzle geometry on pressure drop between nozzle inlet and outlet has been experimentally studied for different gas flow rates and bath depths.
Nozzles with circular, gear-like and four-leaf cross-sectional shape have been studied. The results indicate that, besides the hydraulic diameter of the outlet, the orifice area and the perimeter of the nozzle tip also play significant roles. For the same superficial gas velocity, the average pressure drop from the four-leaf-shaped geometry is the least. The influence of bath depth was found negligible. A correlation for the modified Euler number considering the pressure drop is proposed depending on nozzle geometric parameter AoL o −2 and on the modified Froude number gd o 5 Q−2 with the hydraulic diameter of the nozzle do as characteristic length.

Keywords: submerged gas injection; nozzle geometry; hydraulic diameter; pressure drop; modified Euler number

Permalink: https://www.hzdr.de/publications/Publ-29718
Publ.-Id: 29718


Effect of Bath Depth and Nozzle Geometry on Spout Height in Submerged Gas Injection at Bottom

Xiao, J.; Yan, H.; Liu, L.; Möller, F.; Hu, Z.; Unger, S.

Spout height is a widely used parameter to quantitatively analyze the performance of the submerged gas injection in industrial applications. However, the effect of bath depth and nozzle geometry on spout height in submerged gas injection is still unclear. In this work, the effect of bath depth and nozzle geometry on spout height in submerged gas injection at bottom was experimentally investigated. Circular-shaped, three-leaf-shaped, four-leaf-shaped, and four-flower-shaped nozzles were used for this study. Spout height was extracted from the images captured by high-speed camera and analyzed by digital image processing. The results indicate that the effect of nozzle geometry on spout height is as important as gas flow rate and bath depth. Through dimensional analysis, predictive correlations of spout height from circular shape and four-leaf shape were developed with dimensionless bath depth and a modified Froude number using orifice perimeter and opening area as characteristic parameters. Experimental data were compared with the correlations from literature and good agreement was found.

Permalink: https://www.hzdr.de/publications/Publ-29717
Publ.-Id: 29717


Control and stimulation of three-magnon scattering in a magnetic vortex

Körber, L.; Schultheiß, K.; Hula, T.; Verba, R.; Hache, T.; Schultheiß, H.

When applying a large enough RF field amplitude, spin waves in a magnetic vortex disk can decay into two other spin waves via three-magnon scattering. In order to reach the threshold of this process, the energy flux from the decay of the directly excited mode must overcome the internal losses of the secondary modes. The resulting scattering processes obey certain selection rules which result in the two output frequencies to be distinct from one another. Moreover, three-magnon scattering of the directly excited mode into multiple pairs of secondary modes is possible. However, typically one of these scattering channels has a lower threshold than the others which leads to this channel being activated first and limiting the energy flux in the other possible “silent” channels. Here, we show that three-magnon scattering in such a system can be stimulated below the usual instability threshold by additionaly pumping one of the secondary modes. This is achieved by coupling the magnetic vortex to an adjacent magnonic wave guide. The response to the stimulation is instantaneous and can be used to activate the silent three-magnon channels, as well.

Keywords: nonlinear; magnon; vortex; magnetism; magnonics

  • Lecture (Conference)
    Magnonics 2019, 28.07.-01.08.2019, Carovigno, Italien

Permalink: https://www.hzdr.de/publications/Publ-29716
Publ.-Id: 29716


Liquid metal battery research activities at HZDR

Weier, T.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Stefani, F.; Weber, N.

Liquid metal batteries are promising candidates for low-cost, large-scale stationary electricity storage. Different systems investigated at HZDR are discussed with a focus on fluid dynamic phenomena like interfacial wave interactions, mass transfer, and electro-vortex flows.

Keywords: liquid metal batteries; mass transfer; electro-vortex flows

  • Invited lecture (Conferences)
    Institutskolloquium Institut für Thermo- und Fluiddynamik TU Ilmenau, 12.09.2019, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29715
Publ.-Id: 29715


Multi-modality bedding platform for combined imaging and irradiation of mice

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

Preclinical imaging and irradiation yields valuable insights into clinically relevant research topics. While complementary imaging methods such as computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) can be combined within single devices, this is technically demanding and cost-intensive. Similarly, bedding and setup solutions are often specific to certain devices and research questions. We present a bedding platform for mice that is compatible with various preclinical imaging modalities (combined PET/MRI, cone beam CT) and irradiation with photons and protons.
It consists of a 3D-printed bedding unit (acrylonitrile butadiene styrene, ABS) holding the animal and features an inhalation anesthesia mask, jaw fixation, ear pins, and immobilization for the hind leg. It can be embedded on mounting adaptors for multi-modal imaging and into a transport box (polymethyl methacrylate, PMMA) for experiments outside dedicated animal facilities while maintaining the animal’s hygiene status. A vital support unit provides heating, inhalation anesthesia, and a respiration monitor. We dosimetrically evaluated used materials in order to assess their interaction with incident irradiation. Proof-of-concept multi-modal imaging protocols were used on phantoms and mice.
The measured attenuation of the bedding unit for 40/60/80/200 kV x-rays was less than 3 %. The measured stopping-power-ratio of ABS was 0.951, the combined water-equivalent thickness of bedding unit and transport box was 4.2 mm for proton energies of 150 MeV and 200 MeV. Proof-of-concept imaging showed no loss of image quality. Imaging data of individual mice from different imaging modalities could be aligned rigidly.
The presented bed aims to provide a platform for experiments related to both multi-modal imaging and irradiation, thus offering the possibility for image-guided irradiation which relies on precise imaging and positioning. The usage as a self-contained, stand-alone unit outside dedicated animal facilities represents an advantage over setups designed for specific devices.

Keywords: Small animal; Imaging; Irradiation; Protons; preclinical; transport; hyiene status

Permalink: https://www.hzdr.de/publications/Publ-29714
Publ.-Id: 29714


Anisotropic temperature-field phase diagram of single crystalline β-Li2IrO3: Magnetization, specific heat, and 7Li NMR study

Majumder, M.; Freund, F.; Dey, T.; Prinz-Zwick, M.; Büttgen, N.; Scurschii, I.; Jesche, A.; Tsirlin, A. A.; Gegenwart, P.

Detailed magnetization, specific heat, and 7Li nuclear magnetic resonance (NMR) measurements on single crystals of the hyperhoneycomb Kitaev magnet β-Li2IrO3 are reported. At high temperatures, anisotropy of the magnetization is reflected by the different Curie-Weiss temperatures for different field directions, in agreement with the combination of a ferromagnetic Kitaev interaction (K) and a negative off-diagonal anisotropy (Γ) as two leading terms in the spin Hamiltonian. At low temperatures, magnetic fields applied along a or c have only a weak effect on the system and reduce the Néel temperature from 38 K at 0 T to about 35.5 K at 14 T, with no field-induced transitions observed up to 58 T on a powder sample. In contrast, the field applied along b causes a drastic reduction in the TN that vanishes around Hc = 2.8 T, giving way to a crossover toward a quantum paramagnetic state. Li NMR measurements in this field-induced state reveal a gradual line broadening and a continuous evolution of the line shift with temperature, suggesting the development of local magnetic fields. The spin-lattice relaxation rate shows a peak around the crossover temperature 40 K and follows power-law behavior below this temperature.

Permalink: https://www.hzdr.de/publications/Publ-29713
Publ.-Id: 29713


A SERPENT2-SUBCHANFLOW-TRANSURANUS coupling for pin-by-pin depletion calculations in Light Water Reactors

Garcia, M.; Tuominen, R.; Gommlich, A.; Ferraro, D.; Valtavirta, V.; Imke, U.; van Uffelen, P.; Mercatali, L.; Sanchez, V.; Leppänen, J.; Kliem, S.

This work presents the development of a coupling scheme for Serpent2, a continuous-energy Monte Carlo particle transport code, SUBCHANFLOW,
a subchannel thermalhydraulics code, and TRANSURANUS, a fuel-performance code, suitable for large-scale high-fidelity depletion calculations for Light Water Reactors. The calculation method is based on the standard neutronic/thermalhydraulic approach, replacing the simple fuel-rod solver in SUBCHANFLOW with the more complex thermomechanic model of TRANSURANUS. The depletion method is fully coupled and semi-implicit, and the implementation relies on an object-oriented design with mesh-based feedback exchange. The results of the three-code system for a 360-day depletion calculation of a VVER-1000 fuel assembly with a pin-by-pin modelling approach are presented and analyzed. The performance of this tool, as well as the bottlenecks for its application to full-core problems, are discussed.

Keywords: SERPENT2; SUBCHANFLOW; TRANSURANUS; Multiphysics; LWR

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29712
Publ.-Id: 29712


Microstructural Characterization of a VVER-440 type Reactor Pressure Vessel Steel by Electron Microscopy

Chekhonin, P.; Röder, F.; Müller, G.; Roßner, M.; Heintze, C.; Bergner, F.

A microstructural investigation of a VVER400-type reactor pressure vessel (RPV) steel in the initial state (unirradiated) is presented. Key points include a detailed characterization by electron backscatter diffraction and an analysis of precipitates and inclusions performed by transmission as well as scanning electron microscopy.

Keywords: Microstructure; Reactor Pressure Vessel Steels; Electron Microscopy

  • Lecture (Conference)
    IGRDM-21 - 21st meeting of International Group on Radiation Damage Mechanism, 19.-24.05.2019, Gifu, Japan
  • Lecture (Conference)
    Kompetenzverbund Ost für Kerntechnik, 05.12.2019, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-29711
Publ.-Id: 29711


Bainitic and Martensitic Microstructures Revealed by EBSD

Chekhonin, P.; Bergner, F.

To understand and to tailor the properties of nuclear materials, it is essential to investigate their microstructure. EBSD systems in SEMs facilitate local crystal orientation measurements providing surface mappings in which each point is characterized by three Euler angles [1]. This data is used to reveal microstructural features such as grains, their size and -shape, grain boundaries and other details.
In the present work, a dedicated EBSD evaluation software was developed and applied to study the type of grain boundaries. Former austenite grain boundaries are revealed and within certain limitations, it is possible to differentiate between packets and blocks. Additionally, details about the variant selection during the martensitic transformation are provided and differences between bainitic steels and ferritic/martensitic steels are identified. This information may be of use to understand grain boundary related differences regarding cluster formation and sink strength.

Keywords: EBSD; Microstructure; Steels; Bainite; Martensite

  • Poster
    M4F PhD and post-doc event, 23.-25.06.2019, Miraflores de la Sierra, Spain

Permalink: https://www.hzdr.de/publications/Publ-29710
Publ.-Id: 29710


Electronic properties of GaAs/InₓGa₁₋ₓAs and GaAs/InₓAl₁₋ₓAs core/shell nanowires studied by pump – probe THz spectroscopy

Fotev, I.; Balaghi, L.; Shan, S.; Hübner, R.; Schmidt, J.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, A.

We report terahertz response of photoexcited core/shell nanowires. The obtained parameters of the localized surface plasmon mode allow us to estimate electron mobilities, concentrations and recombination lifetimes. The extracted mobilities reach 4000 cm²/V·s at room temperature, while the carrier lifetimes range from 80 to 300 ps, depending on the shell composition and the photoexcitation level.

  • Lecture (Conference)
    French-German THz Conference 2019, 02.-05.04.2019, Kaiserslautern, Germany

Permalink: https://www.hzdr.de/publications/Publ-29709
Publ.-Id: 29709


Thz User Operation With 200 pC CW Beam Generated by the ELBE SRF Gun II

Arnold, A.; Awari, N.; Chen, M.; Deinert, J.-C.; Evtushenko, P.; Green, B. W.; Klopf, J. M.; Kovalev, S.; Lehnert, U.; Ma, S.; Murcek, P.; Michel, P.; Schaber, J.; Teichert, J.; Xiang, R.; Zwartek, P.

As a new electron source with higher brilliance, the second superconducting RF photoinjector (SRF Gun II) has been built at the ELBE radiation center for high power radiation sources. One of the main goals of SRF gun II is to achieve a higher bunch charge (>200 pC) and lower emittance (3 mm mrad) than the present ELBE thermionic DC gun. SRF Gun II features a 3.5-cell niobium cavity as well as a superconducting solenoid in the same cryomodule. With Mg photocathodes the gun is able to provide medium current beam with bunch charge of more than 200 pC and sub-ps bunch length at 100 kHz repetition rate. With this contribution we present convincing results from long-term user operation of SRF gun II in combination with the bunching concept of the ELBE accelerator in order to produce THz radiation with much higher stability and power than available using the existing thermionic gun.

Keywords: SRF Gun; THz; ELBE; electron source; photoinjector

  • Open Access Logo Poster
    63rd ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs, 15.-20.09.2019, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29708
Publ.-Id: 29708


Developing multi-sensor drones for geological mapping and mineral exploration: setup and first results from the MULSEDRO project

Heincke, B.; Jackisch, R.; Saartenoja, A.; Salmirinne, H.; Rapp, S.; Zimmermann, R.; Pirttijärvi, M.; Vest Sörensen, E.; Gloaguen, R.; Ek, L.; Bergström, J.; Karinen, A.; Salehi, S.; Madriz Diaz, Y. C.; Middleton, M.

The use of Unmanned Aerial Systems (UAS), also known as drones, is becoming increasingly important for geological applications. Thanks to lower operational costs and ease of use, UAS offer an alternative approach to aircraft-based and ground-based geoscientific measurements (Colomina & Molina 2014). Magnetic and hyperspectral UAS surveys hold particular promise for mineral exploration, and several groups have recently published studies of magnetic data collected by UAS for such applications (Malehmir et al. 2017; Cunningham et al. 2018), although equivalent studies using hyperspectral data are still rare (Kirsch et al. 2018). Combining both techniques is particularly useful. Magnetic measurements play an important role in mineral exploration, since magnetisation in rocks is mainly associated with magnetite and other iron minerals, which can be used in mapping and targeting of mineral deposits (Dentith & Mudge 2014). Hyperspectral imaging (HSI) is a powerful exploration and mapping technique in areas where the rock surface is well-exposed, and where geological units and mineral compositions can be estimated from spectral features of the electromagnetic spectrum in the visual and infrared range.

Keywords: Drones; Geological Mapping; Unmanned Aerial System; Hyperspectral imaging; Magnetic survey

Permalink: https://www.hzdr.de/publications/Publ-29707
Publ.-Id: 29707


Pump – Probe THz Spectroscopy Study of Electronic Properties of Semiconductor Nanowires

Fotev, I.; Balaghi, L.; Shan, S.; Hübner, R.; Schmidt, J.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, O.

THz radiation is a perfect tool for probing electrical properties of semiconductor nanostructures in a contactless way. When applied to semiconductor nanowires, THz probe pulses can drive the oscillations of photoexcited electrons and holes in the form of localized surface plasmon. We used optical pump – THz probe spectroscopy to study plasmonic response of charge carriers in GaAs/InₓGa₁₋ₓAs core/shell nanowires. The carrier lifetimes are about 80-100 ps, depending on the shell composition and the photoexcitation level, while the extracted mobilities reach 3700 cm²/V·s at room temperature.

Keywords: GaAs nanowires; terahertz spectroscopy; ultrafast dynamics; electron mobility; plasmon; carrier lifetime

  • Lecture (Conference)
    44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz), 01.-06.09.2019, Paris, France
  • Contribution to proceedings
    44th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, 01.-06.09.2019, Paris, France
    44th International Conference on Infrared, Millimeter, and Terahertz Waves, IRMMW-THz, 153046
    DOI: 10.1109/IRMMW-THz.2019.8874068

Permalink: https://www.hzdr.de/publications/Publ-29706
Publ.-Id: 29706


Current management of pheochromocytoma/paraganglioma: A guide for the practicing clinician in the era of precision medicine

Nölting, S.; Ullrich, M.; Pietzsch, J.; Ziegler, C. G.; Eisenhofer, G.; Grossman, A.; Pacak, K.

Pheochromocytomas and paragangliomas (PCC/PGLs) are rare, mostly catecholamine-producing neuroendocrine tumors of the adrenal gland (PCCs) or the extra-adrenal paraganglia (PGL). They can be separated into three different molecular clusters depending on their underlying gene mutations in any of the at least 20 known susceptibility genes: the pseudohypoxia-associated cluster 1, the kinase signaling-associated cluster 2, and the Wnt signaling-associated cluster 3. Besides tumor size, location (adrenal vs. extra-adrenal), age of first diagnosis, and presence of metastatic disease (including tumor burden), other decisive factors for best clinical management of PCC/PGL include the underlying germline mutation. The above factors can impact the choice of different biomarkers and imaging modalities for diagnosis, as well as screening for other neoplasms, staging, follow-up, and therapy options. This review provides a guide for practicing clinicians summarizing current management of PCC/PGL according to tumor size, location, age of first diagnosis, presence of metastases and especially underlying mutations in the era of precision medicine.

Keywords: pheochromocytoma; paraganglioma; guideline; genetics; diagnosis; imaging; follow-up; therapy; precision medicine

Permalink: https://www.hzdr.de/publications/Publ-29705
Publ.-Id: 29705


Probing the Local Structure of Nanoscaled Actinide Oxides: A Comparison between PuO2 and ThO2 Nanoparticles Rules out PuO2+x Hypothesis

Bonato, L.; Virot, M.; Dumas, T.; Mesbah, A.; Dalodière, E.; Dieste Blanco, O.; Wiss, T.; Le Goff, X.; Odorico, M.; Prieur, D.; Roßberg, A.; Venault, L.; Dacheux, N.; Moisy, P.; Nikitenko, S. I.

Actinide research at the nanoscale is gaining fundamental interest due to environmental and industrial issues. The knowledge of the local structure and speciation of actinide nanoparticles, which possibly exhibit specific physico-chemical properties in comparison to bulk materials, would help in a better and reliable description of their behavior and reactivity. Herein, the synthesis and relevant characterization of PuO2 and ThO2 nanoparticles displayed as dispersed colloids, nanopowders or nanostructured oxide powders, allow to establish a clear relationship between the size of the nanocrystals composing these oxides and their corresponding An(IV) local structure investigated by EXAFS spectroscopy. Particularly, the probed An(IV) first oxygen shell evidences an analogous behavior for both Pu and Th oxides. This observation suggests that the often observed and controversial splitting of the Pu-O shell on the Fourier transformed EXAFS signal of PuO2 samples is attributed to a local structural disorder driven by a nanoparticle surface effect rather than to the presence of PuO2+x species.

Permalink: https://www.hzdr.de/publications/Publ-29704
Publ.-Id: 29704


Investigating the fate of manufactured nanoparticles in waste water treatment by the use of radiolabeled nanoparticles

Schymura, S.; Hildebrand, H.; Neugebauer, M.; Lange, T.; Franke, K.

Waste water treatment plants (WWTP) are considered one of the largest sinks for manufactured nanoparticles (NPs), as well as a potential source for the reintroduction of NPs into the environment via the WWTP effluents. Consequently, the fate of NPs in WWT is an important factor for the risk assessment of the impact of manufactured NPs on Nature and human health. However the investigation of NP fate in WWT is hindered by large elemental and particulate backgrounds. To overcome these problems we used the radiolabeling of NPs as a means of sensitive selective detection of NPs in the complex media of activated sludge and cleared waste water in a model WWTP study. TiO2, CeO2, MWCNTs and quantum dots (QDs) were radiolabeled either by activation ([48V]TiO2), in-diffusion ([139Ce]CeO2), recoil labeling ([7Be]MWCNT) or radiosynthesis ([75Se]CdSe/[65Zn]ZnS QDs). The radiolabeling allowed us to quantify NP distribution between sludge and water phase in the WWTP and in the WWTP effluents. A distribution of about 10000 : 1 between sludge-associated NPs and free NPs in water is reached in the WWTP already shortly after injection of the NPs. Thus the elimination of the NPs from the WWTP is mainly controlled by the removal of surplus sludge taking place every day of operation. The NPs are eliminated from the WWTP with a half-life of about 6 days reflecting the pre-set sludge age. After about 22 days of operation 10 % of the initial NPs remain in the WWTP. Approximately 1 % of the NPs leave the WWTP via the cleared waste water, mainly associated with non-sedimented sludge particles, such that only about 1 ‰ of the NPs leave the WWTP as free particles via the cleared water. An impact of the NPs on the clearing process, as monitored by chemical oxygen demand of the inflow vs. the outflow, was not observed.

Keywords: Nanopartikel; nanoparticles; Radiomarkierung; radiolabeling; Abwasserbehandlung; waste water treatment; Kläranlage; waste water treatment plant

  • Lecture (Conference)
    Cycleur Workshop, 08.-09.05.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29702
Publ.-Id: 29702


Radiolabeling of Nanoparticles - A versatile Tool in Nanosafety Research

Schymura, S.; Hildebrand, H.; Rybkin, I.; Ma, M.; Fricke, T.; Mansel, A.; Neugebauer, M.; Freyer, A.; Rijavec, T.; Lapanje, A.; Jacimovic, R.; Strok, M.; Lange, T.; Holzwarth, U.; Gibson, N.; Franke, K.

The employment of radiotracers is a versatile tool for the detection of nano-particulate materials in complex systems such as environmental samples or organisms. With the increasing usage of nanoparticles in applications outside of research laboratories a careful risk assessment of their release into the environment becomes mandatory. However, the monitoring of nanoparticles in such complex natural systems as soil, natural waters, plants, sewage sludge, etc. is very challenging using conventional methods, especially at environmentally relevant concentrations. This obstacle can be overcome by radiolabeling, which may be of crucial value in enabling such research. We have developed various methods of introducing radiotracers into some of the most common nanoparticles, such as Ag, carbon, SiO2, CeO2 and TiO2 nanoparticles. The labeling techniques are the synthesis of the nanoparticles using radioactive starting materials, the binding of the radiotracer to the nanoparticles, the activation of the nanoparticles using proton irradiation, the recoil labeling utilizing the recoil of a nuclear reaction to implant a radiotracer into the nanoparticle, and the in-diffusion of radiotracers into the nanoparticles at elevated temperatures. Using these methods we have produced [105/110mAg]Ag, [124/125/131I]CNTs, [48V]TiO2, [139Ce]CeO2, [7Be]MWCNT, [64Cu]SiO2, [44/45Ti]TiO2, etc.. The methods are adaptable for a wide range of other nanoparticles. The so-labelled nanoparticles can be detected at minimal concentrations well in the ng/L range even with a background of the same element and without complicated sample preparations necessary.
Using our methods one can radiolabel commercial nanoparticle samples for sensitive detection in environmentally relevant trace concentrations. The labeled particles have been successfully used in release studies, environmental mobility studies, fate studies in waste water treatment and plant uptake studies.

Keywords: Radiomarkierung; radiolabeling; Nanopartikel; nanoparticles; Zyklotron; cyclotron

  • Poster
    GDCh Fachgruppentagung Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29701
Publ.-Id: 29701


Migration of Actinide-Analogues visualized by Positron Emission Tomography GeoPET

Schymura, S.; Karimzadeh, L.; Mansel, A.; Franke, K.; Eichelbaum, S.; Frühwirt, T.; Zakhnini, A.; Jankovsky, F.; Zuna, M.; Molodtsov, K.; Kulenkampff, J.; Schmidt, M.; Lippmann-Pipke, J.; Fischer, C.

The search of a final repository for nuclear wastes from energy and weapon production calls for knowledge of actinide migration from molecular to kilometer scales. The migration behaviour on the mm to centimetre scale bridges a crucial step for the up- scaling of molecular knowledge and the validation of models based thereupon. Using the positron-emitting analogue for trivalent actinides 86Y we visualized its migration behaviour in a fractured granite core using positron emission tomography.
A granite drill core was obtained from the Bukov underground research facility in the Czech Republic. An artificial fracture was induced into the core by a geomechanical shear test and the core was subsequently encased in a plexiglas column. Radiotracers 18F and 86Y were produced at the in-house cyclotron at the HZDR Research Site Leipzig. 18F was produced by proton irradiation of 18O enriched water via 18O(p,n)18F. 86Y was obtained by proton irradiation of 86Sr enriched SrCO3 via 86Sr(p,n)86Y. Positon emission tomography was performed using the GeoPET setup at the HZDR Research Site Leipzig.
A transport experiment consisting of two steps was performed. First, aqueous [18F]KF solution was injected into the core to establish the conservative flow path through the fracture. Second, an aqueous 10-5 M [86Y]Y(NO3)3 solution in 0.1 M NaCl at pH 7.5 was flown through the fracture, followed by the eluent. The transport behaviour of the actinide analogue was monitored for a throughput of several pore volumes. After the conclusion of the experiment the core was opened and the sorption pattern on the fracture surface was additionally imaged by autoradiography.
Under the chosen conditions most of the 86Y got sorbed in the area close to the inlet and only 1% got eluted. The sorption pattern follows the conservative flow path. More detailed investigations of the sorbed species by μTRLFS (using Eu as a luminescent probe) and a modelling of the experiment based on the extracted flow path from the GeoPET data are planned.

Keywords: Positronenemissionstomographie; Positron Emission Tomography; Aktinide; Actinides

  • Poster
    GDCh Fachgruppentagung Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29700
Publ.-Id: 29700


Production of metal oxide nanoparticles through solvent extraction and crystallization stripping

Loredo, M. G. S.; Scharf, C.

In this work, the extraction of vanadium from alkaline solution, and the production of metal oxides through precipitation stripping, were carried out. The crystallization of calcium, copper, and iron vanadates from the extracts was performed using a solution containing a metal source as a stripping agent. In some experiments, a stabilizing polymer for controlling growth and avoiding agglomeration was added to the stripping solution. The structural characteristics of the crystallized products were studied. From the results, the synthesis of nanostructured vanadates is a simple and versatile method for the fabrication of valuable vanadium compounds.

  • Other report
    DAAD: DAAD-Bericht, 2019
    15 Seiten

Permalink: https://www.hzdr.de/publications/Publ-29698
Publ.-Id: 29698


Effect of DTPA on europium sorption onto quartz – Batch sorption experiments and surface complexation modeling

Karimzadeh, L.; Lippold, H.; Stockmann, M.; Fischer, C.

Sorption of radionuclides on mineral surfaces retards their migration in the environment of a repository. Presence of organic ligands, however, affects sorption and consequently influences their transport behavior. In this study, we quantify the sorption of Eu(III) onto quartz surfaces as a function of pH in the absence and presence of diethylenetriaminepentaacetic acid (DTPA). Batch sorption experiments show a pH-dependent sorption of Eu(III) on quartz. The presence of DTPA results in slightly higher sorption of Eu(III) at neutral to slightly acidic pH and considerably lower sorption at alkaline conditions. Sorption experiments were simulated using the Diffuse Double Layer Model (DDLM) with single sorption sites (≡QOH) and monodentate surface complexation. The reactions were established based on the aqueous speciation calculation under the experimental conditions, and the thermodynamic constants of surface reactions were obtained and refined by numerical optimization. Results of surface complexation modeling show the formation of a surface species ≡QOHEuDTPA2-, explaining the elevated sorption of Eu(III) at neutral to slightly acidic pH. In contrast, dissolved EuDTPA2- complex species are present at alkaline pH, resulting in an enhanced mobility of Eu(III).

Keywords: Sorption; Europium; Radionuclides; Diethylenetriaminepentaacetic acid; Surface complexation modeling

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-29697
Publ.-Id: 29697


Influence of microturbulence on the bubble-particle interaction investigated with Positron Emission Particle Tracking (PEPT)

Sommer, A.-E.; Ortmann, K.; van Heerden, M.; Richter, T.; Leadbeater, T.; Cole, K.; Heitkam, S.; Brito-Parada, P.; Eckert, K.

In a flotation cell, turbulence significantly affects the recovery rate. Microturbulence influences the motion of solid particles and thus, the probability of bubble-particle aggregation. We investigated the effect of microturbulence on bubble-particle interactions with positron emission particle tracking (PEPT). Single air bubbles (db=2.5mm) were captured generated on a needle in a water flow channel. Upstream, a mesh produced an isotropic turbulent flow with 5-15% turbulence intensity. Depending on the distance to the grid, the incident flow near the captive bubble (Re=600) was characterized by eddies of different length scales and magnitude. The liquid contained up to 0.3% PMMA particles (dp=200-400µm) and up to six radiolabelled particles coated with PMMA (dp=300-400µm). The trajectories of the labelled particles were recorded, allowing us to determine the average particle distribution in the turbulent field and describe the bubble-particle interactions. These results provide valuable information to enhance our understanding of key flotation phenomena.

Keywords: PEPT; Bubble-Particle interaction; grid turbulence

  • Lecture (Conference)
    Flotation'19, 10.-14.11.2019, Kapstadt, Südafrika
  • Contribution to proceedings
    Flotation 19, 11.-14.11.2019, Kapstadt, Südafrika

Permalink: https://www.hzdr.de/publications/Publ-29696
Publ.-Id: 29696


Enhanced ion acceleration from a non-ideal laser pulse contrast

Garten, M.; Huebl, A.; Widera, R.; Göthel, I.; Obst-Huebl, L.; Ziegler, T.; Zeil, K.; Cowan, T.; Schramm, U.; Bussmann, M.; Kluge, T.

The major challenges of compact proton sources driven by an ultrashort high-intensity laser are currently to establish precise control over proton beam parameters and shot-to-shot stability. Shooting ultrathin targets has shown to yield higher proton energies, which became recently accessible due to temporal laser pulse shape control using plasma-mirror techniques. We find that the intensity ramp, transmitted to the target by the plasma mirror during the last picosecond before the pulse peak, becomes significantly decisive for the subsequent acceleration performance. Reliable characterization of this ramp with modern laser diagnostics remains challenging and immense computational needs required to fully resolve the plasma kinetics leave it mostly unexplored in today's simulations of laser-solid interaction. We present the results of 3D large-scale simulations with PIConGPU, taking into account realistic contrast conditions, bridging the scales from picosecond pre-plasma formation over transient, non-equilibrium dynamics of the tens of femtosecond laser duration down to attosecond plasma oscillations. Adding to beneficial acceleration conditions presented by hybrid acceleration mechanisms and the onset of relativistic transparency, we show that the maximum proton energy can be optimized by a specific leading pulse edge via a combination of pre-thermal and thermal TNSA, surpassing the performance of the ideal diffraction-limited Gaussian pulse.

Keywords: laser-ion acceleration; TNSA; simulation; PIConGPU; CSCS; Piz Daint; PRACE; HPC

  • Lecture (Conference)
    4th European Advanced Accelerator Concepts Workshop, 15.-21.09.2019, Isola d'Elba, Italia
  • Lecture (Conference)
    2nd WHELMI Annual Meeting, 18.-19.11.2019, Helmholtz-Zentrum Dresden - Rossendorf, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29695
Publ.-Id: 29695


Uranium(VI) reduction by anaerobic microorganisms within the mine water of a former uranium mine at pilot scale

Gerber, U.; Schäfer, S.; Paul, M.; Krawczyk-Bärsch, E.

Environmental pollution by metals and radionuclides is one of the biggest challenges which have to be solved globally. In the uranium mine of the Wismut GmbH near Königstein (Germany) uranium production was achieved by leaching the sandstone with sulfuric acid. As a consequence the geochemical nature of the mine water has been substantially changed leading to an increase in sulfate, metals and uranium concentrations. For remediation purposes the mine is currently in the process of being flooded. Mine water is pumped to the surface, where it is treated by a conventional water treatment plant which is cost-intensive and long-lasting. For that reason, biological concepts for remediation could be appropriate alternatives.
In our studies, we designed a pilot plant for a bioremediation approach using the mine water with the naturally occurring microorganisms. We added 10 mM glycerol to 100 L of the mine water and incubated the solution over six weeks at ambient temperature. During this time, we performed online-measurements of pH, redox potential (Eh) and temperature. The uranium concentration as well as the iron(II) and sulfate concentrations were measured periodically. Within the six weeks of incubation, we monitored a drastic decrease of Eh, from 650 mV to 80 mV. Theoretical predictions showed that this decrease could be associated with a uranium(VI) reduction. Thus, the prediction was confirmed using UV-vis and EXAFS/ XANES measurements. After 17 days of incubation uranium(IV) was detectable. In addition to the uranium(VI) reduction, we detected an iron(III) to iron(II) reduction during the first three weeks as well as a slight sulfate reduction after 30 days of incubation.
In summary, our results demonstrate a biological influence within the mine water of the former uranium mine only by adding 10 mM glycerol. As a result, uranium(VI) is reduced to uranium(IV). The investigation in pilot-plant scale confirmed our previous lab scale experiments. We were able to prove the microbial induced reduction of uranium(VI) which could by a possible bioremediation approach in combination with or instead of conventional water treatment.

Keywords: uranium; reduction; mine water; microorganisms

  • Poster
    WISSYM 2019 International Mining Symposium, 09.-11.10.2019, Chemnitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-29694
Publ.-Id: 29694


Biofilms as a sink for radionuclides in future granitic nuclear waste repositories

Krawczyk-Bärsch, E.; Lehtinen, A.; Pedersen, K.

Usually, bacteria do not occur as individual cells in nature but as multicellular communities called biofilms. Biofilms are characterized by building up their own microenvironment, which can differ significantly from that of the bulk solution. They are known to provide a sink for dissolved heavy metals and actinides since EPS, cell walls, cell membranes, and cell cytoplasm can serve as sorption sites. In safety assessment studies for future nuclear waste repositories research on biofilms are becoming more important due to the potential retention for actinides in these microbial communities. For example, in the future underground rock characterization facility tunnel for high-level radioactive waste ONKALO in Finland, massive biofilms are growing next to fracture zones in a granitic rock environment, where groundwater is seeping from bedrock fractures. The biofilms are described as a pink and solid slime, consisting of Pseudomonas anguilliseptica, Arthrobacter bergeri, Hydrogenophaga sp., Methylobacter tundripaludum, Rhodoferrax ferrireducens, and Haliscomenobacter hydrossis. In laboratory experiments uranium was added to the circulating groundwater obtained from the fracture. EF-TEM investigations indicated that uranium in the biofilm was immobilized intracellularly in cells by the formation of metabolically mediated calcium uranyl phosphate, similar to needle-shaped autunite (Ca[UO2]2[PO4]2 ● 2–6H2O) or meta-autunite (Ca[UO2]2[PO4]2 .● 10–12H2O) [1].
Biofilms are also present in open fracture zones and on granitic tunnel walls at the Äspö Hard Rock Laboratory (HRL) in Sweden. The biofilms are predominantly formed by the indigenous iron-oxidizing bacterium Gallionella ferruginea with up to 90 wt% precipitated ferric oxyhydroxide. The combination of the biological material and iron oxides resulted in a large reactive surface area leading to a remarkably high bioaccumulation and adsorption of radionuclides.

Keywords: uranium; nuclear waste repository; biofilms; gallionella ferruginea

  • Invited lecture (Conferences)
    18. Sanierungskolloquium, Jena, 01.-02.10.2019, Jena, Germany

Permalink: https://www.hzdr.de/publications/Publ-29693
Publ.-Id: 29693


Conventional CARs versus modular CARs

Feldmann, A.; Arndt, C.; Koristka, S.; Berndt, N.; Bergmann, R.; Bachmann, M.

The clinical application of immune effector cells genetically modified to express chimeric antigen receptors (CARs) has shown impressive results including complete remissions of certain malignant hematological diseases. However, their application can also cause severe side effects such as cytokine release syndrome (CRS) or tumor lysis syndrome (TLS). One limitation of currently applied CAR T cells is their lack of regulation. Especially, an emergency shutdown of CAR T cells in case of life-threatening side effects is missing. Moreover, targeting of tumor-associated antigens (TAAs) that are not only expressed on tumor cells but also on vital tissues requires the possibility of a switch allowing to repeatedly turn the activity of CAR T cells on and off. Here we summarize the development of a modular CAR variant termed universal CAR (UniCAR) system that promises to overcome these limitations of conventional CARs.

Keywords: Immunotherapy; Chimeric antigen receptor; T cells; UniCAR; BiTE; TIMO XIV

Permalink: https://www.hzdr.de/publications/Publ-29692
Publ.-Id: 29692


Nanoscale Ferromagnetism in Alloy Thin Film via Lattice Disordering

Bali, R.; Schmeink, A. H.; Eggert, B.; Ehrler, J.; Liersch, V.; Semisalova, A.; Hlawacek, G.; Potzger, K.; Faßbender, J.; Thomson, T.; Wende, H.; Lindner, J.

Structural disorder in certain alloys leads to the onset of strong ferromagnetism. Disorder can be induced in desired locations, at the nanoscale, making such materials useful for magnetic nano-patterning. Examples of these alloys include Fe60Al40,[1] Fe50Rh50,[2] and Fe60V40. Disorder can be generated locally using focussed ion- as well as laser- beams,[1 - 3] inducing nanoscale ferromagnetism. Furthermore, the effect can be reversed via thermal re-ordering of the alloy, achieving re-writeable magnetic structures.
Insights into the mechanisms of the ferromagnetic onset in prototype systems, helps achieve a broader understanding of magneto-structural correlations in general. For instance, in paramagnetic B2-ordered Fe60Al40 as well as D8b-type Fe60V40, the ferromagnetic onset is caused by antisite defects i.e. site swapping of the Fe and Al (V) atoms, resulting in a transition to the bcc (A2) structure. An increase of antisite defects can cause the Ms of Fe60Al40 as well as Fe60V40 to increase from nearly-zero in the ordered structures to 780 and 660 kAm-1, in their respective disordered structures. In contrast, in B2 Fe50Rh50 the well-ordered film is antiferromagnetic, and static disordering may be sufficient to fully transform the alloy to the ferromagnetic phase, possessing an Ms of ~ 1250 kAm-1 at 300 K. Thus, whereas the Ms in the above alloys increases drastically with lattice disorder, the microscopic nature of the disordering varies.
Here we deploy ion-irradiation to sensitively induce lattice disorder in the above binary alloy systems, while tracing the manifested ferromagnetic onsets, thereby obtaining insights into the correlation between magnetic behaviour and the structure. Properties of magnetic arrays and magneto-transport devices produced using lattice disorder will be discussed.
References:
[1] “Printing Nearly-Discrete Magnetic Patterns Using Chemical Disorder Induced Ferromagnetism”, R. Bali et al., Nano Letters 14, 435 (2014).
[2] “Tuning the antiferromagnetic to ferromagnetic phase transition in FeRh thin films by means of low-energy/low fluence ion irradiation”, A. Heidarian et al., Nucl. Instrum. Methods Phys. Res. B 358, 251 (2015).
[3] “Laser-Rewriteable Ferromagnetism at Thin-Film Surfaces”, J. Ehrler et al., ACS Appl. Mater. Interfaces 10, 15232 (2018).

  • Invited lecture (Conferences)
    6th International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems (6th IC4N), 30.06.-03.07.2019, Corfu, Greece
  • Invited lecture (Conferences)
    Symposium „Spins, Waves and Interactions“, 03.-05.09.2019, Greifswald, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-29691
Publ.-Id: 29691


Strain Anisotropy and Magnetic Domains in Embedded Nanomagnets

Nord, M.; Semisalova, A.; Kákay, A.; Hlawacek, G.; Maclaren, I.; Liersch, V.; Volkov, O.; Makarov, D.; Paterson, G. W.; Potzger, K.; Lindner, J.; Faßbender, J.; Mcgrouther, D.; Bali, R.

Nanoscale modifications of strain and magnetic anisotropy can open pathways to engineering magnetic domains for device applications. A periodic magnetic domain structure can be stabilized in sub-200 nm wide linear as well as curved magnets, embedded within a flat non-ferromagnetic thin film. The nanomagnets are produced within a non-ferromagnetic B2-ordered Fe60Al40 thin film, where local irradiation by a focused ion beam causes the formation of disordered and strongly ferromagnetic regions of A2 Fe60Al40. An anisotropic lattice relaxation is observed, such that the in-plane lattice parameter is larger when measured parallel to the magnet short-axis as compared to its length. This in-plane structural anisotropy manifests a magnetic anisotropy contribution, generating an easy-axis parallel to the short axis. The competing effect of the strain and shape anisotropies stabilizes a periodic domain pattern, in linear as well as spiral nanomagnets, providing a versatile and geometrically controllable path to engineering the strain and thereby the magnetic anisotropy at the nanoscale.

Keywords: embedded nanomagnets; curved magnets; strain anisotropy; ion-induced patterning; magnetic domains

Permalink: https://www.hzdr.de/publications/Publ-29690
Publ.-Id: 29690


Multi-analytical characterization of slags to determine the chromium concentration for a possible re-extraction

Horckmans, L.; Möckel, R.; Nielsen, P.; Kukurugya, F.; Vanhoof, C.; Morillon, A.; Algermissen, D.

The CHROMIC project aims to recover chromium from steelmaking and ferrochrome slags to regain valuable resources and simultaneously reduce potential environmental impacts. To develop the recovery flowsheets, and reliably calculate metal recovery, an accurate assessment of chromium concentration and distribution is essential. Therefore, model streams were thoroughly characterized using a combination of analytical techniques . In all materials, chromium is present in distinct but often small spinel phases, intertwined with other minerals and showing a considerable zonation in Cr-content with higher amounts in the cores. The small size of the Cr-rich particles makes recovery by mineral processing challenging. Measured chromium content was found to differ largely based on the chemical dissolution method applied. Analysis of insoluble residues and comparison with a standard reference material evidenced that standard acid dissolution procedures based on HCl/HNO₃/HBF₄ and HNO₃/HF/H₂O₂ are insufficient to fully dissolve spinel structures, leading to severe underestimations of chromium content. A sodium peroxide treatment is required for a full dissolution of spinel. This is noteworthy since most legislation for reuse of slags are currently based on acid dissolution methods.

Keywords: steel slag; ferrochromium slag; chromium extraction; multi-analytical characterization; method comparison

Permalink: https://www.hzdr.de/publications/Publ-29689
Publ.-Id: 29689


Filling the 5-10 THz gap using Ge-based photoconductive emitter

Singh, A.; Pashkin, O.; Winnerl, S.; Helm, M.; Schneider, H.

We present here a Ge photoconductive emitter generating THz pulses with a spectrum up to 13 THz free from any absorption lines if detected with a proper detector. Ge is a centrosymmetric non-polar crystal and hence its phonons are not IR-active. Therefore, Ge shows high and almost uniform transmission of THz radiation up to frequencies more than 20 THz besides a weak two-phonon absorption band near 10 THz [1]. Ge also has high carrier mobility required for efficient THz emission. Bowtie-like electrode structures with 10 µm electrode gap are deposited on a pure Ge substrate to fabricate the photoconductive THz emitter. The carrier lifetime in pure Ge is of the order of µs, thus it requires a pump laser with pulse repetition rate less than a MHz. A Ti:sapphire amplified laser system operating at 800 nm wavelength, 250 kHz repetition rate and ~ 65 fs pulse width is used to pump the Ge emitter and probe the radiated THz pulse using the electro optic sampling technique.
[1] A. Singh, A. Pashkin, S. Winnerl, M. Helm and H. Schneider, “Gapless broadband terahertz emission from a germanium photoconductive emitter”, ACS Photonics 5, 2718−2723 (2018).

Keywords: terahertz emitter; germanium

  • Lecture (Conference)
    Conference on Lasers and Electro-Optics (CLEO), 06.-10.05.2019, San José, USA
  • Contribution to proceedings
    Conference on Lasers and Electro-Optics (CLEO), 05.-10.05.2019, San José, USA
    Conference on Lasers and Electro-Optics OSA Technical Digest (Optical Society of America, 2019), 345 E 47TH ST, NEW YORK, NY 10017 USA: IEEE, 978-1-943580-57-6
    DOI: 10.1364/CLEO_SI.2019.STu3F.3

Permalink: https://www.hzdr.de/publications/Publ-29688
Publ.-Id: 29688


Scalable Large-Area Terahertz Emitters with Improved Electrode Design

Singh, A.; Welsch, M.; Winnerl, S.; Helm, M.; Schneider, H.

We have systematically investigated the influence of electrode parameters on the emission efficiency of scalable large-area photoconductive THz emitters. We identify two contributions to THz emission, originating from the photoexcited carriers in the semiconductor and from the interdigitated metal electrodes acting as dipole antennae, respectively. Both contributions are optimized for maximum THz emission efficiency by varying the gap and stripe widths of the interdigitated metal electrodes. Using this approach we achieve a 50% improvement of the radiated THz electric field as compared to electrodes with equal stripe and gap widths.

Keywords: terahertz emitter; large-area emitter

  • Lecture (Conference)
    The 44th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz'2019), 01.-06.09.2019, Paris, France
  • Contribution to proceedings
    44th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz'2019), 01.-06.09.2019, Paris, France
    44th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz'2019)
    DOI: 10.1109/IRMMW-THz.2019.8874010

Permalink: https://www.hzdr.de/publications/Publ-29687
Publ.-Id: 29687


Pages: [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37] [38] [39] [40] [41] [42] [43] [44] [45] [46] [47] [48] [49] [50] [51] [52] [53] [54] [55] [56] [57] [58] [59] [60] [61] [62] [63] [64] [65] [66] [67] [68] [69] [70] [71] [72] [73] [74] [75] [76] [77] [78] [79] [80] [81] [82] [83] [84] [85] [86] [87] [88] [89] [90] [91] [92] [93] [94] [95] [96] [97] [98] [99] [100] [101] [102] [103] [104] [105] [106] [107] [108] [109] [110] [111] [112] [113] [114] [115] [116] [117] [118] [119] [120] [121] [122] [123] [124] [125] [126] [127] [128] [129] [130] [131] [132] [133] [134] [135] [136] [137] [138] [139] [140] [141] [142] [143] [144] [145] [146] [147] [148] [149] [150] [151] [152] [153] [154] [155] [156] [157] [158] [159] [160] [161] [162] [163] [164] [165] [166] [167] [168] [169] [170] [171] [172] [173] [174] [175] [176] [177] [178] [179] [180] [181] [182] [183] [184] [185] [186] [187] [188] [189] [190] [191] [192] [193] [194] [195] [196] [197] [198] [199] [200] [201] [202] [203] [204] [205] [206] [207] [208] [209] [210] [211] [212] [213] [214] [215] [216] [217] [218] [219] [220] [221] [222] [223] [224] [225] [226] [227] [228] [229] [230] [231] [232] [233] [234] [235] [236] [237] [238] [239] [240] [241] [242] [243] [244] [245] [246] [247] [248] [249] [250] [251] [252] [253] [254] [255] [256] [257] [258] [259] [260] [261] [262] [263] [264] [265] [266] [267] [268] [269] [270] [271] [272] [273] [274] [275] [276] [277] [278] [279] [280] [281] [282] [283] [284] [285] [286] [287] [288] [289] [290] [291] [292] [293] [294] [295] [296] [297] [298] [299]