Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf
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High spin-wave propagation length consistent with low damping in a metallic ferromagnet
We report ultra-low intrinsic magnetic damping in Co25Fe75 heterostructures, reaching the low 10E−4 regime at room temperature. By using a broadband ferromagnetic resonance technique, we extracted the dynamic magnetic properties of several Co25Fe75-based heterostructures with varying ferromagnetic layer thickness. By estimating the eddy current contribution to damping, measuring radiative damping and spin pumping effects, we extrapolated an intrinsic damping of α0 ≤ 3.05 × 10E−4. Furthermore, using Brillouin light scattering microscopy we measured spin-wave propagation lengths of up to (21 ± 1) μm in a 26 nm thick Co25 Fe75 heterostructure at room temperature, which is in excellent agreement with the measured damping.
Keywords: spin-wave propagation; low magnetic damping; ferromagnetic resonance; Brillouin light scattering
Applied Physics Letters 115(2019)12, 122402
Nonlinear ferromagnetic resonance in the presence of 3-magnon scattering in magnetic nanostructures
Bulk and patterned ferromagnets can exhibit various nonlinear phenomena at moderate excitation power, making them a nice test bed for study of nonlinear dynamics. We investigate nonlinear ferromagnetic resonance in magnetic nanostructures with discrete spectra of spin-wave modes in the case of allowed 3-magnon scattering processes. These processes result in the splitting of a directly driven spin-wave mode into two secondary modes if a certain excitation threshold is overcome. The 3-magnon splitting manifests itself as a characteristic distortion of the resonance curve, which can be detected in a simple ferromagnetic resonance experiment. Theoretical results are also compared to the experimental study of nonlinear spin-wave dynamics in a vortex-state magnetic disk, in which 3-magnon splitting is confirmed by direct measurements using Brillouin light scattering microscopy.
Keywords: nonlinear ferromagnetic resonance; 3-magnon scattering; spin-wave modes; magnetic vortex; Brillouin light scattering; magnetic nanoelements
IEEE Magnetics Letters 10(2019), 6103405
Absorption edge, Urbach tail, and electron-phonon interactions in topological insulator Bi2Se3 and band insulator (Bi0.89In0.11)2Se3
We employ infrared transmission spectroscopy to explore the temperature-dependent absorption edge and electron-phonon (e-ph) interaction in topological insulator Bi2Se3 and band insulator (Bi0.89In0.11)2Se3 films. Upon heating from 5 K to 300 K, the absorption edge shifts from 262 to 249 meV for Bi2Se3 and from 367 to 343 meV for (Bi0.89In0.11)2Se3. By analyzing the temperature dependence of the Urbach tail, the significant role of Raman-active phonon mode E2g in e-ph interaction is identified, which agrees well with the ab initio calculation.
Applied Physics Letters 114(2019), 162105
- Final Draft PDF 676 kB Secondary publication
Electron-Beam-Driven Structure Evolution of Single-Layer MoTe2 for Quantum Devices
40 kV high-resolution transmission electron microscopy (TEM) experiments are performed to understand defect formation and evolution of their atomic structure in single-layer 2H MoTe2 under electron beam irradiation. We show that Te vacancies can agglomerate either in single Te-vacancy lines or in extended defects composed of column Te vacancies, including rotational trefoil-like defects, with some of them being never reported before. The formation of inversion domains with mirror twin boundaries of different types, along with the islands of the metallic T’ phase was also observed. Our first-principles calculations provide insights into the energetics of the transformations as well as the electronic structure of the system with defects and point out that some of the observed defects have localized magnetic moments. Our results indicate that various nano-scale structures, including metallic quantum dots consisting of T’-phase islands and one-dimensional metallic quantum systems such as vacancy lines and mirror twin boundaries embedded into a semiconducting host material can be realized in single-layer 2H MoTe2, and defect-associated magnetism can also be added, which may allow prospective control of optical and electronic properties of two-dimensional materials.
Keywords: Defects; 2D MoTe2; transmission electron microscopy; transition metal dichalcogenide; DFT; quantum devices
ACS Applied Nano Materials 2(2019), 3262
- Final Draft PDF 6,1 MB Secondary publication
Impact of Extrinsic and Intrinsic Hypoxia on Catecholamine Biosynthesis in Absence or Presence of Hif2α in Pheochromocytoma Cells
Abstract: Pheochromocytomas and paragangliomas (PPGLs) with activated pseudohypoxic pathways are associated with an immature catecholamine phenotype and carry a higher risk for metastasis. For improved understanding of the underlying mechanisms we investigated the impact of hypoxia and pseudohypoxia on catecholamine biosynthesis in pheochromocytoma cells naturally lacking Hif2α (MPC and MTT) or expressing both Hif1α and Hif2α (PC12). Cultivation under extrinsic hypoxia or in spheroid culture (intrinsic hypoxia) increased cellular dopamine and norepinephrine contents in all cell lines. To distinguish further between Hif1α- and Hif2α-driven effects we expressed Hif2α in MTT and MPC-mCherry cells (naturally lacking Hif2α). Presence of Hif2α resulted in similarly increased cellular dopamine and norepinephrine under hypoxia as in the control cells. Furthermore, hypoxia resulted in enhanced phosphorylation of tyrosine hydroxylase (TH). A specific knockdown of Hif1α in PC12 diminished these effects. Pseudohypoxic conditions, simulated by expression of Hif2α under normoxia resulted in increased TH phosphorylation, further stimulated by extrinsic hypoxia. Correlations with PPGL tissue data led us to conclude that catecholamine biosynthesis under hypoxia is mainly mediated through increased phosphorylation of TH, regulated as a short-term response
(24–48 h) by HIF1α. Continuous activation of hypoxia-related genes under pseudohypoxia leads to a HIF2α-mediated phosphorylation of TH (permanent status).
Keywords: hypoxia; pseudohypoxia; spheroids; HIF; EPAS1; catecholamine; pheochromocytoma and paraganglioma; phosphorylation tyrosine hydroxylase
Cancers 11(2019), 594
Silver Particles with Rhombicuboctahedral Shape and Effective Isotropic Interactions with Light
Steiner, A. M.; Mayer, M.; Schletz, D.; Wolf, D.; Formanek, P.; Hübner, R.; Dulle, M.; Förster, S.; König, T. A. F.; Fery, A.
Truly spherical silver nanoparticles are of great importance for fundamental studies including plasmonic applications, but their direct synthesis in aqueous media is not feasible. Using the commonly employed copper-based etching processes, an isotropic plasmonic response can be achieved by etching well-defined silver nanocubes. Whilst spherical-like shape is typically prevailing in such processes, we established that there is a preferential growth toward silver rhombicuboctahedra, which is the thermodynamically most stable product of this synthesis. The rhombicuboctahedral morphology is further evidenced by comprehensive characterization with small-angle X-ray scattering in combination with transmission electron microscopy (TEM) tomography and high-resolution TEM. We also elucidate the complete reaction mechanism based on UV-vis kinetic studies, and the postulated mechanism can also be extended to all copper-based etching processes.
Chemistry of Materials 31(2019), 2822-2827
Carboranyl analogues of ketoprofen with cytostatic activity against human melanoma and colon cancer cell lines
Ketoprofen is a widely used nonsteroidal anti-inflammatory drug (NSAID) that also exhibits cytotoxic activity against various cancers. This makes ketoprofen an attractive structural lead for the development of new NSAIDs and cytotoxic agents. Recently, the incorporation of carboranes as phenyl mimetics in structures of established drugs has emerged as an attractive strategy in drug design. Herein, we report the synthesis and evaluation of four novel carborane-containing derivatives of ketoprofen, two of which are prodrug esters with an nitric oxide-releasing moiety. One of these prodrug esters exhibited high cytostatic activity against melanoma and colon cancer cell lines. The most pronounced activity was found in cell lines that are sensitive to oxidative stress, which was apparently induced by the ketoprofen analogue.
ACS Omega 4(2019)5, 8824-8833
General guideline for closure model development for gas-liquid flows in the multi-fluid framework
Lucas, D.; Krepper, E.; Liao, Y.; Rzehak, R.; Ziegenhein, T.
The two- or multi-fluid approach is frequently used for Nuclear Reactor Safety (NRS)-related simulations of gas-liquid flows. To enable reliable predictions the closure models have to reflect the involved local physical phenomena at the non-resolved scale properly. To consolidate the CFD-modelling in the frame of the multi-fluid approach the so-called baseline model strategy was recently proposed (Lucas et al., 2016). The present technical note discusses a long-term strategy for the baseline model development and ways to obtain or improve closure models. Guidelines for the model development are given by listing requirements for appropriate closure models as well as frequently made mistakes. This is illustrated by examples for recent developments done for HZDR baseline models for poly-disperse bubbly flows.
Keywords: CFD; multi-fluid model; closure models
Nuclear Engineering and Design 357(2020), 110396
- Final Draft PDF 185 kB Secondary publication
A Five-MicroRNA Signature Predicts Survival and Disease Control of Patients with Head and Neck Cancer Negative for HPV Infection
Hess, J.; Unger, K.; Maihoefer, C.; Schuettrumpf, L.; Wintergerst, L.; Heider, T.; Weber, P.; Marschner, S.; Braselmann, H.; Samaga, D.; Kuger, S.; Pflugradt, U.; Baumeister, P.; Walch, A.; Woischke, C.; Kirchner, T.; Werner, M.; Werner, K.; Baumann, M.; Budach, V.; Combs, S. E.; Debus, J.; Grosu, A.-L.; Krause, M.; Linge, A.; Roedel, C.; Stuschke, M.; Zips, D.; Zitzelsberger, H.; Ganswindt, U.; Henke, M.; Belka, C.
Purpose: Human papillomavirus (HPV)-negative head and neck squamous cell carcinoma (HNSCC) is associated with unfavorable prognosis, while independent prognostic markers remain to be defined.
Experimental Design: We retrospectively performed miRNA expression profiling. Patients were operated for locally advanced HPV-negative HNSCC and had received radiochemotherapy in eight different hospitals (DKTK-ROG; n = 85). Selection fulfilled comparable demographic, treatment, and follow-up characteristics. Findings were validated in an independent single-center patient sample (LMU-KKG; n = 77). A prognostic miRNA signature was developed for freedom from recurrence and tested for other endpoints. Recursivepartitioning analysis was performed on the miRNA signature, tumor and nodal stage, and extracapsular nodal spread.
Technical validation used qRT-PCR. An miRNA-mRNA target network was generated and analyzed.
Results: For DKTK-ROG and LMU-KKG patients, the median follow-up was 5.1 and 5.3 years, and the 5-year freedom from recurrence rate was 63.5% and 75.3%, respectively. A five-miRNA signature (hsa-let-7g-3p, hsamiR- 6508-5p, hsa-miR-210-5p, hsa-miR-4306, and hsa-miR-7161-3p) predicted freedom from recurrence in DKTK-ROG [hazard ratio (HR) 4.42; 95% confidence interval (CI), 1.98-9.88, P < 0.001], which was confirmed in LMU-KKG (HR 4.24; 95% CI, 1.40-12.81, P = 0.005). The signature also predicted overall survival (HR 3.03; 95% CI, 1.50-6.12, P = 0.001), recurrence-free survival (HR 3.16; 95% CI, 1.65-6.04, P < 0.001), and disease-specific survival (HR 5.12; 95% CI, 1.88-13.92, P < 0.001), all confirmed in LMU-KKG data. Adjustment for relevant covariates maintained the miRNA signature predicting all endpoints. Recursive- partitioning analysis of both samples combined classified patients into low (n = 17), low-intermediate (n = 80), high-intermediate (n = 48), or high risk (n = 17) for recurrence (P < 0.001).
Conclusions: The five-miRNA signature is a strong and independent prognostic factor for disease recurrence and survival of patients with HPV-negative HNSCC.
Clinical Cancer Research 25(2019)5, 1505-1516
Thermal Transport in MoS2 from Molecular Dynamics using Different Empirical Potentials
Thermal properties of molybdenum disulfide (MoS2) have recently attracted attention related to fundamentals of heat propagation in strongly anisotropic materials, and in the context of potential applications to optoelec- tronics and thermoelectrics. Multiple empirical potentials have been developed for classical molecular dynamics (MD) simulations of this material, but it has been unclear which provides the most realistic results. Here, we calculate lattice thermal conductivity of single- and multilayer pristine MoS2 by employing three different thermal transport MD methods: equilibrium, nonequilibrium, and homogeneous nonequilibrium ones. We mainly use the Graphics Processing Units Molecular Dynamics code for numerical calculations, and the Large-scale Atomic/Molecular Massively Parallel Simulator code for crosschecks. Using different methods and computer codes allows us to verify the consistency of our results and facilitate comparisons with previous studies, where different schemes have been adopted. Our results using variants of the Stillinger-Weber potential are at odds with some previous ones and we analyze the possible origins of the discrepancies in detail. We show that, among the potentials considered here, the reactive empirical bond order (REBO) potential gives the most reasonable predictions of thermal transport properties as compared to experimental data. With the REBO potential, we further find that isotope scattering has only a small effect on thermal conduction in MoS2 and the in-plane thermal conductivity decreases with increasing layer number and saturates beyond about three layers. We identify the REBO potential as a transferable empirical potential for MD simulations of MoS2 which can be used to study thermal transport properties in more complicated situations such as in systems containing defects or engineered nanoscale features. This work establishes a firm foundation for understanding heat transport properties of MoS2 using MD simulations.
Keywords: 2D materials; thermal transport; atomistic simulations
Physical Review B 99(2019), 054303
Tomonaga-Luttinger liquid in a box: electrons confined within MoS2 mirror twin boundaries
Two- or three-dimensional metals are usually well described by weakly interacting, fermionic quasiparticles. This concept breaks down in one dimension due to strong Coulomb interactions. There, low-energy electronic excitations are expected to be bosonic collective modes, which fractionalize into independent spin- and charge-density waves. Experimental research on one-dimensional metals is still hampered by their difficult realization, their limited accessibility to measurements, and by competing or obscuring effects such as Peierls distortions or zero bias anomalies. Here we overcome these difficulties by constructing a well-isolated, one-dimensional metal of finite length present in MoS2 mirror-twin boundaries. Using scanning tunneling spectroscopy we measure the single-particle density of the interacting electron system as a function of energy and position in the 1D box. Comparison to theoretical modeling provides unambiguous evidence that we are observing spin-charge separation in real space.
Keywords: 2D materials; Tomonaga-Luttinger liquid; First-principles calculations
Physical Review X 9(2019), 011055
Room temperature ferromagnetism in MoTe2 by post-growth incorporation of vanadium impurities
Post-synthesis doping of 2D materials is demonstrated by incorporation of vapor-deposited transition metals into a MoTe2 lattice. Using this approach, vanadium doping of 2H-MoTe2 produces a 2D ferromagnetic semiconductor with a Curie temperature above room temperature (RT). Surprisingly, ferromagnetic properties can be induced with very low vanadium concentrations, down to ≈0.2%. The vanadium species introduced at RT are metastable, and annealing to above ≈500 K results in the formation of a thermodynamically favored impurity configuration that, however, exhibits reduced ferromagnetic properties. Doping with titanium, instead of vanadium, shows a similar incorporation behavior, but no ferromagnetism is induced in MoTe2. This indicates that the type of impurities in addition to their atomic configuration is responsible for the induced magnetism. The interpretation of the experimental results is consistent with ab initio calculations, which confirm that the proposed vanadium impurity configurations exhibit magnetic moments, in contrast to the same configurations with titanium impurities. This study illustrates the possibility to induce ferromagnetic properties in layered van der Waals semiconductors by controlled magnetic impurity doping and thus to add magnetic functionalities to 2D materials.
Keywords: 2D materials; STM; electronic structure calculations; doping
Advanced Electronic Materials 5(2019)5, 1900044
- Final Draft PDF 10,5 MB Secondary publication
Efficient method for calculating Raman spectra of solids with impurities and alloys and its application to two-dimensional transition metal dichalcogenides
Raman spectroscopy is a widely used, powerful, and nondestructive tool for studying the vibrational properties of bulk and low-dimensional materials. Raman spectra can be simulated using first-principles methods but due to the high computational cost calculations are usually limited only to fairly small unit cells, which makes it difficult to carry out simulations for alloys and defects. Here, we develop an efficient method for simulating Raman spectra of alloys, benchmark it against full density-functional theory calculations, and apply it to several alloys of two-dimensional (2D) transition metal dichalcogenides. In this method, the Raman tensor for the supercell mode is constructed by summing up the Raman tensors of the pristine system weighted by the projections of the supercell vibrational modes to those of the pristine system. This approach is not limited to 2D materials and should be applicable to any crystalline solid with defects and impurities. To efficiently evaluate vibrational modes of very large supercells, we adopt mass approximation, although it is limited to chemically and structurally similar atomic substitutions. To benchmark our method, we first apply it to the MoxW(1-x)S2 monolayer in the H phase where several experimental reports are available for comparison. Second, we consider MoxW(1-x)Te2 in the T' phase, which has been proposed to be a 2D topological insulator but where experimental results for the monolayer alloy are still missing. We show that the projection scheme also provides a powerful tool for analyzing the origin of the alloy Raman-active modes in terms of the parent system eigenmodes. Finally, we examine the trends in characteristic Raman signatures for dilute concentrations of impurities in MoS2.
Keywords: 2D materials; atomistic simulation
Physical Review Materials 3(2019), 023806
Cathepsin B-Activatable Cell-Penetrating Peptides
Protease activity is increasingly drawn into the spotlight as a crucial modulator in cancer angiogenesis, invasion, and metastasis . Elevated activity of multiple members of the family of cysteine cathepsins has been shown to correlate with increased metastasis and therapy resistance [2, 3]. Especially high expression levels of extracellular cathepsin B (CatB) indicate poor prognosis in neoplastic diseases, making CatB an interesting target for functional characterization of cancers by activity-based molecular imaging. It is our aim to develop such an imaging probe for CatB by combination of a polyarginine-based, activatable cell-penetrating peptide  (ACPP) and an optimised endopeptidase substrate for CatB. Substrate optimisation proofed to be challenging as two entirely opposite factors needed to be balanced – high stability against serum proteases to prevent premature cleavage of the activation sequence, while retaining efficient and specific endoproteolytic cleavability by CatB. We have generated a CatB-endoprotease substrate by C-terminally elongating the CatB carboxydipeptidase substrate Abz GIVR*AK(Dnp) OH  (Abz – amino-benzoyl, Dnp – dinitrophenyl, * – cleavage site) to the octapeptide Abz GIVR*AK(Dnp)GX CONH2, which could be used as activation site in the final ACPP. Introduction of any amino acid other than glycine at the P4’ position resulted in hysteretic kinetics for the CatB-catalysed hydrolysis of the octapeptides, which might indicate the displacement of the occluding loop from the active site upon interaction with the substrates. Using LC-ESI-MS-based analysis of serum-incubated substrates, the positions P1 and P3’ where determined to be primary determinants of serum stability. After suppression of the P3’ instability by Nα-methylation and optimisation within the positions P1-P3, we were able to increase serum half-life from < 5 min to > 24 h under concomitant improvement of kinetic substrate efficiency towards CatB. Based on this optimised CatB-endopeptidase substrate, we have synthesised a fluorescently labelled ACPP with which we were able to demonstrate CatB-dependent uptake and subsequent nucleolar accumulation of the activated peptide in human U87 MG glioma cells. Radiolabelling of the probe with copper-64 was enabled by conjugating the ACPP to NODAGA as chelating moiety. Its evaluation in vivo using PET imaging is under current investigation.
 Yang et al., Cancer Growth Metastasis 2009, 2, 13
 Aggarwal and Sloane, Proteomics Clin. Appl. 2014, 8, 427
 Löser and Pietzsch, Front. Chem. 2015, 3, article 37
 Jiang et al., PNAS, 2004, 101, 17867
 Cotrin et al., Anal. Biochem. 2004, 335, 244
Frontiers in Medicinal Chemistry, 24.-27.03.2019, Würzburg, Deutschland
Optical properties of ZnSxTe1-x synthesized by sulfur implantation
ZnSxTe1-x thin films were prepared by sulfur implantation into ZnTe grown by molecular beam epitaxy and subsequent pulsed laser melting. The chemical composition and layer thickness of the ZnSxTe1-x layer have been analyzed based on Rutherford backscattering spectrometry. Raman and photoluminescence spectroscopies were employed to reveal the optical properties of the ZnSxTe1-x layer. Raman spectra exhibit a redshift of the longitudinal optical photon modes with increasing sulfur concentration. The room temperature photoluminescence measurement indicates the appearance of the sulfur induced energy state in the bandgap.
Nuclear Instruments and Methods in Physics Research B 442(2019), 24-27
Dipeptide-derived Alkynes as Irreversible Inhibitors of Cysteine Cathepsins
Even though the C-C triple bond is largely considered as a bioinert functional group, two research groups observed the irreversible inhibition of a cysteine protease by an alkyne-functionalised substrate derivative: both EKKEBUS et al. and SOMMER et al. independently described the unexpected inactivation of de-ubiquitinating enzymes by ubiquitin or ubiquitin-like modifiers bearing propargylamine in place of C-terminal glycine by covalent targeting of the active-site cysteine residue [1, 2]. We intended to harness that finding for the design of inhibitor-based probes for the imaging of tumour-associated cysteine proteases.
All 11 human cysteine cathepsins have been linked to tumour progression. Especially high expression levels of the cathepsins B, K, L, S and X are correlated with an increased metastatic potential and poor prognosis.  Therefore, those enzymes represent promising targets for the therapy and imaging of tumours.
GREENSPAN et al. reported a potent, highly selective dipeptidyl nitrile-based cathepsin B inhibitor (1, structure shown above) . Based on that lead compound, dipeptide alkynes were designed by isoelectronic replacement of the nitrile nitrogen atom by a methine group (2) and consecutive variation of the 2,4-difluorobenzoyl group and the amino acid-derived side chains. Formation of the C-C triple bond by reaction of the corresponding open-chain serine-derived aldehyde with the Bestmann-Ohira reagent was accompanied by partial enantiomerisation. Therefore, the synthesis was performed via Garner’s aldehyde to ensure high stereochemical purity of the final compounds.
By investigating the inhibitory potential against cathepsin B, S, L and K potent alkyne-based inhibitors were identified for all tested cathepsins, with second-order inactivation constants (kinact/KI) up to 10133 M-1s-1 and interesting selectivity profiles. Based on these promising results and considering their absent indiscriminate thiol reactivity, dipeptidyl alkynes have the potential to be translated into activity-based probes for molecular imaging in vivo. In further studies, selected inhibitors will be labelled with suitable radionuclides such as fluorine-18, which will in turn enable further pharmacological evaluations.
 Ekkebus et al., J. Am. Chem. Soc., 2013, 135, 2867-2870.
 Sommer et al., Bioorg. Med. Chem., 2013, 21, 2511-2517.
 Löser and Pietzsch, Front. Chem., 2015, 3, 37.
 Greenspan et al., J. Med. Chem., 2001, 44, 4524-4534.
Frontiers in Medicinal Chemistry, 24.-27.03.2019, Würzburg, Deutschland
Deciphering the Crystal Structure of a Scarce 1D Polymeric Thorium Peroxo Sulfate
The preparation and structural characterization of an original Th peroxo sulfate dihydrate crystallizing at room temperature in the form of stable 1D polymeric microfibers is described. A combination of laboratory and synchrotron techniques allowed to solve the structure of Th(O2)(SO4)(H2O)2 compound which crystallizes in a new structure type in the Pna21 space group of the orthorhombic system. Particularly, peroxide ligand coordinates Th cations in a scarce μ3–η2:η2:η2 bridging mode forming an infinite 1D chain decorated with sulfato ligands exhibiting simultaneously both monodentate and bidentate coordination modes.
Chemistry - A European Journal 25(2019)41, 9580-9585
Collective flow and correlations measurements with HADES in Au plus Au collisions at 1.23 AGeV
Kardan, B.; Adamczewski-Musch, J.; Arnold, O.; Arnoldi-Meadows, B.; Belounnas, A.; Belyaev, A.; Biernat, J.; Blanco, A.; Blume, C.; Boehmer, M.; Bordalo, P.; Chlad, L.; Chudoba, P.; Ciepal, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gillitzer, A.; Golosov, O.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hoehne, C.; Holzmann, R.; Ierusalimov, A.; Ivanov, V.; Ivashkin, A.; Kaempfer, B.; Kajetanowicz, M.; Kampert, K.-H.; Kardan, B.; Khomyakov, V.; Koenig, I.; Koenig, W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kozela, A.; Kubos, J.; Kugler, A.; Kunz, T.; Kurilkin, P.; Kushpil, V.; Ladygin, V.; Lalik, R.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Lykasov, G.; Mahmoud, T.; Malakhov, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Muentz, C.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Patel, V.; Pauly, C.; Pechenov, V.; Pechenova, O.; Pereira, A.; Petousis, V.; Petukhov, O.; Pfeifer, D.; Pietraszko, J.; Prozorov, A. P.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Reshetin, A.; Ritman, L.; Rodriguez-Ramos, P.; Rost, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Silva, L.; Smyrski, J.; Sobiella, M.; Spataro, S.; Spies, S.; Strikhanov, M.; Stroebele, H.; Stroth, J.; Strzempek, P.; Svoboda, O.; Szala, M.; Taranenko, A.; Tlusty, P.; Traxler, M.; Troyan, A.; Tsertos, H.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wintz, P.; Wirth, J.; Wloch, B.; Zhilin, A.; Zinchenko, A.; Zumbruch, P.
The HADES experiment provides a large acceptance combined with a high mass resolution and therefore makes it possible to study dielectron and hadron production in heavy-ion collisions with unprecedented precision. With the high statistics of seven billion Au+Au collisions at 1.23 AGeV recorded in 2012 the investigation of collective effects and particle correlations is possible with unprecedented accuracy. We present multi-differential data on directed (v(1)) and elliptic (v(2)) flow, and the first measurement of triangular flow (v(3)), of protons and deuterons.
Nuclear Physics A 982(2019), 431
Multi-differential pattern of low-mass e(+)e(-) excess from root S-NN=2.4 GeV Au+Au collisions with HADES
Harabasz, S.; Adamczewski-Musch, J.; Arnold, O.; Arnoldi-Meadows, B.; Belounnas, A.; Belyaev, A.; Biernat, J.; Blanco, A.; Blume, C.; Boehmer, M.; Bordalo, P.; Chlad, L.; Chudoba, P.; Ciepal, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gillitzer, A.; Golosov, O.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hoehne, C.; Holzmann, R.; Ierusalimov, A.; Ivanov, V.; Ivashkin, A.; Kaempfer, B.; Kajetanowicz, M.; Kampert, K.-H.; Kardan, B.; Khomyakov, V.; Koenig, I.; Koenig, W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kozela, A.; Kubos, J.; Kugler, A.; Kunz, T.; Kurilkin, P.; Kushpil, V.; Ladygin, V.; Lalik, R.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Lykasov, G.; Mahmoud, T.; Malakhov, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Muentz, C.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Patel, V.; Pauly, C.; Pechenov, V.; Pechenova, O.; Pereira, A.; Petousis, V.; Petukhov, O.; Pfeifer, D.; Pietraszko, J.; Prozorov, A. P.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Reshetin, A.; Ritman, L.; Rodriguez-Ramos, P.; Rost, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Silva, L.; Smyrski, J.; Sobiella, M.; Spataro, S.; Spies, S.; Strikhanov, M.; Stroebele, H.; Stroth, J.; Strzempek, P.; Svoboda, O.; Szala, M.; Taranenko, A.; Tlusty, P.; Traxler, M.; Troyan, A.; Tsertos, H.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wintz, P.; Wirth, J.; Wloch, B.; Zhilin, A.; Zinchenko, A.; Zumbruch, P.
The matter formed in central heavy-ion collisions at a few GeV per nucleon is commonly understood as resonance matter, a gas of nucleons and excited baryon states with a substantial contribution from mesonic, mostly pionic excitations. Yet, in the initial phase of the reaction the system is compressed to beyond nuclear ground state density and hence substantial modifications of the hadron properties are expected to occur. The spectral distribution of virtual photons measured in Au+Au collisions at 2.4 GeV center of mass energy indicates strong medium effects beyond pure superposition of individual NN collisions. We present multi-differential distributions of low-mass electron pairs. This radiation is remarkably well described assuming emission from a thermalized system. To gain deeper understanding of the microscopic origin of the radiation, we extracted the centrality dependent true (not blue-shifted) temperature, its azimuthal distribution, as well as mass-dependent effective slope parameter. Virtual photon spectra are confronted with available model calculations.
Nuclear Physics A 982(2019), 771
Sub-threshold strangeness production measured with HADES
Kornakov, G.; Adamczewski-Musch, J.; Arnold, O.; Arnoldi-Meadows, B.; Belounnas, A.; Belyaev, A.; Biernat, J.; Blanco, A.; Blume, C.; Boehmer, M.; Bordalo, P.; Chlad, L.; Chudoba, P.; Ciepal, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Gillitzer, A.; Golosov, O.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hoehne, C.; Holzmann, R.; Ierusalimov, A.; Ivanov, V.; Ivashkin, A.; Kaempfer, B.; Kajetanowicz, M.; Kampert, K.-H.; Kardan, B.; Khomyakov, V.; Koenig, I.; Koenig, W.; Korcyl, G.; Kornas, F.; Kotte, R.; Kozela, A.; Kubos, J.; Kugler, A.; Kunz, T.; Kurilkin, P.; Kushpil, V.; Ladygin, V.; Lalik, R.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Lykasov, G.; Mahmoud, T.; Malakhov, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Muentz, C.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Patel, V.; Pauly, C.; Pechenov, V.; Pechenova, O.; Pereira, A.; Petousis, V.; Petukhov, O.; Pfeifer, D.; Pietraszko, J.; Prozorov, A. P.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Reshetin, A.; Ritman, L.; Rodriguez-Ramos, P.; Rost, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Silva, L.; Smyrski, J.; Sobiella, M.; Spataro, S.; Spies, S.; Strikhanov, M.; Stroebele, H.; Stroth, J.; Strzempek, P.; Svoboda, O.; Szala, M.; Taranenko, A.; Tlusty, P.; Traxler, M.; Troyan, A.; Tsertos, H.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wintz, P.; Wirth, J.; Wloch, B.; Zhilin, A.; Zinchenko, A.; Zumbruch, P.
At energies below sqrt(sNN) approximate to 2.55 GeV, strange quarks cannot be produced in binary nucleon-nucleon collisions because of the higher production threshold of the lightest hadrons carrying strangeness. Hence, the investigation of sub-threshold strangeness production in heavy-ion collisions is one of the most promising probes, to access the properties of the created system, as the missing energy must be provided by the latter one. For the first time, a nearly complete set of strange particles has been reconstructed in the 40% most central Au+Au collisions at sqrt(sNN) = 2.42 GeV. The data sample includes multi-differential representations of charged and neutral particles containing strangeness (K+,-,Ks
0, φ, Λ). To achieve a better understanding of strangeness production the properties of the short-lived resonances have to be investigated. The first steps in this direction are presented here, including the reconstruction of baryon resonances using a new iterative technique, comparison to microscopic transport model calculations and interpretation of the pion transverse momentum distribution.
Nuclear Physics A 982(2019), 803
Ferromagnetic (In,Ga,Mn)As films prepared by ion implantation and pulsed laser melting
In the present work, we show the preparation of (In,Ga,Mn)As films with different Ga concentration by Mn ion implantation and pulsed laser melting. All films are confirmed to be well recrystallized by Rutherford backscattering spectrometry/channeling and to be ferromagnetic by magnetometry measurements, respectively. Their Curie temperatures depend on the Ga concentration. Our results show the perspective of ion implantation in the preparation of different III-Mn-V quaternary alloys as new members of diluted ferromagnetic semiconductors.
Keywords: Thin film; Ion implantation; Pulsed laser melting; III-V compounds
Nuclear Instruments and Methods in Physics Research B 442(2019), 31-35
Coupled dissolution-precipitation reactive transport modeling at the pore scale
Coupled dissolution-precipitation processes are of critical importance for the evolution of porosity and permeability in materials and for multiple applications, such as waste management, reservoir rocks, and corrosion. Here, we study the impact of saturation and fluid flow velocity with high spatial resolution, i.e., in the micrometer to submicrometer scale. Utilizing a time series of datasets of corroded crystal surfaces, collected using interferometry techniques, we analyze the impact of local fluid flow heterogeneity and resulting saturation variability. Systematically, the series of surface data is used (i) to constrain the initial topography for reactive transport modeling, and (ii) to compare the model vs. experimental results.
In this work, a reactive transport model is presented which simulates the complex chemical reaction of mineral dissolution/precipitation and subsequent pore-geometry evolution at a single pore scale . We used the finite element package COMSOL Multiphysics® 5.4 for the simulation, utilizing the arbitary-Lagrangian Eulerian (ALE) method for the free-moving domain boundary.
Experimental and modeling studies have shown both the spatial  and temporal  heterogeneity of reaction rates and their impact on topography evolution at the pore scale. We expect an improved predictability of reactive transport modeling by using an approach combining the heterogeneities of surface reactivity and flow velocity at the pore scale.
 Karimzadeh, L., et al., 2018. Benchmark 3D reactive transport modelling of leaching of fractured calcareous sulfide ores, in: Lottermoser, B.G. (Ed.), Aachen International Mining Symposia (AIMS 2018), Aachen, Germany, p. 88 pp.
 Fischer, C., and Luttge, A., 2018, Pulsating dissolution of crystalline matter. PNAS 115.
 Fischer, C., Kurganskaya, I., and Luttge, A., 2018, Inherited control of crystal surface reactivity. Applied Geochemistry 91, 140.
EGU General Assembly 2019, 08.-12.04.2019, Wien, Österreich
Improving fracture-flow models by experimental evidence from process tomography
Advective fluid flow transport controls the migration of radionuclides in fractured crystalline rocks. Thus, the
safety assessment of deep geological repositories in crystalline rocks relies critically on fracture flow properties
and the reliability of transport modelling approaches. Here, we focus on heterogeneity and complexity of transport
processes, typically of limited predictability. In order to tackle this issue, we suggest experimental observations by
using tomographic methods, as well as feedback with and improvement of existing transport modelling approaches.
As an example, tracer propagation through fractured crystalline rock cores from the Czech Republic (Bukov URL,
depth of 500 m below the surface), was studied in collaboration between HZDR (Germany) and UJV (Czech
Republic). Spatiotemporal data of the tracer concentration during conservative transport are based on positron
emission tomography (PET), and the underlying fracture structure was characterized by microCT-imaging. The latter
yields a structural model for reactive transport modelling. The PET data sequences provide (i) the validation of
existing simulation approaches, and (ii) serve as input or the parameterization of advanced simulation concepts.
First results underscore the outlined approach. In particular, the PET measurements clearly show preferential and
localized pathways, a feature of the process that significantly reduces the effect of interactions at the fracture
surface (and thus retention by adsorption); although repeat experiments are suggesting that the identified pathways
are not constant over the experimental periods.
As a consequence of the combined experimental and simulation approach, we expect (i) advanced model concepts
based on experimental insights and (ii) an improved understanding of reactive transport processes with a focus on
temporal heterogeneity of preferential pathways.
EGU General Assembly 2019, 08.-12.04.2019, Wien, Österreich
Photoconductive germanium antenna emitting broadband THz pulses
The spectral range between 5 and 10 THz is hardly accessible for time-resolved THz spectroscopy due to strong phonon absorption in many polar materials utilized for the generation of THz transients. We demonstrate that non-polar germanium is a promising semiconductor for a realization of a photoconductive THz emitter with a continuous spectrum spanning well above 10 THz.
Invited lecture (Conferences)
AES 2019, the 7th Advanced Electromagnetics Symposium, 24.-26.07.2019, Lisbon, Portugal
A correlation study of layer growth rate, thickness uniformity, stoichiometry, and hydrogen impurity level of ALD grown HfO2 thin films
Hafnium oxide was deposited from tetrakis(dimethylamino)hafnium (TDMAHf) and water by atomic layer deposition (ALD) on heated 400 Si wafers covered with native oxide in the temperature range from 100 C to 350 C. Optimized self-limiting ALD reaction and smallest hydrogen impurity level have been realized for a substrate temperature of 300 C. The stoichiometry of deposited films and hydrogen impurity level were measured by elastic recoil detection analysis. The hafnium to oxygen ratio showed the expected 1:2 value. Besides hydrogen, no other impurities could be detected.
Furthermore, a strong correlation between the growth rate per cycle (GPC), film uniformity and level of hydrogen impurities was observed. Based on this result, the easily accessible GPC can be used as a first indication for the hydrogen impurity level in ALD grown thin films.
Furthermore, the characterization of the crystal structure showed the appearance of some crystallites in an amorphous matrix already for a growth temperature of 250 C and a pure crystalline layer at a growth temperature of 350 C. The increased crystallinity with increasing growth temperature was attributed to a higher seed concentration and a constant crystal size.
Keywords: ALD; TDMAHf; HfO₂; growth rate per cycle; thickness uniformity; ERDA; H impurity level; GIXRD; AFM
Applied Surface Science 506(2020), 144188
- Final Draft PDF 2,1 MB Secondary publication
Simulación numérica en pilas de combustible PEMFC tipo Air-Breathing
Weber, N.; Chaparro, A.; Ferreira Aparicio, P.
Der Vortrag gibt eine Übersicht über die Simulation von Luft atmenden Brennstoffzellen.
Institutsseminar am CIEMAT, 24.04.2019, Madrid, Spanien
Maximizing magnetic field generation in high power laser–solid interactions
In order to understand the transport of fast electrons within solid density targets driven by an optical high power laser, wehave numerically investigated the dynamics and structure of strong self-generated magnetic fields in such experiments.Here we present a systematic study of the bulk magnetic field generation due to the ponderomotive current, Weibel-likeinstability and resistivity gradient between two solid layers. Using particle-in-cell simulations, we observe the effect ofvarying the laser and target parameters, including laser intensity, focal size, incident angle, preplasma scale length, targetthickness and material and experimental geometry. The simulation results suggest that the strongest magnetic field isgenerated with laser incident angles and preplasma scale lengths that maximize laser absorption efficiency. The recentcommissioning of experimental platforms equipped with both optical high power laser and X-ray free electron laser(XFEL), such as European XFEL-HED, LCLS-MEC and SACLA beamlines, provides unprecedented opportunities toprobe the self-generated bulk magnetic field by X-ray polarimetry via Faraday rotation with simultaneous high spatialand temporal resolution. We expect that this systematic numerical investigation will pave the way to design and optimizenear future experimental setups to probe the magnetic fields in such experimental platforms
Keywords: laser–plasmas interaction; high energy density physics; X-ray free electron laser probi
High Power Laser Science and Engineering 7(2019)e22
Kinetic Simulations of Target Heating, Ionization and Micro-Explosion with High Intensity XFEL Beams
Huang, L.; Hartley, N.; Hau-Riege, S.; Inubushi, Y.; Kamimura, N.; Katagiri, K.; Kodama, R.; Kon, A.; Makita, M.; Matsuoka, T.; Nakajima, S.; Pikuz, T.; Rode, A.; Rohatsch, K.; Sagae, D.; Schuster, A.; Tono, K.; Lu, W.; Yabuuchi, T.; Ozaki, N.; Kraus, D.; Cowan, T.
High intensity X-ray Free Electron Lasers (XFEL) are an ideal tool to heat materials directly and isochorically, which can cause them to be modified and damaged irreversibly. During XFEL-matter interactions, the energy of an XFEL beam will be mainly absorbed by photoionization, creating numerous high-energy photo- and Auger electrons. Modelling this process is quite complex since both atomic physics and plasma physics are involved. Atomic collisional-radiative (CR) codes such as FLYCHK are widely used to simulate such processes. However, the CR codes typically assume local thermodynamic equilibrium (LTE) and are limited to zero dimension.
In order to understand the sample damaging mechanisms, we performed two-dimensional kinetic particle-in-cell simulations with radiation transport (PIC-RT) to retrieve the temporal processes of XFEL-matter interactions. The dynamics of XFEL-Matter interactions can roughly divide into three different time scales: 1) electron heating and photoionization by XFEL in ~ 10 fs ; 2) collisional heating and ionization by high-energy photo- and Auger electrons with several keV energy in tens of fs to sub-ps; and 3) collective hydrodynamic explosion driven by ~ TPa thermal pressure from ~100 fs to nanoseconds.
The simulation results are compared to our recent experiment that a variety of samples were irradiated by Japanese XFEL SACLA with intensities on the order of 10^20 W/cm^2. The post-analysis of the irradiated samples showed that large holes with radius sizes more than one order of magnitude higher than the XFEL spot were created for metallic samples. The hole size is also much larger than the stopping range of high energy electrons. According to our PIC-RT simulations, we attribute the generation of such large holes to the micro-explosion process. Kinect simulation of the hole generation with multiple time scales is also useful and complementary to understand the change of X-Ray diffraction pattern in the experiment that infers significant material structural change on femtosecond timescales.
Keywords: XFEL; Pump-Probe Experiment; Kinect Simulations; Radiation Transport
SPIE Optics + Optoelectronics, 01.-04.04.2019, Prague, Czech Republic
Uncertainty limits of range verification in proton therapy by means of prompt gamma-ray timing (PGT)
Range verification during clinical treatments is a key for further improving the precision and for reducing the normal-tissue toxicity of radiotherapy with proton beams. In spite of the breakthrough achieved with IBA’s knife-edge slit camera, capable of imaging single beam spots in pencil-beam scanning (PBS) treatment fractions delivered to cancer patients, there are ongoing activities aiming at systems distinguished by lower expense, lower weight, easier integration in the therapy facility, and potentially higher precision. In this context, OncoRay’s Prompt Gamma-Ray Timing (PGT) technology has been further explored with the focus on quantifying uncertainty contributions in potential clinical applications. Experimental data acquired in the treatment room of the University Proton Therapy Dresden (UPTD) during single pencil beam delivery to a polymethyl methacrylate (PMMA) target with arbitrary air cavities have been carefully analyzed. Besides the limited number of events the instable phase relation between proton-beam bunches and accelerating RF turned out to be the weakest point at the given facility. Technical means for monitoring this phase relation at a time scale of split seconds without touching the medical beamline are being developed and will be discussed in the paper. Altogether PGT could provide range verification with 3 mm accuracy at PBS spot level, if (at least) eight PGT detection units are deployed. Technically even a larger number of detectors could be arranged around the nozzle, which would further reduce the uncertainty.
Keywords: proton therapy; treatment verification; range verification; prompt gamma ray; prompt gamma-ray imaging; PGI; prompt gamma-ray timing; PGT
2019 IEEE Nuclear Science Symposium and Medical Imaging Conference, 26.10.-02.11.2019, Manchester, Great Britain
Fast 2D laser-induced fluorescence spectroscopy mapping of rare earth elements in rock samples
Due to the rapidly increasing use of energy-efficient technologies, the need for complex materials containing rare earth elements (REEs) is steadily growing. The high demand for REEs requires the exploration of new mineral deposits of these valuable elements, as recovery by recycling is still very low. Easy-to-deploy sensors technologies featuring high sensitivity to REE are required to overcome limitations by traditional techniques such as X-ray fluorescence. We demonstrate the ability of laser-induced fluorescence (LIF) to detect REEs rapidly in relevant geological samples. We introduce two-dimensional LIF mapping to scan rock samples from two Namibian REE deposits and cross-validate the obtained results by employing mineral liberation analysis (MLA) and hyperspectral imaging (HSI). Technique-specific parameters, such as acquisition speed, spatial resolution, and detection limits, are discussed and compared to established analysis methods. We also focus on the attribution of REEs occurrences to mineralogical features, which may helpful for the further geological interpretation of the deposit. This study sets the basis for the development of a combined mapping sensor for HSI and 2D LIF measurements, which could be used for drill-core logging in REE exploration as well as in recovery plants.
Keywords: laser-induced fluorescence; rare earth elements; imaging sensor; reflectance spectroscopy; optical spectroscopy
Sensors 19(2019), 2219
Successful immunotherapy and irradiation in a HIV-positive patient with metastatic Merkel cell carcinoma
This case report presents a HIV-positive 60-year old male with Merkel cell carcinoma of his right forearm and pulmonary sarcoidosis, who, after excisions and irradiations of the primary tumour site and subsequent lymph node metastases developed distant metastases. He received radiotherapy to symptomatic mediastinal lymph node metastases followed by Doxorubicin and, after two cycles, by the PD-1 Inhibitor Pembrolizumab due to mixed response. Re-staging showed a para-mediastinal, radiotherapy-induced pneumonitis, which was treated by prednisolone due to clinical symptoms. In September 2017, the patient developed a solitary lymph node metastasis next to the right atrium, for which he received stereotactic radiotherapy. The systemic treatment with Pembrolizumab was replaced by the PD-L1 inhibitor Avelumab and is being continued since. The patient has been in complete remission for one year now and the HIV-infection is well-controlled.
Keywords: Merkel cell carcinoma; Avelumab; Immunotherapy; Pembrolizumab; Immune checkpoint Inhibition; Radiotherapy; HIV; Sarcoidosis
Clinical and Translational Radiation Oncology 15(2019), 42-45
Implementierung von CT-basierten Schwächungskarten am PET/MRT für die Bestrahlungsplanung von Prostatakrebspatienten
Das Ziel der Einbindung von PSMA-PET/MRT-Daten in die Bestrahlungsplanung (RT) von Prostatakrebspatienten ist es, die Tumorabgrenzung zu verbessern und eventuell die
Dosisverschreibung zu individualisieren. Da diese Scans in Behandlungsposition aufgenommen werden müssen, ist eine Schwächungskorrektur für die RT-Positionierungshilfsmittel erforderlich. Die hier vorgestellte Methode implementiert CT-basierte Schwächungskarten von RT-Positionierungshilfsmitteln in die Rekonstruktion von PET/MRT-Bildern und wird anschließend hinsichtlich der Genauigkeit ihrer Schwächungskorrektur analysiert.
Material & Methode:
Eine RT-Tischplattenauflage (hausinterne Herstellung) wurde an einem CT (SOMATOM Definition Flash, Siemens) mit einer Röhrenspannung von 120 kV und einem effektiven Röhrenstrom von 320 mAs gescannt. Basierend auf den CT-Bildern wurde eine Schwächungskarte der RT-Tischplattenauflage berechnet. Anschließend wurde die RT-Tischplattenauflage auf den Patiententisch des PET/MRTs (Biograph mMR, Siemens) montiert. PET-Messungen mit (RT-Scan) und ohne (Referenzscan) RT-Tischplattenauflage wurden mithilfe eines aktiven, homogen gefüllten 68Ge-Phantoms (32 MBq, 10 Minuten Scanzeit) aufgenommen. Beide Scans wurden mit identischen Rekonstruktionsparametern rekonstruiert. Die Rekonstruktion des RT-Scans wurde mit (korrigiert) und ohne (unkorrigiert) Implementierung der Schwächungskarte der RT-Tischplattenauflage durchgeführt. Die PET-Aktivitäten der RT- und Referenzscans wurden verglichen, indem die Mittelwerte der ROIs im Abstand von 10 Schichten entlang des Phantoms in Längsrichtung ausgewertet wurden.
Tabelle 1 zeigt den Vergleich der gemessenen PET-Aktivitäten des unkorrigiertem und des korrigiertem RT-Scans mit dem Referenzscan. Der mittlere prozentuale Unterschied zwischen dem unkorrigierten RT- und dem Referenzscan beträgt 4,8%. Zwischen dem korrigierten RT- und dem Referenzscan wurde eine mittlere prozentuale Differenz von 0,5% ermittelt.
Die PET-Signalschwächung durch die RT-Tischplattenauflage ist mit durchschnittlich 5% klinisch relevant und kann mithilfe von CT-basierten Schwächungskarten erfolgreich korrigiert werden. Dieser Schritt ist Voraussetzung für die Integration von PET/MRT-Daten in die Bestrahlungsplanung.
50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) e. V., 18.-21.09.2019, Stuttgart, Deutschland
Midostaurin abrogates CD33-directed UniCAR and CD33-CD3 bispecific antibody therapy in acute myeloid leukemia
Combinatory therapeutic approaches of different targeted therapies in acute myeloid leukemia (AML) are currently under preclinical and early clinical investigation. To enhance anti-tumor effects, we combined tyrosine kinase inhibitor (TKI) Midostaurin and T cell-mediated immunotherapy directed against CD33. We show that clinically relevant concentrations of Midostaurin abrogate T cell-mediated cytotoxicity both after activation with bispecific antibodies (bsAbs) and chimeric antigen receptor (CAR) T cells. This information is of relevance for clinicians exploring T cell-mediated immunotherapy in early clinical trials. Given the profound inhibition of T cell functionality and anti-tumor activity, we recommend favoring specific fms-like tyrosine kinase 3 (FLT3) TKIs for further clinical testing of combinatory approaches with T cell-based immunotherapy.
British Journal of Haematology 186(2019)5, 735-740
T Cell Based Immunotherapy of Acute Myeloid Leukemia is Abrogated by the Tyrosine Kinase Inhibitor Midostaurin
Fasslrinner, F.; Arndt, C.; Koristka, S.; Feldmann, A.; Altmann, H.; von Bonin, M.; Schmitz, M.; Bornhäuser, M.; Bachmann, M.
Induction chemotherapy is currently the standard of care for treatment of acute myeloid leukemia (AML) with 5-year disease-free survival of 33%. Given the large proportion of non-responders and relapsed patients, novel adjuvant drugs are urgently needed. Especially, targeted therapies including small molecules and T cell based immunotherapies are under intensive preclinical and clinical investigation. The tyrosine kinase inhibitor Midostaurin recently received approval for treatment of FLT3-positive AML. In addition to chemotherapy, it significantly deepens remission rates and improves overall survival of patients. In light of future combinatorial approaches, simultaneous application of different targeted therapies should theoretically augment anti-tumor effects.
Therefore, we questioned whether Midostaurin could strengthen cytotoxic effector mechanisms of redirected switchable UniCAR T cells or bispecific antibody-redirected T cells against primary AML cells.
By performing in vitro co-cultivation assays with patient-derived AML cells, it was shown that Midostaurin concentrations ≥ 1 µM significantly impair the activation, proliferation, cytokine production and cytotoxicity of autologous and allogeneic T cells after engagement via bsAb or the UniCAR system. Data could be also verified in a solid tumor model.
At concentrations ranging between 0.1 and 10 M, it was shown that Midostaurin and its metabolites are indeed able to inhibit several components of the TCR signaling pathway including LcK, Zeta-chain-associated protein kinase 70 (ZAP-70), mitogen-activated protein kinase (MAPK) and Protein kinase C (PKC) in vitro. Therefore, we argue that the observed T cell inhibition by Midostaurin in our studies is caused by the inhibition of several of these kinases. This hypothesis is supported by the work of two individual research groups that were able to show synergistic effects by combining FLT3 selective TKIs with different T cell-based immunotherapies. Because Midostaurin through concentrations above ≥ 1 µM have been observed in earlier performed dose finding studies, we speculate that current standard Midostaurin therapy will inhibit T cell function in vivo.
In summary, our data underline that combination of Midostaurin and T cell-based immunotherapies in FLT3-positive AML patients is not recommended due to the suppressive effect of Midostaurin on T cells. Therefore, more selective TKI or other small molecules should be chosen to avoid impairment of T cell functions.
1st European CAR T Cell Meeting, 14.-16.02.2019, Paris, France
Integriertes Management und Publikation von wissenschaftlichen Artikeln, Software und Forschungsdaten am Helmholtz-Zentrum Dresden-Rossendorf (HZDR)
Mit dem Ziel, das Publizieren von Artikeln, Forschungsdaten und wissenschaftlicher Software gemäß den FAIR-Prinzipien 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.
Zusammenfassend werden unsere Erfahrungen im integrierten Publikationsmanagement für Artikel, Forschungsdaten und Forschungssoftware vorgestellt. Es wird ein Ausblick auf die nächsten Schritte und Aufgaben gegeben und Aspekte der Integration im Kontext der europäischen und nationalen Forschungsorganisationen herausgearbeitet.
Keywords: Publikationsmanagement; Forschungsdaten; Forschungssoftware; publication management; research data; research software; FAIR; Open Access
Contribution to proceedings
WissKom2019: Forschungsdaten - Sammeln, sichern, strukturieren, 04.-06.06.2019, Jülich, Deutschland
WissKom2019: Forschungsdaten - Sammeln, sichern, strukturieren. 8. Konferenz der Zentralbibliothek, Forschungszentrum Jülich, Jülich: Forschungszentrum Jülich, 978-3-95806-405-8, 167-177
Invited lecture (Conferences)
WissKom2019 – Forschungsdaten: Sammeln, sichern, strukturieren. 8. Konferenz der Zentralbibliothek, Forschungszentrum Jülich, 04.-06.06.2019, Jülich, Deutschland
X-ray radioscopic visualization of bubbly flows injected through a top submerged lance into a liquid metal
We present an experimental study on the formation and behaviour of a liquid metal bubbly flow arising from a downward gas injection through a top submerged lance (TSL). A visualization of the bubble dynamics was achieved by the X-ray radiography combined with high-speed imaging. The experiments were carried out in a parallelepiped container (144×144×12 mm3) using GaInSn, a ternary alloy that is liquid at room temperature. The gas flow rate Qgas was adjusted in a range between 0.033 and 0.1 l/s. Three different injection positions were considered with respect to the submergence depth L. X-ray images allow for a characterization of the flow regimes and provide the properties of the individual bubbles such as size, shape and trajectory. Formation and entrainment of smaller gas bubbles are observed at the free surface. These small bubbles can be trapped in the fluid for a long time by recirculation vortices. Bubbles size distributions are determined for different Qgas. The bubble detachment frequency is measured as a function of Qgas and L. The results are compared with previously published data for water. The X-ray radiography offers an effective method for determining the local void fraction and allows for an estimation of the bubble volume.
Keywords: Two phase flow; X-ray radiography; Top submerged lance
Metallurgical and Materials Transactions B 51B(2019), 124-139
- Final Draft PDF 918 kB Secondary publication
An oligo-His-tag of a targeting module does not influence its biodistribution and the retargeting capabilities of UniCAR T cells
Recently, we established the controllable modular UniCAR platform technology to advance the efficacy and safety of CAR T cell therapy. The UniCAR system is composed of (i) target modules (TMs) and (ii) UniCAR armed T cells. TMs are bispecific molecules that are able to bind to the tumor cell surface and simultaneously to UniCAR T cells. For interaction with UniCAR T cells, TMs contain a peptide epitope sequence which is recognised by UniCAR T cells. So far, a series of TMs against a variety of tumor targets including against the prostate stem cell antigen (PSCA) were constructed and functionally characterised. In order to facilitate their purification all these TMs are expressed as recombinant proteins equipped with an oligo-His-tag. The aim of the here presented manuscript was to learn whether or not the oligo-His-tag of the TM influences the UniCAR system. For this purpose, we constructed TMs against PSCA equipped with or lacking an oligo-His-tag. Both TMs were compared side by side including for functionality and biodistribution. According to our data, an oligo-His-tag of a UniCAR TM has only little if any effect on its binding affinity, in vitro and in vivo killing capability and in vivo biodistribution.
Scientific Reports 9(2019)1, 10547
Eulerian/Lagrangian formulation for the elasto-capillary deformation of a flexible fibre
The capillary-induced bending of flexible fibres, a process also known as elasto-capillary deformation, is central to a variety of industrial and non-industrial applications, among which stand out textile flotation, stabilization of emulsions, micro-folding of elastic structures, and clogging of feather fibres by oil droplets. A consistent formulation for the direct numerical simulation of a flexible fibre interacting with a fluidic interface is presently suggested. The fibre is geometrically decomposed into a chain of spherical beads, which undergo stretching, bending, and twisting. interactions. The capillary force, acting at the three-phase contact line, is calculated using a ternary diffuse-interface model. In a first stage, the fibre deformation model and the ternary diffuse-interface model are validated against theoretical solutions. In a second stage, the two- and three-dimensional elasto-capillary bending of a fibre by an immersed droplet are numerically investigated. Partial wrapping and complete encapsulation could be simulated. The results show that the fibre curvature increases linearly with the square of the elasto-capillary length, for both low and large structural deformation.
Keywords: Elasto-capillary deformation; fibre at fluidic interface; ternary diffuse interface model; direct numerical simulation; droplet encapsulation
Journal of Computational Physics 409(2020), 109324
- Final Draft PDF 4,3 MB Secondary publication
Fluid Flow and Transport Phenomena in Liquid Metal Batteries
Fluid flows in liquid metal batteries can be generated by a number of effects. We start with a short overview of different driving mechanisms and then address questions specific to the metal pad role instabilities in three-layer systems. Besides introducing a term accounting for the interfacial tension that should be considered for smaller cells, we focus on the role of the conductivity distribution in the cell.
Keywords: Liquid metal batteries; metal pad roll; sloshing
Contribution to proceedings
11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich, 188-192
11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich
Mass Transport in the Positive Electrode of a Liquid Metal Battery
Personnettaz, P.; Landgraf, S.; Nimtz, M.; Weber, N.; Weier, T.
Liquid metal electrodes are one of the key components of different electrical energy storage technologies. The understanding of transport phenomena behind liquid electrodes is mandatory in order to ensure efficient operation, however it would certainly gain by further investigations. In the present study we focus our attention on the positive electrode of a Li||Bi liquid metal battery. Starting from a real experimental setup, we investigate mass transport with numerical simulations. During the charge of the cell, compositional convection becomes apparent. The time evolution of the fluid flow and the flow structure are studied. First results on compositional convection are presented, highlighting its capability to affect the flow in the positive electrode.
Keywords: electrorefining; liquid electrode; liquid metal batteries; mass transport; solutal convection
Contribution to proceedings
11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, France
Mass Transport in the Positive Electrode of a Liquid Metal Battery
11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, France
Oscillating hydrogen bubbles at Pt microelectrodes
The dynamics of hydrogen bubbles produced via electrolysis in acidic electrolytes is studied in a combination of experiments and numerical simulations.
A transition from monotonous to oscillatory bubble growth is observed after 2/3 of the bubble lifetime, if the electric potential exceeds -3V. This work analyzes characteristic features of the oscillations in terms of bubble geometry, the thickness of the microbubble carpet and the oscillation frequency. An explanation of the oscillation mechanisms is provided by the competition between buoyancy and electric force, the magnitude of which depends on the carpet thickness. Both the critical carpet thickness at detachment and the oscillation frequencies of the bubble as predicted by the model agree well with the experiment.
Keywords: electrolysis; hydrogen bubble; oscillations; charged bubble; electric force
Physical Review Letters 123(2019)21, 214503-1-214503-6
Integral multi-scenario robustness evaluation of anatomical robust optimization in head and neck
Classical robust optimization considers uncertainties in patient setup and particle range. Usually plan robustness is evaluated from calculation of perturbed dose distributions based on the planning CT, without considering potential anatomical changes that may occur during the treatment course. Our aim was to compare the overall plan robustness of classical robust optimization (cRO) with the recently proposed anatomical robust optimization (aRO) based on an integral multi-scenario evaluation, considering all types of uncertainties including anatomical variations.
Datasets for 20 head and neck cancer patients, including a planning CT and weekly control CTs, were analyzed. Two intensity-modulated proton therapy (IMPT) plans were calculated: cRO, using solely the planning CT, and aRO, including additionally the first two control CTs in the plan optimization. For the robustness analysis, perturbed dose distributions with random setup uncertainties and fixed range uncertainty values of -3.5%, 0% and +3.5% were generated, drawing for each fraction n a random number from a Gaussian distribution around 0 mm with a standard deviation of 2.5 mm for the isocenter shift in each cardinal direction (xn, yn, zn). Moreover, in each fraction n the correspondent weekly control CT was used to consider the anatomical changes during therapy. 33 single-fraction perturbed doses were calculated and summed to generate a perturbed whole-treatment dose distribution. The procedure was repeated 10 times for each of the three range uncertainty values, resulting in 30 perturbed dose distributions per plan (Figure 1).
Both nominal plans fulfilled the clinical objective for target coverage (D98% ≥ 95% of the prescribed dose). The median values calculated from the 30 perturbed dose distributions for each patient showed a reduction in the target coverage for the cRO plan, with mean (minimum) values of 94.9% (88.1%) and 95.4% (89.3%) for the low- and high-risk CTV, respectively, in comparison with 96.6% (92.0%) and 96.8% (93.6%), respectively, for aRO (Figure 2a). The variation in CTV coverage between the 30 scenarios, i.e. the width of the perturbed dose distributions, was found to be larger for cRO plans, with median (maximum) values of 1.9 (8.3) and 1.4 (5.6) for low- and high-risk CTV, respectively, in comparison with 1.4 (3.4) and 0.9 (5.2) for aRO plans, respectively. Moreover, the cRO case showed reduced robustness in comparison with aRO for some patients, where certain scenarios violate the clinical objective, as shown in Figure 2b.
Anatomical robust optimization showed superior plan robustness in comparison with the classical approach in a comprehensive multi-scenario evaluation. Anatomical variations play an important role in the overall plan robustness together with setup and range uncertainties, therefore their effect should not be underestimated or neglected.
ESTRO 38, 26.-30.04.2019, Mailand, Italien
Abstract in refereed journal
Radiotherapy and Oncology 133(2019)Sup 1, S488-S489
Quantification of plan robustness against different uncertainty sources for classical and anatomical robust optimized treatment plans in head and neck cancer proton therapy
Objective: Classical robust optimization (cRO) in intensity-modulated proton therapy (IMPT) considers isocenter position and particle range uncertainties; anatomical robust optimization (aRO) aims to consider additional non-rigid positioning variations. This work compares the influence of different uncertainty sources on the robustness of cRO and aRO IMPT plans for head and neck squamous cell carcinoma (HNSCC).
Methods: Two IMPT plans were optimized for twenty HNSCC patients who received weekly control CTs (cCT): cRO, using solely the planning CT, and aRO, including two additional cCTs. The robustness of the plans in terms of clinical target volume (CTV) coverage and organ at risk (OAR) sparing was analyzed considering stepwise the influence of (1) non-rigid anatomical variations given by the weekly cCT, (2) with fraction-wise added rigid random setup errors and (3) additional systematic proton range uncertainties.
Results: cRO plans presented significantly higher nominal CTV coverage but are outperformed by aRO plans when considering non-rigid anatomical variations only, as cRO and aRO plans presented a median target coverage (D98%) decrease for the low-risk/high-risk CTV of 1.8/1.1 percentage points (pp) and -0.2pp/-0.3pp, respectively. Setup and range uncertainties had larger influence on cRO CTV coverage, but led to similar OAR dose changes in both plans. Considering all error sources, 10/2 cRO/aRO patients missed the CTV coverage and a limited number exceeded some OAR constraints in both plans.
Conclusions: Non-rigid anatomical variations are mainly responsible for critical target coverage loss of cRO plans, whereas the aRO approach was robust against such variations. Both plans provide similar robustness of OAR parameters.
Advances in knowledge: The influence of different uncertainty sources was quantified for robust IMPT HNSCC plans.
Keywords: Robust optimization; robustness analysis; head and neck cancer; proton therapy
British Journal of Radiology (2020), 20190573
Bestimmung der Gas-Flüssigkeits-Grenzfläche in Anstaupackungen mittels ultraschneller Röntgentomographie
Durch die alternierend angeordneten Packungslagen mit unterschiedlichen geometrischen Oberflächen bilden sich in Anstaupackungen abhängig von den Betriebsbedingungen Filmströmung und Sprudelschicht gleichzeitig aus. Der intensive Kontakt zwischen der Gas- und Flüssigkeitsphase in den sprudelnden Bereichen der Anstaupackung führt zu einer Trenneffizienzsteigerung von bis zu 30 % im Vergleich zu konventionell gepackten Kolonnen . Zur Abschätzung der Beiträge der jeweiligen Bereiche mit unterschiedlichen Strömungsregimen zur Gesamttrennleistung ist die Kenntnis der Gas-Flüssigkeits-Grenzfläche erforderlich. Die Grenzfläche kann mittels ultraschneller Röntgentomographie bestimmt werden, welche die dynamischen Strömungsstrukturen mit einer Bildrate von 1000 Bildern pro Sekunde erfasst. Mithilfe eines modifizierten Level-set-Algorithmus wird die Phasengrenze zwischen Gas einerseits und Flüssigkeit sowie Metallpackung andererseits in den Querschnittsbildern detektiert (Abb.1).
In diesem Beitrag werden sowohl die Methodik zur Bestimmung der Phasengrenzfläche als auch Ergebnisse für unterschiedliche Gas- und Flüssigkeitsbelastungen bei verschiedenen Packungskombinationen präsentiert.
Wir danken der DFG für die finanzielle Unterstützung des Kooperationsprojekts "Experimentelle und theoretische Untersuchung der Fluiddynamik und des Stofftrennverhaltens von Anstaupackungen" (KE 837/26-1, HA 3088/10-1).
 M. Jödecke, T. Friese, G. Schuch, B. Kaibel, H. Jansen, Institution of Chemical Engineers Symposium Series, Institution of Chemical Engineers, 2006, Vol.152, pp. 786–789.
Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Deutschland
Partieller Einsatz von teilweise gefluteten Packungen
Ein Weg zur Reduzierung des hohen Energiebedarfs thermischer Trennverfahren ist die Prozessintegration. Ein Beispiel dafür ist die Integration verschiedener Strömungsformen in einem Trennapparat durch den Einsatz von Anstaupackungen, wodurch eine Erhöhung der Trennleistung im Vergleich zu Strukturpackungen erzielt wird. Anstaupackungen bestehen aus zwei alternierend angeordneten Lagen von industriell verfügbaren Standardpackungen mit unterschiedlichen spezifischen Oberflächen. Die untere Anstaulage weist eine geringere Lastgrenze als die darüber angeordnete Abscheidelage auf, wodurch im Betrieb zwischen den Flutpunkten
beider Lagen ein heterogenes Strömungsmuster entsteht. Dabei bildet sich in der gezielt gefluteten Anstaulage eine bis in die Abscheidelage hineinreichende Sprudelschicht, die durch eine intensive Phasenvermischung und große
Phasengrenzflächen geprägt ist.
Um die Leistungscharakteristik von Anstaupackungen mit der von anderen Einbauten vergleichen zu können, wurde in einer vorherigen Arbeit  ein rate-based-Modell entwickelt, welches die Auswirkungen der belastungsabhängig auftretenden Regime in Anstaupackungen berücksichtigt. Basierend auf experimentellen Daten zur CO2-Absorption mit wässrigen Aminlösungen im Technikumsmaßstab sowie tomographischen Untersuchungen wurden Abhängigkeiten der modellspezifischen Parameter identifiziert und anschließend regimespezifisch ins Modell implementiert. Mittels Prozesssimulationen der CO2-Absorption aus Abgasen gasbefeuerter Kraftwerke im industriellen Maßstab werden im Rahmen dieser Arbeit Anstaupackungen und Strukturpackungen hinsichtlich der benötigten Kolonnenabmessungen und des zu überwindenden Druckverlustes verglichen. Um eine abschließende Bewertung durchzuführen, wurden mithilfe von Aspen Process Economic AnalyzerTM die Anlagen- und Betriebskosten für die CO2-Abscheidung bestimmt. Zusätzlich wurde zur Ermittlung eines optimalen Designs der Einfluss der wesentlichen Geometrieparameter von Anstaupackungen auf die Kosten untersucht.
 S. Flechsig, J. Sohr, M. Schubert, U. Hampel, E.Y. Kenig, Chem. Eng. Trans., 2018, 69, 169-174, DOI: 10.3303/CET1869029.
Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Deutschland
Mass transfer and electrolyte flow during electrodeposition on a conically shaped electrode under the influence of a magnetic field
The electrodeposition of copper on a conically shaped diamagnetic electrode was studied under the influence of a vertical magnetic field. Numerical simulations combined with measurements of the velocity and the concentration field were conducted to provide understanding of the influence of the Lorentz force on the deposition process. The secondary flow caused by the magnetic field is directed downward along the cone surface and thus supporting conical growth. Since the cathode is placed at the bottom of the electrochemical cell, natural convection is counteracting the influence of the Lorentz force. However, the different time scales of both forces involved allow to utilize the beneficial influence of the Lorentz force, e.g. in pulsed deposition regimes.
Keywords: copper electrodeposition; magnetic field; surface-structured electrode; Mach-Zehnder interferometry; shadowgraphy; numerical simulation
Journal of Electroanalytical Chemistry 842(2019), 203-213
- Final Draft PDF 1,9 MB Secondary publication
Degradation of natural uranium containing micro-mineral phases: Implications to contaminats transport at abandoned mining sites
In this work a combination of multiple synchrotron and laboratory based micro-techniques is utilized to unveil the speciation, heterogeneities and degradation of uranium (U) micro-mineral phases accumulated on rock outcrop from natural U deposit area. The investigated system is sampled from the abandoned Krunkelbach U mine in Southern Germany with 2-3 km surrounding area which represents a natural analogue site with an unique accumulation of U minerals suitable for investigations of potential mobilization-immobilization processes expected in a real spent nuclear fuel repository. A specific feature of the site is the occurrence of more than forty secondary U minerals, from uraninite, mixed U oxy-hydroxides to uranyl silicates, representing a wide scale of U ore weathering events. Available data on the age of the secondary U mineralization indicates that oxidizing processes at the site started some 340,000 years ago and continues up to date. Several phases close to Cu(UO2)2(PO4)2-x(AsO4)x·8H2O are identified on 1×2 mm2 area with presumably older, more evenly distributed uranyl silicate and uranyl tungstate mineralization. Based on a multi-technique investigation 10-200 μm Cu(UO2)2(PO4)2-x(AsO4)x·8H2O particles with widely varying arsenic-phosphorus (As-P) content are analyzed. The evidences of a degradation on some zones of selected crystals are found which are associated with higher As content. This observation can be apparently attributed to different degradation properties of the mixed As-P phases depending on As-P ratio and originate from drastically different solubility properties of Cu(UO2)2(PO4)2·8H2O and Cu(UO2)2(AsO4)2·8H2O species. The conditions for preferential formation of As rich Cu(UO2)2(XO4)2·8H2O [X=As, P] phases and its possible role on U transport in environment under oxidizing conditions are discussed.
21st Mendeleev Congress on General and Applied Chemistry, 09.-13.09.2019, Saint Petersburg, Russia
Multidimensional fluid mixing study during an asymmetric injection of cold water in the primary side of a generic PWR KONVOI with ATHLET 3.1A
The presented paper gathers the insights obtained during the study of the multidimensional fluid mixing in the reactor pressure vessel (RPV) during an asymmetric injection of cold or overcooled water in the primary side of a generic German PWR KONVOI reactor by means of the thermal-hydraulic system code ATHLET 3.1A. With this aim, the paper provides first an overview on the selection procedure of the accident scenarios to be studied together with the plant model development, with special emphasis on the pseudo multidimensional RPV configuration. Later on the fluid mixing study in the RPV is performed during an overcooling transient by means of two different developed vessel configurations and the obtained results are assessed against experimental data from analogous tests carried out at the ROCOM test facility, showing good agreement to each other.
Contribution to proceedings
50th Annual Meeting on Nuclear Technology (AMNT) 2019, 07.05.2019, Berlin, Germany
50th Annual meeting on Nuclear Technology (AMNT) 2019, 07.-08.05.2019, Berlin, Germany
Accelerated time-of-flight scatter correction for whole-body PET
Utilization of Time-Of-Flight (TOF) information allows to improve image quality and convergence rate in PET image reconstruction. In order to obtain quantitatively correct images accurate scatter correction (SC) is required that accounts for the study-specific scatter time distribution.
The currently accepted TOF-SC gold standard - the TOF extension of the single scatter simulation approach (TOF-SSS), see  - is computationally demanding and can substantially slow down the reconstruction which becomes a substantial problem in whole-body investigations. On the other hand, the accuracy of existing simplified TOF-SC algorithms is limited in many cases. We have developed a new TOF-SC algorithm in order to improve this situation.
Our TOF-SC method is based on a separate estimation of scatter spatial distribution (via SSS) and scatter time distribution via a dedicated fast algorithm. The key idea of the algorithm is the use of an immediate scatter approximation (ISA) for scatter time distributions calculation. The underlying assumption is that for this calculation a distinction between the emission point from which the annihilation event originates and actual scatter point is not crucial.
The proposed approach was evaluated in phantom measurements providing challenging high activity contrast conditions as well as in representative clinical patient data sets.
The reconstructed images are in excellent quantitative agreement with those obtained with TOF-SSS while scatter estimation time was reduced by a factor of four and overall reconstruction time by a factor of two in whole-body studies, even when using a listmode reconstruction not optimized for speed.
Our results show that ISA is a viable alternative to TOF-SSS offering a factor of four TOF scatter estimation acceleration without compromising the image quality.
 C. C. Watson, Extension of Single Scatter Simulation to Scatter Correction of Time-of-Flight PET, IEEE Transations Nucl. Sci., vol. 54(5), pp. 1679–1686, 2007
Keywords: PET; TOF; TOF-SC; TOF-SSS; ISA
57. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 03.-06.04.2019, Bremen, Deutschland
Predictive Geometallurgy- State of the Art
The 45 minutes talk gives a brief overview of the approach of the Helmholtz Institute Freiberg for Resource Technology, followed by an introduction into Geometallurgy, Predictive Geometallurgy respectively. From the analytical perspective there will be a focus on SEM based automated image analysis. This data is the basis for further data processing, statistical assesment and interpretations. Depending on data availability, operational stage (exploration extraction) different levels of geometallurgical models can be created. This will be illustrated in case studies, showing the work flow and result for the development of 1) 3D resource potential model of a historic tailings dam to recover Sn, 2) Methodology for mineralogical deportment prediction of In as a by- product from complex ore types, 3) 3D first order geomet model of a primary deposit to recover PGE as by product
Keywords: Geometallurgy; predictive geometallurgical model; SEM based automated mineralogy; data analysis
Invited lecture (Conferences)
InRec Stakeholder Meeting (Geometallurgy applied to industrial Mineral operations), 24.-25.04.2019, Trondheim, Norway
Geostatistical Compositional Analysis of Regional Geochemical Stream Sediments of West Java, Indonesia
As analytical tools evolve, more geochemical data are obtained so that eﬀective and robust tools are demanded for capturing detailed information of underlying geological processes such as alteration, mineralization and weathering. The data are formed by a number of elements, whose concentrations are interdependent due to the fact that their total sum is bounded to a constant (e.g. 100%). Classical statistical analysis of this type of data may provide misleading results because it does not consider the closure eﬀects: for instance, one of the correlation coeﬃcients will always be negative regardless of whether the two elements with negative correlation are incompatible or not. Consequently, methods employing variance cannot be used on the raw dataset. To manage this problem, one can adopt Compositional Data Analysis (CoDa) which acknowledges the compositional nature of the data.
In the last decade, CoDa has been widely applied to geochemical data. Thus, combined with geological information, we apply CoDa to the regional geochemical stream sediment data of West Java to address our understanding of the underlying geological processes of the area. The ﬁrst process carried out is a log-ratio transformation to eliminate both constant-sum constraints and non-negativity problems. Then to distinguish features in the data a Principal Component Analysis (PCA) can be performed. Here we can get linear components that have a large eﬀect on variations in the data. The ﬁnal stage is the spatial estimation of important PCA components through experimental variogram calculation, variogram modeling, and geostatistical estimation. The interpolated maps can be back-transformed to obtain maps of the original components. In this way, the results will not violate the compositional nature of the data, while spatially representing the captured processes.
Keywords: Geochemical exploration; Geology of Java; Mining
HAGI-IAGI-IAFMI-IATMI Joint Convention 2019, 25.-28.11.2019, Yogyakarta, Indonesia
Mid-Treatment Gd-EOB-DTPA-Enhanced MRI and Interleukin 6 Cytokine as Biomarkers of Radiation-induced Liver Toxicity in Metastatic Liver Patients
Purpose: In the era of precision medicine and personalized radiation treatment (RT), there is an ever-growing need to find predictive biomarkers of treatment response in patients. Here we investigate the potentials of using mid-treatment MR images and inflammatory cytokines as biomarkers of liver toxicity.
Method and Materials: Eleven intrahepatic metastatic patients who had proton stereotactic body radiotherapy (SBRT) to the liver lesion were retrospectively analyzed. Two Gd-EOB-DTPA (a hepatobiliary-directed contrast agent)-enhanced MR scans as well as three inflammatory cytokines (interleukin 6 [IL-6], IL-8, and tumor necrosis factor α [TNF- α]) were acquired during the RT course. Deformable image registrations were done among mid-treatment (fx4 and 5) MR images and the planning CT. MR signal changes and delivered dose were then calculated for each voxel. Mid-treatment changes in the expression of the cytokines were calculated with respect to the pre-treatment baseline. Liver toxicity was assessed at 3 months post-RT, using Child-Pugh (CP) and ALBI score. Patients were subsequently classified into high-risk (HR) and low-risk (LR) groups. Statistical analysis was performed to compare the changes in the MR signals and cytokine expressions between these groups.
Results: On average, high-risk patients had lower high-dose/low-dose mid-treatment signal changes (i.e., decreased/increased signal in high-dose/low-dose). In CP classification, there was a significant difference in MR signal change between two group means (0.61 and 1.04 for HR and LR groups; p-value=0.005). The ALBI classification showed more pronounced difference (0.61 vs. 1.11, p-value = 0.002). High-risk patients also showed larger IL-6 changes during their treatment (86% vs. 0.33%, p-value=0.01).
Conclusion: Using mid-treatment MR scans and interleukin 6 as biomarkers, it is possible to predict the risk of acute liver toxicity, already during the RT course. This biomarker information can be potentially used for adaptive planning and RT plan personalization.
Keywords: Liver metastasis; MR; mid-treatment; adaptations; biomarker; cytokine
2019 AAPM Annual Meeting, 14.-18.07.2019, San Antonio, USA
Abstract in refereed journal
Medical Physics 46(2019)6, E499-E499
Late life brain perfusion after prenatal famine exposure
Early nutritional deprivation may cause irreversible damage to the brain and seems to affect cognitive function in older age. We investigated whether prenatal undernutrition was associated with brain perfusion differences in older age. We acquired Arterial spin labelling scans in 118 Dutch famine birth cohort members. Cerebral blood flow (CBF) was compared between exposed and unexposed groups in grey and white matter, perfusion territories, neurodegeneration-related regions anterior and posterior cingulate cortex and precuneus. Furthermore, we compared the GM/WM-ratio and the spatial coefficient of variation (CoV) as a proxy of overall cerebrovascular health. The WM ASL signal and the GM/WM-ratio were significantly lower and higher respectively among exposed participants. Exposed men had lower CBF in anterior and posterior cingulate cortices and higher spatial CoV. The latter seemed largely mediated by higher 2h-glucose levels at age 50. Our findings suggest that overall brain perfusion was worse in exposed participants, especially men exposed to undernutrition in early gestation. These results provide further evidence for life-long effects of undernutrition during early brain development.
Keywords: brain perfusion; prenatal famine; fetal programming
Neurobiology of Aging 82(2019), 1-9
- Final Draft PDF 1,7 MB Secondary publication
Numerical optimization of a finned tube bundle heat exchanger arrangement for passive spent fuel pool cooling to ambient air
The passive cooling of nuclear spent fuel pools is a promising alternative to active cooling. Since such systems work even in safety-critical situations, e.g. station blackout, the reliability of nuclear power plants would be enhanced. As in such systems heat needs to be transfer to the environment, the heat exchanger to air has a crucial influence on the system performance. This paper describes investigations of the Nusselt number, the achievable efficiency and the volumetric heat flux density of the tube bundle heat exchangers for a passive cooling system located at the bottom of a chimney. The effect of tube bundle configuration, tube shape, longitudinal tube pitch, transversal tube pitch and tube row number on natural convection heat transfer was numerical studied. These parameters were varied to optimize the heat transfer performance of the heat exchanger. It was found, that the staggered configuration performs better than the inline arrangement, since the flow mixing is higher. Furthermore circular tube shape and an oval tube shape with the aspect ratio of 1:2.1 were optimum for the inline and staggered configuration respectively. The longitudinal and transversal tube pitches of 63 mm and 65 mm performed best, since higher values reduced heat transfer. A tube row number greater than 5 did not improve the heat transfer and therefore a tube row number of 5 is recommended. The Nusselt number and volumetric heat flux density of the optimized tube bundle arrangement enhanced by 15.4 % and 47.8 % respectively at a temperature difference of 40 K compared to the initial design.
Keywords: passive cooling; spent fuel pool; natural convection; tube bundle heat exchanger; air cooling; design optimization
- Numerical optimization of a finned tube bundle heat … (Id 30638) HZDR-primary research data are used by this (Id 29116) publication
Nuclear Engineering and Design 361(2020), 110549
Quantifying the value of geometallurgical information and optimization
Predictive Geometallurgy can use thorough quantitative characterisation of the ores microstructure and mineralogy to predict and adaptively optimize the processing and blending of the ore. Adaptive processing allows to exploit this variation to achieve higher overall recovery at lower costs, e.g. by adapting milling to mineral grain sizes or grades.
The geometallurgical properties of the ore are however typically only known with some geostatistical uncertainty. The talk demonstrates in model calculation, that naive optimization of processing parameters based on expected ore properties might lead to performance losses relative to non-adaptive processing, while overestimating its own expected performance. The contribution shows how to outperform non-adpative processsing decissions substantially based on a stochastic optimization approach and how to quantify the value of geometallurgical information in a certain setting.
Indeed in the context of predictive geometallurgy the value of a blend is no longer defined only by its acutally physical properties, but also by the information we have about it at the time of processing. This makes geometallurgical exploration activity a relevant part of the mine plan, which can actually change and on average increase the value of blocks.
Keywords: Geometallurgy; Mine Scheduling; Stochastic Optimization; Geostatistics
2019 COSMO Technical Day, 27.-28.06.2019, Montreal, Canada
Nuclear Data Sensitivity and Uncertainty Analysis of Critical VENUS-F Cores with the Serpent Monte Carlo Code
In the framework of the FP7 Euratom project FREYA, the Serpent Monte Code was used to characterize a number of critical VENUS-F core configurations. Several neutronic parameters calculated by Serpent were compared to the available experimental data and reported in a previous study. Although a generally reasonable agreement between the calculated and experimental values was obtained, the study also revealed some important issues related to the numerical results such as a systematic overestimation of reactivity and a systematic underestimation of U238 to U235 fission rate ratio (designated as F28/F25 spectral index).
The objective of the current follow-up study is to quantify the effect of nuclear data uncertainties on the Monte Carlo estimates of reactivity and spectral indices. The analysis is carried out for two critical VENUS-F cores using a recently upgraded version of Serpent which is capable to perform sensitivity analysis based on the collision history method and to propagate and quantify nuclear data uncertainties using multi-group covariance libraries in an automated way. The criticality calculations were performed using the ENDV/B-VII.1 based cross sections while the uncertainties due to nuclear data were obtained using 56-group neutron cross section covariance library from the SCALE-6.2 package.
The estimated uncertainties due to nuclear data are of the order of 2200 pcm and 8% on k-eff and F28/F25 spectral index respectively. It was found that the major contributor to the k-eff uncertainty is capture cross section of U235. In the F28/F25 case, the total uncertainty is dominated by inelastic cross section of U238, fission spectrum of U235, and capture cross section of U235.
Keywords: Serpent; Monte Carlo; uncertainty quantification; FREYA; VENUS-F; critical experiments
Annals of Nuclear Energy 138(2020), 107196
- Secondary publication expected
Simulating air-breathing fuel cells using openFuelCell
Weber, N.; Chaparro, A. M.; Ferreira-Aparicio, P.; Zhang, S.; Reimer, U.; Beale, S.
The talk will be dedicated to modelling polymer electrolyte fuel cells. In the first part, the theory of the fuel cell model is presented. Details on its implementation in the open source library openFuelCell will be given. Secondly, numerical results on modelling an air-breathing fuel cell operated at CIEMAT will be shown and discussed.
OpenFOAM Workshop, 23.07.2019, Duisburg, Germany
Modelling electric potential distributions in batteries and fuel cells: an overview
Weber, N.; Personnettaz, P.; Weier, T.; Sadoway, D.
The talk will give an overview on simulating electric potential and current distributions in the frame of the finite volume method. Special attention will be paid to modelling internal discontinuities of the electric potential, as they appear at the electrode-electrolyte interface in fuel cells, electrolysers and batteries. The theoretical background will be explained and illustrated with simple examples.
OpenFOAM Workshop, 23.07.2019, Duisburg, Deutschland
Detection of the pulp-froth interface using the ultrasound transit time technique
The vertical position of the pulp-froth interface in a flotation cell is an important parameter in froth flotation processes which needs to be controlled in situ. For this purpose, we introduce the ultrasound transit time technique (UTTT), a non-invasive technique for detecting and measuring the position of this interface. Based on lab-scale experiments, the method is evaluated for a pulp-air and a pulp-froth interface. The technique was found to be well applicable in pulp with up to 21% particle mass fraction. In a container with 80 mm height the accuracy is found to equal 1mm.
Keywords: lab-scale flotation; level height detection; pulp-froth interface; ultrasound transit time technique
Minerals Engineering 160(2021), 106679
- Secondary publication expected from 26.10.2021
Interaction of uranium with halophilic microorganisms
Rock salts are considered as potential host rocks for the long-term storage of highly radioactive waste in a deep geological repository. In addition to bacteria and fungi, extremely halophilic archaea, e.g. Halobacterium species, are predominantly present in this habitat. For long-term risk assessment it is of high interest to study how these microorganisms can potentially interact with radionuclides if the radionuclides are released from the waste repository. Given this fact, the interactions of extremely halophilic archaea from the genus Halobacterium and the moderately halophilic bacterium Brachybacterium sp. G1 with uranium, one of the major radionuclides of concern in the geological repository of radioactive wastes, were investigated in detail in batch experiments. The archaea and the bacterium showed different association mechanisms with uranium. Brachybacterium sp. G1 cells sorbed uranium within a short time, whereas a much longer and a multi-stage bioassociation process, dependent on the uranium concentration, occurred with the archaea. Furthermore, a multi-spectroscopic (time-resolved laser-induced fluorescence spectroscopy and X-ray absorption spectroscopy) and -microscopic (scanning electron microscopy coupled with energy-dispersive X-ray analysis for elemental mapping) approach was used to elucidate the U(VI) bioassociation behavior. By using these spectroscopic and microscopic tools, the formation of a U(VI) phosphate mineral, such as meta-autunite, by the Halobacterium species was demonstrated. These findings offer new insights into the microbe-actinide interactions at highly saline conditions relevant to the disposal of nuclear waste.
Halophiles 2019, 24.-28.06.2019, Cluj-Napoca, Romania
Prediction of Bubble Departure in Forced Convection Boiling with a Mechanistic Model that Considers Dynamic Contact Angle and Base Expansion
A mechanistic model for bubble dynamics in flow boiling that is based on a force balance approach for a growing bubble is introduced. It considers evaporation of the microlayer underneath the bubble, thermal diffusion and condensation around the bubble cap as well as dynamic inclination and contact angles between the bubble and the heating wall. It requires no recalibration of parameters to predict the bubble growth. Validation against different experimental flow boiling data was carried out with no case-dependent recalibration and yielded good agreement. The simulations confirmed the dependency of bubble departure and lift-off diameters on different parameters, such as heat flux, liquid properties, subcooling temperature, system pressure, inclination angle of channel, channel geometry and mass flow rate.
Keywords: flow boiling; bubble growth; bubble departure; force balance
Energies 12(2019)10, 1950
Mechanical compliancy for magnetic field sensors
Augmented reality gadgets are becoming common for our information intensive society assisting us to acquire and process the data. Although impressive in the realization and demonstrations, the obvious drawback of the state-of-the-art augmented and virtual reality devices relying on optical detection systems is their bulkiness, energy inefficiency and the stringent requirement for an operator to be at the line of sight of the device.
We envision that prospective augmented reality systems will strongly benefit from the recent developments in compliant on-skin electronics [1-3]. The fabrication of highly conformable gadgets requires the realization of the electronic replica of the exteroceptive sensory system of humans as well as calls for the acquiring new perception skills beyond those prescribed by the evolution. The representative example of the missing exteroceptive sense of humans is the magnetoception, which allows some of the mammals but not humans perceiving the location in space or directions based on the detection of magnetic fields. The first crucial step towards the realization of this vision was accomplished with the development of interactive magnetosensitive skins [4-6]. The key enabler for this technology is the shapeable magnetoelectronics  –namely, flexible [5,6], stretchable [8,9] and imperceptible [4,10-12]– magnetic field sensorics.
Here, we present the first on-skin gadgets, which replicate our natural proprioceptive sensory ability of detecting the motion [4,10-12]. The technology is put forth to realize distributed arrays of magnetic field sensors on ultra-thin polymeric foils. Relying on this magnetically enabled electronic proprioception, we visualize the bodily motion and demonstrate the touchless manipulation of virtual objects for augmented reality systems.
Those highly conformable interactive devices possess great potential to extend the portfolio of tasks, which can be performed in virtual or augmented reality. The integration of gadgets in imperceptible electronic skins will open not only exciting possibilities for business or gaming industry but is also beneficial for safety and security applications, where the somatic manipulation of objects, e.g. turning regulation knobs located in a restricted environment is undesirable or even prohibited.
1. J. A. Rogers et al., Nature 477, 45 (2011).
2. S. Bauer et al., Adv. Mater. 26, 149 (2014).
3. M. Kaltenbrunner et al., Nature 499, 458 (2013).
4. M. Melzer et al., Nature Commun. 6, 6080 (2015).
5. M. Melzer et al., Adv. Mater. 27, 1274 (2015).
6. N. Münzenrieder et al., Adv. Electron. Mater. 2, 1600188 (2016).
7. D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
8. M. Melzer et al., Nano Lett. 11, 2522 (2011).
9. M. Melzer et al., Adv. Mater. 27, 1333 (2015).
10. G. S. Canon Bermudez et al., Science Advances 4, eaao2623 (2018).
11. G. S. Canon Bermudez et al., Nature Electronics 1, 589 (2018).
12. P. Granell et al., npj Flexible Electronics 3, 3 (2019).
Keywords: flexible electronics; flexible magnetic field sensors
Invited lecture (Conferences)
Magnetic Frontiers 2019: Magnetic Sensors, 24.-27.06.2019, Lisbon, Portugal
There is one aspect, which is in common to the majority of fundamentally appealing and technologically relevant novel magnetic materials, namely their non-collinear magnetic textures like spin spirals, chiral domain walls or skyrmions . These textures are typically driven by the Dzyaloshinskii-Moriya interaction (DMI). Recently, curvature effects emerged as a novel mean to design chiral magnetic properties by relying on extrinsic parameters, e.g. geometry of thin films . In particular, novel effects occur when the magnetization is modulated by curvature leading to new magnetization configurations and is implications on the spin dynamics due to topological constraints. Advances in this novel field solely rely on the understanding of the fundamentals behind the modifications of magnetic responses of 3D-curved magnetic thin films [3,4] and nanowires . The lack of an inversion symmetry and the emergence of a curvature induced effective anisotropy and DMI are characteristic of curved surfaces, leading to curvature-driven magnetochiral effects and topologically induced magnetization patterning [6,7]. The application potential of 3D-shaped objects is currently being explored as mechanically reshapeable magnetic field sensorics  for flexible interactive electronics [9,10], spin-wave ﬁlters and high-speed racetrack memory devices . The fundamentals as well as application relevant aspects of curvilinear nanomagnets will be covered in this presentation.
 “The 2017 Magnetism Roadmap”, D. Sander et al., J. Phys. D 50, 363001 (2017).
 “Magnetism in curved geometries”, R. Streubel, et al., J. Phys. D 49, 363001 (2016).
 “Curvature Effects in Thin Magnetic Shells”, Y. Gaididei et al., Phys. Rev. Lett. 112, 257203 (2014).
 “Multiplet of Skyrmion States on a Curvilinear Defect: Reconfigurable Skyrmion Lattices”, V. Kravchuk et al., Phys. Rev. Lett. 120, 067201 (2018).
 “Mesoscale Dzyaloshinskii-Moriya interaction: geometrical tailoring of the magnetochirality”, O. M. Volkov et al., Scientific Reports 8, 866 (2018).
 “Coupling of Chiralities in Spin and Physical Spaces: The Möbius Ring as a Case Study”, O. V. Pylypovskyi et al., Phys. Rev. Lett. 114, 197204 (2015).
 “Curvature-Induced Asymmetric Spin-Wave Dispersion”, J. A. Otalora et al., Phys. Rev. Lett. 117, 227203 (2016).
 “Shapeable magnetoelectronics”, D.Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
 “Magnetosensitive e-skins with directional perception for augmented reality”, S. Canon Bermudez et al., Science Advances 4, eaao2623 (2018).
 “Electronic-skin compasses for geomagnetic field driven artificial magnetoreception and interactive electronics”, S. Canon Bermudez et al., Nature Electronics 1, 589 (2018).
 “Beating the Walker Limit with Massless Domain Walls in Cylindrical Nanowires”, M. Yan et al., Phys. Rev. Lett. 104, 057201 (2010).
Keywords: curvature effects in magnetism; curved magnetic thin films
Invited lecture (Conferences)
6th International Conference from Nanoparticles and Nanomaterials to Nanodevices and Nanosystems, 30.06.-03.07.2019, Corfu, Greece
Revealing the Formation Dynamics of the Electric Double Layer by means of in-situ Rutherford Backscattering Spectrometry
We report on a new versatile experimental setup for in-situ Rutherford backscattering spectrometry at solid- liquid interfaces that enables investigations of electric double layers directly, in-situ and in a quantitative manner. A liquid cell equipped with a three electrode arrangement is mounted in front of the beam line and a thin Si3N4 window down to a thickness of 150 nm separates the vacuum of the detector chamber from the electrolyte in the cell. Since the contribution of the window to the measured spectra is minimized, a large variety of elements at the solid-liquid interface with sensitivities far below one mono layer can be monitored. The attachment of Ba onto the Si3N4 surface as a function of contact time and pH value of the electrolyte solution was chosen as example system. From our measurement we can not only read the evolution of the double layer but also derive limits for the point of zero charge for the Si3N4 surface. Our findings of 5.7 ≤ pH_PZC ≤ 6.2 are in good accordance with values found in the literature obtained by other techniques. Despite the measurements shown in this work, the presented setup allows for a large variety of in-situ investigations at solid-liquid interfaces such as tracing electro-chemical reactions, monitoring segregation, adsorption and dissolution and corrosion processes.
Keywords: Electric Double Layer; in-situ RBS; solid-liquid interface
Review of Scientific Instruments 90(2019)8, 085107
Indium thiospinel In1-xxIn2S4 – structural characterization and thermoelectric properties
Wyżga, P.; Veremchuk, I.; Himcinshi, C.; Burkhardt, U.; Carrillo-Cabrera, W.; Bobnar, M.; Hennig, C.; Leithe-Jasper, A.; Kortus, J.; Gumeniuk, R.
A detailed study of polycrystalline indium-based In1-xxIn2S4 (x = 0.16, 0.22, 0.28, 0.33) thiospinel is presented. The comprehensive description of synthesis conditions, phase composition and thermoelectric properties is performed applying various diffraction, microscopic and spectroscopic methods. Single-phase α- and β-In1-xxIn2S4 were found in the samples with 0.16 x 0.22 and x = 0.33 (In2S3), respectively, while In0.720.28In2S4 is proven to contain both α- and β-polymorphic modifications. Consequently, thermoelectric characterization of well-defined α-and β-In1-xxIn2S4 is conducted for the first time. α-In1-xxIn2S4 (x = 0.16, 0.22 and 0.28) revealed n-type semiconducting behavior, large Seebeck coefficient (< - 200 μV∙K-1) and moderate charge carrier mobility on the level of ~ 20 cm2V-1s-1 at room temperature (RT). The evident decrease of charge carrier concentration (increase of electrical resistivity) and thermal conductivity (even below 0.6 W∙m-1K-1 at 760 K) for larger In-content is observed. Although β-In0.670.33In2S4 (β-In2S3) is a distinct polymorphic modification, it followed the above-mentioned trend in thermal conductivity and displayed significantly higher charge carrier mobility (~ 104 cm2V-1s-1 at RT). These findings indicate that structural disorder in α-modification affects both electronic and thermal properties in this thiospinel. The reduction of thermal conductivity counterbalances lowered power factor and thus, thermoelectric figure of merit ZTmax = 0.2 at 760 K is nearly the same for both α- and β-In1-xxIn2S4.
Keywords: In2S3; thermoelectric properties; thiospinel; Raman spectroscopy; transmission electron microscopy
Dalton Transactions 48(2019), 8350-8360
Structural stability and thermoelectric performance of high quality synthetic and natural pyrites (FeS2)
Zuñiga-Puelles, E.; Cardoso-Gil, R.; Bobnar, M.; Veremchuk, I.; Himcinschi, C.; Hennig, C.; Kortus, J.; Heide, G.; Gumeniuk, R.
Synthetic bulk and natural pyrite from the hydrothermal mine in Schönbrunn (Saxony, Germany) are confirmed to be stoichiometric compounds with the composition FeS2 and to be stable up to ~600 K by combined chemical, spectroscopic and X-ray diffraction analyses. Natural pyrite with negligibly small amount (< 0.6 wt.%) of well-defined transition metal carbonates impurities revealed characteristics of a nondegenerate semiconductor and is considered as a model system for investigation of thermoelectric performance. In the temperature range 50-600 K both natural and synthetic high quality bulk FeS2 samples show electrical resistivity varying within (220)-(5×10-3) Ω m and Seebeck coefficients of (4)-(-450) μV K-1. The thermal conductivity is large (~40 W m-1 K-1 at 300 K) and exclusively due to phononic contribution. It reveals a well pronounced maximum centered at ~75 K for natural pyrite (grain size ≤ 5 mm), which becomes almost completely suppressed in the sintered bulk samples due to increase of the point defects concentration and additional scattering on the grain boundaries (grain size ≤ 100 μm). The thermoelectric efficiency of a pure pyrite with ZT ~ 10-6 at 600 K is indeed by a factor of ~1000 worse than those reported earlier for some minerals and synthetic samples.
Keywords: crystal structure; thermoelectric; natural mineral; pyrite
Dalton Transactions 48(2019), 10703-10713
CeMo2B5: a new type of arrangement of puckered boron hexagonal rings
Flipo, S.; Kohut, M.; Roth, F.; Weigel, T.; Schnelle, W.; Bobnar, M.; Ormeci, A.; Burkhardt, U.; Hennig, C.; Leisegang, T.; Meyer, D.-C.; Leithe-Jasper, A.; Gumeniuk, R.
REMo2B5 (RE = Ce, Pr, Nd) and CeW2B5 have been synthesized by arc melting with further annealing at 1300 °C.
CeMo2B5 crystallizes in a new structure type with space group REMo2B5 (RE = Ce, Pr, Nd) and CeW2B5 have synthesized by arc melting with further annealing at 1300 °C. CeMo2B5 crystallizes in a new structure type with space group Pnma, a = 11.0298(2) Å, b = 3.12080(5) Å, c = 9.9594(2) Å, Z = 4. Its structural arrangement reveals puckered [B6]-hexagonal rings, trigonal-prismatic- and empty pyramidal-tetrahedralslabs.The structure can be related to the derivatives of AlB2 and CrB prototypes. The boron atoms form a two-dimensional network of corrugated ribbons, each composed of four edgelinked [B6] rings infinitely extending along the b-axis. CeMo2B5 is a Pauli paramagnet. Electrical transport measurements together with the calculated density of states at the Fermi level of 3.81 states eV–1 f.u.–1 indicate CeMo2B5 to be a typical metallic system. Electronic structure calculations reveal significant hybridization of Ce 4f5d states with Mo 4d states. The chemical bonding scenario is dominated by chains of [Ce2Mo2] clusters with multi-center bonds. These clusters are connected via metallic Mo–Mo bonds. This metal-framework, in turn, is stabilized by bonding interactions with the boron ribbons to which it donates electrons.
Keywords: intermetallic borides; crystal structure; X-ray diffraction; magnetism
European Journal of Inorganic Chemistry (2019)31, 3572-3580
High-Quality LWFA-Based Electron Sources
Invited lecture (Conferences)
ALEGRO workshop 2019, 27.03.2019, Genève, Confédération suisse
Reduced diffusion in normal appearing white matter of glioma patients following radio(chemo)therapy
Raschke, F.; Wesemann, T.; Wahl, H.; Appold, S.; Krause, M.; Linn, J.; Troost, E. G. C.
Background and purpose:
Standard treatment of high grade gliomas includes gross tumour resection followed by radio(chemo)therapy. Radiotherapy inevitably leads to irradiation of normal brain tissue. The goal of this prospective, longitudinal study was to use MRI to quantify normal appearing white and grey matter changes following radiation treatment as a function of dose and time after radiotherapy.
Materials and methods:
Pre-radiotherapy MRI (proton or photon therapy) and follow-up MRIs collected in 3 monthly intervals thereafter were analysed for 22 glioma patients and included diffusion tensor imaging, quantitative T1, T2* and proton density mapping. Abnormal tissue was excluded from analysis. MR signal changes were quantified within different dose bin regions for grey and white matter and subsequently for whole brain white matter.
We found significant reductions of mean diffusivity, radial diffusivity, axial diffusivity and T2* in normal appearing white matter regions receiving a radiation dose as low as 10-20 Gy within the observational period of up to 18 months. The magnitude of these changes increased with the received radiation dose and progressed with time after radiotherapy. Whole brain white matter also showed a significant reduction in radial diffusivity as a function of radiation dose and time after radiotherapy. No significant changes were observed in grey matter.
Diffusion tensor imaging and T2* imaging revealed normal appearing white matter changes following radiation treatment. The changes were dose dependant and progressed over time. Further work is needed to understand the underlying tissue changes and to correlate the observed diffusion changes with late brain malfunctions.
Keywords: White Matter; Grey Matter; Diffusion Tensor Imaging; Radiotherapy; quantitative MRI; Proton Therapy; Photon Therapy; glioma; normal tissue
Radiotherapy and Oncology 140(2019), 110-115
- Final Draft PDF 423 kB Secondary publication
Calcium binding to a disordered domain of a type III-secreted protein from a coral pathogen promotes secondary structure formation and catalytic activity
Hoyer, E.; Knöppel, J.; Liebmann, M.; Steppert, M.; Raiwa, M.; Herczynski, O.; Hanspach, E.; Zehner, S.; Göttfert, M.; Tsushima, S.; Fahmy, K.; Oertel, J.
Strains of the Gram-negative bacterium Vibrio coralliilyticus cause the bleaching of corals due to decomposition of symbiotic microalgae. The V. coralliilyticus strain ATCC BAA-450 (Vc450) encodes a type III secretion system (T3SS). The gene cluster also encodes a protein (locus tag VIC_001052) with sequence homology to the T3SS-secreted nodulation proteins NopE1 and NopE2 of Bradyrhizobium japonicum (USDA110). VIC_001052 has been shown to undergo auto-cleavage in the presence of Ca2+ similar to the NopE proteins. We have studied the hitherto unknown secondary structure, Ca2+-binding affinity and stoichiometry of the “metal ion-inducible autocleavage” (MIIA) domain of VIC_001052 which does not possess a classical Ca2+-binding motif. CD and fluorescence spectroscopy revealed that the MIIA domain is intrinsically largely disordered. Binding of Ca2+ and other di- and trivalent cations induced secondary structure and hydrophobic packing after partial neutralization of the highly negatively charged MIIA domain. Mass spectrometry and isothermal titration calorimetry showed two Ca2+-binding sites which promote structure formation with a total binding enthalpy of -110 kJ mol-1 at a low micromolar Kd. Putative binding motifs were identified by sequence similarity to EF-hand domains and their structure analyzed by molecular dynamics calculations. The stoichiometric Ca2+-dependent induction of structure correlated with catalytic activity and may provide a “host-sensing” mechanism that is shared among pathogens that use a T3SS for efficient secretion of disordered proteins.
Keywords: metal protein interactions; protein folding; rhizobium; intrinsically disordered protein
Scientific Reports 9(2019), 7115
Frontiers of applications of Petawatt lasers, Plasma accelerator development in Dresden
Discussion on progress of PW laser applications and advanced accelerators of protons and electrons
Keywords: Petawatt laser; laser particle acceleration; LWFA; secondary sources
Invited lecture (Conferences)
SPIE Optics + Optoelectronics, 02.-04.04.2019, Prag, Czech Republic
Invited lecture (Conferences)
JuSPARC Kick-off Workshop, 27.-29.03.2019, Vaals, Niederlande
Laser plasma proton accelerators for therapy ?
Workshop discussion on advanced accelerators for therapy.
Keywords: particle cancer therapy; laser acceleration
Invited lecture (Conferences)
2nd ARIES Annual Meeting, 10.-11.04.2019, Budapest, Ungarn
Phonon Magnetochiral Effect
Nomura, T.; Zhang, X.-X.; Zherlitsyn, S.; Wosnitza, J.; Tokura, Y.; Nagaosa, N.; Seki, S.
The magnetochiral effect (MCE) of phonons, a nonreciprocal acoustic propagation arising due to symmetry principles, is demonstrated in the chiral-lattice ferrimagnet Cu2OSeO3. Our high-resolution ultrasound experiments reveal that the sound velocity differs for parallel and antiparallel propagation with respect to the external magnetic field. The sign of the nonreciprocity depends on the chirality of the crystal in accordance with the selection rule of the MCE. The nonreciprocity is enhanced below the magnetic ordering temperature and at higher ultrasound frequencies, which is quantitatively explained by a proposed magnon-phonon hybridization mechanism.
Physical Review Letters 122(2019), 145901
Quantification of the metabolic uptake rate in whole body F-18 FDG PET: a comparison between dynamic and static imaging
van den Hoff, J.; Hofheinz, F.; Weise, R.; Maus, J.; Preuß, R.; Burchert, W.
Dynamic whole body (DWB) FDG PET has become available with the recent introduction of the "flow motion" package by Siemens which offers fully automated generation of parametric images of the metabolic uptake rate K[m]. While this approach is superior to SUV-based quantification, it requires substantially more scan time and reduces patient throughput. On the other hand, the tumor to blood standard uptake ratio (SUR) has outperformed SUV in several clinical studies, which is attributed to a very high correlation between SUR and K[m]. However, direct evidence for this correlation is scarce. Our study compares K[sur], the SUR-derived "static" estimate of K[m], with the Patlak-derived K[m].
Altogether, 12 oncological patients are enclosed and scheduled for DWB PET. Parametric images of K[m] and K[sur] are computed using the vendor provided Patlak procedure and in-house software, respectively. Evaluation of the voxel intensity correlation between both parametric images as well as ROI-based analysis is performed.
So far, 4 patients have been evaluated. K[m] and K[sur] are highly correlated (R^2=0.97) in areas with nonnegligible irreversible uptake (so far we investigated the range K[m]=[0.01,0.07]). K[m] and K[sur] images have very similar image contrast between such areas. Minor contrast differences exist in healthy soft tissue and regions where the Patlak approach is invalid (notably the liver). The relative scale factor between both parametric images is 0.86.
Our results suggest that SUR and K[sur] are proportional surrogates of true K[m]. The unquestionable potential of DWB PET might thus be more relevant for applications beyond oncological FDG PET. To test this conjecture, comprehensive studies in homogeneous patient groups are required in order to compare the prognostic value of K[m] and SUR/K[sur] in the context of survival analysis
Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland
Quantifizierung von pulmonalen 18F-FDG-PET/CT-Untersuchungen: Vergleich von Standard Uptake Ratio (SUR) und Patlak (Ki)
Braune, A.; Bluth, T.; Kiss, T.; Hofheinz, F.; Gama De Abreu, M.; Kotzerke, J.
Dynamische PET/CT Scans gefolgt von Patlak Modellierung der 18F-FDG-Aufnahmerate (Ki) ist eine etablierte Methode zur Quantifizierung der Lungenentzündung im tierexp. Modell des akuten Lungenversagens (ARDS), erfordert aber zeitintensive Aufnahmen und erlaubt nur ein begrenztes cranio-caudales FoV. Dyn. PET/CT Scans von Patienten mit Lebermetastasen zeigten gute Korrelationen zwischen Ki und Standard Uptake Ratio (SUR = ROI-SUV / Blut-SUV) . Wir analysierten in einem tierexp. ARDS-Modell, ob stat. PET/CT Messungen und SUR-Analysen alternativ zu dyn. PET/CT und Ki für die Quantifizierung der pulmonalen Inflammation genutzt werden können.
In 14 Schweinen erfolgten nach Induktion eines schweren ARDS sowie nach 24h Beatmung dyn. 18F-FDG-PET/CT Scans und Patlak Ki-Analysen. Anschließende stat. PET/CT Scans (77-81min p.i.) wurden für die Bestimmung von mittleren, zeitkorrigierten SUR-Werte genutzt. SUR- und Ki-Werte wurden für 5 ventro-dorsale ROIs mittels linearer Regression verglichen (Variationskoeffizient, r2). Anhand von Blutproben wurde die Variabilität der arteriellen Inputfunktion (AIF) zwischen Tieren und Messzeitpunkten verglichen.
SUR- und Ki-Werte korrelierten vor und nach 24h Beatmung (r2=0.84 bzw. 0.97). Der zeitliche Verlauf der AIF war zwischen Tieren und Aufnahmezeitpunkten vergleichbar und konnte mittels einer inversen Potenzfunktion beschrieben werden (r2 = 0.99). Die Patlak-Zeit war Zeit-, aber nicht AIF-abhängig, und wies eine geringe Variabilität auf (t=70min: 153.6 ± 13.3min).
Für die Quantifizierung der pulmonalen Inflammation in exp. Studien der Anästhesie können stat. PET/CT Scans und SUR-Analysen alternativ zu dyn. 18F-FDG-PET/CT und Patlak genutzt werden. Dies ermöglicht eine schnellere Datenakquisition, die Erfassung der gesamten Lunge und eine Reduktion der erforderlichen Blutproben. Grundlage der guten Ki-SUR Korrelation bildete die geringe Variabilität des AIF.
Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland
Validation of an independent prognostic value of the asphericity of FDG uptake in non-small cell cancer patients undergoing treatment in curative intent
Rogasch, J.; Chibolela, C.; Frost, N.; Wedel, F.; Hofheinz, F.; Rückert, J.; Neudecker, J.; Böhmer, D.; von Laffert, M.; Amthauer, H.; Furth, C.
In patients with non-small cell lung cancer (NSCLC) undergoing treatment with curative intent, the asphericity (ASP) of the primary tumor’s metabolic tumor volume (MTV) has been demonstrated as a prognostic factor. This study aimed at validation in an independent cohort with sufficient sample size.
Retrospective study in 313 NSCLC patients (203 men; median age, 67 [41-87] a) undergoing FDG-PET/CT with the same scanner prior to treatment in curative intent (always including resection of the primary tumor). 137 patients had UICC stage I, 79 patients stage II and 97 patients stage III disease (adenocarcinoma [ADC], 153; squamous cell carcinoma [SCC], 143, other, 17). Delineation of primary tumor MTV with semiautomated background-adapted threshold relative to its SUVmax. Univariable Cox regression for progression-free (PFS) and overall survival (OS) for PET parameters (MTV, ASP, SUVmax, SUVmean), clinical (UICC stage I vs. II vs. III), histological (SCC vs. ADC) and treatment variables (Rx/1 vs. R0 resection, chemotherapy yes/no, radiotherapy yes/no). Multivariable Cox of parameters significant in univariate Cox.
Events (progression, relapse, death) occurred in 169/313 patients, 139 patients died (median follow-up in survivors, 37 months). In multivariable Cox for OS, ASP >33.3% (hazard ratio [HR], 1.53 [95%-confidence interval, 1.02-2.3]), Rx/1 vs. R0 resection (HR, 2.47 [1.5-4.2]) and SCC vs. ADC (HR, 1.53 [1.1-2.2]) were significant. Log-rank test for ASP was significant at any cut-off from 18% upwards. Among separate UICC stages, ASP was only prognostic for OS in stage II (optimal, >19.5%; median OS, 33 vs. 59 months; p<0.01). In multivariable Cox for PFS, ASP >21.2% (HR, 1.75 [1.2-2.5]) and Rx/1 vs. R0 (HR, 2.48 [1.5-4.1]) were significant. Log-rank test for ASP was significant at any cut-off from 10-60%.
ASP was validated as an independent predictor of PFS and OS in NSCLC patients with curative treatment intent. Subdividing UICC stages, ASP remained prognostic in stage II.
Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland
Interobserver variability of image–derived arterial blood SUV in FDG–PET
Hofheinz, F.; Maus, J.; Zschaeck, S.; Rogasch, J.; Schramm, G.; Oehme, L.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.
The standardized uptake value (SUV) is essentially the only means for quantitative evaluation of static FDG PET. However, the SUV approach has well-known shortcomings which adversely affect the reliability of the SUV as a surrogate of the metabolic rate of glucose consumption. The standard uptake ratio (SUR), i.e. the uptake time corrected ratio of tumor SUV to image-derived arterial blood SUV, has been shown to overcome most of these shortcomings and to increase the prognostic value in comparison to SUV. However, it is unclear, to what extent the SUR approach is vulnerable to observer variability of the required blood SUV (BSUV) determination. The goal of the present work was the investigation of the interobserver variability of image-derived BSUV.
FDG PET/CT scans from 83 patients were included. BSUV was determined by 8 individuals, each applying a dedicated delineation tool for the BSUV determination in the aorta. Altogether 5 different delineation tools were used. With each used tool, delineation was performed for the whole patient group, resulting in 12 distinct observations per patient. Interobserver variability of BSUV determination was assessed using the fractional deviations of the individual observers from the observer-average for the considered patient.
Interobserver variability in the pooled data amounts to SD=2.8% and is much smaller than the intersubject variability of BSUV (SD=16%). Averaged over the whole patient group, deviations of individual observers from the observer average are very small and fall in the range [-0.96,1.05]%. However, interobserver variability partly differs distinctly for different patients (range: [0.7,7.4]%).
The present investigation proofs unambiguously that the image-based manual determination of BSUV in the aorta provides sufficient accuracy and reproducibility for the purposes of the SUR approach. This finding is in line with the already demonstrated superiority of SUR in comparison to SUV in first clinical studies.
Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland
Die Asphärizität neuroendokriner Tumore in der prätherapeutischen Somatostatinrezeptor-Bildgebung: Ein innovativer Prädiktor für das progressionsfreie Überleben unter Everolimus?
Wetz, C.; Genseke, P.; Pape, U.; Jann, H.; Furth, C.; Kreißl, M.; Hofheinz, F.; Venrito, M.; Stüven, A.; Amthauer, H.
Bei Patienten mit pulmonalen oder gastrointestinalen neuroendokrinen Tumoren (NET) kann der teils nebenwirkungsreiche mTOR-Inhibitor Everolimus das progressionsfreie Überleben (PFS) verlängern. Ziel dieser Studie war die Evaluation der läsionalen Asphärizität (ASP) in der prätherapeutischen Somatostatinrezeptor (SSR)-Bildgebung hinsichtlich einer weiteren Spezifizierung von Patientensubgruppen die von der Therapie im Besonderen profitieren.
Retrospektive, bizentrische Analyse von 30 Patienten (m=17; w=13; medianes Alter, 59 [38-75] Jahre) mit einer prätherapeutischen [111In-DTPA0]octreotid Szintigraphie. Die funktionellen Volumina von bis zu 3 führenden Läsionen je Patient (n=74) wurden mittels halbautomatischer, hintergrundadaptierter Segmentierung erhoben (ROVER, Version 2.1.20) und jeweils die sphärische Heterogenität des SSR-Besatzes - die ASP - berechnet. Für die maximal gemessene ASP je Patient erfolgten Kaplan-Meier-Analysen inklusive log-rank-Tests sowie eine univariate Cox Regression bzgl. des PFS.
Alle 30 Patienten waren unter Everolimus progredient oder entwickelten ein Rezidiv. In der univariaten Analyse erwies sich die ASP [Median, 12,7%; Spannweite, 1,1–43,5] als Prädiktor des PFS (p=0,033; Hazard Ratio [HR], 2,391 je eine Einheit). Patienten mit einer hohen ASP (>14%) zeigten ein medianes PFS von 6,7 Monaten (95%-Konfidenzintervall [CI], 2,1-11,4 Monate) gegenüber 14,4 Monaten (95%-CI, 12,5-16,3 Monate; p=0,028) für eine ASP ≤14%.
Mittels ASP kann im untersuchten Patientenkollektiv eine Prädiktion des PFS erreicht werden. In Bezug auf eine Nutzen-/Risiko-Abwägung zur Indikationsstellung der Everolimusgabe erscheint der Einsatz der prätherapeutischen ASP bzgl. einer optimalen Patientenauswahl bedeutsam; Patienten mit einer ASP >14% hatten ein signifikant kürzeres PFS.
Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland
Application of Fourier Analysis of Cerebral Glucose Metabolism in Color Induced Long-term Potentiation: A Novel Functional PET Spectroscopy (fPETS) Study in Mice
Njemanze, P. C.; Kranz, M.; Brust, P.
Fourier time series analysis could be used to segregate changes in the ventral and dorsal streams of the visual system in male and female mice. Color memory processes of long-term potentiation and long-term depression could be identified through spectral analysis. We used small animal positron emission tomography and magnetic resonance imaging (PET/MRI) to measure the accumulation of [18F]fluorodeoxyglucose ([18F]FDG) in the mouse brain during light stimulation with blue and yellow filters compared to darkness condition. The mean standardized uptake values (SUV) of [18F]FDG for each stimulus condition was analyzed using standard Fourier analysis software to derive spectral density estimates for each condition. Spectral peaks were identified as originating from the subcortical region (S-peak) by subcortical long-term potentiation (SLTP) or depression (SLTD), and originating from the cortical region (C-peak) by cortical long-term potentiation (CLTP) or depression (CLTD). Luminance opponency occurred at S-peak by SLTP in the dorsal stream in the left visual cortex in male mice. On the other hand, chromatic opponency occurred by wavelength-differencing at C-peak by CLTP in the cortico-subcortical pathways in the ventral stream of the left visual cortex in male mice. In contrast in female mice, during luminance processing, there was resonance phenomenon at C-peak in the ventral stream in the right visual cortex. Chromatic opponency occurred at S-peak by SLTP in the dorsal stream in the right visual cortex in female mice. Application of Fourier analysis improved spatial and temporal resolutions of conventional fPET/MRI methods. Computation of colour processing as a conscious experience has wide range applications in neuroscience and artificial intelligence.
Keywords: Chromatic Opponency; Brain; Light Stimulation; Sex; Asymmetry; Spectroscopy; Memory
Dr. Goran S. Nikolić, Dr. Dragana Marković-Nikolić: Application of Fourier Analysis of Cerebral Glucose Metabolism in Color Induced Long-term Potentiation: A Novel Functional PET Spectroscopy (fPETS) Study in Mice / Fourier Transforms - Century of Digitalization and Increasing Expectations, London: IntechOpen, 2019, 1-23-1
Nanomagnetism of Magnetoelectric Granular Thin-Film Antiferromagnets
Appel, P.; Shields, B. J.; Kosub, T.; Hedrich, N.; Hübner, R.; Fassbender, J.; Makarov, D.; Maletinsky, P.
Antiferromagnets have recently emerged as attractive platforms for spintronics applications, offering fundamentally new functionalities compared with their ferromagnetic counterparts. Whereas nanoscale thin-film materials are key to the development of future antiferromagnetic spintronic technologies, existing experimental tools tend to suffer from low resolution or expensive and complex equipment requirements. We offer a simple, high-resolution alternative by addressing the ubiquitous surface magnetization of magnetoelectric antiferromagnets in a granular thin-film sample on the nanoscale using single-spin magnetometry in combination with spin-sensitive transport experiments. Specifically, we quantitatively image the evolution of individual nanoscale antiferromagnetic domains in 200 nm thin films of Cr2O3 in real space and across the paramagnet-to-antiferromagnet phase transition, finding an average domain size of 230 nm, several times larger than the average grain size in the film. These experiments allow us to discern key properties of the Cr2O3 thin film, including the boundary magnetic moment density, the variation of critical temperature throughout the film, the mechanism of domain formation, and the strength of exchange coupling between individual grains comprising the film. Our work offers novel insights into the magnetic ordering mechanism of Cr2O3 and firmly establishes single-spin magnetometry as a versatile and widely applicable tool for addressing antiferromagnetic thin films on the nanoscale.
Nano Letters 19(2019)3, 1682-1687
Modelling high resolution XANES for nuclear materials
Amidani, L.; Pidchenko, I.; Kvashnina, K.
X-ray Absorption Spectroscopy (XAS) is an invaluable tool in nuclear material research, allowing to probe the oxidation state and the local coordination of a selected atomic species. The first part of the spectrum, the X-ray Near Edge Structure (XANES), is less exploited than the Extended X-ray Absorption Fine Structure (EXAFS). However XANES conceals a wealth of information on the electronic structure and the local geometry around the absorber. Nowadays important progresses in the interpretation of XANES have been made thanks to i) the development of dedicated ab-initio codes using powerful computational resources and ii) the use of high resolution XANES, which is especially advantageous for actinides.
We present here an example of how to extracted valuable information from XANES. We performed a systematic study of U L₃ edge XANES for U⁵⁺ and U⁶⁺ in different local coordination. It is well known that the presence uranyl bonds gives a characteristic feature in the post-edge of U L₃ XANES and it has been observed experimentally that this feature shifts to lower energy when going from the uranyl to the uranate coordination. We found that in U⁶⁺ and U⁵⁺ mixed systems the U⁵⁺ in octahedral coordination gives a characteristic shoulder just before the uranyl feature due to the splitting of the 6d DOS from the octahedral crystal field. We think that the shift of the uranyl feature going to uranate configuration indeed points to the presence of U⁵⁺.
E-MRS spring meeting, 27.-31.05.2019, Nice, France
Modeling XANES of U⁵⁺ and U⁶⁺ in different local coordination geometries
Amidani, L.; Pidchenko, I.; Kvashnina, K.
X-ray Absorption Spectroscopy (XAS) is an invaluable tool in nuclear material research, allowing to probe the oxidation state and the local coordination of selected atomic species. The first part of the spectrum, the X-ray Near Edge Structure (XANES), is less exploited than the Extended X-ray Absorption Fine Structure (EXAFS). However XANES conceals a wealth of information on the electronic structure and on the local geometry around the absorber. What prevents XANES to become a more common technique is the complexity of its analysis, which still gives more qualitative than quantitative information. Nowadays important progresses in the interpretation of XANES have been made thanks to i) the development of dedicated ab-initio codes using powerful computational resources and ii) the use of High Energy Fluorescence Detected (HERFD) XANES, which boosted spectral resolution especially in the case of actinides. These recent developments make the systematic studies based on XANES simulations an invaluable tool to strengthen our understanding of XANES.
In this regards we present a detailed investigation on how the local coordination of U⁵⁺ and U⁶⁺ affects the U L₃ edge HERFD XANES. By simulating a large number of structures containing U⁵⁺ and/or U⁶⁺ in different local coordination geometries we found systematic trends, especially correlated with the presence of longer or shorter U – O bonds. It is well established that the presence of the short uranyl bond shows up in U L₃ edge XANES by the presence of a characteristic post-edge feature . Interestingly, some experimental investigations reported that the uranyl post-edge feature shifts to lower energy when going from the uranyl to the uranate coordination, i.e. identical U – O distances [2,3]. Our systematic investigation confirms that this behavior correlates with the presence of U coordinated with 6 oxygen atoms in a regular octahedron and it is a consequence of the splitting of U 6d Density of States (DOS) induced by the crystal field. The possibility to detect the presence of U⁵⁺ in systems with both U⁵⁺ and U⁶⁺ by HERFD XANES will be discussed on the bases of our systematic investigation.
49èmes Journées des Actinides, 14.-18.04.2019, Erice, Italy
Plant cell (Brassica napus) response to europium(III) and uranium(VI) exposure
Experiments conducted over a period of 6 weeks using Brassica napus callus cells grown in vitro under Eu(III) or U(VI) stress showed that B. napus cells were able to bioassociate both potentially toxic metals (PTM), 762 nmol Eu/gfresh cells and 995 nmol U/gfresh cells. Most of the Eu(III) and U(VI) was found to be enriched in the cell wall fraction. Under high metal stress (200 µM), cells responded with reduced cell viability and growth. Subsequent speciation analyses using both metals as luminescence probes confirmed that B. napus callus cells provided multiple-binding environments for Eu(III) and U(VI). Moreover, two different inner-sphere Eu3+ species could be distinguished. For U(VI), a dominant binding by organic and/or inorganic phosphate groups of the plant biomass can be concluded.
Keywords: uranium; europium; plant cells; luminescence spectroscopy; viability
Environmental Science and Pollution Research 27(2020), 32048-32061
Numerical investigation on the effects of vortex generators on sub-channel flow in a rod bundle
Tas, S.; Krepper, E.; Unger, S.; Hampel, U.
Spacer grids of fuel assemblies are equipped with vanes, which promote mixing and turbulence within and across the sub-channels and thereby enhance the heat transfer. In this study, we investigated the impact of vortex generating vanes on the downstream flow evolution and heat transfer from the fuel rods by numerical analyses. Simulations were performed with ANSYS CFX. We investigated the turbulence change along the channel in the presence of the vanes depending on vorticity. The use of vanes results in a vortex, in which the vorticity enhances with increasing vane angle. These change induce turbulence kinetic energy variations. Physical conditions for optimum heat transfer along the sub-channel were determined in terms of Nusselt number. The Nusselt numbers of the present simulation were compared with experimental results from literature and a slight over prediction of the simulation compare to the experiment was found.
Keywords: Turbulent flow; Heat transfer; Numerical analysis
50th Annual Meeting on Nuclear Technology, 07.-08.05.2019, Berlin, Deutschland
Magnetic interactions and spin dynamics in the bond-disordered pyrochlore fluoride NaCaCo2F7
Zeisner, J.; Bräuninger, S. A.; Opherden, L.; Sarkar, R.; Gorbunov, D. I.; Krizan, J. W.; Herrmannsdörfer, T.; Cava, R. J.; Wosnitza, J.; Büchner, B.; Klauss, H. H.; Kataev, V.
We report high-frequency/high-field electron spin resonance (ESR) and high-field magnetization studies on single crystals of the bond-disordered pyrochlore NaCaCo2F7. Frequency- and temperature-dependent ESR investigations above the freezing temperature Tf ∼ 2.4 K reveal the coexistence of two distinct magnetic phases. A cooperative paramagnetic phase, evidenced by a gapless excitation mode, is found along with a spin-glass phase developing below 20 K which is associated with a gapped low-energy excitation. Effective g factors close to 2 are obtained for both modes, in line with pulsed high-field magnetization measurements which show an unsaturated isotropic behavior up to 58 T at 2 K. In order to describe the field-dependent magnetization in high magnetic fields, we propose an empirical model accounting for highly anisotropic ionic g tensors expected for this material and taking into account the strongly competing interactions between the spins which lead to a frustrated ground state. As a detailed quantitative relation between effective g factors as determined from ESR and the local g tensors obtained by neutron scattering [Ross et al., Phys. Rev. B 93, 014433 (2016)] is still sought after, our work motivates further theoretical investigations of the low-energy excitations in bond-disordered pyrochlores.
Physical Review B 99(2019), 155104
Reference Database for Photon Strength Functions
Goriely, S.; Dimitriou, P.; Wiedeking, M.; Belgya, T.; Firestone, R.; Kopecky, J.; Krticka, M.; Plujko, V.; Schwengner, R.; Siem, S.; Utsunomiya, H.; Hilaire, S.; Peru, S.; Cho, Y. S.; Filipescu, S. M.; Iwamoto, N.; Kawano, T.; Oblozinsky, P.; Tao, X.; Varlamov, V.; Xu, R.
Photon strength functions describing the average response of the nucleus to an electromagnetic probe are key input information in the theoretical modelling of nuclear reactions and consequently they are highly relevant to a wide range of fields in basic sciences and applications such as nuclear structure, nuclear astrophysics, medical isotope production, fission and fusion reactor technologies, activation analyses and safeguards. They are also sources of information for widely used databases such as the IAEA Reference Input Parameter Library, the evaluated data files, such as ENSDF, EGAF, and the astrophysical reaction databases (e.g. BRUSLIB, STARLIB, REACLIB). In the past two decades, there has been considerable growth in the amount of reaction gamma-ray data measured to determine photon strength functions. Quite often the different experimental techniques lead to discrepant results and users are faced with the dilemma of deciding which (if any) amongst the divergent data they should adopt.
Keywords: Photon strength functions; gamma-ray strength; data base
European Physical Journal A 55(2019), 172
I will review our activities on shapeable magnetoelectronics. Fabrication and application potential of flexible magnetic field sensors will be in the focus of the talk.
Keywords: flexible electronics; magnetoelectronics
Invited lecture (Conferences)
Nanoforum 2019, 17.05.2019, Linz, Austria
Current status of the PEnELOPE laser system
We present an update on the development of the PENELOPE laser system currently under construction at the Helmholtz-Zentrum Dresden-Rossendorf, Germany. Pulses from an oscillator are stretched to the nanosecond scale before several amplification stages will boost the energy up to the 150 J level on target. About 150 fs are foreseen at repetition rates of up to 1 Hz, ultimately yielding a peak power of 1 PW.
Our primary objective lies currently on the compression of the amplified pulses on the Joule scale. First tests used a direct compression of the stretched oscillator output (hence a small beam size), while the amplified compression will be performed with the full sized beam. Compressibility of the full scale beam is therefore of major interest. The second target is the improvement of the average power capacity of especially the second to the last amplifiers section. Room temperature operation is the main aim for the close future with lower temperature operation envisioned.
Keywords: laser; diode pumping; ytterbium; CaF2
The 11th International Workshop of High Energy Class Diode Pumped Solid State Lasers (HEC-DPSSL), 13.-16.01.2019, Daejeon, Süd-Korea
Microscopic Nature of the First-Order Field-Induced Phase Transition in the Strongly Anisotropic Ferrimagnet HoFe5Al7
Gorbunov, D. I.; Strohm, C.; Henriques, M. S.; van der Linden, P.; Pedersen, B.; Mushnikov, N. V.; Rosenfeld, E. V.; Petricek, V.; Mathon, O.; Wosnitza, J.
We report on x-ray magnetic circular dichroism experiments in pulsed fields up to 30 T to follow the rotations of individual magnetic moments through the field-induced phase transition in the ferrimagnet HoFe5Al7. Near the ground state, we observe simultaneous stepwise rotations of the Ho and Fe moments and explain them using a two-sublattice model for an anisotropic ferrimagnet with weak intersublattice exchange interactions. Near the compensation point, we find two phase transitions. The additional magnetization jump reflects the fact that the Ho moment is no longer rigid as the applied field acts against the intersublattice exchange field.
Physical Review Letters 122(2019), 127205
- Original PDF 768 kB Secondary publication
Inductive Heating Using a High-Magnetic-Field Pulse to Initiate Chemical Reactions to Generate Composite Materials
Zimmerer, C.; Salazar Mejia, C.; Utech, T.; Arnhold, K.; Janke, A.; Wosnitza, J.
Induction heating is efficient, precise, cost-effective, and clean. The heating process is coupled to an electrically conducting material, usually a metal. As most polymers are dielectric and non-conducting, induction heating is not applicable. In order to transfer energy from an electromagnetic field into polymer induction structures, conducting materials or materials that absorb the radiation are required. This report gives a brief overview of induction heating processes used in polymer technology. In contrast to metals, most polymer materials are not affected by electromagnetic fields. However, an unwanted temperature rise of the polymer can occur when a radio frequency field is applied. The now available high-field magnetic sources provide a new platform for induction heating at very low frequencies, avoiding unwanted thermal effects within the material. Using polycarbonate and octadecylamine as an example, it is demonstrated that induction heating performed by a magnetic-field pulse with a maximum flux density of 59 T can be used to initiate chemical reactions. A 50 nm thick Ag loop, with a mean diameter of 7 mm, placed in the polymer-polymer interface acts as susceptor and a resistive heating element. The formation of urethane as a linker compound was examined by infrared spectroscopic imaging and differential scanning calorimetry.
Upgrade of the ERDA setup at the HZDR 6 MV tandem accelerator
Julin, J.; Aniol, R.; Munnik, F.; Heller, R.
During 2019 the elastic recoil detection (ERD) beamline attached to the 6 MV tandem accelerator at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has been modernized completely. Since many of the vacuum and electrical components of the previous setup had been showing signs of aging or failing, the decision was made to replace these and rebuild the setup. Additionally, during 2018 the construction of a new time-of-flight spectrometer for ERD was also completed, and it was seen that the ERD setup as a whole would benefit from a combination of a new chamber, mechanical supports and a control system.
The new setup incorporates the previously used Z-separating Bragg ionization chamber (BIC), which is typically used with 43 MeV 35Cl beam. It is connected to a port on the chamber giving 30 degree scattering angle. The time-of-flight branch is attached to the other side of the chamber at a 40 degree scattering angle. Various beams up to an energy of 20 MeV for 35Cl or 30 MeV for 63Cu can be used, or even higher if hydrogen depth profiling is not necessary. The detector branches can be operated independently of each other, minimizing downtime due to breakdowns of detectors or maintenance. This is exceedingly important since the ion beam center (IBC) is a user facility and the beam time for the 6 MV accelerator is allocated based on proposals and scheduled long in advance to the actual measurement.
This presentation will give an overview of the new ERD setup, including specifics on the design of the new chamber, control and vacuum systems, detectors and data acquisition as well as some experimental data, performance figures and experiences gained during the construction of the setup.
Keywords: IBA; ERDA
ECAART13 - 13th European Conference on Accelerators in Applied Research and Technology, 05.-10.05.2019, Split, Croatia
The influence of orifice types on the flow structure of a bubble-driven liquid-metal flow in a horizontal magnetic field
Richter, T.; Wondrak, T.; Eckert, K.; Eckert, S.; Odenbach, S.
Bubble plumes play an important role in metallurgical applications in order to stir and refine melts. Static electromagnetic fields allow a contactless control of those bubble plumes. However, for a tailored control the effects of the magnetic field to the bubble motion are important.
It is well known, that a bubble plume rising in a bulk of liquid metal has an axially symmetric shape. But the motion becomes asymmetric, when a static magnetic field (B) is applied in horizontal direction to the liquid metal. The direction of the flow parallel to B is upward, while the direction of the flow perpendicular to B is downward close to the plume.
Measurements of Zhang et al. of a bubble plume in the liquid metal GaInSn, emerging from a single orifice in a cylindrical vessel by the usage of the ultrasound Doppler velocimetry (UDV), confirmed this asymmetric motion. They observed traveling vortex structures in the direction perpendicular to B for moderate Hartmann numbers (Ha). This vortex structure became frozen, when high Ha were reached.
The focal point of this paper is the measurement of the bubble features in a similar container instead of measuring the flow of the liquid metal. The ultrasound transit time technique (UTTT) is employed, which was previously utilized to detect and analyze the motion of single bubbles rising in GaInSn. In comparison to the previous setup, a square vessel instead of round one is used and a sharp injection needle instead of a polished one was placed at the bottom of the vessel. During these new measurements, almost contradictory results are obtained: for small Ha numbers static vortex structures, which were deduced from the bubble motion, were observed, while traveling vortices were measured, when higher Ha were reached. The cause of this discrepancy is presumably the sharp orifice in the new setup, because the different cross section of the tank would rarely influence the motion.
We want to analyze the influence of the orifice type, by the comparison of two different shaped orifices, on the flow behavior in a new measurement campaign, where the bubble motion and the flow structure are detected by UTTT and UDV.
Keywords: ultrasound transit time technique; liquid metal; bubble plume
11th PAMIR international conference fundamental and applied MHD, 01.-05.07.2019, Reims, France
Contribution to proceedings
11th PAMIR International Conference Fundamental and Applied MHD, 01.-05.07.2019, Reims, France
The influence of orifice types on the flow structure of a bubble-driven liquid-metal flow in a horizontal magnetic field
Radiopharmakologische Charakterisierung eines neuen Chelators konjugiert an das PSMA-Bindungsmotiv Glutamat-Urea-Lysin
Sihver, W.; Böhme, J.; Wodtke, R.; Walther, M.; Steinbach, J.; Pietzsch, J.; Pietzsch, H.-J.
Molekulare Bildgebung mittels PET bzw. SPECT ist in der Krebsforschung ein unverzichtbares Werkzeug geworden, da diese genaue Informationen zu molekularen Eigenschaften von Tumoren liefern kann. Auf der Suche nach vielseitig einsetzbaren Chelatoren wurde für die Radionuklidmarkierung zielgerichteter PET/SPECT-Liganden ein Cyclohexandiamin-Triazol-Chelator entwickelt und an das Bindungsmotiv des prostata-spezifischen Antigens (PSMA) Glutamat-Urea-Lysin gekoppelt (Ligand in Abb. 1 = L). Dieses Motiv ist bekannt für seine gute Affinität an PSMA , welches bei verschiedenen Tumorentitäten stark exprimiert wird [2–4].
Ziel der Untersuchung war es, das radiopharmakologische Potential von L nach Radiomarkierung mit 68Ga, 111In und 18F bezüglich der Bindungseigenschaften und Zell-Internalisierung abzuschätzen und mit dem ‚Gold-Standard‘ PSMA-617 (177Lu- oder 64Cu-markiert) zu vergleichen.
Für den nichtmarkierten Liganden L wurde in Kompetitionsassays versus [177Lu]Lu-PSMA-617 eine etwas geringere Affinität als für PSMA-617 ermittelt. Sättigungsanalysen von [68Ga]Ga-L, [111In]In-L und [18F]F-L an LNCaP-Zellhomogenaten ergaben ähnliche Affinitäten (Kd 18–30 nM), die wiederum etwas niedriger waren als die von [177Lu]Lu-PSMA-617 (11 nM). Die Ergebnisse der Internalisierungsversuche zeigten eine stärkere Aufnahme von [64Cu]Cu-PSMA-617 in LNCaP-Zellen als vom verschieden radiomarkierten L.
Mit dem Konjugat L konnten nach erfolgreicher Radiomarkierung mit 68Ga, 111In und 18F vielversprechende Bindungseigenschaften gegenüber PSMA bestimmt werden. Die Vielseitigkeit dieses Chelators bietet die Möglichkeit mit entsprechendem Radionuklid sowohl für PET (68Ga, 18F) als auch für SPECT (111In) einsetzbar zu sein.
 K. Kopka, J. Nucl. Med. 2017, 58,17S.  H.R. Kulkarni, Br. J. Radiol. 2018, 91,20180308.  Y. Tolkach, Breast Cancer Res.Treat. 2018, 169,447.  M.C. Haffner, Hum.Pathol. 2009, 40,1754.
Radiopharmakologische Charakterisierung eines neuen Chelators konjugiert an das PSMA-Bindungsmotiv Glutamat-Urea-Lysin /GDCh Nuklearchemie, 25.-27.09.2019, Dresden, Deutschland
Nature and Surface Interactions of Sulfur-Containing Deposits on V2O5-WO3/TiO2- Catalysts for SCR-DeNOx
Rammelt, T.; Kuc, A.; Böhm, J.; Heine, T.; Gläser, R.
Sulfur-containing deposits form on a monolithic V2O5-WO3/TiO2 (VWT) catalyst during SCR-DeNOx with NH3 at 473 and 523 K and pressures up to 500 kPa in the presence of SO2 with sulfate contents of 1.7 to 13.0 wt.-%. Using TGA and DRIFTS, these deposits are determined to be mainly NH4HSO4 for SCR temperatures > 523 K. At lower temperatures, (NH4)2SO4 is formed. The thermal stability of NH4HSO4 supported on different transition metal oxides including V2O5, WO3, TiO2, MoO3 and Al2O3 varies with decomposition temperatures from 620 to 820 K. Using DFT calculations, it is show that the thermal stability of supported NH4HSO4 is mainly determined by hydrogen bonding of the HSO4- anions with the metal oxide surface. Increasing electronegativity of the metal atoms of the support oxide leads to weakening of the S-O bonds in the HSO4- anions and to lower decomposition temperatures of the supported NH4HSO4.
Emission Control Science and Technology 5(2019), 297-306
- Final Draft PDF 966 kB Secondary publication
Selective CO2 Electroreduction to Ethylene and Multicarbon Alcohols via Electrolyte-Driven Nanostructuring
Gao, D.; Sinev, I.; Scholten, F.; Arán-Ais, R. M.; Divins, N. J.; Kvashnina, K.; Timoshenko, J.; Roldan Cuenya, B.
The production of multicarbon products (C2+) from CO2 electroreduction reaction (CO2RR) is highly desirable for storing renewable energy and reducing carbon emission. Here we report the electrochemical synthesis of CO2RR catalysts that are highly selective for C2+ products via electrolyte-driven nanostructuring. Nanostructured Cu catalysts synthesized in the presence of specific anions can selectively convert CO2 to ethylene and multicarbon alcohols in aqueous 0.1 M KHCO3 solution, with the iodine-modified catalyst displaying the highest Faradaic efficiency of ~80% and partial current density of ~34 mA cm−2 for C2+ products at −0.9 V vs RHE. Operando X-ray absorption spectroscopy and quasi in situ X-ray photoelectron spectroscopy measurements revealed that the high C2+ selectivity of these nanostructured Cu catalysts can be mainly attributed to their nanoporous structure, presence of subsurface oxygen and Cu+ species, and the adsorbed halides. This work provides new insight into the parameters that should be tuned in order to rationally design C2+-selective CO2RR catalysts.
Angewandte Chemie 131(2019)47, 17203-17209
Predicting late magnetic resonance image changes in glioma patients after proton therapy
Eulitz, J.; Troost, E. G. C.; Raschk, F.; Schulz, E.; Lutz, B.; Dutz, A.; Löck, S.; Wohlfahrt, P.; Enghardt, W.; Karpowitz, C.; Krause, M.; Lühr, A.
Proton radiation therapy is an effective treatment for glioma patients. To exploit its full potential, a better description of regional differences in radiation response within the brain is required. In this study, we present a model for predicting magnetic resonance (MR) image changes in glioma patients that considers the variability in proton relative biological effectiveness (RBE) as well as the regional susceptibility of brain tissue to radiation damage.
Material and methods:
Six glioma patients treated with adjuvant proton radio(chemo)therapy showed contrast enhancement on follow-up T1-weighted MR imaging corresponding to treatment-related changes. Physical dose and linear energy transfer (LET) were obtained from high-precision Monte-Carlo simulations. The periventricular region (PVR) was contoured as a 4 mm expansion around the ventricles. Correlations between the image changes and dose, LET, and the PVR were evaluated voxel-wise in univariable and multivariable logistic regression analyses. Model performance was assessed by the area under the curve (AUC) using leave-one-out cross validation. The tolerance dose TD50, at which 50% of the tissue voxels show toxicity was interpolated from the model and used for RBE estimation.
The spatial distribution of MR image changes in the brain was highly non-uniform and correlated poorly with the considered predictors in univariable analysis. Multivariable modelling with either only dose and LET or PVR as third predictor revealed AUC values of 0.89 and 0.92, respectively. TD50 decreased with increasing LET and the modelled RBE was found to vary between 0.9 and 2.3. No relevant difference in model performance was found for track- or dose-averaged LET.
The strong correlation of MR image changes with dose, LET, and the PVR demonstrates the relevance of non-uniform dose response models. A larger patient cohort including patients without image changes will be used to validate the clinically observed indication of a variable proton RBE.
Keywords: Proton Therapy; Glioma; Variable RBE; MR image changes
Acta Oncologica 58(2019)10, 1536-1539
Performance Analysis for Large Scale GPU Applications and DL Frameworks
Get your hands on the latest versions of Score-P and Vampir to profile the execution behavior of your large-scale GPU-Accelerated applications. See how these HPC community tools pick up as other tools (such as NVVP) drop off when your application spans multiple compute nodes. Regardless of whether your application uses CUDA, OpenACC, OpenMP or OpenCL for acceleration, or whether it is written in C, C++, Fortran or Python, you will receive a high-resolution timeline view of all program activity alongside the standard profiles to identify hot spots and avenues for optimization. The novel Python support now also enables performance studies for optimizing the inner workings of deep learning frameworks.
GPU Technology Conference 2019, 17.-21.03.2019, San Jose, CA, USA
The dominating mechanisms for the formation of solute-rich clusters in steels under irradiation
The formation of nano-sized, coherent, solute-rich clusters (NSRC) is known to be an important factor causing the degradation of the macroscopic properties of steels under irradiation. The mechanisms driving their formation are still debated. This work focuses on low-Cu reactor pressure vessel (RPV) steels, where solute species are generally not expected to precipitate. We rationalize the processes that take place at the nanometer scale under irradiation, relying on the latest theoretical and experimental evidence on atomic-level diffusion and transport processes. These are compiled in a new model, based on the object kinetic Monte Carlo (OKMC) technique. We evaluate the relevance of the underlying physical assumptions by applying the model to a large variety of irradiation experiments. Our model predictions are compared with new experimental data obtained with atom probe tomography and small angle neutron scattering, complemented with information from the literature. The results of this study reveal that the role of immobilized self-interstitial atoms (SIA) loops dominates the nucleation process of NSRC.
Keywords: Hardening; Embrittlement; Steel; Modelling
Materials Today Energy 17(2020), 100472
Inter-observer variability in target delineation increases during adaptive treatment of head-and-neck and lung cancer
Apolle, R.; Appold, S.; Bijl, H. P.; Blanchard, P.; Bussink, J.; Faivre-Finn, C.; Khalifa, J.; Laprie, A.; Lievens, Y.; Madani, I.; Ruffier, A.; de Ruysscher, D.; van Elmpt, W.; Troost, E. G. C.
Inter-observer variability (IOV) in target volume delineation is a well-documented source of geometric uncertainty in radiotherapy. Such variability has not yet been explored in the context of adaptive re-delineation based on imaging data acquired during treatment. We compared IOV in the pre- and mid-treatment setting using expert primary gross tumour volume (GTV) and clinical target volume (CTV) delineations in locoregionally advanced head-and-neck squamous cell carcinoma (HNSCC) and (non-)small cell lung cancer [(N)SCLC].
Materials and Methods
Five and six observers participated in the HNSCC and (N)SCLC arm, respectively, and provided delineations for five cases each. Imaging data consisted of CT studies partly complemented by FDG-PET and was provided in two separate phases for pre- and mid-treatment. Global delineation compatibility was assessed with a volume overlap metric (the Generalised Conformity Index), while local extremes of IOV were identified through the standard deviation of surface distances from observer delineations to a median consensus delineation. Details of delineation procedures, in particular GTV to CTV expansion and adaptation strategies, were collected through a questionnaire.
Volume overlap analysis revealed a worsening of IOV in all but one case per disease site, which failed to reach significance in this small sample (p-value range 0.063- 0.125). Changes in agreement were propagated from GTV to CTV delineations, but correlation could not be formally demonstrated. Surface distance based analysis identified longitudinal target extent as a pervasive source of disagreement for HNSCC. High variability in (N)SCLC was often associated with tumours abutting consolidated lung tissue or potentially invading the mediastinum. Adaptation practices were variable between observers with fewer than half stating that they consistently adapted pre-treatment delineations during treatment.
IOV in target volume delineation increases during treatment, where a disparity in institutional adaptation practices adds to the conventional causes of IOV. Consensus guidelines are urgently needed.
Keywords: Target volume delineation; Inter-observer variability; Adaptive radiotherapy; Head-and-neck squamous cell carcinoma; (Non-)small cell lung cancer
Acta Oncologica 58(2019)10, 1378-1385
- Final Draft PDF 1,4 MB Secondary publication
Einfluss von Protonen-Reichweiteunsicherheiten auf LET-Verteilungen am Beispiel von Hirntumor-Patienten
Hahn, C.; Peters, N.; Wohlfahrt, P.; Richter, C.; Eulitz, J.; Enghardt, W.; Lühr, A.
Erste klinische Evidenz zeigt, dass die relative biologische Wirksamkeit (RBW) von Protonen auch vom linearen Energietransfer (LET) bestimmt wird. Die patientenspezifische LET-Verteilung folgt aus der Eindringtiefe der Protonenstrahlen und wird daher unmittelbar von Reichweiteunsicherheiten beeinflusst. Diese Studie quantifiziert den Einfluss von Reichweiteunsicherheiten auf LET-Verteilungen im klinischen Zielvolumen (CTV) und angrenzenden Risikoorganen am Beispiel von Hirntumor-Patienten.
Material & Methoden
Für jeden Patienten wurden zwei nominelle, robust-optimierte Bestrahlungspläne mit Pencil-Beam-Scanning unter Verwendung von Single-Field-Uniform-Dose und Multi-Field-Optimization erstellt. Dabei wurde jeweils ein Simultan-Integrierter-Boost mit zwei Einstrahlrichtungen geplant. Das Protonenbremsvermögen jedes Voxels folgte direkt aus dem Dual-Energy-CT-Scan für die Therapieplanung. Systematische Reichweiteunterschiede wurden durch Skalierung des Bremsvermögens erzeugt. Die Bestrahlungspläne wurden mittels Monte-Carlo-Methode für drei Reichweiteszenarien (nominell, ±3.5%) simuliert und der dosisgemittelte LET voxelweise bestimmt (RayStation, Forschungsversion 5.99.50). Die Auswertungen der LET-Differenzen erfolgte voxelweise, organspezifisch und auf einem Signifikanzniveau von 5% (zweiseitiger t-Test).
Der mittlere LET im Zielvolumen änderte sich weder signifikant durch die simulierten Reichweiteunsicherheiten noch durch die verwendete Planungsstrategie. Gemittelt über Patienten, Planungsstrategie und Reichweiteszenarien betrug der mittlere LET (±Standardabweichung) im CTV 2.78 (±0.07) keV/µm. Im Vergleich zum CTV war der mittlere LET in Risikoorganen signifikant erhöht. Reichweiteunsicherheiten führten innerhalb einer Planungsstrategie patientenspezifisch zu einer Veränderung des mittleren LET um bis zu 0.70 keV/µm (rechter Sehnerv) bzw. 0.38 keV/µm (Hirnstamm). Die Reichweiteunsicherheiten führten zu relevanten Änderungen der LET-Varianz in angrenzenden Risikoorganen mit LET-Maxima bei einzelnen Patienten, z.B. im Hirnstamm (maximale Dosis von 51.8 Gy(RBW)) oder im rechten Sehnerv (53.6 Gy(RBW)).
Die Reichweiteunsicherheit der Protonentherapie bei Hirn-Tumor-Patienten beeinflusste die LET-Verteilungen in Risikoorganen, aber nicht im Zielvolumen. Beobachtete hohe, lokale LET-Varianzen sowie LET-Maxima in Risikoorganen könnten zu einer erhöhten biologischen Wirksamkeit führen und bei Dosen nahe dem Grenzwert unerwartete Normalgewebskomplikationen hervorrufen.
50. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik, 18.-21.09.2019, Stuttgart, Deutschland
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