Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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32228 Publications
Interaction of O-Y and O-Y-Ti clusters embedded in bcc Fe with He, vacancies and self-interstitial atoms
Vallinayagam, M.; Posselt, M.; Faßbender, J.;
Calculations based on Density Functional Theory are performed to investigate the interaction of O-Y and O-Y-Ti clusters in bcc Fe with He atoms, vacancies (V) and self-interstitial atoms (SIA). The four different cluster structures studied in our previous work (J Phys Condens Matter 31 095701) are considered. He, V and SIA are inserted on different positions inside and in the environment of the clusters, the total energy of the corresponding supercell is minimized and the binding and incorporation energy of the three kinds of defects is determined. He in the center of a cage-like (CL) cluster is more stable than on interfacial vacant sites (IVS). In CL O-Y clusters He on an IVS is more stable than in the cluster structure with oxygen in the center (OC), whereas there is no significant difference between the two kinds for clusters with Ti. Up to a distance of 1.5 times the iron lattice constant from the cluster center He is not stable on most of the octahedral and tetrahedral interstitial sites in the Fe matrix near the interface. Instead He is shifted towards positions closer to the cluster. Relaxation occurs to known IVS as well as to previously unknown interfacial interstitial sites (IIS). Moreover, two or three He atoms are placed on sites found to be stable after adding a single He. The corresponding binding and incorporation energies obtained after relaxation are nearly equal to the sum of the values for the interaction with a single He atom. However, placing He dimers or trimers in the environment of a vacancy may also lead to relatively low values of the incorporation energy. Also, barriers for jumps of He atoms between interfacial sites and the center of CL clusters are determined. In the CL O-Y cluster the barriers are lower than in the CL O-Y-Ti cluster, i.e. trapping and release of He is easier in the former than in the latter. V and SIA interaction with the clusters is also attractive. The binding energy of V strongly depends on the site where V is inserted while in all the studied cases the SIA is annihilated at the cluster-iron interface. Present results clearly demonstrate that the oxide-based nanoclusters are strong traps for irradiation induced defects which is in agreement with experimental findings.
Keywords: density functional theory calculations, oxide dispersion strengthened steels, interaction with He, vacancies and self-interstitial atoms

Publ.-Id: 29178 - Permalink


Magnetic Orders and Origin of Exchange Bias in Co Clusters Embedded Oxide Nanocomposite Films
Li, H.; Wang, C.; Li, D.-Y.; Pereira, L. M. C.; Homm, P.; Menghini, M.; Locquet, J.-P.; Temst, K.; Vantomme, A.; van Haesendonck, C.; van Bael, M. J.; Ruan, S.; Zeng, Y.-J.;
Magnetic nanoparticles embedded oxide semiconductors are interesting candidates for spintronics in view of combining ferromagnetic (FM) and semiconducting properties. Co-ZnO and Co-V2O3 nanocomposite thin films are synthesized by Co ion implantation in crystalline thin films. Magnetic order varies with the implantation fluence in Co-ZnO, where the superparamagnetic (SPM) order appears in the low-fluence films (2×1016 and 4×1016 ions/cm2) while the FM order coexists with the SPM phase in high-fluence ones (1×1017 ions/cm2). The exchange bias (EB) effect is evident in high-fluence films, which gives an EB field of about 100 Oe at 2 K and a blocking temperature of around 100 K. In parallel, 3.5×1016 ions/cm2 Co-V2O3 hybrid thin film exhibits a clear antiferromagnetic (AFM) coupling at low temperature with a weak EB effect. The different magnetic behaviors in the two Co-implanted systems lead us to believe on one hand, that the observed EB effect in the Co-ZnO system is the result of the FM/AFM coupling between large Co nanoparticles and their CoO/Co3O4 surroundings in the (Zn,Co)O matrix. While, on the other hand, the EB effect in Co-V2O3 system originates from the interaction between FM Co nanoparticles and AFM V2O3 matrix. Detailed studies of magnetic orders as well as EB effect in magnetic nanocomposite semiconductors pave the way for their application in spintronics.
Keywords: nanocomposite, exchange bias, antiferromagnetic, superparamagnetic

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Publ.-Id: 29176 - Permalink


Thermal stability of Te-hyperdoped Si: Atomic-scale correlation of the structural, electrical, and optical properties
Wang, M.; Hübner, R.; Xu, C.; Xie, Y.; Berencén, Y.; Heller, R.; Rebohle, L.; Helm, M.; Prucnal, S.; Zhou, S.;
Si hyperdoped with chalcogens (S,Se,Te) is well known to possess unique properties such as an insulator-tometal transition and a room-temperature sub-band-gap absorption. These properties are expected to be sensitive to a postsynthesis thermal annealing, since hyperdoped Si is a thermodynamically metastable material. Thermal stability of the as-fabricated hyperdoped Si is of great importance for the device fabrication process involving temperature-dependent steps such as Ohmic contact formation. Here, we report on the thermal stability of the as-fabricated Te-hyperdoped Si subjected to isochronal furnace anneals from 250 to 1200 °C. We demonstrate that Te-hyperdoped Si exhibits thermal stability up to 400 °C for 10 min, which even helps to further improve the crystalline quality, the electrical activation of Te dopants, and the room-temperature sub-band-gap absorption. At higher temperatures, however, Te atoms are found to move out from the substitutional sites with a maximum migration energy of EM = 2.3 eV forming inactive clusters and precipitates that impair the structural, electrical, and optical properties. These results provide further insight into the underlying physical state transformation of Te dopants in a metastable compositional regime caused by postsynthesis thermal annealing. They also pave the way for the fabrication of advanced hyperdoped Si-based devices.

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Publ.-Id: 29175 - Permalink


Controllable defect driven symmetry change and domain structure evolution in BiFeO3 with enhanced tetragonality
Chen, C.; Wang, C.; Cai, X.; Xu, C.; Li, C.; Zhou, J.; Luo, Z.; Fan, Z.; Qin, M.; Zeng, M.; Lu, X.; Gao, X.; Kentsch, U.; Yang, P.; Zhou, G.; Wang, N.; Zhu, Y.; Zhou, S.; Chen, D.; Liu, J.;
Defect engineering has been a powerful tool to enable the creation of exotic phases and the discovery of intriguing phenomena in ferroelectric oxides. However, the accurate control of the concentration of defects remains a big challenge. In this work, ion implantation, which can provide controllable point defects, allows us to produce a controlled defect driven true super-tetragonal (T) phase with a single-domain-state in ferroelectric BiFeO3 thin films. This point-defect engineering is found to drive the phase transition from the as-grown mixed rhombohedral-like (R) and tetragonal-like (MC) phase to true tetragonal (T) symmetry and induce the stripe multi-nanodomains to a single domain state. By further increasing the injected dose of the He ion, we demonstrate an enhanced tetragonality super-tetragonal (super-T) phase with the largest c/a ratio of ∼1.3 that has ever been experimentally achieved in BiFeO3. A combination of the morphology change and domain evolution further confirms that the mixed R/MC phase structure transforms to the single-domain-state true tetragonal phase. Moreover, the re-emergence of the R phase and in-plane nanoscale multi-domains after heat treatment reveal the memory effect and reversible phase transition and domain evolution. Our findings demonstrate the reversible control of R-Mc-T-super T symmetry changes (leading to the creation of true T phase BiFeO3 with enhanced tetragonality) and multidomain-single domain structure evolution through controllable defect engineering. This work also provides a pathway to generate large tetragonality (or c/a ratio) that could be extended to other ferroelectric material systems (such as PbTiO3, BaTiO3 and HfO2) which might lead to strong polarization enhancement.

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  • Secondary publication expected from 05.04.2020

Publ.-Id: 29174 - Permalink


Absorption edge, Urbach tail, and electron-phonon interactions in topological insulator Bi2Se3 and band insulator (Bi0.89In0.11)2Se3
Zhu, JiajunORC; Xia, Y.; Li, G.; Zhou, S.ORC; Wimmer, S.; Springholz, G.ORC; Pashkin, A.ORC; Helm, M.; Schneider, H.ORC
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.

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Publ.-Id: 29170 - Permalink


Electron-Beam-Driven Structure Evolution of Single-Layer MoTe2 for Quantum Devices
Lehnert, T.; Ghorbani-Asl, MahdiORC; Köster, J.; Lee, Z.; V. Krasheninnikov, A.ORC; Kaiser, U.
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

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  • Secondary publication expected from 26.04.2020

Publ.-Id: 29169 - Permalink


Impact of Extrinsic and Intrinsic Hypoxia on Catecholamine Biosynthesis in Absence or Presence of Hif2α in Pheochromocytoma Cells
Bechmann, N.; Poser, I.; Seifert, V.; Greunke, C.; Ullrich, M.ORC; Qin, N.; Walch, A.; Peitzsch, M.; Robledo, M.; Pacak, K.; Pietzsch, J.ORC; Richter, S.; Eisenhofer, G.
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

Publ.-Id: 29168 - Permalink


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.

Publ.-Id: 29167 - Permalink


Carboranyl analogues of ketoprofen with cytostatic activity against human melanoma and colon cancer cell lines
Buzharevski, A.; Paskas, S.; Laube, M.ORC; Lönnecke, P.; Neumann, W.; Murganic, B.; Mijatovic, S.; Maksimovic-Ivanic, D.; Pietzsch, J.ORC; Hey-Hawkins, E.
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.

Publ.-Id: 29166 - Permalink


Thermal Transport in MoS2 from Molecular Dynamics using Different Empirical Potentials
Xu, K.; Gabourie, A. J.; Hashemi, A.; Fan, Z.; Wei, N.; Farimani, A. B.; Komsa, H.-P.; Krasheninnikov, A. V.ORC; Pop, E.; Ala-Nissila, T.
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

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Publ.-Id: 29163 - Permalink


Tomonaga-Luttinger liquid in a box: electrons confined within MoS2 mirror twin boundaries
Jolie, W.; Murray, C.; Weiß, P. S.; Hall, J.; Portner, F.; Atodiresei, N.; Krasheninnikov, A. V.ORC; Busse, C.; Komsa, H.-P.; Rosch, A.; Michely, T.
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

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Publ.-Id: 29162 - Permalink


Room temperature ferromagnetism in MoTe2 by post-growth incorporation of vanadium impurities
Coelho, P. M.; Komsa, H.-P.; Lasek, K.; Kalappattil, V.; Karthikeyan, J.; Phan, M.-H.; Krasheninnikov, A. V.ORC; Batzill, M.
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

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  • Secondary publication expected from 01.04.2020

Publ.-Id: 29161 - Permalink


Efficient method for calculating Raman spectra of solids with impurities and alloys and its application to two-dimensional transition metal dichalcogenides
Hashemi, A.; Krasheninnikov, A.ORC; Puska, M.; Komsa, H.
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

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Publ.-Id: 29160 - Permalink


Cathepsin B-Activatable Cell-Penetrating Peptides
Kuhne, K.; Behring, L.; Belter, B.; Wodtke, R.; Pietzsch, J.; Löser, R.;
Protease activity is increasingly drawn into the spotlight as a crucial modulator in cancer angiogenesis, invasion, and metastasis [1]. 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 [4] (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 [5] (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.

[1] Yang et al., Cancer Growth Metastasis 2009, 2, 13
[2] Aggarwal and Sloane, Proteomics Clin. Appl. 2014, 8, 427
[3] Löser and Pietzsch, Front. Chem. 2015, 3, article 37
[4] Jiang et al., PNAS, 2004, 101, 17867
[5] Cotrin et al., Anal. Biochem. 2004, 335, 244
  • Poster
    Frontiers in Medicinal Chemistry, 24.-27.03.2019, Würzburg, Deutschland

Publ.-Id: 29159 - Permalink


Optical properties of ZnSxTe1-x synthesized by sulfur implantation
Zhang, X.; Xu, M.; Li, Q.ORC; Wang, M.; Akhmadaliev, S.; Zhou, S.; Wu, Y.; Guo, B.
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.

Publ.-Id: 29158 - Permalink


Dipeptide-derived Alkynes as Irreversible Inhibitors of Cysteine Cathepsins
Behring, L.; Trapp, C.; Morales, M.; Wodtke, R.; Kuhne, K.; Belter, B.; Pietzsch, J.; Löser, R.;
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. [3] 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) [4]. 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.
[1] Ekkebus et al., J. Am. Chem. Soc., 2013, 135, 2867-2870.
[2] Sommer et al., Bioorg. Med. Chem., 2013, 21, 2511-2517.
[3] Löser and Pietzsch, Front. Chem., 2015, 3, 37.
[4] Greenspan et al., J. Med. Chem., 2001, 44, 4524-4534.
  • Lecture (Conference)
    Frontiers in Medicinal Chemistry, 24.-27.03.2019, Würzburg, Deutschland

Publ.-Id: 29157 - Permalink


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.

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Publ.-Id: 29155 - Permalink


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.

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Publ.-Id: 29154 - Permalink


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+,-,Ks0, 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.

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Publ.-Id: 29153 - Permalink


Ferromagnetic (In,Ga,Mn)As films prepared by ion implantation and pulsed laser melting
Xu, C.ORC; Wang, M.; Zhang, X.; Yuan, Y.; Zhou, S.
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

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Publ.-Id: 29152 - Permalink


Coupled dissolution-precipitation reactive transport modeling at the pore scale
Karimzadeh, L.; Fischer, C.;
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 [1]. 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 [2] and temporal [3] 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.


[1] 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.
[2] Fischer, C., and Luttge, A., 2018, Pulsating dissolution of crystalline matter. PNAS 115.
[3] Fischer, C., Kurganskaya, I., and Luttge, A., 2018, Inherited control of crystal surface reactivity. Applied Geochemistry 91, 140.
  • Poster
    EGU General Assembly 2019, 08.-12.04.2019, Wien, Österreich

Publ.-Id: 29151 - Permalink


Improving fracture-flow models by experimental evidence from process tomography
Kulenkampff, J.; Karimzadeh, L.; Jankovsky, F.; Zuna, M.; Havlova, V.; Fischer, C.;
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.
  • Poster
    EGU General Assembly 2019, 08.-12.04.2019, Wien, Österreich

Publ.-Id: 29150 - Permalink


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.
  • Lecture (others)
    Institutsseminar am CIEMAT, 24.04.2019, Madrid, Spanien

Publ.-Id: 29147 - Permalink


Maximizing magnetic field generation in high power laser–solid interactions
Huang, L. G.; Takabe, H.; Cowan, T. E.;
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

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Publ.-Id: 29146 - Permalink


Fast 2D laser-induced fluorescence spectroscopy mapping of rare earth elements in rock samples
Seidel, P.; Lorenz, S.; Heinig, T.; Zimmermann, R.; Booysen, R.; Beyer, J.; Heitmann, J.; Gloaguen, R.;
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, optical spectroscopy, reflectance spectroscopy

Publ.-Id: 29143 - Permalink


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.;
Background
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.

Aims
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.

Methods/Results
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.

Summary/Conclusion
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.
  • Poster
    1st European CAR T Cell Meeting, 14.-16.02.2019, Paris, France

Publ.-Id: 29139 - Permalink


Integriertes Management und Publikation von wissenschaftlichen Artikeln, Software und Forschungsdaten am Helmholtz-Zentrum Dresden-Rossendorf (HZDR)
Reschke, E.; Konrad, U.;
Mit dem Ziel, das Publizieren von Artikeln, Forschungsdaten und wissenschaftlicher Software gemäß den FAIR-Prinzipien 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
  • Open Access LogoContribution 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
  • Open Access LogoInvited lecture (Conferences)
    WissKom2019 – Forschungsdaten: Sammeln, sichern, strukturieren. 8. Konferenz der Zentralbibliothek, Forschungszentrum Jülich, 04.-06.06.2019, Jülich, Deutschland
    DOI: 10.13140/RG.2.2.14789.19683

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Publ.-Id: 29138 - Permalink


Fluid Flow and Transport Phenomena in Liquid Metal Batteries
Weier, T.; Horstmann, G. M.; Landgraf, S.; Nimtz, M.; Personnettaz, P.; Stefani, F.; Weber, N.;
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

Publ.-Id: 29134 - Permalink


Integral multi-scenario robustness evaluation of anatomical robust optimization in head and neck
Cubillos Mesías, M.; Troost, E. G. C.; Lohaus, F.; Agolli, L.; Rehm, M.; Richter, C.; Stützer, K.ORC
Purpose/Objective
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.

Material/Methods
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).

Results
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.

Conclusion
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.
  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Mailand, Italien
  • Open Access LogoAbstract in refereed journal
    Radiotherapy and Oncology 133(2019)Sup 1, S488-S489
    DOI: 10.1016/S0167-8140(19)31335-0

Publ.-Id: 29131 - Permalink


Bestimmung der Gas-Flüssigkeits-Grenzfläche in Anstaupackungen mittels ultraschneller Röntgentomographie
Sohr, J.; Bieberle, M.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.;
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 [1]. 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).
[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.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Deutschland

Publ.-Id: 29129 - Permalink


Partieller Einsatz von teilweise gefluteten Packungen
Flechsig, S.; Utchenko, Y.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.;
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 [1] 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.
[1] S. Flechsig, J. Sohr, M. Schubert, U. Hampel, E.Y. Kenig, Chem. Eng. Trans., 2018, 69, 169-174, DOI: 10.3303/CET1869029.
  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Fluidverfahrenstechnik und Membrantechnik, 27.-29.03.2019, Potsdam, Deutschland

Publ.-Id: 29128 - Permalink


Mass transfer and electrolyte flow during electrodeposition on a conically shaped electrode under the influence of a magnetic field
Huang, M.; Marinaro, G.; Yang, X.; Fritzsche, B.; Lei, Z.; Uhlemann, M.; Eckert, K.; Mutschke, G.;
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

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  • Secondary publication expected from 01.06.2020

Publ.-Id: 29127 - Permalink


Multidimensional fluid mixing study during an asymmetric injection of cold water in the primary side of a generic PWR KONVOI with ATHLET 3.1A
Diaz Pescador, E.; Schäfer, F.; Kliem, S.;
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
  • Lecture (Conference)
    50th Annual meeting on Nuclear Technology (AMNT) 2019, 07.-08.05.2019, Berlin, Germany

Publ.-Id: 29125 - Permalink


Late life brain perfusion after prenatal famine exposure
de Rooij, S. R.; Mutsaerts, H. M.; Petr, J.; Asllani, I.; Caan, M. W.; Groot, P.; Nederveen, A.; Schwab, M.; Roseboom, T. J.;
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

Publ.-Id: 29117 - Permalink


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.
  • Lecture (Conference)
    OpenFOAM Workshop, 23.07.2019, Duisburg, Germany

Publ.-Id: 29113 - Permalink


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.
  • Lecture (Conference)
    OpenFOAM Workshop, 23.07.2019, Duisburg, Deutschland

Publ.-Id: 29112 - Permalink


Interaction of uranium with halophilic microorganisms
Bader, M.; Hilpmann, S.; Swanson, J. S.; Steudtner, R.; Drobot, B.; Schmidt, M.; Rossberg, A.; Ikeda-Ohno, A.; Stumpf, T.; Cherkouk, A.;
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.
  • Lecture (Conference)
    Halophiles 2019, 24.-28.06.2019, Cluj-Napoca, Romania

Publ.-Id: 29110 - Permalink


Prediction of Bubble Departure in Forced Convection Boiling with a Mechanistic Model that Considers Dynamic Contact Angle and Base Expansion
Setoodeh, H.; Ding, W.; Lucas, D.; Hampel, U.;
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

Publ.-Id: 29109 - Permalink


Indium thiospinel In1-xxIn2S4 – 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-xxIn2S4 (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-xxIn2S4 were found in the samples with 0.16  x  0.22 and x = 0.33 (In2S3), respectively, while In0.720.28In2S4 is proven to contain both α- and β-polymorphic modifications. Consequently, thermoelectric characterization of well-defined α-and β-In1-xxIn2S4 is conducted for the first time. α-In1-xxIn2S4 (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-In0.670.33In2S4 (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-xxIn2S4.
Keywords: In2S3, thermoelectric properties, thiospinel, Raman spectroscopy, transmission electron microscopy

Publ.-Id: 29105 - Permalink


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

Publ.-Id: 29104 - Permalink


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.
Results:
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.
Conclusion:
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

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  • Secondary publication expected from 29.06.2020

Publ.-Id: 29101 - Permalink


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

Publ.-Id: 29100 - Permalink


Frontiers of applications of Petawatt lasers, Plasma accelerator development in Dresden
Schramm, U.ORC
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

Publ.-Id: 29099 - Permalink


Laser plasma proton accelerators for therapy ?
Schramm, U.ORC
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

Publ.-Id: 29098 - Permalink


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.

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Publ.-Id: 29097 - Permalink


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.;
Ziel/Aim:
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].

Methodik/Methods:
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.

Ergebnisse/Results:
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.

Schlussfolgerungen/Conclusions:
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
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29096 - Permalink


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.;
Ziel/Aim:
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) [1]. 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.

Methodik/Methods:
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.

Ergebnisse/Results:
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).

Schlussfolgerungen/Conclusions:
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.
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29095 - Permalink


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.;
Ziel/Aim:
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.

Methodik/Methods:
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.

Ergebnisse/Results:
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%.

Schlussfolgerungen/Conclusions:
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.
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29094 - Permalink


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.;
Ziel/Aim:
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.

Methodik/Methods:
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.

Ergebnisse/Results:
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]%).

Schlussfolgerungen/Conclusions:
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.
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29093 - Permalink


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.;
Ziel/Aim:
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.

Methodik/Methods:
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.

Ergebnisse/Results:
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%.

Schlussfolgerungen/Conclusions:
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.
  • Lecture (Conference)
    Jahrestagung der DGN, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29092 - Permalink


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
  • Open Access LogoBook chapter
    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
    DOI: 10.5772/intechopen.85641

Publ.-Id: 29091 - Permalink


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.

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Publ.-Id: 29090 - Permalink


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.

Publ.-Id: 29085 - Permalink


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.

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Publ.-Id: 29081 - Permalink


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.

Publ.-Id: 29080 - Permalink


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.

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  • Secondary publication expected from 02.09.2020

Publ.-Id: 29074 - Permalink


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.;
Introduction:

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.

Results:

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.

Conclusion:

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

Publ.-Id: 29073 - Permalink


Performance Analysis for Large Scale GPU Applications and DL Frameworks
Juckeland, G.ORC; Henschel, R.ORC
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.
  • Lecture (Conference)
    GPU Technology Conference 2019, 17.-21.03.2019, San Jose, CA, USA

Publ.-Id: 29070 - Permalink


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.;
Introduction
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.

Results
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.

Conclusion
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

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  • Secondary publication expected

Publ.-Id: 29068 - Permalink


Liquid Metal Model Experiments for Continuous Casting of Steel Under the Influence of Magnetic Fields
Schurmann, D.ORC; Glavinić, I.ORC; Timmel, K.ORC; Willers, B.ORC; Eckert, S.ORC
Magnetic fields are widely applied in the continuous casting process to modify the flow pattern in the mold and thereby improve the quality of the semi-finished product. While the use of Electromagnetic Brakes (EMBr) is common in slab casting, Electromagnetic Stirring (EMS) is mainly applied in bloom and billet casting and recently also in slab casting. Due to the harsh conditions in the real casting process, model experiments in cold liquid metals enable accurate measurements of velocity fields, surface oscillations, gas bubble characteristics, etc. These models improve understanding the effects of electromagnetic actuators and provide data to validate numerical models.

We present experimental results obtained in a model of a continuous caster, the Mini-LIMMCAST facility, where the velocity field is measured by Ultrasound Doppler Velocimetry (UDV). Results of experiments conducted with EMS in a round bloom geometry as well as experiments with EMBr in slab geometries are presented.
Keywords: Model Experiments, Ultrasound Doppler Velocimetry, Continuous Casting, Electromagnetic Brake, Electromagnetic Stirring
  • Contribution to proceedings
    8th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking (STEELSIM2019), 13.-15.08.2019, Toronto, Ontario, Canada, 620-627
    DOI: 10.33313/503/065
  • Lecture (Conference)
    8th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking (STEELSIM2019), 13.-15.08.2019, Toronto, Ontario, Kanada

Publ.-Id: 29064 - Permalink


A spectroscopic investigation of Eu3+ incorporation in LnPO4 (Ln = Tb, Gd1–xLux, x = 0.3, 0.5, 0.7, 1) ceramics
Huittinen, N.; Lösch, H.; Hirsch, A.; Holthausen, J.; Peters, L.; Xiao, B.; Neumeier, S.; Schmidt, M.;
Introduction
In recent years, rare-earth orthophosphates LnPO4 have attracted attention as potential hosts for the immobilization of specific radioactive waste streams.
Objectives
In the present work, the incorporation of Eu3+ in LnPO4 host materials predominantly having the xenotime structure has been investigated on the molecular level. As host cations we used Tb and Lu as well as a solid solution series of Gd1–xLuxPO4 (x = 0.3, 0.5, 0.7). The site selective laser luminescence spectroscopy (TRLFS) technique was applied to study the distribution of Eu3+ in the synthetic xenotime phases, while PXRD and Raman spectroscopy were used for bulk structural investigations direct after synthesis and after one year of storage at ambient conditions.
Results
The PXRD patterns of the solid solution series show the formation of a single xenotime phase up to a substitution of x = 0.5 both before and after aging. The TRLFS emission spectra also show that Eu3+ is substituted for the host cation site in the xenotime hosts. After one year, the emission spectra show a broad dominant signal between the transitions regions of the 7F1‒ and 7F2‒bands, and the luminescence signal no longer corresponds to Eu3+‒incorporation in a xenotime environment, only. These changes indicate a time-dependent change in the local structure of the europium dopant. Based on these observations we suggest an exclusion of Eu3+ from the crystal structure and subsequent migration of the cation to the grain boundaries during aging. The migration of Eu3+ in void spaces through the crystal structure could be responsible for the additional signals in the emission spectra, while the narrow void space forces an overlap between Eu3+ and oxygen atomic orbitals, resulting in the broad signal between the 7F1‒ and 7F2‒bands.
Conclusions
The segregation of Eu3+ to grain boundaries after a relatively short aging in the xenotime materials, indicates that xenotime ceramics will not serve as a suitable waste form for trivalent actinides from high–level nuclear waste.
  • Lecture (Conference)
    27th Annual Meeting of the German Crystallographic Society (DGK), 25.-28.03.2019, Leipzig, Germany

Publ.-Id: 29063 - Permalink


Microorganisms present in bentonites from a deep underground experiment
Lopez-Fernandez, M.; Drozdowski, J.; Kluge, S.; Cherkouk, A.;
The deep geological repository is one of the internationally accepted options to dispose highly radioactive waste. For this, a multi-barrier system where the radioactive waste will be encapsulated in a technical barrier (metal containers) surrounded by a geotechnical barrier (e.g. compacted bentonite) deep underground in a stable geological formation (host rock) can be used. Bentonites might be used as sealing and backfilling material due to their good properties such as high swelling capacity and low hydraulic conductivity. However, indigenous microorganisms and those introduce during the repository construction and operation can affect these properties.
Bentonite core samples were collected from the Full-scale Engineered Barrier Experiment (FEBEX) in the frame of the FEBEX-Dismantling Project [1] at the Grimsel Test Site (Switzerland) to study their microbial diversity. For that, total DNA was extracted directly from the cores. In addition, sulfate- and iron-reducing microorganisms were enriched from the bentonite samples using specific media. From those enrichments total DNA was extracted and sulfate- and iron-reducing microorganisms were isolated. The microbial communities of the cores, the enrichments, as well as the isolates were analyzed by 16S rRNA gene sequencing. The results showed that the FEBEX bentonite microbial population was directly affected by the continuous high temperature. The dominant phylum in both enrichments was Firmicutes. Desulfosporosinus, Clostridium and Bacillus spp. were identified from the medium for sulfate-reducers, while Desulfitobacterium and Bacillus spp. were detected in the iron-reducing enrichment. Pure cultures were isolated from both enrichments, identifying spore-forming bacteria.
This study revealed that microorganisms were detected on the FEBEX bentonite after almost twenty years of continuous heating. Sulfate- and iron-reducing microbes were enriched by using favorable conditions in specific media. Therefore, it is important to characterize the microbial population of the bentonite used as geotechnical barrier, because microbes might compromise the safety of the deep geological repository of highly radioactive waste.

[1] http://www.grimsel.com/gts-phase-vi/febex-dp/febex-dp-introduction
  • Lecture (Conference)
    Goldschmidt 2019, 18.-23.08.2019, Barcelona, Spain

Publ.-Id: 29058 - Permalink


Effect of Anions on the Changes in the Structure and Adsorption Mechanism of Zirconium Species at the Muscovite (001) – Water Interface
Yuan, K.; Bracco, J. N.; Schmidt, M.ORC; Soderholm, L.; Fenter, P.; Lee, S. S.
Multivalent cations primarily exist as polynuclear hydroxo and oxyhydroxo clusters and/or nanoparticles (NPs) in aqueous environments, where their interactions with mineral surfaces can be influenced by complexing anions. Here, we investigated the effect of background electrolyte anions (specifically ClO4-, Cl-, SO42-, and HPO42-) on the distribution of tetravalent Zr adsorbed on the negatively charged basal surface of muscovite mica. The experiments were conducted at constant pH (= 3), total Zr(IV) concentration (= 0.1 mM), and ionic strength (= 0.1 M). The Zr coverages measured by X-ray fluorescence (XRF) in ClO4- and Cl- systems were 1.3 and 2.1 Zr/AUC (where AUC = 46.72 Å2 is the area of the unit cell of the mica (001) surface), respectively, and mostly remained unchanged during the reaction time from 6 to 50 h. In these conditions, Zr adsorption occurred both as small NPs (with an average height of ~4 nm observed by ex situ atomic force microscopy, AFM) and in a ~2 nm-thick molecular layer (observed by in situ resonant anomalous X-ray reflectivity, RAXR). In comparison, higher Zr coverages that increased with reaction time (i.e., from ~4 to ~7 Zr/AUC from 6 to 50 h reactions) were observed in the SO42- system. Ex situ AFM revealed that the Zr uptake in this system occurred predominantly as NPs that were ca. 5 to 15 nm tall and 20 to 40 nm wide, but no evidence of the interfacial molecular-layer formation was observed by RAXR. In the HPO42– solution, all measurements unequivocally showed no significant Zr sorption, in stark contrast to the observations in the other solutions. Details of the Zr surface coverage and sorption modes are consistent with the known clustering of tetravalent Zr in solutions in the presence of these anions. These results demonstrate the significant impact of anions on the adsorption affinity and mechanism of Zr on the negatively charged mica surface.
Keywords: CTF/RAXR, Sorption, Zirconium, Nanoparticles, XRF, AFM

Publ.-Id: 29056 - Permalink


Towards the electronic structure of actinide oxides nanoparticles
Kvashnina, K.;
Understanding the mechanisms of different chemical reactions with actinides at the atomic level is a key step towards safe disposal of nuclear wastes and towards the identification of physical-chemical processes of radionuclides in the environment. This contribution will provide an overview of the recently performed studies on Uranium, Thorium, Plutonium and Cerium oxide nanoparticles at the Rossendorf Beamline (ROBL)[1] of the European Synchrotron (ESRF) in Grenoble (France). This innovative, recently upgraded, world-wide unique experimental station, funded and operated by HZDR in Dresden (Germany) was used to study actinide systems by several experimental methods, mainely by X-ray absorption spectroscopy in high energy resolution fluorescence detection (HERFD) mode and resonant inelastic X-ray scattering (RIXS) at the An/Ln L3 and An M4,5 edge [2–5]. The experimental results have been analysed using a number of theoretical methods based on density functional theory and atomic multiplet theory. This research has received funding from European Research Council (ERC) under grant agreement 759696
  • Lecture (Conference)
    Goldschmidt2019, 18.-23.08.2019, Barcelona, Spain

Publ.-Id: 29055 - Permalink


Reduction of NpO2+ and TcO4- at the FeII-montmorillonite-water interface
Marques Fernandes, M.; Scheinost, A. C.; Baeyens, B.;
The fate of the long-lived, redox-sensitive radionuclides neptunium (237Np) and technetium (99Tc) in deep geological radioactive waste repositories is a major environmental issue. Both elements are highly soluble in their oxidized redox state, and are not (TcO4-) or only weakly sorbed (NpO2+) by negatively charged clay minerals. In the presence of adsorbed and/or structural FeII, however, clay minerals have been shown to reduce (co-)adsorbed contaminants such as U and Se [1, 2], thereby increasing the solid-water distribution coefficient (retention) by several orders of magnitude. In order to investigate if, to which extent, and under which conditions NpV and TcVII are reduced to their tetravalent oxidation states, we conducted Np and Tc batch adsorption experiments with iron-free montmorillonite and with DCB-reduced Wyoming (2.9 wt. % Fe) montmorillonite under different experimental conditions (i.e. anoxic, electrochemical reduction, in the absence and presence of dissolved FeII). The final oxidation state and the type of surface complex formed was elucidated by X-ray absorption spectroscopy at Np-L3, Tc-K and Fe-K edges. We show that both adsorbed and structural FeII are able to reduce NpV and TcVII to NpIV and TcIV, respectively, but the extent strongly depends on the available amount of FeII and on the experimental conditions. The reduced Np strongly complexes towards co-adsorbed Fe and no NpO2 formation is observed. In the case of Tc, mainly TcO2-like nanoparticles form. Surface complexation via Fe is only observed at low Tc surface loadings.
Keywords: Technetium, Neptunium, ROBL, EXAFS, redox, clay, iron
  • Invited lecture (Conferences)
    Goldschmidt Conference, 18.08.2019, Barcelona, Spain

Publ.-Id: 29054 - Permalink


REMOO-2019 Blind Test Calculation Workshop (BTW)
Höhne, T.;
A blind test benchmark of transient 2-phase flow simulation codes will be organized.
The purpose is to give participants an opportunity to test their code capability to predict onset of dryout, post-dryout heat transfer phenomena as well as subsequent rewetting in a boiling water rod bundle geometry under realistic operational conditions. Experimental data that will be used in the blind test have been obtained in a 4 by 4 rod bundle and include pressure drops along the bundle divided into six sub-sections, rod clad temperatures at fourteen elevations and coolant temperatures at six elevations.
For analyzed experimental case, steady-state initial and boundary conditions as well as transient forcing functions have been recorded together with above-mentioned parameters.
Keywords: CFD, Subchannel codes, dryout, post dryout, rod bundle
  • Lecture (Conference)
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China

Publ.-Id: 29053 - Permalink


A 224Ra-labeled polyoxopalladate as putative radiopharmaceutical
Gott, M.; Yang, P.; Kortz, U.; Stephan, H.; Pietzsch, H.-J.; Mamat, C.ORC
Despite its attractive properties, internal targeted alpha therapies using 223/224Ra are limited to bone-seeking applications. As there is no suitable chelator available, the search for new carriers to stably bind Ra2+ and to connect it to biological target molecules is necessary. Polyoxopalladates represent a class of compounds where Ra2+ can be easily introduced into the Pd-POM core during a facile one-pot preparation. Due to the formation of a protein corona the connection to other targeting (bio)macromolecules is possible.
Keywords: Radium, Barium, POM, alpha-therapy

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  • Secondary publication expected from 04.06.2020

Publ.-Id: 29051 - Permalink


Improved electrode design for interdigitated large-area photoconductive terahertz emitters
Singh, A.; Welsch, M.; Winnerl, S.; Helm, M.; Schneider, H.;
We study here the effect of the electrode parameters on the terahertz emission efficiency of large-area emitters based on interdigitated electrodes. Electrode parameters are optimized to get maximum terahertz emission by optimizing the balance condition among the emission efficiency of individual electrode pairs, number of emitters per unit area, and fraction of semiconductor exposed for optical pumping. A maximum enhancement by about 50 % in the peak to peak electric field is observed as compared to the previous state of the art design.
Keywords: Terahertz emitters, photoconductive switch, interdigitated electrode

Publ.-Id: 29048 - Permalink


Implementation of HZDR baseline model for poly-dispersed bubbly flow in OpenFOAM
Liao, Y.;
The predictability of TFM-CFD is largely restricted by the reliability of closures that should reconstruct the information about the phenomena and processes occuring at the interface. The development of physically based models is severely obstructed by insufficient knowledge on the physics and numerous misleading work based on case-by-case tuning. A strategy towards general closures is necessary. A few years ago HZDR proposed a baseline model for TFM-CFD simulation of poly-dispersed bubbly flow with a fixed set of closures. It aims to identify the missing physics in the existing models and improve them step by step. In this work the baseline model is implemented and tested in the open source CFD code OpenFOAM for a large number of bubbly flow cases including vertical pipe flow and bubble column.
  • Lecture (Conference)
    CFD-Verbund, 11.-12.03.2019, Garching bei München, Deutschland

Publ.-Id: 29047 - Permalink


Application of computational fluid dynamics codes for nuclear power plant design
Krause, M.; Smith, B.; Höhne, T.; In, W. K.;
Computational Fluid Dynamics (CFD) codes have reached a level of maturity, at least for single-phase applications, to be utilized in the design process of Nuclear Power Plant (NPP) components, such that advanced NPPs over the past years have increasingly utilized CFD codes in their design. A recently completed Cooperative Research Project (CRP) addressed the application of CFD codes to the process of optimizing the design of components in Pressurized Water-cooled Reactors (PWRs). Following several initiatives within the IAEA where CFD codes have been applied to situations of interest in nuclear reactor technology, this CRP aimed to contribute to a consistent application of CFD codes by establishing a common platform to assess their capabilities and level of qualification.

Eleven participant organizations from nine Member States performed simulations against four “CFD-grade” experiments performed to investigate key phenomena for CFD simulations. Two are based on test data from the ROCOM (ROssendorf COolant Mixing) facility at HZDR in Germany, and another two are based on rod-bundle experiments in the OFEL (Omni Flow Experimental Loop) facility at KAERI in Korea.

This paper outlines the objectives of the CRP, provides a description of the test facilities and experiments, and discusses selected results obtained for the four above benchmark exercises.
Keywords: Computational Fluid Dynamics, Reactor Design, CFD Benchmark
  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
  • Contribution to proceedings
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA

Publ.-Id: 29046 - Permalink


Perfluorinated Calixarene Shuttles for Radium and Barium
Reissig, F.; Bauer, D.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
Alpha therapy is continually discussed in radiopharmaceutical research. [223Ra]RaCl2 is the only EMA- and FDA-approved alpha-emitting radiopharmaceutical so far. Since the use of 223Ra is only based on its calcimimetic behavior. It is directly bond to bone structures in the body. To enhance the therapeutic potential of radium isotopes, it is necessary to develop novel carrier systems for radium ions as a base of biological targeting units. By the combination of 223Ra or 224Ra, which both have suitable physical half-lives for therapeutic applications, and 131Ba which has a similar half-life but diagnostic radiation properties, a theragnostic idea can also be followed. Our project aims at the synthesis of calixarene-based ligands for the stable complexation of barium and radium ions. Recent studies in our group have already shown the high potential of such ligands.
Keywords: Radium-223, Barium-131, Calixarene
  • Poster
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Peking, China
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 62(2019), S261

Publ.-Id: 29045 - Permalink


A multi-scale approach simulating generic pool boiling
Höhne, T.ORC; Lucas, D.
The paper presents an application of the GENTOP model for phase transfer and discusses the sub-models used. Boiling of a heated surface under atmospheric conditions is simulated by the multi-field CFD approach. Sub-cooled water in a generic pool is heated up first in the near wall region leading to the generation of small bubbles. Further away from the bottom wall larger bubbles are generated by coalescence and evaporation. The CFD simulation bases on the recently developed GEneralized TwO Phase flow (GENTOP) concept. It is a multi-field model using the Euler-Euler approach and it allows the consideration of different local flow morphologies including transitions between them. Small steam bubbles are handled as dispersed phases while the interface of large gas structures is statistically resolved. The GENTOP sub-models need a constant improvement and separate, intensive validation effort using CFD grade experiments. Recently, a bubble dynamics model inside the heat partitioning approach has been developed and will be applied in GENTOP in future.
Keywords: multi-phase, boiling, GENTOP, multi-scale, CFD
  • Lecture (Conference)
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA
  • Contribution to proceedings
    18th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-18), 18.-23.08.2019, Portland, USA

Publ.-Id: 29043 - Permalink


Multiphase CFD Modelling: State-of-the-art applications in Energy related Industrial Applications
Höhne, T.ORC
Two-phase flows occur in many industrial processes. Reliable predictions on flow characteristics are necessary for the design, process optimization and safety analysis of related apparatuses and processes. Experimental investigations are expensive and in most cases not transferable to modified geometries or different scales and flow conditions. For this reason there is a clear requirement for numerical tools. Due to the 3D nature of flows and the importance of turbulence in most cases this means a strong need for reliable 3D CFD-tools rather than 1D system codes or simplified correlations. The general aim is to provide simulation tools for the design, optimization and safety analyses of medium and large scale applications in which multiphase flows are involved. Such tools can contribute to improve the efficient use of energy and resources (e.g. in chemical engineering and oil industries) and to guarantee the safe operation (especially nuclear safety) – provided that they are predictive. Since large scale applications are considered such as chemical reactors or components of the cooling system of a nuclear power plant the Euler-Euler two- or multi fluid model is the base for the development. Presently the predictive capabilities for basic hydrodynamics are restricted due to limitations of the closure models. For this reason one focus of our multiphase flow research is the improvement of the closures first for adiabatic flow modelling but also phase transfer, chemical reactions etc. have to be considered. A second focus is to establish modelling frameworks as iMUSIG, AIAD and GENTOP to allow a proper consideration of the local physical phenomena. These activities will help to improve the CFD code capabilities in energy related industrial applications.
Keywords: CFD, Multiphase, Fluid Dynamics, HZDR, AIAD, GENTOP
  • Invited lecture (Conferences)
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China
  • Contribution to proceedings
    The 9th International Conference & Workshop REMOO–2019, 16.-18.04.2019, Hong Kong, China

Publ.-Id: 29041 - Permalink


Radium-doped BaSO4 Nanoparticles for Future Targeted Alpha Therapy
Reissig, F.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
Targeted alpha therapy (TAT) is continually focused and discussed in radiopharmaceutical research [1]. By the combination of an alpha emitting radionuclide with a biological targeting unit, tumor cells can be affected very efficiently by inducing a high number of double strand breaks to the DNA. 223Ra and 224Ra are two alpha-emitting radionuclides with suitable half-lives for TAT. 223Ra in form of [223Ra]RaCl2 (Xofigo®) is the only EMA- and FDA-approved alpha-emitting radiopharmaceutical as well as the prime example for the working principle of TAT. Based on its calcimimetic behavior, radium is built into the bone structure. To exploit the therapeutic potential of alpha emitters like 223Ra and 224Ra, novel targeting strategies and carrier systems have to be developed. Therefore, it is worth to examine alternative carriers like nanoparticles, using the principle of co-precipitation of Ra/BaSO4. By the combination of a therapeutic alpha-emitting radionuclide like 223Ra on the one hand and the diagnostically applicable barium radioisotope 131Ba on the other hand with nearly identical physical half-lives it is also possible pursue theragnostic approaches. Thus, our research aims at developing a simple method for the synthesis of small radiolabeled Ra/BaSO4 nanoparticles and testing further surface functionalization regarding the ability of constructing biological targeting moieties.
Keywords: Radium-224, Barium-131, Nanoparticle
  • Poster
    23rd International Symposium on Radiopharmaceutical Sciences (ISRS 2019), 26.-31.05.2019, Peking, China
  • Open Access LogoAbstract in refereed journal
    Journal of Labelled Compounds and Radiopharmaceuticals 62(2019), S265

Publ.-Id: 29040 - Permalink


Calixarene-based ligands for Radium and Barium
Bauer, D.; Reissig, F.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
Due to their high biological effectiveness and suitable half-lives, there is increased interest in using the radionuclides radium-223 and radium-224 for radiopharmaceutical applications. Xofigo ([223Ra]radium chloride) is a bone-seeking, alpha-emitting radiopharmaceutical with EMA and FDA approval. It is used to treat bone metastasis of castrate-resistant prostate cancer. To expand the possible applications for these promising radionuclides, it is necessary to stably bind the radionuclide within a chelator. Therefore, calixarene-based ligands have been synthesized, which show encouraging affinities to radium ions. In our recent studies, we have already presented the high potential of these ligands. Since radium and barium have similar chemistry, and therefore comparable affinities to our ligands, it is possible to create a matched pair for theragnostic approaches. The radionuclide barium-131 has a suitable physical half-life for therapeutic applications and the potential of being a SPECT nuclide.
Keywords: Radium-224, Barium-131, Calixarene
  • Poster
    11th International Symposium on Targeted-Alpha-Therapy, 01.-06.04.2019, Ottawa, Kanada
  • Open Access LogoAbstract in refereed journal
    Journal of Medical Imaging and Radiation Sciences 50(2019)1, S39
    DOI: 10.1016/j.jmir.2019.03.118

Publ.-Id: 29039 - Permalink


Interobserver variability of image-derived arterial blood SUV in whole-body FDG PET
Hofheinz, F.; Maus, J.; Zschaeck, S.; Rogasch, J.; Schramm, G.; Oehme, L.; Apostolova, I.; Kotzerke, J.; van den Hoff, J.;
Background: Today, the standardized uptake value (SUV) is essentially the only means for quantitative evaluation of static [18 F-]fluorodeoxyglucose (FDG) positron emission tomography (PET) investigations. However, the SUV approach has several 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 in the first clinical studies to overcome most of these shortcomings, to decrease test-retest variability, 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 additionally required blood SUV (BSUV) determination. The goal of the present work was the investigation of the interobserver variability of image-derived BSUV.

Methods: FDG PET/CT scans from 83 patients (72 male, 11 female) with non-small cell lung cancer (N = 46) or head and neck cancer (N = 37) were included. BSUV was determined by 8 individuals, each applying a dedicated delineation tool for the BSUV determination in the aorta. Two of the observers applied two further tools. Altogether, five different delineation tools were used. With each used tool, delineation was performed for the whole patient group, resulting in 12 distinct observations per patient. Intersubject variability of BSUV determination was assessed using the fractional deviations for the individual patients from the patient group average and was quantified as standard deviation (SDis ), 95% confidence interval, and range. Interobserver variability of BSUV determination was assessed using the fractional deviations of the individual observers from the observer-average for the considered patient and quantified as standard deviations (SDp , SDd ) or root mean square (RMS), 95% confidence interval, and range in each patient, each observer, and the pooled data respectively.

Results: Interobserver variability in the pooled data amounts to RMS = 2.8% and is much smaller than the intersubject variability of BSUV (SDis = 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, covering a range of [0.7, 7.4]% in the investigated patient group.

Conclusion: The present investigation demonstrates that the image-based manual determination of BSUV in the aorta is sufficiently reproducible across different observers and delineation tools which is a prerequisite for accurate SUR determination. This finding is in line with the already demonstrated superior prognostic value of SUR in comparison to SUV in the first clinical studies.
Keywords: PET, FDG, Quantification, SUV, SUR, Blood SUV

Publ.-Id: 29038 - Permalink


Flexible IGZO TFTs and their Suitability for Space Applications
Costa, J. C.; Pouryazdan, A.; Panidi, J.; Spina, F.; Anthopoulos, T.; Liedke, M. O.; Schneider, C.; Wagner, A.; Münzenrieder, N.;
In this paper, Low Earth Orbit radiation, temperature and magnetic field conditions are mimicked to investigate the suitability of flexible Indium Gallium Zinc Oxide transistors for lightweight space wearables. Such wearable devices could be incorporated into spacesuits as unobtrusive radiation detectors or physiological monitors. Due to the harsh environment to which these space wearables would be exposed, they have to be able to withstand high radiation doses, low temperatures and magnetic fields. For this reason, the impacts of high energetic electron irradiation with fluences up to 1E12 e−/cm2, low operating temperatures down to 78K and magnetic fields up to 11mT are investigated. This simulates 278 h in Low Earth Orbit. The threshold voltage and mobility of transistors that were exposed to e- irradiation are found to shift by +(0.09 +- 0.05)V and (0.6 +- 0.5) cm 2 V−1 s−1. Subsequent low temperature exposure resulted in additional shifts of +0.38V and -5.95 cm2 V−1 s−1 for the same parameters. These values are larger than the ones obtained from non irradiated reference samples. In addition, the performance of the devices was observed not to be significantly affected by the magnetic fields. Finally, a Cascode amplifier presenting a voltage gain of 10.3 dB and a cutoff frequency of 1.2 kHz is demonstrated after the sample had been irradiate, cooled down and exposed to the magnetic fields. If these notions are considered during the systems’ design, these devices can be used to unobtrusively integrate sensor systems into space suits.
Keywords: Flexible electronics, Space applications, Amorphousnoxides; Wearables, Thin film transistors

Publ.-Id: 29037 - Permalink


Fifteen Years of Radionuclide Research at the KIT Synchrotron Source in the Context of the Nuclear Waste Disposal Safety Case
Rothe, J.; Altmaier, M.; Dagan, R.; Dardenne, K.; Fellhauer, D.; Gaona, X.; González-Robles Corrales, E.; Herm, M.; Kvashnina, K.; Metz, V.; Pidchenko, I.; Schild, D.; Vitova, T.; Geckeis, H.;
For more than 120 years, systematic studies of X-ray interaction with matter have been the basis for our understanding of materials—both of natural or man-made origin—and their structure-function relationships. Beginning with simple radiographic imaging at the end of the 19th century, X-ray based analytical tools such as X-ray diffraction, X-ray fluorescence and photoemission or X-ray absorption techniques are indispensable in almost any field of chemical and material sciences—including basic and applied actinide and radionuclide studies. The advent of dedicated synchrotron radiation (SR) sources in the second half of the last century has revolutionized the analytical power of X-ray probes, while—with increasing number of SR facilities—beamline instrumentation followed a trend towards increasing specialization and adaption to a major research topic. The INE-Beamline and ACT station at the KIT synchrotron source belong to the exclusive club of a few synchrotron beamline facilities—mostly located in Europe—dedicated to the investigation of highly radioactive materials. Since commissioning of the INE-Beamline in 2005, capabilities for synchrotron-based radionuclide and actinide sciences at KIT have been continuously expanded, driven by in-house research programs and external user needs.

Publ.-Id: 29035 - Permalink


Metallgewinnung durch Mikrobiologie – Biologisch assistierte Prozesse in der Rohstofftechnologie
Lederer, F.;
Der Rohstoffsektor ist geprägt von enormem Materialbedarf für die Entwicklung und Produktion neuer High-Tech Produkte. Neben der Optimierung von Bergbauprozessen zur Gewinnung von primären Rohstoffen fokussiert das Helmholtz-Institut Freiberg für Ressourcentechnologie die Vision der Kreislaufwirtschaft. Diese setzte neben dem Schwerpunkt Nachhaltigkeit im Hinblick auf Produktdesign, Produktion, Verteilung, Konsum, Verwendung, Reparatur und Sammlung vor allem auf das Recycling von Wertstoffen.
Mikrobiologisch assistierte Recyclingprozesse zur Rückgewinnung von Wertstoffen aus Elektronikschrott und Bergbauresthalden sowie innovative und umweltfreundliche Lösungen für die Ressourcensicherung standen im Fokus der 29. Jenaer Industriegespräche der DPG.
Themenschwerpunkte des Vortrages waren Interaktionen von Mikroorganismen mit Metallen, das biotechnologische Potential neuer Ressourcentechnologien, Grenzen überwindende Bioflotation, die Metallgewinnung mittels Siderophoren, Evolution im Reagenzglas sowie Biokollektoren für das Recycling von Wertstoffen aus Elektroschrott.
  • Invited lecture (Conferences)
    29. Jenaer Industriegespräche der DPG, 20.03.2019, Jena, Deutschland

Publ.-Id: 29034 - Permalink


Consolidative thoracic radiotherapy in stage IV small cell lung cancer: Selection of patients amongst European IASLC and ESTRO experts
Putora, P. M.; Glatzer, M.; de Ruysscher, D.; Faivre-Finn, C.; Belderbos, J.; Besse, B.; Blackhall, F.; Califano, R.; Cappuzzo, F.; de Marinis, F.; Dziadiuszko, R.; Felip, E.; Früh, M.; Garrido, P.; Le Pechoux, C.; Mcdonald, F.; Nestle, U.; Novello, S.; Brien, M. O.; Paz Ares, L.; Peeters, S.; Pöttgen, S.; Ramella, S.; Reck, M.; Troost, E. G. C.; van Houtte, P.; Westeel, V.; Widder, J.; Mornex, F.; Slotman, B. J.;
Background: The role of consolidative thoracic radiotherapy (TRT) in stage IV small cell lung cancer (SCLC) is not uniformly accepted. Methods: We obtained a list of 13 European medical oncologists from the International Association for the Study of Lung Cancer (IASLC) and 13 European radiation oncologists from the European Society for Therapeutic Radiation Oncology (ESTRO). The strategies in decision making for TRT in stage IV SCLC were collected. Decision trees were created representing these strategies. Frequencies of recommending TRT were analysed for various parameter combinations based on the objective consensus methodology. Results: The factors associated with the recommendation for TRT included fitness of the patient, limited extrathoracic tumour burden, initial bulky thoracic disease and response to chemotherapy. The highest consensus for TRT was in fit patients with limited extrathoracic tumour burden and initial bulky disease with either a complete extrathoracic response or partial thoracic response (92% recommend TRT). For these patients the recommendations were the same for medical and radiation oncologists. In the setting of partial response (intra- and extra-thoracically) without initial bulky thoracic disease radiation oncologists were more likely to recommend TRT than medical oncologists. For unfit patients or for patients with poor overall response to chemotherapy, the majority did not recommend TRT. Conclusion: European radiation and medical oncologists specializing in lung cancer recommend TRT in selected patients with stage IV SCLC and restrict its use primarily to fit patients who responded to chemotherapy with limited extrathoracic tumour burden.
Keywords: ESTRO, Expert opinion, IASLC, Small cell lung cancer, Stage IV, Thoracic radiotherapy

Publ.-Id: 29033 - Permalink


Repeat FMISO-PET imaging weakly correlates with hypoxia-associated gene expressions for locally advanced HNSCC treated by primary radiochemotherapy
Löck, S.; Linge, A.; Seidlitz, A.; Bandurska-Luque, A.; Nowak, A.; Gudziol, V.; Buchholz, F.; Aust, D. E.; Baretton, G. B.; Zöphel, K.; Steinbach, J.; Kotzerke, J.; Overgaard, J.; Zips, D.; Krause, M.; Baumann, M.; Troost, E. G. C.;
Background: Hypoxia is an important factor of tumour resistance to radiotherapy, chemotherapy and potentially immunotherapy. It can be measured e.g. by positron emission tomography (PET) imaging or hypoxia-associated gene expressions from tumour biopsies. Here we correlate [ 18 F]fluoromisonidazole (FMISO)-PET/CT imaging with hypoxia-associated gene expressions on a cohort of 50 head and neck squamous cell carcinoma (HNSCC) patients and compare their prognostic value for response to radiochemotherapy (RCTx). Methods: FMISO-PET/CT images of 50 HNSCC patients were acquired at four time-points before and during RCTx. For 42 of these patients, hypoxia-associated gene expressions were evaluated by nanoString technology based on a biopsy obtained before any treatment. The FMISO-PET parameters tumour-to-background ratio and hypoxic volume were correlated to the expressions of 58 hypoxia-associated genes using the Spearman correlation coefficient ρ. Three hypoxia-associated gene signatures were compared regarding their correlation with the FMISO-PET parameters using their median expression. In addition, the correlation with tumour volume was analysed. The impact of both hypoxia measurement methods on loco-regional tumour control (LRC) and overall survival (OS) was assessed by Cox regression. Results: The median expression of hypoxia-associated genes was weakly correlated to hypoxia measured by FMISO-PET imaging (ρ ≤ 0.43), with higher correlations to imaging after weeks 1 and 2 of treatment (p < 0.001). Moderate correlations were obtained between FMISO-PET imaging and tumour volume (ρ ≤ 0.69). Prognostic models for LRC and OS based on the FMISO-PET parameters could not be improved by including hypoxia classifiers. Conclusion: We observed low correlations between hypoxia FMISO-PET parameters and expressions of hypoxia-associated genes. Since FMISO-PET showed a superior patient stratification, it may be the preferred biomarker over hypoxia-associated genes for stratifying patients with locally advanced HNSCC treated by primary RCTx.
Keywords: FMISO-PET, Gene signature, Hypoxia, Locally advanced HNSCC, Radiochemotherapy

Publ.-Id: 29032 - Permalink


Combining magnetic forces for contactless manipulation of fluids in microelectrode-microfluidic systems
Hähnel, V.; Khan, F. Z.; Mutschke, G.; Cierpka, C.; Uhlemann, M.; Fritsch, I.;
A novel method to drive and manipulate fluid in a contactless way in a microelectrode-microfluidic system is demonstrated by combining the Lorentz and magnetic field gradient forces. The method is based on the redox-reaction [Fe(CN)6]3−/[Fe(CN)6]4− performed in a magnetic field oriented perpendicular to the ionic current that crosses the gap between two arrays of oppositely polarized microelectrodes, generating a magnetohydrodynamic flow. Additionally, a movable magnetized CoFe micro-strip is placed at different positions beneath the gap. In this region, the magnetic flux density is changed locally and a strong magnetic field gradient is formed. The redox-reaction changes the magnetic susceptibility of the electrolyte near the electrodes, and the resulting magnetic field gradient exerts a force on the fluid, which leads to a deflection of the Lorentz force-driven main flow.
Particle Image Velocity measurements and numerical simulations demonstrate that by combining the two magnetic forces, the flow is not only redirected, but also a local change of concentration of paramagnetic species is realized.
Keywords: microfluidics, electrochemistry, redox-reaction, magnetic field, Lorentz force, magnetic gradient force, flow control
  • Open Access LogoScientific Reports 9(2019), 5103
    DOI: 10.1038/s41598-019-41284-0
  • Lecture (Conference)
    11th International PAMIR International Conference - Fundamental and Applied MHD, 01.-05.07.2019, Reims, Frankreich

Publ.-Id: 29031 - Permalink


Avoided energy cost of producing minerals: The case of iron ore
Reuter, M. A.; Palacios, J.-L.; Fernandes, I.; Abadias, A.; Valero, A.; Valero, A.;
There is growing concern about the decline of the ore grade in mines and the increased energy usage for processing and refining metals. In the limit, where no concentrated deposits exist, minerals must be obtained from bare rock. A method for quantitatively assessing the “free bonus” granted by nature in providing concentrated minerals in mines and thus assessing the quality of the different resources is estimating how much energy is needed to concentrate the minerals, as they are already in mines, from bare rock. This bonus granted by nature reduces the costs of human mining and metallurgical processes, as well as the mining effort required of future generations. In this study, the concentration of high-iron-content minerals in common rocks was investigated via a computational model developed using the HSC software. As expected, the range of results for the specific energy for the concentration of iron from common rocks was considerably higher than the energy required by modern processes. This reveals the need to value current iron deposits and the challenge of developing sustainable methods of metal production to satisfy the needs of the present and future generations.
Keywords: Energy consumption, Exergy replacement cost, Iron, Metallurgy, Mining, Thanatia

Publ.-Id: 29030 - Permalink


Doping of silicon nanowires by ion implantation and flash lamp annealing
Berencen, Y.; Prucnal, S.; Wang, M.; Rebohle, L.; Helm, M.; Zhou, S.; Skorupa, W.;
In this work, we report on non-equilibrium processing for controlled doping of Si/SiO2 core/shell nanowires with shallow- and deep-level dopants below and above their equilibrium solid solubility. In detail, the shallow-level dopants B and P as well as the deep-level dopant Se was implanted, followed by millisecond flash lamp annealing. In case of amorphization upon high-fluence implantation, recrystallization takes place via a bottom-up template-assisted solid phase epitaxy. Non-equilibrium Se concentrations lead to the formation of an intermediate band in Si which in turn causes a room-temperature sub-band gap photoresponse of the nanowire when configured as a photoconductor device [1]. Alternatively, the formation of a cross-sectional p-n junction is demonstrated by co-implanting P and B in individual nanowires at different depth along the NW core.
[1] Y. Berencén, et al. Adv. Mater. Interfaces 2018, 1800101
Keywords: doping, nanowires, semiconductor, silicon, ion implantation, flash lamp annealing
  • Lecture (Conference)
    44. Treffen der Nutzergruppe Heißprozesse und RTP, 03.04.2019, Erlangen, Deutschland

Publ.-Id: 29028 - Permalink


Ultrasonic flow measurements in liquid metal flows with partial solidification
Franke, S.; Räbiger, D.; Eckert, S.;
The monitoring of the flow rate is an inherent part of process control in all technical large-scale plants to guarantee process stability and safety. It is particularly important for nuclear applications. In the case of a liquid metal coolant in addition, the control of the aggregate state is important.
The use of ultrasound techniques opens an attractive opportunity to measure both the fluid velocity by evaluating the Doppler phase shift and the phase boundary by the detection of the reflection signal from the interface. In addition, the measuring principle enables a noninvasive implementation of the measuring technique. A test facility is necessary to qualify the measuring technique for real applications.
In this study a new LBE experimental facility has been designed and constructed. The setup enables to control the temperature and the fluid flow in the liquid. Further a partial solidification can be induced. The liquid metal vessel is equipped with ten ports for ultrasonic probes. These ports allow for testing the ultrasound measuring principle for different conditions. It was demonstrated that the ultrasonic sensors can be operated up to 200°C at the piezo element. First measuring results demonstrate the potential of ultrasound measuring techniques for monitoring liquid metal applications.
  • Lecture (Conference)
    SESAME International Workshop, 19.-21.03.2019, Petten, Netherlands

Publ.-Id: 29026 - Permalink


Probing charged lepton flavor violation with the Mu2e experiment
Mueller, S. E.ORC; Ferrari, A.ORC
The Mu2e experiment, currently under construction at the Fermi National Accelerator Laboratory near Chicago, will search for the neutrinoless conversion of muons to electrons in the field of an aluminum nucleus. In the Standard Model, this process, which violates charged lepton flavor, is highly suppressed and therefore undetectable. However, scenarios for physics beyond the Standard Model predict small but observable rates. The Mu2e experiment aims at a sensitivity four orders of magnitude better than existing experiments. This is achieved by a rigorous control of all backgrounds that could mimic the monoenergetic conversion electron.

At HZDR, we use the ELBE radiation facility to study radiation hardness and performance of components for the Mu2e calorimeter and contribute with Monte Carlo simulations to the understanding of the optimal configuration for the detector that will monitor the rate of stopped muons in the aluminum target. Additional simulations are performed for both the pion production target and the muon stopping target.

In the presentation, the design and status of the Mu2e experiment will be presented, and results from the ELBE beamtimes and the simulation studies will be given.
Keywords: Mu2e, CLFV, ELBE
  • Lecture (Conference)
    Spring Meeting DPG, 22.03.2019, Muenchen, Deutschland

Publ.-Id: 29025 - Permalink


Composition and Structure of Surface Oxides on Press-Hardened Hot-Dip Galvanized Steel
Gaderbauer, W.; Arndt, M.; Steck, T.; Klingner, N.; Faderl, J.; Groiß, H.;
Zink-coated press hardened steel (PHS) is due to its extremely high tensile strength and its excellent corrosive protection indispensable for structural elements in modern automotive applications. Different studies clarify the resulting microstructure of the Zn-coating after press hardening [1] of such steel parts. Also, the uppermost surface oxide layer, which can be influenced by steel matrix alloy elements, has a significant impact on the processing properties like coating or welding.
In this study, we investigated these surface oxide layers for alloy compositions of four different PHS systems with scanning and conventional transmission electron microscopy (TEM), Auger electron spectroscopy (AES) and helium ion microscopy (HIM). The complex and porous oxide-layers were stabilized by epoxy before the preparation of cross-sections and TEM-lamellae by focused ion beam milling.
The main oxides on top of the original thin Al2O3 layer, originating from the primary galvanizing process, could be determined with energy dispersive X-ray spectroscopy (EDX), selected area diffraction and AES as Zn-oxides and (Mn,Zn)Mn2O4 spinel (Fig. 1a). Also noticeable was a varying, nanometre thick Cr enrichment at this Al2O3 layer (Fig. 1b), which depends strongly on the steel alloy. Further experiments with secondary mass spectrometry (ToF-SIMS) attached to a HIM [2] allowed reliable distinguishing between ZnO and Zn(OH)2 (Fig. 2c), which are both present in our oxide layers.
Thus, we could show an influence of different steel alloy elements on the final oxide structure after press hardening. The formation of spinel is triggered by Mn, which is transported with the Zn above the Al2O3 layer, which itself is a trap for Cr, leading to a coverage of it with Cr-oxides.

Figure 1. a) AES Mapping. b) STEM-EDX Mapping c) ToF-SIMS Mapping

References:
[1] H. Järvinen et al, Surface and Coatings Technology 352 (2018), 378-391.
[2] N. Klingner et al, Ultramicroscopy 198 (2019), 10-17.

The financial support by the Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development in the frame of the CDL for nanoscale phase transformations is gratefully acknowledged.
  • Lecture (Conference)
    9th Austrian Society for Electron Microscopy workshop, 25.-26.04.2019, Graz, Österreich

Publ.-Id: 29024 - Permalink


Critical heat flux as a mass flux dependent phenomenon: Theoretical analysis, experimental confirmation and further CFD application
Ding, W.; Geißler, T.; Krepper, E.; Hampel, U.;
In this work, we report on a theoretical analysis and experimental investigations on critical heat flux (CHF) in subcooled flow boiling firstly. Commonly, CHF is considered as a local phenomenon. A validated CHF- concept recently developed in our group indicated that CHF may be initiated in two different ways, that is, locally and globally. We designed and conducted an experiment to verify this hypothesis. The experimental results agree well with the expectations from our CHF- modelling and confirm the two mechanisms. Following that, we continued to clarify the role of different parameters, such as channel orientation, channel length and hydraulic diameter. The new concept of CHF is useful to explain and predict CHF at conditions of low pressure and low fluid velocity. Further we applied this concept into an Euler-Euler computational multiphase fluid dynamics (CMFD) approach with wall boiling model which successfully predict the critical volume fraction under different conditions. The simulation results also had a good agreement with the corresponding experimental results.
Keywords: Critical heat flux, Boiling, CMFD
  • Invited lecture (Conferences)
    9th China-Korea Workshop on Nuclear Reactor Thermal-Hydraulics (WORTH-9), 15.-18.05.2019, Chongqing, China

Publ.-Id: 29017 - Permalink


Pulse-front tilt in laser-plasma accelerators with short focal lengths
Steiniger, K.ORC; Albach, D.ORC; Bussmann, M.ORC; Debus, A.ORC; Kluge, T.ORC; Loeser, M.ORC; Pausch, R.ORC; Siebold, M.; Zeil, K.; Schramm, U.ORC
Laser ion accelerators utilize high-power laser pulses in tight-focusing geometries to provide pulsed, high-intensity ion beams. Efficient capturing, transport and application of these beams is an ongoing effort which depends on precise knowledge of the accelerated ion distribution's properties and how to control these. For example, it is known that the propagation direction of the accelerated ions can be controlled by tilting the driving laser pulse-front. Since laser pulse-front tilts can be present accidentally, for example by a small misalignment of the compressor gratings in a chirped-pulse amplification system, knowledge of the scaling of the pulse-front tilt at a target position is desired. The talk gives relations for pulse-front orientation dependent on setup parameters and identifies regimes were pulse-front tilt has a sizable impact.
Keywords: Pulse-front tilt, high-power laser
  • Lecture (Conference)
    DPG-Frühjahrstagung, 17.-22.03.2019, München, Deutschland

Publ.-Id: 29015 - Permalink


Flüssigmetallbatterien als Großspeicher - Technologie, Scale-Up und Optionen zur Sektorkopplung
Nimtz, M.;
Es werden die grundsätzlichen Eigenschaften von Flüssigmetallbatterien beschrieben sowie Methoden und Ergebnisse zum Scale-Up vorgestellt. Des weiteren werden Funktionsweise und Anwendung der LMB-System-Calculator Software erläutert sowie Anwendungsoptionen für Flüssigmetallbbatterien, insbesondere bei der Sektorkoppelung vorgestellt.

Basic properties of Liquid Metal Batteries are described and methods and results for scale-up calculations are presented.
Also, functioning and usage of the LMB-System-Calculator software are discussed and options for the operation of Liquid Metal Batteries, especially for the sector-coupling are presented.
Keywords: LMB, Flüssigmetallbatterien, Scale-Up, Speicher, Sektorkoppelung, LMB, liquid metal battery, scale-up, storage, sectro-coupling
  • Lecture (others)
    Energie System 2050 Forschungsthema 1, 1. Workshop 2019, 19.-20.03.2019, Karlsruhe, Deutschland

Publ.-Id: 29014 - Permalink


Chemistry and accelerator mass spectrometry – A life happily ever after?
Merchel, S.ORC
Accelerator mass spectrometry (AMS) is the most sensitive analytical method to measure long-lived radionuclides. The detection limits are generally several orders of magnitude better, i.e. as low as 10-16 (radionuclide/stable nuclide), than any other mass spectrometry or decay counting method. AMS needs smaller sample sizes and measurements are finished within a few minutes to hours.

However, it is often forgotten that research projects applying AMS start with taking appropriate samples, followed by labour- and cost-intensive sample preparation. The goal can easily be described as “making the big samples (up to several kg’s) to fit in an AMS target holder (< 10 mg)”. This includes getting rid of the matrix and the troublesome isobars. By technical improvements of AMS leading to lower detection limits or better mass-and-element discrimination, sample masses can be reduced to gram-quantities instead of kg’s allowing easier, faster, and cheaper chemistry. Recent AMS developments also address very efficiently isobar elimination.

Nevertheless, some samples can contain different sources of the radionuclide-of-interest such as ¹⁰Be produced in the Earth’s atmosphere polluting the ¹⁰Be of interest produced in-situ in quartz. Hence, in this case chemistry is inevitable for cleaning the samples from the contamination. Another “mission” of chemistry might be the reduction of corresponding stable nuclides, e.g. 35,37Cl, ²⁷Al, natFe by preceding cleaning or by gentle leaching to enhance the radionuclide/stable nuclide ratio or to minimize interfering nuclear reactions such as thermal-neutron capture on ³⁵Cl. When applying isotope-dilution AMS to simultaneously determine the natCl content of a sample, which is an absolute requirement for surface exposure dating of Ca- or K-rich minerals, chemical sample preparation is also mandatory.

As the majority of research projects involving AMS is of true interdisciplinary character, knowledge of sample preparation is usually passed-on to (young) non-chemists. These are trained learning-by-doing to perform the chemical preparation of their own samples. Therefore, the development of “routine” AMS sample preparation needs to have a strong focus on safety and easy-to-be-trained aspects with the least opportunity for failure.

In conclusion, although new AMS technical developments for isobar suppression like the laser-negative ion interaction system at VERA promise to reduce elaborate chemistry in some cases, we should keep in mind that chemical knowledge will always be needed for a lot of interdisciplinary research projects.
Keywords: AMS
  • Lecture (others)
    VERA-Seminar, Institut für Isotopenphysik, Universität Wien, 28.03.2019, Wien, Österreich

Publ.-Id: 29013 - Permalink


Li-containing liquid metal alloy ion sources for focused-ion beam instrumentation
Mazarov, P.; Nadzeyka, A.; Richter, T.; Yu, Y.; Sanabia, J. E.; Bischoff, L.; Hlawacek, G.; Pilz, W.; Klingner, N.;
Focused Ion Beams (FIB) gain an increasing interest in the field of nanotechnology particular for prototyping of microelectronic devices, patterning of 2D materials, high resolution imaging or high resolution ion lithography1. Concerning ion beam resolution and minimization of unwanted damage, light ions like He or Li are preferred candidates. Liquid metal alloy ion sources (LMAIS) with a life time of more than 1000 µAh on the basis of Ga35Bi60Li5 and Sn95Li5 alloys were developed, characterized and finally applied in a commercial mass-separated VELION FIB-SEM system (Raith GmbH). The resolution for imaging and also for the formation of nanostructures using a thin gold film was determined.
In the case of Li ions from the mass separated FIB a lateral resolution of 5.6 nm could be obtained in first experiments2 and the sputter yield was determined to 0.4 for 35 keV Li ions on Au. For reference, the helium ion microscope (HIM) has a lateral resolution of about 0.5 nm and 1.8 nm, for He and Ne respectively, He has a sputter yield of 0.13. For sub-10 nm focused ion beam nanofabrication and microscopy, the GaBiLi-FIB or the SnLi-FIB could therefore be considered alternatives to the HIM with the benefit of providing additional ion species in a mass separated FIB without changing the ion source.

1 L. Bischoff et al. Appl. Phys. Rev. 3, 021 101 (2016).
2 W. Pilz et al. J. Vac. Sci. Technol. B A-18-399 (submitted, 2018).
3 G. Hlawacek et al. J. Vac. Sci. Technol. B 32, 020 801 (2014).
  • Lecture (Conference)
    The 63rd International Conference On ELECTRON, ION, AND PHOTON BEAM TECHNOLOGY AND NANOFABRICATION, 28.-31.05.2019, Minneapolis, United States of America

Publ.-Id: 29012 - Permalink


SiCxNy:Fe films as a tunable ferromagnetic material with tailored conductivity
Pushkarev, R.; Fainer, N.; Kirienko, V.; Matsynin, A.; Nadolinnyy, V.; Merenkov, I.; Trubina, S.; Ehrenburg, S.; Kvashnina, K.;
Amorphous ferromagnetic materials with the variable composition are promising candidates for application in rapidlygrowing technological fields, such as spintronics. However, the significant downside of current state-of-art materials is a conductivity mismatch between injector and semiconductor which often is associated with the unavailability to control and precisely tailor magnetic properties and conductivity. We report on the synthesis of soft-magnetic SiCxNy:Fe films with the saturation magnetization of 20 e.m.u./cm3 and conductivity similar to the one of Si, which is crucial for possible applications.
XRD with synchrotron radiation and EXAFS revealed the complex composite structure of the films: crystals of Fe3Si, Fe5Si3, SiC and graphite are embedded into the amorphous matrix of SiCxNy. The variation of deposition conditions allowed us to separately control the magnetic properties through the iron concentration and the conductivity of the material through the amorphous SiCxNy matrix composition. The reported results revealed a significant potential of SiCxNy:Fe films as a prospective object for analysis of spin-polarized transport in amorphous semiconductors and for application in field of spintronics.

Downloads:

  • Secondary publication expected from 13.03.2020

Publ.-Id: 29011 - Permalink


Bridging the Green Gap: Metal–Organic Framework Heteromultilayers Assembled from Porphyrinic Linkers Identified by Using Computational Screening
Haldar, R.; Batra, K.; Marschner, S. M.; Kuc, A. B.; Zahn, S.; Fischer, R. A.; Bräse, S.; Heine, T.; Wöll, C.;
In organic photovoltaics, porphyrins (PPs) are among the most promising compounds owing to their large absorption cross section, wide spectral range, and stability. Nevertheless, a precise adjustment of absorption band positions to reach a full coverage of the so-called green gap has not been achieved yet. We demonstrate that a tuning of the PP Q- and the Soret bands can be done using a computational approach where substitution patterns are optimized in silico. The Most promising candidate structures were then synthesized. The experimental UV/Vis data for the solvated compounds were in excellent agreement with the theoretical predictions. By attaching further functionalities, which allow using the PP chromophores as linkers for the assembly of metal-organic frameworks (MOFs), we were additionally able to exploit packing effects resulting in pronounced red shifts, which allowed to further optimizing the photophysical properties of PP assemblies. Finally, we use a layer-by-layer method to assemble the PP linkers into surface-mounted MOFs (SURMOFs), thus obtaining high optical quality, homogeneous and crystalline multilayer films. Experimental results are in full accord with the calculations, demonstrating a huge potential of computational screening methods in the tailoring of MOF and SURMOF photophysical properties.

Downloads:

  • Secondary publication expected from 10.04.2020

Publ.-Id: 29010 - Permalink


Synthesis and Functionalization of Radium-doped Barium Sulfate Nanoparticles
Reissig, F.; Bauer, D.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.ORC
The radionuclides radium-223 and radium-224 are two alpha-emitting radionuclides with suitable properties for the TAT. To this date, radium-223 in form of [223Ra]radium chloride (Xofigo) is the only EMA and FDA approved alpha-emitting radiopharmaceutical. Due to its calcimimetic behavior, the radium ion is a bone-seeking therapeutic. To extend the radiopharmaceutical potential of both radionuclides, novel carrier systems have to be developed. Therefore, it is appropriate to investigate different kinds of nanoparticles for their ability to transport radium. Especially, a barium sulfate matrix seems to be sufficient since the principle of co-precipitating the sulfates of radium and barium allows an easy and fast synthesis of radium-doped nanoparticles. Beyond the incorporation of alpha-emitting radionuclides like radium-223 and radium-224, the homologue radionuclide barium-131 can be incorporated as well. Barium 131 decays by electron capture and provides suitable properties for diagnostic applications in nuclear medicine. Radium-223/-224 and barium-131 form a matched pair for new theragnostic approaches. In our research group, we are developing simple methods for the synthesis of small radiolabeled radium/barium sulfate nanoparticles. Furthermore, we are investigating suitable surface functionalizations to attach biological targeting moieties.
Keywords: Bariumsulfat, Radium-224, Nanopartikel
  • Poster
    11th International Symposium on Targeted-Alpha-Therapy, 01.-06.04.2019, Ottawa, Kanada
  • Open Access LogoAbstract in refereed journal
    Journal of Medical Imaging and Radiation Sciences 50(2019)1, S38-S38
    DOI: 10.1016/j.jmir.2019.03.117

Publ.-Id: 29009 - Permalink


Synthese neuartiger Calix[4]arenkäfige für die stabile Bindung von Ba2+ und Ra2+
Mamat, C.ORC; Reissig, F.; Steinbach, J.; Pietzsch, H.-J.
Therapieansätze in der Nuklearmedizin mit Radium-223 beschränken sich zurzeit auf die Behandlung von Knochenmetastasen. Ziel ist es, das Anwendungsfeld für Radium-223 zu erweitern. Dafür werden Liganden entwickelt, die Radium-223 stabil binden und gleichzeitig eine spezifische Erkennungssequenz für diverse Krebsentitäten besitzen. Calixkronen mit funktionalisierten Seitenketten sind dafür vielversprechend.

Calix[4]krone-6-derivate mit Trifluormethylsulfonyl- [1] und 4-Nitrophenylsulfonyl-Seitenketten wurden synthetisiert und mittels NMR und UV/Vis auf ihre Komplexierungseigenschaften für Ba2+ untersucht. Anschließend wurden mittels eines Extraktionsassays Komplexierungen durchgeführt und die resultierenden Komplexe auf ihre Stabilität in Gegenwart anderer Ionen wie Ca2+ untersucht. Die Extraktionsversuche wurden im Chloroform/Wasser-Zweiphasensystem durchgeführt. Dabei wurde eine wässrige Metallsalzlösung ([133Ba]Ba2+ c.a. bzw. [224Ra]Ra2+ n.c.a.) definierter Konzentration vorgelegt und mit einer definierten Stoffmenge des jeweiligen Liganden in Chloroform für 1 h bei RT extrahiert.
Die beiden Calixarenderivate wurden in einer vierstufigen Synthese hergestellt. Anschließende Komplexierungsversuche mit Ba(ClO4)2 verliefen erfolgreich und die Komplexe wurden mittels NMR-Spektroskopie nachgewiesen. Für beide Liganden wurden Stabilitätskonstanten von 5,3-6,3 (Ba2+) bzw. 5,8 (Ra2+) berechnet. Die Radiumkomplexe beider Liganden waren gegenüber Ca2+-Ionen stabil (Release <5%), der Bariumkomplex des Nitrophenylsulfonylliganden war ebenfalls stabil (Release <5%), der des Trifluormethylsulfonylliganden zeigte 30% Release.
Die Wahl der sterisch anspruchsvollen und elektronenziehenden Sulfonylgruppen hatte positive Auswirkungen sowohl auf das Komplexierungsverhalten mit Ba2+ und Ra2+ als auch auf die Stabilität der resultierenden Komplexe in Gegenwart von zweiwertigen Fremdionen.
Keywords: Barium-133, Radium-224, Calixaren
  • Lecture (Conference)
    57. Jahrestagung der DGN 2019, 03.-06.04.2019, Bremen, Deutschland

Publ.-Id: 29008 - Permalink


Synthesis and Biological Investigation of A Novel Fluorine-18 Labeled Benzoimidazotriazine: A Potential Radioligand for In Vivo Phosphodiesterase 2A (PDE2A) PET imaging
Ritawidya, R.; Teodoro, R.; Wenzel, B.; Kranz, M.; Toussaint, M.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Scheunemann, M.; Brust, P.;
Objectives: Cyclic nucleotide phosphodiesterase 2A (PDE2A), an enzyme which hydrolyzes the second messengers cAMP and cGMP, is highly enriched in distinct areas of the brain. Accordingly, PDE2A is involved in important signaling pathways related to normal brain function but also to
neurodegeneration and neuro-oncology [1]. To enable the visualization of this protein in the brainwith PET, we developed a novel fluorine-18 radioligand for PDE2A.
Methods: Based on the benzoimidazotriazine (BIT) tricyclic scaffold, several fluorine-containing derivatives were synthesized via a multi-step synthesis route, and their inhibitory profiles were assessed by PDE isoenzyme-specific activity assays. The most potent and selective PDE2A ligand
BIT1 was radiolabeled via nucleophilic aromatic substitution of the corresponding 2-nitro pyridine precursor by [18F]fluoride in DMSO with thermal heating (Figure 1). [18F]BIT1 was isolated using semi-preparative HPLC (Reprosil-Pur C18-AQ column, 250 x 10 mm, 46% ACN/aqu. 20 mM
NH4OAc, flow 5.5 mL/min) followed by final purification with solid-phase extraction and formulation in isotonic saline containing 10% ethanol. Preliminary in vitro autoradiography and in vivo PET studies (60 min dynamic PET imaging, nanoScan® PET/MRI, MEDISO, Budapest, Hungary) of [18F]BIT1 were performed using pig brain slices and female CD-1 mice, respectively. The in vivo metabolism of [18F]BIT1 was investigated by radio-HPLC analysis of mouse plasma and brain samples at 30 min p.i.
Results: From the series of BIT derivatives, BIT1 was selected as candidate for PET imaging of PDE2A based on the most suitable inhibitory potential and profile (IC50 PDE2A3 = 3.3 nM;16-fold selectivity over PDE10A). [18F]BIT1 was successfully synthesized with a radiochemical yield of 54 ± 2% (n = 3, EOB), molar activities of 155 – 175 GBq/μmol (EOS) and radiochemical purities of ≥99%. [18F]BIT1 was stable in saline, pig plasma, and n-octanol up to 60 min at 37 °C. The distribution pattern of [ 18F]BIT1 in pig brain cryosections corresponds to the spatial distribution of PDE2A with accumulation in the striatal regions caudate nucleus and nucleus accumbens. Additionally, the displacement of [18F]BIT1 with BIT1 as well as TA1 (a potent PDE2A ligand) indicated saturability and selectivity of these binding sites. Uptake of [18F]BIT1 in the brain was shown by subsequent imaging studies in mice (SUVwhole brain = 0.7 at 5 min p.i.); however, more detailed analyses revealed nonspecific distribution of the tracer in the brain (78% parent compound at 30 min p.i.).
Conclusions: The potent and selective PDE2A inhibitor [18F]BIT1 binds in vitro in brain regions known to express PDE2A. Further structural modifications will be performed to develop radiotracers with improved brain uptake and target-selective accumulation in vivo.
Acknowledgement
1. Deutsche Forschungsgemeinschaft (German Research Foundation, SCHE 1825/3-1).
2. Scholarship Program for Research and Innovation in Science and Technology Project
(RISET-PRO)-Indonesia Ministry of Research, Technology and Higher Education (World
Bank Loan No: 8245-ID)

References
[1] S. Schröder, B. Wenzel, W. Deuther-Conrad, M. Scheunemann, P. Brust, Novel Radioligands
for Cyclic Nucleotide Phosphodiesterase Imaging with Positron Emission Tomography: An Update
on Developments Since 2012, Molecules 21 (2016) 650–685.
Keywords: Phosphodiesterases, positron emission tomography, molecular imaging, benzoimidazotriazines
  • Poster
    International Symposium in Radiopharmaceutical Sciences, 26.-31.05.2019, Beijing, China

Publ.-Id: 29007 - Permalink


Solving the Kuramoto Oscillator Model on Random Graphs
Kelling, J.ORC; Ódor, G.ORC; Gemming, G.
The problem of synchronization is recently attracting much attention because it relates to current topics in science. The dynamics of electrical grids can be affected by de-synchronizations between supplier and consumer nodes. In brains, synchronization of neuronal activity plays an important role in most functions. The Kuramoto model describes systems of coupled oscillators which, which exhibit non-trivial behavior on complex graphs, making it a suitable tool to study the synchronization dynamics of brains an other systems.

Numerical solution of Kuramoto type ordinary differential equations for long times and large systems requires strong computation power, due to the inherent chaoticity of this nonlinear system.

This poster presents a GPU implementation of a solver achieving large speedups over CPU on sparse random graphs. The key to performance here, is the presented memory layout which supplements the SIMT usage of our design.

# extended abstract
The problem of synchronization is recently attracting much attention because it relates to current topics in science. The dynamics of electrical grids can be affected by de-synchronizations between supplier and consumer nodes. In brains, synchronization of neuronal activity plays an important role in most functions.

Using the Kuramoto model[1], we are studying a range of problems, from basinc questions about synnchronisation transitions on disordered lattices and random graphs to problems mentioned in the short abstract. The model shows komplex behavior on human connectome graph, which allow the study of synchronization in the human brain[2]. An extension of the model allows modeling power grid networks[3,4].

Very intensive Simulations are required to obtain precise result especiall near criticality, which these systems show at synchronization transitons. To enable the study of these systems at sufficent precision, we implemented a GPU code, which we are presenting in this poster. To this end we used boost::odeint to get the standart numerical integartion out of the way an focus on the most performance critical aspect: the evaluation of the model itself. The key to our implementation is the choice of SIMT vectorization and a suitable memory layout, which are presented in the poster. The aspects also remain the same, when we add the extension to the second-order Kuramoto Model[2], which is required to model powergrids.

[1] Kuramoto, Y. In Araki, H. (ed.) Mathematical Problems in Theoretical Physics, vol. 39 of Lecture Notes in Physics, Berlin, 420
[2] Villegas, P., Moretti, P. & Muñoz, M. A. Scientific Reports 4, 5990 (2014).
[3] Filatrella, G., Nielsen, A. H. & Pedersen, N. F. Eur. Phys. J. B 61, 485–491 (2008)
[4] Ódor, G. & Hartmann, B. Phys. Rev. E 98, 022305 (2018).
Keywords: GPGPU, random graph, Kuramoto model

Publ.-Id: 29004 - Permalink


Fragment molecular orbital (FMO) method for studying actinide/lanthanide interaction with DNA/protein
Tsushima, S.; Mochizuki, Y.; Fahmy, K.;
Due to its potential health and environmental impacts, actinide binding to biomolecules has been a subject of intensive investigations. A large number of experimental works have been carried out but our understanding remains mostly in a macroscopic scale. Modeling actinide interaction with large biomolecules using ab initio quantum chemical calculations may drastically expand our molecular level knowledge but is challenged by a demand for huge computational resources.
Our strategy to overcome this difficulty is to apply fragment molecular orbital (FMO) method. In FMO, the molecular system of interest is partitioned into small fragments. Each fragment and fragment pair is subject to self-consistent field calculations under environmental electrostatic potentials and the electronic structure of the whole system is reconstituted [1]. This procedure drastically reduces computational cost of Hartree Fock calculations from N3 to N2 (or less) and is readily parallelizable. FMO has been extended to MP2 and to DFT to include electron correlation and was successfully applied to the systems such as hydrated DNA [2].
Currently we are upgrading the FMO program Abinit-MP [3] to implement 5f elements into the program. We first choose uranyl-bound DNA for a case study. Calculations are performed as follows. UO22+-bound d(CGCGAATTCGCG)2 (Dickerson-Drew dodecamer) with 20 Na+ ions and SPC/E water shell with 10 Å thickness is first thermally equilibrated and subsequently submitted to MD simulation at 300 K for 100 ns interval using AMBER 14 program. Force field parameters for UO22+ and coordinating water are those developed by Pomogaev et al. [4]. At each 1 ns time step of MD simulation, the structure is extracted and submitted to FMO single point energy calculation at the MP2 level. In FMO, nucleic unit is appropriately divided into sugar, base, and phosphate fragments. Inter-fragment interaction energy analysis is performed to explore the binding affinity of uranyl to DNA and its influence on base pairing.
[1] K.Kitaura et al. (1999) Chem. Phys. Lett. 313, 701–706.
[2] K.Fukuzawa et al. (2015) Comput.Theor.Chem. 1054, 29–37.
[3] S.Tanaka et al. (2014) Phys. Chem. Chem. Phys. 16, 10310–10344.
[4] V.Pomogaev et al. (2013) Phys. Chem. Chem. Phys. 15, 15954–15963.
  • Poster
    Joint 12th EBSA and 10th ICBP-IUPAP Biophysics Congress, 20.-24.07.2019, Madrid, Spain

Publ.-Id: 29002 - Permalink


Observations of Coherent Optical Transition Radiation Interference Fringes Generated by Laser Plasma Accelerator Electron Beamlets
Lumpkin, A.; Laberge, M.; Rule, D.; Zgadzaj, R.; Hannasch, A.; Downer, M.; Zarini, O.; Bowers, B.; Irman, A.; Couperus, J.ORC; Debus, A.; Kohler, A.; Schramm, U.
We report initial observations of coherent optical transition radiation interferometry (COTRI) patterns generated by microbunched electrons from laser-driven plasma accelerators (LPAs). These are revealed in the angular distribution patterns obtained by a CCD camera with the optics focused at infinity, or the far-field, viewing a Wartski two-foil interferometer. The beam divergences deduced by comparison to results from an analytical model are sub-mrad, and they are smaller than the ensemble vertical beam divergences measured at the downstream screen of the electron spectrometer. The transverse sizes of the beamlet images were obtained with focus at the object, or near field, and were in the few-micron regime as reported by LaBerge et al. [8]. The enhancements in intensity are significant relative to incoherent optical transition radiation (OTR) enabling multiple cameras to view each shot. We present two-foil interferometry effects coherently enhanced in both the 100-TW LPA at 215 MeV energy at Helmholtz-Zentrum Dresden-Rossendorf and the PW LPA at 1.0-GeV energy at the University of Texas-Austin. A transverse emittance estimate is reported for a microbunched beamlet example generated within the plasma bubble.
Keywords: LPA, microbunching, COTR, beam size, divergence
  • Contribution to proceedings
    18th Advanced Accelerator Concepts Workshop (AAC 2018), 12.-17.08.2018, Breckenridge, CO, USA
    2018 IEEE Advanced Accelerator Concepts Workshop (AAC): IEEE, 978-1-5386-7721-6
    DOI: 10.1109/AAC.2018.8659381

Publ.-Id: 29001 - Permalink


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