Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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31828 Publications
Entwicklung induktiver Strömungs- und Füllstandssensoren für flüssige Metalle
Krauter, N.;
In dieser Arbeit werden die Weiterentwicklung bestehender und die Entwicklung neuer Sensoren für die induktive Strömungs- und Füllstandsmessung in flüssigen Metallen sowie die zugehörigen Simulations- und Messergebnisse vorgestellt: Dabei handelt es sich um die Entwicklung und Charakterisierung eines miniaturisierten Eddy Current Flow Meters, das z.B. als Bestandteil der Sicherheitstechnik in flüssigmetallgekühlten Reaktoren zur Überwachung der Kühlmittelströmung bei hohen Umgebungstemperaturen eingesetzt werden kann. Außerdem wird das im Rahmen dieser Arbeit entwickelte Immersed Transient Eddy Current Flow Meter vorgestellt, welches eine direkte und kalibrierungsfreie Fließgeschwindigkeitsmessung ermöglicht und damit einen entscheidenden Vorteil gegenüber herkömmlichen induktiven Strömungssensoren besitzt. Anschließend werden neue Konzepte und ein Sensor für die Füllstandsüberwachung bei industriellen Prozessen, hier am Beispiel der Aluminium-Elektrolyse bei Temperaturen bis zu 1000 °C und der Titanherstellung vorgestellt.
Keywords: Induktive Messverfahren, Fließgeschwindigkeitsmessung, Füllstandsmessung
  • Doctoral thesis
    TUDpress, 2019
    Mentor: Prof. Dr. Uwe Hampel und Dr. Frank Stefani
    248 Seiten

Publ.-Id: 29336 - Permalink


Local inductive flow measurements
Krauter, N.; Stefani, F.;
An overview of current research on inductive local flow rate measurement techniques in liquid metals at the HZDR.
Keywords: Inductive Flow Measurements, Eddy Current Flow Meter, Immersed Transient Eddy Current Flow Meter
  • Lecture (Conference)
    ESFR-SMART European Workshop on Instrumentation for the Safety of Liquid Metal Facilities, 10.-12.04.2019, Dresden, Deutschland

Publ.-Id: 29335 - Permalink


Inductive Level Sensors
Krauter, N.; Stefani, F.; Zürner, T.; Wondrak, T.; Ratajczak, M.;
An overview of current research on inductive level measurement techniques in liquid metals at the HZDR.
Keywords: Eddy Current Level Sensor, Free Surface Detection, Look-Up-Table Method
  • Lecture (Conference)
    ESFR-SMART European Workshop on Instrumentation for the Safety of Liquid Metal Facilities, 10.-12.04.2019, Dresden, Deutschland

Publ.-Id: 29334 - Permalink


I-BEAT: Ultrasonic method for online measurement of the energy distribution of a single ion bunch
Haffa, D.; Yang, R.; Bin, J.; Lehrack, S.; Brack, F.-E.; Ding, H.; Englbrecht, F.; Gao, Y.; Gaus, L.; Gebhard, J.; Gilljohann, M.; Götzfried, J.; Hartmann, J.; Herr, S.; Hilz, P.; Kraft, S.; Kreuzer, C.; Kroll, F.; Lindner, F. H.; Metzkes-Ng, J.; Ostermayr, T. M.; Ridente, E.; Rösch, T. F.; Schilling, G.; Schlenvoigt, H.-P.; Speicher, M.; Taray, D.; Würl, M.; Zeil, K.; Schramm, U.ORC; Karsch, S.; Parodi, K.; Bolton, P.; Schreiber, J.; Assmann, W.
the shape of a wave carries all information about the spatial and temporal structure of its source, given that the medium and its properties are known. Most modern imaging methods seek to utilize this nature of waves originating from Huygens’ principle. We discuss the retrieval of the complete kinetic energy distribution from the acoustic trace that is recorded when a short ion bunch deposits its energy in water. this novel method, which we refer to as Ion-Bunch energy Acoustic tracing (I-BeAt), is a refinement of the ionoacoustic approach. With its capability of completely monitoring a single, focused proton bunch with prompt readout and high repetition rate, I-BeAt is a promising approach to meet future requirements of experiments and applications in the field of laser-based ion acceleration. We demonstrate its functionality at two laser-driven ion sources for quantitative online determination of the kinetic energy distribution in the focus of single proton bunches
Keywords: laser ion acceleration, ion spectrometer

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Publ.-Id: 29332 - Permalink


Direct Observation of Plasma Waves and Dynamics Induced by Laser-Accelerated Electron Beams
Gilljohann, M. F.; Ding, H.; Döpp, A.; Götzfried, J.; Schindler, S.; Schilling, G.; Corde, S.; Debus, A.; Heinemann, T.; Hidding, B.; Hooker, S. M.; Irman, A.; Kononenko, O.; Kurz, T.; Martinez De La Ossa, A.; Schramm, U.ORC; Karsch, S.
Plasma wakefield acceleration (PWFA) is a novel acceleration technique with promising prospects for both particle colliders and light sources. However, PWFA research has so far been limited to a few large-scale accelerator facilities worldwide. Here, we present first results on plasma wakefield generation using electron beams accelerated with a 100-TW-class Ti:sapphire laser. Because of their ultrashort duration and high charge density, the laser-accelerated electron bunches are suitable to drive plasma waves at electron densities in the order of 1019  cm−3. We capture the beam-induced plasma dynamics with femtosecond resolution using few-cycle optical probing and, in addition to the plasma wave itself, we observe a distinctive transverse ion motion in its trail. This previously unobserved phenomenon can be explained by the ponderomotive force of the plasma wave acting on the ions, resulting in a modulation of the plasma density over many picoseconds. Because of the scaling laws of plasma wakefield generation, results obtained at high plasma density using high-current laser-accelerated electron beams can be readily scaled to low-density systems. Laser-driven PWFA experiments can thus act as miniature models for their larger, conventional counterparts. Furthermore, our results pave the way towards a novel generation of laser-driven PWFA, which can potentially provide ultralow emittance beams within a compact setup.
Keywords: laser wakefield, plasma wakefield electron acceleration, high power laser, advanced accelerator

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Publ.-Id: 29331 - Permalink


Exciton localization in MoSe₂ monolayer induced by adsorbed gas molecules
Venanzi, T.; Arora, H.; Erbe, A.; Pashkin, A.; Winnerl, S.; Helm, M.; Schneider, H.;
Lattice defects and dielectric environment play a crucial role for 2D materials. Gas molecules can get physisorbed easily on the surface through van der Waals forces and can modify dramatically the electronic and optical properties. In this work we investigate the impact of the physisorbed gas molecules on the optical properties of MoSe₂ monolayers by means of low-temperature photoluminescence (PL). More specifically we focus on the physics of excitons localized by gas molecules. The associated PL peak is observed to show a systematic and large red-shift with temperature and a blue-shift with laser irradiation. Both energy shifts are explained in terms of thermal instability of the localization in combination with hopping effects. Finally a model is presented which can reproduce the experimental data with excellent agreement.
Keywords: MoSe2, photoluminescence, localized excitons, TMD, physisorption
  • Applied Physics Letters 114(2019), 172106
    Online First (2019) DOI: 10.1063/1.5094118

Publ.-Id: 29321 - Permalink


A model of a tidally synchronized solar dynamo
Stefani, F.; Giesecke, A.; Weier, T.;
We discuss a solar dynamo model of Tayler–Spruit type whose Omega-effect is conventionally produced by a solar-like differential rotation but whose alpha-effect is assumed to be periodically modulated by planetary tidal forcing. This resonance-like effect has its rationale in the tendency of the current-driven Tayler instability to undergo intrinsic helicity oscillations which, in turn, can be synchronized by periodic tidal perturbations. Specifically, we focus on the 11.07-years alignment periodicity of the tidally dominant planets Venus, Earth, and Jupiter, whose persistent synchronization with the solar dynamo is briefly touched upon. The typically emerging dynamo modes are dipolar fields, oscillating with a 22.14-years period or pulsating with a 11.07-years period, but also quadrupolar fields with corresponding periodicities. In the absence of any constant part of alpha, we prove the sub-critical nature of this Tayler–Spruit type dynamo. The resulting amplitude of the alpha oscillation that is required for dynamo action turns out to lie in the order of 1 m/s, which seems not implausible for the Sun. When starting with a more classical, non-periodic part of alpha, even less of the oscillatory alpha part is needed to synchronize the entire dynamo. Typically, the dipole solutions show butterfly diagrams, although their shapes are not convincing yet. Phase coherent transitions between dipoles and quadrupoles, which are reminiscent of the observed behavior during the Maunder minimum, can easily be triggered by long-term variations of dynamo parameters, but may also occur spontaneously even for fixed parameters. Further interesting features of the model are the typical second intensity peak and the intermittent appearance of reversed helicities in both hemispheres.

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  • Secondary publication expected from 22.05.2020

Publ.-Id: 29317 - Permalink


Horizon-2020 ESFR-SMART project on SFR safety: status after first 15 months
Mikityuk, K.; Girardi, E.; Krepel, J.; Bubelis, E.; Fridman, E.; Rineiski, A.; Girault, N.; Payot, F.; Buligins, L.; Gerbeth, G.; Chauvin, N.; Latge, C.; Guidez, J.;
Devoted to the Generation-IV European Sodium Fast Reactor safety, the Horizon-2020 ESFR-SMART project was launched in September 2017. Selected results and milestones achieved during the first fifteen months of the project are briefly reviewed in the paper, including 1)proposal of new safety measures for ESFR; 2)evaluation of ESFR core performance; 3) benchmarking of codes; 4) experimental programs; and 5) education and training.
  • Contribution to proceedings
    27th International Conference on Nuclear Engineering - ICONE27, 19.-24.05.2019, Ibaraki, Japan

Publ.-Id: 29314 - Permalink


Benchmarking KENO-VI against MCNP/Serpent using a simplified SFR pin cell problem
Fridman, E.; Jiménez-Carrascosa, A.; García-Herranz, N.; Alvarez-Velarde, F.; Romojaro, P.; Bostelmann, F.;
Benchmarking KENO-VI against MCNP/Serpent using a simplified SFR pin cell problem
  • Lecture (Conference)
    OECD/NEA UAM Workshop 2019, 13.-17.05.2019, Oak Ridge National Laboratory, USA

Publ.-Id: 29313 - Permalink


Initial solution of the SFR-UAM Exercises I-1 and I-2 with Serpent
Fridman, E.;
Initial solution of the SFR-UAM Exercises I-1 and I-2 with Serpent
  • Lecture (Conference)
    OECD/NEA UAM Workshop 2019, 13.-17.05.2019, Oak Ridge National Laboratory, USA

Publ.-Id: 29312 - Permalink


About the impact of the Unresolved Resonance Region in Monte Carlo simulations of Sodium Fast Reactors
Jiménez-Carrascosa, A.; Fridman, E.ORC; García-Herranz, N.; Alvarez-Velarde, F.; Romojaro, P.; Bostelmann, F.
In the last few years, and within the framework of different European projects, KENO-VI code from SCALE system has been employed to perform detailed continuous-energy Monte Carlo transport calculations for advanced fast reactors. The core characterization of both the sodium-cooled ASTRID and the lead-cooled ALFRED reactors was performed during the FP7 cross-cutting ESNII+ project; more recently, core calculations for the sodium-cooled Superphénix reactor and the improved European Sodium Fast Reactor design were performed within the HORIZON2020 ESFR-SMART project. In all cases, the effective multiplication factor predicted by KENO-VI was systematically higher (around 400-500 pcm) than the values computed by MCNP and Serpent Monte Carlo codes, using the same nuclear data library.

In order to provide insight into the origin of the observed discrepancies, a simplified 2D MOX-fueled SFR pin-cell benchmark has been launched. The multiplication factor, as well as 1-group and VITAMINJ 175-group cross-sections computed by KENO-VI, Serpent and MCNP codes employing ENDF/B-VII.1 data library, have been compared.

Significant differences between KENO-VI and the other codes have been found in the unresolved resonance regions of 239Pu and 241Pu capture and production cross sections, while negligible differences appeared outside those energy ranges. On the other hand, calculations without using probability tables have shown very good agreement. Quantita-tive comparison is presented and analyzed, along with a discussion of the impact of the probability-table treatment in the three codes for MOX-fueled systems with typical SFR spectrum.
Keywords: Unresolved Resonance Region, Probability Tables, Monte Carlo simulations of SFR
  • Contribution to proceedings
    ICAPP 2019 – International Congress on Advances in Nuclear Power Plants, 12.-15.05.2019, Juan-les-pins, France
    Proceedings of ICAPP 2019

Publ.-Id: 29311 - Permalink


Preparation of non-oxidized Ge quantum dot lattices in amorphous Al2O3, Si3N4 and SiC matrices
Nekić, N.; Šarić, I.; Salamon, K.; Basioli, L.; Sancho-Parramon, J.; Grenzer, J.; Hübner, R.; Bernstorff, S.; Petravić, M.; Mičetić, M.;
The preparation of non-oxidized Ge quantum dot (QD) lattices embedded in Al2O3, Si3N4, SiC matrices by self-assembled growth was studied. The materials were produced by magnetron sputtering deposition, using different substrate temperatures. The deposition regimes leading to the self-assembled growth type and the formation of three-dimensionally ordered Ge QD lattices in different matrices were investigated and determined. The oxidation of the Ge QDs in different matrices was monitored and the best conditions for the production of non-oxidized Ge QDs were found. The optical properties of the Ge QD lattices in different matrices show a strong dependence on the Ge oxidation and the matrix type.
Keywords: Ge QD lattices, Ge oxidation, self-assembled growth, influence of matrix

Publ.-Id: 29309 - Permalink


The magnetic structure of L10 ordered MnPt at room temperature determined using polarized neutron diffraction
Solina, D.; Schmidt, W.; Kaltofen, R.; Krien, C.; Lai, C.-H.; Schreyer, A.;
Neutron scattering studies have been carried out on single crystal films of [001] orientated L10 ordered MnPt grown epitaxially onMgO(001) usingDCmagnetron sputtering. Polarized neutron diffraction studies at room temperature show that the moments in ordered MnPt are aligned perpendicular to the [001] axis with a tilt of 45° to the [100] axis and not parallel to [100] as inferred from previous powder neutron diffraction measurements.
Keywords: antiferromagnetic, neutron diffraction, platinum alloys

Publ.-Id: 29308 - Permalink


Detection of ultra-low protein concentrations with the simplest possible field effect transistor
Georgiev, Y. M.ORC; Petkov, N.; Yu, R.; Nightingale, A. M.; Buitrago, E.; Lotty, O.; Demello, J. C.; Ionescu, A.; Holmes, J. D.
Silicon nanowire (Si NW) sensors have attracted great attention due to their ability to provide fast, low-cost, label-free, real-time detection of chemical and biological species. Usually configured as field effect transistors (FETs), they have already demonstrated remarkable sensitivity with high selectivity (through appropriate functionalisation) towards a large number of analyses in both liquid and gas phases. Despite these excellent results, Si NW FET sensors have not yet been successfully employed to detect single molecules of either a chemical or biological target species. Here we show that sensors based on silicon junctionless nanowire transistors (JNTs), the simplest possible transistors, are capable of detecting the protein streptavidin at a concentration as low as 580 zM closely approaching the single molecule level. This ultrahigh detection sensitivity is due to the intrinsic advantages of junctionless devices over conventional FETs.

Apart from their superior functionality, JNTs are much easier to fabricate by standard microelectronic processes than transistors containing p-n junctions. The ability of JNT sensors to detect ultra-low concentrations (in the zeptomolar range) of target species, and their potential for low-cost mass production, will permit their deployment in numerous environments, including life sciences, biotechnology, medicine, pharmacology, product safety, environmental monitoring and security.
Keywords: Si nanowire biosensor, junctionless nanowire transistor, ultrahigh detection sensitivity, protein, streptavidin, single-molecule detection

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  • Secondary publication expected from 08.05.2020

Publ.-Id: 29306 - Permalink


Prompt-gamma based range verification in proton therapy: Can we do better? Shall we do better?
Pausch, G.ORC
Prompt gamma-ray imaging (PGI) with a knife-edge slit camera has proven to be useful for range monitoring in proton therapy (PT). It is meanwhile applied in a prostate patient study at OncoRay. Together with an improved range prediction based on dual-energy CT and robust planning methods it could finally allow reducing the range margins, thus saving normal tissue in PT treatments. Translating these emerging techniques in clinical routine is a long but important process that will require considerable efforts.
Nevertheless we are also dealing with the far end of the translational conveyer, asking if and how in-vivo range verification could be improved. So far, PGI does not allow measuring range deviations of single pencil beams with the necessary precision. The reason is the short delivery time of such a beam spot, and the poor event statistics that can be accessed in this period. It is obvious to exploit not only spatial, but also spectroscopic and timing information of the gamma rays registered for range verification. The prompt gamma-ray spectroscopy method developed at MGH in Boston and the prompt gamma-ray timing technique explored at OncoRay in Dresden represent reasonable alternatives to PGI; but can these approaches be combined in a single, preferable simple and light-weight, clinically applicable system distinguished by minimum interference with beam and patient couch? Could such a combination improve the accuracy and allow single-spot range verification, maybe even for the non-distal spots comprising much less protons?
The talk will present our thoughts and approaches to answer this question. This includes recent results concerning prompt gamma-ray timing (PGT) and single-plane Compton imaging (SPCI). Part of the research performed in this context could also affect gamma-ray imaging in nuclear medicine.
Keywords: PGI, PGT, prompt gamma ray, proton therapy, range verification, treatment verification
  • Lecture (others)
    Medizinphysik-Seminar, 12.06.2019, Heidelberg, Deutschland

Publ.-Id: 29293 - Permalink


Band gap renormalization in n-type GeSn alloys made by ion implantation and flash lamp annealing
Prucnal, S.; Berencén, Y.; Wang, M.; Rebohle, L.; Kudrawiec, R.; Polak, M.; Zviagin, V.; Schmidt-Grund, R.; Grundmann, M.; Grenzer, J.; Turek, M.; Droździel, A.; Pyszniak, K.; Zuk, J.; Helm, M.; Skorupa, W.; Zhou, S.;
The last missing piece of the puzzle for the full functionalization of group IV optoelectronic devices is a direct bandgap semiconductor made by CMOS compatible technology. Here, we report on the fabrication of GeSn alloys with Sn concentrations up to 4.5% using ion implantation followed by millisecond-range explosive solid phase epitaxy. The n-type single crystalline GeSn alloys are realized by coimplantation of Sn and P into Ge. Both the activation of P and the formation of GeSn are performed during a single-step flash lamp annealing for 3 ms. The bandgap engineering in GeSn as a function of the doping level and Sn concentration is theoretically predicted by density functional theory and experimentally verified using ellipsometric spectroscopy. We demonstrate that both the diffusion and the segregation of Sn and P atoms in Ge are fully suppressed by millisecond-range nonequilibrium thermal processing.
Keywords: ion implantation, flash lamp annealing, Ge, GeSn, n-type doping

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  • Secondary publication expected from 30.05.2020

Publ.-Id: 29290 - Permalink


Benchmarking ATHLET against TRACE as applied to Superphénix start-up tests
Di Nora, V. A.; Fridman, E.; Mikityuk, K.;
ATHLET is a thermal-hydraulic (TH) system code developed at the GRS for the modeling of Light Water Reactors (LWRs). To extend the applicability of ATHLET to the analyses of Sodium Fast Reactors (SFRs), the code was recently upgraded with the thermal-physical properties of the liquid sodium. The new extension is still under verification and validation phases. The present work contributes to the verification efforts. This study investigated the perfor-mance of the extended version of ATHLET as applied to the transient analysis of a set of start-up tests conducted at the Superphénix SFR. The specifications of the corresponding tests such as the simplified SPX reactor core models and the set of reactivity coefficients were adopted primarily from a previous dedicated study performed at PSI and at KIT. The reactivity effects accounted for by ATHLET included fuel Doppler effect and thermal expansion effects of sodium, fuel, diagrid, control rods driveline, strongback, and reactor vessel. The results obtained by ATHLET for main stationary TH parameters, power evolutions, and reactivity feedback components were benchmarked against the reference solutions provided by TRACE. Employing an identical set of reactivity coefficients, either in steady-state or transient calculations, the codes produce consistent and close results.
Keywords: ATHLET against TRACE; ATHLET verification; Superphénix start-up tests;
  • Contribution to proceedings
    International Congress on Advances in Nuclear Power Plants - ICAPP2019, 12.-15.05.2019, Juan-les-Pins, France

Publ.-Id: 29289 - Permalink


Cross section of 3He(α , γ)7Be around the 7Be proton separation threshold
Szücs, T.ORC; Kiss, G. G.; Gyürky, G.; Halász, Z.; Szegedi, T. N.; Fülöp, Z.
Background: The 3He(α,γ)7Be reaction is a widely studied nuclear reaction; however, it is still not understood with the required precision. It has a great importance both in Big Bang nucleosynthesis and in solar hydrogen burning. The low mass number of the reaction partners makes it also suitable for testing microscopic calculations.

Purpose: Despite the high number of experimental studies, none of them addresses the 3He(α,γ)7Be reaction cross sections above 3.1-MeV center-of-mass energy. Recently, a previously unobserved resonance in the 6Li(p,γ)7Be reaction suggested a new level in 7Be, which would also have an impact on the 3He(α,γ)7Be reaction in the energy range above 4.0 MeV. The aim of the present experiment is to measure the 3He(α,γ)7Be reaction cross section in the energy range of the proposed level.

Method: For this investigation the activation technique was used. A thin window gas-cell target confining 3He gas was irradiated using an α beam. The 7Be produced was implanted into the exit foil. The 7Be activity was determined by counting the γ rays following its decay by a well-shielded high-purity germanium detector.

Results: Reaction cross sections have been determined between Ecm=4.0and4.4 MeV with 0.04-MeV steps covering the energy range of the proposed nuclear level. One lower-energy cross-section point was also determined to be able to compare the results with previous studies.

Conclusions: A constant cross section of around 10.5 μb was observed around the 7Be proton separation energy. An upper limit of 45 neV for the strength of a 3He(α,γ)7Be resonance is derived.
Keywords: Nuclear Astrophysics, alpha induced reaction, light element nucleosynthesis

Publ.-Id: 29287 - Permalink


Electromagnetic forcing of a flow with the azimuthal wavenumber m=2 in cylindrical geometry
Stepanov, R.; Stefani, F.;
In this paper, we consider a liquid metal flow generated in a cylindrical volume by AC currents in various coil configurations. The final aim of this study is to design and optimize a Rayleigh-Bénard experiment with a large scale circulation, the helicity oscillation of which is synchronized by a periodically modulated tide-like m=2 perturbation.
Keywords: Rayleigh-Bénard

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  • Secondary publication expected from 10.05.2020

Publ.-Id: 29286 - Permalink


Incorporation of Europium into GaN Nanowires by Ion Implantation
Faye, D. N. A.; Biquard, X. B.; Nogales, E. C.; Felizardo, M. A.; Peres, M. A.; Redondo-Cubero, A. A.; Auzelle, T. B.; Daudin, B.; Tizei, L. H. G.; Kociak, M.; Ruterana, P.; Möller, W.; Méndez, B.; Alves, E.; Lorenz, K.;
Rare earth (RE)-doped GaN nanowires (NWs), combining the well-defined and controllable optical emission lines of trivalent RE ions with the high crystalline quality, versatility, and small dimension of the NW host, are promising building blocks for future nanoscale devices in optoelectronics and quantum technologies. Europium doping of GaN NWs was performed by ion implantation, and structural and optical properties were assessed in comparison to thin film reference samples. Despite some surface degradation for high implantation fluences, the NW core remains of high crystalline quality with lower concentrations of extended defects than observed in ion-implanted thin films. Strain introduced by implantation defects is efficiently relaxed in NWs and the measured deformation stays much below that in thin films implanted in the same conditions. Optical activation is achieved for all samples after annealing, and while optical centers are similar in all samples, Eu 3+ emission from NW samples is shown to be less affected by residual implantation damage than for the case of thin films. The incorporation of Eu in GaN NWs was further investigated by nano-cathodoluminescence and X-ray absorption spectroscopy (XAS). Maps of the Eu-emission intensity within a single NW agree well with the Eu-distribution predicted by Monte Carlo simulations, suggesting that no pronounced Eu-diffusion takes place. XAS shows that 70-80% of Eu is found in the 3+ charge state while 20-30% is 2+ attributed to residual implantation defects. A similar local environment was found for Eu in NWs and thin films: for low fluences, Eu is mainly incorporated on substitutional Ga-sites, while for high fluences XAS points at the formation of a local EuN-like next neighbor structure. The results reveal the high potential of ion implantation as a processing tool at the nanoscale.

Publ.-Id: 29285 - Permalink


Electron Paramagnetic Resonance in Ge/Si Heterostructures with Mn-Doped Quantum Dots
Zinovieva, A. F.; Zinovyev, V. A.; Stepina, N. P.; Katsuba, A. V.; Dvurechenskii, A. V.; Gutakovskii, A. K.; Kulik, L. V.; Bogomyakov, A. S.; Erenburg, S. B.; Trubina, S. V.; Voelskow, M.;
Ge/Si quantum dot (QD) structures doped with Mn have been tested by the EPR method to find the optimal conditions for formation of the diluted magnetic semiconductor (DMS) phase inside QDs. The effect of Mn doping has been studied for two series of samples: series A with QDs grown at 450 degrees C and varied Mn concentration and series B with QDs grown at different temperature with Mn concentration x = 0.02. Several effects of modification of the EPR spectra due to Mn presence in the samples have been obtained. These effects are related to (i) strain reduction due to GeSi intermixing, (ii) QD enlargement and change in QD shape, (iii) presence of an additional magnetic field produced by Mn atoms incorporated in QDs. The data obtained allow us to understand the reasons for irreproducibility of the results available in the literature on the creation of magnetic Ge1 - xMnx quantum dots.

Publ.-Id: 29283 - Permalink


Numerical modelling of air-breathing PEMFC
Weber, N.; Chaparro, A.; Ferreira-Aparicio, P.;
Übersicht über die Simulation von Luft atmenden Brennstoffzellen mit OpenFOAM
  • Lecture (others)
    Vortrag am IEK3 des Forschungszentrums Jülich, 22.05.2019, Jülich, Deutschland

Publ.-Id: 29279 - Permalink


Improved 242Pu(n,γ) thermal cross section combining activation and prompt gamma analysis
Lerendegui-Marco, J.; Guerrero, C.; Belgya, T.; Maróti, B.; Eberhardt, K.; Düllmann, C. E.; Junghans, A. R.; Mokry, C.; Quesada, J. M.; Runke, J.; Thörle-Pospiech, P.;
A good knowledge of the radiative capture cross section of 242Pu is required for innovative nuclear reactor studies, especially for MoX fuel reactors. However, the experimental data available show discrepancies in the energy regions of interest: the thermal point and the keV region. Previous experimental results of the thermal cross section deviate from each other by 20% and these discrepancies are reflected also in the evaluated libraries, each of them giving more credit to different data sets. A recent measurement by Genreith et al. did not succeed to solve the existing discrepancy due to the large uncertainties and correction factors in the analysis. This work presents a new measurement of the thermal capture cross section of 242Pu carried out in the Budapest Research Reactor using the same thin targets of a previous measurement at n_TOF-EAR1, each containing 30mg of 99.995% pure 242Pu . The combined analysis of the full prompt γ-ray spectrum and the 243Pu decay has led to three compatible values for the thermal cross section. Their average value, 18.9(9)b, has an improved accuracy compared to recent measurements. Leaving aside the activation value of Genreith using an outdated intensity value for the 84 keV decay line of 243Pu , our average result is in very good agreement with the JEFF-3.2 evaluation and all the previous measurements, with the exception of the highest value 22.5(11)b reported by Marie et al., which has a strong influence in the ENDF evaluation.242
Keywords: neutron capture cross section, 242Pu, thermal neutron spectrum

Publ.-Id: 29278 - Permalink


Analysis of studies and research projects regarding the detection of nanomaterials in different environmental compartments and deduction of need for action regarding method development
Hildebrand, H.; Franke, K.; Fischer, C.; Schymura, S.;
Exertengespräch und Präsentation der Ergebnisse aus der Literaturstudie zum Nachweis von Nanomaterialien in den verschiedenen Umweltkompartimenten, Projekt NanoExperte
Keywords: nanomaterials in environemtal media, detection, quantification
  • Invited lecture (Conferences)
    Abschlusspräsentation des Sachverständigengutachtens „NanoExperte“, 17.04.2019, Dessau-Roßlau, Deutschland

Publ.-Id: 29277 - Permalink


Specific ion effects directed noble metal aerogels: Versatile manipulation for electrocatalysis and beyond
Du, R.; Hu, Y.; Hübner, R.; Joswig, J.-O.; Fan, X.; Schneider, K.; Eychmüller, A.;
Noble metal foams (NMFs) are a new class of functional materials featuring properties of both noble metals and monolithic porous materials, providing impressive prospects in diverse fields. Among reported synthetic methods, the sol-gel approach manifests overwhelming advantages for versatile synthesis of nanostructured NMFs (i.e., noble metal aerogels) under mild conditions. However, limited gelation methods and elusive formation mechanisms retard structure/composition manipulation, hampering on-demand design for practical applications. Here, highly tunable NMFs are fabricated by activating specific ion effects, enabling various single/alloy aerogels with adjustable composition (Au, Ag, Pd, and Pt), ligament sizes (3.1 to 142.0 nm), and special morphologies. Their superior performance in programmable self-propulsion devices and electrocatalytic alcohol oxidation is also demonstrated. This study provides a conceptually new approach to fabricate and manipulate NMFs and an overall framework for understanding the gelation mechanism, paving the way for on-target design of NMFs and investigating structure-performance
relationships for versatile applications.

Publ.-Id: 29276 - Permalink


Radiobiology of high dose-rate particle beams
Beyreuther, E.; Karsch, L.; Pawelke, J.;
In the past few years, the normal tissue protecting effect of Flash electron irradiation was shown for several endpoints and in different species [1], [2]. Contrary to conventional, clinical beam delivery over minutes, the therapeutic dose is administered within less than 0.5 s by Flash irradiation. Hence, this treatment regime is linked to high mean dose rates of ~100 Gy/s and high pulse dose rates of ≥105 Gy/s, clearly exceeding the parameters of a few Gy/min on time average and of ~ 102 Gy/s within one pulse of conventional, clinical Linacs. Of note, tumors were cured by electron Flash as efficient as by conventional electron beam treatment over minutes [1]. Moreover, the protecting Flash effect was recently validated for photons [3], which promises a general validity of this effect also for other types of clinically used radiation.
First attempts testing the feasibility of proton Flash were conducted at clinical proton beam facilities in France [4] and at the University Proton Therapy Dresden (UPTD), Germany. At UPTD, a setup was established that allows for the irradiation of zebrafish embryo either with dose rates of 100 Gy/s for Flash or of 5 Gy/min for conventional reference. The zebrafish embryo were treated with graded doses up to 40 Gy and embryonic survival as well as the manifestation of morphological abnormalities were followed for up to four days. However, analysing the different endpoints, a clear dependency on dose but no significant dependence on proton dose rate was revealed.
This unexpected result implies, that more studies are needed to resolve the influence on beam time structure for the induction of a protective Flash effect. Here, research facilities like FAIR with a broader parameter space regarding ion species, particle fluence, LET, pulsing and beam time structure provide the possibility to study the physical limits of Flash in more detail. Therewith also questions on a potential influence or interaction of high dose-rate particle beam, high LET and oxygen level of the irradiated tissue could be investigated systematically. The results obtained therein could help to further develop dedicated clinical accelerators, like superconducting or heavy ion synchrotrons, to make clinical use of the Flash effect.



[1] V. Favaudon et al., “Ultrahigh dose-rate FLASH irradiation increases the differential response between normal and tumor tissue in mice,” Sci. Transl. Med., vol. 6, no. 245, p. 245ra93, Jul. 2014.
[2] P. Montay-Gruel et al., “Irradiation in a flash: Unique sparing of memory in mice after whole brain irradiation with dose rates above 100Gy/s,” Radiother. Oncol. J. Eur. Soc. Ther. Radiol. Oncol., vol. 124, no. 3, pp. 365–369, 2017.
[3] P. Montay-Gruel et al., “X-rays can trigger the FLASH effect: Ultra-high dose-rate synchrotron light source prevents normal brain injury after whole brain irradiation in mice,” Radiother. Oncol. J. Eur. Soc. Ther. Radiol. Oncol., vol. 129, no. 3, pp. 582–588, Dec. 2018.
[4] A. Patriarca et al., “Experimental Set-up for FLASH Proton Irradiation of Small Animals Using a Clinical System,” Int. J. Radiat. Oncol. Biol. Phys., vol. 102, no. 3, pp. 619–626, Nov. 2018.
  • Contribution to proceedings
    International Biophysics Collaboration Meeting, 20.-22.05.2019, Darmstadt, Deutschland
    DOI: 10.15120/GSI-2019-00596

Publ.-Id: 29270 - Permalink


Superconductivity in single-crystalline aluminum- and gallium-hyperdoped germanium
Prucnal, S.; Heera, V.; Hübner, R.; Wang, M.; Mazur, G. P.; Grzybowski, M. J.; Qin, X.; Yuan, Y.; Voelskow, M.; Skorupa, W.; Rebohle, L.; Helm, M.; Sawicki, M.; Zhou, S.;
Superconductivity in group IV semiconductors is desired for hybrid devices combining both semiconducting and superconducting properties. Following boron-doped diamond and Si, superconductivity has been observed in gallium-doped Ge; however, the obtained specimen is in polycrystalline form [Phys. Rev. Lett. 102, 217003 (2009)]. Here we present superconducting single-crystalline Ge hyperdoped with gallium or aluminum by ion implantation and rear-side flash lamp annealing. The maximum concentration of Al and Ga incorporated into substitutional positions in Ge is 8 times higher than the equilibrium solid solubility. This corresponds to a hole concentration above 1021 cm−3. Using density functional theory in the local-density approximation and pseudopotential plane-wave approach, we show that the superconductivity in p-type Ge is phonon mediated. According to the ab initio calculations, the critical superconducting temperature for Al- and Ga-doped Ge is in the range of 0.45 K for 6.25at.% of dopant concentration, being in qualitative agreement with experimentally obtained values.
Keywords: superconductivity, ion implantation, Germanium, flash lamp annealing

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Publ.-Id: 29266 - Permalink


Monolithic waveguide laser mode-locked by embedded Ag nanoparticles operating at 1 μm
Li, R.; Pang, C.; Li, Z.; Dong, N.; Wang, J.; Ren, F.; Akhmadaliev, S.; Zhou, S.; Chen, F.;
Monolithic waveguide laser devices are required to achieve on-chip lasing. In this work, a new design of a monolithic device with embedded Ag nanoparticles (NPs) plus the Nd:YAG ridge waveguide has been proposed and implemented. By using Ag+ ion implantation, the embedded Ag NPs are synthesized on the near-surface region of the Nd:YAG crystal, resulting in the significant enhancement of the optical nonlinearity of Nd:YAG and offering saturable absorption properties of the crystal at a wide wavelength band. The subsequent processing of the O5+ ion implantation and diamond saw dicing of crystal finally leads to the fabrication of monolithic waveguide with embedded Ag NPs. Under an optical pump, the Q-switched mode-locked waveguide lasers operating at 1 μm is realized with the pulse duration of 29.5 ps and fundamental repetition rate of 10.53 GHz, owing to the modulation of Ag NPs through evanescent field interaction with waveguide modes. This work introduces a new approach in the application of monolithic ultrafast laser devices by using embedded metallic NPs.

Publ.-Id: 29264 - Permalink


Laser-driven proton beam profiles in ultra-high fields
Obst-Hübl, L.ORC; Bernert, C.; Brack, F.-E.; Branco, J.; Bussmann, M.; Cochran, G.; Cowan, T. E.; Curry, C. B.; Gaus, L.; Fiuza, F.; Garten, M.; Gauthier, M.; Glenzer, S. H.; Göde, S.; Huebl, A.; Irman, A.; Kim, J. B.; Kluge, T.; Kraft, S.; Kroll, F.; Macdonald, M. J.; Metzkes-Ng, J.; Mishra, R.; Pausch, R.; Poole, P.; Prencipe, I.; Rehwald, M.; Rödel, C.; Ruyer, C.; Schlenvoigt, H.-P.; Sommer, P.; Schoenwalder, C.; Schumaker, W.; Ziegler, T.; Schramm, U.; Schumacher, D. W.; Zeil, K.
Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact multi-MeV proton accelerators with unique bunch characteristics. Protons are accelerated in TV/m fields that are established within the micrometer-scale vicinity of the high-power laser focus. This initial acceleration phase is followed by ballistic proton bunch propagation with negligible space-charge effects over millimeters to hundreds of centimeters to the particle detector or a proton target at a dedicated irradiation site. The detected proton emission distribution can be influenced by the spatio-temporal intensity distribution in the laser focus, electron transport through the target, potential plasma instabilities, as well as local and global target geometry and surface properties.
Substantially extending this picture, our recent results show a critical influence of the milimeter scale vacuum environment on the accelerated proton bunch, where residual gas molecules are ionized by the remnant laser light that is not absorbed into the target plasma but reflected or transmitted. In an experiment with µm-sized hydrogen jet targets, this effect lead to the counter-intuitive observation of laser near-field feature imprints in the detected proton beam profiles. Our results show that the remnant laser pulse induces a quasi-static deflecting field map in the ionized residual background gas that serves as a memorizing medium and allows for asynchronous information transfer to the naturally delayed proton bunch. Occurring under typical experimental laser, target and vacuum conditions, all-optical imprinting needs to be taken into account for sensible interpretation of modulated proton beam profiles.
Keywords: laser-driven plasmas, high-power lasers, novel accelerator concepts, laser-ion acceleration, plasma mirrors
  • Invited lecture (Conferences)
    Laser Plasma Accelerator Workshop 2019, 05.-10.05.2019, Split, Kroatien

Publ.-Id: 29261 - Permalink


Synthetic radiation diagnostics as a pathway for studying plasma dynamics from advanced accelerators to astrophysical observations
Pausch, R.;
PhD defense talk
Keywords: PhD defense
  • Lecture (others)
    Disputation, 25.03.2019, Dresden, Deutschland

Publ.-Id: 29259 - Permalink


Modeling hybrid plasma accelerator experiments with PIConGPU
Pausch, R.; Bussmann, M.; Garten, M.; Huebl, A.; Steiniger, K.; Widera, R.; Kurz, T.; Schöbel, S.; Chang, Y.-Y.; Couperus Cabadağ, J.; Köhler, A.; Zarini, O.; Heinemann, T.; Ding, H.; Döpp, A.; Gilljohann, M. F.; Kononeko, O.; Raj, G.; Corde, S.; Hidding, B.; Karsch, S.; Martinez De La Ossa, A.; Irman, A.; Schramm, U.; Debus, A.;
Utilizing laser-wakefield accelerated (LWFA) electrons to drive aplasma-wakefield accelerator (PWFA) holds great promise for realizingcentimeter-scale electron accelerators providing ultra-high brightnessbeams. Recent experiments at HZDR could demonstrate for the first timesuch an electron acceleration in a nonlinear PWFA plasma wakefield. Fordriving this compact hybrid accelerator setup, high-charge electronbunches from LWFA self-truncated ionization injection were used.In this talk, we present recent results of the accompanying simulationcampaign performed with the 3D3V particle-in-cell code PIConGPU. Thesesimulations model the geometry, density distributions, laser modes, andgas dopings as determined in the experiments. The simulation conditionsresemble the experiment to a very high degree and thus provide goodcomparability between experiment and simulation. Additionally, thewealth of information provided by the in-situ data analysis of PIConGPU provides insight into the plasma dynamics, otherwise inaccessible inexperiments.From an algorithmic and computational perspective, we modeled the hybridaccelerator from start to end in a single simulation scenario. Wediscuss the associated challenges in maintaining numerical stability andexperimental comparability of these long-duration simulations.
Keywords: LPWFA, hybrid, PIConGPU
  • Lecture (Conference)
    Laser-Plasma AcceleratorWorkshop 2019, 05.-10.05.2019, Split, Croatia

Publ.-Id: 29258 - Permalink


Hybrid plasma accelerators - LWFA-PWFA simulations with PIConGPU
Pausch, R.; Debus, A.; Garten, M.; Huebl, A.; Steiniger, K.; Widera, R.; Kurz, T.; Schöbel, S.; Couperus Cabadağ, J.; Irman, A.; Schramm, U.; Bussmann, M.;
Utilizing laser-wakefield accelerated (LWFA) electrons to drive a plasma-wakefield accelerator (PWFA) holds great promise for realizing centimeter-scale electron accelerators providing ultra-high brightness beams. Recent experiments at HZDR could demonstrate for the first time such an electron acceleration in a nonlinear PWFA plasma wakefield using this compact setup.

On this poster, we show recent results of the accompanying simulation campaign performed with the 3D3V particle-in-cell code PIConGPU. These simulations model the geometry, density distributions, laser modes, and gas dopings as determined in the experiments. The simulation conditions resemble the experiment to a very high degree and thus provide precise comparability between experiment and simulation. Additionally, the wealth of information provided by the in-situ data analysis of PIConGPU provides insight into the plasma dynamic, otherwise inaccessible in experiments. Algorithmic and computational challenges essential for the numerical stability of these long-duration simulations will be presented as well.
Keywords: PIConGPU, LPWFA, hybrid, ISAAC
  • Poster
    The fifth annual meeting of the programme "Matter and Technologies", 05.-07.03.2019, Jena, Deutschland

Publ.-Id: 29257 - Permalink


Approaching predictive capabilities for LWFA experiments with PIConGPU
Pausch, R.; Couperus Cabadağ, J.; Garten, M.; Huebl, A.; Köhler, A.; Kurz, T.; Schöbel, S.; Schramm, U.; Steiniger, K.; Widera, R.; Zarini, O.; Irman, A.; Bussmann, M.; Debus, A.;
State-of-the-art particle-in-cell simulations are becoming faster in terms of time to solution by utilizing modern hardware accelerators like GPUs and more accurate by improving the underlying algorithms. However, in order to model experiments, methods to include realistic laser pulses and gas distributions as well as efficient techniques to predict experimental observables, so-called synthetic diagnostics, need to be included in these simulations.

In this talk, we present extensions to the particle-in-cell code PIConGPU that were essential to accurately model LWFA experiments based on self-truncated ionization injection performed at HZDR. We discuss the significant impact of the implementation of higher order laser modes on the plasma dynamics and the resulting acceleration process. Furthermore, we discuss in detail the advantage of efficient in situ data analysis on the example of studying electron phase space evolution and of predicting spectrally and directionally radiation emission by all particles.

These improvements set the stage for quantitatively predicting the results of experiments in the near future.
Keywords: PIConGPU, LWFA, radiation, synthetic diagnostics
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Materie und Kosmos (SMuK), 18.-22.03.2019, München, Deutschland

Publ.-Id: 29256 - Permalink


Radiation imprint of ultra-intense laser heating of solids
Garten, M.ORC; Huebl, A.; Widera, R.; Goethel, I.; Obst-Huebl, L.; Ziegler, T.; Zeil, K.; Cowan, T.; Schramm, U.; Bussmann, M.; Kluge, T.
Laser-accelerated ions are increasingly recognized as a promising alternative to conventionally accelerated ion beams. Possible applications range from fast ignition in laser fusion to ion tumor therapy as well as studies of transient high-current and high-field phenomena in laboratory astrophysics and material science. A combination of ultra-short duration and very high charge density is the most sought-after characteristic of these beams which are produced in the violent interaction of an ultra-intense short pulse laser with a solid target. We have performed the – to our knowledge – very first full 3D particle-in-cell simulations of this interaction that includes the picosecond time span prior to the arrival of the main laser pulse. This time period is thought to be decisive for the following main pulse interaction, yet it is poorly explored – partly due to the immense computational needs to resolve the plasma kinetically with full precision. Here, we bridge scales hitherto inaccessible, from attosecond plasma oscillations over few-femtosecond laser oscillations and transient, non-equilibrium plasma dynamics on the tens of femtosecond laser duration to picosecond pre-plasma development. We study the influence of pre-pulse laser conditions and material on the ion acceleration performance. Additionally, we aim to infer radiative signatures of the plasma dynamics and link them to isochoric heating, instability development, and other complex dynamics. Beyond gaining a fundamental understanding of the governing fundamental principle plasma dynamics, the results will be used in the ongoing development of novel diagnostics analyzing the bremsstrahlung and synchrotron radiation in order to experimentally probe the sub-ps interaction. The simulations have been performed at Piz Daint at CSCS, Switzerland, using the 3D particle-in-cell code PIConGPU developed at HZDR.
Keywords: laser ion acceleration, laser-driven proton sources, particle-in-cell, PIConGPU, openPMD, HPC, throughput, PRACE, CSCS, Piz Daint
  • Invited lecture (Conferences)
    EuroHPC Summit Week 2019 / PRACEdays19, 13.-17.05.2019, Poznań, Polska

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Publ.-Id: 29255 - Permalink


Synthetic radiation simulations as a path to study the relativistic Kelvin-Helmholtz instability in interstellar jets
Pausch, R.; Bussmann, M.; Huebl, A.; Schramm, U.; Steiniger, K.; Widera, R.; Debus, A.;
The relativistic Kelvin-Helmholtz instability (KHI) is expected in shear flow regions of astrophysical plasma jets originating from AGNs and SNR. It generates magnetic fields that influence the jet dynamics significantly.

We present 3D3V particle-in-cell simulations of unprecedented resolution and extent that not only allow studying the plasma dynamics during the KHI but also making quantitative predictions on the emitted radiation. We present a diagnostic method that allows identifying the linear phase of the instability via a polarization anisotropy observable light years away on Earth and to quantify the growth rate of the instability.

A microscopic model, that describes the fundamental origin of the radiation signature, will be covered in detail during the talk. Technical aspects relevant for performing these large-scale simulations with the particle-in-cell code PIConGPU and for making quantitative predictions with synthetic radiation diagnostics, based on Liénard-Wiechert potentials, will be discussed, and observation limits both for interstellar jets and in lab astrophysics experiments will be covered.
Keywords: KHI, PIConGPU, radiation, synthetic diagnostics, polarization, AGN, SNR
  • Invited lecture (Conferences)
    DPG-Frühjahrstagung der Sektion Materie und Kosmos (SMuK), 18.-22.03.2019, München, Deutschland

Publ.-Id: 29254 - Permalink


Large-scale simulations of plasma acceleration
Pausch, R.; Huebl, A.; Bastrakov, S.; Debus, A.; Garten, M.; Matthes, A.; Steiniger, K.; Schramm, U.; Widera, R.; Zenker, E.; Bussmann, M.;
A brief presentation of the MuT/DMA activities of the Computational radiation group and solutions that might be of interest for the Matter in the Universe community.
Keywords: DMA, MUT, ARD, PIConGPU, alpaka
  • Lecture (Conference)
    "Matter and the Universe" Days 2019, 14.-15.02.2019, Hamburg, Deutschland

Publ.-Id: 29253 - Permalink


From studying the self-truncated ionization injection during LWFA to hybrid LPWFA simulations
Pausch, R.; Debus, A.; Bussmann, M.; Couperus Cabadag, J.; Garten, M.; Heinemann, T.; Huebl, A.; Martinez De La Ossa, A.; Irman, A.; Kurz, T.; Schöbel, S.; Steiniger, K.; Schramm, U.;
This talk gives a brief summary of the current status of the start-to-end simulations of the hybrid LPWFA setup using PIConGPU.
Keywords: PIConGPU, hybrid, LPWFA, LWFA, PWFA
  • Lecture (others)
    hybrid collaboration meeting, 09.-11.01.2019, Hamburg, Deutschland

Publ.-Id: 29252 - Permalink


Investigations on stationary measurements at COSMEA-I facility - CT part
Bieberle, A.ORC; Beyer, M.; Pietruske, H.; Hampel, U.ORC; Boden, S.ORC

This repository contains reconstructed and analysed CT data obtained from the COSMEA-I test facility that is operated under stationary operating conditions. Furthermore, a full CAD drawing set is provided.

Keywords: Passive Heat Transfer; Stream Condensation; Heat Flux Probe; Process Computed Tomography
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2019-05-20
    DOI: 10.14278/rodare.126

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Publ.-Id: 29250 - Permalink


Breaking the Doping Limit in Silicon by Deep Impurities
Wang, M.ORC; Debernardi, A.; Berencén, Y.; Heller, R.; Xu, C.; Yuan, Y.; Xie, Y.; Böttger, R.; Rebohle, L.; Skorupa, W.; Helm, M.; Prucnal, S.; Zhou, S.
n-type doping in Si by shallow impurities, such as P, As, and Sb, exhibits an intrinsic limit due to the Fermi-level pinning via defect complexes at high doping concentrations. Here, we demonstrate that doping Si with the deep chalcogen donor Te by nonequilibrium processing can exceed this limit and yield higher electron concentrations. In contrast to shallow impurities, the interstitial Te fraction decreases with increasing doping concentration and substitutional Te dimers become the dominant configuration as effective donors, leading to a nonsaturating carrier concentration as well as to an insulator-to-metal transition. First-principles calculations reveal that the Te dimers possess the lowest formation energy and donate two electrons per dimer to the conduction band. These results provide an alternative insight into the physics of deep impurities and lead to a possible solution for the ultrahigh electron concentration needed in today’s Si-based nanoelectronics.

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Publ.-Id: 29247 - Permalink


Nano-sandwiched metal hexacyanoferrate/graphene hybrid thin films for in-plane asymmetric micro-supercapacitors with ultrahigh energy density
He, Y.; Zhang, P.; Wang, M.ORC; Wang, F.; Tan, D.; Li, Y.; Zhuang, X.; Zhang, F.; Feng, X.
In-plane micro-supercapacitors (MSCs) with high power density, remarkable rate capability, and long cycling stability, exhibit promising application potential in modern electronic devices. To satisfy the fast-growing energy demands for the next-generation advanced micro-devices, increasing the energy density of MSCs is urgently desirable but still remains a great challenge. In this work, a series of in-plane asymmetric MSCs (AMSCs) are rationally constructed using a family of nano-sandwiched metal hexacyanoferrate/graphene hybrid thin films with interdigital patterns. The voltage output window of the resultant AMSCs is able to reach up to 1.8 V, delivering superior areal capacitances of up to 19.84 mF cm-2, and ultrahigh energy density of 44.6 mW h cm-3 which is among the best performances of the state-of-the-art MSCs. Moreover, the achieved AMSCs show outstanding mechanical flexibility and integration capability. Thus, this work will promote the development of novel high-performance AMSCs.

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Publ.-Id: 29246 - Permalink


Interface stability, mechanical and corrosion properties of AlCrMoNbZr/(AlCrMoNbZr)N high-entropy alloy multilayer coatings under helium ion irradiation
Zhang, W.; Wang, M.ORC; Wang, L.; Liu, C. H.; Chang, H.; Yang, J. J.; Liao, J. L.; Yang, Y. Y.; Liu, N.
High entropy alloy (HEA) coatings are promising for use as accident-tolerant fuel cladding due to their outstanding high-temperature corrosion resistance. In this work, we investigated the interface stability, mechanical properties and corrosion resistance of AlCrMoNbZr/(AlCrMoNbZr)N multilayer coatings with individual layer thickness of 5 nm, 10 nm and 50 nm, subjected to helium (He) ion irradiations: 400 keV He+ ions with fluences of 8×1015 ion/cm2 and 8×1016 ion/cm2. We determined that He bubbles are not observed in any of the multilayer coatings after a helium ion irradiation process with 400 keV He ions and a fluence as high as 8×1016 ion/cm2. Although intermixing and chemical reaction in the peak damage region of the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with 5 nm monolayer thickness are induced by the high fluence He ion irradiation, the FCC structure remained, and no intermetallic compounds are detected. Moreover, we found that the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with the monolayer thickness of 50 nm has better interface stability during the irradiation process. Nanoindentation tests reveal that the hardness of all multilayer coatings decreased for low and high fluences, which is mainly due to the thermal effect caused by irradiation. In addition, the electrochemical corrosion test show that AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating 50 nm coatings has better corrosion resistance than AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating 5 nm coatings under high fluence He irradiation. The corrosion resistance of the multilayer coating depends on the stability of the multilayer interface. Our results show that the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with a monolayer thickness of 50 nm had better interface stability, mechanical properties and corrosion resistance than the AlCrMoNbZr/(AlCrMoNbZr)N multilayer coating with a per layer thickness of 5 nm under high fluence He irradiation. This work reveals that high-entropy alloy multilayer coatings have potential applications as an accident-tolerant fuel cladding coating in light water reactors.
Keywords: AlCrMoNbZr/(AlCrMoNbZr)N, Multilayer coating, High-entropy alloy, Ion irradiation, Interfaces, Nanoindentation, Electrochemical corrosion, Accident-tolerant fuel (ATF)

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Publ.-Id: 29245 - Permalink


Targeting Cyclooxygenase-2 in Pheochromocytoma and Paraganglioma: Focus on Genetic Background
Ullrich, M.ORC; Richter, S.; Seifert, V.; Hauser, S.; Calsina, B.; Martínez-Montes, A. M.; Ter Laak, M.; Ziegler, C. G.; Timmers, H.; Eisenhofer, G.; Robledo, M.; Pietzsch, J.ORC
Cyclooxygenase 2 (COX-2) is a key enzyme of the tumorigenesis-inflammation interface and can be induced by hypoxia. A pseudohypoxic transcriptional signature characterizes pheochromocytomas and paragangliomas (PPGLs) of the cluster I, mainly represented by tumors with mutations in von Hippel-Lindau (VHL), endothelial PAS domain-containing protein 1 (EPAS1), or succinate dehydrogenase (SDH) subunit genes. The aim of this study was to investigate a possible association between underlying tumor driver mutations and COX-2 in PPGLs. COX-2 gene expression and immunoreactivity were examined in clinical specimens with documented mutations as well as in spheroids and allografts derived from mouse pheochromocytoma (MPC) cells. COX-2 in vivo imaging was performed in allograft mice. We observed significantly higher COX-2 expression in cluster I, especially in VHL-mutant PPGLs, however, no specific association between COX-2 mRNA levels and a hypoxia-related transcriptional signature was found. COX-2 immunoreactivity was present in about 60 % of clinical specimens as well as in MPC spheroids and allografts. A selective COX-2 tracer specifically accumulated in MPC allografts. This study demonstrates that, although, pseudohypoxia is not the major determinant for high COX-2 levels in PPGLs, COX-2 is a relevant molecular target. This potentially allows for employing selective COX-2 inhibitors as targeted chemotherapeutic agents and radiosensitizers. Moreover, available models are suitable for preclinical testing of these treatments.
Keywords: VHL; NF1; EPAS1; hypoxia-inducible factor; inflammation; radiosensitization; succinate dehydrogenase; mouse pheochromocytoma cells; immunohistochemistry; fluorescence imaging

Publ.-Id: 29242 - Permalink


Damage accumulation and implanted Gd and Au position in a- and c-plane GaN
Macková, A.; Malinský, P.; Jagerová, A.; Mikšová, R.; Sofer, Z.; Klímová, K.; Mikulics, M.; Böttger, R.; Akhmadaliev, S.; Oswald, J.;
(0001) c-plane and (11−20) a-plane GaN epitaxial layers were implanted with 400 keV Au+ and Gd+ ions using ion implantation fluences of 5×1014, 1×1015 and 5×1015 cm-2. Rutherford Back-Scattering spectrometry in channelling mode (RBS/C) was used to follow the dopant depth profiles and the introduced disorder; the angular dependence of the backscattered ions (angular scans) in c- and a-plane GaN was measured to get insight into structural modification and dopant position in various crystallographic orientations. Defect-accumulation depth profiles exhibited differences for a- and c-plane GaN, with a-plane showing significantly lower accumulated disorder in the buried layer, accompanied by the shift of the maximum damage accumulation into the deeper layer with respect to the theoretical prediction, than c-plane GaN. Angular scans showed channelling preservation in as-implanted samples and better channelling recovery in the annealed a-plane GaN compared to cplane GaN. The angular scan widths were simulated by FLUX code as well as the half-width modifications of angular scans were discussed in connection to the damage accumulation. Photoluminescence measurement followed in detail yellow band and band edge luminescence decline after the implantation and the recovery of luminescence spectra features after annealing.
Keywords: Implanted (0001) and (11–20) GaN, Damage accumulation asymmetry in GaN, Ion implantation in semiconductors, RBS channelling, Damage-depth profiling

Publ.-Id: 29240 - Permalink


Surface nanobubbles on the rare earth fluorcarbonate mineral synchysite
Owens, C. L.ORC; Schach, E.; Heinig, T.; Rudolph, M.ORC; Nash, G. R.
Surface nanobubbles have been identified to play an important role in a range of industries from mineral processing to food science. The formation of surface nanobubbles is of importance for mineral processing in the extraction of complex ores, such as those containing rare earth elements. This is due to the way minerals are extracted utilising froth flotation. In this study, surface nanobubbles were imaged using non-contact atomic force microscopy on a polished cross section containing rare earth minerals. Nanobubbles were found on synchysite under reagent conditions expected to induce hydrophobicity in rare earth minerals, which is required for efficient processing.

Synchysite –(Ce) is a rare earth fluorcarbonate mineral containing over 30% rare earth elements. Relatively little research has been conducted on synchysite, with only a few papers on its surface behaviour and flotation. The resulting nanobubbles were analysed and showed an average contact angle of 24 degrees± 8. These are in line with contact angles found on dolomite and galena by previous studies.
Keywords: non-contact atomic force microscopy; synchysite; bastnäsite; rare earth elements; fluorcarbonate; surface nanobubbles; carbonatite

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Publ.-Id: 29231 - Permalink


Synthesis of Mg and Zn diolates and their use in metal oxide deposition
Frenzel, P.; Preuß, A.; Bankwitz, J.; Georgi, C.; Ganss, F.; Mertens, L.; Schulz, S.; Hellwig, O.; Mehring, M.; Lang, H.;
The synthesis of complexes [M(OCHMeCH₂NMeCH₂)₂] (5, M = Mg; 7, M = Zn) is described. Treatment of MeHNCH2CH2NMeH (1) with 2-methyloxirane (2) gave diol (HOCHMeCH₂NMeCH₂)₂ (3), which upon reaction with equimolar amounts of MR₂ (4, M = Mg, R = Bu; 6, M = Zn, R = Et) gave 5 and 7. The thermal behavior and vapor pressure of 5 and 7 were investigated to show whether they are suited as CVD (= chemical vapor deposition) and/or spin-coating precursors for MgO or ZnO layer formation. Thermogravimetric (TG) studies revealed that 5 and 7 decompose between 80–530 °C forming MgO and ZnO as evidenced by PXRD studies. In addition, TG-MS-coupled experiments were carried out with 7 proving that decomposition occurs by M–O, C–O, C–N and C–C bond cleavages, as evidenced from the detection of fragments such as CH𔔢N+, C₂H𔔢N+, C₂H₅N+, CH₂O+, C₂H₂O+ and C₂H₃O+. The vapor pressure of 7 was measured at 10.4 mbar at 160 °C, while 5 is non-volatile. The layers obtained by CVD are dense and conformal with a somewhat granulated surface morphology as evidenced by SEM studies. In addition, spin–coating experiments using 5 and 7 as precursors were applied. The corresponding MO layer thicknesses are between 7–140 nm (CVD) or 80 nm and 65 nm (5, 7; spin-coating). EDX and XPS measurements confirm the formation of MgO and ZnO films, however, containing 12–24 mol% (CVD) or 5–9 mol% (spin-coating) carbon. GIXRD studies verify the crystalline character of the deposited layers obtained by CVD and the spin-coating processes.

Publ.-Id: 29229 - Permalink


Residual gammaH2AX foci in head and neck squamous cell carcinomas as predictors for tumour radiosensitivity: Evaluation in pre-clinical xenograft models and clinical specimens
Meneceur, S.; Löck, S.; Gudziol, V.; Hering, S.; Bütof, R.; Rehm, M.; Baumann, M.; Krause, M.; von Neubeck, C.;
Background and purpose: Predictive biomarkers can be instrumental to treatment individualisation of cancer patients and improve therapy outcome. Residual γH2AX foci represent a promising biomarker to predict tumour radiosensitivity. In this pre-clinical study, the slope of the dose–response curve was evaluated for its predictive relevance in head and neck squamous cell carcinoma xenografts (HNSCC). Additionally, the feasibility of the translated assay was tested in a clinical setting in patient derived HNSCC samples, and associations between residual γH2AX foci and clinical parameters were analysed. Materials and methods: Seven HNSCC xenografts models (FaDu, SAS, SKX, UT-SCC-5, UT-SCC-14, UT-SCC-45, XF354)were used. Tumour bearing NMRI nude mice were randomly distributed to five treatment arms (0–8 Gy). Residual γH2AX foci (24 h post irradiation)were counted by visual scoring in a micromilieu dependent manner (assessed with BrdU and pimonidazole). The local tumour control values measured as TCD 50 (tumour control dose 50%)have previously been published. Patient derived HNSCC biopsies were cultivated ex vivo for 24 h including 4 h of pimonidazole and BrdU treatment, subsequently irradiated with 0–8 Gy and fixed after 24 h. Results: In the pre-clinical study, the dose–response curve slopes negatively correlated with the tumour control dose after fractionated irradiation (TCD 50,fx , R 2 = 0.63, p = 0.032)and after single dose irradiation under homogeneous hypoxia (TCD 50,SD,clamp , R 2 = 0.66, p = 0.027). The γH2AX assay in clinical HNSCC samples showed a dose–response relationship, with the values of the slopes ranging from 0.099 Gy −1 to 0.920 Gy −1 (coefficient of variation = 52.8%). Slopes derived from patients were in the same ranges as the sensitive, moderate and resistant models of the pre-clinical study. Statistical analysis revealed a significant negative correlation between the slope and the patients’ age (R 2 = 0.65, p = 0.001). Conclusion: These results further support the promise of the slope of the residual γH2AX foci dose–response as a biomarker for radiosensitivity. In the clinical samples, the variation in the slopes reveals patients’ specific repair capacities, which could hold potential value for treatment individualisation. © 2019 Elsevier B.V.
Keywords: Clinical specimens, HNSCC, Predictive biomarker, Radiosensitivity, Xenograft modelsγH2AX

Publ.-Id: 29228 - Permalink


Advanced Methods for Temporal Reconstruction of Modulated Electron Bunches
Zarini, O.; Köhler, A.; Couperus, J.; Pausch, R.; Kurz, T.; Schöbel, S.; Meißner, H.; Bussmann, M.; Schramm, U.; Irman, A.; Debus, A.;
We describe optimizations of phase-retrieval algorithms for the reconstruction of the temporal structure of highly modulated electron bunches from coherent transition radiation (CTR) spectra. Synthetic data is used to quantitatively analyze capabilities and limitations of the approach taking into account realistic bandwidth constraints of ultra-broadband spectrometers. Established algorithms are combined with information from independent channels as charge calibrated electron spectra and absolute intensity calibration of the spectrometer. With this set of data, in principle available in experiments, we demonstrate a promising fidelity for the detailed analysis of substructured laser wakefield accelerated electron bunches.
Keywords: Electron bunch duration, reconstruction algorithm, transition radiation
  • Contribution to proceedings
    Advanced Accelerator Concepts Workshop (AAC2018), 12.-17.08.2018, Breckenridge, Colorado, USA: IEEE, 978-1-5386-7721-6
    DOI: 10.1109/AAC.2018.8659388

Publ.-Id: 29225 - Permalink


Measuring sub-femtosecond temporal structures in multi-ten kiloampere electron beams
Zarini, O.ORC
In laser wakefield acceleration, an ultra-short high-intensity laser pulse excites a plasma wave, which can sustain accelerating electric fields of several hundred GV/m.
This scheme advances a novel concept for compact and less expensive electron accelerators, which can be hosted in a typical university size laboratory. Furthermore, laser wakefield accelerators (LWFA) feature unique electron bunch characteristics, namely micrometer size with duration ranging from several fs to tens of fs. Precise knowledge of the longitudinal profile of such ultra-short electron bunches is essential for the design of future table-top X-ray light-sources and remains a big challenge due to the resolution limit of existing diagnostic techniques.

Spectral measurement of broadband coherent and incoherent transition radiation (TR) produced when electron bunches passing through a metal foil is a promising way to analyze longitudinal characteristics of these bunches. Due to the limited reproducibility of the electron source this measurement highly requires single-shot capability.
An ultra-broadband spectrometer combines the TR spectrum in UV/NIR (200-1000 nm), NIR (0.9-1.7 µm) and mid-IR (1.6-12 µm). A high spectral sensitivity, dynamic bandwidth and spectral resolution are realized by three optimized dispersion and detection systems integrated into a single-shot spectrometer.
A complete characterization and calibration of the spectrometer have been done concerning wavelengths, relative spectral sensitivities, and absolute photometric sensitivities, also taking into account for the light polarization.
The TR spectrometer is able to characterize electron bunches with charges as low as 1pC and can resolve time-scales of 0.4 fs. Electron bunches up to 16 fs (rms width) can be reconstructed from their TR spectrum.

In the presented work, the self-truncated ionization induced injection (STII) scheme has been explored to study the relevant beam parameters especially its longitudinal bunch profile and the resulting peak current.
Proper focusing of a high power laser pulse into a supersonic gas-jet target and tailoring the conditional laser and plasma density and taking advantage of the relativistic self-focusing effects are investigated in this PhD thesis in order to study the final beam parameters as well as the consequent beam loading effects by producing nC-class mono-energetic electron beams.

In the experiment at HZDR, the DRACO 100TW Ti:Sa based laser system is used in conjunction with a He-N₂ mixed, supersonic gas-jet target. Under optimized conditions, mono-energetic electron bunches are accelerated, which are massively loaded up to several 100 pC at 300 MeV peak energy with a narrow energy spread of a few 10 MeV. Reconstruction results of TR spectra, measured by TR spectrometer, show that the shortest electron bunch duration is at about 13 fs FWHM corresponding to a peak current as high as 20 kA.
Such peak current is about one order of magnitude higher than those generated by conventional RF linear accelerator. This landmarks a significant finding of this thesis.
Keywords: Laser wakefield acceleration, laser plasma accelerator, self-truncated ionization injection, high peak current, high bunch charge, beam loading, bunch duration measurement, coherent transition radiation, broadband spectrometer, infrared spectrometer, prism spectrometer, echelle spectrometer, phase reconstruction algorithm, Foldwrap reconstruction algorithm, PIConGPU
  • Open Access LogoWissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-100 2019

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Publ.-Id: 29222 - Permalink


Recent application of the solid targetry system
Alexander, M.; Karsten, F.;
The solid targetry system was used both, at port 4 directly mounted at the yoke and at the beamline at port 3. We will give an overview about the purification or separation of n.c.a. radionuclides like Sr-85, V-48, Cu-64, Cr-51, Co-56, Y-88, La-135, Zr-89, Ce-139 and Pb-203.
  • Lecture (Conference)
    14th CYCLEUR workshop 2019, 08.-10.05.2019, Dresden, Germany

Publ.-Id: 29221 - Permalink


Competence Center for Ion Beams in Materials Research and Medicine
Fassbender, J.;
Competence Center for Ion Beams in Materials Research and Medicine
Keywords: ion beams, high-energy, materials research, user facility
  • Invited lecture (Conferences)
    Competence Center for Ion Beams in Materials Research and Medicine, 02.05.2019, München, Deutschland

Publ.-Id: 29220 - Permalink


Improvement of UniCAR T cell effectiveness against EGFR+ tumor cells by using different αEGFR targeting module formats
Jureczek, J.; Feldmann, A.; Albert, S.; Bergmann, R.; Berndt, N.; Arndt, C.; Koristka, S.; Bachmann, M.;
Since epithelial growth factor receptor (EGFR) mutations or overexpression is linked with variety of malignancies, including lung, breast, stomach, colorectal, head and neck, and pancreatic carcinomas as well as glioblastomas it is an attractive target for tailored treatment of solid cancer. Thus over the last twenty years many strategies targeting EGFR were developed and even clinically approved, including disrupting intracellular signalling involving tyrosine kinase inhibitors (TKIs) or the inhibition of ligand binding using therapeutic monoclonal antibodies like e.g. Cetuximab, Panitumumab or Necitumumab. Unfortunately, cancers treated with these targeted drugs commonly become resistant to them. These limitations justify the need of more efficient therapy options. As chimeric antigen receptor (CAR) engineered T cells highly effectively eliminate hematological malignancies already in the clinics, one idea is to redirect CAR T cells also against EGFR expressing solid cancers. However, CAR T cell therapy can lead to severe even life-threatening side effects and its effectiveness against solid tumors is still limited. Particular worrying is that EGFR is a widespread antigen commonly expressed also on healthy tissues bearing a high risk of severe on-target/off-tumor side effects due to EGFR-targeted therapies, which cannot be controlled in patients. In order to overcome these challenges our UniCAR technology might be an appropriate answer combining high anti-tumor effectiveness, tumor specificity, flexibility, and safety control mechanisms. In contrast to conventional CARs, UniCAR T cells are per se inert because UniCARs are directed against a small peptide epitope, which is not present on living cells. The redirection of UniCAR T cells to tumor cells occurs only in the presence of a tumor specific targeting module (TM). TMs, on one hand carry the specificity for a certain tumor antigen and on the other hand contain the UniCAR peptide epitope recognized by UniCARs mediating the cross-linkage of UniCAR T cells and antigen presenting tumor cells. As TMs have a very short half-life in vivo they can be used as a switch to control UniCAR T cell activity on demand in patients. In detail, UniCAR T cells are only switched on in the presence of antigen specific TMs realized by permanent TM infusion, but could be rapidly switched off when the application of the TM is stopped and the TM is eliminated. Meanwhile we successfully generated a series of different TMs against different tumor antigens and entities. Interestingly, TMs can be made of different molecules showing various structures and can flexible be exchanged in order to target any tumor antigen and overcome tumor escape variants. Commonly our TMs consist of a humanized single-chain variable fragment (scFv) derived from the variable heavy and light chain domains of a murine monoclonal antibody. In addition, we successfully generated TMs based on different monovalent and bivalent antibody derivatives, nanobodies derived from one variable camelid antibody domain, affibodies and even small peptide molecules.
Recently we demonstrated proof-of-concept for the redirection of UniCAR T cells to EGFR expressing tumor cells by a nanobody based αEGFR TM derived from the camelid αEGFR antibody 7C12. Considering that the affinity and anti-tumor efficiency of the eucaryotically expressed αEGFR nanobody based TM was limited, we therefore asked the question, whether we could further improve the therapeutic effect against EGFR positive tumor cells using the UniCAR technology. In order to answer this question, we generated a novel TM based on a scFv derived from the clinically used chimeric monoclonal antibody Cetuximab (IMC C-225). In detail, we designed a murine and humanized αEGFR scFv TM, successfully expressed them in mammalian cell lines and compared their functionality with the eucaryotic αEGFR nanobody-based TM in vitro and in vivo. In principle, we observed that both TM formats, the αEGFR nanobody as well as the scFv-based TM, are able to redirect UniCAR T cells eliminate EGFR-expressing tumor cells in an antigen-specific and TM-dependent manner. As both the murine and humanized scFv TM variants worked equally well, obviously humanization of the αEGFR scFv does not affect its functionality. However most interestingly, the tumor killing efficiency of the αEGFR scFv TM was significantly superior in comparison to the αEGFR nanobody based TM. Here, the half maximal effective TM concentration (EC50) value of scFv based TM was improved 1000-fold, from nM to pM range. Consequently, UniCAR T cells in combination with the scFv based TM efficiently eliminate also target cells expressing a low EGFR density level, while UniCAR T cells redirected by the nb based TM clearly attack only highly EGFR expressing tumor cells. Furthermore, the high anti-tumor efficacy of the αEGFR scFv TM over nb TM was manifested in experimental mice.
In summary, we successfully established different αEGFR TM formats that are able to redirect UniCAR T cells to eliminate EGFR-positive tumor cells. However, the analysed αEGFR TM formats differ with respect to their anti-tumor efficiency, which might decide whether UniCAR T cells attack target cells showing different EGFR density levels.
  • Poster
    Tumor immunology meets oncology (TIMO XV), 25.-27.04.2019, Halle, Deutschland

Publ.-Id: 29214 - Permalink


Engineering human T cells with a novel switchable CAR technology for tumor immunotherapy
Hoffmann, A.; Feldmann, A.; Kittel-Boselli, E.; Bergmann, R.; Koristka, S.; Berndt, N.; Arndt, C.; Bachmann, M.;
With the first approvals of chimeric antigen receptor (CAR) T cell therapies by the FDA the use of genetically modified T cells in the immunotherapy of tumors has recently become a very promising approach. CAR T cells are able to recognize tumor-associated antigens (TAAs) via specific single-chain variable fragments (scFvs) in a major histocompatibility-complex (MHC)-independent manner. Although highly efficient, the inability to regulate the activity of CAR T cells can cause severe even
life-threatening side effects such as cytokine-release syndrome (CRS) and on-target, off-tumor toxicities. Modular CAR systems may overcome these limitations allowing to switch the activity of CAR T cells repeatedly “ON” and “OFF”. Alternatively or in addition, the safety of CAR T cells could also be improved by “gated” targeting strategies e.g. by splitting the signaling and costimulatory motifs to independent CARs of different specificities. Theoretically, the idea of gated targeting could be extended to include further e.g. inhibitory signals. However, the size of current CARs limit the number of specificities that can be simultaneously transduced into a T cell. We therefore developed a novel switchable modular universal artificial receptor having a minimal size. The platform was termed RevCAR system.
In order to reduce the size of the artificial receptor the original idea was to replace the extracellular scFv domain of a conventional CAR with a small peptide epitope and to engage the resulting RevCAR T cell via a bispecific target module which we termed RevTM. For proof of concept two small peptide epitopes were selected and the respective RevCARs constructed. In addition, a series of different RevTMs were constructed. On the one hand the RevTM recognized one of the two peptide epitopes on the other hand the RevTM was directed to a potential tumor associated antigen (TAA). Until now a series of such pairs of RevTMs were constructed and functionally analyzed. RevCAR T cells armed via the respective RevTM were able to specifically lyse their respective target cell in a peptide epitope specific and target specific as well as target dependent manner. These data are supported by analysis of cytokine secretion. We only observed a specific cytokine release from RevCAR T cells in the presence of both target cells and the respective RevTM. Released cytokines detected were IFN-gamma, GM-CSF, TNF, and IL-2.
Taken together these results demonstrate the high anti-tumor efficiency of the novel RevCAR platform which is characterized by a small size, an improved safety, easy controllability as well as high flexibility.
  • Poster
    Tumor immunology meets oncology (TIMO XV), 25.-27.04.2019, Halle, Deutschland

Publ.-Id: 29213 - Permalink


Thermal expansion of magnetron sputtered TiCxN1-x coatings studied by high-temperature X-ray diffraction
Saringer, C.; Kickinger, C.; Munnik, F.; Mitterer, C.; Schalk, N.; Tkadletz, M.;
The coefficient of thermal expansion (CTE) of TiCxN1-x can be adjusted by changing the value x between 0 (i.e. pure TiN) and 1 (pure TiC), which makes this material exceptionally useful as base layer to adapt the mismatch between the CTEs of substrate and coating. However, no comprehensive data on the CTE of sputtered TiCxN1-x has been reported up to now. Thus, in this work eleven coatings with compositions ranging from pure TiN to pure TiC were deposited using non-reactive magnetron sputtering. The elemental and phase composition were obtained by elastic recoil detection analysis and Raman spectroscopy, respectively. Powders of the coating material were analyzed using high-temperature X-ray diffraction between room temperature and up to 1000 °C to determine the temperature dependent lattice parameters. Subsequently, these lattice parameters were fitted using second order polynomials with coefficients linearly depending on the carbon content. Thus, a formula for the CTE of TiCxN1-x valid between 25 and 1000 °C was deduced which showed that at room temperature TiN has the highest CTE of 8.12 × 10-6 K-1. The CTE gradually decreases with increasing carbon content to 7.55 × 10-6 K-1 for pure TiC. While the value for TiC only shows a small increase with temperature, the CTE of TiN increases strongly up to 11.1 × 10-6 K-1 at 1000 °C. The presented formula for the temperature dependent CTE of sputtered TiCxN1-x coatings allows to calculate the required composition for TiCxN1-x base layers, in order to tune their thermal expansion for the use in complex multilayered coatings.
Keywords: Thermal expansion; Titanium carbonitride; High-temperature X-ray diffraction; Physical vapor deposition; Hard coatings

Publ.-Id: 29211 - Permalink


The UniCAR system: A modular CAR T cell approach to improve the safety of CAR T cells
Bachmann, M.;
The idea to eliminate tumor cells via our own immune system is more than a hundred years old. However, a real break through came first with the development of check point inhibitors, bispecific antibodies (bsAbs) and T cells genetically modified to express Chimeric Antigen Receptors (CARs). Eventhough the clinical application of T cells equipped with CARs can lead to a complete remission, unfortunately, their application can also cause severe or even life threatening side effects as their activity can no more be adjusted once given to the patient. For targeting of tumor cells expressing tumor associated antigens (TAAs) which are not limited to tumor cells but also accessible on healthy tissues CAR T cells should not be permanently in a killing mode but be equipped with some kind of a switch whereby the activity of CAR T cells can reversely be turned “on and off “. Moreover, in case of cytokine release syndrome (CRS), tumor lysis syndrome (TLS), or other deadly side effects the possibility of an emergency shut down of the CAR T cell activity should exist. Modular CAR variants such as the UniCAR system may fulfill these requirements.
Keywords: Immunotherapy, Chimeric antigen receptor, T cells, UniCAR, BiTE, Bispecific antibody

Publ.-Id: 29209 - Permalink


Bulk analysis of meteorites using INAA at FRM II
Li, X.; Merchel, S.ORC; Lierse Von Gostomski, C.
In March 2017, the 49th German meteorite was found lying on top of a rock pile on the side of a potato field, near the city of Cloppenburg, Lower Saxony, Germany [1,2]. With two other meteorites (Oldenburg (fall in 1930), Benthullen (find in 1948 or 1951)) from the same region and meteorites from other countries, we started a program to analyze extraterrestrial samples in 2017. We have analyzed in total three chondrites, three achondrites of the HED
group (Howardite-Eucrite-Diogenite) (Dhofar 1675, NWA 2690, NWA 2698), a lunar and a Martian meteorite (NWA 7986, NWA 4925), two iron meteorites (Gibeon, yet unnamed new find from Libya/Chad in 2019) and six potential micrometeorites. The bigger samples (10-20 mg) were normally irradiated twice: for 3-5 min and for a long time up to 1 h in the rabbit position. The much smaller micrometeorites (9-38 μg) were irradiated for 24 h in the high-flux capsule irradiation position (Φth>1E14 cm-2s-1). We used the k0-method for the analysis [3].
With the high and pure thermal neutron flux at the FRM II, up to 45 elements could be determined in most samples [3]. According to the element compositions, the meteorites could be classified or earlier classifications could be confirmed. Although, the sample weights of the micrometeorites are very small and manipulating them was challenging, we could determine up to 16 elements. All of them show a rather high Fe concentration, i.e. 55-70 weight-%. However, for Ni and Ir, we can only give a detection limit of about 0.4% and 2 ng/g, respectively. Their potential origin are under discussion.
Acknowledgments
We thank A. Muszynski and M. Szyszko (Poznan, PL), A. Bischoff (Uni. Münster), D. Heinlein, J. Feige (TU Berlin) and A. Gärtner (Senckenberg Dresden) for providing and preparation of samples and the TUM-Kolleg program for financial supports.
References
1. J. Gattacceca et al., Meteorit. Planet. Sci., 2019, 54, 469-471.
2. J. Storz et al., www.paneth.eu/PanethKolloquium/2017/0075.pdf (Jan. 2019)
3. X. Li et al., J. Radioanal. Nucl. Chem. 2014, 300, 457-463.
Keywords: INAA, k0-method, meteorite, micrometeorite
  • Lecture (Conference)
    2nd International Conference on Radioanalytical and Nuclear Chemistry (RANC 2019), 05.-10.05.2019, Budapest, Hungary

Publ.-Id: 29206 - Permalink


Preliminary Report on the Study of Beam-induced Background Effects at a Muon Collider
Bartosik, N.; Bertolin, A.; Casarsa, M.; Collamati, F.; Ferrari, A.; Ferrari, A.ORC; Gianelle, A.; Lucchesi, D.; Mokhov, N.; Mueller, S.ORC; Pastrone, N.; Sala, P.; Sestini, L.; Striganov, S.
Physics at a multi-TeV muon collider needs a change of perspective for the detector design due to the large amount of background induced by muon beam decays. Preliminary studies, based on simulated data, on the composition and the characteristics of the particles originated from the muon decays and reaching the detectors are presented here. The reconstruction performance of the physics processes H→bb¯ and Z→bb¯ has been investigated for the time being without the effect of the machine induced background. A preliminary study of the environment hazard due to the radiation induced by neutrino interactions with the matter is presented using the FLUKA simulation program.
Keywords: Detectors in high-intensity environments, future accelerators, muon beams, neutrino-induced radiation
  • Open Access LogoarXiv:1905.03725 (2019)

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Publ.-Id: 29205 - Permalink


Vertical Organic Thin-Film Transistors with an Anodized Permeable Base for Very Low Leakage Current
Dollinger, F.; Lim, K.-G.; Li, Y.; Guo, E.; Formánek, P.; Hübner, R.; Fischer, A.; Kleemann, H.; Leo, K.;
The organic permeable base transistor (OPBT) is currently the fastest organic transistor with a transition frequency of 40 MHz. It relies on a thin aluminum base electrode to control the transistor current. This electrode is surrounded by a native oxide layer for passivation, currently created by oxidation in air. However, this process is not reliable and leads to large performance variations between samples, slow production, and relatively high leakage currents. Here, for the first time it is demonstrated that electrochemical anodization can be conveniently employed for the fabrication of high-performance OPBTs with vastly reduced leakage currents and more controlled process parameters. Very large transmission factors of 99.9996 % are achieved, while excellent on/off ratios of 5 × 105 and high on-currents greater than 300 mA cm−2 show that the C60 semiconductor layer can withstand the electrochemical anodization. These results make anodization an intriguing option for innovative organic transistor design.
Keywords: aluminum oxide, anodization, organic permeable base transistors (OPBTs), organic transistors, organic thin-film transistors (OTFTs), vertical transistors

Publ.-Id: 29204 - Permalink


Wave-shaped polycyclic hydrocarbons with controlled aromaticity
Ma, J.ORC; Zhang, K.; Schellhammer, K. S.; Fu, Y.ORC; Komber, H.ORC; Xu, C.ORC; Popov, A. A.ORC; Hennersdorf, F.ORC; Weigand, J. J.ORC; Zhou, S.ORC; Pisula, W.ORC; Ortmann, F.; Berger, R.ORC; Liu, J.ORC; Feng, X.ORC
Controlling the aromaticity and electronic properties of curved π-conjugated systems has been increasingly attractive for the development of novel functional materials for organic electronics. Herein, we demonstrate an efficient synthesis of two novel wave-shaped polycyclic hydrocarbons (PHs) 1 and 2 with 64 π-electrons. Among them, the wave-shaped π-conjugated carbon skeleton of 2 is unambiguously revealed by single-crystal X-ray crystallography analysis. The wave-shaped geometry is induced by steric congestion in the cove and fjord regions. Remarkably, the aromaticity of these two structural isomers can be tailored by the annulated direction of cyclopenta[b]fluorene units. Isomer 1 (Eoptg = 1.13 eV) behaves as a closed-shell compound with weakly antiaromatic feature, whereas its structural isomer 2 displays a highly stable tetraradical character (y0 = 0.23; y1 = 0.22; t1/2 = 91 days) with a narrow optical energy gap of 0.96 eV. Moreover, the curved PH 2 exhibits remarkable ambipolar charge transport in solution-processed organic thin-film transistors. Our research provides a new insight into the design and synthesis of stable functional curved aromatics with multiradical characters.

Publ.-Id: 29201 - Permalink


Measurement-Protocol Dependence of the Magnetocaloric Effect in Ni-Co-Mn-Sb Heusler Alloys
Salazar-Mejia, C.; Kumar, V.; Felser, C.; Skourski, Y.; Wosnitza, J.; Nayak, A. K.;
Ni-Co-Mn-Sb-based Heusler shape-memory alloys that undergo a martensitic-structural transition around room temperature are well known for exhibiting large magnetic entropy change and elastocaloric effect. Here, we report the observation of a large adiabatic temperature change of −11 K in a Ni-Co-Mn-Sb system by using direct adiabatic temperature-change measurements in pulsed magnetic fields. We show that a large magnetic cooling can be achieved in a wide temperature range spanning from 120 to 270 K by purposefully varying the chemical composition. The temperature- and field-dependent irreversibility of the effect is analyzed through a detailed experimental study of the protocol-dependent magnetocaloric effect. The present study is an important contribution towards the understanding of irreversible magnetocaloric effects in materials with magnetostructural transition.

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Publ.-Id: 29199 - Permalink


Magnetocaloric effect of gadolinium in high magnetic fields
Gottschall, T.; Kuz'Min, M. D.; Skokov, K. P.; Skourski, Y.; Fries, M.; Gutfleisch, O.; Ghorbani Zavareh, M.; Schlagel, D. L.; Mudryk, Y.; Pecharsky, V.; Wosnitza, J.;
The magnetocaloric effect of gadolinium has been measured directly in pulsed magnetic fields up to 62 T. The maximum observed adiabatic temperature change is ΔTad = 60.5 K, the initial temperature T0 being just above 300 K. The field dependence of ΔTad is found to follow the usual H2/3 law, with a small correction in H4/3. However, as H is increased, a radical change is observed in the dependence of ΔTad on T0, at H = const. The familiar caret-shaped peak situated at T0 = TC becomes distinctly asymmetric, its high-temperature slope becoming more gentle and evolving into a broad plateau. For yet higher magnetic fields, μ0H ≥ 140 T, calculations predict a complete disappearance of the maximum near TC and an emergence of a new very broad maximum far above TC.

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Publ.-Id: 29198 - Permalink


Field-induced instability of the quantum spin liquid ground state in the Jeff = 1/2 triangular-lattice compound NaYbO2
Ranjith, K. M.; Dmytriieva, D.; Khim, S.; Sichelschmidt, J.; Luther, S.; Ehlers, D.; Yasuoka, H.; Wosnitza, J.; Tsirlin, A. A.; Kühne, H.; Baenitz, M.;
Polycrystalline samples of NaYbO2 are investigated by bulk agnetization and specific-heat measurements, as well as by nuclear magnetic resonance (NMR) and electron spin resonance (ESR) as local probes. No signatures of long-range magnetic order are found down to 0.3 K, evidencing a highly frustrated spin-liquid-like ground state in zero field. Above 2 T, signatures of magnetic order are observed in thermodynamic measurements, suggesting the possibility of a field-induced quantum phase transition. The 23Na NMR relaxation rates reveal the absence of magnetic order and persistent fluctuations down to 0.3 K at very low fields and confirm the bulk magnetic order above 2 T. The H-T phase diagram is obtained and discussed along with the existing theoretical concepts for layered spin- 1/2 triangular-lattice antiferromagnets.

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Publ.-Id: 29197 - Permalink


Geometry description in the FLUKA MC transport code
Mueller, S. E.ORC
Geometry description in the FLUKA MC transport code
Keywords: FLUKA, MU2E, CLFV
  • Lecture (others)
    MU2E SimWG meeting, 11.04.2019, Fermilab, Batavia, USA

Publ.-Id: 29187 - Permalink


Tunable disorder and localization in the rare-earth nickelates
Wang, C.; Chang, C.-H.; Huang, A.; Wang, P.-C.; Wu, P.-C.; Yang, L.; Xu, C.; Pandey, P.; Zeng, M.; Böttger, R.; Jeng, H.-T.; Zeng, Y.-J.; Helm, M.; Chu, Y.-H.; Ganesh, R.; Zhou, S.;
We demonstrate that transport in metallic rare-earth nickelates can be engineered by directly tuning the electronic mean free path. Using irradiation as a tool to induce disorder, we drive this system from a metallic phase into an Anderson insulator. This proceeds via an intermediate regime which shows a thermal crossover from insulating to metallic behavior. We argue that this phase falls within the paradigm of weak localization in three dimensions. We develop a theoretical model for the temperature dependence of resistivity which shows good agreement with our data. The three-dimensional weak localization picture is supported by magnetoconductivity, which scales as ∼B2 up to several tesla. Interestingly, our data indicate that this phase lies in the Mott-Ioffe-Regel regime with the mean free path approaching the lattice constant. Upon further increasing disorder, the charge carriers are localized, leading to insulating behavior at all temperatures. Our results show that irradiation provides a “clean” tuning knob for the mean free path, without altering other system parameters. This suggests promising directions for studies of Anderson localization.
Keywords: Anderson localization; Metal-insulator transition; Weak localization; Magnetoresistance

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Publ.-Id: 29185 - Permalink


AMS at Big Accelerators: 53Mn and 60Fe in Meteorites
Rugel, G.; Faestermann, T.; Fimiani, L.; Korschinek, G.; Leya, I.; Ludwig, P.; Pavetich, S.; Smith, T.; Wallner, A.;
The poster describes that big tandem accelerators are essential to measure 53Mn and 60Fe in meteorites.
Keywords: AMS Accelerator Fe-60 Mn-53 Meteorites
  • Poster
    KIMM Workshop 2019, 02.05.2019, München, Deutschland

Publ.-Id: 29179 - 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, AvORC; 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


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


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


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


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


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


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