Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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33661 Publications

Element- and orbital-selective magnetic coherent rotation at the first-order phase transition of a hard uniaxial ferrimagnet

Yamamoto, S.; Gorbunov, D.; Akai, H.; Yasumura, H.; Kotani, Y.; Nakamura, T.; Kato, T.; Mushnikov, N. V.; Andreev, A. V.; Nojiri, H.; Wosnitza, J.
3d-4 f intermetalic compounds with heavy rare-earth elements show first-order phase transitions in high magnetic fields due to the competition between the exchange interaction and the magnetocrystalline anisotropy. However, the microscopic picture of the field-induced noncollinear magnetic structures remains elusive. Here we report the direct experimental observation of the coherent stepwise rotation of the 3d and 4 f magnetic moments of the uniaxial hard ferrimagnet TmFe5Al7 by using soft x-ray magnetic circular dichroism in pulsed magnetic fields up to 25 T. The element- and shell-selective moments show a transition from the collinear ferrimagnet toward the forced ferromagnetic state via a canted phase, which is explained by a two-sublattice model.

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Permalink: https://www.hzdr.de/publications/Publ-31083
Publ.-Id: 31083


Advanced characterization of multicaloric materials in pulsed magnetic fields

Gottschall, T.; Bykov, E.; Gràcia-Condal, A.; Beckmann, B.; Taubel, A.; Pfeuffer, L.; Gutfleisch, O.; Manosa, L.; Planes, A.; Scurschii, I.; Wosnitza, J.
The multicaloric effect is described by a temperature or entropy change of a material triggered by external stimuli applied or removed simultaneously or sequentially. The prerequisite for this is a material exhibiting multiple ferroic states. However, direct measurements of the effect are rarely reported. Now, for this reason, we built a measurement device allowing to determine the adiabatic temperature change in pulsed magnetic fields and, simultaneously, under the influence of a uniaxial load. We selected the all-d-metal Heusler alloy Ni–Mn–Ti–Co for our first test because of its enhanced mechanical properties and enormous magneto- and elastocaloric effects. Ni–Mn–Ti–Co was exposed to pulsed magnetic fields up to 10 T and uniaxial stresses up to 80 MPa, and the corresponding adiabatic temperature changes were measured. With our new experimental tool, we are able to better understand multicaloric materials and determine their cross-coupling responses to different stimuli.

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  • Secondary publication expected from 11.05.2021

Permalink: https://www.hzdr.de/publications/Publ-31082
Publ.-Id: 31082


Unexpected magnetic phase in the weakly ordered spin-1/2 chain cuprate Sr2CuO3

Sergeicheva, E. G.; Sosin, S. S.; Gorbunov, D.; Zherlitsyn, S.; Gu, G. D.; Zaliznyak, I. A.
The magnetic phase diagram of a spin- 1/2 chain antiferromagnet Sr2CuO3 is studied by an ultrasound phase-sensitive detection technique. The system is in the extreme proximity of the Luttinger-liquid quantum-critical point and we observe an unusually strong effect of magnetic field, which is very weak compared to the in-chain interaction, on the Néel ordering temperature. Inside the ordered phase, we detect an unexpected, field-induced continuous phase transition. The transition is accompanied by softening of magnetic excitation observed by electron-spin resonance, which in previous work [E. G. Sergeicheva et al., Phys. Rev. B 95, 020411(R) (2017)] was associated with a longitudinal (amplitude) mode of the order parameter. These results suggest a transition from a transverse collinear antiferromagnet to an amplitude-modulated spin-density-wave phase in a very weak magnetic field, which is unexpected for a system of weakly coupled Heisenberg spin- 1/2 chains.

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Permalink: https://www.hzdr.de/publications/Publ-31081
Publ.-Id: 31081


Para-ferroelectric phase transition driven by swift heavy-ion irradiation in KTN crystal

He, S.; Yang, Q.; Li, X.; Liu, H.; Cao, L.; Akhmadaliev, S.; Wang, X.; Ren, Y.; Zhou, S.; Wu, P.
We report a novel approach of using swift O5+ ion irradiation to implement para-ferroelectric phase transition in a relaxor ferroelectric KTa0.62Nb0.38O3 (KTN) single crystal. With 15-MeV swift O5+ ion irradiation, a well-defined two-layer structure has been formed in the KTN sample due to the interaction between the O ions and KTN via electronic stopping and the nuclear stopping, respectively. The microstructures in these two layers are characterized by using a micro-Raman (μ-Raman) spectral technique. The significant changes of both spectral intensities and locations in three characteristic Raman peaks suggest that the top layer of the KTN sample due to electronic stopping exists a single-domain-ferroelectric state with a uniform and enhanced polarization orientation along [0 0 1]c direction. More importantly, we observe the irradiated region can effectively confine the light propagation in the ferroelectric layer, which can be further controlled by external fields. The results are promising for designing new integrated photonic devices.
Keywords: Phase transition; Swift heavy ion irradiation; Relaxor ferroeletrics

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  • Secondary publication expected from 08.04.2021

Permalink: https://www.hzdr.de/publications/Publ-31070
Publ.-Id: 31070


Tailoring Magnetic Features in Zigzag-Edged Nanographenes by Controlled Diels–Alder Reactions

Ajayakumar, M.; Fu, Y.; Liu, F.; Komber, H.; Tkachova, V.; Xu, C.; Zhou, S.; Popov, A.; Liu, J.; Feng, X.
Nanographenes (NGs) with tunable electronic and magnetic properties have attracted enormous attention in the realm of carbon-based nanoelectronics. In particular, NGs with biradical character at the ground state are promising building units for molecular spintronics. However, most of the biradicaloids are susceptible to oxidation under ambient conditions and photolytic degradation, which hamper their further applications. Herein, we demonstrated the feasibility of tuning the magnetic properties of zigzag-edged NGs in order to enhance their stability via the controlled Diels–Alder reactions of peri-tetracene (4-PA). The unstable 4-PA (y0=0.72; half-life, t1/2=3 h) was transformed into the unprecedented benzo-peri-tetracenes (BPTs) by a one-side Diels–Alder reaction, which featured a biradical character at the ground state (y0=0.60) and exhibited remarkable stability under ambient conditions for several months. In addition, the fully zigzag-edged circumanthracenes (CAs) were achieved by two-fold or stepwise Diels–Alder reactions of 4-PA, in which the magnetic properties could be controlled by employing the corresponding dienophiles. Our work reported herein opens avenues for the synthesis of novel zigzag-edged NGs with tailor-made magnetic properties.

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Permalink: https://www.hzdr.de/publications/Publ-31068
Publ.-Id: 31068


openTIV

Ziegenhein, T.; Heßenkemper, H.; Lucas, D.
openTIV is a computer vision library mainly developed to evaluate pictures taken from multiphase flows. Specifically, the application of identifying phase interfaces and tracking particles (PTV and PIV) was intended by the authors. Besides that, post-processing libraries to calculate, for example, the standard dimensionless numbers (Reynolds, Morton, Eoetvoes (Bond), etc.) and void fraction profiles are provided as well. All libraries are based on the standard mathematical and physical library, which consists of essential solvers and mathematical structures, inside the package. The library includes the tools to help develop new methods for evaluating images from multiphase flows. It is not intended to provide a complete package of image processing methods, as can be found in the OpenCV package (which can be used with the openTIV libraries).
Keywords: Computer Vision, Multiphase Flow, PIV, PTV, Boundary Tracking, Image Processing

Permalink: https://www.hzdr.de/publications/Publ-31066
Publ.-Id: 31066


Figure and data from 'https://www.hzdr.de/publications/Publ-30945'

Baraban, L.; Klinghammer, S.; Rauch, S.; Uhlmann, P.; Pregl, S.; Cuniberti, G.

Figure compilations with the access to the origin files of the graphs. Created by Stephanie Klinghammer and Larysa Baraban: fabrication of SiNQ, measurements)

Keywords: polymer brushes functionalization; iv curves
Related publications
Surface Modification of Silicon Nanowire Based Field … (Id 30945) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-20
    DOI: 10.14278/rodare.339

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Permalink: https://www.hzdr.de/publications/Publ-31055
Publ.-Id: 31055


Particle dataset for constructing mineral processing case studies

Pereira, L.; Frenzel, M.; Khodadadzadeh, M.; Tolosana Delgado, R.; Gutzmer, J.

This file contains a train and a test datasets that can be used to construct fictional mineral processing studies, on a particle level, using known equations for different separation techniques. This data was collected with a mineral liberation analyzer at the Helmholtz Institute Freiberg for Resource Technology. The probabilities, and classes present together with the data are part of a publication in the journal of cleaner production. These could be simply removed in order to construct new cases.

Keywords: particle-tracking; geometallurgy; mineral processing modelling; flotation; resource efficiency; automated mineralogy
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-19
    DOI: 10.14278/rodare.335
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31053
Publ.-Id: 31053


Charged pion production in Au+Au collisions at sqrt(s_NN) = 2.4 GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Boehmer, M.; Bordalo, P.; Chernenko, S.; Chlad, L.; Ciepal, I.; Deveaux, C.; Dreyer, J.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Filip, P.; Fonte, P.; Franco, C.; Friese, J.; Froehlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhaeuser, R.; Glaessel, S.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Hlavac, S.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Karavicheva, T.; Kardan, B.; Koenig, I.; Koenig, W.; Kohls, M.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Malige, A.; Mangiarotti, A.; Markert, J.; Matulewicz, T.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Morozov, S.; Muentz, C.; Muenzer, R.; Naumann, L.; Nowakowski, K.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Piasecki, K.; Pietraszko, J.; Przygoda, W.; Pysz, K.; Ramos, S.; Ramstein, B.; Reshetin, A.; Rodriguez-Ramos, P.; Rathod, N.; Rosier, P.; Rost, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Selyuzhenkov, I.; Siebenson, J.; Silva, L.; Singh, U.; Smyrski, J.; Sobolev, Y. G.; Spataro, S.; Spies, S.; Stroebele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Usenko, E.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Wojcik, D.; Zanevsky, Y.; Zumbruch, P.
We present high-statistic data on charged pion emission from Au+Au collisions at sqrt(s_NN) = 2.4 GeV (corresponding to E_beam = 1.23 A GeV) in four centrality classes in the range 0 - 40% of the most central collisions. The data are analyzed as a function of transverse momentum, transverse mass, rapidity, and polar angle. Pion multiplicity per participating nucleon decreases moderately with increasing centrality. The polar angular distributions are found to be non-isotropic even for the most central event class. Our results on pion multiplicity fit well into the general trend of the world data, but undershoot by 2.5σ data from the FOPI experiment measured at slightly lower beam energy. We compare our data to state-of-the-art transport model calculations (PHSD, IQMD, PHQMD, GiBUU and SMASH) and find substantial differences between the measurement and the results of these calculations.

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Permalink: https://www.hzdr.de/publications/Publ-31052
Publ.-Id: 31052


Anisotropic exclusion effect between photocatalytic Ag/AgCl Janus particles and passive beads in a dense colloidal matrix

Huang, T.; Gobeil, S.; Wang, X.; Misko, V.; Nori, F.; de Malsche, W.; Faßbender, J.; Makarov, D.; Cuniberti, G.; Baraban, L.

Synthetic nano- and micromotors interact with each other and their surroundings in a complex manner. Here, we report on the anisotropy of active-passive particle interaction in a soft matter system containing an immobile yet photochemical Ag/AgCl-based Janus particle embedded in a dense matrix of passive beads in pure water. The asymmetry in the chemical gradient around the Janus particle, triggered upon visible light illumination, distorts the isotropy of the surrounding electric potential and results in the repulsion of adjacent passive beads to a certain distance away from the Janus particle. This exclusion effect is found to be anisotropic with larger distances to passive beads in front of the Ag/AgCl cap of the Janus particle. We provide insight into this phenomenon by performing the angular analysis of the radii of exclusion and tracking their time evolution at the level of a single bead. Our study provides a novel fundamental insight into the collective behavior of a complex mixture of active and passive particles and is relevant for various application scenarios, e.g., particle transport at micro- and nanoscale and local chemical sensing.

Keywords: photocatalytic reaction; micro and nanomotors; visible light; active Janus particles; spherical colloidal particles; exclusion phenomena
Related publications
Anisotropic exclusion effect between photocatalytic … (Id 30943) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-18
    DOI: 10.14278/rodare.329
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-31046
Publ.-Id: 31046


Soft Hydrothermal Synthesis of Hafnon, HfSiO4

Estevenon, P.; Kaczmarek, T.; Rafiuddin, M. R.; Welcomme, E.; Szenknect, S.; Mesbah, A.; Moisy, P.; Poinssot, C.; Dacheux, N.

The conditions allowing the preparation of single phase HfSiO4 has been determined through a multiparametric study by varying the concentrations of the reactants, the pH of the reactive media or the temperature and duration of the hydrothermal treatment. HfSiO4 was prepared through relatively soft conditions (pH ≤ 1.6, CSi ≈ CHf 0.21 mol·L‑1, T ≥ 150°C for t ≥ 24 hours).


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Soft hydrothermal synthesis of hafnon, HfSiO4 (Id 30004) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-01-29
    DOI: 10.14278/rodare.327

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Permalink: https://www.hzdr.de/publications/Publ-31043
Publ.-Id: 31043


In situ study of the synthesis of thorite (ThSiO4) under environmental representative conditions

Estevenon, P.; Causse, J.; Szenknect, S.; Welcomme, E.; Mesbah, A.; Moisy, P.; Poinssot, C.; Dacheux, N.

Thorite, ThSiO4 with Zircon structure type, is one of the most abundant natural source of thorium on earth. While actinides are known to form nanoparticles in silicate medium, no direct link between those colloids and crystalline form of thorite was evidenced until now. Here we show that thorite can be produced in experimental conditions close to environmental pH and temperature. Thanks to in-situ Small and Wide Angle X-rays Scattering (SWAXS) measurements, colloids of a few nanometers are first evidenced for low reaction time. These colloids exhibit elongated shapes and finally tend to aggregate after the size has reached 10 nm. Once aggregated, the system goes through a maturation step finishing with the emergence of nanocrystallites presenting thorite zircon structure. This maturation step is longer when the reaction temperature is decreased highlighting kinetic considerations. The conclusions of this article have potential implications in the paragenesis of Th minerals deposits, but also in the behaviour of Th and, by analogy, tetravalent actinides in the environment. The Th-silicate colloids evidenced in this work have, at low temperature and at near neutral pH, a long-term stability and a morphology in favor of a high mobility in groundwaters. If these species are formed in more diluted media, this could be problematic regarding to the spreading of Th and, by analogy of others tetravalent actinides in the environment.


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In situ study of the synthesis of thorite (ThSiO4) under … (Id 30965) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-12
    DOI: 10.14278/rodare.325

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Permalink: https://www.hzdr.de/publications/Publ-31041
Publ.-Id: 31041


Formation of PuSiO4 under hydrothermal conditions

Estevenon, P.; Welcomme, E.; Tamain, C.; Jouan, G.; Szenknect, S.; Mesbah, A.; Poinssot, C.; Moisy, P.; Dacheux, N.

Attempts to synthesize plutonium (IV) silicate, PuSiO4, have been performed on the basis of the results recently reported in the literature for CeSiO4, ThSiO4 and USiO4 under hydrothermal conditions. Although it was not possible to prepare PuSiO4 by applying the conditions reported for thorium and uranium, an efficient way of PuSiO4 synthesis was established following those optimized for CeSiO4 system. This method was based on the slow oxidation of plutonium (III) silicate reactants under hydrothermal conditions at 150°C in hydrochloric acid (pH = 3 – 4). This result shed a new light on the potential behavior of plutonium in reductive environment, highlighted the representativeness of cerium surrogates to study plutonium in such conditions and brought some important pieces of information on plutonium chemistry in silicate solutions.


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Formation of PuSiO4 under hydrothermal conditions (Id 30869) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-20
    DOI: 10.14278/rodare.295

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Permalink: https://www.hzdr.de/publications/Publ-31040
Publ.-Id: 31040


The Serial Interface Package -- v3.0

Seilmayer, M.
The package enables reading and writing binary and ASCII data to RS232/RS422/RS485 or any other virtual serial interface of the computer. The major extensions are made with new functions and an improved robustness.
Keywords: RS232, RS485, serial interface, R
  • Software in external data repository
    Publication year 2020
    Programming language: R, Tcl/TK
    System requirements: Windows, Linux, MacOS
    License: GPL-2Link to location

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Permalink: https://www.hzdr.de/publications/Publ-31039
Publ.-Id: 31039


Clinical outcome of PSMA-guided radiotherapy for patients with oligorecurrent prostate cancer

Koerber, S. A.; Sprute, K.; Kratochwil, C.; Winter, E.; Haefner, M. F.; Katayama, S.; Schlampp, I.; Herfarth, K.; Kopka, K.; Afshar-Oromieh, A.; Zschaebitz, S.; Holland-Letz, T.; Choyke, P. L.; Jaeger, D.; Hohenfellner, M.; Haberkorn, U.; Debus, J.; Giesel, F. L.
Purpose.
First-line treatment of patients with recurrent, metastatic prostate cancer involves hormone therapy with or without additional systemic therapies. Prostate-specific membrane antigen (PSMA) positron emission tomography (PET)/computed tomography (CT) allows the detection of oligometastatic disease that may be amenable to image-guided radiotherapy. The current study classifies the type and localization of metastases and the clinical outcome of PSMA-PET/CT-guided radiotherapy to selected metastases.
Materials and methods.
Between 2011 and 2019, 86 patients with recurrent, oligometastatic prostate carcinoma were identified by PSMA-PET/CT and were treated with image-guided radiotherapy of their metastases. Sites of relapse were characterized, and the primary endpoint overall survival (OS), biochemical progression-free survival (bPFS), and androgen deprivation therapy (ADT)-free survival were tabulated.
Results
In total, 37% of the metastases were bone metastases, 48% were pelvic nodalmetastases, and 15% were nodalmetastases outside of the pelvis. After PSMA-guided radiotherapy, a biochemical response was detected in 83% of the cohort. A statistically significant decrease in the standard uptake value (SUV) was seen in irradiated metastases. After a median follow-up of 26 months, the 3-year OS and bPFS were 84% and 55%, respectively. The median time of ADT-free survival was 13.5 months. A better clinical outcome was observed for patients receiving concomitant ADT or more than 24 fractions of radiation.
Conclusion.
PSMA-guided radiotherapy is a promising therapeutic approach with excellent infield control for men with oligorecurrent prostate carcinoma. However, prospective, randomized trials are necessary to determine if this approach confers a survival advantage.
Keywords: Prostate cancer; PSMA; PET; Metastases; SUV; OS

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Permalink: https://www.hzdr.de/publications/Publ-31037
Publ.-Id: 31037


The role of postoperative thoracic radiotherapy and prophylactic cranial irradiation in early stage small cell lung cancer: patient selection among ESTRO experts

Putora, P.; de Ruysscher, D.; Glatzer, M.; Widder, J.; van Houtte, P.; Troost, E. G. C.; Slotman, B.; Ramella, S.; Pöttgen, C.; Peeters, S.; Nestle, U.; Mcdonald, F.; Le, P. C.; Dziadziuszko, R.; Belderbos, J.; Faivre-Finn, C.
The role of prophylactic cranial irradiation (PCI) and thoracic radiotherapy (TRT) is unclear in resected small cell lung cancer (SCLC). Methods: Thirteen European radiotherapy experts on SCLC were asked to describe their strategies on PCI and TRT for patients with resected SCLC. The treatment strategies were converted into decision trees and analyzed for consensus and discrepancies. Results: For patients with resected SCLC and positive lymph nodes most experts recommend prophylactic cranial irradiation and thoracic radiotherapy. For elderly patients with resected node negative SCLC, most experts do not recommend thoracic radiotherapy or prophylactic cranial irradiation. Conclusion: PCI and TRT are considered in patients with resected SCLC and these treatments should be discussed with the patient in the context of shared decision-making.
  • Radiotherapy and Oncology 145(2020), 45-48

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Permalink: https://www.hzdr.de/publications/Publ-31032
Publ.-Id: 31032


Is reducing irradiated margins key to improving outcomes for radiotherapy

van Herk, M.; Osorio, E.; Troost, E. G. C.
Radiotherapy is a four-dimensional geometrical challenge. For modern radiotherapy planning, gross tumour volume (GTV) is pictured before treatment using CT scanning fused with anatomical and functional imaging. To account for microscopic tumour spread, a safety margin is added to the GTV and corrected for anatomical boundaries to determine the clinical target volume (CTV). Finally, systematic and random errors occurring during the fractionated course of radiotherapy are corrected for by adding another safety margin.
  • Lancet Oncology 20(2019)9, 1208-1210

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Permalink: https://www.hzdr.de/publications/Publ-31031
Publ.-Id: 31031


Integral multi-scenario robustness evaluation of classical and anatomical robust optimization in head and neck cancer proton therapy

Cubillos Mesias, M.; Troost, E. G. C.; Lohaus, F.; Agolli, L.; Rehm, M.; Richter, C.; Stützer, K.
Classical robust optimization considers uncertainties in patient setup and particle range. Usually plan robustness is evaluated from calculation of perturbed dose distributions based on the planning CT, without considering potential anatomical changes that may occur during the treatment course. Our aim was to compare the overall plan robustness of classical robust optimization (cRO) with the recently proposed anatomical robust optimization (aRO) based on an integral multi-scenario evaluation, considering all types of uncertainties including anatomical variations.
  • Abstract in refereed journal
    Radiotherapy and Oncology 133(2019)1, S488-S489

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Permalink: https://www.hzdr.de/publications/Publ-31030
Publ.-Id: 31030


Visualizing Magnetic Structure in 3D Nanoscale Ni–Fe Gyroid Networks

Llandro, J.; Love, D. M.; Kovács, A.; Caron, J.; Vyas, K. N.; Kakay, A.; Salikhov, R.; Lenz, K.; Faßbender, J.; Scherer, M. R. J.; Cimorra, C.; Steiner, U.; Barnes, C. H. W.; Dunin-Borkowski, R. E.; Fukami, S.; Ohno, H.
Arrays of interacting 2D nanomagnets display unprecedented electromagnetic properties via collective effects, demonstrated in artificial spin ices and magnonic crystals. Progress toward 3D magnetic metamaterials is hampered by two challenges: fabricating 3D structures near intrinsic magnetic length scales (sub-100 nm) and visualizing their magnetic configurations. Here, we fabricate and measure nanoscale magnetic gyroids, periodic chiral networks comprising nanowire-like struts forming three-connected vertices. Via block copolymer templating, we produce Ni75Fe25 single-gyroid and double-gyroid (an inversion pair of single-gyroids) nanostructures with a 42 nm unit cell and 11 nm diameter struts, comparable to the exchange length in Ni–Fe. We visualize their magnetization distributions via off-axis electron holography with nanometer spatial resolution and interpret the patterns using finite-element micromagnetic simulations. Our results suggest an intricate, frustrated remanent state which is ferromagnetic but without a unique equilibrium configuration, opening new possibilities for collective phenomena in magnetism, including 3D magnonic crystals and unconventional computing.
Keywords: magnetic metamaterials gyroids transmission electron microscopy off-axis electron holography

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Permalink: https://www.hzdr.de/publications/Publ-31026
Publ.-Id: 31026


Electron Concentration Limit in Ge Doped by Ion Implantation and Flash Lamp Annealing

Prucnal, S.; Żuk, J.; Hübner, R.; Duan, J.; Wang, M.; Pyszniak, K.; Drozdziel, A.; Turek, M.; Zhou, S.
Controlled doping with an effective carrier concentration higher than 10^20 cm-3 is a key challenge for the full integration of Ge into silicon-based technology. Such a highly doped layer of both p- and n type is needed to provide ohmic contacts with low specific resistance. We have studied the effect of ion implantation parameters i.e., ion energy, fluence, ion type, and protective layer on the effective concentration of electrons. We have shown that the maximum electron concentration increases as the thickness of the doping layer decreases. The degradation of the implanted Ge surface can be minimized by performing ion implantation at temperatures that are below -100 C with ion flux less than 60 nAcm-2 and maximum ion energy less than 120 keV. The implanted layers are flash-lamp annealed for 20 ms in order to inhibit the diffusion of the implanted ions during the recrystallization process.
Keywords: Ge; ion implantation; flash lamp annealing; n-type doping; Raman spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-31025
Publ.-Id: 31025


High-field magnetoacoustics of a Dy2Fe14Si3 single crystal

Andreev, A. V.; Gorbunov, D.; Nomura, T.; Zvyagin, A. A.; Zvyagina, G. A.; Zherlitsyn, S.
Dy2Fe14Si3 (hexagonal crystal structure of the Th2Ni17 type) is a highly-anisotropic ferrimagnet with spontaneous magnetic moment Ms=8µB per formula unit (at 2 K), directed along the Fe sublattice, and Curie temperature TC=500 K. The magnetic anisotropy is of the easy-plane type with the [100] axis as an easy magnetization direction. Large anisotropy is observed also within the basal plane. In fields applied along the [100] and [120] axes, field-induced phase transitions were observed at 33 T (of thefirst order) and at 41 T (of the second order), respectively (at 2 K). Relative changes of sound velocity and changes of sound attenuation at these phase transitions in a Dy2Fe14Si3 single crystal were measured in pulsed magneticfields up to 58 T at 2 K and elevated temperatures. The performed theoretical analysis suggests that the interaction of the elastic subsystem with the magnetic one is of the exchange-striction nature.

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Permalink: https://www.hzdr.de/publications/Publ-31022
Publ.-Id: 31022


Quantum and classical phase-space dynamics of a free-electron laser

Carmesin, C. M.; Peter, K.; Enno, G.; Sauerbrey, R.; Schleich, W. P.
In a quantum mechanical description of the free-electron laser (FEL), the electrons jump on discrete momentum ladders, while they follow continuous trajectories according to the classical description. In order to observe the transition from quantum to classical dynamics, it is not sufficient that many momentum levels are involved. Only if additionally the initial momentum spread of the electron beam is larger than the quantum mechanical recoil, caused by the emission and absorption of photons, the quantum dynamics in phase space resembles the classical one. Beyond these criteria, quantum signatures of averaged quantities like the FEL gain might be washed out.

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Permalink: https://www.hzdr.de/publications/Publ-31016
Publ.-Id: 31016


Crystal Growth of Spin-frustrated Ba4Nb0.8Ir3.2O12: A Possible Spin Liquid Material

Thakur, G. S.; Chattopadhyay, S.; Doert, T.; Herrmannsdörfer, T.; Felser, C.
Polycrystalline Ba4NbIr3O12 has recently been shown to be a promising spin liquid candidate. We report an easy and reliable method to grow millimeter-sized single crystals of this trimer-based spin liquid candidate material with the actual stoichiometry of Ba4Nb0.8Ir3.2O12. The growth of large crystals is achieved using BaCl as flux. The crystals show a hexagonal platelike habit with edges up to 3 mm in length. The structure is confirmed by single-crystal X-ray diffraction and is found to be the same as that of the previously reported phase Ba12Nb2.4Ir9.6O36 [Ba4Nb0.8Ir3.2O12], indeed with a mixed occupancy of Nb/Ir at the 3a site. The magnetic and calorimetric study on the individual single crystals confirms the possibility of a spin liquid state consistent with a recent report on a polycrystalline sample.

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Fermion sign problem in path integral Monte Carlo simulations: Quantum dots, ultracold atoms, and warm dense matter

Dornheim, T.
The ab initio thermodynamic simulation of correlated Fermi systems is of central importance for many applications, such as warm dense matter, electrons in quantum dots, and ultracold atoms. Unfortunately, path integral Monte Carlo (PIMC) simulations of fermions are severely restricted by the notorious fermion sign problem (FSP). In this paper, we present a hands-on discussion of the FSP and investigate in detail its manifestation with respect to temperature, system size, interaction-strength and -type, and the dimensionality of the system. Moreover, we analyze the probability distribution of fermionic expectation values, which can be non-Gaussian and fat-tailed when the FSP is severe. As a practical application, we consider electrons and dipolar atoms in a harmonic confinement, and the uniform electron gas in the warm dense matter regime. In addition, we provide extensive PIMC data, which can be used as a reference for the development of new methods and as a benchmark for approximations.
Keywords: path integral Monte Carlo, statistical physics, sign problem, computational physics

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Publ.-Id: 31012


Natural convection heat transfer performance of additively manufactured tube bundle heat exchangers with novel fin design

Unger, S.; Beyer, M.; Pietruske, H.; Szalinski, L.; Hampel, U.

These are the raw data and the processed data of the journal paper " Natural convection heat transfer performance of additively manufactured tube bundle heat exchangers with novel fin desigs".

 

The raw data contains the measured values on the experimental setup and the processed data contains the data of the data used in the corresponding journal publication.


Related publications
Natural convection heat transfer performance of additively … (Id 31008) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-10
    DOI: 10.14278/rodare.319
    License: CC-BY-4.0

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DNA damage in human whole blood caused by radiopharmaceuticals evaluated by the comet assay

Schmeiser, H.; Muehlbauer, K.; Mier, W.; Baranski, A.; Neels, O.; Dimitrakopolou-Strauss, A.; Schmezer, P.; Kratochwil, C.; Bruchertseifer, F.; Morgenstern, A.; Kopka, K.
Radiopharmaceuticals used for diagnosis or therapy induce DNA strand breaks, which may be detectable by single-cell gel electrophoresis (called comet assay). Blood was taken from patients before and at different time points after treatment with radiopharmaceuticals; blood cells were investigated by the comet assay using the percentage of DNA in the tail as the critical parameter. Whereas [225Ac]Ac-prostate-specific membrane antigen (PSMA)-617 alpha therapy showed no difference relative to the blood sample taken before treatment, beta therapy with [177Lu]Lu-PSMA-617 3 h post-injection revealed a small but significant increase in DNA strand breaks. In blood of patients who underwent positron emission tomography (PET) with either [18F]2-fluor-2-deoxy-D-glucose (FDG) or [68Ga]Ga-PSMA-11, an increase of DNA migration determined by the comet assay was not found when analysed at different time points (2–70 min) after intravenous tracer injection. Human whole blood was incubated with the targeted clinically relevant therapeutic radiopharmaceuticals [225Ac]Ac-PSMA-617, [177Lu]Lu-PSMA-617 and [90Y]Y-DOTA(0)-Phe(1)-Tyr(3)-octreotide (DOTA-TOC) at different activity concentrations (kBq/ml) for 5 days and then analysed by the comet assay. DNA damage increased with higher concentrations of all radiolabeled compounds tested. [177Lu]Lu-PSMA-617 caused higher blood cell radiotoxicity than equal activity concentrations of 90Y]Y-DOTATOC. Likewise, whole human blood was exposed to the positron emitters [18F]FDG and [68Ga]Ga-PSMA-11 in vitro for 24 h with activity concentrations ranging between 5 and 40 MBq/ml. The same activity concentration dependent elevated DNA migration was observed for both compounds although decay energies are different. This study demonstrated that the amount of DNA damage detected by the comet assay in whole human blood is similar among different positron emitters and divergent by a factor of 200 between alpha particles and beta radiation.

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Gallium-68 Complex of a Macrobicyclic Cage Amine Chelator Tethered to Two Integrin-Targeting Peptides for Diagnostic Tumor Imaging

Ma, M.; Neels, O.; Denoyer, D.; Roselt, P.; Karas, J.; Scanlon, D.; White, J.; Hicks, R.; Donnelly, P.
Tumor-targeting peptides radiolabeled with positron-emitting 68Ga are promising candidates as new noninvasive diagnostic agents for positron emission tomography (PET). The targeting peptides are tethered to a chelator that forms a stable coordination complex with Ga3+ that is inert to dissociation of Ga3+in vivo. Metal complexes of macrobicyclic hexaamine “sarcophagine” (sar = 3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane) ligands exhibit remarkable stability as a result of the encapsulating nature of the cage amine ligand. A Ga3+ sarcophagine complex, [Ga-(1-NH3-8-NH2-sar)]4+, has been characterized using X-ray crystallography, demonstrating that Ga3+ is coordinated to six nitrogen atoms in a distorted octahedral complex. A bifunctional derivative of (NH2)2sar, possessing two aliphatic linkers with carboxylic acid functional groups has been attached to two cyclic-RGD peptides that target the αvβ3 integrin receptor that is overexpressed in some types of tumor tissue. This dimeric species can be radiolabeled with 68Ga3+ in >98% radiochemical yield and 68Ga3+ does not dissociate from the ligand in the presence of transferrin, an endogenous protein with high affinity for Ga3+. Biodistribution and micro-PET imaging studies in tumor-bearing mice indicate that the tracer accumulates specifically in tumors with high integrin expression. The high tumor uptake is coupled with low nonspecific uptake and clearance predominantly through the kidneys resulting in high-quality PET images in animal models.

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Initiierung klinischer Multicenter-Studien mit lokaler Radiotracer-Herstellung

Zippel, C.; Neels, O.; Hennrich, U.; Giesel, F.; Kopka, K.
Ziel des Aufsatzes ist es, wesentliche gesetzliche und regulatorische Aspekte zu beleuchten, die bei multizentrischen klinischen Prüfungen mit kurzlebigen PSMA-PET-Radiopharmaka im Hinblick auf die Etablierung einer dezentralen Herstellung des klinischen Prüfpräparats zu beachten sind. Solche prospektiven Studien spielen in der nuklearmedizinischen Forschung und Entwicklung eine zunehmend wichtige Rolle. Um PSMA-PET-Tracer mit kurzer Halbwertzeit für die Prostatakrebsdiagnostik weiter im behördlichen Zulassungsverfahren und schließlich im Gesundheitssystem etablieren zu können, schließen sich nuklearmedizinische Zentren zunehmend standortübergreifend zusammen, um in angemessener Zeit hierfür die notwendige Anzahl von Studienpatienten zu erreichen. Im Folgenden gehen wir auf das regulatorische Umfeld zur Herstellung von PSMA-PET-Radiopharmaka als klinisches Prüfpräparat (engl. Investigational Medicinal Product, IMP) ein, und führen am Beispiel der frühen multizentrischen klinischen Prüfung der Phasen-I und -II „[68Ga]Ga-PSMA-11 in high-risk Prostate Cancer“ wesentliche Aspekte an, die bei der Initiierung einer prospektiven Studie mit dezentraler PSMA-Tracer-Herstellung aus radiopharmazeutisch-organisatorischer Sicht zu berücksichtigen und im Vorfeld abzustimmen sind.
Keywords: Radiopharmaka-Herstellung, gute Herstellungspraxis, PSMA-Tracer, multizentrische Studie, prospektive klinische Prüfung, Qualitätsmanagement

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Impact of 18F-PSMA-1007 Uptake in Prostate Cancer Using Different Peptide Concentrations: Preclinical PET/CT Study on Mice

Soeda, F.; Watabe, T.; Naka, S.; Liu, Y.; Horitsugi, G.; Neels, O.; Kopka, K.; Tatsumi, M.; Shimosegawa, E.; Giesel, F.; Hatazawa, J.
PET radioligands with low molar activity (MA) may underestimate the quantity of the target of interest because of competitive binding of the target with unlabeled ligand. The aim of this study was to evaluate the change in the whole-body distribution of 18F-PSMA-1007 targeting prostate-specific membrane antigen (PSMA) when solutions with different peptide concentrations are used. Methods: Mouse xenograft models of LNCaP (PSMA-positive prostate cancer) (n = 18) were prepared and divided into 3 groups according to the peptide concentration injected: a high-MA group (1,013 ± 146 GBq/μmol; n = 6), a medium-MA group (100.7 ± 23.1 GBq/μmol; n 5 6), and a low-MA group (10.80 ± 2.84 GBq/μmol; n = 6). Static PET scans were performed 1 h after injection (scan duration, 10 min). SUVmean in tumor and normal organs was compared by the multiple-comparison test. Immunohistochemical staining and Western blot analysis were performed to confirm expression of PSMA in tumor, salivary gland, and kidney. Results: The low-MA group (SUVmean, 1.12 ± 0.30) showed significantly lower uptake of 18F-PSMA-1007 in tumor than did the high-MA group (1.97 ± 0.77) and the medium-MA group (1.81 ± 0.57). On the other hand, in salivary gland, both the low-MA group (SUVmean, 0.24 ± 0.04) and the medium-MA group (0.57 ± 0.08) showed significantly lower uptake than the high MA group (1.27 ± 0.28). The tumor-to-salivary gland SUVmean ratio was 1.73 ± 0.55 in the high-MA group, 3.16 ± 0.86 in the medium-MA group, and 4.78 ± 1.29 in the low-MA group. The immunohistochemical staining and Western blot analysis revealed significant overexpression of PSMA in tumor and low expression in salivary gland and kidney. Conclusion: A decrease in the MA level of the injected 18F-PSMA-1007 solution resulted in decreased uptake in tumor and, to a greater degree, in normal salivary gland. Thus, there is a possibility of minimizing the adverse effects in salivary gland by setting an appropriate MA level in PSMA targeting therapy.
Keywords: 18F-PSMA-1007; peptide concentration; molar activity; prostate cancer; salivary gland

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Production of Ga-68 radiotracers under GMP and regulatory aspects - a German perspective

Neels, O.
Radiopharmaceuticals labelled with the positron emitter Gallium-68 have had an enormous impact on the diagnostic imaging of neuroendocrine tumors using somatostatin receptor ligands and in recent years on the diagnosis of prostate cancer using PSMA ligands and subsequently their application for radioendotherapy using Yttrium-90, Lutetium-177 or more recently Actinium-225. The release of the monographs for ‘Gallium-68 chloride solution for radiolabelling’ and ‘Gallium-68 Edotreotide injection’ within the European Pharmacopoeia in 2013 tightened the requirements for specifications of Gallium-68 labelled radiotracers and will be enhanced with the ongoing elaboration of monographs for ‘Gallium-68 DOTA-TATE injection’, ‘Gallium-68 DOTA-NOC injection’ and ‘68Ga-PSMA’. In the same way the work environment of the responsible radiochemists and radiopharmacists in terms of quality control has been improved but also the workload has reached a high level with the increasing number of clinical applications and the limitation of the maximum achievable amount of starting activity from the currently available generators and therefore a limited dose number. The change of conditions for the production and quality control of Gallium-68 labelled radiopharmaceuticals will be reviewed with regards to legislating and practical aspects from ‘on bench’ to ‘full GMP’ preparation linked to the specific requirements for a multi-centre clinical trial using 68Ga-PSMA-11 in high-risk prostate cancer.
  • Open Access Logo Invited lecture (Conferences)
    4th Theranostics World Congress 2016, 07.-09.11.2016, Melbourne, Australia
    DOI: 10.1530/endoabs.47.OC2

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Publ.-Id: 31003


Thermal kinetics of free volume in porous spin-on dielectrics: exploring the network- and pore-properties

Elsherif, A. G. A.; Koehler, N.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Ecke, R.; Schulz, S. E.; Wagner, A.

Data to ULK-kinetics by Positron annihilation spectroscopy and Fourier transform infrared spectroscopy

Keywords: PALS, FTIR, ULK, Curing
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-11
    DOI: 10.14278/rodare.321
    License: CC-BY-4.0

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Manipulation of [11C]-5-Hydroxytryptophan and 6-[18F]Fluoro-3,4-Dihydroxy-L-Phenylalanine Accumulation in Neuroendocrine Tumor Cells

Neels, O.; Koopmans, K.; Jager, P.; Vercauteren, L.; van Waarde, A.; Doorduin, J.; Timmer-Bosscha, H.; Brouwers, A.; de Vries, E.; Dierckx, R.; Kema, I.; Elsinga, P.
[11C]-5-Hydroxytryptophan ([11C]HTP) and 6-[18F]fluoro-3,4-dihydroxy-L-phenylalanine ([18F]FDOPA) are used to image neuroendocrine tumors with positron emission tomography. The precise mechanism by which these tracers accumulate in tumor cells is unknown. We aimed to study tracer uptake via large amino acid transporters, peripheral decarboxylation (inhibited by carbidopa), and intracellular breakdown by monoamine oxidase (MAO). [11C]HTP and [18F]FDOPA tracer accumulation was assessed in a human neuroendocrine tumor cell line, BON. The carbidopa experiments were done in a tumor-bearing mouse model. Intracellular [11C]HTP accumulation was 2-fold higher than that of [18F]FDOPA. Cellular transport of both tracers was inhibited by amino-2-norbornanecarboxylic acid. The MAO inhibitors clorgyline and pargyline increased tracer accumulation in vitro. Carbidopa did not influence tracer accumulation in vitro but improved tumor imaging in vivo. Despite lower accumulation in vitro, visualization of [18F]FDOPA is superior to [11C]HTP in the neuroendocrine pancreatic tumor xenograft model. This could be a consequence of the serotonin saturation of BON cells in the in vivo model.

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Staging of carcinoid tumours with 18F-DOPA PET: a prospective, diagnostic accuracy study

Koopmans, K.; de Vries, E.; Kema, I.; Elsinga, P.; Neels, O.; Sluiter, W.; van der Horst-Schrivers, A.; Jager, P.
To assess individual treatment options for patients with carcinoid tumours, accurate knowledge of tumour localisation is essential. We aimed to test the diagnostic sensitivity of 6-[fluoride-18]fluoro-levodopa (18F-DOPA PET), compared with conventional imaging methods, in patients with carcinoid tumours. In a prospective, single-centre, diagnostic accuracy study, 18F-DOPA PET with carbidopa pretreatment was compared with somatostatin-receptor scintigraphy (SRS), CT, and combined SRS and CT in 53 patients with a metastatic carcinoid tumour. The performance of all imaging methods was analysed for individual patients, for eight body regions, and for the detection of individual lesions. PET and CT images were fused to improve localisation. To produce a composite reference standard, we used cytological and histological findings; all imaging tests, including secondary assessments for newly found lesions; follow-up; and biochemical data. Sensitivities were calculated and compared. In patient-based analysis, we recorded sensitivities of 100% (95% CI 93-100) for 18F-DOPA-PET, 92% (82-98) for SRS, 87% (75-95) for CT, and 96% (87-100) for combined SRS and CT (p=0.45 for 18F-DOPA PET vs combined SRS and CT). However, 18F-DOPA PET detected more lesions, more positive regions, and more lesions per region than combined SRS and CT. In region-based analysis, sensitivity of 18F-DOPA PET was 95% (90-98) versus 66% (57-74) for SRS, 57% (48-66) for CT, and 79% (70-86) for combined SRS and CT (p=0.0001, PET vs combined SRS and CT). In individual-lesion analysis, corresponding sensitivities were 96% (95-98), 46% (43-50), 54% (51-58), and 65% (62-69; p<0.0001 for PET vs combined SRS and CT). If the improved tumour localisation seen with 18F-DOPA-PET compared with conventional imaging is confirmed in future studies, this imaging method could replace use of SRS, help improve prediction of prognosis, and be used to assess patients' response to treatment for carcinoid tumours.

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Improved Staging of Patients With Carcinoid and Islet Cell Tumors With 18F-Dihydroxy-Phenyl-Alanine and 11C-5-Hydroxy-Tryptophan Positron Emission Tomography

Koopmans, K.; Neels, O.; Kema, I.; Elsinga, P.; Sluiter, W.; Vanghillewe, K.; Brouwers, A.; Jager, P.; de Vries, E.
Purpose
To evaluate and compare diagnostic sensitivity of positron emission tomography (PET) scanning in carcinoid and islet cell tumor patients with a serotonin and a catecholamine precursor as tracers.
Patients and Methods
Carcinoid (n = 24) or pancreatic islet cell tumor (n = 23) patients with at least one lesion on
conventional imaging including somatostatin receptor scintigraphy (SRS) and computed tomography (CT) scan underwent 11C-5-hydroxytryptophan (11C-5-HTP) PET and 6-[F-18]fluoro-L-dihydroxyphenylalanin (18F-DOPA) PET. PET findings were compared with a composite reference standard derived from all available imaging along with clinical and cytologic/histologic information.
Results
In carcinoid tumor patients, per-patient analysis showed sensitivities for 11C-5-HTP PET, 18F-DOPA PET, SRS, and CT of 100%, 96%, 86%, 96%, respectively, and in islet cell tumors of 100%, 89%, 78%, 87%, respectively. In carcinoid patients, per-lesion analysis revealed sensitivities for 11C-5-HTP PET, 11C-5-HTP PET/CT, 18F-DOPA PET, 18F-DOPA PET/CT, SRS, SRS/CT, and CT alone of, respectively, 78%, 89%, 87%, 98%, 49%, 73%, and 63% and in islet cell tumors of 67%, 96%, 41%, 80%, 46%, 77%, and 68%, respectively. In all carcinoid patients 18F-DOPA PET and 11C-5-HTP PET detected more lesions than SRS (P < .001). 11C-5-HTP PET was superior to 18F-DOPA PET in islet cell tumors (P < .0001). In all cases, CT improved the sensitivity of the nuclear scans.
Conclusion
18F-DOPA PET/CT is the optimal imaging modality for staging in carcinoid patients and 11C-5-HTP PET/CT in islet cell tumor patients.

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Molecular imaging in neuroendocrine tumors: Molecular uptake mechanisms and clinical results

Koopmans, K.; Neels, O.; Kema, I.; Elsinga, P.; Links, T.; de Vries, E.; Jager, P.
Neuroendocrine tumors can originate almost everywhere in the body and consist of a great variety of subtypes. This paper focuses on molecular imaging methods using nuclear medicine techniques in neuroendocrine tumors, coupling molecular uptake mechanisms ofradiotracers with clinical results. A non-systematic review is presented on receptor based and metabolic imaging methods. Receptor-based imaging covers the molecular backgrounds of somatostatin, vaso-intestinal peptide (VIP), bombesin and cholecystokinin (CCK) receptors and their link with nuclear imaging. Imaging methods based on specific metabolic properties include meta-iodo-benzylguanide (MIBG) and dimercapto-sulphuric acid (DMSA-V) scintigraphy as well as more modern positron emission tomography (PET)-based methods using radio-labeled analogues of amino acids, glucose, dihydroxyphenylalanine (DOPA), dopamine and tryptophan. Diagnostic sensitivities are presented for each imaging method and for each neuroendocrine tumor subtype. Finally, a Forest plot analysis of diagnostic performance is presented for each tumor type in order to provide a comprehensive overview for clinical use.
Keywords: Neuroendocrine tumors; Review; Diagnostic imaging; Radiopharmaceuticals/diagnostic use; Positron emission tomography; Gamma camera imaging

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The static local field correction of the warm dense electron gas: An ab initio path integral Monte Carlo study and machine learning representation

Dornheim, T.; Vorberger, J.; Groth, S.; Hoffmann, N.; Moldabekov, Z.; Bonitz, M.
The response of the uniform electron gas (UEG) to an external perturbation is of paramount importance for many applications. Recently, highly accurate results for the static density response function and the corresponding local field correction have been provided both for warm dense matter [J. Chem. Phys. 151, 194 104 (2019)] and strongly coupled electron liquid [Phys. Rev. B 101, 045 129 (2020)] conditions based on exact ab initio path integral Monte Carlo (PIMC) simulations. In the present work, we further complete our current description of the UEG by exploring the high energy density regime, which is relevant for, e.g. astrophysical applications and inertial confinement fusion experiments. To this end, we present extensive new PIMC results for the static density response in the range of 0.05 ≤ r s ≤ 0.5 and 0.85 ≤ θ ≤ 8.
These data are subsequently used to benchmark the accuracy of the widely used random phase approximation and the dielectric theory by Singwi, Tosi, Land, and Sjölander (STLS). Moreover, we compare our results to configuration PIMC data where they are available and find perfect agreement with a relative accuracy of 0.001 − 0.01%. All PIMC data are available online.
Keywords: uniform electron gas, path integral monte carlo, density response

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Development of an Ionization Chamber for the Measurement of the 16O(n, alpha)13C Cross-Section at the CERN n_TOF Facility.

Urlaß, S.; Junghans, A.; Mingrone, F.; Hartmann, A.; Sobiella, M.; Stach, D.; Tassan-Got, L.; Weinberger, D.
The 16O(n, alpha)13 C reaction, as the inverse reaction of the astrophysically important 13C(alpha, n)16O reaction, is proposed to be measured at the neutron time-of-flight (nTOF) facility of CERN. To this purpose, a Double Frisch Grid Ionization Chamber (DFGIC) containing the oxygen atoms as a component in the counting gas has been developed and a prototype was constructed at Helmholtz-Zentrum Dresden-Rossendorf(HZDR), in Germany. The first in-beam tests of the detector have been performed in November 2017 in the first (EAR1) and in April 2018 in the second (EAR2) experimental areas of the nTOF facility.
Keywords: NIC2018; oxygen; n_alpha; 16O; O-16
  • Contribution to proceedings
    15th International Symposium on Nuclei in the Cosmos, 24.-29.06.2018, Assergi, Italien
    Proceedings of the 15th International Symposium on Nuclei in the Cosmos: Springer Proceedings in Physics, 978-3-030-13875-2, 457-460
    DOI: 10.1007/978-3-030-13876-9_89

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PIMC data for the uniform electron gas in the high energy density regime

Dornheim, T.; Groth, S.

PIMC data for the static density response obtained by Dornheim et al. (Plasma Phys. Control. Fusion, https://doi.org/10.1088/1361-6587/ab8bb4). These data can be freely used by other researchers and contain a README file with additional information.

Keywords: Path integral Monte Carlo, uniform electron gas
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Ab initio path integral Monte Carlo simulation of the … (Id 30990) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-05-08
    DOI: 10.14278/rodare.317
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30992
Publ.-Id: 30992


Ab initio path integral Monte Carlo simulation of the uniform electron gas in the high energy density regime

Dornheim, T.; Moldabekov, Z.; Vorberger, J.; Groth, S.
The response of the uniform electron gas (UEG) to an external perturbation is of paramount importance for many applications. Recently, highly accurate results for the static density response function and the corresponding local field correction have been provided both for warm dense matter [J. Chem. Phys.151,194104 (2019)] and strongly coupled electron liquid [Phys. Rev. B101, 045129 (2020)] conditions based on exact ab initio path integral Monte Carlo (PIMC) simulations. In the present work, we further complete our current description of the UEG by exploring the high energy density regime, which is relevant for, e.g., astrophysical applications and inertial confinement fusion experiments. To this end, we present extensive new PIMC results for the static density response in the range of 0.05≤rs≤0.5 and 0.85≤θ≤8. These data are subsequently used to benchmark the accuracy of the widely used random phase approximation and the dielectric theory by Singwi, Tosi, Land, and Sjölander (STLS). Moreover, we compare our results to configuration PIMC data where they are available and find perfect agreement with a relative accuracy of 0.001−0.01%. All PIMC data are available online.
Keywords: Uniform Electron Gas, Path Integral Monte Carlo, Density Response
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PIMC data for the uniform electron gas in the high energy … (Id 30992) HZDR-primary research data are used by this publication

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Development of a reliable remote-controlled synthesis of β-[11C]-5-hydroxy-L-tryptophan on a Zymark robotic system

Neels, O.; Jager, P.; Koopmans, K.; Eriks, E.; de Vries, E.; Kema, I.; Elsinga, P.
Precise staging of neuroendocrine tumors (NET) using positron emission tomography (PET) tracers visualizing their specific metabolic activity is of interest. Besides [18F]FDOPA, staging NET with carbon-11 labeled 5-hydroxytryptophan (5-HTP) is reported in recent literature. We implemented the multi-enzymatic synthesis of enantiomerically pure [11C]-L-5-HTP on a Zymark robotic system to compare both tracers in patient studies. [11C]-5-HTP can be synthesized in up to 24% radiochemical yields (EOB). Average specific activity is 44 000GBq/mmol in ca. 50 min from [11C]methyl iodide in radiochemical purities >99 %. The synthesis of 5-HTP is difficult due to its multi-enzymatic reaction steps but typical yields can be achieved of ca. 400 MBq. [11C]-5-HTP is now reliably used in ongoing studies for staging NET.
Keywords: [11C]-5-HTP; neuroendocrine tumors; robot; carbon-11; enzyme
  • Journal of Labelled Compounds and Radiopharmaceuticals 49(2006)10, 889-895
    DOI: 10.1002/jlcr.1110

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Novel Preclinical and Radiopharmaceutical Aspects of [68Ga]Ga-PSMA-HBED-CC: A New PET Tracer for Imaging of Prostate Cancer

Eder, M.; Neels, O.; Müller, M.; Bauder-Wüst, U.; Remde, Y.; Schäfer, M.; Hennrich, U.; Eisenhut, M.; Afshar-Oromieh, A.; Haberkorn, U.; Kopka, K.
The detection of prostate cancer lesions by PET imaging of the prostate-specific membrane antigen (PSMA) has gained highest clinical impact during the last years. 68Ga-labelled Glu-urea-Lys(Ahx)-HBED-CC ([68Ga]Ga-PSMA-HBED-CC) represents a
successful novel PSMA inhibitor radiotracer which has recently demonstrated its suitability in individual first-in-man studies. The radiometal chelator HBED-CC used in this molecule represents a rather rarely used acyclic complexing agent with chemical characteristics favourably influencing the biological functionality of the PSMA inhibitor. The simple replacement of HBED-CC by the prominent radiometal chelator DOTA was shown to dramatically reduce the in vivo imaging quality of the respective 68Ga-labelled PSMA-targeted tracer proving that HBED-CC contributes intrinsically to the PSMA binding of the Glu-urea-Lys(Ahx) pharmacophore. Owing to the obvious growing clinical impact, this work aims to reflect the properties of HBED-CC as acyclic radiometal chelator and presents novel preclinical data and relevant aspects of the radiopharmaceutical production process of [68Ga]Ga-PSMA-HBED-CC.
Keywords: 68Ga-PET imaging; PSMA; HBED-CC; prostate cancer; radiopharmaceutical production; good manufacturing practice; GMP

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Publ.-Id: 30981


Radionuclides: medicinal products or rather starting materials?

Neels, O.; Patt, M.; Decristoforo, C.
The EU directive 2001/83 describes the community code for medicinal products for human use including radiopharmaceuticals. In its current definition, also radionuclide precursors, such as fluorine-18, need to hold a marketing authorization before being placed on the market. The potential of novel radiopharmaceuticals for nuclear medicine is, although encouraged by European legislation and its respective guidance documents, therefore hampered by the regulatory framework. An update of EU directive 2001/83 would be beneficial for the development of novel radiopharmaceuticals and a safe advance in nuclear medicine.

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Publ.-Id: 30980


Magnetic and magnetocaloric properties of Ni47Mn40Sn13−xZnx alloys: Direct measurements and first-principles calculations

Ghotbi Varzaneh, A.; Kameli, P.; Abdolhosseini Sarsani, I.; Ghorbani Zavareh, M.; Salazar Mejia, C.; Amiri, T.; Scurschii, I.; Luo, J. L.; Etsell, T. H.; Chernenko, V. A.
In the present study, the martensitic transformation (MT) and magnetic properties exhibited by the Ni-Mn-Sn Heusle-type magnetic shape memory alloys (MSMAs) doped with Zn have been investigated experimentally and theoretically. The inverse magnetocaloric effect (MCE) in Ni47Mn40Sn13−xZnx (x = 0, 1) was studied by direct measurements of the adiabatic temperature change, ΔTad, in pulsed magnetic fields of 5, 10, and 20 T. The Zn doping of the Ni-Mn-Sn alloy led to a striking enhancement of the value of ΔTad, e.g., from –2.5 for undoped to –11 K for Zn-doped alloys under a magnetic field amplitude of 20 T. The first-principles calculations were used to understand the origin of Zn-doping influence on MT, magnetic, and magnetocaloric properties. Particularly, the crystal structure and magnetic ordering influenced by the site occupancy in the undoped and Zn-doped alloys were analyzed. The results show that, whereas the usual transition metal elements with more valence electrons tend to enter the Ni sites, Zn atom prefers to occupy the Sn sublattice. The underlying physics of the drastic enhancement of MCE by Zn doping is discussed in terms of a partial disorder in the occupation sites of Zn atoms.

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Publ.-Id: 30977


Enantiomerically pure Tetravalent Neptunium Amidinates: Synthesis and Characterization

Fichter, S.; Kaufmann, S.; Kaden, P.; Brunner, T. S.; Stumpf, T.; Roesky, P. W.; März, J.
The synthesis of a tetravalent neptunium amidinate [NpCl((S)-PEBA)₃] (1) ((S)-PEBA = (S,S)-N,N’-bis-(1-phenylethyl)-benzamidinate) is reported. This complex represents the first structurally characterized enantiopure transuranic compound. Reactivity studies with halide/pseudohalides yielding [NpX((S)-PEBA)₃] (X = F (2), Br (3), N3 (4)) have shown that the chirality-atmetal is preserved for all compounds in the solid state. Furthermore, they represent an unprecedented example of a structurally characterized metal-organic Np complex featuring a Np–Br (3) bond. In addition, 4 is the only reported tetravalent transuranic azide. All compounds were additionally characterized in solution using paramagnetic NMR spectroscopy showing an expected C₃ symmetry at low temperatures.
Keywords: transuranium chemistry • actinides • neptunium • coordination chemistry • amidinates

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Publ.-Id: 30964


Silicon nanowire sensorS for immunological treatment

Nguyen Le, T. A.; Sandoval Bojorquez, D. I.; Pérez Roig, A.; Bergoi, I.; Kihyun, K.; Gianaurelio, C.; Bachmann, M.; Baraban, L.
As of April 28, 2020, a pandemic called coronavirus disease 2019 (COVID-19) has spread to every continent of the world, infecting around three million people, and taken nearly 200,000 lives [1]. Although such deadly events are not new throughout human history, they often cause fear and uncertainty, mostly because of lacking information about the new strain of the virus. Insight about the virus and its working mechanism is perhaps important yet understanding the human immune response is the key to reducing mortality. Our immune system reacts differently depends on ages, genders, races, and health background. That explains dissimilar disease progression in patients where some develop critical conditions while others only have mild symptoms [2]. Accumulating evidences suggest patient with severe COVID-19 symptoms is due to cytokine - a common name for a broad spectrum of small proteins important in cell signalling, especially in the immune system - dysregulation [3-5]. Therefore, many studies have suggested a screening of cytokine profiles together with other immune cells responses for the determination of correct treatment [3,5]. Meanwhile, nanosensors such as silicon nanowire (SiNW) own advantages of being sensitive to small molecules, rapid and label-free [6]. In this poster, we demonstrate the use of a SiNW sensor in immunotherapy research, more specifically, in a system of switchable T-cell expressing chimeric antigen receptors (CARs). The sensor showed better sensitivity and a lower limit of detection compare to standard ELISA test. Moreover, thanks to its compatibility with CMOS technology which enables mass production, reproducibility is ensured [7]. Since the cytokine release syndrome (CRS) found in COVID-19 patients is also observed in patients receiving CAR-T therapy [4], the knowledge and tools generated by the SiNW sensor developed in this field of study may benefit the community. In the end, a full understanding and control of our immune system might be the key to fight any other pandemic in the future.
  • Open Access Logo Contribution to proceedings
    Biosensors for Pandemics: Reliable and efficient nanotech-based diagnostics in emergency situations 2020, 06.05.2020, Online, Online

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Publ.-Id: 30963


Logarithmic Elastic Response in the Dilute non-Kramers System Y1-xPrxIr2Zn20

Yanagisawa, T.; Hidaka, H.; Amitsuka, H.; Zherlitsyn, S.; Wosnitza, J.; Yamane, Y.; Onimaru, T.
Ultrasonic investigations of the single-site quadrupolar Kondo effect in diluted Pr system Y0.966Pr0.034Ir2Zn20 are reported. The elastic constant (C11C12)/2 is measured down to ~40 mK using ultrasound for the dilute system Y0.966Pr0.034Ir2Zn20 and the pure compound Yir2Zn20. We found that the elastic constant (C11C12)/2 of the Pr-dilute system exhibits a logarithmic temperature dependence below T0 ∼ 0.3 K, where non-Fermi-liquid (NFL) behavior in the specific heat and electrical resistivity is observed. This logarithmic temperature variation manifested in the Γ3-symmetry quadrupolar susceptibility is consistent with the theoretical prediction of the quadrupolar Kondo effect by D. L. Cox [1]. On the other hand, the pure compound Yir2Zn20 without 4f-electron contributions shows nearly no change in its elastic constants evidencing negligible phonon contributions. In addition, clear acoustic de Haas-van Alphen (dHvA) oscillations in the elastic constant were detected for both compounds on applying magnetic field. This is mainly interpreted as contribution from the Fermi surface of Yir2Zn20.

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Publ.-Id: 30951


Observation of giant spin-split Fermi-arc with maximal Chern number in the chiral topological semimetal PtGa

Yao, M.; Manna, K.; Yang, Q.; Fedorov, A.; Voroshnin, V.; Schwarze, B. V.; Hornung, J.; Chattopadhyay, S.; Sun, Z.; Guin, S. N.; Wosnitza, J.; Borrmann, H.; Shekhar, C.; Kumar, N.; Fink, J.; Sun, Y.; Felser, C.
Non-symmorphic chiral topological crystals host exotic multifold fermions, and their associated Fermi arcs helically wrap around and expand throughout the Brillouin zone between the high-symmetry center and surface-corner momenta. However, Fermi-arc splitting and realization of the theoretically proposed maximal Chern number rely heavily on the spin-orbit coupling (SOC) strength. In the present work, we investigate the topological states of a new chiral crystal, PtGa, which has the strongest SOC among all chiral crystals reported to date. With a comprehensive investigation using high-resolution angle-resolved photoemission spectroscopy, quantum-oscillation measurements, and state-of-the-art ab initio calculations, we report a giant SOC-induced splitting of both Fermi arcs and bulk states. Consequently, this study experimentally confirms the realization of a maximal Chern number equal to ±4 in multifold fermionic systems, thereby providing a platform to observe large-quantized photogalvanic currents in optical experiments.

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Publ.-Id: 30950


Quadrupolar susceptibility and magnetic phase diagram of PrNi2Cd20 with non-Kramers doublet ground state

Yanagisawa, T.; Hidaka, H.; Amitsuka, H.; Nakamura, S.; Awaji, S.; Green, E. L.; Zherlitsyn, S.; Wosnitza, J.; Yazici, D.; White, B. D.; Maple, M. B.
In this study, ultrasonic measurements were performed on a single crystal of cubic PrNi2Cd20, down to a temperature of 0.02 K, to investigate the crystalline electric field ground state and search for possible phase transitions at low temperatures. The elastic constant (C11−C12)/2, which is related to the Γ3-symmetry quadrupolar response, exhibits the Curie-type softening at temperatures below ∼30 K, which indicates that the present system has a Γ3 non-Kramers doublet ground state. A leveling-off of the elastic response appears below ∼0.1 K toward the lowest temperatures, which implies the presence of level splitting owing to a long-range order in a finite-volume fraction associated with Γ3-symmetry multipoles. A magnetic field–temperature phase diagram of the present compound is constructed up to 28 T for H || [110]. A clear acoustic de Haas–van Alphen signal and a possible magnetic-field-induced phase transition at H ∼26 T are also detected by high-magnetic-field measurements.

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Publ.-Id: 30949


Sub-lattice of Jahn-Teller centers in hexaferrite crystal

Gudkov, V. V.; Sarychev, M. N.; Zherlitsyn, S.; Zhevstovskikh, I. V.; Averkiev, N. S.; Vinnik, D. A.; Gudkova, S. A.; Niewa, R.; Dressel, M.; Alyabyeva, L. N.; Gorshunov, B. P.; Bersuker, I. B.
A novel type of sub-lattice of the Jahn-Teller (JT) centers was arranged in Ti-doped barium hexaferrite BaFe12O19. In the un-doped crystal all iron ions, sitting in five different crystallographic positions, are Fe3+ in the high-spin configuration (S = 5/2) and have a non-degenerate ground state. We show that the electron-donor Ti substitution converts the ions to Fe2+ predominantly in tetrahedral coordination, resulting in doubly-degenerate states subject to the E ⊗ e problem of the JT effect. The arranged JT complexes, Fe2+O4, their adiabatic potential energy, non-linear and quantum dynamics, have been studied by means of ultrasound and terahertz-infrared spectroscopies. The JT complexes are sensitive to external stress and applied magnetic field. For that reason, the properties of the doped crystal can be controlled by the amount and state of the JT complexes.

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Publ.-Id: 30948


Synthesis and crystal structures of transition metal(II) fluoridometallate(IV) hydrates of neptunium and plutonium: AIIMIVF₆∙3H₂O (AII = Mn, Zn; MIV = Np, Pu)

Scheibe, B.; März, J.; Schmidt, M.; Stumpf, T.; Kraus, F.
Transition metal(II) fluoridometallates(IV) AIIMIVF6∙3H2O (AII = Mn, Zn; MIV = Np, Pu) were synthesized from NpO2 or PuO2 and the respective transition metal chlorides from hydrofluoric acid under mild conditions. The olive-green (Np) or orange (Pu) compounds were obtained as single-crystals and the respective structures were determined by single-crystal X-ray diffraction. In the isotypic compounds, chains of edgesharing tricapped trigonal prismatic polyhedra, [MIVF8/2(H2O)1/1] ∞1, are present and an overall threedimensional network structure is observed in which the AII and MIV atoms are arranged according to the simple NaCl structure type. Within the respective U-Pu series of the Zn and Mn salts the cell volumes and the MIV−F distances decrease due to the actinoid contraction.
Keywords: actinoid, neptunium, plutonium, fluoride, single-crystal X-ray diffraction

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Publ.-Id: 30947


Surface Modification of Silicon Nanowire Based Field Effect Transistors with Stimuli Responsive Polymer Brushes for Biosensing Applications

Klinghammer, S.; Rauch, S.; Pregl, S.; Uhlmann, P.; Baraban, L.; Cuniberti, G.
We demonstrate the functionalization of silicon nanowire based field effect transistors (SiNW FETs) FETs with stimuli-responsive polymer brushes of poly(N-isopropylacrylamide) (PNIPAAM) and poly(acrylic acid) (PAA). Surface functionalization was confirmed by atomic force microscopy, contact angle measurements, and verified electrically using a silicon nanowire based field effect transistor sensor device. For thermo-responsive PNIPAAM, the physicochemical properties (i.e., a reversible phase transition, wettability) were induced by crossing the lower critical solution temperature (LCST) of about 32 °C. Taking advantage of this property, osteosarcomic SaoS-2 cells were cultured on PNIPAAM-modified sensors at temperatures above the LCST, and completely detached by simply cooling. Next, the weak polyelectrolyte PAA, that is sensitive towards alteration of pH and ionic strength, was used to cover the silicon nanowire based device. Here, the increase of pH will cause deprotonation of the present carboxylic (COOH) groups along the chains into negatively charged COO− moieties that repel each other and cause swelling of the polymer. Our experimental results suggest that this functionalization enhances the pH sensitivity of the SiNW FETs. Specific receptor (bio-)molecules can be added to the polymer brushes by simple click chemistry so that functionality of the brush layer can be tuned optionally. We demonstrate at the proof-of concept-level that osteosarcomic Saos-2 cells can adhere to PNIPAAM-modified FETs, and cell signals could be recorded electrically. This study presents an applicable route for the modification of highly sensitive, versatile FETs that can be applied for detection of a variety of biological analytes.
Keywords: Si NW sensors, polymer brushes
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Figure and data from 'https://www.hzdr … (Id 31055) HZDR-primary research data are used by this publication

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Publ.-Id: 30945


Two‐Dimensional Boronate Ester Covalent Organic Framework Thin Films with Large Single Crystalline Domains for Neuromorphic Memory Device

Sangwook, P.; Zhongquan, L.; Bergoi, I.; Haoyuan, Q.; Hung-Hsuan, L.; Daniel, B.; Jason, M.; Tao, Z.; Hafeesudeen, S.; Larysa, Baraban; Chang-Ki, B.; Zhikun, Z.; Ehrenfried, Z.; Andreas, F.; Thomas, H.; Ute, K.; Gianaurelio, C.; Renhao, D.; Xinliang, F.
Despite the recent progress in the synthesis of crystalline boronate ester covalent organic frameworks (BECOFs) in powder and thin‐film through solvothermal method and on‐solid‐surface synthesis, respectively, their applications in electronics, remain less explored due to the challenges in thin‐film processability and device integration associated with the control of film thickness, layer orientation, stability and crystallinity. Moreover, although the crystalline domain sizes of the powder samples can reach micrometer scale (up to ≈1.5 μm), the reported thin‐film samples have so far rather small crystalline domains up to 100 nm. Here we demonstrate a general and efficient synthesis of crystalline two‐dimensional (2D) BECOF films composed of porphyrin macrocycles and phenyl or naphthyl linkers (named as 2D BECOF‐PP or 2D BECOF‐PN) by employing a surfactant‐monolayer‐assisted interfacial synthesis (SMAIS) on the water surface. The achieved 2D BECOF‐PP is featured as free‐standing thin film with large single‐crystalline domains up to ≈60 μm2 and tunable thickness from 6 to 16 nm. A hybrid memory device composed of 2D BECOF‐PP film on silicon nanowire‐based field‐effect transistor is demonstrated as a bio‐inspired system to mimic neuronal synapses, displaying a learning–erasing–forgetting memory process.
Keywords: neuromorphic computing, emulation of synaptic plasticity, 2D materials

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Permalink: https://www.hzdr.de/publications/Publ-30944
Publ.-Id: 30944


High-field quantum disordered state in α−RuCl3: Spin flips, bound states, and multiparticle continuum

Sahasrabudhe, A.; Kaib, D. A. S.; Reschke, S.; German, R.; Koethe, T. C.; Buhot, J.; Kamenskyi, D.; Hickey, C.; Becker, P.; Tsurkan, V.; Loidl, A.; Do, S. H.; Choi, K. Y.; Grüninger, M.; Winter, S. M.; Wang, Z.; Valentí, R.; van Loosdrecht, P. H. M.
Layered α−RuCl3 has been discussed as a proximate Kitaev spin-liquid compound. Raman and terahertz spectroscopy of magnetic excitations confirms that the low-temperature antiferromagnetic ordered phase features a broad Raman continuum, together with two magnonlike excitations at 2.7 and 3.6 meV, respectively. The continuum strength is maximized as long-range order is suppressed by an external magnetic field. The state above the field-induced quantum phase transition around 7.5 T is characterized by a gapped multiparticle continuum out of which a two-particle bound state emerges, together with a well-defined single-particle excitation at lower energy. Exact diagonalization calculations demonstrate that Kitaev and off-diagonal exchange terms in the Fleury-Loudon operator give rise to a pronounced intensity of these features in the Raman spectra. Our Rapid Communication firmly establishes the partially polarized quantum disordered character of the high-field phase.

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Permalink: https://www.hzdr.de/publications/Publ-30940
Publ.-Id: 30940


Increased static dielectric constant in ZnMnO and ZnCoO thin films with bound magnetic polarons

Vegesna, S. V.; Bath, V. J.; Bürger, D.; Dellith, J.; Skorupa, I.; Schmidt, O. G.; Schmidt, H.
A novel small signal equivalent circuit model is proposed in the inversion regime of metal/(ZnO, ZnMnO, and ZnCoO) semiconductor/Si3N4 insulator/p-Si semiconductor (MSIS) structures to describe the distinctive nonlinear frequency dependent capacitance (C-F) and conductance (G-F) behaviour in the frequency range from 50 Hz to 1 MHz. We modelled the fully depleted ZnO thin films to extract the static dielectric constant (εr) of ZnO, ZnMnO, and ZnCoO. The extracted enhancement of static dielectric constant in magnetic n-type conducting ZnCoO (εr ≥ 13.0) and ZnMnO (εr ≥ 25.8) in comparison to unmagnetic ZnO (εr = 8.3–9.3) is related to the electrical polarizability of donor-type bound magnetic polarons (BMP) in the several hundred GHz range (120 GHz for CdMnTe). The formation of donor-BMP is enabled in n-type conducting, magnetic ZnO by the s-d exchange interaction between the electron spin of positively charged oxygen vacancies Vo + in the BMP center and the electron spins of substitutional Mn2+ and Co2+ ions in ZnMnO and ZnCoO, respectively. The BMP radius scales with the Bohr radius which is proportional to the static dielectric constant. Here we show how BMP overlap can be realized in magnetic n-ZnO by increasing its static dielectric constant and guide researchers in the field of transparent spintronics towards ferromagnetism in magnetic, n-ZnO.

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Permalink: https://www.hzdr.de/publications/Publ-30939
Publ.-Id: 30939


Hybrid graphene-based material promising target in laser matter interaction

Cutroneo, M.; Torrisi, L.; Badziak, J.; Rosinski, M.; Torrisi, A.; Fazio, M.; Sofer, Z. E.; Böttger, R.; Akhmadaliev, S.
Graphene oxide foils implanted with copper ions at low energy and high dose, have been proposed as hybrid graphene-based materials suitable to be laser irradiated in vacuum to produce hot plasmas. The special lattice structure of the graphene oxide foil can improve the propagation of the laser accelerated electrons inside the foil and to enhance the electron density emerging from the rear foil surface. In such conditions the electric field developed in the non-equilibrium plasma increases and consequently in the forward ion acceleration. The foils have been optimized in thickness and they were irradiated with optimized laser parameters in order to produce high energy and quasi-monoenergetic proton beams by the femtosecond laser at the Institute of Plasma Physics and Laser Microfusion in Warsaw, Poland. Gaf chromic film and silicon carbide detectors were used to monitor the plasma properties and to measure the velocity of the emitted protons and carbon ions from plasma.
Keywords: Data analysis; Lasers

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Permalink: https://www.hzdr.de/publications/Publ-30937
Publ.-Id: 30937


Radiation damage tolerance of a novel metastable refractory high entropy alloy V2.5Cr1.2WMoCo0.04

Patel, D.; Richardson, M. D.; Jim, B.; Akhmadaliev, Sh.; Goodall, R.; Gandy, A. S.
A novel multicomponent alloy, V2.5Cr1.2WMoCo0.04, produced from elements expected to favour a BCC crystal structure, and to be suitable for high temperature environments, was fabricated by arc melting and found to exhibit a multiphase dendritic microstructure with W-rich dendrites and V-Cr segregated to the inter-dendritic cores. The as-cast alloy displayed an apparent single-phase XRD pattern. Following heat treatment at 1187 °C for 500 h the alloy transformed into three different distinct phases - BCC, orthorhombic, and tetragonal in crystal structure. This attests to the BCC crystal structure observed in the as-cast state being metastable. The radiation damage response was investigated through room temperature 5 MeV Au+ ion irradiation studies. Metastable as-cast V2.5Cr1.2WMoCo0.04 shows good resistance to radiation induced damage up to 40 displacements per atom (dpa). 96 wt% of the as-cast single-phase BCC crystal structure remained intact, as exhibited by grazing incidence X-ray diffraction (GI-XRD) patterns, whilst the remainder of the alloy transformed into an additional BCC crystal structure with a similar lattice parameter. The exceptional phase stability seen here is attributed to a combination of self-healing processes and the BCC structure, rather than a high configurational entropy, as has been suggested for some of these multicomponent "High Entropy Alloy" types. The importance of the stability of metastable high entropy alloy phases for behaviour under irradiation is for the first time highlighted and the findings thus challenge the current understanding of phase stability after irradiation of systems like the HEAs.
Keywords: High entropy alloy (HEA); Structural materials; Ion implantation; Radiation damage; Metastability

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Permalink: https://www.hzdr.de/publications/Publ-30936
Publ.-Id: 30936


Diamond-blade diced trapezoidal ridge waveguides in YCOB crystal for second harmonic generation

Chen, C.; Lu, Q.; Akhmadaliev, S.; Zhou, S.
Trapezoidal ridge waveguides have been fabricated in YCOB nonlinear optical crystals by carbon ion irradiation and precise diamond-blade dicing. The diced ridges with smooth side-walls allow for near-infrared (1064 nm) light guiding with propagation losses around 1 dB/cm. Refractive index profile of a waveguide has been reconstructed in a reasonable manner. Green second harmonic light have been generated at room temperature via type I birefringent phase matching. Under the pump of continuous and pulsed lasers, conversion efficiencies for guided-wave frequency doubling can be up to ~1.10% Wsup-1 and ~6.22%, respectively.
Keywords: Trapezoidal ridge waveguides, YCOB crystal, SHG

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Permalink: https://www.hzdr.de/publications/Publ-30935
Publ.-Id: 30935


Freeze–Thaw-Promoted Fabrication of Clean and Hierarchically Structured Noble-Metal Aerogels for Electrocatalysis and Photoelectrocatalysis

Du, R.; Joswig, J.-O.; Hübner, R.; Zhou, L.; Wei, W.; Hu, Y.; Eychmüller, A.
Noble-metal aerogels (NMAs) have drawn increasing attention because of their self-supported conductive networks, high surface areas, and numerous optically/catalytically active sites, enabling their impressive performance in diverse fields. However, the fabrication methods suffer from tedious procedures, long preparation times, unavoidable impurities, and uncontrolled multiscale structures, discouraging their developments. By utilizing the self-healing properties of noble-metal aggregates, the freezing-promoted salting-out behavior, and the ice-templating effect, a freeze-thaw method is crafted that is capable of preparing various hierarchically structured noble-metal gels within one day without extra additives. In light of their cleanliness, the multi-scale structures, and combined catalytic/optical properties, the electrocatalytic and photoelectrocatalytic performance of NMAs are demonstrated, which surpasses that of commercial noble-metal catalysts.
Keywords: electrochemistry, gels, nanostructures, photocatalysis, sol-gel process

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Permalink: https://www.hzdr.de/publications/Publ-30929
Publ.-Id: 30929


Magnetic transition due to the inter-singlet spin-exchange interaction and elastic softening by the interplay of electric quadrupoles in the distorted kagome lattice antiferromagnet Tb3Ru4Al12

Ishii, I.; Mizuno, T.; Kumano, S.; Umeno, T.; Suzuki, D.; Kurata, Y.; Suzuki, T.; Gorbunov, D.; Henriques, M. S.; Andreev, A. V.
The distorted kagome lattice antiferromagnet Tb3Ru4Al12 with a hexagonal structure has the Néel temperature TN = 22 K. To clarify the 4 f -electronic state and an influence of electric quadrupoles in Tb3Ru4Al12, ultrasonic measurements on a single-crystalline sample at zero magnetic field and under fields were carried. A characteristic elastic softening of the transverse modulus C66 originating from a quadrupole interaction was found. The crystal electric field parameters were determined to reproduce C66, magnetic susceptibilities, and magnetization curves. The obtained level scheme is that the ground and first excited states are singlets, despite the existence of both the magnetic transition and the quadrupole interaction, indicating that Tb3Ru4Al12 is a curious compound. The positive sign of the quadrupole-quadrupole coupling constant for C66 indicates a ferroquadrupolar-type interaction of the electric quadrupole Oxy or O2. The anisotropic magnetic field dependencies of TN in the field along [100] and [001] were also clarified.

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Permalink: https://www.hzdr.de/publications/Publ-30927
Publ.-Id: 30927


The role of microorganisms in the bentonite barrier of high-level radioactive waste repositories

Matschiavelli, N.; Dressler, M.; Neubert, T.; Kluge, S.; Schierz, A.; Cherkouk, A.
The global production of 12,000 metric tonnes of high-level radioactive waste (HLW) every year is a big challenge with respect to its safe long-term storage. In the favored multi-barrier system, bentonite is used as a geo-technical barrier in many disposal programs worldwide. The bentonite seals the space between the canister containing the HLW and the surrounding host rock, thereby fulfilling two major tasks: 1) slow down the process of corrosion when water enters the disposal site, and 2) hinder the discharge of radionuclides into the bio-geosphere in case of a leaking canister. Due to their metabolic activity, microorganisms could influence the properties of the bentonite barrier. In order to investigate the metabolic potential of naturally occurring microorganisms, we conducted anaerobic bentonite-slurry experiments containing uncompact bentonite and a synthetic Opalinus Clay pore water solution. Within one-year incubation at 30 and 60 °C, lactate- or H2-stimulated microcosms at 30 °C showed the dominance and activity of strictly anaerobic, sulfate-reducing and spore-forming microorganisms. Consequently, hydrogen sulfide gas was generated in the respective set ups, leading to the formation of fractures and iron-sulfur precipitations. Experiments that incubated at 60 °C, showed the dominance of thermophilic bacteria, independent of the presence of substrates. The respective set ups showed no significant changes in the analyzed bio-geochemical parameters. The obtained results clearly show that indigenous microorganisms evolve in a temperature- and substrate-dependent manner. The formed metabolites can potentially affect the dissolution behavior of minerals and ions within the bentonite as well as the corrosion process of the canister material and require further investigations.
  • Open Access Logo Lecture (Conference) (Online presentation)
    EGU General Assembly 2020, 04.-08.05.2020, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-30926
Publ.-Id: 30926


Characterization of blood coagulation dynamics and oxygenation in ex‐vivo retinal vessels by fluorescence hyperspectral imaging (fHSI)

Podlipec, R.; Arsov, Z.; Koklic, T.; Strancar, J.
Blood coagulation mechanisms forming a blood clot and preventing hemorrhage have been extensively studied in the last decades. Knowing the mechanisms behind becomes very important particularly in the case of blood vessel diseases. Real‐time and accurate diagnostics accompanied by the therapy are particularly needed for example in diseases related to retinal vasculature. In our study, we employ for the first time fluorescence hyperspectral imaging (fHSI) combined with the spectral analysis algorithm concept to assess physical as well as functional information of blood coagulation in real‐time. By laser‐induced local disruption of retinal vessels to mimic blood leaking and subsequent coagulation and a proper fitting algorithm, we were able to reveal and quantify the extent of local blood coagulation through direct identification of the change of oxyhemoglobin concentration within few minutes. We confirmed and illuminated the spatio‐temporal evolution of the essential role of erythrocytes in the coagulation cascade as the suppliers of oxygenated hemoglobin. By additional optical tweezers force manipulation, we showed immediate aggregation of erythrocytes at the coagulation site. The presented fluorescence‐based imaging concept could become a valuable tool in various blood coagulation diagnostics as well as theranostic systems if coupled with the laser therapy.
Keywords: Blood coagulation, hemoglobin oxygenation, fluorescence hyperspectral imaging, optical tweezers, comparative animal models, biomedical optics and biophotonics, diagnostics

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Permalink: https://www.hzdr.de/publications/Publ-30922
Publ.-Id: 30922


Photoluminescence dynamics in few-layer InSe

Venanzi, T.; Arora, H.; Winnerl, S.; Pashkin, O.; Chava, P.; Patane, A.; Kovalyuk, Z.; Kudrynskyi, Z.; Watanabe, K.; Taniguchi, T.; Erbe, A.; Helm, M.; Schneider, H.

We study the optical properties of thin flakes of InSe encapsulated in hexagonal boron nitride. Mores pecifically, we investigate the photoluminescence (PL) emission and its dependence on sample thickness and temperature. Through the analysis of the PL line shape, we discuss the relative weights of the exciton and electron-hole contributions. Thereafter we investigate the PL dynamics. Two contributions are distinguishable at low temperature: direct band-gap electron-hole and defect-assisted recombination. The two recombination processes have lifetimes ofτ1∼8ns andτ2∼100 ns, respectively. The relative weights of the direct band-gap and defect-assisted contributions show a strong layer dependence due to the direct-to-indirect band-gap crossover. Electron-hole PL lifetime is limited by population transfer to lower-energy states and no dependence on the number of layers was observed. The lifetime of the defect-assisted recombination gets longer for thinner samples. Finally, we show that the PL lifetime decreases at high temperatures as a consequence of more efficient nonradiative recombinations.

Keywords: 2D semiconductors, time-resolved photoluminescence

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Permalink: https://www.hzdr.de/publications/Publ-30918
Publ.-Id: 30918


Photoluminescence dynamics in few-layer InSe

Venanzi, T.; Arora, H.; Winnerl, S.; Pashkin, O.; Chava, P.; Patanè, A.; Kovalyuk, Z. D.; Kudrynskyi, Z. R.; Watanabe, K.; Taniguchi, T.; Erbe, A.; Helm, M.; Schneider, H.
We study the optical properties of thin flakes of InSe encapsulated in hexagonal boron nitride. More specifically, we investigate the photoluminescence (PL) emission and its dependence on sample thickness and temperature. Through the analysis of the PL line shape, we discuss the relative weights of the exciton and electron-hole contributions. Thereafter we investigate the PL dynamics. Two contributions are distinguishable at low temperature: direct band-gap electron-hole and defect-assisted recombination. The two recombination processes have lifetimes ofτ1∼8ns andτ2∼100 ns, respectively. The relative weights of the direct band-gap and defect-assisted contributions show a strong layer dependence due to the direct-to-indirect band-gap crossover. Electron-hole PL lifetime is limited by population transfer to lower-energy states and no dependence on the number of layers was observed. The lifetime of the defect-assisted recombination gets longer for thinner samples. Finally, we show that the PL lifetime decreases at high temperatures as a consequence of more efficient nonradiative recombinations.
Keywords: 2D semiconductors, time-resolved photoluminescence

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Permalink: https://www.hzdr.de/publications/Publ-30917
Publ.-Id: 30917


Two-Pion production in the second resonance region in π−p collisions with HADES

Adamczewski-Musch, J.; Arnold, O.; Atomssa, E. T.; Behnke, C.; Belounnas, A.; Belyaev, A.; Berger-Chen, J. C.; Biernat, J.; Blanco, A.; Blume, C.; Böhmer, M.; Chernenko, S.; Chlad, L.; Chudoba, P.; Ciepał, I.; Deveaux, C.; Dittert, D.; Dreyer, J.; Epple, E.; Fabbietti, L.; Fateev, O.; Fonte, P.; Franco, C.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Golubeva, M.; Greifenhagen, R.; Guber, F.; Gumberidze, M.; Harabasz, S.; Heinz, T.; Hennino, T.; Höhne, C.; Holzmann, R.; Ierusalimov, A.; Ivashkin, A.; Kämpfer, B.; Kardan, B.; Koenig, I.; Koenig, W.; Kolb, B. W.; Korcyl, G.; Kornakov, G.; Kornas, F.; Kotte, R.; Kuboś, J.; Kugler, A.; Kunz, T.; Kurepin, A.; Kurilkin, A.; Kurilkin, P.; Ladygin, V.; Lalik, R.; Lapidus, K.; Lebedev, A.; Linev, S.; Lopes, L.; Lorenz, M.; Mahmoud, T.; Maier, L.; Malige, A.; Markert, J.; Maurus, S.; Metag, V.; Michel, J.; Mihaylov, D. M.; Mikhaylov, V.; Morozov, S.; Müntz, C.; Münzer, R.; Naumann, L.; Nowakowski, K.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Petukhov, O.; Pietraszko, J.; Prozorov, A. P.; Przygoda, W.; Ramstein, B.; Rathod, N.; Reshetin, A.; Rodriguez-Ramos, P.; Rost, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmidt-Sommerfeld, K.; Schuldes, H.; Schwab, E.; Scozzi, F.; Seck, F.; Sellheim, P.; Siebenson, J.; Silva, L.; Sing, U.; Smyrski, J.; Spataro, S.; Spies, S.; Ströbele, H.; Stroth, J.; Strzempek, P.; Sturm, C.; Svoboda, O.; Szala, M.; Tlusty, P.; Traxler, M.; Tsertos, H.; Ungethüm, C.; Vazquez-Doce, O.; Wagner, V.; Wendisch, C.; Wiebusch, M. G.; Wirth, J.; Wójcik, D.; Zanevsky, Y.; Zumbruch, P.
Pion induced reactions provide unique opportunities for an unambiguous description of baryonic resonances and their coupling channels by means of a partial wave analysis. Using the secondary pion beam at SIS18, the two pion production in the second resonance region has been investigated to unravel the role of the N(1520)32− resonance in the intermediate ρ production. Results on exclusive channels with one pion (π−p) and two pions (π+π−n, π0π−p) in the final state measured in the π−−p reaction at four different pion beam momenta (0.650, 0.685, 0.733, and 0.786 GeV/c) are presented. The excitation function of the different partial waves and Δπ, Nσ and Nρ isobar configurations is obtained, using the Bonn-Gatchina partial wave analysis. The N(1520)32− resonance is found to dominate the Nρ final state with the branching ratio BR=12.2±1.9%.

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Permalink: https://www.hzdr.de/publications/Publ-30916
Publ.-Id: 30916


Argon gas flow investigations in liquid Sodium using ultrafast electron beam X-ray computed tomography (NaFEX) - Data set

Bieberle, A.

For investigations on Argon gas bubbles in liquid Sodium ultrafast electron beam X-ray computed tomography is applied. The repository comprises imaging data obtained at

  • different heights of the test facility and
  • various gas volume rates.

The CT scanner is operated in dual-plane mode with a deflection frequency of 2 kHz for approximately 30s.

Keywords: ultrafast X-ray CT; gas-liquid two-phase flow
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-16
    DOI: 10.14278/rodare.291
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30915
Publ.-Id: 30915


Measurements to verify different concepts of multi-plane detectors for ultrafast electron beam X-ray computed tomography

Bieberle, A.

The measurements in this dataset repository contain raw signal data obtained from novel multi-plane detectors that are experimentally tested with the ultrafast electron beam X-ray CT (UFXCT) scanner at the HZDR. The CT scanner is operated with a constant deflection frequency of 2 kHz, an acceleration voltage of +150 keV and in dual-plane CT scanning mode. The voltage output signals of four multi-plane detector channels are sampled with 2 MHz and 24 bit (±5 V) using a commercial eight-channel data acquisition system (LTT24, Labortechnik Tasler GmbH). The applied reverse voltage to the avalanche photodiodes and the three deflection coil signals are recorded simultaneously. The detectors are collimated with lead and are analysed for

  • various electron beam currents,
  • various detector heights and
  • two different designs.

Keywords: ultrafast X-ray CT; scintillation detectors; multi-plane imaging
Related publications
A novel multi-plane detector concept for ultrafast … (Id 30878) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-17
    DOI: 10.14278/rodare.288
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30914
Publ.-Id: 30914


Passive Shutdown Systems for Fast Neutron Reactors

International Atomic Energy Agency; Batra, C.; Baudrand, O.; Bubelis, E.; Burgazzi, L.; Farmer, M.; Fomin, O.; Gugiu, D.; Hidemasa, Y.; Kriventsev, V.; Kuzina, J.; Kuznetsov, V.; Lamberts, D.; Lee, J.; Lüley, J.; Monti, S.; Nikitin, E.; Qvist, S.; Rineiski, A.; Schikorr, M.; Sorokin, A.; van Wert, C.; Vijayashree, R.; Vrban, B.; Yllera, J.
Designs for nuclear power plants increasingly include passive features. A major focus of the design of modern fast reactors is on inherent and passive safety. Inherent and passive safety features are especially important when active systems such as emergency shutdown systems for reactor shutdown are not functioning properly. This publication discusses the past experience in the development of such systems along with the research that is ongoing. It is a comprehensive publication which provides information on the basic design principles for passive shutdown systems and the related operational experience gathered so far, and also reviews the innovative concepts under development and the needs for research and development and qualification tests.
Keywords: Fast reactors; Passive safety measures; Nuclear reactors; Safety measures
  • Other report
    IAEA Nuclear Energy Series No. NR-T-1.16: International Atomic Energy Agency, 2020
    110 Seiten

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Permalink: https://www.hzdr.de/publications/Publ-30909
Publ.-Id: 30909


Tuning the Tailored Single-Walled Carbon Nanotubes by Highly Energetic Heavy Ions

El-Said, A. S.; Rao, S.; Akhmadaliev, S.; Facsko, S.
Carbon-based nanomaterials have attracted a lot of interest lately due to their highly promising applications. Here, we report on the modifications of single-walled carbon nanotubes (SWCNTs) induced by swift (highly energetic) heavy ions. Using scanning force microscopy and Raman spec- troscopy, we observed a dramatic change in the structure of the irradiated SWCNTs, accompanied by an increase of the adhesion force as a function of ion fluence and electronic energy loss. With increasing ion fluence the SWCNTs exhibit a partial transformation from metallic to more semicon- ducting. Moreover, at high fluence they break into segments of 10–20 nm length.
Keywords: Swift Heavy Ion, Ion Irradiation, Carbon Nanotubes

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Permalink: https://www.hzdr.de/publications/Publ-30908
Publ.-Id: 30908


Chemical manipulation of hydrogen induced high p-type and n-type conductivity in Ga₂O₃

Islam, M. M.; Liedke, M. O.; Winarski, D.; Butterling, M.; Wagner, A.; Hosemann, P.; Wang, Y.; Uberuaga, B. P.; Selim, F. A.
Advancement of optoelectronic and high-power devices is tied to the development of wide band gap materials with excellent transport properties. However, bipolar doping (n-type and p-type doping) and realizing high carrier density while maintaining good mobility have been big challenges in wide band gap materials. Here P-type and n-type conductivity was introduced in β-Ga₂O₃, an ultra-wide band gap oxide, by controlling hydrogen incorporation in the lattice without further doping. Hydrogen induced a 9-order of magnitude increase of n-type conductivity with donor ionization energy of 20 meV and resistivity of 10⁻⁴ Ωcm. The conductivity was switched to p-type with acceptor ionization energy of 42 meV by altering hydrogen incorporation in the lattice. Density functional theory calculations were used to examine hydrogen location in the Ga₂O₃ lattice and identified a new donor type as the source of this remarkable n-type conductivity. Positron annihilation spectroscopy measurements confirm this finding and the interpretation of the experimental results. This work illustrates a new approach that allows a tunable and reversible way of modifying the conductivity of semiconductors and it is expected to have profound implications on semiconductor field. At the same time, it demonstrates for the first time p-type and remarkable n-type conductivity in Ga₂O₃ which should usher in the development of Ga₂O₃ devices and advance optoelectronics and high-power devices.
Keywords: optoelectronics high-power wide band gap transport bipolar doping β-Ga₂O₃ semiconductors

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Permalink: https://www.hzdr.de/publications/Publ-30907
Publ.-Id: 30907


Phase-resolved Higgs response in superconducting cuprates

Chu, H.; Kim, M.-J.; Katsumi, K.; Kovalev, S.; Dawson, R. D.; Schwarz, L.; Yoshikawa, N.; Kim, G.; Putzky, D.; Li, Z. Z.; Raffy, H.; Germanskiy, S.; Deinert, J.-C.; Awari, N.; Ilyakov, I.; Green, B. W.; Chen, M.; Bawatna, M.; Christiani, G.; Logvenov, G.; Gallais, Y.; Boris, A. V.; Keimer, B.; Schnyder, A.; Manske, D.; Gensch, M.; Wang, Z.; Shimano, R.; Kaiser, S.

In high energy physics, the Higgs field couples to gauge bosons and fermions and gives mass to their elementary excitations. Experimentally, such couplings can be verified from the decay product of the Higgs boson, the scalar (amplitude) excitation of the Higgs field. In superconductors, Cooper pairs bear a certain analogy to the Higgs field. Coulomb interactions between the Cooper pairs give mass to the electromagnetic field, which leads to the Meissner effect. Additional coupling with other types of interactions or collective modes is foreseeable, and even highly probable for high-Tc superconductors, where multiple degrees of freedom are intertwined. The superconducting Higgs mode may reveal such couplings spectroscopically and uncover interactions directly relevant to Cooper pairing. To this end, we investigate the Higgs mode of several cuprate thin films using phase-resolved terahertz third harmonic generation (THG) to. In addition to the heavily damped Higgs mode itself, we observe a universal jump in the phase of the driven Higgs oscillation as well as a non-vanishing THG above Tc. These findings indicate coupling of the Higgs mode to other collective modes and a nonzero pairing amplitude above Tc. Our study demonstrates a new approach for investigating unconventional superconductivity. We foresee a fruitful future for phase-resolved spectroscopy in various superconducting systems.

Keywords: Superconductors; terahertz; Higgs; Nonlinear dynamics; ultrafast
Related publications
Phase-resolved Higgs response in superconducting cuprates (Id 29647) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-15
    DOI: 10.14278/rodare.276
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30902
Publ.-Id: 30902


Role of Hydrogen-Related Defects in Photocatalytic Activity of ZnO Films Grown by Atomic Layer Deposition

Peter, R.; Salamon, K.; Omerzu, A.; Grenzer, J.; Badovinac, I. J.; Saric, I.; Petravic, M.
The photocatalytic activity of ZnO films, grown by atomic layer deposition on sapphire, was investigated for different amounts of residual hydrogen incorporated unintentionally into the matrix during the crystal growth. A close correlation was found between the level of incorporated hydrogen ; the rate of photocatalytic degradation of methylene blue on ZnO films. The rate of degradation is consistent with predominantly zero-order reaction kinetics. An enhanced photocatalytic activity, observed for films of predominantly (001)-oriented grains ; low concentration of residual hydrogen, is explained by the reduced number of hydrogen-related defects responsible for recombination of charge carriers in combination with the preferential adsorption of water on polar (001) surfaces of ZnO grains.
Keywords: atomic layer deposition; photocatalytic degradation

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Permalink: https://www.hzdr.de/publications/Publ-30899
Publ.-Id: 30899


Formation of Defects in Two-Dimensional MoS2 in the Transmission Electron Microscope at Electron Energies below the Knock-on Threshold: The Role of Electronic Excitations

Kretschmer, S.; Lehnert, T.; Kaiser, U.; Krasheninnikov, A.
Production of defects under electron irradiation in a transmission electron microscope (TEM) due to inelastic effects has been reported for various materials, but the microscopic mechanism of damage development in periodic solids through this channel is not fully understood. We employ non-adiabatic Ehrenfest, along with constrained density functional theory molecular dynamics, and simulate defect production in two-dimensional MoS2 under electron beam. We show that when excitations are present in the electronic system, formation of vacancies through ballistic energy transfer is possible at electron energies which are much lower than the knock-on threshold for the ground state. We further carry out TEM experiments on single layers of MoS2 at electron voltages in the range of 20−80 kV and demonstrate that indeed there is an additional channel for defect production. The mechanism involving a combination of the knock-on damage and electronic excitations we propose is relevant to other bulk and nanostructured semiconducting materials.
Keywords: Two-dimensional materials, transition-metal dichalcogenides, high-resolution transmission electron microscopy, defects

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  • Secondary publication expected from 20.03.2021

Permalink: https://www.hzdr.de/publications/Publ-30894
Publ.-Id: 30894


Anomalous Lattice Softening Near a Quantum Critical Point in a Transverse Ising Magnet

Matsuura, K.; Pham, T. C.; Zherlitsyn, S.; Wosnitza, J.; Abe, N.; Arima, T.
We have investigated the elastic response of a transverse Ising magnet CoNb2O6 by means of ultrasound velocity measurement. A huge elastic anomaly in the C66 mode is observed near a quantum critical Point when sweeping a magnetic field perpendicular to the Ising axis. This anomaly appears to become critical only for the Faraday configuration (field parallel to the sound propagation direction) but is much less pronounced for the Voigt geometry (field perpendicular to the sound propagation direction). We propose that the relativistic spin-orbit interaction plays a crucial role in the quantum critical regime resulting in the elastic anomaly, which is enhanced by quantum fluctuations.

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Permalink: https://www.hzdr.de/publications/Publ-30889
Publ.-Id: 30889


Single Photon Emission Computed Tomography Tracer

Pietzsch, H.-J.; Mamat, C.; Müller, C.; Schibli, R.
Single photon emission computed tomography (SPECT) is the state-of-the-art imaging modality in nuclear medicine despite the fact that only a few new SPECT tracers have become available in the past 20 years.
Critical for the future success of SPECT is the design of new and specific tracers for the detection, localization, and staging of a disease and for monitoring therapy. The utility of SPECT imaging to address oncologic questions is dependent on radiotracers that ideally exhibit excellent tissue penetration, high affinity to the tumor-associated target structure, specific uptake and retention in the malignant lesions, and rapid clearance from non-targeted tissues and organs. In general, a target-specific SPECT radiopharmaceutical can be divided into two main parts: a targeting biomolecule (e.g., peptide, antibody fragment) and a γ-radiation-emitting radionuclide (e.g., 99mTc, 123I). If radiometals are used as the radiation source, a bifunctional chelator is needed to link the radioisotope to the targeting entity. In a rational SPECT tracer design, these single components have to be critically evaluated in order to achieve a balance among the demands for adequate target binding, and a rapid clearance of the radiotracer. The focus of this chapter is to depict recent developments of tumor-targeted SPECT radiotracers for imaging of cancer diseases.
Possibilities for optimization of tracer design and potential causes for design failure are discussed and highlighted with selected examples.
  • Book chapter
    Schober, Otmar, Kiessling, Fabian, Debus, Jürgen: Molecular Imaging in Oncology, Switzerland: SpringerNature, 2020, 978-3-030-42617-0
    DOI: 10.1007/978-3-030-42618-7

Permalink: https://www.hzdr.de/publications/Publ-30888
Publ.-Id: 30888


Wieviel 'normales' Risiko birgt COVID in sich?

Spiegelhalter, D.; Steinbach, P.
Eine Übersetzung des Artikels "How much ‘normal’ risk does Covid represent?" von David Spiegelhalter, der am 21. März 2020 auf https://medium.com/wintoncentre/how-much-normal-risk-does-covid-represent-4539118e1196 erschien. Sir David John Spiegelhalter ist britischer Statistiker und Winton Professor für das öffentliche Verständnis von Risiko an der the Universität Cambridge. Er ist Fellow am Churchill College, Cambridge.
Keywords: COVID19; Corona; Risk; Statistics; Mortality

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Permalink: https://www.hzdr.de/publications/Publ-30887
Publ.-Id: 30887


Nonlinear Charge Transport in InGaAs Nanowires at Terahertz Frequencies

Rana, R.; Balaghi, L.; Fotev, I.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, O.
We probe the electron transport properties in the shell of GaAs/In0.2Ga0.8As core/shell nanowires at high electric fields using optical pump/THz probe spectroscopy with broadband THz pulses and peak electric fields up to 0.6 MV/cm. The plasmon resonance of the photoexcited charge carriers exhibits a systematic redshift and a suppression of its spectral weight for THz driving fields exceeding 0.4 MV/cm. This behavior is attributed to the intervalley electron scattering that results in the doubling of the average electron effective mass. Correspondingly, the electron mobility at the highest fields drops to about half of the original value. We demonstrate that the increase of the effective mass is nonuniform along the nanowires and takes place mainly in their middle part, leading to a spatially inhomogeneous carrier response. Our results quantify the nonlinear transport regime in GaAs-based nanowires and show their high potential for development of nanodevices operating at THz frequencies.
Keywords: Terahertz (THz); Nanowire; Localized Plasmon; Intervalley Scattering

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Permalink: https://www.hzdr.de/publications/Publ-30886
Publ.-Id: 30886


Numerical framework for a morphology adaptive multi-field two-fuid model in OpenFOAM

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

A solver for multiphase flows based on the incompressible Eulerian multi-field two-fluid model for the OpenFOAM release of The OpenFOAM Foundation for numerical simulations of multiphase flows with morphology changes and resolved interfaces.

Features:

  • morphology adaptive modeling framework for modelling of dispersed and resolved interfaces based on Eulerian multi-field two-fluid model
  • compact interpolation method according to Cubero et al. (Comput Chem Eng, 2014, Vol. 62, 96-107), including virtual mass
  • numerical drag according to Strubelj and Tiselj (Int J Numer Methods Eng, 2011, Vol. 85, 575-590) to describe resolved interfaces in a volume-of-fluid like manner
  • strong phase coupling resolved by partial elimination algorithm
  • selected test cases:
    • a two-dimensional gas bubble, rising in a liquid, which is laden with micro gas bubbles, and
    • a two-dimensional stagnant stratification of water and oil, sharing a large-scale interface

Keywords: OpenFOAM, C++, CFD, Finite volume method, Multiphase flow, Multi-field two-fluid model, Eulerian-Eulerian model, Momentum interpolation, Partial elimination algorithm
  • Software in the HZDR data repository RODARE
    Publication date: 2020-04-06
    DOI: 10.14278/rodare.286
    License: GPL-3.0

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Permalink: https://www.hzdr.de/publications/Publ-30885
Publ.-Id: 30885


Establishment and Characterisation of Heterotopic Patient-Derived Xenografts for Glioblastoma

Meneceur, S.; Annett, L.; Matthias, M.; Sandra, H.; Steffen, L.; Rebecca, B.; Dietmar, K.; Gabriele, S.; Achim, T.; Baumann, M.; Krause, M.; Cläre, V. N.
Glioblastoma is an aggressive brain tumour with a patient median survival of approximately 14 months. The development of innovative treatment strategies to increase the life span and quality of life of patients is hence essential. This requires the use of appropriate glioblastoma models for preclinical testing, which faithfully reflect human cancers. The aim of this study was to establish glioblastoma patient-derived xenografts (PDXs) by heterotopic transplantation of tumour pieces in the axillae of NMRI nude mice. Ten out of 22 patients’ samples gave rise to tumours in mice. Their human origin was confirmed by microsatellite analyses, though minor changes were observed. The glioblastoma nature of the PDXs was corroborated by pathological evaluation. Latency times spanned from 48.5 to 370.5 days in the first generation. Growth curve analyses revealed an increase in the growth rate with increasing passages. The methylation status of the MGMT promoter in the primary material was maintained in the PDXs. However, a trend towards a more methylated pattern could be found. A correlation was observed between the take in mice and the proportion of Sox2+ cells (r = 0.49, p = 0.016) and nestin+ cells (r = 0.55, p = 0.007). Our results show that many PDXs maintain key features of the patients’ samples they derive from. They could thus be used as preclinical models to test new therapies and biomarkers.
Keywords: patient-derived xenografts; preclinical models; cancer stem cell markers; glioblastoma; growth data

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Permalink: https://www.hzdr.de/publications/Publ-30881
Publ.-Id: 30881


Photocatalytic biocidal effect of copper doped TiO2 nanotube coated surfaces under laminar flow, illuminated with UVA light on Legionella pneumophila

Podlipec, R.

Raw datasets and images performed on the Helium Ion Microscope for the published study with the title Photocatalytic biocidal effect of copper doped TiO2 nanotube coated surfaces under laminar flow, illuminated with UVA light on Legionella pneumophila.


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Photocatalytic biocidal effect of copper doped TiO2 … (Id 30539) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-01-17
    DOI: 10.14278/rodare.284
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-30880
Publ.-Id: 30880


Disturbance-Promoted Unconventional and Rapid Fabrication of Self-Healable Noble Metal Gels for (Photo-)Electrocatalysis

Du, R.; Joswig, J.-O.; Fan, X.; Hübner, R.; Spittel, D.; Hu, Y.; Eychmüller, A.
As an emerging class of porous materials, noble metal aerogels (NMAs) have drawn tremendous attention and displayed unprecedented potential in diverse fields. However, the development of NMAs is impeded by the fabrication methods because of their time- and cost-consuming procedures, limited generality, and elusive understanding of the formation mechanisms. Here, by revealing the self-healing behavior of noble metal gels and applying it in the gelation process at a disturbing environment, an unconventional and conceptually new strategy, i.e., a disturbance-promoted gelation method, is developed by introducing an external force field. It overcomes the diffusion limitation in the gelation process, thus producing monolithic gels within 1–10 min at room temperature, 2–4 orders of magnitude faster than for most reported methods. Moreover, versatile NMAs are acquired by using this method, and their superior (photo-)electrocatalytic properties are demonstrated for the first time in light of combined catalytic and optic properties.

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Permalink: https://www.hzdr.de/publications/Publ-30879
Publ.-Id: 30879


data of " A detailed EP and PAS study of porous structure of OSG films with various ratios of methyl terminal and ethylene bridging groups"

Rasadujjaman, M.; Wang, Y.; Zhang, L.; Naumov, S.; Elsherif, A. G. A.; Liedke, M. O.; Koehler, N.; Redzheb, M.; Vishnevskiy, A. S.; Seregin, D. S.; Wu, Y.; Zhang, J. L.; Wagner, A.; Vorotilov, K. A.; Schulz, S. E.; Baklanov, M. R.

Raw data of "A detailed EP and PAS study of porous structure of OSG films with various ratios of methyl terminal and ethylene bridging groups"- The positron part only.


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A detailed EP and PAS study of porous structure of OSG … (Id 30874) has used this publication of HZDR-primary research data
  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-02
    DOI: 10.14278/rodare.280

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Permalink: https://www.hzdr.de/publications/Publ-30876
Publ.-Id: 30876


Adjuvant drug-assisted bone healing: advances and challenges in drug delivery approaches

Rothe, R.; Hauser, S.; Neuber, C.; Laube, M.; Schulze, S.; Rammelt, S.; Pietzsch, J.
Bone defects of critical size after compound fractures, infections, or tumor resections are a challenge in treatment. Particularly, this applies to bone defects in patients with impaired bone healing due to frequently occurring metabolic diseases (above all diabetes mellitus and osteoporosis), chronic inflammation, and cancer. Adjuvant therapeutic agents such as recombinant growth factors, lipid mediators, antibiotics, antiphlogistics, and proangiogenics as well as other promising anti-resorptive and anabolic molecules contribute to improving bone healing in these disorders, especially when they are released in a targeted and controlled manner during crucial bone healing phases. In this regard, the development of smart biocompatible and biostable polymers such as implant coatings, scaffolds, or particle-based materials for drug release is crucial. Innovative chemical, physico- and biochemical approaches for controlled tailor-made degradation or the stimulus-responsive release of substances from these materials, and more, are advantageous. In this review, we discuss current developments, progress, but also pitfalls and setbacks of such approaches in supporting or controlling bone healing. The focus is on the critical evaluation of recent preclinical studies investigating different carrier systems, dual- or co-delivery systems as well as triggered- or targeted delivery systems for release of a panoply of drugs.
Keywords: Angiogenesis; bioactive scaffolds; bone grafting; critical-size bone defects; drugs; inflammation; tissue regeneration; osteoconduction; osteoinduction; osseointegration

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Permalink: https://www.hzdr.de/publications/Publ-30872
Publ.-Id: 30872


Formation of PuSiO4 under hydrothermal conditions

Estevenon, P.; Welcomme, E.; Tamain, C.; Jouan, G.; Szenknect, S.; Mesbah, A.; Poinssot, C.; Moisy, P.; Dacheux, N.
Attempts to synthesize plutonium (IV) silicate, PuSiO4, have been performed on the basis of the results recently reported in the literature for CeSiO4, ThSiO4 and USiO4 under hydrothermal conditions. Although it was not possible to prepare PuSiO4 by applying the conditions reported for thorium and uranium, an efficient way of PuSiO4 synthesis was established following those optimized for CeSiO4 system. This method was based on the slow oxidation of plutonium (III) silicate reactants under hydrothermal conditions at 150°C in hydrochloric acid (pH = 3 – 4). This result shed a new light on the potential behavior of plutonium in reductive environment, highlighted the representativeness of cerium surrogates to study plutonium in such conditions and brought some important pieces of information on plutonium chemistry in silicate solutions.
Related publications
Formation of PuSiO4 under hydrothermal conditions (Id 31040) HZDR-primary research data are used by this publication

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Publ.-Id: 30869


Unveiling reductant chemistry in fabricating noble metal aerogels for superior oxygen evolution and ethanol oxidation

Du, R.; Wang, J.; Wang, Y.; Hübner, R.; Fan, X.; Senkovska, I.; Hu, Y.; Kaskel, S.; Eychmüller, A.
Amongst various porous materials, noble metal aerogels attract wide attention due to their concurrently featured catalytic properties and large surface areas. However, insufficient understanding and investigation of key factors (e.g. reductants and ligands) in the fabrication process limits on-target design, impeding material diversity and available applications. Herein, unveiling multiple roles of reductants, we develop an efficient method, i.e. the excessive-reductant-directed gelation strategy. It enables to integrate ligand chemistry for creating gold aerogels with a record-high specific surface area (59.8 m2 g−1), and to expand the composition to all common noble metals. Moreover, we demonstrate impressive electrocatalytic performance of these aerogels for the ethanol oxidation and oxygen evolution reaction, and discover an unconventional organic-ligand-enhancing effect. The present work not only enriches the composition and structural diversity of noble metal aerogels, but also opens up new dimensions for devising efficient electrocatalysts for broad material systems.

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Permalink: https://www.hzdr.de/publications/Publ-30866
Publ.-Id: 30866


Development of a radiofluorinated adenosine A2B receptor antagonist as potential ligand for PET imaging

Lindemann, M.; Moldovan, R.-P.; Hinz, S.; Deuther-Conrad, W.; Gündel, D.; Dukic-Stefanovic, S.; Toussaint, M.; Teodoro, R.; Juhl, C.; Steinbach, J.; Brust, P.; Müller, C. E.; Wenzel, B.
The adenosine A2B receptor has been proposed as a novel therapeutic target in cancer, as for example, its expression is drastically elevated in several tumors and cancer cells. Noninvasive molecular imaging by using positron emission tomography (PET) would allow the in vivo quantification of this receptor in pathological processes and most likely enable the identification and clinical monitoring of respective cancer therapies. On the basis of a bicyclic pyridopyrimidine-2,4-dione core structure, the new adenosine A2B receptor ligand 9 was synthesized containing a 2-fluoropyridine moiety suitable for labeling with the short-lived PET radionuclide fluorine-18. Compound 9 showed a high binding affinity for the human A2B receptor (Ki(A2B) = 2.51 nM) along with high selectivities versus the A1, A2A, and A3 receptor subtypes. Therefore, it was radiofluorinated via nucleophilic aromatic substitution of the corresponding nitro precursor using [18F]F-/K2.2.2./K2CO3 in DMSO at 120 °C. Metabolism studies of [18F]9 in mice revealed about 60 % of intact radiotracer in plasma at 30 minutes p.i. A preliminary PET study in healthy mice showed an overall biodistribution of [18F]9 corresponding to the known ubiquitous but low expression of the A2B receptor. Consequently, [18F]9 represents a novel PET radiotracer with high affinity and selectivity toward the adenosine A2B receptor and a suitable in vivo profile. Subsequent studies are envisaged to investigate the applicability of [18F]9 to detect alterations in the receptor density in certain cancer-related disease models.
Keywords: A2B receptor; adenosine, PET; fluorine-18; metabolism; radiofluorination

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Publ.-Id: 30865


Microstructure and Nanoscopic Porosity in Black Pd Films

Melikhova, O.; Čížek, J.; Hruška, P.; Lukáč, F.; Novotný, M.; More-Chevalier, J.; Fitl, P.; Liedke, M. O.; Butterling, M.; Wagner, A.
In the present work the microstructure of a black Pd film prepared by thermal evaporation and a glossy Pd film deposited by magnetron sputtering was compared. While the glossy Pd film exhibits typical polycrystalline structure with column-like grains, the black Pd film has fractal-like porous structure. Positron annihilation spectroscopy revealed that positronium is formed in nanoscopic cavities of the black Pd film. In conventional metals positronium does not form due to screening by conduction electrons. However, in porous metals containing nanoscopic porosity a thermalized positron may pick an electron on inner surface of a pore and escape into a cavity forming positronium. The average size of nanoscopic pores in the black Pd film was determined from the lifetime of long-lived ortho-positronium component.
Keywords: thin film ; positron annihilation ; porosity ; black metal; black gold; magnetron sputtering

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Publ.-Id: 30864


Defects in Thin Layers of High Entropy Alloy HfNbTaTiZr

Lukáč, F.; Hruška, P.; Cichoň, S.; Vlasák, T.; Cížek, J.; Kmječ, T.; Melikhova, O.; Butterling, M.; Liedke, M. O.; Wagner, A.
High entropy alloys represent a new type of materials with unique combination of physical properties originating due to occurrence of single phase solid solution of numerous elements. Preparation of high entropy alloys films with nanosized grains promises increased effective surface and high intergranular diffusion of elements. In the present work HfNbTaTiZr films were deposited by magnetron sputtering from single phase HfNbTaTiZr target prepared by spark plasma sintering. Chemical composition of high entropy alloys thin films prepared this way was enriched in Ti and depleted in Zr and Nb. Very fine microstructure of the film was documented and defect distribution was found to be non-uniform with depth.
Keywords: high entropy alloy; thin film ; positron annihilation; nano grain

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Permalink: https://www.hzdr.de/publications/Publ-30863
Publ.-Id: 30863


Positron Structural Analysis of ScN Films Deposited on MgO Substrate

More-Chevalier, J.; Horák, L.; Cichoň, S.; Hruška, P.; Čížek, J.; Liedke, M. O.; Butterling, M.; Wagner, A.; Bulíř, J.; Hubík, P.; Gedeonová, Z.; Lančok, J.
Scandium nitride (ScN) is a semiconductor with a rocksalt-structure that has attracted attention for its potential applications in thermoelectric energy conversion devices, as a semiconducting component in epitaxial metal/semiconductor superlattices. Two ScN films of 118 nm and 950 nm thicknesses were deposited at the same conditions on MgO (001) substrate by reactive magnetron sputtering. Poly-orientation of films was observed with first an epitaxial growth on MgO and then a change in the orientation growth due to the decrease of the adatom mobility during the film growth. Positron lifetime measurements showed a high concentration of nitrogen vacancies in both films with a slightly higher concentration for the thicker ScN film. Presence of nitrogen vacancies explains the values of direct band gaps of 2:53+-0:01 eV, and 2:56+-0:01 eV which has been measured on ScN films of 118 nm and 950 nm thicknesses, respectively.
Keywords: positron annihilation; semiconductor ; ScN; band gap; defects; vacancies

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Permalink: https://www.hzdr.de/publications/Publ-30862
Publ.-Id: 30862


Interplay between MycN and c-Myc regulates radioresistance and cancer stem cell phenotype in neuroblastoma upon glutamine deprivation

Le, G. M.; Mukha, A.; Püschel, J.; Valli, E.; Kamili, A.; Vittorio, O.; Dubrovska, A.; Kavallaris, M.
Targeting glutamine metabolism has emerged as a potential therapeutic strategy for Myc overexpressing cancer cells. Myc proteins contribute to an aggressive neuroblastoma phenotype. Radiotherapy is one of the treatment modalities for high-risk neuroblastoma patients. Herein, we investigated the effect of glutamine deprivation in combination with irradiation in neuroblastoma cells representative of high-risk disease and studied the role of Myc member interplay in regulating neuroblastoma cell radioresistance. Methods: Cell proliferation and viability assays were used to establish the effect of glutamine deprivation in neuroblastoma cells expressing c-Myc or MycN. Gene silencing and overexpression were used to modulate the expression of Myc genes to determine their role in neuroblastoma radioresistance. qPCR and western blot investigated interplay between expression of Myc members. The impact of glutamine deprivation on cell response following irradiation was explored using a radiobiological 3D colony assay. DNA repair gene pathways as well as CSC-related genes were studied by qPCR array. Reactive Oxygen Species (ROS) and glutathione (GSH) levels were detected by fluorescence and luminescence probes respectively. Cancer-stem cell (CSC) properties were investigated by sphere-forming assay and flow cytometry to quantify CSC markers. Expression of DNA repair genes and CSC-related genes was analysed by mining publicly available patient datasets. Results: Our results showed that glutamine deprivation decreased neuroblastoma cell proliferation and viability and modulated Myc member expression. We then demonstrated for the first time that combined glutamine deprivation with irradiation led to a selective radioresistance of MYCN-amplified neuroblastoma cells. By exploring the underlying mechanism of neuroblastoma radioresistance properties, our results highlight interplay between c-Myc and MycN expression suggesting compensatory mechanisms in Myc proteins leading to radioresistance in MYCN-amplified cells. This result was associated with the ability of MYCN-amplified cells to dysregulate the DNA repair gene pathway, maintain GSH and ROS levels and to increase the CSC-like population and properties. Conversely, glutamine deprivation led to radiosensitization in non-MYCN amplified cell lines through a disruption of the cell redox balance and a trend to decrease in the CSC-like populations. Mining publicly available gene expression dataset obtained from pediatric neuroblastoma patients, we identified a correlation pattern between Myc members and CSC-related genes as well as a specific group of DNA repair gene pathways. Conclusions: This study demonstrated that MycN and c-Myc tightly cooperate in regulation of the neuroblastoma CSC phenotypes and radioresistance upon glutamine deprivation. Pharmacologically, strategies targeting glutamine metabolism may prove beneficial in Myc-driven tumors. Consideration of MycN/c-Myc status in selecting neuroblastoma patients for glutamine metabolism treatment will be important to avoid potential radioresistance.
Keywords: Myc members, glutamine metabolism, neuroblastoma, radioresistance, Cancer-Stem Cells

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Publ.-Id: 30860


Enhanced room temperature ferromagnetism in MoS2 by N plasma treatment

Wang, B.; Zhang, D.; Wang, H.; Zhao, H.; Liu, R.; Li, Q.; Zhou, S.; Du, J.; Xu, Q.
The introduction of ferromagnetism in MoS2 is important for its applications in semiconductor spintronics. MoS2 powders were synthesized by hydrothermal method, followed by the N plasma treatment at room temperature. Weak ferromagnetism with saturated ferromagnetic magnetization of 0.64 memu/g has been observed in the as-synthesized MoS2 at room temperature, which is significant enhanced to 3.67 memu/g after the N plasma treatment for the proper duration. X-ray photoelectron spectroscopy demonstrates the adsorption of N, and higher valence state of Mo than +4 due to the bonding with N after the N plasma treatment. First principle calculation has been performed to disclose the possible origin of ferromagnetism. One chemical adsorbed N ion on S ion may form conjugated π bonds with adjacent two Mo ions to have a total magnetic moment of 0.75 μB, contributing to the enhanced ferromagnetism.

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Publ.-Id: 30859


3D-Ising critical behavior in antiperovskite-type ferromagneticlike Mn3GaN

Yuan, Y.; Liu, Y.; Xu, C.; Kang, J.; Wang, W.; Wang, Q.; Song, B.; Zhou, S.; Wang, X.
In this work, a systematic investigation on magnetic critical behavior is performed for the first time on an antiperovskite-type Mn3GaN, which is prepared by intentionally modifying stoichiometry. According to the XRD results, the antiperovskite structure is well preserved, even though all lattice parameters shrink upon reducing Ga and N content down to 60%. The sample exhibits a ferromagneticlike feature with a Curie temperature (T_C) of 394 K rather than frustrated behavior in stoichiometric Mn3GaN. Most importantly, the modified Arrott plots, Kouvel–Fisher plots, as well as critical isotherm method self-consistently co-confirm the critical exponents of β = 0.33, γ = 1.23, and δ = 4.7, unambiguously indicating that the critical behavior follows the 3D-Ising model around T_C.

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Permalink: https://www.hzdr.de/publications/Publ-30858
Publ.-Id: 30858


An Infrared Transmission Study of Ge:Mn Thick Films Prepared by Ion Implantation and Post-Annealing

Obied, L. H.; Roorda, S.; Prucnal, S.; Zhou, S.; Crandles, D. A.
Ge:Mn thick films (t$\approx 3\mu$m) with low average Mn concentration (< 0.3 %) were prepared by ion implantation at 77K followed by either conventional or flash lamp annealing. The films were characterized by Xray diffraction, Secondary Ion Mass Spectrometry, magnetometry and infrared transmission (100-6500 cm^{-1}). Post-annealing at high enough temperature recrystallizes the amorphous Ge:Mn films without significant migration of Mn to the surface while solid phase epitaxy does not occur, resulting in polycrystalline films. Annealing causes an estimated 50-80\% of the implanted Mn to migrate to Mn-rich clusters or form Mn_5Ge_3 while the remainder enters the Ge lattice substitutionally creating free holes. Evidence for free holes comes from structure in the mid-infrared absorption coefficient that is similar to previous observations in p-type Ge. The data suggest that the maximum solubility of Mn in the Ge crystalline lattice has an upper limit of <0.08%.

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Permalink: https://www.hzdr.de/publications/Publ-30857
Publ.-Id: 30857


Size Dependence of Lattice Parameter and Electronic Structure in CeO2 Nanoparticles

Prieur, D.; Bonani, W.; Popa, K.; Walter, O.; Kriegsman, K.; Engelhard, M.; Guo, X.; Eloirdi, R.; Gouder, T.; Beck, A.; Vitova, T.; Scheinost, A.; Kvashnina, K.; Martin, P.
Intrinsic properties of a compound (e.g. electronic structure, crystallographic structure, optical and magnetic properties) define notably its chemical and physical behavior. In the case of nanomaterials, these fundamental properties depend on the occurrence of quantum mechanical size effects and on the considerable increase of the surface to bulk ratio.
Here, we explore the size-dependence of both crystal and electronic properties of CeO2 nanoparticles (NPs) with different sizes by state-of-the art spectroscopic techniques. XRD, XPS and HERFD-XANES demonstrate that the as-synthesized NPs crystallize in the fluorite structure and they are predominantly composed of CeIV ions. The strong dependence of the lattice parameter with the NPs size was attributed to the presence of adsorbed species at the NPs surface thanks to FTIR and TGA measurements. In addition, the size-dependence of the t2g states in the Ce LIII XANES spectra was experimentally observed by HERFD-XANES and confirmed by theoretical calculations.
Keywords: Lanthanide, CeO2, HEFRD-XANES, Electronic Structure

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Publ.-Id: 30856


Quadrupolar response from the crystal electric field level scheme consisting of only Kramers doublets in DyNiAl

Suzuki, D.; Ishii, I.; Kumano, S.; Umeno, T.; Andreev, A. V.; Gorbunov, D.; Suzuki, T.
The rare earth compound DyNiAl shows ferromagnetic and antiferromagnetic phase transitions at TC = 30 K and T1 = 15 K, respectively. Elastic properties of DyNiAl have been investigated by means of ultrasonic spectroscopy. The transverse elastic modulus C44 shows an elastic softening below 60 K and exhibits a bend at TC. The softening continues down to T1 and an elastic hardening is observed below T1. The softening above TC is well reproduced by Curie-Weiss-type equation including a quadrupole interaction. A quadrupole-quadrupole coupling constant obtained from C44 is negative, suggesting an antiferroquadrupolar-type interaction between quadrupoles Oyz or Ozx.
  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011165
    DOI: 10.7566/JPSCP.30.011165

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Publ.-Id: 30855


Magnetocaloric Effect in Alloy Fe49Rh51in Pulsed Magnetic Fields up to 50 T

Kamantsev, A. P.; Amirov, A. A.; Koshkid'Ko, Y. S.; Salazar Mejia, C.; Mashirov, A. V.; Aliev, A. M.; Koledov, V. V.; Shavrov, V. G.
Magnetocaloric effect (MCE) in pulsed magnetic fields up to 50 T was directly studied in alloyFe49Rh51. An inverse MCE ΔT ≈ –8 K is observed at different initial temperatures around the metamagneticphase transition upon field rising to 20 T; further growth of the field to 50 T leads to a decrease in the absoluteadiabatic temperature change by nearly 1 K, which is due to the direct MCE and proves that the whole sampleundergoes a transition into the ferromagnetic phase. Upon the field decrease, the maximal absolute value ofthe adiabatic temperature change of |ΔT| = 9.8 K was revealed at 6 T when the initial temperature is 310 K.

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Publ.-Id: 30854


Local Structure in U(IV) and U(V) Environments: The Case of U3O7

Leinders, G.; Bes, R.; Kvashnina, K.; Verwerft, M.
A comprehensive analysis of X-ray absorption data obtained at theUL3-edge for a systematic series of single-valence (UO2, KUO3,UO3) and mixed-valence uranium compounds (U4O9,U3O7,U3O8) is reported. High-energyresolutionfluorescence detection (HERFD) X-ray absorption near-edge spectros-copy (XANES) and extended X-ray absorptionfine structure (EXAFS) methodswere applied to evaluate U(IV) and U(V) environments, and in particular, toinvestigate the U3O7local structure. Wefind that the valence state distribution inmixed-valence uranium compounds cannot be confidently quantified from aprincipal component analysis of the UL3-edge XANES data. The spectral linebroadening, even when applying the HERFD-XANES method, is sensibly higher(∼3.9 eV) than the observed chemical shifts (∼2.4 eV). Additionally, the white line shape and position are affected not only by thechemical state, but also by crystalfield effects, which appear well-resolved in KUO3. The EXAFS of a phase-pure U3O7sample wasassessed based on an average representation of the expanded U60O140structure. Interatomic U−O distances are found mainly tooccur at 2.18 (2), 2.33 (1), and 3.33 (5) Å, and can be seen to correspond to the spatial arrangement of cuboctahedral oxygenclusters. The interatomic distances derived from the EXAFS investigation support a mixed U(IV)−U(V) valence character in U3O7

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Publ.-Id: 30852


Topological Hall effect in single thick SrRuO3 layers induced by defect engineering

Wang, C.; Chang, C.-H.; Herklotz, A.; Chen, C.; Ganss, F.; Kentsch, U.; Chen, D.; Gao, X.; Zeng, Y.-J.; Hellwig, O.; Helm, M.; Gemming, S.; Chu, Y.-H.; Zhou, S.
The topological Hall effect (THE) has been discovered in ultrathin SrRuO3 (SRO) films, where the interface between the SRO layer and another oxide layer breaks the inversion symmetry resulting in the appearance of THE. Thus, THE only occurs in ultra-thin SRO films of several unit cells. In addition to employing a heterostructure, the inversion symmetry can be broken intrinsically in bulk by introducing defects. In this study THE is observed in 60 nm thick SRO films, in which defects and lattice distortions are introduced by helium ion irradiation. The irradiated SRO films exhibit a pronounced THE in a wide temperature range from 5 K to 80 K. These observations can be attributed to the emergence of Dzyaloshinskii-Moriya interaction as a result of artificial inversion symmetry breaking associated with the lattice defect engineering. The creation and control of the THE in oxide single layers can be realized by ex situ film processing. Therefore, this work provides new insights into the THE and illustrates a promising strategy to design novel spintronic devices.
Keywords: defect engineering, Dzyaloshinskii-Moriya interaction, lattice distortion, oxide thin film, topological Hall effect

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Publ.-Id: 30851


CFD simulation of aeration and mixing processes in a full-scale oxidation ditch

Höhne, T.; Mamedov, T.
This study aims to build a computational fluid dynamics (CFD) model that can be used to predict fluid flow pattern and to analyse the mixing process in a full-scale OD. CFD is a widely used numerical tool for analysing, modelling and simulating fluid flow patterns in wastewater treatment processes. In this study, a three-dimensional (3D) computational geometry was used, and the Eulerian-Eulerian multiphase flow model was built. Pure water was considered as the continuous phase, whereas air was modelled as the dispersed phase. The Shear Stress Transport (SST) turbulence model was specified which predicts turbulence eddies in free stream and wall-bounded region with high accuracy. The momentum source term approach and the transient rotor-stator approach were implemented for the modelling of the submersible agitators. The hydrodynamic analysis was successfully performed for four different scenarios. In order to prevent the incorrect positioning of the submerged agitators, thrust analysis was also done. The results show that the minimum required water velocity was reached to maintain the solid particles suspended in the liquid media and adequate mixing was determined.
Keywords: CFD, Multiphase flow, Hydrodynamics, Oxidation ditch

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Permalink: https://www.hzdr.de/publications/Publ-30850
Publ.-Id: 30850


The Crystal Electric Field Effect in the Distorted Kagome Lattice Ferromagnet Nd3Ru4Al12

Ishii, I.; Mizuno, T.; Kumano, S.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Henriques, M. S.; Suzuki, T.
The distorted kagome lattice compound Nd3Ru4Al12 shows a ferromagnetic phase transition at TC =39 K. Reduced Nd magnetic moments with two different values of 2.66 and 0.95 µB are aligned along the c-axis below TC. It was previously reported that a crystal electric field (CEF) effect may affect the reduced magnetic moments. To clarify the 4f -electronic state in Nd3Ru4Al12, we performed CEF analyses for the inverse magnetic susceptibility and magnetization. We proposed the CEF level scheme of which the inverse magnetic susceptibilities along both a- and c-axes are reproduced. The ferromagnetic phase transition at TC along the c-axis can be explained by a simple CEF model. In contrast, reduced magnetic moments cannot be understood by the simple CEF model, because calculated magnetization curves are quite larger than the experimental data.
  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011161
    DOI: 10.7566/JPSCP.30.011161

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Permalink: https://www.hzdr.de/publications/Publ-30849
Publ.-Id: 30849


Phonon-induced near-field resonances in multiferroic BiFeO₃ thin films at infrared and THz wavelengths

Wehmeier, L.; Nörenberg, T.; de Oliveira, T. V. A. G.; Klopf, J. M.; Yang, S.-Y.; Martin, L. W.; Ramesh, R.; Eng, L. M.; Kehr, S. C.
Multiferroic BiFeO3 (BFO) shows several phonon modes at infrared (IR) to THz energies, which are expected to carry information on any sample property coupled to crystal lattice vibrations. While macroscopic IR studies of BFO are often limited by single-crystal size, scattering-type scanning near-field optical microscopy (s-SNOM) allows for IR thin film spectroscopy of nanoscopic probing volumes with negligible direct substrate contribution to the optical signal. In fact, polaritons such as phonon polaritons of BFO introduce a resonant tip–sample coupling in s-SNOM, leading to both stronger signals and enhanced sensitivity to local material properties. Here, we explore the near-field response of BFO thin films at three consecutive resonances (centered around 5 THz, 13 THz, and 16 THz), by combining s-SNOM with a free-electron laser. We study the dependence of these near-field resonances on both the wavelength and tip–sample distance. Enabled by the broad spectral range of the measurement, we probe phonon modes connected to the predominant motion of either the bismuth or oxygen ions. Therefore, we propose s-SNOM at multiple near-field resonances as a versatile and very sensitive tool for the simultaneous investigation of various sample properties.

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Permalink: https://www.hzdr.de/publications/Publ-30848
Publ.-Id: 30848


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