Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35174 Publications

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.

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.

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

Publ.-Id: 30947

Experimentelle Untersuchung der Zweiphasenströmung im Rührkessel

Rox, H.

Die Kenntnis des Strömungsfeldes einer Zweiphasenströmung (fest/flüssig) in Rührkesseln, insbesondere hinsichtlich der Turbulenz, stellt einen Schwerpunkt für das Verständnis des industriell relevanten Flotationsprozesses sowie dessen numerischen Simulation dar. In dieser Arbeit werden die Strömungsfelder der Fluidphase (deionisiertes Wasser) und Feststoffphase (Polyethylen- bzw. Glaspartikel mit d_P = 63...70 μm; d_P = 150...180 μm; d_P = 425...500 μm) mithilfe von Particle Image Velocimetry und Particle Shadow Velocimetry ermittelt sowie mit Ergebnissen aus der Literatur und numerischen Simulationen verglichen. Es wird der Einfluss der Feststoffpartikel auf das Geschwindigkeitsfeld, die turbulenten Schwankungsgeschwindigkeiten sowie die Verteilung der Partikel im Rührkessel (D_K = 90 mm) betrachtet. Hierfür wird die Volumenkonzentration der Partikel in drei Schritten von 0,025 vol-% auf 0,1 vol-% erhöht und die Partikel werden mittels Scheibenrührer (Re_R = 9,7; 14,9 oder 22,4*10⁴) suspendiert. Entscheidend für den Einfluss der Partikel auf die Flüssigphase sind der Partikeldurchmesser und die Partikeldichte. Bei den betrachteten Volumenkonzentrationen scheint diese vernachlässigbar zu sein. Innerhalb des Rührerstrahls wird in Lauflänge eine zunehmende Dämpfung der radialen Geschwindigkeit sowie teilweise eine leichte Ablenkung des Rührerstrahls Richtung Rührkesselboden festgestellt. Bei den axialen Geschwindigkeiten dominieren Partikel großer Stokes-Zahlen die abwärtsgerichtete Zweiphasenströmung und können dem Fluid nicht folgen. Die turbulenten Schwankungsgeschwindigkeiten werden generell durch die Partikel (Re_P < 170) gedämpft. Es wird bestätigt, dass die konkrete Rührerstellung keinen Einfluss auf das Strömungsfeld im äußeren Bereich des Rührkessels besitzt.

Keywords: Zweiphasenströmung; Rührkessel; Particle Image Velocimetry; PIV; Particle Shadow Velocimetry; PSV; Turbulenz; Feststoffpartikel; Flotation

  • Diploma thesis
    TU Dresden, 2020
    Mentor: Prof. Dr. et Ing. habil. Kerstin Eckert
    161 Seiten

Publ.-Id: 30946

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

Related publications

Publ.-Id: 30945

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

Park, S.; Liao, Z.; Ibarlucea, B.; Qi, H.; Lin, H.-H.; Becker, D.; Melidonie, J.; Zhang, T.; Sahabudeen, H.; Baraban, L.; Baek, C.-K.; Zheng, Z.; Zschech, E.; Fery, A.; Heine, T.; Kaiser, U.; Cuniberti, G.; Dong, R.; Feng, X.

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

Publ.-Id: 30944

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


  • Secondary publication expected

Publ.-Id: 30943

Interaction of cyanobacteria with calcium facilitates the sedimentation of microplastics in a eutrophic reservoir

Leiser, R.; Jongsma, R.; Bakenhus, I.; Möckel, R.; Philipp, B.; Neu, T.; Wendt-Potthoff, K.

Low-density microplastics are frequently found in sediments of many lakes and reservoirs. The processes leading to sedimentation of initially buoyant polymers are poorly understood for inland waters. This study investigated the impact of biofilm formation and aggregation on the density of buoyant polyethylene microplastics. Biofilm formation on polyethylene films (4 × 4 × 0.15 mm) was studied in a eutrophic reservoir (Bautzen, Saxony, Germany). Additionally, aggregation dynamics of small PE microplastics (∼85 µm) with cyanobacteria were investigated in laboratory experiments. During summer phototrophic sessile cyanobacteria (Chamaesiphon spp. and Leptolyngbya spp.) precipitated calcite while forming biofilms on microplastics incubated in Bautzen reservoir. Subsequently the density of the biofilms led to sinking of roughly 10 % of the polyethylene particles within 29 days of incubation. In the laboratory experiments planktonic cyanobacteria (Microcystis spp.) formed large and dense cell aggregates under the influence of elevated Ca2+ concentrations. These aggregates enclosed microplastic particles and led to sinking of a small portion (∼0.4 %) of polyethylene microplastics. This study showed that both sessile and planktonic phototrophic microorganisms mediate processes influenced by calcium which facilitates densification and sinking of microplastics in freshwater reservoirs. Loss of buoyancy leads to particle sedimentation and could be a prerequisite for the permanent burial of microplastics within reservoir sediments.

Keywords: Microplastics; Reservoirs; Cyanobacteria; Calcite; Biofouling; Biofilms; Sedimentation

Publ.-Id: 30941

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.

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.

Publ.-Id: 30939

Controls on strath terrace formation and evolution: The lower Guadiana River, Pulo do Lobo, Portugal

Ortega-Becerril, J. A.; Garzón, G.; Tejero, R.; Meriaux, A.-S.; Delunel, R.; Merchel, S.; Rugel, G.

The lower Guadiana River carves a wide canyon in the Variscan metamorphic rocks of the SW Iberian Peninsula and presents an exceptionally homogeneous and well-preserved case of a strath terrace (ST) some 40 km long and 400 m wide. The rocky surface or strath shows different characteristics and development stages. Upstream, the lateral erosion level forms a flooded riverbed, or submerged strath, that gradually rises above the thalweg and develops into an active floodplain. Downstream, below the 15 m high Pulo do Lobo waterfall, the strath is incised by an inner canyon that forms a terrace on both sides. The inner channel increasingly widens and the ST loses its longitudinal continuity, yet remains prone to flooding during extraordinary magnitude floods. To assess the factors controlling the formation of this ST, we examined the roles of key drivers of ST formation: lithological hardness, tectonic structures and climate change, using cosmogenic data to create a chronologic context. The ST developed favoured by a monotonous succession of phyllites, as shown by Schmidt hammer resistance data, and interbedded more resistant quartz veins do not significantly alter its flat configuration. Variscan structures and measured joints determine the main orientation of the river and control the drainage network pattern. The intersection of the NS and NE-SW fractures promotes a wavy surface due to three-dimensional minor fold trains that act as discontinuities and play an important role in ST erosion through quarrying and plucking. However, we detected no evidence of ST deformation attributable to recent or Late Cenozoic tectonic activity.

The upstream active riverbed progressively changes downstream into an ST. This implies that Be radiometric ages obtained at Pulo do Lobo may not represent the ST's genetic age but rather the time of dismantling of its alluvial or sedimentary cover. This means the strath surface formed prior to its cosmogenic age and was therefore controlled by a higher base level, indicating a higher sea level than the current one, given the downstream area studied. The Quaternary sea level fluctuations show records of only a few meters above the current level. Instead, the sea level low stand maintains an average depth of −60 m, reaching −140 m during the last glacial period. This low base level context could justify the strong incision of the inner channel within the ST, but not the age of strath surface genesis and expansion and thus this surface should have evolved previously. The highest possible sea level stand corresponds to the Pliocene transgression, which reached an elevation of 120 m in the region, covering Miocene paleorelief. The mouth of the Guadiana River at that time resembled a fluvio-deltaic embayment between the Algarve domain and the Guadalquivir depression, which was infilled with fluvial deposits at the end of the transgression. Collectively, these data suggest that cosmogenic dating would define the time of exhumation of this Pliocene sedimentary cover.

Despite great variation of the ST ages, estimated incision rates at the knickpoint area are consistent with the total entrenchment of the Pulo do Lobo fall, especially if we consider that data correspond to an active erosion site. Highest erosion rates were found for the pothole area compared to those obtained for the higher ST surface. Radiometric ages correspond to the period of lowest Quaternary sea level and during which headward erosion would have been very active in the inner channel. The waterfall area shows more resistant lithology in its concentrated quartz veins, but this effect is inconspicuous at the ST surface. The regular gradient of 0.02 m/m and vast extension of this perched strath, linked upstream to the Guadiana riverbed, indicates a relic exhumed surface beneath its sedimentary cover. Notwithstanding the subsiding activity of the Gulf of Cádiz, the continental margin behaves as a tectonically stable block, which allows for the persistence of former morphologies in these ancient landscapes reshaped by bedrock river dissection.

Keywords: Strath terrace; Knickpoint; Inner channel; Bedrock rivers; Guadiana canyon

Publ.-Id: 30938

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

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

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

Publ.-Id: 30935

Validation of AIAD sub-models for advanced numerical modelling of horizontal two-phase flows

Höhne, T.; Porombka, P.; Moya Saez, S.

In this work the modelling of horizontal two-phase flows within the two-fluid Euler-Euler approach is investigated. A modified formulation of the morphology detection functions within the Algebraic Interfacial Area Density (AIAD) model is presented in combination with different models for the drag force acting on a sheared gas-liquid interface. In case of free surface flows, those closure laws are often based on experimental correlations whose applicability is limited to certain flow regimes. It is investigated here whether the implementation of the modified blending functions in ANSYS CFX avoids this limitation. The influence of the new functions on the prediction of turbulence parameters in free surface flows is also examined quantitatively for the k-ω and k-ε two-equations turbulence models. Transient simulations of the WENKA counter-current stratified two-phase flow experiment were performed for validation. Predict of the correct flow pattern as observed in the experiment improved dramatically when a turbulence damping term was included in the standard two-equation models. Using the k-ω and a modified k-ε turbulence model with damping terms close to the interface, better agreement with the experimental data was achieved. The morphology detection mechanism of the unified blending functions within the AIAD is seen as an improvement with respect to the detection of sharp interfaces. Satisfactory quantitative agreement is achieved for the modified free surface drag. Furthermore, it is demonstrated that turbulence dampening has to be accounted for both turbulence models to qualitatively reproduce the mean flow and turbulence quantities from the experiment.

Keywords: Two-phase flow; CFD; AIAD; Horizontal flow; Turbulence

Publ.-Id: 30932

Detailed Simulation of the Nominal Flow and Temperature Conditions in a Pre-Konvoi PWR Using Coupled CFD and Neutron Kinetics

Höhne, T.; Kliem, S.

Since 2005, events have occurred involving increased operational oxidation of M5 fuel rod claddings at several German pressurized water reactors (PWRs). The conspicuous corrosion was observed mainly in the area between the two uppermost spacer grids (SG), i.e. the 8th and the 9th SG. In this area the transition from the active fuel rod area (filled with fuel) to the fuel rod plenum takes place. In some cases, the increased oxide layer was even found in the region of the fuel rod plenum, where no appreciable power is transferred from the fuel rod to the coolant.

One of the hypotheses assumes that an initial oxide layer first arises more or less over the entire length of the fuel rod. Depending on the height position different thermal conditions may occur in the form of temperature fluctuations. According to this hypothesis, it is assumed that the oxide layer ruptures due to the load from alternating temperatures, creating pathways where oxidizing species reach the metallic cladding rod surface. As a result, the oxide layer loses its protective effect and thicker oxide layers can grow up. From earlier experimental investigations at ROCOM (Rossendorf Coolant Mixing Test Facility) it is known that strong, large-scale vortex structures are present in the upper plenum of the RPV.

The aim of the present study was the detection of possible vortices in the upper part of the core. Therefore, a numerical simulation of the flow conditions in a Pre-Konvoi Pressurized Water Reactor (PWR) was carried out based on a complex 3D CFD model. The geometry of the CFD model includes the entire Reactor Pressure Vessel (RPV) plus all relevant internals. The core is modelled as a porous body, the different pressure losses along and transverse to the main flow direction were considered. The spacer-grid levels were taken into account to the extent that in these areas no cross-flow is possible. The calculation was carried out for nominal operating conditions, i.e. for full load operation. Furthermore, a prototypical End of Cycle (EOC) power distribution was assumed. For this, a power distribution was applied as obtained from a stationary full-core calculation with the 3D neutron kinetics code DYN3D. In order to be able to adequately reproduce flow vortexes, the calculation was performed transiently with suitable Detached Eddy Simulations (DES) turbulence models.

The calculation showed fluctuating transverse flow in the upper part of the core, starting at the 8th spacer grid but also revealed that no large dominant vortices exists in this region. It seems that the core acts as a rectifier attenuating large-scale vortices. The analyses included several spacer grid levels in the core and showed that in some areas of the core cross-section an upward increasingly directed transversal flow to the outlet nozzle occurs. In other areas of the core cross-section, on the other hand, there is nearly any cross-flow. However, the following limitations of the model apply: In the model all fuel elements are treated identical and cross flows due to different axial pressure losses for different FA types cannot be displayed. The complex structure of the FAs (eg. flow vanes in spacer grids) could also influence the formation of large-scale vortices. This effect could only be resolved with a very high number of grid elements (several billions). This is currently not possible from a computational point of view. Also, the possible influence of two-phase flows was not considered.

Keywords: PWR; CFD; Neutron Kinetics; Turbulence

  • Contribution to proceedings
    CFD4NRS-8 : Computational Fluid Dynamics for Nuclear Reactor Safety - OECD/NEA Workshop, 25.-27.11.2020, Palaiseau, Frankreich
  • Lecture (Conference)
    CFD4NRS-8 : Computational Fluid Dynamics for Nuclear Reactor Safety - OECD/NEA Workshop, 25.-27.11.2020, Palaiseau, Frankreich
  • Open Access Logo Fluids 5(2020)3, 161
    DOI: 10.3390/fluids5030161

Publ.-Id: 30930

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

Publ.-Id: 30929

Dose-escalated simultaneously integrated boost photon or proton therapy in pancreatic cancer in an in silico study: gastrointestinal organs remain critical

Stefanowicz, S.; Waldemar, W.; Susanne, F.; Sebastian, Z.; Troost, E. G. C.

To compare the dosimetric results of an in silico study among intensity-modulated photon (IMRT) and robust multi-field optimized intensity-modulated proton (rMFO-IMPT) treatment techniques using a dose-escalated simultaneously integrated boost (SIB) approach in locally recurrent or locally advanced pancreatic cancer patients.

Material and Methods
For each of 15 locally advanced pancreatic cancer patients, a volumetric modulated arc therapy (VMAT), a Tomotherapy (TOMO), and an rMFO-IMPT treatment plan was optimized on free-breathing treatment planning computed tomography (CT) images. For the photon treatment plans, doses of 66Gy and 51Gy, both as SIB in 30 fractions, were prescribed to the gross tumor volume (GTV) and to the planning target volume (PTV), respectively. For the proton plans, a dose prescription of 66Gy(RBE) to the GTV and of 51Gy(RBE) to the clinical target volume (CTV) was planned. For each SIB-treatment plan, doses to the targets and OARs were evaluated and statistically compared.

All treatment techniques reached the prescribed doses to the GTV and CTV or PTV. The stomach and the bowel, of the latter in particular the duodenum and the small bowel, were found to be frequently exposed to doses exceeding 50Gy, irrespective of the treatment technique. For doses below 50Gy, the IMPT technique was statistically significant superior to both IMRT techniques regarding decreasing dose to the OARs, e.g. volume of the bowel receiving 15Gy (V15Gy) was reduced for rMFO compared to VMAT (p=0.003) and TOMO (p<0.001).

With all photon and proton techniques investigated, the radiation dose to gastrointestinal OARs remained critical when treating patients with unresectable locally advanced or locally recurrent pancreatic cancer using a dose-escalated SIB approach.

Keywords: Pancreatic cancer; intensity-modulated radiation therapy; intensity-modulated proton therapy; robust optimization; simultaneously integrated boost; dose escalation

Publ.-Id: 30928

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.

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

Publ.-Id: 30926

Solid-liquid Flow in Stirred Tanks: Euler-Euler / RANS Modeling

Shi, P.; Rzehak, R.

Stirred tanks are widely used equipment in process engineering. CFD simulations of such equipment on industrial scales are feasible within the Euler-Euler / RANS approach. In this approach, phenomena on particle scale are not resolved and, accordingly, suitable closure models are required. The present work applies a set of closure relations that originates from a comprehensive review of existing results. Focus is on the modeling of interfacial forces which include drag, lift, turbulent dispersion, and virtual mass. Specifically, new models for the drag and lift forces are considered based on the best currently available description. To validate the model a comprehensive set of experimental data including solid velocity and volume fraction as well as liquid velocity and turbulence has been assembled. The currently proposed model compares reasonably well with this dataset and shows generally better prediction compared with other model variants that originate from different combinations of force correlations.

Keywords: stirred tanks; solid-liquid flow; Euler-Euler two-fluid model; closure relations; Reynolds-stress turbulence model


  • Secondary publication expected from 20.06.2021

Publ.-Id: 30925

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

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

Related publications


  • Secondary publication expected

Publ.-Id: 30922

How to integrate geochemistry at affordable costs into reactive transport for large-scale systems

Stockmann, M.; Brendler, V.

This international workshop entitled “How to integrate geochemistry at affordable costs into reac-tive transport for large-scale systems” was organized by the Institute of Resource Ecology of the Helmholtz-Zentrum Dresden Rossendorf in Feb-ruary 2020. A mechanistic understanding and building on that an appropriate modelling of geochemical processes is essential for reliably predicting contaminant transport in groundwater systems, but also in many other cases where migration of hazardous substances is expected and consequently has to be assessed and limited. In case of already present contaminations, such modelling may help to quantify the threads and to support the development and application of suitable remediation measures. Typical application areas are nuclear waste disposal, environmental remediation, mining and milling, carbon capture & storage, or geothermal energy production. Experts from these fields were brought together to discuss large-scale reactive transport modelling (RTM) because the scales covered by such pre-dictions may reach up to one million year and dozens of kilometers. Full-fledged incorporation of geochemical processes, e.g. sorption, precipitation, or redox reactions (to name just a few important basic processes) will thus create inacceptable long computing times. As an effective way to integrate geochemistry at affordable costs into RTM different geochemical concepts (e.g. multidimensional look-up tables, surrogate functions, machine learning, utilization of uncertainty and sensitivity analysis etc.) exist and were extensively discussed throughout the workshop. During the 3-day program of the workshop keynote and regular lectures from experts in the field, a poster session, and a radio lab tour had been offered. In total, 40 scientists from 28 re-search institutes and 8 countries participated. The focus of the workshop was: (1) To provide and discuss existing geochemical concepts in reactive transport modelling to describe sorption and related retardation processes of contaminants on a variety of sedi-ments and rocks. (2) To explicitly set focus on large-scale natural systems as experienced, e.g., in nuclear waste disposal, carbon capture & storage, environmental remediation, or geothermal applications. (3) To explore how the discussed approaches can be integrated at affordable costs into cur-rent paradigms in THMC models and long-term safety assessments in general. (4) To promote the exchange of scientific knowledge and practical experience between the workshop participants in an efficient way. Based on the intensive discussions and very posi-tive feedback on the workshop, a continuation is intended to bundle and strengthen the respective research activities and stipulate the international network that started to form during the conference days.

Keywords: Geochemistry; Large-scale reactive transport modelling; Workshop

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-111 2020
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 30921

Highly efficient targeting of EGFR-expressing tumor cells with UniCAR T cells via target modules based on Cetuximab®

Jureczek, J.; Feldmann, A.; Bergmann, R.; Arndt, C.; Berndt, N.; Koristka, S.; Rodrigues Loureiro, L. R.; Metwasi, N.; Hoffmann, A.; Kegler, A.; Bartsch, T.; Bachmann, M.

Introduction: Since epithelial growth factor receptor (EGFR) overexpression is linked to a variety of malignancies, it is an attractive target for immune therapy including with chimeric antigen receptor (CAR)-engineered T cells. Unfortunately, CAR T cell therapy harbors the risk of severe, even life-threatening side effects. Adaptor CAR T cell platforms such as the previously described UniCAR system might be able to overcome these problems. In contrast to conventional CARs, UniCAR T cells are per se inert. Their redirection towards target cells occurs only in the presence of a tumor-specific target molecule (TM). TMs are bifunctional molecules being able to recognize a tumor-associated antigen (TAA) and to cross-link the CAR T cell via a peptide epitope recognized by the UniCAR domain.
Methods: Here, we compare anti-EGFR TMs: a nanobody (nb)-based αEGFR TM derived from the camelid αEGFR antibody 7C12 with a murine and humanized single-chain fragment variable (scFv) based on the clinically used antibody Cetuximab®.
Results: In principle, both the nb- and scFv-based TM formats are able to redirect UniCAR T cells to eliminate EGFR-expressing tumor cells in an antigen-specific and TM-dependent manner. However, the scFv-based αEGFR TM was significantly superior to the nb-based TM especially with respect to lysis of tumor cells.
Discussion: Improved efficiency of the scFv-based TM allowed the redirection of UniCAR T cells towards tumor cells expressing high as well as low EGFR levels in comparison to nb-based αEGFR TMs.

Keywords: EGFR; UniCAR; CAR T cells; adaptor CARs; solid tumors; immunotherapy

Publ.-Id: 30919

Data for: 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

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-14
    DOI: 10.14278/rodare.412
    License: CC-BY-1.0


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

Related publications


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%.


Publ.-Id: 30916

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

Bieberle, A.
DataCollector: Barthel, Frank; DataCollector: Sprewitz, Uwe; DataCurator: Bieberle, Martina; DataManager: Bieberle, André; Project Member: Gundrum, Thomas; Project Member: Räbiger, Dirk; RelatedPerson: Eckert, Sven; Project Member: Neumann-Kipping, Martin

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


Publ.-Id: 30915

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

Bieberle, A.
Project Member: Barthel, Frank; Project Member: Windisch, Dominic; DataCollector: Bieberle, André

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

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-17
    DOI: 10.14278/rodare.288
    License: CC-BY-4.0


Publ.-Id: 30914

Voxel-based finite element modelling of wood elements based on spatial density and geometry data using computed tomography

Hartig, J. U.; Bieberle, A.; Engmann, C.; Haller, P.

In this paper, voxel-based finite element modelling based on spatial geometry and density data is applied to simulate the detailed stress and strain distribution in a large wooden element. As example, a moulded wooden tube with a length of 3 m and a diameter of 0.3 m is examined. Gamma-ray computed tomography is used to obtain the spatial distribution of elastic properties based on the correlation with density. Correlation functions between density and elastic material properties are experimentally determined and serve as link for defining the non-uniform distribution of the material properties in the finite element model. Moreover, also the geometry is obtained by the computed tomography. Due to the consideration of both the geometric imperfections and the spatial variation of the material properties, a detailed analysis of the stress and strain distribution of the wood element is performed. Additionally, a non-destructive axial compression test is performed on the wooden tube to analyse the load-bearing behaviour. By means of digital image correlation, the deformation of the surface is obtained, which also serves for validation of the finite element model.

Keywords: large wooden elements; gamma-ray computed tomography; finite element model

Related publications

  • Wood Research and Technology - Holzforschung (2021), HOLZ.2020.0105
    Online First (2021) DOI: 10.1515/hf-2020-0105

Publ.-Id: 30913

Ferromagnetism in Undoped ZnO Grown by Pulsed Laser Deposition

Waqar, A.; Cai-Qin, L.; Xu, C.; Zhou, S.; Wagner, A.; Butterling, M.; Muhammad, Y.; Francis, C.-C. L.

Undoped ZnO films grown on sapphire by pulsed laser deposition are magnetic at room temperature. A comprehensive study involving x-ray diffraction, positron annihilation spectroscopy, and superconducting quantum Interference device-vibrating sample magnetometer is performed to study the origin of the observed magnetization. Correlations between the saturation magnetization, VZn-2VO concentration and surface to volume ratio of the grain found experimentally show that the magnetization is associated with the vacancy cluster and probably VZn-2VO residing on the grain surface.

Keywords: ZnO films; pulsed laser deposition; magnetic x-ray diffraction; positron annihilation spectroscopy; magnetization vacancy; cluster grain surface

Publ.-Id: 30912

Extended half-life target module for sustainable UniCAR T-cell treatment of STn-expressing cancers

Rodrigues Loureiro, L. R.; Feldmann, A.; Bergmann, R.; Koristka, S.; Berndt, N.; Máthé, D.; Hegedüs, N.; Szigeti, K.; Videira, P. A.; Bachmann, M.; Arndt, C.

Adapter chimeric antigen receptor (CAR) approaches have emerged has promising strategies to increase clinical safety of CAR T-cell therapy. In the UniCAR system, the safety switch is controlled via a target module (TM) which is characterized by a small-size and short half-life. The rapid clearance of these TMs from the blood allows a quick steering and self-limiting safety switch of UniCAR T-cells by TM dosing. This is mainly important during onset of therapy when tumor burden and the risk for severe side effects are high. For long-term UniCAR therapy, the continuous infusion of TMs may not be an optimal setting for the patients. Thus, in later stages of treatment, single infusions of TMs with an increased half-life might play an important role in long-term surveillance and eradication of residual tumor cells. Given this, we aimed to develop and characterize a novel TM with extended half-life targeting the tumor-associated carbohydrate sialyl-Tn (STn).

Keywords: Immunotherapy; UniCAR T-cells; IgG4-based TM; Sialyl-Tn (STn)

Publ.-Id: 30911

Novel Therapeutic Strategies for Ovarian Cancer Stem Cells

Terraneo, N.; Jacob, F.; Dubrovska, A.; Grünberg, J.

Ovarian cancer (OC) is one of the most lethal gynecologic malignancies. Due to the lack of specific symptoms and screening methods, this disease is usually diagnosed only at an advanced and metastatic stage. The gold-standard treatment for OC patients consists of debulking surgery followed by taxane combined with platinum-based chemotherapy. Most patients show complete clinical remission after first-line therapy, but the majority of them ultimately relapse, developing radio- and chemoresistant tumors. It is now proposed that the cause of recurrence and reduced therapy efficacy is the presence of small populations of cancer stem cells (CSCs). These cells are usually resistant against conventional cancer therapies and for this reason, effective targeted therapies for the complete eradication of CSCs are urgently needed. In this review article, we highlight the mechanisms of CSC therapy resistance, epithelial-to-mesenchymal transition, stemness, and novel therapeutic strategies for ovarian CSCs.

Keywords: Auger electron and alpha particle emitter; scancer stem cells; epithelial-to-mesenchymal transition; L1CAM; ovarian cancer; radioimmunotherapy; therapeutic strategies

Publ.-Id: 30910

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


Publ.-Id: 30909

Tuning 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


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

Publ.-Id: 30907

Lift force coefficient of ellipsoidal single bubbles in water

Hessenkemper, H.; Ziegenhein, T.; Rzehak, R.; Lucas, D.; Tomiyama, A.

For the simulation of bubbly flows, knowledge of the lift force as an interaction between gas bubbles and a surrounding shear field is of great importance. The sign of the lift coefficient Cᴸ changes with increasing bubble size, i.e. with more pronounced bubble deformation. Beside this, impurities in terms of surface-active components are well-known to change the complete hydrodynamic behavior of a bubble even if the amount is very small. In the present work, the lift coefficient of single ellipsoidal bubbles is determined with a recently developed method, which is suitable to overcome difficulties connected to low viscous systems. In order to investigate the influence of impurities on the lift force, we conducted experiments with single bubbles of different sizes in purified, deionized and tap water. Overall, the determined lift coefficients show no difference between deionized and tap water but reveal differences to results obtained with purified water. As no significant differences in shape and velocity are found between the different water qualities, it remains unclear how the impurities cause the observed differences. For the deionized and tap water results that are more relevant in practice, a new correlation is proposed to account for the observed differences in comparison to data from the literature. It can be used to calculate Cᴸ of ellipsoidal bubbles in the investigated size range.

Keywords: Lift coefficient; Bubbly flows; Turbulent flow; Impurities

Publ.-Id: 30905

Sigma-1 and dopamine D2/D3 receptor occupancy of pridopidine in healthy volunteers and patients with Huntington disease: a [18F] fluspidine and [18F] fallypride PET study

Grachev, I.; Meyer, P.; Becker, G.; Bronzel, M.; Marsteller, D.; Pastino, G.; Voges, O.; Rabinovich, L.; Knebel, H.; Zientek, F.; Rullmann, M.; Sattler, B.; Patt, M.; Gerhards, T.; Strauss, M.; Kluge, A.; Brust, P.; Savola, J.; Gordon, M.; Geva, M.; Hesse, S.; Barthel, H.; Hayden, M.; Sabri, O.

Pridopidine is an investigational drug in late stage development for the treatment of Huntington disease and originally postulated to act as dopamine stabilizer by modulating dopamine-dependent motor behavior. However, preclinical studies show pridopidine has highest affinity to sigma-1 receptors. Importantly, mediated by sigma-1 receptors, pridopidine has neuroprotective properties and enhances neuronal plasticity. The aim of our study was to determine the in-vivo the target engagement (receptor occupancy) of pridopidine at clinically relevant doses in healthy volunteers and Huntington disease patients. We used sigma-1 receptor-specific (S)-(-)-[18F]Fluspidine and dopamine D2/D3 receptor-specific [18F]Fallypride PET imaging to quantify the sigma-1 and dopamine D2/D3 receptor occupancy of pridopidine. Eleven male healthy volunteers (pridopidine 0.5 to 90 mg in six dose groups) and three male Huntington disease patients (pridopidine 90 mg) were studied twice before and 2h following single oral doses of pridopidine using S-(-)-[18F]Fluspidine PET (300 MBq, 0-90min p.i.). Distribution volume VT was quantified using kinetic modeling (One-tissue compartment model; metabolite correction). Four male healthy volunteers were studied twice using [18F]Fallpride PET (200 MBq, 0-210min p.i.) before and 2h after a single oral dose of pridopidine (90 mg). Binding potential BPND was assessed by the simplified reference model. Volume-of-interest analyses were performed. For each subject/tracer, the receptor occupancy was calculated by the Lassen plot analysis. In healthy volunteers, there was high sigma-1 receptor occupancy (87 to 91%) across all brain regions at doses ranging from 22.5 to 90 mg. The sigma-1 receptor occupancy was 43% at 1 mg pridopidine. In Huntington disease patients, very similar to healthy volunteers, at 90 mg pridopidine, there was high sigma-1 receptor occupancy (87±7%, n.s.). In contrast, in healthy volunteers, there was only negligible dopamine D2/D3 receptor occupancy (3±2%) at 90 mg pridopidine. We established a sigmoid-shaped dose/sigma-1 receptor occupancy relation (Hill equation) with Hill coefficient larger than 1 in healthy volunteers, suggesting a positive cooperative binding nature of the sigma-1 receptor. Using PET, we report for the first time in the living human brain that after a single dose of 90 mg, pridopidine acts as a selective sigma-1 receptor ligand showing near to complete sigma-1 receptor occupancy (~90%) but only minimal (~3%) dopamine D2/D3 receptor occupancy. Our findings provide significant clarification about pridopidine’s mechanism of action and support further use of the 45 mg bidaily dose to achieve full and selective targeting of the sigma-1 receptor in future clinical trials in Huntington disease and amyotrophic lateral sclerosis.

Keywords: PET; pridopidine; sigma-1 receptor occupancy; dopamine D2/D3 receptor occupancy; Huntington disease

Publ.-Id: 30903

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

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-15
    DOI: 10.14278/rodare.276
    License: CC-BY-4.0


Publ.-Id: 30902

PET Imaging of Sigma1 Receptors

Toyohara, J.; Brust, P.; Jia, H.; Sakata, M.; Ishiwata, K.

Sigma receptors are classified into sigma1 and sigma2 subtypes. Sigma1 receptors are widely distributed in the central nervous system (CNS) and in peripheral tissues. Sigma1 receptors play a role in a variety of human CNS diseases, including mood disorders, stroke, neurodegenerative disease, and drug addiction. Therefore, there is a great deal of interest in imaging of sigma1 receptors in the living human brain. In contrast, sigma2 receptors have also been the focus of tumor imaging studies. A number of radioligands have been developed for imaging of sigma1 receptors in the human brain, and a few, including [11C]SA4503 and (-)-S-[18F]fluspidine, have been used in clinical studies. Sigma1 receptors are distributed throughout the grey matter of the human brain. A widespread decrease in [11C]SA4503 binding in patients with Alzheimer’s disease and a significant decrease in binding on the more affected side of the anterior putamen in patients with Parkinson’s disease have been reported. Receptor occupancy studies with [11C]SA4503-PET have shown that some antidepressants and antipsychotics have an affinity for sigma1 receptors in the human brain in addition to their main targets. Recently, it has been reported that the binding of (-)-S-[18F]fluspidine is increased in patients with untreated major depressive disorder (MDD).

  • Book chapter
    RAJO Dierckx et al.: PET and SPECT of Neurobiological Systems, 2nd edition, Heidelberg: Springer, 2021, 978-3-030-53175-1, 943-972
    DOI: 10.1007/978-3-030-53176-8

Publ.-Id: 30901

Preclinical and clinical aspects of nicotinic acetylcholine receptor imaging

Brust, P.; Deuther-Conrad, W.; Donat, C.; Barthel, H.; Riss, P.; Paterson, L.; Hoepping, A.; Sabri, O.; Cumming, P.

Innovations in radiochemistry and pharmacology are opening new vistas for studies of nicotinergic acetylcholine receptors (nAChRs) in human brain by positron emission tomography (PET) and by single-photon emission computed tomography (SPECT). In parallel, instrumentation optimized for molecular imaging in rodents facilitates preclinical studies in models of human diseases with perturbed nAChR signalling, notably Alzheimer’s disease and other neurodegenerative conditions, schizophrenia and other neuropsychiatric disorders, substance abuse, and traumatic brain injury. The nAChRs are ligand-gated ion channels composed of five subunits forming a central pore for cation flux. The most abundant nAChRs in the central nervous system are heteropentamers (designated α4β2), followed by the α7 homopentamer. We present a systematic review of published findings with the various nAChR ligands using imaging techniques in vivo, emphasizing preclinical models and human studies.. Molecular PET imaging of the α4β2 nAChR subtype with the antagonist 2-[18F]fluoro-A-85380 is hampered by the long acquisition times. Newer agents such as (-)-[18F]flubatine, [18F]XTRA or [18F]nifene permit quantitation of α4β2 receptors with PET recordings lasting 90 minutes or less, and without the toxicity risk of earlier epibatidine derivatives. The early PET studies of α7 nAChRs suffered from low pharmacological specificity, further hampered by low natural abundance of the receptor. However, several good α7 nAChR ligands such as [18F]ASEM and [18F]DBT10 have emerged in the past few years. There are still no ligands selective for α6-containing nAChRs, despite their importance for nicotine-induced dopamine release in striatum. Selective α3β4 nAChR radioligands are under development, but remain untested in clinical studies of depression and addiction. Several nAChR ligands find use for pharmacological occupancy studies, and competition from endogenous acetylcholine reduces α4β2 binding site availability, a property that enables monitoring by PET of acetylcholine release in living brain.

Keywords: PET; molecular imaging; nicotinic receptors; acetylcholine; Alzheimer’s disease

  • Book chapter
    RAJO Dierckx et al.: PET and SPECT of Neurobiological Systems, 2nd edition, Heidelberg: Springer, 2021, 978-3-030-53175-1, 593-660
    DOI: 10.1007/978-3-030-53176-8

Publ.-Id: 30900

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

Publ.-Id: 30899

Simulation of diffusive uranium transport and sorption processes in the Opalinus Clay

Hennig, T.; Stockmann, M.; Kühn, M.

Diffusive transport and sorption processes of uranium in the Swiss Opalinus Clay were investigated as a function of partial pressure of carbon dioxide pCO2, varying mineralogy in the facies and associated changes in porewater composition. Simulations were conducted in one-dimensional diffusion models on the 100m-scale for a time of one million years using a bottom-up approach based on mechanistic surface complexation models as well as cation exchange to quantify sorption. Speciation calculations have shown, uranium is mainly present as U(VI) and must therefore be considered as mobile for in-situ conditions. Uranium migrated up to 26m in both, the sandy and the carbonate-rich facies, whereas in the shaly facies 16m was the maximum. The main species was the anionic complex CaUO2(CO3)3-2 and hence the effect of anion exclusion was taken into account. This further reduced the migration distances by 30%. The concentrations of calcium and Carbonates reflected by the set pCO2 determine speciation and activity of uranium due to the formation of ternary uranyl complexes and consequently the sorption behaviour. Our simulation results showed, that sorption processes are controlled in descending priority by the carbonate and calcium concentrations, pH, pe and the clay mineral content. Therefore, the variation in porewater composition resulting from the heterogeneity of the facies in the Opalinus Clay formation needs to be considered in the assessment of uranium migration in the far field of a potential repository.

Keywords: Reactive transport; facies; heterogeneity; carbonate; PHREEQC; Mont Terri; speciation

Publ.-Id: 30898

Electronic structure and thermoelectric properties of Mo-based dichalcogenide monolayers locally and randomly modified by substitutional atoms

Vallinayagam, M.; Posselt, M.; Chandra, S.

Density Functional Theory and Boltzmann transport equations are used to investigate electronic band structure and thermoelectric (TE) properties of different two-dimensional (2D) materials containing Mo, S, Nb, Se, and Te. In MoS2-based monolayers (MLs) the substitution of S atoms by Te atoms up to the concentrations of 12.5 at % leads to a more significant change of the band structure than in the corresponding case with Se atoms. In particular, the bandgap is reduced. At the high concentration of Se or Te the electronic structure becomes more similar to that of the SeMoS or TeMoS Janus layers, and the MoSe2 or MoTe2 MLs. It is found that local and random introduction of substitutional Se or Te atoms yields not very different results. The substitution of Mo by Nb, at the concentration of 2.1 at% leads to hole levels. The thermoelectric properties of the considered 2D materials are quantified by the Seebeck coefficient and thermoelectric figure of merit. The two characteristics are determined for different levels of p- or n-doping of the MLs and for different temperatures. Compared to the pristine MoS2 ML, Te substitutional atoms cause more changes of the thermoelectric properties than Se atoms. However, MLs with Se substitutional atoms show a high thermoelectric figure of merit in a broader range of possible p- or n-doping levels. In most cases, the maximum thermoelectric figure of merit is about one, both in p- and n-type material, and for temperatures between 300 and 1200 K. This is not only found for MoS2-based MLs with substitutional atoms but also for the Janus layers and for MoSe2 or MoTe2 MLs. Interestingly, for MLs with one Nb as well as two or four Te substitutional atoms highest values of the TE figure of merit of 1.2 and 1.40, respectively, are obtained at a temperature of 1200 K.

Keywords: Mo-based dichalcogenide monolayers; Electronic structure; Thermoelectric properties

Publ.-Id: 30897

Sigma-1 Receptor Positron Emission Tomography: A New Molecular Imaging Approach Using ( S)-(-)-[ 18 F]Fluspidine in Glioblastoma

Toussaint, M.; Deuther-Conrad, W.; Kranz, M.; Fischer, S.; Ludwig, F.-A.; Juratli, T.; Patt, M.; Wünsch, B.; Schackert, G.; Sabri, O.; Brust, P.

Glioblastoma multiforme (GBM) is the most devastating primary brain tumour characterised by infiltrative growth and resistance to therapies. According to recent research, the sigma-1 receptor (sigmaR1), an endoplasmic reticulum chaperone protein, is involved in signaling pathways assumed to control the proliferation of cancer cells and thus could serve as candidate for molecular characterisation of GBM. To test this hypothesis, we used the clinically applied sigmaR1-ligand (S)-(−)-[18F]fluspidine in imaging studies in an orthotopic mouse model of GBM (U87-MG) as well as in human GBM tissue. A tumour-specific overexpression of sigmaR1 in the U87-MG model, revealed in vitro by autoradiography, was confirmed by dynamic PET. The binding parameters demonstrated target-selective binding according to identical KD values in the tumour area and the contralateral side but a higher density of sigmaR1 in the tumour. Different kinetic profiles were observed in both areas, with a slower washout in the tumour tissue compared to the contralateral side. The translational relevance of sigmaR1 imaging in oncology is reflected by the autoradiographic detection of tumour-specific expression of sigmaR1 in samples obtained from patients with glioblastoma. Thus, the herein presented data support further research on sigmaR1 in neuro-oncology.

Keywords: Sigma-1 receptor availability; orthotopic xenograft of glioblastoma in mouse; small animal PET/MR imaging; (S)-(−)-[18F]fluspidine; imaging-based biomarker

Publ.-Id: 30895

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


Publ.-Id: 30894

Mirror to measure Small Angle X-ray Scattering signal in high energy density experiments

Smid, M.; Bähtz, C.; Laso García, A.; Göde, S.; Grenzer, J.; Kluge, T.; Konôpková, Z.; Makita, M.; Pelka, A.; Prencipe, I.; Preston, T.; Rödel, M.; Cowan, T.

Small angle x-ray scattering (SAXS) is a well established technique to detect nanometer scale structure in matter. In typical setup, this diagnostics has an detector directly opened towards the scattering target. However, in a harsh environment of high intensity laser interaction, many high energetic particles and strong radiation are emerging from the laser target interaction. Such setup would therefore suffer a significant increase of noise due to this background which could eventually disable this measurement. In this paper, we present a novel tool consisting of mosaic graphite crystal which works as a mirror for the SAXS signal and allows to hide the detector behind proper shielding. This paper studies the performance of such mirror both by experiment at the European XFEL laboratory and by simulations.

Keywords: HAPG crystal; SAXS; XFEL; Bragg reflection; x-ray diagnostics


Publ.-Id: 30891

Recent advances in experimental techniques for flow and mass transfer analyses in thermal separation systems

Hampel, U.; Schubert, M.; Döß, A.; Sohr, J.; Vishwakarma, V.; Repke, J.-U.; Gerke, S. J.; Leuner, H.; Rädle, M.; Kapoustina, V.; Schmitt, L.; Grünewald, M.; Brinkmann, J. H.; Plate, D.; Kenig, E. Y.; Lutters, N.; Bolenz, L.; Buckmann, F.; Toye, D.; Arlt, W.; Linder, T.; Hoffmann, R.; Klein, H.; Rehfeldt, S.; Winkler, T.; Bart, H.-J.; Wirz, D.; Schulz, J.; Scholl, S.; Augustin, W.; Jasch, K.; Schlüter, F.; Schwerdtfeger, N.; Jupke, A.; Kabatnik, C.; Braeuer, A. S.; D'Auria, M.; Runowski, T.; Casal, M. F.; Becker, K.; David, A.-L.; Górak, A.; Skiborowski, M.; Groß, K.; Qammar, H.

Modelling flow and mass transfer of thermal separation equipment constitutes one of the most challenging tasks in fluids process engineering. The difficulty of this task comes from the multiscale multiphase flow phenomena in rather complex geometries. Both analysis of flow and mass transfer on different scales as well as validation of models and simulation results require advanced experimental and measurement techniques. As a follow-up to intensive discussions during the 2019 Tutzing Symposium “Separation Units 4.0” we present in this article a wide set of available modern experimental technologies, which are used in different research and industry laboratories.

Keywords: Thermal separation systems; experimental techniques; measurement techniques

Publ.-Id: 30890

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.

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

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 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


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


Publ.-Id: 30886

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

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

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.


  • 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
  • n-phase partial elimination algorithm for momentum equations to resolve strong phase coupling
  • bubble induced turbulence model of Ma et al. (Phys Rev Fluids, 2017, Vol. 2, 034301)
  • turbulent wall functions of Menter according to Rzehak & Kriebitzsch (Int J Multiphase Flow, 2015, Vol. 68, 135–152)
  • free surface turbulence damping for k-ω SST (symmetric and asymmetric damping, Frederix et al., Nucl Eng Des, 2018, Vol. 333, 122-130)
  • dynamic time step adjustment via PID controller
  • 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
    • a two-dimensional stratified flow based on WENKA experiment (Stäbler, Ph.D. thesis, 2007)

Keywords: OpenFOAM; C++; CFD; Finite volume method; Multiphase flow; Multi-field two-fluid model; Eulerian-Eulerian model; Momentum interpolation; Partial elimination algorithm; Free Surface

Related publications

  • Software in the HZDR data repository RODARE
    Publication date: 2020-04-06
    DOI: 10.14278/rodare.286
    License: GPL-3.0-only


Publ.-Id: 30885

Rühr- und Mischvorgänge in Biogasanlagen: Potentiale und Erfolgschancen

Annas, S.; Elfering, M.; Jantzen, H.-A.; Scholz, J.; Janoske, U.; Heller, A.; Buntkiel, L.

Im Rahmen des Forschungsvorhabens NeoBio wird die Problematik des optimalen Mischprozesses in Biogasanlagen aufgegriffen, um praktikable Lösungsansätze für die optimale Auslegung der Mischprozesse zu finden.
In diesem Zusammenhang steht die Bestimmung instationärer Geschwindigkeitsfelder in Biogasanlagen über in der Fermentersuspension mitschwimmende Funksensoren im Fokus, welche ihre Position über Laufzeitmessungen detektieren. In Kombination mit Inertialsensoren können Bewegungen auch unterhalb des Flüssigkeitsspiegels be-stimmt werden. Die ermittelten Geschwindigkeitsdaten werden für die Auslegung von Rührwerksgeometrien, -korrespondenzen und die Validierung von Modellversuchen genutzt.
In modellmaßstäblichen Untersuchungen an einem Fermenter mit Paddelrührwerk (Maßstab 1:40) konnte bereits gezeigt werden, welchen Einfluss alternative Rührwerk-spositionen auf den Mischprozess haben. Eine Verringerung von Totzonen sowie die Reduzierung der Rühr- bzw. Mischzeit um bis zu 80 % sind erreichbar. Dabei sind die notwendigen Anpassungen überschaubar und somit in der Praxis leicht zu realisieren.
Diese Erkenntnisse werden bereits in aktuellen Anlagen umgesetzt und sind ein Bau-stein bei der Wirkungsgradsteigerung. Um das Optimierungspotential sicher bewerten zu können, müssen die Ergebnisse noch im Originalmaßstab validiert werden. In die-sem Zusammenhang soll die beschriebene Messtechnik eingesetzt werden

  • Open Access Logo Contribution to proceedings
    14. Rostocker Bioenergieforum, 16.-17.06.2020, Rostock, Deutschland
    Tagungsband zum 14. Rostocker Bioenergieforum / 19. DIALOG Abfallwirtschaft MV
    DOI: 10.18453/rosdok_id00002650

Publ.-Id: 30884

Convective Instability in Sheared Foam

Heitkam, S.; Eckert, K.

This work provides evidence that anisotropic drainage in sheared foam is at the origin of convective instability (CI) in very long foam channels. CI occurs in foam under forced drainage when a critical liquid fraction is exceeded. Liquid spontaneously accumulates at one side of the channel. The weight imbalance induces convection rolls in the foam. Experiments in a very long vertical foam channel demonstrate that the critical liquid fraction is smaller than in previous findings by a factor of five. The critical liquid fraction depends on both the channel length and the inhomogeneity of the liquid feed. Well below the critical liquid fraction, a static, elastic shear deformation of the foam structure occurs. At the critical liquid fraction, initial steady convection rolls are located at the lower region of the channel and expand as the liquid fraction further increases. Combining the drainage equation with both the elastic response of the foam and a model for anisotropic drainage, a critical liquid fraction for the growth of an initial liquid imbalance is derived analytically, which corresponds very well to the experimental findings. Numerical simulations of the drainage equation and the elastic response of the foam reproduce these experimental and analytical findings.

Keywords: Foam Drainage; Convective Instability; Yield Stress

Publ.-Id: 30883

Synthesis and evaluation of new 1-oxa-8-azaspiro[4.5]decane derivatives as candidate radioligands for sigma-1 receptors

Tian, J.; He, Y.; Deuther-Conrad, W.; Fu, H.; Xie, F.; Zhang, Y.; Wang, T.; Zhang, X.; Zhang, J.; Brust, P.; Huang, Y.; Jia, H.

We report the design, synthesis, and evaluation of a series of 1-oxa-8-azaspiro[4.5]decane and 1,5-dioxa-9-azaspiro[5.5]undecane derivatives as selective σ1 receptor ligands. All seven ligands exhibited nanomolar affinity for σ1 receptors (Ki(σ1) = 0.61 – 12.0 nM) and moderate selectivity toward σ2 receptors (Ki(σ2)/ Ki(σ1) = 2 – 44). Compound 8 with the best selectivity among these ligands was selected for radiolabeling and further evaluation. Radioligand [18F]8 was prepared via nucleophilic 18F-substitution of the corresponding tosylate precursor, with an overall isolated radiochemical yield of 12-35%, a radiochemical purity of >99%, and molar activity of 94 – 121 GBq/μmol. Biodistribution studies of [18F]8 in mice demonstrated high initial brain uptake at 2 min. Pretreatment with SA4503 resulted in significantly reduced brain-to-blood ratio (70% - 75% at 30 min). Ex vivo autoradiography in ICR mice demonstrated high accumulation of the radiotracer in σ1 receptor-rich brain areas. These findings suggest that [18F]8 could be a lead compound for further structural modification to develop potential brain imaging agent for σ1 receptors.

Keywords: 1-oxa-8-azaspiro[4.5]decane derivatives; 1,5-dioxa-9-azaspiro[5.5]undecane derivatives; σ1 receptor; fluorine-18; positron emission tomography

Publ.-Id: 30882

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

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.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-01-17
    DOI: 10.14278/rodare.284
    License: CC-BY-4.0


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.

Publ.-Id: 30879

A smart multi-plane detector design for ultrafast electron beam X-ray computed tomography

Bieberle, A.; Windisch, D.; Iskander, K.; Bieberle, M.; Hampel, U.

In this paper, a novel concept for multi-plane ultrafast electron beam X-ray computed tomography (UFXCT) is presented. The concept is based on multi-plane electron beam scanning on a semi-transparent X-ray target and cuboid-shape scintillation detectors for radiation detection over an extended axial range. The optical part of the scintillation detector acts as both a scintillator and a light guide. With that, we achieve a low detector complexity and number of detector elements, overall power consumption and detector costs. We investigated the performance of this new concept with a prototypical detector module made of cerium doped lutetium yttrium orthosilicate (LYSO:Ce) as scintillator and an avalanche photodiode (APD) array. Thereby, we assessed two design variants: a monolithic LYSO bar detector and a sandwich detector made of multiple LYSO crystals and glass light-guides.

Keywords: Ultrafast computed tomography; 3D tomography; scintillation detectors

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Publ.-Id: 30878

Synthesis, Structural, and Electronic Properties of K2PuVIO2(CO3)3(cr): An Environmentally Relevant Plutonium Carbonate Complex

Pidchenko, I.; März, J.; Hunault, M. O. J. Y.; Bauters, S.; Butorin, S. M.; Kvashnina, K.

The chemical properties of actinide materials are often predefined and described based on the data available for isostructural species. This is the case for potassium plutonyl (PuVI) carbonate, K4PuVIO2(CO3)3(cr), a complex relevant for nuclear technology and the environment, of which the crystallographic and thermodynamic properties of which are still lacking. We report here the synthesis and characterization of PuVI achieved by single-crystal X-ray diffraction analysis and high-energy-resolution fluorescence-detected X-ray absorption near-edge structure at the Pu M4-edge coupled with electronic structure calculations. The crystallographic properties of PuVI are compared with isostructural uranium (U) and neptunium (Np) compounds. Actinyl (AnVI) axial bond lengths, [O-AnVI-O]2+, are correlated between solid, K4AnVIO2(CO3)3(cr), and aqueous, [AnVIO2(CO3)3]4-(aq) species for the UVI-NpVI-PuVI series. The spectroscopic data are compared to KPuVO2CO3(cr) and PuIVO2(cr) to tackle the trend in the electronic structure of PuVI regarding the oxidation state changes and local structural modifications around the Pu atom.

Keywords: Plutonium (Pu); Actinide; Carbonate Complex; X-ray absorption spectroscopy

Publ.-Id: 30877

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.

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-04-02
    DOI: 10.14278/rodare.280


Publ.-Id: 30876

Lithium Diffusion in Ion-Beam Sputter-Deposited Lithium-Silicon Layers

Strauss, F.; Hüger, E.; Julin, J. A.; Munnik, F.; Schmidt, H.

Lithium-silicon compounds are used as active material in negative electrodes of Li-ion batteries. The knowledge of Li diffusion in these materials is of importance for an optimization of charging/discharging rates and achievable maximum specific capacity as well as for an understanding of the basic lithiation mechanism. We carried out Li tracer self-diffusion experiments on ion-beam sputter-deposited LixSi(O) thin films for x ~ 0.25 and x ~ 4.5 using LixSi/6LixSi hetero-structures in combination with secondary ion mass spectrometry in line scan like mode. Measurements with elastic recoil detection analysis revealed the presence of a considerable amount of oxygen in the films. The diffusivities follow the Arrhenius law in the temperature range between 300 and 500 °C with an activation energy of 0.8 – 0.9 eV. The film containing a higher amount of Li shows faster diffusion by one order of magnitude. The Li diffusivities in the investigated Li-rich materials are several orders of magnitude higher than in Li-poor LixSi films (x = 0.02 to 0.06) as given in literature because of a lower activation energy. This indicates the presence of a direct interstitial-like mechanism. Oxygen present in samples with the same Li concentration of x = 0.06 also enhances diffusion but does not lead to a reduction in the activation energy.

Publ.-Id: 30875

A detailed ellipsometric porosimetry and positron annihilation spectroscopy study of porous organosilicate-glass 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.

Organosilicate-glass films with a varying ratio of terminal methyl and bridging ethylene groups are synthesized using BTMSE/MTMS mixtures and sol-gel technology. The films have been characterized by Fourier Transform Infrared spectroscopy, Ellipsometric Porosimetry and Positron Annihilation Spectroscopy. The hard bake at 400 ºC generates the final pore structure, which depends on the curing environment. It is shown that ethylene bridge is destructed during the hard bake in air via formation of peroxide radicals that form ΞSiOH during the further transformation. Continuous hard bake leads to condensation of silanol groups and form a structure similar to the ordinary silica.
The pore size of highly porous materials (>30%) is larger in air cured films. Destruction of the ethylene bridge makes the films matrix soft and micropores collapse during the template evaporation due to the capillary forces. It leads to the film shrinkage, increases the size of internal voids. The air cured samples showed better mechanical properties than N 2 cured ones although in the last case ethylene bridging groups were preserved. The reason is that the collapse of micropores increases internal density and creates more favorable condition for condensation of silanol groups.

Keywords: Low-k films; Pore structure; Ellipsometric Porosimetry; Positron annihilation spectroscopy; Young's Modulus

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Publ.-Id: 30874

Development of a Fluorine-18-labeled Benzoimidazotriazine-based radioligand for the imaging of Phosphodiesterase 2A in the brain with positron emission tomography

Ritawidya, R.

Cyclic nucleotide phosphodiesterase 2A (PDE2A) is highly expressed in distinct areas of the brain associated with neurodegenerative and neuropsychiatric diseases like Alzheimer's disease, dementia, and schizophrenia. Specific PDE2A radioligands for the imaging of PDE2A via positron emission tomography (PET) would be helpful for the research related to the disease-related changes in the expression of this enzyme in the brain. Therefore, this thesis aims to develop a specific PDE2A radioligand for the imaging of PDE2A in the brain via PET. A series of novel fluorinated PDE2A inhibitors on the basis of a benzoimidazotriazine (BIT) scaffold was prepared by a multistep synthesis route, and their inhibitory potency towards PDE2A and selectivity over other PDEs were evaluated. Based on the in vitro inhibitory activity evaluation, one derivative, 1-(2-chloro-5-methoxy phenyl)-8-(2-fluoropyridin-4-yl)-3-methylbenzo[e]imidazo[5,1-c][1,2,4]triazine turned out to be the prospective compound. Additional in vitro studies of this ligand using mouse liver microsomes (MLM) revealed this ligand has a promising microsomal stability for 18F-labeling.This novel radioligand was prepared by nucleophilic aromatic substitution of the corresponding nitro precursor and evaluated for the potential application for imaging of PDE2A. In vitro autoradiography on pig brain cryosections demonstrated a heterogeneous spatial distribution of this radiotracer corresponding to PDE2A regions. The investigation of the in vivo metabolism of this radiotracer in mice revealed sufficient metabolic stability. PET studies in mice exhibited a moderate brain uptake of the radiotracer. Further, in vivo blocking studies showed a non-target specific binding of the radiotracer. Therefore, further structural modifications are required to improve target selectivity.

  • Doctoral thesis
    Universität Leipzig, 2020
    Mentor: Prof. Dr. Peter Brust (FWPN)
    158 Seiten

Publ.-Id: 30873

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

Publ.-Id: 30872

Influence of structure and cation distribution on magnetic anisotropy and damping in Zn/Al doped nickel ferrites

Lumetzberger, J.; Buchner, M.; Pile, S.; Ney, V.; Gaderbauer, W.; Daffé, N.; Moro, M. V.; Primetzhofer, D.; Lenz, K.; Ney, A.

An in-depth analysis of Zn/Al doped nickel ferrite thin films grown by reactive magnetron sputtering was conducted to gain insight into the magnetic properties interesting for applications in spintronics. The material is insulating, ferromagnetic at room temperature and has a low magnetic damping with additional strong magnetoelastic coupling. The sample system is analyzed with regard to crystal structure, chemical composition and static as well as dynamic magnetic properties. Thus a correlation between composition, strain, cation distribution, magnetocrystalline anisotropy and damping is evidenced. X-ray magnetic circular dichroism spectra and field dependent curves at the L3;2 edges of Ni and Fe are performed to complement integral magnetometry measurements and identify their magnetic contributions to the hysteresis. In particular, a strong in uence of the lattice site occupation of Ni2+ Td and cation coordination of Fe2+ Oh on the intrinsic damping is found. Furthermore, the vital role of the incorporation of Zn2+ and Al3+ is evidenced by comparison with a sample of altered composition. A strain-independent reduction of the magnetic anisotropy and damping by adapting the cation distribution is demonstrated.

Keywords: ferrites; ferromagnetic resonance; x-rays; XMCD; cation distribution; damping; hysteresis; magnetic properties; thin films


Publ.-Id: 30870

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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Publ.-Id: 30869

High-sensitivity investigation of low-lying dipole strengths in 120Sn

Müscher, M.; Wilhelmy, J.; Savran, D.; Schwengner, R.; Massarczyk, R.; Grieger, M.; Isaak, J.; Junghans, A. R.; Kögler, T.; Ludwig, F.; Symochko, D.; Takacs, M. P.; Tamkas, M.; Wagner, A.; Zilges, A.

Background: The term Pygmy Dipole Resonance (PDR) denotes electric dipole excitations below and around the neutron separation threshold. It may be important, e.g., for the nucleosynthesis of heavy nuclei or the symmetry energy in the Equation of State (EoS). For a deeper understanding of the PDR systematic studies are essential.
Purpose: The tin isotopic chain is a well-suited candidate to investigate the systematics of the PDR and the (g,g') reactions on 112,116,120,124Sn have already been measured in experiments using bremsstrahlung. It was claimed that the extracted electric dipole transition strengths of these isotopes increase with increasing neutron-to-proton ratio with the exception of 120 Sn. Furthermore, previous results from elastic photon scattering experiments on 120Sn are in disagreement with corresponding (p,p') Coulomb excitation data. To examine this discrepancy an additional high-sensitivity bremsstrahlung experiment on 120Sn was performed.
Method: The Nuclear Resonance Fluorescence (NRF) method is used which bases on real photon scattering. The bremsstrahlung experiment presented in this work was performed with a maximum energy of E = 9.5 MeV at the gELBE facility at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). Besides a state-to-state analysis, the quasi-continuum was investigated as well.
Results: Above Ex = 4 MeV 236 dipole transitions were clearly identified and 168 of those were observed for the first time. Assuming that all analyzed transitions have electric dipole character the summed electric dipole strength equals B(E1) = 374(35) e2 fm2 (0.54(5) % of the TRK sum rule) for transitions from 4 MeV to Sn = 9.1 MeV. This is an enhancement of a factor 2.3 compared to the previously published 120Sn(g,g') results.
Especially, the observation of many weaker transitions in the state-to-state analysis lead to this increase. The photo-absorption cross sections deduced from the quasi-continuum analysis are about two times higher than the results of the (p,p') experiment.
Conclusion: The newly extracted summed B(E1) value of the state-to-state analysis is larger than those of 112,116Sn and smaller than that of 124 Sn. The difference between the present (g,g') data and the results of the inelastic proton scattering experiment above 6.3 MeV is still striking. The deviation may be explained by unobserved decay branchings and unresolved strength. Up to now, there is no explanation for the discrepancy between the extracted photo-absorption cross sections of the analysis of the quasi-continuum and the (p,p')
measurement. Additional experiments may shed light on this deviation.

Keywords: Photon scattering; Photoabsorption cross section; Electromagnetic transition strengths

Publ.-Id: 30867

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.

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

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

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

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

Publ.-Id: 30862

Cation exchange protocols to radiolabel aqueous stabilized ZnS, ZnSe and CuFeS2 nanocrystals with 64Cu for dual radio- and photo-thermal therapy

Avellini, T.; Soni, N.; Silvestri, N.; Fiorito, S.; de Donato, F.; de Mei, C.; Cassani, M.; Ghosh, S.; Walther, M.; Manna, L.; Stephan, H.; Pellegrino, T.

In metal chalcogenide nanocrystals (NCs), the cations can be partially or fully replaced with other cations through the so-called cation exchange (CE) reactions. Here, we took advantage of these CE reactions to replace the cations on different chalcogenides NCs with 64Cu ions in order to radiolabel them. With respect to other approaches reported in the literature, our CE protocol is easily transferable to the clinic. It requires indeed one single step, in which the water-soluble NCs are mixed with a 64Cu copper(II) chloride solution of high specific activity, in the presence of vitamin C used as a reducing agent for Cu(II) to Cu(I)). Given the quantitative replacement of the cations of the NCs with 64Cu(I), a high radiochemical yield up to 90-95% can be reached. Provided that there is no free 64Cu, no purification step is needed, making the protocol straightforward. At the same time, the amount of NCs required for the exchange is so low (in the range of μg) that the dose of NCs shows no intrinsic cytotoxicity. This protocol works on different types of metal chalcogenide NCs. In ZnSe and ZnS NCs, the Zn(II) ions are exchanged with 64Cu (I) ions, and in CuFeS2 NCs the Fe(III) ions are exchanged with 64Cu(I). To ensure the stability of the NCs during and after the CE reaction, a multi-anchoring coating procedure based on PEG, cysteamine and poly-maleic anhydride was proven to be more efficient than the use of monothiol PEG ligands. With our approach we managed to achieve an unprecedented high specific activity, i.e. the amount of 64Cu radionuclide loaded per NC dose, to dispatch remarkable ionizing effects. Indeed, by exploiting a volumetric cations exchange, our strategy enables to concentrate a large dose of 64Cu (18.5 MBq) in a small NC dose (0.4 μg), reaching a specific activity of about 50 TBq/g. Remarkably, for CuFeS2 NCs even after the CE, the radiolabeled 64Cu:CuFeS2 NCs still show the characteristic dielectric resonance that enables the generation of heat under laser exposure for clinical use (1 W/cm2). The synergic toxicity of photo-ablation and 64Cu radiation exposure is here demonstrated in an in vitro study on glioblastoma and epidermoid carcinoma tumor cells.

Publ.-Id: 30861

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

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.

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.


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%.


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

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

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.

Publ.-Id: 30854

Development of novel analogs of the monocarboxylate transporter ligand FACH and biological validation of one potential radiotracer for PET imaging

Sadeghzadeh, M.; Wenzel, B.; Gündel, D.; Deuther-Conrad, W.; Toussaint, M.; Moldovan, R.-P.; Fischer, S.; Teodoro, R.; Jonnalagadda, S.; Jonnalagadda, S. K.; Mereddy, V. R.; Drewes, L. R.; Brust, P.

Monocarboxylate transporters 1-4 (MCT1-4) are involved in several metabolism-related diseases, especially cancer, providing the chance to be considered as relevant targets for diagnosis and therapy. [18F]FACH was recently developed and showed very promising preclinical results as a potential PET radiotracer for imaging of MCTs, which encouraged us to develop the novel analogs 1 and 2 of FACH. They were synthesized via Buchwald-Hartwig amination starting from m-anisidine followed by Vilsmeier-Haack formylation and Knoevenagel condensation in moderate overall yields. MCT1 inhibition was estimated by [14C]lactate uptake assay on rat brain endothelial (RBE4) cells. Although 2 showed 25-times lower MCT1 inhibitory potency than FACH (IC50 = 11 nM), compound 1 could be a suitable PET candidate with an IC50 value of 118 nM. Therefore, 1 was selected for radiosynthesis of [18F]1 and subsequent biological evaluation as a potential PET radiotracer for imaging of the MCT expression in mouse brain. By in vitro autoradiography in cryosections of the mouse kidney, 50% displacement of [18F]1 by 10 µM of the specific MCT1 inhibitor α-cyano-4-hydroxycinnamic acid (α-CHC) was observed. Despite a higher lipophilicity of [18F]1 compared to [18F]FACH, in vivo brain uptake of [18F]1 was in a similar range, likely to be related to similar transport rates by MCTs on RBE4 cells. The high uptake of the new radiotracer in kidney and other peripheral MCT-expressing organs together with significant reduction by α-CHC, suggests the suitability of [18F]1 for imaging of the MCTs expression in vivo.

Keywords: monocarboxylate transporters (MCTs); FACH; 18F-labeled analog of FACH; α-CHC; blood-brain barrier (BBB); positron emission tomography (PET) imaging

Publ.-Id: 30853

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

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

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

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

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.

Publ.-Id: 30848

Low frequency dependent elastic modulus in UCo1-xOsxAl

Kumano, S.; Ishii, I.; Horio, R.; Mizuno, T.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Yamamura, T.; Suzuki, T.

UCoAl with the hexagonal ZrNiAl-type structure shows an itinerant metamagnetic phase transition at 0.7 T in the magnetic field along the c-axis. Whereas, this compound becomes to undergo a ferromagnetic phase transition in zero field by substituting Os for Co. UCo0.995Os0.005Al exhibits the ferromagnetic phase transition at TC = 8 K. At high temperatures, the temperature dependence of the transverse elastic modulus C44 in UCo0.995Os0.005 Al shows a slight softening below 50 K. The softening turns to an abrupt hardening below 30 K. With further decreasing temperature, a bending is observed at TC. Although TC changes sensitively by applying the magnetic fields, the temperature of the elastic hardening is robust in the magnetic fields. This elastic hardening is not caused by a magnetic origin. We measured ultrasonic frequency dependences of C44 and found that the temperature of the elastic hardening increases with increasing ultrasonic frequency. We propose that this ultrasonic frequency dependence is due to a large amplitude atomic motion of constituent atoms.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011173
    DOI: 10.7566/JPSCP.30.011173

Publ.-Id: 30847

Preclinical incorporation dosimetry of [18F]FACH - a novel 18F-labeled MCT1/MCT4 lactate transporter inhibitor for imaging cancer metabolism with PET

Sattler, B.; Kranz, M.; Wenzel, B.; Thachaantara Jain, N.; Moldovan, R.-P.; Toussaint, M.; Deuther-Conrad, W.; Ludwig, F.-A.; Teodoro, R.; Sattler, T.; Sadeghzadeh, M.; Sabri, O.; Brust, P.

Overexpression of monocarboxylate transporters (MCTs) has been shown for a variety of human cancers (e.g. colon, brain, breast, and kidney) and inhibition resulted in intracellular lactate accumulation, acidosis and cell death. Thus, MCTs are promising targets to investigate tumor cancer metabolism with positron emission tomography (PET). Here, the organ doses (OD) and the effective dose (ED) of the first 18F-labeled MCT1/MCT4 inhibitor were estimated in juvenile pigs. Whole-body dosimetry was performed in three piglets (age: ~6 weeks, weight: ~13-15 kg). The animals were anaesthetized and subjected to sequential PET/CT up to 5h after i.v. injection of 156 ± 54 MBq [18F]FACH. All relevant organs were defined by volumes of interest. Exponential curves were fitted to the time-activity data. Time and mass scales were adapted to the human order of magnitude and the ODs calculated using the ICRP 89 adult male phantom with OLINDA 2.1. The ED was calculated using tissue weighting factors as published in the ICRP103. The highest organ dose was received by the urinary bladder (62.6 ± 28.9 µSv/MBq), followed by the gall bladder(50.4 ± 37.5 µSv/MBq) and the pancreas (30.5 ± 27.3 µSv/MBq). The highest contribution to the ED was by the urinary bladder (2.5 ± 1.1 µSv/MBq) followed by the red marrow (1.7 ± 0.3 µSv/MBq) and the stomach (1.3 ± 0.4 µSv/MBq). According to this preclinical analysis,the ED to humans is 12.4 µSv/MBq when applying the ICRP103 tissue weighing factors. Taking into account that preclinical dosimetry underestimates the dose to humans by up to 40%, the conversion factor applied for estimation of the ED to humans would raise to 20.6 µSv/MBq. Resultantly, the ED to humans upon an i.v. application of ~300 MBq [18F]FACH would be about 6.2mSv. This risk assessment encourages to translate [18F]FACH to clinical study phases and to further investigate its potential as a clinical tool for cancer imaging with PET.

Keywords: preclinical radiopharmaceutical dosimetry; [18F]FACH; radiation safety; image based internal dosimetry; OLINDA; MCT1/MCT4 lactate transporter inhibitor

Publ.-Id: 30846

Crystal-field effects in Er3RuAl12with a distorted kagome lattice

Gorbunov, D.; Ishii, I.; Kurata, Y.; Andreev, A. V.; Suzuki, T.; Zherlitsyn, S.; Wosnitza, J.

We report on the magnetic and elastic properties of Er3Ru4Al12 in static and pulsed magnetic fields up to 58 T. From the ultrasound results, we obtain evidence for a phase transition at 2 K related to magnetic ordering. Furthermore, in the paramagnetic state, Er3Ru4Al12 shows pronounced anomalies in the magnetization and elastic moduli as a function of temperature and magnetic field. We explain our findings using a crystal-electricfield (CEF) model that includes quadrupolar interactions and propose a CEF level scheme for this material. However, the CEF effects cannot explain all field-induced anomalies, which indicates that refined models are needed for explaining these.


Publ.-Id: 30845

Ultrasonic Dispersion in the Hexagonal Ferromagnet Nd3Ru4Al12

Suzuki, T.; Mizuno, T.; Kumano, S.; Umeno, T.; Suzuki, D.; Andreev, A. V.; Gorbunov, D.; Henriques, M. S.; Ishii, I.

The rare-earth ferromagnet Nd3Ru4Al12 has Curie temperature TC= 39 K and crystallizes in the hexagonal Gd3Ru4Al12-type structure (space group P63/mmc), which is a non-caged structure. A previous measurement of the elastic moduli has shown an upturn around 10 K in the temperature dependence of the longitudinal modulus C33. The upturn is not caused by any phase transition. To investigate the origin of the upturn in Nd3Ru4Al12, we have measured the temperature dependence of C33 at various ultrasonic frequencies. The temperature of the upturn increases with increasing ultrasonic frequency indicating the ultrasonic dispersion, and it does not change under applied magnetic fields. These results suggest that the upturn originates from the rattling effect at one of the aluminium sites in the crystal structure. Assuming a Debye-type relaxation for the elastic modulus and an Arrhenius-type relaxation time for the rattling, the activation energy was estimated as E = 115 K and the relaxation time as Ƭ0 = 1.5 x 10-13s.

  • Contribution to proceedings
    International Conference on Strongly Correlated Electron Systems (SCES2019), 23.-28.09.2019, Okayama, Japan
    JPS Conference Proceedings 30(2020), 011091
    DOI: 10.7566/JPSCP.30.011091

Publ.-Id: 30843

Air-side thermal and flow performance study of additively manufactured tube bundle heat exchangers with novel fin design

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

Finned tube bundle heat exchangers are used in a variety of applications with the plain circular fin being the most common design. In the present investigation we proposed two novel heat exchanger designs integrated pins, which improve the heat conduction from the fin base to the fin tip as well as the convective heat transfer along the fin surface. Tubes with conventional circular plain fins (CPF) as well as novel circular integrated pin fins (CIPF) and serrated integrated pin fins (SIPF) were additively generated by a Selective Laser Melting (SLM) process. They were tested in a flow channel in a 2-row and a 3-row configuration under forced convection with Reynolds numbers between 1600 and 6600. For the new SIPF and CIPF designed we found an improved Nusselt number compare to the CPF and higher Nusselt number for the 2-row compared to the 3-row configuration. From the analysis of the single tube rows it was found that the Nusselt number is highest for the first row and reduces downstream. The friction factor was lowest for the SIPF at all Reynolds number and the CIPF gave lower friction factor compared to CPF for Reynolds numbers up to approximately Re=4000. Furthermore, the performance of the heat transfer surface was evaluated by the performance evaluation criterion. Hence, an enhancement of 72.6 % and 33.6 % for the 2-row configuration as well as 63.4 % and 29.1 % for the 3-row configuration for the SIPF and CIPF compared to the CPF was found. The compactness of the heat exchanger was evaluated by the volumetric heat flux density, which was greatest for the CIPF followed by the SIPF and lowest for the conventional CPF design. In general the 2-row heat exchanger configuration reached greater performance and volumetric heat flux density than the 3-row configuration. The global performance criterion strongly depends on the flow conditions. Thus, the SIPF heat exchanger performs best at lower and intermediate Reynolds numbers up to Re=5000 and the CPF design is best at higher Reynolds numbers. Eventually, the surface area and the volume of the heat exchanger with SIPF are 30.7 % and 6.9 % lower compared to the conventional heat exchanger. Based on the experimental results an empirical heat transfer correlation was derived, which includes Nusselt number, Reynolds number, Prandtl number, fin design and tube row number.

Keywords: Novel heat exchanger designs; Heat transfer; Friction factor; Thermal-flow performance; Additive Manufacturing; Integrated pin fin

Related publications

Publ.-Id: 30842

Thermal and flow performance of tilted oval tubes with novel fin designs

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

We studied the thermal and flow performance of tube heat exchangers with novel fin designs for tube tilt angles of "0°,20°,30°" and "40°" to the horizontal. The novel fin designs target to enhance the conduction heat transfer within the fin and the convective heat transfer along the fin surface simultaneously. Tubes with three different fin designs, the circular plain fin (CPF), the circular integrated pin fin (CIPF) and the serrated integrated pin fin (SIPF), were additively manufactured by selective laser melting and experimentally investigated in an air flow channel for Reynolds number between "1800" and "7800" . We analysed the performance evaluation criterion, the volumetric heat flux density and the global performance criterion. It was found, that the SIPF achieves highest performance evaluation criterion and the CPF performs worst. Thus, the SIPF is recommended, when the required surface area, the material cost and the weight of the finned tube heat exchanger are relevant. Highest heat transfer per volume heat exchanger and temperature difference was achieved for the CIPF at highest tube tilt angle. The value of the global performance criterion strongly depends on the fin design and the tube tilt angle. For the horizontal orientation the CPF reaches highest global performance and for the 40° tube tilt angle the CIPF gives best performance. From the experimental data we derived appropriate heat transfer correlations for Reynolds number, Prandtl number, tube tilt angle and fin designs.

Keywords: Finned tube heat exchanger; Novel fin designs; Heat transfer; Friction factor; Tube tilt angle; Thermal-flow performance; Additive Manufacturing

Related publications

Publ.-Id: 30841

Air-side thermal and flow performance study of additively manufactred tube bundle heat exchagers with novel fin designs

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

These are the raw data and the processed data of the journal paper "Air-side thermal and flow performance study of additively manufactred tube bundle heat exchagers with novel fin designs".

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

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2020-03-23
    DOI: 10.14278/rodare.271
    License: CC-BY-4.0


Publ.-Id: 30840

Rhenium and technetium-complexed silicon rhodamines as near-infrared imaging probes for bimodal SPECT- and optical imaging

Kanagasundaram, T.; Kramer, C. S.; Boros, E.; Kopka, K.

Radiolabelled fluorescent dyes are decisive for bimodal imaging and currently in demand for scintigraphic and optical imaging. This powerful method allows the combination of nuclear imaging (e.g. SPECT-imaging) and optical imaging which leads to synergistic effects, resulting in high spatial resolution and high tissue penetration from the whole body to the subcellular level. The new approaches in tumor imaging and its resection enables the accurate differentiation of healthy and diseased (e.g. tumor) tissues. Organic dyes belonging to the rhodamine family show unique optical properties such as high quantum yields, large extinction coefficients, absorption and emission properties in the optical window. The goal of this work was the development of small molecule near-infrared (NIR) light-emitting silicon-rhodamines (SiR) for scintigraphic and optical imaging. We utilized the dyes for copper(I)-catalyzed alkyne-azide [3+2]-cycloaddition to receive respective 1,2,3-triazoles for complexing the prominent SPECT-radiometal 99mTc(I)- and rheniumtricarbonyl core using the click-to-chelate concept from Mindt et al. The dyes were fully characterized using NMR-, UV/VIS/NIR-spectroscopy, IR and mass spectrometry. The presented silicon rhodamines with optical properties in the near-infrared region with emission wavelengths of ca. 650 nm and quantum yields in aqueous solution of up to 0.10 were received in seven reaction steps. The determined extinction coefficients of ca. 150.000 M-1cm-1 show promising results, making them potentially useful for bimodal imaging. Furthermore the dyes were prepared as precursors for radiolabelling with the SPECT-compatible radiometal technetium-99m. Corresponding rhenium-Si-rhodamines [used as a non-radioactive technetium-surrogate] were chemically characterized as well. Subsequently perfomed radiolabelling experiments have shown radiochemical yields of up to 59% and a radiochemical purity greater than 98%. The complexes show high stability both in aqueous solution and even in challenging experiments with histidine under physiological conditions. The first-in-class dyes have been synthesized to elucidate their potential for fluorescence- and radio-guided surgery. The non-targeted radiolabelled rhodamine dyes are subject of ongoing biological evaluations and the incorporation of biovectors into the dye for selective (tumor) targeting are topics of current research.

Keywords: Radiochemistry; Organic Synthesis; Click Chemistry; Technetium-99m Chemistry; Fluorescent Dyes; Silicon Rhodamines; Bimodal Imaging; Multimodal Imaging; SPECT Imaging; Optical Imaging


Publ.-Id: 30839

The application of HEXS and HERFD XANES for accurate structural characterization of actinide nanomaterials: application to ThO₂.

Amidani, L.; Vaughan, G. B. M.; Plakhova, T. V.; Romanchuk, A. Y.; Gerber, E.; Svetogorov, R.; Weiß, S.; Joly, Y.; Kalmykov, S. N.; Kvashnina, K.

Structural characterization of actinide nanoparticles (NPs) is of primary importance and hard to achieve, especially for non‐homogeneous samples with NPs below 3 nm. By combining High Energy X‐ray Scattering (HEXS) and High‐Energy‐Resolution Fluorescence Detected X‐ray Near‐Edge Structure (HERFD XANES), we characterized for the first time both short‐ and medium‐range order of ThO₂ NPs obtained by chemical precipitation. With this methodology, a novel insight into the structure of NPs at different steps of their formation process is achieved. The Pair Distribution Function (PDF) reveals a high concentration of ThO₂ small units similar to Th hexamer clusters mixed with 1 nm ThO₂ NPs in the initial steps of formation. Drying the precipitates at ⁓150 °C promotes recrystallization of the smallest units into more thermodynamically stable ThO₂ NPs. HERFD XANES at Th M₄ edge, a direct probe of the f states, shows variations that we correlate to the break of the local symmetry around Th atoms, which most likely concerns surface atoms. Together, HEXS and HERFD are a powerful methodology to investigate actinide NPs and their formation mechanism.

Keywords: actinides; HERFD; HEXS; nanoparticles; ThO₂

Publ.-Id: 30838

Photoexcited organic molecules en route to highly efficient autoionization

Vempati, S.; Bogner, L.; Richter, C.; Deinert, J.-C.; Foglia, L.; Gierster, L.; Stähler, J.

The conversion of optical and electrical energies in novel materials is key to modern optoelectronic and light-harvesting applications. Here, we investigate the equilibration dynamics of photoexcited 2,7-bis(biphenyl-4-yl)-2′,7′-ditertbutyl-9,9′-spirobifluorene (SP6) molecules adsorbed on ZnO(10-10) using femtosecond time-resolved two-photon photoelectron and optical spectroscopies. We find that, after initial ultrafast relaxation on femtosecond and picosecond time scales, an optically dark state is populated, likely the SP6 triplet (T) state, that undergoes Dexter-type energy transfer (rDex = 1.3 nm) and exhibits a long decay time of 0.1 s. Because of this long lifetime, a photostationary state with average T–T distances below 2 nm is established at excitation densities in the 1020 cm−2 s−1 range. This large density enables decay by T–T annihilation (TTA) mediating autoionization despite an extremely low TTA rate of kTTA = 4.5 ⋅ 10−26 m3 s−1. The large external quantum efficiency of the autoionization process (up to 15%) and photocurrent densities in the mA cm−2 range offer great potential for light-harvesting applications.

Keywords: Autoionization; Photoelectron spectroscopy; organic electronics

Publ.-Id: 30837

Drone-based surveys of mineral deposits

Jackisch, R.

Drones are becoming important tools for mineral exploration by contributing to the safe, efficient and sustainable provision of the high-tech metals that are required by modern society.

Keywords: economic geology; mineralogy; UAV; hyperspectral; magnetics

Publ.-Id: 30836

UniCAR T cell immunotherapy enables efficient elimination of radioresistant cancer cells

Arndt, C.; Loureiro, L. R.; Feldmann, A.; Jureczek, J.; Bergmann, R.; Máthé, D.; Hegedüs, N.; Berndt, N.; Koristka, S.; Metwasi, N.; Fasslrinner, F.; Lamprecht, C.; Kegler, A.; Hoffmann, A.; Bartsch, T.; Köseer, A. S.; Egan, G.; Schmitz, M.; Hořejší, V.; Krause, M.; Dubrovska, A.; Bachmann, M.

Induction or selection of radioresistant cancer (stem) cells following standard radiotherapy is presumably one of the major causes for recurrence of metastatic disease. One possibility to prevent tumor relapse is application of targeted immunotherapies including e.g. chimeric antigen receptor (CAR) T cells. In light of long-term remissions it is highly relevant to clarify whether radioresistant cancer cells are susceptible to CAR T cell-mediated killing. To answer this question, we evaluated the anti-tumor activity of the switchable universal chimeric antigen receptor (UniCAR) system against highly radioresistant head and neck squamous cell carcinoma cells both in vitro and in vivo. Following specific UniCAR T cell engagement via EGFR or CD98 target modules, T cell effector mechanisms were induced including secretion of pro-inflammatory cytokines, up-regulation of granzyme B and perforin as well as T cell proliferation. CD98- or EGFR-redirected UniCAR T cells further possess the capability to efficiently lyse radioresistant tumor cells. Observed anti-tumor effects were comparable to those against the radiosensitive parental cell lines. Finally, redirected UniCAR T cells significantly inhibited growth of radioresistant cancer cells in immunodeficient mice. Taken together, our obtained data underline that the UniCAR system is able to overcome radio-resistance. Thus, it represents an attractive technology for the development of combined radioimmunotherapeutic approaches that might improve the outcome of patients with metastatic radioresistant tumor diseases.

Keywords: radio-resistance; CD98; EGFR; adaptor CAR; T cell immunotherapy

Publ.-Id: 30835

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