Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41397 Publications

Efforts towards PET-activatable red-shifted silicon rhodamines and silicon pyronine dyes

Kramer, C. S.; Kanagasundaram, T.; Matthias, J.; Kopka, K.

Tracers for bimodal optical imaging and positron emission tomography unite multiple ad-vantages in a single molecule. Their tumor-specific uptake can be visualized after their PET-activation by radiofluorination via PET/CT or PET/MRI allowing for staging or therapy planning, while their non-radioactive moiety additionally facilitates the visualization of malig-nant tissue during intraoperative fluorescence-guided surgery or in histological assessments. The silicon-bridged xanthene core offers the opportunity for radiofluorination with SiFA isotope exchange to obtain a small molecule PET-activatable NIR dye that can be linked to different tar-get vectors. Herein, we demonstrate the PET-activation of a fluorinated silicon pyronine, be-longing to a class of low-molecular weight fluorescence dyes with a large Stokes shift and sol-vent-dependent NIR dye properties, with successful radiochemical conversion. Moreover, a li-brary of unusually functionalized, red-shifted silicon rhodamines was synthesized, which can be easily conjugated by amide bond formation or ‘click-reaction’ approaches.

Keywords: tracer; bimodal imaging; PET tracer; fluorine-18; radiofluorination; optical imaging; pyronine; silicon rhodamine; fluorescence dye; near-infrared dye; SiFA-IE

Permalink: https://www.hzdr.de/publications/Publ-36254
Publ.-Id: 36254


Using mini-CT specimens for the fracture characterization of ferritic steels within the ductile to brittle transition range: a review

Sánchez, M.; Cicero, S.; Kirk, M.; Altstadt, E.; Server, W.; Yamamoto, M.

The use of mini-CT specimens for the fracture characterization of structural steels is currently a topic of great interest from both scientific and technical points of view, mainly driven by the needs and requirements of the nuclear industry. In fact, the long-term operation of nuclear plants requires accurate characterization of the reactor pressure vessel materials and evaluation of the embrittlement caused by neutron irradiation without applying excessive conservatism. However, the amount of material placed inside the surveillance capsules used to characterize the resulting degradation is generally small. Consequently, in order to increase the reliability of fracture toughness measurements and reduce the volume of material needed for the tests, it is necessary to develop innovative characterization techniques, among which the use of mini-CT specimens stands out. In this context, this paper provides a review of the use of mini-CT specimens for the fracture characterization of ferritic steels, with particular emphasis on those used by the nuclear industry. The main results obtained so far, revealing the potential of this technique, together with the main scientific and technical issues will be thoroughly discussed. Recommendations for several key topics for future research are also provided.

Keywords: mini-CT; ductile-to-brittle transition range; reference temperature; master curve

Permalink: https://www.hzdr.de/publications/Publ-36253
Publ.-Id: 36253


PIConGPU -- High-Fidelity Plasma Simulations on Desktop Computers up to Exascale Compute Systems and a View on its Recent Applications

Debus, A.; Steiniger, K.; Bastrakov, S.; Bastrakova, K.; Bussmann, M.; Carstens, F.-O.; Chandrasekaran, S.; Garten, M.; Gruber, B. M.; Hernandez Arreguin, B.; Hübl, A.; Juckeland, G.; Kelling, J.; Lebedev, A.; Leinhauser, M.; Marre, B. E.; Meyer, F.; Ordyna, P.; Pausch, R.; Pöschel, F.; Rogers, D.; Schramm, U.; Sprenger, L.; Starke, S.; Thévenet, M.; Trojok, J.; Wang, M.; Widera, R.; Young, J.

PIConGPU’s latest release 0.6.0 in December 2021 brought a number of new features. Among these are an arbitrary-order Maxwell solver, the Higuera-Cary pusher, collisions, and incident field generation via the total field/scattered field technique enhancing its numerical stability and predictive capabilities.
Furthermore, there are various technical advances, most notably support of the HIP computational backend allowing to run on AMD GPUs. These advances are mainly driven by our participation in OLCF’s Frontier Center for Accelerated Application Readiness providing access to the hardware platform of the Frontier exascale supercomputer scheduled for deployment in 2022. We show performance data and present recent applications of PIConGPU profiting from these developments. To these applications belongs the advanced laser-plasma accelerator scheme Traveling-wave electron acceleration (TWEAC), providing scalability to energies beyond 10 GeV while avoiding staging. We further present simulation campaigns modeling and delivering valuable insight into the micrometer and femtosecond plasma dynamics of existing experimental
campaigns.

Keywords: particle-in-cell code; TWEAC; PIConGPU; performance portable

  • Poster
    767. WE-Heraeus-Seminar: Science and Applications of Plasma‐Based Accelerators, 15.-18.05.2022, Physikzentrum, Bad Honnef, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36252
Publ.-Id: 36252


minterpy: Multivariate Interpolation in Python

Schreiber, J.; Wicaksono, D. C.; Thekke Veettil, S. K.; Hajizade, A.; Zavalani, G.; Suarez Cardona, J. E.; Hernandez Acosta, U.; Hecht, M.

Many solutions to the computational challenges arising in the fields of computational science and engineering rely on solving interpolation tasks of highly-varying sparse and scattered data. The tasks include surrogate modeling, sparse data regression, global black-box optimization, model inference, as well as solutions for partial differential equations (PDE) on complex geometries.

Interpolation tasks in multi-dimensional space typically suffer from the curse of dimensionality in which the computational cost of interpolation scales exponentially with the number of dimensions.

The open-source Python package minterpy developed and maintained by the Hecht-Lab, CASUS, aims to lift the curse of dimensionality from a brand field of interpolation tasks arising across scientific disciplines.

Keywords: interpolation; multivariate interpolation; surrogate modeling; sparse data regression; global black-box optimization; model inference; partial differential equations (PDE)

  • Open Access Logo Poster
    Big data analytical methods for complex systems, 06.-07.10.2022, Wroclaw, Poland

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Permalink: https://www.hzdr.de/publications/Publ-36251
Publ.-Id: 36251


Transverse Emittance Measurements and Optimization for a Superconducting RF Photon Injector

Ma, S.

As one of the most promising continuous wave (CW) injectors for high brightness electron
beams, ELBE superconducting radio-frequency (SRF) gun has been developed and optimized.
This gun can provide beams with good quality for the ELBE user facility. One important
aspect is to measure the transverse emittance accurately and efficiently. This thesis contributes
to the progress in this field and focuses on measuring and optimizing the transverse emittance
for ELBE SRF gun. The slit-scan, quadrupole scan, and an advanced thermal emittance
measurement method, called single shot cathode transverse momentum imaging, have been
studied and applied at this SRF gun.
A fast slit-scan emittance measurement system consisting of a continuously moving slit and
a yttrium aluminium garnet (YAG) screen has been developed. During the beamlet image
processing, the machine learning (ML) algorithms have been integrated in order to improve
the signal-to-noise ratio effectively. This is the first time to successfully apply the ML in such
diagnostic methods. The measurement speed is improved about ten times and accuracy is also
better than before. The errors of slit-scan emittance measurement, arising from slit position,
beamlet intensity, center position and root mean square (RMS) width uncertainties, have been
analyzed. The quadrupole scan emittance measurement method has been studied too. The
influence of the space charge effect on quadrupole scan results has been revealed. The error of
the quadrupole scan measurement has also been analyzed.
To compensate the transverse emittance due to space charge effect, a superconducting (SC)
solenoid is placed as close as possible to the exit of the SRF cavity. Another important part in
this thesis is the investigation and optimization of the SC solenoid. The spherical aberration
of the SC solenoid has been analyzed. In order to decrease it, a new yoke geometry of SC
solenoid for the next generation SRF gun has been designed. The multipole transverse field
modes of the solenoid caused by an axis tilt have bean analyzed by means of simulations and
experimental investigations using a formalism fitting method. The influences of the multipole
modes, especially the quadrupole and sextupole fields on transverse emittance have been
calculated. A pair of a normal quadrupole and a skew quadrupole, called correctors, have been
adopted to compensate the influence of the quadrupole field on the emittance.
The cathode intrinsic emittance can contribute a non-negligible part to the transverse emittance.
So in this thesis the cathode intrinsic emitttance is measured too. The single shot transverse
momentum imaging method has been used to measure the cathode intrinsic emittance. A
further advantage is that this method allows to determine the transverse momentum locally at
different positions on the cathode.

Keywords: accelerator; superconducting RF photo injector; beam dynamic; emittance measurement

Related publications

  • Doctoral thesis
    Universität Hamburg, 2022
    125 Seiten

Permalink: https://www.hzdr.de/publications/Publ-36250
Publ.-Id: 36250


Numerical Transfer Towards Unresolved Morphology Representation in the MultiMorph Model

Meller, R.; Krull, B.; Schlegel, F.; Tekavcic, M.

The morphology adaptive multifield two-fluid model OpenFOAM-Hybrid focuses on the reliable and robust simulation of interfacial two-phase flows in real size industrial applications. This requires to combine the Volume-of-Fluid approach with the Euler-Euler model for large and small scale interfacial structures, respectively. The choice of the local representation of interfacial structures, such as bubbles or droplets, by either the first or the second of the aforementioned basic method strongly depends on the ratio of the length scale of the interface feature to the grid spacing. In case the computational grid gets too coarse to locally resolve an interfacial structure anymore, a morphology transfer is required. Such a transfer process allows to convert resolved fluid into non-resolved one, i.e. changing from a continuous description to a dispersed one. A formulation for such a numerically motivated disintegration process is presented and validated with a case of a two-dimensional single rising bubble on a grid with gradually varying cell size. The model is then applied to two further cases: an oil-water phase inversion and a water jet plunging into a free water surface. Hereby, functionality, robustness and feasibility of the proposed morphology transfer mechanism are demonstrated. This work contributes to a hybrid modelling approach for the simulation of two-phase flows adapting the numerical representation depending on local flow morphology and on available computational resources.

Keywords: Multiphase Flows; Numerical Simulation; Euler-Euler; OpenFOAM; Morphology-adaptive Model

Related publications

  • Contribution to proceedings
    20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20), 20.-25.08.2023, Washington, D.C., USA
    Proceedings of the 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20), Downers Grove, Illinois, 60515: American Nuclear Society, Incorporated, 978-0-89448-793-4, 693-706

Permalink: https://www.hzdr.de/publications/Publ-36249
Publ.-Id: 36249


In-situ observation of ion-induced nanoscale patterning on a crystalline Ge(001) surface

Erb, D.; Myint, P.; Evans-Lutterodt, K.; Ludwig, K.; Facsko, S.

Ion-induced surface patterning has turned out to be a highly versatile technique for many applications where large areas of nanostructured surfaces or thin films are required. Both fundamental and applied research may benefit from in-situ studies revealing the kinetics of the patterning process, yielding further insight into the dominant mechanisms and thus enabling to gain precise process control. The surface-sensitive X-ray scattering technique of Grazing Incidence Small Angle X-Ray Scattering (GISAXS) is a well-suited method for such in-situ investigations, allowing for contact-less examination under various external conditions.

Here, we present a real-time in-situ GISAXS investigation of reverse epitaxy patterning in crystalline Ge(001). From the X-ray scattering pattern we deduce the significant morphological parameters of the surface, thus tracking the development of the surface morphology with time during ion irradiation.

These findings are compared with results from simulations based on a continuum equation of the local surface height. Good agreement of the simulation with both experiment and theory was only achieved when including in the continuum equation an additional term for regulating the pattern anisotropy. We then find that a continuum equation considering only diffusive effects reproduces the experimentally observed surface patterning kinetics well.

Observing the kinetics of pattern formation in the non-linear regime, we find that the temporal evolutions of characteristic length and roughness conform to power laws, their exponents agreeing with scaling laws for conserved continuum equations with four-fold symmetry. Moreover, we find that the facet angle kinetics can be described by the Austin-Rickett equation for diffusion-controlled transformation processes, corroborating our assumption of a predominantly diffusive mechanism of pattern formation.

Related publications

  • Lecture (Conference)
    International Conference on Ion Beam Modification of Materials IBMM-2022, 10.-15.07.2022, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-36248
Publ.-Id: 36248


Nanopatterning of the (001) surface of crystalline Ge by ion irradiation at off-normal incidence

Erb, D.; de Schultz, R.; Ilinov, A.; Nordlund, K.; Bradley, R. M.; Facsko, S.

Intricate topographical patterns can form on the surface of crystalline Ge(001) subject to low-energy ion irradiation in the reverse epitaxy regime, i.e., at elevated temperatures which enable dynamic recrystallization. We compare such nanoscale patterns produced by irradiation from varied polar and azimuthal ion incidence angles with corresponding calculated surface topographies. To this end, we propose a continuum equation including both anisotropic erosive and anisotropic diffusive effects. Molecular dynamics simulations provide the coefficients of angle-dependent sputter erosion for the calculations. By merely changing these coefficients accordingly, the experimentally observed surface morphologies can be reproduced, except for extreme ion incidence angles. Angle-dependent sputter erosion is thereby identified as a dominant mechanism in ion-induced pattern formation on crystalline surfaces under irradiation from off-normal incidence angles.

Related publications

  • Invited lecture (Conferences) (Online presentation)
    6th International Conference on Nanostructuring by Ion Beams ICNIB 2021, 05.-08.10.2021, online only, online

Permalink: https://www.hzdr.de/publications/Publ-36247
Publ.-Id: 36247


Capture the morphology transfer process in a pool-scrubbing column with a hybrid multi-field two-fluid model

Liao, Y.; Li, S.

The role of pool scrubbing in attenuating radioactivity release after severe accidents has been explored extensively. It is known that the scrubbing efficiency is largely determined by the hydrodynamic phenomenology in pools. The aerosol gas forms large globules at the nozzle exit, which subsequently break up to a swarm of stable bubbles, where the change of bubble size can reach over two orders. Furthermore, with the increase of flow rates, the injection regime changes from globule to jet characterized by a continuous gas structure. The flow field in the pool can be divided into injection and rise (swarm) two zones according to the gas-liquid interface morphology. In different zones, the scrubbing is governed by different mechanisms such as inertial impact, diffusion and gravity, and bubble shape, size and velocity in addition to particle size are major influential parameters. So far, numerical analysis of pool scrubbing is routinely based on system codes, which rely on empirical correlations for the determination of these parameters. More recently, owing to the increasing availability of computational resources, the knowledge is improved through three-dimensional computational fluid hydrodynamics simulations. Nevertheless, the morphology and regime change represents still a challenge. The conventional two-fluid model is generally effective for bubble size smaller than the cell size, while interface-tracking (capturing) methods demands dozens of cells per bubble size. The present work aims to capture the complex hydrodynamic process in the pool scrubbing with a hybrid multi-field two-fluid model. By comparing with experimental data, the results are shown to be promising.

Keywords: Computational Fluid Dynamics; Hybrid Two-Fluid Model; Pool Scrubbing; Severe Accident

  • Contribution to proceedings
    20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20), 20.-25.08.2023, Washington, D.C., USA
  • Lecture (Conference)
    20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20), 20.-25.08.2023, Washington, D.C., USA

Permalink: https://www.hzdr.de/publications/Publ-36246
Publ.-Id: 36246


Multiscale approach for boiling flow simulation

Ding, W.; Zhang, J.; Setoodeh, H.; Lucas, D.; Hampel, U.

Numerical modeling of boiling flow is challenging due to the wide range characteristic lengths of the physics at play: from nano/micrometers bubble nucleus to sub-meters flow pattern, particularly, when the role of the nano/micro surface structure attracts more attention recently. To address this, we present here our activities in multiscale approaches e.g the Euler Euler (EE) of boiling flow considering the bubble void fraction distribution and GEneralized TwO Phase flow (GENTOP) model to simulate the large free surface structure, the Direct Numerical Simulation (DNS) of bubble dynamics considering detailed surface structure, the Molecular Dynamics (MD) simulation of bubble static/dynamics wetting, and also the bridging concept between each scale activities. The works are demonstrated on several problems including the contact line region of a nucleation bubble, microlayer beneath the bubble, bubble dynamics on a structured surface, bubble population balance, interfacial forces between dispersed phases, and free surface. These activities highlight the capability of the developed multiscale concept to enhance the robustness of boiling flow simulation, though whose application in nuclear-related processes should be an industry-oriented theme that should be with low time and computer hardware requirements.

Keywords: boiling flow; MD; DNS; EE; GENTOP

  • Lecture (Conference)
    20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20), 20.-25.08.2023, Washington D.C., USA

Permalink: https://www.hzdr.de/publications/Publ-36245
Publ.-Id: 36245


15-N NRA Data for article: Tracer diffusion in proton-exchanged congruent LiNbO3 crystals as a function of hydrogen content

Dörrer, L.; Heller, R.; Schmidt, H.

Raw data from 15N NRA measurements including data evaluation.

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Permalink: https://www.hzdr.de/publications/Publ-36244
Publ.-Id: 36244


Tracer diffusion in proton-exchanged congruent LiNbO3 crystals as a function of hydrogen content

Dörrer, L.; Heller, R.; Schmidt, H.

The proton-exchange process is an effective method of fabricating low-loss waveguides based on LiNbO3 crystals. During proton-exchange, lithium is replaced by hydrogen and Li1 xHxNbO3 is formed.
Currently, mechanisms and kinetics of the proton-exchange process are unclear, primarily due to a lack in reliable tracer diffusion data. We studied lithium and hydrogen tracer diffusion in proton-exchanged congruent LiNbO3 single crystals in the temperature range between 130–230 1C. Proton-exchange was done in benzoic acid with 0, 1, 2, or 3.6 mol% lithium benzoate added, resulting in micrometre thick surface layers where Li is substituted by H with relative fractions between x = 0.45 and 0.85 as determined by Nuclear Reaction Analysis. For the diffusion experiments, ion-beam sputtered isotope enriched 6LiNbO3 was used as a Li tracer source and deuterated benzoic acid as a H tracer source.
Isotope depth profile analysis was carried out by secondary ion mass spectrometry. From the experimental results, effective diffusivities governing the lithium/hydrogen exchange as well as individual hydrogen and lithium tracer diffusivities are extracted. All three types of diffusivities can be described by the Arrhenius law with an activation enthalpy of about 1.0–1.2 eV and increase as a function of hydrogen content nearly independent of temperature. The effective diffusivities and the lithium tracer diffusivities are identical within a factor of two to five, while the hydrogen diffusivities are higher by three orders of magnitude. The results show that the diffusion of Li is the rate determining step governing the protonexchange process. Exponential dependencies between diffusivities and hydrogen concentrations are determined. The observed increase of Li tracer diffusivities and effective diffusivities as a function of hydrogen concentration is attributed to a continuous reduction of the migration enthalpy of diffusion by a maximum factor of about 0.2 eV. Simulations based on the determined diffusivities can reproduce the step-like profile of hydrogen penetration during proton-exchange.

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Permalink: https://www.hzdr.de/publications/Publ-36243
Publ.-Id: 36243


RBS Raw Data for publication: Investigation of matrix independent calibration of oxygen in glow discharge optical emission spectrometry

Hoffmann, V.; Gebel, B.; Heller, R.; Gemming, T.

Raw RBS data for article Investigation of matrix independent calibration of oxygen in glow discharge optical emission spectrometry. All raw data as well as simulation files (SIMNRA) are included.

Keywords: glow discharge; optical emission spectroscopy; material science

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Permalink: https://www.hzdr.de/publications/Publ-36242
Publ.-Id: 36242


Investigation of matrix independent calibration of oxygen in glow discharge optical emission spectrometry

Hoffmann, V.; Gebel, B.; Heller, R.; Gemming, T.

The performance of glow discharge optical emission spectrometry for matrix independent oxygen determination was
investigated using the spectral lines of atomic oxygen at 130 nm and 777 nm and standard conditions for dc discharge with a
4 mm anode (700 V, 20 mA). Using hot-pressed calibration samples of Cu-, Al- and Mg-powder mixed with their oxides, at
130 nm the dependence of the emission yield on these matrices was confirmed. However, at 777 nm oxygen has the same
emission yield in these matrices. In order to compare the emission yield of oxygen with the emission yield in iron a thick 43
μm FeO-layer was prepared and characterized by Rutherford backscattering spectrometry, X-ray diffraction and glow
discharge optical emission spectrometry. At 130 nm, the emission yield of oxygen in FeO is most similar to that in an Almatrix.
At 777 nm, the calibration revealed a higher emission yield of oxygen in FeO in comparison to the common emission
yield of oxygen in Cu-, Al- and Mg-matrices. © 2022 The Royal Society of Chemistry

Keywords: glow discharge; optical emission spectroscopy; material science

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36241
Publ.-Id: 36241


Applicability of gas flow modulation technique for measuring axial gas dispersion coefficients in bubble columns

Marchini, S.; Bieberle, A.; Schubert, M.; Hampel, U.

Dispersion phenomena significantly influence the residence time of the fluid phases in gas-liquid contactors and, thus, their yield. With the axial dispersion model (ADM), the effect of dispersion is considered during the process design. However, this requires a reliable quantification of the axial dispersion coefficients.
A novel non-intrusive approach to determine the axial gas dispersion coefficient in bubble columns was recently pronounced by Hampel [1], called gas flow modulation technique (GFM). This approach is based on an imposed marginal sinusoidal modulation on the constant gas inlet flow. This leads to a modulation of the gas holdup in the bubble column, called holdup wave. Along the column axial direction, the gas dispersion damps the rising holdup wave in amplitude and shifts its phase. Amplitude damping and phase shift can be non-invasively determined, e.g., using gamma-ray densitometry to relate it to the value of the axial dispersion coefficient using the ADM. Figure 1 shows the principle of GFM and a simplified scheme of the experimental setup.
Döß et al. [2] applied the GFM to bubble columns for the first time, although only for a narrow range of operating conditions in a 100 mm ID bubble column. The present study proves the applicability of the GFM to larger columns and for a wider range of gas superficial velocities and liquid properties. Experiments were performed in columns of 100, 150 and 330 mm ID at gas superficial velocities ranging from 17 to 47 mm/s. Air was used as the gas phase. Water, aqueous solutions with 2% wt. ethanol and 30% wt. glycerin were used as the liquid phase. This study, together with the uncertainty analyses recently performed by Marchini et al. [3, 4], qualifies the GFM as a viable non-invasive alternative to traditional tracer studies, for measuring the axial gas dispersion coefficient in bubble columns.

Keywords: gas flow modulation; bubble columns; axial gas dispersion coefficient

  • Contribution to proceedings
    ECCE14, 17.-20.09.2023, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-36240
Publ.-Id: 36240


Analysis of sparger effects on axial gas dispersion in bubble columns

Marchini, S.; Caggia, V.; Bieberle, A.; Schubert, M.; Brunazzi, E.; Hampel, U.

The uniformity of the gas distribution in bubble columns strongly depends on the gas sparger design. For example, not all holes of a perforated plate sparger with relatively high fractional free area are active at the same time. This is true especially at low gas flow rates. Consequently, the random activation of the holes causes gas maldistribution in the radial as well as in the axial directions. Contrary, needle spargers provide rather uniform distribution at the same operating conditions.
Since dispersion phenomena depend on the gas holdup gradient, the gas maldistribution is expected to affect the dispersion. Surprisingly, only few publications address the possible influence of the sparger on gas dispersion. An exception is the study of Kölbel [1]. They measured the axial gas dispersion coefficient in a bubble column using a monolithic type of sparger. Here, the obtained gas dispersion coefficients run through a minimum while increasing the gas superficial velocity. Contrary, literature frequently reports axial dispersion coefficients that increase monotonously with the gas superficial velocity (e.g., [2], [3]).
The objective of the present study was to resolve this discrepancy. Experiments were performed in a 100 mm ID column using three different spargers, namely: a perforated plate sparger with (a) 50 holes of 0.6 mm diameter corresponding to a fractional free area of 0.18%, (b) with 38 holes of 1.0 mm and 12 holes of 1.5 mm corresponding to a fractional free area of 0.66%, and (c) a needle sparger made of 31 needles with 0.8 mm inner diameter each.
Axial dispersion was experimentally measured applying the gas flow modulation technique, which is a tracer-free approach explained by Marchini et al. [4, 5].
The results showed that the above mentioned minimum found by Kölbel [1] is reproducible for spargers with high fractional free area. Figure 1 reports the determined axial dispersion coefficients as a function of the gas superficial velocity for all considered spargers. The minimum is less evident for the considered sparger with lower fractional free area and, finally, it is not identified for the needle sparger.
Considering that dispersion causes back-mixing, which often has a detrimental effect on process yield, the presence of such a dispersion minimum can be considered as an additional option for process optimization in the future. However, more studies are required to reliably predict the occurrence of such dispersion minimum depending on sparger design and operating conditions.

Keywords: gas flow modulation; bubble column; axial disperision coefficient; gas sparger

  • Contribution to proceedings
    ECCE14, 17.-20.09.2023, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-36239
Publ.-Id: 36239


Survey of spatio-temporal couplings throughout high-power ultrashort lasers

Jeandet, A.; Jolly, S. W.; Borot, A.; Bussière, B.; Dumont, P.; Gautier, J.; Gobert, O.; Goddet, J.-P.; Gonsalves, A.; Irman, A.; Leemans, W. P.; Lopez-Martens, R.; Mennerat, G.; Nakamura, K.; Ouillé, M.; Pariente, G.; Pittman, M.; Püschel, T.; Sanson, F.; Sylla, F.; Thaury, C.; Zeil, K.; Fabien Quéré, A.

The investigation of spatio-temporal couplings (STCs) of broadband light beams is
becoming a key topic for the optimization as well as applications of ultrashort laser systems.
This calls for accurate measurements of STCs. Yet, it is only recently that such complete
spatio-temporal or spatio-spectral characterization has become possible, and it has so far mostly
been implemented at the output of the laser systems, where experiments take place. In this survey,
we present for the first time STC measurements at different stages of a collection of high-power
ultrashort laser systems, all based on the chirped-pulse amplification (CPA) technique, but with
very different output characteristics. This measurement campaign reveals spatio-temporal effects
with various sources, and motivates the expanded use of STC characterization throughout CPA
laser chains, as well as in a wider range of types of ultrafast laser systems. In this way knowledge
will be gained not only about potential defects, but also about the fundamental dynamics and
operating regimes of advanced ultrashort laser systems.

Permalink: https://www.hzdr.de/publications/Publ-36238
Publ.-Id: 36238


Characterization of the plasma mirror system at the J-KAREN-P facility

Kon, A.; Nishiuchi, M.; Fukuda, Y.; Kondo, K.; Ogura, K.; Sagisaka, A.; Miyasaka, Y.; Dover, N. P.; Kando, M.; Pirozhkov, A. S.; Daito, I.; Chang, L.; Woo Choi, I.; Hee Nam, C.; Ziegler, T.; Schlenvoigt, H.-P.; Zeil, K.; Schramm, U.; Kiriyama, H.

We report on the design and characterization of the plasma mirror system installed on the J-KAREN-P laser at the Kansai
Photon Science Institute, National Institutes for Quantum Science and Technology. The reflectivity of the single plasma
mirror system exceeded 80%. In addition, the temporal contrast was improved by two orders of magnitude at 1 ps before
the main pulse. Furthermore, the laser near-field spatial distribution after the plasma mirror was kept constant at plasma
mirror fluence of less than 100 kJ/cm2. We also present the results of investigating the difference and the fluctuation in
energy, pulse width and pointing stability with and without the plasma mirror system.

Permalink: https://www.hzdr.de/publications/Publ-36237
Publ.-Id: 36237


High energy proton acceleration at DRACO-PW and radio-biological applications

Zeil, K.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser driven compact plasma accelerators can generate short, high-intensity pulses of high energy ions with special beam properties. By that they may expand the portfolio of conventional machines in many application areas. The maturation of laser driven ion accelerators from physics experiments to turn-key sources for these applications will rely on breakthroughs in both, generated beam parameters (kinetic energy, flux), as well as increased reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production of polychromatic proton beams with unprecedented stability [1]. This allowed the first in vivo radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to achieve energies beyond the 100 MeV frontier is matter of ongoing research, mainly addressed by exploring advanced acceleration schemes like the relativistically induced transparency (RIT) regime.
In this talk we report on experimental proton acceleration studies at the onset of relativistic transparency using pre-expanded plastic foils. Combined hydrodynamic and 3D particle-in-cell (PIC) simulations helped to identify the most promising target parameter range matched to the prevailing laser contrast conditions carefully mapped out in great detail beforehand. A complex suite of particle and optical diagnostics allowed characterization of spatial and spectral proton beam parameters and the stability of the regime of best acceleration performance, yielding cut-off energies larger than 100 MeV in the best shots.

  • Invited lecture (Conferences)
    20th Advanced Accelerator Concepts Workshop (AAC’22), 07.11.2022, Long Island, USA

Permalink: https://www.hzdr.de/publications/Publ-36236
Publ.-Id: 36236


Laser-plasma ion accelerators for radio-biological research

Zeil, K.

Particle accelerators have always been fundamental engines of discovery and drivers of innovations in industry, basic research, and life sciences. Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power laser-driven compact plasma accelerators can generate short, high-intensity pulses of high energy electrons and ions with special beam properties. By that they may expand the portfolio of conventional machines in many application areas.

For laser-driven ion accelerators, the full application in ultra-high dose rate radiotherapy (RT) research marks one of the most important research objectives and is perfectly timed with the emerging interest on ultra-high dose rate RT. Laser proton accelerators are ideal instruments to investigate ultra-high dose rate effects, yet their ability to provide radiobiological in-vivo data comparable in quality to a clinical reference standard has called for demonstration for a long time.

The talk will introduce the concept of laser-driven ion accelerators and challenges of this technology. For the example of the high power laser source DRACO operated at HZDR, key developments for the production of reliable polychromatic proton beams with maximum energies of around 60 MeV are presented. Most recently, these achievements enabled the first successful small animal pilot study on radiation-induced tumor growth delay in mice using a laser-driven proton source and a clinical reference.

  • Invited lecture (Conferences) (Online presentation)
    Virtual DPG Spring Meeting - Symposium Plasma Induced Accelerators, 31.03.2022, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36235
Publ.-Id: 36235


Laser driven proton accelerators with solid hydrogen jets for application

Zeil, K.

Laser plasma-based particle accelerators attract great interest in fields where conventional accelerators reach limits based on size, cost or beam parameters. However, despite the fact that first principles particle in cell simulations have predicted several advantageous ion acceleration schemes,
laser accelerators have not yet reached their full potential in producing simultaneous high-radiation
doses at high particle energies. The most stringent limitation is the lack of a suitable high-repetition
rate target that also provides a high degree of control of the plasma conditions which is required
to access these advanced regimes. Here, we demonstrate that the interaction of petawatt-class laser
pulses with a pre-formed micrometer-sized cryogenic hydrogen jet plasma overcomes these limitations. Controlled pre-expansion of the initially solid target by low intensity pre-pulses allowed for tailored density scans from the solid to the underdense regime. Our experiment demonstrates that
the near-critical plasma density profile produces proton energies of 80 MeV. This energy presents
more than a factor of two increase compared to the solid hydrogen target. Our three-dimensional
particle in cell simulations show the transition between different acceleration mechanisms and suggest enhanced proton acceleration at the relativistic transparency front for the optimal case.

  • Invited lecture (Conferences)
    13th International Particle Accelerator Conference (IPAC’22), 15.06.2022, Bangkok, Thailand

Permalink: https://www.hzdr.de/publications/Publ-36234
Publ.-Id: 36234


High energy proton detection in Draco PW experiments

Zeil, K.; Assenbaum, S.; Bernert, C.; Brack, F.-E.; Cowan, T.; Garten, M.; Gaus, L.; Göthel, I.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Reimold, M.; Rehwald, M.; Schlenvoigt, H.-P.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Ziegler, T.; Schramm, U.

Exploiting the strong electromagnetic fields that can be supported by a plasma, high-power
laser driven compact plasma accelerators can generate short, high-intensity pulses of high
energy ions with special beam properties interesting for many application areas. The transition
of laser driven ion accelerators from physics experiments to turn-key sources for these
applications relies on improvement of generated beam parameters (kinetic energy, flux), as
well as increased reproducibility, robustness and scalability to high repetition rate.
Recent developments at the high-power laser facility DRACO-PW enabled the production
of polychromatic proton beams with unprecedented stability [1] which enabled the first in vivo
radiobiological study to be conducted using a laser-driven proton source [2]. Yet, the ability to
achieve highest energies around or even beyond the 100 MeV frontier is matter of ongoing
research, mainly addressed by exploring advanced acceleration schemes.
In parallel to the testing of these schemes an important challenge is to provide convincing
evidence that these very high energies could be reached at all for a significant number of
particles. Occurring complications are due to the nature of the multi-species beams with
typically exponentially decaying spectra and low shot statistics of laser-plasma experiments
at the necessary laser pulse energy levels. The latter is in particular complicated for highly
non-linear acceleration regimes with intrinsically low reproducibility.
In this talk we summarize our approaches for the spatial and spectral characterization of our
proton beam parameters with cut-off energies larger than 80 MeV. Key is the combination of
a multitude of different methods based on different detection principles established for single
shot measurements. Time-of-flight methods are discussed for energy cross-calibration of our
Thomson parabola spectrometers and the use of different screen types for on-shot particle
number calibration is presented.

  • Lecture (Conference)
    BLIN5 Workshop 2022, 14.10.2022, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36233
Publ.-Id: 36233


Preliminary results from the x-ray spectrometers at Draco PW laser facility

Stefanikova, R.; Pan, X.; Smid, M.; Schlenvoigt, H.-P.; Prencipe, I.; Gaus, L.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Reimold, M.; Ziegler, T.; Kroll, F.; Kraft, S.; Schramm, U.; Zeil, K.; Metzkes-Ng, J.; Falk, K.

A large amount of complex processes within laser-produced plasmas put a huge demand for precise diagnostics methods. For example, x-ray emission spectroscopy can be used to study atomic physics and plasma conditions. Here, we introduce two new x-ray spectrometers installed in the Ion acceleration lab at the Draco PW laser facility. Availability of such diagnostics at the Draco PW Ti:sapphire 30 fs laser system (i.e. ultra-short pulse system) allows not only for studying unique plasma conditions driving the ion acceleration, but also exploring new possibilities for x-ray backlighters suitable for high energy density experiments.
Both spectrometers are utilized for acquisition of Ti spectral lines, but offer different spectral resolution and range. Quartz crystal spectrometer has wider spectral range, including Ti K-α and He-α emission lines in the spectrum, whereas Ge crystal spectrometer focuses on K-α emission lines and offers 1D spatial imaging. We present first results demonstrating the capabilities of both spectrometers.
The first spectroscopic measurements include the emission spectra measurements from flat Ti targets used for proton acceleration calibration and optimization with and without laser pre-pulse and the use of structured targets for enhanced x-ray emission as well as tailoring of the electron spectra for optimization of the proton acceleration process.

Keywords: x-ray spectrometer; laser-produced plasma; characteristic emission lines

  • Poster
    17th International Conference on the Physics of Non-Ideal Plasmas, 22.09.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36232
Publ.-Id: 36232


Fabrication of highly n-type-doped germanium nanowires and Ohmic contacts using ion implantation and flash lamp annealing

Echresh, A.; Prucnal, S.; Li, Z.; Hübner, R.; Ganss, F.; Steuer, O.; Bärwolf, F.; Jazavandi Ghamsari, S.; Helm, M.; Zhou, S.; Erbe, A.; Rebohle, L.; Georgiev, Y.

Accurate control of doping and fabrication of metal contacts on n-type germanium nanowires (GeNWs) with low resistance and linear characteristics remain a major challenge in germanium-based nanoelectronics. Here, we present a combined approach to fabricate Ohmic contacts on n-type-doped GeNWs. Phosphorus (P) implantation followed by millisecond rear-side flash lamp annealing was used to produce highly n-type doped Ge with an electron concentration in the order of 10^19 − 10^20 cm^(−3). Electron beam lithography, inductively coupled plasma reactive ion etching, and nickel (Ni) deposition were used to fabricate GeNW-based devices with symmetric Hall bar configuration, which allows detailed electrical characterization of the NWs. Afterward, rear-side flash lamp annealing was applied to form Ni germanide at the Ni-GeNWs contacts to reduce the Schottky barrier height. The two-probe current-voltage measurements on n-type-doped GeNWs exhibit linear Ohmic behavior. Also, the size-dependent electrical measurements showed that carrier scattering near the NW surfaces and reduction of the effective NW cross-section dominate the charge transport in the GeNWs.

Keywords: Germanium nanowires; ion implantation; flash lamp annealing; n-type doped; Ohmic contacts; Hall bar configuration

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-36230
Publ.-Id: 36230


Impact of pre-plasma tailoring on K-ɑ emission and proton acceleration

Stefanikova, R.; Pan, X.; Smid, M.; Gaus, L.; Kraft, S.; Kroll, F.; Kozlová, M.; Prencipe, I.; Reimold, M.; Schlenvoigt, H.-P.; Umlandt, M. E. P.; Schramm, U.; Zeil, K.; Metzkes-Ng, J.; Falk, K.

Laser-produced plasmas are widely studied complex systems. In order to get better understanding of their inner processes, advanced diagnostics methods have to be used to get a valuable insight – for example, x-ray emission spectroscopy has the capability to unfold atomic processes and plasma conditions and reveal information about the hot electron population.
Recently, two x-ray crystal spectrometers were installed in the Ion Acceleration Lab at Draco PW laser facility, which allows to acquire characteristic emission spectra including Ti K-α and He-α lines from Ti targets. While quartz spectrometer offers wide spectral range and excellent spectral resolution of ∼ 0.3 eV, Ge spectrometer focuses on Ti K-α emission lines and provides 1D spatial imaging with resolution below 10 μm.
Here, we present the first results from the x-ray spectroscopic measurements from proton acceleration targets at the DRACO PW laser facility uncovering the plasma conditions and electron dynamics for various target and laser configurations including inclusion artificial pre-pulse or the use of reduced mass targets.

  • Poster (Online presentation)
    The 48th European Conference on Plasma Physics (2022), 01.07.2022, Maastricht (online), Netherlands

Permalink: https://www.hzdr.de/publications/Publ-36229
Publ.-Id: 36229


Clarifying space use concepts in ecology: range vs. occurrence distributions

Alston, J.; Fleming, C.; Noonan, M.; Tucker, M.; Silva, I.; Folta, C.; Akre, T.; Ali, A.; Belant, J.; Beyer, D.; Blaum, N.; Boehning-Gaese, K.; Cunha De Paula, R.; Dekker, J.; Drescher-Lehman, J.; Farwig, N.; Fichtel, C.; Fischer, C.; Ford, A.; Janssen, R.; Jeltsch, F.; Kappeler, P.; Lapoint, S.; Markham, A.; Medici, P.; Morato, R.; Nathan, R.; Olson, K.; Patterson, B.; Petroelje, T.; Ramalho, E.; Roesner, S.; Santos, L.; Schabo, D.; Selva, N.; Sergiel, A.; Spiegel, O.; Ullman, W.; Zieba, F.; Zwijacz-Kozica, T.; Wittemyer, G.; Fagan, W.; Mueller, T.; Calabrese, J.

Quantifying animal movements is necessary for answering a wide array of research questions in ecology and conservation biology. Consequently, ecologists have made considerable efforts to identify the best way to estimate an animal’s home range, and many methods of estimating home ranges have arisen over the past half century. Most of these methods fall into two distinct categories of estimators that have only recently been described in statistical detail: those that measure range distributions (methods such as Kernel Density Estimation that quantify the long-run behavior of a movement process that features restricted space use) and those that measure occurrence distributions (methods such as Brownian Bridge Movement Models and the Correlated Random Walk Library that quantify uncertainty in an animal movement path during a specific period of observation). In this paper, we use theory, simulations, and empirical analysis to demonstrate the importance of applying these two classes of space use estimators appropriately and distinctly. Conflating range and occurrence distributions can have serious consequences for ecological inference and conservation practice. For example, in most situations, home-range estimates quantified using occurrence estimators are too small, and this problem is exacerbated by ongoing improvements in tracking technology that enable more frequent and more accurate data on animal movements. We encourage researchers to use range estimators to estimate the area of home ranges and occurrence estimators to answer other questions in movement ecology, such as when and where an animal crosses a linear feature, visits a location of interest, or interacts with other animals.

Permalink: https://www.hzdr.de/publications/Publ-36228
Publ.-Id: 36228


Study of x-ray emission from proton acceleration targets at Draco PW laser facility

Stefanikova, R.; Pan, X.; Meckel, N.; Smid, M.; Schlenvoigt, H.-P.; Prencipe, I.; Kozlová, M.; Gaus, L.; Umlandt, M. E. P.; Vescovi Pinochet, M. A.; Reimold, M.; Ziegler, T.; Kroll, F.; Kraft, S.; Schramm, U.; Zeil, K.; Metzkes-Ng, J.; Falk, K.

Laser plasma-based ion accelerators are very promising candidates for many applications. In order to ensure the reliability of such accelerators a comprehensive set of diagnostics is required. X-ray emission spectroscopy allows us to directly measure the plasma conditions of the laser-plasma interaction and also provides information about the hot electron population through the cold K-α emission production.
Here, we present preliminary results from two new x-ray spectrometers used to study interaction regimes relevant for laser-driven ion acceleration at ultra-short pulse PW-class laser facility. We acquired the emission spectra from flat Ti targets for a range of target thicknesses and laser energies. Additionally, artificial laser pre-pulses were added to alter the laser absorption efficiency.

Keywords: x-ray spectroscopy; laser-produced plasma; characteristic emission lines; laser-plasma ion acceleration

  • Lecture (Conference) (Online presentation)
    DPG-Frühjahrstagung, 28.03.2022, Mainz, online, Germany

Permalink: https://www.hzdr.de/publications/Publ-36227
Publ.-Id: 36227


Study of the influence of various pre-plasma conditions on laser-proton acceleration via x-ray spectroscopy

Stefanikova, R.; Pan, X.; Smid, M.; Gaus, L.; Kozlová, M.; Kraft, S.; Kroll, F.; Prencipe, I.; Reimold, M.; Schlenvoigt, H.-P.; Umlandt, M. E. P.; Schramm, U.; Zeil, K.; Metzkes-Ng, J.; Falk, K.

Laser driven ion acceleration is a fast growing field, where understanding of the internal processes of laser-plasma interaction is crucial for optimization of such ion sources. Namely, x-ray spectroscopy offers a unique in-situ view at plasma conditions and electron signatures from within the target, which can help to identify important parameters for optimization of the laser-driven acceleration process.
Here, we present an x-ray spectroscopy platform installed at the Draco PW laser facility (Ti:sapphire 30 fs laser system) and how the addition of x-
ray spectroscopy reveals the suprathermal electron population, which provides insight into the energy conversion from laser to the proton-accelerating sheath.
As an example, we study the impact of pre-plasma tailoring on characteristic x-ray emission and proton acceleration via controlled introduction of various pre-pulses on the Ti 2 μm thick target that precede the arrival of the main laser pulse by 2.5 − 30 ps. Based on our data from x-ray spectroscopy combined with proton diagnostics we then gain understand-
ing of the underlying processes in proton acceleration and the influence of pre-plasma formation.

Keywords: x-ray spectrometer; laser-produced plasma; characteristic emission lines

  • Lecture (Conference) (Online presentation)
    64th Annual Meeting of the APS Division of Plasma Physics, 20.10.2022, Spokane, USA

Permalink: https://www.hzdr.de/publications/Publ-36226
Publ.-Id: 36226


The relationship between controllability, optimal testing resource allocation, and incubation-latent period mismatch as revealed by COVID-19

Demers, J.; Fagan, W.; Potluri, S.; Calabrese, J.

The severe shortfall in testing supplies during the initial phases of the COVID-19 pandemic and ensuing struggle to control disease spread have affirmed the need to plan rigorous optimized supply-constrained resource allocation strategies for the next inevitable novel disease epidemic. To address the challenge of optimizing limited resource usage in the face of complicated disease dynamics, we develop an integro partial differential equation disease model which incorporates realistic latent, incubation, and infectious period distributions along with limited testing supplies for identifying and quarantining infected individuals, and we analyze the influence of these ele- ments on controllability and optimal resource allocation between two testing strategies, ‘clinical’ targeting symptomatic individuals and ‘non-clinical’ targeting non-symptomatic individuals, for reducing total infection sizes. We apply our model to not only the original, delta, and omicron COVID-19 variants, but also to generic diseases which have different offsets between latent and incubation period distributions which allow for or prevent varying degrees of presymptomatic transmission or preinfectiousness symptom onset. We find that factors which reduce control- lability generally call for reduced levels of non-clinical testing, while the relationship between symptom onset, controllability, and optimal strategies is complicated. Although greater degrees of presymptomatic transmission reduce disease controllability, they may enhance or reduce the role of non-clinical testing in optimal strategies depending on other disease factors like overall transmissibility and latent period length. Our model allows a spectrum of diseases to be com- pared under the same lens such that the lessons learned from COVID-19 can be adapted to resource constraints in the next emerging epidemic and analyzed for optimal strategies under a consistent mathematical framework.

Permalink: https://www.hzdr.de/publications/Publ-36225
Publ.-Id: 36225


Characterization of low-density rear-driven collisional plasma jets from thin foil targets

Perez-Martin, P.; Smid, M.; Hronová, L.; Bouffetier, V.; Brack, F.-E.; Cagas, P.; Červenák, M.; Gajdos, P.; He, Z.; Holec, M.; Kagan, G.; Kaniz, K.; Kozlová, M.; Kroll, F.; Liu, H.; Pan, X.; Prencipe, I.; Schaumann, G.; Singh, S.; Sobiella, M.; Srinivasan, B.; Stafford, J.; Xie, Z.; Xiong, J.; Suzuki-Vidal, F.; Krůs, M.; Ren, L.; Kang, N.; Falk, K.

Magnetized low density, collisional plasma jets are found in astrophysical systems, such as accretion
discs or polars, and they also show potential as a platform to study transport properties in
astrophysical plasmas. However, no systematic study of their properties has been conducted yet.
Through experiments in kilojoule laser facilities, we aim to benchmark a range of rear-driven
jets from foils of different thicknesses and materials.
We studied free propagation of jets, their collisions with a static object and the collisions
between two counterpropagating jets. The setup was also placed inside a split pair coil, which
provides an external magnetic field of 5-10 T. A streak camera was used to track jet velocity
and density was measured with 4-frame interferometry and x-ray radiography.
The results can be used to plan experiments with focus on specific jet properties, as well as
providing a benchmark for hydrodynamic codes. The data on collisions and magnetized jets
provides insight into compression waves and the effects of strong external magnetic fields,
which are used for the study of transport properties of plasmas.

Keywords: Plasma flows; Laboratory astrophysics; Magnetized plasma; High magnetic fields; Interferometry

  • Lecture (Conference) (Online presentation)
    48th EPS Conference on Plasma Physics, 28.06.-01.07.2022, Online, N/A

Permalink: https://www.hzdr.de/publications/Publ-36224
Publ.-Id: 36224


Modeling of magnetized astrophysical objects through the study of magnetized rear-driven plasma jets from thin foil targets

Perez-Martin, P.; Smid, M.; Hronová, L.; Bouffetier, V.; Bott, A.; Brack, F.-E.; Červenák, M.; Donat, F.; Gajdoš, P.; Kozlová, M.; Kroll, F.; Manuel, M.; Pan, X.; Prencipe, I.; Singh, S.; Sobiella, M.; Krus, M.; Falk, K.

Plasma jets can be found in astrophysical systems (Accretion disks[1][2], Polars [3] or Young
Stellar Objects [4]), but they are also useful as a platform to study plasma properties and transport
effects. On a experiment at the PALS facility, we have studied the formation and propagation
of rear-driven, collisional plasma jets from different foil thicknesses and materials when
subject to an intense external magnetic field.
Magnetic fields were generated using a pair of Helmholtz coils that provide 5-10 T in the
direction perpendicular to the jet propagation. The diagnostics used were the streaked optical
self-emission as a measurement of jet velocity, and 4-frame interferometry as a measurement of
the jet density.
With the right scaling factors, this data can help model the accretion of matter into magnetized
astrophysical systems, such as the surface of Young Stellar Objects, as well as the role that
instabilities play in this process [4].
The work was supported by the Helmholtz Association under Grant No. VH-NG-1338
[1] G. Revet et al., Science Advances 3, 11 (2017)
[2] Kulkarni, A. K. & Romanova, M. M. , Monthly Notices RAS 386, (2008)
[3] E. Falize, et al., Astrophysics and Space Science 336, 81 (2011)
[4] Burdonov, K. et al., A&A 657, A112 (2022)

Keywords: Plasma flows; Laboratory astrophysics; Magnetized plasma; High magnetic fields; Magnetosphere physics; Young Stellar Objects

  • Lecture (Conference)
    64th Annual Meeting of the APS Division of Plasma Physics, 16.-21.10.2022, Spokane, United States of America

Permalink: https://www.hzdr.de/publications/Publ-36223
Publ.-Id: 36223


Atomic Layer Etching of Nanowires Using Conventional RIE Tool

Khan, M. B.; Shakeel, S.; Richter, K.; Ghosh, S.; Erbe, A.; Georgiev, Y.

Innovative material and processing concepts are needed to further enhance the performance of complementary metal-oxide-semiconductor (CMOS) transistors-based circuits as the scaling limits are being reached. To achieve that, we report on the development of an atomic layer etching (ALE) [1] process to fabricate smooth and thin nanowires using a conventional dry etching tool. Firstly, a negative tone resist (hydrogen silsesquioxane) is spin-coated on SiGe-on-insulator (SiGeOI) samples and electron beam lithography performed to create nano-patterns. These patterns act as an etch mask and are transferred into the SiGeOI layer using an inductively-coupled plasma reactive ion etching (ICP-RIE) process. Subsequently, an SF6 and Ar+ based ALE process is employed to smoothen the nanowires and reduce their widths. SF6 modifies the surface of the samples, while in the next step Ar+ removes the modified surface. The ALE cycle sequence is surface modification with 60 sccm SF6 for 20 s, 60 sccm Ar purge for 15 s, removal of the layer with 60 sccm Ar for 10 s at 25 W platen power, and 40 sccm Ar purge for 10 s.
To investigate the effect of ALE on the nanowire roughness and width, several ALE cycles are performed. The surface of the etched features is studied using scanning electron microscopy and atomic force microscopy. With the increasing number of ALE cycles, a reduction in the width of the nanowires, as well as surface roughness, is observed. The roughness reduced from ca. 6 nm to 1 nm (the resolution of the AFM tip) as the number of ALE cycles is increased from 78 to 102.
An etch per cycle of 1.1 Å is obtained. Sub-12 nm nanowires with smooth sidewalls were achieved after performing 63 ALE cycles. This process, developed on a conventional ICP-RIE tool, can be used to further down-scale semiconductor nanowires.

1. Kanarik, Keren J., et al. "Overview of atomic layer etching in the semiconductor industry." Journal of Vacuum Science & Technology A: Vacuum, Surfaces, and Films 33.2 (2015): 020802.

Related publications

  • Lecture (Conference)
    14th EBT 2022 International conference, 26.06.-01.07.2022, Varna, Bulgaria
  • Open Access Logo Contribution to proceedings
    14th International Conference on Electron Beam Technologies (EBT 2022), 27.06.-01.07.2022, Varna, Bulgaria
    Journal of Physics: Conference Series, Volume 2443
    DOI: 10.1088/1742-6596/2443/1/012004

Permalink: https://www.hzdr.de/publications/Publ-36222
Publ.-Id: 36222


Partial Reduction in BRCA1 Gene Dose Modulates DNA Replication Stress Level and Thereby Contributes to Sensitivity or Resistance

Classen, S.; Rahlf, E.; Jungwirth, J.; Albers, N.; Hebestreit, L.; Zielinski, A.; Poole, L.; Groth, M.; Koch, P.; Liehr, T.; Kankel, S.; Cordes, N.; Petersen, C.; Rothkamm, K.; Pospiech, H.; Borgmann, K.

BRCA1 is a well-known breast cancer risk gene, involved in DNA damage repair via homologous recombination (HR) and replication fork protection. Therapy resistance was linked to loss and amplification of the BRCA1 gene causing inferior survival of breast cancer patients. Most studies have focused on the analysis of complete loss or mutations in functional domains of BRCA1. How mutations in non-functional domains contribute to resistance mechanisms remains elusive and was the focus of this study. Therefore, clones of the breast cancer cell line MCF7 with indels in BRCA1 exon 9 and 14 were generated using CRISPR/Cas9. Clones with successful introduced BRCA1 mutations were evaluated regarding their capacity to perform HR, how they handle DNA replication stress (RS), and the consequences on the sensitivity to MMC, PARP1 inhibition, and ionizing radiation. Unexpectedly, BRCA1 mutations resulted in both increased sensitivity and resistance to exogenous DNA damage, despite a reduction of HR capacity in all clones. Resistance was associated with improved DNA double-strand break repair and reduction in replication stress (RS). Lower RS was accompanied by increased activation and interaction of proteins essential for the S phase-specific DNA damage response consisting of HR proteins, FANCD2, and CHK1.

Keywords: Breast cancer; BRCA1; DNA repair

Permalink: https://www.hzdr.de/publications/Publ-36221
Publ.-Id: 36221


Chemical Vapor Deposition and High-Resolution Patterning of a Highly Conductive Two-Dimensional Coordination Polymer Film

Rubio-Giménez, V.; Arnauts, G.; Wang, M.; Oliveros Mata, E. S.; Huang, X.; Lan, T.; Tietze, M. L.; Kravchenko, D. E.; Smets, J.; Wauteraerts, N.; Khadiev, A.; Novikov, D. V.; Makarov, D.; Dong, R.; Ameloot, R.

Crystalline coordination polymers with high electrical conductivities and charge carrier mobilities might open new opportunities for electronic devices. However, current solvent-based synthesis methods hinder compatibility with microfabrication standards. Here, we describe a solvent-free chemical vapor deposition method to prepare high-quality films of the two-dimensional conjugated coordination polymer Cu-BHT (BHT = benzenehexanothiolate). This approach involves the conversion of a metal oxide precursor into Cu-BHT nanofilms with a controllable thickness (20–85 nm) and low roughness (<10 nm) through exposure to the vaporized organic linker. Moreover, the restricted metal ion mobility during the vapor–solid reaction enables high-resolution patterning via both bottom-up lithography, including the fabrication of micron-sized Hall bar and electrode patterns to accurately evaluate the conductivity and mobility values of the Cu-BHT films.

Permalink: https://www.hzdr.de/publications/Publ-36220
Publ.-Id: 36220


Defect-assisted ion transport in magneto-ionic nitrides probed by positrons

Liedke, M. O.; Butterling, M.; de Rojas, J.; Quintana, A.; Lopeandía, A.; Menéndez, E.; Costa-Krämer, J. L.; Hirschmann, E.; Elsherif, A. G. A.; Sort, J.; Wagner, A.

Magneto-ionics deals with a class of spintronic materials where the external electrical field induces ion migration and leads to a raise of magnetization, a consequence of magnetic species local segregations or increased magnetic interactions between them. Since this ion transport is activated by the voltage actuation, no large electrical currents are required and heat dissipation processes are mostly negligible. In addition, simply reversing the direction of the voltage bias, the generated ferromagnetic state returns to its original magnetic configuration, which realizes the magnetic switch concept. Using magnetometry and electron microscopy supported with positron annihilation spectroscopy techniques different nitrides (CoN, FeN, NiN) have been investigated. CoN and FeN are promising candidates for fast magneto-ionic switching, whereas NiN clearly underperforms. Positron annihilation spectroscopy provides a unique probe of open volume defects, e.g. dislocations, vacancies and their agglomerations at grain boundaries, and it was successfully utilized to study the defect nanostructure here. As a reference, we first present electrolyte-gated and defect-mediated oxygen migration in single-layer, paramagnetic Co3O4 at room temperature, which allows voltage-controlled ON-OFF magnetic switching via internal reduction/oxidation processes [1]. Here, the bias-induced motion of oxygen ions was caused by dominant vacancy clusters, with oxygen motion promoted at grain boundaries and assisted by the development of O-rich diffusion channels and Co-rich grain inner regions. In the case of nitrides, on the other hand, nitrogen transport is found to occur uniformly throughout the film, creating a plane-wave-like migration front (Fig. 1), without assistance of diffusion channels [2,3]. Using positrons as a probe, we will show that the initial average open volume is larger in nitrides compared to oxides, which likely governs the migration process and allows for enhanced switching rates and cyclability as well as lowers threshold voltages. We will try to propose factors playing a role in case of hindered ionic migration in NiN, too.

Figure 1: Depth profile of the S-parameter as a function of increasing electrical field.

[1] A. Quintana, E. Menéndez, M. O. Liedke et al., ACS Nano, 12, 10291 (2018)
[2] J. de Rojas, A. Quintana, A. Lopeandía et al., Nature Communications, 11, 5871 (2020)
[3] J. de Rojas, J. Salguero, F. Ibrahim et al. ACS Appl. Mater. Interfaces, 13, 30826 (2021)

Keywords: magneto-ionics; Co3O4; CoN; NiN; positron annihilation spectroscopy; defects

Related publications

  • Poster (Online presentation)
    ICPA-19 (International Conference on Positron Annihilation), 22.-26.08.2022, Helsinki, Finnland

Permalink: https://www.hzdr.de/publications/Publ-36219
Publ.-Id: 36219


Defect-assisted ion transport in magneto-ionic functional oxides and nitrides probed by positrons

Liedke, M. O.; Butterling, M.; de Rojas, J.; Quintana, A.; Lopeandía, A.; Menéndez, E.; Costa-Krämer, J. L.; Hirschmann, E.; Sort, J.; Wagner, A.

Magneto-ionics deals with a class of spintronic materials where the external electrical field induces ion migration and leads to a raise of magnetization as a consequence of magnetic species local segregations or increased magnetic interactions between them. Since this ion transport is activated by the voltage actuation, no large electrical currents are required and heat dissipation processes are mostly negligible. Moreover, by simply reversing the direction of the voltage bias, the generated ferromagnetic state is brought back to its original magnetic configuration, which realizes the magnetic switch concept. Using magnetometry and electron microscopy supported with positron annihilation spectroscopy techniques, oxides (Co3O4) and different nitrides (CoN and FeN) have been investigated, which are promising candidates for fast magneto-ionic switching. Positron annihilation spectroscopy provides a unique probe of open volume defects, e.g. dislocations, vacancies within crystal and at interfaces, vacancy agglomerations at grain boundaries, macro- and mesopores and it was successfully utilized to study the defect nanostructure here. We first present electrolyte-gated and defect-mediated oxygen migration in single-layer, paramagnetic Co3O4 at room temperature, which allows voltage-controlled ON-OFF magnetic switching via internal reduction/oxidation processes [1]. Here, the bias-induced motion of oxygen ions is caused by dominant vacancy clusters, with oxygen motion promoted at grain boundaries and assisted by the development of O-rich diffusion channels and Co-rich grain inner regions. In the case of nitrides, on the other hand, nitrogen transport is found to occur uniformly throughout the film, creating a plane-wave-like migration front, without assistance of diffusion channels [2,3]. Using positrons as a probe, we will show that the initial average open volume is larger compared to oxides, which likely governs the migration process and allows, moreover, for enhanced switching rates and cyclability as well as lower threshold voltages.
[1] A. Quintana, E. Menéndez, M. O. Liedke et al., ACS Nano, Vol. 12, p. 10291 (2018)
[2] J. de Rojas, A. Quintana, A. Lopeandía et al., Nature Communications, Vol. 11, p. 5871 (2020)
[3] J. de Rojas, J. Salguero, F. Ibrahim et al. ACS Appl. Mater. Interfaces Vol. 13, p. 30826 (2021)

Keywords: magneto-ionics; Co3O4; CoN; FeN; positron annihilation spectroscopy; defects

Related publications

  • Lecture (Conference)
    E-MRS Fall Meeting 2022, 19.-22.09.2022, Warsaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-36218
Publ.-Id: 36218


Data publication : Tailoring crosstalk between localized 1D spin-wave nanochannels using focused ion beams

Iurchuk, V.; Pablo-Navarro, J.; Hula, T.; Narkowicz, R.; Hlawacek, G.; Koerber, L.; Kakay, A.; Schultheiss, H.; Fassbender, J.; Lenz, K.; Lindner, J.

This dataset contains raw data (SEM images, AFM, FMR, BLS, TetraX) used to study the dynamical edge modes in closely spaced permalloy microstrips.

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Permalink: https://www.hzdr.de/publications/Publ-36217
Publ.-Id: 36217


Investigation of laser reflectivity and transmissivity of laser-plasma interaction with thin foil targets

Umlandt, M. E. P.; Ziegler, T.; Bernert, C.; Garten, M.; Gaus, L.; Göthel, I.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Prencipe, I.; Rehwald, M.; Reimold, M.; Schlenvoigt, H.-P.; Vescovi Pinochet, M. A.; Zeil, K.; Schramm, U.

Ion acceleration by compact laser-plasma sources promises a variety of applications ranging from medical relevance to fusion experiments.Reaching the required beam quality parameters for those applications demands a very high level of understanding and control over the laserplasma interaction process. Central components in this context are the absorption of the electromagnetic laser field by the plasma and the quality of the resulting acceleration field structure.
Measuring and analyzing unabsorbed light - as transmitted and/or specularly reflected parts - thus allows insight into properties of the underlying laser-plasma interaction. We experimentally investigate these interactions for high and low-contrast laser pulses with thin solid density foil targets at the Draco PW laser system (HZDR). The results of spectral, spatial, and energy analysis of transmitted and reflected light indicate changes in the plasma interaction and will be presented.

Keywords: laser plasma; laser proton acceleration; high power laser

  • Lecture (Conference) (Online presentation)
    DPG-Frühjahrstagung 2022, 28.03.-01.04.2022, Mainz / virtuell, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36216
Publ.-Id: 36216


Data publication: Underground hyperspectral outcrop scanning for automated mine-face mapping — the Lithium deposit of Zinnwald/Cínovec

Kirsch, M.; Mavroudi, M.; Thiele, S. T.; Lorenz, S.; Tusa, L.; Booysen, R.; Herrmann, E.; Fatihi, A.; Möckel, R.; Dittrich, T.; Gloaguen, R.

As part of a project on the development of hyperspectral scanning to support geological mapping in underground mines, we acquired hyperspectral data from three adjacent outcrops of Sn-W-Li greisen rocks in the visitor’s mine of Zinnwald, Germany. The hyperspectral scans were pre-processed and then back-projected onto photogrammetric, three-dimensional digital outcrop models resulting in so-called "hyperclouds". The here presented hyperclouds from the three outcrops (Z1, Z2, and Z3) contain the following attributes:

ZX_Absorbance.ply
RGB colours: Mica/clay-zinnwaldite-topaz abundance based on absorbance (1 – hull-corrected reflectance) at 2200 nm (red), 2250 nm (green), and 2085 nm (blue)
Scalars: Absorbance at 2086.88 nm, 2160.69 nm, 2197.53 nm, 2209.8 nm, 2252.7 nm, and 2338.31 nm

ZX_Iron.ply
RGB colours: Composite (Fe3+ Fe2+ FeOH) iron index (red: 600/570 nm, green:(920 nm + 1650 nm)/ (1035 nm 1230 nm), blue: (2230 nm 2290 nm)/(2245 nm + 2260 nm)
Scalars: Fe3+ = 600/570 nm, Fe2+ = (920 nm + 1650 nm)/ (1035 nm + 1230 nm), FeOH = (2230 nm + 2290 nm)/(2245 nm + 2260 nm)

ZX_MNF.ply
RGB colours: Minimum noise fraction false colour (red: band 4, green: band 7, blue: band 5)
Scalars: Minimum noise fraction bands 4, 7, 5)

ZX_RGB_mineralogy_Li.ply
RGB colours: True colour RGB from photogrammetric outcrop model
Scalars: Mineral abundances derived by combining sample mineralogy from quantitative XRD measurements and hyperspectral unmixing approaches: Quartz/Feldspar, Zinnwaldite, Muscovite/Illite, Kaolinite, Topaz, Lithium (by multiplying the zinnwaldite abundance by its average lithium content of 1.7%)

Keywords: hyperspectral; underground mining; point cloud; lithium; mineral mapping

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Permalink: https://www.hzdr.de/publications/Publ-36215
Publ.-Id: 36215


Wild herbivores enhance resistance to invasion by exotic cacti in an African savanna

Wells, H. B. M.; Crego, R. D.; Alston, J.; Ndungu, S. K.; Khasoha, L. M.; Reed, C. G.; Hassan, A. A.; Kurukura, S.; Ekadeli, J.; Namoni, M.; Stewart, P. S.; Kimuyu, D. M.; Wolf, A. A.; Young, T. P.; Kartzinel, T. R.; Palmer, T. M.; Goheen, J. R.; Pringle, R. M.

Whether wild herbivores confer biotic resistance to invasion by exotic plants remains a key question in ecology. There is evidence that wild herbivores can impede invasion by exotic plants, but it is unclear whether and how this generalises across ecosystems with varying wild herbivore diversity and functional groups of plants, particularly over long-term (decadal) time frames. Using data from three long-term (13- to 26-year) exclosure experiments in central Kenya, we tested the effects of wild herbivores on the density of exotic invasive cacti, Opuntia stricta and O. ficus-indica (collectively, Opuntia), which are among the worst invasive species globally. We also examined relationships between wild herbivore richness and elephant occurrence probability with the probability of O. stricta presence at the landscape level (6150 km2). Opuntia densities were 74% to 99% lower in almost all plots accessible to wild herbivores compared to exclosure plots. Opuntia densities also increased more rapidly across time in plots excluding wild herbivores. These effects were largely driven by megaherbivores (≥1000 kg), particularly elephants. At the landscape level, modelled Opuntia stricta occurrence probability was negatively correlated with estimated species richness of wild herbivores and elephant occurrence probability. On average, O. stricta occurrence probability fell from ~0.56 to ~0.45 as wild herbivore richness increased from 6 to 10 species and fell from ~0.57 to ~0.40 as elephant occurrence probability increased from ~0.41 to ~0.84. These multi-scale results suggest that any facilitative effects of Opuntia by wild herbivores (e.g. seed/vegetative dispersal) are overridden by suppression (e.g. consumption, uprooting, trampling). Synthesis. Our experimental and observational findings that wild herbivores confer resistance to invasion by exotic cacti add to evidence that conserving and restoring native herbivore assemblages (particularly megaherbivores) can increase community resistance to plant invasions. © 2022 The Authors. Journal of Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

Keywords: biotic resistance; elephants; invasion ecology; long-term exclosure experiments; megaherbivores; multi-trophic interactions; Opuntia stricta; prickly pear

Permalink: https://www.hzdr.de/publications/Publ-36214
Publ.-Id: 36214


Foam Targets as Extreme Magnetic Field Drivers

Laso García, A.; Toncian, T.; Habibi, M.; Prencipe, I.; Cowan, T.; Rinderknecht, H. G.; Wei, M. S.; Bruhaug, G.; Arefiev, A.; Wang, T.; Doria, D.; Crăciun, V.; Ghenuche, P.; Năstasă, V.

Structured foam targets are of great interest for the laser-plasma community. Recent studies have shown how low density foams could be used to generate extreme magnetic fields in the MegaTesla range. A result of the interaction of the fields with the accelerated electrons in the foam is a large increase in the electron kinetic energy, and the generation of bright flashes of synchrotron radiation in the MeV range.

In this talk we introduce experimental results obtained at HED/HiBEF at the European XFEL on the structural changes and homogenization of the foam during the laser interaction. Then we will show results on synchrotron emission at Texas Petawatt. Finally we will provide an overview of our roadmap towards implementing foam experiments at the 10 PW level at ELI-NP

Keywords: laser-plasma; foams; HiBEF; XFEL; ELI-NP; texas PW; synchrotron; bright gamma flashes

  • Invited lecture (Conferences)
    Foam Target Workshop, 02.11.2022, Dolní Břežany, Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-36213
Publ.-Id: 36213


Towards High-Field Experiments in Existing and Upcoming Laser Facilities

Laso García, A.; Toncian, T.; Habibi, M.; Prencipe, I.; Rinderknecht, H. G.; Wei, M. S.; Bruhaug, G.; Arefiev, A.; Wang, T.; Doria, D.; Crăciun, V.; Ghenuche, P.; Năstasă, V.; Cernăianu, M.; Dreghici, D.-B.; Talposi, A.-M.; Quevedo, H.; Ditmire, T.; Schlenvoigt, H.-P.; Smid, M.; Cowan, T.

The Helmholtz International Beamline for Extreme Fields is a user consortium providing drivers for high-energy density and high-field science at the HED station of EuXFEL. This presentation will give an overview of the current implementation and commissioning results as well as future plans and exemplary science cases.
In parallel, new exciting opportunities for high-field science are opening with the first user call at the ELI facilities. Here, we will discuss first results on Megatesla magnetic field generation in overdense plasmas. We will also discuss future plans to exploit the high intensities, up to 10 PW, to be delivered at ELI-NP.

Keywords: Extreme fields; Laser-plasmas; HiBEF; XFEL; bright gamma flashes; high energy density

  • Invited lecture (Conferences)
    QED Laser Plasmas, 26.-30.09.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-36212
Publ.-Id: 36212


Combined Phase Contrast Imaging and Small-Angle X-Ray Scattering Diagnostic of Relativistic Plasmas at the High Energy Density Instrument at European XFEL

Laso García, A.; Arefiev, A.; Kemp, A.; Allen, C. H.; Bähtz, C.; Nagler, B.; Palmer, C. A. J.; Murphy, C. D.; Spindloe, C.; Brown, C. R. D.; Neely, D.; Kraus, D.; Marley, E.; Hartouni, E. P.; Fiuza, F.; Grim, G. P.; Cochran, G. E.; Schlenvoigt, H.-P.; Prencipe, I.; Williams, J.; Green, J.; Eggert, J. H.; Zeil, K.; Lancaster, K. L.; Divol, L.; Gaus, L.; Huang, L.; Schoelmerich, M.; Rehwald, M.; Oliver, M.; Rödel, M.; Macdonald, M.; Smid, M.; Makita, M.; Nakatsutsumi, M.; Humphries, O. S.; Neumayer, P. B.; Mabey, P.; Shepherd, R. L.; Gray, R.; Wilks, S. C.; Le Pape, S.; Kerr, S. M.; Glenzer, S. H.; Funk, S.; Gales, S. G.; Cowan, T.; White, T. G.; Kluge, T.; Doeppner, T.; Toncian, T.; Zastrau, U.; Schramm, U.; Ping, Y.; He, Z.; Höppner, H.; Pelka, A.

The High Energy Density (HED) instrument at the European XFEL provides a platform to study hot and warm dense matter. The Helmholtz International Beamline for Extreme Fields (HiBEF) is a User Consortium supplying HED with two laser systems (the high-intensity ReLaX laser, by Amplitude Technologies, and the high-energy Dipole-100X laser, by STFC), Diamond Anvil Cells setup and high-pulsed magnetic fields. These tools in combination with the XFEL beam enable the investigation of relativistic laser plasmas, strong-field QED phenomena, high-pressure astro- and planetary physics as well as magnetic phenomena in condensed matter. The successful commissioning of the ultra-short pulse high-intensity ReLaX laser, provides new unique opportunities in the plasma and high-field physics fields [1].
ReLaX is a double CPA Ti:Sa laser capable of delivering up to 300 TW pulses on target. In the first commissioning phase, 100 TW pulses were used, reaching
intensities up to 1020 W/cm2. Small-Angle X-Ray Scattering (SAXS) without the need of a beamstop was first commissioned at HED in September 2019. Two highly annealed pyrolytic graphite (HAPG) crystals were used to reflect the SAXS photons onto a detector while allowing the main XFEL beam to go through [2]. In April and May 2021, Small Angle X-Ray Scattering and Phase Contrast Imaging (PCI) were simultaneously demonstrated in pump-probe experiments at HED in a community experiment involving 15 institutions from all over the world. In this talk we will present the preliminary results of this community experiment probing ultrafast phenomena in a wide array of target configurations: hole boring in wires, shockwave generation in CH blocks, buried heating of a wire inside a CH medium, foam ionization and collective effects in heated foils.

[1] A. Laso Garcia, H. Hoeppner, A. Pelka et al., “ReLaX: the HiBEF high-intensity short-pulse laser driver for relativistic laser-matter interaction and strong-field science at the HED instrument at EuXFEL”. High Power Laser Science and Engineering, 1-15. doi:10.1017/hpl.2021.47
[2] M. Šmíd, et al., "Mirror to measure small angle x-ray scattering signal in high energy density experiments", Review of Scientific Instruments 91, 123501 (2020). doi:10.1063/5.0021691

Keywords: Laser-plasma; High energy density; XFEL; HiBEF; ReLaX; SAXS; PCI

  • Invited lecture (Conferences)
    DPG-Frühjahrstagung Mainz 2022, 01.04.2022, Mainz, Germany

Permalink: https://www.hzdr.de/publications/Publ-36211
Publ.-Id: 36211


Commissioning and First User Experiments with ReLaX and XFEL Beam

Laso García, A.; Arefiev, A.; Kemp, A.; Allen, C. H.; Bähtz, C.; Nagler, B.; Palmer, C. A. J.; Murphy, C. D.; Spindloe, C.; Brown, C. R. D.; Neely, D.; Kraus, D.; Marley, E.; Hartouni, E. P.; Fiuza, F.; Grim, G. P.; Cochran, G. E.; Schlenvoigt, H.-P.; Prencipe, I.; Williams, J.; Green, J.; Eggert, J. H.; Zeil, K.; Lancaster, K. L.; Divol, L.; Gaus, L.; Huang, L.; Schoelmerich, M.; Rehwald, M.; Oliver, M.; Rödel, M.; Macdonald, M.; Smid, M.; Makita, M.; Nakatsutsumi, M.; Humphries, O. S.; Neumayer, P. B.; Mabey, P.; Shepherd, R. L.; Gray, R.; Wilks, S. C.; Le Pape, S.; Kerr, S. M.; Glenzer, S. H.; Funk, S.; Gales, S. G.; Cowan, T.; White, T. G.; Kluge, T.; Doeppner, T.; Toncian, T.; Zastrau, U.; Schramm, U.; Ping, Y.; He, Z.; Höppner, H.; Pelka, A.

In this presentation we provide an overview of the commissioning and first user experiment of ReLaX in combination with the XFEL beam. We will introduce the setup and laser parameters. We will show the established standard setup combining small-angle x-ray scattering (SAXS), phase-contrast imaging (PCI) and spectroscopy techniques. Finally we will show examples of the data obtained in the interaction of the ReLaX laser with targets of interested for the short-pulse laser community.

Keywords: Laser-plasma; HiBEF; XFEL; SAXS; PCI

  • Lecture (Conference)
    Current status and future completion of the HED instrument and the HIBEF contributions, 25.01.2022, European XFEL, Germany

Permalink: https://www.hzdr.de/publications/Publ-36210
Publ.-Id: 36210


Influence of substrate composition on size and chemical state of ion beam synthesised Co nanoparticles – Towards fabrication of electrodes for energy devices

Gupta, P.; Jovic, V.; Hübner, R.; Anquillare, E.; Suschke, K.; Smith, K. E.; Markwitz, A.; Waterhouse, G. I. N.; Kennedy, J.

A one-step approach to synthesize ultrafine transition metal particles (size < 5 nm) in carbon substrates is highly desirable for fabricating electrodes for energy devices. Herein, cobalt ion implantation into amorphous carbon films (a:C) and hydrogenated amorphous carbon films (a:CH) was explored, with the aim of synthesizing ultrafine metallic cobalt nanoparticles at room temperature. Co ions of 30 keV energy were implanted into the carbon films to achieve a Co areal density of 1.0 ± 0.1 × 1017 atoms cm-2. Rutherford backscattering measurements revealed that hydrogenated amorphous carbon films gave a broader Co depth distribution compared to the amorphous carbon films. Further, cross-sectional TEM analysis revealed that hydrogenated carbon films suppressed metallic Co nanoparticle aggregation, leading to the creation of ultrafine Co nanoparticles (size < 5 nm). Co L-edge X-ray absorption spectroscopy measurements confirmed the formation of predominantly metallic Co nanoparticles by ion implantation. Results conclusively demonstrate that the presence of hydrogen (~ 28 at %) in the carbon matrix facilitates the synthesis of ultrafine metallic Co nanoparticles during Co ion implantation.

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Permalink: https://www.hzdr.de/publications/Publ-36209
Publ.-Id: 36209


Energy-chirp compensation of laser-driven ion beams enabled by structured targets

Gong, Z.; Bulanov, S. S.; Toncian, T.; Arefiev, A.

We show using three-dimensional (3D) simulations that the challenge of generating dense monoenergetic laser-driven ion beams with low angular divergence can be overcome by utilizing structured targets with a relativistically transparent channel and an overdense wall. In contrast to a uniform target that produces a chirped ion beam, the target structure facilitates the formation of a dense electron bunch whose longitudinal electric field reverses the energy chirp. This approach works in conjunction with existing acceleration mechanisms, augmenting the ion spectra. For example, our 3D simulations predict a significant improvement for a 2 PW laser pulse with a peak intensity of 5×1022 W/cm2. The simulations show a monoenergetic proton peak in a highly desirable energy range of 200 MeV with an unprecedented charge of several nC and a relatively low divergence that is below 10°.

Keywords: Acceleration; Electric fields; Ions; 3D simulations; Acceleration mechanisms; Angular divergence; Chirp compensation; Electron bunch; Energy; Ion spectrum; Monoenergetic; Target structure; Three-dimensional (3-D) simulation; Ion beams

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Permalink: https://www.hzdr.de/publications/Publ-36208
Publ.-Id: 36208


Ultra-high dose rate radiobiology and dosimetry at the laser-driven proton accelerator Draco-PW

Brack, F.-E.; Reimold, M.; Kroll, F.; Beyreuther, E.; Karsch, L.; Kraft, S.; Leßmann, E.; Pawelke, J.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Ziegler, T.; Zeil, K.; Metzkes-Ng, J.

Background and Aims
Laser-plasma accelerators (LPA) are a viable addition to the ultra-high dose rate accelerator portfolio, as they generate extremely intense proton bunches of several 10 MeV kinetic energy. Efficiently transported and spectrally shaped, a single LPA proton bunch enables homogeneous dose delivery above 20 Gy to mm-scale volumes with a dose rate well above 108 Gy/s. At Draco PW we have recently shown the successful establishment of a proton LPA research platform for small animal studies employing a multi-shot accumulated dose delivery for a mouse model pilot study. [Kroll et al, Nature Physics 2022].
Methods
Reaching the range of FLASH-associated parameters at an LPA proton source requires single-shot irradiation. We performed such irradiations with zebrafish embryos and dosimeters using the pulsed beamline at Draco PW. Since LPA based accelerators are prone to inherent fluctuations of the source, to measure the applied dose, a minimally invasive, online spectral characterization of the delivered proton bunches is necessary. Clinically used ionization chambers saturate under LPA beam conditions. Therefore, we present a scintillator-based time-of-flight (ToF) beam monitoring system for the recording of kinetic energy spectra of single LPA proton bunches. The deduced spectra are used as an input for Monte-Carlo simulations to predict the delivered dose to the irradiated sample.
Results
The ToF ansatz enabled the reconstruction of the kinetic energy spectrum of the transported protons with a relative energy uncertainty down to ca. 11% (2σ). Subsequent Monte-Carlo simulations predict the applied depth dose distribution with an uncertainty of ca. 6% (2σ).
Conclusions
We present a laser-based proton irradiation platform at the Draco PW facility that enables systematic radiobiological studies within an unprecedented range of beam parameters and demonstrate a solution for minimally invasive volumetric dosimetry at ultra-high dose rates.

  • Lecture (Conference)
    Flash Radiotherapy and Particle Therapy Conference - FRPT 2022, 29.11.-02.12.2022, Barcelona, Spanien

Permalink: https://www.hzdr.de/publications/Publ-36207
Publ.-Id: 36207


Machine learning-based quantum accurate interatomic potentials for warm dense matter

Kumar, S.; Tahmasbi, H.; Lokamani, M.; Ramakrishna, K.; Cangi, A.

Modeling warm dense matter is relevant for various applications including the interior of gas giants and exoplanets, inertial confinement fusion, and ablation of metals. Ongoing and upcoming experimental campaigns in photon sources around the globe rely on numerical simulations that are accurate on the level of electronic structures. In that regard, density functional theory molecular dynamics (DFT-MD) simulations [1] have been widely used to compute thermodynamical properties of warm dense matter. However, two challenges impede further progress: (1) DFT-MD becomes computationally infeasible with increasing temperature (2) finite-size effects render many computational observables inaccurate because DFT-MD is limited to a few hundred atoms on current HPC platforms. Recently, molecular dynamics simulations using machine learning-based interatomic potentials (ML-IAP) could overcome these computational limitations. Here, we propose a method to construct ML-IAPs from DFT data based on SNAP descriptors [2]. We investigate the transferability of ML-IAPs over a large range of temperatures (1,000 to 100,000 K) which currently is a topic of active research.

References:

[1] G. Kresse and J. Hafner, Physical Review B 47, 558 (1993).
[2] A. P. Thompson, L. P. Swiler, C. R. Trott, S. M. Foiles, and G. J. Tucker, Journal of Computational Physics, 285, 316-330, 2015.

Keywords: Computational Physics; Warm Dense Matter; Machine Learning; Transport Coefficients; Molecular Dynamics

  • Lecture (Conference)
    APS March Meeting 2023, 08.03.2023, Las Vegas, Nevada, USA

Permalink: https://www.hzdr.de/publications/Publ-36206
Publ.-Id: 36206


Data publication: Modification of Porous Ultralow‑k Film by Vacuum Ultraviolet Emission

Zotovich, A. I.; Zyryanov, S. M.; Lopaev, D. V.; Rezvanov, A. A.; Attallah, A. G.; Liedke, M. O.; Butterling, M.; Bogdanova, M. A.; Vishnevskiy, A. S.; Seregin, D. S.; Vorotyntsev, D. A. V.; Palov, A. P.; Hirschmann, E.; Wagner, A.; Naumov, S.; Vorotilov, K. A.; Rakhimova, T. V.; Rakhimov, A. T. R.; Baklanov, M.

Modification of spin-on-deposited porous PMO (periodic mesoporous organosilica) ultralow-k (ULK) SiCOH films (k = 2.33) containing both methyl terminal and methylene bridging groups by vacuum ultraviolet (VUV) emission from Xe plasma is studied. The temporal evolution of chemical composition, internal defects, and morphological properties (pore structure transformation) is studied by using Fourier transform infrared spectroscopy, in situ laser ellipsometry, spectroscopic ellipsometry, ellipsometric porosimetry (EP), positron-annihilation lifetime spectroscopy (PALS), and Doppler broadening positron-annihilation spectroscopy. Application of the different advanced diagnostics allows making conclusions on the dynamics of the chemical composition and pore structure. The time frame of the VUV exposure in the current investigation can be divided into two phases. During the first short phase, film loses almost all of its surface methyl and matrix bridging groups. An increase of material porosity due to removal of methyl groups with simultaneous matrix shrinkage is found by in situ ellipsometry. The removal of bridging bonds leads to an increase of matrix intrinsic porosity. Nevertheless, when the treated material is exposed to the ambient air, the sizes of micro- and mesopores and pores interconnectivity decrease with the VUV exposure time according to PAS and EP data. The last is the result of the additional film shrinkage caused by atmosphere exposure. During the second phase the increase of mesopore size is detected by both EP and PAS. The increase of mesopore size goes all the time as it is expected from in situ ellipsometry, but it is masked by the air exposure.

Keywords: ultralow-k materials; vacuum ultraviolet emission; porosimetry; positron-annihilation spectroscopy; in situ ellipsometry

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Permalink: https://www.hzdr.de/publications/Publ-36205
Publ.-Id: 36205


Radiopharmazie

Kopka, K.

kein Abstrakt verfügbar

  • Invited lecture (Conferences)
    Branchendialog zur Resilienz pharmazeutischer Lieferketten, 19.07.2022, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36204
Publ.-Id: 36204


Optical Fingerprints of Unconventional Carriers in Kagome Metals

Uykur, E.

Kagome metals are the newly emerging class of quantum materials, where the peculiar kagome structure along with the itinerant character of the electrons give rise to a non-trivial combination of entangled magnetic states, electronic correlations, and topological orders. Two dissimilar features of massive, localized carriers at dispersionless flat bands and the massless Dirac fermions at the linearly dispersing bands coexist in their electronic structure, giving rise to various exotic phenomena. While the magnetic kagome metals are at the center of interest due to the proximity of the flatband magnetism, newly discovered non-magnetic counterparts possess a peculiar density wave order along with the unconventional superconductivity.

Optical spectroscopy is a useful method that shows excellent sensitivity to both linear and flat bands. Furthermore, (partial)gaps at the density of state at Fermi energy can be identified with clear signatures in optical spectra and the energy scale can be discussed. The opportunity to combine with other external stimuli such as magnetic field and pressure offers a viable route to disentangle different contributions. In this talk, I will highlight the optical fingerprints of unconventional carriers in these unique materials.

  • Invited lecture (Conferences)
    APS March Meeting, 14.-18.03.2022, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-36203
Publ.-Id: 36203


Core-Shell Nanostructures of Tungsten Oxide and Hydrogen Titanate for H2 Gas Adsorption

Rajbhar, M.; Das, P.; Möller, W.; Chatterjee, S.

Nanostructured tungsten oxide is a promising material for sensing reducing gases such as hydrogen. However, this material exhibits limitations due to a poor response toward sensing at room temperature, incomplete recovery to the initial state, long response time, and a low response factor, which is not desired for explosive gases like hydrogen. In this work, we, for the first time, demonstrate that these limitations can be significantly overcome using the core-shell structure of tungsten oxide (WO3) nanorods and hydrogen titanate (H2Ti3O7) nanotubes developed and suitably defect-engineered by low-energy ion irradiation. The sensor based on the pristine core-shell heterostructure of tungsten oxide nanorods and hydrogen titanate nanotubes exhibits excellent response and selectivity to different concentrations of H2 ranging from 10 to 500 ppm. However, it requires a quite high temperature of 300 °C with response and recovery times of about 38 and 99.8 s, respectively. After irradiation, the hybrid form shows a similar level of response and selectivity, however, at a much lower temperature of about 120 °C with significantly faster response and recovery times of about 16 and 18 s, respectively. Such an ion beam-modified structure addresses critical issues of developing a gas-sensing device, such as the effects of moisture and power consumption. The experimental observations are very well in agreement with the predictions of the state-of-the-art Monte Carlo-based TRI3DYN ion-solid interaction simulation, and the gas-sensing mechanism was explained using first principles-based calculation. The study reveals that low-energy ion-induced defect engineering yields better charge transport, better binding of the gas with the surface, as well as the superior moisture-repelling ability of the surface, leading to better sensing performance than the pristine core-shell structure. This heterostructure between two nanomaterials carries complementary advantages in various aspects, such as the surface area, conductivity, and sensitivity toward a wide range and mixture of gases. Additionally, the wrapping yields good mechanical strength and flexibility, making it possible to use as a flexible sensing device made through a bottom-up fabrication technique.

Keywords: core-shell heterostructure; DFT simulation; gas sensing; H2adsorption; ion beam irradiation; TRI3DYN

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Permalink: https://www.hzdr.de/publications/Publ-36202
Publ.-Id: 36202


Facile and scalable preparation of cage-like mesoporous carbon from lignin-based phenolic resin and its application in supercapacitor electrodes

Li, W.; Wang, G.; Sui, W.; Xu, T.; Li, Z.; Rumpel, A.; Si, C.; Parvez, A. M.

Due to the similarity in chemical structure, lignin has presented great potential in the synthesis of bio-based phenolic resin. Herein, a facile and scalable synthesis strategy for a novel cage-like lignin-based phenolic resin was proposed through direct spray drying of the mixture of phenolic resin and unmodified lignin. The as-prepared lignin-based phenolic resin was pre-carbonized and carbonized using KOH to produce mesoporous carbon materials (LPRAC) that were further employed as supercapacitor electrodes. The results revealed that the lignin addition led to the noticeable change of the resin shape from perfect sphere to cage-like structure owing to the surfactivity and hydrophilicity of lignin. The cage-like structure promoted the KOH-activated pore generation and expansion in the carbonization process, resulting in the significantly increased specific surface area of the phenolic carbon and the intensified mesoporous formation. The electrochemical performance determination indicated that the specific capacitance of LPRAC-20% (20% lignin addition) was 217.3 F/g at 0.5 A/g, which was considerably higher than that of the lignin-free phenolic carbon (122.6 F/g). Moreover, the LPRAC-20% also exhibited preferable capacitance retention and excellent cycling stability. Accordingly, the present work offers a simple and scalable approach to prepare cage-like mesoporous carbon with excellent electrochemical performance from lignin-based phenolic resin and thus provides a promising route for lignin valorization in energy storage materials.

Keywords: Lignin-based phenolic resin; Cage-like mesoporous carbon; KOH activation; Supercapacitor electrodes

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36201
Publ.-Id: 36201


Reduction of lignin heterogeneity for improved catalytic performance of lignin nanosphere supported Pd nanoparticles

Hao, S.; Guanhua, W.; Jing, G.; Ni, W.; Wenjie, S.; Zicheng, C.; Hongyu, J.; Parvez, A. M.; Chuanling, S.

Lignin heterogeneity, including molecular weight polydispersity and structural complexity, causes undesirable properties of lignin in its valorization. In this regard, the current work focuses on the effect of lignin heterogeneity on the green synthesis of lignin nanosphere (LNS) supported Pd nanoparticles (Pd@LNS) and their catalytic performance. Three lignin fractions with reduced heterogeneity (F1, F2, and F3) were used for LNS fabrication and the as-prepared LNSs were further applied as carriers for Pd nanoparticles (Pd NPs) synthesized using lignin as an in-situ reducer. It was found that the three LNSs exhibited a gradually decreased particle size from F1 to F3, while all of them revealed improved particle size uniformity compared to that from the initial lignin. Owing to the superior reducing power of F1, the LNS prepared from F1 presented the highest loading amount of Pd NPs among the three LNSs. Moreover, these Pd NPs had the smallest particle size and they were dispersed in a much more uniform way than those on the LNSs from F2 and F3. Therefore, the Pd@LNS prepared from F1 exhibited significantly increased catalytic activity in the Cr(VI) reduction compared with those from F2 and F3, as well as the initial lignin. Consequently, the work implies that lignin heterogeneity has considerable influences on the green formation of Pd NPs on LNS, and the catalytic performance of Pd@LNS can be substantially improved using low molecular weight lignin fraction as the feedstock.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36200
Publ.-Id: 36200


Effects of surface microbubbles on the adhesion between air bubble/oil droplet and graphite surfaces

Ming, L.; Xu, M.; Lijuan, S.; Chunyun, Z.; Jincheng, L.; Qinshan, L.; Yaowen, X.; Xiahui, G.

The surface microbubbles (SMBs) induced by air nucleation on mineral surfaces exert a powerful influence over enhancing the adhesion of air bubbles or oil droplets on mineral surfaces in flotation. The contact angles and TPLs were characterized by captive-bubble/oil droplet on the graphite surfaces. They were combined with dynamic bubble/oil droplet-graphite surface attachment and detachment visualization and force measurements using a microbalance system equipped with a camera to demonstrate the role of SMBs in bubble/oil dropletgraphite surface adhesion. The results show that after depressurization, the dissolved air in water nucleates on both hydrophobic and oxidized graphite surfaces, resulting in SMBs formation, which can enhance the adhesion of bubbles/oil droplets with the different graphite surfaces. For bubble-solid adhesion, these enhancements are attributed to the bridging effect of the SMBs coalescing with the large bubble increasing threephrase contact lines (TPLs) and with this the adhesion forces. For oil-solid interactions, SMBs induce the attachment and spreading of the oil droplet on the graphite surfaces, as the TPLs and spreading forces are increased. SMBs also result in a more stable oil droplet-graphite interface, as the adhesion forces are improved. Therefore, SMBs are efficient for improving graphite flotation by increasing the stability of the mineralized bubble and promoting the spreading and adhesion of dodecane oil. Hence, SMBs coupled with the modification of the surface hydrophobicity may be more beneficial for flotation separation.

Keywords: Surface microbubbles; Adhesion; Graphite; Depressurization; Air bubble/oil droplet

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36199
Publ.-Id: 36199


Controllable fabrication of nanofibrillated cellulose supported HKUST-1 hierarchically porous membranes for highly efficient removal of formaldehyde in air

Zicheng, C.; Xiangyang, H.; Jing, G.; Guangyuan, F.; Lanhe, Z.; Parvez, A. M.; Guanhua, W.

Nanofibrillated cellulose (NFC) has presented great potential as supports for functional membrane materials owing to its unique advantages. In this work, NFC-supported MOF hierarchically porous membranes were synthesized by anchoring HKUST-1 (copper 1,3,5-benzenetricarboxylate open-framework) on NFC membrane through a green DMF-free (N,N-Dimethylformamide) method at room temperature and afterward, the as-prepared composite membrane was used to remove formaldehyde from the air. The addition of HKUST-1 particles significantly increased the specific surface area of NFC membrane without affecting the NFC properties. Meanwhile, the nucleation and growth process of HKUST-1 on the NFC membrane could be effectively regulated, which further controlled the morphology of HKUST-1 as well as the anchored position of HKUST-1. When HKUST-1 was anchored on the interior and surface of the membrane, HKUST-1 reduced the compactness of the arrangement between fibers, which resulted in a hierarchical porous structure and then exposed more active adsorption sites of HKUST-1 particles. Thus, the flexible composite membranes exhibited effective formaldehyde adsorption from a low formaldehyde concentration environment (3.0 mg/m3). Under the optimum conditions, the maximum adsorption capacity of the HKUST-1@NFC-1 for formaldehyde reached 378.09 mg/g (based on HKUST-1 wt), which was considerably higher than support-free HKUST-1 powders. Consequently, the present work offers a green and controllable route to prepare NFC-supported MOF composite membranes with highly effective formaldehyde adsorption capacity and thus provides a promising option for NFC application as a flexible adsorbent support.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-36198
Publ.-Id: 36198


Acid-promoted lignin reductive depolymerization under mild conditions via a condensation minimizing approach: From organosolv lignin to woody biomass

Ni, W.; Shuang, Q.; Guanhua, W.; Jing, G.; Wenjie, S.; Hao, S.; Parvez, A. M.; Hongyu, J.; Chuanling, S.

Lignin reductive depolymerization into phenolic monomers is a critical step for the scale-conversion of lignin into liquid fuels but its scale-up is still compromised by harsh reaction conditions (e.g. high temperature and high external H2 pressure) and inevitable condensations. Herein, we present an efficient acid-promoted reductive depolymerization of lignin over Ni/C without external H2 via a condensation minimizing approach using lignin monomer analogue (p-hydroxybenzyl alcohol, HBA) as the capping agent. With addition of 0.4 % H2SO4 and 0.4 mmol/g HBA, 20.42 % of phenolic monomer yield along with 31.70 % oligomer yield was achieved at 160 °C while the condensated/undepolymerized lignin yield was less than 10 %. HBA inhibited the acid-induced condensation by competitive reaction with the nucleophilic C6 in guaiacyl unit. When the approach was applied in lignin-first reductive fractionation of poplar, 32.72 % of phenolic monomer yield and 76.59 % of delignification were achieved at 160 °C in the presence of acid and HBA. Additionally, xylan was dissociated concurrently owing to the acid-catalyzed hydrolysis, resulting in a cellulose-rich solid residue. Consequently, this work proposes an efficient approach for lignin reductive depolymerization and lignin-first biomass fractionation under mild conditions through the synergism of acid and capping agent.

Keywords: Lignin reductive depolymerization; Liquid fuels; Condensation minimizing; Oligomer characterization

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  • Secondary publication expected from 15.04.2024

Permalink: https://www.hzdr.de/publications/Publ-36197
Publ.-Id: 36197


Proton, deuteron and triton flow measurements in Au+Au collisions at √sNN=2.4 GeV

Adamczewski-Musch, J.; Arnold, O.; Behnke, C.; ...; Dreyer, J.; Kämpfer, B.; Kotte, R.; Naumann, L.; HADES Collaboration

High precision measurements of flow coefficients vn (n=1−4) for protons, deuterons and tritons relative to the first-order spectator plane have been performed in Au+Au collisions at √sNN=2.4 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at the SIS18/GSI. Flow coefficients are studied as a function of transverse momentum pt and rapidity ycm over a large region of phase space and for several classes of collision centrality. A clear mass hierarchy is found for the slope of v1, dv1/dy′|y′=0 where y′ is the scaled rapidity, and for v2 at mid-rapidity. Scaling with the number of nucleons is observed for the pt dependence of v2 and v4 at mid-rapidity, which is indicative for nuclear coalescence as the main process responsible for light nuclei formation. v2 is found to scale with the initial eccentricity ⟨ϵ2⟩, while v4 scales with ⟨ϵ2⟩2 and ⟨ϵ4⟩. The multi-differential high-precision data on v1, v2, v3, and v4 provides important constraints on the equation-of-state of compressed baryonic matter.

Permalink: https://www.hzdr.de/publications/Publ-36196
Publ.-Id: 36196


First measurement of massive virtual photon emission from N* baryon resonances

Abou Yassine, R.; Adamczewski-Musch, J.; Arnold, O.; ...; Dreyer, J.; Kämpfer, B.; Kotte, R.; Naumann, L.; HADES Collaboration

First information on the timelike electromagnetic structure of baryons in the second resonance region has been obtained from measurements of invariant mass and angular distributions in the quasi-free reaction π−p→nee at sπ−p−−−−√ = 1.49 GeV with the High Acceptance Di-Electron Spectrometer (HADES) detector at GSI using the pion beam impinging on a CH2 target. We find a total cross section σ(π−p→nee)=2.97±0.07data±0.21acc±0.31Zeffμb. Combined with the Partial Wave Analysis of the concurrently measured two-pion channel, these data sets provide a crucial test of Vector Meson Dominance (VMD) inspired models. The commonly used "strict VMD" approach strongly overestimates the e+e− yield. Instead, approaches based on a VMD amplitude vanishing at small e+e− invariant masses supplemented coherently by a direct photon amplitude provide a better agreement. A good description of the data is also obtained using a calculation of electromagnetic timelike baryon transition form factors in a covariant spectator-quark model, demonstrating the dominance of meson cloud effects. The angular distributions of e+e− pairs demonstrate the contributions of virtual photons with longitudinal polarization, in contrast to real photons. The virtual photon angular dependence supports the dominance of J=3/2, I=1/2 contributions observed in both the γ⋆n and the ππn channels.

Permalink: https://www.hzdr.de/publications/Publ-36195
Publ.-Id: 36195


Machine-learning in warm dense matter theory: Neural-net representation of the local field correction

Dornheim, T.

I give an introduction to the application of deep neural networks for the surrogate modelling of electron--electron correlations in warm dense matter theory.

  • Lecture (others) (Online presentation)
    Forschungsseminar "Vielteilchentheorie - Schwerpunkt machine learning", 10.01.2023, Kiel, Germany

Permalink: https://www.hzdr.de/publications/Publ-36194
Publ.-Id: 36194


New results on light nuclei, hyperons and hypernuclei from HADES

Abou Yassine, R.; Adamczewski-Musch, J.; Asal, C.; ...; Dreyer, J.; Kämpfer, B.; Kotte, R.; Naumann, L.; Hades, Collaboration

In March 2019 the HADES experiment recorded 14 billion Ag+Ag collisions at √sNN = 2.55 GeV as a part of the FAIR phase-0 physics program. In this contribution, we present and investigate our capabilities to reconstruct and analyze weakly decaying strange hadrons and hypernuclei emerging from these collisions. The focus is put on measuring the mean lifetimes of these particles.

Permalink: https://www.hzdr.de/publications/Publ-36193
Publ.-Id: 36193


3D modeling of solute transport through natural fractures with microrough walls in crystalline host rocks: The effects of asperities and surface characteristics on hydrodynamics

Zhou, W.; Fischer, C.

Low-permeability granites are considered as host rocks for nuclear waste repositories. Understanding fluid flow and solute transport in granite fractures are essential in assessing the feasibility and safety of a nuclear waste repository. The internal variability of fractures, such as aperture distribution and asperities, dictates the hydrodynamics of reactive fluid, thus affecting the dispersion and retention of radionuclides. Numerical studies using 2-D models have focused on the heterogeneity of aperture distribution, but the effects of fracture asperities and additional surface features on the evolution of flow paths have not been systematically examined. In this study, the nonreactive solute transport behavior in a single fracture was numerically investigated considering the effects of fracture aperture and surface asperity by comparing 2.5-D and 3-D modeling results on a realistic fracture. The additional motivation here was to identify the limitations of model simplification. The 3-D fracture geometry was extracted from a micro-computed tomography of a natural fracture several centimeters long. Then, 2.5-D models were generated by mapping the aperture distribution of the 2-D fracture geometry on the x-y plane. Flow simulations were performed in both numerical models to detect the respective effects of fracture shape and surface asperities. For validation, we performed a sensitivity analysis by decreasing the 3-D fracture geometry mesh according to the quadric edge-collapse strategy, simulating the solute transport behavior under different fracture surface properties. The size variability of the isometric grid blocks ranges from 6.5 µm to 2.2 mm. Thus, we provide a function that can be used to quantitatively estimate the concentration error due to the simplification of the geometry mesh. The results show which fracture asperities and surface properties can significantly affect the solute transport behavior. Above a certain geometry complexity, the 3-D model results show less retention in the rather stagnant zones and thus better agreement with breakthrough curves (BTCs) of experiments compared to the 2.5-D model approaches. The results of the 3-D models also agree well with previous studies that less pronounced tailing is observed in the case of lower surface roughness. Simplifying the model geometry leads to more distorted results, with the 3-D model being more sensitive than the 2.5-D model. Moreover, based on a function summarized from the BTCs, the error in the simulated concentration due to mesh simplification can be estimated within a certain range that varies with the fracture geometry. The results presented show the capabilities and limitations of using 2.5D models in comparison with more elaborate 3-D models in predicting fluid dispersion in fractured crystalline rocks. Our study can serve as a guideline for the construction of fracture geometry and model design in future reactive transport modeling.

  • Poster
    EGU General Assembly 2023, 23.-28.04.2023, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-36192
Publ.-Id: 36192


Measurement of global polarization of Λ hyperons in few-GeV heavy-ion collisions

Abou Yassine, R.; Adamczewski-Musch, J.; Asal, C.; ...; Dreyer, J.; Kämpfer, B.; Kotte, R.; Naumann, L.; HADES Collaboration

The global polarization of Λ hyperons along the total orbital angular momentum of a relativistic heavy-ion collision is presented based on the high statistics data samples collected in Au+Au collisions at sqr(SNN)=2.4 GeV and Ag+Ag at 2.55 GeV with the High-Acceptance Di-Electron Spectrometer (HADES) at GSI, Darmstadt. This is the first measurement below the strangeness production threshold in nucleon-nucleon collisions. Results are reported as a function of the collision centrality as well as a function of the hyperon's transverse momentum () and rapidity () for the range of centrality 0–40%. We observe a strong centrality dependence of the polarization with an increasing signal towards peripheral collisions. For mid-central (20 – 40%) collisions the polarization magnitudes are (PΛ)(%) = 6.8 ± 1.3 (stat.) ±
2.1 (syst.) for Au+Au and (PΛ)(%) = 6.2 ± 0.4 (stat.) ± 0.6 (syst.) for Ag+Ag, which are the largest values observed so far. This observation thus provides a continuation of the increasing trend previously observed by STAR and contrasts expectations from recent theoretical calculations predicting a maximum in the region of collision energies about 3 GeV. The observed polarization is of a similar magnitude as predicted by 3D-fluid-dynamics and the UrQMD plus thermal vorticity model and significantly above results from the AMPT model.

Permalink: https://www.hzdr.de/publications/Publ-36191
Publ.-Id: 36191


Source-to-sample characterization of laser-driven proton beams for radiobiological applications

Reimold, M.; Assenbaum, S.; Bernert, C.; Beyreuther, E.; Brack, F.-E.; Corvino, A.; Kraft, S.; Kroll, F.; Löser, M.; Pawelke, J.; Püschel, T.; Schlenvoigt, H.-P.; Schneider, M.; Schramm, U.; Umlandt, M. E. P.; Zeil, K.; Ziegler, T.; Metzkes-Ng, J.

Laser-driven plasma accelerators (LPA) are compact sources of ultra-short, intense proton pulses in the multi-10-MeV energy range. These unique parameters predestine LPAs as powerful tools for ultra-high dose rate radiobiology research. The sources’ capabilities were recently demonstrated in the first successful small animal pilot study on radiation-induced tumor growth delay in mice using an LPA proton source [1].
To promote further sophisticated radiobiological studies at LPAs, adapted approaches for primary LPA source characterization, beam monitoring and dosimeters are required. Here, most prominent challenges are LPA-inherent pulse-to-pulse fluctuation in terms of intensity as well as proton energy distribution, the ultra-high pulse dose rate and the harsh plasma environment, featuring a strong electromagnetic pulse (EMP) and an intense mixed radiation background. These conditions call for robust online monitoring solutions.
We present the solutions for source-to-sample characterization implemented at the ALBUS-2S beamline [2] at the Draco Petawatt laser system [3] at Helmholtz-Zentrum Dresden-Rossendorf. These include firstly an online beam monitoring system based on a time-of-flight spectrometer (ToF BMS). A core feature of the ToF BMS method is a precise spectrum-based forward-calculation of the corresponding volumetric dose distribution via Monte-Carlo simulation. Secondly, a dosimetric system for volumetric mm-scale sample irradiations was conceptualized and tested during an in vivo irradiation study, showing a solution for precise dosimetric characterization of ultra-high dose rate pulses at the ~500 mGy pulse dose range.
Lastly, with the OCTOPOD and MiniSCIDOM, two devices for online, single pulse characterization of volumetric dose distributions are presented, applicable for the primary LPA source and mm-scale dose distributions at the sample site, respectively. Both devices are based on volumetric scintillators as active detector material and rely on tomographic reconstruction for signal retrieval.

[1] F. Kroll, et al., Tumour irradiation in mice with a laser-accelerated proton beam, Nat Phys, 18, (2022), 316.
[2] F.-E. Brack, et al., Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline, Sci Rep, 10, (2020), 9118.
[3] U. Schramm, et al., First results with the novel petawatt laser acceleration facility in Dresden, J. Physics: Conf. Ser, 874, (2017), 012028.

  • Lecture (Conference) (Online presentation)
    BLIN5, 12.-14.10.2022, Garching, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36190
Publ.-Id: 36190


Development of a peptides-based approach for metal recovery

Schönberger, N.

Here we demonstrate how a peptide-based material can be obtained for the biosorptive recovery of metals from contaminated industrial wastewater, starting with Phage surface display for the initial identification and optimization of gallium-binding peptides.
Two chromatography-based biopanning methods for the identification of gallium-binding peptides from a commercial phage display library were developed. Five gallium-binding peptide sequences were identified and evaluated to show good gallium-binding properties.
Furthermore, the biosorption of free gallium and arsenic by gallium-binding bacteriophage clones was investigated. A large influence of the pH-value on the respective interactions was demonstrated.
Mutagenesis experiments were also carried out for a bacteriophage clone expressed peptide, in which a cysteine pair systematically replaced amino acids. Biosorption experiments with the resulting seven different bacteriophage mutants suggested a relationship between the rigidity of the peptide structure and the gallium-binding properties.
In isothermal titration experiments, the thermodynamics of the interaction between gallium and the peptides as chemically synthesized derivatives were characterized, independent of the bacteriophage. The peptides differed strongly in their interaction with gallium, and in some cases, the complex formation with gallium depended strongly on the surrounding buffer conditions.
The peptide with the amino acid sequence NYLPHQSSSPSR has particularly promising gallium-binding properties. Computer modeling suggests the probable structure of the peptide in aqueous solution and postulates a possible binding site for gallium.
The side-selective and covalent immobilization of the peptides on a polystyrene matrix led to the creation of a biocomposite for the biosorptive recovery of gallium. The sorption performance and desorbability of the peptide-based biosorption materials were determined in studies with model solutions and real waters from the semiconductor industry.

  • Lecture (others) (Online presentation)
    BioCuInGe Workshop on Waste to Wealth, 25.-26.11.2022, New Delhi, India

Permalink: https://www.hzdr.de/publications/Publ-36189
Publ.-Id: 36189


Laser-plasma based proton accelerators for small animal pre-clinical radiation research

Kroll, F.; Brack, F.-E.; Bernert, C.; Bock, S.; Bodenstein, E.; Brüchner, K.; Cowan, T.; Gaus, L.; Gebhardt, R.; Helbig, U.; Karsch, L.; Kluge, T.; Kraft, S.; Krause, M.; Leßmann, E.; Masood, U.; Meister, S.; Nossula, A.; Pawelke, J.; Pietzsch, J.; Püschel, T.; Reimold, M.; Rehwald, M.; Richter, C.; Schlenvoigt, H.-P.; Schramm, U.; Umlandt, M. E. P.; Ziegler, T.; Zeil, K.; Beyreuther, E.; Metzkes-Ng, J.

Laser-plasma based proton accelerators as a novel accelerator technology have matured to a level at which laboratory-scale setups for the emerging topic of image-guided precision small animal irradiation studies come into reach [Bra2019]. Providing a high proton energy bandwidth [Sch2016] which is filtered in a tunable pulsed magnet beam transport, these accelerators enable flexibility in terms of scattering-free irradiation field formation [Mas2014, Mas2015]. Regarding temporal dose delivery, with single pulse doses reaching the Gy level at unprecedented peak dose rates of up to 1012 Gy/s [Sch2016], laser-plasma based proton accelerator setups can give access to the dose rate regime of FLASH [Fav2014, Voz2019].
The realization of a full-scale setup for image-guided precision radiobiological studies for small animals focusing on dose rate dependent effects is currently prepared at the PENELOPE laser-plasma based proton accelerator at HZDR and will be presented with a focus on the technological requirements and solutions for dose delivery at laser-plasma based sources.
This development relies on our experience in performing dose-controlled radiobiological in vitro studies [Kra2010, Zei2013] and first in vivo irradiation experiments at the DRACO laser-plasma based proton accelerator at HZDR, where we have established a pulsed solenoid beamline for 3D irradiation field formation, yielding a (5 mm)³ homogeneous volumetric dose distribution at a Gy single pulse dose level [8].
[Bra2019] F.-E. Brack, F. Kroll, L. Gaus, C. Bernert, E. Beyreuther, T. E. Cowan, L. Karsch, S. D. Kraft, L. A. Kunz-Schughart, E. Lessmann, J. Metzkes-Ng, L. Obst-Hübl, J. Pawelke, M. Rehwald, H.-P. Schlenvoigt, U. Schramm, M. Sobiella, E. R. Szabó, T. Ziegler, K. Zeil, Spectral and spatial shaping of laser-driven proton beams using a pulsed high-field magnet beamline. arXiv:1910.08430 (2019)
[Sch2016] J. Schreiber, P. Bolton, K. Parodi, “Hands-on” laser-driven ion acceleration: A primer for laser-driven source development and potential applications, Rev. Sci. Instr. 87, 071101 (2016)

  • Lecture (Conference) (Online presentation)
    5th Conference on Smal animal Precision Image-Guided Radiotherapy, 21.-23.03.2022, München, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36188
Publ.-Id: 36188


Liquid metal alloy ion sources for quantum applications

Klingner, N.; Bischoff, L.; Pilz, W.; Mazarov, P.; Hlawacek, G.

Most approaches to implant single or few ions for quantum applications require the use of focused ion beams (FIB). In addition to the detection of ion implantation and laterally precise placement, the first consideration should also be the species as well as the emittance of the ion beam itself. While elements that are gaseous at room temperature can mainly provided by Gas Field Ion Sources or Plasma Ion Sources, most of the metals and semimetals afford the utilization of Liquid Metal Ion Sources (LMIS).

Gallium has established in industry and science as easiest and most stable type of LMIS. For quantum applications other ion species like Li, B, C, N, Al, Si, P, Sb, Bi or the rare earth elements became from higher interest [1-6]. We give an overview about published metal alloys for FIBs and give an insight into the development and production of new sources. Finally, we give an outlook on current and future applications and activities.

[1] L. Bischoff, et al., Micro Eng. 13, 367 (1991), 10.1016/0167-9317(91)90113-R
[2] P. Mazarov, et al., JVST B 27, L47-L49 (2009), 10.1116/1.3253471
[3] L. Bischoff, et al., Appl. Phys. Rev. 3, 021101 (2016), 10.1063/1.4947095
[4] W. Pilz, et al., JVST B 37, 021802 (2019), 10.1116/1.5086271
[5] L. Bischoff, et al., JVST B 38, 042801 (2020), 10.1116/6.0000073
[6] N. Klingner, et al., BJNANO 11, 1742 (2020), 10.3762/bjnano.11.156

Related publications

  • Lecture (Conference)
    RAISIN Workshop 2022, 05.-08.09.2022, London, Großbritanien

Permalink: https://www.hzdr.de/publications/Publ-36187
Publ.-Id: 36187


Focused Ion Beam Modification using Gas and Liquid Metal Alloy Ion Sources

Klingner, N.; Heinig, K.-H.; Tucholski, D.; Möller, W.; Hübner, R.; Bischoff, L.; Pilz, W.; Hlawacek, G.; Facsko, S.

Broad ion beams have shown their wide applications for materials modification. Focused ion beams can be used in a similar way while simultaneously providing process monitoring. Here, we demonstrate this on a new kind of ion-induced structural evolution.

Sub-micrometer Sn spheres were irradiated in a helium ion microscope with a sub-nm beam of 30 keV He ions. Above a fluence of ~10^17/cm², Sn extrusions appeared on the surface of the spheres, which were imaged using the secondary electron signal. Initially, small, pyramid-like faceted extrusions form at the equator of the spheres (north pole pointing to the ion source). Later, each sphere becomes completely covered by the extrusions.

A model was developed that assumes that each He ion generate ~70 Frenkel pairs. The implanted helium atoms, interstitials, and vacancies will be confined by the oxide skin of the spheres. Some He atoms will occupy vacancies, which partially prevent their recombination with interstitials. Furthermore, the ion irradiation leads to erosion and opening of the SnO skin. The interstitials can now escape from the interior of the Sn sphere and form an epitaxial regular Sn lattice on the exterior.

Transmission electron microscopy, Auger electron spectroscopy as well as TRI3DYN [1] and 3D kinetic lattice Monte Carlo [2] simulations support these findings.

In addition, we provide a perspective on focused ion beams from our in-house development and production of liquid metal alloy ion sources, which can be used for applications from self-organized patterning, over altering magnetic or electrical properties, to quantum photonics and computation [3].

[1] Möller, Nucl. Instr. Meth. B 322 (2014) 23
[2] Strobel et al., Phys. Rev. B 64 (2001) 245422
[3] www.hzdr.de/fib

Related publications

  • Poster
    22nd International Conference on Ion Beam Modification of Materials IBMM2022, 10.-15.07.2022, Lisbon, Portugal
  • Poster
    ICMAT 2023, 26.06.2023, Singapore, Singapore

Permalink: https://www.hzdr.de/publications/Publ-36186
Publ.-Id: 36186


Directed evolution biology in resource technology – From the identification of novel inorganic-binding biomolecules to their provision in future resource recovery and recycling processes

Braun, R.; Kießlich, T.; Schönberger, N.; Matys, S.; Lederer, F.; Pollmann, K.

This work focuses on the identification and characterization of inorganic-binding peptidic biomolecules for resource recovery. Manifold biological molecules are used in pharmaceutical and nutrition industries but have so far only limited use in resource technology. Geopolitical tensions, decreasing ore grades combined with increasing demand due to the development of new products and markets result in resource scarcity and the need for new (green) innovative recycling and recovery technologies. Here, we present a novel approach for the design and construction of tailor-made selective target-specific proteinaceous molecules for the creation of innovative bio-based resource recovery applications. Novel peptides with high affinity towards minerals, metals and metalloids such as cobalt, nickel, gallium, arsenic and recently plastics have been identified in our working group using directed evolution phage display technology based on large peptide libraries. Until recently, identification of novel peptides was solely based on ten to hundreds of sequences out of libraries consisting of billions of peptides. As of late, next-generation sequencing (NGS) high throughput analysis of phage display libraries allowed for unprecedented insight into said libraries and accelerated identification of target-specific molecules. Here, we present the NGS-guided phage display-based identification of novel metal- and plastic-binding peptides for surface modification including new findings to the underlying selection process. The characterization of said sequences was successfully achieved in nanomolar ranges with solution- and surface interaction technologies such as isothermal titration calorimetry and quartz crystal microbalance with dissipation monitoring. The here presented results and approaches indicate possibilities for the design and the future provision of innovative bio-based recovery and recycling processes.

Keywords: adsorption; ITC Isothermal Titration Calorimetry; metal recovery; next generation sequencing; peptide; peptide-inorganic interaction; phage display; QCM Quartz Crystal Microbalance

  • Lecture (Conference) (Online presentation)
    24th International Biohydrometallurgy Symposium IBS, 20.-23.11.2022, Perth, Australia

Permalink: https://www.hzdr.de/publications/Publ-36185
Publ.-Id: 36185


A Decade of Electrocatalysis with Metal Aerogels: A Perspective

Li, W.; Weng, B.; Sun, X.; Cai, B.; Hübner, R.; Luo, Y.; Du, R.

Nowadays, great efforts have been spent on addressing concerns over energy and environmental crises. Among these efforts, electrocatalysis is widely recognized and studied for its high efficiency and easy processability. As a class of emerging electrocatalysts, metal aerogels (MAs) stand out in the last decade. In virtue of their three‐dimensional conductive pathways, their library of catalytically/optically active sites, and their robust network structures, MAs have unique advantages in electrocatalysis. However, due to the short history of MAs, there is insufficient research on them, leaving significant room for material design and performance optimization. This perspective will mainly focus on electrocatalysis with MAs, aiming to summarize the state‐of‐the‐art progress and to guide the on‐target design of efficient MAs‐based electrocatalysts towards energy‐ and environment‐related applications.

Related publications

Permalink: https://www.hzdr.de/publications/Publ-36184
Publ.-Id: 36184


GaLIOphore technology for Metal Recovery from Primary and Secondary Resources

Jain, R.

GaLIOphore technology for Metal Recovery from Primary and Secondary Resources

Keywords: GaLIophore; Gallium; Wastewater; IPGP

  • Lecture (others)
    Internal IPGP meeting, 08.07.2022, Paris, France

Permalink: https://www.hzdr.de/publications/Publ-36183
Publ.-Id: 36183


Recovery of critical metals from the low concentrated wastewater and wastes

Jain, R.

Recovery of critical metals from the low concentrated wastewater and wastes

Keywords: Critical metals; GaLIophore; Upscaling; Commercialization

  • Invited lecture (Conferences)
    Securing sustainable treatment for drinking water production and water recycling with focus on anionic contaminants, 20.-22.07.2022, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-36182
Publ.-Id: 36182


Biotechnology for the recovery of germanium, indium and copper from industrial copper dust waste

Jain, R.; Pollmann, K.; Sarvanan, G. V.; Pinka, J.; Ahammad, S. Z.

Biotechnology for the recovery of germanium, indium and copper from industrial copper dust waste

Keywords: Indo-German; IGSTC; Critical metals; Siderophores

  • Lecture (others)
    IGSTC Partners Meet: 14-15 June 2022, 13.-15.06.2022, Frankfurt, Germany

Permalink: https://www.hzdr.de/publications/Publ-36181
Publ.-Id: 36181


Endovascular treatment effects onrecovery of hemodynamics and cognitionin asymptomatic carotid artery stenosis

Kaczmarz, S.; Goettler, J.; Sollmann, N.; Petr, J.; Schmitzer, L.; Kufer, J.; Weiss, K.; Hansen, M.; Mouridsen, K.; Zimmer, C.; Hyder, F.; Preibisch, C.

Background:Internal carotid-artery stenosis (ICAS)accounts for approximately 10–20% of all strokes.1While effective endovascular treatment is available bycarotid artery stenting (CAS) or carotid endarterectomy(CEA), they come with substantial risks.2Those compet-ing risks complicate treatment decisions especially inasymptomatic ICAS and create the need for improvedpostoperative outcome evaluations. Moreover, revascular-ization effects on cognitive impairments are widelyunknown.3Aim:This MRI-study evaluated endovascular treatmentefficacy in asymptomatic ICAS by clinically applicablehemodynamic imaging. We evaluated capillarytransit-time heterogeneity (CTH) and relative cerebralblood volume (rCBV) with additional visual attentiontesting.Method:16 asymptomatic unilateral high-grade ICAS-patients (age 71.4>5.8y) and 17 age-matched healthycontrols (HC,age 70.8>5.3y) underwent MRI on a 3TPhilips Ingenia twice (10.5 months mean follow-up time).White matter lesions (WML) were derived from FLAIR,4CTH and rCBV from dynamic susceptibility contrast5andtheir lateralization compared within grey matter of themiddle cerebral arterial circulation.6Cognitive testingwith inter-hemispheric sensitivity was based on thetheory of visual attention.7Results/Conclusions:Ipsilateral increases of CTH byþ21.4% (p<0.01, Figure 1(a)) and rCBV byþ4.3%(p<0.03, Figure 1(a)) indicate microvascular impair-ments5 and chronic vasodilation8in ICAS at baseline.After endovascular treatment, hemodynamics recoveredby reduced lateralization of 80% (p<0.04, Figure 1(a)) inline with known short-term effects.9,10However, visualattention deficits persisted (Figure 1(b)).10Here, improvedCTH11might counteract with cognitive decline by microemboli,12as postoperative WML increased slightly butnon-significantly (Figure 1(c)). In conclusion, hemodynam-ics recovered after asymptomatic ICAS revascularization,whereas cognitive impairments seem irreversible

  • Contribution to proceedings
    BRAIN & BRAIN PET 2022, the 30th International Symposium on Cerebral Blood Flow, Metabolism and Function, 29.05.-01.06.2022, Glasgow, UK
  • Poster
    BRAIN & BRAIN PET 2022, the 30th International Symposium on Cerebral Blood Flow, Metabolism and Function, 29.05.-01.06.2022, Glasgow, UK

Permalink: https://www.hzdr.de/publications/Publ-36180
Publ.-Id: 36180


Functionality of a co-culture kidney model: testing the renal barrier with [18F]fluorodeoxyglucose

Sihver, W.; Nitt-Weber, A.-K.; Behrens, S.; Ullrich, M.; Pietzsch, H.-J.; Sonntag, F.; Namazian Jam, N.; Schmieder, F.

Introduction:

When administering radiopharmaceuticals, the kidney is one of the dose-limiting organs [1]. Micro-physiological systems (MPS) for the in vitro evaluation of new potential radiopharmaceutical candidates should therefore be equipped with a functional kidney equivalent [2]. Hence the proximal tubule is responsible for most toxic interactions we generated a model of this part using a co-culture of human renal proximal tubule epithelial cells (RPTEC) and human umbilical vein endothelial cells (HUVEC) [3]. The functionality of the renal barrier was characterized by measuring transepithelial/transendothelial electrical resistance (TEER) and permeation of [18F]fluorodeoxyglucose (FDG).
Methods:
Investigations were performed in 24-well plates equipped with transwell inserts with a permeable membrane (pore size 0.4 µm). Viability and density of the cellular bilayer were measured using calcein staining. Apical and basolateral sites of the membrane were populated with RPTEC and HUVEC, respectively (each site 8x104 cells). Ionic conductance in the cell layers was measured using TEER. Basolateral-apical passage of [18F]FDG (produced in-house; 4 MBq/mL, equivalent to about 5 nmol/mL) through the cellular bilayer was measured using a gamma counter and expressed as percent passage.
Results:
In the proximal renal tubule model, calcein staining showed that the cellular bilayer reached confluence after 3 to 4 days. At this time point, the barrier showed a higher electrical resistance of 533 ± 47 Ω*cm2 across the cellular bilayer compared to 306 ± 26 Ω*cm2 across transwell blanks. Consistent with these results, [18F]FDG showed only 4 ± 1 % basolateral-apical passage through the intact cellular bilayer compared to 13.5 ± 1.5 % across transwell blanks. Morphological, electrical, and functional readouts therefore confirmed the integrity of the renal barrier in this model.
Conclusions:
This study demonstrates that measurement of [18F]FDG passage provides a functional test of the renal barrier in a proximal renal tubule model of the kidney. While the TEER value reflects the ionic conductance of the paracellular pathway in the epithelial layer, the flux of nonelectrolyte tracers such as [18F]FDG indicates the paracellular water flux as well as the pore size of the tight junctions [4]. In the next steps, apical-basolateral [18F]FDG transport will be investigated to functionally characterize reabsorption via sodium/glucose cotransporter 2 (SGLT2), which is mainly found in the proximal part of the renal tubule [5]. After characterization of the proximal renal tubule model in the static system, this kidney equivalent will be integrated into the fluidics system of a multicompartment MPS chip that also contains a liver equivalent and a tumor spheroid for use in radiopharmacological assays. With kidney and liver organoids first evidence for uptake, metabolism and excretion of a radioligand will be investigated.

Acknowledgements:
The authors like to express great appreciation for the financial support from the German Federal Ministry of Education and Research (BMBF) (Funding number 161L0275A/B).
References:
[1] Klaus et al., Radiat Oncol 2021, 16, 43. [2] Sihver et al., Curr Dir Biomed Eng 2022, 8, 532. [3] Schmieder et al., Curr Dir Biomed Eng 2019, 5, 1. [4] Srinivasan et al., J Lab Autom 2015, 20, 107. [5] Weber et al., Kidney Int 2016, 90, 627.

Keywords: micro physiological systems; co-culture kidney model; [18F]fluorodeoxyglucose; reduction experimental animals; preclinical trials

  • Open Access Logo Abstract in refereed journal
    Nuclear Medicine and Biology 126-127S(2023), S277

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Publ.-Id: 36179


Radiopharmacological comparison of an Al18F- and 68Ga-labeled somatostatin agonist and antagonist in 2D and 3D models of BON-SSTR2 cells

Sihver, W.; Liske, N.; Nitt-Weber, A.-K.; Wodtke, R.; Brandt, F.; Walther, M.; Kopka, K.; Pietzsch, H.-J.

Introduction:

Due to the upregulation of somatostatin receptor subtype-2 (SSTR2) in neuroendocrine tumors, radiolabeled somatostatin analogs have been successfully used so far for diagnostic investigations and peptide receptor radionuclide therapy [1]. In the present work, both the somatostatin agonist (Tyr3)octreotate (TATE) and the somatostatin antagonist JR11 were conjugated with a cyclohexanediaminetriazole (CHDT) chelator for the potential labeling with Al18F, 68Ga or 111In. The radiopharmacological behavior of Al18F and 68Ga labeled CHDT-TATE and CHDT-JR11 were studied in BON-SSTR2 cells [2] in both monolayer (ML) and spheroid (SP) culture. The binding data were determined in static cell culture to have a basis for further assays using a microphysiological system (MPS) with dynamic properties [3].
Methods:
Spheroids of BON-SSTR2 cells were created according to a protocol by the vendor (Greiner Bio-One GmbH, Germany). Freshly harvested cells were incubated with magnetic nanoparticles in RPMI medium overnight. After loading, the cells were distributed in a 24-well-plate (3 x 10-4 cells/well) and placed on a plate with corresponding 24-point magnets in order to form SPs in the incubator for up to 5 days [4].
18F-labeling was performed with Al[18F]F2+ (TR-FLEX Cyclotron, Canada) and 68Ga-labeling with [68Ga]GaCl3 (68Ge/68Ga generator, iThemba Labs, South Africa) under mild conditions (20 min at 40°C). After incubation with the radiolabeled ligands the cells were washed; for internalization purpose the cells were treated with acidic glycine buffer (pH 3.0) to remove the bound molecules from the outer cellular membrane [5]. These samples correspond to the ligand-bound fraction and are measured in a gamma counter alongside the samples with the internalized ligand molecules.
Results:
Saturation binding analysis of Al18F-labeled CHDT-TATE and CHDT-JR11 revealed very good binding affinities with similar Kd-values toward ML (Al[18F]F-CHDT-TATE 12.4 ± 2.1 nM, Al[18F]F-CHDT-JR11 11.4 ± 0.3 nM) and for SPs (Al[18F]-CHDT-TATE 30 ± 6.6 nM, Al18F-CHDT-JR11 56 ± 20 nM). In contrast, [68Ga]Ga-CHDT-TATE had better binding affinities toward ML and SPs compared to [68Ga]Ga-CHDT-JR11 ([68Ga]Ga-CHDT-TATE ML 4.3 ± 0.5 nM, SPs 19 ± 2.2 nM; [68Ga]Ga-CHDT-JR11 ML 25.3 ± 13.9 nM, SPs 118 ± 38 nM). The maximal binding capacity (Bmax) was about 25-times higher for radiolabeled CHDT-JR11 (average 5.8 ± 0.3 pmol/mg) than for CHDT-TATE (average 0.23 ± 0.08 pmol/mg) both for ML and SPs.
The internalization assays showed that radiolabeled CHDT-TATE internalized about 4-times stronger than radiolabeled CHDT-JR11 based on percent of administered dose per µg of protein both for ML and for SPs (radiolabeled CHDT-TATE 0.22 ± 0.03 %AD/µg protein, radiolabeled CHDT-JR11 0.06 ± 0.02 %AD/µg protein).
Conclusions:
Both the agonist conjugate CHDT-TATE and the antagonist conjugate CHDT-JR11 were successfully labeled with Al18F and with 68Ga and assayed with SSTR2-expressing BON-SSTR2 cells in monolayer and spheroid form. The 25-times higher Bmax values of the radiolabeled antagonist appear advantageously regarding a potential theranostic application. Despite the fact that the SSTR2 antagonist only weakly internalizes in the cells the antagonists show effective treatment in clinical studies [6]. The next step is to compare the results with assays in dynamic MPS chips.
Acknowledgements:
The authors like to express great appreciation for the financial support from the LifeScience-Stiftung (Funding code: HZDR 2021.01).
The SSTR2 expressing BON-SSTR2 cells were kindly given by Dr. Grötzinger, University Hospital Charité Berlin.
References:
[1] Eychenne et al., Molecules 2020, 25, 4012. [2] Exner et al., Front Endocrinol 2018, 9, 146. [3] Busek et al., J Sens Sens Syst 2016, 5, 228. [4] Noel et al., J Vis Exp 2017, 126, e56081. [5] Matzku et al., Cancer Res 1986, 46, 3848. [6] Borgna et al., Eur J Nucl Med Mol Imaging 2022, 49, 1113.

Keywords: SSTR2; Antagonist JR11; Agonist TATE; cyclohexanediaminetriazole chelator; 18F

  • Open Access Logo Abstract in refereed journal
    Nuclear Medicine and Biology 126-127S(2023), 108602

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Publ.-Id: 36178


A Low-Level Abstraction of Memory Access

Gruber, B. M.

Choosing the best memory layout for each hardware architecture is
increasingly important as more and more programs become memory
bound. Memory related optimizations typically depend on full control
over data layout. Thus, for portable codes that run across
heterogeneous hardware architectures, such a data layout is ideally
decoupled from the rest of a program.

The low-level abstraction of memory access (LLAMA) is a C++ library
that provides a zero-runtime-overhead abstraction layer, underneath
which memory layouts can be freely exchanged, focusing on
multidimensional arrays of nested, structured data. It provides a
framework for defining and switching custom memory mappings at compile
time to define data layouts, data access and access instrumentation,
making LLAMA an ideal tool to tackle memory-related optimization
challenges in heterogeneous computing.

  • Invited lecture (Conferences)
    ZIH Doktorandenklausur, 25.-26.11.2022, Tharandt, Germany

Permalink: https://www.hzdr.de/publications/Publ-36176
Publ.-Id: 36176


5th HEP C++ Course and Hands-on Training - Advanced C++

Ponce, S.; Hageböck, S.; Gruber, B. M.

The lecture sessions contain the following topics

Core Modern C++ (Move semantics, copy elision, advanced STL, ...)
Expert C++ (variadic templates, perfect forwarding, concepts, ...)
Tools (valgrind, static code analysis, profiling, ...)
Concurrency (threads, mutexes, atomic types, ...)
... more C++'20 features (modules, ranges, ...)

  • Open Access Logo Lecture (others)
    5th HEP C++ Course and Hands-on Training - Advanced C++, 11.-13.10.2022, CERN, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-36175
Publ.-Id: 36175


4th HEP C++ Course and Hands-on Training - The Essentials

Ponce, S.; Hageböck, S.; Gruber, B. M.

Welcome to the fourth iteration of a C++ course for the high energy physics community organised in collaboration between the Software Institute for Data Intensive Sciences and the Training Working Group of the HEP Software Foundation.

  • Open Access Logo Lecture (others)
    4th HEP C++ Course and Hands-on Training - The Essentials, 15.-17.03.2022, CERN, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-36174
Publ.-Id: 36174


Integrated Hyperspectral and Raman sensors for fast characterization of plastics in e-waste recycling streams

de Lima Ribeiro, A.

In this talk, I presented the main findings from the project RAMSES-4-CE regarding polymer characterisation using different sensors. This activity was part of the HZDR innovation tour 2022.

  • Lecture (others)
    HZDR Innovation Tour, 13.10.2022, Freiberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-36173
Publ.-Id: 36173


Experimental study of Relativistic High Harmonic Generation with a PW level short pulse laser system

Vescovi Pinochet, M. A.; Umlandt, M. E. P.; Assenbaum, S.; Meric, T.; Kroll, F.; Rehwald, M.; Stefanikova, R.; Püschel, T.; Prencipe, I.; Kraft, S.; Zeil, K.; Schramm, U.

Surface High harmonic generation (SHHG) arising from the interaction of high and ultra-
high intensity lasers with solid density targets has been extensively studied during recent
years. Besides being a promising source for applications on ultrafast science, the
sensitivity of SHHG mechanisms with respect to changes of pump laser parameters or
target pre-plasma conditions makes the harmonic spectrum a useful diagnostic to gain
insight into the interaction between the laser and the target front surface where, in case of
a solid density target, most of the energy absorption between laser and target takes place.
In the present work, the first measurements of high harmonic spectra on the Draco PW
laser system at HZDR are presented. Most measurements were done using a single
plasma mirror system, achieving a contrast of 10-7 at -1ps for a 5.4x1021W/cm2, 30fs
800nm pulse. XUV spectra were measured for a wide range of different target materials
(plastic, metal, glass), thicknesses; from bulk SiO2 substrates to few tens of nm foils where
relativistic transparency starts to occur; as well as different laser energies (a0~7-50). The
spectral range of the spectrometer (53nm to ~17nm, 15th to 47th harmonic, limited by the
filtering) allowed us to measure changes in SHHG along the spectrum for different
interaction conditions. These measurements were carried in parallel with proton
acceleration experiments, aiming at using the harmonic generation as a gauge for the
laser-plasma interaction at different interaction regimes, and to our knowledge constitute
one of the first measurements of relativistic surface harmonics with a PW short pulse laser.

Keywords: High Harmonic Generation; Laser Proton acceleration; High Power Laser

  • Lecture (Conference)
    Conference on High Intensity Lasers and attosecond science, 05.12.2022, Tel Aviv, Israel

Permalink: https://www.hzdr.de/publications/Publ-36172
Publ.-Id: 36172


Personnel Scheduling and Testing Strategy during Pandemics: The case of COVID-19

Davoodi Monfared, M.; Senapati, A.; Batista, A.; Calabrese, J.

Efficient personnel scheduling plays a significant role in matching workload demand in organizations. However, staff scheduling is sometimes affected by unexpected events, such as the COVID-19 pandemic, that disrupt regular operations. Since infectious diseases like COVID-19 transmit mainly through close contact with individuals, an efficient way to prevent the spread is by limiting the number of on-site employees in the workplace along with regular testing. Thus, determining an optimal scheduling and testing strategy that meets the organization's goals and prevents the spread of the virus is crucial during disease outbreaks.
In this paper, we formulate these challenges in the framework of two Mixed Integer Non-linear Programming (MINLP) models. The first model aims to derive optimal staff occupancy and testing strategies to minimize the risk of infection among employees, while the second model aims at only optimal staff occupancy under a random testing strategy. To solve the problems expressed in the models, we propose a canonical genetic algorithm as well as two commercial solvers. Using both real and synthetic contact networks of employees, our results show that following the recommended occupancy and testing strategy reduces the risk of infection 25\%--60\% under different scenarios.

Keywords: Personnel scheduling; presence strategy; testing strategy; pandemic; optimization

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Publ.-Id: 36171


Pump-probe XUV platform for ultrafast laser-matter interaction research

Vescovi Pinochet, M. A.; Umlandt, M. E. P.; Zeil, K.; Schramm, U.

Interaction of ultrafast relativistic intensity laser pulses with matter has shown to be a promising field for the study of matter at extreme conditions, electromagnetic fields generation/amplification, high energy radiation emission and particle acceleration. For most of the aforementioned applications, advanced proposed schemes require stringent tailoring and monitoring of the target/plasma parameters during the interaction. The short (fs) temporal and small (sub-micron) spatial scales of the evolution of these parameters make direct measurements a challening task, even more considering that these plasmas are usually overdense for conventional optical diagnostics.

Currently, a pump-probe set up is being developed at HZDR to gain insight into the internal evolution of overdense laser driven plasmas. The XUV beam generated by one of the arms of the Draco laser, through Relativistic Oscillating Mirror High Harmonic Generation, will be used to probe a plasma driven by a second arm of the laser system. The initial set up for these experiments will be shown and probing options of the platform will be discussed.

Keywords: High Harmonic Generation; High Power Lasers

  • Lecture (Conference) (Online presentation)
    DPG-Frühjahrstagung 2022, 28.3.2022, Mainz, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36170
Publ.-Id: 36170


Assessing the binding affinity of a 64Cu-labeled PSMA ligand in a micro physiological system

Sihver, W.; Nitt-Weber, A.-K.; Behrens, S.; Schmieder, F.; Reissig, F.; Walther, M.; Ullrich, M.; Pietzsch, H.-J.; Sonntag, F.

Introduction:

Radiolabeled prostate-specific membrane antigen (PSMA) ligands have been successfully developed in recent years for diagnosis and therapy of prostate cancer [1]. A potential new PSMA radioligand would, after in vitro characterization, normally be further evaluated in small animals. However, the use of micro-physiological systems (MPS), an organ-on-chip technology in which human cell spheroids and organoids are treated in a circuit under defined conditions [2,3], should lead to a reduction of animal experiments.
In the present study, experiments with the novel 64Cu-labeled PSMA antagonist FR52 were performed using 2D or 3D cultures of LNCaP cells in MPS chips. Our aim was to determine binding parameters (Kd, Bmax) in the MPS chip and to compare them with the results of assays in well plates (WP).
Methods:
Derived from the compound PSMA-617 [4], instead of DOTA a cyclohexanediamine-triazole (CHDT) chelator was conjugated, resulting in the conjugate FR52 (in-house synthesis). FR52 was radiolabeled with 64Cu (molar activity: 14.2 ± 2.2 MBq/nmol).
For the assays, 5 x 104 LNCaP cells were placed in 3 wells of an MPS module (à 0.2 cm2), either as monolayer or as spheroids and cultured for 2 to 7 days. The MPS chips include an integrated micropump, driven by a controller, that generates a pulsatile flow of media that runs through the capillaries and keeps the cells alive [5] (Fig. 1).
After blocking of adjacent cell samples (PSMA pharmacophore 0.8 mM; 30 min) [64Cu]Cu-FR52 (6 to 200 nM) was added to all samples and pumped through the MPS for 10 min (volume: 0.1 mL/well; 80 bpm; volume flow 6.4 µL/s). After PBS washing and exposing the MPS chips to an imaging plate, the cells were lysed and in vials measured in a gamma counter. Evaluation was processed with the analysis program GraphPad Prism.
Results:
Saturation assays with [64Cu]Cu-FR52 in MPS revealed similar high binding affinities (Kd) for LNCaP monolayer and spheroids (MPS-monolayer Kd: 33 ± 6 nM; MPS-spheroids Kd: 36 ± 8 nM). Also the binding capacities (Bmax) were in the same range (MPS-monolayer Bmax: 0.57 ± 0.04 pmol/mg; MPS-spheroids Bmax: 0.35 ± 0.03 pmol/mg). The binding affinity to LNCaP spheroids in WP was similar to that in MPS, but the binding capacity was slightly lower than in the chip experiments (WP-spheroids Kd: 59 ± 6 nM; WP-spheroids Bmax: 0.22 ± 0.01 pmol/mg). LNCaP monolayer treatment in WP was performed in previous experiments with 18F, 68Ga or 111In labeled FR52. Those Kd values were slightly lower (WP-monolayer Kd: 18 ± 2 nM) and the Bmax values were slightly higher (WP-monolayer Bmax: 0.7 to 3.5 pmol/mg).
Conclusions:
The successful evaluation of the binding parameters of the 64Cu-labeled PSMA antagonist FR52 using MPS is a promising step to foster the reduction of animal experiments in preclinical evaluation. Moreover [64Cu]Cu-FR52 seems to be a promising candidate. Nevertheless, further experiments with kidney and liver organoids in MPS should investigate first evidence for uptake, metabolism and excretion of [64Cu]Cu-FR52.
Acknowledgements:
The authors like to express great appreciation for the financial support from the German Federal Ministry of Education and Research (BMBF) (Funding number 161L0275A/B).
References:
[1] Neels et al., Cancers 2021, 13, 6255 [2] Busek et al., J Sens Sens Syst 2016, 5, 228. [3] Schmieder et al., Proc SPIE 2020, 11268, 1126804_1. [4] Benešová et al., J Nucl Med 2015, 56, 914. [5] Sihver et al., Curr Dir Biomed Eng 2022, 8, 532.

Keywords: radiopharmaceuticals; micro physiological systems; radiopharmacological parameters; preclinical trials; reduction experimental animals

  • Open Access Logo Abstract in refereed journal
    Nuclear Medicine and Biology 127-127S(2023), S24-S25

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Publ.-Id: 36169


Characterisation of a cyclohexanediamine-triazole-PSMA conjugate on spheroids of prostate cancer cells

Sihver, W.; Saager, M.; Walther, M.; Wodtke, R.; Reissig, F.; Mamat, C.; Kopka, K.; Pietzsch, J.; Pietzsch, H.-J.

Aim/Introduction: A recently developed cyclohexanediaminetriazole- chelator enabling 18F-labelling using the Al[18F]F approach was conjugated via copper-catalysed azide-alkyne cycloaddition to the PSMA-binding motif glutamate-urea-lysine connected with 1-naphthyl-D-alanine[1] (ligand L). In the present study radiolabelled L will be characterized on PSMA-positive prostate cancerspheroids. Three-dimensional cell models offer structure and functional properties closer to in vivo conditions than two-dimensional cell culture models. Spheroids show altered cell-cell and cell-extracellular matrix interactions and are useful for better understanding the nature of tumours concerning drug uptake, toxicity, hypoxia, tissue growth and therapeutic effects. The aim of this study was to investigate the radiopharmacological potential of 18F- and 68Ga-labelled L using LNCaP-spheroids regarding binding properties and internalisation behaviour. The results will be compared with data obtained from LNCaP-monolayer cell culture.
Materials and Methods: Spheroids of LNCaP and PC3 (PSMA-negative) cells were created according to a protocol by the vendor. Freshly harvested cells were incubated with magnetic nanoparticles overnight. After loading, the cells were distributed in a 24-well-plate (10-4 cells/well), covered with a lid equipped with 24 small magnet devices for 5 days and kept in an incubator so that the cells could form spheroids [2]. After incubation with radiolabelled ligand (RCY >95%) the spheroids were washed, exposed to a phosphor imaging plate and the data analysed. Internalisation experiments were carried out by the “acid wash” method.
Results: The method of creating spheroids by magnetised prostate cancer cell lines and treating them with a magnet device was applied successfully and resulted in spheroids with a diameter size of about 500 μm. The evaluation of first saturation experiments with LNCaP spheroids provided preliminary affinity data with Kd values in the range of 30 to 40 nM. These results are comparable to that of monolayer cell homogenate. Internalisation experiments with LNCaP-spheroids are ongoing.
Conclusion: The novel radiolabelled PSMA-ligand L can be radiopharmacologically characterised on prostate cancer cell homogenate but also spheroids. The establishing of three-dimensional cell aggregates by magnetised cells and, moreover, the investigation of new radiolabelled conjugates for potential PET/SPECT application or even therapeutic treatment of cancer entities using spheroids is a valuable and promising method. Next, it is planned to use the LNCaP-spheroids for evaluation of PSMA-radioligands in a proof-of-conceptstudy applying the technology of Micro-Physiological Systems (multiorgan-chips) [3].
References: [1] Sihver, Eur. J. Nucl. Med. Mol. Imaging 2019, 26 (Suppl 1), S132. [2] Turker, ACS Biomater. Sci. Eng. 2018, 4, 787. [3] Maschmeyer, Lab Chip 2015, 15, 2688.

Keywords: PSMA-conjugate; cyclohexanediamine-triazole chelator; 18F; 68Ga

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Publ.-Id: 36168


Tailored Particle Catalysts for Multistep One-pot Chemoenzymatic Cascade in Pickering Emulsions

Wang, S.; Scandurra, L.; Hübner, R.; Gro Nielsen, U.; Wu, C.

Chemoenzymatic cascades are an important tool for advanced synthesis in chemistry. However, these cascades are often limited due to the incompatibility issue between two distinct catalysts and reactions. To address this issue, we present a simple multistep one-pot platform, in which nanoparticle catalysts are prepared to allow chemo- and biocatalytic reactions performed sequentially in water and Pickering emulsions. The preparation of particle catalysts is accomplished in just two steps by polymer modifications and [RuCl2(pcymene)]2 coordination, while the benefits of using them for chemoenzymatic synthesis are multifaceted. They act not only as asymmetric catalysts for asymmetric transfer hydrogenation from acetophenone to 1-phenylethanol in water with up to 99 % conversion and 93 % ee, but also as an emulsifier to form stable Pickering emulsions. By the addition of Candida antarctica lipase B into the emulsions, the second-step reaction of enantioselective acylation was achieved with 38 % conversion and 99 % ee. Therefore, we successfully present a simple method to enable chemoenzymatic cascades by combining particle catalysts and enzymes in water and Pickering emulsions in a sequential fashion, which can be generalized for other cascade syntheses with different chemo- and biocatalysts in the future.

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Permalink: https://www.hzdr.de/publications/Publ-36167
Publ.-Id: 36167


U(VI)- und Eu(III)-Immobilisierung durch Pilzmyzel

Günther, A.; Wollenberg, A.; Vogel, M.; Drobot, B.; Steudtner, R.; Hübner, R.; Stumpf, T.; Raff, J.

Actinide und Lanthanide spielen eine wichtige Rolle bei vielen industriellen Anwendungen und können durch den Abbau, die Nutzung und Entsorgung in die Umwelt gelangen. Genaue Kenntnisse über das komplexe Verhalten und die Wechselwirkung dieser Metalle mit der Biosphäre, z. B. mit Bakterien, Pilzen und Pflanzen sind notwendig, um ein mögliches Gefährdungspotential für den Menschen abschätzen und entsprechende Schutzmaßnahmen ergreifen zu können. Darüber hinaus ermöglicht dieses Wissen die Entwicklung biologischer Verfahren zur Entfernung radioaktiver und toxischer Metalle und Schadstoffe aus Abwässern und kontaminierten Böden. Nach den Unfällen in Tschernobyl und Fukushima ist deutlich geworden, dass insbesondere Pilze große Mengen an Radionukliden und Schwermetallen aufnehmen und anreichern können, allerdings sind die zugrundeliegenden Prozesse noch nicht gut verstanden.
Ziel dieser Studie war es die Wechselwirkungen von Myzel ausgewählter holz- und bodenbewohnender Pilze mit Uran und Europium als Analogon für die dreiwertigen Actinide Americium und Curium zu untersuchen. Neben der Bestimmung der Metall-komplexe in den Sorptionslösungen wurden die gebildeten Metall-Pilzspezies mittels Rastertransmissionselektronenmikroskopie gekoppelt mit energiedispersiver Röntgen-mikroanalyse, zeitaufgelöster laser-induzierter Fluoreszenzspektroskopie und chemischer Mikroskopie charakterisiert. Schizophyllum commune zeigte signifikant höhere Metall-Bindungskapazitäten im Vergleich zu den anderen holzbewohnenden Pilzen Pleurotus ostreatus und Lentinus tigrinus sowie zu dem bodenbewohnenden Pilz Leucoagaricus naucinus. Die Metalle werden insbesondere an der Zelloberfläche, in den Zellmembranen und Membranen verschiedener Organellen, aber teilweise auch im Zytoplasma gebunden. Die spektroskopischen Untersuchungen des metallbelasteten Pilzmyzels haben gezeigt, dass Phosphatgruppen verschiedener Biomoleküle neben den Carboxylgruppen eine große Rolle bei der Immobilisierung des Urans und des Europiums durch Pilze spielen.

Keywords: Pilz; Europium; Speziation; TEM; Chemische Mikroskopie; TRLFS

Related publications

  • Lecture (Conference)
    Jahrestagung Nuklearchemie, 04.-06.10.2022, Bergisch Gladbach, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36166
Publ.-Id: 36166


Comparison of a radiolabeled somatostatin agonist with an antagonist using the SSTR2 expressing cell line BON-1S in 2D and 3D models

Sihver, W.; Liske, N.; Wodtke, R.; Brandt, F.; Walther, M.; Bachmann, M.; Kopka, K.; Pietzsch, H.-J.

Objective: The somatostatin receptor subtype 2 (SSTR2) is a suitable target for the diagnosis and therapy of neuroendocrine tumors using radiolabeled ligands [1]. BON-1S cells have been described to express SSTR2 receptors in vitro [2]. We therefore established 2D and 3D cell culture systems of BON-1S cells. For SSTR2 ligand binding, BON-1S cells cultured as monolayer or spheroids were incubated with an SSTR2 agonist (NODAGA-TATE) or an SSTR2 antagonist (NODAGA-JR11). Both were labeled with either 68Ga- or 64Cu and their respective binding and uptake were determined. Understanding the binding data is a prerequisite for using spheroids of BON-1S cells in a
Micro Physiological System (MPS) [3].
Methods: Spheroids of SSTR2 containing BON-1S cells were created as follows: Freshly harvested cells were incubated with magnetic nanoparticles in RPMI medium overnight. After magnetic particle uptake, cells were split into a 24-well-plate (1.5 x 10-4 cells/well). In an incubator, the magnetic particles were moved via a magnetic drive for five days, to allow the formation of spheroids [4]. After incubation with the 68Ga- or 64Cu-labeled radioligands (RCY>95%), the BON-1S cells, either as monolayer or as spheroids, were washed and treated with acidic glycine buffer (pH 3.0) to remove the bound but not yet internalized molecules from the outer cellular membrane.
After this washing step, the remaining radioligand molecules are assumed to represent internalized molecules [5]. In the monolayer,
internalization was determined after 10 minutes, 1 hour and 3 hours after addition of the radioligand to the respective culture.
Results: Saturation analysis of radiolabeled NODAGA-TATE as well as NODAGA-JR11 on BON-S1 monolayer yielded similar Kd values in the low nanomolar range (2.3 to 8.6 nM). Affinity of the respective radiolabeled ligand was much lower on BON-1S spheroids, with Kd values around 30 nM for both 64Cu-labeled ligands and almost 60 nM for the 68Ga-labeled ligands. The maximal binding capacity (Bmax) was higher on monolayers and spheroids for radiolabeled JR11 (NODAGA-TATE: monolayer 0.3 pmol/mg, spheroids 0.8 pmol/mg; NODAGA-JR11: monolayer and spheroids 1.2 pmol/mg). The internalization assay showed a ratio of internalized to surface bound radiolabeled NODAGA-TATE of about 80% to 20% for both forms of cell culture, for radiolabeled JR11 a ratio of 8% to 92% was determined, each after a 60 min-incubation time. The internalization after the three time points was ca. 10 times lower in case of radiolabeled JR11 (0.25% (TATE) versus maximal 0.03% (JR11) of administered activity amount/µg protein).
Conclusions: Using monolayer or spheroids of BON-1S cells (the latter were generated by the iron nanoparticle method) we could
estimate reliable and reproducible binding parameters for a radiolabeled agonist and antagonist of SSTR2. There are obvious differences in binding affinities of the examined radiolabeled conjugates in monolayer cell culture compared to the spheroids.
Acknowledgements: The SSTR2 expressing BON-1S cells were kindly given by Prof. Dr. Wiedenmann, University Hospital Charité
Berlin.
References:
[1] Eychenne, Molecules 2020, 25, 4012.
[2] Exner, Front Endocrinol 2018, 9, 146.
[3] Busek, J Sens Sens Syst 2016, 5, 228.
[4] Noel, J Vis Exp 2017, 126, e56081.
[5] Matzku, Cancer Res 1986, 46, 3848.

Keywords: SSTR2; NODAGA-JR11; NODAGA-TATE; 68Ga; 64Cu; in vitro; Spheroids

  • Abstract in refereed journal
    Nuclear Medicine and Biology 108-109(2022)Suppl. 1, P-300
    ISSN: 0969-8051

Permalink: https://www.hzdr.de/publications/Publ-36164
Publ.-Id: 36164


Integrated hyperspectral and Raman sensors for fast characterization of plastics in e-waste recycling streams

de Lima Ribeiro, A.; Fuchs, M.; Lorenz, S.; Madriz Diaz, Y. C.; Herrmann, E.; Gloaguen, R.

Electronic waste (e-waste) is a fast-growing and complex material stream, and its adequate management requires robust identification tools. Plastics are major components of e-waste (~25% of its total) and polymer compositions vary depending on its initial function in the electronic device, including the presence of additives to compensate for function loss and polymer blends (e.g ABS/PS). Recycling of these increasingly complex e-waste polymers calls for innovative, fast, and spatially-resolved identification tools compatible with conveyor belt operations.
We propose fast identification of polymers in e-waste using hyperspectral imagery (HSI) and Raman spectroscopy. We evaluated the potential of such methods for resolving diagnostic spectral features (fingerprints) in 23 polymer types, including black plastics, and determined the minimum acquisition requirements for robust identification of polymers considering the recycling industry demands. We employed short-wave infrared (SWIR-HSI, SPECIM AisaFENIX
We identified fingerprints for each material based on previous literature reports: a positive identification was assigned for fingerprints with signal-to-noise-ratios > 4 (hull-corrected reflectance - HSI) or > 3 (Raman). We identified 60% of the transparent and light-colored plastic types using SWIR-HSI, and two out of five black plastic types using MWIR-HSI information. In total, HSI-reflectance methods were suitable for characterization of 16 plastic types (70%), acquiring simultaneous spectral and spatial information at fast rates. Still, the need for characterizing black plastics was not fully met using HSI-reflectance sensors.
We propose to employ point Raman spectroscopy as the ultimate tool for polymer identification and evaluated its potential for integration with HSI data. We performed short-time point Raman measurements (≤ 2 seconds), investigating if the method is compatible with the fast-paced data acquisition rates required by the recycling industry. We identified fingerprints for all polymers using signals from short-time point Raman measurements (transparent plastics: 0.5 seconds, black plastics: 1 second).
We elaborated sensor-specific libraries for each plastic type for future cross-validation and correlation in automated polymer detection during recycling operations (dictionary learning). This reference data represents maps which capture the spectral variability within the reference materials as a training dataset. To evaluate the added value of the spatial variability recorded by HSI sensors, we showcase the application of our spectral library for polymer identification and mapping in artificially mixed samples of plastic debris.
Our RAMSES network, a project financed by the EU via the KIC Raw Materials, develops the tools for combining different sensor types: HSI-reflectance sensors and RGB cameras at the beginning of the line record information needed to determine representative spectral domains. This signal is then used, along with the polymer’s spectral library, to identify transparent and light-colored plastics. The spatial and spectral domain information are used to direct Raman point acquisitions for identification of black plastics and polymer blends. This intertwined multi- sensor network relies on fast data acquisition and processing supported by spectral libraries and machine learning algorithms targeting object detection and spectral data fusion. This investigation contributes to enabling highly accurate identification of polymers, specifying the conditions for rapid smart multi-sensor data acquisition and processing.

Keywords: WEEE; polymers

  • Contribution to proceedings
    Workshop on hyperspectral images and signal processing, 13.-16.09.2022, Rome, Italy

Permalink: https://www.hzdr.de/publications/Publ-36163
Publ.-Id: 36163


Sustainable electrode materials processing using flash lamp annealing

Cherkouk, C.; Folgner, C.; Worbs, A.; Hübner, R.; Prucnal, S.; Schumann, T.; Krüger, S.; Zhou, S.; Rebohle, L.

Advanced energy materials and effective manufacturing facilities of battery cells production are key parameters to overcome the economic barrier to entry into the market. This poster shows an annealing technology using the millisecond range flash lamp annealing (FLA), which takes place without preheating and can be both a vacuum and vacuum-free method. This procedure at a pilot stage is characterized by significant savings in time, energy, resource and production costs enabling to enhance the sustainability of the battery production generally. It will review, as example, the advances that are obtained using FLA on new materials for high energy density thin film electrodes based on silicon. These new materials have the capability of realizing an excellent performance of the energy storage system, e.g. of lithium ion batteries and beyond, for vehicles and stationary applications. It will be demonstrated how it is possible to develop a silicon metal electrode (SiMe) with outstanding properties with a higher capacity than the standard of the day, compatible to many variants of lithium cells, solvents free, cost-effective and capable to be integrated on roll-to- roll processing.

Keywords: flash lamp annealing (FLA); silicon anode; Lithium-ion-Battery (LIB); Energy material

  • Poster
    Batterieforum Deutschland 2022, 19.01.-08.02.2022, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-36162
Publ.-Id: 36162


Hyperdoped superconducting Ge for quantum technology

Prucnal, S.; Hübner, R.; Sawicki, M.; Helm, M.; Zhou, S.

Superconductivity in group IV semiconductors is desired for hybrid devices combining both semiconducting and superconducting properties. Following boron-doped diamond and Si, superconductivity has been observed in gallium-doped Ge; however, the obtained specimen is in polycrystalline form [Phys. Rev. Lett. 102, 217003 (2009)]. Here we present superconducting single-crystalline Ge hyperdoped with gallium or aluminum by ion implantation and rear-side flash lamp annealing. The maximum concentration of Al and Ga incorporated into substitutional positions in Ge is 8 times higher than the equilibrium solid solubility. This corresponds to a hole concentration above 1021cm-3. Using density functional theory in the local-density approximation and pseudopotential plane-wave approach, we show that the superconductivity in p-type Ge is phonon mediated. According to the ab initio calculations, the critical superconducting temperature for Al- and Ga-doped Ge is in the range of 0.45 K for 6.25at.% of dopant concentration, being in qualitative agreement with experimentally obtained values. Being Si-chip technology compatible, superconducting Ge can find wide applications in quantum technology.

Related publications

  • Poster
    LEAPS meets Quantum Technology, 15.-19.05.2022, La Biodola, Italy

Permalink: https://www.hzdr.de/publications/Publ-36161
Publ.-Id: 36161


Phase transition in La0.6Sr0.4CoO3-δ thin films by ion irradiation

Zhou, Y.; Cao, L.; Herklotz, A.; Rata, D.; Hübner, R.; He, S.; Gunkel, F.; Duchon, T.; Kentsch, U.; Helm, M.; Zhou, S.

Perovskite oxides exhibit rich physics related to ionic defects. In particular, the defect concentration and distribution alter the lattice parameters and affect the competitive interplay between strongly correlated electrons, enabling numerous applications as sensors, catalysts, and memristive devices. In this work, helium-ion irradiation is demonstrated as an effective, low-temperature tool to modulate the vacancy profiles in epitaxial La0.6Sr0.4CoO3-δ thin films. A significant lattice expansion solely along the out-of-plane direction is observed. By proper tuning of the irradiation parameters, the resistivity is increased up to several orders of magnitude. These results offer a new playground for optimizing oxide-based spintronic and electronic devices.

Related publications

  • Poster
    German Conference for Research with Synchrotron Radiation, Neutrons and Ion Beams at Large Facilities, SNI 2022, 05.-07.09.2022, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-36160
Publ.-Id: 36160


Fission products speciation in spent mixed oxide nuclear fuel: synthesis and characterisation of Pu-bearing SIMfuel

Caprani, R.; Martin, P.; Prieur, D.; Martinez, J.; Lebreton, F.; Desagulier, M.-M.; Aloin, C.; Alibert, M.; Picard, L.; Gabriel, G.; Signoret, P.; Clavier, N.

In the context of the nuclear fuel cycle, U1-yPuyO2-x Mixed Oxides (MOx) are currently the most employed fuels. These materials have to meet accurate physico-chemical properties, known to change drastically during irradiation with the formation of Fission Products (FP). Investigating the FP behaviour is thus crucial to predict the fuel properties evolution during irradiation. Model Uranium-based materials called SIMfuel have been developed in the last decades to overcome the high radiotoxicity of UO2 spent fuel, and to enable separation-of-effect studies on its otherwise overwhelmingly complicated chemistry.In this work, a fabrication route for U1-yPuyO2-x SIMfuel (SIMMOx) has been developed, in order to study the speciation of soluble FP (Ce, La, Nd, Sr, Y, Zr) inside spent MOx fuel, and their interaction with the U1-yPuyO2-x matrix. The resulting material is representative of irradiated MOx fuel with Pu content of 24 mass% (PU/(U+Pu) : 26%)and a burnup of 13 at.%. XRD and EPMA show a material representative of real spent fuel (U,Pu)O2 matrix: globally monophasic, and compliant with the homogeneity requirement of irradiated MOx. Raman microscopy confirmed the samples homogeneity, showing that all the FP successfully entered the solid solution. Pu-enriched zones (<30 μm) contain higher FP concentration, showing that this phenomenon, already observed in irradiated fuel, is due also to thermodynamics and not only to burnup, as previously assumed. XAS analysis supplied crucial information such as the oxidation states, the O/M ratio, and the prevalent chemical form of each actinide, and FP. A charge compensation mechanism between the (U,Pu)O2 matrix and the FP in solution has been observed.

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  • Secondary publication expected from 18.07.2024

Permalink: https://www.hzdr.de/publications/Publ-36159
Publ.-Id: 36159


Radiation-induced changes of relative cerebral blood volume in normal-appearing white matter of glioma patients following proton therapy

Witzmann, K.; Raschke, F.; Wesemann, T.; Krause, M.; Linn, J.; Troost, E. G. C.

Introduction
Adjuvant radio(chemo)therapy (RT) is a common treatment of primary brain tumor patients. Irradiation with protons reduced radiation exposure to the tumor-surrounding tissue. As the normal tissue is still unavoidably exposed to a certain amount of radiation, the aim of this study was to determine the radiation effect on normal appearing white matter (WM) of glioma patients treated with proton RT based on the changes of the relative cerebral blood volume (rCBV).

Methods
MRI data of 14 glioma patients (grade II-IV) undergoing gross tumor resection followed by proton RT were acquired prior to RT and 3, 6 and 9 months after RT and included T1-weighted images and dynamic susceptibility contrast (DSC) imaging.
Planning CTs, dose maps and CTV contours were registered to the T1w-images using ANTs1 and WM segmentation was done on T1w-images using SPM122. Normal-appearing tissue was censored by excluding the CTV and voxels appearing abnormal on FLAIR imaging.
CBV-maps were calculated voxel wisely as the area under curve determined by integrating the y-variate fit to the time curves of the 4D DSC image. Relative CBV (rCBV) maps were normalized to a reference region of white matter receiving less than 1Gy. Time-dependent alterations ΔrCBV were determined by the percentage difference between follow-up and baseline measurement for the whole brain WM as well as for dose-separated bins of low (1-20Gy), medium (20-40Gy) and high dose regions (>40Gy).

Results and conclusion
The evaluation of whole brain WM as well as of dose-separated regions showed no significant alterations between baseline and follow-up rCBV. A trend toward decreasing perfusion appeared after 9 months after RT in the high-dose range. Previous studies measured a radiation-induced decrease in WM blood volume prominently appearing in the high-dose range3,4,5. A study showing early radiation response of decreasing rCBV followed by a recovery 3 months after RT agrees with our observation of constant rCBV 3-9 months after radiation6. In future studies our focus will be on the evaluation of brain subregions as well as the analysis of GM radiation response.

  • Poster
    BIGART2021 - Acta Oncologica conference, 06.10.2021, online, online

Permalink: https://www.hzdr.de/publications/Publ-36157
Publ.-Id: 36157


Diffusion changes in normal-appearing white matter tracts following irradiation in glioma patients

Witzmann, K.; Raschke, F.; Wesemann, T.; Wahl, H.; Appold, S.; Krause, M.; Linn, J.; Troost, E. G. C.

Purpose: Adjuvant radio(chemo)therapy (RT) is part of the standard treatment of gliomas. Safety margins ensuring the coverage of microscopic tumour expansion of diffusely infiltrating gliomas and compensating for systematic positioning errors inevitably result in the normal-appearing (NA) brain tissue surrounding the tumour to be affected by radiation. The aim of the study was to investigate dose- and time-dependent diffusion alterations of NA white matter (WM) structures following RT using tract-based spatial statistics (TBSS).

Methods: As part of a prospective, longitudinal study, magnetic resonance imaging (MRI) data of 24 grade II-IV glioma patients treated with photons, protons or mixed-modality therapy were acquired. MRIs before RT and 3-monthly during follow-up obtained up to three years after RT included diffusion tensor images (DTI) (TR/TE=6500/66ms, 2×2×2mm³, 32 directions, b=1000mm/s²). Fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated from the DTI data. Corresponding radiation dose maps and clinical target volume (CTV) contours were aligned to MRI using ANTs. NA tissue was defined as brain tissue, excluding the CTV and areas of T2-hyperintensities. All FA images were nonlinearly registered to the “FMRI58B-FA atlas” from FSL with ANTs before applying parts of the TBSS algorithm to create a FA skeleton (Figure 1).
The FA skeleton was combined with the “JHU-ICBM-labels-1mm atlas” to measure the diffusion in 19 WM structures. Relative signal changes of each WM structure were calculated as the difference between follow-up and the corresponding baseline signal and evaluated using a paired t-test. A multivariate linear mixed effects model was applied to determine diffusion changes as function of time after RT and mean dose delivered to the corresponding structure. Data from paired structures of the right and left hemispheres were combined for the analysis. Structures containing less than 50 voxels were excluded.

Results: Figure 2 shows nine structures exhibiting significant DTI signal changes after RT. Posterior thalamic radiation showed the greatest alterations of the DTI parameters and a significant dose- and time-dependency of MD (-0.111%/month, -0.135%/Gy), RD (-0.14%/month, -0.171%/Gy) and AD (-0.09%/month, -0.1%/Gy). The strongest correlation of FA with time appeared in superior longitudinal fasciculus (0.045%/month) and with dose in internal capsula (0.056%/Gy). All significant changes represented decreasing MD, RD, and AD and increasing FA after irradiation. No significant correlations were detected in medial lemniscus.

Conclusion: Several WM structures showed significant time- and dose-dependent DTI signal changes after RT, which might indicate a stronger radiosensitivity of these structures. The results are in agreement with the investigation of the dose-dependent irradiation effects on WM diffusion already performed by Raschke et al. (Radiother Oncol. 2019;140:110–115) and Dünger et al. (Radiother Oncol. 2021;164:66–72).

  • Contribution to proceedings
    ESTRO 2023, 12.-16.05.2023, Wien, Österreich
  • Poster
    ESTRO 2023, 12.-16.05.2023, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-36156
Publ.-Id: 36156


The relative cerebral blood volume in normal-appearing white and grey matter remains almost constant following radio(chemo)therapy

Witzmann, K.; Raschke, F.; Wesemann, T.; Krause, M.; Linn, J.; Troost, E. G. C.

Introduction:

Adjuvant radio(chemo)therapy (RT) is part of the treatment of primary brain tumor patients. In order to capture microscopic tumor extension and to compensate for random and systematic positioning uncertainties, it is inevitable that tumor-surrounding normal brain tissue is irradiated. The aim of this study was to determine relative cerebral blood volume (rCBV) changes in glioma patients before and after RT in normal appearing white matter (WM) and grey matter (GM).

Methods:

As part of an ongoing study, anatomical and functional MRI data of glioma patients undergoing gross tumor resection followed by RT is being collected. The analysis of a subset of this cohort, 17 glioma patients (3 grade II, 11 grade III, 3 grade IV, average age 46.9y ± 13.2y) is presented here. Two patients were treated with photon therapy, 14 patients with proton therapy and one patient received treatment modalities. MRI scans acquired prior to RT and at least one follow-up MRI obtained 3, 6 and 9 months after RT was evaluated. All MRI data were collected on a 3T Philips Ingenuity PET/MR scanner (Philips, Eindhoven, The Netherlands) using an 8 channel head coil and included anatomical T1w-images (3D-GRE, TR/TE=10/3.7ms, FA=20°, voxel size 1×1×1mm3) and dynamic susceptibility contrast (DSC) imaging using a PRESTO sequence (TR/TE=15/21ms, 60 dynamics, dynamic scantime=1.7s, voxel size 3.6×3.6×3.5mm3) with intravenous gadolinium contrast agent (0.1mol/kg, 4ml/s, 7s delay) followed by a saline flush (20ml, 4ml/s). The CBV-map (fig. 1D) was calculated as the area under curve (AUC) of the voxelwise time course of the 4D PRESTO image.
Computed tomographies (CTs) used for planning, radiation dose (fig.1C) and clinical target volume (CTV) contours were registered to the T1w images using ANTs1 . T1w-images were segmented into GM and WM using SPM122 and the corresponding 95% tissue probability maps were rigidly registered with ANTs1 to the CBV-map. B1 inhomogeneities as well as voxels with strong signal loss due to susceptibility artefacts were excluded. Only voxels outside the CTV and without any abnormalities appearing on the FLAIR image were considered.
Symmetrical GM and WM ROIs in supraventricular contralateral and ipsilateral hemisphere (fig.1A,B) were evaluated. The relative CBV (rCBV) was calculated as the ratio of the mean ipsilateral and contralateral CBV:
rCBV=(CBV_ipsi)/(CBV_contra )
The radiation dose in the ROI was determined as the dose difference of ipsilateral to contralateral side.
In a second analysis, the ROI was divided into bins of relative dose differences (ΔRD): low (0-20Gy), medium (20-40Gy) and high (>40Gy). Time-dependent alteration of rCBV was determined by the normalized difference between follow-up (v0x) and baseline measurement:
ΔrCBV=(rCBV_v0x–rCBV_baseline)/(rCBV_baseline )
Dose- and time-dependent ΔrCBV distributions were compared with the paired Wilcoxon signed-rank test.

Results:

The entire ROIs (fig. 2G,H) as well as the dose-separated regions (fig. 2A-F) of GM and WM rCBV did not show significant changes between baseline and follow-up, neither over time nor with increasing dose. One exception was the statistically significantly reduced mean ΔrCBV of -7.6% (p<0.008) after 6 months in WM volumes receiving a ΔRD of 0-20Gy (fig. 2A). In volumes receiving a ΔRD of <40Gy a trend towards increasing rCBV was detected 9 months after RT [mean WM +22,4% (p=0.063) and mean GM +3.1% (p=0.098); fig. 2C and 2F]. Patient-dependent fluctuations were higher in WM-regions than in GM-regions, however, the deviations remained below 20%.

Discussion:

The evaluation of radiation-induced rCBV changes in normal-appearing tissue resulted mainly in constant perfusion without continuous changes after RT, while the majority of the previous studies reported a perfusion reduction prominently appearing in high radiation dose regions3–7. Significant rCBV reduction 6-9 months after RT with a recovery after 18 month in low-dose areas was reported in combined grey and white matter region7, which is in line with our results of WM perfusion decrease in low- ΔRD volumes. However, the authors7 also reported similar behavior for high-dose regions not consistent with our results. An early radiation response of decreasing rCBV followed by a recovery 3 months after RT has also been measured8, which agrees with our observation of constant rCBV 3, 6 and 9 months after radiation. One study reported increasing rCBV in the low-dose region9, while our results indicated a trend for increasing rCBV in the high ΔRD area. It is possible, that the trend to perfusion increase did not reach significance due to the low number of patients especially for the WM evaluation.

  • Open Access Logo Contribution to proceedings
    2021 ISMRM & SMRT Annual Meeting & Exhibition, 15.-20.05.2021, Online, Online
  • Poster
    2021 ISMRM & SMRT Annual Meeting & Exhibition, 15.-20.05.2021, Online, Online

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Permalink: https://www.hzdr.de/publications/Publ-36155
Publ.-Id: 36155


A note on the rate of convergence of integration schemes for closed surfaces

Zavalani, G.; Shehu, E.

In this paper, we issue an error analysis for integration over discrete surfaces using the surface
parametrization presented in [PS22] as well as prove why even-degree polynomials exhibit a higher
convergence rate than odd-degree polynomials. Additionally, we provide some numerical examples
that illustrate our findings and propose a potential approach that overcomes the problems associated
with the original one.

Permalink: https://www.hzdr.de/publications/Publ-36154
Publ.-Id: 36154


A fresh look at the generalized parton distributions of light pseudoscalar mesons

Xing, Z.; Ding, M.; Raya, K.; Chang, L.

We present a symmetry-preserving scheme to derive the pion and kaon generalized parton distributions (GPDs) in Euclidean space. The key to maintaining crucial symmetries under this approach is the treatment of the scattering amplitude, such that it contains both the traditional leading-order contributions and the scalar/vector pole contribution automatically, the latter being necessary to ensure the soft-pion theorem. The GPD is extracted analytically via the uniqueness and definition of the Mellin moments and we find that it naturally matches the double distribution; consequently, the polynomiality condition and sum rules are satisfied. The present scheme thus paves the way for the extraction of the GPD in Euclidean space using the Dyson-Schwinger equation framework or similar continuum approaches.

Permalink: https://www.hzdr.de/publications/Publ-36153
Publ.-Id: 36153


Nanocrystal formation by thermal treatment of Ge/Sn/TaZrOx superlattice structures

Honeit, F.; Hübner, R.; Röder, C.; Beyer, J.; Heitmann, J.

Ge nanocrystals embedded in amorphous TaZrOx matrices were synthesized by a magnetron co-sputtering process in a size-controlled manner, separated from each other by a superlattice approach of alternating TaZrOx-Ge/TaZrOx layers. Ge offers, in contrast to silicon, a large Exciton-Bohr radius, which allows the regulation of the bandgap by the diameter.

After annealing at 725 °C, Ge nanostructures were found to phase-separate and crystallize [1]. The addition of Sn to Ge promises a way towards a direct bandgap Ge-based semiconductor material [2] in a wide concentration range between 6 at.-% and 22 at.-% of Sn [3]. A direct bandgap material, which is fully compatible to common Si-CMOS processes would enable the integration in future devices, like light emitters or detectors.

The fabrication of GeSn alloys is challenging, due to the low solubility of Sn in Ge [4] but it is known that Ge nanocrystals after annealing contain a higher concentration of foreign atoms than expected in thermodynamic equilibrium [1].

Different structural measurements like EDX or Raman scattering monitor the structural changes within the Ge nanostructures by addition of Sn to the superlattice structure under annealing temperatures between 600 °C and 800 °C. TEM EDX measurements revealed that the TaZrOx, which acts as an efficient diffusion barrier for Ge, does not prohibit the diffusion of the Sn completely. However, the formation of pure Sn nanocrystals was not observed. In addition, crystallization of the matrix material can be avoided for appropriate annealing temperatures.

1. D. Lehninger, F. Honeit, D. Rafaja, V. Klemm, C. Röder, L. Khomenkova, F. Schneider, J. von Borany, and J. Heitmann, MRS Bull. 511–512, 654 (2022).
2. A. Slav, C. Palade, C. Logofatu, I. Dascalescu, A. M. Lepadatu, I. Stavarache, F. Comanescu, S. Iftimie, S. Antohe, S. Lazanu, V. S. Teodorescu, D. Buca, M. L. Ciurea, M. Braic, and T. Stoica, ACS Appl. Nano Mater. 2, 3626 (2019).
3. W.-J. Yin, X.-G. Gong, and S.-H. Wei, Phys. Rev. B 78, 161203(4) (2008).
4. H. Li, J. Brouillet, A. Salas, X. Wang, and J. Liu, Opt. Mater. Express 3, 1385 (2013).

Related publications

  • Lecture (Conference)
    E-MRS 2022 Fall Meeting, 19.-22.09.2022, Warsaw, Poland
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Permalink: https://www.hzdr.de/publications/Publ-36152
Publ.-Id: 36152


Scanning high-sensitive x-ray polarization microscopy

Marx-Glowna, B.; Grabiger, B.; Lötzsch, R.; Uschmann, I.; Schmitt, A.; Schulze, K. S.; Last, A.; Roth, T.; Antipov, S.; Schlenvoigt, H.-P.; Sergueev, I.; Leupold, O.; Roehlsberger, R.; Paulus, G. G.

We report on the realization of an extremely sensitive x-ray polarization microscope, allowing to detect tiniest polarization changes of 1 in 100 billion (10^−11) with a μm-size focused beam. The extreme degree of polarization purity places the most stringent requirements on the orientation of the polarizer and analyzer crystals as well as the composition and the form fidelity of the lenses, which must not exhibit any birefringence. The results show that these requirements are currently only met by polymer lenses. Highly sensitive scanning x-ray polarization microscopy thus is established as a new method. It can provide new insights in a wide range of applications ranging from quantum electrodynamics and quantum optics to x-ray spectroscopy, materials research, and laser physics.

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Permalink: https://www.hzdr.de/publications/Publ-36151
Publ.-Id: 36151


Pages: [1.] [2.] [3.] [4.] [5.] [6.] [7.] [8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.] [16.] [17.] [18.] [19.] [20.] [21.] [22.] [23.] [24.] [25.] [26.] [27.] [28.] [29.] [30.] [31.] [32.] [33.] [34.] [35.] [36.] [37.] [38.] [39.] [40.] [41.] [42.] [43.] [44.] [45.] [46.] [47.] [48.] [49.] [50.] [51.] [52.] [53.] [54.] [55.] [56.] [57.] [58.] [59.] [60.] [61.] [62.] [63.] [64.] [65.] [66.] [67.] [68.] [69.] [70.] [71.] [72.] [73.] [74.] [75.] [76.] [77.] [78.] [79.] [80.] [81.] [82.] [83.] [84.] [85.] [86.] [87.] [88.] [89.] [90.] [91.] [92.] [93.] [94.] [95.] [96.] [97.] [98.] [99.] [100.] [101.] [102.] [103.] [104.] [105.] [106.] [107.] [108.] [109.] [110.] [111.] [112.] [113.] [114.] [115.] [116.] [117.] [118.] [119.] [120.] [121.] [122.] [123.] [124.] [125.] [126.] [127.] [128.] [129.] [130.] [131.] [132.] [133.] [134.] [135.] [136.] [137.] [138.] [139.] [140.] [141.] [142.] [143.] [144.] [145.] [146.] [147.] [148.] [149.] [150.] [151.] [152.] [153.] [154.] [155.] [156.] [157.] [158.] [159.] [160.] [161.] [162.] [163.] [164.] [165.] [166.] [167.] [168.] [169.] [170.] [171.] [172.] [173.] [174.] [175.] [176.] [177.] [178.] [179.] [180.] [181.] [182.] [183.] [184.] [185.] [186.] [187.] [188.] [189.] [190.] [191.] [192.] [193.] [194.] [195.] [196.] [197.] [198.] [199.] [200.] [201.] [202.] [203.] [204.] [205.] [206.] [207.] [208.] [209.] [210.] [211.] [212.] [213.] [214.] [215.] [216.] [217.] [218.] [219.] [220.] [221.] [222.] [223.] [224.] [225.] [226.] [227.] [228.] [229.] [230.] [231.] [232.] [233.] [234.] [235.] [236.] [237.] [238.] [239.] [240.] [241.] [242.] [243.] [244.] [245.] [246.] [247.] [248.] [249.] [250.] [251.] [252.] [253.] [254.] [255.] [256.] [257.] [258.] [259.] [260.] [261.] [262.] [263.] [264.] [265.] [266.] [267.] [268.] [269.] [270.] [271.] [272.] [273.] [274.] [275.] [276.] [277.] [278.] [279.] [280.] [281.] [282.] [283.] [284.] [285.] [286.] [287.] [288.] [289.] [290.] [291.] [292.] [293.] [294.] [295.] [296.] [297.] [298.] [299.] [300.] [301.] [302.] [303.] [304.] [305.] [306.] [307.] [308.] [309.] [310.] [311.] [312.] [313.] [314.] [315.] [316.] [317.] [318.] [319.] [320.] [321.] [322.] [323.] [324.] [325.] [326.] [327.] [328.] [329.] [330.] [331.] [332.] [333.] [334.] [335.] [336.] [337.] [338.] [339.] [340.] [341.] [342.] [343.] [344.] [345.] [346.] [347.] [348.] [349.]