Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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41421 Publications

Crystal field effects in the zig-zag chain compound SrTm2O4

Kademane, A. B.; Quintero-Castro, D. L.; Siemensmeyer, K.; Salazar Mejia, C.; Gorbunov, D.; Stewart, J. R.; Luetkens, H.; Baines, C.; Li, H.

The single ion properties of the zig-zag chain compound SrTm2O4 have been investigated using heat capacity, magnetic susceptibility, magnetization, inelastic neutron scattering, and polarized muon spectroscopy. Two crystal field models are employed to estimate the single ion properties; a Density Function Theory based model and an effective charge model based on the Hutchings point charge model. The latter describes our experimental results well. This model estimates an easy-axis anisotropy for one of the Tm3+ sites and an easyplane anisotropy for the second site. It also predicts a mixed ground state with dominating 𝐽 = 0 characteristics for both sites. Additionally, muon spin rotation/relaxation (𝜇+SR) spectra reveal oscillations, typically a sign of long-range magnetic order. However, the temperature dependence of the precession frequency and the relaxation rates indicate that the system is in an extended critical regime and the observed relaxation is actually dynamic.

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Permalink: https://www.hzdr.de/publications/Publ-34248
Publ.-Id: 34248


Numerical Simulation of the Two-Phase Flow at a Single Trapezoid Fixed Valve Using a Hybrid CFD Approach

Wiedemann, P.; Kota, S. P.; Weckesser, S.; Schleicher, E.; Schubert, M.; Hampel, U.

In the present contribution, we demonstrate the application of a hybrid CFD approach, which allows for simulating dispersed phases as well as resolved interfaces within an Eulerian framework, for the flow on distillation trays for the first time. The morphology adaptive multi-field two-fluid model is exemplified for a generic tray setup with a single trapezoid fixed valve. Instead of fully resolving its geometry in the computational grid, we emulate the gas inlets by implementing local mass and momentum sources. Different source term implementations are tested and compared: continuous gas vs. dispersed gas sources and steady vs. dynamic sources. The simulation results are verified with experimental data from a lab-scale test rig with air-water flow. Local phase fractions were measured using a conductivity sensor array. The comparison of simulated and experimental results reveals that the relevant time-averaged and transient flow characteristics can be predicted satisfactorily when choosing proper source term implementations.

Keywords: fixed valve; morphology adaptive multi-field two-fluid model; local source terms; CFD

  • Contribution to proceedings
    12th international conference on Distillation & Absorption 2022, 18.-21.09.2022, Toulouse, France
  • Lecture (Conference)
    12th international conference on Distillation & Absorption 2022, 20.09.2022, Toulouse, France

Permalink: https://www.hzdr.de/publications/Publ-34247
Publ.-Id: 34247


On the agglomeration and breakage of particles in turbulent flows through pipe bends using CFD-PBE

Bilde, K. G.; Hærvig, J.; Lehnigk, R.; Schlegel, F.; Sørensen, K.

Particle agglomeration and breakage through pipe bends in turbulent flows are important for a wide range of industries and applications. A computational fluid dynamics (CFD) model is presented where the population balance equation (PBE) is applied to track the particle size distribution for a periodic turbulent pipe flow with 180◦ bends with a fluid Reynolds number in the range 15, 000 < Ref < 35, 000 and for three different pipe bend radii of rB = 1dh, rB = 1.5dh and rB = 2.5dh. The critical parameters in the Eulerian framework are analysed and suitable parameters are chosen to describe the agglomeration of soot-like particles suspended in water based on an experimentally obtained particle size distribution. The experimental particle size distribution of flocculated
soot particles was measured using a Malvern Mastersizer 3000 at the outlet of a static flocculator with a bend radius of rb = 1.5D. It is concluded that for the particle properties applied, the particle Sauter mean diameter converges to a constant value independent of the pipe bend radius when the fluid Reynolds number exceeds Ref = 30, 000. The agglomeration and breakage kernels for solid particles in a turbulent fluid flow are implemented in the open-source CFD library by the OpenFOAM Foundation.

Keywords: Multiphase flows; Population balance equation; Particle agglomeration; Particle breakage; Turbulence

Permalink: https://www.hzdr.de/publications/Publ-34246
Publ.-Id: 34246


Laboratory Investigation of Tomography-Controlled Continuous Steel Casting

Glavinic, I.; Muttakin, I.; Abouelazayem, S.; Blishchik, A.; Stefani, F.; Eckert, S.; Soleimani, M.; Saidani, I.; Hlava, J.; Kenjereš, S.; Wondrak, T.

More than 96% of steel in the world is produced via the method of continuous casting. The flow condition in the mould, where the initial solidification occurs, has a significant impact on the quality of steel products. It is important to have timely, and perhaps automated, control of the flow during casting. This work presents a new concept of using contactless inductive flow tomography (CIFT) as a sensor for a novel controller, which alters the strength of an electromagnetic brake (EMBr) of ruler type based on the reconstructed flow structure in the mould. The method was developed for the small-scale Liquid Metal Model for Continuous Casting (mini-LIMMCAST) facility available at the Helmholtz-Zentrum Dresden-Rossendorf. As an example of an undesired flow condition, clogging of the submerged entry nozzle (SEN) was modelled by partly closing one of the side ports of the SEN; in combination with an active EMBr, the jet penetrates deeper into the mould than when the EMBr is switched off. Corresponding flow patterns are detected by extracting the impingement position of the jets at the narrow faces of the mould from the CIFT reconstruction. The controller is designed to detect to undesired flow condition and switch off the EMBr. The temporal resolution of CIFT is 0.5 s.

Keywords: Contactless Inductive Flow Tomography; Continuous casting; Clogging; Flow control; EMBr; Inductive measurements; Mini-LIMMCAST

Related publications

Permalink: https://www.hzdr.de/publications/Publ-34245
Publ.-Id: 34245


Kaon and pion parton distributions

Cui, Z.-F.; Ding, M.; Gao, F.; Raya, K.; Binosi, D.; Chang, L.; Roberts, C. D.; Rodriguez-Quintero, J.; Schmidt, S. M.

Beginning with results for the leading-twist two-particle distribution amplitudes of π- and K-mesons, each of which exhibits dilation driven by the mechanism responsible for the emergence of hadronic mass, we develop parameter-free predictions for the pointwise behaviour of all π and K distribution functions (DFs), including glue and sea. The large-x behaviour of each DF meets expectations based on quantum chromodynamics; the valence-quark distributions match extractions from available data, including the pion case when threshold resummation effects are included; and at ζ5=5.2GeV, the scale of existing measurements, the light-front momentum of these hadrons is shared as follows: ⟨xvalence⟩π=0.41(4), ⟨xglue⟩π=0.45(2), ⟨xsea⟩π=0.14(2); and ⟨xvalence⟩K=0.42(3), ⟨xglue⟩K=0.44(2), ⟨xsea⟩K=0.14(2). The kaon’s glue and sea distributions are similar to those in the pion, although the inclusion of mass-dependent splitting functions introduces some differences on the valence-quark domain. This study should stimulate improved analyses of existing data and motivate new experiments sensitive to all π and K DFs. With little known empirically about the structure of the Standard Model’s (pseudo-) Nambu-Goldstone modes and analyses of existing, limited data being controversial, it is likely that new generation experiments at upgraded and anticipated facilities will provide the information needed to resolve the puzzles and complete the picture of these complex bound states.

Keywords: parton; Kaon

Permalink: https://www.hzdr.de/publications/Publ-34244
Publ.-Id: 34244


Towards attosecond imaging at the nanoscale using broadband holography-assisted coherent imaging in the extreme ultraviolet

Eschen, W.; Wang, S.; Liu, C.; Klas, R.; Steinert, M.; Yulin, S.; Meißner, H.; Bussmann, M.; Pertsch, T.; Limpert, J.; Rothhardt, J.

Nanoscale coherent imaging has emerged as an indispensable modality, allowing to surpass the resolution limit given by classical imaging optics. At the same time, attosecond science has experienced enormous progress and has revealed the ultrafast dynamics in complex materials. Combining attosecond temporal resolution of pump-probe experiments with nanometer spatial resolution would allow studying ultrafast dynamics on the smallest spatio-temporal scales but has not been demonstrated yet. To date, the large bandwidth of attosecond pulses poses a major challenge to high-resolution coherent imaging. Here, we present broadband holography-enhanced coherent imaging, which enables the combination of high-resolution coherent imaging with a large spectral bandwidth. By implementing our method at a high harmonic source, we demonstrate a spatial resolution of 34 nm in combination with a spectral bandwidth of 5.5 eV at a central photon energy of 92 eV. The method is single-shot capable and retrieves the spectrum from the measured diffraction pattern.

Permalink: https://www.hzdr.de/publications/Publ-34243
Publ.-Id: 34243


Reflections upon the Emergence of Hadronic Mass

Roberts, C. D.; Schmidt, S. M.

With discovery of the Higgs boson, science has located the source for ≲2% of the mass of visible matter. The focus of attention can now shift to the search for the origin of the remaining ≳98%. The instruments at work here must be capable of simultaneously generating the 1 GeV mass-scale associated with the nucleon and ensuring that this mass-scale is completely hidden in the chiral-limit pion. This hunt for an understanding of the emergence of hadronic mass (EHM) has actually been underway for many years. What is changing are the impacts of QCD-related theory, through the elucidation of clear signals for EHM in hadron observables, and the ability of modern and planned experimental facilities to access these observables. These developments are exemplified in a discussion of the evolving understanding of pion and kaon parton distributions.

Keywords: hadronic; Phenomenology; physics

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Permalink: https://www.hzdr.de/publications/Publ-34242
Publ.-Id: 34242


Nucleon elastic form factors at accessible large spacelike momenta

Schmidt, S. M.; Cui, Z.-F.; Roberts, C. D.; Chen, C.; Binosi, D.; de Soto, F.; Rodríguez-Quintero, J.; Segovia, J.

A Poincaré-covariant quark+diquark Faddeev equation is used to compute nucleon elastic form factors on 0≤Q2≤18m2N (mN is the nucleon mass) and elucidate their role as probes of emergent hadronic mass in the Standard Model. The calculations expose features of the form factors that can be tested in new generation experiments at existing facilities, e.g. a zero in GpE/GpM; a maximum in GnE/GnM; and a zero in the proton's d-quark Dirac form factor, Fd1. Additionally, examination of the associated light-front-transverse number and anomalous magnetisation densities reveals, inter alia: a marked excess of valence u-quarks in the neighbourhood of the proton's centre of transverse momentum; and that the valence d-quark is markedly more active magnetically than either of the valence u-quarks. The calculations and analysis also reveal other aspects of nucleon structure that could be tested with a high-luminosity accelerator capable of delivering higher beam energies than are currently available.

Keywords: nucleon; quark

Permalink: https://www.hzdr.de/publications/Publ-34241
Publ.-Id: 34241


Valence quark ratio in the proton

Cui, Z.-F.; Gao, F.; Binosi, D.; Chang, L.; Roberts, C. D.; Schmidt, S. M.

Beginning with precise data on the ratio of structure functions in deep inelastic scattering (DIS) from 3He and 3H, collected on the domain 0.19≤xB≤0.83, where xB is the Bjorken scaling variable, we employ a robust method for extrapolating such data to arrive at a model-independent result for the xB=1 value of the ratio of neutron and proton structure functions. Combining this with information obtained in analyses of DIS from nuclei, corrected for target-structure dependence, we arrive at a prediction for the proton's valence-quark ratio: dv/uv|xB→1=0.230(57). Requiring consistency with this result presents a challenge to many descriptions of proton structure.

Keywords: quark; proton; valence; ratio

Permalink: https://www.hzdr.de/publications/Publ-34240
Publ.-Id: 34240


Pauli Radius of the Proton

Cui, Z.-F.; Binosi, D.; Roberts, C. D.; Schmidt, S. M.

Using a procedure based on interpolation via continued fractions supplemented by statistical sampling, we analyze proton magnetic form factor data obtained via electron+proton scattering on Q2∈[0.027,0.55] GeV2 with the goal of determining the proton magnetic radius. The approach avoids assumptions about the function form used for data interpolation and ensuing extrapolation onto Q2≃0 for extraction of the form factor slope. In this way, we find Tm=0.817(27) fm. Regarding the difference between proton electric and magnetic radii calculated in this way, extant data are seen to be compatible with the possibility that the slopes of the proton Dirac and Pauli form factors, F1,2(Q2), are not truly independent observables; to wit, the difference F′1(0)−F′2(0)/κp=[1+κp]/[4m2p], viz., the proton Foldy term.

Keywords: pauli; radius; proton

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Permalink: https://www.hzdr.de/publications/Publ-34239
Publ.-Id: 34239


Pion charge radius from pion and electron elastic scattering data

Schmidt, S. M.; Cui, Z.-F.; Binosi, D.; Roberts, C. D.

With the aim of extracting the pion charge radius, we analyse extant precise pion+electron elastic scattering data on Q2∈[0.015,0.144]GeV2 using a method based on interpolation via continued fractions augmented by statistical sampling. The scheme avoids any assumptions on the form of function used for the representation of data and subsequent extrapolation onto Q2≃0. Combining results obtained from the two available data sets, we obtain rπ=0.640(7)fm, a value 2.4σ below today's commonly quoted average. The tension may be relieved by collection and similar analysis of new precise data that densely cover a domain which reaches well below Q2=0.015GeV2. Considering available kaon+electron elastic scattering data sets, our analysis reveals that they contain insufficient information to extract an objective result for the charged-kaon radius, rK. New data with much improved precision, low-Q2 reach and coverage are necessary before a sound result for rK can be recorded.

Keywords: pion; electron; scattering

Permalink: https://www.hzdr.de/publications/Publ-34238
Publ.-Id: 34238


Fresh Extraction of the Proton Charge Radius from Electron Scattering

Schmidt, S. M.; Cui, Z.-F.; Roberts, C. D.; Binosi, D.

We present a novel method for extracting the proton radius from elastic electron-proton (ep) scattering data. The approach is based on interpolation via continued fractions augmented by statistical sampling and avoids any assumptions on the form of function used for the representation of data and subsequent
extrapolation onto Q2 ≃ 0. Applying the method to extant modern ep datasets, we find that all results are mutually consistent and, combining them, we arrive at rp = 0.847(8) fm. This result compares favorably with values obtained from contemporary measurements of the Lamb shift in muonic hydrogen, transitions
in electronic hydrogen, and muonic deuterium spectroscopy.

Keywords: electron; scattering; proton

Permalink: https://www.hzdr.de/publications/Publ-34237
Publ.-Id: 34237


Prolificacy Assessment of Spermatozoan via State-of-the-Art Deep Learning Frameworks

Chandra, S.; Gourisaria, M. K.; Konar, D.; Gao, X.; Wang, T.; Min, X.; Gm, H.

Childlessness or infertility among couples has become a global health concern. Due to the rise in infertility, couples are looking for medical supports to attain reproduction. This paper deals with diagnosing infertility among men and the major factor in diagnosing infertility among men is the Sperm Morphology Analysis (SMA). In this manuscript, we explore establishing deep learning frameworks to automate the classification problem in the fertilization of sperm cells. We investigate the performance of multiple state-of-the-art deep neural networks on the MHSMA dataset. The experimental results demonstrate that the deep learning-based framework outperforms human experts on sperm classification in terms of accuracy, throughput and reliability. We further analyse the sperm cell data by visualizing the feature activations of the deep learning models, providing a new perspective to understand the data. Finally, a comprehensive analysis is also demonstrated on the experimental results obtained and attributing them to pertinent reasons.

Keywords: Sperm abnormality; deep learning; transfer learning

Permalink: https://www.hzdr.de/publications/Publ-34236
Publ.-Id: 34236


A correspondence between the free and interacting field theories

Gao, F.; Ding, M.; Liu, Y.; Schmidt, S. M.

We discover a correspondence between the free field and the interacting states. This correspondence is firstly given from the fact that the free propagator can be converted into a tower of propagators for massive states, when expanded with the Hermite function basis. The equivalence of propagators reveals that in this particular case the duality can naturally be regarded as the equivalence of one theory on the plane wave basis to the other on the Hermite function basis. More generally, the Hermite function basis provides an alternative quantization process with the creation/annihilation operators that correspond directly to the interacting fields. Moreover, the Hermite function basis defines an exact way of dimensional reduction. As an illustration, we apply this basis on 3+1 dimensional Yang-Mills theory with three dimensional space being reduced through the Hermite function basis, and if with only the lowest order Hermite function, the equivalent action becomes the Banks-Fischler-Shenker-Susskind (BFSS) matrix model.

Permalink: https://www.hzdr.de/publications/Publ-34235
Publ.-Id: 34235


Strahlenschutz im HZDR und im Institut für Radiopharmazeutische Krebsforschung

Wendler, M.

Vorstellung des Strahlenschutzes und der Strahlenschutzstruktur am HZDR. Es wird die Strahlenschutzpraxis im Institut für radiopharmazeutische Krebsforschung erläutert und aktuelle Projekte wie die Beantragung von Freigabewerten und das Alpha-Projekt aus Strahlenschutzsicht erläutert.

Keywords: Institut für radiopharmazeutische Krebsforschung; Radiation Protection; Betrieblicher Strahlenschutz

  • Lecture (others) (Online presentation)
    Sitzung des Arbeitskreis Praktischer Strahlenschutz im Fachverband Strahlenschutz, 17.03.2022, Deutsch, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34234
Publ.-Id: 34234


Quantum Zeno Manipulation of Quantum Dots

Ahmadiniaz, N.; Paul Geller, M.; König, J.; Kratzer, P.; Lorke, A.; Schaller, G.; Schützhold, R.

We investigate whether and how the quantum Zeno effect, i.e., the inhibition of quantum evolution by frequent measurements, can be employed to isolate a quantum dot from its surrounding electron reservoir. In contrast to the often studied case of tunneling between discrete levels, we consider the tunnelling of an electron from a continuum reservoir to a discrete level in the dot. Realizing the quantum Zeno effect in this scenario can be much harder because the measurements should be repeated before the wave packet of the hole left behind in the reservoir moves away from the vicinity of the dot. Thus, the required repetition rate could be lowered by having a flat band (with a slow group velocity) in resonance with the dot or a sufficiently small Fermi velocity or a strong external magnetic field.

Keywords: Quantum Zeno effect; quantum dots; wave packet decay; measurement problem; perturbation theory

Permalink: https://www.hzdr.de/publications/Publ-34233
Publ.-Id: 34233


Decay of quantum sensitivity due to three-body loss in Bose-Einstein condensates

Schützhold, R.; Rätzel, D.

In view of the coherent properties of a large number of atoms, Bose-Einstein condensates (BECs) have a high potential for sensing applications. Several proposals have been put forward to use collective excitations such as phonons in BECs for quantum-enhanced sensing in quantum metrology. However, the associated highly nonclassical states tend to be very vulnerable to decoherence. In this article, we investigate the effect of decoherence due to the omnipresent process of three-body loss in BECs.We find strong restrictions for a wide range of parameters, and we discuss possibilities to limit these restrictions.

Keywords: quantum; Bose-Einstein

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Permalink: https://www.hzdr.de/publications/Publ-34231
Publ.-Id: 34231


Technische Umsetzung von RDM Services: RODARE - InvenioRDM am HZDR

Knodel, O.; Fiedler, M.

The presentation highlights the research data repository of the HZDR RODARE.
In the first part Maik Fiedler gives an overview of the current use of the repository, shows features and statistics on the development and embeds the system in the publication economy of the HZDR.
In the second part the update upgrade from Rodare to an InvenioRDM-based RODARE-RDM is introduced with the technical background and conditions by Oliver Knodel. Furthermore, the concept for the integration of Rodare into the HELIPORT data management system HELIPORT is presented.

Keywords: Helmholtz Open Science Office; Research data; Research software; Data Management

  • Invited lecture (Conferences) (Online presentation)
    Praxisforum Forschungsdatenmanagement, 03.02.2022, Online, Deutschland
    DOI: 10.48440/os.helmholtz.044

Permalink: https://www.hzdr.de/publications/Publ-34230
Publ.-Id: 34230


Radiocarbon-dated evidence for Late Pleistocene and Holocene coastal change at Yzerfontein, Western Cape, South Africa

Woodborne, S.; Miller, D.; Evans, M.; Winkler, S.

We report radiocarbon dates obtained from on-shore marine and near-shore terrestrial deposits near Yzerfontein, on the West Coast of South Africa. These include Late Pleistocene shell concretions from the southern end of 16 Mile Beach and a marine shell deposit inland of the coastal Rooipan; mid-Holocene coastal pan deposits exposed by modern storm erosion of the sandy 16 Mile Beach; and four Holocene storm beach deposits on a rocky shore to the south. We interpret the results in terms of local geomorphology constraints on sea-level fluctuations. The eastern margin of Rooipan is a >40 ka elevated beach deposit in a dune cordon that separates it from the adjacent Yzerfonteinpan. Both pans have gypsum deposits up to 2 m thick formed by repeated marine overwash. Saline pan deposits that are exposed intermittently on the beach are mid-Holocene and indicate a former westward extension of Rooipan. This is in contrast to storm beaches dating 9 000–3 000 cal BP at higher elevations on a rocky platform further south. This suggests that a dune barrier existed seaward of the present shoreline near Rooipan at this time. The coastal changes described here show that deposition and erosion can be affected significantly by the local palaeo-geomorphology and cannot be ascribed solely to sea-level change.

Permalink: https://www.hzdr.de/publications/Publ-34229
Publ.-Id: 34229


Highlight selection of radiochemistry and radiopharmacy developments by editorial board

Bernardes, E.; Caravan, P.; van Dam, M.; Deuther-Conrad, W.; Ellis, B.; Furumoto, S.; Guillet, B.; Huang, Y.-Y.; Jia, H.; Laverman, P.; Li, Z.; Liu, Z.; Lodi, F.; Miao, Y.; Perk, L.; Schirrmacher, R.; Vercoullie, J.; Yang, H.; Yang, M.; Yang, X.; Zhang, J.; Zhang, M.-R.; Zhu, H.

Background: The Editorial Board of EJNMMI Radiopharmacy and Chemistry releases a biyearly highlight commentary to update the readership on trends in the field of radiopharmaceutical development.
Results: This commentary of highlights has resulted in 23 different topics selected by each member of the Editorial Board addressing a variety of aspects ranging from novel radiochemistry to first in man application of novel radiopharmaceuticals and also a contribution in relation to MRI-agents is included.
Conclusion: Trends in (radio)chemistry and radiopharmacy are highlighted demonstrating the progress in the research field being the scope of EJNMMI Radiopharmacy and Chemistry.

Keywords: Radiopharmacy; Radiochemistry; Radiopharmaceuticals

Permalink: https://www.hzdr.de/publications/Publ-34228
Publ.-Id: 34228


The effects of Calcigel bentonite naturally occurring microorganisms on corrosion of cast iron

Sushko, V.; Matschiavelli, N.; Wei, T.; Stumpf, T.; Cherkouk, A.

In light of Germany's exploration of clay formations as potential hosts for deep geological repositories (DGR), and the most likely use of bentonite as a buffer material, copper or carbon steel/cast iron would be the most appropriate container material [1]. The surface of the metal containers is a subject to anaerobic corrosion and microbially influenced corrosion in a DGR. The interactions at the metal/bentonite interface can determine the performance of such a multi barrier system [2].
This study investigates the microbial processes that can occur at the interface between metal container and bentonite, and evaluates the effects of the microbial communities naturally occurring in bentonite may have on the corrosion of the nuclear waste
container.
Microcosm experiments as described in [3] were performed with Calcigel bentonite. The microcosms, containing GGG40 cast iron coupons, artificial Opalinus Clay porewater and bentonite, were incubated in N2-atmosphere at 37 °C. Some of the microcosms were supplemented with sodium lactate to stimulate microbial activity. After the incubation period the content of the microcosms was investigated by various geochemical analysis, DNA isolation and amplification for microbial community analysis, SEM-EDX and RAMAN spectroscopy to characterize the surface structure of the cast iron coupons. Geochemical investigation of the samples showed a slight
lactate consumption. Surface analysis of the coupons with SEM confirmed a corrosion ofr the coupons incubated with Calcigel bentonite, as well as crystalline structures covering the coupons to some extent. The cast iron coupons incubated with bentonite including naturally occurring microorganisms showed a faster corrosion than control samples with sterilized bentonite. To get a better overview about the ongoing microbial processes, microbial diversity analysis and incubations for a longer time-frame are currently still under investigation.

References
1. Nieder-Westerman, G.H., et al. 2013, Radioactive Waste Management and Contaminated Site Clean-Up, 462-488.
2. Kaufhold, S., et al. 2020, ACS Earth Space Chem. 4, 5, 711–721.
3. Matschiavelli, N. et al., 2019, Environ. Sci. Technol., 53, 17, 10514–10524

Keywords: Microbially influenced corrosion; Microcosm experiment; SEM

  • Poster
    EUROCORR 2022, 28.08.-1.09.2022, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34227
Publ.-Id: 34227


Numerical simulations of counter-current two-phase flow experiments in a PWR hot leg model

Höhne, T.

In order to improve the understanding of counter-current two-phase flows and to validate new physical
models, CFD simulations of 1/3rd scale model of the hot leg of a German Konvoi PWR with rectangular
cross section was performed. Selected counter-current flow limitation (CCFL) experiments at the Helmholtz–
Zentrum Dresden–Rossendorf (HZDR) were calculated with ANSYS CFX 12.1 using the multi-fluid
Euler–Euler modeling approach. The transient calculations were carried out using a gas/liquid inhomogeneous
multiphase flow model coupled with a k-x turbulence model for each phase. In the simulation, the
surface drag was approached by a new correlation inside the Algebraic Interfacial Area Density (AIAD)
model. The AIAD model allows the detection of the morphological form of the two phase flow and the
corresponding switching via a blending function of each correlation from one object pair to another.
As a result this model can distinguish between bubbles, droplets and the free surface using the local
liquid phase volume fraction value. A comparison with the high-speed video observations shows a good
qualitative agreement. The results indicated that quantitative agreement of the CCFL characteristics
between calculation and experimental data was obtained. The goal is to provide an easy usable AIAD
framework for all Code users, with the possibility of the implementation of their own correlations.

Keywords: Numerical simulation; CFD; CCFL; AIAD model; Reflux condensation; PWR hot leg; Air–water experiment

  • Invited lecture (Conferences) (Online presentation)
    NURETH19, 09.03.2022, Brüssel, Belgien

Permalink: https://www.hzdr.de/publications/Publ-34226
Publ.-Id: 34226


Prompt-gamma based treatment verification: Multi-institutional benchmark experiment of a prompt-gamma-imaging and a prompt-gamma-spectroscopy prototype system using an anthropomorphic head phantom

Berthold, J.; Hueso González, F.; Wohlfahrt, P.; Bortfeld, T.; Khamfongkhruea, C.; Tattenberg, S.; Zarifi, M.; Richter, C.; Verburg, J.

Introduction
Prompt-gamma-based range verification has been clinically implemented using either prompt-gamma-imaging (PGI) or prompt-gamma-spectroscopy (PGS). Here, two proton therapy centers, currently investigating the clinical benefit of PGI and PGS, collaborated to systematically compare the two techniques in a set of benchmark experiments under equalized conditions.

Materials&Methods
The same anthropomorphic head phantom (CIRS, USA) was used for treatment planning, beam delivery and PG monitoring in both centers. Two pencil-beam-scanning fields (1GyE) targeting a brain lesion were optimized on a Dual-energy-CT using the same spot positions and energies in both centers, enabling spot-wise comparison. The horizontal short-range field was clinically realistic. The long-range, oblique field served as stress test. Absolute range verification accuracy against a blinded ground truth (SPR map) for both fields as well as the capability to detect relative range shifts, introduced by plastic slabs (2 and 5mm) on half of the short-range field, was assessed.

Results (µ±σ)
The absolute accuracy of PGI and PGS were (-0.5±0.8)mm or (2.4±0.8)mm for the short-range and (2.4±1.9)mm or (1.3±1.5)mm for the long-range field, respectively. Relative range shifts were detected with (2.0±0.9)mm or (4.2±0.8)mm accuracy for PGI, and (1.8±0.5)mm or (4.8±0.4)mm for PGS. Both systems show a performance worthy of clinical application for the detection of range deviations. Future improvements of their sensitivity are ongoing.

Conclusion
For the first time, two independent PG range verification systems utilizing different PG information have been successfully benchmarked under equalized conditions in two proton therapy centers. This marks an important milestone for translational research on proton treatment verification.

Permalink: https://www.hzdr.de/publications/Publ-34225
Publ.-Id: 34225


MOFs with 12-coordinate 5f-block metal centers

Lv, K.; Urbank, C.; Patzschke, M.; März, J.; Kaden, P.; Weiß, S.; Schmidt, M.

We have constructed an unprecedented MOF platform that accommodates a range of 5f-block metal ions (Th4+, U4+, Np4+, Pu4+) as the primary building block. The isoreticular actinide metal-organic frameworks (An-MOFs) exhibit periodic trends in the 12-coordinate metal environment, ligand configuration, and resulting ultramicroporosity. It holds potential in distinguishing neighboring tetravalent actinides. The metal ionic radius, carboxylate bite angle, anthracene plane twisting, inter-ligand interac-tions, and countercation templating collectively determine an interplay between solvation, modulation, and complexation, re-sulting in a coordination saturation of the central actinide while lanthanide counterparts are stabilized by the formation of a dimer-based motif. Quantum chemical calculations indicate that this large coordination number is only feasible in the high-symmetry environment provided by the An-MOFs. This category of MOFs not only demonstrates autoluminescence (4.16 ×104 counts per second per gram) but also portends a wide-bandgap (2.84 eV) semiconducting property with implications for a multitude of applications such as hard radiation detection.

Keywords: Actinides; Metal-Organic Frameworks; Autoluminescence; Semiconductor

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Permalink: https://www.hzdr.de/publications/Publ-34224
Publ.-Id: 34224


A multimodal approach to revisiting oxidation defects in Cr2O3

Auguste, R.; Chan, H. L.; Romanovskaia, E.; Qiu, J.; Schoell, R.; Liedke, M. O.; Butterling, M.; Hirschmann, E.; Elsherif, A. G. A.; Wagner, A.; Selim, F. A.; Kaoumi, D.; Uberuaga, B. P.; Hosemann, P.; Scully, J. R.

The oxidation of chromium in air at 700 °C was investigated with a focus on point defect behavior and transport during oxide layer growth. A comprehensive set of characterization techniques targeted characteristics of chromium oxide microstructure and chemical composition analysis. TEM showed that the oxide was thicker with longer oxidation times and that, for the thicker oxides, voids formed at the metal/oxide interface. PAS revealed that the longer the oxidation time, there was an overall reduction in vacancy-type defects, though chromium monovacancies were not found in either case. EIS found that the longer oxidized material was more electrochemically stable and that, while all oxides displayed p-type character, the thicker oxide had an overall lower charge carrier density. Together, the results suggest anion oxygen interstitials and chromium vacancy cluster complexes drive transport in an oxidizing environment at this temperature, providing invaluable insight into the mechanisms that regulate corrosion.

Keywords: Cr2O3; oxidation; defects; positron annihilation spectroscopy; transmission electron microscopy; Raman spectroscopy

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Permalink: https://www.hzdr.de/publications/Publ-34223
Publ.-Id: 34223


Spatially resolved temperature distribution in a rare-earth-doped transparent glass-ceramic

Sedmak, I.; Podlipec, R.; Urbancic, I.; Strancar, J.; Mortier, M.; Golobic, I.

Knowing the temperature distribution within the conducting walls of various multilayer-type materials is crucial for a better understanding of heat-transfer processes. This applies to many engineering fields, good examples being photovoltaics and microelectronics. In this work, we present a novel fluorescence technique that makes possible the non-invasive imaging of local temperature distributions within a transparent, temperature-sensitive, co-doped Er:GPF1Yb0.5Er glass-ceramic with micrometer spatial resolution. The thermal imaging was performed with a high-resolution, fluorescence microscopy system, measuring different focal planes along the z-axis. This ultimately enabled a precise axial reconstruction of the temperature distribution across a 500-µm-thick glass-ceramic sample. The experimental measurements showed excellent agreement with computer-modeled heat simulations and suggest that the technique could be adopted for the spatial analyses of local thermal processes within optically transparent materials. For instance, the technique could be used to measure the temperature distribution of intermediate, transparent layers of novel ultra-high-efficiency solar cells at the micron and sub-micron levels.

Keywords: Temperature-dependent fluorescence; co-doped glass-ceramic; axial temperature distribution; micro-scale temperature measurements

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Permalink: https://www.hzdr.de/publications/Publ-34222
Publ.-Id: 34222


f-electron hybridised Fermi surface in magnetic field-induced metallic YbB12

Liu, H.; Hickey, A. J.; Hartstein, M.; Davies, A. J.; Eaton, A. G.; Elvin, T.; Polyakov, E.; Vu, T. H.; Wichitwechkarn, V.; Förster, T.; Wosnitza, J.; Murphy, T. P.; Shitsevalova, N.; Johannes, M. D.; Ciomaga Hatnean, M.; Balakrishnan, G.; Lonzarich, G. G.; Sebastian, S. E.

The nature of the Fermi surface observed in the recently discovered family of unconventional insulators starting with SmB6 is a subject of intense inquiry. Here we shed light on this question by accessing quantum oscillations in the high magnetic field-induced metallic regime above ≈47 T in YbB12, which we compare with the unconventional insulating regime. In the field-induced metallic regime, we find prominent quantum oscillations in the electrical resistivity characterised by multiple frequencies and heavy effective masses. The close similarity in Lifshitz-Kosevich low-temperature growth of quantum oscillation amplitude in insulating YbB12 to field-induced metallic YbB12, points to an origin of quantum oscillations in insulating YbB12 from in-gap neutral low energy excitations. Higher frequency Fermi surface sheets of heavy quasiparticle effective mass emerge in the field-induced metallic regime of YbB12 in addition to multiple heavy Fermi surface sheets observed in both insulating and metallic regimes. f-electron hybridisation is thus observed to persist from the unconventional insulating to the field-induced metallic regime of YbB12, in contrast to the unhybridised conduction electron Fermi surface observed in unconventional insulating SmB6. Our findings thus require an alternative model for YbB12, of neutral in-gap low energy excitations, wherein the f-electron hybridisation is retained.

Permalink: https://www.hzdr.de/publications/Publ-34221
Publ.-Id: 34221


The importance of understanding Technetium environmental behaviour

Mayordomo, N.

The talk shows the work carried out at Institute of Resource Ecology in the last four years in the frame of Tc immobilization by Fe(II)-minerals and the future perspectives for collaboration between Freie Universität Berlin.

Keywords: Technetium; Environment; Remediation; Sorption

  • Lecture (others) (Online presentation)
    Seminar at Freie Universität Berlin, 07.02.2022, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-34220
Publ.-Id: 34220


Annual Report 2021 - Institute of Resource Ecology

Stumpf, T.; Foerstendorf, H.; Bok, F.; Richter, A.

The Institute of Resource Ecology (IRE) is one of the eight institutes of the Helmholtz-Zentrum Dresden–Rossendorf (HZDR). Our research activities are mainly integrated into the program “Nuclear Waste Management, Safety and Radiation Research (NUSAFE)” of the Helmholtz Association (HGF) and focus on the topics “Safety of Nuclear Waste Disposal” and “Safety Research for Nuclear Reactors”. The program NUSAFE, and therefore all work which is done at IRE, belong to the research field “Energy” of the HGF.
IRE conducts applied basic research to protect humans and the environment from the effects of radioactive radiation.
For this purpose, we develop molecular process understand-ing using state-of-the-art methods of microscopy, spectroscopy, diffraction, numerical simulation, theoretical chemistry and systems biology. We implement this in a cross-institutional research environment at the HZDR. Our active interdisciplinarity combines radiochemistry, geosciences and biosciences as well as materials science and reactor physics.
We provide knowledge that is applied in particular to reactor and repository safety as well as in radioecology.
We achieve this goal with a unique infrastructure comprising chemical and biological laboratories as well as hot cells in corresponding radiation and biology safety laboratories in Dresden, Leipzig and Grenoble. In Grenoble, at the European Synchrotron Radiation Facility (ESRF), the institute operates a beamline with four experimental stations for continuously advanced X-ray spectroscopy and diffraction of radio-active samples, which is also available to external users.

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-119 2022
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-34219
Publ.-Id: 34219


A pharmacokinetic and metabolism study of the TRPC6 inhibitor SH045 in mice by LC-MS/MS

Chai, X.-N.; Ludwig, F.-A.; Müglitz, A.; Gong, Y.; Schaefer, M.; Regenthal, R.; Krügel, U.

TRPC6, the sixth member of the family of canonical transient receptor potential (TRP) channels, contributes to a variety of physiological processes and human pathologies. This study extends the knowledge on the newly developed TRPC6 blocker SH045 with respect to its main target organs beyond the description of plasma kinetics. According to the concentration-time course in mice plasma, SH045 is available in pharmacological effective plasma concentrations up to 24 h after administration of 20 mg/kg BW (i.v.) and up to the 5-fold of its IC50 until 6 hours, orally. The short plasma half-life and rather low oral bioavailability are contrasted by its high potency. Dosage limits were not worked out, but absence of safety concerns for 20 mg/kg BW supports further dose exploration. The disposition of SH045 is described. In particular, a high extravascular distribution, most prominent in lung, and a considerable renal elimination of SH045 were observed. SH045 is substrate of CYP3A4 and CYP2A6. Hydroxylated and glucuronidated metabolites were identified under optimized LC-MS/MS conditions. The results guide a reasonable selection of dose and application route of SH045 for target-directed preclinical studies in vivo with one of the rare high potent and subtype-selective TRPC6 inhibitors available.

Keywords: cytochrome P450 enzyme; kidney; larixol; LC-MS/MS; lung; mice; microsomes; pharmacokinetics; toxicity; SH045; TRPC6 inhibitor

Permalink: https://www.hzdr.de/publications/Publ-34218
Publ.-Id: 34218


Prototype system for first-in-human MR-integrated proton therapy combining a 0.32T open MR scanner with a horizontal proton pencil beam scanning beamline

Schneider, S.; Karsch, L.; Hoffmann, A. L.

Target audience: Audience interested in image-guided radiation therapy, innovative use-cases for MRI and experimental hardware developments.

Purpose: The physical integration of magnetic resonance imaging (MRI) with proton therapy (PT) into an MR-integrated PT (MRiPT) system is expected to improve the targeting accuracy of PT [1]. However, a successful integration has so far only been achieved in a proof-of-concept study [2], which demonstrated that in-beam MR imaging during proton beam irradiation at a fixed PT beamline is feasible. The purpose of this study was to develop a prototype system combining a low-field MRI scanner with a proton pencil beam scanning (PBS) beamline to enable a first in-human MRiPT treatment. This contribution presents first results of the installation and commissioning of the MRiPT system where the positioning reproducibility, magnet shimming performance and image quality were analyzed.

Methods: The setup consists of an open C-shaped 0.32 T MRI scanner (MRJ3300, ASG Superconductors SpA, Genoa, Italy) positioned in close proximity of the nozzle of a horizontal proton PBS beamline (Figure 1). The MRI scanner, which utilizes a permanent magnet, was encased in a custom-designed compact aluminum Faraday cage. At the location of the beam exit window of the nozzle, a beam entrance opening was incorporated in the wall of the RF cage, which was sealed by a thin (40 µm) aluminum foil to combine high RF attenuation and small lateral spreading of the traversing proton beam. The scanner and RF cage were mounted on top of an air-cushion-based transport platform, allowing the assembly to be accurately positioned in the beam path exiting the nozzle. The maneuvering of the assembly into treatment position was thereby visually guided based on room lasers that intersect at the natural beam isocenter and project onto the outer wall of the cage. The magnet was shimmed in treatment position close to ferromagnetic components of the nozzle where field homogeneity was measured using a magnetic field camera (MFC3045, Metrolab Technology SA, Geneva, Switzerland). During commissioning the MR image quality was assessed both quantitatively and quantitatively using the ACR Small MRI Phantom [3] and images of a healthy volunteer’s extremities acquired in coronal and transversal directions using various scan protocols (T1w SE, T2w TSE, T2w STIR, T1w 3D GE), respectively.

Results: The positioning accuracy and precision of the mobile in-beam MRI system was below 1 mm. A peak-to-peak B0 field homogeneity of 43 ppm over a 25 cm diameter spherical volume (DSV) around the MR magnetic isocenter was achieved during magnet shimming. Phantom imaging revealed a signal-to-noise ratio (SNR) of >80 and a geometric distortion of <1 mm over a 10 cm DSV around the magnetic isocenter. The quality of the MR images was deemed clinically useful for structural imaging and promising for the localization and monitoring of extremity soft-tissue tumors.

Discussion: Tumor visualization capabilities should be further investigated in patients with malignant soft-tissue tumors. A full workflow for patient positioning and irradiation is currently under development, including the development of accurate methods for PT treatment planning and dose verification that take into account the presence of the MR magnetic fields during dose delivery.

Conclusion: A 0.32 T in-beam MRI scanner was successfully installed and commissioned in front of a horizontal proton PBS beamline in preparation for the development of a first clinical prototype MRiPT system. Further developments in patient positioning, dosimetry and treatment planning are indispensable before a first in-human irradiation can be safely performed.

References:

[1] A. Hoffmann et al. 2020 Radiat. Oncol.
[2] S. Schellhammer et al. 2018 Phys. Med. Biol.
[3] Small Phantom Guide 4/17/18. American College of Radiology

Keywords: Magnetic resonance integrated proton therapy; Image guided proton therapy; Magnetic resonance imaging; Proton therapy

  • Lecture (others) (Online presentation)
    ISMRM Workshop on Low Field MRI 2022, 17.-18.03.2022, Virtuell, Virtuell

Permalink: https://www.hzdr.de/publications/Publ-34215
Publ.-Id: 34215


Multivariate statistical modelling enhances the predictive power of Prompt Gamma-Ray Timing for proton treatment verification

Schellhammer, S.; Wiedkamp, J.; Löck, S.; Kögler, T.

Given its sensitivity to anatomical variations, proton therapy is expected to benefit strongly from reliable on-line treatment verification. As a light-weight, collimator-free technique that can be easily integrated into existing systems, Prompt Gamma-Ray Timing is a promising candidate for this purpose. The development of such a system is challenging, as the proton range delivered in the patient needs to be reconstructed with high accuracy from the temporal distribution of a very limited number of gamma-rays. So far, this reconstruction has been based on the mean and standard deviation of the distribution, but the accuracy of this method was found to be insufficient. We therefore developed multivariate statistical models based on additional histogram characteristics to improve proton range reconstruction.

Prompt Gamma-Ray Timing distributions acquired during pencil beam irradiation of an acrylic glass phantom with air cavities of different thicknesses were analysed. Relevant histogram features were chosen using forward selection and the Least Absolute Shrinkage and Selection Operator (LASSO) from a feature assortment based on recommendations of the Image Biomarker Standardisation Initiative. Candidate models were defined by multivariate linear regression and evaluated based on their coefficient of determination R2 and root mean square error RMSE on an independent dataset.

The newly developed models showed a strongly improved predictive power (R2 > 0.6) compared to the previously used models (R2 < 0.1). These results demonstrate that elaborate statistical modelling is a valuable tool to enhance the Prompt Gamma-Ray Timing method and increase its potential to be used for proton treatment verification.

  • Lecture (Conference)
    PTCOG 60, 27.06.-02.07.2022, Miami, USA

Permalink: https://www.hzdr.de/publications/Publ-34214
Publ.-Id: 34214


Caenorhabditis elegans microscopy dataset with lifespan, movement and segmentation annotations.

Galimov, E.; Pincus, Z.; Yakimovich, A.

The nematode Caenorhabditis elegans (C. elegans) is an established model for studying various interventions into the ageing process, which allowed to find numerous genes and drugs interfering with agein. This dataset of widefield time-lapse (days 1 to 3) &&>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>micrographs of C. elegans was initially obtained in the Pincus lab (Pincus et al. 2011, Zhang et al. 2016). Here, the dataset was annotated for lifespan, movement and segmentation of C. elegans, and was employed for developing a machine learning framework (Yakimovich et al. 2021). &&>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>lt>&&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>nbsp&>&&>lt>nbsp&>lt>lt>&&>lt>nbsp&>lt>All files are in 8-bit PNG format. Movement and lifespan annotations are provided using folder structure. Segmentation annotation is provided by the accompanying masks.

Keywords: C. elegans; Caenorhabditis elegans; lifespan; movement; segmentation; microscopy

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Permalink: https://www.hzdr.de/publications/Publ-34213
Publ.-Id: 34213


Plasmonic gratings from highly doped Ge1-y Sn (y) films on Si

Berkmann, F.; Ayasse, M.; Schlipf, J.; Mörz, F.; Weißhaupt, D.; Oehme, M.; Prucnal, S.; Kawaguchi, Y.; Schwarz, D.; Fischer, I. A.; Schulze, J.

Plasmonic modes in metal structures are of great interest for optical applications. While metals such as Au and Ag are highly suitable for such applications at visible wavelengths, their high Drude losses limit their usefulness at mid-infrared wavelengths. Highly n-doped Ge1−ySny alloys are interesting possible alternative materials for plasmonic applications in this wavelength range. Here, we investigate the use of highly n-doped Ge1−ySny films grown directly on Si by molecular beam epitaxy with varying Sn-content from 0% up to 7.6% for plasmonic grating structures. We compare plasma wavelengths and relaxation times obtained from electrical and optical characterization. While theoretical considerations indicate that the decreasing effective mass with increasing Sn content in Ge1−ySny films could improve performance for plasmonic applications, our optical characterization results show that the utilization of Ge1−ySny films grown directly on Si is only beneficial if material quality can be improved.

Keywords: GeSn; plasmonics; doping

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Permalink: https://www.hzdr.de/publications/Publ-34212
Publ.-Id: 34212


A review on fast tomographic imaging techniques and their potential application in industrial process control

Hampel, U.; Babout, L.; Banasiak, R.; Schleicher, E.; Soleimani, M.; Wondrak, T.; Vauhkonen, M.; Lähivaara, T.; Tan, C.; Hoyle, B.; Penn, A.

With the ongoing digitalization of industry, imaging sensors are becoming increasingly im-portant for industrial process control. In addition to direct imaging techniques such as those provided by video or infrared cameras, tomographic sensors are of interest in the process indus-try where harsh process conditions and opaque fluids require non-intrusive and non-optical sensing techniques. Because most tomographic sensors rely on complex and often time-multiplexed excitation and measurement schemes and require computationally intensive image reconstruction, their application in the control of highly dynamic processes is often hindered. This article provides an overview of the current state of the art in fast process tomography and its potential for use in industry.

Keywords: Process tomography; Tomographic sensors; Image reconstruction; Industrial process monitoring and control

Permalink: https://www.hzdr.de/publications/Publ-34211
Publ.-Id: 34211


Data for: Spin-wave frequency combs

Hula, T.; Schultheiß, K.; Trindade Goncalves, F. J.; Körber, L.; Bejarano, M.; Copus, M.; Flacke, L.; Liensberger, L.; Buzdakov, A.; Kakay, A.; Weiler, M.; Camley, R.; Faßbender, J.; Schultheiß, H.

Data were obtained by means of Brillouin light scattering microscopy, micro magnetic simulations in MuMax3 and analytic calculations.

Keywords: Brillouin light scattering; micro magnetic simulations; spin waves; magnons; nonlinear

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Permalink: https://www.hzdr.de/publications/Publ-34210
Publ.-Id: 34210


Fully Chelating N3O2-Pentadentate Planar Ligands Designed for Strongest and Selective Capture of Uranium from Seawater

Mizumachi, T.; Sato, M.; Kaneko, M.; Takeyama, T.; Tsushima, S.; Takao, K.

Based on unique 5-fold equatorial coordination of UO22+, water-compatible pentadentate planar ligands, H2saldian and its derivatives, were designed as strong and selective capture of UO22+ in seawater. In the simulated seawater condition (0.5 M NaCl + 2.3 mM HCO3−/CO32−, pH 8), saldian2− shows the strongest complexation with UO22+ to form UO2(saldian) (log β11 = 27.5), which is more than 10 order of magnitude greater than amidoxime-based or -inspired ligand systems most commonly employed for U capture from seawater. Good selectivity for UO22+ from other metal ions coexisting in seawater was also demonstrated.

Permalink: https://www.hzdr.de/publications/Publ-34209
Publ.-Id: 34209


Hydrophobic Core Formation and Secondary Structure Elements in Uranyl(VI)–Binding Peptides

Tsushima, S.; Takao, K.

Cyclic peptides as well as modified EF-hand of calmodulin have been newly designed to achieve high affinity towards uranyl(VI). Cyclic peptides may be engineered to bind uranyl(VI) to its backbone under acidic condition, which may enhance its selectivity. For the modified EF-Hand motif of calmodulin, strong electrostatic interactions between uranyl(VI) and negatively charged side chains play important role in achieving high affinity, however, it is also essential to have secondary structure element and formation of hydrophobic cores in the metal-bound state of the peptide.

Permalink: https://www.hzdr.de/publications/Publ-34208
Publ.-Id: 34208


Synthesis and characterization of a uranyl(vi) complex with 2,6-pyridine-bis(methylaminophenolato) and its ligand-centred aerobic oxidation mechanism to a diimino derivative

Takeyama, T.; Iwatsuki, S.; Tsushima, S.; Takao, K.

A uranyl(VI) complex with 2,6-bis(3,5-di-tert-butyl-ophenolateaminomethyl) pyridine (UO2(tBu-pdaop), 1) was synthesized and thoroughly characterized by 1H NMR, IR, elemental analysis, and single-crystal XRD. Right after dissolution of complex 1 in pyridine or DMSO, the solutions were pale red, whereas it gradually turned to dark purple under ambient atmosphere. 1H NMR spectra at the initial and final states suggested that both of the two aminomethyl groups in 1 were converted to azomethine ones through aerobic oxidation. Indeed, a uranyl(VI) complex with 2,6-bis(3,5-di-tert-butyl-ophenolateiminomethyl) pyridine (UO2(tBu-pdiop), 2) was obtained from the concentrated solution once the reaction is completed, which was characterized by IR, elemental analysis, and singlecrystal XRD. Kinetic analyses as well as mechanistic study based on quantum chemical calculations suggested that hydrogen atom transfer from one of the amino groups in complex 1 to nearby O2 initiates the stepwise oxidation processes to finally afford 2. To the best of our knowledge, this is the first report on an air-oxidizable uranyl(VI) complex. The present findings demonstrate the novel reactivity of a uranyl(VI) complex, and provide new insights to construct thermally-driven molecular conversion system by a UO22+ complex catalyst.

Permalink: https://www.hzdr.de/publications/Publ-34207
Publ.-Id: 34207


Terahertz control of photoluminescence emission in few-layer InSe

Venanzi, T.; Selig, M.; Pashkin, A.; Winnerl, S.; Katzer, M.; Arora, H.; Erbe, A.; Patanè, A.; Kudrynskyi, Z. R.; Kovalyuk, Z. D.; Baldassarre, L.; Knorr, A.; Helm, M.; Schneider, H.

A promising route for the development of new technology is to use terahertz radiation to modulate the optical properties of semiconductors. Here we demonstrate the dynamical control of photoluminescence (PL) emission in few-layer InSe using picosecond terahertz pulses. We observe a strong PL quenching (up to 50%) after the arrival of the terahertz pulse followed by a reversible recovery of the emission on the time scale of 50ps at T =10K.Microscopic calculations reveal that the origin of the photoluminescence quenching is the terahertz absorption by photo-excited carriers: this leads to a heating of the carrier distribution that reduces the overlap of the hole and electron wavefunctions in the proximity of the band edges and, therefore, the luminescence. By numerically evaluating the Boltzmann equation, we are able to clarify the individual roles of optical and acoustic phonons in the subsequent cooling process. The same PL quenching mechanism is expected in other van der Waals semiconductors and the effect will be particularly strong for materials with low carrier masses and long carrier relaxation time, which is the case for InSe. This work gives a solid background for the development of opto-electronic applications based on InSe, such as THz detectors and optical modulators.

Keywords: 2D materials; InSe; photoluminescence; hot carrier response

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Permalink: https://www.hzdr.de/publications/Publ-34205
Publ.-Id: 34205


Standalone extended gate FET-based multiplexed sensing platform

Janićijević, Ž.; Nguyen Le, T. A.; Baraban, L.

Reliable biosensing is crucial in demanding fields such as theranostics and drug discovery. Multiplexing can improve biosensing performance and stability by enabling simultaneous multimarker sensing, more accurate differential measurements, and robust measurement statistics. Biosensing platforms based on field-effect transistors (FETs) comprising extended gate (EG) as a disposable cost-effective sensing element and reusable FET transducer are widely used for electrical label-free detection of biological and chemical analytes. EG electrodes can be modified to detect various analytes while allowing for easy integration of many sensing elements within the same chip. Useful features of EG open the possibility for multiplexed analyte sensing with an EG electrode array and a single FET transducer. Current EG FET-based platforms do not include large-scale multiplexing and rely on external modules such as specialized instruments for electrical measurements and bulky reference electrodes. We present the concept of a standalone EG FET platform for multiplexed sensing based on custom-built electronics interfaced with the EG chip comprising a common integrated reference electrode and microfluidic reservoir. Arduino Uno board enables the digital control of the reed relay-based multiplexing module and FET transducer readout circuit. Readout of the sensor signal is performed by sweeping in constant charge mode. Our platform is a practical and versatile laboratory tool adaptable for sensing different analytes.

  • Poster
    NanoNet+ Annual Workshop 2021, 21.-23.09.2021, Klingenberg, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-34204
Publ.-Id: 34204


Flashing Feed and Mist Eliminator Performance at Critical Fluid Properties

Döß, A.; Schubert, M.; Schleicher, E.; Flegiel, F.; Hampel, U.

The design and construction of thermal separation equipment for processing mixtures with critical fluid properties, i.e. low surface tensions and viscosities, is challenging. Conventional design rules are hardly applicable and experimental data are limited. The corresponding design uncertainties lead to costly safety margins and oversized equipment. A separation column mockup with refrigerant cycle setup at our TOPFLOW laboratory allows studying isenthalpic feed flashing and knitted mesh separation capacities at such critical conditions. Liquid surface tension and viscosities can reach below 10 mN/m and 0.5 mPas, respectively, at vapor-liquid density differences between 1400 and 937 kg/m³. This study provides a comprehensive analysis of morphologies in the feed pipe evolving downstream a flash valve. Additionally, knitted mesh flooding points were determined and utilized for a modified design approach for mist eliminators.

Keywords: Critical fluid parameters; Refrigerant cycle; Two-phase feed; Droplet separation

  • Contribution to proceedings
    The 12th international conference Distillation & Absorption 2022, 18.-21.09.2022, Toulouse, Frankreich
    Proceedings of the 12th international conference Distillation & Absorption 2022
  • Poster
    The 12th international conference Distillation & Absorption 2022, 19.-21.09.2022, Toulouse, France

Permalink: https://www.hzdr.de/publications/Publ-34203
Publ.-Id: 34203


Improved Germanium photoswitch for cavity dumping of a free-electron laser

Rana, R.; Klopf, J. M.; Ciano, C.; Singh, A.; Winnerl, S.; Schneider, H.; Helm, M.; Pashkin, O.

We demonstrate an optical switch based on gold implanted germanium (Ge:Au) suitable for cavity dumping of a free-electron laser (FEL). We achieve a switching contrast of more than 50 % in a broad range of FEL wavelengths from 6 to 90 µm. A linear relationship between the switching fluence and the frequency of the FEL optical field supported by our simulation highlights the role of a photoinduced finite sub-µm thickness of the reflecting plasma layer. The plasma switch exhibits negligible absorption of the FEL radiation in the ʻoffʼ state and requires only a moderate thermoelectric cooling at incident FEL power of several Watts.

Keywords: Free eletron laser; Photoswitch; Ion implantation; Terahertz radiation

Related publications

  • Contribution to proceedings
    46th International Conference on Infrared, Millimeter and Terahertz Waves (IRMMW-THz) 2021, 29.08.-03.09.2021, Chengdu, China

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Permalink: https://www.hzdr.de/publications/Publ-34202
Publ.-Id: 34202


Self-driven Broadband Photodetector Based on MoSe2/FePS3 Van der Waals n-p Type-II Heterostructures

Duan, J.; Chava, P.; Ghorbani Asl, M.; Lu, Y.; Erb, D.; Hu, L.; Echresh, A.; Rebohle, L.; Erbe, A.; Krasheninnikov, A.; Helm, M.; Zeng, Y.-J.; Zhou, S.; Prucnal, S.

2D van der Waals materials with broad-band optical absorption are promising candidates for next-generation UV-vis-NIR photodetectors. FePS3, one of the emerging antiferromagnetic van der Waals materials with a wide bandgap and p-type conductivity, has been reported as an excellent candidate for UV optoelectronics. However, a high sensitivity photodetector with a self-driven mode based on FePS3 has not yet been realized. Here, we report a high-performance and self-powered photodetector based on multilayer MoSe2/FePS3 type-II n-p heterojunction with a working range from 350 to 900 nm. The presented photodetector, operating at zero bias and at room temperature under ambient conditions, exhibits the maximum responsivity (Rmax) of 52 mA W-1 and external quantum efficiency (EQEmax) of 12% at 522 nm, which are better than the characteristics of its individual constituents and many other photodetectors made of 2D heterostructures. The high performance of MoSe2/FePS3 is attributed to the built-in electric field in the MoSe2/FePS3 n-p junction. Our approach provides a promising platform for broadband self-driven photodetector applications.

Keywords: Molybdenum diselenide; Iron Phosphorus Trisulfide; Van der Waals heterojunction; Broadband photodetector; Type-II band alignment

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Permalink: https://www.hzdr.de/publications/Publ-34200
Publ.-Id: 34200


Ores drive operations: Economic geology is the foundation for geometallurgy (geomet)

Olson Hoal, K. E.; Frenzel, M.

Economic geology and geometallurgy are intimately linked. Geologists understand the value in knowing the details of ore variability, the formation of mineral deposits, the continuity and the spatial distribution of ore types, and the mineral and textural characteristics that control grades. Beyond exploration and discovery, however, explorers may not recognize that the geological knowledge developed around a mineral prospect is also of great value to the miners and metallurgists, reclamation and environmental specialists, and economists and investors who are interested in developing the discovery. Geometallurgy is the interdisciplinary method that links geological, mineralogical and geochemical characteristics of mineral deposits to the mining, processing, and metallurgical activities that are involved in the development of mines. Geometallurgy is not a new field, but recent developments in analytical capabilities and the ability to conduct predictive, statistical data analysis and modeling of very large data sets have made geometallurgy an impactful and widely used method for optimizing mining operations. While there are many approaches, depending upon the nature of the ore deposit and the mine operating conditions and goals, the most important step explorers can take is to establish partnerships with the other areas of specialization in the project (mining, metallurgy, environmental, economics) and work together to understand the critical factors to use in order to best develop the deposit. Representative sampling of geological variability and understanding the controls of throughput and recovery in the mining operation are fundamental to making projects more effective. Here, we describe some of the technical drivers of geometallurgy as well as workflows and outcomes of which explorers should be aware. For exploration and prefeasibility timelines, information on spatial ore characteristics can provide some preliminary assessment of the processibility of a deposit. These steps can be taken in advance of, during, and in partnership with mine designers and plant flowsheet developers and may help avoid large capital expenditures made on erroneous assumptions of ore characteristics.

Permalink: https://www.hzdr.de/publications/Publ-34196
Publ.-Id: 34196


Global tellurium supply potential

Nassar, N.; Kim, H.; Frenzel, M.; Moats, M.; Hayes, S.

The transition towards renewable energy generation requires increasing quantities of nonfuel mineral commodities, including tellurium (Te) used in cadmium-telluride based thin-film photovoltaics. While demand for Te may be poised to increase markedly, the potential to increase Te supply is not well-understood. In this analysis, we provide detailed by-country estimates of the quantity of Te contained in anode slimes generated by electrolytic copper (Cu) refining between 1986 and 2018, including uncertainties. We do this by combining all available data on facility-level Cu cathode production and Cu anode compositions. For 2018, the results of Monte Carlo simulations indicate a total of 1,930 t of Te was contained in anode slimes, with the 95% confidence interval ranging from 1,500 to 2,770 t. This quantity is nearly quadruple the reported Te production for the same year (~ 500 t), indicating a great potential to increase Te supplies. The results also indicate that China is not only the largest Te producer but also has the greatest potential to increase Te supplies. However, most of the Te produced by or potentially recoverable from Chinese refineries appears to come from Cu ores mined elsewhere. Translating the physical availability of Te into economic availability requires further research into the costs associated with Te recovery. Nevertheless, this study represents an important development in the assessment of Te supply potential and, further, presents a methodology that could be extended to other byproduct critical elements.

Keywords: critical minerals; solar photovoltaics; minor metals; byproducts; copper

Permalink: https://www.hzdr.de/publications/Publ-34195
Publ.-Id: 34195


The Dyadic Radionuclide System 60Fe / 53Mn to Distinguish Interstellar from Interplanetary 60Fe

Koll, D.; Faestermann, T.; Korschinek, G.; Leya, I.; Merchel, S.; Wallner, A.

The discovery of live 60Fe in a deep-sea crust with proposed interstellar origin followed by evidence
for elevated interplanetary 3He in the same crust raised the question on how to unambiguously identify the true
production site of the identified 60Fe. Here, we show the implementation of the dyadic radionuclide system
60Fe / 53Mn to serve as a tool for the identification of surplus interstellar 60Fe over interplanetary production.
The recent updates in experimental 60Fe and 53Mn data from iron meteorites as well as in production rate models
confirm the validity and robustness of this dyadic system for future applications.

Permalink: https://www.hzdr.de/publications/Publ-34194
Publ.-Id: 34194


Kinetic Monte-Carlo simulation of exciton hopping: Urbach-tails in gas-molecule decorated MoSe2

Wagner, C.; Schwuchow, M.; Venanzi, T.; Schneider, H.; Winnerl, S.; Thränhardt, A.

We quantitatively investigate disorder parameters of gas-molecule decorated monolayer MoSe2. This material system is interesting because disorder may be introduced and removed at will by regulating the number of adsorbed gas molecules through laser annealing. These molecules electrostatically trap excitons leading to localized defect states, which are exponentially distributed in energy. Here, experiments are described by kinetic Monte-Carlo simulations, in summary enabling richer studies than within crystalline materials with a fixed degree of disorder. We find that the surface coverage of the MoSe2 may reach up to one molecule per 2nm2 and that the density of adsorbed molecules depends on the laser power by a power law.

Keywords: two-dimensional materials; dichalcogenide; molybdenum selenide; optical properties; low temperature; disorder; Urbach tail

Permalink: https://www.hzdr.de/publications/Publ-34193
Publ.-Id: 34193


Complex quantum dots in III-As nanowires

Hilliard, D.; Tauchnitz, T.; Hübner, R.; Schneider, H.; Helm, M.; Dimakis, E.

Single quantum dots embedded in the core of freestanding semiconductor nanowires grown directly on Si offer a novel and promising scheme for the realization of on-demand sources of single photons or entangled photon pairs in quantum technology systems. The primary challenge in using the nanowire growth medium lies in reducing the compositional grading effect of the axial barrier’s constituent materials.
Here, we have investigated the Ga-catalyzed vapor-liquid-solid growth mechanism and optical properties of axial GaAs quantum dots confined between two Al(x)Ga(1-x)As/Al(y)Ga(1-y)As short-period superlattices inside GaAs/InxAl(1-x)As and GaAs/Al(x)Ga(1-x)As core/shell nanowires. By increasing the interfacial abruptness between the axial barrier and quantum dot, its relevance was highlighted by significant improvements in the quantum dot emission linewidth. Using tensile strain, the tuneabilty of the quantum dot emission energy was clearly demonstrated across a wide range of wavelengths by employing lattice mismatched InxAl1-xAs shells as radial barriers, showing the potential for telecom band access.

Keywords: Nanowire; Quantum dot; Superlattice; Interface; Strain

Related publications

  • Poster (Online presentation)
    From Matter to Materials and Life (MML), 22.-24.11.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-34192
Publ.-Id: 34192


Complex quantum dots in III-As nanowires

Hilliard, D.; Tauchnitz, T.; Hübner, R.; Schneider, H.; Helm, M.; Dimakis, E.

Single quantum dots embedded in the core of freestanding semiconductor nanowires grown directly on Si offer a novel and promising scheme for the realization of on-demand sources of single photons or entangled photon pairs in quantum technology systems. Here, we have investigated the growth mechanism and optical properties of axial quantum dots embedded in GaAs nanowires grown in self-catalyzed vapor-liquid-solid mode while demonstrating the tuneabilty of their emission energy across a wide range of wavelengths with the potential for telecom band access.
We have incorporated GaAs complex quantum dots inside GaAs/In(x)Al(1-x)As and GaAs/Al(x)Ga(1-x)As core/shell nanowires grown via our nanowire growth technique called droplet-confined alternate pulsed-epitaxy (DCAPE)[1] (an adaptation of conventional molecular beam epitaxy (MBE)), which grants precise control over the axial growth rate and droplet composition. Using a combination of conventional MBE and DCAPE the growth of highly symmetrical quantum dots, as little as 10 nm in diameter and just a few nanometers in height, were made possible. Strong axial confinement was achieved in the form of a double axial heterostructure by incorporating two Al(x)Ga(1-x)As/Al(y)Ga(1-y)As short-period superlattices separated by a thin GaAs segment (figure 1(a)). The complexity of our quantum dots is derived from the unique possibility of using different ternary alloys for the axial and radial confinement. By introducing a latticed mismatched ternary alloy shell as the radial barrier (In(x)Al(1-x)As), we demonstrated controlled hydrostatic strain induced redshifts of the highly polarized quantum dot emission energy by adjusting the In content of the shell. For 39% In we measured a redshift in the quantum dot emission of 320 meV, from an unstrained quantum dot reference (Al(x)Ga(1-x)As shell), as shown by the photoluminescence measurements in figure 1 (b).
To optimize the emission quality, the compositional grading effect of the constituent superlattice materials across the interfaces must be addressed. High-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and nanowire growth models were utilized to gain an understanding of the compositional grading mechanism at the quantum dot/superlattice interface. We found that interfacial sharpness increases significantly by reducing the superlattice growth temperature and nanowire radius. Notwithstanding, limitations in what can be achieved ensue and possible strategies to overcome them will be presented.

[1] Balaghi et al., Nano Lett. 16, 4032 (2016)

Keywords: Nanowire; Quantum dot; Superlattice; Interface; Strain

Related publications

  • Lecture (Conference) (Online presentation)
    24th International Conference on Electronic Properties of Two-Dimensional Systems / 20th International Conference on Modulated Semiconductor Structures (EP2DS-24/MSS-20), 31.10.-05.11.2021, Toyama, Japan

Permalink: https://www.hzdr.de/publications/Publ-34191
Publ.-Id: 34191


Al(x)Ga(1-x)As /Al(y)Ga(1-y)As axial short-period superlattices in self-catalyzed nanowires

Hilliard, D.; Tauchnitz, T.; Hübner, R.; Schneider, H.; Helm, M.; Dimakis, E.

Short-period superlattices have diverse functionality in electronic and optoelectronic devices. Implementing such systems as axial heterostructures in freestanding semiconducting nanowires further broadens the scope of potential applications, for example: distributed Bragg reflectors, high-efficiency light-emitting diodes, and quantum dot heterostructures. The challenge, however, lies in reducing the compositional grading effect of the constituent superlattice materials across the interfaces in nanowires grown in vapor-liquid-solid mode.
Here, our previously developed nanowire growth technique called droplet-confined alternate pulsed-epitaxy[1] (an adaptation of conventional molecular beam epitaxy), which grants precise control over the axial growth rate and droplet composition, was employed to grow Al(x)Ga(1-x)As/Al(y)Ga(1-y)As axial superlattices in self-catalyzed GaAs nanowires with diameters as thin as 25 nm. High-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, and growth models were utilized to gain an understanding of the compositional grading mechanism. By varying several growth parameters involving growth temperature, nanowire diameter, and droplet contact angle, the link between them and the superlattice characteristics was explored. We found that interfacial abruptness increases significantly by reducing the superlattice growth temperature and nanowire radius. Moreover, we studied the impact of an unstable contact angle on the superlattice growth rate, showing good agreement with analytical growth models and demonstrating the importance of growth rate stability in obtaining reproducible Al contents across successive superlattice periods.
Finally, we confirmed with monolayer resolution, controlled Al contents in the whole compositional range and superlattice period widths of just a few monolayers. Notwithstanding, limitations in what can be accomplished are present and possible strategies to overcome them will be presented. The quality of our short-period superlattices was successfully tested via their employment as barriers in quantum dot nanowire heterostructures.

[1] Balaghi et al., Nano Lett. 16, 4032 (2016)

Keywords: Nanowire; Quantum dot; Superlattice; Interface

Related publications

  • Lecture (Conference) (Online presentation)
    European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2021), 13.-17.09.2021, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-34190
Publ.-Id: 34190


Al(x)Ga(1-x)As /Al(y)Ga(1-y)As axial short-period superlattices in self-catalyzed nanowires

Hilliard, D.; Tauchnitz, T.; Hübner, R.; Schneider, H.; Helm, M.; Dimakis, E.

Shrt abstract:

Using our nanowire growth technique called droplet-confined alternate pulsed-epitaxy, which provides precise control over the axial growth rate and droplet composition, the growth mechanism of self-catalyzed GaAs epitaxial nanowires containing AlxGa1-xAs/AlyGa1-yAs axial short-period superlattices, was systematically examined. Significant increases in interfacial abruptness were confirmed by reducing the nanowire diameter and superlattice growth temperature. Additionally, we found that an unstable droplet contact angle impacts the superlattice growth rate considerably. The unique versatility of our short-period superlattices was tested by using them as axial barriers for GaAs quantum dot heterostructures embedded in nanowires. Furthermore, encapsulating the nanowire in lattice-mismatched shells operating as radial barriers, we demonstrated the tuneabilty of the quantum dot emission energy via strain engineering.

Long abstract
Short-period superlattices have diverse functionality in electronic and optoelectronic devices. Implementing such systems as axial heterostructures in freestanding semiconducting nanowires further broadens the scope of potential applications, for example: distributed Bragg reflectors, high-efficiency light-emitting diodes, and quantum dot heterostructures. The challenge, however, lies in reducing the compositional grading effect of the constituent superlattice materials across the interfaces in nanowires grown in self-catalyzed vapor-liquid-solid mode.
Here, our previously developed nanowire growth technique called droplet-confined alternate pulsed-epitaxy[1] (an adaptation of conventional molecular beam epitaxy), which grants precise control over the axial growth rate and droplet composition, was employed to grow Al(x)Ga(1-x)As/Al(y)Ga(1-y)As axial superlattices in self-catalyzed GaAs nanowires with diameters as thin as 20 nm. High-angle annular dark-field scanning transmission electron microscopy (figure 1(a)), energy-dispersive X-ray spectroscopy, and growth models were utilized to gain an understanding of the compositional grading mechanism. By varying several growth parameters involving growth temperature, nanowire diameter, and droplet contact angle, the link between them and the superlattice characteristics was explored. We found that interfacial abruptness increases significantly by reducing the superlattice growth temperature and nanowire radius. Moreover, we studied the impact of an unstable contact angle on the superlattice growth rate, showing good agreement with analytical growth models and demonstrating the importance of growth rate stability in obtaining reproducible Al contents across successive superlattice periods. We confirmed with monolayer resolution, controlled Al contents in a wide compositional range and superlattice period widths of just a few monolayers (figure 1 (b)).
The quality of our short-period superlattices was successfully tested via their employment as axial barriers in quantum dot nanowire heterostructures (figure 1 (c)). Additionally, by introducing a lattice-mismatched ternary alloy shell as the radial barrier (In(x)Al(1-x)As in this case), we demonstrated controlled strain-induced redshifts of the quantum dot emission energy by adjusting the In content of the shell. For 39% In, we measured a redshift in the quantum dot emission of 180 meV as shown by the photoluminescence measurements in figure 1 (d). Notwithstanding, limitations in what can be accomplished are present and possible strategies to overcome them will be presented.

[1] Balaghi et al., Nano Lett. 16, 4032 (2016)

Keywords: Nanowire; Quantum dot; Superlattice; Interface; Strain

Related publications

  • Lecture (Conference) (Online presentation)
    21st International Conference on Molecular Beam Epitaxy (21st ICMBE), 06.-09.09.2021, Puerto Vallarta, Mexico

Permalink: https://www.hzdr.de/publications/Publ-34189
Publ.-Id: 34189


Characterization of protein corona formation on nanoparticles via the analysis of dynamic interfacial properties: Bovine serum albumin - silica particle interaction

Shourni, S.; Javadi, A.; Hosseinpour, N.; Bahramian, A.; Raoufi, M.

Protein corona adsorption layers on nanoparticle surfaces, dispersed in biological fluids, can significantly change the interfacial interactions, reactivity, and mobility of the original nanoparticles designed as a drug carrier or existing as bioaerosols, bacteria, or viruses. The evaluation of the level of interactions (hard/soft corona), dispersion stability, and the ratio of the attached proteins per nanoparticle are essential parameters for the characterization of the protein corona formation on nanoparticle (PCN). In spite of development of several experimental techniques for this purpose, still more powerful, economical and fast measuring techniques are needed to work in-situ at original solution samples (near the physiological conditions), without requirement of additional sample preparation which can change the quality/quantity of the original interactions. In this study, a novel experimental protocol based on the analysis of dynamic interfacial properties (ADIP) is developed for in-situ evaluation of the protein–nanoparticle interactions under original conditions. For this purpose, dynamic surface tension and interfacial elasticity values of the bovine serum albumin (BSA) solutions alone and in mixed solutions with silica nanofluids are measured using drop profile analysis tensiometry. A considerable difference between the dynamic surface tension of BSA and protein corona solutions (BSA + SiO2 NPs complexes) demonstrates significant adsorption of the protein molecules at nanoparticles, confirmed by Fourier Transform Infrared Spectroscopy (FTIR) analysis. PCN complexes illustrate much slower kinetics of adsorption due to a smaller diffusion coefficient according to their larger size. The free proteins available in the solution were estimated considering early-time values of the dynamic surface tension, used for estimation of the adsorbed proteins per unit area of the silica surface (mol/cm2), considering the initial protein concentration in the bulk. The results show very good agreement with others’ results provided by AFM, DLS, UV–vis Spectroscopy, Multi-Parametric Surface Plasmon Resonance (MP-SPR), and Quartz Crystal Microbalance (QCM). Our novel experimental protocols and data analysis, demonstrates promising results for differentiation of the hard and soft corona layers, and unique for soft corona layer recognition, which is difficult by other available techniques, due to quick disturbances of weak protein-protein interaction in soft corona. The measured interfacial elasticity values confirm PCN formation and provides additional information for better differentiations of the corona layers.

Keywords: Protein corona on nanoparticle (PCN); Bovine serum albumin (BSA); SiO2 nanoparticles; Dynamic surface tension; Kinetics of adsorption; Interfacial elasticity; Drug delivery

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Permalink: https://www.hzdr.de/publications/Publ-34188
Publ.-Id: 34188


Experimental techniques to study protein–surfactant interactions: New insights into competitive adsorptions via drop subphase and Interface exchange

Javadi, A.; Dowlati, S.; Shourni, S.; Miller, R.; Kraume, M.; Kopka, K.; Eckert, K.

Experimental techniques to study protein–surfactant interactions: New insights into competitive adsorptions via drop subphase and Interface exchange

Keywords: Protein–surfactant interactions; Mixed adsorbed layers; Coaxial double capillary; Profile analysis tensiometry; Dynamic surface properties; Bovin serum albumin; Lysozyme; Lipase Enzyme

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Permalink: https://www.hzdr.de/publications/Publ-34186
Publ.-Id: 34186


Studies of Pyrroloquinoline Quinone Species in Solution and in Lanthanide-dependent Methanol Dehydrogenases

Al Danaf, N.; Kretzschmar, J.; Jahn, B.; Singer, H.; Pol, A.; Op Den Camp, H. J. M.; Steudtner, R.; Lamb, D. C.; Drobot, B.; Daumann, L. J.

Pyrroloquinoline quinone (PQQ) is a redox cofactor in calcium- and lanthanide-dependent alcohol dehydrogenases that has been known and studied for over 40 years. Despite its long history, many questions regarding its fluorescence properties, speciation in solution and in the active site of alcohol dehydrogenase remain open. Here we investigate the effects of pH and temperature on the distribution of different PQQ species (H₃PQQ to PQQ³⁻ as well as water adducts and in complex with lanthanides (Lns)) using NMR and UV-Vis spectroscopy as well as time-resolved laser-induced fluorescence spectroscopy (TRLFS). Using a europium derivative from a new, recently-discovered class of lanthanide-dependent methanol dehydrogenase (MDH) enzymes, we utilized two techniques to monitor Ln binding to the active sites of these enzymes. Using TRLFS, we were able to follow Eu(III) binding directly to the active site of MDH using its luminescence and could quantify three Eu states: Eu in the active site of MDH, but also in solution as PQQ-bound Eu and in the aquo-ion form. Additionally, we used the antenna effect to study PQQ and simultaneously Eu in the active site.

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Permalink: https://www.hzdr.de/publications/Publ-34185
Publ.-Id: 34185


Data publication: Terahertz-Induced Energy Transfer from Hot Carriers to Trions in a MoSe2 Monolayer

Venanzi, T.; Selig, M.; Winnerl, S.; Pashkin, A.; Knorr, A.; Helm, M.; Schneider, H.

Orginaldaten der in der Publikation verwendet Bilder

Keywords: 2D materials; terahertz; hot carriers; trions; MoSe2

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Permalink: https://www.hzdr.de/publications/Publ-34184
Publ.-Id: 34184


Terahertz-Induced Energy Transfer from Hot Carriers to Trions in a MoSe2 Monolayer

Venanzi, T.; Selig, M.; Winnerl, S.; Pashkin, A.; Knorr, A.; Helm, M.; Schneider, H.

Interaction of terahertz (THz) radiation with van der Waals semiconductors represents a considerable interest for optoelectronic applications. Here we report a redshift (around 1 meV) of the trion resonance in the MoSe2 monolayer induced by picosecond THz pulses. As its origin, we identify the kinetic excess energy gained by hot carriers due to absorption of THz light which is transferred during the formation of trions. By performing time-resolved measurements, we have determined the electron cooling time (tau = 70 ps) and estimated the absorption at 7.7 THz (α = 0.3%). A quantitative model based on the Heisenberg equation of motion explains the experimental observations and can reproduce the data with good accuracy. The present work gives important insights for understanding the trions in van der Waals semiconductors and their interaction with hot electrons driven by THz radiation.

Keywords: 2D materials; terahertz; hot carriers; trions; MoSe2

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Permalink: https://www.hzdr.de/publications/Publ-34182
Publ.-Id: 34182


Ultrafast Pump-Probe Spectroscopy of BaFe₂As₂ under High Pressures

Fotev, I.; Aswartham, S.; Büchner, B.; Schneider, H.; Helm, M.; Pashkin, O.

An important member of the iron-based high-temperature superconductor family, BaFe₂As₂ undergoes a transition to a spin-density wave (SDW) state on cooling below 137 K. Under application of external pressure the SDW transition temperature gradually decreases, and the SDW phase gets completely suppressed above 3 GPa, enabling the onset of superconductivity. Such phenomenon is often referred to as quantum phase transition. Optical pump-probe spectroscopy has been used previously to investigate the dynamics of the SDW and the superconducting order at various temperatures and different doping levels. However, a direct study of the quantum phase transition induced by external high pressure has not been carried out until now.
In our study, pump and probe pulses with the central wavelength of 800 nm were focused onto the sample inside the diamond anvil cell, mounted inside a cryostat. The reflected probe signal was collected using a confocal microscopy scheme. From the measured pump-probe traces the quasiparticle lifetimes and the condensation energy of the SDW state were obtained at various pressures up to 4.4 GPa and the fixed temperature of 8 K. The SDW condensation energy decreases with pressure, and already below 4.4 GPa the SDW state is completely suppressed. At the same time, the decrease of the condensation energy is accompanied by the increase of the quasiparticle lifetimes. Since the lifetimes should be inversely proportional to the SDW gap energy, this critical slowing down of the quasiparticle relaxation dynamics confirms the vanishing of the SDW gap at the quantum phase transition.

  • Poster
    International Conference on Low Energy Electrodynamics in Solids (LEES), 28.06.-08.07.2021, Portland, Maine, USA

Permalink: https://www.hzdr.de/publications/Publ-34181
Publ.-Id: 34181


BaFe₂As₂ Investigated by Pump-Probe Spectroscopy under High Pressures

Fotev, I.; Aswartham, S.; Büchner, B.; Schneider, H.; Helm, M.; Pashkin, O.

We utilize pump-probe spectroscopy at pressures in the GPa range to measure the quasiparticle relaxation dynamics of BaFe₂As₂. The results reveal the pressure dependences of the spin-density wave condensate energy and the photoexcited quasiparticle lifetimes.

  • Contribution to proceedings
    CLEO Conference, 09.-14.05.2021, San Jose, California, USA: OSA
  • Lecture (Conference) (Online presentation)
    CLEO Conference, 09.-14.05.2021, San Jose, California, USA

Permalink: https://www.hzdr.de/publications/Publ-34180
Publ.-Id: 34180


Subsecond Thermal Processing Using Flash Lamps for the Nanoscale and Beyond

Skorupa, W.; Prucnal, S.; Cherkouk, C.; Zhou, S. Q.; Rebohle, L.

Undoubtedly, thermal activation processes in advanced materials technologies underwent a dramatic development during the last 40 years. Especially, the use of lasers and lamps allowed the move from long time (10 min to several hours) to short time (several fs-1 min) annealing approaches. From the application viewpoint, the main driver was semiconductor-based chip technology. After 1980, annealing with halogen lamp arrangements allowed annealing times in the range of 10 min and below arriving in advanced chip technology the limit of about 1 sec around the year 2000. To reach annealing times down to the ns range lasers and xenon-filled flash lamps came on stream. In this talk a short introduction to flash lamp annealing technology will be presented together with a few promising research approaches: dissolution of point defect clusters, doping of 2D materials, lithium battery electrode engineering.

Keywords: subsecond thermal processing; flash lamp annealing; silicon; 2D materials; lithium battery electrode; point defects

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  • Lecture (Conference)
    International Symposium on Nanostructure Research, 19.-21.09.2021, Leoben, Oesterreich

Permalink: https://www.hzdr.de/publications/Publ-34179
Publ.-Id: 34179


Anisotropic nonlinear terahertz response of bilayer graphene

Seidl, A.; Anvari, R.; Dignam, M. M.; Richter, P.; Seyller, T.; Schneider, H.; Helm, M.; Winnerl, S.

We studied the pump-induced anisotropy of the intraband excitation
in bilayer graphene in degenerate terahertz pump-probe experiments.
The differential transmission signal increases approximately linearly
with the excitation field, in qualitative agreement with our microscopic
model.

Keywords: bilayer graphene; pump-probe; density matrix formalism; anisotropy; terahertz

Related publications

  • Lecture (Conference) (Online presentation)
    The European Conference on Lasers and Electro-Optics, 23.06.2021, digital, digital

Permalink: https://www.hzdr.de/publications/Publ-34178
Publ.-Id: 34178


Spectroscopy on Landau-quantized charge neutral graphene

Seidl, A.; Lara-Avila, S.; Orlita, M.; Wyzula, J.; Anvari, R.; Dignam, M.; Schneider, H.; Helm, M.; Winnerl, S.

Landau level spectroscopy is a powerful tool to determine the Fermi velocity in Dirac-like
materials. In our study, we investigate the optical properties of charge neutral graphene on
SiC in presence of strong magnetic fields applied perpendicularly to the sample. For details
about this neutral large-area monolayer graphene, see [1]. We measured the linear
transmission in dependence of the magnitude of the magnetic fields from 0 to 8 T for photon
energies up to 100 meV. We observe a broad resonance resulting from the LL-1(LL0)→LL0(LL1)
transition. It corresponds to a low Fermi velocity of 0.85x106 m/s, which is the limit of low
electron-electron interaction [2]. The efficient screening is supported by the dielectric
environment of the polymer layer on top of the graphene [3]. We support our understanding
of the low Fermi velocity by density functional theory (DFT) calculations. In addition, we
studied the dynamics of the LL-1→LL0 and LL0→LL1 transitions using circularly polarized light
at 75 meV. We observe a fast decay of about 10 ps. Addressing the transitions with all four
combinations of pump and probe beam polarizations, we obtain only one negative
differential transmission signal. Following [4], we attribute this and the fast decay to very
efficient Auger scattering processes. The observed fluence dependence of the relaxation
with time constants decreasing with increasing fluence is also in accordance with this
interpretation.
[1] H. He, K. H. Kim, A. Danilov et al., Nat. Comm., 9, (2018) 3956.
[2] D. Siegel, C.-H. Park, C. Hwang et al., PNAS, 108, 28 (2011) pp. 11365-11369.
[3] P. Yadav and S. Ghosh, AIP Conference Proceedings, 1665, (2015) 050075.
[4] M. Mittendorff, F. Wendler, E. Malic et al., Nat. Phys., 11 (2015) pp. 75-81.

Keywords: charge-neutral; graphene; pump-probe; screening

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  • Lecture (Conference)
    Graphene 2021, 28.10.2021, Grenoble, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-34177
Publ.-Id: 34177


Coulomb-mediated crosstalk between selection-rule separated pairs of Landau-level transitions in graphene

Seidl, A.; Wyzula, J.; Orlita, M.; Kunc, J.; Schneider, H.; Helm, M.; Winnerl, S.

We investigate the carrier dynamics in the system of Landau-levels LL-2, LL-1, LL1, and LL2 of multi-layer graphene on SiC at 10 K. We perform degenerate pump-probe experiments at 75 meV with circularly polarized radiation addressing the transitions LL-2 → LL1 and LL-1 → LL2 selectively. In the co-polarized configurations, we observe bleaching of the LL-2 → LL1 and LL-1 → LL2 transition, respectively. We discuss the dependence of scattering on the number of photoexcited carriers. The existence of a pump-probe signal in cross-polarized configurations points towards thermalization of carriers across the Landau ladder on a ps timescale.

Keywords: graphene; Landau levels; pump-probe; carrier dynamics

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  • Poster (Online presentation)
    Graphene Week 2021, 21.09.2021, digital, digital

Permalink: https://www.hzdr.de/publications/Publ-34176
Publ.-Id: 34176


Data publication: Optimal test-kit-based intervention strategy of epidemic spreading in heterogeneous complex networks

Ghosh, S.; Senapati, A.; Chattopadhyay, J.; Hens, C.; Ghosh, D.

This contains all the python script and related data required for reproducing the results presented in the article

Keywords: Infectious disease modelling; Test-kit; Complex network; Intervention strategy

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Permalink: https://www.hzdr.de/publications/Publ-34174
Publ.-Id: 34174


Optimal test-kit-based intervention strategy of epidemic spreading in heterogeneous complex networks

Ghosh, S.; Senapati, A.; Chattopadhyay, J.; Hens, C.; Ghosh, D.

We propose a deterministic compartmental model of infectious disease that considers the test kits as an important ingredient for the suppression and mitigation of epidemics. A rigorous simulation (with an analytical argument) is provided to reveal the effective reduction of the final outbreak size and the peak of infection as a function of basic reproduction number in a single patch. Furthermore, to study the impact of long and short-distance human migration among the patches, we consider heterogeneous networks where the linear diffusive connectivity
is determined by the network link structure. We numerically confirm that implementation of test kits in a fraction of nodes (patches) having larger degrees or betweenness centralities can reduce the peak of infection (as well as the final outbreak size) significantly. A next-generation matrix-based analytical treatment is provided to find out the critical transmission probability in the entire network for the onset of epidemics. Finally, the optimal intervention strategy is validated in two real networks: the global airport network and the transportation network of Kolkata, India.

Keywords: Infectious disease modelling; Test-kit; Complex network; Intervention strategy

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Permalink: https://www.hzdr.de/publications/Publ-34173
Publ.-Id: 34173


Data publication: Reservoir computing on epidemic spreading: A case study on COVID-19 cases

Ghosh, S.; Senapati, A.; Mishra, A.; Chattopadhyay, J.; Dana, S. K.; Hens, C.; Ghosh, D.

Python scripts and relevant data required for reproducing the figures in the article

Keywords: COVID-19; Mathematical modelling; Prediction; Machine Learning

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Permalink: https://www.hzdr.de/publications/Publ-34172
Publ.-Id: 34172


Reservoir computing on epidemic spreading: A case study on COVID-19 cases

Ghosh, S.; Senapati, A.; Mishra, A.; Chattopadhyay, J.; Dana, S. K.; Hens, C.; Ghosh, D.

A reservoir computing based echo state network (ESN) is used here for the purpose of predicting the spread
of a disease. The current infection trends of a disease in some targeted locations are efficiently captured by
the ESN when it is fed with the infection data for other locations. The performance of the ESN is first tested
with synthetic data generated by numerical simulations of independent uncoupled patches, each governed by the
classical susceptible-infected-recovery model for a choice of distributed infection parameters. From a large pool
of synthetic data, the ESN predicts the current trend of infection in 5% patches by exploiting the uncorrelated
infection trend of 95% patches. The prediction remains consistent for most of the patches for approximately 4 to 5
weeks. The machine’s performance is further tested with real data on the current COVID-19 pandemic collected
for different countries. We show that our proposed scheme is able to predict the trend of the disease for up to
3 weeks for some targeted locations. An important point is that no detailed information on the epidemiological
rate parameters is needed; the success of the machine rather depends on the history of the disease progress
represented by the time-evolving data sets of a large number of locations. Finally, we apply a modified version
of our proposed scheme for the purpose of future forecasting.

Keywords: COVID-19; Mathematical modelling; Prediction; Machine Learning

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Permalink: https://www.hzdr.de/publications/Publ-34171
Publ.-Id: 34171


Energy relaxation and electron-phonon coupling in laser-excited metals

Zhang, J.; Qin, R.; Zhu, W.; Vorberger, J.

The rate of energy transfer between electrons and phonons is investigated by a first principles framework for electron temperatures up to $T_e=50000$~K while considering the lattice at ground state. Two typical but differently complex metals are investigated, namely Aluminium and Copper. In order to reasonably take the electronic excitation effect into account, we adopt finite temperature density functional theory and linear response to determine the electron-temperature-dependent Eliashberg function and electron density of states. Of the three branch-dependent electron-phonon coupling strengths, the longitudinal acoustic mode plays a dominant role in the electron-phonon coupling for Aluminium for all temperatures considered here, but for Copper it only dominates above an electron temperature of $T_e=40000$~K. The second moment of the Eliashberg function and the electron phonon coupling constant at room temperature $T_e=315$~K show good agreement with other results. For increasing electron temperatures, we show the limits of the $T=0$ approximation for the Eliashberg function. Our present work provides a rich perspective on the phonon dynamics and this will help to improve insight into the underlying mechanism of energy flow in ultra-fast laser-metal interaction.

Keywords: electron-phonon; DFT; laser; laser-matter interaction; two-temperature model; relaxation; energy transfer

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Permalink: https://www.hzdr.de/publications/Publ-34170
Publ.-Id: 34170


Development and Biological Evaluation of the First Highly Potent and Specific Benzamide-Based Radiotracer [¹⁸F]BA3 for Imaging of Histone Deacetylases 1 and 2 in Brain

Clauß, O.; Schäker-Hübner, L.; Wenzel, B.; Toussaint, M.; Deuther-Conrad, W.; Gündel, D.; Teodoro, R.; Dukic-Stefanovic, S.; Ludwig, F.-A.; Kopka, K.; Brust, P.; Hansen, F. K.; Scheunemann, M.

The degree of acetylation of lysine residues on histones influences the accessibility of DNA and, furthermore, the gene expression. Histone deacetylases (HDACs) are overexpressed in various tumour diseases, resulting in the interest in HDAC inhibitors for cancer therapy. The aim of this work is the development of a novel ¹⁸F-labelled HDAC1/2-specific inhibitor with a benzamide-based zinc-binding group to visualize these enzymes in brain tumours by positron emission tomography (PET). BA3, exhibiting high inhibitory potency for HDAC1 (IC50 = 4.8 nM) and HDAC2 (IC50 = 39.9 nM), and specificity towards HDAC3 and HDAC6 (specificity ratios >230 and >2080, respectively), was selected for radiofluorination. The two-step one-pot radiosynthesis of [¹⁸F]BA3 was performed in a TRACERlab FX2 N radiosynthesizer by a nucleophilic aliphatic substitution reaction. The automated radiosynthesis of [¹⁸F]BA3 resulted in a radiochemical yield of 1%, a radiochemical purity of >96% and a molar activity between 21 and 51 GBq/µmol (n = 5, EOS). For the characterization of BA3, in vitro and in vivo experiments were carried out. The results of these pharmacological and pharmacokinetic studies indicate a suitable inhibitory potency of BA3, whereas the applicability for non-invasive imaging of HDAC1/2 by PET requires further optimization of the properties of this compound.

Keywords: histone deacetylase inhibitor; HDAC1/2-specific; radiochemistry; fluorine-18 labelling; positron emission tomography (PET); brain-penetration; glioblastoma; glioma

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Permalink: https://www.hzdr.de/publications/Publ-34169
Publ.-Id: 34169


Acquired resistance to irradiation or docetaxel is not associated with cross-resistance to cisplatin in prostate cancer cell lines

Donix, L.; Erb, H. H.; Peitzsch, C.; Dubrovska, A.; Pfeifer, M.; Thomas, C.; Fuessel, S.; Erdmann, K.

Purpose: Platinum chemotherapy can be considered to treat metastatic castration-resistant prostate cancer (mCRPC) with
features of neuroendocrine differentiation. However, platinum compounds are generally only applied after the failure of
multiple prior-line treatment options. This study investigated whether acquired resistance against ionizing radiation or doc-
etaxel chemotherapy—two commonly applied treatment modalities in prostate cancer—influences the cisplatin (CDDP)
tolerance in mCRPC cell line models.
Methods: Age-matched parental as well as radio- or docetaxel-resistant DU145 and PC-3 cell lines were treated with CDDP
and their sensitivity was assessed by measurements of growth rates, viability, apoptosis, metabolic activity and colony
formation ability.
Results: The data suggest that docetaxel resistance does not influence CDDP tolerance in all tested docetaxel-resistant cell
lines. Radio-resistance was associated with sensitization to CDDP in PC-3, but not in DU145 cells. In general, DU145 cells
tolerated higher CDDP concentrations than PC-3 cells regardless of acquired resistances. Furthermore, non-age-matched
treatment-naïve PC-3 cells exhibited significantly different CDDP tolerances.
Conclusion: Like patients, different mCRPC cell lines exhibit significant variability regarding CDDP tolerance. The presented
in vitro data suggest that previous radiation treatment may be associated with a moderate sensitization to CDDP in an isogenic
and age-matched setting. Therefore, previous radiotherapy or docetaxel chemotherapy might be no contraindication against
initiation of platinum chemotherapy in selected mCRPC patients.

Keywords: Cisplatin; Docetaxel; mCRPC; NEPC; Prostate cancer; Radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-34168
Publ.-Id: 34168


Efficient doping of TMDs using NH₃ plasma treatment

Li, Y.; Duan, J.; Helm, M.; Zhou, S.; Prucnal, S.

The precise control of dopant concentration and distribution in two-dimensional materials (2D), e.g. transition metal dichalcogenides (TMDs), is a major problem on the way to their successful application in modern nanoelectronics. Efficient doping can be achieved by substituting chalcogenide atoms with group V or VII atoms, intercalations or electrostatic doping. In the present work, both the optical and electrical properties of mechanically exfoliated 2D TMDs have been modified using NH₃ plasma treatment for 10 s followed by short-time annealing. After plasma treatment, the TMDs flakes were investigated by photoluminescence (PL) and Raman spectroscopies and current-voltage (I-V) characteristics. After NH₃ plasma treatment, the PL-peak intensity of the MoSe₂ monolayer degrades and shifts towards lower energy (higher wavelength) due to hydrogen doping. Annealing after plasma treatment releases hydrogen and the PL emission returns to normal. The same has been observed in Raman spectra. H-doping causes a shift of the main phonon modes due to the phonon-plasmon coupling, i.e. Fano effect. The I-V characteristics also clearly confirm the efficient hydrogen doping of the MoSe₂ monolayer. This work shows new insights into controllable doping in 2D materials.

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  • Poster
    European Materials Research Society 2021 Fall Meeting, 20.-23.09.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-34167
Publ.-Id: 34167


The design-construction interface of Ti₂.₅O₃ (010)/GaAs (001): minimizing the lattice mismatch and impeding ions diffusions

Zhou, Y.; Zhu, J.; Zhou, S.

Feasible interface lattice design is a really key issue for a high-quality hybrid of functional oxide thin films on GaAs semiconductor substrates. But interfacial defects induced by lattice mismatch cause the problem to become challenging. Here, we reported a novel sub-titanium oxide (Ti₂.₅O₃) thin film epitaxially grown on GaAs substrate using pulsed laser deposition, the high-quality Ti₂.₅O₃/GaAs heterostructure significantly reduced the lattice mismatch between titanium sub-oxides and the GaAs substrate. Besides, our work theoretically and experimentally demonstrated that high crystalline Ti₂.₅O₃ (010) film can be grown layer-by-layer on GaAs (001) substrate with highly compatible interfaces. Extremely low lattice mismatch values of 0.3% and 0.6% along different orientations can be achieved in combination with the notably suppressed formation of arsenic oxides (AsOx) and gallium oxides (GaOx) between Ti₂.₅O₃/GaAs interfaces. Owing to the favorable interface and high crystalline, integrated BaTiO₃(250 nm)/STO/Ti₂.₅O₃/GaAs heterostructure demonstrates hysteresis loops with a remnant polarization of 9.85 µC/cm² at 600 kV/cm and a small leakage current density of 1×10−5 A/cm² at -500 kV/cm. Not only the excellent performances pave the path for the further application of Ti₂.₅O₃/GaAs heterostructure in electronics, but also the unique strategy gives a good inspiration for coupling other functional oxides on GaAs with expected excellent performances.

Keywords: Ti₂.₅O₃/GaAs

  • Lecture (Conference) (Online presentation)
    European Materials Research Society 2021 Fall, 20.-23.09.2021, Online meeting, Germany

Permalink: https://www.hzdr.de/publications/Publ-34166
Publ.-Id: 34166


Lifetime measurements in 80Br and a new region for observation of chiral electromagnetic selection rule

Guoa, R. J.; Wang, S. Y.; Schwengner, R.; Xu, W. Z.; Qi, B.; Liu, C.; Rohilla, A.; Dönau, F.; Servene, T.; Schnare, H.; Reif, J.; Winter, G.; Käubler, L.; Prade, H.; Skoda, S.; Eberth, J.; Thomas, H. G.; Becker, F.; Fiedler, B.; Freund, S.; Kasemann, S.; Steinhardt, T.; Thelen, O.; Härtlein, T.; Ender, C.; Köck, F.; Reiter, P.; Schwalm, D.

Level lifetimes for the candidate chiral doublet bands of 80 Br were extracted
by means of the Doppler-shift attenuation method. The absolute transition
probabilities derived from the lifetimes agree well with the M 1 and E2 chiral
electromagnetic selection rules, and the calculations reported in the frame-
work of triaxial particle rotor model [S.Y. Wang et al., Phys. Lett. B 703
(2011) 40] also support firmly for the chirality in 80 Br. Such good agree-
ments among the experimental data, selection rules of chiral doublet bands
and theoretical calculations are rare and outstanding in researches of nuclear
chirality. Besides odd-odd Cs isotopes, odd-odd Br isotopes in the A ≈ 80
mass region represent another territory that exhibits the ideal selection rules
expected for chiral doublet bands.

Keywords: Nuclear Structure; Level lifetime measurements; Transition probabilities; Chiral bands

Permalink: https://www.hzdr.de/publications/Publ-34164
Publ.-Id: 34164


Modeling the oscillatory dynamics of gas bubbles growing at microelectrodes

Hossain, S. S.; Bashkatov, A.; Yang, X.; Mutschke, G.; Eckert, K.

The working mechanism of the recently observed bubble oscillation on microelectrodes is explained [1]. The force balance
includes contributions from a thermocapillary force and a Columb force on the charged bubble. Comparison between model predictions
and experimental measurements is presented.

  • Open Access Logo Contribution to proceedings
    The 25th International Congress of Theoretical and Applied Mechanics, 22.-27.08.2021, Milan, Italy
    25th International Congress of Theoretical and Applied Mechanics – Book of Abstracts
  • Open Access Logo Poster
    The 25th International Congress of Theoretical and Applied Mechanics, 22.-27.08.2021, Milan, Italy, 22.-27.08.2021, Milan, Italy

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Permalink: https://www.hzdr.de/publications/Publ-34163
Publ.-Id: 34163


Geostatistics for compositional data: from spatial interpolation to high dimensional prediction

Tolosana Delgado, R.; van den Boogaart, K. G.

Geostatistics is a name given to a series of statistical and machine learning tools devised to treat a spatially dependent variable with the goal of interpolating it. The key tool of classical geostatistics is the covariance function, capturing the covariance (matrix) between the variable (vector) observed at two locations in space. Pawlwowsky-Glahn and Olea (2004; "Geostatistical analysis for compositional data") already extended this framework to deal with spatially dependent compositional data, taking a logratio transformation, i.e. by means of the covariance function of the logratio transformed scores. Given a spatially dependent compositional data set, if we had available a model for the covariance function, it would be possible to predict the composition at a new location by means of multivariate multiple linear regression. The typical approach to obtain this covariance is to restrict it to be location-independent (but still depend on the lag difference between locations), and give it a parametric form. This vector of parameters is then either fitted via maximum likelihood, or else data-driven to specific collections of spread statistics of the sample. Similar approaches can be followed with compositions. Several such data driven methods have been proposed for compositions, which can be seen as choosing an \emph{oblique logratio} such that the covariance function becomes a diagonal matrix for all lags (and by extension, for all pairs of locations), with the resulting diagonal elements easily modelled separately. In this contribution we will discuss the several implications of these methodologies to obtain a parametric model for the covariance function, how to use this function to predict the composition at any location, the subcompositional properties of this predictor, and how this whole framework can be used beyond spatial statistics, to establish (almost) non-parametric predictive models for compositional responses with high dimensional regressors.

Keywords: variogram; auto-covariance; cross-covariance; minimum-maximum autocorrelation factors; kriging

  • Open Access Logo Contribution to proceedings
    CoDaWork2022: 9th International Workshop on Compositional Data Analysis, 28.06.-01.07.2022, Tolouse, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-34162
Publ.-Id: 34162


Flash lamp annealing for thin film processing

Rebohle, L.; Begeza, V.; Cherkouk, C.; Neubert, M.; Prucnal, S.; Hübner, R.; Zhou, S.

Flash lamp annealing is, like laser annealing, a non-equilibrium annealing method on the sub-second time scale which excellently meets the requirements of thin film processing: it allows the use of temperature-sensible substrates for thin films, leads to energy and cost savings compared to long-time annealing methods, and enables the formation of new materials in thermal non-equilibrium. Originally developed for microelectronics, flash lamp annealing has opened up new areas of application like thin films on glass, sensors, printed electronics, flexible electronics, batteries etc.

In this presentation, we shortly compare the pros and cons of flash lamp and laser annealing for thin film processing and discuss these issues at the example of thin semiconductor films on glass. In detail, the crystallization of amorphous Si on borosilicate glass, the crystallization of amorphous Ge on SiO2/Si substrates, and the formation of NiGe on different Ge substrates (amorphous, polycrystalline and monocrystalline) have been investigated. In all cases, the thin films were deposited by magnetron sputtering, followed by flash lamp annealing. The evolution of microstructure and its electrical properties was traced by corresponding characterization methods such as Raman spectroscopy, transmission electron microscopy, atomic force microscopy, X-ray diffraction, sheet resistance and Hall effect measurements.

Keywords: flash lamp annealing; thin film; crystallization amorphous Ge; NiGe

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  • Lecture (Conference) (Online presentation)
    E-MRS Spring 2021, Symposium H, 31.05.-03.06.2021, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-34161
Publ.-Id: 34161


Liquid Distribution in Industrial Structured-Packed Columns via Gamma-Ray Computed Tomography

Berger, A.; Houghton, P.; Wilson, J.; Schubert, M.; Bieberle, A.

A 600-mm diameter test column was constructed and packed with 3 layers of aluminum Sulzer 500Y packing. Liquid maldistribution was studied using a mechanical mechanism for blocking two rows of distributor holes. Two-phase counter-current flow was studied using air and water. Surfactant was added to mimic fluids with low surface tension. Gamma-ray CT scans were performed over a range of liquid and vapor rates, and visualization of flow details with pixel size down to 1mm was demonstrated. Generally, liquid holdup approached a characteristic value moving down the column. The characteristic holdup increased with liquid and/or vapor rates, as expected. When a distributor blocking mechanism was deployed, the decreased liquid fraction in the under-irrigated area is easily detectable in cross-sectional tomographic scans of the topmost packing layer. Liquid holdup data and tomographic images show that liquid distribution recovers substantially from gross maldistribution after three packing layers in water and two layers with surfactant-water.

Keywords: Gamma Ray Tomography; Structured packing; Liquid distribution

  • Contribution to proceedings
    12th International Conference Distillation & Absorption, 18.-21.09.2022, Toulouse, France
    Proceedings of the 12th International Conference Distillation & Absorption

Permalink: https://www.hzdr.de/publications/Publ-34160
Publ.-Id: 34160


Decoating of Electrode Foils from EOL Lithium-Ion Batteries by Electrohydraulic Fragmentation

Lyon, T.; Mütze, T.; Peuker, U. A.

In order to ensure environmentally friendly mobility, electric drives are increasingly being used. As a result, the number of used lithium-ion batteries has been rising steadily for years. To ensure a closed recycling loop, these batteries must be recycled in an energy- and raw materialefficient manner. For this purpose, hydrometallurgical processes are combined with mechanical pretreatment, including disintegration by mills, crushers and/or shears. Alternatively, lectrohydraulic fragmentation (EHF) is also of great interest, as it is considered to have a selective fragmentation effect. For a better comparison, different application scenarios of EHF with other methods of mechanical process engineering for the treatment of lithium-ion batteries are investigated in the present study.

Keywords: electrohydraulic fragmentation; EHF; lithium-ion batteries; decoating; active material; black mass; granulator; recycling

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Permalink: https://www.hzdr.de/publications/Publ-34158
Publ.-Id: 34158


AMS with a 14 million volt accelerator – 53Mn and 60Fe measurements at ANU

Wallnera, A.; Fifield, L. K.; Froehlich, M. B.; Koll, D.; Martschini, M.; Pavetich, S.; Tims, S. G.; Schumann, D.; Slavkovská, Z.

The AMS program at ANU’s Department of Nuclear Physics is based on a 14UD tandem accelerator which runs regularly above 14 MV with stable measurement conditions. This setup provides particle energies between ~24 MeV (actinides) and >200 MeV (e.g. 53Mn, 93Zr). The facility is equipped with a dedicated SNICS ion source, provides typically 155 keV beam injection energy and is capable of a simultaneous use of both gas and foil stripper. Dedicated beamlines feature multi-anode ionisation chambers, an ENGE gas-filled magnet and a 6m TOF flight path. Further, a new fast cycling system is now being implemented (see contribution by L.K. Fifield et al.) that will replace our slow cycling method.

The ANU has a strong focus in projects in environmental, safeguards and geological research with several nuclear astrophysics projects added recently as an additional major research topic. New isotopes recently introduced include 60Fe, 93Zr, 210Pb, 210mBi and 231Pa. We will give an overview of recent research activities and will summarize the performance of the different AMS setups. The potential of the ENGE setup for isobaric suppression will be exemplified for the two isotopes 60Fe and 53Mn. Measurement reproducibility and absolute detection efficiency will be compared.

Keywords: AMS; gas filled magnet; high energy aMS; ANU; 14UD

  • Poster (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry, 15.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-34157
Publ.-Id: 34157


A multi-parameter approach for recognition of anthropogenic noise in aeromagnetic data collected over populated areas: Erzgebirge, Germany

Morris, W.; Ugalde, H.; Kirsch, M.; Gloaguen, R.; Ibs-Von Seht, M.; Siemon, B.; Meyer, U.

Aeromagnetic data is routinely acquired by mineral exploration programs. The objective is to obtain a raster image of the spatial variations of magnetic field intensity, these variations are associated with mineralogical variations in the subsurface. When the survey is conducted in a populated area much of the signal, however may be associated with anthropogenic sources such as buildings and roads. Identification, and minimisation of the anthropogenic related signal then is essential to derive a useful product for geological mapping. In this work we examine a scalar magnetic dataset from Geyer, Saxony, and we apply five approaches for locating regions of anomalous anthropogenic signal: signal amplitude, absolute 4th difference, signal standard deviation, enhanced horizontal gradient, and curvedness. All are shown to produce similar responses, and the summation of the five results compares favorably with the standard Keating kimberlite (circular anomaly) approach for detecting anthropogenic signals. Complications arise when geological features produce signals of similar amplitude to anthropogenic sources. Differentiating the probable origin of any specific pattern can be assessed by using a 2D shape index and increased flight height. Verification of an anthropogenic anomaly is achieved by comparison of anomalous solution grids with GIS based reference data.

Keywords: Data processing; Magnetics; Noise

Permalink: https://www.hzdr.de/publications/Publ-34156
Publ.-Id: 34156


The radioactive nuclei 26Al and 60Fe in the Cosmos and in the solar system

Diehl, R.; Lugaro, M.; Heger, A.; Sieverding, A.; Tang, X.; Li, K. A.; Li, E. T.; Doherty, C. L.; Krause, M. G. H.; Wallner, A.; Prantzos, N.; Brinkman, H. E.; Den, H. J. W.; Wehmeyer, B.; Yagüe López, A.; Pleintinger, M. M. M.; Banerjee, P.; Wang, W.

The cosmic evolution of the chemical elements from the Big Bang to the present time is driven by nuclear fusion reactions inside stars and stellar explosions. A cycle of matter recurrently re-processes metal-enriched stellar ejecta into the next generation of stars. The study of cosmic nucleosynthesis and this matter cycle requires the understanding of the physics of nuclear reactions, of the conditions at which the nuclear reactions are activated inside the stars and stellar explosions, of the stellar ejection mechanisms through winds and explosions, and of the transport of the ejecta towards the next cycle, from hot plasma to cold, star-forming gas. Due to the long timescales of stellar evolution, and because of the infrequent occurrence of stellar explosions, observational studies are challenging, as they have biases in time and space as well as different sensitivities related to the various astronomical methods. Here, we describe in detail the astrophysical and nuclear-physical processes involved in creating two radioactive isotopes useful in such studies, $^{26}\mathrm{Al}$ and $^{60}\mathrm{Fe}$ . Due to their radioactive lifetime of the order of a million years, these isotopes are suitable to characterise simultaneously the processes of nuclear fusion reactions and of interstellar transport. We describe and discuss the nuclear reactions involved in the production and destruction of $^{26}\mathrm{Al}$ and $^{60}\mathrm{Fe}$ , the key characteristics of the stellar sites of their nucleosynthesis and their interstellar journey after ejection from the nucleosynthesis sites. This allows us to connect the theoretical astrophysical aspects to the variety of astronomical messengers presented here, from stardust and cosmic-ray composition measurements, through observation of $\gamma$ rays produced by radioactivity, to material deposited in deep-sea ocean crusts and to the inferred composition of the first solids that have formed in the Solar System. We show that considering measurements of the isotopic ratio of $^{26}\mathrm{Al}$ to $^{60}\mathrm{Fe}$ eliminate some of the unknowns when interpreting astronomical results, and discuss the lessons learned from these two isotopes on cosmic chemical evolution. This review paper has emerged from an ISSI-BJ Team project in 2017–2019, bringing together nuclear physicists, astronomers, and astrophysicists in this inter-disciplinary discussion.

Keywords: radioactive nuclei; interstellar medium; 60Fe; 26Al; 244Pu; accelerator mass spectrometry; review

Permalink: https://www.hzdr.de/publications/Publ-34155
Publ.-Id: 34155


High-field charge transport in InGaAs nanowires

Rana, R.; Balaghi, L.; Fotev, I.; Schneider, H.; Helm, M.; Dimakis, E.; Pashkin, O.

Charge transport in GaAs/InGaAs nanowires is studied using high-field terahertz pulses. With increasing terahertz field, the plasmon resonance redshifts and loses its spectral weight. The results provide evidence for inhomogeneous intervalley scattering across the nanowire.

Keywords: Intense Terahertz pulses; Nanowires; Plasmon

  • Poster (Online presentation)
    CLEO: Applications and Technology 2021, 09.-14.05.2021, San Jose, California, United States

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Permalink: https://www.hzdr.de/publications/Publ-34154
Publ.-Id: 34154


Biokollektoren - Die innovative Lösung für das Recycling der Zukunft

Lederer, F.

Die Nachwuchsforschergruppe BioKollekt entwickelt derzeit ein neues, effizientes Recyclingverfahren für Hochtechnologiemetalle aus EoLEP. Dabei wird der „Proof-of-Principle“ am Beispiel der Energiesparlampe und dem darin enthaltenen Leuchtpulver erbracht. Dieses besteht aus Selten-Erd-Element (SEE)-haltigen Partikeln, welche im Moment noch nicht voneinander getrennt und daher nicht wiederverwendet werden können. An dieser Stelle kommt die Biologie zum Recycling. Unsere biologischen Bausteine sind SEE-erkennende Peptide, also kurze Eiweißketten. Peptide sind aus Aminosäuren aufgebaut, wovon es in der Natur mehr als 20 verschiedene gibt. Die unterschiedliche Zusammensetzung der Peptide bestimmt darüber, ob ein Zielmaterial erkannt wird oder nicht. Der Gruppe BioKollekt ist es gelungen, für die SEE-haltigen Partikel des Leuchtpulvers stark bindende Peptide mit Hilfe des Phage Surface Display (PSD) zu finden. Das Verfahren an sich ist bereits lange bekannt. Der Erfinder dieser Methode erhielt 2018 dafür den Chemienobelpreis. Er öffnete damit den Weg für die Entwicklung neuer medizinischer Ansätze aber eben auch für das gezielte Finden von Peptiden für das Recycling von SEE aus Leuchtpulver.

Keywords: Biokollektoren; Phagendisplay; Peptide; Seltene Erden; Recycling; Kreislaufwirtschaft

  • Open Access Logo Technik in Bayern 03/2021(2021), 12-13

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Permalink: https://www.hzdr.de/publications/Publ-34153
Publ.-Id: 34153


X-ray Free Electron Laser-Induced Synthesis of ε-Iron Nitride at High Pressures

Hwang, H.; Kim, T.; Cynn, H.; Vogt, T.; Husband, R. J.; Appel, K.; Bähtz, C.; Ball, O. B.; Baron, M. A.; Briggs, R.; Bykov, M.; Bykova, E.; Cerantola, V.; Chantel, J.; Coleman, A. L.; Dattlebaum, D.; Dresselhaus-Marais, L. E.; Eggert, J. H.; Ehm, L.; Evans, W. J.; Fiquet, G.; Frost, M.; Glazyrin, K.; Goncharov, A. F.; Jenei, Z.; Kim, J.; Konôpková, Z.; Mainberger, J.; Makita, M.; Marquardt, H.; McBride, E. E.; McHardy, J. D.; Merkel, S.; Morard, G.; O’Bannon Iii, E. F.; Otzen, C.; Pace, E. J.; Pelka, A.; Pépin, C. M.; Pigott, J. S.; Prakapenka, V. B.; Prescher, C.; Redmer, R.; Speziale, S.; Spiekermann, G.; Strohm, C.; Sturtevant, B. T.; Velisavljevic, N.; Wilke, M.; Yoo, C.-S.; Zastrau, U.; Liermann, H.-P.; McMahon, M. I.; Stewart McWilliams, R.; Lee, Y.

The ultrafast synthesis of ε-Fe3N1+x in a diamond-anvil cell (DAC) from Fe and N2 under pressure was observed using serial exposures of an X-ray free electron laser (XFEL). When the sample at 5 GPa was irradiated by a pulse train separated by 443 ns, the estimated sample temperature at the delay time was above 1400 K, confirmed by in situ transformation of α- to γ-iron. Ultimately, the Fe and N2 reacted uniformly throughout the beam path to form Fe3N1.33, as deduced from its established equation of state (EOS). We thus demonstrate that the activation energy provided by intense X-ray exposures in an XFEL can be coupled with the source time structure to enable exploration of the time-dependence of reactions under high-pressure conditions.

Keywords: Iron; X-rays; Chemical reactions; Nitrogen; Diffraction

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Permalink: https://www.hzdr.de/publications/Publ-34149
Publ.-Id: 34149


Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL)

Liermann, H. P.; Konôpková, Z.; Appel, K.; Prescher, C.; Schropp, A.; Cerantola, V.; Husband, R. J.; McHardy, J. D.; McMahon, M. I.; McWilliams, R. S.; Pépin, C. M.; Mainberger, J.; Roeper, M.; Berghäuser, A.; Damker, H.; Talkovski, P.; Foese, M.; Kujala, N.; Ball, O. B.; Baron, M. A.; Briggs, R.; Bykov, M.; Bykova, E.; Chantel, J.; Coleman, A. L.; Cynn, H.; Dattelbaum, D.; Dresselhaus-Marais, L. E.; Eggert, J. H.; Ehm, L.; Evans, W. J.; Fiquet, G.; Frost, M.; Glazyrin, K.; Goncharov, A. F.; Hwang, H.; Jenei, Z.; Kim, J.-Y.; Langenhorst, F.; Lee, Y.; Makita, M.; Marquardt, H.; McBride, E. E.; Merkel, S.; Morard, G.; Obannon, E. F.; Otzen, C.; Pace, E. J.; Pelka, A.; Pigott, J. S.; Prakapenka, V. B.; Redmer, R.; Sanchez-Valle, C.; Schölmerich, M.; Speziale, S.; Spiekermann, G.; Sturtevant, B. T.; Toleikis, S.; Velisavljevic, N.; Wilke, M.; Yoo, C.-S.; Baehtz, C.; Zastrau, U.; Strohm, C.

The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump–probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.

Keywords: diamond anvil cells; x-ray free electron lasers; high precision x-ray diffraction; finite element modeling

Permalink: https://www.hzdr.de/publications/Publ-34147
Publ.-Id: 34147


Exchange and anisotropy-driven effects in antiferromagnetic spin chains

Pylypovskyi, O.

Antiferromagnets (AFMs) represent a class of materials with complex magnetic subsystem involving more than one ferromagnetically ordered sublattice. Such properties as high resonance frequencies in THz range, negligible net magnetic moment and respective weak stray fields, strong spin-orbit interaction make them promising for applications. The field of curvilinear magnetism offers additional degrees of freedom to tailor chiral and anisotropic responses of magnets and is well-established for ferromagnetic materials. Curvilinear AFMs possess additional features, important for for spintronic and spin-orbitronic applications [1].

The simplest curvilinear AFM is a spin chain arranged along flat or space curve. This geometry is characterized by the scalar functions of curvature K(s) and torsion T(s) with s being a coordinate along the curve. In the absence of intrinsic anisotropy, the dipolar interaction renders the tangential direction as the hard axis of the anisotropy [2]. Competition of this geometry-tracking interaction with the nearest-neighbor exchange leads to the emergence of additional anisotropic and chiral energy terms, whose coefficients are determined by K and T only. The geometry-driven anisotropic term brings about the easy axis determining direction of the order parameter within the dipole-driven easy-plane. The geometry-driven inhomogeneous Dzyaloshinskii-Moriya interaction (DMI) renders the curvilinear spin chain as a chiral helimagnet. For example, the spin chain along the helix with the given radius and pitch possesses one of two magnetic states depending on the geometrical parameters. For a dominating curvature K, the ground state is the homogeneous in the local reference frame, while for the dominating torsion T, the ground state is helicoidal. In contrast to ferromagnetic nanowires [3], there is no critical curvature, separating the ground states in the limiting case of small torsion. This reflects the presence of the only one ground state along the binormal direction for the spin chains along the flat curves [2].

The local variation of the anisotropy axis can result in the non-collinearity of the neighboring spins in curvilinear chains. 1D AFMs exhibit the parity-breaking effect, which forbids to exchange sublattices once they are selected. This leads to the emergent magnetization at non-collinear AFM textures [4]. Therefore, in any spin chain arranged along the space curve, there is a weak ferromagnetism proportional to the curvature and torsion of the curve [5].

In the presence of strong intrinsic anisotropy in AFM spin chain with the anisotropy axis following the tangential direction, one can observe the effects of geometry proportional to the anisotropy constant and curvature K [5]. Both models of the single- and inter-ion anisotropies lead to the tilt of the anisotropy axes, which is pronounced in the spin-flop phase. In addition, the single-ion anisotropy leads to the emergence of the additional anisotropic term of the homogeneous DMI symmetry. The latter is described by the tensor product of the ferro- and antiferromagnetic order parameters, which scales with K.

References

[1] V. Baltz, A. Manchon, M. Tsoi et al, Rev. Mod. Phys. Vol. 90, P. 015005 (2018); H. Yan, Z. Feng, P. Qin et al, Avd. Mat. Vol. 32, P. 1905603 (2020); D. D. Sheka, Appl. Phys. Lett. Vol. 118, P. 230502 (2021).
[2] O. V. Pylypovskyi, D. Y. Kononenko, K. V. Yershov et al, Nano Lett. Vol. 20, P. 8157 (2020).
[3] D. D. Sheka, V. P. Kravchuk, K. V. Yershov, Y. Gaididei, Phys. Rev. B Vol. 92, P. 054417 (2015).
[4] N. Papanicolaou, Phys. Rev. B Vol. 51, P. 15062 (1995); E. G. Tveten, T. Mueller, J. Linder et al, Phys. Rev. B Vol. 93, P. 104408 (2016).
[5] O. V. Pylypovskyi, Y. A. Borysenko, J. Fassbender et al, Appl. Phys. Lett., Vol. 118, P. 182405 (2021)

Keywords: antiferromagnetism; curvilinear magnetism

  • Invited lecture (Conferences) (Online presentation)
    Yuri Gaididei memorial workshop, 02.-03.02.2022, Kyiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-34146
Publ.-Id: 34146


Computer simulations of magnetic nanoarchitectures

Pylypovskyi, O.

Computer simulations of strongly non-linear systems with many degrees of freedom represent an important tool for physicists in both, theory an experiment. These systems are typical for the modern nanomagnetism, which leads to the development of plenty of special computational tools. Here, we consider an investigation of ferro- and antiferromagnetic nanoarchitectures, properties of magnetic solitons and numerical tools to address them.

Keywords: nanomagnetism; numerics

  • Invited lecture (Conferences) (Online presentation)
    Winter school on theoretical physics, 20.01.2022, Kyiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-34145
Publ.-Id: 34145


CFD simulation of a heat pipe using the homogeneous model

Höhne, T.

Heat-pipes are important in many industrial applications improving the thermal performance of heat exchangers and increasing energy savings. Computational Fluid Dynamics (CFD) were used to simulate the steam/water two-phase flow and heat transfer processes of a heat-pipe. The novelty of the study is that the evaporation, condensation and phase change processes were modelled using a homogeneous multiphase model and implemented source terms inspired by the Lee phase change model. The 3D CFD simulations could reproduce the heat and mass transfer processes in comparison with experiments from the literature. Reasonable good agreement was not only observed between CFD temperature profiles in relation with experimental data but also in comparing the thermal performance of the heat-pipe. It was found that the heating power should not increase above 1000 W for the analyzed type of heat-pipe design using copper material. In future, the use of the improved advanced numerical models is planned.

Keywords: Two-phase flow; Boiling; CFD; Condensation; Heat-pipe

Permalink: https://www.hzdr.de/publications/Publ-34144
Publ.-Id: 34144


Electron spin- and photon polarization-resolved probabilities of strong-field QED processes

Chen, Y.-Y.; Hatsagortsyan, K. Z.; Keitel, C. H.; Shaisultanov, R.

A derivation of fully polarization-resolved probabilities is provided for high-energy photon emission and electron-positron pair production in ultrastrong laser fields. The probabilities resolved in both electron spin and photon polarization of incoming and outgoing particles are indispensable for developing QED Monte Carlo and QED-Particle-in-Cell codes, aimed at the investigation of polarization effects in nonlinear QED processes in ultraintense laser-plasma and laser-electron beam interactions, and other nonlinear QED processes in external ultrastrong fields, which involve multiple elementary processes of a photon emission and pair production. The quantum operator method introduced by Baier and Katkov is employed for the calculation of probabilities within the quasiclassical approach and the local constant field approximation. The probabilities for the ultrarelativistic regime are given in a compact form and are suitable to describe polarization effects in strong laser fields of arbitrary configuration, rendering them very well suited for applications.

Permalink: https://www.hzdr.de/publications/Publ-34143
Publ.-Id: 34143


Data publication: Collapse of Coherent Large Scale Flow in Strongly Turbulent Liquid Metal Convection

Schindler, F.; Eckert, S.; Zürner, T.; Schumacher, J.; Vogt, T.

Rawdata on which the publication is based on. .BDD binary files for Ultrasound measurements. .dat: direct temperature measurement data.

Keywords: Rayleigh-Benard Convection; liquid metal; low Pr; cylinder; Aspect Ratio 0.5; Ultrasound Doppler Velocimetry

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Permalink: https://www.hzdr.de/publications/Publ-34142
Publ.-Id: 34142


Ion implantation and Subsecond annealing: a versatile approach for hyperdoping semiconductors

Zhou, S.

Doping allows us to modify semiconductor materials for desired electrical, optical and magnetic properties. The solubility limit is a fundamental barrier for dopants incorporated into a specific semiconductor. Hyperdoping refers to doping a semiconductor much beyond the corresponding solid solubility limit and often results in exotic properties. For example, Ga hyperdoped Ge reveals superconductivity and Mn hyperdoped GaAs represents a typical ferromagnetic semiconductor. Ion implantation followed by annealing is a well-established method to dope Si and Ge. This approach has been maturely integrated with the IC industry production line. However, being applied to hyperdoping, the annealing duration has to be shortenedto millisecond or even nanosecond. The intrinsic physical parameters related to dopants and semiconductors (e.g. Solubility, diffusivity, melting point and thermal conductivity) have to be considered to choose the right annealing time regime. In this talk, we propose that ion implantation combined with flash lamp annealing in millisecond and pulsed laser melting in nanosecond can be a versatile approach to fabricate hyperdoped semiconductors. The examples include magnetic semiconductors [1-5], highly mismatched semiconductor alloys (Ge1-xSnx [6] and GaAs1-xNx [7]), n++ Ge [8, 9] and chalcogen doped Si [10-12].

[1] M. Khalid, et al., Phys. Rev. B 89, 121301(R) (2014).
[2] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001(2015).
[3] S. Prucnal, et al., Phys. Rev. B 92, 222407 (2015).
[4] Y. Yuan, et al., ACS Appl. Mater. Interfaces, 8, 3912 (2016).
[5] Y. Yuan, et al., Phys. Rev. Mater. 1, 054401 (2017).
[6] K. Gao, et al., Appl. Phys. Lett.,105, 042107 (2014).
[7] K. Gao, et al., Appl. Phys. Lett.,105, 012107 (2014).
[8] S. Prucnal, et al., Sci.Reports 6, 27643(2016).
[9] S. Prucnal, et al., Semicond. Sci. Technol. 32 115006 (2017).
[10] S. Zhou, et al., Sci. Reports 5, 8329(2015).
[11] Y. Berencén, et al., Adv. Mater. Inter. 5, 1800101 (2018).
[12] M. Wang, et al., Phys. Rev. Applied. 10, 024054 (2018).

Related publications

  • Lecture (others) (Online presentation)
    Invited talk at Brandenburgische Technische Universität Cottbus-Senftenberg, 25.11.2021, Cottbus, Germany
  • Lecture (Conference)
    2021 Spring Meeting of the European Materials Research Society (E-MRS), 31.05.-04.06.2021, Strasbourg, France

Permalink: https://www.hzdr.de/publications/Publ-34141
Publ.-Id: 34141


Tailoring oxide thin films by ion beam

Zhou, S.

Complex oxides host a multitude of novel phenomena in condensed matter physics, such as various forms of multiferroicity, colossal magnetoresistance, quantum magnetism and superconductivity. Defect engineering via ion irradiation can be a useful knob to control these physical properties for future practical applications. Two prominent effects are disorder and uniaxial strain. Particularly, the uniaxial strain, manifesting as the elongation of the out-of-plane lattice spacing, is not limited to available substrates, the conventional and well-known strain engineering approach. In this talk, I will introduce the basics of ion irradiation and its applications to oxide thin films, including the modification of magnetic properties of NiCo2O4 [1], SrRuO3 [2], the magneto-transport properties of rare-earth nickelates [3] and SrRuO3 [4] and the structural properties of BiFeO3 [5]. It is worth to note that ion beam technology has been well developed for microelectronics. Once the principle of concept is approved, the approach can be easily scaled up and integrated to the industry production line.

References:

[1] P. Pandey, Y. Bitla, M. Zschornak, M. Wang, C. Xu, J. Grenzer, D. C. Meyer, Y. Y. Chin, H. J. Lin, C. T. Chen, S. Gemming, M. Helm, Y. H. Chu, S. Zhou, APL Materials 6 (2018) 066109 (2018).
[2] C. A. Wang, C. Chen, C-H. Chang, H-S, Tsai, P. Pandey, C. Xu, R. Böttger, D. Y. Chen, Y-J Zeng, X. S. Gao, M. Helm, S. Q. Zhou, ACS Appl. Mater. Interfaces 10 (2018) 27472-27476.
[3] C. A. Wang, C-H, Chang, A. Huang, P-C. Wang, P-C. Wu, L. Yang, C. Xu, P. Pandey, M. Zeng, R. Böttger, H-T. Jeng, Y-J. Zeng, M. Helm, Y-H. Chu, R. Ganesh, and S. Q. Zhou, Phys. Rev. Materials 3 (2019) 053801
[4] C. A. Wang, C-H Chang, A. Herklotz, C. Chen, F. Ganss, U. Kentsch, D. Y. Chen, X. S. Gao, Y-J. Zeng, O. Hellwig, M. Helm, S. Gemming, Y-H. Chu, and S. Q. Zhou, Adv. Electron. Mater. 6 (2020) 2000184.
[5] C. Chen, C. Wang, X. Cai, C. Xu, C. Li, J. Zhou, Z. Luo, Z. Fan, M. Qin, M. Zeng, X. Lu, X. Gao, U. Kentsch, P. Yang, G. Zhou, N. Wang, Y. Zhu, S. Zhou, D. Chen, J. Liu, Nanoscale 11 (2019) 8110-8118.

Related publications

  • Invited lecture (Conferences) (Online presentation)
    2nd International Workshop on Advanced Magnetic Oxides, 24.-26.11.2021, Aveiro, PORTUGAL
  • Invited lecture (Conferences) (Online presentation)
    10th Vacuum and Surface Sciences Conference of Asia and Australia, 11.-14.10.2021, Shanghai, China
  • Lecture (Conference)
    22nd International Conference on Ion Beam Modification of Materials, 10.-15.07.2022, Lisbon, Portugal

Permalink: https://www.hzdr.de/publications/Publ-34140
Publ.-Id: 34140


Simulation-Based Inference for Beam Parameter Inversion

Steinbach, P.; Hartmann, G.

In this talk, I'd like to present modern machine learning tools for estimating the posterior of the inverse problem exposed in a beam control setting. That is, given an experimental beam profile, I'd like to demonstrate tools that help to estimate which simulation parameters might have produced a similar beam profile with high likelihood.

We summarize preliminary findings bound to optimize a xray beamline located at a synchrotron accelerator. With this, we hope to tackle the challenge to characterize beam quality with minimal invasion as possible. The basis of my discussion will be a surrogate model that emulates experimental conditions of beam profile knife-edge scans. We hope that this discussion is of interest to this accelerator physics community at LPA.

Keywords: laser-plasma acceleration; simulation based inference; machine learning; modelling

  • Open Access Logo Poster (Online presentation)
    LPA Online Workshop on Control Systems and Machine Learning 24-27 January 2022, 24.-28.01.2022, online, www
    DOI: 10.6084/m9.figshare.19071641.v1

Permalink: https://www.hzdr.de/publications/Publ-34139
Publ.-Id: 34139


Selektion hochaffiner Peptide zur Bindung von f-Elementen und deren physikochemische Charakterisierung

Claus, G.

Das wesentliche Ziel der vorliegenden Arbeit bestand darin, hochaffine Peptide zur Bindung des Lanthanoides Europium zu selektieren, zu identifizieren und hinsichtlich ihrer Affinität zu charakterisieren. Die Elemente der Seltenen Erden (REE) sind aufgrund ihrer besonderen Eigenschaften von enormer Wichtigkeit in Zeiten der modernen Technologie. Die Selektion von Peptid-Biosorbenzien mit hoher REE-Affinität würde den ersten Schritt bilden, um die Herstellung von sogenannten Biokollektoren zu verwirklichen. Diese sollen zukünftig für das Recycling von Seltenen Erdmetallen wie Europium aus Elektroschrott oder für deren Extraktion aus primären Rohstoffgemischen angewendet werden.
Für die Realisierung dieser Zielstellung kam zunächst die Technik des Phage Surface Display zum Einsatz, mit dessen Hilfe gut bindende Phagenvarianten über mehrere Runden einer Affinitätsselektion angereichert und schließlich mittels Sanger-Sequenzierung identifiziert wurden. Die ermittelten Peptidsequenzmotive wurden in einem kompetitiven Bindeversuch weiter reduziert und die daraus resultierten besten Binder in Einzelbindeversuchen sowie in der zeitaufgelösten Laser-induzierten Fluoreszenz-spektroskopie (TRLFS) auf ihre Bindungsaffinität für Europium-Ionen hin untersucht. Die EF-Hand 4 des Calmodulins diente als Modellsystem zur Bestimmung der Bindungsparameter unter Verwendung der TRLFS sowie der isothermen Titrationskalorimetrie (ITC).
Die am stärksten gebundenen Peptidmotive sind durch eine hohe Anzahl an basischen Aminosäuren (AS), insbesondere Histidin, wie auch durch eine vergleichsweise hohe Anzahl an hydrophoben Resten und einen relativ geringen Anteil an sauren AS charakterisiert. Die Histidine deuteten aufgrund der freien Elektronenpaare ihrer Stickstoffatome auf eine vielversprechende Europium-Komplexierung hin. In der TRLFS stellte sich jedoch heraus, dass keines der sechs ausgewählten und synthetisierten Peptide die Europium-Ionen komplexiert. Auch in den Einzelbindeversuchen zeigte keiner der selektierten Phageneinzelklone eine gegenüber dem Phagenwildtyp verbesserte Bindung an die Zielmoleküle. Mögliche Gründe dafür werden diskutiert und sollen in fortführenden Versuchen überprüft werden.
Die TRLFS- sowie ITC-basierten Modelluntersuchungen der EF-Hand 4 des Calmodulins ergaben zwei Komplexspezies mit einer 1:1- und einer 1:2-Stöchiometrie. Es wurde die Parallele Faktoranalyse angewandt, um die Einzelkomponenten aus den experimentellen TRLFS-Spektren zu extrahieren und ihre Bindungsaffinität zu bestimmen. Anhand der ermittelten Dissoziationskonstanten von 5,66*10-6 M bzw. 1,00*10-4 M für den 1:1- bzw. 1:2-Eu(III)-EF-Hand-4-Komplex konnte eine hohe Affinität der EF-Hand 4 für Europium-Ionen nachgewiesen werden. Dies steht grundsätzlich in Übereinstimmung mit den Ergebnissen der Komplexbildungsstudie zum Calmodulin (Drobot et al. 2019). Eine Ausnahme bildet jedoch der 1:2-Eu(III)-EF-Hand-4-Komplex, da er in dieser Form nicht im nativen Calmodulin-Protein vorkommt.
Die wesentliche Fragestellung, ob es Peptidmotive gibt, die noch besser an Europium-Ionen binden als die EF-Hände des Calmodulins, kann in der vorliegenden Arbeit nicht beantwortet werden. Aufgrund dessen sollte zukünftig das Peptidmotiv der EF-Hand 4 modifiziert und weiter optimiert werden, um eine noch höhere Europium-Affinität zu erhalten und somit dem Anwendungsziel, dem Recycling oder der Extraktion von Europium aus Elektroschrott bzw. primären Rohstoffquellen, einen Schritt näher zu kommen.

Keywords: Phage Surface Display; Biopanning; Europium; f-Elemente; TRLFS; Peptide

  • Master thesis
    TU Dresden/ IHI Zittau, 2020
    Mentor: Dr. Björn Drobot
    143 Seiten

Permalink: https://www.hzdr.de/publications/Publ-34138
Publ.-Id: 34138


Blaubeuren, Cloppenburg, and Machtenstein—Three recently recognized H-group chondrite finds in Germany with distinct terrestrial ages and weathering effects

Bischoff, A.; Storz, J.; Barrat, J.-A.; Heinlein, D.; Jull, A. J. T.; Merchel, S.; Pack, A.; Rugel, G.

In the last 7 years, three meteorites (Blaubeuren, Cloppenburg, and Machtenstein) found in Germany were identified as
chondrites. Two of these rocks had been recovered from the impact sites decades ago but not considered to be meteorites.
The aim of this study is to fully characterize these three meteorites. Based on the compositional data on the silicates, namely
olivine and low-Ca pyroxene, these meteorites fit nicely within the H-group ordinary chondrites. The brecciated texture of
Blaubeuren and Cloppenburg (both H4-5) is perfectly visible, whereas that of Machtenstein, officially classified as an H5
chondrite, is less obvious but was detected and described in this study. Considering chondrites in general, brecciated rocks
are very common rather than an exception. The bulk rock degree of shock is S2 for Blaubeuren and Machtenstein and S3
for Cloppenburg. All samples show significant features of weathering. They have lost their original fusion crust and more
than half (W3) or about half (W2-3) of their original metal abundances. The oxygen isotope compositions of the three
chondrites are consistent with those of other H chondrites; however, the Cloppenburg values are heavily disturbed and
influenced by terrestrial weathering. This is supported by the occurrence of the very rare hydrated iron phosphate mineral
vivianite (Fe2+Fe2+2[PO4]2·8H2O), which indicates that the chondrite was weathered in a very wet environment. The
terrestrial ages of Blaubeuren (~9.2 ka), Cloppenburg (~5.4 ka), and Machtenstein (~1.8 ka) show that these chondrites are
very similar in their degree of alteration and terrestrial age compared to meteorite finds from relatively wet terrestrial
environments. They still contain abundant metal, although, as noted, the oxygen isotope data indicate substantial weathering
of Cloppenburg. The bulk compositions of the three meteorites are typical for H chondrites, although terrestrial alteration has
slightly modified the concentrations, leading in general to a loss of Fe, Co, and Ni due to preferential alteration of metals and
sulfides. As exceptions, Co and Ni concentrations in Machtenstein, which has the shortest terrestrial age, are typical for H
chondrites. The chemical data show no enrichments in Ba and Sr, as is often observed in different meteorite groups of
desert finds.

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Permalink: https://www.hzdr.de/publications/Publ-34136
Publ.-Id: 34136


A rigorous single period micromagnetic model of stripe domains - comparison with analytics and experiment

Deussner, S.; Süss, D.; Abert, C.; Bruckner, F.; Fähler, S.; Heistracher, P.; Reichel, L.; Neu, V.

Stripe domains in thin films form through a complex competition of perpendicular anisotropy and demagnetizing energy and are still lacking a complete micromagnetic description, despite being investigated since 50 years. This work elucidates the formation of stripe domains with a special focus on the dependence of stripe domain width on film thickness with varying ratio of the two major energy contributions. An overview and review of the most established analytical models for the calculation of this dependency is given with respect to existing experimental data as well as to new experimental data on epitaxial Fe-Co-C films with perpendicular anisotropy. Since the analytical models are limited in their predictive power and compatibility in terms of the suitable material parameter range, an effcient but rigorous micromagnetic simulation method was developed, which proved to be comparable or better than
previous models in describing experimental finding, especially for films with strongly dominating demagnetizing. Comprehensive simulations where performed to determine thickness dependent stripe width for various material parameters which can serve as a benchmark for analytical theories or can be used directly for comparison with experimental results. At a given combination of exchange constant and saturation polarization there exists a specifc thickness at which the stripe width is independent of the uniaxial anisotropy.

Keywords: Stripe domains; perpendicular anisotropy; thin magnetic films

Permalink: https://www.hzdr.de/publications/Publ-34134
Publ.-Id: 34134


Data publication: Data-Driven Quest for Two-Dimensional Non-van der Waals Materials

Friedrich, R.; Ghorbani-Asl, M.; Curtarolo, S.; Krasheninnikov, A. V.

This dataset includes the primary research data for the publication "Data-Driven Quest for Two-Dimensional Non-van der Waals Materials", https://doi.org/10.1021/acs.nanolett.1c03841.

Keywords: 2D materials; exfoliation; data-driven research; computational materials science; high-throughput computing

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Permalink: https://www.hzdr.de/publications/Publ-34133
Publ.-Id: 34133


Data publication: Three-dimensional distribution of platinum group minerals in natural MSS-ISS ores from the Norilsk 1 Deposit, Russia

Sittner, J.; Brovchenko, V.; Siddique, A.; Buyse, F.; Boone, M.; Renno, A.; Cnudde, V.; Merkulova, M.; Sluzhenikin, S.

Datensatz zur 2D und 3D Verteilung von Platin Gruppen Mineralen (PGM) . Außerdem verschiedene spektren welche mittels spektraler tomographie gemessen wurden. Außerdem enthält der Datensatz 3-dimensionale Parameter einzelner PGMs in den Proben.

Keywords: Norilsk; Platinum Group Minerals; X-ray computed tomography; Spectral X-ray computed tomography; 3D imaging; SEM-EDS

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Permalink: https://www.hzdr.de/publications/Publ-34132
Publ.-Id: 34132


Impedance characterization of particles one by one using a nanosensor electronic platform

Sandoval Bojorquez, D. I.; Oliveros Mata, E. S.; Schütt, J.; Bachmann, M.; Baraban, L.

Impedance cytometry represents a technique that allows the electronic characterization of colloids and living cells in a highly miniaturized way. In contrast with impedance spectroscopy, the measurements are performed at a fixed frequency, providing real-time monitoring of the species traveling over the sensor. By measuring the electrical properties of particles in suspension, the dielectric characteristics (electric conductivity and capacitance) of both cells and particles can be readily determined. During the last years, this technique has been broadly investigated; however, it is still not trivial to differentiate particles of similar size based on their dielectric characteristics. A way to increase the discrimination abilities of this technique could be the integration of nanostructures into the impedance platforms. In this work, we present the impedance cytometry study of particles using microfluidic channels aligned over interdigitated gold nanowire structures as our impedimetric sensor. The characterization of particles of different sizes and their comparison with particles of different compositions will provide an understanding of the correlation between the electrical signal and the own characteristics of each particle. This approach is an attractive element for label-free detection platforms that can be integrated into lab-on-a-chip systems, and that can be further implemented for single-cell analysis.

  • Open Access Logo Poster (Online presentation)
    8th International Symposium on Sensor Science, 20.-26.05.2021, Dresden, Germany
    DOI: 10.3390/I3S2021Dresden-10110

Permalink: https://www.hzdr.de/publications/Publ-34131
Publ.-Id: 34131


TOMOCON Continuous Casting Demonstration

Glavinic, I.; Wondrak, T.; Eckert, S.

More than 95% of steel produced in the entire world is produced by continuous casting. Flow condition in the mould, where the initial solidification occurs, are important for the end quality of the product. It is important to understand these conditions and react accordingly. The process is modeled at the mini-LIMMCAST facility which is operated with a eutectic alloy of GaInSn. The flow in the mould is monitored with Contactless Inductive Flow Tomography (CIFT) and the flow is influenced with an Electromagnetic Brake (EMBr). The EMBr has a great influence on the CIFT measurement system which needs to be compensated. The video explains basics of continuous casting and the experimental setup; it highlights the challenges and implemented solutions, and gives and outlook to the related research.

Keywords: Contactless inductive flow tomography; Continuous casting; Electromagnetic Brake

  • Communication & Media Relations
    Video 06.10.2021

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Permalink: https://www.hzdr.de/publications/Publ-34130
Publ.-Id: 34130


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