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41449 Publications

Strained Ammonium Precursors for Radiofluorinations

Reissig, F.; Mamat, C.

The increasing application of positron emission tomography (PET) in nuclear medicine has stimulated the extensive development of a multitude of novel and versatile techniques to introduce fluorine-18 especially for the radiolabelling of biologically or pharmacology active molecules. Taking into consideration that the introduction of fluorine-18 (t1/2 = 109.8 min) mostly proceeds under harsh conditions, radiolabelling of such molecules represents a challenge and is of enormous interest. Ideally, it should proceed in a regioselective manner under mild physiological conditions, in an acceptable time span, with high yields and high specific activities. Special attention has been drawn to 2-fluoroethyl and 3-fluoropropyl groups, respectively, which are often the active site of radiofluorinated compounds. Precursors containing an ammonium leaving group which consists of a strained azetidinium or aziridinium moiety can help to overcome these obstacles leading to a mild introduction of [18F]fluoride with high radiochemical yields.

Keywords: strained rings; ring opening; aziridines; azetidinium; fluorination

Permalink: https://www.hzdr.de/publications/Publ-34277


CeO2-azacrown conjugate as a nanoplatform for combined radiopharmaceuticals

Khabirova, S. Y.; Aleshin, G. Y.; Plakhova, T. V.; Zubenko, A. D.; Shchukina, A. A.; Fedorova, O. A.; Averin, A. A.; Belova, E. V.; Bazarkina, E. F.; Kvashnina, K. O.; Kalmykov, S. N.

This communication is one of the first attempts to assess CeO2 nanoparticles as a nanoplatform for radiopharmaceuticals with radionuclides. The process of functionalization using a bifunctional azacrown ligand is described, and the resulting conjugates are characterized by IR and Raman spectroscopy. Their complexes with 207Bi show a high stability in medically relevant media, thus encouraging the further study of these conjugates in vivo as potential combined radiopharmaceuticals

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Permalink: https://www.hzdr.de/publications/Publ-34276


Data publication: Effects of gravity modulation on the dynamics of a radial A + B → C reaction front

Stergiou, Y.; Hauser, M. J. B.; Comolli, A.; Brau, F.; de Wit, A.; Schuszter, G.; Papp, P.; Horvath, D.; Roux, C.; Pimienta, V.; Eckert, K.; Schwarzenberger, K.

Raw image data of the reaction-diffusion-advection front experiments in radial Hele-Shaw cells. Including experiments in ground 1-g conditions and parabolic flight experiments.

Keywords: Reaction-diffusion-advection; reaction front; microgravity; convection; radial Hele-Shaw; parabolic flight

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Permalink: https://www.hzdr.de/publications/Publ-34275


Cr2+ solid solution in UO2 evidenced by advanced spectroscopy

Smith, H.; Townsend, L. T.; Mohun, R.; Cordara, T.; Stennett, M.; Mosselmans, F.; Kvashnina, K.; Hyatt, N.; Corkhill, C.

Advanced Cr-doped UO2 fuels are essential for driving safe and efficient generation of nuclear energy. Although widely deployed, little is known about their fundamental chemistry, which is a critical gap for development of new fuel materials and radioactive waste management strategies. Utilising an original approach, we directly evidence the chemistry of Cr(3+)2O3–doped U(4+)O2. Advanced high-flux, high-spectral purity X-ray absorption spectroscopy (XAS), corroborated by diffraction, Raman spectroscopy and high energy resolved fluorescence detection-XAS, is used to establish that Cr2+ directly substitutes for U4+, accompanied by U5+ and oxygen vacancy charge compensation. Extension of the analysis to heat-treated simulant nuclear fuel reveals a mixed Cr2+/3+ oxidation state, with Cr in more than one physical form, explaining the substantial discrepancies that exist in the literature. Successful demonstration of this analytical advance, and the scientific underpinning it provides, opens opportunities for an expansion in the range of dopants utilised in advanced UO2 fuels.

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Permalink: https://www.hzdr.de/publications/Publ-34274


High surface area “3D Graphene Oxide” for enhanced sorption of radionuclides

Boulanger, N.; Kuzenkova, A. S.; Iakunkov, A.; Nordenström, A.; Romanchuk, A. Y.; Trigub, A. L.; Zasimov, P. V.; Podana, M.; Enachescu, M.; Bauters, S.; Amidani, L.; Kvashnina, K. O.; Kalmykov, S. N.; Talyzin, A. V.

Earlier studies demonstrated that graphene oxide (GO)
with large number of defects is favorable for the sorption of
radionuclides. Here we report oxidation treatment which converts high
surface area activated reduced graphene oxide (arGO) into a 3D
analogue of defect-rich GO (dGO). Oxidation of arGO using
ammonium persulfate results in oxidation corresponding to carbon to
oxygen ratio C/O=3.3, similar to the oxidation state of graphene oxide
while preserving high BET surface area of about 880 m2/g. Analysis
of surface oxidized arGO shows high abundance of oxygen functional
groups very similar to dGO and hydrophilic properties. The “3D
graphene oxide” showed high sorption capacity for U(VI) removal in
an extraordinary broad interval of pH. Notably, the surface oxidized
carbon material has a rigid 3D structure with micropores accessible
for penetration of radionuclide ions. Therefore, the bulk “3D GO” can
be used as a sorbent directly without dispersing, the step required for
GO to make its surface area accessible for pollutants

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Permalink: https://www.hzdr.de/publications/Publ-34273


Data publication: MOFs with 12-coordinate 5f-block metal centers

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

Autoluminescence CO2 BET Elemental analysis Leaching test results Powder XRD TGA-DSC UV/vis

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

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Permalink: https://www.hzdr.de/publications/Publ-34272


A study on the wettability of metal oxides as cathode active materials to improve lithium-ion battery recycling

Sandbrink, J.; Vanderbruggen, A.; Rudolph, M.

One of the main tasks for today’s researchers in order to ensure the supply of critical raw materials is the efficient recovery and recycling of secondary resources. Lithium-ion batteries (LIB) are the key technology to electrify transport, which is one of the multiple measures proposed to prevent global warming. Therefore, the recycling of spent LIBs is of great interest and unvoidable. A major challenge in spent LIBs recycling, is the beneficiation of fine powder resulting from the battery crushing, so-called “black mass”, which contains the valuable lithium metal oxides (from the cathode) and the critical graphite (from the anode). One promising way to separate the graphitic material from the lithium metal oxides is through froth flotation, which separates the particles according to their differences in wettability.
In order to improve the separation process, one must first have a proper understanding of the particle properties. In particular, the lithium metal oxides are rather declared as hydrophilic and should therefore be easily separated from the hydrophobic graphite. Nevertheless, many studies report on their recovery into the froth product, along with the graphite, thus lowering its grade, which is most probably due to the residual hydrophobic binder that causes a change in their wettability.
In this study, different battery materials, including fresh lithium metal oxides and graphite, as well as real spent materials from LIBs were used. The particles were analysed for their wettability and wetting ability using optical contour analysis, inverse gas chromatography, particle attachment to bubbles, analytical particle solvent extraction as well as the Washburn method. These results are set into context with flotation tests and shed light on the particle wettability and its effect on the flotation separation efficiency, as well as the difficulties that arise when it comes to the recycling of spent LIBs.

Keywords: Flotation; lithium-ion batteries; wettability; recycling

  • Lecture (Conference) (Online presentation)
    Jahrestreffen der ProcessNet-Fachgruppen Grenzflächenbestimmte Systeme und Prozesse, Partikelmesstechnik sowie Aerosoltechnik, 16.-17.02.2022, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-34271


Sustainable Bioengineering of Gold Structured Wide-Area Supported Catalysts for Hand-Recyclable Ultra-Efficient Heterogeneous Catalysis

Bhatt, C. S.; Parimi, D. S.; Bollu, T. K.; Madhura, H. U.; Jacob, N.; Korivi, R.; Ponugoti, S. S.; Mannathan, S.; Ojha, S.; Klingner, N.; Motapothula, M.; Suresh, A. K.

Metal nanoparticles grafted within inert and porous wide-area supports are emerging as recyclable, sustainable catalysts for modern industry applications. Here, we develop gold nanoparticle-anchored supported catalysts by utilizing the natural metal binding and reductive potential of natural eggshell. Variable hand-recyclable wide-area catalysts between ~(80±7) and (0.5±0.1) cm2 are generated by varying the support dimensions. The catalyst possesses high-porosity (17.1 Å) and stability against high-temperatures (300°C), polar and non-polar solvents, electrolytes, acids and bases, facilitating compatible ultra-efficient catalysis. As validated by large-volume (2.8 liters) sewage-dye detoxification, gram-scale hydrogenation of nitroarenes and synthesis of propargylamine. Moreover, persistent-recyclability, monitoring of reaction kinetics and product intermediates are possible due to retrievability and interchangeability of the catalyst. Finally, the bio-nature of support permits ~76.9% recovery of noble gold simply by immersing in royal solution. Our naturally-created, low-cost, scalable, hand-recyclable and resilient supported mega-catalyst dwarfs most challenges for large-scale metal-based heterogeneous catalysis.

Keywords: supported-catalyst; sustainable; hand-recyclable; gram-scale; large-volume; dye-detoxification; sewa

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Permalink: https://www.hzdr.de/publications/Publ-34270


Perspective paper about the joint EANM/SNMMI/ESTRO practice recommendations for the use of 2-[18F]FDG-PET/CT external beam radiation treatment planning in lung cancer

Vaz, S.; Adam, J.; Bolton Delgado, R.; Vera, P.; van Elmpt, W.; Herrmann, K.; Hicks, R.; Lievens, Y.; Santos, A.; Schöder, H.; Dubray, B.; Visvikis, D.; Troost, E. G. C.; de Geus-Oei, L.

In ‘‘Joint EANM/SNMMI/ESTRO Practice Recommendations for the Use of 2-[18F]FDG-PET/CT External Beam Radiation Treatment Planning in Lung Cancer V1.0” clinical indications for PET-CT in (non-)small cell lung cancer are highlighted and selective nodal irradiation is discussed. Additionally, concepts about target definition, target delineation and treatment evaluation are reviewed.

Permalink: https://www.hzdr.de/publications/Publ-34269


Spinning Particles in Quantum Mechanics and Quantum Field Theory

Corradini, O.; Schubert, C.; Edwards, J. P.; Ahmadiniaz, N.

These are notes of lectures on spinning particles and the worldline formalism originally given by Olindo Corradini and Christian Schubert at the School on spinning Particles in Quantum Field Theory: Worldline Formalism, HigherSpins, and Conformal Geometry, held at Morelia, Mexico, from November 19 through November 23, 2012. The lectures were addressed to graduate-level students with a background in relativistic quantum mechanics and at least a rudimentary knowledge of field theory. They have since been up-dated to include a further set of lecture notes on tree level processes from a worldline perspective based on a mini-course by James P. Edwards at the Instituto de Fisica y Matematicas in Morelia, Mexico given to graduatesand visiting professors during July 2017 and in various later classes, com-plemented by a series of three lectures titled New techniques for amplitude calculation in QED given by Naser Ahmadiniaz at the Center for Relativistic Laser Science (CoReLS), Institute for Basic Science (IBS), November 2015, Gwangju, South Korea and as an invited lecturer at the Helmholtz International Summer School (HISS) - Dubna International Advanced School of Theoretical Physics (DIAS-TH): “Quantum Field Theory at the Limits: from strong Fields to Heavy Quarks”, July-August 2019, Dubna, Russia. These additional notes complete the picture of first quantised techniques and bring the worldline description up to date.

Keywords: Worldline formalism; loop-level processes; Tree-level processes

  • Open Access Logo Invited lecture (Conferences)
    Quantum Field Theory at the Limits: from Strong Fields to Heavy Quarks, 22.07.-02.08.2019, Dubna, Russia

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Permalink: https://www.hzdr.de/publications/Publ-34268


Breakup with benefits - hydrothermal mineral systems related to the disintegration of a supercontinent

Burisch, M.; Markl, G.; Gutzmer, J.

Mesozoic hydrothermal systems host the majority of Europe's fluorspar and barite resources as well as significant amounts
of metals such as Ag, Co, Zn, Pb, Ni and Cu. Their genetic link to extensional tectonics in conjunction with the opening of
the North Atlantic has long been suspected, but their spatial and temporal relation to the tectonic evolution of Europe has
remained enigmatic. A thorough evaluation of available geochronological data for fluorite-barite-Pb-Zn, native-metalarsenide-
carbonate and MVT-type mineralization in Continental Europe and North Africa reveals a distinct, as yet
unrecognized, time-space relationship between the distribution of hydrothermal mineral systems and the tectonic evolution
of the Tethys-Atlantic-Caribbean rift system. The observed time-space relationship and ore-forming mechanisms are
evaluated to constrain the underlying driving force for hydrothermal mineralization in the context of the geodynamic evolution
of the European lithosphere. Based on this assessment we propose the first continental-scale model for the genesis of
Mesozoic hydrothermal ore deposits associated to the breakup of the supercontinent Pangea.

Keywords: continental rifting; critical raw materials; hydrothermal ore deposits; North Atlantic; Pangea supercontinent

Permalink: https://www.hzdr.de/publications/Publ-34267


Linking Diffraction Techniques with XRF and XAS Spectroscopy at the German CRG Beamline ROBL / ESRF

Hennig, C.; Svitlyk, V.

The recent upgrade of the Rossendorf Beamline at ESRF allows simultaneous collection of diffraction and spectroscopy (XRF and XANES). A 6-circle Huber diffractometer (XRD-1) with Eulerian cradle geometry is used for high-resolution powder diffraction and surface diffraction. The powder diffraction module uses an Eiger CdTe 500k detector, the surface diffraction module is equipped with a Pilatus Si 100k detector. PXRD data suitable for Rietveld refinement can be collected between 10 and 31 keV in an 2θ angular range of 0-65°. The Bragg reflexes in PXRD are extracted by radial integration using a modified pyFAI code. Diffraction measurements can be combined with XRF and XAS spectroscopy using a single-element Si drift detector (Vortex X90 CUBE, 1mm SDD, 25 mm Be window) with a FalconX1 processor.

The second diffractometer (XRD-2) consists of a heavy optical bench with an exchangeable goniometer and a Pilatus3 X 2M detector. It is used for single crystal diffraction and in situ or operando powder diffraction. Devices for non-ambient sample conditions are a hot-air blower (RT-1100K), a heating chamber (RT-1470K), and a LN2 cryostream (90-400K). This diffractometer is controlled with the Pylatus software. The single crystal data extraction is performed with CrysAlisPro. The Si drift detector can be placed in different positions to combine diffraction with XRF and XAS measurements.

Keywords: single-crystal diffraction ScXRD; high resolution powder diffraction HR-PXRD; in situ and perando applications

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  • Lecture (Conference) (Online presentation)
    30th Annual Meeting of the German Crystallographic Society, 14.-17.03.2022, Munich, Germany

Permalink: https://www.hzdr.de/publications/Publ-34265


“X-ray diffraction spectroscopy” – Refinement of dispersion correction parameters for XRD measurements of Mo(CO)6 at the Mo K-edge

Meurer, F.; Dolomanov, O. V.; Hennig, C.; Peyerimhoff, N.; Kleemiss, F.; Puschmann, H.; Bodensteiner, M.

Correcting for anomalous dispersion is part of any refinement of an X-ray
diffraction crystal structure determination. The procedure takes the inelastic
scattering in the diffraction experiment into account. This X-ray absorption effect
is specific to each chemical compound and is particularly sensitive to radiation
energies in the region of the absorption edges of the elements in the compound.
Therefore, the widely used tabulated values for these corrections can only be
approximations as they are based on calculations for isolated atoms. Features of
the unique spatial and electronic environment that are directly related to the
anomalous dispersion are ignored, although these can be observed spectroscopically.
This significantly affects the fit between the crystallographic model and
the measured intensities when the excitation wavelength in an X-ray diffraction
experiment is close to an element’s absorption edge. Herein, we report on
synchrotron multi-wavelength single-crystal X-ray diffraction, as well as X-ray
absorption spectroscopy experiments which we performed on the molecular
compound Mo(CO)6 at energies around the molybdenum K edge. The dispersive
(f 0) and absorptive (f 00) terms of the anomalous dispersion can be refined as
independent parameters in the full-matrix least-squares refinement. This procedure
has been implemented as a new feature in the well-established OLEX2 software
suite. These refined parameters are in good agreement with the independently
recorded X-ray absorption spectrum. The resulting crystallographic models show
significant improvement compared to those employing tabulated values.

Keywords: X-ray diffraction; anomalous dispersion; crystal structure determination

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Permalink: https://www.hzdr.de/publications/Publ-34263


Improved ⁴¹Ca AMS measurements at DREAMS

Vivo Vilches, C.; Rugel, G.; Lachner, J.; Wallner, A.; Koll, D.; Stübner, K.; Fichter, S.; Winkler, S.

Sensitivity of ⁴¹Ca measurements at the 6 MV AMS system at HZDR, DREAMS, using calcium fluoride (CaF₂) targets, is mainly limited by 2 factors: the total efficiency of the measurements; and the fraction of ions of its isobar ⁴¹K which mimic the signal of ⁴¹Ca in the gas ionization chamber detector.
The addition of lead fluoride (PbF₂) to the target mixture has been proven to boost the production of different (MFₙ)- ions. At DREAMS, changing the previously used mixture of CaF₂+Ag (1:4 w/w) by CaF₂+Ag+PbF₂ (1:4:4 w/w), ionization efficiency is increased from ∼0.15% to ∼0.45%.
The ⁴¹K suppression by the detector can also be improved, even without changes in the instrumentation itself. With an optimized analysis of the 4-dimensional signals from the gas ionization chamber detector, the suppression factor can be increased, at least, a factor 2: from 2 × 10⁴ to 4 × 10⁴.
The reported changes improve the total efficiency of ⁴¹Ca detection as well as the suppression of the ⁴¹K isobar and lead to a ⁴¹Ca/⁴⁰Ca sensitivity of 2-3 × 10⁻¹⁵ with an overall efficiency of ∼0.03%.

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  • Lecture (Conference) (Online presentation)
    85th Annual Conference of the DPG and DPG Spring Meeting, 14.-18.03.2022, Erlagen, Germany

Permalink: https://www.hzdr.de/publications/Publ-34262


Evaluation of [18F]LU14 and [18F]LU13 in a rat model with a local overexpression of the human cannabinoid receptor 2 in the brain with PET

Gündel, D.; Deuther-Conrad, W.; Ueberham, L.; Teodoro, R.; Bormans, G.; Toussaint, M.; Kopka, K.; Bachmann, M.; Brust, P.; Moldovan, R.-P.

Objectives: An upregulation of cannabinoid receptors type 2 (CB2) has been reported in association with inflammation processes, traumatic brain injury, neurodegeneration and cancer.[1] The activation of CB2 leads to an anti-inflammatory action. Therefore, the non-invasive assessment of the CB2 availability with PET could improve the decision-making for CB2-directed therapies. We developed a series of fluorinated naphthyridine-2-one-carboxamides as CB2 ligands, of which [18F]LU14[2] and [18F]LU13 were radiosynthesized and biologically evaluated.
Methods: The two radioligands [18F]LU14[2] and [18F]LU13 were developed starting from appropriate precursor compounds.The fraction of radiometabolites was quantified in isolated plasma and brain samples at 30 min p.i. The CB2 binding affinities selectivities (expressed and determined from KD and Ki values of both radioligands were determined in vitro. PET studies were performed to evaluate the radioligand uptake into the brains of rats overexpressing the hCB2(D80N) in the right striatum[3].
Results: Favourable properties where achieved for [18F]LU14, which could be further improved for [18F]LU13 (AM, affinity, selectivity and metabolic stability). In rats bearing the local overexpression of the hCB2 a target-specific and reversible uptake for both radioligands was demonstrated. [18F]LU14 reached a TAC peak SUV of 3.3 ± 0.6 at 7.4 ± 2.8 min p.i., and the SUVr (target region–to–cerebellum) was stable between 6.6 and 7.0 after 30 min p.i. For [18F]LU13 a stable SUV of 3.6 ± 0.9 after 26 min p.i. was reached and a close to linearly increasing SUVr (target region–to–cerebellum) up to 8.8 ± 4.3 at 60 min p.i. was determined (slope = 0.15 SUV/min; R² =.0.8).
Conclusion: [18F]LU14 and [18F]LU13 showed an excellent ability to image the CB2 receptors in vivo. Additionally, [18F]LU14 revealed a faster washout from the non-target regions in the brain, compared to [18F]LU13.
References: [1] Stasiulewicz et al. IJMS, 2020, 21, 2778; [2] Teodoro et al. IJMS, 2021, 22, 15; [3] Attili et al. BJP, 2019, 176, 1481

Keywords: cannabinoid receptor 2; PET; brain; [18F]LU13; [18F]LU14[2]; CB2

  • Lecture (Conference)
    Turku PET Symposium 2022, 03.-06.06.2022, Turku, Finland

Permalink: https://www.hzdr.de/publications/Publ-34261


Effects of gravity modulation on the dynamics of a radial A + B → C reaction front

Stergiou, Y.; Hauser, M. J. B.; Comolli, A.; Brau, F.; de Wit, A.; Schuszter, G.; Papp, P.; Horvath, D.; Roux, C.; Pimienta, V.; Eckert, K.; Schwarzenberger, K.

The dynamics of radial A + B → C reaction fronts can be affected by buoyancy-driven convection. Motivated by recent advances in reaction-diffusion-advection (RDA) systems theory, we investigated experimentally a radial A + B → C RDA system under modulated gravity, using a Hele-Shaw cell setup onboard a parabolic flight. We evaluated characteristic properties of the RDA models, such as the temporal evolution of the total amount of product C, the width and position of the reaction front and compared them with theoretical predictions. During increased gravity, we observed an increase in the total amount of product C, formed and the front width, compared to the corresponding normal-gravity experiments, caused by the stronger buoyancy-driven convection in the former case. Finally, we report on experiments performed entirely in absence of gravity, eliminating buoyancy-driven convection. Despite the short observation time, comparison with ground experiments showed the effect of buoyant convection on radial RDA fronts, enhancing mixing and increasing product generation.

Keywords: Reaction-diffusion-advection; reaction front; microgravity; convection; radial Hele-Shaw; parabolic flight

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Permalink: https://www.hzdr.de/publications/Publ-34260


Beyond Active Colloids: From Functional Materials to Microscale Robotics

Simmchen, J.; Baraban, L.; Wang, W.

Guest editors Juliane Simmchen, Larysa Baraban, and Wei Wang introduce the topics covered in this special collection covering the synthesis, applications, and dynamics of active colloids.

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Permalink: https://www.hzdr.de/publications/Publ-34259


Development of explanatory movies for the delineation of new organs at risk in neuro-oncology

Di Perri, D.; Hofstede, D.; Postma, A.; Zegers, C.; In’T Ven, L.; Hoebers, F.; van Elmpt, W.; Verheesen, L.; Beurskens, H.; Troost, E. G. C.; Compter, I.; Eekers, D.

Ten new organs at risk (OARs) were recently introduced in the updated European Particle Therapy Network neurological contouring atlas. Despite the use of the illustrated atlas and descriptive text, interindividual contouring variations may persist. To further facilitate the contouring of these OARs, educational films were developed and published on www.cancerdata.org.

Keywords: atlas for neuro-oncology; brain; organs at risk; film; particle therapy; radiotherapy

Permalink: https://www.hzdr.de/publications/Publ-34258


A systematic review of clinical studies on proton Relative Biological Effectiveness (RBE)

Underwood, T.; McNamara, A.; Appelt, A.; Haviland, J.; Sørensen, B.; Troost, E. G. C.

Recently, a number of clinical studies have explored links between possible Relative Biological Effectiveness (RBE) elevations and patient toxicities and/or image changes following proton therapy. Our objective was to perform a systematic review of such studies. We applied a "Problem [RBE], Intervention [Protons], Population [Patients], Outcome [Side effect]” search strategy to the PubMed database. From our search, we retrieved studies which: (a) performed novel voxel-wise analyses of patient effects versus dose and LET (n= 13), and (b) compared image changes between proton and photon cohorts with regard to proton RBE (n=9). For each retrieved study, we extracted data regarding: primary tumour type; size of patient cohort; type of image change studied; image-registration method (deformable or rigid); LET calculation method, and statistical methodology. We compared and contrasted their methods in order to discuss the weight of clinical evidence for variable proton RBE. We concluded that clinical evidence for variable proton RBE remains statistically weak at present. Our principal recommendation is that proton centres and clinical trial teams collaborate to standardize follow-up protocols and statistical analysis methods, so that larger patient cohorts can ultimately be considered for RBE analyses.

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Permalink: https://www.hzdr.de/publications/Publ-34256


Optical study of RbV₃Sb₅: Multiple density-wave gaps and phonon anomalies

Wenzel, M.; Ortiz, B. R.; Wilson, S. D.; Dressel, M.; Tsirlin, A. A.; Uykur, E.

Temperature-dependent reflectivity studies on the non-magnetic kagome metal RbV₃Sb₅ in a broad energy range (50 cm$^{-1}$ - 20000 cm$^{-1}$, equivalent to 6 meV - 2.5 eV) down to 10 K are reported. Below T_CDW=102 K, the optical spectra demonstrate a prominent spectral-weight transfer from low to higher energies as the fingerprint of the charge-density wave (CDW) formation with the opening of a partial gap. A detailed analysis reveals two energy scales of, respectively, ~800 cm$^{-1}$ (100 meV) and 360 cm$^{-1}$ (45 meV), the latter appearing below 50 K only. Additionally, two modes at, respectively, 160 cm$^{-1}$ (20 meV) and 430 cm$^{-1}$ (53 meV) can be traced both above and below T_CDW. They show strong anomalies already above T_CDW with a further renormalization across the transition, suggesting the importance of the electron-phonon coupling in RbV₃Sb₅ in both normal and CDW states. While the 160 cm$^{-1}$mode can be attributed to the E_1u phonon, the 430 cm$^{-1}$ mode could not be reproduced in our phonon calculations. The antiresonance nature of this mode suggests a nontrivial electron-phonon coupling in RbV₃Sb₅. A distinct localization peak observed at all temperatures signals damped electron dynamics, whereas the reduced Drude spectral weight manifests moderate deviations from the band picture in RbV₃Sb₅.

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Permalink: https://www.hzdr.de/publications/Publ-34255


Amphiphilic Anionic Oligomer-Stabilized Calcium Phosphate Nanoparticles with Prospects in siRNA Delivery via Convection-Enhanced Delivery

Mitrach, F.; Schmid, M.; Toussaint, M.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Franke, H.; Ewe, A.; Aigner, A.; Wölk, C.; Brust, P.; Hacker, M. C.; Schulz-Siegmund, M.

Convection-enhanced delivery (CED) has been introduced as a concept in cancer treatment to generate high local concentrations of anticancer therapeutics and overcome the limited diffusional distribution, e.g., in the brain. RNA interference provides interesting therapeutic options to fight cancer cells but requires nanoparticulate (NP) carriers with a size below 100 nm as well as a low zeta potential for CED application. In this study, we investigated calcium phosphate NPs (CaP-NPs) as siRNA carriers for CED application. Since CaP-NPs tend to aggregate, we introduced a new terpolymer (o14PEGMA(1:1:2.5) NH3) for stabilization of CaP-NPs intended for delivery of siRNA to brain cancer cells. This small terpolymer provides PEG chains for steric stabilization, and a fat alcohol to improve interfacial activity, as well as maleic anhydrides that allow for both labeling and high affinity to Ca(II) in the hydrolyzed state. In a systematic approach, we varied the Ca/P ratio as well as the terpolymer concentration and successfully stabilized NPs with the desired properties. Labeling
of the terpolymer with the fluorescent dye Cy5 revealed the terpolymer’s high affinity to CaP. Importantly, we also determined a high efficiency of siRNA binding to the NPs that caused very effective survivin siRNA silencing in F98 rat brain cancer cells. Cytotoxicity investigations with a standard cell line resulted in minor and transient effects; no adverse effects were observed in organotypic brain slice cultures. However, more specific cytotoxicity investigations are required. This study provides a systematic and mechanistic analysis characterizing the effects of the first oligomer of a new class of stabilizers for siRNA-loaded CaP-NPs.

Keywords: Calcium phosphate nanoparticles; Cell transfection; Particle characterization; PEGylated terpolymer

Permalink: https://www.hzdr.de/publications/Publ-34254


Platinum-group elements in Late Quaternary high-Mg basalts of eastern Kamchatka: Evidence for minor cryptic sulfide fractionation in primitive arc magmas

Nekrylov, N.; Kamenetsky, V. S.; Savelyev, D. P.; Gorbach, N. V.; Kontonikas-Charos, A.; Palesskii, S. V.; Shcherbakov, V. D.; Kutyrev, A. V.; Savelyeva, O. L.; Korneeva, A. A.; Kozmenko, O. A.; Zelenski, M. E.

The geochemical variations of magmas across and along supra-subduction zones (SSZ) have been commonly attributed to profound changes in the phase and chemical compositions of the mantle source and subduction-derived melt and fluid fluxes, as well as the physical parameters (e.g. depth, temperature, oxygen fugacity etc) of slab dehydration, mineral breakdown and melting. Here we test the variability of the Late Quaternary primitive magmas in the southern and northern parts of the meridionally oriented Eastern Volcanic Belt (EVB) of Kamchatka, with a slab depth varying from 60 to 160 km. Eight high-Mg (Mg# > 60 mol%) basalts were characterized for major, trace and platinum-group element (PGE) abundances, as well as the compositions of olivine phenocrysts and olivine-hosted spinel inclusions. The basalts in our study are geochemically typical of SSZ magmas and contain similar liquidus assemblages of forsteritic olivine (Mg# 78–92 mol%), low-Ti Cr-spinel and clinopyroxene. Although the absolute abundances of major and trace elements, and their ratios, in the basalts fluctuate to some extent, the observed variability cannot be correlated with any of considered parameters in the geometry of the Kamchatka SSZ and conditions of melting. This unexpected result led to the evaluation of the platinumgroup element (PGE) systematics against the lithophile and chalcophile trace element geochemistry and the compositions of phenocrysts. Total whole-rock PGE content varies from 2.3 to 11.7 ppb, whereas the normalized PGE concentration patterns are typical for supra-subduction zones magmas and broadly similar in all studied samples. They are enriched in Rh, Pd and Pt relative to mid-ocean ridge basalts (MORB) and have nearly identical concentrations of Ir-group PGE. The only parameter that correlates well with PGE contents is the average Mg# of olivine phenocrysts from 84 to 90.3 mol%. This is interpreted to result from minor cryptic fractionation of sulfide melt, together with primitive olivine, in low-to-mid crustal conditions. Negative Ru anomalies on chondrite-normalized diagrams correspond to the Fe2+/Fe3+ ratios in spinel (a proxy for magma redox conditions), which reflects a replacement of monosulfide solid solution by laurite in the mantle wedge during oxidation.

Keywords: Kamchatka; Olivine; Laurite; PGE; Sulfide

Permalink: https://www.hzdr.de/publications/Publ-34252


Analysis of MRI and CT-based radiomics features for personalized treatment in locally advanced rectal cancer and external validation of published radiomics models

Shahzadi, I.; Zwanenburg, A.; Lattermann, A.; Linge, A.; Baldus, C.; Peeken, J.; Combs, S.; Diefenhardt, M.; Rödel, C.; Kirste, S.; Grosu, A.-L.; Baumann, M.; Krause, M.; Troost, E. G. C.; Löck, S.

Radiomics analyses commonly apply imaging features of different complexity for the prediction of the endpoint of interest. However, the prognostic value of each feature class is generally unclear. Furthermore, many radiomics models lack independent external validation that is decisive for their clinical application. Therefore, in this manuscript we present two complementary studies. In our modelling study, we developed and validated different radiomics signatures for outcome prediction after neoadjuvant chemoradiotherapy (nCRT) in patients with locally advanced rectal cancer (LARC) based on computed tomography (CT) and T2-weighted (T2w) magnetic resonance (MR) imaging datasets of 4 independent institutions (training: 122, validation 68 patients). We compared different feature classes extracted from the gross tumour volume for the prognosis of tumour response and freedom from distant metastases (FFDM): morphological and first order (MFO) features, second order texture (SOT) features, and Laplacian of Gaussian (LoG) transformed intensity features. Analyses were performed for CT and MRI separately and combined. Model performance was assessed by the area under the curve (AUC) and the concordance index (CI) for tumour response and FFDM, respectively. Overall, intensity features of LoG transformed CT and MR imaging combined with clinical T stage (cT) showed the best performance for tumour response prediction, while SOT features showed good performance for FFDM in independent validation (AUC = 0.70, CI = 0.69). In our external validation study, we aimed to validate previously published radiomics signatures on our multicentre cohort. We identified relevant publications on comparable patient datasets through a literature search and applied the reported radiomics models to our dataset. Only one of the identified studies could be validated, indicating an overall lack of reproducibility and the need of further standardization of radiomics before clinical application.

Permalink: https://www.hzdr.de/publications/Publ-34251


Uptake of Np(V) by zirconia: a combined batch, spectroscopic, and surface complexation modeling study

Jessat, I.; Roßberg, A.; Scheinost, A.; Lützenkirchen, J.; Foerstendorf, H.; Jordan, N.

The interactions of long-lived actinides, such as the transuranium element neptunium, with corrosion products in the near-field of a repository are important processes that have to be considered when assessing the safety of a nuclear waste repository. As a main corrosion product of the zircaloy cladding material of spent nuclear fuel rods, zirconia (ZrO₂) constitutes a first possible barrier against the release of radionuclides.
To gain a detailed understanding of the surface processes in the Np(V)−zirconia system, a comprehensive, multi-method approach was applied. The Np(V)−ZrO₂ system has been studied on the macroscopic level by conducting pH-dependent batch sorption experiments under varying conditions (ionic strength, Np(V) concentration, and solid-to-liquid ratio (m/V)). In addition, a Np(V) sorption isotherm at pH 6 was collected. The results revealed that Np(V) sorption onto ZrO₂ was affected by pH, Np(V) concentration, and solid-to-liquid ratio. Uptake of Np(V) increased with pH, starting around pH 3 with maximum sorption reached from pH 6. The shift of the sorption edge towards lower pH with increase of the m/V ratio points to the presence of different kinds of sorption sites. This is supported by the Np(V) sorption isotherm results, where the shape suggests strong and weak binding sites. Furthermore, Np(V) uptake was found to be independent of ionic strength and zeta potential measurements revealed a shift towards higher pH values of the isoelectric point of the neat ZrO₂ in the presence of Np(V). Hence, the formation of Np(V) inner-sphere surface complexes is indicated.
Molecular information about the surface species were obtained by Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) and in situ Infrared (IR) Spectroscopy, revealing the predominant formation of inner-sphere Np(V) surface complexes. A short Np−Zr distance derived from EXAFS suggests the presence of Np(V) bidentate inner-sphere complexes on the ZrO₂ surface.
These information obtained on a macroscopic and a molecular level can be used to restrict the number of surface species as well as their denticity in a surface complexation model. The thermodynamic surface complexation parameters of the Np(V)−zirconia system derived in this study will help to make more reliable predictions about the fate of Np(V) in the environment.

Keywords: neptunium(V); zirconia; ZrO₂; sorption; spectroscopy; EXAFS; IR

Involved research facilities

Related publications

  • Lecture (Conference)
    19th Radiochemical Conference (RadChem), 15.-20.05.2022, Mariánské Lázně (Marienbad), Czech Republic

Permalink: https://www.hzdr.de/publications/Publ-34249


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.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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


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

Involved research facilities

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

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


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


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


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


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.

Involved research facilities

  • High Magnetic Field Laboratory (HLD)

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


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.

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  • 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


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


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


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


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


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


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

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  • TOPFLOW Facility

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


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


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


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


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


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


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

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  • TOPFLOW Facility
  • 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


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

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  • 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


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


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


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


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


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


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

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

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

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  • 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


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

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  • 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


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

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  • 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


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


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


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


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


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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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

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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

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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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    International Symposium on Nanostructure Research, 19.-21.09.2021, Leoben, Oesterreich

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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

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    The European Conference on Lasers and Electro-Optics, 23.06.2021, digital, digital

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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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    Graphene 2021, 28.10.2021, Grenoble, Frankreich

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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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    Graphene Week 2021, 21.09.2021, digital, digital

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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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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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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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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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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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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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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


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

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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

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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

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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
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    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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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

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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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    E-MRS Spring 2021, Symposium H, 31.05.-03.06.2021, Strasbourg, France

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