Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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36140 Publications

Cation exchange on colloidal copper selenide nanosheets: a route to two-dimensional metal selenide nanomaterials

Shamraienko, V.; Spittel, D.; Hübner, R.; Khoshkhoo, M. S.; Weiß, N.; Georgi, M.; Borchert, K. B. L.; Schwarz, D.; Lesnyak, V.; Eychmüller, A.

We report a synthesis route to two-dimensional PbSe, HgSe, ZnSe, SnSe, and Cu-Zn-Sn-Se (CZTSe) nanomaterials based on cation exchange (CE) reactions. This approach includes two steps: it starts with the synthesis of hexagonal, up to several micrometers large yet approx. 5 nm-thick CuSe nanosheets (NSs), followed by CE of the host copper ions with the desired guest cation (Pb2+, Hg2+, Zn2+, or Sn4+). In the case of CZTSe, both guest cations can be added simultaneously since the variation of the guest cation ratio and reaction time can lead to various compositions. Mild reaction conditions allow for a preservation of the size and the 2D shape of the parent NSs accompanied by corresponding changes in their crystal structure. We furthermore demonstrate that the crystal structure of CuSe NSs can be rearranged even without addition of guest cations in the presence of tri-n-octylphosphine. Thus, the obtained NSs were further subjected to ligand exchange reactions in order to replace insulating bulky organic molecules on their surface with compact iodide and sulfide ions, a step crucial for the application of nanomaterials in (opto)electronic devices. The resulting NS dispersions were processed into thin films by spray-coating onto commercially available interdigitated platinum electrodes. Light response measurements of PbSe and CZTSe NS-films demonstrated their potential for applications as light-sensitive materials in photodetection or photovoltaics.

Permalink: https://www.hzdr.de/publications/Publ-33532
Publ.-Id: 33532


Measurement of the photon strength function in ¹¹⁵In at the gELBE facility

Makinaga, A.; Schwengner, R.; Beyer, R.; Grieger, M.; Hammer, S.; Hensel, T.; Junghans, A.; Ludwig, F.; Trinh, T. T.; Turkat, S.

The photon strength function (PSF) in 115In is an important parameter for the estimate of the neutron capture cross section on 114In in the field of astrophysics and nuclear engineering. Until now, the so-called PSF method for 115In was applied only above the neutron-separation energy (Sn), and the evaluated 114In (n,g) cross section has uncertainties caused by the lack of the PSF below Sn. We studied the dipole strength distribution of 115In with a photon-scattering experiment using bremsstrahlung produced by an electron beam of an energy of 10.3 MeV at the linear accelerator ELBE at HZDR.

Keywords: ELBE; gELBE; NRF; photon-scattering; bremsstrahlung; 115In

  • Open Access Logo Contribution to proceedings
    2019 Symposium on Nuclear Data, 28.-30.11.2019, Fukuoka, Japan
    Proceedings of the 2019 Symposium on Nuclear Data, 101-105
    DOI: 10.11484/jaea-conf-2020-001

Permalink: https://www.hzdr.de/publications/Publ-33529
Publ.-Id: 33529


Die Rolle des TRPC6 Kanals im Rahmen der akuten Nierenschädigung

Zheng, Z.; Tsvetkov, D.; Bartolomaeus, T. U. P.; Erdogan, C.; Krügel, U.; Schleifenbaum, J.; Schaefer, M.; Nürnberg, B.; Chai, X.; Ludwig, F.-A.; N’Diaye, G.; Köhler, M.-B.; Wu, K.; Gollasch, M.; Marko, L.

Aims: Transient receptor potential (TRP) channels are non-selective cation channels that promote influx of Ca2+, Mg2+ and monovalent cations into cells. TRP channel subfamily C, member 6 (TRPC6) is widely expressed - next to several other tissues - in the kidney, and gene variations were linked to fibrosing renal disease. Here we aimed to investigate the putative role of TRPC6 channels in acute kidney injury (AKI). Since ischemia/reperfusion injury is known relate to Ca2+ overload, we hypothesized that inhibition of TRPC6 ameliorates AKI.
Methods: We used Trpc6-/- mice and SH045, a pharmacological inhibitor of TRPC6, to evaluate short-term AKI outcomes. Ischemia was induced after right–sided nephrectomy by clipping the renal pedicle of the left kidney for 20 or 17.5 minutes. SH045 was used for intravenous injection (2 mg/kg) 30 minutes before I/R surgery in the pharmacological studies with WT mice.
Results: Here, we demonstrate that neither Trpc6 deficiency nor pharmacological inhibition of TRPC6 influence the short-term outcomes of AKI. Blood markers (Creatinine in WT [131.4±33.3 µmol/l] vs Trpc6-/- [159.6±41.7 µmol/l] mice after 24 hours of reperfusion and in the pharmacological study: 17.5 min-I/R vehicle [199.5±21.8 µmol/l] versus 17.5 min-I/R SH045 [172.6±31.6 µmol/l], and 20 min-I/R vehicle [212.2±8.4 µmol/l] versus 20 min-I/R SH045 [226.2±28.6 µmol/l], all comparisons are n.s.), renal expression of epithelial damage markers, tubular injury and renal inflammatory response assessed by histological analysis were similar in wild-type mice compared to Trpc6-/- mice as well as in vehicle-treated versus SH045-treated mice. In addition, our results also found no effect of TRPC6 modulation on renal myogenic tone by using SH045 to perfuse isolated kidneys.
Conclusion: Therefore, we conclude that TRPC6 does not play role on the acute phase of AKI. Further studies should focus if TRPC6 inhibition could be protective in terms of long-term outcome of an AKI.

  • Poster
    Kongress für Nephrologie 2021, 23.-26.09.2021, Rostock, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33510
Publ.-Id: 33510


Rapid Detection of SARS-CoV-2 Antigens and Antibodies Using OFET Biosensors Based on a Soft and Stretchable Semiconducting Polymer

Ditte, K.; Anh Nguyen Le, Trang; Ditzer, O.; Isabel Sandoval Bojorquez, D.; Chae, S.; Bachmann, Michael; Baraban, Larysa; Lissel, F.

In the midst of the COVID-19 pandemic, adaptive solutions are needed to allow us to make fast decisions and take effective sanitation measures, e.g., the fast screening of large groups (employees, passengers, pupils, etc.). Although being reliable, most of the existing SARS-CoV-2 detection methods cannot be integrated into garments to be used on demand. Here, we report an organic field-effect transistor (OFET)-based biosensing device detecting of both SARS-CoV-2 antigens and anti-SARS-CoV-2 antibodies in less than 20 min. The biosensor was produced by functionalizing an intrinsically stretchable and semiconducting triblock copolymer (TBC) film either with the anti-S1 protein antibodies (S1 Abs) or receptor-binding domain (RBD) of the S1 protein, targeting CoV-2-specific RBDs and anti-S1 Abs, respectively. The obtained sensing platform is easy to realize due to the straightforward fabrication of the TBC film and the utilization of the reliable physical adsorption technique for the molecular immobilization. The device demonstrates a high sensitivity of about 19%/dec and a limit of detection (LOD) of 0.36 fg/mL for anti-SARS-Cov-2 antibodies and, at the same time, a sensitivity of 32%/dec and a LOD of 76.61 pg/mL for the virus antigen detection. The TBC used as active layer is soft, has a low modulus of 24 MPa, and can be stretched up to 90% with no crack formation of the film. The TBC is compatible with roll-to-roll printing, potentially enabling the fabrication of low-cost wearable or on-skin diagnostic platforms aiming at point-of-care concepts.

Permalink: https://www.hzdr.de/publications/Publ-33509
Publ.-Id: 33509


Multidisciplinary Characterization of Uranium Mine Waters: A Bioremediation Perspective.

Newman-Portela, A. M.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Raff, J.; Merroun, M. L.

An intensive uranium mining took place for decades in East Germany. These intensive mining activities have left many uranium contaminated areas. For a remediation purpose, the mine water has to be pumped to the surface and treated by a conventional chemical wastewater treatment plant. However, such chemical treatments are time- and cost-intensive. The resulting release of the soluble uranium into the mine water represents a major health risk. Remediation approaches using indigenous microbial communities are an efficient strategy [1,2]. In this study, we have characterized the microbial diversity and geochemistry of water samples from a german former uranium mine to design bioremediation approach based on uranium enzymatic reduction.

Inductively Coupled Plasma-Mass Spectrometry and Ion-Chromatography studies showed that the mine water exhibited a high concentration of uranium (1.01 mg/L), sulfate (335 mg/L), iron (0.99 mg/L) and manganese (144 mg/L). Cryo-Time-resolved Laser-induced Fluorescence Spectroscopy studies identified an aqueous uranyl carbonate species [UO2(CO3)3]. The 16S and ITS1 rRNA gene sequencing revealed an extensive microbial diversity. The total bacterial community composition indicated a high relative abundance of sulfate-reducing-bacteria (e.g., Desulfovibrio) and iron-oxidizing-bacteria (e.g., Gallionella, Sideroxydans). These bacterial groups are reported to be involved in uranium (VI) reduction as a key process in the bioremediation of anoxic uranium contaminated sites [2].

To design a bioremediation strategy for this uranium-contaminated mine water, the original mine water was used directly as a reference to set up anoxic microcosms. Concretely, uranium-reducing-bacteria were stimulated by glycerol (10mM) as electron donor. ICP-MS and Ion-Chromatography analysis from the microcosms revealed a decrease of uranium (≈90%), sulfate (≈60%), iron (≈86%) and manganese (≈88%). In addition, a drop of Eh and pH of the system was detected. A theoretical thermodynamic Eh-pH predominance diagram was calculated by Geochemist ́s Workbench, indicating the formation of uranium (IV) precipitates, probably uraninite, after 3 months at the latest. Finally, uranium (IV) was detected by UV-Visible spectroscopy in the precipitate at the end of the experiment.

These results show that the uranium reduction of soluble uranium (VI) to insoluble uranium (IV) is favoured by the addition of an electron donor (glycerol) in low concentrated uranium contaminated mines water by biostimulating their native microbial community.

Keywords: Uranium; Bioremediation; Reduction; Spectroscopy

  • Poster (Online presentation)
    Mineralogical Society. New Topics in Mineralogy 2: The mineral–microbe interface through time and space., 02.-03.12.2021, Manchester, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-33506
Publ.-Id: 33506


Indications for a bound tetraneutron

Faestermann, T.; Bergmaier, A.; Gernhäuser, R.; Koll, D.; Mahgoub, M.

Using the reaction 7Li(7Li,10C) we tried to populate states in the tetraneutron. A peak in the energy spectrum of identified 10C, which we cannot attribute to a reaction with any other of the target components, corresponds to an excitation of the 10C+4n system of 2.93 ± 0.16 MeV. Under different kinematic conditions an equivalent peak was observed. For a binding energy of the tetraneutron of −2.93 MeV a much larger width than the observed upper limit of Gamma < 0.24 MeV (mainly due to experimental spread) is expected. Therefore, we favor the interpretation that this peak corresponds to 10C in the first excited state at 3.354 MeV and a tetraneutron with a binding energy of +0.42 ± 0.16 MeV

Keywords: Tetraneutron; 4n; Nuclear Physics; stable beams; resonance; nuclear structure; magnetic spectrograph; Q3D

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33502
Publ.-Id: 33502


Single Atom Counting of Stellar and r-Process Nuclei in Time-Resolved Deep-Sea Archives

Koll, D.; Wallner, A.; Hotchkis, M.; Child, D.; Fifield, K.; Froehlich, M.; Hartnett, M.; Lachner, J.; Merchel, S.; Pavetich, S.; Rugel, G.; Slavkovská, Z.; Tims, S.

Stars are the major element factories in the universe. In 1999, live supernova Fe-60 (t1/2 =2.6 Myr)
was detected in a deep-sea ferromanganese crust (1 ) indicating the accumulation of supernova
dust on Earth about 2 million years ago. This was followed by several projects reinforcing the
initial evidence for a global influx of supernova Fe-60. Recently, a much younger continuous
influx was found in Antarctic snow and in deep-sea sediments (2 –4 ) and an older peak around
6 - 8 Myr in deep-sea crusts (5 , 6 ).
In contrast to the well-known production mechanism and synthesis site of Fe-60, the long-lived
plutonium isotope Pu-244 (t1/2 =80 Myr) is a pure r-process nucleus. The nucleosynthesis site for
the astrophysical r-process is still debated in the astrophysics community. Potential candidates
involve rare supernovae and neutron star mergers. To date no evidence was presented that would
point to an exclusive r-process site and combinations of different sites are considered.
Experimentally, we can search for Pu-244 signatures in samples with known Fe-60 signatures to
test for either common influx patterns or independent Pu-244 influxes disentangled from stellar
Fe-60. Accordingly, this information provides a unique and direct experimental approach for
identifying the production site of the heavy elements.
Based on the recent publication of the first detection of interstellar Pu-244 in a ferromanganese
crust with a time resolution of 4.5 Myr (integrating over much shorter Fe-60 influxes) (6 ), we are
now working on a highly time-resolved profile of Fe-60 and Pu-244 in the large ferromanganese
crust VA13/237KD. This direct experimental input will further constrain models for r-process
nucleosynthesis in the galaxy. The recently determined profile of Fe-60 clearly shows two influxes,
one at 2 Myr, the other at 7 Myr, confirming and refining previous results. Preliminary data on
Pu-244 and an outlook for future measurement campaigns will be given.

References
1. K. Knie et al., Phys. Rev. Lett. 83, 18–21 (1999).
2. D. Koll et al., Phys. Rev. Lett. 123, 072701 (2019).
3. A. Wallner et al., Proceedings of the National Academy of Sciences 117, 21873–21879 (2020).
4. D. Koll et al., EPJ Web Conf. 232, 02001 (2020).
5. A. Wallner et al., Nature 532, 69–72 (2016).
6. A. Wallner et al., Science 372, 742–745 (2021).

Keywords: 60Fe; 244Pu; AMS; Stars; Supernovae; r-process

  • Lecture (Conference) (Online presentation)
    Schools on Nuclear Astrophysics Questions, 13.10.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33501
Publ.-Id: 33501


Fe-60 and Mn-53: The Radionuclide System to Study Meteorites, the Solar Neighborhood and Past Supernova Activity

Koll, D.; Faestermann, T.; Korschinek, G.; Ingo, L.; Merchel, S.; Wallner, A.

Astrophysical studies on extraterrestrial samples often involve long-lived radionuclides to study the evolution
of the solar system and the galaxy on long timescales. Dyadic radionuclide/stable nuclide systems such as
U-Pb, Sm-Nd or Rb-Sr are well-established and widely used for dating and characterization of meteorites and
lunar rocks. Such systems rely on the decay of a long-lived radionuclide and the resulting isotopic anomalies
of the daughter isotope compared to natural abundances.
In contrast, in this talk, the two live radionuclides Fe-60 and Mn-53 are shown to be versatile tools to study
meteorites and past supernova activity. Both radionuclides with half-lives around 3 Myr are produced in massive
stars as well as by spallation in extraterrestrial materials, planetary surfaces and cosmic dust. Measured
and modelled production rates [1,2] and the first use as a dyadic system to disentangle the origin of supernovaproduced
Fe-60 on the surface of the moon [3] and in Antarctic snow [4] will be presented amongst recent
discoveries of the individual radionucides in geological archives.

[1] Leya et al., Meteoritics & Planetary Science 55, 818–831 (2020)
[2] Merchel et al., Nucl. Instr. Meth. Phys. Res. B 172, 806-811 (2000)
[3] Fimiani et al., Phys. Rev. Lett. 116, 151104 (2016)
[4] Koll et al., Phys. Rev. Lett. 123, 072701 (2019)

Keywords: Meteorites; 60Fe; 53Mn; Supernova; Interstellar; Interplanetary

  • Poster (Online presentation)
    The 16th International Symposium on Nuclei in the Cosmos, 21.09.2021, Chengdu, China

Permalink: https://www.hzdr.de/publications/Publ-33499
Publ.-Id: 33499


Time-Resolved Interstellar Pu-244 and Fe-60 Profiles in a Be-10 Dated Ferromanganese Crust

Koll, D.; Wallner, A.; Hotchkis, M.; Child, D.; Fifield, K.; Froehlich, M.; Hartnett, M.; Lachner, J.; Merchel, S.; Pavetich, S.; Rugel, G.; Slavkovská, Z.; Tims, S.

More than 20 years have passed since the first attempts to find live supernova Fe-60
(t1/2 = 2.6 Myr) in a deep-sea ferromanganese crust [1]. Within these 20 years, strong evidence was presented for a global influx of supernova dust into several geological samples around 2 Myr ago. Recently, a much younger continuous influx was found in Antarctic snow and in deep-sea sediments [2-4] and an older peak around 7 Myr in deep-sea crusts [5,6].

The long-lived isotope Pu-244 (t1/2 = 80 Myr) is produced in the astrophysical r-process similarly to most of the heaviest elements. Although the production mechanism is believed to be understood, the astrophysical site is heavily disputed. Most likely scenarios involve a combination of rare supernovae and neutron star mergers. The search for Pu-244 signatures in samples with known Fe-60 signatures allows to test for either common influx patterns or a independent Pu-244 influxes disentangled from stellar Fe-60. Accordingly, this information provides a unique and direct experimental approach for identifying the production site of the heavy elements.

Very recently and first reported in the AMS-14 conference, the first detection of interstellar Pu-244 was published [6]. This was only feasible by achieving the highest detection efficiencies for plutonium in AMS ever reported [7]. The achieved time resolution of 4.5 Myr integrates over the supernova influxes and is therefore not high enough to unequivocally show a correlated influx pattern of Fe-60 and Pu-244.
Based on this progress, we are now aiming to measure highly time-resolved profiles of Fe-60 and Pu-244 in the largest ferromanganese crust used so far. Results on the characterisation of the crust including cosmogenic Be-10 (t1/2 = 1.4 Myr) dating and a 10 Myr profile of interstellar Fe-60 including the confirmation of the 7 Myr influx will be presented along with first data on interstellar Pu-244.

[1] Knie et. al., Phys. Rev. Lett. 83 (1999).
[2] Koll et al., Phys. Rev. Lett. 123 (2019).
[3] Koll et al., EPJ 232 (2020).
[4] Wallner et al., PNAS 117 (2020).
[5] Wallner et al., Nature 532 (2016)
[6] Wallner et al., Science 372 (2021)
[7] Hotchkis et al., NIMB 438 (2019)

Keywords: Supernova; 60Fe; 244Pu; 10Be; r-process; ferromanganese crust; pacific; AMS

  • Lecture (Conference) (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry, 19.11.2021, Sydney, Australia

Permalink: https://www.hzdr.de/publications/Publ-33498
Publ.-Id: 33498


Band-selective third-harmonic generation in superconducting MgB2: Possible evidence for the Higgs amplitude mode in the dirty limit

Kovalev, S.; Dong, T.; Shi, L.-Y.; Reinhoffer, C.; Xu, T.-Q.; Wang, H.-Z.; Wang, Y.; Gan, Z.-Z.; Germanskiy, S.; Deinert, J.-C.; Ilyakov, I.; van Loosdrecht, P. H. M.; Wu, D.; Wang, N.-L.; Demsar, J.; Wang, Z.

We report on time-resolved linear and nonlinear terahertz spectroscopy of the two-band superconductor MgB2
with a superconducting transition temperature Tc ≈ 36 K. Third-harmonic generation (THG) is observed below
Tc by driving the system with intense narrow-band THz pulses. For the pump-pulse frequencies f = 0.3, 0.4,
and 0.5 THz, the temperature-dependent evolution of the THG signals exhibits a resonance maximum at the
temperatures with the resonance conditions 2 f = 2Delta π (T ) fulfilled, for the dirty-limit superconducting gap
2Delta π . In contrast, for f = 0.6 and 0.7 THz with 2 f > 2Delta π (T → 0) = 1.03 THz, the THG intensity increases
monotonically with decreasing temperature. Moreover, for 2 f < 2Delta π (T → 0) the THG is found nearly isotropic
with respect to the pump-pulse polarization. These results suggest a predominant contribution of the driven
Higgs amplitude mode of the dirty-limit π -band superconducting gap, pointing to the importance of scattering
for observation of the Higgs mode in superconductors.


Data publication: Temperature-induced surface faceting of M-plane Al₂O₃: An in-situ GISAXS study

Erb, D.; Perlich, J.; Roth, S.; Röhlsberger, R.; Schlage, K.

-- raw data of GISAXS experiment

-- AFM data

-- GISAXS simulation files

Keywords: crystal surface reconstruction; nanofaceted Al₂O₃; pattern formation; in-situ GISAXS; AFM

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-30
    DOI: 10.14278/rodare.1285
    License: CC-BY-4.0
    Embargo: 31.12.2022

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33492
Publ.-Id: 33492


Spin-wave focusing induced by dipole-dipole interaction in synthetic antiferromagnets

Gallardo, R. A.; Alvarado-Seguel, P.; Kákay, A.; Lindner, J.; Landeros, P.

Under certain conditions, spin waves can be channeled into a broad angular spectrum of wave vectors, where the direction
of the group velocity becomes independent of those wave vectors. Such highly focused waves are called caustic waves,
whose properties can be manipulated by anisotropies or chiral interactions, like the Dzyaloshinskii-Moriya interaction. In this
paper, we theoretically study the focusing features of the spin waves induced by the dipole-dipole interaction in synthetic
antiferromagnets. For stacked systems, the dipolar interaction causes a noticeable frequency nonreciprocity when the
magnetizations in both films are antiparallelly aligned, and then the focusing properties of the spin waves are enhanced. The
role of thicknesses and magnetic graduation along the film's normal are systematically analyzed. We found that the degree
of focalization of the spin waves can be manipulated by increasing the layers' thickness. Also, we show that the low- and
high-frequency modes exhibit different focalization properties; the low-frequency mode manifests a similar behavior to the
heavy-metal/ferromagnet systems with interfacial Dzyaloshinskii-Moriya interaction, while the high-frequency one tends the
generate almost reciprocal interference patterns along one axis. In the case of magnetization-graded synthetic
antiferromagnets, we demonstrate that the graduation slightly influences the low-frequency mode, while the focusing and
nonreciprocal dynamic properties of the high-frequency ones are notoriously altered. The theoretical calculations are
compared with micromagnetic simulations, where a good agreement is found between both methods. Our results
demonstrate that a synthetic antiferromagnetic system allows for controlling the propagation of spin waves, assisting in the
transfer of angular momentum and energy.

Keywords: Spin waves; Wave focusing; synthetic antiferromagnets; Dzyaloshinskii-Moriya interaction; Spectrum analysis; dipole-dipole interaction; multilayers

Permalink: https://www.hzdr.de/publications/Publ-33489
Publ.-Id: 33489


Data to 18F-AW09

Wodtke, R.; Löser, R.

radio-TLC, radio-HPLC, radio-SDS, in vitro autoradiography

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-29
    DOI: 10.14278/rodare.1281

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33487
Publ.-Id: 33487


NMR data FBz/FBn polyamines

Wodtke, R.; Löser, R.

Files of NMR data for the different fluorobenz(o)ylated polyamines and radiosynthesis data

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-29
    DOI: 10.14278/rodare.1279

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33486
Publ.-Id: 33486


Americium preferred: LanM, a natural lanthanide-binding protein favors an actinide over lanthanides

Singer, H.; Drobot, B.; Zeymer, C.; Steudtner, R.; Daumann, L.

The separation and recycling of lanthanides is an active area of research with a growing demand that calls for more environmentally friendly lanthanide sources. Likewise, the efficient and industrial separation of lanthanides from the minor actinides (Np, Am - Fm) is one of the key questions for closing the nuclear fuel cycle; reducing costs and increasing safety. With the advent of the field of lanthanide dependent bacterial metabolism, bio-inspired applications are in reach. Here, we utilize the natural lanthanide chelator Lanmodulin and the luminescent probes Eu3+ and Cm3+ to investigate the inter-metal competition behavior of all lanthanides (except Pm) and the major actinide plutonium as well as three minor actinides neptunium, americium and curium to Lanmodulin. Using time resolved laser induced fluorescence spectroscopy we show that Lanmodulin has the highest relative binding affinity to Nd3+ and Eu3+ among the lanthanide series. When equimolar mixtures of Cm3+ and Am3+ are added to Lanmodulin, Lanmodulin preferentially binds to Am3+ over Cm3+ whilst Nd3+ and Cm3+ bind with similar relative affinity. The results presented show that a natural lanthanide binding protein can bind a major and various minor actinides with high relative affinity, paving the way to bio inspired separation applications. In addition, an easy and versatile method was developed, using the fluorescence properties of only two elements, Eu and Cm, for inter-metal competition studies regarding lanthanides and selected actinides and their binding to biological molecules.

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Permalink: https://www.hzdr.de/publications/Publ-33485
Publ.-Id: 33485


Development of “clickable” albumin binders and application to theranostic radioligands for somatostatin receptor subtype 2

Brandt, F.; Ullrich, M.; Löser, R.; Pietzsch, H.-J.; Kopka, K.; Pietzsch, J.; Wodtke, R.

Despite given high affinity and selectivity towards their distinct biological targets, theranostic radioligands can suffer strongly from fast blood clearance and metabolism, which limits the enrichment of the compounds in the tumour tissue. A viable strategy to increase the bioavailability of substances is the conjugation to human serum albumin (HSA). In this context, Nε-4-(4-iodophenyl)butanoyllysine (Nε-IPB-lysine) was recently discovered as potent albumin binder.[1] However, conjugation of Nε-IPB-lysine via its α-amino group to proteins, peptides or small molecules is challenging, as a free α-carboxyl group is required to maintain good binding to HSA.
To allow the broad applicability and late-stage introduction of Nε-IPB-lysine we present a novel approach of Cu-catalyzed azide-alkyne cycloaddition (CuAAC) using Nε-IPB-lysine derivatives with azide/alkyne bearing moieties at the α-amino group. For small scales, a solid phase synthesis strategy starting from Fmoc-Lys(Alloc)-OH was developed. For upscaling, a 3-step synthesis starting from Boc-Lys-OH has been established. The HSA binding affinities were determined using microscale thermophoresis and a fluorescence-based competition assay. A library of azide/alkyne containing compounds with a binding affinity to HSA ranging from 0.4 µM to 100 µM could be obtained.
To demonstrate the suitability of the novel albumin binders, Nα-5-azidopentanoyl-Nε-IPB-D-lysine (Kd = 8 µM) was coupled to the somatostatin receptor subtype 2 ligand NODAGA-Pra-O2Oc-TATE 1 by on-resin CuAAC. For radiolabelling, copper-64 was used. The resulting conjugate [64Cu]Cu-2 showed significantly improved binding to HSA compared to [⁶⁴Cu]Cu-1, [⁶⁴Cu]Cu-NODAGA-TATE, and [⁶⁴Cu]Cu-DOTA-TATE. All TATE derivatives were studied by PET imaging using a mouse phaechromocytoma (MPC)-allograft model highlighting an increased blood circulation time of [⁶⁴Cu]Cu-2 and higher tumor uptake at late time points (24 h) compared to the other radiotracers. Current studies aim to further optimise the biodistribution by selecting HSA binders of higher or lower binding affinity.

Literature:
[1] Dumelin et al. Angew. Chem. Int. Ed. Engl. 2008, 47(17), 3196-3201.

  • Poster (Online presentation)
    Frontiers in Medicinal Chemistry, 08.-10.03.2021, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33484
Publ.-Id: 33484


Synthesis and characterisation of irreversible transglutaminase 2-inhibitors with albumin binding moiety

Wodtke, R.; Schlitterlau, P.; Brandt, F.; Laube, M.; Kopka, K.; Pietzsch, H.-J.; Pietzsch, J.; Löser, R.

The development of radiotracers for transglutaminase 2 (TGase 2) based on irreversible inhibitors appears highly attractive to further uncover the role of that enzyme for the emergence and progression of various tumours. [1] In this context, the ¹⁸F-labelled analogue of Nε-acryloyl-L-lysine 1, developed in our lab, showed great potential as radiometric tool for in vitro investigations. However, application for in vivo imaging is strongly limited by its unfavourable pharmacokinetic properties such as fast blood clearance and metabolism. A common approach to improve biodistribution and blood circulation time of drugs is the reversible conjugation to human serum albumin (HSA). Recently, compound 2 was identified as HSA binder with good affinity (Kd = 3.2 µM). [2] Successful application of 2 was demonstrated for pharmacokinetic tuning of various radiolabelled compounds, but rather for hydrophilic than for hydrophobic molecules. [3] Moreover, compound 2 offers the possibility for radiolabelling with iodine-123. [4]
For the purpose to develop radiotracers for TGase 2 with HSA binding capability, we designed compound 3 as lead structure containing the HSA binding moiety of 2 linked via a triazole ring as an amide bioisostere to the part of the TGase 2-inhibitor. Conjugation of alkyne-functionalised Nε-acryloyl-L-lysines and Boc-protected (R)-6-amino-2-azidohexanoic acid by copper-catalysed azide/alkyne cycloaddition followed by Boc deprotection and introduction of 4-(4-iodophenyl)butanoic acid via the respective N-hydroxysuccinimide ester gave access to 3 and two further derivatives with 3,5 and 2,5 substitution pattern at the pyridine ring. Evaluation of these compounds (and their alkyne precursors) by in-house assay methods revealed excellent inhibitory potencies towards TGase 2 (kinact/KI = 10,800 and 3,880 M-1s-1 for 3 and 1, respectively) and good binding affinities to HSA (Kd = 2.3 µM for 3). Overall, this indicates a promising basis for the application of this dual-targeting approach. Current studies focus on the radiolabelling of compound 3 with iodine-123 using the respective arylboronic acid as precursor which can be obtained via the same synthetic route.

Literature:
[1] Pietsch et al. Bioorg. Med. Chem. Lett. 2013, 23, 6528. [2] Dumelin et al. Angew. Chem. Int. Ed. 2008, 47, 3196. [3] Brandt et al. Nucl. Med. Biol. 2019, 70, 46. [4] Wen et al. Mol. Pharmaceutics 2019, 16, 816.

  • Lecture (Conference) (Online presentation)
    Frontiers in Medicinal Chemistry, 08.-10.03.2021, Darmstadt, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33483
Publ.-Id: 33483


Development of ¹²³I-labelled acrylamides as radiotracer candidates for transglutaminase 2

Laube, M.; Brandt, F.; Kopka, K.; Pietzsch, H.-J.; Pietzsch, J.; Löser, R.; Wodtke, R.

Objectives: The development of radiotracers for transglutaminase 2 (TGase 2) based on irreversible inhibitors appears highly attractive to further uncover the role of this enzyme for the emergence and progression of various tumour entities. However, the present imaging probes labeled with carbon-11 or fluorine-18 suffer from unfavourable pharmacokinetic properties such as fast blood clearance and metabolism. [1] Furthermore, incorporation of radionuclides with a longer half-life is desirable as the irreversible reaction between the molecular target and the probe might lead to a better signal-to-noise ratio at later time points. To tackle these two aspects, we developed the potent inhibitors 1 and 2 (Scheme) containing pyridine-3-yl residues with electron withdrawing groups and a iodinated phenylacetyl moiety. Herein, we present the radiosynthesis of [¹²³I]1 and [¹²³I]2 using their respective boronic acid pinacol esters as precursors.
Methods: Compounds 1 and 2 and the precursors 1-P and 2-P were synthesised starting from Nα-Boc-L-lysine in a sequence consisting of Nε-acrylation, PyBOP-mediated amide bond formation, Boc deprotection and HATU-mediated Nα-acylation. [2] For optimisation of radioiodination, reactions were performed in HPLC vials as reaction vessels applying 0.5-2 MBq [¹²³I]iodide in 50-100 µL of solvent. In addition to varying additive/precursor/water concentrations, the storage life and premixing time of reagent solutions were investigated. Radiolabelling at higher activity levels (up to 600 MBq) was conducted using 15-50 µL [¹²³I]iodide in total reaction volumes of 200-300 µL. Radiotracers were separated by semi-preparative HPLC. Solid-phase extraction was performed to provide [¹²³I]1 and [¹²³I]2 in suitable formulations for preclinical studies.
Results: 80-100 mg of each reference and precursor compound were obtained in sufficient purities (>95%). While chloramine T did not lead to the formation of [¹²³I]1 and [¹²³I]2, both compounds were accessible by the use of copper(II) trifluoroacetate and 1,10-phenanthroline [3] or tetrakis(pyridine)copper(II) triflate (Cu(OTf)₂(py)₄) [4]. In this context, Cu(OTf)₂(py)₄ in a 4-fold excess to precursor appeared to be most favourable leading to radiochemical conversions of >90% already after 10 min at room temperature (Scheme). These conditions allow for efficient radioiodinations even at 0.1 mM of precursor as well as with a water portion of up to 26%. Furthermore, the reagent solutions can be stored up to 3 month (at -20°C) without significant loss of radiochemical conversion. [¹²³I]1 and [¹²³I]2 were obtained as solutions in ethanol (2 MBq/µL) with (radio)chemical purities of ≥98% and radiochemical yields of >80%.
Conclusion: ¹²³I-labelled irreversible inhibitors of TGase 2 were prepared for the first time. The use of boronic acid pinacol ester as precursor and Cu(OTf)₂(py)₄ as catalyst facilitated the efficient radiolabelling with [¹²³I]iodide. This enables the radiopharmacological characterisation of these potential radiotracers towards their target TGase 2 in vitro and in vivo.
Acknowledgments: The authors thank ROTOP Radiopharmacy for continuously providing [¹²³I]iodide. Financial support by “Europäischer Fonds für regionale Entwicklung (EFRE)” (ML, HJP, and RW) is gratefully acknowledged.
References: [1] van der Wildt et al. Amino Acids 2017, 49, 585; [2] Wodtke et al. J. Med. Chem. 2018, 61, 4528; [3] Wilson et al. Chem. Comm. 2016, 52, 13277; [4] Reilly et al. Org. Lett. 2018, 20, 1752.

  • Lecture (Conference) (Online presentation)
    eSRS 2021, 17.-19.05.2021, Fredericksburg, United States of America
    DOI: 10.1016/S0969-8051(21)00396-6

Permalink: https://www.hzdr.de/publications/Publ-33481
Publ.-Id: 33481


Transition-metal-free reductive coupling of an 18F-labeled nitro-arene with boronic acids as a potential access to 18F-labeled fenamates

Laube, M.; Roscales Garcia, S.; Pietzsch, J.; Csákÿ, A. G.

Objectives

A recently developed synthetic route for the transition metal-free reductive coupling of aryl boronic acids with nitro1 or nitroso2 substituted arenes gives access to a variety of diaryl amines like fenamates.3 Radiotracers targeting COX-2 have been developed and tested as PET tracer but no clinically approved radiotracer emerged up to now. Aim of this project is to evaluate this novel synthetic route as a general access to 18F-labeled N,N-diaryl amines which are principally not activated for 18F-labeling by nucleophilic aromatic substitution, and by that access to fenamates like flufenamic acid as COX-targeting radiotracers in a wider sense. In this report, we present first results with focus on radiolabeling and reactivity of an asymmetric 18F-labeled nitro-arene.

Methods

The asymmetric sydnone-substituted nitroarene was radiolabeled under optimized conditions with fluorine-18 using K222/K2CO3 in DMF at 90°C and was purified by a C18-based solid phase extraction (SPE). Elution from the dried C18 SPE-cartridge with ortho-dichlorobenzene over a SEP-Pak Dry cartridge provided the intermediate [18F]A for further testing and optimization of the reductive coupling step. Subsequent radiochemical conversion of [18F]A with different boronic acids was monitored via radio-UHPLC. 3-Cyanophenyl boronic acid was used to optimize the coupling reaction with [18F]A with respect to the parameters base/reducing agent, temperature, reaction time. Furthermore, [18F]A was subjected to the reaction with other ortho-, meta-, and para-substituted boronic acids to get a first impression about the scope of this reaction.

Results

[18F]A was isolated after radiolabeling and purification by SPE in 16-54% isolated RCY (n=4). Optimizations using aliquots of 50 µL allowed for optimization of several reaction conditions with one batch of [18F]A. Triphenylphosphine but not triethylphosphite was found to mediate the reductive coupling of 3-cyanophenylboronic acid at reaction temperatures of 140°C and 170°C. Compared to 170°C, radiochemical conversion of [18F]A was found to be slightly higher at 180°C. A clear rationale for the amount of boronic acid and PPh3 was not found since both ratios of 5.4 to 2.5 as well as 2.4 to 4.2 gave highest RCC at 180°C. [18F]A was found to react with a variety of different boronic acids, although proof of identity for the reaction products to the respective diarylamines has still to be performed. In general, however, reaction kinetics were found to be slow leading to radiochemical conversions above 80% only after a reaction time of 80 min which represents a main limitation for radiochemical reactions using fluorine-18.

Conclusion

18F-labeling of N,N-diarylamines represents a challenge for classical nucleophilic aromatic substitution approaches. The use of an 18F-labeled nitroarene and a transition-metal free reductive coupling methodology gave access to this type of compounds but slow reaction kinetics likely hinders the general use in 18F-chemistry. Hence, the evaluation of a respective nitrosoarene is currently under the way representing a highly attractive alternative in this regard due to the much faster reaction kinetics.

References

1. a) Nykaza, J.Am.Chem.Soc. 2020, 142, 6786. b) Roscales, Adv.Synth.Catal. 2020, 362, 111.

2. Roscales, Org.Lett. 2018, 20, 1667; 3. Roscales, J.Chem.Educ. 2019, 96, 1738.

Figure 1. Radiosynthesis of flufenamic acid derivates by transition metal-free reductive coupling with [18F]A

  • Poster (Online presentation)
    eSRS 2021, 17.-19.05.2021, Online, Online

Permalink: https://www.hzdr.de/publications/Publ-33480
Publ.-Id: 33480


An interdisciplinary view of the long-term evolution of repository systems across scales: the iCROSS project

Bosbach, D.; Geckeis, H.; Heberling, F.; Kolditz, O.; Kühn, M.; Müller, K.; Stumpf, T.; Heberling, F.

The interdisciplinary project “Integrity of nuclear waste repository systems – Cross-scale system understanding and analysis (iCROSS)” combines research competencies of Helmholtz scientists related to the topics of nuclear, geosciences, biosciences and environmental simulations in collaborations overarching the research fields energy and earth and environment. The focus is to understand and analyze close-to-real long-term evolutionary pathways of radioactive waste repositories across nanoscales to repository scales.

The project is subdivided into work packages dealing with laboratory studies, field experiments in underground research laboratories (URLs), advanced modelling studies and the integration and alignment of data and information using virtual reality methods. In this sense, the project structure aims at a holistic view on relevant processes across scales in order to comprehensively simulate potential repository evolutions.

Within the multi-barrier system of a repository for heat-generating radioactive waste, a number of complex reactions proceed, including dissolution, redox processes, biochemical reactions, gas evolution and solid/liquid interface and (co)precipitation reactions. At the same time, thermal and external mechanical stress has an impact on the conditions in a deep geological repository. All those processes are highly coupled, with multiple interdependencies on various scales and have a strong impact on radionuclide mobility and retention. In recent years, substantial progress was achieved in describing coupled thermal-hydro-mechanical-chemical-biological (THM/CB) processes in numerical simulations. A realistic and concise description of these coupled processes on different time and spatial scales is, at present, a largely unresolved scientific and computational challenge. The close interaction of experimental and simulation teams aims at a more accurate quantification and assessment of processes and thus, the reduction of uncertainties and of conservative assumptions and eventually to a close-to-real perception of the repository evolution.

One focus of iCROSS is directed to relevant processes in a clay rock repository. In this context, the iCROSS team became a full member of the international Mont Terri consortium and worked in close collaboration with international and German institutions in URL projects. Respective experiments specifically deal with coupled processes at the reactive interfaces in a repository near field (e.g. the steel/bentonite and bentonite/concrete interfaces). Within iCROSS, the impact of secondary phase formation on radionuclide transport is investigated. At Mont Terri, experiments are in preparation to study radionuclide transport phenomena in clay rock formations within temperature gradients and in facies exhibiting significant heterogeneities on different scales (nm to cm). Beside those studies, high resolution exploration methods for rock characterization are developed and tested and the effect of temperature and other boundary conditions on the strength, creep properties and healing of faults within Opalinus clay are quantified. Multiphysics models coupled to reactive transport simulation have been further developed and applied to laboratory and field experiments. Results are digitally analyzed and illustrated in a visualization center, in order to enhance the comprehension of coupled processes in repository systems across scales.

The present contribution provides an overview on the project and reports selected results. The impact of considering complex coupled processes in repository subsystems for the assessment of the integrity of a given (generic) repository arrangement is discussed.
How to cite.

Bosbach, D., Geckeis, H., Heberling, F., Kolditz, O., Kühn, M., Müller, K., Stumpf, T., and the iCROSS team: An interdisciplinary view of the long-term evolution of repository systems across scales: the iCROSS project, Saf. Nucl. Waste Disposal, 1, 85–87, https://doi.org/10.5194/sand-1-85-2021, 2021.

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Im interdisziplinären Projekt iCROSS („Integrität von Endlagern für nukleare Abfälle – Übergreifendes Systemverständnis und Analyse“) werden Forschungskompetenzen von Wissenschaftlern der Helmholtz-Institute mit den Themen Nuklearwissenschaften, Geowissenschaften, Biowissenschaften und Umweltsimulationen in einer die Forschungsbereiche Energie sowie Erde und Umwelt übergreifenden Zusammenarbeit kombiniert. Der Fokus richtet sich darauf, realitätsnahe Langzeitentwicklungspfade von Endlagern für radioaktive Abfälle von der Nano- bis zur Endlagerskala zu verstehen und auszuwerten.

Das Projekt ist unterteilt in Arbeitspakete zu Laborstudien, Feldexperimenten in unterirdischen Forschungslaboren (URL), fortgeschrittenen Modellierungsstudien und der Integration sowie der Ausrichtung von Daten und Informationen unter Verwendung von Methoden der virtuellen Realität. In diesem Sinne zielt die Projektstruktur auf eine ganzheitliche Sicht auf relevante Prozesse über Skalen hinweg ab, um potenzielle Entwicklungen von Endlagern umfassend zu simulieren.

Innerhalb des Multi-Barrieren-Systems eines Endlagers für wärmeerzeugende radioaktive Abfälle laufen eine Reihe komplexer Reaktionen, einschließlich Zerfallsreaktionen, Redoxreaktionen, biochemischer Reaktionen, Gasentwicklung und Fest-Flüssig-Grenzflächen- sowie (Ko-)Präzipitationsreaktionen ab. Gleichzeitig haben thermische und externe mechanische Belastungen einen Einfluss auf die Bedingungen in einem geologischen Tiefenlager. Sämtliche dieser Prozesse sind eng miteinander verbunden – mit multiplen Interdependenzen auf verschiedenen Ebenen – und haben einen großen Einfluss auf die Radionuklidmobilität und -retention. In den vergangenen Jahren wurden wesentliche Fortschritte bei der Beschreibung gekoppelter thermo-hydromechanisch-chemisch-biologischer (THM/CB-)Prozesse in numerischen Simulationen erzielt. Eine realistische Beschreibung dieser gekoppelten Prozesse auf unterschiedlichen Zeit- und Raumskalen ist zum gegenwärtigen Zeitpunkt eine großenteils ungelöste wissenschaftliche und rechnerische Herausforderung. Die enge Interaktion von Experimentier- und Simulationsteams zielt auf eine genauere Quantifizierung und Beurteilung von Prozessen ab und somit auf die Verminderung von Ungewissheiten und von konservativen Annahmen und schließlich auf eine realitätsnahe Wahrnehmung der Entwicklung des Endlagers.

Ein Fokus von iCROSS richtet sich auf relevante Prozesse in einem Tongestein-Endlager. In diesem Zusammenhang wurde das iCROSS-Team Vollmitglied des internationalen Mont-Terri-Konsortiums und arbeitet in enger Kooperation mit internationalen und deutschen Institutionen in URL-Projekten zusammen. Die entsprechenden Experimente befassen sich insbesondere mit gekoppelten Prozessen an den reaktiven Grenzflächen im Nahfeld eines Endlagers (z. B. die Stahl-Bentonit- und Bentonit-Beton-Grenzflächen). Innerhalb von iCROSS werden die Auswirkungen der Sekundärphasenbildung auf den Radionuklidtransport untersucht. Im Mont-Terri-Labor befinden sich Experimente in Vorbereitung, um Radionuklidtransportphänomene in Tongesteinsformationen innerhalb von Temperaturgradienten und angesichts erheblicher Heterogenitäten in unterschiedlichen Maßstäben (nm bis cm) zu untersuchen. Neben diesen Untersuchungen werden hochauflösende Untersuchungsmethoden für die Gesteinscharakterisierung entwickelt und geprüft, und die Auswirkungen von Temperatur und anderen Randbedingungen auf die Festigkeit, Kriecheigenschaften und Heilung von Verwerfungen innerhalb von Opalinus-Ton werden quantifiziert. Multiphysikalische Modelle in Kombination mit reaktiver Transportsimulation werden weiterentwickelt worden und in Labor- sowie Feldexperimenten eingesetzt. Die Ergebnisse werden digital ausgewertet und in einem Visualisierungszentrum dargestellt, um das Verständnis gekoppelter Prozesse in Endlagersystemen skalenübergreifend zu verbessern.

Der vorliegende Beitrag bietet einen Überblick über das Projekt und legt ausgewählte Ergebnisse dar. Die Auswirkungen der Betrachtung komplexer gekoppelter Prozesse in Endlager-Subsystemen auf die Beurteilung der Integrität einer gegebenen exemplarischen Endlageranordnung werden erörtert.

  • Lecture (Conference)
    SafeND Interdisziplinäres Forschungssymposium für die Sicherheit der nuklearen Entsorgung, 10.-12.11.2021, Berlin, Deutschland
  • ORA-00933: SQL-Befehl wurde nicht korrekt beendet

Data publication: Symmetry- and curvature effects on spin waves in vortex-state hexagonal nanotubes

Körber, L.; Zimmermann, M.; Wintz, S.; Finizio, S.; Kronseder, M.; Bougeard, D.; Dirnberger, F.; Weigand, M.; Raabe, J.; Otálora, J. A.; Schultheiß, H.; Josten, E.; Lindner, J.; Kézsmárki, I.; Back, C. H.; Kakay, A.

This dataset contains the experimental and numerical raw data for our publication "Symmetry- and curvature effects on spin waves in vortex-state hexagonal nanotubes" published in Physical Review B. The experimental data is described in detail in the PDF "MAXYMUS_Tube210nm_antje500nm_2017_10_14". 

The dynamic matrix data contains eparam.yaml and sparam.yaml files containing the simulation and sample parameters used for micromagnetic modeling.

Keywords: spin wave; dispersion; curvature; micromagnetic modeling; hexagonal; symmetry; STXM

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-26
    DOI: 10.14278/rodare.1277
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33475
Publ.-Id: 33475


Magnetotactic bacteria as an effective sorbent for uranium in contaminated water.

Krawczyk-Bärsch, E.; Ramtke, J.; Drobot, B.; Steudtner, R.; Hübner, R.; Raff, J.

There are many ideas for using radionuclide- and heavy metal-binding microorganisms to remediate contaminated waters after e.g. uranium mining and processing. In particular, magnetotactic bacteria are moving into the focus of interest since they are able to survive in environments with very limited oxygen. Due to their organelles containing magnetic crystals, they can align themselves along the Earth's magnetic field for reaching regions of optimal oxygen concentrations. In laboratory studies we used the α-proteobacterium Magnetospirillum magneticum AMB-1, which is a motile, magnetotactic, gram-negative bacterium. It is facultative anaerobe and usually found in oxic-anoxic transition zones. In kinetic batch sorption experiments, cells of Magnetospirillum magneticum AMB-1 were contacted with different uranium concentrations and different pH. Independent of the initial U concentration, the cells were able to remove most of the uranium from the solution during the first hours of incubation. Microscopic studies, such as Transmission Electron Microscopy (TEM) in combination with Energy-Dispersive X-ray Spectroscopy (EDXS), clearly indicated that uranium is entirely accumulated in the cell membrane. Using spectroscopic methods like Time-Resolved Laser-Induced Fluorescence Spectroscopy at low temperature (cryo-TRLFS at 153 K), it was shown that uranium is mainly bound to the carboxylic functionality groups of peptidoglycan at the outer membrane of Magnetospirillum magneticum AMB-1 cells. With the obtained results we demonstrate that magnetotactic bacteria may play an important role in the bioremediation of contaminated sites, and probably not only for uranium, but also for other heavy metals.

Keywords: Magnetotactic bacteria; Uranium; Sorption; Remediation; TRLFS; TEM

  • Lecture (Conference) (Online presentation)
    4th International Caparica Conference on Pollutant Toxic Ions and Molecules 2021, 31.10.-04.11.2021, Caparica, Portugal

Permalink: https://www.hzdr.de/publications/Publ-33473
Publ.-Id: 33473


Bioremediación de aguas contaminadas: Estudio multidisciplinar de la reducción microbiana de uranio (U) en aguas de mina.

Newman-Portela, A. M.; Krawczyk-Bärsch, E.; Lopez-Fernandez, M.; Bok, F.; Kassahun, A.; Raff, J.; Merroun, M. L.

Tras el cese de la minería en Alemania oriental, restos de U y otros metales pesados siguen contaminando el territorio. Actualmente, estas minas están en proceso de remediación mediante estrategias convencionales. En este estudio, hemos caracterizado la geoquímica y la diversidad microbiana del agua de dos antiguas minas de U (Schlema-Alberoda y Pöhla) con el objetivo de diseñar una estrategia de biorremediación. Los análisis de ICP-MS y cromatografía iónica (CI) mostraron en el agua una alta concentración de U, sulfato, hierro y manganeso en Schlema-Alberoda respecto a Pöhla (U: 1,01 y 0,11mg/L;
Sulfato: 335 y 0,26mg/L; Hierro: 0,99 y 0,13mg/L; Manganeso: 1,44 y 0,16mg/L, respectivamente). El estudio de los genes 16S del ARNr e ITS1 de ambas minas reveló una gran diversidad microbiana implicada en la biorremediación de U(VI), destacando una abundanciarelativa de bacterias sulfatorreductoras (p.ej., Sulfuricuvum, Sulfurimonas y Sulfurovum) y bacterias hierro-oxidadoras (p.ej., Gallionella y Sideroxydans). Además, se diseñaron microcosmos-anóxicos-bioestimulados (glicerol [10mM]) tomando agua original de Schlema-Alberoda. Los análisis de ICP-MS y CI de los microcosmos revelaron aproximadamente una disminución del 90% de U, sulfato, hierro y manganeso, junto a un descenso del Eh y pH del sistema. Se calculó un diagrama termodinámico de predominio Eh-pH que indica la formación de precipitados de U(IV) insolubles. Estos resultados muestran que la reducción enzimática del U(VI), es favorecida por la adición de un donador de electrones en aguas mineras contaminadas. Por ende, podría ser un enfoque eficiente de biorremediación para las aguas contaminadas con U, bioestimulando su comunidad microbiana nativa.

Keywords: uranium; bacteria; bioremediation; uranium reduction

  • Lecture (Conference) (Online presentation)
    XXVIII Congreso Nacional de Microbiología (SEM21), 28.06.-02.07.2021, virtuell, Espana

Permalink: https://www.hzdr.de/publications/Publ-33472
Publ.-Id: 33472


Electrical and structural properties of NixGey thin films made by Magnetron sputtering and flash lamp annealing

Begeza, V.; Rebohle, L.; Mehner, E.; Zhou, S.

Due to its higher charge carrier mobility compared to silicon, germanium belongs to the promising materials to surpass the physical limitations of the silicon based CMOS technology. For the integration of germanium into the CMOS process, the ohmic contact material with sufficiently low resistivity plays a crucial role. One of the promising candidates is nickel-germanide (NiGe) with a specific resistivity of (13.5 – 22) cm. Those values are comparable with the nickel-silicides used in the CMOS process with electrical resistivities of around 17 cm
This work is focused on the formation process of NiGe films on different germanium layer morphologies, by the flash lamp annealing approach. Furthermore, the investigation on the NixGey phase formation at different annealing temperatures was performed by grazing incidence X-ray diffraction and cross section transmission electron microscopy. The electrical properties were investigated by the application of four-point-probe, Hall effect and circular transfer length measurement techniques.

Keywords: Germanium; Nickel-germanide; Thin films; Flash Lamp Annealing; Millisecond Thermal Treatment; Phase Formation

  • Open Access Logo Poster (Online presentation)
    From Matter to Materials and Life 2021, 22.-24.11.2021, Online, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33471
Publ.-Id: 33471


Plasmonic terahertz nonlinearity in graphene disks

Han, J.; Chin, M. L.; Matschy, S.; Poojali, J.; Seidl, A.; Winnerl, S.; Hafez, H. A.; Kumar, G.; Myers-Ward, R. L.; Dejarld, M. T.; Daniels, K. M.; Drew, H. D.; Murphy, T. E.; Mittendorff, M.

"Analysis_code_Final" contains the theoretical calculations. "FELmeasurements" contains the raw data of the pump-probe measurements with the FEL. "LabBook" contains the corresponding lab book pages.

Keywords: graphene; terahertz; nonlinearity

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-25
    DOI: 10.14278/rodare.1275

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Permalink: https://www.hzdr.de/publications/Publ-33469
Publ.-Id: 33469


Helmholtz AI Consulting for matter research at HZDR

Steinbach, P.; Hoffmann, H.; Pape, D.; Schmerler, S.; Starke, S.

In this presentation, I'd like to present the current status of Helmholtz AI consultancy for matter research in Helmholtz. I'd provide sneak previews into past and ongoing vouchers we embarked upon for the accelerator physics community and other collaborators. I'll try my best to give some insights on what we use our cluster for and why. Last but not least, I'll discuss challenges we faced along the way and will highlight some future directions if time allows.

Keywords: machine learning; HPC; history; artificial intelligence

  • Open Access Logo Invited lecture (Conferences) (Online presentation)
    Hardware & Numerics Seminar at HZDR, 23.11.2021, Dresden, Germany

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Publ.-Id: 33467


Asymptotic properties of Dirichlet kernel density estimators

Ouimet, F.; Tolosana Delgado, R.

We study theoretically, for the first time, the Dirichlet kernel estimator introduced by Aitchison and Lauder (1985) for the estimation of multivariate densities supported on the d-dimensional simplex. The simplex is an important case as it is the natural domain of compositional data and has been neglected in the literature on asymmetric kernels. The Dirichlet kernel estimator, which generalizes the (non-modified) unidimensional Beta kernel estimator from Chen (1999), is free of boundary bias and non-negative everywhere on the simplex. We show that it achieves the optimal convergence rate O(n−4/(d+4)) for the mean squared error and the mean integrated squared error, we prove its asymptotic normality and uniform strong consistency, and we also find an asymptotic expression for the mean integrated absolute error. To illustrate the Dirichlet kernel method and its favorable boundary properties, we present a case study on minerals processing.

Keywords: Asymmetric kernel; Asymptotic normality; Beta kernel; Boundary bias; Density estimation; Dirichlet kernel; Mean integrated absolute error; Multivariate associated kernel; Simplex; Strong consistency

Permalink: https://www.hzdr.de/publications/Publ-33466
Publ.-Id: 33466


Data publication: MHT-X: Offline Multiple Hypothesis Tracking with Algorithm X

Akashi, M.; Eckert, S.

There are images of bubbles in the liquid metal obtained through X-ray radiography. Bubbles are injected by a top-submerged lance. Experiments were performed in ELBE in HZDR.

Keywords: Algorithm X; two-phase flow; bubble dynamics; liquid metal; X-ray radiography; neutron imaging; image processing

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-25
    DOI: 10.14278/rodare.1273
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33465
Publ.-Id: 33465


Data publication: Prograde and retrograde precession of a fluid-filled cylinder

Pizzi, F.; Giesecke, A.; Simkanin, J.; Stefani, F.

This dataset included the data and figures for the associated publication "Prograde and retrograde precession of a fluid-filled cylinder".

Keywords: precession; core flow; dynamo; instability; transition

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-25
    DOI: 10.14278/rodare.1271
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33464
Publ.-Id: 33464


Numerical and experimental methods for the analysis of complex particulate systems

Lecrivain, G.; Hampel, U.

In this presentation, experimental and numerical tools available at HZDR are presented for the analysis of complex particulate systems. Energy-intensive particulate systems includes, for example, high-temperature reactors, mixers for the mineral and cement industries, flotation apparatuses for the selective of separation minerals, textile fibers, micro-algae as well as plastics.

Keywords: Particle transport; Resource efficiency; Particulate systems

  • Lecture (Conference)
    M0-Workshop des Topic 5 „Ressourcen- und Energieeffizienz“ des Helmholtz-Programms Materialien und Technologien für die Energiewende, 18.11.2021, Karlsruhe, Germany

Permalink: https://www.hzdr.de/publications/Publ-33460
Publ.-Id: 33460


Autocorrected off-axis holography of two-dimensional materials

Kern, F.; Linck, M.; Wolf, D.; Alem, N.; Arora, H.; Gemming, S.; Erbe, A.; Zettl, A.; Büchner, B.; Lubk, A.

The reduced dimensionality in two-dimensional materials leads to a wealth of unusual properties, which are currently explored for both fundamental and applied sciences. In order to study the crystal structure, edge states, the formation of defects and grain boundaries, or the impact of adsorbates, high-resolution microscopy techniques are indispensable. Here we report on the development of an electron holography (EH) transmission electron microscopy (TEM) technique, which facilitates high spatial resolution by an automatic correction of geometric aberrations. Distinguished features of EH beyond conventional TEM imaging are gap-free spatial information signal transfer and higher dose efficiency for certain spatial frequency bands as well as direct access to the projected electrostatic potential of the two-dimensional material. We demonstrate these features with the example of h-BN, for which we measure the electrostatic potential as a function of layer number down to the monolayer limit and obtain evidence for a systematic increase of the potential at the zig-zag edges.

Permalink: https://www.hzdr.de/publications/Publ-33457
Publ.-Id: 33457


Prograde and retrograde precession of a fluid-filled cylinder

Pizzi, F.; Giesecke, A.; Simkanin, J.; Stefani, F.

We numerically study precession driven flows in a cylindrical container whose nutation angle varies between 60 and 90 degrees for prograde and retrograde precession. For prograde precession we observe sharp transitions between a laminar and a turbulent flow state with low and high geostrophic axisymmetric flow components related with a centrifugal instability, while for retrograde precession a rather smooth transition between a low state and a high state occurs. At the same time prograde and perpendicular precession shows an abrupt breakdown of the flow directly excited by the forcing mechanism, which is not the case for retrograde motion. We characterize the corresponding flow states in terms of the directly driven, non-axisymmetric Kelvin mode, the axisymmetric geostrophic mode, and an axisymmetric poloidal flow which is promising for precession-driven dynamo action. The latter issue is discussed with particular view on an optimal parameter choice for the DRESDYN dynamo project.

Keywords: precession; core flow; dynamo; instability; transition

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-33455
Publ.-Id: 33455


Data publication: Controlled Silicidation of SiNW using FLA

Khan, M. B.; Prucnal, S.; Ghosh, S.; Deb, D.; Hübner, R.; Pohl, D.; Rebohle, L.; Mikolajick, T.; Erbe, A.; Georgiev, Y.

The folder contains the following: 1. all the SEM and TEM images. 2. The schematics of fabrication 3. comparison of silicidation with FLA and RTA and 4. temperature simulations to estimate temperature during FLA process.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-23
    DOI: 10.14278/rodare.1269
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33452
Publ.-Id: 33452


Effect of Interfacial Defects on the Electronic Properties of MoS₂ Based Lateral T-H Heterophase Junctions

Bahmani, M.; Ghorbani Asl, M.; Frauenheim, T.

The coexistence of semiconducting (2H) and metallic (1T) phases of MoS₂ monolayers have further pushed their strong potential for applications in the next generation of electronic devices based on two-dimensional lateral heterojunctions. Structural defects have considerable effects on the properties of these 2D devices. In particular, the interfaces of two phases are often imperfect and may contain numerous vacancies created by phase engineering techniques, e.g. under the electron beam. Here, the transport behaviors of the heterojunctions in the existence of point defects are explored by means of first-principles calculations and non-equilibrium Green's function approach. While vacancies in semiconducting MoS₂ act as scattering centers, their presence at the interface improves the flow of the charge carriers. In the case of Vmo, the current has been increased by two orders of magnitude in comparison to the perfect device. The enhancement of transmission was explained by changes in the electronic densities at the T-H interface, which open new transport channels for electron conduction.

Keywords: two-dimensional materials; defects; lateral heterostructure; conductivity; quantum transport; DFT

Permalink: https://www.hzdr.de/publications/Publ-33451
Publ.-Id: 33451


Direct visualization of highly resistive areas in GaN by means of low-voltage scanning electron microscopy

Jóźwik, I.; Jagielski, J.; Caban, P.; Kamiński, M.; Kentsch, U.

The damage-induced voltage alteration (DIVA) contrast mechanism in scanning
electron microscope (SEM) at low electron energy has been presented as a fast and
convenient method of direct visualization of increased resistivity induced by energetic
ions irradiation in gallium nitride (GaN). Epitaxially grown GaN layers on sapphire
covered with a metallic masks with etched windows were subjected to He 2+
irradiations at 600 keV energy. The resulting two-dimensional damage profiles at the
samples cross-sections were imaged at SEM at different e-beam energies and scan
speeds. The gradual development of image contrast was observed with the increase of
cumulative charge deposited by electron beam irradiation, to finally reach the
saturation level of the contrast related to the local resistivity of the ion-irradiated part of
GaN.
The presented method allows one to directly visualize the ion-irradiated zone even for
the lowest resistivity changes resulting from ion damage, i.e. all levels of insulation
build-up in GaN upon irradiation with ions. Taking into account that it is not possible to
apply the etch-stop technique by wet chemistry to GaN, it makes the presented
technique the only available method of visualization of highly resistant and insulating
regions in GaN-based electronic devices.
Main aim of the presented work is to get a deeper insight into a DIVA contrast in GaN
with the special emphasize to discuss the role of rastering speed and electron beam
current, i.e. details of charge build-up ion the sample surface.

Keywords: GaN; Ion damage; Ion implantation; Low-kV SEM

Permalink: https://www.hzdr.de/publications/Publ-33450
Publ.-Id: 33450


Process simulation for comprehensive sustainability assessment of the silicon photovoltaic life cycle

Bartie, N.; Cobos-Becerra, L.; Froehling, M.; Schlatmann, R.; Reuter, M.

The photovoltaic industry has shown vigorous growth over the last decade and will continue on its trajectory to reach terawatt-level deployment by 2022–2023 and an estimated 4.5 TW by 2050. Presently, its elaboration is driven primarily by cost reduction. Growth will, however, be fuelled by the consumption of various resources, bringing with it unavoidable losses and environmental, economic, and societal impacts. Additionally, strong deployment growth will be trailed by waste growth, which needs to be managed, to support Sustainable Development and Circular Economy (CE). A rigorous approach to quantifying the resource efficiency, circularity and sustainability of complex PV life cycles, and exploring opportunities for partially sustaining industry growth through the recovery of high-quality secondary resources is needed. We create a high-detail digital twin of a Silicon PV life cycle using process simulation. The scalable, predictive simulation model accounts for the system's non-linearities by incorporating the physical and thermochemical principles that govern processes down to the unit operation level. Neural network-based surrogate functions are subsequently used to analyse the system's response to variations in end-of-life and kerf recycling in terms of primary resource and power consumption, PV power generation capacity, and CO2 emission. Applying the second law of thermodynamics, opportunities for improving the sustainability of unit operations, the larger processes they are the building blocks of, and the system as a whole are pinpointed, and the technical limits of circularity highlighted. We show the significant effects changes in technology can have on the conclusions drawn from such analyses.

Keywords: Silicon photovoltaics; Circular Economy; Digital twin simulation; Neural networks Exergy

Permalink: https://www.hzdr.de/publications/Publ-33448
Publ.-Id: 33448


Coordination and Electrochemical Switching on Paddle-Wheel Complexes Containing an As−Ru or a Sb−Ru Axis

Gericke, R.; Wagler, J.

Inspired by the known complex [PhP(μ-PyO)₄Ru(CO)] (PyO = 2-pyridyloxy), the family of group 15 paddle-wheel complexes has been expanded to [PhPn(μ-PyO)₄Ru(L)] (Pn = P, As, Sb; L = NCMe, CO). Solvent-dependent reversible switching between [PhAs(μ-PyO)₄Ru(NCMe)] and [PhAs(μ-PyO)₃Ru(κ²-PyO)] was detected. Electrochemical investigations of the [PhPn(μ-PyO)₄Ru(L)] complexes showed reversible oxidation of the complexes with L = NCMe and back-formation of the complexes with L = NCMe upon oxidation of the complexes with L = CO in NCMe. In the series of [PhPn(μ-PyO)₄RuL)] complexes, the Pn→Ru bonding mode is shifted from L-type Pn to X-type upon going from Pn = P and As to Pn = Sb, resulting in a pronounced electron-rich Ru site in the latter case. The easily accessible complex [PhSb(μ-PyO)₄RuCl] exhibits reversible electrochemical and coordinative exchange with its reduced analogue [PhSb(μ-PyO)₄Ru(NCMe)] under retention of the paddle-wheel motif and Sb−Ru bond properties.

Keywords: ambidentate ligands; ruthenium; pnictogen; hetero bimetallic; electrochemical switching

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  • Secondary publication expected from 23.11.2022

Permalink: https://www.hzdr.de/publications/Publ-33447
Publ.-Id: 33447


The precession dynamo experiment at HZDR

Giesecke, A.; Pizzi, F.; Kumar, V.; Anders, S.; Ratajczak, M.; Gundrum, T.; Stefani, F.

Cosmic magnetic fields exist on all scales, from planets and stars to
galaxies and beyond. The generation of these fields via the
hydromagnetic dynamo effect involves the formation of electrical
currents by means of complex flows of conducting fluids or plasmas. At
HZDR a related experiment is under construction within the project
DRESDYN. In that experiment a precessing flow of liquid sodium will
provide the required energy for magnetic field generation.

Here we address preliminary numerical and experimental studies aimed
at the identification of parameter ranges where a dynamo can be
expected. Our kinematic dynamo models show that dynamo action is
possible just before the transition from a laminar flow state to
vigorous turbulence where the flow structure is determined by a
combination of axisymmetric and nonaxisymmetric large scale modes. By
applying the derived scaling laws, the results can be directly applied
to the parameters of the planned large device.

Keywords: Dynamo

  • Poster (Online presentation)
    MML-Workshop 2021, 22.-24.11.2021, virtuell, virtuell

Permalink: https://www.hzdr.de/publications/Publ-33446
Publ.-Id: 33446


Polyoxoplatinates as Covalently Dynamic Electron Sponges and Molecular Electronics Materials

Kondinski, A.; Ghorbani Asl, M.

Dynamic covalent chemistry is an adaptive approach that utilizes thermodynamic equilibriums towards tailoring the structural and the electronic properties of molecular assemblies. The primary application of the latter approach lies in the design of organic self-healing materials, sensors, and actuators. Herein we apply density functional theory (DFT) to explore the structural, electronic and transport properties of the [Pt₁₂O8(SO₄)₁₂]⁴⁻ cluster and its derivatives. The cluster is a polyoxometalate (POM) that exhibits six {O−Pt−Pt−O} moieties. The latter moieties are redox responsive and covalently dynamic, allowing the POM to store up to twelve electrons. In our proposed Au/POM/Au junction, the simulations show that the electron conduction strongly depends on the redox of POM but more weakly on its rotations with respect to the Au surface. Moreover, the POM shows promising spin-polarized current behaviour, which can be modulated using bias and gate voltages.

Keywords: polyoxometalates (POMs); platinum; computational modelling; DFT; charge storage; molecular electronics

Permalink: https://www.hzdr.de/publications/Publ-33445
Publ.-Id: 33445


Resonant SAXS data used in publication: "Probing ultrafast laser plasma processes inside solids with resonant small angle X-ray scattering"

Gaus, L.; Bischoff, L.; Bussmann, M.; Cunningham, E.; Curry, C. B.; E, Juncheng; Galtier, E.; Gauthier, M.; Laso García, A.; Garten, M.; Glenzer, S.; Grenzer, J.; Gutt, C.; Hartley, N.; Huang, L.; Hübner, U.; Kraus, D.; Lee, H. J.; McBride, E. E.; Metzkes-Ng, J.; Nagler, B.; Nakatsutsumi, M.; Nikl, J.; Ota, M.; Pelka, A.; Prencipe, I.; Randolph, L.; Rödel, M.; Sakawa, Y.; Schlenvoigt, H.-P.; Smid, M.; Treffert, F.; Voigt, K.; Zeil, K.; Cowan, T.; Schramm, U.; Kluge, T.

Resonant Small-angle x-ray scattering raw data obtained in measurements at MEC at LCLS and evalutation of the asymmetry in the scattering patterns. The data set is structured in case 1/Si-Cu-compound targets and case 2/Cu-only-targets as presented in the publication for on- and off-resonant XFEL probe energies.

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-22
    DOI: 10.14278/rodare.596
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33444
Publ.-Id: 33444


Dynamo action of the large scale flow in a precessing cylinder

Giesecke, A.; Pizzi, F.; Stefani, F.

Precession is a well known phenomenon that (in a very general sense) paraphrases the
temporal change of the orientation of the spin axis of rotating objects. In rotating celestial bodies
with liquid interior precession causes a volume force that directly drives a non-axisymmetric fluid
flow [1]. Paradigmatic example is the liquid core of the Earth [2], for which the forcing is
considerably strong due to the rather large angle between rotation axis and precession axis. An even
stronger forcing is assumed for the ancient moon three to four billion years ago [3]. Precessional
forcing of the fluid interior of planets or moons is of interest because the resulting internal flows in
terms of inertial modes or turbulence back-react on the rotation of the whole body, which may
become evident for example in length of day variations or periodic changes of the nutation angle.
Furthermore a precession-driven flow of an electrically conductive fluid is capable of generating a
large scale magnetic field [4]. From an energetic point of view, the directly driven non-
axissymmetric flow is not sufficient to generate a magnetic field [5], however, multifaceted
instabilities of the primary flow provide the possibility to extract a large a amount of kinetic energy
from the rotational fluid motions into a fluid flow, which may be more suitable of generating a
magnetic field via electromagnetic induction [6].
In order to investigate to what extent a precession-driven flow can power a dynamo, and what
properties the related magnetic field would have, an experiment is currently being constructed at
HZDR, in which 6 tons of liquid sodium will precess in a cylinder with 2 meters height and 2
meters in diameter [7]. The design of the experiment is attended by comprehensive numerical
simulations, which showed that at the edge of the transition between a complex but still laminar
flow to a fully developed turbulent state, onset of dynamo action can be expected [8]. This state of
flow is characterized by an almost complete transformation of the original rotation into large-scale
inertial waves and small-scale turbulent flow. The dynamo effect found in the simulations is mainly
due to an evolving axially symmetric flow component and the strong shear layer near the outer
walls due to the massive extraction of rotational energy [9]. Free inertial waves in the form of
triadic resonances as the first instability, which describe the transition from the stationary to the
time-dependent state, do not seem to play any special role for the dynamo-effect. Open questions
concern the role of this triadic instability as a trigger for the transition to turbulence, the character of
the turbulence itself (is it three-dimensional or quasi-geostrophic) and the very mechanism that
causes the redistribution of the internal angular momentum and/or torque that goes along with the
significant modification of the large scale pattern of the velocity field.

1.
2.
3.
4.
5.
6.
7.
8.
9.
Stewartson & Roberts 1963, J. Fluid Mech. 17 (1), 1-20.
Malkus 1968, Science, 160, 259
Cebron et al. 2019, Geophys. J. Int., 219 (1), 34-57
Tilgner 2005, Phys. Fluids, 17, 034104
Loper 1975, Phys. Earth Planet. Inter. 11 (1), 43-60
Kerswell 1999, J. Fluid Mech. 382, 283-306
Stefani et al. 2015, Magnetohydrodynamics, 51 (2), 275-284
Giesecke et al. 2018, Phys. Rev. Lett. 120, 024502
Giesecke et al. 2018, Geophys. Astrophys. Fluid Mech., 113 (1-2), 235-255

Keywords: Dynamo

  • Invited lecture (Conferences)
    IV Russian Conference on Magnetohydrodynamics, 20.-22.09.2021, Perm, Russland

Permalink: https://www.hzdr.de/publications/Publ-33443
Publ.-Id: 33443


Rational Linker Design to Accelerate Excretion and Reduce Background Uptake of Peptidomimetic PSMA-Targeting Hybrid Molecules.

Eder, A.; Schäfer, M.; Schmidt, J.; Bauder-Wüst, U.; Roscher, M.; Leotta, K.; Haberkorn, U.; Kopka, K.; Eder, M.

The evolution of peptidomimetic hybrid molecules for preoperative imaging and guided surgery targeting the prostate-specific membrane antigen (PSMA) significantly progressed over the past few years, and some approaches are currently being evaluated for further clinical translation. However, accumulation in nonmalignant tissue such as kidney, bladder, spleen, or liver might limit tumor-to-background contrast for precise lesion delineation, particularly in a surgical setting. To overcome these limitations, a rational linker design aims at the development of a second generation of PSMA-11-based hybrid molecules with an enhanced pharmacokinetic profile and improved imaging contrast. Methods: A selection of rationally designed linkers was introduced to the PSMA-targeting hybrid molecule Glu-urea-Lys-HBED-CC-IRDye800CW, resulting in a second-generation peptidomimetic hybrid molecule library. The biologic properties were investigated in cell-based assays. In a preclinical proof-of-concept study with the radionuclide 68Ga, the impact of the modifications was evaluated by determination of specific tumor uptake, pharmacokinetics, and fluorescence imaging in tumor-bearing mice. Results: The modified hybrid molecules carrying various selected linkers revealed high PSMA-specific binding affinity and effective internalization. The highest tumor-to-background contrast of all modifications investigated was identified for the introduction of a histidine- (H) and glutamic acid (E)-containing linker ((HE)3-linker) between the PSMA-binding motif and the chelator. In comparison to the parental core structure, uptake in nonmalignant tissue was significantly reduced to a minimum, as exemplified by an 11-fold reduced spleen uptake from 38.12 ± 14.62 percentage injected dose (%ID)/g to 3.47 ± 1.39 %ID/g (1 h after injection). The specific tumor uptake of this compound (7.59 ± 0.95 %ID/g, 1 h after injection) was detected to be significantly higher than that of the parental tracer PSMA-11. These findings confirmed by PET and fluorescence imaging are accompanied by an enhanced pharmacokinetic profile with accelerated background clearance at early time points after injection. Conclusion: The novel generation of PSMA-targeting hybrid molecules reveals fast elimination, reduced background organ enrichment, and high PSMA-specific tumor uptake meeting the key demands for potent tracers in nuclear medicine and fluorescence-guided surgery. The approach's efficacy in improving the pharmacokinetic profile highlights the strengths of rational linker design as a powerful tool in strategic hybrid-molecule development.

Keywords: PSMA; guided surgery; hybrid molecules; pharmacokinetic profile; prostate cancer

Permalink: https://www.hzdr.de/publications/Publ-33442
Publ.-Id: 33442


Spectroscopic and modeling study of the sorption of Ln³⁺ (Eu) and An³⁺ (Am, Cm) on Ca-feldspars

Lessing, J.; Neumann, J.; Bezzina, J. P.; Bok, F.; Lützenkirchen, J.; Brendler, V.; Stumpf, T.; Schmidt, M.

INTRODUCTION
Deep geological repositories are considered as a safe disposal strategy for radioactive waste due their ability to isolate toxic components from the biosphere over hundreds of thousands of years. Minor actinides and Pu dominate the radiotoxicity of spent nuclear fuel over these long time scales. Due to the expected reducing conditions in the underground repository, the trivalent oxidation state is dominant for Am and Cm, and will also be relevant for Pu. For investigations of the mobility of the trivalent actinides Am(III) and Cm(III), the less toxic trivalent rare earth elements, in particular Eu(III), are commonly used.
In Germany and many other countries, crystalline rock is being considered as a possible host rock. Therefore, there is a need for understanding the sorption behavior of radionuclides on this material. Crystalline rock (e.g. granite), consists mainly of quartz, feldspars, and mica. Recently, the retention of trivalent actinides by K-feldspar was investigated from a thermodynamic and structural point of view.[1] Here, we extend this study towards Ca-feldspars (plagioclases), which may show a different sorption behavior due to their different elemental composition, crystal structure, and surface charge behavior.
DESCRIPTION OF THE WORK
Synthetic Ca-feldspar and natural plagioclases of different Ca amounts were used for zeta potential measurements and batch sorption experiments under different geochemical conditions ([M³⁺] = 52 nM – 10 μM; solid-liquid ratio = 1 – 3 g/L, I = 0,1 M NaCl, pH = 3 – 9) to quantify the uptake of Am(III) and Eu(III). For analysis of the sorption structure of trivalent f-elements on the molecular level, time-resolved laser-induced spectroscopy (TRLFS) using Cm(III) as a luminescent probe was carried out on synthetic Ca-feldspar. The obtained data were used to develop a surface complexation model (SCM) and to derive surface complexation parameters for the spectroscopically identified surface complexes.
RESULTS AND DISCUSSION
Zeta potential investigations of all Ca-feldspars show a decrease of the potential for pH = 2 – 4 due to surface site deprotonation. In contrast to the previously reported trend for K-feldspar, the zeta potential increases for pH = 4 – 7, with a stronger increase with higher Ca²⁺ concentration in the crystal lattice of the investigated plagioclases, even reaching positive values in the case of the synthetic Ca-feldspar. This effect can be traced to dissolved Al³⁺: Due to differences in solubility, Al³⁺ concentration in solution increases with increasing Ca²⁺ in the crystal lattice. Experiments on K-feldspar with added Al³⁺ reveal a connection between its concentration and the increase of the zeta potential.
All observed Ca-feldspars show a strong sorption uptake of trivalent f-elements for pH > 6. K- and Ca-feldspars seem to have a similar sorption behavior for low [M³⁺].[1] In contrast, Ca-feldspar has a slightly stronger sorption affinity when the metal concentrations is increased. This leads to a steeper sorption edge with increasing Ca²⁺ concentration in the crystal lattice of the mineral.
Spectroscopic studies with Cm(III) on synthetic Ca-feldspar reveal three sorption complexes: one inner sphere complex (IS) and its two hydrolysis forms, which have the same band positions as previously determined for K-feldspar.[1] Therefore, it can be concluded that the structure of the formed IS complexes is independent on the feldspar type. Differences are only observed for the quantitative contributions of the surface complexes. In particular, hydrolysis of the IS complex is stronger in the case of the Ca-feldspar.
Batch sorption data and the information about spectroscopically identified surface complexes were then combined to develop a SCM for Ca-feldspar that describes the experimental data. The formation constants of the surface complexes were determined to be −8.37; −10.81, and −16.35, respectively and are very similar to those of the K-feldspar.[1]
From the applied multi-method approach, we conclude that the sorption of trivalent f-elements on K- and Ca-feldspar is most likely comparable for relevant, natural conditions. Therefore, it may be possible not to distinguish between the two minerals in reactive transport simulations, which will reduce calculation resources needed for a reliable risk assessment of repositories for radioactive waste.
REFERENCES
[1] J. Neumann et al., “A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar,” Journal of Colloid Interface Science, vol. 591, pp. 490–499 (2021)
[2] Neumann and Lessing et al., “Structural and modeling study of the retention of trivalent f-elements (Am, Cm, Eu) by natural and synthetic Ca-feldspars”, in preparation.

Keywords: Sorption; Trivalent metal ions; Actinides; Ca-feldspar; Surface complexation model; TRLFS; Zeta potential

  • Poster
    TransRet2020, 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33441
Publ.-Id: 33441


The disappearance and return of nanoparticles upon low energy ion irradiation

Choupanian, S.; Nagel, A.; Möller, W.; Pacholski, C.; Ronning, C.

Ion irradiation of bulk and thin film materials is tightly connected to well described effects such as sputtering or/and ion beam mixing. However, when a nanoparticle is ion irradiated and the ion range is comparable to the nanoparticle size, these effects are to be reconsidered essentially. This study investigates the morphology changes of silver nanoparticles on top of silicon substrates, being irradiated with Ga+ ions in an energy range from 1 to 30 keV. The hemispherical shaped nanoparticles become conical due to an enhanced and curvature-dependent sputtering, before they finally disappear. The sputter yield and morphology changes can be well described by 3D Monte Carlo TRI3DYN simulations. However, the combination of sputtering, ion beam mixing, ion beam induced diffusion, and Ostwald ripening at ion energies lower than 8 keV results in the reappearance of new particles. These newly formed nanoparticles appear in various structures depending on the material and ion energy

Keywords: Ag nanoparticles; Ion beam mixing; Ion-nanoparticle interaction; Ostwald ripening; Phase sepereation

Permalink: https://www.hzdr.de/publications/Publ-33440
Publ.-Id: 33440


Deterministic Shallow Dopant Implantation in Silicon with Detection Confidence Upper-Bound to 99.85% by Ion–Solid Interactions

Jakob, A. M.; Robson, S. G.; Schmitt, V.; Mourik, V.; Posselt, M.; Spemann, D.; Johnson, B. C.; Firgau, H. R.; Mayes, E.; McCallum, J. C.; Morello, A.; Jamieson, D. N.

Silicon chips containing arrays of single dopant atoms can be the material of choice for classical and quantum devices that exploit single donor spins. For example, group-V donors implanted in isotopically purified 28Si crystals are attractive for large-scale quantum computers. Useful attributes include long nuclear and electron spin lifetimes of 31P, hyperfine clock transitions in 209Bi or electrically controllable 123Sb nuclear spins. Promising architectures require the ability to fabricate arrays of individual near-surface dopant atoms with high yield. Here, an on-chip detector electrode system with 70 eV root-mean-square noise (≈20 electrons) is employed to demonstrate near-room-temperature implantation of single 14 keV 31P+ ions. The physics model for the ion–solid interaction shows an unprecedented upper-bound single-ion-detection confidence of 99.85 ± 0.02% for near-surface implants. As a result, the practical controlled silicon doping yield is limited by materials engineering factors including surface gate oxides in which detected ions may stop. For a device with 6 nm gate oxide and 14 keV 31P+ implants, a yield limit of 98.1% is demonstrated. Thinner gate oxides allow this limit to converge to the upper-bound. Deterministic single-ion implantation can therefore be a viable materials engineering strategy for scalable dopant architectures in silicon devices.

Keywords: Deterministic single-ion implantation; Near-surface dopant location; Quantum computers; Ion Beam Induced Charge Collection

Permalink: https://www.hzdr.de/publications/Publ-33439
Publ.-Id: 33439


Stable acceleration of intense proton beams to energies beyond 80 MeV at rep-rated laser systems

Ziegler, T.; Bernert, C.; Bock, S.; Brack, F.-E.; Cowan, T.; Dover, N. P.; Garten, M.; Gaus, L.; Göthel, I.; Kiriyama, H.; Kluge, T.; Kraft, S.; Kroll, F.; Metzkes-Ng, J.; Nishiuchi, M.; Püschel, T.; Rehwald, M.; Schlenvoigt, H.-P.; Schramm, U.; Zeil, K.

We report on experimental investigations of proton acceleration from laser-irradiated solid foils with the Draco-PW laser, where highest proton cut-off energies were achieved for temporal pulse parameters that varied significantlyfrom those of an ideally Fourier transform limited (FTL) pulse. Controlled spectral phase modulation of the driver laser by means of an acousto-optic programmable dispersive filter enabled us to manipulate the temporal shape ofthe last picoseconds around the main pulse and to study the effect on proton acceleration from thin foil targets. The results show that short and asymmetric pulses generated by positive third order dispersion values are favourable for proton acceleration and can lead to maximum energies above 60 MeV at 18 J laser energy for thin plastic foils, effectively doubling the maximum energy compared to ideally compressed FTL pulses. This performance optimization was the key to perform worlds first dose-controlled in-vivo studies with laser accelerated protons.

The talk will further report on experiments we have carried out in the relativistically induced transparancy regime where the target turns transparent during the laser pulse interaction. We show recent data how the experimental signatures of the accelerated protons in this regime change compared to standard TNSA conditions and how we could reproduce those results at another similar laser laser system.

  • Invited lecture (Conferences)
    5th European Advanced Accelerator Concepts Workshop, 20.-23.09.2021, Rome, Italy

Permalink: https://www.hzdr.de/publications/Publ-33435
Publ.-Id: 33435


Assessment of the validity of a log-law for wall-bounded turbulent bubbly flows

Bragg, A.; Liao, Y.; Fröhlich, J.; Ma, T.

There has been considerable discussion in recent years concerning whether a log-law exists for wall-bounded,
turbulent bubbly flows. Previous studies have argued for the existence of such a log-law, with a modified von
K´arm´an constant, and this is used in various modelling studies. We provide a critique of this idea, and present
several theoretical reasons why a log-law need not be expected in general for wall-bounded, turbulent bubbly
flows. We then demonstrate using recent data from interface-resolving Direct Numerical Simulations that when
the bubbles make a significant contribution to the channel flow dynamics, the mean flow profile of the fluid can
deviate significantly from the log-law behaviour that approximately holds for the single-phase case. The departures
are not surprising and the basic reason for them is simple, namely that for bubbly flows, the mean flow is
affected by a number of additional dynamical parameters, such as the void fraction, that do not play a role for the
single-phase case. As a result, the inner/outer asymptotic regimes that form the basis of the derivation of the loglaw
for single-phase flow do not exist in general for bubbly turbulent flows. Nevertheless, we do find that for
some cases, the bubbles do not cause significant departures from the unladen log-law behaviour. Moreover, we
show that if departures occur these cannot be understood simply in terms of the averaged void fraction, but that
more subtle effects such as the bubble Reynolds number and the competition between the wall-induced turbulence
and the bubble-induced turbulence must play a role.

Keywords: Bubbly flow; Log-law; Wall-bounded turbulent flows

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  • Secondary publication expected from 16.09.2022

Permalink: https://www.hzdr.de/publications/Publ-33434
Publ.-Id: 33434


A Machine-Learning Surrogate Model for ab initio Electronic Correlations at Extreme Conditions

Dornheim, T.; Moldabekov, Z.; Cangi, A.

The electronic structure in matter under extreme conditions is a challenging complex system prevalent in astrophysical objects and highly relevant for technological applications. We show how machine-learning surrogates in terms of neural networks have a profound impact on the efficient modeling of matter under extreme conditions. We demonstrate the utility of a surrogate model that is trained on \emph{ab initio} quantum Monte Carlo data for various applications in the emerging field of warm dense matter research.

Keywords: Machine Learning; Surrogate model; warm dense matter

Permalink: https://www.hzdr.de/publications/Publ-33432
Publ.-Id: 33432


Robust formation of nanoscale magnetic skyrmions in easy-plane anisotropy thin film multilayers with low damping

Flacke, L.; Ahrens, V.; Mendisch, S.; Körber, L.; Böttcher, T.; Meidinger, E.; Yaqoob, M.; Müller, M.; Liensberger, L.; Kakay, A.; Becherer, M.; Pirro, P.; Althammer, M.; Geprägs, S.; Huebl, H.; Gross, R.; Weiler, M.

We experimentally demonstrate the formation of room-temperature skyrmions with radii of about 25 nm in easy-plane anisotropy multilayers with an interfacial Dzyaloshinskii-Moriya interaction (DMI). We detect the formation of individual magnetic skyrmions by magnetic force microscopy and find that the skyrmions are stable in out-of-plane fields up to about 200 mT. We determine the interlayer exchange coupling as well as the strength of the interfacial DMI. Additionally, we investigate the dynamic microwave spin excitations by broadband
magnetic resonance spectroscopy. From the uniform Kittel mode we determine the magnetic anisotropy and lowdamping α < 0.04. We also find clear magnetic resonance signatures in the nonuniform (skyrmion) state. Our findings demonstrate that skyrmions in easy-plane multilayers are promising for spin-dynamical applications.

Keywords: skyrmion; ferromagnetic resonance; DMI; low damping

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Permalink: https://www.hzdr.de/publications/Publ-33420
Publ.-Id: 33420


Leptin counteracts hypothermia in hypothyroidism through its pyrexic effects and by stabilizing serum thyroid hormone levels

Weiner, J.; Roth, L.; Kranz, M.; Brust, P.; Boelen, A.; Klöting, N.; Heiker, J. T.; Blüher, M.; Tönjes, A.; Pfluger, P. T.; Stumvoll, M.; Mittag, J.; Krause, K.

Objective: Thyroid hormones (TH) are essential for the homeostatic control of energy metabolism and the regulation of bodytemperature. The hypothalamic–pituitary–thyroid (HPT) axis is regulated by negative feedback mechanisms, ensuring that TH levels are maintained at a constant level. However, the feedback mechanisms underlying the resetting of the HPT axis regulation in the control of body temperature are still not fully understood. Here, we aimed to determine the thermoregulatory response in hypothyroid mice to different environmental temperatures and the underlying mechanisms. Methods: Distinct
thermogenic challenges were induced in hypothyroid female C57BL/6N and leptin-deficient ob/ob mice through housing at either room temperature or thermoneutrality. The thermogenic and metabolic effects were analyzed through metabolic chambers, 18F-FDG-PET/MRI, infrared thermography, metabolic profiling, histology, gene expression and Western blot analysis. Results: In hypothyroid mice maintained at room temperature, high leptin serum levels induce a pyrexic effect leading to the stabilization of body temperature through brown adipose tissue thermogenesis and white adipose tissue browning. Housing at thermoneutrality leads to the normalization of leptin levels and a reduction of the central temperature set point, resulting in decreased thermogenesis in brown and white adipose tissue and skeletal muscle and a significant decline in body temperature. Furthermore, anapyrexia in hypothyroid leptin-deficient ob/ob mice indicates that besides its pyrexic actions, leptin exerts a stimulatory effect on the HPT axis to stabilize the remaining TH serum levels in hypothyroid mice. Conclusion: This study led to the identification of a previously unknown endocrine loop in which leptin acts in concert with the HPT axis to stabilize body temperature in hypothyroid mice.

Keywords: Beige adipose tissue; Brown adipose tissue; Leptin; Thermogenesis; Thyroid hormone; White adipose tissue browning

Permalink: https://www.hzdr.de/publications/Publ-33417
Publ.-Id: 33417


Data publication: Uptake of niobium by cement systems relevant for nuclear waste disposal: impact of ISA and chloride

Franke, K.

Daten zur Bestrahlung und Gammaspektroskopiemessung des Targets

Keywords: niobium; cyclotron; gamma spectroscopy

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-19
    DOI: 10.14278/rodare.1265
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33416
Publ.-Id: 33416


High-gain quantum free-electron laser: Long-time dynamics and requirements

Kling, P.; Giese, E.; Carmesin, C. M.; Sauerbrey, R.; Schleich, W. P.

We solve the long-time dynamics of a high-gain free-electron laser in the quantum regime. In this regime each electron emits at most one photon on average, independently of the initial field. In contrast, the variance of the photon statistics shows a qualitatively different behavior for different initial states of the field. We find that the realization of a seeded quantum free-electron laser is more feasible than self-amplified spontaneous emission.

Permalink: https://www.hzdr.de/publications/Publ-33415
Publ.-Id: 33415


Zr-PAPER

Mansel, A.

Rohdaten Zr-PAPER

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-18
    DOI: 10.14278/rodare.1263
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33414
Publ.-Id: 33414


Ghost and Gluon Propagators at Finite Temperatures within a Rainbow Truncation of Dyson–Schwinger Equations

Kaptari, L. P.; Kämpfer, B.

The finite-temperature behaviour of ghost and gluon propagators is investigated within an approach based on the rainbow truncated Dyson–Schwinger equations in Landau gauge. In Euclidean space, within the Matsubara imaginary-time formalism, the gluon propagator is not longer a O(4) symmetric function and possesses a discrete spectrum of the fourth momentum component. This leads to a different treatment of the transversal and longitudinal (with respect to the heat bath) parts of the propagator. Correspondingly, the gluon Dyson–Schwinger equation splits also into two parts. The resulting system of coupled equations is considered within the rainbow approximation and solved numerically. The solutions for the ghost and gluon propagators are obtained as a function of temperature T, Matsubara frequency Ωn and three-momentum squared k2. The effective parameters of the approach are taken from our previous fit of the corresponding Dyson–Schwinger solution to the lattice QCD data at zero temperature. It is found that, for zero Matsubara frequency, the dependence of the ghost and gluon dressing functions on k2 are not sensitive to the temperature T, while at k2 = 0 their dependence on T is quite strong. Dependence on the Matsubara frequency Ωn is investigated as well.

Permalink: https://www.hzdr.de/publications/Publ-33413
Publ.-Id: 33413


Therapy-naïve and radioresistant 3D pancreatic cancer cell cultures are effectively radiosensitized by β1 integrin targeting

Görte, J.; Danen, E.; Cordes, N.

Purpose: Pancreatic ductal adenocarcinoma (PDAC) is one of the cancers with unmet need. The role of highly conformal radiotherapy is still under debate for PDAC. Owing to its desmoplastic nature, integrin-mediated interactions between PDAC cells and extracellular matrix (ECM) profoundly contribute to PDAC resistance. In this study, we investigated the radiochemosensitizing potential of β1 integrin targeting in therapy-naïve and radioresistant PDAC cell cultures grown in three-dimensional (3D) extracellular matrix (ECM).
Materials and Methods: In a panel of 3D, ECM based PDAC cell cultures, β1 integrin was inhibited by antibodies or siRNA-mediated knockdown. Together with X-ray irradiation and specific chemotherapies, we determined 3D colony formation capacity in therapy-naïve and radioresistant PDAC cultures. Kinome profiling, Western blotting and immunofluorescence stainings were employed to characterize these cell lines. Various siRNA screens were conducted to identify novel therapeutic targets.
Results: A significant radiosensitizing potential of β1 integrin inhibition was found both in therapy-naïve and radioresistant PDAC cell cultures. Kinome profiling upon β1 integrin targeting identified a generally declined tyrosine and serine/threonine kinase activity, which presented less prominent in radioresistant than in therapy-naïve PDAC cells. siRNA screens employing the top 34 deregulated kinases in combination with β1 integrin inhibition revealed less efficacy and less radiosensitization in radioresistant relative to therapy-naïve PDAC cell cultures. Triple inhibition of β1 integrin, protein kinase D1 (PDK1) and rearranged during transfection (RET) turned out to be most effective in reducing 3D colony formation of radioresistant PDAC cells.
Conclusion: Our study clearly shows that β1 integrins are robust targets for overcoming radioresistance in PDAC. This seems to apply equally to therapy-sensitive and radioresistant cells. Concerning tumor heterogeneity, this dual therapy-sensitizing potential might be exploitable for a significant improvement of patient survival.

Keywords: Radiotherapy; Integrins; Resistance; PDAC

Permalink: https://www.hzdr.de/publications/Publ-33412
Publ.-Id: 33412


Control of Stripe-Domain-Wall Magnetization in Multilayers Featuring Perpendicular Magnetic Anisotropy

Salikhov, R.; Samad, F.; Böhm, B.; Schneider, S.; Pohl, D.; Rellinghaus, B.; Ullrich, A.; Albrecht, M.; Lindner, J.; Kiselev, N. S.; Hellwig, O.

We report on the controlled switching of domain-wall (DW) magnetization in aligned stripe-domain
structures, stabilized in [Co(0.44 nm)/Pt(0.7 nm)]X (X = 48, 100, 150) multilayers with perpendicular
magnetic anisotropy. The switching process, induced by an external magnetic field, is monitored by measuring the evolution of the in-plane magnetization. We show that the remanent in-plane magnetization originates from the polarization of the Bloch-type DWs. With micromagnetic simulations, we reveal that
the reversal of the DW polarization is the result of the emergence and collapse of horizontal Bloch lines
within the DWs at particular strengths of the external magnetic field, applied opposite to the DW polarization. Our findings are relevant for DW-based magnonics and bubble-skyrmion applications in magnetic multilayers.

Keywords: Magnetic domains; Domain walls; Magnetization switching; Skyrmions; Spintronics; Micromagnetism

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Permalink: https://www.hzdr.de/publications/Publ-33411
Publ.-Id: 33411


Microscopic and spectroscopic investigations of uranium(VI) reduction by Desulfosporosinus hippei DSM 8344

Hilpmann, S.; Drobot, B.; Steudtner, R.; Hübner, R.; Bok, F.; Stumpf, T.; Cherkouk, A.

Clay formations are potential host rocks for the long-term storage of high-level radioactive waste in a deep geological repository. Bentonites are supposed to serve as backfill material, not only for a final disposal site in clay formations but also in crystalline rock. For a long-term safety assessment, various aspects must be taken into account. Besides geological, geochemical, and geophysical considerations, also naturally occurring microorganisms play a crucial part in the environment of such a repository. In the event of a worst-case scenario, if water enters the disposal site, they can interact with the radionuclides and change for example the chemical speciation or the oxidation state (Lloyd et al., 2002).
Desulfosporosinus spp. are an important representative of anaerobic, sulfate-reducing microorganisms, which are present in clay formations as well as in bentonites. Various studies show that they are playing a major role in the microbial communities of these surroundings (Bagnoud et al., 2016; Matschiavelli et al., 2019). A closely related microorganism to the isolated species is Desulfosporosinus hippei DSM 8344, which was originally found in permafrost soil (Vatsurina et al., 2008). This bacterium was used to investigate its interactions with uranium(VI) especially regarding the reduction to the less mobile uranium(IV).
Time-dependent reduction experiments in artificial Opalinus Clay pore water (Wersin et al., 2011) (100 µM uranium(VI), pH 5.5) showed the removal of about 80% of the uranium(VI) from the supernatants within 48 h. Corresponding UV/Vis measurements of the dissolved cell pellets exhibit an increasing proportion of uranium(IV) in the cell-bound uranium. Calculations with the inclusion of extinction coefficients lead to a ratio of 39% uranium(IV) after one week. Therefore, a combined sorption-reduction process is a possible interaction mechanism.
Time-resolved laser-induced luminescence spectroscopy verifies the presence of two uranium(VI) species in the supernatant. A comparison with reference spectra leads to an assignment to a uranyl(VI) lactate and a uranyl(VI) carbonate complex. The species distribution shows a decrease of the proportion of the lactate species with time, whereas the proportion of the carbonate species remains almost constant.
Uranium aggregates are formed on the cell surface during the process, as determined by transmission electron microscopy (TEM). Furthermore, uranium occurs inside and outside the cells as well as uranium-containing vesicles.
These findings help to close existing gaps in a comprehensive safeguards concept for a repository for high-level radioactive waste in clay rock. Moreover, this study provides new insights into the interactions of sulfate-reducing microorganisms with uranium(VI).

References
Bagnoud, A., Chourey, K., Hettich, R. L., De Bruijn, I., Andersson, A. F., Leupin, O. X., Schwyn, B., and Bernier-Latmani, R.: Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock, Nat. Commun., 7, 1-10, 2016.
Lloyd, J. R. and Macaskie, L. E.: Biochemical basis of microbe-radionuclide interactions, in: Interactions of Microorganisms with Radionuclides, edited by: Keith-Roach, M. J. and Livens, F. R., Elsevier, 313-381, 2002.
Matschiavelli, N., Kluge, S., Podlech, C., Standhaft, D., Grathoff, G., Ikeda-Ohno, A., Warr, L. N., Chukharkina, A., Arnold, T., and Cherkouk, A.: The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C, Environ. Sci. Technol., 53, 10514-10524, 2019.
Vatsurina, A., Badrutdinova, D., Schumann, P., Spring, S., Vainshtein, M.: Desulfosporosinus hippei sp. nov., a mesophilic sulfate-reducing bacterium isolated from permafrost, Int. J. Syst. Evol. Microbiol., 58, 1228-1232, 2008.
Wersin, P., Leupin, O. X., Mettler, S., Gaucher, E. C., Mäder, U., De Cannière, P., Vinsot, A., Gäbler, H. E., Kunimaro, T., Kiho, K., Eichinger, L.: Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland, Appl. Geochemistry, 26, 931-953, 2011.

Keywords: uranium(VI) reduction; sulfate-reducing microorganisms; Opalinus Clay

  • Poster
    Interdisziplinäres Forschungssymposium für die Sicherheit der nuklearen Entsorgung, 10.-12.11.2021, Berlin, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33410
Publ.-Id: 33410


Microscopic and spectroscopic study of the uranium(VI) reduction by a sulfate-reducing microorganism

Hilpmann, S.; Steudtner, R.; Hübner, R.; Roßberg, A.; Prieur, D.; Bauters, S.; Kvashnina, K.; Stumpf, T.; Cherkouk, A.

INTRODUCTION

Clay rock is a possible host rock for the long-term storage of high-level radioactive waste and bentonites are a suitable backfill material for a final repository in clay rock and crystalline rock. For a comprehensive safety assessment of such a repository over a long period, different aspects must be taken into account. Besides intensive research regarding geological, geochemical and geophysical properties, these surroundings represent a habitat for naturally occurring microorganisms. In the event of a worst-case scenario, water can enter the repository. It is possible that microorganisms can interact with the radionuclides and thereby change the chemical speciation or the oxidation state by various processes.
Desulfosporosinus spp. play an important role as a representative of anaerobic, sulfate-reducing and spore-forming microorganisms. These bacteria occur in different clay formations as well as in bentonites.1,2 A very closely related bacterium to an isolated species from bentonite is Desulfosporosinus hippei DSM 8344, which was originally found in permafrost soils.3 Therefore, this strain was selected to get a more profound insight into the uranium(VI) interactions with naturally occurring microorganisms from deep geological layers by different microscopic and spectroscopic techniques.

DESCRIPTION OF THE WORK

For the time-dependent experiments in artificial Opalinus Clay pore water4 (100/500 µM uranium(VI), pH 5.5) the cells were cultivated in specific media and harvested in the late exponential growing phase. After washing, suspensions containing cells, uranium(VI) and lactate, were incubated at room temperature and samples were taken between zero hours and one week.

RESULTS AND DISCUSSION

The experiments showed the removal of about 80% of the uranium(VI) from the supernatants within 48 h at a concentration of 100 µM. Corresponding UV/Vis measurements of the dissolved cell pellets revealed an increasing proportion of uranium(IV) in the samples with time. After one week round about 40% of the uranium in the cell pellets was reduced. Therefore, the interaction mechanisms can be assigned to a combined sorption-reduction process.
TEM images of the uranium-incubated cells reveal the formation of uranium aggregates on the cell surface. Uranium can be found not only outside the cell in vesicles, but also inside the cell.
HERFD-XANES measurements show the presence of three oxidation states in the cell pellets. Besides uranium(VI) and uranium(IV), also uranium(V) plays a major role in the cellular reduction process. With the help of EXAFS measurements, three cell-related uranium species were detected.
This study helps to close existing gaps in a comprehensive safeguard concept for a final repository for high-level radioactive waste in clay rock. Moreover, new insights into the interaction mechanisms of sulfate-reducing microorganisms with uranium are presented.

REFERENCES

1. A. BAGNOUD et al., “Reconstructing a hydrogen-driven microbial metabolic network in Opalinus Clay rock” Nat. Commun., 7, 1-10 (2016).

2. N. MATSCHIVELLI et al., “The year-long development of microorganisms in uncompacted Bavarian bentonite slurries at 30 °C and 60 °C” Environ. Sci. Technol., 53, 10514-10524 (2019).

3. A. VATSURINA et al., “Desulfosporosinus hippei sp. nov., a mesophilic sulfate-reducing bacterium isolated from permafrost” Int. J. Syst. Evol. Microbiol., 58, 1228-1232 (2008).

4. P. WERSIN et al., “Biogeochemical processes in a clay formation in situ experiment: Part A - Overview, experimental design and water data of an experiment in the Opalinus Clay at the Mont Terri Underground Research Laboratory, Switzerland” Appl. Geochemistry, 26, 931-953 (2011).

Keywords: uranium(VI) reduction; sulfate-reducing microorganisms; Opalinus Clay

  • Poster (Online presentation)
    TransRet2020, 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33409
Publ.-Id: 33409


Tungsten (VI) speciation in hydrothermal solutions up to 400°c as revealed by in-situ Raman spectroscopy

Carocci, E.; Truche, L.; Cathelineau, M.; Bazarkina, E.

Tungsten (VI) speciation in hydrothermal solutions is investigated through in-situ Raman spectroscopy coupled to the fused silica glass capillary technique at temperatures up to 400 °C. The effect of temperature, pH, chlorinity and carbonate speciation are evaluated in systems with highly soluble salts Na2WO4 and Na6W12O39. At all investigated temperatures, the tungstate ion WO42- (927 cm-1) is the only W species in solution at pH > 10. At a given pH, the presence of dissolved carbonates and chloride does not affect the tungsten speciation. Tungsten polymers reveal to be stable up to 400 °C under acidic to circum-neutral pH conditions and total tungsten concentration above 0.01 molkgH2O-1-. Among the three observed polymers, namely [W7O24]6- (paratungstate-A, ~ 960 cm-1), [W10O32]4- (tungstate-Y, ~ 970 cm-1), and α-[H2W12O40]6- (α-metatungstate, ~ 990 cm-1), only the hepta and dodeca-tungstate are stable at elevated temperature. Combined with revised literature data, these results allow the thermodynamic stability constants of these W polymers to be constrained, enabling quantitative predictions of their relative abundance at T up to 300 °C. These predictions suggest that W polymerization occurs under hydrothermal conditions even at low W concentration (down to 10-5 mol·kgH2O-1) under acidic conditions. These observations imply that the currently available geochemical models on W transport and deposition in deep and hot geological fluids need to be revised.

Keywords: Tungsten polymers; Polytungstates; Fused silica glass capillary technique; Ore deposits

Permalink: https://www.hzdr.de/publications/Publ-33405
Publ.-Id: 33405


Ein „Wireless Sensor Network“ zur Prozesscharakterisierung in Biogasfermentern

Buntkiel, L.; Budelmann, C.; Heller, A.; Annas, S.; Reinecke, S.; Hampel, U.

Kenntnisse über die Durchmischung und die Strömungsvorgänge in Biogasfermentern ermöglichen Optimierungspotenziale bezogen auf die Vermischung, aber auch auf die Biogasausbeute und Energieeinsparung. Aufgrund der Beschaffenheit der Fermenter (große Abmessungen, Stahlbeton) und des Biosubstrats (nicht opakes Fluid) gibt es derzeit kein Messsystem, um Strömungen und räumlich verteilte Prozessparameter zu vermessen. In dem Projekt „NeoBio“ wurde dazu eine Wireless Sensor Network (WSN) entwickelt.

Keywords: Wireless Sensor Network; Sensorpartikel; Biogas; Abwasser

  • Open Access Logo Contribution to proceedings
    Biogas in der Landwirtschaft, 29.-30.09.2021, Online, Deutschland
    Biogas in der Landwirtschft - Stand und Perspektiven, Darmstadt: KTBL, 978-3-945088-83-8
  • ORA-00933: SQL-Befehl wurde nicht korrekt beendet

Radiolabeled Silicon-Rhodamines as Bimodal PET/SPECT-NIR Imaging Agents

Kanagasundaram, T.; Laube, M.; Wodtke, J.; Kramer, S. C.; Stadlbauer, S.; Pietzsch, J.; Kopka, K.

Radiolabeled fluorescent dyes are decisive for bimodal imaging as well as highly in demand for nuclear- and optical imaging. Silicon-rhodamines (SiRs) show unique near-infrared (NIR) optical properties, large quantum yields and extinction coefficients as well as high photostability. Here, we describe the synthesis, characterization and radiolabeling of novel NIR absorbing and emitting fluorophores from the silicon-rhodamine family for use in optical imaging (OI) combined with positron emission tomography (PET) or single photon emission computed tomography (SPECT), respectively. The presented photostable SiRs were characterized using NMR-, UV-Vis-NIR-spectroscopy and mass spectrometry. Moreover, the radiolabeling conditions using fluorine-18 or iodine-123 were extensively explored. After optimization, the radiofluorinated NIR imaging agents were obtained with radiochemical conversions (RCC) up to 70% and isolated radiochemical yields (RCY) up to 54% at molar activities of g.t. 70 GBq/µmol. Radioiodination delivered RCCs over 92% and allowed to isolate the 123I-labeled product in RCY of 54% at a molar activity of g.t. 7.6 TBq/µmol. The radiofluorinated SiRs exhibit in vitro stabilities g.t. 70% after two hours in human serum. The first described radiolabeled SiRs are a promising step toward their further development as multimodal PET/SPECT-NIR imaging agents for planning and subsequent imaging-guided oncological surgery.

Keywords: multimodal imaging; PET imaging; SPECT imaging; optical imaging; organic chemistry; near-infrared fluorophores; silicon-rhodamines; radiochemistry; radiofluorination; radioiodination

Permalink: https://www.hzdr.de/publications/Publ-33401
Publ.-Id: 33401


Dynamically assisted tunneling in the impulse regime

Kohlfürst, C.; Queißer, F.; Schützhold, R.

We study the enhancement of tunneling through a potential barrier V(x) by a time-dependent electric field with special emphasis on pulse-shaped vector potentials such as A(t)=A0/cosh^2(ωt). In addition to the known effects of pre-acceleration and potential deformation already present in the adiabatic regime, as well as energy mixing in analogy to the Franz-Keldysh effect in the non-adiabatic (impulse) regime, the pulse A(t) can enhance tunneling by ``pushing'' part of the wave-function out of the rear end of the barrier. Besides the natural applications in condensed matter and atomic physics, these findings could be relevant for nuclear fusion, where pulses A(t) with ω=1 keV and peak field strengths of 10^16 V/m might enhance tunneling rates significantly.

Keywords: Tunneling & traversal time; Nuclear fusion; Schroedinger equation

Permalink: https://www.hzdr.de/publications/Publ-33399
Publ.-Id: 33399


Towards Optimized Bioavailability of 99mTc‑Labeled Barbiturates for Non‑invasive Imaging of Matrix Metalloproteinase Activity

Honold, L.; Austrup, M.; Faust, A.; Konken, C.; Schwegmann, K.; Zinnhardt, B.; Daniliuc, C.; Haufe, G.; Schäfers, M.; Kopka, K.; Hermann, S.

Introduction: Dysregulated activity of matrix metalloproteinases (MMPs) drives a variety of pathophysiological conditions. Non-invasive imaging of MMP activity in vivo promises diagnostic and prognostic value. However, current targeting strategies by small molecules are typically limited with respect to the bioavailability of the labeled MMP binders in vivo. To this end, we here introduce and compare three chemical modifications of a recently developed barbiturate-based radiotracer with respect to bioavailability and potential to image MMP activity in vivo.
Methods: Barbiturate-based MMP inhibitors with an identical targeting unit but varying hydrophilicity were synthesized, labeled with technetium-99m, and evaluated in vitro and in vivo. Biodistribution and radiotracer elimination were determined in C57/BL6 mice by serial SPECT imaging. MMP activity was imaged in a MMP-positive subcutaneous xenograft model of human K1 papillary thyroid tumors. In vivo data were validated by scintillation counting, autoradiography, and MMP immunohistochemistry.
Results: We prepared three new 99mTc-labeled MMP inhibitors, bearing either a glycine ([99mTc]MEA39), lysine ([99mTc]MEA61), or the ligand HYNIC with the ionic co-ligand TPPTS ([99mTc]MEA223) yielding gradually increasing hydrophilicity. [99mTc]MEA39 and [99mTc]MEA61 were rapidly eliminated via hepatobiliary pathways. In contrast, [99mTc]MEA223 showed delayed in vivo clearance and primary renal elimination. In a thyroid tumor xenograft model, only [99mTc]MEA223 exhibited a high tumor-to-blood ratio that could easily be delineated in SPECT images.
Conclusion: Introduction of HYNIC/TPPTS into the barbiturate lead structure ([99mTc]MEA223) results in delayed renal elimination and allows non-invasive MMP imaging with high signal-to-noise ratios in a papillary thyroid tumor xenograft model.

Keywords: Barbiturates; Matrix metalloproteinase inhibitors; Pyrimidine-2,4,6-triones Single photon emission; Single photon emission computed tomography; Tumor imaging

Permalink: https://www.hzdr.de/publications/Publ-33397
Publ.-Id: 33397


Impact of background electrolyte composition on the interfacial formation of Th(IV) NPs on mica (001)

Neumann, J.; Qiu, C.; Eng, P.; Stumpf, T.; Schmidt, M.

A mechanistic understanding of the formation of actinide nanoparticles (NPs) and its impact on the mobility of radionuclides in the environment is important for a reliable risk assessment of repositories for radioactive waste. Previous studies using surface x-ray diffraction (SXD) reported an unexpected impact of electrolyte composition on the sorption of Th(IV) on the muscovite (001) basal plane. Th uptake decreased following an unexpected trend: LiClO4 > KClO4 > NaClO4. A significantly higher coverage than needed for surface charge compensation (0.25 Th/AUC, AUC = 46.72 Ų, area of mica (001) unit cell) was observed for LiClO4 (4.9 Th/AUC), suggesting the formation of Th-NPs [1]. It remained unclear, if the electrolyte affects a reaction at the mineral surface or in solution.
We combined SXD and in situ AFM to address this question. At low [Th] (0.1 mM), the investigated electrolytes include LiCl and KCl, in comparison with the reported Th uptakes for the respective perchlorate electrolytes, and the series is extended to NH4Cl and CsCl. The results are compared to reported value for NaCl [2]. The interfacial structures show an extremely broad distribution of Th electron density up to 50 Å from the surface for LiCl and KCl. A decrease of Th uptake within the alkali series is found (Figure 1). A strong linear correlation (R2 = 0.9962) between Th uptake and ionic radius of the alkali metal ion is found, indicating that sorption competition between Th4+ and the electrolyte cation is the origin of the observed effect. The value for NaCl is a clear outlier in this series, showing a much lower uptake of Th than expected according to the trend.
Perfect agreement between the number of formed particles per area, obtained by in situ AFM, and Th uptake, observed by SXD, is found. Particles show a vertical size of ~1 – 2 nm and lateral dimensions of ~10 – 20 nm, indicating that retention occurs by the formation of NPs at the mineral-solution interface (heterogeneous nucleation), which is strongly influenced by the electrolyte.
Additionally, SXD was performed at higher [Th] = 3 mM, where the formation of Th oligomers in solution is expected. Under these conditions, LiCl (2.0 Th/AUC), NaCl (1.4 Th/AUC), and KCl (1.7 Th/AUC) show similar Th uptake, indicating a much smaller impact of electrolyte composition. The obtained interfacial structures are dominated by a high Th loading at a distinct distance (~ 6.5 Å) from the muscovite surface. Therefore, the main retention mechanism at high [Th] is suggested to be the (electrolyte-independent) formation of Th oligomers in solution and their subsequent sorption on the mineral surface.

References
[1] - M. Schmidt et al., Geochim. Cosmochim. Acta. 165, 280–293 (2015).
[2] - M. Schmidt et al., Geochim. Cosmochim. Acta. 88, 66–76 (2012).

  • Poster (Online presentation)
    ESRF User Meeting 1-2021, 08.-10.02.2021, Grenoble, Frankreich
  • ORA-00933: SQL-Befehl wurde nicht korrekt beendet

Structural Investigation of the Adsorption von Y(III) on Orthoclase (001) Single Crystals using Resonant Surface X ray Diffraction

Neumann, J.; Lessing, J.; Demnitz, M.; Eng, P.; Stubbs, J.; Stumpf, T.; Schmidt, M.

INTRODUCTION

Transport of radionuclides (RNs), from deep geological repositories for radioactive waste, such as the highly toxic trivalent minor actinides (An(III)) Am and Cm, will be controlled by their interactions with charged mineral phases. Many countries such as Finland, Sweden, and Germany consider a repository in crystalline rock, which contains large amounts of feldspars, e.g. orthoclase (K-feldspar). Hence, reliable risk assessments of potential repository sites depend on a fundamental understanding of sorption quantity and structure of An(III) on feldspars. Typically, those interactions are investigated using mineral powder samples [1], which depict an idealization of the natural system due to the small grain size of the mineral. In those studies, information about macroscopic effects on sorption processes, like crystal orientation or surface roughness, are not accessible. Therefore, in this work we study the adsorption of Y(III), as an inactive rare earth analogue for An(III), on natural single crystal orthoclase samples of the (001) crystal orientation using the modern synchrotron-based, surface X-ray diffraction technique.

DESCRIPTION OF THE WORK

Natural single crystal orthoclase samples were freshly cleaved along their (001) orientation and reacted overnight in a solution of [Y3+] = 0.01 M at pH = 5.0 or 6.9. After the reaction was finished, surface X-ray diffraction (SXRD) was measured in situ at beamline 13 ID-C (GeoSoilEnviroCARS) of the Advanced Photon Source at Argonne National Laboratory. SXRD yields the total electron density profile of the mineral/water interface by measuring crystal truncation rods (CTR). For the first time, resonant anomalous X-ray reflectivity (RAXR) is applied on orthoclase for identification and quantification of sorption species, in our case Y3+. Coverage of adsorbed Y3+ is given in units of Y/AUC (area of the orthoclase (001) unit cell = 55.57 Å2).

RESULTS AND DISCUSSION

The study investigates the adsorption of Y3+ on orthoclase (001) at two different pH values. RAXR spectra of both samples show strong modulations at the Y X-ray absorption edge (17.038 keV), indicating that Y3+ has been adsorbed to the orthoclase surface. Analysis of amplitudes and phases of the RAXR spectra yield information about coverage and distance of the adsorbed species from the surface.
At pH 5.0, two sorption species at a distance of 2.47 (Species A) and 8.35 Å (Species B1) from the uppermost oxygen-atoms (Osurf) of the mineral surface are identified. At higher pH (6.9), the adsorbed Y is located at a distance of 1.50 (Species C) and 4.38 Å (B2) from Osurf. The Y3+ aquo ion has hydration shells in a distance of 2.36 and 4.40 Å. Therefore, Species A can be attributed to an outer-sphere (OS) and species B1 and B2 to extended outer-sphere (EOS) sorption complexes. In contrast, Species C is closer to the surface than any other sorption species observed in this study. At the investigated pH of 6.9, more sites of the orthoclase surface are deprotonated, obviously leading to the release of parts of the hydration shell of Y. Therefore, Species C is interpreted as an inner-sphere (IS) sorption complex. A plausible, bidentate binding motif for Species C is suggested based on the obtained results, where Y3+ is bound to two nearest Osurf resulting in a Y-O bond length of 2.46 Å in an angle of 39.0°.
While the interfacial speciation between the two samples is different, the total Y coverage is found to be similar for both samples (~0.6 Y/AUC). At pH 6.9 more than 70 % of the adsorbed Y3+ is bound as IS complex (Species C, 0.43 Y/AUC). The obtained coverage of the IS complex corresponds to ~2/3 of an adsorbed Y3+ monolayer, assuming bidentate coordination to two Osurf. Overall, the obtained sorption quantity and interfacial speciation are in good agreement with the powder studies, supporting the applicability of the previously developed SCMs to simulate retention of An(III) by K-feldspar for macroscopic systems.
However, we also identify reasonable amounts of adsorbed EOS complexes that are typically not found in studies using mineral powders and therefore not considered thermodynamic models. This result points out the need of studies working on macroscopic mineral samples to assess the impact of those species, and more general the controlling parameters relevant for natural systems, such as crystal orientation, surface roughness, and a realistic solid-liquid ratio. In conclusion, the results of this study contribute to a more realistic and reliable prediction of the mobility of trivalent actinides in the environment, and will enable a better risk assessment for deep geological repositories for radioactive waste.

  • Lecture (Conference)
    TransRet Workshop: Processes Influencing Radionuclide Transport and Retention, 12.-13.10.2021, Karlsruhe, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33393
Publ.-Id: 33393


f-element sorption onto K-feldspar – A comprehensive characterization of mechanism and thermodynamics

Neumann, J.; Brinkmann, H.; Britz, S.; Lützenkirchen, J.; Bok, F.; Stockmann, M.; Brendler, V.; Stumpf, T.; Schmidt, M.

The mobility of radionuclides in the environment, in particular in the context of a deep geological repository for radioactive waste, is heavily influenced by their interactions with charged mineral surfaces. This study investigates the retention potential of feldspars, a main component of granite as one potential host rock for a repository. The focus is on the sorption of trivalent actinides (Am, Cm) and their rare earth analogues (Eu, La, Lu, Nd, Y) as a main source of radiotoxicity in spent nuclear fuel.
A multi-method approach was used, consisting of traditional batch sorption experiments over a broad range of experimental conditions to determine uptake. Generally, retention increases with increasing pH and reaches quantitative retention at near neutral conditions. Furthermore, a spectroscopic study of the sorption structure on the molecular level was conducted. Time-resolved laser-induced fluorescence spectroscopy (TRLFS) using the actinide Cm as a luminescent probe, shows that four surface complexes are formed, an inner sphere sorption complex and its two hydrolysis forms, as well as a ternary feldspar/Cm/silicate complex at alkaline conditions (pH > 10).
Based on the observed comprehensive batch sorption dataset a generic surface complexation model (SCM-A) was developed that describes sorption of trivalent actinides and their rare earth analogues as a function of a variety of geochemical parameters (pH, ionic strength, metal concentration, solid-liquid ratio,…). In a second step, the dataset for the model was further increased by taking the quantitative spectroscopic results into consideration (SCM-B).
The developed SCMs deliver surface complexation parameters of the formed sorption species, which are included in thermodynamic databases. This data is essential for the subsequent calculation of distribution coefficients in modern approaches like the Smart KD-concept[1] as well as reactive transport modeling. Therefore, this study provides a contribution to a more reliable safety assessment of repositories for radioactive waste.[2]
[1] Stockmann, M. et al., "Smart Kd-values, their uncertainties and sensitivities - Applying a new approach for realistic distribution coefficients in geochemical modeling of complex systems", Chemosphere., 187, 277–285 (2017).
[2] Neumann, J. et al., "A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar", J. Colloid Interface Sci. (2020). https://doi.org/10.1016/j.jcis.2020.11.041.

  • Lecture (Conference) (Online presentation)
    Goldschmidt Konferenz, 04.-09.07.2021, Lyon, Frankreich

Permalink: https://www.hzdr.de/publications/Publ-33392
Publ.-Id: 33392


Umfassende Untersuchung und Bestimmung thermodynamischer Daten der Sorption von dreiwertigen Metallionen an K-Feldspat

Neumann, J.; Brinkmann, H.; Britz, S.; Lützenkirchen, J.; Bok, F.; Stockmann, M.; Brendler, V.; Stumpf, T.; Schmidt, M.

1 Introduction
Transport of contaminants, e.g. radionuclides, in the environment depends strongly on their interactions with mineral phases. In a repository for radioactive waste, crystalline rock (e.g. granite) as one potential host rock in Germany and many other countries, may affect the mobility of radionuclides. Main constituents of granite are feldspars. In spent nuclear fuel, trivalent actinides (Am, Cm, but also Pu) contribute strongly to the radiotoxicity. Therefore, this work studies the retention of Am and Cm, as well as their rare earths element analogues (Eu, La, Lu, Nd, Y) on K-feldspar. By combining batch sorption experiments and time-resolved laser-induced fluorescence spectroscopy (TRLFS), a generic surface complexation model (SCM) was obtained that is valid for all investigated M3+. Thermodynamic sorption data were obtained and an understanding of sorption mechanisms on the molecular level was achieved.
2 Results
Batch sorption experiments were performed over a broad range of environmental conditions (pH 4 – 10, [M3+] = 52 nM – 10 µM, 3 – 50 g/L K-feldspar (dp < 21 µm; 63 – 200 µm))[1]. Sorption is weak for pH < 5, strongly increases between pH 5 – 7 and reaches complete uptake at higher pH. By deconvolution of Cm emission spectra, an inner-sphere complex and its first two hydrolysis forms were found to be responsible for retention in this pH range.
For determination of the deprotonation constant pKa of K-feldspar, as one important input parameter of the model, column titration experiments were conducted. Batch sorption results of all studied M3+ were used to develop two alternative SCMs. The experimental sorption data were used to determine surface complexation parameters by coupling the parameter estimation code UCODE with PHREEQC (SCM-A). In a second approach, spectroscopic data were also considered (SCM-B). A generic approach was used to develop the geochemical models that satisfactorily describe all of the derived M3+/K feldspar sorption edges as well as TRLFS-derived speciation. The model delivered respective stability constants of the sorption complexes, which were added to the data base of the Smart Kd-concept[2]. Therefore, this work improves the risk assessment of repositories for radioactive waste.

Figure 1: Experimental batch sorption data (symbols) and calculation results using the two developed SCMs for different experimental conditions.[1]
References
[1] Neumann, J. et al., "A comprehensive study of the sorption mechanism and thermodynamics of f-element sorption onto K-feldspar", J. Colloid Interface Sci. (2020). https://doi.org/10.1016/j.jcis.2020.11.041.
[2] Stockmann, M. et al., "Smart Kd-values, their uncertainties and sensitivities - Applying a new approach for realistic distribution coefficients in geochemical modeling of complex systems", Chemosphere., 187, 277–285 (2017).

Keywords: sorption; trivalent; lanthanides; actinides; K-feldspar; TRLFS; SCM

  • Lecture (Conference) (Online presentation)
    Tage der Standortauswahl, 11.-12.02.2021, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33391
Publ.-Id: 33391


Boosting the Electrocatalytic Conversion of Nitrogen to Ammonia on Metal-Phthalocyanine-based Two-Dimensional Conjugated Covalent Organic Frameworks

Zhong, H.; Wang, M.; Ghorbani Asl, M.; Zhang, J.; Hoang Ly, K.; Liao, Z.-Q.; Chen, G.; Wei, Y.; Biswal, B. P.; Zschech, E.; Weidinger, I. M.; Krasheninnikov, A.; Dong, R.; Feng, X.

Electrochemical N₂ reduction reaction (NRR) under ambient conditions is attractive for the great potential in replacing the current Haber-Bosch process towards sustainable ammonia production. Metal-heteroatom-doped carbon-rich materials have emerged as the most promising electrocatalysts for NRR. However, simultaneously boosting their activity and selectivity toward NRR remains a grand challenge, while the principle for precisely tailoring the active sites has been elusive. Herein, we report the first case of crystalline two-dimensional conjugated covalent organic frameworks (2D c-COFs) incorporated with M-N₄-C centers as novel, defined and effective catalysts, and achieve a simultaneous enhancement in the activity and selectivity towards electrochemical NRR to yield ammonia. Such 2D c-COFs are synthesized based on metal-phthalocyanine (M = Fe, Co, Ni, Mn, Zn and Cu) and pyrene building blocks bonded by pyrazine linkages. Significantly, the 2D c-COF catalysts with Fe-N₄-C center exhibit higher ammonia yield rate (33.6 μg h⁻¹mg⁻¹cat) and Faradaic efficiency (FE, 31.9 %) at -0.1 V vs. reversible hydrogen electrode than those with other M-N₄-C centers, making them among the best NRR electrocatalysts (yield rate >30 μg h⁻¹mg⁻¹cat and FE >30 %). In-situ X-ray absorption spectroscopy, Raman spectroelectrochemistry and theoretical calculations unveil that the Fe-N₄-C center acts as a catalytic site. It shows a unique electronic structure with localized electronic states at the Fermi level, allowing for higher N₂ affinity and stronger binding energy of N₂, enabling faster N₂ activation and NRR kinetics than other M-N₄-C centers. Our work opens the possibility of developing metal-nitrogen-doped carbon-rich 2D c-COFs as superior NRR electrocatalysts and provides an atomic understanding of the NRR process on M-Nx-C based electrocatalysts for the design of high-performance NRR catalysts

Keywords: Covalent Organic Frameworks; Two-dimensional; Electrocatalyst; Nitrogen reduction reaction

  • Journal of the American Chemical Society 143(2021)47, 19992-20000
    Online First (2021) DOI: 10.1021/jacs.1c11158

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  • Secondary publication expected from 16.11.2022

Permalink: https://www.hzdr.de/publications/Publ-33390
Publ.-Id: 33390


Data Publication: Development of [18F]LU14 for PET Imaging of Cannabinoid Receptor Type 2 in the Brain

Moldovan, R.-P.

Cannabinoid receptors type 2 (CB2R) represent an attractive therapeutic target for neurodegenerative diseases and cancer. Aiming at a positron emission tomography (PET) radiotracer to monitor receptor density and/or occupancy during a CB2R-tailored therapy, we developed here cis-[18F]1-(4-fluorobutyl-N-((1s,4s)-4-methylcyclohexyl)-2-oxo-1,2-dihydro-1,8-naphthyridine-3-carboxamide ([18F]LU14) starting from the corresponding mesylate precursor. First biological evaluation revealed that [18F]LU14 is a highly affine CB2R radioligand with >80% intact tracer in brain at 30 min p.i. Its further evaluation in a well-established rat model of CB2R overexpression by PET demonstrated its ability to selectively image the CB2R in the brain and its potential as tracer to further investigate diseased related CB2R changes in expression.

Keywords: Cannabinoid receptor type 2; naphtyrid-2-one; binding affinity; radiochemistry; fluorine-18 labeling; brain; positron emission tomography

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-11
    DOI: 10.14278/rodare.1260
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33389
Publ.-Id: 33389


An AMS-world without any chemistry? – Untypical measurements of ²⁶Al, ⁴¹Ca and ⁵⁵Fe

Merchel, S.; Golser, R.; Lachner, J.; Marchhart, O.; Martschini, M.; Rugel, G.; Wallner, A.; Walther, D.; Wieser, A.

AMS measurements typically are lasting minutes to hours, but are usually preceded by time-consuming (typically days to weeks of) chemical preparation. Both, physicists and chemists are dreaming of an AMS-world without any chemistry.

Some of our earlier studies have already proven AMS being reasonable, fast and easily accessible for ⁷Be [1] and ⁴¹Ca [2] analysis if largely reducing radiochemical separation. However, to our knowledge there are only a few cases completely omitting wet chemical separation, e.g., ¹⁰Be/⁹Be in a Be mineral (phenakite) [3] and ¹⁴C/¹²C by laser-ablation AMS of stalagmites and corals [4]. Here, we focus on two new examples for “Instrumental” AMS (IAMS) at the DREsden AMS (DREAMS) facility and the Vienna Environmental Research Accelerator (VERA):

First, a pilot study to quantify ⁵⁵Fe (t₁/₂=2.76 a) in steel from a reactor vessel of a nuclear power plant by IAMS was validated (after radiochemical separation) by liquid scintillation counting (LSC) and AMS [5]. DREAMS reaches an uncertainty <10% at the 1 kBq g(Fe)⁻¹ level within 10 min measuring unprocessed steel chips. The background (<3 Bq g(Fe)⁻¹) is limited by the short measurement time. IAMS for analysing ⁵⁵Fe from neutron-capture production is reasonable and fast compared to other analytical methods.

Secondly, the ILIAMS set-up at VERA (Martschini et al., this meeting) allows to determine ratios of ²⁶Al (t₁/₂=0.7 Ma) to ²⁷Al and ⁴¹Ca (t₁/₂=0.104 Ma) to ⁴⁰Ca in stony meteorites by IAMS. The nearly complete suppression of isobars, i.e., ²⁶MgO⁻, when extracting AlO⁻, and ⁴¹KF₃⁻ when extracting CaF₃⁻, make pressure digestion (HF/HNO₃), ion exchange and precipitations unnecessary. Most stony meteorites contain ~1% Al, mainly in the form of Na-rich-Ca-poor plagioclase ((Na,Ca)(Si,Al)₄O₈)). Additional sources for >1% Ca are pyroxene (CaMgSi₂O₆) and phosphates (mainly apatite: Ca₅(PO₄)₃Cl)) [6]. IAMS has been performed using 1-2 mg representative powder of the previously-investigated chondrite Dhurmsala [7], either pure, mixed with Fe or PbF₂ powder.

For IAMS of ²⁶Al, AlO⁻ currents from Dhurmsala were - independent of mixing with Fe or pure - about 2% of Al₂O₃(Fe) ones. At ²⁶Al/²⁷Al of ~1.3x10⁻¹⁰ statistical uncertainties of 3% are reached within 15 min sputtering while cathodes last several hours. IAMS data at VERA - in the presence of about 15% Mg - are comparable to earlier (chemical processing) AMS results at DREAMS and ETH Zurich.

For IAMS of ⁴¹Ca, very stable CaF₃⁻ currents from Dhurmsala are ~5% of chemically-processed CaF₂ ones (each mixed with PbF₂). At ~1x10⁻¹¹ ⁴¹Ca/Ca, count rates of 1 min⁻¹ sputtering time are reached. IAMS data measured in the presence of about 1‰ K at VERA are comparable to earlier (chemical processing) AMS results at ANU, DREAMS and ETH Zurich.

The major uncertainty for both nuclides, originating from the current differences of standards and samples, will be addressed soon.

References: [1] Tiessen et al., JRNCh 319 (2017) 965. [2] Hampe et al., JRNCh 296 (2013) 617. [3] Merchel et al., JRNCh 298 (2013) 1871. [4] Welte et al., Anal.Chem. 88 (2016) 8570. [5] Merchel et al., JRNCh, submitted. [6] A. Bischoff, pers.comm. (2021.) [7] Merchel, PhD thesis, (1998).

  • Poster (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australien, 14.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-33385
Publ.-Id: 33385


¹⁰Be from commercial ⁹Be and ²⁷Al carrier solution – Some measurements

Merchel, S.; Braucher, R.; Lachner, J.; Rugel, G.

In the DREsden Acclerator Mass Spectrometry (DREAMS) chemistry laboratory, we see elevated but constant ¹⁰Be/⁹Be levels (1.2-2.0x10⁻¹⁵) when using a customised ⁹Be carrier [1]. In satellite and DREAMS laboratories unexperienced researchers and students are performing their own chemical separation, but the “human influence” is unlikely the sole explanation. Different levels of processing blanks as a function of the preparation laboratory are well-known also at other AMS facilities [2]. In our constant approach lowering processing blank levels for ¹⁰Be/⁹Be we have investigated two potential ¹⁰Be sources: ⁹Be and ²⁷Al carrier solutions.

Beryllium-9 carrier solutions are obvious ¹⁰Be sources and commercial and customised ones from minerals were already investigated earlier [3]. Inspired by numerous users asking for ⁹Be carrier analysis, we have compiled all (new) results from different AMS facilities. Remarkably, ¹⁰Be/⁹Be varies in the range of 1-10x10⁻¹⁵ from batch to batch (LOT) of the same company, very likely related to production date [4]. Currently, Australian Chemical Reagents and LGC provide carriers with the lowest intrinsic ¹⁰Be/⁹Be. For AMS users not affording a customised ⁹Be carrier, we advise buying larger quantities of commercial carriers to guarantee long-time low ¹⁰Be/⁹Be and saving precious AMS time from analysing new batches.

Another potential source for elevated and varying ¹⁰Be/⁹Be in processing blanks are Al carrier solutions (added to processing blanks) when performing ¹⁰Be/²⁶Al projects. According to [5] commercial aluminium contained ¹⁰Be in the range of 4-10x10⁷ ¹⁰Be atoms/g(Al). Nowadays, laboratories use 0.5-3.0 mg Al for processing blanks, which would yield into 4-10x10⁵ ¹⁰Be atoms/blank increasing the ¹⁰Be/⁹Be ratio to 6-10x10⁻¹⁵.

We asked in-situ dating researchers to provide their Al solutions. To differentiate between ¹⁰Be from Al and other sources (contamination in the chemistry laboratory or the ion source) we used a “basic standard-addition approach”: For each Al solution, two AMS targets containing ~300 µg ⁹Be and either 1 mg ²⁷Al or 3 mg ²⁷Al were prepared. After minimal chemistry (hydroxide precipitation, cation exchange, Be(OH)₂ precipitation, washing, drying, ignition, mixing with Nb) samples were measured at DREAMS.

Todays’ Al solutions are lower in ¹⁰Be compared to the Al investigated by [5]. None of our results is higher than 3.55x10⁻¹⁵, however, the two processing blanks without any Al have ¹⁰Be/⁹Be ratios of 1.2-1.7x10⁻¹⁵, which is in the same range as 12 out of 14 samples from ACROS, MERCK, ROTH and Traceselect, but 2-3 times higher than the machine blank. This means ~5x10⁴ ¹⁰Be atoms/sample are added from chemicals-consumables-materials or laboratory air-dust.
For more quantitative results about the ¹⁰Be concentration of Al carriers and to identify the main sources of the ¹⁰Be contribution for the processing blanks, additional experiments with larger amounts of Al (10-50 mg) and chemicals are needed.

Acknowledgments: Thanks to ASTER, DREAMS, Trondheim, VERA colleagues for ¹⁰Be data, and ANU, AWI, BOKU, CENIEH, CSFK, U Bratislava, U Jerusalem, U Potsdam colleagues for carrier solutions.

References: [1] Merchel et al., JRNCh (2013). [2] Wilcken et al., NIMB (2019). [3] Merchel et al., NIMB (2008). [4] Merchel et al., MethodsX (2021). [5] Middleton et al., NIMB (1994).

  • Poster (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry (AMS-15), 15.-19.11.2021, Sydney, Australien, 14.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-33384
Publ.-Id: 33384


Using in-situ cosmogenic 36Cl exposure dating of glacial erratics to establish a retreat chronology of the Iller Piedmont Glacier (Southern Germany)

Hildebrandt, D.; Hofmann, F.; Merchel, S.; Rugel, G.; Lachner, J.; Martschini, M.; Friedrich, A.

The dynamic behavior of glacial retreat following the globally diachronous Last Glacial Maximum (LGM) is poorly understood. In the Northern Alpine Foreland, multiple lobes of foreland glaciers produced a complex morpho-sedimentary record. While the reconstructed LGM ice extent is laterally constant in the west, it shows significant variations in the central and eastern parts. We explore how these geological differences relate to local climatic variability and global paleoclimate during a period of rapid climate change in the late Pleistocene.

In this study, we employ cosmogenic ³⁶Cl in limestone to constrain the in-situ exposure age of glacial erratics situated on moraine walls of the Iller Piedmont Glacier. We sampled erratic boulders from three moraine crests previously interpreted to represent the LGM and two post-LGM retreat stands. We measured ³⁶Cl/Cl and Cl-nat of seven samples from all three locations by applying routine chemistry protocols (Merchel et al., 2013) and isotope-dilution AMS measurements using a dedicated ion source for halogenides (Pavetich et al., 2014) at the DREsden AMS facility.

Preliminary results show that the sampled boulder surfaces provide internally consistent, reproducible, and geologically meaningful dates. Field investigations indicate that some of the erratic boulders were affected by chemical weathering, slope processes or human activities after their glacial deposition, thereby influencing the measured in-situ ³⁶Cl concentrations. In order to account for these complexities, we apply appropriate correction factors to obtain more accurate ages and discuss the related uncertainties.

Sample preparation of 14 additional samples was performed at the Laboratory for cosmogenic nuclide extraction at the University of Natural Resources and Life Sciences (BOKU) in Vienna. We will likely present ³⁶Cl/Cl and Cl-nat data of these additional samples measured at the Vienna Environmental Research Accelerator (VERA) at the time of the meeting. The exposure age data elucidate the spatio-temporal patterns of receding glaciers in the Northern Alpine Foreland, and place constraints on climate reconstructions for Central Europe during the late Pleistocene.

Acknowledgements:
We are grateful to Stephanie Neuhuber (BOKU Vienna) for providing access to her CN laboratory. Kathrin Strößner, Hagen Hoemann, Paul Herwegh, Kaja Schulz and Sami Akber (all LMU Munich) are thanked for assistance with sample preparation. This work was funded by DFG (German Science Foundation) grant FR 1673/15-1. Parts of this research were carried out at the Ion Beam Centre (IBC) at the Helmholtz-Zentrum Dresden–Rossendorf (HZDR) e. V., a member of the Helmholtz Association, supported by the HZDR Beamtime Proposal 20002195-ST. AMS measurements and sample preparation in Vienna are supported by the RADIATE project under the Grant Agreement 824096319 from the EU Research and Innovation programme HORIZON 2020 trough the Transnational Access grant 21002431-ST.

References:
Merchel et al., Quat. Geochron. 18 (2013) 54.
Pavetich et al., NIMB 329 (2014) 22.

  • Poster (Online presentation)
    The 15th International Conference on Accelerator Mass Spectrometry (AMS-15), 14.-19.11.2021, Sydney, Australien

Permalink: https://www.hzdr.de/publications/Publ-33383
Publ.-Id: 33383


Domain wall damping in ultrathin nanostripes with Dzyaloshinskii-Moriya interaction

Volkov, O.; Pylypovskyi, O.; Kronast, F.; Abert, C.; Oliveros Mata, E. S.; Makushko, P.; Mawass, M.-A.; Kravchuk, V.; Sheka, D.; Faßbender, J.; Makarov, D.

Structural inversion symmetry breaking in low-dimensional magnetic systems determines their electronic and magnetic properties at interfaces [1,2]. Asymmetrically sandwiched magnetic films can provide strong perpendicular magnetic anisotropy and Dzyaloshinskii-Moriya interactions (DMI), which is necessary for prospective memory and logic devices based on chiral non-collinear magnetic textures, e.g. skyrmions [3,4], skyrmion bubbles and chiral domain walls (DWs) [5]. The device performance is determined by the static and dynamic micromagnetic parameters [6,7]. In particular, the speed of a DW-based racetrack memory is defined by both the strength of the external driving, e.g. magnetic field or spin-polarized current, and internal magnetic parameters, e.g. the DMI constant and damping parameter [6,7]. The necessity of having a strong DMI in asymmetrically sandwiched magnetic structures requires the utilization of ultrathin (in the range of 1 nm) magnetic films, which implies the polycrystalinity and compromized structural quality of the layer stack. Structural imperfections in addition to the spin-pumping mechanism [8,9], that arises due to the proximity of a ferromagnetic material with a heavy-metal, lead to a substantial enhancement of the magnetic damping parameter of ultrathin films compared to bulk. Accessing this parameter typically requires dynamic experiments on the motion of DWs in confined geometries, which are usually done in the creep regime due to the pronounced pinning.

Here, we demonstrate both experimentally and theoretically the presence of tilted DWs in statics in perpendicularly magnetized asymmetric //CrOx/Co/Pt layer stacks with surface-induced DMI, Fig. 1. We show that in such systems there are two possible theoretical mechanism for the appearance of titled DWs: (I) A unidirectional tilt could appear in equilibrium as a result of the competition between the DMI and additional in-plane easy-axis anisotropy, which breaks the symmetry of the magnetic texture and introduce tilts [10]. (II) A static DW tilt could appear due to the spatial variation of magnetic parameters, which introduce pinning centers for DWs. A moving DW can be trapped in a tilted state after the external driving field is off. Based on these theoretical approaches, we perform a statistical analysis of the DW tilt angles obtained in staticts after the external magnetic field used for the sample demagnetization was off. We found that the second approach corresponds better to the experimental observations and allows to determine self-consistently the range of DW damping parameters and DMI constants for the particular layer stack. Using two reference fields, which provide two characteristic tilt angles, allow us to retrieve the range of DMI strength mJ/m2 and DW damping parameters . The upper limit for the DMI constant agrees with an independent transport-based measurement giving mJ/m2, which further refines our estimate of the damping parameter . This value lies in a typical DW damping range for the Co-based asymmetrical layer stacks, that are obtained from dynamic experiments [11,12]. Thus, the combination of the proposed method with standard metrological techniques opens up opportunities for the quantification of both static and dynamic micromagnetic parameters based on static measurements of the DW morphology.
[1] A. Fert, N. Reyren, and V. Cros, Nature Reviews Materials 2, 17031 (2017).
[2] R. Wiesendanger, Nature Reviews Materials 1, 16044 (2016).
[3] A. N. Bogdanov and D. A. Yablonskiı̆, Zh. Eksp. Teor. Fiz. 95, 178 (1989).
[4] S. Woo, K. Litzius, B. Krüger, et al., Nature Materials 15, 501 (2016).
[5] S. Emori, U. Bauer, S.-M. Ahn, et al., Nature Materials 12, 611 (2013).
[6] C. Garg, S.-H. Yang, T. Phung, et al., Science Advances 3, e1602804 (2017).
[7] S. Parkin and S.-H. Yang, Nature Nanotechnology 10, 195 (2015).
[8] Y. Tserkovnyak, A. Brataas, G. E. W. Bauer, et al., Reviews of Modern Physics 77, 1375 (2005).
[9] A. Brataas, Y. Tserkovnyak, and G. E. W. Bauer, Physical Review Letters 101, 037207 (2008).
[10] O. V. Pylypovskyi, V. P. Kravchuk, O. M. Volkov, et al., Journal of Physics D: Applied Physics 53, 395003 (2020).
[11] J.-M. L. Beaujour, J. H. Lee, A. D. Kent, et al., Physical Review B 74 (2006).
[12] A. J. Schellekens, L. Deen, D. Wang, et al., Applied Physics Letters 102, 082405 (2013).

Keywords: Nanomagnetism; Dzyaloshinskii-Moriya interaction

  • Open Access Logo Lecture (Conference) (Online presentation)
    INTERMAG 2021, 26.-30.04.2021, Online, France

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Permalink: https://www.hzdr.de/publications/Publ-33381
Publ.-Id: 33381


Experimental confirmation of curvature-induced effects in magnetic nanosystems

Volkov, O.; Kakay, A.; Kronast, F.; Mawass, M.-A.; van den Brink, J.; Kravchuk, V.; Sheka, D.; Faßbender, J.; Makarov, D.

Curvilinear magnetism is the emerging field in micromagnetism which studies influences of external geometry and its topology on magnetic vector fields [1]. Much attention was paid to fundamental theoretical investigations of curvature-induced effects for local [2,3] and non-local magnetic interactions [4], which results in the prediction of various magnetochiral effects [2,5], topologically-induced magnetic patterns [5,6], stabilization of individual skyrmions [7,8] and skyrmion lattices [9] on curvilinear defects. Recently, we provided the very first experimental confirmation and quantitative assessment of the existence of the curvature-induced chiral interaction of exchange origin in a conventional soft ferromagnetic material [10]. In its turn, the interplay between the intrinsic and exchange-induced Dzyaloshinskii-Moriya interaction (DMI) paves the way to a mesoscale DMI [3], whose symmetry and strength depends both on the geometrical and material parameters of the magnetic system. Extending this concept we proposed a novel approach towards artificial magnetoelectric materials with helimagnetic nanohelices embedded in a piezoelectric matrix [11], where electric field could control magnetic states through the utilization of curvature-induced effects.

[1] R. Streubel et. al., J. Phys. D: Appl. Phys. 49,363001 (2016).
[2] Y. Gaididei et al., Phys. Rev. Lett. 112, 257203 (2014).
[3] O. Volkov et al., Sci. Rep. 8, 866 (2018).
[4] D. D. Sheka et al., Commun. Phys. 3, 128 (2020).
[5] V. P. Kravchuk et al., Phys. Rev. B 85, 144433 (2012).
[6] O. V. Pylypovskyi et al., Phys. Rev. Lett. 114, 197204 (2015).
[7] V. P. Kravchuk et al., Phys. Rev. B 94, 144402 (2016).
[8] O. V. Pylypovskyi et al., Physical Review Applied 10, 064057 (2018).
[9] V. P. Kravchuk et al., Phys. Rev. Lett. 120, 067201 (2018).
[10] O. M. Volkov et al., Phys. Rev. Lett. 123, 077201 (2019).
[11] O. M. Volkov et al., J. Phys. D: Appl. Phys. 52, 345001 (2019).

Keywords: Nanomagnetism; Curvilinear magnetism

  • Poster (Online presentation)
    717. WE-Heraeus-Seminar — Curvilinear Condensed Matter: Fundamentals and Applications, 24.-26.06.2021, Online, Germany

Permalink: https://www.hzdr.de/publications/Publ-33378
Publ.-Id: 33378


RevCAR platform as a combinatorial approach for targeting acute myeloid leukemia

Rodrigues Loureiro, L. R.; González Soto, K. E.; Kittel-Boselli, E.; Hoffmann, A.; Bergmann, R.; Arndt, C.; Mitwasi, N.; Kegler, A.; Bartsch, T.; Berndt, N.; Altmann, H.; Fasslrinner, F.; Bornhäuser, M.; Bachmann, M.; Feldmann, A.

Background:
In the past years, the treatment of acute myeloid leukemia (AML) has been significantly shifted towards the development of targeted approaches. Nonetheless, clinical translation of novel immunotherapeutic strategies such as chimeric antigen receptor (CAR) T-cells in AML is still at an early stage. Given the heterogeneity of such disease, major challenges include immune escape and disease relapse, which demand for further improvements in the CAR design. To overcome such hurdles, we have invented the switchable, flexible and programmable adaptor RevCAR platform. This consists of T-cells engineered with RevCARs that are primarily inactive as they express an extracellular short peptide epitope incapable of recognizing surface antigens. RevCAR T-cells can be redirected to tumor antigens and controlled by bispecific antibodies cross-linking RevCAR T- and tumor cells resulting in tumor lysis. Remarkably, the RevCAR platform enables combinatorial tumor targeting following Boolean logic gates in which two separate RevCARs with different specificities can be simultaneously expressed and used to accomplish dual gated targeting of prominent AML antigens such as CD33 and CD123. We herein show for the first time the applicability of the RevCAR platform to target myeloid malignancies such as AML.

Methods:
Binding, functionality and proof-of-concept for combinatorial tumor targeting using the RevCAR system was assessed using both in vitro and in vivo models in different settings. For that, flow cytometry-based, cytokine release and cytotoxicity assays were performed using established AML cell lines or patient-derived material.

Results:
We have proven that AML cell lines as well as patient-derived AML blasts could be efficiently killed by redirected RevCAR T-cells targeting CD33 and CD123 in a flexible manner. Furthermore, by targeting both antigens, an AND gate logic targeting could be achieved using the RevCAR platform. This is a particular important approach to overcome existing or treatment related tumor escape variants and to tackle AML cancer heterogeneity.

Conclusions:
These accomplishments validate the preclinical versatility and controllability of the RevCAR platform embedded in one single system thereby paving the way for an improved and personalized immunotherapy of AML patients.

  • Lecture (Conference) (Online presentation)
    World Immunotherapy Council´s 4th Young Investigator Symposium (WIC), 10.11.2021, Washington, USA

Permalink: https://www.hzdr.de/publications/Publ-33377
Publ.-Id: 33377


Curvature-induced effects in magnetic nanosystems

Volkov, O.; Sheka, D.; Kravchuk, V.; Rößler, U.; Faßbender, J.; Makarov, D.

Curvilinear magnetic objects are in focus of intensive research due to the possibility to obtain new
fundamental effects and stabilize topologically non-trivial magnetic textures at the nanoscale [1]. In
geometrically-broken magnetic objects all energy functionals, that contains spatial derivatives, e.g.
exchange, magnetostatic and intrinsic Dzyaloshinskii-Moriya (DMI) interactions, are reshaping in a
way of appearance additional curvature-induced chiral and anisotropy terms. These novel chiral
magnetic responses arise in the physical space, by introducing bends and twists to magnetic
architectures even of conventional materials. We address both experimentally and theoretically the
appearance of curvature-induced exchange effects in parabolic nanostripes with different
geometrical parameters [2]. We show that a pinning of transversal domain wall at the parabolic apex
is originated due to the presence of local curvature-induced DMI that creates a subsequent pinning
potential. Measuring the depinning field enables to quantify the effective exchange-driven DMI
interaction constant. In its turn, the interplay between the intrinsic and exchange-induced DMI
paves the way to a mesoscale DMI, whose symmetry and strength depend both on the geometrical
and material parameters [3]. Developing this concept we propose a novel approach towards
artificial ME materials with helimagnetic nanohelices embedded in a piezoelectric matrix [4]. By
applying an electric field, small geometrical changes of pitch and radius could lead to the phase
transition from a homogeneously magnetized state (full average magnetic moment) to a periodical
one (zero average magnetic moment).

[1] R. Streubel et. al., J. Phys. D: Appl. Phys. 49,363001 (2016).
[2] O. Volkov et al.. Phys. Rev. Lett. 123, 077201 (2019).
[3] O. Volkov et al., Sci. Rep. 8, 866 (2018).
[4] O. Volkov et al., J. Phys. D: Appl. Phys. 52, 345001 (2019).

Keywords: Nanomagnetism; Curvilinear magnetism

  • Lecture (Conference) (Online presentation)
    APS March Meeting 2021, 15.-19.03.2021, Online, USA

Permalink: https://www.hzdr.de/publications/Publ-33375
Publ.-Id: 33375


Application of multi-edge HERFD-XAS to assess the uranium valence electronic structure in potassium uranate (KUO3)

Bes, R.; Leinders, G.; Kvashnina, K.

The uranium valence electronic structure in the prototypical undistorted perovskite
KUO3 is reported on the basis of a comprehensive experimental study using multi-
edge HERFD-XAS and relativistic quantum chemistry calculations based on DFT.
Very good agreement is obtained between theory and experiments, including the con-
firmation of previously reported Laporte forbidden f-f transitions and X-ray photo-
electron spectroscopic measurements. Many spectral features are clearly identified in
the probed U-f, U-p and U-d states and the contribution of the O-p states in those fea-
tures could be assessed. The octahedral crystal field strength, 10Dq, was found to be 6.6(1.5) eV and 6.9(4) eV from experiment and calculations respectively. Calculated
electron binding energies down to U-4f states are also reported.

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  • Secondary publication expected

Permalink: https://www.hzdr.de/publications/Publ-33370
Publ.-Id: 33370


Symmetry- and curvature effects on spin waves in vortex-state hexagonal nanotubes

Körber, L.; Zimmermann, M.; Wintz, S.; Finizio, S.; Kronseder, M.; Bougeard, D.; Dirnberger, F.; Weigand, M.; Raabe, J.; Otálora, J. A.; Schultheiß, H.; Josten, E.; Lindner, J.; Kézsmárki, I.; Back, C. H.; Kakay, A.

Analytic and numerical studies on curved magnetic nano-objects predict numerous exciting effects that can be referred to as magneto-chiral effects, which do not originate from intrinsic Dzyaloshinskii–Moriya interaction or interface-induced anisotropies. In constrast, these chiral effects stem from isotropic exchange or dipole-dipole interaction, present in all magnetic materials, which acquire asymmetric contributions in case of curved geometry of the specimen. As a result, for example, the spin-wave dispersion in round magnetic nanotubes becomes asymmetric, namely spin waves of the same frequency propagating in opposite directions along the nanotube exhibit different wavelenghts. Here, using time-resolved scanning transmission X-ray microscopy experiments, standard micromagntic simulations and a dynamic-matrix approach, we show that the spin-wave spectrum undergoes additional drastic changes when transitioning from a continuous to a discrete rotational symmetry, \textit{i.e.} from round to hexagonal nanotubes, which are much easier to fabricate. The polygonal shape introduces localization of the modes both to the sharp, highly curved corners and flat edges. Moreover, due to the discrete rotational symmetry, the degenerate nature of the modes with azimuthal wave vectors known from round tubes is partly lifted, resulting in singlet and duplet modes. For comparison with our experiments, we calculate the microwave absorption from the numerically obtained mode profiles which shows that a dedicated antenna design is paramount for magnonic applications in 3D nano-structures. To our knowledge these are the first experiments directly showing real space spin-wave propagation in 3D nano objects.

Keywords: spin wave; dispersion; curvature; micromagnetic modeling; hexagonal; symmetry; STXM

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Permalink: https://www.hzdr.de/publications/Publ-33367
Publ.-Id: 33367


Numerical reverse engineering of general spin-wave dispersions: Bridge between numerics and analytics using a dynamic-matrix approach

Körber, L.; Kakay, A.

Modern problems in magnetization dynamics require more and more the numerical determination of the spin-wave spectra and -dispersion in magnetic systems where analytic theories are not yet available. Micromagnetic simulations can be used to compute the spatial mode profiles and oscillation frequencies of spin-waves in magnetic system with almost arbitrary geometry and different magnetic interactions. Although numerical approaches are very versatile, they often do not give the same insight and physical understanding as analytical theories. For example, it is not always possible to decide whether a certain feature (such as dispersion asymmetry, for example) is governed by one magnetic interaction or the other. Moreover, since numerical approaches typically yield the normal modes of the system, it is not always feasible to disentangle hybridized modes. In this manuscript, we build a bridge between numerics and analytics by presenting a methodology to calculate the individual contributions to general spin-wave dispersions in a fully numerical manner. We discuss the general form of any spin-wave dispersion in terms of the effective (stiffness) fields produced by the modes. Based on a special type of micromagnetic simulation, the numerical dynamic-matrix approach, we show how to calculate each stiffness field in the respective dispersion law, separately for each magnetic interaction. In particular, it becomes possible to disentangle contributions of different magnetic interactions to the dispersion asymmetry in systems where non-reciprocity is present. At the same time, dipolar-hybridized modes can be easily disentangled. Since this methodology is independent of the geometry or the involved magnetic interactions at hand, we believe it is attractive for experimental and theoretical studies of magnetic systems where there are no analytics available yet, but also to aid the development of new analytical theories.

Keywords: spin wave; Micromagnetic simulations; theory; dispersion; dynamic-matrix approach; normal modes; hybridization; numerics

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Permalink: https://www.hzdr.de/publications/Publ-33366
Publ.-Id: 33366


Data for: Heterogeneous sorption of radionuclides predicted by crystal surface nanoroughness

Yuan, T.; Schymura, S.; Bollermann, T.; Molodtsov, K.; Chekhonin, P.; Schmidt, M.; Stumpf, T.; Fischer, C.

Reactive transport modeling (RTM) is an essential tool for the prediction of contaminants’ behavior in the bio- and geosphere. However, RTM of sorption reactions is constrained by the reactive surface site assessment. The reactive site density variability of the crystal surface nanotopography provides an “energetic landscape”, responsible for heterogeneous sorption efficiency, not covered in current RTM approaches.  Here, we study the spatially heterogeneous sorption behavior of Eu(III), as an analogue to trivalent actinides, on a polycrystalline nanotopographic calcite surface and quantify the sorption efficiency as a function of surface nanoroughness. Based on experimental data from micro-focus time-resolved laser-induced luminescence spectroscopy (µTRLFS), vertical scanning interferometry, and electron back-scattering diffraction (EBSD), we parameterize a surface complexation model (SCM) using surface nanotopography data. The validation of the quantitatively predicted spatial sorption heterogeneity suggests that retention reactions can be considerably influenced by nanotopographic surface features. Our study presents a way to implement heterogeneous surface reactivity into a predictive SCM for enhanced prediction of radionuclide retention.

Keywords: Sorption reactions; Crystal surface reactivity; µTRLFS; Surface complexation modeling; Radionuclide migration

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-08
    DOI: 10.14278/rodare.1254

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Permalink: https://www.hzdr.de/publications/Publ-33364
Publ.-Id: 33364


Data publication: Nanoindentation response of ion-irradiated Fe, Fe-Cr alloys and ferritic-martensitic steel Eurofer 97: The effect of ion energy

Das, A.; Altstadt, E.; Kaden, C.; Kapoor, G.; Akhmadaliev, S.; Bergner, F.

The dataset consists of inputs from ion irradiation experiments, nanoindentation and empirical modeling results for Fe (G379), ferrritic Fe-9Cr (G385), martensitic Fe-9Cr (L252) and Eurofer 97 steel. The dataset also includes the basic characterization of microstructure.

Keywords: iron; Fe-Cr alloy; ferritic-martensitic steel; ion irradiation; displacement damage; nanoindentation; irradiation hardeníng; indentation size effect

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-08
    DOI: 10.14278/rodare.1250
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33362
Publ.-Id: 33362


A Small Step, a Giant Leap: Somatic Hypermutation of a Single Amino Acid Leads to Anti-La Autoreactivity

Bartsch, T.; Arndt, C.; Rodrigues Loureiro, L. R.; Kegler, A.; Puentes-Cala, E.; Soto, J. A.; Kurien, B. T.; Feldmann, A.; Berndt, N.; Bachmann, M.

The anti-La mab 312B, which was established by hybridoma technology from human-La transgenic mice after adoptive transfer of anti-human La T cells, immunoprecipitates both native eukaryotic human and murine La protein. Therefore, it represents a true anti-La autoantibody. During maturation, the anti-La mab 312B acquired somatic hypermutations (SHMs) which resulted in the replacement of four aa in the complementarity determining regions (CDR) and seven aa in the framework regions. The recombinant derivative of the anti-La mab 312B in which all the SHMs were corrected to the germline sequence failed to recognize the La antigen. We therefore wanted to learn which SHM(s) is (are) responsible for anti-La autoreactivity. Humanization of the 312B ab by grafting its CDR regions to a human Ig backbone confirms that the CDR sequences are mainly responsible for anti-La autoreactivity. Finally, we identified that a single amino acid replacement (D > Y) in the germline sequence of the CDR3 region of the heavy chain of the anti-La mab 312B is sufficient for anti-La autoreactivity.

  • Open Access Logo International Journal of Molecular Sciences 22(2021)21, 12046
    Online First (2021) DOI: 10.3390/ijms222112046

Permalink: https://www.hzdr.de/publications/Publ-33361
Publ.-Id: 33361


Characterizing material liberation of multi-material lightweight structures from shredding experiments and finite element simulations

Heibeck, M.; Rudolph, M.; Modler, N.; Reuter, M.; Filippatos, A.

Most products in automotive, aerospace, and household appliance industry are multi-material structures. Materials are connected through a variety of joining techniques with the aim of optimizing performance during production and operation phase. However, during recycling in the end-of-life phase, different materials combined in multi-material structures need to be liberated, e.g. disconnected, and separated again to enable high material recoveries. Typical recycling approaches use shredding technologies to liberate materials. Efficient material liberation contributes to achieving high recycling rates for end-of-life products set by the European Union, thereby reducing the need for primary resource extraction and leading to a more sustainable development.

To characterize material liberation, we conducted an experimental shredding study with multi-material lightweight structures typical for automotive A-frames consisting of steel and composite materials, which were shredded in two sequences in a pilot rotary shear. We characterized feed and resulting progeny particles through a set of quantitative and qualitative metrics, thereby tracking changes in joint characteristics, material composition and particle sizes over the course of two processing steps. We found that material liberation is dependent on many design and shredding parameters. Our characterization approach for feed and progeny particles allows for linking design parameters to liberation behaviour. Due to high variability of design and shredding parameters experimental data acquisition is effortful. Therefore, we present an outlook on first results of our physics-based, numerical simulation model using Finite Element Method. Once validated, shredding simulations of many design configurations shall inform the designer about the liberation behaviour of a multi-material structure, such as the A-frame specimens.

Keywords: Recycling; Shredding; Multi-material design; Material liberation; Joint characterization; Composites; Finite Element Method

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Permalink: https://www.hzdr.de/publications/Publ-33360
Publ.-Id: 33360


Chelators for treatment of iron and copper overload: Shift from low-molecular-weight compounds to polymers

Hruby, M.; Santana Martinez, I. I.; Stephan, H.; Pouckova, P.; Benes, J.; Stepanek, P.

Iron and copper are essential micronutrients needed for the proper function of every cell. However, in excessive amounts these elements are toxic as they may cause oxidative stress resulting in damage of liver and other organs. This may happen due to poisoning, as side effect of thalassemia infusion thera-py or due to hereditary diseases hemochromatosis or Wilson´s disease. The current golden standard of therapy of iron and copper overload is the use of low-molecular-weight chelators of these elements. However, these agents suffer from severe side effects, are often expensive and possess unfavourable pharmacokinetics, which is all limiting useability of such therapy. The emerging concept are poly-mer-supported iron- and copper-chelating therapeutics, either for parenteral or oral use, which show vivid potential to keep therapeutic efficacy of low-molecular-weight agents while avoiding their draw-backs and especially side effects. Critical evaluation of this new perspective polymer approach is the purpose of this review article.

Keywords: iron; copper; polymer; chelator; Wilson's disease; hemochromatosis

Permalink: https://www.hzdr.de/publications/Publ-33358
Publ.-Id: 33358


SOLSTICE - Na-Zn molten salt batteries

Duczek, C.; Lee, J.; Monrrabal Marquez, G.; Weber, N.; Weier, T.

The first results of the EU project SOLSTICE will be presented.

  • Communication & Media Relations
    Battery Innovation Days (online Messestand) 23.11.2021

Permalink: https://www.hzdr.de/publications/Publ-33357
Publ.-Id: 33357


SOLSTICE - Na-Zn molten salt batteries

Weber, N.; Heinz, M.; Lee, J.; Weier, T.

The talk gives a very short overview on the EU project SOLSTICE.

  • Invited lecture (Conferences) (Online presentation)
    Horizon 2020 Batteries Projects clustering event, 17.-18.11.2021, Brüssel, Belgien

Permalink: https://www.hzdr.de/publications/Publ-33356
Publ.-Id: 33356


Germanium as an ultrabroadband THz material

Helm, M.; Singh, A.; Pashkin, O.; Winnerl, S.; Beckh, C.; Sulzer, P.; Leitenstorfer, A.; Schneider, H.

Germanium, as an elemental semiconductor, has no Reststrahlen band and is thus suited as a broadband THz material, even for THz generation. The drawback of its long carrier lifetime due to the indirect band gap can be remedied through ion implantation, and the relatively small size of the gap allows excitation with fiber lasers in the telecom range. We demonstrate THz emission from Ge photoconductive antennas reaching as far as 70 THz.

Keywords: germanium; THz; photoconductive antenna; braodband

  • Invited lecture (Conferences) (Online presentation)
    RJUSE TeraTech 2021, 01.-04.11.2021, Sendai, Japan
  • ORA-00933: SQL-Befehl wurde nicht korrekt beendet

Data publication: How 5f electron polarizability drives covalency and selectivity in actinide N-donor complexes

Köhler, L.; Patzschke, M.; Schmidt, M.; Stumpf, T.; März, J.

Diese Daten beinhalten die Synthese und Charakterisierung neuartiger Actinid (Th, U, Np, Pu) Komplexe mit pyrrolbasierten Liganden, sowie ebenfalls die Ligandsynthese. Darunter fallen SC-XRD, NMR, IR, UV-VIS und EA Daten. Des weiteren quantenchemische Berechnungen zu den Systemen, sowie der Vergleich zum bereits bekannten Salen System.

Keywords: actinides; N donor ligands; bonding analysis; f electrons; pyrrole

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-05
    DOI: 10.14278/rodare.1245
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33353
Publ.-Id: 33353


Computational Science at HZDR: Tools, Services, and Consulting to Empower Your Research

Pape, D.; Lokamani, M.; Knodel, O.; Müller, S.; Huste, T.; Steinbach, P.; Juckeland, G.; Fiedler, M.

The Computational Science Department FWCC and its sister departments offer various tools and services to empower scientists at HZDR in their research. This presentation held at the 2021 PhD seminar aims at introducing the working groups DMS and MT-DMA as well as the Helmholtz Incubator Platforms HIFIS and Helmholtz AI, all hosted by FWCC, and the library FWCB. It presents a selection of said services and shows options of contact for receiving help in the topics presented.

Keywords: Computational Science; Research Software Engineering; High Performance Computing; Data Management; Machine Learning; Artificial Intelligence; Data Science

  • Lecture (others)
    PhD Seminar 2021, 18.10.2021, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-33351
Publ.-Id: 33351


Data publication: Strong Binding of Noble Gases to [B₁₂X₁₁]⁻: a theoretical study

Wöhner, K.; Wulf, T.; Vankova, N.; Heine, T.

This dataset contains output files of DFT and DLPNO calculations of the investigated species. At the DFT level of theory full geometry optimizations and frequency analysis where done. At DLPNO level of theory single point calculations were done.

Keywords: Boron; Anions; Complexation; Cluster chemistry; Group 17 compounds

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-04
    DOI: 10.14278/rodare.1241
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33348
Publ.-Id: 33348


Data publication: Development of fluorinated and methoxylated benzothiazole derivatives as highly potent and selective cannabinoid CB2 receptor ligands

Aly, M. W.; Ludwig, F.-A.; Deuther-Conrad, W.; Brust, P.; Abadi, A. H.; Moldovan, R.-P.; Osman, N. A.

Numerous studies have indicated the upregulation of the cannabinoid type 2 receptors (CB2 receptors) in neuroinflammation and cancer, and that their visualization with PET (Positron emission tomography) could provide a valuable diagnostic and/or therapy-monitoring tool in such disorders. However, the availability of reliable CB2-selective imaging probes is still lacking in clinical practice. Encouraged by promising CB2 affinity results obtained for a benzothiazole lead compound, 6a, further structural optimizations led to the development of a series of fluorinated and methoxylated benzothiazole derivatives, endowed with extremely high CB2 binding affinity and an exclusive selectivity to the CB2 receptor, along with structural sites suitable for radiolabeling. Compounds 20, 21, 24, 25, 29, 32 and 33 displayed subnanomolar CB2 Ki values (ranging from 0.16 nM to 0.68 nM) while lacked affinity to the CB1 receptor subtype. The fluorinated analogs, 21 and 29, were evaluated for their in vitro metabolic stability in mouse and human liver microsomes (MLM and HLM). Both 21 and 29 displayed an exceptionally high stability (98% and 91% intact compounds, respectively) after 60 min incubation with MLM. Contrastingly, compound 29 revealed an almost 2-fold greater metabolic stability after incubation with HLM for 60 min. Taken together, our data represent remarkably potent and selective CB2 ligands as credible leads that can be further exploited for 18F- or 11C-radiolabeling and utilization as PET tracers.

Keywords: Benzothiazole; Cannabinoid receptor type 2; CB2 ligands; Fluorine; Metabolic studies; PET

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  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-19
    DOI: 10.14278/rodare.1267
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33347
Publ.-Id: 33347


Data publication: Design, radiosynthesis and preliminary biological evaluation in mice of a brain-penetrant 18F-labelled σ2 receptor ligand

Moldovan, R.-P.; Gündel, D.; Teodoro, R.; Ludwig, F.-A.; Fischer, S.; Toussaint, M.; Schepmann, D.; Wünsch, B.; Brust, P.; Deuther-Conrad, W.

The σ2 receptor (transmembrane protein 97), which is involved in cholesterol homeostasis, is of high relevance for neoplastic processes. The upregulated expression of σ2 receptors in cancer cells and tissue in combination with the antiproliferative potency of σ2 receptor ligands motivates the research in the field of 2 receptors for the diagnosis and therapy of different types of cancer. Starting from the well described 2-(4-(1H-indol-1-yl)butyl)-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline class of compounds, we synthesized a novel series of fluorinated derivatives, bearing the F-atom at the aromatic indole/azaindole subunit. RM273 (2-[4-(6-fluoro-1H-pyrrolo[2,3-b]pyridin-1-yl)butyl]-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline) was selected for labelling with 18F and evaluation regarding detection of σ2 receptors in the brain by positron emission tomography. Initial metabolism and biodistribution studies of [18F]RM273 in healthy mice revealed promising penetration of the radioligand into the brain. Preliminary in vitro autoradiography on brain cryosections of an orthotopic rat glioblastoma model proved the potential of the radioligand to detect the upregulation of σ2 receptor in glioblastoma cells compared to healthy brain. The results indicate that the herein developed σ2 receptor ligand [18F]RM273 has potential to assess by non-invasive molecular imaging the correlation between the availability of σ2 receptors with properties of brain tumors such as tumor proliferation or resistance towards particular therapies

Keywords: σ2 receptor; transmembrane protein 97; azaindoles; binding affinity; radiochemistry; fluorine-18 labeling; positron emission tomography (PET); brain-penetration; glioblastoma; orthotopic

Related publications

  • Reseach data in the HZDR data repository RODARE
    Publication date: 2021-11-09
    DOI: 10.14278/rodare.1256
    License: CC-BY-4.0

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Permalink: https://www.hzdr.de/publications/Publ-33346
Publ.-Id: 33346


Continuous-time movement modeling

Alston, J.; Simoes Silva, I. M.; Fleming, C. F.; Noonan, M. J.

In this workshop, we presented an introduction to continuous-time movement models for modeling animal movement

  • Lecture (Conference) (Online presentation)
    2021 The Wildlife Society Annual Meeting, 01.11.2021, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-33341
Publ.-Id: 33341


Movement ecology research at CASUS

Alston, J.; Calabrese, J.

In this presentation, we provided an introduction to the animal movement research we conduct at CASUS.

  • Open Access Logo Lecture (Conference) (Online presentation)
    2021 EuroBoar Annual Meeting, 25.10.2021, virtual, virtual

Permalink: https://www.hzdr.de/publications/Publ-33340
Publ.-Id: 33340


State with spontaneously broken time-reversal symmetry above the superconducting phase transition

Grinenko, V.; Weston, D.; Caglieris, F.; Wuttke, C.; Hess, C.; Gottschall, T.; Maccari, I.; Gorbunov, D.; Zherlitsyn, S.; Wosnitza, J.; Rydh, A.; Kihou, K.; Lee, C.-H.; Sarkar, R.; Dengre, S.; Garaud, J.; Charnukha, A.; Hühne, R.; Nielsch, K.; Büchner, B.; Klauss, H.-H.; Babaev, E.

The most well-known example of an ordered quantum state—superconductivity—is caused by the formation and condensation of pairs of electrons. Fundamentally, what distinguishes a superconducting state from a normal state is a spontaneously broken symmetry corresponding to the long-range coherence of pairs of electrons, leading to zero resistivity and diamagnetism. Here we report a set of experimental observations in hole-doped Ba1−xKxFe2As2. Our specific-heat measurements indicate the formation of fermionic bound states when the temperature is lowered from the normal state. However, when the doping level is x ≈ 0.8, instead of the characteristic onset of diamagnetic screening and zero resistance expected below the superconducting phase transition, we observe the opposite effect: the generation of self-induced magnetic fields in the resistive state, measured by spontaneous Nernst effect and muon spin rotation experiments. This combined evidence indicates the existence of a bosonic metal state in which Cooper pairs of electrons lack coherence, but the system spontaneously breaks time-reversal symmetry. The observations are consistent with the theory of a state with fermionic quadrupling, in which long-range order exists not between Cooper pairs but only between pairs of pairs.

  • Nature Physics 17(2021)11, 1254-1259
    Online First (2021) DOI: 10.1038/s41567-021-01350-9
  • ORA-00933: SQL-Befehl wurde nicht korrekt beendet

A two-sublattice model for extracting rare-earth anisotropy constants from measurements on (Nd,Ce)2(Fe,Co)14B single crystals

Gomez Eslava, G.; Fayyazi, B.; Skokov, K.; Scurschii, I.; Gorbunov, D.; Gutfleisch, O.; Dempsey, N. M.; Givord, D.

Anisotropy constants are obtained from an analysis of single crystal magnetization curves measured up to high fields. The anisotropy of the 3d transition metal sublattice is considered, as well as molecular exchange field coupling between the rare-earth (R) and transition metal sublattices (M). This procedure allows for non colinear R and M magnetic moments, meaning that their angles with respect to the easy axis are independent variables. With this approach we obtain anisotropy constants that are larger than those reported in the literature, which reflects the anisotropy of the isolated R sublattice. Results for Co and/or Ce doped Nd2Fe14B single crystals are presented, showing the influence of such substitutions on the magnetocrystalline anisotropy. These results indicate that the enhanced performance of NdFeB-based magnets co-doped with Ce and Co can be ascribed to an improvement in intrinsic properties.

  • Journal of Magnetism and Magnetic Materials 520(2021), 167470
    DOI: 10.1016/j.jmmm.2020.167470
  • ORA-00933: SQL-Befehl wurde nicht korrekt beendet

Data publication: Inverse-Dirichlet Weighting Enables Reliable Training of Physics Informed Neural Networks

Maddu, S.; Sturm, D.; Müller, C. L.; Sbalzarini, I. F.

Scripts and notebooks to reproduce the results presented in the paper "Inverse-Dirichlet Weighting Enables Reliable Training of Physics Informed Neural
Networks", Maddu et al., 2021

Keywords: physics informed neural networks; sobolev training; computational physics; deep learning; data-driven modeling; multi-objective optimization; catastrophic forgetting; active turbulence

Related publications

  • Software in external data repository
    Publication year 2021
    Programming language: Python
    System requirements: python, numpy, scipy, sklearn, torch, matplotlib, seaborn, pandas
    License: MIT
    Hosted on GitHub: Link to location

Permalink: https://www.hzdr.de/publications/Publ-33337
Publ.-Id: 33337


Antiferromagnetic resonance in the cubic iridium hexahalides (NH4)2IrCl6 and K2IrCl6

Bhaskaran, L.; Ponomaryov, O.; Wosnitza, J.; Khan, N.; Tsirlin, A. A.; Zhitomirsky, M. E.; Zvyagin, S.

We report on high-field electron spin resonance studies of two iridium hexahalide compounds (NH4)2IrCl6 and K2IrCl6. In the paramagnetic state, our measurements reveal isotropic g factors g = 1.79(1) for the Ir4+ ions, in agreement with their cubic symmetries. Most importantly, in the magnetically ordered state, we observe two magnon modes with zero-field gaps of 11.3 and 14.2 K for (NH4)2IrCl6 and K2IrCl6, respectively. Based on that and using linear spin-wave theory, we estimate the nearest-neighbor exchange couplings and anisotropic Kitaev interactions J1/kB = 10.3 K, K/kB = 0.7 K for (NH4)2IrCl6, and J1/kB = 13.8 K, K/k = 0.9 K for K2IrCl6, revealing the nearest-neighbor Heisenberg coupling as the leading interaction term, with only a weak Kitaev anisotropy.

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-33336
Publ.-Id: 33336


Inverse-Dirichlet Weighting Enables Reliable Training of Physics Informed Neural Networks

Maddu, S.; Sturm, D.; Müller, C. L.; Sbalzarini, I. F.

We characterize and remedy a failure mode that may arise from multi-scale dynamics with scale
imbalances during training of deep neural networks, such as Physics Informed Neural Networks
(PINNs). PINNs are popular machine-learning templates that allow for seamless integration of
physical equation models with data. Their training amounts to solving an optimization problem over
a weighted sum of data-fidelity and equation-fidelity objectives. Conflicts between objectives can
arise from scale imbalances, heteroscedasticity in the data, stiffness of the physical equation, or from
catastrophic interference during sequential training. We explain the training pathology arising from
this and propose a simple yet effective inverse-Dirichlet weighting strategy to alleviate the issue. We
compare with Sobolev training of neural networks, providing the baseline of analytically
$\epsilon$-optimal training. We demonstrate the effectiveness of inverse-Dirichlet weighting in various applications,
including a multi-scale model of active turbulence, where we show orders of magnitude improvement
in accuracy and convergence over conventional PINN training. For inverse modeling using sequential
training, we find that inverse-Dirichlet weighting protects a PINN against catastrophic forgetting.

Keywords: physics informed neural networks; sobolev training; computational physics; deep learning; data-driven modeling; multi-objective optimization; catastrophic forgetting; active turbulence

Related publications

Permalink: https://www.hzdr.de/publications/Publ-33335
Publ.-Id: 33335


Electric-field manipulation of the magnetocaloric effect in a Fe49Rh51/PZT composite

Amirov, A. A.; Gottschall, T.; Chirkova, A. M.; Aliev, A. M.; Baranov, N. V.; Skokov, K. P.; Gutfleisch, O.

By simultaneous measurements in a purpose-built setup, an electric-field manipulation of the magnetocaloric effect and strain in a Fe49Rh51/PZT composite with a sandwich-type connection was demonstrated. Using the strain measurements from two gauges attached to the opposite sides of the composite, as well as finite element modeling (FEM) simulations, it was shown that the deformation in the composite is of a bending type. Mechanical strain induced by the electric field does not exceed ∼500 ppm, which is four times smaller than the expansion of FeRh during the transition ∼2000 ppm. Applying an electric voltage to the PZT favors the transition, but the further expansion of FeRh is hindered and thus blocks the antiferromagnetic-ferromagnetic transition. Obtained experimental results and FEM simulations can be used in the design of new multicaloric composites with optimal ratio between PZT and multicaloric material.

Permalink: https://www.hzdr.de/publications/Publ-33334
Publ.-Id: 33334


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