Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Melt flow is critical to microstructural evolution during various solidification processes, such as directional solidification and additive manufacturing. Applying an external magnetic field interacts with the intrinsic thermoelectric currents during solidification, generating a new flow field, due to thermoelectric magnetohydrodynamics (TEMHD). The introduction of TEMHD flow can disrupt the existing buoyancy-dominated flow and potentially tailor the microstructure. However, the physical mechanisms remain unclear, hindering its further application. Here, using in situ synchrotron X-ray imaging coupled with numerical simulation, we demonstrated that the macroscopic TEMHD flow ahead of the solidification front, along with the interstitial TEMHD flow arising within the mushy zone are the primary mechanisms controlling melt flow in the thin sample. Two thermoelectric regimes were revealed, each with distinctive mechanisms that control flow. Additionally, we developed a methodology on characterising melt pool in 3D during additive manufacturing process and demonstrated the significant TEMHD effect on the melt pool.

The current work presents an experimental study focusing on pulsed electromagnetic fields (PEMF) effects on dendrite microstructure and melt flow during the solidification of low-melting temperature Ga-In alloy. This alloy is solidified in a flat sample bottom-to-top applying a vertical temperature gradient [1-2]. The dendritic microstructure is visualized using synchrotron X-ray imaging at the Diamond Light Source. The magnetic system used generates field intensities of 8 - 11 mT and frequencies in the domain between 10 and 300 Hz, a duty cycle of 50%. The solidification under frequencies above 100 Hz leads to dendrite fragmentation and solute redistribution in the mushy zone. Moreover, direct observations show that large dendrite blocks (10 - 20 dendrites) can individually move or turn in the mushy zone leading to the formation of new sub-grain boundaries. We consider this phenomenon as an alternative mechanism of grain refinement. The next step is to validate a Cellular Automata Lattice Boltzmann-based numerical model [3-4] using the same set-up as the experiment and directly compare it with the synchrotron radiographic data.
References
[1]Shevchenko N., Boden S., Gerbeth G., Eckert S. Metall. Mater. Trans. A, 44: 3797-3808. 2013.
[2] Shevchenko N., Roshchupkina O., Sokolova O., Eckert S. Journal of Crystal Growth, 417: 1-8. 2015.
[3] Kao A., Shevchenko N., Alexandrakis M. et al. Phil. Trans. R. Soc. A, 377: 20180206. 2019.
[4] Kao A., Krastins I., Alexandrakis M. et al. JOM, 71: 48-58. 2019.

Melt flow is critical to microstructural evolution during various solidification processes, whether in directional solidification, or additive manufacturing. Applying an external magnetic field interacts with the intrinsic thermoelectric currents during solidification, generating a new flowfield, due to thermoelectric magnetohydrodynamics (TEMHD). The introduction of TEMHD flow can disrupt the existing buoyancy-dominated flow and potentially tailor the microstructure. However, the physical mechanisms remain unclear, hindering its further application. Here with a focus on directional solidification, using in situ synchrotron X-ray imaging coupled with numerical simulation, we demonstrated that the macroscopic TEMHD flow ahead of the solidification front, along with the microscopic TEMHD flow arising within the mushy zone are the primary mechanisms controlling melt flow. Two thermoelectric regimes were revealed, each with distinctive mechanisms that control flow. Further, we demonstrated how the TEMHD effect can also manipulate melt flow in a rapid solidification process, i.e., additive manufacturing.

Modification of flow during solidification has been shown to have a large effect on the microstructural dendritic growth during directional solidification, causing changes to convective solute transport. In our previous reported study, we modified flow using the interaction of thermoelectric currents with static magnetic fields, employing the phenomenon known as Thermoelectric Magnetohydrodynamics (TEMHD). Our current work expands on this to look at the effect of pulsed magnetic fields and the interaction with the induced currents generated. Pulsed fields are known to influence microstructure evolution, and we hypothesise that this is also due to fluid flow. Modelling work of this process in thin Hele-Shaw quartz cells has been performed on both a micro and macro-scales, looking at both the gross flow patterns within the cells and the microstructural solidification and inter-dendritic flow. We compare our modelling work to experimental work in situ at Diamond Light Source.

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Mn-doped UO2 is considered a potential advanced nuclear fuel due to ameliorated microstructural grain growth compared to non-doped variants. However, recent experimental investigations have highlighted limitations in grain growth apparently arising from misunderstandings of its redox-structural chemistry. To resolve this, we use synchrotron X-ray diffraction and spectroscopy measurements supported by ab initio calculations to cross-examine the redox and structural chemistry of Mn-doped UO2 single crystal grains and ceramic specimens. Measurements reveal Mn enters the UO2 matrix divalently as with the additional formation of fluorite Mn+2O in the bulk material. Extended X-ray absorption near edge structure measurements unveil that during sintering, the isostructural relationship between fluorite UO2 and Mn+2O results in inadvertent interaction and subsequent incorporation of diffusing U species within MnO, rather than neighbouring UO2 grains, inhibiting grain growth. The investigation consequently highlights the significance of considering total redox-structural chemistry of main and minor phases in advanced ceramic material design.

We present an entangling gate scheme for trapped-ion chains that achieves high-fidelity operations with excited motional states despite multiple error sources. Our approach incorporates all relevant motional modes and exhibits enhanced robustness against both motional heating effects and detuning errors, critical features for building robust and scalable trapped-ion quantum computers.

The surface code is a spin-1/2 lattice system that can exhibit non-trivial topological order when defects are punctured in the lattice and thus can be used as a stabiliser code. The protocols developed to create defects in the system have previously relied on adiabatic dynamics. In this work we use techniques of quantum optimal control to overcome the requirement for adiabaticity and achieve defect creation and implemention of other important operations required for quantum computation at much faster timescales.

The mTeSS-X (Multi-tenanting TeSS eXchange) project aims to build upon the ELIXIR TeSS platform to address the fragmentation of training resources across
Research Infrastructures (RIs) and scientific domains. RIs and EOSC projects have limited training catalogue capability beyond sparse, outdated lists on web pages,
while cross-portal exchange has been discussed but not practised. Fragmentation of resources prevents the reuse of valuable training materials and limits the dissemination. By fostering the federation of interoperable training catalogues, mTeSS-X will significantly enhance the findability, accessibility, and reuse of high-quality training resources, improve the sustainability of training portals by reducing operational duplication and enabling resource-sharing across portals.

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In der Natur gehören chemische und biologische Prozesse untrennbar zusammen. Wie sehr sich diese Porzesse gegenseitig beeinflussen lässt sich am Beispiel des Verhaltens von Uran in der Umwelt und seiner Wechselwirkung mit verschiedenen biologischen Systemen sehr eindrücklich darlegen. Der Vortrag zeigt dies an einigen Beispielen auf und verdeutlicht damit die Verflechtung beider Fachdisziplinen.

The contrasting reactivity of hydrogen isotopes, including tritium, is of interest in several research areas, including nuclear fusion, pharmaceutical synthesis, and fundamental isotope separation research [1]. In our work on hydrogen isotope separation, we focus on approaches for gaseous isotopologue separation, other than the currently employed methods, e.g. cryogenic distillation. A promising approach is the selective ad- and desorption on nanoporous materials, i.e. MOFs (metal organic frameworks) and zeolites, in temperature-controlled environments. Previous work has shown positive results with respect to hydrogen and deuterium separation. [2, 3]

We investigated the separation efficiency of an Ag(I)-exchanged zeolite using thermal desorption spectroscopy (TDS). The zeolite was exposed to H2/T2 gas mixtures at low temperatures, obtained by liquid N2 cooling. The experimental approach with gaseous tritium requires a specific analytical strategy. Therefore, the desorbed tritium was collected after conversion to HTO and analyzed by liquid scintillation counting (LSC). This allowed us to safely handle and remove the tritium gas, while knowing exactly how much tritium was initially adsorbed. Using this analytical strategy, we exposed the sample to low gas pressures (10 mbar) in a temperature range from 80 K up to 100 K. We were able to achieve separation efficiencies of up to 6, for extremely asymmetric gas mixtures (approx. 0.5% T2).

References:

[1] L. Shere, A. K. Hill, T. J. Mays, R. Lawless, R. Brown, S. P. Perera Int. J. Hydrogen Energy 2024, 55, 319-338. [2] L. Zhang, T. Wulf, F. Baum, W. Schmidt, T. Heine, M Hirscher Inorg. Chem. 2022, 61, 25, 9413–9420. [3] J. Y. Kim, R. Balderas-Xicohténcatl, L. Zhang, S. G. Kang, M. Hirscher, H. Oh, H. R. Moon J. Am. Chem. Soc. 2017, 139, 42, 15135–15141.

The lecture described methods for analyzing uranium-containing samples and for determining dominant and relevant binding forms of uranium in complex environmental samples, and pointed out possible future development opportunities.

This lecture dealt with various interaction mechanisms between radionuclides and biosystems in general and with uranium in particular

Tritium has recently become a topic in numerous fundamental and applied research areas. This includes fields such as storage[1], fusion and isotope separation[2]. In our work, we specifically focus on investigating potential approaches on gaseous hydrogen isotopologue separation, which are supposed to yield a higher separation efficiency than currently employed methods. One approach is the selective permeation through a proton conducting polymer (i.e. Nafion) via electrochemical pumping. Combination with graphene, a monoatomic carbon material, is being explored to further increase the separation efficiency.[3, 4] This has already shown promising results for protium-deuterium mixtures.

One currently unanswered question is how the exposure to tritium as a beta emitter may modify the graphene structure, which could in turn affect the separation efficiency. To investigate this, graphene samples on SiO2/Si substrate were modified by either electron irradiation from an SEM electron beam or by direct exposure to tritium using a specific setup. A comparable electron dose was applied in both cases, but in contrast to the SEM electrons, the emitted beta particles are not focused and show a broad energy distribution. The samples were analyzed using a Raman spectroscope, including a pristine sample. From the spectra, the intensity ratios of the D- and the G-band were calculated as an indicator for the defect or modification density.
The results show just a very slight increase in the intensity ratio for the SEM irradiated sample, which could suggest minor changes in the structure. In comparison, the tritium exposed sample exhibits a much higher intensity ratio. This indicates not only a higher modification density but also structural changes, which cannot be solely contributed the electrons from the tritium decay. It appears likely that a tritiation reaction[1] occurs, facilitated by the beta emission.

Literature:

[1] Zeller, G. et al. Nanoscale Adv. 2024, 6, 2838.
[2] Shere, L. et al. Int. J. Hydrogen Energy 2024, 55, 319.
[3] Lozada-Hidalgo, M. et al. Science 2016, 351, 68.
[4] Lozada-Hidalgo, M. et al. Nat. Commun. 2017, 8, 15215.

In current electronic structure research endeavors such as warm dense matter or machine learning applications, efficient development necessitates non-monolithic software, providing an extendable and flexible interface. The open-source idea offers the advantage of having a source code base that can be reviewed and modified by the community. However, practical implementations can often diverge significantly from their theoretical counterpart. Leveraging the efforts of recent theoretical formulations and the features of Python, we try to mitigate these problems. We present eminus, an education- and development-friendly electronic structure package designed for convenient and customizable workflows, yet built with intelligible and modular implementations.

In order to assess the feasibility of bioremediation strategies, it is crucial to understand the interaction processes between the biosphere and the geosphere. In particular, this means understanding the specific mechanisms of fluid-solid interactions and their alteration by the biosphere. Soil fluids are chemically modified by biological activity and can potentially induce desorption reactions of contaminants from the solid soil components.
Positron emission tomography (PET), a method mainly employed in nuclear medicine, has been proven as a reliable tool for investigating a multitude of transport processes in natural[1] and technical materials. However, previous investigations focused on analyzing hydrodynamic parameters only. Because this tomographic method can quantitatively track radiotracers with high temporal and spatial resolution, it is well suited for analyzing the complex system created when plants are introduced into soil-like materials for phytoremediation purposes. As plants release chelating ligands into the rhizosphere via their root exudates, they induce highly localized changes in soil chemistry, which leads to changes in the mobility of metals and other nutrients. This affects not only the uptake of contaminants by plants, but also the overall mobility of metals in the soil. Reliable data on these effects are crucial for analyzing remediation processes for both nuclear and chemical waste.
To understand and quantify the effects of the interaction between the bio- and geosphere, PET techniques offer unique capabilities by providing in-situ volumetric radiotracer propagation and concentration data in with high temporal and spatial resolution, surpassing traditional flow and lysimeter experiments.
In this presentation, we discuss the possibilities of utilizing PET with various inert and reactive tracers in combination with µ-XRCT to assess the phytoremediation potential of contaminated soils by in-situ analysis of sorption and mobilization processes. Using both simplified substrates and complex soil systems, we demonstrate the impact of plants on the hydrodynamics and solute transport in complex materials such as soils and sediments.

Referenzen:

[1] T. Bollermann, T. Yuan, J. Kulenkampff, T. Stumpf, C. Fischer, Chemical Geology 2022, 606.

Remediation of former industrial or nuclear sites, as well as the evaluation of long-term storage strategies for nuclear and chemical waste, depends highly on a comprehensive understanding of contaminant mobility. This includes not only the hydrodynamics in the particular geomaterials, but also the kinetics of ion retention and mobilization. Although sorption coefficients are known for most materials, studying the in-situ behavior of solutes in natural materials under varying chemical conditions provides results that are crucial for predicting the feasibility of specific strategies for either decontamination or containment.
Utilizing radiotracers, positron emission tomography (PET) is capable of providing three-dimensional tracer concentration data with high temporal resolution. While previous studies using tomographic methods have focused on the acquisition of hydrodynamic parameters [1,2], the method also allows for the in situ monitoring of reactive transport experiments while providing spatially resolved data – enabling the possibility of extracting material-specific reactivities from complex natural and technical samples.

In this presentation, we discuss contaminant retention and subsequent mobilization in various materials, induced by changes in the chemical environment. Experiments using 86Y as a radiotracer analog for the lanthanide series, in conjunction with traditional hydrodynamic studies, allow the prediction of spatially resolved surface reactivities as well as gaining a holistic understanding into the transport of contaminants in subsurface environments.

[1] J.L. Pingel, J. Kulenkampff, D. Jara-Heredia, M. Stoll, W. Zhou, C. Fischer, T. Schäfer (2023), Geothermics 111, 102705.

[2] T. Bollermann, T. Yuan, J. Kulenkampff, T. Stumpf, C. Fischer (2022), Chemical Geology 606, 120997.

The formation of cyanopyridine (CN-py) adducts of silicon tetrahalides was investigated for 3- and 4-cyanopyridine in combination with SiF₄ and SiCl₄. Whereas bubbling of SiF₄ through toluene solutions of 3-CN-py and 4-CN-py afforded white precipitates, which should possess the respective composition SiF₄(CN-py)₂, addition of SiCl₄ did not cause any precipitation. Upon storage of the toluene solution of SiCl₄ and 4-CN-py at 6°C for several weeks, some crystals of the composition SiCl₄(4-CN-py)₂⋅2(4-CN-py)⋅(toluene) were obtained. The use of SiCl₄ as the solvent (i.e. SiCl₄ in large excess) and dissolving 4-CN-py therein gave access to a crystalline adduct of the composition SiCl₄(4-CN-py)₂⋅2(4-CN-py)⋅3-CN-py instead recrystallized from SiCl₄ without forming an adduct with the silane. Computational analyses (B2T-PLYP level) of the single-point energy differences between starting materials SiX₄ (X = F, Cl) and 'pyridine’ (‘pyridine’ = pyridine, 3-CN-py, 4-CN-py) and their adducts SiX₄(‘pyridine’)₂ revealed the tendencies toward adduct formation to decrease in the order SiF₄ > SiCl₄ as well as pyridine >> 4-CN-py > 3-CN-py. For SiCl₄ with 4- and 3-CN-py, the energy of adduct formation (−7.0 and−5.7 kcal mol⁻¹, respectively) is easily compensated by entropy effects at room temperature. Whereas the former explains as to why cyanopyridines and SiCl₄ may co-exist without noticeable adduct formation, the crystal structures of the adducts SiCl₄(4-CN-py)₄⋅2(4-CN-py)⋅(toluene) and SiCl₄(4-CN-py)₂⋅2(4-CN-py) reveal the additional stabilization of these solids by co-crystallization with 4-cyanopyridine, which eventually enabled the isolation of the SiCl₄(4-CN-py)₂ moiety in a solid. Partial decomposition (hydrolysis) during attempts of recrystallization of SiF₄(4-CN-py)₂ and SiF₄(3-CN-py)₂ afforded crystals of the ionic compounds [4-CN-PyH]⁺[SiF₅(4-CN-py)]⁻ and [3-CN-PyH]⁺₂[SiF₆]²⁻, respectively.

Predicting the migration behavior of dissolved contaminants in the pore space of rock and soil is crucial for assessing the feasibility of remediation and long term waste storage strategies.
Positron emission tomography (PET) using conservative radiotracers is an established and reliable method for investigating advective flow and diffusive flux in porous geomaterials and for validating transport models [1, 2]. However, solute transport is often significantly influenced by sorption effects. Reliable data concerning these effects are crucial for analyzing remediation processes as well as predicting desired immobilization in waste storage applications.
To understand and quantify the effects of solute-mineral surface interactions, analyses beyond breakthrough curve measurements are essential. PET techniques offer unique capabilities by providing in-situ tracer propagation and concentration data with high temporal and spatial resolution, surpassing traditional flow and lysimeter experiments.
For many materials, it is desirable to quantify both reactivity and hydrodynamic flow. The simultaneous quantification of both effects requires the use of a dual tracer system. In this presentation, we discuss the possibilities of utilizing a tracer pair consisting of
F as a reactive tracer and
Br as its conservative counterpart. This allows the prediction of spatially resolved surface reactivities as well as the evaluation of advective flow. Using different sandy sediments as model systems, we demonstrate the quantifiability of localized sorption effects as low as 10 pmol/mm³.

References
[1] J.L. Pingel, J. Kulenkampff, D. Jara-Heredia, M. Stoll, W. Zhou, C. Fischer, T. Schäfer, In-situ flow visualization with Geo-Positron-Emission-Tomography in a granite fracture from Soultz-sous-Forêts, France, Geothermics 111 (2023) 102705.
[2] T. Bollermann, T. Yuan, J. Kulenkampff, T. Stumpf, C. Fischer, Pore network and solute flux pattern analysis towards improved predictability of diffusive transport in argillaceous host rocks, Chemical Geology 606 (2022) 120997.

This lecture provided the theoretical background of the bioleaching of uranium ores using microbiological processes, with a particular focus on microbiological, biochemical and technical aspects. This was supplemented by the identification of relevant influencing factors.

The experimental evaluation ofmany quantum mechanical quantities requires the estimation of several directly measurable observables, such as local observables. Due to the necessity to repeat experiments on individual quantum systems in order to estimate expectation values of observables, the question of how many repetitions to allocate to a given directly measurable observable arises. We show that an active learning scheme can help to improve such allocations, and the resultant decrease in experimental repetitions required to evaluate a quantity with the desired accuracy increases with the size of the underlying quantum mechanical system.

We review a scheme for the systematic design of quantum control protocols based on shortcuts to adiabaticity in few-level quantum systems. The adiabatic dynamics is accelerated by introducing high-frequency modulations in the control Hamiltonian, which mimic a timedependent counterdiabatic correction. We present a number of applications for the high-fidelity realization of quantum state transfers and quantum gates based on effective counterdiabatic driving, in platforms ranging from superconducting circuits to Rydberg atoms.

We experimentally investigate the viability of a variational quantum gate optimization protocol informed by the underlying physical Hamiltonian of fixed-frequency transmon qubits. Through the successful experimental optimization of two and three qubit quantum gates the utility of the scheme for obtaining gates based on static effective Hamiltonians is demonstrated. The limits of such a strategy are investigated through the optimization of a time-dependent, Floquet-engineered gate, however parameter drift is identified as a key limiting factor preventing the implementation of such a scheme which the variational optimization protocol is unable to overcome.

Noise resilience of quantum information processing is a crucial precondition to reach the fault-tolerance threshold. While resilience to many types of noise can be achieved through suitable control schemes, resilience to amplitude noise seems to be elusive within the common harmonic approximation for the bus mode of trapped ions. We show that weak an-harmonicities admit control schemes that achieve amplitude noise-resilience consistent with state-of-the-art experimental requirements, and that the required an-harmonicities can be achieved with current standards of micro-structured traps or even the intrinsically an-harmonic Coulomb interaction.

We present photoconductive emitters for broadband THz emission based on Ge and GeSn. Ge is attractive for this purpose due to its high carrier mobility and because of the absence of infrared-active phonons that suppress the THz emission. Emitters based on Ge, with Au trapping centers for carrier lifetime reduction, excited with 11 fs near-infrared pulses emit gapless THz spectra extending up to 70 THz. For excitation at the telecom wavelength 1550 nm a slight reduction of the bandgap of Ge is desirable. We show that this can be achieved in layers of GeSn with 2 % of Sn, grown by molecular beam epitaxy on Si. THz devices on a silicon platform offer the perspective to develop CMOS compatible THz systems with photonic integration both for the near-infrared radiation and the broadband THz radiation.

We propose a new quantum simulation method for simulating N-body interactions, which are tensor products of N Pauli operators, in an analytically exact manner. This method iteratively attaches many two-body interactions on one two-body interaction to simulate an N-body interaction. Those controlled two-body interactions can be untunable and act only on neighboring spins. The strength difference between controlled and target Hamiltonians is normally not more than one order of magnitude. This simulation is theoretically error-free, and errors due to experimental imperfections are ignorable. A major obstacle to simulating the toric code model and modified toric codes used in topological quantum computation is to simulate N-body interactions. We employ the new quantum simulation method to solve this issue and thus simulate the toric code model and its modifications.

After providing a short overview of the activities of our activities in the spectroscopy department including materials and technology for THz generation [1] we focus on two topics regarding the excitation of low-dimensional semiconductor systems with intense THz radiation. Here, the free-electron laser FLEBE is used as a source of spectrally tunable, intense, narrowband radiation pulses [2]. In the first case, graphene discs featuring a plasmonic resonance in the THz frequency range are excited with circularly polarized THz radiation. The THz-induced current in the discs is accompanied by a rather strong transient magnetic fields of the order of 0.5 T perpendicular to the plane of the discs [3]. The second nanostructure under investigation is core-shell GaAs/InGaAs nanowires, a system that can reach high carrier mobilities via strain engineering [3]. THz-pump broadband mid-infrared-probe spectroscopy combined with near-field microscopy reveals the transient heating behavior and intervalley transfer of electrons in the single quantum wires. In summary we discuss the potential to study materials properties and discover new physical phenomena via the interaction with intense THz radiation.
[1] A. Singh, A. Pashkin, S. Winnerl, M. Welsch, C. Beckh, P. Sulzer, A. Leitenstorfer, M. Helm and H. Schneider, Light: Sci. and Appl. 9, 30 (2020).
[2] M. Helm, S. Winnerl, A. Pashkin, J. M. Klopf, J.-C. Deinert, S. Kovalev, P. Evtushenko, U. Lehnert, R. Xiang, A. Arnold, A. Wagner, S. M. Schmidt, U. Schramm, T. Cowan and P. Michel, Eur. Phys. J. Plus 138, 158 (2023).
[3] J.W. Han, P. Sai, D-B. But, E. Uykur, S. Winnerl, G. Kumar, M.L. Chin, R.L. Myers-Ward, M.T. Dejarld, K.M. Daniels, T.E. Murphy, W. Knap, M. Mittendorff: Strong transient magnetic fields induced by THz-driven plasmons in graphene disks, Nature Commun. 14, 7493 (2023).

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Gain dynamics of graphene in the mid-infrared regime has attracted significant academic interest. Here, by utilizing a three-pulse pump-probe technique, we are able find evidence for transient gain and discuss relevant carrier relaxation channels.

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Ion irradiation is a powerful tool to tune the properties of two-dimensional (2D) materials by creating defects and introducing impurities. At the same time, efficient defect production and especially ion implantation into 2D materials require a careful choice of ion energies, as when energies are too low or too high, production of defects and implantation rate will be unsatisfactory low. As for the bulk systems, various approaches have been employed to predict optimum ion energies for specific tasks, but they not always can be directly applied to 2D materials. Here we carry out ab-initio molecular dynamics (MD) and analytical potential (AP) MD simulations and compare the results to those obtained with a simple binary collision approximation (BCA) model. We show that when chemical interactions between the ions and target atoms are essential, as in the case of B and N ion implantation into graphene, as compared to inert gas ions, the AP MD or the BCA model are inadequate. We further suggest a modified BCA approach with the corrected
displacement threshold energies, which account for chemical interactions between the ion and target atoms. The threshold energy can be obtained from first-principles calculations, and the modified BCA model gives qualitatively and for some ions even quantitatively correct results for the energies corresponding to the onset of defect production and substitution probabilities while being at same time many orders of magnitude computationally less expensive than the first-principles MD. We show that in any case the BCA and modified BCA calculations give the upper and lower bound on the optimum ion energy.

Protactinium-231 (Pa-231) is a long lived (t1/2 = 3.28 · 10⁴ a), naturally occurring radionuclide, produced in the natural decay series of uranium-235 (U-235). A measurement of Pa-231 at environmental concentrations would enable the investigation of the migration pattern of Pa-231 in the environment and thus improve the radiological risk assessment of the U-235 decay chain.

Pa-231 is not yet routinely measured by Accelerator Mass Spectrometry (AMS) but procedures for the chemical sample preparation for AMS measurements of Pa-231 are currently being developed (Medley et al. 2019, Christl at al. 2007). The biggest challenge in establishing a Pa-231 measurement procedure is the lack of knowledge on the chemical behavior of Pa. High losses of Pa in the sample preparation pose the biggest issue in the development of a reliable and reproducable chemical sample preparation procedure.

Using the short-lived isotope, Pa-233 (t1/2 = 27 days), we tested the AMS sample preparation procedure for different environmental samples. By conducting
gamma activity measurements of Pa-233 after every sample preparation step, a comprehensive overview of the biggest Pa sinks is established.

Large Language Models (LLMs) have gained significant popularity in recent years for their ability to answer questions in various fields. However, these models have a tendency to "hallucinate" their responses, making it challenging to evaluate their performance. A major challenge is determining how to assess a model's certainty of its predictions and how it correlates with accuracy. In this work, we introduce an analysis for evaluating the performance of popular open-source LLMs, as well as gpt-3.5 Turbo, on multiple choice physics questionnaires. We focus on the relationship between answer accuracy and variability in topics related to physics. Our findings suggest that most models provide accurate replies in cases where they are certain, but this is by far not a general behavior. The relationship between accuracy and uncertainty exposes a broad horizontal bell-shaped distribution. We report how the asymmetry between accuracy and uncertainty intensifies as the questions demand more logical reasoning of the LLM agent while the same relationship remain sharp for knowledge retrieval tasks.

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The THz frequency domain offers unique capabilities for applications in wireless communication, spectroscopy, and imaging. Communication technologies rely on frequency mixing, but traditional methods using nonlinear components such as diodes and transistors are limited to sub-THz bands.

This presentation will discuss our demonstration of THz upconversion using a high-mobility HgTe-based topological insulator, characterized by its exceptional third-order nonlinearity. We employ intense sub-THz radiation, facilitating efficient nonlinear mixing with signals from a photoconductive antenna. This method results in a strong THz response at the sum and difference frequencies, achieving a field conversion efficiency of approximately 2% with a tensile-strained HgTe nanolayer at room temperature.

The cross section of the 89Y(n,g) reaction has important implications in nuclear astrophysics and for advanced nuclear technology. Given its neutron magic number N = 50 and a consequent small neutron capture cross section, 89Y represents one of the key nuclides for the stellar s-process. It acts as a bottleneck in the neutron capture chain between the Fe seed and the heavier elements. Moreover, it is located at the overlapping region, where both the weak and main s-process components take place. 89Y, the only stable yttrium isotope, is also used in innovative nuclear reactors. Neutron capture and transmission measurements were performed at the time-of-flight facilities n_TOF at CERN and GELINA at JRC-Geel. Resonance parameters of individual resonances were extracted from a resonance analysis of the experimental transmission and capture yields, up to a neutron incident energy of 95 keV. Even though a comparison with results reported in the literature shows differences in resonance parameters, the present data are consistent with the Maxwellian averaged cross section suggested by the astrophysical database KADoNiS.

The neutron time-of-flight facility n_TOF at CERN is a spallation source dedicated to measurements of neutron-induced reaction cross-sections of interest in nuclear technologies, astrophysics, and other applications. Since 2014, Experimental ARea 2 (EAR2) is operational and delivers a neutron fluence of 4E7 neutrons per nominal proton pulse, which is 50 times higher than the one of Experimental ARea 1 (EAR1) of 8E5 neutrons per pulse. The high neutron flux at EAR2 results in high counting rates in the detectors that challenged the previously existing capture detection systems. For this reason, a Segmented Total Energy Detector (sTED) has been developed to overcome the limitations in the detector’s response, by reducing the active volume per module and by using a photo-multiplier (PMT) optimized for high counting rates. This paper presents the main characteristics of the sTED, including energy and time resolution, response to g-rays, and provides as well details of the use of the Pulse Height Weighting Technique (PHWT) with this detector. The sTED has been validated to perform neutron-capture cross-section measurements in EAR2 in the neutron energy range from thermal up to at least 400 keV. The detector has already been successfully used in several measurements at n_TOF EAR2.

The average energy and multiplicity of prompt g-rays from slow neutron-induced fission of 235U have been measured using the STEFF spectrometer at the neutron time-of-flight facility n_TOF. The individual responses from 11 NaI scintillators were corrected for multiple g-ray interactions, prompt fission neutrons and background counts before being deconvolved to estimate the emitted spectrum of prompt fission g-rays. The results give an average g-ray energy Eg of 1.71(5) MeV and nu multiplicity of 2.66(18) considering g-rays emitted within the energy range 0.8–6.8 MeV. The n_TOF data has a slightly larger Eg and smaller nu than other recent measurements, however the product of the two is in agreement within quoted uncertainties.

The 246Cm(n,g) and 248Cm(n,g) cross-sections have been measured at the Experimental Area 2 (EAR2) of the n_TOF facility at CERN with three C6D6 detectors. This measurement is part of a collective effort to improve the capture cross-section data for Minor Actinides (MAs), which are required to estimate the production and transmutation rates of these isotopes in light water reactors and innovative reactor systems. In particular, the neutron capture in 246Cm and 248Cm open the path for the formation of other Cm isotopes and heavier elements such as Bk and Cf and the knowledge of (n,g) cross-sections of these Cm isotopes plays an important role in the transport, transmutation and storage of the spent nuclear fuel. The reactions Cm(n,) and Cm(n,) have been the two first capture measurements analyzed at n_TOF EAR2. Until this experiment and two recent measurements performed at J-PARC, there was only one set of data of the capture cross-sections of 246Cm and 248Cm, that was obtained in 1969 in an underground nuclear explosion experiment. In the measurement at n_TOF a total of 13 resonances of 246Cm between 4 and 400 eV and 5 of 248Cm between 7 and 100 eV have been identified and fitted. The radiative kernels obtained for 246Cm are compatible with JENDL-5, but some of them are not with JENDL-4, which has been adopted by JEFF-3.3 and ENDF/B-VIII.0. The radiative kernels obtained for the first three 248Cm resonances are compatible with JENDL-5, however, the other two are not compatible with any other evaluation and are 20 and 60% larger than JENDL-5.

The 78Se⁢(n,g)⁢79Se cross section has a high impact on the abundances of 78Se produced during the slow neutron capture process (s process) in massive stars. A measurement of the 78Se radiative neutron capture cross section has been performed at the Neutron Time-of-Flight facility at CERN using a set of liquid scintillation detectors that have been optimized for a low sensitivity to neutrons. We present resonance capture kernels up to 70 keV and cross section from 70 to 600 keV. Maxwellian-averaged cross section (MACS) values were calculated for stellar temperatures between kT=5 and 100 keV, with uncertainties between 4.6% and 5.8%. The new MACS values result in substantial decreases of 20–30% of 78Se abundances produced in the s process in massive stars and AGB stars. Massive stars are now predicted to produce subsolar 78Se/76Se ratios, which is expected since 76Se is an s-only isotope, while solar 78Se abundances have also contributions from other nucleosynthesis processes.

Background: The 176Yb⁢(n,g)⁢177Yb -177Lu reaction is of interest in nuclear medicine as it is the preferred production route for 177Lu. This radioisotope has seen a very fast growth of usage in nuclear medicine in recent years due to its outstanding properties. New data on this reaction could provide useful information for production at new facilities.

Purpose: We aim to resolve resonances in the 176Yb⁢(n,g)⁢177Yb reaction for the first time. Previous capture measurement provided data at thermal point and encompassed integral measurements in the range from 3 keV to 1 MeV, where three time-of-flight measurements are available, but with low resolution to resolve the resonances. Transmission measurements from the 1970s resolved and analyzed some resonances.

Method: We measure the neutron capture cross section of 176Yb⁢(n,g)⁢177Yb by means of the time-of-flight technique at the Experimental Area 1 of the n_TOF facility at CERN using an enriched 176Yb2⁢O3 sample and an array of four C6⁢D6 liquid scintillation detectors.

Results: We have resolved 164 resonances up to 21 keV, including 96 new ones. We also provide new capture experimental data from 90 eV to 3 keV, and we extend the resolved resonance region up to 21 keV. In addition, resonance decay widths, Gamma_gamma and Gamma_n, are provided for all resonances together with resonance energies.

Conclusions: The 176Yb⁢(n,g)⁢177Yb reaction has been measured, providing resonance parameters for the first time from a few eV to 21 keV. The analysis of the resonances has been carried out and compared with previous works and existing libraries, revealing discrepancies due to the new information on Gamma_gamma parameters. Our results are consistent with the Gamma_n parameters obtained in transmission measurements.

The 235U(n, f) reaction cross section was measured relative to neutron-proton elastic scattering for the first time in the energy region from 10 MeV to 440 MeV at the CERN n_TOF facility, extending the upper limit of the only previous measurement in the literature by more than 200 MeV. For neutron energies below 200 MeV, our results agree within one standard deviation with data in literature. Above 200 MeV, the comparison of model calculations to our data indicates the need to introduce a transient time in neutron-induced fission to allow the simultaneous description of (n, f) and (p, f) reactions.

Challenging neutron-capture cross-section measurements of small cross sections and samples with a very limited number of atoms require high-flux time-of-flight facilities. In turn, such facilities need innovative detection setups that are fast, have low sensitivity to neutrons, can quickly recover from the so-called -flash, and offer the highest possible detection sensitivity. In this paper, we present several steps towards such advanced systems. Specifically, we describe the performance of a high-sensitivity experimental setup at CERN n_TOF EAR2. It consists of nine sTED detector modules in a compact cylindrical configuration, two conventional used large-volume C6D6 detectors, and one LaCl3(Ce) detector. The performance of these detection systems is compared using 93Nb(, ) data. We also developed a detailed Geant4 Monte Carlo model of the experimental EAR2 setup, which allows for a better understanding of the detector features, including their efficiency determination. This Monte Carlo model has been used for further optimization, thus leading to a new conceptual design of a detector array, STAR, based on a deuterated-stilbene crystal array. Finally, the suitability of deuterated-stilbene crystals for the future STAR array is investigated experimentally utilizing a small stilbene-d12 prototype. The results suggest a similar or superior performance of STAR with respect to other setups based on liquid-scintillators, and allow for additional features such as neutron-gamma discrimination and a higher level of customization capability.

Asymptotic giant branch stars are responsible for the production of most of the heavy isotopes beyond Sr observed in the solar system. Among them, isotopes shielded from the r-process contribution by their stable isobars are defined as s-only nuclei. For a long time the abundance of 204Pb, the heaviest s-only isotope, has been a topic of debate because state-of-the-art stellar models appeared to systematically underestimate its solar abundance. Besides the impact of uncertainties from stellar models and galactic chemical evolution simulations, this discrepancy was further obscured by rather divergent theoretical estimates for the neutron capture cross section of its radioactive precursor in the neutron-capture flow, 204Tl (t1/2=3.78  yr), and by the lack of experimental data on this reaction. We present the first ever neutron capture measurement on 204Tl, conducted at the CERN neutron time-of-flight facility n_TOF, employing a sample of only 9 mg of 204Tl produced at the Institute Laue Langevin high flux reactor. By complementing our new results with semiempirical calculations we obtained, at the s-process temperatures of kT ≈8  keV and kT ≈30  keV, Maxwellian-averaged cross sections (MACS) of 580(168) mb and 260(90) mb, respectively. These figures are about 3% lower and 20% higher than the corresponding values widely used in astrophysical calculations, which were based only on theoretical calculations. By using the new 204Tl MACS, the uncertainty arising from the 204Tl⁢(n,gamma) cross section on the s-process abundance of 204Pb has been reduced from ∼30% down to +8%/−6%, and the s-process calculations are in agreement with the latest solar system abundance of 204Pb reported by K. Lodders in 2021.

Accelerator Mass Spectrometry (AMS) represents a single atom counting technique which allows the detection of radioisotopes at natural concentrations in our environment. Its high abundance sensitivity offers a variety of interdisciplinary applications in the fields of geosciences, environmental sciences or nuclear astrophysics. A new AMS facility, HAMSTER (Helmholtz AMS Tracing Environmental Radionuclides), will be installed at Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in 2024. This facility will incorporate major recent technological developments which will open up new research areas.
With HAMSTER we will expand our measurement capabilities to new isotopes, including actinides, fission products and a number of additional new radionuclides. In this presentation, examples of our research portfolio will be presented, e.g. searches for traces on Earth of Supernovae and neutron star mergers, as well as new applications for studying past variations of solar and geomagnetic fields and also the distribution of releases of man-made radioactivity into our environment.

Earth is exposed to nearby cosmic events. Freshly produced radionuclides in the interstellar medium contain information about how and where the heavy elements are made in nature. The solar system moves through the interstellar medium (ISM) and collects interstellar dust particles that contain fresh nucleosynthetic signatures, including the radionuclides Fe-60 (t1/2=2.6 Myr) and Pu-244 (t1/2=81 Myr). These nuclides are incorporated into terrestrial archives over millions of years.
Detection of interstellar nuclides remains extremely challenging and so far was successful only with Accelerator Mass Spectrometry (AMS). Recent technical developments have seen an exceptional gain in measurement efficiency and sensitivity, in particular for actinides, including Pu-244 and more recently for Hf-182 (t1/2=9 Myr). On the other hand, very large accelerators with >10 million volts are required for the identification of small traces of interstellar Fe-60.
Recent data demonstrate a global Fe-60 influx and is evidence for exposure of Earth to recent (<10 Myr) supernova explosions. In addition, first evidence of ISM-Pu-244 presence in deep-sea archives, an actinide nuclide exclusively produced by the r-process, supports the hypothesis that the dominant heavy element r-process nucleosynthesis is rare.
Besides new data for the direct search for interstellar signatures I will also present preliminary results of recent laboratory measurements using AMS for understanding Fe-60 and Hf-182 production in massive stars - both nuclides predominantly produced via double neutron capture reactions.

The long-lived radionuclides Fe-60 (t1/2=2.6 Myr) and Hf-182 (t1/2=8.9 Myr) are sensitive monitors to the neutron environment under different stellar conditions. Production of both nuclides requires neutron fluxes high enough to compete with the decay of the shorter-lived nuclides Fe-59 (t1/2=44d) and Hf-181 (t1/2=42d) which separate Fe-60 and Hf-182 from stable isotopes Fe-58 and Hf-180. Such conditions are predicted for the s (slow neutron capture) process in massive stars only at their late burning phases, e.g., shortly before they end in a supernova, as well as in the r process (rapid neutron capture). The site and frequency of the r process is heavily debated and attributed either to some rare cases of supernovae or neutron star mergers.
On Earth, (n,α) reactions do not contribute to their natural production as the parent nuclides for both cases are not stable. Fission yields are also very low, consequently, both Fe-60 and Hf-182 are very rare on Earth. Accordingly, any presence of either nuclides on Earth may indicate signatures of interstellar influx with their nucleosynthesis within a time period of a few half-lives. Indeed, two distinct interstellar Fe-60 influxes had been found in terrestrial and lunar archives demonstrating recent (within 10 Myr) and ‘nearby’ supernova activity (<150 pc distance). No interstellar Hf-182 had been detected so far. This reflects either the expected low production yields of Hf-182 or a low interstellar influx into the solar system. However, more importantly, the difficulty to chemically extract and measure Hf-182 at the expected low concentrations in terrestrial archives makes detection of interstellar Hf-182 extremely challenging.
The production yields of both nuclides at astrophysical energies are not yet measured and predictions are highly uncertain. This is crucial not only for interpreting the supernova-produced Fe 60 data, but also for Hf-182, as both, s and r process may contribute to an interstellar signal, potentially still undetected in terrestrial or lunar archives.
In this contribution, we present new and precise data for both double neutron-capture reactions as well as give an outlook on Fe-60 production via 63Ni(n,α). Samples, highly enriched in Fe-58, Ni-62 and Hf-180, were irradiated at the nuclear reactor at the Institut Laue-Langevin (ILL), Grenoble, with a high, predominantly thermal, neutron flux. At the Atominstitut in Vienna, additional Fe-58 samples were exposed to a mix of thermal and epithermal neutrons extending the energy range to the astrophysical interesting keV-energies. The induced Fe-59 and Hf-181 activities were utilised as intrinsic monitors for the neutron fluence. After the decay of intermediate Fe-59, the produced Fe-60 was measured with AMS at the ANU. The number of Hf-182 nuclides, however – owing to the much higher capture cross sections – was high enough for a direct activity measurement of the irradiated sample without the need for AMS.
These new experimental data will provide important anchor points for a better understanding of heavy element nucleosynthesis in massive stars and explosive stellar environments.

In the quest for achieving the principles of a circular economy, our Helios Lab seeks to optimize the e-waste recycling industry with its innovative Ramses-4-CE project. Ramses focuses on the development of a smart network comprising multimodal optical non-invasive sensors mimicking industrial scenarios with a conveyor belt that can attain speeds of several meters per second. The primary objective is to facilitate the comprehensive identification and characterization of e-waste materials, particularly printed circuit boards (PCBs), plastics, and rare earth elements (REE).
The sensor ensemble encompasses a laser profiler generating height maps, an RGB camera capturing surface spatial features, hyperspectral cameras capturing the spectral features, and chemical characteristics obtained with a Raman spectroscopy sensor affixed to a robotic arm. Each sensor type offers unique advantages and inherent challenges. RGB cameras with their data facilitate fast, highly accurate, and smart data processing e.g., using machine learning (ML) and deep learning (DL) object detection and segmentation techniques in shredded plastics, while hyperspectral imaging (HSI) aids in polymer identification based on spectral fingerprint libraries. Nonetheless, HSI poses challenges such as large data size due to its abundant information, noise interference, and overlong processing times.
To optimize the data processing pipeline, meticulous preprocessing and processing methods have been devised. Upon data acquisition of different objects and materials, data co-registration is executed on the resulting RGB images and hyperspectral cubes, followed by object detection and segmentation of valuable objects on both data types. For objects eluding identification via RGB and hyperspectral imagery, a Raman spectroscopy-based validation is involved for detailed chemical analysis.
Yet, exerting high accuracy in HSI pixel-wise classification on multi-unseen data cubes necessitates HSI classification models with robust generalization capabilities. Towards this aim, smart automated masking of undesired objects in the hyperspectral scene is developed. HS cube contains abundant data causing their large volume size. This abundance highlights the useful information, while concurrently amplifying noises and artifacts, detrimentally affecting both data processing speed and model generalization. Masking undesired objects in the HSI reduces the number of pixel vectors skewing calculations in preprocessing steps and DL models training routines, leading to enhanced segmentation models, i.e., masking unwanted data vectors from HSI allows exclusive processing for desired targets elevating processing speed without compromising accuracy.

new hexadentate picolinic-acid based bispidine ligand was attached to anti-FAP IgG4 target module
Radiolabelling with copper-64 and PET images in tumour-bearing mice

The degeneration of axon terminals before the soma, referred to as “dying back”, is a feature of Parkinson’s disease (PD). Axonal assays are needed to model early PD pathogenesis as well as identify protective therapeutics. We hypothesized that defects in axon lysosomal trafficking as well as injury repair might be important contributing factors to “dying back” pathology in PD. Since primary human PD neurons are inaccessible, we developed assays to quantify axonal trafficking and injury repair using induced pluripotent stem cell (iPSC)-derived neurons with LRRK2 G2019S, which is one of the most common known PD mutations, and isogenic controls. We observed a subtle axonal trafficking phenotype that was partially rescued by a LRRK2 inhibitor. Mutant LRRK2 neurons showed increased phosphorylated Rab10-positive lysosomes, and lysosomal membrane damage increased LRRK2-dependent Rab10 phosphorylation. Neurons with mutant LRRK2 showed a transient increase in lysosomes at axotomy injury sites. This was a pilot study that used two patient-derived lines to develop its methodology; we observed subtle phenotypes that might correlate with heterogeneity in LRRK2-PD patients. Further analysis using additional iPSC lines is needed. Therefore, our axonal lysosomal assays can potentially be used to characterize early PD pathogenesis and test possible therapeutics.

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease which currently lacks effective treatments. Mutations in the RNA-binding protein FUS are a common cause of familial ALS, accounting for around 4% of the cases. Understanding the mechanisms by which mutant FUS becomes toxic to neurons can provide insight into the pathogenesis of both familial and sporadic ALS. We have previously observed that overexpression of wild-type or ALS-mutant FUS in Drosophila motor neurons is toxic, which allowed us to screen for novel genetic modifiers of the disease. Using a genome-wide screening approach, we identified Protein Phosphatase 2A (PP2A) and Glycogen Synthase Kinase 3 (GSK3) as novel modifiers of FUS-ALS. Loss of function or pharmacological inhibition of either protein rescued FUS-associated lethality in Drosophila. Consistent with a conserved role in disease pathogenesis, pharmacological inhibition of both proteins rescued disease-relevant phenotypes, including mitochondrial trafficking defects and neuromuscular junction failure, in patient iPSC-derived spinal motor neurons (iPSC-sMNs). In FUS-ALS flies, mice, and human iPSC-sMNs, we observed reduced GSK3 inhibitory phosphorylation, suggesting that FUS dysfunction results in GSK3 hyperactivity. Furthermore, we found that PP2A acts upstream of GSK3, affecting its inhibitory phosphorylation. GSK3 has previously been linked to kinesin-1 hyperphosphorylation. We observed this in both flies and iPSC-sMNs, and we rescued this hyperphosphorylation by inhibiting GSK3 or PP2A. Moreover, increasing the level of kinesin-1 expression in our Drosophila model strongly rescued toxicity, confirming the relevance of kinesin-1 hyperphosphorylation. Our data provide in vivo evidence that PP2A and GSK3 are disease modifiers, and reveal an unexplored mechanistic link between PP2A, GSK3, and kinesin-1, that may be central to the pathogenesis of FUS-ALS and sporadic forms of the disease.

Frontotemporal dementia (FTD) is a neurodegenerative disease characterized by the progressive loss of neurons mainly in the frontal and temporal lobes of the brain. Mutations (e.g., V337M, N297K) in the microtubule-associated protein TAU (MAPT) are responsible 5–20% of familial FTD cases and have been associated with defects in organelle trafficking that plays a critical role in the proper function of cells, including transport of essential molecules and degradation of waste products. Due to the critical role of TAU mutations in microtubule stabilization and organelle transportation, it is of great interest to study these molecular mechanisms to develop effective therapeutic strategies. Therefore, herein, we analyzed mitochondrial and lysosomal trafficking in disease-specific spinal motor neurons by using live cell imaging in undirected (uncompartmentalized) and directed (compartmentalized) cell culture systems. While V337M neurons only expressed 3R TAU, the N297K mutant neurons expressed both 3R and 4R TAU. Axonal trafficking was affected differentially in V337M and N297 MAPT mutated neurons. These findings suggest that the MAPT mutations V337M and N297K impaired axon physiology differentially, which highlights the need for mutation- and/or 3R/4R TAU-specific therapeutic approaches.

The interaction of highly charged ions with surfaces leads to various inelastic processes in which energy is transferred to the surface in an area of few nm2 and within the time scale of femtoseconds [1]. Numerous experiments were conducted over the past years to investigate the interaction of highly charged ions (HCI) with 2D materials where the interaction is reduced to a monolayer and thus the pre-equilibrium regime is investigated [2]. In the case of surfaces and 2D materials, one challenge is to ensure that the surface is free of contaminations [2]. The interaction of gas targets on the other hand are dominated by charge exchange processes with the atoms and molecules of the gas. Our primary goal is to study the interaction of HCI with gas targets in a systematic manner and to compare them to recent results on graphene and other 2D materials. Therefore, a huge parameter space of various ion charge states, ion energies, gas target species and gas pressure needs to be explored.

The experiments conducted at the IBC’s new HCI–transmission setup with Xe projectiles and different target gases, demonstrated the capability of the setup to investigate the interaction of highly charged ions of varying charge states (Xe5+ to Xe37+) with gas targets. The major advantage of this setup is the possibility to make use of different gas targets and the ability to vary pressure, ion energy and charge state in an easy manner, providing the opportunity to conduct extensive systematic studies of the dependency on the interaction of these parameters. The initial set of experiments were conducted at varying pressures ranging from 1E-9mbar up to 5E-4mbar. Fig. 1. shows the related charge state spectra of the incoming Xe25+ ions after passing the gas cell.

[1] Schenkel, T., Hamza, A. V., Barnes, A. V., & Schneider, D. H, Progress in Surface Science, 61(2-4), 23-84 (1999); Aumayr, F., Facsko, S., El-Said, A. S., Trautmann, C., & Schleberger, M., Journal of Physics: Condensed Matter, 23(39), 393001 (2011).
[2] R. Wilhelm, E. Gruber, J. Schwestka, R. Heller, S. Facsko, and F. Aumayr, Applied Sciences 8, 1050 (2018).

Diazabicyclic adamantan derivatives termed “bispidines” show a favorable CuII coordination chemistry. With the availability of the theranostic triple 61/64Cu/67Cu [1], bispidine ligands are in the focus as bifunctional chelators for radiopharmaceutical applications. They provide fast labeling at high molar activities under mild conditions and the resulting complexes exhibit a high thermodynamic stability.[2] However, a significant hepatic uptake has been observed for bispidine peptide conjugates. One possible cause could be the protonation of donor atoms in the acidic environment of tumor cells, leading to alterations of donor atom pattern and a change in the complex net charge accompanied by an accumulation in nontargeted organs. By increasing the basicity of the donor atoms, more stable complexes can be formed minimizing this effect.[3] The impact of different substituents leading to changes in the basicity have been observed in pentadentate bispidine ligands and were further explored in hexadentate ligands, which are known to form more stable complexes with CuII.[1,2]
Herein, electron-withdrawing or -donating groups were attached to the para-position of the pyridine substituents at the scaffold of the known hexadentate ligand N2Py4.[1,4] The new ligands were investigated with respect to complex stability and radiolabeling efficacy and furthermore characterized in terms of lipophilicity compared to the known copper bispidine complexes [CuII(N2Py4)]2+ and [CuII(bispa)]+1.[4] For this purpose, a fast gradient reversed-phased HPLC method was carried out on an immobilized artificial membrane (IAM) to determine the chromatographic hydrophobicity index (CHI). The index is derived from the retention time of compounds and provides information about the lipophilicity of the measured compound, which correlates with octanol/water partition coefficients.

The secure disposal of nuclear waste is of high societal concern, necessitating the development of deep geological repositories as a reliable solution. A key aspect of repository safety lies in understanding the far field, particularly the host rock, to predict the long-term behavior and migration of radionuclides within the geological environment from the deposit up to the ecosphere. This study addresses the specific challenges associated with crystalline host rocks.
Crystalline host rocks could be on the one hand of granitic composition and texture, but the term is also used for host rocks of metamorphic origin. While inside a large granitic intrusion there is little petrological variation expected, metamorphic rocks or the intrusion rim can exhibit complex structures in terms of structural geology as well as mineral composition, especially along potential fluid migration pathways. Consequently, this leads to a multitude of possible rock-
composition/fluid-composition interactions and thus significantly affects the retention potential of radionuclides as opposed to the simplified model of an isotropic, uniform granite. The results of the study will allow to determine which components of the host rock are important to be included
in geostatistical models which in turn serve as basis to estimate uncertainties of reactive transport through crystalline rocks.
Our study involves the development of Python code to feed chemical modelling software like PHREEQC or Geochemist’s Workbench© with varying mineral compositions and chemical conditions of the aqueous phase, following a specific Quasi-Monte-Carlo sampling scheme. The application of compositional data analysis principles is essential to guarantee a meaningful sampling of constraint concentration data, such as mineralogical rock compositions or element
concentrations in aqueous phases. Given that compositional data sum to a fixed total, each mineral content becomes a dependent variable in relation to the other contents. Recognizing and accounting for these interdependencies is crucial to ensuring the integrity of the sampling. The chemical modelling software relies on Surface Complexation Models (SCM) for each mineral phase to calculate the distribution coefficient (Kd-value) for the radionuclide (here: uranium) in the respective setting. Furthermore, a global sensitivity analysis is employed to investigate the complex interactions between mineralogical variations and radionuclide behavior. In this study, two techniques are employed namely, High-Dimensional Model Representation (HDMR) and Cumulative Sum of Univariate Nonlinear Regression (CUSUNORO) plots. The application of HDMR allows for a detailed investigation of high-dimensional parameter spaces, while CUSUNORO plots provide a visual representation of cumulative sensitivity effects.
This study presents a complete workflow of modelling how petrological variations in crystalline host rocks, including both granitic and metamorphic compositions, affects radionuclide retention. This approach advances the understanding of nuclear waste disposal and provides valuable tools for assessing the retention potential of radionuclides in diverse geological settings.

Analytical methods for inorganic chemistry are found to be differentially effective for specific combinations of target elements, sample matrices and concentration ranges. Consequently, it is a significant challenge to ensure that the results provided in element concentrations are independent of the analytical method employed on the sample matrix. In order to address this issue, reference materials are produced and certified. However, even with the most rigorous production and certification procedures, it remains challenging to accurately determine the "true" concentration values due to the combined effects of measurement protocols and sample matrix. In particular, when dealing with "normal" (non-reference) samples, these effects may introduce a bias into the measurements. When compiling measurements from different analytical approaches and time periods into consistent data sets for further data analysis these method induced biases present a significant challenge. To explore and quantify the extent of methods/matrix-specific offsets between measurement batches, we exploited chemical analysis data from the database for reference materials, GeoReM. The selected data sets from GeoREM of the standards AGV-1&2, BCR-1&2, BHVO-1&2, BIR-1, BRP-1, JA-2, JB-1, OU-6 and W-1&2 initially comprised 83,158 measurements. Following homogenisation and filtering of the samples to ensure robust statistical analysis, 55,413 measurements remained. The statistical analysis (ANOVA) shows that the most frequently occurring offsets between methods are LA-ICP-MS to ICP-MS, followed by XRF to ICP-MS and finally XRF to LA-ICP-MS.

Ensuring the safety for deep geological repositories for nuclear waste in crystlline host rock necessitates a comprehensive understanding of the far field and it's potential for radionuclide retention. In case of a repository leakage, radionuclides may get mobile and migrate through pathways in rock and aquifers. To asses the uncertainties in forcasting the migration of radionuclides it is essential to incorporate naturally occurring heterogeneities in rock composition and geological structures into the models, e.g. heterogeneities occurring near intrusion margins, tectonically influenced granitic bodies, or metamorphic formations like gneisses. This complexity significantly impacts the modeled radionuclide retention potential compared to simplistic isotropic granite models.
The SANGUR project (Systematic Sensitivity Analysis for Mechanistic Geochemical Models using Field Data from Crystalline Rock) aims to identify crucial parameters and their uncertainties essential for modeling radionuclide retention in crystalline rock. Our study presents a comprehensive workflow modeling how petrological variations in both granitic and metamorphic crystalline host rocks influence radionuclide retention. Utilizing Multinary Random Fields geostatistics, we simulate crystalline rocks based on analyzed spatial rock data to quantify uncertaintiesand to determine the appropriate model scale. The petrological variance is then considered for the chemical modeling through software such as PHREEQC or Geochemist's Workbench©: Surface Complexation Models (SCM) in chemical modeling software calculate partition coefficients (Kd values) for radionuclides, such as uranium, in diverse mineral environments in combination with varying aqueous phases. To enhance and simplify models, global sensitivity anlsysis is applied to determine critical features for radionuclide retention.

DREAMS, the DREsden AMS-facility, in operation since 2011 is based on a 6 MV Tandetron (manu-
factured by High Voltage Engineering Europa) and shared with other research groups at the Helmholtz-
Zentrum Dresden-Rossendorf (HZDR). DREAMS has been applied primarily in the measurement of cos-
mogenic isotopes. However, with radiocarbon not in the mix, a focal point has always been the routine
measurement of 10Be and 26Al. Over the years, we have improved the AMS facility in various aspects
for increased performance, particularly for these two isotopes. In this report we will give details on the
performance of our routine measurements over the past 12 years of operation with a focus on the impact of
methodological developments since 2021. We will present our recent investigations and improvements on
the performance of 10Be and 26Al measurements, highlight key challenges remaining, and point to potential
future optimisations. Finally, we have reinvestigated our in-house standard material for 26Al against the
standards provided by Nishiizumi (2004) -“KNSTD” to ensure compatibility of reported results with
exposure-age calculators such as CRONUS-Earth.

Accelerator Mass Spectrometry (AMS) is an ultrasensitive method for
detection of naturally or anthropogenically produced long-lived
radionuclides in our environment. Up to now we use the DREsden
AMS-facility (DREAMS) at the Helmholtz-Zentrum Dresden-Rossendorf
(HZDR). In operation since 2011 and based on a 6 MV Tandetron
(manufactured by High Voltage Engineering Europa), this accelerator
facility is shared with other research groups. A focus of DREAMS is the
measurement of the cosmogenic radionuclides Be and Al.
Over the years, we have improved the DREAMS measurement capabilities in
various aspects. One example is an improvement in the Be measurement efficiency by a factor of 1.4 [1].

Currently a second, dedicated AMS facility, HAMSTER (Helmholtz
Accelerator Mass Spectrometer Tracing Environmental Radionuclides), is
being set up at the Department of Accelerator Mass Spectrometry and
Isotope Research. HAMSTER is based on a 1-MV tandem accelerator from NEC
(National Electronics Corp.) and will have enhanced actinide
measurement capabilities. In addition, it is featuring a new ion cooler
we develop in cooperation with the University of Vienna [see talk of A.
Wieser] allowing laser-based isobar separation. In this presentation, I
will highlight present and future AMS capabilities at HZDR.
References:

[1] Lachner, J., et al. (2023) Nucl. Inst. Meth. B 535, 29.

During the last years the performance of DREAMS, the DREsden AMS-facility, at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) was improved in various aspects. The system is based on a 6 MV tandetron manufactured by High Voltage Engineering Europa (HVEE) and shared with various other groups at HZDR. This report will give detail on the performance of our routine measurements and an overview of the range of research topics of user projects at DREAMS. Moreover, we will present recent improvements and investigations on the performance of 10Be and 26Al measurements and highlight key challenges remaining, and potential future developments.

This paper presents a systematic study of the charge transport behavior of heavily doped n-type Ge layers with As and Sb. A nonequilibrium method ion implantation followed by milliseconds flash lamp annealing is applied to synthesize the n++ Ge layers (Ge:As and Ge:Sb). The resulting materials contain free electrons with a density above 3x10^19 /cm3 and mobility more than 220 cm2/(V s). Quantum corrections to the conductance in a magnetic field are observed at low temperatures. Weak localization persists up to 30 K in Ge:Sb, while only up to 10 K in Ge:As. Using the Hikami–Larkin–Nagaoka model to fit the magnetoconductance data, we obtain the phase coherence length l/ of the hyperdoped Ge samples in the range of 70–163 nm. This study may pave a way to explore possible applications for quantum technologies utilizing As- and Sb-hyperdoped Ge.

In this Letter, we employed atomic layer deposition (ALD) and flash lamp annealing (FLA) to form a wafer-scale ultra-shallow junction (USJ, ∼5 nm) in silicon.
The deep ultraviolet light is almost completely absorbed in the PN junction depletion region near the surface, resulting in a high collection efficiency of photogenerated carriers. The junction-based photodiode exhibits outstanding performances with internal quantum efficiency reaching ∼95% from 200 nm to 400 nm and a linear response to the UV light within a wide range of 0.4–10^3 μW.

We report on electroluminescence spectroscopy experiments demonstrating room-temperature light emission from heavily alloyed SiGe quantum dots, for which the light emission properties are enhanced by incorporated split-[110] self-interstitials. The quantum dots are formed during molecular beam epitaxy deposition of Si0.6Ge0.4 alloys on n-doped silicon-on-insulator substrates. To create the split-[110] self-interstitials the quantum dots were co-implantated in-situ using Si and Ge ions. The hybrid emitters were further embedded into the intrinsic region of a p-i-n diode structure to enable electrical pumping. Similar to previous theoretical results on unstrained Ge-based quantum dots containing these defects, radiative direct transitions are possible for these SiGe light emitters. However, in SiGe dots these transitions are not at the Brillouin zone center. Instead, first-principles calculations indicate that the presence of the split-[110] self-interstitial defect in strained and unstrained SiGe can lead to optically direct transitions in momentum space in the X-direction of the Brillouin zone.

Zinc oxide (ZnO) is a wide bandgap semiconductor that holds significant potential for various applications. However, most of the native point defects in ZnO like Zn interstitials typically cause an n-type conductivity. Consequently, achieving p-type doping in ZnO is challenging but crucial for comprehensive applications in the field of optoelectronics. In this work, we investigated the electrical and optical properties of ex situ doped p-type ZnO films. The p-type conductivity has been realized by ion implantation of group V elements followed by rapid thermal annealing (RTA) for 60 s or flash lamp annealing (FLA) on the millisecond time scale in nitrogen or oxygen ambience. The phosphorus (P)-doped ZnO films exhibit stable p-type doping with a hole concentration in the range of 10^14 to 10^18/cm^3, while antimony (Sb) implantation produces only n-type layers independently of the annealing procedure. Microstructural studies of Sb-doped ZnO show the formation of metallic clusters after ms range annealing and SbZn-oxides after RTA.

Thin films of silver-doped zinc oxide (SZO) were deposited at room temperature using a DC reactive magnetron co-sputtering technique using two independent Zn and Ag targets. The crystallographic structure, chemical composition and surface morphology of SZO films with different silver concentrations were correlated with the photocatalytic (PC) properties. The crystallization of the SZO films was made using millisecond range flash-lamp-annealing (FLA) treatments. FLA induces significant structural ordering of the wurtzite structure and an in-depth redistribution of silver, resulting in the formation of silver agglomerates. The wurtzite ZnO structure is observed for silver contents below 10 at.% where Ag is partially incorporated into the oxide matrix, inducing a decrease in the optical band-gap. Regardless of the silver content, all the as-grown SZO films do not exhibit any significant PC activity. The best PC response is achieved for samples with a relatively low Ag content (2–5 at.%) after FLA treatment. The enhanced PC activity of SZO upon FLA can be attributed to structural ordering and the effective band-gap narrowing through the combination of silver doping and the plasmonic effect caused by the formation of Ag clusters.

Modifying the energy band structure in heterostructured photocatalysts enhances charge separation efficiency and improves photoelectrochemical (PEC) performance by decreasing the charge transfer barrier. In this study, cobalt doping into WO3/TiO2 core/shell heterojunction nanorod arrays introduces versatile valence states of cobalt altering the oxygen coordination environment around W atoms in WO3, resulting in an increase in W5+ ions and oxygen vacancy defects in WO3 lattice, facilitating the water splitting reaction. Photogenerated electrons transfer easily from the WO3:Co shell to the TiO2 core due to the lower conduction band minimum (CBM) of WO3:Co shell. Moreover, photogenerated holes transfer from the TiO2 core to the WO3:Co shell efficiently due to the higher valence band maximum (VBM) of TiO2 core. The heterostructure has a high photogenerated carrier density (9.89 × 1018 cm-3), improving photoconversion efficiency (2.55 mA cm-2 at 1.23 V vs. RHE) and reducing charge recombination rates (6.51 × 10–4 s-1). Co doping increases the -OH bond on WO3/TiO2 surface, improves
its hydrophilicity, and is more conducive to the reaction in aqueous electrolyte. Additionally, the nanorod array
structure facilitates PEC reaction kinetics by providing open spaces for mass exchange. This work proposes a
feasible strategy for improving photogenerated charge transport and enhancing PEC by combining regulation of
the band structure of WO3/TiO2 heterostructures with morphology design.

We report the impact of flash-lamp-annealing (FLA) on the structural evolution of amorphous titania (TiO2) films produced by DC reactive magnetron sputtering. TiO2 films were grown at room-temperature at different oxygen partial pressure (PO2) and subsequently annealed as a function of the FLA energy density. X-ray diffraction confirms that FLA induces phase formation from the initial amorphous state with a general transition from anatase to rutile by increasing the FLA energy density (temperature). Interestingly, the transformation onset of anatase to rutile is achieved at lower energy densities for higher PO2. On the contrary, films with a highly resilient anatase phase can be produced at relatively low PO2. A detailed analysis of the pristine amorphous structure carried out by X-ray absorption near-edge structure indicates the role of oxygen sites in the observed phase transformation. In particular, oxygen vacancies seem to stabilize the anatase phase at high temperatures. The results show the relevance of subtle changes in the initial amorphous structure for phase selectivity in TiO2 films
upon FLA.

Fixed valve trays are increasingly considered in energy-intensive distillation columns, since they cope well with demanded partial load and overload scenarios. However, considering the vast number of possible valve arrangements and their respective impact on the complex vapor-liquid flow, the tray design is a challenging task in practice. Therefore, we aim at establishing a coarse-grid CFD approach that enables engineers to simulate two-phase flow scenarios on such trays at reasonable computational effort.

The approach is based on a morphology adaptive multifield two-fluid model, which allows for simulating resolved interfaces of continuous gas and liquid as well as dispersed phases, i.e. bubbles and droplets, within a single Eulerian framework. Additionally, the valves are emulated by local mass and momentum sources that are applied to cell zones, which result from a reasonable approximation of the valve geometry in the computational grid.

In the present contribution we demonstrate the simulation of the complex two-phase flow in a pilot scale setup of 1.2 m nominal diameter that exhibits 189 fixed valves and is operated with air and water. The simulated phase distribution is compared against three-dimensional experimental data obtained with a conductivity sensor array. Finally, we discuss capabilities and further perspectives of the suggested approach.

Kagome metals emerged as a promising playground synergizing the fields of strongly correlated localized electrons, topology, and non-trivial Dirac fermions [1]. The tunability of these different contributions via external means opens interesting new directions in the research of quantum materials. In this contribution, we present the pressure evolution of the electronic structure of the ferromagnetic kagome metal Fe3Sn2 revealed by single-crystal XRD (ESRF, ID15B), high-pressure infrared spectroscopy (SOLEIL, SMIS beamline), and density-functional calculations (DFT).

Different contributions to the optical spectra have been separated and analyzed using the DFT calculations, performed with the experimental atomic positions determined by XRD. Infrared spectra pinpoint the coexistence of the conventional and unconventional charge carriers in the compound [2]. While the low-energy spectral range reflects the response of the mobile charge carriers and is significantly modified as the pressure increases, the high-energy range shows slight modifications of the interband transitions in the compound.

The plasma frequency reflecting the carrier density in the compound shows a gradual increase with pressure and reveals notable anomalies at ~10 and 16 GPa despite the gradual evolution of crystal structure. Our DFT calculations indicate the appearance of new Fermi surfaces at the identified pressures. We, therefore, ascribe these anomalies to Lifshitz transitions in the kagome metal. Furthermore, the unconventional carrier dynamics present a non-monotonous change with pressure that we can link to the morphology of the kagome network as resolved by our XRD studies.

1. L. Ye, et al. Nature, 555, 638 (2018)
2. A. Biswas, E.U, et al. Phys. Rev. Lett., 125, 076403 (2020)

The Sichuan–Yunnan–Guizhou metallogenic province (SYGMP) includes > 400 Zn - Pb deposits and prospects, eight of which are large-scale deposits with large reserves of critical metals such as Cd and Ge, including the Huize Zn-Pb-Cd-Ge and Daliangzi Zn–Pb–Ge–Cd deposits. The newly discovered Zhugongtang Zn-Pb deposit is a super-large deposit with Zn–Pb reserves of > 3 Mt. Its geochemical features are similar to those of the Huize deposit, with similar sulfide δ34S values and concentrations of critical elements in sphalerite (e.g., Cd and Ge). However, the two deposits have different host strata, and it remains unclear as to whether they have similar oregenesis. In this study, δ114/110Cd values and major- and trace-element compositions of sphalerites collected from a drill-core and tunnels of the Zhugongtang deposit were determined in an investigation of metal sources. Drill-core samples were impure and exhibited strong correlation (R2 = 0.89) between Zn and Cd contents. For samples from mining tunnels, the Cd and Fe contents of selected sphalerites were positively correlated, especially yellow sphalerites (R2 = 0.76). Cadmium is likely hosted in sphalerite by the substitution mechanism of (Fe2+, Cd2+) ↔ Zn2+. The δ114/110Cd values of all samples ranged from - 0.43 ‰ to 0.06 ‰. Based on Zn/Cd ratios, and excluding geochemical processes that may have caused the variable Cd isotopic compositions, we suggest that the metal sources of the deposit were derived from the mixing of sedimentary and basement rocks. This model is supported by the strong relationship between the 114/110Cd and 1/Cd values of sphalerites from 11 typical Zn–Pb deposits in the SYGMP (R2 = 0.81). The quantification of metal contributions of source rocks indicates that deposits derived mainly from sedimentary rocks generally have relatively low sphalerite Ge contents and small Ge reserves, whereas those derived mainly from basement rocks have higher Ge contents and larger Ge reserves. This study provides a new model for explaining the enrichment of critical metals in Zn–Pb deposits of the SYGMP, thus extending the applications of Cd isotopes in hydrothermal systems

The newly discovered Danaopo algal limestone hosted Zn-Pb deposit (150 Mt ores @ an average of 3.06% Zn + Pb) is a representative and the second largest scale Zn-Pb deposit in the western Hunan-eastern Guizhou metallogenic belt (WHEGMB). In this study, the in-situ trace elements of sphalerite and C-O isotopes and rare earth elements of calcite were investigated in the Danaopo deposit, aiming to provide new insights into the mineralization potential of critical metals and origin of Zn-Pb deposits controlled by reef zone and Huayuan-Zhangjiajie regional fault at WHEGMB. The in-situ trace element researches show that the distribution of critical metals, including Cd (1520 to 11570 ppm), Ge (0.73 to 236 ppm), Ga (0.04 to 26.90 ppm), Tl (0.01 to 3.62 ppm), are inhomogeneous in sphalerite, in which Cd and Ge are over the standard of Chinese comprehensive utilization. The LA-ICP-MS elemental map and inter-element correlations imply that Cd and Ge enter the sphalerite lattice via the substitution of Zn2+ ↔ Cd2+ and 4Zn2+ ↔ Ge4+ + 2Fe2+ + □, respectively. Besides, the δ13CPDB (-3.93 to -0.12‰) values of the ore-stage calcites are plotted as a horizontal linear trend near the marine carbonate dissolution baseline, indicating that the carbon in hydrothermal fluids was mainly derived from the dissolution of Cambrian algal limestone. The measured δ18OSMOW (+14.58 to +21.19‰) and calculated δ18Ofluid (+5.23 to +9.95‰) values of these calcites overlap with oxygen isotopic compositions of the algal limestone (+18.76 to +23.87‰) and basinal hot brine (+4 to +10‰), respectively, implying that the oxygen was sourced from a binary mixing of ore-host rocks and basinal brine. In addition, the calcite REE data show that ΣREE concentration of Cal-Ⅰ (avg. 1.35 ppm) is lower than that of the Cal-Ⅱ (avg. 10.76 ppm), and REE distribution pattern of Cal-Ⅰ fall close to the field of ore-host rocks, while the Cal-Ⅱ are plotted between the ore-host and rocks from Proterozoic Banxi Group to Cambrian Niutitang Fm., which suggest that REE in Cal-Ⅰ was mainly sourced from the surrounding carbonate rocks, whilst Cal-Ⅱ have a mixed REE origin from wallrocks and underlying sedimentary and metamorphic basement rocks. Overall, based on our detailed deposit geology, sphalerite trace element, and calcite C-O and REE evidences, it was concluded that the Danaopo, with low-T and low fO2 reductive ore-forming fluid, belong to a typical Mississippi Valley-type Zn-Pb deposit.

Metal stable isotopes (e.g., Zn, Cd, and Cu) have been used to track metal sources in different types of hydrothermal systems. However, metal isotopic variations in sulphides could be triggered by various factors such as mineral precipitation and fluid mixing. Thus, tracking the metal sources of hydrothermal systems is still a big challenge for metal isotopes. In this study, we investigated the Cd isotopic systematics of sphalerite from the Nayongzhi Zn–Pb deposit, which is a Mississippi Valley‐type (MVT) deposit in the Sichuan–Yunnan–Guizhou mineralization province (SYGMP). We reinterpreted the published S isotope data for the SYGMP and found that the large S isotopic variations were controlled by Rayleigh fractionation between sulphide and reduced S. As such, a model that involves mixing of a metal‐rich fluid with a reduced S pool formed by thermochemical sulfate reduction (TSR) can explain the ore formation in the Nayongzhi deposit. Based on this model, no Cd isotopic fractionation was observed due to its low solubility in fluids during mixing, and thus the Cd isotopic variations of sphalerite were inherited from the source rocks. The large range of Zn/Cd ratios and uniform Cd isotopic compositions of the sulphides are similar to those of igneous rocks but different from those of sedimentary rocks, indicating that Zn and Cd were derived mainly from basement rocks (e.g., migmatite, gneiss, and granulite). Our results reaffirm that metal stable isotopes, particularly Cd isotope compositions of sphalerite, are powerful geochemical tracers for investigating the formation mechanisms of ore deposits.

Unraveling the precise mineralization age is vital to understand the geodynamic setting and ore-forming mechanism of the sediment-hosted Pb-Zn deposit; this has long been a challenge. The Sichuan-Yunnan-Guizhou (SYG) triangle in the southwestern margin of the Yangtze Block is a globally recognized carbonate-hosted Pb-Zn metallogenic province and also an essential part of the South China low-temperature metallogenic domain. This region has > 30 million tons (Mt) Zn and Pb resources and shows the enrichment of dispersed metals, such as Ga, Ge, Cd, Se, and Tl. During the past 2 decades, abundant data on mineralization ages of Pb-Zn deposits within the SYG triangle have been documented based on various radioisotopic dating methods, resulting in significant progress in understanding the geodynamic background and ore formation of Pb-Zn deposits hosted in sedimentary rocks at SYG triangle. This paper provides a comprehensive summary of the geochronological results and Pb-Sr isotopic data regarding Pb-Zn deposits in the SYG triangle, which identified two distinct Pb-Zn mineralization periods influencing the dynamic processes associated with the expansion and closure of the Paleo-Tethys Ocean in the western margin of the Yangtze Block. The predominant phase of Pb-Zn mineralization at SYG triangle spanned from the Middle Triassic to Early Jurassic (226–191 Ma), which was intensely correlated with the large-scale basin fluid transport triggered by the closure of the Paleo-Tethys Ocean and Indosinian orogeny. The secondary Pb-Zn mineralization phase occurred during the Late Devonian to Late Carboniferous and was controlled by extensional structures associated with the expansion of the Paleo-Tethys Ocean. Further investigation is necessary to clarify the occurrence and potential factors involved in the Pb-Zn mineralization events during the Late Devonian to Late Carboniferous.

Cambrian carbonate formations are widespread in the western Hunan-eastern Guizhou region (southwestern China), which hosts many Mississippi Valley-Type (MVT) lead–zinc (Pb-Zn) deposits. Regional Pb-Zn mineralization is well developed in the low-grade metamorphic rocks of the basal Proterozoic Banxi Group. The mineralization is associated with quartz veins and generally distributed along NE-trending fault zones. Moreover, these deposits have an extensive distribution and high grade, and are associated with Cu-Ag endowment. However, geological and geochemical research on these Pb-Zn vein-type deposits is relatively limited, and their relationship with the regional MVT mineralization remains unclear. The representative Xinhua deposit in Danzhai district is selected as the study subject. We conducted in situ trace element analyses on the sphalerite and chalcopyrite from the various metallogenic stages, and compared them with published sphalerite trace element data from the MVT Pb-Zn deposits in the western Hunan-eastern Guizhou metallogenic belt. Seven orebodies in Xinhua Pb-Zn deposit have been discovered so far, with a metal resource of over 120,000 metric tonnes of Zn + Pb. Field geology and microscopic petrography have revealed two mineralization stages: An earlystage black sphalerite (Sp-I) followed by reddish-brown sphalerite (Sp-II) mineralization, which corresponds to the main chalcopyrite mineralization stage, and a later-stage light-yellow sphalerite (Sp-III), Cu ore-barren mineralization.
LA-ICPMS data indicate that the sphalerite from Xinhua has similar trace element compositions to those from the MVT Pb-Zn deposits in the region. They are relatively enriched in Ga, Cd, and Ge, while depleted in Fe, Co, and Mn. Critical metal Ge and Ga are particularly enriched in sphalerite, especially in Sp-I (Ge max 937 ppm, Ga max 824 ppm). The substitution mechanism of Ge and Ga in sphalerite are likely 2Cu+ + Ge4+ ↔ 3Zn2+ and Cu+ + Ga3+ ↔ 2Zn2+. Indium and Sn are mainly present in Sp-I and Sp-III. Chalcopyrite contains Zn and Sn both exceeding 100 ppm. Contents of Se, Ag, In, and Sn in chalcopyrite are significantly higher than those in sphalerite. Calculation of the sphalerite trace element geothermometer (GGIMFis) suggests that the average sphalerite ore-forming temperatures are 164 ◦C (Sp-I), 156 ◦C (Sp-II), and 205 ◦C Sp-III), implying medium- to low-temperature mineralization. This indicates a possible influx of high-temperature, in-bearing fluid during the late-stage mineralization.
In summary, the faults-controlled vein-type Pb-Zn deposits (e.g., Xinhua) may have been products of the same Kwangsian orogeny as other strata bound MVT deposits, and the Xinhua deposit features two mineralization stages with multiple ore metal sources. During the ore-forming fluid ascent, some ore-forming materials may have precipitated in the fluid conduits. And exposed after the erosion of the shallower stratiform orebodies and strata. Consequently, the Xinhua Pb-Zn deposit represents the preserved ore-fluid conduit phase (in the basement strata) of the MVT mineralization.

The production of nuclear energy generates radioactive waste in various steps of the nuclear cycle: from mining, fuel preparation, irradiation of the fuel, to fuel reprocessing. Such waste has to be properly stored to ensure its isolation from the biosphere.
This talk will give an overview of the general aspects of the nuclear fuel cycle and the radioactive waste management.

Ziel:

Despite the successful development and clinical translation of novel PET tracers for the diagnosis of cancer in recent years, the complete surgical removal of solid tumors remains challenging.1 Fluorescent-guided surgery provides a valuable tool to facilitate the navigation during surgery and ultimately can improve the therapeutic outcome for cancer patients.1 Combining preoperative PET imaging and intraoperative optical imaging within the same molecule has proven to be a promising approach.2 In recent years the fibroblast activation protein alpha (FAPα) arose as a highly interesting target for radiotracer development, applicable for a broad variety of tumor entities.3,4 The aim of this project is the development of the, to the best of our knowledge, first literature-known dual-labelled FAP inhibitor-near-infrared (NIR) dye conjugate radiotracer to be utilized in fluorescent-guided surgery.

Methoden:

Two derivatives have been designed based on the structure of the established radiotracer FAPI-46.5 NODAGA as chelator was attached via the ε-amine function of a lysine amino acid. The NIR dye IRDye800CW or AlexaFluor647 was coupled to the α-amino function via a pegylated spacer. These ligands were radiolabeled with the radionuclides 68Ga and 67Ga.The resulting radiotracers underwent stability studies in human serum.

Ergebnisse:

The radiotracers were successfully synthesized and chemically characterized. Radiolabeling was optimized to achieve sufficient molar activitiesof 22 – 30 GBq/ µmol for both radionuclides 68Ga and 67Ga, for subsequent biological evaluations. Both derivatives were stable in human serum at 37 °C over 4 hours. The log D7.4 values for the AlexaFluor647 and the IRDye800CW derivatives were –4.10 and –3.58, respectively.

Schlussfolgerungen:

Two novel FAPI radiotracers have been successfully synthesized and characterized. Preliminary stability studies in human serum indicated sufficient stability of the radiotracers. Further biological assessment is currently ongoing.

Referenzen:

[1] Lauwerends L, et al. The Lancet Oncology 2021, 22, e186 – e195
[2] Baranski AC, et al. Journal of Nuclear Medicine 2018, 54, 639 – 645.
[3] Kratochwil, C, et al. Journal of Nuclear Medicine 2019, 60, 801 – 805
[4] Huang R, et al. Frontiers in Oncology 2022, 12, 854658
[5] Loktev A, et al. Journal of Nuclear Medicine 2019, 60, 1421 – 1429

Ziel/ Aim:

Fluorescence-guided surgery provides a valuable tool, facilitating intraoperative differentiation of tumor and healthy tissue, thereby improving resection results and potentially therapeutic outcome. [1] The aim of this work is the development of novel multimodal fibroblast activation protein alpha (FAPα) inhibitors for PET and optical imaging.

Methodik/ Methods:

Two derivatives were designed, based on the structure of the radiotracer FAPI-46. The chelator NODA-GA and the infrared dyes Alexa Fluor 647 and IRDye800CW were introduced via a lysine amino acid as linker moiety. The compounds were labeled with gallium-68 and stability investigated in human serum. Using HT1080 cells stably transduced with human FAP, affinities were determined via saturation binding. Small animal PET and fluorescence imaging (IVIS) studies were performed in mice carrying a tumor from each HT1080 FAP overexpressing and wild-type cells, thereby complementing in vitro data.

Ergebnisse/ Results:

The gallium-68-labeled radiotracers were stable in human serum at 37 °C over 4 hours and showed affinities in the low nanomolar range (K_D = 1.33 ± 0.33 nM). Small animal PET imaging revealed a favorable pharmacokinetic profile, with a fast and exclusively renal clearance. Uptake into FAP-overexpressing tumors was rapid (SUV_max = 2.82 ± 0.48, 90 min after i.v. injection) and similarly observed using IVIS. In contrast, wild-type tumors exhibited negligible uptake in bot PET and IVIS, along with no apparent off-target binding in major organs.

Schlussfolgerungen/ Conclusions:

In summary, first evaluation of both multimodal FAPα-targeting molecules illustrates their suitability in vitro and in vivo. Prior to clinical translation, in vivo metabolic stability and toxicity need to be assessed.
Literatur/ References:
[1] Lauwerends L, et al. The Lancet Oncology, 22, 2021

Early results on the plasma deposition of dielectric thin films on acoustic wave (AW) activated substrates revealed a densification pattern arisen from the focusing of plasma ions and their impact on specific areas of the piezoelectric substrate. Herein, we extend this methodology to tailor the plasma deposition of metals onto AW-activated LiNbO3 piezoelectric substrates. Our investigation reveals the tracking of the initial stages of nanoparticle (NP) formation and growth during the submonolayer deposition of silver. We elucidate the specific role of AW activation in reducing particle size, enhancing particle circularity, and retarding NP agglomeration and account for the physical phenomena making these processes differ from those occurring on non-activated substrates. We provide a comparative analysis of the results obtained under two representative plasma conditions: diode DC sputtering and magnetron sputtering. In the latter case, the AW activation gives rise to a 2D pattern of domains with different amounts of silver and a distinct size and circularity for the silver NPs. This difference was attributed to the specific characteristics of the plasma sheath formed onto the substrate in each case. The possibilities of tuning the plasmon resonance absorption of silver NPs by AW activation of the sputtering deposition process are discussed.

Introduction
Tetrahedral amorphous carbon (ta-C) is characterized by very high hardness up to 80 GPa and elastic moduli up to 800 GPa, a relatively high transparency and a high electric resistivity. As solid lubricant, ta-C coatings can exhibit coefficients of friction (COF) lower than 0.1 in humid conditions. However, in dry and inert atmospheres as well as in vacuum the majority of reported COF values of ta-C coatings are high up to 0.8, independently of the friction partner. In this contribution we studied the effect of "near-surface" ion implantation on the structural, mechanical, and friction properties of ta-C coatings.

Methods
Ta-C coatings with 2 to 4 μm thickness were deposited by the Laser-Arc technique on 100Cr6 substrates. Based on SRIM calculations, a sequence of ion energies was used to implant oxygen, silicon, chromium, copper, and tantalum ions within a thickness of 100 nm into the ta-C coatings. The as-implanted ta-C:X samples were characterized by Rutherford backscattering spectrometry, Raman spectroscopy, X-ray diffraction, and transmission electron microscopy and subjected to friction experiments in humid, dry, and vacuum atmospheres.

Results
RBS spectra representing a homogeneous, single-layer implantation profile were obtained for the elements O, Si, and Cr, and to a good approximation also for Ta (Figure 1). Different to these four coatings, the Cu depth profile varied as a function of the implantation depth. The Raman spectra show a broad, nonresolved line structure in the D- and G-line range that is typical for amorphous carbon. However, the increase of the intensity for the shoulder of the D line indicates a distinct dopant-element dependence of the sp2-C/sp3-C ratio in the "near-surface" range of the samples. Similarly, an element-dependent friction behaviour was observed. Si- and Ta-implanted ta-C coatings showed the smallest environment dependence and might be potential candidates as solid ta-C-based lubricants for different atmospheres.

Conclusion
Tetrahedral amorphous carbon coatings were successfully modified by ion implantation in a depth range 100 nm. Element specific properties were demonstrated, and Si- and Ta-implantation were identified as promising routes to reduce the environment-dependent friction properties of ta-C.