Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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38996 Publications

Activation calculations of selected RPV internal components for optimal decommissioning of nuclear power plants

Rachamin, R.; Konheiser, J.; Seidl, M.

In this study, the specific activities of selected RPV components’ segments (such as the RPV, core barrel, etc.) of a German PWR were calculated with a novel method based on the combined use of two Monte-Carlo codes, MCNP6.2 and FLUKA2021. In the first step, the MCNP6.2 code was used to calculate the neutron fluence rate characteristics (spectrum, distribution, and current entering the segment surfaces) in the studied segment using a 3D detailed reactor model. The neutron fluence rate prediction capability of the MCNP6.2 model has been validated via metal foil-activation measurements carried out in two German PWRs. The validation studies showed that the MCNP6.2 model is reliable and suitable for evaluating the neutron radiation field in the reactor for the ensuing activation calculations. In the second step, the FLUKA2021 code was used to calculate the specific activity distribution in the studied segment using a 3D exact model of the segment and complex source terms built based on the neutron fluence rate parameters calculated using the MCNP6.2 code. The results of the calculations were obtained with great accuracy and evidenced that the used method can serve as a powerful and non-destructive tool for the radiological characterization of the RPV and its internals.

Keywords: German PWR; Decommissioning; Neutron fluence; Activation; MCNP; FLUKA

  • Open Access Logo Lecture (Conference)
    15th workshop on Shielding aspects of Accelerators, Targets, and Irradiation Facilities (SATIF-15), 20.-23.09.2022, East Lansing, USA
  • Open Access Logo Contribution to proceedings
    15th workshop on Shielding aspects of Accelerators, Targets, and Irradiation Facilities (SATIF-15), 20.-23.09.2022, East Lansing, USA

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Permalink: https://www.hzdr.de/publications/Publ-35542
Publ.-Id: 35542


Dosimetry for Decommissioning of Nuclear Power Plants

Rachamin, R.; Konheiser, J.; Barkleit, A.; Seidl, M.

In this study, a 3D detailed Monte-Carlo (MC) model of a German PWR was developed to calculate the neutron fluence characteristics within the ex-vessel components of the reactor. The neutron fluence prediction capability of the developed model was validated based on metal foil-activation measurements. Metal foil-activation measurement has been successfully used in reactor dosimetry for many years. It is an ideal method for collecting information on neutron fluence in an active reactor. This paper gives an overview of the MC model of the reactor and presents the foils activation measurement procedure. Then, the results of the MC simulations and the experimental measurements are presented and discussed.

Keywords: German PWR; Decommissioning; Neutron fluence; Activation; MCNP; Validation

  • Contribution to proceedings
    14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division (ICRS 14/RPSD 2022), 25.-29.09.2022, Seattle, USA
  • Lecture (Conference)
    14th International Conference on Radiation Shielding and 21st Topical Meeting of the Radiation Protection and Shielding Division (ICRS 14/RPSD 2022), 25.-29.09.2022, Seattle, USA

Permalink: https://www.hzdr.de/publications/Publ-35541
Publ.-Id: 35541


Phasenverteilung in Zickzack-Packungen für Rotating Packed Beds

Loll, R.; Bieberle, A.; Schubert, M.; Koop, J.; Held, C.; Schembecker, G.

Rotierende Stoffaustauschmaschinen (engl. „Rotating Packed Beds“, RPBs) sind ein vielversprechender Ansatz, um Trennprozesse effizienter und flexibler zu gestalten. Die durch die Rotation der RPB-Packung wirkenden Zentrifugalkräfte resultieren in hohen Scherraten und damit dünnen Flüssigkeitsfilmen nahezu auf der gesamten Packungsoberfläche, die zu großer effektiver Phasengrenzfläche und hohem volumetrischen Stofftransport führen. Dadurch benötigen RPBs ein drastisch kleineres Packungsvolumen als herkömmliche Trennkolonnen.
Allerdings sind beim Betrieb von RPBs – insbesondere in den äußeren Regionen von isotropen Drahtgestrick- oder Metallschaumpackungen – Phasenfehlverteilungen und lokal geringe Stofftransportraten zu beobachten, die das enorme Intensivierungspotential von RPBs noch limitieren. Daher sind spezielle RPB-Packungsdesigns erforderlich, die gleichmäßige fluiddynamische Bedingungen im gesamten Packungsvolumen ermöglichen.
In dieser Arbeit wird untersucht, ob und wie neu entwickelte Zickzack-Packungen zu einer Homogenisierung der Phasenverteilung in der Packung beitragen können. Dazu wird mithilfe der nicht-invasiven winkelaufgelösten Gammastrahlen-Computertomographie die Phasenverteilung während des rotierenden Betriebs untersucht und anschließend analysiert. Die rekonstruierten Schnittbilder geben einen detaillierten Einblick auf die Flüssigkeitsverteilung innerhalb der Packung bei verschiedenen Betriebsbedingungen. Komplementäre Stofftransportmessungen geben ein verbessertes Verständnis über das Zusammenspiel von Packungsstruktur, Fluiddynamik und Trennleistung.

Keywords: Stoffaustauschmaschinen; Trennprozesse; Gammastrahlen-Computertomographie

  • Contribution to proceedings
    Jahrestreffen der "Prozess-, Apparate- und Anlagentechnik", 21.-22.11.2022, Frankfurt am Main, Deutschland
  • Poster
    Jahrestreffen der "Prozess-, Apparate- und Anlagentechnik", 21.-22.11.2022, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35540
Publ.-Id: 35540


Population Kinetics for Particle in Cell Simulations

Marre, B. E.; Hübl, A.; Bastrakov, S.; Bussmann, M.; Widera, R.; Schramm, U.; Cowan, T.; Kluge, T.

Population Kinetics for PIC

Standard atomic physics models in PIC simulation either neglect excited states, predict
atomic state population in post processing only, or assume quasi-thermal plasma conditions.

This is no longer sufficient for high-intensity short-pulse laser generated plasmas, due
to their non-equilibrium, transient and non-thermal plasma conditions, which are now becoming
accessible in XFEL experiments at HIBEF (EuropeanXFEL), SACLA (Japan) or at MEC (LCLS/SLAC).
To remedy this, we have developed a new extension for our ParticleInCell simulation
framework PIConGPU to allow us to model atomic population kinetics in situ in PIC-Simulations,
in transient plasmas and without assuming temperatures.
This extension is based on a reduced atomic state model, which is directly coupled to the
existing PIC-simulation and for which the atomic rate equation is solved explicitly in
time, depending on local interaction spectra and with feedback to the host simulation.
This allows us to model de-/excitation and ionization and of ions in transient plasma
conditions, as typically encountered in laser generated plasmas.
This new approach to atomic physics modeling will be very useful in plasma
emission prediction, plasma condition probing with XFELs and better understanding
of isochoric heating processes, since all of these rely on an accurate prediction of
atomic state populations inside transient plasmas.

Keywords: Atomic Population Kinetics; FLYonPIC; PIConGPU; PIC; Particle in Cell; Simulation; Atomic Physics

  • Lecture (Conference)
    Radiation Properties of Hot Dense Matter, 14.-18.11.2022, Santa Fe, New Mexico, United States of America

Permalink: https://www.hzdr.de/publications/Publ-35539
Publ.-Id: 35539


Response of a surfactant- and particle-laden bubble surface to asymmetric shear flow

Eftekhari, M.; Schwarzenberger, K.; Heitkam, S.; Javadi, A.; Eckert, K.

The shear stress of an axisymmetric flow field triggers a nonuniform distribution of adsorbed surfactants at the surface of a rising bubble. This creates a surface tension gradient that counteracts the viscous shear stress of the flow and thus reduces the mobility of the interface. However, in technological processes the flow field often is asymmetric, e.g. due to the vorticity in the flow. Under such conditions, the interface experiences an unbalanced shear stress that is not free of curl, i.e. it cannot be compensated by the redistribution of the surfactants at the interface (Vlahovska et al., 2009).
Here, we conduct model experiments with a bubble at the tip of a capillary placed in a defined asymmetric flow field, in the presence of surfactants and nanoparticles. Unlike classical surfactants, nanoparticles adsorb irreversibly at the bubble surface. Thus, a different interaction between the bulk flow and the interface is expected.
In this study, we show a direct experimental observation of the circulating flow at the interface under asymmetric shear stress (Eftekhari et al., 2021a,b). The results indicate that the interface remains mobile regardless of the surfactant concentration. Additionally, we show that the nanoparticle-laden interface adopts a solid-like state and resists the interfacial flow upon surface compression. Our results imply that the immobilization of the interface can be described by the ratio of the interfacial elasticity to the bulk viscous forces.

  • Lecture (Conference)
    Annual European Rheology Conference (AERC 2022), 26.-28.04.2022, Seville, Spain

Permalink: https://www.hzdr.de/publications/Publ-35538
Publ.-Id: 35538


Complex Dissipative Structures Mainly at Liquid/Liquid and Liquid/Gas Interfaces

Linde, H.; Schwarzenberger, K.; Eckert, K.

Well-known - and often to see in the daily weather forecast - are the chaotic macroscopic flow-systems of air and sea-water in one`s own land and occasional also about the whole world.

Permalink: https://www.hzdr.de/publications/Publ-35537
Publ.-Id: 35537


Induction of pulmonary HLA-G expression by SARS-CoV-2 infection

Seliger, B.; Jasinski-Bergner, S.; Masssa, C.; Müller, A.; Biehl, K.; Yang, B.; Bachmann, M.; Jonigk, D.; Eichhorn, P.; Hartmann, A.; Wickenhauser, C.; Bauer, M.

The non-classical human leukocyte antigen (HLA)-G exerts immune-suppressive properties modulating both NK and T cell responses. While it is physiologically expressed at the maternal–fetal interface and in immune-privileged organs, HLA-G expression is found in tumors and in virus-infected cells. So far, there exists little information about the role of HLA-G and its interplay with immune cells in biopsies, surgical specimen or autopsy tissues of lung, kidney and/or heart muscle from SARS-CoV-2-infected patients compared to control tissues. Heterogeneous, but higher HLA-G protein expression levels were detected in lung alveolar epithelial cells of SARS-CoV-2-infected patients compared to lung epithelial cells from influenza-infected patients, but not in other organs or lung epithelia from non-viral-infected patients, which was not accompanied by high levels of SARS-CoV-2 nucleocapsid antigen and spike protein, but inversely correlated to the HLA-G-specific miRNA expression. High HLA-G expression levels not only in SARS-CoV-2-, but also in influenza-infected lung tissues were associated with a high frequency of tissue-infiltrating immune cells, but low numbers of CD8+ cells and an altered expression of hyperactivation and exhaustion markers in the lung epithelia combined with changes in the spatial distribution of macrophages and T cells. Thus, our data provide evidence for an involvement of HLA-G and HLA-G-specific miRNAs in immune escape and as suitable therapeutic targets for the treatment of SARS-CoV-2 infections.

Keywords: HLA-G; Immune cell infiltration; Immune response; microRNA; SARS-CoV-2

Permalink: https://www.hzdr.de/publications/Publ-35535
Publ.-Id: 35535


Technological Pathways to Produce Compressed and Highly Pure Hydrogen from Solar Power

Ivanova, M. E.; Peters, R.; Müller, M.; Haas, S.; Seidler, F.; Mutschke, G.; Eckert, K.; Röse, P.; Calnan, S.; Bagacki, R.; Grosslindemann, C.; Schäfer, L.-A.; Weber, A.; van de Krol, R.; Liang, F.; Abdi, F. F.; Brendelberger, S.; Neumann, N.; Grobbel, I.; Roeb, M.; Sattler, C.; Duran, I.; Dietrich, B.; Hofberger, C.; Stoppel, L.; Uhlenbruck, N.; Wetzel, T.; Rauner, D.; Hecimovic, A.; Frantz, U.; Kulyk, N.; Harting, J.; Guillon, O.

Hydrogen (H 2 ) produced from renewables will have a
growing impact on the global energy dynamics towards sustainable
and carbon-neutral standards. The share of green H 2 is still too low to
meet the net-zero target, while the demand for high-quality hydrogen
continues to rise. These factors amplify the need for economically
viable H 2 generation technologies. The present article aims at
evaluating the existing technologies for high-quality H 2 production
based on solar energy. Technologies such as water electrolysis,
photoelectrochemical and solar thermochemical water splitting, liquid
metal reactors and plasma conversion utilize solar power directly or
indirectly (as carbon-neutral electrons) and are reviewed from the
prospective of their current development level, technical limitations
and future potential.

Keywords: electrolysis; hydrogen; green hydrogen; pure hydrogen; energy conversion; renewable energy; technology

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  • Secondary publication expected from 13.01.2024

Permalink: https://www.hzdr.de/publications/Publ-35534
Publ.-Id: 35534


Advanced thermal-hydraulic experiments and instrumentation for heavy liquid metal reactors

Pacio, J.; van Tichelen, K.; Eckert, S.; Wondrak, T.; Di Piazza, I.; Lorusso, P.; Tarantino, M.; Daubner, M.; Litfin, K.; Ariyoshi, G.; Obayashi, H.; Sasa, T.

Heavy-liquid metals (HLMs), such as lead and lead–bismuth eutectic (LBE), are proposed as primary coolants in accelerator driven systems and next-generation fast reactors. In Europe, the reference systems using HLMs are MYRRHA (LBE) and ALFRED (lead). Extensive R&D programs have been established for supporting their detailed design and safety assessment, including thermal–hydraulic experiments at representative operating conditions in an HLM environment. These experiments aim both at a design verification and at the validation of numerical models, which allow an extrapolation of the results. Advanced instrumentation, capable of sustaining high temperatures and corrosion, is necessary for accurate measurements, often in compact geometries. This article presents an overview of recent experiences and ongoing activities on pool-type and loop-type HLM experiments. Pool tests include the measurement of forced- and natural-circulation flow patterns in several scenarios representative of nominal and decay heat removal conditions. Loop tests are focused on the evaluation of specific components, like mockups of the fuel assembly, control rod and heat exchangers. They involve the measurement of global variables, such as flow rate and pressure difference, and local quantities like temperature, velocity and vibrations. In addition to traditional techniques, other instrumentation based on optical fibers, ultrasonic and electromagnetic methods are discussed.

Keywords: liquid metal; experiment; instrumentation

Permalink: https://www.hzdr.de/publications/Publ-35532
Publ.-Id: 35532


Nano- and Flexomagnetism in Magnetoelectric Cr2O3 Thin-Film Antiferromagnets

Makarov, D.

In this presentation, we will review our recent activities on thin films and bulk of Cr2O3 for energy efficient memory devices and antiferromagnetic spintronic applications. The newly discovered flexomagnetic effect in thin films of Cr2O3 will be presented as well.
[1] Nature Physics 17, 574 (2021).
[2] Nature Comm. 13, 6745 (2022).
[3] Small 18, 2201228 (2022).
[4] ACS Appl. Electron. Mater. 4, 2943 (2022).

Keywords: antiferromagnetic spintronics; magnetic thin films; Cr2O3

Related publications

  • Lecture (others) (Online presentation)
    Lu Jiaxi International Team Annual Meeting, 02.12.2022, Ningbo, China

Permalink: https://www.hzdr.de/publications/Publ-35530
Publ.-Id: 35530


Flexible, printed and self-healable high-performance magnetoelectronics for human-machine interfaces and soft robotics

Makarov, D.

In this overview talk, we will discuss on our recent activities on the realization of flexible, printed and self-healable magnetic field sensors and their potential application scenarios.

Keywords: flexible magnetic field sensors; printable magnetic field sensors; magnetic soft robots

Related publications

  • Lecture (others)
    Seminar of the Graduiertenkolleg 2430 „Interaktive Faser-Elastomer-Verbunde“, 06.12.2022, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-35529
Publ.-Id: 35529


Curvilinear micromagnetism: from fundamentals to applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics, superconductivity and magnetism [1,2]. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape of magnetic thin films [3] and nanowires [4]. In this talk, we will address fundamentals of curvature-induced effects and discuss experimental realisations of geometrically curved low-dimensional architectures and their characterization, which among others resulted in the experimental confirmation of the exchange-driven chiral effects [5]. Geometrically curved magnetic thin films are interesting not only fundamentally. They are the key component of mechanically flexible magnetic field sensors. We will briefly outline activities on shapeable magnetoelectronics [6,7], which includes flexible, stretchable and printable magnetic field sensors for the realisation of human-machine interfaces [8,9], interactive electronics for virtual [10] and augmented [11] reality applications and soft robotics [12] to mention just a few. Very recently, self-healable magnetic field sensors for interactive printed electronics were reported [13]. The presence of the geometrical curvature in a magnetic thin film influences pinning of magnetic domain walls and in this respect it affects the sensitivity of mechanically flexible magnetic field sensors. This is an intimate link between the fundamental topic of curvilinear magnetism and application-oriented activities on shapeable magnetoelectronics. This link will be discussed in the presentation as well.

[1] P. Gentile et al., Electronic materials with nanoscale curved geometries. Nature Electronics (Review) 5, 551 (2022).
[2] D. Makarov et al., Curvilinear micromagnetism: from fundamentals to applications. Springer Nature Switzerland (2022). https://link.springer.com/book/10.1007/978-3-031-09086-8
[3] D. Makarov et al., New Dimension in Magnetism and Superconductivity: 3D and Curvilinear Nanoarchitectures. Advanced Materials (Review) 34, 2101758 (2022).
[4] D. Sheka et al., Fundamentals of Curvilinear Ferromagnetism: Statics and Dynamics of Geometrically Curved Wires and Narrow Ribbons. Small (Review) 18, 2105219 (2022).
[5] O. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Physical Review Letters 123, 077201 (2019).
[6] D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[7] G. S. Canon Bermudez et al., Magnetosensitive e-skins for interactive devices. Advanced Functional Materials (Review) 31, 2007788 (2021).
[8] P. Makushko et al., Flexible Magnetoreceptor with Tunable Intrinsic Logic for On-Skin Skin Touchless Human-Machine Interfaces. Advanced Functional Materials 31, 2101089 (2021).
[9] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[10] G. S. Canon Bermudez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[11] G. S. Canon Bermudez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[12] M. Ha et al., Reconfigurable Magnetic Origami Actuators with On-Board Sensing for Guided Assembly. Advanced Materials 33, 2008751 (2021).
[13] R. Xu et al., Self-healable printed magnetic field sensors using alternating magnetic fields. Nature Communications 13, 6587 (2022).

Keywords: flexible magnetic field sensors; printable magnetic field sensors; curved magnetic thin films

Related publications

  • Lecture (others)
    Seminar at the Northeastern University, Electrical and Computer Engineering, 28.11.2022, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-35528
Publ.-Id: 35528


Stability and structure of platinum sulfide complexes in hydrothermal fluids

Laskar, C.; Bazarkina, E.; Kokh, M.; Hazemann, J.-L.; Vuilleumier, R.; Desmale, E.; Pokrovski, G. S.

Knowledge of the chemical speciation of platinum and the solubility of Pt-bearing minerals in hydrothermal fluids is required to assess Pt transport, remobilization and concentration in the Earth’s crust. In this study, we combined PtS(s) solubility measurements in a hydrothermal reactor allowing fluid sampling, in situ X-ray absorption spectroscopy, and first-principles molecular dynamics simulations to systematically investigate the structure, composition and stability of Pt sulfide complexes in model aqueous H2S-bearing solutions up to 300 °C and 600 bar. The results demonstrate that tetrahydrosulfide, PtII(HS)42–, is the major Pt-bearing complex in aqueous solutions saturated with PtS(s) over a wide range of dissolved hydrogen sulfide concentrations, from < 0.2 to ∼ 2 molal. The equilibrium constants of the dissolution reaction of PtS(s) generated in this study, PtS(s) + 3 H2S(aq) = Pt(HS)42– + 2 H+ (β4), are described by the equation log10β4 = 0.9 × 1000/T(K) – 19.7 (± 0.5) over the temperature range 25–300 °C and pressure range Psat–600 bar. Furthermore, the stepwise formation constants of four PtII-HS complexes, Pt(HS)+, Pt(HS)20, Pt(HS)3–, and Pt(HS)42–, were estimated, for the first time, from molecular dynamics simulations. The generated constants indicate that the maximum solubility of platinum in the form of Pt(HS)42– in reduced H2S-dominated hydrothermal fluids at moderate temperatures (≤ 350 °C) is close to 1 ppb Pt at near-neutral pH of 6–8 and hydrogen sulfide concentrations of 0.1 molal. Although this solubility is much greater than that of Pt-Cl, Pt-OH and Pt-SO4 complexes at such conditions, it is yet too low to account for significant Pt transport in most shallow-crust hydrothermal settings, characterized by the presence of both sulfide and sulfate. Complexes with S-bearing ligands, very likely other than H2S/HS–, such as S3–, would be required to account for Pt hydrothermal mobility. Our results provide a basis for more systematic future studies, using combined approaches, of the role of hydrothermal fluids in the behavior of platinum group elements in nature.

Keywords: Platinum sulfide complexes; Hydrothermal fluid; Solubility; X-ray absorption spectroscopy; Molecular dynamics; Stability constant

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Permalink: https://www.hzdr.de/publications/Publ-35527
Publ.-Id: 35527


Neutron scattering methods

Bergner, F.

This lecture is about neutron scattering methods and their applications in the field of nuclear material science.

Keywords: Small-angle neutron scattering; Diffuse neutron scattering; Nuclear materials

  • Lecture (others)
    European School on Nuclear Materials Science, 07.-11.11.2022, Cargèse, France

Permalink: https://www.hzdr.de/publications/Publ-35523
Publ.-Id: 35523


X-ray and electron diffraction methods

Bergner, F.

This lecture is about X-ray and electron diffraction methods and their application in the field of nuclear material science

Keywords: X-ray diffraction; Electron diffraction; Nuclear materials

  • Lecture (others)
    European School on Nuclear Materials Science, 07.-11.11.2022, Institut d'Etudes Scientifiques (IESC) Cargèse, France

Permalink: https://www.hzdr.de/publications/Publ-35522
Publ.-Id: 35522


Germanium Monosulfide as a Natural Platform for Highly Anisotropic THz Polaritons

Nörenberg, T.; Álvarez-Pérez, G.; Obst, M.; Wehmeier, L.; Hempel, F.; Klopf, J. M.; Nikitin, A. Y.; Kehr, S. C.; Eng, L. M.; Alonso-Gonzaléz, P.; de Oliveira, T.

Terahertz (THz) electromagnetic radiation is key to access collective excitations such as magnons (spins), plasmons (electrons), or phonons (atomic vibrations), thus bridging topics between optics and solid-state physics. Confinement of THz light to the nanometer length scale is desirable for local probing of such excitations in low-dimensional systems, thereby circumventing the large footprint and
inherently low spectral power density of far−field THz radiation. For that purpose, phonon polaritons (PhPs) in anisotropic van der Waals (vdW) materials have recently emerged as a promising platform for THz nanooptics. Hence, there is a demand for the exploration of materials that feature not only THz PhPs at different spectral regimes, but also host anisotropic (directional) electrical, thermoelectric,
and vibronic properties. To that end, we introduce here the semiconducting vdW material alpha−germanium (II) sulfide (GeS) as an intriguing candidate. By employing THz nanospectroscopy supported by theoretical analysis, we provide a thorough characterization of the different in−plane hyperbolic and elliptical PhP modes in GeS. We find not only PhPs with long lifetimes (τ > 2 ps) and excellent THz light confinement (λ[₀]/λ) 45), but also an intrinsic, phonon-induced anomalous dispersion as well as signatures of naturally
occurring, substrate-mediated PhP canalization within a single GeS slab.

Keywords: van der Waals materials; optical anisotropy; terahertz; phonon polaritons; polariton interferometry

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-35521
Publ.-Id: 35521


Emergence of Hadron Mass and Structure

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

Visible matter is characterised by a single mass scale; namely, the proton mass. The proton’s existence and structure are supposed to be described by quantum chromodynamics (QCD); yet, absent Higgs boson couplings, chromodynamics is scale invariant. Thus, if the Standard Model is truly a part of the theory of Nature, then the proton mass is an emergent feature of QCD; and emergent hadron mass (EHM) must provide the basic link between theory and observation. Nonperturbative tools are necessary if such connections are to be made; and in this context, we sketch recent progress in the application of continuum Schwinger function methods to an array of related problems in hadron and particle physics. Special emphasis is given to the three pillars of EHM – namely, the running gluon mass, process-independent effective charge, and running quark mass; their role in stabilising QCD; and their measurable expressions in a diverse array of observables.

Keywords: confinement of gluons and quarks; continuum Schwinger function methods; Dyson- Schwinger equations

Permalink: https://www.hzdr.de/publications/Publ-35519
Publ.-Id: 35519


Study on kinetics and mechanism of Re(VII) ion adsorption and desorption using commercially available activated carbon and solutions containing Se(VI) as an impurity

Kołczyk-Siedlecka, K.; Socha, R. P.; Yang, X.; Eckert, K.; Wojnicki, M.

This paper presents the potential use of carbon sorbents in recovering rhenium(VII) from highly diluted electrolytes. Tests were performed using synthetic solutions containing selenium(VI) as an impurity. Adsorption of Re(VII) is selective with respect to selenium(VI). Activated carbon is a suitable sorbent for rhenium recovery because unlike ion-exchange resins, it has high chemical resistance and osmotic-shock resistance. The results show that the sorption mechanism is complex. Two follow-up processes occurred—physical adsorption and the reduction of Re(VII) to Re(VI). The processes were strongly influenced by the temperature. The lower the temperature, the higher the process efficiency. The observed sorption capacity was as high as 7.6 mg/g at 298 K and decreased as the temperature increased. The adsorption was a mixed-control process. Increasing the temperature altered the rate-limiting process. The activation parameters were determined using rate constant (k) and Arrhenius equation. In the first step, the activation energy was approximately 0 kJ mol-1. In the second step, the activation energy for k2,obs and k3,obs was determined as 57.3 kJ mol-1. The pre-exponential factors were calculated; their value was 2.98 × 107 min-1. For k1,obs, the activation energy was nearly 0 kJ mol-1.

Keywords: Rhenium(VII) adsorption; selenium(VI) adsorption; chemical reduction; activated carbon; kinetic studies; selenium ions

Permalink: https://www.hzdr.de/publications/Publ-35514
Publ.-Id: 35514


Molecular Dynamics Simulation on Bubble Related Issues

Ding, W.

Activities introduction of Molecular Dynamics simulation on bubble related issues in FWDF, HZDR.

Keywords: Molecular Dynamics; Bubble

  • Lecture (others)
    ECCM Kick off meeting, 27.-28.10.2022, TU Twent, Niederland

Permalink: https://www.hzdr.de/publications/Publ-35512
Publ.-Id: 35512


Nanobending of the microscopic liquid-gas interface on the solid surface and its potential impact on nanobubbles

Zhang, J.; Ding, W.; Hampel, U.

Young contact angle is widely applied to evaluate liquid wetting phenomena on solid surfaces. For example, it gives a truncated-spherical shape prediction of a droplet/bubble profile through the Young-Laplace equation. However, recent measurements have shown the deviation of a microscopic droplet profile from the spherical shape, indicating that the conventional Young contact angle as the boundary condition is insufficient to describe the microscopic liquid wetting phenomena which play a critical role when nanobubbles on the wall. Here, we reveal a liquid-gas interface nano-bending, which is caused by the nonlinear coupling between the effects of the microscopic interface geometry and solid-liquid interactions and is responsible for this deviation. Based on molecular dynamics simulations and mathematical modeling, we describe the structure of the nano-bending and explain the mechanism of the nonlinear-coupled effect. We further apply our findings to illustrate the saddle-shaped profile in the vicinity near the contact region. The interface nano-bending, rather than the Young contact angle, acts as the boundary at the contact line and dictates the liquid wetting system. In this way, we succeed in accurately predicting the microlayer profile (µm thickness liquid film beneath a nucleation bubble) captured by different experiments. These findings not only provide insight into recent nano-scale droplet- and bubble-related wetting phenomena, but are also helpful for surface engineering concerning nano-scale wetting control.

Keywords: Nano Bending; Nano Bubble; nonlinear coupled effect

  • Poster
    Nanobubble, 19.-21.09.2022, Magdeburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35511
Publ.-Id: 35511


The effect of the microscopic liquid film interface on the heat transfer in multiphase dynamics

Zhang, J.; Ding, W.; Hampel, U.

Microlayer plays a critical role in the bubble dynamics and heat transfer in nucleate boiling. Yet, an accurate description of the microlayer has been a challenge for decades. In this work, we investigate the microlayer profile in the inertia-controlled bubble growth stage by using molecular simulations and mathematical modeling. A multiscale microlayer model was established through the disjoining pressure method and lubrication theory. Our model succeeds in accurately describing the microlayer profile captured by different experiments for the first time in decades. We reveal that the nonlinear coupling between microscopic liquid/vapor interface geometry and surface energy near the surface has a dominant effect on the overall microlayer profile. An interface nano-bending caused by the coupling acts as a three-dimensional boundary for the liquid wetting system and governs the wetting behavior. These findings provide insight into the understanding of heat transfer in nucleate boiling.

Keywords: Microlayer; Bubble; Molecular force; mutual effect; nano bending

  • Poster
    Annual Meeting on Reaction Engineering and ProcessNet Subject Division Heat and Mass Transfer 2022, 18.-20.07.2022, Würzburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35510
Publ.-Id: 35510


Introduction to Density Functional Theory

Cangi, A.

A formal introduction to density functional theory.

Keywords: Density Functional Theory

  • Invited lecture (Conferences) (Online presentation)
    Forschungsseminar "Vielteilchentheorie", Christian-Albrechts-Universität zu Kiel, 25.10.2022-14.02.2023, Kiel, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35509
Publ.-Id: 35509


Recovery of valuable elements from tailings dumps accompanied by environmental remediation – the pilot plant project “ReMiningPlus”

Pinka, J.; Haubrich, F.; Werner, A.; Büttner, P.; Meißner, S.; Puschmann, R.; Pretzsch, E.

Flotation tailings from a former lead-zinc mine near Freiberg (Germany) consist of fine-grained quartz, feldspar, mica and the sulfide minerals pyrite, galena and sphalerite, which are not recovered by flotation. Sphalerite contains significant amounts of indium (up to 0.38 % (w/w)) in addition to iron, copper and cadmium, resulting in assumed average indium content of 30 mg/kg in the tailings. The presentation shows the development of biohydrometallurgical recovery of indium from laboratory to pilot scale. In a 2 m³ bioreactor, maximum zinc and indium leaching rates of 80 % were obtained at a pulp density of 25%. For the recovery of indium from the PLS (pregnant leaching solution), a stepwise precipitation process is being developed consisting of a combined iron/indium precipitation and a subsequent treatment of the indium precipitate product. A new project has been started in which a modular plant for the utilization of valuable materials from these sulfide tailings and their environmentally friendly remediation is being set up directly at the tailings site. Combining resource technology to utilize valuable elements (indium and zinc) from tailings and environmental technology to eliminate harmful substances (arsenic and cadmium) with the use of inert components (e.g. as building material) represents a win-win situation. After its completion, the modular plant consists of three parts: the leaching, the recyclables and the environmental modules. Results and findings of the project will be processed for environmental education in schools and used for the development of a web application (app) that can be used to content for integration into existing tourism concepts. Through the implementation of the aforementioned goals, the project provides a decisive contribution to the structural change in the region, as it a concept for linking rehabilitation and secondary raw material extraction and a possible economic and touristic reuse.

Keywords: Bioleaching; Circular Economy; Indium; Tailings; Zinc

  • Contribution to proceedings
    The 24th International Biohydrometallurgy Symposium, 20.-23.11.2022, Perth, Australia
    Biotechnology for resource sustainability and circular economy. Book of Abstracts., Australia: CSIRO, 101-101

Permalink: https://www.hzdr.de/publications/Publ-35508
Publ.-Id: 35508


Editorial: Experimental and simulation research on nuclear reactor thermal-hydraulics

Zhang, L.; Pan, L.-M.; Wang, J.; Ding, W.

The researches on nuclear reactor thermal-hydraulics have achieved outstanding progresses in the past decades. In recent years, basic research on multiphase flow dynamics and corresponding measurement technology, as well as preliminary research on Gen IV reactors based on experiments and simulations are attracting more and more attention. However, the inside complicated physics and outside extreme conditions will also bring risks and challenges to the development of nuclear industry.

Keywords: nuclear reactor; thermal; hydraulics; experiments; simulation

Permalink: https://www.hzdr.de/publications/Publ-35507
Publ.-Id: 35507


Precession-driven fluid flows and their ability to drive a dynamo

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

It is well known that a magnetohydrodynamic dynamo, i.e. the
generation of a magnetic field from a flow of an electrically
conductive fluid, takes or took place in the interior of the Sun or
stars as well as in planets and smaller celestial bodies like the
ancient moon or the asteroid Vesta. The ubiquity and diversity of
astrophysical dynamo action and its great importance for formation and
evolution of the objects generating them has motivated related studies
in the laboratory. Currently, a new dynamo experiment is under
construction at Helmholtz-Zentrum Dresden-Rossendorf within the
project DRESDYN (DREsden Sodium facility for DYNamo and
thermohydraulic studies). In that experiment a flow of liquid sodium
will be driven by precession of a cylindrical container. Previous
experiments by Gans (1971) and more recent numerical models
indicate that dynamo action can be expected in the vicinity of the
transition from a laminar flow state to vigorous turbulence if the
system is sufficiently large.

In our contribution we describe the progress in construction of the
experiment and present new results from simulations and accompanying
water experiments in which the precession-driven flow was recorded
with Ultrasonic Doppler Velocimetry (UDV) and Particle Image
Velocimetry (PIV). The analysis of the data by means of the
decomposition into different classes of inertial modes provides an
impression of flow features, which are supposed to be beneficial for
the dynamo, like axisymmetric large scale flow modes, shear layers due
to the modification of the rotational base flow, or the appearance of
intermittent mid-scale vortices. Our focus will be on the influence of
the precession angle on the fluid flow and the dynamo, as well as
on investigating the possibility of increasing the internal flow
amplitude by means of baffles mounted at the end caps of the
container. The main aim is to provide general global characteristics
that are also relevant for a more natural spherical/spheroidal
geometry.

Keywords: Dynamo; DRESDYN

  • Lecture (Conference)
    AGU Fall Meeting, 12.-16.12.2022, Chicago, USA

Permalink: https://www.hzdr.de/publications/Publ-35506
Publ.-Id: 35506


Preparatory simulations and experiments for the DRESDYN precession dynamo

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

Precession represents a possibility to power the early geodynamo or the ancient lunar dynamo.
Precession driven dynamo action was found in simulations in various geometries (sph/cyl/cube).
related experiments by R. Gans yield an amplification of an external field by a factor of three.

Keywords: Dynamo; DRESDYN

  • Poster
    Fluid flow and magnetic field generation in fluids and plasmas - theory and laboratory experiments, 16.-21.10.2022, Leeds, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35505
Publ.-Id: 35505


Boundary conditions in MRI and Dynamo Experiments

Ji, H.; Giesecke, A.

There is no abtract.

Keywords: Dynamo; DRESDYN; MRI; Boundary Conditions

  • Invited lecture (Conferences)
    Frontiers in dynamo theory: from the Earth to the stars, 27.10.2022, Cambridge, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35504
Publ.-Id: 35504


The Fluid Flow in a Precessing Cylinder

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

The planned liquid sodium facility DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies) is a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics. Most ambitious experiment will be a large-scale precession driven dynamo experiment. The experiment is motivated by the idea of a precession-driven flow as a complementary energy source for the geodynamo (Malkus, Science 1968, 160, 3825) or the ancient lunar dynamo (Noir and Cebron 2013, JFM, 737, 412; Dwyer et al. 2011, Nature, 479, 7372; Weiss et al. 2014, Science 346, 1246753). Precessional forcing is of great interest from the experimental point of view, because it represents a natural mechanism which allows an efficient driving of conducting fluid flows on the laboratory scale without making use of propellers or pumps. Currently, we conduct preparative studies that involve numerical simulations and flow measurements at a downscaled model experiment filled with water. These studies aim at the design of the planned large scale experiment and provide parameter island where dynamo action is most likely.

Keywords: Dynamo; DRESDYN

  • Invited lecture (Conferences)
    Frontiers in dynamo theory: from the Earth to the stars, 12.10.2022, Cambridge, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35503
Publ.-Id: 35503


On the Growth Regimes of Hydrogen Bubbles at Microelectrodes

Bashkatov, A.; Hossain, S. S.; Mutschke, G.; Yang, X.; Rox, H.; Weidinger, I. M.; Eckert, K.

The growth of single hydrogen bubbles at micro-electrodes is studied in an acidic electrolyte over a wide range of concentrations and cathodic potentials. New bubble growth regimes have been identified which differ in terms of whether the bubble evolution proceeds in the presence of a monotonic or oscillatory variation in the electric current and a carpet of microbubbles underneath the bubble. Key features such as the growth law of the bubble radius, the dynamics of the microbubble carpet, the onset time of the oscillations and the oscillation frequencies have been characterized as a function of the concentration and electric potential. Furthermore, the system's response to jumps in the cathodic potential has been studied. Based on the analysis of the forces involved and their scaling with the concentration, potential and electric current, a sound hypothesis is formulated regarding the mechanisms underlying the micro-bubble carpet and oscillations.

Keywords: hydrogen; bubble dynamics; water electrolysis; force balance; electric force; marangoni convection; bubble oscillations

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  • Secondary publication expected from 12.10.2023

Permalink: https://www.hzdr.de/publications/Publ-35502
Publ.-Id: 35502


Formation of In-Plane Semiconductor-Metal Contacts in 2D Platinum Telluride by Converting PtTe₂ to Pt₂Te₂

Lasek, K.; Li, J.; Ghorbani Asl, M.; Khatun, S.; Alanwoko, O.; Pathirage, V.; Krasheninnikov, A.; Batzill, M.

Monolayers of platinum tellurides are particularly interesting 2D materials because they exhibit phases with different stoichiometries and electronic properties. Specifically, PtTe₂ is a narrow gap semiconductor while Pt₂Te₂ is a metal. Here we show that the former can be transformed into the latter by reaction with vapor-deposited Pt atoms. Owing to low surface diffusion barriers of Pt ad-atoms, the transformation occurs by nucleating the Pt₂Te₂ phase within the PtTe₂ islands, so that a metal-semiconductor lateral junction is formed. Using scanning tunneling microscopy/spectroscopy, the electronic structure of this lateral junction is studied. A flat band structure is found with the Fermi-level of the metal aligning with the Fermi-level of the intrinsically p-doped PtTe₂ suggesting low contact resistance. This flat band is achieved by an interface dipole that accommodates the ~0.2 eV shift in the work functions of the two materials. First-principles calculations indicate that the origin of the interface dipole is the atomic scale charge redistributions at the heterojunction. The demonstrated compositional phase transformation of a 2D semiconductor into a 2D metal is a promising approach for making in-plane metal contacts that are required for efficient charge injection and is of particular interest for semiconductors with large spin-orbit coupling, like PtTe₂.

Keywords: lateral heterojunctions; two-dimensional materials; platinum Telluride; electronics

Related publications

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  • Secondary publication expected from 18.11.2023

Permalink: https://www.hzdr.de/publications/Publ-35498
Publ.-Id: 35498


Liquid Metal Batteries: Numerical Investigations on Fluid Flow and Mass Transfer

Duczek, C.; Weber, N.; Weier, T.

Charge transfer and mass transport are directly linked with operating batteries. In liquid metal batteries (LMBs) additional flow phenomena heavily influence the cell performance. Those have widely been investigate numerically as well as experimentally. But, concentration gradients due to mass transport were mostly neglected in previous research – especially in the electrolyte. Implementing the prevalent equations into the finite volume solver OpenFOAM and investigating mass transfer overpotentials in the electrolyte independently revealed that they can have a significant influence on the cell performance. So, the interplay between flow phenomena and electrochemical transport should be subject of future investigations.
Na||Zn batteries differ from the previously investigated “classical” LMBs, hence it is important to asses the possible flow phenomena and their area of occurrence.

  • Poster
    Liquid Metal Batteries, 15.-16.11.2022, Cambridge, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35495
Publ.-Id: 35495


Shell engineering in soft alginate-based capsules for culturing liver spheroids

Peng, X.; Janićijević, Ž.; Lemm, S.; Laube, M.; Pietzsch, J.; Bachmann, M.; Baraban, L.

We demonstrate the fluidics-based low-cost methodology to reproducibly generate the alginate and alginate-chitosan microcapsules and apply it to grow human hepatoma (HepG2) spheroids of different dimensions and geometries. Focusing specifically on the composition and thickness of the hydrogel shell, permeability of the microcapsules was selectively tuned. The diffusion of the selected benchmark molecules through the shell has been systematically investigated using both, experiments and simulations, which is essential to ensure efficient mass transfer and/or filtering of the biochemical species. Depending on available space, phenotypically different 3D cell assemblies have been observed inside the capsules, varying in the tightness of cell aggregations and their shapes. Metabolic activity of spheroids in microcapsules was confirmed by tracking the turnover of testosterone to androstenedione with chromatography studies in a metabolic assay. Because of the facile tuning of the shell thickness and permeability, we believe that our system is suitable for studying the formation of cancer spheroids and their functional interaction with the surrounding microenvironment.

Permalink: https://www.hzdr.de/publications/Publ-35494
Publ.-Id: 35494


Energiespeicherung mit Flüssigmetallen und Salzschmelzen

Weier, T.; Horstmann, G. M.; Landgraf, S.; Personnettaz, P.; Stefani, F.; Weber, N.

Der zunehmende Anteil fluktuierender Stromerzeuger erfordert den Ausbau der Speicherkapazität, wenn die Elektrizitätsversorgung weitgehend nachfrageorientiert geschehen soll. Der Vortrag geht auf verschiedene Aspekte der Speicherproblematik ein und legt den Schwerpunkt dabei auf Flüssigmetall- und Salzschmelzenbatterien.

Keywords: Flüssigmetallbatterie; Salzschmelzenbatterie

  • Invited lecture (Conferences)
    Dresdner Seniorenakademie Wissenschaft und Kunst, 01.10.2022-31.03.2023, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35493
Publ.-Id: 35493


Transport Phenomena in Liquid Metal Batteries

Weier, T.; Benard, S.; Horstmann, G. M.; Kim, C.; Klopper, T.; Kubeil, C.; Landgraf, S.; Personnettaz, P.; Stefani, F.; Weber, N.

There is a close and multifaceted relation between fluid dynamics and
the charge/discharge behavior of liquid metal batteries. The talk will
give an overview of experimental and - to a minor extend - numerical
work on instabilities that might be relevant for the operational
safety of large cells and on flows that are able influence mass
transport overvoltages, like solutal and thermal convection.

Keywords: liquid metal batteries; AMTEC; solutal convection; waves

  • Invited lecture (Conferences)
    Liquid Metal Batteries, 15.-16.11.2022, Cambridge, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-35492
Publ.-Id: 35492


Using ultrasound for characterizing overflowing froth

Knüpfer, L.; Emmerich, H.; Büttner, L.; Czarske, J.; Eckert, K.; Heitkam, S.

Flotation is a separation process in which hydrophobic particles inside a liquid bath
attach to uprising bubbles, which subsequently form a froth layer on the liquid
surface. This froth phase, which consist of foam with particles, has a large impact on
the transport of separated materials and therefore the overall process efficiency.
Despite the importance for process control, a notable lack of suitable techniques for
on-line characterization of the froth’s properties such as the liquid fraction or particle
content can be found. An potential approach to gain information on the different
phase fractions in froth is the application of low-frequency ultrasound measurement
techniques. In this contribution an overflowing froth containing varying mass fractions
of Quartz particles and liquid is analyzed using combined optical and ultrasonic
measurements. The measured intensity of the ultrasonic reflections sent from above
the froth’s surface correlate to the fraction of solids inside the froth (Figure 1).
Therefore it is shown, that current optical froth characterization techniques can be
improved by incorporating ultrasonic measurements, which can be seen as a first
step towards advanced process control in industrial flotation processes.

Keywords: froth; flotation; ultrasound

  • Poster
    4th International Symposium on Multiscale Multiphase Process Engineering (MMPE), 25.-28.09.2022, Berlin, Deutschland
  • Poster
    Tagung Aufbereitung und Recycling, 10.-11.11.2022, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35489
Publ.-Id: 35489


A particle-center-averaged Euler-Euler model for bubbly flow simulations

Lyu, H.; Lucas, D.; Rzehak, R.; Schlegel, F.

An inconsistency exists in bubble force models used in the standard Euler-Euler simulations. The bubble force models are typically developed by assuming that the forces act on the bubbles' centers of mass. However, in the standard Euler-Euler model, each bubble force is a function of the local gas volume fraction because the phase-averaging method is used. This inconsistency can lead to gas over-concentration in the center or near the wall of a channel when the bubble diameter is larger than the computational cell size. Besides, a mesh-independent solution may not exist in such cases. In addition, the bubble dimension is not fully considered in the standard Euler-Euler model.
In the present study, a particle-center-averaging method is used to represent the bubble forces as forces that act on the bubbles' centers of mass. A particle-center-averaged Euler-Euler approach for bubbly flow simulations is developed by combining the particle-center-averaged Euler-Euler framework with a Gaussian convolution method. The convolution method is used to convert the phase-averaged and the particle-center-averaged quantities. The test results illustrate that the particle-center-averaging method alleviates the over-prediction of the gas volume fraction peak in the channel center and provides a mesh-independent solution. In the particle-center-averaged Euler-Euler model, the bubble dimension is fully considered and bubble deformation can be considered by using anisotropic diffusion in quantities conversion.

Keywords: CFD; bubbly flow; Euler-Euler

  • Lecture (Conference)
    International Conference on Numerical Methods in Multiphase Flows 4, 28.-30.09.2022, Venice, Italy

Permalink: https://www.hzdr.de/publications/Publ-35488
Publ.-Id: 35488


Future Liquid Metal Battery Projects at HZDR

Horstmann, G. M.; Weber, N.; Duczek, C.; Sarma, M.; Weier, T.

Since 2011, fluid dynamics research in liquid metal batteries has been pursued at HZDR, with multiple flow instabilities identified as critical for safe and efficient operation. This is still an ongoing process from which new research topics are constantly emerging. In the poster presentation, I will introduce two future research projects closely connected to liquid metal batteries: firstly, a new model experiment to study the metal pad roll instability, which is currently under preparation in the framework of a recently approved DFG project. Secondly, we are planning another project on the investigation of different solutal- and electrocapillary flow phenomena, hitherto widely disregarded in the context of liquid metal batteries.

  • Poster
    Liquid Metal Batteries, 15.-16.11.2022, Cambridge, United Kingdom

Permalink: https://www.hzdr.de/publications/Publ-35487
Publ.-Id: 35487


Advancements in the fabrication and characterization of actinide targets for superheavy element production

Düllmann, C. E.; Artes, E.; Dragoun, A.; Haas, R.; Jäger, E.; Kindler, B.; Lommel, B.; Mangold, K. ‑.; Meyer, C. ‑.; Mokry, C.; Munnik, F.; Rapps, M.; Renisch, D.; Runke, J.; Seibert, A.; Stöckl, M.; Thörle‑Pospiech, P.; Trautmann, C.; Trautmann, N.; Yakushev, A.

The heaviest elements can exclusively be produced in actinide-target based nuclear fusion reactions with intense heavy-ion beams. Ever more powerful accelerators deliver beams of continuously increasing intensity, which brings targets of current technology to their limits and beyond. We motivate efforts to produce targets with improved properties, which calls for a better understanding of targets produced by molecular plating, the current standard method. Complementary analytical methods will help shedding more light on their chemical and physical changes in the beam. Special emphasis is devoted to the aspect of the optimum target thickness and the choice of the backing material.

Keywords: Superheavy elements; Actinide targets; Heavy-ion beam; Target backing; Molecular plating; Thin film analytics

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35486
Publ.-Id: 35486


Theory on Tidally Forced Planetary Waves in the Tachocline of Solar-like Stars

Horstmann, G. M.; Mamatsashvili, G.; Giesecke, A.; Stefani, F.

We present a new shallow-water formulation of forced magnetohydrodynamic Ross-
by waves originating in the tachocline of solar-like stars. As a novelty to former descriptions,
we add an external tidal potential to the equations and further include a linear damping law,
allowing us to study wave motions driven by arbitrary tidal forces. The model is applied to the
specific case of our sun, where we consider the action of the tidally dominant planet Jupiter.
We present an explicit analytic solution to this problem, which we finally use to estimate
characteristic responding wave amplitudes.

  • Lecture (Conference)
    5th Dynamo Thinkshop, 26.-28.06.2022, Freiburg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35485
Publ.-Id: 35485


Electrolysis in Reduced Gravitational Environments: Current Research Perspectives and Future Applications

Akay, Ö.; Bashkatov, A.; Coy, E.; Eckert, K.; Einarsrud, K. E.; Friedrich, A.; Loos, S.; Röntzsch, L.; Mutschke, G.; Symes, M. D.; Yang, X.; Brinkert, K.

Electrochemical energy conversion technologies play a crucial role in space missions,
for example, in the Environmental Control and Life Support System (ECLSS) on the
International Space Station (ISS). They are also vitally important for future long-term
space travel for oxygen, fuel and chemical production, where a re-supply of resources
from Earth is not possible. Here, we provide an overview of currently existing
electrolytic energy conversion technologies for space applications such as proton
exchange membrane (PEM) and alkaline electrolyzer systems. We discuss the
governing interfacial processes in these devices influenced by reduced gravitation and
provide an outlook on future applications of (photo)-electrolysis systems in, e.g., in-
situ resource utilization (ISRU) technologies. A perspective of computational modelling
to predict the impact of the reduced gravitational environment on governing
electrochemical processes is also discussed and experimental suggestions to better
understand efficiency-impacting processes such as gas bubble formation and
detachment in reduced gravitational environments are outlined

Keywords: Electrolysis; Micro-Gravity; hydrogen production; energy conversion; computational methods

Permalink: https://www.hzdr.de/publications/Publ-35484
Publ.-Id: 35484


Magnetic properties of red diamonds produced by high-temperature electron irradiation

Barzola-Quiquia, J.; Osmic, E.; Lühmann, T.; Böhlmann, W.; Meijer, J.; Knolle, W.; Abel, B.

The magnetization of crystalline red diamond bulk samples were investigated in the temperature range between 2 K and 125 K and with the applied maximal magnetic field of ±7 T. The investigated diamond samples are of Type Ib with a nitrogen content less than 200 ppm. Diamonds without any treatment display a yellow color and were transformed to red color after irradiation with 10 MeV electrons at T = 900 °C, in vacuum, owing to the formation of nitrogen-vacancy centers. Field dependent magnetization m(H) measurements for temperatures T ≲ 10 K show unusual hysteresis loops, which we interpret as consequence of the superposition of coexisting superconducting and paramagnetic regions present in the sample. Temperature dependence of the magnetization m(T) measured in the zero field and field cooled modus shows a paramagnetic behavior accompanied with an irreversibility for T ≲ 13 K, while at higher temperatures shows a diamagnetic behavior which is similar to undoped diamond. Coexistence of superconductivity and paramagnetism is established because both phenomena exist in the same temperature range and fits done to the m(H) using an equation based upon Bean model, support our conclusion. Room temperature confocal photoluminescence measurements were done on both yellow and red diamond, showing that in the red diamond the amount of neutral NV° and negative charged nitrogen-vacancy centers NV° have been significantly created. The transformation process from yellow to red diamond has mainly caused the alteration of the superparamagnetic regions into paramagnetic, while the superconducting contribution of the sample was less affected, according to the parameters obtained after we fitted the field dependent magnetization results.

Permalink: https://www.hzdr.de/publications/Publ-35482
Publ.-Id: 35482


High-Pressure and High-Temperature Chemistry of Phosphorus and Nitrogen: Synthesis and Characterization of α- and γ‑P3N5

Ceppatelli, M.; Scelta, D.; Serrano-Ruiz, M.; Dziubek, K.; Izquierdo-Ruiz, F.; Manuel Recio, J.; Garbarino, G.; Svitlyk, V.; Mezouar, M.; Peruzzini, M.; Bini, R.

The direct chemical reactivity between phosphorus and nitrogen was induced under high-pressure and high-temperature conditions (9.1 GPa and 2000−2500 K), generated by a laser heated diamond anvil cell and studied by synchrotron X-ray diffraction, Raman spectroscopy, and DFT calculations. α-P3N5 and γ-P3N5 were identified as reaction products. The structural parameters and vibrational frequencies of γ-P3N5 were characterized as a function of pressure during room-temperature compression and decompression to ambient conditions, determining the equation of state of the material up to 32.6 GPa and providing insight about the lattice dynamics of the unit cell during compression, which essentially proceeds through the rotation of the PN5 square pyramids and the distortion of the PN4 tetrahedra. Although the identification of α-P3N5 demonstrates for the first time the direct synthesis of this compound from the elements, its detection in the outer regions of the laser-heated area suggests α-P3N5 as an intermediate step in the progressive nitridation of phosphorus toward the formation of γ-P3N5 with increasing coordination number of P by N from 4 to 5. No evidence of a higher pressure phase transition was observed, excluding the existence of predicted structures containing octahedrally hexacoordinated P atoms in the investigated pressure range.

Permalink: https://www.hzdr.de/publications/Publ-35481
Publ.-Id: 35481


Effect of Magnetic Impurities on Superconductivity in LaH10

Semenok, D. V.; Troyan, I. A.; Sadakov, A. V.; Zhou, D.; Galasso, M.; Kvashnin, A. G.; Ivanova, A. G.; Kruglov, I. A.; Bykov, A. A.; Terent'Ev, K. Y.; Cherepakhin, A. V.; Sobolevskiy, O. A.; Pervakov, K. S.; Seregin, A. Y.; Helm, T.; Förster, T.; Grockowiak, A. D.; Tozer, S. W.; Nakamoto, Y.; Shimizu, K.; Pudalov, V. M.; Lyubutin, I. S.; Oganov, A. R.

Polyhydrides are a novel class of superconducting materials with extremely high critical parameters, which is very promising for sensor applications.
On the other hand, a complete experimental study of the best so far known superconductor, lanthanum superhydride LaH10, encounters a serious complication because of the large upper critical magnetic field Hc2(0), exceeding 120–160 T. It is found that partial replacement of La atoms by magnetic Nd atoms results in significant suppression of superconductivity in LaH10: each at% of Nd causes a decrease in Tc by 10–11 K, helping to control the critical parameters of this compound. Strong pulsed magnetic fields up to 68 T are used to study the Hall effect, magnetoresistance, and the magnetic phase diagram of ternary metal polyhydrides for the first time. Surprisingly, (La,Nd)H10 demonstrates completely linear Hc2(T) ∝ |T – Tc|, which calls into question the applicability of the Werthamer–Helfand–Hohenberg model for polyhydrides. The suppression of superconductivity in LaH10 by magnetic Nd atoms and the robustness of Tc with respect to nonmagnetic impurities (e.g., Y, Al, C) under Anderson’s theorem gives new experimental evidence of the isotropic (s-wave) character of conventional electron–phonon pairing in lanthanum decahydride.

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Permalink: https://www.hzdr.de/publications/Publ-35480
Publ.-Id: 35480


Micrometer thick Sm-Co films for applications on flexible systems

Tzanis, A.; Koutsokostas, N.; Helm, T.; Kollia, C.; Speliotis, T.

In the industry 4.0 eco-system, flexible electronic devices bear a huge potential for a broad range of applications due to their diverse properties, such as high stretchability, biocompatibility, portability, light weight, and low costs. In this work, Cobalt-samarium permanent magnetic thin films on flexible polyimide substrate are studied. The influence of the sputter deposition pressure on the structural, morphological, and magnetic properties is analyzed. A method for growing flexible magnetic films is proposed by achieving a maximum coercivity of 13.86 kOe and an energy product of 16.9 MGOe. These results lay the foundations for the design and fabrication of flexible magnetic devices.

Permalink: https://www.hzdr.de/publications/Publ-35479
Publ.-Id: 35479


Static magnetic and ESR spectroscopic properties of the dimer-chain antiferromagnet BiCoPO5

Iakovleva, M.; Petersen, T.; Alfonsov, A.; Skourski, Y.; Grafe, H.-J.; Vavilova, E.; Nath, R.; Hozoi, L.; Kataev, V.

We report a comprehensive study of the static susceptibility, high-field magnetization and highfrequency/high-magnetic field electron spin resonance (HF-ESR) spectroscopy of polycrystalline samples of the bismuth cobalt oxyphosphate BiCoPO5. This compound features a peculiar spin system that can be considered as antiferromagnetic (AFM) chains built of pairs of ferromagnetically coupled Co spins and interconnected in all three spatial directions. It was previously shown that BiCoPO5 orders antiferromagnetically at TN ≈ 10 K and this order can be continuously suppressed by magnetic field towards the critical value μ0Hc ≈ 15 T. In our experiments we find strongly enhanced magnetic moments and spectroscopic g factors as compared to the expected spin-only values, suggesting a strong contribution of orbital magnetism for the Co2+ ions. This is quantitatively confirmed by ab initio quantum chemical calculations.Within the AFM ordered phase, we observe a distinct field-induced magnetic phase transition. Its critical field rises to ∼6 T at T << TN. The HF-ESR spectra recorded at T << TN are very rich comprising up to six resonance modes possibly of the multimagnonic nature that soften towards the critical region around 6 T. Interestingly, we find that the Co moments are not yet fully polarized at Hc which supports a theoretical proposal identifying Hc as the quantum critical point for the transition of the spin system in BiCoPO5 to the quantum disordered state at stronger fields.

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Permalink: https://www.hzdr.de/publications/Publ-35478
Publ.-Id: 35478


Nanoscale magnetic bubbles in Nd2Fe14B at room temperature

He, Y.; Helm, T.; Soldatov, I.; Schneider, S.; Pohl, D.; Srivastava, A. K.; Sharma, A. K.; Kroder, J.; Schnelle, W.; Schaefer, R.; Rellinghaus, B.; Fecher, G. H.; Parkin, S. S. P.; Felser, C.

The increasing demand for computer data storage with a higher recording density can be addressed by using smaller magnetic objects, such as bubble domains. Small bubbles predominantly require a strong saturation magnetization combined with a large magnetocrystalline anisotropy to resist self-demagnetization. These conditions are well satisfied for highly anisotropic materials. Here, we study the domain structure of thin Nd2Fe14B lamellae. Magnetic bubbles with a minimum diameter of 74 nm were observed at room temperature, approaching even the range of magnetic skyrmions. The stripe domain width and the bubble size are both thickness dependent. Furthermore, a kind of bubble was observed below the spin-reorientation transition temperature that combine bubbles with opposite helicity. In this paper, we reveal Nd2Fe14B to be a good candidate for a high-density magnetic bubble-based memory.

Permalink: https://www.hzdr.de/publications/Publ-35477
Publ.-Id: 35477


Deformed spin-1/2 square lattice in antiferromagnetic NaZnVOPO4(HPO4)

Guchhait, S.; Ambika, D. V.; Ging, Q.-P.; Uhlarz, M.; Furukawa, Y.; Tsirlin, A. A.; Nath, R.

We report the structural and magnetic properties of a new spin-1/2 antiferromagnet NaZnVOPO4(HPO4) studied via x-ray diffraction, magnetic susceptibility, high-field magnetization, specific heat, and 31P nuclear magnetic resonance (NMR) measurements, as well as density-functional band-structure calculations. While thermodynamic properties of this compound are well described by the J1-J2 square-lattice model, ab initio calculations suggest a significant deformation of the spin lattice. From fits to the magnetic susceptibility we determine the averaged nearest-neighbor and second-neighbor exchange couplings of J1 ≃ −1.3 K and J2 ≃ 5.6 K, respectively, resulting in the effective frustration ratio α = J2/J1 ≃ −4.3 that implies columnar antiferromagnetic order as the ground state. Experimental saturation field of 15.3 T is consistent with these estimates if 20 % spatial anisotropy in J1 is taken into account. Specific heat data signal the onset of a magnetic long-range order at TN ≃ 2.1 K, which is further supported by a sharp peak in the NMR spin-lattice relaxation rate. The NMR spectra mark the superposition of two P lines due to two nonequivalent P sites where the broad line with the strong hyperfine coupling and short T1 is identified as the P(1) site located within the magnetic planes, while the narrow line with the weak hyperfine coupling and long T1 is designated as the P(2) site located between the planes.

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Permalink: https://www.hzdr.de/publications/Publ-35476
Publ.-Id: 35476


Ce and Dy substitutions in Nd2Fe14B: Site-specific magnetic anisotropy from first principles

Boust, J.; Aubert, A.; Fayyazi, B.; Skokov, K. P.; Skourski, Y.; Gutfleisch, O.; Pourovskii, L. V.

A first-principles approach combining density-functional and dynamical mean-field theories in conjunction with a quasiatomic approximation for the strongly localized 4 f shell is applied to Nd2Fe14B-based hard magnets to evaluate crystal-field and exchange-field parameters at rare-earth sites and their corresponding single-ion contribution to the magnetic anisotropy. In pure Nd2Fe14B, our calculations reproduce the easy-cone to easy-axis transition; theoretical magnetization curves agree quantitatively with experiment. Our study reveals that the rare-earth single-ion anisotropy in the 2-14-1 structure is strongly site dependent, with the g rare-earth site exhibiting a larger value. In particular, we predict that increased f- and g-site occupancy of R = Ce and Dy, respectively, leads to an increase of the magnetic anisotropy of the corresponding (Nd, R)2Fe14B-substituted
compounds.

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Permalink: https://www.hzdr.de/publications/Publ-35475
Publ.-Id: 35475


Martensitic fcc-hcp transformation pathway in solid krypton and xenon and its effect on their equations of state

Rosa, A. D.; Dewaele, A.; Garbarino, G.; Svitlyk, V.; Morard, G.; de Angelis, F.; Krstulovic, M.; Briggs, R.; Irifune, T.; Mathon, O.; Bouhifd, M. A.

The martensitic transformation is a fundamental physical phenomenon at the origin of important industrial applications. However, the underlying microscopic mechanism, which is of critical importance to explain the outstanding mechanical properties of martensitic materials, is still not fully understood. This is because for most martensitic materials the transformation is a fast process that makes in situ studies extremely challenging. Noble solids krypton and xenon undergo a progressive pressure-induced face-centered cubic (fcc) to hexagonal close-packed (hcp) martensitic transition with a very wide coexistence domain. Here, we took advantage of this unique feature to study the detailed transformation progress at the atomic level by employing in situ x-ray diffraction and absorption spectroscopy.We evidenced a four-stage pathway and suggest that the lattice mismatch between the fcc and hcp forms plays a key role in the generation of strain.We also determined precisely the effect of the transformation on the compression behavior of these materials.

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Permalink: https://www.hzdr.de/publications/Publ-35474
Publ.-Id: 35474


Data publication: Variability of radionuclide sorption efficiency on muscovite cleavage planes

Schabernack, J.; Faria Oliveira, A.; Heine, T.; Fischer, C.

Dataset of outputs produced by DFT and KMC simulation described in the associated paper.

KMC data:

  • Adsorption distribution (Ad_mov_01.pdb to Ad_mov_10.pdb)
  • Surface nanotopography (surface_1.pdb)
  • Statistic files for dissolution and adsorption (Ad_num.txt, Ad_Sites_Stat.txt, sites_stat_1.txt, diss_num.txt)
  • Input files (testmusc9_KMC_Mica_1_6.inp, EuAdsorption_2_0.inp)
  • Excel files for adsorption evaluation (Adsorption_Results_File), input energy calculation (EnergyParameterCalc) and site sorting (Site-INDL-Sorting)

DFT data:

  • Excel file adsorption energy barriers (Adsorption_Energy_Barrier)
  • Site adsorption energies (.cvs files)
  • Site adsorption trajectories (.xyz files)

Excel file for the estimation of the desorption factor

Keywords: Radionuclide Sorption; Kinetic Monte Carlo; Density Functional Theory; Muscovite; Europium

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Permalink: https://www.hzdr.de/publications/Publ-35469
Publ.-Id: 35469


Resolving surface chemical states of p-GaN:Cs photocathodes by XPS analysis

Schaber, J.; Xiang, R.; Arnold, A.; Teichert, J.; Ryzhov, A.; Murcek, P.; Zwartek, P.; Ma, S.; Gatzmaga, S.

An x-ray photoelectron spectrometer (XPS) is used in the HZDR photocathode lab to understand the surface states of GaN photocathodes during its cleaning, cesium activation and degradation. The XPS probes the electronic structure of the p-doped GaN photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels and auger photoemission peaks of Ga, N, O, C and Cs are monitored.

Keywords: GaN photocathode; quantum efficiency; cesium activation; photocathode degradation; organic - cesium

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  • Open Access Logo Invited lecture (Conferences)
    EWPAA 2022: European workshop on photocathodes for particle accelerator applications, 20.-22.09.2022, Mailand, Italien

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Permalink: https://www.hzdr.de/publications/Publ-35467
Publ.-Id: 35467


Effect of Medium on Fundamental Interactions in Gravity and Condensed Matter

Zhuk, O.; Shulga, V.

Recently, it was shown that the gravitational field undergoes exponential cutoff at large cosmological scales due to the presence of background matter. In this article, we demonstrate that there is a close mathematical analogy between this effect and the behavior of the magnetic field induced by a solenoid placed in a superconductor.

Permalink: https://www.hzdr.de/publications/Publ-35466
Publ.-Id: 35466


Resolving surface chemical states of p-GaN:Cs photocathodes by XPS analysis

Schaber, J.; Xiang, R.; Teichert, J.; Murcek, P.; Zwartek, P.; Arnold, A.; Ryzhov, A.; Ma, S.

An x-ray photoelectron spectrometer (XPS) is used in the HZDR photocathode lab to understand the surface states of GaN photocathodes during its cleaning, cesium activation and degradation. The XPS probes the electronic structure of the p-doped GaN photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels and auger photoemission peaks of Ga, N, O, C and Cs are monitored.
In our experiments, p-GaN on sapphire samples were cleaned with 99 % ethanol in an ultrasonic bath, followed by a thermal cleaning in a vacuum with the intention to remove carbon and oxygen contaminations on the p-GaN surface. Although still some carbon remained on the surface, the p-GaN was successfully activated by the deposition of a thin layer of cesium. Quantum efficiencies (QE) of
3 - 9 % were achieved. XPS photoemission spectra show a shift towards higher binding energies for the photoemission peaks, which is caused by a new component, so-called organic – cesium.
During the storage under ultra – high vacuum, the GaN:Cs photocathodes were measured from time to time in the photocurrent and by XPS. We found a shift of 0.35 eV towards lower binding energies, which is related to the formation of the organic – cesium islands. This island growth is assumed to be in close correlation to the photocathode degradation.
The p-GaN:Cs photocathodes showed a big QE loss after XPS analysis and therefore we investigated the potential damage from x-ray irradiation. The long-time irradiation experiments show that the x-ray damage has a high influence on the cesium component and the degradation of the p-GaN:Cs photocathode.

Keywords: GaN photocathode; photocathode degradation; cesium deposition

Related publications

  • Open Access Logo Poster
    International Workshop on Nitride Semiconductors (IWN), 09.-14.10.2022, Berlin, Deutschland

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Permalink: https://www.hzdr.de/publications/Publ-35465
Publ.-Id: 35465


Cleaning influence on p-GaN surfaces for photocathodes with negative electron affinity

Schaber, J.; Xiang, R.; Arnold, A.; Murcek, P.; Zwartek, P.; Ryzhov, A.; Ma, S.; Gatzmaga, S.

Achieving an atomically clean surface is an important step to improving the quality of semiconductor photocathodes, but it is a challenging requirement for surface treatment [1]. In order to understand the surface during the cleaning, the cesium deposition, and the storage of the photocathode, the use of an x-ray photoelectron spectrometer (XPS) is needed. The XPS probes the electronic structure of the p-doped gallium nitride (GaN) photocathode after each step of the preparation process. Using energies between 1200-0 eV the core levels of Ga, N, O, C and Cs are monitored.

Keywords: GaN photocathode; cesium deposition; quantum efficiency; photocathode degradation

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  • Open Access Logo Poster
    ECASIA 2022-European Conference on Applications of Surface and Interface Analysis, 30.05.-03.06.2022, Limerick, Irland

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Permalink: https://www.hzdr.de/publications/Publ-35463
Publ.-Id: 35463


New Perspectives for Warm Dense Matter Theory: from Quantum Monte Carlo to Temperature Diagnostics

Dornheim, T.

Warm dense matter (WDM) an extreme state that is characterized by extreme densities and temperatures has emerged as
one of the most active frontiers in plasma physics and material science. In nature, WDM occurs in astrophysical objects
such as giant planet interiors and brown dwarfs. In addition, WDM is highly important for cutting-edge technological
applications such as inertial confinement fusion and the discovery of novel materials.
In the laboratory, WDM is studied experimentally in large facilities around the globe, and new techniques have facilitated
unprecedented insights into exciting phenomena like the formation of nanodiamonds at planetary interior conditions [1].
Yet, the interpretation of these experiments requires a reliable diagnostics based on accurate theoretical modeling, which is
a notoriously difficult task [2].
In this talk, I give an overview of recent developments in this field [3,4,5], which will allow for a rigorous treatment of the
intricate interplay of Coulomb coupling with thermal excitations and quantum degeneracy effects based on approximation-
free quantum Monte Carlo (QMC) simulations. Finally, I will present a new idea to extract the exact temperature [6] and
other material properties [7] from an X-ray Thomson scattering experiment without any models or simulations.
[1] D. Kraus et al., Nature Astronomy 1, 606-611 (2017)
[2] M. Bonitz et al., Physics of Plasmas 27, 042710 (2020)
[3] T. Dornheim et al., Physics Reports 744, 1-86 (2018)
[4] T. Dornheim et al., Physical Review Letters 121, 255001 (2018)
[5] M. Böhme et al., Physical Review Letters 129, 066402 (2022)
[6] T. Dornheim et al., arXiv:2206.12805
[7] T. Dornheim et al., arXiv:2209.02254

  • Lecture (others)
    Physikseminar der Universität Rostock, 15.11.2022, Rostock, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-35462
Publ.-Id: 35462


Crystal Structures of Ce(IV) Nitrates with Bis(2-pyrrolidone) Linker Molecules Deposited from Aqueous Solutions with Different HNO3 Concentrations

Ono, R.; Kazama, H.; März, J.; Tsushima, S.; Takao, K.

Previously, we found that tetravalent actinides (An4+, An = Th, U, Np) in HNO3(aq) commonly afford sparingly soluble salts of [An(NO3)6]- with anhydrous H+ countercations stabilized by hydrogenbonding with bis(2-pyrrolidone) linker molecules selected appropriately. In contrast, this is not the case for Zr4+ in Group IV probably due to difference in the ionic radius. This fact motivated us to know how Ce(IV) behaves under the same condition. As a result, we have found that, after loading bis(2-pyrrolidone) linker molecule having trans-1,4-cyclohexyl bridging moiety (L), Ce(IV) in HNO3(aq) exclusively provides one of different crystalline phases, (HL)2[Ce(NO3)6] or [Ce2(mu-O)(NO3)6(L)2]n 2D MOF, depending on [HNO3]. The former has been obtained at [HNO3] = 4.70-9.00 M, and is isomorphous with the analogous (HL)2[An(NO3)6] we reported previously. In contrast, deposition of the latter phase at the lower [HNO3] conditions (1.00-4.30 M) demonstrates that hydrolysis and oxolation of Ce4+ proceeds even below pH 0 to provide a [Ce-O-Ce]6+ unit included in this compound. These different Ce(IV) phases are exchangeable each other under soaking in HNO3(aq), implying those chemical equilibria of dissolution/deposition of these crystalline phases, hydrolysis and oxolation of Ce4+, and its complexation with NO3- occur in parallel. Indeed, such coordination chemistry of Ce(IV) in HNO3(aq) was well corroborated by 17O NMR, Raman, and IR spectroscopy.

Permalink: https://www.hzdr.de/publications/Publ-35459
Publ.-Id: 35459


Data publication: One chelator for imaging and therapy with lutetium-177 and actinium-225

Cieslik, P.; Kubeil, M.; Zarschler, K.; Ullrich, M.; Brandt, F.; Anger, K.; Wadepohl, H.; Kopka, K.; Bachmann, M.; Pietzsch, J.; Stephan, H.; Comba, P.

Bei diesem Datensatz handelt es sich um analytische Charakterisierungen (ESI-MS, HR-MS, MALDI-TOF-MS) und Radiomarkierungsuntersuchungen zum nonadentaten Bispidin-Chelator bzw. Bispidin-TATE Konjugat mit Lutetium-177, Indium-111 und/oder Actinium-225.

1H, 13 C NMR and crystallographic data stored by collaboration partner (Heidelberg University)

Keywords: bispidine; trivalent metal ions; radionuclide theranostics; somatostatin analogue; actinium; lutetium

Related publications

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Permalink: https://www.hzdr.de/publications/Publ-35458
Publ.-Id: 35458


Effects of static magnetic fields in antiferromagnetic ring-shaped spin chains

Borysenko, Y.; Sheka, D.; Faßbender, J.; van den Brink, J.; Makarov, D.; Pylypovskyi, O.

While antiferromagnets with the easy axis of anisotropy are considered to be robust against external magnetic fields of a moderate strength, strong-field-driven spin reorientations provide an insight into subtle properties of the material usually hidden by the high symmetry of the ground state. Here, we address theoretically the effects of curvature in the curvilinear antiferromagnetic achiral anisotropic ring-shaped spin chains in strong magnetic fields. We identify the geometry-driven helimagnetic phase transition above the spin-flop field between the vortex and onion states. The spin-flop transition is of the first- or second-order depending on the ring curvature, which is influenced by the geometry-induced Dzyaloshinskii–Moriya interaction. Inhomogeneity of the Néel vector distribution in spin-flop phase generates weakly ferromagnetic response, which lies in the plane perpendicular to the applied magnetic field. Our findings provide an understanding of complex responses of curvilinear antiferromagnets on magnetic fields and allow further experimental study of geometrical effects relying on spin-chain-based nanomagnets.

Keywords: antiferromagnetism; spin chains; ring

  • Lecture (Conference)
    DPG Meeting of the Condensed Matter Section: Magnetism Division, 04.-09.09.2022, Regensburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-35457
Publ.-Id: 35457


Uncertainty quantification for neural network models

Schmerler, S.

Uncertainty quantification for neural network models

Keywords: machine learning; uncertainty

  • Open Access Logo Lecture (others) (Online presentation)
    ML at HZDR symposium, 06.12.2021, Dresden, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35456
Publ.-Id: 35456


Uncertainty quantification in machine learning applications

Schmerler, S.; Starke, S.; Steinbach, P.; M. K. Siddiqui, Q.; Fiedler, L.; Cangi, A.; Kulkarni, S. H.

We strive to popularize the usage of uncertainty quantification methods in machine learning through publications and application in various projects covering diverse fields from regression and classification to instance segmentation. In addition, we employ domain shift detection techniques to tackle population-level out-of-distribution scenarios. In all cases, the goal is to assess model prediction validity given unseen test data.

Keywords: machine learning; uncertainty

  • Open Access Logo Poster
    Helmholtz AI Evaluation 2022, 05.-07.10.2022, München, Germany

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Permalink: https://www.hzdr.de/publications/Publ-35454
Publ.-Id: 35454


Aqueous vs. high-temperature syntheses of crystalline zirconia (ZrO2) containing Cm3+

Huittinen, N. M.; Opitz, L.; Eibl, M.

The zirconia (ZrO2) crystal structure can incorporate a variety of metal cations with differing oxidation states up to high dopant loadings, which is why the material has been considered as a potential host phase for the immobilization of especially actinide elements present in specific high-level waste streams. Furthermore, zirconia is the main corrosion product of the Zircaloy cladding material surrounding nuclear fuel rods. The corrosion of Zircaloy and subsequent formation of zirconia already occurs during reactor operation and is expected to proceed during long-term disposal of the spent nuclear fuel (SNF) assemblies. Thus, during final storage, zirconia may play an important role as the first retention barrier for released radionuclides. ZrO2 is monoclinic phase at ambient conditions, and transforms into tetragonal and cubic phases at high temperatures of around 1200 °C and 2370 °C, respectively. However, particle size effects, the incorporation of foreign ions such as the actinides, as well as high radiation fields are known to also influence the stability fields of the polymorphs.
In the present work, the incorporation of the trivalent actinide curium in the pristine, monoclinic ZrO2 structure has been investigated following synthesis (i) in aqueous solution at 80°C for several weeks [1], and (ii) at high temperatures (1000°C, 5h) [2]. The evolution of the ZrO2 crystal structure during synthesis was analyzed with powder x-ray diffraction, while the Cm-environment was studied via luminescence spectroscopy. For the syntheses, a hydrous zirconia phase was precipitated in the presence of Cm from alkaline NaCl solutions at pH 12. The precipitate was thereafter either re-suspended in 0.5 M NaCl at pH 5 or pH 12 and hydrothermally treated at 80°C for up to 117 days, or calcined at 1000°C for 5 hours. The hydrothermal samples at pH 12, show crystallization of the amorphous ZrO(OH)2 phase to a mixture of monoclinic and tetragonal ZrO2 after 16 d at 80°C. In contrast, the samples at pH 5 show no crystallinity even after 32 days. Luminescence emission spectra indicate the presence of two Cm-environments in the amorphous precipitate. With increasing crystallinity, a bathochromic shift and a narrowing of the emission spectra can be seen. The shift is untypically large, resulting in emission peak maxima at around 650 nm for crystalline ZrO2. A similar, equally pronounced shift is obtained for Cm incorporated into the monoclinic ZrO2 structure following calcination. Therefore, the actinide speciation seems to be identical in the solid phases obtained with the two different synthesis methods, at least for the fully crystalline solids. These combined results imply that actinides are incorporated into the crystal structure of ZrO2, even at low concentrations where no structural transformations take place, which in turn speaks for zirconia as a good retention barrier for released trivalent actinides from the SNF matrix.

  • Lecture (Conference)
    Jahrestagung der Fachgruppe Nuklearchemie 2022, 04.-06.10.2022, Bergisch Gladbach, Germany

Permalink: https://www.hzdr.de/publications/Publ-35453
Publ.-Id: 35453


Editorial for "Decreased cerebral blood flow in non-hospitalized adults who self-isolated due to COVID-19"

Petr, J.; Keil, V. C.

Neurological manifestations are well-recognized in patients with COVID-19, with inflammation and damage to the brain vasculature being the common neuroimaging findings (1). A considerable number of individuals continue to experience – or even develop secondarily – neurological symptoms such as cognitive impairment (2.2% of individuals after SARS-CoV-2 infection) and fatigue or mood swings (3.2%) lasting up to several months after the recovery from COVID-19 (2). This condition is commonly referred to as “long COVID” or “post-COVID condition,” and it creates a substantial burden for social networks, health care, and economics beyond the personal suffering of the patient (3). Understanding the pathophysiological mechanisms of the condition plays a pivotal role in the quest for treatment approaches. Neuroimaging is a key diagnostic technique in this process.

An interesting neuroimaging method potentially sensitive to the long-term effects of COVID-19 is MRI perfusion measurement with arterial spin labeling (ASL). Previously, ASL was employed in applications assessing cognitive decline related to microvascular damage and neuroinflammation in the context of cancer therapy or dementia. In these cases, ASL was able to document longitudinal perfusion decrease following radiochemotherapy (4) or to help to detect changes in severe Alzheimer’s disease and even in the prodromal stage (5).

The use of ASL perfusion MRI to measure acute and chronic effects of COVID-19 remains limited. ASL was used to demonstrate that a post-COVID olfactory dysfunction was associated with lower tissue perfusion in the orbital and medial frontal regions (6). ASL also showed decreased perfusion in hospitalized subjects with the severe disease three months after discharge (7). However, perfusion still needs to be systematically studied in the largest group of individuals that underwent COVID-19 but did not require hospitalization.

In this issue of JMRI, an article by [AuthorName] et al. provides new results in a cross-sectional ASL study of 39 subjects who self-isolated at home due to COVID-19 and were scanned on average four months after the positive test (10). Typically, CBF measured with ASL have a relatively large intra-subject variability due to instrumental issues and physiological confounders. In theory, CBF could be influenced by various physiological and psychological factors related to contracting an infectious disease other than COVID-19. To address this, the authors have included a control group of eleven subjects who experienced flu-like symptoms but tested negative for COVID-19. Decreased perfusion in the COVID-19 group relative to the control group was found in several brain regions, including the basal ganglia, thalami, and orbitofrontal gyri. Further differences were discovered between COVID-19 subgroups with and without fatigue.

Despite the smaller size of this study, it backs findings from the UK Biobank study, which have demonstrated gray matter tissue loss in the orbitofrontal cortex and whole brain and higher cognitive decline longitudinally in participants infected with SARS-CoV-2 (8). Further population studies are currently being conducted (9), and the presented study by [AuthorName] et al. indicated the value ASL could have to provide quantifiable perfusion information.

Limitations of the study are a lack of pre-COVID baseline measurements and long-term outcomes of the post-COVID symptoms. In addition, the limited sample size did not allow more detailed subgroup analyses. However, showing a correlation between severity and worsened perfusion compared with patients recovering from a non-COVID flu-like respiratory illness is a step in the right direction in shedding light on the long-term effects of COVID-19 on brain perfusion.

  • Abstract in refereed journal
    Journal of Magnetic Resonance Imaging (2023)
    Online First (2022) DOI: 10.1002/jmri.28556

Permalink: https://www.hzdr.de/publications/Publ-35452
Publ.-Id: 35452


Physics-informed and data-driven modeling of matter under extreme conditions

Cangi, A.; Fiedler, L.; Shah, K.; Callow, T. J.; Ramakrishna, K.; Kotik, D.; Schmerler, S.

Understanding the properties of matter under extreme conditions is essential for advancing our fundamental understanding of astrophysical objects and guides the search for exoplanets, it propels the discovery of materials exhibiting novel properties that emerge under high temperatures and pressure, it enables novel technologies such as nuclear fusion, and supports diagnostics of experiments at large-scale brilliant photon sources. While modeling in this challenging research domain has so far relied on first-principles methods [1,2], these turn out to be computationally too expensive for simulations at the required time and length scales. Reduced models, such as average-atom models [3], come at a reduced computational and are useful by connecting atomistic details with hydrodynamics simulations, but they provide less accuracy. Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [4]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations with deep neural networks in terms of our Materials Learning Algorithms framework [5,6] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [7].

[1] T. Dornheim, A. Cangi, K. Ramakrishna, M. Böhme, S. Tanaka, J. Vorberger, Phys. Rev. Lett. 125, 235001 (2020).
[2] K. Ramakrishna, A. Cangi, T. Dornheim, J. Vorberger, Phys. Rev. B 103, 125118 (2021).
[3] T. J. Callow, E. Kraisler, S. B. Hansen, A. Cangi, Phys. Rev. Research 4, 023055 (2022).
[4] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301 (2022).
[5] A. Cangi et al., MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[6] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022).

Keywords: Materials science; Electronic structure theory; Density functional theory; Machine learning; Neural networks

  • Lecture (Conference)
    Big data analytical methods for complex systems, 06.-07.10.2022, Wroclaw, Poland

Permalink: https://www.hzdr.de/publications/Publ-35451
Publ.-Id: 35451


Accelerating Kohn-Sham Density Functional Theory with Neural Networks

Cangi, A.

Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [1]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations at finite temperatures with deep neural networks in terms of our Materials Learning Algorithms framework [2,3] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [4]. Finally, I will conclude with a preview of our most recent result that enables neural-network-driven electronic structure calculations for systems containing more than 100,000 atoms.

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, Phys. Rev. B 104, 035120 (2021).
[4] o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022).

Keywords: Materials science; Electronic structure theory; Density functional theory; Machine learning; Neural networks

  • Invited lecture (Conferences)
    Multiscale Modeling of Matter under Extreme Conditions, 11.-16.09.2022, Görlitz, Germany
  • Invited lecture (Conferences) (Online presentation)
    NHR-Atomistic Simulation Symposium 2022, 28.-29.11.2022, Online, Deutschland

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35450
Publ.-Id: 35450


Accelerating Kohn-Sham Density Functional Theory at Finite Temperature with Deep Neural Networks

Cangi, A.

Artificial intelligence (AI) has great potential for accelerating electronic structure calculations to hitherto unattainable scales [1]. I will present our recent efforts on accomplishing speeding up Kohn-Sham density functional theory calculations at finite temperature with deep neural networks in terms of our Materials Learning Algorithms framework [2,3] by illustrating results for metals across their melting point. Furthermore, our results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural networks and set the stage for large-scale AI-driven investigations [4]. Finally, I will conclude with a preview on our most recent result that enables neural-network-driven electronic structure calculations for systems containing more than 100,000 atoms.

[1] L. Fiedler, K. Shah, M. Bussmann, and A. Cangi, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi et al., MALA, https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, and S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] o L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, Mach. Learn.: Sci. Technol. 3 045008 (2022). (2022).

Keywords: Electronic structure theory; Density functional theory; Machine learning; Neural networks; Hyperparameter optimization

  • Lecture (Conference)
    Psi-k Conference 2022, 22.-25.08.2022, Lausanne, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-35449
Publ.-Id: 35449


Data-Driven and Physics-Informed Modeling of Matter under Extreme Conditions

Cangi, A.

The successful characterization of high energy density (HED) phenomena in laboratories using photon sources or pulsed power facilities is possible only with numerical modeling for design, diagnostic development, and data interpretation. The persistence of electron correlation is one of the greatest challenges for accurate numerical modeling and has hitherto impeded our ability to model HED phenomena across multiple length and time scales at sufficient accuracy. Standard methods from electronic structure theory capture electron correlation at high accuracy, but are limited to small scales due to their high computational cost.
Artificial intelligence (AI) has emerged as a powerful tool for analyzing complex datasets. It has the potential to accelerate electronic structure calculations to hitherto unattainable scales [1].
In this talk, I will present our recent efforts on devising a data-driven and physics-informed machine-learning workflow to tackle this challenge. Based on first-principles data we generate machine-learning surrogate models that replace traditional density functional theory calculations. Our Materials Learning Algorithms framework [2] predicts the electronic structure and related properties of matter under extreme conditions highly efficiently while maintaining the accuracy of traditional methods [3]. Our most recent results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural network models and set the stage for large-scale investigations based on AI-driven methods [4].

References:

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, A Deep Dive into Machine Learning Density Functional Theory for Materials Science and Chemistry, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA (Version 0.2.0), https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, arXiv:2202.09186 (2022).

  • Invited lecture (Conferences)
    Helmholtz AI Conference 2022, 02.-03.06.2022, Dresden, Germany
  • Invited lecture (Conferences)
    UWr – CASUS – HZDR International Conference on Advanced Systems Research, 11.-15.07.2022, Wroclaw, Poland
  • Lecture (Conference)
    Strongly Coupled Coulomb Systems 2022, 24.-29.07.2022, Görlitz, Germany

Permalink: https://www.hzdr.de/publications/Publ-35448
Publ.-Id: 35448


Machine-Learning Surrogate Models for Predicting Electronic Structures

Cangi, A.

The successful characterization of high energy density (HED) phenomena in laboratories using photon sources or pulsed power facilities is possible only with numerical modeling for design, diagnostic development, and data interpretation. The persistence of electron correlation is one of the greatest challenges for accurate numerical modeling and has hitherto impeded our ability to model HED phenomena across multiple length and time scales at sufficient accuracy. Standard methods from electronic structure theory capture electron correlation at high accuracy, but are limited to small scales due to their high computational cost.
Artificial intelligence (AI) has emerged as a powerful tool for analyzing complex datasets. It has the potential to accelerate electronic structure calculations to hitherto unattainable scales [1].
In this talk, I will present our recent efforts on devising a data-driven and physics-informed machine-learning workflow to tackle this challenge. Based on first-principles data we generate machine-learning surrogate models that replace traditional density functional theory calculations. Our Materials Learning Algorithms framework [2] predicts the electronic structure and related properties of matter under extreme conditions highly efficiently while maintaining the accuracy of traditional methods [3]. Our most recent results towards automated machine-learning save orders of magnitude in computational efforts for finding suitable neural network models and set the stage for large-scale investigations based on AI-driven methods [4].

References:

[1] L. Fiedler, K. Shah, M. Bussmann, A. Cangi, A Deep Dive into Machine Learning Density Functional Theory for Materials Science and Chemistry, Phys. Rev. Materials 6, 040301, (2022).
[2] A. Cangi, J. A. Ellis, L. Fiedler, D. Kotik, N. A. Modine, V. Oles, G. A. Popoola, S. Rajamanickam, S. Schmerler, J. A. Stephens, A. P. Thompson, MALA (Version 0.2.0), https://doi.org/10.5281/zenodo.5557254 (2021).
[3] J. A. Ellis, L. Fiedler, G. A. Popoola, N. A. Modine, J. A. Stephens, A. P. Thompson, A. Cangi, S. Rajamanickam, Phys. Rev. B 104, 035120 (2021).
[4] L. Fiedler, N. Hoffmann, P. Mohammed, G. A. Popoola, T. Yovell, V. Oles, J. A. Ellis, S. Rajamanickam, A. Cangi, arXiv:2202.09186 (2022).

Keywords: Quantum mechanics; Electronic structure theory; Density functional theory; Machine learning; Neural networks

  • Poster
    Advancing Quantum Mechanics with Mathematics and Statistics, Workshop IV: Monte Carlo and Machine Learning Approaches in Quantum Mechanics, 23.-27.05.2022, University of California, Los Angeles, United States
  • Lecture (others)
    Invitation to the Department of Chemistry, University of California, Irvine, 19.05.2022, Irvine, CA, United States

Permalink: https://www.hzdr.de/publications/Publ-35447
Publ.-Id: 35447


KLOE data and prospects with 1.7 fb −1 for a_\mu^HLO

Müller, S.

Invited Presentation at "Workshop on Muon Precision Physics" in Liverpool

Keywords: a_mu; g-2; muon; KLOE

  • Invited lecture (Conferences)
    Workshop on Muon Precision Physics, 07.-10.11.2022, Liverpool, Great Britain

Permalink: https://www.hzdr.de/publications/Publ-35446
Publ.-Id: 35446


Effect of medium on fundamental interaction

Zhuk, O.

We show that the gravitational field undergoes exponential cutoff at large cosmological scales due to the presence of background matter. This reflects the nonlinear nature of the gravitational interaction. This effect is illustrated by the example of different types of background matter, which confirms its universality. We also demonstrate that there is a close mathematical analogy between this effect and the behavior of the magnetic field induced by a solenoid placed in a superconductor.

  • Invited lecture (Conferences) (Online presentation)
    2022 International Conference on the Cooperation and Integration of Industry, Education, Research and Application, 25.10.2022, Changchun City, China

Permalink: https://www.hzdr.de/publications/Publ-35445
Publ.-Id: 35445


A fascinating story of the discovery of a non-stationary Universe: from a great "blunder" to experimental confirmation

Zhuk, O.

Today it is well known that our universe is expanding. However, even 100 years ago, the notion of a static universe was considered correct. In my talk, I will tell a fascinating story about how a few great men have changed our mind.

  • Invited lecture (Conferences) (Online presentation)
    22nd Gamow Conference : “ASTRONOMY AND BEYOND: ASTROPHYSICS, COSMOLOGY AND GRAVITATION, ASTROPARTICLE PHYSICS, RADIOASTRONOMY AND ASTROBIOLOGY, 22.-26.08.2022, Odessa, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-35443
Publ.-Id: 35443


Effect of peculiar velocities of inhomogeneities on the shape of gravitational potential in spatially curved universe

Canay, E.; Eingorn, M.; McLaughlin, I. A.; Arapoglu, A. S.; Zhuk, O.

We investigate the effect of peculiar velocities of inhomogeneities and the spatial curvature of the universe on the shape of the gravitating potential. To this end, we consider scalar perturbations of the FLRW metric. The gravitational potential satisfies a Helmholtz-type equation which follows from the system of linearized Einstein equations. We obtain analytical solutions of this equation in the cases of open and closed universes, filled with cold dark matter in presence of the cosmological constant. We demonstrate that, first, peculiar velocities significantly affect the screening length of the gravitational interaction and, second, the form of the gravitational potential depends on the sign of the spatial curvature.

Keywords: Scalar perturbations Peculiar velocities Gravitational potential

Permalink: https://www.hzdr.de/publications/Publ-35442
Publ.-Id: 35442


Relativistic approach to the large-scale structure formation: cosmic screening vs. gevolution

Zhuk, O.

Due to the modern telescopes, we found that the Universe is filled with a cosmic web which is composed of interconnected filaments of galaxies separated by giant voids. The emergence of this large-scale structure is one of the major challenges of modern cosmology. We study this phenomenon with the help of relativistic N-body cosmological simulation based on General Relativity. It is well known that gravity is the main force responsible for the structure formation in the Universe. In the first part of my talk, I demonstrate that in the cosmological setting gravitational interaction undergoes an exponential cutoff at large cosmological scales.
This effect is called cosmic screening. It arises due to the interaction of the gravitational field with the background matter. Then, I compare two competing relativistic approaches to the N-body simulation of the Universe large-scale structure: “gevolution” vs. “screening”.
To this end, employing the corresponding alternative computer codes, I demonstrate that
the corresponding power spectra are in very good agreement between the compared schemes.
However, since the perturbed Einstein equations have much simpler form in the “screening” approach, the simulation with this code consumes less computational time, saving almost 40% of CPU (central processing unit) hours.

  • Lecture (others)
    The Central European Institute for Cosmology and Fundamental Physics (CEICO), Institute of Physics of the Czech Academy of Sciences, 16.06.2022, Prag, Czech Republic
  • Lecture (others)
    Ludwig-Maximilians-Universität, 28.06.2022, München, Deutschland
  • Lecture (others)
    Universität Oldenburg, Fakultät V, Institut für Physik, 12.07.2022, Oldenburg, Germany
  • Lecture (others)
    CERN, the European Organization for Nuclear Research, Department of Theoretical Physics, 21.09.2022, Geneva, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-35441
Publ.-Id: 35441


c2st: Classifier Two-Sample Testing for comparing high-dimensional point sets

Schmerler, S.; Steinbach, P.

Test whether two sets of points are samples from the same D-dimensional probability distribution without
having access to the PDF.

Keywords: c2st; two-sample testing

  • Open Access Logo Poster
    Helmholtz AI conference, 02.-03.06.2022, Dresden, Germany

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35437
Publ.-Id: 35437


Long term operation of Cs2Te in SRF-gun for TELBE user facility

Xiang, R.

We share the status of long term operation of Cs2Te in SRF-gun for CW mode facility, which is intested for the ERL society.

Related publications

  • Invited lecture (Conferences)
    66th ICFA Advanced Beam Dynamics Workshop on Energy Recovery Linacs (ERL 2022), 03.-06.10.2022, Ithaca, USA

Permalink: https://www.hzdr.de/publications/Publ-35436
Publ.-Id: 35436


Operation of Cs2Te in SRF gun for ELBE

Xiang, R.

we share the experience of Cs2Te operation in SRF gun for ELBE user facility.

Related publications

  • Open Access Logo Invited lecture (Conferences)
    European Workshop on Photocathodes for Particle Accelerator Applications (EWPAA 2022), 20.-22.09.2022, Milano, Italy

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35435
Publ.-Id: 35435


Study on Cs2Te photocathode degradation in SRF gun-II during user operation

Xiang, R.; Schaber, J.; Arnold, A.; Gatzmaga, S.; Hallilingaiah, G.; Ma, S.; Michel, P.; Murcek, P.; Ryzhov, A.; Teichert, J.; Zwartek, P.

The quality of the photocathodes is critical for the stable operation of the photoinjector. Thanks to the robust Cs2Te photocathodes, SRF gun at HZDR has been proven to be a type of successful CW e- source. In this contribution, we will present the operation experience of Cs2Te photocathodes in SRF gun, especially the QE evolution of Cs2Te photocathode during user operation. The possible reason for QE degradation will be discussed.

Related publications

  • Poster
    The 31st Linear Accelerator Conference (LINAC2022), 28.08.-02.09.2022, Liverpool, UK

Permalink: https://www.hzdr.de/publications/Publ-35434
Publ.-Id: 35434


A Quarter Wave Resonator based SRF Gun for the LCLS II High Energy project

Xiang, R.

A Quarter Wave Resonator based SRF Gun for the LCLS II High Energy project

Related publications

  • Open Access Logo Invited lecture (Conferences)
    The 8th annual meeting of the programme "Matter and Technologies", 26.-27.09.2022, Hamburg, Germany

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35433
Publ.-Id: 35433


Cs2Te photocathodes for SRF gun-II at ELBE

Xiang, R.

Status report of Cs2Te photocathodes for SRF gun-II at ELBE

Related publications

  • Open Access Logo Invited lecture (Conferences)
    PITZ collaboration meeting (DESY), 06.-07.06.2022, Zeuthen, Germany

Permalink: https://www.hzdr.de/publications/Publ-35432
Publ.-Id: 35432


Wash water addition on protein foam for removal of soluble impurities in foam fractionation process

Keshavarzi, B.; Krause, T.; Schwarzenberger, K.; Eckert, K.; Ansorge-Schumacher, M. B.; Heitkam, S.

This work evaluates the addition of wash water to a foam fractionation cell in order to remove the soluble impurities from a protein foam. Due to the irreversible adsorption of the proteins at the air interface, the addition of wash water to the foam can displace the entrained substances downward together with the liquid, while the adsorbed proteins are not desorbed from the foam surface. Here, we performed experiments on bovine serum albumin (BSA), as a model protein and NaCl salt, as a model of soluble impurities. The experiments were conducted in a glass foam fractionation cell, where the liquid level was kept constant. The wash water was added on the foam top with different flow rates and BSA and NaCl concentrations were measured at the outlets for further analysis. The influence of initial bubble size and the wash water rate on purification efficiency were investigated. The results show that wash water displaces the entrained liquid in foam and reduces the salt content of the foam. The process shows higher salt removal for higher wash water rates as well as for foams with larger bubble sizes, where up to 93 % of the salt was removed from the main solution. A lower air flow rate can further enhance the washing efficiency. However, it intensifies the foam collapse and hence diminishes the foam outflow.

Keywords: Protein purification; Foam fractionation; Flotation; Wash water; Separation; BSA

Downloads

  • Secondary publication expected from 20.09.2023

Permalink: https://www.hzdr.de/publications/Publ-35430
Publ.-Id: 35430


Thermal-hydraulic and particle deposition analysis of supercritical CO2 in different tubes

Mao, S.; Zhou, T.; Liao, Y.; Tang, J.; Liu, X.

To compare the thermo-hydraulic and particle deposition characteristics of supercritical CO2 (SCO2) in different tubes, the SCO2 thermal-hydraulic performance and particle deposition characteristics were numerically investigated. Three different tube types, including circular tubes, semi-circular tubes and square tubes, were created. The effects of cross sections on heat transfer and particle type, mass flux and heat flux on particle deposition were investigated and discussed. The results indicated that the heat transfer coefficients (h) reach the peaks when the bulk temperature (Tb) is just below pseudo-critical temperature (Tpc) among three tubes. The h peaks are 4.8 kW/(m2·K), 8.4 kW/(m2·K) and 7.9 kW/(m2·K) for circular, semi-circular and square tubes, respectively. The semi-circular tube has the best heat transfer performance and it could alleviate the buoyancy effect efficiently. Moreover, the corners of the semicircular and square tubes should be further optimized to avoid excessive temperatures. The particle deposition efficiency (η) is 79.6%, 76.1% and 84.4% for circular, semicircular and square tubes, respectively, at dp=1 μm. Therefore, the semi-circular tube has a certain anti-deposition. The η for steel and graphite overlaps at dp<1 μm and steel is obvious higher than graphite at dp≥1 μm. Furthermore, small particles are impacted by mass and heat fluxes, whereas large particles are hardly affected. The η of small particles (dp<10 μm) increase with increasing mass flux. However, the η of small particles (dp<1 μm) decrease with increasing heat flux. It would be desirable that the flow channels can be further optimized to obtain the high thermal performance and anti-deposition for heat exchangers using SCO2 as working fluid.

Keywords: Supercritical carbon dioxide (SCO2); Thermal-hydraulic performance; Particle deposition; Different channels

Permalink: https://www.hzdr.de/publications/Publ-35429
Publ.-Id: 35429


Software publication: Estimating cross-border mobility from the difference in peak-timing: A case study in Poland-Germany border regions

Senapati, A.; Mertel, A.; Schlechte-Welnicz, W.; Calabrese, J.

Codes for reproducing the results in the research article "Estimating cross-border mobility from the difference in peak-timing: A case study in Poland-Germany border regions"

Keywords: Coupling strength; Disease outbreak; Spatio-temporal model; Stochastic simulation; Maximum likelihood estimation

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35428
Publ.-Id: 35428


Estimating cross-border mobility from the difference in peak-timing: A case study in Poland-Germany border regions

Senapati, A.; Mertel, A.; Schlechte-Welnicz, W.; Calabrese, J.

Human mobility contributes to the fast spatio-temporal propagation of infectious diseases. During an outbreak, monitoring the infection situation on either side of an international border is very crucial as there is always a higher risk of disease importation associated with cross-border migration. Mechanistic models are effective tools to investigate the consequences of cross-border mobility on disease dynamics and help in designing effective control strategies. However, in practice, due to the unavailability of cross-border mobility data, it becomes difficult to propose reliable, model-based strategies. In this study, we propose a method for estimating cross-border mobility flux between any pair of regions that share an international border from the observed difference in the timing of the infection peak in each region. Assuming the underlying disease dynamics is governed by a Susceptible-Infected-Recovered (SIR) model, we employ stochastic simulations to obtain the maximum likelihood cross-border mobility estimate for any pair of regions where the difference in peak time can be measured. We then investigate how the estimate of cross-border mobility flux varies depending on the disease transmission rate, which is a key epidemiological parameter. We further show that the uncertainty in mobility flux estimates decreases for higher disease transmission rates and larger observed differences in peak timing. Finally, as a case study, we apply the method to some selected regions along the Poland-Germany border which are directly connected through multiple modes of transportation and quantify the cross-border fluxes from the COVID-19 cases data during the period $20^{\rm th}$ February $2021$ to $20^{\rm th}$ June $2021$.

Keywords: Coupling strength; Disease outbreak; Spatio-temporal model; Stochastic simulation; Maximum likelihood estimation

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35427
Publ.-Id: 35427


Challenges and opportunities integrating LLAMA into AdePT

Gruber, B. M.; Amadio, G.; Hageböck, S.

Particle transport simulations are a cornerstone of high-energy physics (HEP), constituting almost half of the entire computing workload performed in HEP. To boost the simulation throughput and energy efficiency, GPUs as accelerators have been explored in recent years, further driven by the increasing use of GPUs on HPCs. The Accelerated demonstrator of electromagnetic Particle Transport (AdePT) is an advanced prototype for offloading the simulation of electromagnetic showers in Geant4 to GPUs, and still undergoes continuous development and optimization. Improving memory layout and data access is vital to use modern, massively parallel GPU hardware efficiently, contributing to the challenge of migrating traditional CPU based data structures to GPUs in AdePT. The low-level abstraction of memory access (LLAMA) is a C++ library that provides a zero-runtime-overhead data structure abstraction layer, focusing on multidimensional arrays of nested, structured data. It provides a framework for defining and switching custom memory mappings at compile time to define data layouts and instrument data access, making LLAMA an ideal tool to tackle the memory-related optimization challenges in AdePT. Our contribution shares insights gained with LLAMA when instrumenting data access inside AdePT, complementing traditional GPU profiler outputs. We demonstrate traces of read/write counts to data structure elements as well as memory heatmaps. The acquired knowledge allowed for subsequent data layout optimizations.

Keywords: AdePT; LLAMA; particle transport simulation; GPU

  • Open Access Logo Lecture (Conference)
    ACAT 2022, 23.-28.10.2022, Bari, Italia

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35425
Publ.-Id: 35425


Updates on the Low-Level Abstraction of Memory Access

Gruber, B. M.

Choosing the best memory layout for each hardware architecture is increasingly important as more and more programs become memory bound. For portable codes that run across heterogeneous hardware architectures, the choice of the memory layout for data structures is ideally decoupled from the rest of a program.
The low-level abstraction of memory access (LLAMA) is a C++ library that provides a zero-runtime-overhead abstraction layer, underneath which memory layouts can be freely exchanged, focusing on multidimensional arrays of nested, structured data.
It provides a framework for defining and switching custom memory mappings at compile time to define data layouts, data access and access instrumentation, making LLAMA an ideal tool to tackle memory-related optimization challenges in heterogeneous computing.
After its scientific debut, several improvements and extensions have been added to LLAMA. This includes compile-time array extents for zero memory overhead, support for computations during memory access, new mappings (e.g. int/float bit-packing or byte-swapping) and more. This contribution provides an overview of the LLAMA library, its recent development and an outlook of future activities.

Keywords: memory layout; struct of arrays; performance portability

  • Open Access Logo Poster
    ACAT 2022, 23.-28.10.2022, Bari, Italia

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35424
Publ.-Id: 35424


Software publication: Optimal workplace occupancy strategies during the COVID-19 pandemic

Davoodi Monfared, M.; Senapati, A.; Mertel, A.; Schlechte-Welnicz, W.; Calabrese, J.

Codes for "Optimal workplace occupancy strategies during the COVID-19 pandemic"

Keywords: COVID-19; Pandemic; Optimal Presence Strategy; Productivity\sep Infection

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35422
Publ.-Id: 35422


Data publication: Learning-based systems for assessing hazard places of contagious diseases and diagnosing patient possibility

Davoodi Monfared, M.; Ghaffari, M.

The codes and data for the paper "Learning-based systems for assessing hazard places of contagious diseases and diagnosing patient possibility"

Keywords: Machine learning; Trajectory tracking; Patient prediction; Hidden Markov model; Covid-19; Trajectory clustering

Related publications

Downloads

Permalink: https://www.hzdr.de/publications/Publ-35419
Publ.-Id: 35419


Predicting electronic structures at any length scale with machine learning

Fiedler, L.; Modine, N.; Schmerler, S.; Vogel, D. J.; Popoola, G. A.; Thompson, A.; Rajamanickam, S.; Cangi, A.

The properties of electrons in matter are of fundamental importance. They give rise to virtually all molecular and material properties and determine the physics at play in objects ranging from semiconductor devices to the interior of giant gas planets. Modeling and simulation of such diverse applications rely primarily on density functional theory (DFT), which has become the principal method for predicting the electronic structure of matter. While DFT calculations have proven to be very useful to the point of being recognized with a Nobel prize in 1998, their computational scaling limits them to small systems. We have developed a machine learning framework for predicting the electronic structure on any length scale. It shows up to three orders of magnitude speedup on systems where DFT is tractable and, more importantly, enables predictions on scales where DFT calculations are infeasible. Our work demonstrates how machine learning circumvents a long-standing computational bottleneck and advances science to frontiers intractable with any current solutions. This unprecedented modeling capability opens up an inexhaustible range of applications in astrophysics, novel materials discovery, and energy solutions for a sustainable future.

Keywords: Machine learning; density functional theory; Surrogate Model

Permalink: https://www.hzdr.de/publications/Publ-35418
Publ.-Id: 35418


Study on QE Evolution of Cs2Te photocathodes in ELBE SRF GUN-II

Xiang, R.; Arnold, A.; Ma, S.; Michel, P.; Murcek, P.; Schaber, J.; Teichert, J.; Ryzhov, A.; Zwartek, P.

The quality of the photocathodes is critical for the stability and reliability of the photoinjector’s operation. Thanks
to the robust magnesium and Cs2Te photocathodes, SRFgun-II at HZDR has been proven to be a successful example
in CW mode for high current user operation.
In this contribution, we will present our observation of the QE evolution of Cs2Te photocathodes during SRF gun
operation. The variables including substrate surface, film thickness, Cs/Te stoichiometric, multipacting, RF loading
and charge extract are considered in the analysis.

Keywords: SRF gun; photocathode; QE Evolution

Related publications

Permalink: https://www.hzdr.de/publications/Publ-35417
Publ.-Id: 35417


Joint recovery of graphite and lithium metal oxides from spent lithium-ion batteries using froth flotation and investigation on process water re-use

Salces, A. M.; Bremerstein, I.; Rudolph, M.; Vanderbruggen, A.

Spent lithium-ion batteries (LIBs) contain critical raw materials that need to be recovered and recirculated into the battery
supply chain. This work proposes the joint recovery of graphite and lithium metal oxides (LMOs) from pyrolyzed black mass
of spent LIBs using froth flotation. Since flotation is a water-intensive process, the quality of the aqueous phase directly
impacts its performance. In pursuit of an improved water-management strategy, the effect of process water recirculation on
black mass flotation is also investigated. The fine fraction (<90 μm) of the black mass from pyrolyzed and crushed spent
LIBs was used. After flotation, 85% of the graphite in the overflow product and 80% of the LMOs in the underflow product
were recovered. After flotation with 8 wt% solids, the process water contained about 1,000 mg/L Li and accumulated up to
2,600 mg/L Li after three cycles. The flotation with process water showed no significant impact on the recovery and grade of
flotation products, suggesting the feasibility of water recirculation in black mass flotation.

Keywords: Black mass; Froth flotation; Lithium metal oxide; Lithium-ion batteries; Recycling; Spheroidized graphite; Water recirculation

Downloads

  • Secondary publication expected from 11.06.2023

Permalink: https://www.hzdr.de/publications/Publ-35416
Publ.-Id: 35416


Head-to-Head Comparison of PET and ASL-MRI BBB Permeability measurements for Dementia Imaging: Study Protocol

Moyaert, P.; Oyeniran, O.; Dassanayake, P.; Liu, L.; Petr, J.; Achten, E.; Mutsaerts, H.; Hicks, J.; Guenther, M.; Anazodo, U.

Aim/Introduction: Blood-brain barrier (BBB) breakdown has been suggested to be an early biomarker of cognitive dysfunction. Currently, PET using [15O]-water and [11C]-Butanol is the standard for measuring BBB permeability. Arterial Spin Labeling (ASL) MRI is a promising alternative as no exogenous contrast is used. This study will validate BBB-ASL MRI by comparing it with PET and assess if BBB-ASL indeed robustly quantifes BBB permeability. Here we present our protocol and preliminary results using image-derived input function (IDIF) to quantify BBB-PET, noninvasively. Materials and Methods: Integrated PET/MR imaging provides a unique opportunity to assess - for the frst time - the ability of ASL to noninvasively image BBB permeability by comparing it to PET in the same subjects and under the same conditions. First, the BBBASL (1) sensitivity in pigs will be investigated by mimicking BBB dysfunction using an Aquaporin-4 inhibitor that will block the fow of water (2). Absolute BBB measurements (as obtained by arterial sampling) will be compared to BBB-ASL measurements. Second, to determine whether any changes in BBB permeability measured by MRI translate to humans, permeability measured by PET and MRI in 10 ischemic stroke patients will be compared. Third, the accuracy of BBB-ASL will be assessed in humans with subtle BBB dysfunction in 12 patients with Alzheimer’s disease, 12 with mild cognitive impairment and 12 age-matched controls. Results: While the preclinical validation studies are underway, we evaluated our PET/MRI IDIF approach (3) for absolute PET quantifcation to eliminate the need for arterial sampling in the two clinical studies. In three pigs, the [15O]-water PET/MR IDIFs were similar to arterial-sampled input functions with area-under-the-curve ratio (IDIF/AIF) of 1.03 - 1.1, demonstrating the potential of IDIF for BBB permeability estimates. Conclusion: The goal of this work is twofold. On one hand, it will demonstrate the potential of ASL measurements as a reliable imaging approach for assessing BBB permeability changes, particularly for early dysfunction detection in otherwise healthy individuals. On the other hand, it will optimize PET for clinical use by integrating IDIF for quantifcation, thereby representing a clinically viable alternative to arterial blood sampling.

  • Contribution to proceedings
    Annual Congress of the European Association of Nuclear Medicine, 15.09.2022, Barcelona, Spain, 550-550
    DOI: 10.1007/s00259-022-05924-4
  • Poster
    Annual Congress of the European Association of Nuclear Medicine, 15.09.2022, Barcelona, Spain

Permalink: https://www.hzdr.de/publications/Publ-35415
Publ.-Id: 35415


Synthese neuer Chelatliganden für Radium-223/-224 und Barium-131

Höffmann, L.

Ziel dieser Masterarbeit ist es, neue Chelatliganden für die Alphastrahler Radium-223/-224 als zweiwertige Kationen und deren diagnostischem Pendant Barium-131 zu synthetisieren. Als Ausgangsverbindung für weitere Funktionalisierungen soll ein durch Lehn beschriebener Kryptand dienen.
Dieser wird über sechs Syntheseschritte hergestellt und besitzt neun Koordinationsstellen, welche durch die Funktionalisierung der sekundären Aminofunktionen mit Seitenketten modifiziert werden sollen. Durch die Verwendung von Carbonsäurederivaten können auf diesem Weg auch Bindungsstellen für ein späteres Trägermolekül eingeführt werden. Während dieser Arbeit sollen vier verschiedene Funktionalisierungen auf Basis von armoatischen Carbonsäurefunktionen (Picolinsäure, Pyrimidincarbonsäure und Bipyridylcarbonsäure) untersucht werden.
Die entstandenen Verbindungen sollen charakterisiert und mittels NMR-Spektroskopie auf ihr Komplexbildungsverhalten mit unterschiedlichen in der Radiopharmazie verwendeten Metallionen wie Barium, Scandium, Blei, Lanthan, Lutetium und Indium untersucht werden. Dazu sollen NMR-Titrationen mit den oben genannten Metallen durchgeführt werden, auf deren Grundlage es möglich ist, die Komplexbildungskonstanten zu berechnen. Zusätzlich sollen die finalen Verbindungen mit Barium-131 und Actinium-225 radiomarkiert und mit dem Bindungsverhalten von macropa verglichen werden.

Keywords: Theranostics; Barium-131; Kryptand; Radium-123

  • Master thesis
    TU Dresden, 2022
    Mentor: PD Dr. habil. Constantin Mamat
    98 Seiten

Permalink: https://www.hzdr.de/publications/Publ-35414
Publ.-Id: 35414


Temporal and spatial evolution of enzymatic degradation of amorphous PET plastics

Lippold, H.; Kahle, L.; Sonnendecker, C.; Matysik, J.; Fischer, C.

Biocatalytic degradation is an emerging strategy aiming for an energy-efficient recycling of poly(ethylene terephthalate) (PET), the most commonly used thermoplastic polyester. Besides material composition and physico-chemical parameters, the degradation kinetics is co-determined by the evolving nanotopography. In this study, the 3-dimensional development of the surface characteristics of an amorphous PET film, reacted with a highly effective hydrolase enzyme for up to 24 hours, was explored by vertical scanning interferometry and confocal microscopy. The spatio-temporal analysis unveiled that the degradation process is not uniform with respect to reaction time and spatial reactivity distribution. An early phase of an unspecific roughness evolution is followed by an advanced phase characterized by a circular degradation pattern, consisting of shallow pits that are steadily renewed over time. The data suggest a hindrance of degradation during the initial roughening process, demonstrating the potential role of targeted surface modification in the large-scale treatment of plastic waste.

Permalink: https://www.hzdr.de/publications/Publ-35413
Publ.-Id: 35413


Reactivity Map Code

Winardhi, C. W.; Da Assuncao Godinho, J. R.; Gutzmer, J.

Matlab code to generate reactivity map of the galena particle

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Permalink: https://www.hzdr.de/publications/Publ-35411
Publ.-Id: 35411


Segmented Galena Dissolution Data

Winardhi, C. W.; Da Assuncao Godinho, J. R.; Gutzmer, J.

Raw CT data which are used to calculate the dissolution rates spectra and to generate reactivity map.

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Permalink: https://www.hzdr.de/publications/Publ-35410
Publ.-Id: 35410


Understanding of the evolution of mechanical properties of steels under irradiation: micromechanics and microstructure

Pareige, C.; Gupta, J.; Vrellou, M.; Kaden, C.; Moldovan, S.; Nomoto, A.; Pareige, P.; Radiguet, B.

Steels are the main structural materials in current and future nuclear power plants. Radiation induced segregation/precipitation and radiation enhanced precipitation at the nanoscale impact significantly their mechanical properties. Under ion irradiation, the small thickness of the irradiated layer imposes micro-mechanical testing methods to be used such as nanoindentation and micropillar compression. The objective is to make the link between microstructural evolution and hardening owing to the combination of: atom probe tomography, transmission electron microscopy,
SEM/FIB/EBSD on one hand and nanoindentation and micropillar compression on the other hand. This correlative approach can also be used on the same materials irradiated with neutrons allowing the comparison between ion and neutron irradiation.

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  • Lecture (Conference)
    26th International Conference on the Application of Accelerators in Research & Industry (CAARI-SNEAP 2022), 30.10.-03.11.2022, Denton, Texas, USA

Permalink: https://www.hzdr.de/publications/Publ-35408
Publ.-Id: 35408


Comparing Wire-Mesh sensor with neutron radiography for measurement of liquid fraction in foam

Ziauddin, M.; Schleicher, E.; Trtik, P.; Knüpfer, L.; Skrypnik, A.; Lappan, T.; Eckert, K.; Heitkam, S.

The liquid fraction of foam is an important quantity in engineering process control and essential to interpret foam rheology.
Established measurement tools for the liquid fraction of foam, such as optical measurement or radiography techniques
as well as weighing the foam, are mostly laboratory-based, whereas conductivity-based measurements are limited to the
global measurement without detailed spatial information of liquid fraction. In this work, which combines both types of
measurement techniques, the conductivity-based wire-mesh sensor is compared with neutron radiography. We found a
linear dependency between the liquid fraction of the foam and the wire-mesh readings with a statistical deviation less than
15%. However, the wire-mesh sensor systematically overestimates the liquid fraction which we attribute to liquid bridge
formation between the wires.

Keywords: foam; Wire-mesh-sensor; Neutron radiography

Permalink: https://www.hzdr.de/publications/Publ-35407
Publ.-Id: 35407


Data publication: Discovery, nuclear properties, synthesis and applications of technetium-101

Johnstone, E. V.; Mayordomo, N.; Mausolf, E. J.
ContactPerson: Johnstone, Erik V.; ContactPerson: Mausolf, Edward J.; ContactPerson: Mayordomo, Natalia

This article is a review paper, it is not based in experimental data

Keywords: Tc-101; Synthesis; Discovery; Properties; Applications

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Permalink: https://www.hzdr.de/publications/Publ-35406
Publ.-Id: 35406


Discovery, nuclear properties, synthesis and applications of technetium-101

Johnstone, E. V.; Mayordomo, N.; Mausolf, E. J.

Technetium-101 ( 101 Tc) has been poorly studied in comparison with other Tc isotopes, although it was first identified over ~80 years ago shortly after the discovery of the element Tc itself. Its workable half-life and array of production modes, i.e., light/heavy particle reactions, fission, fusion-evaporation, etc., allow it to be produced and isolated using an equally diverse selection of chemical separation pathways. The inherent nuclear properties of 101 Tc make it important for research and applications related to radioanalytical tracer studies, as a fission signature, fusion materials, fission reactor fuels, and potentially as a radioisotope for nuclear medicine. In this review, an aggregation of the known literature concerning the chemical, nuclear, and physical properties of 101 Tc and some its applications are presented. This work aims at providing an up-to-date and first-of-its-kind overview of 101 Tc that could be of importance for further development of the fundamental and applied nuclear and radiochemistry of 101 Tc.

Keywords: Tc-101; Synthesis; Discovery; Properties; Applications

Permalink: https://www.hzdr.de/publications/Publ-35405
Publ.-Id: 35405


Tc(VII) reductive immobilization by Sn(II) pre-sorbed on alumina nanoparticles

Mayordomo, N.; Roßberg, A.; Prieur, D.; Scheinost, A.; Kvashnina, K.; Müller, K.

The interaction of highly mobile radioactive elements in the spent fuel with the different technical and geological barriers of a nuclear waste repository needs quantification and mechanistic understanding to allow a reliable safety assessment.
One of the most concerning mobile fission products is Tc-99. It is a long-lived radionuclide (half-life of 0.213 million years) that is expected to occur as Tc(VII) under oxidizing conditions and as Tc(IV) under reducing conditions. The anion pertechnetate (TcO4) is the main species of Tc(VII) and it is known to be a highly mobile species since it barely interacts with mineral surfaces. On the contrary, TcO2 is the main species of Tc(IV) and it is a hardly soluble solid. Therefore, the reduction of Tc(VII) to Tc(IV) limits the mobility of Tc in water and is triggered by reducing agents such as Fe(II) or Sn(II). [1] In a previous work, we have observed that pre-sorption of Fe(II) on alumina enabled the Tc(VII) reduction at the interface, even at low pH values when Tc(VII) reduction by Fe(II) was expected to be limited due to the low sorption of Fe(II) on alumina. [2] In this study we focus on the impact of Sn(II).
We have performed sorption experiments following a stepwise strategy to ensure that Tc(VII) reduction by Sn(II) occurred at the interface (heteroreduction). i) Sn(II) was sorbed on alumina, ii) the Sn(II) pre-sorbed on alumina solid was isolated and dried, iii) a solution of Tc(VII) was added to this modified alumina, and iv) the yield of Tc removal by Sn(II) pre-sorbed on alumina was analyzed. The resulting Tc-containing solid was analyzed by X-ray absorption spectroscopy (XAS) at the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility in Grenoble (France). Bothe Tc K-Edge and Sn K-Edge were recorded at 15 K.
Re-oxidation experiments were performed in samples where Tc(VII) reduction by Sn(II) was obtained by different pathways: i) Tc(VII) direct reduction by dissolved Sn(II) (homoreduction) and ii) Tc(VII) reduction by Sn(II) pre-sorbed on alumina (heteroreduction).
The results show that Tc is removed from solution with a high yield (85-100% removal from solution), being maximum at pH values between 3.5 and 9.5, and minimum at pH 10. Re-oxidation studies show that Tc(IV) obtained by heteroreduction presents lower oxidation kinetics than Tc(IV) obtained by homoreduction. These results support that the presence of alumina plays an important role by preventing Tc(IV) re-oxidation.
Figure 1 shows that the spectrum of TcO2 differs from those preliminar X-ray absorption fine structure (EXAFS) fits for the Tc-loaded samples. This indicates that Al or Sn might also interact with the resulting Tc(IV) species. Further analysis are needed to determine the exact molecular structure of Tc(IV) in the interaction.

Keywords: Technetium; Heteroreduction; Oxidation; EXAFS; Tin

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  • Lecture (Conference)
    ATAS-AnXAS 2022 - Joint Workshop, 17.-21.10.2022, Grenoble, France

Permalink: https://www.hzdr.de/publications/Publ-35404
Publ.-Id: 35404


Data publication: Path integral Monte Carlo results for electrons in 2D and 3D quantum dots

Dornheim, T.

This repository contains a collection of raw path integral Monte Carlo simulation results for various properties of electrons in 2D and 3D quantum dots published in Ref. [1].

[1] http://iopscience.iop.org/article/10.1088/1367-2630/ac9f29

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Permalink: https://www.hzdr.de/publications/Publ-35402
Publ.-Id: 35402


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