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39127 Publications

Untethered and Ultrafast Soft-bodied Robots

Wang, X.; Mao, G.; Ge, J.; Michael, D.; Canon Bermudez, G. S.; Wirthl, D.; Illing, R.; Kosub, T.; Bischoff, L.; Wang, C.; Faßbender, J.; Kaltenbrunner, M.; Makarov, D.

Acting at high speed enables creatures to survive in their harsh natural environments. They developed strategies for fast actuation that inspire technological embodiments like soft robots. Here, we demonstrate a series of simulation-guided lightweight, durable, and untethered soft-bodied robots performing large-degree deformations at unprecedentedly high frequencies of up to 200 Hz, driven at very low magnetic fields down to 0.5 mT, and exhibit a record high specific energy density of 10.8 kJ/m3/mT. Unforeseen nonlinear behavior of our robots is observed in experiments and analyzed by simulation, guiding future designs of soft-bodied robots. Our robots walk, swim, levitate, transport cargo, and can even catch a living fly unharmed. Such ultrafast soft robots with high-frequency oscillations can rapidly adapt to varying environmental conditions, inspire biomedical applications in confined environment, and serve as model systems to develop complex movements inspired by nature.

Keywords: soft robot; soft actuator; magnetic field; nonlinear actuation

Related publications

Publ.-Id: 30284

Current status of PSMA-radiotracers for prostate cancer: data analysis of prospective trials listed on

Zippel, C.; Ronski, S. C.; Bohnet-Joschko, S.; Giesel, F. L.; Kopka, K.

The recent development of dedicated prostate-specific membrane antigen (PSMA) targeted radioligands shows the potential to change and improve the diagnosis and therapy of prostate cancer. There is an increasing number of prospective trials to further establish these tracers in the clinical setting. We analyzed data from the registry including all listed prospective trials with PSMA-ligands for prostate cancer as of October 2019 concerning the different tracers and study characteristics. We found n = 104 eligible studies with a total of n = 25 different tracers in use: most frequently [68Ga] Ga-PSMA-11 (32%), followed by [18F] DCFPyL (24%) and [177Lu] Lu-PSMA-617 (10%). 85% are single-center, 15% multi-center studies. 95% national and 5% international studies. 34% are phase-II, 24% phase-I, 13% phase-I/-II, 12% phase-II/-III and phase-III and 7% early-phase-I. The primary purpose was classified as diagnostic in 72% of cases and therapeutic in 23% of cases. Most studies were executed in the USA (70%), followed by Canada (13%) and France (6%). This quantitative descriptive registry analysis indicates the rapid and global clinical developments and current status of PSMA-radioligands with emphasis on radiopharmaceutical and organizational aspects. It will be very interesting to see which tracers will prevail in the clinical setting.

Keywords: prostate cancer; PSMA tracer; registry data analysis;; theranostics

Publ.-Id: 30280

Thermodynamics and determination of the exchange stiffness of asymmetrically sandwiched ultrathin ferromagnetic films with perpendicular anisotropy

Iastremskyi, I.; Volkov, O.; Kopte, M.; Kosub, T.; Stienen, S.; Lenz, K.; Lindner, J.; Faßbender, J.; Ivanov, B. A.; Makarov, D.

Thermodynamic properties, in particular, the temperature dependencies of magnetization of asymmetrically sandwiched ultrathin cobalt films with perpendicular anisotropy are investigated. The experimental results are described theoretically in the frame of magnon thermodynamics consistently accounting for the finite thickness of the films. The analysis includes both three-dimensional (Bloch’s T3/2 law) and two-dimensional (the 2D Bloch law) theories as limiting cases. By fitting the experimental temperature dependencies of magnetization to the theoretical model, the exchange stiffness parameter is extracted. This approach provides access to the exchange stiffness without the need to know the strength of the Dzyaloshinskii-Moriya interaction in the stack. The exchange stiffness of sub-nm-thick Co films is found to be about three times smaller compared to the case of bulk cobalt. In the temperature range T<170±30 K the temperature dependencies of magnetization follow the 2D Bloch law. The applicability of Bloch’s T3/2 law and analysis of the Curie temperature (two-dimensional and three-dimensional pictures) to extract the exchange stiffness for sub-nm-thick Co films are tested as well. The closest value of the exchange stiffness to the magnon thermodynamics turned out to be within the analysis of the Curie temperature in the three-dimensional picture.

Keywords: Exchange interaction; Ferromagnetism; Magnetic anisotropy; Micromagnetism; Skyrmions; Spintronics; Thermodynamics; Magnetic multilayers


  • Secondary publication expected

Publ.-Id: 30278

Non-local symmetry breaking effects, induced by magnetostatics in curvilinear ferromagnetic shells

Sheka, D.; Pylypovskyi, O.; Landeros, P.; Gaididei, Y.; Kakay, A.; Makarov, D.

We present a micromagnetic theory of curvilinear ferromagnetic shells. We show the appearance of new chiral effects, originating from the magnetostatic interaction. They manifest themselves even in statics and are essentially nonlocal. This is in contrast to conventional Dzyaloshinskii--Moriya interaction (material intrinsic or curvature-induced, stemming from the exchange). The physical origin is in a non-zero mean curvature of a shell and non-equivalence between the top and bottom surfaces of the shell. To describe the new effects, we split a conventional volume magnetostatic charge into two terms: (i) magnetostatic charge, governed by the tangent to the sample's surface, and (ii) geometrical charge, given by the normal component of magnetization and the mean curvature. We classify the interplay between the symmetry of the shell, its local curvature and magnetic textures and apply the proposed formalism to analyse magnetic textures in corrugated shells with perpendicular anisotropy.

Keywords: magnetism; curvilinear shells; magnetostatics

  • Lecture (Conference)
    DPG Spring Meeting of the Condensed Matter Section (Conference is cancelled due to COVID-19), 15.-20.03.2020, Dresden, Germany

Publ.-Id: 30277

Radioimmunotherapy in Combination with Reduced-Intensity Conditioning for Allogeneic Hematopoietic Cell Transplantation in Patients with Advanced Multiple Myeloma

Fasslrinner, F.; Stölzel, F.; Kramer, M.; Teipel, R.; Brogsitter, C.; Morgner, A.; Arndt, C.; Bachmann, M.; Hänel, M.; Röllig, C.; Kotzerke, J.; Schetelig, J.; Bornhäuser, M.

Radioimmunotherapy (RIT) has the potential to reduce the incidence of relapse after allogeneic hematopoietic cell transplantation (allo-HCT) in patients with advanced-stage multiple myeloma (MM). In this study, we evaluated the efficacy of RIT in combination with chemotherapy-based reduced-intensity conditioning (RIC). RIT was based on the coupling of an anti-CD66 antibody to the beta emitter 188-rhenium (188-re) for targeted bone marrow irradiation. Between 2012 and 2018, 30 patients with MM, most of them heavily pretreated with various therapies including proteasome inhibitors, immunomodulatory drugs, anti-CD38 antibodies, and autologous hematopoietic cell transplantation (auto-HCT), were treated with a RIT-RIC combination before allo-HCT. In addition to a fludarabine plus melphalan- or treosulfan-based RIC, a median dose of 18.1 Gy (interquartile range [IQR], 14.6 to 24.1 Gy) was applied to the bone marrow. After a median duration of follow-up for surviving patients of 2.1 years (IQR, 1.3 to 3.0 years), the 2-year progression-free survival and overall survival rates were 43% (95% confidence interval [CI], 26% to 73%) and 55% (95% CI, 38% to 79%), respectively. The 2-year nonrelapse mortality and cumulative incidence of progression were 17% (95% CI, 3% to 30%) and 46% (95% CI, 25% to 67%), respectively. Renal toxicity and mucositis were the most frequent extramedullary side effects. In conclusion, the addition of RIT to RIC was safe and feasible and resulted in promising outcomes compared with those previously reported for RIC-based allo-HCT without the addition of RIT in patients with relapsed/refractory MM. Nevertheless, despite the addition of RIT, relapse after allo-HCT remained a major determinant of therapeutic failure. Therefore, the development of novel RIT strategies (eg, dual targeting strategies or combinations with adapter chimeric antigen receptor T cell-based therapies) is needed.

Publ.-Id: 30276

Unidirectionally tilted domain walls in chiral biaxial stripes

Pylypovskyi, O.; Kravchuk, V. P.; Volkov, O.; Faßbender, J.; Sheka, D.; Makarov, D.

The orientation of a chiral magnetic domain wall in a racetrack determines its dynamical properties. In equilibrium, magnetic domain walls are expected to be oriented perpendicular to the stripe axis. We demonstrate the appearance of a unidirectional domain wall tilt in an out-of-plane magnetized stripes with biaxial anisotropy (the firsrt easy axis is perpendicular to the plane and the second one is tilted with respect to the stripe axis) and interfacial Dzyaloshinskii--Moriya interaction (DMI). The tilt is a result of the interplay between the in-plane easy-axis anisotropy and DMI. We show that the additional anisotropy and DMI prefer different domain wall structure: anisotropy links the magnetization azimuthal angle inside the domain wall with the stripe main axis in contrast to DMI, which prefers the magnetization perpendicular to the domain wall plane. Their balance with the energy gain due to domain wall extension defines the equilibrium magnetization and domain wall tilt angles. We demonstrate that the Walker field and the corresponding Walker velocity of the domain wall can be enhanced in the system supporting tilted walls.

Keywords: magnetism; domain walls; Walker limit; Dzyaloshinskii-Moriya interaction

  • Lecture (Conference)
    DPG Spring Meeting of the Condensed Matter Section (Conference is cancelled due to COVID-19), 15.-20.03.2020, Dresden, Germany

Publ.-Id: 30275

Geometry-induced effects in antiferromagnetic spin chains

Kononenko, D. Y.; Pylypovskyi, O.; Roessler, U. K.; Yershov, K.; van den Brink, J.; Gaididei, Y.; Makarov, D.; Sheka, D.

Antiferromagnetic nanostructures as objects with ultrahigh eigenfrequencies and low sensitivity to demagnetizing fields are promising candidates for applications in data storage and information processing. Three-dimensional architectures enable new ways for tuning magnetic responses and extend ideas of spintronic devices. Here, we analyze anitferromagnetically ordered curvilinear spin chains and derive a Lagrangian taking into account the exchange interaction and effective anisotropy arising from the dipolar interaction. The static and dynamic properties of the spin system are influenced by emergent geometry-induced anisotropies and Dzyaloshinskii--Moriya interaction, which are illustrated by ring and helix geometries as case studies. Ground states and coupling of spin wave modes due to curvilinear geometry are described.

Keywords: magnetism; anitferromagnets; curvilinear magnetism; spin chains

  • Lecture (Conference)
    DPG Spring Meeting of the Condensed Matter Section (Conference is cancelled due to COVID-19), 15.-20.03.2020, Dresden, Germany

Publ.-Id: 30274

Combination of short-lived and extended half-life target modules for optimized UniCAR T cell therapy

Arndt, C.; Loureiro, L.; Feldmann, A.; Koristka, S.; Mitwasi, N.; Jureczek, J.; Hoffmann, A.; Berndt, N.; Bergmann, R.; Bachmann, M.

Background: Chimeric antigen receptor (CAR) T cells are powerful living drugs to fight against cancer. However, they also possess the capacity to elicit moderate to severe toxicities that might be even fatal. Thus, one major issue of CAR T cell engineering is to reduce the risk for side effects while maintaining high anti-tumor activity. In order to improve the safety profile of CAR, we developed the so-called UniCAR system. In this modular platform technology, soluble, tumor-specific target modules (TM) act as molecular switches of per se inactive universal (Uni)CAR T cells. TM consist of tumor-specific binding domains fused to the E5B9 peptide epitope that is recognized by the UniCAR. All so far developed TMs have a low molecular weight and are therefore rapidly eliminated. This allows to specifically and repeatedly turn on/off UniCAR T cell activity via TM dosing.
Aims: Tumor patients with bulky disease present the highest risk for CAR T cell-related toxicities. At this stage, a high level of safety and therefore controllability of (Uni)CAR T cells is required. However, for convenient treatment of patients with lower tumor burden, we intended to develop extended half-life TM to foster anti-tumor responses and to ease the clinical TM administration at later stages of tumor therapy.
Methods: Based on the human IgG4 Fc-domain, we engineered a set of novel extended half-life TM each consisting of tumor-specific single-chain fragments variable (scFv), the IgG4 hinge and Fc domain as well as the E5B9 peptide epitope. Functionality of these IgG4-based TMs was analyzed in vitro and in vivo in comparison to originally developed scFv-based TM. Pharmacokinetic properties were studied in experimental mice.
Results: In presence of extended half-life TM, UniCAR T cells are able to efficiently mediate tumor cell lysis in vitro and in vivo. Anti-tumor responses are comparable or even improved in comparison to smaller TM, whereas bioavailability and plasma half-life are prolonged.
Summary: Overall, combination of both short-lived and longer lasting (IgG4-based) TM is a highly promising approach for redirection of UniCAR T cells to various cancer cells. At the beginning of tumor treatment, rapidly eliminated TM should be chosen to provide a fast safety switch. After significant reduction in tumor burden, IgG4-based TM with increased serum half-lives could be administered to avoid continuous TM infusions and to improve the elimination of residual tumor cells. This strategy might allow a more convenient, individualized and safe treatment of cancer patients.

  • Invited lecture (Conferences)
    34th Annunal Meeting and Pre-Conference Programs of the Society for Immunotherapy of Cancer (SITC) / World Immunotherapy Council´s 3rd Young Investigator Symposium, 06.-10.11.2019, National Habor, MD, USA

Publ.-Id: 30273

Nonlocal chiral symmetry breaking in curvilinear magnetic shells

Sheka, D. D.; Pylypovskyi, O.; Landeros, P.; Gaididei, Y.; Kakay, A.; Makarov, D.

The concept of curvature and chirality in space and time are foundational for the understanding of the organic life and formation of matter in the Universe. Chiral interactions but also curvature effects are tacitly accepted to be local. A prototypical condensed matter example is a local spin-orbit- or curvature-induced Rashba or Dzyaloshinskii-Moriya interactions. Here, we introduce a chiral effect, which is essentially non-local and resembles itself even in static spin textures living in curvilinear magnetic nanoshells. Its physical origin is the non-local magnetostatic interaction. To identify this interaction, we put forth a self-consistent micromagnetic framework of curvilinear magnetism. Understanding of the non-local physics of curved magnetic shells requires a curvature-induced geometrical charge, which couples the magnetic sub-system with the curvilinear geometry. The chiral interaction brings about a non-local chiral symmetry breaking effect: it introduces handedness in an intrinsically achiral material and enables the design of magnetolectric and ferrotoroidic responses.

Keywords: magnetism; curvilinear shells; magnetostatics

Publ.-Id: 30272

Engaging UniCAR T cells via short-lived and longer lasting target modules

Arndt, C.; Loureiro, L.; Feldmann, A.; Koristka, S.; Mitwasi, N.; Jureczek, J.; Hoffmann, A.; Berndt, N.; Bergmann, R.; Bachmann, M.

Background: Chimeric antigen receptor (CAR) T cell therapy has demonstrated impressive clinical efficiency, but can also cause moderate to severe adverse effects that might be even fatal. Thus, preventing or managing CAR T cell toxicity is still an important issue for successful treatment of tumor patients. In order to provide a novel CAR technology platform with an improved safety profile, we established the switchable UniCAR system. This platform consists of (I) universal CAR (UniCAR) T cells that are per se inactive. Their anti-tumor activity can be specifically and repeatedly turned on/off in dependence of soluble tumor-binding target modules (TM).e.g.1-4 TMs are constructed by fusing an antigen-specific binding moiety with the E5B9 peptide epitope recognized by UniCARs. As these molecules are rapidly eliminated, UniCAR T cells can be easily controlled by TM dosing.
Aims: As the risk for CAR T cell-related toxicities will also decrease with reduction of tumor burden, we intended to develop TMs with prolonged half-life that might ease clinical application and improve elimination of residual tumor cells in late phase of tumor therapy.
Methods: We constructed a set of novel, longer lasting TMs by fusion of different tumor-specific single-chain fragment variables (scFv) and the E5B9 peptide epitope to the Fc domain of human IgG4 antibodies. The resulting IgG4-based TMs were functionally compared with smaller, scFv-based TMs in vitro and characterized for their pharmacokinetic properties in experimental mice.
Results: The novel IgG4-based TMs are able to efficiently activate UniCAR T cells for killing of various tumor cell lines. In comparison to short-lived TMs, they are characterized by a comparable or increased efficiency at low TM concentrations. Pharmacokinetic studies in tumor-bearing mice further revealed that IgG4-based TM have a prolonged plasma half-life and enhanced bioavailability.
Summary: Our data demonstrate that IgG4-based TMs in combination with smaller TMs are highly promising tools for redirection of UniCAR T cells to various cancer cells. Once the tumor burden is reduced, UniCAR T cells can be combined with IgG4-based TMs instead of small TMs. This is more convenient for patients as IgG4-based TM have not to be continuously infused due to their prolonged serum half-lives. Overall, the combination of UniCAR T cells with TMs of different size and specificity should allow a more convenient, individualized and safe treatment regimen of cancer patients.

  • Open Access Logo Lecture (Conference)
    Tumorimmunology meets Oncology (TIMO) XV, 25.-27.04.2019, Halle, Deutschland

Publ.-Id: 30271

What we can learn from the ’f’ in f-elements

Drobot, B.; Steudtner, R.; Raff, J.; Brendler, V.; Bauer, A.; Bok, F.; Patzschke, M.; Tsushima, S.

An introduction of spectroscopy with f-elements (actinides/lanthanides)

  • Invited lecture (Conferences)
    14. PhD seminar Kompetenzverbundes für Kerntechnik Ost, 05.12.2019, Dresden, Deutschland

Publ.-Id: 30270

Magnetoelectronics and nanomagnetism of magnetoelectric antiferromagnetic thin films

Makarov, D.

Thin film antiferromagnets (AF) have potential to revolutionize spintronics due to their inherently magnetic-field stable magnetic order and high-frequency operation. To explore their application potential, it is necessary to understand modifications of the magnetic properties and magnetoelectric responses of AF thin films with respect to their bulk counterparts. Considering grainy morphology of thin films, questions regarding the change of the intergranular exchange, criticality behavior and switching of the order parameter need to be addressed.
Our approach is based on the electron transport characterization of magnetic responses of thin film antiferromagnets [1-3]. This task is difficult as minute uncompensated surface magnetization of antiferromagnets needs to be detected, which imposes strict requirements to the sensitivity of the method. I will outline our developments of zero-offset anomalous Hall magnetometry [2] applied to study the physics of conventional metallic IrMn and insulating magnetoelectric Cr2O3 antiferromagnets. To build a reliable description of the material properties, the analysis of the transport data is backed up by structural characterization and real space imaging of AF domain patterns using NV microscopy [1,4].
The fundamental understanding of the magnetic microstructure of magnetoelectric α-Cr2O3 thin films and the possibility to read-out its antiferromagnetic order parameter all-electrically enabled the entirely new recording concept where a magnetoelectric memory cell can be addressed without using a ferromagnet. With this approach, we opened an appealing topic of purely antiferromagnetic magnetoelectric random access memory (AF-MERAM) [1].

[1] T. Kosub, D. Makarov et al., Nat. Commun. 8, 13985 (2017).
[2] T. Kosub, D. Makarov et al., Phys. Rev. Lett. 115, 097201 (2015).
[3] R. Schlitz, D. Makarov et al., Appl. Phys. Lett. 112, 132401 (2018).
[4] P. Appel, D. Makarov et al., Nano Lett. 19, 1682 (2019).

Keywords: magnetoelectric effect; Cr2O3

Related publications

  • Lecture (others)
    Seminar at the department of Physics and Astronomy, University of California, Riverside, 21.02.2020, Riverside, USA

Publ.-Id: 30268

From shapeable magnetoelectronics to soft robotics with embedded magnetic cognition

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We explore the potential of these 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [Makarov et al., Appl. Phys. Rev. 3, 011101 (2016)] for automotive applications [Melzer et al., Adv. Mater. 27, 1274 (2015)], point-of-care diagnostics [Lin et al, Lab Chip 14, 4050 (2014)], virtual and augmented reality appliances [Canon et al., Nature Electronics 1, 589 (2018) & Science Advances 4, eaao2623 (2018); Granell et al., npj Flexible Electronics 3, 3 (2019)]. Combining compliant magnetic field sensors with soft (magnetic) actuators allows realizing ultrafast soft robots with embedded cognition and feedback. These developments pave the way towards intelligent soft robots, autonomous and responsive soft devices, and novel human-machine interfaces.

Keywords: magnetic soft robots; shapeable magnetic field sensors

Related publications

  • Invited lecture (Conferences)
    2020 TMS Annual Meeting & Exhibition, Symposium: Advanced Magnetic Materials for Energy and Power Conversion Applications, 24.02.2020, San Diego, USA

Publ.-Id: 30267

From curvilinear magnetism to shapeable magnetoelectronics

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines including electronics, photonics, and magnetics. This approach provides means to enrich conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-3]. On the other hand, we explore the application potential of 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [4] for automotive but also virtual and augmented reality appliances [5-7]. To advance in this research field, we develop novel theoretical methods and fabrication/characterization techniques [8-10]. In this talk, recent fundamental and technological advancements in this research field will be reviewed.

[1] R. Streubel, DM et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander, DM et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov, DM et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Makarov et al., Shapeable magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[5] G. S. Cañón Bermúdez, DM et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[6] G. S. Cañón Bermúdez, DM et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[7] J. Ge, DM et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[8] R. Streubel, DM et al., Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies. Nature Communications 6, 7612 (2015).
[9] T. Kosub, DM et al., All-electric access to the magnetic-field-invariant magnetization of antiferromagnets. Phys. Rev. Lett. 115, 097201 (2015).
[10] T. Kosub, DM et al., Purely antiferromagnetic magnetoelectric random access memory. Nature Communications 8, 13985 (2017).

Keywords: curvilinear magnetism; shapeable magnetoelectronics

Related publications

  • Lecture (others)
    Seminar of the Department of Physics, University of Bielefeld, 03.02.2020, Bielefeld, Germany

Publ.-Id: 30266

Synergistic Electroreduction of Carbon Dioxide to Carbon Monoxide on Bimetallic Layered Conjugated Metal-Organic Frameworks

Zhong, H.; Ghorbani-Asl, M.; Ly, K. H.; Ge, J.; Zhang, J.; Wang, M.; Liao, Z.; Makarov, D.; Zschech, E.; Brunner, E.; Weidinger, I. M.; Zhang, J.; Krasheninnikov, A.; Kaskel, S.; Dong, R.; Feng, X.

The development of highly selective and active electrocatalysts promoting the CO2 reduction reaction (CO2RR) is highly desirable to address current environmental challenges and to produce value-added chemicals and carbon-based fuels. Herein, we develop a layer-stacked, bimetallic two-dimensional conjugated metal-organic framework (2D c-MOF) with copper-phthalocyanine as ligand (CuN4) and zinc-bis(dihydroxy) complex (ZnO4) as linkage, named as PcCu-O8-Zn. The PcCu-O8-Zn exhibits high CO selectivity of 88%, a TOF of 1408 h1 and long-term durability (> 10 h), which surpasses thus by far the reported MOF-based electrocatalysts. The molar H2/CO ratio can be tuned by varying the metal centers and the applied potential rendering the 2D c-MOFs highly relevant for syngas industry applications. The contrast experiments combined with operando surface-enhanced IR-absorption spectroelectrochemistry and theoretical calculation unveil a synergistic catalytic mechanism; the ZnO4 complexes act as catalytic sites for the CO2 conversion while the CuN4 centers promote the protonation of adsorbed CO2 during the CO2RR. This work offers a strategy on developing bimetallic MOF electrocatalysts for synergistically catalyzing CO2RR toward syngas synthesis.

Keywords: CO2 reduction; metal-organic framework

Related publications

Publ.-Id: 30265

Gilbert damping in NiFeGd compounds: Ferromagnetic resonance versus time-resolved spectroscopy

Salikhov, R.; Alekhin, A.; Parpiiev, T.; Pezeril, T.; Makarov, D.; Abrudan, R.; Meckenstock, R.; Radu, F.; Farle, M.; Zabel, H.; Temnov, V. V.

Engineering the magnetic properties (Gilbert damping, saturation magnetization, exchange stiffness, and
magnetic anisotropy) of multicomponent magnetic compounds plays a key role in fundamental magnetism
and its applications. Here, we perform a systematic study of (Ni81Fe19 )100−xGdx films with x = 0%, 5%, 9%,
and 13% using ferromagnetic resonance (FMR), element-specific time-resolved x-ray magnetic resonance, and
femtosecond time-resolved magneto-optical pump-probe techniques. The comparative analysis of field and
time domain FMR methods, with complimentary information extracted from the dynamics of high-frequency
exchange magnons in ferromagnetic thin films, is used to investigate the dependence of Gilbert damping on the
Gd concentration.

Keywords: Gilbert damping; Ferromagnetic resonance

Related publications

Publ.-Id: 30263

A review on stretchable magnetic field sensorics

Melzer, M.; Makarov, D.; Schmidt, O. G.

The current establishment of stretchable electronics to form a seamless link between soft or
even living materials and the digital world is at the forefront of multidisciplinary research
efforts, bridging physics, engineering and materials science. Magnetic functionalities can
provide a sense of displacement, orientation or proximity to this novel formulation of
electronics. This work reviews the recent development of stretchable magnetic field sensorics
relying on the combination of metallic thin films revealing a giant magnetoresistance effect
with elastomeric materials. Stretchability of the magnetic nanomembranes is achieved
by specific morphologic features (e.g. wrinkles or microcracks), which accommodate the
applied tensile deformation while maintaining the electrical and magnetic integrity of the
sensor device. The entire development, from the demonstration of the world’s first elastically
stretchable magnetic sensor to the realization of a technology platform for robust, ready-touse
elastic magnetosensorics is described. Soft giant magnetoresistive elements exhibiting the
same sensing performance as on conventional rigid supports, but with fully strain invariant
properties up to 270% stretching have been demonstrated. With their unique mechanical
properties, these sensor elements readily conform to ubiquitous objects of arbitrary shapes
including the human skin. Stretchable magnetoelectronic sensors can equip soft and epidermal
electronic systems with navigation, orientation, motion tracking and touchless control
capabilities. A variety of novel technologies, like electronic skins, smart textiles, soft robotics
and actuators, active medical implants and soft consumer electronics will benefit from these
new magnetic functionalities.

Keywords: shapeable magnetic field sensors; stretchable electronics

Related publications

Publ.-Id: 30262

Neutron Fluence Calculations for the Dismantling and Decommissioning of a German PWR

Rachamin, R.; Konheiser, J.; Barkleit, A.; Marcus, S.

Presentation at AAA Workshop 02.12.2019

Keywords: Decommissioning studies; Neutron fluence; Monte-Carlo

  • Lecture (Conference)
    AAA Workshop, GRS GmbH, 02.12.2019, Garching, Germany

Publ.-Id: 30261

Curvilinear magnetic nanomembranes: fundamentals and technologies

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-3]. On the other hand, we explore the application potential of these 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [4] for automotive but also virtual and augmented reality appliances [5-8]. The balance between the fundamental and applied inputs stimulates even further the development of new theoretical methods and novel fabrication/characterization techniques [9-11].
In this talk, recent fundamental and technological advancements in this exciting research field will be reviewed.

[1] R. Streubel et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[5] G. S. Cañón Bermúdez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[6] G. S. Cañón Bermúdez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[7] P. N. Granell et al., Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).
[8] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[9] R. Streubel et al., Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies. Nature Communications 6, 7612 (2015).
[10] T. Kosub et al., All-electric access to the magnetic-field-invariant magnetization of antiferromagnets. Phys. Rev. Lett. 115, 097201 (2015).
[11] T. Kosub et al., Purely antiferromagnetic magnetoelectric random access memory. Nature Communications 8, 13985 (2017).

Keywords: shapeable magnetoelectronics; curved magnetic nanomembranes

Related publications

  • Lecture (others)
    Seminar at the Key Lab of Magnetic Materials and Devices, 01.11.2019, Ningbo, China

Publ.-Id: 30260

Fundamentals and applications of curved magnetic thin films

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study 3D curved magnetic thin films and nanowires where new fundamental effects emerge from the interplay of the geometry of an object and topology of a magnetic sub-system [1-3]. On the other hand, we explore the application potential of these 3D magnetic architectures for the realization of mechanically shapeable magnetoelectronics [4] for automotive but also virtual and augmented reality appliances [5-8]. The balance between the fundamental and applied inputs stimulates even further the development of new theoretical methods and novel fabrication/characterization techniques [9-11].
In this talk, recent fundamental and technological advancements in this exciting research field will be reviewed.

[1] R. Streubel et al., Magnetism in curved geometries. J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016).
[2] D. Sander et al., The 2017 magnetism roadmap. J. Phys. D: Appl. Phys. (Review) 50, 363001 (2017).
[3] O. M. Volkov et al., Experimental observation of exchange-driven chiral effects in curvilinear magnetism. Phys. Rev. Lett. 123, 077201 (2019).
[4] D. Makarov et al., Shapeable Magnetoelectronics. Appl. Phys. Rev. (Review) 3, 011101 (2016).
[5] G. S. Cañón Bermúdez et al., Magnetosensitive e-skins with directional perception for augmented reality. Science Advances 4, eaao2623 (2018).
[6] G. S. Cañón Bermúdez et al., Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics. Nature Electronics 1, 589 (2018).
[7] P. N. Granell et al., Highly compliant planar Hall effect sensor with sub 200 nT sensitivity. npj Flexible Electronics 3, 3 (2019).
[8] J. Ge et al., A bimodal soft electronic skin for tactile and touchless interaction in real time. Nature Communications 10, 4405 (2019).
[9] R. Streubel et al., Retrieving spin textures on curved magnetic thin films with full-field soft X-ray microscopies. Nature Communications 6, 7612 (2015).
[10] T. Kosub et al., All-electric access to the magnetic-field-invariant magnetization of antiferromagnets. Phys. Rev. Lett. 115, 097201 (2015).
[11] T. Kosub et al., Purely antiferromagnetic magnetoelectric random access memory. Nature Communications 8, 13985 (2017).

Keywords: curvilinear magentism; magnetic field sensors; shapeable magnetoelectronics

Related publications

  • Lecture (others)
    Seminar at the Department of Materials Science, 11.11.2019, Shanghai, China

Publ.-Id: 30259

Flexible electronics: from interactive on-skin devices to bio/medical applications

Makarov, D.

Extending 2D structures into 3D space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring curvature and 3D shape. We study fundamentals of 3D curved magnetic thin films [1] and explore their application potential for flexible electronics, eMobility and health. We put forth the concept of shapeable magnetoelectronics [2] for various applications ranging from automotive [3] through consumer electronics to virtual and augmented reality [4-7] applications. These activities impact several emerging research fields of smart skins, soft robotics and human-machine interfaces.
Highly compliant functional elements are exceptionally suited for bio/medical applications. Very recently we realized an implantable, multifunctional and highly compliant device for targeted thermal treatment of cancer [8]. We fabricated a flexible light weight diagnostic platform based on highly sensitive Si nanowire field effect transistors revealing remarkable limit of detection at 40 pM for Avian Influenza Virus (AIV) subtype H1N1 DNA sequences [9].
For the emerging field of biosensing technologies, we developed droplet-based magnetofluidic platforms encompassing integrated novel functionalities [10] including analytics in a flow cytometry format [11], magnetic barcoding and sorting of magnetically encoded emulsion droplets using flexible microfluidic devices [12]. These features are crucial to address the needs of modern medical research, e.g. drug discovery.

[1] R. Streubel et al., J. Phys. D: Appl. Phys. (Review) 49, 363001 (2016)
[2] D. Makarov et al., Appl. Phys. Rev. (Review) 3, 011101 (2016).
[3] M. Melzer et al., Adv. Mater. 27, 1274 (2015).
[4] G. S. Cañón Bermúdez et al., Science Advances 4, eaao2623 (2018).
[5] G. S. Cañón Bermúdez et al., Nature Electronics 1, 589 (2018).
[6] P. N. Granell et al., npj Flexible Electronics 3, 3 (2019).
[7] J. Ge et al., Nature Communications 10, 4405 (2019).
[8] G. S. Cañón Bermúdez et al., Adv. Eng. Mater. 21, 1900407 (2019).
[9] D. Karnaushenko et al., Adv. Healthcare Mater. 4, 1517 (2015).
[10] G. Lin, D. Makarov et al., Lab Chip (Review) 17, 1884 (2017).
[11] G. Lin, D. Makarov et al., Small 12, 4553 (2016).
[12] G. Lin, D. Makarov et al., Lab Chip 14, 4050 (2014).

Keywords: flexible electronics; magentic field sensors

Related publications

  • Invited lecture (Conferences)
    Workshop on Active and Passive Materials for Tissue Engineering and Biomedical Applications, 30.10.2019, Shanghai, China

Publ.-Id: 30258

Thermal Stability of Defect-Enhanced Ge on Si Quantum Dot Luminescence upon Millisecond Flash Lamp Annealing

Spindlberger, L.; Prucnal, S.; Aberl, J.; Brehm, M.

The intentional merging of epitaxial Ge on Si(001) quantum dots with optically active defect sites promises low-cost applications such as room temperature (RT)light emitters in Si photonics. Despite recent progress in this field, important benchmarks, for example, the thermal stability of such a combination of low-dimensional nanosystems, as well as the curing of parasitic charge-carrier recombination channels, have been barely investigated thus far. Herein, the structural robustness of defect-enhanced quantum dots (DEQDs) is examined under millisecond flash lamp annealing (FLA), carried out at sample temperatures up to 800oC. Changes in the optical DEQD properties are investigated using photoluminescence spectroscopy performed in a sample temperature range from10 to 300 K. It is demonstrated that FLA—in contrast to in situ thermal annealing—leads to only negligible modifications of the electronic band alignment. Moreover, upon proper conditions of FLA, the RT emission intensity of DEQDs is improved by almost 50% with respect to untreated reference samples.

Keywords: Ge QDs; MBE; FLA; PL

Related publications


Publ.-Id: 30256

Modification of optical, electrical and structural properties of two-dimensional materials using millisecond range flash lamp annealing

Prucnal, S.; Juanmei, D.; Tsai, H.-S.; Chia-Nung, K.; Chin, S. L.; Zhou, S.

The two-dimensional materials with direct band gap are attractive for optoelectronics operated in the visible and near infrared spectral range. The number of new van der Waals crystals increases systematically but the doping and the modification of their optoelectronic properties remain challenging. Here we present the tuning of the fundamental properties of different 2D mono- and dichalcogenides using millisecond range flash lamp annealing (FLA) in the controlled atmosphere. Those investigated 2D flakes are made by mechanical exfoliation onto the SiN/Si substrates. The change of internal properties of 2D chalcogenides is monitored by micro-Raman, photoluminescence and photoreflectance spectroscopies as well as conductive atomic force microscope (c-AFM). Using ms-range FLA in N2 ambient the transition metal dichalcogenides are stable up to the annealing at 1200 oC, while upon high temperature annealing the group IV-dichalcogenides can be reduced to monochalcogenides which opens new route for the fabrication of heterostructures. The formation of SnSe/SnSe2 heterostructures is proven by micro-Raman spectroscopy and current-voltage characteristic obtained by c-AFM measurements.

Keywords: 2D materials; MoSe2; MnPS3; FLA; ion implantation; Raman spectroscopy

Related publications

  • Lecture (Conference)
    EMRS Fall Meeting 2019, 16.-19.09.2019, Warsaw, Poland

Publ.-Id: 30255

Tuning of the photocatalytic efficiency in anatase-TiO2 using millisecond range flash lamp annealing

Prucnal, S.; Gago, R.; Esteban-Mendoza, D.; Jiménez, I.; Aktas, O. C.; Faupel, F.; Zhou, S.

Semiconducting metal oxides often exhibit high photocatalytic efficiency (PE) and, among them, the anatase-TiO2 (A-TiO2) is the most promising material for the water splitting under sun light illumination. The PE of TiO2-based materials mainly depends on the surface state density, Fermi level position, band gap and crystalline structure (anatase, rutile, brookite). Here, we present the optical, electrical and structural properties of A-TiO2 thin films made by RT magnetron sputtering followed by ms-range flash lamp annealing (FLA) in N2 ambient. X-ray diffraction (XRD), X-ray absorption near-edge structure, and Raman spectroscopies reveal the transformation from amorphous to single-phase A-TiO2 during FLA for 20 ms. The FLA energy density was in the range of 65 to 110 Jcm-2, corresponding to peak temperatures in the range of 500oC to 1100 oC, respectively. XRD and scanning electron microscopy shows that with increasing FLA energy the average crystal size of the A-TiO2 increases from a few nm?s up to ~200 nm after annealing at energy density of 110 Jcm-2. On the other hand, the optical band-gap, as determined by spectroscopic ellipsometry, remains at ~3.4 eV. The bleaching of methylene blue under irradiation with a high-intensity light-emitting-diode (4.5 W/cm2) at 365 nm has been used to test the photoactivity of the samples after FLA. The PE of the samples is enhanced with increasing the annealing temperature, which we assign to the engineering of surface states and carrier lifetime upon FLA in N2 ambient.

Keywords: TiO2; doping; FLA

Related publications

  • Poster
    EMRS Fall Meeting 2019, 16.-19.09.2019, Warsaw, Poland

Publ.-Id: 30254

Band gap renormalization in n-type Ge and GeSn alloys made by millisecond range flash lamp annealing

Prucnal, S.; Berencen, Y.; Wang, M.; Rebohle, L.; Kudrawiec, R.; Polak, M.; Zviagin, V.; Schmidt-Grund, R.; Grundmann, M.; Grenzer, J.; Turek, M.; Droździel, A.; Pyszniak, K.; Zuk, J.; Helm, M.; Skorupa, W.; Zhou, S.

The last missing piece of puzzle for the full functionalization of group IV optoelectronic devices is the direct band gap semiconductor made by CMOS compatible technology. Here we report on the fabrication of GeSn alloys with a Sn concentration of up to 6 % using ion implantation followed by ms-range explosive solid phase epitaxy. The n-type single crystalline GeSn alloys are made by co-doping of Sn and P into Ge. Both the activation of P and the formation of GeSn are performed during a single-step flash lamp annealing for 3 ms. The band gap engineering in ultra-doped n-type Ge and GeSn alloys is theoretically predicted by density functional theory and experimentally verified using ellipsometric spectroscopy. We demonstrate that both the diffusion and the segregation of Sn and P atoms in Ge are fully supressed by ms-range non-equilibrium thermal processing.

Keywords: Ge; GeSn; ion implantation; FLA; Raman

Related publications

  • Poster
    EMRS Fall Meeting 2019, 16.-19.09.2019, Warsaw, Poland

Publ.-Id: 30253

Developing a solvent extraction process for recovery of chromium and vanadium from steel slags

O'Toole, N.; Mansel, A.; Kelly, N.; Scharf, C.

The demand for strategic metals such as chromium and vanadium is predicted to rise in the future. These metals can currently be found in the slag by-products of certain steel production processes. We are developing a solvent extraction process for the separation and purification of these valuable resources from alkaline oxidative leach feed streams. This process shows potential to be applicable to alternative feed streams in addition. The extractant phase used is commercially available Aliquat 336 with kerosene as diluent and long-chain alcohol or ketone as phase modifiers. The use of the radiotracer technique allows simple and precise measurement of the metal concentration at each step of the process. Chromium-51 and vanadium-48 radionuclides are produced in-house at the HZDR cyclotron facility. Early results have shown that this process effectively removes chromium and vanadium together from model feed streams, indicating the need for a further separation step of the two species. To this end, a chromate scrub step is suggested.

  • Lecture (Conference)
    Developing a solvent extraction process for recovery of chromium and vanadium from steel slags, 23.-26.06.2019, Düsseldorf, Deutschland

Publ.-Id: 30252

Evolution of donor-vacancy clusters in Ge, GeSn and SiGeSn during ms-range FLA monitored by positron annihilation spectroscopy

Prucnal, S.; Liedke, M. O.; Wang, X.; Posselt, M.; Knoch, J.; Berencen, Y.; Rebohle, L.; Napolitani, E.; Frigerio, J.; Ballabio, A.; Isella, G.; Hübner, R.; Wagner, A.; Zuk, J.; Turek, M.; Helm, M.; Zhou, S.

The n-type doping of Ge and Ge-based alloys is a self-limiting process due to the formation of vacancy-donor complexes (DnV with n ≤ 4) that deactivate the donors. This work clearly demonstrates that the dissolution of the DnV clusters in a heavily n-doped Ge, GeSn and SiGeSn layers can be achieved by millisecond-flash lamp annealing. This DnV cluster dissolution results in a considerable increase of the electrical activation together with a suppression of donor diffusion. Using electrical measurements and positron annihilation lifetime spectroscopy, combined with theoretical calculations, it is possible to address, understand and solve the fundamental problem of achieving ultra-high doping level in Ge, that has hindered so far the full integration of Ge and Ge-based alloys with complementary-metal-oxide-semiconductor technology.

Keywords: Ge; GeSn alloy; defects; flash lamp annealing; ion implantation

Related publications

  • Lecture (Conference)
    EMRS Fall Meeting 2019, 16.-19.09.2019, Warsaw, Poland

Publ.-Id: 30251

Separation and recovery of chromium and vanadium from alkaline leaching solutions of Cr-V-bearing slags

O'Toole, N.; Mansel, A.; Kelly, N.; Scharf, C.

To address the projected requirements of future technology and ecology, and move towards a circular economy, a comprehensive consideration of the sources, processing methods, and life cycles of natural resources is needed. Certain important metal resources, such as chromium and vanadium, are currently available but unexploited in the slag by-products of steel production processes. This represents a significant potential source of these elements for European enterprise. To help meet the rising demand, the CHROMIC project seeks to develop a hydrometallurgical process for the recovery and purification of these valuable resources. By utilising an oxidative, high-alkaline leaching method, the process aims to avoid the destruction of the saleable slag matrix, as well as the presence of Si or Fe in the leachate solution. Various methods are being investigated for separation of the metal value from the resulting alkaline leach feeds, including solvent extraction (SX) which is the focus of this work.
In developing this SX process, the radiotracer technique has been employed, utilising chromium-51 and vanadium-48 radionuclides produced in-house at the HZDR cyclotron facility. The use of this technique, in combination with more conventional methods such as ICP-OES, allows for precise and powerful analysis of the process with minimal workup after experiments.
Aliquat 336, a quaternary ammonium based IL, is suitable for the separation of oxoanions from such alkaline solutions due to the presence of the organic cation species, independently of pH. This extractant is mostly used in its commercially available chloride form, although experiments involving alternative anions (e.g. OCl⁻, OH⁻, S₂O₈²⁻, CO₃²⁻) are also necessary to investigate the influence of competing anions (arising from the leaching conditions) on the SX process. Scrubbing and back extraction of the loaded IL phase has been demonstrated, using solutions of sodium chromate and sodium chloride. Experiments have now begun on the real leaching solutions of steel slags relevant to the CHROMIC project.

  • Poster
    Separation and recovery of chromium and vanadium from alkaline leaching solutions obtained from Cr-V-bearing slags, 08.-11.09.2019, Sitges, Spanien

Publ.-Id: 30250

Dissolution of donor-vacancy clusters in heavily doped n-type germanium via millisecond annealing

Prucnal, S.; Liedke, M. O.; Butterling, M.; Posselt, M.; Wang, X.; Knoch, J.; Windgassen, H.; Hirschmann, E.; Berencén, Y.; Napolitani, E.; Frigerio, J.; Ballabio, A.; Isella, G.; Hübner, R.; Wagner, A.; Helm, M.; Zhou, S.

The n-type doping of Ge is self-limiting process due to formation of the vacancy-donor complexes (Dn V with n≤4). Here we report on experiments and density functional theory (DFT) calculations solving the basic problem of donor deactivation in heavily doped Ge. The self-healing process of heavily doped n-type Ge is achieved by rear-side flash lamp annealing (r-FLA) for 20 ms with the peak temperature of about 1050 K. The positron-annihilation lifetime spectroscopy (PALS) reveals that the P4V clusters are main defects in the as-grown Ge:P samples. Millisecond range high-temperature treatment dissociates the phosphorus-vacancy cluster (P4V) and, as shown by SIMS, fully supress the P diffusion. The electrochemical capacitance-voltage (ECV) profiling shows that the effective carrier concentration in P doped Ge (P concentration - 1×1020 cm-3) increases from about 3×1019 cm-3 in as-grown sample to above 8×1019 cm-3 after r-FLA. For the first time using structural (PALS, SIMS) and electrical (ECV) characterization combined with DFT calculations we were able to addressed, explained and solved the fundamental problem hindering the full integration of Ge with CMOS technology.

Keywords: ion implantation; germanium; FLA; defects

Related publications

  • Lecture (Conference)
    Gettering and Defect Engineering in Semiconductor Technology, 22.-27.09.2019, Zeuthen, Germany

Publ.-Id: 30249

Range Verification in Particle Therapy – From Physics in the Lab Towards Clinical Applications

Kögler, T.

Reichweiteverifikation ist ein wesentlicher Baustein zur Reduzierung der Sicherheitssäume in der Partikeltherapie. Da eine direkte Messung der Reichweite schwerer geladener Teilchen im menschlichen Gewebe schwierig ist, ist man derzeit auf den Informationsgehalt von Sekundärstrahlung angewiesen, die bei der Abbremsung der primären Teilchen im Körper entstehen.
Die durch Kernwechselwirkungen entstehende prompte Gammastrahlung ist hierfür ein vielversprechende Sonde.
Mehrere Ansätze zur Verifikation der Reichweite von therapeutischen Protonen mittels prompter Gammastrahlung wurden in den vergangenen Jahren untersucht. Bisher wurde erst eine, das Prompt Gamma Ray Timing, erfolgreich am Patienten angewendet. Andere Methoden befinden sich kurz vor den ersten klinischen Anwendungen.
Auf dem Weg von der Idee eines Reichweiteverifikationsverfahrens bis hin zu dessen klinischer Implementierung ist es jedoch ein langer und schwieriger Weg. Dieser Beitrag zeigt welche Schwierigkeiten bei der erfolgreichen Einführung eines derartigen Systems in den klinischen Alltag existieren und geht dabei auf mehrere konkrete Beispiele ein.

Keywords: Range verification; proton therapy; prompt gamma rays

Related publications

  • Invited lecture (Conferences)
    Young Investigator's Workshop on Photon Detection in Medicine and Medical Physics, 02.-03.12.2019, Siegen, Deutschland

Publ.-Id: 30248

Nanodiamonds from Laser-induced Shock Compression of Polystyrene: Extraction Under Way

Schuster, A.; Hartley, N.; Voigt, K.; Zhang, M.; Lütgert, B. J.; Rack, A.; Vorberger, J.; Klemmed, B.; Benad, A.; Schumacher, D.; Tomut, M.; Molares, M. E. T.; Grenzer, J.; Christalle, E.; Hübner, R.; Merchel, S.; Turner, S. J.; Zettl, A.; Gericke, D. O.; Kraus, D.

In Uranus and Neptune methane and other hydrocarbons are highly abundant. Their planetary interior conditions can be mimicked using high intensity lasers in the laboratory on a nanosecond timescale. Nanodiamond formation from shock-compressed polystyrene (~150GPa, ~5000K) was demonstrated via in situ X-ray diffraction with a XFEL. The lower size estimate is 4nm. 60% of the carbon atoms in the plastic are
transferred to a diamond lattice. However, in total a maximum of ~16μg of nanodiamonds are expected from a 125nm CH foil and a 500μm focal spot. In order to understand the underlying hydrocarbon separation mechanism the physical recovery of nanodiamonds is pursued to learn from their shape, size, surface modifications and defects.

Keywords: nanodiamonds; recovery; laser-induced shock compression; icy planets

Related publications

  • Open Access Logo Poster
    8th Joint Workshop on High Pressure, Planetary and Plasma Physics (HP4), 09.-11.10.2019, Dresden, Deutschland


Publ.-Id: 30247

The role of microlayer for bubble sliding in nucleate boiling: A new view point for heat transfer enhancement via surface engineering

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

In an experimental study with a stainless steel heater (surface with maximum roughness Rt = 0.82 µm and contact angle hysteresis θhys = 53°), we investigated the bubble growth and motion during nucleation and departure. Complementary to that we analysed the formation of microlayer during the bubble growth and motion with computational fluid dynamics (CFD) simulation. From the simulations we found that the bubble motion leads to an expansion of the microlayer. From the experiments we obtained the drag coefficient on the bubble during bubble growth with an assumption of the absence of the wall surface tension force. From the comparison of this drag coefficient and the proposed values from the literature, we conclude that the vapour bubble does not directly contact the solid wall during the sliding. Using well-known mechanistic bubble growth models for further analysis of available microlayer area with the experimental data we conclude that a microlayer exists and the bubble must slide completely on this microlayer after leaving its originating cavity. From the change of microlayer size we can also explain the bubble regrowth after departure.

Keywords: Wall boiling; Bubble sliding; Microlayer; Nucleation


Publ.-Id: 30246

Cerebral Oxygen Metabolism in Adults with Sickle Cell Disease

Václavů, L.; Petr, J.; Petersen, E. T.; Mutsaerts, H. J. M. M.; Majoie, C. B. L.; Wood, J. C.; Vanbavel, E.; Nederveen, A. J.; Biemond, B. J.

In sickle cell disease (SCD), oxygen delivery is impaired due to anemia, especially during times of increased metabolic demand, and cerebral blood flow (CBF) must increase to meet changing physiologic needs. But hyperemia limits cerebrovascular reserve (CVR) and ischemic risk prevails despite elevated CBF. The cerebral metabolic rate of oxygen (CMRO 2 ) reflects oxygen supply and consumption so may be more insightful than flow-based CVR measures for ischemic risk in SCD. We hypothesized that adults with SCD have impaired CMRO 2 at rest and that a vasodilatory challenge with acetazolamide would improve CMRO 2 . CMRO 2 was calculated from CBF and oxygen extraction fraction (OEF), measured with arterial spin labeling and T 2 -prepared tissue relaxation with inversion recovery (T 2 -TRIR) MRI. We studied 36 adults with SCD without a clinical history of overt stroke and 9 healthy controls. As expected, CBF was higher in patients with SCD versus controls (mean ± standard deviation: 74±16 vs 46±5 mL/100g/min, P<.001), resulting in similar oxygen delivery (SCD: 377±67 vs controls: 368±42 μmol O 2 /100g/min, P=.69). OEF was lower in patients versus controls (27±4 vs 35±4 %, P<.001), resulting in lower CMRO 2 in patients versus controls (102±24 vs 127±20 μmol O 2 /100g/min, P=.002). After acetazolamide, CMRO 2 declined further in patients (P<.01) and did not decline significantly in controls (P=.78), indicating that forcing higher CBF worsened oxygen utilization in SCD patients. This lower CMRO 2 could reflect variation between healthy and unhealthy vascular beds in terms of dilatory capacity and resistance whereby dysfunctional vessels become more oxygen-deprived, hence increasing the risk of localized ischemia.

Publ.-Id: 30245

Ferromagnetic writing on B2 Fe50Rh50 thin films using ultra-short laser pulses

Schmeink, A. H.; Eggert, B.; Ehrler, J.; Mawass, M.; Hübner, R.; Potzger, K.; Lindner, J.; Fassbender, J.; Kronast, F.; Wende, H.; Bali, R.

The chemically ordered B2 Fe50Rh50 alloy is antiferromagnetic. By inducing chemical disorder its structure can be changed to the ferromagnetic A2 structure. Following the laser writing method published here [1] we used a pulsed laser to induce ferromagnetism locally in Fe50Rh50 thin films of 10, 20, and 30nm thickness. XMCD measurements on the laser-treated region revealed the formation of an annulus of FM contrast and a non-FM center. Transmission electron microscopy (TEM) on a section through the annulus found the FM region to be A2 and the enclosed non-contrast region of the fcc A1 structure. The surrounding untreated region remained in the B2 structure.

Related publications

  • Poster
    DPG Frühjahrstagung Regensburg, 31.03.-05.04.2019, Regensburg, Deutschland

Publ.-Id: 30244

Supervised machine learning for the quantification of mineral phases in drill-core hyperspectral data

Tusa, L.; Khodadadzadeh, M.; Contreras Acosta, I. C.; Fuchs, M.; Gloaguen, R.; Gutzmer, J.

Discovery and delineation of new ore deposits require substantial investment into diamond-drilling. Traditionally, the extracted drill-cores are visually analysed by site geologists and subjected to geochemical analyses for metal grade evaluation. Frequently, the geochemical information is insufficient for the evaluation of the mineralization and system morphology, mineralogical information being therefore required. Traditional mineralogical analyses such as optical microscopy, scanning electron microscopy, and X-ray diffraction are time consuming, require extensive sample preparation and deliver non-continuous point information. Due to its fast acquisition time, low sample handling requirements, and non-invasive character hyperspectral drill-core scanning has recently become an efficient tool for lithological / alteration drill core logging. Most commonly used for drill core scanning are visible to near-infrared (VNIR) and short-wave infrared (SWIR) hyperspectral sensors. These sensors allow the identification of mineral groups that show a specific signature as they absorb parts of the incoming light between 400 and 2500 nm. Many of the spectrally active minerals such as white micas, chlorites, epidotes or gypsum play an important role in exploration mapping as they have specific associations with the ore minerals and strong zonality in their distribution within the deposit. They can, therefore, be used as proxies for exploration vectoring and ore deposit modelling. Their compositional analysis and quantification has thus become an important tool for exploration. Commonly used methods for mineral abundance estimation from hyperspectral data consist in unmixing algorithms, which strongly rely on endmember extraction techniques. However, the obtained endmembers in hyperspectral drill-core data using conventional tools usually consist of mineral mixtures due to the spatial resolution of most hyperspectral sensors; the unmixing results will thus only define abundances of mixed compositions.
We propose a supervised machine learning-based methodology that uses the abundance of SWIR active mineral groups in selected representative known areas of the drill-core samples for predicting the content of these groups at the drill-core scale.
The training data consists of high-resolution scanning electron microscopy-based mineral maps resampled to the resolution of the hyperspectral image. As a result, the resampled image contains in each pixel the abundance of each selected mineral or mineral group. An artificial neural network-based regression is used in order to upscale the mineral abundances from the training set to the entire drill-core sample. Preliminary results show a great potential for automation and allow for the evaluation of the individual abundance of each mineral or mineral group.

  • Contribution to proceedings
    EGU General Assembly, 07.-12.04.2019, Vienna, Austria
    Proceedings of the EGU General Assembly
  • Poster
    EGU General Assembly, 07.-12.04.2019, Vienna, Austria

Publ.-Id: 30243

Evaluating the performance of hyperspectral short-wave infrared sensors for the pre-sorting of complex ores using machine learning methods

Tusa, L.; Kern, M.; Khodadadzadeh, M.; Blannin, R.; Gloaguen, R.; Gutzmer, J.

Sensor-based sorting is increasingly used for the concentration of ores. To assess the sorting performance for a specific ore type, the raw materials industry currently conducts trial-and-error batch tests. In this study, a new methodology to assess the potential of hyperspectral visible to near-infrared (VNIR) and short-wave infrared (SWIR) sensors, combined with machine-learning routines to improve the sorting potential evaluation, is pre- sented. The methodology is tested on two complex ores. The first is a tin ore in which cassiterite—the target mineral—is variable in grain size, heterogeneously distributed and has no diagnostic response in the VNIR-SWIR range of the electromagnetic spectrum. However, cassiterite is intimately associated with SWIR active minerals, such as chlorite and fluorite, which can be used as proxies for its presence. The second case study consists of a copper-gold porphyry, where copper occurs mainly in chalcopyrite, bornite, covellite and chalcocite, while gold is present as inclusions in the copper minerals and in pyrite. Machine-learning techniques such as Random Forest and Support Vector Machine applied to the hyperspectral data predict excellent sorting results in terms of grade and recovery. The approach can be adjusted to optimize sorting for a variety of ore types and thus could increase the attractivity of VNIR-SWIR sensor sorting in the minerals industry.

Keywords: Sensor-based sorting; Hyperspectral imaging; SWIR; Machine learning; Complex ores

  • Minerals Engineering 146(2020), 106150
    Online First (2019) DOI: 10.1016/j.mineng.2019.106150
    Cited 18 times in Scopus
  • Contribution to proceedings
    MEI Physical Separation, 13.-14.06.2019, Fallmouth, United Kingdom
  • Lecture (Conference)
    MEI Physical Separation, 13.-14.06.2019, Fallmouth, United Kingdom


  • Secondary publication expected

Publ.-Id: 30242

Mineral Mapping and Vein Detection in Hyperspectral Drill-Core Scans: Application to Porphyry-Type Mineralization

Tusa, L.; Andreani, L.; Khodadadzadeh, M.; Contreras Acosta, I. C.; Ivascanu, P.; Gloaguen, R.; Gutzmer, J.

The rapid mapping and characterization of specific porphyry vein types in geological samples represent a challenge for the mineral exploration and mining industry. In this paper, a methodology to integrate mineralogical and structural data extracted from hyperspectral drill-core scans is proposed. The workflow allows for the identification of vein types based on minerals having significant absorption features in the short-wave infrared. The method not only targets alteration halos of known compositions but also allows for the identification of any vein-like structure. The results consist of vein distribution maps, quantified vein abundances, and their azimuths. Three drill-cores from the Bolcana porphyry system hosting veins of variable density, composition, orientation, and thickness are analysed for this purpose. The results are validated using high-resolution scanning electron microscopy-based mineral mapping techniques. We demonstrate that the use of hyperspectral scanning allows for faster, non-invasive and more efficient drill-core mapping, providing a useful tool for complementing core-logging performed by on-site geologists.

Keywords: hyperspectral imaging; drill-core; mineral mapping; short-wave infrared; porphyry-type veins

Publ.-Id: 30241

Ligand-Exchange-Mediated Fabrication of Gold Aerogels Containing Different Au(I) Content with Peroxidase-like Behavior

Fan, X.; Cai, B.; Du, R.; Hübner, R.; Georgi, M.; Jiang, G.; Li, L.; Samadi Khoshkhoo, M.; Sun, H.; Eychmüller, A.

Noble-metal aerogels are emerging functional porous materials that have been applied in diverse fields. Among them, gold (Au) aerogels have displayed grand potentials in a wide range of catalytic processes. However, current fabrication methods fall short in obtaining Au gels with small ligament sizes and controlled surface valence states, which hinder the study of the underlying catalytic mechanisms. Here, a new approach of producing Au aerogels is reported. Via a two-phase ligand exchange, the long-chain ligands (oleylamine) of the as-prepared Au nanoparticles were replaced by short sulfide ions and subsequently self-assembled into three-dimensional gels. As a result, Au aerogels with small ligament sizes (ca. 3−4 nm) and tunable surface valence states are acquired. Taking the application for peroxidase mimics as an example, by correlating the surface valence with the catalytic properties, Au(I) is found to be the active site for H2O2 and substrate-binding site for 3,3′,5,5′-tetramethylbenzidine, paving a new avenue for on-target devising Au-based catalysts.

Related publications

Publ.-Id: 30240

Linear stability analysis of magnetized relativistic rotating jets

Bodo, G.; Mamatsashvili, G.; Rossi, P.; Mignone, A.

We carry out a linear stability analysis of a magnetized relativistic rotating cylindrical jet flow using the approximation of zero thermal pressure. We identify several modes of instability in the jet: Kelvin-Helmholtz, current-driven and two kinds of centrifugal-buoyancy modes - toroidal and poloidal. The Kelvin-Helmholtz mode is found at low magnetization and its growth rate depends very weakly on the pitch parameter of the background magnetic field and on rotation. The current-driven mode is found at high magnetization, the values of its growth rate and the wavenumber, corresponding to the maximum growth, increase as we decrease the pitch parameter of the background magnetic field. This mode is stabilized by rotation, especially, at high magnetization. The centrifugal-buoyancy modes, arising due to rotation, tend also to be more stable when magnetization is increased. Overall, relativistic jet flows appear to be more stable with respect to their non-relativistic counterpart.

Keywords: instabilities; MHD; galaxies: jets; Astrophysics; High Energy Astrophysical Phenomena


Publ.-Id: 30239

Application of Flash Lamp Annealing for Controlled Nickel Silicidation of Silicon Nanowires

Khan, M. B.; Deb, D.; Prucnal, S.; Erbe, A.; Georgiev, Y.

Silicon (Si) nanowires (NWs) have potential applications in various areas including electronics, opto-electronics and biochemical sensing. These wires are used to fabricate electronic devices with new architectures to complement the scaling down of electronic circuits. Our work focuses on one such architecture called Reconfigurable field effect transistors (RFET). An RFET is a Nickel(Ni)Si2-Si-NiSi2 Schottky junctions based device, which has an intrinsic Si channel. To fabricate an RFET, SiNWs are silicided at both ends to form Schottky junctions with the Si channel. Typically, it has two gates placed on each of the two Schottky junctions. It can be tuned to p- or n- polarity by applying appropriate electrostatic potential at one of the gates. Therefore, functional complexity and performance of electronic circuits can be enhanced using such FETs. Formation of NiSi2 is a pre-requisite for proper operation of these devices because metal work function of NiSi2 aligns itself near the mid-bandgap of Si. This enables band bending by application of an appropriate electrostatic potential for the operation of devices either as p- or as n- FET. We report our results on Ni silicidation using flash lamp annealing. By optimizing the silicidation process, control over the diffusion of Ni into the nanowire and proper silicide phase formation is achieved.

Related publications

  • Open Access Logo Lecture (Conference)
    DPG-Frühjahrstagung, Regensburg, 2019, 31.03.-05.04.2019, Regensburg, Germany

Publ.-Id: 30238

Fabrication and Characterization of Reconfigurable Field Effect Transistors

Khan, M. B.; Prucnal, S.; Hübner, R.; Erbe, A.; Georgiev, Y.

To complement scaling of field effect transistors, new device concepts were introduced recently. One such concept is the reconfigurable field effect transistor (RFET). These transistors are based on nickel silicide-Si-nickel silicide Schottky junctions and their polarity can be switched between p- and n- type at runtime by the application of an electrostatic potential [1]. Control over silicide length and phase is important for scaling and proper functioning of these devices [2]. NiSi2 is the desirable silicide phase as its metal work function aligns itself near mid bandgap of Si, which enables reconfigurability of the device [1, 3].
We report on fabrication and electrical characterization results of RFETs. Si nanowires (SiNWs) are fabricated on undoped silicon-on-insulator (SOI) substrates by a top-down process based on electron beam lithography and inductively coupled plasma etching. Then, Ni is placed at both ends of the SiNWs by metal evaporation and lift-off processes. Afterwards, flash lamp annealing (FLA) is performed for silicidation of the NWs.
FLA has enabled better control over silicidation length since flash times are much shorter (of the order of milli-seconds) than rapid thermal annealing (RTA) times. Transmission electron microscopy (TEM) shows the formation of the desired NiSi2 phase near the silicide-Si interface. Electrical characterization of the devices with back gating shows ambipolar behaviour. For unipolar behaviour, top gates need to be fabricated, results of which will be presented at the conference.

Keywords: Schottky junction; reconfigurability; field effect transistors; nickel silicide; annealing

Related publications

  • Open Access Logo Poster
    45th International Conference on Micro and Nano Engineering (MNE), 23.09.-26.12.2019, Rhodes, Greece

Publ.-Id: 30237

Understanding the role of carbon in active trap centre formation in porous alumina for ion beam dosimetry

Bhowmick, S.; Pal, S.; Das, D.; Singh, V.; Khan, S.; Hübner, R.; Roybarman, S.; Kanjilal, D.; Kanjilal, A.

In recent days, due to increased use of hadron therapy for cancer and tumor treatment, precise online dose monitoring is an important issue for safety purpose. Regarding hadron therapy, recently carbon ion beam with high Linear Energy Transfer (LET) is found to be more effective than the photon beams. Among several known TL/OSL oxides phosphors, C-doped alumina (Al2O3) is favorable for radiation dosimetry, especially in medical field due to its tissue equivalent in terms of radiation absorption, simple glow curve, and high sensitivity. A facile approach to improve thermoluminescence sensitivity of electrochemically anodized porous Al2O3 (AAO) is presented by introducing carbon ions for ion beam dosimetry. Initially, ion implantation technique has been carried out for Carbon doping in AAO in controlled manner. HAADF-STEM, EDS mapping, SEM studies reveal the evolution of a porous structure followed by the carbon distribution up to 200 nm. However, the evolution of optically active F+ centres with increasing ion fluence has been examined by photoluminescence investigation at room temperature and thermoluminescence (TL) measurement while the chemical nature of such defect centres has been extracted by depth dependent XPS analysis.

Related publications

  • Lecture (Conference)
    APS March Meeting 2019, 04.-08.03.2019, Boston, MA, USA

Publ.-Id: 30236

Development of highly affine fluorinated ligands and 18F-labelled radiotracers for PET imaging of the adenosine A2A receptor

Lai, T. H.

Adenosine is an essential neuromodulatory molecule that acts via four G-protein coupled receptors (A1R, A2AR, A2BR, A3R). In the central nervous system (CNS), the A2AR is highly concentrated in the striatum. The A2AR is a promising target for positron emission tomography (PET) imaging of neurodegenerative diseases, such as Huntington’s disease (HD), Alzheimer’s disease (AD) and Parkinson’s disease (PD). Istradefylline is the first A2AR antagonist that is approved by the U.S. Food and Drug Administration (FDA) for adjunctive treatment in patients with PD. So far, [18F]MNI-444 [Ki (hA2AR) = 2.8 nM] is the only 18F-labelled A2AR radiotracer evaluated in healthy subjects.

Aiming at the development of A2AR radiotracers with improved molecular imaging properties, this study is based on three recently published lead compounds with a pyrazolo[3,4-d]pyridine, a morpholinobenzo[d]thiazol-2-amine and a pyrazolo[4,3‑e]‑1,2,4-triazolo[1,5‑ c]-pyrimidine scaffold. Herein, a series of 30 fluorinated derivatives was developed by systematic modification of selected lead compounds. The binding affinities torwards the A2AR and the adenosine A1 receptor (A1R) subtypes were determined by in vitro radioligand binding assays. Regarding the binding affinity and selectivity, PYP1 [Ki (hA2AR) = 5.29 nM, Ki (hA1R) = 220 nM)], PYP2 [Ki (hA2AR) = 2.13 nM, Ki (hA1R) = 147 nM)] und TOZ1 [Ki (hA2AR) = 1.00 nM, Ki (hA1R) = 618 nM)] were radiolabelled as the most suitable A2AR ligands in order to perform first preclinical studies in mice. Additionally, FLUDA [Ki (hA2AR) = 0.61 nM, Ki (hA1R) = 767 nM] was developed and radiolabelled based on the known PET radiotracer [18F]FESCH. [18F]FESCH was selected as reference compound and thus, its radio-synthesis was established as well as optimised in our laboratories.

Three different labelling strategies have been investigated in the frame of this work: (i) two-step one-pot radiolabelling procedures using 18F-labelled prosthetic groups, (ii) alcohol-enhanced copper-mediated one-step radiolabelling procedures starting from boronic acid pinacol ester precursors and (iii) conventional one-step radiolabelling procedures starting from nitro precursors. After the successful radiosynthesis, all five A2AR radiotracers were evaluated by in vitro and in vivo experiments. In vitro autoradiography on mice brain slices revealed specific binding of [18F]PPY2, [18F]TOZ1 and [18F]FLUDA in the region of interest (striatum). Metabolism studies in mice showed a fast metabolic degradation of [18F]PPY1 and [18F]PPY2 with the formation of brain penetrating radiometabolites. In contrast, [18F]TOZ1 and [18F]FLUDA displayed a higher metabolic stability in vivo as the reference [18F]FESCH. PET studies of [18F]PPY1, [18F]PPY1 and [18F]TOZ1 in CD-1 mice revealed no specific accumulation in striatum which would be non-consistent with the known A2AR distribution pattern. The findings indicate that these radiotracers may not demonstrate sufficient affinity in vivo for PET imaging of the A2AR in the brain. In contrast to the previous results, striatum was clearly visualized in PET studies with [18F]FLUDA. Altogether [18F]FLUDA revealed improved molecular imaging properties compared [18F]FESCH which might be a result of the introduction of deuterium atoms in the [18F]fluoroethyl chain, thus resulting in an increased metabolic stability.

In conclusion, the preclinical evaluation of the new developed radiotracers demonstrated that [18F]FLUDA has the highest potential to provide information about the A2AR expression by PET imaging of the brain. Hence, we focus on the clinical translation of [18F]FLUDA to study the A2AR expression in patients with Parkinson’s disease.

Keywords: adenosine A2A receptor; radiofluorination; PET imaging; Parkinson’s disease

  • Doctoral thesis
    Universität Leipzig, 2020
    Mentor: Prof. Peter Brust
    185 Seiten

Publ.-Id: 30235

Development and biological evaluation of [18F]FLUDA for clinical translation to image the adenosine A2A receptor with PET

Lai, T. H.; Teodoro, R.; Toussaint, M.; Gündel, D.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Schröder, S.; Moldovan, R.-P.; Brust, P.

The adenosine A2A receptor (A2AR) is related to the pathogenesis of several brain diseases and is assumed to mediate immunsuppressive processes related to cancer pathology. Thus, A2AR radiotracers for PET imaging are promising candidates for the differential diagnosis of neurodegenerative diseases, in particular Parkinson’s disease, and to study the A2AR within the tumor environment. We developed [18F]FLUDA based on the deuteration of the [18F]fluoroethoxy chain of [18F]FESCH [1,2] to improve imaging properties in mice. [18F]FLUDA was evaluated pre-clinically prior to a first-in-human trial.

Binding affinities of FLUDA towards the human A2AR and A1R subtypes were estimated in vitro by competitive radioligand binding assays. [18F]FLUDA was synthesized by a two-step one-pot approach. In vitro autoradiography of [18F]FLUDA was performed on mice brain cryosections. In vivo evaluation of [18F]FLUDA was carried out in a CD-1 mouse by radio-HPLC analysis of plasma and brain samples (15 min p.i.) and dynamic PET/MR studies under baseline (n = 4) and blocking conditions (2.5 mg tozadenant per kg, 15 min before tracer, n = 4). The cerebellum was used as a reference tissue. The time-activity curves were obtained and the SUV ratio (SUVR) of striatum over cerebellum were used as measure for specific uptake.

In vitro binding studies revealed no influence of deuteration on the estimated binding affinities with Ki values of FLUDA and FESCH towards human A2AR of 0.60 nM and 0.61 nM, respectively. The radiosynthesis of [18F]FLUDA was successfully established (Fig.1). A single experiment indicates that [18F]FLUDA is metabolically more stable in mouse than [18F]FESCH. While no radiometabolites were found for [18F]FLUDA in plasma and brain samples at 15 min p.i., for [18F]FESCH the percentages of intact radiotracer were 71% and 41% in brain and plasma samples, respectively. By in vitro autoradiography [18F]FLUDA demonstrated a specific accumulation in the striatum, which is characterized by the binding parameters KD = 4.3 ± 0.7 nM and Bmax = 556 ± 143 fmol/mg wet weight (Fig.2A). PET scans revealed a selective binding of [18F]FLUDA in striatum (SUVR15 30 min p.i. >8), which was significantly reduced by tozadenant pre-treatment by 30% (p<0.05, Fig.2B/C).

The two-step one-pot radiosynthesis of [18F]FLUDA was successfully implemented for preclinical studies. Due to the promising preclinical results in mice, we focus on the clinical translation of [18F]FLUDA. Based on the performed single dose toxicity study of FLUDA we don’t expect any adverse effects. Currently, we are working on the radiation dosimetry of [18F]FLUDA in piglets and its implementation for clinical application.

The authors thank the European Regional Development Fund and Sächsische Aufbaubank (SAB) for financial support (project no. 100226753).

(1) Bhattacharjee et al., Nucl Med Biol 2011, 38, 897-906; (2) Khanapur et al., J Med Chem 2014, 57, 6765-80

Keywords: Adenosine A2A Receptor; [18F]FLUDA; Fluorine-18; PET; Brain

  • Lecture (Conference) (Online presentation)
    15th European Molecular Imaging Meeting, 24.-28.08.2020, online, online

Publ.-Id: 30234

Ion beams for information technology

Zhou, S.

Taking the advancing of accelerator technologies, a variety of ions (all stable elements and some radioactive elements) in a wide energy range from eV to GeV can be produced and injected into targets. Using the chemical effect of injected ions, “ion implantation" has been well established to dope semiconductors and integrated into the standard microelectronics production line in Si-chip technology. Ion irradiation refers to using other effects rather than the doping effect in materials and has been used for defect (or lifetime) engineering in microelectronics. Moreover, ion beams are also instrument for the analysis of solid state surfaces to get the information about the composition and impurity lattice location. In this talk, I will give some examples for the application of ion beams in information technologies. The following topics will be included: (1) Doping semiconductors well above the solid solidity limits: by doing so the semiconductors can be ferromagnetic or superconducting [1-5]. (2) Defect engineering in SiC: defects can carry magnetic moments giving possibilities for ferromagnetic coupling in SiC as well as for manipulating single defect center for quantum technology [6, 7]. (3) Defect engineering in oxides: it can introduce uniaxial strain and change the properties rather than by choosing different growth substrates [8, 9]. It is worthy to note that ion beam technology has been well developed for applications at wafer (450 mm) scale. Once the proof-of-concept is done, these applications mentioned above can be easily transferred to industries.

[1] M. Khalid, et al., Phys. Rev. B 89, 121301(R) (2014).
[2] S. Zhou, J. Phys. D: Appl. Phys. 48, 263001(2015).
[3] Y. Yuan, et al., Phys. Rev. Materials 1, 054401 (2017).
[4] M. Wang, et al., Phys. Rev. Applied. 11, 054039 (2019).
[5] S. Prucnal, et al., Phys. Rev. Materials 3, 054802 (2019).
[6] S. Zhou, X. Chen, J. Phys. D: Appl. Phys. 52, 393001 (2019).
[7] C. Kasper, et al., arXiv:1908.06829v1 (2019).
[8] P. Pandey, et al., APL Materials 6, 066109 (2018).
[9] C. Wang, et al., Topological Hall effect in single thick SrRuO3 layers induced by defect engineering, submitted (2019).

Related publications

  • Lecture (others)
    Invited seminar at Institute of Semiconductors, CAS, 14.11.2019, Beijing, China
  • Lecture (others)
    Invited seminar at Tsinghua University, 15.11.2019, Beijing, China

Publ.-Id: 30233

Extended room-temperature infrared photoresponse in hyperdoped Si by ion implantation

Zhou, S.

Presently, silicon photonics requires photodetectors that are sensitive in a broad infrared range, can operate at room temperature, and are suitable for integration with the existing Si technology process. Here, we demonstrate strong room-temperature sub-bandgap photoresponse of photodiodes based on Si hyperdoped with chacolgen ions. The epitaxially recrystallized hyperdoped Si layers are developed by ion implantation combined with pulsed laser melting and incorporate Se/Te dopant concentrations several orders of magnitude above the solid solubility limit. With increasing the impurity concentration, the hyperdoped Si is changed from insulating to quasi-metallic with a finite conductivity as the temperature tends to zero. The optical absorptance is found to increase monotonically with increasing dopant concentration and extends well into the mid-infrared range. Temperature-dependent optoelectronic photoresponse unambiguously demonstrates that the extended infrared photoresponsivity from hyperdoped Si p-n photodiodes is mediated by an impurity band within the upper half of the Si bandgap. This work contributes to pave the way towards establishing a Si-based broadband infrared photonic system operating at room temperature.
References: Sci. Reports 7, 43688 (2017), Phys. Rev. Appl. 10, 024054 (2018) and Adv. Mater. Inter. 5, 1800101 (2018), Phys. Rev. Applied 11, 054039 (2019).

Related publications

  • Invited lecture (Conferences)
    14th National Conference on Laser Technology and Optoelectronics, 17.-20.03.2019, Shanghai, China
  • Invited lecture (Conferences)
    2nd International Conference on Radiation and Emission in Materials, 15.-18.12.2019, Bangkok, Thailand

Publ.-Id: 30232

Ion irradiation effect in complex oxides: Another degree of freedom or complexity?

Zhou, S.; Wang, C.; Pandey, P.; Chang, C. H.; Ganesh, R.; Chen, D.; Gemming, S.; Chu, Y.-H.; Helm, M.

Inter-relations among charge, spin, orbital and lattice parameters are largely demonstrated in multi-functional oxide materials, which exhibit a variety of exotic properties, ranging from superconductivity, insulator-metal transition, colossal magnetoresistance, charge ordering, and orbital ordering, etc. In particular, tilting a delicate energy balance in lattice interactions and kinetics, achieved by temperature, pressure or chemical control, may result in exotic phenomena in these systems. However, fine-tailoring such interactions has proven difficult. In this context, defect engineering by ion irradiation, which can introduce strain and electronic disorder, has emerged as a powerful technique to fine tune complex phases of oxide thin films. In this contribution, we show that ion irradiation can modify the magnetic and electrical transport properties in a broad variety of materials, including spinel NiCo2O4, perovskite BiFeO3, SrRuO3 and LaNiO3 [1-4]. Diverse magnetic, structure and magneto-transport modifications, which are inaccessible by conventional film growth methods, have been obtained. For instance, the transport in LaNiO3 can be driven from metallic phase into an Anderson insulator by directly tuning the electronic mean free path via irradiation-induced disorder [4]. In BiFeO3, we have obtained a super-tetragonal phase with the largest c/a ratio ~ 1.3 that has ever been experimentally achieved in BiFeO3 [2]. This may lead to strong polarization enhancement. By comparing the effect in different materials, we will also point out the complexity in understanding the tailoring of oxides by ion beams.

[1] P. Pandey, Y. Bitla, M. Zschornak, M. Wang, C. Xu, J. Grenzer, D. C. Meyer, Y. Y. Chin, H. J. Lin, C. T. Chen, S. Gemming, M. Helm, Y. H. Chu, S. Zhou, Enhancing the Magnetic Moment of Ferrimagnetic NiCo2O4 via Ion Irradiation driven Oxygen Vacancies, APL Materials 6, 066109 (2018)
[2] C. Chen, C. Wang, X. Cai, C. Xu, C. Li, J. Zhou, Z. Luo, Z. Fan, M. Qin, M. Zeng, X. Lu, X. Gao, U. Kentsch, P. Yang, G. Zhou, N. Wang, Y. Zhu, S. Zhou, D. Chen, J. Liu, Controllable defect driven symmetry change and domain structure evolution in BiFeO3 with enhanced tetragonality, Nanoscale 11, 8110 (2019)
[3] C. Wang, C. Chen, C.-H. Chang, H.-S. Tsai, P. Pandey, C. Xu, R. Böttger, D. Chen, Y.-J. Zeng, X. Gao, M. Helm, S. Zhou, Defect-induced exchange bias in a single SrRuO3 layer, ACS Appl. Mater. Interfaces, 27472 (2018).
[4] C. Wang, C.-H. Chang, A. Huang, P.-C. Wang, P.-C. Wu, L. Yang, C. Xu, P. Pandey, M. Zeng, R. Böttger, H.-T. Jeng, Y.-J. Zeng, M. Helm, Y.-H. Chu, R. Ganesh, S. Zhou, Tunable disorder and localization in the rare-earth nickelates, Phys. Rev. Materials 3, 053801 (2019)

Related publications

  • Lecture (Conference)
    64th Annual Conference on Magnetism and Magnetic Materials, 03.-08.11.2019, Las Vegas, US
  • Lecture (others)
    Seminar talk at DESY, 06.-07.05.2019, Hamburg, Deutschland

Publ.-Id: 30231

Ferromagnetism and Anisotropic Spinodal Phase Separation in (In,Fe)As

Yuan, Y.; Hübner, R.; Birowska, M.; Helm, M.; Sawicki, M.; Dietl, T.; Zhou, S.

We report on the experimental observation and theoretical studies of a self-assembled Fe-rich (In,Fe)As nano-lamellar structure that is driven by anisotropic spinodal decomposition at the growth front during laser heating-induced recrystallization of Fe-implanted InAs [1]. Pseudomorphically embedded in the InAs lattice, those Fe-rich nano-lamellae are perpendicular to the (001) surface and parallel to the in-plane [110] crystallographic direction. The Fe atoms are substitutionally incorporated at the indium sites. Magnetic measurements indicate a typical blocked superparamagnetic behavior suggesting strong ferromagnetic orderings inside the Fe-rich nanostructures, but weak coupling between the nano-lamellae. Our findings explain the surprisingly high apparent Curie temperatures and unexpected eight-fold symmetry of crystalline anisotropic magnetoresistance found previously in Be-doped n-type (In,Fe)As grown by molecular beam epitaxy [2]. Prompted by these results we discuss how a different d-level electronic configuration of Fe in InAs and Mn in GaAs [3] affects the magnetic ion incorporation and spatial distribution and, thus, magnetism and anisotropy. Our results also indicate that the directional distribution of impurities or alloy components setting in during the growth may account for the observed nematicity in other classes of correlated systems.

[1] Y. Yuan, R. Hübner, M. Birowska, C. Xu, M. Wang, S. Prucnal, R. Jakiela, K. Potzger, R. Böttger, S. Facsko, J.A. Majewski, M. Helm, M. Sawicki, S. Zhou, T. Dietl, Nematicity of correlated systems driven by anisotropic chemical phase separation, in Phys. Rev. Materials 2, 114601 (2018).
[2] Pham Nam Hai, D. Sasaki, Le Duc Anh, and M. Tanaka, Crystalline anisotropic magnetoresistance with twofold and eight-fold symmetry in (In,Fe)As ferromagnetic semiconductor, Appl. Phys. Lett. 100, 262409 (2012).
[3] M. Birowska, C. Śliwa, J. A. Majewski, and T. Dietl, Origin of Bulk Uniaxial Anisotropy in Zinc-Blende Dilute Magnetic Semiconductors, Phys. Rev. Lett. 108, 237203 (2012).

Related publications

  • Lecture (Conference)
    64th Annual Conference on Magnetism and Magnetic Materials, 03.-08.11.2019, Las Vegas, US

Publ.-Id: 30230

Near-Surface Cobalt Implantation Into Amorphous Carbon Films: Observation Of Complex Magnetic Nanostructures And Multiple Magnetic Phases

Suschke, K.; Gupta, P. G. S.; Williams, G. V. M.; Hübner, R.; Kennedy, J.; Markwitz, A.

Magnetic nanoclusters in amorphous carbon have promising applications for highly responsive magnetic sensors, where decreasing the size of the nanoclusters can lead to superparamagnetism and therefore low remanence. The insulating properties (wide bandgap) of amorphous carbon are also potentially useful for designing high frequency components. Both these properties are crucial to achieve ultra-high density magnetic data storage.

High fluence (1.2×1017 Co/cm2) near-surface implantation of 30 keV Co ions into amorphous carbon results in the formation of complex magnetic nanostructures and multiple magnetic phases. Next to small segregated cobalt carbide nanoclusters, starting forming at a depth of 25 nm within the amorphous carbon film, a nearly continuous network of cobalt carbide thin nanocrystalline regions can be observed at a depth of 8 nm. On the surface a 3 nm thin cobalt oxide nanostructured layer is seen separated from the cobalt carbide by a 1 nm thin Co-depleted region. TEM and magnetic measurements show superparamagnetic nanoclusters with a blocking temperature of 5 K. However, a small proportion of larger cobalt carbide nanoclusters exhibits magnetic hysteresis even at room-temperature. The magnetic saturation moment is as high as 0.51 µB/Co at 2 K and 0.32 µB/Co at room temperature - ten times larger than previously reported on hydrogenated amorphous carbon [1]. The structural disorder of the nanoparticles results in a spin glass behaviour with a range of transition temperatures below ~70 K, suggesting a spin disordered shell model [2]. Thus high fluence Co-implantation into amorphous carbon at room temperature created complex magnetic nanostructures consisting of cobalt oxide and cobalt carbide. Multiple magnetic phases such as superparamagnetism, spin glass, ferromagnetism and also antiferromagnetism can be observed.


1. P.G. Sridhar Gupta, G.V.M. Williams and A. Markwitz, Journal of Physics D: Applied Physics, 2016, 49, 5, 055002.
2. T. Prakash, G.V.M. Williams, J. Kennedy and S. Rubanov, Materials Research Express, 2016, 3, 12, 126102.

Related publications

  • Lecture (Conference)
    9th International Conference on Advanced Materials and Nanotechnology, AMN9, 10.-14.02.2019, Wellington, New Zealand

Publ.-Id: 30228

Simultaneous optical measurement of temperature and velocity fields in solidifying liquids

Anders, S.; Noto, D.; Tasaka, Y.; Eckert, S.

We introduce a complex image processing scheme for the simultaneous application of liquid crystal thermometry (LCT), in addition to the previously established method in Anders et al. (Exp Fluids 60(4):68, 2019. https :// for particle tracking velocimetry and particle image velocimetry. This scheme was developed for an experimental study on the double-diffusive convection in an aqueous ammonium chloride solution NH4Cl(aq) during crystallization. The use of thermochromic liquid crystals (TLC) enables to visualize the flow and temperature field simultaneously. We present a color interpolation method that enhances the accuracy of the LCT by yielding RGB images only representative of the TLC’s coloration. An artificial neural network (ANN) which processes RGB triplets and spatial color dependencies transforms these images into temperature fields. The combination of the ANN system and a corresponding calibration procedure enhances the accuracy and measurable temperature range of the LCT compared to state-of-the-art procedures. By using the here established measurement scheme, quantitative global studies of the mutual influence between solidification and convection are enabled and exemplary results are presented.

Keywords: multiphase flow; double-diffusive convection; solidification; liquid crystal thermometry; artificial neural network; TLC; PIV; PTV; PITV


Publ.-Id: 30227

Selektive Trennung von Rhenium und Molybdän mittels Solventextraktion – Untersuchung von supramolekularen Wechselwirkungen und Komplexbildung

Nestel, J.; Helbig, T.; Kelly, N.

Rhenium ist ein sehr seltenes Element. Die Häufigkeit in der Lithosphäre liegt in der Größenordnung von Gold. Als Hochtechnologiemetall erfährt Rhenium insbesondere zur Fertigung hochwarmfester Superlegierungen steigende Nachfrage. Sowohl in den natürlichen Lagerstätten, als auch in Sekundärrohstoffen, liegt Rhenium häufig gemeinsam mit Molybdän vor.
Im Rahmen der Solventextraktion von Re(VII) und Mo(VI) aus saurer Lösung mittels aliphatischer Amine wurde bereits in den 1980er Jahren ein Effekt beschrieben, der bei Zusatz von Organophosphorderivaten eine selektive Trennung von Re(VII) und Mo(VI) bei der Reextraktion ermöglicht. Die vorliegende Arbeit nutzt FTIR-Spektroskopie und mehrdimensionale NMR-Experimente, um die Ursachen für die selektive Trennung der beiden Elemente zu belegen und Wege zu ihrer Optimierung aufzuzeigen.
Die Ergebnisse der selektiven Reextraktion (Stripping) werden in Übereinstimmung mit den spektroskopischen Befunden vor dem Hintergrund ihrer supramolekularen Ursachen präsentiert.

  • Lecture (Conference)
    DECHEMA Jahrestagung der Fachgruppen Extraktion und Phytoextraktion, 07.-08.02.2019, Muttenz, Schweiz

Publ.-Id: 30226

Probing the role of bound excitons in optical properties of titanium dioxide anatase from first principles

Sruthil, L. S. B.; Devaraj, M.; Posselt, M.; Alok, S.

The electronic structure and optical spectra of anatase titanium dioxide is computed by combining state-of-the-art density functional theory (DFT) and many-body perturbation theory (MBPT). Excitonic optical spectra is computed by solving Bethe-SalpeterEquation (BSE). From the solution of BSE and also from the analysis of charge distribution the photo-generated excitons in anatase is shown to be strongly bound and localized. Such typical behavior of intrinsic excitons in bulk anatase makes it a material which shows superior performance in photo catalysis, photovoltaics, optoelectronics and in nonlinear optical regime.

Keywords: Excitons; optical properties; titanium dioxide; first-principle calculations

  • Poster
    64th DAE Solid State Physics Symposium, 18.-22.12.2019, Jodhpur, Rajasthan, India

Publ.-Id: 30225

Correlative microscopy of relevant ex-vivo and in-vitro biological systems by multimodal optical and high resolution ion/electron based techniques

Podlipec, R.; Klingner, N.; Heller, R.; Kriselj, A.; Pelicon, P.; Strancar, J.; von Borany, J.

Correlative microscopy combining light and electron microscopy (CLEM) has become one of the important and unmissable tools in various investigations of complex biological systems revealing high-resolution structural and highly-specific functional information [1]. In the last years more combinations of other advanced techniques have been developed, such as combining optical microscopy with atomic force spectroscopy/microscopy (AFM) or with magnetic resonance imaging, etc [2] whereas in our study multimodal optical microscopy has been correlated with ion and electron based techniques such as is helium ion microscopy (HIM) [3]. The purpose for using combination of the complementary techniques was to elucidate or better interpret specific biological problems which could not be explained just by one technique lacking of whether resolution, sensitivity of specificity. We focused on toxicology related scientific questions of how inhaled nanoparticles interact with lung epithelial cells/tissue once get into direct contact and why interactions can eventually lead to diseases and potentially persistent inflammation [4,5]. In order to better understand the interaction on nanometer scales we first developed proper lung in-vitro model which was followed by proper sample preparation for efficient correlative microscopy using multimodal optical microscopy and high resolution HIM microscopy. By latter we managed to image single metal oxide nanoparticles on cell surfaces interacting with cell membranes, while functional information of the same events was prior measured with confocal and super-resolution optical microscopy. Besides, we implemented described correlative microscopies also for scientific problem related to rejection of hip implants where material debris is found everywhere in the surrounding periprosthetic tissue with lack of knowledge what happens on a molecular scale. The latest findings of both ongoing studies will be presented.


1. P. de Boer, JP Hoogenboom, BNG Giepmans, Nature Methods 12, 503-513 (2015).
2. T Ando, et. Al, Journal of Physics D: Applied physics 44, (2018)
3. G Hlawacek. et Al. Helium Ion Microscopy. J. Vac. Sci. Technol. 32, (2014)
4. Li, X., Jin, L. & Kan, H. Air pollution: a global problem needs local fixes. Nature 570, 437–439 (2019).
5. E Underwood. The polluted brain. Science 355, 342–345 (2017).

Keywords: CLEM; Helium Ion Microscopy; FLIM microscopy; lung epithelium; TiO2 nanotubes; hip implants; periprosthetic tissue; metal debris

Related publications

  • Invited lecture (Conferences)
    Seminar of Croatian Biophysical Society, 16.12.2019, Zagreb, Croatia

Publ.-Id: 30224

Upscaling High-Resolution Mineralogical Analyses to Estimate Mineral Abundances in Drill Core Hyperspectral Data

Khodadadzadeh, M.; Gloaguen, R.

In this paper, we propose a supervised learning method for estimating mineral quantities in drill core hyperspectral data. Our proposed method links the high-resolution mineralogical analyses and hyperspectral data to learn a dictionary. The learned dictionary is then used for linear unmixing and estimating mineral abundances of the entire drill core sample. To evaluate the performance of the proposed method, we use a drill core data set, which is composed of the VNIR-SWIR hyperspectral data and high-resolution mineralogical analyses performed by a Scanning Electron Microscopy (SEM) instrument equipped with the Mineral Liberation Analysis (MLA) software. The quantitative and qualitative analysis of the experimental results shows that the proposed method provides reliable mineral quantity estimates.

Keywords: Hyperspectral drill core data; highresolution mineralogical analysis; upscaling; dictionary learning

  • Contribution to proceedings
    IGARSS 2019-2019 IEEE International Geoscience and Remote Sensing Symposium, 28.07.-02.08.2019, Yokohama, Japan

Publ.-Id: 30223

Zustandsüberwachung von Transport- und Lagerbehältern für abgebrannte Brennelemente und wärmeentwickelnde HAW bei verlängerter Zwischenlagerung – strahlungsbasierte, thermographische und akustische Messverfahren

Wagner, M.; Fiß, D.; Schmidt, S.; Reinicke, S.; Kratzsch, A.; Hampel, U.

Bis ein Endlager in tiefen geologischen Formationen zur Verfügung steht, besteht in Deutschland Bedarf für die sichere Zwischenlagerung abgebrannter Brennelemente an den Kraftwerksstandorten. Es wird davon ausgegangen, dass erhebliche Zeiträume von mehr als 50 Jahren zu berücksichtigen sind. Dadurch ergeben sich verschiedene regulatorische und sicherheitstechnische Fragestellungen. Eine davon ist die nach der Langzeitintegrität der Brennelemente in den Behältern. Ihre Beantwortung hat direkte Relevanz für den späteren Transport zum Endlager und die Umladung des abgebrannten Kernbrennstoffs in andere Behälter. Im Rahmen des vom BMWi geförderten Vorhabens DCS-MONITOR untersuchen wir Potenziale und Grenzen von nichtinvasiven Verfahren zur Überwachung des Zustands des radioaktiven Inventars von Trockenlagerbehältern. Als solche betrachten wir die Thermographie, strahlungsbasierte Messverfahren sowie akustische Messverfahren.

  • Invited lecture (Conferences)
    Fachworkshop Zwischenlagerung, 22.-23.10.2019, Berlin, Deutschland

Publ.-Id: 30222

An analysis for detecting potential relocation of the inventory of dry storage containers during prolonged interim storage via changes in the wall temperature fields

Wagner, M.; Reinicke, S.; Kratzsch, A.; Hampel, U.

We investigated the suitability of thermography for detecting a potential relocation of the inventory of dry storage containers of type CASTOR V/19. We used numerical simulations of the heat transfer in the container to determine the sensitivity of the wall temperature distribution to such changes. We conducted an analysis for three different hypothetical damage cases: a 9 cm compaction of the fuel in all fuel rods of a single fuel assembly, the same compaction in all fuel assemblies and a compaction of all fuel assemblies by 50 %. The analysis shows that the temperature difference between intact case and all three damage cases after 40 years is too low for an accurate detection becoming even lower for longer storage periods. Temporal thermal insulation of the containers may increase the temperature gradients but reducing the spatial resolution.

Keywords: interim storage; heat transfer

Publ.-Id: 30221

Ternary MIn2S4 (M = Mn, Fe, Co, Ni) thiospinels - crystal structure and thermoelectric properties

Wyżga, P.; Veremchuk, I.; Bobnar, M.; Hennig, C.; Leithe-Jasper, A.; Gumeniuk, R.

The combined structural, magnetic and thermoelectric study of polycrystalline ternary MIn2S4 (M = Mn, Fe, Co, Ni) thiospinels is presented. All compounds crystallize with MgAl2O4-type structure. Rietveld refinement analysis confirmed that the preferred crystallographic position of transition metal element changes from mainly tetrahedral 8a for Mn to exclusively octahedral 16d for Ni (i.e. increase of the inversion parameter). The magnetic susceptibility measurements revealed M-elements to possess 2+ oxidation state in MIn2S4. All these compounds order antiferromagnetic with Néel temperature TN ranging from 5–13 K. Studied thiospinels are n-type semiconductors with large values of electrical resistivity ρ > 0.6 Ω∙m at RT. An increase of inversion parameter leads to reduction of determined activation energies, as well as to the more disorder-like behavior of thermal conductivity. The highest thermoelectric figure of merit ZT was observed for MIn2S4 with M = Fe, Ni, which adopt inverse spinel structure.

Keywords: thiospinel; powder diffraction; magnetic susceptibility; thermoelectric properties

Related publications

Publ.-Id: 30220

Ultra-trace Detection of 99Tc in Environmental Samples by Accelerator Mass Spectrometry

Pitters, J.; Faestermann, T.; Gülce, F.; Hain, K.; Koll, D.; Korschinek, G.; Martschini, M.; Quinto, F.; Rugel, G.; Golser, R.

In our project we are developing methods for the detection of the anthropogenic radionuclide 99-Technetium by Accelerator Mass Spectrometry (AMS). For environmental samples, a highly effective chemical sample preparation method was developed, that removes a large fraction of the interfering elements Ruthenium and Molybdenum and embeds the Tc in a Niobium matrix. The samples were measured at the AMS setup of the Maier-Leibnitz-Laboratory in Munich by extraction of 99TcO− from the ion source, stripping to 99Tc12+ and normalizing to the 93Nb11+ current. A particle energy of 150 MeV in combination with the detection via a Time-of-Flight path and the Gas-filled Analyzing Magnet System (GAMS) allows for a sensitivity of 5·1E6 atoms per sample. The method is discussed together with results from environmental samples. In particular, 99Tc concentrations along a water column from the Pacific Ocean, as well as in porewater from an Austrian peat-bog are presented.

Keywords: AMS 99Tc

Publ.-Id: 30219

AMS of 90Sr at the sub-fg-level using laser photodetachment at VERA

Marchhart, O.; Martschini, M.; Honda, M.; Hanstorp, D.; Lachner, J.; Liang, H.; Priller, A.; Steier, P.; Wieser, A.; Golser, R.

The fission product 90Sr (T1/2 = 28.9 a) is of interest in environmental sciences for its radiotoxicity as well as a potential tracer. Limits of detection (LoD) of mass spectrometric methods such as ICP-MS, RIMS or conventional AMS are close to the radiometric limit of 3 mBq.
The main problem in AMS of 90Sr is the strong interference of the stable isobar 90Zr. This problem can be overcome with the new Ion Laser InterAction Mass Spectrometry (ILIAMS) setup at the Vienna Environmental Research Accelerator (VERA). It provides near complete suppression of elemental or molecular isobars via selective laser photodetachment inside a gas-filled radiofrequency quadrupole (RFQ). With 10W of laser power from a 532nm cw-laser and a He+O2 mixture as buffer gas, ILIAMS achieves a suppression factor for 90Zr of 10⁷. Extracting SrF₃^− out of the ion source and elemental separation inside an ionization chamber gives an additional Zr suppression of 10⁵.
Measurements with dilution series of reference materials were successfully conducted. The overall Sr detection efficiency is 0.4 %₀ and the
blank level 90Sr/Sr=(4.5 ± 3.2)×10^−15. This corresponds to a more than tenfold improved LoD of 0.1 mBq.

Publ.-Id: 30218

Application of AMS to the research on nuclear waste disposal safety

Quinto, F.; Blechschmidt, I.; Faestermann, T.; Hain, K.; Koll, D.; Korschinek, G.; Kraft, S.; Pitters, J.; Plaschke, M.; Rugel, G.; Schäfer, T.; Steier, P.; Geckeis, H.

At the Grimsel Test Site (Switzerland), several in situ tracer tests aim at studying the possible radionuclide release from the bentonite engineered barrier system and the processes which may lead to their subsequent migration though the granodiorite host rock. We investigate the diffusion of Tc-99 and actinides (AN) through bentonite and the remobilization over a time period of several years of the AN tracers employed in previous in situ tests. AMS is the ultra-trace analysis method of choice for studying the behaviour of Tc-99 and AN with concentration at and below fg/g levels in such dedicated long-term in situ tests, providing results that contribute to the safety evaluation of future nuclear waste repositories.

Keywords: AMS Tc-99

Publ.-Id: 30217

Modeling of the free-surface vortex driven bubble entrainment into water

Putra, R. A.; Lucas, D.

The recently developed GENTOP (Generalized Two Phase Flow) concept which bases on the multi-field Euler-Euler approach was applied to model a free-surface vortex - a flow situation which is relevant for hydraulic intake. A new bubble entrainment model has been developed and implemented in the concept. In general a satisfying agreement with the experimental data can be achieved. However, the gas entrainment can be largely affected by several parameters or models used in the CFD (Computational Fluid Dynamics) simulation. The scale of curvature correction C_scale in the turbulence model, the coefficient in the entrainment model C_ent and the assigned bubble size to be entrained has significant influence on the gas entrainment rate. The gas entrainment increases with higher C_scale which can be attributed to the stronger rotation captured by the simulation. A smaller bubble size gives higher gas entrainment while a larger bubble size leads to a smaller entrainment with a periodical peak of entrainment in its transient profile. The results also show that the gas entrainment can be controlled by adjusting the entrainment coefficient C_ent. Basing on the modeling framework presented in this paper further improvement on the physical modeling of the entrainment process should be done.

Keywords: Multiphase flow; Bubble entrainment; Free-surface vortex; Rotating flow; GENTOP

Publ.-Id: 30216

Ion Laser Interaction Mass Spectrometry - status and prospects

Martschini, M.; Lachner, J.; Hain, K.; Marchhart, O.; Pitters, J.; Priller, A.; Steier, P.; Wieser, A.; Golser, R.

The Ion Laser InterAction Mass Spectrometry (ILIAMS) technique at the Vienna Environmental Research Accelerator (VERA) tackles the problem of elemental selectivity in AMS. It achieves near-complete suppression of isobar contaminants via selective laser photodetachment of decelerated anion beams in a gas-filled radio frequency quadrupole cooler. The technique exploits differences in electron affinities (EA) within elemental or molecular isobaric systems neutralizing anions with EAs smaller than the photon energy. Collisional detachment or chemical reactions with the buffer gas can further enhance anion separation.
In AMS of 36Cl and 26Al, ILIAMS reliably provides isobar suppression of more than 10 orders of magnitude. Furthermore it already enables measurements of 90Sr, 135,137Cs and 182Hf with unprecedented sensitivity at VERA and allows to study anion chemistry at eV energies.
Current research focusses on extending this technique to 41Ca, 53Mn, 59Ni, 99Tc and 107Pd. Exotic species such as double-negatively charged carbon clusters complete the cooler ’guestbook’. This contribution will give an overview over these achievements and prospects of the ILIAMS-technique for the near future.

Publ.-Id: 30215

Supernova-produced 53Mn on Earth

Korschinek, G.; Faestermann, T.; Poutivtsev, M.; Arazi, A.; Knie, K.; Rugel, G.; Wallner, A.

For the age range from 1.5 to 4 Myr ago we found in deep ocean ferromanganese crusts an excess concentration in terms of 53Mn/Mn of about 4 · 10−14 over that expected for cosmogenic production. We conclude that this 53Mn is of supernova origin because it is detected in the same time window, about 2.5 Myr ago, where 60Fe has been found earlier. This overabundance confirms unambiguously the supernova (SN) origin of that 60Fe. For the first time supernova-formed 53Mn has been detected and it is the second positively verified radioisotope from the same supernovae. The ratio 53Mn/60Fe of about 12 is consistent with that expected for a SN with a 11 - 25 M⊙ progenitor mass and
solar metallicity. A fit over the whole range until 10 Myr shows also a second increase of 53Mn/Mn in the range around 6 Myr matching
recent 60Fe detection in sediments at ANU.

Keywords: AMS; 53Mn; Supernova

Publ.-Id: 30214

Development of novel α-CEA target modules (RevTMs) for the switchable RevCAR system

González Soto, K. E.

Cancer is one of the main causes of death and represents a worldwide health problem. Most of the cancer-related deaths are associated with the appearance and progression of a solid tumor. Even though effective conventional treatments exist, they share a common drawback, which is their incapacity to strictly distinguish between malignant and healthy cells. Since it was observed that immune cells are capable to eliminate cancer cells, extensive research has been made to retarget immune cells towards malignant cells without damaging healthy tissue. This type of approach is termed as immunotherapy and involves diverse strategies ranging from the use of Abs to engineered immune cells. One of the most attractive immunotherapeutic strategies is based on the engineering of T cells to express chimeric antigen receptors (CARs), which can recognize specific antigens localized on the surface of cancer cells, leading to an activation of the CAR T cells and a subsequently killing of the malignant cells. Even though CAR technology has shown a strong potential in targeting cancer cells during pre-clinical and clinical studies, numerous clinical trials have also revealed that once they are infused into the patient, the activity of the modified T cells becomes uncontrollable, which represents the main safety problem from the system. For this reason, a novel modular and switchable CAR platform, termed as RevCAR system, was developed in the group of Prof. Bachmann. A crucial element of mentioned system is the design of the RevCAR. In contrast to conventional CARs, RevCARs lack an extracellular binding moiety and comprise only a short peptide epitope instead. Thus, RevCAR T cells are per se inert because they cannot bind to any antigen. Only in the presence of target modules (RevTMs), which bind on the one hand to the peptide epitope of RevCARs and on the other hand simultaneously to tumor targets, RevCAR T cells can be redirected and consequently activated against tumor cells. An attractive tumor-associated antigen (TAA) for the development of immunotherapies is the carcinoembryonic antigen (CEA), because it is highly overexpressed on certain cancer types associated with solid tumor formation, such as breast and lung cancer. In order to show the proof of concept that CEA is an optimal TAA to redirect the RevCAR system, two different formats of RevTMs (scFv- or IgG-based) were produced and tested for their functionality. Here we have shown, that both RevTMs were able to efficiently redirect RevCAR T cells to eliminate CEA-expressing tumor cells in an antigenand epitope-specific as well as TM-dependent manner. Moreover, here, the IgG4-based RevTM worked more efficient than the scFv-based RevTM.

  • Master thesis
    HZDR, 2019

Publ.-Id: 30213

Off-harmonic optical probing of high intensity laser interaction with cryogenic hydrogen jet target

Bernert, C.; Kraft, S.; Löser, M.; Metzkes-Ng, J.; Obst-Hübl, L.; Rehwald, M.; Schlenvoigt, H.-P.; Siebold, M.; Zeil, K.; Ziegler, T.; Schramm, U.

High-intensity short-pulse lasers in the Petawatt regime offer the possibility to study new compact accelerator schemes by utilizing high-density targets for the generation of energetic ion beams. The optimization of the acceleration process demands comprehensive exploration of the plasma dynamics involved, for example via optical probing. In particular, experiments using low density cryogenic hydrogen jet targets with µm-scale transverse size are well suited to deliver new results which can then be compared to predictive particle-in-cell simulations. However, strong plasma self-emission and conversion of the plasma’s drive laser wavelength into its harmonics often masks the interaction region and complicates data analysis. Here, we present a stand-alone probe laser system operating at 1030 nm, far off the plasma’s drive laser wavelength of 800 nm and its implementation into an experiment dedicated to laser-proton acceleration from the hydrogen jet target irradiated by the DRACO PW laser at Helmholtz-Zentrum Dresden – Rossendorf. We show that the plasma self-emission in the probe images is significantly suppressed and we are able to measure the pre-expansion of the target by the DRACO PW laser for intrinsic and for plasma mirror enhanced laser contrast. The influence of the plasma pre-expansion on the measured proton acceleration performance is presented.

Keywords: optical probing; laser; laser particle acceleration

  • Lecture (Conference)
    European Advanced Accelerator Concepts Workshop, 15.-20.09.2019, Isola d'Elba, Italy

Publ.-Id: 30212

Antigen-specific redirection of immune effector cells against GD2-expressing tumors

Metwasi, N.

Extensive research in the last decades has revealed the dynamic role of the immune system in surveillance, recognition and elimination of cancer cells. However, resistant variants can rise and overcome these immune responses by various escape mechanisms. Therefore, huge efforts have been invested in developing of immunotherapies that can overcome these hurdles and allow the specific activation and retargeting of immune cells toward tumor cells. Immunotherapy includes diverse strategies ranging from cytokines to antibodies and their derivatives reaching to engineered immune cells.
One of the very promising immunotherapeutic approaches is based on the engineering of T cells to express chimeric antigen receptors (CARs) which can redirect immune cells to specific antigens leading to T cell activation and subsequent killing of target cells. The CAR technology has shown a strong therapeutic potential in targeting of cancer both in preclinical as well as clinical studies, especially with hematological malignancies, which lead to FDA approval of CD19-specific CAR T cells for the treatment of leukemia. Despite the success of CAR T cells, clinical trials have also revealed various toxicities and adverse events that can be life-threatening for patients. Moreover, the CAR technology still faces many hurdles to achieve an effective targeting of solid tumors due to the structure, immunosuppressive microenvironment and heterogeneity of the disease. Therefore, a novel modular and switchable CAR platform, called the UniCAR system, was developed in the group of Prof. Bachmann in order to address these obstacles. The UniCAR system consists of UniCAR T cells that cannot bind surface antigens. Instead, UniCARs recognize an epitope (E5B9) which is derived from the nuclear protein La-SS/B. Therefore, UniCAR T cells can only be redirected via target modules (TMs) that have the E5B9 tag on one hand and an antigen-binding domain on the other hand. These TMs provide a bridge with tumor cells that allow the activation of UniCAR T cells. Once these TMs are eliminated, the UniCAR T cells can no more be activated, and thus they are switched off. This approach provides not only a safety switch but also a flexible platform for multi-targeting of diverse antigens by using various TMs with different antigen specificities. Alternatively, the UniCAR system can be applied on NK cells or NK cell lines, which have a natural anti-tumor response. Cell lines like NK-92 are of especial interest because they can be used allogenically, and thus provide an off-the-shelf therapy that might reduce the cost and time of therapy development.
For my thesis work, disialoganglioside GD2 was selected as a target for the UniCAR system. GD2 is overexpressed on many tumors including neuroblastoma, Ewing’s sarcoma, melanoma, osteosarcoma and others. In fact, GD2 is considered as one of the priority antigens to be targeted for cancer therapy according to a pilot project of the national cancer institute. Moreover, targeting GD2 with CAR T cells has shown very positive clinical outcome in previously published clinical trials. However, as other tumor-associated antigens, GD2 has also some limited expression on normal tissues including some regions of the central nervous system and peripheral nerves. Therefore, using a safety switch like the UniCAR system emerges as a necessary step to assure better controlling of any on-target/off-tumor side effects.
Driven by these facts, several formats of anti-GD2 TMs were developed in order to redirect UniCAR T cells to GD2-expressing tumors. Three TMs were designed based on a single chain fragment variable (scFv) connected to the E5B9 epitope. However, they differed in the orientation of the variable light and variable heavy chain domains and their linker components in order to find the best functional conformation. In vitro functional assays showed that all of the three TMs were able to redirect UniCAR T cells toward tumor cells leading to efficient tumor cell killing and release of cytokines in an antigen-specific and TM-dependent manner. Furthermore, the TMs showed dose-dependent killing with half-maximal effective concentration (EC50) in the picomolar range. As all the TM formats showed comparable results in vitro, further in vivo studies were restricted to one TM. This anti-GD2 TM was able to activate UniCAR T cells to eradicate GD2-positive tumor cells in experimental mice. Furthermore, the TM was modified and radiolabeled with 64Cu, in order to investigate its pharmacokinetic properties and biodistribution in tumor-bearing mice. PET analysis of the radiolabeled anti-GD2 TM showed enrichment in the GD2-expressing tumors with blood elimination half-life of less than one hour, which makes it a suitable key for a fast safety switch of UniCAR T cells.
In contrast to UniCAR T cells, the UniCAR NK-92 cell line provides an-off-the shelf therapy that can be expanded for allogenic use. Since these cells are usually irradiated before infusion into patients, their life-span as well as the possibility of side effects is reduced. Therefore, we have further created an IgG4-based anti-GD2 TM with an extended half-life that fits to the life-span of irradiated NK-92 cells. PET imaging of the radiolabeled IgG4-based TM showed an increase in the half-life of about 24 folds in comparison to the scFv TM format. Further testing has shown that UniCAR NK-92 cells are functional with both scFv- and IgG4-based TM formats leading to specific killing of GD2-expressing tumor cells as well as secretion of pro-inflammatory cytokines in vitro. In addition, UniCAR NK-92 showed specific killing of tumor cells in vivo when combined with the anti-GD2 TM.
In summary, we have shown that the UniCAR system can be used to redirect both T cells and NK-92 cells against GD2-expressing tumors in vitro as well as in vivo in an antigen-specific and TM-dependent manner. The UniCAR system allows an on/off safety switch as well as fine controlling of the activity of UniCAR T/NK-92 cells via titration (dosing) of the anti-GD2 TMs. Furthermore, it provides a flexible platform that allows the use of several antibody formats for an effective and safe targeting of cancer.

  • Doctoral thesis
    HZDR, 2019

Publ.-Id: 30211

Off-harmonic optical probing of high intensity laser interaction with hydrogen targets using a stand-alone probe laser system

Bernert, C.; Kraft, S.; Löser, M.; Metzkes-Ng, J.; Obst-Hübl, L.; Rehwald, M.; Schlenvoigt, H.-P.; Siebold, M.; Zeil, K.; Ziegler, T.; Schramm, U.

The development of high-intensity short-pulse lasers in the Petawatt regime offers the possibility to design new compact accelerator schemes by utilizing high-density targets for the generation of ion beams with multiple 10 MeV energy per nucleon. The optimization of the acceleration process demands comprehensive exploration of the plasma dynamics involved, for example via spatially and temporally resolved optical probing. Experimental results can then be compared to numerical particle-in-cell simulations, which is particularly sensible in the case of cryogenic hydrogen jet targets. However, strong plasma self-emission and conversion of the plasma’s drive laser wavelength into its harmonics often masks the interaction region and interferes with the data analysis. Recently, the development of a stand-alone and synchronized probe laser system for off-harmonic probing at the DRACO laser operated at the Helmholtz-Zentrum Dresden–Rossendorf showed promising performance.
Here, we present an updated stand-alone probe laser system applying a compact CPA system based on a synchronized fs mode-locked oscillator operating at 1030 nm, far off the plasma’s drive laser wavelength of 800 nm. A chirped volume Bragg grating (Optigrate Corp) is used as a hybrid stretcher and compressor unit. The system delivers 160 fs pulses with a maximum energy of 0.9 mJ. By deploying the upgraded probe laser system in the laser-proton acceleration experiment with the renewable cryogenic hydrogen jet target, the plasma self-emission could be significantly suppressed while studying the temporal evolution of the expanding plasma jet. Recorded probe images resemble those of z-pinch experiments with metal wires and indicate a sausage-like instability along the jet axis, which will be discussed.

Keywords: optical probing; laser; laser particle acceleration

  • Lecture (Conference)
    SPIE Optics + Optoelectronics 2019, 01.-04.04.2019, Prague, Czech Republic

Publ.-Id: 30210

Stand-alone laser system for off-harmonic optical probing of high intensity laser interaction with cryogenic hydrogen jet targets

Bernert, C.; Kraft, S.; Löser, M.; Metzkes-Ng, J.; Obst-Hübl, L.; Rehwald, M.; Schlenvoigt, H.-P.; Siebold, M.; Zeil, K.; Ziegler, T.; Schramm, U.

The availability of high-intensity short-pulse lasers in the Peta-Watt regime drives the development of new and compact accelerator schemes like for example the generation of multiple 10 MeV proton beams from high-density targets. To optimize the acceleration performance and to pave the way towards medical applications of these particle beams both target and diagnostic development are of great importance. Particularly cryogenic hydrogen jet-targets offer the benefit of being debris-free and capable of high-repetition rate applications. Together with spatially and temporally resolved optical probing techniques this target is most suitable for a comparison to numerical particle-in-cell simulations. However, the strong plasma self-emission often masks the laser-target interaction point and thus complicates the data analysis. Recently, the development of a synchronized stand-alone probe-laser-system operating off the harmonics of the driver laser showed promising performance.
Here we show the performance of an upgraded probe-laser-system operating at a central wavelength of 1030nm far off the fundamental wavelength of the drive laser at 800nm. It consists of a synchronized fs-oscillator and a novel and robust CPA system based on a chirped volume Bragg grating as a hybrid stretcher and compressor unit, chirped mirrors for GDD compensation and a regenerative amplifier with Yb.CaF2 as laser medium. The system delivers 160fs pulse duration together with 0.9mJ energy at a repetition rate of 200Hz.
The application of the upgraded probe-laser-system in an experimental campaign dedicated to laser-proton acceleration together with cryogenic hydrogen jet-targets showed a significant improvement of imaging quality for the laser-target interaction concerning the plasmas self-emission. The recorded probe-images resemble those of z-pinch experiments with metal wires and indicate a sausage-like instability along the hydrogen jet axis.

Keywords: optical probing; laser; particle acceleration

  • Open Access Logo Lecture (Conference)
    DPG Frühjahrstagung, 17.-22.03.2019, München, Deutschland

Publ.-Id: 30209

Introducing a novel switchable CAR platform with reduced CAR size for immunotherapy of tumors

Hoffmann, A.; Feldmann, A.; Kittel-Boselli, E.; Bergmann, R.; Koristka, S.; Berndt, N.; Arndt, C.; Rodrigues Loureiro, L. R.; Bachmann, M.

1. Introduction
Recently the use of chimeric antigen receptor (CAR) modified T cells in the immunotherapy of tumors has become a promising approach. CAR T cells are able to recognize tumor-associated antigens (TAAs) in a major histocompatibility-complex (MHC)-independent manner. Although highly efficient, the inability to regulate the activity of CAR T cells can cause severe side effects and thus needs to be considered in future developments. Here, we introduce the RevCAR system – a novel switchable modular universal CAR system having a minimal size to overcome the obstacles of conventional CAR therapy.
2. Objectives
In order to improve the controllability of CAR T cells a modular CAR system, which allows switching the activity of CAR T cells repeatedly “ON” and “OFF”, was generated. Furthermore, to avoid unspecific side effects and minimize tonic signaling of conventional CAR T cells, the extracellular single chain variable fragment (scFv) was removed. Thus, resulting RevCARs have a smaller size allowing “gated” targeting strategies, e.g. by facilitating simultaneous transduction of two independent CARs with different specificities and split motifs, which could further improve the safety of CAR T cells.
3. Materials & methods
In order to reduce the size of the artificial receptor the original idea was to replace the extracellular scFv domain of a conventional CAR with a small peptide epitope and to engage the resulting RevCAR
T cell via a bispecific target module which we termed RevTM. For proof of concept two small peptide epitopes were selected and the respective RevCARs constructed. In addition, a series of different RevTMs was generated. On the one hand the RevTM recognizes one of the two peptide epitopes on the other hand the RevTM can be directed to any potential TAA.
4. Results
Until now a series of RevTMs was constructed and functionally analyzed. RevCAR T cells armed via the respective RevTM were able to efficiently lyse their respective target cells in a peptide epitope and target specific, as well as target module dependent manner. These data are supported by the analysis of cytokine secretion from RevCAR T cells which was only observed in the presence of both target cells and the respective RevTM.
5. Conclusion
Taken together these results demonstrate the high anti-tumor efficiency of the novel RevCAR platform which is characterized by a small size, an improved safety, easy controllability as well as high flexibility.

  • Open Access Logo Abstract in refereed journal
    European Journal of Immunology 49(2019), 266-267
    DOI: 10.1002/eji.201970300
  • Poster
    Annual Meeting of the German Society for Immunology (DGfI 2019), 10.-13.09.2019, München, Deutschland


Publ.-Id: 30208

Convective and Surface Tension Sub-Filter Scale Models

Meller, R.; Klein, M.; Lucas, D.; Schlegel, F.

Industrial applications feature a huge variety of different flow patterns, such as bubbly flow, slug flow or annular flow. Thereby the issue of a big range of different physical scales is involved. With the objective of reproduction of occurring phenomena with one single multifluid solver, we present an Euler-Euler-approach, which combines a number of different methods for treatment of the partial aspects. The implementation into OpenFOAM is always with focus on sustainable research. A segregated approach is used for treatment of the phase momentum equations, phase fraction equations and the pressure equation, featuring a consistent momentum interpolation scheme (Cubero et al., 2014). To fulfill the kinematic condition at resolved interfaces between different continuous phases, the latter may be coupled by an isotropic drag (Strubelj and Tiselj, 2011). In this case, the immensely strong phase coupling requires an adapted numerical method. The overall objective is to take interactions between the all different aspects, such as disperse phases, resolved interfaces and turbulence with effects on momentum and mass transfer into account.

  • Lecture (others)
    Seminar des Instituts für Mathematik und Rechneranwendungen der Universität der Bundeswehr München, 05.11.2019, München, Deutschland

Publ.-Id: 30207

(+)-[18F]Flubatine as a novel α4β2 nicotinic acetylcholine receptor PET ligand – Results of the first-in-human brain imaging application in patients with β-amyloid PET-confirmed Alzheimer’s disease and healthy controls

Tiepolt, S.; Becker, G.-A.; Wilke, S.; Cecchin, D.; Rullmann, M.; Meyer, P. M.; Barthel, H.; Hesse, S.; Patt, M.; Luthardt, J.; Wagenknecht, G.; Sattler, B.; Deuther-Conrad, W.; Ludwig, F.-A.; Fischer, S.; Gertz, H.-J.; Smits, R.; Hoepping, A.; Steinbach, J.; Brust, P.; Sabri, O.

The cerebral cholinergic system is involved in several cognitive processes and neuropsychiatric 2 diseases. For research purposes and later on in routine clinical settings new PET radioligands with more favorable characteristics than the established 3-pyridylether derivatives with their slow kinetics are necessary. Here we present the first in-human brain PET imaging data of the new α4β2 nicotinic acetylcholine receptor (nAChR)-targeting radioligand (+)-[18F]Flubatine. Primary aim of this study was to develop a kinetic modeling-based approach to quantify the α4β2 nAChR availability in the human brain and to compare respective data of healthy controls (HCs) with those of patients with Alzheimer’s disease (AD). Secondary aims were to investigate whether (+)-[18F]Flubatine binding was correlated to cognitive test data or β-amyloid radiotracer accumulation. Furthermore, the partial volume effect (PVE) on regional (+)-[18F]Flubatine binding was investigated. We examined 11 non-smoking HCs and 9 non-smoking patients with mild AD without anti-dementive drugs. Prior to (+)-[18F]Flubatine PET, all subjects underwent an extensive neuropsychological testing and a β-amyloid [11C]PiB PET/MRI examination. To evaluate the (+)-[18F]Flubatine PET data, we used full kinetic modeling (one and two tissue compartment 16 modeling (1TCM and 2TCM)) and regional as well as voxel-based analyses. 270 min p.i., the unchanged parent compound in arterial blood amounted to 97±2%. As revealed by regional analysis, (+)-[18F]Flubatine distribution volume (binding) was significantly reduced in the bilateral mesial temporal cortex in AD patients compared to HCs (right: AD: 10.6±1.1 vs HC: 11.6±1.4, p=0.049; left: AD: 11.0±1.1 vs HCs:12.2±1.8, p=0.046). Voxel-based analysis detected further clusters of reduced (+)-[18F]Flubatine in left precuneus/posterior cingulate cortex, right superior temporal and left middle temporal cortex (k>30, p<0.001). PVE correction revealed an increase of regional (+)-[18F]Flubatine binding of approximately 15% but also an increase of the standard deviation of 0.4-70% resulting in a loss of statistical significances. Thus, we also estimated the cortical thickness to investigate whether cortical atrophy significantly affects the regional (+)-[18F]Flubatine binding. Here, we found that mesial temporal cortical thickness did not correlate with (+)-[18F]Flubatine binding (right: r=0.10, p=0.69; left: r=0.17, p=0.48). Using a reference region (occipital cortex), also the right parietal cortex showed reduced relative (+)-[18F]Flubatine binding in AD patients compared to HCs (1.1±0.1 vs. 1.2±0.1, p=0.033). Cognitive test data and (+)-[18F]Flubatine binding were significantly correlated in left anterior cingulate cortex, right posterior cingulate cortex and right parietal cortex (r>0.5, p<0.05 each). In the AD patients, (+)-[18F]Flubatine binding and [11C]PiB standardized uptake value ratios were negatively correlated in several regions, whereas in HCs a positive correlation between cortical (+)-[18F]Flubatine binding and [11C]PiB accumulation in the white matter was found. No serious adverse events were registered, and seven adverse events which were not related to the investigational product. Taken together, (+)-[18F]Flubatine is a safe and stable PET ligand. Full kinetic modeling of the PET data can be realized by 1TCM without metabolite correction. (+)-[18F]Flubatine binding affinity was high enough to detect group differences without the use of a reference region. However, the use of the occipital cortex as reference region increased the sensitivity. Of interest, correlation between white matter β-amyloid PET uptake and (+)-[18F]Flubatine binding indicated a connection between white matter integrity and availability of α4β2 nAChRs. Overall, (+)-[18F]Flubatine showed favorable characteristics and has therefore the potential to serve as α4β2 nAChR-targeting PET ligand in further clinical trials.

Keywords: (+)-[18F]Flubatine; α4β2 nicotinic acetylcholine receptors; human brain; kinetic modeling; PET; (+)-[18F]NCFHEB

Publ.-Id: 30206

A-Posteriori Assessment of Sub-Filter Scale Models for Turbulence-Interface Interaction with the Two-Fluid Formulation Considering a Single Rising Gas Bubble in Liquid

Meller, R.; Klein, M.; Lucas, D.; Schlegel, F.

Gas-liquid flows are of great importance for a large number of different industrial applications, e.g. in energy sector or metal processing industry. From there arises a strong need for numerical tools, which help to predict dynamics of two-phase flows in technical facilities with high predictive accuracy, reasonable computational expense and without any need for initial knowledge of the present flow regime. A big challenge in investigations of such problems is the large range of interfacial and turbulent scales, which need to be accounted for in numerical simulations. A typical approach to capture all these dynamics and their interactions are multi-scale multi-regime methods, which make use of coupling of different individual modeling concepts.
The overall aim is to adopt the hybrid approach of H ̈ ansch et al. (2012), which combines an Eulerian-Eulerian approach with a volume-of-fluid(VOF)-like method in a two-fluid model in order to represent interfacial structures on subgrid-scale and on grid-scale, respectively. In situations, where transitions between different morphologies occur, interfacial structures appear to be too large for an Eulerian-Eulerian model approach and, at the same time, too small for the flow dynamics to be fully resolved in a VOF-like model. In other words, in the range of mesh scale and slightly above, interfacial and turbulent structures need to be simulated in an under-resolved manner. For this to deliver physically reasonable results, modeling of subgrid-scale (SGS) dynamics becomes necessary.

  • Contribution to proceedings
    Direct and Large Eddy Simulation 12 (DLES12), 05.-07.06.2019, Madrid, Spanien
    ERCOFTAC Series: Direct and Large-Eddy Simulation XII, Cham, Switzerland: Springer, 978-3-030-42821-1, 167-173
    DOI: 10.1007/978-3-030-42822-8
  • Lecture (Conference)
    Direct and Large Eddy Simulation 12 (DLES12), 05.-07.06.2019, Madrid, Spanien

Publ.-Id: 30205

On the enstrophy in a precessing cylinder

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

Within the project DRESDYN (DREsden Sodium facility for DYNnamo and thermohy-
draulic studies) a precession driven a fluid flow of liquid sodium will be examined with regard
to the possibility of serving as source for magnetic field generation. Hydrodynamic studies
and simulations are essential to understand the behaviour of the fluid flow. Here we present
the direct numerical simulations of a fluid flow forced by precession conducted in a cylindrical
domain, with the focus on the relation between dissipation and enstrophy.

Keywords: Precessing Cylinder; enstrophy; flow field

  • Open Access Logo Invited lecture (Conferences)
    9th European Postgraduate Fluid Dynamics Conference, 16.-19.07.2019, Ilmenau, Germany

Publ.-Id: 30204

The Dresdyn Precession Dynamo Experiment

Pizzi, F.; Giesecke, A.; Gundrum, T.; Vogt, T.; Stefani, F.

In the most ambitious experiment of DRESDYN (DREsden Sodium facility
for DYNnamo and thermohydraulic studies) a fluid flow of liquid sodium, solely driven
by precession, will be considered as a possible source for magnetic field generation. Here,
after the description of the experimental facility, we are going to present the results (in
particular the hydrodynamic ones) from the direct numerical simulation conducted in a
cylindrical domain. We will discuss the dynamics of the system and show that the m = 1
Kelvin mode is crucial for the dynamo action. The second part will be dedicated to the
influence of the nutation angle; finally we will quantify the dissipation and the role of
turbulent fluctuations on the flow.

Keywords: cylinder; dissipation; dynamo; precession; turbulence

  • Contribution to proceedings
    11 th PAMIR International Conference - Fundamental and Applied MHD, 01.-05.07.2019, Reims, France
  • Invited lecture (Conferences)
    11 th PAMIR International Conference - Fundamental and Applied MHD, 01.07.2019, Reims, France

Publ.-Id: 30202

Start-to-end simulations of L|PWFA hybrid accelerator experiments using PIConGPU

Pausch, R.; Debus, A.; Steiniger, K.; Garten, M.; Hübl, A.; Widera, R.; Kurz, T.; Schöbel, S.; Couperus Cabadağ, J. P.; Chang, Y.-Y.; Köhler, A.; Zarini, O.; Heinemann, T.; Gilljohann, M. F.; Ding, H.; Götzfried, J.; Döpp, A.; Kononenko, O.; Raj, G.; Martines De La Ossa, A.; Assmann, R.; Hidding, B.; Karsch, S.; Code, S.; Irman, A.; Schramm, U.; Bussmann, M.

The poster gives an overview of the LPWFA experimental setup and explains in detail the accompanying simulation campaign.

Keywords: LPWFA; hybrid; PIConGPU; ISAAC; alpaka

  • Poster
    CASUS Eröffnungsworkshop, 26.-28.08.2019, Görlitz, Deutschland

Publ.-Id: 30200

Current status of the L|PWFA start-to-end simulations using PIConGPU

Pausch, R.; Debus, A.; Steiniger, K.; Garten, M.; Widera, R.; Bussmann, M.

A summary of the LPWFA simulations of the last half year as performed within the hybrid collaboration.

Keywords: PIConGPU; LPWFA; hybrid

  • Lecture (others)
    LPWFA hybrid-collaboration meeting, 04.-05.07.2019, Glasgow, United Kingdom

Publ.-Id: 30199

Ultra-intense laser pulse characterization using ponderomotive electron scattering.

Mackenroth, F.; Holkundkar, A.; Schlenvoigt, H.-P.

We present a new analytical solution for the equation of motion of relativistic electrons in the focus of a high-intensity laser pulse. We approximate the electron's transverse dynamics in the averaged field of a long laser pulse focused to a Gaussian transverse profile. The resultant ponderomotive scattering is found to feature an upper boundary of the electrons' scattering angles, depending on the laser parameters and the electrons' initial state of motion. In particular, we demonstrate the angles into which the electrons are scattered by the laser scale as a simple relation of their initial energy to the laser's amplitude. We find two regimes to be distinguished in which either the laser's focusing or peak power are the main drivers of ponderomotive scattering. Based on this result, we demonstrate how the intensity of a laser pulse can be determined from a ring-shaped pattern in the spatial distribution of a high-energy electron beam scattered from the laser. We confirm our analysis by means of detailed relativistic test particle simulations of the electrons' averaged ponderomotive dynamics in the full electromagnetic fields of the focused laser pulse.


Publ.-Id: 30198

Characterization of laser-driven proton acceleration from water microdroplets

Becker, G. A.; Schwab, M. B.; Lötzsch, R.; Tietze, S.; Klöpfel, D.; Rehwald, M.; Schlenvoigt, H.-P.; Sävert, A.; Schramm, U.; Zepf, M.; Kaluza, M. C.

We report on a proton acceleration experiment in which high-intensity laser pulses with a wavelength of 0.4 μm and with varying temporal intensity contrast have been used to irradiate water droplets of 20 μm diameter. Such droplets are a reliable and easy-to-implement type of target for proton acceleration experiments with the potential to be used at very high repetition rates. We have investigated the influence of the laser’s angle of incidence by moving the droplet along the laser polarization axis. This position, which is coupled with the angle of incidence, has a crucial impact on the maximum proton energy. Central irradiation leads to an inefficient coupling of the laser energy into hot electrons, resulting in a low maximum proton energy. The introduction of a controlled pre-pulse produces an enhancement of hot electron generation in this geometry and therefore higher proton energies. However, two-dimensional particle-in-cell simulations support our experimental results confirming, that even slightly higher proton energies are achieved under grazing laser incidence when no additional pre-plasma is present. Illuminating a droplet under grazing incidence generates a stream of hot electrons that flows along the droplet’s surface due to self-generated electric and magnetic fields and ultimately generates a strong electric field responsible for proton acceleration. The interaction conditions were monitored with the help of an ultra-short optical probe laser, with which the plasma expansion could be observed.


Publ.-Id: 30197

Standing inertial waves, energy scaling and dissipation in precession driven flows

Giesecke, A.; Pizzi, F.; Gundrum, T.; Vogt, T.; Stefani, F.

A precession dynamo experiment is currently under construction at
Helmholtz-Zentrum Dresden-Rossendorf (HZDR). The experiment is
motivated by the question whether the geodynamo or the ancient lunar
dynamo were powered by a flow driven by precession instead of
or in addition to convection. In the present study we address related
numerical simulations in order to characterize the hydrodynamic flow
field and to make energetic estimations that allow conclusions on the
global power balance.

Simulations of precessing fluids in cylindrical geometry show that
precession is an efficient mechanism to drive substantial flows even
on the lab scale. Using the time-averaged flow field obtained in these
simulations, kinematic dynamo models exhibit dynamo action at
parameters that are well within the range of the planned dynamo
experiment. Our analysis further shows that the standing inertial
wave directly excited by precession is responsible for the magnetic
field excitation when the forcing is sufficiently strong, so that
nonlinear interactions modify the flow and contributions beyond the
resonant Kelvin mode become important. This requires large precession
ratios with the Poincare number (the ratio of precession
frequency to rotation frequency) above Po = 0.10. At this
value we observe an abrupt transition of the flow into a turbulent
behavior with large-scale flow structures becoming less significant.
Our simulations give a detailed characterization of the corresponding
transition. The scaling of global quantities, like flow amplitudes and
energies as well as the laminar and the turbulent dissipation are used
to constrain the energetics of the magnetic field generation and to
predict the most promising parameter regimes suitable for dynamo
action including the specific magnetic field pattern that may emerge
in the planned dynamo experiment.

Keywords: Dynamo; DRESDYN; Precession

  • Lecture (Conference)
    AGU Fall Meeting, 08.-13.12.2019, San Francisco, USA

Publ.-Id: 30196

Synchronization in mean field dynamo models

Giesecke, A.; Seilmayer, M.; Stefani, F.; Weier, T.

Synchronization is a fundamental phenomenon in nonlinear dynamical systems.
In my presentation I will refer to essential features of synchronized
systems with focus on a kinematic dynamo model driven by two
counter-rotating disks including weak periodic perturbations. Similar
concepts can be used to explain the behavior of triadic resonances in a
precession driven flow, which may be seen as a precursor for the
transition into a turbulent regime found at a critical precession ratio
in the DRESDYN water experiment. Finally, I show the connection to the
synchronized solar dynamo model presented by Frank Stefani, where the
magnetic field frequencies are determined by the tidal forces caused by
planets surrounding the sun.

Keywords: Dynamo; Synchronization

  • Lecture (Conference)
    Dynamo Thinkshop, 25.-26.12.2019, Rom, Italien

Publ.-Id: 30195

Inverse Problems in (nonlinear) Magnetohydrodynamics

Giesecke, A.

Modal acoustic velocimetry and time-of-flight tomography require
inversion of measurement data for determination of 3D velocity fields.
Another example is the Inductive flow tomography that allows the estimatation
of flow structures in an electrically conducting fluid impacted by an imposed
magnetic field.

Keywords: Magnetohydrodynamics

  • Lecture (Conference)
    Symposium "Domain Coupling with Workflow-supported Algorithms of Artificial Intelligence", 29.05.2019, Berlin, Deutschland

Publ.-Id: 30194

Euler-Euler Multiphase Flow Simulation @ HZDR

Rzehak, R.

Research on multiphase flows has a long history at Helmholtz-Zentrum Dresden - Rossendorf. Concerning simulations we focus on the Euler-Euler method, which facilitates CFD simulations on the scale of technical equipment by applying the two-fluid framework of interpenetrating continua. Since phenomena occurring on the scale of individual bubbles or groups thereof are not resolved in this approach, accurate numerical predictions rely on suitable closure relations describing the physics of these small-scale phenomena. Development and validation of such closure relations are a core focus of our research.
A brief general overview of topics and methods will be given, followed by a collection of specific application examples. The latter center around dispersed multiphase flows in different types of equipment commonly encountered in chemical engineering, minerals processing, and biotechnology. The fluid dynamics of bubbly flow are covered in greater detail highlighting the modeling of bubble forces, bubble-induced turbulence as well as bubble-coalescence and breakup. Less comprehensive results are shown for reactive mass-transfer and particulate flows.

Keywords: disperse gas-liquid multiphase flow; Euler-Euler two-fluid model; fluid dynamics; mass transfer; chemical reaction; CFD simulation; validation

  • Lecture (Conference)
    Institute Seminar, 13.12.2019, Magdeburg, Deutschland

Publ.-Id: 30193

Euler-Euler Simulation of Bubbly Flow in Stirred Tanks

Rzehak, R.; Shi, P.

Aerated stirred tanks are frequently used equipment in industries ranging from chemical engineering and biotechnology to minerals processing. In principle, CFD simulation of such equipment on industrial scales is feasible within the Euler-Euler framework of interpenetrating continua. Practical application, however, requires suitable closure models to account for phenomena on the scale of individual bubbles, which are not resolved in this approach. Validation of such models is the purpose of the present contribution.

Keywords: aerated stirred tanks; dispersed gas-liquid multiphase flow; Euler-Euler two-fluid model; closure relations; Reynolds-stress turbulence model; CFD simulation

  • Lecture (Conference)
    ECCE12 & ECAB5, 15.-19.09.2019, Florence, Italy

Publ.-Id: 30192

TEM investigation of Compact Tellurium Thin Films with Bismut Atomic Doping

Damm, C.; Guodong, L.; Hübner, R.; Nielsch, K.

Compact tellurium (Te) thin films show important applications in micro-thermoelectric modules, which are able to convert waste heat to electrical energy (μTEG) or vice versa to use electricity to generate cooling (μTEC). The as-fabricated μTECs, which are based on electrochemically deposited n-type Bi2(TexSe1-x)3 (in short BiTeSe) and p-type tellurium, demonstrate a rapid response time of 1ms, a high cycling reliability of up to 10 million cycles and a long-term cooling stability of more than 1 month at constant electric current. However, a mismatch of electrical conductivity between pure Te and BiTeSe often leads to some difficulties in the geometry design of micro-thermoelectric modules. In order to enhance the electrical property of Te, we have introduced an atomic bismuth (Bi) doping.

In this report, we have performed transmission electron microscopy (TEM, FEI Tecnai G2/ 200 kV) analysis to observe the presence and distribution of Bi within Te. To this end, cross-sectional TEM specimens were prepared using the Focused Ion Beam technique (FIB, FEI Helios NanoLab 600i). The Bi-doped Te samples have a columnar grain structure. Selected-area electron diffraction proves the presence of crystalline Te. Results of Nanodiffraction in numerous areas also suggest Te (hexagonal, space group 152, a = b = 0,4458 nm, c = 0,5925 nm, α = ß = 90°, γ = 120°) but could be explained with Bi (rhomboedral, space group 166, a = b = 0,4550 nm, c = 1,1850 nm, α= ß = 90°, γ = 120°), too. Unfortunately, the geometry of the Bi and Te unit cells differ only in the length of the c-axis. In addition, HRTEM images show lattice fringes, which could belong to Bi or Te. To unambiguously distinguish between both elements, chemical analysis is necessary.

Performing energy-dispersive X-ray spectroscopy (EDXS) analysis with a conventional Si(Li) detector, no Bi counts appear in the EDX spectra during reasonable measuring times of several minutes. To finally get the distribution of Bi in the Te matrix, we employed a FEI Talos F200X microscope operated at 200 kV and equipped with an X-FEG electron source and a Super-X EDX detector system and performed spectrum imaging analysis based on EDXS.

Related publications

  • Poster
    Microscopy Conference MC 2019, 01.-05.09.2019, Berlin, Germany

Publ.-Id: 30191

Investigation on the working mechanism of the nitrile based sulfide collector Tecflote

Schach, E.; Lewis, A.; Rudolph, M.

Tecflote is a new group of nitrile-based collectors for sulphide flotation. The fact that it is insoluble in water results in some interesting implications for its actual working mechanism. It can be assumed that the Tecflote-molecules are adsorbed in the air water interface having first contact with the mineral surface during the particle bubble collision rather than conventional theories where particles are hydrophobized within the pulp in a conditioning step. Therefore, the adsorption of Tecflote and the spreading of the three-phase contact line between the mineral surface and the air bubble must be related to each other. Different investigations including contact angle measurements and AFM studies are conducted to obtain a better understanding of the working mechanism of Tecflote. Due to the insoluble character, the Langmuir-Blodgett technique is used to investigate the behaviour of Tecflote in the air-water interface and to deposit layers of Tecflote on mineral substrates for the above-mentioned studies.

  • Lecture (Conference)
    Flotation '19, 11.-14.11.2019, Kapstadt, Südafrika

Publ.-Id: 30190

A Recirculation Cell Approach for Hydrodynamic and Mass Transfer Modeling in Bubble Columns with and without Internals

Möller, F.; Dehmelt, T.; Schmidt, N.; Lau, Y. M.; Hampel, U.; Schubert, M.

An advanced recirculation cell model is proposed, which describes fluid dynamics and mass transfer in bubble columns with and without internals. The new model incorporates the cell approach of Shimizu et al. [Chem. Eng. J. 2000, 78, 21-28.] with latest breakup and coalescence kernels. Additionally, the gas flow structure is divided according to the two-bubble class assignment with fast-rising large bubbles in the column center and descending small bubbles near the wall following the liquid circulation pattern within the column’s cross-section. The effect of internals is considered dividing the column further into ‘sub-columns’ derived from the internals’ radial profile, which physically refines the liquid circulation pattern. The model was validated with experimental data of Möller et al. [Chem. Eng. Sci. 2018, 179,265-283; Chem. Eng. Res. Des. 2018, 134; Chem. Eng. Sci. 2019] for narrow (0.1 m diameter) and pilot-scale (0.39 m diameter) columns, respectively, with and without internals operated up to the well-developed churn-turbulent flow regime. Predictions for bubble size distribution, total gas holdup, Sauter mean diameter as well as interfacial area and volumetric mass transfer coefficients agree well with the experiments.

Keywords: Bubble column; tube bundle internals; recirculation cell model; two-bubble class approach; hydrodynamics; mass transfer


Publ.-Id: 30189

WKB approach to pair creation in spacetime-dependent fields: The case of a spacetime-dependent mass

Oertel, J.; Schützhold, R.

Besides tunneling in static potential landscapes, for example, the Wentzel-Kramers-Brillouin (WKB) approach is a powerful nonperturbative approximation tool to study particle creation due to time-dependent background fields, such as cosmological particle production or the Sauter-Schwinger effect, i.e., electron-positron pair creation in a strong electric field. However, our understanding of particle creation processes in background fields depending on both space and time is rather incomplete. In order to venture into this direction, we propose a generalization of the WKB method to truly spacetime-dependent fields and apply it to the case of a spacetime-dependent mass.


Publ.-Id: 30188

Boltzmann relaxation dynamics in the strongly interacting Fermi-Hubbard model

Queißer, F.; Schützhold, R.

Via the hierarchy of correlations, we study the Mott insulator phase of the Fermi-Hubbard model in the limit of strong interactions and derive a quantum Boltzmann equation describing its relaxation dynamics. In stark contrast to the weakly interacting case, we find that the scattering cross sections strongly depend on the momenta of the colliding quasi-particles and holes. Therefore, the relaxation towards equilibrium crucially depends on the spectrum of excitations. For example, for particle-hole excitations directly at the minimum of the (direct) Mott gap, the scattering cross sections vanish such that these excitations can have a very long life-time.


Publ.-Id: 30187

The impact of mineralogy on processing for recovery of chromite and PGE in the Bushveld Complex, South Africa

Bachmann, K.; Chetty, D.; Tolosana Delgado, R.; Gutzmer, J.

The Lower and Middle Group (LG and MG) chromitites of the Bushveld Complex in South Africa are the source of a very large portion of the global chrome supply. The recovery of platinum group elements and base metals (Ni, Cu) as by-products has the potential to add value to these chrome resources. Yet, the effectiveness of chromite and platinum-group element beneficiation circuits is highly sensitive to variations in feed composition. Mineral assemblages have been noted to be affected by surficial weathering (down to 50 m) and hydrothermal alteration. Of particular relevance is the abundance of alteration silicates, the prevailing base metal sulphides (BMS) and platinum group mineral (PGM) assemblages and mineral association which have a significant impact on recoveries and concentrate grade. The goal of this particular case study was to evaluate the potential recoverability of platinum group elements (PGE) as a by-product during chromite production in the Thaba Mine. As shown by a lot of studies, only a very minor amount of the economically important 3E (Pt,Pd,Rh) is enclosed in chromite and will therefore report to the chromite concentrate. On the other hand, the 6E (Pt, Pd, Rh, Ru, Ir and Au) grades of the mined chromitites are usually below 2 g/t and the feasibility of an additional PGE processing plant will be challenging. Therefore, a versatile and flexible geometallurgical framework is needed to identify potential PGE targets within the mine and to predict the recoverability of PGE in the ore. To extract a maximum of information at a minimal cost and material use, the framework proposed iterates between analytical work and statistical/ mathematical modelling.
Here, we focus on the metallurgical test work results of unweathered LG and MG chromitites. More than 100 different diamond drill core intersections of chromitite seams were used as sample material and analyzed by automated scanning electron-based image analysis. Several properties of each sample were fed into a statistical unsupervised classification scheme to create seven mineralogically distinct clusters for a subsequent metallurgical test work at Mintek. Composited batch samples were milled and fed to a shaking table to separate the chromite as efficiently as possible. Tailings were milled to 80 % < 75 µm, sampled and fed to flotation cells. The tailings of the rougher circuit were discharged and the rougher concentrate was subsequently fed to a cleaner flotation stage. Finally, the cleaner concentrate was sampled and chemically analyzed. Batch sample results display rather homogeneous shaking table feed 3E grades, ranging from 0.43 to 0.69 ppm, while Cr2O3 concentrations display a larger variability, ranging from 35 wt% to 42 wt%. Flotation feed grades range from 0.75 to 1.96 ppm. Cleaner flotation concentrates display grades between ca. 4 ppm and 16 ppm, resulting in upgrading factors between 2 and 11. Overall 3E recovery is between 25 and above 40 %. One reason for these PGE losses could be either large and liberated PGM grains or BMS agglomerates associated with PGM and/or PGE, which would go with the chromite concentrate. To reduce losses at the chromite concentration stage a possible PGM removal upfront with coarse flotation should be considered. Secondly, creating flotation reagent regimes and increasing residence time of the ore in the flotation cells to handle complex PGM assemblages (PGE-alloys and –sulpharsenides) will increase the flotation performance. To further increase the recovery, new flotation technology for better mineral surface cleaning may promote flotation of liberated PGM, as well as increasing liberation (e.g. Mach reactor).

  • Lecture (Conference)
    Tagung Aufbereitung und Recycling, 07.-08.11.2019, Freiberg, Deutschland

Publ.-Id: 30186

Highly sensitive ²⁶Al measurements assisted by ILIAMS

Lachner, J.; Kern, M.; Marchhart, O.; Martschini, M.; Priller, A.; Steier, P.; Wallner, A.; Wieser, A.; Golser, R.

The higher ion source output from Al2O3 for AlO− compared to Al− can improve the sensitivity of 26Al AMS measurements. One obstacle is the more complicated isobar suppression after AlO− extraction: For the metallic Al anion the 26Mg background is suppressed in the ion scource. With ion-laser interaction mass spectrometry (ILIAMS), however, the 26Mg isobar can also be completely suppressed for extracted AlO− ions. This now allows the use of the more prolific AlO− beam at facilities with terminal voltages <10 MV.
At the 3MV Vienna Environmental Research Accelerator (VERA) routine ILIAMS assisted AMS measurements of 26Al are performed utilizing AlO− and charge states 2+ and 3+ on the high-energy (HE) side of the spectrometer. Tests of Al2O3 mixtures with different metals were conducted to achieve the optimal generation of AlO− currents.
Admixtures of Cu or Ag powder showed good results but were surpassed by mixing Al2O3 with Fe powder. In addition, results of first experiments will be presented regarding the utilization of ILIAMS assisted 26Al measurements with lower terminal voltages and using the 1+ charge state on the HE side.

Keywords: Accelerator Mass Spectrometry and Applications

Publ.-Id: 30185

From Ore to Metal - Advanced Materials Characterisation by Automated Mineralogy

Sandmann, D.; Bachmann, K.; Gutzmer, J.

‘Automated Mineralogy’ terms an analytical method that is based on a combination of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). We suggest to use the term ‘Automated Materials Characterisation’ instead in certain cases, since not only minerals but other solid substances can be characterised by this method. The range of solid natural and artificial materials that has been investigated includes minerals, ores, rocks, mineral beneficiation products and tailings, metals, alloys, slags, construction materials, ceramics, glasses as well as recycling and semiconductor materials and even extraterrestrial materials.
Automated mineralogical investigations provide the unique opportunity to place quantitative constraints on a multitude of parameters tangible for the development and critical evaluation of beneficiation test work. This includes modal mineralogy, calculated elemental content, elemental distributions, mineral associations, particle and mineral size distributions, particle density distributions as well as liberation [3]. Sample overview images (‘mineral maps’) and images of specific mineral groups can also be extracted from the analysis data.
Of particular value is Automated Mineralogy in the field of processing of mineral raw materials. Here, the analyses generate an improved material understanding and are used for evaluation and optimisation of mineral beneficiation processes. Application leads to the reduction of raw material losses coupled with an increased resource and energy efficiency, and thus higher revenue for the operation. Recent research has shown that automated mineralogy data can be used to establish particle-based grade-recovery curves for minerals and elements from feed compositions – and expand the assessment of process efficiencies to include particle distribution probabilities.
The value of Automated Mineralogy is widely recognized in the minerals industry. Yet, its application is most widespread in the characterization of noble (Au, PGE) and base metal (especially Cu, but also Ni) ores and processing streams. The two case studies presented here for Li and Co ores serve to illustrate the potential of Automated Mineralogy during the beneficiation of minor commodities (such as Li) and beneficiation products, including by-products (such as Co). Automated Mineralogy is found to be an analytical method suitable to provide robust quantitative mineralogical data on very complex raw materials; current research extends its application to the characterization of recycling materials. The method is already very well established and an essential part of most studies in the field of processing of primary raw materials, whereas in the case of recycling raw materials only a few sample studies indicate the potential of the method.

  • World of Mining 71(2019)5, 283-291
    ISSN: 1613-2408

Publ.-Id: 30184

An open source platform for predictive geometallurgy

Tolosana Delgado, R.; Schach, E.; Kupka, N.; Buchmann, M.; Bachmann, K.; Frenzel, M.; Pereira, L.; Rudolph, M.; van den Boogaart, K. G.

Geometallurgy (the science of predicting the behaviour of ores along the value chain on the basis of their geoscientific characteristics) has barely moved beyond process mineralogy studies. These studies typically describe the mineralogical and microstructural characteristics of pristine or processed ores, for qualitative or semi-quantitative assessment of the processing performance and, eventually, a trial-and-error optimisation of the operation. But to deliver on its promise, geometallurgy should progress beyond this to provide fully quantitative models of such primary ore characteristics and the performance of their processing, both in average value and, most importantly, keeping track of their uncertainty. Only then it will be possible to optimise the operation in a predictive way. For this goal, we have developed a data mining platform consisting on a SQL database, an R front-end in-house package, and back-ends interpreting data from several analytical instruments into the database. A structured relational SQL database is useful to organise all available information (geometry, phase, chemistry, physical properties) of mineral grains, particles and samples. The R front-end allows to use the statistical and data mining power of this open-source environment in a transparent way for any geomet task, from ore characterisation to process fitting and forecasting, from geostatistical prediction to operational optimisation.
With regard to the back-ends, currently we import XRD, XRF and mineral liberation analysis measurements, and we will incorporate other data sources. The scripting abilities of R allow to process many streams in loop freeing the user of repeating tedious click-and-drop tasks; compute virtually any quantity; distribute the work among several clusters; or keep a log file of the calculations done, for accountability. This contribution presents the building blocks of this package, and their use with several examples in geometallurgical tasks.

  • Contribution to proceedings
    IMPC 2020, 18.-22.10.2020, Cape Town, South Africa

Publ.-Id: 30183

A THz View on Magnetization Dynamics: Opportunities at the THz User Facility TELBE

Awari, N.; Wang, Z.; Deinert, J.-C.; Chen, M.; Green, B. W.; Germanskiy, S.; Ilyakov, I.; de Oliveira, T.; Bawatna, M.; Deac, A. M.; Bonetti, S.; Gensch, M.; Kovalev, S.

The control of magnetic order by intense THz radiation is an emerging area in today’s ultra-fast Science community. Many different studies have investigated the interaction between THz fields and magnetic order on sub-picosecond timescales and have demonstrated different mechanisms for THz control. In this contribution, we discuss the opportunities to control the magnetic order of the material using spectrally dense, high repetition rate, narrow band THz pulses at TELBE.

Related publications

  • Poster
    GRC Spin dynamics in nanostructures, 07.07.2019, Les delbrates, Switzerland

Publ.-Id: 30182

All-optical structuring of laser-driven proton beam profiles

Metzkes-Ng, J.; Bernert, C.; Brack, F.-E.; Branco, J.; Bussmann, M.; Cowan, T.; Curry, C. B.; Gaus, L.; Fiuza, F.; Garten, M.; Gauthier, M.; Glenzer, S. H.; Göde, S.; Hübl, A.; Irman, A.; Kim, J. B.; Kluge, T.; Kraft, S.; Kroll, F.; Macdonald, M. J.; Mishra, R.; Obst-Hübl, L.; Pausch, R.; Prencipe, I.; Rehwald, M.; Rödel, C.; Ruyer, C.; Schlenvoigt, H.-P.; Sommer, P.; Schoenwalder, C.; Schumaker, W.; Ziegler, T.; Schramm, U.; Zeil, K.

Extreme field gradients intrinsic to relativistic laser-interactions with thin solid targets enable compact multi-MeV proton accelerators. The initial µm-scale acceleration phase is followed by ballistic proton propagation with negligible space-charge effects over millimeters to hundreds of centimeters to a site of analysis/application. The detected proton distribution can be influenced by the spatio-temporal intensity distribution in the laser focus, electron transport, plasma instabilities, as well as target geometry and surface properties.
Substantially extending this picture, our recent results show a critical influence of the mm-scale vacuum environment on the accelerated proton bunch, where residual gas molecules are ionized by the remnant laser light not absorbed into the target plasma but reflected or transmitted. In an experiment with µm-sized hydrogen jet targets, this effect lead to the counter-intuitive observation of laser near-field feature imprints in the detected proton beam profiles. Our results show that the remnant laser pulse induces a quasi-static deflecting field in the ionized residual background gas that serves as a memorizing medium and allows for asynchronous information transfer to the naturally delayed proton bunch. Occurring under typical experimental laser, target and vacuum conditions, all-optical imprinting needs to be taken into account for sensible interpretation of modulated proton beam profiles.

Keywords: laser-driven ion acceleration

  • Invited lecture (Conferences)
    European Advanced Accelerator Concepts Workshop (EAAC 2019), 15.-21.09.2019, La Biodola, Isola d'Elba, Italien

Publ.-Id: 30181

A THz View on Magnetization Dynamics: Opportunities at the THz User Facility TELBE

Awari, N.; Wang, Z.; Deinert, J.-C.; Chen, M.; Green, B. W.; Germanskiy, S.; Ilyakov, I.; de Oliveira, T.; Bawatna, M.; Deac, A. M.; Bonetti, S.; Gensch, M.; Kovalev, S.

The control of magnetic order by intense THz radiation is an emerging area in today’s ultra-fast Science community. Many different studies have investigated the interaction between THz fields and magnetic order on sub-picosecond timescales and have demonstrated different mechanisms for THz control. In this contribution, we discuss the opportunities to control the magnetic order of the material using spectrally dense, high repetition rate, narrow band THz pulses at TELBE. The THz facility at ELBE (TELBE) is one of only a few superradiant THz light sources operated at an SRF accelerator and the only facility worldwide that provides: high THz fields at quasi-CW repetition rates. TELBE is operated in early-stage user operation since 08/2016.

Related publications

  • Poster
    IRMMW 2019, 01.-06.09.2019, Paris, France

Publ.-Id: 30180

Narrow band tunable spintronic THz emission from ferrimagnetic nano-films

Awari, N.; Ilaykov, I.; Fowley, C.; Rode, K.; Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Green, B. W.; Yildrim, O.; Lindner, J.; Faßbender, J.; Coey, M.; Deac, A. M.; Gensch, M.; Kovalev, S.

We report on narrow band THz emission from ferrimagnetic Mn3-xGa nano-films based. The emission originates from coherently excited spin precession. The central frequency of the emitted radiation is determined by the anisotropy field, while the bandwidth relates to Gilbert damping. It is shown how THz emission can be used for the characterization dynamical properties of ultra-thin magnetic films. We furthermore discuss the potential of these types of films as efficient on-chip spintronic THz emitter.
Keywords: Spintronics, THz emitter, nano-films.

  • Invited lecture (Conferences)
    International Conference on Optics and Electro-Optics 2019, 19.-22.10.2019, Dehradun, India

Publ.-Id: 30179

Active Modes and Dynamical Balances in MRI Turbulence of Keplerian Disks with a Net Vertical Magnetic Field

Gogichaishvili, D.; Mamatsashvili, G.; Horton, W.; Chagelishvili, G.

We studied dynamical balances in magnetorotational instability (MRI) turbulence with a net vertical field in the shearing box model of disks. Analyzing the turbulence dynamics in Fourier (k-)space, we identified three types of active modes that define the turbulence characteristics. These modes have lengths similar to the box size, i.e., lie in the small wavenumber region in Fourier space labeled "the vital area" and are (i) the channel mode, uniform in the disk plane with the smallest vertical wavenumber; (ii) the zonal flow mode, azimuthally and vertically uniform with the smallest radial wavenumber; and (iii) the rest (parasitic) modes. The rest modes comprise those harmonics in the vital area whose energies reach more than 50% of the maximum spectral energy. The rest modes individually are not so significant compared to the channel and zonal flow modes; however, the combined action of their multitude is dominant over these two modes. These three mode types are governed by the interplay of the linear and nonlinear processes, leading to their interdependent dynamics. The linear processes consist of disk flow nonmodality modified classical MRI with a net vertical field. The main nonlinear process is the transfer of modes over wavevector angles in Fourier space—the transverse cascade. The channel mode exhibits episodic bursts supplied by linear MRI growth, while the nonlinear processes mostly oppose this, draining the channel energy and redistributing it to the rest modes. As for the zonal flow, it does not have a linear source and is fed by nonlinear interactions of the rest modes.

Keywords: accretion,; dynamo; instabilities; magnetohydrodynamics (MHD); turbulence; accretion disks


Publ.-Id: 30178

Ionenstrahlen erzeugen periodische, magnetische Domänenstrukturen

Nord, M.; Mcgrouther, D.; Potzger, K.; Bali, R.

Bei der Ausbildung magnetischer Domänen in Nanostrukturen spielt die magnetische Anisotropie eine wesentliche Rolle. Sie kann durch die äußere Form der magnetischen Struktur, aber auch durch Verzerrungen im Kristallgitter beeinflusst werden. In einem Material, dessen magnetische Eigenschaften durch Ionenbestrahlung verändert werden, lassen sich beide Beiträge gleichzeitig erzeugen. Dieses Phänomen hat unsere Gruppe am Helmholtz-Zentrum Dresden-Rossendorf ausgenutzt, um Domänenstrukturen gezielt einzustellen.

Keywords: Magnetismus; Ionenbestrahlung; FeAl

Related publications

  • Physik in unserer Zeit 51(2020)2, 58-59

Publ.-Id: 30177

Ultrasmall silicon nanoparticles as promising platform for multimodal imaging

Singh, G.; Ddungu, L. Z. J.; Licciardello, N.; Bergmann, R.; de Cola, L.; Stephan, H.

Ultrasmall renal clearable nanoparticles possess enormous potential as cancer imaging agents [1, 2]. In this perspective, biocompatible silicon nanoparticles (Si NPs) are highly attractive. Their facile surface functionalization allows the introduction of different labels for in vivo imaging. Recently, we have reported on biodistribution of ultrasmall silicon particles (size ~ 4 nm) in small animals by in vivo positron emission tomography (PET) to provide reliable information about absorption, distribution, metabolism, and excretion (ADME) [3].
Subsequent functionalization of Si NPs with a near-infrared dye (IR800-CW) and a radiolabel (64Cu) enabled a detailed in vitro and in vivo study of the particles of these dual labeled particles. Both PET and fluorescence imaging studies showed a rapid renal clearance from small animals. It has been proven that ultrasmall Si NPs with a surface charge close to zero show fast distribution kinetics and rapid renal clearance. Despite the very small size, multiple and different functionalities can be grafted on the nanoparticle surface. In this way, the pharmacokinetic properties can be tailored and the behavior can be studied in vitro and in vivo in detail.

[1] Zarschler et al. Nanomedicine: Nanotechnology, Biology, and Medicine. 2016, 12: 1663-1701.
[2] Kunz-Schughart et al. Biomaterials 2017, 120: 155-184.

  • Lecture (others)
    Faraday Discussion: Luminescent silicon nanostructures, 12.-14.02.2020, York, UK

Publ.-Id: 30176

Multifunctional Stealth Nanoparticles for Biomedical Applications

Stephan, H.

Due to their size and surface charge, nanoparticles are often recognised as foreign objects by the body's own immune system and eliminated by its scavenger cells. A special role is played by the opsonisation of the particles, i.e. the surface is coated with special proteins (protein corona) in order to be more easily recognised and absorbed by phagocytic cells. Basically, there are two strategies to avoid phagocytosis. Firstly, the formation of a protein corona on nanoparticles is dramatically reduced by ultrasmall particles (< 5 nm) [1-2] and secondly, there is the possibility of producing so-called "stealth" particles that are invisible to the immune system. Here, the application of a zwitterionic protective coating (see Figure) is frequently used, which minimizes or prevents the surface binding of proteins [3-7].
This lecture will focus on the development and characterization of tiny nanoparticles, embracing silicon quantum dots, superparamagnetic iron oxide and upconverting nanophosphors for biomedical applications.
[1] L. Boselli, E. Polo, V. Castagnola, K. A. Dawson, Angew. Chem. Int. Ed. 56 (2017) 4215-4218.
[2] N. Liccardello, S. Hunoldt, R. Bergmann, G. Singh, C. Mamat, A. Faramus, J. L. Z. Ddungu, S. Silvestrini, M, Maggini, L. De Cola, H. Stephan, Nanoscale 10 (2018) 9880-9891.
[3] K. Pombo-García, K. Zarschler, L. Barbaro, J. A. Barreto, W. O’ Malley, L. Spiccia, H. Stephan, B. Graham, Small 10 (2014) 2516-2529.
[4] K. Pombo-García, S. Weiss, K. Zarschler, C.-S. Ang, R. Hübner, J. Pufe, S. Meister, J. Seidel, J. Pietzsch, L. Spiccia, H. Stephan, B.Graham, ChemNanoMat 2 (2016) 959-971.
[5] K. Pombo-García, C. L. Rühl, R. Lam, J. A. Barreto, C.-S. Ang, P. J. Scammels, P. Comba, L. Spiccia, B. Graham, T. Joshi, H. Stephan, ChemPlusChem 82 (2017) 638-646.
[6] A. Nsubuga, M. Sgarzi, K. Zarschler, M. Kubeil, R. Hübner, R. Steudtner, B. Graham, T. Joshi, H. Stephan, Dalton Trans. 47 (2018) 8595-8604.
[7] A. Nsubuga, K. Zarschler, M. Sgarzi, B. Graham, H. Stephan, T. Joshi, Angew. Chem. Int. Ed. 57 (2018) 16036-16040.

  • Invited lecture (Conferences)
    3nd International Conference on Translational Chemistry, 02.-05.12.2019, Lissabon-Caparica, Portugal

Publ.-Id: 30175

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