Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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35836 Publications

Microstructure, strengthening mechanisms & properties of ODS alloys developed under MatISSE project

Chauhan, C.; Bergner, F.; Etienne, A.; Aktaa, J.; de Carlan, Y.; Heintze, C.; Litvinov, D.; Hernandez-Mayoral, M.; Oñorbe, E.; Radiguet, B.; Ulbricht, A.

The invited talk aims at summarizing results from a publication that received the best paper award 2017 of the Journal of Nuclear Materials. Microstructure, strengthening mechanisms and properties of ODS alloys are addressed.

Keywords: ODS alloys; microstructure characterization; strengthening mechanisms

  • Invited lecture (Conferences)
    NuMat2018: The Nuclear Materials Conference, 14.-18.10.2018, Seattle, USA

Permalink: https://www.hzdr.de/publications/Publ-28091
Publ.-Id: 28091


High Energy Fast X-ray Tomography

Barthel, F.; Windisch, D.; Hampel, U.

Ultrafast X-ray computed tomography with ROFEX scanners has become a common tool for investigations of multiphase phenomena in science and industrial application within recent years. Though being very successful in giving unprecedented insights into dynamic processes, ROFEX scanners yet have some limitations in terms of permissible sizes and density of the investigated objects. Due to the limited penetration capability of X-rays at photon energy of up to 150 keV experimental mock-ups need to be made out of light construction materials and many experimental setups had to be scaled down from their real size to fit into the scanner. Often this limits the transferability of results to larger industrial facilities.
This contribution introduces the new High-Energy Computed Tomography scanner of Rossendorf (HECToR) as the next step towards improved industrial applicability. The facility utilizes a 1 MeV electron accelerator with a continuous beam power of up to 100 kW. The functional principle has been adapted from the ROFEX scanners. HECToR is able to scan objects with a maximum diameter of 400 mm at a temporal resolution of up to 5000 frames per second and with a spatial resolution of 3 mm at best conditions. The paper introduces the scanner concept, its components and presents first dynamic studies on generic two-phase flows in steel vessels. Furthermore, the imaging characteristics are discussed in detail.

Keywords: ROFEX; ultrafast X-ray CT; high energy; HECToR

  • Contribution to proceedings
    9th World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK
    Proceedings of the 9th world cogress on industrial process tomography
  • Lecture (Conference)
    9th World Congress on Industrial Process Tomography, 02.-06.09.2018, Bath, UK

Permalink: https://www.hzdr.de/publications/Publ-28090
Publ.-Id: 28090


Minor changes in neurocognition and quality of life after proton therapy for brain tumour patients

Dutz, A.; Agolli, L.; Valentini, C.; Bütof, R.; Troost, E. G. C.; Baumann, M.; Lühr, A.; Krause, M.; Löck, S.

Purpose: To investigate changes in neurocognitive function and quality of life (QoL) and their association with dosimetric parameters of various brain structures as well as clinical cofactors in adult brain tumour patients following proton beam therapy (PBT).

Material and methods: Sixty-nine adult patients with primary brain tumours who received conventionally fractionated PBT were included in this study. Neurocognitive function according to the Montreal Cognitive Assessment (MoCA) test and QoL according to general EORTC-QLQ-C30 and brain tumour specific QLQ-BN20 questionnaires were scored prospectively at baseline and within 3-month-intervals up to one year after PBT. Dose-volume parameters of the retrospectively contoured structures hippocampus, thalamus, frontal and temporal lobes, amygdala, entire cerebellum, anterior cerebellum, and posterior cerebellum were extracted. Clinical parameters comprised age, sex, diagnosis and WHO grading, tumour volume, prescribed dose, concomitant chemotherapy, tumour resection and administration of corticosteroids. MoCA scores and differences to baseline values at different time points were correlated with self-reported QoL items (Spearman correlation rs), clinical and dosimetric parameters (Mann-Whitney U test, logistic regression). A change of ≥3 points of the MoCA total score compared to baseline was considered clinically relevant. Unless otherwise stated, differences at 3 months after PBT compared to baseline are given.

Results: The MoCA total score remained stable over time for the majority of patients: Less than 10% of the patients had clinically relevant changes at respective time points. The QLQ-C30 items did not change over time. On the QLQ-BN20 symptom scale, significant increases were observed for the items hair loss (p=0.002) and seizure (p<0.042, up to 9 months after PBT). However, future uncertainty decreased significantly (p<0.042). MoCA scores were significantly correlated with self-reported QoL scores. At all time-points, MoCA total score correlated with QLQ-C30 cognitive function (rs: 0.31-0.57) and MoCA language scores with QLQ-BN20 communication deficit (rs: 0.36-0.59).
Clinically relevant differences in the MoCA total score were significantly associated with high dose parameters in the anterior, posterior and entire cerebellum (V55Gy, p<0.05), but not with clinical parameters.

Conclusion: Neurocognitive function and QoL remained stable in the majority of brain tumour patients following PBT. Self-reported QoL was in accordance with the results of the objective MoCA test. Significant associations between dose-volume parameters and clinically relevant neurocognitive changes suggest that further sparing of organs at risk in treatment planning may lead to increased neurocognitive function and QoL for brain tumour patients. New planning constraints for further potential organs at risk, such as the cerebellum [1], should be discussed.

[1] Eekers DBP et al. (2017) Clin Transl Radiat Oncol 8, 22–26.

Keywords: Quality of Life

Permalink: https://www.hzdr.de/publications/Publ-28089
Publ.-Id: 28089


Review Article: Review of electrohydrodynamical ion sources and their applications to focused ion beam technology

Gierak, J.; Mazarov, P.; Bruchhaus, L.; Jede, R.; Bischoff, L.

In this article, the authors review, compare, and discuss the characteristics and applicative potential of a variety of nongallium ion liquid metal ion sources they have developed and successfully applied to nanopatterning. These sources allow generating on-demand ion beams and are promising for extending focused ion beams applications. They detail the operating characteristics of such sources capable to emit metal projectiles ranging from atomic ions with different charge states to polyatomic ions and to large metal clusters having sizes up to a few nanometers. They highlight their interest and relevance to current nanoscience challenges in terms of ultimate patterning or bottom-up nanofabrication capabilities.

Keywords: Liquid Metal Ion Source; nongallium; nanoscience

  • Open Access Logo Journal of Vacuum Science & Technology B 36(2018)6, 06J101-1-06J101-6
    DOI: 10.1116/1.5047150

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Permalink: https://www.hzdr.de/publications/Publ-28088
Publ.-Id: 28088


Forschungsdatenmanagement am Helmholtz-Zentrum Dresden-Rossendorf und am Helmholtz-Zentrum Berlin (RDM@DB)

Konrad, U.; Görzig, H.; Juckeland, G.

Das BMBF Verbundprojekt RDMatDB wird im Rahmen der Förderrichtlinie "Erforschung des Managements von Forschungsdaten in ihrem Lebenszyklus“ realisiert. Ziel des Projektes ist es, Forschungsdaten-Management-Lösungen zu entwickeln, die das HZDR und HZB als Betreiber von Infrastrukturen in die Lage versetzen, die sich aus den FAIR-Prinzipien des Datenmanagements ergebenden Anforderungen zu erfüllen. Im dem Vortrag auf der BMBF-Veranstaltung "Forschungsdatenmanagement - künftige Entwicklungen und aktuelle Fragen der Wissenschaft" wird das Projekt und die Perspektiven vorgestellt.
The BMBF joint project RDMatDB of the HZDR and HZB is implemented within the scope of the funding program "Research on the management of research data in its life cycle".
The goal of the project is to develop research data management solutions which the HZDR and HZB consider to meet the requirements of the FAIR data management principles.
The project and perspectives are presented at the BMBF event "Research Data Management - Future Developments and Current Issues of Science".

  • Invited lecture (Conferences)
    Forschungsdatenmanagement - künftige Entwicklungen und aktuelle Fragen der Wissenschaft, 17.-18.10.2018, Berlin, Deutschland
    DOI: 10.14278/rodare.62

Permalink: https://www.hzdr.de/publications/Publ-28087
Publ.-Id: 28087


Influence of the magnetic field on the stability of the multiferroic conical spin arrangement of Mn0.80Co0.20WO4

Urcelay-Olabarria, I.; Ressouche, E.; Ivanov, V. Y.; Skumryev, V.; Wang, Z.; Skourski, Y.; Balbashov, A. M.; Popov, Y. F.; Vorob'En, G. P.; Qureshi, N.; Garcia-Munoz, J. L.; Mukhin, A. A.

The evolution of the low temperature antiferromagnetic conical (characterized by two, commensurate and incommensurate propagation vectors), and the high temperature collinear spin arrangements of the 20% Co-doped MnWO4 multiferroic has been studied in the presence of magnetic field up to 60 T by means of macroscopicmagnetic and pyroelectricmeasurements, and by neutron diffraction experiments in fields up to 12 T on a single crystal. The complete magnetoelectric phase diagrams for magnetic fields along distinct magnetic directions with respect to the spin structure have been constructed up to magnetic field values exceeding those necessary to induce a spin-flip transition into the paramagnetic state. The differences in the topology of the diagrams are discussed. The obtained results might be common for other magnetic materials possessing conical antiferromagnetic structures.

Permalink: https://www.hzdr.de/publications/Publ-28085
Publ.-Id: 28085


Anomalous Hall effect in Weyl semimetal half-Heusler compounds RPtBi (R = Gd and Nd)

Shekhar, C.; Kumar, N.; Grinenko, V.; Singh, S.; Sarkar, R.; Luetkens, H.; Wu, S.-C.; Zhang, Y.; Komarek, A.; Kampert, E.; Skourski, Y.; Wosnitza, J.; Schnelle, W.; Mccollam, A.; Zeitler, U.; Kübler, J.; Yan, B.; Klauss, H.-H.; Parkin, S. P.; Felser, C.

Topological materials ranging from topological insulators to Weyl and Dirac semimetals form one of the most exciting current fields in condensed-matter research. Many half-Heusler compounds, RPtBi (R = rare earth), have been theoretically predicted to be topological semimetals. Among various topological attributes envisaged in RPtBi, topological surface states, chiral anomaly, and planar Hall effect have been observed experimentally. Here, we report an unusual intrinsic anomalous Hall effect (AHE) in the antiferromagnetic Heusler Weyl semimetal compounds GdPtBi and NdPtBi that is observed over a wide temperature range. In particular, GdPtBi exhibits an anomalous Hall conductivity of up to 60 Ω−1·cm−1 and an anomalous Hall angle as large as 23%.Muon spin-resonance (μSR) studies of GdPtBi indicate a sharp antiferromagnetic transition (TN) at 9 K without any noticeable magnetic correlations above TN. Our studies indicate that Weyl points in these half-Heuslers are induced by a magnetic field via exchange splitting of the electronic bands at or near the Fermi energy, which is the source of the chiral anomaly and the AHE.

  • Proceedings of the National Academy of Sciences of the United States of America 115(2018)37, 9140-9144
    DOI: 10.1073/pnas.1810842115

Permalink: https://www.hzdr.de/publications/Publ-28084
Publ.-Id: 28084


Low-Temperature Magnetic Hysteresis in Nd(Pr)-Fe-B Nanostructured Alloys with Nd2Fe14B Type Main Phase Composition

Neznakhin, D. S.; Politova, G. A.; Ivanov, L. A.; Volegov, A. S.; Gorbunov, D. I.; Tereshina, I. S.; Kudrevatykh, N. V.

Magnetic hysteresis properties of nanostructured industrially manufactured Nd-Fe-B and Pr-Fe-B alloys on the base of a tetragonal Nd2Fe14B (2-14-1) hard magnetic phase (MQP-B, MQP-B+ and MQP-16-7 brands) have been investigated at 4.2 K in magnetic fields up to 58 T. The chemical composition of the alloys given in the certificates was defined more precisely. The grain sizes of the main 2-14-1 phase were determined. The average grain size is much smaller than a critical single domain diameter. Coercivity, remanence magnetization, saturation magnetization and maximal magnetic energy product were determined at 4.2 K and compared with those obtained at room temperature.

Permalink: https://www.hzdr.de/publications/Publ-28083
Publ.-Id: 28083


Millisecond Dynamics of the Magnetocaloric Effect in a First- and Second-Order Phase Transition Material

Döntgen, J.; Rudolph, J.; Gottschall, T.; Gutfleisch, O.; Hägele, D.

The millisecond-dynamics of the magnetocaloric effect in Gd and La-Fe-Si-Mn, which exhibit first- and second-order phase-transitions, respectively, are investigated. Direct measurements of the adiabatic temperature change ΔT are obtained from modulation infrared thermometry with field-cycling frequencies exceeding 1 kHz at amplitudes of up to 45 mT. The peak amplitude of ΔT(T) shows a dependence on sample thickness and decreases with increasing modulation frequency for both materials despite a frequency independent susceptibility of Gd. The adiabatic DT depends quadratically on the external field for Gd while La-Fe-Si-Mn shows a peculiar bucket-shaped curve for temperatures below the peak maximum. A comparative study of non-caloric samples shows that dissipative heating by eddy currents or magnetic hysteresis does not explain the observed behavior. The transient ΔT(t) instead suggests a mechanism involving strong temperature gradients at the ferromagnetic–paramagnetic boundaries and underlines the importance of further dynamical studies for a fundamental understanding of the magnetocaloric effect in first-order materials.

Permalink: https://www.hzdr.de/publications/Publ-28082
Publ.-Id: 28082


Molecular interaction of fungi with uranium

Wollenberg, A.; Merroun, M.; Günther, A.; Raff, J.; Stumpf, T.

The radioactive and toxic element uranium is mined in large quantities, for example for industrial or research purposes, and subsequently stored as waste. This increases the risk of anthropogenic release into the environment, where it can enter the groundwater and thus the food chain through leaching and migration. However, the surrounding microbial community can influence the migration behavior of uranium. An important part of this community are fungi that can interact with uranium through various processes such as sorption, accumulation or mineralization. These processes can restrict the mobility of uranium and prevent migration into the waterways and subsequently the food chain.
The aim of this study is to investigate the potential of fungi for precautionary radiation protection methods or even bioremediation procedures for contaminated soils. In assessing the suitability of fungi, the first task is to investigate the molecular interactions with uranium in detail. For this purpose, binding experiments with the two fungi Schizophyllum commune and Leucoagaricus naucinus are conducted in various media to determine the influence of the environment on the uranium binding behavior of fungi. Time-resolved laser-induced fluorescence spectroscopy was used to investigate the speciation of fungal bound uranium. Furthermore, the location of bound uranium was determined using transmission electron microscopy with energy dispersive X-ray spectroscopy. In addition, microcosm experiments were carried out with soil to investigate the interactions of fungi with uranium under natural conditions.
The results so far show that the uranium binding of the fungi is very different but largely independent of the surrounding medium. This suggests that the interactions are mainly determined by the biochemistry of fungi.

Keywords: Fungi; Uranium; Interaction

  • Poster
    International conference Uranium biogeochemistry, 21.-26.10.2018, Ascona, Switzerland

Permalink: https://www.hzdr.de/publications/Publ-28081
Publ.-Id: 28081


Optimal beam loading in a nanocoulomb-class laser wakefield accelerator

Couperus, J. P.

Laser plasma wakefield accelerators have seen tremendous progress in the last years, now capable of producing electron beams in the GeV energy range. The inherent few-femtoseconds short bunch duration of these accelerators leads to ultra-high peak-currents. Reducing the energy spread found in these accelerators, while scaling their output to hundreds of kiloampere peak current would stimulate the next generation of radiation sources covering high-field THz, high-brightness X-ray and -ray sources, compact free-electron lasers and laboratory-size beam-driven plasma accelerators. At such high currents, an accelerator operates in the beam loaded regime where the accelerating field is strongly modified by the self-fields of the injected bunch, potentially deteriorating key beam parameters. However, if appropriately controlled, the beam loading effect can be employed to improve the accelerator’s performance, specifically to reduce the energy spread.

In this thesis the beam-loading effect is systematically studied at a quasi-monoenergetic nanocoulomb-class laser wakefield accelerator. For this purpose, a tailored scheme of the self-truncated ionisation injection process is introduced for the non-linear bubble regime. This scheme facilitates stable and tunable injection of high-charge electron bunches within a short and limited time-frame, ensuring low energy spread right after injection. Employing a three millimetres gas-jet acceleration medium and a moderate 150 TW short pulse laser system as driver, unprecedented charges of up to 0.5 nC within a quasi-monoenergetic peak and energies of ~0.5 GeV are achieved. Studying the beam loading mechanism, it is demonstrated that at the optimal loading condition, i.e. at a specific amount of injected charge, performance of the accelerator is optimised with a minimisation of the energy spread. At a relative energy spread of only 15%, the associated peak current is around 10 kA, while scaling this scheme to operate with a petawatt driver laser promises peak-currents up to 100 kA.

Keywords: beam loading; plasma acceleration; electron acceleration; LWFA; laser wakefield acceleration; LPA

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-093 2018
    ISSN: 2191-8708, eISSN: 2191-8716
  • Lecture (Conference)
    Laser-Plasma Accelerator Workshop (LPAW) 2019, 05.-10.05.2019, Split, Republika Hrvatska

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Permalink: https://www.hzdr.de/publications/Publ-28080
Publ.-Id: 28080


Experimental investigation of bubble breakup in bubble chains rising in a liquid metal

Keplinger, O.; Shevchenko, N.; Eckert, S.

The process of bubble breakup in a liquid metal was studied by X-ray radiography and high-speed video imaging. Argon gas bubbles were injected through a single orifice at the bottom of a rectangular vessel filled with the eutectic GaInSn alloy. Moderate gas flow rates were applied at isothermal conditions resulting in the formation of bubble chains. The bubble breakup events observed in the chosen experimental geometry were mainly initiated by bubble collisions or by the effect of local shear flow. We present experimental results accompanied by statistical analysis of the bubble breakup frequency, number of daughter bubbles and their size distribution, bubble velocities before and after the breakup process for a broad range of Argon gas flow rates.

Keywords: Liquid metal; Two-phase flow; Bubble chain; Bubble breakup; X-ray radiography

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Permalink: https://www.hzdr.de/publications/Publ-28079
Publ.-Id: 28079


Bubble motion in liquid metal with and without a magnetic field

Keplinger, O.; Shevchenko, N.; Eckert, S.

Liquid metal two-phase flows are widely used in metallurgical processes. For example Argon gas bubbles are injected into a bulk liquid to enhance mixing and homogenization of the melt. Also the Argon gas bubbles remove undesired inclusions by transporting them towards the slag layer at the free surface improving the melt cleanliness. This process is highly dependent both on the properties of the inclusions and on the size and surface characteristics of the dispersed gas phase. The bubble size distribution and interfacial area inside the melt are strongly influenced by the bubble coalescence and breakup which are controlled by the turbulent flow that develops inside the melt. In order to improve the final product quality an external magnetic field is applied to control the fluid motion and bubble behavior. Despite an increasing number of numerical and experimental studies on bubble rise in liquid metals only few experimental data on bubble rise in the presence of a magnetic field exists. These works are mainly focused on investigations of single bubbles in the absence of turbulence. Since bubble rising dynamics in a bubble chain or cluster is often affected by bubble-wake and bubble-bubble interactions direct investigation of bubble chains and clusters rising in liquid metals under the influence of magnetic field becomes crucial.
Bubble chain ascending in non-transparent liquid metal under the influence of magnetic field was examined by X-ray radiography through high-speed video imaging. The Argon gas bubbles were injected through a single bevel-shaped nozzle positioned in the middle at the bottom of a flat Plexiglas vessel. The vessel was filled with eutectic GaInSn alloy at isothermal conditions. We present experimental results accompanied by statistical analysis of the bubble size distribution, shape deformation, velocities, etc. for Argon gas flow rates lying in the range 150-1200 cm³ /min. In general, the increase of the gas flow rate leads to increase in bubble size and velocity. In turn, the velocity shows periodic oscillations related to the zig-zag motion of the bubbles. Both the velocity and oscillation amplitude decrease with increasing the magnetic field strength. Bubble pairing regime appears at higher gas flow rates for bubbles moving in the magnetic field: at 400 cm³ /min against 300 cm³ /min for bubbles moving without magnetic field. Therefore, the appearance of bubble coalescence and breakup is also shifted to higher gas flow rates. The integral gas distribution for bubbles moving without magnetic field is symmetrical due to the bubble chain oscillation in the observation plane. In contrast, the bubbles move almost along the same bubble path in a magnetic field leading to the asymmetry of gas distribution. Further image processing reveals that the major axis of the ellipses fitted to the bubbles at moderate gas flow rates (≤400 cm³ /min) is aligned almost parallel to the bottom of the vessel in the presence of the highest magnetic field used in our experiments (for B ~270 mT). Also the bubble shape oscillations are damped with increasing magnetic field at moderate gas flow rates (≤400 cm³ /min) when the turbulence is strongly suppressed.

Keywords: Liquid metal; Two-phase flow; Bubble chain; Magnetic field; X-ray radiography

  • Poster
    16th Multiphase Flow Conference & Short Course, 13.-16.11.2018, Helmholtz-Zentrum Dresden-Rossendorf, Germany

Permalink: https://www.hzdr.de/publications/Publ-28078
Publ.-Id: 28078


Influence of beamline and scanning magnets on the magnetic fringe field of a proton PBS nozzle

Gantz, S.; Riemann, L.; Smeets, J.; Pawelke, J.; Hoffmann, A.

Purpose/Objective
Real-time soft-tissue image guidance is a desirable concept to improve the targeting precision of proton therapy. In 2017, the first prototype of an MR-integrated proton therapy setup was realised at our horizontal fixed research beamline. Moving towards a clinical application this in-beam MRI system shall be transferred to a pencil beam scanning (PBS) research beamline that provides volumetric dose spot delivery. A magnetic survey was performed to quantify the effects of beamline and scanning magnets on the environmental magnetic field.
Material and Methods
The magnetic fringe field at the PBS nozzle was measured by a tri-axial Hall-probe magnetometer (THM 1176-LF, Metrolab) at two positions: (P1) at a lateral position 700 mm from the center of the scanning magnets, and (P2) at the planned magnetic isocenter of the in-beam MR scanner, which is 2270 mm downstream from the last scanning magnet on the beam central axis. Measurement point P1 was chosen to be able to differentiate between magnetic field changes due to energizing the beamline (quadrupole) and the scanning (dipole) magnets. Two maps of PBS spots were delivered by the PBS nozzle: (M1) consisted of 16 energy layers ranging from 70 to 230 MeV (steps of 10 MeV) with a single central spot for each layer, and (M2) used a single energy of 200 MeV with a field size of (200 x 200) mm2 and a step width of 5 mm, resulting in 41x41 spots. The magnets were energized to deliver maps M1 and M2 to study the magnetic field effects of changing beam energies and changing spot positions, respectively, but no beam was transported for radiation protection reasons. The Hall-probe logged all 3 magnetic field components during spot map scanning by Labview-based software (THM1176 v4.0, Metrolab) at a sample frequency of 10 Hz.
Results
For position P1, the magnetic field changes due to setting the beamline magnets to the 16 energy levels, as well as operating the scanning magnets to the 41 spot rows can be clearly observed (Fig. 1), with maximum amplitudes |ΔBmax| of up to 28.6 µT and 55.3 µT, for maps M1 and M2, respectively. For position P2, the |ΔBmax| was 9.0 µT and 10.1 µT for M1 and M2, respectively. This translates into an off-resonance frequency shift of 383.4 Hz and 430.3 Hz for 1H-MR imaging, respectively.
Conclusion
Significant changes in the environmental magnetic fringe field of a proton PBS beamline are measurable due to the operation of its beamline and scanning magnets. These changes translate into off-resonance frequency shifts that could cause significant MR image shifts in the frequency encoding direction. This needs to be confirmed by magnetic field mapping around the magnetic isocenter of the MRI scanner once it has been installed at the PBS nozzle. To counteract this effect, either the image shifts need to be compensated for or the PBS nozzle needs to be magnetically shielded from the MRI scanner.

  • Poster
    ESTRO 38, 26.-30.04.2019, Milano, Italy

Permalink: https://www.hzdr.de/publications/Publ-28077
Publ.-Id: 28077


Deep-learning based estimation of loco-regional control for patients with locally advanced HNSCC

Starke, S.; Leger, S.; Zwanenburg, A.; Pilz, K.; Lohaus, F.; Linge, A.; Zöphel, K.; Kotzerke, J.; Schreiber, A.; Tinhofer, I.; Budach, V.; Stuschke, M.; Balermpas, P.; Rödel, C.; Ganswindt, U.; Belka, C.; Pigorsch, S.; Combs, S. E.; Mönnich, D.; Zips, D.; Krause, M.; Baumann, M.; Richter, C.; Troost, E. G. C.; Löck, S.

Purpose/Objective: In order to improve radiotherapy outcomes, further treatment personalisation is considered beneficial. Radiomics analyses aim to predict treatment outcomes based on medical imaging data. Commonly, hand-crafted imaging features are used that require domain knowledge and further feature selection steps. This may cause relevant information to be lost. Deep convolutional neural networks (CNNs) on the other hand can act as automatic feature detectors and are able to learn highly nonlinear relationships directly from imaging data, thus addressing the drawbacks of conventional radiomics approaches and enabling end-to-end learning. We investigated whether CNNs are capable of quantifying loco-regional tumour control (LRC) based on CT imaging of patients with locally advanced head and neck squamous cell carcinoma (HNSCC).
Material/Methods: A multicentre cohort consisting of 302 patients with locally advanced HNSCC was collected and divided into an exploratory and a validation cohort (207 and 95 patients, respectively). All patients received a non-contrast-enhanced CT scan for treatment-planning and were treated by primary radio(chemo)therapy. 9725 transverse CT slices from the exploratory cohort were used to train a CNN with eight convolutional layers. For every patient (with one exception) we used 23 CT slices cranial and caudal of the slice with the largest tumour area, resulting in 47 slices per patient. Discriminative performance was evaluated using 4465 slices of the validation data set. The hazard of loco-regional recurrence was estimated by the CNN maximising the likelihood of the Cox proportional hazards model, which allows for incorporation of nonlinear relationships between the imaging features and the hazard prediction. The final hazard for every patient was obtained by averaging the results of the individual slices. The prognostic value of the model was evaluated by the concordance index (C-Index). Patients were stratified into groups of low and high risk of recurrence using the median hazard in the exploratory cohort.
Results: The validation of our CNN model revealed a C-Index of 0.68 (95% confidence interval: 0.57-0.79) for the prognosis of LRC. The estimated hazards were used to stratify patients into two risk groups. LRC significantly differed between these groups, both in the exploratory and the validation cohort (log-rank p<0.0001 and p=0.0005, respectively). Compared to previously published results with an average validation C-Index of 0.62 based on conventional radiomics [1], prognostic performance was slightly improved.
Conclusions: We showed that CNNs are capable of automatically stratifying patients with locally advanced HNSCC into high and low-risk groups for loco-regional tumour recurrence. The obtained results suggest that deep-learning based approaches can become useful for non-invasively evaluating individual recurrence risks encouraging future research in this area.
[1] Leger et al. Sci Rep 7: 13206 (2017).

Keywords: Deep-learning; HNSCC; loco-regional control; Radiomics

  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Mailand, Italien

Permalink: https://www.hzdr.de/publications/Publ-28076
Publ.-Id: 28076


Highly compliant planar Hall effect sensor with sub 200 nT sensitivity

Granell, P.; Wang, G.; Canon Bermudez, G. S.; Kosub, T.; Golmar, F.; Steren, L.; Fassbender, J.; Makarov, D.

Being a facet of flexible electronics, mechanically reshapeable magnetic field sensorics enable novel device ideas for soft robotics, interactive devices for virtual- and augmented reality and point of care diagnostics. These applications demand mechanically compliant yet robust sensor devices revealing high sensitivity to small magnetic fields. To push the detection limit of highly compliant and linear magnetic field sensors to be in the sub-µT range, we explore a new fundamental concept for magnetic field sensing, namely the planar Hall effect in magnetic thin films. With their remarkable bendability down to 1 mm, these compliant planar Hall effect sensors allow for an efficient detection of magnetic fields as small as 20 nT. We demonstrate the application potential of these devices as a direction (angle) as well as proximity (distance) sensors of tiny magnetic fields emanating from magnetically functionalized objects. With their intrinsic linearity and simplicity of fabrication, these compliant planar Hall effect sensors have the potential to become a standard solution for low field applications of shapeable magnetoelectronics in point of care applications and on-skin interactive electronics.

Keywords: Flexible electronics; shapeable magnetoelectronics; planar Hall effect

Permalink: https://www.hzdr.de/publications/Publ-28075
Publ.-Id: 28075


Electronic-skin compasses for geomagnetic field driven artificial magnetoception and interactive electronics

Cañón Bermúdez, G. S.; Fuchs, H.; Bischoff, L.; Fassbender, J.; Makarov, D.

Magnetoception is the ability to detect and respond to magnetic fields that allows certain organisms to orientate themselves with respect to the Earth’s magnetic field for navigation purposes. The development of an artificial magnetoception, which is based solely on an interaction with geomagnetic fields and can be used by humans, has, however, proved challenging. Here we report a compliant and mechanically robust electronic-skin compass system that allows a person to orient with respect to Earth’s magnetic field. The compass is fabricated on 6-μm-thin polymeric foils and accommodates magnetic field sensors based on the anisotropic magnetoresistance effect. The response of these compliant sensors is tailored to be linear and possess maximum sensitivity around the earth’s magnetic field by using geometric conditioning. Our approach can also be a used to create interactive devices for virtual and augmented reality applications, and we illustrate the potential of this by using our electronic-skin compass in the touchless-control of virtual units in a game engine.

Keywords: Flexible electronics; magnetic sensors; geomagnetic field; magnetoception; virtual reality

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Permalink: https://www.hzdr.de/publications/Publ-28074
Publ.-Id: 28074


Improving landslide susceptibility mapping using morphometric features in the Mawat area, Kurdistan Region, NE Iraq: Comparison of different statistical models

Othman, A. A.; Gloaguen, R.; Andreani, L.; Rahnama, M.

Susceptibility mapping provides information about vulnerable locations and thus helps to potentially decrease infrastructure damage due to mass wasting. During the past decades, expansion of settlements into areas prone to landslides in Iraq has highlighted the importance of accurate landslide susceptibility studies. The main goal of this research is to implement selected morphometric parameters to improve prediction of landslide susceptibility in the Zagros Mountain region. We used the Mawat area, in the Kurdistan Region (NE Iraq) to test the added value of morphometric indicators. Sixteen morphometric factors, mainly derived from a Digital Elevation Model (DEM), extracted using the stereo-ability of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite, as well as geological and environmental predictive factors, were appraised. We evaluated and compared Frequency Ratio (FR), Weight of Evidence (WOE), Logistic Regression (LR) and Probit Regression (PR) approaches in combination with morphometric indices to determine the Landslide Susceptibility (LS). The areas under the curve (AUC) of the Prediction Rate Curve (PRC), Relative landslide density Index (R index), and True Positive Percentage (TPP) for the four models show that all models perform similarly, and the focus should be on careful selection of the predictive factors, which is far more important than the methods used. Results indicate that lithology and slope aspects are the more dominant factors that lead to detect possible occurrence of landslides. Furthermore, this work demonstrates that the hypsometric integral performs better than the commonly used slope curvature as a predictor and thus increases the prediction accuracy of the susceptibility map. We argue that the use of adequate morphometric parameters can increase the efficiency of the LS mapping in other regions of the world.

Keywords: Frequency ratio; Weight of evidence; Logistic regression; Probit regression; Landslide susceptibility (LS); Iraq

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Permalink: https://www.hzdr.de/publications/Publ-28073
Publ.-Id: 28073


Beyond a phenomenological description of magnetostriction

Reid, A. H.; Shen, X.; Maldonado, P.; Chase, T.; Jal, E.; Granitzka, P. W.; Carva, K.; Li, R. K.; Li, J.; Wu, L.; Vecchione, T.; Liu, T.; Chen, Z.; Higley, D. J.; Hartmann, N.; Coffee, R.; Wu, J.; Dakovski, G. L.; Schlotter, W. F.; Ohldag, H.; Takahashi, Y. K.; Mehta, V.; Hellwig, O.; Fry, A.; Zhu, Y.; Cao, J.; Fullerton, E. E.; Stöhr, J.; Oppeneer, P. M.; Wang, X. J.; Dürr, H. A.

Magnetostriction, the strain induced by a change in magnetization, is a universal effect in magnetic materials. Owing to the difficulty in unraveling its microscopic origin, it has been largely treated phenomenologically. Here, we show how the source of magnetostriction—the underlying magnetoelastic stress—can be separated in the time domain, opening the door for an atomistic understanding. X-ray and electron diffraction are used to separate the sub-picosecond spin and lattice responses of FePt nanoparticles. Following excitation with a 50-fs laser pulse, time-resolved X-ray diffraction demonstrates that magnetic order is lost within the nanoparticles with a time constant of 146 fs. Ultrafast electron diffraction reveals that this demagnetization is followed by an anisotropic, three-dimensional lattice motion. Analysis of the size, speed, and symmetry of the lattice motion, together with ab initio calculations accounting for the stresses due to electrons and phonons, allow us to reveal the magnetoelastic stress generated by demagnetization.

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Permalink: https://www.hzdr.de/publications/Publ-28072
Publ.-Id: 28072


Measuring the thermal properties of anisotropic materials using beam-offset frequency domain thermoreflectance

Rahman, M.; Shahzadeh, M.; Braeuninger-Weimer, P.; Hofmann, S.; Hellwig, O.; Pisana, S.

Thermoreflectance techniques have become popular to measure the thermal properties of thin films such as thermal conductivity and thermal boundary conductance (TBC). Varying the focused spot sizes of the beams increases the sensitivity to in-plane heat transport, enabling the characterization of thermally anisotropic materials. However, this requires realignment of the optics after each spot size adjustment. Offsetting the probe beam with respect to the pump beam and modulating over a wide range of frequencies (5 kHz to 50 MHz) yield better sensitivity to the thermophysical properties of anisotropic materials without varying the spot sizes. We demonstrate how beam-offset frequency domain thermoreflectance can be used to measure the in- and out-of-plane thermal conductivity as well as the TBC simultaneously from a single data set by working at reduced spot sizes. Lowering the laser spot size allows us to detect signals over a wide range of frequencies and use larger beam offsets, thanks to the increase in the thermoreflectance signal. We measure the anisotropic thermal properties of a range of materials, including single layer Graphene on SiO2, which is of interest for novel electronic devices.

Keywords: Graphene; Thermal conductivity; Optical metrology; Metal oxides; Frequency domain thermoreflectance

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Permalink: https://www.hzdr.de/publications/Publ-28071
Publ.-Id: 28071


Chemical-vapor deposited ultra-fast diamond detectors for temporal measurements of ion bunches

Jahn, D.; Träger, M.; Kis, M.; Brabetz, C.; Schumacher, D.; Blaević, A.; Ciobanu, M.; Pomorski, M.; Bonnes, U.; Busold, S.; Kroll, F.; Brack, F.-E.; Schramm, U.; Roth, M.

This article reports on the development of thin diamond detectors and their characterization for their application in temporal profile measurements of subnanosecond ion bunches. Two types of diamonds were used: a 20 μm thin polycrystalline chemical vapor deposited (CVD) diamond and a membrane with a thickness of (5 ± 1) μm etched out of a single crystal (sc) CVD diamond. The combination of a small detector electrode and an impedance matched signal outlet leads to excellent time response properties with a signal pulse resolution (FWHM) of τ = (113 ± 11) ps. Such a fast diamond detector is a perfect device for the time of flight measurements of MeV ions with bunch durations in the subnanosecond regime. The scCVD diamond membrane detector was successfully implemented within the framework of the laser ion generation handling and transport project, in which ion beams are accelerated via a laser-driven source and shaped with conventional accelerator technology. The detector was used to measure subnanosecond proton bunches with an intensity of 10^8 protons per bunch

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Permalink: https://www.hzdr.de/publications/Publ-28070
Publ.-Id: 28070


A multicaloric cooling cycle that exploits thermal hysteresis

Gottschall, T.; Gràcia-Condal, A.; Fries, M.; Taubel, A.; Pfeuffer, L.; Manosa, L.; Planes, A.; Skokov, K. P.; Gutfleisch, O.

The giant magnetocaloric effect, in which large thermal changes are induced in a material on the application of a magnetic field, can be used for refrigeration applications, such as the cooling of systems from a small to a relatively large scale. However, commercial uptake is limited. We propose an approach to magnetic cooling that rejects the conventional idea that the hysteresis inherent in magnetostructural phase-change materials must be minimized to maximize the reversible magnetocaloric effect. Instead, we introduce a second stimulus, uniaxial stress, so that we can exploit the hysteresis. This allows us to lock-in the ferromagnetic phase as the magnetizing field is removed, which drastically removes the volume of the magnetic field source and so reduces the amount of expensive Nd–Fe–B permanent magnets needed for a magnetic refrigerator. In addition, the mass ratio between the magnetocaloric material and the permanent magnet can be increased, which allows scaling of the cooling power of a device simply by increasing the refrigerant body. The technical feasibility of this hysteresis-positive approach is demonstrated using Ni–Mn–In Heusler alloys. Our study could lead to an enhanced usage of the giant magnetocaloric effect in commercial applications.

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Permalink: https://www.hzdr.de/publications/Publ-28069
Publ.-Id: 28069


High-frequency measurements of thermophysical properties of thin films using a modified broad-band frequency domain thermoreflectance approach

Shahzadeh, M.; Rahman, M.; Hellwig, O.; Pisana, S.

In this work, we present the implementation of a new method to perform high-frequency thermoreflectance measurements on thin films. The so-called differential broad-band frequency domain thermoreflectance method follows broad-band frequency domain thermoreflectance developed previously [Regner et al., Rev. Sci. Instrum. 84 (6), 064901 (2013)], without the use of expensive electro-optic modulators. Two techniques are introduced to recover the thermal phase of interestand to separate it from the unwanted instrumental contributions to the recorded phase. Measuring a differential thermal phase by either varying the spot size or offsetting the pump and probe beams, the thermophysical properties of materials can be extracted. This approach enables the study of nanoscale heat transport where non-equilibrium phenomena are dominating.

Keywords: Thin films; Materials properties; Thermal conductivity; Optical metrology; Frequency domain thermoreflectance

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Permalink: https://www.hzdr.de/publications/Publ-28068
Publ.-Id: 28068


Single-crystal neutron diffraction study of hexagonal multiferroic YbMnO3 under a magnetic field

Chattopadhyay, S.; Simonet, V.; Skumryev, V.; Mukhin, A. A.; Ivanov, V. Y.; Aroyo, M. I.; Dimitrov, D. Z.; Gospodinov, M.; Ressouche, E.

We report a single-crystal neutron diffraction study of the magnetic structure of the multiferroic compound YbMnO3, a member of the hexagonal manganite family, in zero field and under a magnetic field applied along the c axis. We propose a scenario for the zero-field magnetic ordering and for the field-induced magnetic reorientation of the Mn atom and of the two Yb atoms on distinct crystallographic sites, compatible with the macroscopic measurements, as well as with previous powder neutron diffraction experiments and results from other techniques (optical second-harmonic generation and Mössbauer spectroscopy). Our study should contribute to settling some debated issues regarding the magnetic properties of thismaterial as part of a broader investigation of the entire hexagonal RMnO3 (R = Dy, Ho, Er, Tm, Yb, Lu, Y) family.

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Permalink: https://www.hzdr.de/publications/Publ-28067
Publ.-Id: 28067


Ultrafast laser generated strain in granular and continuous FePt thin films

von Reppert, A.; Willig, L.; Pudell, J.-E.; Rössle, M.; Leitenberger, W.; Herzog, M.; Ganss, F.; Hellwig, O.; Bargheer, M.

We employ ultrafast X-ray diffraction to compare the lattice dynamics of laser-excited continuous and granular FePt films on MgO (100) substrates. Contrary to recent results on free-standing granular films, we observe in both cases a pronounced and long-lasting out-of-plane expansion. We attribute this discrepancy to the in-plane expansion, which is suppressed by symmetry in continuous films. Granular films on substrates are less constrained and already show a reduced out-of-plane contraction. Via the Poisson effect, out-of-plane contractions drive in-plane expansion and vice versa. Consistently, the granular film exhibits a short-lived out-of-plane contraction driven by ultrafast demagnetization which is followed by a reduced and delayed expansion. From the acoustic reflections of the observed strain waves at the film-substrate interface, we extract a 13% reduction of the elastic constants in thin 10 nm FePt films compared to bulk-like samples.

Keywords: Epitaxy; Poisson's ratio; Magnetic devices; Magnetic materials; Stress strain relations; Thin films; Ultrafast X-ray diffraction; Lattice dynamics; Phonons; Elastic modulus

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Permalink: https://www.hzdr.de/publications/Publ-28066
Publ.-Id: 28066


Detectability and structural stability of a liquid fiducial marker in fresh ex vivo pancreas cancer resection specimen on CT and 3T MRI

Schneider, S.; Aust, D.; Brückner, S.; Welsch, T.; Hampe, J.; Troost, E.; Hoffmann, A.

Objectives
The aim of this study was to test the visibility of a new liquid fiducial marker injected in ex vivo pancreas tissue on magnetic resonance imaging (MRI) and computed tomography (CT). Furthermore, its injection performance using different needle sizes was investigated as well as its structural stability after fixation in formaldehyde.
Material and Methods
Liquid fiducial markers with a volume of 20-100 µL were injected into the freshly resected pancreas of three patients (two males age 69 and 72, one female age 68) with suspected adenocarcinoma of the pancreatic head. Injection was performed under X-ray guidance using a high precision unit dose injector with different needle sizes (18G, 22G, 25G). While cooled on ice, the specimens were scanned on MRI and CT with routine clinical sequences. Signal threshold based segmentation was performed manually on CT. The marker volume visible on CT was compared to the actually injected volume as a measure of potential marker backflow. After rigid registration of the MR images to the CT data set, marker detectability was assessed by searching for the corresponding hypointense structure in the respective segmentation.
Results
Markers with a volume of ≥ 20 µL were easily detected as hyperintense structures on X-ray and CT. In clinically used T1- and T2-weighted 3T MRI sequences, all marker sizes ranging from 20µL – 100µL were visible as hypointensity. Since most markers were non-spherical however, MRI visibility was relatively poor and their differentiation from hypointensities caused by air cavities or surgical clips was challenging and only feasible with a reference CT. Marker backflow was observed when injected with an 18G needle, which was prevented by injection using a smaller 22G and 25G needle. The marker was stable after 24h fixation in formaldehyde where only small volume degradations were observed (6.6±13.0%) and with the exception of one instance no wash out occurred.
Conclusion
The liquid fiducial marker with injected volumes of 20µL – 100µL, injected in an ex vivo pancreatic cancer resection specimen, was visible as hyperintensity on kV X-ray, CT and hypointensity on MRI and stable over a period of 24 hours in formaldehyde. Since most injected markers were non-spherical, a marker size of ≥50µL is recommended for the clinically used MRI sequences. Most likely, in vivo marker injection will result in more spherical forms due to persisting metabolism, and this in turn will enhance MRI visibility in an hyper intense structure.

Keywords: Liquid fiducial marker; pancreatic adenocarcinoma; MRI visibility; ex vivo

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Permalink: https://www.hzdr.de/publications/Publ-28065
Publ.-Id: 28065


Comparison of respiratory motion management by means of three abdominal corsets for particle therapy

Schneider, S.; Dolde, K.; Alimusaj, M.; Fluegel, B.; Hoffmann, A.; Pfaffenberger, A.

Purpose/Objective:
Particle therapy (PT) has the potential of improving the outcome in radiotherapy (RT) due to its inverse dose profile and the superior sparing of healthy tissues surrounding the target volume compared to photon therapy. However, PT is strongly susceptible to anatomical changes, and especially for the treatment of abdominal tumours, strategies for motion management are required.
The purpose of this study was to investigate and compare the potential usability of three different abdominal corsets in PT by measuring their water equivalent ratio (WER) in proton therapy as well as by analysing their effect on the respiration-induced motion of the pancreas.
Material/Methods:
The corsets differed in terms of geometry (thickness of 2.5mm – 24mm), material (polyethylene (PE) vs. polyurethane (PU)) as well as regarding the method of construction (patient individual vs. patient independent). A healthy volunteer was scanned on a 1.5T MR scanner (Magnetom Aera, Siemens Healthineers) on two consecutive days while he was wearing each of the three respective corsets and without him wearing a corset for reference. A gradient echo sequences with radial golden angel acquisition was used and reconstructed to a 4D data set with 20 phases. The pancreas was delineated in max exhale and max inhale phase using the open-source software MITK (Fig. 1). The centre of mass was calculated as a surrogate for the respiratory motion of the pancreas in each of the four scenarios for both days.
After acquiring CT scans of the three corsets for assessment of material homogeneity and regularity of material thickness, WER measurements were performed at two different proton energies (150MeV, 200MeV) using a multi-layer ionization chamber (Giraffe, IBA Dosimetry) to measure the shift of the single beam Bragg Peak after penetrating the corset sample.
Results:
All three abdominal corsets led to reduced pancreatic motion, and the effect was largest in inferior-superior direction (Table 1). The CT revealed a perfectly homogeneous material for the two PE corsets with a constant thickness of 2.5±0.1mm and 4.9±0.1mm. In case of the PU corset the material was inhomogeneous with air inclusions throughout the whole corset. Furthermore, its thickness varied between 8.0-24.2mm in the relevant region. The WER of the two polyethylene corsets was determined to be 0.990 and 0.956, while the WER of the polyurethane corset was 0.298.
Conclusion:
While all three corsets reduce the respiratory motion to a similar amount, the material analysis revealed that the polyurethane corset is not suitable for PT due to its inhomogeneous structure and irregular thickness. On the other hand, the two PE corsets both show very stable material conditions which could, in terms of physics, easily be included in treatment planning and a fractionated treatment scheme. However, due to their different construction approach, the PE corsets have respective benefits in accuracy of fit, flexibility, cost and the time required for preparation.

  • Lecture (Conference)
    ESTRO 38, 26.-30.04.2019, Mailand, Italien

Permalink: https://www.hzdr.de/publications/Publ-28064
Publ.-Id: 28064


Ultrafast Self-Induced X-Ray Transparency and Loss of Magnetic Diffraction

Chen, Z.; Higley, D. J.; Beye, M.; Hantschmann, M.; Mehta, V.; Hellwig, O.; Mitra, A.; Bonetti, S.; Bucher, M.; Carron, S.; Chase, T.; Jal, E.; Kukreja, R.; Liu, T.; Reid, A. H.; Dakovski, G. L.; Föhlisch, A.; Schlotter, W. F.; Dürr, H. A.; Stöhr, J.

Using ultrafast ≃2.5  fs and ≃25  fs self-amplified spontaneous emission pulses of increasing intensity and a novel experimental scheme, we report the concurrent increase of stimulated emission in the forward direction and loss of out-of-beam diffraction contrast for a Co/Pd multilayer sample. The experimental results are quantitatively accounted for by a statistical description of the pulses in conjunction with the optical Bloch equations. The dependence of the stimulated sample response on the incident intensity, coherence time, and energy jitter of the employed pulses reveals the importance of increased control of x-ray free electron laser radiation.

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Permalink: https://www.hzdr.de/publications/Publ-28063
Publ.-Id: 28063


Adaptive Micromixer Based on the Solutocapillary Marangoni Effect in a Continuous-Flow Microreactor

Bratsun, D.; Kostarev, K.; Mizev, A.; Aland, S.; Mokbel, M.; Schwarzenberger, K.; Eckert, K.

Continuous-flow microreactors are an important development in chemical engineering technology, since the pharmaceutical production needs flexibility in reconfiguring the synthesis system rather than large volumes of product yield. Microreactors of this type have a special vessel, in which the convective vortices are organized to mix the reagents in order to increase the product output. We propose a new type of micromixer based on the intensive relaxation oscillations induced by a fundamental effect discovered recently. The mechanism of these oscillations was found to be a coupling of the solutal Marangoni effect, buoyancy and diffusion. The phenomenon can be observed in the vicinity of an air-liquid (or liquid-liquid) interface with inhomogeneous concentration of a surface-active solute. Important features of the oscillations are demonstrated experimentally and numerically. The periodicity of the oscillations is a result of the repeated regeneration of the Marangoni driving force.
This feature is used in our design of a micromixer with a single air bubble inside the reaction zone.
We show that the micromixer does not consume external energy and adapts to the medium state due to feedback. It switches on automatically each time when a concentration inhomogeneity in the reaction zone occurs, and stops to mix when the solution becomes sufficiently uniform.

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Permalink: https://www.hzdr.de/publications/Publ-28062
Publ.-Id: 28062


Information transmission by Marangoni-driven relaxation oscillations at droplets

Mokbel, M.; Schwarzenberger, K.; Aland, S.; Eckert, K.

Marangoni-driven relaxation oscillations can be observed in many systems where concentration gradients of surface-active substances exist. In the present paper, we describe the experimentally observed coupling between relaxation oscillations at neighboring droplets in a concentration gradient. By a numerical parameter study, we evaluate the oscillation characteristics depending on relevant material parameters and the pairwise droplet distance. Based on these findings, we demonstrate that hydrodynamic interaction in multidroplet configurations can lead to a synchronization of the oscillations over the whole ensemble. This effect has the potential to be used as a novel approach for information transmission in microfluidic applications.

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Permalink: https://www.hzdr.de/publications/Publ-28061
Publ.-Id: 28061


FMISO-PET-based lymph node hypoxia adds to the prognostic value of tumor only hypoxia in HNSCC patients

Bandurska-Luque, A.; Löck, S.; Haase, R.; Richter, C.; Zöphel, K.; Abolmaali, N.; Seidlitz, A.; Appold, S.; Krause, M.; Steinbach, J.; Kotzerke, J.; Zips, D.; Baumann, M.; Troost, E.

Purpose: This secondary analysis of the prospective study on repeat [18F]fluoromisonidazole (FMISO)-PET in patients with locally advanced head and neck squamous cell carcinomas (HNSCC) assessed the prognostic value of synchronous hypoxia in primary tumor (Tu) and lymph node metastases (LN), and evaluated whether the combined reading was of higher prognostic value than that of primary tumor hypoxia only. Methods: This analysis included forty-five LN-positive HNSCC patients. FMISO-PET/CTs were performed at baseline, weeks 1, 2 and 5 of radiochemotherapy. Based on a binary scale, Tu and LN were categorized as hypoxic or normoxic, and two prognostic parameters were defined: Tu-hypoxia (independent of the LN oxygenation status) and synchronous Tu-and-LN-hypoxia. In fifteen patients with large LN (N = 21), additional quantitative analyses of FMISO-PET/CTs were performed. Imaging parameters at different time-points were correlated to the endpoints, i.e., locoregional control (LRC), local control (LC), regional control (RC) and time to progression (TTP). Survival curves were estimated using the cumulative incidence function. Univariable and multivariable Cox regression was used to evaluate the prognostic impact of hypoxia on the endpoints. Results: Synchronous Tu-and-LN-hypoxia was a strong adverse prognostic factor for LC, LRC and TTP at any of the four time-points (p ≤ 0.004), whereas Tu-hypoxia only was significantly associated with poor LC and LRC in weeks 2 and 5 (p ≤ 0.047), and with TTP in week 1 (p = 0.046). The multivariable analysis confirmed the prognostic value of synchronous Tu-and-LN-hypoxia regarding LRC (HR = 14.8, p = 0.017). The quantitative FMISO-PET/CT parameters correlated with qualitative hypoxia scale and RC (p < 0.001, p ≤ 0.033 at week 2, respectively). Conclusions: This secondary analysis suggests that combined reading of primary tumor and LN hypoxia adds to the prognostic information of FMSIO-PET in comparison to primary tumor assessment alone in particular prior and early during radiochemotherapy. Confirmation in ongoing trials is needed before using this marker for personalized radiation oncology. © 2018 Elsevier B.V.

Keywords: FMISO-PETHypoxia; Locally advanced HNSCC; Lymph node; Prognostic biomarker

Permalink: https://www.hzdr.de/publications/Publ-28060
Publ.-Id: 28060


Irradiation effects in monazite-(Ce) and zircon: Raman and photoluminescence study of Au-irradiated FIB foils

Nasdala, L.; Akhmadaliev, S.; Artac, A.; Chanmuang, N. C.; Habler, G.; Lenz, C.

Lamellae of 1.5 µm thickness, prepared from well-crystallised monazite-(Ce) and zircon samples using the focused-ion-beam technique, were subjected to triple irradiation with 1 MeV Au+ ions (15.6% of the respective total fluence), 4 MeV Au2+ ions (21.9%) and 10 MeV Au3+ ions (62.5%). Total irradiation fluences were varied in the range 4.5E12 -1.2E14 ions/cm2. The highest fluence resulted in amorphisation of both minerals; all other irradiations (i.e. up to 4.5E13 ions/cm2) resulted in moderate to severe damage. Lamellae were subjected to Raman and laser-induced photoluminescence analysis, in order to provide a means of quantifying irradiation effects using these two micro-spectroscopy techniques. Based on extensive Monte Carlo calculations and subsequent defect-density estimates, irradiation-induced spectroscopic changes are compared with those of naturally self-irradiated samples. The finding that ion irradiation of monazite-(Ce) may cause severe damage or even amorphisation, is in apparent contrast to the general observation that naturally self-irradiated monazite-(Ce) does not become metamict (i.e. irradiation-amorphised), in spite of high self-irradiation doses. This is predominantly assigned to the continuous low-temperature damage annealing undergone by this mineral; other possible causes are discussed. According to cautious estimates, monazite-(Ce) samples of Mesoproterozoic to Cretaceous ages have stored only about 1% of the total damage experienced. In contrast, damage in ion-irradiated and naturally self-irradiated zircon is on the same order; reasons for the observed slight differences are discussed. We may assess that in zircon, alpha decays create significantly less than 1000 Frenkel-type defect pairs per event, which is much lower than previous estimates. Amorphisation occurs at defect densities of about 0.10 dpa (displacements per lattice atom).

Keywords: Radiation damage; Heavy-ion irradiation; Focused ion beam; Raman spectroscopy; Photoluminescence

Permalink: https://www.hzdr.de/publications/Publ-28059
Publ.-Id: 28059


Site-controlled formation of single Si nanocrystals in a buried SiO₂ matrix using ion beam mixing

Xu, X.; Prüfer, T.; Wolf, D.; Engelmann, H.-J.; Bischoff, L.; Hübner, R.; Heinig, K.-H.; Möller, W.; Facsko, S.; von Borany, J.; Hlawacek, G.

For future nanoelectronic devices—such as room-temperature single electron transistors—the site controlled formation of single Si Nanocrystal (NC) is a crucial prerequisite. Here, we report an approach to fabricate single Si NCs via medium-energy Si+ or Ne+ ion beam mixing of Si into a buried SiO₂ layer followed by thermally activated phase separation. Binary Collision Approximation and kinetic Monto Carlo methods are conducted to gain atomistic insight into the influence of relevant experimental parameters on the Si NC formation process. Energy Filtered Transmission Electron Microscopy is performed to obtain quantitative values on the Si NC size and distribution in dependence of the layer stack geometry, ion fluence and thermal budget. Employing a focused Ne+ beam from a Helium Ion Microscope, we demonstrate site-controlled self-assembly of single Si NCs. Line irradiation with a fluence of 3000Ne+/nm² and a line width of 4 nm leads to the formation of a chain of Si NCs, and a single NC with 2.2 nm diameter is subsequently isolated and visualized in a few nm thin lamella prepared by Focused Ion Beam (FIB). The Si NC is centered between the SiO₂ layers and the perpendicular to the incident Ne+ beam.

Keywords: Helium Ion Microscopy; ion beam mixing; single electron transistor; phase separation; Monte Carlo simulations

Permalink: https://www.hzdr.de/publications/Publ-28058
Publ.-Id: 28058


Smart Tomographic Sensors for Advanced Industrial Process Control - TOMOCON

Hampel, U.; Wondrak, T.; Bieberle, M.; Lecrivain, G.; Schubert, M.; Eckert, K.; Reinecke, S.

With the recent developments in high-power massive parallel computing, process tomography has gained the required real-time capability of being employed as sensors in advanced control systems. Process tomography techniques are of great value as they provide distributed process parameters for opaque processes.
The European Training Network TOMOCON joins 27 international academic and industry partners working together in the emerging field of industrial process control using smart tomographic sensors to lay the scientific and technological fundamentals of integrating imaging sensors into industrial processes and to demonstrate its functional feasibility on lab and pilot-scale applications. Particular focus is on the training of the doctoral researchers in the fields of process tomography hardware, control systems design, industrial process design, multi-physics modelling, and human-computer interaction.
The teams are engaged in multi-disciplinary research on various tomographic imaging modalities, tomographic image processing as well as advanced multi-physics modelling of processes, sensors and actuators. Proof-of-principle demonstrations of tomography-based processes focus on important industrial processes, such as inline fluid separation, microwave drying of porous materials, continuous steel casting and ultrasound-controlled crystallization.

  • Poster
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-15.09.2018, Aachen, Deutschland
  • Open Access Logo Abstract in refereed journal
    Chemie Ingenieur Technik 90(2018)9, 1238-1239
    Online First (2018) DOI: 10.1002/cite.201855235

Permalink: https://www.hzdr.de/publications/Publ-28057
Publ.-Id: 28057


Investigation of bioreactors by smart sensor particles

Reinecke, S. F.; Hampel, U.

Advanced monitoring of the spatio-temporal distribution of process parameters in the large-scale vessels of chemical or bioreactors, such as industrial fermenters, biogas digesters and activated sludge basins, offers a high potential for the investigation and further optimization of plants and embedded processes. However, in most industrial scale applications the acquisition of these parameters and their spatial distributions in the large-scale vessels is hampered by the limited access to the process itself, because sensor mounting or cable connections are not feasible or desired. Therefore, state of the art instrumentation of such reactors is commonly limited to few spatial positions where it is doubtfully assumed that the measured parameters are representative for the whole reaction mixture.
Instrumented sensor particles have been developed by Thiele et al. [1] for investigation of hydrodynamic and biochemical processes chemical reactors and bioreactors. The sensor particles allow autonomous long-term measurement of spatially distributed process parameters in the chemically and mechanically harsh environments of agitated industrial vessels. Each sensor particle comprises of an on-board measurement electronics that logs the signals of the embedded sensors. A buoyancy control unit enables automated taring to achieve neutral buoyancy and thus flow-following capabilities of the sensor particles [2]. Moreover, controlled floating of the sensor particles is possible to expose them for recovery from the fluid surface. The paper presents results of the sensor system validation and tests in an air-water column reactor, a pilot biogas digester and a waste water treatment plant. Moreover, ongoing developments of smart sensor particles features, i.e. magnetic position detection and inertial position tracking, are presented.

  • Lecture (Conference)
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-15.09.2018, Aachen, Deutschland
  • Open Access Logo Abstract in refereed journal
    Chemie Ingenieur Technik 90(2018)9, 1268-1268
    Online First (2018) DOI: 10.1002/cite.201855298

Permalink: https://www.hzdr.de/publications/Publ-28056
Publ.-Id: 28056


Inertial position tracking of flow following sensor particles

Reinecke, S. F.; Hampel, U.

In this paper, a concept for inertial position tracking of flow following sensor particles based on data fusion of inertial sensors is presented. The employed data fusion technique is quaternion based and uses an extended Kalman filter algo-rithm. A generalized sensor system kinematics has been developed to test the filter algorithm where two data conditions have been considered. Eventually, first simulation results are compared which shows the performance of the filter re-garding sensor drift and noise.

  • Contribution to proceedings
    Sensoren und Messsysteme 2018 ∙ 26. – 27.06.2018 in Nürnberg, 26.-27.06.2018, Nürnberg, Deutschland
    Beiträge der 19. ITG/GMA-Fachtagung 26. – 27. Juni 2018 in Nürnberg, 978-3-8007-4683-5
  • Lecture (Conference)
    Sensoren und Messsysteme 19. ITG/GMA-Fachtagung 26. – 27. Juni 2018 in Nürnberg, 26.-27.06.2018, Nürnberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28055
Publ.-Id: 28055


Magnetic Communication Using High-Sensitivity Magnetic Field Detectors

Hott, M.; Hoeher, P. A.; Reinecke, S. F.

In this article, an innovative approach for magnetic data communication is presented. For
this purpose, the receiver coil of a conventional magneto-inductive communication system is replaced by a high-sensitive wideband magnetic field sensor. The results show decisive advantages offered by sensitive magnetic field sensors, including a higher communication range for small receiver units. This approach supports numerous mobile applications where receiver size is limited, possibly in conjunction with multiple detectors. Numerical results are supported by a prototype implementation employing an anisotropic magnetoresistive sensor.

Keywords: wireless communication; magnetic induction communication; mobile sensing systems; magnetic sensors; RF-challenging environments

Permalink: https://www.hzdr.de/publications/Publ-28054
Publ.-Id: 28054


Destabilization of DNA through interstrand crosslinking by UO22+

Rossberg, A.; Abe, T.; Okuwaki, K.; Barkleit, A.; Fukuzawa, K.; Nakano, T.; Mochizuki, Y.; Tsushima, S.

UO22+ forms an interstrand crosslink between two different strands from a single DNA, which hardly affects the hydrogen bonds between nucleobase pairs whereas it destabilizes the π–π stacking between the two nucleobases in the vicinity of UO22+– bound phosphate. Thereby, fragility of DNA backbone increases upon UO22+ binding.

Keywords: Fragment molecular orbital method; DNA; chemotoxicity; uranyl(VI); interstrand crosslink; EXAFS

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Permalink: https://www.hzdr.de/publications/Publ-28053
Publ.-Id: 28053


HEFIB2018 – Helium and emerging focused ion beams

Hlawacek, G.

Die zweite HEFIB – Helium and emerging focused ion beams Konferenz fand vom 11. bis zum 13. Juni in Dresden statt. Das ers­te Treffen unter diesem Namen fand 2016 in Luxemburg statt. Zwei Jahre später fand planmäßig die zweite HEFIB statt. Ein Teil des bewährten Organisationsteams aus Lu­xemburg und Deutschland wurde mit neu­en Mitgliedern aus Japan und den USA vervollständigt.

Keywords: Konferenzreport

  • Open Access Logo Elektronenmikroskopie 44(2018), 21-22

Permalink: https://www.hzdr.de/publications/Publ-28052
Publ.-Id: 28052


Visible Light Actuated Efficient Exclusion Between Plasmonic Ag/AgCl Micromotors and Passive Beads

Wang, X.; Baraban, L.; R. Misko, V.; Nori, F.; Huang, T.; Cuniberti, G.; Fassbender, J.; Makarov, D.

Insight is provided into the collective behavior of visible‐light photochemically driven plasmonic Ag/AgCl Janus particles surrounded by passive polystyrene (PS) beads. The active diffusion of single Janus particles and their clusters (small: consisting of two or three Janus particles and large: consisting of more than ten Janus particles), and their interaction with passive PS beads, are analyzed experimentally and in simulations. The diffusivity of active Janus particles, and thus the exclusive effect to passive PS beads, can be regulated by the number of single Janus particles in the cluster. On the simulation side, the Langevin equations of motion for self‐propelled Janus particles and diffusing passive PS beads are numerically solved using Molecular‐Dynamics simulations. The complex interactions of both subsystems, including elastic core‐to‐core interactions, short‐range attraction, and effective repulsion due to light‐induced chemical reactions are considered. This complex mixed system not only provides insight to the interactive effect between active visible light‐driven self‐propelled micromotors and passive beads, but also offers promise for implications in light‐controlled propulsion transport and chemical sensing.

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Permalink: https://www.hzdr.de/publications/Publ-28051
Publ.-Id: 28051


High-Motility Visible Light-Driven Ag/AgCl Janus Micromotors

Wang, X.; Baraban, L.; Nguyen, A.; Ge, J.; R. Misko, V.; Tempere, J.; Nori, F.; Formanek, P.; Huang, T.; Cuniberti, G.; Fassbender, J.; Makarov, D.

Visible light‐driven nano/micromotors are promising candidates for biomedical and environmental applications. This study demonstrates blue light‐driven Ag/AgCl‐based spherical Janus micromotors, which couple plasmonic light absorption with the photochemical decomposition of AgCl. These micromotors reveal high motility in pure water, i.e., mean squared displacements (MSD) reaching 800 µm2 within 8 s, which is 100× higher compared to previous visible light‐driven Janus micromotors and 7× higher than reported ultraviolet (UV) light‐driven AgCl micromotors. In addition to providing design rules to realize efficient Janus micromotors, the complex dynamics revealed by individual and assemblies of Janus motors is investigated experimentally and in simulations. The effect of suppressed rotational diffusion is focused on, compared to UV light‐driven AgCl micromotors, as a reason for this remarkable increase of the MSD. Moreover, this study demonstrates the potential of using visible light‐driven plasmonic Ag/AgCl‐based Janus micromotors in human saliva, phosphate‐buffered saline solution, the most common isotonic buffer that mimics the environment of human body fluids, and Rhodamine B solution, which is a typical polluted dye for demonstrations of photocatalytic environmental remediation. This new knowledge is useful for designing visible light driven nano/micromotors based on the surface plasmon resonance effect and their applications in assays relevant for biomedical and ecological sciences.

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Permalink: https://www.hzdr.de/publications/Publ-28050
Publ.-Id: 28050


Control of domain structure and magnetization reversal in thick Co/Pt multilayers

Fallarino, L.; Oelschlägel, A.; Arregi, J. A.; Bashkatov, A.; Samad, F.; Böhm, B.; Chesnel, K.; Hellwig, O.

We present a study of the magnetic properties of [Co(3.0nm)/Pt(0.6nm)]N multilayers as a function of Co/Pt bilayer repetitions N. Magnetometry investigation reveals that samples with high N exhibit two characteristic magnetization reversal mechanisms, giving rise to two different morphologies of the remanent domain pattern. For applied magnetic field angles near the in-plane field orientation, the magnetization reversal proceeds via a spontaneous instability of the uniform magnetic state resulting in perpendicular stripe domains. Conversely, for field angles close to the out-of-plane orientation, the reversal occurs via domain nucleation and propagation leading to a maze-like domain pattern at remanence. Our measurements further enable the characterization of the N-dependent energy balance between the magnetic anisotropy and magnetostatic energy contributions, revealing a gradual disappearance of the domain nucleation process during magnetization reversal for N < 14. This leads to the exclusive occurrence of an instability reversal mechanism for all field orientations as well as aligned-like stripe domains at remanence. Furthermore, a detailed study of the influence of the magnetic history allows the determination of a range of material properties and magnetic field strengths, where a lattice of bubble domains with remarkably high density is stabilized. These modulations of the ferromagnetic order parameter are found to strongly depend on N, in terms of center-to-center bubble distance as well as of bubble diameter. Moreover, such Co/Pt multilayers could be utilized to engineer field reconfigurable bubble domain lattices, which can resemble magnonic crystals.

Keywords: Co/Pt thick multilayers; Magnetic bubble domains; magnonic crystals

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Permalink: https://www.hzdr.de/publications/Publ-28049
Publ.-Id: 28049


Crystal Structure of Regularly Th-Symmetric [U(NO3)6]2− Salts with Hydrogen Bond Polymers of Diamide Building Blocks

Takao, K.; Kazama, H.; Ikeda, Y.; Tsushima, S.

Hexanitratouranate(IV), [U(NO3)6]2−, has been crystallized with anhydrous H+ counter cations stabilized by formation of hydrogen bond polymers with selected diamide building blocks. Thanks to the significant moderation of electrostatic interactions between the anions and cations, the molecular structure of [U(NO3)6]2− in these compounds is regularly Th-symmetric. The f-f transitions stemming from 5f2 configuration of U4+ is strictly forbidden by the Laporte selection rule in such a centrosymmetric system , so that the obtained compounds are nearly colourless in contrast to other U(IV) species usually coloured in green.

Permalink: https://www.hzdr.de/publications/Publ-28048
Publ.-Id: 28048


Towards Utilising Photocrosslinking of Polydiacetylenes for the Preparation of “Stealth” Upconverting Nanoparticles

Nsubuga, A.; Zarschler, K.; Sgarzi, M.; Graham, B.; Stephan, H.; Joshi, T.

We demonstrate a novel strategy for preparing hydrophilic upconverting nanoparticles (UCNPs) by harnessing the photocrosslinking ability of diacetylenes. Replacement of the hydrophobic oleate coating on the UCNPs with 10,12-pentacosadiynoic acid, followed by overcoating with diacetylene phospholipid and subsequent photocrosslinking under 254 nm irradiation produces water-dispersible polydiacetylene-coated UCNPs. These UCNPs resist the formation of a biomolecular corona and show great colloidal stability. Furthermore, amine groups on the diacetylene phospholipid allow for functionalisation of the UCNPs with, for example, radiolabels or targeting moieties. These results demonstrate that this new surface coating method has great potential for use in the preparation of UCNPs with improved biocompatibility.

Keywords: Crosslinking; Diacetylene; Lanthanides; Nanomaterials; Upconversion

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Permalink: https://www.hzdr.de/publications/Publ-28047
Publ.-Id: 28047


From curvilinear magnetism to shapeable magnetoelectronics (plenary)

Makarov, D.

Extending two-dimensional structures into the three-dimensional (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. In the case of 3D curved magnetic thin films and nanowires the physics is driven by the interplay between exchange and magnetostatic interactions, which contain spatial derivatives in their energy functionals [1,2]. This makes both interactions sensitive to the appearance of bends and twists in the physical space. Theoretical works predict the curvature-induced effective anisotropy and effective Dzyaloshinskii-Moriya interaction resulting in a multitude of novel effects including magnetochiral effects (chirality symmetry breaking) and topologically induced magnetization patterning.
Those 3D magnetic architectures are already proven to be application relevant for life sciences, targeted delivery, realization of 3D spin-wave filters, and magneto-encephalography devices to name just a few. To this end, the initially fundamental topic of the magnetism in curved geometries strongly benefited from the input of the application-oriented community, which among others explores the shapeability aspect of the curved magnetic thin films. These activities resulted in the development of the family of shapeable magnetoelectronics [3], which already includes flexible, printable, stretchable and even mechanically imperceptible magnetic field sensorics [4,5].
The balance between the fundamental and applied inputs into the topic of magnetism in curved geometries is rather unique. This stimulates even further the development of new theoretical methods and novel fabrication/characterization techniques. The synergy will definitely enable us surpassing the exploratory research and will pave the way towards novel device concepts, where the geometry of a functional thin film will play a decisive role in determining the device performance.

References
[1] R. Streubel, D. Makarov et al., J. Phys. D: Appl. Phys. 49, 363001 (2016).
[2] D. Sander, D. Makarov et al., J. Phys. D: Appl. Phys. 50, 363001 (2017).
[3] D. Makarov et al., Appl. Phys. Rev. 3, 011101 (2016).
[4] G. S. Canon Bermudez, D. Makarov et al., Science Advances 4, eaao2623 (2018).
[5] M. Melzer, D. Makarov et al., Nat. Commun. 6, 6080 (2015).

Keywords: curvilinear magnetism; flexible electronics; magnetic field sensors

  • Invited lecture (Conferences)
    XIV International Conference on Applied Physics and Electronics, 24.-26.10.2018, Kyiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-28046
Publ.-Id: 28046


Intelligent materials and devices

Makarov, D.

In this invited talk I will Highlight activities of the Group FWIN-I "Intelligent materials and devices".

Keywords: anitiferromagnetic spintronics; flexible electronics; curvilinear magnetism

  • Invited lecture (Conferences)
    Advancing Science through International Cooperation: Forum of the Ukrainian Research Diaspora, 20.-22.10.2018, Kyiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-28045
Publ.-Id: 28045


Flexible electronics: from interactive on-skin devices to in vivo applications

Makarov, D.

In this invited talk I will Review our recent activities on flexible electronics including interactive magnetic Skins and highly compliant devices for in vivo applications.

Keywords: flexible electronics; magnetic field sensors

  • Invited lecture (Conferences)
    Seminar at the Kyiv Academic University, 19.10.2018, Kyiv, Ukraine

Permalink: https://www.hzdr.de/publications/Publ-28044
Publ.-Id: 28044


Injection locking of multiple auto-oscillation modes in a tapered nanowire spin Hall oscillator

Wagner, K.; Smith, A.; Hache, T.; Chen, J.-R.; Yang, L.; Montoya, E.; Schultheiss, K.; Lindner, J.; Fassbender, J.; Krivorotov, I.; Schultheiss, H.

Spin Hall oscillators (SHO) are promising candidates for the generation, detection and amplification of high frequency signals, that are tunable through a wide range of operating frequencies. They offer to be read out electrically, magnetically and optically in combination with a simple bilayer design. Here, we experimentally study the spatial dependence and spectral properties of auto-oscillations in SHO devices based on Pt(7 nm)/ Ni80Fe20(5nm) tapered nanowires. Using Brillouin light scattering microscopy, we observe two individual self- localized spin-wave bullets that oscillate at two distinct frequencies (5.2 GHz and 5.45 GHz) and are localized at different positions separated by about 750 nm within the SHO. This state of a tapered SHO has been predicted by a Ginzburg-Landau auto-oscillator model, but not yet been directly confirmed experimentally. We demonstrate that the observed bullets can be individually synchronized to external microwave signals, leading to a frequency entrainment, linewidth reduction and increase in oscillation amplitude for the bullet that is selected by the microwave frequency. At the same time, the amplitude of other parasitic modes decreases, which promotes the single-mode operation of the SHO. Finally, the synchronization of the spin-wave bullets is studied as a function of the microwave power. We believe that our findings promote the realization of extended spin Hall oscillators accomodating several distinct spin-wave bullets, that jointly cover an extended range of tunability.

Keywords: Magnonik; auto-oscillation; magnetic auto-oscillator; spin Hall oscillator; magnetization dynamic; Brillouin-Light-Scattering

Permalink: https://www.hzdr.de/publications/Publ-28043
Publ.-Id: 28043


Giant impact of self-photothermal on light-induced ultrafast insulator-to-metal transition in VO₂ nanofilms at terahertz frequency

Zhai, Z.-H.; Chen, S.-C.; Du, L.-H.; Zhong, S.-C.; Huang, W.; Li, Z.-R.; Schneider, H.; Shi, Q.; Zhu, L.-G.

Ultrafast detection and switching of light are key processes in high-speed optoelectronic devices. However, the performances of VO₂-based optoelectronics are strongly degraded by photothermal. The mechanism of the latter is still unclear. Here, by using femtosecond-laser (fs-laser) driven kinetic terahertz wave absorption, we quantitatively separate slow photothermal response and ultrafast photodoping response (e.g. light-induced insulator-to-metal transition) from second- to picosecond-timescales, and discover the competing interplay between them. With self-photothermal (mainly determined by fs-laser pulse repetition rate and pump fluence), the ultrafast transition time was degraded by 190% from 50 ps to 95 ps, the ultrafast transition threshold was decreased to 82% from 11mJ/cm² to 9mJ/cm², while the amplitudes of the two photoresponse are competing. Percolation theory, along with the macroscopic conductivity response, is used to explain the competing interplay. Our findings are relevant for designing and optimizing VO₂-based ultrafast optoelectronic devices.

Keywords: vanadium-dioxide; insulator-to-metal transition; photo-thermal effect

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Permalink: https://www.hzdr.de/publications/Publ-28042
Publ.-Id: 28042


Interaction of U(VI) with α-isosaccharinic acid: structural elucidation of the formed complexes and implications for the retention of U(VI) on bentonite

Brinkmann, H.; Philipp, T.; Dullies, P.; Shams Aldin Azzam, S.; Patzschke, M.; Roßberg, A.; Moll, H.; Stumpf, T.

Low and intermediate level waste contains considerable amounts of cellulosic materials, which will be degraded relatively fast under alkaline conditions, with isosaccharinic acid (ISA), a polyhydroxy-carboxylic acid, being the main degradation product. It has been shown that the α-form is a stronger complexant for certain radionuclides compared to the β-form and that the complex formation affects the sorption as well as the solubility adversely.[1]
In the particular case of U(VI) the number of studies concerning the speciation in the presence of ISA is small. The excellent spectroscopic properties of the uranyl-entity were used to determine the speciation by UV-vis, luminescence, ATR-FTIR and EXAFS spectroscopy properly under acidic conditions. To understand the complex formation mechanism on a molecular level, the behavior of the ligand was simultaneously investigated by ATR-FTIR and NMR spectroscopy and the results were compared to theoretical data from DFT-calculations, whereby a dominant chelate binding motif via the carboxylic and the α-hydroxy-group was identified.
Whereas hydrolysis of U(VI) and carbonate-complexation can be neglected under acidic conditions, they have to be carefully considered under neutral and alkaline conditions as competitive reactions in addition to the complex formation with ISA. In this context the influence of ISA on the retention of U(VI) on bentonite was investigated. Sorption experiments were performed under anaerobic (carbonate-free) and aerobic (with carbonate) conditions between pH 8 and 13 in the presence of ISA. Time-resolved laser-induced fluorescence spectroscopy was used to determine the aqueous speciation of U(VI) and the results will be compared to measurements without ISA.

[1] Van Loon, L. R., et al., Radiochimica Acta, 1999, Vol. 86, https://doi.org/10.1524/ract.1999.86.34.183.

Keywords: uranium; isosaccharinic acid; spectroscopy; bentonite; sorption

  • Lecture (Conference)
    International conference Uranium Biogeochemistry, 21.-26.10.2018, Monte Veritá Ascona, Schweiz

Permalink: https://www.hzdr.de/publications/Publ-28041
Publ.-Id: 28041


Detailed characterization of uranyl complexes with small organic ligands on a molecular level: a spectroscopic approach

Brinkmann, H.; Heim, K.; Kaden, P.; Kloditz, R.; Moll, H.; Patzschke, M.

The fundamental aspects of uranyl-spectroscopy (absorption, luminescence, IR), data interpretation and subsequent conclusions to interpret the U(VI)-speciation will be discussed. Furthermore, it will be explained how spectroscopy (NMR and IR) can be used to identify the binding properties of organic molecules, exemplarily explained for a polyhydroxy-carboxylic acid.

Keywords: uranium; spectroscopy; isosaccharinic acid

  • Lecture (others)
    MIND Advanced training course | Geomicrobiology in radioactive waste disposal, 08.-11.10.2018, Mol, Belgien

Permalink: https://www.hzdr.de/publications/Publ-28040
Publ.-Id: 28040


Age and provenance of detrital zircons from the Oligocene formations of the Marseille–Aubagne basins (SE France): consequences on the geodynamic and palaeogeographic evolution of the northern Gondwana margin

Villeneuve, M.; Gärtner, A.; Nury, D.; Fournier, F.; Arlhac, P.; Linnemann, U.; Caron, J. P.

Eight samples from Oligocene sedimentary rocks of the Marseille–Aubagne basins have been analysed for their detrital zircon age spectra. These age spectra provide information about the regional evolution, from Oligocene to Archaean times. The Carboniferous Variscan and the Late Cretaceous to Eocene Pyreneo-Provençal belts represent the latest main tectonic, magmatic, and volcanic events that formed the major zircon age populations found in studied sediments. The obtained detrital zircon age record of the Marseille–Aubagne basins comprises eleven detrital zircon age clusters. They reflect the long and complex geologic history of the sediments source areas and can be ascribed to the opening of the western Mediterranean, the Variscan, Cadomian and Pan-African belts, to an unknown Mesoproterozoic event, to the Eburnean orogeny of West Africa and to the different tectono-metamorphic events that took place in Archaean times. In general, the Palaeo- and Mesozoic events are ascribed to the dispersal of Western and Eastern Gondwana and the Pangaean supercontinent cycle. Thus, the successive recycling of zircon grains from older and the incorporation of them to younger belts lead to new geodynamical models for the northern Gondwana margin evolution. Significant amounts of Mesoproterozoic detrital zircon are at odds with previous hypotheses and re-open the question of the provenance of these zircon age populations. Therefore, this tiny Tertiary basin is a natural archive which records the main geological events in SE France and its vicinity.

Keywords: U–Th–Pb zircon dating; Oligocene; Variscan; Provence; Mediterranean; Palaeogeography; Geodynamic

Permalink: https://www.hzdr.de/publications/Publ-28039
Publ.-Id: 28039


Morphological and Functional Modifications of Optical Thin Films for Space Applications Irradiated with Low-Energy Helium Ions

Pelizzo, M. G.; Corso, A. J.; Tessarolo, E.; Böttger, R.; Hübner, R.; Napolitani, E.; Bazzan, M.; Rancan, M.; Armelao, L.; Jark, W.; Eichert, D.; Martucci, A.

Future space missions will operate in increasingly hostile environments, such as those in low-perihelion solar orbits and Jovian magnetosphere. This exploration involves the selection of optical materials and components resistant to the environmental agents. The conditions in space are reproduced on ground through the use of ion accelerators. The effects of He particles coming from the solar wind impinging on a gold thin film have been systematically investigated, considering absorbed doses compatible with the duration of the European Space Agency Solar Orbiter mission. Structural and morphological changes have been proved to be dependent not only on the dose but also on the irradiation flux. A predictive model of the variation of thin film reflectance has been developed for the case of lower flux irradiation. The results are discussed regarding reliability and limitations of laboratory testing. The outcomes are important to address the procedures for the space qualification tests of optical coatings.

Keywords: optical thin films; gold coatings; ion irradiation; helium ions; space weather

Permalink: https://www.hzdr.de/publications/Publ-28038
Publ.-Id: 28038


Correction for volume recombination in liquid ionization chambers at high dose-per-pulse

Gotz, M.; Karsch, L.; Tölli, H.; Pawelke, J.

Purpose: To determine the volume recombination at high dose-per-pulse in liquid ionization chambers (LIC) and to ascertain whether existing calculation methods verified in air-filled chambers may be used to calculate a correction factor.

Methods: Two LICs, one filled with 2,2,4-trimethylpentane (isooctane) the other with tetramethylsilane (TMS), were irradiated in a pulsed, 20 MeV electron beam. Via reference measurements with a Faraday-cup the saturation correction for volume recombination was determined for dose-per-pulse values ranging from about 5 mGy to 1 Gy for both chambers at a pulse duration of 693 ns. In addition, the isooctane-chamber was irradiated with pulses of varying duration, ranging from 5 ps to 10 ms, at a dose-per-pulse of about 76.5 mGy. The dose-per-pulse dependent measurements were compared to calculations based on Boag’s models (with and without a free electron fraction) and the two-dose-rate method. The pulse duration dependent measurements were compared to a numerical calculation that iteratively calculates the charge transport and loss in a 1D model of an ionization chamber.

Results: In TMS only Boag’s model with a free electron fraction is in good agreement with the experimental data. However, in isooctane good agreement is observed between the experimental data, the two-dose-rate method, Boag’s model including a free electron fraction and to a lesser extend also Boag’s model without a free-electron fraction. Furthermore, the pulse duration dependent data for isooctane is well described by the numerical model.

Conclusion: With isooctane as an active medium a LIC could be directly used in a field with high dose-per-pulse utilizing the well established two-dose-rate method to correct for volume recombination. In addition, pulsed fields with variable pulse duration are easily modeled for this medium using a numerical calculation. Other media, as exemplified by the TMS-filled chamber, might require additional considerations, such as including a fraction of free electrons in the consideration of volume recombination.

Keywords: volume recombination correction; liquid ionization chamber; pulsed radiation field

Permalink: https://www.hzdr.de/publications/Publ-28037
Publ.-Id: 28037


Competing risks in survival data analysis

Dutz, A.; Löck, S.

Clinical trials and retrospective studies in the field of radiation oncology often consider time-to-event data as their primary endpoint. Such studies are susceptible to competing risks, i.e. competing events may preclude the occurrence of the event of interest or modify the chance that the primary endpoint occurs. Competing risks are frequently neglected and the event of interest is analysed with standard statistical methods. Here, we would like to create awareness of the problem and demonstrate different methods for survival data analysis in the presence of competing risks.

Keywords: Competing risk; Survival data; Time-to-event data; Cox regression

Permalink: https://www.hzdr.de/publications/Publ-28036
Publ.-Id: 28036


Alkyl Branching Position in Diketopyrrolopyrrole Polymers: Interplay between Fibrillar Morphology and Crystallinity and Their Effect on Photogeneration and Recombination in Bulk-Heterojunction Solar Cells

Shivhare, R.; Erdmann, T.; Hörmann, U.; Collado-Fregoso, E.; Zeiske, S.; Benduhn, J.; Ullbrich, S.; Hübner, R.; Hambsch, M.; Kiriy, A.; Voit, B.; Neher, D.; Vandewal, K.; Mannsfeld, S. C. B.

Diketopyrrolopyrrole (DPP)-based donor-acceptor copolymers have gained a significant amount of research interest in the organic electronics community because of their high charge carrier mobilities in organic field-effect transistors (OFETs) and their ability to harvest near-infrared (NIR) photons in solar cells. In this study, we have synthesized four DPP-based donor-acceptor copolymers with variations in the donor unit and the branching point of the solubilizing alkyl chains (at the second or sixth carbon position). Grazing incidence wide-angle X-ray scattering (GIWAXS) results suggest that moving the branching point further away from the polymer backbone increases the tendency for aggregation and yields polymer phases with a higher degree of crystallinity (DoC). The polymers were blended with PC70BM and used as active layers in solar cells. A careful analysis of the energetics of the neat polymer and blend films reveals that the charge-transfer state energy (ECT) of the blend films lies exceptionally close to the singlet energy of the donor (ED*), indicating near zero electron transfer losses. The difference between the optical gap and open-circuit voltage (VOC) is therefore determined to be due to rather high nonradiative (≈ 418 ± 13 mV) and unavoidable radiative voltage losses (≈ 255 ± 8 mV). Even though the four materials have similar optical gaps, the short-circuit current density (JSC) covers a vast span from 7 to 18 mA cm-2 for the best performing system. Using photoluminescence (PL) quenching and transient charge extraction techniques, we quantify geminate and nongeminate losses and find that fewer excitons reach the donor-acceptor interface in polymers with further away branching points due to larger aggregate sizes. In these material systems, the photogeneration is therefore mainly limited by exciton harvesting efficiency.

Permalink: https://www.hzdr.de/publications/Publ-28035
Publ.-Id: 28035


Dezentrale Produktion werthaltiger Kohlenwasserstoffe mit Hilfe lastflexibler, integrierter Elektrolyse-Synthese-Apparate

Schwarze, L.; Fogel, S.; Schwabe, F.; Partmann, C.; Lippmann, W.; Kryk, H.; Hurtado, A.; Hampel, U.

Der stetige Ausbau von Wind- und Solarenergie in Deutschland erfordert effiziente Technologien zur räumlich-zeitlichen Flexibilisierung des Energieversorgungssystems. Infolge der Netzeinbindung fluktuierender Energien ergeben sich grundlegend neue Anforderungen an die bestehende, grundlastbasierte Energiewirtschaft und deren Infrastruktur. Technologien zur direkten Speicherung von Elektroenergie in relevanten Größenordnungen scheitern derzeit aus verschiedenen Gründen, bspw. der Standort-Limitierung von Pumpspeicherkraftwerken oder der Kostenineffizienz von Batterien. Im Rahmen des Verbundforschungsvorhabens „DELTA“ (EF-RE-Förderkennzeichen: 100240618) wird ein frei skalierbarer, dezentral einsetzbarer, modular aufgebauter, wirtschaftlich attraktiver und technisch flexibler Demonstrator zur chemischen Langzeitspeicherung von Elektroenergie (Power-to-Liquid) entwickelt und erprobt. Strom wird einem tubularen, protonenleitenden Dampf-Elektrolyseur zur Erzeugung von hochreinem Wasserstoff zugeführt. Dieser wird direkt unter stofflicher Verwertung von CO2 einer integrierten, heterogen katalysierten Methanolsynthese unterzogen. Durch die Kopplung stationärer CO2-Emittenten und -Verbraucher wird CO2 in einem geschlossenen Kreislauf nutzbar. Flüssige Kohlenwasserstoffe finden sektorübergreifend sowohl als synthetische Kraftstoffe als auch als Grundstoffe für weitere chemische Produkte oder zur Rückverstromung Verwendung und stellen somit eine interessante Wertschöpfungsalternative innerhalb der Chemie- und Energiewirtschaft dar. Die hohe Systemintegration innerhalb des Demonstrators ermöglicht eine energetisch optimierte Prozessführung sowie ein effizientes Energie- und Stoffstrom-Management, weshalb sich das Reaktorsystem durch geringe Energieverluste, hohe Systemwirkungsgrade, Kosteneffizienz und eine hohe Zuverlässigkeit sowie Lastwechselfähigkeit auszeichnet. Der Demonstrator stellt in einer späteren technischen Anwendung ein Basismodul dar, welches mit weiteren Modulen zu einer flexiblen Gesamtanlage verschaltet werden kann. Im Rahmen der Präsentation soll das grundlegende Anlagenkonzept sowie die ersten Ergebnisse des Basic Engineerings und der rechnergestützten Modellierung und Simulation vorgestellt werden.

Keywords: Elektrolyse; Methanolsynthese; Power-to-X; Lastflexibel; Energiespeicher

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppe Energieverfahrenstechnik, 07.-08.03.2018, Frankfurt am Main, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28034
Publ.-Id: 28034


Simulation des dynamischen Betriebsverhaltens eines gekoppelten Elektrolyse-Synthese-Prozesses für lastflexible Anwendungen

Schöne, C.

Im Rahmen der Bachelorarbeit wurde der aktuelle Stand von Wissenschaft und Technik für die Modellierung und Simulation des dynamischen Verhaltens von Hochtemperaturelektrolyseuren sowie für die Synthese von Methanol durch direkte Hydrierung von Kohlenstoffdioxid dargestellt. Aufbauend auf einem 0D-Prozessmodell für die Kopplung einer protonenleitenden Hochtemperaturelektrolysezelle (H-SOEC) mit einer Methanolsynthese wurde das grundlegende stationäre Betriebsverhalten beschrieben und mit Literaturdaten verglichen. Außerdem wurde das dynamische Betriebsverhalten des Gesamtprozesses im Falle von transienten Lastprofilen (Teil-/Volllastsprünge und fluktuierende Profile), verschiedenen Betriebsmodi (An- und Abfahrprozesse) und transienten Randbedingungen charakterisiert sowie wesentliche Strategien zur Steuerung und Regelung abgeleitet.

Keywords: Modellierung und Simulation; Prozessdynamik; Dynamisches Verhalten; Steuerung und Regelung

  • Bachelor thesis
    TU Dresden, 2018
    Mentor: Stefan Fogel, Holger Kryk
    70 Seiten

Permalink: https://www.hzdr.de/publications/Publ-28033
Publ.-Id: 28033


Bestimmung des stationären und dynamischen Betriebsverhaltens einer gekoppelten Elektrolyse-Synthese-Stufe mittels 2D-FEM-Simulationen

Knitt, F.

Im Rahmen der Diplomarbeit wurde der aktuelle Stand von Wissenschaft und Technik für die Synthese von Methanol durch direkte Hydrierung von Kohlenstoffdioxid, deren Modellierung und Simulation sowie für das dynamische Verhalten von Hochtemperaturelektrolyseuren dargestellt. Aufbauend auf einer zu ermittelnden Reaktionskinetik wurde ein Modell für die beschriebene Methanolsynthese erstellt und mit vorgegebenen Betriebsparametern simuliert sowie mit Literaturdaten verglichen. Anschließend wurde das Synthesemodell mit einem bereits vorhandenen Modell eines protonenleitenden Hochtemperaturelektrolyseurs (H-SOEC) kombiniert. Mit Hilfe der Modellkombination konnten wesentliche Betriebsparameter (Mengenströme, Produktzusammensetzungen, Temperaturen, etc.) und Betriebslimitationen für einen räumlich eng gekoppelten Betrieb von Elektrolyse und Synthese bestimmt werden.

Keywords: Modellierung; Simulation; SOEC; Methanolsynthese; Dynamisches Verhalten

  • Diploma thesis
    TU Dresden, 2018
    Mentor: Stefan Fogel, Holger Kryk
    94 Seiten

Permalink: https://www.hzdr.de/publications/Publ-28032
Publ.-Id: 28032


Development and evaluation of a 99mTc(III) ‘4 + 1’ complex derived from estradiol for imaging breast cancer

Tejería, E.; Pietzsch, H.-J.; Giglio, J.; Rey, A.

Estrogen receptors are overexpressed in about 70% of breast cancer and identification of their presence is important to select the appropriate treatment and evaluate the response.
With this objective, an estradiol derivative (L) 5-((1-carboxy-2-(4-((13S,17S)-3,17-dihydroxy-13-methyl-7,8,9,11,12,13,14,15,16,17-decahydro-6H-cyclopenta[a]phenanthren-17-yl)-1H-1,2,3-triazol-1-yl)ethyl)amino)-N-methylidyne-5-oxopentan-1-aminium, was used to develop a ‘4+1’ complex of Tc(III) for estrogen receptor imaging.
The synthesis of L involved the coupling of the amino group of 3-azido-L-alanine with an activated isonitrile, to then perform a "click chemistry" reaction with the ethinyl group of ethinylestradiol.
Labelling was carried out in two stages, preparation of the precursor [99mTc]Tc-EDTA, using mannitol, EDTA and SnCl2 as reducing agent and simultaneous substitution (30 min at 75°C) with L (20 mg) and the tetradentate coligand 2-[Bis(2-mercaptoethyl)amino]ethanethiol (NS3) (2 mg). The HPLC analysis showed a major peak (tr=13 min). The radiochemical purity of the HPLC purified complex was greater than 95%.
The lipophilicity expressed as logP (partition coefficient between octanol and phosphate buffer 0.1M, pH = 7.4) was 0.48±0.06. The plasma protein binding was (46 ± 6) % at 60 minutes. The complex was stable in the labelling milieu and in human serum for at least 4 hours. Cell uptake in MCF7 cells are in progress.
A potential radiopharmaceutical derived from estradiol was obtained with high radiochemical purity. The complex presents adequate stability and physicochemical properties. In vitro and in vivo studies including nude mice bearing xenografted breast tumors will be used to validate the clinical potentiality.

  • Lecture (Conference)
    TeraChen 2018, 26.-29.09.2018, Brixen, Italien

Permalink: https://www.hzdr.de/publications/Publ-28031
Publ.-Id: 28031


Cross-bridged cyclams with bis(phosphinic acid) pendants for a fast Cu(II) complexation: towards efficient 64-Cu labeling

Kubíček, V.; David, T.; Lubal, P.; Pietzsch, H.-J.; Hermanna, P.

Copper radioisotopes chelators are commonly based on macrocycles but they mostly suffer from in vivo instability, slow (not efficient) radiolabeling and low selectivity over competing ions. Cyclam derivatives offer high selectivity for Cu(II). Complexes of cross-bridged (CB-) cyclams are very stable in-vivo, however, their radiolabelling is not efficient.
We have found that bis(phosphinic acid) pendant arm (BPi) highly accelerate Cu(II) complexation.[1] It was also found, on Me3cyclam derivatives as model ligands, that phosphonic acid (Po) and bis(phosphorus acid) pendant arms are the most suitable ones for fast chelation.[2]
Chelators with BPi-like pendants on CB-cyclam (cb-BPC) were synthesized. Their complexation properties (structure, thermodynamics, formation/decomplexation kinetics) were investigated and analogous data were also obtained for known phosphorus chelators as cb-TE2P. All ligands are basic (last pKa>13.5) and form thermodynamically stable copper complexes. Other metal ion complexes are hardly formed in water. The Cu(II) complexes are formed quickly with some dependence on a kind of the pendant arms. Complexes of BPi containing chelators are significantly less kinetically inert than those of cb-TE2P but still much more inert than complexes of most of common chelators as DOTA. The phosphonic acid and BPi on CB-cyclams exhibit fast radiolabeling with 64-Cu even at room temperature and the labelled chelators are obtained with a high specific activity. These radiolabelling properties are not altered after conjugations.[3] The ligands can be suggested as a new chelator family for copper radioisotopes.

  • Poster
    TeraChem 2018, 26.-29.09.2018, Brixen, Italien

Permalink: https://www.hzdr.de/publications/Publ-28030
Publ.-Id: 28030


Bifunctional cyclam derivatives with a bis(phosphinate) pendant arm as efficient chelators for copper radionuclides

David, T.; Hlinová, V.; Kubíček, V.; Bergmann, R.; Pietzsch, H.-J.; Hermann, P.

Bifunctional cyclam derivatives with one bis(phosphinic acid) pendant arm bearing carboxylate, amine, isothiocyanate, azide or cyclooctyne functions in the pendant arm side chain were synthesized (Figure). The bifunctional groups were introduced far from the metal-binding site, either by using newly synthesized bis(phosphinic acid) precursors or by modifying the reactive groups. Direct coupling without protecting the pendant phosphinate or ring secondary amine groups was feasible. The ligands were successfully conjugated to model compounds including oligopeptides, biotin or fluorescent dye.
Labeling of the bifunctional ligands with 64Cu showed very high radiolabeling efficiency, leading to a significantly higher molar activity than that described for other commonly used macrocyclic chelators. It confirms that using properly designed phosphinic acid pendant arm(s) is a good strategy to achieve conjugation flexibility (due to the distant bifunctional site) without compromising the radiolabeling efficiency or the high specific activity of radiopharmaceuticals.
A prototypic representative was evaluated in-vivo by metabolite analysis, biodistribution studies and PET scans. The data clearly showed the very high metabolic stability of the 64Cu chelate unit as no decomplexation was detected. Except for the excretory organs, no prominent uptake and retention was observed.
Thus, bis(phosphinate)-bearing cyclam-based ligands are highly promising radiocopper chelators for conjugation to targeting units, such as peptides, oligonucleotides or antibodies and their fragments.

  • Poster
    TeraChem 2018, 26.-29.09.2018, Brixen, Italien

Permalink: https://www.hzdr.de/publications/Publ-28029
Publ.-Id: 28029


On the effect of water hardness in fluorite flotation – the role of ion specificity

Michaux, B.; Rudolph, M.; Reuter, M. A.

It is relatively well-established in the literature that the flotation of calcium minerals using fatty acids as collector is very sensitive to the process water composition. In particular, hard waters have often been reported to strongly reduce the target mineral recoveries due to the formation of insoluble compounds such as calcium and / or magnesium dioleate, thus reducing the amount of collector available for adsorption onto the mineral surface. In this study, the flotation of a fluorite pre-concentrate was performed with tall oil, an industrial collector essentially containing fatty acids. The tests were performed in a variety of synthetic waters to simulate multiple degrees of water hardness, and to differentiate the role of magnesium and calcium ions on the flotation performance. The flotation tests revealed that, under the studied conditions, a significant difference between flotation in calcium-rich and magnesium-rich waters was observed, suggesting strong ion-specific effects in the system. Specifically, calcium-rich waters slightly improved the fluorite recovery, whereas magnesium-rich waters caused a decrease in recovery by as much as 20%. This paper is focused on the flotation kinetics aspect of the system. This approach highlighted the interesting finding that calcium ions did not simply increase the fluorite recovery, but also significantly increased its flotation kinetics. The magnesium ions, on the other hand, had the exact opposite effect.

Keywords: Water hardness; ion specificity; flotation kinetics; fluorite; fatty acids

  • Contribution to proceedings
    International Mineral Processing Congress, 17.-21.09.2018, Moscow, Russia

Permalink: https://www.hzdr.de/publications/Publ-28028
Publ.-Id: 28028


Water-saving strategies in the mining industry – the potential of mineral processing simulators as a tool for their implementation

Michaux, B.; Hannula, J.; Rudolph, M.; Reuter, M. A.; van den Boogaart, K. G.; Möckel, R.; Kobylin, P.; Hultgren, M.; Peltomäki, M.; Roine, A.; Remes, A.

As the mining industry is facing an increasing number of issues related to its fresh water consumption, water-saving strategies are progressively being implemented in the mineral processing plants, often leading to variations in the process water chemistry. However, the impact of water chemistry variations on the process performance is rarely known beforehand, thus creating an obstacle to the implementation of those water-saving strategies. To tackle this problem, the effect the different dissolved species present in the process water have on the processing plant performance must be quantified, and this information must be digitalized in a practical and suitable form to be used in mineral processing simulators. To achieve this goal, a methodology to digitalize the influence of the process water composition on the flotation performance is presented in this paper. Using the flotation of a fluorite ore as case study, the relationship between process water composition and the flotation kinetics of that fluorite ore was determined. This relationship was digitalized in HSC Sim, a mineral processing simulator, turning it into a tool capable of simulating the flotation performance under a variety of process water compositions. Finally, the potential of this new tool to help implementing water-saving strategies on the mine site is discussed, and the challenges that need to be overcome in order to apply this tool at industrial scale are being addressed.

Keywords: Water-saving strategies; Water chemistry; Flotation kinetics; Simulation-based optimization

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-28027
Publ.-Id: 28027


Ligand development for the Radiometal Hg-197(m)

Gilpin, M.; Walther, M.; Pietzsch, H.-J.; Steinbach, J.

Reactor-produced Hg-197 had previous medical use for imaging[1] but was discontinued due to low stability and low specific-activity. Cyclotron-produced Hg-197(m) can overcome the toxicity problem, due to much higher molar activity[2], allowing access to the radiometal’s useful decay modes (γ for SPECT-imaging. Conversion & auger electrons for therapy) at sub-toxic Hg-concentrations.
Development in Hg ligands for medicinal applications necessitates stability in vivo but the poor long-term stability of Mercury compounds in solution is an ongoing issue[3]. Hg-organometallics show good water-stability and bypass the issue of Hg-S bonds suffering from competition by common biomolecules, e.g. cysteine. Therefore, our focus is on Hg-C chemistry, specifically the strongest bond kind: the mercury-phenyl bond[4].
As prior research has shown that the synthetically simpler route of monodentate ligands (κ1-L2Hg) suffers from significant cleavage[5], this research is centred on the syntheses of bidentate chelators benefitting from entropic stability. Purification of the Hg-197(m) leaves it in an acidic aqueous medium as the chloride salt, thus transmetallation, via stannyl or boronic acid derivatives, was chosen as a viable option for mercury attachment. Chelator designs began with a dibenzylisophthalamide template but low selectivity for the 1:1-compound encouraged a better fitting structure. Recent radio-labelling experiments show promise for specific binding with a design based on the bispidine backbone (attractive for being known in co-ordination chemistry for a variety of metals[6] and possessing bridge linking-functionalisation).
Analyses are performed through radio-TLC and HPLC, whilst stable mercury compound analysis includes Hg-199 NMR.

References :
(1) Sodee. J. Nucl. Med. 1968; 9: 645.
(2) Walther et al. Appl. Radiat. Isot. 2015; 97: 177–181.
(3) Henke et al. Wat. Res. 2000; 34: 3005-3013.
(4) Dean. Lange’s Handbook of Chemistry, 15th ed.; McGraw-Hill Inc, 1998; 606.
(5) Wilhelm. et al. Z. Naturforsch. 2000; 55b: 35–38.
(6) Comba et al. Inorg. Chem. 2009; 48: 6604–6614.

Keywords: Mercury 197; Chelator; Ligand; Radiometal; Bispidine; Cancer; Theragnostics

  • Poster
    TERACHEM 2018, 24.-29.09.2018, Bressanone, Italy

Permalink: https://www.hzdr.de/publications/Publ-28026
Publ.-Id: 28026


Development and characterization of a 177Lu-labeled anti-prostate stem cell antigen (PSCA) monoclonal antibody for metastatic prostate cancer

Striese, F.; Bergmann, R.; Bachmann, M.; Arndt, C.; Feldmann, A.; Weißflog, S.; Steinbach, J.; Pietzsch, H.

The clinical need of new therapeutics for advanced prostate cancer is continuingly high because there still exist no curative treatment options. It has been shown that especially targeted therapies using radionuclides gives enhanced specificity and increased overall survival of prostate cancer patients. Antibodies represent attractive transport vehicles for the delivery of radionuclides to prostate cancer cells for several reasons, such as: metastatic site location and small volume disease. Here, we describe the development and characterization of a novel 177Lu-labeled antibody-conjugate that offers encouraging features to be used for the therapy PSCA-expressing prostate tumors. The PSCA is a cell surface antigen that is present in nearly all primary prostate tumors and further upregulated in many bone and lymph node metastases. Therefore, it is proposed as a promising tumor target structure for both, therapy and diagnosis, of prostate cancer. Purified PSCA-directed antibody demonstrated a high specificity and affinity, with dissociation constant of 10 nM to PC3-PSCA cells. The antibody was conjugated with, on average, three CHX-A’’-DTPA molecules, as verified by MALDI-TOF analysis. Subsequent radiolabeling of the antibody-chelator-conjugate with Lutetium-177 could be performed at high radiochemical purity (>95%, radio HPLC) while preserving binding properties to the PSCA. SPECT scanning with the 177Lu-labeled antibody-conjugate was used to investigate the targeting potential in mice with established PSCA-expressing tumors. The outcome was the production of excellent high contrast images from 3 to 170 h post injection. With these promising results, we next want to evaluate the antitumor activity in vivo.

Keywords: prostate cancer; metastatic; Prostate Stem Cell Antigen (PSCA); radiolabeled monoclonal antibody; Lu-177; theragnostics

  • Lecture (Conference)
    TERACHEM 2018, 26.-29.09.2018, Bressanone, Italy

Permalink: https://www.hzdr.de/publications/Publ-28025
Publ.-Id: 28025


Evaluation of [Tc-99m]Tc-tricarbonyl labeled alpha-melanocyte stimulating hormone derived peptide conjugates for melanoma imaging

Gao, F.; Sihver, W.; Bergmann, R.; Weißflog, S.; Bolzati, C.; Salvarese, N.; Belter, B.; Steinbach, J.; Pietzsch, J.; Pietzsch, H.

The melanocortin 1 receptor (MC1R), since overexpressed in melanoma cells, is an attractive target for imaging or treatment of this type of malignancies. The α-melanocyte stimulating hormone (α-MSH) derived peptide NAP-NS1 (Nle-Asp-His-D-Phe-Arg-Trp-Gly-NH2) binds with high affinity [1] and was engineered in three different ways for labeling with [Tc-99m]Tc-tricarbonyl. ɛ-Ahx-β-Ala-NAP-NS1, ethylenglycol (EG)-based linker NAP-NS1 and NAP-NS1 without linker were conjugated with bis(pyridin-2-ylmethyl)amine (DPA) obtaining yields of 42%, 38% and 45%, respectively. For standard purpose non-radioactive Re-DPA-peptides were prepared [2] with yields > 55%. The labeling with a one-pot method was faster than with a two steps method, and even receiving slightly higher radiochemical yields. High stability as well as negligible transschelation was observed for the [Tc-99m]Tc-tricarbonyl-peptide conjugates. The ethylenglycol based linker increased the hydrophilicity. Binding results, first of competition assays with the non-radioactive α-MSH conjugates, and second of saturation assays with the [Tc-99m]Tc-tricarbonyl-DPA peptides resulted in high affinity (low nanomolar range) where the labeled peptides showed a marginal loss of affinity; that was relevant for murine B16F10, as well as for human MeWo and TXM13 cells. The number of binding sites was considerably higher in murine melanoma cells. The three [Tc-99m]Tc-tricarbonyl-peptide conjugates exhibited similar in vitro properties. Preliminary in vivo studies were performed with [Tc-99m]Tc-tricarbonyl-DPA-ɛ-Ahx-β-Ala-NAP-NS1 in rats and showed good metabolic stability in blood and both a renal and hepatobiliary excretion. Hence, it displayed prospective radiochemical and radiopharmacological properties, suggesting a promising candidate for further investigation in a melanoma xenograft model.

[1] Gao et al. J. Amino Acids 2016; 48: 833-847.
[2] Alberto et al. J. Chem. Soc. Dalton 1994; 19: 2815-2820.

Keywords: Melanocortin-1 receptor; α-MSH analogs; Tc-99m labeling; Malignant melanoma

  • Poster
    TERACHEM 2018, 26.-29.09.2018, Bressanone, Italy

Permalink: https://www.hzdr.de/publications/Publ-28024
Publ.-Id: 28024


Dynamic Imaging of the Delay-and Tilt-Free Motion of Neel Domain Walls in Perpendicularly Magnetized Superlattices

Finizio, S.; Wintz, S.; Zeissler, K.; Sadovnikov, A. V.; Mayr, S.; Nikitov, S. A.; Marrows, C. H.; Raabe, J.

We report on the time-resolved investigation of current- and field-induced domain wall motion in perpendicularly magnetized microwires exhibiting asymmetric exchange interaction by means of scanning transmission x-ray microscopy using a time step of 200 ps. Dynamical domain wall velocities on the order of 50-100 m s−1 were observed. The improvement in the temporal resolution allowed us to observe the absence of incubation times for the motion of the domain wall, together with indications for a negligible inertia. Furthermore, we observed that, for short current and magnetic field pulses, the magnetic domain walls do not exhibit a tilting during its motion, providing a mechanism for the fast, tilt-free, motion of magnetic domain walls.

Keywords: domain wall motion; x-ray microscopy; spin-orbit torques

Permalink: https://www.hzdr.de/publications/Publ-28022
Publ.-Id: 28022


Impact of Haloarchaea on speciation of uranium – a multi-spectroscopic approach

Bader, M.; Rossberg, A.; Steudtner, R.; Drobot, B.; Großmann, K.; Schmidt, M.; Musat, N.; Stumpf, T.; Ikeda-Ohno, A.; Cherkouk, A.

Haloarchaea represent a predominant part of the microbial community in rock salt, which can serve as host rock for the disposal of high level radioactive waste. However, knowledge is missing about how Haloarchaea interact with radionuclides. Here, we used a combination of spectroscopic and microscopic methods to study the interactions of an extremely halophilic archaeon with uranium, one of the major radionuclides in high level radioactive waste, on a molecular level. The obtained results show that Halobacterium noricense DSM 15987T influences uranium speciation as a function of uranium concentration and incubation time. X-ray absorption spectroscopy reveals the formation of U(VI) phosphate minerals, such as meta-autunite, as the major species at a lower uranium concentration of 30 µM, while U(VI) is mostly associated with carboxylate groups of the cell wall and extracellular polymeric substances at a higher uranium concentration of 85 µM. For the first time, we identified uranium biomineralization in the presence of Halobacterium noricense DSM 15987T cells. These findings highlight the potential importance of Archaea in geochemical cycling of uranium and their role in biomineralization in hypersaline environments, offering new insights into the microbe-actinide interactions in highly saline conditions relevant to the disposal of highly radioactive waste as well as bioremediation.

Permalink: https://www.hzdr.de/publications/Publ-28021
Publ.-Id: 28021


1,4,7-Triazacyclononane: An effective chelator for copper-64

Kubeil, M.; Pant, K.; Joshi, T.; Stephan, H.

1,4,7-Triazacyclononane (TACN) is a versatile platform from which various ligands can be derived to form effective chelators for (radio)copper(II) complexation. [1] The ability of TACN-derivatives to form highly stable complexes with copper(II) is greatly influenced by the number and type of substituents on the macrocyclic ring. The formed copper(II) complexes show a broad variability in their thermodynamic stability and kinetic inertness, varying in structure from square-pyramidal to distorted octahedral. TACN-based BFCAs have also been used for indirect radiolabelling of biomolecules, rendering them suitable for imaging and therapy.
Herein, examples of various copper-64 TACN complexes will be presented which provide a picture of how different substituents influence the coordination mode, electronic properties and in vivo stability of. By applying principles of coordination chemistry, it is possible to tune the affinity of TACN-based ligands for copper ligation, as well as their availability for subsequent biomolecular functionalisation. Target-specific TACN based conjugates (peptides, antibody fragments) and bio(nano)materials labelled with copper-64 enabling tumour imaging and biodistribution studies via positron emission tomography will be discussed as well. [2, 3, 4]

[1] T. Joshi et al. ChemPlusChem 2018; DOI: 10.100 2/cplu.201800103.
[2] K. Pant et al. Bioconjugate Chem. 2015; 26: 906-918.
[3] K. Viehweger et al. Bioconjugate Chem. 2014; 25: 1011-1022.
[4] R. Bergmann et al. Sci. Rep. 2017; 7.

Keywords: TACN; copper-64; chelator

  • Poster
    The third International Symposium on Technetium and Other Radiometals in Chemistry and Medicine, 26.-29.09.2018, Brixen, Bressanone, Italia

Permalink: https://www.hzdr.de/publications/Publ-28020
Publ.-Id: 28020


Carbon doping controlled thermoluminescent defect centers in nanoporous alumina for ion beam dosimetry

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

The flexibility of amorphous anodized alumina (AAO) in developing radiation dosimeter for hadron therapy is reported by controlled carbon ion implantation, followed by thermoluminescence (TL) measurements. The efficacy of amorphous AAO in controlling TL sensitivity is found to be governed by an increase in F+ defect centers as a function of carbon concentration, as revealed from the close resemblance of the trend in photoluminescence intensity. Moreover, its nanoporous structure is demonstrated to be advantageous for defect engineering due to the increase in the surface-to-volume ratio. Detailed X-ray photoelectron spectroscopy analysis suggests the formation of F+ centers by substituting Al3+ ions with C2+ in the vicinity of oxygen vacancies, where depth-dependent study showed the evolution of conducting channels owing to sp2 hybridized C–C bonding, leading to a differential charging effect. This work provides a direction to tune nanoporous AAO in its amorphous form for future ion beam dosimetry.

Permalink: https://www.hzdr.de/publications/Publ-28018
Publ.-Id: 28018


GitLab-Runner fork

Frust, T.

This is a fork of the official gitlab-runner repository at https://gitlab.com/gitlab-org/gitlab-runner and is used to generate binaries and the helper image for the Power architecture (ppc64le), since this architecture is not officially supported by GitLab itself.

  • Software in external data repository
    Publication year 2018
    Programming language: Go
    System requirements: Power architecture (ppc64le)
    License: MIT (Link to license text)
    Hosted on HZDR GitLab: Link to location

Permalink: https://www.hzdr.de/publications/Publ-28017
Publ.-Id: 28017


Improved Conjugation, 64-Cu Radiolabeling, in Vivo Stability, and Imaging Using Nonprotected Bifunctional Macrocyclic Ligands: Bis(Phosphinate) Cyclam (BPC) Chelators

David, T.; Hlinová, V.; Kubíček, V.; Bergmann, R.; Striese, F.; Berndt, N.; Szöllösi, D.; Hegedus, N.; Mathe, D.; Bachmann, M.; Pietzsch, H.-J.; Hermann, P.

Bifunctional derivatives of bis(phosphinate)-bearing cyclam (BPC) chelators bearing a carboxylate, amine, isothiocyanate, azide, or cyclooctyne in the BP side chain were synthesized. Conjugations required no protection of phosphinate or ring secondary amine groups. The ring amines were not reactive (proton protected) at pH < ∼8. For isothiocyanate coupling, oligopeptide N-terminal α-amines were more suitable than alkyl amines, e.g., Lys ω-amine (pKa ∼7.5−8.5 and ∼10−11, respectively) due to lower basicity.
The Cu-64 labeling was efficient at room temperature (specific activity ∼100 GBq/μmol; 25 °C, pH 6.2, ∼100 ligand equiv, 10 min). A representative Cu-64-BPC was tested in vivo showing fast clearance and no nonspecific radioactivity deposition. The monoclonal anti-PSCA antibody 7F5 conjugates with thiocyanate BPC derivative or NODAGA were radiolabeled and studied in PC3-PSCA tumor bearing mice by PET. The radiolabeled BPC conjugate was accumulated in the prostate tumor with a low off-target uptake, unlike Cu-64-labeled NODAGA−antibody conjugate. The BPC chelators have a great potential for theranostic applications of the Cu-64/Cu-67 matched pair.

Permalink: https://www.hzdr.de/publications/Publ-28015
Publ.-Id: 28015


Progress on High Peak Current Laser Wakefield Electron Acceleration

Schramm, U.

Report on the generation of multi 10 kA electron bunches with LWFA and related applications.

  • Invited lecture (Conferences)
    60th ICFA Advanced Beam Dynamics Workshop on Future Light Sources (FLS2018), 05.-09.03.2018, Shanghai, China

Permalink: https://www.hzdr.de/publications/Publ-28014
Publ.-Id: 28014


From plasma acceleration to accelerators ?

Schramm, U.

Status of PW laser experiments

  • Invited lecture (Conferences)
    OPIC OPTICS & PHOTONICS International Congress, 23.-26.04.2018, Pacifico Yokohama, Japan
  • Invited lecture (Conferences)
    Freitagsseminar IAP-Frankfurt, 22.06.2018, Frankfurt, Deutschland
  • Invited lecture (Conferences)
    HICforFAIR-Kolloquium Giessen, 21.06.2018, Giessen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-28013
Publ.-Id: 28013


Accelerator mass spectrometry (AMS) for beryllium-7 measurements in smallest rainwater samples

Tiessen, C.; Bemmerer, D.; Rugel, G.; Querfeld, R.; Scharf, A.; Steinhauser, G.; Merchel, S.

Beryllium-7, mainly measured via γ-spectrometry, is used as a (natural) radiotracer for education and science. For lower activities (<0.1 Bq) and samples containing also longer-lived ¹⁰Be, accelerator mass spectrometry (AMS) is the method-of-choice. We demonstrate that ⁷Be- and ¹⁰Be can be quantified at the Dresden AMS facility on the same prepared BeO. Detection limits (⁷Be) are ~0.6 mBq. Samples as small as tens of millilitre of rainwater can be chemically processed (after acidification) within a few hours without expensive and slow ion exchange. Isobar (⁷Li) suppression by chemistry and AMS is sufficient to guarantee for an ultrasensitive, cheap, and fast detection method for ⁷Be allowing high sample throughput.

Keywords: ⁷Be; ¹⁰Be; accelerator mass spectrometry; AMS; rain

Permalink: https://www.hzdr.de/publications/Publ-28012
Publ.-Id: 28012


Stability and Electronic Properties of Palladium Dichalcogenide Polytypes as Nanomaterials

Kempt, R.; Kuc, A.; Heine, T.

We present a detailed computational investigation of the stability and electronic properties of three different polytypes of the palladium dichalcogenides PdX2. These are intriguing for electronic and optical applications as nanomaterials, including logical junctions because of a potential metal-semiconductor transition in the 1T polytype when going from bulk to monolayers.[1,2]
Both PdS2 and PdSe2 crystallize in a layered pyrite-type structure or 2O (see Fig. 1) as bulk materials.[3] Only for high pressures, they adopt the cubic pyrite-type structure.[4] Recently, monolayers of PdSe2 have been exfoliated and shown to maintain their pentagonal structure found in the bulk material.[5] In contrast to PdS2 and PdSe2, bulk PdTe2 occurs naturally in 1T.[6]
We evaluate the differences in chemical bonding between the possible polytypes by density functional theory and show that it requires a hybrid approach in order to properly account for the electron correlation effects in these systems. From there, we estimate their electronic properties and stabilities as nanomaterials.

  • Lecture (Conference)
    Flatlands Beyond Graphene 2018, 03.-07.09.2018, Universität Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-28011
Publ.-Id: 28011


On the chemistry and mobility of hydrogen in the interstitial space of layered crystals h-BN, MoS2, and graphite

An, Y.; Kuc, A.; Petkov, P.; Lozada-Hidalgo, M.; Heine, T.

Recently, transport and separation of hydrogen isotopes in the layered materials hexagonal boron nitride and molybdenum disulphide have been reported.[1] Here, based on first-principles calculations combined with well-tempered metadynamics simulations, we report the chemical interactions and mobility of protons (H+) and protium (H) atoms in the interstitial space of these layered materials. We show that both H as well as H+ can be transported between the layers of h-BN and MoS2 with low free energy barriers, while they are immobilized in graphite, in a good agreement with experiments. In h-BN and MoS2 the transport mechanism involves a hopping process between the nearby layers, which is assisted by the low-energy phonon shear modes of layers.

  • Poster
    Flatlands Beyond Graphene 2018, 03.-07.09.2018, Universität Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-28010
Publ.-Id: 28010


Electronic Properties of 2D van der Waals TMDCs Heterostructures from First Principles Calculations

Ramzan, M. S.; Kuc., A.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs) MX2 (M = Mo, W; X = S, Se) have attracted considerable attention in electronics and optoelectronic due to their intrinsic band gap[1]. Moreover, weak van der Waals interaction between layers make it possible to stack different TMDCs layers to form heterostructures with new electronic properties. In this work we have studies effect of interfacing TMDCs with different chalcogen atoms and/or different transition atoms to study effect of interface and dielectric constant on electronics. We will show that by controlling ratio of layers and hero-interfaces, direct gap can be achieved in more than four layers which might be ideal for solar energy harvesting.

  • Poster
    Flatlands Beyond Graphene 2018, 03.-07.09.2018, Universität Leipzig, Germany

Permalink: https://www.hzdr.de/publications/Publ-28009
Publ.-Id: 28009


Conformational isomerism controls collective flexibility in metal-organic framework DUT-8(Ni)

Petkov, P. S.; Bon, V.; Hobday, C. L.; Kuc, A.; Melix, P.; Kaskel, S.; Düren, T.; Heine, T.

Metal-organic frameworks (MOFs) are crystalline compounds, typically with large pores. Some MOFs show pronounced structural flexibility that may result in closing and re-opening these pores. Here we show that collective flexibility in a MOF – DUT-8(Ni) – is controlled by conformational isomerism. DUT-8(Ni), a pillared-layer MOF with Ni2 paddle-wheels, dabco pillars and naphthalene dicarboxylate (ndc) linkers, can crystallize in many conformational isomers that depend on the orientation of the non-linear ndc linkers with respect to each other. While the open form is compatible with several of these conformations, only one of them, with alternating linker orientations, is stable as closed form. We show, by means of first principles calculations, that in the stable closed form, the appreciable lattice strain is compensated by London-dispersion between the ndc linkers that arrange with maximum overlap in a stacking order similar to the stacking in graphite. We substantiate these results by well-tempered metadynamics calculations at the DFT-based Born-Oppenheimer potential energy surface, by refined X-ray diffraction data and by nitrogen adsorption data obtained by experiment and Grand-Canonical Monte-Carlo simulations based on the DFT-optimized and PXRD-derived geometries. While the reported origin of flexibility cannot be generalized to all flexible MOFs, it offers a rational design concept of folding mechanisms in switchable MOFs by exploitation of the stabilization effect of linker stacking in the closed form.

Permalink: https://www.hzdr.de/publications/Publ-28008
Publ.-Id: 28008


Non equilibrium anisotropic excitons in atomically thin ReS2

Urban, J. M.; Baranowski, M.; Kuc, A.; Klopotowski, L.; Surrente, A.; Ma, Y.; Wlodarczyk, D.; Suchocki, A.; Ovchinnikov, D.; Heine, T.; Maude, D. K.; Kis, A.; Plochocka, P.

We present a systematic investigation of the electronic properties of bulk and few layer ReS2 van der Waals crystals using low temperature optical spectroscopy. Weak photoluminescence emission is observed from two non-degenerate band edge excitonic transitions separated by ∼ 20 meV. The comparable emission intensity of both excitonic transitions is incompatible with a fully thermalized (Boltzmann) distribution of excitons, indicating the hot nature of the emission. While DFT calcu- lations predict bilayer ReS2 to have a direct fundamental band gap, our optical data suggests that the fundamental gap is indirect in all cases.

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Permalink: https://www.hzdr.de/publications/Publ-28007
Publ.-Id: 28007


2D Crystals in Three Dimensions: Electronic Decoupling of Single-Layered Platelets in Colloidal Nanoparticles

Kempt, R.; Kuc, A.; Han, J. H.; Cheon, J.; Heine, T.

Two-dimensional crystals, single sheets of layered materials, often show distinct properties desired for optoelectronic applications, such as larger and direct band gaps, valley- and spin-orbit effects. Being atomically thin, the low amount of material is a bottleneck in photophysical and photochemical applications. Here, we propose the formation of stacks of two-dimensional crystals intercalated with small surfactant molecules. We show, using first principles calculations, that already very short surfactant methyl amine electronically decouples the layers. We demonstrate the indirect-direct band gap transition characteristic for Group 6 transition metal dichalcogenides experimentally by observing the emergence of a strong photoluminescence signal for ethoxide-intercalated WSe2 and MoSe2 multilayered nanoparticles with lateral size of about 10 nm and beyond. The proposed hybrid materials offer the highest possible density of the two-dimensional crystals with electronic properties typical for monolayers. Variation of the surfactant’s chemical potential allows fine-tuning of electronic properties and potentially elimination of trap states caused by defects.

Permalink: https://www.hzdr.de/publications/Publ-28006
Publ.-Id: 28006


Electronic properties of 2D and 1D inorganic materials for applications in nano(opto)electronics

Kuc, A.

The nanoelectronic industry is rapidly approaching limits of the silicon-technology, what leads to a necessity of developing new technologies, which would replace silicon in the future. Therefore, searching for materials that perform better than silicon at the atomic scale became a very important topic in the electronic and materials sciences in the past decades. Recently, two-dimensional (2D) layered materials, such as graphene, black phosphorous, silicene, or transition-metal dichalcogenides (TMCs), have attracted great attention, because of their extraordinary electronic properties and, at the same time, very good mechanical stability, which are desired features for nanoelectornic applications. The progress in the production of such 2D crystals grows rapidly every year, therefore, it is very important to estimate, understand, and explore the fundamental physics of these materials, in order to boost breakthrough technologies.
Layered transition-metal dichalcogenides have gained increasing attention ever since the seminal works published in 2010 and 2011, showing phenomenal electronic properties of monolayered systems, their easy exfoliation from bulk materials, due to the weak interlayer interactions, as well as, their applications as building blocks in the nanoelectronic logical devices. In this thesis, we present selected research based of density-functional theory, which has been carried out on the subject of electronic structure of TMC and other 2D crystals. These materials exhibit electronic properties, which are easily tuned by external modulators, such as tensile strain, doping, electric or magnetic fields, formation of different polytypes. The change in the electronic properties of semiconducting TMCs due to these external modulators vary in a wide range, e.g., semiconductor-metal transition, Rashba, Zeeman and Stark effects, induced spin-orbit coupling in centrosymmetric bilayered forms by breaking of inversion symmetry, topologically protected states in topological insulators. We also present the coherent transport properties of these 2D materials using calculations based on the density functional based tight-binding method in combination with the non-equilibrium Green’s function technique and the Landauer-Büttiker formula.
We show that the intrinsic electronic structure of MoS2 and other semiconducting TMCs change with the number of layers in the film. The indirect-band gap in the bulks changes to a direct-band gap in the monolayers and the size of the band gap is nearly 1 eV larger for the latter forms. On top of the electronic band gaps, which are mainly discussed in this thesis, TMC exhibit also very large exciton binding energies, which need to be taken into account, when discussing overall electronic properties. TMC monolayers exhibit very large spin-orbit splitting in the valence bands, which varies between 150 and almost 500 meV, depending on the stoichiometry. Stacking different monolayers of TMC materials results in reduced direct-band gaps with much smaller values than the respective pure materials, which comes from the formation of the type II heterostructures. In such heterostructures, the valence band maximum is formed from the states of different layers. This results in materials with excitons localized in such a way that the electron is located in one layer and the hole in the other.
We believe that the knowledge gained from the research presented in this thesis can provide new perspectives for the applications of TMC materials in the next generation of nano(opto)electronic devices.

  • Other
    Jacobs University Bremen, 2018
    Mentor: Prof. Thomas Heine

Permalink: https://www.hzdr.de/publications/Publ-28005
Publ.-Id: 28005


Photochemical creation of covalent organic 2D monolayer objects in defined shapes via a lithographic 2D-polymerization

Servalli, M.; Celebi, K.; Payamyar, P.; Zheng, L.; Polozij, M.; Lowe∥, B.; Kuc, A.; Schwarz, T.; Thorwarth, K.; Borgschulte○, A.; Heine, T.; Zenobi, R.; Schlüter, A. D.

In this work, we prepare Langmuir-Blodgett monolayers with a trifunctional amphiphilic anthraphane monomer. Upon spreading at the air/water interface, the monomers self-assemble into 1 nm-thin monolayer islands, which are highly fluorescent and can be visualized by naked eye upon excitation. In-situ fluorescence spectroscopy indicates that in the monolayers, all the anthracene units of the monomers are stacked face-to-face forming excimer pairs, whereas at the edges of the monolayers free anthracenes are present acting as edge groups. Irradiation of the monolayer triggers [4+4]-cycloadditions among the excimer pairs, effectively resulting in a two-dimensional polymerization. The polymerization reaction also completely quenches the fluorescence, allowing to draw patterns on the monomer monolayers. More interestingly, after transferring the monomer monolayer on a solid substrate, by employing masks or the laser of a confo-cal scanning microscope, it is possible to arbitrarily select the parts of the monolayer that one wants to polymerize. The unpolymerized regions can then be washed away from the substrate, leaving two-dimensional macromolecular monolayer objects of the desired shape. This is the first photolithographic process that employs 2D-polymerizations and affords 1 nm-thin coatings.

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Permalink: https://www.hzdr.de/publications/Publ-28004
Publ.-Id: 28004


Probing charge transfer characteristics in a donor–acceptor metal–organic framework by Raman spectroelectrochemistry and pressure-dependence studies

Usov, P. M.; Leong, C. F.; Chan, B.; Hayashi, M.; Kitagawa, H.; Sutton, J. J.; Gordon, K. C.; Hod, I.; Farha, O. K.; Hupp, J. T.; Addicoat, M.; Kuc, A. B.; Heine, T.; D’Alessandro, D. M.

The stimuli responsive behaviour of charge transfer donor–acceptor metal–organic frameworks (MOFs) remains an understudied phenomenon which may have applications in tuneable electronic materials. We now report the modification of donor–acceptor charge transfer characteristics in a semiconducting tet- rathiafulvalene–naphthalene diimide-based MOF under applied electrochemical bias and pressure. We employ a facile solid state in situ Raman spectroelectrochemical technique, applied for the first time in the characterisation of electroactive MOFs, to monitor the formation of a new complex TTFTC􏰀+–DPNI from a largely neutral system, upon electrochemical oxidation of the framework. In situ pressure- dependent Raman spectroscopy and powder X-ray diffraction experiments performed in a diamond anvil cell revealed blue shifts in the donor and acceptor vibrational modes in addition to contractions in the unit cell which are indicative of bond shortening. This study demonstrates the utility of in situ Raman spectroscopic techniques in the characterisation of redox-active MOFs and the elucidation of their electronic behaviours.

  • Open Access Logo Physical Chemistry Chemical Physics 20(2018)40, 25772-25779
    Online First (2018) DOI: 10.1039/C8CP04157A

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Permalink: https://www.hzdr.de/publications/Publ-28003
Publ.-Id: 28003


Electronic structure of defective transition-metal dichalcogenides: theoretical investigations

Kuc, A.

We have investigated the electronic structure changes of transition-metal dichalcogenides (TMCs), when various structural defects are present [1]. Healing of the defects by formation of sandwich materials will be also discussed [2]. Moreover, adsorption of small molecules on the defect sites were investigeted and the resulting the band structures will be presented [3].
Defects have very strong influence on the electronic properties of TMC materials, especially on their electronic transport, which could be strongly suppressed in the presence of large defect concentration. Defects can be healed by donation of, e.g. chalcogen atoms, from other TMC layers in a sandwich materials. Moreover, in experiments, the defect sites are not free and different molecules could be adsorbed, depending on the conditions in which the defects are formed.

Keywords: Electronic properties of TMDCs

  • Lecture (Conference)
    Hengstberger Symposium, 22.-24.10.2018, Heidelberg, Germany

Permalink: https://www.hzdr.de/publications/Publ-28002
Publ.-Id: 28002


Effiziente Merkmalsextraktion für eine Echtzeit- Bilddatenauswertung der ultraschnellen Röntgentomographie

Boesler, M.

In dieser Arbeit wurde eine Bildverarbeitungsstrategie entwickelt, die eine automatische Erkennung von Objekten in Bildern der ultraschnellen Elektronenstrahl Röntgentomographie ermöglicht. Diese basiert auf einer pixelorientierten Segmentierung des geglätteten dynamischen Bildanteils.
Dabei wurden in der Auswahl der Algorithmen die problemspezifischen Voraussetzungen und Anforderungen, insbesondere an den Rechenaufwand und die Parallelisierbarkeit, berücksichtigt. Die entwickelte Bildverarbeitungsstrategie wurde an simulierten Bildern validiert. Dabei wurde zuerst eine für den betrachteten Parameterbereich optimale Filtergröße von 2 in z-Richtung bestimmt, sodass Objekte im Rahmen des gewählten Parameterbereiches sicher detektiert werden. Schließlich wurde der Einfluss unterschiedlicher Signal-Rausch-Verhältnisse, realisiert durch verschiedene Rauschamplituden, untersucht. Dabei hat sich gezeigt, dass die automatische Auswahl des Algorithmus zur Schwellwertbestimmung und eine damit zusammenhängende Fehleinschätzung der Pixelzahlen erheblich vom Signal-Rausch-Verhältnis abhängt. Abschließend wurde der Einfluss der Bildqualität, hervorgerufen durch eine Anpassung der Rekonstruktionsparameter, auf die Funktionsfähigkeit der Bildverarbeitungsstrategie studiert. Hierbei wurde festgestellt, dass eine Änderung der Zahl virtueller Parallelprojektionen qualitativ mit der Variation der Rauschamplitude übereinstimmt. Des Weiteren konnte beobachtet werden, dass sich eine geringere Bildauflösung auswirkt, als würde man kleinere Objekte betrachten.

Keywords: ultrafast X-ray; computed tomography; image processing; segmentation

  • Bachelor thesis
    TU Chemnitz, 2018
    Mentor: Dominic Windisch, Martina Bieberle, Guido Juckeland, Sibylle Gemming
    35 Seiten

Permalink: https://www.hzdr.de/publications/Publ-28001
Publ.-Id: 28001


Targeting cyclic nucleotide phosphodiesterase 5 (PDE5) in brain: Toward the development of a PET radioligand labeled with fluorine-18

Wenzel, B.; Liu, J.; Dukic-Stefanovic, S.; Deuther-Conrad, W.; Teodoro, R.; Ludwig, F.-A.; Chezal, J.-M.; Moreau, E.; Brust, P.; Maisonial-Besset, A.

With the aim to develop a specific radioligand for imaging the cyclic nucleotide phosphodiesterase PDE5 in brain by positron emission tomography (PET), seven new fluorinated inhibitors (3 – 9) were synthesized on the basis of a quinoline core. The inhibitory activity for PDE5 together with a panel of other PDEs was determined in vitro and two derivatives were selected for IC50 value determination. The most promising compound 7 (IC50 = 5.92 nM), containing a 3-fluoroazetidine moiety, was further radiolabeled by nucleophilic aliphatic substitution of two different leaving groups (nosylate and tosylate) using [18F]fluoride. The use of the nosylate precursor and tetra-n-butyl ammonium [18F]fluoride ([18F]TBAF) in 3-methyl-3-pentanol combined with the addition of a small amount of water proved to be best labeling conditions achieving a RCY of 4.9 ± 1.5% in an automated procedure. Preliminary biological investigations in vitro and in vivo were performed to characterize the new PDE5 radioligand. Metabolism studies of [18F]7 in mice revealed a fast metabolic degradation with the formation of radiometabolites which have been detected in the brain.

Keywords: PDE5; 18F-radiolabeling; nosylate; tosylate; 18F-fluoroazetidine

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Permalink: https://www.hzdr.de/publications/Publ-28000
Publ.-Id: 28000


High-Level Programming Approaches For Accelerators

Chandrasekaran, S.; Juckeland, G.

The Third Workshop on Accelerator Programming using Directives (WACCPD) was co-located with SC 2016 held on November 14, 2016, at Salt Lake City, Utah, USA. The workshop solicited papers on topics including hybrid heterogeneous or many-core programming with accelerator directives with other models (i.e., OpenMP, MPI, OpenSHMEM), scientific libraries interoperability with accelerator directives, programming experience porting applications in any domain, language-based extensions, and modelling and performance analysis tools.
Among the 20 submissions to the WACCPD workshop, we invited authors of seven papers to submit their extended manuscripts to a special issue with IJHPCN. The authors were asked to extend their paper by at the least 30% for the special issue by adding newer contents.
These seven manuscripts were peer-reviewed and the review process for the special issue was not double blind, i.e., authors were known to reviewers. Submissions were judged on correctness, originality, technical strength, and significance, quality of presentation, and interest and relevance to the conference scope. All the sevenmanuscripts were accepted to the special issue after two rounds of review.

  • Book (Editorship)
    Olney: Inderscience Enterprises Ltd., 2019
    128 Seiten
    ISBN: 1740-0570

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Permalink: https://www.hzdr.de/publications/Publ-27999
Publ.-Id: 27999


Strong Uranium(VI) Binding onto Bovine Milk Proteins, Selected Protein Sequences and Model Peptides

Zänker, H.; Heine, K.; Weiss, S.; Brendler, V.; Husar, R.; Bernhard, G.; Gloe, K.; Henle, T.; Barkleit, A.

Hexavalent uranium is ubiquitous in the environment. In view of the chemical and radiochemical toxicity of uranium(VI) a good knowledge of its possible interactions in the environment is crucial. The aim of this work was to identify typical binding and sorption characteristics of uranium(VI) with both the pure bovine milk protein β-casein and diverse related protein mixtures (caseins, whey proteins). For comparison selected model peptides representing the amino acid sequence 13-16 of β-casein and dephosphorylated β-casein were also studied. Complexation studies using potentiometric titration and time-resolved laser-induced fluorescence spectroscopy revealed that the phosphoryl-containing proteins form uranium(VI) complexes of higher stability than the structure-analog phosphoryl-free proteins. That is in agreement with the sorption experiments showing a significantly higher affinity of caseins towards uranium(VI) in comparison to whey proteins. On the other hand, the total sorption capacity of caseins is lower than that of whey proteins. The discussed binding behavior of milk proteins to uranium(VI) might open up interesting perspectives for sustainable techniques of uranium(VI) removal from aqueous solutions. That was further demonstrated by batch experiments on the removal of uranium(VI) from mineral water samples.

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Permalink: https://www.hzdr.de/publications/Publ-27998
Publ.-Id: 27998


Bioflotation: Verwendung der amphiphilen Siderophore Marinobactin im Prozess der Schaumflotation

Schrader, S.; Kutschke, S.; Pollmann, K.; Rudolph, M.

Der Bedarf metallischer Rohstoffe ist in den vergangenen Jahren stetig gestiegen. Dieser Nachfrage allerdings gerecht zu werden, gestaltet sich zunehmen schwieriger, da sowohl primäre als auch sekundäre Rohstoffquellen immer komplexer werden. Um dieser Herausforderung gegenüber zu treten, müssen neue Wege beschritten werden. Eine Möglichkeit stellt dabei die Kombination der Biotechnologie mit klassischen Methoden der Aufbereitung dar. So soll in dieser Arbeit die biotechnologische Produktion von Siderophoren und deren Anwendung im Prozess der Schaumflotation vorgestellt werden. Siderophoren sind kleine organische Moleküle, welche eine hohe Affinität besitzen Eisen zu binden, aber auch starke Komplexe mit anderen Metallen formen können. Ihre Bildung erfolgt durch Mikroorganismen (aerobe Bakterien und Pilze) sowie Pflanzen bei einer geringen Bioverfügbarkeit von Eisen in deren Umgebung. Speziell die Gruppe der amphiphilen Siderophoren ist für die vorgesehene Anwendung von besonderem Interesse. Der hydrophile Bereich, welcher die funktionellen Hydroxamaten-Gruppen beinhalte, ist für die Bindung des Metalls zuständig, wohingegen der hydrophobe Teil, dargestellt durch unterschiedlich lange Fettsäureschwänze, in Interaktion mit der Blase treten soll. Beide Struktureinheiten finden bereits unabhängig erfolgreich Anwendung im Prozess der Flotation, werden allerdings bisher vorwiegend durch die chemische Industrie zur Verfügung gestellt.
Diese Arbeit stellt zum einen eine verbesserte Produktion der amphiphilen Siderophore Marinobactin unter der erstmaligen Verwendung eines Bioreaktors dar.
Weiterhin werden erste Experimente unterschiedlichster Maßstäbe zur Untersuchung von Interaktions- und Flotationsvorgängen vorgestellt. Dies erfolgt mit Hilfe des „Bubble-pick-up-Tests“, der Mikroflotation in der Halimond Röhre sowie Flotationsversuchen im ein Liter Labormaßstab. Dabei wurden eisen- und kupferhaltige Minerale getestet.
Die Verwendung amphiphiler Siderophoren als Biochemikalie in der Schaumflotation birgt das Potenzial diesen klassischen Prozess der Aufbereitung nachhaltiger zu gestalten und als Bioflotation zu definieren. Dies soll zum einen mit der Reduktion der bisher verwendeten Chemikalien erfolgen. Zum anderen sollen spezifische Metallbindungen mit Hilfe der Siderophoren einen gezielteren und effizienteren Prozess formen. Die erfolgreiche Etablierung eines Bioflotation Prozesses würde dann auch eine wichtige Ergänzung für den Bereich der Biohydrometallurgie darstellen.

Keywords: Marinobactin; Marinobacter; Flotation; Bioflotation; Siderophore

  • Poster
    Tagung Aufbereitung und Recycling, 14.-15.11.2018, Freiberg, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27997
Publ.-Id: 27997


Application of amphiphilic siderophores in froth flotation process

Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.

Siderophores are biomolecules, which can form strong complexes with different metals. They are produced by microorganisms and a biotechnological production of these chelators offers an application in different processing methods. Particularly amphiphilic siderophores are very interesting for the froth flotation process. The hydrophilic part, carrying hydroxamate groups is responsible for the binding of the metals. Flotation agents produced by the chemical industry with the same functional groups have already been applied successfully in this processing method. It can be suggested, that siderophores carrying the same functional groups, also work well as collectors. The fatty acid tail, that is representing the hydrophobic part, gets in contact with the bubbles and avoid additional chemicals and further working steps for making the target mineral particles hydrophobic. The aim of this study is to show the usage of amphiphilic siderophores in froth flotation process in different scales and with different minerals.

Keywords: Siderophore; Marinobactin; Marinobacter; Flotation; Bioflotation

  • Lecture (Conference)
    Sustainable Minerals 2018, 14.-15.06.2018, Windhoek, Namibia

Permalink: https://www.hzdr.de/publications/Publ-27996
Publ.-Id: 27996


Production of amphiphilic siderophores for bioflotation process

Schrader, S.; Kutschke, S.; Rudolph, M.; Pollmann, K.

Siderophores are small organic molecules with a high affinity for binding Fe(III) and to form strong complexes also with other metals. They are produced by microorganisms (aerobic bacteria and fungi) and some plants to equalize the low bioavailability of iron in their environment.
A lot of microorganisms and their produced siderophores have already been identified and analyzed in detail. Until now, siderophores are only used as medicine against iron or heavy metal poisoning. The biotechnological production offers the application in very different fields, like extraction, recovery and treating of different metals. Especially the group of amphiphilic siderophores are very interesting for the classical froth flotation process. The aim of this study is the optimized and efficient biotechnological production of the amphiphilic siderophore Marinobactin by the marine bacterium Marinobacter sp. DS40M6 and to show for the first time that it is possible to use these biomolecules in froth flotation process.

Keywords: Siderophore; Marinobactin; Marinobacter; Flotation; Bioflotation

  • Poster
    Biohydrometallurgy 2018, 11.-13.06.2018, Windhoek, Namibia

Permalink: https://www.hzdr.de/publications/Publ-27995
Publ.-Id: 27995


Voltage-controlled ON-OFF ferromagnetism at room temperature in a single metal oxide film

Quintana, A.; Menéndez, E.; Liedke, M. O.; Butterling, M.; Wagner, A.; Sireus, V.; Torruella, P.; Estradé, S.; Peiró, F.; Dendooven, J.; Detavernier, C.; Murray, P.; Gilbert, D. A.; Liu, K.; Pellicer, E.; Nogués, J.; Sort, J.

Electric-field controlled magnetism can boost energy-efficiency in widespread applications. However, technologically, this effect is facing important challenges: mechanical failure in strain-mediated piezoelectric/magnetostrictive devices, dearth of room-temperature multiferroics or stringent thickness limitations in electrically-charged metallic films. Voltage driven ion motion (magneto-ionics) circumvents most of these drawbacks while offering unprecedented magnetoelectric phenomena. Nevertheless, magneto-ionics typically requires heat-treatments and multi-component heterostructures. Here we report on the electrolytegated and defect-mediated O and Co transport in a Co3O4 single layer which allows for roomtemperature voltage-controlled ON-OFF ferromagnetism (magnetic switch) via internal reduction/oxidation processes. Negative voltages partially reduce Co3O4 to Co (ferromagnetism: ON), resulting in graded films including Co- and O-rich areas. Positive bias oxidizes Co back to Co3O4 (paramagnetism: OFF). This electric-field-induced atomic-scale reconfiguration process is compositionally, structurally and magnetically reversible and self sustained since no oxygen source other than the Co3O4 itself is required. This novel process could lead to new electric-field-controlled device concepts for spintronics

Keywords: electric field; ionic transport; magnetic phase transition; Co3O4; positron annihilation; spintronic

Permalink: https://www.hzdr.de/publications/Publ-27994
Publ.-Id: 27994


Fourier Analysis of Cerebral Metabolism of Glucose: Gender Differences in Mechanisms of Color Processing in the Ventral and Dorsal Streams in Mice

Njemanze, P. C.; Kranz, M.; Brust, P.

Conventional imaging methods could not distinguish processes within the ventral and dorsal streams. The application of Fourier time series analysis was helpful to segregate changes in the ventral and dorsal streams of the visual system in male and female mice. The present study measured the accumulation of [18F]fluorodeoxyglucose ([18F]FDG) in the mouse brain using small animal positron emission tomography and magnetic resonance imaging (PET/MRI) during light stimulation with blue and yellow filters compared to darkness condition. Fourier analysis was performed using mean standardized uptake values (SUV) of [18F]FDG for each stimulus condition to derive spectral density estimates for each condition. In male mice, luminance opponency occurred by S-peak changes in the sub-cortical retino-geniculate pathways in the dorsal stream supplied by ganglionic arteries in the left visual cortex, while chromatic opponency involved C-peak changes in the cortico-subcortical pathways in the ventral stream perfused by cortical arteries in the left visual cortex. In female mice, there was resonance phenomenon at C-peak in the ventral stream perfused by the cortical arteries in the right visual cortex in female mice during luminance processing. Conversely, chromatic opponency occurred by S-peak changes in the subcortical retino-geniculate pathways in the dorsal stream supplied by the ganglionic arteries in the right visual cortex. In conclusion, Fourier time series analysis uncovered distinct mechanisms of color processing in the ventral stream in male, while in female mice color processing was in the dorsal stream. It demonstrated that computation of colour processing as a conscious experience could have a wide range of applications neuroscience, artificial intelligence and quantum mechanics.

Keywords: chromatic opponency; sex differences; light wave; light particle; blood flow; frequency; resonance

Permalink: https://www.hzdr.de/publications/Publ-27992
Publ.-Id: 27992


Highly Sensitive Electromechanical Piezoresistive Pressure Sensors Based on Large-Area Layered PtSe2 Films

Wagner, S.; Yim, C.; Mcevoy, N.; Kataria, S.; Yokaribas, V.; Kuc, A. B.; Pindl, S.; Fritzen, C.-P.; Heine, T.; Duesberg, G. S.; Lemme, M. C.

Two-dimensional (2D) layered materials are ideal for micro- and nanoelectromechanical systems (MEMS/NEMS) due to their ultimate thinness. Platinum diselenide (PtSe2), an exciting and unexplored 2D transition metal dichalcogenide material, is particularly interesting because its low temperature growth process is scalable and compatible with silicon technology. Here, we report the potential of thin PtSe2 films as electromechanical piezoresistive sensors. All experiments have been conducted with semimetallic PtSe2 films grown by thermally assisted conversion of platinum at a complementary metal−oxide−semiconductor (CMOS)-compatible temperature of 400 °C. We report high negative gauge factors of up to −85 obtained experimentally from PtSe2 strain gauges in a bending cantilever beam setup. Integrated NEMS piezoresistive pressure sensors with freestanding PMMA/PtSe2 membranes confirm the negative gauge factor and exhibit very high sensitivity, outperforming previously reported values by orders of magnitude. We employ density functional theory calculations to understand the origin of the measured negative gauge factor. Our results suggest PtSe2 as a very promising candidate for future NEMS applications, including integration into CMOS production lines.

Keywords: Pressure sensors; platinum diselenide; two-dimensional; gauge factors; strain sensors

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Permalink: https://www.hzdr.de/publications/Publ-27990
Publ.-Id: 27990


Ionenstrahlanalytik im Helium-Ionen-Mikroskop

Klingner, N.

Die vorliegende Arbeit beschreibt die Implementierung ionenstrahlanalytischer Methoden zur Charakterisierung der Probenzusammensetzung in einem Helium-Ionen-Mikroskop mit einem auf unter einen Nanometer fokussierten Ionenstrahl. Zur Bildgebung wird dieser im Mikroskop über Probenoberflächen gerastert und die lokale Ausbeute an Sekundärelektronen gemessen. Obwohl sich damit ein hoher topografischer Kontrast erzeugen lässt, lassen sich weder aus der Ausbeute noch aus der Energieverteilung der Sekundärelektronen verlässliche Aussagen zur chemischen Zusammensetzung der Probe treffen. Daher wurden in dieser Arbeit verschiedene ionenstrahlinduzierte Sekundärteilchen hinsichtlich ihrer Eignung für die Elementanalytik im Helium-Ionen-Mikroskop verglichen. Zur Evaluation standen der Informationsgehalt der Teilchen, deren Analysierbarkeit sowie deren verwertbare Ausbeute. Die Spektrometrie rückgestreuter Teilchen sowie die Sekundärionen-Massenspektrometrie wurden dabei als die geeignetsten Methoden identifiziert und im Detail untersucht. Gegenstand der Untersuchung waren physikalische Limitierungen und Nachweisgrenzen der Methoden sowie deren Eignung zum Einbau in ein Helium-Ionen-Mikroskop. Dazu wurden verschiedene Konzepte von Spektrometern evaluiert, erprobt und hinsichtlich ihrer Effizienz, Energieauflösung und Umsetzbarkeit im Mikroskop bewertet. Die Flugzeitspektrometrie durch Pulsen des primären Ionenstrahls konnte als die geeignetste Technik identifiziert werden und wurde erfolgreich in einem Helium-Ionen-Mikroskop implementiert. Der Messaufbau, die Signal- und Datenverarbeitung sowie vergleichende Simulationen werden detailliert beschrieben. Das Spektrometer wurde weiterhin ausführlich hinsichtlich Zeit-, Energie- und Massenauflösung charakterisiert. Es werden ortsaufgelöste Rückstreuspektren vorgestellt und damit erstmalig die Möglichkeit zur Ionenstrahlanalytik im Helium-Ionen-Mikroskop auf einer Größenskala von ≤ 60 nm aufgezeigt. Das Pulsen des primären Ionenstrahls erlaubt es zudem, die Technik der Sekundärionen-Massenspektrometrie anzuwenden. Diese Methode bietet Informationen zur molekularen Probenzusammensetzung und erreicht für einige Elemente niedrigere Nachweisgrenzen als die Rückstreuspektrometrie. Damit konnten erstmalig im Helium-Ionen-Mikroskop gemessene Sekundärionen-Massenspektren sowie die ortsaufgelöste Elementanalyse durch spektrometrierte Sekundärionen demonstriert werden. Die Ergebnisse dieser Arbeit sind in der Fachzeitschrift Ultramicroscopy Band 162 (2016) S. 91–97 veröffentlicht. Ab Oktober 2016 werden diese auch in Form eines Buchkapitels in dem Buch „Helium Ion Microscopy“, Springer Verlag Heidelberg zur Verfügung stehen.

Keywords: Helium-Ionen-Mikroskop; Ionenstrahlanalytik

  • Doctoral thesis
    TU Dresden, 2017
    Mentor: Jürgen Faßbender
    153 Seiten

Permalink: https://www.hzdr.de/publications/Publ-27989
Publ.-Id: 27989


NMR-based investigations of acyl-functionalized piperazines concerning their conformational behavior in solution

Steinberg, J.; Köckerling, M.; Wodtke, R.; Löser, R.; Mamat, C.

Selected N-benzoylated piperazine derivatives were synthesized to study their conformational behavior using temperature-dependent 1H NMR spectroscopy. All investigated piperazine compounds occur as conformers at room temperature resulting from the reduced rotation of the partial amide double bond. Furthermore, a second conformational shape was observed for selected mono-N-benzoylated and unsymmetrically N,N’-substituted derivatives due to the limited change of the piperazine chair conformation. Therefore, two different coalescence points TC were determined and their resulting activation energy barriers ΔG# were calculated to be between 50 and 70 kJ/mol. In most of the cases, TC and ΔG# for the amide site appeared to be higher as for the amine site. Furthermore, benzoate moieties with electron withdrawing substituents like nitro show a higher rotational barrier compared to electron-releasing substitutents like methoxy. An additional aryl substituent connected at the amine site led to a reduced rotational barrier compared to the free secondary amine. To support and evidence the findings from the NMR analyses, single crystals of piperazines were obtained and XRD analyses were performed. To underline the results, two potential Tgase 2 inhibitors were investigated showing energy barriers with similar values.

Keywords: NMR; rotation barrier; piperazines; coalescence

Permalink: https://www.hzdr.de/publications/Publ-27988
Publ.-Id: 27988


Calix[4]crown-6 scaffold for the complexation of barium and radium

Bauer, D.; Reissig, F.; Steinberg, J.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.

Radium is the heaviest known member of the alkaline earth metals and all 33 of its isotopes are radioactive. Two of these, radium-223 and radium-224, have suitable half-lives with 11.4 d and 3.6 d, respectively, and nuclear decay properties that make them useful tools for alpha particle therapy. Unfortunately, no suitable chelating agents are available for a stable complexation. Thus, radium-223 is only in use as radium chloride to treat bone metastases. For this purpose, a series of modified calix[4]crown-6 derivatives was synthesized to chelate heavy group 2 metal ions like barium, which serves as a non-radioactive surrogate for radium-223/-224.
The calix[4]arene framework can be seen as an ideal platform to build an optimized chelator. Two of the four hydroxy groups of the lower rim can be functionalized as deprotonizable groups to form a neutral complex with barium or radium; the remaining two are bridged by a crown ether moiety. With this concept, the advantages of the electrostatic, macrocyclic, and cryptate effect are combined. Another benefit of the calixcrowns is their easy access.
As a result, our calix[4]crowns were functionalized with either cyclic amide moieties or with deprotonizable groups like carboxylic acids or hydroxyl amines, and the corresponding barium complexes were synthesized.
To prove the ability of these chelators for a further usage in radiopharmacy, stability constants of the corresponding barium complexes were determined by using NMR and UV/Vis titration to determine logK values. Further extraction studies were performed to characterize the binding affinity of calixcrowns to barium-133 and radium-224.

Keywords: calixarene; alkaline earth metals; barium; radium

  • Poster
    The Third International Symposium on Technetium and other Radiometals in Chemistry and Medicine, 26.-29.09.2018, Bressanone, Italien

Permalink: https://www.hzdr.de/publications/Publ-27987
Publ.-Id: 27987


Chelatoren für die Komplexierung schwerer Erdalkalimetallionen

Reissig, F.; Bauer, D.; Pietzsch, H.-J.; Steinbach, J.; Mamat, C.

Ziel:
Nach dem heutigen Stand sind keine geeigneten Chelatoren zur stabilen Komplexierung von schweren Erdalkalimetallen Barium und Radium bekannt. Da die Alphaemitter Radium-223 Radium-224 jedoch hohes therapeutisches Potential besitzen, ist die Entwicklung von multimodalen Liganden von großem Interesse. Ein solcher Ligand könnte eine Matched-Pair-Strategie eröffnen. Während Radium-223 und Radium-224 therapeutisch einsetzbar sind, besitzt Barium-131, welches analoge chemische Eigenschaften aufzeigt, gute diagnostische Eigenschaften. Bis jetzt ist die klinische Nutzung von Radium auf die Behandlung von Knochenmetastasen durch das calcimimetische Radiopharmakon [223Ra]RaCl2 (Xofigo®) beschränkt. Diese Anwendung gilt es zu erweitern.

Methodik:
Radium-224 wurde in Form seines Nitrats mittels Ionenaustauschchromatographie aus einem Thorium-228-Generator gewonnen. Als Bariumisotop für Extraktionsstudien wurde das langlebige und kommerziell erhältliche Radionuklid Barium-133 genutzt. Die Radiomarkierungen wurden mittels HPLC und Extraktionsstudien charakterisiert.
Stabilitätskonstanten wurden mit stabilem Barium mittels UV/Vis und Kalorimetrie berechnet. Mit den Radiometallen Barium-133 und Radium-224 konnten vergleichbare Konstanten mittels Zwei-Phasen-Extraktion (Wasser/Chloroform) bestimmt werden.
Als Liganden dienten unter anderem verschieden funktionalisierte, 18-Krone-6-überbrückte Calix[4]-arene.

Ergebnisse:
Es wurden vier Liganden auf Calix[4]-aren-Basis dargestellt und deren Interaktion mit Bariumionen untersucht. Ein relativ hohe Stabilitätskonstante konnte vor allem für ein Sulfonamid-Derivat ermittelt werden. Angeschlossene Extraktionsstudien zeigten für diesen Liganden eine nahezu vollständige Extraktion von [133Ba]Ba2+ aus der wässrigen Phase unter physiologischen Bedingungen.
Analoge Versuche wurden mit [224Ra]Ra2+ durchgeführt. Der Komplex zeigte dabei eine ähnliche Stabilität.
Schlussfolgerungen:
Der Sulfonamid-Ligand wurde als potenter Chelator für Radium/Barium identifiziert. Weitere Modifikationen werden erfolgen, um die Stabilität weiter zu erhöhen und eine Biokompatibilität zu ermöglichen. In-vitro- und in-vivo-Studien müssen vorbereitet werden.

Keywords: Calixarene; Erdalkalimetalle; Komplexierung; Barium; Radium

  • Lecture (Conference)
    23. Jahrestagung der Arbeitsgemeinschaft Radiochemie & Radiopharmazie, 20.-22.09.2018, Aachen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-27986
Publ.-Id: 27986


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