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39109 Publications

Long-term stability of the microstructure of austenitic ODS steel rods produced with a carbon-containing process control agent

Gräning, T.; Klimenkov, M.; Rieth, M.; Heintze, C.; Möslang, A.


Oxide dispersion strengthened (ODS) steels have proven to be a viable candidate as a structural material in a fusion power plant, due to their enhanced mechanical properties and resilience under irradiation and at high temperatures. A high interest in the development of austenitic ODS (AODS) steel became noticeable, which is shown by the increased amount of publications in that field in the recent years. That can be related to the inherently better corrosion resistance and superior creep properties compared to its ferritic counterpart. However, one of the major drawbacks of AODS steels was the more challenging mechanical alloying (MA) process and a lower powder production yield, caused by a more ductile and adhesive powder. This disadvantage was tackled by the addition of a process control agent (PCA) during the MA, but it was yet to be shown how the addition of a PCA affects the microstructure of the AODS.


AODS with a carbon-containing PCA was mechanical alloyed, hot-extruded, and subsequently annealed at 700, 900, and 1100 °C for 2, 750, 1000, 1250 and 1500 hours to investigation the influence of carbon on the formation and stability of precipitates as well as on the grain size in comparison to available literature data. Scanning and transmission electron microscopy and atom probe tomography methods were applied in this systematic study to identify the possible growth of nano-precipitates. An Arrhenius-equation was used to determine the activation energy of the growth of precipitates.

Results and Discussion:

A growth of precipitates is barely detectable at temperatures equal or lower than 900 °C. The grain size remains stable. However, an unexpected increase of the grain and precipitates sizes and a decreased activation energy was measured at temperatures of 1100 °C for all annealing times. Recently published results of similar AODS steels have shown a stability of the microstructure up to 1250 °C. Due to this contradiction, we concluded that the growth of precipitates and the reduction of the grain boundary pinning force was supported by the diffusion of carbon and the formation of carbides.

Related publications

Publ.-Id: 27908

On the role of Ni, Si and P on the microstructural evolution of FeCr alloys under irradiation

Gómez-Ferrer, B.; Heintze, C.; Pareige, C.

In this experimental work the behaviour of Ni, Si and P, typical impurities or low alloying elements in ferritic/martensitic nuclear steels, with increasing irradiation dose was investigated in model FeCrX (X = Ni, Si, P, NiSiP) alloys using atom-probe 3D maps. These elements are known to increase the embrittlement and the hardening of steels by segregating at internal surfaces and creating solute-rich clusters at 300°C. This study is focused on the analysis of the clusters and the influence of every chemical specie in their formation. The model alloys have been irradiated with 5 MeV Fe2+ ions up to 0.1 and 0.5 dpa at 300°C and the 3D atom maps have been analysed using statistical tools and iso-concentration algorithms. P is proven to be the fastest diffuser whereas Ni and Si are slower. The three species segregate together strengthening the idea that they are decorating stable defect clusters by dumbbell or vacancy dragging. And no apparent influence on the clustering of every element over the others is observed up to 0.1dpa, suggesting the absence of synergistic effect between these species.

Related publications

Publ.-Id: 27907

The (Geo) Metallurgy of the Circular Economy

Reuter, M. A.

Circular economy (CE) is defined here in terms of the metallurgical Internet of Things (m-IoT). This is the digitalized Web of Metals (WoM) or, in other words, the system integrated material production (SIMP). Its digitalization provides the real-time detail that quantifies the three pillars of sustainability: social, environmental, and economical. This is termed ‘‘circular economy engineering’’ (CEE), i.e., the digitalization of the CE, using among others the theory and technology of minerals processing, metallurgy, recycling, computer-aided engineering (CAE), and product design. This provides the basis for the estimation of the metrics of resource efficiency (RE) and, hence, provides a direction for innovation and also enables the m-IoT.

Geometallurgy is now largely accepted as the process to quantify and understand a mineral deposit in terms of its structure, composition and ultimately to determine its economic value.
Geometallurgy 2018 will bring together experts from academia and industrial research, practitioners from operating mines, consultants and contractors as well as industry bodies with the aim of increasing the understanding and value of mineral assets.

Keywords: Circular economy; digitalization; metallurgy; recycling; resource efficiency

  • Invited lecture (Conferences)
    GEOMETALLURGY 2018, 19.-20.04.2018, London, Großbritannien

Publ.-Id: 27906

Redirecting switchable UniCAR T cells for elimination of radioresistant cancer cells

Feldmann, A.; Arndt, C.; Bergmann, R.; Berndt, N.; Jureczek, J.; Albert, S.; Lindner, D.; Koristka, S.; Steinbach, J.; Ehninger, G.; Krause, M.; Kurth, I.; Dubrovska, A.; Bachmann, M.

Radiation therapy represents a commonly applied treatment regimen for solid tumors. Unfortunately, it is often accompanied by a high risk for the outgrowth of radioresistant cancer cells against which treatment options are limited. We challenged the idea whether or not chimeric antigen receptor (CAR)-modified T cells could be exploited as an adjuvant immunotherapy in combination with standard radiotherapy. Over the past several years, we have established switchable universal CAR constructs (UniCARs) that recognize a short peptide epitope (E5B9) which does not exist on the surface of living cells. UniCAR T cells are redirected to malignant cells exclusively in the presence of a target module (TM) that contains the epitope E5B9 and specifically binds to a tumor-associated antigen (TAA) on the tumor cell surface.
For providing a rationale for the combination of CAR and radiation therapy, we used different radioresistant sublines of the head and neck cancer cell line Cal33. Expression of various TAAs including of PSCA, EGFR and CD98 was confirmed by flow cytometry analysis. Subsequently, TMs recognizing these potential targets were generated from the variable domains of monoclonal antibodies, cloned into lentiviral vectors and purified from cell culture supernatants of TM-producing stable cell lines. In parallel, T cells isolated from healthy donors were engrafted with UniCARs by lentiviral transduction. Armed with our anti-TAA TMs, UniCAR T cells efficiently lysed radioresistant Cal33 tumor cells both in vitro and in vivo.
Taken together, we could demonstrate that radioresistant cancer cells can effectively be killed by retargeting UniCAR T cells against PSCA, CD98 and EGFR. Thus, resistance to standard of care radiotherapy can be overcome by concomitant or subsequent immunotherapy using the flexible UniCAR technology.

Keywords: radiation therapy; immunotherapy; chimeric antigen receptors

  • Lecture (Conference)
    ICLE 2018, International Conference on Lymphocyte Engineering 2018, 13.-15.09.2018, Madrid, Spanien
  • Open Access Logo Abstract in refereed journal
    Human Gene Therapy 29(2018)11, ICLE8-0040
    DOI: 10.1089/hum.2018.29071.abstracts

Publ.-Id: 27904

Directionality of nickel-induced layer exchange during graphitization in carbon-nickel thin films

Janke, D.; Wenisch, R.; Munnik, F.; Hübner, R.; Grenzer, J.; Gemming, S.; Rafaja, D.; Krause, M.

Metal-induced crystallization with layer exchange (MIC w LE) can reduce the crystallization temperature of group 14 elements by several hundred degrees. This is especially interesting for device fabrication on substrates with limited thermal stability. Ideally, the process allows the transfer of defined amounts of an initially amorphous material onto a randomly selected substrate. In this contribution, MIC w LE is studied for Ni/ a-C thin films with different stacking sequences in order to quantify the influence of the stacking sequence on the layer exchange degree αLE and on the degree of graphitic ordering. The process was monitored in situ by temperature-dependent Rutherford backscattering spectrometry (RBS) and Raman spectroscopy up to 700 °C. RBS, Raman, elastic recoil detection, X-ray diffraction and transmission electron microscopy were applied for ex situ characterization.
The highest αLE of 96% was found for the initial Ni/a-C stacking sequence. In contrast, the inverse sequence resulted in an incomplete LE. The formation of 2D-layered carbon structures occurred independently of the initial stacking sequence.1 Beyond the threshold of 580 °C, increasing the temperature to up to 700 °C had a negligible impact on the degree of 2D-ordering. Since LE and graphitization occur simultaneously at high temperatures, MIC w LE rather than dissolution/ precipitation is proposed as responsible mechanism for carbon crystallization.

Keywords: metal-induced crystallization; directionality; amorphous carbon; nickel; graphitization; layer exchange; ERD; Raman; TEM

Related publications

  • Lecture (Conference)
    Flatlands 2018, 03.-07.09.2018, Leipzig, Deutschland

Publ.-Id: 27903

Digitalizing the Circular Economy - Metallurgical process system is the carrier

Reuter, M. A.

Metallurgy is a key enabler of a circular economy (CE), its digitization is the metallurgical Internet of Things (m-IoT). In short: Metallurgy is at the heart of a CE, as metals all have strong intrinsic recycling potentials. Process metallurgy, as a key enabler for a CE, will help much to deliver its goals. The first-principles models of process engineering help quantify the resource efficiency (RE) of the CE system, connecting all stakeholders via digitization. This provides well-argued and first-principles environmental information to empower a tax paying consumer society, policy, legislators, and environmentalists. It provides the details of capital expenditure and operational expenditure estimates. Through this path, the opportunities and limits of a CE, recycling, and its technology can be estimated. The true boundaries of sustainability can be determined in addition to the techno-economic evaluation of RE. The integration of metallurgical reactor technology and systems digitally, not only on one site but linking different sites globally via hardware, is the basis for describing CE systems as dynamic feedback control loops, i.e., the m-IoT. It is the linkage of the global carrier metallurgical processing system infrastructure that maximizes the recovery of all minor and technology elements in its associated refining metallurgical infrastructure.

Keywords: circular economy; digitization; recycling; resource efficiency; sustainability

  • Invited lecture (Conferences)
    8th Forum of Non-Ferrous Metals, 21.-23.02.2018, Krakau, Polen

Publ.-Id: 27902

Digitalizing the Circular Economy - Fairphone as example

Reuter, M. A.

The limitations to materials flows from recycling in the circular economy are discussed using as a case a simulation-based analysis of the recyclability of the Fairphone 2. Three different recycling routes are analysed using simulation models that link the bill of materials and full material declarations to the final metal recovery via physical separation models. The recycling and recovery rates are depicted in an innovative recycling index and material flower that helps drive the discussion about the inevitable trade-offs between the recyclability of different target materials and debunks the myth of a total recyclability of materials. Modular design is shown to have clear recycling as well as environmental advantages. This study is part of the SustainablySMART project.

Keywords: Circular Economy; Design for Recycling; Fairphone; Simulation; Recycling-Index

  • Invited lecture (Conferences)
    Circular Materials Conference, 07.-08.03.2018, Göteborg, Schweden

Publ.-Id: 27901

Simulation based Design for Recycling - Fairphone as an example

Reuter, M. A.

The limitations to materials flows from recycling in the circular economy are discussed using as a case a simulation-based analysis of the recyclability of the Fairphone 2. Three different recycling routes are analysed using simulation models that link the bill of materials and full material declarations to the final metal recovery via physical separation models. The recycling and recovery rates are depicted in an innovative recycling index and material flower that helps drive the discussion about the inevitable tradeoffs between the recyclability of different target materials and debunks the myth of a total recyclability of materials. Modular design is shown to have clear recycling as well as environmental advantages. This study is part of the SustainablySMART project.

Keywords: Circular Economy; Design for Recycling; Fairphone; Simulation; Recycling-Index

  • Invited lecture (Conferences)
    Berliner Recycling- und Rohstoffkonferenz, 19.03.2018, Berlin, Deutschland

Publ.-Id: 27900

Neoadjuvant radiochemotherapy significantly alters the phenotype of plasmacytoid dendritic cells and 6-sulfo LacNAc+ monocytes in rectal cancer

Wagner, F.; Hölig, U.; Wilczkowski, F.; Sommer, U.; Wehner, R.; Kießler, M.; Jarosch, A.; Plesca, I.; Flecke, K.; Arsova, M.; Tunger, A.; Bogner, A.; Reißfelder, C.; Weitz, J.; Schäkel, K.; Troost, E.; Krause, M.; Folprecht, G.; Bornhäuser, M.; Bachmann, M.; Aust, D.; Baretton, G.; Schmitz, M.

Neoadjuvant radiochemotherapy (nRCT) can significantly influence the tumor immune architecture that plays a pivotal role in regulating tumor growth. Whereas various studies have investigated the effect of nRCT on tumor-infiltrating T cells, little is known about its impact on the frequency and activation status of human dendritic cells (DCs). Plasmacytoid DCs (pDCs) essentially contribute to the regulation of innate and adaptive immunity and may profoundly influence tumor progression. Recent studies have revealed that higher pDC numbers are associated with poor prognosis in cancer patients. 6-sulfo LacNAc-expressing monocytes (slanMo) represent a particular proinflammatory subset of human non-classical blood monocytes that can differentiate into DCs. Recently, we have reported that activated slanMo produce various proinflammatory cytokines and efficiently stimulate natural killer cells and T lymphocytes. slanMo were also shown to accumulate in clear cell renal cell carcinoma and in metastatic lymph nodes from cancer patients.
In the present study, we investigated the influence of nRCT on frequency and phenotype of rectal cancer-infiltrating pDCs and slanMo. When evaluating rectal cancer tissues obtained from patients after nRCT, a significantly higher frequency of pDCs in comparison to non-matched pre-nRCT tissue samples was found. In contrast, the density of slanMo was not significantly altered by nRCT. These findings were confirmed when analyzing matched pre-nRCT and post-nRCT rectal cancer specimens. Further studies revealed that nRCT significantly increases the percentage of mature CD83+ pDCs in rectal cancer tissues. Moreover, the proportion of pDCs locally expressing interferon-alpha, which plays a major role in antitumor immunity, was significantly higher in post-nRCT. In addition, nRCT markedly enhanced the percentage of inducible nitric oxide synthase- or tumor necrosis factor alpha-producing slanMo in rectal cancer tissues. These novel findings indicate that nRCT significantly influences the frequency and/or phenotype of pDCs and slanMo, which may influence the clinical response of rectal cancer patients to nRCT.

Keywords: plasmacytoid dendritic cells; 6-sulfo LacNAc+ monocytes; tumor immune architecture; radiochemotherapy; rectal cancer

Publ.-Id: 27899

Structure-property relationship of Co2MnSi thin films in response to He+-irradiation

Hammerath, F.; Bali, R.; Hübner, R.; Brandt, M. R. D.; Rodan, S.; Potzger, K.; Böttger, R.; Sakuraba, Y.; Büchner, B.; Wurmehl, S.

We investigated the structure-property relationship of Co2MnSi Heusler thin films upon the irradiation with He+ ions. The variation of the crystal structure with increasing ion fluence has been probed using nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM), and associated with the corresponding changes of the magnetic behavior. A decrease of both the structural order and the moment in saturation is observed. Specifically, we detect a direct transition from a highly L21-ordered to a fully A2-disordered structure type and quantify the evolution of the A2 structural contribution as a function of ion fluence. Complementary TEM analysis reveals a spatially-resolved distribution of the L21 and A2 phases showing that the A2 disorder starts at the upper part of the films. The structural degradation in turn leads to a decreasing magnetic moment in saturation in response to the increasing fluence.

Keywords: Structure-property relationship; Heusler; thin films; Ion irradiation

Related publications

  • Open Access Logo Scientific Reports 9(2019), 2766
    DOI: 10.1038/s41598-019-39435-4
    Cited 6 times in Scopus
  • Lecture (Conference)
    DPG-Frühjahrstagung der Sektion Kondensierte Materie (SKM) gemeinsam mit der European Physical Society (CMD), 11.-16.03.2018, Berlin, Deutschland

Publ.-Id: 27898

Data Analysis and Machine Learning at the Computational Science Group

Kelling, J.

In this talk I will summarize the current activities of the computational science group at HZDR, which range from establishing research data publication (RODARE) and management platforms to providing numerical and computational expertise in various research projects. The latter aspect will be presented in detail through two selected ongoing projects.

In a project with the institute for resource ecology at HZDR, we developed a framework for the analysis of spectra of mixed solutions. The goal of the analysis is to discover how many species are in a given sample and in what concentration while at the same time extracting their unknown spectrum. A number of numerical techniques can be employed to this end, each requiring different amounts prior knowledge and different types of measurements. Here the primary task of the analysis framework is to unify a zoo of different implementations of similar methods and making all methods available to all scientists. Additionally, it enables simple use of remote computing resources, which allow for more computationally intensive analysis which can add a more reliable way to estimate confidence bounds.

In another project, we are using deep learning approaches to develop an automated safety system for the high-power laser systems DRACO and PENELOPE at HZDR. Here the goal is to detect defects or scatterers which focus parts of a yet unfocussed beam. These can, when left unchecked, cause cascades of failing mirrors, lenses, and non-linear crystals and should thus be detected in the time between two shots. This work uses deep convolutional neural networks implemented through the Caffe framework to achieve real-time detection and localization of impurities in the beam profile.

Keywords: computational science; data management; machine learning

  • Lecture (Conference)
    IHRS NanoNet Annual Workshop, 05.-07.09.2018, Bad Gottleuba, Deutschland

Publ.-Id: 27897

Applicability of a prognostic CT-based radiomic signature model trained on stage I-III non-small cell lung cancer in stage IV non-small cell lung cancer

de Jonga, E.; van Elmpt, W.; Rizzo, S.; Colarieti, A.; Spitaleri, G.; Leijenaar, R.; Jochems, A.; Hendriks, L.; Troost, E.; Reymen, B.; Dingemans, A.-M.; Lambin, P.

Recently it has been shown that radiomic features of computed tomography (CT) have prognostic information in stage I-III non-small cell lung cancer (NSCLC) patients. We aim to validate this prognostic radiomic signature in stage IV adenocarcinoma patients undergoing chemotherapy.
Materials and Methods
Two datasets of chemo-naive stage IV adenocarcinoma patients were investigated, dataset 1: 285 patients with CTs performed in a single center; dataset 2: 223 patients included in a multicenter clinical trial. The main exclusion criteria were EGFR mutation or unknown mutation status and non-delineated primary tumor. Radiomic features were calculated for the primary tumor. The c-index of cox regression was calculated and compared to the signature performance for overall survival (OS).
In total CT scans from 195 patients were eligible for analysis. Patients having a Prognostic Index (PI) lower than the signature median (n = 92) had a significantly better OS than patients with a PI higher than the median (n = 103, HR 1.445, 95% CI 1.07-1.95, p = 0.02, c-index 0.576, 95% CI 0.527-0.624).
The radiomic signature, derived from daily practice CT scans, has prognostic value for stage IV NSCLC, however the signature performs less than previously described for stage I-III NSCLC stages. In the future, machine learning techniques can potentially lead to a better prognostic imaging based model for stage IV NSCLC.

Keywords: stage IV NSCLC; prognostic model; Radiomics; CT

Publ.-Id: 27896

CT imaging during treatment improves radiomic models for patients with locally advanced head and neck cancer

Leger, S.; Zwanenburg, A.; Pilz, K.; Zschaeck, S.; Zöphel, K.; Kotzerke, J.; Schreiber, A.; Zips, D.; Krause, M.; Baumann, M.; Troost, E.; Richter, C.; Löck, S.

Background and purpose: The development of radiomic risk models to predict clinical outcome is usually based on pre-treatment imaging, such as computed tomography (CT) scans used for radiation treatment planning. Imaging data acquired during the course of treatment may improve their prognostic performance. We compared the performance of radiomic risk models based on the pre-treatment CT and CT scans acquired in the second week of therapy.
Material and methods: Treatment planning and second week CT scans of 78 head and neck squamous cell carcinoma patients treated with primary radiochemotherapy were collected. 1538 image features were extracted from each image. Prognostic models for loco-regional tumour control (LRC) and overall survival (OS) were built using 6 feature selection methods and 6 machine learning algorithms. Prognostic performance was assessed using the concordance index (C-Index). Furthermore, patients were stratified into risk groups and differences in LRC and OS were evaluated by log-rank tests.
Results: The performance of radiomic risk model in predicting LRC was improved using the second week CT scans (C-Index: 0.79), in comparison to the pre-treatment CT scans (C-Index: 0.65). This was confirmed by Kaplan–Meier analyses, in which risk stratification based on the second week CT could be improved for LRC (p = 0.002) compared to pre-treatment CT (p = 0.063).
Conclusion: Incorporation of imaging during treatment may be a promising way to improve radiomic risk models for clinical treatment adaption, i.e., to select patients that may benefit from dose modification.

Keywords: Radiomic risk modelling; Computed tomography; Imaging during treatment; Patient stratification


Publ.-Id: 27895

Radiation dose constraints for organs at risk in neuro-oncology; the European Particle Therapy Network consensus

Lambrecht, M.; Eekers, D.; Alapetite, C.; Burnet, N.; Calugaru, V.; Coremans, I.; Fossati, P.; Høyer, M.; Langendijk, J.; Romero, A. M.; Paulsen, F.; Perpar, A.; Renard, L.; de Ruysscher, D.; Timmermann, B.; Vitek, P.; Weber, D.; van der Weide, H.; Whitfield, G.; Wiggenraad, R.; Roelofs, E.; Nyström, P. W.; Troost, E.


For unbiased comparison of different radiation modalities and techniques, consensus on delineation of radiation sensitive organs at risk (OARs) and on their dose constraints is warranted. Following the publication of a digital, online atlas for OAR delineation in neuro-oncology by the same group, we assessed the brain OAR-dose constraints in a follow-up study.
We performed a comprehensive search to identify the current papers on OAR dose constraints for normofractionated photon and particle therapy in PubMed, Ovid Medline, Cochrane Library, Embase and Web of Science. Moreover, the included articles' reference lists were cross-checked for potential studies that met the inclusion criteria. Consensus was reached among 20 radiation oncology experts in the field of neuro-oncology.
For the OARs published in the neuro-oncology literature, we summarized the available literature and recommended dose constraints associated with certain levels of normal tissue complication probability (NTCP) according to the recent ICRU recommendations. For those OARs with lacking or insufficient NTCP data, a proposal for effective and efficient data collection is given.
The use of the European Particle Therapy Network-consensus OAR dose constraints summarized in this article is recommended for the model-based approach comparing photon and proton beam irradiation as well as for prospective clinical trials including novel radiation techniques and/or modalities.

Keywords: Dose constraints; Organs at risk; Particle therapy; European Particle Therapy Network

Publ.-Id: 27894

In vivo imaging in the oral cavity by endoscopic optical coherence tomography

Walther, J.; Schnabel, C.; Tetschke, F.; Rosenauer, T.; Golde, J.; Ebert, N.; Baumann, M.; Hannig, C.; Koch, E.

The common way to diagnose hard and soft tissue irregularities in the oral cavity is initially the visual inspection by an experienced dentist followed by further medical examinations, such as radiological imaging and/or histopathological investigation. For the diagnosis of oral hard and soft tissues, the detection of early transformations is mostly hampered by poor visual access, low specificity of the diagnosis techniques, and/or limited feasibility of frequent screenings. Therefore, optical noninvasive diagnosis of oral tissue is promising to improve the accuracy of oral screening. Considering this demand, a rigid handheld endoscopic scanner was developed for optical coherence tomography (OCT). The novelty is the usage of a commercially near-infrared endoscope with fitting optics in combination with an established spectral-domain OCT system of our workgroup. By reaching a high spatial resolution, in vivo images of anterior and especially posterior dental and mucosal tissues were obtained from the oral cavity of two volunteers. The convincing image quality of the endoscopic OCT device is particularly obvious for the imaging of different regions of the human soft palate with highly scattering fibrous layer and capillary network within the lamina propria

Keywords: optical coherence tomography; endoscopic imaging; dentistry; medical and biological imaging optics; medical optics instrumentation; tissue

Publ.-Id: 27893

Independent validation of a new reirradiation risk score (RRRS) for glioma patients predicting post-recurrence survival: A multicenter DKTK/ROG analysis

Niyazi, M.; Adeberg, S.; Kaul, D.; Boulesteix, A.; Bougatf, N.; Fleischmann, D.; Grün, A.; Krämer, A.; Rödel, C.; Eckert, F.; Paulsen, F.; Kessel, K.; Combs, S.; Oehlke, O.; Grosu, A.; Seidlitz, A.; Lattermann, A.; Krause, M.; Baumann, M.; Guberina, M.; Stuschke, M.; Budach, V.; Belka, C.; Debus, J.

Background and purpose: Reirradiation (reRT) is a valid option with considerable efficacy in patients with recurrent high-grade glioma, but it is still not known which patients might be optimal candidates for a second course of irradiation. This study validated a newly developed prognostic score independently in an external patient cohort.
Material and methods: The reRT risk score (RRRS) is based on a linear combination of initial histology, clinical performance status, and age derived from a multivariable model of 353 patients. This score can predict post-recurrence survival (PRS) after reRT. The validation dataset consisted of 212 patients.
Results: The RRRS differentiates three prognostic groups. Discrimination and calibration were maintained in the validation group. Median PRS times in the development cohort for the good/intermediate/poor risk categories were 14.2, 9.1, and 5.3 months, respectively. The respective groups within the validation cohort displayed median PRS times of 13.8, 8.8, and 3.8 months, respectively. Uno's C for development data was 0.64
(CI: 0.60-0.69) and for validation data 0.63 (CI: 0.58-0.68).
Conclusions: The RRRS has been successfully validated in an independent patient cohort. This linear combination of three easily determined clinicopathological factors allows for a reliable classification of patients and may be used as stratification factor for future trials.

Publ.-Id: 27891

Peptide für die spezifische Interaktion mit Mineralen

Lederer, F. L.; Braun, R.; Pollmann, K.

Recycling ist eine wichtige Komponente der Kreislaufwirtschaft, um Ressourcen zu schonen.
Auch die Biologie wird dazu zukünftig ihren Beitrag leisten. Dabei steht das Recycling von Edelmetallen und Selten-Erd-Elementen (SEE), die in Elektronikprodukten verbaut sind, im Mittelpunkt eines Forschungszweigs der Abteilung Biotechnologie am Helmholtz-Institut Freiberg für Ressourcentechnologie (HIF).

  • ACAMONTA - Zeitschrift für Freunde und Förderer der Technischen Universität Bergakademie Freiberg 25(2018), 60-63

Publ.-Id: 27890

Identification of Peptides as alternative recycling tools via Phage Surface Display – How biology supports Geosciences

Lederer, F. L.; Braun, R.; Schöne, L. M.; Pollmann, K.

The application of biological tools in Geosciences such as bacteria or microbial products that mobilize metallic components raises increasing interest in classical mining industries. Today, 10% of the total copper production in Chile originated from bioleaching operations (Gentina and Acevedo, 2016). However, the application of biological tools is limited due to poor specificity, complex material composition and heterogenous particle size. New studies focus on smaller biological components such as peptides with higher material specificity to mobilize and recycle materials of interest.
End-of-life electronic products like smart phones or compact fluorescent lamps (CFL) contain a wide variety of precious elements in very low concentrations. Currently, no cost-efficient and environmentally friendly technology exists for the separation and recycling of the majority of high-tech industry supporting elements such as the rare earth element (REE) Lanthanum phosphate (LAP) from electronic scrap. The focus of this project was the identification of peptides with high specificity for the rare earth mineral LAP, a component of CFL, for future material recycling. By using a biological method called phage surface display and the random PVIII phage peptide library f88.4/Cys6, the phage-bound peptide TSTQCPSHIRACLKKR was identified and characterized as not only an efficient LAP binder, which is furthermore able to discriminate between LAP and other components of fluorescent lamps. The application of phage particles displaying the recombinant PVIII fused peptide TSTQCPSHIRACLKKR in recycling processes is not possible due to limited scale-up, critical public perception, low biological efficiency and fast mutation rates in phage particles. Future applications will be based on peptides that are stable under a variety of challenging conditions such as heat, varying pH or in the presence of toxic scrap components. The development of peptide-based separation tools represents a new way of recycling of electronic scrap.

Keywords: LaPO4:Ce; Tb; phage surface display; peptide; recycling; rare earth element

Publ.-Id: 27889

Synthese Dipeptid-abgeleiteter Alkine als irreversible Inhibitoren von Cathepsin B

Trapp, C.

Die hier dargelegte Arbeit knüpft an den bereits vorhandenen Erkenntnissen unserer Forschungsgruppe am HZDR an und gründet auf den bisherigen Arbeiten von L. Behring. Der Schwerpunkt dieser Forschungsgruppe liegt auf der Hemmung von Cathepsin B, einem in malignen Tumoren überexprimierten Enzym. Durch die Arbeiten von GREENSPAN et al. konnte bisher gezeigt werden, dass der nitrilfunktionalisierte Inhibitor mit einem Carboxybenzyl-Rest in P1 und einem 3-Methylphenyl-Rest in P2 sich besonders für die Hemmung des Enzyms eignet. Ausgehend von diesen Erkenntnissen sollte das durch GREENSPAN et al. synthetisierte Molekül als Leitstruktur verwendet werden, um daraus irreversible alkinfunktionalisierte Inhibitoren zu synthetisieren. Der Vorteil dieser Inhibitoren ist, dass sie sich, im Gegensatz zu Nitrilen, nicht vom Target ablösen. Um einen Vergleich in ihrer Hemmwirkung festzustellen, sollten die analogen reversibel bindenden nitrilfunktionalisierten Inhibitoren hergestellt werden. Im Vorfeld wurde bereits der alkinfunktionalisierte Inhibitor der analogen Greenspan-Verbindung synthetisiert. Da dieser jedoch als Diastereomerengemisch vorlag, stand die Synthese stereo-chemisch reiner alkinfunktionalisierte Inhibitor im Vordergrund. Die enzymatischen Messungen der synthetisierten Inhibitoren übernahm L. Behring. Die im Folgenden diskutierten Ergebnisse aus den Messungen sind in Tabelle 3 zusammengefasst.
Die Synthese des nitrilfunktionalisierten Inhibitors mit 4-Fluorbenzoyl-Rest in P3, 3-Methylphenylalanyl-Rest in P2 und zwei Protonen in P1 gestaltete sich schwieriger, als die des analogen Alkin-Derivats. In den RP-HPLC-Spektren des nitrilfunktionalisierten Inhibitors konnten, besonders während der Boc-Entschützung, viele Nebenprodukten nachgewiesen werden. Diese entstanden aufgrund der höheren Elektrophile der Nitrilgruppe. Diese Nebenprodukte bedeuteten eine zusätzliche Reinigung, welche sich auf die Ausbeuten auswirkte. Es wurde daher für die weiteren nitrilfunktionalisierten Inhibitoren beschlossen, die Dehydratisierung des weniger reaktiveren Amids zum Nitril auf das Ende der Synthese zu planen. Die Ausbeute des nitrilfunktionalisierten Inhibitors lag über drei Schritte bei 30 %. Im Vergleich dazu wurde der alkinfunktionalisierte Inhibitor mit 60 % über drei Schritte erhalten. Der bestimmte Ki-Wert zeigte für den nitrilfunktionalisierten Inhibitor 6 einen Wert von 1,19 µM. Der analog synthetisierte alkinfunktionalisierte Inhibitor 3 zeigte keine enzymatische Hemmung. Es ist davon auszugehen, dass dieser unzureichend im Enzym fixiert wurde und die Addition des Thiolats im aktiven Zentrum an das Alkin nicht stattfinden konnte.
Die zweite Gruppe der synthetisierten Inhibitoren unterschied sich im Rest P1 zu den Vorangegangenen. Es konnte gezeigt werden, dass die Inhibitorwirkung mit zwei Protonen in Position P1 für nur geringe Hemmung am Cathepsin B sorgt. Durch die Arbeiten von GREENSPAN et al. wurde daher der Carboxybenzylserin-Baustein in P1 gewählt. Die Synthese des nitrilfunktionalisierten Inhibitors verlief über eine zehnstufige Synthese und brachte eine Ausbeute von 8 % hervor. Der größte Verlust bei der Synthese von 16 und 30 wurde in der Alkylierung des Serin-Bausteins mit dem allylgeschützten Carboxybenzyl-Rest beobachtet. Die Reaktion verlief nur mit Ausbeuten von ca. 30 % (Verbindung 16) bzw. 40 % (Verbindung 30) und bereitete während der Synthese die meisten Schwierigkeiten. In der Arbeit wurden daher verschiedene Reaktionsbedingungen getestet. Im Falle des nitrilfunktionalisierten Inhibitors 16 wurde die Temperatur für die Deprotonierung variiert, wobei mit sinkender Temperatur die alkylierende Veresterung des Boc-geschützten Serins der Seitenkettenalkylierung vorgezogen wird. Das entstandene Esterprodukt wurde isoliert, spektroskopisch untersucht und mit dem der alkylierten Verbindung verglichen. Im Falle des alkinfunktionalisierten Inhibitors 30 wurde ebenfalls die Temperatur und die Zeit für die Deprotonierung untersucht. Es konnte gezeigt werden, dass die Temperatur während der Deprotonierung wenig Einfluss auf die Reaktion besitzt. Anders war es bei der Zeit für die Deprotonierung. Hier wurde durch 1H-NMR-Auswertung und RP-HPLC gezeigt, dass sich bei langen Deprotonierungszeiten ein intramolekular entstandenes Oxazolidinon bildete, welches durch anschließende Zugabe des Alkylierungsmittels zur N-Alkylierung neigt.
Die ansonsten stereokonservative Synthese, ausgehend vom L-Serin über den Garner-Aldehyd verlief mit hohen Ausbeuten und einfachen Reinigungsschritten. Die spektroskopische Mosher-Säure-Analyse des rückreduzierten Garner-Aldehyds zeigte, dass die stereochemische Integrität während der Aldehyd-Synthese erhalten blieb. Auch nach der Kupplung zum Dipeptid und damit der Einführung eines zweiten Stereozentrums konnten nur geringe Peakdopplungen (Anteil ≤ 4 % des ungewünschten Diastereomers) im 1H-NMR nachgewiesen werden. Die Messung des Dipeptidalkins 30 führte ebenfalls zum Erfolg. Es konnte durch die Messung am isolierten Enzym bewiesen werden, das er eine irreversible Bindung mit dem Enzym eingeht. Durch vorangegangene Arbeiten unserer Arbeitsgruppe konnte außerdem gezeigt werden, dass sich das Molekül mit 4-Fluorbenzoyl-Rest in P3 besser eignet als das bereits hergestellte Epimerengemisch mit 2,4-Difluorbenzoylrest in P3.
Der fünfte Inhibitor 40 wurde ausgehend vom kommerziell erhältlichen Propargylserin synthetisiert. Die Reaktion verlief mit 9 % Ausbeute über acht Reaktionsschritte. Die Synthese des Inhibitors verlief trotz geringerer Ausbeuten nahezu unproblematisch. Der letzte Schritt der Methylester-Entschützung bereitete zunächst Probleme, wobei es zur partiellen Racemisierung des Inhibitors kam. Diese konnten jedoch durch Verkürzen der Reaktionszeit und Einsatz der Base im Unterschuss fast komplett unterdrückt werden. Der Inhibitor konnte, ähnlich wie das Dipeptidalkin 30 mit ≤ 3 % des unerwünschten Diastereomers synthetisiert werden. Da der Triazol-Inhibitor 40 schlechter ist als der mit einem Proton in P1 (Verbindung 6), ist die Synthese des entsprechenden Alkins nur wenig aussichtsvoll. Durch die unzureichende Bindung des Inhibitors in den Enzymtaschen ist, wie bei Inhibitor 6, keine irreversible Bindung zu erwarten. Ein Ausblick ist die stereoisomerenreine Synthese des 2,4-difluorbenzoylierten Inhibitors zum direkten Vergleich mit dem analogen Diastereomerengemisch. Weiterhin soll der Rest in P3 durch ein 4-Phenylbenzoyl-Rest ersetzt werden. Dieser besitzt ein größeres π-Elektronensystem, wodurch die Wechselwirkungen mit den π-Elektronen des Tyrosins in der Enzymtasche S3 verbessert werden sollen. Da anschließend eine Radiomarkierung der Verbindung erfolgen soll, bietet es sich an, den analogen 4-(4-Fluorbenzyl)-benzoyl-Rest an die Position P3 zu binden. Eine weitere Modifikation, wäre die Än-derung des P2-Rests von Methylphenylalanin zu Monoiodtyrosin. In den Arbeiten von XING et al. zeigten Tyrosin-Derivate, speziell die iodierten Tyrosin-Derivate eine besonders potente Hemmwirkung gegenüber Cathepsin B. Dieser Substituent könnte eine verbesserte Wechselwirkung mit der Aminosäure Glutaminsäure (Glu 245) in Enzymtasche S2 bewirken.

  • Master thesis
    Hochschule Zittau/Görlitz, 2017
    Mentor: Prof. Dr. Dieter Greif, Dr. Reik Löser
    193 Seiten

Publ.-Id: 27888

Extended Infrared Photoresponse in Te-Hyperdoped Si at Room Temperature

Wang, M.; Berencén, Y.; García-Hemme, E.; Prucnal, S.; Hübner, R.; Yuan, Y.; Xu, C.; Rebohle, L.; Böttger, R.; Heller, R.; Schneider, H.; Skorupa, W.; Helm, M.; Zhou, S.

Presently, silicon photonics requires photodetectors that are sensitive in a broad infrared range, can operate at room temperature, and are suitable for integration with the existing Si-technology process. Here, we demonstrate strong room-temperature sub-band-gap photoresponse of photodiodes based on Si hyperdoped with tellurium. The epitaxially recrystallized Te-hyperdoped Si layers are developed by ion implantation combined with pulsed-laser melting and incorporate Te-dopant concentrations several orders of magnitude above the solid solubility limit. With increasing Te concentration, the Te-hyperdoped layer changes from insulating to quasi-metallic behavior with a finite conductivity as the temperature tends to zero. The optical absorptance is found to increase monotonically with increasing Te concentration and extends well into the mid-infrared range. Temperature-dependent optoelectronic photoresponse unambiguously demonstrates that the extended infrared photoresponsivity from Te-hyperdoped Si p-n photodiodes is mediated by a Te intermediate band within the upper half of the Si band gap. This work contributes to pave the way toward establishing a Si-based broadband infrared photonic system operating at room temperature.

Related publications


Publ.-Id: 27886

Tunnel magnetoresistance angular and bias dependence enabling tuneable wireless communication

Kowalska, E.; Fukushima, A.; Sluka, V.; Fowley, C.; Kákay, A.; Aleksandrov, Y.; Lindner, J.; Fassbender, J.; Yuasa, S.; Deac, A. M.

Spin-transfer torques (STTs) can be exploited in order to manipulate the magnetic moments of nanomagnets, thus allowing for new consumer-oriented devices to be designed. Of particular interest here are tuneable radio-frequency (RF) oscillators for wireless communication. Currently, the structure that maximizes the output power is an Fe/MgO/Fe-type magnetic tunnel junction (MTJ) with a fixed layer magnetized in the plane of the layers and a free layer magnetized perpendicular to the plane. This structure allows for most of the tunnel magnetoresistance (TMR) to be converted into output power. Here, we experimentally and theoretically demonstrate that the main mechanism sustaining steady-state precession in such structures is the angular dependence of the magnetoresistance. The TMR of such devices is known to exhibit a broken-linear dependence versus the applied bias. Our results show that the TMR bias dependence effectively quenches spin-transfer-driven precession and introduces a non-monotonic frequency dependence at high applied currents. Thus we expect the bias dependence of the TMR to have an even more dramatic effect in MTJs with Mn-Ga-based free layers, which could be used to design wireless oscillators extending towards the ‘THz gap’, but have been experimentally shown to exhibit a non-trivial TMR bias dependence.

Keywords: spin-torque nano-oscillator (STNO); MgO-based magnetic tunnel junction (MTJ); tunnel magnetoresistance (TMR); spin dynamics

Publ.-Id: 27885

Hydrodynamic analysis in a viscous coupling using angle-resolved gamma-ray computed tomography

Bieberle, A.; Spies, A.; Schlottke, J.
ContactPerson: Bieberle, André; RightsHolder: Schlottke, Jan; Editor: Hampel, Uwe; Sponsor: Kühnel, Wolfram

This work comprises data provided by high-resolution gamma-ray computed tomography that was applied on a viscous coupling to visualize the internal operating fluid distribution. Therefore, angle-resolved time-averaged CT scanning technique was performed at different

  • cross-sectional positions,
  • rotational speeds as well as
  • at primary and secondary side. 

Keywords: viscous coupling; gamma-ray CT; process-synchronized fast imaging


Publ.-Id: 27884

Activity-Based Probes for Tumour-Associated Transglutaminase 2: From Potent and Selective Inhibitors to Radiotracers

Löser, R.

The talk is covering the efforts of our group in the development of inhibitor-based radiotracers for the imaging of tumour-associated transglutaminase 2 (TGase 2). Major emphasis will be put on interesting structure-activity relationships of N6-acryloyllysine-derived inhibitors. In addition, general principles for targeting of TGase 2 by irreversible inhibitors will be highlighted. Labelling of these compounds with fluorine-18 and initial results towards their radiopharmacological evaluation will be presented.

  • Invited lecture (Conferences)
    Gordon Research Conference "Transglutaminases in Human Disease Processes", 17.-22.06.2018, Les Diablerets, Schweiz

Publ.-Id: 27883

Hysteresis Design of Magnetocaloric Materials—From Basic Mechanisms to Applications

Scheibel, F.; Gottschall, T.; Taubel, A.; Fries, M.; Skokov, K. P.; Terwey, A.; Keune, W.; Ollefs, K.; Wende, H.; Farle, M.; Acet, M.; Gutfleisch, O.; Gruner, M. E.

Magnetic refrigeration relies on a substantial entropy change in a magnetocaloric material when a magnetic field is applied. Such entropy changes are present at first-order magnetostructural transitions around a specific temperature at which the applied magnetic field induces a magnetostructural phase transition and causes a conventional or inverse magnetocaloric effect (MCE). First-order magnetostructural transitions show large effects, but involve transitional hysteresis, which is a loss source that hinders the reversibility of the adiabatic temperature change DTad. However, reversibility is required for the efficient operation of the heat pump. Thus, it is the mastering of that hysteresis that is the key challenge to advance magnetocaloric materials. We review the origin of the large MCE and of the hysteresis in the most promising first-order magnetocaloric materials such as Ni–Mn-based Heusler alloys, FeRh, La(FeSi)13-based compounds, Mn3GaC antiperovskites, and Fe2P compounds. We discuss the microscopic contributions of the entropy change, the magnetic interactions, the effect of hysteresis on the reversible MCE, and the size- and time-dependence of the MCE at magnetostructural transitions.

Publ.-Id: 27882

Dipeptide-derived Alkynes as Novel Irreversible Inhibitors of Cathepsin B

Behring, L.; Trapp, C.; Wodtke, R.; Kuhne, K.; Belter, B.; Steinbach, J.; Pietzsch, J.; Löser, R.

Until recently, alkynes were considered bioinert. Thus, they are popular reaction partners in bioorthogonal click reactions in vitro and in vivo. Despite the virtual chemical inertness of the alkyne moiety, two research groups observed the irreversible inhibition of a cysteine protease by an alkyne functionalised substrate derivative: both EKKEBUS et al. and SOMMER et al. independently described the unexpected inactivation of de-ubiquitinating enzymes by propargylated ubiquitin or ubiquitin-like modifiers bearing propargylamine in place of C-terminal glycine [1, 2]. We intended to harness that finding for the design of inhibitor-based probes for the imaging of tumour-associated cysteine proteases.
Cysteine cathepsins play an important role in tumour progression. In particular, cathepsin B is involved in a variety of tumour progression-related processes and an elevated extracellular levels are linked to increased malignancy and poor prognosis [3]. Therefore, this enzyme represents a promising target for the therapy and imaging of tumours.
GREENSPAN et al. reported a potent and highly selective, dipeptidyl nitrile-based cathepsin B inhibitor (N-[2-[(3-Carboxyphenyl)methoxy]-1(S)-cyanoethyl]-3-methyl-N2-(2,4-difluorobenzoyl)-L-phenylalaninamide) [4]. Based on that lead compound, cathepsin B-targeting dipeptide alkynes were designed by isoelectronic replacement of the nitrile nitrogen atom by by a methine group and consecutive variation of the 2,4-difluorobenzoyl and (3-carboxybenzyl)oxymethyl residue. Formation of the C-C triple bond by reaction of the corresponding open-chain serine-derived aldehyde with the Bestmann-Ohira reagent was accompanied by partial enantiomerisation. Therefore, the synthesis was performed via Garner’s aldehyde, which accounted for high stereochemical purity of the final compounds. The inhibitory potential was investigated against cathepsins B, S, L and K. The most potent compound exhibited irreversible inhibition of cathepsin B with an inactivation constant (kinact/KI=771 M-1s-1). Values for cathepsins L, S and K were significantly lower; no irreverisible ihibition was observed for cathepsin K. In addition, inhibition of cathepsin B activity in human glioblastoma cell lysates and living cells has been demonstrated. Based on these promising results, dipeptidyl alkynes have the potential to become a valuable tool for imaging due to the expected low activity towards other cysteine proteases. In further studies, selected inhibitors for cathepsin B will be labelled with suitable radionuclides to obtain an inhibitor-based probe directed towards cathepsin B.

[1] Ekkebus et al., J. Am. Chem. Soc., 2013, 135, 2867-2870
[2] Sommer et al., Bioorg. Med. Chem., 2013, 21, 2511-2517
[3] Löser and Pietzsch, Front. Chem., 2015, 3:37
[4] Greenspan et al., J. Med. Chem., 2001, 44, 4524-4534.

  • Lecture (Conference)
    35th European Peptide Symposium, 26.-31.08.2018, Dublin, Irland
  • Open Access Logo Abstract in refereed journal
    Journal of Peptide Science 24(2018)S2, OP64
    DOI: 10.1002/psc.3127
  • Contribution to proceedings
    35th European Peptide Symposium, 26.-31.08.2018, Dublin, Ireland
    Proceedings of the 35th European Peptide Symposium: European Peptide Society, 64-66
    DOI: 10.17952/35EPS.2018.064

Publ.-Id: 27881

Methyl selenol as precursor in selenite reduction to Se/S species by methane-oxidizing bacteria

Eswayaha, A. S.; Hondow, N.; Scheinost, A. C.; Merroun, M.; Romero-Gonzalez, M.; Smith, T. J.; Gardiner, P. H. E.

In this study, we demonstrate for the first time that in the reduction of selenite by Mc. capsulatus (Bath), a methane oxidizing bacterium, methyl selenol is the precursor for the formation of methylated selenium-containing and mixed chalcogenides species. Subsequent exchange reactions between the species result in the formation of the amorphous allotropic form of selenium, which is cyclic Se8 with sulfur in its structure.

Keywords: selenol; methane reducing bacteria; Mc. capsulatus; XPS; XAFS; FTIR; TEM; Raman; Selenium

Related publications


Publ.-Id: 27880

Cathepsin B-Activatable Cell-Penetrating Peptides for Imaging Cancer-related Cathepsin B

Kuhne, K.; Behring, L.; Belter, B.; Wodtke, R.; von Krüchten, L.; Keller, M.; Steinbach, J.; Pietzsch, J.; Löser, R.

In our understanding of the many drivers of malignant progression and cancer metastasis, proteases are increasingly drawn into the spotlight as crucial agents in cancer angiogenesis, invasion, and metastasis [1]. Elevated activities of multiple members of the cathepsin family have been shown to correlate with increased metastasis and high therapy resistance [2, 3]. Especially high expression levels of extracellular cathepsin B (CTB) indicate poor prognosis in neoplastic diseases, making CTB an interesting target for activity-based molecular imaging in diagnostics as well as in therapy monitoring for personalised therapies.
It is our aim to develop such a probe by combination of a polyarginine-based, activatable cell penetrating peptide (ACPP), as first described by R. Tsien, and an optimised endopeptidase substrate for CTB [4]. Substrate optimisation proofed to be challenging as two entirely opposite factors needed to be balanced – high stability against serum proteases to prevent premature cleavage of the activation sequence, while retaining efficient and specific endoproteolytic cleavability by CTB.
We have generated a CTB-endoprotease substrate by C-terminally elongating the CTB carboxydipeptidase substrate Abz GIVR*AK(Dnp) OH (Abz - aminobenzoyl, Dnp – dinitrophenyl, * – cleavage site), described by Cotrin et al. in 2004, to the octapeptide Abz GIVR*AK(Dnp)GX CONH2, which could be used as activation site in the final ACPP [5]. Introduction of any amino acid other than glycine at the P4’ position resulted in hysteretic kinetics for the CTB-catalysed hydrolysis of the octapeptides, which might indicate the displacement of the occluding loop from the active site upon interaction with the substrates. Using LC-ES-MS-based analysis of serum-incubated substrates, the positions P1 and P3’ were determined to be primary determinants of serum stability. After suppression of the P3’ instability by Nα-methylation and optimisation within the positions P1-P3, we were able to increase serum half-life from < 5 min to > 1440 min under concomitant improvement of kinetic substrate efficiency towards CTB.
Currently, the substrate is optimised towards CTB-specificity within the cathepsin protease family. Additionally, cell uptake studies of a fluorescently labelled ACPP using the optimised CTB-endoprotease substrate sequence are ongoing. Using this fluorescent probe, we plan to study cell uptake, in vivo stability and initial biodistribution. Furthermore, an ACPP conjugated to radiometal-chelating entities is currently prepared, which will allow for PET imaging in vivo.

(1) Yang et al., Cancer Growth Metastasis 2009, 2, 13-27
(2) Aggarwal and Sloane, Proteomics Clin. Appl. 2014, 8(5-6), 427-437
(3) Löser and Pietzsch, Front. Chem. 2015, 3, article 37
(4) Jiang et al., PNAS, 2004, 101(51), 17867-17872
(5) Cotrin et al., Anal. Biochem. 2004, 335, 244-252

  • Lecture (Conference)
    35th European Peptide Symposium, 26.-31.08.2018, Dublin, Irland
  • Abstract in refereed journal
    Journal of Peptide Science 24(2018)S2, OP49
    DOI: 10.1002/psc.3127
  • Contribution to proceedings
    35th European Peptide Symposium, 26.-31.08.2018, Dublin, Ireland
    Proceedings of the 35th European Peptide Symposium: European Peptide Society, 52-55
    DOI: 10.17952/35EPS.2018.052


  • Secondary publication expected

Publ.-Id: 27879

Cathepsin B: Active Site Mapping with Peptidic Substrates and Inhibitors

Schmitz, J.; Gilberg, E.; Löser, R.; Bajorath, J.; Bartz, U.; Gütschow, M.

The potential of papain-like cysteine proteases, such as cathepsin B, as drug discovery targets for systemic human diseases has prevailed over the past years. The development of potent and selective low-molecular cathepsin B inhibitors relies on the detailed expertise on preferred amino acid and inhibitor residues interacting with the corresponding specificity pockets of cathepsin B. Such knowledge might be obtained by mapping the active site of the protease with combinatorial libraries of peptidic substrates and peptidomimetic inhibitors. This review, for the first time, summarizes a wide spectrum of active site mapping approaches. It considers relevant X-ray crystallographic data and discloses propensities towards favorable protein-ligand interactions in case of the therapeutically relevant protease cathepsin B.

Keywords: Active site mapping; Cathepsin B; Fluorescence-quenched substrates; Peptidomimetic inhibitors; Substrate specificity


Publ.-Id: 27878

Building an Optical Free-Electron Laser in the Traveling-Wave Thomson-Scattering Geometry

Steiniger, K.; Albach, D.; Bussmann, M.; Loeser, M.; Pausch, R.; Röser, F.; Schramm, U.; Siebold, M.; Debus, A.

We show how optical free-electron lasers and enhanced incoherent Thomson scattering radiation sources can be realized with Traveling-Wave Thomson-Scattering (TWTS) today. Emphasis is put on the realization of optical free-electron lasers (OFELs) with existing state-of-the-art technology for laser systems and electron accelerators. The conceptual design of optical setups for the preparation of laser pulses suitable for TWTS OFELs and enhanced Thomson sources is presented. We further provide expressions to estimate the acceptable alignment tolerances of optical components for TWTS OFEL operation. Examples of TWTS OFELs radiating at 100 nm, 13.5 nm and 1.5 Å as well as an incoherent source at 40 pm highlight the feasibility of the concept and detail the procedure to determine the optical components parameters of a TWTS setup.

Keywords: optical FEL; traveling-wave; Thomson scattering; pulse-front tilt; out-of-focus interaction

Publ.-Id: 27877

Peptidbasierte Rückgewinnung von Gallium aus Abwässern der Halbleiterindustrie

Schönberger, N.; Braun, R.; Matys, S.; Flemming, K.; Lehmann, F.; Lederer, F.; Pollmann, K.

Gallium (Ga) ist wichtiger Bestandteil vieler Halbleiterprodukte und wird in LEDs und Photovoltaikelementen verwendet. Trotz eines stetig wachsenden Bedarfs und endlicher Ressourcen, fehlen Strategien für seine Rückgewinnung aus sekundären Rohstoffquellen. Abfälle aus der Halbleiterindustrie könnten eine ergiebige Quelle für die Gewinnung von hochreinem Ga sein. Der gezielte Einsatz von spezifischen Peptiden ermöglicht die selektive Abtrennung von Metallionen für die Gewinnung von Reinststoffen. Durch das sogenannte „Phagen Display“ können derartige Peptide selektiert werden. Hier wurde die Technik zur Identifizierung Ga-bindender Peptide angewendet.
Es konnten 5 hoch affine Peptide identifiziert werden, die in Einzelklonexperimenten charakterisiert wurden. Hierfür wurde die Fähigkeit der Klone, freie Galliumionen in wässriger Lösung zu sorbieren, untersucht. Alle 5 Klone zeigten im Vergleich zu einem Kontrollphagen eine verbesserte Biosorption von Ga. Bei 2 der 5 Klone wurde eine deutlich höhere Affinität für Ga gegenüber As festgestellt. In weiterführenden Experimenten wurden die metallbindenden Eigenschaften beider Peptide charakterisiert. Durch ein zusätzliches Cystein am C-Terminus lassen sich diese Peptide auf verschiedenen Oberflächen immobilisieren. Auf diese Weise können Materialien zur selektiven Gewinnung von Gallium aus industriellen Abwässern generiert werden.

Keywords: Gallium; Peptide; Phage Display; Biosorption

  • Contribution to proceedings
    ProcessNet-Jahrestagung und 33. DECHEMA-Jahrestagung der Biotechnologen 2018, 10.-12.09.2018, Aachen, Deutschland
    Chemie Ingenieur Technik; Volume 90, Issue 9; Special Issue: ProcessNet‐Jahrestagung und 33. DECHEMA‐Jahrestagung der Biotechnologen 2018, Weinheim, Deutschland: Wiley-VCH Verlag GmbH & Co. KGaA, 0009-286X, 1287-1288
    DOI: 10.1002/cite.201855340

Publ.-Id: 27876

Peptide-based recovery of gallium

Schönberger, N.; Braun, R.; Lehmann, F.; Flemming, K.; Matys, S.; Lederer, F.; Pollmann, K.

High-tech metals are almost ubiquitous in our everyday lives. Due to their great importance for the electronics industry, the demand is continuously growing. The supply of these important raw materials is currently mainly covered by primary raw material sources. However, with increasing technological progress, the supply situation on the global market becomes tense. The recovery of high-tech metals from secondary raw material sources could help to ease the situation. This task is a major challenge due to a strongly mixed matrix and sometimes low concentrations of valuable metals from such sources. However, highly innovative strategies are required to meet this challenge. Modern biotechnology offers promising concepts for the efficient, economical and sustainable recycling of high-tech metals [1].
Recently we’ve established a phage display technology platform for the highly specific recognition of mineral particles as well as of metal ions in polluted water streams. This is escorted by a newly developed system for the heterologous expression of identified peptides [2-4].
Here we report in detail about the development of high-affinity peptide ligands for the recovery of gallium from industrial wastewater. Various gallium binding peptide sequences were identified by applying a commercial dodecamer peptide library (Ph.D.-12, NEB, US). Biopanning conditions were optimized for the enrichment of metal ion binding phage clones, which allows a more precise selection process. By single clone binding studies and competitive binding experiments, 3 sequences were characterized to show high binding affinity and selectivity for gallium above other metals, especially arsenic.
Gallium binding peptides are now produced for further spectroscopic characterization and evaluation of binding properties. In addition immobilization strategies to create peptide-based materials for the recovery of gallium binding peptides will be discussed.

[1] K. Pollmann, S. Kutschke, S. Matys, J. Raff, G. Hlawacek, F.L. Lederer, Bio-recycling of metals: Recycling of technical products using biological applications, Biotechnology Advances, (2018)
[2] R. Braun, S. Matys, N. Schönberger, F.L. Lederer, K. Pollmann, Simplified Expression and Production of Small Metal Binding Peptides, Solid State Phenomena, (2017)
[3] S. Matys, F.L. Lederer, N. Schönberger, R. Braun, F. Lehmann, K. Flemming, S. Bachmann, S. Curtis, R.T.A. MacGillivray, K. Pollmann, Phage Display - A Promising Tool for the Recovery of Valuable Metals from Primary and Secondary Resources, Solid State Phenomena, (2017)
[4] F.L. Lederer, S.B. Curtis, S. Bachmann, W.S. Dunbar, R.T. MacGillivray, Identification of lanthanum-specific peptides for future recycling of rare earth elements from compact fluorescent lamps, Biotechnol Bioeng, (2017)

Keywords: Gallium; Phage display; peptides; biosorption

  • Poster
    35th European Peptide Symposium, 35EPS, 26.-31.08.2018, Dublin, Irland
  • Open Access Logo Abstract in refereed journal
    Journal of Peptide Science 24(2018)S2, P67
    DOI: 10.1002/psc.3127
  • Contribution to proceedings
    35th European Peptide Symposium, 26.-31.08.2018, Dublin, Irland
    Proceedings of the 35th European Peptide Symposium: Journal of Peptide Science, 133-135
    DOI: 10.17952/35EPS.2018.133

Publ.-Id: 27875

A forward look into the US rare-earth industry; How potential mines can connect to the global REE market

Barakos, G.; Mischo, H.; Gutzmer, J.

It has been nearly eight years since rare-earth elements (REE) became the subject of front-page headlines. It was when the controversial Chinese export policy for these critical commodities was epitomized in a maritime border dispute with Japan in September 2010 that resulted in the big REE crisis and price spike of 2011 (Barakos et al., 2016c; Mancheri, 2015). The world was dismayed, especially in REE-importing countries such as the United States that was, and still is, totally dependent on Chinese production and exports (Barakos et al, 2016c; Kennedy, 2015). The short-lived alarm initiated a treasure hunt by way of exploration for REE deposits all over the world. The continuously growing demand on the one hand, and the Chinese sovereignty of the REE-market on the other, led the rest of the world to explore their own REE resources. In just a few years, more than 400 projects were initiated to explore REE deposits outside of China

Keywords: REE; USA; Mining; Resource Policy

  • Mining Engineering 70(2018)8, 30-37
    ISSN: 00265187

Publ.-Id: 27874

Development of Ga binding Peptides using Phage Display Technology

Schönberger, N.; Matys, S.; Lederer, F.; Pollmann, K.

Gallium is a strategically important metal for the German high-tech industry. It is used essentially in the semiconductor compounds GaAs, GaN or GaP for high-potential future technologies. This is offset by low recycling rates and declining availability on the world market. Therefore, the development of processes for the selective recovery of gallium from secondary raw material sources is a desirable starting point for dealing with the increasing scarcity of this resource on the world market. Particularly interesting is the development of a biotechnological method for selective biosorption by using the Phage Surface Display Technology.
This is a well-established method for the selection of highly specific peptide ligands in medicine and biotechnology. Random, short peptide sequences are presented on the surface according to genetically modified bacteriophages. In a biopanning called process, a pool of different bacteriophage is selected against a particular target, thereby enriching specific binding clone variants. A very effective method has been established for the selection of different phage display libraries. Gallium ions immobilized on a monolithic ion exchanger are made accessible for biopanning in an FPLC system. This chromatopanning allows the selective enrichment of gallium-binding clone variants under strictly controlled process conditions.
In the present study, we report about the enrichment, identification and characterization of several gallium-binding peptide motifs. Some promising gallium binding bacteriophage clones are chosen for further binding studies, including bacteriophage immobilization for real waste water treatment experiments.
The corresponding peptide sequences can be synthesized and used in subsequent experiments to characterize metal-peptide interactions and develop biosorptive materials for selective gallium recovery from industrial waste waters.

Keywords: Phage Display; Gallium; Peptides; Biosorption

  • Poster
    4th EURO bio-inspired materials 2018, 19.-22.03.2018, Potsdam, Deutschland

Publ.-Id: 27873

The Implementation of an Activated Temperature Dependent Wall Boiling Model in an Eulerian-Eulerian Computational Fluid Dynamic Approach for Predicting the Wall Boiling Process

Ding, W.; Krepper, E.; Hampel, U.

In this work, we report on a development of time averaged Eulerian multiphase approach applied in the wall boiling process especially in the forced convective boiling process. Recently in order to get accurate bubble dynamics and reduce the case dependency, a single bubble model for nucleate boiling based on the known published models was developed. The model considers geometry change and dynamic contact and inclination angles during the bubble growth. The model has a good agreement with experiments. However the predicted bubble dynamics is wall superheat (cavity activation temperature) dependent. This single bubble model requires an update of the current nucleation site activation and heat partitioning models in time averaged Eulerian multiphase approaches. In this work, we will introduce this implementation in detail. Further with help of the multiple size group (MUSIG) model and a breakup and coalescence model, the time averaged Eulerian approach could simulate the bubble size distribution in a heated pipe. With the necessary calibration of the nucleation site density the comparisons between the calculation results and the Bartolomej’s experiments demonstrate the success of the implementation and the accuracy of this approach.

Keywords: Wall boiling; Eulerian multi-phase approach; microlayer; cavity group activation; updated heat partitioning


Publ.-Id: 27872

Diagnostics for plasma-based electron accelerators

Downer, M. C.; Zgadzaj, R.; Debus, A.; Schramm, U.; Kaluza, M. C.

Plasma-based accelerators that impart energy gain as high as several GeV to electrons or positrons within a few centimeters have engendered a new class of diagnostic techniques very different from those used in connection with conventional radio-frequency (rf) accelerators. The need for new diagnostics stems from the micrometer scale and transient, dynamic structure of plasma accelerators, which contrasts with the meter scale and static structure of conventional accelerators. Because of this micrometer source size, plasma-accelerated electron bunches can emerge with smaller normalized transverse emittance (εn<0.1  mm mrad) and shorter duration (τb∼1  fs) than bunches from rf linacs. Single-shot diagnostics are reviewed that determine such small εn and τb noninvasively and with high resolution from wide-bandwidth spectral measurement of electromagnetic radiation the electrons emit: εn from x rays emitted as electrons interact with transverse internal fields of the plasma accelerator or with external optical fields or undulators; τb from THz to optical coherent transition radiation emitted upon traversing interfaces. The duration of ∼1  fs bunches can also be measured by sampling individual cycles of a copropagating optical pulse or by measuring the associated magnetic field using a transverse probe pulse. Because of their luminal velocity and micrometer size, the evolving structure of plasma accelerators, the key determinant of accelerator performance, is exceptionally challenging to visualize in the laboratory. Here a new generation of laboratory diagnostics is reviewed that yield snapshots, or even movies, of laser- and particle-beam-generated plasma accelerator structures based on their phase modulation or deflection of femtosecond electromagnetic or electron probe pulses. Spatiotemporal resolution limits of these imaging techniques are discussed, along with insight into plasma-based acceleration physics that has emerged from analyzing the images and comparing them to simulated plasma structures.

Keywords: Beam diagnostics; Electrostatic waves & oscillations; Laser driven electron acceleration; Laser wakefield acceleration; Particle acceleration in plasmas; Radiation & particle generation in plasmas

Related publications


Publ.-Id: 27870

Localization of magnon modes in a curved magnetic nanowire

Gaididei, Y.; Kravchuk, V. P.; Mertens, F. G.; Pylypovskyi, O. V.; Saxena, A.; Sheka, D. D.; Volkov, O. M.

Spin waves in magnetic nanowires can be bound by a local bending of the wire. The eigenfrequency of a truly local magnon mode is determined by the curvature: a general analytical expression is established for any infinitesimally weak localized curvature of the wire. The interaction of the local mode with spin waves, propagating through the bend, results in scattering features, which is well confirmed by spin-lattice simulations.

Keywords: magnetic wire; curvature; local mode; spin wave

Publ.-Id: 27869

Trivalent Actinide Incorporation into Zirconium(IV) oxide – Spectroscopic Investigations of Defect Fluorite Structures

Eibl, M.; Shaw, S.; Morris, K.; Stumpf, T.; Huittinen, N.

The structural incorporation of trivalent ions, i.e. Y(III), Eu(III) and Cm(III) was studied with powder X-ray diffraction (PXRD) and various spectroscopic methods including site-selective time-resolved laser fluorescence-spectroscopy (TRLFS) and extended X-ray absorption fine structure spectroscopy (EXAFS). A clear mismatch of the bulk behavior in the stabilized tetragonal and cubic phases with its local structure was observed. Furthermore, it could be seen, that no quantitative structural incorporation into the monoclinic phase is achieved. A very strong shift of the laser fluorescence emission maximum of Cm(III) doped cubic phases compared to the Cm(III) aquo ion could be measured. It was shown that TRLFS is a powerful method to study defect structures, especially in combination with PXRD as a bulk characterization method.

  • Poster
    Plutonium Futures 2018, 09.-14.09.2018, San Diego, USA

Publ.-Id: 27868

Analysis of Flow Pattern Transition from Segregated to Slug flow in Upward Inclined Pipes

Fan, Y.; Pereyra, E.; Sarica, C.; Schleicher, E.; Hampel, U.

Segregated and slug flows are two of the most common flow patterns encountered in two-phase upward inclined pipe flow. However, the transition between them is ambiguous. Coherent and distinctive structures have been observed within the transition. These structures have been classified as pseudo-slug flow. The nature of pseudo-slug flow is not well understood due to the complexity of the structure. At low liquid loading conditions, this flow pattern can occupy a large operating region and cannot be neglected. This paper presents a detailed experimental work conducted in a facility with a valley configuration, focusing on the transition region between segregated and slug flows. Wire-mesh sensors were employed to investigate the liquid phase distribution within the flow structure.
The current paper investigates the flow patterns and their transition in upward inclined pipe from different perspectives. The investigation includes analysis of images from high-speed videos, evaluation of 2-D liquid holdup axial evolution, 2-D liquid holdup distribution at pipe cross-section, 3-D interfacial structure evolution, and analysis of pressure gradient and liquid holdup measurement, flow characteristics, etc. Differences between slug and pseudo-slug flows are also presented.
Three superficial liquid velocities (0.001, 0.005 and 0.01 m/s) and five inclination angles (2°, 5°, 10°, 15°, and 20°) are studied. Simplified correlations are proposed for pseudo-slug structural velocity, showing fair agreement.

Keywords: Pseudo-slug Flow; Flow Pattern Transition; Two-phase Flow in Inclined Pipe; Wire-mesh Sensor; Low Liquid Loading


Publ.-Id: 27867

Synthesis and Characterization of Tetravalent Actinide Complexes with Nitrogen Donor Ligands

Schöne, S.; Kloditz, R.; März, J.; Kaden, P.; Patzschke, M.; Roesky, P. W.; Stumpf, T.; Ikeda-Ohno, A.

In contrast to the dominant trivalent state for the lanthanide series (Ln(III)), a wide variety of oxidation states (from II to VII) of actinides (An) makes their chemistry intricate but attractive. Especially the early An thorium (Th), uranium (U), neptunium (Np) and plutonium (Pu) form highly charged cations with the oxidation state of four (An4+), which are of particularly interest for the coordination chemistry due to their strong interaction with ligands. Furthermore, the tetravalent oxidation state of these An is also preferred under reductive conditions that could potentially occur in the environment. Hence, the understanding of the interaction mechanisms between tetravalent An (An(IV)) and naturally occurring ligands is of crucial importance particularly for the safety assessment of nuclear waste repository.
The overall aim of our investigations lies in the comprehensive characterization of An(IV) complexes with ligands bearing soft donor atoms, such as nitrogen (N), both in the solid state and in solution. The present study focuses particularly on the interaction of An(IV) with N-donor ligands of amidinate and guanidinate type, which could be considered as a simplified model of naturally occurring N-donor organic compounds.

Recently, the Ln(III) complexes with the chiral benzamidine, (S,S)-N,N-Bis-(1-phenylethyl)-benzamidine ((S)-HPEBA, Fig.1), have been successfully synthesized by the group of Prof. Roesky1,2. Our study is inspired by these precedent studies and has succeeded to obtain the first chiral benzamidinate complexes of An(IV) [An((S)-PEBA)3Cl] (An= Th, U and Np) as well as that of Ce(IV), a chemical analog of An(IV).

The structure of the synthesized complexes was determined by single-crystal X-ray diffraction (SC-XRD), revealing that the An(IV) center is coordinated by three chiral benzamidinates and one chloride in a monocapped distorted octahedral coordination geometry.

The isostructurality of the obtained An(IV) complexes enables a direct comparison of the binding situation across the series. Quantum chemical calculations indicate that the bonding between An(IV) and the N atoms in the ligand strengthens by comparing Th(IV) to U(IV) due to the contribution of 5f-electrons to the chemical bonding.
The complexes were also characterized in solution with NMR spectroscopy. Due to the electronic interactions between the paramagnetic metal center and the ligand, significant NMR chemical shifts are observed, which can be further correlated with the distance between the metal center and the measured nuclei as well as the angle towards the principal axis of the molecule. The Th(IV) complex serves as a diamagnetic reference to subtract non-paramagnetic contributions from the observed chemical shift and to calculate the hyperfine shifts. Hence, the structure information on the paramagnetic complexes in solution can be acquired by the paramagnetic NMR spectroscopy.


This study was supported by the German Federal Ministry of Education and Research (BMBF) funding under the project No. 02NUK046B (FENABIUM).


1. P. BENNDORF, C. PREUẞ, P W. ROESKY: “Synthesis of Enantiomeric Pure Lithium and Potassium Benzamidinate Complexes” J. Organomet. Chem., 696, 1150 (2011).
2. P. BENNDORF, J. KRATSCH, L. HARTENSTEIN, C. PREUẞ, P W. ROESKY: “Chiral Benzamidinate Ligands in Rare-Earth-Metal Coordination Chemistry” Chem. Eur. J., 18, 14454 (2012).

  • Poster
    Plutonium Futures 2018, 09.-14.09.2018, San Diego, USA

Publ.-Id: 27866

Second Reply to “Comment on Methodological accuracy of image-based electron density assessment using dual-energy computed tomography” [Med. Phys. 44, 2429-2437 (2017)]

Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.

To the Editor,
The recent letter by Dr. Saito refers to the theoretical framework of electron-density determination by dual-energy computed tomography (DECT), as presented in the appendix of our article.1 After performing some calculations in this framework, the author of the Comment concludes that “the form of Eq. (A1) […] is not appropriate to rigorously derive Eq. (3)”. This conclusion is clearly illogical and contradictory to other statements by the author.

Keywords: dual-energy computed tomography; proton therapy; range prediction

Publ.-Id: 27865

Surficial and deep earth material prediction from geochemical compositions - a spatial predictive model

Talebi, H.; Mueller, U.; Tolosana-Delgado, R.; Grunsky, E. C.; Mckinley, J. M.; de Caritat, P.

Prediction of true classes of surficial and deep earth materials using multivariate geospatial data is a common challenge for geoscience modellers. Most geological processes leave a footprint that can be explored by geochemical data analysis. These footprints are normally complex statistical and spatial patterns buried deep in the high-dimensional compositional space. This paper proposes a spatial predictive model for classification of surficial and deep earth materials derived from the geochemical composition of surface regolith. The model is based on a combination of geostatistical simulation and machine learning approaches. A random forest predictive model is trained and features are ranked based on their contribution to the predictive model. To generate potential and uncertainty maps, compositional data are simulated at unsampled locations via a chain of transformations (isometric log-ratio transformation followed by the flow anamorphosis) and geostatistical simulation. The simulated results are subsequently back-transformed to the original compositional space. The trained predictive model is used to estimate the probability of classes for simulated compositions. The proposed approach is illustrated through two case studies. In the first case study the major crustal blocks of the Australian continent are predicted from the surface regolith geochemistry of the National Geochemical Survey of Australia project. The aim of the second case study is to discover the superficial deposits (peat) from the regional-scale soil geochemical data of the Tellus project. The accuracy of the results in these two case studies confirms the usefulness of the proposed method for geological class prediction and geological process discovery.

Keywords: Compositional data; Log-ratio; flow anamorphosis; geostatistical simulation; machine learning

Publ.-Id: 27864

Geostatistical Simulation of Geochemical Compositions in the Presence of Multiple Geological Units: Application to Mineral Resource Evaluation

Talebi, H.; Mueller, U.; Tolosana Delgado, R.; van den Boogaart, K. G.

An accurate prediction of benefit in ore deposits with heterogeneous spatial variations requires the definition of geological domains that differentiate the types of mineralogy, alteration, and lithology, as well as the prediction of full mineral and geochemical compositions within each modeled domain and across boundaries between different domains. This paper proposes and compares various approaches (different combinations of log-ratio transformation, Gaussian and flow anamorphosis, and deterministic or probabilistic geological models) for geostatistical simulation of geochemical compositions in the presence of several geological domains. Different approaches are illustrated through an application to a nickel–cobalt laterite deposit located in Western Australia. Four rock types (ferruginous, smectite, saprolite, and ultramafic) are considered to define compositionally homogeneous domains. Geochemical compositions are comprised of six different components of interest (Fe, Al, Mg, Ni, Co, and Filler). The results suggest that the flow anamorphosis is a vital element for geostatistical modeling of geochemical composition due to its invariance properties and capability for reproducing complex patterns in input data, including: presence of outliers, presence of several populations (due to the presence of several geological domains), nonlinearity, and heteroscedasticity.

Keywords: Compositional data; Log-ratio; Flow anamorphosis; Geostatistical simulation; Geological domaining


Publ.-Id: 27863

Experimental modelling of continuous casting of steel in slab moulds using low melting liquid metals

Timmel, K.; Wondrak, T.; Eckert, S.

Electromagnetic actuators are widely used in industry for contactless control of the steel flow in the continuous casting process. However, a real control of the flow structure by those actuators is a challenging task due to the lack of flow monitoring devices. Even a satisfying non real-time characterisation of the melt flow from plant measurements is missing. Beside numerical simulations, only a very few spatially and temporally limited measurements in liquid steel are available to investigate the actual action of the magnetic fields on the fluid.
Therefore, model experiments with low melting point liquid metals are an important tool to investigate the flow structure and related transport processes in the mould of a continuous caster. Their advantage is the availability of a variety of measurement techniques for quantitative flow measurements. The application of the Ultrasonic-Doppler-Velocimetry (UDV) and the Contactless-Inductive-Flow-Tomography (CIFT) allows for a detailed characterization of the mould flow with a reasonable spatial and temporal resolution.
In recent experiments at HZDR, the systematic study on the influence of an electromagnetic brake on the mould flow in a slab caster was continued. The measurements were carried out using a 1:2 scaled model operated with SnBi and a 1:8 scaled model operated with GaInSn, respectively. The melt surface was partly measured by a laser scanner system. In particular, the immersion depth of the submergence entry nozzle (SEN) was varied during the experiments. It became obvious that changes in the mould flow had a strong influence on the free surface of the melt, where strong perturbations can significantly impair the surface quality of the final steel strands. Moreover, effects from the “artificial” clogging of one SEN-port or the injection of Argon gas at the stopper rod were investigated.

Keywords: Continuous Casting; Liquid metal models; ultrasonic wave guides

  • Lecture (Conference)
    The 9th International Symposium on Electromagnetic Processing of Materials, 14.-18.10.2018, Hyogo, Japan
  • Open Access Logo IOP Conference Series: Materials Science and Engineering 424(2018), 012032
    DOI: 10.1088/1757-899X/424/1/012032
    ISSN: 1757-899X
    Cited 1 times in Scopus

Publ.-Id: 27862

LSC-Anwendungen beim Rückbau von Kernkraftwerken

Barkleit, A.

Vorstellung FORKA-Projektskizzen

  • Lecture (Conference)
    LSC-Anwendertreffen, 11.-12.09.2018, Hannover, Deutschland

Publ.-Id: 27861

Do rotating magnetic fields unconditionally lead to grain refinement? – A case study for directionally solidified Al-10wt%Cu alloys

Zimmermann, G.; Pickmann, C.; Schaberger-Zimmermann, E.; Galindo, V.; Eckert, K.; Eckert, S.

The effect of solidification velocity and electromagnetic stirring on grain refining was investigated experimentally during the directional solidification of rod-like Al-10wt%Cu alloy samples. Applying low solidification velocities leads to a dendritic microstructure consisting of elongated equiaxed crystals, which result from fragmented dendrite arms forming new grains. This grain-refining effect vanishes for higher solidification velocities, leading to a microstructure dominated by a lower number of larger columnar grains. Moderate electromagnetic stirring under laminar flow conditions does not promote grain refinement. By contrast, a sufficiently strong forced melt flow induced by a rotating magnetic field significantly increases the number of grains in the range of solidification velocities investigated within this study. It is assumed that a turbulent melt flow supports the fragmentation of dendrite arms and thus the formation of new grains, which finally leads to grain refinement.

Keywords: Aluminium-copper alloy; solidification; grain refinement, melt flow


Publ.-Id: 27860

One-pot Cascade Synthesis of Pyrazole-based Isosteres of Valdecoxib by a [3+2] Cycloaddition/[1,5] Sigmatropic Rearrangement Sequence and Evaluation of their COX Inhibitory Activity

Roscales, S.; Bechmann, N.; Pietzsch, J.; Kniess, T.

A series of 5-methyl-3,4-diaryl-substituted 1H-pyrazoles, N-isosteres of valdecoxib, was synthesized by a [3+2] cycloaddition/[1,5] sigmatropic rearrangement sequence starting from tosylhydrazine, aryl methyl ketones and terminal aryl alkynes bearing various substituents (H, Me, OMe, F, SO2Me, SO2NH2). New pyrazoles were prepared regioselectively in a one-pot process with moderate-good yields. All compounds were used in in vitro cyclooxygenase (COX) assays to determine inhibitory potency and selectivity to COX-1 and COX-2. In general, these new pyrazoles are characterized by selective COX-2 inhibition activity in a micromolar range. Structure-activity relationship studies showed that compounds possessing an electron-withdrawing group (F) in one of the aryl rings displayed higher COX-2 inhibition selectivity and activity than was determined for compounds containing electron-donating groups (Me, OMe).

Keywords: pyrazole; COX inhibition; cycloaddition; sigmatropic rearrangement; tosylhydrazone


Publ.-Id: 27859

Arming human regulatory T cells from healthy donors or multiple sclerosis patients with switchable chimeric antigen receptors for the treatment of inflammatory diseases

Kegler, A.; Koristka, S.; Bergmann, R.; Arndt, C.; Feldmann, A.; Albert, S.; Ehninger, G.; Bornhäuser, M.; Schmitz, M.; Akgün, K.; Ziemssen, T.; Bachmann, M.

Regulatory T cells (Tregs) possess a central role in impeding harmful immune reactions and represent important immunomodulatory players in the pathogenesis of inflammatory diseases. For that reason, Tregs are intensively studied as an innovative cell product for the treatment of autoimmunity e.g. multiple sclerosis (MS) or Graft-versus-Host disease. In recent years, several preclinical mouse model clearly demonstrate a superior suppressive capacity of antigen-specific Tregs compared to polyclonal cells. On the downside, isolation of Tregs with a distinct antigen-specificity is a highly time-consuming and laborious process.
To overcome these challenges, we armed polyclonal Tregs isolated from healthy donors or MS patients with a universal chimeric antigen receptor (UniCAR) construct. As T cells and target cells are indirectly cross-linked by a separate, antigen-binding targeting module (TM), this innovative technology enables side-specific redirection of Tregs to any desired surface structure. Moreover, UniCAR armed Tregs are silenced in the absence of the TM allowing for a finely tuned regulation of Treg activity between an “on” and “off” status.
Here, we demonstrate that highly pure CD4+CD25highCD127dimCD45RA+ Tregs isolated from both healthy donors or MS patients stably express a UniCAR construct with an intracellular 4-1BB/ζ signaling domain. UniCAR-engrafted Tregs vigorously expand and maintain their phenotype even under pro-inflammatory conditions. Most importantly, upon TM-activation UniCAR-endowed Tregs significantly hamper autologous T effector cells both in vitro and in vivo.
Taken together, our results underline the enormous therapeutic potential of the UniCAR system for treatment of inflammatory diseases including MS, as it facilitates an antigen-specific and precisely controlled Treg activation at the side of inflammation. Moreover, this innovative technology allows redirection of Tregs against a wide range of surface structures simply by exchanging the TM and might thereby broaden current treatment modalities.

  • Lecture (Conference)
    First International Conference on Lymphocyte Engineering (ICLE), 13.-15.09.2018, Madrid, Spain
  • Open Access Logo Abstract in refereed journal
    Human Gene Therapy (2018), ICLE8-0038
    DOI: 10.1089/hum.2018.29071.abstracts

Publ.-Id: 27858

Efficient suppression of effector T cells isolated from multiple sclerosis patients by autologous, UniCAR-engrafted Tregs

Kegler, A.; Koristka, S.; Arndt, C.; Feldmann, A.; Seifert, A.; Ehninger, G.; Bornhäuser, M.; Schmit, M.; Akgün, K.; Ziemssen, T.; Bachmann, M.

In multiple sclerosis (MS) patients pathogenic, autoreactive effector T cells (Teffs) provoke demyelination and central nerve system damage. To impede those harmful immune reactions, the adoptive transfer of regulatory T cells (Tregs) emerged as a promising therapeutic strategy. Several preclinical mouse models confirm an inferior functionality of polyclonal compared to antigen-specific Treg cells. However, isolation and expansion of Tregs with a desired antigen-specificity proves to be highly time-consuming and labor-intensive.
To overcome these hurdles, we armed polyclonal Tregs isolated from MS patients with a universal chimeric antigen receptor (UniCAR) construct. This innovative technology allows a site-specific redirection of cells against any desired surface structure, as cross-linkage to target cells is mediated by a separate, antigen-binding targeting module (TM).
Highly pure CD4+CD25highCD127dimCD45RA+ MS-Tregs could be genetically modified to stably express the UniCAR 4-1BB/ζ construct. UniCAR-endowed Tregs strongly expand and show phenotypic stability also upon pro-inflammatory challenge. By adding a TM in the presence of target cells, UniCAR-engrafted Tregs are antigen-specifically activated demonstrated by CD69 and LAP upregulation. Most importantly, upon TM-stimulation UniCAR-armed Tregs efficiently suppress pre-activated, patient-derived Teffs.
Taken together, the UniCAR system holds an enormous therapeutic potential for MS, as it not only allows a site-specific and precisely regulated Treg activation but also confers strong suppressive capacity to Tregs from MS patients. Thereby, this innovate technology might broaden current treatment strategies to overcome impaired functionality of Tregs as well as resistance of pathogenic Teffs to Treg suppression reported for MS patients.

Keywords: Multiple sclerosis; regulatory T cells; chimeric antigen receptor

  • Lecture (Conference)
    5th European Congress of Immunology, 03.-05.09.2018, Amsterdam, The Netherlands

Publ.-Id: 27857

Collision probability of particles within the bubble wake and the influence on the flotation recovery measured by 4D particle tracking velocimetry

Sommer, A.-E.; Heitkam, S.; Rudolph, M.; Eckert, K.

Froth flotation is a fundamental technique to separate minerals. Hydrophobized target particles attach to the fluidic interface of gas bubbles rising in a suspension. The success of the process depends on both the surface chemistry for the hydrophobization of particles and the hydrodynamics for an encounter between bubble and particle. To quantify this performance in terms of recovery, the number of target particles at various times in a reference volume is measured. One of the remaining challenges in this field is the flotation of fine particles with a size below 10µm. Caused by their small inertia, the particles follow the streamlines around the bubble and no collision occurs.

This work focuses on the measurement of the collision probability of particles with a small inertia at the bubble surface to advance our understanding of relevant microprocesses and its influence on the flotation recovery. With a 4D particle tracking velocimetry device the particle and bubble trajectories were measured simultaneously with a high temporal (1000 fps) and spatial resolution (0.03 mm/pixels). We developed an algorithm to evaluate the flotation recovery based on the collision and attachment probability. The three-phase flow within a rectangular bubble column consisted of fluorescent polystyrene particles (33 µm, 1.05 g/cm^3), a bubble chain(1 - 7mm) and deionized water with methanol. The variation of the bubble diameter and methanol concentration led to a change of the fluid flow around the bubble (Re=100 - 1200) and the particle hydrophobization. The results show the preferred collision of the particles at the rear of the bubble due to a higher acceleration within the vortices.

  • Lecture (Conference)
    12th European Fluid Mechanics Conference, 09.-13.09.2018, Wien, Österreich

Publ.-Id: 27856

Elimination of CAR-engineered lymphocytes by autologous anti-CAR T cells

Koristka, S.; Ziller-Walter, P.; Bergmann, R.; Arndt, C.; Feldmann, A.; Kegler, A.; Seifert, A.; Bornhäuser, M.; Bachmann, M.

The adoptive transfer of chimeric antigen receptor (CAR) T cells represents one of the fastest growing areas in cancer immunotherapy. Although gene-modified cells have shown unparalleled antitumor efficiency in patients suffering from hematological malignancies, highly potent CAR T cells can cause severe and partly life-threatening on-target and off-target effects including of cytokine release syndrome and neurological toxicity. Consequently, there is an increasing demand for developing effective strategies to selectively eliminate gene-modified cells in vivo.
One possible approach represents the insertion of a targetable moiety into CAR T cells. In that regard, we previously characterized a small peptide epitope (E-tag) derived from the human nuclear La protein which we incorporated into the extracellular spacer region of CARs. Based on a monoclonal anti-La antibody recognizing this epitope, we generated a CAR construct for specific binding and depletion of E-tag-labelled CAR T cells.
In flow cytometry-based cytotoxicity assays, T cells redirected via the novel CAR construct selectively eliminated E-tag-expressing CAR T cells whilst cells lacking this epitope on their surface were not attacked. Interestingly, T cell killing was reciprocal and dependent on an intracellular signaling domain as well as the effector to target cell ratio. Our studies further indicate that T cells expressing high CAR levels were more efficiently depleted than T cells with low CAR expression. In addition, CD4+ and CD8+ target cells were equally well eliminated by both CD4+ and CD8+ effector T cells.
Altogether, we here provide an approach for specific and efficient depletion of overactive CAR T cells in case patients experience severe side effects. The E-tag can easily be included into all CARs irrespective of the targeted tumor antigen and represents a promising tool to improve safety of cell-based immunotherapies.

Keywords: Chimeric antigen receptor; T lymphocytes; immunotherapy; toxicity management; epitope tag

  • Poster
    First International Conference on Lymphocyte Engineering (ICLE), 13.-15.09.2018, Madrid, Spain
  • Open Access Logo Abstract in refereed journal
    Human Gene Therapy 29(2018)11, ICLE8-0037
    DOI: 10.1089/hum.2018.29071.abstracts

Publ.-Id: 27855

Depletion of CAR-expressing lymphocytes using autologous anti-CAR-engrafted T cells

Koristka, S.; Ziller-Walter, P.; Bergmann, R.; Feldmann, A.; Arndt, C.; Kegler, A.; Seifert, A.; Ehninger, G.; Bornhäuser, M.; Bachmann, M.

Adoptive transfer of chimeric antigen receptor (CAR) T cells represents one of the fastest growing areas in cancer immunotherapy. Albeit gene-modified cells have demonstrated unparalleled antitumor efficiency in B cell malignancies, highly potent CAR T cells can cause severe and partly life-threatening side effects including cytokine release syndrome, neurological toxicity and off-target effects. Hence, there is an increasing demand for developing effective approaches to selectively ablate gene-modified cells in vivo.
Previously, we described an epitope tag (E-tag) derived from the human nuclear protein La that is incorporated into the extracellular domain of CARs and accessible by an anti-La monoclonal antibody (mAb). Based on this mAb, we generated a novel CAR construct for specific binding and depletion of E-tag-expressing CAR T cells.
We demonstrate that anti-E-tag-redirected T cells selectively eliminate CAR T cells that extracellularly express the E-tag whilst CAR T cells lacking this tag are not attacked. Interestingly, T cell killing is reciprocal and occurs in dependence of an intracellular signaling domain. Our studies further indicate that T cells expressing high CAR levels are more efficiently depleted than T cells with low CAR expression. Besides, CD4+ and CD8+ target cells are equally well eliminated by both CD4+ and CD8+ effector T cells.
Overall, we provide an approach for specific and efficient depletion of overactive CAR T cells in case patients experience severe side effects. The E-tag can be incorporated into all CARs irrespective of the targeted tumor antigen and represents a promising tool to improve safety of cell-based immunotherapies.

Keywords: Chimeric antigen receptor; T lymphocytes; immunotherapy; toxicity management; epitope tag

  • Poster
    5th European Congress of Immunology, 03.-05.09.2018, Amsterdam, The Netherlands

Publ.-Id: 27854

Integration of Terrestrial and Drone-Borne Hyperspectral and Photogrammetric Sensing Methods for Exploration Mapping and Mining Monitoring

Kirsch, M.; Lorenz, S.; Zimmermann, R.; Tusa, L.; Möckel, R.; Hödl, P.; Booysen, R.; Khodadadzadeh, M.; Gloaguen, R.

Mapping lithology and geological structures accurately remains a challenge in difficult terrain or in active mining areas. We demonstrate that the integration of terrestrial and drone-borne multi-sensor remote sensing techniques significantly improves the reliability, safety, and efficiency of geological activities during exploration and mining monitoring. We describe an integrated workflow to produce a geometrically and spectrally accurate combination of a Structure-from-Motion Multi-View Stereo point cloud and hyperspectral data cubes in the visible to near-infrared (VNIR) and short-wave infrared (SWIR), as well as long-wave infrared (LWIR) ranges acquired by terrestrial and drone-borne imaging sensors. Vertical outcrops in a quarry in the Freiberg mining district, Saxony (Germany), featuring sulfide-rich hydrothermal zones in a granitoid host, are used to showcase the versatility of our approach. The image data are processed using spectroscopic and machine learning algorithms to generate meaningful 2.5D (i.e., surface) maps that are available to geologists on the ground just shortly after data acquisition. We validate the remote sensing data with thin section analysis and laboratory X-ray diffraction, as well as point spectroscopic data. The combination of ground- and drone-based photogrammetric and hyperspectral VNIR, SWIR, and LWIR imaging allows for safer and more efficient ground surveys, as well as a better, statistically sound sampling strategy for further structural, geochemical, and petrological investigations.

Keywords: hyperspectral imaging; Structure-from-Motion (SfM); mineral mapping; virtual outcrops; geology; hydrothermal; UAV; long-wave infrared

Publ.-Id: 27853

Metal oxide double layer capacitors by electrophoretic deposition of metal oxides. Fabrication, electrical characterization and defect analysis using positron annihilation spectroscopy

Hoffmann, R. C.; Koslowski, N.; Sanctis, S.; Liedke, M. O.; Wagner, A.; Butterling, M.; Schneider, J. J.

Films consisting of nanocrystalline ZnO were deposited on ITO/glass electrodes using an electrophoretic process. The microwave-assisted thermolysis of zinc alkyl-acetoacetates resulted in the formation of stable dispersions for the electrophoretic deposition procedure. Uniform and smooth coatings could be achieved by starting the electrophoresis at lower voltages first and increasing to higher voltages at later stages of the deposition. The ZnO/ITO double layers were integrated in metal oxide semiconductor (MOS) capacitors by completing the set-up with a spin-coated PMMA dielectric layer and gold contacts. The MOS capacitors showed IV curves with a region of negative differential resistance, indicating charge trapping, both in the ZnO grains and at the ZnO/PMMA interface. Doppler broadening positron annihilation (DB-PAS) and positron annihilation life time spectroscopy (PALS) were employed to characterize the point defects and void space within the deposited ZnO layer which allowed to give insight into the bulk composition of the film composition. PALS revealed the presence of micropores in the range of 0.5 to 1.5 nm.

Keywords: positron annihilation spectroscopy; electrophoretic deposition; defect analysis

Related publications

Publ.-Id: 27852

Post-Younger Dryas fault instability and deformations on ice lineations in Finnish Lapland

Sutinen, R.; Andreani, L.; Middleton, M.

The Younger Dryas phase, which occurred between 12.8 and 11.5 ka as a part of the cyclic pattern of global climatic changes, was concurrent with maximum fault instability (13–10 ka) in the Fennoscandian shield. Ice lineations, indicative of glacial streaming toward the Younger Dryas end moraines (YDEMs), may have faced earthquake impacts within the glacial isostatic adjustment (GIA). Morphometric analyses for airborne laser scanning (ALS) revealed that ice lineations were deformed subglacially and subaerially in Finnish Lapland. The subglacial water outburst flows diagonally eroded the drumlins, 50 km from the YDEMs in Utsjoki, northern Finnish Lapland. Similarly north, in the Sevetti area, 40 km from the YDEMs a large portion of the ice lineations were entirely distorted by the subglacial squeeze-up Pulju moraine and liquefaction bowl formations. In the interior part of the Fennoscandian Ice sheet (FIS) in Kemijärvi, representing onset of an ice-stream fan 200 km from the YDEMs, mass flows had reworked the ice lineations. Based on the electrical-sedimentry anisotropy, mass flow sediments deviated from the ice flow pattern. Postglacial liquefaction craters were created on the drumlins in Utsjoki and also in Kuusamo, eastern Finnish Lapland, 70 km from the YDEMs in Russian Karelia. We interpret these features as indications of paleoseismic events associated with GIA.

Keywords: Lidar DEM; Pulju moraine; Liquefaction; Mass flow


Publ.-Id: 27851

The role of sulfate-reducing microorganisms in the barrier-material bentonite

Matschiavelli, N.; Kluge, S.; Standhaft, D.; Podlech, C.; Grathoff, G.; Cherkouk, A.

The “Helmholtz-Zentrum Dresden-Rossendorf” (HZDR) is a registered, non-profit institution supported by the authorities of the Federal Go¬vernment and the Free State of Saxony (Germany). The HZDR conducts research in the sectors energy, health and matter. Besides the headquarters in Dresden, we have four other research sites in Grenoble/France, Freiberg, Leipzig, and Schenefeld near Hamburg.
We are working in the department of Biogeochemistry, which is part of the Institute of Resource Ecology. Here, research focusses on the assessment and reduction of risks related to the nuclear fuel cycle, particularly on the disposal of nuclear waste. Of special interest is the understanding of fundamental processes defining transport and accumulation of radiotoxic elements in the geo- and biosphere including the food chain. Chemists, biologists and physicists at our institute use a multitude of methods and tools to identify dominating processes in the ecosphere to understand the (biogeo-) chemistry of the processes on a molecular level with the objective of estimating their relevance for radionuclide migration and identification of potential risks during long-term storage of nuclear waste. In order to identify and characterize chemical species, varieties of spectroscopic tools are used. For the identification and characterization of microorganisms that could potentially influence migration processes of radionuclides or the geochemical properties of materials that are used in a nuclear waste repository, bio-geochemical and molecular biological methods are applied.

  • Lecture (others)
    Advanced training course in geomicrobiology in radioactive waste disposal, 08.-11.10.2018, Mol, Belgium

Publ.-Id: 27850

Development and characterization of novel anti GD2 target modules for retargeting of Universal CAR T cells toward GD2 expressing tumors

Mitwasi, N.; Feldmann, A.; Bergmann, R.; Berndt, N.; Rössig, C.; Bachmann, M.

Although chimeric antigen receptor (CAR) engineered T cells demonstrated promising therapeutic effect against cancer, they are still associated with adverse side effects which could be life threatening in some cases. Therefore, in our group we have developed a switchable universal CAR T cell platform “UniCAR”, which can be repeatedly switched on and off. This system consists of CAR T cells that cannot bind tumor antigens directly but instead they are redirected with a target module (TM). Such TMs are mainly composed of an epitope on one side, which is recognized by the UniCAR T cells, and on the other side a tumor antigen-binding domain. Once the TM is eliminated, the UniCAR T cells are no more activated. Disialoganglioside GD2 was shown previously to be a very promising target for several tumors such as neuroblastoma and Ewing’s sarcomas. Therefore, anti-GD2 TMs were developed and evaluated regarding their functionality. They were shown to be functional in activating the UniCARs to secrete important pro-inflammatory cytokines and to kill GD2+ tumor cells both in vivo and in vitro. To further characterize the anti-GD2 TM with PET imaging, it was labeled with radioactive Cu64 . The TM showed a specific enrichment at the site of the GD2+ growing tumor, and it was mainly eliminated through the kidneys within half an hour due to its small size. Such short half-life, provides the UniCAR system with the fast safety switch in case any complications occurred in patients treated with the UniCAR T cells.

  • Lecture (Conference)
    5th European Congress of Immunology, 02.09.2018, Amsterdam, the Netherlands

Publ.-Id: 27849

Direct Capture Cross Section and the Ep=71 and 105 keV Resonances in the 22Ne(p,γ)23Na Reaction

Ferraro, F.; Takács, M. P.; Piatti, D.; Cavanna, F.; Depalo, R.; Aliotta, M.; Bemmerer, D.; Best, A.; Boeltzig, A.; Broggini, C.; Bruno, C. G.; Caciolli, A.; Chillery, T.; Ciani, G. F.; Corvisiero, P.; Davinson, T.; D’Erasmo, G.; Dileva, A.; Elekes, Z.; Fiore, E. M.; Formicola, A.; Fülöp, Z.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, G.; Imbriani, G.; Junker, M.; Kochanek, I.; Lugaro, M.; Marigo, P.; Menegazzo, R.; Mossa, V.; Pantaleo, F. R.; Paticchio, V.; Perrino, R.; Prati, P.; Schiavulli, L.; Stöckel, K.; Straniero, O.; Szücs, T.; Trezzi, D.; Zavatarelli, S.

The 22Ne(p,γ)23Na reaction, part of the neon-sodium cycle of hydrogen burning, may explain the observed anticorrelation between sodium and oxygen abundances in globular cluster stars. Its rate is controlled by a number of low-energy resonances and a slowly varying nonresonant component. Three new resonances at Ep=156.2, 189.5, and 259.7 keV have recently been observed and confirmed. However, significant uncertainty on the reaction rate remains due to the nonresonant process and to two suggested resonances at Ep=71 and 105 keV. Here, new 22Ne(p,γ)23Na data with high statistics and low background are reported. Stringent upper limits of 6×10−11 and 7×10−11  eV (90% confidence level), respectively, are placed on the two suggested resonances. In addition, the off-resonant S factor has been measured at unprecedented low energy, constraining the contributions from a subthreshold resonance and the direct capture process. As a result, at a temperature of 0.1 GK the error bar of the 22Ne(p,γ)23Na rate is now reduced by 3 orders of magnitude.

Keywords: asymptotic giant branch stars; nuclear astrophysics; LUNA Laboratory Underground for Nuclear Astrophysics; Hot Bottom Burning; Radiative Capture


Publ.-Id: 27848

Extremely efficient terahertz high harmonic generation in graphene by hot Dirac fermions

Hafez, H. A.; Kovalev, S.; Deinert, J.-C.; Mics, Z.; Green, B.; Awari, N.; Chen, M.; Germanskiy, S.; Lehnert, U.; Teichert, J.; Wang, Z.; Tielrooij, K.-J.; Liu, Z.; Chen, Z.; Narita, A.; Müllen, K.; Bonn, M.; Gensch, M.; Turchinovich, D.

Multiple optical harmonics generation—the multiplication of photon energy as a result of nonlinear interaction between light and matter—has become one of the key technologies in modern electronics and optoelectronics. Owing to its unique electronic band structure featuring massless Dirac fermions, graphene has been repeatedly predicted to have high efficiency of optical harmonics generation in the technologically important terahertz frequency range. So far, experiments have failed to confirm these predictions under technologically relevant operation conditions. Here we report the generation of terahertz harmonics up to the seventh order in single-layer graphene at room temperature and under ambient conditions, driven by terahertz fields of only tens of kilovolts per centimetre, and with field conversion efficiencies in excess of 10⁻³, 10⁻⁴ and 10⁻⁵ for the third, fifth and seventh terahertz harmonics, respectively. The key to such highly efficient harmonics generation in graphene is the collective thermal response of its background Dirac electrons to the driving terahertz fields. The generated terahertz harmonics were observed directly in the time domain as electromagnetic field oscillations at these newly synthesized frequencies. The effective nonlinear optical coefficients of graphene for the third, fifth and seventh harmonics exceed the respective nonlinear coefficients of typical solids by 7–18 orders of magnitude. Our results provide a direct pathway to highly efficient terahertz frequency synthesis that is within the capabilities of the present generation of graphene electronics operating at fundamental frequencies of only a few hundreds of gigahertz.

Keywords: Graphene; Terahertz; High Harmonics; Nonlinear Optics; Ultrafast Electronics; Superradiant Terahertz

Related publications


Publ.-Id: 27847

Irradiation effects on the structural and optical properties of single crystal β-Ga2O3

Liu, C.; Berencén, Y.; Yang, J.; Wei, Y.; Wang, M.; Yuan, Y.; Xu, C.; Xie, Y.; Li, X.; Zhou, S.

In the present work, we report the 25 MeV oxygen irradiation effects in n-type single crystal β-Ga2O3 at different fluences. We demonstrate that the symmetric stretching modes and bending vibrations of GaO4 and GaO6 units are impaired upon increasing O irradiation fluence. Blue and green photoluminescence emission bands are found to be mainly associated with gallium-oxygen divacancies, gallium vacancies and oxygen interstitials. The increase of optically active centers at low fluence and the photoluminescence quenching at high fluence are ascribed to the reduction of carrier density and the production of non-radiative recombination centers, respectively. The results envisage the possibility of obtaining pre-designed spectral behaviours by varying the oxygen irradiation fluence.

Keywords: β-Ga2O3; ion irradiation; photoluminescence; radiation defect


Publ.-Id: 27845

UDV flow measurements in a model of the Czochralski crystal growth process

Franke, S.; Pal, J.; Eckert, S.

This contribution describes a model experiment for the Czochralski crystal growth process. Low melting point liquid metals as GaInSn are an important tool to investigate the flow structure for such industrial processes. UDV flow measurements were conducted in a cylindrical Rayleigh-Bénard (RB) setup with modified thermal boundary conditions with and without the influence of an external rotating magnetic field. The topology of the prevailing thermally-driven convection might be very complex and is mainly determined by the aspect ratio of the liquid volume and the strength of the convection described by the characteristic dimensionless Grashof number. Two kinds of techniques were used to investigate the flow. Firstly, by means of single UDV transducers measurements of the radial velocity component were carried out shortly below the melt surface across the entire diameter of the cylindrical liquid column at various azimuthal angles. Secondly, a vertically arranged UDV array was applied at the side of the cylinder to obtain detailed information about the radial velocities in the covered meridional plane. The results reveal the complex flow structure of natural convection in a Czochralski crucible which gains in complexity with applied rotating magnetic field (RMF).

Keywords: Czochralski crystal growth; Rayleigh-Bénard convection; Ultrasound Doppler velocimetry; Flow measurements; Electromagnetic stirring

  • Lecture (Conference)
    11th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, 05.-07.09.2018, Berlin, Germany
  • Contribution to external collection
    in: Proceedings of the 11th International Symposium on Ultrasonic Doppler Methods for Fluid Mechanics and Fluid Engineering, Berlin: Eigenverlag, 2018

Publ.-Id: 27844

Coordination polymers of tetravalent neptunium with aromatic polycarboxylate ligands

Volkringer, C.; Martin, N. P.; März, J.; Hennig, C.; Ikeda-Ohno, A.; Loiseau, T.

Coordination polymers are organic-inorganic complexes built up from the association of metallic centers with O- or N-donor ligands. In the particular case of actinides (An), previous literature mainly has reported the synthesis of solid networks bearing U(VI) or Th(IV). Trans-uranium elements have been much less studied due to their high radiotoxicity and limited amount of the material source.
In this work, we studied the crystallization of Np(IV) with various aromatic polycarboxylate ligands in different solvents and analyzed their crystal structures. In water, an infinite chain of Np2O2(H2O)2(1,2-bdc)2 were isolated in the presence of phthalate, whereas mellitic acid leads to the oxidation of Np(IV) to Np(V) and the formation of inorganic layers of {NpO7H2O0-2}.1 The use of other solvents allowed the crystallization of large polynuclear discrete Np(IV) clusters. For example, using DMF, the hexanuclear unit of [Np6O4(OH)4] has been obtained with different dicarboxylic ligands and is the basic building unit to form an open-framework structure (Figure 1, left). This framework revealed the isolation of the hexanuclear cluster An6O8 with Np(IV).2 The formation of the giant neptunium-based polyoxo cluster called Np38 will be also presented.

Keywords: Actinides; neptunium; tetravalent; coordination polymers; metal-organic frameworks

  • Lecture (Conference)
    International Conference on Coordination Chemistry 2018, 03.08.2018, Sendai, Japan

Publ.-Id: 27843

Short-Range Order in Amorphous and Crystalline Ferroelectric Hf0.5Zr0.5O2

Erenburg, S. B.; Trubina, S. V.; Kvashnina, K. O.; Kruchinin, V. N.; Gritsenko, V. V.; Chernikova, A. G.; Markeev, A. M.

The microstructures of amorphous and polycrystalline ferroelectric Hf0.5Zr0.5O2 films are studied by X-ray spectroscopy and ellipsometry. EXAFS spectra demonstrate that the amorphous film consists of an “incompletely mixed” solid solution of metallic oxides HfO2 and ZrO2. After rapid thermal annealing, the mixed Hf0.5Zr0.5O2 oxide films have a more ordered polycrystalline structure, and individual Hf and Zr monoxide islands form in the films. These islands are several nanometers in size and have a structure that is similar to the monoclinic structure of HfO2 and ZrO2. The presence of the HfO2 and ZrO2 phases in the Hf0.5Zr0.5O2
films is also detected by ellipsometry

Related publications


Publ.-Id: 27841

When defects are not defects

Krasheninnikov, A. V.

Line defects in two-dimensional borophene can self-assemble into new crystalline phases, blurring the distinctions between perfect and defective crystal.

Keywords: 2D materials; STM; defects; first-principles calculations

Related publications


Publ.-Id: 27840

Ag nanoparticles embedded in Nd:YAG crystals irradiated with tilted beam of 200 MeV Xe ions: optical dichroism correlated to particle reshaping

Li, R.; Pang, C.; Amekura, H.; Ren, F.; Hübner, R.; Zhou, S.; Ishikawa, N.; Okubo, N.; Chen, F.

We report on the fabrication of reshaped Ag nanoparticles (NPs) embedded in a Nd:YAG crystal by combining Ag ion implantation and swift heavy Xe ion irradiation. The localized surface plasmon resonance (LSPR) effect is proved to be efficiently modulated according to the phenomenon of polarization-dependent absorption. The LSPR peak located at 448 nm shows red shift and blue shift at 0° and 90° polarization, respectively, which is in good agreement with calculation by discrete dipole approximation. Based on the near-field intensity distribution, the interaction between reshaped NPs shows a non-ignorable effect on the optical absorption. Furthermore, the polarization-dependence of the photoluminescence (PL) intensity is analyzed, which is positively related to the modulated LSPR absorption. It demonstrates the potential of the enhancement of PL intensity by embedded plasmonic Ag NPs. This work breaks the conventional view of the quenching effect of NPs by ion irradiation and opens a new way to realize the modulation of optical dichroism.

Keywords: nanoparticles; localized surface plasmon resonance; swift heavy ion irradiation; ND:YAG crystal

Related publications

Publ.-Id: 27839

Development and validation of NTCP models for acute side-effects resulting from proton beam therapy of brain tumours

Dutz, A.; Lühr, A.; Agolli, L.; Troost, E. G. C.; Krause, M.; Baumann, M.; Vermeren, X.; Geismar, D.; Schapira, E. F.; Bussière, M.; Daly, J. E.; Bussière, M. R.; Timmermann, B.; Shih, H. A.; Löck, S.

Background: The limited availability of proton beam therapy (PBT) requires individual treatment selection strategies, such as based on normal tissue complication probability (NTCP). We developed and externally validated NTCP models for common acute side-effects following PBT in brain tumour patients in effort to provide guidance on optimising patient quality of life.
Methods: An exploration cohort including 113 adult brain tumour patients who underwent PBT was investigated for the following endpoints: alopecia, scalp erythema, headache, fatigue and nausea. Dose–volume parameters of associated normal tissues were used for logistic regression modelling.
Statistically significant parameters showing high area under the receiver operating characteristic curve (AUC) values in internal cross-validation were externally validated on two cohorts of 71 and 96 patients, respectively.
Results: Statistically significant correlations of dose–volume parameters of the skin for erythema and alopecia were found. In internal cross-validation, the following prognostic parameters were selected: V35Gy (absolute volume receiving 35 Gy) for erythema grade ≥1, D2% (dose to 2% of the volume) for alopecia grade ≥1 and D5% for alopecia grade ≥2. Validation was successful for both cohorts with AUC >0.75. A bivariable model for fatigue grade 1 could not be validated externally. No correlations of dose–volume parameters of the brain were seen for headache or nausea.
Conclusion: We developed and successfully validated NTCP models for scalp erythema and alopecia in primary brain tumour patients treated with PBT.

Keywords: NTCP models; Brain tumours; Acute side-effects; Proton beam therapy


Publ.-Id: 27838

Keine Überlegenheit der Protonentherapie gegenüber der IMRT beim lokal fortgeschrittenen NSCLC

Dutz, A.; Troost, E. G. C.; Löck, S.

Hintergrund: Inoperable und lokal fortgeschrittene nicht-kleinzellige Bronchialkarzinome (NSCLC) werden standardgemäß mit einer simultanen Radiochemotherapie behandelt. In dieser Arbeit untersuchten die Autoren die Hypothese, dass die Lungentoxizität (Strahlenpneumonitis, RP) nach PSPT geringer ist, ohne die Tumorkontrolle zu gefährden.
Methodik: Gemäß Protokoll wurden 149 Patienten behandelt (IMRT: 92, PSPT: 57). Als primärer kombinierter Endpunkt der randomisierten Studie wurde das erste Auftreten einer RP vom Grad ≥3 oder das Auftreten eines Lokalrezidivs innerhalb eines Jahres betrachtet.
Resultate: Die PSPT reduzierte die mittlere Herzdosis signifikant (p = 0,002), während in der mittleren Lungen- und Ösophagusdosis keine Unterschiede zur IMRT auftraten. Eine RP vom Grad ≥3 entwickelten 12 Patienten, je 6 pro Studienarm. Lokalrezidive traten ähnlich häufig in beiden Armen auf. Damit ergab sich kein signifikanter Unterschied im primären kombinierten Endpunkt (IMRT: 17,4 %, PSPT: 21,1 %; p = 0,175). Das mediane Gesamtüberleben betrug 29,5 Monate im IMRT-Arm und 26,1 Monate im PSPT-Arm.
Schlussfolgerung der Autoren: Bei Patienten mit lokal fortgeschrittenem NSCLC konnte kein Unterschied in der Häufigkeit von RP Grad ≥3 oder dem Auftreten von Lokalrezidiven zwischen IMRT und PSPT nachgewiesen werden.
Kommentar: Die vorliegende Arbeit präsentiert die erste abgeschlossene randomisierte klinische Studie, die bei Patienten mit lokal fortgeschrittenem NSCLC prospektiv Ergebnisse von IMRT mit PSPT vergleicht. Das gewählte adaptive Bayes-Studiendesign zur Randomisierung der Patienten erhöht die ethische Vertretbarkeit randomisierter Studien. Allerdings ist der Dosisvergleich in benachbarten Risikoorganen zwischen beiden Strahlungsmodalitäten kritisch zu sehen. Im PSPT-Arm wurden mehr Patienten mit der höheren Dosis von 74 Gy bestrahlt als im IMRT-Arm. Die hohe Rate an RP im PSPT-Arm wird mit einer Lernkurve des Personals erklärt, obwohl eine andere plausible Erklärung die signifikant höheren Tumorvolumina sein können. Eine Analyse der mittleren biologischen Lungendosis könnte vorteilhafter sein als die Analyse der physikalischen Dosis.


Publ.-Id: 27837

Long term investigation of the degradation of coaxial cables in an ionizing radiation environment

Kuntzsch, M.; Schurig, R.; Burger, S.; Weber, T.

For the transport of RF signals coaxial cables with PTFE ("Teflon") as dielectric medium are widely used because they offer a wide bandwidth and low insertion loss. Coaxial cables that are routed in immediate vicinity to the beamline are exposed to ionizing radiation that is mainly generated by beam-loss. In this radiative environment cables change their electrical properties which directly affects the signal on the receiver side and in turn the measured beam parameters. This contribution describes a measurement setup at the superconducting CW accelerator ELBE that was used to investigate the degradation of coaxial cables under well-controlled conditions up to an accumulated dose of 94 kGy. Furthermore the acquired data up to 40 GHz of two coaxial cable samples are presented and the results are discussed.

Keywords: RF; cable; radiation; 40 GHz; ELBE

Related publications

  • Open Access Logo Contribution to proceedings
    International Beam Instrumentation Conference 2018 (IBIC18), 09.-13.09.2018, Shanghai, China
    Proceedings of IBIC18
  • Lecture (Conference)
    International Beam Instrumentation Conference 2018 (IBIC18), 09.-13.09.2018, Shanghai, China

Publ.-Id: 27836

Defect-induced exchange bias in a single SrRuO3 layer

Wang, C.; Chen, C.; Chang, C.-H.; Tsai, H.-S.; Pandey, P.; Xu, C.; Böttger, R.; Chen, D.; Zeng, Y.-J.; Gao, X.; Helm, M.; Zhou, S.

Exchange bias stems from the interaction between different magnetic phases and therefore it generally occurs in magnetic multilayers. Here we present a large exchange bias in a single SrRuO3 layer induced by helium ion irradiation. When the fluence increases, the induced defects not only suppress the magnetization and the Curie temperature, but also drive a metal-insulator transition at a low temperature. In particular, a large exchange bias field up to ~ 0.36 T can be created by the irradiation. This large exchange bias is related to the coexistence of different magnetic and structural phases that are introduced by embedded defects. Our work demonstrates that spintronic properties in complex oxides can be created and enhanced by applying ion irradiation.

Keywords: Exchange bias; Magnetization; Oxide thin film; Lattice distortion; Defect engineering

Related publications


Publ.-Id: 27835

Anti-CAR engineered T cells for epitope-based elimination of autologous CAR T cells

Koristka, S.; Ziller-Walter, P.; Bergmann, R.; Arndt, C.; Feldmann, A.; Kegler, A.; Cartellieri, M.; Ehninger, A.; Ehninger, G.; Bornhäuser, M.; Bachmann, M.

Although CAR T cell therapy has demonstrated tremendous clinical efficacy especially in hematological malignancies, severe treatment-associated toxicities still compromise the widespread application of this innovative technology. Therefore, developing novel approaches to abrogate CAR T cell-mediated side effects is of great relevance. Several promising strategies pursue the selective antibody-based depletion of adoptively transferred T cells via elimination markers. However, given the limited half-life and tissue penetration, dependence on the patients’ immune system and on-target/off-side effects of proposed monoclonal antibodies, we sought to exploit αCAR-engineered T cells to efficiently eliminate CAR T cells. For comprehensive and specific recognition, a small peptide epitope (E-tag) was incorporated into the extracellular spacer region of CAR constructs. We provide first proof-of-concept for targeting this epitope by αE-tag CAR T cells, allowing an effective killing of autologous E-tagged CAR T cells both in vitro and in vivo whilst sparing cells lacking the E-tag. In addition to CAR T cell cytotoxicity, the αE-tag-specific T cells can be empowered with cancer fighting ability in case of relapse, hence, have versatile utility. Our proposed methodology can most probably be implemented in CAR T cell therapies regardless of the targeted tumor antigen aiding in improving overall safety and survival control of highly potent gene-modified cells.

Keywords: Chimeric antigen receptor; immunotherapy; toxicity management; elimination tag

Publ.-Id: 27834

Engineering and coherent control of defects in silicon carbide

Astakhov, G.

Building quantum devices based on silicon carbide (SiC) is highly desirable, facilitated by established SiC CMOS technology. Optoelectronic SiC devices have already been demonstrated, however, the signal- mediating quantum defects are usually introduced in a semi-random manner, by bulk electron or neutron irradiation. We present the controlled generation of quantum centers in silicon carbide (SiC) by focused proton beam in a noncomplex manner without need for pre- or postirradiation treatment [1]. The generation depth and resolution can be predicted by matching the proton energy to the material’s stopping power, and the amount of quantum centers at one specific sample volume is tunable from ensembles of millions to discernible single photon emitters [2]. We identify the generated centers as silicon vacancies through their characteristic magnetic resonance signatures and demonstrate that they possess highy coherent spin properties even at room temperature [3].
[1] H. Kraus et al., Nano Lett. 17, 2865 (2017).
[2] F. Fuchs et al., Nat. Commun. 6, 7578 (2015).
[3] D. Simin et al., Phys. Rev. B 95, 161201(R) (2017).

Keywords: Spin defects; quantum applications; silicon carbide

  • Invited lecture (Conferences)
    25th Conference on Application of Accelerators in Research and Industry (CAARI-2018), 13.08.2018, Grapevine, USA

Publ.-Id: 27833

Feasibility Study for Detection of Fuel Assemblies State inside Sealed Dry Storage Casks using External Gamma Flux Measurements

Rachamin, R.; Hampel, U.

The license for the storage of spent nuclear fuel assemblies in dry casks is limited to 40 years. In Germany, a site for a final repository of spent fuel is not yet available. Therefore, this license has to be renewed for prolonged storage period. Currently, there is no experience with dry cask storage worldwide that goes beyond a period of 40 years. Beside regulatory and security aspects, there are questions concerning the long-term integrity of the spent fuel assemblies as this is of relevance for final transportation and reloading to final waste repository casks. Once the cask is filled and sealed, the knowledge about the state of the fuel assemblies is limited. This study investigates the feasibility of using external gamma flux measurements to detect the state of the spent fuel assemblies inside the cask. Monte-Carlo simulations were performed to evaluate the gamma flux distribution outside the sidewall of a cask with all intact fuel assemblies and a cask with one damaged fuel assembly, mimicking a fuel assembly with expanded rods and fuel relocation. The evaluation was performed for different location of the damaged fuel assembly and different storage times. The results of the investigation showed that the intensity and the shape of the gamma flux outside the sidewall of the cask are sufficient to identify the damaged fuel assembly, in case it is located near the inner wall of the cask. The detection of the inner damaged fuel assemblies, however, is less feasible. Due to the self-shielding of the fuel assemblies, the gamma photons which come from the inner fuel assemblies stopped within the fuel basket and assemblies materials. The gamma photons which do survive the fuel assemblies self-shielding reach the inner cask wall with not enough energy to escape the shielding of the thick cast iron wall. In general, it can be concluded that the more the damaged fuel assembly is close to the cask inner walls and that the damage is in a large scale (i.e., significant fuel relocation), the more it can be detected by external gamma flux measurements.

  • Contribution to proceedings
    ANS RPSD 2018 - 20th Topical Meeting of the Radiation Protection & Shielding Division of ANS, 26.-31.08.2018, Santa Fe, NM, USA
  • Lecture (Conference)
    ANS RPSD 2018 - 20th Topical Meeting of the Radiation Protection & Shielding Division of ANS, 26.-31.08.2018, Santa Fe, NM, USA

Publ.-Id: 27832

Multidentate extracting agents based on calix[4]arene scaffold – UVI/EuIII separation studies

Bauer, A.; Jäschke, A.; Shams Aldin Azzam, S.; Glasneck, F.; Ullmann, S.; Kersting, B.; Brendler, V.; Schmeide, K.; Stumpf, T.

The development of new ligand systems for solvent extraction demands knowledge of the fundamental chemistry behind these processes. Thus, herein, we report the synthesis and structural characterization of a 6-hydroxymethylpyridine functionalized calix[4]arene (L2). Its complexation behavior towards the divalent uranyl cation as well as the trivalent europium cation was spectroscopically studied. In solution the formation of two uranyl complex species with L2 was proven by spectrophotometric titration experiments, with stability constants of log ß1:1 = 5.82±0.04 and log ß2:1 = 5.57±0.05, and of one europium complex species (log ß1:1 = 6.85±0.03). In addition, the concept of the desired proper planar binding pocket for the linear uranyl cation has been verified in solution. Moreover, comparative UVI and EuIII extraction studies with L2 and a structure related 8-hydroxyquinoline modified calix[4]arene (L1) were performed in which the effects of various conditions such as pH of the aqueous phase, presence of relevant anions (sulfate, phosphate, carbonate) and competitive extraction with ethylenediaminetetraacetic acid (EDTA) were investigated. It has been shown that both macrocyclic ligands offer a strong chelate effect, which enables them to extract even stable uranyl hydrolysis species. With these ligands, the selective separation of UVI from EuIII-containing solutions is possible under a variety of conditions.

Keywords: calix[4]arene; uranium(VI); europium(III); liquid-liquid extraction; spectroscopic properties


Publ.-Id: 27831

Complexation of arsenite, arsenate, and monothioarsenate with oxygen-containing functional groups of natural organic matter: An XAS study

Biswas, A.; Besold, J.; Sjöstedt, C.; Gustafsson, J. P.; Scheinost, A. C.; Planer-Friedrich, B.

Arsenic (As) is reported to be effectively sorbed onto natural organic matter (NOM) via thiol coordination and polyvalent metal cation bridged ternary complexation. However, the extent of sorption via complexation to oxygen containing functional groups of NOM is poorly understood. By equilibrating arsenite, arsenate, and monothioarsenate with peat, followed by As K-edge X-ray absorption spectroscopic analysis, this study shows that complexation to the alcoholic groups can be an additional or alternative mode of As sorption to NOM. The extent of complexation was highest for arsenite, followed by monothioarsenate and arsenate. Complexation was higher at pH 7.0 compared to 4.5 for arsenite and arsenate, and vice versa for monothioarsenate due to partial transformation to arsenite at pH 4.5. EXAFS modelling of the As K-edge spectra revealed monodentate and bidentate complexation for arsenite and tridentate complexation for arsenate and monothioarsenate to the alcoholic group. Similarly, the As…C interatomic distance was relatively longer in arsenate- (2.83 ± 0.01 Å) and monothioarsenate-treated peat (2.80 ± 0.02 Å) compared to arsenite-treatment (2.73 ± 0.01 Å). This study implies that depending on acidity of the NOM, arsenate and monothioarsenate can have a higher mobility than arsenite in NOM-rich environments.

Keywords: Arsenic; biogeochemistry; sorption; peat; EXAFS

Related publications


Publ.-Id: 27830

Review of the electrical characterization of metallic nanowires on DNA templates

Bayrak, T.; Jagtap, N.; Erbe, A.

The use of self-assembly techniques may open new possibilities in scaling down electronic circuits to their ultimate limits. Deoxyribonucleic acid (DNA) nanotechnology has already demonstrated that it can provide valuable tools for the creation of nanostructures of arbitrary shape, therefore presenting an ideal platform for the development of nanoelectronic circuits. So far, however, the electronic properties of DNA nanostructures are mostly insulating, thus limiting the use of the nanostructures in electronic circuits. Therefore methods have been investigated, which use the DNA nanostructures as templates for the deposition of electrically conducting materials along the DNA strands. The most simple such structure is given by metallic nanowires formed by deposition of metals along the DNA nanostructures. Here we review the fabrication and the characterization of the electronic properties of nanowires, which were created using these methods.

Keywords: nanoelectronics; DNA origami; self-assembly; electrical characterization; DNA-origami metalization; DNA metalization

Related publications

Publ.-Id: 27829

Molecular interactions of fungi with U(VI) studied by microscopic and spectroscopic methods

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

Fungi play an important role in the microbial community of soil and their metabolic processes can influence the migration of radionuclides in the environment by different interaction processes like mainly sorption, accumulation or mineralization. The immobilization of radionuclides reduces their mobility, which thus prevents also the entry of radionuclide into the water pathway and into the food chain.
For this reasons the aim of this study is to determine the potential of fungi for precautionary radiation protection methods and bioremediation procedures for contaminated soils. In the assessment of the suitability of fungi, the first step is to investigate the molecular interactions with radionuclides in more detail to identify dominant interaction processes. Therefore, binding experiments with different initial conditions were performed and the molecular binding form was investigated with time-resolved laser-induced fluorescence spectroscopy. Furthermore, TEM-EDX analyses were used to determine whether immobilization takes place within the cell or on the cell surface.

Keywords: Fungi; Uranium; TRLFS; TEM-EDX

  • Lecture (Conference)
    Goldschmidt, 12.-17.08.2018, Boston, USA

Publ.-Id: 27828

Nachrechnung von Kondensationsversuchen in der COSMEA-Versuchsanlage mit dem Programm ATHLET

Zhang, Y.; Leyer, S.; Geißler, T.; Hampel, U.

Sicherheit ist ein wesentliches Thema im Entwicklungsprozess von Kernkraftwerken. Mehrere Reaktortypen der Generation III und III+ enthalten ein passives Sicherheitssystem zur Unfallkontrolle ohne externe Stromversorgung. Ein Beispiel ist der Notkondensator (EC) des KERENA-Reaktorkonzeptes. Der EC entzieht dem Reaktordruckbehälter bei Störfällen Wärme. Die Versuchsanlage COSMEA am Helmholtz Zentrum Dresden Rossendorf (HZDR) wurde eingerichtet, um die Strömungsmorphologie und die Wärmeübertragungsstruktur der Kondensation in einem leicht geneigten Rohr zu untersuchen. In diesem Beitrag werden Nachrechnung des Kondensationsprozesses in der Versuchsanlage COSMEA mit den thermohydraulischen Systemcode ATHLET vorgestellt. Die Leistungsfähigkeit der ATHLET Wärmeübertragungsmodelle wurde bestimmt. Die Simulationsergebnisse wurden mit den Experimenten verglichen. Der Wärmefluss, die Kondensationsrate und die Temperatur des Kühlwassers während der Kondensation wurden analysiert.

Publ.-Id: 27827

Analysis of flow patterns in a rotating packed bed using gamma-ray computed tomography

Bieberle, A.; Gross, K.; Gladyszewski, K.
Researcher: Schubert, Markus

In this study, gamma-ray computed tomography is employed to quantify the liquid hold-up and its distribution in a rotating packed bed using:

  • different insets
  • different rotational speeds
  • different fluid rate flows

Keywords: gas-liquid flow pattern; local liquid hold-up; rotating packed bed; fast imaging; computed tomography


Publ.-Id: 27826

Nanostructuring few-layer graphene films with swift heavy ions for electronic application: tuning of electronic and transport properties

Nebogatikova, N. A.; Antonova, I. V.; Erohin, S. V.; Kvashnin, D. G.; Olejniczak, A.; Volodin, V. A.; Skuratov, A. V.; Krasheninnikov, A. V.; Sorokin, P. B.; Chernozatonskii, L. A.

he morphology and electronic properties of single and few-layer graphene films nanostructured by the impact of heavy high-energy ions have been studied. It is found that ion irradiation leads to the formation of nano-sized pores, or antidots, with sizes ranging from 20 to 60 nm, in the upper one or two layers. The sizes of the pores proved to be roughly independent of the energy of the ions, whereas the areal density of the pores increased with the ion dose. With increasing ion energy (>70 MeV), a profound reduction in the concentration of structural defects (by a factor of 2–5), relatively high mobility values of charge car- riers (700–1200 cm2 V−1 s−1) and a transport band gap of about 50 meV were observed in the nano- structured films. The experimental data were rationalized through atomistic simulations of ion impact onto few-layer graphene structures with a thickness matching the experimental samples. We showed that even a single Xe atom with energy in the experimental range produces a considerable amount of damage in the graphene lattice, whereas high dose ion irradiation allows one to propose a high probability of con- secutive impacts of several ions onto an area already amorphized by the previous ions, which increases the average radius of the pore to match the experimental results. We also found that the formation of “welded” sheets due to interlayer covalent bonds at the edges and, hence, defect-free antidot arrays is likely at high ion energies (above 70 MeV).

Keywords: graphene; ion irradiation

Related publications


Publ.-Id: 27825

Erratum: Charged Point Defects in the Flatland: Accurate Formation Energy Calculations in Two-Dimensional Materials [Phys. Rev. X 4, 031044 (2014)]

Komsa, H.-P.; Berseneva, N.; Krasheninnikov, A. V.; Nieminen, R. M.

No "expressive" abstract available.

Keywords: 2D materials; first-principles calculaitons

Related publications

Publ.-Id: 27824

1T phase as an efficient hole injection layer to TMDs transistors: a universal approach to achieve p-type contacts

Hu, X.; Wang, Y.; Shen, X.; Krasheninnikov, A. V.; Sun, L.; Chen, Z.

Recently, the fabricated MoS2 field effect transistors (FETs) with 1T-MoS2 electrodes exhibit excellent performance with rather low contact resistance, as compared with those with metals deposited directly on 2H-MoS2 (Kappera et al 2014 Nat. Mater. 13 1128), but the reason for that remains elusive. By means of density functional theory calculations, we investigated the carrier injection at the 1T/2H MoS2 interface and found that although the Schottky barrier height (SBH) values of 1T/2H MoS2 interfaces can be tuned by controlling the stacking patterns, the p-type SBH values of 1T/2H MoS2 interfaces with different stackings are lower than their corresponding n-type SBH values, which demonstrated that the metallic 1T phase can be used as an efficient hole injection layer for 2H-MoS2. In addition, as compared to the n-type Au/MoS2 and Pd/MoS2 contacts, the p-type SBH values of 1T/2H MoS2 interfaces are much lower, which stem from the efficient hole injection between 1T-MoS2 and 2H-MoS2. This can explain the low contact resistance in the MoS2 FETs with 1T-MoS2 electrodes. Notably, the SBH values can be effectively modulated by an external electric field, and a significantly low p-type SBH value can be achieved under an appropriate electric field. We also demonstrated that this approach is also valid for WS2, WSe2 and MoSe2 systems, which indicates that the method can most likely be extended to other TMDs, and thus may open new promising avenues of contact engineering in these materials.

Keywords: 2D materials; first-principles simulations

Related publications


Publ.-Id: 27823

Fermi surface reconstruction and dimensional topology change in Nd-doped CeCoIn5

Klotz, J.; Götze, K.; Sheikin, I.; Förster, T.; Graf, D.; Park, J.-H.; Choi, E. S.; Hu, R.; Petrovic, C.; Wosnitza, J.; Green, E. L.

We performed low-temperature de Haas–van Alphen effect measurements on a Ce1−xNdxCoIn5 series, for x = 0.02, 0.05, 0.1, and 1, down to T = 40 mK using torque magnetometry in magnetic fields up to 35 T. Our results indicate that a Fermi surface (FS) reconstruction occurs from a quasi-two-dimensional topology for Nd-2% to a rather three-dimensional one for Nd-5%, thus reducing the possibility of perfect FS nesting. The FS evolves further with increasing Nd content with no observed divergence of the effective mass between Nd-2% and 10%, consistent with the crossing of a spin density wave type of quantum critical point. Our results elucidate the origin of the Q phase observed at the 5% Nd-doping level [Raymond et al., J. Phys. Soc. Jpn. 83, 013707 (2014)].


Publ.-Id: 27822

Spontaneous and field-induced magnetic phase transitions in Dy2Co3Al9: Effects of exchange frustration

Gorbunov, D. I.; Henriques, M. S.; Qureshi, N.; Ouladdiaf, B.; Salazar Mejia, C.; Gronemann, J.; Andreev, A. V.; Petricek, V.; Green, E. L.; Wosnitza, J.

Due to the long-range oscillatory character of RKKY exchange interactions, for Dy2Co3Al9 there exist positive and negative couplings between theDymagnetic moments that lead to magnetic frustration. As a result, the ground state can be easily perturbed, and the system displays a number of spontaneous and field-induced phase transitions. We performed magnetization, magnetic-susceptibility, specific-heat, and electrical-resistivity measurements as well as neutron-diffraction experiments on a single crystal. We find two transitions to distinct incommensurate antiferromagnetic phases at 6.2 and 5.2 K that evolve to a commensurate phase at 3.7 K. In applied magnetic field, new phases emerge. Field-dependent magnetization exhibits a multistep metamagnetic process with sharp transitions accompanied by pronounced magnetoresistance changes. The large number of phases and their complex magnetic structures suggest that the physical properties of Dy2Co3Al9 are ruled by exchange frustration in the presence of a large magnetocrystalline anisotropy.


  • Secondary publication expected

Publ.-Id: 27821

New software protocols for enabling laboratory based temporal CT

Gajjar, P.; Jorgensen, J. S.; Da Assuncao Godinho, J. R.; Johnson, C. G.; Ramsey, A.; Withers, P. J.

Temporal micro computed tomography (CT) allows the non-destructive quantification of processes that are evolving over time in 3D. Despite the increasing popularity of temporal CT the practical implementation and optimisation can be dificult. Here, we present new software protocols that enable temporal CT using commercial laboratory CT systems. The first protocol drastically reduces the need for periodic intervention when making time-lapse experiments, allowing a large number of tomograms to be collected automatically.
The automated scanning at regular intervals needed for uninterrupted time-lapse CT is demonstrated by analysing the germination of a mung bean (vigna radiata), whilst the synchronisation with an in-situ rig required for interrupted time-lapse CT is highlighted using a shear cell to observe granular segregation. The second protocol uses golden-ratio angular sampling with an iterative reconstruction scheme and allows the number of projections in a reconstruction to be changed as sample evolution occurs. This overcomes the limitation of the need to know a priori what the best time window for each scan is. The protocol is evaluated by studying barite precipitation within a porous column, allowing a comparison of spatial and temporal resolution of reconstructions with different numbers of projections. Both of the protocols presented here have great potential for wider application, including, but not limited to, in-situ mechanical testing, following battery degradation and chemical reactions.

Keywords: tomography; time-lapse; minerallization; porous media


Publ.-Id: 27820

Applying the Serpent-DYN3D Code Sequence for the Decay Heat Analysis of Metallic Fuel Sodium Fast Reactor

Pereira, G.; Johnson, A. E.; Bilodid, Y.; Fridman, E.; Kotlyar, D.

Recent developments of the reactor dynamics code DYN3D have introduced the micro-depletion model which allows for explicit calculation of radioactive decay heat. Such a unique combination of nodal diffusion, thermal hydraulic (T/H) and depletion solvers allows DYN3D to perform fuel cycle depletion and obtain detailed core isotopic concentration and decay heat distributions. The new sequence utilizes considerably less computational resources than coupled Monte Carlo-T/H-depletion systems, but with comparable accuracy. This capability was recently tested on a limited number of simple unit cell models. The main objective of this work is to further verify the decay heat calculation capabilities of DYN3D by applying it to a considerably more realistic and detailed full core model. For the purpose of the current analysis a 3D full core model of Advanced Burner Reactor (ABR) was adopted from the OECD/NEA Benchmark for Neutronic Analysis of Sodium-Cooled Fast Reactor Cores with Various Fuel Types and Core Sizes. In this work, the Monte Carlo code Serpent was used to generate macro- and microscopic parameters, and the neutron diffusion code, DYN3D, was used to perform neutronic and depletion analyses. Detailed spatial isotopic and decay heat distributions obtained with DYN3D were verified against the equivalent Serpent reference 3D full core solution. Results indicate very good agreement between the Serpent-DYN3D code sequence and the reference Serpent solutions, with a discrepancy in total decay heat on the order of 0.5%.

Keywords: Decay heat; cross section generation; microscopic depletion; DYN3D


Publ.-Id: 27819

Experimental investigation of the froth height in columns with sandwich packings

Sohr, J.; Schubert, M.; Flechsig, S.; Kenig, E. Y.; Hampel, U.

Sandwich packings, consisting of alternatingly stacked conventional structured packings with different geometric surface areas, are promising to increase capacity and efficiency of separation columns. Film and froth flow evolve along a stack, which requires comprehensive fluid dynamic analysis. In particular, the froth height is an essential parameter to determine the spatial extent of the flow regimes. Ultrafast X-ray tomography and a 3D-printed pressure drop profile measurement module were applied to independently estimate this parameter. The results are compared with existing correlations.

Keywords: fluid dynamics; froth height; pressure drop; sandwich packing; ultrafast X-ray tomography

Publ.-Id: 27818

Rate-based-Modellierung von CO₂-Absorptionskolonnen mit Anstaupackungen

Flechsig, S.; Borgolte, T.; Utchenko, Y.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.

Die Effizienz von Trennkolonnen für Fluidgemische kann durch die Anwendung von Anstaupackungen gesteigert werden. Dabei entstehen im Betrieb belastungsabhängige, in ihrer Trennwirkung unterschiedliche Regime. Um die Auswirkungen der einzelnen Strömungsregime in einem Modell erfassen zu können, werden sowohl Trennleis-tungsmessungen als auch tomographische Methoden verwendet. Ein rate-based-Modell wird vorgestellt, in dem die heterogenen Strömungsformen in Anstaupackungen mittels geeigneter Korrelationen berücksichtigt werden. Das Modell wird anhand gemessener Daten zur CO₂-Absorption getestet.

Publ.-Id: 27817

Access to 18F-labelled isoxazoles by Ruthenium-promoted 1,3-dipolar cycloaddition of 4-[18F]fluoro-N-hydroxybenzimidoyl chloride with alkynes.

Roscales, S.; Kniess, T.

4-[18F]Fluoro-N-hydroxybenzimidoyl chloride (18FHBIC) was developed as an 18F-labelled aromatic nitrile oxide precursor. The building block is obtained in a one-pot synthesis in up to 79% radiochemical yield starting from [18F]fluoride in 50 min with 4-[18F]fluorobenzaldehyde (18FBA) and 4-[18F]fluorobenzaldehyde oxime (18FBAO) as intermediates, including the reaction of 18FBAO with N-chlorosuccinimide (NCS) as a key step. 18FHBIC was found to be a suitable and stable synthon to give access to 18F-labelled 3,4-diarylsubstituted isoxazoles by [Cp*RuCl(cod)]-catalyzed 1,3-dipolar cycloaddition with various alkynes. By way of example, the radiosynthesis of a fluorine-18 labelled COX-2 inhibitor [18F]1b, a close derivative of valdecoxib, was performed by 1,3-dipolar cycloaddition of 18FHBIC with 1-ethynyl-4-(methylsulfonyl)benzene, providing purified [18F]1b in RCY up to 40% starting from [18F]fluoride in 85 min. The application of 18FHBIC as a building block in the synthesis of 18F-labelled heterocycles will generally extend the portfolio of available PET radiotracers.


Publ.-Id: 27816

Experimental investigations and rate-based modeling of CO₂ absorption with sandwich packings

Flechsig, S.; Sohr, J.; Schubert, M.; Hampel, U.; Kenig, E. Y.

In the process industry, packed columns are used in a variety of fluid separation operations, e.g. in distillation and absorption, in order to create a desirable flow pattern of two-phase systems. Due to the high energy requirements of separation processes, the interest on their optimization is vital. In particular, column internals have permanently been the focus of investigations.
An improvement of the separation efficiency can be achieved by the application of sandwich packings. The latter consist of two alternating layers of industrially available standard packings with different specific surface areas, one with lower (the so-called holdup layer) and another with higher (the so-called de-entrainment layer) capacity. Sandwich packings are typically used at operating conditions between the flooding points of holdup layer and de-entrainment layer. Above the holdup layer, a froth sublayer is formed, which reveals high separation efficiency due to intensified phase mixing. In the upper section of the de-entrainment layer, film-like flow patterns can be observed [1]. Under certain conditions, this intensive heterogeneous flow pattern can be used in a beneficial way for fluid separation processes. However, the application of this integrated packing type is hindered by lacking validated design methods [2].
An accurate prediction of the performance characteristics is essential for the design of sandwich packings. In our project, the effects of the individual flow regimes on fluid dynamics and mass transfer are investigated complementarily with both experimental and theoretical studies. In order to determine the impact of each individual flow regime, experiments on an absorption/desorption plant are supplemented by flow imaging measurements of sandwich packings. At the Paderborn University, CO2 absorption is examined in a pilot plant for various design and operating parameters. This plant allows measuring temperature profiles of the gas phase as well as concentration profiles of both phases. At the Helmholtz-Zentrum Dresden-Rosendorf, a detailed view on the phase distribution within the sandwich packings is realized bymeans of an ultrafast X-ray tomography. The measured data from both experimental methods are used to establish correlations for mass transfer coefficients, interfacial area, holdup and pressure drop, which are applied in a rate-based stage model for CO2 absorption processes with aqueous amine solutions.
The absorption experiments were performed under ambient conditions in a column with an inner diameter of 0,1 m and 3,2 m packing height. The influence of different operating and design parameters on the separation characteristics in sandwich packings was studied in order to identify appropriate operating conditions and to provide a sufficient basis for the experimental validation of a model, which is able to describe the heterogeneous flow patterns. In particular, we investigated the impact of the holdup-layer height and its corresponding specific surface area. In addition, the inclination angle of the flow channels in the de-entrainment layer was varied.
The rate-based approach, which accounts for the specifics of different column internals via correlations, was applied. We expected that different fluid dynamic regimes would have different impacts on the mass transfer. Therefore, each fluid dynamic regime was considered individually. The column was represented as a sequence of alternating segments, and each segment was described by a corresponding set of correlations. Experimental data of the CO2 absorption with sandwich packings were then compared with simulation results.
The authors are grateful to the Deutsche Forschungsgemeinschaft (DFG) for financial support (KE 837/26-1, HA 3088/10-1).
[1] U. Brinkmann, B. Kaibel, M. Jödecke, J. Mackowiak, E.Y. Kenig: Beschreibung der Fluiddynamik von Anstaupackungen, Chemie Ingenieur Technik 84, 36-45 (2012).
[2] Ö. Yildirim, E.Y. Kenig: Rate-based modelling and simulation of distillation columns with sandwich packings, Chemical Engineering and Processing: Process Intensification 98, 147-154 (2015).

  • Lecture (Conference)
    ACHEMA Congress 2018, 11.-15.06.2018, Frankfurt am Main, Deutschland

Publ.-Id: 27815

Messung des 478 keV Gammaproduktionsquerschnitts nach inelastischer Streuung an ⁷ Li

Frotscher, A.

The inelastic neutron cross section of 7Li has no sharp resonances and a fairly low threshold of 546 keV. Below the breakup threshold at 5291 keV only one gamma-ray is emitted at E = 477,6 keV. It is therefore suited as a reference cross section. Lithium has technical usage as a 3H-producer in future fusion reactors as well as in molten salt reactors. But there are recent measurements disagreeing with already evaluated data. To resolve this dissonance, an 170 h Experiment was carried out at the nELBE facility of the HZDR. A 4 mm thick LiF-disk was used as a target, the neutron flux was determined with a 235U parallel plate fission chamber. The flight path for the 7Li(n,n’ )7Li reaction was 8,3 m. As detectors four two-inch LaBr3-detectors as well as three three-inch LaBr3-detectors and two miniball-type HPGe detectors with three 60 % crystals each were used. The measurement of the cross section is solely a measurement of the de-excitation of the first exited 7Li-State at 477,6 keV. The second exited state at 4,63 MeV already decays via particle emission and thus does not contribute any gamma-radiation. The experiment benefits from the high neutron flux at nELBE (80 n/s/keV @ 1 MeV) as well as from the precise fission chamber of the PTB (H19) for the neutron flux calibration. A Geant4-Simulation is used to determine correction factors as the transmission from the H19 to the target as well as the multiple scattering correction and the self absorption of the 477,6 keV Gamma-Rays. The deduced cross section from both detector types are consistent, but they can’t reproduce the data from Nyman et al. The deviations are up to 20 %. The half life of the by means of bremsstrahlung in air produced positroniums in the experiment is 116(7) ns.

Keywords: nELBE; inelastic neutron scattering; fast neutrons; Li-7

Related publications

  • Master thesis
    TU Dresden, 2017
    Mentor: Dr. Arnd Junghans

Publ.-Id: 27814

[MnO|SiO2,Al2O3,FeO,MgO] balanced log-ratio in chlorites-a tool for chemo-stratigraphic mapping and proxy for the depositional environment

Süssenberger, A.; Pospiech, S.; Schmidt, S.

The [MnO|SiO2,Al2O3,FeO,MgO] balanced ratio, i.e. the isometric log-ratio of the MnO concentration relative to the concentration of SiO2, Al2O3, FeO, and MgO of chlorite and of whole rock composition is an effective discriminant between Mesozoic stratigraphic formations in the Magallanes Basin (Chile). The MnO content in chlorite is only controlled by the host rock chemistry and is dependent on the geological environment. The MnO content in chlorite remains unchanged at low-grade metamorphic conditions. Single grain chlorite analysis (n > 1000, electron microprobe) and whole rock analysis (n = 40, X-ray fluorescence) was used to discriminate stratigraphic formations and to decipher differences in the depositional environment in the Magallanes Basin. The samples are from one Upper Jurassic and three Cretaceous sedimentary units which were affected either by low-grade regional metamorphism or by Miocene contact metamorphism. The highest [MnO|SiO2,Al2O3,FeO,MgO] values are recorded in the upper Zapata Formation. The Punta Barrosa, Cerro Toro and Tobífera Formations show slightly lower [MnO|SiO2,Al2O3,FeO,MgO] values. Elevated [MnO|SiO2,Al2O3,FeO,MgO] values at the transition between Zapata and Punta Barrosa Formation record an oxygenated shallow marine environment that can be linked to the closure of the Rocas Verdes Basin and the onset of fold- and -thrust belt formation. Decreasing [MnO|SiO2,Al2O3,FeO,MgO] values from the Punta Barrosa towards the Cerro Toro Formation indicate gradually increasing water depths during the Upper Cretaceous which correlate well with the global sea level.

Keywords: chlorite; compositional data; low-grade metamorphism; depositional environment; Magallanes Basin

Publ.-Id: 27812

Fano signatures between intersubband and ponderomotive responses in MQW structures

Pedroso, D. D. M.; Schmidt, J.; Passaro, A.; Helm, M.; Schneider, H.

We present an in-depth theoretical and numerical discussion on the Fano signatures observed in differential transmission spectra obtained from multiquantum well structures. These signatures stem from ponderomotive and intersubband polarization currents modified by the coupling between the optical responses of different layers. A detailed discussion of this process is provided, evaluating quantitatively the amplitude and shape of the Fano signatures and their dependence on structural parameters, such as carrier concentration and layer width. The theoretical model described here aims to predict quantitatively the weight of the contributions of the ponderomotive currents in relation to the intersubband ones. In order to include the effect of the entire structure in the theoretical spectra, the optical response of each layer is addressed within the density matrix formalism and encompassed in an optical transfer matrix. This method also ensures the correct inclusion of the phase sensitive superposition of optical responses of different layers on which the Fano signatures are based. Numerical simulations obtained from the presented theoretical approach are in excellent agreement with the behaviour observed in previous experiments.

Keywords: Fano interference; intersubband transition; free-carrier absorption; GaAs; multiple quantum well; MQW

Publ.-Id: 27811

Uranium(VI) complexation with aqueous silicates in the acidic to alkaline pH-range

Lösch, H.; Tits, J.; Marques, M.; Baeyens, B.; Stumpf, T.; Huittinen, N.

An important parameter for safety assessments of radioactive waste respositories is the prediction and modelling of aqueous complex formation reactions between actinides and common dissolved inorganic and organic ligands. For this assessment, the knowledge of dissolved ligands in the groundwater produced by dissolution of waste canisters, backfill material, and host rock is required. Due to the ubiquitous existence of silicon in these materials, aqueous silicate species are important ligands to consider in the metal-ligand speciation, especially in contact zones of cement pore water with clay or granite where high silicate concentrations are expected as a result of alteration processes [1]. Depending on the used host rock and backfill material, the pH of the groundwater will vary between the neutral to alkaline range. However, in this pH-range, reported An-Si species are scarce or non-existent, and there is a lack of reliable thermodynamic data. In the acidic pH-range, only the 1:1 An(VI)-Si complex, i.e. An(VI)O ₂OSiOH₃+, is known for U(VI), Np(VI), and Pu(VI), and the complex formation constants differ by one order of magnitude.
In the alkaline pH-range (pH ~8), Yusof et al. [3] postulated the formation of either a ternary Pu-OH-Si PuO₂(H₂O)₃(OH)OSi(OH)₃ complex with the H₃SiO₄- ligand or a binary Pu-Si PuO₂(H₂O)₃O₂Si(OH)₂ complex with H₂SiO₄ ²-. For other hexavalent actinides, no complexes in the alkaline pH-range have been reported, however, following the analogy of the hexavalent cations comparable complexes should also exist for U(VI) and Np(VI).

In this study the in-situ speciation of U(VI) in solution in the presence of silicates was monitored with laser-induced luminescence spectroscopy (TRLFS) and , the Schubert method. For the TRLFS measurements, a U(VI) concentration of 5×10-⁶ M was used, while the silicon concentration was varied between 3×10-⁴ and 2×10-³ M depending on the pH. Temperature-dependent measurements were performed in the T-range from 1°C to 40°C to improve the signal to noise ratio and to enable the extraction of thermodynamic parameters, such as the enthalpy ΔRH° and entropy ΔRS° of reaction. The TRLFS measurements were performed at two excitation wavelengths of 266 nm and 394 nm.
In the Schubert method, the desorption of U(VI) from an inert solid phase as a result of silicate complex formation in solution, is monitored. Here, monoclinic ZrO₂ was used as a solid phase and investigations were performed for a U(VI) concentration of 1×10-⁷ M and silicate concentrations between 5×10-⁵ and 5×10-³ M, at pH values ranging from 7.0 to 11.5. LSC measurements of the 233U activity were used to determine the U(VI) concentration in solution.

Based on the TRLFS investigations in the acidic pH-range, the formation of the 1:1 U-Si complex UO₂OSi(OH)₃+ could be confirmed in addition to a hitherto unidentified silicate species. The normalized emission spectra clearly show a change in the peak shape with increasing silicate concentration. Next to the change in the spectral shape, a significant increase in the luminescence intensity could be observed. Such an increase of the luminescence intensity speaks for the formation of a polynuclear U(VI)-silicate complex. However, investigations to confirm this hypothesis are still ongoing.

In the alkaline pH-range it was possible to identify a ternary U-OH-Si complex, most likely either a monodentate UO₂(OH)₂OSi(OH)₃- or a bidentate UO ₂(OH)OSi(OH)₂- complex with a complex formation constant of logβ0 = -15.6. Preliminary speciation calculations in clay and cement pore water show, that this ternary U-OH-Si will dominate the U(VI) speciation in the pH-range between 9.0 and 11.5. To resolve the stoichiometry of this complex, TRLFS investigations are planned together with complementary DFT calculations.


1. D. SAVAGE, Mineralogical Magazine, 75, 2401-2418 (2011).
2. R. GUILLAUMONT, Update on the chemical thermodynamics of Uranium, Neptunium, Plutonium, Americium and Technetium 5, p. 252, Nuclear Energy Agency, Elsevier Science Publisher (2003).
3. A.B. YUSOF, A.M. FEDOSEEV, Russ. J. Coord. Chem., 29, 582-590, (2003).

  • Poster
    Plutonium Futures 2018, 09.-14.09.2018, San Diego, USA

Publ.-Id: 27810

Quantitative predictions of LWFA simulation with PIConGPU - from improved modeling to new measurement methods via synthetic radiation diagnostics

Pausch, R.; Debus, A.; Schramm, U.; Bussmann, M.; Steiniger, K.; Widera, R.; Huebl, A.; Garten, M.; Irman, A.; Couperus, J.; Zarini, O.; Köhler, A.

In a close interplay between particle-in-cell simulations and experimental measurements, we present new insights into the modeling of laser wakefield accelerators and discuss the arising challenges for laboratory diagnostics. These challenges were tackled by developing new methods for determining key parameters of the experiment by studying synthetic radiation diagnostics predicted by simulations.

The combination of an unprecedented experimental campaign studying the parameter dependence of beam loading during LWFA and an accompanying, extensive simulation campaign using the 3D3V particle-in-cell code PIConGPU made it possible to provide unique feedback between experiment and theory. This poster shows the step-by-step improvements through this interplay from the simulation perspective. Quantitatively more accurate methods such as the use of Gauss-Laguerre modes or a variety of ionization models are presented as well as more performant computationally procedures. Only through these improvements could the dynamics occurring in the experiment be reproduced and a deeper insight into the self-truncated ionization injection method be gained.

Moreover, this interplay also revealed the limits of current laboratory diagnostics. Synthetic in-situ radiation diagnostics in PIConGPU instigated the development of new diagnostic methods for experiments. For example, the shift of the laser focus position, compared to the vacuum, due to self-focusing in the plasma can now be quantified by spectral radiation signatures. Applying these new methods will enable an even more accurate understanding of laser plasma dynamics in experiments in the near future.

Keywords: Radiation; LWFA; aprticle-in-cell; PIConGPU

  • Poster
    The fourth annual meeting of the programme "Matter and Technologies", 12.-14.06.2018, Berlin, Deutschland
  • Lecture (Conference)
    The fourth annual meeting of the programme "Matter and Technologies", 12.-14.06.2018, Berlin, Deutschland

Publ.-Id: 27809

The cosmic-ray exposure history of the big iron Twannberg (IIG) meteorite

Smith, T.; Hofmann, B. A.; Leya, I.; Merchel, S.; Rugel, G.; Pavetich, S.; Scharf, A.

Introduction: The Twannberg iron meteorite is one out of only six members of the group IIG. This group of iron meteorites is characterized by large amount of schreibersite (Fe,Ni) ₃P, and usually low Ni contents (Hofmann et al., 2009#). With the recent new finds (n = 1119 samples, total recovered mass: ~118 kg, up to June 30th, 2018, communication B. A. Hofmann) we have the opportunity to reinvestigate the cosmic-ray exposure history of Twannberg, with a special focus on its terrestrial age, in order to better understand the distribution of the different masses in the context of the last glaciation occurrences in Europe.
Experimental methods: The isotopic concentrations for He, Ne, and Ar have been measured by noble gas mass spectrometry at the University of Bern, following the procedures described earlier (Ammon et al., 2008#, 2009#). Analyses of the cosmogenic radionuclides (i.e., 10Be, 26Al, 36Cl, and 41Ca) have been performed at the DREsden Accelerator Mass Spectrometry facility (DREAMS, Akhmadaliev et al., 2013#) using chemical procedures previously described in Merchel et al. (1999#). In this work, we measured the cosmogenic noble gas and radionuclide concentrations in 14 and 7 Twannberg samples, respectively, from different find locations (Gruebmatt, Twannbach, and Mont Sujet, cf. Figure 1, Smith et al., 2017#).
Fig. 1. Find locations of Twannberg specimens until June 1st, 2016 (n = 570). The larger (red) squares indicate the find locations of the fragments analyzed in this work. The find location of the first mass (TW1, 15.915 kg) is indicated. Red arrow on Mont Sujet is the linear correlation of all Sujet finds and an approximation of the fall direction. LGM = last glacial maximum based on Bini et al. (2009#); OGM = Older glacial maximum (probably corresponding to Beringen/Riss) corresponding to the upper limit of the occurrence of alpine drift (see the Geological Setting section). The area south of the LGM/OGM lines was covered by alpine ice and the general direction of ice flow was from southwest to northeast. The blue arrow indicates the probable transport vector of Gruebmatt meteorites during the Beringen/Riss glaciation. Contour interval is 100 m.
Results and Discussion: First, we observe a wide range of both cosmogenic noble and radionuclide concentrations, e.g. after corrections (i.e. for trapped components, sulfur and/or phosphorus contributions, cf. Smith et al., 2017#), the cosmogenic 21Necos and 38Arcos concentrations vary by factors of 190 and 110, respectively. Based on model calculation (Ammon et al., 2008#), the observed variation of more than two orders of magnitude within all measured samples is only possible when considering a meteoroid with a minimum preatmospheric radius of ~165 cm.
Another approach is to use the cosmogenic (4He/21Ne)cos ratio as a shielding indicator; doing so, we estimate the preatmospheric radius to be ~250 cm.
To conclude, based on both the spread in cosmogenic noble gases and the (4He/21Ne)cos ratio, we infer Twannberg to have a minimum preatmospheric radius in the range of ~2 m, which, when assuming a density of ~7.8 g cm-3, would correspond to a minimal mass of ~250 tons.
Second, we calculated the cosmic-ray exposure (CRE) age of Twannberg using the well-adopted 36Cl-36Ar method (e.g. Lavielle et al., 1999#). We determined an average CRE age of 182±41 Ma. Note that this value is slightly different from the one that has been recently published in Smith et al. (2017#), due to the fact we are now using a new 41Ca half-life of 0.995×10⁵ years (Jörg et al., 2012#) instead of the previous value of 1.04×10⁵ years (Kutschera and Ahmad, 1992#). This modifies the terrestrial age (cf. below), and in return decreases the CRE age by ~5%. However, the new CRE age is still in agreement with the CRE age of 230±50 calculated previously by Hofmann et al. (2009#), as well determined using the 36Cl-36Ar method.
Third, based on new Monte-Carlo calculations, we used the 36Cl-41Ca radionuclide pair to calculate the terrestrial age of Twannberg; we found an age of 190±48 ka. Again, this age is slightly different from the one we reported in Smith et al. (2017#) since we are using here the new 41Ca half-life (cf. above). This terrestrial age, although quite surprising when considering the humid conditions in Switzerland, is 1) consistent with geological evidences (Hofmann et al., 2009; Smith et al., 2017#); and 2) indicates that the Twannberg meteorite fell most likely during or before the second last glaciation in Europe, 185-130 ka ago. This reveals that some of the masses have been glacially transported from an initial position west of Mont Sujet, in the direction of east-northeast (cf. Figure 1).
Acknowledgments: This study heavily relies on samples collected in a great effort by a joint group of meteorite enthusiasts and scientists. We particularly thank for the collaboration and samples: Marc Jost, Manuel Eggimann, Hannes Weiss, Sergey Vasiliev, Andreas Koppelt, Ernst Wyler, Gino Bernasconi, Marcel Häuselmann, and Edwin Gnos. Parts of this research were carried out at the Ion Beam Centre (IBC) at the Helmholtz-Zentrum Dresden-Rossendorf e. V., a member of the Helmholtz Association. This work was supported by the Swiss National Science Foundation (SNF).
Akhmadaliev S. et al. 2013. Nuclear Instruments and Methods in Physic B 294:5-10
Ammon K. et al. 2008. Meteoritics and Planetary Science 43:685-699
Ammon K. et al. 2011. Meteoritics and Planetary Science 46:785-792
Bini A. et al. 2009. Die Schweiz während des letzteiszeitlichen Maximums (LGM), Map 1:500000. Bern: Swiss Federal Office of Topography
Hofmann B. et al. 2009. Meteoritics and Planetary Science 44:187-199
Jörg G. et al. 2012. Geochimica et Cosmochimica Acta 88:51-65
Kutschera W. et al. 1992. Radiocarbon 34(3):436-446
Lavielle B. et al. 1999. Earth and Planetary Science Letters 170:93-104
Merchel S. and Herpers U. 1999. Radiochimica Acta 84:215-219
Smith T. et al. 2017. Meteoritics and Planetary Science 52:2241-2257

Keywords: AMS; cosmogenic nuclide; meteorite

Related publications

  • Lecture (Conference)
    Annual Meeting of the Chinese Geoscience Union (CGU), 21.-24.10.2018, Beijing, China

Publ.-Id: 27808

Three-Dimensional Composition and Electric Potential Mapping of III−V Core−Multishell Nanowires by Correlative STEM and Holographic Tomography

Wolf, D.; Hübner, R.; Niermann, T.; Sturm, S.; Prete, P.; Lovergine, N.; Büchner, B.; Lubk, A.

The nondestructive characterization of nanoscale devices, such as those based on semiconductor nanowires, in terms of functional potentials is crucial for correlating device properties with their morphological/materials features, as well as for precisely tuning and optimizing their growth process. Electron holographic tomography (EHT) has been used in the past to reconstruct the total potential distribution in three dimension but hitherto lacked a quantitative approach to separate potential variations due to chemical composition changes (mean inner potential, MIP) and space charges. In this letter, we combine and correlate EHT and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) tomography on an individual ⟨111⟩ oriented GaAs-AlGaAs core-multishell nanowire (NW). We obtain excellent agreement between both methods in terms of the determined Al concentration within the AlGaAs shell, as well as thickness variations of the few nanometer thin GaAs shell acting as quantum well tube. Subtracting the MIP determined from the STEM tomogram enables us to observe functional potentials at the NW surfaces and at the Au-NW interface, both ascribed to surface/interface pinning of the semiconductor Fermi level.

Keywords: GaAs-AlGaAs; III−V nanowire; 3D elemental mapping; functional potential; quantum well tube; tomography; holography

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Publ.-Id: 27807

Terahertz pump-induced anisotropy and nonlinear susceptibility in graphene

Schneider, H.; König-Otto, J. C.; Mittendorff, M.; Winzer, T.; Kadi, F.; Malic, E.; Knorr, A.; Wang, Y.; Belyanin, A.; Pashkin, A.; Helm, M.; Winnerl, S.

We report on investigations of the carrier dynamics in graphene close to the Dirac point by nonlinear terahertz spectroscopy. At terahertz frequencies and low temperatures, optical-phonon scattering is suppressed. In this case, the decay of the pump-induced anisotropy in the carrier distribution is observed to be very slow, long as several ps, which is theoretically explained by non-collinear Coulomb scattering. In Landau-quantized graphene, degenerate four-wave mixing experiments in resonance to the lowest Landau level transition allow us to investigate the induced coherent polarization and to compare its dependence on THz field strength and B-field detuning with theoretical expectations.

Keywords: graphene; nonlinear terahertz spectroscopy; nonlinear susceptibility; pump-probe

Related publications

  • Poster
    34-th International Conference on the Physics of Semiconductors (ICPS 2018), 29.07.-03.08.2018, Montpellier, Frankreich

Publ.-Id: 27805

High-performance and room-temperature QWIPs & terahertz spectroscopy

Schneider, H.

The topic of this seminar talk is high-performance and room-temperature quantum well photodetectors and terahertz spectroscopy.

Keywords: quantum well infrared photodetector; terahertz spectroscopy

Related publications

  • Lecture (others)
    Seminarvortrag, Yunnan University, 03.05.2018, Kunming, China

Publ.-Id: 27804

Nonlinear THz spectroscopy of graphene and GaAs quantum wells using a free-electron laser

Schneider, H.

This talk reviews some recent experiments using FEL-based intense narrow-band terahertz fields, in particular pump-induced optical anisotropy and nonlinear four-wave mixing in graphene, and dressing of excitons, exciton-polaritons, and intersubband transitions in GaAs quantum wells.

Keywords: nonlinear terahertz spectroscopy; graphene; interaubband; exciton

Related publications

  • Invited lecture (Conferences)
    The 9th International Symposium on Ultrafast Phenomena and Terahertz Waves (ISUPTW 2018), 23.-26.04.2018, Changsha, China
  • Invited lecture (Conferences)
    International Conference on "Synchrotron and Free electron laser Radiation: generation and application" (SFR-2018), Budker Institute of Nuclear Physics, 25.-28.06.2018, Novosibirsk, Russische Föderation

Publ.-Id: 27803

Nonlinear THz free-electron laser spectroscopy of graphene and GaAs quantum wells

Schneider, H.

This talk reviews some recent experiments on graphene and on GaAs quantum wells using FEL-based strong THz fields.
In graphene, we have investigated the pump-induced anisotropy of the carrier distribution upon excitation with linearly polarized light. Since optical-phonon scattering is suppressed at THz frequencies and low temperatures, we observe the decay of this anisotropy to be very slow, as long as several ps, which is theoretically explained by non-collinear Coulomb scattering. We also report on degenerate four-wave mixing experiments in Landau-quantized graphene to investigate the induced coherent polarization. In GaAs quantum wells, intense narrow-band THz fields are exploited for dressing elementary electronic excitations. We will address THz-induced dressing of excitons, exciton-polaritons, and intersubband transitions.

Keywords: Graphene; intersubband; nonlinear terahertz spectroscopy

Related publications

  • Lecture (others)
    Seminarvortrag, University of California at Santa Barbara (UCSB), 05.02.2018, Santa Barbara, USA
  • Lecture (others)
    Physikalisches Kolloquium der TU Chemnitz, 13.06.2018, Chemnitz, Deutschland
  • Lecture (others)
    Seminar, Chengdu Campus of CAEP, 23.07.2018, Chengdu, China

Publ.-Id: 27802

Terahertz orientational relaxation and phase relaxation in graphene

Schneider, H.; König-Otto, J. C.; Mittendorff, M.; Winzer, T.; Kadi, F.; Malic, E.; Knorr, A.; Wang, Y.; Belyanin, A.; Pashkin, A.; Helm, M.; Winnerl, S.

We report on investigations of the carrier dynamics in graphene close to the Dirac point by nonlinear terahertz spectroscopy. At terahertz frequencies and low temperatures, optical-phonon scattering is suppressed. In this case, the decay of the pump-induced anisotropy in the carrier distribution is observed to be very slow, long as several ps, which is theoretically explained by non-collinear Coulomb scattering. In Landau-quantized graphene, degenerate four-wave mixing experiments in resonance to the lowest Landau level transition allow us to investigate the induced coherent polarization and to compare its dependence on THz field strength and B-field detuning with theoretical expectations.

Keywords: graphene; nonlinear terahertz spectroscopy; nonlinear susceptibility; four-wave mixing; pump-probe

Related publications

  • Lecture (Conference)
    SPIE Photonics West, Symposium on "Ultrafast Phenomena and Nanophotonics XXII", 27.01.-01.02.2018, San Francisco, USA

Publ.-Id: 27801

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