Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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34106 Publications

Analysis of granular material flow characteristics during silo discharging process using ultrafast X-ray CT

Waktola, S.; Babout, L.; Grudzień, K.; Bieberle, M.; Barthel, F.; Hampel, U.

In various industrial products, granular materials are required to flow under gravity in different kinds of silo shapes and through openings in horizontal bottoms. There are a number of interrelated parameters, which affect the flow, such as internal friction, bulk and packing density, hopper geometry, material type and so on. Silo gravitational flow has been investigated for many years; however, most published research findings are concerned on the numerical modeling of flow or usually the results are obtained by using equipment with some technical limitations. Due to the lack of possibility to visualize center of silo (as in case of CCD camera systems) or conditions of scanning speed and slightly low resolution of conventional X-ray CT and ECT systems respectively, so far, it was not able to conduct effective analysis of flow characteristics (MICHALOWSKI et al., 1984, CHOI et al., 2005, WILDE et al., 2010 and BABOUT et al., 2013). More in-depth investigation and analysis of silo flow behaviors than being conducting till now, will allow better understand the flow process and additionally to conduct comparison between real measurements and simulation results.
Using the ultra-fast electron beam X-ray CT scanner (ROFEX) from Helmholtz-Zentrum Dresden-Rossendorf, which is a very high temporal resolution system, it is possible to investigate structural changes within a granular material during the flow process. Since the images, which were scanned using this technology have high spatial and temporal resolution, specified particle movements can be tracked and local velocities can be determined. Thus, the dynamic flow behavior of the material during the discharging process can be investigated.
This study gives a new insight into the gravitational flow during silo discharging process inside a cylindrical silo model. The granular material is a mixture of sand and tracer particles. The properties of tracer particles are characterized by higher absorption of X-ray radiation and different shape than sand particles, which allows observing motion of tracking particles (GRUDZIEN et al., 2013). Such type of experiments (using ultra-fast X-ray system and particle tracking methods) were conducted for different construction of silo models, which allows evaluating the radial and axial local velocity of granular materials.

Keywords: granular material; silo discharging; ultrafast X-ray CT

  • Contribution to proceedings
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brazil
    Proceedings of WCIPT8
  • Poster
    WCIPT8 - 8th World Congress on Industrial Process Tomography, 26.-29.09.2016, Iguassu Falls, Brazil

Permalink: https://www.hzdr.de/publications/Publ-23367
Publ.-Id: 23367


Geometallurgy of iron ores - a mineralogists' perspective

Gutzmer, J.

To the superficial observer iron ore deposits appear as huge and uniform bodies comprising of iron oxide - or carbonate - and little else. They should, therefore, be simple to exploit and beneficiate. This may have indeed applied to the giant high-grade BIF-hosted deposits that have dominated global iron supply for the last half a century. However, it does certainly not apply to iron ore deposits that will govern future supply. The latter deposits will still be very large, but of lower grade and marked by increasing concentrations of deleterious elements such as phosphorous, titanium or alkali elements. Careful ore characterization and geometallurgical modelling will be key drivers to convert iron ore resources into reserves – and deposits into new mines.

Keywords: iron ore; geometallurgy

  • Invited lecture (Conferences)
    Mineralteknik 2016, 02.-03.02.2016, Lulea, Sweden
  • Contribution to proceedings
    Mineralteknik 2016, 02.-03.02.2016, Lulea, Sweden
    Mineralteknik 2016 - Proceedings, Lulea: Lulea Technical University, 18-19

Permalink: https://www.hzdr.de/publications/Publ-23366
Publ.-Id: 23366


The Paleoproterozoic Manganese Bonanza in Africa

Gutzmer, J.; Beukes, N. J.

Africa hosts just over 80 percent of the currently known land-based resources of manganese (Mn). The bulk of the African Mn resource is of sedimentary origin and hosted by strata of Paleoproterozoic age, although epigenetic processes, including hydrothermal enrichment and/or deep chemical weathering, have significantly enriched some of the deposits. Host strata and geological context have been used to categorize the deposits into four types, namely BIF-associated, black shale-associated, sandstone-associated (oolitic) and karst-associated. Mn deposits occur geographically clustered and related to a number of prominent sedimentary successions of Late Archean to Late Paleoprozerozoic age. The greatest concentration and genetic diversity occurs undoubtedly on the Kaapvaal Craton of Southern Africa. The Transvaal Supergroup (TVL SG) hosts the ~ 2,2 Ga BIF-associated deposits of the Kalahari Manganese Field – with an estimated 4,2 Gt of contained Mn by far the largest of all land-based Mn deposits globally. However, the TVL SG also hosts the ~ 2,4 Ga BIF-associated Rooinekke deposit and the 2,0-2.2 Ga Postmasburg Manganese Field, the latter comprising the worlds oldest karst-associated Mn deposits. The record of sedimentary Mn deposits of Paleoproterozoic age on the Kaapvaal Craton is complemented by the Tolwe deposit of the ~1,9 Ga Soutpansberg Group, the oldest known example of sandstone-associated oolitic Mn ores.
Other important Paleoproterozoic manganese deposits in Africa are all limited to sedimentary strata of ~ 2,1-2,2 Ga age. These successions may comprise cratonic cover sequences, such as the Francevillian Supergroup on the northwestern part of the Congo Craton, or are associated with the formation of Paleoproterozoic juvenile crust, such as the Birimian Supergroup of West Africa or the Lukoshi Complex in the DRC. Manganiferous carbonate beds closely associated with greywackes and pyritic black shales are geographically and stratigraphically widespread in these successions. In most cases, Late Mesozoic and Cenozoic lateritic weathering markedly enrich the manganiferous strata to form high-grade manganese oxide ores.
All major African Mn deposits occur in strata that immediately postdate the great oxidation event (GOE). Furthermore, they are associated with – or immediately postdate the deposition of banded iron formations. Together with an abundance of geochemical evidence this close temporal affiliation may be used to invoke that the unique concentration of Mn in the sedimentary environment is a consequence of the establishment of oxic conditions in the shallow marine as well as the terrestrial environment.

Keywords: Manganese; Africa; ore deposits

  • Invited lecture (Conferences)
    5th International Geologica Bellica Meeting, 26.-29.01.2016, Mons, Belgium
  • Contribution to proceedings
    5th International Geologica Belgica 2016 Congress, 26.-29.01.2016, Mons, Belgium
    5th International Geologica Belgica 2016 Congress Abstract Book, Mons: Geological Society of Belgium, 197-197

Permalink: https://www.hzdr.de/publications/Publ-23365
Publ.-Id: 23365


Thyroid hormone status defines brown adipose tissue activity and browning of white adipose tissues in mice

Weiner, J.; Kranz, M.; Klöting, N.; Kunath, A.; Steinhoff, K.; Rijntjes, E.; Köhrle, J.; Zeisig, V.; Hankir, M.; Gebhardt, C.; Deuther-Conrad, W.; Heiker, J.; Kralisch, S.; Stumvoll, M.; Bluher, M.; Sabri, O.; Hesse, S.; Brust, P.; Tönjes, A.; Krause, K.

The present study aimed to determine the effect of thyroid hormones dysfunction on brown adipose tissue activity and white adipose tissue browning in mice.
Twenty randomized female C57BL/6NTac mice per treatment group housed at room temperature were rendered hypothyroid or hyperthyroid. In-vivo small animal 18F-FDG PET/MRI was performed to determine the effects of hypo- and hyperthyroidism on BAT mass and BAT activity. Ex-vivo 14C-acetate loading assay and the assessment of expression of thermogenic genes and proteins allowed for the quantification of the oxidative and thermogenic capacities of WAT and BAT of eu-, hyper and hypothyroid mice.
18F-FDG PET/MRI revealed lack of brown adipose tissue activity in hypothyroid mice, whereas hyperthyroid mice displayed increased BAT mass alongside enhanced 18F-FDG uptake. In white adipose tissue of both, hyper- and hypothyroid mice, we found a significant induction of thermogenic genes together with a multilocular adipocytes expressing Ucp1.
Taken together, these results suggest that both the hyperthyroid and hypothyroid state affect WAT thermogenesis most likely as a consequence of enhanced adrenergic signaling or compensation for impaired adaptive thermogenesis, respectively.

Permalink: https://www.hzdr.de/publications/Publ-23364
Publ.-Id: 23364


Multistage uranium bioassociation kinetics of two Halobacterium noricense strains under highly saline conditions

Bader, M.; Müller, K.; Foerstendorf, H.; Swanson, J. S.; Cherkouk, A.

Salt rock is one potential host rock formation being considered by Germany for the final disposal of radioactive waste. In addition to the characterization of geochemical and geophysical parameters, it is of great importance to take microbial activity of indigenous microorganisms into account for the safety assessment. Few studies have been conducted to investigate the microbial influence on the migration of radionuclides at high ionic strength. In this work, the extremely halophilic archaeon Halobacterium (Hbt.) noricense and its interactions with uranium were studied. Two different strains of the in salt rock common Hbt. noricense [1-4] were investigated. One was originally isolated from an Austrian salt mine (Hbt. noricense DSM-15987) [1] and the other from the US nuclear waste disposal site Waste Isolation Pilot Plant (WIPP, Carlsbad, NM) [2].
Biosorption kinetics were monitored in 3 M NaCl containing 40 or 50 µM uranium at pH 5.5 in the presence of Hbt. noricense cells. The fraction of bioassociated uranium was calculated from the uranium remaining in solu-tion analyzed by ICP-MS. Surprisingly, both strains of Hbt. noricense do not reflect typical sorption behavior; i.e. fast sorption within the first hours until reaching a stable equilibrium state. In this study, a fraction of uranium was sorbed within the first two hours of exposure time followed by a release of the radionuclide for a certain time. Subsequently, the amount of bioassociated uranium was found to increase very slowly until a maximum sorption of 80% was reached after 48 h. For a better understanding of this unique behavior, spectroscopic as well as microscopic methods were applied. Results from in situ Attenuated Total Reflection Fourier-transform Infrared (ATR FT-IR) spectroscopy evidenced that within the first two hours the actinide binds to carboxylic as well as to phosphate groups to cells of Hbt. noricense DSM-15987 simultaneously. The viability of Hbt. noricense cells was checked after contact with uranium by using the LIVE/DEAD® Bac LightTM Bacterial Viability Kit and analyzed with fluorescence microscopy. Almost all cells were alive even after one week of exposure to uranium. However, cell agglomeration was observed with increasing incubation time in both Hbt. noricense strains. For Hbt. noricense DSM-15987, a faster agglomeration process with agglomerates up to 200 µm in size was observed compared to the WIPP strain, which formed only microscopically visible agglomerates. The unusual, but reproducible bioassociation kinetics suggests that the WIPP strain and the Austrian strain react in the same way to uranium presence.

REFERENCES
[1] Gruber, C. et al. (2004) Extremophiles, Vol. 8, 431-439.
[2] Swanson, J. et al. (2012) LANL Report, LA-UR-12-22824.
[3] Gramain, A. et al. (2011) Environ. Microbiol., Vol. 13, 2105-2121.
[4] Yildiz, E. et al. (2012) Pol. J. Microbiol., Vol. 61, 111-117.

Keywords: Uranium biosorption; Halobacterium noricense

  • Lecture (Conference)
    Biometals (10th International Biometals Symposium), 10.-15.07.2016, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23363
Publ.-Id: 23363


Euler-Euler Multiphase CFD (with focus on bubbly flows)

Rzehak, R.

Vorstellung der Arbeiten in der Abteilung CFD des Instituts für Fluiddynamik am HZDR

  • Invited lecture (Conferences)
    Arbeitstreffen bei der Firma Bosch, 14.-15.01.2016, Renningen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23362
Publ.-Id: 23362


Euler-Euler Modeling of Mass-Transfer in Bubbly Flows

Rzehak, R.; Krepper, E.

CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions rely on suitable closure models. Concerning the fluid dynamics of bubbly flows a certain degree of predictive capability has been reached recently. However, concerning mass transfer only few studies have been performed to date.
The present contribution gives an overview over the available results on closure relations for physical absorption/desorption, i.e. mass transfer without chemical reactions. Unsolved issues are highlighted, in particular on which parameters a suitable correlation for the mass transfer coefficient should be based.
In addition, a preliminary study on model validation is presented which makes use of experimentally determined mass transfer coefficients. The need for and requirements on suitable data for this purpose are emphasized.

Keywords: mass-transfer; dispersed gas-liquid multiphase flow; Euler-Euler two-fluid-model; closure relations; CFD simulation; model validation

  • Lecture (Conference)
    Jahrestreffen der ProcessNet-Fachgruppen Agglomerations- und Schüttguttechnik, Computational Fluid Dynamics und Mehrphasenströmungen, 29.02.-02.03.2016, Bingen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23361
Publ.-Id: 23361


Euler-Euler Modeling of Hydrodynamics and Mass-Transfer in Bubbly Flows

Rzehak, R.; Kriebitzsch, S.; Krepper, E.

CFD simulations of dispersed bubbly flow on the scale of technical equipment are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, accurate numerical predictions rely on suitable closure models. To achieve predictive capability all details of the closure models have to be fixed in advance without reference to any measured data. Concerning the fluid dynamics of bubbly flows a baseline model has recently been proposed to this end and is shown to work for a range of different applications in a unified manner. This provides a reliable background which is well suited to add more complex physics. The content of the present contribution is such an extension to include also mass-transfer from / to the bubbles to the surrounding liquid. Shrinking / growth of the bubbles is taken into account within the inhomogeneous MUSIG model. A preliminary validation is provided using constant values for the mass transfer coefficient and the bubble size, but comparison is made with a set of experimental data providing axially resolved measurements. This contrasts previous works where comparison has been made only with integral data. A verification of the implementation is provided for the case with shrinking bubbles. The need for and requirements on suitable data for validation of a more refined model is emphasized.

Keywords: : mass-transfer; dispersed gas-liquid multiphase flow; Euler-Euler two-fluid-model; closure relations; CFD simulation; model validation

  • Contribution to proceedings
    9th International Conference on Multiphase Flow, ICMF-2016, 22.-27.05.2016, Firenze, Italia

Permalink: https://www.hzdr.de/publications/Publ-23360
Publ.-Id: 23360


In-situ X-ray observations showing the impact of natural and forced convection on dendritic solidification

Eckert, S.; Shevchenko, N.; Roshchupkina, O.; Sokolova, O.

The directional solidification of Ga–25wt%In alloys was investigated using X-ray radioscopy, which offers a visual access to opaque melts and enables a basic, intuitional understanding of the complex interplay between melt flow and dendritic growth. Natural convection occurs owing to an unstable density stratification at the solid-liquid interface. Forced convection was produced by a rotating wheel. Our observations show a facilitation of the growth of primary trunks or lateral branches, suppression of side branching, dendrite remelting and fragmentation. The manifestation of all phenomena depends on the dendrite orientation, local direction and intensity of the flow. The forced flow eliminates the solutal plumes and damps the local fluctuations of solute concentration. It provokes a preferential growth of the secondary arms at the upstream side of the primary dendrite arms, whereas the high solute concentration at the downstream side of the dendrites can inhibit the formation of secondary arms.

Keywords: solidification; dendritic growth; macrosegregation; fragmentation; X-ray radioscopy

  • Invited lecture (Conferences)
    Michel Rappaz Honory Symposium: Frontiers in Solidification; TMS2016, 145th Annual Meeting and Exhibition, 14.-18.02.2016, Nashville, USA

Permalink: https://www.hzdr.de/publications/Publ-23359
Publ.-Id: 23359


Microbial biomineralization of uranium and its application

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

Microbes are per definition small organisms and are specialists in adapting to changing environmental conditions. Thus they successfully conquer almost all kinds of environments even the harshest and most forbidden ones. One reason for that is, nature is very creative in the development of effective survival strategies. The various interaction mechanisms of microbes with radionuclides are therefor a good example. In general, microbes can not only inactivate reactive oxygen species formed by radiolysis of water or the Fenton reaction, but also detoxify the radio-metals themselves. First of all microbes are able to immobilize radio-metals by sorption, accumulation, mineralization or reduction. Furthermore, they can also mobilize metals by complexation or oxidation.
With regard to a molecular understanding of the microbe-uranium interaction and its possible application for the precautionary radiation protection and/or bio-remediation, sorption, accumulation and mineralization of uranium by living bacteria, fungi and algae were investigated. Interestingly, the different groups of organisms show significant differences in the interaction with uranium proved by different spectroscopic methods combined with electron microscopy. While the gram-positive bacterium Lysinibacillus sphaericus binds uranium via carboxyl and phosphate groups and subsequently forms meta-autunite like minerals outside the cell [1], the alga Chlorella vulgaris first binds uranium via same functional groups but afterwards desorbs the uranium by the secretion of complexing bio-ligands [2]. In contrast, the fungus Schizophyllum commune binds uranium at low concentrations (1 mg/L) outside the cell via organic phosphates but accumulates it inside the cell at higher uranium concentrations (100 mg/L) by forming inorganic phosphates [3]. Due to their high uranium resistance and high accumulation rates a fungal-based concept for the immobilization of released radionuclides was developed and is currently investigated.

[1] Merroun et al. (2005), Appl. Environ. Microbiol. 71(9), 5532-5543. [2] Vogel et. al (2010), Sci. Total Environ. 409, 384-395. [3] Günther et al. (2014), Biometals 27,775-785

Keywords: biomineralization; bacteria; algae; fungi; uranium

  • Invited lecture (Conferences)
    26th Goldschmidt Conference, 26.06.-01.07.2016, Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-23358
Publ.-Id: 23358


Mechanistic sorption models: Species, Thermodynamic, Application

Bok, F.; Richter, C.; Stockmann, M.; Brendler, V.

During the last two decades mechanistic sorption models not only continued their development and parameterization, but also gained ground for application in real-world scenarios such as in the long-term safety analysis of potential nuclear waste repositories. This was only possible because fundamentals such as a proper identification of surface species (their numbers, stoichiometries, structures & denticity) could be based on combinations of spectroscopic experiments, thermodynamic modelling and quantum chemical calculations. Similar progress can be reported for the mineral characterization (specific surface area, binding sites, protolysis reactions). Based on realistic species set and mineral properties, respective formation constants can be derived from batch sorption experiments, also providing information about temperature dependence and kinetics (namely reversibility). Nowadays, mechanistic sorption models are not only a synonym for surface complexation models (SCM), but ideally also account for additional phenomena such as ion exchange or surface precipitation, as well as the formation of secondary phases (smart Kd-values).
The above sketched developments are illustrated for a recent case study about Np(V) and U(VI) sorption onto components of Gorleben overburden sediments. The talk presents the analysis of the on-site data situation. Then own measurements to complete the thermodynamic data base including species identification by means of time-resolved laser-induced fluorescence and attenuated total reflection Fourier-transform infrared spectroscopies are addressed, together with the fit procedure to obtain SCM parameter sets. Next, the scheme utilized for smart Kd computation (including its implementation into reactive transport codes) is explained, and results from an uncertainty and sensitivity analysis are discussed.
Conclusions will incorporate a strategy to join international expertise (and man power) aiming at a comprehensive sorption raw data re-evaluation. This would allow to derive an internally consistent (with respect to EDL definition, mineral characteristics and species set) data set for the computation of smart Kd-values. This strategy covers data assembly, evaluation, processing and storage into an appropriate data structure.

Keywords: smart Kd; Sorption; Surface species; reactive transport modelling

  • Invited lecture (Conferences)
    American Chemical Society Spring meeting, 13.-17.03.2016, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-23357
Publ.-Id: 23357


Directional Spin Wave Emission From Topological Spin Textures

Sluka, V.; Weigand, M.; Kakay, A.; Schultheiss, K.; Warnatz, T.; Erbe, A.; Tyberkevych, V.; Slavin, A.; Deac, A.; Lindner, J.; Fassbender, J.; Raabe, J.; Wintz, S.

The investigation of propagating spin waves is a key topic of magnetism at present. For the excitation of spin waves with short wavelengths, it was typically necessary to either use patterned transducers with sizes on the order of the desired wavelengths (striplines or point-contacts) or to generate those spin waves parametrically by a spatially uniform double-frequency microwave signal. Only recently, a new mechanism for the local excitation of spin waves has been discovered, which overcomes the lower wavelength limit given by the minimum patterning size. This method utilizes the translation of natural topological defects, namely the gyration of magnetic vortex cores to generate isotropically propagating spin waves.

Keywords: spin wave; vortex

  • Lecture (Conference)
    The 9th International Symposium on Metallic Multilayers, 19.-23.06.2016, Uppsala, Schweden
  • Lecture (Conference)
    8th Joint European Symposia, 21.-26.08.2016, Glasgow, United Kingdom
  • Poster
    39th International Conference on Vacuum Ultraviolet and X-Ray Physics, 03.-08.07.2016, Zürich, Schweiz
  • Invited lecture (Conferences)
    1st Baltic Spin, 09.-13.08.2016, Jurmala, Lettland

Permalink: https://www.hzdr.de/publications/Publ-23356
Publ.-Id: 23356


Changes in Binding of [123I]CLINDE, a High-Affinity Translocator Protein 18 kDa (TSPO) Selective Radioligand in a Rat Model of Traumatic Brain Injury

Donat, C. K.; Gaber, K.; Meixensberger, J.; Brust, P.; Pinborg, L. H.; Hansen, H. H.; Mikkelsen, J. D.

The neuropathology following traumatic brain injury (TBI) is poorly understood. From the primary biomechanical injury, secondary injuries develop, including neuro-inflammatory processes. These secondary injuries are regarded as a potential targets for treatment and diagnostics. The translocator protein 18 kDa (TSPO) is robustly upregulated in response to brain injury, making it a suitable biomarker for glia activation and the neuro-inflammatory response. Second-generation radioligands of TSPO, such as [123I]CLINDE, offer higher affinity and signal-to-noise ratio compared to PK11195, the prototypical ligand. Applicability of [123I]CLINDE was demonstrated in both neurodegenerative disease models and patient studies and therefore demonstrate the translational value of this tracer. We therefore investigated TSPO expression in a rat model of TBI with [123I]CLINDE , a selective and clinically relevant TSPO-radioligand.
Adult Sprague-Dawley rats were subjected to moderate Controlled-Cortical-Impact injury (CCI, n=5 per group). Sham (n=5), craniotomy (n=3), and naïve animals (n=3) served as different control groups. Animals were sacrificed at 6h, 24h, 72h, and 28 days post-surgery, and TSPO expression was assessed in brain section employing [123I]CLINDE in vitro autoradiography.
From 24 h to 28 d post-surgery, injured animals exhibited a marked and time-dependent increase of binding in the ipsilateral motor, somatosensory and parietal cortex, as well as in the hippocampus and thalamus. Furthermore, binding was significantly elevated in the contralateral motor cortex following TBI. Craniotomy also caused a significant increase in [123I]CLINDE binding per se. Radioligand binding was consistent with an increase in TSPO mRNA expression and OX-42 immunoreactivity at the contusion site.
In conclusion, this study demonstrates the applicability of [123I]CLINDE for brain regional and quantitative assessment of neuro-inflammatory activity in experimental models of TBI.

Permalink: https://www.hzdr.de/publications/Publ-23355
Publ.-Id: 23355


A Local Superlens

Kehr, S. C.; Mcquaid, R. G. P.; Ortmann, L.; Kämpfe, T.; Kuschewski, F.; Lang, D.; Döring, J.; Gregg, J. M.; Eng, L. M.

Superlenses enable near-field imaging beyond the optical diffraction limit. However, their widespread implementation in optical imaging technology so far has been limited by large-scale fabrication, fixed lens position, and specific object materials. Here we demonstrate that a dielectric lamella of subwavelength size in all three spatial dimensions behaves as a compact superlens that operates at infrared wavelengths and can be positioned to image any local microscopic area of interest on the sample. In particular, the lamella superlens may be placed in contact with any type of object and therefore enables examination of hard-to-scan samples, for example, with high topography or in liquids, without altering the specimen design. This lamella-based local superlens design is directly applicable to subwavelength light-based technology, such as integrated optics.

Keywords: superlens; subwavelength imaging; near-field microscopy; barium titanate; mid-infrared; free-electron laser

Permalink: https://www.hzdr.de/publications/Publ-23354
Publ.-Id: 23354


Concepts for the development of new biosorbents on the base of microbial constituents

Matys, S.; Schönberger, N.; Raff, J.; Günther, T.; Lederer, F.; Lehmann, F.; Flemming, K.; Pollmann, K.

The world's growing demand for high-tech metals together with a simultaneously deteriorating availability is one of the central challenges of our modern society. Thusly, the development of new and innovative processes for a more efficient extraction of raw materials as well as economic methods for recycling is needed. Established methods for reclaiming production residues often include the chemical treatment with concentrated acids or alkalis, and are also polluting and energy-intensive. To overcome existing deficiencies and disadvantages of such methods emphasis is increasingly placed on biological alternatives. Thereby, biosorptive materials are prevalent for the recovery of dissolved chemical species. They are inexpensive and manufacturable in large quantities and often have excellent binding properties as compared to synthetic materials. Microorganisms are particularly in focus for biosorption processes because of their ubiquity and their enormous variability. A number of microbial cell structures and metabolites have been developed evolutionarily in direct interaction with toxic or essential elements, including heavy metals. Mediated by a variety of functional groups combined with the perfect structural fit these molecules are able to bind such elements partially highly selective and specific. In our group we are investigating the potential suitability of biomolecules such as siderophores, short peptides, and S-layer proteins as biosorptive compound. Our presentation discusses the usability of these compounds for the development of novel, selective binding filter materials for removing toxic elements and the recovery of valuable metals from aqueous solutions.

Keywords: biosorption; bioremediation; metal recovery; siderophores; peptides; S-layer proteins

  • Poster
    VAAM 2016, 13.-16.03.2016, Jena, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23353
Publ.-Id: 23353


Electron-phonon coupling and energy flow in a simple metal beyond the two-temperature approximation

Waldecker, L.; Bertoni, R.; Ernstorfer, R.; Vorberger, J.

The electron-phonon coupling and the corresponding energy exchange was investigated experimentally and by ab initio theory in non-equilibrium states of the free-electron metal aluminium. The temporal evolution of the atomic mean squared displacement in laser-excited thin free-standing films was monitored by femtosecond electron diffraction. The electron-phonon coupling strength was obtained for a range of electronic and lattice temperatures from density functional theory molecular dynamics (DFT-MD) simulations. The electron-phonon coupling parameter extracted from the experimental data in the framework of a two-temperature model (TTM) deviates significantly from the ab initio values. We introduce a non-thermal lattice model (NLM) for describing non-thermal phonon distributions as a sum of thermal distributions of the three phonon branches. The contributions of individual phonon branches to the electron-phonon coupling are considered independently and found to be dominated by longitudinal acoustic phonons. Using all material parameters from first-principle calculations besides the phonon-phonon coupling strength, the prediction of the energy transfer from electrons to phonons by the NLM is in excellent agreement with time-resolved diffraction data. Our results suggest that the TTM is insufficient for describing the microscopic energy flow even for simple metals like aluminium and that the determination of the electron-phonon coupling constant from time-resolved experiments by means of the TTM leads to incorrect values. In contrast, the NLM describing transient phonon populations by three parameters appears to be a sufficient model for quantitatively describing electron-lattice equilibration in aluminium. We discuss the general applicability of the NLM and provide a criterion for the suitability of the two-temperature approximation for other metals.

Keywords: two temperature model; electron-phonon coupling; laser interaction with solids; warm dense matter; non-equilibrium

  • Open Access Logo Physical Review X 6(2016), 021003
    DOI: 10.1103/PhysRevX.6.021003
  • Lecture (Conference)
    39th international workshop on High Energy Density Physics using lasers and heavy ion beams, 27.01.-01.02.2019, Hirschegg, Österreich

Permalink: https://www.hzdr.de/publications/Publ-23350
Publ.-Id: 23350


Numerical simulations on copper droplet collisions in an electromagnetic slag cleaning process

Yang, H.; Wolters, J.; Pischke, P.; Soltner, H.; Fröhlich, J.; Eckert, S.

The copper slag cleaning process contains complex physico-chemical phenomena, among which the collisions between liquid metal droplets possess an enormous influence on the cleaning efficiency. An Euler-Lagrange approach is employed to numerically study the slag-copper droplet system with the CFD code FLUENT. For the dispersed phase a new hybrid collision algorithm was implemented to overcome the mesh-dependency problem of the pure stochastic algorithm. It provides better prediction of the collision probability among the in-homogeneously distributed droplets and liberates the Discrete Phase Model calculation from using the mesh of the continuous phase. Due to the high viscosity and density of both phases, the slag-droplet collision system is distinctly different from conventional collision systems, such as liquid droplets in air or gas bubbles in liquids. Therefore a new regime map for droplets in a viscous shear flow with low velocities is proposed on the basis of literature data. The results obtained with the simulations of the entire process highlight the importance of the collision model for the overall efficiency of the process.

Keywords: MHD; copper slag cleaning; stochastic collision; liquid metal droplet; coalescence

  • Lecture (Conference)
    ICMF-2016 – 9th International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy
  • Contribution to proceedings
    ICMF-2016 – 9th International Conference on Multiphase Flow, 22.-27.05.2016, Firenze, Italy

Permalink: https://www.hzdr.de/publications/Publ-23349
Publ.-Id: 23349


Mechanism of attenuation of uranyl toxicity by glutathione in Lactococcus lactis

Obeid, M. H.; Oertel, J.; Solioz, M.; Fahmy, K.

Both prokaryotic and eukaryotic organisms possess mechanisms for the detoxification of heavy metals, which are found among distantly related species. We have investigated the role of intracellular glutathione (GSH), which in a large number of taxa plays a role in the protection against the toxicity of common heavy metals. Anaerobically grown Lactococcus lactis containing an inducible GSH synthesis pathway was used as a model organism This physiological trait allows study of putative GSH-dependent uranyl detoxification mechanisms without interference from additional reactive oxygen species. By microcalorimetric measurements of the metabolic heat during cultivation, it was shown that intracellular GSH attenuates the toxicity of uranium at a concentration in the range of 10-150 µM; in this concentration range, no effect was observed with copper which was used as a reference for redox-metal toxicity. At higher copper concentrations, GSH aggrevates metal toxicity. Isothermal titration calorimetry reveals the endothermic binding of U(VI) to the carboxyl group(s) of GSH, rather than to the reducing thiol group involved in copper interactions. The data indicate that the primary detoxifying mechanism is the intracellular sequestration of carboxyl-coordinated U(VI) into an insoluble complex with GSH. The opposite effects of GSH on uranyl and copper toxicity can be related to the difference in coordination chemistry of the respective metal-GSH complexes, which cause distinct growth phase-specific effects on enzyme metal interactions.

Keywords: Microcalorimetry; Isothermal Calorimetry

  • Poster
    Biometals 2016, 10.-15.06.2016, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-23348
Publ.-Id: 23348


Quantitative experimental monitoring of molecular diffusion in clay with positron emission tomography

Kulenkampff, J.; Gründig, M.; Lippman-Pipke, J.; Zakhnini, A.

Clay plays a prominent role as barrier material in the geosphere. Their small particle sizes cause extremely small pore sizes and induce low permeability and high sorption capacity. Transport of dissolved species by molecular diffusion is less sensitive to the pore size. Heterogeneous structures on centimetre scale could cause heterogeneous effects, like preferential transport zones, which are difficult to assess. Laboratory measurements with diffusion cells yield limited information on heterogeneity, and pore space imaging methods have to consider scale effects. We established positron emission tomography (PET), applying a high-resolution PET-scanner, as spatially resolved quantitative method for direct laboratory observation of the diffusion process of a PET-tracer on the prominent scale of 1 to 100 mm. Although PET is rather insensitive to bulk effects, quantification required significant improvements of the image reconstruction procedure with respect to Compton scatter and attenuation. The experiments were conducted with 22Na and 124I over periods of 100 resp. 25 days. From the images we derived trustable anisotropic diffusion coefficients and, in addition, we identified indications for preferential transport zones. We thus demonstrated the unique potential of the PET imaging modality for geoscientific process monitoring under conditions where other methods fail, taking advantage of the extremely high detection sensitivity that is specific to radiotracer applications.

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Permalink: https://www.hzdr.de/publications/Publ-23346
Publ.-Id: 23346


Development of a High-Affinity PET Radioligand for Imaging Cannabinoid Subtype 2 Receptor

Moldovan, R.-P.; Teodoro, R.; Deuther-Conrad, W.; Kranz, M.; Wang, Y.; Nakano, M.; Valentine, H.; Fischer, S.; Pomper, M.; Wong, D. F.; Dannals, R. F.; Brust, P.; Horti, A. G.

Cannabinoid receptors type 2 (CB2) represent a target with increasing importance for neuroimaging due to its upregulation under various pathological conditions. Encouraged by preliminary results obtained with [11C](Z)-N-(3-(2-methoxyethyl)-4,5-dimethylthiazol-2(3H)-ylidene)-2,2,3,3-tetramethyl-cyclopropanecarboxamide ([11C]A-836339, [11C]1) in a mouse model of acute neuroinflammation (induced by lipopolysaccharide, LPS), we designed a library of fluorinated analogues aiming for an [18F]-labeled radiotracer with improved CB2 binding affinity and selectivity. Compound (Z)-N-(3-(4-fluorobutyl)-4,5-dimethylthiazol-2(3H)-ylidene)-2,2,3,3-tetramethyl-cyclopropanecarboxamide (29) was selected as the ligand with the highest CB2 affinity (Ki = 0.39 nM) and selectivity over those of CB1 (factor of 1000). [18F]29 was prepared starting from the bromo precursor (53). Specific binding was shown in vitro, whereas fast metabolism was observed in vivo in CD-1 mice. Animal PET revealed a brain uptake comparable to that of [11C]1. In the LPS-treated mice, a 20−30% higher uptake in brain was found in comparison to that in nontreated mice (n = 3, P < 0.05).

Keywords: Cannabinoid receptor type 2; Neuroinflammation; A-836339; Radiofluorination; Positron emission tomography

Permalink: https://www.hzdr.de/publications/Publ-23345
Publ.-Id: 23345


Geoscientific process monitoring with positron emission tomography (GeoPET)

Kulenkampff, J.; Gründig, M.; Zakhnini, A.; Lippmann-Pipke, J.

Transport processes in geomaterials can be observed with input-output experiments, which yield no direct information on the impact of heterogeneities, or they can be assessed by model simulations based on structural imaging with µCT. Positron emission tomography (PET) provides an alternative experimental observation method which directly and quantitatively yields the spatiotemporal distribution of tracer concentration. Process observation with PET benefits from its extremely high sensitivity together with a resolution that is acceptable in relation to standard drill core sizes. We strongly recommend applying high-resolution PET scanners in order to achieve a resolution in the order of 1 mm.
We discuss the particularities of PET applications in geoscientific experiments (GeoPET), which essentially are due to the high material density. Although PET is rather insensitive to matrix effects, mass attenuation and Compton scattering have to be corrected thoroughly in order to derive quantitative values.
Examples of process monitoring with GeoPET of advection and diffusion processes are illustrating the procedure and the experimental conditions, as well as the benefits and limits of the method.

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Permalink: https://www.hzdr.de/publications/Publ-23344
Publ.-Id: 23344


Tailoring nonlinear optical properties of Bi2Se3 through ion irradiation

Tan, Y.; Guo, Z.; Shang, Z.; Liu, F.; Böttger, R.; Zhou, S.; Shao, J.; Yu, X.; Zhang, H.; Chen, F.

The nonlinear optical property of topological insulator bismuth selenide (Bi2Se3) is found to be welltailored through ion irradiation by intentionally introducing defects. The increase of the optical modulation depth sensitively depends on the careful selection of the Irradiation condition. By implementing the ion irradiated Bi2Se3 film as an optical saturable absorber device for the Q-switched wave-guide laser, an enhanced laser performance has been obtained including narrower pulse duration and higher peak power. Our work provides a new approach of tailoring the nonlinear optical properties of materials through ion irradiation, a well-developed chip-technology, which could find wider applicability to other layered two-dimensional materials beyond topological insulators, such as graphene, MoS2, black phosphours etc.

Keywords: ion Irradiation; Bi2Se3 film; chip-technology

Permalink: https://www.hzdr.de/publications/Publ-23343
Publ.-Id: 23343


Development of quality-assured Thermodynamic Database for Rare Earth Elements

Jordan, N.; Barkleit, A.; Steudtner, R.; Bok, F.; Heller, A.; Brendler, V.

New materials showing specific magnetic and/or electrooptic properties often incorporate Rare Earth Elements (REE). Due to their very specific technological application, it is necessary to separate and enrich the REE from each other. The optimization of physico-chemical conditions for the design of effective extraction and recycling processes of REE has to rely on accurate and reliable thermodynamic data. However, no fundamental, consolidated and internationally recognized Thermodynamic Databases (TDB) is currently available for REE.
This study aims at providing a reliable, quality assured and internally consistent TDB for Europium. The thorough evaluation of all available primary literature sources for Eu(III) complexation constants (log β) with inorganic ligands (OH−, Cl−, NO3−, SO42− and CO32−) enabled identifying several critical issues: i) inconsistencies between different sources ii) lack of accurate activity coefficient treatment in case of formation of weak complexes iii) absence of independent spectroscopic validation of the stoichiometry of the proposed complexes.
Thus, several actions have been undertaken for the Eu-chloro, -nitrato and -sulfato complexes:
a) recalculation of the log β of weak complexes by using an hypothetical reference state (at trace ligand concentration) [1]
b) use of advanced spectroscopic techniques (e.g. Time-resolved Laser-induced Fluorescence Spectroscopy), allowing to monitor on line the speciation evolution at micromolar range concentrations. This also enabled identifying the prevailing species as well as their stoichiometries. Finally, complexation constants were determined from the spectroscopic data sets.
c) The conditional log β were extrapolated to standard conditions (I = 0 M, T = 298.15 K) using the Specific Ion Interaction Theory.

[1] Spahiu, K. et al. (1998) Radiochim. Acta 82, 413-419.

  • Contribution to proceedings
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan
    Proceedings of Goldschmidt 2016
  • Lecture (Conference)
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-23342
Publ.-Id: 23342


Use of multiple age tracers to estimate groundwater residence times and long-term recharge rates in arid southern Oman

Müller, T.; Osenbrueck, K.; Strauch, G.; Pavetich, S.; Al-Mashikhi, K.-S.; Herb, C.; Merchel, S.; Rugel, G.; Aeschbach, W.; Sanford, W.

Multiple age tracers were measured to estimate groundwater residence times in the regional aquifer system underlying southwestern Oman. The three isotopic age tracers 14C, 4He, and 36Cl were measured in waters collected from 20 wells along a line that extended roughly from the Dhofar Mountains near the Arabian Sea northward 400 km into the Empty Quarter of the Arabian Peninsula. The wells sampled were mostly open to the Umm Er Radhuma confined aquifer, although some were completed in the mostly unconfined Rus aquifer. The combined results from the three tracers indicate the age of the confined groundwater is <40k years in the recharge area in the Dhofar Mountains, >100 k years in the central section north of the mountains, and up to and >1 M years in the Empty Quarter. The 14C data were used to help calibrate the 4He and 36Cl data. Additional measurements of noble gases made were consistent with the age interpretations. Mixing models suggest that long open boreholes north of the mountains compromise 14C-only interpretations there, in contrast to 4He and 36Cl calculations that are less sensitive to borehole mixing. Thus only the latter two tracers from these more distal wells were considered reliable. In addition to the age tracers, 2H and 18O data suggest that seasonal monsoon and infrequent tropical cyclones are both substantial contributors to the recharge. The study highlights the advantages of using multiple chemical and isotopic data when estimating groundwater travel times and recharge rates, and differentiating recharge mechanisms.

Keywords: stable isotopes; groundwater residence times; carbon-14; helium-4; chlorine-36; arid region; groundwater flow; groundwater recharge; accelerator mass spectrometry

Permalink: https://www.hzdr.de/publications/Publ-23341
Publ.-Id: 23341


Comeback of Mercury as 197(m)Hg for Theranostics

Walther, M.; Wang, C.; Bergmann, R.; Pietzsch, H.-J.; Steinbach, J.

The no-carrier-added (NCA) radionuclide 197(m)Hg is accessible in adequate quantity and quality for radiopharmaceutical research through the proton irradiation of gold using a cyclotron.1 The interest in this mercury isotope was prompted primarily by the decay characteristics of both nuclear isomers, like convenient half-life (197mHg = 23.8 h, 197Hg = 64.14 h), low energy gamma radiations useful for diagnosis (197mHg = 133.98 keV, 33.5% , 197Hg = 77.4 keV, 18.7%) and numerous Auger- and conversion electrons with high potential for cancer therapy. Additionally, the unique chemical properties of mercury allow for the development of promising radiolabeling tools and new radiopharmaceuticals. In addition to the typical metal properties to form coordination compounds with sulfur, nitrogen and oxygen containing ligands, mercury has the special ability to build water stable carbon-metal bonds. The reactivity of the mercury(II) ions towards sulfur containing ligands, solvomercuration of alkenes and electrophilic aromatic substitutions were investigated to prepare a stable labeling unit at NCA level with 197(m)Hg. While both the mercury thiolate complexes and the products of solvomercuration exhibited low stability in the presence of competing thiol ligands and are therefore unsuitable for radiopharmaceutical applications, symmetric diarylmercury compounds showed high stability against competing ligands. The development and application of a prelabeling tool based on a bis-benzoyl-mercury derivative as succinimidyl ester will be reported.

Keywords: theranostic; cancer therapy

  • Poster
    42nd edition of the International Conference on Coordination Chemistry, 03.-08.07.2016, Brest, France

Permalink: https://www.hzdr.de/publications/Publ-23340
Publ.-Id: 23340


Insights into binding of S100 proteins to scavenger receptors: class B scavenger receptor CD36 binds S100A12 with high affinity

Tondera, C.; Laube, M.; Pietzsch, J.

The EF-hand type calcium-binding protein S100A12 exerts numerous intra- and extracellular functions of (patho)physiological relevance. Therefore, receptors of S100A12 are of high interest for research and clinical applications. Beside the extensively studied receptor for advanced glycation endproducts (RAGE), G-protein coupled receptors and, more recently, scavenger receptors are suggested to be putative S100A12 receptors. Own findings and further information from the literature predestined CD36, a class B scavenger receptor, as promising candidate. In order to substantiate or prove against this hypothesis the present study aimed at investigation of interaction of S100A12 and CD36 on molecular and cellular level by the use of surface plasmon resonance (SPR), radio- and fluorescence-tracer-based cell binding, and cell activation experiments. S100A12 revealed binding affinity to CD36 in the low nanomolar range, essentially, at the CD36 thrombospondin-1 binding site. Additionally, S100A12-mediated translocation of CD36 to the membrane and elevation of both CD36 and peroxisome proliferator-activated receptor γ (PPARγ) expression was observed, which suggest a potential regulatory function of S100A12-CD36 interaction.

Keywords: EF-hand calcium-binding proteins; surface plasmon resonance; pattern recognition receptors; damage-associated molecular patterns; receptor for advanced glycation endproducts (RAGE)

Permalink: https://www.hzdr.de/publications/Publ-23339
Publ.-Id: 23339


Ultrasmall inorganic nanoparticles: state-of-the-art and perspectives for biomedical applications

Zarschler, K.; Rocks, L.; Licciardello, N.; Boselli, L.; Polo, E.; Pombo Garcia, K.; de Cola, L.; Stephan, H.; Dawson, K. A.

Ultrasmall nanoparticulate materials with core sizes in the 1-3 nm range bridge the gap between single molecules and classical, larger-sized nanomaterials, not only in terms of spatial dimension, but also as regards physicochemical and pharmacokinetic properties. Due to these unique properties, ultrasmall nanoparticles appear to be promising materials for nanomedicinal applications.
This review overviews the different synthetic methods of inorganic ultrasmall nanoparticles as well as their properties, characterization, surface modification and toxicity. We moreover summarize the current state of knowledge regarding pharmacokinetics, biodistribution and targeting of nanoscale materials. Aside from addressing the issue of biomolecular corona formation and elaborating on the interactions of ultrasmall nanoparticles with individual cells, we discuss the potential diagnostic, therapeutic and theranostic applications of ultrasmall nanoparticles in the emerging field of nanomedicine in the final part of this review.

Keywords: ultrasmall nanoparticles; nanomedicine; pharmacokinetics; protein corona; active targeting; cancer; renal excretion

Permalink: https://www.hzdr.de/publications/Publ-23338
Publ.-Id: 23338


Atomistic study on mixed-mode fracture mechanisms of ferrite iron interacting with coherent copper and nickel nanoclusters

Al-Motasem, A. T.; Mai, N. T.; Choi, S. T.; Posselt, M.

The effect of copper and/or nickel nanoclusters, generally formed by neutron irradiation, on fracture mechanisms of ferrite iron was investigated by using molecular statics simulation. The equilibrium configuration of nanoclusters was obtained by using a combination of an on-lattice annealing based on Metropolis Monte Carlo method and an off-lattice relaxation by molecular dynamics simulation. Residual stress distributions near the nanoclusters were also calculated, since compressive or tensile residual stresses may retard or accelerate, respectively, the propagation of a crack running into a nanocluster. One of the nanoclusters was located in front of a straight crack in ferrite iron with a body-centered cubic crystal structure. Two crystallographic directions, of which the crack plane and crack front direction are (010)[001] and (111)[-110], were considered, representing cleavage and non-cleavage orientations in ferrite iron, respectively. Displacements corresponding to pure opening-mode and mixed-mode loadings were imposed on the boundary region and the energy minimizationwas performed. It was observed that the fracture mechanisms of ferrite iron under the pure opening-mode loading are strongly influenced by the presence of nanoclusters, while under the mixed-mode loading the nanoclusters have no significant effect on the crack propagation behavior of ferrite iron.

Keywords: fracture; Molecular Dynamics; Monte Carlo; nanoclusters; deformation twinning; dislocation

Permalink: https://www.hzdr.de/publications/Publ-23336
Publ.-Id: 23336


High-Rate Timing Resistive Plate Chambers with Ceramic Electrodes

Laso Garcia, A.; Kotte, R.; Naumann, L.; Stach, D.; Wendisch, C.; Wüstenfeld, J.; Kämpfer, B.

We describe recent advances in developing radiation-hard ceramic resistive plate chambers (CRPCs) with Si3N4/SiC composites. Bulk resistivity measurements for this material for different manufacturing processes are reported. The results show that the bulk resistivity can vary between 10^7 - 10^13 Ohm cm. The varistor type behaviour of the material is analyzed. A comparison with other materials used in timing RPCs is given.
We describe the assembly and tests of CRPC prototypes in electron and proton beams. For a prototype with bulk resistivity 5 x 10^9 Ohm cm, the effciency of the detectors is 95% at a fux of 2 x 10^5 cm^-2 s^-1. The time resolution at the same fux is about 120 ps. A prototype with bulk resistivity 2 x 10^10 Ohm cm shows an effciency of about 85% up to fuxes of 5 x 10^4 cm^-2 s^-1 with a time resolution better than 80 ps. The results are compared with RPC models.

Keywords: RPC; Timing; Ceramic; High-rate capabilities; High flux

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Permalink: https://www.hzdr.de/publications/Publ-23335
Publ.-Id: 23335


Uptake mechanisms of selenium oxyanions during the ferrihydrite-hematite recrystallization

Börsig, N.; Scheinost, A. C.; Shaw, S.; Schild, D.; Neumann, T.

Se is an essential nutrient at trace levels, but also a toxic environmental contaminant at higher concentrations. The mobility of the trace element Se in natural environments is mainly controlled by the occurrence of the highly soluble Se oxyanions – selenite [Se(IV)] and selenate [Se(VI)] - and their interaction with geological materials. Since iron oxides are ubiquitous in nature, many previous studies investigated Se retention by adsorption onto iron oxides. However, little is known about the retention of Se oxyanions during the formation process of iron oxides. In this paper, we therefore studied the immobilization of Se oxyanions during the crystallization of hematite from ferrihydrite. In coprecipitation studies, hematite was synthesized by the precipitation and aging of ferrihydrite in an oxidized Se(IV)- or Se(VI)-containing system (pH 7.5). Hydrochemical data revealed the complete uptake of all available Se(IV) up to initial concentrations of 10-3 mol/L (m/V ratio = 9.0 g/L), while the retention of Se(VI) was extremely low (max. 15 %). In case of high initial Se(IV) concentrations, the results also demonstrated that the interaction of Se with ferrihydrite can affect the type of the final transformation product. Comparative adsorption studies, performed at identical conditions, allowed a distinction between pure adsorption and coprecipitation and showed a significantly higher Se retention by coprecipitation than by adsorption. Desorption studies indicated that Se coprecipitation leads to the occurrence of a resistant, non-desorbable Se fraction. According to time-resolved studies of Se(IV) or Se(VI) retention during the hematite formation and detailed spectroscopic analyses (XPS, XAS), this fraction is the result of an incorporation process, which is not attributable to Fe-for-Se substitution or the Se occupation of vacancies. Se initially adsorbs to the ferrihydrite surface, but after the transformation of ferrihydrite into hematite, it is mostly incorporated by hematite. In systems without mineral transformation, however, Se remains as a sorption complex. In case of Se(VI), an outersphere complex forms, while Se(IV) forms a mixture of bidentate mononuclear edge-sharing and bidentate binuclear corner-sharing inner-sphere complexes. The results of this study demonstrate that occlusion of Se oxyanions by hematite is an important retention mechanism, in addition to pure adsorption, for immobilizing Se in natural systems, which may control Se migration processes in polluted environments.

Keywords: selenium; structural incorporation; EXAFS; ferrihydrite; hematite

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Permalink: https://www.hzdr.de/publications/Publ-23334
Publ.-Id: 23334


Inter-sublevel dynamics in single InAs/GaAs quantum dots induced by strong terahertz excitation

Stephan, D.; Bhattacharyya, J.; Huo, Y. H.; Schmidt, O. G.; Rastelli, A.; Helm, M.; Schneider, H.

We combine micro-photoluminescence with terahertz excitation to investigate the response of single self-assembled InAs/GaAs quantum dots to intense terahertz pulses tuned to the s-to-p transition. Spectra and transients of single photoluminescence lines reveal the dynamics of electrons upon excitation and subsequent relaxation back into the initial state. Under certain circumstances, the terahertz pulse can release trapped charge carriers which relax into the quantum dot. Furthermore, we demonstrate near-total depletion of the positive trion PL by an intense terahertz pulse.

Keywords: Quantum dots; Photoluminescence; Terahertz; Carrier relaxation

Permalink: https://www.hzdr.de/publications/Publ-23333
Publ.-Id: 23333


Redox dependent interfacial reactivity of hexavalent radionuclides

Hellebrandt, S.; Knope, K. E.; Lee, S. S.; Stubbs, J. E.; Eng, P. J.; Soderholm, L.; Fenter, P.; Schmidt, M.

Understanding the behavior of radionuclides at mineral-water interfaces is important to make reliable statements for the safety assessments of nuclear waste disposals. Here, the interaction of UVIO22+ and PuVIO22+ with muscovite mica were investigated using a combination of surface X-ray diffraction (crystal truncation rods, CTR, and resonant anomalous X ray reflectivity, RAXR), alpha spectrometry and Grazing-incidence X-ray adsorption near-edge spectroscopy (GI-XANES). The interfacial behavior highlights the effect of the actinides’ different redox properties on their environmental mobility.
The interfacial structures obtained by CTR measurements, on the muscovite (001) basal plane after reaction with PuO22+ exhibit a large, broadly distributed electron density, which must be related to Pu uptake. This observation could be confirmed by RAXR and alpha spectrometry. In contrast, no significant uptake of UO22+ür is evident by CTR or RAXR.
GI-XANES identifies Pu on the surface as Pu(IV). The oxidation state of Pu in the reaction solution had been adjusted electrochemically, and was controlled by UV/vis spectroscopy, hence a reduction must have occurred during the experiment. In consequence of this reduction, obviously formation of Pu(IV)-oxo-nanoparticles occurred. We attribute the difference in the observed reactivity to the greater stability of low oxidation states for Pu relative to U, in combination with the increased “hardness” of the Pu4+ cation, relative to U4+. Once a threshold of [Pu4+] interface is reached, oligomerization may occur, and Pu4+ is removed from the redox equilibrium [1]. The reaction then becomes “auto-catalytic”. The results demonstrate how redox behavior strongly influences the sorption behavior of hexavalent actinides.

[1] Hellebrandt, S. et al. (2016), J. Phys. Chem. C. in preparation.

Keywords: Redox; Plutonium; Uranium; Muscovite; Mica; Surface

  • Lecture (Conference)
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-23332
Publ.-Id: 23332


1-(4-[18F]Fluorobenzyl)-4-((tetrahydrofuran-2-yl)methyl)piperazine: A novel radiotracer for mapping sigma-1 receptors in the living brain

He, Y.; Xie, F.; Deuther-Conrad, W.; Huang, Y.; Lu, J.; Yu, Q.; Ye, J.; Wang, L.; Steinbach, J.; Brust, P.; Jia, H.

Objectives: The sigma-1 receptors (Sig-1R) represent a distinct class of intracellular “ligand-operated receptor chaperones”.1 Increasing evidence suggests that the sigma-1 receptors are involved in various human diseases including depression, schizophrenia, drug addiction, Alzheimer’s disease, and neuroinflammation.2 Herein we report the design, synthesis and biological evaluation of 1-(4-[18F]fluorobenzyl)-4-((tetrahydrofuran-2-yl)methyl)piperazine ([18F]1) as a potent PET imaging probe for mapping sigma-1 receptors in the living brain.

Methods: Among a new series of disubstituted piperazine derivatives with binding selectivity for Sig-1R, compound 1 was identified as a candidate for radiolabeling. [18F]1 was synthesized using a one-pot, two-step labeling procedure (Scheme 1). The biological properties of the radioligand were determined in biodistribution and inhibition studies in ICR mice. Effect of P-glycoprotein (P-gp) on brain uptake, and the in vivo metabolic stability of the ligand were also investigated.

Results: In vitro competition binding assays showed that compound 1 exhibited nanomolar affinity for σ1 receptors (Ki (σ1) = 3.70 ± 0.02 nM) and good subtype selectivity (Ki (σ2) = 213.4 ± 13.4 nM; Ki (σ2)/Ki (σ1) = 58). [18F]1 was prepared in 20-30% isolated radiochemical yields with radiochemical purity of >95% and specific activity of 54-86 GBq/μmol (n = 3). The log D value of [18F]1 was determined to be 0.76 ± 0.01. Biodistribution studies in mice revealed high initial brain uptake of [18F]1 with 12.75 ± 0.79 %ID/g at 2 min after injection. The brain-to-blood ratios of [18F]1 were high (22, 21, 20 and 14, respectively, at 15, 30, 60 and 120 min after injection). Administration of the selective Sig-1R ligand SA4503 (5 mol/kg, 0.1 mL, iv) at 5 min prior to injection of [18F]1 significantly reduced the radiotracer uptake in brain (by 79%, 88% and 86%, respectively, at 15, 30 and 60 min after injection) and other organs known to express sigma-1 receptors, suggesting binding specificity of [18F]1 to sigma-1 receptors in vivo. Administration of the P-gp inhibitor cyclosporine A (50 mg/kg, 0.1 mL, iv) before tracer injection slightly increased the uptake of radiotracer both in the brain and the blood at 2 min after injection (saline,0.83 ± 0.07% ID/g in the blood, 10.11 ± 1.0 % ID/g in the brain; cyclosporine A, 0.89 ± 0.03% ID/g in the blood, 10.86 ± 0.69 % ID/g in the brain). But the difference between the control and blocking groups was small and not significant, suggesting that [18F]1 is not a substrate for P-gp. At 30 min after injection, the intact parent tracer [18F]1 accounted for 98% of the radioactivity (n = 2) in the mouse brain, indicating no entry of radioactive metabolites into the brain.

Conclusions: These results suggest that [18F]1 displayed high uptake levels and specific binding in brain. Further investigation is warranted to determine the imaging characteristics of this novel radiotracer, and to assess its potential to image Sig-1R in the living brain.

Acknowledgements: Supported by NSFC (21471019).

References: [1] Hayashi, T.; Su, T.-P. Cell 2007, 131, 596. [2] Maurice, T.; Su, T.-P. Pharmacol. Ther. 2009, 124, 195.

  • Lecture (Conference)
    11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA
  • Contribution to proceedings
    11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA
    Proceedings of the 11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain

Permalink: https://www.hzdr.de/publications/Publ-23331
Publ.-Id: 23331


Kinetic Modeling of (+)-[18F]Flubatine Binding to Nicotinic α4β2* Acetylcholine Receptors in Human Brains

Becker, G. A.; Tiepolt, S.; Patt, M.; Luthardt, J.; Rullmann, M.; Hesse, S.; Wilke, S.; Meyer, P. M.; Barthel, H.; Wagenknecht, G.; Höpping, A.; Gertz, H.; Steinbach, J.; Brust, P.; Sabri, O.

Objectives: Nicotinic α4β2* acetylcholine receptors (nAChR) are an important target for diagnostic neuroimaging because of their involvement e.g. in Alzheimer's and Parkinson's diseases, and nicotine addiction. The development of new PET-tracers for these receptors is an active field of research. Here we present the PET quantification of the new nAChR-ligand (+)-[18F]Flubatine, an enantiomer of (-)-[18F]Flubatine, also known as (-)-[18F]NCFHEB, which is already used for clinical PET imaging of nAChRs.

Methods: After intravenous administration of 284.1±13.2 MBq (+)-[18F]Flubatine PET brain recordings were performed in 11 healthy non-smoking subjects (age 66.6±4.4 years) using an ECAT EXACT HR+ system in 3D-acquisition mode. 41 frames were acquired from 0-270 min post injection and motion corrected with SPM2. Kinetic modeling using 1- and 2-tissue compartment models (1TCM, 2TCM) with arterial input-function was applied to the volume of interest (VOI) based tissue time-activity curves (TACs) generated for 36 brain regions (anatomically defined via MRI co-registration). Time ranges from 0 to 90 and 0 to 270 min were investigated. Model-based receptor parameter was the total distribution volume VT (ml/cm-3). Metabolites in plasma were measured by radioactivity HPLC and the free fraction of (+)-[18F]Flubatine in plasma was determined by ultracentrifugation.

Results: The tracer showed high stability in vivo with more than 97% remaining as untransformed parent compound at 90 and 270 min. The free fraction in plasma was high and showed only small interindividual variations (0.86±0.02, n=11). Given the negligible amounts of metabolites present in plasma the arterial input function was not corrected for metabolites.
TACs of all 36 regions could be described with the 1- or 2TCM. VT in all cortical regions could be reliably estimated from 90 min PET data. VT increased with receptor density as expected. Using the 2TCM and 270 min PET-data: CC (VT: 7.9±1.5, n=11), frontal cortex (10.8±1.2), pons (16.3±3.1), thalamus (41.3±8.7). For 90 min PET data the distribution volumes were very similar: CC (VT: 7.9±1.3), frontal cortex (10.3±1.4), pons (15.4±3.0), thalamus (41.0±9.0). The distribution volumes computed with the 1TCM were comparable to the results of the 2TCM: Frontal cortex (10.9±1.3, 270 min) and (10.2±1.4, 90 min).
The previously investigated enantiomer (-)-[18F]Flubatine showed very similar VT in cortical structures e.g., frontal (10.4±1.3, n=12) but lower VT in pons (12.4±1.9) and especially thalamus (27.6±4.2) (2TCM, 90 min; Sabri et al., 2015).

Conclusions: (+)-[18F]Flubatine has an optimal metabolic profile. The amount of metabolites is very low and no metabolite correction has to be applied to the arterial input function. The high VT values in subcortical structures are favorable. Receptor parameters can be estimated with a 1- or 2TCM from 90 min PET-data. If a model derived receptor parameter is used in a classification problem, e.g., distinguishing patients with Alzheimer’s disease from healthy controls the bias-variance tradeoff problem associated with the simpler 1TCM (higher bias) and the more complex 2TCM (higher variance) has to be solved. The final decision which model should be used will be made on the basis of the PET-data of both groups.

Reference: Sabri O et al. (2015) Neuroimage 118:199-208


Figure Legend: 2TCM fits (270 min) in 8 brain regions. Abscissa: Time in min, ordinate: Activity (kBq/cm3). Computed total tracer amount in tissue is presented but also the tracer amount in the non-displaceable and specific tissue compartment, the total distribution volume V and influx rate constant K1.

  • Poster
    NRM 2016 - 11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-23330
Publ.-Id: 23330


Two Novel Sigma-1 Receptor PET Radiotracers with Favorable Imaging Properties: Evaluation in Nonhuman Primates

Cai, Z.; Baum, E.; Bois, F.; Holden, D.; Lin, S.; Lara-Jaime, T.; Kapinos, M.; Chen, Y.; Deuther-Conrad, W.; Fischer, S.; Wünsch, B.; Brust, P.; Jia, H.; Huang, Y.

Objectives: Sigma-1 receptors (Sig-1Rs) are intramolecular chaperone proteins, the abnormal expression of which has been indicated in a variety of CNS disorders [1]. As a result, Sig-1R is proposed as a therapeutic target for schizophrenia, depression, and Alzheimer’s disease. PET imaging of S1Rs would provide an in vivo tool to investigate the involvement of Sig-1Rs in these diseases, and to assist in drug development. Hence, great efforts have been devoted to the development of effective PET radiotracers for Sig-1Rs, though most have failed to reach the human evaluation stage due to unfavorable pharmacokinetic and imaging properties. Through our Sig-1R PET ligand discovery programs, we have identified a number of spirocyclic piperidine analogs with attractive characteristics for development as in vivo imaging agents [2-4]. The objective of this study was to evaluate the two most promising ligands in rhesus monkeys in preparation for clinical translation.
Methods: The two 18F-labeled radiotracers (1 and 2) were prepared by nucleophilic displacement of the tosylate on the precursors and evaluated in the same rhesus monkeys (n = 2). Baseline scans of 4-h duration were obtained on a FOCUS 220 scanner after injection of ~5 mCi radioactivity. Blocking scans were performed with pre-administration of the selective Sig-1R agonist SA4503. Arterial blood was collected at pre-selected time points for measurement of plasma activity and HPLC analysis of radiometabolites to generate the plasma input functions for the parent tracer. Analysis of regional brain time-activity curves (TACs) was performed with one-tissue (1T), two-tissue (2T), and the multilinear analysis-1 (MA1) models to estimate kinetic parameters and regional volumes of distribution (VT). Tracer free fraction (fP) in plasma was measured via ultrafiltration method. Log D of each radiotracer was determined by the shake-flask method.
Results: Radiotracer 1 and 2 were prepared in high radiochemical purity and specific activity. In rhesus monkeys both tracers displayed moderate rates of metabolism, with 35% and 19% of parent fraction for 1 and 2 at 60 min post-injection. Plasma fP values were 2% and 17% for 1 and 2, in line with their respective measured Log D values of 2.8 and 2.5. Both radiotracers exhibited excellent brain uptake (peak SUV > 4) and fast tissue kinetics (activity peaked in all regions at <30 min post-injection) (Fig. 1). Both the 1T and MA1 models provided good fits of regional TACs and reliable VT estimates. Overall, ligand 2 displayed higher uptake levels, greater differential uptake among brain regions and higher regional VT values than 1. SA4503 (0.5 mg/kg. iv) blocked ~85% (1) and ~95% (2) of radiotracer uptake, indicating the binding specificity of both radiotracers in the monkey brain.
Conclusions: The novel Sig-1R radiotracers 1 and 2 display excellent brain uptake, fast tissue kinetics, and high levels of specific binding in vivo. Both have proved to be suitable for the imaging and quantification of Sig-1R in the monkey brain, therefore, further evaluation in humans is warranted. In comparison, tracer 2 has a ten-fold higher fP, higher brain uptake, and greater VT values in rhesus monkey.
Figure 1. TACs of ligands 1 and 2 in selected monkey brain regions with and without blocking.
References.
1. Maurice T and Su T-P, Pharmacol Ther, 2009. 124:195.
2. Brust P et al., J Nucl Med, 2014. 55:1730.
3. Li Y et al., J Med Chem, 2013. 56:3478.
4. Chen Y-Y et al., Bioorg Med Chem, 2014. 22:5270.

  • Lecture (Conference)
    11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-23329
Publ.-Id: 23329


Direct evidence of defect coordination and magnetic interaction in local structure of wurtzite type Zn1-xCoxO thin films

Satyarthi, P.; Ghosh, S.; Wang, Y.; Zhou, S.; Bürger, D.; Skorupa, I.; Schmidt, H.; Olivi, L.; Srivastava, P.

The local structure of as deposited and post treated Zn0.95Co0.05O films is investigated to understand the origin of their paramagnetic and tunable ferromagnetic properties for scientific advancements in spintronics. The crystallographic perfect short range ordering in the vicinity of tetrahedrally substituted Zn and Co atoms is responsible for mediating purely paramagnetic behavior in Zn0.95Co0.05O film grown by pulsed laser deposition. Irradiating the as deposited Zn0.95Co0.05O films with 500 keV inert xenon ions of different fluences, leads to creation of O, Zn and Co related defects in coordination shells of tetrahedrally substituted Zn and Co atoms. Apart from defect creation, spinel type ZnCo2O4 phase is evident for the film irradiated at highest fluence, in which Zn and Co atoms exist in tetrahedral and octahedral symmetry around the oxygen atoms. The tunable ferromagnetism in post irradiated Zn0.95Co0.05O films is understood from a model that includes strong ferromagnetic and weak antiferromagnetic interactions operating within their local structure. The ferromagnetic interaction is explained from (i) dopant defect hybridization of O vacancies and high spin (S = 3/2) Co atoms and (ii) spin interaction at O 2p orbital's in Zn vacancy rich regions in tetrahedral symmetry. The weak antiferromagnetic interaction is discussed from the presence of octahedral coordinated low spin (S = 0) Co atoms in ZnCo2O4 structure.

Keywords: Diluted Magnetic Semiconductors; Spintronics; EXAFS

Permalink: https://www.hzdr.de/publications/Publ-23328
Publ.-Id: 23328


U(VI) reduction by anaerobic microorganisms isolated from the flooding water of the former uranium mine Königstein (Saxony/Germany)

Gerber, U.; Krawczyk-Bärsch, E.; Scheinost, A. C.; Arnold, T.

The former uranium mine Königstein (Saxony, Germany) is currently in the process of remediation. The underground is flooded in a controlled way, and the flooding water is cleaned up in a dedicated waste water treatment plant. Despite high U concentrations up to 13 mg/L and a low pH of 2.9, these waters contain a high microbial diversity as detected by culture-independent methods. Microorganisms are known to interact with metals and radionuclides in different ways. Anaerobic bacteria which are able to gain energy from the reduction of several metals, are known to change the redox state of metals and radionuclides. For instance, anaerobic sulfate-reducing bacteria (SRB) reduce U(VI) to U(IV) and thus change the migration behavior from the more soluble U(VI) into the less soluble U(IV). Genomic sequence analysis of the flooding water revealed the presence of such anaerobic SRB. By culture-dependent methods it was possible to isolate anaerobic microorganisms from the flooding water. They were incubated with 10 mM glycerol using the flooding water as background medium. During an incubation time of six weeks the redox potential decreased from 660 mV to 300 mV. After four and six weeks of incubation, the cells were separated from the incubation medium by centrifugation and than analyzed by U-LIII edge EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) measurements. By Iterative Target-Factor Analysis (ITFA) we determined that 100 % of U(VI) was reduced to U(IV). Simultaneously, investigations of the supernatant with UV-vis resulted in the same findings. The results show that naturally occurring anaerobic microorganisms within the flooding water of the former uranium mine Königstein are able to reduce U(VI) to U(IV).

Keywords: Uranium reduction; Sulfate-reducing bacteria; Bioremediation

  • Contribution to proceedings
    Goldschmidt 2016, 26.06.-01.07.2016, Yokohama, Japan

Permalink: https://www.hzdr.de/publications/Publ-23326
Publ.-Id: 23326


Assessment of a hybrid CFD model for simulation of complex vertical upward gas-liquid churn flow

Parsi, M.; Agrawal, M.; Srinivasan, V.; Vieira, R. E.; Torres, C. F.; Mclaury, B. S.; Shirazi, S. A.; Schleicher, E.; Hampel, U.

Gas-liquid multiphase flow can be observed within different industrial processes, and Computational Fluid Dynamics (CFD) can be utilized as a tool for scrutiny of this kind of flows. Although the CFD simulations of multiphase are computationally-demanding, they can deliver a great deal of information. But, the larger point is whether the available CFD multiphase flow models are able to deliver a realistic solution for a complex flow pattern like churn flow? And if yes, to what extent are the results accurate?To shed light on these issues, the Eulerian-Eulerian MultiFluid VOF model offered by ANSYS FLUENT 15 (2015 15.0 User's Guide, ANSYS Inc.) was used to simulate high flow rate air-water multiphase flow in a 76.2 mm-diameter pipe upstream of an elbow in the vertical-horizontal configuration. In the simulations, superficial gas velocity ranged from 10.3 m/s to 33.9 m/s, and two superficial liquid velocities of 0.3, and 0.79 m/s were employed. From the CFD simulations, data such as phase distributions, mean void fractions, and average void fraction time series were extracted. They were then compared to experimental Wire Mesh Sensor (WMS) data formerly obtained. Interestingly, evaluation of the model revealed that it was successful in terms of capturing different liquid structures present within the flow and delivering void fraction data which were in agreement with those of experiments.

Keywords: CFD; Churn flow; Huge wave; MultiFluid VOF; Multiphase flow; Wire mesh sensor

Permalink: https://www.hzdr.de/publications/Publ-23324
Publ.-Id: 23324


Ferromagnetic Mn-Implanted GaP: Microstructures vs Magnetic Properties

Yuan, Y.; Hübner, R.; Liu, F.; Sawicki, M.; Gordan, O.; Salvan, G.; Zahn, D. R. T.; Banerjee, D.; Baehtz, C.; Helm, M.; Zhou, S.

Ferromagnetic GaMnP layers were prepared by ion implantation and pulsed laser annealing (PLA). We present a systematic investigation on the evolution of microstructure and magnetic properties depending on the pulsed laser annealing energy. The sample microstructure was analyzed by high-resolution X-ray diffraction (HR-XRD), transmission electron microscopy (TEM), Rutherford backscattering spectrometry (RBS), ultraviolet Raman spectroscopy (UV-RS), and extended X-ray absorption fine structure (EXAFS) spectroscopy. The presence of X-ray Pendellösung fringes around GaP (004) and RBS channeling prove the epitaxial structure of the GaMnP layer annealed at the optimized laser energy density (0.40 J/cm2). However, a forbidden TO vibrational mode of GaP appears and increases with annealing energy, suggesting the formation of defective domains inside the layer. These domains mainly appear in the sample surface region and extend to almost the whole layer with increasing annealing energy. The reduction of the Curie temperature (TC) and of the uniaxial magnetic anisotropy gradually happens when more defects and the domains appear as increasing the annealing energy density. This fact univocally points to the decisive role of the PLA parameters on the resulting magnetic characteristics in the processed layers, which eventually determine the magnetic (or spintronics) figure of merit.

Keywords: GaMnP; ion implantation; pulsed laser annealing; dilute ferromagnetic semiconductors; microstructures; magnetic properties

Permalink: https://www.hzdr.de/publications/Publ-23323
Publ.-Id: 23323


Functional PET/MR Discloses Gender Differences in Color Processing in Mice

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

OBJECTIVES: Color processing is a central component of human vision. There has been much debate about the existence of color vision in animals. Mice have two types of cone pigments, one with a peak sensitivity at about 510 nm, and the other with a peak at 370 nm in the ultraviolet range. Most studies of color vision have used behavioral experiments, and hence uncertainties remain whether the two cone types yield color vision. Since PET has been used to measure changes of rCBF of rhesus monkeys performing color discrimination we have hypothesized that FDG-PET combined with anatomical MR can be used to study color processing in mice. Here we demonstrate gender differences in color processing in mice.
METHODS: Ten anaesthetized CD-1 mice were repeatedly injected on different days with 12 MBq 18F-FDG and subjected in random order to separate monocular stimulation of the left and right eye with white, blue and yellow lights, respectively, for 20 min using gelatin-(Wratten)-filters affixed within a viewing device (Chromatoscope) specially designed for small animals. The SUV of 18F-FDG was determined at 27.5, 32.5, 37.5 and 42.5 min p.i. in the whole cortex and in the left and right visual cortex. Data were analyzed with MANOVA and t-test.
RESULTS: In both genders no hemispheric differences are revealed in dark baseline condition and during stimulation with white light of either eye. Male mice have 13-16% higher SUV (p< 0.001) than female mice in the cortical area, right and left visual cortex in dark baseline condition and during stimulation with white, blue and yellow lights through the right eye but not the left. In male mice, the SUV was higher in the left visual cortex (1.53 ± 0.08) during Blue stimulation through the right eye compared to the right visual cortex (1.47 ± 0.10, p<0.05) (Fig. left) while the SUV did not differ during Blue stimulation through the left eye. Conversely, in female mice, the SUV was higher in the right visual cortex (1.34 ± 0.08) during Blue stimulation through the left eye compared to the left visual cortex (1.30 ± 0.11, p<0.01) (Fig. right) while there was no change during stimulation with Blue through the right eye. Yellow stimulation through the right eye revealed hemispheric differences only in female mice, while Yellow stimulation through the left eye revealed hemispheric differences only in male mice.
CONCLUSION: The experimental setup using FDG-PET combined with anatomical MR is suitable to study color processing in mice. As previously has been shown for human in a functional transcranial Doppler study (Njemanze 2011) gender differences in the perception of blue and yellow colors appear to exist also in rodents. In both species Blue provided the highest stimulation. In opposite to human the visual cortex in male mice revealed higher metabolism than in female.
REFERENCE
Njemanze PC. Gender-related differences in physiologic color space: a functional transcranial Doppler (fTCD) study. Exp. Transl Stroke Med. 2011; 3: 1.

  • Poster
    NMR 2016 - 11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.07.2016, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-23322
Publ.-Id: 23322


Animal PET/MR with the new radioligand [18F]AQ28A demonstrates the involvement of phosphodiesterase 10A in the regulation of energy homeostasis

Kranz, M.; Hankir, M. K.; Deuther-Conrad, W.; Wagner, S.; Teodoro, R.; Fischer, S.; Wenzel, B.; Fenske, W. K.; Brust, P.

OBJECTIVES: Cyclic nucleotide phosphodiesterases (PDEs) are enzymes that cleave the phosphodiester bond in the second messenger molecules cAMP and cGMP. PDE10A is dual-specific and mainly expressed in the striatum, a brain region which coordinates a great variety of cognitive functions, including motor and action planning, decision-making, motivation, reinforcement, and reward perception. Knock-out mice provided evidence for involvement of PDE10A in the regulation of energy balance as shown by their resistance to diet induced obesity (DIO). Therefore, we have used the novel selective radioligand [18F]AQ28A [1] to investigate the expression of PDE10A in the striatum and brown adipose tissue (BAT) of lean, diet-induced (DIO) and leptin-deficient genetically obese mice. As BAT activation could previously be visualized by using [18F]FDG [2], we also assessed whether inhibition of PDE10A modulates BAT activity.
METHODS: Isoflurane-anaesthetized female mice were injected with either [18F]AQ28A (11±3 MBq) or [18F]FDG (14±2 MBq) and subjected to 1 h PET/MR (Mediso nanoScan®). After co-registration of the dual modality image data volumes of interest (striatum, hypothalamus, interscapular BAT and muscle) were drawn manually with reference to the structural MRI data using ROVER software (ABX, Radeberg).The selectivity of [18F]AQ28A towards PDE10A was investigated by baseline (n=3) and blocking (n=3) experiments with the PDE10A inhibitor MP-10 (5 mg/kg). Another set of animals was provided over 16 weeks either with standard food (lean, n=5) or high-fat high-sugar diet (DIO, n=5) and received [18F]AQ28A PET/MR thereafter. A further group of lean mice (n=10), which was overnight fasted and housed under thermoneutral conditions, received either i.p. injection of MP-10 (n=5) or vehicle (n=5) followed 30 min later by 1 h [18F]FDG PET/MR. Thereafter the mice were sacrificed and striatum, hypothalamus and BAT were collected. Relative mRNA expressions of PDE10A, thermoregulatory genes and the indirect neuronal activity marker Fos were analyzed by real-time qPCR.
RESULTS: PDE10A selectivity of [18F]AQ28A was proven by blocking with MP-10 (SUV15min striatum baseline/blocking: 1.02±0.19/0.54±0.08; p<0.01). A 7-fold higher mRNA expression of PDE10A in striatum compared to hypothalamus was found (p<0.001). Acute pharmacological inhibition of PDE10A altered cAMP levels (p<0.01) and thermoregulatory gene and Fos expression in striatum (p<0.05), but not in hypothalamus. DIO resulted in ~60% and 80% higher PDE10A expression (p<0.05) in striatum and BAT, respectively, accompanied by an increased SUV of [18F]AQ28A in both targets (p<0.05). Acute administration of MP-10 to lean mice resulted in significantly higher FDG uptake by BAT (SUV55min: 0.40±0.01) compared to vehicle administration (SUV55min: 0.25±0.02; p<0.01).
CONCLUSION: Distinct alterations of gene expression together with significant changes of PDE10A availability and glucose metabolism in BAT after PDE10A inhibition reveal a novel thermoregulatory role for PDE10A. The data suggest that PDE10A inhibitors offer the potential to treat obesity by increasing thermogenesis and reducing hedonic feeding through recruiting striatal and BAT circuits.
[1]Wagner, S., et al. Eur J Med Chem 2016 107;97.
[2]Gnad, T.;…;Kranz, M.;…Pfeifer, A. Nature. 2014 18;516

  • Poster
    NMR 2016 - 11th International Symposium on Functional NeuroReceptor Mapping of the Living Brain, 13.-16.09.2016, Boston, USA

Permalink: https://www.hzdr.de/publications/Publ-23321
Publ.-Id: 23321


First-order magnetization process as a tool of magnetic-anisotropy determination: Application to the uranium-based intermetallic U3Cu4Ge4

Gorbunov, D. I.; Henriques, M. S.; Andreev, A. V.; Skourski, Y.; Richter, M.; Havela, L.; Wosnitza, J.

Uranium-based intermetallic compounds often display very strong magnetic anisotropies, the energy of which is usually not directly accessible by common experimental methods. Here, we report on static- and pulsed-field studies of U3Cu4Ge4. This material orders ferromagnetically at TC = 73 K with the easy magnetization direction along the a axis and a strong bc-plane anisotropy. The magnetization measured for fields along the hard b direction displays a first-order magnetization process that can be described well by use of a phenomenological theory yielding anisotropy constants up to the sixth order. This phenomenological description,working excellently for U3Cu4Ge4, may also be applied for other uranium-based compounds.

Permalink: https://www.hzdr.de/publications/Publ-23320
Publ.-Id: 23320


LiF – a spectroscopic method for rare earth elements identification

Fuchs, M.; Gloaguen, R.; Beyer, J.; Jakob, S.; Heitmann, J.

Laser-induced fluorescence (LiF) has a great potential for the exploration and identification of rare earth elements (REE) in natural environments. This spectroscopic technique can provide an efficient way to secure resource availability, while the economic and ecological costs are reduced. No time-consuming sample preparation and analysis is needed prior to decisions along the raw material processing chain. Such non-destructive approaches allow for a fast access to analytical results and hence, are the basis for an immediate adjustment of processing steps.
The method uses the material-specific luminescence emissions that are induced by laser-stimulation of a certain wavelength. The distinct emission lines of REE make them well suited for the development of a LiF-based exploration technique. However, typical REE emission peaks known from the free elements may shift or be masked in natural materials due to their position in the crystal lattice, varying compositions of minerals or other natural conditions such as water content. The natural variability therefore, demands for comprehensive investigations of REE and their spectral characteristics in minerals.
To identify those spectral information that are robust and unequivocal, we analyse spectra of REE standards measured in different matrix minerals including phosphates and fluorides. We use variable laser wavelengths from UV (325 nm) to green (532 nm) and a detection range from 340 nm to 1080 nm. Results show spectral characteristics that sort REE in three groups due to: no distinct emission lines, absorption features, distinct luminescence emission lines. Measured in different matrix minerals, we determine shifts for some of the spectral features and some disappear or decline in intensity. Changing the wavelength of the laser allows for a more selective stimulation of REE emissions, especially wavelengths longer than UV can reduce the unspecific emission of all luminescent components of a sample and thus enhance individual spectral information. To test the applicability of LiF, we additionally investigated natural rocks with a well-characterized REE content. First results show that LiF is able to reproduce spectral characteristics of REE in natural rocks.

Keywords: Luminescence; REE; emission spectroscopy

  • Lecture (Conference)
    European Geoscience Union, 17.-22.04.2016, Vienna, Austria

Permalink: https://www.hzdr.de/publications/Publ-23319
Publ.-Id: 23319


LiF - A non-destructive method for raw material identification

Fuchs, M.; Gloaguen, R.; Beyer, J.; Jakob, S.; Heitmann, J.

Laser-induced fluorescence (LiF) provides a spectroscopic technique for identification of rare earth elements (REE) that may be applied to natural environments. The method uses the material-specific luminescence emissions that are induced by laser-stimulation of a certain wavelength. The distinct emission lines of REE make them well suited for the development of a LiF-based exploration technique. However, the natural variability demands for comprehensive investigations of the spectral characteristics of REE and effects from matrix minerals.
To identify those spectral information that are robust and unequivocal, we analyse spectra of REE standards measured in different matrix minerals including phosphates and fluorides. We use variable laser wavelengths from UV (325 nm) and a detection range from 340 nm to 1080 nm. First results show spectral characteristics that sort REE in three groups due to: no distinct emission lines, absorption features, distinct luminescence emission lines. Measured in different matrix minerals, we determine shifts for some of the spectral features and some disappear or decline in intensity. Preliminary tests using wavelengths longer than UV aim at a more selective stimulation of REE emissions and at reducing the unspecific emission of all luminescent components of a sample. Results are promising but highlight that optimized stimulation wavelength may be REE-specific. We additionally investigated natural rocks with a well-characterized REE content. First results show that LiF is able to reproduce spectral characteristics of REE in natural rocks, but also outline the need to reduce matrix mineral emission by selective stimulation and delayed detection windows.

Keywords: Luminescence; REE; emission spectroscopy; raw materials

  • Poster
    German Luminescence and Electron Spin Resonance Dating conference (LED), 06.-08.11.2015, Berlin, Germany

Permalink: https://www.hzdr.de/publications/Publ-23318
Publ.-Id: 23318


The abanico plot: Visualising chronometric data with individual standard errors

Dietze, M.; Kreutzer, S.; Burow, C.; Fuchs, M.; Fischer, M.; Schmidt, C.

Numerical dating methods in Quaternary science are faced with the need to adequately visualise data consisting of estimates that have differing standard errors. Recent approaches either focus on the display of age frequency distributions that ignore the standard errors or on radial plots, that support comparisons between estimates allowing for their differing precisions, but without giving an explicit picture of the age frequency distribution. Hence, visualising both aspects requires at least two plots. Here, an alternative is introduced: The abanico plot. It combines both aspects and therefore allows comprehensive presentation of chronometric data with individual standard errors. It extends the radial plot by a kernel density estimate plot, histogram or dot plot and contains elements that link both plot types. As part of the R package 'Luminescence' (version >0.4.5), the abanico plot is designed as the final part of a comprehensive analysis chain of luminescence data but is open to a wide range of other Quaternary dating communities, as illustrated by several examples.

Keywords: Luminescence dating; Fission track; Cosmogenic nuclides; Radial plot; KDE; R

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Permalink: https://www.hzdr.de/publications/Publ-23317
Publ.-Id: 23317


Relaxation dynamics in photoexcited semiconductor quantum wells studied by time-resolved photoluminiscence

Zybell, S.

Gegenstand der vorliegenden Arbeit ist die Untersuchung der Photolumineszenzdynamik von Halbleiter-Quantentöpfen (Quantum Wells), die durch Anregung von Intraband-Übergängen mittels resonanter Laserpulse im mittleren Infrarot- und Terahertz-Spektralbereich verändert wird. Diese Zweifarbenexperimente wurden mit Hilfe eines optischen Aufbaus für zeitaufgelöste Photolumineszenzspektroskopie am Großgerät Freie-Elektronen Laser FELBE am Helmholtz-Zentrum Dresden-Rossendorf realisiert. Zeitlich verzögert zur gepulsten optischen Anregung über die Bandlücke wurden Intersubband- oder Intraexziton-Übergange in den Quantum Wells resonant angeregt. Die dadurch erreichte Ladungsträgerumverteilung zeigt sich in einer deutlichen Verringerung der Photolumineszenzintensität zum Zeitpunkt des zweiten Anregepulses, die im Folgenden als Photolumineszenz-Quenching bezeichnet wird.
Zunächst wird die Stärke des Photolumineszenz-Quenchings in Abhängigkeit der Polarisationsrichtung des midinfraroten Laserstrahls ausgewertet. Während die Absorption durch freie Ladungsträger für beide Polarisationsrichtungen nachweisbar ist, wird experimentell gezeigt, dass Intersubbandabsorption nur möglich ist, wenn ein Anteil der anregenden Strahlung senkrecht zur Quantum-Well-Ebene polarisiert ist.
Das Photolumineszenzsignal ist überwiegend an der energetischen Position der 1s-Exzitonresonanz unterhalb der Bandkante messbar. Die intraexzitonischen Übergangsenergien in Quantum Wells liegen typischerweise im Terahertzbereich. Unter intraexzitonischer 1s-2p Anregung erscheint auch auf dieser Energieskala ein abrupter Intensitätsverlust in der langsam abklingenden Photolumineszenztransiente. Erstmalig wurde im Photolumineszenzspektrum bei höheren Energien im Abstand der Terahertz-Photonenenergie ein zusätzliches 2s-Photolumineszenzsignal detektiert. Eine detaillierte theoretische Beschreibung dieses Problems durch unsere Kooperationspartner Koch et al. von der Phillips-Universität Marburg zeigt, dass unter intraexzitonischer 1s-2p Anregung eine effiziente Coulombstreuung zwischen den nahezu entarteten exzitonischen 2p- und 2s-Zustanden stattfindet. Während der 2p-Zustand optisch dunkel ist, kann die 2s-Population strahlend rekombinieren, was zu dem besagten 2s-Photolumineszenzsignal führt. Die Zeitkonstanten der untersuchten Ladungsträgerdynamik werden durch ein phänomenologisches Modell bestimmt, das die experimentellen Kurven sehr gut abbildet. Es wird ein Ratengleichungsmodell eingeführt, bei dem die involvierten Zustände auf optisch helle und optisch dunkle Besetzungsdichten reduziert werden.
Darüber hinaus werden mit einem modifizierten Versuchsaufbau die Terahertz-induzierten Photolumineszenzsignaturen von Magnetoexzitonen untersucht. Die Stärke des 1s-Photolumineszenz-Quenchings ändert sich dabei entsprechend der magnetoexzitonischen Übergänge, die im betrachteten Feldstärkebereich zwischen 0T und 7T liegen. Für Magnetfelder größer als 3T sind keine 2s-Photolumineszenzsignale mehr messbar, da durch das externe magnetische Feld die Entartung der 2p- und 2s-Zustände aufgehoben wird.

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-064 2015
    ISSN: 2191-8708, eISSN: 2191-8716

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Permalink: https://www.hzdr.de/publications/Publ-23316
Publ.-Id: 23316


Characterization of three different unusual S-layer proteins from Viridibacillus arvi JG-B58 that exhibits two super-imposed S-layer proteins

Suhr, M.; Lederer, F. L.; Guenther, T. J.; Raff, J.; Pollmann, K.

Viridibacillus arvi JG-B58 that was previously isolated from heavy metal contaminated environment expresses three different surface layer (S-layer) proteins namely Slp1, Slp2, and Slp3. Two of the V. arvi JG-B58 S-layer proteins were visualized on the surface of living cells via atomic force microscopy (AFM). These S-layer proteins form a double layer with p4 symmetry. All examined S-layer proteins lack some typical S-layer protein features. They possess no SLH domains that are usually responsible for the anchoring of the proteins to the cell wall. Further, the pI values are relatively high ranging from 7.84 to 9.25 for the matured proteins. These features are typical for S-layer proteins of Lactobacillus although sequence comparisons indicate a close relationship to S-layer proteins of Lysinibacillus and Bacillus strains. The three S-layer proteins were isolated from the cells using two different strategies. Purified S-layer proteins were recrystallized on SiO2 substrates in order to study the structure of the arrays and self-assembling properties. There are only a few studies reporting the concomitant existence of two different S-layer proteins on cell surfaces. Together with the genomic data, this is the first description of a novel type of S-layer proteins showing features of Lactobacillus as well as of Bacillus-S-layer proteins and the first study of the cell envelope of Viridibacillus arvi.

Keywords: Viridibacillus arvi; S-layer; S-layer protein; S-layer gene; Atomic force microscopy; double layer

Permalink: https://www.hzdr.de/publications/Publ-23313
Publ.-Id: 23313


Detecting and quantifying the Kelvin-Helmholtz instability in interstellar jets by radiation observable on Earth

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

We present particle-in-cell simulations of the relativistic Kelvin-Helmholtz instability (KHI) at unprecedented spatial resolution and size and including, for the first time, complete far field radiation spectra. Based on these simulations we demonstrate that the emitted polarized radiation observable on Earth can be used to identify and characterize the microscopic plasma dynamics of a KHI light-years away.
The KHI is expected in shear flow regions of astrophysical plasma jets, which are significant sites for particle acceleration and radiation.
We have simulated the radiation of the KHI using the particle-in-cell code PIConGPU. Its synthetic in situ radiation diagnostic is capable of calculating the angularly and spectrally radiation of billions of electrons simulated, thereby allowing quantitative predictions for both the coherent and incoherent part of the radiation. The calculations are based on Liénard-Wiechert potentials and were performed for 481 observation directions on a half dome covering frequencies over 3 orders of magnitude. Compared to any previous KHI simulation, we increased the spatial resolution by more than a factor 4 and covered a 46 times larger volume. The simulations were conducted on 18,000 GPUs of the TITAN cluster at Oak Ridge National Laboratory reaching a peak performance of 7.2 Peta FLOPs.
The simulated spectra show that the time-dependent changes in the radiation polarization and power correlate directly with the stages of the KHI, thus allowing to identify the linear growth phase of the KHI and quantifying its characteristic growth rate. In order to support these findings we introduce an analytic kinetic model that is capable of reproducing both polarization and power characteristics. We will discuss both model and simulation in detail. We also focus on the temporal evolution of the plasma dynamic and radiation signature to show why the polarization is a clear signature for the presence of the KHI.
The findings presented are a vital step towards a better understanding of astro-physical jets since observed radiation growth rates can now be linked to kinetic KHI models allowing to constrain jet properties such as jet-to-ambient density contrast and velocity gradients.

Keywords: Kelvin-Helmholtz instability; KHI; radiation; polarization; PIConGPU; spectra; shear flow; particle-in-cell; TITAN; GPU; growth rate; astro physics; plasma physics

  • Lecture (Conference)
    HEDLA 2016, 11th International Conference on High Energy Density Laboratory Astrophysics, 16.-20.05.2016, Standford, California, USA

Permalink: https://www.hzdr.de/publications/Publ-23312
Publ.-Id: 23312


Enhancement of single bullet mode stability in nanowire spin-Hall oscillator with spatially nonuniform current bias

Verba, R. V.; Yang, L.; Tyberkevych, V.; Schneider, T.; Smith, A.; Duan, Z.; Lindner, J.; Slavin, A. N.; Krivorotov, I. N.

Spin torque oscillators (STO) are compact tunable sources of microwave radiation that serve as a test bed for the studies of nonlinear magnetization dynamics at the nanoscale. It has been shown that spin-Hall torque in ferromagnetic - heavy metal bilayers can provide spin torque necessary for the STO operation. However, multimode generation and low spectral purity of the microwave signals generated in spin-Hall oscillators (SHOs) hinders practical applications of these nanoscale devices.
Here we experimentally demonstrate that tapering of a Pt/Ni80Fe20 nanowire that serves as the SHO active region, results in a sizable extension of the bias current range of single-mode generation (Fig.1) and in the significant decrease of the spectral linewidth of the generated signal.
The observed features are explained in the framework of Ginzburg-Landau auto-oscillator model. The model reveals that in both straight and tapered nanowires the spin torque excites a self-localized spin wave bullet mode, which, owing to the increased role of magnetodipolar interaction, has a micrometer size. The key factor leading to the improvement of the generation characteristics in a tapered nanowire SHO is shown to be a nonuniformity of the bias current density. In particular, this nonuniformity leads to a current-induced displacement of the bullet mode from the nanowire center, which results in the extension of the region of stability of the single-mode generation regime. Also, the nonuniform current density provides a restoring force that reduces the amplitude of thermal fluctuations in the position of the bullet mode along the nanowire, and, thereby, decreases the SHO phase noise. Finally, the current-induced spatial separation of two bullets in 2-mode generation regime results in different nonlinear shifts of the bullets frequency, which leads to a larger intermode frequency separation, in accordance with experiment (Fig.1).

  • Lecture (Conference)
    MMM | Intermag 2016, 11.-15.01.2016, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-23311
Publ.-Id: 23311


Nanowire spin Hall oscillators: nanowire width dependence

Smith, A.; Schneider, T.; Yang, L.; Krivorotov, I. N.

We present experimental studies of auto-oscillatory magnetization dynamics in nanowire spin Hall oscillators (SHOs) as a function of the nanowire width. The oscillators schematically shown in Fig. 1 consist of a long Pt(7 nm)/Py(5 nm)/AlOx (2 nm) nanowire on a sapphire substrate with two Cr/Au leads attached to the wire [1]. The 2 μm gap between the leads defines the active region of the oscillator. A 750 Oe saturating magnetic field is applied in the plane of the sample at 85 deg with respect to the nanowire axis, and direct current generating anti-damping spin torque is applied between the leads. Figure 2 shows microwave emission spectra for four oscillator devices with the active region width ranging from 0.17 μm to 1.07 μm. All devices show onset of auto-oscillations at similar critical current densities. For the 0.17 μm wide nanowire SHO, auto-oscillatory modes arising from the bulk and edge eigenmodes of the nanowire are clearly seen in the emission spectra. For SHO devices based on wider wires, the bulk auto-oscillatory modes dominate the emission spectrum due to the larger wire volume occupied by the bulk modes. The maximum integrated power generated is similar for all four SHO devices (~ 10^-10 W). Our work demonstrates robust operation of nanowire-based SHOs over a wide range of nanowire widths and presents an example of a spin torque oscillator with the active area extended into the um^2 domain.

  • Lecture (Conference)
    MMM | Intermag 2016, 11.-15.01.2016, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-23310
Publ.-Id: 23310


Spin Current Control of Damping in YIG/Pt Nanowires

Safranski, C. J.; Barsukov, I.; Lee, H.; Schneider, T.; Jara, A. A.; Smith, A.; Chang, H.; Wu, M.; Krivorotov, I. N.

Insulating ferromagnet(IF)/normal metal(NM) interfaces are important for understanding of pure spin current injection and have great potential for spintronic applications. Here we report studies of the effect of pure spin currents on damping of spin wave eigenmodes in YIG(30 nm)/Pt(6 nm) bilayer nanowires that are 60–250 nm wide and 1–13 um long. The samples show magneto-resistance (MR) arising from two distinct mechanisms: (i) spin Hall magnetoresistance (SMR) and (ii) inverse spin Hall effect (iSHE) in conjunction with spin Seebeck current (SSC) induced by Ohmic heating of the Pt layer. Utilizing the SMR and iSHE effects, we measure the properties of spin wave eigenmodes of the nanowires by spin-torque ferromagnetic resonance (ST-FMR) with magnetic field modulation.
Application of direct current to the Pt layer results in injection of spin Hall current into YIG that acts as either damping or anti-damping spin torque depending on the current polarity. In addition, Ohmic heating in Pt gives rise to a SSC injected into YIG, which acts as anti-damping torque independent of the current polarity. ST-FMR measurements reveal current-induced variation of the linewidth of spin wave modes that is asymmetric in the bias current as shown in Fig. 1. The linewidth decreases to zero for the current polarity that gives rise to anti-damping spin Hall torque. Near this current value, we observe complex interaction among the spin wave eigenmodes of the nanowire that we asses using micromagnetic simulations. Our results advance understanding of magnetization dynamics driven by pure spin currents in nanoscale IF/NM systems.

  • Lecture (Conference)
    MMM | Intermag 2016, 11.-15.01.2016, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-23309
Publ.-Id: 23309


Controlled electron bunch generation in the few-cycle ultra-intense laser-solid interaction scenario

Kluge, T.; Bussmann, M.; Cowan, T. E.; Schramm, U.

The generation of Maxwellian or exponentially decaying spectra in the interaction of ultra-intense ultra-short laser pulses with solid foils is very general observation both in experiments and simulations. Yet, the physical origin of this observation is not well understood. For a very idealized situation of plane wave, plane and cold target interaction, we show that both randomization between individual electron bunches accelerated by the laser through the plasma as well as randomization during a single bunch are not observable in particle-in-cell simulations. Hence they are not accountable for the apparent thermalization (exponential spectrum).

  • Contribution to proceedings
    European Advanced Accelerator Concepts Workshop, 13.09.2015, La Biodola, Isola d'Elba, Italien
    Nuclear Instruments & Methods in Physics Research Section A 829(2016)376-377
    DOI: 10.1016/j.nima.2016.02.041

Permalink: https://www.hzdr.de/publications/Publ-23308
Publ.-Id: 23308


Euler-Euler Simulation of Mass-transfer in Bubbly Flows

Rzehak, R.; Krepper, E.

For practical applications the Euler-Euler two-fluid model relies on suitable closure relations describing interfacial exchange processes. Concerning pure fluid dynamics of dispersed gas-liquid multiphase flow, an ongoing effort has led to a validated set of closures that is applicable under a rather broad range of conditions. Similar results for the technologically even more important field of mass transfer remain to be achieved. Progress so far has been hampered by a lack of local data including measurements of concentration which are suitable for CFD model validation. In addition, correlations proposed to describe the mass transfer coefficient differ widely. Here, a preliminary study of axial concentration profiles in a bubble column is given based on the available experimental data found in the literature. For this purpose simplified assumption of a constant mass transfer coefficient throughout the column is made and experimentally determined values are used. New measurements will be needed to come to a final conclusion.

Keywords: mass-transfer; dispersed gas liquid multiphase flow; Euler Euler two fluid model; closure relations; CFD simulation; model validation

Permalink: https://www.hzdr.de/publications/Publ-23307
Publ.-Id: 23307


Prompt gamma rays detected with a BGO block Compton camera reveal range deviations of therapeutic proton beams

Hueso-González, F.; Pausch, G.; Petzoldt, J.; Römer, K. E.; Enghardt, W.

The dose deposition profile of protons is interesting for tumour treatment due to the increased ionization density at the end of their track. However, the inaccurate knowledge of the proton stopping point limits the precision of the therapy. Prompt gamma rays, a by-product of the irradiation, are candidates for an indirect measurement of the particle range. Compton cameras have been proposed for prompt gamma ray imaging, but struggle with high trigger rates and low coincident efficiency. The feasibility in a clinical environment has yet to be proved. At Universitäts Protonen Therapie Dresden, two bismuth germanate (BGO) block detectors arranged face-to-face are deployed for imaging tests with a homogeneous target irradiated by a proton pencil beam. Shifts of the target, increase of its thickness and beam energy variation experiments are conducted. Each measurement lasts about 15 minutes at a low proton beam current. The effect of one centimetre proton range deviations on the backprojected images is analysed. The number of valid Compton events as well as the trigger rate expected in a realistic treatment plan with pencil beam scanning are estimated. The results support the use of a high density material despite its moderate energy resolution, in order to maximize the coincident efficiency. Nevertheless, they discourage the applicability of a two-plane Compton camera in a clinical scenario with usual beam currents.

Keywords: proton therapy; range verification; prompt gamma ray imaging; Compton camera; BGO block detector

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-23306
Publ.-Id: 23306


Correlation of standard uptake value (SUV) and tumor to blood standard uptake ratio (SUR) with the metabolic uptake rate derived from quantitative dual time point measurements.

Hofheinz, F.; van den Hoff, J.; Lougovski, A.; Ego, K.; Amthauer, H.; Apostolova, I.

Aim:

The standard uptake value (SUV) is widely used for quantitative assessment of tumor metabolism in FDG-PET. However, the SUV approach has well known limitations. Recently, we have shown that SUR overcomes most of these limitations [1,2]. Excellent linear correlation of SUR and Km from Patlak analysis was found using dynamic imaging of liver metastases. However, due to the perfectly standardized uptake period used for SUR determination and the comparatively short uptake period these results are not directly applicable to clinical whole body examinations, in which the uptake periods often vary considerably. Therefore, the aim of this work was to investigate the correlation of SUR and Km in clinical whole body scans, where Km was approximated by Ks derived from dual time point (DTP) measurements [3].

Methods:

DTP FDG-PET/CT was performed in 89 consecutive patients with histologically proven NSCLC. In the PET images the primary tumor was delineated with an adaptive threshold method. For determination of the blood SUV the aorta was delineated manually in the attenuation CT. SUR values were computed as ratio of tumor SUV and blood SUV. SUR values were scan-time-corrected to 60 min p.i. as described in [2]. Metabolic uptake rate Ks was computed similar to the procedure in [3]. The correlation of SUV and SUR with Ks was investigated. The prognostic value of SUV, SUR and Ks for and overall survival (OS) progression free survival (PFS) was investigated with univariate Cox regression in a homogeneous subgroup (N=31).

Results:

There was highly significant correlation of SUR and Ks (R2=0.93). However, the correlation coefficient appeared somewhat lower than previous results obtained from dynamic imaging and standardized uptake times (R2=0.96 [1]). As expected, SUV showed markedly lower correlation with Ks than SUR (R2=0.68). In the survival analysis none of the investigated parameters were prognostic for OS. Univariate Cox regression revealed SUR and Ks as prognostic factors for PFS.

Conclusion:

Our results show that in clinical whole body PET the correlation of uptake values with the metabolic trapping rate can be improved notably by blood normalization and scan-time-correction. Furthermore, the high correlation of SUR with Ks indicates that for histologically unambigous tumor lesions DTP does not provide added value in comparison to SUR.

Literature:

[1] EJNMMI Res 2013,3:77
[2] EJNMMI Res 2014,4:18
[3] EJNMMI Res 2012,3:16

Keywords: none

  • Lecture (Conference)
    54. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 20.-23.04.2016, Dresden, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23305
Publ.-Id: 23305


Magnetic stirring and sonication of liquid metals

Gerbeth, G.

  • Invited lecture (Conferences)
    International Workshop MHD-Days 2015, 07.-09.12.2015, Ilmenau, Germany

Permalink: https://www.hzdr.de/publications/Publ-23303
Publ.-Id: 23303


Thermohydraulic safety issues for liquid metal cooled systems

Gerbeth, G.; Eckert, S.; Stefani, F.

A review is given on recent developments for liquid metal measurement techniques and their application in liquid metal cooled systems.

  • Invited lecture (Conferences)
    1st Sino-German Symposium on Fundamentals of Advanced Nuclear Safety Technology, 08.-12.03.2015, Shanghai, China
  • Kerntechnik 81(2016), 188-191

Permalink: https://www.hzdr.de/publications/Publ-23302
Publ.-Id: 23302


Spin Wave Emission From Topological Spin Textures

Wintz, S.; Sluka, V.; Weigand, M.; Kakay, A.; Schultheiss, K.; Erbe, A.; Tyberkevych, V.; Slavin, A.; Deac, A.; Lindner, J.; Raabe, J.; Fassbender, J.

Today, spin waves are seen as high potential information carrier for next-generation information and communication devices. This is based on the substantially reduced energy dissipation and much smaller wavelengths of spin waves compared to traditional charge current signals. For a device implementation, however, novel concepts for the generation, manipulation, and detection of spin waves are yet to be found. Here, we report on a newly discovered concept for the generation of spin waves, which overcomes typical bandwidth limitations of traditional spin wave excitation methods. Our approach utilizes the gyration of magnetic vortex cores to generate isotropically propagating, non-reciprocal spin waves.

  • Invited lecture (Conferences)
    SPIE Optics and Photonics Conference, Spintronics IX Symposium, 28.08.-01.09.2016, San Diego, USA

Permalink: https://www.hzdr.de/publications/Publ-23301
Publ.-Id: 23301


Aging Universality Classes in Surface Growth Models

Kelling, J.; Ódor, G.; Gemming, S.

Extensive dynamical simluations of a 2 dimensional driven dimer lattice gas are presented, which can be mapped to (2+1) dimensional surface growth in the Kardar-Parisi-Zhang (KPZ) or Edwards-Wilkinson unversality classes. From this autocorrelation and autoresponse functions have been determined for the KPZ universality class and the underlying lattice gas. Studying the effects of different dimer lattice gas dynamics revealed strong differences in the aging behavior of the stochastic cellular automaton (SCA) and the random sequential update models. We show numerical evidence for nontrivial corrections as well as different universal scaling behaviors.

Keywords: Surface Growth; Aging; Kardar-Parisi-Zhang; Monte-Carlo; Cellular Automaton

  • Poster
    DPG-Frühjahrstagung der Sektion Kondensierte Materie, 06.-11.03.2016, Regensburg, Deutschland
  • Poster
    VII GEFENOL Summer School on Statistical Physics of Complex Systems, 19.-30.06.2017, Palma de Mallorca, Spain

Permalink: https://www.hzdr.de/publications/Publ-23300
Publ.-Id: 23300


Non-Local Lattice Encoding for Bit-Vectorized Cellular Automata GPU Implementations

Kelling, J.; Ódor, G.; Gemming, S.

In many areas from physics to economics and social sciences, there are current problems that can be mapped to stochastic cellular automata (SCA). In combination with machine learning techniques, cellular automata with learned rules can be used to efficiently predict real world systems. In physics, they are used to study atomistically the size and shape evolution of micro- and nanostructures, providing insights into processes of self-organization crucial to today's nanotechnology. We present an extremely efficient SCA implementation of a surface growth model using bit-vectorization enhanced by non-local encoding on GPU. The employed technique and non-local encoding can be transfered to other applications.

Keywords: GPGPU; Surface Growth; Kardar-Parisi-Zhang; Monte-Carlo; Cellular Automaton

Permalink: https://www.hzdr.de/publications/Publ-23299
Publ.-Id: 23299


Aging in the (2+1)-Dimensional Kardar-Parisi-Zhang Model under Various Dimer Lattice-Gas Dynamics

Kelling, J.; Ódor, G.; Gemming, S.

Extensive dynamical simluations of a 2 dimensional driven dimer lattice gas are presented, which can be mapped to (2+1) dimensional surface growth in the Kardar-Parisi-Zhang (KPZ) or Edwards-Wilkinson unversality classes. From this autocorrelation and autoresponse functions have been determined for the KPZ universality class and the underlying lattice gas. Studying the effects of different dimer lattice gas dynamics revealed strong differences in the aging behavior of the stochastic cellular automaton (SCA) and the random sequential update models. We show numerical evidence for nontrivial corrections as well as different universal scaling behaviors.

Keywords: Surface Growth; Aging; Kardar-Parisi-Zhang; Monte-Carlo; Cellular Automaton

  • Poster
    Conference of the Middle European Cooperation in Statistical Physics, 14.-17.02.2016, Wien, Österreich

Permalink: https://www.hzdr.de/publications/Publ-23298
Publ.-Id: 23298


Modeling of Mass-transfer in Bubbly Flows Encompassing Different Mechanisms

Rzehak, R.

Models proposed to describe the liquid side mass transfer coefficient in absorption prosesses differ widely in such basic questions as on which of the local flow variables they are based. Comparison of different alternatives with experimental data taken from the literature suggests that there are two basic mechanisms, a laminar and a turbulent one, each of which dominates under suitable conditions. A dimensionless number that allows to identify the corresponding regimes is suggested together with a preliminary model encompassing both. New experiments will be needed to come to a final conclusion.

Keywords: mass-transfer; penetration model; dispersed gas liquid multiphase flow; Euler Euler two fluid model; closure relations; CFD simulation

Downloads:

Permalink: https://www.hzdr.de/publications/Publ-23297
Publ.-Id: 23297


An investigation of the relation between tumor-to-liver ratio (TLR) and tumor-to-blood standard uptake ratio (SUR) in oncological FDG PET.

Hofheinz, F.; Bütof, R.; Apostolova, I.; Zöphel, K.; Steffen, I. G.; Amthauer, H.; Kotzerke, J.; Baumann, M.; van den Hoff, J.

Background: The standardized uptake value (SUV) is the nearly exclusive means for quantitative evaluation of clinical [18F-]fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) whole body investigations. However, the SUV methodology has well known shortcomings. In this context it has been recognized that at least part of the problems can be eliminated if tumor SUV is normalized to the SUV of a reference region in the liver (tumor-to-liver ratio, TLR). In recent publications we have systematically investigated the tumor-to-blood SUV ratio (SUR) for normalization of tumor SUVs which in our view offers principal advantages in comparison to TLR. The aim of this study was a comprehensive comparison of TLR and SUR in terms of quantification of tumor lesions.

Methods: 18F-FDG PET/CT was performed in 424 patients (557 scans) with different tumor entities prior to radio(chemo)therapy. In the PET images SUVmax of the primary tumor was determined. SUVliver was calculated in the inferior right lobe of the liver. SUVblood was determined by manually delineating the aorta in the low dose CT. TLR and SUR were computed and scan time corrected to 60min p.i. (TLRtc and SURtc ). Correlation analysis was performed for SUVliver vs. SUVblood , TLR vs. SUR, SUVliver /SUVblood vs. SUVblood , SURtc /TLR vs. SURtc , and SURtc /TLRtc vs. SURtc . Variability of the respective ratios was assessed via histogram analysis. The prognostic value of TLR and TLRtc for distant metastases-free survival (DM) was investigated with univariate Cox regression in a homogeneous subgroup (N=130) and compared to previously published results for SUV and SURtc .

Results: Correlation analysis revealed a linear correlation of SUVliver vs. SUVblood (R2 =0.83) and of TLR vs. SURtc (R2 =0.92). The SUVliver /SUVblood ratio (mean ± s.d.) was 1.47±0.18. For the SURtc /TLR ratio we obtained 1.14±0.21 and for the SURtc /TLRtc ratio 1.38±0.17. Survival analysis revealed TLR and TLRtc as significant prognostic factors for DM (hazard ratio (HR)=3.3 and HR=3, respectively). Both hazard ratios are lower than that of SURtc (HR=4.1) although this reduction does not reach statistical significance for the given limited group size. HRs of TLR and SURtc are both significantly higher than HR of SUV (HR=2.2).

Conclusion: Suitability of the liver as surrogate of arterial tracer supply for SUV normalization via TLR computation is limited. Further studies in sufficiently large patient groups are required to better characterize the relative performance of SUV, TLR, and SUR in different settings.

Keywords: PET; FDG; tumor to blood ratio; SUR; tumor to liver ratio; TLR

Permalink: https://www.hzdr.de/publications/Publ-23296
Publ.-Id: 23296


Nanopartikel in hoch komplexen Medien - Radiomarkierung als leistungsfähige Methode für die sensitive Detektion im (umwelt)relevanten Konzentrationsbereich

Hildebrand, H.

In dem Vortrag wird die Radiomarkierung von Nanopartikeln als leistungsfähige Methode für die Detektion von Nanopartikeln in wässrigen Systemen vorgestellt. Die Veranstaltungsreihe "nANO meets water VII" des Fraunhofer UMSICHT dient dem Dialog von Fachleuten aus Industrie und Wissenschaft.

Keywords: Nanopartikel; Radiomarkierung; Detektion; Wasser

  • Invited lecture (Conferences)
    nANO meets water VII, Nanotechnik für die Wasserpraxis - Fachleute aus Industrie und Wissenschaft im Dialog, 18.02.2016, Oberhausen, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23295
Publ.-Id: 23295


Wertorientierung im Technologiemanagement von Krankenhäusern

Gurtner, S.; Gurtner, K.

Neue innovative Technologien bieten zahlreiche Möglichkeiten, die Qualität der Behandlung von Patienten und den Behandlungserfolg zu steigern [1]. Neue technologiebasierte Diagnosemethoden, wie z. B. die Computertomografie oder die Magnet-Resonanz-Tomografie ebneten den Weg zur frühzeitigen Erkennung kritischer Erkrankungen wie Krebs oder Durchblutungsstörungen. Die Einführung neuer Methoden und Technologien für die Behandlung akuter Erkrankungen reduzierte die Mortalität und verbesserte die Lebensqualität zahlloser Patienten [2]. Auf der anderen Seite stiegen die Gesundheitsausgaben im Vergleich zum Bruttosozialprodukt in nahezu allen Industrieländern [3]. Der Grund für diesen unverhältnismäßigen Anstieg liegt in der steigenden Lebenserwartung, einer durch den demografischen Wandel verursachten zunehmenden Anzahl an Patienten, häufiger auftretenden Langzeit- oder chronischen Erkrankungen und einer zunehmenden Spezialisierung der Medizin [4]. Als einer der bedeutendsten Treiber von steigenden Gesundheitsausgaben wird häufig die Entwicklung und Implementierung von innovativen Medizintechnologien genannt [5, 6, 7]. Als Resultat der Einführung neuer Technologien kann eine stetige Steigerung des Angebotes medizinischer Dienstleistungen beobachtet werden, was insbesondere bei Krankenhäusern Auswirkungen auf das erforderliche Budget hat. Krankenhäuser als wichtiger Bestandteil des Gesundheitssystems müssen sich dabei einer Reihe strategischer Herausforderungen stellen. Wie jedes andere Unternehmen müssen sie qualitativ hochwertige Dienstleistungen anbieten und gleichzeitig auf ihre Kosten achten. Die Adoption neuer Technologien ist notwendig, um mit anderen Krankenhäusern und Gesundheitsversorgern zu konkurrieren, gleichzeitig müssen sie aber auch mit schrumpfenden Investitions-Budgets und steigenden Kosten umgehen [8].
Im Verlauf dieses Beitrages werden zwei Konzepte näher beleuchtet, die helfen können, mit diesem Dilemma umzugehen. Zum einen wird ein Modell des Technologiemanagementprozesses im Krankenhaus vorgestellt, welcher hilft, strukturierte Entscheidungen im Zusammenhang mit der Beschaffung und Bewirtschaftung von Technologien zu treffen. Zum zweiten werden die zentralen Gesichtspunkte der wertorientierten Gesundheitsversorgung vorgestellt und es wird diskutiert, wie diese dazu beitragen können, sowohl die Qualität der Versorgung zu erhöhen als auch Kosten zu senken.
Die Verbindung beider Konzepte beschreibt abschließend, welchen Herausforderungen sich die einzelnen Akteure im Gesundheitswesen stellen müssen.

Keywords: Technologiemanagement; Value Based Healthcare; Gesundheitsversorgung; Krankenhaus

  • mt-medizintechnik 2(2015), 57-60

Permalink: https://www.hzdr.de/publications/Publ-23294
Publ.-Id: 23294


Feasibility Study for Detection of Reactor State Changes during Severe Accidents via External Gamma Radiation Measurements

Konheiser, J.; Rachamin, R.; Brachem, C.; Hampel, U.

The gamma radiation field outside of a nuclear reactor carries information about the coolant inventory and the nuclear fuel distribution inside the reactor pressure vessel. Hence, it may serve as an indicator for changes in the reactor internal structures, e.g. in the course of a severe accident. To study the feasibility of using external gamma radiation measurements for the detection of reactor state changes, three-dimensional Monte-Carlo simulations were performed to evaluate the vertical gamma flux distribution outside of a generic pressurized water reactor pressure vessel. The gamma flux was calculated for a reactor with different decreased coolant levels and different core melt states. The results indicate that the gamma flux is very sensitive to the reactor states. The shape and magnitude of the gamma flux distribution are unequivocally subject to the coolant levels and to the relocation of corium into the reactor lower head. A simple state detection algorithm was tested to infer predefined reactor states. It yielded an accuracy of 0.983(2) using bootstrapped test data.

Keywords: Monte Carlo simulations; reactor pressure vessel; accident; MCNP

Permalink: https://www.hzdr.de/publications/Publ-23293
Publ.-Id: 23293


Optical components in harsh space environment

Pelizzo, M. G.; Corso, A. J.; Zuppella, P.; Böttger, R.; Tessarolo, E.

Space exploration is linked to the development of increasingly innovative instrumentation, able to withstand the operation environment, rich in ion particles and characterized by high temperatures. Future space missions such as JUICE and SOLAR ORBITER will operate in a very harsh and extreme environments. Electron and ions are considered among causes of potential damage of the optical instrumentation and components. Development of hard coatings capable to preserve their optical properties is pivotal. Different coatings materials have been exposed to ions irradiation in particles accelerators. Change in optical performances has been observed in the extreme ultraviolet and visible spectral region and structural properties has been analyzed by different techniques. The knowledge of the damage mechanisms and thresholds allows the selection of more promising candidate materials to realize the optical components for the new frontiers space missions.

Keywords: optical components; harsh space Environment; ion irradiation; ion damage

  • Invited lecture (Conferences)
    SPIE Meeting - Planetary Defense and Space Environment Applications (Conference OP410), 28.08.-01.09.2016, San Diego, United States

Permalink: https://www.hzdr.de/publications/Publ-23292
Publ.-Id: 23292


Elastic and Piezoresistive Properties of Nickel Carbides from First-Principles

Kelling, J.; Zahn, P.; Schuster, J.; Gemming, S.

The nickel-carbon system has received increased attention over the past years due to the relevance of nickel as a catalyst for carbon nanotube and graphene growth, where Nickel carbide intermediates may be involved or carbide interface layers form in the end. Nickel-carbon composite thin films comprising Ni3C are especially interesting in mechanical sensing applications. Due to the meta-stability of nickel carbides, formation conditions and the coupling between mechanical and electrical properties are not yet well understood. Using first-principles electronic structure methods, we calculated the elastic properties of Ni3C, Ni2C and NiC, as well as changes in electronic properties under mechanical strain. We observe that the electronic density of states around the Fermi level does not change under the considered strains of up to 1%, which correspond to stresses up to 3GPa. Relative changes in conductivity of Ni3C range up to maximum values of about 10%.

Keywords: nickel; carbides; thin films; density functional theory; electronic structure; first-principles calculations; transport theory; electrical conductivity; piezoresistivity; Boltzmann theory

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Permalink: https://www.hzdr.de/publications/Publ-23291
Publ.-Id: 23291


Magnetization Dynamics

Montoya, E.; Sebastian, T.; Schultheiss, H.; Heinrich, B.; Camley, R. E.; Celinski, Z.

Magnetization dynamics measured by means of ferromagnetic resonance (FMR) and Brillouin light scattering (BLS)

Keywords: magnetization dynamics; FMR; BLS

  • Book chapter
    Robert E. Camley, Zbigniew Celinski, Robert L. Stamps: Magnetism of Surfaces, Interfaces, and Nanoscale Materials, Netherlands: Elsevier, 2016, 978-0-444-62634-9, 113-168

Permalink: https://www.hzdr.de/publications/Publ-23290
Publ.-Id: 23290


Bubbly flow in an airlift column: a CFD study

Liao, J.; Ziegenhein, T.; Rzehak, R.

BACKGROUND: Multiphase CFD (Computational Fluid Dynamics) simulation is a valuable tool in chemical and bioprocess engineering that is particularly useful to study reactor concepts and their scale-up from laboratory to production scale. Simulations of bubbly flows up to industrial dimensions are feasible within the Eulerian two-fluid framework of interpenetrating continua. However, for practical applications suitable closure models are needed which describe the physics on the scale of individual bubbles or groups thereof. The quest for such models with a broad range of applicability allowing predictive simulations is an ongoing venture.
RESULTS: A set of closure relations for the fluid dynamics of bubbly flow has been collected that represents the best available knowledge and may serve as a baseline for further improvements and extensions. This model has been successfully validated for bubbly flows in pipes and bubble columns. Here it is applied to the case of an internal loop airlift column which is frequently used in biotechnological processes.
CONCLUSION: Within the limitations of the experimental data available for comparison, the closures are found applicable to this case as well. Further development should account for the polydisperse nature of the flow. To this end reliable measurements of bubble size distribution are needed.

Keywords: bio-process engineering; internal loop airlift column; dispersed gas liquid multiphase flow; Euler Euler two fluid model; closure relations; CFD simulation

  • Open Access Logo Journal of Chemical Technology & Biotechnology 91(2016), 2904-2915
    DOI: 10.1002/jctb.4917

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Permalink: https://www.hzdr.de/publications/Publ-23289
Publ.-Id: 23289


Emerging Role of MRI for Radiation Treatment Planning in Lung Cancer

Cobben, D. C. P.; de Boer, H. C. J.; Tijssen, R. H.; Rutten, E. G. G. M.; van Vulpen, M.; Peerlings, J.; Troost, E. G. C.; Hoffmann, A. L.; van Lier, A. L. H. M. W.

Magnetic resonance imaging (MRI) provides excellent soft-tissue contrast and allows for specific scanning sequences to optimize differentiation between various tissue types and properties. Moreover, it offers the potential for real-time motion imaging. This makes magnetic resonance imaging an ideal candidate imaging modality for radiation treatment planning in lung cancer. Although the number of clinical research protocols for the application of magnetic resonance imaging for lung cancer treatment is increasing (www.clinicaltrials.gov) and the magnetic resonance imaging sequences are becoming faster, there are still some technical challenges. This review describes the opportunities and challenges of magnetic resonance imaging for radiation treatment planning in lung cancer.

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Permalink: https://www.hzdr.de/publications/Publ-23287
Publ.-Id: 23287


Magnetic Nanoparticles in tumour xenografts detected and quantified by Micro-Computer Tomography

Bayer, K.; Eckert, H.; Wiekhorst, F.; Trahms, L.; Krause, M.; Odenbach, S.

In this work we focus on the imaging of magnetic nanoparticles in tumor tissue. The spatial distribution of magnetic nanoparticles in tumor tissue is an essential parameter in the evaluation of the efficiency of magnetic drug targeting (MDT). We developed a volume-based imaging method for x-ray-micro tomography calibrated by magnetorelaxometry to determine the concentration of magnetic nanoparticles in a certain tissue. With this technique, the x-ray absorption information contained in a μ-CT image can be directly related to an absolute mass of magnetic nanoparticles in a certain volume element of the tumor. In contrast to other related methods reported in the literature, the procedure described here is capable of a mass resolution of 0.044μgmm−3, making it possible to map the particle distribution in tumors with extremely low magnetic particle content, such as are usually found in mouse experiments on MDT.

Keywords: magnetic drug targeting; magnetorelaxometry; micro-computer tomography; particle-imaging

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Permalink: https://www.hzdr.de/publications/Publ-23286
Publ.-Id: 23286


Magnetic domain walls as reconfigurable spin-wave nanochannels

Wagner, K.; Kakay, A.; Schultheiss, K.; Henschke, A.; Sebastian, T.; Schultheiss, H.

In the research field of magnonics, it is envisaged that spin waves will be used as information carriers, promoting operation based on their wave properties. However, the field still faces major challenges. To become fully competitive, novel schemes for energy-efficient control of spin-wave propagation in two dimensions have to be realized on much smaller length scales than used before. In this Letter, we address these challenges with the experimental realization of a novel approach to guide spin waves in reconfigurable, nano-sized magnonic waveguides. For this purpose, we make use of two inherent characteristics of magnetism: the non-volatility of magnetic remanence states and the nanometre dimensions of domain walls formed within these magnetic configurations. We present the experi- mental observation and micromagnetic simulations of spin- wave propagation inside nano-sized domain walls and realize a first step towards a reconfigurable domain-wall-based magnonic nanocircuitry.

Keywords: magnetism; magnons; spin waves; domain walls; magnonics; spin wave logic; Brillouin light scattering

  • Nature Nanotechnology 11(2016)5, 432-436
    DOI: 10.1038/NNANO.2015.339
  • Invited lecture (Conferences)
    SPIE 9931, Spintronics IX, 29.08.-1.9.2016, San Diego, U.S.A.
  • Invited lecture (Conferences)
    MMM Conference, 31.10.-04.11.2016, New Orleans, U.S.A.
  • Lecture (Conference)
    MML Conference, 20.-24.06.2016, Uppsala, Schweden
  • Contribution to proceedings
    SPIE 9931, Spintronics IX, 29.08.-01.09.2016, San Diego, U.S.A.
    Magnetic domain walls as reconfigurable spin-wave nano-channels
    DOI: 10.1117/12.2237733

Permalink: https://www.hzdr.de/publications/Publ-23285
Publ.-Id: 23285


NTCP reduction for advanced head and neck cancer patients using proton therapy for complete or sequential boost treatment versus photon therapy

Jakobi, A.; Stützer, K.; Bandurska-Luque, A.; Löck, S.; Haase, R.; Wack, L.-J.; Mönnich, D.; Thorwarth, D.; Perez, D.; Lühr, A.; Zips, D.; Krause, M.; Baumann, M.; Perrin, R.; Richter, C.

Background.To determine by treatment plan comparison differences in toxicity risk reduction for patients with head and neck squamous cell carcinoma (HNSCC) from proton therapy either used for complete treatment or sequential boost treatment only.
Materials and methods. For 45 HNSCC patients, intensity-modulated photon (IMXT) and proton (IMPT) treatment plans were created including a dose escalation via simultaneous integrated boost with a one-step adaptation strategy after 25 fractions for sequential boost treatment. Dose accumulation was performed for pure IMXT treatment, pure IMPT treatment and for a mixed modality treatment with IMXT for the elective target followed by a sequential boost with IMPT. Treatment plan evaluation was based on modern normal tissue complication probability (NTCP) models for mucositis, xerostomia, aspiration, dysphagia, larynx edema and trismus. Individual NTCP differences between IMXT and IMPT ( Δ NTCP IMXT-IMPT ) as well as between IMXT and the mixed modality treatment ( Δ NTCP IMXT-Mix ) were calculated.
Results. Target coverage was similar in all three scenarios. NTCP values could be reduced in all patients using IMPT treatment. However, Δ NTCP IMXT-Mix values were a factor 2 – 10 smaller than Δ NTCP IMXT-IMPT . Assuming a threshold of >= 10% NTCP reduction in xerostomia or dysphagia risk as criterion for patient assignment to IMPT, less than 15% of the patients would be selected for a proton boost, while about 50% would be assigned to pure IMPT treatment. For mucositis and trismus, Δ NTCP >= 10% occurred in six and four patients, respectively, with pure IMPT treatment, while no such difference was identifi ed with the proton boost.
Conclusions. The use of IMPT generally reduces the expected toxicity risk while maintaining good tumor coverage in the examined HNSCC patients. A mixed modality treatment using IMPT solely for a sequential boost reduces the risk by 10% only in rare cases. In contrast, pure IMPT treatment may be reasonable for about half of the examined patient cohort considering the toxicities xerostomia and dysphagia, if a feasible strategy for patient anatomy changes is implemented.

Permalink: https://www.hzdr.de/publications/Publ-23284
Publ.-Id: 23284


CD8+ tumour-infiltrating lymphocytes in relation to HPV status and clinical outcome in patients with head and neck cancer after postoperative chemoradiotherapy: A multicenter study of the German cancer consortium radiation oncology group (DKTK-ROG)

Balermpas, P.; Rödel, F.; Rödel, C.; Krause, M.; Linge, A.; Lohaus, F.; Baumann, M.; Tinhofer, I.; Budach, V.; Gkika, E.; Stuschke, M.; Avlar, M.; Grosu, A.-L.; Abdollahi, A.; Debus, J.; Bayer, C.; Stangl, S.; Belka, C.; Pigorsch, S.; Multhoff, G.; Combs, S. E.; Mönnich, D.; Zips, D.; Fokas, E.

We examined the prognostic value of tumour-infiltrating lymphocytes (TILs) in patients with squamous cell carcinoma of the head and neck (SCCHN) after surgery and postoperative cisplatin-based chemoradiotherapy. FFPE-tissue originating from the surgery of 161 patients treated in 8 DKTK partner sites was immunohistochemically stained for CD3 and CD8. Their expression was correlated with clinicopathological characteristics as well as overall survival (OS), local progression-free survival (LPFS) and distant metastases free-survival (DMFS), also in the context of the HPV16-DNA/p16 status. After a median follow-up of 48 months (range: 4100 months), OS at 4 years was 46.5% for the entire cohort. In multivariate analysis, high CD8 expression was confirmed as an independent prognostic parameter for OS (p 5 0.002), LPFS (p 5 0.004) and DMFS (p 5 0.006), while CD3 expression lacked significance. In multivariate analysis HPV16 DNA positivity was associated with improved OS (p 5 0.025) and LPFS (p 5 0.013) and p16-positive patients showed improved DMFS (p 5 0.008). Interestingly, high CD8 expression was a prognostic parameter for the clinical outcome in both HPV16 DNA-positive and HPV16 DNA-negative patients. Similar findings were observed in the multivariate analysis for the combined HPV16 DNA/p16 status. Altogether, CD81 TILs constitute an independent prognostic marker in SCCHN patients treated with adjuvant chemoradiotherapy. These data indicate that CD8-positive TILs have antitumour activity and could be used for treatment stratification. Further validation of the prognostic value of CD81 TILs as a biomarker and its role in the immune response in SCCHN patients after adjuvant chemoradiotherapy is warranted and will be performed in the prospective DKTK-ROG study.
What’s new?
Squamous cell carcinomas of the head and neck (SCCHN) are not a homogenous group of tumors. This means that biomarkers are urgently needed, so that prognosis and treatment can be individualised. In this study, the authors found that patients with higher levels of CD81 tumor-infiltrating lymphocytes (TILs) within their tumors had improved outcomes after treatment. These results suggest that CD8-positive TILs may have antitumor activity, and that their expression may be a useful prognostic biomarker for treatment stratification.

Keywords: CD8; HPV; prognostic; postoperative chemoradiotherapy; SCCHN; DKTK-ROG

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Permalink: https://www.hzdr.de/publications/Publ-23283
Publ.-Id: 23283


Increase in tumor control and normal tissue complication probabilities in advanced head-and-neck cancer for dose-escalated intensity-modulated photon and proton therapy

Jakobi, A.; Lühr, A.; Stützer, K.; Bandurska-Luque, A.; Löck, S.; Krause, M.; Baumann, M.; Perrin, R.; Richter, C.

Introduction: Presently used radiochemotherapy regimens result in moderate local control rates for patients with advanced head-and-neck squamous cell carcinoma (HNSCC). Dose escalation (DE) may be an option to improve patient outcome, but may also increase the risk of toxicities in healthy tissue. The presented treatment planning study evaluated the feasibility of two DE levels for advanced HNSCC patients, planned with either intensity-modulated photon therapy (IMXT) or proton therapy (IMPT).

Materials and methods: For 45 HNSCC patients, IMXT and IMPT treatment plans were created including DE via a simultaneous integrated boost (SIB) in the high-risk volume, while maintaining standard fractionation with 2 Gy per fraction in the remaining target volume. Two DE levels for the SIB were compared: 2.3 and 2.6 Gy. Treatment plan evaluation included assessment of tumor control probabilities (TCP) and normal tissue complication probabilities (NTCP).

Results: An increase of approximately 10% in TCP was estimated between the DE levels. A pronounced high-dose rim surrounding the SIB volume was identified in IMXT treatment. Compared to IMPT, this extra dose slightly increased the TCP values and to a larger extent the NTCP values. For both modalities, the higher DE level led only to a small increase in NTCP values (mean differences <2%) in all models, except for the risk of aspiration, which increased on average by 8 and 6% with IMXT and IMPT, respectively, but showed a considerable patient dependence.

Conclusion: Both DE levels appear applicable to patients with IMXT and IMPT since all calculated NTCP values, except for one, increased only little for the higher DE level. The estimated TCP increase is of relevant magnitude. The higher DE schedule needs to be investigated carefully in the setting of a prospective clinical trial, especially regarding toxicities caused by high local doses that lack a sound dose–response description, e.g., ulcers.

Keywords: photon radiotherapy; proton radiotherapy; tumor control probability; normal tissue complication probability; head-and-neck cancer

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Permalink: https://www.hzdr.de/publications/Publ-23282
Publ.-Id: 23282


Experimental investigation of rotating liquid metal flows

Vogt, T.; Grants, I.; Raebiger, D.; Eckert, S.; Gerbeth, G.

Several experiments considering electromagnetically driven liquid metal flows in cylindrical vessels will be presented. The focus of the experiments is ranging from meteorological and geophysical effects like inertial waves and tornado-like vortices. Besides, flows with industrial relevance like the mixing of floating particles into a metallic melt or the mixing enhancement in gas stirred ladles is considered. Different ultrasound-based measurement techniques were used in these experiments whereby the ultrasound-Doppler-velocimetry (UDV) is the most important one.

  • Invited lecture (Conferences)
    Guest Colloquia Research Training Group LORENTZ FORCE, 12.04.2016, Ilmenau, Deutschland

Permalink: https://www.hzdr.de/publications/Publ-23281
Publ.-Id: 23281


Towards the nonlinear acousto-magneto-plasmonics

Temnov, V. V.; Razdolski, I.; Pezeril, T.; Makarov, D.; Seletskiy, D.; Melnikov, A.; Nelson, K. A.

Here we review the recent progress in experimental and theoretical research of interactions between the acoustic, magnetic and plasmonic transients in hybrid metal-ferromagnet multilayer structures excited by ultrashort laser pulses. Understanding the nonlinear aspects of the acoustic and magnetic dynamics in the materials as well as the peculiarities in the nonlinear optical detection process play a particular role. For example, the nonlinear optical detection is illustrated in Details by static probing the magneto-optical second harmonic generation using Kretschmann configuration in gold-cobalt-silver trilayer structures. In other experiments we Show how the nonlinear reshaping of giant ultrashort acoustic pulses propagating in Gold can be quantified by time-resolved plasmonic interferometry and how these ultrashort optical pulses dynamically modulate the optical nonlinearities. The effective medium approximation for the optical properties of hybrid multilayers facilitates the peculiarities of novel optical detection techniques. In the discussion we highlight some recent work on the nonlinear magneto-elastic interactions, and strain-induced effects in semiconductor quantum dots.

Keywords: magneto plasmonics; Ultrafast acoustics; hybrid metal-ferromagnet multilayer structures

Permalink: https://www.hzdr.de/publications/Publ-23280
Publ.-Id: 23280


Entirely flexible on-site conditioned magnetic sensorics

Münzenrieder, N.; Karnaushenko, D.; Petti, L.; Cantarella, G.; Vogt, C.; Büthe, L.; Karnaushen, D. D.; Schmidt, O. G.; Makarov, D.; Tröster, G.

Being soft and compliant, flexible electronics conform to synthetic or biological tissues. Processing of the data acquired using flexible devices is typically done using external rigid electronics, which limits the unobtrusiveness, narrows the system bandwidth and lowers the signal-to-noise ratio. Here, we demonstrate the first entirely flexible integrated magnetic field sensor system consisting of a flexible giant magnetoresistive bridge on-site conditioned using high-performance IGZO-based electronic circuitry. The flexible readout electronics yields a record high overall gain of 48.6 dB and a remarkably high signal-to-noise ratio of 56 dB. The system detects magnetic fields with a sensitivity of 25 V/V/kOe and outperforms the responsiveness of commercial fully integrated rigid magnetic sensors by at least one order of magnitude, whereas all components stay fully functional while bent to a radius of 5 mm. We outline potential application directions and realized two demonstrators, namely a magnetic switch and a proximity sensing device with a low power consumption of 250 µW even when used to trigger an external LED, employed as visual output. Our high-performance flexible magnetosensory system represents a key step towards entirely flexible electronics, capable of sensing and processing signals without the need of rigid elements.

Keywords: flexible electronics; flexible magnetic sensors; GMR; IGZO transistors; flexible operational amplifier

Permalink: https://www.hzdr.de/publications/Publ-23279
Publ.-Id: 23279


Bit-Patterned Magnetic Recording

Makarov, D.; Krone, P.; Albrecht, M.

The chapter summarizes recent activities on the realization of bit patterned media for magnetic data storage.

Keywords: magnetic recording; bit patterned media; perpendicular magnetic anisotropy; magnetic caps; FePt alloy; Co/Pt multilayers

  • Book chapter
    Gaspare Varvaro and Francesca Casoli: Ultrahigh-Density Magnetic Recording: Storage Materials and Media Designs, Singapore: Pan Stanford Publishing Pte. Ltd., 2016, 978-981-4669-58-0, 327-384-1
    DOI: 10.1201/b20044

Permalink: https://www.hzdr.de/publications/Publ-23277
Publ.-Id: 23277


Rashba Torque Driven Domain Wall Motion in Magnetic Helices

Pylypovskyi, O. V.; Sheka, D. D.; Kravchuk, V. P.; Yershov, K. V.; Makarov, D.; Gaididei, Y.

Manipulation of the domain wall propagation in magnetic wires is a key practical task for a number of devices including racetrack memory and magnetic logic. Recently, curvilinear effects emerged as an efficient mean to impact substantially the statics and dynamics of magnetic textures. Here, we demonstrate that the curvilinear form of the exchange interaction of a magnetic Helix results in an effective anisotropy term and Dzyaloshinskii–Moriya interaction with a complete set of Lifshitz invariants for a one-dimensional system. In contrast to their planar counterparts, the geometrically induced modifications of the static magnetic texture of the domain walls in magnetic helices offer unconventional means to control the wall dynamics relying on spin-orbit Rashba torque. The chiral symmetry breaking due to the Dzyaloshinskii–Moriya interaction leads to the opposite directions of the domain wall motion in left- or right-handed helices. Furthermore, for the magnetic helices, the emergent effective anisotropy term and Dzyaloshinskii–Moriya interaction can be attributed to the clear geometrical parameters like curvature and torsion offering intuitive understanding of the complex curvilinear effects in magnetism.

Keywords: curvilinear magnetism; Dzyaloshinskii–Moriya interaction; Domain wall Motion; magnetic helices

Permalink: https://www.hzdr.de/publications/Publ-23276
Publ.-Id: 23276


Shapeable magnetoelectronics

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

Inorganic nanomembranes are shapeable (flexible, printable and even stretchable) and transferrable to virtually any substrate. These properties build the core concept for new technologies, which transform otherwise rigid high-speed devices into their shapeable counterparts. This research is motivated by the eagerness of consumer electronics towards being thin, lightweight, flexible, and even wearable. The realization of this concept requires all building blocks as we know them from rigid electronics (e.g. active elements, optoelectronics, magnetoelectronics, energy storage) to be replicated in the form of (multi)functional nanomembranes, which can be reshaped on demand after fabrication. There are already a variety of shapeable devices commercially available, i.e. electronic displays, energy storage elements, and integrated circuitry to name a few. From the beginning, the main focus was on the fabrication of shapeable high-speed electronics and optoelectronics. Only very recently, a new member featuring magnetic functionalities was added to the family of shapeable electronics. With their unique mechanical properties, the shapeable magnetic field sensor elements readily conform to ubiquitous objects of arbitrary shapes including the human skin. This feature leads electronic skin systems beyond imitating the characteristics of its natural archetype and extends their cognition to static and dynamic magnetic fields that by no means can be perceived by human beings naturally. Various application fields of shapeable magnetoelectronics are proposed. The developed sensor platform can equip soft electronic systems with navigation, orientation, motion tracking and touchless control capabilities. A variety of novel technologies, like smart textiles, soft robotics and actuators, active medical implants and soft consumer electronics will benefit from these new magnetic functionalities. This review reflects the establishment of shapeable magnetic sensorics, describing the entire development from the first attempts to verify the functional concept to the realization of ready-to-use highly compliant and strain invariant sensor devices with remarkable robustness.

Keywords: flexible electronics; printable electronics; stretchable electronics; imperceptible electronics; smart skin; Hall effect; magnetoelectronics; giant magnetoresistance; magnetic sensorics; soft matter; thin films; magnetic materials; magnetic nanomembranes; electronic skin

Permalink: https://www.hzdr.de/publications/Publ-23275
Publ.-Id: 23275


Ion irradiated Er:YAG ceramic cladding waveguide amplifier in C and L bands

Tan, Y.; Ma, L.; Akhmadaliev, S.; Zhou, S.; Chen, F.

We report on the optical-signal amplification in a cladding waveguide that was fabricated in Er:YAG ceramic by multiple carbon-ion irradiation. The waveguide has a multilayer structure that assures good overlap between the pump beam and the input signal. Under the pump at 980 nm with a fiber-coupled diode laser, the cladding waveguide possess a peak internal gain of 2.6 dB/cm at 1550 nm and of 4.0 dB/cm at 1585 nm. This work demonstrates the potential use as amplifier in the C and L communication bands of cladding waveguides fabricated in Er:YAG by carbon ion irradiation technique.

Keywords: Ion irradiation; Cladding waveguide; Er:YAG

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Permalink: https://www.hzdr.de/publications/Publ-23274
Publ.-Id: 23274


Q-switched waveguide laser based on two-dimensional semiconducting materials: tungsten disulfide and black phosphorous

Tan, Y.; Guo, Z.; Ma, L.; Zhang, H.; Akhmadaliev, S.; Zhou, S.; Chen, F.

Owing to their unique properties, graphene-like two dimensional semiconducting materials, including Tungsten Disulfide (WS2) and Black Phosphorous (BP), have attracted increasing interest from basic research to practical applications. Herein, we demonstrated the ultrafast nonlinear saturable absorption response of WS2 and BP films in the waveguide structure. Through fabricating WS2 and BP films by evaporating the solutions on glass wafers. Saturable absorber films were attached onto the end-facet of the waveguide, which therefore constitutes a resonant cavity for the waveguide laser. Under a pump laser at 810 nm, we could obtain a stable Q-switched operation in the waveguide structure. This work indicated the significant potential of WS2 and BP for the ultrafast waveguide laser.

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Permalink: https://www.hzdr.de/publications/Publ-23273
Publ.-Id: 23273


Latent endmember identification by means of Gaussian anamorphosis

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

In a geological context compositions are often generated by variable mixtures of different source materials. These sources are called endmembers of the mixture [1,2]. This contribution presents a data-driven exploratory method of detection of the presence of endmembers, and preliminary identification of their possible composition.

  • Contribution to proceedings
    International Geological Congress, 27.08.-04.09.2016, Cape Town, South Africa

Permalink: https://www.hzdr.de/publications/Publ-23272
Publ.-Id: 23272


The serial interface package

Seilmayer, M.

This R package provides the functionality to use the serial communication ports "COM" to use RS232/RS422/RS485 functionality of the corresponding hardware. Also virtual COM-ports via USB do work, as long as they are mapped to COM[n] (win) or tty[n] (Linux) in the operating system.

Keywords: RS232; RS485; RS422; USB; serial communication

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Permalink: https://www.hzdr.de/publications/Publ-23270
Publ.-Id: 23270


THEREDA - Thermodynamische Referenz-Datenbasis. Phase II: Freigabe thermodynamischer Daten. Zusammenfassung der Abschlussberichte

Altmaier, M.; Bok, F.; Gaona, X.; Marquardt, C.; Montoya, V.; Moog, H. C.; Richter, A.; Scharge, T.; Voigt, W.; Wilhem, S.

Die thermodynamische Referenzdatenbasis THEREDA wird im Rahmen eines Ver-bundvorhabens vom Institut für nukleare Entsorgung des Karlsruher Institut für Techno-logie (KIT-INE), dem Institut für Ressourcenökologie des Helmholtz-Zentrums Dresden-Rossendorf (HZRD-IRE), dem Institut für Anorganische Chemie der TU Bergakademie Freiberg (TUBAF), bis 1.4.2015 von AF-Consult/CH (AFC) und der Abteilung Prozessanalyse der Gesellschaft für Anlagen- und Reaktorsicherheit (GRS) erstellt.
Diese Kurzfassung fasst die Arbeiten für die zweite Projektphase des Verbundvorha-bens THEREDA für den Berichtszeitraum 2010-07 bis 2013-12 zusammen. Während in der ersten Projektphase (2006-07 bis 2010-06) vor allem grundlegende Arbeiten an-standen (Implementierung einer Datenbank, Eingabe von Daten, Erstellung eines QM-Systems, Festlegung von gemeinsamen Richtlinien und Kriterien, Erstellung einer In-ternetplattform), standen in der zweiten Projektphase die Freigabe von thermodynami-schen Daten im Vordergrund.
Es wurden insgesamt neun Datenfreigaben realisiert. Für diese wurden Parameterda-teien generiert, die mit den Programmen EQ3/6, PHREEQC, Geochemist‘s Workbench und CHEMAPP genutzt werden können. Wo dies notwendig war, wurden hierzu zu-sätzliche Dokumentationen („Technical Paper“) erstellt, in denen der Nutzer weitere In-formationen findet. Für die dezentrale Eingabe der Daten wurde eine grafische Benut-zeroberfläche entwickelt.
Als Vorbereitung für zukünftige Aktivitäten, etwa im Zusammenhang mit der Suche nach weiteren Endlagerstandorten, wurden die technischen Grundlagen für die Spei-cherung von Sorptionsdaten gelegt.
THEREDA wird derzeit im Rahmen einer durch das Bundesamt für Strahlenschutz ge-förderten dritten Projektphase auf administrativer Ebene fortgeführt. Die Erweiterung der Datenbasis erfolgt im Rahmen anderer FuE-Projekte.
Die vollständigen Berichte aller Verbundteilnehmer sind dieser Kurzfassung auf CD-ROM beigefügt.

Keywords: Actiniden; CO2; Datenbank; Geochemie; Phosphat; Radionuklide; Thermodynamik; Thermodynamische Datenbasis; Zement

  • Other report
    Braunschweig: GRS-396, 2015
    83 Seiten

Permalink: https://www.hzdr.de/publications/Publ-23269
Publ.-Id: 23269


Alkyl aminated nanocelluloses in selective flotation of aluminium oxide and quartz

Laitinen, O.; Hartmann, R.; Sirviö, J. A.; Liimatainen, H.; Rudolph, M.; Ämmälä, A.; Illikainen, M.

There are economic and ecological incentives for developing novel green chemicals from renewable resources in order to reduce the environmental impact of mineral processing. Cellulose, the most abundant natural polymeric source, is a promising green alternative that could replace the synthetic chemicals currently used. In this study, linear alkyl aminated nanocelluloses with increasing chain lengths were used for the selective flotation of aluminium oxide and quartz. Methylamine, ethylamine, n-propylamine, n-butylamine, n-pentylamine and n-hexylamine were introduced into a cellulose backbone using combined periodate oxidation and reductive amination in an aqueous environment. The hydrophobicity of the nanocelluloses was found to be increased by extending the alkyl chain length of the amino groups. Flotation experiments proved that alkyl aminated nanocelluloses can be both effective and selective collectors for quartz in a flotation system if they are sufficiently hydrophobic to allow the particles to effectively attach to the air bubbles. In the case of flotation with a known quartz and alumina mixture, the successful separation solution used aminated nanocelluloses at a pH of around 7.5.

Keywords: Alumina; Collector; Flotation; Nanocellulose; Quartz; Selectivity

Permalink: https://www.hzdr.de/publications/Publ-23268
Publ.-Id: 23268


Transmission electron microscopy investigation of the microstructure of Fe-Cr alloys induced by neutron and ion irradiation at 300ºC

Hernández-Mayoral, M.; Heintze, C.; Onorbe, E.

Four Fe-Cr binary alloys, with Cr content from 2.5 up to 12wt%, were neutron or ion irradiated up to a dose of 0.6 dpa at 300ºC. The microstructural response to irradiation has been characterised using Transmission Electron Microscopy (TEM). Both, neutrons and ions, gave rise to the formation of dislocation loops. The most striking difference between ion and neutron irradiation is the distribution of these loops in the sample. Except for the lowest Cr content, loops are distributed mainly along grain boundaries and dislocations in the neutron irradiated samples. The inhomogeneous distribution of dislocation loops could be related to the presence of α’ precipitates in the matrix. In contrast, a homogeneous distribution is observed in all ion irradiated samples. This important difference is attributed to the orders of magnitude difference in dose rate between these two irradiation conditions. Moreover, the density of loops depends non-monotonically on Cr content in case of neutron irradiation, while it seems to increase with Cr content for ion implantation. Differences are also observed in terms of cluster size, with larger sizes for neutron irradiation than for ion implantation, again pointing towards an effect of the dose rate.

Keywords: transmission electron microscopy (TEM); neutron irradiation; ion irradiation; ferritic and martensitic steels; Fe-Cr alloys

Permalink: https://www.hzdr.de/publications/Publ-23267
Publ.-Id: 23267


A record of paleofluid circulation in faults revealed by hematite (U-Th)/He and apatite fission-track dating: an example from Gower Peninsula fault fissures, Wales

Ault, A. K.; Frenzel, M.; Reiners, P. W.; Woodock, N. H.; Thomson, S. N.

Fault-related fissures on the Gower Peninsula, Wales, preserve evidence of faulting, hematite-calcite mineralization, sediment infill, and paleofluid flow. We combine hematite (U-Th)/He (He) dating with sandstone apatite fission-track (AFT) and apatite and zircon (U-Th)/He (He) thermochronology to constrain the timing of fluid circulation in these structures. Hematite He dates from 141.0 ± 5.1 Ma to 119.9 ± 5.0 Ma overlap with a 131.4 ± 20.1 Ma sandstone infill AFT date. Individual zircon He dates are ~402-260 Ma, reflecting source material erosion, and imply a maximum late Permian infill depositional age. Burial history reconstruction reveals modern exposures were not reheated to temperatures sufficient to reset the AFT or hematite He systems in the Triassic-Early Cretaceous, and thus these dates cannot reflect cooling due to erosion alone. Hot fluids circulating through fissures in the Early Cretaceous reset the AFT system. Hematite was either also reset by fluids or precipitated from these fluids. Similar hematite He dates from fault-related mineralization in south Glamorgan (Wales), and Cumbria (England) imply concomitant regional hot groundwater flow along faults. Hydrothermal fluid circulation, coeval with North Atlantic rifting, occurred in these higher permeability fissures and fault veins long after they initially formed.

Keywords: hematite (U-Th)/He dating; low temperature thermochronology; fluid flow; Gower Peninsula; fault; fissure fills

Permalink: https://www.hzdr.de/publications/Publ-23266
Publ.-Id: 23266


Ion heating, Compression, Instability, Mixing, Interpenetrating and Stagnating of Ultrafast Relativistic Laser Produced Solid Plasmas

Huang, L. G.; Kluge, T.; Bussmann, M.; Cowan, T. E.

We presented ion dynamics in ultrafast relativistic laser produced solid plasmas, which include ionh eating, compression, instability, mixing, interpenetrating and stagnating.

Keywords: Ion dynamics; heating; compression; instability; mixing; interpenetrating; stagnating

  • Poster
    2016 European XFEL Users' Meeting and Satellite Meetings, 27.-29.01.2016, Hamburg, Germany

Permalink: https://www.hzdr.de/publications/Publ-23265
Publ.-Id: 23265


On the electrolyte convection around a hydrogen bubble evolving at a microelectrode under the influence of a magnetic field

Baczyzmalski, D.; Karnbach, F.; Yang, X.; Mutschke, G.; Uhlemann, M.; Eckert, K.; Cierpka, C.

The flow around an evolving hydrogen bubble on a microelectrode (0.1 mm in diameter) under the influence of an electrode-normal magnetic field was investigated to clarify the effect of the imposed flow on the detachment of the bubble from the electrode. Therefore, water electrolysis was carried out in a 1 M H2SO4 solution under potentiostatic conditions for different potentials in the presence of a magnetic field normal to the horizontal electrode surface. Measurements of the current oscillations and microscopic high-speed imaging were used to analyze the periodic bubble growth. The three-dimensional flow in the bulk of the cell and around the evolving bubble was measured in parallel by applying different particle imaging and tracking techniques. In addition, a numerical study of the flow was conducted to support the experimental results. The results demonstrate that the hydrodynamic force imposed by the Lorentz-force-driven-convection has a very small stabilizing effect on the bubble. However, a strong flow in the vicinity of the bubble was observed that may reduce the local supersaturation of dissolved hydrogen. Furthermore, large flow velocities close to the bubble surface indicate a strong motion of the mobile liquid-gas interface that might be significant for the bubble evolution process.

Keywords: electrolysis; gas evolution; hydrogen; magnetic field; Lorentz force; PIV; numerical simulation

Permalink: https://www.hzdr.de/publications/Publ-23262
Publ.-Id: 23262


Monazite characterization in a carbonatite weathering profile – a new tool for landscape geochronology

Le Bras, L.; Renno, A.; Haser, S.; Ziegenruecker, R.; Atanasova, P.; Gutzmer, J.

The Post-Gondwana geology of South Africa is marked by two prominent planation surfaces. These are the result of two distinct phases of uplift and erosion processes that took place under tropical and subtropical conditions: the first of these took place during the mid and late Cretaceous (African planation) whilst the second is tentatively placed into the Miocene (Post-African I planation) [1] or Oligocene [2]. Humid and warm climatic conditions along the African and Post-African I planation surfaces are evidenced by deep lateritic weathering columns of suitable lithologies. The ancient nature of the weathering residues has been well documented by Ar-Ar geochronology on supergene Mn-oxihydroxides [3]. The present study is carried out to test the suitability of U-Th-Pb dating on supergene monazite as a geochronometer for landscape formation and the downward progression of chemical weathering processes.

The study is carried out on material from the Zandkopsdrift carbonatite, Namaqualand, South Africa. The Zandkopsdrift carbonatite is a pipe-shaped intrusion located in the Northern Cape Province of South Africa. Its age of intrusion has been determined as being Eocene (54-56 Ma) [3]. The carbonatite has a well developed lateritic cap that is more than 80 m thick in places. This lateritic cap is greatly enriched in REE – hosted mostly by very fine crystalline monazite that is presumably of supergene origin. Due to the fact that the age of intrusion postdates the African planation surface, the lateritic cap almost certainly marks the Post-African I erosion surface.

There is pre-existing information for the development of the Post-African I planation from geological, paleontological [1] and geochronological evidence [2] [4]. The Post-African I planation surface was carved into the African surface as a consequence of renewed uplift and westward tilting of the African Plate. Climatic conditions during the development of the Post-African I planation surface remained at first humid and warm, but subsequently became more arid and thus less conducive to chemical weathering. The onset and duration of the Post-African I cycle of erosion remains uncertain.

The latter question will be addressed by the current study by dating supergene monazite from different depth in the Zandkopsdrift laterite cap – as intersected in exploration drill core. A detailed description of the petrographic and mineralogical attributes was used to identify the most promising samples for chemical dating using secondary ion mass spectrometry (SIMS). A detailed description of the internal structure, microporosity and inclusions as well as intergrowths and pseudomorphic mineral formations of each analysed monazite crystal allowed us to interpret and evaluate the respective results. The results describe the alteration of the REE minerals, the weathering process as well as the stabilization of the weathering column during arid climatic conditions. These data set important anchor points for the reconstruction of the landscape evolution in South Africa.

References:
[1] Partridge and Maud (1987) S Afr J Geol 90:197-208
[2] Burke (1996) S Afr J Geol 99:339-409
[3] Gutzmer et al. (2012) Ore Geology Reviews 47:136-153
[4] Verwoerd (1993) S Afr J Geol 96(3):75-95

Keywords: African Landscape; Geochronology; Supergene Alteration; Monazite

  • Poster
    35th International Geological Congress, 27.08.-04.09.2016, Cape Town, Republic of South Africa

Permalink: https://www.hzdr.de/publications/Publ-23261
Publ.-Id: 23261


Alternative fabrication routes toward oxide dispersion strengthened steels and model alloys

Bergner, F.; Hilger, I.; Virta, J.; Lagerbom, J.; Gerbeth, G.; Connolly, S.; Hong, Z.; Grant, P. S.; Weissgärber, T.

The standard powder metallurgy (PM) route for the fabrication of oxide-dispersion-strengthened (ODS) steels involves gas atomization to produce a prealloyed powder, mechanical alloying (MA) with fine oxide powders, consolidation, and finally thermal/thermomechanical treatment (TMT). It is well established that ODS steels with superior property combinations, for example, creep and tensile strength, can be produced by this PM/MA route. However, the fabrication process is complex and expensive, and the fitness for scaling up to the industrial scale is limited. At the laboratory scale, production of small amounts of well-controlled model systems continues to be desirable for specific purposes, such as modeling-oriented experiments. Thus, from the laboratory to industrial application, there is growing interest in complementary or alternative fabrication routes for ODS steels and related model systems, which offer a different balance of cost, convenience, properties, and scalability. This article reviews the state of the art in ODS alloy fabrication and identifies promising new routes toward ODS steels. The PM/AM route for the fabrication of ODS steels is also described, as it is the current default process. Hybrid routes that comprise aspects of both the PM route and more radical liquid metal (LM) routes are suggested to be promising approaches for larger volumes and higher throughput of fabricated material. Although similar uniformity and refinement of the critical nanometer-sized oxide particles has not yet been demonstrated, ongoing innovations in the LM route are described, along with recent encouraging preliminary results for both extrinsic nano-oxide additions and intrinsic nano-oxide formation in variants of the LM route. Finally, physicochemical methods such as ion beam synthesis are shown to offer interesting perspectives for the fabrication of model systems. As well as literature sources, examples of progress in the authors’ groups are also highlighted.

Keywords: ODS steel; Fabrication; Powder metallurgy; Liquid metal; Hybrid routes

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Permalink: https://www.hzdr.de/publications/Publ-23260
Publ.-Id: 23260


A synchronous Gigabit Ethernet protocol stack for high-throughput UDP/IP applications

Födisch, P.; Lange, B.; Sandmann, J.; Büchner, A.; Enghardt, W.; Kaever, P.

State of the art detector readout electronics require high-throughput data acquisition (DAQ) systems. In many applications, e. g. for medical imaging, the front-end electronics are set up as separate modules in a distributed DAQ. A standardized interface between the modules and a central data unit is essential. The requirements on such an interface are varied, but demand almost always a high throughput of data. Beyond this challenge, a Gigabit Ethernet interface is predestined for the broad requirements of Systems-on-a-Chip (SoC) up to large-scale DAQ systems. We have implemented an embedded protocol stack for a Field Programmable Gate Array (FPGA) capable of high-throughput data transmission and clock synchronization. A versatile stack architecture for the User Datagram Protocol (UDP) and Internet Control Message Protocol (ICMP) over Internet Protocol (IP) such as Address Resolution Protocol (ARP) as well as Precision Time Protocol (PTP) is presented. With a point-to-point connection to a host in a MicroTCA system we achieved the theoretical maximum data throughput limited by UDP both for 1000BASE-T and 1000BASE-KX links. Furthermore, we show that the random jitter of a synchronous clock over a 1000BASE-T link for a PTP application is below 60 ps.

Keywords: Data acquisition circuits; Data acquisition concepts

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Permalink: https://www.hzdr.de/publications/Publ-23259
Publ.-Id: 23259


Ein VHDL basierter Gigabit Ethernet Protokollstapel für FPGAs

Födisch, P.; Lange, B.; Kaever, P.

Mit diesem Beitrag wird ein Protokollstapel für einen ethernet-basierten Datenaustausch mit einem FPGA vorgestellt. Für den schnellen und verbindungslosen Datenaustausch ist das User Datagram Protocol (UDP) ein schlankes Protokoll der Transportschicht. Die dynamische Erzeugung der UDP Paketrahmen benötigt eine vollständige Abbildung der zugrunde liegenden Netzwerkschichten (Internetschicht und Netzwerkschicht). Es wird eine VHDL basierte Architektur für einen Protokollstapel vorgestellt, welche die Protokolle UDP, IP, ICMP und ARP in einem FPGA integriert. Der Schichtenaufbau soll den maximalen Datendurchsatz ermöglichen. Es werden die Ergebnisse der Implementierung und Tests auf unterschiedlichen FPGA Plattformen gezeigt.

  • Contribution to proceedings
    106. Tagung der Studiengruppe elektronische Instrumentierung im Frühjahr 2015, 02.-04.03.2015, Zeuthen, Deutschland, Hamburg: Verlag Deutsches Elektronen-Synchrotron, 978-3-935702-96-6, 52-76

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Permalink: https://www.hzdr.de/publications/Publ-23257
Publ.-Id: 23257


Droplet-confined alternate pulsed epitaxy of GaAs nanowires on Si substrates down to CMOS-compatible temperatures

Dimakis, E.; Balaghi, L.; Tauchnitz, T.; Hübner, R.; Bischoff, L.; Schneider, H.; Helm, M.

The self-catalyzed epitaxial growth of free-standing GaAs nanowires on Si substrates by molecular beam epitaxy typically requires high enough temperatures, where the Ga adatoms can diffuse efficiently along the surface of the substrate and the nanowire sidewalls before their incorporation into the liquid Ga droplets at the top of the nanowires. On the other hand, the use of high temperatures imposes several limitations concerning the interruption and resumption of the growth in an accurate and defect-free way, the realization of well-defined composition or doping profiles in axial heterostructures and, finally, the compliance with the thermal budget restrictions of fully-processed Si-CMOS circuits that is necessary for the integration of the two material technologies. Here, we introduce the droplet-confined alternate pulsed epitaxy for the self-catalyzed growth of GaAs nanowires on Si(111) substrates in the temperature range from 550 °C down to 450 °C. This unconventional growth mode is a modification of the migration-enhanced epitaxy, where alternating pulses of Ga and As4 are employed instead of a continuous supply. The enhancement of the diffusion length of Ga adatoms on the {1-10} nanowire sidewalls allows for their targeted delivery to the Ga droplets at the top of the nanowires and, thus, for a highly directional growth along the nanowire axis even at temperatures as low as 450 °C. We demonstrate that the axial growth can be controlled with the ultimate accuracy of one monolayer, while it can be simply and abruptly interrupted at any time without the formation of any defects. Taking advantage of these unique possibilities, we were able to probe the growth mechanisms in specially designed experiments and describe quantitatively the population dynamics of As inside the Ga droplets.

Keywords: Nanowire; self-catalyzed; alternate pulsed epitaxy; GaAs; Si substrate

Permalink: https://www.hzdr.de/publications/Publ-23256
Publ.-Id: 23256


Early and late effects of radiochemotherapy on cerebral blood flow in glioblastoma patients measured with non-invasive perfusion MRI

Petr, J.; Platzek, I.; Seidlitz, A.; Mutsaerts, H. J. M. M.; Hofheinz, F.; Schramm, G.; Maus, J.; Beuthien-Baumann, B.; Krause, M.; van den Hoff, J.

Background and purpose: To provide a systematic measure of changes of brain perfusion in healthy tissue following a fractionated radiotherapy of brain tumors.
Materials and methods: Perfusion was assessed before and after radiochemotherapy using arterial spin labeling in a group of 24 patients (mean age 54.3±14.1 years) with glioblastoma multiforme. Mean relative perfusion change in gray matter in the hemisphere contralateral to the tumor was obtained for the whole hemisphere and also for six regions created by thresholding the individual dose maps at 10 Gy steps.
Results: A significant decrease of perfusion of -9.8 ± 20.9% (p = 0.032) compared to the pre-treatment baseline was observed 3 months after the end of radiotherapy. The decrease was more pronounced for high-dose regions above 50 Gy (-16.8 ± 21.0%, p = 0.0014) than for low-dose regions below 10 Gy (-2.3 ± 20.0%, p = 0.54). No further significant decrease compared to the post-treatment baseline was observed 6 months (-0.4 ± 18.4%, p = 0.94) and 9 months (2.0 ± 15.4%, p = 0.74) after the end of radiotherapy. Conclusions: Perfusion decreased significantly during the course of radiochemotherapy. The decrease was higher in regions receiving a higher dose of radiation. This suggests that the perfusion decrease is at least partly caused by radiotherapy. Our results suggest that the detrimental effects of radiochemotherapy on perfusion occur early rather than later.

Keywords: ASL; Arterial spin labeling; Cerebral blood flow; Radiotherapy; Brain tumor; Perfusion

Permalink: https://www.hzdr.de/publications/Publ-23255
Publ.-Id: 23255


A fluorescence anisotropy-based assay for determining the activity of tissue transglutaminase

Hauser, C.; Wodtke, R.; Löser, R.; Pietsch, M.

Tissue transglutaminase (TGase 2) is the most abundantly expressed enzyme of the transglutaminase family and involved in a large variety of pathological processes, such as neurodegenerative diseases, disorders related to autoimmunity and inflammation as well as tumor growth, progression and metastasis. As a result, TGase 2 represents an attractive target for drug discovery and development, which requires assays that allow for the characterization of modulating agents and are appropriate for high-throughput screening. Herein, we report a fluorescence anisotropy‐based approach for the determination of TGase 2’s transamidase activity, following the time-dependent increase in fluorescence anisotropy due to the enzyme-catalyzed incorporation of fluorescein‐ and rhodamine B‐conjugated cadaverines 1-3 (acyl acceptor substrates) into N,N-dimethylated casein (acyl donor substrate). These cadaverine derivatives 1-3 were obtained by solid‐phase synthesis. To allow efficient conjugation of the rhodamine B moiety, different linkers providing secondary amine functions, such as sarcosyl and isonipecotyl, were introduced between the cadaverine and xanthenyl entities in compounds 2 and 3, respectively, with acyl acceptor 3 showing the most optimal substrate properties of the compounds investigated. The assay was validated for the search of both irreversible and reversible TGase 2 inhibitors using the inactivators iodoacetamide and a recently published L‐lysine-derived acrylamide and the allosteric binder GTP, respectively. In addition, the fluorescence anisotropy-based method was proven to be suitable for high-throughput screening (Z’ factor of 0.86) and represents a non-radioactive and highly sensitive assay for determining the active TGase 2 concentration.

Keywords: Active-site titration; Cadaverine; Enzyme inhibition; Fluorescent labeling; Transglutaminases; Xanthene dyes

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Permalink: https://www.hzdr.de/publications/Publ-23254
Publ.-Id: 23254


Liquid metal experiments on astrophysical magnetic fields

Giesecke, A.; Gundrum, T.; Herault, J.; Stefani, F.

Cosmic magnetic fields are ubiquitous phenomena that are observed on all scales, from planets and stars to galaxies and clusters of galaxies. The origin of these fields involves the formation of electrical currents by means of complex flows of conducting fluids or plasmas. Magnetic fields may also be important for cosmic structure formation by destabilizing rotational flows that would otherwise be hydrodynamically stable with the magnetorotational instability (MRI)in accretions disks as the most prominent example. Both processes, magnetic field generation (the so called dynamo effect), and magnetic field induced instabilities have also been observed in experiments, which, however, require considerable technical efforts due to the significantly smaller scales available in the laboratory.

In my talk I will briefly summarize the essential outcome of past, present, and future liquid metal experiments on magnetohydrodynamic dynamos and instabilities. The focus will be on the project DRESDYN (DREsden Sodium facility for DYNamo and thermohydraulic studies), a new platform for a variety of liquid sodium experiments devoted to problems of geo- and astrophysical magnetohydrodynamics conducted at Helmholtz-Zentrum Dresden-Rossendorf. Most ambitious experiments will be a large-scale precession driven dynamo experiment and a combined set-up for investigating different versions of the magnetorotational instability and the Tayler instability, a current driven kink-like instability. For both experiments, recent results of preparatory studies are presented, and the scientific prospects for the final set-ups are delineated.

Keywords: dynamo; dresdyn

  • Invited lecture (Conferences)
    Physikalisches Kolloquium, 18.04.2016, Bochum, Germany

Permalink: https://www.hzdr.de/publications/Publ-23253
Publ.-Id: 23253


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