Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

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39109 Publications

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

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

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 [1]. 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) [2]. 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).

1. Lloyd, J.R.M., L. E. , Interactions of microorganisms with radionuclides. Elsevier Science. 2002.
2. Lovley, D.R., et al., Enzymatic Iron and Uranium Reduction by Sulfate-Reducing Bacteria. Marine Geology, 1993. 113(1-2): p. 41-53.

Keywords: Uranium; Reduction; Sulfate-reducing bacteria; Bioremediation

  • Lecture (others)
    5. Workshop - TransAqua, 06.-07.04.2016, Dresden, Deutschland

Publ.-Id: 23587

Speciation studies of Rn/Ln with selected degradation products of organic LILW – New spectroscopic insights into the uranyl-acetate system –

Brinkmann, H.; Moll, H.; Arnold, T.

Organic polymers (e.g. cellulose, PVC, bitumen) present in low and intermediate level wastes (LILW) are exposed to ionizing radiation, alkaline pH, and organic degrading microorganisms. This may lead to the formation of smaller, water soluble organic compounds, affecting amongst others the chemical behavior and mobility of radionuclides (RN). In the worst case complexation will lead to an increased mobility and a decreased retention of RN in the barriers of a nuclear waste disposal. Therefore, the characterization of RN complexes with degradation products is necessary for the assessment of the safety and the long-term performance of a nuclear waste repository.
The presentation will give an overview of our planned activities in cooperation with our partners (UNIMAN, SCK·CEN, and UGR) to contribute to task 1.2 of WP 1. Here our focus and expertise lies on the application of different modern spectroscopic tools to directly characterize the speciation of Rn/Ln with organic degradation products and/or with selected microbes, to underpin the findings from UNIMAN and SCK·CEN. Current results obtained by TRLFS, cryo-TRLFS, and UV-vis giving new insights into the uranyl-acetate system will be presented.

Keywords: Uranium; Acetate; TRLFS; UV-vis; MIND

  • Lecture (others)
    MIND Project Annual Meeting 2016, 02.-04.05.2016, Granada, Spain

Publ.-Id: 23586

Development of a functional assay for the prediction of NP net removal rates in WWT

Schymura, S.; Hildebrand, H.; Franke, K.

Within recent years the growing application of nanoparticles (NPs) in products of everyday life caused raising concerns about their potential risks for humans and environment. Environmental concentrations of manufactured nanoparticles are predicted to be low, but significant. Key players in regulating NP influx into the environment are wastewater treatment plants (WWTP). The development of removal guidelines and a NP classification based on their likely fate in wastewater treatment (WWT) is mandatory to support WWTP operating companies and regulating agencies.
A potential approach based on suitable functional assays is developed within the project NanoSuppe in cooperation with an US-EPA initialized round robin test with various partners in the US. The idea is to use a simple test program to establish NP affinity coefficients with activated sewage sludge to predict net removal rates during WWT.
Within NanoSuppe, different NPs, such as TiO2, CeO2, MWCNT and Quantum dots, are radiolabeled for easy and highly sensitive detection and employed in batch sorption experiments with activated sludge from a local WWTP. Based on the theory developed by Barton et al., NP affinities for NP hetero-aggregation with the activated sludge are measured from the time-dependent sorption behavior and used as a means of categorizing NP in different groups.
We found that the results of such functional assays depend very much on the experimental setup, such as composition of the dispersion medium (or matrix solution) and consequently NP surface modification (which is to be expected). There is also a significant influence of mixing times and, more dominant, shaking intensity. One of the key parameters is the initial colloidal stability of the NPs in the used media. A suitable procedure that best reflects the situation during WWT is desirable and the predictive strength concerning net removal rates during WWT is to be verified in WWTP model experiments.

Keywords: Nanopartikel; nanoparticle; Kläranlage; Wastewater Treatment Plant; Heteroaggregation; Heteroaggregation

  • Poster
    Clustertreffen NanoCare, 03.-04.05.2016, Frankfurt am Main, Deutschland

Publ.-Id: 23585

Polyglycerol-Based Copper Chelators for the Transport and Release of Copper Ions in Biological Environments

Albrecht, R.; Fehse, S.; Pant, K.; Nowag, S.; Stephan, H.; Haag, R.; Tzschucke, C. C.

Here, the synthesis and characterization of three improved nanosystems is presented based on amino functionalized hyperbranched polyglycerol (hPG; M w = 16.8 kDa) as potential copper( II ) chelators. The ligands, N -methyl- N -picolylglycine amide, 2,6-pyridine dicarboxylic acid monoamide, and cyclam tetraacetic acid (TETA) monoamide, are covalently attached to the polymer with amide bonds. In this paper, the Cu( II ) loading capacity, the stability of the Cu( II )- loaded carriers at different pHs, with competing ligands and in human serum, as well as the transport of Cu( II ) in biological systems are investigated. For the fi rst time, a different cytotoxicity of functionalized polymer nanoparticles with and without Cu( II ) is observed. The cyclam-based carrier combines the highest loading capacity (29 Cu ions/nanoparticle), best stability with respect to pH and EDTA (45% remaining Cu after 24 h), lowest cytotoxicity (IC 50 > 100 × 10 −6 M (unloaded), 1500 × 10 −6 M Cu( II ); Cu:carrier 29:1), and the highest stability in human serum.

Publ.-Id: 23584

Direct and Auger electron-induced, single- and double-strand breaks on plasmid DNA caused by 99mTc-labeled pyrene derivatives and the effect of bonding distance

Reissig, F.; Mamat, C.; Steinbach, J.; Pietzsch, H.-J.; Freudenberg, R.; Kotzerke, J.; Wunderlich, G.

It is evident that 99mTc causes radical-mediated DNA damage due to Auger electrons, which were emitted simultaneously with the known γ-emission of 99mTc. We have synthesized a series of new 99mTc-labeled pyrene derivatives with varied distances between the pyrene moiety and the radionuclide. The pyrene motif is a common DNA intercalator and allowed us to test the influence of the radionuclide distance on damages of the DNA helix. In general, pUC 19 plasmid DNA enables the investigation of the unprotected interactions between the radiotracers and DNA that results in single-strand breaks (SSB) or double-strand breaks (DSB). The resulting DNA fragments were separated by gel electrophoresis and quantified by fluorescent staining. Direct DNA damage and radical-induced indirect DNA damage by radiolysis products of water were evaluated in the presence or absence of the radical scavenger DMSO.
We demonstrated that Auger electrons directly induced both SSB and DSB in high efficiency when 99mTc was tightly bound to the plasmid DNA and this damage could not be completely prevented by DMSO, a free radical scavenger. For the first time, we were able to minimize this effect by increasing the carbon chain lengths between the pyrene moiety and the 99mTc nuclide. However, a critical distance between the 99mTc atom and the DNA helix could not be determined due to the significantly lowered DSB generation resulting from the interaction which is dependent on the type of the 99mTc binding motif. The effectiveness of the DNA-binding 99mTc-labeled pyrene derivatives was demonstrated by comparison to non-DNA-binding 99mTcO4–, since nearly all DNA damage caused by 99mTcO4– was prevented by incubating with DMSO.

Keywords: Auger emitter; 99mTc; plasmid DNA; pyrene; direct DNA damage; radiobiology; DNA

Publ.-Id: 23583

Energy Resolution Improvement through Digital Pulse Shape Analysis at CdZnTe-Cross-Strip-Detectors

Weinberger, D.; Fiedler, F.; Kormoll, T.

CdZnTe is a semiconductor material with very good properties for gamma-ray detection. A relatively large band gap of 1.57 eV allows the use at room temperature without any additional cooling. Since holes are nearly immobile compared to electrons in CdZnTe, spectroscopic readout requires special techniques which reduce the depth dependence of the signal. One possibility is to apply an anode pattern which exploits the small pixel effect which induces a signal as the charge cloud is very close to the anode. However, a small current is already induced as the charge cloud travels the bulk. The additional drift current will be accumulated at the charge sensitive preamplifier and influences the base line determination algorithm and results in an additional energy input. We present a simple approach to eliminate the influence of this drift current with the use of pulse shape discrimination implemented in an FPGA of a sampling ADC board. With this algorithm and the known transfer function of the preamplifier a proper depth correction is possible to improve the spectral resolution.

Keywords: CdZnTe; detectors; Energy Resolution Improvement

  • Contribution to proceedings
    2016 IEEE NSS/MIC/RTSD, 29.10.-06.11.2016, Strasbourg, Frankreich
    Proceedings of 2016 IEEE NSS/MIC/RTSD
  • Poster
    2016 IEEE NSS/MIC/RTSD, 29.10.-06.11.2016, Strasbourg, Frankreich

Publ.-Id: 23581

ESR modes in a Strong-Leg Ladder in the Tomonaga-Luttinger Liquid Phase

Zvyagin, S.; Ozerov, M.; Maksymenko, M.; Wosnitza, J.; Honecker, A.; Landee, C. P.; Turnbull, M.; Furuya, S.; Giamarchi, T.

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  • Lecture (Conference)
    APS March Meeting 2016, 14.-18.03.2016, Baltimore, USA

Publ.-Id: 23580

Numerical simulation of liquid metal batteries

Weber, N.; Beckstein, P.; Galindo, V.; Herreman, W.; Landgraf, S.; Nore, C.; Stefani, F.; Weier, T.

Considering the increasing deployment of renewable energies, large-scale stationary energy storage will be a key-technology for the future. One potentially ideal grid-scale energy storage system is the liquid metal battery (LMB), consisting of a totally liquid interior. The long life time and abundant raw materials of LMBs offer a very cheap way of building batteries.

Building LMBs cheap means to make them large. Strong currents in the order of kA will drive a fluid flow, which may increase the battery's performance, or lead to a short circuit in the worst case.

A numerial model for describing the MHD fluid flow is presented and used to describe the Tayler instability, electro-vortex flow and interface instabilities in LMBs.

  • Lecture (others)
    Vortrag am Departament de Física Aplicada an der Universitat Politècnica de Catalunya, 26.04.2016, Barcelona, Spanien

Publ.-Id: 23578

Open Access-Transformationsinitiative "OA2020"

Reschke, E.

Vorstellung der Open Access Transformationsinitiative OA2020

Keywords: Open Access; OA2020; publication fees; author publication charge; White Paper; DEAL

  • Lecture (others)
    Arbeitskreis Spezialbibliotheken Dresden - Frühjahrstreffen,, 20.04.2016, Dresden, Deutschland

Publ.-Id: 23577

Kerndatensatz Forschung

Reschke, E.

Vorstellung der Kategorien, die sich auf das Publizieren beziehen.

Keywords: Kerndatensatz; Research; Publications

  • Lecture (others)
    Arbeitskreis Spezialbibliotheken Dresden - Frühjahrstreffen, 20.04.2016, Dresden, Deutschland

Publ.-Id: 23576

A novel scheme of Compton imaging for nuclear medicine

Pausch, G.; Golnik, C.; Schulz, A.; Enghardt, W.

The paper introduces a novel concept of gamma imaging, the Single-Plane Compton Imager (SPCI). An SPCI is a compact array of scintillation crystals with separate light readouts, arranged for example in a checkerboard configuration. The passive collimation of conventional gamma cameras is replaced by kind of a “soft” electronic collimation derived from the Compton kinematics. In contrast to Compton cameras, where individual scattering angles are determined event-by-event from coincident energy depositions in separate detector planes, the SPCI reconstructs activity distributions from accumulated “conditional” spectra by using Maximum Likelihood Expectation Maximization algorithms. The condition is a coincident energy deposition in two (adjacent) detector elements of a single plane, which occurs most likely due to Compton scattering in one element followed by absorption in the other one. The SPCI could overcome drawbacks of Anger and Compton cameras: (i) Image resolution and detection efficiency are no competing factors. Both improve with increasing detector area. (ii) The fraction of valid events per hit exceeds that of passively collimated systems or Compton cameras by orders of magnitude. (iii) A single detector construction could fit to a wide range of gamma energies. Last not least, optimal SPCI pixels sizes fit with pixel dimensions in PET scanners. SPCI could thus be based on recent detector developments for PET-MRI featuring individual Si-based pixel readouts.

Keywords: Gamma Kamera; Anger Kamera; Compton Kamera; SPECT; Szintillator; Bildgebung; Bildrekonstruktion; MLEM; Gamma camera; Anger camera; Compton camera; SPECT; scintillator; imaging; image reconstruction; MLEM

  • Lecture (Conference)
    IEEE Nuclear Science Symposium and Medical Imaging Conference, 28.10.-06.11.2016, Strasbourg, France
  • Contribution to proceedings
    2016 IEEE Nuclear Science Symposium and Medical Imaging Conference, 29.10.-05.11.2016, Strasbourg, France
    2016 IEEE NSS/MIC Conference Record
    DOI: 10.1109/NSSMIC.2016.8069921
    Cited 2 times in Scopus

Publ.-Id: 23575

Redox dependent interfacial reactivity of hexavalent radionuclides

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

A solid comprehension of the geochemical behavior of radionuclides on a molecular level is essential to make reliable long-term predictions about the safety of a nuclear waste repository. The mobility of radionuclides in the environment and thus their hazard potential will also be controlled by the reactivity at the water/mineral interface. In order to understand these processes analytical methods shall ideally be both surface specific and sensitive. X-ray reflectivity techniques, particularly resonant anomalous X-ray reflectivity (RAXR) and crystal truncation rod (CTR) measurements have proved to be a successful combination to investigate geochemical interfacial regimes (Fenter 2002).
Plutonium is one of the most important radionuclides in term of nuclear waste disposal due to its long half-life period and high radiotoxicity. That’s why it has been subject of different studies over the last decades. While these studies could show an enhancement of the mobility of plutonium in the presence of colloidal matter, the formation of Pu(IV)-nanoparticles is still content of ongoing research (Walther & Deneke 2013). Recently, Schmidt et al. suggested a surface-catalyzed formation due to an enhanced concentration of Pu(III) at the surface in equilibrium with a small amount of Pu(IV). Part of the current study was to proof the viability of this mechanism, but also to investigate the interfacial reactivity of Pu’s various oxidation states.
The interaction of UO2 2+ and PuO2 2+ with muscovite mica and the effect on the actinides’ different redox properties were investigated using a combination of surface X ray diffraction, alpha spectrometry and grazing-incidence X-ray adsorption near-edge structure (GI-XANES) spectroscopy. Although, U(VI) often is used as a homologue for Pu(VI), this study show a completely different behavior of Pu(VI) and U(VI). Starting with a Pu(VI) solution, Pu(IV)-nanoparticles were formed and adsorbed on the mineral surface. The suggested formation mechanism is similar to that of Pu(III). No such adsorption or nanoparticle formation was observed for U. Our results reveal major differences between Pu and U concerning redox and adsorption behavior, influencing their mobility in the environment. Regarding the prediction of the fate of these contaminants’ in aqueous systems their different interfacial behavior is of importance. This in turn significantly effects the quality of predictions of the allocation of these contaminants in aqueous systems.

  • Lecture (Conference)
    2nd Conference on Key Topics in Deep Geological Disposal, 26.-28.09.2016, Köln, Deutschland

Publ.-Id: 23574

The microbiology of subsurface, salt-based nuclear waste repositories: Toward a realistic prediction of the microbial effects on repository performance

Swanson, J.; Cherkouk, A.; Bader, M.; Reed, D.

Only two countries in the world—Germany and the United States—currently host nuclear waste facilities in subterranean salt formations, although the concept is gaining traction in other countries, as well. The evaluation of such sites for their feasibility as waste repositories is extensive and multidisciplinary. Microbiology has been one of the weaker areas of investigation, and as a result, there is still uncertainty surrounding the possible effects of microbial activity on salt-based repository performance.
The success of a nuclear waste repository is measured as its ability to prevent the release of radionuclides into the surrounding environment or to limit that release to levels deemed acceptable by the appropriate regulatory agencies and public. Microorganisms are predicted to have diverse effects on nuclear waste repository performance, all of which involve their impact on radionuclide migration. These effects are due to any activities that may affect radionuclide speciation, solubility, or mobility, including 1) complexation with carbonate or organic ligands generated from the breakdown of organic waste; 2) complexation with microbially-generated ligands; 3) creation of a reducing environment through the consumption of oxygen or generation of hydrogen; 4) alteration of pH; 5) redox reactions; and 6) bioassociation that could lead to biocolloid transport.
Because the biogeochemistry of other deep geologic (e.g., granite, clay) settings differs significantly from subterranean salt, it is not possible to extrapolate microbial activity from one site type to the other. However, because of a lack of data, this is precisely what has been done in most safety case scenarios in salt. Thus, performance models assume the worst-case scenario: that the organisms present in rock salt will thrive on the organics present in the radioactive waste, leading to the generation of complexing agents that enhance radionuclide solubility, and that they will take up significant amounts of radionuclides and transport them away from the repository. The goal of current research being conducted by Los Alamos National Laboratory for the Waste Isolation Pilot Plant (WIPP) and by the Helmholtz-Zentrum Dresden-Rossendorf for the German repository concept, is to provide a more realistic view of the potential effects of microorganisms on salt-based nuclear waste repositories.
To reach this goal, both laboratories have been performing coordinated, culture-dependent and independent studies on halite and briny groundwater samples from the Salado Formation (US) and the Zechstein Formation (Germany). Isolates (e.g., Halobacterium sp., putatively noricense,
and others) undergo further investigation into their ability to degrade specific organic waste components (e.g., citrate, cellulose) under repository-relevant conditions and into their potential interactions with waste radionuclides (e.g., uptake, toxicity, and transformation). Results thus far suggest: 1) that the activity of repository-indigenous organisms will be constrained by the projected conditions (brine composition, anoxic atmosphere) and also by the lack of suitable organic substrates but that organisms located in the far-field (overlying briny groundwaters) will not; 2) that some organisms alter brine composition in ways that may affect radionuclide solubility; 3) that the radionuclides present in the waste are inhibitory, but not completely lethal, at their soluble concentrations in repository brine; and 4) that bioassociation of radionuclides appears to differ with oxidation state, organism, and brine composition.
An overview of our current knowledge regarding the microbial impact on salt-based nuclear waste repository performance will be presented and will emphasize the much-needed collaboration between those doing basic halophile research and those applying it in non-routine settings.

  • Lecture (Conference)
    Halophiles 2016, 22.-27.05.2016, San Juan, Puerto Rico

Publ.-Id: 23573

The Role of Calcite in Nuclear Waste Disposal Sites

Hellebrandt, S. E.; Hofmann, S.; Jordan, N.; Schmidt, M.

In the safety assessment of nuclear waste disposal sites we have a look on different geochemical processes in the near and far field of a conceivable disposal site. These processes include sorption and incorporation as possibel mechanisms of radionuclide retention in a worst case scenario of an ingress of groundwater. Various minerals in the host rocks as well as primary and secondary phases in the geotechnical barrier were investigated under these conditions elsewhere. Calcite (CaCO3) can be found in every section of the containment and has a couple of features, which makes it interesting for further investigations. A high retention potential because of high sorption capacity as well as the possibility to incorporate guest ions into the crystal lattice at the Ca-ion position is distinctive for calcite [Schmidt 2008, Marques Fernandes 2008]. The long-lived radionuclides (e.g. Plutonium, Curium) determine the long-term radiotoxicity, which defines the considered timespan of the safety analysis. The trivalent radionuclides have an affinity to calcite because of their chemical properties (ionic charge and radius).
To investigate this affinity we conducted different experiments – coprecipitation and batch studies over various periods of time. We can show, that the incorporation of radionuclides and their homologues is dependent on several parameters: i.e. the grain size and specific surface area of calcite, amount and composition of impurities in the calcite and in the background solution. To investigate the structural incorporation we used site-selective timeresolved laser-induced fluorescence spectroscopy with Europium, which serves as a homologue for the trivalent radionuclides because of its great spectroscopic usability [Binnemans 2015] and its similar chemical behavoir. With this method we can distiguish between sorption of the Europium ion onto the calcite surface and incorporation into the crystal bulk by figuring out the amount of water molecules in the first coordination shell of the Europium ion – if there is no water left, incorporation took place. Furthermore we perform X-ray surface diffraction with two high resolution methods, crystal truncation rod and resonant anomalous X-ray-reflectivity. Our experiments were run in situ, which means we have a thin solution film above the crystall. We can demonstrate the influence of different background electolytes (sodium nitrate and sodium iodate) on calcite, which cause a significant surface destabilisation and hence a modification or prevention of sorption and incorporation mechanism. These results are important to examine sorption and structural incorporation on calcite as a process of radionuclide retention in the near and far field of nuclear waste disposal sites.

Binnemans, K. (2015): Interpretation of europium(III) spectra. Coord. Chem. Rev., 295, 1-45.
Schmidt, M. et al. (2008): Charge Compensation in Solid Solutions. Angew. Chem., Int. Ed., 47, 5846-5850
Marques Fernandes, M. et al. (2008): Incorporation of trivalent actinides into calcite: A time resolved laser fluorescence spectroscopy (TRLFS) study. Geochim. Cosmochim. Acta, 72, 464-474.

Keywords: Calcite; nuclear waste disposal site

  • Lecture (Conference)
    Key topics in deep geological disposal, 26.-28.09.2016, Köln, Deutschland

Publ.-Id: 23572

Incorporation of Eu(III) into Calcite under different Recrystallization conditions

Hellebrandt, S. E.; Hofmann, S.; Jordan, N.; Barkleit, A.; Schmidt, M.

Calcite is a ubiquitous mineral in the earth’s crust. Its capacity to incorporate guest ions with similar ionic radius as Ca2+ (e.g. Eu3+, Pu3+, and Am3+) makes it interesting for various environmental issues as well as for safety assessment of nuclear waste disposal sites. Here the trivalent later actinides with long half-lives (like Am and Cm) comprise the most of the long-term radiotoxicity.
For our experiments we used Eu as homologue because of its similar ionic charge and radius and its preferable luminescence properties [1]. We conducted batch studies with three calcite powders, which differ in their specific surface area (SSA) and recrystallization rates (Rr). The speciation of the incorporated Eu(III) was then investigated by site-selective time-resolved laser fluorescence spectroscopy. With increase of the recrystallization rate incorporation occurs faster and the speciation comes to be dominated by one species with its excitation maximum at 578.9 nm. Previous investigations of this process under growth [2] and phase transformation conditions [3] had not identified this species. A long lifetime of ~ 3000 µs demonstrates complete loss of hydration [4], consequently Eu must have been incorporated into the bulk crystal.
The results show a strong dependence of the incorporation kinetics on the recrystallization rate of the different calcites. The predominance of the newly identified species seems to be independent of this kinetic effect, however.
[1] Binnemans (2015) Coord. Chem. Rev. 295, 1-45
[2] Schmidt (2008) Angew. Chem., Int. Ed. 47, 5846-5850
[3] Schmidt (2010) J. Colloid Interface Sci. 351, 50-56
[4] Horrocks (1979) J. Am. Chem. Soc. 101, 334.

Keywords: Calcite; Recristallization; Europium; TRLFS; Incorporation

  • Lecture (Conference)
    Goldschmidt2016, 26.06.-01.07.2016, Yokohama, Japan

Publ.-Id: 23571

Evidence of a new Incorporation Species of Eu(III) in Calcite and its dependence of the background electrolyte

Hellebrandt, S. E.; Hofmann, S.; Jordan, N.; Barkleit, A.; Schmidt, M.

Calcite plays a significant role in nuclear waste disposal sites, both as a constituent of geological formations and as a secondary mineral, e.g. upon weathering of concrete. As such it has a direct impact on a repository’s safety and performance. Geochemically, calcite has the potential to adsorb as well as incorporate guest ions with a similar ionic radius, e.g. Eu(III), Pu(III) and Am(III), for Ca(II) in the host lattice. For the safety assessment of nuclear waste disposal sites these trivalent actinides with long half-lives (especially Am) dominate its long-term radiotoxicity and are thus of particular interest.
Schmidt et al. investigated the influence of different dissolved cations on the incorporation process by [1] time-resolved laser fluorescence spectroscopy (TRLFS) with Eu(III)/Cm(III). They could show that there exists a coupled substitution mechanism [Cm(III)/Eu(III) + Na(I) ↔ 2 Ca(II)]. The experiments by Schmidt, et al. were performed under growth conditions, representative of the formation of a secondary phase. Calcite already present as a constituent of the host rock, however, would be more likely to interact with the contaminants at, or very close to equilibrium. Under these conditions its reactivity will be governed by its recrystallization rate, and different interaction mechanism – and consequently different contaminant speciation – may be expected.
For our experiments we used Eu as homologue because of its similar ionic charge and radius, as well as its desirable luminescence properties [2]. We conducted batch studies with calcite powder in calcite saturated solutions with NaCl or KCl as background electrolyte. The speciation of the incorporated Eu(III) was then investigated by site-selective time-resolved laser fluorescence spectroscopy (TRLFS). The speciation of both systems is dominated by a species with its excitation maximum at 578.9 nm, which had not been identified in previous investigations of this process under growth [1] and phase transformation conditions [3]. A long lifetime of ~ 4000 µs demonstrates complete loss of hydration [4], consequently Eu must have been incorporated into the bulk crystal. The corresponding emission spectrum shows the maximum splitting pattern implying a low symmetry of the ligand field surrounding Eu(III)[2]. After 1 month reaction time the excitation spectrum of the calcite in contact with NaCl shows a strongly blue-shifted excitation spectrum compared to the same calcite with KCl, demonstrating the effect of the background electrolyte on the Eu(III) speciation. As the peak at 579.3 nm belongs to a sorption species, this indicates enhanced incorporation in NaCl background relative to the KCl system. This may indicate that also under recrystallization conditions coupled substitution of Eu(III) and Na(I) for two Ca(II) is required for incorporation. Incorporation remains a significant interaction mechanism in the KCl system, likely due to a considerable amount of naturally occurring Na in the calcite
The results show, that the speciation of Eu(III) in calcite depends on the conditions of its incorporation, i.e. growth versus recrystallization. A hitherto unknown incorporation has been identified, and our results strongly suggest incorporation under recrystallization conditions strongly depends on the availability of Na(I).
[1] M. Schmidt, Angew. Chem., Int. Ed. 2008, 47, 5846-5850.
[2] K.Binnemans, Coord. Chem. Rev. 2015,295, 1-45.
[3] M. Schmidt, J. Colloid Interface Sci. 2010, 351, 50-56.
[4] W. DeW. Horrocks, Jr., J. Am. Chem. Soc. 1979, 101, 334-340.

Keywords: Calcite; TRLFS; Europium; Incorporation

  • Poster
    Ninth international conference on nuclear and radiochemistry - NRC9, 29.08.-02.09.2016, Helsinki, Finland

Publ.-Id: 23570

Porting the Plasma Simulation PIConGPU to Heterogeneous Architectures with Alpaka

Zenker, E.; Widera, R.; Juckeland, G.; Worpitz, B.; Hübl, A.; Knüpfer, A.; Nagel, W. E.; Bussmann, M.

We discuss our experience on porting the CUDA-based plasma simulation code PIConGPU to heterogeneous platforms using the abstract kernel interface Alpaka. With the advent of next-generation architectures such as OpenPower, the full use of the hardware and the mapping of CPUs and GPUs to specific simulation tasks has become important. Performance portability is of great interest, but even more important is the ability to develop against a single interface to keep code testable and maintainable. We show how we can make use of the Alpaka library in real-world applications and how we achieve portability and performance.

Keywords: Supercomputing & HPC; Computational Physics; Performance Optimization

  • Lecture (Conference)
    GPU Technology Conference, 04.-07.04.2016, San Jose, California, USA

Publ.-Id: 23569

Speciation of trivalent actinides and lanthanides in body fluids

Barkleit, A.; Wilke, C.; Heller, A.; Ikeda-Ohno, A.; Stumpf, T.

In case of incorporation into the human body, radionuclides potentially represent serious health risks due to their chemo- and radiotoxicity. In order to assess their toxicological behavior, such as transport, metabolism, deposition, and elimination from the human organisms, the understanding of their in vivo chemical speciation on a molecular level is crucial. Due to their high specific radioactivity with very long half-lives, trivalent actinides (An(III)) are considered to be some of the problematic radionuclides particularly in the geological repository of radioactive wastes. The reliable safety and health assessment of the waste repositories requires the information about the behavior of An(III) in vivo. Nevertheless, little is known about the speciation of not only An(III) but also trivalent lanthanides (Ln(III)), non-radioactive chemical analogs of An(III), in body fluids.
In order to improve our understanding of the behavior of An(III) and Ln(III) in the human body, the present study focuses on the chemical speciation of An(III) and Ln(III) in the gastrointestinal tract. The human gastrointestinal system was simulated by using an in vitro digestion model, which was developed by Oomen et al. [1] and is the basis of an international unified bioaccessibility protocol [2]. To verify the model, natural human saliva samples were included in the speciation investigation. Because An(III) and Ln(III) are excreted mainly by the kidney [3, 4], their speciation in natural human urine was investigated to complete the metabolic pathway from oral ingestion through the digestive system till elimination.
The speciation of curium(III) (Cm(III)) and europium(III) (Eu(III)) in the gastrointestinal tract as well as in human natural saliva and urine has been studied by means of time-resolved laser-induced fluorescence spectroscopy (TRLFS). The standard model body fluids and the natural saliva and urine samples were spiked in vitro with Cm(III) and Eu(III) in trace metal concentrations.
The dominant chemical species in the human saliva was identified by a comparison of the natural human sample spectra with reference spectra obtained for synthetic saliva and individual components of the body fluid. Linear combination fitting analysis on the sample spectra indicates the formation of 60-90% inorganic- and 10-40% organic species of Cm(III)/Eu(III) in the salivary media. Ternary M(III) complexes containing phosphate and carbonate anions with the additional counter-cation calcium are formed as the main inorganic species. Complexes with the digestive enzyme α-amylase and the protein mucin (to a minor extent) represent the major part of the organic species.
When the M(III) reached the stomach, the metal complexes were dissociated due to the high acidic conditions. That is, Cm(III) and Eu(III) are mainly present as the aqua ion, and only a small part (about 20%) is coordinated by the protein pepsin. When entering the intestine the metal ions are strongly bound by the protective protein mucin and inorganic ligands (mainly carbonate and phosphate).
After transporting into the bloodstream and transformation into the urine via the kidney, the speciation of the metal ions strongly depends on the pH of the urine. When the pH is slightly acidic, the formation of Cm(III) and Eu(III) citrate complex dominates, whereas ternary complexes with phosphate and calcium as the main ligands and the additional participation of citrate and/or carbonate occur at around near-neutral pH [5].
These speciation studies in different body fluids pointed out that An(III) and Ln(III) are coordinated by both inorganic and organic molecules in the human body. Proteins (e.g. α-amylase, pepsin, mucin) would be the important organic binding partners. Furthermore, ternary inorganic complexes containing phosphate and carbonate anions with the additional counter-cation calcium are expected to be formed as the main inorganic species in almost all the body fluids.
[1] Oomen, A. G., Rompelberg, C. J. M., Bruil, M. A., Dobbe, C. J. G., Pereboom, D. P. K. H., Sips, A. J. A. M., Arch. Environ. Contam. Toxicol. 44, 281-287 (2003).
[2] Wragg, J., Cave, M., Taylor, H., Basta, N., Brandon, E., Casteel, S., Gron, C., Oomen, A., van de Wiele, T., British Geological Survey Open Report OR/07/027, Keyworth, Nottingham, 90 pp. (2009).
[3] Menetrier, F., Taylor, D. M., and Comte, A., Appl. Radiat. Isot. 66, 632–647 (2008).
[4] Taylor, D. M., Leggett, R. W., Radiat. Prot. Dosim. 105, 193–198 (2003).
[5] Heller, A., Barkleit, A., Bernhard, G., Chem. Res. Toxicol. 24, 193-203 (2011).

  • Poster
    9th International Conference on Nuclear and Radiochemistry NRC9, 29.08.-02.09.2016, Helsinki, Finland

Publ.-Id: 23568

Chemical speciation of An(III) and Ln(III) in human saliva

Barkleit, A.; Wilke, C.; Heller, A.; Stumpf, T.; Ikeda-Ohno, A.

In case of incorporation into the human body, radionuclides potentially represent serious health risks due to their chemo- and radiotoxicity. In order to assess their toxicological behavior, such as transport, metabolism, deposition, and elimination from the human organisms, the understanding of their in vivo chemical speciation on a molecular level is crucial. Due to their high specific radioactivity with very long half-lives, trivalent actinides (An(III)) are considered to be some of the problematic radionuclides particularly in the geological repository of radioactive wastes. The reliable safety and health assessment of the waste repositories requires the information about the behavior of An(III) in vivo. Nevertheless, little is known about the speciation of not only An(III) but also trivalent lanthanides (Ln(III)), non-radioactive chemical analogs of An(III), in body fluids.
In order to improve our understanding of the behavior of An(III) and Ln(III) in the human body, the present study focuses on the chemical speciation of An(III) and Ln(III) in saliva. Saliva is one of the most important body fluids to understand the behavior of these metals in the digestive system, as it is the very first contact medium in the human body in case of oral ingestion.
We report the first speciation study of curium(III) and europium(III) in human saliva by means of time-resolved laser-induced fluorescence spectroscopy (TRLFS). For TRLFS measurements, fresh saliva samples from humans have been spiked in vitro with Cm(III) or Eu(III). The dominant chemical spe-cies in the human saliva was identified by a comparison of the sample spectra with reference spectra obtained for synthetic saliva and individual components of the body fluid. Linear combination analysis on the sample spectra indicates the formation of about 60-90% inorganic- and 10-40% organic species of Cm(III)/Eu(III) in the salivary media. A ternary M(III) complex containing phosphate and carbonate anions with the additional counter-cation calcium is formed as the main inorganic species. Complexes with α-amylase and mucin (to a minor extent) represent the major part of the organic species. Thermodynamic calculation of the speciation, based on the recently determined stability constants for Cm(III) and Eu(III) complexes with α-amylase, also supports the experimentally determined speciation.

  • Poster
    10th International Biometals Symposium (Biometals 2016), 10.-15.07.2016, Dresden, Germany

Publ.-Id: 23567

An online, energy-resolving beam profile detector for laser-driven proton beams

Metzkes, J.; Zeil, K.; Kraft, S. D.; Karsch, L.; Sobiella, M.; Rehwald, M.; Obst, L.; Schlenvoigt, H.-P.; Schramm, U.

In this paper, a scintillator-based online beam profile detector for the characterization of laser-driven proton beams is presented. Using a pixelated matrix with varying absorber thicknesses, the proton beam is spatially resolved in two spatial dimensions and simultaneously energy-resolved. A thin plastic scintillator placed behind the absorber and read out by a CCD camera is used as the active detector material. The spatial detector resolution reaches down to ~4mm and up to 9 energy ranges can be resolved with an energy resolution of ~1 MeV above 8 MeV proton energy. With these detector design parameters, the spatial characteristics of the proton distribution and its cut-off energy can be analyzed online and on-shot under vacuum conditions. The paper discusses the detector design, its characterization and calibration at a conventional proton source as well as the first detector application at a laser-driven proton source.

Keywords: laser-driven proton acceleration; scintillator-based online detectors

Related publications


Publ.-Id: 23566

Performance-Portable Many-Core Plasma Simulations: Porting PIConGPU to OpenPower and Beyond

Zenker, E.; Widera, R.; Hübl, A.; Juckeland, G.; Knüpfer, A.; Nagel, W. E.; Bussmann, M.

With the appearance of the heterogeneous platform OpenPower, many-core accelerator devices have been coupled with Power host processors for the first time. Towards utilizing their full potential, it is worth investigating performance portable algorithms that allow to choose the best-fitting hardware for each domain-specific compute task. Suiting even the high level of parallelism on modern GPGPUs, our presented approach relies heavily on abstract meta-programming techniques, which are essential to focus on fine-grained tuning rather than code porting. With this in mind, the CUDA-based open-source plasma simulation code PIConGPU is currently being abstracted to support the heterogeneous OpenPower platform using our fast porting interface cupla, which wraps the abstract parallel C++11 kernel acceleration library Alpaka.

We demonstrate how PIConGPU can benefit from the tunable kernel execution strategies of the Alpaka library, achieving portability and performance with single-source kernels on conventional CPUs, Power8 CPUs and NVIDIA GPUs.

Keywords: OpenPower; heterogeneous computing; HPC; C++11; CUDA; OpenMP; particle-in-cell; platform portability; performance portability

Publ.-Id: 23565

Alpaka - An Abstraction Library for Parallel Kernel Acceleration

Zenker, E.; Worpitz, B.; Widera, R.; Hübl, A.; Juckeland, G.; Knüpfer, A.; Nagel, W. E.; Bussmann, M.

Porting applications to new hardware or programming models is a tedious and error prone process. Every help that eases these burdens is saving developer time that can then be invested into the advancement of the application itself instead of preserving the status-quo on a new platform.

The Alpaka library defines and implements an abstract hierarchical redundant parallelism model. The model exploits parallelism and memory hierarchies on a node at all levels available in current hardware. By doing so, it allows to achieve platform and performance portability across various types of accelerators by ignoring specific unsupported
levels and utilizing only the ones supported on a specific
accelerator. All hardware types (multi- and many-core CPUs, GPUs and other accelerators) are supported for and can be programmed in the same way.
The Alpaka C++ template interface allows for straightforward extension of the library to support other accelerators and specialization of its internals for optimization.

Running Alpaka applications on a new (and supported) platform requires the change of only one source code line instead of a lot of #ifdefs.

Keywords: Heterogeneous computing; HPC; C++; CUDA; OpenMP; platform portability; performance portability

  • Contribution to proceedings
    The Sixth International Workshop on Accelerators and Hybrid Exascale Systems co-located with the 30th IEEE International Parallel & Distributed Processing Symposium, 23.-27.05.2016, Chicago Hyatt Regency Chicago, Illinois, USA
    Proceedings of the 30th IEEE International Parallel and Distributed Processing Symposium

Publ.-Id: 23564

Spectroscopic studies on the interaction of europium(III) and curium(III) with components of the human mucosa

Wilke, C.; Barkleit, A.; Ikeda-Ohno, A.; Stumpf, T.

Lanthanide and actinide elements are exogenous metals, which have no essential role in normal biochemistry. Through different processes such as nuclear accidents, these heavy metals could be potentially released into the environment where they could be further incorporated eventually into the food chain and furthermore into the human gastrointestinal tract through oral ingestion. Because of their potential chemical- and radiotoxicity, it is important to understand their chemical and biological behavior in the human body. The digestive system is covered by a thick, viscoelastic mucosa membrane, which is a protective barrier to pathogens and toxic substances. The protective response in mucosa relies largely on the glycoprotein mucin. A previous spectroscopic screening with TRLFS (Time-Resolved Laser-Induced Fluorescence Spectroscopy) revealed mucin as a fundamental binding partner of Eu(III) as well as of Cm(III) in the human gastrointestinal tract. Based on these previous results, the present study focuses on this protein and its components to investigate its binding behavior with Eu(III) and Cm(III) as representatives of Ln(III) and An(III), respectively.

Keywords: lanthanides; actinides; Eu(III); Cm(III); TRLFS; spectroscopy; mucin

  • Contribution to proceedings
    Biometals - 10th International Biometals Symposium, 10.-15.07.2016, Dresden, Deutschland
    Proceedings of Biometals
  • Lecture (Conference)
    Biometals - 10th International Biometals Symposium, 10.-15.07.2016, Dresden, Deutschland

Publ.-Id: 23563

Dynamical properties of the sine-Gordon quantum spin magnet Cu-PM at zero and finite temperature

Tiegel, A. C.; Honecker, A.; Pruschke, T.; Ponomaryov, A.; Zvyagin, S. A.; Feyerherm, R.; Manmana, S. R.

The material copper pyrimidine dinitrate (Cu-PM) is a quasi-one-dimensional spin system described by the spin-1/2 XXZ Heisenberg antiferromagnet with Dzyaloshinskii-Moriya interactions. Based on numerical results obtained by the density-matrix renormalization group, exact diagonalization, and accompanying electron spin resonance (ESR) experiments we revisit the spin dynamics of this compound in an applied magnetic field. Our calculations for momentum and frequency-resolved dynamical quantities give direct access to the intensity of the elementary excitations at both zero and finite temperature. This allows us to study the system beyond the low-energy description by the quantum sine-Gordon model. We find a deviation from the Lorentz invariant dispersion for the single-soliton resonance. Furthermore, our calculations only confirm the presence of the strongest boundary bound state previously derived from a boundary sine-Gordon field theory, while composite boundary-bulk excitations have too low intensities to be observable. Upon increasing the temperature, we find a temperature-induced crossover of the soliton and the emergence of new features, such as interbreather transitions. The latter observation is confirmed by our ESR experiments on Cu-PM over a wide range of the applied field.

Publ.-Id: 23562

Comparison Between the Magnetic Irreversibility and Zero Resistance of High-Quality Melt-Processed YBaCuO Superconductors

Dias, F. T.; Vieira, V. D. N.; Wolff-Fabris, F.; Kampert, E.; Hneda, M.; Schaf, J.; Farinela, G. F.; Gouvea, C. D.; Rovira, J. J. R.

This paper portrays a detailed study of the magnetic irreversibility limit Tirr (H) and of the zero resistance point Tc0 (H) of three different top-seeding melt-textured YBa2Cu3O7−δ superconducting samples, with well-aligned c-axis and doped with a high density of nonsuperconducting Y2Ba1Cu1O5 (Y211) pinning centers. We have performed measurements for applied magnetic fields up to 140 kOe and for the whole set of the different field–current configurations. The magnetization measurements were performed using an MPMS-XL SQUID magnetometer and a vibrating sample magnetometer, both from Quantum Design. The electric transport measurements were made using a physical properties measurement system from Quantum Design. The goal of this exhaustive study is obtaining precise data about magnetic flux mobility along the various directions in the sample for the different field–current configurations, thereby defining the nature and effects, due to the strength and anisotropy of the pinning mechanisms and disclosing the various physical mechanisms dissipating electric transport in these systems below the superconducting transition temperature. We discuss our results in terms of the anisotropic flux pinning by the Y211 grains dispersed into the superconducting matrix.

Publ.-Id: 23561

Electron spin resonance in a strong-rung spin-1/2 Heisenberg ladder

Ponomaryov, A. N.; Ozerov, M.; Zviagina, L.; Wosnitza, J.; Povarov, K. Y.; Xiao, F.; Zheludev, A.; Landee, C.; Cizmar, E.; Zvyagin, A. A.; Zvyagin, S. A.

Cu(C8H6N2)Cl2, a strong-rung spin-1/2 Heisenberg ladder compound, is probed by means of electron spin resonance (ESR) spectroscopy in the field-induced gapless phase above Hc1. The temperature dependence of the ESR linewidth is analyzed in the quantum field theory framework, suggesting that the anisotropy of magnetic interactions plays a crucial role, determining the peculiar low-temperature ESR linewidth behavior. In particular, it is argued that the uniform Dzyaloshinskii-Moriya interaction (which is allowed on the bonds along the ladder legs) can be the source of this behavior in Cu(C8H6N2)Cl2.

Publ.-Id: 23560

Tunnelling magnetoresistance of the half-metallic compensated ferrimagnet Mn2RuxGa

Borisov, K.; Betto, D.; Lau, Y. C.; Fowley, C.; Titova, A.; Thiyagarajah, N.; Atcheson, G.; Lindner, J.; Deac, A. M.; Coey, J. M. D.; Stamenov, P.; Rode, K.

Tunnel magnetoresistance ratios of up to 40% are measured between 10K and 300K when the highly spin-polarized compensated ferrimagnet, Mn2RuxGa, is integrated into MgO-based perpendicular magnetic tunnel junctions. Temperature and bias dependences of the tunnel magnetoresistance effect, with a sign change near −0.2 V, reflect the structure of the Mn2RuxGa interface density of states. Despite magnetic moment vanishing at a compensation temperature of 200K for x ≈ 0.8, the tunnel magneto resistance ratio remains non-zero throughout the compensation region, demonstrating that the spin-transport is governed by one of the Mn sub-lattices only. Broad temperature range magnetic field immunity of at least 0.5T is demonstrated in the same sample. The high spin polarization and perpendicular magnetic anisotropy make Mn2RuxGa suitable for applications in both non-volatile magnetic random access memory cells and terahertz spin-transfer oscillators.

Keywords: Tunneling Magnetoresistance; Half-Metal; Mn-based alloys; MRAM; Spin Polarisation; Heusler alloy; Ferrimagnetic; Perpendicular Magnetic Anisotropy

Publ.-Id: 23559

Dual-energy CT-based assessment of patient tissue variability and its influence on particle therapy planning

Wohlfahrt, P.; Möhler, C.; Negwer, F.; Troost, E.; Enghardt, W.; Greilich, S.; Richter, C.

The accuracy of particle therapy is currently limited by uncertainties in range prediction using a heuristic conversion from CT number to stopping-power ratio (SPR). The clinical application of dual-energy CT (DECT) contributes to reduce CT-related uncertainties and to quantify the influence of tissue variability on SPR prediction. DECT offers the opportunity to provide a patient-specific CT-number-to-SPR prediction. Based on routinely used DECT patient scans, this study shows differences between adults and children, which has to be clinically regarded.

  • Lecture (Conference)
    47. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) e. V., 07.-10.09.2016, Würzburg, Deutschland

Publ.-Id: 23558

Cooperative effects of adsorption, reduction, and polymerization observed for hexavalent actinides on the muscovite basal plane

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

Reliable long-term predictions about the safety of a potential nuclear waste repository must be based on a sound, molecular-level comprehension of the geochemical behavior of the radionuclides. Especially, their reactivity at the water/mineral interface will control their mobility and thus hazard potential.1 Understanding the geochemical behavior of plutonium has been particularly challenging, due to its multitude of accessible oxidation states and its capability to form nanoparticles or eigencolloids. Despite the generally accepted importance of Pu(IV)-nanoparticles for Pu’s chemical4-6 and environmental behavior,2, 3, 7, 8 the mechanism of their formation is still the subject of ongoing research.9 Several previous studies have identified Pu(IV) nanoparticles to be the final state of adsorbed Pu, starting from both higher10-12 and lower oxidation states,13 on both redox active10, 12 and redox inactive substrates.11, 13 In our own previous work we suggested a mechanism, in which the enhanced concentration of Pu(III) at the interface, in combination with the presence of minor quantities of Pu(IV) in equilibrium, drives the formation of these nanoparticles in an effectively surface-catalyzed reaction.13 This mechanism would be independent of Pu’s initial oxidation state assuming there is adequate amounts of Pu(IV) present in equilibrium. In order to be able to understand these processes analytical techniques that allow selectively probing the mineral/water interface and elucidating processes at the interface under in situ conditions are required. X-ray reflectivity techniques, such as crystal truncation rod (CTR) measurements and resonant anomalous x-ray reflectivity (RAXR) have proven to be valuable tools for geochemical studies concerning reactions in the interfacial regime14, especially for complex reactions of the actinides.13, 15
To further elucidate the interfacial reactivity of Pu in its various oxidation states, and to test the viability of the mechanisms discussed above for Pu(III), we study the reactivity of hexavalent PuO22+ at the muscovite (001) basal plane and compare it to the behavior of ostensibly analogous UO22+ ([Pu] = 0.1 mmol L-1, [U] = 1 mmol L-1, pH = 3.2 ± 0.2, I(NaCl) = 0.1 mol L-1) using resonant anomalous X-ray reflectivity (RAXR) and crystal truncation rods (CTR), as well as grazing-incidence X-ray adsorption near-edge structure (GI-XANES) spectroscopy and alpha spectrometry. The RAXR data indicate that adsorbed Pu has a broad distribution that extends up to 60 Å from the surface. Independent quantification of the adsorption of Pu by alpha spectrometry finds a coverage of 8.3 Pu/AUC (where AUC = 46.72 Ų is the surface unit cell area). The observed broad structure and large coverage cannot be explained by ionic adsorption of PuO22+, indicating adsorption of Pu(IV) oxo nanoparticles. GI-XANES confirms that most Pu at the interface was tetravalent. These observations corroborate a redox-partner independent mechanism for the interfacial formation of Pu(IV) oxo nanoparticles put forward previously. Uranium exhibits clearly different behavior. No discernible RAXR signal was detected, indicating no adsorption of UO22+. GI-XANES and alpha spectrometry also showed very weak signal, in agreement with the RAXR findings, and in the case of GI-XANES indicating predominantly hexavalent U. Our results reveal significant differences between Pu and U in terms of mineral uptake, greatly impacting their geochemical mobility and potentially useful for predicting the fate of these contaminants’ in the aqueous environment.

1. H. Geckeis, J. Lützenkirchen, R. Polly, T. Rabung and M. Schmidt, Chemical Reviews, 2013, 113, 1016-1062.
2. A. B. Kersting, D. W. Efurd, D. L. Finnegan, D. J. Rokop, D. K. Smith and J. L. Thompson, Nature, 1999, 397, 56-59.
3. A. P. Novikov, S. N. Kalmykov, S. Utsunomiya, R. C. Ewing, F. Horreard, A. Merkulov, S. B. Clark, V. V. Tkachev and B. F. Myasoedov, Science, 2006, 314, 638-641.
4. L. Soderholm, P. M. Almond, S. Skanthakumar, R. E. Wilson and P. C. Burns, Angewandte Chemie-International Edition, 2008, 47, 298-302.
5. K. E. Knope and L. Soderholm, Chemical Reviews, 2012, 113, 944-994.
6. V. Neck, M. Altmaier and T. Fanghänel, Comptes Rendus Chimie, 2007, 10, 959-977.
7. R. J. Silva and H. Nitsche, Radiochimica Acta, 1995, 70/71, 377-396.
8. A. B. Kersting, Inorganic Chemistry, 2013, 52, 3533-3546.
9. C. Walther and M. A. Denecke, Chemical Reviews, 2013, 113, 995-1015.
10. R. Kirsch, D. Fellhauer, M. Altmaier, V. Neck, A. Rossberg, T. Fanghänel, L. Charlet and A. C. Scheinost, Environmental Science & Technology, 2011, 45, 7267-7274.
11. A. E. Hixon, Y. Arai and B. A. Powell, Journal of Colloid and Interface Science, 2013, 403, 105-112.
12. A. E. Hixon and B. A. Powell, Environmental Science & Technology, 2014, 48, 9255-9262.
13. M. Schmidt, S. S. Lee, R. E. Wilson, K. E. Knope, F. Bellucci, P. J. Eng, J. E. Stubbs, L. Soderholm and P. Fenter, Environmental Science & Technology, 2013, 47, 14178-14184.
14. P. Fenter, Reviews in Mineralogy and Geochemistry, 2002, 49, 149-220.
15. M. Schmidt, S. Hellebrandt, K. E. Knope, S. S. Lee, J. E. Stubbs, P. J. Eng, L. Soderholm and P. Fenter, Geochimica et Cosmochimica Acta, 2015, 165, 280-293.

Keywords: sorption; nanoparticles; muscovite; plutonium; uranium; x-ray reflectivity; CTR; RAXR

  • Lecture (Conference)
    Ninth International Conference on Nuclear and Radiochemistry - NRC9, 29.08.-02.09.2016, Helsinki, Finnland

Publ.-Id: 23557

Fate of Plutonium at a Former Nuclear Testing Site in Australia

Ikeda-Ohno, A.; Shahin, L. M.; Howard, D.; Collins, R. N.; Payne, T. E.; Johansen, M. P.

A series of the British nuclear tests conducted on mainland Australia between 1953 and 1963 dispersed long-lived radioactivity and nuclear weapons debris, the legacy of which is a long-lasting source of radioactive contamination to the surrounding biosphere. A reliable assessment of the environmental impact of these types of radioactive contaminants and their implications for human health requires an understanding of their physical/chemical characteristics on the molecular scale. However, mainly due to the technical difficulties associated with the chemical diversity of environmental samples, these contaminants have never been characterized adequately. In this study, we identify the chemical form of plutonium (Pu), one of the most problematic radionuclides dispersed, in the local soils collected from one of the former weapons test sites, Maralinga. We herein reveal the first direct spectroscopic evidence that the Pu legacy exists as particulates of fine Pu oxyhydroxide compounds, a very concentrated and low-soluble form of Pu, which will serve as ongoing radioactive sources far into the future. We also verify that the Pu in the particles originated in the so-called “Minor trials” that involved the dispersal of weapon components by highly explosive chemicals, not in the nuclear explosion tests called “Major trials”. The obtained results help us to understand the chemical transformation of the original Pu materials dispersed in the semi-arid environment more than fifty years ago. These findings further highlight the importance of the comprehensive physical/chemical characterization of Pu contaminants for reliable environmental- and radiotoxicological assessment, which is significantly influenced by the original physical/chemical form of the contaminant.

Keywords: Plutonium; Nuclear weapons tests; Environmental contamination; Characterisation; Synchrotron; X-ray fluorescence microscopy; X-ray absorption spectroscopy


Publ.-Id: 23556

Metal pad roll instability in liquid metal batteries

Weber, N.; Beckstein, P.; Galindo, V.; Stefani, F.; Weier, T.; Herreman, W.; Nore, C.

Considering the increasing deployment of renewable energies, large-scale stationary energy storage will be a key-technology for the future. One potentially ideal grid-scale energy storage system is the liquid metal battery (LMB), consisting of a totally liquid interior. The long life time and abundant raw materials of LMBs offer a very cheap way of building batteries.

Building LMBs cheap means to make them large. Strong currents in the order of kA will drive a fluid flow, which may increase the battery's performance, or lead to a short circuit in the worst case.

A numerial model for describing the MHD fluid flow is presented and used to describe the Tayler instability, electro-vortex flow and interface instabilities in LMBs.

Keywords: simulation OpenFOAM liquid metal battery

  • Contribution to proceedings
    10th PAMIR International Conference: Fundamental and Applied MHD, 20.06.2016, Cagliari, Italien

Publ.-Id: 23555

Statistical Hadronization Model analysis of hadron yields in p+Nb and Ar+KCl at SIS18 energies

Agakishiev, G.; Arnold, O.; Balanda, A.; Belver, D.; Belyaev, A.; Berger-Chen, J. C.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Cabanelas, P.; Castro, E.; Chernenko, S.; Destefanis, M.; Dohrmann, F.; Dybczak, A.; Epple, E.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzon, J. A.; Gernhäuser, R.; Gilardi, C.; Göbel, K.; Golubeva, M.; Gonzalez-Diaz, D.; Guber, F.; Gumberidze, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kornakov, G.; Kotte, R.; Krasa, A.; Krizek, F.; Krücken, R.; Kuc, H.; Kühn, W.; Kugler, A.; Kurepin, A.; Ladygin, V.; Lalik, R.; Lange, J. S.; Lang, S.; Lapidus, K.; Lebedev, A.; Liu, T.; Lopes, L.; Lorenz, M.; Maier, L.; Mangiarotti, A.; Markert, J.; Metag, V.; Michalska, B.; Mihaylov, D.; Michel, J.; Moriniere, E.; Mousa, J.; Müntz, C.; Münzer, R.; Naumann, L.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pietraszko, J.; Przygoda, W.; Ramstein, B.; Rehnisch, L.; Reshetin, A.; Rustamov, A.; Sadovsky, A.; Salabura, P.; Scheib, T.; Schmah, A.; Schuldes, H.; Schwab, E.; Siebenson, J.; Sobolev, Y. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlusty, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Vasiliev, T.; Wagner, V.; Weber, M.; Wendisch, C.; Wirth, J.; Wisniowski, M.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.

The HADES data from p+Nb collisions at a center of mass energy of sqrt(sNN)= 3.2 GeV are analyzed employing a statistical hadronization model. The model can successfully describe the production yields of the identified hadrons π0, η, Λ, K0 s, ω with parameters Tchem = (99+-11) MeV and μb = (619+-34) MeV, which fits well into the chemical freeze-out systematics found in heavy-ion collisions. In addition, we reanalyze our previous HADES data from Ar+KCl collisions at sqrt(sNN= 2.6 GeV with an updated version of the model. We address equilibration in heavy-ion collisions by testing two aspects: the description of yields and the regularity of freeze-out parameters from a statistical model fit. Despite this success, the model fails to describe the observed Ξ- yields in both, p+Nb and Ar+KCl. Special emphasis is put on feed-down contributions from higher-lying resonance states as a possible explanation for the observed excess.


Publ.-Id: 23554

Synthesis and kinetic characterisation of water-soluble fluorogenic acyl donors for transglutaminase 2

Wodtke, R.; Schramm, G.; Pietzsch, J.; Pietsch, M.; Löser, R.

Small glutamate-containing peptides that bear coumarin derivatives as fluorescent leaving groups attached to the gamma-carboxylic group of the Glu residue were synthesised and investigated towards their potential to act as substrates for transglutaminase 2 (TGase 2). Their synthesis was accomplished by an efficient solid-phase approach. The excellent water solubility of the compounds enabled their extensive kinetic characterisation regarding TGase 2-catalysed hydrolysis and aminolysis. The influence of the substitution pattern at the coumarin skeleton on the kinetic properties was studied. Derivatives containing 7-hydroxy-4-methylcoumarin (HMC) revealed superior properties over their 7-hydroxycoumarin counterparts; analogous amides are not accepted as substrates. Z-Glu(HMC)-Gly-OH, which exhibited the most optimal substrate properties among the investigated derivatives, was selected for the exemplary kinetic characterisation of acyl acceptor substrates and irreversible inhibitors.

Keywords: enzyme assays; inhibitors; reactive peptides; solid-phase synthesis; transferases


Publ.-Id: 23553

A Python-based interface for batch processing of image reconstruction jobs for Philips PET systems

Maus, J.; Schramm, G.; Oehme, L.; Hofheinz, F.; Petr, J.; van den Hoff, J.


Retrospective manual processing of large amounts of patient data is time consuming and error prone. This is especially true for repeated image reconstructions since the vendor software usually does not allow batch processing. To overcome this limitation we have developed a batch processing interface for our Philips PET system that is also suitable for application in a clinical context.
We have used Python3 to develop a framework that allows to run reconstructions with vendor-provided protocols and to modify parameters beforehand. The framework includes functions to list patient studies, run/abort a reconstruction, copy patient data from/to servers and to modify incorrectly entered parameters like injection time or dose. The framework targets current Philips PET systems. It has been tested with a Ingenuity-TF PET/MR system consisting of a EBW workstation and PRS+CIRS recon servers. In addition to basic image reconstruction tasks the framework also allows to add custom user defined data processing. In our case we added a MR-based attenuation segmentation algorithms as well as amplitude-based respiratory gating methods which we developed in-house. Furthermore, to facilitate the use by clinical staff the framework also comes with PyQt5-based graphical user interface.
The framework transparently interacts with the recon servers of the vendor. Images reconstructed with both interfaces were verified to be identical. MR-based attenuation segmentation and respiratory gating were also validated. The framework can be used in batch processing environments either via direct use of the implemented functions, the supplied command-line tools or via the graphical user interface.
The developed framework/tools are compatible with all common Philips PET systems and greatly facilitates reprocessing of large amounts of patient data.

  • Poster
    54. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 20.-23.04.2016, Dresden, Deutschland

Publ.-Id: 23552

Relationship between asphericity of FDG uptake in the primary tumor and prognostic molecular signatures in NSCLC

Apostolova, I.; Kalinski, T.; Ego, K.; Steffen, I. G.; Furth, C.; Buchert, R.; Derlin, T.; Hofheinz, F.; Amthauer, H.


Asphericity (ASP) is a novel FDG-PET-based tumor heterogeneity measure which quantitatively characterizes the deviation of the tumor’s metabolic volume from sphere shape. In order to understand its biological correlates we investigated the relationship with molecular signatures known to be prognostic in NSCLC.


The study included 84 consecutive patients (18 females, 66.4±8.8 years) with newly diagnosed NSCLC in whom FDG-PET/CT had been performed prior to therapy. Primary tumor resection specimens and core biopsies were used for basic histopathology and determination of the Ki-67 proliferation index. EGFR status, VEGF, p53 and ALK expression were obtained in a subgroup of 44 patients. The FDG PET image of the primary tumor was delineated by an automatic algorithm based on adaptive thresholding accounting for local background. ASP and SUVmax were considered as quantitative PET measures.


Ki-67 correlated with SUVmax (Spearman rho=0.325, p=0.002) as well as with ASP (rho=0.232, p=0.018). Both correlations were considerably stronger in adenocarcinomas than in squamous cell carcinomas. Multivariate logistic regression of Ki-67 included only ASP. Neither SUVmax nor ASP correlated with p53. ASP but not SUVmax was associated with VEGF (AUC=0.789, p=0.024) and showed a tendency towards association with EGFR positivity (AUC=0.722, p=0.065). All tumors were ALK negative. Univariate Cox regression revealed progression free survival (PFS) to be associated with stage (p=0.004) and ASP (p<0.001). Overall survival (OS) was associated with stage (p=0.001), Ki-67 (p=0.008), and ASP (p<0.001). Multivariate Cox regression included ASP (p=0.001) and stage (p=0.044) for PFS, but only ASP (p=0.015) for OS.


Molecular signatures of proliferation and angiogenesis seem to contribute to asphericity of primary lung tumors.

  • Poster
    54. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-23.04.2016, Dresden, Deutschland

Publ.-Id: 23551

Asphericity of somatostatin receptor expression in SPECT/CT as a predictor of response to PRRT in neuroendocrine neoplasms

Wetz, C.; Apostolova, I.; Hofheinz, F.; Steffen, I. G.; Kupitz, D.; Ruf, J.; Furth, C.; Amthauer, H.


To assess the value of the lesion's spatial heterogeneity, quantified as asphericity (ASP), of somatostatin receptor (SSR)–expression to predict response to peptide receptor radionuclide therapy (PRRT) in patients with metastatic, SSR positive gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN).


From 06/2011 to 05/2013 all GEP-NEN-patients who obtained pretherapeutic In-111-DTPA-Octreotid (Octreoscan®) prior to Lu-177-DOTATATE-PRRT were retrospectively enrolled in this study. SPECT/CT of thorax and abdomen was performed on Discovery NM/CT670, GE. SSR expression in 20 NEN patients (m, n=14; f, n=6; age 54-87, mean 72.6 years) was qualitatively and quantitatively assessed by measuring Krenning Score, a metastases to liver uptake ratio (M/L ratio) and ASP. Response to PRRT was evaluated on lesion basis using RECIST 1.1 and lesion were classified as responding (RL (SD, PR, CR); n=57) and non-responding (NRL (PD); n=20). The value of Krenning Score, M/L ratio and ASP for response prediction was compared by using mann-whitney-u-test and receiver-operating-curves (ROC).


77 NEN metastases (liver n=40; lymph-node n=24; bone n=11; pancreas n=2) showed SSR expression. Higher ASP was significantly associated with poorer response (PD: 10.35±1.09; SD: 2.88±0.36; PR: 1.73±0.49, CR: 0.66±0.18; p<0.001). ROC-analyses revealed the highest ROC for discrimination between RL and NRL for ASP (AUC 0.96, p<0.001) followed by Krenning Score (AUC 0.85, p<0.001) and M/L ratio (AUC 0.82, p<0.001).The best cut-off value for ASP was <5.12 (sensitivity and specificity, 90% and 93%).


ASP of somatostatin expression in pretherapeutic SPECT/CT seems to be a helpful parameter to predict response to PRRT on a lesion basis in patients with metastatic NEN.

  • Poster
    54. Jahrestagung der Deutschen Gesellschaft für Nuklearmedizin, 21.-23.04.2016, Dresden, Deutschland

Publ.-Id: 23550

Novel radioligands for cyclic nucleotide phosphodiesterase imaging with positron emission tomography: An update on developments since 2012

Schröder, S.; Wenzel, B.; Deuther-Conrad, W.; Scheunemann, M.; Brust, P.

Cyclic nucleotide phosphodiesterases (PDEs) are a class of intracellular enzymes that inactivate the secondary messenger molecules, cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Thus, PDEs regulate the signaling cascades mediated by these cyclic nucleotides and affect fundamental intracellular processes. Pharmacological inhibition of PDE activity is a promising strategy for treatment of several diseases. However, the role of the different PDEs in related pathologies is not completely clarified yet. PDE-specific radioligands enable non-invasive visualization and quantification of these enzymes by positron emission tomography (PET) in vivo and provide an important translational tool for elucidation of the relationship between altered expression of PDEs and pathophysiological effects as well as (pre-)clinical evaluation of novel PDE inhibitors developed as therapeutics. Herein we present an overview of novel PDE radioligands for PET published since 2012.

Keywords: Positron emission tomography; phosphodiesterases; cyclic nucleotide signaling; PDE inhibitors; PDE radioligands; imaging


Publ.-Id: 23549

The TurbEFA Field Experiment - Measuring the Influence of a Forest Clearing on the Turbulent Wind Field

Queck, R.; Bernhofer, C.; Bienert, A.; Schlegel, F.

Abstract Forest ecosystems play an important role in the interaction between the land surface and the atmosphere. Measurements and modelling efforts have revealed significant uncertainties in state-of-the-art flux assessments due to spatial inhomogeneities in the air-flow and land surface. Here, a field experiment is used to describe the turbulent flow across a typical Central European forest clearing. A three-dimensional model of the inhomogeneous forest stand was developed using an innovative approach based on terrestrial laser-scanner technology. The comparison of the wind statistics of two measurement campaigns (5 and 12 months long) showed the spatial and temporal representativeness of the ultrasonic anemometer measurements within the canopy. An improved method for the correction of the vertical velocity enables the distinction between the instrumental offsets and the vertical winds due to the inclination of the instrument. Despite a 13 % fraction of deciduous plants within the otherwise evergreen canopy, the effects of phenological seasons on the velocity profiles were small. The data classified according to the wind speed revealed the intermittent nature of recirculating air in the clearing. Furthermore, the development of sub-canopy wind-speed maxima is explained by considering the velocity moments and the momentum equation (including measurements of the local pressure gradient). Clearings deflect the flow downward and feed the sub-canopy flow, i.e., advective fluxes, according to wind speed and, likely, clearing size, whereas local pressure gradients play an important role in the development of sub-canopy flow. The presented dataset is freely available at the project homepage.

Keywords: Forest inhomogeneity; Metström; Momentum balance; Turbulence measurements; Vegetation model


Publ.-Id: 23548

Contactless inductive flow tomography in the presence of electromagnetic brakes

Ratajczak, M.; Wondrak, T.; Martin, R.; Stefani, F.

The contactless inductive flow tomography (CIFT) is a measurement technique that reconstructs the global flow structure of an electrically conducting fluid. This works by applying a magnetic field, measuring the flow-induced perturbations of that field outside the vessel and solving the underlying inverse problem. A promising candidate for the application of CIFT is continuous casting of steel, for which online information of the mould flow could be vitally important to control the casting process with electromagnetic brakes (EMBr). We demonstrate that CIFT magnetic field measurements in the presence of EMBr's are possible in the laboratory scale using gradiometric induction coil sensors and choosing an appropriate excitation frequency.

Keywords: contactless inductive flow tomography; continuous casting of steel; gradiometric sensor; magnetic field measurement; electromagnetic brake

  • Contribution to proceedings
    10th PAMIR International Conference -- Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia
  • Lecture (Conference)
    10th PAMIR International Conference -- Fundamental and Applied MHD, 20.-24.06.2016, Cagliari, Italia

Publ.-Id: 23546

Acoustic signatures of the phases and phase transitions in Yb2Ti2O7

Bhattacharjee, S.; Erfanifam, S.; Green, E. L.; Naumann, M.; Wang, Z.; Granovsky, S.; Doerr, M.; Wosnitza, J.; Zvyagin, A. A.; Moessner, R.; Maljuk, A.; Wurmehl, S.; Büchner, S.; Zherlitsyn, S.

We report on measurements of the sound velocity and attenuation in a single crystal of the candidate quantum-spin-ice material Yb2Ti2O7 as a function of temperature and magnetic field. The acoustic modes couple to the spins magnetoelastically and, hence, carry information about the spin correlations that sheds light on the intricate magnetic phase diagram of Yb2Ti2O7 and the nature of spin dynamics in the material. Particularly, we find a pronounced thermal hysteresis in the acoustic data with a concomitant peak in the specific heat indicating a possible first-order phase transition at about 0.17 K. At low temperatures, the acoustic response to magnetic field saturates hinting at the development of magnetic order. The experimental data are consistent with a first-order phase transition from a cooperative paramagnet to a ferromagnet below T ≈ 0.17 K, as shown by fitting the data with a phenomenological mean-field theory.

Publ.-Id: 23545

Optimized small animal tumor model for the radiobiological characterization of low energy laser accelerated protons

Beyreuther, E.; Brüchner, K.; Baumann, M.; Gotz, M.; Karsch, L.; Krause, M.; Leßmann, E.; Schmidt, M.; Schürer, M.; Pawelke, J.

There is no abstract

  • Poster
    NCRO Retreat, 14.-16.04.2016, Dresden, Germany

Publ.-Id: 23544

Zinc Influence on the Formation and Properties of Pt/Mg(Zn)AlO x Catalysts Synthesized From Layered Hydroxides

Belskaya, O. B.; Stepanova, L. N.; Gulyaeva, T. I.; Erenburg, S. B.; Trubina, S. V.; Kvashnina, K.; Nizovskii, A. I.; Kalinkin, A. V.; Zaikovskii, V. I.; Bukhtiyarov, V. I.; Likholobov, V. A.

Layered double hydroxides (LDH) containing Al3+, Mg2+ and Zn2+ cations in a ratio of Zn/(Mg+Zn) = 0, 0.05, 0.1, 0.2, 0.5, 0.7 and 1.0 were synthesized. The effect of zinc content on the phase composition of LDH and on the structural parameters, textural characteristics and acid-base properties of the corresponding mixed oxides were studied. This type of supports was used to obtain non-acid platinum catalysts Pt/Mg(Zn)AlOx. The formation of supported platinum particles, their composition, dispersion and electronic state were examined by means of TPR, TEM, XPS and EXAFS. The possibility to obtain bimetallic PtZn particles, whose structure and strength of interaction with the support depend on the zinc content of the support, was demonstrated. It was found that the presence of zinc atoms in the platinum environment decreases the particle size of active metal and stabilizes platinum in the active metallic state that ensures high activity of the catalyst in dehydrogenation of propane at a selectivity for propylene above 99%.

Keywords: zinc containing layered double hydroxides; platinum catalysts; propane dehydrogenation; XPS; EXAFS


Publ.-Id: 23543

Modelling horizontal two-phase flows using generalized models

Höhne, T.; Porombka, P.

Stratified two-phase flows are relevant in many industrial applications, e.g. pipelines, horizontal heat exchangers and storage tanks. The numerical simulation of free surface flows can be performed using phase-averaged multi-fluid models, like the homogeneous and the two-fluid approaches, or non-phase-averaged variants. The approach shown in this paper within the two-fluid framework is the Algebraic Interfacial Area Density (AIAD) model. It allows the macroscopic blending between different models for the calculation of the interfacial area density and improved models for momentum transfer in dependence on local morphology. A further step of improvement of modelling the turbulence is the consideration of sub-grid wave turbulence (SWT) that means waves created by Kelvin-Helmholtz instabilities that are smaller than the grid size. A first CFD validation of the approach is performed by means of experimental data of horizontal adiabatic stratified flow from the HAWAC and WENKA facilities. More verification and validation of the approach is necessary – more CFD grade experimental data are required for the validation.


Publ.-Id: 23542

Validation of turbulence parameters at the interface of horizontal multiphase flows

Höhne, T.

Stratified two-phase flows are relevant in many industrial applications, e.g. pipelines, horizontal heat exchangers and storage tanks. The numerical simulation of free surface flows can be performed using phase-averaged multi-fluid models, like the homogeneous and the two-fluid approaches, or non-phase-averaged variants. The approach shown in this paper within the two-fluid framework is the Algebraic Interfacial Area Density (AIAD) model. It allows the macroscopic blending between different models for the calculation of the interfacial area density and improved models for momentum transfer in dependence on local morphology. A further step of improvement of modelling the turbulence was the consideration of sub-grid wave turbulence (SWT) that means waves created by Kelvin-Helmholtz instabilities that are smaller than the grid size. A first CFD validation of the approach was done for an adiabatic case of the HAWAC channel. More verification and validation of the approach is necessary – more CFD grade experimental data are required for the validation.

Keywords: Multiphase flow; AIAD; CFD; HAWAC

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

Publ.-Id: 23541

IAEA CRP benchmark of ROCOM BORON DILUTION and PTS test cases for the use of CFD in reactor design

Höhne, T.; Kliem, S.

Over the last 15 years, considerable effort has been expended in assembling the available information on the use of CFD in the nuclear reactor safety field. Typical application areas here are heterogeneous mixing and heat transfer in complex geometries, buoyancy-induced natural and mixed convection, etc., with specific reference to NRS accident scenarios such as Pressurized Thermal Shock (PTS), boron dilution, hydrogen build-up in containments, thermal fatigue and thermal striping issues, etc.
The nuclear industry now also recognizes that CFD codes have reached the desired level of maturity for them to be used as part of the NPP design process, and it is the objective of a IAEA CRP to assess the current capabilities of such codes in this regard, and contribute to the technology advance in respect to their verification and validation. The development, verification and validation of CFD codes in respect to NPP design necessitates further work on the complex physical modelling processes involved, and on the development of efficient numerical schemes needed to solve the basic equations.
Therefore, two sets of ROCOM CFD-grade test data were made available to set up an IAEA benchmark, relating to boron dilution (pump start-up) and Pressurized Thermal Shock (PTS) scenarios. The first experiment deals with boron dilution scenarios during start-up of the first coolant pump. The second benchmark deals with the injection of the relatively cold Emergency Core Cooling (ECC) water which can induce buoyancy-driven stratification
The Benchmark activities will help to analyse the CFD code capabilities for CFD in nuclear reactor design applications.

Keywords: CFD; ROCOM; IAEA

  • Contribution to proceedings
    Computational Fluid Dynamics for Nuclear Reactor Safety Applications - CFD4NRS-6, 13.-15.09.2016, Cambrigde, USA
  • Lecture (Conference)
    Computational Fluid Dynamics for Nuclear Reactor Safety Applications - CFD4NRS-6, 13.-15.09.2016, Cambrigde, USA

Publ.-Id: 23540

Multimodal Somatostatin Receptor Theranostics Using [64Cu]Cu-/[177Lu]Lu-DOTA-(Tyr3)octreotate and AN-238 in a Mouse Pheochromocytoma Model.

Ullrich, M.; Bergmann, R.; Peitzsch, M.; Zenker, E.; Cartellieri, M.; Bachmann, M.; Ehrhart-Bornstein, M.; Block, N.; Schally, A.; Eisenhofer, G.; Bornstein, S.; Pietzsch, J.; Ziegler, C.

Pheochromocytomas and extra-adrenal paragangliomas (PHEO/PGLs) are rare catecholamine-producing chromaffin cell tumors. For metastatic disease, no effective therapy is available. Overexpression of somatostatin type 2 receptors (SSTR2) in PHEO/PGLs promotes interest in applying therapies using somatostatin analogs linked to radionuclides and/or cytotoxic compounds, such as [(177)Lu]Lu-DOTA-(Tyr(3))octreotate (DOTATATE) and AN-238. Systematic evaluation of such therapies for the treatment of PHEO/PGLs requires sophisticated animal models. In this study, the mouse pheochromocytoma (MPC)-mCherry allograft model showed high tumor densities of murine SSTR2 (mSSTR2) and high tumor uptake of [(64)Cu]Cu-DOTATATE. Using tumor sections, we assessed mSSTR2-specific binding of DOTATATE, AN-238, and somatostatin-14. Therapeutic studies showed substantial reduction of tumor growth and tumor-related renal monoamine excretion in tumor-bearing mice after treatment with [(177)Lu]Lu-DOTATATE compared to AN-238 and doxorubicin. Analyses did not show agonist-dependent receptor downregulation after single mSSTR2-targeting therapies. This study demonstrates that the MPC-mCherry model is a uniquely powerful tool for the preclinical evaluation of SSTR2-targeting theranostic applications in vivo. Our findings highlight the therapeutic potential of somatostatin analogs, especially of [(177)Lu]Lu-DOTATATE, for the treatment of metastatic PHEO/PGLs. Repeated treatment cycles, fractionated combinations of SSTR2-targeting radionuclide and cytotoxic therapies, and other adjuvant compounds addressing additional mechanisms may further enhance therapeutic outcome.

Keywords: neuroendocrine tumors; catecholamines; DOTATATE; PET; SPECT; optical in vivo imaging; doxorubicin

Publ.-Id: 23539

First-in-man incorporation dosimetry of (S)-(-)-[18F]fluspidine

Sattler, B.; Kranz, M.; Wuest, N.; Patt, M.; Meyer, P.; Deuther-Conrad, W.; Fischer, S.; Wuensch, B.; Brust, P.; Sabri, O.

Objectives: (S)-(-)-[18F]fluspidine has been pre-clinically proven to be a distinctive radioligand for imaging 1-receptors with PET [1]. In this study, the biokinetics was studied first in man. To assess the radiation risk, the biodistribution, organ doses (OD) and the effective dose (ED) were determined.
Methods: Whole body dosimetry was performed in 4 healthy volunteers (2m, 2f; age: 22.5±2.7y weight: 62.5±8.4.5kg). They were sequentially PET/CT-imaged up to 7h post i.v. injection of 264±17 MBq, 8 bed positions (BP) per frame, 1.5 to 6 min/BP, followed by CT-attenuation correction and iterative reconstruction. All micturated urine was collected up to 7 hours post injection. Urine was weighed and samples measured for radioactivity concentration [Bq/ccm] in a well counter. All relevant organs were defined by volumes of interest. Exponential curves were fitted to the time-activity-data (%ID/organ). The ODs were calculated using the stylized adult male model as implemented in OLINDA v1. The ED was calculated using tissue weighting factors as published in ICRP60 and 103.
Results: The highest OD [µSv/MBq] was received by the liver (76.0±17.7), the gall bladder wall (60.7±10.6) and the small intestine (56.9±10.6). The highest contribution to the ED [µSv/MBq] was by the stomach wall (3.8±0.4), the lungs (3.4±0.3) and the liver (3.0±0.4). The conversion factor [µSv/MBq] to estimate the ED to humans is 22.1±1.3 (ICRP60) and 21.0±1.3 (ICRP103), respectively.
Conclusions: The effective dose was calculated to be 6.3 mSv/300MBq. This is in the order of magnitude as for other 18F-labeled PET-compounds. The results provide a rationale for further clinical study phases and the development of this tracer as a clinical tool for PET imaging 1-receptors.
[1] Brust P, Deuther-Conrad W, Becker G, Patt M, Donat CK, Stittsworth S, Fischer S, Hiller A, Wenzel B, Dukic-Stefanovic S, Hesse S, Steinbach J, Wunsch B, Lever SZ, and Sabri O (2014) Distinctive in vivo kinetics of the new sigma1 receptor ligands (R)-(+)- and (S)-(-)-18F-fluspidine in porcine brain. J Nucl Med 55[10], 1730-1736.

  • Poster
    Annual Meeting of the Society of Nuclear Medicine, 10.-15.06.2016, San Diego, USA
  • Abstract in refereed journal
    Journal of Nuclear Medicine 57(2016)2, 10P

Publ.-Id: 23538

Gender differences in color processing in mice as revealed with functional PET

Kranz, M.; Njemanze, P.; Amend, M.; Wehrl, H.; Brust, P.

OBJECTIVES: Color processing is a central component of mammalian vision. Noninvasive functional transcranial Doppler ultrasound has recently revealed gender-related differences of color processing which include right hemisphere pattern for Blue/Yellow chromatic opponency by men while a left hemisphere pattern was found for women. In the present study, 18F-FDG was used to investigate a similar paradigm in mice with functional PET.
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. A gelatin-(Wratten)-filters-containing chromatoscope was specially designed for that purpose. Subsequently a whole body T1 weighted MR (gradient echo sequence) was performed for anatomical orientation. 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: Male mice have significantly higher SUV 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 left (Table). In male mice, the change in SUV was responsive to Blue/Yellow pairs, while in female mice, the response was only to Blue. In male mice, the SUV was highest during Blue stimulation in the left visual cortex through the right eye compared to right visual cortex. Similarly, the SUV was highest during Yellow stimulation in the left visual cortex through the right eye compared to the right visual cortex. Conversely, in female mice, the SUV was highest during Blue stimulation in the right visual cortex through the left eye compared to left visual cortex (Figure). In female mice, there was no change during stimulation with Yellow.
CONCLUSION: The observation in mice is opposite to that in humans where right hemisphere cognitive style for Blue/Yellow opponency was found in men, but a left hemisphere style in women. It is postulated, that the ontogenetic and phylogenetic evolutionary trends for cerebral dominance for color underwent a change during mammalian evolution to humans, perhaps related to left hemisphere dominance for language in most subjects.

  • Poster
    Annual Meeting of the Society of Nuclear Medicine, 10.-15.06.2016, San Diego, USA
  • Abstract in refereed journal
    Journal of Nuclear Medicine 57(2016)2, 141P

Publ.-Id: 23537

Preclinical PET/MR: Defining novel roles for phosphodiesterase 10A in brain and brown adipose tissue (BAT) in the regulation of energy homeostasis

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

OBJECTIVES: Phosphodiesterase type 10A (PDE10A) is highly enriched in the striatum and a potential therapeutic target for brain diseases. It is suggested that PDE10A is also involved in the regulation of food intake. By using the novel selective radioligand 18F-AQ28A [1] we evaluated expression of PDE10A in brain and BAT of lean, diet-induced (DIO) and genetically obese mice. As BAT activation could be visualized by using small animal PET/MR using 18F-FDG [2], we also assessed whether inhibition of PDE10A modulates BAT activity.
METHODS: Female CD1 and C57BL/6 mice were studied with either 18F-AQ28A or 18F-FDG. After anesthesia (1.8% isoflurane in 60%O2/40% air) and i.v injection of the tracer, a 1 h PET/MR scan was done for all groups. After image coregistration volumes of interest were created for striatum, hypothalamus, interscapular BAT and skeletal muscle. The selectivity of 18F-AQ28A towards PDE10A was proven by baseline (n=3) and blocking (n=3) experiments with the PDE10A inhibitor MP-10. DIO in CD1 mice was achieved by 16 weeks free access to a high-fat, high-sugar diet. Leptin-deficient ob/ob C57BL/6 mice (n=5) were used as a genetic model of obesity. The first set of CD1 mice (n=10) was divided into lean (n=5) and DIO (n=5) and received 18F-AQ28A. A second group (n=10) of lean CD1 mice were fasted and housed overnight under thermoneutral conditions and received either i.p. injection of MP-10 (n=5) or vehicle (n=5) followed 30 min later by i.v. injection of FDG. After a recovery period, the second group received either an i.p. injection of MP-10 (n=5) or vehicle (n=5) and 2 h later were sacrificed and BAT, hypothalamus and striatum were collected. Relative mRNA expression of PDE10A and thermoregulatory genes in BAT and neuropeptides in striatum and hypothalamus as well as the indirect neuronal activity marker Fos were analyzed by real-time quantitative PCR.
RESULTS: Blocking with MP-10 showed selectivity of 18F-AQ28A towards PDE10A (SUV15min striatum blocking/baseline: 0.54±0.08/1.02±0.19; p<0.01). A 7-fold higher mRNA expression of PDE10A in striatum compared to hypothalamus was found (p<0.001). In lean mice, 18F-AQ28A showed selective symmetrical accumulation in BAT (SUV55min: 0.44±0.04) with low uptake in the adjacent skeletal muscle (SUV55min: 0.20±0.02; p<0.01). Higher PDE10A levels (p<0.05) in striatum and BAT were found for DIO (SUV15min:1.36±0.10 / SUV55min:0.82±0.08) and for ob/ob mice (SUV15min:1.91±0.08 / SUV55min:0.77±0.04) compared to normal weight mice. 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) and an increase in Pgc1alpha (2-fold), Ucp1 (1.6-fold) and Cidea (1.6-fold) mRNA expression (p<0.01, p<0.05 and p<0.05, respectively) was found. In striatum, acute administration of MP-10 increased expression of Fos (4-fold) and preproenkephalin (2.9-fold) (p<0.0001 and p<0.05 respectively) whereas in hypothalamus there were no changes in gene expression found.
CONCLUSION: A novel thermoregulatory role for PDE10A was demonstrated and related to obesity. PDE10A selectively regulates gene expression in striatum. The data suggest that PDE10A inhibitors offer the potential to treat obesity by increasing thermogenesis and reducing hedonic feeding through recruiting BAT and striatal circuits.

  • Lecture (Conference)
    Annual Meeting of the Society of Nuclear Medicine 2016, 11.-15.06.2016, San Diego, USA
  • Abstract in refereed journal
    Journal of Nuclear Medicine 57(2016)2, 200P

Publ.-Id: 23536

Varying Chirality Across Nicotinic Acetylcholine Receptor Subtypes: Selective Binding of Quinuclidine Triazole Compounds

Sarasamkan, J.; Scheunemann, M.; Apaijai, N.; Palee, S.; Parichatikanond, W.; Arunrungvichian, K.; Fischer, S.; Chattipakorn, S.; Deuther-Conrad, W.; Schüürmann, G.; Brust, P.; Vajragupta, O.

The novel quinuclidine anti-1,2,3-triazole derivatives T1-T6 were designed based on the structure of QND8. The binding studies revealed that the stereochemistry at the C3 position of the quinuclidine scaffold plays an important role in the nAChR subtype selectivity. Whereas the (R)-enantiomers are selective to α7 over α4β2 (by factors of 44-225) and to a smaller degree over α3β4 (3-33), their (S)-counterparts prefer α3β4 over α4β2 (62-237) as well as over α7 (5-294). The (R)-derivatives were highly selective to α7 over α3β4 subtypes compared to (RS)- and (R)-QND8. The (S)-enantiomers are 5−10 times more selective to α4β2 than their (R) forms. The overall strongest affinity is observed for the (S)-enantiomer binding to α3β4 (Ki, 2.25-19.5 nM) followed by their (R)-counterpart binding to α7 (Ki, 22.5-117 nM), with a significantly weaker (S)-enantiomer binding to α4β2 (Ki, 414-1980 nM) still above the very weak respective (R)-analogue affinity (Ki, 5059-10436 nM).

Keywords: Nicotinic acetylcholine receptor; positron emission tomography; quinuclidine anti-1; 2; 3-triazole; click chemistry

Publ.-Id: 23535

Prediction and compensation of magnetic beam deflection in MR-integrated proton therapy: A method optimized regarding accuracy, versatility and speed

Schellhammer, S. M.; Hoffmann, A. L.

The integration of magnetic resonance imaging (MRI) and proton therapy for on-line image-guidance is expected to reduce dose delivery uncertainties during treatment. However, the proton beam experiences a Lorentz force induced deflection inside the magnetic field of the MRI scanner, and several methods have been proposed to quantify this effect. We analyze their structural differences and compare results of both analytical and Monte Carlo models. We find that existing analytical models are limited in accuracy and applicability due to critical approximations, especially including the assumption of a uniform magnetic field. As Monte Carlo simulations are too time-consuming for routine treatment planning optimization and on-line plan adaption, we introduce a new method to quantify and correct for the beam deflection, which is optimized regarding accuracy, versatility and speed. We use it to predict the trajectory of a mono-energetic proton beam of energy E 0 traversing a water phantom behind an air gap within an omnipresent uniform transverse magnetic flux density B 0. The magnetic field induced dislocation of the Bragg peak is calculated as function of E 0 and B 0 and compared to results obtained with existing analytical and Monte Carlo methods. The deviation from the Bragg peak position predicted by Monte Carlo simulations is smaller for the new model than for the analytical models by up to 2 cm. The model is faster than Monte Carlo methods, less assumptive than the analytical models and applicable to realistic magnetic fields. To compensate for the Bragg peak dislocation, a numerical optimization strategy is introduced and evaluated. It includes an adjustment of both the proton beam entrance angle and the energy of up to 25° and 5 MeV, depending on E 0 and B 0. This strategy is shown to effectively reposition the BP to its intended location in the presence of a magnetic field.

Keywords: proton therapy; image-guided radiotherapy; IGPT; magnetic resonance imaging; MR guidance; beam trajectory prediction


Publ.-Id: 23534

The strange implications of electron-electron scattering in graphene

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

Electron-electron scattering in graphene gives rise to some unexpected behavior in the electron dynamics, as observed by pump-probe measurements.
When excited with a near-infrared femtosecond laser pulse, the pump-probe signal depends on the angle between the linear polarization of the pump and the probe pulse, which is due to preferential excitation of electrons perpendicular to the laser electric field. This indicates an anisotropic distribution function in momentum space that is preserved by electron-electron scattering, since it mainly occurs collinearly along the Dirac cone. Only after 150 fs the distribution function is rendered isotropic through optical-phonon scattering. The effect is even more pronounced when exciting at small photon energies (88 meV), below the optical-phonon energy: In this case the anisotropic distribution function survives for as long as 5 ps, when it is finally thermalized by non-collinear Coulomb scattering. These results challenge the common view of ultrafast thermalization by electron-electron scattering.
When a magnetic field is applied to graphene, Landau levels are formed that can be selectively excited by circular-polarized radiation. In a pump-probe experiment, exciting and probing all possible transitions between the n=-1, n=0 and n=+1 Landau levels in slightly n-type graphene, we observe an unexpected sign reversal of the n=0 →1 probe signal when pumping the -1→0 transition. This directly reflects the fact that the n=0 Landau level is depleted by electron-electron Auger-type scattering, even though it is optically pumped at the same time.
Both effects can be quantitatively reproduced by a microscopic calculation based on the graphene Bloch equations, and shed new light on the possibility of infrared and THz devices based on hot carriers in graphene.

Keywords: graphene; pump-probe; free-electron laser; Landau levels

Related publications

  • Invited lecture (Conferences)
    International Conference on Terahertz Emission, Metamaterials and Nanophotonics (TERAMETANANO 2016), 03.-10.04.2016, Cartagena, Colombia

Publ.-Id: 23533

Prompt γ-ray based proton range verification: From experiments to clinical application

Priegnitz, M.; Nenoff, L.; Barczyk, S.; Golnik, C.; Hotoiu, L.; Keitz, I.; Smeets, J.; Trezza, A.; Vander Stappen, F.; Werner, T.; Fiedler, F.; Prieels, D.; Baumann, M.; Enghardt, W.; Pausch, G.; Richter, C.

no abstract available

  • Poster
    National Center for Radiation Oncology 2nd Scientific Retreat, 14.-16.04.2016, Dresden, Deutschland

Publ.-Id: 23531

Comparison of in silico, electrochemical, in vitro and in vivo metabolism of a homologous series of (radio)fluorinated sigma1 receptor ligands designed for positron emission tomography

Wiese, C.; Große Maestrup, E.; Galla, F.; Schepmann, D.; Hiller, A.; Fischer, S.; Ludwig, F. A.; Deuther-Conrad, W.; Donat, C. K.; Brust, P.; Büter, L.; Karst, U.; Wünsch, B.

The imaging of σ1 receptors in the brain by fluorinated radiotracers will be used for the validation of σ1 receptors as drug targets as well as for differential diagnosis of diseases in the central nervous system. The biotransformation of four homologous fluorinated PET tracers 1′-benzyl-3-(ω-fluoromethyl to ω-fluorobutyl)-3H-spiro[2]benzofuran-1,4′-piperidine] ([18F]1–4) was investigated. In silico studies using fast metabolizer (FAME) software, electrochemical oxidations, in vitro studies with rat liver microsomes, and in vivo metabolism studies after application of the PET tracers [18F]1–4 to mice were performed. Combined liquid chromatography and mass spectrometry (HPLC–MS) analysis allowed structural identification of non-radioactive metabolites. Radio-HPLC and radio-TLC provided information about the presence of unchanged parent radiotracers and their radiometabolites. Radiometabolites were not found in the brain after application of [18F]2–4, but liver, plasma, and urine samples contained several radiometabolites. Less than 2 % of the injected dose of [18F]4 reached the brain, rendering [18F]4 less appropriate as a PET tracer than [18F]2 and [18F]3. Compounds [18F]2 and [18F]3 possess the most promising properties for imaging of σ1 receptors in the brain. High σ1 affinity (Ki=0.59 nm), low lipophilicity (logD7.4=2.57), high brain penetration (4.6 % of injected dose after 30 min), and the absence of radiometabolites in the brain favor the fluoroethyl derivative [18F]2 slightly over the fluoropropyl derivative [18F]3 for human use.

Keywords: Homologous fluorinated sigma1 receptor ligands; positron emission tomography; biotransformation; electrochemical oxidation; rat liver microsomes; in vivo metabolism

Publ.-Id: 23530

Beta-Amyloid-PET-Bildgebung des Gehirns - DGN-Handlungsempfehlung

Barthel, H.; Meyer, P. T.; Drzezga, A.; Bartenstein, P.; Boecker, H.; Brust, P.; Buchert, R.; Coenen, H. H.; Fougère, C. L.; Gründer, G.; Grünwald, F.; Krause, B. J.; Kuwert, T.; Schreckenberger, M.; Tatsch, K.; Langen, K. J.; Sabri, O.

Seit Kurzem sind mehrere Radiopharmaka für die klinische Positronen-Emissions-Tomographie (PET) von mit der Alzheimer-Krankheit assoziierten zerebralen beta-Amyloid(Aß-Plaques zugelassen. Mit der zunehmenden Verbreitung dieser Methode entsteht der Bedarf für entsprechende Handlungsanweisungen. Diese S1-Leitlinie der Deutschen Gesellschaft für Nuklearmedizin beschreibt die adäquate Vorgehensweise bei der Aß-Plaque-PET-Bildgebung. Maßnahmen zur Patientenvorbereitung, zur Anamnese-Erhebung und zu Vorsichtsmaßnahmen werden ebenso vorgestellt wie die betreffenden Radiopharmaka, Maßnahmen zur PET-Daten-Gewinnung, -Verarbeitung, -Analyse und -Befundung. Damit soll ein Beitrag zur Qualitätssicherung in der Nuklearmedizin in Deutschland geleistet werden.

Keywords: beta-Amyloid; Plaques; Positronen-Emissions-Tomographie; PET; Leitlinie

Publ.-Id: 23529

Rational Structure-Based Rescaffolding Approach to de Novo Design of Interleukin 10 (IL-10) Receptor-1 Mimetics

Ruiz-Gómez, G.; Hawkins, J. C.; Philipp, J.; Künze, G.; Wodtke, R.; Löser, R.; Fahmy, K.; Pisabarro, M. T.

Tackling protein interfaces with small molecules capable of modulating protein-protein interactions remains a challenge in structure-based ligand design. Particularly arduous are cases in which the epitopes involved in molecular recognition have a non-structured and discontinuous nature. Here, the basic strategy of translating continuous binding epitopes into mimetic scaffolds cannot be applied, and other innovative approaches are therefore required. We present a structure-based rational approach involving the use of a novel customized PROSITE-based regular expression syntax to define minimal descriptors of geometric and functional constraints signifying relevant unctionalities for recognition in protein interfaces of non-continuous and unstructured nature. These descriptors feed a search engine that explores the currently available three-dimensional chemical space of the Protein Data Bank (PDB) in order to identify in a straightforward manner regular architectures containing the desired functionalities, which could be used as templates to guide the rational design of small natural-like scaffolds mimicking the targeted recognition site. The application of this rescaffolding strategy to the discovery of natural scaffolds incorporating a selection of functionalities of interleukin-10 receptor-1 (IL-10R1), which are relevant for its interaction with nterleukin-10 (IL-10) has resulted in the de novo design of a new class of potent IL-10 peptidomimetic ligands.

Keywords: de novo design; peptidomimetics; IL-10 receptor mimetic; 3D functional descriptors; proteinprotein interactions

Publ.-Id: 23528

Liquid velocity determination using thermal anemometry in two-phase flows: new developments

Neumann, M.; Bieberle, A.; Hampel, U.

This article is intended to give an overview of novel approaches to apply thermal anemometry measuring technique for the determination of gas and liquid velocities in two-phase flows, which are currently being pursued at Helmholtz-Zentrum Dresden-Rossendorf. Thermal anemometers are commonly used for determination of local fluid velocities within single phase flows. Because of their high temporal resolution they are also capable of determining velocity fluctuations, as they are common in highly turbulent flows in technical applications and devices. These experimental data are, amongst others, required for validation and development of CFD codes. However, since turbulent two-phase flows (e.g. bubbly flows) are predominant in technical applications, the application of thermal anemometers is highly desired there as well. But, interpretation of those measurement signals is rather complex, since they contain information of both phases, e.g. liquid and gas respectively. To overcome these difficulties, application-oriented adoptions of this measurement technique have to be made. The here presented approaches comprise sophisticated design modifications of the probe itself as well as a novel operation mode. It is intended to utilize such a probe especially for the velocity measurement of the liquid phase in two-phase flows within complex geometries at high temporal resolution.

Keywords: Thermal anemometry; two-phase flow

  • Contribution to proceedings
    Specialists Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics (SWINTH) 2016, 15.-17.06.2016, Livorno, Italia
    Liquid velocity determination using thermal anemometry in two-phase flows: new developments, Pisa, Italy: Grafiche Caroti, 978-88-902391-9-9, 3-73
  • Lecture (Conference)
    Specialists Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics (SWINTH) 2016, 15.-17.06.2016, Livorno, Italia

Publ.-Id: 23527

Production and purification of no-carrier-added 139Ce at the Leipzig cyclotron CYCLONE® 18/9

Mansel, A.; Franke, K.

The global demand for the lanthanides has dramatically increased. Therefore, a detailed understanding of ore chemistry and separation methods is needed. To study these processes, the use of the radiotracer technique is a marvellous method to observe the chemical behaviour of such elements. 139Ce (T1/2 = 137.6 d, Eγ = 166 keV, Iγ = 80%) was chosen as a representative element (radionuclide) for the lanthanide elements. We produced 139Ce using the nuclear reaction 139La(p,n)139Ce by means of irradiation of a few tens mg [natLa]La2O3 at the Leipzig cyclotron CYCLONE® 18/9[1]. At an irradiation time of 3 h, an effective proton current of 2.9 µA and a maximal proton energy of 12.5 MeV, an activity of ~0.5 MBq 139Ce was achieved. The irradiated La2O3 was dissolved in conc. nitric acid and fumed to dryness. For the separation of the radionuclide from the target material, we used the tetravalent oxidation state of cerium by means of an oxidative application with a mixture of dichromate/sulfate in 9 M nitric acid. For the first time, UTEVA® Resin was used to separate the tetravalent cerium (Ce4+) in no-carrier-added (n.c.a.) form from the trivalent lanthanum (La3+) by ion exchange chromatography in column technique, as used for plutonium (Pu4+) separations from trivalent actinides (e.g. Am3+)[2]. The 139Ce4+ ions were washed from the column by 1 mM nitric acid. After evaporation of the combined cerium fractions, the 139Ce was dissolved in 1 mM nitric acid to give a stock solution with an activity concentration of ~1 MBq/ml. The radiochemical yield of n.c.a. 139Ce was 94% ± 5%. With a detection limit of 10 Bq/ml, a concentration range down to ~0.3 pmol/l n.c.a. 139Ce can be achieved. From the dissolution of the irradiated target until preparation of the stock solution, only 5 h are necessary. The chemical purity of the stock solution was evaluated by ICP-MS.
By a weekly in-house production of n.c.a. 139Ce, we can use this radionuclide in our institute (or cooperation partners) for actual studies in liquid-liquid extraction by means of calixarenes or radiolabelling of CeO2-nanoparticles.
[1] C. Vermeulen et al. (2007) Nucl. Instr. Meth. B 255, 331. [2] E. P. Horwitz et al. (1992) Anal. Chim. Acta 266, 25.

Keywords: Lanthanides; No-carrier-added Cerium-139; Proton induced nuclear reaction; Radiochemical separation; UTEVA® Resin

  • Poster
    9th International Conference on Nuclear and Radiochemistry NRC9, 29.08.-02.09.2016, Helsinki, Finland

Publ.-Id: 23526

Two-Phase Flow Studies in Complex Geometries

Neumann, M.; Bieberle, A.; Hampel, U.

In many industrial applications, two-phase flows are predominant and consist often of a liquid and a gaseous phase. Especially in nuclear power plants, those multiphase flow regimes are heavily linked to safety related issues, e.g. behavior of vapor phase in BWRs, nucleate boiling at fuel rods or steam generator tubes as well as loss of coolant accident. One approach for the safety evaluation of nuclear facilities and the prediction of hazardous conditions is the utilization of numerical models and CFD tools. Unfortunately, these methods still need a high number of empirical correlations as closure models up to now, which makes a safe prediction nearly impossible.
Additionally, most of the components in industrial applications provide complex geometries, which create pronounced three-dimensional flow phenomena, e.g. in bends, valves, junctions or heat exchangers. Especially the numerical description of those two-phase flow fields is a challenging task, which requires further experimental data for the development and validation of existing models. At the Helmholtz-Zentrum Dresden - Rossendorf (HZDR) studies in a vertical pipe have already been performed [1]–[3]. In these studies, a movable obstacle was used to create three-dimensional flow phenomena, which was analyzed applying wire-mesh sensor technique. Both, the motion unit of the obstacle and the wire-mesh sensor were thereby located in the flow channel, disturbing the flow field. Furthermore, the wire-mesh sensor only provided single-plane measurements.
In this contribution, continued two-phase flow studies will be described using the ultrafast electron beam X-ray scanner ROFEX to additionally measure hydrodynamic parameters of the flow field around new designed obstacles contactless.

  • Contribution to proceedings
    47th Annular Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
  • Lecture (Conference)
    47th Annular Meeting on Nuclear Technology, 12.05.2016, Hamburg, Deutschland

Publ.-Id: 23525

A pilot study to use the 36Cl bomb peak as a tracer for groundwater flow velocities in the Western Dead Sea catchment

Wilske, C.; Suckow, A.; Roediger, T.; Geyer, S.; Weise, S. M.; Merchel, S.; Rugel, G.; Pavetich, S.; Merkel, B. J.; Siebert, C.

The aquifer system of the western Dead Sea catchment is stressed by semi-arid to arid climate conditions, limited groundwater recharge rates and increasing water abstractions for human water needs. The groundwater flow system is dominated by two main Cretaceous limestone aquifers with karst characteristics and discharging in springs in the Lower Jordan Valley and Dead Sea region. The karst properties give reason to assume parts of the flow system having high transmissivities and groundwater flow velocities, respectively. For estimating recharge rates and rain water infiltration time periods, 36Cl and 3H were used, with the anthropogenic bomb peaks as input functions.
The chloride content in groundwater of the limestone aquifers enriches after contact with the saline Quaternary sediments and groundwater in the Lower Jordan Valley. The 36Cl/Cl ratios in groundwater were found to be up to 1E-12 in the recharge area and decrease to 1E-14 in the discharge area. Groundwaters in the recharge area show partly 36Cl/Cl ratios comparable to those in recent precipitation. The wide range of 36Cl/Cl in the recharge area indicates different stages of chlorine isotope and elemental mixing within the recharge area or aquifer system. This may be due to varying Cl input (dependent on altitude and coastal proximity), varying 36Cl input (regional variation in fallout) or both. Together with 3H analyses it is possible to evaluate the recent rain water component in the springs emerging from the uppermost part of the Cretaceous aquifers.
Our results show that a combination of the 36Cl/Cl and 3H measurements in groundwater and a correlation to the atmospheric input curves of 36Cl/Cl and 3H allow estimating the admixture of post-bomb recharge in groundwater.

Keywords: 36Cl/Cl; tritium; groundwater age dating; Western Dead Sea catchment; AMS

Related publications

  • Lecture (Conference)
    43rd IAH International Congress “Groundwater and society: 60 years of IAH”, 25.-29.09.2016, le Corum , Montpellier, France


Publ.-Id: 23523

Bestimmung langlebiger Radionuklide mittels Beschleunigermassenspektrometrie (AMS): Applikationen und metrologische Aspekte

Merchel, S.

Die Bestimmung langlebiger Radionuklide (t1/2 = ~ka bis Ma) profitierte maßgeblich in den letzten Jahrzehnten von den technischen Entwicklungen auf dem Gebiet der hochsensitiven Beschleunigermassenspektrometrie (accelerator mass spectrometry, AMS). Die AMS besitzt gegenüber der konventionellen Massenspektrometrie den Vorteil, dass sie Störsignale, hervorgerufen von Molekülionen oder Isobaren, effektiver unterdrücken kann. Typische Nachweisgrenzen liegen im Bereich von 10-15 (Radionuklid/stabiles Nuklid) bzw. 105 Radionuklidatome oder 10-9 Bq.
Die Anwendungsfelder der Methode haben sich stark ausgeweitet: Die anfänglich bevorzugt untersuchten Proben aus der Kosmochemie, der Astrophysik und den Kernreaktionsdaten, werden zunehmend von Proben aus den Bereichen Strahlenschutz, Nuklearsicherheit, Nuklearentsorgung, Radioökologie, Phytologie, Ernährungswissenschaften, Toxikologie und Pharmakologie verdrängt. Die größte Bedeutung der angewandten AMS-Forschung liegt allerdings in den Geo- und Umweltwissenschaften. So können mit den kosmogen „in-situ“ produzierten Nukliden 10Be, 26Al und 36Cl relativ plötzlich auftretende prähistorische Ereignisse wie Vulkanausbrüche, Bergstürze, Tsunamis, Meteoriteneinschläge, Erdbeben und Gletscherbewegungen datiert werden. Anhand dieser Gletscherbewegungen und Untersuchungen an Eisbohrkernen können zudem Klimaveränderungen rekonstruiert werden.
Die Qualitätssicherung in der AMS (mit Ausnahme von 14C/12C) ist ein wichtiger, aber bisher leider vernachlässigter Aspekt. Wenige Ringversuche mit desaströsen Ergebnissen und das fast komplette Fehlen primärer Referenzmaterialien (mit Ausnahme von 41Ca/Ca) zeigen, dass die AMS zwar extrem nachweisempfindlich und oft auch präzise ist, aber momentan leider keine rückführbaren Daten liefert. Der Einsatz metrologisch rückgeführter Referenzmaterialien wäre allerdings für fast alle AMS-Applikationen wünschenswert und für wenige zwingend erforderlich.

Keywords: AMS; metrology; standard; reference material; radionuclide

Related publications

  • Invited lecture (Conferences)
    Abteilungskolloquium der Abteilung 6 „Ionisierende Strahlung“ der Physikalisch-Technischen Bundesanstalt, 31.05.2016, Braunschweig, Deutschland

Publ.-Id: 23522

Novel Biotechnological Approaches for the Recovery of Metals from Primary and Secondary Resources

Pollmann, K.; Kutschke, S.; Matys, M.; Kostudis, S.; Hopfe, S.; Raff, J.

Microorganisms have developed various mechanisms to deal with metals, thus providing numerous tools that can be used in biohydrometallurgical processes. “Biomining” processes, that includes bioleaching and biooxidation processes, facilitate the degradation of minerals accompanied by a release of metals. These processes are especially attractive for low-grade ores and are used on industrial scale mainly for sulfidic ores. In biosorption processes, biomass or certain biomolecules are used to bind and concentrate selected ions or other molecules from aqueous solutions. Biosorptive materials can be an environmentally friendly and efficient alternative to conventional methods such as ion exchange resins. Other interesting mechanisms are bioaccumulation, bioflotation, bioprecipitation, and biomineralisation. Although these processes are well known and have been studied in detail during the last decades, the recent strong progress of biotechnologies such as genetic enginnering and molecule design as well as their combination with novel developments of material sciences such as nanotechnologies facilitate new strategies for the application of biotechnologies in mineral processing. The article gives a summary of current activities in this field that are performed in our group.

Keywords: biomining; biohydrometallurgy; bioleaching; biosorption; nanomaterials

Publ.-Id: 23521

Role of Transient Reflection in Graphene Nonlinear Infrared Optics

Suess, R. J.; Winnerl, S.; Schneider, H.; Helm, M.; Berger, C.; de Heer, W. A.; Murphy, T. E.; Mittendorff, M.

Understanding the optical response of graphene at terahertz frequencies is of critical importance for designing graphene-based devices that operate in this frequency range. Here we present a terahertz pump-probe measurement that simultaneously measures both the transmitted and reflected probe radiation from multilayer epitaxial graphene, allowing for an unambiguous determination of the pump-induced absorption change in the graphene layers. The photon energy in the experiment (30 meV) is on the order of the doping level in the graphene which enables the exploration of the transition from interband to intraband processes, depending on the amount of pump-induced heating. Our findings establish the presence of a large, photoinduced reflection that contributes to the change in sign of the relative transmitted terahertz radiation, which can be purely positive or predominantly negative depending on the pump fluence, while the change in absorption is found negative at all fluences. We develop a hot carrier model that confirms the sign-reversible nature of the relative transmitted terahertz radiation through the graphene multilayer and determine that this behavior originates from either an absorption-bleached or reflection-dominated regime. The theoretical results are incorporated into a model utilizing an energy balance equation that reproduces the measured pump-probe data. These findings, which extend to mid- and far infrared frequencies, show the importance of considering reflection in graphene-light interactions and have implications for the design of future terahertz photonic components.

Keywords: Ultrafast dynamics; graphene; infrared spectroscopy; terahertz

Related publications


Publ.-Id: 23520

Surface modified ultrasmall nanoparticles as dual labelled imaging agents

Singh, G.; Licciardello, N.; Hunoldt, S.; Bergmann, R.; Faramus, A.; de Cola, L.; Stephan, H.

The development of multimodal imaging agents for biomedical applications is a growing field of research. The idea behind the use of nuclear and optical dual labelled imaging probes is the possibility to synergistically exploit the advantages of positron emission tomography (PET) and optical imaging. The use of dual imaging probes enhances sensitivity, spatial and temporal resolution, tissue penetrability and allows the simultaneous acquisition of complementary information which can improve diagnosis and treatment of diseases.
The utilization of nanomaterials in medicine holds a promising potential in emerging applications of diagnostic imaging as well as the prospect of new capabilities for delivering targeted therapies tailored for specific diseases. Due to their biocompatibility, luminescence properties and the possibility to covalently functionalize their surface, water-soluble ultrasmall (<5 nm) silicon nanoparticles (SiNPs) are excellent candidates in this perspective.(1,2)
Amine-terminated ultrasmall silicon nanoparticles were prepared according to a reported method with slight modifications.(3) Here we report the functionalization of amine-terminated SiNPs with the sulfo-cyanine 5 dye (sCy5) to obtain an optical imaging probe and with biomolecules, such as single-domain antibodies (sdAb) for active targeting of a cancer biomarker. SiNPs are also modified with radiolabel such as 64Cu, coordinated to bispidines(4), to obtain a dual, nuclear and optical, probe.
The functionalization of SiNPs with dyes, radiotracers and targeting molecules will open the path for targeted dual imaging of cancer, possibly allowing diagnosis and therapy in in vivo systems.

1) M. Rosso-Vasic et al., J. Mater. Chem. 2009, 19, 5926.
2) C. -H. Lai et al., Nano Lett. 2016, 16, 807−811.
3) Y. Zhong et al., J. Am. Chem. Soc. 2013, 135, 8350.
4) H. Stephan et al., Chem. Eur. J. 2014, 20, 17011.

Keywords: Silicon nanoparticles; Biomedical applications; Radiolabeling; Positron emission tomography; Optical imaging

  • Poster
    European Chemistry Congress, 11.-15.09.2016, Seville, Spain

Publ.-Id: 23519

Modellierung und Validierung von Feldionisation in parallelen Particle-in-Cell-Codes

Garten, M.

Die Modellierung von Feldionisation in Particle-in-Cell(PIC)-Codes ist eine wichtige Voraussetzung zur Untersuchung der Wechselwirkung hochintensiver, ultrakurzer Laserpulse mit Materie. Es existieren bereits zahlreiche Modelle, die akkurate Vorhersagen im Bereich nicht-relativistischer Intensitäten und oberhalb atomarer Zeitskalen treffen können. Weiterhin existieren auch zahlreiche PIC-Codes, die für den Einsatz auf CPUs konzipiert wurden und Feldionisation berücksichtigen. Das Ziel dieser Arbeit ist die Modellierung von Feldionisation auf neuen, hochparallelen GPU-Architekturen. Diese werden in den letzten Jahren verstärkt für wissenschaftliche Simulationen eingesetzt und bieten einen deutlichen Geschwindigkeitsvorteil gegenüber CPUs. Die Modellierung von Feldionisation auf GPGPUs birgt einige Herausforderungen und es ist das erweiterte Ziel dieser Arbeit, die Implementierung auch zu verifizieren. Dabei wird ein Einblick in die Schwierigkeiten gegeben, die bei der Anwendung existierender Ionisationsmodelle durch Einschränkungen der Modelle selbst, des PIC-Schemas sowie der Plasmadynamik zu beachten sind. In Folge dieser Arbeit wurde PIConGPU, der derzeit schnellste, vollständig relativistische Particle-in-Cell-Code der Welt, um ein allgemeines Werkzeug zur Modellierung von Ionisation erweitert. Dieses ermöglicht die Simulation neuer und spannender physikalischer Anwendungsfälle im Bereich der Laser-Plasmaphysik.

Keywords: Particle-In-Cell; field ionization; GPGPU; PIConGPU; ADK; BSI

  • Master thesis
    HZDR, TU Dresden, 2015
    Mentor: Prof. Dr. Thomas Cowan, Prof. Dr. Ulrich Schramm, Dr. Michael Bussmann
    0097 Seiten

Publ.-Id: 23518

Instrumentation for experiments on a fuel element mock-up for the study of thermal hydraulics for loss of cooling or coolant scenarios in spent fuel pools

Arlit, M.; Partmann, C.; Schleicher, E.; Schuster, C.; Hurtado, A.; Hampel, U.

After the Fukushima accident the focus in nuclear safety research has been extended to the spent fuel pool. In the consequence of a longer persisting station black out or loss of integrity of the pool, the cooling of the fuel elements can potentially not be guaranteed. Thus, the investigation of the thermal hydraulics of potential accident scenarios is of great scientific interest. The German national joint project SINABEL (SIcherheit NAsslager BrennElement-Lagerbecken) deals with the experimental investigation and the modelling of thermal hydraulics during the dry-out of a spent fuel pool in the consequence of a loss of cooling scenario. For this purpose a fuel element mock-up with electrically heated rods is constructed. During a dry-out scenario the water in the fuel element mock-up heats up to boiling temperature and evaporates. The water level decreases due to the continuing heating and the rods will be exposed to steam atmosphere. Parameters that have to be measured are the surface temperature of the rods, the height of the water level and the temperature as well as the velocity of the steam in the subchannels of the rod bundle.
The fuel element mock-up is designed according to the original dimensions of a BWR fuel element with pitch-to-diameter ratio- P/D = 1.24 and rod diameter D = 10 mm in a 10 x 10 square array. The housing consists of several metal boxes. To avoid heat sinks (adiabatic situation with no radial heat flow) the components are produced without flanges and are surrounded by a compact thermal insulation. The accessibility for instrumentation and other installations is reduced to the top side. The surface temperatures of the rods are measured by thermocouples and the water level by pressure transducers and electrical needle probes respectively.
For measuring both the temperature and the velocity of the steam in the small sub-channels no standard instrumentation is available. The applicability of established measurement techniques, such as Particle Imaging Velocimetry or Pitot tube, is not given due to constructional aspects of the test facility and the given flow properties (high temperatures, low velocities). Therefore, in this study a newly developed measurement system will be used. The experimental operating conditions are temperatures up to ϑ = 500 °C and very low local steam velocities down to v = 0.01 m/ s. Furthermore, the flow is expected to be laminar. The requirement for spatial resolution is to have one measurement point per subchannel in all subchannels of one rod bundle quadrant.
The presented solution is a thermal anemometry grid sensor TAGS, that is grid-type arrangement of special temperature-sensor elements measuring both, the temperature and the velocity nearly simultaneously. The sensitive elements are mounted on a ceramic grid-like structured substrate and connected to each other in a matrix arrangement. This sensor is connected to a special excitation and data acquisition electronics, applying the measurement technique of resistance thermometry for temperature measurement and thermal anemometry for velocity measurement. Within the paper a detailed description of the instrumentation of the fuel element mock-up in general and more specifically the TAGS are presented together with first results.

Keywords: Spent fuel pool; temperature measurement; thermal anemometry; grid sensor

  • Contribution to proceedings
    SWINTH-2016 (Specialists Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics), 15.-17.06.2016, Livorno, Italy
    Proceedings of SWINTH-2016
  • Lecture (Conference)
    SWINTH-2016 (Specialists Workshop on Advanced Instrumentation and Measurement Techniques for Nuclear Reactor Thermal Hydraulics), 15.-17.06.2016, Livorno, Italia

Publ.-Id: 23517

Thermal anemometry grid sensor for flow velocity measurement in the subchannels of a fuel element mock-up during dry-out

Arlit, M.; Schleicher, E.; Hampel, U.

For the determination of steam velocities in the subchannels of a fuel element mock-up during dry-out no suitable measurement techniques are available under the given boundary conditions of high temperatures and restricted accessibility. The newly developed thermal anemometry grid sensor closes this gap. Within the paper applied methods, technological aspects as well as a special calibration procedure for the measurement in superheated steam are presented.

Keywords: Thermal Anemometry; Grid Sensor; Temperature grid sensor

  • Contribution to proceedings
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland
    Proceedings of the 47th Annual Meeting on Nuclear Technology
  • Lecture (Conference)
    47th Annual Meeting on Nuclear Technology, 10.-12.05.2016, Hamburg, Deutschland

Publ.-Id: 23516

Investigation of the Radial Effect On the Transition Velocities in a Bubble Column Based On the Modified Shannon Entropy

Nedeltchev, S.; Hampel, U.; Schubert, M.

A new method for flow regime identification in a bubble column (0.15 m in ID) based on a modification of the Shannon entropy (SE) algorithm was developed. The bubble column was equipped with a perforated plate distributor (14 holes, Ø 4×10-3 m) and operated with an air-deionized water system at ambient conditions. The newly introduced dimensionless ratio of minimum SE to maximum SE was capable of identifying the main transition velocities at three different dimensionless radial positions (r/R): 0.0 (core), 0.63 (inversion point) and 0.88 (annulus).
In the core of the column the new parameter identified successfully three transition velocities Utrans at 0.034, 0.089 and 0.134 m/s. They mark the end of the gas maldistribution regime, the onset and the end of the churn-turbulent flow regime, respectively. Three Utrans values (at 0.045, 0.089 and 0.124 m/s) were also identified in the annulus of the column. However, the second transition velocity identified the boundary between the first and second transition sub-regimes. The third transition velocity distinguished the onset of the churn-turbulent flow regime. It was found that in the core of the column both the transition and churn-turbulent flow regimes start earlier, which is due to the earlier onset of the bubble coalescence caused by higher gas fraction in the column center.
At the inversion point of the axial liquid velocity the end of the gas maldistribution regime is shifted to a somewhat higher Utrans value (0.067 m/s). The second transition sub-regime begins at 0.101 m/s, whereas the onset of the churn-turbulent regime is identified at 0.124 m/s.
The SE algorithm was also applied to both the first and second half of the time series and the ratio of both SEs was successfully used as a flow regime identifier.

Keywords: Bubble column; Gas holdup fluctuations; Wire-mesh sensor; Transition velocities; Modified Shannon entropy

Publ.-Id: 23515

Application of X-ray absorption spectroscopy to actinide research

Scheinost, A. C.

An overview will be given on the applications of x-ray absorption spectroscopy to actinide research, including topics in nuclear waste management and development of fourth generation nuclear fuel

Keywords: XAFS; Nuclear fuel; nuclear waste disposal

Related publications

  • Invited lecture (Conferences)
    11th School on the Physics and Chemistry of the Actinides, 13.-16.03.2016, Grenoble, France

Publ.-Id: 23514

Distillation Tray Efficiency Modeling: A Forgotten Chapter

Vishwakarma, V.; Schubert, M.; Hampel, U.

Cross-flow trays are highly reputed among vapour-liquid contacting devices due to their versatility. They have been into existence for two centuries; still the estimation of their mass transfer efficiency relies mostly on experience. There have been numerous attempts in the past to understand the nature of liquid mixing and flow patterns on trays. However, very few have managed to relate their findings with tray efficiency.
The present work aims at reviewing mathematical models developed for predicting distillation tray efficiency. These models were developed by considering simplified assumptions namely plug flow, uniform vapour composition, constant froth height etc. It is needless to mention the requirement of an improved mathematical model accounting real flow scenarios. This work also attempts to encourage the fraternity of fluid separation technology to revive the efficacy of tray modeling.

Keywords: Distillation Trays; Murphree Tray Efficiency; Eddy Diffusion Model; Residence Time Distribution

  • Poster
    Jahrestreffen der ProcessNet-Fachgruppe Fluidverfahrenstechnik, 16.-17.03.2016, Garmisch-Partenkirchen, Germany

Publ.-Id: 23512

A gas cell for stopping, storing and polarizing radioactive particles

Sytema, A.; van den Berg, J. E.; Böll, O.; Chernowitz, D.; Dijck, E. A.; Grasdijk, J. O.; Hoekstra, S.; Jungmann, K.; Mathavan, S. C.; Meinema, C.; Mohanty, A.; Müller, S. E.; Nuñez Portela, M.; Onderwater, C. J. G.; Pijpker, C.; Willmann, L.; Wilschut, H. W.

A radioactive beam of 20Na is stopped in a gas cell filled with Ne gas. The stopped particles are polarized by optical pumping. The degree of polarization that can be achieved is studied. A maximum polarization of 50% was found. The dynamic processes in the cell are described with a phenomenological model.

Keywords: β decay; Gas catcher; Polarization in buffer gas; Plasma

Publ.-Id: 23511

Controlled polar asymmetry of few-cycle and intense mid-infrared pulses

Schmidt, C.; Bühler, J.; Mayer, B.; Pashkin, A.; Leitenstorfer, A.; Seletskiy, D.

We demonstrate synthesis of ultrabroadband and phase-locked two-color transients in the multi-terahertz frequency range with amplitudes exceeding 13 MV cm−1. Subcycle polar asymmetry of the electric field is adjusted by changing the relative phase between superposed fundamental and second harmonic components. The resultant broken symmetry of the field profile is directly resolved via electro-optic sampling. Access to such waveforms provides a direct route for control of low-energy degrees of freedom in condensed matter as well as non-perturbative light–matter interactions under highest non-resonant electric bias.

Keywords: polar asymmetry; THz; harmonic synthesis; quantum control; mid-infrared; high field; non-perturbative light–matter interaction

Publ.-Id: 23510

Magnetically patterned rolled-up exchange bias tubes: A paternoster for superparamagnetic beads

Ueltzhöffer, T.; Streubel, R.; Koch, I.; Holzinger, D.; Makarov, D.; Schmidt, O. G.; Ehresmann, A.

We realized a deterministic transport system for superparamagnetic beads in a paternoster-like manner with position-dependent trajectories and velocities by rolling up exchange bias layer systems with engineered parallel stripe magnetic domains to tubular architectures possessing distinct azimuthally aligned magnetic domain patterns. By applying periodic pulse sequences of very weak external magnetic fields and taking advantage of the magnetic stray field emerging from the tubular structures, we demonstrate the transport for different superparamagnetic beads either in or above the rolled-up tubes acting as channels. This transport mechanism features high step velocities and remote control of not only the direction and trajectory but also the velocity of the transport without the need of fuel or catalytic material. Therefore, this approach paves the way towards novel 3D-applications in biotechnology, including particle transport related phenomena in lab-on-a chip and lab-in-a-tube devices.

Keywords: Rolled-up tube; exchange bias; ion bombardment induced magnetic patterning; particle transport; superparamagnetic beads; lab-in-a-tube; lab-on-a-chip

Related publications

Publ.-Id: 23509

Magnetic Suspension Arrays Technology: Controlled Synthesis and Screening in Microfluidic Networks

Lin, G.; Karnaushenko, D. D.; Canon Bermudez, G. S.; Schmidt, O. G.; Makarov, D.

Information tagging and processing are vital in information-intensive applications, e.g. telecommunication and high-throughput drug screening. Magnetic suspension arrays technology may offer intrinsic advantages to screening applications by enabling high distinguishability, the ease of code generation and the feasibility of fast code readout, though the practical applicability of magnetic suspension arrays technology remains hampered by the lack of quality administration of encoded microcarriers. Here we realize a logic-controlled microfluidic system enabling controlled synthesis of magnetic suspension arrays in multiphase flow networks. The smart and compact system offers a practical solution for the quality administration and screening of encoded magnetic microcarriers and addresses the universal need of process control for synthesis in microfluidic networks, i.e. on-demand creation of droplet templates for high information capacity. The demonstration of magnetic suspension arrays technology enabled by magnetic in-flow cytometry opens the avenue toward point-of-care multiplexed bead-based assays, clinical diagnostics and drug discovery.

Keywords: suspension arrays technology; magnetic flow cytometry; magnetic sorting; droplet microfluidics; controlled synthesis

Related publications

Publ.-Id: 23508

Magnetism in curved geometries

Streubel, R.; Fischer, P.; Kronast, F.; Kravchuk, V. P.; Sheka, D. D.; Gaididei, Y.; Schmidt, O. G.; Makarov, D.

Extending planar two-dimensional structures into the three-dimensional space has become a general trend in multiple disciplines, including electronics, photonics, plasmonics and magnetics. This approach provides means to modify conventional or to launch novel functionalities by tailoring the geometry of an object, e.g. its local curvature. In a generic electronic system curvature results in the appearance of scalar and vector geometric potentials inducing anisotropic and chiral effects. In the specific case of magnetism, even in the simplest case of a curved anisotropic Heisenberg magnet, curvilinear geometry brings about two exchangedriven interactions, namely effective anisotropy and antisymmetric vector exchange, i.e. effective Dzyaloshinskii-Moriya interaction. As a consequence, the family of novel curvature-driven effects emerges, which includes magnetochiral effects and topologically induced magnetization patterning, resulting in theoretically predicted unlimited domain wall velocities, chirality symmetry breaking and Cherenkov-like effects for magnons. The broad range of altered physical properties makes these curved architectures appealing in view of fundamental research on e.g. skyrmionic systems, magnonic crystals or exotic spin configurations. In addition to these rich physics, the application potential of three-dimensionally shaped objects is currently being explored as magnetic field sensorics for magnetofluidic applications, spin-wave filters, advanced magneto-encephalography devices for diagnosis of epilepsy or for energy-efficient racetrack memory devices. These recent developments starting from the theoretical predictions to the fabrication of three-dimensionally curved magnetic thin films, hollow cylinders or wires and their characterization using integral means as well as the development of advanced tomography approaches are in the focus of this review.

Publ.-Id: 23506

Polycrystalline ZnTe thin film on silicon synthesized by pulsed laser deposition and subsequent pulsed laser melting

Xu, M.; Gao, K.; Wu, J.; Cai, H.; Yuan, Y.; Prucnal, S.; Hübner, R.; Skorupa, W.; Helm, M.; Zhou, S.

ZnTe thin films on Si substrates have been prepared by pulsed laser deposition and subsequent pulsed laser melting (PLM) treatment. The crystallization during PLM is confirmed by Raman scattering, x-ray diffraction and room temperature photoluminescence (PL) measurements. The PL results show a broad peak at 574 nm (2.16 eV), which can be assigned to the transitions from the conduction band to the acceptor level located at 0.145 eV above the valence band induced by zinc-vacancy ionization. Our work provides an applicable approach to low temperature preparation of crystalline ZnTe thin films.

Keywords: ZnTe; Pulsed laser melting

Related publications


Publ.-Id: 23505

Crystalline Electric Field and Kondo Effect in SmOs4Sb12

Mombetsu, S.; Yanagisawa, T.; Hidaka, H.; Amitsuka, H.; Yasin, S.; Zherlitsyn, S.; Wosnitza, J.; Ho, P.-C.; Maple, M. B.

Our ultrasound results obtained in pulsed magnetic fields show that the filled-skutterudite compound SmOs4Sb12 has the Γ67 quartet crystalline-electric-field ground state. This fact suggests that the multipolar degrees of freedom of the Γ quartet play an important role in the unusual physical properties of this material. On the other hand, the elastic Response below ≈20 T cannot be explained using the localized 4f-electron model, which does not take into account the Kondo effect or ferromagnetic ordering. The analysis result suggests the presence of a Kondo-like screened state at low magnetic fields and its suppression at high magnetic fields above 20 T even at low temperatures.

Publ.-Id: 23504

Prediction of flow patterns of rotating inclined reactors using a modified permeability approach

Subramanian, K.; Winkler, M.; Härting, H. U.; Schubert, M.

A new inclined rotating tubular fixed bed reactor was recently suggested for process intensification of heterogeneous catalytic multiphase reactions. With that concept, favorable operating conditions can be adjusted operating the reactor in a wetting intermittency mode via periodic catalyst immersion in a stratified gas-liquid flow. This flow pattern adjustment, which requires a careful selection of reactor inclination and rotation, was found to eventually enhance the reaction rate.
In this work an attempt has also been made to predict the flow patterns using computational fluid dynamics. A three-dimensional model based on the relative permeability approach was developed, where gas and liquid phases flow co-currently downwards through the inclined rotating tubular fixed bed reactor. The simulation results are validated against experimental data. The model can clearly predict the four evolving pattern, i.e. stratified, sickle, annular and dispersed flow depending on the operating conditions. In particular, the effect of gas and liquid superficial velocity on liquid saturation and pressure drop for the stratified flow, the most beneficial one with regard to process intensification, was studied in detail, which revealed model predictions within the error range of 15%. It was further verified that the model is capable of correctly predicting the hydrodynamics for aqueous liquid mixtures with varying viscosity and surface tension.

Keywords: Rotating fixed bed; reactor inclination; multiphase flow pattern; computational fluid dynamics; relative permeability concept

Publ.-Id: 23503

Process intensification of gas-liquid downflow and upflow packed beds by a new low-shear rotating reactor concept

Dashliborun, A. M.; Härting, H.-U.; Schubert, M.; Larachi, F.

In the present work, a new low-shear rotating reactor concept was introduced for process intensification of heterogeneous catalytic reactions in cocurrent gas-liquid downflow and upflow packed-bed reactors. In order to properly assess potential advantages of this new reactor concept, exhaustive hydrodynamic experiments were carried out using embedded low-intrusive wire mesh sensors. The effect of rotational velocities on liquid flow patterns in the bed cross-section, liquid saturation, pressure drop, and regime transition was investigated. Furthermore, liquid residence time and Péclet number estimated by a stimulus-response technique and a macro-mixing model were presented and discussed with respect to the prevailing flow patterns. The results revealed that the column rotation induces different flow patterns in the cross-section of packed bed operating in a concurrent downflow or upflow mode. Moreover, the new reactor concept exhibits a more flexible adjustment of pressure drop, liquid saturation, liquid residence time and back-mixing at constant flow rates.

Keywords: Process intensification; low-shear rotating fixed bed; hydrodynamics; upflow and downflow; flow pattern

  • Open Access Logo AIChE Journal 63(2017)1, 283-294
    Online First (2016) DOI: 10.1002/aic.15549
    Cited 16 times in Scopus
  • Lecture (Conference)
    International Symposia on Chemical Reaction Engineering - ISCRE24, 12.-15.06.2016, Minneapolis, USA

Publ.-Id: 23502

Measurement of the photodissociation of the deuteron at energies relevant to Big Bang nucleosynthesis

Hannaske, R.

Zwischen 10 und 1000 s nach dem Urknall bildeten sich während der Big Bang Nukleosynthese (BBN) die ersten leichten Elemente aus Protonen und Neutronen. Die primordialen Häufigkeiten dieser Elemente hingen von denWirkungsquerschnitten der beteiligten Kernreaktionen ab. Vergleiche zwischen den Ergebnissen nuklearer Netzwerkrechnungen mit astronomischen Beobachtungen bieten eine einzigartige Möglichkeit, etwas über das Universum zu dieser Zeit zu erfahren.
Da es für die p(n,g)d-Reaktion, die eine Schlüsselreaktion der BBN ist, kaum Messungen im relevanten Energiebereich gibt, beruht deren Reaktionsrate in Netzwerkrechnungen auf theoretischen Berechnungen. Darin fließen auch experimentelle Daten der Nukleon-Nukleon-Streuung, des Einfangquerschnitts für thermische Neutronen sowie (nach Anwendung des Prinzips des detaillierten Gleichgewichts) der d(g,n)p-Reaktion mit ein. Diese Reaktion, die Photodissoziation des Deuterons, ist bei BBN-Energien (Tcm = 20–200 keV) ebenfalls kaum vermessen. Die großen experimentelle Unsicherheiten machen Vergleiche mit den präzisen theoretischen Berechnungen schwierig. In den letzten Jahren wurde die d(g,n)p-Reaktion und insbesondere der M1-Anteil des Wirkungsquerschnitts mit quasi-monoenergetischen g-Strahlen aus Laser-Compton-Streuung oder durch Elektrodesintegration untersucht. Üblicherweise verwendete man für Messungen des d(g,n)p-Wirkungsquerschnitts entweder die auf wenige diskrete Energien beschränkte Strahlung des g-Zerfalls oder Bremsstrahlung, für die aber eine genaue Photonenflussbestimmung sowie der Nachweis von einem der Reaktionsprodukte und dessen Energie nötig ist. Da diese Energie im Bereich der BBN relativ gering ist, gab es bisher noch keine absoluten Messung des d(g,n)p-Wirkungsquerschnitts bei Tcm < 5 MeV mit Bremsstrahlung.
Das Ziel dieser Dissertation ist eine solche Messung mit einer Unsicherheit von 5 % im für die BBN relevanten Energiebereich und darüber hinaus bis Tcm ~ 2,5 MeV unter Verwendung gepulster Bremsstrahlung an der Strahlungsquelle ELBE. Dieser supraleitende Elektronenbeschleuniger befindet sich am Helmholtz-Zentrum Dresden-Rossendorf und stellte einen Elektronenstrahl hoher Intensität bereit. Die kinetische Elektronenenergie von 5 MeV wurde mit einem Browne-Buechner-Spektrometer präzise gemessen. Die Energieverteilung der in einer Niob-Folie erzeugten Bremsstrahlungsphotonen wurde berechnet. Die Photonenflussbestimmung nutzte die Kernresonanzstreuung an 27Al, das sich mit deuteriertem Polyethylen in einem mehrschichtigen Target befand. Die 27Al-Abregungen wurden mit abgeschirmten, hochreinen Germanium-Detektoren nachgewiesen, deren Effektivität mit GEANT4 simuliert und durch Quellmessungen normiert wurde. Die Messung der Energie der Neutronen aus der d(g,n)p-Reaktion erfolgte mittels deren Flugzeit in Plastikszintillatoren, die an zwei Seiten von Photoelektronenvervielfachern mit hoher Verstärkung ausgelesen wurden. Die Nachweiseffektivität dieser Detektoren wurde in einem eigenen Experiment in den Referenz-Neutronenfeldern der PTB Braunschweig kalibriert. Die Nachweisschwelle lag bei etwa 10 keV kinetischer Neutronenenergie.Wegen der guten Zeitauflösung der Neutronendetektoren und des ELBE-Beschleunigers genügte eine Flugstrecke von nur 1 m. Die Energieauflösung betrug im d(g,n)p-Experiment 1–2 %. Leider gingen viele Neutronen bereits durch Streuung in dem großen Target verloren oder sie wurden erst durch Teile des kompakten Experimentaufbaus in die Detektoren gestreut. Beide Effekte wurden mit Hilfe von FLUKA simuliert um einen Korrekturfaktor zu bestimmen, der aber bei niedrigen Energien relativ groß war.
Der d(g,n)p-Wirkungsquerschnitts wurde daher nur im Bereich 0.7 MeV < Tcm < 2.5 MeV bestimmt. Die Ergebnisse stimmen mit anderen Messungen, Daten-Evaluierungen sowie theoretischen Rechnungen überein. Die Gesamtunsicherheit beträgt circa 6.5 % und kommt zu fast gleichen Teilen von den statistischen und systematischen Unsicherheiten. Die statistische Unsicherheit könnte durch eine längere FLUKA Simulation noch von 3–5 % auf 1 % verringert werden. Die systematische Unsicherheit von 4.5 % ist vorrangig auf die Photonenflussbestimmung, die Neutronen-Nachweiseffektivität und die Target-Zusammensetzung zurückzuführen.

Keywords: Big Bang nucleosynthesis; bremsstrahlung; gamma-ray spectroscopy; neutron time-of-flight; nuclear astrophysics; photon scattering; neutron detector; efficiency; FLUKA

Related publications

  • Open Access Logo Wissenschaftlich-Technische Berichte / Helmholtz-Zentrum Dresden-Rossendorf; HZDR-071 2016
    ISSN: 2191-8708, eISSN: 2191-8716


Publ.-Id: 23501

Investigation of Pressure Hammer with Wire Mesh Sensor and High Speed Imaging Techniques

Traudt, T.; Bombardieri, C.; Schleicher, E.; Manfletti, C.

Previous water hammer tests have revealed pressure spikes in the cavitation area. With the aim of explaining the phenomena and enhancing the understanding of the pressure hammer phenomenon in general, a high speed imaging (HSI) setup was installed at the test bench. To complement the high speed imaging a wire mesh sensor was used. The wire mesh sensor (WMS) allowed the measurement of the cross-sectional void fracture distribution in the pipe while the flow was cavitating. The results of the measurements will be presented and discussed.

  • Contribution to proceedings
    Space Propulsion 2016, 02.-06.05.2016, Rom, Italien
    Proceedings of SP2016
  • Lecture (Conference)
    Space Propulsion Conference, 02.-06.05.2016, Rom, Italien

Publ.-Id: 23500

Single-shot betatron source size measurement from a laser-wakefield accelerator

Köhler, A.; Couperus, J. P.; Zarini, O.; Jochmann, A.; Irman, A.; Schramm, U.

Betatron radiation emitted by accelerated electrons in laser-wakefield accelerators can be used as a diagnostic tool to investigate electron dynamics during the acceleration process. We analyse the spectral characteristics of the emitted betatron pattern utilizing a 2D x-ray imaging spectroscopy technique. Together with simultaneously recorded electron spectra and x-ray images, the betatron source size, thus the electron beam radius, can be deduced at every shot.

Keywords: Betatron radiation; Laser wakefield acceleration; x-rays

Related publications

  • Lecture (Conference)
    DPG-Frühjahrstagung Darmstadt, 14.-18.03.2016, Darmstadt, Deutschland

Publ.-Id: 23499

Quantum oscillations and the Fermi surface topology of the Weyl semimetal NbP

Klotz, J.; Wu, S.-C.; Shekhar, C.; Sun, Y.; Schmidt, M.; Nicklas, M.; Baenitz, M.; Uhlarz, M.; Wosnitza, J.; Felser, C.; Yan, B.

The Weyl semimetal NbP was found to exhibit topological Fermi arcs and exotic magnetotransport properties. Here, we report on magnetic quantum-oscillation measurements on NbP and construct the three-dimensional Fermi surface with the help of band-structure calculations. We reveal a pair of spin-orbit-split electron pockets at the Fermi energy and a similar pair of hole pockets, all of which are strongly anisotropic. The Weyl points that are located in the kz ≈ π/c plane are found to exist 5 meV above the Fermi energy. Therefore, we predict that the chiral anomaly effect can be realized in NbP by electron doping to drive the Fermi energy to the Weyl points.

Publ.-Id: 23498

Exotic Ground State and Elastic Softening under Pulsed Magnetic Fields in PrTr2Zn20 (Tr = Rh, Ir)

Ishii, I.; Goto, H.; Kamikawa, S.; Yasin, S.; Zherlitsyn, S.; Wosnitza, J.; Onimaru, T.; Matsumoto, K. T.; Takabatake, T.; Suzuki, T.

To investigate a field-induced level crossing of the ground-state doublet in PrTr2Zn20 (Tr = Rh, Ir), we performed ultrasonic measurements in pulsed magnetic fields applied along the [110] and [001] directions and analyzed the results in the framework of the strain-susceptibility approach. Above 40 T for H ∣∣ [110], we observed an elastic softening of the transverse modulus (C11 − C12)/2 corresponding to the ground-state doublet. In both compounds the softening is followed by a minimum at about 47 T at low temperatures. We predict the presence of a new field-induced phase boundary in PrTr2Zn20 at this field with two possible cases. The magnetic field of the minimum cannot be explained by only the quadrupole interaction.

Publ.-Id: 23497

Magnetic phase diagram of the helimagnetic spinel compound ZnCr2Se4 revisited by small-angle neutron scattering

Cameron, A. S.; Tymoshenko, Y. V.; Portnichenko, P. Y.; Gavilano, J.; Tsurkan, V.; Felea, V.; Loidl, A.; Zherlitsyn, S.; Wosnitza, J.; Inosov, D. S.

We performed small-angle neutron scattering (SANS) measurements on the helimagnetic spinel compound ZnCr2Se4. The ground state of this material is a multi-domain spin-spiral phase, which undergoes domain selection in a magnetic field and reportedly exhibits a transition to a proposed spin-nematic phase at higher fields. We observed a continuous change in the magnetic structure as a function of field and temperature, as well as a weak discontinuous jump in the spiral pitch across the domain-selection transition upon increasing field. From our SANS results we have established the absence of any long-range magnetic order in the high-field (spin-nematic) phase. We also found that all the observed phase transitions are surprisingly isotropic with respect to the field direction.

Publ.-Id: 23496

Kinetic Monte Carlo simulation of irradiation-induced nanostructure evolution in Oxide Dispersion Strengthened Fe alloys

Liedke, B.; Posselt, M.; Murali, D.; Claisse, A.; Olsson, P.

Rigid-lattice Kinetic Monte Carlo simulations are performed in order to investigate the modification of Y-Ti-O nanoclusters during irradiation, at selected temperatures, doses and dose rates. The simulations use input parameters for the atomic interactions and the migration barriers obtained by DFT calculations as well as data on representative examples of the cascade debris determined by Molecular Dynamics. Before irradiation the nanostructure is prepared by performing thermal relaxation of a system with randomly distributed Y, Ti, O atoms, and vacancies. The concentration of Y, Ti, and O is chosen according to the common 14 YWT ODS alloy and both low and high vacancy contents are considered. The nanostructures obtained in the preparation step were used subsequently in KMC simulations of irradiation. The results demonstrate the competition between ballistic effects leading to the dissolution and the growth of the clusters. While the former effect dominates at high doses and low temperatures the latter prevails at low doses and high temperatures. On the other hand, the nanoclusters formed in the preparation step show a very high stability under irradiation within the temperature and dose range relevant for the application of ODS alloys in advanced nuclear reactors. The findings of this work are consistent with the results of experimental studies of ion and neutron irradiation of ODS alloys.

Keywords: Oxide Dispersion Strengthened Fe-Cr alloys; Kinetic Monte-Carlo; radiation damage; nanoclusters

  • Lecture (Conference)
    3rd International Workshop on ODS Materials, 21.-22.04.2016, HZDR, Germany

Publ.-Id: 23495

Self-assembly of [2+2] Co(II) metallomacrocycles and Ni(II) metallogels with novel bis(pyridylimine) ligands

Kelly, N.; Gloe, K.; Doert, T.; Hennersdorf, F.; Heine, A.; März, J.; Schwarzenbolz, U.; Weigand, J. J.; Gloe, K.

Two novel 46-membered Co(II) metallomacrocycles, Co2Cl4(L1)2]∙CH2Cl2 and [Co2(NO3)2(L1)2(H2O)2 ligand L4 was also demonstrated to form metallogels when reacted with NiCl2∙6H2O in tetrahydrofuran under defined conditions.

Keywords: Bispyridylimine ligands; Cobalt(II); Nickel(II); Metallomacrocycles; Metallogel; Self-assembly; Supramolecular chemistry

Publ.-Id: 23493

Bestimmung langlebiger Radionuklide mittels Beschleunigermassenspektrometrie (AMS) für archäometrische Fragestellungen

Merchel, S.; DREAMS-Team; DREAMS-Users

Die Radiokarbondatierung (C-14) ist insbesondere durch die hochsensitive Beschleunigermassenspektrometrie (accelerator mass spectrometry = AMS) seit Jahrzehnten ein Standardverfahren in der Archäometrie. Das Potential anderer Radionuklide wie Ca-41, Cl-36 und Be-10 mit längeren Halbwertszeiten (0.1-1.4 Ma) ist jedoch noch weitestgehend unausgeschöpft. Dies liegt u. a. an den technologischen, physikalischen und geo- und umweltwissenschaftlichen Einschränkungen und Schwierigkeiten, die zwingend berücksichtigt werden müssen, um eine akkurate Datierung zu ermöglichen.
So ist die indirekte Datierung von in Sedimenten abgelagerten Artefakten bis hin zu einigen Millionen Jahren durch die AMS-Bestimmung des in der Atmosphäre gebildeten Be-10 nur möglich, wenn der lokale Startwert des Be-10/Be-9-Verhältnisses bekannt ist.
Die direkte Altersbestimmung von Knochen über das „in-situ“ gebildete Ca-41 und Aufnahme entlang der Nahrungskette scheint aufgrund der extrem niedrigen Ca-41/Ca-Verhältnisse methodisch noch schwierig zu sein. Technologische Weiterentwicklungen auf dem Gebiet der AMS-Ionenquellen scheinen aber vielversprechend, die Methode in den nächsten Jahren zur Anwendung zu bringen.
Die Datierung von historischen Bauwerken aus kalziumhaltigen Baumaterialien (z. B. Kalkstein) mittels „in-situ“-produzierten Cl-36 ist wegen der Vorbestrahlung der Materialien vor der menschlichen Verwendung bis hin zu Tiefen von 30 m nur eingeschränkt möglich. Sie führt in der Regel zu überschätzten Altern. Gleiches gilt für Einritzungen und Zeichnungen an Oberflächengesteinen.

Keywords: archaeometry; AMS; dating; age; cosmogenic nuclide

Related publications

  • Poster
    Tagung „Archäometrie und Denkmalpflege 2016“, 27.09.-01.10.2016, Göttingen, Deutschland
  • Metalla (2016)8, 30-33
    ISSN: 0947-6229

Publ.-Id: 23492

Retrospective assessment of delivered proton dose in prostate cancer patients based on daily in-room CT imaging

Stützer, K.; Päßler, T.; Valentini, C.; Exner, F.; Thiele, J.; Hölscher, T.; Krause, M.; Richter, C.


Retrospective calculation of the delivered proton dose in prostate cancer patients based on a unique dataset of daily CT images.
Inter-fractional motion in prostate cancer patients treated at our proton facility is counteracted by water-filled endorectal ballon and bladder filling protocol. Typical plans (XiO, Elekta Instruments AB, Stockholm) for 74 Gy(RBE) sequential boost treatment in 37 fractions include two series of opposing lateral double-scattered proton beams covering the respective iCTV. Stability of fiducial markers and anatomy were checked in 12 patients by daily scheduled in-room control CT (cCT) after immobilization and positioning according to bony anatomy utilizing orthogonal X-ray. In RayStation 4.6 (RaySearch Laboritories AB, Stockholm), all cCTs are delineated retrospectively and the treatment plans were recalculated on the planning CT and the registered cCTs. All fraction doses were accumulated on the planning CT after deformable registration. Parameters of delivered dose to iCTV (D98%>95%, D2% <107%), bladder (V75Gy <15%, V70Gy <25%, V65Gy <30%), rectum (V70Gy <10%, V50Gy <40%) and femoral heads (V50Gy <5%) are compared to those in the treatment plan. Intra-therapy variation is represented in DVH bands.
No alarming differences were observed between planned and retrospectively accumulated dose: iCTV constraints were met, except for one patient (D98%=94.6% in non-boosted iCTV). Considered bladder and femoral head values were below the limits. Rectum V70Gy was slightly exceeded (<11.3%) in two patients.
First intra-therapy variability analysis in 4 patients showed no time-dependent parameter drift, revealed strongest variability for bladder dose. In some fractions, iCTV coverage (D98%) and rectum V70Gy was missed.
Double scattered proton plans are accurately delivered to prostate cancer patients due to fractionation effects and the applied precise positioning and immobilization protocols. As a result of rare interventions after daily 3D imaging of the first 12 patients, in-room CT frequency for prostate cancer patients was reduced. The presented study supports this decision.

Keywords: in-room CT; proton therapy; prostate cancer

  • Lecture (Conference)
    AAPM 58th Annual Meeting and Exhibition, 31.07.-04.08.2016, Washington D.C., United States of America
  • Abstract in refereed journal
    Medical Physics 43(2016)6, 3455
    DOI: 10.1118/1.4956111

Publ.-Id: 23491

Retrospective analysis of daily accumulated proton dose in prostate cancer patients

Stützer, K.; Päßler, T.; Valentini, C.; Exner, F.; Thiele, J.; Agolli, L.; Hölscher, T.; Krause, M.; Richter, C.

The study presents the first series of daily in-room CT images acquired from the first 12 prostate cancer patients after proton-specific immobilization and positioning procedures and followed by actual proton radiotherapy at the University Proton Therapy Dresden. Based on this unique dataset, the actually delivered proton dose is calculated retrospectively for each fraction, analyzed for inter-fractional variability and accumulated to a total dose for comparison with the treatment plan.

Introduction: The steep dose gradients and small number of treatment fields require reproducible anatomical geometry and positioning in proton therapy to secure an accurate dose delivery. Prostate cancer is known to be subjected to inter-fractional variation due to day-to-day variation in bowel, rectum and bladder filling. Adequate positioning and treatment protocols were investigated prior the start of proton therapy to prostate cancer patients in our institute [1]. The presented study analyzes the suitability of these protocols by means of a retrospective evaluation of actually delivered proton dose in comparison to the treatment plan.

Material and Methods: Inter-fractional motion in prostate cancer patients treated at the University Proton Therapy Dresden is counteracted by water-filled endorectal ballon and bladder filling protocol. Patient positioning is based on bony anatomy match utilizing orthogonal X-Ray imaging. Stability of implanted fiducial markers and anatomy were checked in the first 12 patients by daily scheduled in-room control CT (cCT) after immobilization and positioning. Typical plans (XiO, Elekta Instruments AB, Stockholm) for 74 Gy(RBE) sequential boost treatment in 37 fractions include two series of opposing lateral double-scattered proton beams covering the respective internal clinical target volume (iCTV). In RayStation 4.6 (RaySearch Laboritories AB, Stockholm), all cCTs are delineated retrospectively and the treatment plans were recalculated on the planning CT and the registered cCTs. All fraction doses were accumulated on the planning CT after deformable registration. Parameters of delivered dose to iCTV (D98% > 95%, D2% < 107%), bladder (V75Gy < 15%, V70Gy < 25%, V65Gy < 30%), rectum (V70Gy < 10%, V50Gy < 40%) and femoral heads (V50Gy < 5%) are compared to those in the treatment plan. Intra-therapy variation is represented in DVH bands.

Result: Due to CT maintenance, physician’s decision and initial workflow optimization, the median number of actually acquired cCTs within 37 fractions was 32 (range: 27-37). Seven patients received the sequential boost series prior the nominal series due to concerns that anatomy might change noticeably during six weeks of therapy and then margin concepts might be insufficient. One patient received a nominal plan of 37 fractions to an iCTV excluding seminal vesicles.
First intra-therapy variability analysis in 5 patients showed no time-dependent parameter drift and revealed strongest variability for bladder dose. In some fractions, iCTV coverage (D98%) and rectum V70Gy was missed. An illustration of the dosimetric evaluation is shown for an exemplary patient in Figure 1.
No alarming differences (cp. Table 1) were observed between planned and retrospectively accumulated dose for all 12 patients: iCTV constraints were met, except for one patient (D98% = 94.4% in non-boosted iCTV). Considered bladder and femoral head dosimetric values were below the limits. Rectum V70Gy was slightly exceeded (<11%) in two patients.

Conclusion: Double scattered proton plans are accurately delivered to prostate cancer patients due to fractionation effects and the applied precise positioning and immobilization protocols. As a result of rare interventions after daily 3D imaging of the first 12 patients, in-room CT frequency for prostate cancer patients was reduced. The presented study supports this decision.

[1] M. Schneidt et al. (2015) Prospective evaluation of patient positioning for interfractional variation in proton therapy of prostate cancer. 3rd ESTRO Forum, Barcelona

Keywords: in-room CT; prostate cancer; proton therapy; dose accumulation

  • Lecture (Conference)
    47. Jahrestagung der Deutschen Gesellschaft für Medizinische Physik (DGMP) e. V. 19. Jahrestagung der Deutschen Sektion der International Society for Magnetic Resonance in Medicine (ISMRM) e. V., 07.-10.09.2016, Würzburg, Deutschland

Publ.-Id: 23489

Clinical use of dual-energy CT for proton treatment planning to reduce CT-based range uncertainties

Wohlfahrt, P.; Möhler, C.; Jakobi, A.; Baumann, M.; Enghardt, W.; Krause, M.; Greilich, S.; Richter, C.


To improve CT-based particle treatment planning the additional tissue information provided by dual-energy CT (DECT) compared to single-energy CT (SECT) can be clinically used to reduce CT-based range uncertainties and to analyze intra- and interpatient tissue variations. First, a DECT scan protocol was optimized and clinically introduced. Second, in a first analysis patient DECT scans were evaluated concerning CT number variability.

Material and Methods:

After an experimental analysis of several CT scan settings concerning beam hardening, image quality and planned dose distribution using tissue surrogates, head and body phantoms and real tissues, an optimized and standardized DECT protocol (voltages: 80/140 kVp, kernel: D34) is clinically applied for patients treated with protons. 45 planning and 360 control DECT scans of overall 70 patients were acquired with a single-source DECT scanner (Siemens SOMATOM Definition AS) until October 2015. Contouring and treatment planning are performed on pseudo-monoenergetic CT scans (MonoCT) derived by a weighted sum of both CT datasets. 25 patients with different tumor sites (head, head & neck, prostate, pelvis) and overall 200 DECT scans were initially investigated to evaluate intra- and interpatient tissue variabilities. Based on the frequency distribution of voxelwise 80/140kVp CT number pairs, a linear correlation of low-density, soft and bony tissues can be determined, respectively.


A DECT-based MonoCT of 79 keV is found optimal for proton treatment planning. Assuming identical CT dose to a SECT scan, the MonoCT shows a signal-to-noise ratio increased by 8% and a CT number constancy raised by 23% on average and up to 69% for bones. Consequently, the current uncertainties of a heuristic conversion of CT numbers into stopping power ratios (SPR) using a look-up table are reduced.
Evaluation of patient variability revealed that 80/140kVp CT number pairs of human tissues are on average well described by linear correlations with a slope (± σ) of (1.023 ± 0.006) for low-density, (0.825 ± 0.008) for soft and (0.696 ± 0.006) for bony tissues. The slope variation between different patients, independent from tumor site and patient size, is comparable to the variability between different control DECT scans of one patient (σ of about 1-3%). However, a band of CT number pairs deviating from the mean linear correlation, e.g. caused by image noise and partial volume effects, reveals potential insuperable uncertainties of a voxel-based heuristic CT number-to-SPR conversion.

The clinical application of DECT-based MonoCT can contribute to a more precise range prediction. Further improvements are expected from a direct, non-heuristic SPR calculation, which is not yet clinically available. The further growing DECT patient database enables not only a detailed analysis of intra- and interpatient variations, but also a robustness analysis for different direct SPR prediction approaches.

Keywords: dual-energy CT; proton therapy

  • Lecture (Conference)
    ESTRO 35 - annual meeting, 29.04.-03.05.2016, Turin, Italy
  • Abstract in refereed journal
    Radiotherapy and Oncology 119(2016)Suppl.1, S70-S71

Publ.-Id: 23488

Non-equilibrium dynamics of magnetically anisotropic particles under oscillating fields

Steinbach, G.; Gemming, S.; Erbe, A.

In this article, we demonstrate how colloidal self-assembly and non-equilibrium dynamic processes can be enhanced by anisotropic particles. As an example, we study spherical particles with radially off-centered net magnetic moment in an oscillating field. Based on complementary data from a numerical simulation of spheres with shifted dipole and experimental observations from particles with hemispherical ferromagnetic coating, it is explained how this magnetic asymmetry gives rise to dynamic structural and orientational phenomena on a two-particle basis. We further present the behavior of ensembles of coated particles. It illustrates the potential for controlled reconfiguration based on the presented two-particle dynamics.

Keywords: Rotational dynamics; Few- and many-body systems; Colloids


Publ.-Id: 23487

Performance and Application Status of the Superconducting Photoinjector at ELBE

Teichert, J.; Arnold, A.; Lu, P.; Murcek, P.; Vennekate, H.; Xiang, R.

A new SRF gun has been commissioned at the ELBE linac. The gun has an improved 3.5-cell cavity and a superconducting solenoid is integrated. Beam parameter measurements have been carried out with a Cu photocathode.

Keywords: photoinjector; superconducting cavity; electron source; photocathode

Related publications

  • Invited lecture (Conferences)
    OSA High-Brightness Sources and Light-Driven Interaction Congress, 20.-22.03.2016, Long Beach, USA

Publ.-Id: 23486

Fabrication of Sub-Micron Surface Structures on Copper, Stainless Steel and Titanium using Picosecond Laser Interference Patterning

Bieda, M.; Siebold, M.; Lasagni, A. F.

Picosecond direct laser interference patterning is investigated theoretically and experimentally for the bulk metals copper, stainless steel and titanium. In the past, results on thermal modelling for nanosecond irradiation were reported for pitches in the range of several micrometers. When nanosecond pulses are utilized, the smallest possible pitch on metals is limited by the thermal diffusion length. In this case, the laser patterning process is predominantly determined by heat conduction mechanisms, and pitches less than 1 μm are not feasible. Picosecond laser pulses allow values below 1 μm pitch size on metallic surfaces. The modelling and simulation of DLIP is based on the two-temperature-model and was carried out for a pulse duration of 35 ps at 515 nm wavelength and a laser fluence of 0.1 J cm-2. The subsurface temperature distribution of both electrons and phonons was computed for periodic structures with a pitch of 0.8 μm. The increase in temperature rises for a lower absorption coefficient and a higher thermal conductivity (larger absorption depth) . The distance, at which the maximum subsurface temperature occurs, increases for a small absorption coefficient. High absorption and low thermal conductivity minimizes internal heating and give rise to a pronounced surface micro topography with pitches smaller than 1 μm. Periodic line-like surface structures were produced using two interfering beams on copper, stainless steel and titanium surfaces with a pitch of 0.7 μm using a Yb:YAG-Laser with 515 nm wavelength and a pulse duration of 35 ps.

Publ.-Id: 23485

Stakeholder integration in new product development – A systematic analysis of drivers and firm capabilities

Martin, M. V.; Reinhardt, R.; Gurtner, S.

In this article, we develop a conceptual model of stakeholder integration in new product development (NPD) that (i) explains the drivers of the process and (ii) proposes a framework of capabilities that firms need for successful stakeholder integration. The focus lies on external stakeholders that directly influence the adoption of new products. We conduct a systematic literature review and content analyze a sample of 96 peer-reviewed journal articles. The study is restricted to the medical device industry to enable the use of specific search terms and the consistent categorization of information. We dedicate a section to showing how the framework applies to other settings. The drivers of stakeholder integration are classified into push factors (i.e., expected benefits for the focal firm) and pull factors (i.e., expected benefits for the stakeholders). This study provides an initial model of how stakeholder integration works based on its drivers. In addition, three related stakeholder integration capabilities emerge: stakeholder identification capability, stakeholder interaction capability and stakeholder input integration capability. The paper proposes a description of these capabilities for stakeholder integration in NPD and, thus, contributes to stakeholder theory and research on the management of NPD. The results open new paths for empirical testing and offer practical guidance on how to successfully integrate stakeholders in NPD processes.

Keywords: Stakeholder; New Product Development; Innovation

Publ.-Id: 23484

Smart Kd‑concept for realistic description of sorption processes

Stockmann, M.; Becker, D.; Flügge, J.; Schikora, J.; Noseck, U.; Brendler, V.

Sorption on mineral surfaces is an important retardation process to be considered in safety assessments of both chemotoxic and radioactive waste repositories. Most often conventional conservative concepts with temporally and spatially constant distribution coefficients (Kd‑values) are applied in reactive transport simulations.
This work describes, for the first time, a new methodology, where temporally and spatially variable distribution coefficients, so‑called smart Kd‑values were calculated for a more realistic description of sorption processes. This concept is based on a Bottom-Up approach (Davis 1998) of a competitive mineral-specific sorption of dissolved species on surfaces, combining surface complexation models with ion exchange and precipitation in a quasi-thermodynamic manner. The respective multi-dimensional matrices are computed a-priori to any run of the reactive transport codes (here: r³t, Fein 2004). During the run of such transport codes respective calls to the Kd–matrix with an appropriate averaging deliver parameter-specific Kd–values.
Three computer codes were coupled to form one tool: PHREEQC, UCODE and SIMLAB. This strategy has various benefits: (1) One can calculate smart Kd‑values for a reasonable number of environmental parameter combinations; (2) It is possible to perform uncertainty and sensitivity analysis based on such smart Kd‑matrices; (3) The approach is highly flexible with respect to chemical reactions and environmental conditions; (4) The overall methodology is much more efficient in computing time than a direct coupling of the geochemical speciation code with reactive transport codes.
The capability of this new methodology is demonstrated for the sorption of radioactive waste repository-relevant elements such as U, Am, or Np on a natural sandy aquifer. This served as a proof-of-concept for the new methodology to describe the sorption behavior in dependence of changing geochemical conditions. Results were compared to conservative Kd–values from literature used so far.

Fig 1: Kd histogramm for Am(III) in the upper aquifer of the Gorleben cap rock
Sensitivity and uncertainty analysis for the nuclides revealed the importance of ternary interaction effects, the non-concervatism of some generic distribution coefficients used so far, and the effects of input parameter correlation. Moreover, a ranking of the sensitivity of the environmental parameters nearly always put pH value, dissolved inorganic carbon and the content of matrix cations in the first places. Consequently, the mechanistic processes involving them (and their error distribution functions) should deserve higher attention in future research schemes.
Davis, J. A., Coston, J. A., Kent, D. B., Fuller, C. C. (1998): Application of the surface complexation concept to complex mineral assemblages. Environ. Sci. Technol. 32, 2820-2828.
Fein, E. (2004): Software Package r³t. Model for Transport and Retention in Porous Media. Report GRS-192, Braunschweig.

Keywords: nuclear waste disposal; safety assessment; modelling; thermodynamics; sorption; uncertainty; sensitivity; radionuclides

  • Lecture (Conference)
    DAEF 2016 - 2nd Conference on Key Topics in Deep Geological Disposal – Challenges of a Site Selection Process: Society – Procedures – Safety, 26.-28.09.2016, Köln, Deutschland

Publ.-Id: 23483

Vacancy Defect Complexes in Silicon: Charge and Spin Order

Liu, Y.; Pan, R.; Zhang, X.; Han, J.; Yuan, Q.; Tian, Y.; Yuan, Y.; Liu, F.; Wang, Y.; N'Diaye, A. T.; Arenholz, E.; Chen, X.; Sun, Y.; Song, B.; Zhou, S.

We investigate the interaction between charges and spin order of the defect complex V6 in silicon. The first-principles calculations predict spin resolved band splitting incurred by a neutral V6 yet with no net spin. Therefore, any shift of Fermi level can trigger the spin polarization. Both s and p states contribute local moments in the positively charged V6. The ferromagnetic coupling is only obtained between a positively charged V6 and a neutral one. In silicon after neutron irradiation, magnetism is achieved even at room temperature. The 3s∗3p∗ hybrid states of V6 are probably responsible for the observed long-range magnetic order. Our results unravel the role of charged V6 in inducing magnetism and will be useful in understanding and further manipulating the intrinsic properties of defect complexes in silicon and other semiconductors.

Keywords: defect-induced ferromagnetism; silicon; neutron irradiation; semiconductors; defect complex; charge state


Publ.-Id: 23482

Late Quaternary paleoenvironmental records from the Chatanika River valley near Fairbanks (Alaska)

Schirrmeister, L.; Meyer, H.; Andreev, A.; Wetterich, S.; Kienast, F.; Bobrove, A.; Fuchs, M.; Sierralta, M.; Herzschuh, U.

Perennially-frozen deposits are considered as excellent paleoenvironmental archives similar to lacustrine, deep marine, and glacier records because of the long-term and good preservation of fossil records under stable permafrost conditions. A permafrost tunnel in the Vault Creek Valley (Chatanika River Valley, near Fairbanks) exposes a sequence of frozen deposits and ground ice that provides a comprehensive set of proxies to reconstruct the late Quaternary environmental history of Interior Alaska. The multi-proxy approach includes different dating techniques (radiocarbon-accelerator mass spectrometry [AMS 14C], optically stimulated luminescence [OSL], thorium/uranium radioisotope disequilibria [230Th/U]), as well as methods of sedimentology, paleoecology, hydrochemistry, and stable isotope geochemistry of ground ice.

The studied sequence consists of 36-m-thick late Quaternary deposits above schistose bedrock. Main portions of the sequence accumulated during the early and middle Wisconsin periods. The lowermost unit A consists of about 9-m-thick ice-bonded fluvial gravels with sand and peat lenses. A late Sangamon (MIS 5a) age of unit A is assumed. Spruce forest with birch, larch, and some shrubby alder dominated the vegetation. High presence of Sphagnum spores and Cyperaceae pollen points to mires in the Vault Creek Valley. The overlying unit B consists of 10-m-thick alternating fluvial gravels, loess-like silt, and sand layers, penetrated by small ice wedges. OSL dates support a stadial early Wisconsin (MIS 4) age of unit B. Pollen and plant macrofossil data point to spruce forests with some birch interspersed with wetlands around the site. The following unit C is composed of 15-m-thick ice-rich loess-like and organic-rich silt with fossil bones and large ice wedges. Unit C formed during the interstadial mid-Wisconsin (MIS 3) and stadial late Wisconsin (MIS 2) as indicated by radiocarbon ages. Post-depositional slope processes significantly deformed both, ground ice and sediments of unit C. Pollen data show that spruce forests and wetlands dominated the area. The macrofossil remains of Picea, Larix, and Alnus incana ssp. tenuifolia also prove the existence of boreal coniferous forests during the mid-Wisconsin interstadial, which were replaced by treeless tundra-steppe vegetation during the late Wisconsin stadial. Unit C is discordantly overlain by the 2-m-thick late Holocene deposits of unit D. The pollen record of unit D indicates boreal forest vegetation similar to the modern one.

The permafrost record from the Vault Creek tunnel reflects more than 90 ka of periglacial landscape dynamics triggered by fluvial and eolian accumulation, and formation of ice-wedge polygons and post-depositional deformation by slope processes. The record represents a typical Wisconsin valley-bottom facies in Central Alaska.

Keywords: Permafrost; Interior Alaska; Loess; Cryolithology; Geochronology; Paleoecology; Landscape dynamics


Publ.-Id: 23481

Synthesis and characterization of modified ultrasmall nanoparticles as multimodal imaging agents

Singh, G.; Hunoldt, S.; Licciardello, N.; Stephan, H.; Faramus, A.; de Cola, L.

The synthesis of multimodal imaging agents is indeed a growing field and a lot of research is currently being done in this area because of its wide biomedical applications.[1] The idea behind this research is to prepare a single molecule/nanoparticle which is suitable for two or more imaging techniques and thus can act as a multimodal imaging agent, for example, the combination of optical and nuclear imaging modalities may provide complementary information for improving diagnosis as well as the treatment of diseases. These imaging agents combat the limitations of sensitivity, spatial and temporal resolution and also tissue penetrability. The high hydrophilicity of the nanoparticles and fast renal clearance of the complex from the body are the major highlights.
Amine terminated ultrasmall Silicon nanoparticles[2] (Si NPs) of size <5 nm were synthesized by hydrothermal method and purified by dialysis. Sulfo-Cyanine 5[3] dye was attached selectively to the amine terminated Si NPs. The single domain antibody is also conjugated with the particles for specific targeting of the cancerous tumors via a molecular handle such as PEG-Maleimide, which facilitates the targeting as well as maintains the hydrophilicity of the particles at the same time. Bispidines[4] are to be used as a copper chelator for radiolabeling the particles by 64Cu and could be used for the in vitro and in vivo studies by Positron emission tomography.
The substituents after coupling with the USNPs are assumed to act as excellent multimodal imaging agent which can be used for the cancer diagnosis and therapy.

[1] G. J. Cheon, Y. Chang, J. Yoo, J. Cheon, Angew. Chem. 2008, 120, 6355 –6358.
[2] Y. Zhong, F. Peng, F. Bao, S. Wang, X. Ji, L. Yang, Y. Su, S. Lee, Y. He, J. Am. Chem. Soc. 2013, 135, 8350−8356.
[3] K. Viehweger, L. Barbaro, K. P. García, T. Joshi, G. Geipel, J. Steinbach, H. Stephan, L. Spiccia, B. Graham, Bioconjugate Chem. 2014, 25, 1011−1022.
[4] H. Stephan, M. Walther, S. Fähnemann, P. Ceroni, J. Molloy, G. Bergamini, F. Heisig, C. E. Müller, W. Kraus, P. Comba, Chem. Eur. J. 2014, 20, 17011-17018.

  • Poster
    Analytica Conference 2016, 10.-12.05.2016, Munich, Germany

Publ.-Id: 23480

Intrinsic diamagnetism in the Weyl semimetal TaAs

Liu, Y.; Li, Z.; Guo, L.; Chen, X.; Yuan, Y.; Liu, F.; Prucnal, S.; Helm, M.; Zhou, S.

We investigate the magnetic properties of TaAs, a prototype Weyl semimetal. TaAs crystals show diamagnetism with magnetic susceptibility of about −7×10−7 emu/(g Oe) at 5 K. A general feature is the appearance of a minimum at around 185 K in magnetization measurements as a function of temperature, which resembles that of graphite. No phase transition is observed in the temperature range between 5 K and 400 K.

Keywords: Diamagnetism; Weyl semimetal; TaAs; Magnetic susceptibility

Publ.-Id: 23479

Pages: [1.] [2.] [3.] [4.] [5.] [6.] [7.] [8.] [9.] [10.] [11.] [12.] [13.] [14.] [15.] [16.] [17.] [18.] [19.] [20.] [21.] [22.] [23.] [24.] [25.] [26.] [27.] [28.] [29.] [30.] [31.] [32.] [33.] [34.] [35.] [36.] [37.] [38.] [39.] [40.] [41.] [42.] [43.] [44.] [45.] [46.] [47.] [48.] [49.] [50.] [51.] [52.] [53.] [54.] [55.] [56.] [57.] [58.] [59.] [60.] [61.] [62.] [63.] [64.] [65.] [66.] [67.] [68.] [69.] [70.] [71.] [72.] [73.] [74.] [75.] [76.] [77.] [78.] [79.] [80.] [81.] [82.] [83.] [84.] [85.] [86.] [87.] [88.] [89.] [90.] [91.] [92.] [93.] [94.] [95.] [96.] [97.] [98.] [99.] [100.] [101.] [102.] [103.] [104.] [105.] [106.] [107.] [108.] [109.] [110.] [111.] [112.] [113.] [114.] [115.] [116.] [117.] [118.] [119.] [120.] [121.] [122.] [123.] [124.] [125.] [126.] [127.] [128.] [129.] [130.] [131.] [132.] [133.] [134.] [135.] [136.] [137.] [138.] [139.] [140.] [141.] [142.] [143.] [144.] [145.] [146.] [147.] [148.] [149.] [150.] [151.] [152.] [153.] [154.] [155.] [156.] [157.] [158.] [159.] [160.] [161.] [162.] [163.] [164.] [165.] [166.] [167.] [168.] [169.] [170.] [171.] [172.] [173.] [174.] [175.] [176.] [177.] [178.] [179.] [180.] [181.] [182.] [183.] [184.] [185.] [186.] [187.] [188.] [189.] [190.] [191.] [192.] [193.] [194.] [195.] [196.] [197.] [198.] [199.] [200.] [201.] [202.] [203.] [204.] [205.] [206.] [207.] [208.] [209.] [210.] [211.] [212.] [213.] [214.] [215.] [216.] [217.] [218.] [219.] [220.] [221.] [222.] [223.] [224.] [225.] [226.] [227.] [228.] [229.] [230.] [231.] [232.] [233.] [234.] [235.] [236.] [237.] [238.] [239.] [240.] [241.] [242.] [243.] [244.] [245.] [246.] [247.] [248.] [249.] [250.] [251.] [252.] [253.] [254.] [255.] [256.] [257.] [258.] [259.] [260.] [261.] [262.] [263.] [264.] [265.] [266.] [267.] [268.] [269.] [270.] [271.] [272.] [273.] [274.] [275.] [276.] [277.] [278.] [279.] [280.] [281.] [282.] [283.] [284.] [285.] [286.] [287.] [288.] [289.] [290.] [291.] [292.] [293.] [294.] [295.] [296.] [297.] [298.] [299.] [300.] [301.] [302.] [303.] [304.] [305.] [306.] [307.] [308.] [309.] [310.] [311.] [312.] [313.] [314.] [315.] [316.] [317.] [318.] [319.] [320.] [321.] [322.] [323.] [324.] [325.] [326.] [327.] [328.]